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Biomedical subjects

K Buchanan

Publications and source records attributed to K Buchanan.

At least 19 recordsLinked to original sources
PubMed2006

Dental screening in schools: the views of parents, teachers and school nurses.

OBJECTIVES: To obtain insight into the views of relevant 'stakeholders' (parents, teachers and school nurses) in dental screening in schools. METHODS: Eight schools in Chester and Ellesmere Port in the UK formed the setting of this study. A teacher from each school participated in one-to-one interviews, and focus groups for parents were carried out in each school. A focus group for school nurses working in the locality was also held. The same trained researcher undertook the interviews and focus groups; all interviews and focus groups were tape recorded, transcribed verbatim and thematically analysed independently by two trained individuals. RESULTS: Teachers, school nurses and parents all perceived the process of negative consent and the current dental examination as acceptable. The follow up procedure for identification of screened positive children was seen as inadequate. There was a strong feeling within each group that parents were ultimately responsible for their children's oral health and that state institutions had a limited role in ensuring children attended and received dental treatment. CONCLUSIONS: All of the groups considered it was primarily the responsibility of parents to take screened positive children to see a dentist. The NHS has limited influence on this process. This fact represents a significant challenge to improving the effectiveness of school dental screening.

Child↗
PubMed2006

The effectiveness of school dental screening: a cluster-randomized control trial.

Dental screening of children in schools is undertaken in many countries. There is no evidence that this activity is effective. The objective of our study was to determine if school dental screening of children reduces untreated disease or improves attendance at the population level. A four-arm cluster-randomized controlled trial was undertaken in the northwest of England. In total, 16,864 children aged 6-9 years in 168 schools were randomly allocated to 3 test groups, which received screening according to different models, and a control, which received no intervention. There were no significant differences in caries increment in the primary and secondary dentitions or in the proportions of children attending a dentist after screening between the control group and the 3 intervention arms. School dental screening delivered according to 3 different models was not effective at reducing levels of active caries and increasing attendance in the population under study.

Attitude to Health↗
PubMed2001

Water-soluble propofol analogues with intravenous anaesthetic activity.

Propofol (2,6-diisopropylphenol) is a widely used intravenous anaesthetic that is formulated as an emulsion since it lacks water solubility. We report a range of water-soluble analogues of propofol, containing a para-alkylamino substituent, which retain good intravenous anaesthetic activity in rodents.

Anesthetics, Intravenous↗
PubMed2001

Quantification of optic nerve axon loss associated with a relative afferent pupillary defect in the monkey.

OBJECTIVE: To quantify the amount of optic nerve axonal loss associated with the presence of a mild relative afferent pupillary defect (RAPD) in an experimental monkey model. METHODS: The right macula of 5 rhesus monkeys (Macaca mulatta) was treated with concentrically enlarging diode laser burns until an RAPD was detected using a transilluminator light and measured with neutral density filters. Intervals between treatments were 3 to 7 days over a period of 2 months. Pupillary responses to light stimulation were recorded with a monocular infrared television pupillometer. Two months after detection of an RAPD, 5 treated and 4 control monkeys underwent euthanasia and enucleation. Histopathologic analysis and quantification of optic nerve axon counts using an image analysis system were performed. RESULTS: No RAPD was observed despite an estimated ganglion cell loss of up to 26%. A 0.6 log unit RAPD was present in 5 monkeys when the laser scar incorporated the entire macula within the temporal vascular arcades. One eye had progressive vitreomacular traction with worsening of the RAPD to 1.8 log units without further laser treatment. Histopathologic evaluation disclosed complete loss of the normal retinal architecture within the macula. The average fiber loss for the 4 treated eyes with 0.6 log unit RAPDs compared with fellow eyes was 53.3% (95% confidence interval [CI], 45.0%-61.6%). The average difference in axon counts between untreated pairs of optic nerves was 12.8% (95% CI, 10.0%-15.6%). Optic nerve axon loss between pairs of experimental and control eyes was statistically significant (P<.001). CONCLUSION: In rhesus monkeys, an RAPD develops after an approximate unilateral loss between 25% and 50% of retinal ganglion cells. CLINICAL RELEVANCE: Owing to redundancy in the anterior visual pathways, unilateral retinal ganglion cell loss may occur prior to the observation of an RAPD. The presence of an RAPD measuring 0.6 log units implies that significant retinal ganglion cell injury has occurred.

Animals↗
PubMed2001

Bacterial contamination of fabric stethoscope covers: the velveteen rabbit of health care?

To determine if fabric stethoscope covers pose an infection control problem, we studied how they are cared for by our healthcare workers and performed microbiological investigations on 22 covers collected over a 3-week period. Our study suggests that fabric stethoscope covers represent a potential infection control problem because they are used for prolonged periods, are infrequently laundered, and are contaminated with bacteria.

Bacteria↗
PubMed2000

Long-latency component of the stretch reflex in human muscle is not mediated by intramuscular stretch receptors.

Reflex responses to mechanical stimulation of muscle (brief imposed movement) were investigated. Reflexes were elicited in the forefinger, recording from the first dorsal interosseous (FDI), and in the foot, recording from soleus. These responses typically consisted of a short-latency component (M1) and a long-latency component (M2) at 33 ms and 53 ms, respectively, after the stimulus in the case of FDI, and 37 ms and 68 ms, respectively, in soleus upon stimulation of the sole of the foot. Normally, when a muscle is stretched by a mechanical stimulus (either naturally or by an experimentally imposed movement), both skin receptors and muscle stretch receptors are activated. It is possible, however, to devise stimulation parameters where this is not the case. Fixating the finger with plasticine enables the effects of skin stimulation to be studied without stretching the FDI muscle. On the other hand, tapping a long tendon allows muscle stretch receptors to be activated without involving skin or subcutaneous structures. Component M1 was always abolished by finger fixation in 40 trials on 10 subjects, with M2 being essentially unchanged in latency, duration, or amplitude. Reflex responses were obtained in soleus muscle in nine experiments by prodding the sole of the foot (thereby stimulating both skin and muscle stretch receptors). Alternatively, the tendo achilles was prodded (which solely activates stretch receptors in the muscle). In the former, M1 and M2 were generated. In the latter, only M1 was produced. It is concluded that the long-latency component of the stretch reflex, M2, originates in skin and/or subcutaneous nerve terminals and that no part of M2 originates in muscle stretch receptors.

Achilles Tendon↗
PubMed1999

Treatment with humanized monoclonal antibody against CD154 prevents acute renal allograft rejection in nonhuman primates.

CD154 is the ligand for the receptor CD40. This ligand-receptor pair mediates endothelial and antigen-presenting cell activation, and facilitates the interaction of these cells with T cells and platelets. We demonstrate here that administration of a CD154-specific monoclonal antibody (hu5C8) allows for renal allotransplantation in outbred, MHC-mismatched rhesus monkeys without acute rejection. The effect persisted for more than 10 months after therapy termination, and no additional drug was required to achieve extended graft survival. Indeed, the use of tacrolimus or chronic steroids seemed to antagonize the anti-rejection effect. Monkeys treated with antibody against CD154 remained healthy during and after therapy. The mechanism of action does not require global depletion of T or B cells. Long-term survivors lost their mixed lymphocyte reactivity in a donor-specific manner, but still formed donor-specific antibody and generated T cells that infiltrated the grafted organ without any obvious effect on graft function. Thus, therapy with antibody against CD154 is a promising agent for clinical use in human allotransplantation.

Animals↗
PubMed1999

Regulatory peptides in the heart and major vessels of man and mammals.

Studies on the distribution of peptides in human tissues have been made either by measuring responses to localized stimuli or by subjecting extracts of different regions to radioimmunoassay (RIA). Attempts at isolating regulatory peptides from the mammalian tissues have resulted in the isolation of many bioactive fragments. Later, modification of initial isolation methods led to the identification of the native molecules in various tissues and body fluids. The present study examined atrial natriuretic peptide (ANP) and several other peptides in cardiac tissues of several species of laboratory mammal and human beings; using a sensitive and highly specific radioimmunoassays. In all the species studied, ANP-like immunoreactivity appeared to be highest in the heart tissue of rat. The peptide was highest in the right atrium (RA) of rat and lowest in the RA of guinea pig (P< 0.002). Neuropeptide Y (NPY) another abundant cardiac peptide was present in the cardiac tissues of all species but was more in the left atrium (LA) than the RA of all species (P<0.05). Calcitonin gene-related peptide (CGRP) was present throughout the cardiovascular system of the rat and guinea pig. Small but detectable amount of Neurotensin (NT) immunoreactivity was found in the rat but was consistently negative in the guinea pig cardiac tissues (P< 0.05). Substance P (SP) immunoreactivity was detected in the rat and higher quantities being in the Aorta but no trace of the peptide was detected in the left ventricle, aorta nor the pulmonary vein of post mortem human. Though the structure of most of the species studied has been elucidated, the primary structure of guinea pig ANP has not been fully generated. Thus the data obtained may suggest that in keeping with these mammalian peptides, the primary structures may be variant. With most of the peptides studied (e.g. ANP, Neuropepdide Y), immunoreactivity occurs predominantly in the atrial tissues, but is also present in vessels outside the heart, a finding which may be of functional significance.

Animals↗
PubMed1998

Type 1 and type 2 cytokines: from basic science to fungal infections.

At the present time, it is clear that Th1 responses afford protection against the fungi; however, the development, maintenance and function of the protective immune responses are complex mechanisms and are influenced by multiple factors. The route of infection has been shown to affect initial cytokine production and, consequently, the induction of protective Th1 responses. The ability of different isolates of the same fungal agent to induce and sustain a protective response has also been emphasized. Protective immune responses have been shown to vary in genetically different mouse strains after infection. In addition, these protective responses, such as cellular influx and cytokine production, also vary within the same animal depending on the tissue infected. The functional dominance of certain cytokines over others in influencing development and maintenance of protective responses has been discussed. Certain cytokines may act differently in hosts lacking important components of their innate or immune repertoire. It is evident from these presentations that a more comprehensive understanding of the protective mechanisms against different fungal agents is emerging. However, there is still much to learn before cytokine modulatory therapy can be used effectively without risk in the human host.

Animals↗
PubMed1994

Increased expression of ICAM-1 during reoxygenation in brain endothelial cells.

BACKGROUND AND PURPOSE: Thrombolysis is a promising therapy for acute ischemic stroke. However, there is evidence that neutrophils may physically plug cerebral microvessels on reperfusion, preventing the full benefit of thrombolysis. We undertook this study to determine whether there was increased endothelial expression of the intercellular adhesion molecule-1 (ICAM-1) gene during hypoxia-reoxygenation. METHODS: We isolated and cultured human brain microvascular endothelial cells and subjected them to hypoxia (PO2 < 10 mm Hg) in an anaerobic chamber followed by variable periods of reoxygenation. RESULTS: Twenty-hour periods of hypoxia did not lead to endothelial cytotoxicity as measured by a chromium-release assay. By Northern blot analysis, ICAM-1 mRNA transcripts were dramatically increased at 4 hours of reoxygenation but fell toward baseline (normoxia) by 12 and 24 hours. Hypoxia alone did not lead to an increase in mRNA levels. Western blot analysis showed an increased expression of ICAM-1 at 4, 12, and 24 hours of reoxygenation. The 4-hour increase in mRNA levels was not attenuated by pretreatment with 100 mumol/L allopurinol but was reduced by 30% with the addition of 20 mmol/L N-acetyl-L-cysteine at the time of reoxygenation and completely prevented by pretreatment with N-acetyl-L-cysteine. CONCLUSIONS: Hypoxia-reoxygenation leads to an increase in ICAM mRNA levels that peaks at 4 hours in human brain microvascular endothelial cells. Pretreatment with N-acetyl-L-cysteine can completely block the increase in ICAM-1 mRNA levels.

Brain↗
PubMed1992

Peptide tyrosine phenylalanine: a novel neuropeptide F-related nonapeptide from the brain of the squid, Loligo vulgaris.

A novel nonapeptide, sequence YAIVARPRFamide, was isolated from brain extracts of the squid, L. vulgaris. Designated peptide tyrosine phenylalanine (PYF), the peptide shows marked homology with the C-terminal nonapeptides of pancreatic polypeptide and neuropeptide F (NPF) from a number of sources. If PYF is the C-terminal nonapeptide of squid NPF, then it may be derived by a novel processing mechanism involving specific cleavage between two TYR residues. PYF may be a highly truncated, receptor-active variant of NPF.

Amino Acid Sequence↗
PubMed1992

Mechanisms of abnormal glucose metabolism during the treatment of acute severe asthma.

Twenty-five patients with acute severe asthma were treated with oxygen, corticosteroids and either salbutamol or aminophylline by intravenous infusion. Blood glucose, plasma insulin and glucagon were measured during the first 24 hours of treatment. Salbutamol and aminophylline rapidly caused hyperglycaemia, accompanied by a rise in insulin and a fall in plasma glucagon. At first the increase in plasma insulin was insufficient to restore normoglycaemia, but by 24 hours homeostasis was restored. The early submaximal insulin response was attributed to the fasting caused by breathlessness. There was no evidence of an increase in hormone secretion caused by direct beta 2-adrenergic stimulation of the pancreatic islets. The effect of corticosteroids on blood glucose over the period of study was considerably less than the contribution of either salbutamol, or aminophylline.

Acute Disease↗
PubMed1989

Inhibition of gastric secretion and motility by simulated upper gastrointestinal haemorrhage: a response to facilitate haemostasis?

As gastric acid and pepsin inhibit blood coagulation and platelet aggregation it is surprising that most upper GI haemorrhages stop spontaneously. To investigate this paradox we have studied acid and pepsin secretion, gastric motility and GI hormones after simulated upper GI haemorrhage. In seven healthy volunteers intraduodenal infusion of 160 ml autologous blood decreased pentagastrin stimulated submaximal acid secretion (mmol/h) from 30.0 (3.2) (mean (SE] in the hour preceding infusion to 21.4 (3.7) in the hour following infusion (p less than 0.02), representing a mean reduction in acid output of 30%. Pepsin output (mg/h) was also decreased from 207.5 (67.7) (mean (SE] in the hour preceding blood infusion to 135.7 (54.7) in the hour after infusion (p less than 0.02) representing a mean reduction in pepsin output of 43%. In six volunteers gastric emptying of a liquid meal was delayed after intraduodenal blood infusion compared with intubation alone with the emptying time (min) to half volume (t 1/2) being prolonged at 75.0 (8.2) (mean (SE] after blood infusion compared with 35.5 (6.6) after intubation alone (p less than 0.02). Plasma GIP concentrations (ng/l) increased to peak levels of 127.9 (62.7) (mean (SE] after intraduodenal blood infusion compared with the pre-infusion value of 58.3 (2.3) (p less than 0.02). These changes may represent protective physiological responses to facilitate haemostasis.

Adult↗
PubMed1987

Effects of nifedipine on gastric acid secretion and gastrin release in man.

As calcium is important in the regulation of gastric acid secretion and gastrin release, we have examined the effect of the calcium antagonist nifedipine on these processes in man. Nifedipine 30 mg orally inhibited basal acid output by 37% (p less than 0.025) and that stimulated by low infusion rates of pentagastrin--that is, 0.031 and 0.062 microgram/kg/h by 44% (p = 0.05) and 39% (p less than 0.02) respectively. On increasing the pentagastrin infusion rate the inhibition was surmounted suggesting it was competitive in type. Nifedipine did not affect basal or Oxo meal stimulated gastrin concentrations in normal volunteers nor did it affect resting serum gastrin or calcium stimulated increase in gastrin in a single patient with Zollinger-Ellison syndrome. These findings are consistent with the transmembrane flux of calcium ions being involved in basal and pentagastrin stimulated acid secretion in man.

Adult↗
PubMed1986

Nerve growth factor increases choline acetyltransferase activity in developing basal forebrain neurons.

Nerve growth factor (NGF) is a neuronotrophic protein. Its effects on developing peripheral sensory and sympathetic neurons have been extensively characterized, but it is not clear whether NGF plays a role during the development of central nervous system neurons. To address this point, we examined the effect of NGF on the activity of neurotransmitter enzymes in several brain regions. Intracerebroventricular injections of highly purified mouse NGF had a marked effect on the activity of choline acetyltransferase (ChAT), a selective marker of cholinergic neurons. NGF elicited prominent increases in ChAT activity in the basal forebrain of neonatal rats, including the septum and a region which contains neurons of the nucleus basalis and substantia innominata. NGF also increased ChAT activity in the hippocampus and neocortex, terminal regions for the fibers of basal forebrain cholinergic neurons. In analogy with the response of developing peripheral neurons, the NGF effect was shown to be selective for basal forebrain cholinergic cells and to be dose-dependent. Furthermore, septal neurons closely resembled sympathetic neurons in the time course of their response to NGF. These observations suggest that endogenous NGF does play a role in the development of basal forebrain cholinergic neurons.

Animals↗
PubMed1986

Effect of low-dose dopamine infusion on insulin and glucagon release in fasting normal man.

The effect of a low-dose infusion of dopamine on basal circulating concentrations of insulin, glucagon and glucose in six healthy male subjects is reported. Dopamine (0.1 microgram/kg/min) or placebo was given intravenously for 60 minutes. During infusion of the catecholamine, circulating plasma dopamine was 3.46 +/- 1 ng/ml. No change in circulating concentrations of insulin, glucagon and glucose were seen during infusion of dopamine when compared with placebo infusion. It is concluded that dopamine acting at a D2 receptor is unlikely to be of physiological importance in regulation of basal pancreatic islet cell function in man.

Blood Glucose↗