MEDICINE AND SURGERY "F" Course of LABORATORY MEDICINE Hypervitaminoses and hypovitaminoses VITAMINS AND OTHER ESSENTIAL NUTRIENTS: EXCESS AND DEFICIENCY THE REGISTRATION OF ATTENDANCE TO THIS ON-LINE LECTURE IS ACTIVE!       To register your attendance please type in your surname and matricola number. Surname: Matricola: Notice that your attendance will be registered only if you completed the reading, questions, and audios, and that you cannot interrupt and resume the session (but you can repeat it as many times as you like). Remember to press the [send] button before leaving this page! A confirmation message will appear at the end of this page.       A comment section has been added at the end of this lecture. Adding a comment or question does not require registration with your matricola number, feel free to comment whenever you like.       Insufficient dietary apport of vitamins and other essential nutrients (essential aminoacids, essential fatty acids, etc.) may be at the origin of disease. The elderly are at special risk, as are some fragile patients (e.g. onchological patients under chemotherapeutic treatment). Deficiency conditions may be in some cases observed because of reduced absorption, the typical example is avitaminosis B12 in patients suffering of atrophic gastritis or having undergone gastric surgery. Hypervitaminoses are observed for lipid soluble vitamins which are physiologically stored in our organism (usually in the liver), and are usually the result of excessive dietary supplementation: thus they are iatrogenic diseases. Vitamins and essential nutrients are many and the diseases due to their insufficient apport are difficut to diagnose; however, provided that the physician asks for the appropriate analysis, the laboratory can determine the concentration of all or almost all these substances and identify the selective deficit. vitamin and its biological function recommended daily allowance deficiency disease normal serum concentration A (retinol) vision, epitelium differentiation 0.5 - 1 mg reduced vision at dusk, skin and mucosal lesions 20 - 50 μg/dL D (calciferols) calcium absorption 10 μg ricketts, osteomalacia 25 - 40 ng/mL of 25-hydroxy D3 E antioxidant 3 - 10 mg oxidative damage of tissues; anemia >0.8 mg/dL K cofactor of carboxylation of Glu in coagulation enzymes produced by intestinal microbiota (deficiency may be simulated by warfarin-like anticoagulants) hemorragic syndrome - (measure PT, PTT) Lipoic acid cofactor of acyl transferases - (deficiency uncommon) B1 (thiamine) cofactor of carboxylases 0.3-1.5 mg neurological symptoms (Beri-Beri, Wernicke-Korsakoff syndrome) - (urinary excretion >50 μg/day) B2 (riboflavin) precursor of FAD 0.5-2 mg skin and mucosal lesions, anemia - (urinary excretion >30 μg/day) B3 (niacin, nicotinic acid) precursor of NAD and NADP 6-20 mg pellagra urinary N-methylnicotinamide and pyridone < 1.5 mg in 24 hours B5, W (pantothenic acid) precursor of CoA-SH B6 (pyridoxine) cofactor of transaminases 0.5-2 mg anemia, neuropathy - B8, H (biotin) cofactor of carboxylases - (deficit uncommon) B9 (folic acid) cofactor of methyl-transferases and some redox reactions 30-400 μg megaloblastic megalocytic anemia 6-15 ng/mL B12 (cobalamine) cofactor of methyl-transferases 0.5-3 μg megaloblastic megalocytic anemia (pernicious anemia, Brill's disease) >200 pg/mL C (ascorbic acid) redox cofactor necessary for the biosynthesis of OH-Pro and OH-Lys in collagen 50 mg scurvy - (>0.1 mg/dL in the leukocyte / platelet fraction)       Diagnosis of hypovitaminoses       As a general rule hypovitaminoses cause diseases with quite uncharacteristic symptoms, thus their diagnosis is difficult. Exceptions to this rule are the macrocytic megaloblastic anemias of folate and B12 deficiency, ricketts, scurvy, and the hemorragic syndrome due to antivitamins K. The diagnosis of hypovitaminoses relies on indirect and direct clinical and laboratory findings. Indirect findings are the effect of the lack of vitamin(s): e.g. macrocytic anemia in folate or vitamin B12 deficiency, or increased prothrombin time in avitaminosis K; direct findings relate to the actual measurement of the vitamin concentration in body fluids (see Table). Symptoms and indirect findings are observed first, and direct measurements are carried out during the subsequent investigation. Since dietary deficiencies may affect more than a single vitamin, it is possible that multiple deficiencies are present at the same time in the same patient. Important causes of multiple vitamin deficiencies are: prolonged antibiotic therapy (e.g. for the treatment of tuberculosis); pregnancy (folate is particularly needed); old age; chronic ethylism; chronic liver failure or malabsorption syndromes; migration, wars or natural catastrophes. Selective avitaminoses are observed in cases of very peculiar diets (e.g. vegan diet and avitaminosis B12), or assumption of antivitamins (e.g. warfarin anticoagulant therapy), or selective defects of absorption (e.g. pernicious anemia in chronic athropic gastritis). Since administration of vitamins has few, if any, collateral effects, dietary supplementation of vitamin tablets can be prescribed when the diagnosis is suspected, even in the absence of a clear direct proof of vitamin deficiency.       Possible common symptoms of avitaminosis: in the majority of vitamin deficiencies the target organs are: (i) the skin and mucosae, which may present degenerative lesions and ulcerations; (ii) the central and peripheral nervous systems; (iii) the blood (anemia) and vessels (hemorragic syndromes); (iv) the gastro-intestinal tract. With the exception of the nervous system, these organs have rapid cell turnover: - skin lesions (deficiency of vitamins B2, B3, A) - anemias (deficiency of vitamins E, B2, B9, B12) - neurological symptoms (deficiency of vitamins B1, B2, B3, B6, B12)       Conditions that favor hypovitaminoses are: - major catastrophes (famines, civil ware, refugees, etc.) - increased requirement (e.g. folate during pregnancy) - prolonged antibiotic therapy, which destroys the vitamin-producing intestinal bacterial flora - malnutrition and malabsorption (e.g. etilism and Wernicke syndrome; athropic gastritis and pernicious anemia) - reduced endogenous production for those vitamins that are partly produced by our body (e.g. nicotinamide and defects of Trp metabolism of Hartnup disease; ricketts due to insfficient exposure to sunlight; antibiotic therapy and vitamin K) - assumption of antivitamins (warfarin anticoagulants and vitamin K; antibacterial and antiparasitic drugs acting as folate antagonists like trimetoprim)       Laboratory diagnosis of avitaminoses. Measuring the concentration of vitamins in the serum, blood or urine is feasible; often the effects of vitamin deficiency can also be quantitatively assessed (e.g. coagulation defects in the case of assumption of antivitamin K; anemias; etc.), but these are rarely characteristic enough to warrant a diagnosis. The risk should be considered that a patient may suffer of deficiency of multiple vitamins. If the patient is at risk for malnutrition and presents cutaneous, neurological or blood-related symptoms, administration of a multivitamin preparation is advisable, because the contraindications to this therapy are virtually non-existent. A very special case to consider, however, is pernicious anemia, because in this case the vitamin must be administered parenterally, as the intestinal absorption if usually impaired due to lack of the intrinsic factor.       Hypovitaminoses are rarely observed in the absence of specific risk factors, which include: (i) social emergency conditions (civil wars, refugees, etc.); (ii) old age; (iii) some types of chronic therapies (e.g. chemotherapy; antibiotic therapy); (iv) chronic intestinal diseases causing malabsorption; (v) very special dietary habits (e.g. veganism, ethylism). By contrast, the "classical hypovitaminoses", which were historically observed in whole populations or groups (e.g. scurvy, pellagra, ricketts, etc.), due to poor diets are nowadays uncommon.       Pellagra (vitamin B3 deficiency) was formerly common in Italy, especially in the Veneto region, due to unbalanced (poor) nutrition, based on maize porridge (polenta). Maize does contain vitamin B3 (niacin, nicotinamide), but special tretaments are required to make it available for non-ruminant mammals (nixtamalization: cooking followed by treatment with alkali). The symptoms of the disease are cutaneous, intestinal and neurological (the 3 Ds: dermatitis, diarrhoea, and dementia). Pellagra is lethal if untreated. Vitamin B3 is abundant in many fresh vegetables and in milk, and can be produced by the metabolism of tryptophan. The diagnosis is difficult because of the aspecific nature of the symptoms, especially cutaneous; notice that sun exposure exacerbates the dermatitis, even though non-exposed areas are affected as well. Serum levels of Trp, nicotinamide, NADH and NADPH are reduced; however, of greater diagnostic relevance is the reduced urinary escretion of metabolytes N- methylnicotinamide and pyridone: less than 1.5 mg in 24 hours suggests niacin deficiency. It is also important to exclude other possible causes of dermatitis (e.g. autoimmune).       Pernicious anemia (Brill's disease) is a potentially lethal disease caused by the deficiency of vitamin B12. This vitamin has a very low recommended daily intake, and is present mostly in food of animal origin. Every "common" diet contains a sufficient amount of this vitamin. The chemical structure of the vitamin is complex and intestinal absorption is mediated by binding to a specific transport protein produced by the gastric mucosa and called the "intrinsic factor". The complex of vitamin B12 and the intrinsic factor is absorbed by the gut via receptor-mediated endocytosis; a reservoir of vitamin B12 is stored in the liver.       Pernicious anemia is only observed in some very special cases, including (i) patients suffering of athropic gastritis, gastric cancer, or having undergone to surgical resection of the stomach (e.g. because of cancer); these patients do not produce the intrinsic factor. (ii) Strictly vegan patients who refuse every food of animal origin, and do not make use of vitamin B12 supplementation. (iii) Newborns of mothers in the two above conditions (these babies may present congenital permanent neurological lesions).       Oral supplementation of vitamin B12 is effective in case (ii), but not in case (i), where intramuscular administration is necessary.       Diagnosis relies on the association of neurological symptoms and macrocytic anemia; a risk condition is always present. Confirmation is by determination of vitamin B12 concentration in the serum by radioimmunoassay, and by the Schilling test (measurement of the urinary excretion of radiolabeled vitamin B12). The intrinsic factor can be measured in gastric secretions. Achloridria is common but not diagnostic. Differential diagnosis is relatively easy because the possible causes of macrocytic anemia are limited: besides vitamin B12 deficiency they include folate deficiency, copper deficiency and, possibly, scurvy.       Folate deficiency may be observed in pregnancy, due to the large demand of this vitamin by the foetus. Dietary supplementation with folate tablets during pregnancy is recommended.       Hypervitaminoses       Diseases due to excess vitamin supply are iatrogenic and due to the patient taking excess vitamin supplementation. No normal diet can cause hypervitaminoses. Moreover, the majority of water-soluble vitamins are not stored in our body and thus any excess is disposed of by the kidney; in practice only liposolube vitamins (A, D, E, and K) are physiologically stored in the liver and can cause hypervitaminoses. Clinical examples 1) 85 year old patient complaining of malaise and muscular weakness. Physical examination reveals: petechiae, loss of some teeth. Blood test reveals: hemoglobin 9 g/dL * erythrocyte count 3 x 106 /mmc * mean corpuscular volume 75 fL (normal value 80-100 fL)* white cell count 8 x 103 /mmc platelets 220 x 103 /mmc Analysis of the case: the main symptoms in this case are microcytic anemia (reduced MCV), loss of teeth, and petechiae. Microcytic anemia may be due to several causes, e.g. vitamin C deficiency, thalassemia minor, or iron deficiency. Loss of teeth and petechiae in a patient having normal platelet count suggest scurvy. Inquire for nutritional habits; prescribe vitamin C tablets; measure serum iron and transferrin; sequence the genes of hemoglobin subunits. 2) 45 year old patient complaining of chronic arthritis, treated with antiinflammatory drugs and methotrexate. Physical examination reveals obesity, chronic arthritis. Blood test reveals: hemoglobin 12 g/dL * erythrocyte count 3.8 x 106 /mmc * mean corpuscular volume 105 fL (normal value 80-100 fL)* white cell count 8.3 x 103 /mmc platelets 180 x 103 /mmc Analysis of the case: in addition to arthritis the patient has macrocytic anemia. Macrocytic anemia may be due to deficiency of vitamin B12 or folic acid, or to hypothyroidism. Folate deficiency may be due to methotrexate, which is an antifolic agent. There is no obvious indication that absorption of vitamin B12 may be reduced. Measure folic acid in the serum. Carry out a complete thyroid investigation (measure T3, T4, TSH, and basal metabolism). 3) 11-years old girl with mild gum inflammation and bleeding, oedema and pain in the legs. In the anamnesis poorly balanced diet (from Medscape). Laboratory findings reveal anemia (Hb 6.5 g/dL), normal PTT and PT, normal sideremia. Analysis of the case: anemia may have several causes, but in the present case it is likely to be post-hemorragic. The coagulation tests are normal. Scurvy was suspected and the serum concentration of ascorbic acid was measured: the low level of the vitamin (< 0.1 mg/dL; reference range, 0.6-2 mg/dL) confirmed the diagnosis. Questions and exercises: 1) Macrocytic and macroblastic anemia is observed in: deficiency of folate or vitamin B6 deficiency of folate or vitamin B12 deficiency of vitamin B6 or B12 2) The normal blood concentration of vitamin A is: 150-750 pg/mL 25 - 40 ng/dL 20 - 50 μg/dL 3) Some vitamins can be produced in our body: B6 from Trp; D from ergosterol; K by the intestinal microfauna B12 from the heme; A from unsaturated fatty acids C from glucuronic acid; panthetein from Cys 4) Wernicke neurological syndrome is due to a deficiency of: vitamin B1 vitamin B2 vitamin B6 your score: 10 Attendance not registered because of insufficient score - Retry! You can type in a comment or question below (max. length=160 chars.); please specifiy that the subject of your comment or question is aminoacid metabolism: All comments posted on the different subjects have been edited and moved to this web page (for optimal reading try to have at least 80 characters per line)! Thank you Professor (lecture on bilirubin and jaundice). The fourth recorded part, the one on hyper and hypoglycemias is not working. Bellelli: I checked and in my computer it seems to work. Can you better specify the problem you observe? This Presentation (electrolytes and blood pH) feels longer than previous lectures Bellelli: it is indeed. Some subjects require more information than others. I was thinking of splitting it in two nest year. Bellelli in response to a question raised by email: when we compare the blood pH with the standard pH we do not mean to compare the "normal" blood pH (7.4) with the standard pH. Rather we compare the actual blood pH of the patient, with the pH of the same blood sample equilibrated under standard conditions. Thus, if we say that standard pH is lower than pH we mean that equilibriation with 40 mmHg CO2 has caused absorption of CO2 and has lowered the pH with respect to its value before equilibration. (Lipoproteins) Is the production of leptin an indirect cause of type 2 diabetes since it works as a stimulus to have more adipose tissue that produces hormones? Bellelli: in a sense yes, sustained increase of leptin causes the hypothalamus to adapt and to stop responding. Obesity ensues and this in turn may cause an increase in the production of resistin and other insulin-suppressing protein hormones produced by the adipose tissue. However, this is quite an indirect link, and most probably other factors contribute as well. (Urea cycle) what is the meaning of "dissimilatory pathway"? Bellelli: a dissimilatory pathway is a catabolic pathway whose function is not to produce energy, but to produce some terminal metabolyte that must be excreted. Dissimilatory pathways are necessary for those metabolytes that cannot be excreted as such by the kidney or the liver because they are toxic or poorly soluble. Examples of metabolytes that require transformation before being eliminated are heme-bilirubin, ammonia, sulfur and nitrogen oxides, etc. Talking about IDDM linked neuropathy can be the C peptide absence considered a cause of it?? Bellelli: The C peptide released during the maturation of insulin, besides being an indicator of the severity of diabetes, plays some incompletely understood physiological roles. For example it has been hypothesized that it may play a role in the reparation of the atherosclerotic damage of the small arteries. Thus said, I am not aware that it plays a direct role in preventing diabetic polyneuropathy. Diabetic neuropathy has at least two causes: the microvascular damage of the arteries of the nerve (the vasa nervorum), and a direct effect of hyperglycemia and decreased and irregular insulin supply on the nerve metabolism. Diabetic neuropathy is observed in both IDDM and NIDDM, and requires several years to develop. Since the levels of the C peptide differ in IDDM and NIDDM, this would suggest that the role of the C peptide in diabetic neuropathy is not a major one. If you do have better information please share it on this site! In acute intermitted porphyria and congenital erythropoietic porphyria why do the end product of the affected enzymes accumulate instead of their substrate?? Bellelli: First of all, congratulations! This is an excellent question. Remember that a condition is which the heme is not produced is lethal in the foetus; thus the affected enzyme(s) must maintain some functionality for the patient to be born and to come to medical attention. All known genetic defects of heme biosynthesis derange but do not block this metabolic pathway. Congenital Erythropoietc Porphyria (CEP) is a genetic defect of uroporphyrinogen III cosynthase. This protein associates to uroporphyrinogen synthase (which is present and functional in CEP) and guarantees that the appropriate uroporphyrinogen isomer is produced (i.e. uroporphyrinogen III). In the absence of a functional uroporphyrinogen III cosynthase other possible isomers of uroporphyrinogen are produced together with uroporpyrinogen III, mostly uroporphyrinogen I. The isomers of uroporphyrinogen that are produced differ because of the positions of propionate and acetate side chains, and this in turn is due to the pseudo symmetric structure of porphobilinogen. Only isomer III can be further used to produce protoporphyrin IX. Thus in the case of CEP we observe accumulation of abnormal uroporphyrinogen derivatives, which, as you correctly observed are the products of the enzymatic synthesis operated by uroporphyrinogen synthase. The case of Acute Intermittent Porphyria (AIP) is similar, although there may be variants of this disease. What happens is that either the affected enzyme is a variant that does not properly associate with uroporphyrinogen III cosynthase or presents active site mutations that impair the proper alignement of the phoprphobilinogen substrates. In either case abnormal isomers of uroporphyrinogen are produced, as in CEP. Also remark that in both AIP and CEP we observe accumulation of the porphobilinogen precursor: this is because the overall efficiency of the biosynthesis of uroporphyrinogens is reduced. Thus: (i) less uroporphyrinogen is produced, and (ii) only a fraction of the uroporphyrinogen that is produced is the correct isomer (uroporphyrinogen III). is it possible to take gulonolactone oxidase to synthesize vitamin C instead of vitamin C supplement? Bellelli: no, this approach does not work. The main reason is that the biosynthesis of vitamin C, as almost all other metabolic processes, occurs intracellularly. If you administer the enzyme it will at most reach the extracellular fluid but will not be transported inside the cells to any significant extent. Besides, there are other problems in this type of therapy (e.g. the enzyme if administered orally, may be degraded by digestive proteases; if administered parenterally, may cause the immune system to react against a non-self protein). In theory one could think of a genetic modification of the inactive human gene of gulonolactone oxidase, but the risk and cost of this intervention would not be justified. In addition to these considerations, except for cases of shipwreckage or other catastrophes, a proper diet or administration of tablets of vitamin C is effective, risk-free and unexpensive, thus no alternative therapy is reasonable. However, I express my congratulations for your search on the biosynthesis pathway of ascorbic acid. Resorption and not reabsorption would lead to hypercalcemia ie bone matrix being broken down. Bellelli: I am not sure to interpret your question correctly. Resorption indicates destruction of the bone matrix and release of calcium and phosphate in the blood, thus it causes an increase of calcemia. Reabsorption usually means active transport of calcium from the renal tubuli to the blood, thus it prevents calcium loss. It prevents hypocalcemia, and thus complement bone resorption. To avoid confusion it is better use the terms "bone resorption" and " renal reabsorption of calcium". If you have a defect in renal reabsorption, parthyroid hormone will be released to maintain a normal calcium level by means of bone resorption; the drawback is osteoporosis. In Reed and Frost model: I haven't understood what is the relationship between K and R reproductive index. Thank you Professor! Bellelli: in the Reed and Frost model K is the theoretical upper limit of R0. R the reproductive index is the ratio (new cases)/(old cases) measured after one serial generation time. R0 is the value of R one measures at the beginning of the epidemics, when in principle all the population is susceptible. What is the link between nucleotide metabolism and immunodeficiencies and mental retardation? Bellelli: the links may be quite complex, but the principal ones are as follows: 1) the immune response requires a replication burst of granulocytes and lymphocytes, which in turn requires a sudden increase of nucleotide production, necessary for DNA replication. Defects of nucleotide metabolism impair this phase of the immune defense. Notice that the mechanism is similar to the one responsible of anemia which requires a sustained biosynthesis of nucleotides at a constant rate, rather than in a burst. 2) Mental retardation is mainly due to the accumulation of nulceotide precursors in the brain of the newborn, due to the incompletely competent blood-brain barrier. How can ornithine transaminase defects cause hyperammonemia? Is it due to the accumulation of ornithine that blocks the urea cycle or for other reasons? Bellelli: ornithine transaminase is required for the reversible interconversion of ornithine and proline, and thus participates to both the biosynthesis and degradation of ornithine. The enzyme is synthesized in the cytoplasm and imported in the mitochondrion. Depending on the metabolic conditions the deficiency of this enzyme may cause both excess (when degradation would be necessary) or defect (when biosynthesis would be necessary) of ornithine; in the latter case, the urea cycle slows down. Thus there is the paradoxical condition in which alternation may occur between episodes of hyperammonemia and of hyperornithinemia. When we use the Berthelot's reaction to measure BUN do we also have to measure the concentration of free ammonia before adding urease? Bellelli: yes, in principle you should. Berthelot's reaction detects ammonia, thus one should take two identical volumes of serum, use one to measure free ammonia, the other to add urease and measure free ammonia plus ammonia released by urea. BUN is obtained by difference. However, free ammonia in our blood is so much lower than urea that you may omit the first sample, if you only want to measure BUN. Why do we have abnormal electrolytes in hematological neoplasia e.g. leukemia? Bellelli: I do not have a good explanation for this effect, which may have multiple causes. However, you should consider two factors: (i) acute leukemias cause a massive proliferation of leukocytes (or lymphocytes depending on the cell type affected) with a very shortened lifetime; thus you observe an excess death rate of the neoplastic cells. The dying cells release in the bloodstream their content, which has an electrolyte composition different from that of plasma: the cell cytoplasm is rich in K and poor in Na, thus causing hyperkalemia. (ii) the kidney may be affected by the accumulation of neoplastic white cells or their lytic products. Gaussian curve: If it is bimodal is it more likely to be a "certain diagnosis" than if it is unimodal or does it only show the distinguishment from health? Bellelli an obviously bimodal Gaussian curve indicates that the disease is clearly separated from health: usually it is a matter of how precise and clear-cut is the definition of the disease. For example tuberculosis is the disease caused by M. tuberculosis, thus if the culture of the sputum is positive for this bacterium you have a "certain" diagnosis (caution: the patient may suffer of two diseases, e.g. tuberculosis and COPD diagnosis of the first does not exclude the second). However, in order to have a "certain" diagnosis it is not enough that distribution of the parameter is bimodal, it is also required that the patient's parameter is out of the range of the healthy condition: this is because a distribution can be bimodal even though it is composed by two Gaussians that present a large overlap, and the patient's parameter may fall in the overlapping region. Thus, in order to obtain a "certain" diagnosis you need to consider not only the distribution of the parameter(s) but also the patient's values and the extent of the overlapping region. Prof can you please elaborate a bit more on the interhuman variability and its difference with the interpopulation variability please? Bellelli: every individual is a unique combination of different alleles of the same genes; this is the source of interindividual variability. Every population is a group of individuals who intermarry and share the same gene pool (better: allele pool). Every allele in a population has its own frequency. Two population may differ because of the diffferent frequencies of the same alleles; in some cases one population may completely lack some alleles. The number and frequencies of alleles of each gene determine the variance. If you take two populations and calculate the cumulative interindividual variance of the population the number you obtain is the sum of two contributions: the interindividual variance within each population, plus the interpopulation variance between the means of the allele frequencies. For example, there are human population in which the frequency of blood group B is close to 0% and other populati ons in which it is 30% or more. Prof can you please explain again the graph you have showed us in class about thromboplastin? (Y axis=abs X axis= time) Bellelli: the graph that I crudely sketched in class represented the signal of the instrument (an absorbance spectrophotometer) used to record the turbidity of the sample (turbidimetry). The plasma is more or less transparent, before coagulation starts. When calcium and the tissue factor (or collagen) are added. thrombin is activated and begins digesting fibrinogen to fibrin; then fibrin aggregates. The macroscopic fibrin aggregates cause the sample to become turbid, which means it scatters the incident light. The instrument reads this as a decrease of transmitted light (i.re an increase of the apparent absorbance) and the time profile of the signal presents an initial lag phase, which is called the protrombin or thromboplastin time depending on the component which was added to start coagulation (tissue factor or collagen). Prof can you please explain the concept you have described in class about the simultaneous hypercoagulation and hemorrhagic syndrome? How can this occur? Bellelli: The condition you describe is observed only in the Disseminated Intravascular Coagulation syndrome. Suppose that the patient experiences an episode of acute pancreatitis: tripsin and chymotripsin are reabsorbed in the blood and proteolytically activate coagulation causing an extensive consumption of fibrinogen and other coagulation factors. Tripsin and chymotripsin also damage the vessel walls and may cause internal hemorrages, but at that point the consumption of fibrinogen may have been so massive that not enough is left to form the clot where the vessel has been damaged, causing an internal hemorrage. Pancreatitis is a very severe, potentially lethal condition, and DIC is only one of the reasons of its severity. You said that certain drugs (ethanol, cocaine, cannabis, opiates...) cause a necessity of higher and higher dosage, for two reasons: the enzyme in the liver is inducible and the receptors in the brain are expressed less and less. So, first, I am not sure I got it right, and second I did not understand how expressing less receptors leads to a necessity of higher dosage. Bellelli: You got it correctly, but the detailed mechanism of resistance may vary among different substances, and not all drugs cause adaptation. The reason why reducing the number of receptors may require an increased dosage of the drug is as follows: suppose that a certain cell has 10,000 receptors for a drug. When bound to its agonist/effector, each receptor produces an intracellular second messenger. Suppose that in order for the cell to respond 1,000 receptors must be activated. The concentration of the effector required is thus the concentration that produces 10% saturation. You can easily calculate that this concentration is approximately 1/10 of the equilibrium dissociation constant of the receptor-effector complex (its Kd), the law being Fraction bound = [X] / ([X]+Kd) where [X] is the concentration of the free drug. After repeated administration, the subject becomes adapted to the drug, and his/her cells express less receptors, say 5,000. The cell response will in any case require that 1,000 receptors are bound to the effector and activated, but this now represents 20% of the total receptors, instead of 10%. The drug concentration required is now 1/4 of the Kd. Continuing administration of the drug further reduces the cell receptors, but the absolute number of activated receptors required to start the response is constant; thus the fewer receptors on the cell membrane, the higher the fraction of activated receptors required. Why does hyperosmolarity happen in type 2 diabetes and not in type 1? Bellelli: Hyperosmolarity can occur also in type 1 diabetes, albeit infrequently. The approximate formula for plasma osmolarity is reported in the lecture on electrolytes: osmolarity = 2 x (Na+ + K+) + BUN/2.8 + glucose/18 this is expressed in the usual clinical laboratory units (mEq/L for electrolytes, g/dL for non- electrolytes). The normal values are: osmolarity = 2 x (135 + 5) + 15/2.8 + 100/18 = 280 + 5.4 + 5.6 = 291 mOsmol/L Let's imagine a diabetic patient having normal values for electrolytes and BUN, and glycemia=400 mg/dL: osmolarity = 280 + 5.4 + 22.4 = 307.8 mOsmol/L The hyperosmolarity in diabetes is mainly due to hyperglycemia, even though other factors may contribute (e.g. diabetic nefropathy); however the contribution of glucose to osmolarity is relatively small. As a consequence in order to observe hyperosmolarity the hyperglycemia should be extremely high; this is more often observed in type 2 than in type 1 diabetes, for several reasons, the most relevant of which is that in type 1 diabetes all cells are starved of glucose, and the global reserve of glycogen in the body is impoverished: there is too much glucose in the blood and too few everywhere else, thus reducing, but not abolishing, the risk of extreme hyperglycemia. Usually in type 2 diabetes the glycogen reserve in the organism is not impoverished, thus the risk of extreme hyperglycemia is higher. Hemostasis and Thrombosis lecture: I don't understand why is sodium citrate added to the serum solution to measure the prothrombin time. Bellelli: in order to measure PT or PTT you want to be able to start the coagulation process at an arbitrary time zero, and measure the increase in turbidity of the serum sample. To do so you need (i) to prevent spontaneous coagulation with an anticoagulant; and (ii) to be able to overcome the anticoagulant at your will. Citrate (or oxaloacetate; or EDTA) has the required characteristics: it chelates calcium, and in this way it prevents coagulation; but you can revert its effect at your will by adding CaCl2 in excess to the amount of citrate. You cannot obtain the same effect with other anticoagulants (e.g. heparin) whose action cannot be easily overcome. Dear professor I cannot do the self evaluation test because it says the the time has expired It is not possible because I havent even started them Bellelli: this is due to the fact that the program registers your name and matricola number from previous attempts. I shall fix this bug. Meanwhile try to use a fake matricola number. How is nephrotic syndrome associated hypoalbuminemia as you described in methods of analysis of protein because seems counterintuitive Bellelli: nephrotic syndrome is an autoimmune disease in which the glomerulus is damaged and the filtration barrier is disrupted; diuresis is normal but there is loss of proteins (mostly albumin) in the urine. I m sorry i confused polyurea with hypoalbuminemia but my question still stands during glomerulonephritis you mentioned something of polyurea as compensation i could not follow how this compensation mechanism works and collapse after some time in glomerulonephritis Bellelli: the condition you describe is NOT characteristic of acute glomerulonephritis. In glomerulonephritis there is damage of the glomerulus and severely impaired GFR. Thus the diuresis is severely reduced, and due to impaired filtration proteins appear in the urine. The condition you describe corresponds to the initial stage of chronic kidney failure, usually due to atherosclerosis, diabetes, hypertension or other type of damage of the kidney tissue. In this case GFR is impaired, albeit to a lesser extent than in glomerulonephritis, and the excretion of urea is reduced. This leads to increased BUN. However the increased concentration of urea reduces the ability of the tubuli to reabsorb water, because of osmotic reasons, yielding compensatory polyuria. The patient has reduced GFR but normal or increased diuresis (urine volume in 24 hours). To some extent this effect is beneficial, as it favors the elimination of urea; however it cannot completely solve the problem and in any case the progression of the disease leads to kidney insufficiency. In its essence the point is that a moderately reduced GFR can be partially compensated by reduced tubular reabsorption; a severely reduced GFR cannot. Lecture on Hemogas analysis interpretation of complex cases standard pH Why if PCO2 is less than 40 mmHg it is absorbed during equilibration? Thank you in advance Bellelli: if PCO2 of the patient's blood sample is less than 40 mmHg, when the machine equilibrates with 40 mmHg CO2 the gas is absorbed: i.e. the new PCO2 becomes 40 mmHg and the total CO2 of the sample increases; as CO2 is the acid of the buffer, the standard pH (in this case) decreases, whereas standard bicarbonate will slightly increase. Professor I don't understand how we arrive to this formula: Accuracy = sensitivity x prevalence specificity x (1-prevalence) Bellelli: ok, this relationship is poorly explained in your text, I shall improve its explanation. We use the following definitions: prevalence = sick individuals / total population; accuracy = (true+ + true-) / total population; sensitivity = true+ / sick individuals = true+ / total population x prevalence; specificity = true- / healthy individuals = true- / total population x (1-prevalence); thus we can rewrite: sensitivity x prevalence = true+ / total population; specificity x (1-prevalence) = true- / total population; accuracy = sensitivity x prevalence + specificity x (1-prevalence) Why do we use RNA primer in PCR and not DNA primers? I thought the beginning of the sequence of the gene segment that is going to be formed is made of DNA Bellelli: DNA polimerases require the RNA primers that are synthesized by the enzyme primase. DNA primers do not exist in vivo and would not be recognized by DNA polimerases.       Home of this course Slides of this lecture