Search PubMed⌕ Search

Biomedical subjects

R John

Publications and source records attributed to R John.

At least 181 records · Page 10Linked to original sources
PubMed1973

Biosynthetic pathway of desmosines in elastin.

1. Elastins purified by various methods from the ligamentum nuchae and the lungs of cattle of various ages were analysed for amino acid compositions and lysine-derived cross-links. 2. In fully mature elastins from adults the main cross-links were desmosine, isodesmosine and lysinonorleucine and the so-called aldol-condensation product. Trace amounts of merodesmosine were also found. 3. During the normal maturation of elastins the amounts of desmosine, isodesmosine and lysinonorleucine increased, whereas the aldol-condensation product and intact lysine residues decreased and merodesmosine remained the same. 4. Elastins from young animals contained significant amounts of dehydromerodesmosine whereas elastins from adults contained virtually nil. Evidence is presented which suggests that the biosynthetic pathway of desmosine and isodesmosine proceeds via the aldol-condensation product and dehydromerodesmosine.

Age Factors↗
PubMed1972

Chemical compositions of elastins isolated from aortas and pulmonary tissues of humans of different ages.

1. Elastins were isolated from the visceral pleuras and parenchymas of lungs of humans of different ages. 2. The elastin content of pleuras increased whereas that of parenchymas remained constant with increasing age. 3. The amino acid compositions and carbohydrate contents of elastins isolated from both pulmonary tissues changed in the same way with increasing age of the subjects. These changes were similar to those observed in elastins isolated from the aorta. 4. Similar glycoproteins were isolated from pleuras and aortas, and were more difficult to extract from the elastins of older subjects. Contamination with these glycoproteins was responsible for the changes in composition of elastin, as the age of the tissue from which it was extracted increased. 5. The amount of the cross-linking amino acids desmosine and isodesmosine was lower in elastins isolated from both aorta and pulmonary tissues of senile subjects than those from younger subjects.

Adolescent↗
PubMedDate not supplied

New technologies for amperometric biosensors.

Amperomeric-based detectors have successfully been used as personal monitors for blood glucose levels. However, there is a desire to increase the number of compounds measured in a small blood sample, the speed of detection and enhance the reliability of the measurement. Furthermore, with the increasing use of microdialysis as a clinical sampling method in metabolic medicine, paediatric medicine and neurointensive care, there is a need for rapid on-line detection of analytes such as lactate, glucose and glutamate in low microlitre volume samples. Two approaches to these problems are described. The first uses enzymes immobilized in a packed bed with electrochemical detection of a ferrocene mediator as a flow-injection assay for use with microdialysis. Results from microdialysis of the brain of freely moving rats are described. In the second approach, thin-film techniques are used to fabricate arrays of microdisk and micro line electrodes. The properties of these arrays in free solution and in a flow cell are presented together with an example using multiple arrays to identify an analyte by oxidation potential. Finally, different enzymes are entrapped onto the surface of two arrays by electrochemical polymerization of o-phenylenediamine. The resulting device detects glucose and lactate in real-time.

Animals↗
PubMedDate not supplied

Novel mitochondrial proteins and decreased intrinsic activity of cytochrome-c oxidase. Characteristics of swayback disease in sheep.

Swayback disease (SD), a fatal neurological disorder affecting lambs and kids, is characterized by abnormal mitochondria and low cytochrome-c oxidase activity. The cytochrome-c oxidase content and activity and the protein composition of mitochondria isolated from the brains of SD lambs were investigated. Difference spectra analysis indicated that the cytochrome-c oxidase content of mitochondria from SD animals was lower than normal, and electrophoresis showed that when compared to mitochondria from normal animals, lipid-depleted mitochondria from SD lambs had a different protein composition, particularly, in the 40-55 kDa region. Polarographic studies, using cytochrome-c as substrate, confirmed low intrinsic activity of cytochrome-c oxidase within the mitochondria of SD lambs. These studies also showed that at low ionic strength, such mitochondria did not yield the expected characteristic biphasic Eadie-Hofstee plots.

Animals↗
PubMedDate not supplied

GH responses to growth hormone releasing factor in depression.

The growth hormone (GH), thyrotrophin (TSH) and prolactin response to growth hormone releasing factor (GRF) was investigated in 18 patients suffering from major depression with melancholia and in 18 age- and sex-matched normal controls. There was no significant difference in the GH response to GRF stimulation between the patients and controls and in neither subject group was there a demonstrable TSH or prolactin response to GRF. These findings indicate that the pathophysiology underlying the blunted GH response to pharmacological challenge, demonstrated in other studies, must lie at a suprapituitary level.

Depressive Disorder↗
PubMedDate not supplied

Bilateral septic arthritis due to Salmonella enteritidis.

We present an unusual case of septic arthritis due to Salmonella enteritidis involving both knee joints of a 29-year-old man with Hodgkin's lymphoma. The role of ciprofloxacin in septic arthritis caused by Gram-negative bacilli is also reviewed.

Administration, Oral↗
PubMedDate not supplied

The clinical value of serum prolactin measurement in the differential diagnosis of complex partial seizures.

The time course of changes in serum prolactin after complex partial seizures has been determined and compared to similar changes after other types of seizure and non-epileptic attacks. Seizures in 33 subjects were recorded on video EEG telemetry. Peak serum prolactin concentrations occurred 15-20 min after tonic-clonic seizures, 10 min after complex partial seizures, and were highest after generalised tonic-clonic seizures. Serum prolactin concentrations remained less than 1000 mU/l after absences and non-epileptic attacks. Application of Bayes' theorem showed that where serum prolactin was greater than 1000 mU/l 5-10 min post event this would identify genuine tonic-clonic or complex partial seizures. The false negative rate of this test was 9% for tonic-clonic seizures and 38% for complex partial seizures. Failure of serum prolactin to rise after an attack is of little value in distinguishing complex partial seizures from non-epileptic attacks.

Adolescent↗
PubMedDate not supplied

Three manual immunoassays for the rapid detection of hepatitis B surface antigen.

We have evaluated 3 commercial test kits for the detection of hepatitis B surface antigen (HBsAg) which do not require elaborate instrumentation and are relatively inexpensive. These included the Immunocomb-II (Orgenics, Israel), Austragen latex agglutination (Span, India) and Daina Screen (Abbott, USA) tests. A panel of 98 sera tested by IMx HBsAg assay (Abbott, USA) were used to evaluate the tests. Sensitivities of 96.6%, 86.2% and 96.6%, and specificities of 95.7%, 94.2% and 100%, respectively, were obtained. We therefore recommend the Immunocomb-II or Daina Screen tests for HBsAg detection in small laboratories where facilities to conduct automated enzyme-linked immunosorbent assays are not available.

Evaluation Studies as Topic↗