摘要:

AbstractArginase from the liver ofXenopus laevishas been purified to homogeneity by heat treatment, acetone fractionation, and isoelectric focussing. The main component had an isoelectric point (I.E.P.) of 7.3; there is a minor component of I.E.P. 7.8. The molecular weight of the enzyme, as determined by gel filtration on Sephadex G200, is 76,000 daltons, substantially less than that of rat liver arginase studied concurrently. The molecular weight of the subunits, as determined by electrophoresis in sodium dodecyl sulfate, is 18,000 daltons, again less than that of rat liver arginase. The data indicate thatXenopusliver arginase, like rat liver arginase, is a tetramer. The molecular weight of arginase from adultXenopus laeviscorresponds to that from larvalRana esculenta.

ISSN:0022-104X    

DOI:10.1002/jez.1402220202

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

年代:1982

数据来源: WILEY

摘要:

AbstractTerrestrial oligochaetes demonstrate significant volume and osmoregulatory abilities that are under neurosecretory control. In the marine Oligochaete, little is known of volume or osmoregulatory capacities. However, histological evidence has linked cerebral neurosecretion and osmoregulation. The present study investigates water, ion, and volume regulation in an intertidal oligochaete and the effects of ablation of primary neurosecretory centers (supra‐and subesophageal ganglia) on these parameters. Control, sham‐operated, and ablatedClitellio arenariuswere acutely transferred to diluted seawaters. Osmolality and Na, K, Cl (mEq/liter) concentrations were determined in total tissue water and in extracellular fluids. Extracellular volume was determined (using micropuncture techniques) as the fraction of the total tissue water in which14C‐polyethylene glycol was distributed. With transfer to diluted seawater, all worms demonstrated hyperosmotic conformity. Tissue osmolality decreased in all animals at the same rate indicating no effect of ablation on integumental water permeability. Two phases of volume regulation were observed. In phase 1 (0–6 hours) osmolality decreased while water content (gm H2O/gm solute free dry weight = s.f.d.w.) increased both intra‐ and extracellularly. During this period, some volume regulation was accomplished in the control groups, particularly during the first 5 minutes, by the excretion of extracellular Na and Cl (μmoles/gm s.f.d.w.) which limited water gain. Ablated worms, reflecting less extracellular solute loss, gained more water than control groups. In phase 2 (6–18 hours) osmolality was constant, and all groups demonstrated a slow intra‐ (IC) and extracellular (EC) regulatory volume decrease. The solutes that accompanied volume loss were Na (EC), Cl (IC), and unmeasured solutes (IC). Reduction in intracellular solute content was the most significant loss occurring during this period with little difference among the groups tested. We hypothesize the primary effect of ablation is on extra‐ rather than intracellular v

ISSN:0022-104X    

DOI:10.1002/jez.1402220203

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe effects of temperature on the firing patterns of the excitatory motor supply to the bender muscle were examined in autotomized walking limbs of the crabPachygrapsus crassipes. A brief electrical shock applied to the limb nerve evoked an action potential in one or both of the excitor axons and an excitatory junctional potential (ejp) in the bender muscle fibers. However, at high temperatures a single shock to one of the excitor axons (E2) resulted in a short train of nerve spikes and a concomitant burst of ejps. Extracellular recordings made from two sites along the E2axon demonstrated that the additional action potentials are generated peripherally. Furthermore, myogram recordings from bender muscles in untethered animals indicate that peripheral generation of spikes does take place in intact crabs exposed to high temperatures.The peripheral generation of action potentials exhibited a critical temperature threshold which could be altered by acclimation and by low levels of ethanol in the saline bathing the autotomized limb preparation. This phenomenon may, therefore, be closely associated with membrane fluidity.

ISSN:0022-104X    

DOI:10.1002/jez.1402220204

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe distribution of enzymes in the blastoderm and the yolk was investigated in the eggs of the bony fish,Misgurnus fossilis. The total activities of lactate dehydrogenase (LDH), glucose‐6‐phosphate dehydrogenase (G‐6‐PD), and aldolase (ALD) did not change during early development. However, the enzymes were redistributed in the egg: at the blastula stage the blastoderm contains about 60% of the total ALD activity and 80% of the total LDH and G‐6‐PD activities.The “free cytoplasm” volume, in which the enzymic proteins can be solubilized, is greater in the yolk than in the blastoderm. Low levels of homologous enzymes from other species injected into the egg are distributed between the blastoderm and the yolk in the same way as are the native enzymes; they are primarily localized in the blastoderm. Injected exogenous enzyme concentrates preferentially in the yolk, apparently being distributed proportionately with respect to the “free cytoplasm” volumes. The ratio of these “free cytoplasmic” volumes, determined by distribution of the injected enzyme (LDH), in the yolk and in the blastoderm is 6.8. On the basis of our results we propose that many egg enzymes are noncovalently bound to blastoderm structures, and that the “nonbound” fraction of the enzymes in the cytosol is distributed proportionally to the “free cytoplasm” volumes in the blastoderm and in the yolk.Fractionation of the subcellular constituents of blastoderm extracts by ultracentrifugation or by gel filtration on Sepharose in the presence of an excess of LDH reveals the high‐molecular weight LDH‐containing complexes. These complexes are absent in the yolk and in the unfertilized eggs. These results are consistent with the hypothesis that the binding of the enzyme to subcellular structures in the blastoderm is an important

ISSN:0022-104X    

DOI:10.1002/jez.1402220205

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe cytochemical localization of acrosin (EC 3.4.21.10) was investigated using a fluorescent technique, based on the use of fluorogenic substrates, derivatives of 4‐methoxy‐β‐naphthylamine, which liberate a fluorescent tag that, if coupled to 5‐nitrosalicylaldehyde, generates an insoluble, fluorescent product. From the data obtained from boar and bull spermatozoa that had been subjected to different treatments, we have found that the acrosomal, trypsinlike proteinase is practically inaccessible in intact, freshly ejaculated spermatozoa. Acrosin activity was detected after subjecting the spermatozoa to a treatment that simulates the process they undergo at the moment of fertilization, showing a particulate localization in the acrosome of some of the spe

ISSN:0022-104X    

DOI:10.1002/jez.1402220206

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

年代:1982

数据来源: WILEY

摘要:

AbstractIn an attempt to understand more fully processes that control the selection or recruitment of follicles for ovulation, the superovulation paradigm in combination with the androgen, 5α‐dihydrotestosterone, or the antiandrogens, cyproterone or cyproterone acetate, was used in the immature mouse to alter the developmental potential of follicles destined to ovulate or to become atretic. Quantitative analysis of the numbers of eggs ovulated after one or more rounds of stimulation by pregnant mare's serum gonadotrophin followed by human chorionic gonadotrophin (PMSG‐hCG), revealed a dose‐dependent ovulation response to exogenous androgen and antiandrogen. Low dosages of androgen improved the ovulation response significantly. Large dosages of cyproterone and cyproterone acetate (100 mg/kg body weight) generally decreased the ovulation number in gonadotrophin‐injected mice, suggesting a role for androgen in preovulatory events that occur within the ripened follicle after the ovulatory stimulus (hCG) has been received. Low dosages of cyproterone, particularly 25 mg/kg, significantly enhanced the ovulatory response, a phenomenon not observed for cyproterone acetate at this dosage. Radioimmunoassays of serum LH suggested that the differential response of the ovary to the two antiandrogens was probably related to endogenous LH release. Experiments in which the time of administration of hCG± cyproterone was varied after PMSG priming suggested that cyproterone at a dosage of 25 mg/kg had a “rescuing” effect on follicles destined to become atretic for up to 96 hr after PMSG priming. Cyproterone at a dosage of 100 mg/kg had no such effect, and actually decreased the magnitude of the ovulatory response at all time points tested, suggesting that follicular atresia was accelerated by this treatment. Experiments in which the time of administration of cyproterone (100 mg/kg) was varied after hCG suggested that whatever the important androgen‐mediated events preceding ovulation, these events occur within 2 to 3 hr after the hCG signal. By quantitating the numbers of eggs over several superovulation cycles, it could be shown that hormonal treatment in one induced cycle could affect significantly the ovulation response in subsequent cycles, suggesting that androgens influence the development of classes of follicles other than preovulatory follicles. These studies suggest that the process through which follicles are selected for ovulation is extremely sensitive to the androgenic environment and that the developmental pathways leading to ovulation or preovulatory follicular atresia are

ISSN:0022-104X    

DOI:10.1002/jez.1402220207

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

年代:1982

数据来源: WILEY

摘要:

AbstractTermination of seasonal breeding in the photoperiodic weaver bird does not occur as a result of photorefractoriness, and yet, in nature birds become refractory. Earlier studies indicated a seasonal variation in photosensitivity of this bird during the reproductive cycle and it was suggested that setting of the photoperiodic response threshold at a higher level might explain gonadal regression. Such a possibility was now examined by keeping birds in constant 13L/11D (the near maximal day length at Varanasi, India) and 15L/9D simultaneously for over 8 mo. While breeding in birds in 15L/9D continued, gonads regressed in 13L/11D indicating that the day length which was stimulatory in spring is no more sufficient to permit gonadal activity. Cyclicity in 13L (and in artificial 12L as well as natural daylength) may be explained on the basis that these schedules exceed the basic photoperiodic response threshold—hence the initiation of gonadal development. Once the gonads are developed due to decline in photosensitivity (caused perhaps by sex hormones) gonadal regression occurs, thus resulting in reproductive periodicit

ISSN:0022-104X    

DOI:10.1002/jez.1402220208

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

年代:1982

数据来源: WILEY

摘要:

AbstractSpermatid/sperm basic chromosomal proteins from 17 species and subspecies of the genusXenopus(Anura, Pipidae) were compared. Electrophoresis on acetic acid/urea/Triton X‐100 polyacrylamide gels revealed that eachXenopusspecies with a diploid chromosome number of 36, 72, or 108 showed multiple, diverse spermatid/sperm‐specific basic chromatin proteins with mobilities greater than the somatic histones. The numbers and mobilities of these proteins were characteristic of eachXenopusspecies and each subspecies ofXenopus laevis. Cytochemical tests revealed that the sperm basic nuclear proteins of theseXenopusspecies and subspecies were rich in arginine and lysine and contained more arginine than the nuclear proteins of somatic cells.X. tropicalis(2n = 20) andX. sp. n. (Zaire) displayed spermatid/sperm‐specific basic chromatin proteins which migrated within the histone H1 region of acetic acid/urea/Triton X‐100 polyacrylamide gels. Cytochemically the sperm nuclei of these species resembled those of somatic cells.These observations suggest that spermatid/sperm basic nuclear proteins can be used as molecular markers for individual species and subspecies of the genus

ISSN:0022-104X    

DOI:10.1002/jez.1402220209

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe interaction of sperm with the zona‐free hamster egg was studied. Hamster sperm were capacitated in Tyrodes media, containing 50% heat‐inactivated serum and used to inseminate zona‐free eggs in BWW containing 10% serum. Capacitated sperm began fusing with eggs within the first hour of insemination and by 3 h penetration had ceased as indicated by the absence of further changes in the mean number of sperm incorporated per egg. Penetration by capacitated hamster sperm was linearly related to the log of the motile sperm concentration at concentrations above 104cells/ml. The viability of sperm and eggs in culture was limited in these studies to approximately 3–5 h. The existence of a block to unlimited sperm penetration of the zona‐free egg was sought in reinsemination experiments. A relatively low sperm concentration was used to initiate egg responses, followed, at timed intervals, by reinsemination with a high challenge concentration of sperm. Subsequent polyspermy levels reflected the presence or absence of the egg's block to polyspermy response. In order to circumvent the problems arising from the rapid aging of hamster sperm in culture, mouse sperm were employed, a convenience afforded by the lack of species specificity in this egg. Reinseminated eggs incorporated additional sperm during the challenge; therefore, the hamster egg is not capable of preventing unlimited sperm penetration. The implications of these findings to the use of the zona‐free hamster egg test in fertility evaluation i

ISSN:0022-104X    

DOI:10.1002/jez.1402220210

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

年代:1982

数据来源: WILEY

摘要:

AbstractTo investigate the cellular mechanisms in preimplantation adhesion of the mammalian blastocyst to uterine epithelium, it is essential to avoid the complexities of the maternal environment but at the same time prevent the introduction of competing artificial surfaces, to which embryos preferentially adhere. We demonstrate here that sealed vesicles of isolated uterine epithelium cultured together with blastocysts in hanging drops provide an optimum system for encouraging and observing the adhesive interactions. The responses of the embryonic and maternal cells were identical to those known in vivo. Microvilli were seen on both surfaces, and in places the membranes were drawn into close apposition with some desmosomelike junctions. After blastocyst adhesion occurred trophoblast cells invaded the epithelium and showed phagocytic activity, closely resembling the invasion that follows adhesion during normal pregnancy in mice.

ISSN:0022-104X    

DOI:10.1002/jez.1402220211

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

年代:1982

数据来源: WILEY