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C D Black

Publications and source records attributed to C D Black.

At least 37 records · Page 2Linked to original sources
PubMed1991

On radical production by PMA-stimulated neutrophils as monitored by luminol-amplified chemiluminescence.

The means by which neutrophils within the body ward off infectious and neoplastic processes by the activation of molecular oxygen, as well as how such mechanisms dysfunction, is the subject of extensive ongoing research. Most previous studies of neutrophil activation indicate that there is a transient production of reactive oxygen species. Luminol-amplified chemiluminescence surveillance of O2-. and H2O2 supported these general findings. Yet, recent studies showed that production of reactive oxygen species by PMA-stimulated neutrophils is not transient but persistent; however, luminol-dependent methods do not corroborate such findings. The kinetics of O2-. production by human neutrophils were studied using luminol-amplified chemiluminescence (CL), spin trapping combined with electron spin resonance detection, and ferricytochrome c reduction. The effects of pH and O2 level on luminol-amplified CL were determined using hypoxanthine/xanthine oxidase to produce O2-. and H2O2 in cell-free systems. As we have found by electron spin resonance and ferricytochrome c reduction, stimulated neutrophils continued to generate O2-. for several hours, yet when luminol-amplified CL was used to continuously follow radical production, CL was shortly lost. Similar loss of CL was observed with continuous enzymatic formation of O2-. and H2O2. The failure of the CL assay to report O2-. and H2O2 formation results from some luminol reaction product which interferes with the light reaction. Our results show that the cells are operative for long periods indicating that cell exposure to prolonged O2-. fluxes does not terminate radical production, and even when pH, [O2], and reagents are optimized, the use of luminol-amplified CL is not a valid assay for continuous monitoring of O2-. and H2O2 generated by either stimulated neutrophils or in cell-free systems.

Cell-Free System↗
PubMed1991

Superoxide production by stimulated neutrophils: temperature effect.

Activation of neutrophils results in a one-electron reduction of oxygen to produce the superoxide anion and other oxygen-derived, microbicidal species. Evidence from many kinetic studies of oxygen-derived radicals generated by stimulated neutrophils in vitro shows that radical production is optimal at 37 degrees C but only lasts several minutes and then rapidly subsides. These findings support the widely held perception that the neutrophil's "oxidative burst" is a transitory event that peaks within minutes of stimulation and ends shortly thereafter. However, while some studies have shown that under controlled conditions stimulated neutrophils can generate superoxide continuously for several hours, others have observed that the superoxide formation by neutrophils stimulated in buffer at 37 degrees C does not persist. To reconcile the conflicting findings and to better understand neutrophil function, we have reinvestigated the effect of temperature on the kinetics of radical generation by PMA-stimulated cells. Electron paramagnetic resonance spectroscopy coupled with spin-trapping and SOD-inhibitable ferricytochrome c reduction were used to monitor superoxide production by neutrophils stimulated at either 25 degrees C or 37 degrees C in RPMI 1640 medium or in Hank's balanced salt solution. When oxygen was supplied continuously, neutrophils stimulated at 25 degrees C in buffer or in medium generated superoxide for several hours but at 37 degrees C, particularly in HBSS, O2- formation strikingly and rapidly decreased. This cessation of superoxide generation was reversible by lowering the temperature back to 25 degrees C. These data imply that in vivo neutrophils may be capable of generating oxy-radicals for prolonged periods. In part, our results may also explain the often observed termination of neutrophil-derived radical formation in vitro and help to dispel the perception that neutrophil-derived oxy-radical production is an ephemeral phenomenon.

Cyclic N-Oxides↗
PubMed1990

Inhibition of HIV-1 in monocyte/macrophage cultures by 2',3'-dideoxycytidine-5'-triphosphate, free and in liposomes.

The antiviral effects of 2',3'-dideoxycytidine (ddC), 2',3'-dideoxycytidine-5'-triphosphate (ddCTP) and liposome-encapsulated ddCTP [L(ddCTP)] were compared in cultured human monocyte-macrophages (M/M) infected with HIV-1. These treatments inhibited virus replication at nanomolar drug levels with activities in the order ddC greater than ddCTP = L(ddCTP). Studies on drug stability and uptake suggest that a large part of the free ddCTP is dephosphorylated before entering the cells, whereas L(ddCTP) remains stable over days and is taken up, probably by endocytosis. The response to L(ddCTP) suggests that the capability of liposomes for targeting drugs to macrophages in vivo could potentially be exploited to improve the therapeutic index of dideoxynucleoside drugs.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Nitroglycerin delivery through a polyethylene-lined intravenous administration set.

Adsorption and delivery of nitroglycerin through a new polyethylene-lined (PEL) i.v. administration set was compared with adsorption and delivery through an identical set composed of polyvinyl chloride (PVC) rather than PEL tubing. The new delivery system consisted of PEL tubing, a transparent PVC chamber, and a silastic segment for insertion in a peristaltic pump. Nitroglycerin was prepared in concentrations of 50, 125, and 200 micrograms/mL in 0.9% sodium chloride injection and run through both administration sets at flow rates of 12 and 60 mL/hr. Samples were obtained at 0, 0.5, 1, 2,4, and 8 hours from each of three sites: bottle, junction before silastic segment, and distal end of tubing. Nitroglycerin content was assayed using a modified high-performance liquid chromatography technique. A slight but significant average loss of nitroglycerin (2.3 +/- 9.3%) was observed at the distal end with the PEL set, whereas the PVC set showed a significant average nitroglycerin loss of 39.7 +/- 12.7% at the distal end. These differences were independent of infusion rate, nitroglycerin concentration, or time of sampling. Flow rate, concentration, and time had no significant effect on nitroglycerin adsorption with the PEL set, but all three had a significant effect on nitroglycerin adsorption with the PVC set. An unexpected finding was the approximately 14% loss of nitroglycerin from the admixture bottle over time. This phenomenon, which has been observed by other investigators, needs further investigation to determine its cause. It appears that a partially PVC-based administration set should provide consistent delivery of i.v. nitroglycerin to the patient.

Chemistry, Pharmaceutical↗
PubMed1988

Hydroxyl radical production by stimulated neutrophils reappraised.

Release of active oxygen species during the human neutrophil respiratory burst is thought to be mandatory for effective defense against bacterial infections and may play an important role in damage to host tissues. Part of the critical bacterial and host tissue damage has been attributed to hydroxyl radicals produced from superoxide and hydrogen peroxide. Because of the short life time of the very reactive hydroxyl radical, direct study of hydroxyl radical production is not possible; therefore, indirect detection methods such as electron spin resonance (ESR) coupled with appropriate spin-trapping agents such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) have been used. Superoxide production during the oxidative burst has been unambiguously demonstrated. Recent reports claim that hydroxyl radicals are not made during neutrophil stimulation and offer as an explanation the presence of granular components that interfere with hydroxyl radical production. When using the spin-trap agent DMPO, absence of the relatively long-lived adducts DMPO-OH and DMPO-CH3 has been assumed to be prima facie evidence for lack of hydroxyl radical participation. We show that high superoxide flux produced during stimulation of human neutrophils rapidly destroys both DMPO-OH and DMPO-CH3. In accord with previous implications, our results provide an alternative explanation for the absence of .OH adduct in spin-trapping studies and corroborate results obtained using other methods that implicate hydroxyl radical production during neutrophil stimulation.

Cyclic N-Oxides↗
PubMed1988

Induction of IL-2 receptor expression in vivo: response to concanavalin A.

The requirements for the induction of IL-2 receptor expression following lymphocyte stimulation in vitro are well understood but little is known about the role of IL-2 and the IL-2 receptor in lymphocyte activation in vivo. Following the subcutaneous injection of concanavalin A, cells from popliteal and lumbar lymph nodes draining the footpad became enlarged and expressed the IL-2 receptor. At the peak of the response, 9-15 hr after injection, more than 70% of all cells were IL-2 receptor positive; the majority were T cells of both Lyt-2+ and L3T4+ subsets. IL-2 receptor expression was closely associated with both spontaneous and IL-2-driven proliferation. Analysis of the biodistribution of 125I-labeled concanavalin A revealed that much of the injectate remains in the footpad injection site but the mitogen also accumulates in the draining lymph nodes and eventually in the major organs. This model of lymphocyte activation was used to demonstrate that in vivo cyclosporin A inhibits both IL-2 receptor expression and the induction of spontaneous proliferation.

Animals↗
PubMed1987

Mechanism of action of cyclosporin A in vivo. I. Cyclosporin A fails to inhibit T lymphocyte activation in response to alloantigens.

Although cyclosporin A (Cy A) has been widely used clinically as a potent suppressor of organ allograft rejection and has been shown to block T lymphocyte activation in vitro by inhibiting the generation of interleukin 2 (IL-2) and other lymphokines, little direct evidence is available to support the view that the immunosuppressive effects of Cy A in vivo are mediated by a similar inhibition of the autocrine lymphokine cascade. We have used a quantitative assay for the assessment of the role of the IL-2/IL-2 receptor system in the activation of the draining popliteal lymph node population after the injection of allogeneic cells in the footpad to define the effects of Cy A on the early events of lymphocyte activation in vivo and to compare them with the effects of Cy A on lymphocyte activation in vitro. The administration of Cy A in vivo had no effect on alloantigen-induced increases in cell size, percentage of cells expressing the IL-2 receptor, the spontaneous or IL-2-driven proliferation of freshly explanted cells, or the induction of cytotoxic T lymphocyte activity. These findings raise major questions about the mechanism of action of Cy A in vivo and suggest that more experimentation is required to probe the mechanisms of Cy A-induced suppression of the response to allografts.

Animals↗
PubMed1987

Biodistribution of monoclonal IgG1, F(ab')2, and Fab' in mice after intravenous injection. Comparison between anti-B cell (anti-Lyb8.2) and irrelevant (MOPC-21) antibodies.

Quantitative pharmacokinetic measurements of uptake and metabolism for two murine immunoglobulin G1 (IgG1) monoclonal antibodies (anti-Lyb8.2, MOPC-21) and their F(ab')2 and Fab' fragments were obtained following i.v. administration into C57BL/6 mice. Anti-Lyb8.2 antibody, reactive with the allelic Lyb8.2 murine B cell antigen, was labeled with 125I, and MOPC-21, an antibody with no known target antigen, was labeled with 131I. The two IgG or their fragments were co-injected, and all major organs were analyzed. Specific uptake of anti-Lyb8.2 IgG, F(ab')2, and Fab' was observed in the spleen with maximum peak values occurring at 1 to 2 hr. For MOPC-21, blood and organ kinetics was indicative of a nontargeted IgG molecule. The kidneys showed significant and rapid uptake of anti-Lyb8.2 and MOPC-21 Fab' fragments. This uptake by kidneys attenuated the maximum peak values of anti-Lyb8.2 Fab' in spleen. Multiexponential data fitting provided mean residence times (MRT) for each organ. The MRT for anti-Lyb8.2 in all organs were greater than those for its F(ab')2 and Fab' fragments. Only the kidneys showed greater MRT for Fab' than for F(ab')2. Blood, spleen, kidneys, and carcass exhibited substantial differences across fragments. When total body MRT for each fragment was compared with that of the respective parent IgG molecule, a progressive decline was observed. For MOPC-21, the decrease in total body MRT for F(ab')2 demonstrates the influence of the Fc portion of the molecule on IgG1 metabolism. This organ-by-organ data set may be pertinent to other monoclonal antibodies and their fragments and should help in optimizing delivery of these molecules to specific sites in vivo for immunologic and clinical purposes.

Animals↗
PubMed1987

Induction of IL-2 receptor expression in vivo. Response to allogeneic cells.

Although the requirements for the induction of IL-2 receptor expression following lymphocyte stimulation in vitro have been well characterized, little information is available on the role of IL-2 and the IL-2 receptor in lymphocyte activation in vivo. We have established a quantitative assay for the measurement of IL-2-receptor-positive cells in the draining popliteal lymph node following the injection of allogeneic cells in the footpad. At the peak of the response more than 20% of the lymph node cells were IL-2-receptor-positive, and the majority of the IL-2-receptor-positive cells were Ly-2+ T cells and B cells. IL-2 receptor expression in vivo was closely associated with an increase in cell size and spontaneous and IL-2-driven proliferation, as well as with the induction of CTL activity specific for the donor strain. The model system described here should be useful in the further characterization of the mechanism of action in vivo of immunosuppressive drugs, antibodies, or lymphokines.

Animals↗
PubMed1986

Pharmacokinetics of monoclonal immunoglobulin G1, F(ab')2, and Fab' in mice.

The pharmacokinetics of an immunoglobulin G1 (IgG1) and its F(ab')2 and Fab' fragments following i.v. administration in mice has been studied by constructing a physiologically based, organ-specific model to describe antibody biodistribution, catabolism, and excretion. The antibody selected for study (MOPC-21) has no known binding sites in the body and therefore is useful for defining antibody metabolism by nontumor tissues. Whole IgG remains in the body for 8.3 days, the majority of time in the carcass (53.0% of the total residence time); has a distribution volume exceeding that of plasma plus interstitial fluid; distributes into these volumes rapidly for most enteral organs (equilibration time less than 2.6 min for liver, spleen, kidney, and lung), slower for the gut (less than 20 min), and slowest for the carcass (less than 260 min); produces interstitial:plasma concentration ratios of greater than 0.5 for enteral organs and 0.18 for carcass; has the greatest percentage of its catabolism due to the gut (72.8%), followed by the liver (20.5%), then the spleen (3.6%); has the highest extraction on a single pass by the gut (0.14%) and cycles through the interstitial spaces of the body at least 2.8 times/g of organ weight before being metabolized or excreted. When compared with whole IgG, the Fab' fragment is cleared from the body 35 times faster; has a larger total distribution volume; distributes more rapidly into this volume; produces higher interstitial:plasma concentration ratios; is catabolized principally by the kidney (73.4% of total catabolism), followed by the gut (22.9%), then the spleen (3.1%); is extracted from the circulation to the extent of 3.4% on each pass through the kidney, and less by gut (1.0%) and spleen (0.14%) and cycles through non-kidney interstitial spaces at least 0.4 cycles/g of tissue weight before metabolism or excretion. The F(ab')2 fragment has pharmacokinetic characteristics that fall between those of whole IgG and Fab'. These results provide pharmacokinetic criteria for selecting whole IgG, F(ab')2, or Fab' for various in vivo applications; provide a framework for predicting cumulative tissue exposure to antibody labeled with different isotopes; and provide a reference metabolic state for the analysis of more complex systems that do include antibody binding.

Animals↗
PubMed1985

Response of tumor-bearing rats to high-fat total parenteral nutrition.

Total parenteral nutrition (TPN) solutions fed to tumor-bearing rats have been shown to affect host and tumor metabolism. This study was initiated to evaluate the effect of two intravenous nutrient regimens on carcass and organ composition as well as tumor composition and growth. Thirty Sprague-Dawley rats were implanted with Walker 256 carcinosarcoma and randomly assigned to one of three diet groups: (1) A, a glucose-based TPN formula; (2) B, a lipid-based TPN formula, isocaloric to A; and (3) C, a purified powdered diet fed ad libitum. Equal assignments were made for non-tumor-bearing controls. Tumor-bearing rats infused with diet B had the highest amount of carcass and organ fat as well as the lowest carcass and organ protein. Tumor composition paralleled carcass composition, but tumor weight and density did not differ among dietary groups. Tumor weight to body weight ratios were highest in the group fed diet B. These data indicate that although tumor growth remains unchanged, alterations in body and tumor composition are effected by a high fat TPN solution.

Animals↗
PubMed1985

Effect of a polyethylene-lined administration set on the availability of diazepam injection.

Delivery of diazepam through a polyethylene-lined i.v. administration set and through a polyvinyl chloride (PVC) set was compared. Diazepam was prepared in concentrations of 50 mg/500 mL and 100 mg/500 mL in 0.9% sodium chloride injection and 5% dextrose injection in glass containers. Diazepam concentrations were measured by high-performance liquid chromatography at 0 through 5 hours in samples collected simultaneously from the glass solution containers and from the distal ends of a PVC administration set and a polyethylene-lined (non-PVC) set. Flow rates of 50 and 100 mL/hr were tested. For the non-PVC sets, diazepam concentration in the infusate was not significantly different from concentration in the glass container at any sampling time. The overall percentage of diazepam recovered was 100.7 +/- 6.8%. For the PVC sets, diazepam concentration in the infusate was less than in the container at all sampling times, and the overall percentage of diazepam recovered was 65.4 +/- 13.3% (significantly different from delivery for the non-PVC sets). Delivery through the non-PVC sets was not affected by flow rate, type of solution, or concentration of diazepam. For infusion periods of up to five hours, delivery of diazepam through polyethylene-lined i.v. administration sets was superior to delivery through polyvinyl chloride sets.

Diazepam↗
PubMed1981

A study of intravenous emulsion compatibility: effects of dextrose, amino acids, and selected electrolytes.

Microscopic and electronic counting procedures as well as visual observations for creaming and flocculation were employed to quantitatively and qualitatively measure the effects of dextrose, amino acids and various mono- and di-valent cations on the globule size distribution of the soybean oil emulsion 10%, Intralipid. A linear regression analysis was demonstrated to successfully profile much of the stability data. Results indicated that divalent cations caused flocculation in the emulsion's internal phase immediately upon or shortly after the addition of their salts. The rate and extent of flocculation intensified with increasing ionic concentration. Amino acids, apparently acting at the oil/water interface, delayed divalent cation-induced flocculation; however, they did not prevent emulsion stability loss. The addition of dextrose 5% or 12.5% brought about a reduction of emulsion pH and significant globule coalescence 72 hours after admixture. Monovalent cations (i.e., Na+, K+) induced a progressive loss of emulsion stability over the 72-hour course of the experiments, the effect of function of ionic concentration. From the data, a model has been generated to predict significant changes (p less than 0.05) in Intralipid's globule size distribution upon addition of solute and exposure to room temperature. Further recommendations of solute admixture with the intravenous emulsion are also included.

Amino Acids↗