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B S Stein

Publications and source records attributed to B S Stein.

At least 19 recordsLinked to original sources
PubMed1992

Degradation of CD4 following phorbol-induced internalization in human T lymphocytes. Evidence for distinct endocytic routing of CD4 and CD3.

Exposure of T lymphocytes to phorbol esters induces endocytosis of CD4 and the CD3/T-cell receptor complex. We compared the pathway of CD4 internalization to that of CD3 following activation of human T lymphocytes with phorbol 12,13-dibutyrate (PDBu). Both CD3 and CD4 were rapidly internalized in response to PDBu, but only CD3, and not CD4, was recycled to the cell surface after removal of PDBu. In support of a degradative fate for internalized CD4, radioimmuno-precipitation studies revealed that the total amount of cellular CD4 was reduced by greater than 90% after exposure to PDBu for 4 h, whereas total CD3 remained constant. PDBu induced CD4 capping and localization consistent with sequestration in intracellular vesicles, presumably lysosomes, prior to becoming degraded. Lysosomotropic agents, such as NH4Cl, chloroquine, and monensin inhibited CD4 degradation, consistent with a lysosomal fate for CD4. Internalization and degradation of CD4 was blocked by staurosporine, an inhibitor of protein kinase C suggestive of a role for protein kinase C in the endocytic fate of CD4. The results of this study demonstrate that CD3 and CD4 follow distinct endocytic pathways which may be relevant to their having distinct roles in T cell activation and function.

Alkaloids↗
PubMed1992

Superficial bladder cancer.

The majority of patients with bladder cancer have superficial disease. Occupational exposure to metabolites of aniline dyes and other aromatic amines has been associated with the development of bladder cancer. Latency periods can reach 50 years. Cigarette smoking has also been strongly linked to bladder cancer as an etiologic factor. The diagnosis of superficial bladder cancer can be elusive because its symptoms mimic those of other common urologic conditions such as urinary tract infection and prostatism. A high index of suspicion is required and a search for bladder cancer should be initiated in any adult (especially those over 50 years of age) who exhibits asymptomatic gross or microscopic hematuria, or irritative voiding symptoms. Cystoscopy is required for the screening and diagnosis of superficial bladder cancer, and resection of the lesion can be performed cystoscopically as well. Laser ablation of superficial lesions provides a treatment alternative that is less invasive and better tolerated by the patient, but it does not yield a tissue specimen for analysis. Urinary cytology has been invaluable in the screening, diagnosis, and follow-up of superficial bladder cancer patients, and now flow cytometry and image analysis techniques can complement it and may eventually supplant it. The key to the management of superficial bladder cancer is to identify those patients that may be at risk for recurrence and, more importantly, those who may progress to invasive or metastatic disease. Fortunately, most superficial bladder cancer remains superficial, and the overall prognosis is good, with 5-year survival rates for superficial disease of approximately 75%. As the natural history of superficial bladder cancer has become more evident through extensive research, risk factors such as tumor size, multiplicity, grade, depth of invasion, and condition of the surrounding mucosa have emerged. T1 lesions, those that invade the lamina propria, have a more ominous course than T0 and TA lesions. The mainstay of treatment for superficial disease is transurethral resection of the lesion or lesions. Intravesical therapy has been shown to have a definite effect in eradicating existing disease as well as reducing recurrences, but it has not been shown to prevent invasive disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Carcinoma, Transitional Cell↗
PubMed1991

Early activation events render T cells susceptible to HIV-1-induced syncytia formation. Role of protein kinase C.

In human immunodeficiency virus-1 (HIV-1)-infected cell cultures, cell-to-cell fusion and the formation of multinucleated giant cells (syncytia) are induced as a consequence of interactions between the viral envelope glycoprotein on infected cells and cell surface CD4 molecules on uninfected cells. Although activated CD4+ T cells rapidly form syncytia when cultured with HIV-1 envelope glycoprotein expressing (env+) cells, freshly isolated, unstimulated CD4+ T cells do so more slowly. In these studies, we sought to explore the role of T cell activation in rendering CD4+ T cells susceptible to HIV-1-mediated syncytia formation. Our results indicate that within 2 h of exposure to immunologic stimuli, CD4+ T cells acquire the ability to form syncytia with HIV-1 env+ cells. Both cholera toxin, an inhibitor of protein kinase C (PKC) through its effects on inositol triphosphate and diacylglycerol production, and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride, a noncompetitive inhibitor (with respect to ATP) of PKC, prevented unstimulated but not previously stimulated CD4+ T cells from forming syncytia with HIV-1 env+ cells. 1-Oleoyl-2-acetyl glycerol, an analog of the PKC activator, diacylglycerol, enhanced syncytia formation whereas ionomycin, a calcium ionophore, had no effect. These results suggest that activation of PKC is essential for previously unstimulated CD4+ T cells to become fusogenic.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Mechanism of HIV-1 entry into CD4+ T cells.

Although the mechanism responsible for HIV-1 entry into susceptible CD4+ T cells is incompletely understood, a number of key components are now known. For example, the tropism of HIV-1 for cells expressing the CD4 membrane glycoprotein reflects the use of this protein as a specific viral receptor to which the HIV-1 gp120 envelope protein binds with high affinity. This binding apparently results in the exposure of hydrophobic domains of the gp41 transmembrane protein to apposing plasma membrane components, resulting in the fusion of viral and plasma membranes to one another which, in turn, releases HIV-1 RNA into the cytosol. This fusion event, which is requisite for viral entry as well as HIV-1 associated syncytia formation, occurs in a pH-independent fashion, but requires antecedent T cell activation. In the absence of T cell stimuli, resting CD4+ cells are resistant to HIV-1 entry, which may explain the observation that at any given time the vast majority of CD4+ T cells in HIV-1 seropositive patients are not infected despite the presence of relatively large quantities of free virus in the blood of such patients. The mechanism of HIV-1 entry into other CD4+ cell types, such as macrophages and dendritic cells, remains to be determined.

CD4-Positive T-Lymphocytes↗
PubMed1990

Chordoma in a cat.

A chordoma within the deep musculature adjacent to C3 and C4 was excised from a 14-year-old castrated domestic cat. Metastatic chordoma developed in a prescapular lymph node 10 months later. At necropsy 11 months after complete excision of the primary tumor, metastases were found in both retropharyngeal lymph nodes.

Animals↗
PubMed1990

Intracellular processing of the gp160 HIV-1 envelope precursor. Endoproteolytic cleavage occurs in a cis or medial compartment of the Golgi complex.

The intracellular processing of the gp160 HIV-1 envelope precursor was characterized in acutely infected CD4+ T cells. Our data show that gp160 undergoes endoproteolytic cleavage by a nonacid dependent protease(s) in the rough endoplasmic reticulum-Golgi complex, within cis or medial cisternae, and is not transported to the cell surface. Two-dimensional electrophoretic pulse-chase analysis indicates that it takes greater than 2 h for gp160 to be transported from the rough endoplasmic reticulum to the site of action of sialyltransferases in the trans Golgi. Evidence is presented that gp160 is subject to mannose trimming in the Golgi complex, which is inhibited by 1-deoxymannojirimycin (a specific Golgi alpha-mannosidase I inhibitor). Preliminary data also suggest that gp120 is post-translationally modified by sialylated O-linked oligosaccharides.

Cell Line↗
PubMed1989

Identification of protein intermediates in the processing of the p55 HIV-1 gag precursor in cells infected with recombinant vaccinia virus.

We have used a recombinant vaccinia virus (VV) which expresses high levels of human immunodeficiency virus-1 (HIV-1) gag proteins to analyze the processing pathway of the gag p55 precursor. HIV-1 gag proteins were isolated from [3H]leucine-labeled VV:gag-infected H9 T lymphocytes by immunoprecipitation with either anti-p24, anti-p17, or anti-p6 antibodies. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that processing of the p55 precursor involves three major intermediates (p41a, p41b, and p39). The p41a and p39 proteins contain the p17 and p24 protein segments, and the p41b is comprised of p24 and p15 segments. On two-dimensional gels, each intermediate as well as the mature p24 and p17 proteins migrated as distinct species. [3H]Myristic acid labeling of the HIV-1 gag proteins revealed that in addition to p55 and p17, the p41a and p39 intermediates, but not p41b, are myristylated, confirming that myristylation occurs at the NH2 terminus before cleavage of the p55 precursor protein. We conclude that the myristylated HIV-1 gag p55 precursor is initially cleaved at random either at the p17/p24 junction or at two sites between p24 and p15 proteins, resulting in three intermediates (p41a, p41b, and p39) which are subsequently cleaved to yield mature gag proteins.

Antigens, Viral↗
PubMed1989

Evidence that T cell activation is required for HIV-1 entry in CD4+ lymphocytes.

The relationship of T cell activation to HIV entry and generation of viral DNA intermediates was studied in freshly isolated CD4+ T lymphocytes. Unstimulated cells exposed to infectious virus for up to 48 h did not synthesize any detectable unintegrated HIV DNA duplex forms or integrated genomic provirus. However, activation of these cells with either PHA or OKT3 (anti-CD3) mAb before viral exposure resulted in the generation of unintegrated HIV DNA after 6 h and integrated copies after 24 h. Cell-to-cell fusion studies showed significantly attenuated fusion between freshly isolated resting T cells and T cells constitutively expressing high levels of HIV envelope glycoprotein (HXB/gpt) compared with T cells first stimulated with either PHA or OKT3 mAb. The baseline fusion observed with resting T cells is believed to be a consequence of allogeneic stimulation by the HXB/gpt cell line. These results provide evidence that HIV entry and HIV envelope-dependent cell-to-cell fusion require T cell activation.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Expression and processing of human immunodeficiency virus type 1 gag and pol genes by cells infected with a recombinant vaccinia virus.

Human cells infected with a recombinant vaccinia virus containing human immunodeficiency virus type 1 gag-pol genes produced large amounts of human immunodeficiency virus gag proteins beginning at 1 h and peaking at 48 h postinfection. We show that these polyproteins are processed accurately into mature forms and that the viral polymerase gene is encoded as a 160-kilodalton gag-pol fusion protein, most likely by translational frameshifting from the gag into the pol reading frame.

Cells, Cultured↗
PubMed1989

Advances in the diagnosis and treatment of bladder cancer.

There have been major advances in the diagnosis and treatment of bladder cancer in the last several years. Flexible cystoscopy and DNA analysis have combined to increase both comfort for the patient and detection rates of early disease. The laser has become an established alternative to transurethral resection of superficial tumors, providing identical cure rates, but with more comfort and less expense. Intravesical installation of BCG has become not only an alternative treatment for recurrent superficial bladder cancer, but the first line of treatment for diffuse carcinoma in situ of the bladder which previously had been best treated with radical cystectomy. There are now numerous alternatives to the ileal conduit, when radical cystectomy is the preferred treatment. Herein we describe the "Providence Pouch," our own variation on the theme. Lastly, metastatic disease, once universally fatal, is now responding to a new combination of chemotherapy agents based on a combination of cisplatinum and methotrexate.

Adult↗
PubMed1986

Age-related changes in tissue levels of prostatic acid phosphatase and prostate specific antigen.

Immunoperoxidase localization of prostatic tissue antigens has become useful in identifying the prostate as the origin of metastatic disease. Much research has been aimed at investigating the presence of these antigens in the adult prostate gland in benign and neoplastic states. Few studies have been done to determine the presence of these markers before puberty. We studied the prostate gland of 42 children of varying ages to determine the presence of these antigens at all age ranges to puberty. Sequential sections of the prostate were cut for prostate specific antigen, prostatic acid phosphatase, and hematoxylin and eosin staining. The degree of immunoperoxidase stain was graded from 0 to 4. The results showed that staining levels of prostate specific antigen and prostatic acid phosphatase were high at birth, decreased by age 6 months, reappeared by age 10 years and increased to puberty. Thus, the levels of prostate specific antigen and prostatic acid phosphatase appear to follow the testosterone levels, suggesting a hormonal dependence.

Acid Phosphatase↗