Effect of estradiol & testosterone on the pituitary prolactin levels in developing male & female rats

Testosterone priopionate (TP) or estradiol-17 beta (E2) were injected into male and female rats from day of birth to 15 days of age to determine the effect of these steroids on the pituitary prolactin (PRL) level in developing rats. Animals were autopsied on Days 5, 7, 10, 14, 17, 22, 25, 30, 37, 45, 52, and 60 and pituitary PRL estimated by radioimmunoassay. Neonatal administration of TP or E2 markedly increased PRL content in male rats. The peak of PRL was advanced to Days 14 and 23, respectively, in E2- and TP-treated groups. The content of pituitary PRL declined sharply and values increased again by Day 52 in TP-treated rats and Day 37 in E2-treated rats. In the female rat both the steroids advanced the time of PRL peak. Peaks were observed on Days 22 and 30, respectively. Although PRL content declined following these peaks, values remained at a significantly higher level than normal. These results suggest that mechanisms controlling the PRL secretion are functional during the neonatal period. It is also suggested that TP acts to increase PRL levels by 1st being converted to E2.     

Effect of neonatal testosterone and oestradiol treatment on the development of the hypothalamo-hypophysial axis in the female rat.

The hypothalamic LH-RH content and the concentrations of pituitary and plasma LH were measured at various ages in female rats treated daily with 10 micrograms testosterone propionate or 10 micrograms oestradiol-17beta from birth to Day 15. Persistent vaginal oestrus was induced in all the treated rats. Both hormones significantly reduced the hypothalamic LH-RH content and pituitary and plasma LH concentrations. Hypothalamic LH-RH increased after cessation of treatment but pituitary LH did not return to normal levels. Plasma LH levels were significantly lower than those in control rats. It is concluded that testosterone propionate and oestradiol-17beta (1) have a direct negative feed-back influence on the hypothalamus in the neonatal female rat; (2) alter the normal pattern of plasma and pituitary LH in developing female rats; (3) prevent the cyclic secretion of plasma LH after maturity; and (4) probably cause a chronic impairment in the release of LH-RH.     

In vitro hemolytic activity ofPlasmodium berghei on red blood cells

A suspension ofPlasmodium berghei obtained by lysis with saponin of red blood cells from an infected rat showed high hemolytic activity, when incubatedin vitro with normal rat red blood cells. The hemolysis was a temperature-dependent process and was dependent on the concentration of the parasite. Plasma ofPlasmodium berghei infected albino rats also possessed lytic activity.     

Epoxidation of aflatoxin B1 by Aspergillus flavus microsomes in vitro: interaction with DNA and formation of aflatoxin B1-glutathione conjugate

Metabolism of aflatoxin B1 (AFB1) by subcellular preparations of Aspergillus flavus is least understood. The results reported here have demonstrated for the first time the epoxidation of AFB1 and subsequent conjugation with glutathione (GSH). Microsomes prepared from toxigenic mycelia catalysed [3H]AFB1 to calf thymus DNA to a greater extent (approximately 2-fold) as compared to that of non-toxigenic. The binding of [3H]AFB1 to exogenous and A. flavus nuclear DNA catalyzed by A. flavus microsomes was found to be comparable with that of mammalian extrahepatic tissue such as lung. Addition of phenobarbitone to the growing cultures resulted in 1.5-fold increase in [3H]AFB1-DNA binding mediated by microsomes prepared from either of the two strains. Tolnaftate, an inhibitor of aflatoxin synthesis enhanced the epoxidation rate in a dose-related manner. The binding of [3H]AFB1 to DNA catalyzed by A. flavus microsomes was significantly reduced (50% of control) upon addition of hamster liver cytosol, thereby substantiating the formation of the carcinogen adduct with DNA as reported in mammalian tissues. The metabolite formed by subcellular preparation of A. flavus was found to be AFB1-GSH having Rf value (6.5) similar to that obtained for mammalian liver preparations.     

Resistance in certain maize cultivars to first and third-instar Chilo partellus larvae

The resistance/susceptibility levels of ten maize (Zea mays L.) cultivars to neonates and 3rd-instar larvae of Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) were measured in the field and screenhouse experiments. The maize cultivars tested were: Inbred A, Mp 704, V-37, Population 10, Hybrid 511, Katumani Composite B, ER-29 SVR, Poza Rica 7832, ICZ2-CM, and MMV 400. Most cultivars were found susceptible to 3rd-instar larvae based on the incidence of dead heart symptoms, foliar feeding and stem tunnelling caused by stem borers in both the field and screenhouse experiments. However, the maize cultivars V-37, MMV 400 and Poza Rica 7832 sustained significantly lesser damage than the other cultivars when infested with neonates or 3rd instar larvae.The screenhouse experiments conducted with five maize cultivars, i.e. Inbred A, Mp 704, V-37, ER-29 SVR, and Poza Rica 7832 showed that neonates fed less on the resistant than the susceptible maize cultivars but feeding by the 3rd instars was equally high on all the maize cultivars except Mp 704 on which the larvae fed less than the others. In the cultivars infested with neonates, the mean period for 50% moth emergence P₅₀ was longest on Mp 704 followed by Poza Rica 7832, ER-29 SVR, V-37 and Inbred A. In the cultivars infested with 3rd-instars, P₅₀ was longest for Poza Rica 7832 followed equally by the remaining cultivars.On the basis of the evidence presented we here conclude that neonates of C. partellus are sensitive to the growth inhibiting effects of the resistant maize cultivars Mp 704, V-37, and Poza Rica 7832 but the older larvae are insensitive to these effects of Mp 704 and V-37 but not of Poza Rica 7832.     

Allozyme variation among biotypes of the brown planthopperNilaparvata lugens in the Philippines

Allozyme variation was studied in threeNilaparvata lugens biotypes infesting specific rice varieties and a biotype infesting a weed grass,Leersia hexandra. Of the 20 enzymes inN. lugens for which activity was noted, 9 were polymorphic. Eleven enzyme loci were monomorphic for the same allele in all biotype populations; the rest were polymorphic for two or more alleles. The mean number of alleles per polymorphic locus was 2.3, while the mean number of alleles per locus was 1.5; heterozygosity ranged from 0.02 to 0.06 (biotype 1 > biotype 3 >Leersia-infesting biotype > biotype 2). Allelic frequency differences were observed in five loci among the four biotypes. However, the coefficient of genetic identity (I) of 0.99+ showed that the four biotype populations were genetically close relatives or merely populations ofN. lugens undergoing genetic differentiation. This work was partly supported by a financial grant received from the Directorate for Technical Cooperation and Humanitarian Aid, Switzerland.     

Influence of phosphate and zinc on growth,nodulation and mineral composition of chickpea (Cicer arietinum L.) under salt stress

Zn²⁺ at 5 ppm and phosphate at 20 and 40 ppm improved the growth and nodulation of chickpea (Cicer arietinum L.) at two levels of salinity (4.34 and 8.3 dS m^–1). Augmentation with Zn²⁺ at 5 ppm provided protection to the plant under saline conditions by reducing the Na⁺:K⁺ ratio in the shoot. The shoot nitrogen content with 5 ppm Zn²⁺ and 20 ppm phosphate was equal to that of a non-saline control. No significant effect on nitrogenase activity was observed.     

In vitro growth of urinaryEscherichia coli related to siderophore production

Thirty seven strains ofEscherichia coli isolated from the urine of patients with acute symptomatic urinary tract infection were examined for siderophore production: hydroxamate (aerobactin) and phenolate (enterochelin). All the strains were found to produce varying amounts of enterochelin. With the chemical assay, 24.3% strains were aerobactin producers, while 43.2% were positive in the bio-assay. All the aerobactin producers carried the aerobactin receptor on their surface. Attempts to correlate siderophore production with growth in minimal and iron-depleted medium showed that there was a positive quantitative correlation between enterochelin production and growth of organisms under iron depletion. Aerobactin production failed to give an additional advantage of growth to strains producing enterochelin.     

Steady-state heat distribution in epidermis,dermis and subdermal tissues

Steady-state temperature distribution is investigated in human skin and subdermal tissue exposed to a dry and cool environment with negligible insensible perspiration. The mathematical model incorporates the effect of blood mass flow and metabolic heat generation. The rates of the two and the tissue thermal conductivity are assumed to have different values in all the three parts, namely epidermis, dermis and subdermal tissues. A simple variational finite element approach is used to find numerical values of the interface temperatures for a wide range of the values of skin surface temperature and for different thicknesses of the above parts. These values are used to obtain approximate temperature profiles in the whole region. The biological and physical implications of the results are also discussed.