Dopaminergic modulation of neurosecretory cells in the crayfish.

The main aims of this paper are (a) to locate possible dopaminergic neurons in the eyestalk with anti-tyrosine hydroxylase antibodies, (b) to search for the presence of dopamine (DA) in the nervous structures of the eyestalk, (c) to explore its release, and (d) to test the effect of DA on neurosecretory cells in the eyestalk. Experiments were performed in adult crayfishes Procambarus clarkii, in isolated optic peduncle. Immunocytochemistry was made with the antibody against its precursor synthesizing enzyme tyrosine-hydroxylase. The content and release studies of DA were made using high performance liquid chromatography (HPLC). Extracellular and intracellular recordings were conducted with conventional recording techniques. A large number (approximately 2000) of immunopositive somata of different sizes and shapes were identified in various regions of the eyestalk. The majority of somata are of the smallest size (5-25 microm diameter). DA content in the eyestalk was 5.6 +/- 0.1 pmol per structure; the greatest content is in the MT (over 60%). A basal level release of DA was observed. Incubation of eyestalks in solution containing a high K+ concentration increased the DA release (79%). Two effects of DA on the excitability of X-organ neurons were observed; an excitatory effect on neurons of approximately 25 microm somata diameter and another inhibitory effect in the group of approximately 35-microm somata diameter neurons. The excitation occurs with a depolarization and decrement of membrane conductance in the cell soma while the inhibition occurs with a hyperpolarization and increment of membrane conductance in soma. We concluded the following: (1) Dopamine is present in each optic ganglia of the crayfish eyestalk. (2) There is a basal release of DA from the isolated eyestalk. (3) DA release is enhanced threefold by eyestalk incubation in 40 mM [K+] solution. (4) DA selectively excites a population of neurons with low-speed conduction axons, and small somata in the X-organ-sinus gland system, while inhibiting another population characterized by higher axonal conduction speed and large somata. (5) These observations support a role for DA as a neurotransmitter or neuromodulator in the X-organ neurons of the crayfish eyestalk.

Circadian oscillations of RPCH gene expression in the eyestalk of the crayfish Cherax quadricarinatus.

The RPCH and beta-actin cDNAs from the crayfish Cherax quadricarinatus were amplified, cloned and sequenced. The primary structure sequences of these cDNAs were compared to other members of the AKH/RPCH family. Fluctuations in the amount of the C. quadricarinatus RPCH and beta-actin mRNAs, as cDNAs, were quantified every 3h by RT-PCR. Single cosinor analysis supports the notion of beta-actin and RPCH mRNA circadian behavior in animals subjected to 12h:12h light/dark regimes. In constant darkness RPCH mRNA concentration changes to ultradian cycles.

A possible molecular ancestor for mollusk APGWamide, insect adipokinetic hormone, and crustacean red pigment concentrating hormone.

Precursor structures of various members of the neuropeptide family adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) of mandibular arthropods and the APGWamide family of mollusks were compared. Amino acid alignments showed a common overall architecture (signal peptide, active peptide, related peptide), with a similar alpha helix-random coil secondary structure. DNA sequence alignments revealed close similarities between the genes encoding for the peptides of the two families. The APGWamide genes are larger than the AKH/RPCH genes. The sequence environment occupied by introns is similar in AKH/RPCH and APGWamide genes. Such similarities suggest that these peptide families might have been originated by gene rearrangements from a common ancestor having either an AKH/RPCH/APGWamide-like structure or both an AKH/RPCH-like and an APGWamide-like structures. In the former model, DNA fragments could have been gained when the ancestor evolved to mollusks and it could have lost nucleotides when the progression to mandibular arthropods took place. In the second model, AKH/RPCH-like structures could have been fused during evolution toward mandibular arthropods, whereas in mollusks they could have been lost with the possible amplification of the APGWamide-like structure. Loss of domains in exon 1 may have originated the signal peptide and the first codon of the active RPCH. In exon 2, loss of domains possibly determined the junctions of codons 2 to 5 with the loss of a APGWamide copy; exon 3 underwent fewer variations. The similarity of the mollusk APGWamide precursors is closer to that of the RPCH family than the insect AKH family, indicating an earlier evolutionary departure.

The genomic organization of the open reading frame of the red pigment concentrating hormone gene in the blue crab Callinectes sapidus.

The open reading frame (ORF) of the gene for the precursor of the octapeptide Red Pigment Concentrating Hormone (RPCH) from the blue crab Callinectes sapidus was cloned by PCR with oligonucleotides targeted to the initiation and the end of the translation coding sequences. A 272 bp intron was characterized between nucleotides 343 and 344 of the reported cDNA, present in the region coding for the last amino acids of the precursor related peptide of RPCH. The intron genomic structure here described is similar to that reported for the gene coding for the Adipokinetic Hormone (AKH) of the grasshopper Schistocerca nitans.

Cn11, the first example of a scorpion toxin that is a true blocker of Na(+) currents in crayfish neurons.

A novel crustacean toxin (Cn11) was isolated and characterized from the venom of the Mexican scorpion Centruroides noxius Hoffmann. It contains 63 amino acid residues and is stabilized by four disulphide bridges. It is lethal to crustaceans (Cambarellus montezumae), less toxic to insects (crickets) and non-toxic to mammals (mice) at the doses assayed. In neurons isolated from the X organ-sinus gland system of the crayfish Procambarus clarkii, it blocks the Na(+) currents with an estimated K(m) of 320 nmol l(-1), without affecting the Ca(2+) and K(+) currents. The voltage-gated tetrodotoxin-sensitive Na(+) current was recorded from X organ neurons in culture 24 h after plating using the whole-cell clamp configuration. The Na(+) current was isolated by blocking Ca(2+) currents with Cd(2+) and Cs(+) and K(+) currents with tetraethylammonium and 4-aminopyridine. Under control conditions, the Na(+) currents were activated at -40 mV with a maximum amplitude at 0 mV. In the presence of 1 micromol l(-1) Cn11, the Na(+) current amplitude was reduced by 75 % without apparent modifications to the gating mechanism. These findings suggest that Cn11 selectively blocks a Na(+) channel. It is the first representative of a new group of scorpion toxins specific for this molecular target.

La bioética y la formación científica del médico / Bioethics and scientific formation of the physician

La bioética es ya una de las grandes corrientes del pensamiento y la acción en la medicina moderna. Dada la juventud de este campo de estudio, aún subsisten importantes debates y controversias sobre su papel en la medicina y en la educación médica, pero se acepta sin reservas que debe ser incorporada cabalmente al proceso formativo del médico, a la par de los componentes científicos, técnicos y humanísticos, integrándola con ellos en forma equilibrada.

El perfil cronobiológico de tensión arterial y de frecuencia cardiaca en un grupo familiar, determinado mediante monitorización automática / The chronobiological profile of blood pressure and cardiac frequency in a family group, determinated via automatic monitoring

Durante una semana se determinaron: la tensión arterial (sistólica, media y diastólica) y la frecuencia cardiaca de los miembros de una familia mediante monitorización automática ininterrumpida. Se elaboró el perfil cronobiológico de cada uno de los miembros de la familia en series de tiempo de diversas periodicidades, identificándose un amplio componente circádico y otro circaseptano de menor amplitud. Se encontraron claras diferencias de fase entre los ritmos de las cuatro variables cardiovasculares estudiadas, y el perfil cronobiológico de los hijos, mostró mayor semejanza con el del padre que con el de la madre

Cronobiología en medicina y cirugía / Chronobiology in medicine and surgery

La cronobiología estudia variaciones predecibles que se producen en todas las formas de vida, es decir, los ritmos y las tendencia. Cada variable o sistema fisiológico presenta una estructura en el tiempo, la cual está cifrada genéticamente, y puede expresarse en ausencia de variaciones cíclicas ambientales; sin embargo, normalmente, los ritmos biológicos están ajustados a ciclos geofísicos. La cronobiología también cuantifica las características de los ritmos biológicos, aportando medidas de la amplitud y del tiempo (fase y período), y una media normalmente más precisa y más correcta que la media aritmética. La correcta medida de los ritmos biológicos ha permitido avances de consideración en el conocimiento de sus mecanismos fisiológicos de origen y expresión. El empleo de la información sobre estos ritmos en medicina está abriendo nuevas perspectivas en la prevención, diagnóstico y tratamiento de las enfermedades. Asimismo, la cronobiología aplicaciones en el mejoramiento de la calidad de vida pues facilita al individuo el realizar un autocontrol de su estado de salud.

An automated system for detection and analysis of locomotor behavior in crustaceans

An efficient and simple system in presented for the analysis of crustacean locomotor behavior. The system is composed by six dual-compartment actographic chambers with photocoupling circuit for movement detection, and a device for acquisition and analysis of cata. Such device is made by a digital interface which feeds in to a microcomputer with disc unit and printer. Information is processed in real time during the experiment, with a simultaneous printout and storage in a floppy disc