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D D Davis

Publications and source records attributed to D D Davis.

33 records · Page 2Linked to original sources
PubMed1987

T cell receptor beta gene sequences in the circular DNA of thymocyte nuclei: direct evidence for intramolecular DNA deletion in V-D-J joining.

We have identified circular DNA containing T cell receptor (TCR) beta gene sequences in mouse thymocytes, thereby providing direct evidence for the intramolecular DNA deletion model of V-D-J joining in TCR beta genes. Two types of excision products of V-D-J joining have been identified. Type I, a circular reciprocal recombinant of normal V-D or D-J joining, contains a 7mer-7mer head-to-head structure expected from an excised product of normal V-D or D-J joining. Type II contains a D beta 2-J beta 1 structure on the circular DNA; the recombination event producing this molecule occurs between an upstream J and a downstream D segment, probably leaving the reciprocal 7mer-7mer structure on the chromosome. Some type I molecules seem to represent excision products of secondary joining after formation of the first D-J or V-D-J structure. The recombination mechanism that generates the circular DNA is discussed.

Amino Acid Sequence↗
PubMed1986

Non-germ-line elements (NGE) are present in the T cell receptor beta-chain genes isolated from the mutant mouse, motheaten (me/me).

Extra nucleotides (which we call NGE, for non-germ-line elements) are inserted at the junctions of rearranged V, D, and J segments in the immunoglobulin heavy and T cell receptor beta-chain V region genes. NGE addition helps diversity HV3 regions of these genes. It is believed that NGE are added enzymatically and without template during the joining process. Terminal deoxynucleotidyl transferase (TdT) is thought to be the cause of NGE formation. TdT is normally detected in murine thymus and bone marrow cells, but its presence in the immunodeficient mutant mouse, Motheaten (me/me), is extremely reduced in these tissues. To determine whether this TdT deficiency could affect NGE formation during the V-D-J joining of antigen receptor genes, we cloned several rearranged T cell receptor beta-chain genes from thymocytes of me/me mice. Our sequence analysis revealed that Motheaten thymus beta-chain genes have approximately 4 base pair NGE, which are comparable in size to the NGE of wild-type genes. These results do not support the idea that TdT is the NGE-forming enzyme, although it is still possible that a low but residual level of TdT is capable of NGE formation in Motheaten. Alternatively, our data may suggest that the TdT activity in Motheaten T cells is normal; however, the number of TdT+ cells is greatly reduced in the Motheaten thymus, due to a severe defect in T cell development.

Animals↗
PubMed1986

The uniqueness of human learning.

It is proposed that humans are capable of a unique type of learning. All other animals are limited to contiguous learning (not more than 60 seconds separating the two events). Only humans are capable of "separated" or scientific learning (learning a connection between two or more events separated by more than 60 seconds). Science itself is a generalized type of non-contiguous learning. It is also proposed that humans' capacity for separated learning is dependent upon the unique ability to hypothesize (to propose a connection or relationship between two or more events separated by time). As a result of separated learning, humans are the only animals capable of "separated foresight" (anticipating which events are likely to occur more than one minute into the future).

Animals↗
PubMed1986

Two types of immunoglobulin-negative Abelson murine leukemia virus-transformed cells: implications for B-lymphocyte differentiation.

Both alleles of immunoglobulin (Ig) heavy-chain joining region (JH) genes in three Ig-negative Abelson murine leukemia virus (Ab-MuLV)-transformed cell lines were characterized by DNA cloning and nucleotide sequence determination. These studies unambiguously identified two distinct types of Ig-negative B-lineage cells. The first type of cell (e.g., R8) is an "immature pre-B cell," and it contains at least one intermediate recombinant structure containing heavy-chain diversity (DH) and JH sequences but no variable region (VH) sequence. This type of cell, which has also been characterized by other investigators, generates mu-positive sublines during subsequent culturing of cells and represents a precursor stage to pre-B cells. The second type of cell (e.g., RAW253) is an "abortive pre-B cell," in that both JH alleles contain nonfunctional VH-DH-JH structures. The nucleotide sequence determinations in this study demonstrated that these nonfunctional V-D-J structures were generated by nonproductive somatic recombinations, involving either out-of-phase joining events, or the formation of termination codons in the DH coding sequences. The identification of abortive pre-B cells suggests that the recombinational joining of Ig VH, DH, and JH segments is not actively regulated by a putative recombinase to preserve the translational reading frame. This in turn implies that a large portion of precursor cells at the early stage of B-cell differentiation are abortive and possibly blocked to further differentiation.

Abelson murine leukemia virus↗
PubMed1985

Biological stress responses in high and low trait anxious students.

In an investigation of biological indicators of stress in normal humans, undergraduate psychology students were differentiated on trait anxiety and assessed under baseline, preexam (stress), and postexam conditions. Assessment at each condition involved drawing 20 ml of blood, followed by self-reporting for selected questionnaires. Self-reports included state anxiety, general psychological symptomatology, dysfunctional attitudes, academic confidence, sleep patterns, and intake of drugs, including alcohol and caffeine. Blood was analyzed for whole blood serotonin content, plasma MHPG, and platelet imipramine binding. Baseline differences between high and low trait anxious students on biological measures were significant only for whole blood serotonin content. Variation across situational conditions was significant for whole blood serotonin, with an increase under the stressful condition for both anxiety groups. Thus, serotonin is highlighted as an important factor in the human response to stress, whereas expected differences in MHPG were not observed. The serotonergic response to stress was not explained by changes in psychological or physical state variables. Changes in serotonin content were positively correlated with changes in platelet imipramine binding.

Adolescent↗
PubMed1982

Participation in community intervention design.

The role of values in the design of community interventions is discussed. It is argued that participation in the design of community interventions by community members and professional staff associated with the problem of interest is congruent with the values of community psychology. The application and empirical support for the use of five methods for eliciting participation are evaluated. A model of intervention design consisting of seven stages is provided to demonstrate the relative efficacy of participation.

Community Mental Health Services↗
PubMed1982

Hemodynamic effects of the antiarrhythmic drug pirmenol.

We examined the hemodynamic effects of pirmenol, a new antiarrhythmic drug, for the first time in man. Right and left heart pressures, Fick cardiac output, and radionuclide ejection fraction were measured before and during infusion of pirmenol in 10 patients with coronary artery disease who were undergoing routine diagnostic cardiac catheterization. Pirmenol was given as a 50-mg IV injection over 2 min followed by a constant infusion of 2.5 mg/min for up to 36 min. Plasma pirmenol levels were within or near the previously determined therapeutic range in all patients. There were no significant changes in systolic blood pressure or cardiac output. Diastolic blood pressure rose from a mean (+/- SD) 78 +/- 7 during the control period to 82 +/- 6 during the infusion, heart rate rose from 66 +/- 6 during the control period to 75 +/- 7 during infusion and ejection fraction fell from 60 +/- 8 during control to 55 +/- 12 during infusion. Although the left ventricular end-diastolic pressure rose from 6 +/- 2 during control to 8 +/- 3 during the infusion, the left ventricular stroke work index fell and the left ventricular work index per minute did not change. The fall in ejection fraction did not correlate with the control ejection fraction, plasma pirmenol levels, or the change in heart rate. The decline in ejection fraction and the failure of the left ventricular work index per minute to rise despite a small rise in left ventricular end-diastolic pressure may indicate a potential myocardial depressant effect of pirmenol.

Anti-Arrhythmia Agents↗
PubMed1981

Home-medication monitoring among older adults: the breach in services.

Available studies reveal alarming rates of substance and medication abuse among older adults. Professionals addressing the substance and medication abuse problems of seniors have argued for a move to medication monitoring in the home. At present, however, there has been only scattered evidence to support the contention that adequate medication monitoring actually occurs. The present study reports two surveys of all home care agencies in the state of Michigan. The first study reports the medication monitoring practices of home care staff. The second study examines possible medication monitoring interventions that might be implemented in home care agencies. Those medication monitoring interventions with the highest likelihood of successful implementation among home care staff are discussed.

Aged↗
PubMed1980

Infrared laser photolysis: a new tool for the study of prebiotic chemistry.

Infrared laser induced dielectric breakdown and multiphoton absorption experiments on CH4/NH3 'atmospheres' are described. It is found that HCN, a central intermediate in prebiotic chemistry, is a principle product. This, combined with the fact that dielectric breakdown appears to have much in common with ordinary electric sparks, suggests that the laser could be a useful tool in studies of prebiotic chemistry. Several possible experiments in this vein are suggested.

Ammonia↗
PubMed1978

An assessment of emergency medical technicians' performance as related to seasonal population influx.

The periodic influx of large numbers of people into resort areas substantially increases the use of emergency medical services. This investigation assesses the effects of such a threefold increase in the summer population of the Cape Cod area upon the accuracy of emergency medical technicians' diagnoses and treatments. The technicians' diagnoses for ambulance patients were evaluated against those given by the emergency room physicians during the months of August 1975 and February 1976. The distribution of conditions was similar for both months and the observed frequency of correct diagnoses for common conditions was more than 90% in both months. The overdiagnosis rate of 25% to 50% for common conditions and the correct treatment rate for suspected myocardial infarction of 65% did not vary significantly between summer and winter. Thus, a large influx in population does not seem to affect adversely EMT diagnosis rates. Although misdiagnoses were uncommon, a failure to follow through with a correct treatment for patients with suspected myocardial infarctions, thus indicating the need for better quality control on EMT performance.

Allied Health Personnel↗
PubMed1975

Isolation and identification of 5,7-dimethoxyisoflavone, an inhibitor of Aspergillus flavus from peanuts.

An inhibitor of Aspergillus flavus has been isolated form peanuts and identified as 5,7-dimethoxyisoflavone, Authentic 5,7-dimethoxyisoflavone, synthesized from benzyl-2-hydroxy-4,6 dimethoxyphenyl (3), and the isolated compound display identical ultraviolet spectra in methanol, in methanol+sodium methoxide, and in methanol+AlCl3; similar behavior in solvent extraction, column chromatography, TLC, and fungal inhibition.

Antifungal Agents↗
PubMedDate not supplied

Meeting the challenge of change.

Health-care organizations and the physicians who work in them today face unprecedented change. This change can be managed successfully through proper use of four organizational practices: strategy, organization design, organization culture, and human resource practices. A fifth practice, pursuit of continuous improvement and personal mastery, allows the physician to adapt personally to change. This article describes how physicians may use these practices to meet the challenge of change.

Health Care Reform↗
PubMedDate not supplied

Assessing interaction patterns of students.

Teaching nursing students how to interact therapeutically with patients is a concern of all nursing faculty members. The verbatim process recording is one available method of analyzing student interactions. An analysis of 86 reported interactions of student nurses with postpartal maternity patients identified patterns of interaction that were related to patient concerns and showed deficits in student communication skills.

Clinical Competence↗
PubMedDate not supplied

Memory performance of young, middle, and old adults.

Young, middle-aged, and older adults were assessed on tasks operationally defining short-term memory structural limitations and process abilities. The tasks were typical of previously related memory research with children and adolescents: monaural and dichotic word lists of variant association structure and rate of presentation. Although a number of minor chronological age-related differences were noted between monaural and dichotic word list performances, the findings indicated both structural capacity and organizational strategy deficiencies over successive adult age groups. In addition, older adults indicated significantly more heterogeneity of performance variance, both between and within age group comparisons. Results were summarized within the Cattell-Horn developmental model of fluid and crystallized abilities.

Adult↗