摘要:

AbstractThe effects of several organic solutes on the activity of the mitochondrial enzyme complex known as the glycine cleavage system (GCS) were examined in two osmoconforming species (soft‐shelled clam,Mya arenariaand little skate,Raja erinacea) and an osmoregulator (winter flounder,Pseudopleuronectes americanus). Taurine, beta‐alanine (BALA), and proline, compatible solutes which typically have no effect on enzyme function, significantly affected GCS activity with pronounced interspecific differences in sensitivity evident. Urea had no effect on skate GCS activity but significantly inhibited the enzymes from clam and flounder. The methylamines, trimethylamine oxide (TMAO) and betaine, did not significantly affect GCS from any species examined. Sarcosine significantly inhibited GCS from all three species, although this response may be of a regulatory nature. Inhibition of flounder GCS by urea was overcome by TMAO when these solutes were added in a 2:1 ratio (urea:TMAO). Pronounced inhibition of skate GCS occurred in response to urea + TMAO (2:1), whereas neither solute added alone had an effect on GCS activity. Although significant interspecific differences in solute effects occurred, each osmoconforming species was less sensitive to its own native osmolytes. BALA, however, stimulated skate GCS and may be important in enhancing sarcosine oxidation during hypoosmotic stress. The potential physiological significance and biochemical implications of these solute effects are discus

ISSN:0022-104X    

DOI:10.1002/jez.1402420102

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

年代:1987

数据来源: WILEY

摘要:

AbstractAn assay is described that allows the measurement of H2O2‐generating mannitol oxidase activity in sucrose‐containing homogenates and subcellular fractions. Using this assay high activity was found in digestive gland and crop of the slugArion ater. The subcellular localization of mannitol oxidase in these tissues was examined using sucrose density gradient centrifugation in a B‐XIV zonal rotor. Mannitol oxidase was found to reside in a lowdensity membrane tentatively identified as golgi or plasma membrane, rather than in mitochondria or peroxisomes as had previously been sup

ISSN:0022-104X    

DOI:10.1002/jez.1402420103

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

年代:1987

数据来源: WILEY

摘要:

AbstractWe have examined the pattern of protein synthesis during wing disc pattern regulation. Although in vivo culture dramatically alters the pattern of abundant protein synthesis in wing discs, only one protein—RG38—changes specifically in response to pattern regulation. This polypeptide, previously identified as being nonuniformly distributed in wing and haltere discs, is synthesized in a graded distribution across the wing disc. During wing disc pattern regulation, it acts as a molecular marker for regeneration of particular wing disc regions. Thus, the rate of RG38 synthesis increases during regeneration (by fragments with initial low levels) with kinetics that parallel those for regeneration as scored by the presence of adult cuticular structu

ISSN:0022-104X    

DOI:10.1002/jez.1402420104

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe developmental fate of single blastomeres from eight‐cell murine embryos reaggregated with intact two‐cell embryos was evaluated after culture. Fluorescein isothiocynate was used to follow developmental fate in preblastocyst chimeric embryos. Expression of stage‐specific embryonic antigen 3 was used to assay developmental fate at the blastocyst stage, and glucosephosphate isomerase variants were used to assay at the blastocyst stage and after implantation. The results suggest that the descendents of the 1/8 component stay in a patch area and do not selectively migrate to the inner cell mass (ICM). This is in contrast to many studies that indicate that smaller blastomeres, which are more advanced in development, migrate to the ICM. The differences in experimental designs are discussed. Possible mechanisms for this phenomena are that the eight‐cell blastomere is physically excluded from the ICM by position or polarization, or that it is differentiating ahead of the two‐cell component and becomes trop

ISSN:0022-104X    

DOI:10.1002/jez.1402420105

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe primary objectives of this study were (1) to determine the embryonic stage at which theOryzias latipesenveloping layer (EVL) begins to contract rhythmically, and (2) to determine where these contractions arise within the EVL. Using time‐lapse video recording, we showed that the contractions begin at stage 14 (the stage of the embryonic shield) and arise in the ventral region of the EVL, which is centered at 180° longitude from the embryonic shield. We have called this the pacemaker region for the contractions. Using fluorescein diacetate as a vital stain, we showed that the ventral region of the EVL continues to act as a pacemaker even after the EVL is detached from the rest of the egg.Rhythmic contractile activity ceased when we removed a group of about 130 cells — 10% of the total EVL— from the pacemaker region; comparably large wounds elsewhere had no effect on the contractions. When we cut detached EVLs into ten pieces, only 2.4 ± 1.8 (X ± SD, N = 11) of them contracted rhythmically, even though a considerably larger proportion of the EVL cells participate in the contractions in undisturbed blastoderms. We conclude that the pacemaker cells are necessary for rhythmic contractile activity and that cells outside this region do not contract spontaneously.The contractile waves are propagated at a velocity of 14–54 μm sec−1. This value, which is two to three orders of magnitude slower than the propagation of epithelial action potentials, is similar to the rate of propagation of waves of increased cytosolic Ca2+in other systems.We propose that the medaka EVL is a good system in which to study certain aspects of epithelial

ISSN:0022-104X    

DOI:10.1002/jez.1402420106

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe developmental processes related to odontogenesis are similar in all vertebrates and they occur during embryogenesis. The dental papilla can exercises directive morphogenetic role on epithelia of different phylogenetic origin. In our laboratory we have previously shown that cultured heterologous tissue recombinations between adult lizards dental papillae and quail epithelia were capable of producing odontogenesis and amelogenesis. Employing sodium dodecyl‐sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) according to Laemmli ('70, Nature, 227:680–685.) and two‐dimensional polyacrylamide gel electrophoresis (2‐D PAGE) (O'Farrell, '75, J. Biol. Chem., 250:4007–4021.), we have examined the distribution of soluble proteins with respect to isoelectric point and molecular weight of dental papillae isolated from tooth germs at bell stage of adult lizardLiolaemus tenuis tenuis(polyphyodont species) and dog fetusesCanis familiaris(diphyodont species). A comparison was also made with dental pulps from adult dogs. Some dental papillae from lizard tooth at bell stage were recombined with quail ectoderm and cultured in explant for 8 days. Furthermore, the histological analysis of dental papillae from lizard and dog fetus showed that dental papillae from both species contain preodontoblast cells, scarce extracellular matrix, and some blood vessels. Dental pulp from adult dogs is composed of odontoblast and fibroblast cells, extracellular matrix, collagen, blood vessels, etc. The control heterologous recombinants after the culture period differentiated chimeric tooth structures, showing that the dental papillae were capable of producing developmental instructions. The electrophoretic study of the supernatants showed differences and similarities. Under SDS‐PAGE the presence of one band of an approximate molecular weight of 49.000 daltons was disclosed, which seems to be unique to dental papilla from adult lizards and dog fetuses. Under 2‐D PAGE protein patterns from adult lizard and dog fetuses disclosed also two protein spots with an approximate molecular weight of 49.000 daltons and isoelectric point of pH ranges between 6 and 7.5. Apparently these spots are unique to both patterns and would have some significance

ISSN:0022-104X    

DOI:10.1002/jez.1402420107

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe aim of this study was to determine the timing of adeno‐hypophysial activation during metamorphosis of the tiger salamander,Ambystoma tigrinum. It consisted of two parts: (1) determination of plasma thyroid hormone concentrations and analysis of thyroid gland histology as a function of metamorphic stage and (2) analysis of the time‐course of uptake of125I by the thyroids during metamorphosis as an indicator of endogenous thyrotropin (TSH) levels. Significant increases in both triiodothyronine (T3) and thyroxine (T4) first were evident at the onset of metamorphic climax (stage II). Maximum levels of both hormones were not observed, however, until the completion of gill resorption (stage VII). No changes in thyroid histology were observed that could be unambiguously related to metamorphic transformation. The thyroids accumulated125I in a slow but linear fashion in premetamorphic larvae (stage I). However, uptake exhibited a rapid peak during early climax (stage II), before maximum concentrations of thyroid hormones were observed. In addition, uptake was maintained above premetamorphic levels at stage VII, in conjunction with maximum levels of T4and T3. Captivity alone produced a small but significant increase in plasma concentrations of T3. It produced no significant effect on either thyroid histology or uptake of125I. These results indicate that adenohypophysial activation occurs rapidly and is maximal at the onset of metamorphic cli

ISSN:0022-104X    

DOI:10.1002/jez.1402420108

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

年代:1987

数据来源: WILEY

摘要:

AbstractWe investigated the anti‐obesity effects of the adrenal androgen, dehydroepiandrosterone (DHEA), on genetically predisposed obese lethal yellow mice (AY/AW). Secondly, we tested the hypothesis that DHEA promotes its anti‐obesity effects by decreasing the activity of glucose‐6‐phosphate dehydrogenase (G6PHD). We subjected four genotype‐sex combinations of yellow and agouti (control) mice to four dietary treatments and determined weight changes, food consumption, and G6PDH activity. Although G6PDH activities of yellow mice were considerably decreased in the 0.4% DHEA treatment group, they were elevated in the 0.0 and 0.1% DHEA treatment groups. In contrast, G6PDH activities of DHEA‐treated control agouti mice remained relatively constant. These studies confirm that DHEA prevents the Aygene from promoting excess fat deposition via some mechanism(s) other than reduced dietary intake. However, the overall absence of agreement between weight change (gain or loss) and G6PDH activity suggests that the anti‐obesity activity of DHEA is not mediated via G6PDH. Since yellow obese (Ay/Aw) mice were found to be more susceptible to DHEA's effects than their agouti (Aw/Aw) littermates, Ayappears to induce an altered metabolism in Ay/Awmice which is more susceptible to the effects of DHEA than the normal metabolism

ISSN:0022-104X    

DOI:10.1002/jez.1402420109

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

年代:1987

数据来源: WILEY

摘要:

AbstractThis study was undertaken to investigate the ferritin content of pore cells in the mantle ofHelisoma duryiand the possibility of these cells being a source of vitellogenic ferritin. Ultrastructurally pore cells in the mantle resemble those previously studied in the heart/kidney region, except that their plasma membrane is less elaborate. The presence of iron is demonstrated in the cells by the Prussian blue reaction, and in the ferritinlike contents of cytoplasmic vesicles by energy dispersive X‐ray analysis. Egg‐laying activity begins 2 days after virgin snails are allowed to mate. By means of radioimmunoassay it is found that mantle (containing pore cells) ferritin content increases rapidly at the onset of egg‐laying, then declines to reproductive levels. As it declines, the blood ferritin content increases to reproductive levels. Ovotestis and digestive gland ferritin contents drop at the onset of egg‐laying, then rapidly return to reproductive levels. The relationships between the ferritin contents of these four tissues at the onset of and subsequent to egg‐laying are discussed. The ferritin contents of various tissues are determined by radioimmunoassay (RIA) after the removal of endocrine dorsal bodies from reproducing snails. The ferritin levels remain unchanged in the blood and digestive gland, increase in the mantle, and decrease in the ovotestis. A possible influence of dorsal body hormone on ferritin uptake by vitellogenic oocytes is

ISSN:0022-104X    

DOI:10.1002/jez.1402420110

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

年代:1987

数据来源: WILEY

摘要:

AbstractKey components for gene transfer to swine embryos using an avian retrovirus are described. A replication‐defective reticuloendotheliosis (REV) viral vector can infect and be expressed in pig embryo fibroblasts (PEF). Infection with a replication‐competent vector (REV‐A) indicates a presumptive block to viral replication in PEF. Swine embryos obtained at the morula stage can be cultured in vitro to the blastocyst stage, injected with retrovirus helper cells or quail embryo fibroblasts producing REV, and transferred to recipient swine with survival to at least 6 wk of gest

ISSN:0022-104X    

DOI:10.1002/jez.1402420111

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

年代:1987

数据来源: WILEY