Neuropeptide Y inhibition of calcium channels in PC-12 pheochromocytoma cells

We previouslydemonstrated, using rat PC-12 pheochromocytoma cells differentiated toa sympathetic neuronal phenotype with nerve growth factor (NGF), thatneuropeptide Y (NPY) inhibits catecholamine synthesis as well asrelease. Inquiry into the mechanisms of these inhibitions implicateddistinct pathways involving reduction ofCa²⁺ influx throughvoltage-activated Ca²⁺ channels.In the present investigation the effects of NPY on whole cellBa²⁺ currents were examined toobtain direct evidence supporting the mechanisms suggested by thosestudies. NPY was found to inhibit the voltage-activatedBa²⁺ current in NGF-differentiatedPC-12 cells in a reversible fashion with anEC₅₀ of 13 nM. This inhibition waspertussis toxin sensitive and resulted from NPY modulation of L- andN-type Ca²⁺ channels. Theinhibition of L-type channels was not seen with <1 nM freeintracellular Ca²⁺ or when proteinkinase C (PKC) was inhibited by chelerythrine or PKC-(1931).Furthermore, the effect of NPY on L-type channels was mimicked by thePKC activator phorbol 12-myristate 13-acetate. These studiesdemonstrate that, in addition to inhibition of N-type Ca²⁺ channels, inNGF-differentiated PC-12 cells NPY inhibits L-type Ca²⁺ channels via an intracellularCa²⁺- and PKC-dependent pathway.

     

Glucose Catabolism of Erysipelothrix rhusiopathiae

The pathways of glucose catabolism in Erysipelothrix rhusiopathiae have been identified by the radiorespirometric technique. The radiorespirometric data showed that 96% of the glucose catabolism was via the Embden-Meyerhof-Parnas pathway with the remaining 4% dissimilated by the hexose monophosphate pathway. The products of the anaerobic dissimilation of glucose were determined. Lactic acid was the major product; ethyl alcohol, acetic acid, formic acid, and carbon dioxide were formed in smaller amounts.     

利用AFLP遗传连锁图定位大麦苗期对叶锈病的部分抗性基因

借助大麦染色体ＡＦＬＰ标记遗传连锁图和ＭａｐＱＴＬＶ３．０作图软件,对大麦叶病的数量抗性基因进行了定位分析,明确了大麦部分抗性品种Ｖａｄａ对叶锈病的潜育期由分别位于染色体１、２、６、７上离短臂末端７９ｃＭ、１８６ｃＭ、５８ｃＭ和１１７ｃＭ处的４个数量抗性基因所控制。     

TREATMENT OF RAT PROXIMAL AND DISTAL COLONIC CELLS WITH SODIUM ORTHOVANADATE ENHANCES THEIR ADHESION AND SURVIVAL IN PRIMARY CULTURE

We have studied the effect of sodium orthovanadate, an inhibitor of protein tyrosine phosphatases, on primary cultures of colonocytes and stromal cells. Everted proximal and distal colonic tissue of adult rats were disintegrated by a collagenase/dispase solution for 60 min at 37°C to prepare viable gland fragments and isolated cells. Cell preparations were inoculated onto plastic substratum or cytodex-3 microcarriers in a defined maintenance medium or in 1% fetal calf serum media. Incorporation of sodium orthovanadate (≥50 μm) in these media constantly enhanced the survival (cell enumeration and trypan blue exclusionP<0.05) and the adhesion (up to four-fold by crystal violet staining,P<0.01) of colonocytes (characterized by cytokeratin-18, transforming growth factor-α or alkaline phosphatase expression) and stromal cells. Removal of sodium orthovanadate from culture media restored cellular death processes. Incorporation of 10 mmn-butyric acid did not promote cell adhesion and survival except for distal cells exposed to 2 mm sodium orthovanadate. Besides studies in the regulation of anoikis in primary culture, the model will help to assay the influences of dietary and growth factors on the biology of non-cancerous colonic cells.     

Sympathomimetic enantiomers and asthma

Airways of asthma patients can become hyperresponsive to airway spasmogens following regular use of isoprenaline or β₂-selective sympathomimetics. Hyperreactivity that results from acute exposure of animals to these drugs is pre-empted by vagal section (a procedure which does not influence spasmolytic efficacy of sympathomimetics), is not diminished by antagonism of β₂-adrenoceptors and is not associated with loss of responsivity of β₂-adrenoceptors in the airways. Since activation, modulation, or blockade of β₂-adrenoceptors does not determine this form of hyperreactivity, the possibility that distomers may induce hyperreactivity must be considered. Ocular and vascular responses to distomers of sympathomimetics have long been recognised and, more recently, comparable observations have been made for the airways. Thus, reactivity of guinea-pig airways to spasmogens was increased following exposure to S-isoprenaline, S-salbutamol, or S-terbutaline and exposure to S-isoprenaline or S-salbutamol can intensify symptoms in asthmatics. Regular exposure to the racemate, especially during or following an allergic reaction, predisposes to expression of hyperreactivity, which is nullified, acutely, by the eutomer. These observations imply that biological effects of sympathomimetic distomers may contribute to morbidity and mortality in asthma patients. Chirality 10:262–272, 1998. © 1998 Wiley-Liss, Inc.     

Benefits of polyandry: Molecular evidence from field‐caught dung beetles

When females mate with multiple males, they set the stage for postcopulatory sexual selection via sperm competition and/or cryptic female choice. Surprisingly little is known about the rates of multiple mating by females in the wild, despite the importance of this information in understanding the potential for postcopulatory sexual selection to drive the evolution of reproductive behaviour, morphology and physiology. Dung beetles in the genus Onthophagus have become a laboratory model for studying pre‐ and postcopulatory sexual selection, yet we still lack information about the reproductive behaviour of female dung beetles in natural populations. Here, we develop microsatellite markers for Onthophagus taurus and use them to genotype the offspring of wild‐caught females and to estimate natural rates of multiple mating and patterns of sperm utilization. We found that O. taurus females are highly polyandrous: 88% of females produced clutches sired by at least two males, and 5% produced clutches with as many as five sires. Several females (23%) produced clutches with significant paternity skew, indicating the potential for strong postcopulatory sexual selection in natural populations. There were also strong positive correlations between the number of offspring produced and both number of fathers and paternity skew, which suggests that females benefit from mating polyandrously by inciting postcopulatory mechanisms that bias paternity towards males that can sire more viable offspring. This study evaluates the fitness consequences of polyandry for an insect in the wild and provides strong evidence that female dung beetles benefit from multiple mating under natural conditions.