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Biomedical subjects

C B Brown

Publications and source records attributed to C B Brown.

At least 55 records · Page 3Linked to original sources
PubMed1995

Recombinant antibodies in bioactive peptide design.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is important in many immune and inflammatory processes. GM-CSF binds to specific cellular receptors which belong to a recently described supergene family. These receptors are potential targets for pharmacologic design, and such design depends on a molecular understanding of ligand-receptor interactions. One approach to dissecting out critical intermolecular interactions is to develop analogs of specific interaction sites of potential importance. Monoclonal antibodies have been employed for these purposes in prior studies. Here we present application of recombinant antibody technology to the development of analogs of a site on GM-CSF bound by a neutralizing anti-GM-CSF monoclonal antibody. Polyclonal antisera with high titer neutralizing activity against human GM-CSF were developed in BALB/c mice. Purified immunoglobulins were prepared and used to immunize syngeneic mice. Anti-anti-GM-CSF was developed which demonstrated biological antagonist activity against GM-CSF-dependent cellular proliferation. RNA was extracted from spleen cells of mice with biologically active anti-anti-GM-CSF, cDNA synthesized, and polymerase chain reaction performed with primers specific for murine kappa light chain V regions. Polymerase chain reaction products were cloned into the pDABL vector and an expression library developed. This was screened with anti-GM-CSF neutralizing mAb 126.213, and several binding clones isolated. One clone (23.2) which inhibited 126.213 binding to GM-CSF was sequenced revealing a murine kappa light chain of subgroup III. Comparison of the 23.2 sequence with the human GM-CSF sequence revealed only weak sequence similarity of specific complementarity determining regions (CDRs) with human GM-CSF. Structural analysis revealed potential mimicry of specific amino acids in the CDR I, CDR II and FR3 regions of 23.2 with residues on the B and C helices of GM-CSF. A synthetic peptide analog of the CDR I was bound by 126.213, specifically antagonized GM-CSF binding to cells and blocked GM-CSF bioactivity. These studies indicate the feasibility of using recombinant antibody libraries as sources of interaction site analogs.

Amino Acid Sequence↗
PubMed1995

In vitro characterization of the human recombinant soluble granulocyte-macrophage colony-stimulating factor receptor.

We have cloned, expressed, and partially purified a naturally occurring, truncated, soluble form of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor alpha subunit to investigate its biochemical and biologic properties. The soluble receptor species lacks the transmembrane and cytoplasmic domains that are presumably removed from the intact receptor cDNA by a mechanism of alternative splicing. The resulting soluble 55- to 60-kD glycosylated receptor species binds GM-CSF with a dissociation constant (kd) of 3.8 nmol/L. The soluble GM-CSF receptor successfully competes for GM-CSF binding not only with the transmembrane-anchored GM-CSF receptor alpha subunit but also with the native oligomeric high-affinity receptor complex. In addition, in human bone marrow colony-forming assays, the soluble GM-CSF receptor species can antagonize the activity of GM-CSF. Our data suggest that the soluble GM-CSF receptor may be capable of acting in vivo as a modulator of the biologic activity of GM-CSF.

Binding, Competitive↗
PubMed1995

Effect of alfacalcidol on natural course of renal bone disease in mild to moderate renal failure.

OBJECTIVE: To determine whether alfacalcidol--used in management of overt renal bone disease--may safely prevent renal bone disease when used earlier in course of renal failure. DESIGN: Double blind, prospective, randomised, placebo controlled study. SETTING: 17 nephrology centres from Belgium, France, the Netherlands, and the United Kingdom. SUBJECTS: 176 patients aged 18-81 with mild to moderate chronic renal failure (creatinine clearance 15-50 ml/min) and with no clinical, biochemical, or radiographic evidence of bone disease. INTERVENTIONS: Alfacalcidol 0.25 micrograms (titrated according to serum calcium concentration) or placebo given for two years. MAIN OUTCOME MEASURES: Quantitative histology of bone to assess efficacy of treatment and renal function to assess safety. RESULTS: 132 patients had histological evidence of bone disease at start of study. Biochemical, radiographic, and histological indices of bone metabolism were similar for the 89 patients given alfacalcidol and the 87 controls given placebo. After treatment, mean serum alkaline phosphatase activity and intact parathyroid hormone concentration had increased by 13% and 126% respectively in controls but had not changed in patients given alfacalcidol (P < 0.001). Hypercalcaemic episodes occurred in 10 patients given alfacalcidol (but responded to decreases in drug dose) and in three controls. Histological indices of bone turnover significantly improved in patients given alfacalcidol and significantly deteriorated in controls: among patients with abnormal bone histology before treatment, bone disease resolved in 23 (42%) of those given alfacalcidol compared with two (4%) of the controls (P < 0.001). There was no difference in rate of progression of renal failure between the two groups. CONCLUSION: Early administration of alfacalcidol can safely and beneficially alter the natural course of renal bone disease in patients with mild to moderate renal failure.

Adolescent↗
PubMed1995

Nutritional profile of continuous ambulatory peritoneal dialysis patients.

Undernutrition in dialysis patients contributes to their morbidity and mortality. This is a cross-sectional study of the nutritional status of 61 patients treated with continuous ambulatory peritoneal dialysis (CAPD). They were studied with emphasis on assessment of their nutritional intake, anthropometric measurements, and evaluation of biochemical parameters. The correlation between the rate of CAPD peritonitis and these measurements was also examined. The majority of the patients (63.1%) had inadequate protein intake ( < or = 1.2 g/kg/day). A comparable percentage had a low energy intake ( < or = 30 kcal/kg/day). Moderate malnutrition, as assessed by a low triceps skinfold thickness (TST) or a reduced midarm muscle circumference (MAMC) of < or = 20th percentile, was detected in 52% and 39% of the patients, respectively. Severe malnutrition (TST or MAMC < or = 10th percentile) was present in 36% of the patients. The serum insulin-like growth factor I (IGF-I) proved to be the most useful biochemical marker of malnutrition. It showed a positive correlation with TST (r = 0.325; p < 0.05). No significant correlation was observed with other short-life proteins such a transferrin or prealbumin. However, stepwise regression analysis showed the predictive value of serum IGF-I for anthropometric values to be low (adjusted R2 = 34.6%). Wasted patients did not appear to have more infections when compared to their healthier counterparts. However, a weak correlation was observed between TST and the number of peritonitis episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Anthropometry↗
PubMed1995

Can immunosuppressive drugs slow the progression of IgA nephropathy?

The role of immunosuppressive drugs in the treatment of IgA nephropathy (IgAN) remains controversial. The effect of treatment with prednisolone and azathioprine on the clinical course of patients with IgA nephropathy is described in this retrospective study. One hundred and fourteen patients, 66 treated (age 13-77 years) and 48 untreated (age 15-64 years), were evaluated. The two groups of patients differed significantly with respect to heavier proteinuria (median 3.6 g/day, range 0.2-18 g/day), lower serum albumin level (< 40 g/l) and more severe renal histopathological involvement in the treated group (P < 0.01). Oral prednisolone 40 mg/day and azathioprine 2 mg/kg BW/day was commenced initially and after gradual tapering was continued at low dose (5 mg/day) for a median duration of 24 months (range 12-98). The median duration of follow-up was 46 months (range 12-180). The clinical course was defined as progressive or non-progressive on the basis of serial serum creatinine (Scr). Of the patients who presented with renal impairment (Scr > 110 mumol/l), a non-progressive course was observed in 79.5% patients of the treated group (n = 39), while only in 36% of the untreated group (n = 22), the difference was statistically significant (P < 0.001). Slopes of reciprocal of Scr versus time were also calculated by linear regression analysis to represent the trend of renal function for patients who had had 3 or more years follow-up (n = 101). An analysis of variance of these trends in patients with renal impairment at presentation (n = 51) showed significant recovery of renal function in the treated group (n = 33) and a decline of renal function in the untreated group (n = 18, P = 0.004). There was no significant effect of the treatment on proteinuria. The histopathological features that favoured response to the treatment were mesangial proliferation, capsular adhesions and interstitial infiltration on light-microscopy, C3 and fibrin deposits on immunofluorescence (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Mapping of human granulocyte-macrophage-colony-stimulating-factor domains interacting with the human granulocyte-macrophage-colony-stimulating-factor-receptor alpha-subunit.

The high-affinity granulocyte-macrophage-colony-stimulating-factor (GM-CSF) receptor (R) is composed of at least two subunits, termed alpha and beta. The alpha subunit is crucial for initiating ligand/receptor interaction and for ligand specificity. The experiments reported in this study sought to identify the domains of human (h)GM-CSF which are responsible for interaction with hGM-CSFR alpha. Anti-(human-GM-CSF) mAb were used as competitors in a 125I-GM-CSF receptor-binding assay on cells expressing the recombinant hGM-CSFR alpha chain. Inhibition of 125I-GM-CSF binding to the GM-CSFR alpha chain was demonstrated by mAb which mapped to the middle third of the third alpha helix (amino acids 78-83), the distal two-thirds of the third alpha helix and the initial 7 residues of the loop between the third and fourth helix (amino acids 78-94), and the extreme carboxy terminus. No inhibition of binding occured with an antibody whose domain begins in the first beta-pleated sheet (amino acids, 39-43), continues through the second helix (amino acids 55-64) and into the proximal third of the third helix (to amino acid 77). mAb which mapped to the distal half of the fourth helix and the carboxy-terminal tail (amino acids 110-127) increased the binding of 125I-GM-CSF to GM-CSFR alpha. Due to the known discontinous epitopes the possibility that the distal portion of the fourth helix contributes to binding cannot be eliminated. However, the domains of hGM-CSF most clearly involved in binding to the hGM-CSFR alpha are the distal two-thirds of the third alpha helix, the immediate downstream residues and the extreme carboxy terminus of hGM-CSF.

Animals↗
PubMed1994

Sarcomatoid renal cell carcinoma arising in hemodialysis-associated acquired cystic kidney disease presenting with disseminated bone marrow infiltration.

A 51-year-old man with a 23-year history of hemodialysis-dependant end-stage renal failure presented with pyrexia, malaise, and progressive pancytopenia. Investigations revealed acquired cystic kidney disease, with one cyst being interpreted as showing evidence of recent hemorrhage, and a malignant sarcomatoid bone marrow infiltrate. The patient rapidly deteriorated and died. At autopsy a seminecrotic and cystic sarcomatoid renal cell carcinoma was identified, with metastases in the adrenals, bone marrow, liver, lungs, and abdominal lymph nodes. The case is reviewed with regard to epithelial membrane antigen- and cytokeratin-negative bone marrow immunohistology as well as the immunophenotype of acquired cystic kidney disease and that expected in renal carcinoma, with reference to the literature on acquired cystic kidney disease.

Bone Marrow↗
PubMed1994

Serum type I procollagen peptide: a non-invasive index of bone formation in patients on haemodialysis?

The value of serum procollagen peptide (PICP) as a non-invasive index of bone formation was studied in 18 patients established on haemodialysis. There was a significant correlation between PICP and serum alkaline phosphatase activity (ALP; r = 0.55, P < 0.05), and between PICP and osteocalcin (r = 0.53, P < 0.05). PICP also correlated significantly with histomorphometric indices of bone formation, particularly bone formation rates (BFR) as estimated by the tetracycline double-labelled technique (r = 0.74, P < 0.01), but not with those of bone resorption. There was a similar relationship between BFR and ALP. From the regression analyses, a normal BFR was associated with normal PICP values despite the absence of renal function, suggesting that the impact of renal function on serum concentrations of PICP may not be large. Seven patients had histochemical evidence for significant aluminum overload. In these patients the expected suppression in biochemical and histological indices of bone formation was associated with inappropriately raised PICP concentrations. The mechanism of this discrepancy is not clear, but caution is advocated in the interpretation of PICP in the presence of significant aluminium overload. Our findings otherwise suggest that PICP may be a useful non-invasive index of bone formation in patients on haemodialysis.

Adolescent↗
PubMed1994

Myofibroblasts, predictors of progression of mesangial IgA nephropathy?

The limited knowledge of the cellular mediators of renal scarring hampers progress in the management of progressive chronic renal failure (CRF). We have studied 38 patients with biopsy-proven mesangial IgA nephropathy with emphasis on attempting to define the role of myofibroblasts (alpha-smooth muscle actin/SMA-positive cells) in renal scarring. In 18 untreated patients, correlations were undertaken between known histological parameters of progression as well as the presence of myofibroblasts in tissues and the clinical outcome. alpha-SMA staining by an avidin-biotin-peroxidase method was confined to a large extent to the vascular smooth muscle cells of normal kidneys but extended to the tubulointerstitium and periglomerular space in scarred kidneys. Mild glomerular staining was also noted. The interstitial immunostain followed a similar distribution to that of interstitial type III collagen. Morphometric analysis showed the interstitial alpha-SMA staining to be a reliable histological predictor of outcome as it discriminated between progressors and non-progressors (chi 2 = 4.923, P = 0.026). The intensity of the interstitial alpha-SMA staining correlated with renal functional outcome; inversely with the reciprocal of serum creatinine slopes (r = -0.466, P < 0.025) and positively with the serum creatinine value at the end of the observation period (r = 0.704, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

The effect of glucose polymers on water removal and protein clearances during CAPD.

Two selected groups of 5 continuous ambulatory peritoneal dialysis (CAPD) patients (3 female, 7 male), mean age 60 years, were studied twice with an interval of 4 weeks. The first study was done with glucose-containing dialysate and the second study with dialysate containing glucose polymers (Dextrin 7.5%) after they had been treated with this solution (night dwell) for 4 weeks. The patients collected night bags for 3 consecutive days during the tests. Protein clearances were determined for beta 2-microglobulin, albumin, IgG, fibronectin, and alpha 2-macroglobulin in both periods to examine the influence of crystalloid-induced convection versus "colloid"-induced convection. Group I normally used 1.50% glucose and was therefore considered to have a "high ultrafiltration";group II was the "low ultrafiltration" group because they needed 4.25% glucose dialysate. For their usual glucose solutions the net ultrafiltration was not different between both groups, but the clearance of beta 2-microglobulin was higher in group II:839 +/- 98 microL/min (group I) and 1135 +/- 131 microL/min (group II) (p = 0.08). For glucose polymers the net ultrafiltration increased in both groups, but this was more pronounced in group II: 657 +/- 104 mL (group I) and 918 +/- 85 mL (group II) (p = 0.06). Also, the clearance of beta 2-microglobulin increased with the glucose polymer solution: 1268 +/- 94 microL/min (for glucose polymer) and 987 +/- 85 microL/min (for glucose) (p < 0.05), but the clearances of the larger serum proteins remained unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Effect of control of hypertension on progressive renal failure.

This study assesses the direct effect of different degrees of blood pressure control on the progression of chronic renal failure (CRF) in 18 patients with nephropathies of varying etiology (Glomerular filtration rate [GFR]: 14.99 +/- 5.94 ml/min/1.73 m2). The study involves three consecutive phases; Phase 1 consisted of a retrospective analysis of blood pressure and biochemical data: mean diastolic blood pressure (MDBP) was 89.9 +/- 7.9 mmHg and the mean rate of decline in renal function was -68.9 1/mol of creatinine/month. Phase 2 consisted of a 6 months prospective period of frequent (monthly) follow-up and optimization of blood pressure control when MDBP was reduced to 83.9 +/- 6.5 mmHg (p < 0.001 cf phase 1) and the rate of decline in renal function fell to -25.2 1/mol/month (p < 0.05 cf phase 1). Phase 3 consisted of another 6-month period when further reduction of MDBP 77.1 +/- 6.6 mmHg (p < 0.01 cf phase 2) was brought about by the addition of the calcium antagonist nifedipine (10 mg thrice/daily). This was not associated with further improvement in the rate of decline of renal function as in this phase the rate of decline was -53.2 1/mol/month. This study confirms that frequent follow-ups with improved blood pressure control slow the rate of decline in renal function. Further reduction of diastolic blood pressure to below 80-85 mmHg could not be shown to confer additional benefit.

Adult↗
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↗