摘要:

AbstractElectrical activity generated by electrical stimuli has been recorded through suction electrodes placed on gastrozooid and dactylozooid polyps of the colonial hydroid,Hydractinia echinataFlemming. The polymorphism so characteristic of aHydractiniacolony extends to the physiological machinery controlling the behavior of the different polyp types. Contraction of gastrozooid polyps, where the muscle elements are uniformly distributed within the epidermis, is correlated to an electrical event termed the symmetrical contraction potential (SCP). The SCP is conducted about 4.4 cm/sec. Two kinds of electrical activity are correlated to distinct behavioral events of the specialized asymmetrically coiled dactylozooid polyps: (1) Dactylozooid coiling potentials (DCPs) are conducted at about 4.6 cm/sec and are correlated with contraction of a thin band of muscles on the concave side resulting in asymmetrical contraction and a marked coiling of the polyp. (2) Dactylozooid lashing potentials (DLPs) are conducted at about 9.1 cm/sec and have a threshold 50 per cent or more higher than DCPs. DLPs are correlated with contraction of well‐developed muscles on the convex side resulting in a rapid uncoiling or “lashing” of the dactylozooid polyp. Dactylozooid coiling is correlated to an incremental spread of conduction within the colony whereas lashing occurs during colony‐wide through‐conducted excitation. Very small electrical spikes (50–200 μV amplitude) have been recorded from both gastrozooids and dactylozooids. These tiny potentials (TPs) are conducted at 15–21 cm/sec, have a threshold below that of the DCPs and SCPs, and are of unknown behavioral significance. On the basis of the characteristics of the electrical events, the differences in threshold, conduction velocity, and related spread of excitation, it is proposed that these three potentials represent activity within separate conducting systems — an incrementing conducting system (ICS), a through conducting system (TS), and a tiny potential system (TPS). Physiological and microscopical evidence suggest a nerve net origin for the ICS, and epithelial condu

ISSN:0022-104X    

DOI:10.1002/jez.1401900102

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

年代:1974

数据来源: WILEY

摘要:

AbstractCorrelative light and electron microscope observations suggest that the colonial hydroid,Hydractinia echinata, possesses a single ectodermal nerve net in gastrozooid and dactylozooid polyps, and in the uppermost ectodermal sheet of the basal mat, but not in free stolon tips. Two distinct cell types comprise this nerve net — ganglion cells and sensory cells, the neurites of which characteristically possess microtubules and electron dense, membrane‐bound vesicles. The sensory cell body possesses an apical ciliary apparatus which distinguishes it from the ganglion cell type. Ultrastructural features of ganglion and sensory cells are presented in relationship to their distribution. Gastrozooids and the basal mat contain ganglion and sensory cells; dactylozooids contain ganglion cells primarily on the concave side of the polyp. Significantly, distinct bundles comprised of several neurites are found directly above the epithelio‐muscular cell processes of the gastrozooid and dactylozooid. Although synaptic junctions have not been found between ectodermal nerve cells and the muscle processes, they have been found bridging two nerve

ISSN:0022-104X    

DOI:10.1002/jez.1401900103

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe appendices of the first and second anal fin spines of mature males of the mediterranean Blennid fish,Blennius pavo, produce a pheromone which attracts females of the same species. Evidence for this is provided by the observation that water from aquaria in which mature males have been kept is strongly attractive to female fish. However, aquarium water from females or from immature males, whose anal appendices are poorly developed, is without effect. Aquarium water from immature males that had been treated with luteinizing hormone at a concentration of 0.15 mg/g bodyweight, but not higher, is effective in attracting females. Such LH treatment leads to enlargement of the anal appendices and to a proportional increase in the behavioral reactions of female fish brought into contact with aquarium water from such treated males. Aquarium water from males whose anal appendices have been removed by surgery or cautery does not elicit behavioral reactions from female fish. Histological examination of the anal appendices reveals the presence of numerous tubular invaginations in the epidermis. It is conjectured that pheromone production is related to the proliferation and degeneration of epidermal cells which can be seen to occur in the tubular structures. The pheromone(s) appears to be produced phasically during spawning under the direct influence of hypophyseal gonadotropin.

ISSN:0022-104X    

DOI:10.1002/jez.1401900104

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

年代:1974

数据来源: WILEY

摘要:

AbstractUltrastructural features of keratinization differ for the inner and outer epidermal surfaces of developing avian scales. Only the alpha stratum develops along the inner scale surface, and it is retained after hatching and is still present in adult birds. The cells of the alpha stratum are characterized by lipid droplets, multigranular bodies, and peripherally located keratohyalin granules. In contrast, the epidermis of the outer scale surface develops both alpha and beta strata. The alpha stratum is lost soon after hatching and only the beta stratum is found in the mature bird. Bundles of 30 Å filaments fill the cells of the beta stratum and keratohyalin granules are not present. The outermost peridermal and subperidermal cell layers develop along both epidermal surfaces of the scale. These two cell layers are characteristic of the embryonic period and are lost at the time of hatching

ISSN:0022-104X    

DOI:10.1002/jez.1401900105

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

年代:1974

数据来源: WILEY

摘要:

AbstractScales do not form on the legs and feet of the scaleless mutant chicken, and consequently, the skin in these regions remains soft and pliable, similar to that covering the rest of the body. By 17 days of embryonic development, both the peridermal and subperidermal cell layers have developed along the surface of the anterior shank epidermis. Subsequently, the scaleless epidermis cornifies, producing an alpha stratum characteristic of the inner epidermal surface of normal scales. The cells of the alpha stratum elaborate lipid droplets, multigranular bodies, and peripherally located keratohyalin granules. The beta stratum found along the outer epidermal surface of normal scales never develops.

ISSN:0022-104X    

DOI:10.1002/jez.1401900106

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

年代:1974

数据来源: WILEY

摘要:

AbstractThree experiments on the administration of HCG to fallow deer bucks are described and analysed together with another experiment described earlier. In two cases the administration of HCG was begun before antler shedding and resulted in retardation of their loss and in an inhibition of new growth. The next antlers were of a smaller size. These effects can be attributed to the influences of HCG on testosterone secretion by the testes.In two other experiments the administration of HCG was begun on the day the antlers were shed. In one case antler growth was stopped completely and no anti‐HCG antibodies were detected in blood. In the second case the antlers grew in spite of HCG injections and a high titre of antibodies was detected in the blood. The anti‐HCG antibodies were only detected in the buck which received HCG injections a second time after a four‐year int

ISSN:0022-104X    

DOI:10.1002/jez.1401900107

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

年代:1974

数据来源: WILEY

摘要:

AbstractA macromolecular “antifreeze” is present in the blood serum of fishes that inhabit subzero waters in winter. During the summer the “antifreeze” is not present. The effect of temperature and photoperiod on this circ‐annual cycle of “antifreeze” production was investigated. Fishes collected from subzero waters were acclimated to various temperature and photoperiod regimes. Only the combination of a long photoperiod and warm temperature resulted in the disappearance of “antifreeze” from the serum, thus providing for an efficient failsafe system. The time necessary for the complete loss of the macromolecular “antifreeze” ranged from 3 to 5 weeks. When summer fish were acclimated to various combinations of temperature and photoperiod, low temperatures resulted in the production of “antifreeze” regardless of the photo‐period. Serum Na and Cl−levels were significantly higher in cold acclimated than in warm acclimated fish. In general, fishes collected from more northerly latitudes had lower serum freezing points than the same species from warmer, more southerly waters. There seemed to be a genetic difference between populations ofAnoplarchus purpurescensfrom Amchitka, Alaska and San Simeon, California since the California fish were unable to produce “antifreeze” whe

ISSN:0022-104X    

DOI:10.1002/jez.1401900108

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

年代:1974

数据来源: WILEY

摘要:

AbstractThe effects of the neurotransmitters 5‐hydroxytryptamine (5HT) and acetylcholine (ACh) on the adenylate and guanylate cyclase activities in the ventricles of two species of bivalve molluscs,Mercenaria mercenariaandMacrocallista nimbosa, were examined. 5HT increased molluscan adenylate cyclase activity and intracellular cyclic AMP; ACh had no effect. Neither of these agents significantly altered ventricular cyclic GMP. A positive correlation between the excitatory action of 5HT and the simultaneous increase in intracellular cyclic AMP strongly suggests that this nucleotide mediates 5HT excitation. This proposal is further supported by experiments on ventricles ofModiolus demissus granosissimusthat are depressed by 5HT and exhibit very low levels of adenyl cyclase activity. However, classical pharmacological evidence is lacking; cyclic AMP, dibutyryl cyclic AMP, and phosphodiesterase inhibitors have no effect on the mechanical activity of isolated bivalve ventricle

ISSN:0022-104X    

DOI:10.1002/jez.1401900109

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

年代:1974

数据来源: WILEY

摘要:

AbstractBoth forelimbs of axolotl larvae were amputated at the elbow and left limbs were immediately denervated. Both the left and right limbs of 4 larvae/day were examined for DNA synthesis (H3‐thymidine‐autoradiography) and mitotic index on days 1 to 7 post‐amputation. DNA synthesis was evident in both innervated regenerating, and denervated non‐regenerating limb stumps, on days 4, 5, 6, and 7. Mitotic index increased only in innervated limbs, beginning o

ISSN:0022-104X    

DOI:10.1002/jez.1401900110

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

年代:1974

数据来源: WILEY

摘要:

AbstractUsing a new technique to stain and count planarian mitotic cells, a very rapid increase in neoblast mitotic activity has been found following feeding. The increase becomes visible 1 hour after feeding, reaches a maximum in 3–8 hours, and lasts for almost a week. These results suggest that a substantial proportion of neoblasts in the intact worm must be in the G2 phase ready to enter mitosis. The fact that the mitotic figures occur throughout the parenchyma also suggests that the stimulus may be of a neurohumoral kin

ISSN:0022-104X    

DOI:10.1002/jez.1401900111

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

年代:1974

数据来源: WILEY