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Biomedical subjects

R D Jones

Publications and source records attributed to R D Jones.

At least 181 records · Page 10Linked to original sources
PubMed1983

Theory of attachment in Giardia.

Using a low Reynold's number hydrodynamic model, the adhesive force in Giardia is calculated. It is shown that this force is larger than typical forces that would tend to detach the organism.

Adhesiveness↗
PubMed1983

Methane Oxidation by Nitrosococcus oceanus and Nitrosomonas europaea.

Chemolithotrophic ammonium-oxidizing and nitrite-oxidizing bacteria including Nitrosomonas europaea, Nitrosococcus oceanus, Nitrobacter sp., Nitiospina gracilis, and Nitrococcus mobilis were examined as to their ability to oxidize methane in the absence of ammonium or nitrite. All ammonium oxidizers tested had the ability to oxidize significant amounts of methane to CO(2) and incorporate various amounts into cellular components. None of the nitrite-oxidizing bacteria were capable of methane oxidation. The methane-oxidizing capabilities of Nitrosococcus oceanus and Nitrosomonas europaea were examined with respect to ammonium and methane concentrations, nitrogen source, and pH. The addition of ammonium stimulated both CO(2) production and cellular incorporation of methane-carbon by both organisms. Less than 0.1 mM CH(4) in solution inhibited the oxidation of ammonium by Nitrosococcus oceanus by 87%. Methane concentrations up to 1.0 mM had no inhibitory effects on ammonium oxidation by Nitrosomonas europaea. In the absence of NH(4)-N, Nitrosococcus oceanus achieved a maximum methane oxidation rate of 2.20 x 10 mumol of CH(4) h mg (dry weight) of cells, which remained constant as the methane concentration was increased. In the presence of NH(4)-N (10 ppm [10 mug/ml]), its maximum rate was 26.4 x 10 mumol of CH(4) h mg (dry weight) of cells at a methane concentration of 1.19 x 10 mM. Increasing the methane concentration above this level decreased CO(2) production, whereas cellular incorporation of methane-carbon continued to increase. Nitrosomonas europaea showed a linear response throughout the test range, with an activity of 196.0 x 10 mumol of CH(4) h mg (dry weight) of cells at a methane concentration of 1.38 x 10 mM. Both nitrite and nitrate stimulated the oxidation of methane. The pH range was similar to that for ammonium oxidation, but the points of maximum activity were at lower values for the oxidation of methane.

Journal Article↗
PubMed1983

Industrial gassing poisonings due to trichlorethylene, perchlorethylene, and 1-1-1 trichloroethane, 1961-80.

During the period 1961-80, 384 cases of industrial gassing poisonings by trichlorethylene, perchlorethylene, and 1-1-1 trichloroethane (methylchloroform) were reported to HM Factory Inspectorate. A study of these data, which have been collated and analysed with particular reference to sex, age, clinical manifestations, and circumstances of the incident, is presented. Possible bias of the data owing to its source and method of extraction is discussed. The study shows the hazards inherent in the use of these narcotic solvents and discusses the circumstances that appear most likely to produce problems. The vulnerability of the younger worker is shown. Toxic effects were most commonly exerted on the central nervous system but no good evidence of cardiac or hepatic toxicity was found. In nine cases evidence of deliberate sniffing of solvent was reported. The problem of solvent abuse in an industrial context is discussed.

Adolescent↗
PubMed1983

Perioperative management of tetralogy of Fallot repair.

Understanding the morphological and haemodynamic changes associated with surgical correction of tetralogy of Fallot is vital in planning a rational basis for the postoperative management. The past five years have seen a fall in mortality figures from more than 10% to 2% and the reasons for this improvement are reviewed. There have been changes in the preoperative assessment and therapy, but perhaps the most significant change has been in operative technique. The correction now is performed by a transatrial approach, whereas in the past a large ventriculotomy was used. There has been a change in emphasis in the various postoperative manoeuvres employed. Early low-dosage inotrope support, cavity drainage, intravenous hyperalimentation, peritoneal dialysis, sequential pacing and ventilation until cardio-respiratory stability is achieved, form the basis of our postoperative regime.

Cardiopulmonary Bypass↗
PubMed1982

Carbon monoxide binding kinetics in "capped" porphyrin compounds.

The rate constants for CO binding to the five-coordinate ferrous iron complexes of 5,10,15,20-[pyromellitoyl(tetrakis-o-oxyoxyphenyl)]porphyrin and 5,10,15,20-[pyromellitoyl(tetrakis-o-oxypropoxyphenyl)]porphyrin have been measured and compared with the corresponding rate constants for other hemes and hemoproteins. The second-order rate constant is independent of cap size and is comparable to that of high-affinity state hemoglobin (k5 approximately 4 X 10(6) M-1s-1). Therefore, these capped porphyrins provide no steric hindrance to CO binding. In addition, a kinetic scheme involving an unusual seven-coordinate porphyrin species is described.

Carbon Monoxide↗
PubMed1982

Trophic effects of gastrin on colorectal neoplasms in the rat.

This study was designed to determine the effect of gastrin on colorectal neoplasms in the rat. Multiple colon and rectal cancers were induced in each of 57 rats with methylazoxymethanol. Animals were randomly assigned to groups: (1) antral exclusion, (2) antrectomy, (3) sham, or (4) sham with subsequent pentagastrin injections. Resulting tumors were analyzed for concentration and synthesis of DNA, RNA, and protein. The number of tumors per rat and distribution of tumors within the colons did not vary among groups. Antrectomy did not alter the gastrin level, and tumors developing in these animals did not differ from those of sham controls. Antral exclusion markedly raised serum gastrin levels. Both chronic endogenous hypergastrinemia and administration of exogenous pentagastrin significantly increased tumor synthesis and concentration of DNA, RNA, and protein. We conclude that gastrin exerts a trophic effect on colorectal neoplasms in rats. This biological phenomenon suggests a tumor regulatory role for the hormone.

Animals↗
PubMed1982

Growth, reproductive performance and nitrogen balance of gilts as affected by protein intake and stage of gestation.

The effects of four levels of crude protein (CP) and stage of gestation on the growth, reproductive performance and N balance of 64 crossbred gilts were examined in two trials. Gilts were fed 147, 256, 309 or 369 g of CP daily in trial 1 and 119, 227, 275 or 326 g/d in trial 2. Total body weight gain and average daily gain (ADG) were not significantly affected by protein intake, although the quadratic effect on ADG approached significance (P less than .1). Both total body weight gain and ADG increased linearly (P less than .01) as stage of gestation progressed. Gilts were slaughtered at 30, 60 or 90 d of gestation and reproductive performance was evaluated. Protein intake did not significantly affect numbers of corpora lutea or live embryos, survival rate or embryo length. But survival rate (P less than .05), number of corpora lutea (P less than .05) and live embryo numbers (P less than .01) declined linearly as gestation stage progressed. Embryo length increased linearly (P less than .05) as stage of gestation progressed. Nitrogen balance studies were conducted before breeding and in early, mid and late gestation. Significant trial x protein level x collection period interactions existed. In trial 1, N retention increased linearly (P less than .01) as dietary protein increased. Retention increased (P less than .01) by 4.1 g/d from prebreeding to early pregnancy. Stage of gestation had a quadratic effect on retained N; retention was higher in early and late gestation than in mid-gestation. In trial 2, mean N retention during pregnancy was -1.7 g/d. Retention was not significantly affected by protein intake but retained N declined quadratically (P less than .05) with stage of gestation to a -16.3 g/d at d 90. In contrast with trial 1, pregnancy did not result in an increase in retention of N. A relationship between protein intake and N balance data and resulting reproductive performance could not be established. The lowest levels of protein intake (147 and 119 g/d in trials 1 and 2, respectively) appeared to be adequate for the first 90 d of gestation in the gilt. However, N retention was not maximized at this protein intake.

Animals↗
PubMed1982

Breath methane excretion in patients with unresected colorectal cancer.

The objective of our study was to verify or refute the observation that patients with unresected colorectal cancer are more likely to be breath methane excretors than the general population. Intracolonic heme had no effect on breath methane excretion of 11 normal volunteers given oral hemoglobin. Laxative-enema colonoscopy preparation had a profound effect on the subsequent measurement of breath methane. Three of 4 volunteer methane excretors became nonexcretors, and 2 remained nonexcretors for 21 days and 7 months, respectively. No significant difference was found in the frequency and the amount of breath methane excretion in 55 patients with unresected colorectal cancer and in 99 control subjects. However, 13 patients with unresected descending or sigmoid colon cancers were almost twice as likely to be breath methane excretors as 38 patients with colorectal cancer at other sites.

Adult↗
PubMed1982

Phase I--II study of the combination of 5-FU, doxorubicin, mitomycin, and semustine (FAMMe) in the treatment of adenocarcinoma of the stomach, gastroesophageal junction, and pancreas.

One hundred and fifteen patients with advanced gastrointestinal cancer (stomach cancer, 42 patients; gastroesophageal junction cancer, ten; pancreatic cancer, 32; and other upper gastrointestinal cancers, 31) were treated with a combination chemotherapy regimen consisting of 5-FU, doxorubicin, mitomycin, and semustine (methyl-CCNU) (FAMMe). Of the 31 patients with stomach cancer who were evaluable for response and had had no previous chemotherapy, 12 (39%) achieved complete or partial remission. One of eight (12%0 patients with gastroesophageal junction cancer and five of 23 (22%) patients with pancreatic cancer achieved a partial remission. The median duration of survival for all patients with adenocarcinoma of the stomach was 7.1 months. The median duration of survival for responding patients with stomach cancer was 13.6 months, and the median survival for nonresponding patients was 6.1 months. FAMMe chemotherapy was generally well-tolerated and can be administered in adequate doses without producing prohibitive myelosuppression. The starting dose should be reduced for patients greater than or equal to 70 years old or for patients who have received pelvic or vertebral radiation therapy. FAMMe is effective against advanced gastric cancer; however, because this was not a randomized comparative study of the relative effectiveness of FAMMe and FAM (5-FU, doxorubicin, and mitomycin), no recommendation for the use of one regimen instead of the other for advanced adenocarcinoma of the stomach can be made. FAMMe chemotherapy cannot recommended for advanced adenocarcinoma of the pancreas and gastroesophageal junction.

Adenocarcinoma↗
PubMed1981

The role of the fibrous capsule in the function of implanted drug-polymer sustained release systems.

Numerous studies have been carried out on drug-polymer sustained release systems designed for implantation. The majority of these efforts have been directed toward determining the in-vitro rate of drug release from specific systems or drug polymer combinations and the in-vivo studies have attempted to utilize analysis of the blood serum and excretory products as a measure of the release rate and behavior. To gain a better understanding of the influence of the local tissue environment and implant site on release behavior, we have investigated the release behavior of a gentamicin-silicone rubber system implanted in canines. Particular attention has been directed toward investigating the role that the fibrous capsule which eventually surrounds the implant plays in determining the rate and pattern of drug release. The drug burst effect was decreased by the use of a drug-free silicone rubber membrane on the gentamicin-silicone rod implant. Analysis for gentamicin in the tissue adjacent to the implant for periods up to four weeks indicated that the release rate was retarded by the development of the fibrous capsule. The temporal and spatial variations in gentamicin levels in the tissue surrounding the rod implants were determined. In addition, the influence of implant coating and gentamicin loading level in the implant on local tissue concentrations with time were also investigated. These studies provide evidence that the fibrous capsule surrounding a drug-polymer sustained release implant may influence the release behavior of the drug in an advantageous or disadvantageous manner depending upon the desired function of the sustained release system.

Animals↗
PubMed1981

Measurement of integrated sensory-motor function following brain damage by a computerized preview tracking task.

A preview tracking task has been developed which has particular application to neurological assessment and rehabilitation. Generated and monitored by a graphic display computer, it permits accurate global quantification of the upper-limb sensory-motor system. The incorporation of 'preview' into the tracking task is considered to significantly increase its effectiveness and relevance in relation to normal daily activities. Applied to three groups of normal subjects, several features of normal psychomotor performance and learning were identified or verified: hand dominance is not significant in overall arm control; learning does not completely plateau; increase in age (15-59 years) results in only a minor overall decrement in performance; an initial wide performance distribution decreases dramatically in subsequent sessions. Applied to brain-damaged patients, particularly head injury or stroke, the preview tracking task allows assessment at regular intervals enabling sensory-motor recovery curves to be generated. The potential of this technique, to help determine the efficacy of therapeutic procedures on the recovery process, is illustrated with the presentation of results from three brain-damaged patients demonstrating zero, significant and disjointed recovery of sensory-motor function. The usefulness of the preview tracking task can be expanded by combination with a less frequently applied but more component specific neurological assessment battery.

Adolescent↗