Esterase activity in the hepatopancreas ofMacrobrachium lamarrei (Crustacea: Decapoda)

Summary The activity of the hepatopancreatic esterase of the fresh water prawnMacrobrachium lamarrei was optimal at pH 7.4 and temperature 40°C. The activity increased with the increase in incubation period and enzyme concentration. The Michaelis constant (K_m) of the enzyme was 2.1×10^–3M.The investigations are a part of the thesis presented to University of Lucknow, India.Acknowledgments. The authors are grateful to the University Grants Commission, India for the award of a Junior Research Fellowship.     

Structure of the foregut cuticle ofPeriplaneta americana

Summary The cuticular lining of the foregut ofPeriplaneta americana did not contain either pore canals or the openings of dermal glands, and the length of the cuticular spines decreased posteriorwards.I am grateful to ProfessorR. Rakshpal, Head, Department of Zoology for supervizing my work and to University Grants Commission, India, for awarding a Junior Research Fellowship.     

Chromosomal abnormalities in starved and marginally malnourished rats and in utero upon rehabilitation

The effects of starvation and marginal malnutrition (MN) on the lymphocytes of rats were evaluated by chromosomal analysis before and after rehabilitation. The effect of parental starvation or malnutrition on chromosomal aberrations in the foetus was also studied. Wistar rats, 30–35 days old, were starved for 5 days or fed a minimally restricted or a severely restricted diet for three weeks. At the end of the period of starvation or malnutrition, lymphocytes were isolated and chromosomal analysis was performed. Starved and severely restricted rats showed significantly higher mean chromosomal aberrations than the controls. These aberrations returned to a normal level when the experimental groups were rehabilitated for a month, indicating that the damage was transient. A chromosomal aberration study done on foetal cells from rehabilitated rats which had previously been starved or fed a severely restricted diet showed significantly increased values, indicating that some damage was permanent. A low number of implantations was also recorded in these experimental groups. These observations clearly indicate that young animals exposed to conditions like starvation or chronic malnutrition are prone to permanent damage of the genetic system.     

Structure of morellin

Zusammenfassung In der vorliegenden Arbeit wird eine neue Strukturformel (I) für Morellin vorgeschlagen, die mit der Summenformel C₃₃H_36–38O₇ übereinstimmt. Neben der strukturellen Ähnlichkeit zeigen auch biologische Eigenschaften des Morellins (I) dessen Verwandtschaft mit Guttiferin.     

Protein elongation factor EEF1A2 is a putative oncogene in ovarian cancer

Telomeres in most immortal cells are maintained by the enzyme telomerase, allowing cells to divide indefinitely. Some telomerase-negative tumors and immortal cell lines maintain long heterogeneous telomeres by the ALT (alternative lengthening of telomeres) mechanism; such tumors are expected to be resistant to anti-telomerase drug therapies. Occasionally telomerase-negative Saccharomyces cerevisiae mutants survive, and 10% of them (type II survivors) have unstable telomeres. As in human ALT+ cells, short telomeres in yeast type II survivors lengthen abruptly; in yeast, this is dependent on the recombination proteins Rad52p and Rad50p. In human cells, ALT involves copying of sequence from a donor to a recipient telomere. We have characterized for the first time a class of complex telomere mutations seen only in ALT+ cells. The mutant telomeres are defined by the replacement of the progenitor telomere at a discrete point (fusion point) with a different telomere repeat array. Among 19 characterized fusion points, one occurred within the first six repeats of the telomere, indicating that these recombination-like events can occur anywhere within the telomere. One mutant telomere may have been involved in a secondary recombination-like mutation event, suggesting that these mutations are sporadic but ongoing in ALT+ cells. We also identified simple intra-allelic mutations at high frequency, which evidently contribute to telomere instability in ALT+ cells.     

Experimental evidence that potassium is a substantial radioactive heat source in planetary cores

The hypothesis that (40)K may be a significant radioactive heat source in the Earth's core was proposed on theoretical grounds over three decades ago, but experiments have provided only ambiguous and contradictory evidence for the solubility of potassium in iron-rich alloys. The existence of such radioactive heat in the core would have important implications for our understanding of the thermal evolution of the Earth and global processes such as the generation of the geomagnetic field, the core-mantle boundary heat flux and the time of formation of the inner core. Here we provide experimental evidence to show that the ambiguous results obtained from earlier experiments are probably due to previously unrecognized experimental and analytical difficulties. The high-pressure, high-temperature data presented here show conclusively that potassium enters iron sulphide melts in a strongly temperature-dependent fashion and that (40)K can serve as a substantial heat source in the cores of the Earth and Mars.     

Biosynthesis of aflatoxins by cell-free preparations fromAspergillus flavus

Résumé Incorporation d'acétate-1-¹⁴C, de leucine-U-¹⁴C et de mévalonate-2-¹⁴C sous forme d'aflatoxine dans les extraits libres des cellulesd'Aspergillus flavus. Dans le cas du mévalonate, l'incorporation de l'ordre de 0,4 pour 100 et les activités spécifiques sont 13 000 à 40 000 cpm/mg d'aflatoxine. La capacité d'incorporation des substrats en aflatoxine s'observe, en particulier, dans les mitochondries.