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Biomedical subjects

R White

Publications and source records attributed to R White.

At least 199 records · Page 11Linked to original sources
PubMed1995

Experience with the second generation UroLume prostatic stent.

OBJECTIVE: To assess the efficacy of the new, second generation UroLume (American Medical Systems) prostatic stent. PATIENTS AND METHODS: Forty-seven men with symptomatic and objective evidence of bladder outflow obstruction who were fit for a transurethral resection accepted, as an alternative, the insertion of a new prostatic stent which shortens less than its predecessor. RESULTS: It was possible to insert the stent into 44 of the 47 men. All patients voided spontaneously following stent insertion. Thirty-three patients had their stent inserted either as a day case or with an overnight stay. Six patients were lost to follow-up and two died. Of the remaining 36 patients 22 have now been followed for 2 years, with a mean obstructive score of 1.6 (range 0-12), a mean irritative score of 2.5 (range 0-10) and a mean peak flow of 16.8 mL/s (range 3-31). Fourteen stents had to be removed; in the majority of cases this was because of stent migration or the development of epithelial hyperplasia within the lumen of the stent. CONCLUSION: Because of the development of epithelial hyperplasia and stent migration in approximately one-third of men in this study, a third generation stent has now been developed. Before permanently implanted stents can be recommended for widespread use, the efficacy of new stents should be assessed in specialist units with large numbers of patients and adequate facilities for follow-up.

Aged↗
PubMed1995

Experience with the Memotherm permanently implanted prostatic stent.

OBJECTIVE: To evaluate the Memotherm (Angiomed) permanently implantable prostatic stent. PATIENTS AND METHODS: Forty-eight men (mean age 70.3 years, range 57-86) with symptoms and urodynamics suggestive of bladder outflow obstruction had a Memotherm stent inserted into the prostatic urethra. Subjective and objective follow-up was performed at 1, 3 and 6 months. RESULTS: All but one patient was eventually able to void. Ten stents have been removed and three patients are awaiting stent removal. Subjective benefits bore no correlation with the maximum urinary flow rate and the findings on cystoscopy. Only 15 of the 48 patients had a satisfactory result. CONCLUSION: Permanently implanted prostatic stents should be considered experimental and only marketed after intensive investigation. As a result of this study, the Memotherm stent is to undergo significant modifications.

Aged↗
PubMed1995

Intraoperative coronary artery dilatation with angioscopic guidance.

The use of intraoperative balloon dilatation during coronary artery bypass surgery has been limited due to relatively unpredictable and potentially damaging results. The development of fiberoptic angioscopy permits safe visualization of the interior of coronary arteries and may be a valuable adjunct to intraoperative balloon dilatation. A 56-year-old male underwent four vessel coronary grafting with progressive intraoperative balloon dilatation of a second more distal stenosis of the left anterior descending coronary artery. Angioscopy was used to determine optimal balloon sizing and allowed visualization of associated intimal changes that occurred during the procedure, resulting in a successful outcome for this patient.

Angioplasty, Balloon, Coronary↗
PubMed1995

The simulation of urban system dynamics in Atlantic Canada, 1951-1991.

"A dynamic urban model is used to study the post-war evolution of the Atlantic Canada urban system. The computer-based simulation model is calibrated for the period 1951-86 and then employed to predict the 1991 population of each CMA and CA within the system. The simulation results show that, to a large extent, the evolution of the system can be understood in terms of endogenous system dynamics rather than exogenous events. Specifically, competition among the cities of the region is a significant factor in the urban system evolution. The high degree of abstraction of the model means that data requirements for application are minimal, and the calibration procedure is relatively simple. The successful predictions show that the model can yield useful results in spite of its simplicity." (SUMMARY IN FRE)

Americas↗
PubMed1995

Peritoneal dialysis complicated by Bipolaris hawaiiensis peritonitis: successful therapy with catheter removal and oral itraconazol without the use of amphotericin-B.

Fungi classified in the genera Bipolaris are an uncommon source of infection in human diseases. It is also a rare source of peritonitis in peritoneal dialysis (PD) patients. All cases of Bipolaris peritonitis reported in the United States have occurred in the southern states. This form of peritonitis appears to have a good prognosis, with cure achieved only after removal of the peritoneal dialysis catheter and antifungal therapy. Systemic or intraperitoneal amphotericin-B with or without oral ketoconazole has been used in all previously reported cases. However, the role of antifungal therapy is unclear. We report a case of Bipolaris hawaiiensis peritonitis in a 73-year-old female on continuous cyclic peritoneal dialysis (CCPD) for 10 months who presented with a nonfunctioning peritoneal catheter. The catheter had characteristic dark gray particles, each composing a fungal ball within the lumen of the catheter. Microscopic examination confirmed the organism attached to the inner wall of the catheter. The patient achieved cure without using either amphotericin-B or ketoconazole. She was treated with removal of the catheter and a 2-week course of oral itraconazole 100 mg twice daily. A new catheter was placed after 1 month and the patient continued to do well on CCPD 12 months later with no evidence of recurrent infection. We conclude that (1) itraconazole can effect cure following removal of the catheter without using amphotericin-B or ketoconazole; (2) peritoneal dialysis can be safely reinstituted after itraconazole therapy for this uncommon fungal infection, and (3) itraconazole therapy allows for out-patient treatment of B. hawaiiensis peritonitis in peritoneal dialysis patients.

Administration, Oral↗
PubMed1995

Predictors of the effect of heparin during cardiac catheterization.

This study was designed to determine if the activated partial thromboplastin time (aPTT) present at the end of a diagnostic cardiac catheterization was correlated with specific patient or procedure characteristics. No relationship between time from heparin bolus and the aPTT was found. Age, weight and body surface area were found to influence the aPTT at catheterization completion (p < 0.05). Patient sex, height, smoking status, hematocrit, and type and volume of contrast used were not correlated with aPTT at the end of catheterization. This suggests possible usefulness of the age and weight of patients to guide the dose of heparin used at cardiac catheterization.

Age Factors↗
PubMed1995

The effect of education on the incidence of dementia and Alzheimer's disease in the Framingham Study.

OBJECTIVE: To evaluate whether low educational attainment is a risk factor for the incidence of dementia and Alzheimer's disease (AD) in the Framingham Study and to determine whether age at onset of dementia is earlier in persons with low educational levels. DESIGN: A community-based cohort was studied longitudinally for the development of dementia. Diagnosis was made according to strict criteria by two neurologists and a neuropsychologist. Subtype of dementia and year at onset were determined. Incidence rates were compared in three education groups: < grade school, < high school, and > or = high school. PARTICIPANTS: A total of 3,330 men and women aged 55 to 88 years. RESULTS: During 17 years of follow-up, 258 incident cases of dementia, including 149 AD cases, were identified. Unadjusted incidence rates were significantly elevated (p < 0.05) for dementia and non-AD dementia among the least educated. The age-adjusted relative risk for subjects with a grade school education or less compared with those who earned a high school diploma was 1.31 (95% confidence interval [CI], 0.90 to 1.90) for dementia generally, 1.04 (95% CI, 0.62 to 1.74) for AD, and 1.75 (95% CI, 1.03 to 2.98) for non-AD dementia. Age at onset of dementia did not vary by educational attainment. CONCLUSIONS: After age adjustment, low educational attainment was not a significant risk factor for the incidence of dementia generally or of AD. Low educational attainment was associated with increased risk of non-AD dementia, perhaps because of deleterious smoking habits and other risk factors for stroke in the least-educated individuals. Adequately adjusting for age and examining subtypes of dementia are important in assessing the influence of education on dementia incidence.

Age of Onset↗
PubMed1995

Feeding behavior in the nocturnal moth Manduca sexta is mediated mainly by blue receptors, but where are they located in the retina?

The spectral sensitivity of nectar feeding by adults of the tobacco hawkmoth Manduca sexta was measured in free-choice experiments. The action spectrum displayed a narrow peak at 450 nm and a low secondary maximum at 560 nm. Thus, the feeding response is mediated primarily by blue-sensitive receptors containing the Manduca sexta photopigment P450, while green-sensitive receptors containing P520 play a minor role. A minimum at 500 nm separating the two peaks suggests mutual inhibition between green and blue receptors or negative interaction more proximally in the visual system. The action spectrum drops off abruptly at 400 nm, in accordance with an earlier finding that ultraviolet wavelengths, discerned by receptors containing P357, obstruct the feeding response. The spectral sensitivity of the Manduca sexta compound eye, determined by electroretinogram recordings, and earlier visual pigment measurements indicate that approximately 75 % of the receptors are green-sensitive, with the remainder divided between blue- and ultraviolet-sensitive cells. The distribution of receptor types in small areas of the retina was measured by their ultrastructural response to light. Green and ultraviolet receptors were found, but not the blue receptors that dominate the feeding response. Possibly they are concentrated in a particular region of the retina that has not yet been found.

Journal Article↗
PubMed1995

A variety of environmentally persistent chemicals, including some phthalate plasticizers, are weakly estrogenic.

Sewage, a complex mixture of organic and inorganic chemicals, is considered to be a major source of environmental pollution. A random screen of 20 organic man-made chemicals present in liquid effluents revealed that half appeared able to interact with the estradiol receptor. This was demonstrated by their ability to inhibit binding of 17 beta-estradiol to the fish estrogen receptor. Further studies, using mammalian estrogen screens in vitro, revealed that the two phthalate esters butylbenzyl phthalate (BBP) and di-n-butylphthalate (DBP) and a food antioxidant, butylated hydroxyanisole (BHA) were estrogenic; however, they were all less estrogenic than the environmental estrogen octylphenol. Phthalate esters, used in the production of various plastics (including PVC), are among the most common industrial chemicals. Their ubiquity in the environment and tendency to bioconcentrate in animal fat are well known. Neither BBP nor DBP were able to act as antagonists, indicating that, in the presence of endogenous estrogens, their overall effect would be cumulative. Recently, it has been suggested that environmental estrogens may be etiological agents in several human diseases, including disorders of the male reproductive tract and breast and testicular cancers. The current finding that some phthalate compounds and some food additives are weakly estrogenic in vitro, needs to be supported by further studies on their effects in vivo before any conclusions can be made regarding their possible role in the development of these conditions.

Animals↗
PubMed1995

An investigation into sound attenuation by earmould tubing.

A major problem in high-gain post-aural hearing aids is acoustic feedback. One of the sources of feedback is the plastic tubing that guides the sound from the hearing aid hook to the ear canal. The objectives of this study were to determine the effects of increases in tubing wall thickness on the amount of acoustic feedback in the hearing aid system and to characterize earmould tubing. Five different samples of Tygon tubing were tested, of which four had different wall thicknesses; the study also compared Tygon tubing with medical grade PVC tubing. Measurement of the wall thickness, taken from scanning electron micrographs, showed that the wall thickness differed from the National Association of Earmould Laboratories standard by less than 6% and was well within the manufacturer's tolerances. Measurement of sound attenuation showed that an increase in the tubing wall thickness of 0.330 mm (Tygon 13 Standard to Tygon 13 Double Wall) caused an increase in sound attenuation of 2 dB, across the frequency range measured (0.5-4 kHz). It was also found that the medical grade PVC had a 5 dB greater sound attenuation than the equivalent Tygon tubing. While these differences are quite small, they could contribute to a reduction in acoustic feedback when used in conjunction with other hearing aid or earmould improvements.

Acoustics↗
PubMed1995

Performance characteristics for the quantitation of plasma HIV-1 RNA using branched DNA signal amplification technology.

Highly sensitive assays that quantitate human immunodeficiency virus type 1 (HIV-1) RNA may be valuable for clinical research and the treatment of HIV-1-infected patients. In this study we evaluated the reproducibility and accuracy of the first-generation branched DNA (bDNA-1.0) signal amplification assay under conditions that are relevant to routine use in a clinical context. We show that the bDNA-1.0 assay was able to discern two- to three-fold changes in plasma HIV-1 RNA levels as significant. Reverse transcription coupled to polymerase chain reaction (RT-PCR) was less reproducible and required a 3.7- to 5.8-fold change in plasma HIV-1 RNA levels to be statistically significant. The accuracy of the bDNA-1.0 assay in RNA quantitation was not affected by HIV-1 genotypic variation or by the presence of hemoglobin, bilirubin, lipemia, or any of a dozen therapeutic drugs. Using the bDNA-1.0 assay, we show that HIV-1 RNA levels in plasma specimens were stable when stored at -80 degrees C and were able to withstand at least three freeze-thaw cycles without significant loss. We also examined the performance of an ultrasensitive bDNA assay with improvements to the signal amplification technology. The ultrasensitive bDNA assay displayed a quantitation limit of approximately 500 RNA Eq/ml, yet maintained a dynamic quantitation range up to 1.6 x 10(6) RNA Eq/ml. Like the bDNA-1.0 assay, the ultrasensitive bDNA assay was not affected by HIV-1 genotype variability.

Anticoagulants↗
PubMed1995

Helping the patient in denial: the role of the family in intervention.

Physicians can play a critical role in influencing patients to seek appropriate treatment for alcoholism and drug dependence. These illnesses are characterized by denial, which may prevent patients from seeking treatment on their own. This article discusses the role of the family in intervening with chemically dependent patients. It is important to gain input from family members in order to make a clear diagnosis and to influence the patient to seek treatment. The family intervention model developed by Vernon Johnson is used to understand the principles for intervening with chemically dependent patients. Three basic tasks for physicians treating chemically dependent patients are reviewed.

Alcoholism↗
PubMed1995

A strategy for constructing high-resolution genetic maps of the human genome: a genetic map of chromosome 17p, ordered with meiotic breakpoint-mapping panels.

Genetic linkage analyses with genotypic data obtained from four CEPH reference families initially assigned 24 new PCR-based markers to chromosome 17 and located the markers at specific intervals of an existing genetic map of chromosome 17p. Each marker was additionally genotyped with an ordered set of obligate, phase-known recombinant chromosomes. The breakpoint-mapping panels for each family consisted of two parents, one sib with a nonrecombinant chromosome, and one or more sibs with obligate recombinant chromosomes. The relative order of markers was determined by sorting segregation patterns of new markers and ordered anchor markers and by minimizing double-recombination events. Consistency of segregation patterns with multiple flanking loci constituted support for order. A genetic map of chromosome 17p was completed with 39 markers in 23 clusters, with an average space of 3 cM between clusters. The collection of informative genotypes was highly efficient, requiring fivefold fewer genotypes than would be collected with all the CEPH families. Given the availability of large numbers of highly informative PCR-based markers, meiotic breakpoint mapping should facilitate construction of a human genomic map with 1-cM resolution.

Base Sequence↗
PubMed1995

Breakpoint analysis: precise localization of genetic markers by means of nonstatistical computation using relatively few genotypes.

Placing new markers on a previously existing genetic map by using conventional methods of multilocus linkage analysis requires that a large number of reference families be genotyped. This paper presents a methodology for placing new markers on existing genetic maps by genotyping only a few individuals in a selected subset of the reference panel. We show that by identifying meiotic breakpoint events within existing genetic maps and genotyping individuals who exhibit these events, along with one nonrecombinant sibling and their parents, we can determine precise location for new markers even within subcentimorgan chromosomal regions. This method also improves detection of errors in genotyping and assists in the observation of chromosome behavior in specific regions.

Algorithms↗
PubMed1994

Demonstration of in vitro infection of chimpanzee hepatocytes with hepatitis C virus using strand-specific RT/PCR.

Analysis of hepatitis C virus (HCV) replication has been hampered due to the difficulty encountered in in vitro cultivation of the virus in conventional tissue culture systems. In this study, primary chimpanzee hepatocyte cultures maintained in a serum-free medium formulation were susceptible to in vitro infection with HCV. In order to document infection, two new methods of reverse transcription/polymerase chain reaction were developed that permit accurate distinction between positive and negative strand HCV RNA. One method relied upon the use of a tagged cDNA primer, while the second method employed a thermostable reverse transcriptase. Following inoculation of chimpanzee hepatocytes with HCV, intracellular positive and negative strand HCV RNA were detectable 4 days postinfection and throughout the remainder of the experimental period, 25 days. Analysis of HCV-inoculated baboon hepatocytes revealed a total absence of negative strand HCV RNA, while residual positive strand RNA from the inoculum could be detected for up to 11 days. The in vitro replication of HCV RNA in chimpanzee hepatocytes could be suppressed by alpha-interferon. This system should be amenable to the study of HCV replication, antiviral compounds, and the development of neutralization assays.

Animals↗
PubMed1994

Physical localization of microsatellite markers at the ataxia-telangiectasia locus at 11q22-q23.

The autosomal recessive disorder ataxia-telangiectasia (A-T) is genetically heterogeneous, with four complementation groups. The genes for the two major groups (ATA and ATC) have been mapped to 11q22-q23. Genetic analysis of the disease has been conducted to date using biallelic polymorphisms. We have physically mapped to this region eight new microsatellite markers that were generated by three laboratories that construct whole-genome linkage maps. These markers should be valuable for refined localization and positional cloning of the A-T genes and for diagnostic purposes. The results demonstrate the value of integrating genetic and physical maps generated by different laboratories.

Ataxia Telangiectasia↗