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Biomedical subjects

M Cramer

Publications and source records attributed to M Cramer.

At least 55 records · Page 3Linked to original sources
PubMed1983

A simple mathematical model for predicting lithium dose requirement.

Available methods of predicting lithium dose have been based on kinetics of a single test dose. A statistically based mathematical model was developed in which lithium dose is derived by stepwise multiple linear regression based on desired level, form of lithium, concomitant tricyclic use, age, sex, and weight. Predictions of the model were correct to within 300 mg in 66% of the 100 initial cases and within 600 mg in 94% of cases. A validation study of 112 additional cases revealed similar percentage. The simple mathematical expression derived from record review allows the clinician to calculate the relationship of steady-state lithium dosage to serum level prior to initiating treatment.

Adult↗
PubMed1982

Sinus node recovery time related to paced cycle length in normals and patients with sinoatrial dysfunction.

Depressed conduction in the sinoatrial junction, common in the sick sinus syndrome (SSS), should decrease the maximum pacing rate at which 1:1 capture of the SA node occurs. This may result in shorter than expected sinus recovery times (SRT) and maximal prolongation of SRT at relatively slow pacing rates. To test this hypothesis we evaluated the range of pacing rates necessary to demonstrate maximal SRT in 34 patients with and 20 patients without sinus node dysfunction. Atrial pacing was performed at multiple paced cycle lengths (PCL) between 400 and greater than or equal to 1000 msec, four times at each. A mean corrected SRT (CSRT) was determined at each PCL, and the PCL of the longest CSRT was determined (PCLp). PCLp varied linearly with sinus cycle length, was dependent on sinoatrial conduction time, and was longer in patients with SSS than in normal persons. Only 2 of 20 normal persons, but 21 of 34 patients with SSS, had a PCLp greater than 600 msec. A long PCLp (greater than 600 msec) suggests the possibility of recovery times that have been limited by A-S entrance block and appears to be indicative of sinus node dysfunction.

Arrhythmias, Cardiac↗
PubMed1982

Pitfall of venous occlusion plethysmography.

The supposition that the lower limb expands uniformly in circumference during venous occlusion has been investigated. The 3 compartments of the calf were found to be expand to differing degrees depending on the volume of muscle within the compartment. The effect of this phenomenon on the measurement of venous outflow and capacitance using an overlapping strain gauge was assessed. When using an overlapping strain gauge, the anatomical site of overlap was found to alter the measured values of outflow and capacitance by as much as 50%. These errors do not arise with strain gauges designed to fit a small range of limb circumferences, so that no overlap occurs. The reproducibility of plethysmography may be enhanced by attention to the site and degree of overlap of gauges which are designed to fit all sizes of limb. Technicians performing venous occlusion plethysmography should be aware of these variations, so that the examination technique can be standardized.

Acute Disease↗
PubMed1981

Isolation of a cloned cell line expressing variant H-2Kk using fluorescence-activated cell sorting.

We describe here a method for the isolation of somatic cell variants that express a structurally altered gene product on their cell surface. The method makes it possible to select positively for cells of the variant phenotype which is defined by loss of a given antigenic determinant. As an example, we present the isolation of a cloned cell line expressing a structurally altered H-2Kk molecule, designated H-2KkS1. Cells of this phenotype were found to be present in the wild-type population at a frequency of 10(-5)-10(-6) and were isolated in three rounds of selection in the fluorescence-activated cell sorter (FACS) and subsequent growth in vitro.

Animals↗
PubMed1981

Locus of control and adjustment to chronic hemodialysis.

The Rotter Inventory was used to assess external vs. internal locus of control in chronic hemodialysis patients. This measure of personality was correlated to psychological and physiologic measures of adaptation to hemodialysis. Patients with high external locus of control had poorer overall compliance with higher interdialytic weight gain, but did not show more psychological distress. Nurses Observation Scale for Inpatient Evaluation correlated negatively with mean K, mean P, Beck Depression rating, and duration of dialysis.

Adult↗
PubMed1980

Psychopathology and shamanism in rural Mexico: a case study of spirit possession.

The so-called mystical possession of Juan Jose Fong, a socially marginal Chinese-Mexican of hysterical personality is directly related to the subject's psychological conflicts and emotional complexes and familial and social standing within the immediate cultural context. The subject is seen as suffering from conflicting emotions and cognitions centering around guilt, inferiority and non-acceptance by his peer group. The personification of his personal problems in the motif of spirit possessions enables the subject to maintain a measure of self-esteem, social status and personality integration.

Catholicism↗
PubMed1980

Antigen-specific receptor molecules isolated from murine T lymphocytes.

Hapten-specific receptor material can be isolated from sensitized murine T and B lymphocytes by the use of hapten-coupled nylon discs. The structural element shared between T and B cell receptors is the variable region of immunoglobulin heavy chains (VH), while known constant immunoglobulin domains appear not to be part of the T cell receptor molecule. The rules governing VH expression (i.e. NPb-idiotype expression) in the B and the T cell compartments are, however, different. Allotype-linked VH (idiotype) expression on T cell molecules was used in genetic reconstitution experiments to prove that the material under study is an endogenous T cell product. With the data available it seems reasonable to view the T cell molecules as representing surface receptors for antigen although this point needs further investigation.

Animals↗
PubMed1979

Effects of digoxin on sinus nodal function before and after vagal blockade in patients with sinus nodal dysfunction: a clue to the mechanisms of the action of digitalis on the sinus node.

To increase the limited knowledge of the effects of digitalis on sinus nodal function in patients with sinus nodal dysfunction and to initiate an investigation into the mechanisms underlying its effects, 34 patients with sinus nodal dysfunction were studied. Twenty patients underwent determination of sinus cycle length, estimated sinoatrial conduction time and maximal corrected sinus recovery time before and after the administration of 0.75 mg of intravenous digoxin. For the group, sinus cycle length did not change, sinoatrial conduction time increased insignificantly and maximal corrected sinus recovery time shortened; however, individual variation occurred. The effects of acute digitalization appeared to predict the effects of chronic digitalis administration on sinus nodal function in the eight patients who subsequently continued to take digoxin. Fourteen patients received digoxin after vagal blockade with atropine. After vagal blockade, digoxin lengthened sinus cycle length, sinoatrial conduction time and maximal corrected sinus recovery time. The effects of digoxin administered after atropine could be antiadrenergic, direct, or both, and are opposite to those induced by atropine alone. Because these effects are similar to those of vagotonia yet are not apparent when the vagi are unblocked, digoxin may have direct excitatory, adrenergic or previously unrecognized vagolytic effects on sinus nodal function in man and their manifestation may be dependent on heart rate or autonomic tone.

Adult↗
PubMed1978

Isolated hapten-binding receptors of sensitized lymphocytes. III. Evidence for idiotypic restriction of T-cell receptors.

The primary antibody response of C57BL/6 mice to the 4-hydroxy-3-nitrophenylacetyl (NP) hapten is restricted to antibody molecules expressing the NPb idiotype. This idiotype is a genetic marker for V genes in the heavy chain linkage group. In the secondary response, the frequency of NPb idiotype-positive molecules within the antibody population drops to very low values. Accordingly, isolated NP binding receptors from NP-sensitized B lymphocytes are largely devoid of this idiotype. In contrast, the NPb idiotype is expressed on the majority of the receptor fractions which we consider T-cell derived. This finding suggests that the antigen receptors of T lymphocytes may be restricted to the expression of major (germ-line encoded?) heavy chain idiotypes.

Animals↗
PubMed1978

Electrograms from the canine sinoatrial pacemaker recorded in vitro and in situ.

We have identified extracell potential changes associated with the electrical activity of the canine sinoatrial pacemaker. Small nonpolarizable electrodes and low frequency high gain amplification were used to record unipolar electrograms from both the epicardial and the endocardial surfaces of the canine sinus node. Initially in vitro studies were performed so that transmembrane action potential changes could be recorded simultaneously with the extracell potentials. The sinus nodal electrogram showed two characteristic potentials when the electrode was in immediate proximity to pacemaking cells: (1) During phase 4 there was a steady slope of about -30 to -100 muv/sec, and (2) during the transition from phase 4 to phase 0 of the transmembrane action potential the slope of the electrogram increased smoothly to approximately -400 to -1,000 muv/sec. These potentials were followed by high frequency deflections as cells in the surrounding atrium depolarized. Tetrodotoxin (5 mg/liter) rendered the atrial muscle inexcitable and delayed and then abolished the high frequency activity in the sinus electrogram, which then appeared as a continuous smooth tracing similar to the sinus pacemaker action potential but reversed in polarity. We then recorded these small localized potentials from the in situ canine heart. Sinus nodal electrograms could be obtained from beating hearts with hand held probes on the epicardial surface and with conventional recording catheters on the endocardial surface. The results demonstrate that the canine sinus node gives rise to detectable and characteristic changes in extracell potential and suggest that similar potentials can be recorded from man to evaluate sinus nodal function.

Action Potentials↗
PubMed1977

Isolated hapten-binding receptors of sensitized lymphocytes. II. Receptors from nylon wool-enriched rabbit T lymphocytes lack serological determinants of immunoglobulin constant domains but carry the A locus allotypic markers.

Hapten-binding receptor material was isolated from sensitized rabbit lymphocytes by a method described previously for murine receptor material. The material was separated into a fraction expressing immunoglobulin determinants (anti-Ig+ fraction) and a fraction lacking known class and type-specific determinants of Ig constant domains (anti-Ig- fraction). We present evidence in support of the notion that--in analogy to the mouse system--the anti-Ig+ fraction is B-cell-derived, whereas the anti-Ig- fraction originates from T lymphocytes. Receptors of the anti-Ig- phenotype are found to express a locus allotypic determinants and, thus, appear to carry variable portions of immunoglobulin heavy chains.

Animals↗