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Biomedical subjects

C Roberts

Publications and source records attributed to C Roberts.

At least 397 records · Page 22Linked to original sources
PubMed1983

Murine auto- and cross-tolerance to volatile anaesthetics.

Auto-tolerance and cross-tolerance to halothane, isoflurane and enflurane were tested on 36 mice divided into three equal groups. Each group was first exposed to increasing concentrations of either of the three anesthetics on 13 occasions. The concentration at which each mouse lost its righting reflex during successive exposures in a rotating cage was noted. Cross-tolerance was assessed by comparing the number of mice which had lost their righting reflexes during their first exposure to a given anaesthetic agent to the number which lost it after having been exposed to another anaesthetic. All animals developed auto-tolerance to halothane, isoflurane and enflurane. Cross-tolerance was noted only between mice exposed to isoflurane and enflurane and between mice exposed to halothane and subsequently anaesthetized with isoflurane, but not vice versa.

Animals↗
PubMed1983

The sensitivity of peripheral blood lymphocytes to growth inhibition by hydrocortisone is not determined by their OKT4:OKT8 ratio.

Normal adult human subjects show considerable variation in sensitivity to depression of the activation phase of mitogen-induced lymphocyte growth by the natural glucocorticoid, hydrocortisone. In a study of 21 subjects, the slope of the log-dose response to hydrocortisone was unrelated to the relative numbers of cells in the two major T-cell subpopulations stained by the OKT4 and OKT8 monoclonal antibodies. It is concluded that the extent of the glucocorticoid-induced suppression of early mitogen-stimulated lymphocyte growth is probably not determined by relative numbers of the various immunoregulatory lymphocytes.

Adult↗
PubMed1983

Effect of circulating fibronectin on stimulation of leukocyte oxygen consumption and serum opsonizing function in burned patients.

In a study of 27 thermally burned patients (mean TBSA, 58%; range, 32-96%) serum fibronectin levels were decreased with parallel decreased oxygen consumption of stimulated peripheral blood phagocytes and decreased EGTA-blocked burn serum opsonizing activity which correlated with serum fibronectin changes postburn. Normal and burn sera fibronectin content also correlated with the opsonizing times for zymosan and Staphylococcus aureus but not for Enterobacteriaceae. Although in vivo 14 cases showed circulating fibronectin 140 micrograms/ml or lower and a marked decrease in Staphylococcus aureus opsonization, only two patients from this group revealed positive Staphylococcus aureus blood cultures and serum fibronectin levels were higher in patients with Staphylococcus aureus sepsis than in patients with Enterobacteriaceae sepsis. Supplementary experiments on leukocyte oxidative response after zymosan stimulation in normal, fibronectin-depleted, and fibronectin-reconstituted serum demonstrated that the lag period of oxygen burst is a fibronectin-dependent reaction.

Adolescent↗
PubMed1983

Anaesthetic uptake by the goldfish: effect of respiratory rate.

In order to assess the uptake of halothane by the goldfish, the respiratory rate of six fish was studied when water temperature was varied with and without changes in oxygen or carbon dioxide tension. The effective dose 50 of halothane (ED-50-H) and the time taken to reach it (T-ED-50-H) at an FIO2 of 0.35 in nitrogen, were studied when temperature and CO2 tension were varied. Nomograms were drawn to predict respiratory rate as a function of water CO2 tension, when CO2 was bubbled in air or in oxygen, and with changes in water temperature. At low temperatures (5 degrees C to 7.5 degrees C), respiratory rate remained below 10 per min, irrespective of CO2 partial pressure. At 28 degrees C, a CO2 partial pressure of 8 +/- 0.2 kPa produced a respiratory rate of 125 +/- 3/min in air, and in oxygen unexpectedly 140 +/- 3/min. Halothane ED-50 varied with temperature (0.8% at 10 degrees C and 1.6% at 23 degrees C). Time to reach ED-50-H decreased with increases in respiratory rate, but increased as water temperature was elevated.

Animals↗
PubMed1983

Sepsis and empyema caused by Yersinia enterocolitica.

Yersinia enterocolitica is the cause of gastrointestinal infection in the overwhelming majority of recognized cases, although extraintestinal sites are occasionally involved. We report a case of Y. enterocolitica septicemia and empyema complicated by the adult respiratory distress syndrome. The organism was also recovered from the patient's feces by alkaline enrichment and persisted through at least 19 days of antibiotic treatment.

Empyema↗
PubMed1983

Human adenovirus type 2 but not adenovirus type 12 is mutagenic at the hypoxanthine phosphoribosyltransferase locus of cloned rat liver epithelial cells.

Using resistance to the base analog 8-azaguanine as a genetic marker, we showed that adenovirus type 2, but not adenovirus type 12, is mutagenic at the hypoxanthine phosphoribosyltransferase locus of cloned diploid rat liver epithelial cells. Adenovirus type 2 increased the frequency of 8-azaguanine-resistant colonies by up to ninefold over the spontaneous frequency, depending on expression time and virus dose.

Adenoviruses, Human↗
PubMed1983

Displacement of chromosomes in mitosis: a technique for assessing differential chromosome error.

To assess whether displacement--the appearance of individual chromosomes inside of the ring of chromosomes attached to spindle fibers--is a valid method of analyzing chromosome misdivision, displacement data from six healthy female subjects were compared with data for mitotic and meiotic nondisjunction. Statistical analysis indicated that nondisjunction and displacement are equivalent methods of assessing differential chromosome error. Tests for homogeneity of the data sets showed no significant heterogeneity for the mitotic data, but chromosomes 1, 2, 11, 16, 17, 19, and 20 were responsible for significant heterogeneity in the meiotic data.

Adult↗
PubMed1983

Risk factors for meningiomas in men in Los Angeles County.

A case-control study among men in Los Angeles County was conducted to investigate further the causes of intracranial meningiomas. Meningioma patients and a neighbor of each one were interviewed about past experiences that might be associated with tumor development. Analysis of information from the 105 matched pairs showed an association with meningioma occurrence for various factors relating to head trauma and head X-rays: 1) ever boxed as a sport [odds ratio (OR) = 2.0, P = 0.03], 2) had a serious head injury (OR = 1.9, P = 0.01), and 3) had X-ray treatment to the head before 20 years of age and/or had five or more full mouth dental X-ray series before 1945 (OR = 3.5, P = 0.02). Of the 105 subjects, 72 (69%) had a history of exposure to at least one of these factors.

Adult↗
PubMed1982

Protein secretions in hamsters with pancreatic carcinoma.

Pancreatic secretions from the hamster model for pancreatic ductal adenocarcinoma were analyzed to determine whether alterations had occurred in the protein composition. CCK-and secretin-stimulated secretions were collected from 13 animals with cancer and 16 normal controls. Subsequent separation of the proteins by isoelectric focusing showed the following: (1) Significant changes occurred in the protein composition from animals with carcinoma. An unusually dark band was present at pH 7.5 just below amylase (pH 7.65); two unidentified bands, present in the normals at pH 6.9 and 7.0, were missing; and marked decreases occurred in the cathodic proteins with isoelectric points above pH 9, (2) CCK provided the optimal stimulus for differentiating specimens from animals with carcinoma from the normal controls. (3) The protein concentrations of CCK-stimulated secretions of animals with carcinoma were significantly lower than the controls. We have concluded that the protein alterations which have occurred in the hamster model for pancreatic ductal adenocarcinoma warrant further investigation.

Animals↗
PubMed1982

Limitation of myocardial infarct size after surgical reperfusion for acute coronary occlusion.

We investigated the effect of different forms of myocardial protection on infarct size and on the necrotic myocardial process after reperfusion for acute occlusion of the left anterior descending coronary artery (LAD) in dogs. Three control groups were formed: a 1 hour, 2 hour, and 6 hour locally ischemic control. Three experimental groups were locally ischemic for 1 hour and then reperfused after an additional hour of local ischemia on cardiopulmonary bypass with the heart protected by intermittent ischemia, cold potassium cardioplegia, or blood cardioplegia. To delineate the area at risk, the LAD was temporarily occluded 30 seconds before the 6 hour sacrifice time, and monastral blue dye was injected through a polyvinyl catheter placed in the left atrial appendage. The LAD area at risk (AR) was not stained. After 6 hours the heart was excised and treated with triphenyltetrazolium chloride (TTC) to define the area of myocardial necrosis (AN). The AN/AR ratio was determined for each animal by planimetry. Mean values were then computed in each of the six groups and evaluated by the Student's t test for paired data. The 1 hour control group had an AN/AR ratio of 64% +/- 5%; the 2 hour control group, 80% +/- 6%; and the 6 hour control group, 92% +/- 1%. The intermittent ischemia group had an AN/AR ratio of 83% +/- 2%; the crystalloid cardioplegic group (2 hours of ischemia) had a ratio of 69% +/- 4%, similar to the 1 hour control but significantly smaller than the 2 hour control (p less than 0.05); and the blood cardioplegia group had an AN/AR ratio of 48% +/- 8%, significantly better than any other group. These data demonstrate that myocardial necrosis after coronary occlusion is a time-related phenomenon and will increase to encompass a large fraction of the area at risk unless there is physical or pharmacologic modification during reperfusion, such as crystalloid or blood cardioplegia.

Animals↗
PubMed1981

Daily requirement for pyridoxine supplements in chronic renal failure.

Vitamin B6 deficiency was evaluated in 37 patients with chronic renal failure and in 71 patients undergoing maintenance hemodialysis (HD) or intermittent peritoneal dialysis (PD). Vitamin B6 deficiency was assessed by the in vitro activity of erythrocyte glutamic pyruvic transaminase (EGPT), without (basal) and with (stimulated) the addition of pyridoxal-5-phosphate to the assay, and the EGPT index (stimulated activity ./. basal activity). Basal and stimulated EGPT activities were below normal in the HD patients, and the EGPT index was increased in each group of patients, indicating vitamin B6 deficiency. Supplemental pyridoxine hydrochloride was given to 30 HD patients who received 1.25 to 50 mg/day (37 studies), 6 PD patients who were given 1.25 or 2.5 mg/day (7 studies), and 8 nondialyzed patients with mild to severe renal failure who received 2.5 mg/ day. In all HD patients, 10 or 50 mg/day of pyridoxine hydrochloride rapidly corrected the abnormal EGPT index and maintained normal values; with supplements of 5.0 mg/day or less, the index was often abnormal, particularly in those who were septic or taking pyridoxine antagonists. In PD patients and nondialyzed patients with renal failure, 2.5 mg/day of pyridoxine hydrochloride was inadequate to correct rapidly the abnormal index in all patients. These findings suggest that HD patients should receive 10 mg/day of supplemental pyridoxine hydrochloride (8.2 mg/day pyridoxine). PD patients and patients with chronic renal failure should receive about 5.0 mg/day of supplemental pyridoxine hydrochloride (4.1 mg/day pyridoxine). When sepsis intervenes or vitamin B6 antagonists are taken, 10 mg/day of pyridoxine hydrochloride may be a safer supplement for all patients.

Adult↗
PubMed1980

Methods for assessing nutritional status of patients with renal failure.

Since wasting and malnutrition are common problems in patients with renal failure, it is important to develop techniques for the longitudinal assessment of nutritional status. This paper reviews available methods for assessing the nutritional status; their possible limitations when applied to uremic patients are discussed. If carefully done, dietary intake can be estimated by recall interviews augmented with dietary diaries. Also, in a stable patient with chronic renal failure, the serum urea nitrogen (N)/creatinine ratio and the rate of urea N appearance reflect dietary protein intake. A comparison of N intake and urea N appearance will give an estimate of N balance. Anthropometric parameters such as the relationship between height and weight, thickness of subcutaneous skinfolds, and midarm muscle circumference are simple methods for evaluating body composition. Other methods for assessing body composition, such as densitometry and total body potassium, may not be readily applicable in patients with renal failure. More traditional biochemical estimates of nutritional status such as serum protein, albumin, transferrin, and selected serum complement determinations show that abnormalities are common among uremic patients. Certain anthropometric and biochemical measurements of nutritional status are abnormal in chronically uremic patients who appear to be particularly robust; thus, factors other than altered nutritional intake may lead to abnormal parameters in such patients. Serial monitoring of selected nutritional parameters in the same individual may improve the sensitivity of these measurements to detect changes. Standards for measuring nutritional status are needed for patients with renal failure so that realistic goals can be established optimal body nutriture.

Adipose Tissue↗