摘要:

AbstractThe potential role of phosphoproteins in the regulation of carbonate biomineralization is examined by comparing the EDTA‐soluble matrix (SM) of bivalve shells from representatives of eight superfamilies having various aragonitic and calcitic microstructures. In each case the SM is separated into two fractions by gel permeation chromatography. The lower molecular weight fractions (Mrrange 15,000–500,000) were assayed for protein and phosphate content, and their ability to regulate calcitic CaCo3formation was determined from their performance as inhibitors in a pH‐stat crystal growth assay. The SM fraction from two species with foliated calcitic shells is 12.9–15.7% phosphate by weight while SM fractions isolated from shells or shell layers of six species with calcitic prismatic or various aragonitic microstructures all contain significantly lower phosphate levels (0–3.3% by weight). The more highly phosphorylated SM fractions are significantly better inhibitors of calcitic crystal growth, requiring approximately 30% of the concentration on a weight basis as the low phosphate fractions to effect a 50% reduction in growth rate. Enzymatic dephosphorylation of the high phosphate SM fractions results in reduced inhibition capabilities that are approximately equal to those of the low phosphate SM fractions. Finally, neither dephosphorylated nor naturally low phosphate SM fractions were as effective as phosphorylated foliated matrix in maintaining inhibition in the pH‐stat assay as crystals continue to grow. In conclusion, it appears that degree of SM phosphorylation in part may be a factor in the regulation of carbonate crystal growth in vivo and thus explain its variability among the various shell micr

ISSN:0022-104X    

DOI:10.1002/jez.1402580102

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

年代:1991

数据来源: WILEY

摘要:

AbstractSerial, paired blood samples were collected via cannulae chronically placed in the common carotid artery (A) to and the internal jugular vein (V) from the brain of the fasted adult American bullfrog (Rana catesbeiana). Plasma glucose, β‐hydroxybutyrate, acetoacetate, lactate, and alanine levels were measured by standard enzymatic procedures. Cannula failure ended sampling after 1–2 days in most animals. The common carotid artery plasma metabolite levels were greatest at the time of surgery and subsequently declined to relatively stable levels. The summarized data indicated glucose uptake and alanine release by the brain, but no significant β‐hydroxybutyrate or lactate A‐V percentage changes. Initially, acetoacetate levels also were measured, but were discontinued in favor of continued β‐hydroxybutyrate determinations when no significant A‐V percentage changes occurred. Separate analysis of the metabolite levels during the surgery and recovery period (⩽ 24 hr) and the “normal”under the experimental conditionsperiod (>24 hr) revealed that summarizing the data masked important A‐V percentage changes during the two different physiological conditions. Glucose was the only metabolite extracted by the brain during the ⩽ 24 hr period of elevated and subsequently declining metabolite levels. In contrast, glucose uptake did not occur during the>24 hr period of stable levels, but there was lactate release.If the bullfrog brain stores substantial glycogen as do the other ectothermic vertebrates studied, glucose uptake when plasma levels are elevated, for example after feeding, may serve both to fuel the brain and to replenish endogenous glycogen reserves that may be mobilized to provide glucose for the brain after plasma glucose levels return to normal. Assuming that mammalian and bullfrog metabolic pathways are the same, the release of lactate and alanine by the brain, possibly to remove excess pyruvate and to regenerate NAD+, is consistent with this hypothesis. It remains to be determined for how long endogenous energy sources alone can support the bullfrog brain, and if plasma glucose, ketones, and/or other energy sources are extracted as endogenous brai

ISSN:0022-104X    

DOI:10.1002/jez.1402580103

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

年代:1991

数据来源: WILEY

摘要:

AbstractTwo different glutamine‐dependent carbamoyl‐phosphate synthetase (CPSase) activities are preset in tissues ofSqualus acanthias(spiny dogfish shark, a representative elasmobranch) (Anderson,Biochem. J. 261:523–529, 1989). CPSase III (acetylglutamate‐dependent) activity is present in liver mitochondria; the function of this enzyme is related to urea synthesis for the purpose of osmoregulation, and the properties are analogous to the classical ammonia and acetylglutamate‐dependent CPSase I in liver mitochondria of ureotelic species (except that the nitrogen‐donating substrate is glutamine). CPSase II activity is present in spleen and other extrahepatic tissues, but is apparently absent from liver; the function of this enzyme is related to pyrimidine nucleotide biosynthesis, and the properties are analogous to mammalian CPSase II activities (independent of acetylglutamate, inhibited by UTP, and activated by 5‐phosphoribosyl 1‐pyrophosphate). Glutamine synthetase in shark liver is localized in the mitochondria, but the spleen glutamine synthetase is localized in the cytosol. Liver of largemouth bass (Micropterus salmoides, a freshwater teleost) also has CPSase III activity; however, unlike shark, aspartate carbamoyltransferase activity is also present in bass liver. Consequently, a major objective of this study was to establish if two different glutamine‐dependent CPSase activities are present in a single tissue (liver). Two different glutamine‐dependent CPSase activites were found to be present in bass liver, a mitochondrial CPSase III and a cytosolic CPSase II. The CPSase II activity, in contrast to the shark spleen CPSase II, appears to be associated with aspartate carbamoyltransferase and dihydro‐orotase activities, as found in mammalian species. As in shark, ornithine carbamoyltransferase, arginase, and phosphoenolpyruvate carboxykinase activities in bass liver are localized in the mitochondria, but, in contrast to shark, glutamine synthetase activity is localized in the cytosol. The properties of isolated, actively respiring bass liver mitochondria were investigated for comparison with previously reported properties of shark liver mitochondria. Respiration of bass mitochondria is supported by succinate and glutamate plus malate, but not by β‐hydroxybutyrate, palmitoyl‐CoA, citrate, or glutamine, all of which serve as excellent substrates for dogfish shark liver mitochondria. In contrast to shark mitochondria, bass mitochondria are not capable of ketone body formation and, of particular interest, do not catalyze citrulline formation from glutamine. CPSase III activity was not present in two other species of teleost fishes closely related to largemouth bass. The occurrence and function of CPSase III in te

ISSN:0022-104X    

DOI:10.1002/jez.1402580104

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

年代:1991

数据来源: WILEY

摘要:

AbstractEmbryos from supervulated female mice that developed in vitro from the twocell stage were compared with in vivo embryos with respect to yield of blastocysts, number and types of cells, morphology in histologic section, and DNA polymerase activities. Significantly more embryos developed into blastocysts in vitro (93%) than in vivo (18%). Inner cell mass (ICM) cells comprised approximately 30% of total cells in late morula/early blastocyst stage embryos developed either in vitro or in vivo. However, the in vitro embryos developed approximately half the number of total cells as in vivo embryos, did not develop endoderm, and did not develop abembryonic trophoblast cells with morphologic characteristics of late preimplantation in vivo embryos. DNA‐dependent DNA polymerase activities in in vitro embryos decreased in correspondence with the decrease in cell number resulting in per cell levels comparable to in vivo embryos. In contrast, the poly (A)·oligo(dT)‐dependent DNA polymerase activity was the same in embryos developing either in vitro or in vivo, indicating different regulatory mechanisms for the two enzyme activities. A variety of nutrients and growth factors in the culture medium did not increase cell numbers or DNA polymerase activities in embryos cultured for 3 days; extending the culture an additional 24 hours resulted in a loss of ICM cells and decreases in both DNA polymerase activities. These results show that the retarded growth of embryos in vitro is equally distributed between ICM and trophoblast, is not reversed by culture conditions that include serum growth factors, and is not due to decreased cellular levels of DNA polymerase activi

ISSN:0022-104X    

DOI:10.1002/jez.1402580105

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe surgically thyroidectomized (Tx) or sham‐operated hatchling slider turtles—Trachemys (Pseudemys) scripta—and measured their growth (mass and carapace length) for 5 to 7 months. Autopsy at the end of the experiments revealed that up to 30% of the thyroidectomized animals had regenerated thyroid follicles (thyroids had few but enlarged follicles). Therefore, we segregated thyroidectomized turtles a posteriori into two groups: those with observable thyroid tissue at autopsy, greater than 3 ng/ml plasma thyroxine (T4), and normal plasma T4binding capacity were designated partial Tx (PTx), and others with no observable thyroid tissue, less than 3 ng/ml plasma T4, and low plasma T4binding capacity were designated Tx. Growth rate was significantly reduced 6–8 weeks after thyroidectomy in the Tx animals; length‐specific growth rate was affected sooner than mass‐specific growth rate. Growth of Tx animals continued to diverge from sham turtles through the end of the experiment; PTx animals did not differ from shams at any time. In a second experiment growth rate was reduced in Tx turtles maintained under both varibale (14L:10D, thermal gradient of 19 to 40°C) and constant (constant light and temperature—30°C) environmental conditions (i.e., reduced growth rate was probably not related to a thermoregulatory dysfunction). However, all animals maintained under the constant conditions stopped growing after 3 months, whereas turtles kept under varibale conditions continued to grow to the end of the experiment (4.5 months). Thyroxine (T4) replacement therapy of long‐term Tx turtles restored growth after 6 weeks.Plasma thyrotropin (TSH) was greatly elevated in Tx turtles (301 ± 48.7 ng/ml) and at low to nondetectable levels in controls (⩾ 1 ng/ml). T4replacement therapy was effective in reducing TSH levels in Tx turtles. Plasma T4and TSH concentrations showed the expected inverse relationship. However, although PTx animals had elevated plasma T4levels that were in the lower range of the sham controls (PTx: 36.6 ± 8.2 vs. 112.7 ± 17.1 ng/ml in sham), their plasma TSH was also significantly elevated (36.5 ± 9.3 ng/ml vs. 0.8 ± 0.2 ng/ml in sham). These results demonstrate the requirement of an intact thyroid gland for normal growth of turtles, and provide the first direct evidence for a role for the thyroid in body growth of a reptile. They also reveal that the set‐point for the feedback between the thyroid and pituitary secretion can be altered by pertur

ISSN:0022-104X    

DOI:10.1002/jez.1402580106

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn this study, we describe a method for the separation of AKH/RPCH‐family peptides using isocratic high performance liquid chromatography (HPLC). This improved method is simple, rapid, and sensitive and bypasses many of the difficulties associated with gradient HPLC. We have previously shown that the lubber grasshopper,Romalea, accumulates large quantities of the native peptides Ro I and Ro II (Spring and Gäde,Journal of Experimental Zoology 241:41–50, 1987). In the present study, we used isocratic HPLC to follow the changes in the amount of Ro I and Ro II during development. Overall the amount of neuropeptide found in the corpora cardiaca (CC) increases 34‐fold from larval instar III to late adult, with the greatest quantitative increase (3,000 pmol total in males) occurring during the 6 weeks of adult life. The Ro I: Ro II ratio also changes during development, from 5.4 in larval instar III to 2.0 in late instar V and finally to 4.0 in mature adults. Under physiological conditions these neuropeptides can be released fromRomaleaCC isolated in vitro, when the CC are depolarized with high‐potassium saline. This release is calcium‐dependent and 10% to 15% of the total peptide stores are mobilized during a 1‐hour treatment with high‐potassium, plus calcium, saline. More than one‐third of the mobilized peptide is released within the first 5 min. In locusts, release of the AKH peptides is reported to be mediated by the neurotransmitter octopamine, acting via the adenylate cyclase pathway. InRomalea, however, we find no evidence for either octopamine or cAMP‐mediated relea

ISSN:0022-104X    

DOI:10.1002/jez.1402580107

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe electrophoretic analysis of the proteins that were extracted from immature caput and mature cauda sperm showed evidence of accumulation of several proteins during the epididymal transit of the sperm. An antiserum, raised against detergent‐extracted proteins from mature spermatozoa, immunostained six epididymal proteins with apparent molecular masses of 16, 22.5, 26, 37, 60, and 80 kDa on Western blots of epididymal fluid. Of these proteins, only the 26 kDa protein was significantly immunodetected in proximal caput epididymal fluid. Its biosynthesis by caput epididymis was confirmed by immunoprecipitation of an in vitro translated product of caput poly (A) RNA. The homology of the 26 kDa epididymal protein with the 26 kDa sperm protein was verified by epitope mapping. The other epididymal proteins were found in the fluid of the more distal portions of the organ. Their presence in the epididymal fluid coincided with their detection on the sperm. These epididymal proteins were considered to be sperm‐coating prote

ISSN:0022-104X    

DOI:10.1002/jez.1402580108

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

年代:1991

数据来源: WILEY

摘要:

AbstractComparative studies were conducted to evaluate the efficacy of estrus synchronization, ovulation induction, nonsurgical embryo collection, and cryopreservatin procedures in the scimitar‐horned oryx (Oryx dammah), bongo (Tragelaphus euryceros), eland (Taurotragus oryx), and greater kudu (Tragelaphus strepsiceros). In the scimitar‐horned oryx, a 6α‐methyl‐17α‐acetoxyprogesterone (MAP) pessary vs. prostaglandin F2α (PGF2α) estrus synchronization treatment was compared; only PGF2α was tested in the other species. Ovarian responsiveness to follicestimulating hormone (FSH‐P, b.i.d. for 5 days) or pregnant mare's serum gonadotropin (PMSG, single injection) was evaluated in all species. MAP and PGF2α were equally effective (P<0.05) for synchronizing estrus in scimitar‐horned oryx. Signs of estrus, including mounting, were observed in 15 of 33 (45.4%) oryx donors, but copulation was observed on only 8 occasions. Mean number of CL/ovulating bongo and eland female was enhanced (P<0.05) by FSH‐P compared to PMSG (4.5 ± 1.8 vs. 1.3 ± 0.3 CL/bongo and 10.6 ± 4.6 vs. 1.0 ± 0.6 CL/eland, respectively) treatment. The difference in mean (± SEM) CL number between FSH‐P‐ and PMSG‐treated oryx donors approached significance (4.6 ± 1.6 vs. 2.7 ± 0.8, respectively;P= 0.08). Embryos and ova were recovered nonsurgically from 10 of 19 (52.6%) of the ovulating oryx, 9 of 10 (90%) bongo, 6 of 10 (60%) eland, and both (100%) greater kudu. A high proportion (60%) of cryopreserved oryx embryos maintained an excellent‐or good‐quality grade (QG) after thawing. A higher proportion (P<0.05) of embryos frozen in 1.5 M dimethyl sulfoxide (6 of 10) or 1.5 M glycerol (6 of 10) solutions maintained their prefreeze QG compared to the propylene glycol counterparts (3 of 10). The transfer of thawed embryos to synchronized oryx recipients (n = 9) resulted in no pregnancies. Conventional techniques for synchronizing ovarian activity, inducing ovulation, and flushing the uterine content of farm livestock largely are adaptive to these African antelope species. However, the overall efficiency of these strategies for consistently promoting superovulation and large numbers of embryos is relatively low. For these species, the primary limitations to effective embryo recovery and transfer appear to be: 1) a lack of estrous behavior which contributes to a low incidence of mating and, thus, poor fertilization and recipient synchrony, and 2) a resilience of the ovaries to

ISSN:0022-104X    

DOI:10.1002/jez.1402580109

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

年代:1991

数据来源: WILEY

摘要:

AbstractPhotoperiod‐induced cycles of gonadal regression and recrudescence in the Syrian hamster were used to determine if epididymal growth in adults involves mitotic activity of principal cells. In Experiment 1, the following groups of adult hamsters were examined: induced recrudescing (5L:19D [5 hr light and 19 hr dark] for 13 wk followed by 14L:10D for at least 3 wk), spontaneous recrudescing (5L:19D for 25 wk), and active gonadal state (14:10D). In Experiment 2, adult hamsters were divided into the following groups: induced recrudescing, active, and regressed (5L:19D for 16 wk). Hamsters received subcutaneous injections of 0.5 μCi3H‐thymidine/g body weight three times/wk for 3 wk. The epididymis was fixed in a glutaraldehyde followed by osmium, embedded in Epon 812, and sectioned at 1 μm. Slides were dipped in Kodak NTB‐3 emulsion, exposed for 2 or 3 months, developed, and evaluated for isotopic labeling of principal and basal cell nuclei by scoring 500 to 1,000 nuclei. In Experiment 1, the percentages of labeled principal cell nuclei for the induced recrudescing, spontaneous recrudescing, and active groups were 26 ± 2%, 23 ± 5%, and 9 ± 1%, respectively. Considering the intermittent availability of3H‐thymidine during 21 days, this represents daily recruitment of 6.3%, 5.6%, and 2.2%, respectively. In Experiment 2, the percentages of labeled principal cell nuclei for induced recrudescing, active, and regressed groups were 12 ± 4%, 3 ± 1%, and 4 ± 1%, respectively. There was no effect of photoperiod on labeling pattern of basal cells (1.5 ± 0.6%, 1.2 ± 0.1%, 0.4 ± 0.1% for the three photoperiod groups, respectively). Regardless of photoperiod, there was no difference in the labeling pattern of principal or basal cells between the head and the tail of the epididymis. In conclusion, photoperiod influenced the recruitment of epididymal principal cells throughout the epididymis, and new principal cells were added continually to the existing population of cells even in gonadally act

ISSN:0022-104X    

DOI:10.1002/jez.1402580110

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe possibility that the intracellular signals generated upon phosphoinositide hydrolysis are involved in regulating bovine oocyte spontaneous meiotic resumption was investigated. Oocytes were mass‐harvested and cultured in 2A‐BMOC medium supplemented with 0.5% bovine serum albumin in the presence or absence of neomycin (an inhibitor of phosphoinositide hydrolysis) or phorbol myristate acetate (an activator of protein kinase C). The role of intracellular calcium was examined by preloading with BAPTA/AM (a calcium chelator) prior to culture. Meiotic maturation was scored cytogenetically. 1) Neomycin induces an irreversible inhibition of germinal vesicle breakdown which does not exceed 60% and is apparent at concentrations of 5 mM or above. Progression of meiosis past metaphase I is inhibited at concentrations of 2.5 mM or above. The full effect of neomycin is only apparent if it is presented to the oocytes within 3 h of follicular release, although germinal vesicle breakdown is not observed until 9 h culture under control conditions. 2) PMA alone has negligible effect on germinal vesicle breakdown, but it acts synergistically with 2 mM IBMX to inhibit this process. PMA has a dual effect on the progression of meiosis past metaphase I: 1 nM PMA has a stimulatory effect while 1 μM PMA blocks the ability of oocytes to reach anaphase I or beyond. These observations are not found with a non‐tumor‐promoting phorbol ester. 3) Spontaneous meiotic resumption is not significantly affected in the absence of added exogenous calcium. However, oocytes preloaded with BAPTA/AM exhibit a dose‐dependent inhibition of germinal vesicle breakdown, even in the presence of extracellular calcium. These results provide indirect evidence for a role for phosphoinositide metabolism in bovine oocyte maturation; it is suggested that intracellular calcium mobilization is prerequisite for meiotic resumption and protein kinase C may modulate cAMP‐dependent inhibition of t

ISSN:0022-104X    

DOI:10.1002/jez.1402580111

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

年代:1991

数据来源: WILEY