摘要:

AbstractThe α2‐macroglobulins are large molecular weight proteinase‐binding proteins that inhibit the ability of proteinases to hydrolyze protein substrates without suppressing activity against amide or ester substrates. They are also able to protect the active site of bound proteinases from active site inhibitors of suitably high molecular weight. The ability to protect the amidolytic activity of trypsin from the macromolecular active site inhibitor, soybean trypsin inhibitor, was used to demonstrate an α2‐macroglobulinlike activity in the blood of the horseshoe crab,Limulus polyphemusand the crustaceansLibinia emarginata(the spider crab) andCancer borealis(the Jonah crab). The α2‐macroglobulinlike activities ofL. polyphemusandL. emarginataare sensitive to methylamine, but that ofC. borealisis relatively insensitive. The molecular weights (mw) of the trypsin‐protecting proteins inL. emarginataandC. borealis, estimated from gelfiltration studies, are, respectively, 480 × 103and 460 × 103, and are significantly smaller than that ofL. polyphemus(M

ISSN:0022-104X    

DOI:10.1002/jez.1402360102

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

年代:1985

数据来源: WILEY

摘要:

AbstractDeterminants of the steady‐state vol of the dogfish shark (Squalus acanthias) rectal gland cells were studied. The cellular levels of trimethylamine oxide (TMAO) in fresh tissue and slices incubated aerobically 60 min in standard (TMAO‐free) elasmobranch saline were close to those in the plasma (71 ± 5 mM S.E.M.); therefore, under these conditions, the cell membrane appears to be impermeable to this solute. However, depolarization of the cells in high‐K+media produced a rapid loss of TMAO. Thus, TMAO is a major, effectively impermeant solute in the rectal gland cells. The osmolarity of cell solutes in tissue water (fresh and incubated slices) did not differ significantly from values in the plasma or incubation medium, demonstrating the absence of an osmotic pressure gradient across the cell membrane. An analysis of a simple model of cell solutes under steady‐state conditions shows that the presence of an (effectively) impermeant osmolyte decreases the cellular concentration of bulk cations. The analysis is consistent with available observations on the distribution of cell Na+and K+in tissues containing high concentrations of (nitrogeneous) osmolytes. One simplifying assumption of the model, i.e., identity (or closeness) of the respective reflection coefficients σ for Na+and K+passage through the cell membranes could not be verified. Compared to available data on the steady‐state cellular fluxes of42K+in slices of the rectal gland, the uptake of22Na+by the tissue was slow (the derived rate constant k′ = 0.017 min−1, i.e., about one tenth of that for K+). Hence, σNa<σK. On the other hand,36Cl−rapidly exchanged with cell Cl−with the first rate constant (k′ = 0.60 + 0.12 min

ISSN:0022-104X    

DOI:10.1002/jez.1402360103

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe opercular epithelium of the teleostFundulus heteroclitus, when mounted in a lucite chamber under short‐circuited conditions, secretes Cl−at a rate equivalent to the short‐circuit current (Isc). The transepithelial Na+movements are passive and proceed by a paracellular pathway. The addition of 2 × 10−3M Ba2+to the serosal bathing solution inhibited the Isc 76.8% with no effect on the transepithelial conductance (Gt). The addition of 5 × 10−4M Cu2+to the mucosal bathing solution inhibited the Isc 79.6% and reduced the Gt 35.6%. These inhibitory effects of Ba2+and Cu2+on the Isc were initiated within 1 minute after exposure with maximum effects occurring within 20 and 30 minutes, respectively. Simultaneous36Cl−and22Na+unidirectional fluxes were performed on paired epithelia from the same fish. Serosal Ba2+and mucosal Cu2+inhibited the Cl−secretory flux 30.2 and 58.9%, respectively. The resulting net Cl−flux after inhibition was not significantly different from the mean measured Isc. Neither ion had significant effects on the Cl−influx (mucosa to serosa) or the unidirectional Na fluxes. These results indicated that the effects of both Ba2+and Cu2+were most likely exclusive to the transcellular Cl−pathway. Ba2+is proposed to inhibit Cl−secretion by blocking the basolateral K+channels, depolarizing the cell, and reducing the electrochemical driving force for Cl−across the apical membrane. Cu2+is proposed to inhibit Cl−secretion by blocking the apical membrane Cl−channels. The results are in keeping with the proposed mechanism for Cl−secretion by indicating that the Cl−exit step across the apical membrane occurs via Cl−conductive channels and is driven passively

ISSN:0022-104X    

DOI:10.1002/jez.1402360104

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

年代:1985

数据来源: WILEY

摘要:

AbstractIntracellular pH (pHi) changes during burst contractile activity in in vitro preparations of phasic adductor muscle of the bay scallop,Argopecten irradians concentricus, were monitored using phosphorus nuclear magnetic resonance (31P‐NMR) spectroscopy. A transient alkalinization (from pHi7.06 to 7.15) was observed during the first period of contractions. The predominant mode of adenosine triphosphate (ATP) production during this period was by hydrolysis of arginine phosphate, a proton consuming process. Subsequent contractions of the muscle resulted in a gradual acidification, with pHiapproaching 6.94. During these later stages of contraction, glycolytic production of octopine was a major source of ATP. The net proton yields of energy transformations were estimated, based on proton consumption by arginine phosphate utilization and proton yield of octopine production. The resulting predicted pattern of proton change was very similar to those of observed changes in pHi. Intracellular pH changes during contractile activity inA. irradians concentricusphasic adductor muscle are strongly correlated with the pattern of proton yield of metabolic energy transformations taking place in the tissu

ISSN:0022-104X    

DOI:10.1002/jez.1402360105

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe rates of glycogenesis, glycogenolysis, lipogenesis and lipolysis were determined in selected tissues of the coho salmon,Oncorhynchus kisutch, during the period of parr‐smolt transformation between February 1983 and June 1983. Glycogen synthesis in the liver, measured by uridine diphosphate formation, decreased 54% from initial levels. Liver glycogen phosphorylase a activity increased by 66%. Neutral lipid (sterol) and fatty acid synthesis in the liver and mesenteric fat was measured by tritium incorporation. Fatty acid synthesis in the liver and mesenteric fat decreased by 88% and 81%, respectively, between late February (parrs) and early June (smolts). There was no significant change in the rate of tritium incorporation into liver or mesenteric fat neutral lipids during the sampling period. Lipolytic rates were assessed by measuring the release of14C‐oleic acid from14C‐triolein in the presence of partially purified triacylglycerol lipase enzyme preparations from the liver, dark muscle and mesenteric fat. Liver, dark muscle and mesenteric fat lipase activity increased by 86%, 146% and 289%, respectively, during the sampling period. Increased glycogen and lipid breakdown, and concomitant decreased glycogen and fatty acid synthesis would contribute to the lipid and glycogen depletion observed in salmonid species undergoing parr‐smolt transfo

ISSN:0022-104X    

DOI:10.1002/jez.1402360106

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

年代:1985

数据来源: WILEY

摘要:

AbstractWe investigated the electrical properties of the egg of the nemertean wormCerebratulus, and found evidence that an electrically‐mediated polyspermy block operates for a period of about 1 hr after fertilization. At fertilization, in natural or artificial sea water, the membrane potential shifts from its resting level of about −66 mV to a peak of about +43 mV, and in most cases remains greater than 0 mV for more than 1 hr. The average potential during the first 30 min is +22 ± 8 mV (SD, n = 12). When the external Na+concentration is reduced from 486 to 51 mM (choline substituted) the fertilization potential amplitude is reduced; the average potential during the first 30 min is −27 ± 21 mV (SD, n = 5). Eggs inseminated in 51 mM Na+sea water become polyspermic, indicating that polyspermy prevention depends on an electrically‐mediated mechanism. The electrical block is required for about 60 min, since transfer to 51 mM Na+sea water during this period results in polyspermy. During the first hour following fertilization, the egg is also developing a permanent, nonelectrical block; the degree of polyspermy which results upon transfer to low Na+sea water decreases progressively with time. The permanent block appears to be at the level of the egg plasma membrane or glycocalyx, since the egg envelope is not a barrier to sperm penetration, nor does its removal induce polyspermy. Electron micrographs show no obvious changes in the morphology of the extracellular layers, plasma membrane or cortex of the egg after fert

ISSN:0022-104X    

DOI:10.1002/jez.1402360107

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

年代:1985

数据来源: WILEY

摘要:

AbstractTotal RNA derived from the imaginal discs ofDrosophila melanogasterwas translated in vitro, and the polypeptide products electrophoresed on two‐dimensional gels. In agreement with previously published examinations of imaginal disc protein synthesis and content, we can detect no reproducible differences in abundant mRNA populations between different disc types (foreleg and wing). Differences can be found, however, between imaginal discs and other tissues. We also present evidence for a nonuniformly distributed wing disc mRN

ISSN:0022-104X    

DOI:10.1002/jez.1402360108

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

年代:1985

数据来源: WILEY

摘要:

AbstractTarget tissue regulation of naturally occurring neuronal death during development has often been studied by removing a limb bud and then analyzing spinal motor neuron number later in development. The present study focuses on the necessity for limb presence in the initiation of the most rapid phase of cell loss from the lateral motor column (LMC) and in the control of neuron number during this restricted developmental period. Unilateral hindlimb amputation in larvalRana pipiensat the time of onset of rapid LMC cell loss resulted in an unequal, bilateral retention of excess motor neurons (i.e., less cell loss than normally occurs) during this phase. Limb traumatization, with axotomy, also resulted in reduced bilateral LMC cell loss, although to a lesser extent than did amputation. Absence of the limb or axonal transection presumably prevents the communication of motor neurons with their differentiating targets and thus interferes with the flow of information required for the selective events of neuronal loss and survival. The presence of the limb with intact axons is essential at the time that LMC cell loss normally ensues for both the initiation and progression of the phase of greatest cell loss.

ISSN:0022-104X    

DOI:10.1002/jez.1402360109

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe size of preimplantation mouse embryos was experimentally manipulated in order to examine the consequences for the allocation of cells to the two primary tissues, trophectoderm and inner cell mass (ICM). Half embryos were produced by the mechanical lysis of one cell at the two‐cell stage and quadruple embryos by the aggregation of four whole eight‐cell embryos. Such procedures are shown not only to alter the absolute number of cells that are assigned to the trophectoderm and ICM, but also to disturb significantly the proportions of these two tissues in the blastocyst. The proportion of trophectoderm is directly related to the surface area of the morula, as is predicted by a purely epigenetic scheme for cell allocat

ISSN:0022-104X    

DOI:10.1002/jez.1402360110

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe settling, spreading and locomotory behaviour of the plasmatocytes from three lepidopteran species (Ephestia kuehniella, Pieris brassicaeandAglais urticae) on a glass substratum in vitro has been examined using light and scanning electron microscopy. Immediately upon withdrawal from the haemocoel plasmatocytes are ovoid (E. kuehniella) or spindle‐shaped. These cells are usually seen to undergo a series of three distinct morphological changes in response to cell‐substratum contact. 1) The initial stable attachment, beneath the nuclear region, is followed by a rapid rounding‐up with a concomitant initiation of surface ruffling and filopod production. 2) Cell‐substratum contact is consolidated by an increase in area and the establishment of additional contacts at suitable (cell‐free) sites around the periphery by filopodia. 3) Spreading proceeds with the production of lamellae which expand within the interfilopodial space.The shape of fully spread plasmatocytes is variable but only locomoting cells are clearly polarized. Locomotion is triggered during spreading in response to cell‐cell contact; colliding partners then polarise and exhibit brief evasive translocations over a short distance. It has also been shown that plasmatocytes translocate over the surface of glass implants during the early stages of encapsulat

ISSN:0022-104X    

DOI:10.1002/jez.1402360111

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

年代:1985

数据来源: WILEY