PubMed Health⌕ Search

Biomedical subjects

D Davis

Publications and source records attributed to D Davis.

At least 145 records · Page 8Linked to original sources
PubMed1994

Neuromotor precursors of schizophrenia.

Previous research suggests that in addition to being a characteristic of schizophrenia, neuromotor dysfunction also predates the onset of the syndrome. The research reported here was intended to examine further the neuromotor development of children with preschizophrenia traits. This study is part of a larger "archival-observational" project that uses childhood home movies to explore the developmental precursors of schizophrenia. Group comparisons revealed a higher rate of neuromotor abnormalities in the preschizophrenia children when compared to their healthy siblings, preaffective disorder subjects, the healthy siblings of patients with affective disorder, and subjects from families with no mental illness. The preschizophrenia subjects also showed poorer motor skills when compared to their healthy siblings and preaffective disorder subjects. When diagnostic group comparisons were made within age spans, the group differences were significant only in the first 2 years of life. Post hoc analyses also revealed that the preschizophrenia subjects' neuromotor abnormalities occurred primarily on the left side of the body. The abnormalities included choreoathetoid movements and posturing of the upper limbs, similar to the motor signs described in earlier reports on diagnosed schizophrenia patients. The findings are discussed in light of their implications for the developmental origins of schizophrenia. Limitations of the study, including problems with sample representativeness and the reliance on observational data, are also discussed.

Adolescent↗
PubMed1994

Age and skill differences in adaptive competence.

Previous research has documented qualitative changes in certain cognitive abilities during the older adult years, such as in short-term memory, perceptual and motor skills, and attentional capacities. Other work has suggested that a number of significant age-related changes, across a variety of cognitive abilities, are based on social experiences, such as occupational or recreational activities. The current study is based on earlier research by Perlmutter and her colleagues (1990) and examines age and skill-related differences among adults engaged in a social-recreational activity. BINGO players, ranging in age from nineteen to seventy-four, and having from less than two months to over twenty years of playing experience, were given a variety of psychometric, cognitive, and experimental measures. The participants were also observed as they played real BINGO games. No age-related differences were found on the psychometric or memory measures, suggesting that BINGO playing experience may have positive benefits for many older adults. Skilled players at all age levels were found to be more efficient in their game-playing actions. The oldest and most experienced players did not differ from the younger, equally experienced, players on the cognitive and skill-based tasks. These findings demonstrate the need to investigate adaptive competence in those situations in which social-environmental factors play a role in enhancing older adults' cognitive skills.

Adaptation, Psychological↗
PubMed1994

Comparison of related perceptual tests.

117 female and 76 male undergraduates were administered the ETS Hidden Figures, ETS Gestalt Completion, Harshman Figures, and the SEK Test. Results were interpreted as indicating that the two types of perceptual tests (flexibility and speed) were not factorially independent as the SEK Test correlations did not load upon the same factor as that for the ETS Hidden Figures Test. Men scored higher on the Hidden Figures and Harshman Figures but on the Gestalt completion task left-handed men and right-handed women scored higher.

Adult↗
PubMed1993

Kinetics and free energy gaps of electron-transfer reactions in Rhodobacter sphaeroides reaction centers.

The rates of the light-driven, electron-transfer reactions in the photosynthetic reaction center (RC) of Rhodobacter sphaeroides are examined in mutant strains in which tyrosine (M)210 is replaced by phenylalanine, isoleucine, or tryptophan. The spectra of the absorbance changes between 700 and 975 nm, following excitation by 0.6-ps pulses at 605 nm, are analyzed globally by singular value decomposition. The spectra measured at room temperature are interpreted in terms of a model in which the excited bacteriochlorophyll dimer (P*) transfers an electron to a bacteriopheophytin (HL) with time constants of 3.5 +/- 0.3, 10.5 +/- 1.0, 16 +/- 2, and 41 +/- 4 ps in wild-type RCs and the Phe, Ile, and Trp mutants, respectively, and an electron then moves from HL- to a quinone (QA) with a time constant of 0.16 ns in wild-type RCs, 0.24 ns in the Phe mutant, and 0.20 ns in the Ile and Trp mutants. The first step speeds up with decreasing temperature in wild-type RCs, remains virtually unchanged in the Phe mutant, and slows down in the Ile and Trp mutants. At 80 K, the signals in the 850-975-nm region include an apparent shift of the stimulated emission or absorption spectrum of P*, with a time constant of 5 ps in the Ile mutant and 13 pcs in the Trp mutant. Most of the electron transfer to HL occurs with time constants of 55 and 155 ps in the Ile and Trp mutants, respectively, and probably occurs from the relaxed form of P*. Electron transfer from the initial state cannot be ruled out, however. Relaxations of P* are not resolved in wild-type RCs or the Phe mutant. The midpoint potential (Em) of the P/P+ redox couple is measured by an electrochemical technique; the Em values are 500 +/- 5, 530 +/- 6, 533 +/- 3, and 552 +/- 10 mV for the wild-type and the Phe, Ile, and Trp mutant RCs, respectively. These values are corroborated by chemical titrations. The free energy change (delta G degrees) associated with formation of the P+HL-radical pair from P* also is determined by measuring the amplitude of fluorescence on the nanosecond time scale after blocking electron transfer from HL- to QA. The free energy of P+HL- is elevated by an amount comparable to that calculated from the increase in the Em of P in the Ile mutant and by about 16 meV more than this in the Phe and Trp mutants.(ABSTRACT TRUNCATED AT 400 WORDS)

Electron Transport↗
PubMed1993

Disruption of potential sites for N-linked glycosylation does not impair hormone binding to the lutropin/choriogonadotropin receptor if Asn-173 is left intact.

The rat lutropin/choriogonadotropin receptor (rLHR) is a G protein-coupled receptor, the large extracellular domain of which binds human choriogonadotropin (hCG) with high affinity. Within the extracellular domain are six potential sites for N-linked glycosylation. Although several studies have attempted to determine if N-linked carbohydrates are necessary for hormone binding, the results have been in apparent disagreement. In this study we have used site-directed mutagenesis to singly and collectively alter the consensus sequences for N-linked glycosylation in the rLHR. In particular, we examined the binding activity in both intact cells as well as detergent-solubilized extracts so that the effects on trafficking to the plasma membrane could be determined. In addition, we independently examined the effects of substituting a particular Asn versus Thr or Ser residue within a given glycosylation consensus sequence. Our data suggest that substitution of Asn-173 with Gln results in both a decreased ability of the receptor to be expressed on the plasma membrane as well as a vastly decreased binding affinity of the receptor for hCG. However, if the consensus sequence for N-linked glycosylation at Asn-173 is altered by substitution of Thr-175 with Ala (instead of Asn-173 to Gln), the resulting receptor binds hCG with high affinity although it is still impaired in its ability to be expressed at the plasma membrane. Furthermore, if all consensus sequences for N-linked glycosylation are mutated collectively while maintaining Asn-173 (by substituting Thr-175 with Ala instead of Asn-173 to Gln), the resulting deglycosylated receptor, although not expressed on the plasma membrane, binds hCG with high affinity.(ABSTRACT TRUNCATED AT 250 WORDS)

Asparagine↗
PubMed1993

Significant improvement of stiff-person syndrome after paraspinal injection of botulinum toxin A.

Following several months of low back pain, a 36-year-old man developed progressive stiffness of the abdominal, low back, and thigh muscles. On examination, these muscles demonstrated marked hypertonia consistent with the clinical diagnosis of stiff-person syndrome. The patient demonstrated increased lumbar lordosis and had focal hyperhidrosis at different sites. Electromyography showed continuous activity of the paraspinal and thigh muscles, and serum and cerebrospinal fluid antibodies to glutamic acid decarboxylase (GAD) were markedly elevated. Diazepam and Lioresal offered partial pain relief. Paraspinal muscle administration of botulinum toxin A reduced the tone of paraspinal and thigh muscles significantly and resulted in marked improvement of ambulation and cessation of pain.

Adult↗
PubMed1993

Factors that influence radioimmunoassay of human plasma melatonin: a modified column procedure to eliminate interference.

We describe here the effect of various agents and conditions that can influence the assay of plasma melatonin and report a modified column method which minimizes these interferences. Melatonin was measured by a sensitive radioimmunoassay which can detect melatonin from 5 to 500 pg/ml; the assay was linear about 0-60 pg/ml range. The hemolysis of samples increases the apparent level of melatonin in plasma. When the hemolyzed samples were passed through the SEP-cartridge and washed with methanol, the normal basal level was restored. Elution from the column was highest at 100% methanol and proportionate with the "spiked" value of melatonin. The addition of hemoglobin standard and serum albumin decreases the assayed value of melatonin while the addition of red blood cells and heparin increases the level. EDTA, oxalate, and citrate do not influence the basal level of melatonin. Samples that have been affected by these various agents and conditions can be normalized by passing samples through the column. Up to three cycles of freezing and quick thawing of plasma had no effect on the assay of melatonin; however, beyond three cycles levels were reduced. Long-term storage (up to 4 years) has no influence on the assay.

Animals↗
PubMed1993

Heart transplantation for tumor.

Unresectable cardiac tumors, although unusual, are often rapidly fatal. A 31-year-old woman presented with a large tumor arising from the left ventricle and causing symptoms of a constrictive cardiomyopathy. After evaluation with echocardiography, angiography, and computed tomography, an exploration was carried out to confirm the extent of disease. Orthotopic heart transplantation was subsequently performed when a donor organ became available. She is now alive and disease-free 12 months after transplantation.

Adult↗
PubMed1993

Preclinical evaluation of microencapsulated CFA/II oral vaccine against enterotoxigenic E. coli.

Colonization Factor Antigen (CFA/II) from enterotoxigenic Escherichia coli (ETEC) prepared under good manufacturing practices (GMP) was successfully incorporated into biodegradable poly(D,L-lactide-co-glycolide) (PLGA) polymer microspheres (BPM) under GMP and found to be safe and immunogenic when administered intraduodenally to rabbits. Following vaccination, Peyer's patch cells responded by lymphocyte proliferation to in vitro challenge with CFA/II. Also, B cells secreting specific anti-CFA/II antibodies were found in spleens following vaccination. No pathological changes were found following total necropsies of ten rabbits vaccinated with CFA/II BPM. Sixty-three per cent of the CFA/II BPM were between 5 and 10 microns diameter by volume particle size distribution; 1.17% protein content; 2.15% moisture; < 0.01% acetonitrile; 1.6% heptane; 22 non-pathogenic bacteria and three fungi per 1 mg protein dose; and passed the general safety test. We conclude that the CFA/II BPM oral vaccine is immunogenic and safe to begin a Phase I clinical safety study following Investigational New Drug approval.

Administration, Oral↗
PubMed1993

"Academic" CME and the social contract.

The term academic continuing medical education (CME) is defined and explored from the perspective of forces that have made its usage necessary. These forces include the new understandings of the place, impact, and scope of CME, and, in particular, the increasing entrepreneurial interests in the field, unrelated to the improvement of physicians' competence or performance, or to health care outcomes. In addition to principles of CME provision promulgated by the Accreditation Council of CME, and those of ethical CME providers, academic CME implies the critical appraisal of the providers' activities, the creation of new knowledge about how physicians learn and change, and the dissemination of information based on such knowledge. Finally, the nature of academic CME providers is discussed, and the potential role of CME in fostering the social contract between the medical professional and society is explored.

Clinical Competence↗
PubMed1993

Antisera raised against the second variable region of the external envelope glycoprotein of human immunodeficiency virus type 1 cross-neutralize and show an increased neutralization index when they act together with antisera to the V3 neutralization epitope.

Antibodies have been raised against a synthetic peptide (IRDKIQKENALFRNL) containing a neutralizing epitope within the second variable region of the human immunodeficiency virus type 1 (HIV-1) SF2 strain external envelope glycoprotein (gp120) and also against equivalent peptides of the HIV-1 LAI, RF and MN isolates. The resulting antisera cross-react with heterologous peptides but binding to heterologous recombinant gp120 is more restricted. Antisera to HIV-1 SF2, RF and MN are able to neutralize homologous virus. Some cross-neutralization is also observed, but a consensus peptide failed to induce neutralizing antibodies to any of the isolates studied. Antibodies to the V2 and V3 epitopes give a higher neutralization index when acting together than when the individual sera are used alone. Antibodies induced in natural infection bind to two sets of hexamers within the region encompassed by the 15-mer peptide, and the response to these can differ between infected individuals and within the same host over time.

Amino Acid Sequence↗
PubMed1993

Effects of exercise intensity and duration on norepinephrine spillover and clearance in humans.

During dynamic exercise, blood flow to exercising muscle is closely matched to metabolic demands. This is made possible by metabolic vasodilation, vasoconstriction in inactive vascular beds, and a rise in cardiac output. The sympathetic nervous system plays an important role in regulating this exercise response. In this study, we used steady-state infusions of tritiated norepinephrine ([3H]NE) to determine the magnitude and time course of the arterial NE spillover response to sustained upright bicycle exercise at low (n = 11) and moderate-to-high (n = 14) exercise intensity (25 and 65% of maximum work load, respectively) in normal young subjects. In addition, we sought to examine whether exercise was associated with a change in NE clearance. During 30 min of low-level exercise, arterial NE spillover increased from 1.45 +/- 0.13 to 3.14 +/- 0.30 nmol.min-1 x m-2 (P < 0.01) and appeared to plateau at 20-30 min of exercise; NE clearance remained unchanged. During 20 min of moderate-to-high-intensity exercise, we found a substantial and progressive rise of arterial NE spillover from 2.15 +/- 0.27 to 13.52 +/- 1.62 nmol.min-1 x m-2 (P < 0.01). NE clearance decreased from 0.91 +/- 0.05 to 0.80 +/- 0.05 l.min-1 x m-2 (P < 0.05). These data suggest that, during dynamic exercise, sympathetic nervous system activity is related to exercise intensity, and there appears to be an interaction between the effects of exercise intensity and duration on NE spillover. In addition, at moderate-to-high exercise intensity, a small decrease of NE clearance contributes to the rise in plasma NE.

Adult↗
PubMed1993

The advanced clinical information system: physician-focused.

The U.S. health care system is being forced to change because of intense demands for better quality, decreased cost, and better service. These demands are driving the implementation of health-oriented computer technologies that will fundamentally change the practice of medicine. These technologies will enable physicians to find new opportunities to improve quality and reduce cost.

Attitude to Computers↗
PubMed1993

Toward successful compliance with JCAHO standard NC.1.

Recommendations resulting from a JCAHO survey can be a true blessing as they force nursing departments to assess critically their professional practice and documentation systems. Systematic preparation, begun at least two years prior to the survey, includes Nursing Administration, a Nursing Documentation Task Force and all staff nurses. Educational consultants assigned to each unit bring nurses up-to-date on nursing process and nursing diagnosis. Mock surveys and cross-training in chart review prepare staff nurses for confident participation in the accreditation process.

Accreditation↗
PubMed1992

Isolation and quantification of soluble Alzheimer's beta-peptide from biological fluids.

Cerebral deposition of the beta-amyloid peptide (A beta) is an invariant feature of Alzheimer's disease. Since the original isolation and characterization of A beta (ref. 1) and the subsequent cloning of its precursor protein, no direct evidence for the actual production of discrete A beta has been reported. Here we investigate whether A beta is present in human biological fluids using antibodies specific for an epitope within A beta that spans the site of normal constitutive cleavage. These antibodies were used to construct a sandwich-type enzyme-linked immunosorbent assay that detects A beta in cerebrospinal fluid, plasma and conditioned medium of human mixed-brain cells grown in vitro (see also ref. 14). By affinity chromatography, we have purified and sequenced A beta and a novel A beta fragment from human cerebrospinal fluid and conditioned medium of human mixed-brain cell cultures. These findings demonstrate that A beta is produced and released both in vivo and in vitro. These observations offer new opportunities for developing diagnostic tests for Alzheimer's disease and therapeutic strategies aimed at reducing the cerebral deposition of A beta.

Alzheimer Disease↗
PubMed1992

Analysis of the p21 ras system during development of meiotic competence in Xenopus laevis oocytes.

The ability of Xenopus oocytes to undergo insulin- or insulin-like growth factor 1-induced meiotic maturation develops during oogenesis, with cells 1.0 mm in diameter or larger responding in a size-dependent manner. Since insulin-induced oocyte maturation was shown previously to be p21 ras-dependent, experiments were performed to test whether a deficiency in the p21 ras system might account for meiotic incompetence in small oocytes (less than or equal to 0.9 mm diameter). Both small and large oocytes were found to contain comparable levels of membrane-associated p21, as determined by protein immunoblotting. Treatment of both small and large oocytes with 2 microM insulin for 2 hr increased endogenous levels of membrane-associated p21 by approximately 70%. Stimulation of microinjected p21-membrane association by insulin was observed to be both time- and concentration-dependent in large oocytes with an EC50 of 50 nM. In addition, comparable levels of GTPase activating protein were measured in extracts prepared from oocytes ranging from 0.8 to 1.3 mm in diameter. Therefore, the p21 system is apparently not limiting during oogenesis, and expression of some other cellular component must account for development of meiotic competence in Xenopus oocytes.

Animals↗