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Biomedical subjects

R M Ward

Publications and source records attributed to R M Ward.

At least 19 recordsLinked to original sources
PubMed1990

Factors modifying the use of anaesthetic drugs in the elderly.

The elderly are forming an ever greater proportion of our hospital population. The process of ageing produces a gradual erosion of all the body's margins of safety coupled with a decreasing ability to adapt. This has significant effects on the physiological responses to the surgical and pharmacological trespass encountered during anaesthesia. In addition elderly people often suffer from multiple pathology and polypharmacy, both of which play important roles in the selection of the optimal anaesthetic regimen.

Aged↗
PubMed1990

Evidence for positional coding in hyperacuity.

Observers performed simple pattern discriminations [tests of orientation (vernier) acuity and spatial-interval acuity] with targets consisting of spatially separated squares. We investigated the effects on acuity of supernumerary squares placed at various mean positions between the two squares constituting the target configuration. The exact position of the supernumerary squares relative to the target squares changed randomly from trial to trial, so that their spatial relationship to the targets could not serve as a cue. Observers attempted to ignore these supernumerary squares and to base their judgments on the outer target squares alone. The supernumerary squares raised thresholds if they were sufficiently close (4.4-arcmin separation) to the target squares but not if they were at a greater distance (21.0 arcmin). The results therefore show that the observers could ignore the supernumerary squares, even when they fell into the space between the target squares. This finding suggests that observers can select a class of length- and orientation-tuned filter that is suited exactly to the requirements of a particular psychophysical task. We argue that filter models of hyperacuity are insufficient unless they address this critical issue of filter selection and that a complete model requires an explicit spatial representation of target feature position.

Humans↗
PubMed1989

Serial renal function in an ovine model of unilateral fetal urinary tract obstruction.

Renal tubular and glomerular function following ovine fetal urinary tract obstruction has been studied predominantly in anesthetized, exteriorized fetuses immediately after relief of obstruction. Since surgery and anesthesia may alter fetal cardiovascular and renal physiology, we developed a chronically catheterized, ovine model of unilateral fetal urinary tract obstruction to compare function of the unobstructed and obstructed kidneys repeatedly after relief of obstruction. Split renal function of the previously obstructed kidneys and unobstructed kidneys was measured serially in 7 fetal sheep after obstruction at 55 to 85 days per 147 days of gestation for 30 to 49 days. Seventy-five split clearances were determined on days 1, 2, 3 to 4 and 5 to 6 postoperatively. Not every fetus was studied each day. By 2-way ANOVA, renal function was stable on day 1 after surgery and did not change with time. Previously obstructed kidneys had lower creatinine clearance (0.16 versus 0.71 ml. per minute, p equals 0.0001), higher fractional sodium excretion (33.04 versus 6.02 per cent, p equals 0.0001) and higher urine sodium/creatinine ratio (4.80 versus 0.90 mEq. per mg., p equals 0.0001). Urine flow in the unobstructed kidneys did not differ significantly from that of the obstructed kidneys (0.122 versus 0.083 ml. per minute, p equals 0.35). Obstruction reduced kidney weight (4.7 versus 9.7 gm., p equals 0.0006), cortical thickness (-39 per cent) and nephrogenic zone (-59 per cent), and it increased collecting duct dilatation and medullary fibrosis. No cysts or dysplasia was noted. Fetal urinary tract obstruction for 39.7 days alters renal histology, glomerular function and tubular function. Renal function is stable by 1 day after catheterization and does not change from days 1 to 6 following relief of obstruction.

Animals↗
PubMed1989

Maternal-placental-fetal unit: unique problems of pharmacologic study.

Fetal exposure to different drugs has increased, but few prospective, controlled, blinded trials have been conducted of adverse fetal effects following fetal drug exposure. The quantitative exposure of the fetus to drugs varies during pregnancy with changes in the MPFU. Prospective, controlled, blinded studies of adverse fetal effects of drugs are very difficult; investigators therefore have used alternative study designs that make the conclusions more tentative. Such studies may be limited by accuracy of recall of drug intake and its timing, oversimplification of complex drug exposure, separating the effects of drugs from that of the underlying disease, and a lack of correlation between human and animal effects of fetal drug exposure. Intentional drug treatment of the fetus has begun but should proceed from thorough laboratory study to clinical applications, not the reverse.

Epidemiologic Methods↗
PubMed1989

Spatial properties of mechanisms for detection of moving dot targets in dynamic visual noise.

The maximum displacement threshold for direction discrimination (dmax) was determined for single or paired dot targets moving discretely against a background of dynamic visual noise. dmax rose as the spatial density of noise was reduced, or when the interframe interval was decreased. dmax was greater for dot pairs than for single dots, and rose progressively as the distance between the dots was reduced. dmax was also greater if the orientation of the target dot pairs differed from the orientation of paired dots in the background noise. Dichoptic presentation of the target and background noise allowed the target to be detected with an accuracy that did not depend on displacement.

Female↗
PubMed1989

Continuous arteriovenous hemofiltration in experimental iron intoxication.

This study evaluated continuous arteriovenous hemofiltration (CAVH) as a method for removing the iron-deferoxamine complex in experimental iron intoxication. Five anesthetized dogs were instrumented for hemodynamic monitoring and then given 600 mg/kg of elemental iron as ferrous sulfate. After a 3-h absorption period, CAVH was begun from the femoral artery to femoral vein. Deferoxamine was infused into the arterial lines of the CAVH cartridge at increasing doses. We found a dose-dependent increase in the ultrafiltrate excretion of iron. However, most of the deferoxamine was excreted unbound. The efficiency of complex formation was greater at lower BP and ultrafiltrate formation rate, suggesting that inadequate mixing of deferoxamine with blood may occur when arterial administration is used. Iron excretion in the urine over the same time period was not significantly greater than that removed by CAVH. We conclude that CAVH can remove iron using deferoxamine as a chelating agent.

Animals↗
PubMed1989

Management of posthemorrhagic hydrocephalus in the low-birth-weight preterm neonate.

Over a period of 34 months from 1987 to 1990 we inserted ventricular catheter reservoirs (VCR) into 20 premature low-birth-weight infants who had developed progressive, symptomatic posthemorrhagic hydrocephalus following grade III or IV intraventricular hemorrhages. The mean estimated gestational age was 27.7 +/- 5.3 weeks and mean birth weight was 1,041 +/- 699 g. The ventricular catheter reservoirs were placed on day of life 30.7 +/- 29.7 and tapped for a total of 3-34 days at varying frequencies and for varying volumes. Of the 20 patients, 4 died on days of life 25, 76, 88, and 187. There were two reservoir infections, both occurring in infants who eventually died. The 16 survivors have been followed from 2 to 24 months (adjusted age). Four (25%) remain shunt-free and 3 have undergone VCR removal. There have been two shunt infections in the 12 shunted patients; ten shunt revisions have been performed overall. At the time of last follow-up, 14 patients were old enough to undergo neurodevelopmental evaluation. Five patients (36%) were 'normal' on gross neurological screening examination, 5 (36%) had 'mild developmental delay' and 4 (28%) had 'significant developmental delay'. We feel these data support the continued use of ventricular catheter reservoirs in the management of posthemorrhagic hydrocephalus and offer hope that some of these patients might remain shunt-free and most will have a normal or mildly delayed neurodevelopmental outcome.

Brain Damage, Chronic↗
PubMed1987

Antibodies to P. acnes and P. acnes exocellular enzymes in the normal population at various ages and in patients with acne vulgaris.

Total serum IgM and IgG agglutinins to P. acnes and neutralizing antibodies to P. acnes lipase, hyaluronate lyase and acid phosphatase were measured in normal individuals of different age groups. Agglutinins to P. acnes were detected in infants at 4 months of age and were present at a high level throughout life. A switch from predominantly IgM agglutinins in children, to IgG agglutinins in adults, occurred during adolescence. Anti-P. acnes lipase antibodies were present in 20% of teenagers and 17-42% of adults. Anti-P. acnes hyaluronate lyase antibodies were found in adults only (4-17%). Antibodies to acid phosphatase were not detected. Agglutinins to P. acnes were measured in individuals with mild, moderate and severe acne, and in normal controls. Only patients with severe acne had significantly higher titres than the controls. IgM and IgG agglutinins were determined in 13-14-year-olds with mild, moderate and severe acne, and in normal controls. Thirty-three per cent, 60% and 100% of the acne patients, respectively, but none of the normal controls, had predominantly IgG agglutinins. No difference in the prevalence or titre of antibodies to P. acnes exocellular enzymes was observed when patients with severe acne were compared with normal controls. There was no evidence to suggest a role for antibodies to P. acnes exocellular enzymes in the initiation of inflammatory acne.

Acne Vulgaris↗
PubMed1978

Prognosis in early carcinoma of the bladder based on chromosomal analysis.

In 53 cases of non-invasive or submucosal invasive well differentiated carcinoma of the bladder observed for 4 to 101 months cytogenetic analysis by the direct technique (non-culture) has been performed repeatedly. Markers, abnormal chromosomes, have been found in 33 patients and recurrence has developed in 32 of these 33 patients, resulting in 9 deaths. All but 1 of the 20 patients without markers have been observed for up to 8 years and have remained free of recurrence. In this 1 recurrence, 8 months post-diagnosis, the mode changed from 69 to 92, evidence of dedifferentiation and development of a new tumor in a bladder prone to neoplasia. Based on our over-all cytogenetic experience with 165 patients with carcinoma of the bladder a simplified classification is presented. This classification, built on measurable characteristics of early carcinoma, including the presence or absence of marker chromosomes, allows accurate prognostication and, thus, provides the foundation for development of standard therapy.

Adult↗
PubMed1978

Cellular immunity to P. acnes in the normal population and patients with acne vulgaris.

Patients with varying degrees of acne, acne-free adult controls and samples of cord blood were investigated for cell mediated immunity to P. acnes using a leukocyte migration inhibition test. Despite the fact that the mean migration index tended to decrease with acne severity, only the patients with severe acne showed cell-mediated immunity. It is suggested that when cellular immunity arises it is a late event which may contribute to inflammation but is probably not a factor in its initiation.

Acne Vulgaris↗
PubMed1977

Prognosis in well differentiated noninvasive carcinoma of the bladder based on chromosomal analysis.

In this series of 27 consecutive patients with well differentiated noninvasive carcinoma of the bladder, cytogenetic analysis repeatedly performed showed marker chromosomes in curative cytoscopic resections of 15 of the patients. In 14 of the 15 patients, recurrent carcinoma developed. Of the 12 patients without markers, one patient had a recurrence; the remaining 11 have been free of recurrence up to eight years after diagnosis. In this long term, although limited, experience with early carcinoma of the bladder, marker chromosomes have been a highly accurate prognostic aid.

Chromosome Aberrations↗
PubMed1976

Meningitis due to combined infections. Association of Haemophilus influenzae type B and Clostridium perfringens.

Haemophilus influenzae type B and Clostridium perfringens were recovered simultaneously from the cerebrospinal fluid of a patient with purulent meningitis. No antecedent history of head trauma was present to explain the coexistence of the anaerobe with Haemophilus organisms. A review of the literature on mixed meningitis indicates that no previous cases of anaerobes have been reported in uncomplicated meningitis due to multiple organisms. In addition, the recovery of clostridia is extremely unusual in the absence of an identifiable portal of entry. We have identified two additional cases of clostridia infection in the central nervous system and recommend that anaerobic organisms be considered in selected cases of meningitis.

Ampicillin↗
PubMed1976

Cytogenetic analysis: a potential index for recurrence of early carcinoma of the bladder.

In 15 cancer patients cystoscopic resection or biopsy coupled with cytogenetic analysis at intervals of 3 to 69 months showed persistence of chromosomal patterns with markers (abnormal chromosomes) in 4 of 7 non-invasive and in 6 of 8 submucosal invasive carcinomas. Recurrence was limited to but constant in those carcinomas containing markers. Marker chromosomes have potential value as a prognostic aid. Further, the triad of tetraploidy, markers and submucusal invasive moderately well differentiated carcinoma appears to carry such a lethal prognosis as to militate for early radical resection.

Carcinoma, Transitional Cell↗
PubMed1976

The aftereffect of tracking eye movements.

When observers tracked moving stripes across a background either of stationary stripes, or of stripes moving in the opposite direction, they saw a clear motion aftereffect when the stripes stopped moving. The direction of this aftereffect was opposite to that of the previously tracked stripes, and was thus the same as the direction of the retinal movement of the non-tracked stripes. This aftereffect of tracking was shown not to depend upon slippage of the tracked contours on the retina during tracking, or upon the saccadic phase of optokinetic nystagmus. The effect showed storage over a period of time with the eyes shut. It appears that the effect is due to induced movement, and arises originally from stimulation of the retina by background contours in the tracking phase. This was shown by confining the view of the moving target to one eye, while permitting both eyes to be exposed to background stimulation during tracking. After such stimulation the magnitude of the aftereffect was equal in the two eyes.

Electroretinography↗