A small RNA targets pokeweed antiviral protein transcript

Ribosome-inactivating proteins (RIPs) are a class of plant defense proteins with N-glycosidase activity (EC 3.2.2.22). Pokeweed antiviral protein (PAP) is a Type I RIP isolated from the pokeweed plant, Phytolacca americana, thought to confer broad-spectrum virus resistance in this plant. Through a combination of standard molecular techniques and RNA sequencing analysis, we report here that a small RNA binds and cleaves the open reading frame of PAP mRNA. Additionally, sRNA targeting of PAP is dependent on jasmonic acid (JA), a plant hormone important for defense against pathogen infection and herbivory. Levels of small RNA increased with JA treatment, as did levels of PAP mRNA and protein, suggesting that the small RNA functions to moderate the expression of PAP in response to this hormone. The association between JA and PAP expression, mediated by sRNA299, situates PAP within a signaling pathway initiated by biotic stress. The consensus sequence of sRNA299 was obtained through bioinformatic analysis of pokeweed small RNA sequencing. To our knowledge, this is the first account of a sRNA targeting a RIP gene.

RNA toxins: mediators of stress adaptation and pathogen defense

RNA toxins are a group of enzymes primarily synthesized by bacteria, fungi, and plants that either cleave or depurinate RNA molecules. These proteins may be divided according to their RNA substrates: ribotoxins are nucleases that cleave ribosomal RNA (rRNA), ribosome inactivating proteins are glycosidases that remove a base from rRNA, messenger RNA (mRNA) interferases are nucleases that cleave mRNAs, and anticodon nucleases cleave transfer RNAs (tRNAs). These modifications to the RNAs may substantially alter gene expression and translation rates. Given that some of these enzymes cause cell death, it has been suggested that they function mainly in defense, either to kill competing cells or to elicit suicide and thereby limit pathogen spread from infected cells. Although good correlations have been drawn between their enzymatic functions and toxicity, recent work has shown that some RNA toxins cause apoptosis in the absence of damage to RNA and that defense against pathogens can be achieved without host cell death. Moreover, a decrease in cellular translation rate, insufficient to cause cell death, allows some organisms to adapt to stress and environmental change. Although ascribing effects observed in vitro to the roles of these toxins in nature has been challenging, recent results have expanded our understanding of their modes of action, and emphasized the importance of these toxins in development, adaptation to stress and defense against pathogens.

Managing space for managed care: the challenge for a multispecialty group practice

A project that began as an architectural study to determine space requirements and remedy space deficiencies for an academic medical center's faculty multispecialty group practice led to development of an analytical methodology for assessing real space needs and viable options for solutions in the context of the group's operational policies, physician practice patterns, and business goals. Major facility investments for new or renovated construction demand significant capital expenditure, which can severely affect a group's ability to complete as a financially viable player in a marketplace environment of increasingly competitive managed care delivery systems. The methodology created during this project helped the group practice to understand how they could optimize the use of existing space, minimize capital costs, and provide flexibility for future developments.

Physicians and group practice: balancing autonomy with market reality

Developing or joining multispecialty group practices is emerging as a premier competitive strategy for physicians. "Physicians and Group Practice: Balancing Autonomy with Market Reality" explores the driving forces causing the restructure of physician services into multispecialty group practices. The growth and characteristics of group practices are outlined as well as the advantages and trade-offs inherent in a group practice.

Strategic business planning for the multispecialty group practice

A clear plan for guiding the activities of the multispecialty group practice (GP) is critical for ensuring success as the health care industry undergoes profound change. This article describes the process of developing a strategic business plan, and includes examples of pertinent analyses as well as practical considerations for ensuring successful development of a strategic business plan for a GP.

Interleukin-2 triggers a novel phosphatidylinositol 3-kinase-dependent MEK activation pathway

Phosphatidylinositol 3-kinase (PI3-K) has been implicated as a signal-transducing component in interleukin-2 (IL-2)-induced mitogenesis. However, the function of this lipid kinase in regulating IL-2-triggered downstream events has remained obscure. Using the potent and specific PI3-K inhibitor, wortmannin, we assessed the role of PI3-K in IL-2-mediated signaling and proliferation in the murine T-cell line CTLL-2. Addition of the drug to exponentially growing cells resulted in an accumulation of cells in the G0/G1 phase of the cell cycle. Furthermore, wortmannin also partially suppressed IL-2-induced S-phase entry in G1-synchronized cells. Analysis of IL-2-triggered signaling pathways revealed that wortmannin pretreatment resulted in complete inhibition of IL-2-provoked p70 S6 kinase activation and also attenuated IL-2-induced MAP kinase activation at drug concentrations identical to those required for inhibition of PI3-K catalytic activity. Wortmannin also diminished the IL-2-triggered activation of the MAP kinase activator, MEK, but did not inhibit activation of Raf, the canonical upstream activator of MEK. These results suggest that a novel wortmannin-sensitive activation pathway regulates MEK and MAP kinase in IL-2-stimulated T lymphocytes.

Gallium arsenide-induced increase in serum corticosterone is not responsible for suppression of the IgM antibody response

Previous investigations demonstrated gallium arsenide (GaAs) to be an immunosuppressive agent that alters the function of all cell types involved in the generation of a primary antibody response. In those studies, GaAs was administered as a particulate compound that remained in the lung at least 14 days after exposure. The extended presence of the particulate in the lung may induce a stress response that leads to the release of endogenous corticosteroids. In addition, some of the observed immunomodulatory effects of GaAs were similar to immunological alterations reported to be induced by corticosteroids. The present studies were designed to determine whether suppression of the immunoglobulin (Ig) M antibody-forming calls (AFC) response by GaAs was a result of a GaAs-induced increase in serum corticosterone. GaAs (50-200 mg/kg) significantly decreased the weights of both the thymus and spleen and the cellularity of the spleen. In addition, there was a GaAs-induced decrease in the CD4+/CD8+ thymocyte subpopulations and a concomitant increase in CD4+ and CD8+ cells. Within the spleen, there were no alterations in the percentages of CD4, CD8 or Ig-positive cells. However, when expressed as an absolute cell number, there was a 50% decrease in the numbers of CD4+ and CD8+ cells in the spleen. GaAs also dose-dependently suppressed (50-75%) the IgM AFC response. The GaAs-induced changes in cell populations and immune organ weights were correlated with an increase (6- to 10-fold) in serum corticosterone levels. The treatment of mice with the glucocorticoid antagonist mifepristone (also called RU 486) blocked the observed alterations in splenic and thymic cell populations induced by GaAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunotoxicity of 2,4-diaminotoluene in female B6C3F1 mice

2,4-Diaminotoluene (DAT) has been demonstrated to be a potent carcinogen. The present studies were carried out to determine the toxic and immunotoxic potential of DAT. Mice exposed to DAT at 25-100 mg/kg per day for 14 days by gavage showed a 42% increase in liver weight and a slight decrease in spleen weight. Histopathologic evaluation of selected organs showed the liver to be the major target with morphological changes which were dose dependent. The high dose (100 mg/kg) was associated with moderate centrilobular necrosis. No abnormal structure was noted in the spleen, lungs, thymus, kidney or mesenteric lymph nodes. The liver toxicity was associated with an elevation in alanine aminotransferase activity. The only change noted in selected hematologic parameters was a 64% increase in peripheral blood leukocytes. Mice exposed to DAT showed a decreased IgM and IgG response to sheep erythrocytes. The decrease was not a function of a decreased number of B cells because the number of B cells increased dose dependently. Proliferative capacity of immunocompetent cells was not impaired by exposure to DAT as measured by the response to several mitogens. The delayed hypersensitivity response to keyhole limpet hemocyanin in mice exposed to DAT was increased. Natural killer cell activity was decreased dose dependently and may represent a spleen cell pool shift because the number of B cells increased in the presence of a decreasing spleen size. Serum C3 was suppressed at the high dose of DAT. Phagocytosis by splenic macrophages, but not peritoneal macrophages, was inhibited by DAT exposure. DAT exposure for 14 days decreased host resistance to the bacteria, Streptococcus pneumoniae and Listeria monocytogenes, while host resistance to the pulmonary tumor model, B16F10, and the PYB6 fibrosarcoma was unaffected by DAT exposure. These data indicate that DAT is hepatotoxic and perturbs the differentiation and maturation of leukocytes.

Immunotoxicity of mono-nitrotoluenes in female B6C3F1 mice: I. Para-nitrotoluene

para-Nitrotoluene (p-nitrotoluene) is used primarily as an intermediate in the production of various dyes, explosives, pharmaceuticals, and in the production of rubber and agricultural products. Previous investigations indicated that p-nitrotoluene was mutagenic in the Ames Test and that other mono-substituted nitrotoluenes bound covalently to hepatic macromolecules. The objective of these studies was to evaluate the potential immunotoxicity of p-nitrotoluene in mice exposed by the oral route. Mice exposed to p-nitrotoluene (200-600 mg/kg) daily for 14 days showed modest dose-dependent increases in liver and spleen weights. The livers of mice exposed subchronically to 400 and 600 mg/kg showed a mild to moderate swelling of the hepatocytes adjacent to the central veins; this swelling appeared to be reversible and there was no evidence of necrosis. The proportion of monocytes in blood was decreased in mice treated with p-nitrotoluene or toluene. Serum chemistries, bone marrow cellularity and the number of CFU-M and CFU-GM were unaffected. Immunologic investigations showed p-nitrotoluene suppressed the IgM response to sRBC and the DHR response to KLH. There was a 24% decrease in the percentage of CD4+ T lymphocytes in the spleen. There was no dose-dependent alteration of peritoneal macrophage numbers or differential count, unstimulated natural killer cell activity, response to B cell mitogen LPS, C3 activity or interferon levels. Exposure of mice to p-nitrotoluene decreased resistance to Listeria monocytogenes but not to Streptococcus pneumoniae, Plasmodium yoelii or the B16F10 melanoma, and increased resistance to the PYB6 tumor. These studies indicated that the immune system is an important target for toxicity of p-nitrotoluene. The decreased host resistance to L. monocytogenes can be attributed to the decrease in T lymphocytes and to a decreased delayed hypersensitivity response to KLH.

Immunotoxicity of nitrobenzene in female B6C3F1 mice

Nitrobenzene (NBZ) is primarily employed as an oxidizing agent in the synthesis of analine and benzene compounds. It produces myelotoxic effects and effects on erythrocytes in both animal models and man. Reported hepatosplenomegaly and effects on the bone marrow are indicators that NBZ may be immunotoxic. In these studies, female B6C3F1 mice were exposed to 30, 100 and 300 mg/kg of NBZ in corn oil by gavage for 14 consecutive days. To assess the immunotoxic potential of NBZ, body and organ weights were determined and selected immunologic and host resistance responses were studied. In these studies, the liver and spleen appeared to be the primary target organs. Both liver and spleen weights were dose dependently increased. Gross histopathologic examinations revealed significant changes in the spleen, consisting of severe congestion of the red pulp areas with erythrocytes and reticulocytes. Serum chemistry profiles showed increases in alanine aminotransferase and aspartate aminotransferase activities, indicating liver toxicity. Hematologic studies showed a decrease in erythrocyte number and a concomitant increase in mean corpuscular hemoglobin and mean corpuscular volume. A dose-dependent increase in peripheral reticulocytes was also seen. DNA synthesis was enhanced, as was the number of formed elements and the number of monocyte/granulocyte stem cells in the bone marrow of treated mice. IgM responses were decreased and the phagocytic activity of macrophages in the liver was dose dependently increased with a concomitant decrease in the activities in the spleen and lung. Other immunological parameters examined were unchanged. Host resistance to microbial or viral infection was not markedly altered by NBZ; however, there were trends towards increased susceptibility where T-cell function contributes to host defense. These data indicate that NBZ-induced hemolysis and liver injury are linked to the observed alterations in bone marrow activity.

Immunotoxicity of mono-nitrotoluenes in female B6C3F1 mice: II. Meta-nitrotoluene

The nitrotoluenes are chemicals used in dyes, agricultural products, pharmaceuticals and explosives. In the present studies, the toxicology and immunotoxicity of meta-nitrotoluene (m-nitrotoluene) were evaluated. Mice, exposed to m-nitrotoluene at dose levels of 200, 400 and 600 mg/kg/body weight for 2 weeks by gastric gavage, gained body weight over the treatment period to a slightly greater extent than the control groups. Of the selected organs weighed, the liver and kidney of mice exposed to m-nitrotoluene were increased in weight while the thymus weight was decreased. The liver of mice exposed to m-nitrotoluene, but not ortho-nitrotoluene, showed slight to moderate swelling of the hepatocytes adjacent to the central veins. The hepatocyte swelling appeared to be reversible and there was no evidence of necrosis. The hematology and serum chemistries examined were unaffected by m-nitrotoluene exposure although there were modest decreases in the percentage of polymorphonuclear leukocytes and eosinophils in differential blood counts. Bone marrow cellularity and the number of CFU/M and CFU/GM were unaffected by m-nitrotoluene exposure. m-Nitrotoluene suppressed the IgM response to sRBC and the DHR response to KLH. There was a slight (8%) decrease in the percentage of B lymphocytes in the spleen. The response to the T cell mitogens was suppressed by as much as 39%. Fc-mediated adherence and phagocytosis of chicken erythrocytes and NK cell activity were increased dose dependently in mice exposed to m-nitrotoluene. Several immune parameters were unaffected by exposure to m-nitrotoluene, including the IgG response to sRBC, responses to the B cell mitogen LPS and to allogeneic cells, and serum interferon levels. Resistance to Streptococcus pneumoniae and Plasmodium yoelii were unaffected also. Resistance to the tumor model PYB6 was increased. Exposure of mice to m-nitrotoluene decreased resistance to Listeria monocytogenes. The decreased resistance to L. monocytogenes may be related to an effect on T cells, evidenced by a decrease in T cell numbers and in the DHR.

Interleukin-2-induced tyrosine phosphorylation of p52shc in T lymphocytes

Stimulation of activated T cells with interleukin-2 (IL-2) results in the tyrosine phosphorylation of several intracellular proteins. The present studies demonstrate that IL-2 stimulation induces phosphorylation of the src homology 2 domain-containing protein, p52shc, on both tyrosine and serine residues. The level of p52shc phosphorylation was maximal within 5 min after growth factor addition and declined gradually thereafter. In addition, anti-Shc immunoprecipitates from IL-2-stimulated T cells contained a co-precipitating protein tyrosine kinase (PTK) activity that phosphorylated p52shc on tyrosine residues in immune complex kinase assays. These results demonstrate that p52shc is an early substrate for IL-2 receptor-coupled PTK activity(s) and suggest that this protein may be involved in the transduction of PTK-dependent regulatory signals in IL-2-stimulated T cells.

Arsenic in the sera of gallium arsenide-exposed mice inhibits bacterial growth and increases host resistance

The objective of the present investigations was to evaluate whether the presence of gallium arsenide (GaAs) in the sera of exposed mice was sufficient to retard bacterial growth. Host resistance studies demonstrated that exposure of GaAs (50-200 mg/kg) produced an increased resistance to Streptococcus pneumoniae and Listeria monocytogenes (50-100 mg/kg GaAs) when microbial challenge occurred 24 hr after exposure. In contrast, exposed mice exhibited a profound and dose-related decrease in resistance to the B16F10 melanoma. Serial dilutions of GaAs (0.039-5 mg/ml) were added to BHI broth and cultures were innoculated with either S. pneumoniae or L. monocytogenes. GaAs slowed the growth of both organisms with a minimal inhibitory concentration (MIC) of 0.625 mg/ml. Sera from mice euthanized at various time intervals after exposure to vehicle (0.05% Tween 80 in saline) or GaAs (200 mg/kg) was also capable of retarding the growth of both organisms with the maximal inhibition noted for euthanization 24 hr after exposure. However, sera from GaAs-exposed mice (24 hr after exposure) was incapable of slowing the growth of the B16F10 melanoma. Addition of the arsenic-binding compound meso-2,3-dimercaptosuccinic acid (100 microM) to sera from mice exposed to GaAs followed by innoculation with L. monocytogenes resulted in growth of this organism, which was comparable to growth observed in vehicle cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of protein tyrosine phosphatase by the antitumor agent gallium nitrate

Protein tyrosine phosphatases (PTPases) play an important role in regulating cell growth and transformation. We report that the antitumor agent gallium nitrate is a potent inhibitor (concentration producing 50% inhibition, 2-6 microM) of detergent-solubilized cellular membrane PTPase from Jurkat human T-cell leukemia cells and HT-29 human colon cancer cells. This is the first report of a selective, small molecule drug inhibitor of PTPase. Gallium nitrate did not inhibit CD45, a PTPase found in the membranes of hemopoietic lineage cells such as Jurkat cells. Studies with gallium nitrate and a series of gallium-containing analogues revealed no correlation between growth-inhibitory activity in Jurkat and HT-29 cells and the ability to inhibit detergent-solubilized PTPase. Gallium nitrate and most of the gallium analogues penetrate poorly into cells. In contrast, a gallium-hydrogen peroxide complex inhibits DNA synthesis in Jurkat cells and induces the accumulation of phosphotyrosines on multiple intracellular proteins in this cell line. Gallium-hydrogen peroxide complex and gallium nitrate have similar inhibitory activity toward detergent-soluble PTPase. This is a new mechanism of action for gallium nitrate but it is not known if the inhibition of PTPase is related to the antitumor activity of gallium nitrate.

Reversal of gallium arsenide-induced suppression of the antibody-forming cell response by vehicle supernatants. I. Pharmacokinetics after in vitro and in vivo exposure

Exposure of splenocytes in vivo or in vitro to gallium arsenide (GaAs) dose-dependently suppresses the ability of these cells to produce antibody after in vitro immunization with sheep red blood cells. In addition, it has been demonstrated that GaAs exerts immunosuppressive effects early (36 hr) in the generation of a primary antibody-forming cell (AFC) response. The objective of this study was to determine if the GaAs-induced suppression was produced as a result of a GaAs-induced alteration in the secretion of soluble mediators. Supernatants from in vivo and in vitro vehicle (VH)-exposed splenocyte cultures time-dependently reversed GaAs-induced suppression of the in vitro-generated primary AFC response produced by both in vitro (50 microM) and in vivo (200 mg/kg) exposure to GaAs. Supernatants from in vitro GaAs-exposed cells suppressed the VH response 40, 89 and 93% at 24, 36 and 48 hr, respectively. Using the arsenic-binding compound meso-2,3-dimercaptosuccinic acid (100 microM), it was determined that the suppression of the VH response by supernatants from in vitro GaAs-exposed cultures was confounded by the presence of free arsenic in the in vitro GaAs-exposed culture supernatant. In contrast, suppression of in vivo VH-exposed AFC responses by supernatants from in vivo GaAs-exposed cells was not seen. The time-dependent reversal of immunosuppression produced by in vivo or in vitro exposure to GaAs, by supernatants from in vivo and in vitro VH-exposed cells mimics the reported kinetics of suppression by addition of GaAs to antibody cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of gallium arsenide-induced suppression of the antibody-forming cell response by vehicle supernatants. II. Nature and identification of reversing factors

Previous studies have demonstrated that several immunological events which are T cell mediated are significantly suppressed by a single exposure to gallium arsenide (GaAs). In addition, in the in vitro-generated antibody-forming cell (AFC) response supernatants from vehicle (VH) cultures were able to time-dependently reverse suppression induced by either in vivo (200 mg/kg) or in vitro (50 microM) exposure to GaAs. The present studies were designed to determine the nature and identification of the reversing factors present in VH supernatants. VH supernatants (25-100%) were able to dose-dependently reverse suppression of the AFC response (from 45% suppression to 48% enhancement of the VH response) induced by GaAs exposure (200 mg/kg). Concentration of 24-hr VH supernatants and treatment with proteinases revealed that the reversing factors were protein in nature with a molecular weight between 5,000 and 50,000 Da. This molecular weight range encompasses many of the lymphokines known to be necessary for the generation of an immune response. In antibody cultures exposed either in vivo or in vitro to VH or GaAs, HT-2 bioassay and antigen capture enzyme-linked immunosorbent assays demonstrated that GaAs exposure alters production of interleukin (IL)-2, IL-4, IL-5 and IL-6. Interestingly, the alterations in lymphokine production differed between the exposure regimes. Direct addition of IL-2 to antibody cultures resulted in a dose-dependent (6.25-50 ng/ml) reversal of GaAs-induced suppression (in vivo exposure) and was also dependent on the concentration of GaAs (50-200 mg/kg). IL-4 suppressed the VH AFC response and failed to reverse GaAs suppression.(ABSTRACT TRUNCATED AT 250 WORDS)

Gallium arsenide selectively inhibits T cell proliferation and alters expression of CD25 (IL-2R/p55)

Exposure (24 hr) to a single intratracheal administration of gallium arsenide (GaAs; 200 mg/kg) has been shown to suppress antibody production as well as other T cell-mediated immunological functions. GaAs has also been shown to exert toxic effects on events occurring early in the antibody-forming cell response which may include lymphocyte activation and proliferation. Studies were undertaken to determine whether GaAs exposure resulted in the inability of T and B lymphocytes to proliferate in response to an antigenic stimulus. During the first 24 hr after in vitro immunization with sheep red blood cells, GaAs-exposed splenocytes were suppressed 51% in their ability to proliferate compared to the vehicle (0.05% Tween 80 in saline; VH) control. There was no significant difference in absolute numbers of cluster designation (CD)8+ cells between VH- and GaAs-exposed cultures. There was, however, a 50% decrease in CD4+ cells evaluated 24 hr after immunization with sheep red blood cells which persisted for the 5-day culture period. T and B cells were isolated and analyzed for proliferative capacity in response to various mitogenic stimuli. Isolated B cells exhibited no difference between VH- and GaAs-exposed cells in proliferative capacity to either lipopolysaccharide or anti-immunoglobulin plus interleukin-4. However, isolated T cells exposed to GaAs were significantly suppressed in their ability to proliferate to concanavalin A, phytohemagglutinin and anti-CD3 epsilon plus interleukin-2 when compared to VH. In addition, expression of CD25, leukocyte function antigen-1 and intercellular adhesion molecule-1 in GaAs-exposed mice were significantly below VH (36, 18 and 18%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulatory effects of the protein tyrosine phosphatase inhibitor, pervanadate, on T-cell activation events

Ligation of the multimeric T-cell antigen receptor complex (TCR) triggers a pleiotropic cellular activation response that includes lymphokine secretion, cell-cycle progression, and ultimately, T-cell proliferation. The earliest detectable biochemical event triggered by TCR cross-linkage is the tyrosine phosphorylation of specific intracellular proteins, which, in turn, propagate receptor-mediated signals into the cytoplasm and nucleus. In this study, we have examined the effects of pervanadate, a powerful inhibitor of protein tyrosine phosphatases (PTP), on the activation state of the human leukemic T-cell line, Jurkat. Treatment of Jurkat cells with pervanadate rapidly induced a series of proximal T-cell activation events that closely resembled those induced by TCR-dependent stimuli. Moreover, pervanadate treatment, like TCR cross-linkage, stimulated interleukin-2 production in wild-type Jurkat cells, indicating that the biochemical events initiated by this TCR-independent stimulus were sufficient to induce lymphokine gene expression. Exposure of intact cells to pervanadate also stimulated the in vitro catalytic activities of both p59fyn and p56lck, src family kinases strongly implicated in TCR-mediated signaling. The stimulatory effects of pervanadate on protein tyrosine kinase-mediated signaling events were accompanied by a marked inhibition of CD45-associated PTP activity. However, the ability of pervanadate to stimulate tyrosine phosphorylation in CD45-negative Jurkat cells suggests that PTPs other than CD45 are important intracellular targets for pervanadate. These studies demonstrate that inhibition of PTP activities in Jurkat cells leads to a T-cell activation response that is remarkably similar to that induced by TCR crosslinkage.

Reversal of gallium arsenide-induced suppression of the antibody response by a mixed disulfide metabolite of meso-2,3-dimercaptosuccinic acid

Meso-2,3-dimercaptosuccinic acid (DMSA) has been demonstrated to be an effective chelator of lead, mercury and arsenic in humans and in rodent experiments. Studies involving cadmium exposure have typically shown DMSA to be less effective than 2,3-dimercapto-1-propanesulfonic acid, and this is possibly due to an inability of DMSA to cross cell membranes and bind intracellularly-bound metal ions. The present studies were designed to determine whether in vitro addition of DMSA could effectively reverse arsenic-induced immunosuppression in splenocytes exposed in vivo to gallium arsenide (GaAs; 200 mg/kg, intratracheally). In those investigations, DMSA (25-100 microM) was incapable of reversing suppression of the in vitro-generated antibody response induced by in vivo exposure to GaAs. Addition of the recently synthesized 2:1 mixed disulfide (L-cysteine-DMSA) metabolite of DMSA (0.1-100 microM) to cultures of splenocytes exposed in vitro to GaAs (50 microM) dose-dependently reversed GaAs-induced suppression of the antibody-forming cell response with no effect on the vehicle (complete media) response or on cell viability, indicating that the metabolite retained binding capacity. Unlike DMSA, however, addition of the 2:1 mixed disulfide metabolite to splenocyte cultures exposed in vivo to vehicle (0.05% Tween 80 in saline) or GaAs dose-dependently partially reversed GaAs-induced suppression. The reversal of suppression could not be attributed to cleavage of L-cysteine from the 2:1 mixed disulfide metabolite, as addition of equimolar concentrations of L-cysteine or L-cystine (0.2-200 microM) to in vitro generated antibody cultures of splenocytes exposed in vivo to vehicle or GaAs had no effect on the GaAs-induced suppression.(ABSTRACT TRUNCATED AT 250 WORDS)

A halo jacket for stabilisation of the paediatric cervical spine

Stabilisation of the paediatric cervical spine may be necessary in the management of trauma, infection and deformity. Surgery is technically difficult due to the immaturity of the bony elements and therefore external support is generally preferred. Our experience of halter traction and Minerva casts is that they either fail to achieve stability or are poorly tolerated. Halo pins are associated with significant pin tract complications in children. The technique for application of a plaster halo jacket is presented, together with the results of its use in eight children. Attention is drawn to the ease of application, tolerance by the patients and absence of significant complications.

Splenic cell targets in gallium arsenide-induced suppression of the primary antibody response

In vivo exposure of female B6C3F1 mice to gallium arsenide (GaAs) was evaluated for its effect on the in vitro IgM antibody-forming cell (AFC) response. In vivo exposure to a single intratracheal dose of GaAs (2.5-200 mg/kg) resulted in a dose-dependent decrease in the in vitro IgM AFC response to the T-dependent antigen sheep red blood cells (SRBC) with a 97% decrease at 200 mg/kg when compared to vehicle controls. The response to the T-independent antigen DNP-Ficoll was significantly reduced at 100 and 200 mg/kg. Spleen cellularity decreased in a dose-related manner with a 54% decrease at 200 mg/kg. Enumeration of splenic subpopulations following GaAs (200 mg/kg) indicated a 58, 61, and 30% decrease in the total number of Thy 1.2 (T cells), Ig (B cells), and F4/80 (macrophages) positive cells, respectively, with no alterations in the percentages of these cells. Mitogenic responsiveness of splenocytes from GaAs-exposed mice was unaltered. To identify the splenic cell populations targeted by GaAs, the AFC response to SRBC was evaluated following cell separation/reconstitution of splenocytes from GaAs- (200 mg/kg, 24-hr exposure) and vehicle-exposed mice. Results demonstrated AFC suppression was due to functional alterations in both adherent (AD; macrophages) and nonadherent, (both T and B lymphocytes) cell populations. Further investigation focused on alterations in the AD population. Separation/reconstitution experiments demonstrated AFC suppression to SRBC was dependent on the concentration of macrophages from GaAs-exposed mice. This macrophage-mediated suppression of the in vitro AFC response could not be attributed to the presence of suppressor macrophages or release of prostaglandins.

Evidence for arsenic as the immunosuppressive component of gallium arsenide

Gallium arsenide (GaAs) has been shown previously to suppress the in vivo antibody-forming cell (AFC) response to sheep erythrocytes (SRBC) when administered intratracheally at concentrations between 50 and 200 mg/kg. In the present studies, direct addition of GaAs to in vitro-generated antibody cultures resulted in dose-dependent suppression of the primary antibody response, and was only seen when GaAs was added within 36 hr following immunization. Using atomic absorption spectrophotometry on tissue samples from mice exposed to 200 mg/kg GaAs, arsenic concentrations were found to peak in the spleen at 24 hr and decline, whereas gallium concentrations continue to rise through 14 days. Concentrations of each metal in the spleen at 24 hr are comparable to the concentrations achieved for each metal when GaAs is added at 25 microM to the in vitro model system. The 24 hr time point was chosen for comparison because all in vivo-in vitro studies were conducted using spleens from mice 24 hr after GaAs exposure. NaAsO2 and Ga(NO3)3 suppressed the AFC response dose-dependently, and in a time-dependent manner similar to GaAs when added to the in vitro system. However, based on IC50 values for each salt, the role of the gallium component in the immunosuppression appears weak. Oxalic acid (OA) and meso-2,3-dimercaptosuccinic acid (DMSA), chelators of gallium and arsenic respectively, were added to cultures with GaAs to confirm that arsenic was the primary immunosuppressive component. DMSA dose-dependently blocked GaAs-induced immunosuppression in vitro, while OA had no effect. The metal-binding compounds were determined to be specific for the metals used in these studies and did not cross-react with one another. DMSA was evaluated for its ability to prevent suppression of the AFC response in splenocytes from GaAs-exposed mice and was able to block GaAs-induced suppression of the AFC response when given sc every 4 hr beginning 1 hr prior to GaAs exposure. These data indicate that the arsenic component of GaAs is the major contributor to the GaAs-induced immunosuppression and that this effect occurs within the first 36 hr of the 5-day culture period in a concentration-dependent manner.

Suppression of splenic accessory cell function in mice exposed to gallium arsenide

Acute exposure of mice to a single intratracheal dose of gallium arsenide (50, 100, and 200 mg/kg) depresses the primary IgM antibody response to the T-dependent antigen sheep red blood cells (SRBC) through alterations in the function of splenic accessory cells. To determine the mechanism by which GaAs exposure influences splenic accessory cells, the cells were isolated by adherence and their functional capability investigated 24 hr following GaAs exposure in the animal. Splenic adherent cells from GaAs-exposed mice were greatly impaired in their ability to process and present the particulate antigen SRBC to a SRBC-primed T-cell population. However, GaAs exposure did not inhibit phagocytosis of fluorescent covaspheres by these cells, nor did it inhibit in vivo phagocytosis of 51Cr-labeled SRBC, indicating that the findings reported here were not due to decreased uptake of antigen by the accessory cells. Furthermore, production of IL-1 by these cells from exposed mice was not different from control and addition of exogenous IL-1 to cultures did not reverse GaAs-induced inhibition of the primary antibody response. GaAs exposure did not affect the percentage of Ia positive macrophages (F4/80 positive cells), but the amount of cell surface IAk molecules expressed was significantly decreased as measured by flow cytometry. In contrast to the SRBC response, GaAs did not suppress the ability of adherent splenocytes to process and present the antigen pigeon cytochrome c to the helper/inducer T cell clone F1.A.2 or the antigen KLH (keyhole limpet hemocyanin) to KLH-primed T cells. Therefore, GaAs exposure interferes with the capacity of splenic macrophages to process and/or present the particulate antigen SRBC, but not the soluble protein antigens pigeon cytochrome c or KLH.

Myocardial metabolic effects of in vivo hydralazine treatment of streptozotocin-diabetic rats

We determined myocardial pumping capacity, glucose oxidation, and mechanical response to ischemia in streptozotocin-diabetic rats treated for 4 wk with or without hydralazine (0.5 mg/g of chow). Plasma triglycerides and cholesterol were decreased 73 and 50%, respectively, in the treated animals. Blood glucose levels were greater than 400 mg/100 g in both groups. Hearts were perfused in the working configuration with buffer containing 5 mM [U-14C]glucose. Starling curves were constructed by increasing left atrial filling pressure from 5 to 20 cm of water. Diabetic heart mechanical function was depressed compared with control and hydralazine treatment restored function to normal. Oxidation of [U-14C]glucose was comparably depressed in the treated and untreated diabetics. The provision of 1 mM dichloroacetate in the perfusate increased glucose oxidation in the hearts from hydralazine-treated rats, however. Twenty minutes of global ischemia resulted in 65% decrease in mechanical function in the hearts of hydralazine-treated group vs. 15% for hearts from nontreated diabetics. The data suggest that measures to normalize lipid metabolism may not normalize myocardial glucose oxidation or permit better mechanical recovery after ischemia in the diabetic myocardium.

Morphological substrate for eyelid movements: innervation and structure of primate levator palpebrae superioris and orbicularis oculi muscles

The levator palpebrae superioris and orbicularis oculi are antagonistic muscles that function during movements of the eyelid. The levator also functions in conjunction with superior and inferior rectus muscles in coordinated eye/lid movements. The present study examined the innervation and morphology of these muscles in Cynomolgous monkeys (Macaca fascicularis) in order to provide a better understanding of the anatomical substrate for lid movements. Motoneurons innervating the levator and orbicularis muscles were identified and localized by retrograde transport of WGA/HRP and HRP. Retrogradely labelled levator motoneurons were distributed bilaterally throughout the caudal central division of the oculomotor nucleus. A few labelled cells were also present within the contralateral superior rectus division, possibly because of the spread of tracer at the injection site. The possibility that individual motoneurons collateralize to innervate the levator muscle bilaterally was tested by using double retrograde labelling techniques. Doubly labelled levator motoneurons could not be detected by using a combination of tracers (HRP and Fast Blue). Motoneurons innervating the upper lid portion of the orbicularis oculi muscle were distributed within the dorsal subdivision of the ipsilateral facial motor nucleus, with a few neurons in the corresponding locus of the contralateral facial nucleus. Species differences in levator motoneuron distribution, particularly distinctions in lateral-eyed versus frontal-eyed mammals, are discussed in relation to the neural control of lid movements. The levator palpebrae superioris contains three of the same ultrastructurally defined types of singly innervated muscle fiber found in the global layer of other extraocular muscles and an additional, unique slow-twitch fiber type. Moreover, the multiply innervated fiber types so characteristic of the other extraocular muscles are conspicuously absent from levator muscles. Unlike the rectus and oblique extraocular muscles, the levator lacks a layered distribution of fiber types. The morphological profiles of levator muscle fiber types are such that they generally do not respect traditional fiber classification schemes, but are consistent with a role for the levator in sustained elevation of the lid. The orbicularis oculi muscle, by contrast, exhibited three distinct fiber types that resembled categories of skeletal muscle twitch fibers. One slow-twitch and two fast-twitch fiber types were noted. On the basis of oxidative enzyme profiles and mitochondrial content, the majority of orbicularis oculi fibers would be fatigue-prone, an assessment consistent with their rapid onset/offset of acti

Denervation of primate extraocular muscle. A unique pattern of structural alterations

Extraocular muscles differ from most other skeletal muscles in terms of constituent fiber types and innervation pattern. The rules that govern fiber responses to various experimental interventions for most skeletal muscles, therefore, may not strictly apply to the extraocular muscles. In this study, denervation of the extraocular muscles of Cynomolgous monkeys, Macaca fascicularis, was accomplished by intracranial transection of the oculomotor nerve. Survival times of 3-167 days were allowed, and muscles were processed for analysis by light and electron microscopy. Short-term alterations involved all muscle fiber types and included retraction of neuromuscular junctions, mild myofibril disruption and inflammatory cell infiltration. Long-term morphopathological changes were most apparent in the orbital singly innervated fiber type and its global layer counterpart. These alterations consisted of dispersion of the mitochondrial aggregates which characterize this fiber type. Only occasional fibers (all types) exhibited severe vacuolar atrophy or myofilament breakdown despite the occurrence of only limited reinnervation. When extensive reinnervation did occur, the characteristic layered organization of the extraocular muscles was preserved and fiber type grouping was not apparent. Taken together, these findings indicate that the extraocular muscles exhibit a resilience to denervation beyond that observed for other skeletal musculature.

Inotropic interactions of dichloroacetate with amrinone and ouabain in isolated hearts from endotoxin-shocked rats

The inotropic effects of ouabain and amrinone singly and in combination with dichloroacetate (DCA) were assessed using isolated working perfused hearts from endotoxin-shocked (LD50/6 h) rats, with glucose and free fatty acids as substrates. Amrinone (2.7 X 10(-4) M) and ouabain (10(-5) M) alone improved myocardial mechanical performance from 25 to 75%, depending on the preload. Amrinone was more effective than ouabain at all left atrial filling pressures tested. DCA enhanced the inotropic effect of both compounds, improving myocardial work greater than 65% in combination with ouabain (at low filling pressures) to 125% with amrinone (at high filling pressures). Glucose oxidation rose two- to threefold when DCA was present with either drug. Ouabain was without effect on pyruvate dehydrogenase (PDH) activity; however, when present with DCA, PDH activity increased fourfold. Amrinone alone augmented PDH activity 2.5 times as compared with controls, and 4.5 times when combined with DCA. All three compounds individually elevated myocardial ATP levels, but in contrast to the inotropic effects, when used in combination caused no further increase in ATP. Myocardial cyclic AMP (cyclic AMP) levels were augmented five times control values in the presence of amrinone. The simultaneous presence of DCA and amrinone did not further augment the myocardial concentration of cAMP. DCA alone enhanced the myocardial oxidation of glucose in isolated myocardial cells from endotoxin-shocked animals. In contrast, ouabain and amrinone did not affect cellular glucose oxidation. These data indicate that the provision of DCA can enhance the inotropic effect of amrinone and ouabain on the isolated working heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Extraocular myotoxicity of the retrobulbar anesthetic bupivacaine hydrochloride

Morphopathological changes induced in the extraocular muscles by the local anesthetic agent bupivacaine hydrochloride were studied in the monkey using light and electron microscopy. Retrobulbar anesthetic blocks, using 0.75% bupivacaine hydrochloride, were performed in five adult cynomolgus monkeys. Morphological alterations in extraocular muscle fiber types were examined following survival periods of 3-27 days. Bupivacaine injections produced a mild and very limited myopathic response, with changes largely restricted to the global layer singly-innervated muscle fiber type which is characterized by low mitochondrial content. For survival times beyond 3 days, this fiber type exhibited peripheral migration and swelling of mitochondria and an outside-in pattern of myofibril dissolution. Some affected fibers also exhibited the Ringbinden or ring fiber pathology. Maximal myotoxic response was observed at 14 days after injections, and pathological changes were largely resolved by 27 days. A more limited analysis of the effects of retrobulbar injection of lidocaine revealed similar morphopathological responses, thereby suggesting that these effects are a property common to the entire class of aminoacyl anesthetics. In contrast to previous observations in other skeletal musculature, the extraocular muscles proved to be unexpectedly resistant to local anesthetic treatment as only limited alterations were observed. The observed muscle fiber type specificity was interpreted to result from differences in the relative ability of muscle fiber types to adapt to anesthetic-induced elevations of intracellular free calcium levels.

Business planning for ambulatory surgical services

Successful responses to the rapid expansion of ambulatory surgical services in the United States require careful planning on the part of current and potential providers. The recommended approach to business' planning includes development of a detailed business concept, assessment of market and competitive characteristics, and analysis of current and projected financial performance.

Are hospitals and physicians allies or rivals in ambulatory care?

Diversification into ambulatory care can pit the hospital against physicians, primarily because of competition for this growing segment of the health care market. The author provides an overview of the growth of ambulatory care services and suggests strategies for boards to ease tensions and promote cooperation, especially through joint ventures with the hospital's medical staff.

Trends and initiatives in hospital ambulatory care

Changes in the financing and delivery of hospital ambulatory care are discussed. Ambulatory care encompasses a wide spectrum of clinical services provided to patients who are not confined overnight to an institutional bed as inpatients. There are a large and growing number of ways hospitals and physicians cooperate to provide ambulatory-care services. Technological advancements, which have spurred changes in other sectors of medicine, have also changed patterns of medical practice in ambulatory care. Some of the reasons why hospitals develop and expand ambulatory-care programs relate to the changing demand for health services, the shifting preferences of third-party payers and regulators, competitive influences, diversification of risk, and use of such programs as feeders for inpatient services and as teaching and research settings. Although outpatient revenues are a small portion of total hospital revenues, they are growing more rapidly than inpatient revenues. Changes in the health industry that offer opportunities to hospitals are described, such as the increasing physician supply and the formation of group practices, the climate of cost consciousness and price competition, and the trend toward new corporate structures for hospitals. These changes portend changes for hospital pharmacists and give them the opportunity to increase their clinical roles in providing ambulatory care.

Lessons learned through hospital involvement in HMO

The major considerations that affect hospital participation in HMOs are motivation, governance, medical staff involvement, financing, and planning and operations/These considerations are discussed in general and as they apply to one particular hospital's experience.

Mobile critical care unit safeguards lives during transfers

Providing access to high-quality critical care services for patients in small or remote hospitals is an important problem faced by many hospitals in this country. In an effort to meet the needs of critically ill patients who might be saved if they could be safely transported from their community hospitals to a large medical center with more specialized care capabilities, the University of Wisconsin Hospitals, Madison, designed a Mobile Critical Care Unit. The details of the unit's construction and of the program's operation are presented herein.