Antagonism by thyrotropin-releasing hormone (TRH) of pentobarbital-induced hypothermia in rats with brain lesions

Summary Anesthesia with a large dose of pentobarbital (55 mg/kg, i.p.) caused a sustained decrease in brain temperature (Tb), which was monitored with a probe placed in the midbrain reticular formation. The administration of TRH to the lateral ventricle antagonized this hypothermia. None of the acute surgeries examined in this paper (adrenal-demedullectomy, septal knife cuts, electrolytic lesions of the hypothalamus and midbrain knife cuts) had any essential effect on this antagonism by TRH. These results suggest that centrally-administered TRH exerts its effect on thermoregulation, at least in part, through brain structure(s) caudal to the midbrain.     

A novel class (H3) of histamine receptors on perivascular nerve terminals

Two types of histamine receptor, the H1- and H2-receptors, are found not only on vascular smooth muscle cells but on the perivascular autonomic nerve terminals. Activation of the prejunctional histamine receptors modifies transmitter release from the nerve terminals. Recently, histamine was shown to inhibit its own release from depolarized slices of rat cerebral cortex. This phenomenon was found to be mediated by a novel class of histamine receptor, the H3-receptor, that was pharmacologically distinct from the H1- and H2-receptors. Up to now, there has been no indication whether this third class of histamine receptor is present in any tissue other than the brain. We report here that histamine depresses sympathetic neurotransmission in the guinea-pig mesenteric artery by interacting with histamine H3-receptors on the perivascular nerve terminals. The pharmacological properties of these receptors are similar to those reported for the H3-receptors in the brain. Our data provide evidence for the existence of H3-receptors in the autonomic nervous system.     

Intraperitoneal growth pattern of murine teratocarcinomas

Summary Ascitic teratocarcinomas showed a unique growth pattern, suggesting size regulation in the peritoneal cavity of syngeneic 129/Sv mice.     

Aging clock: the watchmaker’s masterpiece

The phenomenon of cellular senescence has been known for almost four decades. Yet, until very recently, the molecular mechanisms that lead to senescence have been poorly understood. However, substantial progress has been made in the last few years toward identifying the pathways executing senescence. This r view focuses on two major advances in this field, the telomere aging clock theory and the cell cycle regulatory mechanisms in senescent cells. These recent studies indicate that cellular senescence is a highly elaborate and active process, which presumably works as an anti-oncogenic mechanism.     

Rapid and reversible shape changes of molecular crystals on photoirradiation

The development of actuators based on materials that reversibly change shape and/or size in response to external stimuli has attracted interest for some time. A particularly intriguing possibility is offered by light-responsive materials, which allow remote operation without the need for direct contact to the actuator. The photo-response of these materials is based on the photoisomerization of constituent molecules (typically trans-cis isomerization of azobenzene chromophores), which gives rise to molecular motions and thereby deforms the bulk material. This effect has been used to create light-deformable polymer films and gels, but the response of these systems is relatively slow. Here we report that molecular crystals based on diarylethene chromophores and with sizes ranging from 10 to 100 micrometres exhibit rapid and reversible macroscopic changes in shape and size induced by ultraviolet and visible light. We find that on exposure to ultraviolet light, a single crystal of 1,2-bis(2-ethyl-5-phenyl-3-thienyl)perfluorocyclopentene changes from a square shape to a lozenge shape, whereas a rectangular single crystal of 1,2-bis(5-methyl-2-phenyl-4-thiazolyl)perfluorocyclopentene contracts by about 5-7 per cent. The deformed crystals are thermally stable, and switch back to their original state on irradiation with visible light. We find that our crystals respond in about 25 microseconds (that is, about five orders of magnitude faster than the response time of the azobenzene-based polymer systems) and that they can move microscopic objects, making them promising materials for possible light-driven actuator applications.     

Intraperitoneal growth pattern of murine teratocarcinomas

Ascitic teratocarcinomas showed a unique growth pattern, suggesting size regulation in the peritoneal cavity of syngeneic 129/Sv mice.     

Novel and sensitive noncompetitive enzyme immunoassay for kassinin in rat plasma

Summary A novel and sensitive noncompetitive enzyme immunoassay for kassinin is described. Kassinin was biotinylated using sulfosuccinimidyl-6-(biotinamido)hexanoate. The biotinylated kassinin was trapped on antikassinin IgG-coated polystyrene balls and, after washing to eliminate other biotinylated substances, was eluted with HCl. The biotinylated kassinin eluted was reacted with anti-kassinin Fab'-peroxidase conjugate and trapped onto streptavidin-coated polystyrene balls. Peroxidase activity bound to the polystyrene balls was assayed by fluorimetry. The detection limit of kassinin was 0.13 pg (0.1 fmol)/tube or 0.065 g/l of rat plasma, which was 750-fold or 15-fold lower than that for competitive radioimmunoassay.     

Essential role for phosphatidylinositol 4,5-bisphosphate in yeast cell proliferation

The responses of mammalian cells to external signals are commonly mediated by intracellular secondary messengers, among which are the breakdown products of phosphatidylinositol 4,5-bisphosphate (PIP2): 1,2-diacylglycerol (DG) and inositol 1,4,5-triphosphate (IP3) (refs 1-7). Although phosphoinositide turnover in the yeast Saccharomyces cerevisiae has been shown to be regulated by glucose and sterol, as yet no definitive function has been ascribed to yeast phosphoinositides. We have recently developed a monoclonal antibody specific for PIP2 and reported that it inhibits mitogenesis of mammalian cells stimulated by platelet-derived growth factor and bombesin. We now report that when introduced into yeast cells by electroporation this antibody inhibits their growth. Furthermore, several yeast mutants with temperature-dependent growth defects are altered in their sensitivity to our antibody and are found to have specific alterations in their phosphoinositide metabolism.