Biomedical subjects

D M Hockenbery

Publications and source records attributed to D M Hockenbery.

28 records · Page 2Linked to original sources

PubMed1995

Oral beclomethasone dipropionate for treatment of human intestinal graft-versus-host disease.

Intestinal graft-versus-host disease (GVHD) causes anorexia, vomiting, abdominal pain, and diarrhea. We investigated oral beclomethasone dipropionate (BDP), a potent, topically active corticosteroid, as therapy for this disease. Forty-two allogeneic marrow-graft recipients with biopsy-proven intestinal graft-versus-host disease of mild-to-moderate severity received BDP (8 mg daily) for up to 28 days. Weekly symptom scores, oral intake, and surveillance throat and stool cultures were compared with baseline values. Adrenal testing was performed serially in patients not receiving concurrent prednisone. Improvement was seen in appetite (P < 0.001), oral intake (P < 0.001), nausea (P = 0.013), and diarrhea (P = 0.02) over the course of therapy, and an overall beneficial response was observed in 72% of 40 evaluable patients. Surveillance cultures of throat and stool showed no increase in bacterial or fungal colonization over time. The adrenal axis became suppressed in 11 of 20 evaluable patients (55%) but suppression was not a prerequisite for clinical response, as 6 of 9 patients who retained normal adrenal function improved clinically. We conclude that oral BDP is a safe and effective treatment for mild-to-moderate intestinal graft-versus-host disease. Systemic absorption probably occurs, but adrenal suppression is not a prerequisite for clinical efficacy, suggesting that the biological effect is primarily topical. BDP should be further investigated as a topical therapy for intestinal GVHD.

Administration, Oral↗

PubMed1995

Primitive human hematopoietic precursors express Bcl-x but not Bcl-2.

Bcl-2 and its homologue, bcl-xL, encode membrane-associated proteins that suppress programmed cell death of hematopoietic cell lines after growth factor withdrawal, and are expressed in hematopoietic precursor cells. To better understand the maintenance of long-term survival in the hematopoietic stem cell population, we evaluated the expression patterns of Bcl-2 and Bcl-x in primitive hematopoietic precursor populations. Hematopoietic precursor cells expressing CD34 (CD34+) and lacking maturation-linked surface antigens (lin-) were isolated from adult human bone marrow using two-color immunofluorescence cell sorting and fractionated on the basis of forward light scatter characteristics into blast-sized and small to medium lymphocyte-sized cell populations. Bcl-2 expression was shown in 78% to 90% of CD34+ lin- blast-sized cells versus less than 10% of small to medium lymphocyte-sized CD34+ lin- cells by immunohistochemical analysis. Small to medium lymphocyte-sized CD34+ lin- cells were further enriched for primitive precursors by selecting cells that lacked expression of CD38 (CD34+ lin- CD38-). In parallel experiments, only 1% to 4% of CD34+ lin- CD38- cells expressed Bcl-2, whereas 45% to 56% of these cells generated colony-forming cells. In contrast, > or = 94% of cells in all bone marrow subpopulations studied expressed Bcl-x protein. Both alternatively spliced bcl-x transcripts, bcl-xL and bcl-xs, were present. Our data show that the most primitive hematopoietic precursors express Bcl-x but not Bcl-2. Thus, the functional bcl-2 homologue, bcl-xL, may be essential for the long-term survival of the hematopoietic stem cell population.

ADP-ribosyl Cyclase↗

PubMed1995

bcl-2, a novel regulator of cell death.

The bcl-2 gene product, a 25 kDa membrane protein residing at mitochondrial, microsomal and nuclear membrane sites within many cell types, is a broad and potent inhibitor of cell death by apoptosis. A family of bcl-2-related genes with death-inhibiting or -promoting actvities has recently been described, indicating a potentially quite complex cell death regulatory network at the level of gene expression and protein-protein interactions. The function of bcl-2 may be to regulate a final common pathway in apoptosis. Current hypotheses suggest that oxidative stress, specific proteolytic activity or cell cycle control may be common elements in apoptosis through which bcl-2 exerts its survival function. Based on the extent to which elements of apoptotic pathways overlap with non-apoptotic cellular functions, the physiological role of bcl-2 may also extend to other cellular processes such as differentiation and proliferation.

Amino Acid Sequence↗

PubMed1994

Dysregulated bcl-2 expression inhibits apoptosis but not differentiation of retinoic acid-induced HL-60 granulocytes.

The bcl-2-proto-oncogene appears to contribute to the development of certain malignancies by inhibiting programmed cell death (apoptosis). Mature granulocytes show a markedly limited life span and rapidly undergo apoptosis. To further define the relationship between apoptosis and granulocyte differentiation, we used retroviral vector-mediated gene transduction to introduce the normal bcl-2 gene into the HL-60 myeloid leukemia cell line and determined the response of these bcl-2-transduced HL-60 cells to the induction of granulocyte differentiation by retinoic acid (RA). Although the bcl-2-transduced HL-60 cells showed the same differentiative response to RA as did the parental HL-60 cells, the life span of the RA-induced, bcl-2-transduced HL-60 granulocytes was markedly prolonged compared with that of the RA-induced parental HL-60 granulocytes. DNA fragmentation studies indicate that this prolonged life span resulted from diminished apoptosis in the bcl-2-transduced cells. These studies indicate that bcl-2 is involved in regulating apoptosis in maturing granulocytes. Because bcl-2 over-expression did not interfere with RA-induced granulocyte differentiation, it appears that granulocyte differentiation and apoptosis are under distinct and separate regulatory controls.

Apoptosis↗

PubMed1994

bcl-2 in cancer, development and apoptosis.

The bcl-2 gene provides a window on the basic cellular machinery of apoptosis or programmed cell death, a process involved in virtually all biologic events in multicellular organisms, but particularly relevant to neoplasia and development. bcl-2 gene function supports cell survival and appears to lie at a nodal point in pathways leading to activation or execution of apoptosis. Carcinogenesis may involve several steps at which cell death programs are normally activated and are bypassed in cancer cells, including apoptotic pathways activated by several oncogenes. Functional redundancy and the complexity of the regulation of cell survival are demonstrated by the less than expected phenotype of bcl-2 knockout mice and the cloning of several bcl-2 related genes, some of which promote cell death. The molecular function for bcl-2 is unknown, but several lines of evidence support a role in protection from oxidative stress. These studies suggest that many environmental perturbations and genetic pathways converge to disrupt a metabolic balance between oxidant generation and anti-oxidant defenses.

Amino Acid Sequence↗

PubMed1993

Bcl-2 functions in an antioxidant pathway to prevent apoptosis.

Bcl-2 inhibits most types of apoptotic cell death, implying a common mechanism of lethality. Bcl-2 is localized to intracellular sites of oxygen free radical generation including mitochondria, endoplasmic reticula, and nuclear membranes. Antioxidants that scavenge peroxides, N-acetylcysteine and glutathione peroxidase, countered apoptotic death, while manganese superoxide dismutase did not. Bcl-2 protected cells from H2O2- and menadione-induced oxidative deaths. Bcl-2 did not prevent the cyanide-resistant oxidative burst generated by menadione. Two model systems of apoptosis showed no increment in cyanide-resistant respiration, and generation of endogenous peroxides continued at an inherent rate that was unaltered by Bcl-2. Following an apoptotic signal, cells sustained progressive lipid peroxidation. Overexpression of Bcl-2 functioned to suppress lipid peroxidation completely. We propose a model in which Bcl-2 regulates an antioxidant pathway at sites of free radical generation.

Acetylcysteine↗

PubMed1992

Pericrypt eosinophilic enterocolitis and chronic diarrhea.

An unusual pattern of eosinophilic infiltration around intestinal crypts was detected in mucosal biopsy specimens of 10 patients with chronic diarrhea, half of whom had evidence of systemic connective tissue disease. The median duration of symptoms was 11 months, and no other explanation for diarrhea could be determined in any case. The cellular infiltrate on biopsy specimens was present deep in the mucosa of small and large intestinal specimens, separating crypt bases from the muscularis mucosae and penetrating the latter. Consistent with the microscopic findings, surface mucosal appearance by endoscopy was uniformly normal. These histological features of colonic biopsy specimens were statistically differentiated from those of asymptomatic subjects (n = 8), subjects with diarrhea-predominant irritable bowel syndrome (n = 6), and subjects with collagenous colitis (n = 7) or lymphocytic colitis (n = 5). Diarrhea improved in five of seven subjects treated with oral prednisone or prednisone in conjunction with azathioprine (median follow-up period, 2.2 years). Histological changes on subsequent biopsy specimens correlated closely with symptomatic status. These findings strongly suggest that chronic diarrhea is related to this pericrypt eosinophilic enterocolitis, a pathological lesion often associated with features of systemic connective tissue disease. The disorder appears responsive to corticosteroid therapy in some cases.

Adrenal Cortex Hormones↗

PubMed1992

The bcl-2 oncogene and apoptosis.

The bcl-2 oncogene is activated as a consequence of the t(14;18) chromosomal translocation in human follicular lymphomas. Bcl-2 functions to inhibit apoptosis in a variety of in vitro and in vivo experiments, suggesting interference with a central mechanism of apoptosis. The bcl-2 protein is associated with the inner mitochondrial membrane, however, the biochemical function of bcl-2 is unknown. Transgenic mice which overexpress bcl-2 provide evidence for bcl-2's role in memory B cells and thymic education as an intracellular survival factor. Additional regulators of apoptosis, such as the p53 tumor suppressor gene, may be altered in human cancers as one step in tumorigenesis.

Animals↗

PubMed1991

BCL2 protein is topographically restricted in tissues characterized by apoptotic cell death.

The BCL2 protooncogene encodes an inner mitochondrial membrane protein that blocks programmed cell death. BCL2 was isolated from the chromosomal breakpoint of follicular B-cell lymphoma. Transgenic mice that overexpress BCL2 display extended survival of resting B cells. In this study we use a monospecific anti-human BCL2 antibody to define the distribution of BCL2 protein within organized tissues. BCL2 is restricted within germinal centers to the follicular mantle and to portions of the light zone implicated in the selection and maintenance of plasma cells and memory B cells. BCL2 is present in the surviving T cells in the thymic medulla. All hematopoietic lineages that derive from a renewing stem cell also display BCL2. A limited number of nonlymphoid tissues demonstrate BCL2 and can be grouped as (i) glandular epithelium in which hormones or growth factors regulate hyperplasia and involution, (ii) complex differentiating epithelium such as skin and intestine characterized by long-lived stem cells, and (iii) long-lived postmitotic cells such as neurons. Within these tissues that demonstrate apoptotic cell turnover, BCL2 is often topographically restricted to long-lived or proliferating cell zones. BCL2's function as an antidote to apoptosis may confer longevity to progenitor and effector cells in these tissues.

Adult↗

PubMed1978

Competitive inhibition of benzodiazepine binding by fractions from porcine brain.

Fractions of porcine cerebral cortex extract separated by molecular weight on a Sephadex G-75 column were tested for their activities and potencies to inhibit [3H]benzodiazepine binding to rat brain homogenates. The fractions spanned molecular weights from 500 to 100,000. A potent inhibitor (benzodiazepine-competitive factor I, BCF-I) was discovered in the fraction containing substances with molecular weights from 40,000 to 70,000. Equilibrium binding studies indicated that BCF-I was a competitive inhibitor, making it a candidate as a benzodiazepine endogenous factor or profactor. BCF-I was heat stable, but trypsin digestion destroyed its activity. Another inhibitory fraction (BCF-II) was 1/5th as active as BCF-I and contained substances with molecular weights from 1000 to 2000.

Animals↗