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Biomedical subjects

J P Dixon

Publications and source records attributed to J P Dixon.

11 recordsLinked to original sources
PubMed1997

Following cell fate in the living mouse embryo.

It has been difficult to follow many of the dramatic changes in cell fate and cell migration during mouse development. This is because there has been no enduring marker that would allow cells to be recognised in the living embryo. We believe that we have overcome this problem by developing a novel form of green fluorescent protein, named MmGFP, that proves to be easily visible and non toxic to mouse cells and does not perturb embryogenesis. We show that synthetic mRNA encoding MmGFP can be injected into blastomeres to follow the fate of their progeny during preimplantation development. We have made a stable embryonic stem cell line that expresses MmGFP and introduced these fluorescent cells into mouse embryos. For the first time, we have been able to follow the fate of embryonic stem cells in living embryos and to observe directly the contribution of these cells to distinct lineages of the postimplantation embryo. This approach should lead to a more complete description of the dynamics of cell fate in the mouse.

Animals↗
PubMed1993

Energy as a central factor in the self-assessment of health.

This article explores the role of energy in conceptualization of health, based on self-reported health ratings in 310 women (master's-prepared nurses) ages 50 to 70 years. The health self-assessment instrument consists of 1 global and 10 specific items. The item energy level emerged as central--loading on both the psychosocial health and physiologic health factors and accounting for 48% of variance of Global Health Self-Assessment. These findings build on the World Health Organization definition of health as a synthesis of psychosocial and physiologic well-being; energy level is key to an integrated view of health.

Activities of Daily Living↗
PubMed1991

Tensions between career and interpersonal commitments as a risk factor for cardiovascular disease among women.

For professional women, the tension between the career world and the world of interpersonal commitments to spouses, children and friends is thought to be particularly stressful, and a potential risk factor for cardiovascular disease. The Career-Life Balance Inventory (CLBI) was created to survey a wide variety of these tensions among a group of 202 professional women. In a discriminant analysis, two scales from the CLBI (Career-Sacrifices and Interpersonal Sacrifices) appeared to play an important role in distinguishing those women experiencing serious cardiovascular disease. This model for the discrimination of cardiovascular disease was significant to the .01 level. This result suggests the need for more refined study of the tensions between career and interpersonal commitments, as these may relate to risk for cardiovascular disease.

Aged↗
PubMed1989

Perceptions of life-pattern disintegrity as a link in the relationship between stress and illness.

The weak but significant association between stressful events and illness suggests the importance of understanding the specific conditions under which stress is likely to result in illness. The research was undertaken to determine whether a perception of disintegrity--a perception that life has not gone as it should have--may be such a link. Ninety-one master's-prepared nurses between the ages of 55 and 70 completed a measure of the extent to which they had experienced stress in balancing a career with other life involvements. They also assessed the extent of integrity-disintegrity in their life pattern and recorded the illnesses that had occurred during their middle years. In a path analysis, once the indirect path through disintegrity was considered, the direct path between stress and illness was so minimal that it was considered eliminated. This result suggests that unless stress leads to feelings of disintegrity, it is not likely to lead to illness.

Adaptation, Psychological↗
PubMed1988

Fatal pulmonary decompression sickness: a case report.

A 51-year-old civilian pilot flying a high performance aircraft for the USAF presented for medical attention approximately 1.5 hours after developing substernal chest pain and dyspnea while flying unpressurized at FL 280 (8,534 meters) for 30 minutes. In spite of recompression about 3 hours later, the pilot expired while ascending from 6 atmospheres, 2.5 hours into the dive. This represents the first reported fatality due to altitude-induced decompression sickness since 1959. Pathologically, this case is similar to cases presented in the past. In addition, this case serves to reemphasize many of the "risk factors" for decompression sickness, especially age and obesity. Furthermore, the evidence presented points to maintaining only the highest standards of physical health in those who fly high performance aircraft.

Decompression Sickness↗
PubMed1985

Death at high altitude in the hypobaric chamber.

A small number of accidental and suicidal deaths have occurred in the hypobaric, or high altitude, chamber. A case of an unusual suicide in a hypobaric chamber is presented. The changes that resulted from decompression and hypoxia are discussed.

Adult↗
PubMed1984

An evolutionary-based model of health and viability.

A model of health and viability, as influenced by a wide variety of psychosocial variables, is presented. This model is based on the principle that illness and death sometimes serve an evolutionary function by maximizing natural selection prospects of other group members. Thus, evolutionary viability within the social context (personal contribution to one's social network) is a crucial health factor; life events, life style determiners, control perceptions, and viability emotions are other important concepts within the model. This model points to the possibility that the full scope of clinical practice may require assisting patients in regaining a sense of viability; nursing may be particularly relevant to this need because of the opportunity for intense interpersonal contact with patients.

Attitude↗
PubMed1982

Arterial oxygen saturation at altitude using a nasal cannula.

Oxygen saturation in six subjects wearing a nasal cannula at altitudes of 14,000 ft (4267 m), 20,000 ft (6096 m), 22,500 ft, (6858 m) and 25,000 ft (7620 m) was measured using an ear oximeter (Hewlett-Packard 47201A). Saturation was measured during four activities: at rest breathing through the mouth, at rest breathing through the nose, performing biceps-curls, and talking. Oxygen flow rates of 1.5-2.5 LPM NTPD were used. There was no difference in the saturation levels whether the subject breathed through the nose or through the mouth, and cannula position in the nose was critical to good oxygen saturation. During talking and while exercising, subjects' saturations varied more than during rest conditions, sometimes falling to unacceptable levels. Based upon the lack of hypoxia symptoms and the high levels of oxygen saturation up to 20,000 ft (6096 m), it is concluded that at flow rates of 1.5-2.0 LPM NTPD the nasal cannula can be safely used to maintain adequate oxygenation in healthy individuals in hypobaric chamber operations, aircraft flight, and other operations at altitude. Above 20,000 ft (6096 m), the cannula does not provide sufficient oxygenation for persons to perform these physical activities.

Adult↗
PubMed1979

Properties of superior colliculus neurons in the golden hamster.

A laminar representation of sensory modalities was present in the hamster superior colliculus (SC) with upper laminar cells being exclusively visual, while intermediate and deeper layer cells were visual, somatic, acoustic or multimodal. Receptive field (RF) properties of visual SC cells were studied quantitatively with stationary spots and moving bars of light of various sizes, velocities and directions of movement. The most effective stimuli were usually less than half of the diameter of the RF. Increasing stimulus size beyond a critical range produced progressively lower discharge rates even though the stimulus was confined within the borders of the RF. Low velocities (10-50 degrees/sec) were most frequently optimal for both upper and lower laminar cells and the majority of cells were directionally selective. Movements in the upper nasal direction usually elicited the highest discharge rates and were thus preferred most frequently. However, directional preferences often could be minimized, or obliterated, by employing nonoptimal stimulus sizes and/or velocities. Most intermediate and deeper laminar somatic cells could be activated by gentle cutaneous stimuli and a general somatotopic plan, which was in register with the overlying visuotopy, was noted. Cells optimally, or solely, activated by noxious stimuli were also located, but RFs of such cells were extensive and a somatotopic plan was not apparent. Although species differences are apparent, the similarities between the organization and the RF properties of SC cells of the hamster and distantly related species are striking. Apparently the same SC system is adaptive in diverse species despite the very different behavioral repertories of these animals and their different ecological niches.

Animals↗