Fine structural observations of sperm resorption in the seminal vesicle of a marine snail,Littorina scutulata (Gould, 1849)

Summary Waste sperm and spermatozeugmata in the seminal vesicle of Littorina scutulata are phagocytised either by cell buds (large vesicles given off from the epithelial cells) or by the epithelial cells themselves. Cell buds containing sperm, are in turn engulfed by epithelial cells. In both cases, heterophagic vacuoles are formed inside the cell and subsequently the vacuoles are fused with primary lysosomes or lysosomal derivatives to become secondary lysosomes. Throughout this process the sperm are being digested. The second lysosome transforms further to telolysosome and finally to residual body when the sperm is completely digested.     

The distribution of monoamine oxidase and acetylcholinesterase in the hypothalamus and its relation to the hypothalamo-hypophysial neurosecretory system in the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary The distribution of monoamine-oxidase and acetylcholinesterase activities in the hypothalamus of the White-crowned Sparrow has been studied in relation to the hypothalamohypophysial neurosecretory system. The enzyme activities, as revealed by the methods employed, are unaffected during photoperiodically induced testicular growth. Monoamine oxidase has a distribution distinctly different from that of the aldehyde-fuchsin positive neurosecretory material in that there is high activity in the peripheral palisade layers of both the anterior and posterior divisions of the median eminence. Intimate contact is made between these areas with the primary vessels of the hypophysial portal system. A second concentration of activity lies in a layer between the ependymal cells and the neurosecretory material of the fiber tract. In general, monoamine oxidase appears to be associated with glial elements and non-neurosecretory axons. The pars nervosa has little or no monoamine-oxidase activity. The distribution of acetylcholinesterase activity in the anterior division of the median eminence is very similar to that of the aldehyde-fuchsin positive neurosecretory neurons; however, acetylcholinesterase also occurs in the posterior division without associated neurosecretory fibers. These distribution of enzyme activities are considered in relation to possible adrenergic and cholinergic mechanisms in the median eminence.Dedicated to Professor Berta Scharrer in honor of her 60th birthday.Supported by grant NB-01353 from the National Institutes of Health to Professor Farner. This investigation was conducted while Doctor Kobayashi was a National Science Foundation Senior Foreign Scientist at Washington State University. We are indebted to Doctor Christian Da Lage, Laboratoire de Histologie, Falculté de Médecine de Paris, for the preliminary development of some of the techniques used in these investigations.     

Ischemia reperfusion dysfunction changes model-estimated kinetics of myofilament interaction due to inotropic drugs in isolated hearts

Background  

The phase-space relationship between simultaneously measured myoplasmic [Ca²⁺] and isovolumetric left ventricular pressure (LVP) in guinea pig intact hearts is altered by ischemic and inotropic interventions. Our objective was to mathematically model this phase-space relationship between [Ca²⁺] and LVP with a focus on the changes in cross-bridge kinetics and myofilament Ca²⁺ sensitivity responsible for alterations in Ca²⁺-contraction coupling due to inotropic drugs in the presence and absence of ischemia reperfusion (IR) injury.     

Antinociceptive and hypothermic effects of trimethyltin

Trimethyltin (TMT) induced a dose-dependent antinociceptive and hypothermic effect in mice. Antinociception was not attenuated by naloxone but was reversed by atropine. TMT, however, was ineffective in displacing (³H)-QNB binding $\text{in vitro}$ and did not affect (³H)-QNB binding or acetylcholinesterase activity after $\text{in vivo}$ administration. The ethyl ester of nipecotic acid, a specific inhibitor of synaptosomal GABA uptake, exerted a similar antinociceptive effect that could be blocked by atropine. The GABA receptor antagonist bicuculline attenuated antinociception induced by TMT and nipecotic acid ethyl ester but not by morphine or oxotremorine. γ-Vinyl GABA, an irreversible inhibitor of GABA metabolism, prolonged TMT but not morphine-induced antinociception. In contrast, neither the dose-response nor the time course of TMT-induced hypothermia were affected by any of the drugs tested. The findings suggest that the GABAergic system may be involved in TMT induced antinociception; however, the mechanism responsible for the hypothermic effect of TMT is not apparent.     

Differences in conformational stability between native and phosphorylated acetylcholinesterase as evidenced by a monoclonal antibody.

Monoclonal antibody 25B1 generated against diisopropyl phosphorofluoridate inhibited fetal bovine serum acetylcholinesterase has been extensively characterized with respect to its anticholinesterase properties. This antibody demonstrated considerably different properties from previously reported inhibitory antibodies raised against acetylcholinesterase in terms of the degree of inhibition (greater than 98%), the high degree of specificity, and the stability of the antigen-antibody complex. Monoclonal antibody 25B1 appears to be directed against a conformational epitope located in close proximity to the catalytic center of the enzyme and was found to be most suitable for studying the stabilization of the active site of acetylcholinesterase against denaturation by heat or guanidine following phosphorylation by organophosphorus anticholinesterase compounds. This approach allowed the determination of stability rank order of various phosphorylated acetylcholinesterases. Among all the organophosphates tested, the combination of a methyl group and a negatively charged oxygen attached to the P atom, CH3P(O)(O-)-AChE, conferred the greatest protection to the active site of aged or nonaged organophosphoryl conjugates of acetylcholinesterase.