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Biomedical subjects

R D Lewis

Publications and source records attributed to R D Lewis.

At least 55 records · Page 3Linked to original sources
PubMed1995

[Demographic data and the potential demand for housing: a cohort approach].

"Canada Mortgage and Housing Corporation is actively involved in conducting research on demographic change and housing demand. Household projections are at the center of this research....CMHC is working with the Joint Center for Housing Studies at Harvard University to develop a cohort-based method for extrapolating headship and ownership rates. The method offers advantages over other approaches in that it recognizes differences between generations, provides a useful framework for analysis, and offers considerable flexibility in tailoring projection assumptions. Preliminary cohort-based potential housing demand projections show broad consistency with current low levels of housing market activity and point to continuation of some of the established trends in the past twenty years." (SUMMARY IN ENG AND SPA)

Americas↗
PubMed1995

Bone mineral density and dietary intake of female college gymnasts.

The purposes of this study were to determine bone mineral density (BMD) of female college gymnasts (N = 26) and age- (+/- 1.0 yr), height- (+/- 5.1 cm), and weight- (+/- 2.3 kg) matched controls (N = 26) using dual energy x-ray absorptiometry and to examine the relationship of physical activity, diet, menstrual history, and BMD in these athletes. Energy expenditure, dietary intake and menstruation were assessed using standardized questionnaires. The BMD of the gymnasts were significantly (all P < 0.0001) higher than controls for the lumbar spine (L1-4), total proximal femur, femoral neck, Ward's triangle, and whole body. Mean calcium and kcal intakes for both groups were lower than the Recommended Dietary Allowances, and gymnasts had significantly lower kcal intakes than controls (P < 0.05). More gymnasts than controls (59% vs 24%) reported that their menstrual cycle had been interrupted at some point since menarche (P < 0.02). The major finding of this investigation is that the BMD of gymnasts were higher than matched controls despite the fact that gymnasts as a group had inadequate dietary calcium and a higher propensity to have an interruption of their menstrual cycle.

Absorptiometry, Photon↗
PubMed1995

Eating disorder symptoms in female college gymnasts.

In study 1, 21 females provided both honest and dishonest answers to the Eating Disorders Inventory-2 (EDI-2). It was found that the EDI-2 can be easily faked. The fake profile was used to screen subjects in a second study, in which 25 gymnasts and 25 matched controls were assessed on symptoms of eating disorders, energy intake, menstrual history, and bone mineral density (BMD). A Hotelling's T2 test (Wilks' lambda = 0.70) revealed that the gymnast and control groups did not differ significantly (P > 0.05) on the EDI-2 subscales; however, both groups exhibited scores on the Drive For Thinness (DFT) subscale of the EDI-2 that were higher than the published average for college women. More gymnasts (61%) than controls (24%) reported an absence of their menstrual cycle of 3 months or more. A higher percentage (8/11, 73%; chi 2 = 4.7, P < 0.05) of the subgroup with elevated DFT scores (i.e., > 14) reported having this disruption of their menstrual cycle compared with those with lower DFT scores (13/33, 39%). DFT scores were negatively (P < 0.05) related to energy intake (r = -0.48) and whole body BMD (r = -0.47). It is concluded that (a) DFT scores may be useful in identifying gymnasts at risk for problems associated with eating disorders, and (b) response distortion must be considered in future research using the EDI-2.

Adult↗
PubMed1994

Influence of muscle activation dynamics on reaction time in the elderly.

The aim of this investigation was to determine whether age-related changes in the dynamics of muscle activation were, in part, responsible for longer reaction times (RT) in the elderly. A group of 12 young (mean age, 20.6 years) and 12 elderly (mean age, 64.3 years) women performed a series of ballistic forearm supination movements in response to an auditory stimulus while using a simple reaction time test. Surface electromyographic waveforms from biceps brachii (agonist) and pronator teres (antagonist) muscles were recorded, together with the angle-time curves representing the motion of the forearm, on to an IBM compatible microcomputer. The results showed that an age-related increase (P < 0.05) in motor reaction time (MRT) contributed to longer RT in the elderly. In addition, the longer (P < 0.05) MRTs in the elderly were associated with a significantly slower rate (P < 0.05) of biceps brachii muscle activation and a significantly increased proportion (P < 0.05) of the initial biceps brachii muscle burst required to initiate the movement. This data suggested that an important part of the slowing of motor behaviour, commonly observed with increasing age, may be due to either decreases in the ability of aged skeletal muscle to rapidly generate tension or to a reduction in motor drive.

Adolescent↗
PubMed1994

Modern concepts in nonsurgical management of traumatic biliary fistulas.

The management of traumatic biliary fistulas is controversial. New ideas in nonsurgical treatment have recently evolved, in part because of the rapid advancement of laporoscopic surgery. Three major concepts are important in managing biliary fistulas: diagnosis, drainage, and decompression. These concepts were applied to a trauma patient, then reviewed in detail.

Adult↗
PubMed1993

Cross-validation of the discriminative effectiveness of the Luria-Nebraska Neuropsychological Battery for learning disabled adolescents.

This study was a cross-validation of the discriminative effectiveness and diagnostic accuracy of the Luria-Nebraska Neuropsychological Battery (LNNB). Subjects were a group of 31 LD adolescents and a matched group of 31 non-learning disabled students whose achievement fell within the low average to average range. Multivariate analysis of variance (MANOVA) confirmed that the LNNB was sensitive to group differences in analyses with either the basic or localization scales. Discriminant function analyses with 12 basic scales yielded overall rates of diagnostic accuracy ranging from 87.1% to 98.4%. A classification rule, based on the number of basic scale elevations, yielded 95% overall accuracy. Rates of overall accuracy for the eight localization scales ranged from 82.26% to 85.48% in discriminant function analyses. A classification rule, basedon the number of localization scale elevations, yielded 81% overall accuracy. The significance and accuracy of various indicators of dysfunction were investigated. Implications for the diagnosis of learning disability are discussed

Journal Article↗
PubMed1992

Herpes simplex virus: a possible etiologic agent in some gastroduodenal ulcer disease.

There is increasing evidence that the herpes simplex virus may account for some gastric ulcer disease. To examine this possibility, 62 tissue biopsies from 21 patients were obtained during esophagogastroduodenoscopy for gastroduodenal ulcer disease and from one operative specimen during the procedure for perforation of a gastric ulcer. The samples were collected from the base and rim of the ulcer, as well as from apparently healthy tissue adjacent to the lesion. When the DNA was extracted from these tissues and hybridized to a herpes simplex virus-specific DNA probe, positive results were obtained with 9.5 per cent (2 out of 21) of the patients with benign ulcers. Positive signals were obtained only with ulcer-associated tissues and never with healthy tissue. Hybridization also occurred with DNA from one ulcerative carcinoma in the study. These data suggest that a subset of ulcer disease may be caused by herpes simplex virus or that this virus may be secondarily associating with these lesions.

Adult↗
PubMed1991

Priapism in a stallion with generalized malignant melanoma.

A Thoroughbred stallion developed priapism that was unresponsive to medical treatment and lavage of the corpus cavernosum penis with heparinized 0.9% NaCl solution. Three weeks after onset of priapism, the penis was firm and noncompliant, and penile pain sensation and ability to retract the penis were lost. Ultrasonography confirmed thrombosis of the corpus cavernosum penis. The stallion was euthanatized because of poor prognosis for return to breeding soundness. Necropsy revealed enlargement of numerous lymph nodes. The dorsal penile nerves were demyelinated distal to the crura of the penis. A diagnosis of generalized malignant melanoma was made; however, neither metastasis to the vertebral canal nor compression of spinal nerve roots as they exited the vertebral foramen was found. Priapism is a persistent erection without sexual arousal and is initially unassociated with penile paralysis, but if prolonged, leads to irreversible venous occlusion where collecting veins join the cavernous spaces. Damage to the dorsal penile nerves may explain the long-term penile paralysis and loss of sensation that accompanied priapism in this stallion. Priapism unassociated with the use of phenothiazine-derivative tranquilizers is uncommon in horses.

Animals↗
PubMed1990

Localization of the circadian pacemakers of Hemideina thoracica (Orthoptera; Stenopelmatidae).

The location of the circadian pacemakers of the orthopteran Hemideina thoracica (White) has been investigated through observation of the effects of surgical removal of brain tissues (principally optic lobes and tracts) on free-running and entrained locomotor rhythms. Bilobectomy and severance of optic tracts invariably resulted in arrhythmicity, whereas rhythmicity was sustained following unilateral lobectomy, generally with increases in the free-running period (FRP) and decreases in both the active-phase lengths and activity-to-rest ratios of the rhythm. Bilobectomized subjects could be entrained by temperature cycles, but exhibited no transients or residual rhythmicity, indicating that temperature brought about a direct response or masking effect. These results support the hypothesis that the circadian locomotor pacemakers of Hemideina are located within each optic lobe, and that there are no extraoptic centers for the control of the timing of locomotor activity. Although confirmation of the pacemaker role of the optic lobes requires transplantation of the tissues, the conclusion may be drawn by inference from other studies (e.g., Leucophaea maderae--Page, 1983; Gryllus bimaculatus--Tomioka and Chiba, 1986). Light entrainment continued after surgical binding and blackening of the compound eyes and ocelli, supporting the view that direct illumination of neural tissue through the cuticle may be one possible pathway for light entrainment.

Animals↗
PubMed1989

Effectiveness of vaccination in controlling ovine footrot.

Efficacy of reducing footrot by use of a commercial vaccine was evaluated over 2 yr with 223 ewes from five crossbred genotypes. Ewes were assigned randomly within genotype, age and initial footrot status to a 2 x 3 factorial array of vaccination in the 1st yr and fall vaccination, winter vaccination or control in the 2nd yr. The flock contained a single Bacteroides nodosus serotype (XV) known to be highly cross-reactive with one of the vaccine serotypes (British serotype H). Vaccination reduced footrot incidence by 61% (P less than .01) in the 1st yr and by 45% (P less than .01) in the 2nd yr. Vaccination of previously uninfected ewes did not significantly reduce the rate of new infection, but vaccination of infected ewes reduced re-infection by 92% (P less than .01). Vaccination in the 1st yr failed to produce any carryover or additive protection in the 2nd yr. Genotypes differed in both footrot incidence (P less than .05) and footrot reduction following vaccination (P less than .05), but the effect was inconsistent between years. Vaccination increased serum antibody titers in both years (P less than .01). Among vaccinates in the 1st yr, infected ewes had lower titer levels than uninfected ewes (P less than .01), but no correlation between titer level and incidence was observed in the 2nd yr.

Animals↗
PubMed1988

Riboflavin and thiamin status and birth outcome as a function of maternal aerobic exercise.

Twenty-eight healthy pregnant women taking vitamin-mineral supplements served as controls or participated in a walking program from 22 to 30 wk gestation to determine the effects of aerobic exercise on maternal riboflavin and thiamin status and birth outcome. Aerobic capacity was evaluated by heart rate (HR) and relative oxygen consumption (RVO2) during submaximal treadmill walking. HR responses at 30 wk gestation were significantly lower for walking (n = 18) than nonwalking (n = 10) groups at 2 and 4 min of exercise. RVO2 for walkers decreased significantly from 22 to 30 wk at 2, 4, and 6 min. Riboflavin and thiamin status, determined by erythrocyte glutathione reductase and transketolase activity coefficients, was adequate for 86 and 96% of the subjects, respectively. Birth-outcome measurements were similar for all subjects. Participation in the walking program slightly improved aerobic capacity without affecting riboflavin or thiamin status or birth outcome in pregnant women taking vitamin-mineral supplements.

Adult↗
PubMed1988

Maternal aerobic exercise and vitamin B-6 status.

Effects of an aerobic walking program during gestational weeks 22-30 on vitamin B-6 status and birth outcome were studied in 28 healthy pregnant women, aged 21-36 y, receiving vitamin-mineral supplements. Mean daily vitamin B-6 intake, excluding a 10-mg supplement, was 1.81 mg. Subjects in the walking (n = 18) and nonwalking (n = 10) groups had similar microbiologically assessed plasma total vitamin B-6 levels and radioenzymatically assessed plasma pyridoxal phosphate concentrations. One walker at 22 wk and at 30 wk and a second walker at 30 wk had plasma total vitamin B-6 concentrations in the low-normal range; the same was true for plasma pyridoxal phosphate levels except that the 30-wk value for the walker who was low at 22 wk was missing. Birth-outcome measurements were similar for both groups. Participation in the walking program slightly improved aerobic fitness without affecting vitamin B-6 status or birth outcome in pregnant women taking vitamin-mineral supplements.

Diet↗
PubMed1988

Reproductive response of ewes to immunization with Fecundin (ovandrotone).

Ewes of five crossbred genotypes (total of 221 ewes) were immunized with a commercial preparation of androstenedione-7HSA in DEAE dextran adjuvant in a 2-yr trial. In yr 1 ewes were allocated within genotype to a 2 x 2 application of immunization and premating flushing. In yr 2 they were allocated within previous Fecundin treatment into either Fecundin-treated or control groups. First-time immunization with Fecundin increased ovulation rate by .70 ova/ewe in yr 1 and by .85 ova/ewe in yr 2 (P less than .05). Ewes treated in both years produced fewer ova than those treated in the 2nd yr only (P less than .05), but they did not differ in litter size. Although Fecundin reduced conception to first mating, the overall conception rate was not affected. Litter size of treated ewes was increased by .19 and .38 lambs/ewe lambing (P less than .05) in yr 1 and yr 2, respectively. Fecundin treatment in yr 1 produced a carry-over effect in yr 2 by increasing litter size by .26 lamb/ewe (P less than .05) while reducing conception to first mating. The litter size of ewes with two ovulations was reduced by Fecundin treatment in yr 1 (P less than .05) but showed no consistent pattern in yr 2. Overall, ewes with two ovulations produced .7 to .8 more lambs than ewes with one ovulation, and ewes with three ovulations produced .4 more lambs than those with two ovulations. Ewes of different genotypes did not differ in their response to Fecundin.

Androstenedione↗
PubMed1988

Comparison of Finnish landrace crossbred ewes with Columbia, Rambouillet and Targhee ewes on western range.

The objective of this study was to compare reproductive efficiency and wool production of 1/4 Finn crossbred ewes with straightbred Columbia, Rambouillet and Targhee ewes. In Phase I, white-faces ewes (WF; Columbia, Rambouillet and Targhee) were bred to either rams of their own breed or Finnish Landrace X Rambouillet rams (F X R) to produce 821 lambs from 563 lambings. Ewes bred to F X R had similar average litter size and individual lamb weights at birth, 60 d and weaning as those bred to WF. Lambs sired by F X R had 7% higher (P less than .01) lamb weaned per ewe lambing for ewes bred to F X R rams. For Phase II, approximately equal numbers of F X R-sired (1/4Fx) and WF-sired female lambs produced in Phase I each year were exposed to Suffolk rams at yearly intervals beginning at 7 mo of age. At 1 yr of age, 1/4Fx had higher fertility (P less than .01) than WF (37.7% vs 1.3%), resulting in 14.0 kg more lamb weaned per ewe exposed to breeding. Mature (ages 2 to 6 yr) 1/4Fx ewes had similar fertility to mature WF ewes, but litter size, number of lambs at 60 d and weaning was .36, .24 and .22 lambs higher (P less than .01), respectively, for mature 1/4Fx. Progeny of 1/4Fx were lighter at birth (P less than .01), but not different (P greater than .05) at 60 d and weaning than those of WF. Survival to 60 d unadjusted and adjusted for birth weight was 4.6% (P less than .05) and 7.6% (P less than .01) higher, respectively, for 1/4Fx progeny than for WF progeny.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Surgical treatment of iatrogenic canal blockages.

The endodontist of today is confronted with managing retreatment failures. Some of these can involve the retreatment of intracanal blockages. Many times, conventional endodontics cannot be redone, so a surgical approach may be needed. This article reviews four basic surgical techniques that can be used for retreatment of intracanal blockages. When the blockage cannot be removed, a standard retrograde amalgam technique or the Nygaard Ostby procedure of reverse instrumentation-obturation can be used. Two other surgical techniques used to eliminate the blockage are the apical loosening technique and a true apicoectomy procedure. Each of these procedures is reviewed, and the advantages and disadvantages are discussed.

Adolescent↗
PubMed1983

The circadian locomotor rhythm of Hemideina thoracica (Orthoptera; Stenopelmatidae): a population of weakly coupled feedback oscillators as a model of the underlying pacemaker.

A control systems model consisting of a population of weakly-coupled feedback oscillators has been developed to simulate the circadian locomotor rhythm of the insect, Hemideina thoracica (Orthoptera; Stenopelmatidae). The model is an extension of a previously published single oscillator feedback model (Gander and Lewis, 1979) which successfully simulates entrainment, phase response curves, temperature compensation and Aschoff's Rule for Hemideina activity rhythms. The population model described here has the additional properties of predicting some of the free-run period lability (Pavlidis, 1978a, b) observed in the Hemideina rhythm (Christensen and Lewis, 1982) which is unexplained by single oscillator systems. Model behaviour is compared with the experimental data derived from the insect activity rhythms.

Animals↗
PubMed1983

Zinc toxicity in ruminants.

Four natural occurrences of zinc toxicity in sheep and one in calves were studied. To assist in the confirmation of a diagnosis of zinc toxicity, 2 experiments were conducted in which sheep were given toxic amounts of zinc. The clinical findings, clinical pathology, and gross and microscopic pathology are given. Clinical manifestations included inappetance, loss of condition, diarrhoea with dehydration or subcutaneous oedema, profound weakness and jaundice. Significant rises in the concentration of zinc were usually found in the liver, kidney and pancreas, but occasionally in only 1 or 2 of these organs. Many affected sheep were anaemic. Pathological changes were found in the pancreas, kidney, liver, rumen, abomasum, small intestine and adrenal gland. Lesions in the kidney and abomasum apparently made the most significant contribution to the deterioration in health of affected animals, but the pancreas was the only organ consistently affected. The degenerative changes in the pancreas were mainly restricted to the exocrine portion of the organ, and regeneration of the damaged tissue was observed although exposure to toxic amounts of zinc continued. Attention is drawn to the importance of the pancreas in the diagnosis of zinc toxicity and in estimating the period of exposure.

Animals↗