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Biomedical subjects

R E Lynch

Publications and source records attributed to R E Lynch.

At least 55 records · Page 3Linked to original sources
PubMed1983

Sodium reabsorption during intrarenal diazoxide infusion in the dog.

Infusion of diazoxide, a potent benzothiazide antihypertensive, into the renal artery results in diuresis and natriuresis. The site within the nephron of decreased reabsorption has been controversial. Thus free flow recollection micropuncture studies of the superficial proximal tubule of the dog were undertaken to determine if diazoxide decreased sodium reabsorption from this part of the nephron. Renal blood flow, monitored by an electromagnetic flow meter, was increased by about 15% with the diazoxide infusion. Systemic blood pressure and hematocrit remained unchanged. Glomerular filtration rate increased significantly from 26 +/- 2 to 34 +/- 3 ml/min, urine flow and sodium excretion also increased (0.13 +/- 0.01 to 0.33 +/- 0.06 ml/min and 5.5 +/- 0.90 to 35.5 +/- 11.0 microEq/min, respectively). Decreased sodium reabsorption from the proximal tubule was demonstrated by a decrease in the tubular fluid to plasma inulin ratio (1.62 +/- 0.1 1.47 +/- 0.1) thus giving a reduction in fractional sodium reabsorption to the site of micropuncture (36.1 +/- 4.3 to 29.5 +/- 5.1%, p less than 0.05). To examine peritubular effects of diazoxide infusion, capillary protein concentration and pressure were measured; the former increasing significantly (9.17 +/- 0.32 to 9.80 +/- 0.35, p less than 0.05) and the latter did not change (13.1 +/- 1.0 vs. 15.2 +/- 1.4 mm Hg). Thus intrarenal diazoxide causes whole kidney vasodilatation with diuresis, natriuresis and decreased sodium reabsorption from the superficial proximal tubule. Additional studies provided no data to indicate that changes in peritubular physical factors account for the changes in sodium handling.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1982

Effects of hemodialysis and dimercaprol in acute dichromate poisoning.

A 22-month-old infant died after ingesting sodium dichromate his father had brought from work. Treatment included folic acid and dimercaprol administration, hemodialysis, and exchange transfusion. To evaluate this treatment, four dogs were hemodialyzed after receiving intravenous sodium dichromate: their dialyzer chromate clearance was similar to their renal chromate clearance and their dialyzer chromate clearance was not significantly different before or after dimercaprol administration. This and other cases in the literature indicate that although chromate poisoning is often fatal, supportive care, forced diuresis, and chelating agents may be helpful. Hemodialysis may be required if renal failure occurs. Awareness of toxicity and prevention remain the most important approaches.

Acute Disease↗
PubMed1979

Autoinactivation of xanthine oxidase: the role of superoxide radical and hydrogen peroxide.

Xanthine oxidase suffers autoinactivation in the course of catalyzing the oxidation of acetaldehyde. When no special efforts were made to maintain a high pO2 in these reaction mixtures catalase protected the xanthine oxidase, but superoxide dismutase did not. However, when oxygen depletion was slowed or prevented by working at lower concentrations of xanthine oxidase, at lower temperatures or by vigorous agitation under an atmosphere of 100% oxygen, superoxide dismutase or catalase protected markedly when added separately and protected almost completely when added together. This result correlates with the greater production of O2-, relative to H2O2, by xanthine oxidase, at elevated pO2. Since histidine also provided some protection and the high levels of acetaldehyde used would have precluded any significant effect of OH., we conclude that singlet oxygen, or something with similar reactivity, was generated from O2- plus H2O2 and contributed significantly to the observed autoinactivation.

Histidine↗
PubMed1978

Permeation of the erythrocyte stroma by superoxide radical.

Superoxide anion, generated by xanthine oxidase within vesicles formed from washed erythrocyte ghosts, crosses the vesicle membrane to reduce cytochrome c in the medium (Lynch, R. E., and Fridovich, I. (1978) J. Biol. Chem, 253, 1838-1845). To determine whether O2- could travel through the membrane in the "channel" for the exchange of stable anions, the effects of two specific inhibitors of anion exchange, 4-acetamido-4'-isothiocyano-2,2' disulfonic acid stilbene (SITS) and 4,4'-diisothiocyano-2,2' disulfonic acid stilbene (DIDS), on the escape of O2- from vesicles were studied. The reduction of external cytochrome c, caused by O2- produced by the enzymic turnover of internal xanthine oxidase, was 85 to 90% inhibited by SITS and DIDS. If SITS impeded the egress of O2- from vesicles, it should enhance the internal effects of O2- and antagonize the inhibition of these effects by external superoxide dismutase. External superoxide dismutase inhibited the lysis of vesicles containing xanthine oxidase. SITS (60 micron) partially reversed this inhibition. It appears that O2- can cross the membrane of the erythrocyte in the anion channel.

Cytochrome c Group↗
PubMed1978

High accuracy finite difference approximation to solutions of elliptic partial differential equations.

A flexible finite difference method is described that gives approximate solutions of linear elliptic partial differential equations, Lu = G, subject to general linear boundary conditions. The method gives high-order accuracy. The values of the unknown approximation function U are determined at mesh points by solving a system of finite difference equations L(h)U = I(h)G. L(h)U is a linear combination of values of U at points of a standard stencil (9-point for two-dimensional problems, 27-point for three-dimensional) and I(h)G is a linear combination of values of the given function G at mesh points as well as at other points. A local calculation is carried out to determine the coefficients of the operators L(h) and I(h) so that the approximation is exact on a specific linear space of functions. Having the coefficients of each difference equation, one solves the resulting system by standard techniques to obtain U at all interior mesh points. Special cases generalize the well-known 0(h(6)) approximation of smooth solutions of the Poisson equation to 0(h(6)) approximation for the variable coefficient equation -div(p grad[u]) + Fu = G. The method can be applied to other than elliptic problems.

Journal Article↗
PubMed1978

The evaluation and applications of hemodialyzers for pediatric patients.

It is difficult to determine which pediatric hemodialyzer to use in a given clinical situation since there is no comprehensive comparison of pediatric hemodialyzers. We evaluated five currently available disposable pediatric hemodialyzers in vitro and in vivo during treatment of pediatric patients. Two dialyzers, Gambro Mini-Minor and Viva Cell 0.2 are well suited to small pediatric patients weighing less than 10 kg. Three of the dialyzers are well suited to the pediatric patients weighing greater than 10 kg (Gambro Minor, Cordis Dow 0.6, Viva Cell 0.5). By considering the clinical status of the child and the performance characteristics of the dialyzer (solute removal, priming volume, ultrafiltration, etc.) it is possible to employ a hemodialyzer which more precisely meets the needs of the child without increasing risk factors associated with pediatric hemodialysis.

Adolescent↗