Biomedical subjects

S M Challinor

Publications and source records attributed to S M Challinor.

7 recordsLinked to original sources

PubMed1994

Pattern of oxytocin concentrations in the peripheral blood of healthy women and men: effect of the menstrual cycle and short-term fasting.

A sensitive and specific radioimmunoassay was used to measure basal oxytocin (OT) concentrations in samples of peripheral blood drawn q 10 min for 8 hrs from women during the follicular and luteal phases of the menstrual cycle and from men before and after 20 hrs of fasting. Few, if any, pulses of OT were found in the blood of men and women in this study. The pattern of OT concentrations in the circulation was the same during both stages of the menstrual cycle and was not affected by short-term fasting. The use of frequent sampling and the present assay system for OT did not detect a pulsatile pattern of OT concentrations in the blood of men and women in the basal state.

Adult↗

PubMed1992

Pulses of oxytocin in the cerebrospinal fluid of rhesus monkeys.

Cerebrospinal fluid (CSF) samples were collected at frequent intervals (every 10-15 min) to determine if oxytocin pulses were present in the CSF of monkeys. Temporary indwelling subarachnoid catheters, with the tip of the catheter at the T12-L1 subarachnoid space, were placed in 4 nonlactating and 3 lactating (4 months post partum) female monkeys. Monkeys were maintained on jacket/tether/swivel systems in a constant photoperiod (07.00-19.00 h). CSF was continuously withdrawn at a rate of 1.2 ml/h by peristaltic pump, and CSF was collected in 15-min fractions (from 3 lactating monkeys and 1 nonlactating monkey) or in 10-min fractions (from the other 3 nonlactating monkeys) using a fraction collector. CSF oxytocin was measured by radioimmunoassay. Pulses of oxytocin were analyzed using the computerized Pulsar pulse detection algorithm. A pulsatile pattern of oxytocin concentrations was found in the CSF of lactating and nonlactating monkeys. The ultradian pulses of oxytocin were superimposed upon the diurnal rhythm of oxytocin in CSF. We conclude that frequent sampling of CSF provides a way to monitor moment-to-moment changes in central nervous system concentrations of oxytocin in primates.

Animals↗

PubMed1992

Effect of naloxone administration upon the diurnal concentrations of oxytocin in the cerebrospinal fluid of rhesus and cynomolgus monkeys.

A diurnal pattern in oxytocin concentrations is present in cerebrospinal fluid (CSF) removed from the spinal subarachnoid space of monkeys, with elevated levels occurring in the early light hours. In order to investigate the possible role of endogenous opioid peptides in the generation of this oxytocin rhythm, we administered naloxone (0.4 mg/kg/h x 48 h) to rhesus and cynomolgus monkeys and examined the effects on the diurnal pattern of oxytocin in CSF collected from the lumbar subarachnoid spinal space. Monkeys maintained on jacket/tether/swivel systems and in a 12 h light: 12 h dark cycle (lights on 07.00-19.00 h) were implanted with temporary spinal subarachnoid catheters. CSF was continuously collected from the lumbar subarachnoid space and assayed for oxytocin. Oxytocin concentrations in CSF showed a diurnal variation with peak and nadir concentrations during light and dark hours, respectively. The lumbar CSF concentrations of oxytocin were not significantly different during naloxone vs. saline infusion. Plasma oxytocin concentrations, measured in the same animals, displayed no diurnal variation and were not significantly different during naloxone vs. saline infusion. We conclude that naloxone administration for 48 h does not perturb the diurnal variation in oxytocin concentrations in the CSF of monkeys. Mu opioid receptors are unlikely to be involved in modulating the diurnal rhythm of oxytocin in the CSF of monkeys.

Animals↗

PubMed1990

Pattern of oxytocin concentrations in the plasma and cerebrospinal fluid of lactating rhesus monkeys (Macaca mulatta): evidence for functionally independent oxytocinergic pathways in primates.

Two populations of oxytocin-staining neurons have been identified in the paraventricular nucleus: magnocellular neurons that terminate in the posterior pituitary and parvocellular neurons that terminate elsewhere in the central nervous system. Whether these oxytocin neurons are functionally separate was tested by measuring oxytocin concentrations in samples of peripheral blood and cerebrospinal fluid (CSF) obtained simultaneously from lactating rhesus monkeys during suckling. Lactating animals bearing temporary subarachnoid and venous catheters were maintained in a constant photoperiod (0600-1800 h). Samples of CSF were continuously withdrawn by peristaltic pump (0.1 mL/15 min) for 2-4 consecutive days from subarachnoid catheters with the tips placed at the T12-L1 level of the spinal column in four lactating monkeys 4 months postpartum and again after weaning. On 2 of these days, we observed and recorded periods of infant suckling and collected peripheral blood samples (1.2 mL) from the mother at 5-min intervals for 60 min. Oxytocin was measured in blood and CSF by RIA. Oxytocin concentrations increased in the plasma of the lactating monkeys during periods of nursing, with peak concentrations ranging from 4-16.7 microU/mL. No increase in plasma oxytocin was found on the day after the infant was weaned. Variations in the concentrations of oxytocin in CSF were independent of the suckling stimulus and plasma oxytocin concentrations and occurred during observed periods of no nipple contact by the infant and at the time of weaning after the infant had been removed from the mother. Each lactating animal also displayed a normal circadian variation in CSF oxytocin concentrations, with peak and nadir levels during light and dark hours, respectively. We conclude that release of oxytocin into the CSF of lactating monkeys is disassociated from release into the peripheral circulation. The data further support the conclusion that neuronal pathways giving rise to oxytocin in the CSF and the periphery are anatomically and functionally separate in primates.

Animals↗

PubMed1989

A computer-assisted medical diagnostic consultation service. Implementation and prospective evaluation of a prototype.

STUDY OBJECTIVE: To evaluate the accuracy of a computer-aided consultation service using academic general internists and the Quick Medical Reference (QMR) diagnostic program: and to study the impact of the consultation on the diagnostic behavior of physicians caring for patients. DESIGN: Prospective study of the diagnostic accuracy of computer-aided consultation in 31 cases, as well as a prospective study of ward team diagnoses and opinions before and after consultation. SETTING: General medicine wards of two tertiary care centers. PARTICIPANTS: Thirty-one patients identified as posing a diagnostic challenge and meeting eligibility criteria, as well as the housestaff caring for these patients. MEASUREMENTS AND MAIN RESULTS: After 6 months follow-up, diagnoses were established in 20 of 31 cases. The diagnostic sensitivity of the computer-assisted diagnoses, 85% (95% CI, 56% to 97%), was similar to that of the consult service physicians, 80% (95% CI, 55% to 94%), but better than that of the ward teams, 60% (95% CI, 33% to 81%; P = 0.03 using the binomial test). The consultation influenced the postconsultation differential diagnoses of the ward teams in 26 of the 31 cases (95% CI, 92% to 95%). House officers rated the consultation service as being educationally helpful in 25 of the 31 cases (95% CI, 62% to 94%). CONCLUSIONS: Computer-aided diagnostic consultation, when provided by physicians familiar with the limitations of the system and capable of overriding inappropriate suggestions, was both accurate and educationally helpful in most cases. The system provided reasonable diagnostic suggestions not previously considered by the ward teams and these suggestions were valued sufficiently to cause alteration of the original differential diagnoses.

Diagnosis, Computer-Assisted↗

PubMed1989

Effect of a computer-assisted general medicine diagnostic consultation service on housestaff diagnostic strategy.

Quick Medical Reference (QMR) is a microcomputer-based decision support system designed to provide diagnostic assistance in the field of internal medicine. In addition to providing plausible diagnostic hypotheses based upon patient specific findings, the program highlights history, physical and laboratory items which are potentially useful in discriminating among the diagnoses under consideration. We have evaluated the impact of a computer-assisted diagnostic consultation service on the diagnostic and management strategy of a housestaff in a university internal medicine training program. Differential diagnoses were obtained before and after the use of the program, and a questionnaire was used to assess the educational value of the service and the effect of the service on the diagnosis and planned management. Over an eight week period, 31 cases were identified which met inclusion criteria. The QMR consultation added a diagnosis to the original list in 14 out of 31 cases. The consultation reordered the diagnosis in an additional 7 cases, and in 8 cases a diagnosis was ruled out by the use of the program. After the use of the program the housestaff reported they would obtain an additional lab test in 10 cases, change the order of planned tests in two cases and eliminate a lab test in one case. The use of the program was rated as helpful educationally in 81% of the cases, and helpful with respect to management in also 81% of the cases.

Diagnosis, Computer-Assisted↗

PubMed1986

The INTERNIST-1/QUICK MEDICAL REFERENCE project--status report.

INTERNIST-1 and its successor, QUICK MEDICAL REFERENCE (QMR), are computer programs designed to provide health care professionals with diagnostic assistance in general internal medicine. Both programs rely on the INTERNIST-1 computerized knowledge base, which comprehensively describes 570 diseases in internal medicine. The philosophies behind the development of each program differ. Whereas INTERNIST-1 functions solely as a high-powered diagnostic consultant program, the QMR program acts more as an information tool, providing users with multiple ways of reviewing and manipulating the diagnostic information in the program's knowledge base. At the lowest level, the program can be viewed as an electronic textbook of medicine. In addition, the QMR program has the ability to assist users with generating hypotheses in complex patient cases. The QMR program has not been evaluated formally as an information tool for practicing physicians. A preliminary study indicates that QMR's case-analysis capabilities are of potential benefit in most patients in internal medicine admitted for diagnostic evaluation.

Diagnosis, Computer-Assisted↗