摘要:

AbstractCholinesterase activities in the hearts and ganglia of an oyster (Crassostrea virginica) and a venerid clam (Macrocallista nimbosa) were measured and compared. Tissue extracts were partially purified by ammonium sulfate fractionation followed by gel column chromatography. Enzymatic activity was assayed spectrophotometrically; substrates were acetyl‐, butyryl‐, and propionylthiocholine (ATC, BTC, PTC). Kinetic constants characterizing each enzyme were derived. At all substrate concentrations, the hydrolysis rates of both clam enzymes were in the order: BTC>PTC>ATC. With oyster enzymes the ranking was ATC ≥ PTC>BTC. The specific activities of oyster heart and ganglion enzymes were similar. In contrast, clam ganglion extracts were 75–100 times more active than clam heart extracts and, with any substrate, had greater activity than either oyster enzyme. All enzyme preparations proved to be homogeneous on the bases of constant substrate activity ratios in successive column fractions, and of intermediate velocities with mixed substrates. Six cholinesterase inhibitors were tested. The specific acetylcholinesterase antagonist, B.W. 62c47, was much more effective against oyster enzymes, while the specific antibutylcholinesterase, iso‐OMPA, almost totally inhibited clam enzyme activity, but had little effect on oyster. Eserine was the most effective inhibitor of both enzymes. In conclusion, the enzymes in oyster tissues are acetylcholinesterases, while clam enzymes are butyrylcholinesterases. Nevertheless, clam ganglion esterase is sifficiently active to hydrolyze the physiological substrate, acetyl‐choline. These results explain the long‐observed differences in isolated heart pharmacology between ostreid and ven

ISSN:0022-104X    

DOI:10.1002/jez.1401980202

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

年代:1976

数据来源: WILEY

摘要:

AbstractDuring divisional morphogenesis of the ciliate protozoanChilodonella cucullulusdifferent thermosensitivity is observed at early and advanced stages of development.Thermic shocks (of 31 or 32°C) applied to cells early in division bring about resorption of new developing cortical organelles, while the same shocks do not prevent further development and cell division if applied to advanced dividers. Thus as in many other cells a transition point in thermosensitivity occurs during the cell cycle.The period before the transition point corresponds toprimary pattern formationof primordia of new cortical organelles, the post transitional period corresponds tofinal pattern formationof sets of organelles for offspring. In control (unheated) cells some simultaneous processes of differentiation and dedifferentiation are observed both in the pre‐transitional and post‐transitional periods. Therefore the stability of development at high temperature which is attained in the post‐transitional period concerns specific selection of organelles for further development rather than over‐all stability of formed structures.The effect of preincubation at low temperature and at mild temperature on thermosensitivity at 31°C is compared. Cells preincubated at low temperature can go through one round of divisional morphogenesis, while those preincubated at mild temperature are not able to do this; instead they regress into a resorption stage. Cells preincubated at low temperature and shifted to high temperature also sometimes manifest abnormalities in the number and disposition of contractile vacuole pores (CVPs). Hence in these cells thermosensitivity of pattern formation is dem

ISSN:0022-104X    

DOI:10.1002/jez.1401980203

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe objective of this investigation was to determine if the succinate that accumulates in anoxic or hypoxic tissues of mammals is (a) increased in concentration in the blood, (b) excreted in the urine or (c) recycled in some manner. Rats were subjected to 0.4 atm and the plasma analyzed for succinate and fumarate at 2 hours, 24 hours and 28 days. Significant increases of succinate or succinate plus fumarate were obtained at 2 hours and at 28 days at 0.4 atm. Analysis of 24‐hour samples of urine obtained from controls and animals at 0.4 atm for 28 days demonstrated that no substantial increase in succinate excretion occurred with acclimation. Lung slices were incubated in Krebs‐Ringer bicarbonate and succinate and gassed with O2:CO2(95:5). Such oxygenated lung slices not only utilized succinate but produced a comparable quantity of fumarate plus malate. It is concluded that succinate produced from fumarate and α‐ketoglutarate in peripheral hypoxic tissue is transported by the blood to the oxygenated lungs. There it is oxidized to fumarate and recycled as fumarate and malate to the periphery. In this way metabolites can act as electron shuttles between peripheral cells an

ISSN:0022-104X    

DOI:10.1002/jez.1401980204

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe breakdown of the pig germinal vesicle (GV) was studied in follicular oocytes matured in vivo and in vitro. For better characterization, the whole process was divided into four well‐defined stages, based on the chromatin changes, and on nucleolus and nuclear membrane disappearance. In the intact germinal vesicle (GV I) nuclear membrane and nucleolus are clearly visible and chromatin forms a ring or horseshoe around the nucleolus. In the GV II a few orceinpositive structures (chromocenters) on the nuclear membrane can be detected. For the GV III slightly stained chromatin clumps, localized especially around the nucleolus, and the beginning of strand formation are typical. In the last stage ‐ GV IV ‐ the nuclear membrane is less distinct and the nucleolus disappears completely. Chromatin is seen as an irregular network or as individual bivalents. According to these criteria GV breakdown in vivo was completed in most oocytes between 20 to 24 hours after HCG injection. In culture a similar stage of development was reached between 16 to 20 hours. This difference in the progress of nuclear changes appeared at the beginning of nuclear maturation and remained unchanged throughout the whole period st

ISSN:0022-104X    

DOI:10.1002/jez.1401980205

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe morphology and kinetics of the normal acrosome reaction were examined in vitro using hamster sperm incubated in detoxified sera. The reaction involved either swelling and elevation or crenulation and fragmentation of the acrosomal cap. Swelling and elevation occurred during both normal and degenerative reactions, as reported by others. Crenulation with subsequent fragmentation of the cap was observed during normal reactions. Early crenulation of the acrosome could be induced by cold shock (5°C, 25 minutes), but this did not decrease the incubation time required (at 37°C) for completion of the normal reaction. In appropriate sera, the occurrence of normal and degenerative acrosome reactions in motile sperm was significantly separated in time to study the reactions independently. The duration of the normal reaction, i.e., the time between the first morphological change in the acrosome (initiation) until the actual detachment of the cap (termination) was estimated to be 20 minutes. Saline dilution of these sera delayed initiation of the reaction and increased the duration of the reaction once it had started. Data from cold‐shock and serum dilution experiments indicate that the mechanisms which govern the initiation and termination of the normal reaction are independently variable, and further suggest that initiation involves a change in membrane permeability and that termination includes membrane vesiculat

ISSN:0022-104X    

DOI:10.1002/jez.1401980206

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe O2‐permeability of the avian egg shell and shell membranes is initially low (≅0.1·10−6ml O2STP‐sec−1·cm−2mmHg−1) during incubation but increases about 10‐fold after the first week. This increase correlates with a decline in water content of the membranes. A major increase in colloid osmotic pressure (up to 50 cm Hg) occurs and is the suggested cause for the onset of rapid removal of water from the membranes. A high membrane water content correlates with low O2‐permeability and vice versa. The final degree of membrane hydration reached during incubation is independent of ambient humidity; that is, the O2‐permeability of the shell and its membranes is controlled by conditions inside the egg. An hypothesis is presented to explain the profound increase in O2‐permeability while the rate of water loss from the egg remains stable during incubation. The removal of water from the shell membranes by the increased colloid osmotic pressure will increase the number of gas filled channels in the membranes which in turn will increase the O2‐permeability. In spite of the change in water content, the water vapor pressure in the shell membranes will always be very close to that of a free water surface and water loss will hence be determined by the ambient humidity and the poro

ISSN:0022-104X    

DOI:10.1002/jez.1401980207

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe process of epithelial stratification was studied in the embryonic chick corneal epithelium between 10 and 21 days of incubation. Information was collected on the DNA synthetic activity occurring in individual cell layers, on cell density changes in the basal layer, and on mitotic spindle orientation in each cell layer before, during, and upon the completion of layer formation.Prior to the initiation of stratification, mitotic spindles are oriented parallel to the basement membrane interface. This orientation changes to predominantly vertically directed spindles as layer formation proceeds. Later, the majority of the spindles are horizontally aligned once more. This pattern was observed as each successive cell layer formed. The possible relationship between the spindle data and that obtained on DNA synthetic activity and cell density changes is discussed in terms of the role these factors might play in layer formation in the cornea, as well as in other stratified epithelia.

ISSN:0022-104X    

DOI:10.1002/jez.1401980208

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe frequency and pattern of DNA synthesis were analysed autoradiographically in the developing chick cornea. Each cellular population was studied in time‐sequence fashion from the time of its appearance until hatching.There is a sharp drop in the synthetic index (number of labeled cells/total number of cells) in the anterior corneal epithelium soon after its formation, corresponding in time to the secretion of extracellular matrix material by this tissue. A similar decrease does not occur in adjacent tissues. Continuous labeling experiments show that about 20% of the corneal cells are not in the proliferative pool at this time while 100% of the cells in the underlying lens epithelium and the surrounding head epidermis and head mesenchyme are labeled. Cell cycle measurements indicate that the proliferative kinetics of both the corneal epithelium and the head epidermis are similar at this time even though the percentage of labeled cells in each region differs.The formation of the corneal endothelium and the movement of fibroblasts into the stromal region are events which involve extensive cellular migration. Labeled cells are observed at all stages of both endothelial and stromal fibroblast migration, indicating that DNA synthesis occurs during the course of cellular migration in the developing corne

ISSN:0022-104X    

DOI:10.1002/jez.1401980209

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe purpose of this investigation was to determine whether or not the nasal glands of the roadrunner and theCoturnixquail show cytological specializations for salt secretion. In addition, the Na‐K ATPase content of the quail gland was determined before and after drinking of saline solutions, in an effort to evaluate the functional status of the gland. The ability to maintain weight while drinking salt water was also measured as a general index of tolerance to saline conditions. The ultrastructure of the nasal glands of the roadrunner injected with salt and of quail drinking 200 mM NaCl was similar to that of salt glands in reptiles and the fresh‐water acclimated duck. Numerous lateral cell evaginations and abundant mitochondria were present in the principal cell types. There was a significant increase in quail nasal gland Na‐K ATPase when young birds were offered only saline solutions to drink. The ability ofCoturnixquail to maintain weight while drinking saline solutions improves with age and at adulthood is comparable to that of some North American desert quail. Roadrunners were previously known to possess functional salt glands whereas quail were not. However the characteristic fine structure and the high Na‐K ATPase content of the quail nasal gland suggest that it is a sal

ISSN:0022-104X    

DOI:10.1002/jez.1401980210

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

年代:1976

数据来源: WILEY

摘要:

AbstractPatterns of nuclear protein changes during embryogenesis in two nematode systems:Ascaris lumbricoidesandPanagrellus silusiaewere examined microspectrophotometrically. In both species, development is accompanied by an extensive loss of basic nuclear protein as noted by the diminished intranuclear binding of both the Sakaguchi reagent and fluorodinitrobenzene chromophore. The alkaline fast green (pH 8.1) procedure stained both nuclear and cytoplasmic regions of interphase cells to a similar extent throughout embryogenesis. In cells at metaphase the chromosomes bound the fast green dye intensely while the cytoplasm continued to give a positive reaction. Relative Feulgen stainability of nuclei during embryonic development varied between species. InAscaris, the one‐celled stage nucleus was Feulgen‐negative and the LI juvenile somatic nuclei yielded a mean Feulgen‐DNA value which was considerably less than a postdiminution diploid DNA equivalent. InPanagrellus, the nuclei of one‐celled stage embryos contain DNA in excess of a 4C quantity which subsequently is reduced during embryonic divisions. As inAscaristhe nuclei ofPanagrellus, LI juveniles give hypodiploid Feulgen‐DNA values. The significance of these changes remains to be d

ISSN:0022-104X    

DOI:10.1002/jez.1401980211

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

年代:1976

数据来源: WILEY