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151.
Summary In the spider Dinopis, retinae of the posterior median eyes synthesise new photoreceptor membrane in bulk at dusk and destroy it at dawn (Blest, 1978). During the dawn period, there is a rapid, anticipatory differentiation of unusual organelles from the rough endoplasmic reticulum (RER) in the intermediate segments of the receptors. This system is classified as GERL. Its products appear to play a role in the autolysis of photoreceptor membrane. Consistent topographical relationship to Golgi bodies has not been determined. Circumscribed regions of RER whorls first reorganise to yield fenestrated profiles; these differentiate further to a number of structures by condensation and loss of ribosomes. Smooth tubular profiles are termed rigid tubules to indicate their probable homology with the rigid lamellae of vertebrate secretory cells. More complex smooth multilocular bodies are also produced. Evidence is discussed which implies that both rigid tubules and multilocular bodies give rise to condensing vacuoles. These, in turn, pinch off coated vesicles assembled as Nebenkerne. Some rigid tubules are transported to the interrhabdomeral cytoplasm of the receptive segments. At late stages of differentiation, rigid tubules, multilocular bodies and Nebenkerne give strong, positive responses to zinc iodide-osmium tetroxide (ZIO) treatment; early stages and both cis and trans Golgi components do not. GERL differentiation is independent of immediate illumination of the retina at dawn. It is suggested to mediate the lysis of membrane degradation products by the production of hydrolases.We thank Professor D.T. Anderson F.R.S. for our use of field facilities at the Crommelin Biological Field Station of Sydney University at Warrah, Pearl Beach, N.S.W., and Andrew and Sally Austin and Sally Stowe for help in the field. We are indebted to Rod Whitty and the Electron Microscopy Unit for advice and support throughout these studies 相似文献
152.
Peter H. Byers Karen A. Holbrook Judith G. Hall Paul Bornstein John W. Chandler 《Human genetics》1978,40(2):157-169
Summary Several individuals from one family are described with a unique form of spondyloepiphyseal dysplasia. Characteristic features include shorttrunked short stature, punctate corneal dystrophy and marked disorganization of dermal collagen fibrils when examined by transmission electron microscopy. Inheritance is compatible with either dominance and a variable expression or X-linkage. Although the basic defect has not been determined, the tissue distribution is consistent with a defect in a non-collagenous component that affects collagen fibril formation or stability. 相似文献
153.
154.
Robert L. Trelstad Karen R. Lawley 《Biochemical and biophysical research communications》1977,76(2):376-384
Neutral solutions of pepsin extracted human collagens derived from glomeruli, kidney, aorta, lung, heart, bowel, spleen, skeletal muscle and skin were subjected to heat gelation at 37°C. Centrifugation of the gel provided two fractions: gelled pellet and non-gelled supernatant. Analysis of these two fractions by gel electrophoresis, molecular sieve and ion exchange chromatography, and amino acid and carbohydrate determinations indicated that the non-gelled supernatant contained a substantial enrichment of basement membrane like collagen. The initial characterization of lung derived basement membrane collagen indicated close similarities with those derived from glomeruli and whole kidney and differences with that obtained from the spleen. 相似文献
155.
156.
Robert E. Hruska Karen T. Pitman Ellen K. Silbergeld Lynn M. Ludmer 《Life sciences》1982,30(6):547-553
Administration of prolactin to adult male rats, by s.c. injection, significantly increases the density of the striatal dopamine (DA) receptors, without altering the apparent affinity of the receptors for [3H]spiroperidol. Larger doses of prolactin are required to increase the density of the striatal DA receptors in hypophysectomized rates compared to normal rats. These results suggest that prolactin might be the common mediator of the increase in striatal DA receptor density produced by either estrogen or haloperidol administration. Monitoring and/or altering prolactin levels might be informative in neurologic or psychiatric disorders involving striatal DA neurotransmission. 相似文献
157.
158.
A study of the mechanism of action of cytochalasin A (CA) in relation to its structural features and to its selective inhibition of certain contractile processes has been initiated. Quantitative structure-function analyses with several CA-related cytochalasins — including synthetic 21, 22-dihydro-CA (DHCA), the 22-β-mercaptoethanol CA-adduct, (CA-2ME), and the 22-dithiothreitol CA-adduct (CA-DTT) — have been carried out in a temperature sensitive gel-sol extract from Ehrlich ascites tumor cells. Each drug congener was purified to homogeneity by HPLC prior to biological testing. The undiminished inhibitory indices of DHCA and CA-2ME overrules the prior circumstantial evidence accumulated for the obligatory electrophilic interaction of this drug, at its α-β-unsaturated ketone region, with presumptive receptor nucleophiles. 相似文献
159.
Summary The degree of association between cattle egrets (Bubulcus ibis) and cattle was studied during one summer on Saint Catherines Island, Georgia, USA. Previous work by Grubb (1976) and others indicated that cattle egrets foraging with cattle require fewer steps and less time to catch prey than egrets foraging without cattle and single egrets catch prey at a higher rate than egrets foraging in groups of two or more with cattle. Accordingly, we predicted that when given a choice egrets should forage with cattle rather than alone, egrets should prefer to associate with standing rather than sitting cattle, and single egrets associated with cattle should be more common than expected by chance.In excess of two-thirds of the egrets accompanied cattle. Neither time of day nor month influenced the degree of association, but egrets in forest were more likely to be associated with cattle than egrets in pasture. Standing cattle were more likely to be accompanied by egrets than were sitting cattle. Single egrets occurred more frequently than expected by chance when accompanying standing cattle but not when associated with sitting cattle. Thus, cattle egrets usually distributed themselves among cattle in the way predicted by optimal foraging theory.We dedicate this paper to the memory of Michael D. Sabath 相似文献
160.
Convenient procedures for the biosynthesis, isolation, and isotope labeling of cytochalasins. 下载免费PDF全文
Efforts to improve small-scale yields of useful cytochalasins by fermentation resulted in selection of an enriched aflatoxin medium which increased yields by fivefold over those reported in the literature. With Helminthosporium dematoideum and Zygosporium masonii in stationary culture for 3 weeks, cytochalasins B and D were obtained in quantities approaching 700 and 500 mg/liter, respectively. It appears that the critical component in this growth medium is factors associated with whole wheat. By using these procedures, coupled with improvements in isolation, supplementation with two radioactive phenylalanine species readily produced [14C]- or [3H]cytochalasin B. Oxidation of carrier-free radioactive cytochalasin B to cytochasasin A readily provided this labeled congener as well. The isotopic ocnversion of precursor to crystalline products that met analytical criteria ranged from 2 to 4% of the administered radioactivity. 相似文献