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PubMed1985

Tumor cell generation of thrombin via functional prothrombinase assembly.

Prothrombinase affects the proteolytic conversion of prothrombin to thrombin and is the penultimate enzyme in the common coagulation pathway. Prothrombinase is a complex in which the proteinase, Factor Xa, a cofactor, Factor Va, and calcium are bound to a membrane surface to generate the active enzyme. Guinea pig line 1 and line 10 tumor cells, grown as primary cultures from ascites tumors or as cell lines in culture, provide a surface that interacts with coagulation Factor Va and Xa and with calcium ions to form this enzyme complex. Cultured human colorectal carcinoma cells (Colo 205) also participate in prothrombinase complex assembly and function. Prothrombinase generation was measured by following the kinetics of prothrombin conversion to thrombin. Thrombin generation was monitored continuously using the reversible thrombin inhibitor, dansylarginine N-(3-ethyl-1,5-pentanediyl)amide, which displays enhanced fluorescence upon binding to thrombin. Analyses of kinetic data indicate that the apparent dissociation constants (1-4 X 10(-10) mol/liter) and the number of Factor Va-Xa binding sites per tumor cell are comparable to values reported for human and bovine platelets, human lymphocytes, and monocytes. Guinea pig lymphocytes were also active, while erythrocytes were inactive, in the prothrombinase assay. Membrane vesicles, shed by guinea pig and human tumor cells into conditioned medium, also supported functional prothrombinase activity. Although earlier studies indicated that tumor cells may initiate coagulation, this is the first demonstration that tumor cells are competent to bring clotting to fruition by generating thrombin, a step essential to fibrin generation. These data suggest that tumor cells, in the presence of clotting initiators and appropriate coagulation factors, are sufficient to generate the fibrin deposited in solid tumors.

Animals↗
PubMed1979

Digestion of the fifth component of complement by leukocyte enzymes. Sequential generation of chemotactic activities for leukocytes and for tumor cells.

Leukocytes contain within their lysosomal granules enzymatic activity that will generate from C5 chemotactic activity for leukocytes (neutrophils) and tumor (Walker carcinosarcoma) cells. Similar activity has been found in phagocytic supernatant fluids from neutrophils and in purified preparations of the leukocyte neutral proteases elastase and cathepsin G. White leukotactic activities can be generated from either the third (C3) or the fifth (C5) components of complement, only C5 serves as a source for generation of the chemotactic activity for tumor cells. As has been previously shown with trypsin, the C5-related chemotactic activities generated by leukocyte proteases are time-dependent: leukotactic activity appears early, then disappears, and is replaced by chemotactic activity for tumor cells. The generation of these chemotactic activities from C5 is blocked by prior treatment of leukocyte preparations with the neutral protease inhibitor Trasylol. The demonstration that enzyme activities from leukocytes have the ability to generate tumor cell chemotactic factors from C5 suggests a possible mechanism by which the development of metastatic lesions may be promoted at sites of tissue injury or inflammation.

Animals↗
PubMed1984

Decrease in generation of reactive oxygen species by neutrophils from patients with infectious mononucleosis: role of suppressor T lymphocytes.

We assessed the generation of reactive oxygen species (ROS: O2-, H2O2, OH . , chemiluminescence) by neutrophils and monocytes from six patients with infectious mononucleosis, ten patients with other viral diseases, and ten normal controls. Neutrophils from infectious mononucleosis patients showed markedly decreased generation of all reactive oxygen species, compared with the two control groups; this abnormality persisted for four to eight weeks after disease onset. Monocytes from these patients generated normal levels of ROS. Normal neutrophils incubated with T lymphocytes from infectious mononucleosis patients generated significantly less of each ROS than did those incubated with T cells from either control group. T cell-mediated suppression of ROS generation required both OKT4+ cells from infectious mononucleosis patients and OKT8+ cells from either patients or normals. We conclude that the generation of reaction oxygen species in neutrophils is suppressed in patients with infectious mononucleosis, at least in part, by interacting subsets of T lymphocytes.

Adolescent↗
PubMed1982

Alterability of development of hemoglobin concentration in mice: transmission of changes to the next generation.

The development of hemoglobin concentration was studied in CF1 mice. Significant variations from control values appeared in the offspring of mothers kept in small poorly ventilated cages during gestation; and by providing the pregnant mothers with a solution of RNA as only liquid source. Experimental and control lines were studied for three successive generations. Results were similar in both sets of experiments. The first generation experimentals had significantly higher hemoglobin than controls. The 2nd and 3rd generation experimentals had significantly lower values than their controls. In cross-matings between control females and first generation experimental males, the offspring showed significant differences from the 2nd generation control group. Transmission of the alteration of hemoglobin development persisted for one generation only when an experimental line was no longer exposed to experimental conditions. It is hypothesized that regulatory mechanisms account for these phenomena, and regulatory genes of gametes may participate in this transmission.

Animals↗
PubMed1983

The role of B cell proliferation in the generation of immunoglobulin-secreting cells in man.

The relationship of B cell proliferation and the generation of immunoglobulin-secreting cells (ISC) was explored in vitro by examining the effect of hydroxyurea (HU), an inhibitor of cellular DNA synthesis, on the generation of ISC from human peripheral blood mononuclear cells (PBM). HU completely inhibited the capacity of PBM to generate ISC in response to pokeweed mitogen (PWM) and other polyclonal B cell activators. Inhibition resulted from an effect on B cell proliferation, because HU also prevented the generation of ISC in cultures of purified B cells supplemented with either T cell supernatants or mitomycin C-treated T cells. Inhibiting B cell proliferation by treating them with mitomycin C before culture also abolished the generation of ISC. When ISC were enumerated after a 7-day incubation with PWM, the addition of HU as late as day 6 of culture was found to inhibit responsiveness markedly. This suggested that those cells that had acquired the capacity to secrete lg were actively dividing, and continued division was necessary for ongoing lg secretion. To examine this possibility, experiments were carried out in which responsiveness was assayed on a daily basis. ISC could be detected after a 3- or 4-day incubation and reached maximum at day 6 or 7. Addition of HU on days 3 to 7 caused a highly significant reduction in the number of ISC within 24 hr. ISC did not begin to show resistance to the effects of HU until later in culture. This observation supported the conclusions that ISC were a rapidly cycling cell population and that ongoing lg secretion, as well as expansion in the number of ISC, depended on continued proliferation of the ISC. To confirm directly that ISC were a cycling cell population, PBM were cultured with PWM for 6 days, fixed, stained for both cytoplasmic lg and DNA content, and analyzed on the fluorescence-activated cell sorter. This method made it possible to quantitate the DNA content of individual lg-synthesizing cells and thus to determine their position in the cell cycle. As many as 40% of cytoplasmic lg-positive cells were found to be in the S, G2, or M phases of the cell cycle. These data indicate that ISC generated in man after in vitro stimulation with a number of polyclonal activators are not stable terminally differentiated lg-secreting plasma cells but rather an actively cycling lg-secreting population. Furthermore, the results indicate that proliferation of the ISC themselves plays an important role in determining the magnitude of the resultant antibody response.

Adult↗
PubMed1983

Depletion of human NK cells with monoclonal antibodies allows the generation of cytotoxic T lymphocytes without NK-like cells in mixed cultures.

In vitro stimulation of human mononuclear cells with x-irradiated autologous lymphoblastoid cell line (LCL) or allogeneic normal cells in mixed leukocyte cultures (MLC) was previously shown to result in the generation of OKT3+ OKT8+ cytotoxic T lymphocytes (CTL) lytic for allogeneic and autologous LCLs and also of natural killer- (NK) like cells that are OKT3- and primarily OKT8- and are lytic for HLA- NK-sensitive K562 cells. The origin of the NK-like cells was not previously known because, although the majority of fresh human NK cells react with monoclonal antibodies OKM1 and B73.1, lymphocytes bearing these markers are not detected several days after the onset of MLC, when NK-like cells are present. In this study, experiments were undertaken to determine whether NK-like cells generated after stimulation with x-irradiated pooled allogeneic normal cells (poolx) or with autologous LCL are derived from cells expressing antigens reactive with monoclonal antibodies OKM1 or B73.1, which react with fresh NK cells. Mononuclear cells, depleted of monocytes, were stained with OKM1 or B73.1 and fluorescein-labeled goat anti-mouse IgG. Lymphocytes depleted of OKM1+ or B73.1+ cells, by fluorescence-activated cell sorting, and lymphocytes that were stained but not sorted were stimulated for 7 days with either poolx or autologous LCL. The generation of NK-like activity was decreased at least 90% after depletion of cells reactive with OKM1 or B73.1, whereas the generation of CTL against autologous and allogeneic LCL was minimally affected. These findings show that NK-like cells generated in MLC are derived from cells that express the phenotype of fresh NK cells (OKM1+ or B73.1+) and that CTL can be generated in cultures in which relatively little NK-like activity is concomitantly detected, by depleting NK cells with monoclonal antibodies before stimulation.

Animals↗
PubMed1983

The role of interleukin 1 in human B cell activation: inhibition of B cell proliferation and the generation of immunoglobulin-secreting cells by an antibody against human leukocytic pyrogen.

The role of factors released by monocytes (M phi) in the activation of human B lymphocytes was examined by studying the effect of an antiserum against human leukocytic pyrogen (LP) on mitogen-stimulated B cell proliferation and the generation of immunoglobulin-secreting cells (ISC) by peripheral blood mononuclear cells (PBM). Antiserum against LP was obtained from rabbits immunized with LP-containing human M phi supernatants. The globulin fraction of this antiserum inhibited pokeweed mitogen- (PWM) stimulated B cell proliferation and the generation of ISC in a concentration-dependent manner, with 50% inhibition of responsiveness observed with 10 micrograms/ml. By contrast, PWM-induced T cell [3H]thymidine incorporation was not inhibited by concentrations of anti-LP as great as 2000 micrograms/ml. The F(ab')2 fraction of anti-LP also inhibited the generation of ISC in response to both PWM and formalinized Staphylococcus aureus, but required 50 micrograms/ml to achieve 50% inhibition. Anti-LP inhibited the generation of ISC only if present during the first 24 hr of a 6 to 7-day incubation; later addition was not inhibitory. Inhibition was more marked in cultures partially depleted of M phi than in whole PBM cultures. Whereas absorption of the anti-LP with PBM failed to remove the capacity to inhibit the generation of ISC, anti-LP-mediated inhibition of responsiveness could be reversed by the addition of crude M phi culture supernatants or a variety of highly purified interleukin 1 (IL 1) preparations, but not by T cell supernatants. These results indicate anti-LP inhibits human B cell activation by removing the requisite M phi-derived factor IL 1 and also confirm that IL 1 plays an essential role in B cell proliferation and the generation of ISC in man.

Animals↗
PubMed1984

Chemotactic activity generated in human serum from the fifth component of complement by hydrogen peroxide.

Exposure of normal human serum to various concentrations of hydrogen peroxide as low as 68.8 microM resulted in the generation of chemotactic activity for human neutrophils, which was inhibited by adding catalase prior to the exposure. Maximum chemotactic activity was obtained by hydrogen peroxide at a concentration of 1.1 mM, and the concentration greater than 1.1 mM expressed decreased activity. On the contrary, hydrogen peroxide less than 1.1 mM produced dose-dependent chemotactic activity. The generation of chemotactic activity is initiated at an incubation time of 5 minutes, and subsequently increases with up to 90 minutes. The suppression of chemotactic activity was minimum even after 180 minutes. The maximum activity was obtained by 1024-fold dilution of serum treated with 13.8 mM hydrogen peroxide. These results suggest that the disappearance of chemotactic activity at the high-dose range of hydrogen peroxide is due to neutrophil deactivation rather than inactivation of the chemotactic activity after it was generated. Similarly, purified human C5 exposed to hydrogen peroxide generated chemotactic activity. The chemotactic activity was inhibitable by antiserum to human C5. The molecular weight of chemotactically active substance was approximately 15,000. The generation of chemotactic activity was not inhibited by addition of EGTA or EDTA. These results imply that hydrogen peroxide generates C5a-like chemotactic factor through hydrolysis of C5.

Aminopeptidases↗
PubMedDate not supplied

Third-generation cephalosporins: a critical evaluation.

Six third-generation cephalosporins--cefotaxime, moxalactam, cefoperazone, ceftizoxime, ceftriaxone, and cefmenoxime--are reviewed; covered are chemistry and structure-activity relationships, mechanism of action, spectra of activity, pharmacokinetics, clinical utility, adverse effects, and cost effectiveness. The third-generation cephalosporins have a similar mechanism of action to that of other beta-lactam antibiotics. None of the agents is particularly active against certain gram-positive bacteria, including methicillin-resistant Staphylococcus aureus; the drugs are effective against gonococci, Haemophilus influenzae, and Neisseria meningitidis. Several common gram-negative pathogens are susceptible to the third-generation cephalosporins, including Escherichia coli, Klebsiella, Citrobacter diversus, Proteus, and Morganella. About 50% of Pseudomonas aeruginosa isolates are susceptible. Only moxalactam has good activity against Bacteriodes fragilis. The pharmacokinetic profiles of the six agents reveal some important differences. The half-life of ceftriaxone allows once-daily dosing in many patients; the half-lives of ceftizoxime and cefoperazone permit dosing every 8-12 hours. Cefoperazone and ceftriaxone are highly protein bound, but the clinical relevance of this is unknown. Generally, the agents penetrate most body tissues and fluids well. Moxalactam and cefotaxime and possibly ceftriaxone effectively penetrate into the cerebrospinal fluid well. The third-generation cephalosporins have become the accepted drugs of choice for the treatment of adult gram-negative bacillary meningitis; as more experience is gained, they are likely to become the drugs of first choice for neonatal (with ampicillin) and childhood (except for moxalactam) meningitis. Serious infections of Enterobacteriaceae can be treated with these agents, thereby avoiding use of the aminoglycosides. Moxalactam is comparable with combination therapy in treating intra-abdominal infections. Adverse effects associated with use of the third-generation cephalosporins are generally similar to those that occur with other beta-lactam antibiotics with the exception of coagulopathies and the disulfiram reaction seen with moxalactam and cefoperazone. Despite the relatively high cost of the third-generation cephalosporins, they are often cost effective because of their reduced dosing frequencies, broad spectra of activity, and effectiveness in serious infections for which more toxic antibiotics have been required in the past.

Bacterial Infections↗
PubMed1980

Regulation of immune response in allogeneic mixed spleen cell cultures. I. Influence of I-region on the generation of suppressor cells.

The immune responses of allogeneic mixed spleen cell cultures (MLC) to the T-dependent antigen, SRBC, and to the T-independent antigen, DNP-PAA, were investigated. The immune response to DNP-PAA in MLC with certain strain combinations was always suppressed as compared with the expected PFC response calculated from the PFC responses of the individual strains. This suppression was eliminated by treating the spleen cells with RAMB antiserum plus complement before the incubation of the MLC with DNP-PAA. It can be concluded that the suppression in the PFC response to the T-independent antigen DNP-PAA in MLC is due to the generation of suppressor T-cells. The PFC response to the T-dependent antigen, SRBC, in MLC showed either suppression, no change, or rarely augmenation, suggesting that the allogeneic mixed spleen cell cultures can generate both suppressor and helper T cells and that the balance between helper and suppressor activity regulates the PFC response to a T-dependent antigen. Suppressor activity was also generated in a one-way MLC, but the degree of suppression depended upon which of the two strains was responding. Similar amounts of thymidine were incorporated in the one-way MLR irrespective of which strains was responding. Thus, the extent of proliferation in one-way MLR is not related to the degree of suppressor activity generated. The results further indicate that a difference between two strains in the I-C, S, and G regions of the major histocompatibility complex is required to generate suppressor activitiy that can depress the response to a T-independent antigen, MLC between strains differing in K, I-A, I-B, I-J, I-E, and D regions generate little or no suppressor activity in this system.

Acrylamides↗
PubMed1983

Generation of low m.w., C3-bearing immunoglobulin in human serum.

The generation of low m.w. C3-bearing immunoglobulin (lg) in normal human serum by an immune complex (IC) model was investigated in vitro by using discontinuous sucrose density gradient centrifugation (DGC) and an assay that measures C3-bearing Ig. In this method developed to measure circulating IC, all C3 and C3-bearing material is precipitated from serum by using anti-C3 sera in C3d antibody excess, and immune precipitated, C3-bearing Ig is quantitated by the uptake of 125I-5S-anti-IgG. When plasma from patients with clinically active systemic lupus erythematosus was assayed after DGC, most of the reactive material was low m.w. (7S), rather than greater than or equal to 19S as expected for IC, in agreement with a previous report. Low m.w., C3-bearing Ig was found in normal EDTA plasma after extended storage at -29 degrees C but not after storage at -70 degrees C. Such material was also generated in normal human serum during incubation at 37 degrees C and its generation was stimulated by the addition of an IC model, high m.w., heat-aggregated IgG (HMW-HAIgG). In experiments in which the participation of serum IgG was monitored by the addition of 125I-7S-IgG and 131I-HMW-HAIgG was used as an IC model, low m.w., C3-bearing Ig was generated exclusively from serum IgG and the amount generated was proportional to the concentration of 131I-HMW-HAIgG. No significant decrease in sedimentation of 131I-HMW-HAIgG was observed, but the ability of anti-C3 sera to precipitate 131I-HMW-HAIgG decreased 66% 4 hr after initial C activation. These results indicate that generation of nascent C3b in serum results in its interaction with monomeric serum IgG, producing low m.w., C3-bearing IgG. In addition, the data indicate that circulating IC that activate C have a brief time span during which they can be detected by methods that depend upon the binding of C3.

Animals↗
PubMed1984

Generation of human C3a, C4a, and C5a anaphylatoxins by protein A of Staphylococcus aureus and immobilized protein A reagents used in serotherapy of cancer.

Protein A (SpA) alone or immobilized on bacteria (e.g., Cowan strain I), collodion charcoal, or on Sepharose have been used in serotherapy of cancer in humans and experimental animals. Because SpA forms complexes with IgG that can activate complement, and the physiologic response during treatment often involves hypocomplementemia and reactions that are similar to those induced by anaphylatoxins, we used sensitive and specific radioimmunoassays to test the ability of SpA reagents to generate C3a, C4a, and C5a from human serum. The yield of anaphylatoxins depended on the dose of SpA, with the maximum generation of C3a (47 to 55 micrograms/ml) and C5a (1.4 to 1.9 micrograms/ml) being produced with levels of SpA that were maximally precipitated from serum. Maximum C4a levels (up to 15 micrograms/ml) were obtained at concentrations of SpA equal to or greater than the dose required to give optimal precipitation. The maximum concentrations of anaphylatoxins correspond to essentially quantitative conversions of C3 to C3a, C4 to C4a, and 40% of C5 to C5a after correction for levels found in serum incubated in pyrogen-free saline. Preformed insoluble complexes prepared from either serum or monomeric IgG also were capable of generating anaphylatoxins in fresh whole serum up to levels approximately equal to those observed in serum treated directly with an optimal amount of SpA. The preformed complexes from serum or IgG generated similar high concentrations of anaphylatoxins when carried through four sequential incubations with fresh serum, and complexes that contained approximately 1 microgram SpA were still active. Preincubating the insoluble complexes with chicken anti-SpA serum did not alter their activity. Incubation of serum with collodion charcoal coated with SpA, in a system that models the perfusion technique used to treat cancer, produced complexes that generated significant levels of C3a compared with levels found in serum passaged over albumin charcoal or in untreated serum. The C3a levels in serum from the albumin collodion charcoal were not significantly different from those found in untreated serum. Similar amounts of C3a, C4a, or C5a were observed in serum incubated with differing numbers of bacteria representing a strain of S. aureus rich in cell bound SpA (Cowan strain I) or a strain (Wood 46) deficient in SpA. This suggests that in intact bacteria, cell wall factors other than SpA (e.g., peptidoglycan) are predominantly responsible for generating anaphylatoxins.(ABSTRACT TRUNCATED AT 400 WORDS)

Anaphylatoxins↗
PubMed1995

[The computer-generated occlusion of Cerec-2 inlays and onlays].

The Cerec-2 unit offers three different options to generate the occlusion: anatomically extrapolated ("Extrapolation"), correlated to a wax-up or functionally generated path ("Correlation") and bucco-orally flat ("Linear") as known from Cerec-1. These three computer-generated occlusions were evaluated by measuring the vertical discrepancy and the specific time needed for manufacturing (design, machining, contouring and adjusting the occlusal relation) of inlays and overlays. The occlusion of inlays generated with "Extrapolation" (0.42 +/- 0.16 mm) and "Correlation" (0.80 +/- 0.17 mm) showed significantly (p < 0.001) less vertical discrepancy than "Linear" (2.46 +/- 0.50 mm). The specific production time of inlays differed significantly (p < 0.001) between "Extrapolation" (16.05 +/- 0.80 min), "Linear" (19.25 +/- 1.14 min) and "Correlation" (27.33 +/- 0.75 min). The vertical discrepancies of overlays generated with "Correlation" (1.26 +/- 0.43 mm) were significantly (p < 0.001) lower than with "Extrapolation" (2.46 +/- 0.50 mm) and "Linear" (2.75 +/- 0.57). The specific overlay production time was significantly (p < 0.001) longer with "Correlation" (39.44 +/- 1.36) than with "Linear" (23.9 +/- 1.26 min) and "Extrapolation" (23.71 +/- 1.01 min). Related to the technical status of 10/1994 and as a result of the present evaluation, "Extrapolation" was chosen to be the most practical of the computer-generated occlusions evaluated in the present study.

Ceramics↗
PubMed1995

IgE-dependent activation of cytokine-primed mouse cultured mast cells induces a delayed phase of prostaglandin D2 generation via prostaglandin endoperoxide synthase-2.

Mouse bone marrow-derived mast cells (BMMC) developed with IL-3 generate prostaglandin D2 (PGD2) through the utilization of prostaglandin endoperoxide synthase (PGHS)-1 within several minutes of cross-linking the high affinity Fc receptor for IgE (Fc epsilon RI) by hapten-specific IgE and Ag. We now report that this immediate generation of PGD2 is followed by a 15-fold induction of steady-state transcripts for PGHS-2, with a maximum at 30 min, accompanied by transient expression of PGHS-2 protein. When BMMC were pretreated with c-kit ligand (KL) in combination with IL-10 for 2 h, sensitized with IgE, and activated with Ag, their expression of steady-state transcripts for PGHS-2 increased 111-fold and their expression of PGHS-2 protein was markedly enhanced, with maximal expression at 1 h and 5 h, respectively, after activation. These events were accompanied by PGD2 generation from 1 to 10 h after activation that accounted for approximately 50% of total PGD2 generation. The expression of PGHS-1 protein did not change during this period. The optimal priming interval for the effect of KL plus IL-10 on the IgE-dependent induction of PGHS-2 was 2 h, at which time only this particular cytokine combination acted synergistically with activation by IgE and Ag. In contrast, at 2 days the accessory cytokines that could provide priming with KL included IL-3 and IL-9 in addition to IL-10. Dexamethasone, which inhibited the expression of PGHS-2 but not PGHS-1, and NS-398, a selective inhibitor of PGHS-2, each suppressed the delayed phase but not the immediate phase of PGD2 generation. Conversely, valeryl salicylate, a selective inhibitor of PGHS-1, suppressed the immediate but not the delayed phase of PGD2 generation after cell priming and IgE-dependent activation.

Animals↗
PubMed1993

The need for second-generation antihepatitis C virus testing in uremic patients on continuous ambulatory peritoneal dialysis.

OBJECTIVE: To assess the prevalence and clinical relevance of a hepatitis C virus (HCV) infection in continuous ambulatory peritoneal dialysis (CAPD) patients by first- (Ortho) and second-generation (Abbott and UBI) HCV antibody enzyme immunoassays. DESIGN: Thirty-two serum samples tested by first-generation HCV antibody enzyme immunoassays (EIA's) were reevaluated using two second-generation HCV antibody EIA's. Basic demographic data, history of blood transfusions, and duration of hemodialysis and CAPD were reviewed. Results were analyzed by chi square analysis, Wilcoxon rank sum, and the paired t-test. SETTING: The medical college's affiliated teaching hospital. RESULTS: The prevalence of the antibody anti-HCV increases with the duration of previous hemodialysis, but not with the duration of CAPD. The positive detection of anti-HCV by second-generation HCV antibody EIA's was higher than first-generation EIA's (25% and 34.4% vs 12.5%). CONCLUSION: The prevalence and clinical relevance of HCV infection can be more accurately studied using the second-generation assays in uremic patients.

Adolescent↗
PubMed1993

Hematopoietic precursors resistant to treatment with 4-hydroperoxycyclophosphamide: requirement for an interaction with marrow stroma in addition to hematopoietic growth factors for maximal generation of colony-forming activity.

We tested the ability of CD34+lin- precursor cells isolated from marrow after treatment with 4-hydroperoxycyclophosphamide (4HC) to generate colony-forming cells (CFC). In liquid cultures, recombinant human stem cell factor (SCF), in combination with interleukin-1 (IL-1), IL-3, IL-6, granulocyte-macrophage colony-stimulating factor, or granulocyte colony-stimulating factor caused untreated, but not 4HC-treated, CD34+lin- cells to form CFC. However, generation of CFC from CD34+lin- cells treated with 60 micrograms/mL of 4HC was possible in the presence of an irradiated allogeneic stromal cell layer. This generation was increased when combinations of hematopoietic growth factors including SCF and IL-3 were added. Maximal generation of CFC was seen after 11 to 21 days of culture. At that time, generation of CFC from CD34+lin- 4HC-treated cells equalled that from untreated cells. The phenotype of these 4HC-resistant CD34+lin- precursors was also further defined as CD38-. These studies show that the generation of CFC from the 4HC-resistant, highly immature population of CD34+lin- cells requires an as yet undefined interaction with marrow stroma in addition to known hematopoietic growth factors.

ADP-ribosyl Cyclase↗
PubMed1976

Neurophysiology of the motor output pattern generator for breathing.

In cats, there is a central pattern generator (CPG) capable of producing the motor output to drive breathing without any phasic sensory input. The phrenic activity driven by the CPG is, on each cycle, a long inspiratory discharge with continuously rising intensity, an abrupt turn-off, and a pause. The CPG is normally overridden by a reflex termination of inspiration. A sufficient lung inflation will terminate inspiration early, but has no other effect on the motor output. This is the Hering-Breuer inspiration inhibiting reflex. The lung volume necessary to terminate inspiration decreases during the course of an inspiration. The slowly adapting bronchial stretch receptors running in the vagus are the responsible afferents. These vagal afferents drive cells in the ventrolateral nucleus of the solitary tract. These cells also receive a rising excitation from the CPG. They sum these two inputs and thus show a falling threshold to vagal input. They probably generate the inspiration terminating trigger for the Hering-Breuer reflex. In deeply anesthetized breathing, the only active expiratory cells are in the nucleus retroambigualis. These do not make synapses with inspiratory cells. Thus breathing models based on reciprocal inhibition between inspiratory and expiratory cells cannot be correct. Inspiratory cells must themselves be capable of generating the rhythm. Invertebrates present many examples of repetitive burst generation by a single synergistic population. This usually involves cells that, in the absence of synaptic input, either fire continuous trains or rhythmical bursts of spikes. The cardiac ganglion of crustaceans may be a useful model for burst generation similar to breathing. In deeply anesthetized breathing there are two populations of medullary respiratory cells, those in the nucleus of the solitary tract (NST) and those in the nucleus retroambigualis (NRA). The NST has axons ramifying in the NRA and thus could drive it, but the reverse connections do not exist. Thus the current "best guess" is that the cells of the NST are the central pattern generator for breathing.

Action Potentials↗
PubMed1995

Requirement of CD4+ T cells and antigen-presenting cells for primary in vitro generation of CD8+ cytotoxic T cells against Ld-binding self-peptide p2Ca.

We investigated the cellular requirement for primary in vitro generation of cytotoxic T-lymphocytes (CTL) in BALB/c spleen cells against Ld-binding self-peptide p2Ca. Depletion of CD4+ T-cells in vitro by pretreatment with anti-CD4 monoclonal antibody (mAb) and complement or in vivo by administration of anti-CD4 mAb abrogated generation of CTL. Depletion of adherent cells by passing spleen cells through a nylon wool (NW) column also abrogated generation of CTL. Addition of peritoneal exudate cells (PEC) to spleen cells passed through the NW column restored CTL generation. These findings indicate that both CD4+ T-cells and antigen-presenting cells (APC) were necessary for CTL generation. Treatment of PEC with paraformaldehyde (PFA), but not mitomycin-C (MMC) abrogated their ability to restore CTL generation when mixed with spleen cells from the NW column, suggesting that an endocytic pathway could be involved in presentation of p2Ca on APC.

Amino Acid Sequence↗