Body water relations in two species of gerbil (Tatera indica indica andMeriones hurrianae) of the Indian desert

Summary The relative body water conservation efficiency of two Indian desert gerbil species,Meriones hurrianae (diurnal/crepuscular) andTatera indica (nocturnal), has been examined under near-natural conditons in different seasons.A mean urine osmolarity of 3180 mosmol/l (maximum 4645 mosmol/l) inM. hurrianae and a mean value of 5128 mosmol/l (maximum 7547 mosmol/l) inT. indica have been recorded during summer.Urine osmolarity and urea levels indicated that whileM. hurrianae remain sufficiently hydrated mainly by virtue of their feeding habit,Tatera indica may depend on the relatively higher concentrating capacity of their kidneys.     

The role of alpha-2u-globulin in corticosteroidogenesis in male rats

Administration of estradiol-17 beta for 7 days to the adult male rat results in adrenal hyperplasia, decreased serum corticosterone along with elevation in serum ACTH and inhibition of adrenal 5-ene-3 beta-hydroxysteroid dehydrogenase activity (5-ene-3 beta-HSD). Treatment with alpha 2u-globulin for following 14 days of estrogen-treated rats reversed the effects of estrogen while in normal rats alpha 2u-globulin treatment increased adrenal 5-ene-3 beta-HSD activity and serum corticosterone level while causing a fall in serum ACTH. It is concluded that alpha 2u-globulin may play a role in ACTH secretion by inducing corticosterone synthesis.     

Microtubule rearrangements during mitosis in multinucleate cells

The peroxidase-antiperoxidase (PAP) method for the detection of polymerized tubulin has been used to study the microtubule rearrangements during mitosis in PtK1 and HeLa multinucleate cells obtained by polyethyleneglycol (PEG)-mediated fusion. We demonstrate here that the transition of the microtubular cytoskeleton from interphase to mitosis is an inducible event and independent of the factor(s) responsible for chromatin condensation and nuclear envelope breakdown. However, for the induction of the microtubule rearrangements nuclear envelope breakdown is required. At midprophase, cytoskeletal microtubule rearrangements start for multinucleate PtK1 cells, whereas in HeLa cells such changes are delayed, and a more abrupt transition is observed here. After complete nuclear envelope breakdown (prometaphase) mitotic asters and spindles but no cytoplasmic (interphase) microtubuli can be observed in both systems. Metaphase is characterized by an interaction between the different mitotic poles which show the form of bipolar spindles, but individual separated mitotic poles far removed from the chromatin can also be seen.     

Purification and partial characterization of two azoreductases from Shigella dysenteriae Type 1

Two azoreductases (I and II) were purified to homogeneity from extracts of Shigella dysenteriae (type 1). Azoreductase I was a dimer of identical subunits of M(r) 28,000, whereas azoreductase II was a monomer of 11,000 M(r). Both were flavoproteins, each containing 1 mol of FMN per mol enzyme. Both NADH and NADPH functioned as electron donors for the azoreductases. Azoreductase I used Ponceau SX, Tartrazine, Amaranth and Orange II as substrates. Azoreductase II utilized all the dyes except Amaranth.     

Use of [1-14C]oleate labelled autoclaved Escherichia coli as a membranous substrate for measurement of in vitro phospholipase D activity.

Autoclaved Escherichia coli labelled with [1-14C]oleate in the 2-acyl position have been used extensively to measure phospholipase A2 activity in vitro. The present study demonstrates that this membranous substrate is also useful for the measurement of in vitro phospholipase D activity. Phospholipase D from Streptomyces chromofuscus catalyzed the hydrolysis of [1-14C]oleate labelled, autoclaved E. coli optimally at pH 7.0-8.0 to generate [14C]phosphatidic acid in the presence of 5 mM added Ca2+. Other divalent cations would not substitute for Ca2+. Activity was linear with time and protein up to 30% of the hydrolysis of substrate. Phospholipase D activity was stimulated in a dose-dependent manner by the addition of Triton X-100. The activity was increased 5.5-fold with 0.05% Triton, a concentration that totally inhibited hydrolysis of E. coli by human synovial fluid phospholipase A2. Accumulation of [14C]diglyceride was observed after 10 min of incubation. This accumulation was inhibited by NaF (IC50 = 18 microM) or propanolol (IC50 = 180 microM) suggesting the S. chromofuscus phospholipase D was contaminated with phosphatidate phosphohydrolase. Phosphatidic acid released by the action of cabbage phospholipase D was converted to phosphatidylethanol in an ethanol concentration dependent manner. These results demonstrate that [1-14C]oleate labelled, autoclaved E. coli can be used to measure phospholipase D activity by monitoring accumulation of either [14C]phosphatidic acid or [14C]phosphatidylethanol.     

Helix packing of leucine-rich peptides: a parallel leucine ladder in the structure of Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe.

The packing of peptide helices in crystals of the leucine-rich decapeptide Boc-Aib-Leu-Aib-Aib-Leu-Leu-Leu-Aib-Leu-Aib-OMe provides an example of ladder-like leucylleucyl interactions between neighboring molecules. The peptide molecule forms a helix with five 5----1 hydrogen bonds and two 4----1 hydrogen bonds near the C terminus. Three head-to-tail NH ... O = C hydrogen bonds between helices form continuous columns of helices in the crystal. The helicial columns associate in an antiparallel fashion, except for the association of Leu ... Leu side chains, which occurs along the diagonal of the cell where the peptide helices are parallel. The peptide, with formula C56H102N10O13, crystallizes in space group P2(1)2(1)2(1) with Z = 4 and cell parameters a = 16.774(3) A, b = 20.032(3) A and c = 20.117(3) A; overall agreement factor R = 10.7% for 2014 data with magnitude of F(obs) greater than 3 sigma (F); resolution 1.0 A.     

Response of V79 cells to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment: inhibition of poly(ADP-ribose) and topoisomerase activity.

MNNG-induced killing of V79 cells has been found to be enhanced on inhibition of topoisomerase II activity by nalidixic acid and poly(ADP-ribose) polymerase synthesis by benzamide. Using these 2 inhibitors in conjunction after MNNG treatment, some overlap in the functions of these 2 enzymes was observed. Nalidixic acid and benzamide were found to suppress the yields of mutations and SCEs induced by MNNG. Benzamide was more effective in suppressing the mutation yield whereas nalidixic acid was more effective in suppressing SCEs. A model based on the relative requirement of topoisomerase and poly(ADP-ribose) for the repair of different types of damage has been proposed to explain the results.     

Further observations of stage-specific effects seen after short-term hypophysectomy in the rat.

Although hypophysectomy has been a popular tool to study the effects of hormone deprivation as well as concomitant or subsequent hormone supplementation, there is relatively little morphological information available on the structural manifestation of pituitary removal on the testis. In the report, changes, in addition to those previously reported after short-term (6 days) hypophysectomy in the rat (Russell and Clermont, 1977), are described. Membrane-bound vacuoles (primarily) appeared within the basal region of the Sertoli cell at approximately the level of Sertoli-Sertoli junctions. In stages VIII through XI elongating spermatids were abnormal and manifested manchette indentation of the nucleus, a variety of other abnormal head shapes, acrosomal breaks and enlargement of the subacrosomal space. These defects were interpreted as the effect of declining hormonal levels in stage VII on spermatids that had survived the stage VII hormone sensitivity known to occur with severe hormone depletion. Abnormalities in the flagellum involving the mitochondrial sheath and fibrous sheath were detected. Preleptotene spermatocytes degenerated and could be identified in the process of doing so near the base of the seminiferous epithelium. The contact of preleptotene spermatocytes with the basal lamina was also significantly reduced. The results show that both Sertoli cell and germ cell abnormalities were present although germ cell abnormalities could be a secondary consequence of lack of appropriate stimulation of the Sertoli cell. Degeneration of basal compartment germ cells shows that germ cells other than those located in the adluminal compartment are vulnerable to hormonal withdrawal. The question of how hormone effects are mediated in the testis at midcycle to produce these effects is discussed.