摘要:

AbstractImprovement of the cold resistance capacity of the mole rat (Spalax ehrenbergi, Nehring), a blind subterranean rodent, was achieved following subcutaneous melatonin administration. Melatonin‐treated mole rats exhibited reduction both in initial body temperature (Tbo) and in the decrease of body temperature (ΔTb) after 6 hours of exposure to cold. The tested mole rats were acclimated to and kept during the experiment, under long (16L/8D) photoperiod schedule while the effects of melatonin administration on body temperature simulated the effects of short photoperiod conditions. These results suggest that in mole rats, melatonin biochemically mediates photoperiodic information into body temperature physiological response. As a byproduct of the original experiment, it was found that frequently repeated short (6 hours) exposure to cold (Ta = 5 ± 1°C) can in itself initiate an improvement of cold resistance capacity similar to the effect of melatonin administration. This supports the idea that mole rats may improve their cold resistance in response to either photoperiodic or climatic cha

ISSN:0022-104X    

DOI:10.1002/jez.1402380102

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

年代:1986

数据来源: WILEY

摘要:

AbstractTaurine transport by the flounder gut was characterized in isolated strips of intestine mounted between Ringer's solutions. Taurine was transported into the cell, against its concentration gradient, by a sodiumdependent system present in both the mucosal and serosal membranes. This system appears to be specific for β‐amino acids and is regulated by cyclic nucleotides (cGMP and cAMP). Kinetic analyses indicated that under physiological conditions the magnitudes of the bidirectional taurine uptake rates would favor net absorption of taurine from lumen to blo

ISSN:0022-104X    

DOI:10.1002/jez.1402380103

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

年代:1986

数据来源: WILEY

摘要:

AbstractPlasma levels of 22 endogenous amino acids were measured by ion‐exchange chromatography in four species of snakes:Thamnophis sirtalis,T. radix,Aipysurus laevis, andPython molurus. Despite considerable interspecific variation in the amino acid composition, all species showed relatively high plasma concentrations of histidine, a feature apparently unique to reptiles. The renal handling of these amino acids was studied by renal clearance methods. As in other vertebrates, net tubular absorption of filtered amino acids predominated. However, net tubular secretion of taurine, cysteic acid and/or phosphoserine and β‐alanine was observed, with taurine being the predominant amino acid secreted. The percentage reabsorption of the total amino acids filtered by the snake kidneys ranged from 79 to 95%. Evidence for the postrenal absorption of amino acids in these reptiles is presented. In species that normally undergo hibernation (Thamnophisspp.), the ability of the kidney to reabsorb amino acids was depressed by cold acclimation. Cold acclimation significantly decreased plasma levels of all amino acids except taurine, whose concentration increased. The increase in plasma taurine level may have resulted from cellular osmoregulation. Under these conditions, renal excretion of taurine increased concomitantly with the increase in plasma taurine concentra

ISSN:0022-104X    

DOI:10.1002/jez.1402380104

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

年代:1986

数据来源: WILEY

摘要:

AbstractWe have analyzed the lipid composition of meals fed to chicks and determined the ability of chicks to assimilate wax esters in four species of high latitude, plankton‐feeding seabirds: one alcid (Aethia pusilla; Alcidae: Charadriiformes) and three petrels (Pelecanoides urinatrix, P. georgicus, andPachyptila desolata; Procellariiformes). Up to 63% of the estimated digestible energy in chick meals consists of wax esters. Using14C‐labeled cetyl palmitate, we have shown that chicks of the four study species efficiently hydrolyze wax esters, with less than 1% of the ingested label excreted in most cases. Labeled fatty acids were assimilated and deposited primarily as triacylglycerols in storage fat depots. The one study species known to store lipids in the proventriculus retained much of the labeled wax ester unhydrolyzed in stomach oils. However, the capacity to store stomach oils was not a requisite for efficient assimilation of wax esters. This study provides the first direct evidence that seabirds have the inherent ability to digest and assimilate wax esters efficien

ISSN:0022-104X    

DOI:10.1002/jez.1402380105

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn males of the katydidNeoconocephalus robustus, mesothoracic wings are used in flight (wing stroke frequence = 20 Hz) and stridulation (200 Hz), while the metathoracic wings are used in flight alone. Most mesothoracic wing muscles produce much briefer isometric twitches than metathoracic counterparts. The mesothoracic first tergocoxal muscle (TCX1) has a twitch duration (onset to 50% relaxation, 35°C) of 6–8 ms and the metathoracic TXC1a twitch duration of 12–15 ms. The TCX1muscles from animals one and two instars from adulthood produce twitches similar in duration to those of the adult metathoracic TCX1. The twitch duration of the mesothoracic TCX1acquires its adult brevity gradually over the first 5 days of adult life. Both TCX1muscles increase greatly in size and mitochondrial content around the time of the terminal molt. During this period the mesothoracic TCX1develops narrower myofibrils and a smaller ratio of fibril volume to sarcoplasmic reticulum volume than is characteristic of the metathoracic TCX1. Changes in the ultrastructure of the mesothoracic TCX1precede changes in contraction kinetics around the time of the terminal molt so that there is not a strict correlation between muscle structure and performance during the period of rapid gr

ISSN:0022-104X    

DOI:10.1002/jez.1402380106

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn response to hyperosmotic stress, the harpacticoid copepodTigriopus californicusrapidly accumulates high intracellular concentrations of free alanine and proline. Using14C‐bicarbonate as a tracer, in vivo experiments were carried out to determine if pyruvate or phosphoenolpyruvate carboxylation function in the synthesis of carbon skeletons for free amino acid (FAA) synthesis. Label was incorporated into four FAA (aspartate, glutamate, proline, and alanine) during hyperosmotic stress. Relative specific activities of the FAA synthesized in vivo and in vitro enzyme activities suggest that malic enzyme (EC 1.1.1.40) carries out the carboxylation reaction. Incorporation of label into proline was extensive for at least 24 hr after transfer of adults acclimated to 50% seawater to 100% seawater; the proline pool showed relatively slow turnover following its accumulation (approximately 40% drop in specific activity in 48 hr) compared to the other FAA (complete loss of label in 24 hr). While bicarbonate fixation occurs in animals acclimated to both 50% and 100% seawater, label is observed in glutamate and aspartate but not proline. The results of these experiments suggest that the metabolic pathway by which bicarbonate label is incorporated into proline is activated by hyperosmotic stress and is effectively shut down following 24–48 hr of proline accumulat

ISSN:0022-104X    

DOI:10.1002/jez.1402380107

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

年代:1986

数据来源: WILEY

摘要:

AbstractThigh myogenic cells from 11–12‐day‐old chick embryos were cultured continuously in the presence of medium containing no chick embryo extract (CEE). It is known that CEE contains a muscle‐inducing protein of 35,000 daltons. In spite of the absence of embryo extract and provided that calcium, starting at a concentration as low as 3 × 10−4M, was present in the tested media, typically aligned myotubes with 20 or more nuclei per fiber or abnormal myosymplasts were produced at will. In the first case, the result was systematically obtained when the media were unchanged. Consequently, the cell microenvironment remained undisturbed and therfore was autoconditioned throughout the 7 days of culture. In the second case, the result depended on the feeding schedules. Conversely, no myotubes were formed in cultures in embryo extract‐free medium without calcium, irrespective of the frequency of medium changes. Insulin, a serum factor believed to be involved in syncytium formation processin vitro, was present in all tested media. Undialyzed or dialyzed fetal calf serum (FCS), used for the preparation of the media, contained 11 μunits of insulin per milliliter. The insulin content in all tested media was diluted, however, to one tenth the physiological serum concentration. The hormone did not promote any kind of myoblast fusion in any experiment in which calcium was deleted as a component of the tested media, regardless of the feeding schedule followed. Contrary to former claims, the present results demonstrate that, as in the initial development of chick heart and skeletal musclein vivo, insulin, which is not produced in significant amounts until day 12 of incubation, does not participate in the early differentiation of skeletal musclein vitro. These results lend further support to the idea of the existence of an intrinsically ‘fusion‐

ISSN:0022-104X    

DOI:10.1002/jez.1402380108

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

年代:1986

数据来源: WILEY

摘要:

AbstractHistological and immunological parameters were monitored in carp during the primary immune response againstAeromonas hydrophila. Localization of antigen in the spleen initially ocurred in the ellipsoids, whereas in the head and trunk kidney it was diffusely distributed. When antibody titers increased (from day 9 onwards), antigen accumulated in melano‐macrophage clusters in all three organs, and it was mainly bound to cell membranes. Tissue‐bound immunoglobulin was present on several structures in the lymphoid organs. As a consequence of immunization, the number of cells with cytoplasmic immunoglobulin and the amount of immunoglobulin associated with the reticular sheath of ellipsoids and membranes of melano‐macrophages increased. Pyroninophilia was limited, and occurred in the spleen associated with ellipsoids; in addition, clusters of cells appeared, displaying a small rim of pyroninophilic cytoplasm. In the kidney the reaction was not conspicuous. The number of antibody forming cells in the head kidney peaked at day 9 and the serum antibody response followed with a peak at day 15. When the antigen was emulsified in adjuvant, the antigen processing and the antibody responses were affected. Antigen processing was retarded and a second burst of antibody production occurred from day 15 onwards. The relationship of melano‐macrophage centers with immunological processes is considered. It is suggested that in fish these centers might be primitive analogues of the mammalian germinal

ISSN:0022-104X    

DOI:10.1002/jez.1402380109

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe descriptive kinetics of the spermatogenic process has been studied in the four chromosomal species ofSpalax ehrenbergibetween November and March, the active period of reproduction.Spermatid development can be subdivided into 16 steps in which the acrosome formation is clearly distinguishable and the Golgi, cap and acrosomic phases are identifiable. The first 12 steps of spermiogenesis can be utilized for the definition of characteristic time‐dependent relationships among different germ cell associations (stages): twelve stages, I–XII, are clearly identifiable.In this regard no differences exist among the four chromosomal species. In general, the spermatogenic process in this species has the same pattern as that ofMus domesticus. Two relevant points distinguishSpalaxspermatogenesis fromMusspermatogenesis: 1) the presence, throughout the stages I–XII of the seminiferous epithelium cycle of a larger size, oval shaped spermatogonium type containing heterochromatic granulations; 2) the Sertoli cells show only one heterochromatic clump closely attached to the nucleolus; moreover, the Sertoli cell cytoplasm is more PAS‐positive than tha

ISSN:0022-104X    

DOI:10.1002/jez.1402380110

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

年代:1986

数据来源: WILEY

摘要:

AbstractPhosphorus‐31 nuclear magnetic resonance spectroscopy (31PNMR) was used to monitor changes in the levels of several high‐energy compounds both prior to and following the initiation of motility in spermatozoa of the horseshoe crab,Limulus polyphemusL. These spermatozoa are easily collected and are nonmotile until stimulated with a sperm‐motility‐initiating peptide (SMI) which can be extracted fromLimulus eggs. Following the addition of SMI, several changes in metabolite levels within the spermatozoa were obtained, the most significant of which were a decrease in nucleotide triphosphate (NTP) and phosphoarginine levels and an increase in the levels of inorganic phosphate (Pi), NDP, and phosphomonoesters. An increase in the intracellular pH (0.45 pH units) of the sperm was also noted following the completion of SMI‐stimulated

ISSN:0022-104X    

DOI:10.1002/jez.1402380111

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

年代:1986

数据来源: WILEY