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Biomedical subjects

J A Falk

Publications and source records attributed to J A Falk.

At least 19 recordsLinked to original sources
PubMed2001

Management strategies and financial performance in rural and urban hospitals.

This study identifies the difference in financial performance between rural and urban hospitals and examines whether or not that difference may be attributed to the emphasis of revenue enhancement over cost management strategies. Hospitals in Virginia were included in this study except for the two state university medical centers. Rural and urban hospitals were compared on 10 performance indicators grouped into four categories: revenues, costs, profits, and productivity. The results suggest that rural hospital profitability is dependent on cost management. Since rural hospitals achieved lower cost, better efficiency and productivity level than urban hospitals in Virginia, they demonstrate a significant higher level of profit.

Analysis of Variance↗
PubMed1988

Inhibition of pokeweed mitogen-induced Ig secretion by IgG monoclonal antibodies to MHC class I and class II molecules requires binding of the intact antibody.

Seven purified IgG monoclonal antibodies reactive with different epitopes on DQw1, DR, HLA-A3 or p85 glycoprotein of human lymphocytes have each been shown to inhibit pokeweed mitogen (PWM)-induced IgG and IgM secretion in a dose-dependent manner. Binding of these antibodies to their target antigens was required for the suppression. Antibodies of IgG1, IgG2 alpha, and IgG2b subclasses were able to inhibit both IgG and IgM secretion in the PWM system. The mechanisms by which two of the monoclonal antibodies (MoAbs)-77.34, specific for the class II antigen DQw1, and GAP A3, specific for the class I antigen HLA-A3-caused inhibition--were analyzed. The suppressive effects of 77.34 and GAP A3 were maximal when added at the initiation of the culture period. No inhibition of IL-2 production or cellular proliferation was detected. Supernatants obtained from inhibited cultures were not themselves suppressive. The F(ab')2 fragments of either 77.34 or GAP A3 failed to influence PWM-Ig secretion, indicating that intact IgG molecules were required. This suggests that the observed inhibition might be mediated via Fc receptors. Together F(ab')2 fragments of either 77.34 or GAP A3 and a control IgG2a protein did not reconstitute the inhibitory effects of intact 77.34 or GAP A3. Suppression, therefore, required intact Fc portions on the same IgG molecules as those that bound to DQw1 or HLA-A3. These studies suggest that populations of IgG molecules that crosslink sufficient numbers of Fc receptors with other cell surface antigens on peripheral blood mononuclear cells (PBMs) during the early stages of B-cell activation can inhibit Ig secretion. Crosslinking of B-cell Fc receptors with SIg has been proposed by others to act as a negative signal for Ig production; our data raise the possibility that crosslinking of FcR with B-cell plasma membrane components other than SIg can also suppress Ig secretion.

Adult↗
PubMed1988

The peripheral nerve allograft: a dose-response curve in the rat immunosuppressed with cyclosporin A.

The potential use of peripheral nerve allografts would significantly improve the reconstructive potential for patients with major peripheral nerve deficits. This study evaluated the response of the nerve allograft recipient treated with varying dosages of cyclosporin A (CsA) to determine the minimal effective dosage necessary to prevent nerve graft rejection. Lewis rats (RT1l) were the recipients of syngeneic nerve grafts from identical Lewis donors or allogeneic nerve grafts from ACI (RT1a) donors. Nerve grafts were inlaid next to the intact sciatic nerve of the recipient. The immunologic responsiveness of the recipient animal's lymphocytes to a donor-specific antigenic challenge was assessed by the mixed lymphocyte reaction (MLR). In addition, nerve grafts were evaluated histologically. Animals were monitored for cyclosporin A toxicity. It was found that cyclosporin A (5 mg/kg per day) was effective in rendering the recipient animals unresponsive by mixed lymphocyte reaction at 10, 20, and 40 days after engraftment. This dosage was similarly effective in preventing histologic changes characteristic of nerve allograft rejection. This dosage regimen was nontoxic to the animals. Our study ascertained a minimal nontoxic dosage of cyclosporin A that effectively prevented nerve allograft rejection across a major histocompatibility disparity in rats.

Animals↗
PubMed1988

The peripheral nerve allograft: an assessment of regeneration across nerve allografts in rats immunosuppressed with cyclosporin A.

Lewis rats (RT1(1] were the recipients of 3-cm nerve grafts from syngeneic Lewis donors or allogeneic ACI (RT1a) donors. Microneurosurgical repair of the nerve graft to the transected sciatic nerve of the recipient animal was performed with 10-0 epineurial sutures. Recipients were randomly allocated to cyclosporin A (CsA) immunosuppressed or untreated groups. Cyclosporin A was administered in the minimal effective dosage to prevent nerve allograft rejection across this major histocompatibility disparity (5 mg/kg per day). Nerve regeneration across the nerve grafts was assessed by sciatic function index (SFI) and toe spread index (TSI) determinations serially and by electrophysiologic, histologic, and morphologic assessments 14 weeks after engraftment. Sciatic nerve regeneration across allogeneic nerve grafts in cyclosporin A immunosuppressed recipients was significantly superior compared to the untreated controls (p less than 0.008) and not significantly different from that across the syngeneic control animals.

Animals↗
PubMed1987

Major histocompatibility complex (MHC) restricted antigen recognition: high frequency of human T-cell clones recognizing novel MHC class II determinants.

We have used antigen-specific human T-cell clones to study the relationship between MHC and antigen recognition specificities expressed by T cells. Tetanus toxoid (TT)-specific T-lymphocyte clones were derived from a immunized HLA-DR2,7 heterozygous donor by limiting dilution from peripheral blood mononuclear cells (PBM) restimulated with TT in vitro. Clones were screened for MHC-restricted antigen recognition against antigen-presenting cells (APC) from a panel of HLA-typed donors, using an in vitro T-cell proliferation assay. Several distinct patterns of antigen recognition were identified. In addition to T cells that recognized TT in association with donor class II MHC antigens, we found clones that simultaneously expressed self-restricted antigen recognition and alloreactivity, and clones with specificity for antigen in the context of MHC antigens not expressed by the T-cell donor. This was confirmed in inhibition studies using well-characterized monoclonal antibodies against class II MHC antigens to block specific proliferative responses. We propose a possible structure for the determinant recognized by two of the clones. These results suggest that the T-cell antigen receptor undergoes random or antigen-dependent changes in vitro, and that this may be a mechanism for somatic diversification of the T-cell repertoire.

Antibodies, Monoclonal↗
PubMed1987

16, 16 Dimethyl prostaglandin E2 prevents the development of fulminant hepatitis and blocks the induction of monocyte/macrophage procoagulant activity after murine hepatitis virus strain 3 infection.

16, 16 Dimethyl prostaglandin E2 (dmPGE2), a known cytoprotective agent, was examined for its ability to alter the course of fulminant hepatitis in an experimental model of fulminant viral hepatitis, murine hepatitis murine hepatitis type 3 (MHV-3). Fully susceptible BALB/cJ mice, infected with 100 50% lethal doses (LD50) of MHV-3 developed histologic and biochemical evidence of fulminant hepatitis, as evidenced by massive hepatic necrosis with hypoglycemia, metabolic acidosis, and a markedly elevated serum alanine aminotransferase (ALT) (mean, 1,402 +/- 619 IU/liter). In contrast, animals treated with dmPGE2 either before or after infection (up to 48 h) demonstrated a marked reduction in both histologic and biochemical evidence of liver damage as characterized by normal blood glucose, total CO2, and ALT determinations (mean ALT, 63 +/- 40 IU/liter). Treatment of infected mice with PGF2 alpha demonstrated no cytoprotective effects. High titers of infectious virus were recovered from the livers of both dmPGE2-treated and -untreated animals throughout the course of infection. In a parallel in vitro study, dmPGE2 (10(-4)-10(-8) M) demonstrated a similar cytoprotective effect on monolayers of isolated cultured hepatocytes from fully susceptible BALB/cJ mice infected at a multiplicity of infection of 0.1, 1.0, and 10.0. In addition, splenic macrophages recovered from infected and untreated BALB/cJ mice demonstrated a marked augmentation in procoagulant activity (PCA) from a basal 10 +/- 5 mU/10(6) splenic macrophages to a maximum of 615 +/- 102 mU/10(6) splenic macrophages, whereas no increase in macrophage PCA was detected in infected animals treated with dmPGE2. These results suggest that dmPGE2, without detectably altering viral replication or infectivity in vivo, confers a marked cytoprotective effect on hepatocytes both in vivo and in vitro, and prevents the induction of macrophage PCA in vivo in fully susceptible BALB/cJ mice after murine hepatitis virus type 3 infection.

16,16-Dimethylprostaglandin E2↗
PubMed1986

Comparison of the N-linked glycopeptides of DQw1 and DR1 molecules.

HLA class II molecules have been isolated from a [3H]mannose-labeled GM3104 B lymphoblastoid cell line with the phenotype DQw1, DR1. The DQw1 molecules were purified by affinity to 77-34 IgG specifically reactive with the DQw1 specificity. The DR1 molecules were separated into two subsets, DR1a (70 to 80%) and DR1b (20 to 30%), by sequential affinity to 21r5-IgG and 21w4-IgG Sepharose. The alpha- and beta-chains of [3H]mannose-labeled DQw1, DR1a, and DR1b molecules were separated by SDS-PAGE and were recovered by electrophoretic elution. The isolated chains were digested with pronase and the glycopeptides were fractionated by sequential lectin chromatography on immobilized concanavalin A (Con A), Lens culinaris (Lens), and Ricinus communis agglutinin type I (RCA). The N-linked glycopeptides derived from the alpha-chains of DQw1, DR1a, or DR1b showed similar profiles on Con A Sepharose: 45% unbound (ConA I), 25% weakly bound (ConA II), and 30% tightly bound (ConA III). The glycopeptides derived from the beta-chains of DQw1 or DR1 molecules were found almost exclusively (80%) in the fraction unbound to Con A Sepharose, with only 11% and 9% in ConA II and ConA III fractions, respectively. The observation that most of the binding to Con A is associated with the alpha-chain glycopeptides suggests that binding of membrane-associated class II molecules to that lectin must be mediated by the alpha-chains. Binding to Lens Sepharose was higher for beta-(50%) than for alpha-(15%) chain glycopeptides, suggesting that within the intact glycoproteins, the beta-chains are responsible for the interaction with Lens. The ConA I fractions derived from the alpha-chain glycopeptides of either DQw1 or DR1 molecules were separated on RCA-agarose as follows: 60% unbound, 17% retarded, and 20% bound and eluted with 0.1 M galactose. The ConA I fractions derived from the beta-chain glycopeptides of either subset of class II molecules also had a similar profile on RCA-agarose: 70% unbound, 16% retarded, and 10% bound and eluted specifically. After removal of sialic acid residues, all of the ConA I fractions of alpha- and beta-chains bound to RCA-agarose. A high degree of similarity was observed between the corresponding glycopeptides of the three subsets of class II molecules and between the complex N-linked structures of alpha- and beta-chains. Minor variations were observed between DR1a and DR1b glycopeptides which appear greater than those observed between DR1 and DQw1 glycopeptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗
PubMed1986

Combination therapy for resectable and unresectable adenocarcinoma of the pancreas.

The current report summarizes our experience with 77 patients with cancer of the pancreas treated over 3.5 years. Patients were not assigned to a definite group of therapy, but through the availability of different drugs and different types of treatment several comparable groups have evolved. All patients have received radiofrequency hyperthermia and chemotherapy, but in addition, some have received selective immune stimulation with one of two low-molecular-weight compounds. The data show that radiofrequency hyperthermia permits the use of a lower dose of chemotherapy, with an apparent response to treatment. This response is enhanced significantly by the addition of selective immune stimulation. A further, more rigorously defined study will be undertaken to confirm this data.

Adenocarcinoma↗
PubMed1986

Allogeneic hepatocyte transplantation in the rat spleen under cyclosporine immunosuppression.

An innovative approach for stimulating the rapid growth of allogeneic hepatocytes implanted into splenic tissue with maintenance of the structural integrity is described. Single cell suspensions of hepatocytes from normal male ACI-strain rats (RTIa) were injected (2 X 10(6) cells) into the spleen of allogeneic male Fischer (RTI1) recipient rats. A 70% partial hepatectomy (PH) was performed at the same time as hepatocyte transplantation. Animals were treated for 4 days prior to, and 1 day after, transplantation with a feeding regimen containing 0.05% 2-acetylaminofluorene (AAF) to inhibit regeneration of the residual host liver. Animals received cyclosporine (CsA) 3 mg/kg/day s.c. posttransplantation. Histological examination of a standard longitudinal section of the recipient spleen two days posttransplant revealed an approximately 0.54-mm2 area replaced by hepatocytes. By 7 days this had increased to 0.97 +/- .15 mm2. Without CsA administration, hepatocytes were undetected at 7 days. Both PH and AAF treatment were necessary for successful colonization and sustained proliferation. Withdrawal of CsA treatment at 10 days after transplantation resulted in rapid rejection of established hepatocytes. This study demonstrates that rapid colonization of the rat spleen with allogeneic hepatocytes can be achieved, and that the viability and structural integrity of these transplanted cells can be maintained for at least 14 days using cyclosporine immunosuppression.

2-Acetylaminofluorene↗
PubMed1986

Analysis of HLA B27 in ankylosing spondylitis with human alloreactive cytolytic T lymphocyte clones: failure to detect disease-related T cell epitopes.

We have generated several human alloreactive cytolytic T lymphocyte (CTL) clones specific for HLA B27 expressed on cells of normals or of patients with ankylosing spondylitis (AS). These clonal T cell reagents were used to test the recognition of panels of target cells from B27+AS+, B27+AS- and B27- individuals. None of these CTL clones distinguished differences between B27+AS+ and B27+AS- cells. Three clones recognized subtypes of HLA B27 and two of these were cytolytic with group-reactive epitopes of other HLA antigens. The results suggest that there are no immunogenic disease-specific epitopes of HLA B27 in B27-linked spondyloarthropathy.

Clone Cells↗
PubMed1985

Hyperthermia for cancer: a practical perspective.

A causal relationship between hyperpyrexia and tumor regression was first suggested in 1866, when Busch reported the cure of a histologically diagnosed sarcoma in a middle-aged woman, following a bout of erysipelas. Over the years, interest in the effect of heat on cancer has remained alive, but this interest has increased dramatically in recent years. The literature on this subject is broadly reviewed and the clinical results discussed. It is apparent from clinical studies thus far that it is a relatively simple undertaking to treat superficial neoplasms with hyperthermia. However, the major challenges in clinical thermotherapy pertain to patients with deeply situated tumors. The lack of safe and reliable methods of monitoring temperature in deep tissues is a major impediment to a thorough understanding of thermal dosimetry in clinical hyperthermia, and routine thermal dosimetry in clinical hyperthermia will have to await the development of reliable noninvasive thermometry. As responses have been reported with modest levels of hyperthermia, the need for thermometry is somewhat lessened, given that invasive monitoring is imperfect and somewhat risky when used in deeply seated tumours. The eventual place of thermotherapy in the treatment of malignant tumours in man is as yet unclear and must be rigourously and thoroughly assessed in well-designed, prospective, randomized patient trials.

Animals↗
PubMed1985

Enhanced survival in antibiotic-treated murine fecal peritonitis by administration of copovithane, a selective immunostimulative polymer.

The purpose of this study was to determine the effect of an immunostimulative polymer, Copovithane (Cpv), plus antibiotics (netilmicin and clindamycin) in a murine model of fecal peritonitis. Cpv augments humoral immunity with little effect on T cells and is nontoxic. Cpv 100 mg/kg iv administered at the onset of sepsis increased median survival time (MST) by 40-55% over untreated controls. Four experiments were performed. Cpv in combination with antibiotics when given at the time of onset of sepsis was significantly more effective than antibiotics alone (MST 235 vs 105 hr, P less than 0.05 at 144, 168, 192, 216 hr). In the second and third experiments Cpv alone and with antibiotics was administered 15 hr after the onset of sepsis. Cpv significantly augmented survival over controls in the second experiment (MST 87 vs 60 hr, P less than 0.025 at 96 hr). Cpv plus antibiotics was significantly better than antibiotics alone in the third experiment (MST 111 vs 64 hr, P less than 0.05 at 72 hr, P less than 0.005 at 120 hr). In the final experiment, Cpv did not inhibit growth of 20 bacterial species in agar and liquid media. Cpv significantly enhances survival in murine fecal peritonitis even when administered after the onset of sepsis; furthermore Cpv plus antibiotics in established peritonitis produces longer survival than antibiotics alone. Synthetic immunomodulators such as Cpv could eventually play a significant role in the management of peritoneal infection in humans.

Animals↗
PubMed1985

Human Ia molecules carrying MT1 determinants: purification with a monoclonal antibody.

A monoclonal antibody 77.34, reactive with polymorphic HLA class II molecules, was produced. The allotype specificity of this IgG2a antibody was analyzed by cytotoxicity, flow cytometry, and cellular radioimmunoassay. Cytotoxic reactivity on a panel of B cells from 88 unrelated individuals was concordant with the MT1 (DC1) allospecificity (r = 0.83). Immunoanalysis by flow cytometry showed that cells from MT1+ homozygous cell lines were reactive, whereas MT2+ and MT3+ homozygous cells were not. A cellular radioimmunoassay performed under saturating conditions indicated that three MT1+ cell lines bound 14-45 X 10(5) molecules of antibody per cell representing 30-40% of the amount detected with monomorphic anti-DR monoclonal antibody 21w4. The subset of molecules bearing the MT1 allospecificity was purified with a 77.34 IgG immunoadsorbent. The purified molecules were antigenically reactive with several antibodies directed at DQw1 molecules but were devoid of reactivity to monomorphic anti-DR antibodies. Two-dimensional gel electrophoresis showed that the alpha subunit is composed of several acidic spots of Mr 32,000 whereas the beta subunit was seen as a single spot of Mr 25,000, corresponding to DQw1 molecules. DR molecules purified by monoclonal antibody affinity were unreactive with 77.34 antibody. All of the 77.34 reactivity was observed with the fractions depleted of DR molecules. Two-dimensional gel analysis showed marked differences between the purified DR and DQw1 molecules. The presence of the MT1 determinant on Ia molecules referred to as the DQw1 molecules and distinct from those bearing the DR epitopes was confirmed on two DR1, MT1 homozygous cell lines. Thus, DQw1 molecules can be purified away from DR1 molecules by affinity chromatography to 77.34 IgG, specifically reactive with the MT1 (DQw1) allospecificity. The binding of 77.34 IgG to MT1+ cells was not inhibited by all monoclonal antibodies reported to be correlated with the MT1 allospecificity suggesting that the latter might be comprised of more than a single epitope.

Animals↗
PubMed1985

The characterization and partial purification of hepatocyte proliferation factor.

This report presents further evidence that the liver is the source of the factor responsible for the initiation and/or stimulation of hepatic regeneration. Initial experiments for the isolation and characterization of the active factor are presented. The factor was isolated from the cytosol of regenerating livers (RLC). After an in vivo exposure to RLC, hepatocytes were pulsed in vitro with 3H-thymidine to measure DNA synthesis. Rat and porcine RLC stimulated DNA synthesis in hepatocytes isolated from growing (nonhepatectomized) livers of weanling rats, or from regenerating livers of adult rats. The ability of porcine RLC to stimulate hepatocyte DNA synthesis demonstrated that the factor responsible was not species-specific. In contrast, normal non-regenerating liver cytosol did not stimulate hepatocyte DNA synthesis. Further experiments also revealed that the factor is heat stable. The activity responsible for the increased DNA synthesis was called hepatocyte proliferation factor (HPF). The assay for detecting HPF activity in the nonhepatectomized recipient will facilitate further characterization and purification of HPF.

Animals↗