Biomedical subjects
Publications and source records attributed to C Gross.
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As shown by post-mortem analysis the major neuropathological trait of Huntington's chorea is a degeneration of the intrinsic neurons of the neostriatum (caudate nucleus and putamen). Such a situation can be reproduced by a destruction of the neostriatum by kainic acid. When injected into the caudate nucleus this excitatory amino acid destroys the intrinsic neurons of the neostriatum and spares fairly well the passing fibers. In the present work, we have chosen to examine the influence of neostriatal destruction on the activity of identified dopaminergic cells in the pars compacta of the substantia nigra. As a key element in the nigro-neostriato-nigral loop, this structure is a relevant site for observing the functional effects of neostriatal lesion. Our research hypothesis was based on the generally accepted view that the suppression of the important neostriato-nigral pathway and in particular the inhibitory GABAergic contingent, could generate a hyperactivity of nigral dopaminergic cells. One may therefore consider that the dopaminergic hyperactivity produces abnormal messages which can influence via several pathways the motoneurons, and which participates in the genesis of the hyperkinetic movements characteristic of chorea. After destruction of the neostriatum, we have shown that the pattern of discharge of most identified nigral dopaminergic neurons becomes greatly disorganized. This drastic change in the pattern of activity cannot be interpreted as the simple 'lift of a brake' on these cells by the suppression of the inhibitory GABAergic striato-nigral tract.
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In this study, neuronal activity of dopamine (DA) containing neurons located in pars compacta of the substantia nigra is analysed by the use of the time interval histograms and autocorrelograms. These cells display a regular and rhythmic firing pattern which may possibly subserve the striatal regular spontaneous release of DA, and, then exert an homeostatic function within this part of the extrapyramidal system.
Neostriatal lesions by kainic acid provide a good model for studying Huntington's chorea. The pattern of discharge of nigral dopaminergic neurons of rats subjected to a kainate lesions of the caudate nucleus was compared to the nigral activity in control (saline-injected) and normal rats. The observed changes suggest that neostriatal degeneration does not simply induce a nigral dopaminergic hyperactivity but rather a disorganization of their slow and rhythmic pattern of discharge, thus eliciting in the nigral neurons abnormal messages which may reach the motoneurons and participate in the genesis of choreic movements.
Sixty assessable patients undergoing elective colonic and rectal surgery were randomly allocated to receive prophylaxis with a combination of 1.5 g cefuroxime plus 500 mg metronidazole or 500 mg metronidazole alone as single doses by the intravenous route, given at the beginning of anesthesia. The two groups were matched for age, sex, malignancy, and type of operation. Primary wound infections were observed in one patient (3.7%) in the combination group and six (18.2%) in the group given metronidazole alone. This trend was not statistically significant. Bacteriologic examination of the anastomoses, abdominal walls, and wounds showed significantly more sterile cultures in the combination group, although more aerobic cefuroxime-resistant isolates were seen in this group. There is no evidence that the emergence of resistant strains had any influence on the outcome of patients in the study. It was concluded that an appropriate antibiotic prophylactic regimen for colorectal surgery should be directed against aerobic and anaerobic organisms. Cefuroxime plus metronidazole is an effective regimen for the prevention of postoperative infection.
Unit recordings were made in area 5 of monkeys during the performance of a sound-triggered movement of the forearm. Changes in neuronal activity prior to the movement were observed in 188 neurons recorded in both normal and deafferented animals. When the discharge of these cells was analyzed as peristimulus histograms, it was seen that 152 neurons presented a pattern of discharge which was characterized by a brief modification in activity with a relatively constant latency after the auditory cue. Similar changes were observed in normal and deafferented animals but the latency was not the same for the two groups. These neurons may reflect the presence of a sensorimotor interface for the integration of instructions for movement and the subsequent genesis of motor commands.
Three-dimensional spinal data were collected from AP and lateral spinal radiographs of 24 female adolescent idiopathic scoliotics. Vertebral body end-plate eccentricity (AP vertebral body width divided by lateral vertebral body width) was measured and found to be minimized at the apex of the scoliotic curve in approximately 70 percent of the subjects. Measurement of end-plate eccentricity is suggested as a possible method for assessment of vertebral body rotation in scoliotic subjects.
The Cobb angle is the recommended standard for curvature assessment of scoliotic patients. Because the errors associated with this measure are thought to be significant, we conducted a study to quantify the variability of the Cobb measure among observers, within each observer's repeated measurements, and between the traditional protractor Cobb measurement and a computer-aided technique.
A review of the literature discloses the buckling phenomenon as responsible for the initiation of lateral deformation and the progression of small curves in idiopathic scoliosis. From the point of view of parsimony, buckling explains how ligamentous laxity, increased interdiscal flexibility, muscular asymmetries, neurologic lesions, morphologic, anthropometric, and sexual differences would contribute to development of the deformity. Thus, a buckling theory seems to embody the fragmented character of present information about the etiology of idiopathic scoliosis.
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Unit recordings were performed in the postcentral cortex and focused on area 5 of awake monkeys during the execution of a learned movement of the contralateral forearm so that the time relationship between the motor act and any modification of neuronal activity could be precisely correlated. Recordings were obtained from intact animals (561 neurons) and after deafferentation (C1-T7) of the trained limb (344 neurons). Of the movement-related neurons in normal animals, 243 cells were located in area 5 and these cells were divided into two populations. The first population (66% of movement-related neurons) presented modifications of activity after the onset of movement and receptive fields, often complex, were identifiable for these somaesthetic-like cells. No such neurons were found in the same cortical area after deafferentation. The second population (34% of movement-related neurons) presented modifications of activity related to movement but these changes occurred well before the onset of movement, up to 280 ms before. These cells were also characterized by an absence of sensory modulation and they represented the entire population of movement-related neurons recorded in area 5 after deafferentation (124 neurons). The first population appears to subserve a complex somaesthetic function. The second population is subject to purely central influences which, in part, may be due to corollary discharge or internal feedback. However, this population most likely represents a command apparatus for movement located 'upstream' to the motor cortex.
A duplex scanner is used for noninvasive and semiquantitative flow measurement of Cimino-shunts. Normal venous shunt flow was in 12 chronic shunts 15.2 +/- 3.9 ml/sec and 3 fresh shunts 7.3 +/- 1.8 ml/sec. A noninvasive diagnosis of hemodynamically significant shunt stenoses seems to be possible. Therefore an early and routinely examination of shunts by means of a duplex scanner ist recommended.
The analysis of the first 125 patients, having coronary artery bypass surgery at the community hospital of Linz/Austria, revealed a perioperative mortality of 3% (n = 4) and a myocardial infarction incidence of 4% (n = 5). The angiographic restudy after surgery in 109 patients demonstrated 89% (n = 174) of the 196 vein grafts patent. The degree of revascularisation was 74% and the mean number of grafts per patient 1.8. The ejection fraction of the left ventricle was unchanged postoperatively (preop.: 61%, postop.: 64%). 3 to 6 months after surgery 55% of the patients were without angina pectoris-symptoms, 37% were clinically improved and 8% remained unchanged or deteriorated with respect to chest pain. There was a significant difference in patency rate and degree of revascularisation between pain free (90 resp. 88%) and improved patients (70 resp. 54%, p less than 0.001) and the unchanged (20 resp. 17%, p less than 0.001). Aortocoronary bypass surgery provides relief of pain or improvement in a high percentage (92%). The results are important influenced by graft function and degree of revascularisation.
A technique is presented for the nonradiographic assessment of spinal configuration. Its use in the assessment of scoliotic curvatures is discussed in the light of existing radiographic and nonradiographic techniques. The reproducibility of point-encoding measurements relative to a fixed standard is shown to be 98.8 percent. The correlation of pointencoded spinal angles with similar data taken from x-rays is significant at p less than 0.0005. The average standard deviation in the measurement of spinal angles of 10 successive trials on five test subjects is 3.55 degrees +/- 1.95 degrees.
A temperature-sensitive mutant sigma subunit (rpoD800) purified from Escherichia coli was inactivated in vitro by temperatures in excess of 37 degrees C whereas wild type sigma remained stable up to 49 degrees C. Both temperature-sensitive and wild type sigma formed multimeric aggregates upon thermal inactivation which were visualized by electron microscopy as polymeric chains. Conditions favoring sigma monomer (low sigma concentration and binding to core polymerase) protected temperature-sensitive sigma from heat inactivation. Full activity was recovered from inactivated temperature-sensitive sigma aggregates by incubation in a buffer containing 6 M guanidine HCl and subsequent removal of denaturant by dilution. Both wild type and temperature-sensitive sigma recovered full activity levels, retaining their characteristic thermal inactivation temperatures after denaturation in 6 M guanidine HCl and renaturation. Transcription of T4 DNA by RNA polymerase containing the rpoD800 mutant sigma subunit remained undiminished for 10 min after shift up to 46 degrees C but was almost completely inhibited within the following 10 to 15 min.
We have characterized a new mutation rpoD800 affecting the sigma gene of E. coli. Upon tranfer to high temperature, a strain with the rpoD800 mutation ceases growth within 30 min. We find that this mutation renders sigma about 10-fold more thermolabile than the wild type sigma at 45 degrees C in vitro. We have compared the temperature profile for inactivation of wild type and mutant sigma and find that the mutant inactivates at a temperature about 9 degrees C lower than does the wild type. The chromosomal locus affected by rpoD800 is shown to be allelic to the locus affected by the spontaneous mutants ts285 and alt-1. All three mutations result in altered sigma and in altered growth at high temperature. We argue that the single locus affected is the structural gene for the sigma subunit of E. coli RNA polymerase.
Ca2+-dependent phosphorylation of the 20000-Mr regulatory light chain was found to be a necessary condition for the Ca2+-sensitivity of the Mg2+-dependent ATPase activity and superprecipitation of pig carotid actomyosin. Actin-myosin interaction independent of phosphorylation and Ca2+ (ATPase activity and superprecipitation) were demonstrated in aged actomyosin preparations and in preparations from which the regulatory light chains were removed by papain digestion.