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Biomedical subjects

C B Brown

Publications and source records attributed to C B Brown.

At least 19 recordsLinked to original sources
PubMed1992

Role of carbohydrate modification in the production and secretion of human granulocyte macrophage colony-stimulating factor in genetically engineered and normal mesenchymal cells.

Colony-stimulating factors (CSFs) are a group of acidic glycoproteins which stimulate the proliferation and differentiation of hematopoietic progenitor cells in vitro and stimulate hemopoiesis in vivo. Human GM-CSF contains two N-linked carbohydrate side chains of the complex acidic type and several sites of O-linked carbohydrate clustered on serine and threonine residues near the N-terminus of the molecule. Previous studies have failed to detect a significant functional role for the carbohydrate modification characteristic of human GM-CSF. Using permanent cell lines and transient expression systems which produce moderate to high levels of native or carbohydrate-deficient forms of the growth factor, the role of carbohydrate modification in the biosynthesis and secretion of GM-CSF was studied. Unlike a number of other secreted glycoproteins, the transient time and secretory efficiency of several carbohydrate-deficient mutants of GM-CSF are indistinguishable from those of the native growth factor in BHK, 293, COS, and ldlD cells. Furthermore, normal human endothelial cells and fibroblasts, which normally produce the growth factor, can synthesize and secrete GM-CSF that lacks all forms of carbohydrate modification. These studies help to point out the range of roles played by carbohydrate modification in the biosynthesis, assembly, and secretion of glycoprotein hormones.

Animals↗
PubMed1992

Plasma levels of the anaphylatoxins C3a and C4a in patients with IgA nephropathy/Henoch-Schönlein nephritis.

Measurements of plasma anaphylatoxins C3a and C4a were carried out as an indicator of in vivo complement activation in 46 patients suffering from IgA nephropathy/Henoch-Schönlein nephritis. There was a significant correlation between plasma levels of C4a and plasma creatinine and urea. We also found a significant correlation of plasma levels of C3a with plasma creatinine. We propose that the measurement of anaphylatoxin levels provides a sensitive indicator of in vivo complement activation and may serve as an additional method for monitoring the progress of disease in these patients.

Adult↗
PubMed1992

Decreased granulocyte-macrophage colony-stimulating factor production by human neonatal blood mononuclear cells and T cells.

Impaired production and delivery of neutrophils to the site of infection have been implicated in the increased susceptibility of the neonate to infection. Because granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) play critical roles in the production of neutrophils from marrow precursors, we assessed the ability of leukocytes from neonates and adults to produce GM-CSF, G-CSF, and, for comparison, macrophage colony-stimulating factor (M-CSF) after stimulation with concanavalin A +/- phorbol myristate acetate [blood mononuclear cells (MC) and T lymphocytes] or lipopolysaccharide (monocytes). MC and monocytes from adult and neonatal subjects produced mRNA for GM-CSF, G-CSF, and M-CSF, whereas T cells produced only GM-CSF mRNA. Neonatal MC and T cells accumulated only approximately 30% as much GM-CSF mRNA as did adult MC and T cells. In contrast, the accumulation of GM-CSF mRNA by neonatal and adult monocytes was similar. Neonatal MC also accumulated similar amounts of G-CSF mRNA and somewhat more M-CSF mRNA than did adult MC; results with monocytes were similar to those with MC. Results of colony-stimulating activity bioassays on supernatants from neonatal and adult MC stimulated with concanavalin A paralleled the mRNA results.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Natural history of chronic renal failure: a reappraisal.

In this retrospective study we have analysed the rate of progression of renal insufficiency, ascertained from the slopes of the plot of inverse serum creatinine against time, of 102 patients with moderate to severe chronic renal failure (CRF). We have applied 'breakpoint' analysis of the slopes to identify changes in the rate of progression and attempted to determine the factors associated with these changes. Seventy-one patients were found to have progressive CRF, while the remaining 31 had stable or improving renal function. Of the parameters studied, using weighted least-squares analysis, proteinuria was the most significant predictor of progression (regression coefficient: -0.1775, P = 0.0075, adjusted r2 = 0.1059). A positive correlation was observed between proteinuria and diastolic blood pressure (DBP) (r = 0.336, P = 0.0054). Once the predictive value of proteinuria was taken into account, there was no difference in the progression rate between diagnostic groups, other than those patients with polycystic kidney disease who had a significantly faster rate of progression (P = 0.0037). In 49 patients, there was at least one change in the rate of progression with time. There was an inverse correlation between change in slope and a change in DBP (r = -0.352, P = 0.003). We conclude that changes in DBP are often associated with the frequent changes in the rate of progression of CRF. However, a causal link could not be established as in a large number of cases the two changes appeared to occur simultaneously in the absence of changes in antihypertensive therapy.

Adult↗
PubMed1991

Cytokines in chronic inflammatory arthritis. VI. Analysis of the synovial cells involved in granulocyte-macrophage colony-stimulating factor production and gene expression in rheumatoid arthritis and its regulation by IL-1 and tumor necrosis factor-alpha.

Granulocyte-macrophage CSF (GM-CSF) is a potent stimulator of macrophages and neutrophils and is produced by rheumatoid arthritis (RA) synovium. We now report studies that identify some of the synovial cells and cytokines responsible for local GM-CSF production and gene expression in RA. GM-CSF was assayed by ELISA in supernatants from cultured RA fibroblast-like synoviocytes stimulated with various cytokines (IL-1 beta, TNF-alpha, macrophage-CSF, IFN-gamma, IL-6, and TGF-beta). Immunoreactive GM-CSF was detected in IL-1 beta and TNF-alpha-stimulated cultures, but not in cells cultured in medium or stimulated with any of the other cytokines. IL-1 and TNF-alpha had a synergistic effect on GM-CSF production. GM-CSF gene expression by fibroblast-like synoviocytes was analyzed by ribonuclease protection assay, Northern blot analysis, and in situ hybridization. Both IL-1 beta and TNF-alpha induced GM-CSF mRNA accumulation, with a maximum effect after 4 h of stimulation. We then studied GM-CSF production by macrophage-like synoviocytes (MLS) isolated from fresh synovial specimens by flow microfluorimetry. Fresh MLS spontaneously secreted the cytokine and exogenous IL-1 beta or TNF-alpha had no effect. After 1 wk in culture, additional stimulation with IL-1 beta or TNF-alpha was required for GM-CSF production. Finally, in situ hybridization performed on freshly isolated subpopulations of synovial cells, identified GM-CSF RNA transcripts in MLS.

Arthritis, Rheumatoid↗
PubMed1991

Identification of functionally distinct domains of human granulocyte-macrophage colony-stimulating factor using monoclonal antibodies.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a glycoprotein that is required for the survival, growth, and differentiation of hematopoietic progenitor cells. Although the primary structure of GM-CSF is known from cDNA cloning, the relationship between structure and function of GM-CSF is not fully understood. Fifteen different monoclonal antibodies (MoAbs) to human GM-CSF were generated to map immunologically distinct areas of the molecule. Each of the MoAbs was biotinylated and shown by enzyme-linked immunosorbent assay to bind to recombinant GM-CSF that had been affixed to a solid phase. Each of the 15 unconjugated MoAbs was then used to compete with each biotinylated MoAb for binding to GM-CSF. These cross-blocking studies identified eight distinct epitopes of native GM-CSF. Seven of these epitopes were also present in denatured GM-CSF by Western blotting, and four of the epitopes were at least partially conserved on GM-CSF that was reduced in beta-mercaptoethanol. MoAbs to four of eight epitopes neutralized both recombinant (glycosylated and nonglycosylated) and natural human GM-CSF in a GM colony-forming unit (CFU-GM) assay and blocked GM-CSF-induced activation of neutrophils. For most of the antibodies there was a good correlation between neutralizing activity and the capacity to block binding of 125I-GM-CSF to neutrophils or blasts. Non-neutralizing antibodies to one epitope partially blocked binding of 125I-GM-CSF to neutrophils. None of the MoAbs neutralized interleukin-3, G-CSF, or M-CSF. The locations of seven of the epitopes could be partially mapped with regard to the amino acid structure by determining reactivity to GM-CSF synthetic peptides or to human-mouse chimeric GM-CSFs. The neutralizing antibodies were found to map to amino acids 40-77, 78-94, or 110-127. Thus, these MoAbs are useful to identify functional domains of GM-CSF and in identifying regions that are likely to be involved in receptor interaction.

Amino Acid Sequence↗
PubMed1991

Hematopoietic colony-stimulating factors.

In summary, hematopoietic growth factors have been discovered, biochemically characterized, cloned, produced by recombinant DNA technology, and put into clinical use in a period of 25 years. We are approaching a greater understanding of the cellular anatomy and molecular mechanisms that regulate production of the CSFs, the ways in which the CSFs interact with their cell surface receptors and trigger their biological effects, the nature of these receptors themselves and their mechanisms of signal transduction, and the effects of the CSFs in vitro and in vivo on hematopoietic progenitor cells and mature leukocytes. However, many questions remain. What is the mechanism that couples growth-factor binding to the triggering of cellular proliferation? How do multi-CSF and GM-CSF cross-compete at the level of the cell-surface receptor, and yet show no primary amino acid sequence homology? What are the mechanisms that regulate the tissue expression profile of multi-CSF compared to the genetically similar growth factor GM-CSF? And, what are the optimal dosages, schedules of administration, and combinations of CSFs optimal for each of several conditions of marrow failure? These are but a few of the questions that continue to occupy much current research interest.

Agranulocytosis↗
PubMed1991

Short-term effects of calcium antagonists on renal haemodynamics in patients with chronic renal failure.

Experimental evidence suggests that pharmacological manipulations of glomerular haemodynamics may affect the progression of chronic renal insufficiency and scarring. In this study, we have investigated the short-term (4 weeks) renal haemodynamic effects of nifedipine and nitrendipine (10 mg/thrice daily) in two separate groups of 6 patients with stable chronic renal failure (CRF) (glomerular filtration rate, GFR: 9.7-47.8 ml/min/1.73 m2). Patients were studied on three occasions: (1) before the administration of the calcium antagonist, (2) after 4 weeks of treatment and (3) 4 weeks after the discontinuation of the drug. Mean arterial pressure fell significantly on nifedipine: from 116.33 +/- 12.25 to 107.22 +/- 18.67 mm Hg, p less than 0.05, and on nitrendipine: from 112.22 +/- 10.04 to 102.22 +/- 13.77 mm Hg, p less than 0.05. There was no significant effect of either calcium antagonist on GFR, effective renal plasma flow (ERPF), proteinuria or natriuresis. Consequently, renal vascular resistance (RVR) fell in both experimental groups, nifedipine: from 51.40 +/- 28.77 to 44.97 +/- 30 dyn s cm-5 x 10(3) (mean +/- SD), and nitrendipine: from 37.04 +/- 18.46 to 30.47 +/- 15.56 dyns s cm-5 x 10(3), p less than 0.05. These results show that calcium antagonists reduce systemic blood pressure whilst GFR and ERPF are maintained. The fall in the RVR of patients with CRF treated with calcium antagonists may confer on these agents a therapeutic advantage in the management of progressive renal insufficiency.

Adolescent↗
PubMed1991

Plasma levels and mode of excretion of the anaphylatoxins C3a and C4a in renal disease.

Plasma levels of the anaphylatoxins C3a and C4a were examined in patients suffering with various renal diseases. Raised levels were observed in a considerable number of patients; although such elevation could be ascribed to in vivo complement activation in cases of immune complex glomerulonephritis, we found that raised plasma C4a levels appeared to be related to impaired renal function, suggesting that C4a anaphylatoxin is cleared by the kidneys. No such relationship was found in the case of the anaphylatoxin C3a suggesting the possible existence of another mechanism of elimination of C3a.

Adult↗
PubMed1990

Two neutralizing monoclonal antibodies against human granulocyte-macrophage colony-stimulating factor recognize the receptor binding domain of the molecule.

Using a series of mutant and chimeric human-mouse granulocyte-macrophage-CSF molecules the binding epitopes of two neutralizing mAb antibodies to human GM-CSF have been mapped. Both intact antibody and Fab fragments neutralize the biologic activity of human GM-CSF. The epitope of one of the antibodies contains residues widely separated in the primary structure of the growth factor that suggests that these two regions are adjacent in the tertiary structure of the molecule. In addition, evidence is presented that both mAb neutralize the activity of this cytokine by blocking the receptor binding domain of human GM-CSF.

Animals↗
PubMed1990

Molecular modeling of human granulocyte-macrophage colony-stimulating factor.

The colony-stimulating factors (CSFs) are a group of acidic glycoproteins which are required for the proliferation of hematopoietic progenitor cells and for their differentiation into mature blood cells. Receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF) are present on a wide spectrum of cells including erythroid, mixed erythroid-non-erythroid, mixed myeloid and megakaryocytic progenitors, and on mature neutrophils, eosinophils and monocytes. A number of studies are now available which provide insights into the structure-function relationships of human GM-CSF. In an attempt to further understand the interaction between GM-CSF and its cell surface receptor, we have constructed models of the tertiary structure of human GM-CSF using the known disulfide bonding pattern, predictions of the secondary structure of the growth factor and a model based on conformational homologies among cytokines (Parry et al., J Mol Recognition 1988;1:107-110). When compared to a number of functional mapping studies, structural features of the model are consistent with the experimental data, and the model, in turn, leads to the generation of a number of testable hypotheses. The implications of these features in terms of receptor-ligand interaction are discussed.

Algorithms↗
PubMed1990

IGF-I, a marker of undernutrition in hemodialysis patients.

Early detection and treatment of malnutrition in patients on hemodialysis (HD) is hampered by lack of a sensitive biochemical marker. We compared the value of serum insulin-like growth factor-I (IGF-I) with other biochemical indices in detecting malnutrition in 61 HD patients. Protein and energy intakes were low in the majority of patients. Of all patients, 59.6% had severe reduction in triceps skinfold thickness (TSF thickness, less than or equal to 60% of normal), whereas midarm muscle circumference (MAMC) was mildly reduced (less than or equal to 90%) in 23%. Serum IGF-I proved superior to the other indices in predicting TSF thickness. A serum IGF-I concentration of 300 micrograms/L discriminated between wasted (TSF thickness less than or equal to 60%) and robust patients. In 16 patients with a history of recent infection, IGF-I was significantly reduced well before changes in anthropometric measurements could be detected. IGF-I is a useful and early marker of undernutrition in HD patients.

Adolescent↗
PubMed1990

Elevated platelet-free calcium in uraemia.

Bleeding complications in uraemia are not uncommon. The pathogenesis of haemorrhage in uraemia is still a matter of controversy and the pattern of bleeding suggests a defect of primary haemostasis. Platelet aggregation and biochemistry, including calcium levels, have been studied; however, the results are controversial. We have examined platelet aggregation, platelet-free calcium and calmodulin in platelet-rich plasma because of the significant role of calcium and calmodulin in regulating platelet and other cells' functions. Platelet aggregation in uraemic subjects was similar to that of controls. Platelet basal free cytosolic calcium and platelet calcium in response to 10 microM Ca++ ionophore A23187 in eight subjects with uraemia were 117 +/- 33 nM and 2025 +/- 398 nM (mean +/- SEM) respectively. By contrast in seven matched healthy controls basal calcium and ionophore-stimulated calcium values were 47 +/- 14 nM and 1354 +/- 414 nM, significantly less than in the patients with uraemia (P less than 0.05). The sensitivity of uraemic platelets to A23187 was similar to that of controls. Calmodulin activity in platelet-rich plasma of 12 subjects with uraemia showed no significant difference from that of controls [1.86 +/- 0.29 micrograms/ml (mean +/- SEM) and 2.0 +/- 0.37 micrograms/ml (mean +/- SEM) respectively]. We conclude that despite elevation of platelet calcium in uraemia, which may be due to a plasma factor such as parathyroid hormone, platelet aggregation is normal and bleeding in uraemia is more likely to be due to other factors, including the effect of reduced haematocrit on platelet endothelial interaction. Disturbances in platelet calcium cannot explain the bleeding manifestations in uraemia but warrant further investigation in order to identify the pathogenic mechanisms responsible.

Adolescent↗
PubMed1990

Effects of clodronate in severe hyperparathyroid bone disease in chronic renal failure.

We have examined the effects of the diphosphonate, clodronate, in 9 haemodialysis patients with severe hyperparathyroid bone disease. Clodronate (300-600 mg infused after dialysis on 5 consecutive occasions) significantly decreased mean serum calcium, phosphate and hydroxyproline. This was associated with an increase in serum immunoassayable parathyroid hormone and activity of alkaline phosphatase. These changes reversed 2-4 weeks after stopping treatment but were sustained when treatment with oral clodronate (1.6 g daily) was supplemented for 2 weeks. Our findings suggest that intravenous clodronate is capable of inhibiting osteoclast-mediated bone resorption in chronic renal failure. The therapeutic potential of clodronate alone or with vitamin D derivatives merits further evaluation, particularly in patients with severe hyperparathyroidism, when the use of D metabolites alone is precluded by the presence of hypercalcaemia.

Administration, Oral↗
PubMed1990

Exit-site care and exit-site infection in continuous ambulatory peritoneal dialysis (CAPD): results of a randomized multicenter trial.

A total of 127 patients from 8 hospitals were randomized into 1 of 2 exit-site care regimes to evaluate their effect on rate of exit-site infection (ESI). Group 1 used povidone iodine and nonocclusive dressings changed 2 to 3 times weekly; Group 2 simply cleansed the exit site with nondisinfectant soap and water. Incidence, cause, duration, and treatment of ESI and peritonitis (P) were noted. Groups were analysed for age, sex, end-stage renal disease (ESRD), catheter, and systems. Total cumulative follow up time was 95.6 years. There was a significantly higher rate (p = 0.0183) of ESI in Group 2 (soap and water). The mean rate of ESI was 0.27 episodes/patient year for Group 1 versus 0.71 episodes/patient year for Group 2. Rates of P for the two groups were not significantly different (p greater than 0.50): 0.446 episodes/year for Group 1 versus 0.574 episodes/year for Group 2. S. aureus was responsible for 83% of ESI in Group 1 and 67% of ESI in Group 2. Protective dressing with a disinfectant is associated with significantly less ESI than minimum care. However, further research in exit-site care aimed specifically at reducing S. aureus infection is still required.

Adult↗
PubMed1990

Continuous ambulatory peritoneal dialysis and haemodialysis in the elderly.

The clinical course and outcome of 58 patients receiving haemodialysis or continuous ambulatory peritoneal dialysis aged 65 years and above at the start of dialysis treatment was examined over a six-year period. Method of presentation and mode of treatment did not affect survival, but the presence of ischaemic heart disease or congestive cardiac failure was significantly associated with increased mortality. The actuarial two-year patient survival was 54 per cent. Survival on continuous ambulatory peritoneal dialysis was 75 per cent, and the incidence of peritonitis was one episode per 7.36 patient-treatment months. The mean duration of hospital admission was 57.2 days per patient year for continuous ambulatory peritoneal dialysis, and 19.9 days per patient year for haemodialysis patients.

Acute Kidney Injury↗