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Biomedical subjects

H McKay

Publications and source records attributed to H McKay.

16 recordsLinked to original sources
PubMed2005

Ground reaction forces associated with an effective elementary school based jumping intervention.

BACKGROUND: Mechanical loading during childhood plays a critical role in normal growth and development of the skeleton. Ground reaction forces (GRFs) may provide a surrogate measure for the strain experienced by bone on landing and at take off. However, there appear to be no paediatric studies that assess GRFs across a variety of loading activities. OBJECTIVES: To measure biomechanical variables in commonly performed childhood activities used in an elementary physical education intervention study which augmented bone health in boys and girls. METHODS: Maximal GFR, maximal rates of force, and time to maximum force were measured for 12 different jumping activities on a force platform. The jumps measured were drop jumps from 10, 30, and 50 cm, all followed by a plyometric jump, submaximal and maximal jumping jacks, alternating feet jump, counter movement jumps, and side to side jumps over 10 and 20 cm foam barriers. The subjects were 70 children (36 boys and 34 girls), 8.3-11.7 years old. RESULTS: Subjects ranged in height from 128.4 to 172.6 cm and had a mass of 25.0-57.0 kg. Mean (SD) for vertical jump was 24.2 (5.5) cm and 135.2 (16.6) cm for standing long jump. The children engaged in loaded physical activity 5.7 (5.3) hours a week, on average. The highest mean maximal GRFs, normalised for body weight (BW), were generated from the plyometric portion of the drop jumps and the counter movement jump (about 5 times BW) compared with 3.5 times BW for jumping jacks. Similarly, the highest rates of change in force were 514 times BW/s for the drop jump from 10 cm and 493 times BW/s for the counter movement jump. CONCLUSIONS: Simple jumps requiring minimal equipment produce GRFs of 3.5-5 times BW and rates of force of around 500 times BW/s. As children appear to attenuate higher impact forces when jumping from increased heights, it cannot be assumed that merely increasing the height of the jump will necessarily "progress" the exercise intervention.

Biomechanical Phenomena↗
PubMed2001

Inter-observer variation between general and specialist gastrointestinal pathologists when grading dysplasia in ulcerative colitis.

Histological dysplasia is the cornerstone of colorectal cancer surveillance in ulcerative colitis (UC). Recently, pathologists have received unfavourable media attention concerning other cancer screening programmes. The aim of this study was to determine whether colonic biopsy specimens should be examined by gastrointestinal pathologists as opposed to generalists, by examining inter-observer variation between the two groups. Fifty-one coded slides showing varying degrees of dysplasia were mailed to seven gastrointestinal and six general histopathologists. Pathologists allocated each biopsy into one of four categories without the benefit of a clinical history or an opportunity to use the 'indefinite' category that is included in the Riddell classification. The responses were analysed using kappa statistics. The overall kappa statistic for gastrointestinal pathologists was 0.30 [95% confidence interval (CI)=0.26-0.34] and for general pathologists 0.28 (95% CI=0.23-0.32). Agreement was best for high-grade dysplasia (kappa of 0.54 and 0.61 for GI and general pathologists, respectively). There was total concordance of the 13 pathologists in only four of the 51 slides (7.8%) (95% CI=0.4-15.2%). It is concluded from these results that gastrointestinal pathologists are no better than generalists when grading dysplasia in UC and that agreement is poor in both groups. There is therefore no evidence that there would be any benefit in having specialist histopathology centres concentrating specifically on the interpretation of all surveillance colonoscopy biopsies from around the UK. It must be made clear to the public that surveillance and screening programmes carry a significant rate of histological error and that perfection cannot be expected or achieved with present methods.

Colitis, Ulcerative↗
PubMed2000

The role of physiotherapy in the prevention and treatment of osteoporosis.

Osteoporosis is an increasing public health problem that causes loss of life and reduced quality of life in sufferers. Strategies to improve bone density and reduce the likelihood of falls are important in the prevention of osteoporosis. Physiotherapists have a role to play in this condition through exercise prescription, therapeutic modalities, specific techniques and education. Appropriate treatment goals can be established following a thorough assessment of signs and symptoms, risk factors for osteoporosis and functional status. Levels of bone density measured from dual energy X-ray absorptiometry can help guide patient management. Since the aim is to maximize peak bone mass in children and adolescents, participation in a variety of high-impact activities should be encouraged. In the middle adult years, small increases in bone mass may be achieved by structured weight-training and weight-bearing exercise. In the older adult years, particularly if osteopenia or osteoporosis is present, the aim is to conserve bone mass, reduce the risk of falls, promote extended posture, reduce pain, and improve mobility and function.

Absorptiometry, Photon↗
PubMed1998

Targeted intraparenchymal delivery of human NGF by gene transfer to the primate basal forebrain for 3 months does not accelerate beta-amyloid plaque deposition.

Nerve growth factor therapy has been proposed as a potential means of preventing degeneration of basal forebrain cholinergic neurons in Alzheimer's disease and thereby improving cognition. However, NGF has been reported to upregulate expression of the beta-amyloid precursor protein, which in turn could accelerate deposition of "mature" beta-amyloid in the brain. To address this possibility, the brains of 16 adult and aged rhesus monkeys were examined for beta-amyloid plaque deposition in the presence or absence of NGF treatment. Six aged monkeys received intraparenchymal grafts into the cholinergic basal forebrain of autologous cells genetically modified to secrete NGF, six aged monkeys received intraparenchymal grafts of autologous control cells expressing the reporter gene beta-galactosidase, and four adult nonoperated monkeys served as additional controls. All brains were examined for expression of mature beta-amyloid using an antibody recognizing amino acids 1-40 of the beta-amyloid peptide. Amyloid plaques were systematically quantified in representative sections of the temporal, frontal, cingulate, insular, and parietal cortices and in the amygdala and hippocampus. Results disclosed that aging resulted in an increase in amyloid plaque formation: no plaques at all were detected in nonaged monkeys, whereas a mean of 20 +/- 13 plaques per section were present in control-aged monkeys. Aged subjects with intraparenchymal NGF-secreting grafts for 3 months contained a mean of 29 +/- 14 plaques per section, an amount that did not differ significantly from control-aged monkeys (P = 0.66). Thus, 3 months of intraparenchymal NGF delivery did not significantly increase beta-amyloid deposition.

Aging↗
PubMed1998

Sonohysterographic screening before in vitro fertilization.

OBJECTIVE: To evaluate the use of sonohysterography for uterine screening before IVF. DESIGN: Prospective screening with sonohysterography and comparison with available hysterosalpingographic and hysteroscopic evaluations. SETTING: Private practice. PATIENT(S): Seventy-two women undergoing IVF-ET using their own or donor eggs. INTERVENTION(S): Sonohysterography was performed by instilling saline into the uterine cavity through an intracervical balloon catheter; there was concurrent vaginal sonographic visualization in all cases. MAIN OUTCOME MEASURE(S): Sonohysterographic findings and pregnancy rates. RESULT(S): Cavitary lesions were detected in 8 (11.1%) of 72 sonohysterographic examinations. Six of 8 cases were confirmed and treated by hysteroscopy. After sonohysterographic evaluation, 35 (48.6%) of 72 patients conceived, resulting in 25 ongoing or delivered pregnancies, 5 chemical pregnancies, and 5 spontaneous abortions. No statistically significant difference was observed in the pregnancy outcome for patients undergoing IVF who had sonohysterography compared with that for patients undergoing IVF during the same period who previously had a uterine evaluation by a different method. The estimated cost savings per patient undergoing sonohysterography instead of in-office hysteroscopy was $275. CONCLUSION(S): Sonohysterography offers advantages over in-office hysteroscopy and hysterosalpingography for evaluation of the uterus before IVF.

Adult↗
PubMed1997

Increased N-glycosylation and reduced transferrin-binding capacity of transferrin receptor isolated from placentae of diabetic women.

Infants of diabetic mothers are frequently born iron deficient because their fetal iron demand exceeds placental iron transport capacity. Although transferrin receptor (TfR) expression is increased, binding to diferric transferrin is decreased proportionately to the severity of maternal disease. It is hypothesized that TfR isolated from diabetic placentae has altered N-glycosylation since proper glycosylation of N-linked oligosaccharides is important for normal TfR binding kinetics to diferric transferrin. TfR was obtained from syncytiotrophoblastic membranes of six diabetic and six non-diabetic human placentae. Competitive binding to 125I-transferrin demonstrated a higher Kd in the diabetic TfR (P = 0.04), directly correlated to cord serum C-peptide concentration (r = 0.81, P < 0.001). The molecular weight of the monomeric form of TfR prior to treatment with glycopeptidase F (PNG-F) was greater in the diabetic group (P < 0.001) was directly related to the Kd (r = 0.77, P = 0.002). Treatment with PNG-F eliminated the molecular weight difference between the two groups. Increased glycosylation of the N-linked oligosaccharides of TfR isolated from diabetic placentae may alter the three-dimensional structure or charge of the receptor, thus reducing its binding affinity for transferrin.

Binding, Competitive↗
PubMed1994

Placental transferrin receptor in diabetic pregnancies with increased fetal iron demand.

Augmented fetal hemoglobin synthesis during diabetic pregnancy increases fetal iron demand. To study the effect of increased fetal iron demand on placental transferrin receptor (TR), we utilized a monoclonal antibody to localize placental TR immunoreactivity and 125I-labeled transferrin to study TR binding characteristics in 10 placentas from poorly controlled diabetic mothers with increased fetal iron demand and 10 placentas from nondiabetic mothers. The infants born to the diabetics had higher cord serum C-peptide, erythropoietin, and hemoglobin concentrations, indicating fetal hyperinsulinemia and hypoxia, with augmented erythropoiesis and iron demand. TR immunoreactivity was localized to the syncytiotrophoblast in both groups, was greater in the diabetic group, and was inversely correlated with fetal storage iron (r = -0.75; P < 0.001). Scatchard analysis of 125I transferrin binding data confirmed greater receptor number (Bmax 17.9 +/- 2.2 vs. 12.6 +/- 1.3 pM/mg protein, P = 0.05), but reduced binding affinity [dissociation constant (Kd) 7.6 +/- 0.9 vs. 5.4 +/- 0.4 nM/l, P = 0.03] in the diabetic group. The TR staining intensity, Bmax, and Kd were each correlated with cord C-peptide, suggesting either a primary or secondary role for fetal hyperinsulinemia in TR expression. This study provides in vivo evidence that fetal factors, such as iron demand or hyperinsulinemia, influence regulation of placental TR in humans. The increase in placental syncytiotrophoblastic TR expression associated with reduced cord serum ferritin concentration suggests that the fetus utilizes both increased placental iron transport and mobilization of fetal iron stores to support augmented fetal erythropoiesis.

Erythropoiesis↗
PubMed1993

Exercise-induced stress injuries to the femur.

Seventy-one athletes with 74 stress injuries to the femur were studied using a case-controlled design. Forty-three were females (26.6 yrs) and 28 were males (31.2 yrs). Each patient had exercise-induced pain in the hip, groin or thigh and a Tec-99m-MDP bone scan showing focal uptake of radionuclide in the femur. Running was the most common activity at the time of injury (89.2%) followed by triathlon (4.6%) and aerobic dance (4.6%). Thirty per cent of the runners had increased their training duration immediately prior to their first symptom. Anterior thigh pain was the most frequent site of exercise-induced pain (45.9%) followed by hip pain (27%) and groin pain (8.1%). During the clinical examination, when asked to hop on the affected limb, 70.3% of the patients had pain reproduced in the hip, groin or anterior thigh. There were 39 cases (53%) involving focal uptake of radionuclide in the femoral shaft, 15 (20%) in the lesser trochanter, 11 (15%) in the intertrochanteric region between the femoral neck and the greater trochanter, 8 (11%) in the femoral neck and 1 (1%) in the greater trochanter. Two patients suffered displaced fractures, one at the femoral neck and the other in the shaft of the femur. Neither patient had previously sought medical attention for their leg pain. Of 46 plain radiographs taken, only 11 (24%) were abnormal. The mean time to diagnosis and recovery were 6.6 and 10.4 weeks respectively. Substitution of cycling and water exercise for running were the most common therapeutic interventions.

Adult↗
PubMed1992

Infant-feeding practices and adiposity in 4-y-old Anglo- and Mexican-Americans.

A longer duration of breast-feeding and later introduction to solids may protect against excessive adiposity in infancy. This study investigated infant feeding practices and their relationship to two measures of adiposity--body mass index (BMI) and sum of skinfold thicknesses (SUMSF)--in 331 4-y-old Anglo- (43%) and Mexican-American (57%) children. No associations were detected between any of the infant feeding variables of duration of breast-feeding and introduction to solids and formula and measures of the child's adiposity. Mother's physical measures of BMI and SUMSF explained the largest portion of variance for both measures of childhood adiposity, BMI (9.5%), and SUMSF (8.3%). Genetic and environmental factors other than infant feeding practices appear to have a greater influence on a 4-y-olds' adiposity.

Adipose Tissue↗
PubMed1986

Anthropometric status and body composition in aboriginal women of the Kimberley region.

A detailed cross-sectional anthropometric study in which weight, height, three circumferences and four skinfolds were measured in 114 Aboriginal women aged 15-79 years was undertaken in the Kimberley region of Western Australia. Highly significant increases with age were observed for all measurements except height. Subcutaneous fat distribution in Aboriginal women was found to be more central than in white women, and the use of triceps skinfold to predict body fat in Aboriginal women gave lower estimates of body fat in this group than did the use of multiple skinfolds. Further work is needed to determine the accuracy of applying prediction equations that are based on skinfold measurements in white women, to assess total body fat in Aboriginal women. However, the data from this study do suggest that for a given body mass index Aboriginal women have more subcutaneous fat (as assessed from four skinfold measurements) and, consequently, a higher percentage of body fat than have white women.

Adolescent↗
PubMed1978

Improving cognitive ability in chronically deprived children.

Beginning at different ages in their preschool years, groups of chronically undernourished children from Colombian families of low socioeconomic status participated in a program of treatment combining nutritional, health care, and educational features. By school age the gap in cognitive ability between the treated children and a group of privileged children in the same city had narrowed, the effect being greater the younger the children were when they entered the treatment program. The gains were still evident at the end of the first grade in primary school, a year after the experiment had ended.

Age Factors↗