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J F Case

Publications and source records attributed to J F Case.

At least 19 recordsLinked to original sources
PubMed1998

The pupil response of a teleost fish, Porichthys notatus: description and comparison to other species.

The pupil response of Porichthys notatus to different intensities of illumination is described and compared to that of P. myriaster, Cephaloscyllium ventroisum, and a human. While the fully dark adapted pupil is round, at the highest light intensities it consists of only two small, almost independent, apertures with a total area 4.9% of that observed in the fully dilated animal. The response is at least partially consensual and occurs, albeit at a much reduced rate, in isolated eyes. P. notatus also displays retinomotor movements comparable to those seen in most teleosts, suggesting that, contrary to most previous assumptions, pupillary responses and retinomotor migrations are not mutually exclusive.

Adaptation, Ocular↗
PubMed1997

Shewanella woodyi sp. nov., an exclusively respiratory luminous bacterium isolated from the Alboran Sea.

Thirty-four strains of nonfermentative, respiratory, luminous bacteria were isolated from samples of squid ink and seawater from depths of 200 to 300 m in the Alboran Sea. Although these strains had a few properties similar to properties of Shewanella (Alteromonas) hanedai, they did not cluster phenotypically with any previously described bacterium. The nucleotide sequence of a 740-bp segment of luxA was not homologous with other known luxA sequences but clustered with the luxA sequences of Shewanella hanedai, Vibrio logei, Vibrio fischeri, and Photobacterium species. The 16S RNA gene from two strains was sequenced and was found to be most closely related to the S. hanedai 16S RNA gene. Based on the differences observed, we describe the new isolates as members of new species, Shewanella woodyi sp. nov. Strain ATCC 51908 (= MS32) is the type strain of this new species.

Base Composition↗
PubMed1988

The visual pigments of four deep-sea crustacean species.

The visual pigments of four mesopelagic crustacean species were studied at sea by means of microspectrophotometry. The absorbance maxima obtained for the visual pigments and their metarhodopsins, respectively, were: 493 nm and 481 nm (Systellaspis debilis), 485 nm and 480 nm (Acanthephyra curtirostris), 491 nm and 482 nm (A. smithi), and 495 nm and 487 nm (Sergestes tenuiremis). The spectral characteristics of the rhodopsins and metarhodopsins permit high photosensitivity and facilitate photoregeneration in a nearly monochromatic environment. Photic regeneration of rhodopsins from the deep-sea environment was demonstrated, and data were obtained which are consistent with the occurrence of dark regeneration. Specific optical density of the observed visual pigments was calculated for two species.

Animals↗
PubMed1988

Eye size of pelagic crustaceans as a function of habitat depth and possession of photophores.

Eye diameter, interommatidial angle, and rhabdom dimensions were measured for a variety of crustacean species differing in habitat depth and bioluminescence ability. Eyes are smaller and eye growth rates are lower at greater depths for species in five of the six families examined, and photophore-bearing species tend to have larger eyes than relatives which lack photophores. Rhabdoms are smaller and interommatidial angles are larger in small eyes, factors which, with reduced aperture size, are generally associated with decreased visual sensitivity and acuity. This suggests that the eyes of many deep-sea crustaceans are poorly suited to a dimly lit environment; however, the small eyes of deep-sea crustaceans may still perceive luminescent sources from appropriate distances because of the much higher contrast at depth between luminescent sources and background light. Smaller eyes also impose a lower energetic burden and are potentially less visible to predators than are large eyes.

Animals↗
PubMed1987

A multichannel microspectrophotometer for visual pigment investigations.

The microspectrophotometer described replaces the photomultiplier of conventional scanning systems with a multichannel detector. By eliminating scanning-related artifacts, particularly those associated with mechanical vibrations, this system makes possible ship-based microspectrophotometric studies of visual pigments of marine organisms too fragile for live transport to shore-based laboratories. The performance of the multichannel microspectrophotometer is compared with that of conventional scanning systems and absorbance spectra taken at sea on isolated rhabdoms from Euphausia pacifica are presented. Difference spectra gave a lambda max for rhodopsin of 483 nm and a lambda max for metarhodopsin of 489 nm.

Animals↗
PubMed1983

Effects of abrasion and Na+ on dactyl-mediated chemoreception in mature kelp crabs, Pugettia producta (Randall).

Extracellular recordings from the mixed sensory nerves innervating the abraded dactylopodites of the kelp crab, Pugettia producta (Randall), indicate that at least some chemoreceptors and mechanoreceptors remain functional. The chemoreceptors of the abraded dactyls are sensitive to both the concentration and chemical nature of the stimulants. The responses of the chemoreceptors, but not of the mechanoreceptors, are reduced when choline is substituted for sodium in the stimulant solutions. Only chemoreception is blocked by the topical application of tetrodotoxin (TTX) to the dactyls; partial reversal of the blockage occurs with time. The differential blockage of receptor activity by low Na+ and TTX is consistent with the idea that spike initiation occurs more distally in the dendrites of the chemosensory neurons than in the mechanosensory neurons. The relevance of this to the ability of at least some abraded dactyl setae to remain functional in a long-lived, nonmolting crab is considered.

Animals↗
PubMed1978

Gap junctions suggest epithelial conduction within the comb plates of the ctenophore Pleurobrachia bachei.

Intercellular gap junctions occur between the ciliated cells that make up the comb plates of the ctenophore Pleurobrachia. Similar junctions are found within the ciliated grooves which run from the apical organ to the first plate of each comb row, as well as throughout the endoderm of the meridional canals. Gap junctions were not found in the ectodermal tissue between the comb rows. The distribution of junctions suggests that excitation conduction within the ciliated grooves, comb plates and meridional canal endoderm may be epithelial.

Cilia↗
PubMed1977

The caudal luminous organs of lanternfishes: general innervation and ultrastructure.

Neuroanatomical, light and electron microscopic investigations of the caudal luminous organs of two lanternfish species, Stenobrachius leucopsarus and Parvilux ingens, were conducted in a search for morphological correlates underlying their luminescent behavior and control mechanisms. Complex neural pathways involving the spinal nerves and the sympathetic nerve chain of the caudal peduncle are associated with profuse segmental innervation to both the supracaudal and infracaudal organs. Neural composition of these segmental subunits indicates that pre-ganglionic (spinal) as well as post-ganglionic (sympathetic) fibers are involved in the neural control of luminescence of these organs. Neuro-photocyte units, in which multiple nerve branches are sandwiched between two lamellar photocytes and establish large surface areas of close appposition, as well as gap junctions apparently interconnecting all photocytes throughout the luminous organs, may account for the very rapid and simultaneous displays of spontaneous or electrically driven luminescence. The organization of the caudal luminous organs is compared with that of lanternfish photophores. Relatively few granular and agranular synaptic vesicles are present in some nerve processes of the photocyte units, suggesting that adrenergic neurotransmission as well as electrotonic spread of excitation may be involved at the neuro-photocyte junctions.

Animals↗
PubMed1976

Pharmacomorphological study of denervation induced by 6-hydroxydopamine in Porichthys photophores.

The effects of 6-hydroxydopamine (6-OHDA) on the bioluminescent response of Porichthys photophores were investigated as part of a pharmacological study of the neural control of luminescence in this fish. Subcutaneous injections of 6-OHDA induce a luminescent response similar to that of norepinephrine (NE), suggesting a sympathomimetic action. The luminescent response to electrical stimulation is almost completely and irreversibly abolished within 24 hours following low-dose treatment of the photophores with 6-OHDA, while the sensitivity of these organs to exogenous NE is increased significantly over the few days post-treatment. During this period the photophores continously emitted a steady low-level glow. Electronmicroscopic studies of such photophores revealed progressive destruction of the nerve endings. Photophore luminescent sensitivty to NE subsequently became sub-normal, and at this stage electron microscopy revealed an increasingly larger number of damaged photocytes, supportive cells and, in one case, lens cells. From these results it is suggested that 6-OHDA initially impairs neuro-photocyte transmission by destroying catecholaminergic nerve endings. In turn, the transmitter reuptake mechanism is also impaired, thus accounting for development of supersensitive responses to exogenous NE. Subnormal luminescent responses to NE appear as a result of loss of photocyte competence due to structural deterioration. The latter are interpreted as the consequence of removal of trophic factors supplied by the photophore adrenergic innervation. Suppression of luminescent response to both electrical stimulation and exogenous NE in photophores treated with higher doses of 6-OHDA, may be due to a direct effect of this drug on the receptor sites of the photocytes.

Animals↗
PubMed1976

Neural excitation of the larval firefly photocyte: slow depolarization possibly mediated by a cyclic nucleotide.

1. In firefly larvae, extracellular recordings from the light organ nerve show that a volley of action potentials elicits a glow of an intact animal. 2. Intracellular recordings from the photocytes show that they respond to nerve stimulation with a slow, graded depolarization which precedes light emission. The depolarization begins about 0-5 s after the nerve is stimulated; it peaks about 1 s after stimulation; and subsides about 2-5 s after the stimulus. The glow increases fastest when the photocyte depolarization is at its peak and lasts 5-15 s. 3. Photocyte depolarization is associated with a decrease in the input resistance of the cell. 4. Adrenergic receptors in the light organ are pharmacologically similar to vertebrate alpha-receptors. 5. Phophodiesterase inhbitors, aminophylline and theophylline, cause the light organ to glow, suggesting that cyclic nucleotides may mediate the effect of the adrenergic nerve transmitter.

Action Potentials↗
PubMed1975

Ultrastructure of the larval firefly light organ as related to control of light emission.

The firefly larva has a pair of light organs consisting of a layer of interdigitating, light emitting cells, covered dorsally with a layer of opaque, white cells. Each light organ is ventilated by one large and several smaller tracheal branches and is innervated by a branch of the segmental nerve containing two axons. These axons branch profusely in the photocyte layer so that several nerve profiles are seen around any photocyte. Nerve terminals contain large dense-core vesicles and small light-core vesicles. Clusters of light-core vesicles surrounding irregularly shaped membrane densifications, presumably the synapses between nerve and photocyte, are common in nerve terminals. Light emitting cells in insects characteristically contain photocyte vesicles. In the larva there are both full and empty photocyte vesicles; the full vesicles contain a matrix with tubular membrane invaginations in contrast to the empty vesicles which contain amorphous membrane invaginations.

Animals↗