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Biomedical subjects

K Cho

Publications and source records attributed to K Cho.

At least 163 records · Page 9Linked to original sources
PubMed1996

Physiological actions of the neuropeptide Antho-RNamide on antagonistic muscle systems in sea anemones.

Antagonistic contractions of longitudinal and circular muscles in the body wall cause shape changes in sea anemones. Single electrode voltage clamp recordings from Calliactis parasitica body wall preparations distinguish two cell types (Types 1 and 2) with different time courses of evoked inward current. The anthozoan neuropeptide Antho-RNamide (L-3-phenyllactyl-Leu-Arg-Asn-NH2) excites longitudinal body wall preparations and Type 1 cells, but inhibits circular body wall preparations and Type 2 cells. Type 1 and Type 2 cells may therefore belong to longitudinal and circular myoepithelium respectively. Antho-RNamide may open Ca2+ channels in longitudinal muscle cells and K+ channels in circular muscle cells. This opposite action of a neuropeptide is of significance in the control of antagonistic contractions.

Animals↗
PubMed1996

The anthozoan neuropeptide Antho-RWamide I modulates Ca2+ current in sea anemone myoepithelial cells.

The anthozoan neuropeptide Antho-RWamide I (< Glu-Ser-Leu-Arg-Trp-NH2) excites contraction of endodermal muscles in sea anemones. Single electrode voltage clamp recordings from semi-intact preparations of endodermal myoepithelial cells reveal that Antho-RWamide I increases an inward Ca2+ current. Evidence for the involvement of a Ca2+ current in contraction was supported by the observation that Cd2+ abolished spontaneous contractions and reduced inward current. Contractions and inward currents induced by Antho-RWamide I were not, however, completely abolished in the presence of Cd2+. We conclude that Antho-RWamide, a putative neurotransmitter at sea anemone smooth muscle, acts by opening, either directly or indirectly, Ca2+ channels in the muscle membrane.

Animals↗
PubMed1996

Synaptic potentials recorded from sea anemone muscle cells in situ.

Three pulse types, A,B, and C, can be recorded from column ring preparations of the sea anemone Calliactis parasitica (Couch). Lucifer Yellow injection confirmed that the recording sites are intracellular in endodermal myoepithelial cells. Type C pulses are spontaneously active depolarizing pulses, arising from a resting potential of around -60mV, and are usually < 5 mV in amplitude. When the cells were voltage-clamped these pulses reversed at around 0 mV membrane potential; therefore, we conclude that they are synaptic potentials. In some cells an increase in frequency of type C pulses accompanied contraction of the circular muscle field. Inward currents in these myoepithelial cells are carried by Ca2+, and although Na(+)-free solutions did not affect inward currents they did eliminate type C pulses, i.e., these synaptic potentials may result from activity of Na(+)-dependent nerve cells.

Animals↗
PubMed1996

Developmental changes in the noradrenergic innervations of spinal motoneurons in neonatal rats.

Developmental changes in the noradrenergic innervations of spinal motoneurons in both the cervical and lumbar cords were studied in neonatal rats. The labeling of motoneurons was done using choleratoxin B subunit as a retrograde neurotracer. The noradrenergic fibers were detected by immunohistochemistry for tyrosine hydroxylase. At postnatal day 1, tyrosine hydroxylase immunoreactive fibers were evident in the entire ventral horn, including the triceps brachii motoneuron pools at the cervical level. In contrast, they were observed only in that portion of the ventral horn medial to the quadriceps femoris motoneuron pools at the lumbar level. Subsequently, tyrosine hydroxylase immunoreactive fibers increased at both levels, and they were distributed in most of the gray matter at postnatal day 14. At this age, the distribution pattern of tyrosine hydroxylase immunoreactive fibers in the lumbar level was almost identical to that of the cervical level. The number of closely apposed tyrosine hydroxylase immunoreactive varicosities on motoneurons (close appositions) increased continuously from postnatal day 1 to 14 at both the cervical and lumbar levels. At postnatal day 1, triceps brachii motoneurons had more close appositions than quadriceps femoris motoneurons in number and, after postnatal day 7, there was no difference in the number of close appositions between triceps brachii motoneurons and quadriceps femoris motoneurons. Based on these results, we discuss the significance of monoaminergic influences on the postnatal development of spinal motoneurons and of motor behavior with a rostrocaudal gradient.

Adrenergic Fibers↗
PubMed1996

The putA gene of Agrobacterium tumefaciens is transcriptionally activated in response to proline by an Lrp-like protein and is not autoregulated.

The Agrobacterium tumefaciens putA gene, which encodes proline dehydrogenase, is transcriptionally induced by exogenous proline. In contrast to the putA genes of enteric bacteria, the A. tumefaciens putA gene is not regulated by the PutA protein, as the putA promoter remained strongly proline inducible in strains lacking PutA. A putA null mutation increased the expression of the putA promoter under a variety of conditions. However, this mutation is predicted to increase the cytoplasmic concentration of proline, and this alone probably accounts for its effects on putA expression. The putA promoter was also strongly induced by valine, and the putA genotype did not affect expression by this gratuitous inducer. An open reading frame (ORF) encoding an Lrp-like protein was found transcribed divergently from putA. Disruption of this ORF, designated putR, abolished induction of the putA promoter by proline or valine. In addition to activating putA, PutR also repressed its own transcription, and this autorepression was only slightly affected by exogenous proline. The transcription start sites for the putA and putR genes are separated by 64 nucleotides, suggesting that PutR could regulate both promoters by binding to a single operator.

Agrobacterium tumefaciens↗
PubMed1996

Rate constant of gadolinium (Gd)-DTPA transfer into chronic subdural hematomas.

Gadolinium (Gd) DTPA concentrations in subdural fluid and arterial blood were measured following intravenous Gd-DTPA injection by ion coupled plasma emission spectrometry in 31 chronic subdural hematomas and 12 with subdural effusions. Dynamic biological modeling analysis was used to calculate the unidirectional transfer rate constant (K) for Gd-DTPA influx into the subdural fluid. The Gd concentrations in subdural hematomas and subdural effusions were 36.3 +/- 3.7 nmol ml(-1) and 80.0 +/- 14.0 nmol ml(-1), respectively. The transfer rate constants (K) for subdural hematomas and subdural effusions were 12.4 +/- 1.5 (x10(-4)) min(-1) and 19.7 +/- 2.2(x10(-4)) min(-1), respectively. The Gd concentration and transfer rate constant for subdural effusions were significantly (p<0.05) higher than for subdural hematoma. The Gd transfer rate constant was significantly correlated with the interval from head injury to operation. The present study shows that the immature outer membrane has a high transfer rate constant, allowing extravasation of plasma components into the subdural space and increasing the volume of the subdural effusion; the rate constant decreases with aging of the subdural hematoma.

Adolescent↗