Biomedical subjects

L Rodríguez-Sosa

Publications and source records attributed to L Rodríguez-Sosa.

6 recordsLinked to original sources

PubMed1998

Circadian clock function in isolated eyestalk tissue of crayfish.

Electrical mass response of crayfish photoreceptors (electroretinogram) was recorded continuously for up to seven days in isolated preparations that consisted of the retina and lamina ganglionaris. Electroretinogram amplitude varied in a circadian manner with a nocturnal acrophase and a period of 22-23 h in preparations kept in darkness. Acclimatization of animals to reversed light/dark cycles resulted in a phase reversal of the rhythm in vitro. The per (period) gene of Drosophila has been implicated in the genesis of rhythms in insects and in vertebrates. Immunocytochemical staining with an antibody against the PER gene product revealed immunoreactivity in the retinal photoreceptors, as well as in cell bodies in the lamina ganglionaris. Labelled axons run distally towards the photoreceptors and proximally to other areas of the lamina.

Animals↗

PubMed1997

Seasonal rhythm of red pigment concentrating hormone in the crayfish.

The content of red pigment concentrating hormone (RPCH) in the eye-stalk of the crayfish Procambarus clarkii varies seasonally, with maximum values during the summer months and the lowest values in winter. The responsiveness of tegumentary chromatophores to synthetic RPCH varies concurrently.

Animals↗

PubMed1994

Regional distribution and immunocytological localization of red pigment concentrating hormone in the crayfish eyestalk.

A polyclonal antibody was raised against synthetic tyrosinated crustacean red pigment concentrating hormone (RPCH-Tyr) with the sequence Tyr-Leu-Asn-Phe-Ser-Pro-Gly-Trp-NH2 with a tryptophan amide at the carboxyl terminal end. Its specificity was tested in comparison with peptides of similar structure. It appears to recognize the three to five residues near the carboxyl terminal. Native RPCH in the crayfish eyestalk was determined by two methods: (a) immunoenzymatic assay (ELISA) using the aforementioned antibody; and (b) bioassay on segments of isolated crayfish tegumentary epithelium. The unitary content in whole eyestalks was 5.5 +/- 1.0 nmol for samples (n = 18) taken at night. The regional distribution of RPCH content in the eyestalk was determined. The greatest proportion (40%) was found in the sinus gland, and the lowest in the retina plus lamina ganglionaris (6%). The medulla interna, medulla externa, and medulla terminalis contained similar proportions (about 16% each). The highest specific content was in the sinus gland (65.0 vs 24.4 pmol/micrograms protein for the whole eyestalk). Immunopositive neurons were identified in the various regions of the eyestalk. In 22 preparations, an average of 7 cells were identified in the ventromedial rim of the medulla terminalis, sending axons to the sinus gland, after branching in the neuropil of the medulla terminalis. Dorsally, 2 cells were identified in the medulla interna and 4 large cells and 11 small cells were located in the medulla externa in close proximity to the lamina ganglionaris: none of these cells appeared to project to the sinus gland. Profuse immunopositive fibers were found in the lamina ganglionaris projecting distally toward the base of the retina. Immunopositive axons were also found in the optic nerve.

Amino Acid Sequence↗

PubMed1993

The circadian system of crustaceans.

Crustaceans exhibit a variety of overt circadian rhythms. Observations on intact animals suggest the existence of more than one circadian pacemaker in the nervous system. Ablation experiments so far have been inconclusive in pin-pointing the location of putative pacemakers. However, various structures, most notably the optic peduncle, have been shown to sustain circadian rhythmicity in vitro. Retinal sensitivity and neurosecretory activity display circadian rhythms in the isolated optic peduncle, but they are also responsive to synchronizing influences from other regions of the central nervous system, most notably the supraesophageal ganglion. A model based on a number of circadian pacemakers distributed in the central nervous system best fits the experimental results at present. Coupling of rhythmicity between independent circadian pacemakers is likely to occur, and a neuroendocrine stage of integration has been proposed for several rhythms. Various entraining agents have been identified, and more than one may play a part in the synchronization of a given rhythm.

Animals↗

PubMed1990

Modulation of crayfish retinal sensitivity by 5-hydroxytryptamine.

The responsiveness of crayfish retinal photoreceptors to light was enhanced by exposure to 5-hydroxytryptamine (5-HT), either following injection into whole animals or following topical application to isolated eyestalks or retinas. The effect was measured as an increment in the amplitude of the receptor potential, and was dose-dependent in the range 10(-6)-10(-3) mol l-1 (injected as a 0.1 microliter dose in intact animals). It was more pronounced at low levels of illumination and was reversibly blocked by methysergide. The enhancement was a consequence of a dual effect: (a) retraction of the proximal pigment granules within the photoreceptors, with a corresponding increase in the light-admittance function of the retina; and (b) a direct effect, facilitating a membrane conductance increase which mediated the generation of the receptor potential. A set of axons in the lamina ganglionaris with a 5-HT-like immunoreactivity was found in the vicinity of the photoreceptor axons. 5-HT antagonists were capable of blocking the physiological retraction of pigment granules in photoreceptors at night, suggesting that 5-HT acts as a modulator during the nocturnal phase of the circadian cycle in the crayfish retina.

Animals↗

PubMed1982

Range of modulation of light sensitivity by accessory pigments in the crayfish compound eye.

The compound eye of the crayfish during dark adaptation undergoes an enhancement of light sensitivity within a range of 3 log units. Only 1 log unit can be explained by the increase in responsiveness of the retinula cells. The rest can be accounted for by the migration of the proximal and distal accessory pigments. In isolated retinas, with the distal pigment paralysed in light-adapted position and the proximal pigment only partially responsive, the sensitivity enhancement in darkness is reduced in more than 1 log unit. By hormonally inducing the expansion of the distal pigment while the rest of the system remains dark-adapted, there is a shift of one log unit in the V-log 1 curve. In a crayfish mutant devoid of the two dark accessory pigments, the sensitivity enhancement in dark adaptation only covers one log unit.

Animals↗