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Biomedical subjects

R J Field

Publications and source records attributed to R J Field.

At least 19 recordsLinked to original sources
PubMed2001

HPLC analysis of complete BZ systems. Evolution of the chemical composition in cerium and ferroin catalysed batch oscillators: experiments and model calculations.

In the last few years many new reaction routes and intermediates have been discovered in the mechanism of the Belousov-Zhabotinsky (BZ) reaction with the aid of high performance liquid chromatography (HPLC). These previous HPLC studies, however, were limited to the Ce(4+)-organic substrate (malonic or bromomalonic acid) systems only. Very recently some measurements were made on a cerium catalysed full BZ system but only in its induction period. The present work follows the evolution of the main chemical components in a cerium and in a ferroin catalysed full BZ system from the start until the end of the oscillatory regime in a batch reactor. While recording the potential oscillations of a bromide selective electrode we measured from time to time the concentration of the following components: malonic and bromomalonic acids and bromate as main components; malonyl malonate, ethanetetracarboxylic and bromoethenetricarboxylic acids which are recombination products of organic free radicals; oxidized intermediates: tartronic, oxalic (OA) and mesoxalic (MOA) acids, and brominated products: dibromoacetic and tribromoacetic acids. Recombination products are generated in the intervals when the autocatalytic reaction is "switched off". In the course of the autocatalytic periods, however, the organic radicals react with the inorganic bromine dioxide radical mainly which leads to the formation of MOA and OA. Due to a very fast Ce(4+)-MOA reaction, MOA can be detected in the ferroin catalysed BZ system only. Our model calculations deal exclusively with the cerium catalysed system. The suggested new Marburg-Budapest-Missoula (MBM) model includes both negative feedback loops (bromous acid-bromide ion Oregonator type and bromine dioxide-organic free radicals Radicalator type feedback) and the recently discovered radical-radical recombination reactions. Comparison of the experimental data with the model calculations shows a good qualitative agreement but some open problems still remain. To overcome these problems oxygen atom transfer and other redox reactions are proposed.

Journal Article↗
PubMed2000

Kinetics of formation of Di-D-fructose dianhydrides during thermal treatment of inulin.

Thermal treatments of solid mixtures of inulin and citric acid result in the formation of di-D-fructose dianhydrides and oligomers derived therefrom. The kinetics of formation of these compounds have been investigated and simulated in computer studies. A mechanism is proposed. The conditions used in this study were analogous to the conditions pertaining to the roasting of chicory, during which similar compounds are formed.

Anhydrides↗
PubMed1998

Energy dissipation as a key factor for electroporation of protoplasts.

Energy dissipation (epsilon) during electroporation was theoretically determined to be epsilon = 0.5CV02 for the various combinations of capacitance (C) and initial voltage (V0). Experiments on asparagus protoplasts established that electroporation efficiency (EE) and survival rate were directly proportional to energy dissipation during electroporation. A positive linear relationship exists between energy dissipation per unit volume and EE, whereas energy dissipation per unit volume and survival rate of protoplasts are related in a negative linear manner. At the same energy level, longer time constants were more effective at increasing EE. This suggests that energy dissipation approximating rectangular waveforms is more important than that dissipated as sharply decaying exponential waveforms. With energy as the key parameter, the optimization of electrical parameters for efficient electroporation is greatly simplified, is not machine-dependent, and generally applies to all species.

Cell Survival↗
PubMed1996

A time to heal.

Explore the source record for details and available documents.

Empathy↗
PubMed1995

Beyond the scalpel.

Surgical residency training should be changed to provide much needed surgical manpower to rural America. Small-town and rural surgery practices demand that surgeons see and treat their patients as people. If rural surgery could become a real option for young surgeons, it could bring about a change in the sometimes adversarial relationship between patients and their physicians.

Attitude to Health↗
PubMed1994

The tricarboxylic acid cycle in Dictyostelium discoideum. Two methods of analysis using the same data.

The results of using metabolic control theory versus biochemical systems theory to analyze a model of the tricarboxylic acid cycle in Dictyostelium are described. The two types of analysis give essentially the same results, except that smaller responses to perturbations are observed for the model analyzed by metabolic control theory. The basis for this difference is discussed.

Animals↗
PubMed1994

Total abdominal colectomy for control of massive lower gastrointestinal bleeding.

From 1957-1990 four patients underwent total abdominal colectomy with primary ileoproctostomy for control of massive lower gastrointestinal hemorrhage at Field Memorial Community Hospital in the rural community of Centreville, Mississippi. Surgery was performed emergently in two cases, and urgent/electively in the two remaining cases. Bleeding was controlled in each case. Upper Gastrointestinal and rectal bleeding were excluded, but further attempts to localize bleeding were not performed due to the difficulty of obtaining these studies at our hospital and the questionable likelihood of localizing the bleeding site. Many authors recommend an aggressive diagnostic workup including radio-labeled RBC scintigraphy and mesenteric angiography to localize colonic bleeding. Their aim is to perform a directed colonic resection for control of bleeding. However, most authors support total abdominal colectomy in cases where 1) hemodynamic instability does not allow extensive preoperative evaluation 2) there is a recurrent bleeding 3) more than one site is visualized as bleeding 4) there is widespread diverticulosis in a good-risk patient or 5) diagnostic procedures are unavailable. The low morbidity and good bowel function achieved following total abdominal colectomy, combined with the unavailability of diagnostic radiographic studies leads us to recommend total abdominal colectomy for control of massive lower gastrointestinal bleeding. The mortality of the procedure can be minimized by operating in a timely manner, prior to 10 units transfusion or 4 units within 24 hours, or operating in cases of recurrent bleeding.

Aged↗
PubMed1992

Vertical banded gastroplasty: is obesity worth it?

Obesity is a public health issue of major concern for the United States and other developed nations. In the last several decades, bariatric surgery has developed as a means of treating morbid obesity. Vertical banded gastroplasty (VBG) is an attractive procedure because it has fewer side effects than other forms of bariatric surgery and maintains physiological continuity of the gut. VBG was performed in 36 patients at a rural community hospital from 1982-1990. There was only one intraoperative complication necessitating splenectomy and two early postoperative complications--gastric leak and marginal stress ulcer--necessitating reexploration. Twenty-five patients were available for follow-up, at which time they were an average of 6.4 years out of surgery. Two of these patients had died, both from cardiac arrest months or years after VBG. The remainder had gone from a preoperative average of 86.7% over ideal weight according to 1983 Metropolitan Life insurance Tables to 54.5% over ideal weight. Mean BMI for this group had changed from 41.2 preoperatively to 34.7 at follow-up. Success was defined as weight loss to < 60% over ideal or BMI < 35, removing the individual from the morbidly obese category. According to this criteria, VBG provided successful weight loss in 72% of subjects in the follow-up group. Weight loss results may have been biased as a significant number of patients were lost to follow-up and may have constituted failures. In general, most individuals did not make concomitant changes in diet or sedentary life-style which would have supported weight loss effected by VBG. Moreover, regain of weight was progressive and possibly inexorable. Nearly all individuals nonetheless reported great satisfaction with their surgery. VBG is a viable option in the treatment of morbid obesity, but criteria for success needs to be better defined in order to determine whether the procedure is "worth it."

Adolescent↗
PubMed1982

Pneumococcal polysaccharide immunization of children with sickle cell disease. I. Clinical reactions to immunization and relationship to preimmunization antibody.

Vaccine reaction data were obtained from 154 patients with sickle cell disease immunized with tetradecavalent pneumococcal polysaccharide vaccine. There was a high rate (70%) of mild reactions, primarily at the site of injection. Fever over 100 degrees F was uncommon and precipitation of symptoms similar to sickling crisis was rare. Development of local reactions was associated with the level of preimmunization pneumococcal antibody titer.

Anemia, Sickle Cell↗
PubMed1980

Response of renal allograft recipients to pneumococcal vaccine.

Antibody responses to pneumococcal polysaccharide vaccine were compared in a control group of 17 normal adults and in a group of 27 adult patients with stable renal function (serum creatinine 0.8--2.1 mg/dl) seven months to nine years following renal transplantation. Using the indirect hemagglutination technique, antibody titers to 13 of the 14 capsular antigens contained in the vaccine were determined for each patient just prior to and again three weeks following immunization. There was no significant difference between the two groups in the proportion of patients responding with a fourfold rise in titer to 12 of the 13 antigens tested. The response rate to antigen type 3 was reduced in the transplant group (p less than 0.05). Mean fold increase in indirect hemagglutination titers was likewise determined for each antigen, and a reduced response in the transplant group was noted only to antigen type 23 (p = 0.037). Immunosuppressed renal allograft recipients appear capable of mounting a nearly normal antibody response to pneumococcal vaccine.

Adult↗