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Biomedical subjects

M Walker

Publications and source records attributed to M Walker.

At least 361 records · Page 20Linked to original sources
PubMed1993

Do nonesterified fatty acids regulate skeletal muscle protein turnover in humans?

We examined whether elevated plasma nonesterified fatty acid (NEFA) levels exert a direct effect on protein metabolism by measuring [2H5]phenylalanine skeletal muscle exchange and whole body turnover. [2H5]phenylalanine was infused (0.5 mg.kg-1 x h-1) for 300 min in seven healthy subjects on two occasions. Intralipid (10%; 30 ml/h) or 0.154 mol/l NaCl was infused in random order from 120 min. Measurements were taken during basal (90-120 min) and infusion (270-300 min) periods. Intralipid infusion increased plasma NEFA levels [1.31 +/- 0.13 vs. 0.49 +/- 0.05 (SE) mmol/l; P < 0.05] and forearm NEFA uptake [45 +/- 76 vs. -51 +/- 44 nmol . 100 ml forearm-1 x min-1; P < 0.05]. Serum insulin and blood ketone body levels were similar with the two treatments. Elevated plasma NEFA levels were associated with a comparable decrease in forearm phenylalanine uptake (11 +/- 2 vs. 17 +/- 2 nmol x 100 ml forearm-1 x min-1; lipid vs. control, P < 0.05) and release (20 +/- 2 vs. 26 +/- 3 nmol x 100 ml forearm-1 x min-1; lipid vs. control, P < 0.05). However, there were no significant changes in net forearm phenylalanine exchange and whole body phenylalanine turnover. Therefore, elevated plasma NEFA levels were associated with a comparable decrease in the rates of skeletal muscle protein synthesis and breakdown but did not appear to influence overall protein balance, as assessed using [2H5]phenylalanine.

Adult↗
PubMed1993

A fresh look at the risks of artificial infant feeding.

Declining breastfeeding rates and the aggressive marketing of breastmilk substitutes has blurred the distinction between breastmilk and formula. Claims that infant formula is safe, economical, easy to use, and nutritionally complete are challenged in this article, the intent of which is to raise the awareness of health workers to the non-publicized side of infant formula. Non-proprietary, referenced data is provided to illustrate that formula and breastmilk are not the same thing, and that health outcomes of infants who consume each may be different. Guilt is often cited by health workers as a reason to avoid informing parents about the risks of artificial feeding. Suggestions are offered for addressing this reasoning.

Attitude of Health Personnel↗
PubMed1993

Normal splanchnic but impaired peripheral insulin-stimulated glucose uptake in cirrhosis.

The site of impaired glucose uptake in cirrhosis is uncertain. We therefore performed hyperglycemic clamps (glucose 10 mmol/L) in 10 patients with compensated alcoholic cirrhosis and impaired glucose tolerance and in six control subjects. Muscle glucose uptake was estimated in patients and controls with the forearm technique. In the cirrhotic subjects splanchnic glucose uptake was measured with hepatic vein catheterization and primed continuous infusions of indocyanine green and [6-3H]glucose. To assess insulin-independent glucose uptake and the effects of elevated nonesterified fatty acid levels on glucose uptake, we repeated the study with somatostatin to induce insulin deficiency and a nicotinic acid analog, acipimox, to inhibit lipolysis. Substrate disposal was assessed on indirect calorimetry. Despite similar stimulated insulin levels, total glucose utilization was lower in the cirrhotic subjects (3.9 +/- 0.3 vs. 8.8 +/- 1.7 mg/kg/min, p = 0.006). This deficiency was accounted for by lower nonoxidative glucose disposal (1.2 +/- 0.2 vs. 5.8 +/- 1.6 mg/kg/min, p = 0.002). Forearm glucose uptake was lower in the cirrhotic subjects (0.39 +/- 0.06 vs. 1.21 +/- 0.3 mg/100 ml/min, p = 0.001). However, splanchnic glucose uptake at 1.59 +/- 0.14 mg/kg/min was similar to that reported in other studies of normal subjects. Insulin-independent glucose uptake was normal, and acipimox had no effect on total or forearm glucose utilization. Glucose intolerance in cirrhosis is characterized by impaired peripheral insulin-stimulated non-oxidative glucose disposal. The high nonesterified fatty acid levels seen in cirrhosis most likely do not contribute to this defect. Splanchnic glucose uptake is normal in cirrhosis.

Adult↗
PubMed1993

Effects of aminohydroxybutane bisphosphonate on bone growth when administered after hind-limb bone loss in tail-suspended rats.

The effects of aminohydroxybutane bisphosphonate (AHBuBP) on bone after disuse osteopenia were studied in tail-suspended rats. Male Sprague-Dawley rats (weight range, 313-352 g) randomized into four groups of eight animals received 2 ml kg-1 day-1 of either AHBuBP (0.3 mg kg-1 day-1) or normal saline (vehicle) subcutaneously on days 14 and 15 of a 28-day experiment. The groups were 1) nonsuspended, saline; 2) suspended on days 14 to 28, saline; 3) suspended on days 0 to 28, AHBuBP; and 4) suspended on days 0 to 28, saline. On days 19 and 26, all rats received 15 mg/kg (1 ml/kg) of calcein. On day 28, they were sacrificed and their tibias and femurs were analyzed in vitro for bone density, strength and stiffness. The tibias were also analyzed histomorphometrically. The tibias and femurs from AHBuBP-treated rats were as dense as those in the nonsuspended group, whereas tail suspension in the untreated rats for 14 and 28 days caused a significant decrease in bone density. However, in measurements of bone strength and stiffness, the samples from the rats that received AHBuBP were similar to those of untreated rats suspended for 14 days, suggesting the newly formed bone was weaker. In the AHBuBP group, compared with all others, static histologic measurements of the proximal tibial metaphyses showed an increased bone area and perimeter and a decreased percentage of osteoid perimeter without a difference in the percentage of eroded perimeter. Dynamic histologic studies showed a decreased bone formation rate and decreased longitudinal growth rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Alendronate↗
PubMed1993

Nipple confusion.

Explore the source record for details and available documents.

Bottle Feeding↗
PubMed1993

Contamination of bronchoscopes with Mycobacterium tuberculosis.

Difficulties with disinfection of endoscopes and reports of cross-contamination of bronchoscopy specimens have previously been described. A recent episode of mycobacterial cross-contamination of bronchoscopy specimens was identified in a tertiary care referral centre. Two of eight bronchoscope suction valves cultured positive for Mycobacterium tuberculosis and the cause of the outbreak was traced to a faulty wash/disinfect switch in an automatic washer. The situation was resolved following autoclaving of all suction valves and repair of the endoscope washer. This report highlights the problems with instrument design and supports previous recommendations to autoclave suction valves routinely after each use.

Bronchoscopes↗
PubMed1993

Aminohydroxybutane bisphosphonate and clenbuterol prevent bone changes and retard muscle atrophy respectively in tail-suspended rats.

Hind-limb unloading by tail suspension of rats, an established model of simulated microgravity, was used to examine the efficacy of aminohydroxybutane bisphosphonate (AHBuBP) and clenbuterol in preventing bone loss and muscle atrophy, respectively. Male Sprague-Dawley rats (299-372 g) were randomized into six groups of six: 1) unsuspended, saline, 2) unsuspended, saline, pair fed with group 3, 3) suspended, saline, 4) suspended, 0.03 mg/kg/day x 2 of AHBuBP, 5) suspended, 0.3 mg/kg/day x 2 of AHBuBP and 6) suspended, 0.3 mg/kg/day x 2 of AHBuBP + clenbuterol (0.5 mg/kg/day i.p. x 6, then 1 mg/kg/day i.p. x 6). Animals in groups 3 to 6 were tail suspended for 14 days from a system of double pulleys and allowed free mobility with their hind limbs unloaded. On days -2 and -1, before suspension on day 0, all rats received a single s.c. injection of either 2 ml/kg of normal saline (vehicle) or AHBuBP. All rats were tested for exercise tolerance before day -2 and on day 10, and grip strength before day -2 and on day 13. On day 14, the rats were euthanized and their humeri, tibias and femurs analyzed in vitro for bone density (by single-photon absorptiometry), strength and stiffness (by 3-point bending). Muscles were analyzed for weight, protein concentration and enzyme activity. Pair feeding had no effect other than on food consumption and body weight. AHBuBP caused a dose-dependent increase in bone density in humeri, tibias and femurs, even in tail-suspended rats, relative to control unsuspended animals, with no significant difference in bone strength or stiffness between AHBuBP groups and unsuspended animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Alendronate↗
PubMed1993

Open mouth posture and cross-sectional nasal area in young children.

A biracial sample of two-hundred ninety-six children were assessed for open-mouth posture (OMP) in the natural environment. In addition, rhinometry was performed on 288 of the youngsters. Means were computed for percent OMP and cross-sectional nasal airway. Results indicated that in general these children exhibited relatively high rates of OMP. Boys displayed significantly greater OMP than girls. However, children exhibiting OMP on 80% of the observation intervals had significantly smaller cross-sectional nasal areas than the youngsters who displayed OMP on fewer than 20% of observation intervals. The implications of the findings were discussed.

Analysis of Variance↗
PubMed1992

Pergolide can induce soluble superoxide dismutase in rat striata.

Pergolide, a dopamine receptor agonist, given daily i.p. for three weeks at 0.04 mg/kg and 0.4 mg/kg, significantly induced soluble (Cu-Zn) superoxide dismutase in the rat striatum, while having no effect on the mitochondrial (Mn) form of the enzyme. Such induction, which can also be effected by (-)-deprenyl, may help to protect against nigrostriatal degeneration.

Animals↗
PubMed1992

The effect of a high carbohydrate diet on running performance during a 30-km treadmill time trial.

The purpose of the present study was to examine the influence of a high carbohydrate diet on running performances during a 30-km treadmill time trial. Eighteen runners (12 men and 6 women) took part in this study and completed a 30-km time trial on a level treadmill without modifying their food intake (trial 1). The runners were then randomly assigned to a control or a carbohydrate (CHO) group. The CHO group supplemented their normal diets with additional carbohydrate in the form of confectionery products during the 7 days before trial 2; the control group matched the increased energy intake of the CHO group by consuming additional fat and protein. The mean (SEM) carbohydrate intake of both groups was 334 (22) g before trial 1, after which the CHO group consumed 566 (29) g.day-1 for the first 3 days and 452 (26) g.day-1 for the remaining 4 days of recovery. Although there was no overall difference between the performance times for the two groups during trial 2, the CHO group ran faster during the last 5 km of trial 2 than during trial 1 [3.64 (0.24) m.s-1 vs 3.44 (0.26) m.s-1; P less than 0.05]. Furthermore, the 6 men in the CHO group ran the 30 km faster after carbohydrate loading [131.0 (5.4) min vs 127.4 (4.9) min; P less than 0.05], whereas there was no such improvement in times of the men in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Experimental evaluation of ten clinically used arterial prostheses.

The arterial grafts currently in use are classified into five basic categories; 10 different commercially available prostheses were chosen to represent these categories. The Vascutek and Bionit are made from knitted Dacron and have medium porosity, requiring preclotting by the surgeon. The DeBakey Soft Woven and Plasma TFE grafts are made from woven Dacron and have low porosity, not requiring preclotting under most circumstances. Also studied were woven and knitted grafts with leakage resistance referred to as "impervious" Dacron grafts: the Vascutek Gelseal, the Bard Albumin Coated DeBakey Vasculour II, the Microvel with Hemashield, and the albumin saturated, autoclaved DeBakey Soft Woven graft. Gore-Tex and Impra are expanded polytetrafluoroethylene grafts which do not require preclotting. For each type, five grafts 6 cm long and 8 mm in diameter were implanted in the descending thoracic aorta of healthy adult dogs for 16 weeks. The physical characteristics, biocompatibility, and healing patterns varied according to the structure and treatment of the grafts. Pretreatment with biomaterials during manufacture is quite effective in preventing transinterstices blood loss during implantation, but results in altered physical qualities, increased thrombogenicity and delayed healing in comparison to the effects of preclotting with autogenous blood at the time of implantation.

Anastomosis, Surgical↗
PubMed1992

Selecting controls for schizophrenia research studies: the use of the National Adult Reading Test (NART) is a measure of premorbid ability.

The National Adult Reading Test (NART) has achieved popularity as a measure of pre-morbid intellectual ability, based on the premises that pronunciation of irregular words is unaffected in many clinical disorders and that performance is highly correlated with general intellectual ability. Recently, schizophrenia research studies have begun to appear in the literature, where the NART has been used to estimate pre-morbid ability. However, this use has preceded the basic required demonstration that, in fact, NART performance is unaffected by the schizophrenic process. In the present study, NART performance was compared across three groups; 20 acutely ill unmedicated DSM-IIIR schizophrenics, 10 other unmedicated acute psychotics, and 20 control subjects. When demographic variability between the groups was controlled for, there were no group differences in terms of NART performance. NART performance was not correlated with Brief Psychiatric Rating Scale scores, and in all three groups, no significant differences emerged when demographically predicted intelligence quotients were compared with NART estimated intelligence quotients. NART performance (predicted on the basis of demographic variables) was not significantly different from observed NART performance in any of the three experimental groups. However, within the sample with schizophrenia, NART estimated pre-morbid IQ was significantly higher than currently measured intellectual abilities. These results suggest that the National Adult Reading Test provides a reasonable estimate of pre-morbid ability in acutely ill, unmedicated schizophrenic patients.

Acute Disease↗