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Biomedical subjects

R Weller

Publications and source records attributed to R Weller.

At least 55 records · Page 3Linked to original sources
PubMed1997

Succession and convergence of biofilm communities in fixed-film reactors treating aromatic hydrocarbons in groundwater.

Community composition, succession, and performance were compared in three fluidized bed reactors (FBR) operated to test preemptive colonization and the influence of toluene compared with a mixture of benzene, toluene, and p-xylene (BTX) as feeds. One reactor was inoculated with toluene-degrading strains Pseudomonas putida PaW1, Burkholderia cepacia G4, and B. pickettii PKO1. PaW1 outcompeted the other two strains. When groundwater strains were allowed to challenge the steady-state biofilm developed by inoculated strains, they readily displaced the inoculated strains and further reduced the toluene effluent concentration from 0.140 to 0.063 mg/liter for 98% removal. Amplified ribosomal DNA restriction analysis (ARDRA) of reactor community DNA showed a succession of populations to a pattern that was stable for at least 4 months of operation. Parallel reactors fed toluene and BTX but inoculated directly from groundwater had the same treatment performance and the same ARDRA profiles as each other and as the seeded reactor once the groundwater community took over. Convergence and stability of populations were confirmed by genotype analysis of 120 isolates taken from all reactors and at several times. Ninety percent of the isolates were of 4 of the 12 genotypes found, and their ARDRA patterns accounted for most of the community ARDRA patterns. Estimates of the maximum specific growth rates (mu max), half-saturation constants (K(m)), and maximum substrate utilization rates (Vmax) of the 12 genotypes isolated revealed a rather high diversity of toluene use kinetics even though the toluene in the feed was constant. The climax populations, however, generally showed kinetic parameters indicative of greater competitiveness than the inocula. rRNA sequence analysis of three codominant strains showed them to be members of the alpha, beta, and gamma subdivisions of the Proteobacteria. Two were similar to Comamonas and Pseudomonas putida, but the member of the alpha group was somewhat distant from any organism in the rRNA database. The convergence of communities to the same composition from three different starting conditions and their constancy over several months suggests that a rather stable community was selected.

Biodegradation, Environmental↗
PubMed1997

Nitric oxide--a newly discovered chemical transmitter in human skin.

Nitric oxide (NO) is synthesized by many cells in the body. Low concentrations of NO have homeostatic roles in the circulation and nervous system, whereas high concentrations are biocidal, cytocidal and have immunomodulatory roles. The place of NO in the skin has recently become the focus of much attention, and this review highlights studies on the part played by NO in health and disease.

Dermatitis↗
PubMed1996

Morphology and neuropathology of the pelvic floor in patients with stress incontinence.

Urinary incontinence imposes a considerable workload on urological and gynecological practice. Many treatments exist, but recurrent stress incontinence remains a significant problem and the reasons remain unclear. Pathological and electrophysiological studies have shown that significant pelvic nerve damage and consequent denervation and reinnervation are associated with stress incontinence, and furthermore there are collagenous changes in the pelvic floor which are related to childbirth, endogenous hormone changes and the effects of increasing age. These changes include increased nerve fiber density and pudendal nerve terminal motor latency, hypertrophy of fiber types 1 and 2, type 1 fiber predominance and fiber type grouping. Connective tissue changes involve a reduction in hydroxyproline excretion, increased cross-linking and increased muscle collagen. It is only through a better understanding of the anatomy and pathophysiology of the pelvic floor that we will be able to improve outcome in women with stress incontinence and identify patients that may not be appropriate for surgical therapy. This paper reviews recent advances in the understanding of the etiology of stress incontinence.

Age Factors↗
PubMed1996

Nitric oxide is generated on the skin surface by reduction of sweat nitrate.

Nitric oxide (NO) is known to be synthesized by mammalian cells from L-arginine by a group of NO synthase enzymes. We now show that NO is generated from human skin and propose a different mechanism of production. Whereas enzymatic NO synthesis is inhibited by monomethyl L-arginine, this arginine analog, when infused into the brachial artery at concentrations sufficient to inhibit endothelial NO synthase activity, has little effect on hand skin NO production. Hand skin NO production is increased by topical acidification of the skin surface and greatly increased by the addition of nitrite solutions. We propose that NO generation from skin derives from sweat nitrite (the concentration of which was found to average 3.4 microM in six subjects) due to chemical reduction consequent to the acidic nature of sweat. Sweat contains nitrate in appreciable amounts, and skin commensal bacteria can synthesize nitrate reductase enzyme. Patients on long-term tetracycline antibiotics showed significantly reduced skin NO synthesis, although topical antiseptic and antibiotics had little effect on NO generation in the short-term. We propose that NO generation from skin is dependent on bacterial nitrate reduction to nitrite and subsequent reduction by acidification. We speculate that this has a physiologic role in the inhibition of infection by pathogenic fungi and other susceptible microorganisms and may affect cutaneous T-cell function, keratinocyte differentiation, and skin blood flow.

Administration, Topical↗
PubMed1996

Bullous pemphigoid and penicillamine.

We describe a woman who developed bullous pemphigoid in association with penicillamine therapy. While pemphigus is a well-recognized complication of penicillamine, pemphigoid should also be considered in the differential diagnosis of bullous eruptions induced by this drug.

Antirheumatic Agents↗
PubMed1995

Left ventricular hemodynamic parameters in the course of acute experimental coxsackievirus B 3 myocarditis.

In susceptible DBA/2 mice coxsackievirus B 3-induced myocarditis leads to inflammatory and necrotic lesions in the myocardium 7-10 days after virus inoculation. The purpose of this study was to determine whether hemodynamic changes occur in murine coxsackievirus B 3 myocarditis and whether they are correlated to histological cardiac lesions throughout the infection. Left ventricular function was determined by open chest puncture of the left ventricle in the course of acute coxsackievirus B 3 infection. Histological cross sections of the heart were stained with hematoxylin/eosin and scored blindly for myocarditic lesions. Left ventricular function was preserved until day 7 post-virus inoculation Left ventricular systolic pressure, +dP/dtmax and -dP/dtmax and heart rate declined significantly from day 7 to day 10. The decrease in these parameters did not correlate with viral concentrations in the heart on the day of hemodynamic measurements. The decrease was related to histological changes on day 10, but not on day 7 of the infection. The data suggest (a) that a cumulative loss of cardiac myofibers, induced either by the virus and/or by immune reactions to the heart, is likely to lead to a late depression of cardiac function, and (b) that there is a weak and only temporary structure-function relationship in the heart in coxsackievirus B 3 myocarditis. Therefore, in addition to an analysis of histological changes, the measurement of cardiac function appears to be very important in order to completely evaluate the severity of myocarditis and the usefulness of any therapy.

Animals↗
PubMed1995

Left ventricular haemodynamics in murine viral myocarditis.

In susceptible DBA/2 mice infection with coxsackievirus B3 leads to severe inflammatory and necrotic lesions in the heart. There is a temporal discrepancy of peak concentrations of replicative virus in the heart and maximal cardiac inflammation. Aims of this study were, first, to determine whether haemodynamic changes occur in coxsackievirus B3-induced murine myocarditis and, second, the time frame in which those alterations may be apparent. By puncture of the left ventricle, pressures and the first derivative dp/dt as parameters of left ventricular function could be obtained on several days of the infection. Haematoxylin-eosin stains of cross-sections of the heart showed the course of inflammatory lesions in the heart; a plaque forming assay assessed virus titres in the heart. Cardiac concentrations of replicative virus peaked on day 3, inflammatory lesions in the heart were maximal on day 7. Left ventricular function was almost preserved until day 5 of the infection, then dropped significantly until day 10. The study suggests that either a cumulative virus-mediated destruction of the myofibres or virally triggered immune reactions to heart cells lead to impairment of left ventricular function.

Animals↗
PubMed1994

Adult Still's disease.

Adult Still's disease (ASD) is a rare disorder of unknown aetiology, characterized by an evanescent, erythematous, maculopapular rash, fever, arthralgia, and a variety of systemic features. We report a case which illustrates the typical features of ASD, and manifests the hitherto unreported complication of diffuse cutaneous mucinosis.

Female↗
PubMed1993

Abnormal ventricular contraction patterns in patients with arrhythmogenic substrates using three-dimensional phase analysis.

Arrhythmogenic substrate diagnosis has been achieved by electrophysiological studies and best localized by successful radiofrequency ablation. Pre-invasive localization procedures have been based on surface ECGs and more recently on biomagnetism, but in addition to these electric and magnetic signals a mechanical signal may be utilized: the initial site of contraction may be detected by phase analysis during radionuclide ventriculography. Generation of three-dimensional data set of phases is achieved by incorporating the new emission tomography technique. The performance of this modified phase analysis has been investigated for the detection of the normal contraction pattern during sinus rhythm, the arrhythmogenic substrate of the WPW syndrome and ventricular tachycardia, and further, to define the limitations of the method in experimental studies on pigs. In 30 out of 44 patients with normal sinus rhythm and no ventricular lesion, a characteristic phase pattern was found. Physiologically, the initial site of contraction appeared to be paraseptal and in the anterior wall of the right ventricle close to the apex. In 13 patients with WPW syndrome and in seven with ventricular tachycardia, the phase data were compared to the electrophysiological study. In 14 of 20 there was a complete match, in 3 of 20 a mechanical focus was found in the area adjacent to the electric focus. From experimental pig studies with simulated stimulation, a spatial precision of at least 20 mm was found at a pre-excitation of 20 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Non-invasive three-dimensional localisation of arrhythmogenic foci in Wolff-Parkinson-White syndrome and in ventricular tachycardia by radionuclide ventriculography: phase analysis of double-angulated integrated single photon emission computed tomography (SPECT).

A new tomographic technique combined with phase analysis was used to detect premature and ectopic ventricular contraction patterns in 15 patients with Wolff-Parkinson-White syndrome and during ventricular tachycardia in seven patients. Data generated by gated single-photon emission computed tomography (SPECT) were analysed by backprojection of the Fourier coefficients, double-angulation, and integration to thick slices containing the ventricles, thus allowing visualisation of the contraction patterns in three perpendicular views. The results were compared with those of catheter mapping. In nine patients with Wolff-Parkinson-White syndrome the site of initial contraction detected was identical with the site of the accessory pathway found by catheter mapping. The sites of origin of the ventricular tachycardias determined by catheter mapping were within 3 cm of the sites detected by the new technique. This new technique seems to be a promising non-invasive method for localising ectopic ventricular activity that will considerably shorten the time required for subsequent invasive procedures.

Adult↗
PubMed1993

Gated blood pool SPECT and phase analysis to assess simulated Wolff-Parkinson-White syndrome in the baboon.

This study assesses the diagnostic potential of a tomographic technique with phase analysis to detect premature electroventricular contraction patterns simulated by pacing in the baboon. The data of gated SPECT were analysed by backprojection of the Fourier coefficients, followed by angulation and integration to thick slices of the entire ventricular mass yielding separate ventricular contraction patterns in three perpendicular views. Electrodes were implanted in each baboon: at the sinoatrial node; posterior, left ventricular; anterior left ventricular; on the left and the right lateral ventricular walls. The atrium was stimulated throughout at a fixed rate. Subsequent ventricular stimuli followed during the QRS complex, such to invoke the appearance of pre-excitation QRS morphology. The first points of activation (FPA) from this algorithm were correctly detected for the RV, for the anterior and posterior sites, although the latter two manifested first points in the RV. LV pacing manifested also as a FPA in the RV, but was followed by a true subsequent point in the LV.

Algorithms↗
PubMed1993

[The noninvasive determination of resting myocardial blood flow in patients using 82 Rb in comparison with the argon method].

Resting myocardial blood flow in absolute units was determined in 11 patients without known heart disease using dynamic PET with 82Rb. Based on a modified Fick's approach to measuring myocardial blood flow, originally developed and validated in canine studies by Herrero and coworkers (Circulation 1990; 82: 1377-86), a global flow value of 0.60 +/- 0.10 ml/min/gr myocardium (MV +/- SD, N = 11) was obtained. With the exception of the apex, segmental blood flow was not significantly different in 12 left ventricular myocardial segments, indicating homogenous myocardial blood flow distribution. In 5 patients global myocardial blood flow was determined simultaneously both by 82Rb PET and argon as inert gas method. 82Rb flow did not differ significantly from argon flow (0.60 +/- 0.05 vs. 0.68 +/- 0.15, MV +/- SD, N.S.). These results show that correct quantitation of resting myocardial blood flow with dynamic 82Rb PET is feasible also in patients.

Adult↗
PubMed1993

[The "white hole" phenomenon--a potential functional parameter in non-gated 201Tl-myocardial scintigraphy].

In 50 patients with a "white hole" in their scintigram--among them 44 patients with a history of myocardial infarction--the relation between its relative volume and the ventriculographically determined ejection fraction was studied retrospectively. A relative volume of the "white hole" larger than 13.7% showed a specificity of 93% and a sensitivity of 45% for a decreased ejection fraction and had a significant correlation of r = -0.54 (alpha = 0.01) with the ejection fraction. Thus the relative volume of the "white hole" derived automatically from 201Tl-SPECT is an easy-to-determine additional parameter which allows an at least semiquantitative statement about the function of the left ventricle.

Adult↗