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Biomedical subjects

E Baker

Publications and source records attributed to E Baker.

At least 91 records · Page 5Linked to original sources
PubMed1997

Cerebral microembolism and early recurrent cerebral or retinal ischemic events.

BACKGROUND AND PURPOSE: We investigated whether cerebral microembolism as detected by transcranial Doppler ultrasonography (TCD) identifies patients at an increased risk for early, recurrent cerebral or retinal ischemic events. METHODS: Records of consecutive patients examined during a 40-month period in the Neurovascular Laboratory were reviewed for the presence of cerebral microembolism. Of the original 302 patients, 229 with 310 arteries met inclusionary criteria. Follow-up information was obtained from the laboratory's database as well as the hospital records. Microembolus detection studies were performed on TC-2000 or TC-2020 instruments equipped with special software, and criteria established a priori were used for microembolus selection. TCD testing was performed a median interval of 9 days after the initial symptoms of cerebral ischemia. Severity of arterial stenosis was determined by cerebral angiography or noninvasive methods. RESULTS: Microembolic signals were detected more frequently in symptomatic (40/140; 28.6%) than asymptomatic (21/170; 12.4%) arteries (P < .001). Ten recurrent ischemic events occurred during a median follow-up of 8 days after TCD examination, all in the territories of symptomatic arteries. Nine events occurred in the territories of microembolic signal positive arteries (9/61; 14.8%) and one in the territory of a microembolic signal-negative artery (1/249; 0.4%) (P < .00). No association was detected in the subgroup with known cardiac lesions. Microembolic signals were more frequent in arteries with lesions causing 70% or more stenosis or occlusion (26/99; 26.3%) than in those with a degree of stenosis less than 70% (17/126; 13.5%) (P = .016). CONCLUSIONS: In this retrospective study, microembolic signals were more common in the territories of symptomatic arteries and particularly those with severely stenotic lesions. During a short follow-up, recurrent ischemic events were more common along the territories of arteries with TCD-detected microembolism and previous symptoms of cerebral or retinal ischemia.

Brain↗
PubMed1997

Risk and protective factors as predictors of adolescent alcohol involvement and transitions in alcohol use: a prospective analysis.

OBJECTIVE: Determinants of initial alcohol use may differ from predictors of accelerated or problematic consumption. Social influences may be strong predictors of initial drinking; however, later stages of problem drinking may be linked developmentally to intrapersonal deficits. This study prospectively examined the influence of chronic and changing risk and protective status in predicting adolescent alcohol involvement and transitions in alcohol use. METHOD: Data were obtained from a three-wave cohort (N = 823) of 8th-10th grade nonintervention students participating in a school-based drug abuse prevention trial. Cognitive, attitudinal and social influence measures were dichotomized using empirical cut-offs to designate risk or protective status. Using a conceptually based assignment scheme, additive risk indices were created assessing chronic (averaging across time) and changing features of competence, psychological and interpersonal functioning, cognitive-affective and social influences. Three chronic and change protective indices were created tapping competence, psychological, and interpersonal functioning. RESULTS: Controlling for initial drinking and gender, chronic risk for social influence and psychological functioning and increased risk for social influences and competency predicted subsequent drinking behavior. Chronic psychological protection attenuated subsequent drinking. Using categorical measures of drinking behavior to designate nonuse, experimental or moderate-heavy use, chronic social influence and competency risk were associated with an increased likelihood of accelerated drinking, whereas improved psychological functioning diminished the likelihood of increased drinking behavior. CONCLUSIONS: Findings underscore the need for implementing prevention strategies that reinforce developmentally appropriate skills and enhance personal competence and psychological functioning as effective barriers against initial and more problematic alcohol use. The unique contribution of protective forces also underscores that risk reduction and protection enhancement are complementary processes and are both required to offset social influences for alcohol consumption.

Adolescent↗
PubMed1996

Functional evidence for a colorectal cancer tumor suppressor gene at chromosome 8p22-23 by monochromosome transfer.

Chromosome 8p is considered, from loss of heterozygosity analysis, to be a strong candidate for the location of a tumor suppressor gene inactivated in colorectal cancer. We have found a 53% (27 of 51) rate of allelic loss at the LPL locus on 8p22, with the smallest region of overlap of deletions including the region D8S258 to D8S277. Using microcell-mediated monochromosome 8 transfer into three colorectal cancer cell lines, SW480, SW620 and HT29, we have demonstrated a reduction of tumorigenicity in SW620 hybrids. Partial deletions of chromosome 8 in some SW620/8 hybrids further delineate the critical region(s) to 8p22-23. Hybrids of the colorectal cancer cell lines SW480 and HT29 containing chromosome 8 did not show suppression of tumorigenesis, but the H29/8 hybrid showed total suppression of soft agar clonicity. This indicates an alternate pathway of mutational progression in these three lines, despite the fact that SW480 was derived from the same patient as SW620.

Adenoma↗
PubMed1996

Molecular characterization of a nonneuronal human UNC18 homolog.

A cDNA clone encoding a human homolog of the Caenorhabditis elegans unc-18 gene was identified following random sequencing of clones from IL-2-activated human NK cells. This cDNA clone is related to the nonneuronal Munc-18b and so has been called Hunc-18b. The Hunc-18b transcripts were found in most human tissues, with the exception of brain and skeletal muscle, and in cells from all lymphoid lineages. The Hunc-18b gene was localized to human chromosome 19p13.2-p13.3, and the mouse homolog, Munc-18b, was mapped to the proximal region of mouse Chromosome 8.

Amino Acid Sequence↗
PubMed1996

bcl-w, a novel member of the bcl-2 family, promotes cell survival.

The prototypic mammalian regulator of cell death is bcl-2, the oncogene implicated in the development of human follicular lymphoma. Several homologues of bcl-2 are now known. Using a PCR-based strategy we cloned a novel member of this gene family, denoted bcl-w. The gene, which is highly conserved between mouse and human, resides near the T-cell antigen receptor alpha gene within the central portion of mouse chromosome 14 and on human chromosome 14 at band q11. Enforced expression of bcl-w rendered lymphoid and myeloid cells refractory to several (but not all) cytotoxic conditions. Thus, like Bcl-2 and Bcl-x, the Bcl-w protein promotes cell survival, in contrast to other close homologues, Bax and Bak, which facilitate cell death. Comparison of the expected amino acid sequence of Bcl-w with that of these relatives helps to delineate residues likely to convey survival or anti-survival function. While expression of bcl-w was uncommon in B or T lymphoid cell lines, the mRNA was observed in almost all murine myeloid cell lines analysed and in a wide range of tissues. These findings suggest that bcl-w participates in the control of apoptosis in multiple cell types. Its functional similarity to bcl-2 also makes it an attractive candidate proto-oncogene.

Amino Acid Sequence↗
PubMed1996

Characterization and chromosomal localization of the human A2a adenosine receptor gene: ADORA2A.

The gene for the stimulatory G protein-coupled human A2a adenosine receptor was isolated and sequence analysis revealed two exons that are interrupted by an intron of approximately 6.4 kb. An intron is located in the same region in the human A1 and A2b adenosine receptor genes. Comparison of the A2a genomic and cDNA sequences reveals two nucleotide differences in the coding region and the presence of an aberrant sequence in the 5'208 base pairs of the A2a cDNA including a polymorphism in the third base of codon Tyr-361 and Gly codon which was always detected at residue 392, indicated that the Arg codon present in the cDNA may be an artifact. Fluorescent in situ hybridization and PCR analysis of human-hamster hybrid cell panels shows that the A2a receptor gene is localized to chromosome 22q11.2. This is in contrast with previous reports (subsequently retracted) which mapped the A2a gene to chromosome 11q11-13.

Amino Acid Sequence↗
PubMed1996

Isolation and characterization of cDNA clones for Humly9: the human homologue of mouse Ly9.

Ly9 is a mouse cell membrane antigen found on all lymphocytes and coded for by a gene that maps to chromosome 1. We previously described the isolation and characterization of a full-length cDNA clone for mouse Ly9. Using cross-species hybridization we isolated cDNA clones encoding the human homologue Humly9. Analysis of the predicted protein sequence suggests that the extra-cellular portion of the Humly9 molecules is composed of four Ig-like domains: a V domain (V) without disulphide bonds and a truncated C2 domain (tC2) with two disulphide bonds, a second V domain without disulphide bonds and a second tC2 with two disulphide bonds, i.e., as V-tC2-V-tC2. The gene encoding Humly9 was mapped to chromosome 1 by analysis of human/hamster hybrids, and more specifically to the 1q22 region by in situ hybridization. The protein sequence data support the view that Humly9 belongs to the immunoglobulin-superfamily subgroup which includes CD48, CD2, and LFA-3.

Amino Acid Sequence↗
PubMed1996

Intermediate steps in cellular iron uptake from transferrin. II. A cytoplasmic pool of iron is released from cultured cells via temperature-dependent mechanical wounding.

A previous study described a cytoplasmic, transferrin (Tf)-free, iron (Fe) pool that was detected only when cells were mechanically detached from the culture substratum at 4 degrees C, after initial incubation with 59Fe-125I-Tf at 37 degrees C (Richardson and Baker, 1992a). The release of this internalized 59Fe could be markedly reduced if the cells were treated with proteases or incubated at 37 degrees C prior to detachment. The present study was designed to characterize this Fe pool and understand the mechanism of its release. The results show that cellular 59Fe release increased linearly as a function of preincubation time with 59Fe-Tf subsequent to mechanical detachment at 4 degrees C using a spatula. These data suggest that the 59Fe release was largely composed of end product(s) and was not an "intermediate Fe pool." When the Fe(II) chelator, dipyridyl (DP), was incubated with 59Fe-Tf and the cells, it prevented the accumulation of 59Fe that was released following mechanical detachment at 4 degrees C. Other chelators had much less effect on the proportion of 59Fe released. Examination of the 59Fe released showed that after a 4-h preincubation with 59Fe-Tf, approximately 50% of the 59Fe was present in ferritin. These data indicate that mechanical detachment of cells at 4 degrees C resulted in membrane disruptions that allow the release of high M(r), molecules. Moreover, electron microscopy studies showed that detachment of cells from the substratum at 4 degrees C resulted in pronounced membrane damage. In contrast, when cells were detached at 37 degrees C, or at 4 degrees C after treatment with pronase, membrane damage was minimal or not apparent. These results may imply that temperature-dependent processes prevent the release of intracellular contents on membrane wounding, or alternatively, prevent wounding at 37 degrees C. The evidence also indicates that caution is required when interpreting data from experiments where cells have been mechanically detached at 4 degrees C.

2,2'-Dipyridyl↗
PubMed1996

Role of control and support in occupational stress: an integrated model.

Drawing from the Demand-Control Model and the conceptual framework of the stress process developed by researchers at the University of Michigan's Institute for Social Research, this paper presents and tests an "integrated model" of occupational stress. The results indicate that control and social support are strongly correlated with negative job feelings. The effect of control on health was found to depend on the type of control and organizational level at which control is exercised. Specifically, the effect of participation on health outcomes was found to differ at the job and organizational levels, and participation without influence was associated with increased negative job feelings. The effect of social support was found to depend on the type of support and from whom the support was provided. Results also indicate that it is important to test for moderating, mediating, and direct effects of control on health, and underscore the complementary nature of qualitative and quantitative data in furthering knowledge and understanding.

Automobiles↗
PubMed1996

Cardiac function, metabolism and perfusion in Duchenne and Becker muscular dystrophy.

We studied 23 DMD and eight BMD patients using cardiac echo, 24 h ECG and positron emission tomography (PET) with the radiotracers N-13 ammonia and F-18 fluorine deoxyglucose. The ECG was abnormal in 23 cases with alterations in the PR and/or QT intervals, abnormal Q waves in the lateral leads and ST segment depression. Twenty-four hour ECG showed that patients were more likely to produce premature ventricular ectopic beats with advancing age and 17 patients had paroxysmal ST segment depression. LV function was normal or mildly reduced in 24 cardiac echoes. PET studies were visibly abnormal in 15 patients. Regional perfusion defects involving the apex, lateral or anterior left ventricular walls were present, nine cases demonstrated a corresponding increase in glucose metabolism. Three out of 15 demonstrated matched perfusion/metabolism defects. One BMD had severe LV dilation with globally poor perfusion and metabolism. The abnormalities seen with PET were confirmed with both quantitative and semi-quantitative analysis of radioactive counts. Similar results were obtained for both DMD and BMD, where both groups demonstrated significant regional perfusion/metabolism mismatches. We have shown a reduced uptake of N-13 ammonia which is indicative of a reduction in myocardial perfusion. The use of N-13 ammonia to measure perfusion has been validated in animal studies. PET with either N-13 ammonia- or oxygen labelled water can be used to measure myocardial perfusion. We chose N-13 ammonia as this was most readily available to us.

Adolescent↗
PubMed1996

Human plasma patterns during 14 days ingestion of vitamin E, beta-carotene, ascorbic acid, and their various combinations.

OBJECTIVE: We wanted to learn about plasma patterns of ascorbic acid (AA), beta carotene (BC), and vitamin E (vit E) when each or their various combinations were fed to humans. Conceivably, the combined absorption of these antioxidants could synergize maximum plasma redox potential. METHODS: Vit E (800 mg/day), BC (30 mg/day), and AA (1000 mg/day) were fed individually or in various combinations with each other to 91 volunteers divided into different feeding groups for 14 days. Plasma vit E, carotenes, and AA patterns were analyzed by standardized methods; values were compared with each group's baseline value. RESULTS: AA feeding did not significantly increase already saturated plasma AA concentrations above baseline. Intake of BC did not influence vitamin A (vit A) levels. Feeding of only vit E or only BC, with or without AA addition, or a combination of BC and vit E significantly increased plasma vit E and carotene levels after 2 days. A statistically (ANOVA) significant increase in plasma vit E above baseline was noted when vit E was ingested combined with AA or BC; this increase in plasma vit E was not significant when AA, BC and vit E were taken in combination. CONCLUSION: Our results show that BC or AA ingestion in combination with vit E significantly increases circulating vit E above that seen when vit E is individually ingested. Vit E in combination with BC or AA seems a practical means or increasing the circulating antioxidant potential afforded by vit E. Reasons why such synergism does not exist when an AA, BC, vit E combination is ingested is not yet obvious.

Adult↗
PubMed1996

The integrated model: implications for worksite health promotion and occupational health and safety practice.

Within a single firm it is common to find both occupational safety and health and worksite health promotion interventions operating in isolation from one another, with different intervention targets, methods, and personnel. Overcoming the segmentation of the two fields will require, among other things, the promulgation of an overarching model of work and health. The purpose of this article is to describe an integrated model and to show how it can be applied to improve worksite health interventions for both occupational safety and health and worksite health promotion. Practice examples from both fields are used to illustrate interventions that focus on different areas of the model (individual behavior, psychosocial, organization, and contextual factors). It is argued that occupational safety and health and worksite health promotion practitioners need to develop more comprehensive interventions and rigorously evaluate these programs to determine if they are more effective than programs with a more narrow focus.

Accidents, Occupational↗
PubMed1996

The human glycine receptor beta subunit: primary structure, functional characterisation and chromosomal localisation of the human and murine genes.

The inhibitory glycine receptor (GlyR) is a pentameric receptor comprised of alpha and beta subunits, of which the beta subunit has not been characterised in humans. A 2106 bp cDNA, isolated from a human hippocampal cDNA library, contained an open reading frame of 497 amino acids which encodes the beta subunit of the human GlyR. The mature human GlyR beta polypeptide displays 99% amino acid identity with the rat GlyR beta subunit and 48% identity with the human GlyR alpha 1 subunit. Neither [3H]strychnine binding nor glycine-gated currents were detected when the human GlyR beta subunit cDNA was expressed in the human embryonic kidney 293 cell line. However, co-expression of the beta subunit cDNA with the alpha 1 subunit cDNA resulted in expression of functional GlyRs which showed a 4-fold reduction in the EC50 values when compared to alpha 1 homomeric GlyRs. Glycine-gated currents of alpha 1/beta GlyRs were 17-fold less sensitive than homomeric alpha 1 GlyRs to the antagonists picrotoxin, picrotoxinin and picrotin, providing clear evidence that heteromeric alpha 1/beta GlyRs were expressed. The beta subunit appears to play a structural rather than ligand binding role in GlyR function. Fluorescence in situ hybridisation was used to localise the gene encoding the human GlyR beta subunit (GLRB) to chromosome 4q32, a position syntenic with mouse chromosome 3. In situ hybridisation using the human GlyR beta subunit cDNA showed that the murine GlyR beta subunit gene (Glrb) maps to the spastic (spa) locus on mouse chromosome 3 at bands E3-F1. This is consistent with the recent finding that a mutation in the murine GlyR beta subunit causes the spa phenotype. It also raises the possibility that mutations in the human beta subunit gene may cause inherited disorders of the startle response.

Amino Acid Sequence↗