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Biomedical subjects

F Moss

Publications and source records attributed to F Moss.

108 records · Page 6Linked to original sources
PubMed1981

Survey of antibiotic prescribing in a district general hospital. I. Pattern of use.

In a survey of all antibiotic prescription in a district general hospital during November, 1978, the reason for each prescription was determined by a brief interview with the prescriber. 28% of all inpatients received antibiotics. Older patients were prescribed antibiotics more often than were younger patients. Ampicillin was the most frequently used antibiotic, accounting for over 40% of prescriptions. Over 70% of antibiotic courses were stated by the prescriber as being for the treatment of infection and the remainder were said to be prophylactic. Although 80% of the antibiotics were assessed as suitable treatment for the stated infection, most of the patients were treated without bacteriological evidence of the infecting agent and, for these patients, prescribers were unable to specify the pathogen against which treatment was intended in 50% of the courses they initiated. Only 7% of antibiotics prescribed for conventional surgical prophylaxis fulfilled all the criteria used to assess the suitability of choice of drug and the method and timing of its administration.

Adolescent↗
PubMed1979

Severe hypernatraemia in adults.

In a prospective study of abnormalities of plasma sodium concentration carried out over one year 20 patients were identified who had a concentration exceeding 154 mmol(mEq)/1. Of these, eight patients had diabetes mellitus, eight had primary intracranial disorder, and four had become dehydrated. Five of the eight diabetics presented with hyperosmolar, non-ketotic precoma, and in all eight hypernatraemia developed despite treatment with hypotonic (0.45%) saline. There was a good correlation (r = -0.93) between the rates of change of plasma sodium and blood glucose concentrations, and thus a rise in plasma sodium concentration appeared to be a consequence of the treatment. In the early phase of treatment urinary sodium loss was extremely low despite a brisk diuresis, the infused sodium then predisposing the patients to hypernatraemia. All of the eight patients with intracranial disorders showed evidence of abnormal production of the antidiuretic hormone, six having frank diabetes insipidus. Severe hypernatraemia in this group was associated with a high mortality, fluid balance being difficult to maintain. Two of the four patients who had become dehydrated had had a recent gastrointestinal haemorrhage. In these patients infusion of 0.9% saline contributed to the hypernatraemia since urinary sodium loss was low. Severe hypernatraemia in adults is uncommon, but in established cases plasma and urinary biochemical indices should be measured frequently. Monitoring of the central venous pressure is usually necessary, and patients are best managed in an intensive care unit.

Adult↗
PubMedDate not supplied

Noise-induced impulse pattern modifications at different dynamical period-one situations in a computer model of temperature encoding.

We used a minimal Hodgkin-Huxley type model of cold receptor discharges to examine how noise interferes with the non-linear dynamics of the ionic mechanisms of neuronal stimulus encoding. The model is based on the assumption that spike-generation depends on subthreshold oscillations. With physiologically plausible temperature scaling, it passes through different impulse patterns which, with addition of noise, are in excellent agreement with real experimental data. The interval distributions of purely deterministic simulations, however, exhibit considerable differences compared to the noisy simulations especially at the bifurcations of deterministically period-one discharges. We, therefore, analyzed the effects of noise in different situations of deterministically regular period-one discharges: (1) at high-temperatures near the transition to subthreshold oscillations and to burst discharges, and (2) at low-temperatures close to and more far away from the bifurcations to chaotic dynamics. The data suggest that addition of noise can considerably extend the dynamical behavior of the system with coexistence of different dynamical situations at deterministically fixed parameter constellations. Apart from well-described coexistence of spike-generating and subthreshold oscillations also mixtures of tonic and bursting patterns can be seen and even transitions to unstable period-one orbits seem to appear. The data indicate that cooperative effects between low- and high-dimensional dynamics have to be considered as qualitatively important factors in neuronal encoding.

Computer Simulation↗
PubMedDate not supplied

Low-dimensional dynamics in sensory biology 2: facial cold receptors of the rat.

We report the results of a search for evidence of unstable periodic orbits in the sensory afferents of the facial cold receptors of the rat. Cold receptors are unique in that they exhibit a diversity of action potential firing patterns as well as pronounced transients in firing rate following rapid temperature changes. These characteristics are the result of an internal oscillator operating at the level of the membrane potential. If such oscillators have three or more degree of freedom, and at least one of which also exhibits a nonlinearity, they are potentially capable of complex activity. By detecting the existence of unstable periodic orbits, we demonstrate low-dimensional dynamical behavior whose characteristics depend on the temperature range, impulse pattern, and temperature transients.

Action Potentials↗
PubMedDate not supplied

Augmented sensory nerve action potentials during distant muscle contraction.

We previously reported that the median sensory nerve action potentials (SNAP) increased in amplitude during ipsilateral abductor pollicis brevis contraction. The objectives of the present project were to study the timing and origin of this phenomenon and to eliminate the possibility of local artifact. Ten normal subjects were recruited. The baseline was established using ten threshold stimuli, which were delivered to the median nerve at the wrist at 0.2 Hz. Using the same stimulus strength, the SNAP was recorded while the tibialis anterior was contracted at 25, 50, 75, and 100% of maximum force. Responses were signal-averaged. Results showed an increase in ipsilateral SNAP amplitude between baseline and maximum contraction of 6 +/- 2 microV (standard error, P = 0.004) and contralateral amplitude of 8 +/- 2 microV (standard error, P = 0.01). Statistical analysis was performed with analysis of variance for repeated measures and paired t test. The effect peaked between 0 and 10 min after contraction and lasted from 1.5 to more than 20 min after muscle relaxation. In conclusion, SNAP appear to be enhanced during and after muscle contraction. Theories concerning underlying causes for this event are discussed.

Adult↗
PubMedDate not supplied

Effect of isometric contraction on threshold somatosensory evoked potentials.

We previously described the augmentation of sensory nerve action potential amplitudes after near and remote isometric muscle contraction. In this study, we wished to determine if the sensory cortex was involved in this process. In this prospective, intrinsically controlled study, we studied threshold somatosensory evoked potentials in 12 normal subjects with stimulation of the median nerve at 5.1 Hz. The subjects were tested during the following conditions: baseline, 25%, and 75% maximum isometric abductor digiti minimi contraction for 4 min. Each of these conditions was recorded before, during, and 4 min and 8 min after contraction. Results showed that at 25% contraction, there was a significant temporal increase in N9 amplitude (2.1-2.6 microV; P = 0.05, analysis of variance, repeated measures) and a decrease in N20 amplitude with 75% contraction (1.9-1.6 microV; P = 0.03, analysis of variance, repeated measure). No significant changes were noted in the spinal cord or brainstem recordings. In conclusion, it appears that augmentation of the brachial plexus peripheral nervous system recording occurs concurrently with central inhibitory gating. The possibility of peripheral nervous system adaptability will be discussed.

Adult↗
PubMedDate not supplied

Increased threshold sural amplitude after upper limb isometric contraction in complete paraplegics.

OBJECTIVE: To determine whether the enhancement of threshold sural sensory nerve action potentials (SNAPs) occurred in patients with spinal cord injury after upper limb isometric contraction. DESIGN: This prospective study, in which ten paraplegic patients with spinal cord injury were recruited from the Harris County community and served as his/her own control, was performed in the electromyography laboratory at Harris County Hospital District Quentin Mease Hospital. The baseline SNAP was established using ten threshold, signal-averaged stimuli to the sural nerve. With the same stimulus strength, the SNAP was recorded while the subjects' arms were pulled apart against a force gauge at 50% and 100% maximum force. Responses were recorded every 4 min until the values returned to baseline. RESULTS: Results showed an increase in the SNAP amplitude after 50% and 100% maximum force. The mean preexercise SNAP amplitude was 4.0 +/- 0.6 (SE) microV. At 50% force, the SNAP amplitude was 7.57 +/- 1.2 microV; at 100% force, it was 7.29 +/- 1.2 microV. The post hoc analysis of the data revealed P = 0.009 and P = 0.01 for 50% and 100% maximum force, respectively. CONCLUSIONS: The threshold SNAP of the sural nerve was enhanced after isometric exercise in paraplegic patients with spinal cord injury.

Action Potentials↗
PubMedDate not supplied

Tuberculosis in HIV seropositive individuals--a retrospective analysis.

A retrospective analysis of all culture-positive cases of Mycobacterium tuberculosis infection in HIV positive individuals, over a 5 year period, revealed 18 cases, drawn from a population of approximately 1500. The prevalence of culture proven M. tuberculosis over the 5 year period was therefore 1.2% and was strongly associated with either a concomitant, or a subsequent, AIDS diagnosis. Sixty-one per cent had pulmonary tuberculosis, 17% had both extra-pulmonary and pulmonary infection and 22% had extra-pulmonary infection alone. Although a wide range of radiological abnormalities was seen, segmental consolidation was the commonest, occurring in 57% of cases. Only 55% of the specimens were positive on initial stains for M. tuberculosis, with a mean duration of 4 weeks to become culture positive, emphasizing that early diagnosis rests on clinical suspicion.

Adult↗