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Biomedical subjects

J T Walsh

Publications and source records attributed to J T Walsh.

At least 37 records · Page 2Linked to original sources
PubMed1996

Water flux from partial-thickness skin wounds: comparative study of the effects of Er:YAG and Ho:YAG lasers.

BACKGROUND AND OBJECTIVE: The clinical use of lasers to cut and coagulate tissue necessitates a better understanding of how the residual thermal damage affects healing. This study was designed to evaluate the effects of varying degrees of thermal damage on the healing process. STUDY DESIGN, MATERIALS AND METHODS: Partial-thickness lesions were created in guinea pig skin using an Er:YAG laser, a Ho:YAG laser, and a scalpel. To monitor recovery of the stratum corneum, water flux from the wound sites was quantified and histological data obtained for approximately one week. RESULTS: The data indicate an exponential water loss pattern from all wounds. Water flux from the scalpel- and the Er:YAG laser-induced wounds was initially high but decreased rapidly with decay rates (mean +/- SE) of 0.46 +/- 0.01 day-1 and 0.38 +/- 0.01 day-1, respectively. The Ho:YAG laser-induced wounds demonstrated a different pattern of decay with lower water flux values initially and a decay rate of only 0.13 +/- 0.01 day-1. CONCLUSION: Histological and water flux data reveal that Er:YAG laser-induced wounds achieve epidermal integrity only slightly after scalpel-induced lesions, and Ho:YAG laser-induced wounds heal substantially slower and contain more granulation tissue.

Aluminum Silicates↗
PubMed1996

Erbium laser ablation of dental hard tissue: effect of water cooling.

BACKGROUND AND OBJECTIVE: Several lasers have been explored for hard dental tissue applications; used alone they have resulted in potentially harmful temperature increases in the pulp chamber. MATERIALS AND METHODS: An Er:YAG laser (lambda = 2.94 microns) was used to ablate hard dental tissues. Ablation rates with and without a water-cooling spray were measured. Subsequent experiments investigated the cooling effects of the water. Initially single channels were drilled into dentin; further studies involved ablating rectangular areas with repetition rates up to 10 Hz. RESULTS: The water spray minimally reduced the ablation rates of dentin and did not affect the ablation rates of enamel. The water spray effectively cooled the teeth; while using the maximum average power investigated (10 Hz, 360 mJ/pulse), a water flow rate of 4.5 ml/min limited the temperature rise in the pulp chamber to less than 3 degrees C. CONCLUSION: The studies confirm the feasibility of using an Er:YAG laser in conjunction with a water spray to safely and effectively remove hard dental tissues.

Cold Temperature↗
PubMed1996

Inspiratory muscle endurance in patients with chronic heart failure.

OBJECTIVE: To assess the significance of changes in respiratory muscle endurance in relation to respiratory and limb muscle strength in patients with mild to moderate chronic heart failure using a threshold loading technique. SUBJECTS: 20 patients with chronic heart failure (17 male) aged 63.8 (SD 7.4) years and 10 healthy men aged 63.1 (5.6) years. Heart failure severity was New York Heart Association (NYHA) grade II (n = 11) and NYHA grade III/IV (n = 9). METHODS: Respiratory muscle strength was measured from mouth pressures during maximum inspiratory effort (MIP) at functional residual capacity (FRC) and limb muscle strength was measured using a hand grip dynamometer. Inspiratory muscle endurance was measured using a threshold loading technique. The total endurance duration, the maximum threshold pressure achieved (P-Max), and the inspiratory load (% ratio of P-Max/MIP) were recorded in all subjects. RESULTS: Inspiratory muscles were weaker in patients with heart failure than in the controls [MIP 53.6 (16.5) v 70.9 (20.2) cm H2O, P < 0.05]. Hand grip strength was similar in both subject groups [31.6 (SD) v 36.1 (15.9) dynes]. Total endurance duration was significantly reduced in the patient group [494 (223) v 996 (267) s, P < 0.01], as was the maximal threshold pressure achieved [P-Max 18.5 (6.4) v 30.7 (6.6) cm H2O, P < 0.01]. When expressed as a percentage of MIP, P-Max was also lower in the patients [35.2 (11.8) v 44.8 (11.4)%, P < 0.05]. There was no significant correlation between any measure of endurance and limb muscle strength. CONCLUSIONS: Respiratory muscle endurance is reduced in patients with chronic heart failure. These changes probably reflect a generalised skeletal myopathy and provide further evidence of respiratory muscle dysfunction in patients with this disease. Respiratory muscle endurance needs now to be related to symptoms and the effects of treatment and respiratory muscle training should also be explored.

Chronic Disease↗
PubMed1996

Shear strength of composite bonded to Er:YAG laser-prepared dentin.

An Er:YAG laser coupled with a cooling stream of water effectively removes dental hard tissues. However, before such a system can be deemed clinically viable, some safety and efficacy issues must be addressed. We compared the bonding of composite to dentin following the preparation of the dentinal surface with either an Er:YAG laser (lambda = 2.94 microns) or a standard dental bur and with and without a subsequent acid-etching treatment. The crowns of extracted human molars were removed, revealing the underlying dentin. We removed an additional thickness of material with either a dental handpiece or an Er:YAG laser (350 mJ/pulse at 6 Hz) by raster-scanning the samples under a fixed handpiece or laser. Comparable surface roughnesses were obtained. Several samples from each group received an acid-conditioning treatment. A cylinder of composite was bonded onto the prepared surfaces. The dentin-composite bond was then shear-stressed to failure on a universal testing apparatus. The results indicate that laser-irradiated samples had improved bond strengths compared with acid-etched and handpiece controls. SEM photographs of the surfaces show exposed tubules following the laser treatment: tubules could also be exposed with acid etching. We conclude that Er:YAG laser preparation of dentin leaves a suitable surface for strong bonding or an applied composite material.

Acid Etching, Dental↗
PubMed1995

Lasers in dentistry.

Since the development of the ruby laser by Maiman in 1960, there has been great interest among dental practitioners, scientists, and patients to use this tool to make dental treatment more pleasant. Oral soft tissue uses are becoming more common in dental offices. The possible multiple uses of lasers in dentistry, beyond soft tissue surgery and dental composite curing, unfortunately, have not yet been realized clinically. These include replacement of the dental drill with a laser, laser dental decay prevention, and laser decay detection. The essential question is whether a laser can provide equal or improved treatment over conventional care. Safe use of lasers also must be the underlying goal of proposed or future laser therapy. With the availability and future development of different laser wavelengths and methods of pulsing, much interest is developing in this growing field. This article reviews the role of lasers in dentistry since the early 1960s, summarizes some research reports from the last few years, and proposes what the authors feel the future may hold for lasers in dentistry.

Adult↗
PubMed1995

Haemodynamic and hormonal response to a stream of cooled air.

Many patients with angina note that their symptoms deteriorate in cold weather, although the precise physiological mechanism that explains this remains unclear. Exposure of the face to cool winds may be a contributory factor. The cardiovascular and hormonal response to a localised stream of room (22 degrees C) and cold (4 degrees C) air during submaximal treadmill exercise was therefore studied in nine normal subjects. Cardiac output and respiratory gases were measured with a mass spectrometer, using the indirect Fick principle. Blood samples were taken for plasma noradrenaline. A localised stream of air at 5 m.s-1 produced significant cardiovascular effects at rest, some of which persisted during exercise. In response to cold air, stroke volume, cardiac output, blood pressure and oxygen uptake increased (all P < 0.05). There was a trend towards a reduction in heart rate at rest and increase in plasma noradrenaline. Room air caused a reduction in blood pressure (P = 0.01) but stroke volumes and oxygen uptake were unchanged. The results of this study demonstrate significant cardiovascular effects of a cooled air facial stimulus at rest and during exercise. They may, in part, explain the effects of cold winds on patients with angina.

Adult↗
PubMed1995

Effects of captopril and oxygen on sleep apnoea in patients with mild to moderate congestive cardiac failure.

OBJECTIVES: To determine the effects of captopril and oxygen on sleep quality in patients with mild to moderate cardiac failure. DESIGN: An open observational study. PATIENTS: 12 patients with New York Heart Association class II-III heart failure were studied at baseline. 9 of these patients were then examined at the end of 1 month of treatment with captopril; 9 of the patients were separately assessed during a single night of supplementary oxygen. MAIN OUTCOME MEASURES: Sleep patterns by polysomnography, overnight oximetry, and subjective sleep assessment using visual analogue scores. RESULTS: Abnormal sleep was present in all baseline studies. Complete polysomnograms after treatment with captopril were obtained in 8 patients. Light sleep (stages 1 and 2) was reduced (mean (SEM) 61%(8)% to 48%(6)% actual sleep time, P < 0.05) but slow wave (stages 3 and 4) and REM (rapid eye movement) sleep increased (25%(6)% to 31%(5)%, 14%(2)% to 21%(5)% actual sleep time, P < 0.05). Apnoeic episodes (242(59) to 118(30), P < 0.05), desaturation events (171(60) to 73(37), P < 0.05), and arousals (33(5) to 18(3) P < 0.01) were reduced. Visual analogue scores of sleep quality increased 49(5) to 69(5), P < 0.01). Complete polysomnograms were obtained in 7 patients treated with oxygen. Light sleep duration was reduced (55% (7)% to 42%(5)% actual sleep time, P < 0.05) and slow wave sleep increased (30%(5)% to 38%(6)% actual sleep time, P < 0.05). REM sleep duration was not significantly different. Total arousals (33(6)% to 20(2) P < 0.05), desaturation events (140(33) to 38(10), P < 0.01), and apnoeic episodes (212(53) to 157(33), P < 0.05) were reduced. Visual analogue scores of sleep quality were unchanged. CONCLUSIONS: Captopril and oxygen may improve sleep quality and reduce nocturnal desaturation in patients with mild to moderate cardiac failure. Improved sleep quality could explain the reduction in daytime symptoms seen after treatment in patients with chronic heart failure.

Captopril↗
PubMed1995

ACE for whom? Implications for clinical practice of post-infarct trials.

OBJECTIVE: To determine how many lives would be saved if patients were routinely treated with ACE inhibitors after myocardial infarction according to the criteria of four recent major clinical trials, and to estimate the costs and benefits of these approaches. DESIGN: Retrospective survey. SETTING: The Nottingham Health District. PATIENTS: Data from 7855 patients admitted between 1989 and 1990 were combined and the selection criteria of four major clinical trials (AIRE, SAVE, GISSI-3, and ISIS-4) were applied. RESULTS: Of the patients admitted in Nottingham with confirmed myocardial infarcts 39% were eligible for AIRE and 8% for SAVE. In patients with suspected myocardial infarction as defined by the major trials, 60% would have been eligible for GISSI-3 and 63% for ISIS-4. Treating appropriate patients in accordance with these trials would have saved 20 (AIRE), 3 (SAVE), 4 (GISSI-3) and 5 (ISIS-4) lives each year in Nottingham at a drug cost of 5400 pounds, 33 pounds 791, 2730 pounds, and 4116 pounds per life per year saved respectively. CONCLUSIONS: Short-term treatment with ACE inhibition appears to be cheaper but such an approach would save fewer lives. The AIRE study is the most applicable to current clinical practice but ACE inhibitors should be offered routinely to patients satisfying the criteria of any of the four major clinical trials.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

Failure of "effective" treatment for heart failure to improve normal customary activity.

OBJECTIVES: To examine the effects of drug treatment on laboratory exercise tests in relation to measures of daily activity in patients with chronic heart failure. SETTING: University teaching hospital. SUBJECTS: 18 patients with mild to moderate chronic heart failure (New York Heart Association functional class II-III) and 10 age matched healthy controls. METHODS: Assessments were made before and after 12 weeks of vasodilator drug treatment. Exercise capacity was measured during two different types of treadmill exercise, one using a ramp protocol and the other a fixed work load. Corridor walk tests at three self selected speeds were also undertaken and measures of customary activity assessed from pedometer scores. RESULTS: Exercise times were significantly increased from baseline (P < 0.01) with both treadmill protocols after 12 weeks of drug treatment, with a positive correlation between the duration of treadmill exercise for both protocols (r = 0.69, P < 0.01). Corridor walk tests of 100 m at a self selected slow speed also improved (P < 0.02) but these did not correlate with the changes in treadmill exercise time. The pedometer scores of the patients with heart failure were greatly reduced compared with those of the controls (258 (45) x 10(2) v 619 (67) x 10(2) steps/week, P < 0.001) and after 12 weeks of treatment were unchanged (261 (42) x 10(2) steps/week). CONCLUSIONS: These data confirm the need to use different exercise protocols when assessing the benefits of drug treatment in patients with chronic heart failure. Treatments that seem effective with conventional laboratory based exercise tests may not improve daily activities. This may reflect a failure of apparently successful treatment and should be considered when interpreting clinical trials.

Activities of Daily Living↗
PubMed1994

Effect of the dynamic optical properties of water on midinfrared laser ablation.

Water is a primary tissue chromophore in the midinfrared. Absorption of midinfrared radiation by water is a function of temperature and pressure, both of which rise rapidly during an ablative laser pulse. Data show that the absorption coefficient of water changes, by as much as two orders of magnitude, during a high-irradiance laser pulse. We present an ablation model that is fundamentally based upon Beer's Law but considers changes in the absorption coefficient. The model predicts that Er:YAG laser cuts will be deeper than Er:YSGG laser cuts; an opposite prediction would be made based upon the static, low-intensity absorption coefficient of water. The results of in vitro ablation of skin confirm that the dynamic optical properties of tissue need to be considered in the understanding of laser ablation as well as the design, manufacture, use, and regulation of clinical laser systems.

Animals↗
PubMed1994

Er:YAG laser ablation of prairie dog gallbladder epithelium for the prevention of gallstones.

We hypothesized that laser ablation of gallbladder epithelium would prevent gallstone formation in prairie dogs. An Er:YAG laser (lambda = 2.94 microns) was used to ablate the gallbladder epithelium of 24 prairie dogs; 20 sham-irradiated and 12 non-operated prairie dogs served as controls. Prairie dogs were sacrificed at time periods of 4 days, 2 weeks, and 8-12 weeks and evaluated for the presence of gallstones and cholesterol crystals. Laser-irradiated gallbladders demonstrated a lower rate of gallstone formation at 8-12 weeks than the sham-irradiated gallbladders (39% vs. 79%: P < .02). Crystal formation, however, was not different between laser-irradiated (88%) and sham-irradiated (100%) animals. The laser-irradiated group had less epithelium than the non-operated group at all time periods (P < or = .002) and compared to the sham-irradiated group at 4 days and 8-12 weeks (P < or = .001). These data suggest that laser ablation of gallbladder epithelium can reduce the rate of gallstone formation although this effect may be temporary.

Aluminum Silicates↗
PubMed1994

Unruptured aneurysm of the left sinus of Valsalva presenting with atrial fibrillation.

Congenital aneurysms arising from the left sinus of Valsalva are extremely uncommon, and when unruptured often asymptomatic. Abnormalities of rhythm are more commonly associated with dilatation of the right coronary sinus although the reason for this is unclear. We report the first case of an unruptured aneurysm involving the left sinus of Valsalva presenting with paroxysmal atrial fibrillation. Two-dimensional echocardiography confirmed the diagnosis.

Adult↗
PubMed1994

Pharmacokinetics of hydroxyurea in nude mice.

Extrachromosomal DNA is the predominant form of gene amplification in human tumors. Hydroxyurea (HU) concentrations of 100-150 microM have been promising in vitro for extrachromosomal DNA elimination. The study objective was to determine the HU dose-concentration relationship in nude mice with HU doses from 0 to 200 mg/kg. For HU t1/2 determination, mice were injected with HU 100 mg/kg. A plasma concentration of 159 microM was achieved and a t1/2 of 11.3 min determined. Based on these findings, In vivo elimination studies will require frequent administration of HU to maintain plasma concentrations from 100 to 150 microM.

Animals↗
PubMed1994

ERISA estoppel: say what you mean and mean what you say.

Estoppel is rapidly becoming part of ERISA litigation. However, as employers, TPAs and other entities associated with ERISA plans learn to take precautions against erroneous representations, estoppel litigation may subside.

Health Benefit Plans, Employee↗
PubMed1993

Double minutes are frequently found in ovarian carcinomas.

Double minutes (dmins) are acentric chromosomal-like entities that are important in the etiology of cancer because they are known to harbor amplified oncogenes and drug resistance genes. Because dmins can be unequally partitioned at mitosis they have the ability to confer genetic diversification rapidly. Selective pressures operative in vitro may be quite different than those in vivo; therefore, tumor cells which harbor dmins could be selected against during short-term in vitro propagation. We wanted to determine the incidence of dmins in human ovarian cancer cells obtained from fresh ovarian specimens with an absolute minimum of culture time (6-24 hours). In "direct" chromosomal preparations obtained from these clinical specimens we found dmins present in 88% of these samples. This remarkable finding that dmins are found so frequently in ovarian cancers underscores the importance of gene amplification in human tumor biology. Therefore, the presence of dmins in patient specimens indicates that these unstable genetic elements may play a significant role in the maintenance or progression of malignancy.

Ascites↗
PubMed1993

Evidence of gene amplification in the form of double minute chromosomes is frequently observed in lung cancer.

Amplification of cellular proto-oncogenes, important in tumor progression, has been correlated with a poor clinical outcome in a variety of human tumor types. Amplified genes are observed in two cytogenetically distinct entities, double minutes (DMs) and homogeneously staining regions (HSR). We examined 54 fresh lung tumor specimens obtained from patients with non-small cell lung cancer for cytogenetic evidence of gene amplification in the form of DMs. The majority of these patients had received no prior treatment. The cells were harvested within 24 hours after receiving the specimens, and the slides were stained with Giemsa to specifically look for DMs. We found DMs in 24 of 31 (77%) specimens that exhibited metaphase spreads. Similar incidences of DMs were found when histologic cell types, primary vs. non-primary tumors, and specimens from patients with prior treatment vs. no prior treatment were compared. Therefore, DMs occur frequently in non cultured lung tumor cells, providing evidence that gene amplification may be an important aspect of tumor behavior in patients with non-small cell lung carcinoma. Further investigation is warranted to identify the specific tumor-related genes located on these abnormal chromosomes. This also suggests that ongoing efforts to eliminate amplified drug-resistant genes or oncogenes contained on DMs in tumor cells may be relevant in patients with non-small cell lung cancer.

Carcinoma, Non-Small-Cell Lung↗
PubMed1993

The effect of lasers on dental hard tissues.

There is a quest to find a method to remove diseased and healthy dental hard tissues without the negative stimuli associated with dental handpieces. Today, lasers are being considered as a potential replacement. This report evaluates effects of three lasers on dentin and pulpal tissues. The Er:YAG laser appears to have a lesser thermal effect.

Absorption↗