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Biomedical subjects

C Gross

Publications and source records attributed to C Gross.

At least 145 records · Page 8Linked to original sources
PubMed1988

Postural adjustments in the monkey: effects of velocity on EMG sequence.

Monkeys were trained to perform flexion or extension movements of the elbow in a strictly restrained position. Even in these conditions, postural adjustments were still recorded. They appeared to be organized in a consistent pattern. When trials were ranked with increasing velocity, two kinds of EMG changes could be described: (i) those in the upper part of the body which may be triggered by anticipatory postural motor programs; (ii) those in lower limbs recruited only with higher velocities and that may correspond to semi-automatic programs organized at a lower level of the central nervous system.

Animals↗
PubMed1987

Two classes of spontaneous miniature excitatory junction potentials and one synaptic vesicle class are present in the ray electrocyte.

Cross sections (1-2 mm thick) of the ray (Raja) tail were secured to a dish and immersed in elasmobranch saline. Spontaneous miniature excitatory junction potentials (MEJPs) were recorded by advancing a 50 k omega, KCl filled electrode into the electric organ (20 microV peak-to-peak baseline noise). Data were filmed, and/or recorded on magnetic tape for computer analyses. Intracellularly recorded MEJP amplitude histograms showed a peak at 60 microV and had a right-hand skew with MEJPs up to 0.5 mV. The small peak amplitude and the skewed amplitude distribution of intracellularly recorded MEJPs result from the relatively low input resistance and the short space constant of the electrocyte coupled with the dispersed synapses on the electrocyte. At 23 degrees C the intracellularly recorded MEJP frequency ranged from 1-10 MEJPs/s. The MEJPs became larger and became focally recorded as the electrode was advanced against the intracellular surface of the innervated membrane of the electrocyte. Focal extracellular MEJPs (reversed polarity) were also recorded with the electrode positioned against the outside surface of the innervated side of the electrocyte. The frequency of focally recorded intracellular MEJPs was increased (up to 40/s) when the electrode was pushed against the membrane. Focal MEJP frequencies decreased to a few/min within 5-10 min but the mean amplitude of 3-5 mV remained constant. Decreases in amplitude and frequency in focally recorded intracellular MEJPs are attributed to changes in electrode pressure against the membrane. Amplitude histograms were constructed from focally recorded intracellular or extracellular MEJPs which showed the same time characteristics. The focal MEJP amplitude histograms have two distinct classes, each forming a bell-shaped distribution. It is concluded that both classes are generated at the electrode tip. The smaller class of MEJPs has a mean 1/10th that of the larger class and composes about 2% of the MEJPs. The small class is analogous to the sub-MEPP class found in the frog sartorius (Kriebel and Gross 1974) and mouse diaphragm (Kriebel et al. 1976, 1982). Distributions of synaptic vesicle diameters are slightly log normal (right hand skew) such that the mean diameter (57 nm) is slightly larger than the modal value (52 nm). Vesicles touching the membrane were of the same size and diameter distribution as the entire vesicle population. The profiles of the distributions are smooth and suggest only 1 class of synaptic vesicle based on diameter.

Action Potentials↗
PubMed1986

[Temperature dependence of bronchial and tracheal reactivity of isolated respiratory tract preparations of the guinea pig].

The intrapulmonary loss of heat due to hyperventilation may be considered as essential pathogenetic factor in producing exercise induced asthmatic response. The temperature dependence of smooth muscle contraction was investigated using isolated trachea and isolated lung strips of guinea pigs. The measurements of the contraction responses to cumulative dose administrations of acetylcholine (10(-9) to 10(-3) M) were made in thermostated organ baths (isotonic contraction, modified Krebs-Henseleit solution, pH 7.4, air gassing). The standardized measurement data were adjusted to a non-linear function with the aid of a computer. The reactivity of the isolated trachea remained unchanged with a change of the bath temperature (from 37 degrees C to 30 degrees C), whereas a markedly increased contraction response to acetylcholine was observed in the lung strips. The results indicate that the contraction induced by the drop in temperature is localized in the small airways. The stabilization of reactive oxygen metabolites as an asthma-inducing mechanism is discussed as a possible explanation of the temperature-dependent effects.

Airway Obstruction↗
PubMed1986

[Health manpower in Colombia].

With its great emphasis on community participation, Colombia's health policy aims to check the inordinate demand for free medical care, hospitalization, and health resources and to provide better services for the needy and the community at large. Available data are provided on the proportion of physicians to the population (6,5/10,000), and on the estimated numbers of nurses (6,070), nurse's aides (13,016), auxiliaries (25,771) and professional dentists (10,069). This is followed by data on the estimated numbers of graduates in the health professions and the target for the year 2000 (53,143 physicians, 16,469 nurses, and 21,600 dentists). Finally, recommendations are put forward on policy and education, among them that plans for the training of health manpower be consistent with the country's growth and financial capacity.

Colombia↗
PubMed1985

[Main coronary artery stenosis: significance of the clinical stage for angiographic and surgical risk].

86 patients with significant main coronary artery stenosis (greater than 50%) were divided into 61 with stable and 25 with unstable angina pectoris. The coronary morphology (isolated main coronary artery stenosis, degree of stenosis, additional vessel disease) and the left ventricular function (ejection fraction, left ventricular end-diastolic pressure) were the same in both groups. Deaths due to coronary angiography amounted to 2.3% and involved two patients with unstable angina. 82% (n = 50) of the patients with stable angina and 83% (n = 19) with unstable angina were considered operable. 69% of the stable and 74% of the unstable group were actually revascularised. Operative deaths amounted to 3.4% and again involved two patients with unstable angina. During an average post-operative follow-up period of 38 months 5% of the operated and 28% of the non-operated patients died (P less than 0.05). The investigation demonstrated that for patients with main coronary artery stenosis operability in stable angina is no different from that in unstable angina. Angiographic and operative deaths in patients with unstable symptomatology, however, were markedly higher than in those with stable angina.

Angina Pectoris↗
PubMed1985

Peripheral inputs and early unit activity in area 5 of the monkey during a trained forelimb movement.

Previous studies on area 5 in the monkey showed that an early neuronal activity up to 300 ms before the onset of movement was encountered in this cortical area after deafferentation of the trained forelimb (C1-T7). This present work indicates that none of the EMG activity recorded in other parts of the body may account for these early changes and lends weight to the hypothesis that their activation is purely central.

Animals↗
PubMed1985

MPTP primate model of Parkinson's disease: a mechanographic and electromyographic study.

Movement parameters and electromyographic (EMG) studies were carried out in two macaque monkeys performing a rapid arm movement before and after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Hypokinesia and rigidity were seen after repeated doses. Disturbances in both movements and EMG activity were similar to those reported in Parkinsonian patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1985

Temporary extraanatomic subclavian-to-femoral bypass. An auxiliary method in the treatment of aneurysms of the descending thoracic aorta.

A new technique to perfuse the lower half of the body during clamping of the thoracic aorta is described. Viability of the visceral organs and the spinal cord is maintained using an extraanatomical 10 mm graft inserted between the right subclavian and the left common femoral arteries. The results in 21 cases are analysed. No hypoxic organ damage was encountered. This simple technique probably adds to the safety of the patient undergoing surgery on the descending aorta.

Aorta, Thoracic↗
PubMed1985

Invertase signal and mature sequence substitutions that delay intercompartmental transport of active enzyme.

The role of structural signals in intercompartmental transport has been addressed by the isolation of yeast invertase (SUC2) mutations that cause intracellular accumulation of active enzyme. Two mutations that delay transport of core-glycosylated invertase, but not acid phosphatase, have been mapped in the 5' coding region of SUC2. Both mutations reduce specifically the transport of invertase to a compartment, presumably in the Golgi body, where outer chain carbohydrate is added. Subsequent transport to the cell surface is not similarly delayed. One mutation (SUC2-s1) converts an ala codon to val at position -1 in the signal peptide; the other (SUC2-s2) changes a thr to an ile at position +64 in the mature protein. Mutation s1 results in about a 50-fold reduced rate of invertase transport to the Golgi body which is attributable to defective signal peptide cleavage. While peptide cleavage normally occurs at an ala-ser bond, the s1 mutant form is processed slowly at the adjacent ser-met position giving rise to mature invertase with an N-terminal met residue. s2 mutant invertase is transported about sevenfold more slowly than normal, with no delay in signal peptide cleavage, and no detectable abnormal physical property of the enzyme. This substitution may interfere with the interaction of invertase and a receptor that facilitates transport to the Golgi body.

Biological Transport↗
PubMed1985

Mutations in the rpoH (htpR) gene of Escherichia coli K-12 phenotypically suppress a temperature-sensitive mutant defective in the sigma 70 subunit of RNA polymerase.

Escherichia coli K-12 strain 285c contains a mutation in rpoD, the gene encoding the sigma subunit of RNA polymerase. The 70-kilodalton sigma polypeptide encoded by this allele is unstable, and this instability leads to temperature-sensitive growth. We describe the isolation and characterization of four temperature-resistant pseudorevertants of 285c that can grow at high temperature. Each of these revertants increased the stability of the sigma 70 mutant protein. The map position of the suppressor mutations was close to that of the rpoH (htpR) gene. A multicopy plasmid containing the intact rpoH gene restored the temperature-sensitive phenotype. Marker rescue experiments established the positions of three of the alleles within the rpoH gene. One mutation has been sequenced and causes a leucine-to-tryptophan change 7 amino acids from the carboxyl terminus of the rpoH gene product.

Chromosome Mapping↗
PubMed1985

[Activity of substantia nigra pars reticulata neurons after lesion of the ipsilateral neostriatum by kainic acid in rats].

Huntington's chorea is a degenerative disorder of the human brain characterized by a marked loss of intrinsic neostriatal neurons. This situation can be reproduced by kainic acid injection in the caudate nucleus. Activity of pars reticulata neurons ipsilateral to the injected neostriatum was studied in normal, control (saline-injected) and lesioned rats. They were identified by electrophysiological and histological criteria (Fig. 1). Results obtained in normal and control rats were very similar (Table I). As previously described, the mean frequency of these neurons was high. An important percentage (respectively 72.5 and 73%) and these neurons presented the characteristics of a regular firing pattern (so called "organized neurons"). Results obtained in kainic acid lesioned rats were significantly different (Table I). The mean frequency was lower and only 11% of reticulata cells remained organized after neostriatal lesion. This important dysfunction may be explained in various ways: The neostriato-nigral pathway's destruction involves both the inhibitory GABAergic tract and the excitatory substance P tract (GALE et al., 1978). Other inputs arising from many structures in the brain continue to exert their own action on SN neurons, resulting in an unbalance in the SN inputs. It is well known that the nigral dopamine influences the neuronal activity of pars reticulata neurons (Ruffieux et Schultz, 1980; Waszczak et Walters, 1983). Doudet et al. (1984 b) previously reported a dysfunction of neuronal activity of dopaminergic cells after striatal lesion. A disturbance in the electrical activity may induce a similar disturbance in the intranigral dendritic release of DA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[A model of Parkinson's disease: effect of L-dopa therapy on movement parameters and electromyographic activity in monkeys treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)].

A primate model of Parkinson's disease was obtained by i. v. administration of 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). A behavioural, a mechanographic and an electromyographic (EMG) study were carried out during the execution of a rapid elbow movement, in two normal monkeys and, after the MPTP administration, before and after a L-DOPA therapy. Disturbances in behavior, movement parameters and EMG activity observed in MPTP-treated monkeys mimic those reported in Parkinsonian patients. Treatment with L-DOPA was effective in greatly correcting these disturbances. These results lend weight to the assumption that use of MPTP in primate provides a good model to study Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗