Chronic B cell deficiency from birth prevents age-related alterations in the B lineage

Aging is accompanied by a decline in B lymphopoiesis in the bone marrow and accumulation of long-lived B cells in the periphery. The mechanisms underlying these changes are unclear. To explore whether aging in the B lineage is subjected to homeostatic regulation, we used mutant mice bearing chronic B cell deficiency from birth. We show that chronic B cell deficiency from birth, resulting from impaired maturation (CD19(-/-) and CD74(-/-)) or reduced survival (baff-r(-/-)), prevents age-related changes in the B lineage. Thus, frequencies of early and late hematopoietic stem cells, B lymphopoiesis, and the rate of B cell production do not substantially change with age in these mice, as opposed to wild-type mice where kinetic experiments indicate that the output from the bone marrow is impaired. Further, we found that long-lived B cells did not accumulate and peripheral repertoire was not altered with age in these mice. Collectively, our results suggest that aging in the B lineage is not autonomously progressing but subjected to homeostatic regulation.     

Involvement of mitogen-activated protein kinases in adriamycin-induced cardiomyopathy

The current study investigated the phosphorylation of mitogen-activated protein kinases (MAPKs) as well as pro- and anti-apoptotic proteins in adriamycin (ADR)-induced cardiomyopathy (AIC) and heart failure in rats. Modulatory effects of antioxidant probucol on the activation of MAPKs were also examined. Male rats were administered with ADR (15 mg/kg body wt ip, over 2 wk) with and without probucol (120 mg/kg body wt for 4 wk ip). Hearts from these animals were studied at 1- to 24-h as well as at 3-wk posttreatment durations. In the 3-wk group, ADR depressed cardiac function, increased left ventricular end-diastolic pressure (LVEDP), and caused dyspnea and mortality. These changes were prevented by probucol. Phosphorylation of extracellular signal-regulated kinase (ERK)1/2, in the early stage of AIC, showed a biphasic response, with a maximum increase to 513% seen at 4 h, followed by a decrease to 66.8% at 3 wk after the last injection of ADR. Phosphorylation of p38 and c-Jun NH(2)-terminal kinases (JNKs) showed a steady increase through 2, 4, and 24 h and 3 wk (116% to 148%). In gene microarray analysis at 3 wk (heart failure stage), mRNA expression for both ERK1/2 and p38 kinases was decreased, whereas JNK mRNA was undetectable. Probucol completely prevented these MAPK changes. Activation of caspase-3 as well as the increase in the ratio of Bax to Bcl-xl were seen at early time points (1-24 h) as well as in the heart failure stage (3 wk). It is suggested that a transient increase in ERK1/2 at a shorter interval indicate an early adaptive response, and failure of this response corresponded with heart failure. In contrast, a gradual and persistent increase in p38 and JNK MAPKs as well as in caspase-3 and the Bax-to-Bcl-xl ratio may contribute in the initiation of apoptosis and progression of heart failure. Because probucol modulated changes in cellular signaling pathways and cardiac function, it is likely that oxidative stress plays a key role in AIC and heart failure.     

Estimated fat, bone mineral, total body water and cell solids in females of two communities of Punjab, India

The data for the present study consist of 502 Jat-Sikh and 510 Bania females of Punjab (India), ranging in age from 20 to 80 years. The different components of the body i.e. fat, bone mineral, total body water and cell solids have been calculated from anthropometric measurements by applying different equations given by various investigators. While studying age changes in different components of the body, it is the fat component, which has undergone major fluctuations past maturity. It has increased significantly from age-group 20-29 to 40-49 in both Jat-Sikh and Bania females. A significant decrease in fat has been observed from age-group 60-69 to 70 +. The bone minerals have exhibited little changes with age. The total body water and cell solids show a significant increase from age-group 20-29 to 30-39, followed by a decrease in both the communities. The decrease in these two components is statistically significant from age-group 40-49 to 50-59 in Bania females only. While comparing the two communities it has been observed that bone minerals are significantly larger in Jat-Sikh females, and fat is significantly larger in Bania females except in the last two age-groups. The other two components i.e. total body water and cell solids show statistically non-significant differences in the two communities.     

Adriamycin depresses in vivo and in vitro phosphatidylethanolamine N-methylation in rat heart sarcolemma

Adriamycin, an effective anticancer chemotherapeutic agent, causes an insidious and delayed cardiotoxicity. Different subcellular abnormalities including calcium transport changes in the sarcolemma (SL) as well as downregulation of the adrenergic system have been shown to be associated with the development of this cardiomyopathy. Since both of these activities are influenced by phospholipid methylation, effects of adriamycin on the three catalytic sites of SL phosphatidylethanolamine N-methyltransferase were examined. Rats were administered with a cumulative dose of adriamycin (15 mg/kg) over 2 weeks and examined after 3 weeks. Vehicle injected animals served as controls. Dyspnea, high mortality rate, ascites and decrease in aortic and left ventricular systolic pressure, as well as increase in left ventricular end diastolic pressure were seen in the adriamycin group. Myocardial cell damage typical of adriamycin cardiomyopathy, i.e. sarcotubular swelling, vacuolization and myofibrillar drop-out, was also apparent. Total methyl group incorporation into SL phosphatidylethanolamine using radiolabeled S-adenosyl-L-methionine as the donor was significantly depressed in the 3 week group at catalytic sites II and III. Decreased production of methylated intermediates, phosphatidyl-N-monomethylethanolamine and phosphatidyl-N,N-dimethylethanolamine as well as phosphatidylcholine (PC) was seen. Depression of phosphatidylethanolamine N-methylation was also noticed when SL, isolated from untreated hearts, was exposed in vitro to different concentrations (10, 100 and 1000 µM) of adriamycin. Inhibition of phosphatidylethanolamine N-methylation appears to be mediated by adriamycin-induced increase in the oxidative stress and may contribute in the pathogenesis of subcellular changes associated with this cardiomyopathy.     

Factors important in evolutionary shaping of immunoglobulin gene loci

Background

The extraordinary diversity characterizing the antibody repertoire is generated by both evolution and lymphocyte development. Much of this diversity is due to the existence of immunoglobulin (Ig) variable region gene segment libraries, which were diversified during evolution and, in higher vertebrates, are used in generating the combinatorial diversity of antibody genes. The aim of the present study was to address the following questions: What evolutionary parameters affect the size and structure of gene libraries? Are the number of genes in libraries of contemporary species, and the corresponding gene locus structure, a random result of evolutionary history, or have these properties been optimized with respect to individual or population fitness? If a larger number of genes or different genome structures do not increase the fitness, then the current structure is probably optimized.

Results

We used a simulation of variable region gene library evolution. We measured the effect of different parameters on gene library size and diversity, and the corresponding fitness. We found compensating relationships between parameters, which optimized Ig library size and diversity.

Conclusions

We conclude that contemporary species' Ig libraries have been optimized by evolution in terms of Ig sequence lengths, the number and diversity of Ig genes, and antibody-antigen affinities.