摘要:

AbstractRates of incorporation of 1‐14C‐oleic (18:1n9), ‐linoleic (18:2n6), and ‐linolenic (18:3n3) acids into individual phosphatides were determined in isolated hepatocytes from cold (5°C)‐ and warm (20°C)‐acclimated rainbow trout,Salmo gairdneri.Fatty acid incorporation into phosphatidylcholine (PC) exceeded that into all other phospholipids, but at assay and acclimation temperatures of 5°C, incorporation into phosphatidylethanolamine (PE) was generally intermediate between that of PC and the remaining phosphatides. Specific radioactivities (ratios of percentage isotope incorporation‐to‐mole percentage of phosphatide) were consistently less than one for both PC and PE, and greater than one for phosphatidic acid (PA), lysophosphatidylcholine (LPC), phosphatidylserine (PS), and cardiolipin (CL). For PS, specific radioactivities were greater in cold‐ than warm‐acclimated trout, and greater at 5°C than 20°C. Rates of oleate incorporation were generally higher, and rates of incorporation of 18:2 and 18:3 lower in cold‐ than warm‐acclimated trout. Most phospholipids demonstrated a clear preference for the incorporation of 18:2 when assayed at 20°C; however, at 5°C the incorporation of 18:2 was reduced and 18:3 was generally the preferred substrate A reduction in assay temperature from 20°C to 5°C also shifted the incorporation of 18:2 away from PC into PS and PA. These data were interpreted to indicate 1) a cold‐induced activation of PS metabolism, possibly resulting in elevated levels of PE; 2) lower rates of general acyl group turnover in animals acclimated to 5°C than 20°C; 3) a specificity to the acclimation response that favors the incorporation at cold temperatures of polyunsaturated fatty acids, but not the parent acids from which they are derived; and 4) the participation of a deacylation‐reacylation cycle in the metabolism of phospholip

ISSN:0022-104X    

DOI:10.1002/jez.1402270202

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe gill of the freshwater mussel,Ligumia subrostrata, is composed of 25% calcium concretions on a dry weight basis. These concretions are located extracellularly in the connective tissue of the gill. The concretions have a lamellar structure and occur singly, multiply, and in clumps. The concretions are composed primarily of calcium phosphate and an organic matrix. The concretions are more numerous toward the base of the gill and less frequent in the tip of the gill. The average size of the concretions is 2–3 μm. The concretions are not solubilized in animals exposed to prolonged hypoxic conditions. Instead, as calcium increases in the blood under hypoxic conditions the percentage of the gill dry weight attributed to concretion material increases and the calcium content of the concretion material is elevated. The calcium content of the concretions also is inversely correlated with blood pH. This study indicated that the concretion material in the gills was not mobilized under hypoxic conditions, but served as a calcium reservoir during periods in which the animal was liberating calcium from other sit

ISSN:0022-104X    

DOI:10.1002/jez.1402270203

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

年代:1983

数据来源: WILEY

摘要:

AbstractHistochemical analysis of five muscles from the water monitor,Varanus salvator, identified three major classes of fibers based on histochemical activities of the enzymes myosin ATPase (mATPase), succinic dehydrogenase (SDH), and α‐glycerophosphate dehydrogenase αGPDH. Fast‐twitch, glycolytic (FG) fibers were the most abundant fiber type and exhibited the following reaction product intensities: mATPase, dark; SDH, light; αGPDH, moderate to dark. Fast‐twitch, oxidative, glycolytic (FOG) fibers were characteristically mATPase, dark; SDH, light; αGPDH, moderate to dark. The third class of fibers had the following histochemical characteristics: mATPase, light; SDH, moderate to dark; αGPDH, light. These fibers were considered to be either slow twitch, or tonic, and oxidative (S/O). Pyruvate kinase (PK), αGPDH, and citrate synthase (CS) activities were measured in homogenates of the same muscles studied histochemically. There was a positive relationship between both PK and αgpdh activities and the percentage of glycolytic fiber types within a muscle. Likewise, CS activities were greater in muscles high in FOG and S/O content. Based on CS activities,VaranusS/O fibers were eight‐fold more oxidative than FG fibers within the same muscle. PK/CS ratios suggested that FG fibers possess high anaerobic capacity, similar to the iguanid lizardDipsosaurus. The fiber type composition of the gastrocnemius muscle, relative to that of other lizard species, suggests that varanid lizards may possess a greater proportion of FOG and S/O fibers than

ISSN:0022-104X    

DOI:10.1002/jez.1402270204

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

年代:1983

数据来源: WILEY

摘要:

AbstractMyosin accumulation was examined in developing ascidian embryos by measuring its ATPase activity and by resolving myosin heavy chains on polyacrylamide gels. Both procedures used a myosin‐enriched fraction that was prepared by exploiting the unusual solubility properties of this protein. Myosin ATPase was first observed at neurulation and increased 25‐ to 50‐fold by the time of larval hatching, a sequence similar to that found previously for muscle acetylcholinesterase. This similarity to acetylcholinesterase, and the finding of at least two‐thirds of the ATPase activity in the larval tail, imply that most of the myosin studied was muscle myosin. The pattern of expression based on ATPase assays was confirmed in part by gel analysis, but since this technique was less sensitive the appearance of myosin heavy chain was not demonstrated unambiguously until later in development. As found earlier with acetylcholinesterase, actinomycin D treatment only interfered with accumulation of myosin ATPase during early stages of increasing enzymatic activity. Despite certain similarities noted in their ontogeny, differences in the initial increase in the activity of these enzymes and the time of their first response to actinomycin D suggest that the events concerned with the expression of acetylcholinesterase occur 1 hour before those of myosin ATPase. The appearance of these two proteins, representing different enzymes of the muscle cell, is probably controlled indepe

ISSN:0022-104X    

DOI:10.1002/jez.1402270205

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe physical mechanism which accomplishes cytokinesis in animal cells develops as a consequence of interaction between the mitotic apparatus and the surface. The purpose of this investigation was to determine whether successful furrow establishment depends upon normal geometrical relations between the interactants in some areas but not in others. Blocks were positioned between different regions of the mitotic apparatus and the surface in flattened sea urchin (Tripneustes gratilla) and sand dollar (Echinarachnius parma) eggs. The blocking agents used were slit‐shaped perforations, needles, and oil drops. Results were consistent regardless of which block was used. Blocks located outside the equatorial plane did not affect furrowing. Perforations located in the equatorial plane resulted in furrow formation on the proximal surface of the perforation; no furrows formed distal to the perforation, either in the cell margin or the distal surface of the puncture. Oil drops and glass needles positioned in the equatorial plane affected furrowing. The magnitude of the effect was directly related to the size of the block. The results demonstrate that furrow establishment is not affected by drastic modifications of the geometrical relationship between the mitotic apparatus and the poles, but it is very susceptible to interference in the region between the mitotic apparatus and the equato

ISSN:0022-104X    

DOI:10.1002/jez.1402270206

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

年代:1983

数据来源: WILEY

摘要:

AbstractAcetylcholinesterase (AChE) activity has been studied inArtemia salinaembryos and larvae by quantitative, histochemical, and electrophoretic methods. An AChE activity is present in dehydrated encysted gastrulae and remains low in rehydrated developing embryos, showing at hatching an increase that becomes faster during the nauplius stages (twice the gastrula activity at the nauplius II stage), and continues linearly in the first metanauplius stages. The histochemical staining, faint and diffuse in dehydrated gastrulae, in more advanced embryos becomes localized in cell membranes and stronger in differentiating tissues; most AChE activity is localized in the nervous and muscular cells, and a fainter one in the differentiating metanauplius segments. Dehydrated cysts show one electrophoretic AChE band, that is no longer detectable in rehydrated embryos and larvae, while two other bands appear, that migrate more slowly; in advanced larval stages, the more cathodic band is predominant. In dehydrated cysts, isoelectric focusing separates three AChE bands with isoelectric points (IP) at pH 5.0, 5.7, and 5.9; in hydrated embryos and larvae, the band at pH 5.0 is absent and another is seen at pH 5.5. Eserine, DFP, and BW284c51 inhibit the enzyme activity strongly and cause paralysis of larvae; also tubocurarine blocks the motility. These results are discussed in relation to the differentiation of the neuromuscular system and to the development of motility. As a hypothesis, in early embryonic stages, before any neuromuscular differentiation is evident, a cholinergic‐like system might regulate non‐neural cell activities and interactions, associated with embryogenetic eve

ISSN:0022-104X    

DOI:10.1002/jez.1402270207

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

年代:1983

数据来源: WILEY

摘要:

AbstractWhen the sand dollar egg surface is extensively disrupted by contact with an expanding oil drop, and the egg contents are squeezed out by mechanical pressure, the denuded endoplasm is rapidly covered by a new surface. The original egg surface alters its appearance as the area that it covers diminishes, and the original and the new surfaces become different in appearance and behavior. If a mitotic apparatus is pushed into the endoplasmic fragment, the fragment surface undergoes furrowing activity, which is synchronous with typical cyclical changes in the appearance of the mitotic apparatus. In this circumstance, furrows develop later and progress more slowly than normal. Furrows formed soon after the operation usually regress, but those developing in conjunction with subsequent cell cycles are more nearly normal and are frequently permanent.

ISSN:0022-104X    

DOI:10.1002/jez.1402270208

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

年代:1983

数据来源: WILEY

摘要:

AbstractTritiated‐thymidine autoradiography was used to follow the progress of cells through spermatogenesis in the axolotl,Ambystoma mexicanum. Results indicate that, at 18°C, the most rapidly maturing germ cells spend 5 days in leptotene, 5 days in zygotene, 22 days in pachytene, 1 day in diplotene, 6 days completing meiosis I, 10 days as secondary spermatocytes, and about 12 days in spermiogenesis. In these laboratory bred and raised urodeles, mature sperm spend an additional 60 days in the testes before the first label appears in spermatophores. The data suggest that, at least for some animals, there is minimal storage of mature sperm in the vas deferens. Cyst counts on longitudinal sections through the testes revealed large differences in the proportion of cells at different stages in animals examined during the same season. The results show that spermatogenesis passes through the testes of each animal in a wave that, however, is not coordinated with that of other animals in the colony. The overall timing of spermatogenesis is consistent with the results of mutagenesis studies with the alkylating agent, EMS. EMS reacts preferentially with late spermatids and a dominant lethal effect is seen about 60 days after the mutagen treatment, corresponding to the time interval between late spermatids and mature sperm ready to be laid in spermatophor

ISSN:0022-104X    

DOI:10.1002/jez.1402270209

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

年代:1983

数据来源: WILEY

摘要:

AbstractPrior to ovulation, fully grown oocytes of both the amphibian (Rana pipiens) and the starfish (Piaster ochraceus), like those of many other organisms, are arrested in late prophase I of meiosis. Reinitiation of meiotic maturation in oocytes from either of these organisms is hormonally induced. Although the meiosis‐inducing substance (MIS) for each organism is chemically dissimilar (a steroid in the frog and a purine in the starfish) induction of oocyte maturation in both biological systems appears to be initiated by the interaction of the MIS with the plasma membrane of the oocyte. The objective of this investigation was to determine if elevated hydrostatic pressure affected hormonal induction of oocyte maturation and to compare the effect of pressure on oocytes stimulated with different meiosis‐inducing substances. In isolated oocytes from either the frog or the starfish, increasing ambient pressure reduced the percentage of oocytes which matured, and a stepwise increase in pressure resulted in a corresponding shift in the dose response curves of hormone‐induced, oocyte maturation to the right. In experiments using only starfish oocytes, this inhibitory effect of pressure was found to be reversible and limited to the initial period of the maturation event. Taken together, these data suggest that elevated ambient pressure inhibits an early cellular event in the hormonal induction of meiotic maturation which is common to both amphibian and starfish oo

ISSN:0022-104X    

DOI:10.1002/jez.1402270210

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

年代:1983

数据来源: WILEY

摘要:

AbstractIn the egg‐brooding frogGastrotheca riobambae(Fowler), oocyte maturation is comparable to the situation of other frog species. In isolated follicles, progesterone induces only germinal vesicle breakdown (GVBD), while human chorionic gonadotropin (hCG) induces GVBD and ovulation. In addition, defolliculated oocytes respond with GVBD to the treatment with progesterone, while hCG has no effect. As in other frogs, oocyte maturation in vitro depends on hormonal action and on the presence of divalent cations. In this frog, progesterone or a similar hormone conditions the brooding pouch for reproduction and induces pouch closure. Follicles from frogs with closed pouches showed GVBD after 15–17 hours of incubation with progesterone, while those from frogs with open pouches took 19–24 hours for GVBD. These findings suggest that follicles become stimulated for maturation when the pouch is closed and that this stimulated condition is maintained for several weeks in advance of the process of oocyte maturation. InG. riobambae, the external appearance of the pouch aperture indicates the reproductive condition of the

ISSN:0022-104X    

DOI:10.1002/jez.1402270211

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

年代:1983

数据来源: WILEY