Biomedical subjects

A J Young

Publications and source records attributed to A J Young.

At least 19 recordsLinked to original sources

PubMed2006

Perceptions of patients on the utility or futility of end-of-life treatment.

BACKGROUND AND OBJECTIVES: Definitions of medical futility, offered by healthcare professionals, bioethicists and other experts, have been rigorously debated by many investigators, but the perceptions of patients of futility have been explored only by a few. Patients were allowed to discuss their concerns about end-of-life care, so that their ideas about treatment futility or utility could be extrapolated by us. METHODS: In this cross-sectional study, in-depth, semistructured interviews were conducted with 30 elderly people who were receiving outpatient care in a large, urban Veterans Affairs medical centre in the US. Each of their healthcare providers was also interviewed. Participants were asked to consider four terms commonly used in advance directive forms (ie, life-sustaining treatment, terminal condition, state of permanent unconsciousness and decision-making capacity) and to discuss what these terms meant to them. Audiotapes of the open-ended interviews were transcribed and responses were coded and categorised by constant comparison, a commonly used qualitative method. RESULTS: The following four factors were taken into account by the participants when discussing end-of-life interventions and outcomes: (1) expected quality of life; (2) emotional and financial costs of treatment; (3) likelihood of treatment success; and (4) expected effect on longevity. CONCLUSIONS: Although the terms "utility" or "futility" were not generally used by the participants, segments of speech indicating their perceptions of these terms were identified. Treatment was not always discussed in the same way by patients and providers, but seemed to reflect the same four concerns. Therefore, it may be fruitful for providers to focus on these concerns when discussing end-of-life treatment options with their patients.

Advance Directives↗

PubMed2006

Adoption of security systems by dairy farms to address bioterrorist threats in the intermountain United States.

Data generated from a survey of western dairy farms was used to determine the characteristics of dairy farmers who have undertaken to improve security measures on their farms during the past 2 or 3 yr. The findings suggest that decisions to improve on-farm security are influenced by the producer's awareness of how to develop a security policy, and by the size of the dairy operation. The results also support the notion that farms may be vulnerable to bioterrorist attacks because most farmers do not believe it is important to establish on-farm security policies.

Animal Feed↗

PubMed2004

Dispersal, eviction, and conflict in meerkats (Suricata suricatta): an evolutionarily stable strategy model.

Decisions regarding immigration and emigration are crucial to understanding group dynamics in social animals, but dispersal is rarely treated in models of optimal behavior. We developed a model of evolutionarily stable dispersal and eviction strategies for a cooperative mammal, the meerkat Suricata suricatta. Using rank and group size as state variables, we determined state-specific probabilities that subordinate females would disperse and contrasted these with probabilities of eviction by the dominant female, based on the long-term fitness consequences of these behaviors but incorporating the potential for error. We examined whether long-term fitness considerations explain group size regulation in meerkats; whether long-term fitness considerations can lead to conflict between dominant and subordinate female group members; and under what circumstances those conflicts were likely to lead to stability, dispersal, or eviction. Our results indicated that long-term fitness considerations can explain group size regulation in meerkats. Group size distributions expected from predicted dispersal and eviction strategies matched empirical distributions most closely when emigrant survival was approximately that determined from the field study. Long-term fitness considerations may lead to conflicts between dominant and subordinate female meerkats, and eviction is the most likely result of these conflicts. Our model is computationally intensive but provides a general framework for incorporating future changes in the size of multimember cooperative breeding groups.

Animal Migration↗

PubMed2003

Whole-farm phosphorus balance on western dairy farms.

Environmental concerns have focused attention on animal agriculture and its contribution to P accumulation in soils and runoff to surface waters. Monitoring P inputs and outputs on farms is a means of calculating the potential P build-up in farm soils. The objective of this study was to determine whole-farm P balance and the relative importance of the farm components (herd, manure storage, cropping systems) that contribute to it in dairies of the western United States. Whole-farm balances were computed for 41 commercial dairies in Utah and Idaho using the Maryland Nutrient Balancer. The average whole-farm P balance in the study was 6.6 tonne/yr with an average herd size of 466 cows. Imported feed made up 85.4% of the total P inputs and exported animal products (milk and meat), and manure and compost made up 53.1 and 45.9%, respectively, of the total P outputs. Farms were divided into those that grew crops and those that did not. Whole-farm balance (kg of P balance per animal) for farms that grew crops had more unaccounted for P (difference between P inputs and output) than farms that grew no crops. They also had more imported fertilizer and less imported feed and exported manure and compost. Multiple regression analysis of the relative effects of herd management, manure storage, and cropping system on whole-farm balance per product found that herd P utilization efficiency was the most important factor in determining whole-farm P balance on farms where crops were grown. Crop uptake of available P was the only other subsystem important for these farms. Increased conversion of feed P to P in product is an important way to decrease whole-farm P balance.

Agriculture↗

PubMed2003

The association between milk urea nitrogen and DHI production variables in western commercial dairy herds.

A retrospective observational study was conducted using data from Dairy Herd Improvement monthly tests to investigate the association between milk urea nitrogen (MUN) concentration and milk yield, milk protein, milk fat percentage, SCC, and parity for commercial Holstein and Jersey herds in Utah, Idaho, and Montana. Mean MUN for Holstein cows was 15.5 mg/ dl (5.5 mmol/L) MUN and 14.1 mg/dl (5.0 mmol/L) for Jersey cows. Mean MUN, categorized by 30-d increments of days in milk (DIM), paralleled changes in milk values and followed a curvilinear shape. For Holstein cows, concentrations of MUN were different among lactation groups 1, 2, and 3+ for the first 90 DIM for Holsteins. Overall, concentrations of MUN were lower during for the first 30 DIM compared with all other DIM categories for both Holstein and Jersey cows. Multivariate regression models of MUN by milk protein showed that as the milk protein percentage increased, MUN concentration decreased; however, models for Jersey cows showed that MUN did not decrease significantly until above 3.4% milk protein. Milk fat percentage also decreased as MUN increased, but by only 1 mg/dl MUN over the range of 2.2 to 5.8% milk fat. Somatic cell count showed a negative relationship with MUN. Holstein cows with milk protein percentage >3.2% had lower MUN compared with cows having milk protein <3.2% for milk yields from 27.3 to 54.5 kg/d and lower than cows having a milk protein <3.0% for milk yield of 54.5 to 63.6 kg/d. In Jersey cows, MUN concentrations were not different among milk protein percentage categorized by milk yield. This study found that MUN was inversely associated with milk protein percentage and paralleled change in milk yield over time.

Animals↗

PubMed2003

Whole-farm nitrogen balance on western dairy farms.

Environmental legislation has made it necessary for livestock producers to be able to quantify and adjust the N balance on their farms. Whole-farm N balance and efficiencies were computed for 41 commercial dairies in Utah and Idaho using the University of Maryland Nutrient Balancer. The average N balance, or unaccounted for N, was 81 tonnes per year for the average herd size of 466 cows with 35.8% of the inputs accounted for in the outputs. The major inputs for farms that grew crops (n = 23, herd size = 284 total cows) were imported feed (57.4% of all inputs) and nitrogen fixation (30% of inputs). The major outputs were animal products (primarily milk and some meat, 80% of outputs). For farms that grew no crops (n = 18, herd size = 700 total cows), 98% of the inputs were from imported feed. Of the outputs, 57% of the N was in animal products and 42.9% in manure and compost. Whole-farm balance per product for those farms that grew crops was most affected by herd N utilization efficiency (kg feed N per kg product N), crop N utilization efficiency, and availability of manure N applied to crops, while manure N storage efficiency was of lesser importance. For farms that grew no crops, whole-farm N balance per product was most affected by herd N utilization efficiency and manure N storage efficiency. Maximizing conversion of feed N to product N was the best way to reduce whole-farm N balance.

Agriculture↗

PubMed2002

Evolution and development of sex differences in cooperative behavior in meerkats.

In cooperatively breeding birds, where helpers of both sexes assist with the provisioning and upbringing of offspring who are not their own, males tend to contribute more than females to rearing young. This sex difference has been attributed to paternity uncertainty, but could also occur because males contribute more where they are likely to remain and breed in their group of origin. In contrast to most birds, female meerkats (Suricata suricatta) are more likely to breed in their natal group than males. We show that female meerkat helpers contribute more to rearing young than males and that female helpers feed female pups more frequently than males. Our results suggest that sex differences in cooperative behavior are generated by sex differences in philopatry and occur because females derive greater direct benefits than males from raising recruits to their natal group. These findings support the view that direct, mutualistic benefits are important in the evolution of specialized cooperative behavior.

Aging↗

PubMed2002

Spatial variation of plasma flow in the oxazolone-stimulated microcirculation.

INTRODUCTION: In cutaneous lymphocytic inflammation, enhanced regional blood flow is suggested by persistent erythema and warmth. Direct assessment of the microcirculation, however, has been limited by tissue edema and skin thickness. METHODS: To assess the microcirculatory adaptations to the epicutaneous antigen oxazolone, we studied the first pass kinetics and microvascular topography of the inflammatory skin microcirculation using a specially adapted epi-illumination intravital microscopy system. The fluorescence intravital videomicroscopy and streaming image acquisition of fluorescein-labeled dextran (approximately 500,000 MW) injections were used to assess changes in plasma flow. RESULTS: Direct plasma tracer injections of both the oxazolone-stimulated and control microcirculation demonstrated comparable transit times (leading edge and intensity-weighted peak times) from the carotid artery to the superficial vascular plexus (p > 0.05). In contrast to transit times, continuous infusion of the plasma tracer demonstrated a significant increase in the delivery of the fluorescein-labeled dextran to the oxazolone-stimulated microcirculation. Quantitative morphometry of intravital microscopic images demonstrated a 2.2-fold increase in the mean diameter of vessels in the superficial vascular plexus (p < 0.01). Further, fluorescence intensity mapping indicated that the increase was associated with increased perfusion of focal regions of the superficial vascular plexus (p < 0.001). CONCLUSIONS: These results indicate that the oxazolone-stimulated adaptations of the inflammatory microcirculation include both microvascular dilatation and the redistribution of plasma flow.

Animals↗

PubMed2002

Bioelectrical impedance to estimate changes in hydration status.

Bioelectrical impedance analysis (BIA) has been suggested as a simple, rapid method to assess changes in hydration status. BIA measures the electrical impedance to a low amperage current that is affected by both water and electrolyte content of the body. While BIA can reliably estimate total body water and body density in euhydrated individuals under standardized clinical conditions, changes in fluid and electrolyte content can independently alter bioimpedance measurements. Because hydration changes typically involve concomitant changes in fluid and electrolyte content, the interpretation of a change in bioimpedance will often be confounded. This paper examines the assumptions underlying estimations of total body water from BIA and addresses the factors known to influence bioimpedance independently from actual change in total body water. The results indicate that current BIA methodology may not provide valid estimates of total body water when hydration state is altered.

Body Water↗

PubMed2002

Relationship between DHI production values and Myers-Briggs type indicator as a measure of management ability.

Associations between owners' Myers-Briggs Type Indicator (MBTI) preferences (E = extraversion vs. I = introversion; S = sensing vs. N = intuition; T = thinking vs F = feeling; J = judging vs. P = perceiving) and 21 Dairy Herd Improvement (DHI) production variables were determined on 60 farms. Of 60 dairy farmers participating, 51 were from Holstein farms (85%) and nine from farms with other breeds, primarily Jersey. Cows were milked either twice (n = 44 herds, 73%) or three times (n = 16) per day. Farmers were evenly split between the "E" and "I" dimension, whereas 93% of the farmers were "S," 75% "T," and 62% "J.". Individuals with a preference for the "I" dimension were associated with higher peak and mature equivalent milk yield than those individuals with a preference for the "E" dimension. The "T" and "J" dimensions had a significantly higher percentage of the herd with records usable by USDA and a lower percentage of animals pregnant by the goal set by the dairy producer than the "F" and "P" dimensions. Herds managed by individuals with a combination preference of "E" and "P" produced 7 to 10 kg of 3.5% FCM/cow per day less or 1,820 to 2,752 kg/ cow RHA ECM less than other combinations of the "E-I" and "J-P" dimensions. Those herds also had longer days dry and a lower percentage of records usable by USDA, suggesting that the "E-P" preference is less favorably associated to those measures of herd performance. The MBTI had limited association with many DHI production variables, but relationships to measures of labor and business management should be examined.

Administrative Personnel↗

PubMed2002

Physiological responses to cold exposure in men: a disabled submarine study.

A disabled submarine (DISSUB) lacking power and/or environmental control will become cold, and the ambient air may become hypercapnic and hypoxic. This study examined if the combination of hypoxia, hypercapnia, and cold exposure would adversely affect thermoregulatory responses to acute cold exposure in survivors awaiting rescue. Seven male submariners (33 +/- 6 yrs) completed a series of cold-air tests (CAT) that consisted of 20-min at T(air) = 22 degrees C, followed by a linear decline (1 degrees C x min(-1)) in T(air) to 12 degrees C, which was then held constant for an additional 150-min. CAT were performed under normoxic, normocapnic conditions (D0), acute hypoxia (D1, 16.75% O2), after 4 days of chronic hypoxia, hypercapnia and cold (D5, 16.75% O2, 2.5% CO2, 4 degrees C), and hypoxia-only again (D8, 16.75% O2). The deltaTsk during CAT was larger (P < 0.05) on D0 (-5.2 degrees C), vs. D1 (-4.8 degrees C), D5 (-4.5 degrees C), and D8 (-4.4 degrees C). The change (relative to 0-min) in metabolic heat production (deltaM) at 20-min of CAT was lower (P < 0.05) on D1, D5, and D8, vs. D0, with no differences between D1, D5 and D8. DeltaM was not different among trials at any time point after 20-min. The mean body temperature threshold for the onset of shivering was lower on D1 (35.08 degrees C), D5 (34.85 degrees C), and D8 (34.69 degrees C), compared to D0 (36.01 degrees C). Changes in heat storage did not differ among trials and rectal temperature was not different in D0 vs. D1, D5, and D8. Thus, mild hypoxia (16.75% F1O2) impairs vasoconstrictor and initial shivering responses, but the addition of elevated F1CO2 and cold had no further effect. These thermoregulatory effector changes do not increase the risk for hypothermia in DISSUB survivors who are adequately clothed.

Adult↗

PubMed2002

Subjective symptoms and postural control during a disabled submarine simulation.

To simulate conditions aboard a disabled submarine, 7 submariners were confined for 5 d to a normobaric environment of 16.75% O2, 2.5% CO2, 4 degrees C, and 85% relative humidity (RH). After 2 control days and 1 d of hypoxia, the remaining environmental conditions were imposed for the next 5 d, followed by 1 additional day of just hypoxia. Daily morning symptoms were assessed using the Environmental Symptoms Questionnaire (ESQ). Postural stability was determined on 4 occasions using a computerized balance system: control period, after 2.7 and 4.7 d of steady-state test conditions, and after 5.7 d (with return to normal ambient temp, RH, and CO2). Three balance tests were performed: eyes open, eyes closed, and a dynamic test. Postural stability deteriorated after 2.7 d (87% eyes open, P < 0.001 and 26% eyes closed, P = 0.01). ESQ symptom subsets for acute mountain sickness, exertion, fatigue, alertness, and ear/nose/throat were not significantly different. Cold symptom subsets were increased after 3-7 d (P < 0.001); distress and muscle discomfort subsets after 7 d (P = 0.02). Continued exposure to the combination of cold and hypoxia elicited subjective symptom changes and disturbances in postural stability that are statistically significant. These observations may be of practical importance when tasks aboard a disabled submarine involve balance and mobility.

Adult↗

PubMed2001

Biphasic response of the regional lymphatics in the normal lymphocyte transfer reaction.

BACKGROUND: Initially developed for histocompatibility testing, the normal lymphocyte transfer (NLT) reaction involves the intradermal injection of allogeneic lymphocytes from one individual to another. Because of the unique kinetics of the immunological response to allogeneic lymphocytes, the NLT reaction has been considered an informative system for the analysis of transplant immunity. METHODS: In this study, we used bilateral efferent lymph duct cannulations in sheep to examine the regional lymphatic response to the NLT reaction. Our studies used monoclonal antibodies to define lymphocyte population dynamics and DNA flow cytometry to reflect lymphocyte proliferative responses. RESULTS: The results confirmed a biphasic NLT reaction. An unexpected finding was the marked differences between the early and late NLT responses. The early response was characterized by T-lymphocyte proliferation, as reflected by S-phase DNA, which was comparable in both the NLT-stimulated and contralateral control efferent lymphocytes. This bilateral proliferative response was observed in both CD4+ and CD8+ lymphocytes. In contrast, the late response was restricted to the efferent lymph from the NLT-stimulated lymph node. Dual-parameter flow cytometry demonstrated that the dominant component of this unilateral NLT response was CD8+ lymphocytes. CONCLUSIONS: These results suggest important functional distinctions between systemic and regional lymphatic responses to intradermal alloantigens.

Animals↗

PubMed2001

Antioxidant and prooxidant properties of carotenoids.

The ability of dietary carotenoids such as beta-carotene and lycopene to act as antioxidants in biological systems is dependent upon a number of factors. While the structure of carotenoids, especially the conjugated double bond system, gives rise to many of the fundamental properties of these molecules, it also affects how these molecules are incorporated into biological membranes. This, in turn, alters the way these molecules interact with reactive oxygen species, so that the in vivo behavior may be quite different from that seen in solution. The effectiveness of carotenoids as antioxidants is also dependent upon their interaction with other coantioxidants, especially vitamins E and C. Carotenoids may, however, lose their effectiveness as antioxidants at high concentrations or at high partial pressures of oxygen. It is unlikely that carotenoids actually act as prooxidants in biological systems; rather they exhibit a tendency to lose their effectiveness as antioxidants.

Animals↗

PubMed2001

Exertion-induced fatigue and thermoregulation in the cold.

Cold exposure facilitates body heat loss which can reduce body temperature, unless mitigated by enhanced heat conservation or increased heat production. When behavioral strategies inadequately defend body temperature, vasomotor and thermogenic responses are elicited, both of which are modulated if not mediated by sympathetic nervous activation. Both exercise and shivering increase metabolic heat production which helps offset body heat losses in the cold. However, exercise also increases peripheral blood flow, in turn facilitating heat loss, an effect that can persist for some time after exercise ceases. Whether exercise alleviates or exacerbates heat debt during cold exposure depends on the heat transfer coefficient of the environment, mode of activity and exercise intensity. Prolonged exhaustive exercise leading to energy substrate depletion could compromise maintenance of thermal balance in the cold simply by precluding continuation of further exercise and the associated thermogenesis. Hypoglycemia impairs shivering, but this appears to be centrally mediated, rather than a limitation to peripheral energy metabolism. Research is equivocal regarding the importance of muscle glycogen depletion in explaining shivering impairments. Recent research suggests that when acute exercise leads to fatigue without depleting energy stores, vasoconstrictor responses to cold are impaired, thus body heat conservation becomes degraded. Fatigue that was induced by chronic overexertion sustained over many weeks, appeared to delay the onset of shivering until body temperature fell lower than when subjects were rested, as well as impair vasoconstrictor responses. When heavy physical activity is coupled with underfeeding for prolonged periods, the resulting negative energy balance leads to loss of body mass, and the corresponding reduction in tissue insulation, in turn, compromises thermal balance by facilitating conductive transfer of body heat from core to shell. The possibility that impairments in thermoregulatory responses to cold associated with exertional fatigue are mediated by blunted sympathetic nervous responsiveness to cold is suggested by some experimental observations and merits further study.

Body Temperature Regulation↗

PubMed2001

Focal topographic changes in inflammatory microcirculation associated with lymphocyte slowing and transmigration.

Microcirculation is the primary mechanism for delivering lymphocytes to inflammatory tissues. Blood flow within microvessels ensures a supply of lymphocytes at the blood-endothelial interface. Whether the structure of the inflammatory microcirculation facilitates lymphocyte transmigration is less clear. To illuminate the microcirculatory changes associated with lymphocyte transmigration, we used intravital videomicroscopy to examine the dermal microcirculation after application of the epicutaneous antigen oxazolone. Intravascular injection of fluorescein-labeled dextran demonstrated focal topographic changes in the microcirculation. These focal changes had the appearance of loops or hairpin turns in the oxazolone-stimulated skin. Changes were maximal at 96 h and coincided with peak lymphocyte recruitment. To determine whether these changes were associated with lymphocyte transmigration, lymphocytes obtained from efferent lymph of draining lymph nodes at 96 h were fluorescently labeled and reinjected into inflammatory microcirculation. Epifuorescence intravital video microscopy demonstrated focal areas were associated with lymphocyte slowing and occasional transmigration. In contrast, focal loops and lymphocyte slowing were rarely observed in the contralateral control microcirculation. Results suggest that structural adaptations in inflammatory microcirculation represented by focal topographic changes may contribute to regulation of tissue entry by recirculating lymphocytes.

Adjuvants, Immunologic↗

PubMed2001

Intracellular monocyte and serum cytokine expression is modulated by exhausting exercise and cold exposure.

This study tested the hypothesis that exercise elicits monocytic cytokine expression and that prolonged cold exposure modulates such responses. Nine men (age, 24.6 +/- 3.8 y; VO(2 peak), 56.8 +/- 5.6 ml. kg(-1). min(-1)) completed 7 days of exhausting exercise (aerobic, anaerobic, resistive) and underwent three cold, wet exposures (CW). CW trials comprised </=6 h (six 1-h rest-work cycles) exposure to cold (5 degrees C, 20 km/h wind) and wet (5 cm/h rain) conditions. Blood samples for the determination of intracellular and serum cytokine levels and circulating hormone concentrations were drawn at rest (0700), after exercise (approximately 1130), and after CW (~2000). Whole blood was incubated with (stimulated) or without (spontaneous) lipopolysaccharide (LPS; 1 microgram/ml) and stained for CD14 monocyte surface antigens. Cell suspensions were stained for intracellular cytokine expression and analyzed by flow cytometry. The proportion of CD14(+) monocytes exhibiting spontaneous and stimulated intracellular expression of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha increased after exercise, but these cells produced less IL-1beta and TNF-alpha after CW when CW was preceded by exhausting exercise. Serum cytokine concentrations followed a parallel trend. These findings suggest that blood monocytes contribute to exercise-induced cytokinemia and that cold exposure can differentially modulate cytokine production, upregulating expression of IL-6 and IL-1 receptor antagonist but downregulating IL-1beta and TNF-alpha. The cold-induced changes in cytokine expression appear to be linked to enhanced catecholamine secretion associated with cold exposure.

Adult↗

PubMed2001

Cold strain index applied to exercising men in cold-wet conditions.

A cold strain index (CSI) based on rectal (T(re)) and mean skin temperatures ((sk)) using data from seminude resting subjects has been proposed (Moran DS, Castellani JW, O'Brien C, Young AJ, and Pandolf KB. Am J Physiol Regulatory Integrative Comp Physiol 277: R556-R564, 1999). The current study determined whether CSI could provide meaningful data for clothed subjects exercising in the cold with compromised insulation. Ten men exercised in cold-wet conditions (CW) for 6 h before (D0) and after 3 days of exhaustive exercise (D3). Each hour of CW consisted of 10 min of standing in rain (5.4 cm/h, 5 degrees C air) followed by 45 min of walking (1.34 m/s, 5.4 m/s wind, 5 degrees C air). The change in T(re) across time was greater (P < 0.05) on D3 than on D0, and the change in (sk) was less (P < 0.05) on D3 than on D0. Although CSI increased across time, the index at the end of both trials (D3 = 4.6 +/- 0.6; D0 = 4.2 +/- 0.8) was similar (P > 0.05). Thus, while (sk) was 1.3 degrees C higher (P < 0.05) and T(re) was 0.3 degrees C lower (P < 0.05) on D3 than on D0, CSI did not discriminate the greater heat loss that occurred on D3. These findings indicate that when vasoconstrictor responses to cold are altered, such as after exhaustive exercise, CSI does not adequately quantify the different physiological strain between treatments. CSI may be useful for indicating increased strain across time, but its utility as a marker of strain between different treatments or studies is uncertain because no independent measure of strain has been used to determine to what extent CSI is a valid and reliable measure of strain.

Adult↗