摘要:

AbstractThe euryhaline shrimpCrangon franciscorumis a hyper‐hypoosmotic regulator, its hemolymph being iso‐osmotic with the medium near 27‰ salinity. Shrimp collected from low salinity environments are physiologically very distinct from those collected from high salinity environments. Individuals from low salinity habitats exhibit better survival, a lower water content and apparent permeability to water, and a decreased rate of sodium loss in low salinities when compared to shrimp from high salinity habitats. These differences persist after several days of adaptation to low salinity, however after acclimation to a low salinity for a longer time (5–6 weeks in this study), these differences di

ISSN:0022-104X    

DOI:10.1002/jez.1402350302

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

年代:1985

数据来源: WILEY

摘要:

AbstractRadioactively‐labeled microspheres were used to quantify adjustments of regional blood flows in 15 snakes (Elaphe obsoleta) subjected to 45° head‐up tilt. Heart rate and peripheral vascular resistance increased during tilt to compensate for the passive drop of pressure at the head. Two snakes failed to regulate blood pressure, but in 13 others arterial pressure increased at midbody (where passive changes in pressure are unexpected due to tilt alone) and arterial pressure at the head averaged 67% of the pretilt value. Tissue blood flow was reduced significantly in visceral organs, posterior skin and posterior skeletal muscle, but was maintained at pretilt levels in brain, heart, lung and anterior tissues. Ventricular systemic output averaged 24 ml/min·kg in horizontal posture and 9.4 ml/min·kg during tilt. Comparable values for pulmonary output were 4 and 6.5 ml/min·kg. Patterns of intraventricular shunting of blood acted to maintain pulmonary flow during tilt. A large right‐to‐left shunt (mean 76%) was present in horizontal snakes, but the shunted fraction declined during tilt (mean 54%). Left‐to‐right shunt increased during tilt

ISSN:0022-104X    

DOI:10.1002/jez.1402350303

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe enzyme N‐acetyl‐β‐D‐glucosaminidase was purified from the cortical granules ofXenopus laeviseggs using affinity chromatography, gel filtration, and density gradient centrifugation. The enzyme had a molecular weight of 37,000–40,000 as determined by polyacrylamide gel electrophoresis and density gradient centrifugation, had a Km for p‐nitrophenyl‐β‐D‐N‐acetyl‐glucosaminide of 0.66 mM and a Ki for glucosamine of 4.3 mM. The kinetic properties of the cortical granule enzyme were similar to the enzyme isolated from jack bean. Treatment of unfertilized eggs with the enzyme isolated from cortical granules or jack bean rendered eggs unfertilizable. Loss of fertilizability was proportional to the product of time and enzyme concentration, consistent with an enzymatic mechanism being responsible for the loss of fertilizability. The amount of enzyme present in the perivitelline space was approximately the same as that which reduced fertilizability by 50% in one hour. We suggest that the action of cortical granule N‐acetyl‐β‐D‐glucosaminidase on egg integuments may function as a bloc

ISSN:0022-104X    

DOI:10.1002/jez.1402350304

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

年代:1985

数据来源: WILEY

摘要:

AbstractAlthough it is generally held that panting is a physiological mechanism for the regulation of brain temperature during heat stress, a number of studies have pointed to the importance of peripheral input for the initiation of the panting response in a variety of animals. By presenting ambient heat loads of 47°, 54°, 58°, and 65°C, and measuring skin, ear and core temperatures of the desert iguana,Dipsosaurus dorsalis, at the onset of panting, we found that the skin temperature at panting onset was independent of ambient heat load. This suggests that skin (peripheral) temperature is the body temperature on which the central thermoregulatory center cues to initiate thermal panting. Peripheral temperature control of panting was retained when the plasma osmolality of the desert iguana was increased by 100 mOsm/kg H2O to simulate dehydration. Dehydration to 80% initial body weight (IBW) resulted in a progressive increase in panting threshold (skin) from 42°C for untreated lizards to 42.5°C at 90% IBW to 43.3°C at 80% IBW. Injection of 80% IBW lizards with a volume of 10 mM NaCl equivalent to weight loss resulted in a decrease in panting threshold to 40.8°C. Injection with 1% body weight 3000 mM NaCl produced a dramatic increase in panting threshold to 45.9°C. These data suggest that the desert iguana responds to dehydration by elevating panting threshold, thus promoting water conservation. These data also suggest that changes in plasma osmolality may be involved in the “setting” of panti

ISSN:0022-104X    

DOI:10.1002/jez.1402350305

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

年代:1985

数据来源: WILEY

摘要:

AbstractEmbryos of the agamid lizardAmphibolurus barbatusare at developmental stage 29 of Dufaure and Hubert at the time of oviposition. Mobilization of calcium and other nutrients from the yolk proceeds slowly for the first half of incubation, during which time embryonic growth also proceeds slowly. During the second half of incubation, however, embryos withdraw calcium and other nutrients from the yolk very rapidly, and growth rates are correspondingly high. Approximately 60% of the calcium used by developing embryos is obtained from the yolk, but fully 40% of their requirement is met by calcium mobilized from the eggshell. Very little calcium remains in residual yolk of hatchlings, so this yolk must be used in maintenance metabolism rather than in growth of neonates. No dichotomy exists among oviparous, amniotic vertebrates with respect to sources of calcium used by developing embryos, but one does exist with respect to patterns of mobilization of this element. Whereas calcium is extracted from yolk of embryonic reptiles throughout incubation, it actually is deposited in yolk of embryonic birds after the midpoint in development.

ISSN:0022-104X    

DOI:10.1002/jez.1402350306

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

年代:1985

数据来源: WILEY

摘要:

AbstractWhen discs of frontal periosteum from presumptive antler sites of 6–8 month old male fawns of the fallow deer are grafted beneath the foreleg skin, they will differentiate into pedicle bones and induce small antlers in the overlying integument. These antlers shed their velvet in the fall, and in succeeding years are replaced by larger outgrowths not exceeding 7 cm in length. Periosteal transplants 1.5 cm in diameter gave rise to ectopic antlers in 100% of the grafts, while discs measuring 1.05 cm, 0.75 cm and 0.4 cm did so in only 20% of the cases. Conversely, the donor sites produced antlers in 20–23% of the cases following removal of 1.05 cm or 1.5 cm of periosteum, while 80% and 100% grew antlers after deletions of 0.75 cm and 0.4 cm discs of periosteum, respectively. Semicircular grafts of periosteum induced antler development in most cases, especially when derived from the lateral halves of the antlerogenic region on the frontal bone. These findings confirm that the histogenesis of a deer's first pedicle and antler resides in the frontal periosteum over an area about 1.5 cm wide. They also show that leg skin is capable of antlerogenic development under the inductive influence of frontal periosteum, and that integumental wounding may enhance inductive interacti

ISSN:0022-104X    

DOI:10.1002/jez.1402350307

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe distribution of actin in sheep ovaries has been examined using immunofluorescent techniques. The germinal epithelium, which contained abundant microfibrils, fluoresced strongly while the underlying stroma was only weakly positive. During early follicular growth a band of fluorescence was associated with the base of those granulosa cells abutting onto the basal lamina. This transitional polarity of actin distribution was correlated with cell shape changes in the basal granulosa.

ISSN:0022-104X    

DOI:10.1002/jez.1402350308

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

年代:1985

数据来源: WILEY

摘要:

AbstractSeasonal gonadal regression in the photoperiodic weaver finchPloceus philippinusoccurs in the late summer despite the presence of long days. Earlier studies indicated a decline in photosensitivity in late summer, which might explain the failure of birds to respond to long days, resulting in gonadal regression. Results obtained in the present study suggest that 1) birds become refractory only to the stimulatory day lengths experienced in nature (longest day at 25° N 13.34 hr) and not to all long day lengths as in many other photoperiodic passerine species 2) birds become refractory in accordance with the day length they experience during the growth phase of the gonadal cycle. Thus birds held on 12 L/12 D become refractory to 12 L/12 D but are photosensitive to longer day lengths. Similarly, birds on natural day length become photorefractory to the longest day but are sensitive to higher day length, viz 15 L/9 D. 3) The long summer day lengths experienced in nature might cause the seasonal decline in photosensitivity

ISSN:0022-104X    

DOI:10.1002/jez.1402350309

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

年代:1985

数据来源: WILEY

摘要:

AbstractIntensity of hair pigmentation of dorsal scrotum, nose, cheek and forehead areas of seven mature, male white‐tailed deer were determined from close‐up colour slides taken once a month during a 2‐year period. Blood samples and skin biopsies from forehead areas were taken at the same time as the photographs. Plasma testosterone (T) levels were measured by radioimmunoassay and T in the skin was investigated by immunohistology. Seasonal variations of hair pigmentation are most pronounced in the forehead region followed by the cheek, scrotum, and nose area. Peak blood levels of T (15.4 ng/ml) were detected in November. The highest correlation between T levels and pigmentation of the forehead area (R = 93%; R2= 0.87), was established when pigmentation values were shifted two months ahead. Immunohistologically detectable T was localized in hair follicles, hair sheets and apocrine glands but not in the sebaceous glands. It is hypothesized that pigmentation of head regions might serve as a visual cue indicating the sexual status of an indiv

ISSN:0022-104X    

DOI:10.1002/jez.1402350310

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

年代:1985

数据来源: WILEY

摘要:

AbstractAn improved method for the isolation of pure plasma and acrosomal membranes from bull spermatozoa is presented. Plasma membranes were isolated from the spermatozoa of bulls of different breeds, and some enzymatic activity, such as (Na+‐K+) ATPase, Ca++ATPase, Mg++ATPase, alkaline and acidic phosphatases were assayed. Such enzymatic activity levels differ noticeably from those published by other authors, whose preparations were probably contaminated by other cellular components. Highly statistically significant differences of these activities have been found among the several breed

ISSN:0022-104X    

DOI:10.1002/jez.1402350311

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

年代:1985

数据来源: WILEY