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Biomedical subjects

A Meisel

Publications and source records attributed to A Meisel.

At least 19 recordsLinked to original sources
PubMed1992

Type III restriction enzymes need two inversely oriented recognition sites for DNA cleavage.

Type III restriction/modification enzyme recognize short, non-palindromic sequences that can be methylated on only one strand, with the paradoxical consequence that during replication of what is in effect hemimethylated DNA totally unmodified sites arise. Why the unmodified sites are not subject to suicidal restriction was not clear. Here we show that restriction requires two unmodified recognition sites that can be separated by different distances but which must be in inverse orientation. All of the unmodified sites in newly replicated DNA are of course in the same orientation, which explains why they are not restricted. This result may be of relevance to other manifestations of anisotropy in double-stranded DNA, such as genetic imprinting.

Base Sequence↗
PubMed1992

Informed consent.

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Disclosure↗
PubMed1991

Activation of restriction endonuclease EcoRII does not depend on the cleavage of stimulator DNA.

The restriction endonuclease EcoRII is unable to cleave DNA molecules when recognition sites are very far apart. The enzyme, however can be activated in the presence of DNA molecules with a high frequency of EcoRII sites or by oligonucleotides containing recognition sites: Addition of the activator molecules stimulates cleavage of the refractory substrate. We now show that endonucleolysis of the stimulator molecules is not a necessary prerequisite of enzyme activation. A total EcoRII digest of pBR322 DNA or oligonucleotide duplexes with simulated EcoRII ends (containing the 5' phosphate group), as well as oligonucleotide duplexes containing modified bases within the EcoRII site, making them resistant to cleavage, are all capable of enzyme activation. For activation EcoRII requires the interaction with at least two recognition sites. The two sites may be on the same DNA molecule, on different oligonucleotide duplexes, or on one DNA molecule and one oligonucleotide duplex. The efficiency of functional intramolecular cooperation decreases with increasing distance between the sites. Intermolecular site interaction is inversely related to the size of the stimulator oligonucleotide duplex. The data are in agreement with a model whereby EcoRII simultaneously interacts with two recognition sites in the active complex, but cleavage of the site serving as an allosteric activator is not necessary.

Allosteric Site↗
PubMed1991

Legal myths about terminating life support.

There are a number of myths about what the law permits concerning the termination of life support, some of which spring from a fundamental misconception of what law is. A serious misunderstanding of the law can lead to tragic results for physicians, health care institutions, patients, and families. These misunderstandings are (1) anything that is not specifically permitted by law is prohibited; (2) termination of life support is murder or suicide; (3) a patient must be terminally ill for life support to be stopped; (4) it is permissible to terminate extraordinary treatments, but not ordinary ones; (5) it is permissible to withhold treatment, but once started, it must be continued; (6) stopping tube feeding is legally different from stopping other treatments; (7) termination of life support requires going to court; and (8) living wills are not legal.

Advance Directives↗
PubMed1990

Lessons from Cruzan.

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Government Regulation↗
PubMed1977

A question of zeal.

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Bipolar Disorder↗
PubMed1977

Tests of competency to consent to treatment.

The authors describe the various tests of competency to consent to treatment used today, which include the following: 1)evidencing a choice, 2)"reasonable" outcome of choice, 3)choice based on "rational" reasons, 4)ability to understand, and 5)actual understanding. They analyze the applicability of these tests to patients' decisions to accept or refuse psychiatric treatment and illustrate the problems of ap-lying these tests by citing clinical case examples. They find that the circumstances in which competency becomes an issue determine which elements of which tests are stressed and which are underplayed.

Adult↗
PubMed1977

Toward a model of the legal doctrine of informed consent.

The authors draw together the disparate scholarly and judicial commentaries on consent to medical treatment to develop a model of the components in the decision-making process regarding consent to or refusal of psychiatric treatment. The components consist of the precondition of voluntariness, the provision of information, the patient's competency and understanding, and, finally, consent or refusal. They offer two models of valid consent: the objective model, which focuses on the congruence or lack of it between the patient and a "reasonable" person, and the subjective model, which focuses entirely on the patient's actual understanding.

Civil Rights↗
PubMed1977

Dangerousness, confidentiality, and the duty to warn.

The Tarasoff decision, by imposing on psychiatrists an obligation to warn the intended victim of threats made by a patient, but only under certain vaguely specified circumstances, may stampede psychiatrists into issuing such warnings to avoid possible legal liability no matter how remote the risk of harm may actually be. The authors suggest that the ill effects of such a reaction by psychiatrists--breach of confidentiality and the attendant erosion of trust and harm to the therapeutic alliance--can often be easily avoided by taking less drastic steps, some of which are illustrated by case presentations.

Adult↗
PubMed1976

Effect of vasopressin on uric acid excretion: evidence for distal nephron reabsorption of urate in man.

1. When changes in urine flow rate were induced by vasopressin administration in eight subjects, urate excretion decreased by a mean of 14% and was positively correlated with urine flow rate (r = 0.88, P less than 0.01). The effect of vasopressin on urate excretion was not influenced by prior changes in extracellular fluid volume. 2. Mannitol administration in a dose sufficient to prevent vasopressin-induced alterations in urine flow rate blocked the effect of vasopressin on urate excretion. 3. Alterations in urate excretion produced by changes in extracellular fluid volume could be distinguished from the urate-retaining effect of vasopressin-mediated decrease in urine flow. Urate retention after vasopressin was entirely attributed to a decrease in pyrazinamide-suppressible urate excretion, consistent with either decreased secretion or enhanced post-secretory reabsorption of urate. 4. Since diminished urine flow rate in the distal part of the nephron is more likely to lead to enhanced reabsorption of urate, these results provide additional evidence for urate reabsorption in the distal part of the nephron.

Adult↗