Prajitha Thampi

Musashi regulates the temporal order of mRNA translation during Xenopus oocyte maturation

A strict temporal order of maternal mRNA translation is essential for meiotic cell cycle progression in oocytes of the frog Xenopus laevis. The molecular mechanisms controlling the ordered pattern of mRNA translational activation have not been elucidated. We report a novel role for the neural stem cell regulatory protein, Musashi, in controlling the translational activation of the mRNA encoding the Mos proto‐oncogene during meiotic cell cycle progression. We demonstrate that Musashi interacts specifically with the polyadenylation response element in the 3′ untranslated region of the Mos mRNA and that this interaction is necessary for early Mos mRNA translational activation. A dominant inhibitory form of Musashi blocks maternal mRNA cytoplasmic polyadenylation and meiotic cell cycle progression. Our data suggest that Musashi is a target of the initiating progesterone signaling pathway and reveal that late cytoplasmic polyadenylation element‐directed mRNA translation requires early, Musashi‐dependent mRNA translation. These findings indicate that Musashi function is necessary to establish the temporal order of maternal mRNA translation during Xenopus meiotic cell cycle progression.

α-Crystallin chaperone function in diabetic rat and human lenses

This study focussed on the effect of diabetes on the chaperone function of α-crystallin. The authors relied on diabetic rats with a wide range of plasma glucose levels and non-diabetic control rats to establish a possible relationship between severity of diabetes and α-crystallin chaperone activity. In addition, 52–56 and 63–69 year-old diabetic and non-diabetic human lenses were used to show whether diabetes affects α-crystallin chaperone activity in human lenses. Correlation between plasma glucose levels and loss of chaperone activity of the αL-crystallin fraction in diabetic rats indicated good correlation. The glycemic threshold, reported before for cataract development in diabetic rats, seems to be valid for the chaperone activity loss as well. Analysis of the human lens αL-crystallin showed lower chaperone activity in all the diabetic lenses than in the age-matched control lenses. In the 63–69 age group, the loss in chaperone activity due to diabetes was significantly larger than in the 52–56 age group suggesting a dominant effect of duration of diabetes.

Diet Regulates the Development of Gut-Associated Lymphoid Tissue in Neonatal Piglets

Background: Controversy exists concerning diet-induced changes to gut epithelia and immunocytes that occur during weaning. Furthermore, studies on dietary effects on the development of the neonatal immune system, especially gut-associated lymphoid tissue (GALT), are lacking. Objective: The purpose of this study was to investigate growth and development, intestinal morphology, and GALT immune maturation in sow-reared littermates in comparison with early-weaned piglets fed a casein-based liquid diet. Method: Piglets were breast fed by the sow or were weaned at 48 h to a casein-based diet (formula) that provided the amount of nutrient requirements recommended by the National Research Council. Results: Gross physical appearance and visual inspection of the gastrointestinal tract and other organs at necropsy revealed normal organogenesis in both cohorts. On postnatal day 21, body weight, liver and kidney weight relative to body weight, small intestine length, and weight-to-length ratio were greater in formula-fed piglets as compared with sow-reared piglets (p < 0.05). The CD21+ B lymphocyte component of GALT and spleen was reduced in the formula-fed piglets. This was associated with lower circulating IgG and IgM levels in the formula-fed as compared with the breast-fed neonatal piglets (p < 0.001). Conclusions: Feeding a casein-based formula to newborn piglets may compromise the development of GALT and systemic immune system. Further, the neonatal piglet model may be used to identify the effects of dietary factors on the development of the neonatal immune system.

Cleavage of in vitro and in vivo formed lens protein cross-links by a novel cross-link breaker

The purpose of this study was to investigate the effect of N-phenacyl-4,5-dimethylthiazolium bromide (DMPTB), an advanced glycation end product (AGE) cross-link breaker, on lens protein cross-links formed in vitro and in vivo. DMPTB was synthesized and its structure confirmed by its NMR spectrum. To show whether DMPTB can inhibit AGE cross-linking, recombinant human αA-crystallin was glycated with glucose-6-phosphate (G6P) in the presence and absence of DMPTB. Reversal of the already formed cross-links was studied by treating pre-glycated αA-crystallin with DMPTB. The ability of DMPTB to cleave in vivo formed cross-links was ascertained by treating water-insoluble protein fractions from diabetic human lenses with this compound. Glycation of αA-crystallin with G6P showed several high molecular weight (HMW) protein bands on the SDS-PAGE gel; DMPTB inhibited the formation of these HMW proteins. Molecular sieve HPLC confirmed the inhibition of formation of larger aggregates not separated by SDS-PAGE. Treatment of pre-glycated αA-crystallin with DMPTB gave evidence for the degradation of the already formed cross--linked HMW aggregates. Both molecular sieve HPLC and reverse-phase HPLC of the water-insoluble protein fractions from two diabetic human lenses showed that DMPTB could degrade a major portion of the cross-linked HMW aggregates to lower molecular weight proteins. This suggests that the cross-linked proteins in human lenses are formed predominantly by the advanced glycation process and cross-link breakers like DMPTB may have application for the intervention of protein cross-linking in the eye lens.