摘要:

AbstractThe gross morphology, ultrastructure, and the physiological properties of the tergotrochanteral depressor muscle (TTM) of the housefly are described. Under transmission and scanning electron microscopy, the TTM is a highly modified multinucleated tubular muscle of the synchronous class of insect muscle. Mitochondria appear few in number (5% of muscle volume) but there is an extensive sarcoplasmic reticulum (20% of muscle volume). Two types of neuromuscular junctions were observed, but these junctions are considered functionally similar. Three neurons innervate the muscle, and when the muscle is orthodromically stimulated, three well‐defined thresholds are observed. Under repeated stimulation, the TTM fatigues rapidly but recovers in a short time. The TTM has a long “length constant” of 132.1 μm, 7.3 μF/cm2membrane capacity, and a specific resistance of 394 Ωcm2.The tergotrochanteral or “jumping” muscle has a behaviorally unique function. It is used only in the jump response preparatory to flight. TTM development is believed to have coevolved with an associated giant neuron to optimize the escape behavior response (response time 2.5 msec) in the housefly. The muscle has become specialized and more massive to increase the jump response. The TTM appears to be adapted physiologically and ultrastructurally for fast response and short twitch du

ISSN:0022-104X    

DOI:10.1002/jez.1402390202

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

年代:1986

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1402390203

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

年代:1986

数据来源: WILEY

摘要:

AbstractA new enzyme was partially purified fromD. melanogaster. The enzyme catalyzes the reduction of xanthommatin to dihydroxanthommatin in the presence of NADH/H+as confactor. FAD, FMN, p‐chloromercuribenzoate, 2‐amino‐4‐hydroxypteridine and biopterin inhibited the enzyme activity. The inhibitory effect of some pterines suggests a correlation between the synthesis of dihydroxanthommatin and that of pterines. It has been suggested that the enzyme may participate, in vivo, in the reduction of xanth

ISSN:0022-104X    

DOI:10.1002/jez.1402390204

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

年代:1986

数据来源: WILEY

摘要:

AbstractMembrane potentials were recorded from two species of Heliozoa,Echinosphaerium akamaeandE. nucleofilum. The resting potential ranged from −20 to −50 mV with an average value of −33.7 ± 12.9 mV (± SD, n = 10) and −31.6 ± 9.5 mV (± SD, n = 10) inE. akamaeandE. nucleofilum, respectively. Action potentials were elicited spontaneously or in response to applied current. They were abolished in Ca2+‐deficient solution with no effect by Na+or Mg2+, indicating Ca‐spikes. Membrane hyperpolarization, which correlated with the contraction of contractile vacuole (H‐CV), was recorded. The onset of hyperpolarization appeared to be simultaneous with the initiation of contraction. The amplitude of H‐CV was dependent on K+‐concentration in the external fluid with reduction by increasing K+. The results suggested that H‐CV was caused mainly by the increase in K+‐conductance of the membrane with a co

ISSN:0022-104X    

DOI:10.1002/jez.1402390205

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

年代:1986

数据来源: WILEY

摘要:

AbstractAmmonia excretion rates of channel catfish,Ictalurus punctatus, little skate (Raja erinacea), and blue crab (Callinectes sapidus) were measured in experimental regimes which permitted simultaneous assessment of the partial pressure gradients for nonionized NH3and the chemical concentration gradients of NH4+. Under conditions of low external ammonia, the average ammonia excretion was +295 μM kg−1h−1for catfish, + 149 μM kg−1h−1for blue crabs, and +59 μM kg−1h−1for skates with partial pressure gradients of +72.5 μTorr, + 413 μTorr, and +24.4 μTorr, respectively; and [NH4+] gradients of +189 μM l−1, +643 μM l−1, and +107 μM l−1(positive indicating greater from inside to medium). When the external ammonia was increased to 1.15 mM l−1, both gradients were reversed, and the net ammonia movement was initially from the external water into all three species. In the catfish the inward movement ceased, however, and ammonia excretion eventually resumed in the face of reversed gradients of both NH3partial pressure and [NH4+]. Unidirectional Na+influx, indicative of a Na+/NH4+exchange, did not increase. The ammonia data, changes in titratable acidity, and net apparent H+efflux were all consistent with a linked extrusion of internal NH4+for external H+. Incorporation of such an exchange into a computer simulation model of the ammonia equilibrium and exchange system duplicated the experimental data. Other hypotheses failed to match experimental data, or failed to predict internal ammonia levels lower than outside. In the crab, internal ammonia levels rose rapidly to concentrations and partial pressures above the external medium until excretion was reestablished, with no evidence of maintenance of a reversed gradient. In the skate, internal concentrations rose appreciably in the first hour and continued to rise for 6–8 h, with no resumption of ammonia excretion. The interspecies differences appear to be due at least partly to differences in amm

ISSN:0022-104X    

DOI:10.1002/jez.1402390206

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe lobsterHomarus americanushas five pairs of serially homologous thoracic limbs, the most anterior being the paired chelae followed by four pairs of walking limbs (WLs). We have examined the opener and closer muscles of the WLs in terms of their fiber composition, axonal branching pattern, and synaptic properties. The opener muscle is similar in these serially homologous limbs being composed of all slow fibers. The closer muscle, however, differs in fiber composition amongst the limbs. In the small, nonchelate 3rd and 4th WL, it consists of only slow fibers, while in the much larger, chelate 1st and 2nd WL it has 40% fast and 60% slow fibers. In the chelae, which are bilaterally asymmetric, the closer muscle is known to consist of 70% fast and 30% slow fibers in the cutter chela and all slow fibers in the crusher chela. These differences in the closer muscle reflect differences in the function of the thoracic limbs. Differentiation in the serially homologous limbs occurs to a lesser extent in the pattern of axonal branching and excitatory innervation. Thus bifurcation of the motor axons into two primary branches each supplying one‐half of the bipinnate muscle is found in the anterior limbs but tends to disappear in the most posterior limb. Fast axon synapses are more prevalent in the closer muscle of the 1st WL than in the 4th WL. Such differences in distribution between 1st and 4th WLs are also found for the single excitor axon synapses to the opener muscl

ISSN:0022-104X    

DOI:10.1002/jez.1402390207

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe innermost shell lamella, which coats the inner surface of the shells in the estuarine clamRangia cuneata, is a dynamic structure with a variable composition. In some populations the lamella is a phosphoprotein‐rich structure devoid of crystalline mineral, and in others it is a glucosamine‐rich structure often containing barite (BaSO4) inclusions. Mineral depositions was artificially stimulated inRangiacontaining glucosamine‐rich lamellae by scratching the inner shell surface. After stimulation, the lamellae were transformed into phosphoprotein‐rich structures in which aragonite (CaCO3) was deposited. The mineral grew in spherulitic and dumbbell‐shaped clusters characteristic of aragonite precipitated from strictly inorganic solutions. This study demonstrates that phosphoprotein particles accumulate in the innermost shell lamella during stimulated biomineralization but neither inhibit mineral deposition nor influence the crystal habits. Since phosphoprotein particles are high capacity calcium‐binding proteins, they may be the source and transport vehicle for the calcium ions utilized in shell min

ISSN:0022-104X    

DOI:10.1002/jez.1402390208

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe ability of seven lectins to bind to newt epidermal cells and influence their motility was examined. Of the seven fluoresceinated lectins applied to frozen sections containing intact newt skin and migrating epidermis (wound epithelium), only Con A (concanavalin A), WGA (wheat germ agglutinin), and PNA (peanut agglutinin) produced detectable epidermal fluorescence. Con A and WGA each heavily labeled all layers of intact epidermis, but PNA bound only to the more superficial layers. In contrast to a single population of labeled cells in migrating epidermal sheets after treatment with Con A, there were both labeled and unlabeled cells after exposure to either WGA or PNA. The wound bed was labeled by both Con A and WGA, but not by PNA. DBA (Dolichos biflorisagglutinin), RCA I (Ricinus communisagglutinin), and UEA (Ulex europaeusagglutinin), did not produce significant fluorescence with either migrating or intact epidermis. In general, inhibitory effects on epidermal motility correlated with the binding studies. Thus, Con A, WGA, and PNA, the lectins which clearly bound to the epidermis, all produced a concentration‐dependent depression in the rate of epidermal wound closure. RCA was somewhat paradoxical in that it was moderately inhibitory despite showing essentially no binding. The effects of SBA and UEA were equivocal. DBA had no effect. These results indicate that the inhibition of motility produced by Con A that we have described previously is not peculiar to this mannose‐binding lectin, but is shared by at least one lectin with an affinity for D‐GlcNAc (WGA), and one with an affinity for B‐D‐Gal(1‐3)‐D‐GalNAc (PNA). The fact that PNA labeled some migrating cells and the superficial layers of intact epidermis suggests that wound epithelium is derived, in part, from cells in the outer layers of the epidermis, or that the cell surface of the deeper cells becomes more like superficial cells d

ISSN:0022-104X    

DOI:10.1002/jez.1402390209

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

年代:1986

数据来源: WILEY

摘要:

AbstractA search for specific proteins involved in newt limb regeneration, using monoclonal antibodies against forelimb blastemas, led to the detection of an antigen in the regenerate epithelium. Fluorescent‐antibody‐labeled cells first appeared just prior to blastema outgrowth. From bud through early digit stages this antibody reacted with nearly all of the regenerate epithelial cells. Other tissues also reacted, including nerve, blood vessels, and gastrointestinal tract. The behavior of the reactive cells in the regenerate epithelium, and their close association with immediately adjacent skin glands, raises several new possibilities for the origin of the regenerate epithel

ISSN:0022-104X    

DOI:10.1002/jez.1402390210

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

年代:1986

数据来源: WILEY

摘要:

AbstractIn order to test the effect of acute stress on gonadal hormone secretion in reptiles, six mature male alligators were captured, and a blood sample was taken within 5 min of capture. Additional blood samples were taken at timed intervals for up to 41 hr, and plasma testosterone and corticosterone were measured by radioimmunoassay. Plasma testosterone declined to 50% of the initial value by 4 hr and dropped to less than 10% of initial by 24 hr. Plasma corticosterone increased during the first 12 hr, declined at 24 hr, and rose again at 40 hr. Blood samples from male alligators collected in North and South Carolina, south Florida, and in south Louisiana in two consecutive breeding seasons were also assayed for testosterone and corticosterone. In these populations there were significant differences in mean plasma testosterone and corticosterone levels. Elevated corticosterone levels were consistently seen in alligators caught in traps and from which a blood sample was taken several hours later. Plasma testosterone, although consistently lower in trapped alligators, did not show a negative correlation with plasma corticosterone. Farm‐reared alligators bled once, released, and bled again at 24 hr also showed a highly significant suppression of testosterone secretion. These results demonstrate that stress has a rapid and dramatic effect on testicular steroid secretion in both farm‐reared and wild alligat

ISSN:0022-104X    

DOI:10.1002/jez.1402390211

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

年代:1986

数据来源: WILEY