摘要:

AbstractMany marine bivalve molluscs produce byssal threads for attachment to solid substrata. Small (<10 mm) consecutive sections of the byssal threads ofMytilus edulis, M. californianus, Geukensia demissa, Atrina vexillum, andA. rigidawere analyzed by amino acid analysis to determine if chemical composition remains constant as a function of location in thread segments. Nonlinear longitudinal protein gradients, probably involving collagen and an elastic protein, were found in theMytilusspecies. In these, collagen peaks in the distal third of the thread. InGeukensiaand theAtrinaspecies, although the two differed greatly in composition, there is a clear nonvariability in composition of the thread within each species as a function of location in the thread. The adhesive plaque at the tip of the thread of all species examined differs substantially in composition from the remainder of the thread. Protein gradients in the threads of some bivalves may reflect specific adaptations evolved to respond to exposed habitats in high‐energy environment

ISSN:0022-104X    

DOI:10.1002/jez.1402400102

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

年代:1986

数据来源: WILEY

摘要:

AbstractDuring embryonic development, allantoic fluid represents the shifting balance between renal excretion and reabsorption by chorioallantoic membranes. Allantoic contents of Na+, K+, Cl−, urate, pH, and water were followed over days 10–15 of the 16 day incubation. Water volume remained near 0.9 ml until day 13, then declined very rapidly. The pH declined more steadily, from 8 to 5.5. Contents of Na+and Cl−fell regularly to final values 80–88% below day 10. The K+content changed differently and nearly doubled by day 13 but returned to day 10 values at the end. Urate content rose until day 13, then fell suddenly to low levels. This was due to the abrupt precipitation of most urate into masses not sampled by our method, so that after day 13, urate was underestimated (probably by 90–96%). Ion binding by urates was low (about 3% of Na+and Cl−, 10% of K+) and appeared to be nonspecific. The underestimate of urate contents means, however, that in late incubation about one third of allantoic Na+and 65–70% of K+and Cl−are bound to precipitated urate and do not appear in balance sheets of allantoic ions. These precipitated ions account for the significant amounts of Na+and K+that remain in the allantoic remnant, left in the eggshell after hatching, but whose presence is not predicted by analysis of

ISSN:0022-104X    

DOI:10.1002/jez.1402400103

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of epinephrine, norepinephrine, phenylephrine, and isoproterenol on blood pressure and heart rate were studied in cannulated American bullfrogs,Rana catesbeiana. The bullfrogs were chronically cannulated with a T cannula in the right sciatic artery. In warm‐acclimated (22°C) bullfrogs, preinjection mean systemic arterial pressure (SAP) prior to experimental treatment was 13.1 ± 0.7 mm Hg. Preinjection heart rate was 34.8 ± 1.8 beats per minute. These parameters were lower in cold‐acclimated (12°C) bullfrogs. Cold‐acclimated animals had mean SAP values of 8.2 ± 0.3 mm Hg, and heart rate was 11.1 ± 1.1 beats per minute. Epinephrine, norepinephrine, and phenylephrine increased blood pressure to an equivalent degree in warm‐and cold‐acclimated animals. Dose‐related decreases in heart rate in response to these catecholamines were observed in warm‐ but not in cold‐acclimated bullfrogs. Warm‐acclimated animals were more responsive to isoproterenol from 0.03 μg/kg body weight (bw) to 10 μg/kg bw than were cold‐acclimated animals. The response to isoproterenol was effectively blocked by propranolol (5 mg/kg bw) in both warm‐ and cold‐acclimated animals. Propranolol alone decreased mean SAP in both warm‐ and cold‐acclimated animals, suggesting blockade of endogenous sympathetic activity. Beta receptor response thus appears diminished, but not absent at 12°C. However, the alpha receptors responsible for elevation of blood pressur

ISSN:0022-104X    

DOI:10.1002/jez.1402400104

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe effects of temperature on contractile function of isolated, chemically skinned red (slow oxidative) and white (fast glycolytic) fibers of skeletal muscle from thermally acclimated striped bass (Morone saxatilis) were determined. Acclimation to 10° or 25°C has no significant effect on maximum isometric tension (Po) or maximum unloaded contraction velocity (Vo) of fibers of either muscle type. Sensitivity to acute changes in temperature is markedly greater for slow‐twitch fibers than for white, fast‐twitch fibers. Q10(15–5°C) of Vois 1.58 and 2.27 and R10(15–5°C; analogous to Q10, but for parameters that are not rate functions) of Pois 1.57 and 2.17 for fibers from white and red muscle, respectively. R10of maximum attainable power output is 1.29 for white and 4.50 for red fibers. Power for low speed, sustained swimming is derived exclusively from red muscle in striped bass, permitting comparisons between swimming performance and contractile capacity to be drawn. For maximum sustainable swimming speed at 15°C, calculated contraction velocity of a red muscle fiber corresponds to the maximum power output of a single fiber of red muscle at 15°C. Thermal sensitivity of red muscle power output predicts that maximum sustained swimming speed of striped bass will be severely impaired at cold temperatures. However, cold acclimation induces a proliferation of the red muscle mass that may ameliorate the thermal sensitivity of red muscle contrac

ISSN:0022-104X    

DOI:10.1002/jez.1402400105

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe teeth of the sea urchinLytechinus variegatusgrow continuously. The mineral phase, a high magnesium calcite, grows into single crystals within numerous compartments bounded by an organic matrix deposited by the odontoblasts. Electron microscopic examination of glutaraldehyde‐fixed Ethylene Diamine Tetra acetic acid (EDTA) demineralized teeth shows the compartment walls to be organized from multiple layers of cell membrane which might contain cytoplasmic protein inclusions. Proteins extracted during demineralization of unfixed teeth were examined by gel electrophoresis, high performance liquid chromatography, and amino acid analysis. The tooth proteins were acidic, they contained phosphoserine, and they were rich in aspartic acid. By contrast, the proteins of similarly extracted mineralized Aristotle's lantern skeletal elements were nonphosphorylated and were rich in glutamic acid. Vertebrate tooth and bone matrix proteins show similar differences. Surprisingly, an antibody to the principle rat incisor phosphoprotein showed a significant cross‐reactivity with the urchin tooth protein, by dot‐blot and enzyme‐linked immunosorbent assay procedures. Thus, the urchin tooth proteins contain epitope regions similar to those which are phenotypic markers of vertebrate odontoblasts. Whether this is an expression of convergent or divergent evolutionary processes, it is likely that the matrix proteins play a similar role in matrix mineralization. The sea urchin tooth may thus be an excellent model for the study of odontoblast‐mediated mineral–matrix re

ISSN:0022-104X    

DOI:10.1002/jez.1402400106

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe regenerative capability ofXenopus laevishindlimbs was studied at different developmental stages. Three types of surgical deletion of the autopod were performed: simple amputations, 3‐digit wedge‐shaped deletions and 1‐digit wedge‐shaped deletions. The frequency of regenerative response and the digital patterns of the regenerates were analyzed. Regenerative capacity declines with developmental stage for all three types of deletions. For simple amputations this decline occurs in an orderly manner with the failure of anterior digits to regenerate at progressively later stages. A comparison between 1‐digit and 3‐digit deletions shows that for all stages of development, 3‐digit deletions regenerate better than one‐digit deletions. These data indicate that the amount of tissue removed is directly related to whether a regenerative response is observed. At any given stage, larger deletions are more likely to regenerate than smaller ones. These results are discussed with regard to the mechanisms by which growth during regeneratio

ISSN:0022-104X    

DOI:10.1002/jez.1402400107

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe purpose of this investigation was to determine whether the mechanism of cytokinesis inAmoeba proteusdepends primarily upon locomotion and traction (fission) or whether the mechanism resembles that of metazoan cells. Cytokinesis is unaffected by measures that prevent attachment of the organism to the substratum. Amoebae divided when they were (1) detached from the substratum and repeatedly shifted, (2) suspended in fluid medium by one pole, (3) placed on an oil–water interface, and (4) transferred to de‐ionized water so that attachment was prevented. Unilateral furrows formed when the mitotic apparatus was shifted to an eccentric position. Enucleated portions of cytoplasm containing part of the equatorial region were amputated at different phases of the mitotic cycle. Enucleated pieces amputated at later prophase never formed permanent furrows, although 3 of 17 showed furrowlike activity. Of 26 enucleated pieces amputated at metaphase, 23 showed division activity. Of these, 21 formed temporary furrows and 2 completed division.Although attachment and locomotion may be normal during division ofA. proteus, they were not essential for cytokinesis, and their involvement is restricted to the final parting of the cytoplasmic thread that connects the daughter cells. The mechanism responsible for the greater part of the constriction activity in the furrow region resembles that of metazoan cells in that it is localized in the surface and it is established by the mitotic appara

ISSN:0022-104X    

DOI:10.1002/jez.1402400108

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe organic matrix from sea urchin tests was extracted using 2% acetic acid. This material contained 81–85% protein, 14–19% carbohydrate, and<1% phosphate. The whole matrix was separated into aqueous soluble and insoluble fractions to determine their individual characteristics and functional activities. Electrophoresis of the soluble matrix (SM) resulted in a single band of approximately 170kD. The SM was capable of inhibiting in vitro CaCO3precipitation (at nanomolar concentrations) in solutions supersaturated with Ca2+and CO32‐. It was also capable of inhibiting CaCO3spicule formation in sea urchin larvae at 10 μg SM per ml of larvae as measured by14C incorporation. The insoluble matrix (IM) fraction had a higher protein content than the SM component and a lower PO4content.That the SM from urchin tests is capable of inhibiting both in vitro crystallization and organismal calcification lends credence to its probable role as a mineralization regulator. What role it plays in vivo can only be surmised at this point, and whether or not this role is the same when it acts in conjunction with other components of matrix is u

ISSN:0022-104X    

DOI:10.1002/jez.1402400109

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

年代:1986

数据来源: WILEY

摘要:

AbstractTestes or the isolated sheaths of testes from late‐last‐instar larvae of the tobacco budworm,Heliothis virescens, spontaneously secreted ecdysteroids in vitro. Exogenous 20‐hydroxyecdysone, incubated with the testes or isolated testis sheaths, functioned in a local positive feedback system to increase production of the several ecdysteroids typical ofH. virescenstestes. The increase in ecdysteroid production by testis tissue was dependent on discrete ranges in exogenous ecdysteroid titer. Activation ratios of 2–5 resulted from exogenous 20‐hydroxyecdysone titers of 0.5 to 15 pg/μl, while activation ratios of 10–30 resulted from exogenous titers of 15–100 pg/μl of 20‐hydroxyecdysone. Activation ratios approached 200 with exogenous titers of 100–1,000 pg/μl o

ISSN:0022-104X    

DOI:10.1002/jez.1402400110

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe segmentally arranged Verson's glands are epidermal derivatives comprised of three cells: the duct, saccule, and secretory cells. The development of these glands was followed through the 5th instar and larvalpupal transition ofManduca sexta. The glands are relatively small during the feeding stage, begin to grow at wandering, and undergo about a 50‐fold increase in size during the prepupal period. The increase in size is due mainly to the hypertrophy of the secretory cell which synthesizes a heterogeneous set of proteinaceous secretory products. Three prominent 11 to 12 kiloDalton (kD) polypeptides are made by the pharate fifth larval gland, whereas the pupal gland produces polypeptides ranging from 14 to 75 kD with a major complex at 30 to 34 kD. The secretory product is poured out onto the surface of the new cuticle at the time of ecdysis and contains all of the major proteins detected in extracts of the whole gland. The accumulation of secretory products by the gland occurs during the prepupal peak of ecdysteroid and is blocked if this rise is prevented by abdominal isolation. Infusion of 30 μg 20‐hydroxyecdysone (20‐HE) into such isolated abdomens caused synthesis of the pupal products. Treatment with the juvenile hormone mimic, methoprene, during the fifth instar showed that the commitment of the glands to produce the pupal proteins is independent of and occurs before the overlying epidermis becomes committed to make pupal c

ISSN:0022-104X    

DOI:10.1002/jez.1402400111

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

年代:1986

数据来源: WILEY