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Biomedical subjects

R Smith

Publications and source records attributed to R Smith.

At least 1,729 records · Page 96Linked to original sources
PubMedDate not supplied

Determination of binding constants of diabodies directed against prostate-specific antigen using electrochemiluminescence-based immunoassays.

Two diabody molecules directed against the prostate-specific antigen (PSA) were generated from a combinatorial phage display library. The C-termini of diabodies incorporated the FLAG peptide epitope (P008D diabody) or the myc epitope (P001D). Both diabodies have the same antigen-binding site. Equilibrium-binding constants of these molecules were determined in two immunoassays using the ORIGEN detection system based on electrochemiluminescence. The binding of diabodies to biotinylated PSA was detected with either polyclonal antimouse Fab F(ab')2 or a monoclonal antibody directed against the FLAG epitope. Both detecting antibody preparations were covalently labeled with a ruthenium (II) tris (bipyridyl) moiety, Ru(bpy)3(2+), which allows quantification via an electrochemically triggered light reaction in an ORIGEN analyzer. The binding constants obtained by Scatchard analysis of non-linear curve fitting calculations from electrochemiluminescence immunoassays were compared with data derived from kinetic-binding studies using the BIAcore technology based on surface plasmon resonance. Depending on the detecting antibody, the dissociation constants KD determined at equilibrium with the ORIGEN technology are between 0.1 and 0.4 nM for both diabodies. From the kinetic constants kon and koff measured with the BIAcore instrument KD was calculated to be 0.2 nM for P001D and 0.6 nM for P008D. It is concluded that these two very different methods generate comparable affinity data for the diabodies.

Animals↗
PubMedDate not supplied

Multi-ribozyme targeting of human alpha-globin gene expression.

One approach to gene therapy for the treatment of hemoglobinopathies has been focused on increasing normal globin gene expression. However, because of the high concentration of hemoglobin in the red blood cell (32-34 g/dl), merely introducing the normal globin gene may not be enough to counteract the effect of an abnormal globin. We propose that in addition to strategies to add normal beta- or gamma-globin production to sickle erythrocytes, a decrease in overall hemoglobin concentration would further decrease the polymerization potential and should be considered with other gene therapy approaches. Ribozymes offer the potential to target a selected gene product. A model system has been set up using the human alpha-globin gene for specific gene suppression by ribozymes by cleaving alpha-globin mRNA transcripts. Ribozymes, specifically targeted to five different sites in the 5' portion of human alpha-globin mRNA, have been designed and tested in vitro. Cleavage of 32P-labeled alpha-globin mRNA by these ribozymes has been observed in vitro and the highest level of activity has been found for a multi-ribozyme combining all five ribozymes. The multi-ribozyme gene along with promoters with varying activities in erythroid cells was transfected into human erythroleukemia K562 cells. The multi-ribozyme gene, under the control of human alpha-2-globin promoter alone and combined with the locus control region enhancer, caused a decrease in the level of alpha-globin mRNA of 50-75% compared to the control, determined by RNase protection and by real-time quantitative PCR. The decrease in alpha-globin transcripts has been found to be correlated with expression of the multi-ribozyme in a dose-dependent manner and does not appear to be mediated by an antisense effect. These results suggest that the multi-ribozyme may be useful in gene therapy as an effective suppressor of a specific globin gene.

Antisense Elements (Genetics)↗
PubMedDate not supplied

Pathophysiology of a sickle cell trait mouse model: human alpha(beta)(S) transgenes with one mouse beta-globin allele.

As a potential model for sickle cell trait (AS), we examined mice containing one normal mouse beta-globin allele in combination with a human hemoglobin S (h(alpha)beta(S)) transgene (m(beta)/hS). The mice segregated into two subpopulations containing low and high proportions of hemoglobin S (m(beta)/hS1 and m(beta)/hS2, respectively) that was associated with one or two human h(alpha)beta(S) transgenes. We noted striking kidney pathology (cortical cysts, hyperplastic tubules, and glomerulonephritis), increasing with age and with greater severity in m(beta)/hS1. mBeta/hS2 animals were largely tolerant to 5% O(2) for 1 h, whereas 80% of m(beta)/hS1 mice died, exhibiting acute sequestration of erythrocytes in spleen, liver, and heart. These pathologies appear to result from a decreased oxygen affinity of the hybrid (human alpha/mouse beta) hemoglobins with a mild beta-thalassemia phenotype. Thus, these mouse models of sickle trait seem to manifest their renal pathology and sensitivity to hypoxia by mechanisms related to low tissue oxygen delivery and are different from the human syndrome. Analyses of parameters such as P(50), red cell indices, and genetic background are necessary in establishing potential relevance of any mouse model of the sickle cell syndromes.

Alleles↗
PubMedDate not supplied

Recognition of depression by internists in primary care: a comparison of internist and "gold standard" psychiatric assessments.

In an effort to elucidate the process of internists' recognition of depression in primary care settings, a comparison of internist and "gold standard" psychiatric assessments of patients was undertaken in a rural primary care practice over a 15-month period. Clinical characteristics and diagnoses, global assessments of psychosocial stress, and two aspects of chief-complaint presentation style, clarity and somatization, were recorded by the internists for each patient, who was independently assessed by a psychiatrist for the presence of any specific depressive disorder by structured interview. Internists correctly labeled 57% of the interview-assessed depressives as depressed; 13% of patients with "no psychiatric disorder" were assessed as depressed by internists. Clinical and demographic characteristics of the "false-negative" and "false-positive" internists' diagnoses were examined to clarify how internists think of "depression" in the primary care context.

Adult↗
PubMedDate not supplied

The relationship of presenting physical complaints to depressive symptoms in primary care patients.

OBJECTIVE: To assess the relationship of specific patient chief physical complaints to underlying depressive symptoms in primary care practice. DESIGN: A cross-sectional study that was part of a larger prevalence study of depression in primary care. SETTING: A general medical primary care practice in a teaching medical center in rural New England. PATIENTS: 1,042 consecutive outpatients screened for depression with the Hopkins Symptom Checklist 49-item depression scale and for whom physicians filled out a form recording both specific chief complaints and two aspects of complaint presentation style, clarity and amplification. INTERVENTIONS: None. RESULTS: Complaints that discriminated between depressed and non-depressed patients (at the p = 0.05 level) were sleep disturbance (PPV 61%), fatigue (PPV 60%), multiple (3+) complaints (PPV 56%), nonspecific musculoskeletal complaints (PPV 43%), back pain (PPV 39%), shortness of breath (PPV 39%), amplified complaints (PPV 39%), and vaguely stated complaints (PPV 37%). CONCLUSIONS: Depressed patients are common in primary care practice and important to recognize. Certain specific complaints and complaint presentation styles are associated with underlying depressive symptoms.

Adolescent↗
PubMedDate not supplied

Selection and rapid purification of murine antibody fragments that bind a transition-state analog by phage display.

Functional antibody fragments may be displayed on the surface of filamentous bacteriophage by introducing variable region genes into the viral genome at a gene encoding a viral coat protein. "Phage display" enables the isolation of antibody genes from large libraries according to the binding specificities they encode. We have constructed a new phage-display vector encoding a polyhistidine tag that has been used for rapid purification of soluble antibody fragments. An antibody library derived from immunized mice was cloned into this vector. This library was panned against the transition state analog RT3, and a high proportion of binders isolated after two rounds of panning. PCR analysis revealed that there were 24 different pattern groups. Sequencing of 15 clones within the major pattern group revealed 10 related clones with a range of point mutations. Thus, phage display can provide a large diverse repertoire of candidate catalytic antibodies based on TSA selection and screening.

Animals↗
PubMedDate not supplied

Endorectal surface coil MR imaging as a staging technique for rectal carcinoma: a comparison study to rectal endosonography.

BACKGROUND: Preoperative staging of rectal cancer is critical for guiding therapy and prescribing the most appropriate treatment option. The purpose of this investigation was to compare the accuracy of endorectal surface coil magnetic resonance imaging (ERSCMRI) with endosonography (EUS) in staging rectal lesions. METHODS: Fourteen patients with rectal carcinoma, initially detected by barium enema or sigmoidoscopy underwent ERSCMRI and EUS. Subsequent resection of the lesions was performed, and the staging accuracies of these two modalities are compared. RESULTS: MR T-staging agreement with pathologic T-staging was similar to that of EUS, but MR enabled more accurate identification of nodal involvement. CONCLUSION: ERSCMRI produced greater overall accuracy in staging for rectal carcinoma than did EUS.

Adenocarcinoma↗
PubMedDate not supplied

Familial psychiatric illness in chronic posttraumatic stress disorder.

One hundred and eight veterans with posttraumatic stress disorder (PTSD) were compared with 60 age-matched controls with regard to family history of psychiatric illness. Depressed controls had a higher morbidity risk (MR) for depression and generalized anxiety in siblings/parents and children, respectively. Patients with PTSD did not differ from alcoholics or nonpsychiatric controls on the basis of family history. PTSD was associated with greater familial anxiety when compared with controls who had experienced combat. When World War II and Vietnam veterans with PTSD were compared, a higher MR for alcohol and drug abuse was found in siblings/parents of Vietnam veterans, and a higher MR was found for other chronic psychiatric disorders in the children of Vietnam veterans.

Adolescent↗
PubMedDate not supplied

Interleukin-2 and interleukin-6 in schizophrenia and mania: effects of neuroleptics and mood stabilizers.

There is some evidence that schizophrenia may be accompanied by alterations in cell-mediated immunity (CMI) and that antipsychotic agents may modulate CMI. The purpose of this study was to investigate the plasma levels of interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6R), sIL-2R, and transferrin-receptor (TfR) in schizophrenia and mania, and the effects of treatment with neuroleptics or mood stabilizers on these variables. The subjects were 14 schizophrenic patients, 10 manic patients and 21 healthy volunteers. The above immune variables were measured in baseline conditions and after treatment with neuroleptics in schizophrenic patients and valproate in manic patients. Plasma concentrations of IL-6, sIL-6R, sIL-2R and TfR were significantly higher in the combined group of psychotic patients than in healthy volunteers. Plasma IL-6 was significantly higher in schizophrenic patients, while plasma sIL-6R and sIL-2R were significantly higher in mania than in normal controls. In schizophrenic patients, plasma levels of IL-6, sIL-6R and TfR were significantly lower after treatment with neuroleptics than before treatment. No significant effects of valproate on the immune-inflammatory markers could be found in the manic patients. It is suggested that activation of CMI may occur in both schizophrenia and mania and that neuroleptics may have immunosuppressive effects through suppression of IL-6 or IL-6R-related mechanisms.

Adult↗
PubMedDate not supplied

Evidence for inhibition by endothelium-derived relaxing factor of thromboxane A2 receptor-mediated vasoconstriction in the fetal vessels of the human perfused placenta.

Three inhibitors of the release or effects of endothelium-derived relaxing factor (EDRF), N-nitro-L-arginine, methylene blue and oxyhemoglobin, caused further increases in perfusion pressure during vascular constriction with submaximal concentrations of the thromboxane A2-mimetic, U46619 in fetal vessels of human placental lobules perfused in vitro. The results suggest the EDRF, released during constriction of fetal placental vessels in response to thromboxane A2 receptor stimulation, attenuates the vasoconstrictor response. Hence, impairment of EDRF release or function could contribute to the reduced placental blood flow observed in various disease states associated with increased thromboxane A2 production such as pre-eclampsia.

Arginine↗
PubMedDate not supplied

Post-partum psychoses and the dexamethasone suppression test.

The hypothesis that post-partum psychoses are predominantly mixed affective disorders was tested by administering the dexamethasone suppression test (DST) to seven puerperal psychotics, six puerperal depressives and comparison groups of non-puerperal psychotic and depressed women. The hypothesis received support from the finding that two-third of the puerperal patients had positive DSTs versus one-third of similar non-puerperal patients. An 80% rate of positive DSTs in 19 normal women 5 days post-partum, however, suggested this was an invalid interpretation of this finding, particularly as the majority of these tests returned to normal when repeated several weeks later.

Brief Psychiatric Rating Scale↗
PubMedDate not supplied

Modulation of mitogen-induced spleen cell proliferation and the antibody-forming cell response by beta-endorphin in vivo.

Experiments were conducted which compared the in vivo effects of beta-endorphin (BEP), gamma-endorphin (gamma EP), methionine-enkephalin (Met-ENK), and acetylated BEP(1-27) on the in vitro proliferative response of rat spleen cells to concanavalin A (ConA). In addition, the influence of BEP administration on the primary and secondary antibody-forming cell (AFC) response to the soluble antigen keyhole-limpet hemocyanin (KLH) was examined. Intravenous administration of BEP enhanced the spleen cell proliferative response to ConA assessed 3 hr after a single bolus infusion. Conversely, infusion with AcBEP(1-27) suppressed the proliferative response, whereas no effects of intravenous gamma EP or Met-ENK treatment were observed. The enhancing effect of BEP administration was not detectable 24 hr after a single infusion, but could be maintained over a 44 hr period by multiple infusions. The primary AFC response to KLH was suppressed by a dose of 1 nmole BEP only. On the other hand, the secondary IgG AFC response to KLH was enhanced by 10 pmoles BEP, while the IgM and IgA AFC responses remained unaltered by BEP treatment. The anamnestic in vitro proliferative response of spleen cells cultured with KLH was not altered if BEP was administered at the time of secondary KLH immunization. These results extend previous observations of BEP-induced modulation of in vitro immune function by demonstrating that opioid and nonopioid forms of BEP administered in vivo alter the capacity of spleen cells to proliferate and develop antibody responses to antigen.

Animals↗
PubMedDate not supplied

Structure of equine corticotropin releasing factor.

A 41 amino acid peptide, probably identical in structure to human corticotropin releasing factor, was isolated from 70 equine hypothalami by methanol extraction, immunoaffinity chromatography and single step of reverse phase HPLC. The amino acid sequence was determined by gas phase sequence analysis. Probable carboxyl terminal amidation was demonstrated by similar retention times for equine and human corticotropin releasing factor on reverse phase HPLC at pH 8. The likely structure of equine corticotropin releasing factor is: Ser-Glu-Glu-Pro-Pro- Ile-Ser-Leu-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Met-Ala-Arg- Ala-Glu - Gln-Leu-Ala-Gln-Gln-Ala-His-Ser-Asn-Arg-Lys-Leu-Met-Glu-Ile-Ile-NH2. The purified peptide is equipotent with human corticotropin releasing factor in an in vitro bioassay and in a human plasma binding protein assay.

Amino Acid Sequence↗
PubMedDate not supplied

Reactivity of the glycocalyx of endocarditis-producing viridans group streptococci.

We correlated quantity of streptococcal polysaccharides and endocarditis production by those bacterial strains. To investigate this finding further, we studied the composition of the glycocalyx using a spectrophotometric assay and lectin analysis of exopolysaccharides from endocarditis- and non-endocarditis-producing strains of viridans streptococci. Identical weights of glycocalyx from the clinical endocarditis isolates produced significantly different absorbances as compared with the nonendocarditis isolates (P < 0.0012, Wilcoxon rank test). Lectin-binding experiments showed that endocarditis-producing streptococci contained increased amounts of glucose, galactose, sialic acid, and mannose. These data suggest that the glycocalyx of endocarditis-producing viridans streptococci is both qualitatively and quantitatively different from non-endocarditis-producing isolates. These differences can be measured in vitro.

Endocarditis, Bacterial↗
PubMedDate not supplied

Allocation of time in three academic specialties.

A survey was done to: 1) characterize the allocation and distribution of time by tenure track emergency physicians, and 2) compare the time distribution of emergency physicians to two other academic disciplines. All emergency medicine residency programs were surveyed by telephone to determine if faculty were eligible for tenure and if tenure was available, how many hours per week were spent on clinical duties, research, and administrative tasks. Similar information was compiled from cardiology and orthopedic surgery faculty at the same universities. Data from the survey revealed that a tenure track assistant professor spends 23 hours (46%) working clinical shifts in the emergency department; 11 hours (20%) doing research and 18 hours (34%) in administrative tasks. In contrast, cardiologists spend significantly more time in clinical duties (32 hours) and research (18 hours). However, cardiologists spend significantly less time in administrative duties (10 hours). Data for orthopedic surgeons show a similar pattern. Distributions within each academic discipline were also analyzed and a significant difference in research time was found between four tenure track emergency medicine programs and the other eighteen. Data from this survey may help academic emergency physicians evaluate how they are allocating their time in comparison to other busy clinical specialties.

Cardiology↗
PubMedDate not supplied

Anesthesia rebreathing bags: physical characteristics and use as portable oxygen reservoirs.

STUDY OBJECTIVE: To examine the physical characteristics of 3-liter anesthesia rebreathing bags and assess their use for oxygen (O2) storage and delivery during transport of patients from the operating room (OR) to the recovery area. SETTING: Anesthesia laboratory and pulmonary function laboratory. INTERVENTIONS: Five anesthesia rebreathing bags were inflated in 2-liter increments with 50 liters of air and then deflated in 2-liter increments. A sixth bag was inflated twice in 1-liter increments. Five bags were inflated with 60 liters of gas and allowed to deflate through a cannula functioning as a flow restrictor. Five bags were inflated with 100 liters of gas and checked for damage. MEASUREMENTS AND MAIN RESULTS: Pressure measurements done at 2-liter increments during inflation of the bags to 50 liters and deflation showed a consistent pattern of pressure-volume relationships. Assessment of gas flow during deflation through the cannula showed flow rates ranging from 3.1 to 3.8 L/min after 5 minutes of continuous flow and from 2.8 to 3.8 L/min after 10 minutes. No weakness or damage was apparent in bags inflated with 100 liters of gas. CONCLUSIONS: It is feasible for anesthesia rebreathing bags distended with O2 to serve as lightweight, inexpensive, and easily monitored alternatives to O2 tanks for O2 delivery during transport of patients from the OR to the recovery area.

Anesthesia Recovery Period↗