Search PubMed⌕ Search

Biomedical subjects

J F Morrison

Publications and source records attributed to J F Morrison.

At least 163 records · Page 9Linked to original sources
PubMed1977

The analysis of progress curves for enzyme-catalysed reactions by non-linear regression.

A procedure, based on the Gauss-Newton method for non-linear regression, has been developed to obtain enzyme kinetic constants from the analysis of progress curve data. Rules are presented which greatly simplify the derivation of the necessary equations. The method has been applied to the reactions catalysed by prephenate dehydratase, acid phosphatase and lactate dehydrogenase and has yielded values for kinetic parameters which agree well with those obtained from steady-state rate measurements.

Acid Phosphatase↗
PubMed1977

Effects of bradykinin mediated by autonomic efferent nerves.

Intra-arterial injections of bradykinin cause increases in blood pressure and increased impulse rates in single sympathetic efferent fibres. The peptide also causes one or more large bladder contractions, which are associated with increased impulse rates in pelvic nerve efferent fibres whose spontaneous discharges are temporally associated with increases in intravesical pressure. These induced increases in pelvic nerve discharge and intravesical pressure could be abolished or greatly reduced by interference with conduction in pathways which mediate reflex bladder contractions. It is concluded that bradykinin has little direct action on the bladder, and that the large contractions which result from its administration are mediated by the central nervous system.

Action Potentials↗
PubMed1977

The effects of bradykinin on afferent units in intra-abdominal sympathetic nerve trunks.

The effects of intra-arterial injections of bradykinin on afferent discharges in the splanchnic and hypogastric nerves have been studied. All units which were excited by the peptide were mechanosensitive. Following i.a. bradykinin, the slowly adapting mechanoreceptors associated with the bladder showed increased discharge rates which appear to be related to changes in intravesical pressure. When the effects of bradykinin on the bladder were blocked by cord cooling, the afferents were not excited. It is concluded that bradykinin causes discharges in the slowly adapting mechanoreceptors around the bladder because it causes bladder contractions, and not because of any chemosensitivity of the nerve ending.

Action Potentials↗
PubMed1976

Studies on inosine monophosphate dehydrogenase. An associating-dissociating system.

The techniques of polyacrylamide gel electrophoresis, sedimentation velocity and frontal analysis on Sephadex have been used to demonstrate that preparations of IMP dehydrogenase (IMP: NAD+ oxidoreductase, EC 1.2.1.14) from Aerobacter aerogenes consist of a mixture of molecular weight isomers. Further, it has been shown that dissociation of the higher molecular weight forms is promoted by urea, sodium dodecyl sulphate and dithiothreitol. Under conditions comparable to those used for kinetic analyses, the enzyme has a molecular weight of about 86000 and this is the smallest active species that has been observed. In the absence of a reducing agent, the enzyme undergoes polymerization and is devoid of catalytic activity. From the amino acid composition and peptide map, it appears that the molecule with a molecular weight of 86000 is made up of two identical polypeptide chains.

Amino Acids↗
PubMed1976

Studies on inosine monophosphate dehydrogenase. Steady state kinetics.

The reaction catalyzed by IMP dehydrogenase (IMP: NAD+ oxidoreductase EC 1.2.1.14) from Aerobacter aerogenes has been investigated kinetically at pH 8.1 as a three reactant system by means of steady-state velocity studies in the absence of products, as well as by inhibition studies using products and substrate analogues. The mechanism appears to be a partially random one in which IMP and K+ can bind randomly to the free enzyme while NAD does not react unless K+ or both K+ and IMP are present on the enzyme. While the steady-state velocity data can be analysed adequately on the basis that rapid equilibrium conditions apply, this is only an approximate description of the mechanism since product inhibition studies indicate that there is a significant concentration of an enzyme-XMP (enzyme-K-XMP) complex in the steady-state.

Enterobacter↗
PubMed1976

Studies on inosine monophosphate dehydrogenase. Isotope exchange at equilibrium.

Investigations on the mechanism of the IMP dehydrogenase (IMP: NAD+ oxidoreductase, EC 1.2.1.14) reactions have been made at pH 7.0 by measuring rates of isotope exchange at chemical equilibrium with K+ maintained at a constant concentration. The results are generally in accord with the conclusions reached on the basis of the steady-state kinetic data obtained previously and confirm that there is random addition of IMP and NAD to the enzyme. The data also indicate clearly that at pH 7.0 catalysis is faster than the rate of IMP and/or XMP release which is rate limiting for the reaction sequence. The binding of IMP to the enzyme at pH 8.1 has been demonstrated to occur in the absence of both K+ and NAD and id independent of the K+ concentration.

Carbon Radioisotopes↗
PubMed1976

Mechanosensitive afferent units in the hypogastric nerve of the cat.

1. Recordings have been made from ninety single afferent units in the hypogastric and lumbar splanchnic nerves of the cat. 2. The majority of units examined had properties similar to those previously described in the splanchnic nerve: they were slowly adapting mechanoreceptors with one to six punctate mechanosensitive sites distributed mainly along blood vessels as they approached the viscera in peritoneal ligaments; they had a wide range of mechanical thresholds and conduction velocities in the range 0.5-24 m s-1. 3. Receptive fields were found over the bladder base or its peritoneal ligaments or both, on the uterus or broad ligament or both, on the colon or mesocolon or both, and in association with the ureter, vas deferens, prostate or pelvic fat pads. 4. Discharges from afferent units associated with the bladder were investigated during spontaneous (or reflex) bladder contractions, passive distensions, and tetanic contractions induced by electrical stimulation of the sacral spinal cord. The mean spike rates of the adapted (tonic) discharges, observed during distensions and induced tetani, differed over part of the range of intravesical pressures examined. Their behaviour is discussed in relation to the concept of 'in series' tension receptors within the bladder wall.

Action Potentials↗
PubMed1975

The mechanical properties of oesophageal striated muscle in the cat and sheep.

1. A study has been made of the mechanical behaviour of isolated strips of cat and sheep oesophageal muscle. 2. At 37 degrees C, time to peak tension in an isometric twitch was about 80 ms in both muscles. Tetanic fusion frequency was 30 s-minus 1, twitch: tetanus ratio 0.4-0.47, and maximum velocity of shortening was 3 lengths. s-minus1. 3. The results are compared with the prperties of other muscles.

Animals↗