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Biomedical subjects

T Williams

Publications and source records attributed to T Williams.

At least 181 records · Page 10Linked to original sources
PubMed1994

Assessment of blood flow changes at multiple sites in rabbit skin using a 133Xenon clearance technique.

133Xenon clearance represents a clinically useful method of measuring local circulatory function in a variety of different tissues. The method detailed in this article describes how the 133Xenon clearance technique can be adapted to simultaneously measure cutaneous blood flow, over a 15-min period, at a large number of skin sites within the same animal. Blood flow changes are measured in response to intradermally injected vasoactive test agents. The multisite injection plan which forms part of the method removes bias due to site variations and generates data that can be analysed statistically. Results are expressed as the percent change in 133Xenon clearance at test agent-injected sites as compared to control, saline-injected sites. The method provides an accurate and time-efficient measure of skin blood flow. In the present study, the technique is used to assess the receptor-mediated mechanism of action of the vasodilator calcitonin gene-related peptide (CGRP) and the possibility that the vasoconstrictor endothelin-1 acts to stimulate the release of vasodilator quantities of endogenous CGRP.

Animals↗
PubMed1994

Prevention of photocarcinogenesis and UV-induced immunosuppression in mice by topical tannic acid.

Topical application of tannic acid, a phenolic antioxidant derived from plants, was found to inhibit the cutaneous carcinogenesis and the immunosuppression induced by ultraviolet B (UVB) irradiation with no visible toxicity. BALB/cAnNTacfBR mice were treated with 200 micrograms of tannic acid three times weekly for two weeks before UV treatments began and throughout the experiment. UVB irradiation consisted of five 30-minute exposures per week to banks of six FS40 Westinghouse sunlamps. In the photocarcinogenesis study, mice received a total dose of approximately 1.09 x 10(6) J/m2. Skin cancer incidence in UV-irradiated mice was 75% at 26 weeks after the first UV exposure; tannic acid reduced this to 42%. Immunosuppression induced by UVB irradiation normally prevents the host from rejecting antigenic syngeneic UV-induced tumors. Immunosuppression in these experiments was measured by a passive transfer assay. Tumor challenges grew to an average of 88 +/- 20, 36 +/- 11, and 20 +/- 8 mm2 in naive recipients of splenocytes from UVB-irradiated mice, nonirradiated control mice, and UVB-irradiated mice treated with tannic acid, respectively. Thus topical tannic acid treatment prevented the transfer of enhanced tumor susceptibility with splenocytes from UVB-irradiated mice.

Administration, Topical↗
PubMed1994

Proposals for a new classification of iridescent viruses.

The need for comparative studies of iridoviruses to elucidate the relationships between them has been well appreciated. Sixteen iridoviruses, including type species from each of the four recognized genera of the Iridoviridae, were compared by restriction endonuclease characterization, hybridization to the major structural protein (MSP) gene of an invertebrate iridescent virus (IV) isolate at various stringencies, PCR amplification of the MSP gene region and by dot-blot hybridization studies. The results broadly supported previous serological studies. The vertebrate iridoviruses, frog virus 3 (genus Ranavirus) and flounder lymphocystivirus (genus Lymphocystivirus), appeared distinct from one another and from the invertebrate isolates. Naming and numbering invertebrate IV isolates according to history and host is no longer useful since IVs infect a number of species. A revised system, involving names based on the geographical origin of the isolate is proposed, in line with other virus families. The large IVs of invertebrates represented by Vero Beach IV (previously IV3 or mosquito IV; genus Chloriridovirus) showed little similarity to any other IVs. Members of the genus Iridovirus, the small invertebrate IVs, fell into three distinct groups of interrelated isolates. The largest group, containing the Plowden (IV1), Tia (IV2), Nelson (IV9, IV10 and IV18), Aberystwyth (IV22), Srinagar (IV24), Fort Collins (IV29) and Stoneville (IV30) iridoviruses, is named the Polyiridovirus complex. The Plowden iridovirus (IV1) is suggested as type species for this complex given the data available on its molecular biology. Based on previously published data, Timaru (IV16 and IV19) and Uitenhage (IV23) iridoviruses are also assigned to this complex. The second but smaller group is named the Oligoiridovirus complex, which includes Dazaifu (IV6) as the type species and contains Ntondwe (IV21 and IV28) on a tentative basis. Riverside IV (IV31) was distinct from both of the other groups, and is proposed as a third complex, Crustaceoiridovirus.

Animals↗
PubMed1994

Short AV interval VDD pacing does not prevent tilt induced vasovagal syncope in patients with cardioinhibitory vasovagal syndrome.

Eleven subjects (mean age 50 years, range 33-71 years), who had previously received permanent dual chamber pacemakers for cardioinhibitory vasovagal syncope, underwent paired Westminster protocol tilt tests, one with short AV delay VDD pacing and one without pacing, to test the hypothesis that continuous ventricular pacing would prevent the cardiac initiation of vasovagal syncope. Nine (82%) of the paced tilts produced positive vasovagal outcomes compared with seven (64%) of the unpaced tilts. No important differences in the heart rate or blood pressure behavior during tilt or the time to positive vasovagal outcomes were observed between the paired tilts. There was more accelerated syncope/presyncope once symptoms had developed during the paced tilts of subjects in whom both study tilts were positive, although this did not reach statistical significance (P = 0.054). This study shows that atrial synchronous ventricular pacing does not prevent the initiation, or progression, of tilt induced vasovagal syncope in predisposed subjects.

Adult↗
PubMed1994

Permanent pacing for cardioinhibitory malignant vasovagal syndrome.

OBJECTIVE: To evaluate the effect of permanent pacing in cardioinhibitory malignant vasovagal syndrome. PATIENTS AND METHODS: 37 patients with permanent pacemakers for cardioinhibitory malignant vasovagal syndrome. All presented with syncope (median six episodes, median frequency two episodes a year) and after conventional investigation and invasive electrophysiological assessment they remained undiagnosed, and without a generally accepted indication for pacemaker implantation. In all vasovagal syncope with cardioinhibition (heart rate at syncope < 60 beats/min) developed during tilt tests performed according to the Westminster protocol (head up tilt at 60 degrees with a footplate support for 45 minutes or until syncope intervenes). Dual chamber pacemakers were implanted in 35 (95%) and VVI pacemakers in the remaining two (5%). RESULTS: Over a mean (SD) follow up since implantation of 50.2 (23.9) months symptomatic improvement occurred in 89%: 62% remained free of syncope and 27% were completely symptom free. The collective syncopal burden of these 37 patients was reduced from 136 to 11 episodes each year. During follow up three patients died from unrelated causes. Patients who become asystolic during the tilt test (sinus pause of at least four seconds) experienced no greater benefit from pacing than those with less extreme cardioinhibition. Patients who remained free of syncope since implantation were younger than those who continued to experience syncope. Patients who remained completely symptom free after implantation were younger, more likely to be male, and had had fewer syncopal episodes before implantation than those who continued to experience syncope or presyncope. No other demographic, clinical, investigative, or pacing variable suggested a more favourable outcome after implant. CONCLUSIONS: This retrospective and uncontrolled experience suggests a possible role for permanent pacing in selected patients with cardioinhibitory malignant vasovagal syndrome. Improved acquisition of tilt test data may enable better selection of patients who are suitable for permanent pacing. A randomised prospective study to compare permanent pacing with no treatment or with medical treatment in cardioinhibitory malignant vasovagal syndrome is indicated.

Adult↗
PubMed1994

Safe removal of combat body armour lightweight following battlefield wounding -- a timely reminder.

Medical Support Troop Bravo (MST Bravo) provides third line medical support for the United Kingdom Battle Group currently deployed on operation Grapple 2 in Bosnia Herzegovina. Standing operating procedures for the initial assessment and resuscitation of all casualties are based on the protocols taught on Advanced Trauma Life Support (ATLS) and Battlefield Advanced Trauma Life Support (BATLS) courses. These protocols dictate a period of initial assessment and resuscitation with the casualty immobilised in the supine position. Recent experience in casualty management at MST Bravo has identified inadvertent spinal movement taking place during removal of Combat Body Armour Lightweight (CBA) which might have detrimental effects for casualties with occult spinal injury. This has led to an appraisal of CBA removal and the identification of a drill for rapid, safe and reliable means of undressing without jeopardy to the integrity of the spine. The method is described.

Humans↗
PubMed1994

Value of prostate cancer screening in a comprehensive community cancer center.

Early detection of prostate cancer may help decrease cancer deaths from this disease despite the increased incidence of prostate cancer. In 1990 and 1991 we conducted one-day "screens" for prostate cancer. This analysis was undertaken to determine the value of the screening procedures for detecting prostate cancer in the community. A total of 579 men, aged 39-84 years (mean 58 years), were evaluated by digital rectal examination (DRE) by a urologist, serum prostate specific antigen (PSA) determination by monoclonal antibody assay, and completion of a detailed questionnaire. Forty-eight percent had not seen a physician in over 2 years; 17% had a 1st- or 2nd-degree relative with prostate cancer. There was a 25% "suspicious" rate including 76 (13%) men with abnormal DRE only, 48 (8%) with abnormal PSA only, and 21 (4%) with abnormal DRE and PSA. Patients with findings suspicious for cancer were recontacted by telephone at 2-month intervals for 6 months to determine outcome because subsequent diagnostic management was at the discretion of practicing physicians. By 6 months, 84% of patients with abnormal findings had seen a physician as recommended. Of the 76 with abnormal DRE only, 11 were biopsied and only one cancer was found (9%). Of 48 with an elevated PSA only, 19 were biopsied; 11 (58%) had cancer (9/9 positive transrectal ultrasound) and 8 had no cancer at biopsy (5/5 negative transrectal ultrasound). Of 21 with both tests suspicious, 11 were biopsied and 9 had cancer (82%). Thus, by 6 months after each screen there was a 3.5% overall cancer detection rate for the whole population screened, a 67% positive biopsy rate among those with an elevated PSA, a 45% positive biopsy detection rate among those with an abnormal DRE, and a 51% positive biopsy rate among all those biopsied. Eighty percent of the PSA elevations were between 4.1 and 10.0 ng/ml. This screening experience yielded several new diagnoses of prostate cancer, and the use of serum PSA levels and ultrasound-guided biopsy was associated with a high positive biopsy rate for cancer.

Adult↗
PubMed1994

Quality of life: is it a practical tool in patients with vascular disease?

With increasing pressure on resources, health care managers are interested in evaluating both drug and surgical treatments. A single measure of the quality of life of patients may be a useful tool in such an evaluation. We have assessed two methods of measuring quality of life in this preliminary study and have found them to be useful and simple to assess in patients undergoing vascular surgery. Changes between the preoperative values and postoperative values correlate well with the clinical impression.

Activities of Daily Living↗
PubMed1994

Porcine peritoneal sepsis: modeling for clinical relevance.

The characteristics of two types of intraperitoneal (i.p.) soilage sepsis models, autologous fecal inoculum (FEC) and a pure culture of Escherichia coli (EC), were studied in 26 male Yucatan minipigs (20-30 kg). Early (1-4 h) and late (24-72 h) changes were different between the two groups. The EC group was characterized early by hypotension, low cardiac output, and increased systemic and pulmonary vascular resistances, along with leukopenia, hypoglycemia, lactacidemia, and elevated blood urea nitrogen. Of the pigs in the EC group that survived the early effects, there were few significant differences in physiological parameters, compared to control pigs, that would indicate ongoing pathological processes. In contrast, the FEC group pigs demonstrated early hypotension, but with increased cardiac output and reduced systemic vascular resistance. Other parameter changes were similar to those seen in the EC pigs, but to a lesser degree, with the exception of elevations in serum lactate dehydrogenase. Also in contrast to the EC group, most of the changes in the FEC group persisted in later days, and FEC pigs demonstrated leukocytosis. There were also greater elevations in circulating lipopolysaccharide (LPS) concentrations in the EC group that returned later to baseline levels. In the FEC group, there were persistently elevated LPS concentrations over 72 h. These observations suggest that pigs challenged with intraperitoneal E. coli demonstrated an initial acute peritonitis and damaging physiologic effects of high levels of circulating LPS. Survivors in this group improved and were physiologically stable after 24 h. Pigs that received i.p. autologous feces developed an early acute peritonitis phase with lower levels of circulating LPS, and later developed pronounced peritoneal reaction as demonstrated by multiple abdominal abscesses, pyogenic granuloma formation, and adhesions with physiological evidence of developing sepsis over 72 h. These observations indicate that i.p. EC models evoke a systemic response not unlike intravenous administration of LPS or EC, however, the FEC model produced a systemic response akin to a slower developing septic process.

Animals↗
PubMed1994

Coadministration of fluvoxamine increases serum concentrations of haloperidol.

Four patients with chronic schizophrenia were treated with a combination of fluvoxamine, haloperidol, and benztropine. The combination significantly impaired performance on tests of delayed recall memory and attentional function. Haloperidol concentrations in serum were monitored in three patients and were robustly elevated by fluvoxamine.

Adult↗
PubMed1994

Crohn's disease with unusual enterouterine fistula in pregnancy.

Pregnancy complicated by development of Crohn's disease is rare. The presentation of symptomatic Crohn's disease during pregnancy was initially described in 1946. Crohn's disease has been described in a number of atypical locations and with development of unusual fistulas. The cases associated with pregnancy have in common a clinical picture of (1) delay in diagnosis, (2) frequent premature delivery, (3) surgical intervention during pregnancy, and (4) high fetal and maternal morbidity and mortality. To our knowledge, this case is the first to describe the radiologic findings of an enterouterine fistula in a case of Crohn's disease beginning during pregnancy.

Adolescent↗
PubMed1994

A unique rat model of bile ductular hyperplasia in which liver is almost totally replaced with well-differentiated bile ductules.

A novel rat model was developed in which furan combined in a unique synergistic manner with bile duct ligation to induce replacement of most of liver with well-differentiated hyperplastic bile ductules. Multiple tissue sections of liver from Fischer 344 male rats first subjected to a bile duct ligation and 1 week later given furan by gavage at 45 mg/kg body weight, once a day, five times weekly for 5 to 6 weeks, exhibited a mean percent of bile ductule tissue per total liver section area of 72.6 +/- 16.3% compared to control values of 20.0 +/- 4.2% for bile duct-ligated rats that received corn oil by gavage instead of furan and 11.9 +/- 3.1% for rats that were given a sham operation followed by furan. This dramatic difference was also reflected by the very high mean gamma-glutamyl transpeptidase specific activity of liver homogenates from the bile duct-ligated/furan-treated rats, which was approximately 8 x 10(3) nmoles p-nitroaniline/mg protein/hour versus values of approximately 2 x 10(3) for bile duct-ligated/corn oil control, approximately 1 x 10(3) for sham-operated/furan-treated control, and 44.9 for untreated rat. The data presented support a potentially powerful experimental model for investigating bile ductular cell functions, differentiation, and proliferation.

Animals↗
PubMed1994

Porcelain veneer fabrication. Platinum foil and refractory model techniques.

A quality porcelain veneer restoration can be made by either the refractory die method or by platinum foil. The platinum foil method produces excellent results with more traditional means. The refractory method can produce equally excellent results as well, but requires more effort in model making.

Dental Casting Technique↗
PubMed1993

Non-viraemic transmission of tick-borne encephalitis virus: a mechanism for arbovirus survival in nature.

The vectors of arthropod-borne viruses (arboviruses) become infected by feeding on the viraemic blood of an infected animal. This theory is based on transmission studies involving artificial infection of vertebrate hosts by syringe inoculation. To reproduce natural conditions of virus transmission, infected and uninfected vectors (ticks) of tick-borne encephalitis virus, the most important arbovirus in Europe, were allowed to feed together on uninfected wild vertebrate hosts. The greatest numbers of infected ticks were obtained from susceptible host species that had undetectable or very low levels of viraemia. The results suggest that 'nonviremic transmission' is an important mechanism for the survival of certain arboviruses in nature.

Animals↗
PubMed1993

Low-dose tumour necrosis factor alpha and melphalan in hyperthermic isolated limb perfusion.

Nine patients with soft tissue tumours of the lower limb not amenable to treatment other than by isolated limb perfusion or amputation underwent hyperthermic isolated limb perfusion at the level of the superficial femoral vessels, using a combination of recombinant tumour necrosis factor (TNF) alpha and melphalan. In seven patients with superficial tumours, necrosis and sloughing was apparent within 48 h of perfusion. All patients experienced a complete tumour response. There were no systemic side-effects associated with the use of TNF-alpha although local side-effects, particularly oedema, were pronounced. Three patients ultimately required amputation because of the large soft tissue defects that resulted from necrosis of the tumour and overlying skin.

Adult↗