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Biomedical subjects

J B Walter

Publications and source records attributed to J B Walter.

14 recordsLinked to original sources
PubMed2002

Mathematical modeling of laser ablation in liquids with application to laser ultrasonics.

The use of laser ablation as a means of generating ultrasonic waves in liquid metals is studied in this paper. A mathematical model for predicting the onset of ablation is developed, as is a model of the ablation process based on steady state, one-dimensional gas dynamics in which the vapor phase is treated as an ideal gas. The results of this model are then used in a quasi-two-dimensional model of laser ablation that accounts for the spatial distribution of intensity in the laser beam. Model predictions are compared with experiments conducted on liquid mercury and excellent agreement is obtained. Based on these results, a simplified model is developed that shows excellent agreement with both the theory and the experiments.

Journal Article↗
PubMed1998

A mutant human beta2-microglobulin can be used to generate diverse multimeric class I peptide complexes as specific probes for T cell receptors.

Antigen-specific receptors (TCR) on CD8 T lymphocytes form relatively short-lived complexes with their natural ligands: peptides in association with major histocompatibility complex (MHC) class I molecules, which consist of a polymorphic heavy chain and a conserved light chain, beta2-microglobulin (beta2-M). To produce soluble MHC-peptide complexes in a form that would bind more stably and could be used to identify, count, and isolate CD8 T cells having the appropriate TCR, we prepared multimeric MHC-peptide complexes. Our work builds on the assembly of recombinant MHC class I peptide complexes using a mutant human beta2-M chain (Tyr 67 > Cys) which can form stable heterodimers with diverse MHC heavy chains. With biotin added to the SH group, the assembled MHC-peptide monomers formed multimers with avidin linked to a fluorochrome. The specific reactivity of the multimeric reagents with human and mouse cytotoxic T cells (CTL) is described. The present approach permits the production of class I multimers, without the necessity of genetic engineering each heavy chain, a significant advantage in view of the enormous polymorphism of MHC heavy chains. Because human beta2-M forms stable heterodimers with diverse class I heavy chains from various species (human and non human primates, mouse, etc.), this procedure is a general method for producing multimers of MHC-peptide complexes as T cell receptor-specific probes.

Animals↗
PubMed1997

Stimulation of human cytotoxic T cells with HIV-1-derived peptides presented by recombinant HLA-A2 peptide complexes.

HLA-A2 heavy chain and beta 2-microglobulin were expressed in Escherichia coli, and refolded in the presence of peptides derived from HIV-1 RT and gag proteins. When recombinant HLA-A2 molecules were attached to cells lacking HLA-A2, the cells became susceptible to lysis by HLA-A2-restricted cytotoxic T lymphocyte (CTL) clones specific for peptides derived from RT and gag proteins. Limiting dilution analyses of peripheral blood mononuclear cells from HIV-1-infected individuals showed that the recombinant HLA-A2 peptide complexes covalently immobilized on microspheres stimulated the development of HLA-A2 peptide-specific CTL. Preformed HLA-peptide complexes may provide an alternative to immunization procedures that depend upon intracellular processing of antigen to elicit T cell responses.

Antigen Presentation↗
PubMed1989

Granuloma annulare in patients with human immunodeficiency virus infections.

We present four cases of granuloma annulare occurring in patients with human immunodeficiency virus (HIV) infection. These patients had either an extensive localized form or generalized granuloma annulare. The patient with generalized granuloma annulare was clinically reminiscent of the previously described papular eruption seen in HIV-positive patients. In several patients with the localized form, Kaposi's sarcoma was considered in the differential diagnosis. In all patients, however, the eruptions were surprisingly transient. The similarity of the localized form of granuloma annulare to Kaposi's sarcoma and the generalized micropapular form to the papular eruption of acquired immunodeficiency syndrome seen in HIV-positive patients illustrates the usefulness of skin biopsies in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Metastatic squamous cell carcinoma in linear porokeratosis of Mibelli.

We describe the clinical and pathologic observations of a 45-year-old woman with linear porokeratosis who developed squamous cell carcinoma in lesional sites. The squamous cell carcinoma metastasized to a regional lymph node. This is the second case of metastatic squamous cell carcinoma reported in porokeratosis and the first reported in the linear variety.

Carcinoma, Squamous Cell↗
PubMed1987

Lymphomatoid granulomatosis.

The clinical and pathologic appearance of seven patients with lymphomatoid granulomatosis who had skin lesions when first seen is reviewed. Six patients subsequently developed systemic disease. Although the gross morphology of the skin lesions is variable, the pathology is distinctive. An adequate deep biopsy shows the characteristic lymphohistiocytic infiltrate with variable numbers of atypical cells. Angiodestruction is less evident in the skin compared to other organs. The infiltrate surrounds and invades not only vessels but also nerves and epidermal appendages. The skin biopsy specimen can be differentiated from the lymphomatous infiltrates and Wegener's granulomatosis. Two of the patients who developed systemic disease were diagnosed by skin biopsy but clinicians failed to institute therapy, preferring to wait for other organ involvement. In addition, two patients developed lymphoma, one of which was confirmed at autopsy and one on subcutaneous and bone marrow biopsy 5 years after the initial skin diagnosis. Lymphomatoid granulomatosis can be diagnosed by performing a skin biopsy. Appropriate chemotherapy may result in a high percentage of complete remissions and therefore the dermatopathologist can play an important role in the early diagnosis of this potentially fatal disease.

Adult↗
PubMed1986

Regional differences in relaxation of electric field-stimulated canine airway smooth muscle by verapamil, isoproterenol and prostaglandin E2.

Regional differences in contraction produced by methacholine and electric field stimulation (EFS) and in relaxation produced by isoproterenol, prostaglandin E2 and verapamil were studied in isolated canine airway smooth muscle in vitro. Low-frequency EFS (3 Hz, 0.5 msec, 50 V) contracted thoracic trachealis to 43% of maximal EFS response, whereas cervical trachealis contracted to only 14% of maximum. EFS at 10 Hz produced 75% of the maximal response in both regions of the trachea. These EFS responses were abolished by 0.1 microM tetrodotoxin and 1.0 microM atropine. Contraction produced by EFS was also matched in each tissue by contraction with methacholine. The concentrations of methacholine that matched EFS at 10 Hz were 52 +/- 7, 378 +/- 84 and 66 +/- 11 nM for cervical and thoracic trachealis and lobar bronchi, respectively. Both EFS and matched methacholine contractions of cervical trachealis and lobar bronchi were completely relaxed by isoproterenol, whereas thoracic trachealis relaxed maximally to only 60% of induced tone. When verapamil was used to relax EFS and matched methacholine contractions, cervical trachealis was completely relaxed whereas thoracic trachealis relaxed to 15% of induced tone. Although there was a regional difference in the relaxant potency of isoproterenol and, to some extent, verapamil, there was no difference in isoproterenol or verapamil EC50 values for EFS vs. matched methacholine contractions within each region. In contrast, EFS contractions of thoracic trachealis were more sensitive to prostaglandin E2-induced relaxation than were matched methacholine contractions. These data demonstrate marked differences in cholinergic and beta adrenergic receptor-mediated responses between regions of the tracheobronchial tree.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Effect of food on the bioavailability and pattern of release of a sustained-release theophylline tablet.

The effect of food on the bioavailability, time to peak level, and pattern of release of a sustained-release theophylline preparation was examined in six normal volunteers. The average bioavailability for the 100- and 300-mg tablets was 98 +/- 0.03% (S.E.M.). This is consistent with previously published data. Food decreased measured theophylline concentration during the first 4 hours for the 100-mg tablets and at the fourth-hour sample following the 300-mg tablets. The decreased rate of absorption resulted in a shift of the absorption curve to the right with a delay in the time to peak level. Peak serum concentrations for tablets given with a meal occurred 6 hours after the 100-mg tablets and 8 hours after the 300-mg tablets, as opposed to 4 and 6 hours, respectively, for tablets in the fasting state. The release pattern of the theophylline preparation approximated zero-order kinetics for all fasting and food treatments.

Adult↗
PubMed1980

Verrucous carcinoma of the nasopharynx--a clinicopathologic case report.

The purpose of this case presentation is to alert the clinician and pathologist to the unique features of verrucous carcinoma. Although the nasopharynx is an unusual site for this tumor, the features inherent to verrucous carcinoma are apparent; a misleadingly benign histologic appearance which contrasts dramatically with the inexorable progressive destruction of normal structures. Secondary infection is common and should not be mistaken for a primary process. Diagnosis rests on dialogue between clinician and pathologist.

Aged↗
PubMed1976

Wound healing.

This paper briefly summarizes some aspects of wound healing with particular reference to: the healing of a simple skin incision as compared to that of a wound with separated edges; granulation tissue formation and the nature of myofibroblasts; wound contraction; and, finally, the structure and biosynthesis of collagen.

Collagen↗