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Biomedical subjects

L Carmichael

Publications and source records attributed to L Carmichael.

At least 19 recordsLinked to original sources
PubMed2000

Extratympanic electrocochleography: diagnostic and predictive value.

OBJECTIVE: To define the clinical value of extratympanic electrocochleography (ECoG) in the diagnosis of Meniere's disease. STUDY DESIGN: Retrospective case review. SETTING: An otology/neurotology referral center. PATIENTS: A group of 252 patients with symptoms consistent with Meniere's disease and 20 normal-hearing control subjects. INTERVENTION: All patients underwent audiologic testing and extratympanic ECoG at the time of initial evaluation and, when possible, following treatment. MAIN OUTCOME MEASURES: Audiologic thresholds and summating and action potential ratios (SP:AP). RESULTS: Patients were classified into definite, probable, possible, and bilateral Meniere's disease groups according to American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines. The definite Meniere's group demonstrated an elevated SP:AP ratio in 74% of cases, the possible Meniere's group in 64%, and the bilateral group demonstrated elevated ratios in both ears in 66%. Contralateral ears produced elevated ratios in 42% for unilateral cases, whereas 40% of these ears reported at least one contralateral symptom. All 40 control ears were normal (SP:AP > or = 0.50). Results statistically correlated (p = 0.004) with the Meniere's staging system set forth in the 1995 AAO-HNS guidelines. No correlation was found between ECoG results and disease duration. Although 72% of the 86 follow-up patients reported complete or substantial vertigo control, changes from initial ECoG results did not specifically correlate to vertigo, tinnitus, or aural fullness improvement. CONCLUSIONS: Extratympanic ECoG can be useful in the diagnosis of Meniere's disease, lending promise to possible cases where objective audiologic data are lacking. Each testing center should study its own results to establish meaningful parameters and confidence levels.

Adolescent↗
PubMed2000

Assessing the feasibility of an in vitro cytotoxicity method to detect harmful ubiquitous chemicals (detection of non-warfare hazardous chemicals in the operational theater).

The objective of this work was to assess the feasibility of accomplishing aqueous extracts of soil samples and determining if the extracted solution induced adverse effects in the human myelomonocytic cell line, HL60. Dosing of HL60 cells was accomplished over a 24-hour period using 100% of extracted media from standard soil samples containing known contaminants. Assessments of viability, apoptosis, reduced thiols, and mitochondrial membrane integrity were accomplished by argon-ion laser flow cytometric analysis, using chemical labels specific for each end-point. The in vitro cytotoxicity data was compared with the results of Microtox and Mutatox tests as well as earthworm and plant toxicity tests. In vitro cytotoxicity tests' results exhibited good correlation with other tests' results.

Adult↗
PubMed1999

Effect of steroids on posttonsillectomy pain in adults.

OBJECTIVE: To determine whether a single intraoperative dose of intravenous dexamethasone has an effect on pain after tonsillectomy. DESIGN: Double-blinded randomized controlled clinical trial. SUBJECTS: Thirty-four consecutive nonpediatric patients presenting for tonsillectomy. INTERVENTION: Patients scheduled for electrocautery tonsillectomy were randomized to receive either intravenous dexamethasone or placebo during surgery. Pain was measured twice daily for 10 days by means of a visual analog scale. RESULTS: There were no statistically significant differences between the groups, but the dexamethasone group had a trend to report less pain over the first several days. The dexamethasone group received less analgesic in the recovery room, but there were no differences between the groups in the 10 days afterward. CONCLUSIONS: There is evidence that a single dose of dexamethasone reduces pain after tonsillectomy to a small degree. A single dose was not associated with adverse effects, so the risk-benefit ratio may be favorable for this practice.

Adolescent↗
PubMed1997

The effects of 'sleep promoting agents' on behavioural state in the ovine fetus.

Fetal behavioural states, with similarities to adult sleep states, exist in both the human and ovine fetus near term. The purpose of the present study was to determine the effects of intracerebral administration of pharmacologic agents, known to affect sleep states in the adult, on fetal behavioural states and physiologic correlates using the chronically catheterized ovine fetus near term. Each drug was infused into either the cisterna magna or lateral ventricle for 90 min in one of two doses. Carbachol (1.35 x 10(-5) and 4.25 x 10(-6) M) led to an increase in low-voltage ECOG, eye movement and FBM activities, while scopolamine (4.68 x 10(-4) and 1.56 x 10(-4) M) led to a decrease in low-voltage ECOG and eye movement activity with an increase in high-voltage ECOG activity. L-5-Hydroxytryptophan (5-HTP) (2.04 x 10(-3) and 6.81 x 10(-4) M) infusion led to an increase in FBM, while VIP (3.00 x 10(-7) and 1.00 x 10(-7) M) infusion had no effect on fetal behavioural state parameters. Study results indicate that fetal behavioural states can be altered pharmacologically and in a manner similar to that seen in the adult but with notable differences that may relate to species, developmental or dose-response issues.

5-Hydroxytryptophan↗
PubMed1996

Fetal cerebral, circulatory, and metabolic responses during heart rate decelerations with umbilical cord compression.

OBJECTIVE: The purpose of this study was to determine the cerebral, circulatory, and metabolic responses of the ovine fetus near term to umbilical cord compression with variable-type fetal heart rate decelerations. STUDY DESIGN: Nine fetal sheep, at 0.9 of gestation, were studied before, during, and after umbilical cord occlusion for 1-minute and again after repetitive 1-minute cord occlusions every 5 minutes for 1 hour, with resultant fetal heart rate decelerations of approximately 90 beats/min. Brachiocephalic arterial and sagittal venous blood was analyzed for oxygen content, blood gases and pH, glucose, and lactate. Cerebral and upper body blood flow was measured with the microsphere technique. RESULTS: Umbilical cord occlusion with moderate to severe variable-type fetal heart rate deceleration resulted in an immediate drop in arterial PO2 by approximately 7 torr, an increase in PCO2 by approximately 9 torr, and a small but significant increase in lactate levels. Cerebral oxidative metabolism was well maintained but required an increase in fractional oxygen extraction because the variable change in cerebral blood flow was insufficient to maintain oxygen delivery. A redistribution of upper body blood flow was evident, with that to the bran and heart variably maintained or increased whereas that to muscle tissue was markedly decreased. Repetitive umbilical cord occlusion over 1 hour resulted in a significant drop in fetal arterial pH, with the acidemia mixed as PCO2 increased approximately 6 torr, whereas lactate levels increased almost fourfold. CONCLUSION: Although cerebral oxidative metabolism appears to be well maintained during moderate to severe variable-type fetal heart rate decelerations with umbilical cord occlusion, the need to increase fractional oxygen extraction and the redistribution of blood flow from carcass tissues may contribute to an accumulation of lactic acid both within the brain and systemically when such an insult occurs repeatedly.

Animals↗
PubMed1994

Regional brain blood flow in the ovine fetus during transition to the low-voltage electrocortical state.

Sequential changes in cerebral blood flow and regional distribution were studied in nine chronically catheterized fetal sheep during the transition to the low-voltage ECOG (REM) state to determine the time course for blood flow change within the brain and whether executive centres for REM state generation might thus be identified. Blood flows were measured during the first, second and third minutes after the transition to the low-voltage ECOG state and during the third minute of the subsequent high-voltage ECOG (NREM) state using the radioactive labelled microsphere technique. Blood flow to the brain was increased during the low-voltage REM state when compared to that of the high-voltage NREM state, with the increase evident when measured during the first minute after the state transition and with no sequential change thereafter. Regional blood flow increases during the low-voltage state were greatest to those areas variously associated with the generation of REM state activity, but were again remarkably stable through the first 3 minutes after the state transition. This rapid increase in blood flow within the brain and the regional hierarchy for such, supports the participation of multiple anatomical areas which are highly integrated and act in concert to give rise to what is known as the REM state.

Animals↗
PubMed1994

Recovery of the ovine fetus from sustained hypoxia: effects on endocrine, cardiovascular, and biophysical activity.

OBJECTIVE: The purpose of this study was (1) to determine the ability of the ovine fetus to recover from a self-limiting asphyxial insult and (2) to monitor cardiovascular and biophysical activity as potential markers of such an insult or underlying neurologic impairment. STUDY DESIGN: Nineteen fetal sheep were studied (12 hypoxia and 7 control) at 0.9 of gestation during a 24-hour control period, up to 8 hours of either sustained hypoxemia or room air, and for a 40-hour recovery period. Fetal heart rate, blood pressure, electrocortical activity, electroocular activity, and breathing movements were monitored continuously. Fetal arterial blood was sampled at set times for blood gases, pH, lactate, and catecholamine levels. RESULT: Induced fetal hypoxemia resulted in a lactic metabolic acidosis that progressively worsened, with death occurring in three of the animals during the early recovery period. The remaining animals showed a rapid metabolic and endocrine normalization of values by 24 hours. Fetal cardiovascular and biophysical measurements likewise returned to control values during the early recovery period, although three animals had seizure-like activity. CONCLUSION: The near-term ovine fetus surviving a sustained asphyxial insult sufficient to induce neuropathologic change within the brain demonstrates a normalization of biophysical activity during the early period of recovery, although seizure-like activity may subsequently be evident.

Animals↗
PubMed1994

Cerebral metabolism during sustained hypoxemia in preterm fetal sheep.

OBJECTIVE: The purpose of this study was to determine the effect of sustained hypoxia with resulting metabolic acidosis on cerebral metabolism in the preterm ovine fetus. STUDY DESIGN: Twelve fetal sheep were studied at 0.75 of gestation during a normoxic control period, after 1 and 8 hours of sustained hypoxemia, and again after a 1-hour recovery period. Cerebral arteriovenous differences were analyzed for oxygen content, blood gases and pH, glucose, and lactate. Cerebral blood flow was measured with the microsphere technique. RESULTS: Induced hypoxemia resulted in a variable degree of fetal acidemia that was entirely metabolic. Although cerebral oxidative metabolism was well maintained throughout the study, cerebral glucose consumption was variably increased when measured after 1 hour of sustained hypoxemia, with a subsequent decrease after 1 hour of recovery. Although lactate was neither consumed nor produced during the control period, by 8 hours of hypoxic study a significant efflux of lactate from the brain was evident, which continued into the recovery period. CONCLUSION: Sustained hypoxemia results in an increase in the anaerobic metabolism of glucose by the preterm fetal brain independent of any change in cerebral oxidative metabolism, which may give rise to an accumulation of lactic acid and contribute to neurologic impairment.

Animals↗
PubMed1993

Increased uteroplacental production of prostaglandin E2 during ethanol infusion.

Experiments were conducted in 14 pregnant sheep to determine the effect of a 1-h maternal infusion of ethanol (1 g/kg maternal body wt) on placental efflux of prostaglandin E2 (PGE2), umbilical blood flow (Qum), and carbohydrate metabolism at 123-130 days gestation. This ethanol dosage regimen produced peak ethanol concentrations in fetal and maternal blood in the range of 1.48-1.64 mg/ml at the end of the infusion. Umbilical venous and fetal arterial PGE2 concentrations increased (P < 0.05) from 315 +/- 47 and 202 +/- 25 pg/ml to 740 +/- 172 and 489 +/- 67 pg/ml, respectively, at the end of the infusion. Placental secretion of PGE2 into the fetal circulation increased by 45% (P < 0.05). Uterine venous and maternal arterial PGE2 concentration increased (P < 0.05) from 370 +/- 27 and 262 +/- 28 pg/ml to 705 +/- 51 and 487 +/- 69 pg/ml, respectively. Fetal and maternal blood glucose concentration decreased (P < 0.05) from 0.98 +/- 0.11 and 2.88 +/- 0.25 mmol/l to 0.81 +/- 0.21 and 2.44 +/- 0.16 mmol/l, respectively. Fetal and maternal blood lactate concentration increased (P < 0.05) from 1.40 +/- 0.11 and 0.68 +/- 0.07 mmol/l to 1.67 +/- 0.14 and 1.82 +/- 0.16 mmol/l, respectively. Qum, fetal heart rate, fetal blood pressure, and fetal and maternal blood gases were unchanged by the ethanol infusion. These results support the hypothesis that the placenta is the major source of the elevated fetal and maternal plasma PGE2 concentrations produced in pregnant sheep by maternal ethanol administration.

Animals↗
PubMed1993

Repeated canine herpesvirus (CHV) reactivation in dogs by an immunosuppressive drug.

To examine the possibility of repeated reactivation of canine herpesvirus (CHV), 2 serial treatments with the corticosteroid drug prednisolone (PD) were given at different periods following oral-nasal infection of pups and adult dogs. CHV was not recovered from infected, untreated dogs or from uninfected, treated controls. Viral reactivation of CHV, without clinical signs, was induced twice in 2/3 adults and in 2/3 pups treated at intervals that ranged from 1 to 3 months following the initial infections. Highest viral titers were obtained from nasal swab samples, with lower titers found in the oral pharynx, penis or vagina. In some, but not all dogs, the infectivity titers of the nasal secretion samples were higher after the initial prednisolone treatments than after the second treatments. The duration of viral shedding after the second series of steroid treatments also was shorter than the shedding period following the initial reactivations. The results presented here suggest that latent CHV occurs in both pups and adults dogs following infection and that active infections, with viral shedding, may occur repeatedly for prolonged, but undetermined, periods.

Age Factors↗
PubMed1993

Cerebral oxidative metabolism in fetal sheep with prolonged and graded hypoxemia.

Cerebral oxidative metabolism and associated circulatory responses were determined in 14 unanesthetized fetal sheep near term, during a normoxic control period and subsequently, during four days of prolonged and graded hypoxemia induced by progressively lowering maternal inspired oxygen concentration with 1-2% CO2 added; first day 18%, second day 16%, third day 12-14%, fourth day 10-12%. Preductal arterial and sagittal vein blood samples were analyzed for oxygen content, blood gas tensions and pH. Regional blood flow was measured with a microsphere technique. Cerebral blood flow increased in a stepwise manner with the graded reduction in fetal arterial O2 saturation and continued to be well predicted by blood gas and metabolic alterations, with no adaptive change evident. Cerebral oxidative metabolism remained little changed with chronically induced hypoxemia until arterial O2 saturation was less than 30% and with fetal acidemia evident when decreased to 70% of normoxic control values. Whether the decrease in oxidative metabolism by the brain at this time represents an adaptive response whereby growth and functional alterations lead to a decrease in nonessential energy utilization or rather a pathological change, remains to be determined.

Animals↗
PubMed1992

Effects of sustained hypoxemia on the sheep fetus at midgestation: endocrine, cardiovascular, and biophysical responses.

OBJECTIVE: The purpose of our study was to examine the effects of induced hypoxia on endocrine, cardiovascular, and biophysical measurements of the ovine fetus at 0.6 (83 to 93 days) of gestation and to compare the fetal responses at this earlier gestation with those reported near term. STUDY DESIGN: Fourteen fetal sheep were studied (9 in the hypoxia group and 5 in the control group) at 0.6 of gestation during a 24-hour control period, 8 hours of either sustained hypoxemia or room air, and a 40-hour recovery period. RESULTS: Induced fetal hypoxemia resulted in a progressive lactic metabolic acidosis; however, all fetuses had recovered within 24 hours. The fetal endocrine response was variable with norepinephrine, the only measured hormone showing a significant hypoxia-related increase (p less than 0.05). Fetal heart rate and mean arterial blood pressure showed little hypoxia-induced change, although fetal heart rate was significantly increased over the first 2 hours (p less than 0.05). The percent time fetal breathing movements, electroocular activity, and nuchal muscle activity likewise showed little hypoxia-induced change. CONCLUSION: The cardiovascular and biophysical response of the preterm fetus to induced hypoxemia is thus much less pronounced than that of the older gestational-aged fetus; this difference may impact on survival and the success of antenatal assessment protocols.

Animals↗
PubMed1992

Electrocortical activity, electroocular activity, and breathing movements in fetal sheep with prolonged and graded hypoxemia.

OBJECTIVE: Our objective was to determine the effect of a prolonged and graded reduction in fetal arterial oxygen saturation on electrocortical activity and associated biophysical variables. STUDY DESIGN: Fourteen unanesthetized fetal sheep were studied between 126 and 135 days' gestation with continuous monitoring of electrocortical and electroocular activity and breathing movements, during a 24-hour control period, and subsequently during 4 days of prolonged and graded hypoxemia induced by progressively lowering the maternal inspired oxygen concentration. RESULTS: Graded reduction in fetal arterial oxygen saturation resulted in little change in arterial pH until close to 30% when metabolic acidemia was apparent. The incidence of low-voltage electrocortical activity, electroocular activity, and breathing movements were marginally decreased with hypoxemia alone; however, a significant decrease was not apparent until associated with the onset of fetal acidemia. CONCLUSION: Hypoxemia of a chronic nature must approach the level at which acidemia becomes apparent before a marked change in fetal behavioral activity is noted.

Animals↗
PubMed1992

Voices from family medicine: Lynn Carmichael. Interview by William B. Ventres and John J. Frey.

Now that the 25th anniversary of the Society of Teachers of Family Medicine is upon us, educators are likely to look back at the history, which set the stage for family medicine. This is a history replete with reports, politics, and ultimately, the development of family practice training programs. It is a history, as well, made through the labors of individuals. The vantage points we have chosen to examine in this series are those of some of the people who lent their efforts to the founding of family medicine. Common personal needs prompted us to explore these vantage points. Although we are at different points in our professional trajectories--one of us is a recent graduate from residency and fellowship training, the other has many years of experience as a teacher and journal editor--the same themes emerged in our self-explorations. Where do we fit into the family medicine movement? What satisfaction do we get out of our day-to-day routines of practice, teaching, and research? What meaning sustains our activities in the discipline? To help answer these questions, we looked to some of the leaders of family medicine. In this transcript, an abridged and edited version of interviews conducted in April and May of 1991, Lynn Carmichael, MD, discusses his involvement with the founding of family medicine, his perspectives on the importance of family practice, and his thoughts and concerns about the future. Dr. Carmichael is professor and founding chair of the Department of Family Medicine at the University of Miami School of Medicine. He was the first president of the Society of Teachers of Family Medicine, the founding editor of Family Medicine (then Family Medicine Teacher), and the initial recipient of the STFM Certificate of Excellence in 1978.

Career Choice↗
PubMed1991

The effects of indomethacin and prostaglandin E2 on the ethanol-induced suppression of ovine fetal breathing movements.

A study was performed to examine the role of prostaglandins (PGs) in the mechanism of the ethanol-induced suppression of FBM, in which the objective was to test the hypothesis that fetal administration of PGE2 can suppress the incidence of FBM following reversal of ethanol-induced suppression of FBM by indomethacin, a fatty acid cyclooxygenase inhibitor. Instrumented near-term pregnant ewes received 1-h maternal infusion of ethanol (1 g/kg maternal body weight) followed 0.5 h later by a 3-h fetal infusion of indomethacin (1 mg/kg fetal body weight/h), and then a 2-h fetal infusion of PGE2 (400 ng/kg fetal body weight/min). Prior to drug administration, FBM occurred approximately 36.1 +/- 2.6% of the time. FBM were suppressed during the period of ethanol infusion (9.6 +/- 1.7%); the ethanol-induced suppression of FBM was reversed by fetal indomethacin treatment (77.5 +/- 14.1%); shortly after the onset of fetal PGE2 infusion, the incidence of FBM decreased to a 2-h mean incidence of 14.1 +/- 4.2%, which was similar in magnitude to that observed after maternal ethanol infusion. After the completion of PGE2 infusion, the incidence of FBM rapidly increased to a peak incidence of 83.4 +/- 19.2%, which was indicative of a prolonged effect of indomethacin on FBM. The data indicate that PGs mediate the ethanol-induced suppression of ovine FBM and that the action of indomethacin to antagonize ethanol-induced suppression of FBM is primarily due to its inhibition of PG synthesis.

Animals↗
PubMed1990

Oxygen consumption in the fetal lamb during sustained hypoxemia with progressive acidemia.

To investigate the fetal ability to compensate for a sustained reduction in O2 delivery (DO2; umbilical blood flow X umbilical venous O2 content), studies were carried out on eight chronically instrumented fetal lambs made hypoxemic for 7.8 +/- 0.8 (+/- SE) h by lowering maternal inspired O2 concentration to 9-10%. After 1.7 h of hypoxemia, fetal arterial PO2 had fallen from 18.4 +/- 1.2 to 10.4 +/- 0.5 mmHg. Umbilical venous O2 content fell initially by 41.1 +/- 1.8%, but the fall in DO2 was only 23.7 +/- 5.6%, caused by a 29.3 +/- 7.9% rise in umbilical blood flow. Fetal O2 consumption (VO2) was increased significantly by 29.5 +/- 15.2%. However, fetal vascular pH (7.332-7.281) and base excess (0.5 to -4.3 meq/l) were decreased while blood lactate levels were increased (1.55-7.22 mM). With continued hypoxemia, the metabolic acidemia worsened and led to progressive declines in umbilical venous O2 content and DO2. However, VO2 was maintained at the control level until delivery had fallen by 72.5% and arterial pH was 6.843, at which time VO2 decreased by 37.5 +/- 10.7%. It is concluded that the ability of the fetus to compensate for sustained hypoxemia is limited by the progressive metabolic acidemia.

Acid-Base Equilibrium↗
PubMed1990

Blood flow and oxygen delivery to fetal organs and tissues during sustained hypoxemia.

To examine the fetal cardiovascular responses to a sustained reduction in O2 delivery (DO2), studies were conducted on 13 chronically instrumented fetal lambs (128-138 days gestation) made hypoxemic for 7.9 +/- 0.5 h by lowering maternal inspired O2 concentration to 9-10%. Fetal descending aortic PO2 fell initially from 18.0 +/- 1.0 to 10.7 +/- 0.6 mmHg, whereas pH decreased progressively from 7.326 +/- 0.006 to 6.843 +/- 0.023. Blood flow to the cerebral hemispheres, myocardium, and adrenal glands rose maximally by 110.2 +/- 22.5, 253.7 +/- 41.1, and 338.7 +/- 55.0%. Cerebral hemispheric DO2 fell progressively, whereas DO2 to the myocardium and adrenal was maintained until 7.9 h, when it fell significantly. There was also a rise in blood flow to brown adipose tissue. Blood flow to the gut and skeletal muscle was maintained, whereas flow to the spleen and kidney fell. DO2 to all these tissues fell markedly because of the progressive decline in blood O2 content. It is concluded that fetal cardiovascular function was well maintained in the face of severe hypoxemia and marked acidemia.

Animals↗