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Biomedical subjects

F Hofman

Publications and source records attributed to F Hofman.

At least 19 recordsLinked to original sources
PubMed2001

Anti-inflammatory, antithrombotic, and neuroprotective effects of activated protein C in a murine model of focal ischemic stroke.

BACKGROUND: Activated protein C (APC) contributes to systemic anticoagulant and anti-inflammatory activities. APC may reduce organ damage by inhibiting thrombin generation and leukocyte activation. Neutrophils and cerebrovascular thrombosis contribute to ischemic neuronal injury, suggesting that APC may be a potential protective agent for stroke. METHODS AND RESULTS: We examined the effects of APC in a murine model of focal ischemia. After middle cerebral artery occlusion/reperfusion, the average survival time in controls was 13.6 hours. Animals that received purified human plasma-derived APC 2 mg/kg IV either 15 minutes before or 10 minutes after stroke induction survived 24 hours and were killed for neuropathological analysis. APC 2 mg/kg given before or after onset of ischemia restored cerebral blood flow, reduced brain infarct volume (59% to 69%; P:<0.003) and brain edema (50% to 61%; P:<0.05), eliminated brain infiltration with neutrophils, and reduced the number of fibrin-positive cerebral vessels by 57% (P:<0.05) and 25% (nonsignificant), respectively. The neuroprotective effect of APC was dose-dependent and associated with significant inhibition of ICAM-1 expression on ischemic cerebral blood vessels (eg, 61% inhibition with 2 mg/kg APC). Intracerebral bleeding was not observed with APC. CONCLUSIONS: APC exerts anti-inflammatory, antithrombotic, and neuroprotective effects in stroke. Central effects of APC are likely to be related to improved maintenance of the blood-brain barrier to neutrophils and to reduced microvascular obstructions and fibrin deposition.

Animals↗
PubMed1998

Human immunodeficiency virus Tat protein induces interleukin 6 mRNA expression in human brain endothelial cells via protein kinase C- and cAMP-dependent protein kinase pathways.

The intracellular signal transduction pathways utilized by the HIV-1-derived protein, Tat, in the activation of human central nervous system-derived endothelial cells (CNS-ECs) were examined using specific enzymatic assays. Tat induced an increase in interleukin 6 (IL-6) mRNA within 1 hr of treatment. This biological effect of Tat involved activation of both protein kinase C (PK-C) and cAMP-dependent protein kinase (PK-A) in CNS-ECs. Tat at 10 ng/ml induced a sharp, transient increase in membrane PK-C activity within 30 sec of incubation, and reached maximum levels at 2 min, declining to control values within 10 min. Tat also induced a sharp increase in intracellular cAMP levels and PK-A activity in these cells, with the PK-A activity reaching a maximum at 10 min and slowly declining to control values in 4 hr of incubation. Activation of PK-A was dependent on a Tat-induced increase in membrane PK-C activity as demonstrated by calphostin C (a PK-C inhibitor) abolishing this effect. Incubation of cells with the cyclooxygenase inhibitor indomethacin did not affect Tat-induced activation of PK-A, indicating that prostacyclins are not involved in this process. Tat-induced increase in IL-6 mRNA was abolished in the presence on PK-A inhibitor H-89, demonstrating that activation of PK-A is necessary and sufficient for the increase in IL-6 production by these cells. Both the Tat-induced increase in intracellular cAMP and IL-6 mRNA levels in CNS-ECs may play a role in altering the blood-brain barrier and thereby inducing pathology often observed in AIDS dementia.

Brain↗
PubMed1997

Nonspecific interstitial pneumonitis mimicking Pneumocystis carinii pneumonia.

Bronchoalveolar lavage (BAL) and transbronchial biopsies from 351 human immunodeficiency virus (HIV)-positive patients with presumed Pneumocystis pneumonia were analyzed to determine the spectrum and frequency of interstitial lung disease mimicking Pneumocystis pneumonia. Among 67 patients without Pneumocystis, nonspecific interstitial pneumonitis (NSIP) was the most common histologic diagnosis (n = 16). Tissue sections from patients with NSIP were tested by in situ hybridization for Epstein-Barr virus, cytomegalovirus (CMV), and HIV; sections were also tested with the polymerase chain reaction (PCR) for HIV env and gag protein DNA. In patients with NSIP, Epstein-Barr virus and CMV could not be detected by in situ hybridization; HIV nucleic acid was amplifiable with PCR in 10 of 15 formalin-fixed, paraffin-embedded tissue sections. Symptoms, physical findings, and blood gas values were similar in patients with NSIP and matched controls with Pneumocystis. Patients with NSIP presented earlier in the course of HIV, with higher weight, serum albumin levels, and CD4+ T-lymphocyte counts (492 +/- 828 cells/mm3 versus 57 +/- 60 cells/mm3), and more normal lactate dehydrogenase (LDH) levels (280 +/- 113 IU/L versus 432 +/- 141 IU/L; means +/- SD). Seven to 10 d later, improvement in blood gas values was of similar magnitude for the two groups. Only one other unequivocal, treatable infection was diagnosed only with transbronchial biopsy. These results indicate that NSIP may be the most common diagnosis mimicking Pneumocystis pneumonia in acquired immune deficiency syndrome (AIDS), and that NSIP may improve during empiric therapy.

AIDS-Related Opportunistic Infections↗
PubMed1995

Transgenic mice support replication of hepatitis delta virus RNA in multiple tissues, particularly in skeletal muscle.

Hepatitis delta virus (HDV) is hepatotropic and frequently causes fulminant hepatitis in both human and nonhuman primate hosts. To understand the molecular basis of HDV tissue tropism and the mechanism of pathogenesis, transgenic mice in which replication-competent HDV dimeric RNA is expressed under the control of either liver-specific or universal transcriptional promoters were developed. The expressed RNA replicated efficiently in the liver and several tissues of nonhepatic origin. Surprisingly, maximal replication of HDV RNA occurred in skeletal muscle and was almost 100-fold greater than in the liver. These findings suggest that the hepatotropism of HDV is most likely a receptor-mediated restriction and that muscle-specific factors may facilitate HDV RNA replication. No evidence of cytopathology was apparent in most of the tissues examined, including the liver, supporting the contention that hepatocellular disease is not mediated by direct cytopathological effects associated with HDV RNA replication and gene expression. However, mild muscle atrophy in some of the transgenic mice was noted. Delta antigen was detected in the nuclei of myocytes. Only the small form, not the large form, of delta antigen was detected, suggesting that the RNA editing event which causes the conversion of delta antigen did not occur in transgenic mice. Furthermore, the 0.8-kb antigenomic RNA species, which is postulated to be the mRNA for delta antigen, was not detected in mice. The preferential replication of HDV RNA in skeletal muscle suggests that HDV RNA replication can be facilitated by certain muscle-specific factors.

Actins↗
PubMed1993

Active specific immunotherapy of melanoma with allogeneic cell lysates. Rationale, results, and possible mechanisms of action.

Since 1985, we have conducted clinical trials with a therapeutic melanoma vaccine (melanoma theraccine). Mechanical lysates of two melanoma cell lines chosen for their complementary characteristics were combined with the adjuvant DETOX and injected subcutaneously on weeks 1, 2, 3, 4, and 6 for one or two courses and then monthly in patients with objective clinical responses. Of 106 patients, 20 had objective clinical regression of tumor masses, 5 with complete responses. The median duration of response was 21 months. Twelve patients lived at least 2 years, with a median survival of nearly 3 years. Two of them are free of disease for > 2 and > 6 years, respectively. However, it was not necessary to achieve complete remissions to cause an increase in survival, and most of the long-surviving patients have one or more (stable) residual nodules. The pace of the disease process was clearly slowed in those individuals. A rise in the level of cytotoxic T-lymphocyte precursors in the blood (pTC) correlated with clinical response. Only those patients who had a rise in pTC had a remission. In addition to "classical" CD8+ Tc, CD4+ Tc were cloned from the blood of immunized patients. Melanoma-specific Tc of both types that killed autologous melanoma but not matched lymphoblastoid cells were detected. Allogeneic melanoma cell lines were also killed, with mainly HLA-A2/28 and HLA-B12/44/45 degenerate restriction. CD4+ Tc were restricted by HLA Class I antigens, as judged by their killing of HLA Class II-negative melanomas and blocking by anti-class I antibodies. Other CD4+ clones were blocked by both anti-HLA Class I or anti-Class II MHC monoclonal antibodies, and only two were blocked only by anti-HLA Class II. Immunohistory revealed CD4+ and CD8+ T cells in lesions under rejection, but the predominant cells were macrophages, suggesting delayed-type hypersensitivity as a possible mechanism. Clinical responses were found most often in patients with HLA-A2/28, -B12/44/45, and -C3, particularly when two or more of those alleles were present. This may have been due either to (1) similarity of MHC antigens between one of the immunizing melanomas and the patient's melanoma or (2) the intrinsic importance of these MHC molecules in presenting melanoma-associated antigens to Tc in vivo. IFN-alpha 2 b salvaged 8 of 18 patients who failed with the theraccine, regardless of MHC phenotype, perhaps through upregulation of MHC and tumor epitopes on the autochthonous tumor.

Antibodies, Neoplasm↗
PubMed1991

Expression of adhesion molecules in leprosy lesions.

Leprosy presents as a clinical spectrum that is precisely paralleled by a spectrum of immunological reactivity. The disease provides a useful and accessible model, in this case in the skin, in which to study the dynamics of cellular immune responses to an infectious pathogen, including the role of adhesion molecules in those responses. In lesions characterized by strong delayed-type hypersensitivity against Mycobacterium leprae (tuberculoid, reversal reaction, and Mitsuda reaction), the overlying epidermis exhibited pronounced keratinocyte intracellular adhesion molecule 1 (ICAM-1) expression and contained lymphocytes expressing the ICAM-1 ligand, LFA-1. Conversely, in lesions in which delayed-type hypersensitivity was lacking (lepromatous), keratinocyte ICAM-1 expression was low and LFA-1+ lymphocytes were rare. Expression of these adhesion molecules on the cells within the dermal granulomas was equivalent throughout the spectrum of leprosy. The percentage of lymphocytes in these granulomas containing mRNA coding for gamma interferon and tumor necrosis factor alpha, synergistic regulators of ICAM-1 expression, paralleled epidermal ICAM-1 expression. In lesions of erythema nodosum leprosum, a reactional state of lepromatous leprosy thought to be due to immune complex deposition, keratinocyte ICAM-1 expression and gamma interferon mRNA+ cells were both prominent. Antibodies to LFA-1 and ICAM-1 blocked the response of both alpha beta and gamma delta T-cell clones in vitro to mycobacteria. Overall, the expression of adhesion molecules by immunocompetent epidermal cells, as well as the cytokines which regulate such expression, correlates with the outcome of the host response to infection.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Expression of Fc epsilon receptors and surface and cytoplasmic IgE on human fetal and adult lymphopoietic tissue.

The appearance during ontogeny of IgE-positive and Fc epsilon receptor (FcER)-bearing cells was studied. Monoclonal antibody to the constant region (Fc) of IgE (CIA-E-7.12) was used to detect cytoplasmic and surface IgE. A monoclonal antibody to the low-affinity Fc epsilon receptor (FcER-II = CD23) and immune complexes composed of human IgE and mouse monoclonal anti-human IgE Fc were used to detect FcER. Cryostat sections of human fetal tissues (liver, lung, spleen, and thymus) from 11 to 22 weeks gestation as well as adult tonsil tissues were examined for IgE, FcER, and other lymphoid markers by immunoperoxidase staining. Although both IgE- and FcER-positive cells were present in adult tissues, we found that, in contrast to an earlier report, such cells were not present in the fetal tissues examined. The in situ location of FcER on cells in human lymphoid tissues revealed that the FcER-bearing cells were localized predominantly in the germinal centers (mature B cell and macrophage areas) of the tonsil follicles with some staining in the mantle (resting and less mature B cell areas).

Adult↗
PubMed1984

Syntheses of spinal cord field potentials in the terrapin.

A compartmental model of a terrapin motoneuron has been set up to compute membrane potential variations associated with synaptic input at different locations or with antidromic invasion. Membrane potential distributions obtained in that way were used to compute field potentials by means of a volume conduction formalism. The model was used to simulate field potentials measured in the spinal cord in response to stimulation of a muscle nerve with the intention to discriminate between different activation hypothesis for the generation of the spinal cord potential. Extracellular potentials calculated with an excitatory input distributed over the whole dorsal dendritic tree were found to give better reconstruction when compared with excitation restricted to the distal part of the dorsal dendrites, or with somatic inhibition.

Animals↗
PubMed1984

Mycosis fungoides/Sezary's syndrome progressing to immunoblastic sarcoma. A T-cell lymphoproliferation with both helper and suppressor phenotypes.

Multiparameter studies of an unusual patient exhibiting cutaneous manifestations of both mycosis fungoides and Sezary's syndrome are presented. The neoplastic cells of dermal and nodal infiltrates and peripheral blood expressed both helper and suppressor immunologic phenotypes. Cytofluorographic analysis of cells isolated from lymph node and peripheral blood showed a population of neoplastic cells that were stained with the monoclonal antibodies OKT 3, 4, 8, and 11. Immunoperoxidase staining of frozen sections with monoclonal antibodies Leu 1, 2, and 3 provided a topographical identification of an identically marking population of cells in dermis and lymph node. In light of current models depicting normal T-cell lineage, the authors suggest that the neoplastic population in this patient, expressing both helper and suppressor phenotypes, reflected a phenotypic stage of immunologic maturation (OKT 6-, OKT 10-, OKT 3+, OKT 11+, OKT 4+, OKT 8+) in which the neoplastic cells had not yet segregated into distinctive T-cell subsets. While excess helper activity was suggested by serum hypergammaglobulinemia, in vitro helper and suppressor function was not determined. The range of studies employed illustrates the wide variety of technics required to adequately characterize complex clinico-immunopathologic disorders, as represented by this case, and the wealth of information that can be gleaned.

Antibodies, Monoclonal↗
PubMed1984

A cytotoxic monoclonal antibody detecting a novel B cell membrane antigen expressed predominantly on cells bearing surface membrane immunoglobulin.

A new human B lymphocyte membrane antigen, CB2, has been detected by a mouse monoclonal IgM antibody. CB2 appears to be predominantly expressed on normal and malignant cells expressing surface membrane immunoglobulin (SmIg). By indirect immunofluorescence, the number of CB2-positive cells in normal peripheral blood correlated well with the number of SmIg-positive cells. Cytotoxicity studies on isolated cell populations showed that CB2 was present on normal B cells isolated from the spleens of 52 donors and on peripheral blood B cells from 8 donors. Monocytes, T cells, granulocytes, platelets, and red cells were CB2 negative. Only malignant cells expressing SmIg were positive. These included B-CLL, B lymphoma, prolymphocytic leukemia, and B lymphoma cell lines Daudi, Raji, and Conception. SmIg-negative leukemia cells, such as common acute lymphoblastic leukemia, acute and chronic myelogenous leukemia, and T cell leukemias, were negative. Blocking studies with human immunoglobulin suggests that the CB2 antigen is not directed against immunoglobulin determinants. Immunoperoxidase studies on normal lymph node sections show that CB2-positive cells are predominantly present in the mantle region of the follicle, whereas B1-positive cells are mainly in the germinal center.

Animals↗
PubMed1981

Functional properties of subsets of T lymphocytes defined by specific antigens.

Heteroantisera raised to the acute lymphocytic T (ALL) cell line HSB2 and to Sézary cells react with distinct subpopulations of T lymphocytes. Each antiserum reacts with a different T cell antigen and defines a distinct subpopulation that represents approximately 50% of peripheral blood T lymphocytes. The anti-HSB2-positive subpopulation contained suppressor cells for pokeweed mitogen-dependent immunoglobin (Ig) synthesis whereas the anti-Sézary cell serum-positive population included helper cells for Ig synthesis and mixed lymphocyte responder cells.

Antigens↗
PubMed1976

Immunological potential of yolk sac cells.

Mouse yolk sac cells on day 9 of gestation were found to elicit a GVH response, measured by enlargement of the local popliteal lymph nodes. The response cannot be attributed to contaminating maternal cells, since F1 (Balb/c x C57B1) yolk sac cells did not cause a reaction in F1 (Balb/c x C57B1) hosts. On the other hand, yolk sac cells did not elicit a detectable MLC reaction, nor did they respond to PHA or Con A. Hence, mouse yolk sac cells have the potential to express a certain limited array of immunological reactivities, before the development of embryonic thymus and liver.

Animals↗