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Biomedical subjects

M John

Publications and source records attributed to M John.

At least 181 records · Page 10Linked to original sources
PubMed1984

Ribonucleoprotein particles from Xenopus eggs and embryos. Neural-archencephalic-inducing activity of the protein moiety.

Ribonucleoprotein particles were isolated from unfertilized eggs and gastrula stages of Xenopus laevis. The particles from both stages induce in gastrula ectoderm the formation of large foreheads (neural-archencephalic-inducing activity), whereas ribosomal subunits have no inducing activity. The inducing activity of particles from both stages is largely abolished after treatment with proteolytic enzymes and to some extent with ribonuclease. The protein moiety of gastrula ribonucleoprotein particles was extracted with phenol and the protein reduced with 2-mercaptoethanol. The protein induces foreheads, but at a lower rate than the intact particles. The protein was fractionated by high-performance liquid size-exclusion chromatography on a derivatized silica gel with 75% formic acid as eluent. The fraction which includes proteins from 10 000 to 16 000 Da has the highest neural-archencephalic-inducing activity.

Animals↗
PubMed1984

Phosphorylation site sequence of smooth muscle myosin light chain (Mr = 20 000).

The amino terminal sequence of the myosin light chain (Mr = 20 000) isolated from chicken gizzards was found to be (sequence in text). This sequence assignment differs from that reported by Maita et al. [(1981) European J. Biochem. 117, 417] in the order of the tryptic peptides. The revised amino acid sequence exhibits greater homology with the phosphorylation site sequences of the regulatory light chains from cardiac and skeletal muscle. Moreover it is now apparent why synthetic peptides corresponding to the previously reported sequence were very poor substrates for the myosin light chain kinase.

Amino Acid Sequence↗
PubMed1984

Mapping of the protein-coding regions of Rhizobium meliloti common nodulation genes.

An 8.5-kb EcoRI fragment containing the common nod region of the megaplasmid pRme41b of Rhizobium meliloti was recloned in plasmids of Escherichia coli, and a detailed restriction map was established. The region can express at least eight proteins in E. coli minicells and in an in vitro transcription/translation system, prepared from E. coli. Protein coding regions were determined by subcloning of restriction fragments, deletion mutations and by transposon mutagenesis. The coding regions for at least three polypeptide chains (mol. wts. 23 000, 28 500 and 44 000) were mapped on a 3.3-kb nod gene cluster. The 44 000 mol. wt. protein is expressed from a nod region, which is highly conserved in two Rhizobium species. The protein map of the 8.5-kb fragment was correlated to a map of insertion mutations with Nod and Fix phenotypes. The data suggest that the proteins encoded by the nod gene cluster may be involved in early steps of the nodulation process. Nod Fix symbiotic mutations were localized in the coding region for a 33 000 mol. wt. protein, suggesting that this polypeptide might be a fix gene product.

Journal Article↗
PubMed1984

Relaxin gene expression in human ovaries and the predicted structure of a human preprorelaxin by analysis of cDNA clones.

In earlier studies we identified in a human genomic library a gene (human relaxin gene H1) coding for a relaxin-related peptide. We now have evidence that the human genome possesses an additional relaxin-related gene (designated human relaxin gene H2) which appears to be selectively expressed in the ovary during pregnancy. Nucleotide sequence analysis revealed striking differences in the predicted structures of relaxin encoded by these two genes. Chemical synthesis of biologically active relaxin based on the sequence obtained from ovarian cDNA clones confirmed that the expressed gene (H2) encodes an authentic human relaxin. The expressed gene appears to be transcribed into two different sized mRNAs and preliminary evidence suggests that the mRNA transcripts possess different 3'-untranslated regions. There was no evidence for the expression of human relaxin gene H1 in the ovary and so far it is unclear whether gene H1 is expressed in another tissue or whether it represents a pseudogene. From the sequence data presented here it will now be possible to construct oligonucleotide probes and raise antibodies against synthetic peptides which could then be used to identify sites of relaxin biosynthesis and specifically quantitate the expression from either the H1 or H2 relaxin genes.

Amino Acid Sequence↗
PubMed1984

High-resolution hydroxyapatite chromatography of proteins.

Hydroxyapatite chromatography has been used to separate all five isozymes of lactic dehydrogenase, six enzymatically active forms of bovine pancreatic DNase I, and a standard protein mixture. The proteins were eluted with a linear gradient of sodium phosphate. Enzyme activity recoveries were greater than 90%. Packing materials were obtained from commercial fine-particle-sized hydroxyapatite (DNA grade Bio-Gel HTP) by an elutriation procedure. Long columns packed with small crystals were run under low pressure at acceptable flow rates, and were used over prolonged periods.

Bacillus↗
PubMed1983

Definitive nonsurgical therapy of epithelial malignancies of the anal canal. A report of 12 cases.

Twelve patients with epidermoid carcinoma of the anal region ranging in age from 40-89 years were treated with combined chemotherapy (CT) and radiotherapy (RT) in lieu of abdominal-perineal resection. Ten patients received no prior treatment and two patients were treated for local recurrence following limited surgical excision. Two courses of 5-FU infusion and mitomycin C were given 3-4 weeks apart simultaneously with whole pelvis RT to 3000-4140 rad. One patient received an additional tumor volume dose of 3094 rad by interstitial Iridium implant and one patient received an orthovoltage boost of 1000 rad to the anal ring. All patients completed treatment. Complete regression of the anal mass occurred in all patients. Biopsies of the anal region performed after completion of therapy revealed no evidence of residual cancer. Ten of the 12 patients are alive without evidence of disease 4-24 months (median, 14 months) after completion of treatment. Two patients have died seven months after treatment of unrelated causes and were tumor-free at autopsy. All patients developed proctitis, diarrhea, and moist perineal desquamation which resolved by four weeks posttreatment. Based on their experience and that of others recently reported, the authors conclude that the described CT-RT protocol offers a definitive alternative to surgery of epidermoid cancer of the anal region.

Adult↗
PubMed1983

Control of poliomyelitis by pulse immunisation in Vellore, India.

In a simple study into the control of polio in the Third World a town was divided into 16 zones and pulses or oral polio vaccine given at one station in each zone, after extensive publicity about the campaign. Some 62% of children received three doses of the vaccine and the incidence of polio fell dramatically over the study period. It is suggested that this method is applicable to similar communities because it is cheap, effective, and able to be extended to unimmunised communities when resources allow.

Child, Preschool↗
PubMed1983

Cerebral blood flow and cerebral metabolism in normal and intrauterine growth retarded neonatal piglets.

1. Cerebral blood flow and cerebral metabolism were measured in conscious, normally grown neonatal piglets and in littermates which had undergone intrauterine growth retardation. 2. Cerebral blood flow was measured by the Kety-Schmidt technique using [125I]iodoantipyrine as the tracer. The tissue: blood partition coefficient of this tracer was measured in separate groups of growth retarded and normal animals. Cerebral utilization rates of glucose and oxygen were calculated from the arteriovenous concentration differences on the Fick principle. 3. The mean body weight of the growth retarded animals was about half that of their normally grown littermates, and liver weight was reduced in proportion. Brain weight was slightly but significantly lower in the growth retarded animals. 4. Cerebral blood flow was lower in the growth retarded piglets but the rates of cerebral utilization of oxygen and glucose were not significantly different in the two groups. The fractional extraction of arterial oxygen by the brain was significantly higher in the growth retarded animals. 5. The partition coefficient of iodoantipyrine was significantly lower in the growth retarded animals, being about 75% of the normal value. It is clear that had the partition coefficients been assumed to have been the same in both groups the calculated cerebral blood flows would have been identical. 6. It is concluded that growth retarded neonatal piglets have relatively normal sized brains, with a rate of glucose and oxygen consumption that is not significantly different from normal, despite a reduction in cerebral blood flow of about 35%. Consequently the fractional extraction rate of arterial oxygen by the brain is increased from 50% to 70%.

Animals↗
PubMed1983

The accuracy of measurement required for acceptable estimation of non-steady rates of appearance and disappearance by the tracer method using a two-compartment model.

The two-compartment method for measuring non-steady-state glucose turnover rates was examined by computer simulation and by in vivo experiment. Given perfectly accurate input data, the simulations showed that the calculated turnover rates agreed closely with the true answer (agreement was not perfect however, because of the necessity for interpolation between the observed points). Contaminating the input data with a single erroneous observation of either tracee or tracer concentration produced large, spurious oscillations in the calculated turnover rates, the duration of which was inversely proportional to the frequency with which the infused compartment was sampled. Contaminating the perfect input data with observational noise of a magnitude approximately equal to the known measurement uncertainties showed that the calculations were very sensitive to noise and this was verified by in vivo experiment. It is concluded that non-steady-state glucose kinetics can be successfully measured by the two-compartment technique, but that measurements to an accuracy of at least 1% (coefficient of variation) are required.

Animals↗
PubMed1983

The tissue-blood partition coefficient of iodoantipyrine in pig brain and its change with age.

The tissue-blood partition coefficient of 125I-labelled iodoantipyrine was measured in pig brain. The mean coefficient for 11 neonatal piglets (aged 0.5 to 4 days) was 0.718 mL/g (SD 0.083). Measurements in a further 11 animals up to 144 days old (at which time pigs are sexually mature), showed that the partition coefficient increased significantly with age, possibly as a result of the accumulation of brain lipid during growth. The change in partition coefficient with age was curvilinear, rising to unity as the animals reached maturity. There were significant differences between the partition coefficients in grey and in white matter, but these were so small relative to the differences between pigs that they could be neglected for all practical purposes. Since the accuracy of measurement of cerebral blood flow (CBF) by the Kety-Schmidt technique depends directly on the partition coefficient of the tracer, it is important to confirm that apparent changes of CBF do not simply reflect alterations in the partition coefficient rather than real changes in blood flow.

Age Factors↗
PubMed1983

Clinical assessment of a trimethoprim-sulfamethopyrazine combination (Kelfiprim) in lower respiratory tract infections.

The new combination of trimethoprim 250 mg and sulfamethopyrazine 200 mg was used in fourteen out-patients and eighteen in-patients with acute exacerbation of chronic bronchitis, pneumonia or bronchopneumonia due to sensitive bacteria. The drug was given for 1 to 2 weeks as one capsule daily (following a double loading dose on the first day), and ampicillin, 500 mg capsules q.i.d., was administered to another group of eleven in-patients for comparison. Overall results, based on clinical, radiological and laboratory findings, were excellent or good in 85% and 67%, respectively, of out- and in-patients receiving the combination drug; definite failures were one out of fourteen and two out of eighteen cases, and the remainder were assessed as fair. In three out of thirty-two patients mild to moderate gastro-intestinal side-effects were observed during treatment. The drug compared favourably to ampicillin for both effectiveness and safety.

Adult↗
PubMed1983

Injectable anaesthetic techniques in 2 species of gerbil (Meriones libycus and Meriones unguiculatus).

The effects of a range of injectable anaesthetic agents were assessed in two species of gerbil (M. libycus and M. unguiculatus). The drug combination of metomidate and fentanyl was the only preparation that consistently produced surgical anaesthesia. Considerable species variation in drug response was noted, indicating that caution should be exercised in recommending standard anaesthetic dose rates for these animals.

Anesthesia, General↗
PubMed1983

Neuroleptanalgesia in the rabbit.

The efficacy of the neuroleptanalgesic combinations of fentanyl-fluanisone with diazepam; and etorphine-methotrimeprazine, either alone, or with diazepam, was investigated in the rabbit. The effects of these drugs on some cardiovascular variables were studied in chronically catheterized rabbits. Fentanyl-fluanisone and diazepam produced good surgical anaesthesia. Although respiratory depression occurred, this had little effect on blood gas values. In contrast, etorphine-methotrimeprazine and diazepam produced severe respiratory depression with consequent hypercapnia and acidosis.

Acidosis↗
PubMed1983

Intrauterine growth retardation detected in several species by non-normal birthweight distributions.

The statistical distribution of birthweights in 64 litters of pigs, 48 litters of dogs, 59 litters of rabbits, 130 litters of rats and 46 litters of mice was examined. Birthweight followed a Gaussian or normal distribution in about two-thirds of the litters inspected, as judged visually using a normal probability plot, and by the W-test statistic. In the remainder, a single outlying observation in an otherwise normal sample was detected by Dixon's test, and/or a separate sub-population of low birthweight animals could be identified by fitting two normal populations to the observed samples. In the non-Gaussian litters, the average proportion of affected members was 40% of the litter. These results suggest that growth-retarded neonates should not be regarded simply as the tail-end of a normal distribution.

Animals↗
PubMed1983

Comparison of techniques for the estimation of the prevalence of poliomyelitis in developing countries.

Although reliable data on the prevalence and trends of paralytic poliomyelitis are necessary for health planning, they are often difficult to obtain in developing countries. Comparisons were made of the cost and the time taken to obtain prevalence rates of residual poliomyelitis paralysis in a single community by (1) a surveillance and reporting system using physicians and other practitioners, (2) a school survey covering grades 1 to 12, (3) annual surveys of grade 1 schoolchildren, and (4) a house-to-house questionnaire survey. These techniques gave poliomyelitis prevalence rates of 3-5 per 1000 school-age children, and poliomyelitis incidence rates of 12-29 per 100 000 population per year. The annual grade 1 school survey was the cheapest and easiest to carry out and appears reliable in areas with a high rate of school enrolment.

Adolescent↗
PubMed1982

Porcine relaxin: molecular cloning and cDNA structure.

Relaxin is a peptide hormone produced by the corpora lutea of ovaries during pregnancy, softening and lengthening the ligaments of the pelvis and softening the cervix in order to make childbirth easier. In attempts to determine the nucleotide sequence coding for relaxin, recombinant DNA techniques were used to obtain a cDNA clone bank from total mRNA isolated from the ovaries of pigs in late pregnancy. Clones were screened using cDNA initiated by synthetic oligonucleotide primers coding for the Trp Val Glu Ile sequence of the porcine relaxin B chain. The synthetic undecamer [5'-ATCTCCACCCA-3'] was found to prime a specific 32P-labeled cDNA of approximately 300 nucleotides containing B chain and signal peptide coding sequences, as verified by nucleic acid sequence analysis. This cDNA was used to probe the ovarian clone bank. Several clones containing large inserts which hybridized to this probe were subjected to sequence analysis and some of these were found to contain the preprorelaxin coding region, comprising a signal peptide of 24 amino acids, a B chain of 32 amino acids, a large C peptide of 104 amino acids, and an A chain of 22 amino acids. From the amino acid sequence of prorelaxin derived in this way, it appears that the processing of prorelaxin involves two enzymes with chymotrypsin-like and trypsin-like specificity, respectively. In comparisons of porcine and rat preprorelaxins, the C region had as much amino acid sequence homology as the B and A chains. The C region is also rich in charged amino acids, suggesting a role for it beyond simply ensuring proper disulfide bond formation.

Animals↗