Dietary Docosahexaenoic Acid Supplementation Modulates Hippocampal Development in the Pemt?/? Mouse

The development of fetal brain is influenced by nutrients such as docosahexaenoic acid (DHA, 22:6) and choline. Phosphatidylethanolamine-N-methyltransferase (PEMT) catalyzes the biosynthesis of phosphatidylcholine from phosphatidylethanolamine enriched in DHA and many humans have functional genetic polymorphisms in the PEMT gene. Previously, it was reported that Pemt^−/− mice have altered hippocampal development. The present study explores whether abnormal phosphatidylcholine biosynthesis causes altered incorporation of DHA into membranes, thereby influencing brain development, and determines whether supplemental dietary DHA can reverse some of these changes. Pregnant C57BL/6 wild type (WT) and Pemt^−/− mice were fed a control diet, or a diet supplemented with 3 g/kg of DHA, from gestational day 11 to 17. Brains from embryonic day 17 fetuses derived from Pemt^−/− dams fed the control diet had 25–50% less phospholipid-DHA as compared with WT (p < 0.05). Also, they had 60% more neural progenitor cell proliferation (p < 0.05), 60% more neuronal apoptosis (p < 0.01), and 30% less calretinin expression (p < 0.05; a marker of neuronal differentiation) in the hippocampus compared with WT. The DHA-supplemented diet increased fetal brain Pemt^−/− phospholipid-DHA to WT levels, and abrogated the neural progenitor cell proliferation and apoptosis differences. Although this diet did not change proliferation in the WT group, it halved the rate of apoptosis (p < 0.05). In both genotypes, the DHA-supplemented diet increased calretinin expression 2-fold (p < 0.05). These results suggest that the changes in hippocampal development in the Pemt^−/− mouse could be mediated by altered DHA incorporation into membrane phospholipids, and that maternal dietary DHA can influence fetal brain development.     

A review of the prognostic role of cytogenetic, phenotypic, morphologic, and immune function characteristics in chronic lymphocytic leukemia

Recent reports of successfully completed cytogenetic studies using polyclonal B-cell activators demonstrate that trisomy-12 and 14 q+ are the most frequently observed chromosomal abnormalities in B-cell chronic lymphocytic leukemia (CLL). It appears that when trisomy-12 is accompanied by yet another abnormality, the prognosis of patients is uniformly poor. Patients in early stages of CLL retain delayed hypersensitivity reactivity, while those in advanced stages are usually anergic. The lymphocytes from venous blood of patients with CLL appear to retain at least some ability to respond to stimulation with mitogens in early stages, whereas in advanced stages they show no response to mitogens. Serum immunoglobulin levels are normal in the early (0 and I) stages, are markedly decreased in the advanced (III and IV) stages, and are somewhat between these extremes in the intermediate (II) stage of CLL. Prolymphocytic leukemia and prolymphocytoid transformation of CLL are indicators of poor prognosis, while a morphological variant characterized by large granular lymphocyte is associated with good prognosis. At this time it is not possible to ascribe strong prognostic significance to phenotypic features of lymphocytes in B-CLL; however, studies currently in progress may soon provide important insights on this subject. We have reviewed the pertinent literature and we also present a summary of results from our laboratory.     

Multi-Sample Slippage Test for Ordered Observations

A multi-sample slippage test based on ordered observations has been given. The test statistic is based on the sum of ranks of the sample. The probability distribution of the test statistic has been worked out for small sample and it turns out to be chi-square distribution for large sample. The analytical procedure has been explained by a numerical example.     

Genetics of mosquitoes

Beginning in the mid-1950s, much progress has been made in studying various aspects of the genetics of mosquitoes, particularly involving several species of three principal genera,Aedes, Culex andAnopheles, that transmit important human diseases. Here I discuss selected areas of research involving formal genetics; genome structure, organization and evolution at the interspecific and intraspecific level; and evolutionary genetics of theAedes scutellaris group. Information and insights gained from in-depth analyses of these areas, particularly transmission genetics, cytogenetics and genetics of chromosomal rearrangements, and of mutagen-induced sexual sterility, have proved invaluable for the development of the theory and evaluation of feasibility of genetic control of natural populations. As a result, mosquitoes represent some of the best studied taxa at various levels of genetic organization. Recent developments in molecular genetics offer exciting possibilities for extension of these concepts.     

Relationship of combined nitrogen sources to salt tolerance in freshwater cyanobacterium Anabaena doliolum

Higher concentrations of NaCl inhibit the growth and reduce the specific growth rate of the freshwater cyanobacterium Anabaena doliolum. Among the nitrogen sources tried, nitrate protected the cyanobacterial cells most from salt toxicity. However, supplementing of medium with nitrate could increase the adaptability of the cells at sublethal doses but it would not permit growth at otherwise lethal doses of 300 mmol 1^-1 NaCl. Nitrate uptake was proportionally related to the NaCl level in the medium. The uptake of sodium was minimum when nitrate was simultaneously available to the cells, indicating the interaction of nitrate with the Na⁺ carrier. Na⁺ efflux was maximum in N², ammonia, urea and nitrate in decreasing order. This led to the conclusion that Na⁺ influx plays the critical role in salt tolerance, rather than its efflux.     

Endophytic bacterial flora in the stem tissue of a tropical maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) genotype: isolation,identification and enumeration

The genotypic diversity of indigenous bacterial endophytes within stem of tropical maize (Zea mays L.) was determined in field and greenhouse experiments. Strains were isolated from stem tissues of a tropical maize cultivar (PEHM-1) by trituration and surface disinfestation and their population dynamics was determined. Endophytes were found in most of the growing season at populations ranging from 1.36–6.12 × 10⁵ colony-forming units per gram fresh weight (c.f.u./gm fw) of stem. Analysis of these bacterial endophytes using Gas Chromatography—Fatty Acid Methyl Ester (GC-FAME) led to the identification of Bacillus pumilus, B. subtilis, Pseudomonas aeruginosa and P. fluorescens as the relatively more predominant group of bacterial species residing in maize stem. When the maize seedlings grown in a greenhouse were inoculated with these four isolates individually, their population densities decreased (1.6–3.1 × 10⁵ c.f.u./gm fw of stem) as compared to the field-grown maize (1.8–3.8 × 10⁵ c.f.u./gm fw of stem). The highest persistence, however, was recovered in the case of B. subtilis with a population density of 3.1 × 10⁵ c.f.u./gm fw of stem tissue on 28 days after emergence (DAE). This is the first report on population dynamics of bacterial endophytes from tropical maize and the results establish that symptomless populations of bacteria exist in the maize stem.