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Biomedical subjects

D L Clark

Publications and source records attributed to D L Clark.

At least 19 recordsLinked 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↗
PubMed1985

Effects of colloid or crystalloid administration on pulmonary extravascular water in the postoperative period after coronary artery bypass grafting.

The effect of postoperative fluid management on pulmonary extravascular thermal volume (ETVL) as in index of pulmonary extravascular water after coronary artery bypass grafting was compared, using the thermal-dye technique, among five patients who received 5% albumin (group A), five patients who received 6% hydroxyethyl starch (group H), and five who received lactated Ringer's solution (group C). Intraoperatively, all patients received lactated Ringer's solution intravenously, and the cardiopulmonary bypass (CPB) circuit prime included 5% albumin. No statistically significant changes in ETVL occurred postoperatively in any group, nor did ETVL differ significantly between groups. After CPB, colloid osmotic pressure (COP) significantly decreased and pulmonary artery wedge pressure (WP) and the WP-COP gradient significantly increased in each group, implying an increase in transcapillary fluid flux. Cardiac index changed variably. Pulmonary shunt fraction (Qsp/Qt) did not change in groups A and C but decreased during CPB in group H (from 0.22 +/- 0.03 to 0.16 +/- 0.11). Postoperatively, patients in the three groups received similar volumes of fluids and had similar perioperative weight gains. By the next morning (AM1), COP increased in all groups, returning to levels noted before CPB in group C, and exceeding these levels in groups A and H. Wedge pressure was similar in all three groups on AM1. PaO2 decreased significantly, and alveolar-arterial oxygen partial pressure difference increased significantly in all groups on AM1. In Group H, Qsp/Qt returned to levels observed before CPB by AM1 (0.27 +/- 0.09). We conclude that in patients without postoperative increases in WP, ETVL changes minimally during CPB and is not influenced by the type of fluid administered as the primary volume replacement in the postoperative period.

Aged↗
PubMed1979

Purification and characterization of multiple species (isolectins) of a slime mold lectin implicated in intercellular adhesion.

An improved purification procedure for the carbohydrate-binding proteins (lectins) of cohesive Polysphondylium pallidum cells has been devised. The procedure uses extraction of cells with lactose-containing buffer followed by ammonium sulfate precipitation and affinity chromatography of the redissolved precipitate on a column of acid-treated Sepharose 6B. All hemagglutination activity is adsorbed to the column and recoveries are about 70% of the activity of the starting cell lysate. Sodium dodecyl sulfate-gel electrophoresis of the protein obtained with this procedure resolved three subunits with molecular weights of 26,500 (A), 26,000 (B), and 25,000 (C). Three species are resolved by isoelectric focusing with apparent pI values of 6.4 (I), 7.3 (II), and 7.5 (III) which contain Subunits A, B, and C in the following ratios: I, B:C at 2:1; II, A:B at 2:1, and III, A:B at 1:2. All three isoforms agglutinate rabbit and human type O erythrocytes and are thus isolectins. Isoforms II and III are separated from Isoform I by galactose-gradient elution of the Sepharose 6B column. Isoforms II and III aggregate extensively (nonamers and multiples thereof), but reduction with 2-mercaptoethanol reverses this process yielding a single species of Mr = 73,000 (trimer). Isoform I exists as trimers and hexamers and reduction has no effect on this distribution. Amino acid compositions and tryptic peptide maps of S-[14C]carboxymethyl-isolectins indicate that Subunits A and B are very similar and may represent the same peptide chain, while Subunit C is a peptide quite distinct from A and B.

Amino Acids↗
PubMed1978

Aggression increase and water competition decrease in squirrel monkeys given physostigmine injections.

Six adult squirrel monkeys (Samiri sciureus) were tested in pairs for social dominance in a water competition task. Dominance was defined by two methods: (1) number and direction of aggressive responses, and (2) successful water competition as assessed by latency to the water bottle, latency to accumulate 15 seconds of drinking, and total drinking duration. Monkeys were assigned to pairs on a "round robin" basis so that each monkey was paired with all other monkeys under control, saline, and three levels of physostigmine sulfate (6.25, 12.5, and 25.0 microgram/kg). Under drug conditions only one member of each pair was drugged. The 12.5 microgram/kg dose of physostigmine resulted in a significant increase in aggressive responses. Both drinking duration and general motor activity decreased with increasing dose level of drug. It was also noted that the non-drugged partners of drugged monkeys accumulated 15 seconds of drinking faster and drank more at the 25 and 12.5 microgram/kg dose levels than under control and saline conditions. Physostigmine resulted in an increase in one measure of social dominance and a decrease in the other.

Aggression↗
PubMed1978

Semicircular canal stimulation in cerebral palsied children.

Twelve cerebral palsied children were exposed to 16 sessions of horizontal and vertical semicircular canal stimulation over a four-week period in order to determine the effectiveness of this form of stimulation as a therapeutic procedure. A control group of 11 cerebral palsied children was included. A quantitative evaluation of a series of reflexes and of gross motor skills showed a highly significant degree of improvement following the four weeks of treatment. A qualitative evaluation of each subject corroborated these findings and suggested improvements in fine motor control and in social/emotional behavior. A possible central nervous system mechanism underlying the improvement in motor skills is discussed.

Cerebral Palsy↗
PubMed1977

Vestibular stimulation influence on motor development in infants.

Preambulatory, normal human infants were exposed to sessions of mild semicircular canal stimulation on 2 days per week for 4 weeks. The gross motor ability of each child was assessed before and after the 4-week period. The vestibular stimulation effected a significant improvement in gross motor skills.

Child Development↗
PubMed1977

Mercury and organomercurial resistances determined by plasmids in Pseudomonas.

Mercury and organomercurial resistance determined by genes on ten Pseudomonas aeruginosa plasmids and one Pseudomonas putida plasmid have been studied with regard to the range of substrates and the range of inducers. The plasmidless strains were sensitive to growth inhibition by Hg(2+) and did not volatilize Hg(0) from Hg(2+). A strain with plasmid RP1 (which does not confer resistance to Hg(2+)) similarly did not volatilize mercury. All 10 plasmids determine mercury resistance by way of an inducible enzyme system. Hg(2+) was reduced to Hg(0), which is insoluble in water and rapidly volatilizes from the growth medium. Plasmids pMG1, pMG2, R26, R933, R93-1, and pVS1 in P. aeruginosa and MER in P. putida conferred resistance to and the ability to volatilize mercury from Hg(2+), but strains with these plasmids were sensitive to and could not volatilize mercury from the organomercurials methylmercury, ethylmercury, phenylmercury, and thimerosal. These plasmids, in addition, conferred resistance to the organomercurials merbromin, p-hydroxymercuribenzoate, and fluorescein mercuric acetate. The other plasmids, FP2, R38, R3108, and pVS2, determined resistance to and decomposition of a range of organomercurials, including methylmercury, ethylmercury, phenylmercury, and thimerosal. These plasmids also conferred resistance to the organomercurials merbromin, p-hydroxymercuribenzoate, and fluorescein mercuric acetate by a mechanism not involving degradation. In all cases, organomercurial decomposition and mercury volatilization were induced by exposure to Hg(2+) or organomercurials. The plasmids differed in the relative efficacy of inducers. Hg(2+) resistance with strains that are organomercurial sensitive appeared to be induced preferentially by Hg(2+) and only poorly by organomercurials to which the cells are sensitive. However, the organomercurials p-hydroxymercuribenzoate, merbromin, and fluorescein mercuric acetate were strong gratuitous inducers but not substrates for the Hg(2+) volatilization system. With strains resistant to phenylmercury and thimerosal, these organomercurials were both inducers and substrates.

Chemical Phenomena↗
PubMed1976

Vectorial characteristics of ventricular extrasystoles stimulated during cardiac catheterization.

Ventricular extrasystoles (VES) from different areas of the ventricular muscle mass were obtained by mechanical stimulation of inflow and outflow regions of the right ventricle (RV) and apical and basal portions of the left ventricle (LV) during cardiac catheterization. Cube system vectorcardiogram (VCG) patterns of VES from each location were analyzed to determine the specificity of vector orientation from each site. Transverse plane VCG distinguished between nonseptal LVES and RVES, while a combination of transverse and either sagittal or frontal planes permitted further localization of septal VES to inflow or outflow regions of the RV and apical and basal areas of the LV.

Adult↗
PubMed1976

Effects of vestibular stimulation on nystagmus response and motor performance in the developmentally delayed infant.

The effects were studied of 10 days' exposure to daily repetitive, specific vestibular stimulation on motor performance of children with Down's syndrome and normal children. A quantitative assessment of vestibular function was made in these children including the habituation response of postrotatory nystagmus. Control groups were included. Both the children with Down's syndrome and the normal children who received vestibular therapy demonstrated positive effects when evaluated using a quantitative motor skills assessment test. Control and treatment children showed vestibular habituation, with treatment children evidencing the greater change. This change may reflect the acquisition of an increased level of central nervous system inhibitory control.

Child, Preschool↗
PubMed1976

Hypergravity effects on normal and avulsed developing avian radii.

Rhode Island Red female chicks were subjected to complete closed fracture of the right radius at 2 weeks post-hatching. The animals were allowed to heal for 1 week at either earth gravity or 2 G hypergravity state with control and estrogen-injected groups. Intact and fractured radial length, weight, average epiphysial-diaphysial diameters, and length, width, and weight of healing fracture callus were measured. Daily 2000 IU estrogen administration for 7 d increased intact radial length. Estrogen augments the effects of the 2-G state by inhibiting growth and depleting the mass of both intact and fractured radii and by decreasing the average distal epiphysial diameter of fractured bones. Animals exposed to the hypergravity state without hormonal treatment showed decreased fractured radial length, weight, and smaller proximal epiphysial diameters. The measurable parameters of the fracture callus (width, length, and weight) were depressed by the hypergravity state regardless of whether the animal was untreated or supplemented with estrogen.

Animals↗
PubMed1975

Factors affecting assay of myoglobin by complement fixation or immunodiffusion.

Quantitative micro-scale complement-fixation and semi-quantitative gel immunodiffusion assays for myoglobin have been evaluated experimentally and used to measure myoglobin in the sera of more than 1500 patients. We report certain problems, observations, and methodological improvements. Serum caused enhancement of precipitin lines in the immunodiffusion assay. In the complement-fixation assay, serum interfered both by enhancing or inhibiting complement fixation. Suggested modifications in the complement-fixation assay are: (a) routine threefold or greater dilution of serum with buffer and (b) use of serum-based rather than buffer-based calibration materials in preparing standard curves. Three cycles of freeze-thaw of serum or buffer decreased detectable myoglobin by 50-100%. We conclude that certain serum-related factors and freeze-thaw phenomena are important causes of error in immunological assays for myoglobin.

Complement Fixation Tests↗
PubMedDate not supplied

Metabolic stability and tumor inhibition of bombesin/GRP receptor antagonists.

Small cell lung cancers (SCLC) synthesize and secrete bombesin/gastrin releasing peptide (BN/GRP). The autocrine growth cycle of BN/GRP in SCLC can be disrupted by BN/GRP receptor antagonists such as [Psi13,14]BN. Here several BN analogues were solid-phase synthesized and incubated with intact SCLC cells at 37 degrees C in RPMI medium in a time-course fashion (0-1080 minutes) to determine enzymatic stability. The proteolytic stability of the compounds was determined by subsequent HPLC analysis. The metabolic half-life ranged from 154 minutes to 1388 minutes for the six analogues studied. [Psi13,14]BN was found to be very stable to metabolic enzymes (T1/2 = 646 mm) and also inhibited SCLC xenograft formation in vivo in a dose-dependent manner. When [Psi13,14]BN was incubated with NCI-H345 cells, it inhibited 125I-GRP binding with an IC50 value of 30 nM. These data suggest that BN/GRP receptor antagonists such as [Psi13,14]BN may be useful for the treatment of SCLC.

Amino Acid Sequence↗