Age-related changes of the pattern of non-histone proteins in active and condensed fractions of mouse liver chromatin and hepatocarcinoma

Summary Electrophoretic analysis of histones and non-histone acid-soluble proteins in active (nuclease sensitive) and inactive chromatin from liver of young and old CBA mice and in age-related hepatocarcinomas showed a higher ratio of NHP: histones in active chromatin in old cells. Some liver- and hepatoma-specific fractions of non-histone proteins have been identified as chromatin matrix proteins.     

Identification of a pre-hibernating state in myocardium from nonhibernating chipmunks

Summary During the hibermating season, the amplitude of the cardiac action potential plateau of nonhibernating chipmunks was reduced. Replacing external Ca by Sr inhibited the electromechanical responses of these preparations. Similar properties were observed in hibernating animal preparations, suggesting that changes in cardiac function are already triggered before hibernation begins.15 December 1986     

Interferon enhances 2-5A synthetase in embryonal carcinoma cells

Mouse teratocarcinomas provide a useful model of mammalian differentiation, because the malignant embryonal carcinoma (EC) stem cells of such tumours may produce various differential cell types in vivo or in vitro. Many EC cell lines have now been established and classified on the basis of their ability to differentiate in vivo into cell types characteristically derived from any of the three germ layers. There is convincing evidence that EC cells can neither produce interferon, nor respond to it by becoming resistant to virus, whereas differentiated cells derived from EC lines behave normally in both respects. We investigated the lack of responsiveness of EC cells towards interferon by measuring the levels of two double-stranded RNA-dependent enzyme activities recently shown to be enhanced by interferon. We report here that on treatment with interferon, EC cells show increased 2-5A synthetase levels comparable to those found in differentiated cells, while there is little or no effect on kinase activity in EC cells, in contrast to their differentiated counterparts.     

The effect of mouse erythrocyte rosette forming lymphocytes on lymphokine production in T-cell cultures

Summary An enhancement effect of mouse erythrocyte rosette forming (MERF) cells on the production of migration inhibitory factor, chemotactic factor for neutrophils and skin reactive factor in T-lymphocyte cultures stimulated with the purified protein derivative of tuberculin was observed. We consider it likely that the MERF cells, possessing the appropriate cell surface constituents to construct an immunogenic moiety, present antigen on their surfaces to elicit lymphokine production.This work was supported by the Scientific Research Council, Ministry of Health, Hungary, Code No. 421030401 1/s     

Gonadotropin-releasing hormone analogue binds to luteal cells and inhibits progesterone production.

Although gonadotropin-releasing hormone (GnRH) is believed to mediate the hypothalamic control of pituitary gonadotropin secretion, continuous or repeated administration of GnRH or its agonist analogues has been shown to cause paradoxical antifertility effects in several species, including primates. GnRH-induced interruption of reproductive cycles and pregnancy is associated with diminished progesterone production, implying defective function of the corpus luteum. These luteolytic effects have been attributed to the well recognized desensitising actions of elevated luteinising hormone (LH) levels on ovarian LH receptors and steroidogenesis, subsequent to GnRH-induced gonadotropin release from the anterior pituitary. However, treatment with high doses of exogenous LH did not cause suppression of serum progesterone levels during early pregnancy in rats, whereas a highly active GnRH analogue was effective in this regard. These observations suggested that GnRH and its agonist analogues, given in high or sustained doses, can exert a direct action on the ovary that is independent of the pituitary. This hypothesis was further supported by the ability of GnRH and its agonists to inhibit human chorionic gonadotropin (HCG)-induced ovarian and uterine weight gain in hypophysectomised rats and to delay the onset of puberty in intact female rats. Also, GnRH and its agonist analogues have recently been shown to inhibit steroidogenesis induced by follicle-stimulating hormone (FSH) in cultured granulosa cells, confirming the direct action of such peptides on the ovarian follicle. The marked inhibitory effects of GnRH and its agonists on corpus luteum function suggest that these compounds could exert direct actions by binding to specific receptors on luteal cells. The present experiments, which examine the effects of GnRH agonists on luteal steroidogenesis, demonstrate the existence of such actions and their mediation by specific high-affinity receptor sites present in luteal cell membranes.     

Effect of physical exercise on the specific activity of carbonic anhydrase isozyme in human erythrocytes

Summary Significant decreases in the levels of both carbonic anhydrase type B and total esterase activity of human erythrocytes were observed after physical exercise (bicycle ergometer, 150 W for 30 min). Since carbonic anhydrase B-dependent esterase activity likewise decreased, the decrease in the total esterase activity would be caused by the decrease of carbonic anhydrase B activity. The specific activity of carbonic anhydrase B tended to decrease after the exercise. On the other hand no such effects were noted for carbonic anhydrase type C.     

Starfish encounters: An experimental study of its advantages

Summary The predatory starfishCrossaster papposus exploits a chemically mediated escape response in another predatory starfishAsteria rubens when a common food resource is available to both species. Intraspecific avoidance amongC. papposus is strong and functions in dispersal. Responses to inter- and intraspecific encounters among starfish may be important to the predatory ecology of species in high positions in their food webs.I thank the MAFF. Fisheries Lab., Burnham-on-Crouch for hospitality and facilities, Prof. N.B. Marshall, F.R.S. and Dr A.C. Campbell for laboratory facilities at Q.M.C.     

Appearance of sperm activation factors in the ovary of the sea urchinHemicentrotus pulcherrimus with maturation

Summary Ovaries of the sea urchinHemicentrotus pulcherrimus were extracted with 70% ethanol. The extracts were polarographically assayed for respiration-stimulating activity toward homologous spermatozoa. The data of the bioassay and light microscopic observation on thin sections of the ovaries showed detectable activity only in mature ovaries.We thank the Misaki Marine Biological Station for kindly supplying us with specimens. This work was supported in part by a grant from the Ministry of Education, Science and Culture of Japan.