Search PubMed⌕ Search

Biomedical subjects

S L Clark

Publications and source records attributed to S L Clark.

At least 109 records · Page 6Linked to original sources
PubMed1984

Effect of indication for previous cesarean section on subsequent delivery outcome in patients undergoing a trial of labor.

During the period January 1 through December 31, 1980, 308 patients who had undergone previous cesarean sections (C/Ss) underwent a trial of labor (TOL). Hospital records of these patients were examined retrospectively in an effort to correlate delivery outcome with the indication for the prior C/S. Patients with a previous C/S for breech had the highest incidence of subsequent vaginal delivery (81 of 94, or 86%), and patients with a previous C/S for cephalopelvic disproportion or failure to progress had the lowest (22 of 64, or 64%). However, the lower rate of vaginal delivery in the latter group was found only among the subpopulation who had never delivered vaginally. Fetal distress does not appear to be a significant recurring factor in patients given a TOL. Exclusion of patients from a TOL after a previous C/S for cephalopelvic disproportion/failure to progress does not appear to be justified.

Adult↗
PubMed1984

Vaginal delivery after cesarean section in women with unknown types of uterine scar.

Documentation of a prior cesarean and the type of uterine scar has been used as one criterion for permitting patients a trial of labor. In a highly mobile patient population such as ours, these medical facts are often difficult or impossible to obtain. As a result, we retrospectively examined the performance of patients with unknown types of cesarean scar and found no difference between them and a similar population with documented low cervical scars. Although obtaining an old record is useful, its absence probably should not interdict a trial of labor in a patient who desires to attempt vaginal delivery.

Cesarean Section↗
PubMed1984

Previous cesarean birth. Trial of labor in women with macrosomic infants.

Patients with previous cesarean births who delivered macrosomic infants (greater than or equal to 4,000 gm) during the study periods January 1 to December 31, 1980, and July 1, 1982, to June 30, 1983, were analyzed to determine the impact of fetal weight on a trial of labor (TOL). Of 140 women with macrosomic infants given a TOL, 94 (67%) delivered vaginally. The most common indication for cesarean delivery was cephalopelvic disproportion (CPD). The dehiscence rates were similar when patients who underwent a TOL were compared with those who did not. Factors associated with a successful TOL were a previous vaginal delivery after the original cesarean section, no oxytocin usage during the TOL and an indication for the previous cesarean section other than CPD. The risk associated with a TOL in a patient with a previous cesarean birth and a macrosomic infant appears to be no greater than that encountered in a similar group of patients without uterine scars.

Adult↗
PubMed1983

The antinociceptive action of etorphine in the dorsal horn is due to a direct spinal action and not to activation of descending inhibition.

1--Etorphine, microinjected into the brainstem or administered intravenously, inhibited the firing of dorsal horn neurones to noxious heat in spinal or non-spinal anaesthetized cats and in decerebrate, non-anaesthetized cats with intact spinal cords. 2--Small doses of etorphine sometimes caused facilitation, especially when the cord was intact, but this was invariably followed by inhibition at higher doses. 3--The ED50 for inhibition (mean 3.9 micrograms/kg) after microinjection into nucleus raphe magnus, nucleus reticularis magnocellularis or the lateral tegmental field was similar at all sites in anaesthetized, non-spinal cats. 4--The ED50 for microinjection was not increased by spinal transection in anaesthetized cats (mean ED50, 2.6 micrograms/kg) and was similar to the ED50 in decerebrate, non-anaesthetized cats. 5--Intravenous administration was 2 to 3 times more effective than microinjection and the time course of inhibition was faster after intravenous administration than after microinjection. 6--It is concluded that etorphine inhibits dorsal horn neurones after microinjection or intravenous administration by a direct action on the spinal cord and not by activating a descending inhibition. After microinjection it rapidly enters the general circulation and subsequently distributes into the spinal cord. 7--It is also concluded that naloxone readily gains entry to the circulation from the brain because microinjection antagonized the effects of systemic etorphine on dorsal horn neurones in spinal cats.

Analgesics↗
PubMed1983

The relative significance of spinal and supraspinal actions in the antinociceptive effect of morphine in the dorsal horn: an evaluation of the microinjection technique.

Large quantities of morphine injected directly into the brainstem of spinal anaesthetized cats inhibited the noxious heat-evoked excitation of dorsal horn neurones. The amounts required were similar to those that were required intravenously in cats with the spinal cord intact or transected. When the spinal cord was intact the amount of morphine microinjected into the brainstem required to inhibit the excitation of dorsal horn neurones was about ten fold less than it was in spinal animals. It is concluded that large, but not small doses of morphine microinjected into the brainstem can exert effects on the spinal cord after first entering the circulation. The effects of small doses are attributed to a local action in the brainstem which causes inhibition of spinal neurones either by activating descending inhibitory neuronal systems or by liberating endogenous substances which reach the spinal cord via the cerebro-spinal fluid. The concentrations of morphine achieved at various distances from the site of injection by the microinjection of microgram quantities and the time courses of the concentration changes were calculated from diffusion equations, assuming diffusion coefficients of 3 or 5 X 10(6) cm2 s-1. The curves obtained closely approximated those obtained experimentally. The concentrations achieved at distances up to 2 mm from the site of injection of 10 micrograms of morphine were calculated to exceed 10(-4)M and the time-courses of these concentration changes were compatible with the time course of inhibition of spinal neurones, or the production of analgesia after microinjection. Such concentrations are vastly in excess of those achieved in the brain after the systemic administration of morphine in analgesic doses. It is concluded that the local effects in the brainstem produced by the microinjection of microgram quantities of morphine have no relevance to the mechanism of analgesia produced by systemic administration.

Animals↗
PubMed1983

Simultaneous bilateral tubal pregnancy. A case report.

A woman was treated for a simultaneous bilateral tubal pregnancy that had an unusual presentation and unusual diagnostic problems. The diagnosis of ectopic pregnancy may be overlooked in a semiconscious patient if a proper history and examination are not carried out. During surgery for ectopic pregnancy it is important to look at both adnexae.

Adult↗
PubMed1982

Fetal heart rate response to scalp blood sampling.

Fetal heart rate acceleration in response to various stimuli has long been considered to be a reliable sign of fetal well-being in both the intrapartum and antepartum periods. In an effort to define the correlation between fetal heart rate response and fetal blood pH, we analyzed 200 fetal heart rate tracings of fetuses who had undergone scalp blood sampling in early labor. Data in regard to fetal heart rate response to endoscope placement, scalp puncture, and resultant scalp pH were then analyzed. In no case did a fetus with a scalp blood pH less than 7.20 respond to scalp puncture with an acceleration (defined as an elevation above the baseline of 15 bpm for at least 15 seconds). Among fetuses with a scalp blood pH greater than 7.28, 142 of 144 responded to scalp puncture with an acceleration. Exception occurred in one fetus who was 32 to 33 weeks' gestation, and in one fetus who was moderately Rh isoimmunized. Fetuses with scalp pH in the range of 7.21 to 7.28 showed a variable response. The correlation noted between a reassuring fetal heart rate pattern and the absence of acidosis in conjunction with the inverse (73% of fetuses in whom no acceleration occurred were acidotic) is further verification of both the reliability and complementary nature of intrapartum fetal assessment by both biophysical and biochemical techniques.

Blood Specimen Collection↗
PubMed1982

Inhibition by substance P of some peripheral actions of acetylcholine in the cat.

1 The effect of substance P on contractions of the nictitating membrane and pressor responses to acetylcholine (ACh) and dimethylphenyl-piperazinium (DMPP) which were mediated via nocotinic receptors was studied in cats anaesthetized with chloralose.2 Substance P (2-20 nmol) injected into the lingual artery giving estimated concentrations in arterial blood of 10(-6) to 10(-5) M, or intravenously giving estimated concentrations in blood of 10(-8) to 10(-7) M, reduced hexamethonium-sensitive but not atropine-sensitive responses.3 The pressor effects of ACh and DMPP injected intra-arterially in atropinized and non-atropinized cats respectively were consistently attenuated by substance P given intra-arterially or intravenously.4 The contractile effect of ACh in atropinized and of DMPP in non-atropinized cats was attenuated by substance P injected intra-arterially but only rarely when the polypeptide was injected intravenously.5 The depressor effects of substance P per se were variable in magnitude and duration as were the inhibitory effects upon nicotinic receptors. The depressor and inhibitory effects of substance P were unrelated.6 There was desensitization to all of these effects of substance P which probably contributed to the variation in the magnitude of the effects observed.7 Substance P had no effect on muscarinic actions of acetyl-beta-methylcholine on the nictitating membrane or blood pressure.8 The results are discussed in relation to the ubiquity of the modulatory actions of substance P on nicotinic receptors and in relation to the possible physiological significance of the action.

Acetylcholine↗
PubMed1981

Development of clinical education sites in an area health education system.

In 1974 the University of Kentucky was faced with two problems: 1) overburdening of local clinical facilities by students and 2) a large exodus of graduates from the state. The advent of the Area Health Education System offered the opportunity for the clinical education program to develop nontraditional clinical sites across the state. The development and use of these nontraditional sites in predominantly rural areas has become an integral part of the clinical education program. Local facilities are no longer inundated with students. The retention rate of graduates has improved in the seven years of the program from 36 percent to 1972 to 81 percent in 1979.

Area Health Education Centers↗
PubMed1968

Incorporation of sulfate by the mouse thymus: its relation to secretion by medullary epithelial cells and to thymic lymphopoiesis.

The thymus was examined in suckling mice during normal development and the involution and regeneration produced by injection of cortisol, in experiments designed to test the hypothesis that medullary epithelial cells secrete a ymphopoietic hormone responsible for controlling the magnitude of thymic lymphopoiesis. Cellular events were observed by light and electron microscopy. Lymphopoiesis was assessed, after injection of thymidine-(3)H, by counting the proportion of lymphocytes labeled in radioautographs of thymus. Cortical lymphopoiesis was distributed heterogeneously, being concentrated in the subcapsular region, but medullary lymphopoiesis was statistically homogeneous in distribution and similar in magnitude to the average level of cortical lymphopoiesis in suckling mice. Therefore counts of the labeling index in the medulla were used to estimate the size of the proliferating population of lymphocytes. Epithelial secretory activity was estimated by measuring the incorporation of (36)sulfate by the thymus, using gel filtration chromatography to isolate soluble macromolecular (35)sulfate-presumed on radioautographic evidence to represent the mucoid epithelial secretory product. Incorporated (35)sulfate accumulated rapidly for 4 hr, reached a peak at 12 hr, and had fallen to half that level by 24 hr after a single injection-as would be expected of a secretory product. During normal postnatal development the size of the proliferating population of lymphocytes and the magnitude of (35)sulfate incorporation increased in parallel. During acute involution induced by cortisol both parameters diminished greatly but rose to high levels during subsequent regeneration. Accordingly, lymphopoiesis and sulfate incorporation -as defined and measured in these experiments-correlated linearly over a wide range of variation, providing circumstantial evidence to support the hypothesis that medullary epithelial cells secrete a sulfated mucoid lymphopoietic hormone. This conclusion is discussed in terms of the roles of thymus and adrenal cortex in development of the lymphoid system and maturation of immunological competence.

Adrenal Glands↗