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Biomedical subjects

W Walker

Publications and source records attributed to W Walker.

At least 55 records · Page 3Linked to original sources
PubMed1991

Influence of dietary citric acid and calcium on the bioavailability of orally administered chlortetracycline in piglets.

In a study involving 18 piglets divided into three groups (A, B and C), the effects of dietary calcium and citric acid, and feeding technique on chlortetracycline bioavailability were examined. Groups of 6 animals received a basal diet with either 0.7% (group A) or 1.4% calcium (groups B and C). Citric acid was not included in diets of the first experimental period. In the second period, either 1.5% (groups A and B) or 3.0% (group C) citric acid was added to the diet. In both experimental periods, chlortetracycline was administered once intravenously (7.5 mg/kg b.w.) and once orally (30 mg/kg b.w.). After each administration, blood samples were taken at regular intervals in order to determine chlortetracycline serum concentrations by a microbiological method. Following oral chlortetracycline intake, low dietary calcium or citric acid addition to the diet produced increased chlortetracycline serum concentrations. Chlortetracycline bioavailability was 12.6% at 0.7% dietary calcium, and 9.5% at 1.4% dietary calcium. Enteral chlortetracycline absorption was improved 65% with 1.5% or 3.0% dietary citric acid supplementation. An 8-hour delay of feed intake following oral chlortetracycline intake did not significantly influence chlortetracycline bioavailability.

Administration, Oral↗
PubMed1990

Critical care for clonidine poisoning in toddlers.

Clonidine may be a source of serious toxicity when ingested by toddlers. We describe 11 cases of clonidine ingestion by toddlers (mean dose 0.15 mg/kg; range 0.01 to 0.57). The source of the clonidine was a grand-parent in six of 11 cases. Symptoms included altered level of consciousness (n = 11), miosis (n = 5), bradycardia (n = 8), hypotension (n = 5), apnea and respiratory depression (n = 6), hypothermia (n = 5) and hypertension (n = 3). Therapeutic interventions included naloxone (n = 8) and atropine (n = 4), dopamine (n = 1), fluid resuscitation (n = 4), and endotracheal intubation (n = 1). There were no deaths. Symptoms of clonidine ingestion were typically mild if the dose ingested was less than 0.01 mg/kg, while bradycardia and hypotension occurred usually with doses of greater than 0.01 mg/kg. Apnea and respiratory depression were common when the dose exceeded 0.02 mg/kg. More effective measures are needed to prevent these potentially serious intoxications.

Atropine↗
PubMed1989

The homeless experience: clinic building in a community health discovery-learning project.

The concept of discovery learning is exemplified in this account of four students and their instructor who began and developed a nurse-run clinic for the homeless in a community health project. The students were registered nurses returning for their bachelor's degrees. They experienced frustration at learning the difference between care based on their assessments of patients' needs and care geared to clients' assessments of desired interventions. The journals that they kept reveal self-discovery as well as new respect for other humans. In addition, a new type of community care emerged, which gives all indications of surviving.

Ambulatory Care Facilities↗
PubMed1989

The RGO Generation II: muscle stimulation powered orthosis as a practical walking system for thoracic paraplegics.

The RGO Generation II reciprocating gait orthosis was jointly developed by Louisiana State University Medical Center and Durr-Fillauer Medical, Inc, to overcome four problems encountered with the existing model: 1) The high energy cost of locomotion; 2) the great arm strength required for patients to stand up from the seated position without assistance; 3) difficulty (especially for patients with hamstring contracture) in remaining standing owing to failure of the knee latch to lock except in full extension; and 4) problems in balancing when ambulating on an incline. The RGO Generation II employs concurrent electrostimulation of the rectus femoris and hamstrings to assist in rising and balancing and a ratchet-type latching device to improve safety and stability in standing. Alternating stimulation of the rectus femoris and contralateral hamstrings are used for locomotion. Testing in six patients with thoracic paraplegia demonstrated an average 30+% reduction in energy expenditure at a walking speed of .05 m/s and a 15+% reduction at .37 m/s; improved mobility and better balance on inclines; and unassisted rising in all patients. Walking range was increased from an average of 100 m to an average of 800 m. More research is needed to provide stair-climbing ability and to further reduce energy expenditure.

Adult↗
PubMed1986

Splenunculectomy in thrombocytopenic purpura.

In six patients with thrombocytopenic purpura not cured by splenectomy platelets fell to less than 150 X 10(9)/l within six weeks of splenectomy. They 'failed to respond'. Two underwent splenunculectomy without improvement. Splenuculectomy offered little chance of improvement to published cases who failed to respond but may well be helpful after true relapse.

Child↗
PubMed1985

Natural killer cell activity in childhood acute lymphoblastic leukaemia in remission.

Fifteen children with acute lymphoblastic leukaemia (ALL) in remission receiving maintenance chemotherapy and 12 ALL patients off treatment and in remission were tested for natural killer (NK) cell activity in vitro. Compared with a control population the children with ALL receiving maintenance chemotherapy had low levels of NK cell activity. This effect was not due to a specific reduction in NK cell numbers since proportions of mononuclear cells detected by the monoclonal antibodies HNK-1 (Leu-7) and Leu-11a were normal. Furthermore NK cell activity in patients could only be partially increased by pre-incubation of effector cells with interferon (alpha IFN). These studies confirm the lack of NK cell activity in children with ALL and show that this phenomenon is directly related to functional NK cell impairment. Our study has further shown that this effect is transient since ALL patients off treatment and in remission showed normal levels and augmentation of NK cell activity.

Acute Disease↗
PubMed1985

Platelet values during normal pregnancy.

Blood samples were obtained from 26 healthy women at regular intervals throughout pregnancy and analysed using a Coulter Counter Model S Plus III. The mean values for the various haematological indices at each stage of gestation were first calculated; the platelet count showed a small decrease throughout pregnancy as did haemoglobin concentration while there was an apparent increase in mean platelet volume, platelet distribution width and white cell count. However, analysis of the trends within patients did not always reflect these mean changes; there was considerable variation in platelet count within individuals and the apparent fall in the group as a whole was accounted for by a considerable fall in a few individuals. The assumption that the trends in platelet values determined from groups of patients will indicate how individual pregnant women behave is misleading.

Adult↗
PubMed1984

Idiopathic thrombocytopenia, initial illness and long term follow up.

One hundred and eighty one children with thrombocytopenia for which no cause could be found have been studied. One patient died with severe bleeding possibly from disseminated intravascular coagulation and one developed cerebral haemorrhage, both within two weeks of onset. Ninety one per cent of the 135 with acute disease but only 36% of those with chronic disease remitted spontaneously. Twenty per cent of spontaneous remission occurred more than one year after onset. Six patients have run an intermittent course for 10 to 20 years. Four patients have had symptomless thrombocytopenia for between 10 and 30 years. Of 32 children treated by splenectomy 24 maintained normal platelet values thereafter. One boy died from pneumococcal septicaemia two years after splenectomy but he had not received prophylactic penicillin. One hundred and fifty eight patients were followed up 3 to 37 years (mean 16.4 years) after onset. None who recovered spontaneously or after splenectomy had had further bleeding problems. No patient nor immediate relative had developed other autoimmune disease. We consider that a short course of corticosteroids immediately after diagnosis is justified in all cases even though we cannot produce proof that it influences the course of the disease. We do not accept any place for long term immunosuppressant treatment.

Acute Disease↗
PubMed1983

Role of calcium and calmodulin in activation of the oxyntic cell by histamine and carbamylcholine in the guinea pig.

The role of calcium in stimulation of the oxyntic cell by histamine and carbamylcholine was studied using a sensitive quantitative cytochemical staining technique that measures oxyntic cell hydroxyl ion production (HIP) as an index of acid secretion. Histamine (10(-17)-10(-14) M), carbamylcholine (10(-12)-10(-9) M), and extracellular calcium (10(-7)-10(-3) M) caused a linear, dose-dependent stimulation of the oxyntic cell. EGTA (10(-6) M) inhibited carbamylcholine by 50% but not histamine-stimulated activity. Lanthanum chloride (10(-6) M) caused 100% inhibition of carbamylcholine-induced activity but did not affect histamine-stimulated activity. A maximally effective dose of calcium (10(-4) M) caused additive effects on HIP at low doses of carbamylcholine without alteration of the maximal effect of carbamylcholine. Calcium (10(-4) M) did not enhance the effects of histamine. The calmodulin antagonists, trifluoperazine (10(-5) M), pimozide (10(-5) M), and a naphthalenesulfonamide (W-7), inhibited the integrated response to histamine by 54, 56, and 53%, and that of carbamylcholine by 65, 64, and 99%, respectively. Thus, extracellular calcium per se, stimulates the oxyntic cell. The action of carbamylcholine is completely dependent upon calcium/calmodulin mediation, supporting the concept that cholinergic actions are mediated via calcium-calmodulin events. Although histamine does not require extracellular or membrane calcium events to stimulate the oxyntic cell, calmodulin appears to participate in histamine action.

Animals↗
PubMed1982

Beneficial effects of intracoronary thrombolysis up to eighteen hours after onset of pain in evolving myocardial infarction.

Coronary arteriography and intracoronary streptokinase (STK) infusion were performed on 89 patients with evolving acute myocardial infarction (AMI). Ventricular function was followed in these patients during their hospitalization by gated radionuclide ventriculography. In 35 of these patients thallium imaging was performed on admission and 4 hours after reperfusion. An additional 30 patients with AMI who either met exclusion criteria for the STK protocol or refused study served as a control group. In patients admitted 0 to 6, 6 to 12, or 12 to 18 hours after onset of pain, there was no difference in change in left ventricular ejection fraction (LVEF) from admission to discharge, in percent of patients with total occlusion demonstrating reperfusion, or in percent of patients demonstrating a significant increase in LVEF. The average increase in LVEF from admission to discharge in patients reperfused ws 8% (40% +/- 14% to 48% +/- 13%, p less than 0.001). No change in LVEF was demonstrated in the control population or in patients in whom coronary reperfusion was unsuccessful. Reperfusion produced an increase in thallium uptake in the infarct-related myocardium that was accompanied by an improvement in regional function. Failure of reperfusion produced no change in either thallium uptake or regional function.

Adult↗
PubMed1981

Effect of variations in islet size and shape on glucose-stimulated insulin secretion.

The present study considers the effects of differences islet size and shape on in vitro glucose-stimulated insulin secretion. Islets were obtained from young rats and rapidly sorted into different size categories before incubation with 16.7 mM glucose. Subsequently, the diameters of each islet were measured and estimates of surface area and volume, assuming various spheroidal or ellipsoidal shapes, were obtained for each islet. These various figures were correlated with the amount of insulin secreted from the same islets and a regression curve was generated for each different islet shape. The results indicate that insulin secretion rates increased directly as a function of islet size (volume or surface area), regardless of islet shape (r = 0.78, p less than .01); thus, islet size is of major importance in predicting insulin secretion and studies utilizing isolated islets should be normalized for this factor. Measurements of islet diameter provide an easy solution to this problem.

Animals↗
PubMed1981

Terminal deoxynucleotidyl transferase activity in childhood and adult acute lymphoblastic leukaemia.

The measurement of terminal deoxynucleotidyl transferase (TDT) activity in leukaemic blasts of 26 cases of acute lymphoblastic leukaemia (ALL) (13 children less than 14 years, 13 adults greater than 14 years) demonstrated significantly greater activities of the enzyme on a proportion of the adults. The predominant cytological sub-type in the adult patients was L2 (FAB classification) whereas L1 cytological sub-type dominated in the childhood group. There was no relation between TDT values and FAB sub-type but the highest activities in the childhood group were seen in patients assessed at the time of relapse. We conclude that continued use of quantitative TDT estimations may provide useful information in further characterising the currently recognised cytological and immunological sub-types in ALL.

Acute Disease↗