Biomedical subjects

B D Clark

Publications and source records attributed to B D Clark.

At least 37 records · Page 2Linked to original sources

PubMed1995

Coagulation of whole blood stimulates interleukin-1 beta gene expression.

To study interleukin (IL)-1 beta gene expression, reverse transcription-polymerase chain reaction was used on 25-microL whole blood samples from 11 healthy subjects. Coagulated and unclotted whole blood was compared. There was no evidence of IL-1 beta gene expression in any time zero samples (i.e., whole blood from which mRNA was immediately extracted) from 11 subjects, whereas a 388-bp band representing IL-1 beta mRNA was detected in all coagulated samples. No mRNA for IL-1 beta was detected in EDTA-anticoagulated whole blood, although in these samples the addition of lipopolysaccharide as a positive control induced the expression of IL-1 beta. In time course studies on samples allowed to clot, mRNA for IL-1 beta was detectable after 30 min. These findings demonstrate that IL-1 beta gene expression is not present in circulating cells of healthy subjects and that coagulation is a stimulus for IL-1 beta gene expression. This may be a mechanism by which thrombosis produces inflammation and fever.

Adult↗

PubMed1995

A meta-analysis of breast implants and connective tissue disease.

Case reports have raised questions about an increased risk of connective tissue diseases (CTDs) among women with breast implants. From the reviews of more than 2,600 manuscripts, abstracts, and dissertations, this meta-analysis included 13 epidemiology studies that provided a relative risk (RR) estimate for the possible association between breast implants and CTDs. The meta-analysis summary RR was 0.76 for CTD in general (95% confidence interval [CI]: 0.55, 1.04; homogeneity p-value = 0.073) and was 0.98 for scleroderma (95% CI: 0.57, 1.64; homogeneity p = 0.006). Irrespective of which studies were aggregated in this meta-analysis, there was no significant increased risk for scleroderma, rheumatoid arthritis, or CTD in general. Conclusions from this study are consistent with the most recent review by the British Medical Devices Agency that found no scientific evidence to date of an increased risk of CTD associated with silicone gel breast implants.

Arthritis, Rheumatoid↗

PubMed1994

Altered interleukin-1 and tumor necrosis factor production and secretion during pyrogenic tolerance to LPS in rabbits.

Rabbits were injected intravenously with 10 micrograms/kg of endotoxin [lipopolysaccharide (LPS)] on days 0, 1, and 7, and rectal temperatures were monitored. The febrile responses were compared with circulating levels of interleukin-1 beta (IL-1 beta) and tumor necrosis factor (TNF) and in vitro synthesis of these cytokines by peripheral blood mononuclear cells (PBMC) isolated just before the injection of LPS. Fever after the first LPS injection was biphasic on day 0, attenuated and monophasic after the second LPS injection on day 1, and augmented after third injection of LPS on day 7. On day 1, circulating TNF and IL-1 beta levels were significantly (P < 0.05) decreased compared with those on days 0 and 7. Similarly, TNF and IL-1 beta synthesis by LPS-stimulated PBMC were significantly reduced on day 1. On day 7, cellular synthesis and secretion of IL-1 beta were significantly increased compared with that on day 0. A significant positive correlation was observed between fever index and total in vitro IL-1 beta synthesis by LPS-stimulated PBMC (r = 0.866, P = 0.001). These data demonstrate that pyrogenic tolerance in the rabbit after a single LPS injection is associated with decreased circulating IL-1 beta and TNF levels as well as decreased production of these cytokines in vitro. In addition, the pyrogenic hyperresponsiveness to LPS after 7 days is associated with increased synthesis and secretion of IL-1 beta from PBMC in vitro.

Animals↗

PubMed1994

Suppression of thyrotropin-releasing hormone gene expression by interleukin-1-beta in the rat: implications for nonthyroidal illness.

Nonthyroidal illness is characterized by low thyroid hormone levels and inappropriately normal or decreased TSH levels. To determine whether the hypothalamus contributes to these responses, TRH gene expression in hypophysiotropic neurons of the paraventricular nucleus (PVN) was investigated using semiquantitative in situ hybridization histochemistry in an animal model of nonthyroidal illness. Following the systemic administration of bacterial lipopolysaccharide (LPS; 250 micrograms/100 g BW), plasma T4, T3 and TSH were reduced but this was not associated with an increase in the content of proTRH mRNA in the PVN as occurs when plasma T4 and T3 concentrations fall during primary hypothyroidism. Constant infusion of human interleukin-1 beta (IL-1 beta) into the cerebrospinal fluid also reduced plasma T4 concentration. This persisted for the duration of the infusion but TSH was only suppressed after 7 days of infusion when body weight had declined. By 24 h, the content of proTRH mRNA in the PVN in IL-1 beta infused animals was significantly reduced from control values. These studies indicate that the peripheral administration of endotoxin or central administration of IL-1 beta in the rat is associated with a proTRH mRNA content in the PVN that may be inappropriately normal or reduced for the level of circulating thyroid hormone. We propose that the inability of hypophysiotropic neurons to induce TRH gene expression in nonthyroidal illness, when circulating thyroid hormone levels are low, is one of several factors that contributes to the inability of the anterior pituitary to increase its secretion of TSH.

Animals↗

PubMed1994

Chlorpromazine specifically inhibits peripheral and brain TNF production, and up-regulates IL-10 production, in mice.

We have previously shown that chlorpromazine (CPZ) inhibits tumour necrosis factor (TNF) production and protects against endotoxic shock in mice. In this paper we investigated the effect of pretreatment with CPZ, 4 mg/kg i.p. 30 min before, compared with dexamethasone (DEX; 3 mg/kg) on the induction of other endotoxin (lipopolysaccharide; LPS)-induced cytokines in the serum of mice, i.e. interleukin-1 alpha (IL-1 alpha), IL-6 and IL-10, and TNF. We also studied the effect of CPZ on serum and spleen-associated TNF. Both DEX and CPZ inhibited TNF production, whereas induction of IL-1 and IL-6 was inhibited by DEX but not by CPZ. DEX did not affect IL-10, while CPZ potentiated its induction. CPZ also inhibited spleen-associated TNF induction in LPS-treated mice, suggesting an effect on the synthesis of TNF. CPZ inhibited TNF induction by Gram-positive bacteria (heat-killed Staphylococcus epidermidis) and by anti-CD3 monoclonal antibodies. Intraperitoneal administration of CPZ also inhibited the induction of brain-associated TNF induced by intra-cerebroventricular injection of LPS. Therefore, CPZ is a more specific inhibitor of TNF production than DEX; in particular, CPZ increased the induction of IL-10, which is a 'protective' cytokine known to inhibit LPS toxicity and TNF production. CPZ inhibited TNF production in vivo, irrespective of the TNF stimulus used to induce TNF. Finally, CPZ did not induce the 'rebound' effect of DEX that, when given 24 hr before LPS, potentiates TNF production, but it did inhibit TNF production after 24 hr.

Animals↗

PubMed1994

Thermal injury induces very early production of interleukin-1 alpha in the rat by mechanisms other than endotoxemia.

BACKGROUND: Cytokines are putative mediators of thermal injury-induced systemic changes. We studied the effects of thermal injury on cytokine activation in vivo with a sensitive radioimmunoassay specific for rat interleukin-1 alpha (IL-1 alpha). METHODS: We characterized the organ distribution and expression kinetics of IL-1 alpha in rats submitted to either 20% total body surface area cutaneous burn, muscle burn, or endotoxic shock. Rats were killed at various time points, and liver, lung, spleen, ileum, thymus, kidney, skin, and plasma were harvested. Tissues were homogenized, and the supernates were assayed for rat IL-1 alpha. The assay detection limit was 1.5 ng/gm wet tissue (WT). RESULTS: Thermal injury induced marked elevations of IL-1 alpha levels in the liver and lung, and maximal levels were reached at 2.5 hours when compared with controls. In the liver mean IL-1 alpha levels in cutaneous burn injury were 16.5 +/- 6.2 ng/gm WT, whereas in sham injury they were 1.7 +/- 0.1 ng/gm WT, p < or = 0.05; in the lung IL-1 alpha levels with cutaneous burn injury were 10.3 +/- 1.3 ng/gm WT, whereas sham injury levels were 1.9 +/- 0.8 ng/gm WT, p < or = 0.002). Levels in all other organs and plasma were below detection limits. Muscle burn injury had similar elevated levels of IL-1 alpha in the liver at 1 hour, indistinguishable from cutaneous burn. In contrast, endotoxin challenge resulted in dramatic elevation of IL-1 alpha levels in all organs tested except for the kidney, whereas the skin maintained its usual large amounts of IL-1 alpha. CONCLUSIONS: These data indicate that thermal or mechanical injury induce very early and organ-specific association of IL-1 alpha in vivo by mechanisms other than endotoxemia.

Animals↗

PubMed1993

Identification of the promoter region of human interleukin 1 type I receptor gene: multiple initiation sites, high G+C content, and constitutive expression.

To better understand the role of interleukin 1 (IL-1) and its receptor in disease, we have isolated a genomic clone of the human IL-1 type I receptor and have identified the promoter region. There are multiple transcriptional initiation sites as demonstrated by primer extension. DNA sequence analysis shows that the promoter region contains neither a TATA nor a CAAT box; however, the 5' upstream regulatory elements contain two AP-1-like binding sites. The internal regulatory sequences found immediately downstream to the 5' transcriptional start site contain four Sp1 binding domains and have a high G+C content of 75%. This portion of the 5' untranslated region of the mRNA can form stable secondary structure as predicted by computer modeling. Base pairs -4 to + 10 share striking resemblance to an initiator sequence that directs basal expression of certain TATA-less genes-e.g., terminal deoxynucleotidyltransferase in lymphocytes. The IL-1 receptor promoter directs basal expression of chloramphenicol acetyltransferase in transiently transfected cells. Overall, the promoter of the IL-1 type I receptor gene resembles that of constitutively expressed genes that have housekeeping- and/or growth-related functions. The constitutive nature of the promoter may account for this gene being expressed at low levels in diverse cell types. Our finding sheds more understanding into the mechanisms governing the regulation of the IL-1 receptor in health and disease.

Base Composition↗

PubMed1993

Intestinal production of interleukin-1 alpha during endotoxemia in the mouse.

Interleukin-1 (IL-1) may be involved in gut permeability to macromolecules and gut glutamine metabolism during endotoxemia. We developed a sensitive radioimmunoassay specific for mouse IL-1 alpha (detection limit of 100 pg/ml, or 5 pM) and measured intestinal levels of IL-1 alpha in response to endotoxin. CD-1 mice (N = 190) were randomized to intraperitoneal (ip) or intravenous (i.v.) lipopolysaccharide (LPS) infusion (15 micrograms/g or 1.5 micrograms/g Escherichia coli 0111:B4 LPS) or saline. Mice were sacrificed at Time 0, 30 min, 1 hr, 2.5 hr, 4 hr, 6 hr, 12 hr, and 24 hr (3 mice/group/time point). Small bowel (SB) and large bowel (LB) were harvested and compared to liver. Duodenum, upper jejunum, midjejunum, terminal ileum, cecum, ascending colon, and sigmoid were analyzed in separate experiments. Tissues were frozen, weighed, and homogenized, the homogenates were centrifuged, and the supernates were assayed for immunoreactive IL-1 alpha. IL-1 alpha was expressed as pg/g wt +/- SEM (lowest detectable amount = 1000 pg/g wet tissue (WT)). SB but not LB from normal controls had constitutively elevated levels of IL-1 alpha (6177 +/- 1640 pg/g WT). LPS ip or i.v. produced lethargy, diarrhea, and a dramatic elevation of IL-1 alpha levels in both SB and LB. In SB, IL-1 alpha was elevated compared to baseline at 1 hr (19201 +/- 626 pg/g WT) and reached a fivefold maximal increase at 2.5 hr (31775 +/- 503 pg/g WT) following 15 micrograms/g ip.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Detection of tumor necrosis factor soluble receptor p55 in blood samples from healthy and endotoxemic humans.

The tumor necrosis factor (TNF) soluble receptor derived from the cell surface p55 TNF receptor (TNFsRp55) is a naturally occurring substance generated during infection and inflammation. TNFsRp55 inhibits biologic effects of TNF. An RIA was developed to quantitate TNFsRp55 in human blood. Recovery of TNFsRp55 from blood anticoagulated with EDTA was optimal compared with recovery from serum or heparinized plasma. TNF did not interfere with the assay. With the RIA based on radiolabeled nonglycosylated Escherichia coli-derived recombinant TNFsRp55, a mean concentration of 198 +/- 15 pg/mL was found in 14 volunteers. When glycosylated CHO cell-derived TNFsRp55 was used, the mean level was 1656 +/- 95 pg/mL. Infusion of endotoxin into volunteers induced TNFsRp55, which peaked at 517 +/- 99 pg/mL for the E. coli-based RIA and 7300 +/- 1810 pg/mL for the CHO cell-based RIA. These findings demonstrate that blood collected in EDTA is optimal for measuring circulating TNFsRp55 and that this soluble receptor is present in health but elevated during endotoxemia.

Adolescent↗

PubMed1993

Differential regulation of cytokine production in lipopolysaccharide tolerance in mice.

We investigated the pattern of down-regulation of cytokine production in endotoxin (lipopolysaccharide [LPS]) tolerance. A 4-day treatment with LPS (35 micrograms per mouse) was followed by a challenge on day 6 with one more injection of LPS. Circulating tumor necrosis factor (TNF) and interleukin-6 (IL-6) could not be induced (> 99% inhibition) by LPS in LPS-tolerant mice; colony-stimulating factor (CSF) was also down-regulated by more than 95%, whereas interferon (IFN) and IL-1 syntheses were only partially inhibited. To study the mechanism of cytokine down-regulation in tolerance, we attempted to reverse the tolerant state by pretreatment with phorbol 12-myristate 13-acetate (PMA) (4 micrograms per mouse) 10 min before the LPS challenge. PMA completely restored IL-6 production and partially that of CSF. PMA had no effect on IFN production and inhibited the induction of IL-1. TNF production was also not restored by PMA. To investigate the role of endogenously produced cytokines in the development of LPS tolerance, we administered IL-6, TNF, or IL-1 alpha, using the same treatment schedule as that for LPS. Whereas IL-6 had no effect, IL-1 alpha or TNF induced partial tolerance to LPS in terms of inhibition of LPS-stimulated TNF and IL-6 production. However, a full LPS-tolerant state could not be induced by administration of recombinant cytokines, suggesting the existence of additional mechanisms, such as a loss of LPS receptors or changes in release of soluble binding proteins.

Animals↗

PubMed1993

Cutaneous stimulation fails to alter motor unit recruitment in the decerebrate cat.

1. An attempt was made to repeat the observation that cutaneous input to the cat medial gastrocnemius (MG) muscle sometimes had the differential effect of inhibiting motoneurons with slow axonal conduction velocity while simultaneously exciting others with fast conduction velocity. Dual microelectrode recording from intact ventral root filaments was used to study the effects of cutaneous inputs on recruitment order and on firing frequency of physiologically characterized MG motor units in decerebrate cats. Motor responses to pinch of the skin over the lateral surface of the ankle as well as electrical stimulation of the caudal cutaneous sural (CCS) nerve were contrasted with the responses to static muscle stretch as well as muscle vibration. 2. In contrast to the prediction, recruitment order in pairwise tests was the same for skin pinch or CCS stimulation as it was for MG stretch or vibration in all 32 tested pairs of motor units. This sample included seven pairs comprising one slow-twitch (S) and one fast-twitch motor unit, where the predicted reversal of recruitment should have been most apparent. Regardless of the source of excitation, recruitment of motor units of the MG was consistent with Henneman's size principle in approximately 90% of trials. 3. Skin pinch increased the firing rate of 30 of 32 individual motor units previously activated by stretch or vibration, including 7 slow-twitch units. In the remaining two units, skin pinch transiently (100-400 ms) slowed the firing of an S unit in 11 of 13 vibration + pinch trials. The other unit (type unknown) showed one or two retarded spikes in each of four vibration + pinch trials. In three S units, including the lone inhibitable unit and two others that were only excited by skin pinch, there was a significant positive rank correlation between change in unit firing frequency and change in soleus integrated electromyographic activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Motor-unit recruitment in self-reinnervated muscle.

1. Recruitment order of motor units in self-reinnervated medial gastrocnemius (MG) muscles was studied in decerebrate cats 16 mo after surgical reunion of the cut MG nerve. Pairs of MG motor units were isolated by dual microelectrode penetration of ventral roots to measure their recruitment sequence during cutaneous reflexes in relation to their physiological properties. 2. Physiological properties of reconstituted motor units appeared normal, as expected. Also normal were the relationships among these properties: twitch and tetanic tension tended to increase with axonal conduction velocity and decrease with twitch contraction time. A small fraction of motor units (10/116) in reinnervated muscles produced either no measurable tension or unusually large amounts of tension compared with controls. This was the only distinct feature of the sample of reconstituted units. 3. In muscles reinnervated after nerve section, stretch was notably ineffective in eliciting reflex contraction of MG muscles or their constituent motor units (only 5/116 units). Incomplete recovery from nerve section was probably the cause of this impairment, because stretch reflexes were readily evoked in adjacent untreated muscles and in one reinnervated MG muscle that was studied 16 mo after nerve crush. In contrast with the ineffectiveness of muscle stretch, sural nerve stimulation succeeded in recruiting 49/116 units, a proportion fairly typical of normal MG muscles. 4. The contractions of the first unit recruited in cutaneous reflexes tended to be slower and less forceful than those of the other unit in a pair. By these measures, recruitment obeyed the size principle. This recruitment order with respect to unit contractile properties was not significantly different (P > 0.05) between untreated and reinnervated muscles but was significantly (P < 0.005) different from random order in both groups. The same recruitment pattern was observed for pairs of motor units sampled from the muscle reinnervated after nerve crush, whether units were recruited by muscle stretch or sural nerve stimulation. 5. The usual tendency for motor units with slower conduction velocity (CV) to be recruited in sural nerve reflexes before those with faster CV was not strong in reinnervated muscles. After nerve section the proportion of units exhibiting the usual recruitment pattern was not significantly different (P > 0.05) from a random pattern for CV. 6. The central finding is that the normal recruitment patterns recover from nerve injury in a muscle that is reinnervated by its original nerve. By contrast, stretch reflexes do not recover well from nerve section, and this deficiency may contribute to motor disability.

Animals↗

PubMed1993

Endotoxin-induced corticotropin-releasing hormone gene expression in the hypothalamic paraventricular nucleus is mediated centrally by interleukin-1.

In the acute phase of bacterial infection, a variety of cytokines, including interleukin-1 (IL-1), are elicited by bacterial endotoxin in both the periphery and the central nervous system. Bacterial endotoxin has been previously reported to profoundly activate the hypothalamic-pituitary-adrenal axis, resulting in elevated glucocorticoid secretion that may serve an important role as part of the inhibitory feedback mechanisms on the activated immune system. To determine whether IL-1 acts within the brain to mediate endotoxin-induced CRH gene expression in the hypothalamic paraventricular nucleus (PVN), we studied the effect of administering the human IL-1 receptor antagonist (IL-1ra) into the brain, a competitive inhibitor of IL-1, on CRH gene expression in the PVN after systemic lipopolysaccharide (LPS) treatment. Eight hours after the ip administration of LPS, the paraventricular CRH mRNA content was elevated 3-to 4-fold (P < 0.01) compared to the control value, and this elevation could be completely abolished by central IL-1ra pretreatment (P < 0.05 compared to LPS-treated group; P > 0.05 compared to controls). In contrast, systemic IL-1ra administration did not inhibit endotoxin-induced CRH gene expression in the PVN. These studies demonstrate that LPS stimulates hypothalamic CRH by a mechanism that involves the action of IL-1 within the central nervous system and may proceed independently of peripheral actions of IL-1 circulating in the bloodstream.

Animals↗

PubMed1992

Effect of interleukin-1 (IL-1) blockade on cytokine synthesis: I. IL-1 receptor antagonist inhibits IL-1-induced cytokine synthesis and blocks the binding of IL-1 to its type II receptor on human monocytes.

Interleukin-1 (IL-1) induces IL-1, tumor necrosis factor alpha (TNF alpha), and IL-6 gene expression and synthesis in a variety of cells. In this study, we investigated the ability of human recombinant IL-1 receptor antagonist (IL-1ra) to inhibit IL-1-induced cytokine production in human peripheral blood mononuclear cells (PBMC) and isolated monocytes. IL-1ra alone at concentrations as high as 1 microgram/mL did not induce IL-1 alpha, IL-1 beta, TNF alpha, or IL-6 synthesis. Suppression of IL-1-induced IL-1, TNF alpha, or IL-6 synthesis was dose-dependent (P less than or equal to .0001). At a twofold molar excess, IL-1ra inhibited IL-1-induced IL-1 or TNF alpha synthesis by 50% (P less than .01); an equimolar concentration of IL-1ra inhibited synthesis of these two cytokines by over 20% (P less than .05). A 10-fold molar excess of IL-1ra over IL-1 beta reduced IL-1 beta-induced IL-1 alpha by 95% (P = .01) and IL-1 alpha-induced IL-1 beta by 73% (P less than .01). IL-1ra added to PBMC 8 hours after stimulation with IL-1 beta was still able to inhibit IL-1 alpha, TNF alpha, and IL-6 synthesis (P less than or equal to .01). A similar reduction in IL-1 beta-induced IL-1 alpha was observed when IL-1 beta was removed from the cultures after 8 hours of stimulation (P less than .05), suggesting a prolonged presence of IL-1 or restimulation of IL-1 receptors on monocytes is required for the induction of cytokines. In elutriated monocytes, a 10-fold molar excess of IL-1ra reduced IL-1 beta-induced IL-1 alpha by 82% (P less than .05), TNF alpha by 64% (P = .05), and IL-6 by 47% (P less than .05). 125I-IL-1 beta was bound to purified monocytes, cross-linked, and immunoprecipitated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed a band at 85 Kd corresponding to the 68-Kd IL-1 receptor type II (IL-1RtII). Excess unlabeled IL-1 beta or IL-1ra blocked the binding of 125I-IL-1 beta to the IL-1RtII. We conclude that IL-1ra inhibits IL-1-induced cytokine synthesis and competes with IL-1 for the IL-1RtII on human monocytes.

Cytokines↗

PubMed1992

Interleukin 4 (IL) 4 up-regulates gene and surface IL 1 receptor type I in murine T helper type 2 cells.

The T cell-derived cytokine interleukin (IL) 4 is known to increase the proliferative response of T cells stimulated with IL 1. IL 4 is also an autocrine growth factor for type II T helper cells (Th2) cells. In the present studies, we examined the effect of murine recombinant IL 4 on the expression of the IL 1 receptor type I (IL 1RtI) in murine Th2 cell lines at the mRNA and surface level. Using a specific anti-murine IL 1RtI monoclonal antibody and flow microfluorometry, we found that IL 4 increased the surface expression of IL 1RtI in a dose-dependent manner. In D10S cells, a subline of the Th2 cell line D10.G4.1, 50-500 pg/ml IL 4 up-regulated the receptor 1.8- to 3.2-fold (p less than 0.05). This up-regulation was also seen at the mRNA level. The effect was not due to increased stability of the mRNA, since IL 4 did not modify the half-life of IL 1RtI mRNA. IL 4 also up-regulated IL 1RtI on CDC25 cells, another Th2 cell line. However, we did not observe an effect of IL 4 on gene expression of IL 1RtI in BALB/c 3T3 fibroblasts. IL 2 and IL 4 showed an additive effect in up-regulating IL 1RtI and D10S cells. These studies indicate that IL 4 up-regulates IL 1RtI in murine Th2 cells by increasing gene expression for IL 1RtI without affecting mRNA stability. Thus, IL 4 production by Th2 cells may amplify the immune response via up-regulation of IL 1RtI.

Animals↗

PubMed1992

N-acetylcysteine and glutathione as inhibitors of tumor necrosis factor production.

TNF is a major mediator in the pathogenesis of endotoxic shock, and its inhibition has a protective effect in various animal models of sepsis or endotoxin (lipopolysaccharide, LPS) toxicity. LPS treatment also induces an oxidative damage mediated by increased production of reactive oxygen intermediates. N-Acetylcysteine (NAC) is an antioxidant and a precursor of the synthesis of glutathione (GSH) and was reported to protect against LPS toxicity and LPS-induced pulmonary edema. In this study we investigated the effect of NAC on TNF production and LPS lethality in mice. The results indicated that oral administration of NAC protects against LPS toxicity and inhibits the increase in serum TNF levels in LPS-treated mice. The inhibition was not confined to the released form of TNF, since NAC also inhibited LPS-induced spleen-associated TNF. On the other hand, the inhibitor of GSH synthesis, DL-buthionine-(SR)-sulfoximine (BSO), had the opposite effect of potentiating LPS-induced TNF production, and this was associated with a decrease in liver GSH levels. Repletion of liver GSH with NAC reversed this effect. NAC was also active in inhibiting TNF production and hepatotoxicity in mice treated with LPS in association with a sensitizing dose of Actinomycin D. These data indicate that GSH can be an endogenous modulator of TNF production in vivo. On the other hand, NAC pretreatment did not inhibit other effects of LPS, particularly induction of serum IL-6, spleen IL-1 alpha, and corticosterone, in the same experimental model, suggesting that the observed effect could be specific for TNF.

Acetylcysteine↗

PubMed1992

Crossmatch prediction of highly sensitized patients.

1. A subset of negative reactions of sera from highly sensitized patients to donor lymphocytes are predicted with high accuracy (96.5% negative correct). 2. The prediction is performed by a hybrid expert system (HES) which uses multiple knowledge of stochastic (SCORES), artificial neural net (ANN), and genetic algorithm (GA) techniques. 3. All knowledge for the T-cell predictions is derived from serological reactions of the investigated sera (93) to a large panel (284). 4. When analyzing 5 HLA Class I typing sera controls, HES performs better than a standard serum analysis method in 3 measurement categories: r value; percent correct; and percent negative correct. 5. SCORES and ANN produce the strongest complementary association. SCORES is the best method with low PRA sera, while ANN is better at predicting high PRA sera. GA performs very poorly with high PRA sera. 6. HES can acquire knowledge from any of the various methods used for serum screening and crossmatch testing. Therefore, there is no need for method standardization as each laboratory will produce its own program incorporating its patients' data. High standardization of HLA Class I typing is necessary. 7. Most recipients for whom donors are never selected by HES are in the PRA range of 97-100%. 8. Certainty level categorization of a crossmatch gives clinical flexibility in judgement of potential donors. 9. All programs are written in the C language and are portable to numerous platforms. HES is implemented on an inexpensive IBM-PC compatible computer and can calculate predictions quickly. 10. HES predicts negative crossmatches with enough accuracy to initiate an organ sharing protocol to increase the chance for highly sensitized patients to obtain a transplant.

Algorithms↗

PubMed1992

Effect of mismatching serologically defined residues on kidney transplant survival.

Amino acids within the HLA class I and II molecules were first examined individually for correlation with antibody reactions of over 50,000 antisera. The amino acids that correlated with the serologic reactions were classified as serologically defined: approximately half of the amino acids fell within that category, and the other half were employed as controls. The cadaver donor kidney transplant survival for patients who were mismatched for each of the sera-defined amino acids were compared to mismatches of the nonserologically defined amino acids. No differences were noted in the graft survivals of patients with mismatches for the serologically defined amino acids of HLA-A, -B, and -DR loci and for the nonserologically defined amino acids. Since many of the patients also had additional amino acids of mismatch, we cannot yet conclude that the serologically defined amino acids do not significantly influence graft outcome. In other words, the test may not have been sensitive enough to detect the degree of immunogenicity that may exist. However, we can conclude that mismatches for no single amino acid are strongly immunogenic.

Amino Acid Sequence↗