An analytical model of temperature regulation in human head

An analytical model of human brain temperature regulation is proposed. The model describes the distribution of brain temperature as a function of internal and external parameters, such as temperature of the incoming arterial blood, blood flow, oxygen consumption rate, ambient temperature, and heat exchange with the environment. It is shown that substantial changes in human brain temperature can be accomplished only through changes in the temperature of the incoming arterial blood or substantial suppression of blood flow. Other parameters can lead only to temperature changes near the brain surface.     

Experimental modifications of the circadian rythm of Plasmodium vinckei petteri following cryopreservation; probable resistance of the merozo?te to thawing

Plasmodium vinckei petteri, in white mice, is a particularly useful strain for studies on the circadian rythm of Plasmodium. An experimental model was set up: it showed that the rythm of asexual schizogony in the blood varies with the time and the mode of inoculation (cryopreserved blood or syringe passage). When frozen blood is injected, the time of schizogony depends on the time of injection; on the contrary, when the passage is by syringe from mouse to mouse, the rythm of schizogony is the same in the donor and the receptor mouse, regardless of the time of injection. The only possible explanation is that all intracellular parasites are destroyed by the thawing of blood and the free merozo?te is the only resistant stage.     

Preliminary observation of blood cells and hematopoietic organs in Lutjanus herenbergi and Lutjanus flaviflammus

The morphology of differentiated and differentiating cells of the red and white series in Lutjanus herenbergi and in Lutjanus flaviflammus is described. Early stages of red and white blood cells may be found only in smears of hemopoietic organs. Polychromatic erythroblasts, myelocytes and lymphoblasts may also occasionally be found in blood smears. Mature blood cells may be found both in blood smears and in hemopoietic organs. Differential white cell counts seem to demonstrate that the granulocytic series elements are the most common leukocytes in blood smears. Almost all granulocytes may be classified in the first three Arneth classes. An analysis of hemopoietic organs in these species was also performed. It was found that the only organs carrying on a hemopoietic function are the kidney and the spleen. The kidney is essentially a site of granulocytic differentiation while the spleen is a lymphopoietic organ. An erythropoietic activity may generally be observed in the kidney although weak erythropoietic activity may at times be found in the spleen.     

The impact of uniform and mixed species blood meals on the fitness of the mosquito vector Anopheles gambiae s.s: does a specialist pay for diversifying its host species diet?

We investigated the fitness consequences of specialization in an organism whose host choice has an immense impact on human health: the African malaria vector Anopheles gambiae s.s. We tested whether this mosquito’s specialism on humans can be attributed to the relative fitness benefits of specialist vs. generalist feeding strategies by contrasting their fecundity and survival on human‐only and mixed host diets consisting of blood meals from humans and animals. When given only one blood meal, An. gambiae s.s. survived significantly longer on human and bovine blood, than on canine or avian blood. However, when blood fed repeatedly, there was no evidence that the fitness of An. gambiae s.s. fed a human‐only diet was greater than those fed generalist diets. This suggests that the adoption of generalist host feeding strategies in An. gambiae s.s. is not constrained by intraspecific variation in the resource quality of blood from other available host species.     

Mechanism of heat transfer in different regions of human body

The processes of heat transfer in a human body were studied with the use of a mathematical model. It has been shown that only conductive or only convective heat transfer may occur in different body areas. The rate of blood-mediated heat transfer in the presence of blood circulation is many times higher than heat transfer due to temperature gradient; therefore, the convective process prevails over the conductive process. The body core contains a variety of blood vessels, and the bulk of blood concentrates there in the norm. Hence, heat transfer in it is mainly convective. In surface tissues, where the rate of blood circulation is lower and the vasculature has certain specific features, heat transfer is mainly conductive. Hence, the core and surface tissues are absolutely different body zones in terms of heat transfer.     

Comparison of three kinetic models of HIV-1 infection: implications for optimization of treatment

Clinical markers in the peripheral blood guide the treatment of human immunodeficiency virus type 1 (HIV-1). Likewise, many of the theoretical models developed to simulate infection only incorporate variables in the blood. To test the suitability of blood-only models, three distinct models of HIV infection kinetics are compared: "full model" including latently and actively infected cells and virus in the peripheral blood and lymphoid tissue (LT); "reduced model", including peripheral blood and LT without latent cells; and "blood model" including only actively infected cells and virus in the peripheral blood. Using the same parameter values for all three, qualitative differences are demonstrated between the blood model and its more inclusive counterparts. Additionally, optimization studies show that the reduced and blood models generate progressively lower optimal treatment levels relative to the full model when constant-level treatment is considered. These findings indicate that including the lymphoid tissue and latently infected cells into kinetic models may lead to differing conclusions with regard to optimal treatment and could be useful in guiding therapy even when plasma viral levels are below detectable limits.     

Trace element changes in sclerotic heart valves from patients are expressed in their blood

The pathogenesis of some heart diseases has been associated with changes in the balance of certain trace elements. However, whether blood trace element changes exist that are related to changes in the cardiovascular system are, in most cases, unknown. In this study, blood trace element levels were analysed in 46 patients with non-rheumatic aortic valve sclerosis that were previously shown to have a disturbed trace element balance in their valve tissue, including 11/15 elements. Results showed significant changes of blood levels of 8/15 trace elements in these patients when compared with blood levels in 46 healthy controls. Of these elements, Cd and Mg were the only elements that increased in both blood and valves. Cu and Se were increased in blood but decreased in valves, whereas Co and Zn were decreased in blood but increased in valves. Several elements (As, Ca, Fe, Pb, and V) were unchanged in blood although changed in valves. Although Mn and Hg showed changes in blood, this was not evident in the valves. Al and Ag were the only elements that did not change in both blood and valves. Significant covariation in blood and valve levels was only observed for Al and Pb. The recorded pattern of trace element changes indicates a complex competition/exchange between body compartments in this disease, where the increased blood Cu/Zn ratio suggests an ongoing infectious/inflammatory process.     

Calcitonin antibodies in experimental diabetes mellitus

Antibodies to calcitonin appear in blood of rats with experimental alloxan diabetes. This phenomenon is observed only under high blood sugar. At the stage of latent diabetes, i.e. during alloxan administration to the body and low blood sugar no antibodies to calcitonin are detected. It is possible that appearance of autoantibodies to calcitonin is one of pathogenetic factors of hyperglycemia development in rats with alloxan diabetes.     

The use of infants in drug research when there is no direct benefit to them: a survey of Canadian health care professionals serving on ethics committees.

Canadian health care professionals and lawyers serving on ethics committees were questioned about their views on pharmacokinetic research in newborn infants who are not likely to benefit directly from the results. Of the 50 respondents 13 felt that blood samples should be taken only for therapeutic reasons; 10 of the 13 argued that additional blood samples should not be taken, because there is no direct benefit to the infant; and 8 felt that proxy consent cannot be given for invasive nontherapeutic research. Four of the five participating lawyers would not permit additional blood samples to be taken. Of the 37 respondents who would permit additional blood samples to be taken, 27 felt that the number of samples taken should depend on the researcher''s justification for that number of samples; only 7 of the respondents had a clear idea of what the "upper limit" of the number of blood samples should be.     

The hydraulic interaction between prosoma and opisthosoma in Amaurobius ferox (Chelicerata,Araneae)

Summary Experiments are described which demonstrate that blood moves from the prosoma into the opisthosoma in Amaurobius ferox when the spider is held on a plasticine block and is stimulated with a small brush. This movement of blood is also seen during bouts of struggling when the spider is trying to free itself. The return flow of blood from the opisthosoma is to a large extent due to the pumping action of the heart.It is proposed that the locomotory exhaustion shown by artificially stimulated spiders is due to this loss of blood from the prosoma which leads not only to hydraulic insufficiency, but also to a lack of oxygen through interruption of the normal blood flow.     

一氧化氮对脑血流的调节

一氧化氮是近年来发现的一种重要的血管活性因子,它通过激活平滑肌细胞内水溶性鸟苷酸环化酶,而产生血管舒张作用,在正常生理条件下,ＮＯ不仅对外因管有作用,对脑血管也有作用,但关于它在低氧和高二氧化碳条件下脑血管是否具有调节作用还存在着争议。     

Blood groups of anthropoid apes and their relationship to human blood groups

Affinity between blood groups of man and those of anthropoid apes is reflected not only in similarities or identities of reactions of the red cells with many specific typing reagents, but also in overall structures of some of the main blood group systems defined in man and in apes.Besides specificities of human-type, such as A-B-O, M-N, Rh-Hr, I-i, etc. known to be present on the red cells of various species of apes, specific reagents were produced by iso- or cross-immunization of chimpanzees that detect red cell specificities characteristic for apes only. Some of those specificities were found to be shared by several ape species and to fall into separate blood group systems that are counterparts of the human blood group systems. Recently obtained serological, as well as population data, indicate that the chimpanzee R-C-E-F blood group system is the counterpart of the human Rh-Hr system. Similarly to the Rh-Hr system, it is built around a main antigen, the R^c antigen, to which secondary specificities are attached by means of multiple allelic genes. The R^c is not only the principal factor of the chimpanzee R-C-E-F group system, but also constitutes a direct link with the human Rh-Hr blood group system, since anti-R^c reagents also detect Rh₀ specificity on the human red cells. Another chimpanzee blood group system, the V-A-B-D system, is counterpart of the M-N-S-s system, and is built around the central antigen V^c. the V^c is not only the principal specificity of the chimpanzee V-A-B-D system, but it also constitutes the direct link with the human M-N-S-s system since anti-V^c reagent gives with chimpanzee red cells reactions parralleling those obtained with anti-N lectin (N^v) while in tests with human red cells it detects specificity identical or closely related to the Mi^a specificity.     

Measurement of gonadal hormones in dried blood spots versus serum: verification of menstrual cycle phase

In the present study, we show that blood spot assays for estradiol, progesterone, and testosterone are a reliable, accurate, and sensitive means for measuring circulating gonadal hormones. The lower limit of sensitivity of each blood spot assay is sufficient to determine gonadal hormone levels in adult females. Correspondence of serum to blood spot measures is high, with blood spot hormone levels explaining an average of 88.60% of the variance in serum gonadal hormones in females, but only 46.20% in males. We provide formulas for converting hormone levels in blood to hormone levels in serum (which traditional endocrinology studies report). Finally, we show that careful attempts to estimate hormone status by day-count methods are unreliable when compared to hormone assay in blood spots.     

South East Asia faces severe shortage of safe blood

South East Asia is experiencing a severe shortage of safe blood. The region collects only 7 million units a year but needs a total of 15 million units. This problem is worsened by inappropriate use of blood without separation into its components, with 80-85% of blood being used as whole blood. In addition, the Supreme Court in India has banned the use of blood from professional blood sellers because they were considered to be a high-risk group of HIV. Unscreened blood is also allowed to flourish in both Bangladesh and Pakistan because these countries do not have any national blood policy. Moreover, even with blood screening in India, hepatitis B and C are present because the virus is not tested in this country. In the screened blood in India, the seroprevalence of hepatitis B is 0.06-8.5% and that of hepatitis C is 1.2-3%. While in Islamabad, Pakistan, testing results showed that 8.1% of blood was infected with hepatitis C. Lastly, 5-10% of HIV infections in Southeast Asia are transfusion-induced.     

Are our blood donors in danger of iron deficiency?]

In blood donors the question arises for eventual endangering by iron deficiency. The results of this work show that ferritin determinations for blood donors will indicate a latent, in some cases a manifest iron deficiency. The examination of testing components such as PVC, MCH, Fe i. S., transferrin and transferrin saturation produced no special advantages concerning sensitivity and specificity, in terms of ferritin determination. It is indispensable, however, to know the ferritin value because the control of the Hb value prior to blood donation will usually characterize the blood donor's situation in a sufficient manner. For control purposes it is possible to use capillary or venous blood. It is only in general, but particularly in special clinical situations that you have to be aware of the blood donor's condition concerning his/her Fe-metabolism.     

A significant pool of amino acids is adsorbed on blood cell membranes

It is well known that the amino acids in the blood are distributed between the plasma and inside the cells. This study was conducted to determine whether amino acids can be located adsorbed on blood cell membranes. The amino acid concentration in the deproteinized haemolysed blood was higher than that in the fraction of blood after removal of the blood cell membranes by centrifugation. These results showed that a pool of amino acids representing 21.1% of the whole blood cell amino acids was adsorbed on the blood cell membranes of adult Wistar rats. The non-polar amino acids showed high adsorption on the membrane, whereas out of the polar amino acid group, only the non-ionic amino acids did adsorb.Bioquimica i Biologia Molecular. Dept. de Biologia Fonamental i Ciencies de la Salut.     

Haemopoietic centres in the developing angelfish,Pterophyllum scalare (cuvier and valenciennes)

Summary The first haemopoietic centres in the embryo ofPterophyllum scalare are found in the blood islands of the yolk sac. These results are in contrast to the classical theory of blood formation in teleosts, which maintains that the first blood formation occurs intraembryonically, in the so-called intermediate cell mass of Oellacher. InPterophyllum, the intermediate cell mass forms only the axial blood vessels. Haemopoiesis in the post-embryo is carried out by the pronephros. This organ remains haemopoietic to the adult stage. In the adult, the pronephric tubules are degenerated; the organ is filled with haemopoietic tissue and also contains strands of adrenal tissue. The adult kidney (mesonephros) is also haemopoietic, though to a much lesser degree than the pronephros.The blood islands in the yolk sac form only stem cells (haemocytoblasts) and proerythroblasts. Released into the circulation, they differentiate and mature into round, disc-like erythrocytes (erythrocytes-E). Erythropoiesis in the pronephros produces elliptical erythrocytes (erythrocytes-ImA). Thus for the latter part of the postembryonic phase, until complete absorption of the yolk, there is a mixed erythrocyte population in circulation. During metamorphosis into the laterally-compressed adult, the adult type of erythrocyte (erythrocyte-A) makes its first appearance. Leucocytes and thrombocytes appear much later in development than the red blood cells. They are formed in the pronephros and are seen in circulation only after the yolk has been absorbed.     

Study of the effects of various physiological endocrine relations at the liver level

It is shown that predominance of male sex hormones in the rat organism decreases corticosterone in the liver, while that of female sex hormones increases it. The abundance of the thyroxine promotes a rise of blood in testosterone of males and reduces the estradiol in the females, but the blood content of corticosterone significantly decreases in blood and increases in the liver of rats of both sexes. While performing thyroidectomy the level of sex hormones reduces, but the content of glucocorticoid in the liver only slightly changes.     

Limitations imposed by testicular blood flow on the function of Leydig cells in rats in vivo

Testis blood flow per testis closely follows testis weight in rats made aspermatogenic by a single exposure of the testis to 43 degrees C for 30 min or 500 rad (5 Gy) of irradiation from a caesium source, or following ligation of the efferent ducts. Aspermatogenesis following these treatments was associated with only minor changes in the concentrations of testosterone in peripheral blood before stimulation with human chorionic gonadotrophin (hCG), and a reduced responsiveness to hCG when testis weight had fallen after heating. The concentrations of testosterone in testicular venous blood was normal or above normal during aspermatogenesis resulting from heat or irradiation, and only slightly reduced following efferent duct ligation. Consequently testosterone production (defined as the product of plasma flow and the veno-arterial concentration difference for testosterone) was markedly reduced during aspermatogenesis, both before and after stimulation with hCG. It appears that the reduced blood flow limits the amount of testosterone leaving the testis, and while the Leydig cells are capable under some circumstances of compensating partially for this fall by increasing the concentration of testosterone in the testicular venous blood, this compensation is not complete when there are severe reductions in blood flow. Therefore one can conclude that the mass of the tubules is the main determinant of testis blood flow and the Leydig cells must manage with what the tubules require.     

Recruitment of blood donors in Burkina Faso: how to avoid donations from family members?

Burkina Faso is a continental West African country of approximately 16 M people whose transfusion needs were covered by 66,210 blood units collected mostly in 4 regional transfusion centers part of a national network but also from hospital-based smaller blood centers. The first group of blood centers relies almost exclusively on volunteer, non-remunerated, blood donors and only approximately 32.7% of them are repeating donation. In contrast, hospital-based blood centers rely nearly exclusively on family/replacement donors. The general strategy of the national blood transfusion network was to base the system exclusively on volunteer donors, which was nearly accomplished overall and completely at Bobo-Dioulasso, the largest center. However, despite considerable increase in blood collection, the overall blood supply remains low (4.7 units/1000 inhabitants) and worsens during the secondary school recesses since young student blood constitutes the most part of volunteer donors. To overcome such shortages, mobile blood collection sessions are organized in alternate sites such as military barracks or places of worship but with limited success. Another critical issue is that despite considerable efforts and help from community advocates, only 32.7% of volunteers repeat donation limiting the considerably safety advantage of a pool of regular donors.