摘要:

AbstractThe ciliated gill of bivalve molluscs is situated at an interface between animal and environment. Cilia propel water past the gills to deliver oxygen and nutrition to the animal. Ciliary activity is driven by dynein ATPases and requires a continual supply of ATP at a rate sufficient to match the rate of ATP hydrolysis. Control of the balance between ATP supply and demand in the ciliated gill, and how this balance may be altered by environmental stresses, is unknown. In this pilot study, metabolic flux of excised gills from the marine musselMytilus eduliswas examined in response to oxygen availability and to serotonin‐stimulated ciliary activity. Heat flux and oxygen flux were measured simultaneously with calorespirometry. In parallel experiments, the redox state of mitochondrial cytochromes was determined with in vivo spectrophotometry. Above 4 kPapO2, heat flux was supported by aerobic metabolism. Anoxic heat flux was less than 5% of aerobic heat flux. Heat and oxygen fluxes nearly doubled in gills in the presence of 10 μM serotonin; however, half‐maximalpO2for heat and oxygen fluxes and for reduction of mitochondrial cytochromes remained unchanged from control levels. In gills having inactive cilia in half‐strength seawater, half‐maximalpO2for heat and oxygen fluxes and for cytochrome reduction nearly doubled compared with values in full‐strength seawater. These data indicate that limitation to oxygen delivery imposed by boundary layers may be reduced when ciliary beat frequency is elevated, leading to enhanced oxygen flux to intracellular mitochondria which matches the increased energy demand by the cilia. © 1993 Wile

ISSN:0022-104X    

DOI:10.1002/jez.1402650102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe sarcoplasmic reticulum (SR) was prepared from the ordinary white muscle of carpCyprinus carpioacclimated to either 10 or 30°C over 5 weeks, and its Ca2+‐ATPase and Ca2+uptake activities measured.The SR Ca2+‐ATPase activities of the 10 and 30°C‐acclimated carp were 0.2 and 0.1 μmol Pi/min.mg at a reaction temperature of 10°C, respectively, and 1.1 and 0.6 μmol Pi/min.mg at 30°C, respectively. The corresponding Ca2+uptake activities in the presence of sodium oxalate were 1.1 and 0.4 μmol Ca/min.mg at 10°C, and 2.1 and 1.5 μmol Ca/min·mg at 30°C, respectively. The break point in the Arrhenius plot of Ca2+‐ATPase activity was 9.2°C for the 10°C‐acclimated SR and 15.9°C for the 30°C‐acclimated SR. The activation energy of Ca2+‐ATPase for the 10°C‐acclimated SR between 10 and 40°C was 75 kJ/mol and similar to that for the 30°C‐acclimated SR between 16 and 40°C, 81 kJ/mol. The membrane fluidity of SR, which was determined with a fluorescence probe, Py(3)Py, was higher for the 10°C‐ than 30°C‐acclimated carp at any reaction temperature from 0 to 30°C. The peptide map in SDS‐gels of Ca2+‐ATPase with α‐chymotrypsin gave different patterns in the 40–70 kDa region between the two acclimated groups: the peptide of about 63k Da was specific to the 10°C‐acclimated SR, while the peptide of about 50 kDa to the 30°C‐acclimated SR. Tryptic peptide mapping also resulted in different fragmentation patterns in SDS‐gels for the two Ca2+‐ATPases. These results suggest that carp would modify the fluidity of SR membrane and the molecular structure of Ca2+‐ATPase to compens

ISSN:0022-104X    

DOI:10.1002/jez.1402650103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractMost fish species tolerate a narrower range of temperatures during their early life history. To ascertain whether this might be related to development of the capacity to regulate membrane fluidity (homeoviscous adaptation), we examined the fatty acid composition of tissue phospholipids from developing white sturgeon eggs, embryos, and prefeeding larvae incubated at temperatures both within the range of natural spawning temperatures (14°), and above (20°) and below (8°). Mortality was highest at low temperature, with the greatest losses prior to neurulation. High temperature also resulted in increased mortality relative to 14°, with peak mortality between neurulation and hatch. At a constant temperature of 14°, significant changes in the fatty acid composition of tissue phospholipids were observed during development, but the patterns of change were altered by development at low and high temperature. Contrary to homeoviscous theory, embryos incubated at low temperature exhibited a decline in the ratio of unsaturated to saturated fatty acids (U/S ratio). In contrast, posthatch larvae exposed to low and high temperature exhibited, respectively, higher and lower U/S ratios than larvae maintained at 14°, implying that the capacity for homeoviscous adaptation is acquired at the time of hatch. Although the lack of a homeoviscous response by embryos may account for low survival at temperature extremes, the specific influences of the observed changes in phospholipid fatty acid composition on the biophysical properties of cell membranes remain to be determined. © 1993 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402650104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe present experiments, using a combination of thermal‐neutron activation analysis for the determination of vanadium and an immunofluorescence method for the recognition of the manifestation of an antigen specific to vanadocytes, clearly revealed the time at which ascidians gain their unusual ability to accumulate vanadium ions during their development. Significant accumulation of these ions was observed after metamorphosis. Two and half months after fertilization, the amount of vanadium in juveniles was about 930 ng per individual, a concentration corresponding to more than 5 orders of magnitude greater than that in unfertilized eggs. A vanadocyte‐specific antigen, recognized by a monoclonal antibody specific to the signet ring cells, first appeared in the body wall after metamorphosis. Three weeks after metamorphosis, the antigen became evident within the cytoplasm of the coelomic cells, which have a single, small vacuole. One and a half months after metamorphosis, signet ring cells appeared for the first time and were specifically recognized by the monoclonal antibody. It is suggested that the accumulation of the vanadium coincides with the differentiation of the vanadocytes during the development of ascidians. © 1993 Wiley‐Lis

ISSN:0022-104X    

DOI:10.1002/jez.1402650105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractFreshwater catfish,Heteropneustes fossilis, were injected daily intraperitoneally either with vehicle (0.1 ml of 0.6% NaCl/100 g body wt) or calcitonin (0.5 MRC U/100 g body wt) and maintained either in artificial freshwater, calcium‐rich freshwater, or calcium‐deficient freshwater for 10 days. The blood samples were collected on days 1, 3, 5, and 10 after initiation of the experiment, and serum calcium and inorganic phosphate levels were analysed.(i) Artificial freshwater: There is no change in the serum calcium and inorganic phosphate levels of calcitonin‐injected fish.(ii) Calcium‐rich freshwater: In vehicle‐injected fish there is a progressive hypercalcemia from day 1 to day 5. On day 10 the value decreases but it is still hypercalcemic. No change has been noticed in the serum calcium level of calcitonin‐treated fish. In vehicle‐treated fish the serum inorganic phosphate level indicates a decrease on day 10. The serum inorganic phosphate level of calcitonin‐treated specimens exhibits no change.(iii) Calcium‐deficient freshwater: There is a progressive decrease from day 1 to day 3 in serum calcium level of vehicle‐injected fish. Thereafter, from day 5 the level increases thus resulting in hypercalcemia on day 10. Calcitonin treatment to the fish evokes a decrease in the serum calcium level from day 1 to day 3. Thereafter a significant hypercalcemia is recorded on day 5 and day 10. In vehicle‐injected fish the serum inorganic phosphate levels decrease from day 3 to day 5. However, the value increases on day 10. Serum inorganic phosphate level of calcitonin‐treated fish exhibits a decrease on day 1. Thereafter, it rises progressively from day 3 to day 10.

ISSN:0022-104X    

DOI:10.1002/jez.1402650106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractNew observations on thin strips of cells from the leading edge of the involuting presumptive mesoderm explanted onto FN‐coated substrata show a striking preferential cellular emigration from the leading edge of explants. Microinjected probes (Fab′ anti‐FN, Fab' anti‐integrin and RGD‐peptides) that disrupt cell adhesion to the FN‐matrix on basal surface of the blastocoel roof also disrupt normal anuran gastrulation, producing blocked embryos with no adhesion of leading edge mesodermal cells to the blastocoel roof, abnormal epiboly, and defects of mesodermal cell spreading across the basal surface of the blastocoel roof toward the animal pole. These results show that the FN‐rich fibrillar extracellular matrix on the basal surface of the blastocoel roof is required for normal gastrulation inRana pipiensembryos. © 1993 W

ISSN:0022-104X    

DOI:10.1002/jez.1402650107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractProminent among the various types of cell that differentiate from the trophectoderm of the mouse blastocyst are trophoblastic giant cells. Repeated endoreduplication of the genome accompanies the growth of these cells, which have been shown to be polytene rather than polyploid. Early stages in giant transformation have been examined, mainly in the mural trophectoderm of the implanting blastocyst which gives rise to the primary trophoblastic giant cells. One confusing issue is whether these early stages include the onset of endoreduplication of the genome. This issue has been addressed in the present study by comparing the DNA content of nuclei in isolated trophectoderm and ICM tissue rather than, as previously, by relating measurements on air‐dry preparations of entire blastocysts to those of adult liver. The results, particularly those from delayed and reactivated blastocysts, show that genome endoreduplication is not an obligatory early event in the transformation of mural trophectoderm cells. © 1993 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402650108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractNormal male rats generate vaginal plugs that appear to be firmly apposed to the vagino‐cervical junction and permit a large number of spermatozoa to reach the uterus. A few spermatozoa form entangled masses inside these plugs, as revealed by light microscopy. Males in which the seminal vesicles have been partially removed produce plugs that are smaller and softer than those generated by normal males, and the plugs display a cup‐like structure at the proximal end. The cup‐like structure is completely filled with spermatozoa that exhibit a characteristic arrangement in relation to the plug material. In this situation, the number of spermatozoa that reach the uterus is very much reduced. Experiments were also carried out to explore the restoration of sperm transport by addition of a vaginal plug. Such experiments involved successive matings of individual females with a seminal vesicle‐deprived male and with a vasectomized male (which generated the plug) and also the intravaginal injection of seminal vesicle secretions after mating with a seminal vesicle‐deprived male. In none of the experimental situations was transport of spermatozoa to the uterus restored, and the plug consisted of a large quantity of trapped spermatozoa inside a mass of coagulated proteins. The results suggest that the structure of the plug depends on the amount of seminal vesicle secretion present in the ejaculate and that the vaginal plug must be formed immediately after deposition of the sperm if spermatozoa are to reach the uterus. © 1993 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402650109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe role of calcium (Ca+ +) during spontaneous meiotic maturation of pig oocytes was examined. The hypothesis that elevations of endogenously derived intracellular Ca+ +are prerequisite for germinal vesicle breakdown (GVBD) and progression through meiosis was tested. In addition, investigations were carried out to determine whether GVBD and meiotic progression were dependent upon extracellular Ca+ +influx. Elevation of endogenously derived Ca+ +was inhibited directly by loading cells with BAPTA, a specific Ca+ +chelator, or indirectly with neomycin. Extracellular Ca+ +influx was prevented by culturing oocytes in Ca+ +‐deficient medium, with EGTA, or in the presence of the Ca+ +channel blocker verapamil. Pretreatment with BAPTA/AM and subsequent culture in the absence of added exogenous Ca+ +resulted in a similar inhibition of GVBD (1 μM BAPTA/AM vs. untreated,P<0.01). After 4 h following follicular release, oocytes were no longer sensitive to BAPTA/AM treatment. Neomycin also significantly inhibited GVBD (0.5 mM neomycin vs. untreated,P<0.05) as well as meiotic progression past metaphase I (0.25 mM neomycin vs. untreated,P<0.05). The incidence of GVBD was not significantly affected when oocytes were simply cultured in Ca+ +deficient medium or when cultured in the presence of EGTA or verapamil. However, progression of meiosis past GVBD to metaphase II was suppressed by reducing levels of Ca+ +in the culture medium (0.68 mM Ca+ +vs. 1.7 mM Ca+ +,P<0.05) and by treatment with verapamil (0.25 mM verapamil vs. untreated,P<0.05). Meiotic progression was completely blocked at metaphase I in the presence of 0.85 mM EGTA. These results implicate a central role for the mobilisation of intracellular Ca+ +for the initiation of GVBD, and suggest that external Ca+ +influx is not a direct requirement for GVBD, although it may be required for development past metaphase I in pig oocytes. © 1993 Wiley‐Liss

ISSN:0022-104X    

DOI:10.1002/jez.1402650110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractFour monoclonal antibodies (MAbs) were produced in rat cells against materials obtained from the bovine oviduct. The MAbs (1H10, 2A4, 2C5, and 1B12) reacted strongly with the oviductal epithelium of cows in the follicular phase. An immunohistochemical study demonstrated that each of the MAbs bound strongly to the supranuclear cytoplasm of epithelial cells of the oviduct, but not of the stromal cells. Antigens that reacted with the MAbs were characterized by immunoblotting analysis of proteins after fractionation by SDS‐PAGE under reducing conditions of oviductal flushings obtained from cows at estrus. All MAbs strongly stained a band of protein with a molecular weight (MW) of 85–97 kD. MAb 1H10 also reacted with the minor band of a 55‐kD protein. Similar antigens were not detected in uterine flushings, follicular fluid, and serum. No specific immunohistochemical reactivity with the MAbs was observed with other tissues from the reproductive tract and with nonreproductive tissues. The immunohistochemical reactions were completely eliminated by pretreatment of tissues with trypsin, but not with periodic acid, results that suggest that the antigenic determinants that react with the MAbs were proteinaceous rather than carbohydrate. We have thus established clones that produce 4 MAbs that are specific for oviduct‐specific glycoproteins of the cow. © 1993 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402650111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY