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Biomedical subjects

V Cameron

Publications and source records attributed to V Cameron.

28 records · Page 2Linked to original sources
PubMed1985

Stress hormones in blood and cerebrospinal fluid of conscious sheep: effect of hemorrhage.

Acute moderate hemorrhage (15 ml/kg withdrawn over 10 min) was used to study stress hormone changes in blood and cerebrospinal fluid (CSF) of conscious sheep with chronic indwelling intracerebroventricular catheters. Mean plasma arginine vasopressin (AVP) and ACTH rose 150- and 14-fold, respectively, above basal values to peak levels at 20 min after onset of hemorrhage. A smaller (4- to 5-fold) rise occurred in plasma angiotensin II (AII) to peak levels at 10 min. The corticosteroid response (cortisol and aldosterone) occurred later (peak at 45 min) and was consistent with the dependence of these steroids on plasma ACTH and AII changes. Increases in plasma epinephrine and norepinephrine were small and transient. Compared to changes in plasma, changes in CSF hormone levels after hemorrhage were small and independent of plasma concentrations. Mean CSF AVP increased to peak levels at 15 min whereas rises in CSF ACTH, AII-like immunoreactivity, and cortisol were slower and delayed in comparison with the patterns observed in plasma. Despite evidence of increased sympathetic activity, and rise in plasma catecholamines, CSF epinephrine fell after hemorrhage and CSF norepinephrine did not change. These results show that in conscious sheep rapid and major increases in plasma AVP, ACTH, and AII follow acute moderate hemorrhage. Concomitant changes in CSF hormone levels are small and delayed. With the possible exception of AVP it appears unlikely that the acute systemic hormone response to hemorrhage is determined by hormone changes in CSF.

Adrenocorticotropic Hormone↗
PubMed1984

Failure of translational repression in the phage f2 op3 mutant is not due to an altered coat protein-RNA interaction.

A secondary phenotype of the op3 mutant of RNA bacteriophage f2 is the absence of translational repression of the phage replicase gene by the phage coat protein. We have synthesized RNA fragments corresponding to the site of translational repression for both the wild type and the op3 mutant. Using a quantitative assay, we show that the affinity of the closely related R17 coat protein for the mutant and wild type RNA fragments is the same. In addition, we find that the op3 and R17 coat proteins bind to the wild type RNA fragment with essentially identical dissociation constants. Thus, the altered regulation of replicase protein synthesis in the op3 mutant does not appear to be due simply to a reduced affinity of the translational repressor for its target site.

Bacteriophages↗
PubMed1983

Sequence-specific interaction of R17 coat protein with its ribonucleic acid binding site.

The interaction between phage R17 coat protein and its RNA binding site for translational repression was studied as an example of a sequence-specific RNA--protein interaction. Nuclease protection and selection experiments define the binding site to about 20 contiguous nucleotides which form a hairpin. A nitrocellulose filter retention assay is used to show that the binding between the coat protein and a synthetic 21-nucleotide RNA fragment conforms to a simple bimolecular reaction. Unit stoichiometry and a Kd of about 1 nM are obtained at 2 degrees C in buffer containing 0.19 M salt. The interaction is highly sequence specific since a variety of RNAs failed to compete with the 21-nucleotide fragment for coat protein binding.

Amino Acid Sequence↗
PubMed1983

The hormonal actions of corticotropin-releasing factor in sheep: effect of intravenous and intracerebroventricular injection.

The 41-residue ovine corticotropin releasing factor (CRF) was administered iv and intracerebroventricularly (icv) to merino sheep. A significant rise in plasma ACTH, beta-lipotropin (beta LPH) and cortisol was demonstrated after the administration of 200 micrograms, iv. A highly significant correlation between the increments in plasma ACTH and beta LPH was observed. The plasma ACTH rise was evident within 5 min and was abolished by the prior administration of 0.4-4.0 mg dexamethasone. No significant rise in plasma GH, LH, PRL, insulin, glucagon, pancreatic polypeptide, met-enkephalin, angiotensin II, aldosterone, or vasopressin could be demonstrated. Although smaller doses of CRF (50 ng to 5 micrograms) were effective when given icv, the ACTH response was more delayed. It is concluded that CRF stimulates a rapid increase in the secretion of ACTH and beta LPH in sheep. Suppression of this response by dexamethasone indicates that glucocorticoids are capable of acting on the pituitary to inhibit the ACTH response to CRF. The delayed response when CRF is given icv may be due to diffusion. The action of CRF appears to be relatively specific, in that the plasma concentrations of the other pancreatic, pituitary, and adrenal hormones measured were not affected.

Adrenal Cortex Hormones↗
PubMed1978

Polynucleotide kinase from a T4 mutant which lacks the 3' phosphatase activity.

Polynucleotide kinase from E. coli infected with the PseT 1 mutant of bacteriophage T4 has been isolated. The PseT 1 enzyme purifies similarly to normal polynucleotide kinase and effectively transfers the gamma phosphate of ATP to the 5' terminal hydroxyl of DNA and RNA. The PseT 1 and normal enzymes require similar magnesium ion concentrations, have the same pH optima and are both inhibited by inorganic phosphate. However, the PseT 1 enzyme is totally lacking the 3' phosphatase activity associated with normal polynucleotide kinase. The PseT 1 enzyme is a useful tool for the preparation of oligonucleotides with 3' and 5' terminal phosphates for use as susbstrates for RNA ligase.

Coliphages↗
PubMed1977

3'-Phosphatase activity in T4 polynucleotide kinase.

The purification of T4 polynucleotide kinase results in the copurification of an activity which will specifically remove the 3'-terminal phosphate from a variety of deoxyribonucleotides and ribonucleotides in the absence of ATP. This phosphatase activity requires magnesium, has a pH optiumum of 6.0, and is more active with deoxyribonucleotides than ribonucleotides. T4 polynucleotide kinase and the 3'-phosphatase activity copurify by gradient elution column chromatography on DEAE-cellulose, phosphocellulose, and hydroxylapatite. The two activities are included in and comigrate on Sephadex G-200. Polyacrylamide gel electrophoresis at PH 9.2 results in conigration of the two activities together with the major protein band. The two activities respond in parallel to heat inactivation at 35 degrees C and ATP, a substrate for the kinase only, protects both activities from heat inactivation. It is therefore suggested that the two activities are functions of the same protein molecule.

Coliphages↗
PubMed1977

Equimolar addition of oligoribonucleotides with T4 RNA ligase.

T4 induced RNA ligase will join equimolar concentrations of two oligoribonucleotides, (Ap)3C and p(Up) 5, to form a single product, (Ap)3Cp(Up) 5, in high yield. The presence of the 3' phosphate on p(Up)5 prevents the oligomer from adding to itself. The pH optimum of the reaction is about 7.5, but less of the undesirable adenylated intermediate, App(Up) 5, forms at pH 8.2. The reaction rate is a linear function of oligomer concentration from 3 micronM to 0.6 mM. The data suggest that T4 RNA ligase will be a useful enzyme for the synthesis of oligomers of defined sequence.

Adenosine Triphosphate↗
PubMedDate not supplied

Some scanning electron microscopic features of human cervical epithelium in cell culture.

Human cervical epithelial cells, growing out in confluent monolayers from small explants, develop cytoplasmic extensions from the margins of the growth, extending out and terminating on the glass substrate. The marginal fibrils are particularly frequent on the edges of cellular lamellipodia, protruding in advance of the growing edges. Marginal cells with microvilli tend to have more marginal fibrils on their leading edges than smooth more differentiated cells, and occasionally there is continuity between microvilli and marginal fibrils. Where there is cellular overlap, marginal fibrils extending over the surface of another cell can be seen; where these is an intercellular cleft, cytoplasmic bridges have the same appearance as marginal fibrils. Colchicine (10-6 M) did not affect marginal fibril formation.

Cells, Cultured↗