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Biomedical subjects

T Hogan

Publications and source records attributed to T Hogan.

At least 19 recordsLinked to original sources
PubMed2001

Structure and thermoelectric properties of the new quaternary bismuth selenides A(1-x)M(4-x)Bi(11+x)Se21 (A = K and Rb and Cs; M = Sn and Pb)--members of the grand homologous series Km(M6Se8)m(M(5+n)Se(9+n)).

Several members of the new family A(1-x)M(4-x)Bi(11+x)Se21 (A = K, Rb, Cs; M = Sn, Pb) were prepared by direct combination of A2Se, Bi2Se3, Sn (or Pb), and Se at 800 degrees C. The single-crystal structures of K(0.54)Sn(3.54)Bi(11.46)Se21, K(1.46)Pb(3.08)Bi(11.46)Se21, Rb(0.69)Pb(3.69)Bi(11.31)Se21, and Cs(0.65)Pb(3.65)Bi(11.35)Se21 were determined. The compounds A(1-x)M(4-x)Bi(11+x) Se21 crystallize in a new structure type with the monoclinic space group C2/m, in which building units of the Bi2Te3 and NaCl structure type join to give rise to a novel kind of three-dimensional anionic framework with alkali-ion-filled tunnels. The building units are assembled from distorted, edge-sharing (Bi,Sn)Se6 octahedra. Bi and Sn/Pb atoms are disordered over the metal sites of the chalcogenide network, while the alkali site is not fully occupied. A grand homologous series Km(M6Se8)m(M(5+n)Se(9+n)) has been identified of which the compounds A(1-x)M(4-x)Bi(11+x)Se21 are members. We discuss here the crystal structure, charge-transport properties, and very low thermal conductivity of A(1-x)M(4-x)Bi(11+x)Se21.

Journal Article↗
PubMed2001

High rates of depressive symptoms in STD clinic patients.

BACKGROUND: Depressed mood syndromes may limit the ability of patients with sexually transmitted diseases (STDs) to process risk reduction messages and change behavior. We undertook screening for depression in an urban STD clinic. GOAL: To define the prevalence of depressed mood among STD patients in Baltimore, Maryland. STUDY DESIGN: A convenience sample of 125 patients presenting to an STD clinic completed the 30-item General Health Questionnaire (GHQ). Endorsement of > or = 6 depressive symptom items on the GHQ was considered probable depression. RESULTS: Of 125 patients screened, 39.2% had GHQ scores above the threshold. Women were more likely to have probable depression than men (51.9% versus 31.9%, P = 0.023). There was no association of substance use and depressed mood, nor of a diagnosed STD and depressed mood. CONCLUSIONS: Depressive symptom rates are extremely high among STD patients, which may compromise the success of risk reduction counseling.

Adult↗
PubMed2001

Rapid dendritic cell recruitment to the bronchial mucosa of patients with atopic asthma in response to local allergen challenge.

BACKGROUND: Airway dendritic cells (DC) play an important role in chronic allergic airway inflammation in experimental animals, but a similar role for DC in human allergic asthma has been difficult to define. This pilot study was undertaken to elucidate the role of DC in allergic asthma by examining their potential to migrate to the lower airways in response to bronchial challenge with specific allergen. METHODS: Bronchial biopsy specimens were obtained from seven patients with allergic asthma before and 4-5 hours after allergen challenge. Multicolour immunofluorescence staining was performed on mucosal cryosections to identify changes in the number and phenotypes of DC. RESULTS: A dramatic increase in the number of CD1c+HLA-DR+ DC were observed in the lamina propria after challenge compared with baseline (22.4 v 7.8 cells/mm(2)). The rapid accumulation (within 4-5 hours) of these cells strongly suggests that they were directly recruited from peripheral blood. CONCLUSION: We have shown for the first time that a specific DC subset rapidly emigrates into the human bronchial mucosa during allergic inflammation. While this study is based on relatively few patients, the consistency of the overall results strongly suggests that the rapid population dynamics of human airway DC closely parallel those in animal models of acute inflammation. These findings support suggestions that DC have an important role in human airway allergy.

Adolescent↗
PubMed2000

Analysis of the HIV-1 LTR NF-kappaB-proximal Sp site III: evidence for cell type-specific gene regulation and viral replication.

It has been widely demonstrated that the human immunodeficiency virus type 1 (HIV-1) envelope, specifically the V3 loop of the gp120 spike, evolves to facilitate adaptation to different cellular populations within an infected host. Less energy has been directed at determining whether the viral promoter, designated the long terminal repeat (LTR), also exhibits this adaptive quality. Because of the unique nature of the cell populations infected during the course of HIV-1 infection, one might expect the opportunity for such adaptation to exist. This would permit select viral species to take advantage of the different array of conditions and factors influencing transcription within a given cell type. To investigate this hypothesis, the function of natural variants of the NF-kappaB-proximal Sp element (Sp site III) was examined in human cell line models of the two major cell types infected during the natural course of HIV-1 infection, T cells and monocytes. Utilizing the HIV-1 LAI molecular clone, which naturally contains a high-affinity Sp site III, substitution of low-affinity Sp sites in place of the natural site III element markedly decreased viral replication in Jurkat T cells. However, these substitutions had relatively small effects on viral replication in U-937 monocytic cells. Transient transfections of HIV-1 LAI-based LTR-luciferase constructs into these cell lines suggest that the large reduction in viral replication in Jurkat T cells, caused by low-affinity Sp site III variants, may result from reduced basal as well as Vpr- and Tat-activated LTR activities in Jurkat T cells compared to those in U-937 monocytic cells. When the function of Sp site III was examined in the context of HIV-1 YU-2-based LTR-luciferase constructs, substitution of a high-affinity element in place of the natural low-affinity element resulted in increased basal YU-2 LTR activity in Jurkat T cells and reduced activity in U-937 monocytic cells. These observations suggest that recruitment of Sp family members to Sp site III is of greater importance to the function of the viral promoter in the Jurkat T cell line as compared to the U-937 monocytic cell line. These observations also suggest that other regions of the LTR may compensate for Sp recruitment defects in specific cell populations.

Base Sequence↗
PubMed2000

CsBi(4)Te(6): A high-performance thermoelectric material for low-temperature applications

Thermoelectric (Peltier) heat pumps are capable of refrigerating solid or fluid objects, and unlike conventional vapor compressor systems, they can be miniaturized without loss of efficiency. More efficient thermoelectric materials need to be identified, especially for low-temperature applications in electronics and devices. The material CsBi(4)Te(6) has been synthesized and its properties have been studied. When doped appropriately, it exhibits a high thermoelectric figure of merit below room temperature (ZT(max) approximately 0.8 at 225 kelvin). At cryogenic temperatures, the thermoelectric properties of CsBi(4)Te(6) appear to match or exceed those of Bi(2-x)Sb(x)Te(3-y)Se(y) alloys.

Journal Article↗
PubMed1998

Suicide prevention effects associated with clozapine therapy in schizophrenia and schizoaffective disorder.

OBJECTIVE AND METHODS: Suicide is a significant cause of death among patients with schizophrenia and schizoaffective disorder, affecting some 10 to 15 percent of these patients. This study examined annual suicide rates over a two-year period (1993-1995) among more than 30,000 patients with schizophrenia and schizoaffective disorder who received services from the Texas Department of Mental Health and Mental Retardation and suicide rates over a six-year period (1991-1996) among a subgroup of patients treated with clozapine. RESULTS: The annual suicide rate for all patients with schizophrenia and schizoaffective disorder was 63.1 per 100,000 patients, approximately five times higher than in the general population. In contrast, only one suicide occurred in six years among patients treated with clozapine who were of similar diagnosis, age, and sex, for a suicide rate of about 12.7 per 100,000 patients per year. This rate is similar to the 15.7 per 100,000 patients per year for all U.S. patients treated with clozapine, calculated from data reported as of June 1996 to the clozapine national registry system maintained by Novartis Pharmaceuticals Corporation, the U.S. manufacturer of clozapine. CONCLUSIONS: The study results suggest that clozapine therapy is associated with a reduced risk of suicide among patients with schizophrenia and schizoaffective disorder.

Adult↗
PubMed1996

In-vivo microdialysis study of extracellular glutamate response to temperature variance in subarachnoid hemorrhage.

Neurochemical changes may precede the development of clinical signs in neurological disease. Early identification of such changes may offer an opportunity to avoid or treat complications. Under experimental conditions, extracellular levels of glutamate and other amino acids can be monitored by in-vivo microdialysis in cerebral ischemia, head trauma and epilepsy. Data on the release of glutamate under ischemic conditions in humans are limited. There is no published data on the effects of temperature variation or other manipulations on the extracellular glutamate levels in humans. We report for the first time, the effects of changes in temperature on the extracellular cerebral glutamate levels as measured by in-vivo microdialysis, the dialysate being collected before, during and after cooling in four patients with subarachnoid hemorrhage. Three of the patients had in-vivo microdialysis carried out postoperatively. One patient underwent microdialysis three days prior to the surgical clipping of the aneurysm. In all patients, mild head cooling resulted in a significant decrease in extracellular glutamate levels. The effect of cooling was most apparent when the extracellular glutamate concentrations were high. In two patients, the extracellular glutamate levels increased sharply with fever but returned to normal once the temperature normalized. In vivo microdialysis can be used to measure extracellular glutamate and other neurotransmitters with minimal discomfort in awake humans. This technique offers a unique opportunity to monitor the neurochemistry in critically ill patients and it may aid in developing therapeutic intervention strategies to minimize undesired chemical responses.

Cold Temperature↗
PubMed1996

Prevalence of antimicrobial resistance among 723 outpatient clinical isolates of Moraxella catarrhalis in the United States in 1994 and 1995: results of a 30-center national surveillance study.

Seven hundred twenty-three isolates of Moraxella catarrhalis obtained from outpatients with a variety of infections in 30 medical centers in the United States between 1 November 1994 and 30 April 1995 were characterized in a central laboratory. The overall rate of beta-lactamase production was 95.3%. When the National Committee for Clinical Laboratory Standards MIC interpretive breakpoints for Haemophilus influenzae were applied, percentages of strains found to be susceptible to selected oral antimicrobial agents were as follows: azithromycin, clarithromycin, and erythromycin, 100%; tetracycline and chloramphenicol, 100%; amoxicillin-clavulanate, 100%; cefixime, 99.3%; cefpodoxime, 99.0%; cefaclor, 99.4%; loracarbef, 99.0%; cefuroxime, 98.5%; cefprozil, 94.3%; and trimethoprim-sulfamethoxazole, 93.5%.

Anti-Bacterial Agents↗
PubMed1993

Involvement of the accessory gene regulator (agr) in expression of type 5 capsular polysaccharide by Staphylococcus aureus.

The effect of an agr mutation on expression of type 5 capsular polysaccharide (CP) by Staphylococcus aureus Newman was investigated in different complex and synthetic media. CP expression by the agr mutant was strongly reduced in certain media but slightly in others, indicating that CP synthesis is positively controlled by agr. CP expression occurred in the post-exponential growth phase in both wild-type and mutant strains, suggesting that other regulatory systems could act in conjunction with agr.

Bacterial Capsules↗
PubMed1993

Co-elimination of mec and spa genes in Staphylococcus aureus and the effect of agr and protein A production on bacterial adherence to cell monolayers.

Phenotypic loss of protein A production was tested in six methicillin-resistant (McR) Staphylococcus aureus (MRSA) isolates and their isogenic methicillin-sensitive (McS) variants by a radiolabelled IgG-binding assay with washed cells and by Western blotting of supernates prepared from lysed washed cells. Genomic DNA was probed for homology with the protein A gene (spa) in EcoRI digests and for homology to the methicillin resistance gene (mec) in HindIII digests. The McS variants had lost homology with mec. An isogenic pair of McR and McS strains, and derivatives of S. aureus 8325-4 with site-specific mutations of the accessory gene regulator locus (agr) and spa, were tested for adherence to human peritoneal mesothelial cells in monolayer culture. The isogenic pair were also tested for adherence to HEp-2 and Vero cell monolayers in assays with 3H thymidine-labelled bacteria. McR isolates produced protein A which was absent from three strains that had become McS. This correlated with deletion of the spa locus. Spa homology, but reduced production of protein A, was retained in one McS strain which also showed reduced adherence to HEp-2, Vero and mesothelial cells (p < 0.05) compared with the parent McR strain. A spa mutation in strain 8325-4 did not significantly affect adherence to mesothelial cells but mutation in agr increased adherence significantly in both Spa+ and Spa- strains.

Animals↗
PubMed1992

Establishing goals and priorities in a surgery department.

Limitation of resources necessitates prioritization in the planning of goals for a clinical discipline such as surgery. Private practitioners and academic surgeons have their own priorities which reflect their specific, often conflicting, interests. We describe a model (modification of Davies & Morgan, 1983) for establishing goals and priorities with input from both private practitioners and academic full-time surgeons in a large Department of Surgery. The model consists of four phases each of which is divided into input, process and output stages. During the input stage general large group discussion allows identification of disparate views. This is followed by refinement of these ideas in small group discussions (process) which results in the formulation of a report (output). Application of this model resulted in a clear definition of goals and priorities by consensus and placed education first on this list of priorities in spite of a department in which there is a predominance of private practitioners whose major area of activity is in the realm of patient care.

Attitude of Health Personnel↗
PubMed1990

Activation of the interleukin-3 gene by chromosome translocation in acute lymphocytic leukemia with eosinophilia.

The t(5;14)(q31;q32) translocation from B-lineage acute lymphocytic leukemia with eosinophilia has been cloned from two leukemia samples. In both cases, this translocation joined the IgH gene and the interleukin-3 (IL-3) gene. In one patient, excess IL-3 mRNA was produced by the leukemic cells. In the second patient, serum IL-3 levels were measured and shown to correlate with disease activity. There was no evidence of excess granulocyte/macrophage colony stimulating factor (GM-CSF) or IL-5 expression. Our data support the formulation that this subtype of leukemia may arise in part because of a chromosome translocation that activates the IL-3 gene, resulting in autocrine and paracrine growth effects.

Base Sequence↗
PubMed1990

Factors affecting interictal spike discharges in adults with epilepsy.

We investigated various factors affecting interictal spike discharges (ISDs) in standard interictal EEGs of 203 consecutive cases with seizure(s). 94 EEGs (46%) showed ISDs. Yield was maximum (68%) when recordings were done within 2 days of a seizure; beyond this period, incidence of ISD did not change with time from the last seizure. EEGs of patients having greater than 12 seizures/year were more likely to contain ISD (68%) than the records of cases with less than 12 attacks/year (37-41%; P less than 0.001). Age and neurological status at the time of EEG, etiology and anticonvulsants did not influence the frequency of ISD. Analysis of serial EEGs (n = 512) from the study group showed that if initial 3 EEGs lacked ISD, yield from further standard EEGs is small.

Action Potentials↗
PubMed1989

Rhythmic auditory stimulation in generalized epilepsy.

Activation of spike-wave discharges by photic stimulations (PS) and rhythmic auditory stimulations (AS) was investigated in 40 patients with generalized epilepsy and 25 controls. PS produced spike-wave discharges in 23 (55%) and AS in 12 (33%) cases. In 4 patients AS activated spike-wave discharges but PS failed to do so. AS may be occasionally used in generalized epilepsy as an activating method when standard procedures such as hyperventilation and PS fail.

Acoustic Stimulation↗
PubMed1989

High dose ketoconazole for the treatment of hormone refractory metastatic prostate carcinoma: 16 cases and review of the literature.

We treated 16 patients who had hormone refractory metastatic prostate cancer with 400 mg. ketoconazole orally every 8 hours. None of the patients had an objective response, although 6 (37.5 per cent) had stable disease (2 of whom had a subjective decrease in bone pain). The median duration of stable disease was 6.8 months (range 2 to 12 months) and side effects were seen in 14 patients. Nausea, vomiting or anorexia was noted in 10 patients, rash and pruritus in 2, transient abnormal liver function tests in 1 and transient pulmonary infiltrates in 1. Nine prior studies investigating the use of ketoconazole in hormone refractory metastatic prostate cancer were reviewed. Only 1 complete response was reported. A partial response was noted in 14 per cent of the patients. Most of the patients had stable or progressive disease. High dose ketoconazole as a single agent appears to have limited use in patients who have failed prior systemic therapy.

Adenocarcinoma↗