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Biomedical subjects

D Williams

Publications and source records attributed to D Williams.

At least 307 records · Page 17Linked to original sources
PubMed1994

Diminished oesophageal traction forces with swallowing in gastro-oesophageal reflux disease and in functional dysphagia.

Relations between primary oesophageal peristaltic amplitude and traction force were studied in 30 normal volunteers, 12 patients with functional dysphagia, and 48 patients with gastro-oesophageal reflux disease, using a new intraluminal strain gauge device. Forces generated by swallowing in the normal oesophagus were 42 (35-60) g (median and interquartile range), a close positive correlation existing between traction force and contractile amplitude for each subject (r = 0.5 (0.38-0.6). Traction force increased with increasing balloon volume from 62 (50-73) g at 2 ml to 86 (70-105) g at 4 ml (p < 0.05), indicating distension related modulation of peristaltic force. Patients with oesophagitis generated lower traction forces on swallowing 30 (20-40) g compared with the normal subjects (p < 0.01), the degree of impairment being greatest in those patients with the most severe mucosal damage. Patients with gastro-oesophageal reflux without endoscopic oesophagitis also showed abnormal forces (32 22-38) g p < 0.01 v controls), which were similar to those patients with mild oesophagitis but were greater than those with severe oesophagitis (p < 0.05). In patients with functional dysphagia, forces were also impaired (28 (10-60) g p < 0.05 v controls) despite normal standard manometry. Our results show that measurement of the traction force generated by primary peristalsis provides information about oesophageal neuromuscular function that is not demonstrable by manometry alone and can be abnormal in patients with oesophageal symptoms in whom standard techniques are normal.

Adolescent↗
PubMed1994

Balloon dilatation of the aortic valve after previous surgical valvotomy: immediate and follow up results.

OBJECTIVE: To evaluate the immediate and long-term results of transcatheter balloon dilatation of the aortic valve for restenosis after previous surgical valvotomy. DESIGN: Prospective follow up by clinical examination and cross sectional Doppler echocardiography of all patients fulfilling the above criteria. SETTING: Tertiary paediatric cardiology referral centre. PATIENTS AND METHODS: 22 patients (18 male, 4 female)--median (range) age 157.5 (12-254) months--underwent 25 balloon dilatation procedures at a median of 72 (8-155) months after surgery. The median age at surgical valvotomy was 82.5 (0.5-230) months and the systolic gradient across the aortic valve immediately after surgery was 31 (0-49) mm Hg. The indication for dilatation was a Doppler derived peak instantaneous gradient of > 60 mm Hg with grade 2 or less aortic regurgitation. A single balloon was used, and the median balloon to annulus ratio was 1 (0.9-1). RESULTS: After dilatation the catheter pullback gradient decreased acutely from 55 (35-75) to 30 (0-75) mm Hg (p < 0.01) and the Doppler gradient from 74 (52-92) to 40.5 (30-96) mm Hg (p < 0.01). In three patients who underwent a second dilatation of the aortic valve eight months after the first procedure, the pullback gradient decreased from 50 (50-60) to 15 (15-16) mm Hg. Aortic regurgitation grade increased from 1 (0-2) to 2 (1-3); only one patient had grade 3 regurgitation. Over a median follow up of 33 (2-67) months seven patients had aortic valve replacement for recurrent stenosis (six patients) or severe regurgitation (one patient with grade 3 regurgitation after dilatation, who had partial detachment of one of the valve leaflets). There was no significant difference for the pullback gradient (median of 19 v 32.5 mm Hg), Doppler gradient 24 hours after dilatation (33.5 v 50.5 mm Hg; p = 0.03), or the duration of follow up (27.5 v 18 months) between the 12 patients who did not require further dilatation or surgery and the 10 patients who did. CONCLUSIONS: Balloon dilatation of the aortic valve is a safe and feasible option for palliation of restenosis after surgical valvotomy for congenital aortic valve stenosis. In many patients, however, stenosis progressed and a further intervention was required.

Adolescent↗
PubMed1994

Spinal evoked potentials are predictive of neurologic function in a porcine model of aortic occlusion.

The limitations of somatosensory evoked potentials during aortic occlusion stimulated us to evaluate the sensitivity and specificity of spinal (T10 and L4) evoked potentials (SpEPs) in predicting neurologic function after aortic occlusion. Thirty-six swine were assigned randomly to three equal groups (Group 1, control; Group 2, cerebrospinal fluid (CSF) drainage; Group 3, CSF drainage with 20-mg intrathecal papaverine). After induction of anesthesia and initiation of physiologic monitoring, a left-sided thoracotomy was performed to provide access to the descending aorta. SpEPs were generated by stimulating the thoracic spinal cord and recording the conducted response at the T10 and L4 level. After baseline measurements were recorded, the descending aorta was occluded 1 cm distal to the left subclavian artery. SpEPs were recorded every 2.5 min and physiologic variables every 5 min. The aorta was unclamped 10, 15, or 20 min after loss of the L4 SpEP. If the L4 SpEP was not lost, the aortic occlusion interval was terminated at 90 min. Attenuation of the SpEPs occurred earlier at the L4 level. Group 1 experienced the earliest loss of the L4 SpEP (18.3 +/- 7.8 min, P < 0.005). Loss of the L4 SpEP in Group 2 (49.3 +/- 27.8 min) was earlier than in Group 3 (73.7 +/- 26.1 min, P < 0.05). Early postoperative motor function (modified Tarlov scale) correlated with time from loss of the L4 SpEP until reperfusion of the distal aorta (r = 0.93). The sensitivity, specificity, and accuracy of the L4 SpEP in predicting neurologic dysfunction was 92.8% (13 abnormal/14 predicted), 90.9% (20/22), and 91.7% (33/36).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Brain buffering is restored in hyponatremic rats by correcting their plasma sodium concentration.

Previous studies from this laboratory showed that both acute and chronic hyponatremia impaired active brain buffering. These studies were performed to determine whether correcting the plasma sodium restored normal buffering in hyponatremic rats. Acute (1- and 2-day) and chronic (7- and 14-day) hyponatremia was induced in male Sprague-Dawley rats by constant desmopressin administration combined with a liquid diet. Plasma sodium was corrected by stopping desmopressin for 6 h, substituting solid chow, and allowing free access to water. Studies were performed 24 h later. Uncorrected hyponatremic rats who continued to receive desmopressin and liquid diet served as controls. Brain pH was determined by [31P]NMR in rats anesthetized with N2O and paralyzed with pancuronium. Brain buffering was determined by the response to CO2 loading. Resting brain pH was the same in corrected and uncorrected rats, but the two groups responded differently to CO2 loading. Thus, 55 min after ventilation with 20% CO2, corrected rat brain pH was 0.13 pH units higher than in uncorrected rats despite statistically similar changes in CO2 tension and arterial pH in both groups. Moreover, 15 min into recovery from CO2 exposure, brain pH in corrected rats overshot resting pH by 0.07, whereas no overshoot occurred in uncorrected rats. Buffering in corrected rats was identical to that shown previously in normonatremic rats. The complete restoration of late-phase buffering achieved by normalizing the plasma sodium of hyponatremic rats indicates that at least some portion of active hydrogen ion transport is sodium dependent in the brain.

Acute Disease↗
PubMed1994

Adult attachment, love styles, and self-defeating personality characteristics.

The present research showed for 79 men and 79 women that people with more characteristics of the proposed self-defeating personality diagnosis had less secure adult attachments. In addition, self-defeating women described their style of loving as game playing and being less romantically involved. Both men and women who were more self-defeating, once in a relationship, reported feeling dependent, jealous, and desperate to maintain it. These results are consistent with the 1993 findings of Williams and Schill that people with more self-defeating characteristics were more likely to lack secure attachments with parents.

Adult↗
PubMed1994

The role of ethylene oxide allergy in sterile shunt malfunctions.

Failure of an intact ventriculoperitoneal shunt, in the absence of an overt infection, is often due to its occlusion by cellular debris and/or an abdominal pseudocyst. This failure is thought to be caused by an infection by an organism which is difficult to culture or by some poorly defined allergic response to the shunt materials. Little attention has been directed to the treatment that the shunts receive prior to implantation: specifically, their exposure to ethylene oxide as a means of sterilization. We have found ethylene oxide metabolites in the spinal fluid of children with shunt malfunction months after their systems were implanted. Many of these patients had coincident CSF eosinophilia. In addition, two of the children had detectable serum IgE antibody directed against an albumin-ethylene oxide conjugated protein. Both of these children had several shunt malfunctions within a short period, yet neither child could be shown to have a shunt infection despite multiple cultures. We therefore suggest that in some patients proteins altered by ethylene oxide incite an IgE mediated response which may lead to shunt malfunction.

Adolescent↗
PubMed1994

Glycothiohexide alpha, a novel antibiotic produced by "Sebekia" sp., LL-14E605. II. Isolation and physical-chemical characterization.

Glycothiohexide alpha was recovered from the fermentation broth of a "Sebekia" sp. by mixed solvent extraction, selective precipitation and adsorption chromatography on Diaion HP-20. The amount of glycothiohexide alpha present in the crude preparation was enriched by photolysis. Purification of glycothiohexide alpha was accomplished by repetitive countercurrent chromatography.

Actinomycetales↗
PubMed1994

Lipid content of microparticulate (1-->3)-beta-D-glucan isolated from Saccharomyces cerevisiae.

The preparation of pharmaceutical grade (1-->3)-beta-D-glucans from Saccharomyces cerevisiae requires that the microparticulate glucans which are employed as the starting material for drug production be of the highest purity. Potential contaminants of the (1-->3)-beta-D-glucan isolation process are yeast cell wall lipids, which are frequently found in association with glucans. The lipid content of yeast-derived (1-->3)-beta-D-glucan during various stages of the isolation process by methyl esterification and total ion gas chromatography and mass spectrometry (GC-MS) was examined. Following sequential alkaline and acid hydrolyses, the total lipid content of (1-->3)-beta-D-glucan was 100.4 nmol/mg with 9-cis-C 18:1 fatty acid accounting for 45.3 nmol/mg glucan (45%). Following ethanol extraction of the (1-->3)-beta-D-glucan, lipid was not detected. Indeed, fatty acid methyl esters were not detectable by total ion GC-MS in all twelve samples investigated. These data demonstrate that the isolation process for yeast-derived (1-->3)-beta-D-glucan effectively reduces contamination by yeast cell wall lipids.

Cell Wall↗
PubMed1994

Comparative use of various mydriatic drugs in kestrels (Falco tinnunculus).

The mydriatic effect of 3 curare-like neuromuscular blocking agents was tested in European kestrels (Falco tinnunculus) after topical application. Alcuronium chloride (5 mg/ml) was found to be effective at a dose of 1 drop (20 drops = 1 ml) administered twice at a 15-minute interval. Mydriasis was achieved at t = 26 +/- 11 minutes, maximal effect was reached at t = 60 +/- 39 minutes, and sufficient mydriasis ended at t = 364 +/- 134 minutes. Nevertheless, side effects, including temporary full paralysis in 1 bird, indicated that this drug should not be used. Pancuronium bromide (2 mg/ml) had an inconsistent effect on each bird at a dose of 2 drops administered twice at 15-minute intervals, and total mydriasis was not reached in 5 of 8 birds. Mydriasis was achieved at t = 34 +/- 11 minutes, maximal effect was reduced and reached at t = 43 +/- 13 minutes, and sufficient mydriasis ended at t = 90 +/- 39 minutes. Vecuronium bromide (4 mg/ml) was administered at a dose of 2 drops, 3 times, at 15-minute intervals. Mydriasis was achieved at t = 23 +/- 8 minutes, maximal effect was reached at t = 65 +/- 12 minutes, and sufficient mydriasis ended at t = 253 +/- 65 minutes. Side effects were not detected. Vecuronium bromide should be used in raptorial birds whenever retinal examination requires fundoscopy.

Alcuronium↗
PubMed1994

Immunization of patients with rheumatoid arthritis against influenza: a study of vaccine safety and immunogenicity.

OBJECTIVE: To address the issues of immunogenicity and local and systemic reactions to vaccination with influenza vaccine in patients with rheumatoid arthritis (RA). METHODS: One hundred and twenty-six patients with RA were stratified into 3 groups: (1) those with a history of vaccination with influenza vaccine within 24 months who were receiving usual therapy for RA, (2) those receiving usual therapy for RA but without prior vaccine, and (3) those receiving immunosuppressive medication or prednisone > or = 7.5 mg/day, irrespective of their prior immunization status. Within each group, patients were randomized to receive vaccine or placebo. A group of age matched, healthy controls were also vaccinated. RESULTS: During a one month followup period, adverse reactions occurred with equal frequency among patients with RA and healthy controls. Similar significant increases in titers to the vaccine were seen in all groups of patients with arthritis and in the controls. CONCLUSION: The potential increase in susceptibility to influenza and death from respiratory illness in patients with RA and the demonstrated safety and immunogenicity of influenza vaccine should require the inclusion of patients with RA in standard immunization programs.

Arthritis, Rheumatoid↗
PubMed1994

Automation at the point of care.

Clinical Information Systems (CISs) are systems of microcomputers used at patient bedsides to collect, process, retrieve and display information related to patient care. At our facility, 65 terminals are used in selected units and the CIS has virtually replaced paper charts in daily practice and documentation. Though currently employed in only a small number of hospitals, the use of CISs is expected to grow rapidly during the coming decade.

Computer Systems↗
PubMed1993

Telomere processing in Euplotes.

In Euplotes crassus millions of telomeres are synthesized during the sexual phase of the life cycle. Since these newly synthesized telomeres are longer than normal macronuclear telomeres, they must be trimmed to the mature size. We have examined the timing and mechanism of this trimming step. We have shown that a sudden decrease in telomere length takes place at a specific time during macronuclear development. The decrease in telomere length is not caused by incomplete replication of the most terminal DNA sequences; rather it is the result of an active processing event that occurs independently of DNA replication. The developmentally regulated telomere shortening that takes place in Euplotes is reminiscent of the sudden reductions in telomere length which have been observed in other eukaryotes.

Animals↗
PubMed1993

Color, contrast sensitivity, and the cone mosaic.

This paper evaluates the role of various stages in the human visual system in the detection of spatial patterns. Contrast sensitivity measurements were made for interference fringe stimuli in three directions in color space with a psychophysical technique that avoided blurring by the eye's optics including chromatic aberration. These measurements were compared with the performance of an ideal observer that incorporated optical factors, such as photon catch in the cone mosaic, that influence the detection of interference fringes. The comparison of human and ideal observer performance showed that neural factors influence the shape as well as the height of the foveal contrast sensitivity function for all color directions, including those that involve luminance modulation. Furthermore, when optical factors are taken into account, the neural visual system has the same contrast sensitivity for isoluminant stimuli seen by the middle-wavelength-sensitive (M) and long-wavelength-sensitive (L) cones and isoluminant stimuli seen by the short-wavelength-sensitive (S) cones. Though the cone submosaics that feed these chromatic mechanisms have very different spatial properties, the later neural stages apparently have similar spatial properties. Finally, we review the evidence that cone sampling can produce aliasing distortion for gratings with spatial frequencies exceeding the resolution limit. Aliasing can be observed with gratings modulated in any of the three directions in color space we used. We discuss mechanisms that prevent aliasing in most ordinary viewing conditions.

Color Perception↗