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Biomedical subjects

P Rapp

Publications and source records attributed to P Rapp.

At least 19 recordsLinked to original sources
PubMed2003

[Bilateral uveitis with definitive hypotony caused by systemic cidofovir].

We report the case of a 52-year-old man with AIDS and CMV bilateral retinitis, treated first with ganciclovir (cymevan) and then with cidofovir. During the treatment, the patient complained of a sharp decrease in visual acuity. Cycloplegics and topical corticosteroids were given. Then cidofovir was stopped and replaced with intravenous Foscavir because of the clinical inefficacy. The anterior uveitis resolved but the ciliary secretion has not stopped after 12 months of follow-up. The patient presented +11 hypermetropia with a choroidal edema and bilateral cataract. This case is interesting for its permanent hypotony and bilateral uveitis. A literature search has brought out a rate of only 3% of chronic hypotony. We hypothesize bilateral iatrogenic ciliary body necrosis, as described in the animal models.

AIDS-Related Opportunistic Infections↗
PubMed2001

Multiphasic kinetics of transformation of 1,2,4-trichlorobenzene at nano- and micromolar concentrations by Burkholderia sp. strain PS14.

The transformation of 1,2,4-trichlorobenzene (1,2,4-TCB) at initial concentrations in nano- and micromolar ranges was studied in batch experiments with Burkholderia sp. strain PS14. 1,2,4-TCB was metabolized from nano- and micromolar concentrations to below its detection limit of 0.5 nM. At low initial 1,2,4-TCB concentrations, a first-order relationship between specific transformation rate and substrate concentration was observed with a specific affinity (a(0)(A)) of 0.32 liter. mg (dry weight)(-1). h(-1) followed by a second one at higher concentrations with an a(o)(A) of 0.77 liter. mg (dry weight)(-1). h(-1). This transition from the first-order kinetics at low initial 1,2,4-TCB concentrations to the second first-order kinetics at higher 1,2,4-TCB concentrations was shifted towards higher initial 1,2,4-TCB concentrations with increasing cell mass. At high initial concentrations of 1,2,4-TCB, a maximal transformation rate of approximately 37 nmol. min(-1). mg (dry weight)(-1) was measured, irrespective of the cell concentration.

Biodegradation, Environmental↗
PubMed1999

Degradation of chlorobenzenes at nanomolar concentrations by Burkholderia sp. strain PS14 in liquid cultures and in soil.

The utilization of 1,2,4,5-tetrachloro-, 1,2,4-trichloro-, the three isomeric dichlorobenzenes and fructose as the sole carbon and energy sources at nanomolar concentrations was studied in batch experiments with Burkholderia sp. strain PS14. In liquid culture, all chlorobenzenes were metabolized within 1 h from their initial concentration of 500 nM to below their detection limits of 0.5 nM for 1,2,4,5-tetrachloro- and 1,2,4-trichlorobenzene and 7.5 nM for the three dichlorobenzene isomers, with 63% mineralization of the tetra- and trichloroisomers. Fructose at the same initial concentration was, in contrast, metabolized over a 4-h incubation period down to a residual concentration of approximately 125 nM with 38% mineralization during this time. In soil microcosms, Burkholderia sp. strain PS14 metabolized tetrachlorobenzene present at 64.8 ppb and trichlorobenzene present at 54.4 ppb over a 72-h incubation period to below the detection limits of 0.108 and 0.09 ppb, respectively, with approximately 80% mineralization. A high sorptive capacity of Burkholderia sp. strain PS14 for 1,2,4, 5-tetrachlorobenzene was found at very low cell density. The results demonstrate that Burkholderia sp. strain PS14 exhibits a very high affinity for chlorobenzenes at nanomolar concentrations.

Biodegradation, Environmental↗
PubMed1996

Traumatic and non-traumatic pancreatitis in pediatric surgery.

Today pancreatitis is classified only as acute or chronic. In pediatric surgery it seems more practical to distinguish traumatic from non-traumatic cases. To show whether there is also a difference in the management of these two groups we analysed all patients treated between 1977 and 1991 for pancreatitis. It was most impressive that traumatic cases were operated on in 86% and the rate of pseudocysts reached 61.5% whereas non-traumatic pancreatitis required surgical intervention in 50% and developed pseudocysts in 17%. Following trauma elevation of serum enzyme concentration lasted longer in a significant number of patients but became normal without any hint of further complications. In non-traumatic pancreatitis it is recommended that surgery should be avoided and reserved for complications. Exceptions are obstructions of the pancreaticobiliary ducts which need early removal to prevent chronicity of the disease and functional loss of the organ.

Abdominal Injuries↗
PubMed1992

Formation, separation and characterization of three beta-1,3-glucanases from Sclerotium glucanicum.

The appearance of beta-1,3-glucanases in supernatants of Sclerotium glucanicum cultures was followed by SDS-PAGE and shown to be dependent on cultivation time. Three beta-1,3-glucanases were isolated and purified. Glucanase I and III appeared homogeneous on SDS-PAGE with molecular masses of 85 and 33.5 kDa, respectively. Enzyme I was an endo-splitting beta-1,3-glucanase. In hydrolyzing laminarin it released glucose, laminaritriose and laminaribiose as major endproducts and smaller amounts of higher oligosaccharides. Enzyme III was an exo-beta-1,3-glucanase removing glucose from laminarin and gentiobiose and glucose from scleroglucan. For laminarin as substrate the Km of enzyme I and III was 2.5 and 3.33 mg/ml, respectively. Enzyme II was only partially purified and found to be also an exo-beta-1,3-glucanase, releasing glucose as the only hydrolysis product from laminarin. It did not attack scleroglucan. Its molecular weight was determined to be 78 kDa. Optimum pH and temperature of the three enzymes were determined. The three activities were significantly inhibited by 1 mM Hg2+.

Electrophoresis, Polyacrylamide Gel↗
PubMed1991

Properties of the polyalcohol prepared from the beta-D-glucan schizophyllan by periodate oxidation and borohydride reduction.

The structure of the title polyalcohol was confirmed by 13C-n.m.r. spectroscopy. The polyalcohol was more soluble in water than schizophyllan and the aqueous solutions were more viscous than those of schizophyllan. The viscosity slightly decreased during 1 h on heating at 121 degrees, was not influenced by high concentrations of salt, and was independent of pH in the range 3-11. However, the viscosity markedly declined on storage of an aqueous solution of the polyalcohol at pH 2 and 20 degrees for 100 h. The polyalcohol was more susceptible to hydrodynamic shear than schizophyllan and the proportion of glycerol released indicated that both the main and side chains in the polyalcohol were cleaved.

Borohydrides↗
PubMed1990

1,3-Beta-glucan synthase in cell-free extracts from mycelium and protoplasts of Sclerotium glucanicum.

Conditions for obtaining stable protoplasts from Sclerotium glucanicum and their reversion to hyphal growth were determined. 1,3-beta-Glucan synthase activity was detected in particulate enzyme fractions from mycelium and protoplasts of Scl. glucanicum. UDP-[U-14C]glucose was linearly incorporated into a beta-glucan for about 20 min at 25 degrees C. Optimum pH and temperature values, as well as thermal stabilities of the 1,3-beta-glucan synthase activity, were determined. High concentrations of EDTA were inhibitory. Enzyme activity was stimulated by ATP and GTP. The apparent Km value for UDP-glucose was 0.54 mM. The reaction product was characterized as 1,3-beta-glucan by 13C NMR spectroscopy and hydrolysis products of an exo-1,3-beta-glucanase.

Adenosine Triphosphate↗
PubMed1989

Using a multidisciplinary follow-up program to assist patient adjustment following temporal lobectomy.

A follow-up program for patients following temporal lobectomy for seizure control was established in 1983 at the UCLA Neuropsychiatric Hospital in response to patients' requests for information and assistance. The purpose of this program was to identify changes requiring adaptation and to offer assistance. Forty patients were contacted monthly by telephone for one year after surgery. They were interviewed by either a nurse or occupational therapist about medical and psychosocial issues. The information, support or referral needed were provided by the nurse, occupational therapist or social worker in consultation with appropriate member(s) of the multidisciplinary team. Problems encountered when beginning a less disabled lifestyle might not have been detected or resolved without active intervention through a multidisciplinary follow-up program.

Adaptation, Psychological↗
PubMed1986

Production and Properties of Xylan-Degrading Enzymes from Cellulomonas uda.

Xylan degradation and production of beta-xylanase and beta-xylosidase activities were studied in cultures of Cellulomonas uda grown on purified xylan from birchwood. beta-Xylanase activity was found to be associated with the cells, although in various degrees. The formation of beta-xylanase activity was induced by xylotriose and repressed by xylose. beta-Xylosidase activity was cell bound. Both constitutive and inducible beta-xylosidase activities were suggested. beta-Xylanase and beta-xylosidase activities were inhibited competitively by xylose. beta-Xylanase activity had a pronounced optimum pH of 5.8, whereas the optimum pH of beta-xylosidase activity ranged from 5.4 to 6.1. The major products of xylan degradation by a crude preparation of beta-xylanase activity, in decreasing order of amount, were xylobiose, xylotriose, xylose, and small amounts of xylotetraose. This pattern suggests that beta-xylanase activity secreted by C. uda is of the endosplitting type. Supernatants of cultures grown on cellulose showed not only beta-glucanase but also beta-xylanase activity. The latter could be attributed to an endo-1,4-beta-glucanase activity which had a low beta-xylanase activity.

Journal Article↗
PubMed1982

Formation, Location, and Regulation of Endo-1,4-beta-Glucanases and beta-Glucosidases from Cellulomonas uda.

The formation and location of endo-1,4-beta-glucanases and beta-glucosidases were studied in cultures of Cellulomonas uda grown on microcrystalline cellulose, carboxymethyl cellulose, printed newspaper, and some mono- or disaccharides. Endo-1,4-Glucanases were found to be extracellular, but a very small amount of cell-bound endo-1,4-beta-glucanase was considered to be the basal endoglucanase level of the cells. The formation of extracellular endo-1,4-beta-glucanases was induced by cellobiose and repressed by glucose. Extracellular endoglucanase activity was inhibited by cellobiose but not by glucose. beta-Glucosidases, on the other hand, were formed constitutively and found to be cell bound. beta-Glucosidase activity was inhibited noncompetitively by glucose. Some characteristics such as the optimal pH for and the thermostability of the endoglucanases and beta-glucosidases and the end products of cellulose degradation were determined.

Journal Article↗
PubMed1982

Repression of endo-1,4-beta-glucanase formation in Penicillium janthinellum and product inhibition of its 1,4-beta-glucanases and cellobiases.

Endo-1,4-beta-glucanase formation of Penicillium janthinellum was repressed by glucose, sophorose, and glycerol. Chromatography on DEAE-Sephadex A-50 was employed to separate the 1,4-beta-glucanases from two cellobiases. The 1,4-beta-glucanases were inhibited competitively by cellobiose and glucose, and the two cellobiases were inhibited by glucose and glucono-delta-lactone.

Cellulase↗
PubMed1981

Formation and Location of 1,4-beta-Glucanases and 1,4-beta-Glucosidases from Penicillium janthinellum.

Formation and location of 1,4-beta-glucanases and 1,4-beta-glucosidases were studied in cultures of Penicillium janthinellum grown on Avicel, sodium carboxymethyl cellulose, cellobiose, glucose, mannose, and maltose. Endo-1,4-beta-glucanases were found to be cell free, and their formation was induced by cellobiose. 1,4-beta-Glucosidases, on the other hand, were formed constitutively and were primarily cell free, but with a small amount strongly associated with the cell wall. Low 1,4-beta-glucosidase activities of periplasmic or intracellular origin were also found. A rotational viscosimetric method was developed to measure the total endo-1,4-beta-glucanase activity of the culture (broth and solids). By this method, it was possible to determine the endo-1,4-beta-glucanase activity not only in the supernatant of the culture but also on the surface of the mycelium or absorbed on residual Avicel. During a 70-liter batch cultivation of P. janthinellum, the adsorption of endo-1,4-beta-glucanases by residual and newly added 10% Avicel was measured. The adsorption of soluble protein and endo-1,4-beta-glucanases by Avicel was found to be largely independent of the pH value but dependent on temperature.

Journal Article↗
PubMed1976

Analysis of biochemical phase shift oscillators by a harmonic balancing technique.

The use of harmonic balancing techniques for theoretically investigating a large class of biochemical phase shift oscillators is outlined and the accuracy of this approximate technique for large dimension nonlinear chemical systems is considered. It is concluded that for the equations under study these techniques can be successfully employed to both find periodic solutions and to indicate those cases which can not oscillate. The technique is a general one and it is possible to state a step by step procedure for its application. It has a substantial advantage in producing results which are immediately valid for arbitrary dimension. As the accuracy of the method increases with dimension, it complements classical small dimension methods. The results obtained by harmonic balancing analysis are compared with those obtained by studying the local stability properties of the singular points of the differential equation. A general theorem is derived which identifies those special cases where the results of first order harmonic balancing are identical to those of local stability analysis, and a necessary condition for this equivalence is derived. As a concrete example, the n-dimensional Goodwin oscillator is considered where p, the Hill coefficient of the feedback metabolite, is equal to three and four. It is shown that for p = 3 or 4 and n less than or equal to 4 the approximation indicates that it is impossible to construct a set of physically permissible reaction constants such that the system possesses a periodic solution. However for n greater than or equal to 5 it is always possible to find a large domain in the reaction constant space giving stable oscillations. A means of constructing such a parameter set is given. The results obtained here are compared with previously derived results for p = 1 and p = 2.

Metabolism↗
PubMed1975

Analytic procedures for large dimention nonlinear biochemical oscillators.

An analytic method is presented which can be used to determine if the following system of nonlinear differential equations has periodic solutions x1 = h(xn)-b1x1 xj = gj-1xj-1-bjxj j = 2, ... n A systematic dual input describing function procedure is given for constructing a function of the reaction constants R, where if R greater than 1 a periodic solution exists and if R smaller than 1 there is no periodic solution. The form of R constructed generalizes immediately to an arbitrarily large dimension. The method generalizes to cover systems displaying hysteresis kinetics, systems subject to chemical noise, and systems containing delay components. The method has been applied to a well known biochemical problem where h(xn)-k/(1 + alphaxnrho). For rho = 1, for all n, there are no stable limit cycles such that xj(t) greater than O, t larger than or equal to O. For rho = 2,n larger than or equal to 8 it is possible to construct a parameter set such that stable oscillations appear.

Biological Clocks↗