摘要:

AbstractThe effect of calcium ions on the chemical induction of conjugation inParamecium caudatumwas examined in the simplest medium that induces conjugation, containing either KCI or MnCl2in TRIS‐HCI buffer. The concentration of K ions necessary for induction increased with the concentration of Ca ions added. The maximum induction of conjugation took place at a constant ratio of the K+concentration to the square root of the Ca2+concentration regardless of their ionic strengths. Similar results were obtained in the induction by Mn2+, where the square root of the Mn2+concentration is proportional to the square root of the Ca2+concentration for maximum induction. The results strongly suggest that the activation for conjugation is closely related to removal of Caions bound to the cell surface and that an ion exchange system on the cell surface governed by Gibbs‐Donnan principle has an essential role in the chemical induction of conjugation inParamec

ISSN:0022-104X    

DOI:10.1002/jez.1402310302

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

年代:1984

数据来源: WILEY

摘要:

AbstractLittle is known about the characteristics of hemolymph (blood) flow in animals with open circulatory systems. We measured cardiac output and blood flow to specific tissues in the black abalone,Haliotis cracherodii, a gastropod mollusk. The use of thermodilution allowed us to make repeated measurements of cardiac output and cardiac stroke volume over relatively short time intervals (5–10 heart beats) in resting, unrestrained abalone while disturbing the animals minimally. Anatomical studies of the abalone circulation showed that the arterial system terminated in small diameter (approaching 10–20 μm in some cases) lacunar tissue spaces. Because of this, we used radioactive microspheres (which must be trapped in the tissue vasculature) to measure blood flow rates to selected tissues. The major findings of our study were that 1) cardiac output in the black abalone ranged from about 100 to 150 ml · kg−1· min−1, and was highly correlated with body size; 2) weight‐specific cardiac stroke volume was about 5 ml · kg−1, considerably larger than that of a mammal; 3) tissue blood flow rates ranged from 10 ml · 100 g−1· min−1(foot muscle) to 80 ml · 100 g−1· min−1(nephridial tissue), similar to typical tissue blood flow rates in mammals. Our data suggest that the blood in the abalone is directed to the tissues not in proportion to percent total body weight the tissues represent (as might be expected in an open vascular system), but apparently in proporti

ISSN:0022-104X    

DOI:10.1002/jez.1402310303

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

年代:1984

数据来源: WILEY

摘要:

AbstractAlligators in fresh water regulate their plasma and cloacal fluid electrolytes at concentrations similar to those of other crocodilians. They have an exchangeable Na pool of 60.8 μmol/gm and a unidirectional Na efflux of 3.9 μmol/100 gm·hr. Of this 11% is excreted from the cloaca, 43% presumably diffuses across the body integument, and the remaining 46% is lost from the head region. The integumental Na efflux is estimated to be 0.01 μmol/cm2·hr. In fresh water the net flux is 0.5 μmol/100 gm·hr, which suggests that nondietary Na uptake can compensate for 86% of unidirectional N

ISSN:0022-104X    

DOI:10.1002/jez.1402310304

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

年代:1984

数据来源: WILEY

摘要:

AbstractLocomotor activity of rough‐skinned newts (Taricha granulosa) was significantly higher in intact and hypophysectomized males injected intracranially with 100 ng CRF (ovine corticotropin‐releasing factor) than in those injected with 10 ng CRF or saline. In addition, an injection of corticosterone or dexamethasone failed to stimulate newt locomotor activity. These results provide evidence that CRF can act independently of pituitary hormones to stimulate locomotor activity in a nonmammalian vertebr

ISSN:0022-104X    

DOI:10.1002/jez.1402310305

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

年代:1984

数据来源: WILEY

摘要:

AbstractAnalysis of purified Na,K‐ATPase from brine shrimp nauplii revealed two molecular forms of the α subunit separable by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis [G.L. Peterson, R.D. Ewing, S.R. Hootman, and F.P. Conte (1978) J. Biol. Chem.253:4762]. The molecular form with lower mobility is designated α1and the one with higher mobility, α2in a neutral or alkaline gel system. Differences in Na+‐dependent, K+‐sensitive phosphorylation of these two molecular forms have been investigated by directly measuring the radioactivity present in each phosphoprotein after separation of the two forms by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. In the presence of Na+, Mg2+, and ATP, when the ATP concentration is above 1 μM, both α subunits are phosphorylated, although the phosphoprotein content of α1is considerably greater than that of α2. Below 1 μM ATP, the phosphoprotein content of α2is even further reduced. These striking differences in phosphorylation at low ATP concentrations are not due to a greater instability of the α2phosphoprotein during the long electrophoresis times or during fixation, staining, and destaining. The proportion of total phosphoprotein content in α2, as well as the relationship between phosphoprotein content and ATP concentration, is unchanged when the radioactive analysis is performed on frozen gels that have been electrophoresed for shorter times, even though the actual amount of phosphorylation is 15 times greater than with fixed gels. Since the concentration of α1and α2vary during development [G.L. Peterson, L. Churchill, J.A. Fisher, and L.E. Hokin (1982) J. Exp. Zool.221:295], the differences in phosphorylation may be relevant to differences in Na,K‐ATPase activity during diff

ISSN:0022-104X    

DOI:10.1002/jez.1402310306

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

年代:1984

数据来源: WILEY

摘要:

AbstractAnalysis of purified Na,K‐ATPase from brine shrimp nauplii by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis reveals two large (α) subunits [G.L. Peterson, R.D. Ewing, S.R. Hootman, and F.P. Conte (1978) J. Biol. Chem.253:4762]. The band with lower mobility in a neutral or alkaline gel is designated α1and the band with higher mobility α2. Ouabain prevents dephosphorylation of both α1and α2as documented by gel analysis, but a higher concentration of ouabain is required to prevent dephosphorylation of α2. The photoaffinity label, [3H]4′(2‐ethyldiazomalonyl) digitoxigenin monodi‐gitoxiside, specifically labels α in a ouabain‐protectable manner without labeling other contaminating proteins in the preparation. Greater than 93% of the total ouabain‐protectable labeling of the α subunits is associated with α1. The photoaffinity label, [3H]4‴ (2‐ethyldiazomalonyl) digitoxin, specifically labels α1and β in a ouabain‐protectable manner without labeling other contaminating proteins. These data show that in the brine shrimp the third digitoxose residue of digitoxin binds in a region in which the α1and β chains are in close proximity. Less than 5% of the specific ouabain‐protectable labeling of total α is associated with α2. These studies indicate that cardioactive steriods ha

ISSN:0022-104X    

DOI:10.1002/jez.1402310307

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe two large subunits of brine shrimp Na,K‐ATPase can be resolved by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis at neutral pH and at acidic pH. These subunits appear to reverse their positions on the gel relative to each other when resolved at acidic pH relative to neutral pH. The migration of both subunits is apparently affected by charge, even in the presence of 2.5% sodium dodecyl sulf

ISSN:0022-104X    

DOI:10.1002/jez.1402310308

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe growth of presomite mouse embryos in culture was studied using mouse Ehrlich ascites tumor fluid and bovine serum albumin as supplements to the tissue culture medium. The best development was observed with a mixture of 10–20% ascites fluid and 2% bovine serum albumin. During 48 h of culture under these condition, embryos grew from egg cylinders to complex structures with neural folds and other organ rudiments. Most embryos had beating hearts, numerous pigmented red blood cells, and a fused chorioallantoic placenta. The results suggest that factors in ascites fluid support differentiation and growth of mouse embryos. Addition of bovine serum albumin was also beneficial for development. Differential sister chromatid staining of cultured embryos showed that ascites fluid increased the rate of clel proliferation as compared with medium containing bovine serum albumin alone, or bovine serum albumin and fetal calf serum. These results with abundant, and readily available supplements may facilitate certain studies of mouse embryo developmen

ISSN:0022-104X    

DOI:10.1002/jez.1402310309

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

年代:1984

数据来源: WILEY

摘要:

AbstractSmall quantities of urea and soluble urates are present in eggs of redwing blackbirds at oviposition, but no ammonia can be detected in eggs before the ninth day of a 12‐day incubation. Urea‐nitrogen accumulates relatively slowly in eggs during development, whereas urate‐nitrogen accumulates more rapidly. At hatching, 71% of the waste‐nitrogen accumulated in eggs is in the form of urates, 26% in urea, and 3% in ammonia. Thus, the general pattern of nitrogen excretion described for embryos of precocial birds applies also to those of an altricial

ISSN:0022-104X    

DOI:10.1002/jez.1402310310

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

年代:1984

数据来源: WILEY

摘要:

AbstractCyclic changes in cortical stiffness, condensation‐decondensation of chromosomes, and breakdown‐reformation of the nuclear envelope were found to continue in eggs ofDendraster excentricustreated with colchicine even though mitosis and cleavage were suppressed. Furthermore, a consistent and precise synchronization persisted between these cyclic phenomena; each rise and fall of cortical stiffness coincided with the breakdown and reformation, respectively, of the nuclear envelope. The overall cycle length was prolonged relative to controls because of an extended intermitotic phase, indicating that assembled mitotic microtubules do not influence cell cycle timing in this species. In colchicine‐treated eggs ofStrongylocentrotus purpuratus, however, the cortex and the nucleus became arrested in conditions equivalent to metaphase, as if the mitotic phase was indefinitely prolonged. The cortex was stabilized in a state of high stiffness, the chromosomes remained condensed, and the nuclear envelopes remained broken down. In this species, even in the absence of rhythmic change, a strict correlation between the cortical status and the nuclear condition was still consistently observed. The persistence of coordination, in spite of diverse species‐specific responses to colchicine, suggests the existence of a common control mechanism between the cytoplasm and nucleus in normal eggs that is important in cell cycle timing. The insensitivity to colchicine indicates that the mechanism of coordination is independent of micro

ISSN:0022-104X    

DOI:10.1002/jez.1402310311

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

年代:1984

数据来源: WILEY