摘要:

AbstractKinetic and structural properties of muscle pyruvate kinases from species adapted to different temperatures and hydrostatic pressures were examined. Most muscle pyruvate kinases can exist in two temperature‐dependent conformational states. For the low temperature conformers, activation free energies and enthalpies were proportional to the species' adaptation temperatures. The interspecific differences in activation parameters may be due to different amounts of weak bond formation/rupture during the rate‐limiting event(s) in catalysis. When comparisons of substrate binding ability at physiological temperature, is are made, a marked conservation in apparent Kmvalues is observed among species. Structural rigidity, as estimated by heat inactivation temperature, is positively correlated with adaptation temperature. The apparent size of the conformational change which occurs during catalysis is also positively correlated with cell temperature, except for enzymes for deep‐sea sp

ISSN:0022-104X    

DOI:10.1002/jez.1401980102

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

年代:1976

数据来源: WILEY

摘要:

AbstractRats raised from day 2 of life at an ambient temperature of 10° showed delayed vaginal opening when compared to controls raised at 22°. Coldraised animals were also lighter in weight at the time of vaginal opening and had significantly longer estrous cycles. Low temperature may cause these effects either by suppressing prolactin secretion or, more probably, by elevating thyroid hormone levels which in turn suppress serum gonadotropin concentration

ISSN:0022-104X    

DOI:10.1002/jez.1401980103

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

年代:1976

数据来源: WILEY

摘要:

AbstractThermal behavior of parietalectomized, sham‐parietalectomized or intact lizards (Anolis carolinensis) was recorded in a test chamber containing moving photothermal gradients. Following parietalectomy, animals chose significantly higher temperatures than sham‐parietalectomized or intact control animals, which chose lower and statistically identical temperatures. When pre‐surgical and post‐surgical means are compared within groups, the eccritic temperature was 2.10°C higher following parietalectomy, 0.72°C higher following sham‐parietalectomy, and 0.31°C higher in intact controls during the postoperative measurements. The effects of parietalectomy indicate that the parietalpineal complex may be involved in behavioral thermoregulation by precisely regulating exposure to heat sources (e.g

ISSN:0022-104X    

DOI:10.1002/jez.1401980104

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

年代:1976

数据来源: WILEY

摘要:

AbstractLizards were acclimatized to various regimes of temperature (15°, 35°C) and photoperiod (LD 08:16, 16:8). Parietalectomized, sham operated, and control animals were placed in thermal gradients and their body temperatures monitored for periods of up to 15 days. Daily rhythms of thermal selection were evident with higher temperatures selected in late photophase and lower temperatures selected in scotophase. Thermal selection was more variable in scotophase than in photophase. Parietalectomized lizards chose significantly higher body temperatures than did shams or controls. Acclimatization to temperature and photoperiod had little or no effect on the thermal preferendum. The preferred body temperature of controls was 33.2°C ± 3.59. Length of time in the gradient tended to change thermal preference, especially in lizards acclimated to 15°C. Through interactions with the pineal gland the parietal eye is probably important in synchronizing many bodily functions with photope

ISSN:0022-104X    

DOI:10.1002/jez.1401980105

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

年代:1976

数据来源: WILEY

摘要:

AbstractPhospholipase activity of egg‐water treatedArbacia punctulataandLytechinus variegatussperm was shown to result from the sequential action of phospholipase A and lysophospholipase. A transient burst of phospholipase A activity followed induction of the acrosome reaction with egg water. The time of appearance suggested an acrosomal localization of the enzyme. The peak activity of phospholipase A correlated with initiation of sperm‐egg fusion, suggesting a role for sea urchin sperm phospholipase A in membrane fusion and/or egg activation during fertilizat

ISSN:0022-104X    

DOI:10.1002/jez.1401980106

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe majority of RNA in spermatozoa from the epididymis and ductus deferens of mice was found to be 28 s and 18 s RNA. This RNA was also seen in human ejaculated spermatozoa. Our evidence indicates that little or none of the 28 s and 18 s RNA is transcribed in the maturing mouse spermatozoa and that the majority is synthesized in the primary spermatocyte. This RNA may be necessary to maintain post‐meiotic translation during spermatogenesi

ISSN:0022-104X    

DOI:10.1002/jez.1401980107

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe ruthenium red (RR) stained forelimb musculature of three species of urodelesTriturus(Notophthalmus)viridescens,Amblystoma maculatum,Amblystoma opacumin various stages of growth were examined with the electron microscope for the presence of satellite cells. It was found that RR staining facilitated greatly the identification of satellite cells. In young larvae of all three species satellite cells were detected with a frequency of 29% to 48% per total number of nuclei. In adult Triturus andAmblystoma maculatumsatellite cells were no longer detected; instead “pericytes” as described by Hay ('74) were seen with a frequency of 12% and 3% respectively. During metamorphosis of Triturus satellite cells, with part of their myofiber‐satellite cell intercellular space filled with basement membrane material, occurred at a peak frequency. The cells presumably are intermediate in the formation of “pericytes.” At ten days after metamorphosis satellite cells and intermediate cells were no longer detected and the limb musculature contained only “pericytes” similar to the ones observed in adult newts. The significance of the presence of satellite cells in relation to limb regeneration and muscle regeneration

ISSN:0022-104X    

DOI:10.1002/jez.1401980108

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe Ca and Mg content of unfertilized sea urchin eggs (3 and 21 μmole/ml eggs) remains remarkably constant over periods of hours, even when the eggs are suspended in Ca‐ or Mg‐free sea water. After fertilization the Ca content of eggs in regular sea water increases sharply by about 20%, followed by a decrease to the unfertilized level by 40 minutes. However, if the fertilized eggs are washed three minutes in Ca‐free sea water a sharp decrease in the Ca content occurs amounting to 30% of the total in the first 40 minutes, with little change thereafter. Suspension of the eggs in Ca‐free sea water results in an even greater loss of Ca amounting to about 43% of the total in the same time interval, followed by a continuing slow loss. It is concluded that fertilization initiates the intracellular release of Ca, which is then extruded. For unwashed eggs this change is masked by the simultaneous generation of new extracellular coats with high affinity for Ca.Changes in the Mg content of fertilized eggs follow the same general pattern except that absorption of this divalent cation to the extracellular coats is

ISSN:0022-104X    

DOI:10.1002/jez.1401980109

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

年代:1976

数据来源: WILEY

摘要:

AbstractDependence of bristle pattern on size and joint formation was studied for male first leg tarsi offj(four jointed) andd(dachs) mutants in homozygotes and in mosaics resulting from X‐ray induced mitotic recombination. Homozygotes have four tarsal segments, lacking a third tarsal joint in most cases. The two proximal segments are shortened, the first by one‐third, and altered in bristle pattern, whereas the distal two segments are little affected. Expressivity offjis high, and ofdis low, for the extent and frequency of joint failure. The longer the second segment, the more complete the third joint and the greater the bristle number. Only the jointed side of the segment approximates two segments in its bristle pattern. Mosaic studies show that joint failure occurs autonomously infj, or in the majority ofdclones, and that joint formation by heterozygous clones is autonomous except in the border area contacting afjordspot lacking a joint, in which area joint failure occurs. Bristle pattern in this jointless heterozygous area switches to that of a single segment. Localized nonautonomy also occurs in the t‐rows of heterozygous tissue contacting afjordspot. Both mutant genes are interpreted as reducing longitudinal growth of the proximal tarsi, with joint failure as a consequence, and with alterations of bristle pattern resulting directly from size reduction, or indirectly through joint fa

ISSN:0022-104X    

DOI:10.1002/jez.1401980110

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

年代:1976

数据来源: WILEY

摘要:

AbstractLight microscopic observations of the accessory lobes of Lachi of one‐day‐old chicks show that this tissue contains abundant amounts of glycogen and consists of cells which are similar in appearance to those of the glycogen body. Ultrastructural studies reported here for the first time confirm the presence of glycogen‐rich cells in the accessory lobes and reveal that these cells are intimately associated with nerve axons. The finding of synaptic complexes and other junctional specializations between nerves and accessory lobe cells suggests that they may have a functional relationship with the nervous system. It is felt that the accessory lobe cells may be neuroglia, possibly of the astrocytic type, which have an innate capacity for glycogen storage. While the functional significance of such glycogen remains obscure, the close morphological association between neurons and the accessory lobe cells enhances the hypothesis put forth by us regarding the glycogen body, namely that neural glycogen is involved in myelin synthesis in the avian nervous s

ISSN:0022-104X    

DOI:10.1002/jez.1401980111

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

年代:1976

数据来源: WILEY