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Biomedical subjects

L J Weber

Publications and source records attributed to L J Weber.

At least 19 recordsLinked to original sources
PubMed1997

The prevalence of colonic neoplasia in patients with Barrett's esophagus: prospective assessment in patients 50-80 years old.

OBJECTIVE: An association between Barrett's esophagus and colorectal neoplasia has been suggested; however, several studies addressing this issue have reported conflicting results. The purpose of this study, therefore, was to determine the prevalence of colorectal neoplasia in a large group of patients (50-80 yr old; mean, 65 yr) with Barrett's esophagus and compare it with that of a similar group of asymptomatic, average-risk controls. METHODS: Seventy-nine subjects (71 men, eight women) with well-documented Barrett's esophagus underwent complete colonoscopy (cecum reached), which was performed as part of an initial screening evaluation for enrollment in a prospective study of Barrett's esophagus. The control population (N = 930) is represented by the cumulative results of four recent studies in which screening colonoscopy was performed in asymptomatic subjects of average risk. The age of the two groups were similar. RESULTS: A total of 38 adenomatous polyps were found in 26 patients in the study group. Three patients (4%) had polyps > 1 cm in size or with villous change, which was similar to the prevalence among asymptomatic controls (5%). The overall prevalence of colon adenomas was 32%, and the prevalence of colorectal cancer was 1% in the Barrett's group. In the control group, 30% had adenomas and 0.5% had cancer. CONCLUSION: The prevalence of adenomatous polyps, both large and small, in a group of patients (ages 50-80 yr) with well-documented Barrett's esophagus is no different from that in asymptomatic controls. These results do not support the assumption of an association between Barrett's esophagus and an increased risk of colon neoplasia, or justify an aggressive surveillance strategy for colon neoplasia in patients with Barrett's esophagus.

Adenomatous Polyps↗
PubMed1996

Medical futility and life-sustaining treatment decisions.

By focusing our attention on the questions of "what are we trying to achieve" and "are we able to do it", the discussion of medical futility has contributed an important dimension to the ethics of treatment decision making near the end of life. It is not simply enough to ask and answer the question of what the patient wants. Healthcare professionals have a responsibility to offer only those life-sustaining efforts that have a reasonable chance of being beneficial. Futility policies should permit treatment-limiting decisions to be made without the agreement of the patient or surrogate at times, but such policies should also provide opportunities to challenge a judgement of futility. Above all, such policies should not be used as a reason to avoid communication. Patients or surrogates need to be informed about what treatments are options and what are not. The futility criterion for limiting treatment should be recognized as a means of contributing to communication and discussion regarding benefits, harms and medical goals. It should not be permitted to bypass such discussions. The recognition of the significance of the concept of futility means that discussion needs to continue at another level as well. The questions of "what are we trying to achieve" and "are we able to do it" are not easily answered. It is especially important, we think, that those who are experienced in working with patients with neurological impairments contribute to the on-going reflection on what constitutes benefit or what is the appropriate use of life-sustaining interventions for such patients.

Adult↗
PubMed1996

"Biospheric medicine" as viewed from the two-year first closure of Biosphere 2.

Biosphere 2 is a 3.15-acre, 7-million ft. enclosed ecological space near Tucson, AZ. It contains five wilderness and two domestic biomes (rain forest, savanna, desert, ocean, marsh; agricultural station, living quarters), an original introduction of 3,800 species (approximately 20% extinctions have occurred), and a large basement "technosphere." Sealed inside Biosphere 2 in September 1991, four women and four men, including two of the authors, maintained themselves and the various systems for 2 yr, the longest-sustained "isolated confined environment" period on record. MMPI psychological profile scores for Biosphere 2 crewmembers correlated closely with those reported for astronauts and shuttle applicants. Major medical problems encountered during the 2 yr included adaptation to a low-calorie (1800-2200 kcal.d-1 per person) but otherwise nutritionally adequate diet, with substantial weight loss (18% for men, 10% for women), and a declining oxygen atmosphere (down to 14.2%). Life in a miniworld such as Biosphere 2 may differ substantially from life in a space station or temporary planetary base. These differences include multiple, shifting, sometimes opposing post-launch objectives; complete self-sustenance with recycling of virtually all materials within a highly complex biologic system; retooling of some areas of practical medicine; an attention to "culture" as a social dynamic and how that may influence crew and leadership selection in a societal rather than a quasi-military community. Assuming that long-term planetary colonies must be largely self-sustaining (due to costs of supply over great distances), they must of necessity approach the condition of biospheres. Subject to chaos dynamic (nonlinear dynamic) perturbations, the behavior of complex biospheres will be inherently non-predictable--as opposed to the linear dynamic situation of most space missions--and will require of the inhabitants, including the medical team, a wide range of coping abilities. Under the circumstances, and while strong similarities exist, important differences may serve to distinguish "biospheric medicine" from "space medicine."

Adaptation, Psychological↗
PubMed1995

Procuring organs from a non-heart-beating cadaver: commentary on a case report.

Procurement of organs from non-heart-beating cadaver donors raises concerns. Standards for optimal patient care during withdrawal of life-sustaining therapy are evolving and continue to be debated and studied. Consensus on specific procedures and methods has not been attained, however, and protocols for the procurement of organs from patients following the withdrawal of life-sustaining therapies may compromise the evolving standards and harm the patient and the attendant family. In addition, there is little evidence to suggest that such protocols will significantly increase the number of organs procured. "Non-heart-beating cadaver" protocols that do not give comprehensive attention to optimal patient/family care at the time of withdrawal of life-sustaining therapy ought not to be endorsed.

Cadaver↗
PubMed1994

Testes size and testosterone levels in a model for weightlessness.

The purpose of this study was to test whether the lack of testicular growth found in suspended rats would affect testosterone production in a way that might have consequences on muscle atrophy and function studies. Body and testes weight, food consumption, and testosterone levels in testes and plasma were measured at the beginning of the experiment and after 1, 3 or 8 weeks of suspension. Suspended animals ate more but gained less weight than their pair-fed controls. Testes testosterone concentration (microgram/g tissue) was increased at 3 and 8 weeks, but total tissue testosterone (microgram/testes) was not. Up to 3 weeks of suspension, tissue concentration was dependent on testes size and independent of treatment. Plasma testosterone was increased only after 8 weeks of suspension. At 8 weeks, plasma levels correlated with total testes testosterone. Our results show that use of the Morey-Holton rat tail-suspension model up to 3 weeks did not induce testosterone changes of consequence to a skeletal muscle study. For long term studies consideration should be given to possible hormonal effects as tissue and plasma testosterone levels increase after 8 weeks of suspension.

Animals↗
PubMed1993

The patient as citizen. A common-good approach to medical treatment decisions balances the emphasis on patient desires.

Individualism plays too strong a role in the arena of treatment decision making, frequently to the exclusion of any other consideration. Using a common-good or community-based ethic as a framework for treatment decision making may provide appropriate balance to the emphasis on patient desires. Self-determination is a good that must be balanced with other goods. When it is not, to quote Daniel Callahan, "Self-determination runs amok." For example, in the state of New Jersey, individuals are permitted to choose the criteria to be used in determining that their own death has occurred. Some of the principles that may lead to a reasonable understanding of the patient's rights in a "patient-as-citizen" ethical perspective are: Everyone has a legitimate claim to a basic level of healthcare. Everyone has a legitimate claim to respect for his or her refusal of recommended treatment. No one has a legitimate claim to nonbeneficial or futile treatment. No one has a legitimate claim to treatment that is being withheld as part of a just rationing system. No one has a legitimate claim to the ability to determine the medical criteria to be used for the diagnosis of his or her death. A just healthcare system is one in which individual desires for medical treatment beyond the basic level are accommodated whenever possible but not when they undermine the primary purpose of medicine to meet the basic healthcare needs of all persons.

Consensus↗
PubMed1990

Limiting the role of the family in discontinuation of life sustaining treatment.

In matters of discontinuation of life-sustaining treatment, traditional role of the family to speak on behalf of the incompetent patient is questionable. We explore the reasons why physicians perceive patient autonomy to be transferrable to family members. Principle of patient autonomy may not suffice when futile treatment is demanded and may serve to erode the ethical integrity of medical profession. An enhanced role for bioethics committees is proposed when physicians propose to discontinue life-sustaining treatment against the wishes of the patient or their families.

Beneficence↗
PubMed1989

Oxidation of cardiac myoglobin in vivo by sodium nitrite or hydroxylamine.

A non-vascularized fish heart model was used to assess the oxidation of cardiac myoglobin in vivo by compounds known to cause methemoglobinemia. Buffalo sculpin (Enophrys bison) were cannulated from the afferent branchial artery to permit repeated blood sampling and injected intraperitoneally with sodium nitrite, hydroxylamine or aniline. Methemoglobin was formed by sublethal levels of sodium nitrite or hydroxylamine. For hydroxylamine, the time to peak effect was less than 1 h. For sodium nitrite, the onset was less rapid and the effect more prolonged. Aniline had no effect on hemoglobin at any concentration tested. Cardiac myoglobin, assayed at the time of peak effect on hemoglobin, was oxidized in a dose-dependent manner by sodium nitrite or hydroxylamine. At high doses of sodium nitrite (50 and 100 mg/kg), the oxidation of myoglobin exceeded that of hemoglobin. The reverse was true of hydroxylamine at all concentrations tested. This study suggests that possibility that cardiac myoglobin is oxidized in occupational or other exposures to sodium nitrite, hydroxylamine and related compounds.

Animals↗
PubMed1989

Comparative oxygen affinity of fish and mammalian myoglobins.

Myoglobins from rat, coho salmon (Oncorhynchus kisutch), buffalo sculpin (Enophrys bison) hearts, and yellowfin tuna (Thunnus albacares) red skeletal muscle were partially purified and their O2 binding affinities determined. Commercially prepared sperm whale myoglobin was employed as an internal standard. Tested at 20 degrees C, myoglobins from salmon and sculpin bound O2 with lower affinity than myoglobins from the rat or sperm whale. Oxygen binding studies at 12 degrees C and 37 degrees C suggest that this difference is adaptive, permitting myoglobins from cold-adapted fish to function at physiologically relevant temperatures. Taken together, purification and O2 binding data obtained in this study reveal a previously unrecognized diversity of myoglobin structure and function.

Animals↗
PubMed1984

Effects of neuromuscular blocking agents and acetylcholinesterase inhibitors on the response of pectoral fin muscle of the sculpin (Enophrys bison) to indirect stimulation.

The neuromuscular junction of the buffalo sculpin (Enophrys bison) was characterized in situ by examining the effects of various neuromuscular blocking agents and acetylcholinesterase inhibitors (ACHE-I) on pectoral muscle response to indirect stimulation. The injection of either d-tubocurarine (350 micrograms/kg) or alpha-bungarotoxin (alpha-Butx) (1 mg/kg) resulted in a flaccid paralysis. The depolarizing agents, succinylcholine (11 micrograms/kg) and decamethonium (42 micrograms/kg), produced a spontaneous contraction. The administration of the ACHE-I, diisopropyl fluorophosphate (DFP), and eserine resulted in responses which were contrary to those expected based on similar experiments using mammalian skeletal muscle. Twitch potentiation did not occur and the ability to maintain a tetanic response was not abolished even after the administration of clearly lethal concentrations of ACHE-I.

Acetylcholinesterase↗