Blood coagulation studies in guineapigs (Cavia porcellus)

Blood coagulation studies were performed on 45 healthy, adult guinea pigs. Additionally thrombelastograms of 30 animals were recorded. Guineapigs revealed short partial thromboplastin times and euglobulin lysis times, but long prothrombin times and thrombin times. Fibrinogen values were within the range of human normal values. Biphasic ADP-induced aggregation of platelets, as occurs in man, was found in 29% of the animals. Short r (reaction time until the beginning of clot formation) and k times (time from the beginning of clot formation until an amplitude of 20 mm) of their thrombelastograms indicate, that whole blood clotting is enhanced in guineapigs. Higher maximum amplitudes in this species suggest a stronger clot stability than in man.     

Maternal age at last birth in Egypt

To assess the effects of women's education, residence, and marital experience on their age at the birth of their last child, a proportional hazards regression model was applied to 1980 Egyptian Fertility Survey (EFS) data. The detailed data include the date of birth of each child for every women interviewed, and the woman's date of birth and age at interview. Age at last birth was examined by regression analysis on birth history and socioeconomic information. 4 hypotheses were tested: women who are well educated have a greater probability of ending childbearing earlier than women with less education; women in rural areas have a higher probability of having their last child at older ages than urban women; marital disruption without remarriage lowers the probability of older maternal age at last birth; and marital disruption with remarriage increases the probability that a woman stops reproducing at an older age. The overall chi-square indicates a significant regression. All coefficients were significant, except the coefficient for women with intact 1st marriages. Women with more education had a greater probability of ending childbearing earlier than women with less education. Rural women tended to have their last children at ages significantly older than overall age at last birth. Current residence in urban areas had the opposite effect. The coefficient for those with intact 1st marriages was insignificant, meaning that the mean age at last birth for this group of women was not much different from the overall mean. Remarried women tended to end childbearing at ages significantly older than the overall average age at last birth, suggesting that these women tended to have children by their new husbands. Those with dissolved 1st marriages who had not remarried had a higher probability of ending childbearing earlier than did older women. Marriage age and final parity had highly significant negative coefficients; as marriage age and number of children born increased, so did the "survival" time or the age at last birth. Results from the hazards model indicate that the effects were as anticipated. The median age at last birth for the total sample of women aged 45-49 was 45-49 years. The median age at last birth was about 2 years older for rural compared to urban women. Illiterate women had the oldest median age at last birth of the education groups. There was little differences between median ages at last birth for women with intact 1st marriages and those whose 1st unions were dissolved and who had remarried. The median age at last birth increased with final parity.     

The multicollisional, obstructed, long-range diffusional nature of mitochondrial electron transport

Data are presented which reveal that ubiquinone (Q)-mediated electron transport is a multicollisional, obstructed, long-range diffusion process, where factors that affect the rate of lateral diffusion also affect the rate of electron transport. Based on fluorescence recovery after photobleaching measurements, it was concluded that Q-mediated electron transport occurs by the random collision of redox components which are independent lateral diffusants, each greater than 86% mobile and diffusing in a common pool. The diffusion process of Q-mediated electron transport is 1) multicollisional since the transfers of reducing equivalents between appropriate redox partners occur with less than 100% collision efficiency; 2) obstructed since its maximal rate as well as the rates of diffusion of all redox components involved vary as a function of the membrane protein density; and 3) long-range since the diffusion of all redox components is protein density-dependent, and the diffusion distance required for Q to catalyze the transfer of a reducing equivalent from Complex II to III must be, on average, greater than 37.6 nm. These findings and other theoretical treatments reveal that measurements of short-range diffusion (less than 10 nm), in which collisions between appropriate redox partners do not occur, on average, and which are not affected by membrane protein density, are irrelevant to the collisional process of electron transport. Thus, the data show that the maximum electron transport rate is dependent on both the diffusion rate and the concentration of the redox components. Sucrose was found to inhibit both the mobility of redox components as well as their electron transport rates. Data presented on the relationships between membrane viscosity, rates of lateral and rotational diffusion, and mobile fractions of redox components do not support rotationally immobile aggregates in the functional inner membrane. The high degree of unsaturated phospholipids and the absence of cholesterol in the bilayer of the native inner membrane reflect a requirement for a low resistance to motion of the redox components to compensate for the multicollisional, obstructive nature of their catalytically important collisions in this membrane. These findings support the Random Collision Model of electron transport in which the diffusion and concentration of redox components limit the maximum rate of electron transport.     

The relationship between glucose transport and the production of succinoglucan exopolysaccharide by Agrobacterium radiobacter

Agrobacterium radiobacter NCIB 11883 was grown in ammonia-limited continuous culture at low dilution rate with glucose as the carbon source. Under these conditions the organism produced an extracellular succinoglucan polysaccharide and transported glucose using the same periplasmic glucose-binding proteins (GBP1 and GBP2) as during glucose-limited growth. Transition from glucose- to ammonia-limited growth was accompanied by a very rapid decrease in glucose uptake capacity, whereas the glucose-binding proteins were diluted out much more slowly (t1/2 approximately 1 h and 14 h respectively). Although the rate of glucose uptake and the concentrations of GBP1 and GBP2 were much lower during ammonia limitation, the activities of enzymes involved in the early stages of glucose metabolism and in the production of succinoglucan precursors were essentially unchanged. Glucose transport was also investigated in two new strains of A. radiobacter which had been isolated following prolonged growth under glucose limitation. Glucose uptake by strain AR18 was significantly less repressed during ammonia limitation compared with either the original parent strain or strain AR9, and this was reflected both in its relatively high concentration of GBP1 and in its significantly higher rate of succinoglucan synthesis. Flux control analysis using 6-chloro-6-deoxy-D-glucose as an inhibitor of glucose transport showed that the latter was a major kinetic control point for succinoglucan production. It is concluded that glucose uptake by A. radiobacter, particularly via the GBP1-dependent system, is only moderately repressed during ammonia-limited growth and that the organism avoids the potentially deleterious effects of accumulating excess glucose by converting the surplus into succinoglucan.     

Localization of immunoreactive epidermal growth factor receptors in human nervous system

Epidermal growth factor is a well-defined peptide which stimulates cell growth and elicits cell responses in a variety of tissues by binding to specific receptors, EGF-R. A specific antiserum against the EGF receptor, which has previously been used to characterize EGF-R in human skin, fibroblasts, and smooth muscle, was used to survey the distribution of EGF-R in human nervous system. Portions of formalin-fixed, paraffin-embedded autopsy specimens were examined by use of immunohistochemical staining (PAP technique) with EGF-R antiserum. Many types of nerve cells, e.g., cerebral cortical pyramidal cells, hippocampal pyramidal cells, Purkinje cells, anterior horn cells, and dorsal root ganglion neurons, contained immunoreactive EGF-R. However, immunoreactive EGF-R were not detected in astrocytes, oligodendrogliocytes, and other small neurons such as granule cells. Intense immunostaining for EGF-R was also detected in ependymal cells from choroidal and extrachoroidal locations. Although immunoreactive EGF-R is widely distributed in human nervous system, the functional role of EGF and its receptor in the nervous system remains unknown.     

The E beta hot spot of recombination in wild-derived natural recombinant MHC haplotypes. Cross-over site mapping and the identification of a 1.0-kb E beta deletion in the p and w14 haplotypes

Detailed molecular analysis of three wild-derived MHC haplotypes provided evidence for an important role of the E beta recombinational hot spot in the recent evolution of the mouse I region. Examination of RFLP and restriction maps of cloned DNA permitted the mapping of the natural cross-over events in the haplotypes carried by strains B10.GAA37 (w21) and B10.KPB128 (w19) to a fragment of DNA not exceeding 4.1 kb, which lies almost entirely within the intron separating the beta 1 and beta 2 exons of the E beta gene. In the w14 haplotype (strain B10.STC77), which appears to be a natural recombinant between a p-like parental haplotype and another wild-derived haplotype, the site of crossing over can be mapped to a segment between the beta 2 exon of the E beta gene (left border) and the E beta 2 gene (right border). This segment containing the cross-over site in the w14 haplotype includes the E beta hot spot. In addition, the w14 haplotype as well as the standard p haplotype contain a deletion of approximately 1.0 kb in the second intron of the E beta gene, which may represent the product of an unequal cross-over event in a E beta recombinational hot spot.     

Protein Rou. A human IgA hybrid

Protein Rou is a human IgA2 myeloma protein that carries the isoallotype marker n A2m(2). Partial amino acid sequence of its H chain (alpha) shows that the hinge region and the CH2 domain are homologous to alpha 2-chain and the CH1 and the CH3 domains homologous to alpha 1. Moreover, the CH1 domain contains the H-L disulfide bond identical to alpha 1. It is concluded that Rou H chain is a hybrid molecule caused by a recombination between alpha 1 and alpha 2 genes. The recombination event occurred between alpha 1-exon 1 and alpha 2-exon hinge and corresponds to position 222-223 of the alpha-chain.     

Role of central histaminergic mechanism in behavioural depression (swimming despair) in mice

The role of the central histaminergic system in depression was studied by using swimming despair test in mice - a behavioural model of depression. In this test, immobility of mice reflects a state of depression. Intracerebral (ic) injection of histamine (50-200 micrograms) increased significantly the immobility. The H1-receptor blocker mepyramine (2.5-20 mg/kg ip) had no effect while H2-receptor blocker cimetidine (100-200 micrograms ic) caused a significant decrease in immobility. The histamine induced facilitation was blocked completely by cimetidine and antidepressant drugs-imipramine and desipramine, but remained unaffected in mice pretreated with mepyramine or atropine. The H2 agonist impromidine (20-40 micrograms ic) also enhanced significantly, the immobility which was blocked by cimetidine and antidepressant drugs. It has been concluded that central H2-receptors facilitate depression and antidepressant drugs block central H2-receptors.     

Immunogold localization of acyl carrier protein in plants and Escherichia coli: Evidence for membrane association in plants

Immunogold labelling was used to study the distribution of acyl carrier protein (ACP) in Escherichia coli and a variety of plant tissues. In E. coli, ACP is distributed throughout the cytoplasm, confirming the observation of S. Jackowski et al. (1985, J. Bacteriol., 162, 5–8_. In the mesocarp of Avocado (Persea americana) and maturing seeds of oil-seed rape (Brassica napus cv. Jet Neuf), over 95% of the ACP is localised to plastids. The protein is almost exclusively located in the chloroplasts of leaf material from oil-seed rape. Approximately 80% of the gold particles associated with the ACP were further localized to the thylakoid membrane of the chloroplast. Since acetyl-CoA carboxylase has been reported to be localized to the thylakoid membrane (C.G. Kannangara and C.J. Jensen, 1975, Eur. J. Biochem., 54, 25–30), these results are consistent with the view that the two sequential enzymes in fatty-acid synthesis are in close spacial proximity.Abbreviations ACC acetyl CoA carboxylase - ACP acyl carrier protein - FAS fatty-acid synthetase