摘要:

AbstractPhosphoenolpyruvate carboxykinase (E.C. 4.1.32) from ribbed mussel gill cytosol exists as a monomer with Mr70,000. Low levels of Mn2+or Zn2+were required for activity when assayed at high physiological Mg2+levels. Mg2+alone would not activate the enzyme. Optimal activity was observed at pH 6.6. The apparent Kms for phosphoenolpyruvate (PEP) and NaHCO3were 396 μM and 13 mM, respectively, when assayed at pH 6.8 in the presence of 1 mM Mn2+, 1 mM Mg2+, and 1.5 mM IDP. GDP (Kmapp 24 μM) and IDP (Kmapp 46 μM) were both reactive; other nucleoside diphosphates were not. Under standard assay conditions at pH 6.8, the reaction was freely reversible with the rate of PEP carboxylation two to three times the rate of OAA decarboxylation. When assayed in the PEP synthesizing direction at pH 6.8 with 2 mM Mn2+and Mg2+, the apparent Kms for GTP and OAA were 55 μM and 24 μM, respectively. Chloride ion was inhibitory (I50120 mM); 3‐mercaptopicolinic acid (MPA) and 3‐aminopicolinic acid (APA) were competitive inhibitors with respect to PEP and noncompetitive with respect to IDP. MPA was a more effective inhibitor (Kiapp 8–34 μM) than APA (Kiapp 250–500 μM). Aminooxyacetate and N‐butylmalonate (BMA) were not inhibitory and hydroxymalonate was slightly inhibitory (Kiapp 15 mM). ATP showed mixed competitive inhibition with respect to PEP (Kiapp 0.54 mM); inhibition by ATP was not reversed by L‐alanine. Experiments employing BMA and MPA with gill tissue pieces subjected to hyperosmotic stress indicated that the PEPCK reaction in gill tissue was not significantly involved in the regulation of carbon flow for the synthesis of L‐alanine as an intracel

ISSN:0022-104X    

DOI:10.1002/jez.1402570302

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe effects of hypoxia on acid‐base balance and blood gases were examined in larvalAmbystoma tigrinum. Environmental hypoxia (P o 2= 24 mm Hg) resulted in a severe metabolic acidosis. During approximately 4 hr of hypoxia, arterial P o 2fell from 23 to 8 mm Hg while P co 2did not change; plasma lactate concentrations rose from 1.7 to 11 mM; pH fell from 7.9 to 7.3 and [HCO3−] decreased by 8.2 mM. After restoration of normoxia, P o 2rose to 40 mm Hg within 1 hr. All variables returned to control levels between 4 and 24 hr. Circulating levels of norepinephrine were significantly increased and highly correlated with pH after 4 hr of hypoxia. Net and unidirectional Na+and Cl−flux rates were measured before, during, and after hypoxia to determine if cutaneous ion exchange is associated with the acid‐base disturbance. Neither Na+nor Cl−flux rates changed significantly during hyp

ISSN:0022-104X    

DOI:10.1002/jez.1402570303

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe reported pH values of ascidian blood cells vary considerably. It is likely that one or two of several different types of blood cell must have a highly acidic solution within their vacuoles, in which vanadium ions would be present in a reduced state. Thus, one of the reasons for the variation in reported pH values may be that measurements of pH were made without fractionation of the total population of cells. In the present experiments, the combination of fractionation of whole cells by density‐gradient centrifugation, use of a microelectrode that allows measurements of pH under anaerobic conditions, and atomic absorption spectrometry for determinations of vanadium revealed that the contents of signet ring cells, recently identified as vanadocytes, of three ascidian species,Ascidia gemmata, A. ahodori, andA. sydneiensis samea, had low pH values of 2.4, 2.7, and 4.2, respectively. Results obtained by ESR (electron spin resonance) spectrometry confirmed the values of pH obtained with the microelectrod

ISSN:0022-104X    

DOI:10.1002/jez.1402570304

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe activity of theNotchlocus ofDrosophila melanogasterduring embryogenesis is necessary for the correct segregation of neural from epidermal lineages. The action ofNotchis not confined to embryogenesis but is also essential for normal development during the postembryonic stages. Its action is pleiotropic, as revealed by the existence of several classes of mutations which affect various imaginal structures. Here, we examine a group of six recessive mutations, thefacets(fa, fa3, fag, fag−2, fafxandfasw), which affect eye and optic lobe morphology and have been previously shown to be associated with the insertion of transposable elements into an intronic region ofNotch. Using both somatic recombination and gynandromorph analysis, we find that their behavior in a mosaic analysis is not identical. While in the majority of alleles abnormalNotchfunction in the retina is sufficient to induce optic lobe abnormalities, in the case offag−2, a considerable number of individuals having mosaic retinas exhibit normal optic lobe structure. All thefacetalleles appear to behave in a cell‐autonomous manner. A developmental analysis of the eye and optic lobe defects associated with thefacetmutations support the contention thatNotchmay be involved not only in the formation of certain structures but also in their mainte

ISSN:0022-104X    

DOI:10.1002/jez.1402570305

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe objectives of the present study were to determine the levels of serotonin (5‐HT), its major catabolic metabolite, 5‐hydroxyindoleacetic acid (5‐HIAA), and norepinephrine (NE) in chick spinal cord before, during, and after hatching and also to determine if changes in the levels of these chemicals are directly related to the hatching behavior. The levels of 5‐HT, 5‐HIAA, and NE were measured by high performance liquid chromatography with electrochemical detection in whole spinal cords of 20‐day‐old “pre‐hatching” embryos, 21‐day‐old “normal hatching” embryos, 0‐day‐old “post‐hatching” chicks, and 0‐day‐old “glass egg hatching” chicks. NE was measured but no significant differences were found in NE levels among experimental groups. The concentration of 5‐HT was elevated in chick embryo spinal cords during normal hatching compared to pre‐hatching embryos and post‐hatching chicks. The concentration of 5‐HIAA was elevated during and after normal hatching compared to pre‐hatching embryos. However, neither 5‐HT nor 5‐HIAA levels were found to be elevated in chick spinal cords during glass egg hatching compared to pre‐hatching embryos or post‐hatching chicks. Therefore, there appears to be an activation of the serotonergic system in chick spinal cord related to the specific event of hatching but this activation is not directly related

ISSN:0022-104X    

DOI:10.1002/jez.1402570306

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

年代:1991

数据来源: WILEY

摘要:

AbstractMonoclonal antibody 9G1 (mAb 9G1) is reactive to the wound epithelium of axolotl larvae and therefore provided the opportunity to examine the interaction between the wound epithelium, nerves, and blastemal mesenchyme during axolotl limb regeneration. In unamputated limbs, mAb 9G1 is reactive to most or all cells of the dermis, skeletal elements, blood vessels, and nerves, to a few unidentified cells in muscle, and to none in epidermis. During regeneration of axolotl limbs, mAb 9G1 reacts strongly to an intracellular antigen of the blastemal mesenchyme and of the distal‐most portion of the wound epithelium, the so‐called apical epithelial cap (AEC). Because this thickened wound epithelium of regenerating amphibian limbs has been suggested as functioning in a manner similar to the apical ectodermal ridge (AER) of embryonic limb buds, it was of interest to further examine the reactivity of mAb 9G1 during various stages of regeneration. Whether mAb 9G1 reactivity in the AEC depended on mesenchyme and/or nerves was also tested. Monoclonal antibody 9G1 reactivity appears in the AEC of regenerating limbs prior to outgrowth of the blastema and persists throughout blastemal stages. Apical epithelial cap reactivity to mAb 9G1 is nerve dependent during early stages of blastema development and becomes nerve‐independent at later stages. When epithelium‐free blastemal mesenchyme is grafted onto injured flank musculature, ectopic limb regeneration occurs and the AEC derived from flank epidermis exhibits mAb 9G1 reactivity. These results show that a mAb 9G1 reactive AEC is characteristic of regenerating limbs and that expression of the 9G1 antigen by the AEC is dependent upon underlying blastemal mesenchyme and

ISSN:0022-104X    

DOI:10.1002/jez.1402570307

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe influence of culture medium and protein supplements on in vitro fertilization (IVF) and morula‐to‐blastocyst development in culture was examined in the domestic cat. In Study I, follicular oocytes were fertilized and cultured in 1) modified Krebs Ringer bicarbonate (mKRB); 2) modified Tyrode's solution (TALP) without phosphate or glucose; or 3) Ham's F10. All media contained bovine serum albumin (BSA). Fertilization rates were similar (P>.05) among mKRB (75.0%), TALP (70.6%), and Ham's F10 (80.0%) treatments. Compared to TALP (77.8%), more (P.05). Study II evaluated the effects of protein availability and type on IVF and embryo growth. Ham's F10 was supplemented with polyvinylalcohol (PVA, 2 mg/ml), BSA (4 mg/ml), fetal calf serum (FCS, 5%), or estrous cat serum (ECS, 5%) and used to fertilize and culture embryos. Fertilization was enhanced (P.05) of becoming morulae. However, more FCS‐ or ECS‐supplemented morulae continued to the early blastocyst stage (30.8%, 22.2%, respectively,P<.05) than PVA‐ (10.3%) or BSA‐ (13.8%) exposed morulae. In the domestic cat IVF system, the type of medium and protein supplement used appears to have a greater impact on embryo development in vitro than on fertilization. There also is a morula‐to‐blastocyst developmental block for cat embryos resulting from IVF which is partially circumvented by adding serum to the culture medium. Ham's F10 containing FCS or ECS produces the highest incidence of fertilization (∼85%), and ∼2‐fold more of these embryos develop in culture to blastocysts compared to embryos supplem

ISSN:0022-104X    

DOI:10.1002/jez.1402570308

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

年代:1991

数据来源: WILEY

摘要:

AbstractTo examine the biological significance of thyroid hormones contained in eggs, the hormones were depleted from eggs by treating the mother fish with thiourea. Constantly spawning medaka (Oryzias latipes) were reared in fresh water containing 0.03% thiourea. The plasma thyroxine (T4) and triiodothyronine (T3) concentrations in the mother fish were about 8 and 5 ng/ml, respectively, before the treatment, and decreased to 1/5 of the initial levels within 1 day. Initial concentrations of T4 and T3 in eggs just after fertilization were about 4 and 1 ng/g, respectively, and decreased to less than 1/4 when the mother was treated with thiourea for 7 days. Minimum effective concentration of thiourea to decrease the hormone concentrations in mother's plasma and the eggs was 0.003%. During the course of normal development, egg thyroid hormones are maintained at the initial levels during the first 4 days, and continuously decrease toward hatching (10 days after fertilization). There was no difference between the normal eggs (derived from the mother fish without thiourea treatment) and hormone‐deficient eggs (hormone concentrations were less than 1/10 of the control) in hatchability, the time of hatching, and survival under starvation. No difference was seen between the two groups in body weight, body length, condition factor, and survival rate 16 days after hatching. These findings indicate that more than 90% of the hormones contained in eggs are not essential for early development in medak

ISSN:0022-104X    

DOI:10.1002/jez.1402570309

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

年代:1991

数据来源: WILEY

摘要:

AbstractHomozygous gynogenetic (GE) rainbow trout (Oncorhynchus mykiss) were produced, using diploid gynogenesis with UV rays as an agent of sperm inactivation and heat shock as treatment for inhibition of first cleavage and restoration of diploid status. Their survival and growth performances were analysed in progenies from individual females, and compared with both diploid outbred control (D) and gynogenetics resulting from inhibition of meiosis II (GP).The homozygous status of GE fry was proved by electrophoretic control.Mean survival of GE groups was quite low (around 19% of D control at feeding start, vs. 63% in GP) but much depended on the founder female. A positive correlation was found between early survival of haploids and late survival of diploid GE fry from the same mother.Growth was also very reduced in both gynogenetics, though to a lesser extent (90 and 80% of D control at day 103 in GP and GE groups respectively).

ISSN:0022-104X    

DOI:10.1002/jez.1402570310

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

年代:1991

数据来源: WILEY

摘要:

AbstractWe report that parthenogenetic activation (pronuclear formation) is induced during in vitro culture of recently ovulated (13–14 hr post‐hCG) mouse oocytes in pyruvate deficient medium. Pronuclear formation occurred when oocytes were cultured in medium containing 1/10X (Pyr−) or lower concentrations of pyruvate but failed to occur either in oocytes cultured in the presence of 0.47 mM (1X, Pyr+) or 1/2X pyruvate or in oocytes cultured in the absence of pyruvate but with cumulus cells. Pronuclear formation was evident within 8 hr of culture and completed by 16 hr and remained intact during continuous culture in Pyr−medium. Transfer of pronuclear oocytes to Pyr+medium resulted in pronuclear membrane disassembly and further parthenogenetic development. A similar incidence of parthenogenetic activation occurred when recently ovulated oocytes were cultured in the presence of cycloheximide but not following ethanol or hyaluronidase treatment. However, both ethanol and hyaluronidase induced pronuclear formation in in vivo aged oocytes. Results suggest that the type of activation induced varies with the age of the oocyte and the nature of the stimulus. Amino acid uptake ([35S]methionine) by oocytes was unaffected by Pyr−culture whereas incorporation into protein was markedly inhibited. Gel electrophoretic analysis of labeled egg extracts revealed a marked inhibition of egg protein synthesis after 4 hr of culture in Pyr−. The occurrence of a cortical reaction was monitored by binding of fluorescent labeled lectin to the oocyte surface. A cortical reaction occurred in response to ethanol treatment of freshly ovulated and in vivo aged oocytes cultured in Pyr+medium but not in pronucleate oocytes induced by Pyr−culture. Suppression of ethanol‐induced cortical reaction by Pyr−culture was restored following transfer of oocytes to Pyr+medium. Results demonstrate that nuclear events as well as plasma membrane events can be simply regulated by controlling the amount of energy substrate available to the germ cell. Effects of Pyr−culture in inducing pronuclear formation appear to be mediated in a large part via inhibition o

ISSN:0022-104X    

DOI:10.1002/jez.1402570311

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

年代:1991

数据来源: WILEY