Search PubMed⌕ Search

Biomedical subjects

M John

Publications and source records attributed to M John.

At least 199 records · Page 11Linked to original sources
PubMed1982

Accurate measurement of cerebral metabolism in the conscious, unrestrained neonatal piglet. I. Blood flow.

A technique has been developed for the accurate and precise measurement of cerebral blood flow in the conscious, unrestrained neonatal piglet. Repeat determinations under conditions in which the animals could observe the experimenters showed that there was a significant fall in cerebral perfusion rate between first and second measurement, amounting to about 15 ml/min/100g. This systematic error was subsequently avoided by use of screens and the reproducibility of the technique was then estimated to be 5.9 ml/min/100 g (SD). When 5 animals were subjected to moderate stress by handling, there was a significant (p less than 0.001) increase in cerebral perfusion rate to a mean value of 172.6 +/- 35.0 ml/min/100g (+/- SEM). Mean resting cerebral perfusion rate in 18 normal animals was 65.6 +/- 4.6 ml/min/100 g (+/- SEM), which is similar to that reported in the conscious neonates of other species including man.

Animals↗
PubMed1981

Prognostic factors in cervical carcinoma: implications in staging and management.

Individualization of treatment using judicious combinations of external and intracavitary irradiation remains the cornerstone of the radiation management of carcinoma of the cervix. The inherent propensity of this cancer to either confine itself to the pelvis or else spread in a systematic and predictable manner through lymphatic channels has facilitated its therapeutic control. The treatment of most early invasive cervical carcinomas is equally advantageous using either intracavitary radium or surgery. However, certain Stage I patients have morphologic and histologic characteristics that militate against tumor control. Factors such as tumor size, depth of invasion, vascular infiltration, uterine extension, and barrel-shaped presentation affect the course of the disease and survival. A clinical-pathologic staging for cervical carcinoma incorporating the above mentioned factors into the current clinical FIGO staging system has been suggested. It aims to facilitate the recognition of those early tumors that require additional external radiotherapy. A description of the role of surgery, intracavitary and external radiation, and their combinations is included. In advanced carcinoma of the cervix, failure can be attributed to either large tumors containing cores of hypoxic cells resistant to conventional radiation therapy or to uncontrolled subclinical disease in the lymphatics at or near the border of the irradiated area. Radiotherapy combined with surgery, oxygen enhancers, infusion chemotherapy, and large particle high LET radiation has been implemented to increase local control; for distal failures, extended field irradiation of paraaortic nodes has been found to be technically feasible and well tolerated and is being studied for its effects on increased survival. The rationale for newer treatment procedures, including preliminary results and their complications, is discussed.

Antineoplastic Agents↗
PubMed1981

Total body-glucose turnover in normal and intra-uterine growth-retarded neonatal piglets.

1. Because studies of the metabolic problems of the human intra-uterine growth-retarded neonate are limited by ethical considerations we have used the intra-uterine growth-retarded piglet as an animal model. Total body-glucose kinetics were measured in 16 intra-uterine growth-retarded and 11 normal piglets from the same litters with [3H]glucose as a tracer. 2. The intra-uterine growth-retarded animals had marginally smaller brains than their normal littermates, but substantially smaller livers. Liver weight was reduced in proportion to body weight. 3. Total body-glucose turnover rate was significantly lower (P less than 0.001) in the intra-uterine growth-retarded animals in comparison with their normal littermates, but was appropriate for their smaller body and liver weights. Brain weight was only slightly reduced in the intra-uterine growth-retarded group so that glucose turnover adjusted to a common brain weight was significantly lower (P less than 0.001) in these animals. 4. Total body-glucose pool size was lower in the intra-uterine growth-retarded animals (P less than 0.01), but was appropriate for their body and liver weights. It was significantly reduced in relation to brain weight (P less than 0.001). 5. Resting plasma glucose concentration was lower in the intra-uterine growth-retarded animals (P less than 0.001). There was no relationship between concentration and turnover in either group. 6. It is suggested that the observed differences in total body-glucose turnover may be associated with profound differences in cerebral metabolism in the intra-uterine growth-retarded animals.

Animals↗
PubMed1981

Steady state glucose kinetics and their relation to plasma glucose concentration in the premature and full term neonatal piglet.

Steady state glucose kinetics were measured in 19 premature and 16 full-term piglets. Bodyweight, plasma glucose concentration, total body glucose turnover rate, and glucose pool size were not significantly different between the two groups. This suggests that the premature piglet is capable of maintaining glucose homeostasis during the first 24 h of life. Although there appeared to be a correlation between glucose turnover and plasma glucose concentration, analysis of covariance showed that it was spurious, suggesting that glucose utilization proceeds independently of the glucose concentration in plasma. Glucose turnover rate in the premature piglet is closely comparable with that reported in the premature human infant. These findings encourage the use of the neonatal piglet as an animal model for the study of the problems of the neonatal human.

Analysis of Variance↗
PubMed1980

Total body glucose metabolism in the conscious, unrestrained piglet and its relation to body- and organ weight.

1. Neonatal hypoglycaemia is a relatively common clinical problem in children but ethical constraints limit the investigations that may be made in the newborn. 2. As a preliminary step to assess the suitability of the piglet as a model for glucose metabolism in man, whole-body glucose turnover and glucose pool size were measured using [2-3H]glucose in forty piglets from ten litters. 3. Glucose pool size was linearly related to brain weight. However, multiple regression showed that the most useful predictors of pool size were body-weight and resting plasma glucose concentaration. 4. Glucose turnover was related to both brain weight and body-weight alone, but multiple regression showed that better predictors of turnover were liver weight, spleen weight and pancreas weight. 5. Similarities between our own results in piglets and those obtained in human neonates by Bier et al. (1977) extend not only to glucose turnover, but also to its relationship with body- and brain weight. These findings suggest that the piglet may be a useful model for the study of glucose metabolism in babies.

Animals↗
PubMed1980

Fetal development in relation to gestational age in the piglet.

Body and organ weights were measured in piglets from 44 litters which had been delivered by caesarean section at various times during the last 20 days of gestation. An attempt has been made to assess the usefulness of these measurements as predictors of gestational age. In this series of animals there was a highly significant correlation between mean litter weight and age. However, a considerable degree of uncertainty about the true gestational age must be accepted if mean litter weight is to be used as the sole predictor: at a mean litter weight of 1 kg, the 95% confidence limits were found to be +/- 10.2 days. No extra information was afforded by the inclusion of the organ weight data one the mean litter weight was known.

Animals↗
PubMed1980

[The NBT test--a review].

The NBT-test is a technique particularly used in its stimulated variant for testing granulocyte metabolism and in this capacity it is an integrated part of the test programme for differentiating neutrophilic dysfunctions. Its sphere of application is the diagnosis of progressive septic granulomatosis. The variety of the methods used makes it difficult to compare the results described by the various authors. Therefore, standardization is urgently necessary. A differentiation of bacterial and non-bacterial infections as well as of other febrile diseases is not possible with the unstimulated test. Investigations of the longitudinal section, however, allow the activity of the disease to be evaluated (with initially high numbers of granulocytes being positive in the nitroblue tetrazolium test).

Animals↗
PubMed1979

Starch metabolism in Pseudomonas stutzeri. I. Studies on maltotetraose-forming amylase.

The extracellular maltotetraose-forming amylase of Pseudomonas stutzeri was purified to homogeneity by a combination of affinity and hydroxyapatite chromatography. Sodium dodecyl sulfate-gel electrophoresis indicated that the oligomeric enzyme contains two different subunits with molecular weights of 48 000 and 58 000. Cross-linking studies using dimethyl suberimidate have demonstrated that the native enzyme consists of dimers. Seven isozymes of the amylase have been identified after polyacrylamide gel electrophoresis and amylose-digestion zymograms. The amylase of Ps. stutzeri is known to produce maltotetraose from linear and branched alpha-glucans by an exomechanism. The relatively high conversion rate of starch (75% hydrolysis), and the hydrolysis of cross-linked blue starch by this amylase indicate that the enzyme can cleave its substrates also by an endomechanism. Further strong evidence for an endomechanism was obtained from the action of the amylase on maltotetraose units which are located within the pullulan molecule. Dextran, pullulan, and maltotetraose are compeititve inhibitors. EDTA caused reversible inactivation. Amylase activity could be restored by addition of Ca2+. Heavy metals are inhibitory.

Amylases↗
PubMed1979

Starch metabolism in Pseudomonas stutzeri. II. Purification and properties of a dextrin glycosyl-transferase (D-enzyme) and amylomaltase.

Amylomaltase and disproportionating enzyme (D-enzyme) were purified to homogeneity from cell-free extracts of Pseudomonas stutzeri using a six-step procedure. The presence of both glycosyltransferases in the same organism has not been reported before. Molecular weight determination by gel chromatography gave a value of 74,000 for the amylomaltase and 115 000 for the D-enzyme. Two subunits of different molecular weight were found in each enzyme as proved by sodium dodecyl sulfate-gel electrophoresis. The optimum pH of amylomaltase and D-enzyme activity is 7.6--7.7. Action of both glycosyltransferases on different maltodextrins showed that amylomaltase is most active with maltotetraose, and the Km value for this substrate is 7.1 mM. D-Enzyme catalyzed glucose release from maltose (Km = 8.3 mM) at a higher rate than from maltotriose and maltotetraose. With maltotriose as initial substrate, D-enzyme forms glucose, maltopentaose, maltoheptaose, maltononaose, maltoundecaose as major products. Amylomaltase acts on maltotriose, maltotetraose, and maltopentaose to form a series of homologous 1,4-alpha-glucans. No essential chain-lengthening reaction occurred with maltohexaose.

Glucans↗
PubMed1979

Purification and some properties of five endo-1,4-beta-D-xylanases and a beta-D-xylosidase produced by a strain of Aspergillus niger.

Five different xylanases and a beta-D-xylosidase in the culture medium of Aspergillus niger have been purified to homogeneity from 13- to 52-fold by a procedure of gel and hydroxylapatite chromatography. The strain was isolated from soil of the African equatorial forest. Gel chromatography of the purified enzymes indicated that three of the xylanases have molecular weights of 31,000 and the other two xylanases have molecular weights of 50,000. beta-D-Xylosidase has a molecular weight of 78,000. The pH curves of the xylanases were quite diverse and showed pH optima ranging from 4.0 to 6.5. Characteristic action patterns were obtained for each of the purified xylanases by gel chromatography of the xylan digests on Bio-Gel P-2. The enzymes degraded arabinoxylan by an endomechanism, producing L-arabinose, D-xylose, xylobiose, and a mixture of branched arabinose-xylose and D-xylose oligosaccharides. All xylanases seemed to be capable of liberating L-arabinose from either arabinoxylan or the arabinose-xylose oligosaccharides. Branched arabinose-containing D-xylose oligosaccharides were slowly hydrolyzed, so that these sugars accumulate in the digest. Two xylanases showed relatively broad substrate specificity and were able to degrade also crystalline cellulose. beta-D-Xylosidase showed optimal activity at pH 6.7 to 7.0 and at 42 degrees C. The Km for o-nitrophenyl-beta-D-xylopyranoside was 0.22 mM and xylotriose was hydrolyzed more rapidly than xylobiose.

Aspergillus niger↗
PubMed1979

The effect of in vitro antibacterial properties of bovine milk diets on the natural colonisation of newborn piglets with coliform bacteria.

The diets suitable for the hand rearing of piglets in incubators were examined. Diet A was based on cows' milk heated to 56 degrees C and had bacteriostatic and antiadhesive properties against Escherichia coli. Diet B was based on evaporated cows' milk and did not have these properties. The numbers of coliform bacteria naturally colonising the small intestines of newborn piglets fed entirely on these diets for one week did not differ significantly, however both were significantly higher than in control piglets suckled from birth. Faecal counts of coliforms were similar in all three groups. Examination of the bacteriostatic sensitivity of the isolated strains to sows' milk indicated a predominance of milk-sensitive strains colonising the suckled piglets and a predominance of milk-resistant strains in the piglets fed diet B. This diet-dependent colonisation could not be explained by the in vitro bacteriostatic properties of the diets alone.

Animals↗