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31.
Edward A. Bayer Ehud Skutelsky T. Viswanatha Meir Wilchek 《Molecular and cellular biochemistry》1978,19(1):23-29
Summary Two approaches are described for the localization and quantification of biotin transport components in yeast cells. One approach is based on tracing the fate of a radioactive affinity label for the biotin transport system, [14C]-biotinyl-p-nitrophenyl ester (pBNP), through various stages of subcellular fractionations. A complementary method involves the use of a biotinderivatized, impermeant, electron-dense, affinity-cytochemical label (ferritin-biotin conjugates) for subsequent visualization by electron microscopy. Values of approximately 8,000 and 4,000 sites/cell, respectively, were achieved by the two methods. Complicating factors, future perspectives and the relevance of the two methods to the isolation of transport components are discussed. 相似文献
32.
Meir Wilchek Sarah Spiegel Yitzhak Spiegel 《Biochemical and biophysical research communications》1980,92(4):1215-1222
Rhodamine and fluoresceine containing hydrazides were synthesized and used for fluorescent labeling of glycoconjugates on cell surface or in solution. The procedure involves the oxidation of the glycoconjugates with sodium metaperiodate or galactose oxidase to form an aldehyde group which reacts with the respective hydrazides. The method was applied for the modification of cell surface sialic acid and galactose residues on thymocytes and nematodes as well as for the labeling of glycoproteins and gangliosides in solution. The many possible application of these highly fluorescent compounds in the study of cell surface events is considered. 相似文献
33.
The visual pigment and visual cycle of the lobster,Homarus 总被引:1,自引:0,他引:1
Merle S. Bruno Stephen N. Barnes Timothy H. Goldsmith 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1977,120(2):123-142
Summary The visual pigment of the American lobster,Homarus americanus, has been studied in individual isolated rhabdoms by microspectrophotometry. Lobster rhodopsin has max at 515 nm and is converted by light to a stable metarhodopsin with max at 490 nm. These figures are in good agreement with corresponding values obtained by Wald and Hubbard (1957) in digitonin extracts. Photoregeneration of rhodopsin to metarhodopsin is also observed. The absorbance spectrum of lobster metarhodopsin is invariant with pH in the range 5.4–9, indicating that even after isomerization of the chromophore fromcis totrans, the binding site of the chromophore remains sequestered from the solvent environment. Total axial density of the lobster rhabdom to unpolarized light is about 0.7.As described for several other Crustacea, aldehyde fixation renders the metarhodopsin susceptible to photobleaching, a process that is faster at alkaline than at neutral or acid pH. Small amounts of a photoproduct with max at 370 nm are occasionally seen. A slower dark bleaching of lobster rhabdoms (1/2–2 h) also occurs, frequently through intermediates with absorption similar to metarhodopsin.The molar extinction coefficient of metarhodopsin is about 1.2 times greater than that of rhodopsin, each measured at their respective max. Isomerization of the chromophore fromcis totrans is accompanied by a change in the orientation of the absorption vector of about 3°. The absorption vector of metarhodopsin is either tilted more steeply into the membrane or is less tightly oriented with respect to the microvillar axes.When living lobsters are kept at room temperature, light adaptation does not result in an accumulation of metarhodopsin. At 4 °C, however, the same adapting lights cause a reduction of rhodopsin and an increase in metarhodopsin. There is thus a temperature-sensitive regeneration mechanism that supplements photoregeneration. Following 1 ms, 0.1 joule xenon flashes that convert about 70% of the rhodopsin to metarhodopsin in vivo, dark regeneration occurs in the living eye with half-times of about 25 and 55 min at 22 °C and 15 °C respectively.This work was supported by USPHS research grant EY 00222 to Yale University. S.N.B. was aided by NIH Postdoctoral Fellowship EY 52378. 相似文献
34.
Stephen N. Barnes Timothy H. Goldsmith 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1977,120(2):143-159
Summary Dark adaptation of living lobsters was measured by recording the ERG at several temperatures in the range 5–20 °C following adapting flashes that convert about 70% of the rhodopsin to metarhodopsin. Recovery of log threshold is rapid, and at 10–20° is nearly complete in 10 min. Only at 5 °C is dark adaptation significantly slowed. Comparison of dark adaptation with data on regeneration of pigment (Bruno et al., 1977) is consistent with the hypothesis that as rhodopsin concentration rises and falls, its only effect on sensitivity is to alter the probability of quantum catch. This interpretation is further bolstered by observations on winter lobsters that have a 70% deficiency of rhodopsin without the concomitant increase in metarhodopsin that accompanies light adaptation. No effect of metarhodopsin on sensitivity was detected. These experiments support the growing body of evidence indicating that the relationship between rhodopsin concentration and log threshold is fundamentally different in the rhabdomeric photoreceptors of invertebrates and the rods and cones of vertebrates.This work was supported by USPHS research grant EY 00222 to Yale University. S.N.B. was aided by NIH Postdoctoral Fellowship EY 52378, by funds made available through the Unidel Foundation, and by a grant from the University of Delaware Research Foundation. 相似文献
35.
Plasma levels of prolactin and FSH in free-living Pied flycatchers were studied in relation to breeding stage, clutch size and diurnal variations. In the female, the concentration of prolactin started to increase during the egg-laying and reached maximal values at the end of the incubation period. After hatching prolactin levels decreased. Male Pied flycatchers showed an increase in plasma levels of prolactin at the time when they returned to their home-territories, i.e. at the end of the incubation period. Males still occupying secondary territories at this time had low levels of prolactin. In the males, as in the females, plasma levels of prolactin decreased after hatching.
Male Pied flycatchers showed at all times higher plasma levels of FSH than did females. In both sexes FSH levels were high during the early part of the breeding season and started to decrease after the egg-laying period. After hatching time plasma levels of FSH were below the sensitivity of the assay. No differences in FSH were found between males occupying secondary territories and males in home-territories.
In incubating females FSH, but not prolactin, showed a distinct unimodal daily cycle.
No differences were found in plasma levels of prolactin and FSH between females incubating different sized clutches. 相似文献
Male Pied flycatchers showed at all times higher plasma levels of FSH than did females. In both sexes FSH levels were high during the early part of the breeding season and started to decrease after the egg-laying period. After hatching time plasma levels of FSH were below the sensitivity of the assay. No differences in FSH were found between males occupying secondary territories and males in home-territories.
In incubating females FSH, but not prolactin, showed a distinct unimodal daily cycle.
No differences were found in plasma levels of prolactin and FSH between females incubating different sized clutches. 相似文献
36.
A new approach for the reaction of Sepharose with cyanogen bromide is described, using triethylamine as a “cyano-transfer” reagent. An optimized procedure for activation at neutral pH was developed. This procedure requires only about 5% of the usual amount of cyanogen bromide. Activated resins are free of imidocarbonates and carbamates, containing only active cyanate esters. Extremely high coupling capacities (75 μmol ligand/g wet Sepharose 4B) can be obtained using this method. 相似文献
37.
J L Meinkoth P K Goldsmith A M Spiegel J R Feramisco G N Burrow 《The Journal of biological chemistry》1992,267(19):13239-13245
Thyrotropin (TSH) is an important regulator of thyroid follicular cells. While its role in the maintenance of differentiated functions is undisputed, its role as a mitogen is less clear. TSH induces DNA synthesis and cell proliferation in some cells, while in others, TSH is mitogenic only in the presence of additional growth factors such as insulin-like growth factor-1. TSH causes elevations in intracellular cAMP and is thought to utilize this second messenger system in its mitogenic action. We studied TSH as a mitogen in Wistar rat thyroid cells (WRT) (Brandi, M. L., Rotella, C. M., Mavilia, C., Franceschelli, F., Tanini, A., and Toccafondi, R. (1987) Mol. Cell. Endocrinol. 54, 91-103) and examined the role of the guanine nucleotide binding protein, Gs, in its mitogenic action. WRT cells synthesized DNA in response to TSH and elevations in cAMP. In addition, TSH caused a rapid stimulation of an indicator gene whose expression is regulated by cAMP response elements. Following microinjection of an inhibitory polyclonal antibody raised against the Gs protein, both TSH-induced changes in gene expression and DNA synthesis were significantly reduced. These results demonstrate that virtually all of the mitogenic action of TSH is transduced through the Gs protein in WRT cells, presumably through the regulation of adenylate cyclase. Whether all or only part of TSH action is mediated by cAMP and the cAMP-dependent protein kinase remains to be determined. 相似文献
38.
Hip joints (280) from 140 human fetuses, obtained from abortions and deaths in the perinatal period, were studied. The fetuses ranged from 8.7 to 40 cm in crown-rump length and are believed to be between 12 and 42 weeks in age. The joints were dissected, morphology inspected, and measurements taken of the depth and diameter of the acetabulum, the diameter of the femoral head, length and width of the ligament of the head, the neck-shaft, and torsion angles of the proximal femur. Regression models were fitted to determine which would best predict the growth pattern. Multivariate analysis of variance showed no significant differences between males and females or between the right and left sides. Acetabular depth was shown to be the slowest-growing hip variable, increasing less than fourfold in the period studied. Acetabular indices less than 50 percent indicate a shallow socket at term. Femoral head and acetabular diameter demonstrated a strong relationship (r = 0.860) and in many joints the femoral head diameter exceeded that of the acetabulum. Considerable variability was demonstrated in both femoral angles. The femoral angles showed only low correlation with the other hip variables. These observations indicate that soft tissue structures about the joint must play an important role in neonatal joint stability. The explanation of greater female and left side involvement in congenital hip disease must lie in factors other than growth changes of hip dimensions. Neither angle appears to be a useful indicator of normal joint development. 相似文献
39.
Undifferentiated Friend erythroleukemic cells (FL cells) acquire membrane microviscosity (
), in accord with the culture cell density. At low cell density
poise, whereas at confluency it increases to
poise. Concomitantly, the total number of available transferrin receptors per cell decreases by about 80% upon increase in
cell density. Modulation of membrane microviscosity, by artificial alteration of the membrane cholesterol level, mediates
similar modulations of the availability of the transferrin receptors. The correlation between the availability of the transferrin
receptors and the membrane lipid fluidity may take part in the overt decrease in iron uptake by erythroid cells along the
erythropoiesis pathway. 相似文献
40.
Mink pseudodistemper, a recessive disease associated with high blood tyrosinelevels, is an animal analogue of the human inborn error of metabolism, tyrosinemia II. Affected mink and man have eye and skin lesions. Affected mink have no hepatic tyrosine aminotransferase (TAT) activity, as measured immunologically and biochemically. Hepatic mitochondrial aspartate aminotransferase is increased to 188% of control. This new genetic animal model of TAT deficiency should allow new studies of tyrosine metabolism.Supported by NIH Grants AM-17253 (LAG), 5T32-AM-07093 (LAG), and RCDA AM-0008 (LAG), grants from the Wisconsin State Mink Advisory Board, and a BRSG grant for the Graduate School of the University of Wisconsin, Madison, Publication No. 82 of the dermatology research laboratories of Duke University Medical Center. 相似文献