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Biomedical subjects

D L Clark

Publications and source records attributed to D L Clark.

At least 37 records · Page 2Linked to original sources
PubMed1992

Detection of virulence factors in culturable Escherichia coli isolates from water samples by DNA probes and recovery of toxin-bearing strains in minimal o-nitrophenol-beta-D-galactopyranoside-4-methylumbelliferyl-beta-D-g luc uronide media.

A total of 449 Escherichia coli isolates in treated and raw water sources were submitted to DNA-DNA hybridization using seven different DNA probes to detect homology to sequences that code for Shiga-like toxins I and II; heat-stabile and heat-labile toxins, adherence factors EAF and eae, and the fimbrial antigen of entero-hemorrhagic E. coli. Fifty-nine (13%) of the isolates demonstrated homology with one or more specific DNA probes. More than 50% of the isolates in treated water were not recovered in MMO-4-methylumbelliferyl-beta-D-glucuronide media designed for detection of this indicator.

Bacterial Toxins↗
PubMed1991

Influence of ocular gaze and head position on 4 m heterophoria and fixation disparity.

Four-meter heterophoria and fixation disparity measurements were taken from a sample of 40 young adults in primary gaze, 33 degrees left and right lateral gaze, and in 2 head/gaze positions related to golf putting. Comparisons using analysis of variance were made between the mean values in each gaze position and between the test-retest range of values in each gaze position. Mean heterophoria was more eso (p less than 0.05) in the two head/gaze positions related to golf putting than in other gaze positions, whereas mean fixation disparity was more eso (p less than 0.05) in rightward than in primary gaze. Phoria test-retest range was less (p less than 0.05) in all nonprimary gaze positions than in primary gaze. One of the putting-related gaze positions showed smaller (p less than 0.05) fixation disparity ranges than the primary or leftward position of gaze. All measures were highly variable among subjects. Trends present in the data suggested greater esophoria and eso fixation disparity mean values, and lesser heterophoria and fixation disparity test-retest range values in all nonprimary positions relative to primary gaze. The behavior of exophoric and esophoric subjects differed only in regard to changes in heterophoria associated with left and right lateral gaze. These data indicate differences in oculomotor postural tendencies relative to position of gaze. Relevance of the results to athletes is discussed.

Adult↗
PubMed1991

Comparative study of commercial 4-methylumbelliferyl-beta-D-glucuronide preparations with the Standard Methods membrane filtration fecal coliform test for the detection of Escherichia coli in water samples.

The performance capabilities of two commercial 4-methylumbelliferyl-beta-D-glucuronide preparations were evaluated for the detection of Escherichia coli from water samples. Eighty-three water samples were collected from a treated water reservoir, and 32 samples were collected from untreated surface water. There was a statistically significant difference between the two commercial preparations compared with the Standard Methods membrane filtration fecal coliform (MFC) method for the detection of E. coli from treated water samples. However, there was no difference between the two methods and the MFC test for E. coli detection from the untreated surface water samples. The disagreement between the two commercial products and the MFC method was primarily due to the occurrence of false-negative results with the two commercial products. The data indicate that the occurrence of false-negative samples could be attributed to impaired substrate specificity and sensitivity of the two tests for E. coli detection. There was no apparent relationship between the occurrence of false-negative results and heterotrophic plate counts in samples.

California↗
PubMed1991

Total coliform detection in drinking water: comparison of membrane filtration with Colilert and Coliquik.

The Colilert (CL) and Coliquik (CQ) systems were compared in a presence-absence format against the Standard Methods membrane filtration (MF) technique to determine whether differences existed in total coliform detection. Approximately 750 water samples were collected from distribution systems, covered and uncovered storage reservoirs, well sites, and the influent to drinking water treatment plants. Samples were analyzed for total coliforms and heterotrophic bacteria with MF, CL, and CQ. The agreements between CL and MF and between CQ and MF were both greater than 94.8%, which indicates that both may be acceptable methods for total coliform detection. Disagreement between the CL and CQ methods was primarily due to false-negative results. Furthermore, laboratory and field inoculation methods were compared for CL, more than 98% agreement was obtained. This finding indicates that sampling and immediate field inoculation may be an alternative to the traditional laboratory inoculation.

California↗
PubMed1989

Effects of rocking on neuromuscular development in the premature.

It has been postulated that motion stimulation accelerates postnatal development. To test this hypothesis, 26 premature infants participated in a randomized controlled study of the effects of rocking on body weight gain and measures of neuromuscular development. Treatment infants were exposed to 15-min sessions of sinusoidal oscillation about the longitudinal axis, three times a day for 2 weeks. Infants were evaluated at the beginning and end of the 2-week treatment period and 2 weeks later. Neuromuscular development at these three times was measured with the comprehensive Dubowitz examination. Following treatment, large as compared with small premature infants showed a marked, but not statistically significant increase in weight gain. Duration of treatment appears to be a critical factor in influencing weight gain. All infants exposed to motion stimulation showed significant gains over controls in overall neuromuscular development. Passive muscle tone (posture, arm recoil and popliteal angle) and active motility (arm traction, head lag and ventral suspension) showed significant improvement in the treatment group at posttest. Similar results were recorded with auditory and visual orientation, alertness and defensive reaction. These specific areas of behavior have been recognized to be delayed in premature infants not exposed to a program of sensory stimulation.

Body Weight↗
PubMed1988

One hospital's solution to the shortage of coders.

The program described enabled St. Mary's Hospital to recruit individuals with pre-requisite knowledge in anatomy, pathophysiology and medical terminology and then have them receive comprehensive training in ICD-9-CM coding which addressed the unique demands imposed by the medical record department and the PRO. In this way, the department's immediate and future needs for coders appears to have been satisfied. An evaluation on the success of this training program will be assessed in three months and reported upon at that time.

Abstracting and Indexing↗
PubMed1987

Demonstration of mitral and aortic valves by ultrafast computed tomography.

Contrast medium-enhanced ultrafast computed tomography has sufficient spatial and temporal resolution to permit imaging of the mitral and aortic valves. The conventional transaxial planar scan projection is not adequate for this purpose. This communication describes the planar configurations and technique required to image the mitral and aortic valves by ultrafast computed tomography.

Aortic Valve↗
PubMed1987

Determination of the pulmonary capillary wedge position in patients with giant left atrial V waves.

Thirteen patients with giant left atrial V waves during preoperative cardiac catheterization were admitted into the study group. While awake and breathing spontaneously, simultaneous recordings of electrocardiographic leads II and V5, radial arterial traces, and pulmonary arterial or pulmonary capillary wedge traces were obtained. Measurements were made on four consecutive cardiac cycles in the unwedged and wedged positions for the following intervals: Q wave to the radial arterial upstroke (220 +/- 20 milliseconds) and peak (360 +/- 10 milliseconds), Q wave to the pulmonary arterial upstroke (170 +/- 20 milliseconds) and peak (350 +/- 20 milliseconds), Q wave to the V wave upstroke (280 +/- 20 milliseconds) and peak (570 +/- 20 milliseconds), and QT interval (420 +/- 20 milliseconds). These findings indicate that the radial arterial and pulmonary arterial upstrokes and peaks occur nearly simultaneously. Upon wedging, the V wave upstroke occurs significantly later in the cardiac cycle (P less than .05) compared with the pulmonary arterial upstroke, and the V wave peak occurs significantly later compared with both the pulmonary arterial and the radial arterial peak (P less than .05). A rapid, simple beat-to-beat method for differentiating pulmonary arterial from pulmonary capillary wedge positions in the presence of giant left atrial V waves is the superimposition of the pulmonary arterial trace on the radial arterial trace. When a wedge position is attained, there is an immediate rightward shift in the upstroke and peak of the pulmonary arterial pressure trace, which can be easily identified by observing the relationship between the pulmonary arterial and systemic arterial traces.

Adult↗
PubMed1986

Quantitation of shunting at the atrial level using rapid acquisition computed tomography with comparison with cardiac catheterization.

Contrast-enhanced rapid acquisition computed tomography was employed to quantitate intracardiac shunts in two adult patients. Contrast medium was injected through a median antecubital vein and data were accumulated using the R wave-triggered flow mode. Time-density curves from a region of interest were generated by a gamma variate fit method and areas under the curves were calculated. Comparisons of calculated left to right shunts (Cases 1 and 2) with results of computed tomography and right to left shunt (Case 2) with cardiac catheterization data resulted in close agreement. This is the first report of quantitation of intracardiac shunts at the atrial level in humans by rapid acquisition computed tomography.

Adult↗
PubMed1986

Effects of vestibular stimulation on sleep states in premature infants.

Seventeen appropriate-for-gestational-age premature infants (birthweights 1000-1530 gm) were randomly assigned to control (7) and vestibular stimulation (10) groups. Those in the treatment group were exposed daily to three 15-minute sessions of sinusoidal vestibular stimulation over a 2-week period. At the end of that period, postconceptional age ranged from 34 to 37 weeks. As a measure of neurologic maturation, behavioral and physiologic parameters characterizing sleep states were recorded at the onset and termination of the 2-week period. The ratio of active-to-quiet sleep did not change significantly in control patients. Those exposed to vestibular stimulation showed a significant decrease in proportion of active and a concomitant increase in the proportion of quiet sleep. These results may indicate that vestibular stimulation, even at this early postconceptional age, results in a more mature sleep pattern.

Birth Weight↗
PubMed1986

Prophylactic nitroglycerin infusions during coronary artery bypass surgery.

The effects of prophylactic infusion of 1 microgram X kg-1 X min-1 nitroglycerin (NTG) on the incidence of ischemia, hypertension, hypotension and perioperative myocardial infarction were studied in 81 patients during coronary artery bypass grafting (CABG). Forty-one patients (Group 1) received NTG and 40 patients (Group 2) received placebo. All patients received fentanyl for anesthesia and pancuronium. Mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), heart rate (HR), and cardiac output (CO) were measured before and after induction of anesthesia, after intubation, before and after chest incision, after sternotomy, after the pericardium was opened, and during normothermic cardiopulmonary bypass. Myocardial ischemia and infarction were diagnosed from the ECG, hypertension was defined as a 20% increase in MAP, and hypotension was defined as a 20% decrease in MAP compared with preinduction values. No significant differences between Groups 1 and 2 in HR, PCWP, or CO were seen. MAP was significantly lower in Group 1 than Group 2 (P less than 0.05) before chest incision, but increased to levels equal to Group 2 after sternotomy. Hypertension occurred in 32 Group 2 patients and 25 Group 1 patients (0.05 less than P less than 0.1). Group 1 patients had 0.95 +/- 0.14 episodes per patient of hypertension, while Group 2 patients had 2.10 +/- 0.31 episodes (P less than 0.05). Hypotension occurred in 20 Group 1 patients but only six Group 2 patients (P less than 0.05). There was no difference in the incidence of ischemia. In Group 1, nine patients (22%) had ECG changes of ischemia, while 12 patients in Group 2 (30%) had ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1986

Heart evaluation by cine CT: use of two new oblique views.

Two new oblique views on cine computed tomography for examination of the left ventricle of the heart are described. A short-axis view sections the left ventricle transversely, demonstrating all the ventricular walls; a long-axis view sections the left ventricle longitudinally, demonstrating the mitral valve, proximal aortic root, aortic outflow tract, and ventricular apex. These views are produced by a combination of table slew and patient positioning. Reproducible short-axis views were obtained in 16 healthy volunteers and 11 patients. Long-axis views were obtained in 11 patients. Patient studies in the long-and short-axis views were compared with results from angiocardiography, with nearly identical findings.

Adult↗
PubMed1986

Modulation of guanylate cyclase by lipoxygenase inhibitors.

Drugs that inhibit endothelium-dependent relaxation were tested to determine their effect on soluble guanylate cyclase purified from dog aorta. Basal, arachidonic acid (10(-5) M)-stimulated, and nitroprusside (5 X 10(-5) M)-stimulated guanylate cyclase activities were inhibited by methylene blue and the lipoxygenase inhibitors nordihydroguaiaretic acid and eicosatetraynoic acid. The effective inhibitory doses were in the range of those that have been reported to inhibit endothelium-dependent relaxation. Other compounds known to inhibit endothelium-dependent relaxation had little or no effect on guanylate cyclase activity. Basal guanylate cyclase activity was more resistant to inhibition than were activated states of the enzyme. The data suggest that reported inhibition of endothelium-dependent relaxation by some lipoxygenase inhibitors may be the result, at least in part, of their direct effect on guanylate cyclase activity.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1986

Demonstration of mitral valve function by cine computed tomography using a new long axis view.

Comparison was made between contrast enhanced cine computed tomography (Cine/CT) and echocardiography in the imaging of the mitral valve in 14 patients. The mitral valve was seen in all 14 patients by Cine/CT using a new long axis view. There was agreement with echocardiography in 12 patients. Abnormalities in mitral valve movement were detected by Cine/CT. Left atrial size and contraction was measured by Cine/CT with a difference in left atrial ejection fraction observed between 13 patients with no evidence of mitral disease and 3 patients with mitral disease.

Adult↗
PubMed1986

Comparison of left ventricular ejection fraction by cine computed tomography and single plane right anterior oblique ventriculography.

Cine Computed Tomography (CCT) is a minimally invasive technique which offers high temporal (50 msec scan time) and spatial (2 line pairs) resolution. Left ventricular ejection fraction (LVEF) has been determined by this technique in dogs and normal subjects but no comparison has been made with contrast left ventriculography by cardiac catheterization. Ten patients, 9 male and 1 female, mean age 61 (range 46-70) had LVEF determined by both single plane RAO left ventriculography and CCT. Patients were studied in the fasting state, on different days without change in medication. LVEF by CCT was determined in the long axis, a new view which has been developed for CCT to be comparable to the RAO view of contrast left ventriculography by catheterization. This view is obtained by positioning the patient head first into the scanner, supine, with a counterclockwise table slew (20 degrees) without table tilt. Contrast is introduced via a median antecubital vein, and injected in a prolonged bolus of 7-13 seconds dependent on arm to heart circulation time. Scans are performed in the cine mode (17 frames/sec) timed during maximal opacification of the right and left ventricles. Four or six contiguous levels are imaged as required to slice the entire left ventricular cavity. End-systolic and end-diastolic frames are identified. Left ventricular cavity areas are determined by computerized planimetry after the Hounsfield level number is set at half the difference between the contrast in the cavity and the myocardium and setting the window width at one giving a black and white image. Left ventricular end-diastolic volume (LVEDV) and end-systolic volume (LVESV) per slice are summated to obtain LVEDV and LVESV from which LVEF is desired.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Rapid acquisition computed tomographic assessment of left ventricular regional wall motion using a new long axis view.

A long axis view to demonstrate left ventricular regional wall motion was devised for the ultrafast CT scanner. The patients are positioned supine, head first, into the scanner. The scan table is slewed 20 degrees counter-clockwise in the horizontal plane without tilt. A bolus of contrast is injected via a median antecubital vein. Contiguous level R wave triggered cine studies are obtained during peak passage of contrast through the heart to image the entire left ventricular cavity. Fourteen patients had left ventricular wall motion compared by long axis CT and RAO 30 degrees single plane ventriculography at catheterization. In all cases, regional wall motion in comparable segments by both methods was in agreement. It is concluded that the ultrafast CT long axis view permits diagnosis of left ventricular regional wall motion abnormalities. This view images the apex and sections the interventricular septum and lateral free wall horizontally. Unlike conventional CT views, it is comparable to the RAO left ventriculogram.

Cardiac Catheterization↗