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Biomedical subjects

J D Williams

Publications and source records attributed to J D Williams.

At least 127 records · Page 7Linked to original sources
PubMed1994

Large-scale preparation and biochemical characterization of a new high purity factor IX concentrate prepared by metal chelate affinity chromatography.

Metal chelate affinity chromatography on copper-charged Chelating Sepharose has been used to purify a factor IX concentrate from 4,000- to 5,000-kg pools of human plasma, with an overall yield of 194 IU/kg. Unwanted proteins and solvent-detergent reagents added to inactivate lipid-enveloped viruses were removed during the chromatographic step. The freeze-dried product was > 80% pure factor IX with a mean specific activity of > 160 IU/mg protein. The concentrate showed no evidence of clotting factor activation by in vitro tests for potential thrombogenicity or by direct assay for activated factor IX. The concentrate did not exhibit proteolytic activity against a range of synthetic peptide chromogenic substrates. Full functional factor IX activity was retained and there was no evidence of protein degradation. Metal chelate affinity chromatography therefore appears to present less physicochemical challenge to the protein than other factor IX purification methods, while allowing the preparation of a clinical factor IX concentrate at a large scale.

Chelating Agents↗
PubMed1994

Permselectivity in thin membrane nephropathy.

The glomerular permselectivity to polydisperse neutral dextrans was compared in 6 patients with thin membrane nephropathy (TMN) and 10 healthy controls. Despite having normal renal hemodynamics and minimal proteinuria, the patients with TMN had significantly increased fractional clearance of neutral molecules with Stokes radius > 42 A. Conventional theories of glomerular barrier size selectivity cannot fully explain these data since they would predict that our patients would have had nephrotic range proteinuria.

Adult↗
PubMed1994

Induction of chondrogenesis: requirement for synergistic interaction of basic fibroblast growth factor and transforming growth factor-beta.

Interactions between the epithelial anlage of the developing mouse inner ear and its associated periotic mesenchyme control the differentiation of the cartilaginous otic capsule. Transforming growth factor-beta 1 (TGF-beta 1) is a naturally occurring signal peptide that is present in these tissues at times of active differentiation and morphogenesis. Previous studies have shown that TGF-beta 1 alone is not a sufficient stimulus to initiate chondrogenesis in cultured periotic mesenchyme. In this study, we provide evidence that basic fibroblast growth factor (bFGF) can elicit a specific but limited chondrogenic response in cultured periotic mesenchymal cells. We also demonstrate that simultaneous addition of bFGF and TGF-beta 1 to cultured periotic mesenchyme results in a full chondrogenic response comparable to that which occurs when periotic mesenchyme is grown in the presence of its natural inductor tissue (i.e. otic epithelium). Utilizing antibodies directed against bFGF, we show localization of endogenous bFGF in the otic epithelium in vivo and in mixed epithelial-mesenchymal cultures. Additionally, we demonstrate the presence of FGF-like activity in medium conditioned by otic epithelium. Blocking of epithelial elicited chondrogenesis by a combination of both alpha bFGF and alpha TGF-beta 1 antibodies provides further evidence of the necessity for these growth factors in the chondrogenic differentiation of periotic mesenchyme in vitro. Our results suggest a role for both bFGF and TGF-beta 1 in the regulation of chondrogenesis during otic capsule formation in situ.

Animals↗
PubMed1994

Dietary menhaden oil contributes to hepatic lipidosis in laying hens.

Clinical and epidemiological investigations have indicated that there may be substantial human cardiovascular benefits associated with increased consumption of n-3 fatty acids commonly found in fish oils. Recent studies have indicated that egg yolk n-3 fatty acid content is significantly increased when hens are fed diets enriched with selected fish oils such as menhaden oil (MO). In the present study, reproductively active females but not males exhibited increased hepatic lipidosis following 6 mo of feeding 3% MO. Hens fed 3% animal-vegetable oil (AV) did not exhibit hepatic lipid accumulation. Serum triglyceride and cholesterol concentrations were reduced (P < or = .05) in hens fed MO. Subsequently, yolk and total egg weights of hens fed MO were decreased as compared with those of hens fed AV. A significant interaction of dietary MO and exogenous 17 beta-estradiol was noted among chick liver and gallbladder weights. These data suggest that dietary MO and estradiol may interact in a manner that enhances the lipogenic activity of the liver, thereby inducing hepatic lipidosis in laying hens.

Animals↗
PubMed1994

Synthesis of phospholipids by human peritoneal mesothelial cells.

OBJECTIVE: To assess the capacity of cultured human peritoneal mesothelial cells to synthesize choline-containing phospholipids. The study compares the phospholipids secreted from cultured cells with those which we, and others, have identified in the dialysate of patients treated by continuous ambulatory peritoneal dialysis (CAPD). PATIENTS: CAPD effluent was collected from 8 patients who had been receiving CAPD treatment for at least 11 months and who had normal ultrafiltration. CELL CULTURES: Using human omental tissue, homogeneous cultures of mesothelial cells were established. METHODS: Synthesis of phospholipids by mesothelial cells was assessed following incubation with [methyl-14C] choline chloride--a precursor capable of being incorporated into phosphatidylcholine (PtdCho) and sphingomyelin. Lipids from CAPD effluent, cultured cells, and cell medium were extracted in chloroform/methanol. Phospholipids were separated and identified by thin layer chromatography. Synthesis and secretion of PtdCho and other choline-containing lipids by the mesothelial cells were determined by beta scintillation counting of the appropriate bands, while the fatty acid composition of the phospholipids was ascertained by gas liquid chromatography. RESULTS: Synthesis and secretion of PtdCho by mesothelial cells were observed during a 96-hour period. When maintained in medium replete with essential fatty acids, the fatty acid composition of the PtdCho synthesized by cultured mesothelial cells closely resembled that isolated from the peritoneal cavity. CONCLUSION: The demonstration of phospholipid secretion from mesothelial cells, with a fatty acid composition similar to the phospholipids isolated from peritoneal dialysate, lends added support to the hypothesis that the mesothelial cells are the source of the peritoneal phospholipids. As such they offer a useful experimental system in which to study peritoneal phospholipid synthesis.

Cells, Cultured↗
PubMed1994

Biocompatibility studies on peritoneal cells.

This review outlines the problems involved in assessing the biocompatibility of PD fluids. It has summarized the data available from conventional in vitro studies and highlights many of the inadequacies of this approach. In vivo data are lacking both on host defense and on the clinical effect of changing conventional PD fluids for a more "ideal" formulation. The best parameters for assessing biocompatibility need to be defined. Alternative formulation of fluids must be aimed towards (1) a system that interferes minimally with host defense, and (2) a system that maintains the integrity of the peritoneal membrane for ultrafiltration and clearance. Cell culture studies should be designed to model the in vivo situation. Ex vivo studies (cells exposed within the peritoneal cavity) should be used to support in vivo findings. Finally, in vitro results must be related to clinical significance, and changes in fluid composition should be followed by improvements in clinical outcome.

Biocompatible Materials↗
PubMed1993

Impact of initial treatment on renal function in newly-diagnosed type 2 (non-insulin-dependent) diabetes mellitus.

The impact of improved glycaemic control on renal function in newly-presenting Type 2 (non-insulin-dependent) diabetic patients has not been adequately researched. Consequently, glomerular filtration rate and effective renal plasma flow and urinary albumin excretion rates were determined in 76 subjects (age (mean (SD)): 54 (9.5) years; 50 male) of an original cohort of 110 newly-presenting normotensive non-proteinuric Type 2 diabetic patients following 6 months treatment with diet alone (n = 42) or with oral hypoglycaemic agents (n = 34). Significant reductions were observed in (presentation vs 6 months): body mass index (p < 0.001); fasting plasma glucose (p < 0.001); glycated haemoglobin (HbA1) (p < 0.001); systolic blood pressure (p < 0.01); and diastolic blood pressure (p < 0.001). Glomerular filtration rate declined from 117 (22) to 112 (21) ml.min-1 (p < 0.01), with unchanged effective renal plasma flow (534 (123) vs 523 (113) ml.min-1) and filtration fraction (22.4 (3.0) vs 21.8 (3.4)%). Albumin excretion rate (median (range)) declined from 1.1 (0.1-34.7) to 0.5 (0.1-29.9) micrograms.min-1 (p < 0.01). Changes in glomerular filtration rate (delta values) were inversely correlated with presentation values (p < 0.001), and positive relationships were observed with delta effective renal plasma flow (p < 0.01), and delta glycated haemoglobin (p < 0.05). Type 2 diabetic patients with glomerular filtration rate values at presentation over 120 ml.min-1 demonstrated significant reduction in glomerular filtration rate (n = 31; p < 0.001), whilst those with original values less than 120 ml.min-1 remained unchanged (n = 45).(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1993

Immunodominant neutralizing antigens depend on the virus strain during a primary immune response in calves to bovine rotaviruses.

Sera obtained from gnotobiotic calves (GC antisera) infected with bovine rotavirus strain NCDV or B223 from a previous study (Woode et al., 1987), which have different G (G6 and G10 respectively) and P serotypes, were compared for their neutralization (NT) properties to a number of human and animal rotaviruses (representing G serotype 1-6, 8-10). Two distinct patterns of neutralization were identified from these GC antisera. Of all the serotypes tested, NCDV GC antisera neutralized only B641 to a relatively high titer compared with the homologous titer, implying a narrow pattern of NT response. Analysis with reassortants indicated that the response was primarily to VP4. In contrast, B223 GC antisera neutralized most of the G serotypes tested to titers within 3-7 fold of the homologous titer, demonstrating a broad pattern of NT response. In the earlier study B223 was shown to induce a heterotypic protection against bovine rotavirus B641 (G serotype 6), and the serologic data obtained from this study indicates that a B223 vaccine might provide broad protection against several different serotypes of human and animal rotaviruses.

Animals↗
PubMed1993

Reduced renal hemodynamic response to atrial natriuretic peptide in elderly volunteers.

Aging is associated with decreased ability to excrete salt and water, thus increasing the susceptibility to volume overload in older individuals. Meanwhile, plasma levels of atrial natriuretic peptide (ANP) increase progressively with age for unknown reasons. We compared the natriuretic and renal hemodynamic responses to low-dose ANP infusion in an elderly group of volunteers (mean age, 74 years) with those of a group of younger subjects (mean age, 29 years). A significant reduction below baseline values in effective renal plasma flow occurred in the young group after the 2-hour peptide infusion (657 +/- 125 v 476 +/- 92 mL/min [mean +/- 1 SD]) when compared with the elderly group (two-way analysis of variance; P < 0.02). A concomitant increase in renal vascular resistance was noted in the young group only during the same period (6,631 +/- 1,384 v 9,136 +/- 2,126 dyn s cm2 x 10(6)). This increase was also significantly higher than that in the elderly group (analysis of variance; P < 0.02). Both groups demonstrated similar natriuretic responses. Absolute sodium excretion had increased significantly above baseline values in both young and elderly subjects at the end of the 2-hour peptide infusion (111 +/- 25 mumol/min to 183 +/- 33 mumol/min v 107 +/- 23 mumol/min to 198 +/- 56 mumol/min) and remained elevated until 1 hour postinfusion. We conclude that the elderly subjects in our study demonstrated a diminished renal hemodynamic response to infusion of ANP while preserving a natriuretic response similar to that found in the younger subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Intra-peritoneal free elastase in CAPD peritonitis.

Neutrophil (PMN) recruitment into the peritoneum during acute bacterial peritonitis is an important part of the host defense barrier in CAPD patients. However, the subsequent phagocytosis of bacteria may also lead to PMN degranulation and the release of lysosomal enzymes. We determined the concentration of neutrophil elastase, both in complex with its natural inhibitor alpha 1Pi (E alpha 1Pi), and in uncomplexed, free form, in infected and normal CAPD peritoneal fluid by ELISA. In addition elastase activity was estimated in a casein degradation assay. Infected fluid contained a median (range) of 1.4 nM (0 to 9.2) free elastase by ELISA and 1.2 nM (0 to 11.9) activity. There were strong correlations between the peritoneal leukocyte count and both immunoreactive elastase and activity (r = 0.816, P < 0.001, 0.687, P < 0.01, respectively). In contrast, normal fluid contained 0.0 nM (0 to 0.32) immunoreactive elastase (P < 0.01) and 0.0 nM (0 to 0.6) elastase activity (P < 0.001). E alpha 1Pi complexes were raised significantly during peritonitis at 6.2 nM (0 to 34.3) and were barely detectable in normal fluid 0.0 nM (0 to 0.17; P < 0.005). The study shows that small but significant quantities of uninhibited elastase can be detected in the peritoneal fluid of CAPD patients with acute bacterial peritonitis. This observation may have important implications for the pathogenesis of peritoneal membrane damage and the phlogistic response to infection.

Acute Disease↗
PubMed1993

Tamm Horsfall protein binds to a single class of carbohydrate specific receptors on human neutrophils.

Several studies have implicated urinary Tamm Horsfall protein (THP) in the aetiology of tubulointerstitial inflammation. Previous research has demonstrated that particulate THP will initiate inflammatory activation of human polymorphonuclear leukocytes (PMN) through a trypsin sensitive mechanism. The present study describes the binding of 125I-monomeric THP to human PMN at 4 degrees C and demonstrates that radiolabeled THP binds to PMN in a saturable, reversible and time dependent manner. The addition of 400 to 600 ng 125I-THP/2 x 10(6) PMN was sufficient to achieve saturable binding. Scatchard analysis of binding data yielded linear plots suggesting a single class of receptors with a mean density of 26218/cell and a dissociation constant (KD) of 4.2 x 10(-9) M. Binding reached steady state by 15 minutes and could be rapidly displaced by the addition of an excess of unlabeled THP. The KD calculated from experimentally derived kinetic rate constants (k1 and k2) was of a similar order of magnitude (0.9 x 10(-9) M) to that generated from Scatchard plots. In addition 125I-THP bound specifically to PMN plasma membrane immobilized on nitrocellulose filters, a process which could be inhibited by unlabeled monomeric THP. Chemical modification of unlabeled THP abolished its capacity to inhibit binding. Specific inhibition studies showed that N-acetylneuraminic (sialic) acid dose dependently displaced the binding of 125I-THP to immobilized PMN membranes at concentrations up to 100 mM. These results indicate that the reported activation of human PMN by THP is mediated through a single class of sialic acid-specific cell surface receptors.

Carbohydrate Metabolism↗