Search PubMed⌕ Search

Biomedical subjects

K Parker

Publications and source records attributed to K Parker.

At least 109 records · Page 6Linked to original sources
PubMed1980

Stimulation of ornithine decarboxylase activity in neural cell culture: potential role of insulin.

Age-dependent decreases in the levels of ornithine decarboxylase activity were observed in the optic lobes, cerebral hemispheres, and midbrain-diencephalon of 6--17-day-old chick embryos. In dissociated cell cultures from chick embryonic brains a similar pattern of declining ornithine decarboxylase activity with time in culture was observed. Ornithine decarboxylase activity in the dissociated brain cell cultures was stimulated by changing the culture medium. The peak stimulatory effect was shown to occur 12 h after changing the medium. Although serum-free medium stimulated ornithine decarboxylase activity slightly, the presence of serum in the medium was the primary stimulatory factor. Both fetal calf serum and heat-inactivated fetal calf serum produced dose-dependent stimulation of ornithine decarboxylase activity. Dialyzed fetal calf sera stimulated ornithine decarboxylase, but to a lower level than that produced by nondialyzed sera. Insulin (0.5--10 microgram/ml) stimulated ornithine decarboxylase activity in a dose-dependent manner in serum free medium. In addition, 10(-2) M-L-asparagine stimulated ornithine decarboxylase activity in serum-free medium.

Animals↗
PubMed1975

The jumping mechanism of Xenopsylla cheopis. III. Execution of the jump and activity.

The flea's hind legs are the chief source of jumping power, but in species which execute large jumps, take-off is accelerated by elastic energy released from a resilin pad (homologous with the wing hinge ligaments of flying insects) situated in the pleural arch. A central click mechanism, operated by a rapid twitch of the trochanteral depressor (the starter muscle), synchronizes the separate sources of energy which power the jump. Ciné photos confirm the morphological evidence that the flea takes off from the trochanters, not the tarsi. The loss of wings, associated with lateral compression of the body and the shortening of the pleural ridge (which thus lowers the position of the pleural arch) together with modifications of the direct and indirect flight muscles, are some of the main morphological features associated with the change from a flying to a saltatorial mode of progression. The flea's take-off basically resembles that of other Panorpoid insects (Diptera, Mecoptera, etc.). The release of elastic energy from the pleural arch is a system by which the force used to move the wings of flying insects is rapidly fed back into the legs and adds power to the jump.

Animals↗
PubMed1975

Uptake of 125I albumin by the endothelial surface of the isolated dog common carotid artery: effect of certain physical factors and metabolic inhibitors.

A study has been made, under transient conditions, of the uptake of 125I albumin by the endothelial surface of isolated dog carotid arteries. Effective rate constants were determined and the apparent activation energy was calculated to be about 13 kcal/mol in the range 25-37 degrees C. Label uptake was not significantly altered by the presence of 1 mmol/1 potassium cyanide or 10 mmol/1 iodoacetate in the incubating medium, or by the absence of substrate from it, consistent with the process being primarily passive. It appeared that the label entered the wall mainly by other routes than the endothelial inter-cell clefts.

Animals↗
PubMedDate not supplied

Delineation of contiguous determinants essential for biological functions of the pre-S sequence of the hepatitis B virus envelope protein: its antigenicity, immunogenicity and cell-receptor recognition.

The preS region of the hepatitis B virus (HBV) envelope protein has the following properties: (1) exposure on the surface of the virus; (2) high immunogenicity; (3) involvement in the reaction of the virus with cell receptors and (4) elicitation of antibodies protective against infection. Attempts to mimic B- and T-cell epitopes on the native protein by synthetic peptides were highly successful. This success depended on identification of those regions within the preS sequences which are the most important for biological function of the virus and for immunity, and on the synthesis of long peptides (20-40 residues) containing both B- and T-cell epitopes. Results presented here highlight those subregions of the preS sequence which are the most essential for the antigenicity and immunogenicity of HBV.

Amino Acid Sequence↗
PubMedDate not supplied

Evidence-based care: can we overcome the barriers?

Evidence-based care has become the new mantra within the NHS, despite the fact that the concept of applying research to practice has been promoted for several decades. However, literature on the subject suggests that formidable obstacles remain to the integration of research into care delivery. This article describes a study which used Funk et al's (1991a,b) Barriers Scale with a population of nurses in a large teaching hospital in the UK. This scale was specifically developed to identify barriers to the introduction of research into practice, and modified for a UK context. The results suggest that a complex array of barriers exist but that foremost among these is the nature of the organizations within which nurses work. Comparisons are made with data from the USA, and the need to create time for nurses to implement change, and to empower them to do so, is stressed.

Attitude of Health Personnel↗
PubMedDate not supplied

Pressure damage prevention: basing practice on evidence.

As part of an initiative to develop evidence-based practice at the Northern General Hospital, Sheffield, a three-part project was undertaken. The aims were to identify barriers to using research in nursing, establish a baseline of nurses' knowledge and its influence on their practice in one essential area of nursing care--pressure damage prevention--and develop a strategy for change which took account of the findings from the first two parts of the project. In this article, the authors describe the second part of the project which examined nursing knowledge and practice with reference to the management of pressure damage prevention. The findings are discussed and the authors recommend that nurses integrate into their practice evidence from sources such as systematic reviews.

Bandages↗
PubMedDate not supplied

Off-the-shelf audit: is it feasible?

Increasing interest in audit in the health service has focused attention on the tools and methods used to achieve it. These can be extremely expensive, so a tendency to opt for off-the-shelf packages has developed. This article reviews how one such instrument, The Central Nottinghamshire Psychiatric Nursing Audit, has been used in two settings over the past three years, with particular emphasis on its cost-effectiveness.

England↗
PubMedDate not supplied

Morphological, immunocytochemical and flow cytometric in vitro characterisation of a surface-adherent medulloblastoma.

Well-characterised cell lines derived from paediatric intrinsic brain tumours are rare. The different repertoire of cell adhesion molecules expressed by primitive neuro-ectodermal tumours, when compared with gliomas, results in a general lack of propensity for surface adherence. In this study, a highly cellular, medulloblastoma biopsy with a Ki-67 index of 20%, obtained by posterior fossa craniotomy of a two-year-old boy, was maintained in surface- adherent culture for twelve sequential in vitro passages. The culture (VC312R) was characterised by immunocytochemistry and flow cytometry using antibodies against cluster of differentiation 44 (CD44), glialfibrillary acidic protein (GFAP), intermediate filament proteins (Nestin and Vimentin), neural cell adhesion molecules (NCAMs) (ERIC and UJ13A), ganglioside (GD3) and neuron-glial 2 (NG2). GD3, GFAP, ERIC-1, UJ13A and NG2 were detected by neither immunocytochemistry nor flow cytometry. It is of particular interest that we have previously reported that the progenitor cell-associated NG2 heparan sulphate proteoglycan was not expressed in a series of medulloblastoma biopsy sections in our laboratories, while NG2 positivity was seen in supratentorial primitive neuro-ectodermal tumours (PNETs). Strong CD44 positivity was detected on most cells (mean = 93.5% of cells on flow cytometry). In one previous case of medulloblastoma, maintained in our laboratories (IPNN-8) as a substrate-adherent culture, no CD44 staining was detected. Twenty-five percent of cells were strongly Vimentin-positive while 54.5% of cells showed Nestin positivity. The expression of Nestin, Vimentin and CD44 is consistent with primitive neural cell evolution. Non-expression of NCAMs may be consistent with the lack of cell-cell adhesion in this culture, which results in surface adherence. The high expression of CD44 may also indicate a distinct phenotype within primitive neuroectodermal tumours, which determines cell-cell and cell-extra cellular matrix adhesive properties.

Antibodies, Monoclonal↗