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Biomedical subjects

M Lewis

Publications and source records attributed to M Lewis.

At least 685 records · Page 38Linked to original sources
PubMedDate not supplied

A new method for imaging perfusion and contrast extraction fraction: input functions derived from reference tissues.

This study describes a new method for analysis of dynamic MR contrast data that greatly increases the time available for data acquisition. The capillary input function, CB(t), is estimated from the rate of contrast agent uptake in a reference tissue such as muscle, based on literature values for perfusion rate, extraction fraction, and extracellular volume. The rate constant for contrast uptake (the product of perfusion rate, F, and extraction fraction, E; F x E) is then determined in each image pixel using CB(t), extracellular volume (relative to the reference tissue) measured from MR and the tissue concentration of contrast media as a function of time calculated from the MR data. The "reference tissue method" was tested using rats with mammary (n = 10) or prostate (n = 15) tumors implanted in the hindlimb. Dynamic MR images at 4.7 T were acquired before and after Gd-DTPA intravenous bolus injections to determine F x E(Gd-DTPA). Acquisition parameters were optimized for detection of the first pass of the contrast agent bolus, so that "first-pass analysis" could be used as the "gold standard" for determination of F x E. The accuracy of values of F x E determined using the reference tissue method was determined based on comparison with first-pass analysis. In some cases, deuterated water (D2O) was injected i.v. immediately after Gd-DTPA measurements, and the reference tissue method was used to calculate F, based on the rate of uptake of D2O. Comparison of rate constants for Gd-DTPA uptake and D2O uptake allowed calculation of E(Gd-DTPA). Values for F x E(Gd-DTPA), F, and E(Gd-DTPA) were determined for selected regions and on a pixel-by-pixel basis. Values for F x E and E(Gd-DTPA) measured using the reference tissue method correlated well (P = .90 with a standard error of +/- .016, n = 15) with values determined based on first-pass contrast media uptake. The reference tissue method has important advantages: (a) A large volume of reference tissue can be used to determine the contrast agent input function with high precision. (b) Data obtained for 20 minutes after injection are used to calculate F or F x E. The greatly increased acquisition time can be used to increase the spatial resolution, field of view or SNR of measurements. The reference tissue method is most useful when the volume of tissue that must be imaged and/or the spatial resolution required precludes use of traditional first-pass methods.

Animals↗
PubMedDate not supplied

Catecholaminergic interactions in the regulation of thyrotropin (TSH) secretion in man.

The TSH responses to the catecholamine depleting agent monoiodotyrosine (1 g po) and the dopamine receptor blocking drug metoclopramide (10 mg po) have been compared in euthyroid and hypothyroid subjects. Both drugs lead to a prompt and significant rise in TSH levels (peak values at 60-75 min) which is very much greater in hypothyroid than euthyroid subjects. The findings lend further support to the inhibitory role of dopamine in the control of TSH release in man, since TSH release follows either dopamine depletion with monoiodotyrosine or dopamine receptor blockade with metoclopramide.

Adolescent↗
PubMedDate not supplied

Isolated congenital absence of a single pulmonary valve cusp.

Isolated absence of a single pulmonary valve is extremely unusual. We present a 16-year-old male with the absence of one cusp resulting in significant pulmonary regurgitation, right ventricular enlargement, and dilatation of the main pulmonary artery and its branches. Surgery consisted of creating a valve cusp from the posterior wall of the pulmonary artery at the base of the pulmonary trunk. Follow-up at 3.5 years revealed good results with only mild pulmonary stenosis and regurgitation.

Adolescent↗
PubMedDate not supplied

Early anesthesia evaluation of the ambulatory surgical patient: does it really help?

STUDY OBJECTIVE: To evaluate whether early evaluation by the anesthesiologist is more beneficial for the ambulatory surgical patient than a day-of-surgery visit. DESIGN: A randomized study evaluating patients with different surgical procedures. SETTING: Ambulatory surgical outpatients at a university-affiliated integrated ambulatory surgical unit. PATIENTS: Sixty-three ASA physical status I and II women scheduled to undergo elective dilatation and curettage or gynecologic laser surgery. INTERVENTIONS: Approximately half of the patients received an early (1 to 7 days preoperative) anesthesia evaluation, and half received a day-of-surgery evaluation. All patients underwent the surgical procedures with a standardized general anesthetic. MEASUREMENTS AND MAIN RESULTS: The effect of an early versus a day-of-surgery anesthesia visit was evaluated with regard to patient anxiety levels; patient satisfaction with the surgical and anesthetic experience; operating room, recovery room, and ambulatory surgery unit time; anesthetic and analgesic requirements; and frequency of postoperative problems within 72 hours at home. There were no differences between the groups in demographic characteristics, anesthesia or analgesic requirements, degree of satisfaction with the ambulatory surgical experience, time spent in recovery room, or frequency of problems on postoperative follow-up. We were unable to demonstrate any differences between those patients seen early versus those seen on the day of surgery in anxiety levels preoperatively and postoperatively. CONCLUSIONS: Healthy ASA physical status I and II ambulatory surgical patients do not benefit from reducing preoperative anxiety by visiting the anesthesiologist prior to the day of surgery.

Adult↗
PubMedDate not supplied

Comparison of physical treatments versus a brief pain-management programme for back pain in primary care: a randomised clinical trial in physiotherapy practice.

BACKGROUND: Recommendations for the management of low back pain in primary care emphasise the importance of recognising and addressing psychosocial factors at an early stage. We compared the effectiveness of a brief pain-management programme with physiotherapy incorporating manual therapy for the reduction of disability at 12 months in patients consulting primary care with subacute low back pain. METHODS: For this pragmatic, multicentre, randomised clinical trial, eligible participants consulted primary care with non-specific low back pain of less than 12 weeks' duration. They were randomly assigned either a programme of pain management (n=201) or manual therapy (n=201). The primary outcome was change in the score on the Roland and Morris disability questionnaire at 12 months. Analysis was by intention to treat. FINDINGS: Of 544 patients assessed for eligibility, 402 were recruited (mean age 40.6 years) and 329 (82%) reached 12-month follow-up. Mean disability scores were 13.8 (SD 4.8) for the pain-management group and 13.3 (4.9) for the manual-therapy group. The mean decreases in disability scores were 8.8 (6.4) and 8.8 (6.1) at 12 months (difference 0 [95% CI -1.3 to 1.4], p=0.99), and median numbers of physiotherapy visits per patient were three (IQR one to five) and four (two to five), respectively (p=0.001). One adverse reaction (an exacerbation of pain after the initial assessment) was recorded. INTERPRETATION: Brief pain management techniques delivered by appropriately trained clinicians offer an alternative to physiotherapy incorporating manual therapy and could provide a more efficient first-line approach for management of non-specific subacute low back pain in primary care.

Acute Disease↗
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Sex determination by PCR analysis of DNA extracted from incinerated, deciduous teeth.

Establishing the biological sex of human remains is a very important part of identifying victims of fire when severe soft tissue destruction has occurred. Deciduous (children's) teeth were exposed to a range of incineration temperatures 100-500 degrees C for 15 minutes. Polymerase Chain Reaction (PCR) amplification was used to identify specific human amelogenin regions. There was successful identification of human biological sex, from deciduous teeth exposed to incineration temperatures of 200 degrees C and below, using standard ethidium bromide gel staining. There was greater sensitivity using fragment analysis by laser induced fluorescence which achieved sex identification from some teeth heated to 400 degrees C.

DNA↗
PubMedDate not supplied

Alpha-lactalbumin possesses a novel calcium binding loop.

Calcium performs a unique role in biology, achieving biological effects through highly specific interactions with and modulation of target proteins. It has been proposed that calcium-modulated proteins possess a characteristic, evolutionarily related, binding fold, known as the EF-hand. The high-resolution X-ray structure of alpha-lactalbumin reveals a Ca2+ binding fold that resembles an EF-hand only superficially and presumably has no evolutionary relationship with it. However, there is clear homology with the corresponding loop in c-type lysozyme (the 'parent' molecule of alpha-lactalbumin). This study, at 1.7 A resolution, represents one of the most accurate analyses of a calcium binding protein yet reported.

Binding Sites↗
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The Colton blood group locus. A linkage analysis.

Accumulated family information was compiled in an attempt to verify the chromosomal location of the Colton blood group locus (CO). Two-point linkage analysis of CO and 46 other polymorphic loci excludes CO from 1p36 to 1q23, 3q21 to 3q26, 4q13 to 4q28, 6p24 to 6 cen, and 19p13.2 to 19 cen and from linkage groups bounded by ABO and ORM, PI and IGHG, and HP and GOT2. The dwindling odds of linkage between CO:JK are reinforced (z = -5.28 at theta = 0.20). Close linkage of CO with ACP1 and D2S5 could not be demonstrated. The proposed chromosome 2 location of CO is therefore questioned.

Chromosome Mapping↗
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A serologic relationship among the NFLD, BOW, and Wu red cell antigens.

A survey of sera containing antibodies to multiple low-incidence antigens revealed a variety of patterns of reactions with NFLD+, BOW+, and Wu+ red cell samples. Although NFLD, BOW, and Wu are distinct antigenic determinants (International Society of Blood Transfusion numbers 700.37, 700.46, and 700.13, respectively), their ability to absorb and elute "crossreactive" antibodies indicates a serologic and possibly a genetic relationship among the three.

Blood Group Antigens↗
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Children's blood lead levels in the lead smelting town of Port Pirie, South Australia.

This survey included 1,239 children, representing 50% of the elementary school population of the lead smelting town of Port Pirie. Of these children, 7% had a capillary blood lead level equal to or greater than 30 micrograms/dl, which is the Australian National Health and Medical Research Council's "level of concern." There was a statistically significant difference in capillary lead levels by area of residence that was independent of age, sex, soil lead, rainwater tank lead, and school attended. A case-control study indicated that the following subset of factors was most predictive of an elevated blood lead level: household members who worked with lead in their occupations; living in a house with flaking paint on the outside walls; biting finger nails; eating lunch at home on school days; when at school, appearing to have relatively dirty clothing; when at school, appearing to have relatively dirty hands; and living on a household block with a large area of exposed dirt. A program to reduce the risk of elevated blood lead levels in Port Pirie children has been introduced.

Adolescent↗
PubMedDate not supplied

Development of cardiorespiratory patterns associated with terrestrial apneas in free-ranging southern elephant seals.

Elephant seals resting on land show an irregular breathing pattern that combines periods of eupnea and apnea. In this article we describe ontogenetic changes in the breathing pattern and in the associated cardiac response in resting pups and weanlings of the southern elephant seal, Mirounga leonina. Apnea duration and the percentage of time spent in apnea were positively correlated with age: mean apnea length was greater in weanlings than in pups, with weanlings holding their breath for up to 8.7 min. Apnea length was not correlated with the duration of preceding or subsequent eupneas. The heart rate of pups and weanlings on land followed the pattern of bradycardia during apnea and tachycardia during eupnea. Young weanlings had a significantly smaller decrease in heart rate during apnea than older weanlings (28% vs. 36%). The instantaneous heart rate response to breathing changed from a variable to a regular pattern. These results suggest that the control processes that modulate the physiological cardiorespiratory changes necessary for diving start to develop on land during the first 11 wk of life.

Age Factors↗
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The prevalence of genital Chlamydia trachomatis and mycoplasmal infections during pregnancy in an American Indian population.

The epidemiology of cervical infection with Chlamydia trachomatis, Mycoplasma hominis, and Ureaplasma urealyticum among a group of pregnant American Indian women was investigated. The prevalences of these microorganisms were 24-30% for C. trachomatis, 50% for M. hominis, and 80% for U. urealyticum. These rates are unusually high for an unselected sample. Infection with C. trachomatis was correlated with younger age but not with primigravidity or educational level. Neither M. hominis nor U. urealyticum infection was correlated with younger age, primigravidity, or level of education. The possible consequences of the increased prevalences of C. trachomatis, M. hominis, and U. urealyticum in this group of American Indians are of concern and are being investigated.

Chlamydia Infections↗
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Effect of maternal soothing on infant stress response.

The effect of maternal soothing to infant inoculation as well as everyday distress on infant cortisol and behavioral responses to stress was examined in two longitudinal samples of 55 and 74 infants, respectively, between 2 and 6 months of age. There was no evidence that maternal soothing was effective in reducing infants' cortisol or behavioral responses to stress. The absence of this relation occurred despite evidence for cross-time stability and cross-situation consistency in maternal soothing. That maternal soothing plays little role in lowering infant responses to stress leaves open the possibilities that other maternal behaviors may mediate children's distress or that infant temperament may be related to infant stress.

Age Factors↗
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The relations among body image, physical attractiveness, and body mass in adolescence.

Body dissatisfaction, a measure of body image, physical attractiveness, and body mass index were assessed in the same 115 participants at ages 13, 15, and 18 years. Sex differences in body dissatisfaction emerged between 13 and 15 years of age and were maintained at 18. Over adolescence, girls increased, while boys decreased, their body dissatisfaction. Body dissatisfaction was weakly related to others' ratings of the adolescents' physical attractiveness and their body mass index. The results support the idea that, overall, adolescents' body image has little to do with how others perceive them, but once developed remains constant through much of adolescence.

Adolescent↗
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Attachment over time.

Continuity in attachment classification from infancy to late adolescence was examined and related to autobiographical memories of childhood, divorce, and maladjustment. Eighty-four White middle-class children (48 girls) were seen in a modified Strange Situation at 12 months and given the Adult Attachment Interview at 18 years. In addition, data were collected on 13-year-olds' childhood recollections as well as adolescent, mother, and teacher ratings of maladjustment at 13 and 18 years of age. Divorce status of parents also was obtained. Results indicated no continuity in attachment classification from 1 to 18 years of age and no relation between infant attachment status and adolescent maladjustment. Divorce was related to 13-year-olds' childhood recollections as well as to insecure attachment status at 18 years. Eighteen-year-olds with insecure attachment classification were more likely to rate themselves as maladjusted. The results support the idea of attachment as an evolving representation dependent upon the nature of the family environment as indexed by divorce.

Adolescent↗
PubMedDate not supplied

Relaxin induces vascular endothelial growth factor expression and angiogenesis selectively at wound sites.

Relaxin is a reproductive hormone that has historically been characterized as being responsible for pubic ligament loosening and cervical ripening. Recently, relaxin has been associated with neovascularization of the endometrial lining of the uterus, potentially via specific induction of vascular endothelial growth factor. Previously conducted clinical studies using partially purified porcine relaxin have described relaxin's ability to stimulate the healing of ischemic wounds, suggesting that relaxin may also have angiogenic effects at sites of ischemic wound healing. In the present study, relaxin's angiogenic effects in the context of wound repair were tested in rodent models of angiogenesis and wound healing. Relaxin showed an ability to stimulate new blood vessel formation, particularly at ischemic wound sites, and to induce both vascular endothelial growth factor and basic fibroblast growth factor specifically in cells, presumably including macrophages, collected from wound sites. Resident macrophages collected from nonwound sites, such as the lung, did not show altered expression of these cytokines following relaxin administration. Because angiogenic wound cells are frequently macrophages, THP-1 cells, a cell line of monocyte lineage that binds relaxin specifically, were tested for and shown to induce vascular endothelial growth factor and basic fibroblast growth factor in response to relaxin. In conclusion, relaxin may be useful in the treatment of ischemic wounds by stimulating angiogenesis via the induction of vascular endothelial growth factor and basic fibroblast growth factor in wound macrophages.

Animals↗