摘要:

AbstractThe abdominal ganglion of the molluskAplysia californicareceives most of its blood supply through a small caudal artery that branches off the anterior aorta near its junction with the heart. Injection of an ink/gelatin mixture into the caudal artery revealed a consistent pattern of arterial branching within the ganglion and a general proximity of larger vessels to identified neurons controlling circulation in this animal. This morphological arrangement was particularly evident for the heart excitor interneuron, cell L10, which lies next to the caudal artery near its entry into the ganglion. In electrophysiological experiments, L10 was excited when blood flow or oxygen tension within the ganglion was reduced. This effect was expressed as a gradual increase in impulse frequency of L10 and conversion from tonic to bursting mode of spike discharge. L10 follower cells in the RB and LD neuron clusters were affected synaptically by the changes in L10 activity, while other follower cells (L3 and RD neurons) responded independently of L10's synaptic influence. The neurosecretory white cells (R3 to R14) that innervate the major arteries and pericardial tissues were also excited when ganglionic circulation was interrupted. In innervated preparations of the heart and respiratory organs, decreased circulation through the abdominal ganglion stimulated a transient increase in the rate and amplitude of respiratory (gill) pumping and pericardial contractions and caused a sustained increase in activity of the heart. Both responses increase cardiac output and both appear to involve a direct influence of ganglionic circulation on interneurons controlling the gill and heart. These results indicate that the cell‐specific patterns of excitation and inhibition caused by fluctuations in ganglionic circulation may be important factors for maintaining circulatory homeostasis in this anima

ISSN:0022-104X    

DOI:10.1002/jez.1402440302

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe mussel foot secretes a variety of unusual hydroxyproline‐containing collagenous and noncollagenous proteins. Prolyl 4‐hydroxylase acting on one or more of the secreted proteins was isolated from the foot by using conventional gel filtration and ion exchange chromatography. Mrof the intact enzyme was 230,000 (α2β2) composed of two subunits with Mrof 60,000 (α) and 57,000 (β) as estimated by HPLC gel filtration and SDS‐PAGE. The enzyme utilized (Pro‐Pro‐Gly)10as a substrate with an apparent Kmvalue of 0.17 mM. Cofactors and inhibitors were very similar to animal, plant, and microbial prolyl hydroxylases previously described. The enzyme had a relatively sharp pH optimum in the range of 7.8–8.3 and the hydroxyproline formed increased in proportion to the rise in the temperature between 5 and 20°C. No detectable hydroxylation occurred with poly‐L‐proline or the unhydroxylated decapeptide analog (Ala‐Lys‐Pro‐Ser‐Tyr‐Pro‐Pro‐Thr‐Tyr‐Lys) of the polyphenolic protein. Kinetic studies, however, revealed that the mussel prolyl 4‐hydroxylase was competitively inhibited by poly‐L‐proline and uncompetitively inhibited by the decapeptide. These results suggest that the decapeptide binds the enzymesubstrate i.e. (Pro‐Pro‐Gly)10complex. It is not yet clear whether this enzyme acts exclusively on collagenous substrates or whether its catalytic pur

ISSN:0022-104X    

DOI:10.1002/jez.1402440303

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe microbial proteinase inhibitors bestatin, leupeptin, chymostatin, antipain, and pepstatin (all at 10−4M) inhibit the proteolytic activity of gill homogenates of the ribbed musselGeukensia demissaby 20–30%. In combination, these inhibitors reduced the hydrolysis of casein by 50%.Isolated gills fromG. demissaacclimated to 500 mOsm seawater (SW) were incubated in 1000 mOsm SW for 8 h in the presence of the following proteinase and lysosome inhibitors: bestatin, pepstatin, leupeptin, antipain, chymostatin, NH4Cl, imidazole, and chloroquine. In control tissues the amino acid pool increased by 155 μmol/g dry wt. Imidazole (10 mM), NH4Cl (10 mM), and chloroquine (10−4M) inhibited this increase by 70, 60, and 50%, respectively. Pepstatin, bestatin, and leupeptin (all 10−4M) also inhibited the accumulation of amino acids in gills exposed to higher ambient salinity by 30–40%. In combination, these three microbial proteinase inhibitors reduced the enlargement of the amino acid pool by 60%. Chymostatin and antipain had no effect on the increase in the amino acid content of the tissues.The effects of these inhibitors on the amino acid levels of gill tissues incubated in isomotic seawater were minor. None of the inhibitors had significant effects on the oxygen uptake of isolated gills.The results from gills exposed to the amines and chloroquine suggest that lysosome‐mediated proteolysis is involved in the accumulation of alanine and glycine during cellular adjustment to hyperosmotic stress in marine bivalves. The effectiveness of pepstatin, leupeptin, and bestatin in reducing this accumulation implicates aminopeptidase I and cathepsins B and D as the specific enzymes involved in the proteolysis associated with adjustment to hyperos

ISSN:0022-104X    

DOI:10.1002/jez.1402440304

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe effects of magnesium on the influx, net entry, and efflux of amino acids by larvae of the sea urchinStrongylocentrotus purpuratuswere investigated. Kinetic studies revealed that the influx of alanine is not dependent on external magnesium. In addition, influx and net entry are equivalent, as determined by high performance liquid chromatography (HPLC), and are independent of ambient magnesium concentrations.

ISSN:0022-104X    

DOI:10.1002/jez.1402440305

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

年代:1987

数据来源: WILEY

摘要:

AbstractA study of tissue and cell water content was carried out on eyestalk‐ablated (EA) and intact control juvenile lobsters (Homarus americanus). Both parameters were significantly higher in abdominal muscle and hepatopancreas from EA lobsters compared to controls. Similarly, the extracellular spaces of these tissues were larger in EA animals as were estimates of total hemolymph volume. The density and dry solids content of hemolymph from EA lobsters were less than controls, although hemolymph osmotic pressures of both groups were indistinguishable. The results are discussed in relation to other relevant studies on the effects of eyestalk ablation. Possible osmoregulatory and endocrine consequences are also considere

ISSN:0022-104X    

DOI:10.1002/jez.1402440306

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

年代:1987

数据来源: WILEY

摘要:

AbstractPreimplantation mouse embryos were metabolically labelled with3H or14C‐fucose to investigate the synthesis of fucosylated macromolecules. Scintillation counting revealed that there was a progressive increase in both total fucose taken up by the embryo and incorporation of fucose into TCA‐precipitable material as embryos developed from the 4‐cell to the blastocyst stage. This was reflected in the increasing intensity of bands on autoradiographs of radioactive fucose labelled proteins separated on 10% SDS‐PAGs between the 4‐cell embryo (at which stage bands were first detectable) and the blastocyst. Minor qualitative changes in fucoproteins were detected at the time of compaction and additional bands appeared at the blastocyst stage. Preliminary analysis of fucolipids in 6‐ to 8‐cell embryos indicated that an approximately equal amount of fucose was incorporated into lipid and protein. Autoradiographs of semi‐thin sections of3H‐fucose‐labelled embryos showed substantial amounts of radioactive material in the vicinity of the plasma membrane both adjacent to other cells and facing the zona pellucida. These data would support a predominant role for fucoconjugates in cell surface events in the preimplantation embryo fr

ISSN:0022-104X    

DOI:10.1002/jez.1402440307

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

年代:1987

数据来源: WILEY

摘要:

AbstractPrevious studies withNotophthalmus viridescenshave shown that forelimb stumps covered by flank skin do not regenerate when amputated through the graft of nonlimb skin [Tank, P.W. (1984) J. Exp. Zool.,229:143–153]. In an attempt to determine whether or not cells derived from nonlimb skin dedifferentiate and enter the regeneration blastema, four experimental series were prepared using triploid (3N) marked cells grafted into diploid (2N) hosts of the axolotl (Ambystoma mexicanum). In the first series, head skin was used to replace limb skin followed by amputation through the graft 30 days later. Fully 96% (24/25) of the limbs failed to regenerate an externally visible outgrowth and 4.4% of the blastemal mesenchyme cells were observed to be 3N based on the characteristic of three nucleoli per nucleus. In the second series, flank skin replaced limb skin and 38% (8/21) of the limbs failed to regenerate. The remaining limbs regenerated an assortment of hypomorphic, normal, abnormal, or multiple structures. Only 2.4% of the cells in the blastemal mesenchyme were observed to be 3N in the second series. In the third series, head dermis was implanted in place of limb musculature and 20% (3/15) of the limbs failed to regenerate. The other limbs in series three were either abnormal, hypomorphic, or multiple in morphology. Histological analysis revealed that 3.4% of the cells in the blastemal mesenchyme of the head dermis group were 3N. In the fourth series, flank dermis replaced limb musculature and only 7% (1/15) failed to regenerate. Ten limbs (66%) formed hypomorphic regenerates and the remainder were normal, abnormal, or multiple in morphology. Histological analysis revealed that 6.8% of the cells were 3N in the blastemal mesenchyme of limbs in series four. Sham‐operated controls for all four series regenerated normally and histological analysis of contralateral control limb regenerates revealed background 3N marker that averaged from 0.1 to 0.8%. The regenerate epidermis of limbs that were covered by 3N head skin or flank skin contained approximately 25% 3N cells, indicating that the epidermis was of nonlimb origin. The regenerate epidermis of limbs bearing 3N dermis implants did not contain marked cells. These results indicate that non‐limb cells are capable of undergoing dedifferentiation and entering the limb regeneration blastema. An explanation of regenerative failure is provided that is based on interference with short range cellular interactions by nonlimb

ISSN:0022-104X    

DOI:10.1002/jez.1402440308

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

年代:1987

数据来源: WILEY

摘要:

AbstractChanges in the shape of neuroepithelial cells, particularly apical constriction, are generally thought to play a major role in generating the driving forces for neural tube formation. Our previous study [Nagele and Lee (1987) J. Exp. Zool.,241:197–205] has shown that, in the developing midbrain region of stage 8+chick embryos, neuroepithelial cells showing the greatest degree of apical constriction are concentrated at sites of enhanced bending of the neuroepithelium (i.e., the floor and midlateral walls of developing neural tube), suggesting that driving forces resulting from apical constriction are concentrated at these sites during closure of the neural tube. In the present study, we have used morphometric methods to 1) measure regional variations in the degree of apical constriction and apical surface folding at selected regions along the anteroposterior axis of stage 8+chick embryos, which closely resemble the various ontogenetic phases of neural tube formation, and 2) investigate how forces resulting from apical constriction are distributed within the neuroepithelium during transformation of the neural plate into a neural tube. Results show that, during neural tube formation, driving forces resulting from apical constriction are not distributed uniformly throughout the neuroepithelium but rather are concentrated sequentially at three distinct locations: 1) the floor (during transformation of the neural plate to a V‐shaped neuroepithelium), 2) the midlateral walls (during transformation of the V‐shaped neuroepithelium into a C‐shaped neuroepithelium), and 3) the upper walls (during the transformation of the C‐shaped neuroepithelium into a closed neu

ISSN:0022-104X    

DOI:10.1002/jez.1402440309

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

年代:1987

数据来源: WILEY

摘要:

AbstractSerum prolactin (PRL) decreases in Syrian (Mesocricetus auratus) and Siberian (Phodopus sungorus sungorus) hamsters following short‐photoperiod exposure. Both species also exhibit short‐photoperiod‐induced changes in body and lipid mass, but in opposite directions; Syrian hamsters increase and Siberian hamsters decrease their body weight, changes reflected nearly exclusively in their carcass lipid content. The purpose of these experiments was to determine whether the photoperiod‐induced changes in PRL were responsible for the seasonal changes in energy balance in Syrian and Siberian hamsters by using the strategy of experimentally producing serum PRL levels opposite to those normally associated with the photoperiod in which the animals were housed. In long photoperiods serum PRL was reduced to short‐day levels by subcutaneous (s.c.) CB‐154 (bromoergocryptine, a dopamine agonist) injections. In short photoperiods, serum PRL was elevated to long‐day levels in Syrian hamsters by ectopic pituitary explants, and in Siberian hamsters, serum PRL was elevated by chronic s.c. infusions of ovine PRL (oPRL). In both species, manipulations of serum PRL did not affect food intake, carcass composition, or the wet weight of various white and brown adipose tissue pads (WAT and BAT, respectively). Body weight increased in CB‐154‐treated Syrian hamsters and decreased in Siberian hamsters, an effect partially reversed by coadministration of oPRL in Syrian, but not Siberian, hamsters. Thus, lowering serum PRL to short‐day levels in long‐day‐housed hamsters of both species mimicked the directional change in body weight appropriate for each species when they are exposed to short days. This effect of CB‐154 on body weight may be a result of some as yet unidentified effect of dopaminergic stimulation on overall growth since 1) these changes in body weight were not reflected as changes in lipid mass, as occurs naturally following short‐day exposure for each species, and 2) neither species exhibited a reciprocal change in body weight when serum PRL was experimentally elevated in short days. Alternatively, it may be that once the energetic responses to short‐day exposure have been fully expressed, the ability of PRL to stimulate the target sites of action for PRL for these responses may be decreased. BAT protein content, cytochrome oxidase activity (measures of metabolic growth of this tissue), and retroperitoneal total and specific lipoprotein lipase (LPL) activities were increased by CB‐154 treatment in Syrian hamsters. These measures, as well as total and specific BAT LPL activities, and resting, minimal, and norepinephrine (NE)‐stimulated oxygen consumption were not affected by the PRL manipulations per se. However, CB‐154‐treated Siberian hamsters had increased NE‐stimulated oxygen consumption. Chronic s.c. infusions of oPRL in short‐day‐housed Siberian hamsters did not alter in vivo lipogensis in WAT or BAT pads or in liver or muscle. The results of these experiments suggest that the changes in energy balance associated with changes in the photoperiod (melatonin) in these hamster species cannot s

ISSN:0022-104X    

DOI:10.1002/jez.1402440310

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

年代:1987

数据来源: WILEY

摘要:

AbstractEnvironmental factors are known to affect the growth rates of fishes through most of their adult life. In the hermaphroditic saddleback wrasse (Thalassoma duperrey), the effects of social factors on growth were studied experimentally by subjecting individuals in submerged enclosures to various social environments that induce sex change. The results showed that social factors may either stimulate or inhibit the growth of adult fish. Individuals with one or more pen mates grew better than isolated individuals. Conspecifics stimulated more growth than heterospecifics. In paired fish, larger individuals inhibited the growth of smaller individuals. Growth rates were independent of both the sex and color phase of associates. Placing a tactile barrier between fish did not alter growth rates, but a tactile—visual barrier did. Increasing the space available to a fish did not increase the growth rate. Dominance relationships based on relative size and visual stimuli best explain the results obtained. Since all fish that showed growth acceleration also changed sex, a unitary, hypothalamically mediated, causal system is suggested. From an evolutionary perspective, sex‐change linked growth acceleration may reduce the cost of changing sex by shortening the nonreproductive interim in species in which males must be large to compete successfully for multiple mati

ISSN:0022-104X    

DOI:10.1002/jez.1402440311

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

年代:1987

数据来源: WILEY