New place and new object reactions in the brown spiny mouse,Mus platythrix Bennett

The behavioural response of the brown spiny mouse, Mus platythrix Bennett to new place and new object was studied in a plus (+) maze. The new place reaction was observed by allowing the mice to access an area which had previously been not exposed to them and the new object reaction was studied by introducing a change at the feeding point. The experiment suggested new place philia and new object philia in this species.     

Adrenocorticotrophin secreting cells in the hypophysis of the brown spiny mouseMus platythrix (Bennett)

Adrenocorticotrophin secreting cells are identified in the hypophysis of the brown spiny mouseMus platythrix by conventional methods of light microscopy. Quantitative data showed that certain smaller acidophilic cells in thepars distalis, under conditions provoking their hypersecretion such as unilateral adrenalectomy and metopirone treatment, increase in number and size from the pre-existing corticotrophs. There is no evidence for the transmigration of these cells from the chromophobes, basophils or any other cell type. Thepars intermedia revealed two types of cells of which the type II cells are histochemically identical to adrenocorticotrophin secreting cells of thepars distalis     

Prolactin secreting cells in the hypophysis of the brown spiny mouseMus platythrix (Bennett)

Prolactin secreting cells are identified in thepars distalis of Mus platythrix by conventional methods of light and electron microscopy. Two types of prolactin secreting cells are recognised. These types are estrone-sensitive, mammotrophic type I, and luteotrophic type II, respectively. Histochemical analysis revealed that the cells are rich in RNA, basic proteins, alkaline phosphatase and are resistant to extraction with 0·5% trichloroacetic acid. Quantitative data showed that the prolactin secreting cells increase during pregnancy, lactation and estrone treatment. Estrone at low dose levels caused immense hyperplasia whereas at higher levels there was no corresponding increase in the percentage of type I cells. Ultrastructurally, prolactin secreting cells are characterised by the presence of stacked endoplasmic reticulum, oval or irregular secretory granules. The Golgi apparatus is seen rich in vacuolar system.     

Effect of deuterium oxide on actomyosin motility in vitro.

Actin filament velocities in an in vitro motility assay system were measured both in heavy water (deuterium oxide, D(2)O) and water (H(2)O) to examine the effect of D(2)O on the actomyosin interaction. The dependence of the sliding velocity on pD of the D(2)O assay solution showed a broad pD optimum of around pD 8.5 which resembled the broad pH optimum (pH 8.5) of the H(2)O assay solution, but the maximum velocity (4.1+/-0.5 microm/s, n=11) at pD 8.5 in D(2)O was about 60% of that (7.1+/-1.1 microm/s, n=11) at pH 8.5 in H(2)O. The K(m) values of 95 and 80 microM and V(max) values of 3.2 and 5.1 microm/s for the D(2)O and H(2)O assay were obtained by fitting the ATP concentration dependence of the velocity (at pD and pH 7.5) to the Michaelis-Menten equation. The K(m) value of actin-activated Mg-ATPase activity of myosin subfragment 1 (S1) was decreased from 50 microM [actin] in H(2)O to 33 microM [actin] in D(2)O without any significant changes in V(max) (9.4 s(-1) in D(2)O and 9.3 s(-1) in H(2)O). The rate constants of ADP release from the acto-S1-ADP complex measured by the stopped flow method were 361+/-26 s(-1) (n=27) in D(2)O and 512+/-39 s(-1) (n=27) in H(2)O at 6 degrees C. These results suggest that the decrease in the in vitro actin-myosin sliding velocity in D(2)O results from a slowing of the release of ADP from the actomyosin-ADP complex and the increase in the affinity of actin for myosin in the presence of ATP in D(2)O.     

Ultrastructural immunocytochemistry of gonadotrophs in the goldfish pituitary gland

Summary The immunocytochemical distribution of gonadotropin (GTH) in the goldfish pituitary gland was studied applying the peroxidase-antiperoxidase (PAP) method and the protein A-gold technique at lightand electron-microscopic levels, respectively, with an antiserum raised against silver carp GTH. In the light-microscopic immunocytochemistry, PAS-positive cells in the proximal pars distalis showed strong reaction with the antiserum. Gold particles were concentrated both on globules (large) and on granules (small) of the gonadotrophs (PAS-positive cells) in the electron-microscopic immunocytochemistry. Other cells in the pituitary gland, including thyrotrophs, displayed no immunoreactivity with the antiserum at the dilutions tested. These results indicate, not only immunocytochemical distribution of GTH both in globules and in granules in the gonadotrophs, but also the high purity of the antigen (silver carp GTH) and specificity of the antiserum.     

Effect of phorbol ester on stimulus-secretion coupling mechanisms in gonadotropin releasing hormone-stimulated pituitary gonadotrophs

The feedback regulatory control mechanism exerted by activated Ca2+/phospholipid-dependent protein C kinase upon gonadotropin releasing hormone (GnRH) binding, stimulation of phosphoinositide turnover and gonadotropin secretion was investigated in cultured pituitary cells. Addition of the tumor promoter phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), at concentrations which activate pituitary protein C kinase, to cultured pituitary cells resulted in up-regulation of GnRH receptors (155% at 4 h). The stimulatory effect of GnRH on [3H]inositol phosphates (Ins-P) production in myo-[2-3H]inositol prelabeled pituitary cells was not inhibited by prior treatment of the cells with TPA (10(-9)-10(-7) M). Higher concentrations of TPA (10(-6)-10(-5) M) inhibited the effect of GnRH on [3H]Ins-P production. Increasing concentrations of TPA or the permeable analog of diacylglycerol 1-oleoyl-2-acetylglycerol (OAG) stimulated luteinizing hormone (LH) release from cultured pituitary cells with ED50 values of 5 x 10(-9) M and 10 micrograms/ml, respectively. No consistent inhibition or additivity of LH release was observed when increasing doses of TPA or OAG were added with a submaximal dose of GnRH. These results suggest that protein C kinase might mediate the known homologous up-regulation of GnRH receptors during the reproductive cycle. Protein C kinase is positively involved in mediating the process of gonadotropin secretion. Unlike many other systems, activation of protein C kinase in pituitary gonadotrophs is not involved in negative feed-back regulation of stimulus-secretion-coupling mechanisms in GnRH-stimulated gonadotrophs.     

Quantitative immunocytochemical studies on the gonadotrophs isolated from the pituitary of the male rat

Summary Quantitative studies on the population of the gonadotropic cells in the pituitary of adult male rats were performed after trypsic dissociation of the pituitary glands and immunoenzymatic staining with anti--LH or anti--FSH antisera. Number, area and extinction of labelled cells were measured by use of an image analyser and a cytophotometer. The gonadotrophs represent approximately 14% of the pituitary cells. The mean area of gonadotrophs is significantly larger after staining with anti--LH serum than after staining with anti--FSH serum. Planimetric measurement of the gonadotrophs reveals their variability in size ranging between 30 and 160 m². Moreover, the size distribution depends on the staining serum used: more numerous small-sized cells (<75 m²) are stained with anti--FSH serum than with anti--LH serum, which conversely stains more numerous large-sized cells. Cytophotometric measurements indicate that immunostaining varies greatly among cells of the same size class and that the staining intensity appears to increase according to the cell size. These results emphasize the morphofunctional heterogeneity of the gonadotropic cell population.     

Studies on salmonellosis in the house mouse, Mus musculus.

Salmonellae were isolated from the faeces from 17 of 170 (10%) wild house mice. Salmonella typhimurium was isolated from 10, S. typhimurium, var. Copenhagen from 2, S. thompson from 1, and S. muenchen from 4. It was concluded that house mice could be a reservoir of infection and play an important role in human and animal salmonellosis.     

A study of gramicidin using deuterium oxide.

The single channel conductivity of the gramicidin channel has been measured for all the alkali ions using both H2O and 2H2O as a medium. Significant changes in conductivity with medium have been observed in all cases except lithium.     

Effect of deuterium oxide on gastrin release from rat antral mucosal fragments

The effects of the microtubule stabilizing agent, deuterium oxide, on in vitro rat antral gastrin release were examined under basal conditions and during stimulation with isobutyl methylxanthine and bombesin plus isobutyl methylxanthine. Basal gastrin release from antral mucosal fragments was unaffected by increasing media concentration of deuterium oxide (12.5 to 75% v/v) during 1 h incubations. Gastrin release stimulated by isobutyl methylxanthine (0.1 mM), a potent inhibitor of phosphodiesterase activity, was inhibited completely by 12.5% deuterium oxide. Bombesin (1 × 10^?8 M) in the presence of IBMX (0.1 mM) stimulated gastrin release (29.7 ± 1.9% of total gastrin). This was significantly greater than gastrin released under control conditions and with IBMX alone: 12.0 ± 1.1 (P < 0.001) and 20.2 ± 2.6% of total gastrin (P < 0.02), respectively. Partial inhibition of bombesin-IBMX stimulated gastrin release was achieved with 12.5% and 25% deuterium oxide and stimulation of gastrin release was inhibited completely by 50% deuterium oxide. In contrast to these results, gastrin release stimulated by the calcium ionophore A23187 was not inhibited by 50% deuterium oxide. Additional studies were performed to assess reversibility of the effects of deuterium oxide on stimulated gastrin release. Antral tissue exposed to initial culture medium containing deuterium oxide (50%) and bombesin-IBMX for 60 min was exchanged for medium without deuterium oxide. Restimulation of antral tissue during the second hour of culture resulted in gastrin release that was comparable to that observed in cultures not exposed to deuterium oxide during the first hour of culture. Reversibility of the effects of deuterium oxide suggest that a functional alteration in microtubular function is restored by removal of heavy water from the culture medium. Results of these experiments indicate that deuterium oxide is capable of inhibiting gastrin release stimulated by the peptide hormone bombesin and by the phosphodiesterase inhibitor isobutyl methylxanthine. Furthermore, these results suggest that increased levels of intracellular calcium achieved by the action of ionophore A23187 prevent microtubular stabilization by deuterium oxide.     

The effects of deuterium oxide on bacteria

Summary The growth of several strains of bacteria was inhibited by D₂O-media. The degree of inhibition was strain specific. The incorporation of 0.5% NaCl (w/v) to the D₂O-medium decreased the inhibition of growth. No adaptation to better growth in deuterium was obtained in any of the strains tested; however a deuterium resistant mutant was obtained from one strain. Two strains tested formed enlarged, distorted cells when grown for more than eight generations in D₂O-media. Cells grown in D₂O-media and washed and resuspended in H₂O-0.85% NaCl (w/v), were up to sixty times more sensitive to ultraviolet irradiation than control cells. Deuterium induces the occurrence of forward mutants in some strains. Many loci, but not all, showed an increase in the back-mutation rate over the spontaneous level, indicating some specificity of action by deuterium. Deuterated bases, obtained from a strain grown in D₂O-medium, did not induce any phenotypic or genotypic effects when supplied to specific baserequiring strains. The amout of deuterium incorporated into the bacteria may be related to the mutagenic effect induced. The genotypic and phenotypic effects induced by deuterium are probably the result of an overall isotope effect.With 2 Figures in the TextThe work reported here was supported by the Atomic Energy Commission research grant AT(30-1) 2184 to Dr.Stephen Zamenhof, Columbia University. This work was submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Faculty of Pure Science, Columbia University.I dedicate this paper to Prof.L. C. Dunn with thanks for his enthusiastic and inspiring instruction.     

Effect of weaning time on the growth rate and food intake of the spiny mouse pup

The spiny mouse Acomys cahirinus produces well-developed pups although it is a relatively small mammal (45 g). We envisioned two opposing hypotheses on the effect of early weaning on the growth rate of pups. The first predicts little effect since the increase in energy intake of dams above non-reproducing females is relatively low, suggesting that pups consume a large portion of their energy as solid food, and the pups are very well developed at birth. The second predicts a substantial effect since the 'index of precociality', that is the energy intake for maintenance of a pup as a proportion of that predicted for a rodent of its body mass, falls within values for altricial rodents, suggesting an extended maternal dependence of the young. To test these hypotheses, we measured the growth rate and food intake of pups weaned after either 7, 14, 21 or 28 days. Only three of 12 pups weaned after 7 days survived and, consequently, the latter hypothesis was supported. All pups weaned at 14–28 days survived. There was a significant decrease in growth rate during the first day after weaning in pups weaned at 7, 14 and 21 days but not after 28 days, suggesting that pups did not require parental care by day 28. Peak growth rate in pups weaned at 14 days occurred in the second week but occurred in the third week in pups weaned at 21 and 28 days. In spite of these differences, pups in all treatments had similar body mass at 64 days, indicating compensatory growth. We concluded that pups of A. cahirinus are precocial from a morphological aspect in that they are well developed at birth but altricial from a nutritional aspect in that they require extended maternal support.