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Biomedical subjects

M Allison

Publications and source records attributed to M Allison.

At least 19 recordsLinked to original sources
PubMed2007

The lakes of Titan.

The surface of Saturn's haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface. Initial visible and radar imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface. Here we provide definitive evidence for the presence of lakes on the surface of Titan, obtained during the Cassini Radar flyby of Titan on 22 July 2006 (T16). The radar imaging polewards of 70 degrees north shows more than 75 circular to irregular radar-dark patches, in a region where liquid methane and ethane are expected to be abundant and stable on the surface. The radar-dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes, including associated channels and location in topographic depressions. Some of the lakes do not completely fill the depressions in which they lie, and apparently dry depressions are present. We interpret this to indicate that lakes are present in a number of states, including partly dry and liquid-filled. These northern-hemisphere lakes constitute the strongest evidence yet that a condensable-liquid hydrological cycle is active in Titan's surface and atmosphere, in which the lakes are filled through rainfall and/or intersection with the subsurface 'liquid methane' table.

Journal Article↗
PubMed2006

Titan Radar Mapper observations from Cassini's T3 fly-by.

Cassini's Titan Radar Mapper imaged the surface of Saturn's moon Titan on its February 2005 fly-by (denoted T3), collecting high-resolution synthetic-aperture radar and larger-scale radiometry and scatterometry data. These data provide the first definitive identification of impact craters on the surface of Titan, networks of fluvial channels and surficial dark streaks that may be longitudinal dunes. Here we describe this great diversity of landforms. We conclude that much of the surface thus far imaged by radar of the haze-shrouded Titan is very young, with persistent geologic activity.

Journal Article↗
PubMed2006

The sand seas of Titan: Cassini RADAR observations of longitudinal dunes.

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.

Extraterrestrial Environment↗
PubMed2006

Oxalobacter sp. reduces urinary oxalate excretion by promoting enteric oxalate secretion.

The primary goal of this study was to test the hypothesis that Oxalobacter colonization alters colonic oxalate transport thereby reducing urinary oxalate excretion. In addition, we examined the effects of intraluminal calcium on Oxalobacter colonization and tested the hypothesis that endogenously derived colonic oxalate could be degraded by lyophilized Oxalobacter enzymes targeted to this segment of the alimentary tract. Oxalate fluxes were measured across short-circuited, in vitro preparations of proximal and distal colon removed from Sprague-Dawley rats and placed in Ussing chambers. For these studies, rats were colonized with Oxalobacter either artificially or naturally, and urinary oxalate, creatinine and calcium excretions were determined. Colonized rats placed on various dietary treatment regimens were used to evaluate the impact of calcium on Oxalobacter colonization and whether exogenous or endogenous oxalate influenced colonization. Hyperoxaluric rats with some degree of renal insufficiency were also used to determine the effects of administering encapsulated Oxalobacter lysate on colonic oxalate transport and urinary oxalate excretion. We conclude that in addition to its intraluminal oxalate-degrading capacity, Oxalobacter interacts physiologically with colonic mucosa by inducing enteric oxalate secretion/excretion leading to reduced urinary excretion. Whether Oxalobacter, or products of Oxalobacter, can therapeutically reduce urinary oxalate excretion and influence stone disease warrants further investigation in long-term studies in various patient populations.

Animals↗
PubMed2005

The vertical profile of winds on Titan.

One of Titan's most intriguing attributes is its copious but featureless atmosphere. The Voyager 1 fly-by and occultation in 1980 provided the first radial survey of Titan's atmospheric pressure and temperature and evidence for the presence of strong zonal winds. It was realized that the motion of an atmospheric probe could be used to study the winds, which led to the inclusion of the Doppler Wind Experiment on the Huygens probe. Here we report a high resolution vertical profile of Titan's winds, with an estimated accuracy of better than 1 m s(-1). The zonal winds were prograde during most of the atmospheric descent, providing in situ confirmation of superrotation on Titan. A layer with surprisingly slow wind, where the velocity decreased to near zero, was detected at altitudes between 60 and 100 km. Generally weak winds (approximately 1 m s(-1)) were seen in the lowest 5 km of descent.

Journal Article↗
PubMed2005

Cassini radar views the surface of Titan.

The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of approximately 0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

Atmosphere↗
PubMed2001

The incidence and epidemiology of congenital upper limb anomalies: a total population study.

An 11-year total population study of Western Australia examined the prevalence and epidemiology of congenital upper limb anomalies. All anomalies were classified according to the International Federation of Surgical Societies of the Hand classification. We found the prevalence of babies born with upper limb anomalies to be 1 in 506. Forty-six percent of those affected had another nonhand congenital anomaly. Fifty-one percent had bilateral hand anomalies, and 17% had multiple different hand anomalies. The most common anomalies were failures of differentiation (35%), duplications (33%), and failures of formation (15%). Congenital upper limb anomalies were more common in boys; preterm, postterm, and multiple births; and older mothers. No significant differences in prevalence or frequency of anomalies were found between whites and nonwhites, left and right sides, and in babies that survived and those who died shortly after birth.

Female↗
PubMed2000

An audit of phase II cardiac rehabilitation at Auckland hospital.

AIM: To audit Phase II cardiac rehabilitation services available to patients admitted to Auckland Hospital in order to assess patient uptake and to identify problems with patient recruitment to the service. METHODS: We performed a retrospective review from 1/8/ 97 to 30/9/97 of all patients admitted to the coronary care/ cardiology departments in Auckland Hospital. RESULTS: There were 289 patient admissions in this two month period, of which 22 (8%) were readmissions. 154 (54%) were admissions with provisional diagnoses of chest pain, of whom eight were readmissions. A total of 113 (39%) patients were felt to be suitable for the rehabilitation programme, of whom 50 (44%) attended one or more sessions and 22 (19%) completed the six week programme. 63 (56%) of the eligible patients did not attend any session. Reasons for non-attendance included the distance to be travelled, availability of transport and problems associated with taking time off work. A major finding of the audit was that the systems currently in place to follow patients are inadequate to allow formal audit and evaluation of the rehabilitation service. CONCLUSIONS: Although a reasonable rehabilitation service exists for Auckland Hospital patients, less than half of suitable patients attend a single session. There is a need for better collection and recording of patient data in order to facilitate the development of evaluation and audit tools.

Aged↗
PubMed1998

The relationship between fat distribution and coronary risk factors in sedentary postmenopausal women on and off hormone replacement therapy.

The purpose of this study was to examine the relationship between fat distribution and coronary risk factors (CRF) in sedentary overweight postmenopausal women both on and off hormone replacement therapy (HRT). Medical records and information were abstracted from nonsmoking women entering a weight loss program. A total of 33 women on HRT (mean age=50.12+/-5.2) and 51 nonusers (mean age=52.52+/-7.8) fulfilled subject eligibility requirements and were included in the data analysis. Results showed a significantly lower waist-to-hip ratio (WHR) (p=0.009) and waist (p=0.010) and greater levels of high-density lipoprotein cholesterol (HDL-C) (p=0.035) in HRT users than in nonusers. After converting correlations to standard Z-scores and performing z-tests, the correlation between total cholesterol (T-Chol) and WHR was significantly greater in nonusers than in HRT users (p=0.038). A multiple regression analysis showed differences between groups in the ability of age and anthropometric variables to predict CRF. Although T-Chol could be predicted in nonusers (r2=0.24; p=0.011), very low-density lipoprotein cholesterol (VLDL-C) and systolic blood pressure (SBP) could be significantly predicted in HRT users only (r2=0.28, p=0.055 and r2=0.40, p=0.005 for VLDL-C and SBP, respectively). These data suggest that there are differences between HRT users and nonusers in predictors of CRF, central adiposity, HDL-C, and the relationship between WHR and T-Chol. It is concluded that the significantly lower levels of central adiposity observed in HRT users may have clinical benefits with regard to CRF.

Adipose Tissue↗
PubMed1997

Identification and classification of Oxalobacter formigenes strains by using oligonucleotide probes and primers.

Genomic DNAs of various strains of Oxalobacter formigenes were subjected to restriction endonuclease fragment length polymorphism- and PCR-based amplification analyses with DNA probes and primers complementary to sequences within either the oxc gene, encoding oxalyl coenzyme A (oxalyl-CoA) decarboxylase, or the frc gene, encoding formyl-CoA transferase. Oligonucleotide probes based on nonconserved sequences of oxc or frc were able to divide O. formigenes strains into at least two groups, consistent with the current separation of O. formigenes strains into groups I and II on the basis of 16S rRNA sequence similarities and lipid content. In contrast, an oligonucleotide probe based on the conserved 5' end of oxc appeared to bind all group I and the majority of group II strains. PCR amplification of the oxc gene showed even greater sensitivity in detecting O. formigenes and provided support for further division of the strains into subgroups. In addition, these oligonucleotides failed to hybridize to or amplify PCR products from whole fecal DNA isolated from fresh stool samples from an individual not colonized with O. formigenes, indicating unique specificity. Thus, these DNA analyses permit both detection as well as classification of O. formigenes strains.

Bacterial Typing Techniques↗
PubMed1997

Physical activity in the elderly: benefits and intervention strategies.

In spite of the well-documented evidence that physical activity is beneficial, only 30% of individuals over the age of 65 report exercising regularly. Regular physical activity can minimize and prevent chronic problems and increase functional ability in the elderly. Designing physical activity for the elderly requires initial assessment of functional ability, exercise tolerance, physical limitations, and psychologic and social support of the individual. The exercise prescription should address the intensity, frequency, and duration of the exercise. Several factors affect the elderly's initiation and adherence to a physical activity program. These include the elder's perception of factors preventing physical activity, individual goal setting, and personal and therapist support in the effort.

Aged↗
PubMed1997

Pragmatic assessment of physical activity.

Nurse practitioners are confronted with the need to measure the physical activity levels of clients. There is no "gold standard" for measurement in the field. Nurses increasingly use physical activity for assessment, intervention, and evaluation. Selection of the appropriate tool depends on the purpose of the assessment, the client population, practicality, and psychometric properties of the instrument. Nine physical activity instruments with good psychometric properties, economy, and acceptability are presented to assist with instrument selection.

Activities of Daily Living↗
PubMed1996

Self-renewal of B-1 lymphocytes is dependent on CD19.

The B-1 subset of B lymphocytes is maintained by self-renewal of mature cells, and this process may involve signaling through membrane immunoglobulin (mIg). We determined whether CD19, a membrane protein that co-stimulates B cells by mIg, has a role in this process. Pre-natal treatment of mice with 1D3, a rat anti-mouse CD19 monoclonal antibody, down-regulated CD19 expression and reduced by sixfold the number of B-1a cells at birth; B-2 cells were relatively unaffected. Prolonged treatment of adult mice with 1D3 caused the loss of approximately 2% per day of peritoneal B-1a cells, without diminishing the recovery of splenic B-2 cells. The loss of B-1a cells was associated with inhibition of their replication rather than with accelerated turnover. Therefore, CD19 is involved in the development and self-renewal of B-1a cells, perhaps through its ability to amplify signaling through mIgM.

Animals↗
PubMed1996

Environmental factors and nutritional status of rural children.

The nutritional status of school-aged children is a growing concern of health care professionals today. In collaboration with a Kellogg Project in the deep south, students from a large university school of nursing participated in a project to improve the nutritional status of rural school-aged children. The project goals focused on educating thd children about the U.S. Department of Agriculture (USDA) Food Guide Pyramid, reading nutritional labels and recognizing foods with high fat content, and the importance of exercise along with diet. The nursing students created a nutritional assessment tool to use with each child to determine their educational needs. The project involved lecture, interactive class discussion, and hands-on activities. Information from the assessment tool revealed that fast food and foods high in fat were the most popular with the children. After project completion, the posttest revealed an increase in cognitive knowledge of nutrition among all the children. In addition to this positive learning experience for the children, improving the health status of children in the community was an excellent educational opportunity for the nursing students.

Child↗
PubMed1992

Factors influencing medical interns trained at U.W.I. to work subsequently in a rural area in Jamaica.

Recognising the present paucity of doctors trained at the University of the West Indies who are working in rural government health facilities in Jamaica, and its impact on the health services, this study was done to determine the factors influencing the decision of UWI-trained interns to work in these facilities post-internship. A questionnaire was administered to 57 UWI-trained medical graduates presently doing their internship in Jamaica. The results showed that there was no significant difference in the choice of placement with respect to sex, or residential background of the intern, though the latter seemed to indicate a trend. Of those who thought they would work in a rural government health facility, two-thirds would do so immediately post-internship but 50% did not plan to work there for more than five years. Opportunities for postgraduate training and lack of equipment were the most important deterrents to working in a rural government health facility.

Choice Behavior↗
PubMed1989

Dietary practices and pregnancy discomforts among urban blacks.

In this prospective study, we investigated the relationship between dietary practices and pregnancy discomforts among 50 urban black American women during their first and third trimesters of pregnancy. Subjects were interviewed during their regular prenatal clinic visits for information about their previous 24-hour dietary intake, the presence and severity of pregnancy discomforts occurring in the previous month, and pertinent demographic data. Findings indicated that high intake of meat products but low or no intake of vegetables was correlated with nausea, little or no intake of milk products was correlated with heartburn, and low or no intake of citrus fruit but intake of vitamin and iron supplements was correlated with heartburn, constipation, and sleeping difficulty. Replication of the study with a larger sample is warranted so as to provide further validity to the findings.

Black or African American↗