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J S Cameron

Publications and source records attributed to J S Cameron.

At least 109 records · Page 6Linked to original sources
PubMed1991

Effect of H+ on ATP-regulated K+ channels in feline ventricular myocytes.

Using patch-clamp techniques, we examined the effects of pH on properties of ATP-regulated K+ channels in single myocytes isolated from cat left ventricles. ATP-K+ channels of inside-out patches were bilaterally exposed to 140 mM K+ solutions (22 degrees C). In the absence of ATP and Mg2+, the channels had a linear current-voltage relationship during hyperpolarizing pulses (20-100 mV negative to the reversal potential) at both intracellular pH (pHi) 7.4 and 6.5, but the slope conductance was 66 +/- 2 pS at pHi 7.4 and 46 +/- 2 pS at pHi 6.5. Lowering pHi from 7.4 to 6.5 increased the mean open time (from 15.9 +/- 4.6 to 35.9 +/- 7.9 ms, P less than 0.01) but decreased the open-state probability measured at 50 mV positive to the reversal potential (from 0.35 +/- 0.04 to 0.16 +/- 0.04, P less than 0.01). However, in the presence of both 0.2 mM ATP and 1 mM MgCl2, lowering pHi from 7.4 to 6.5 increased the mean open time (from 5.0 +/- 2.6 to 17.9 +/- 5.9 ms, P less than 0.01) and the open-state probability (from 0.025 +/- 0.010 to 0.098 +/- 0.024, P less than 0.01). These data indicate that increases in intracellular H+ concentration modulate cardiac ATP-K+ channel properties. Ischemia-associated decreases in pHi may enhance the opening of cardiac ATP-regulated K+ channels and resultant action potential shortening.

Adenosine Triphosphate↗
PubMed1991

Renal vasculitis: microscopic polyarteritis and Wegener's granuloma.

Thus, although the prognosis for small vessel vasculitis affecting the kidney has improved from almost inevitable death 30 years ago, through a 30-35% 5-year survival 10-15 years ago, many problems remain. Although it seems likely that the more intense immunosuppression used in most units over the past 10-15 years has improved immediate survival, a number of these elderly and often frail patients die directly as a result of these treatment regimens; in our present series, 5/16 deaths (31%) could be related directly to immunosuppression. In some patients extrarenal complications of the vasculitis, particularly in the gastrointestinal tract, still may lead to early death. The relative roles (if any) of methylprednisolone and/or plasma exchange in treatment of renal vasculitis are not clear yet, although a recent controlled trial in patients with crescentic nephritis, mainly the result of small vessel renal vasculitis, showed a modest benefit from plasma exchange in addition to prednisolone and cyclophosphamide, but only in those patients requiring dialysis. In the longer term, we do not know for how long, with what agent and with what intensity immunosuppression must be maintained. In our series, in which most patients were maintained on modest immunosuppression for many years, relapse of the vasculitis was almost absent, suggesting some merit in this strategy. We used azathioprine rather than intermittent intravenous cyclophosphamide, as others have advocated; there are no data to choose between these regimens at the moment, although even in this relatively elderly population long-term oral cyclophosphamide is better avoided because of risks to the bladder, gonadal toxicity and oncogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

The outcome of pregnancy in women with lupus nephritis.

We analysed the outcome of pregnancy in patients with pre-existing lupus nephritis, seen in a tertiary referral centre for nephrology. Fifty-three pregnancies in 25 patients who already had clinical and histological evidence of lupus nephritis were recorded between January 1970 and June 1989, and data were analysed retrospectively. All 53 pregnancies occurred in patients with more or less stable disease, while three pregnancies during which lupus first presented were excluded. Six pregnancies were ended by therapeutic abortions (four for social reasons), and in eight spontaneous abortion occurred. Thus, 39 deliveries occurred, 28 at 36 weeks or more, while 11 were delivered prematurely, of which one was a stillbirth. After allowance was made for therapeutic abortions, the fetal loss rate (9/47) was 19%. Seventeen Caesarian sections were performed in the 39 completed pregnancies (44%), 11 as emergencies. Although the overall fetal loss, incidence of premature births and Caesarian section rate were all higher than expected for a population of normal women, neither initial histology, treated hypertension, the presence of proteinuria or a nephrotic syndrome showed statistically significant relationships with the outcome of completed pregnancies. In no case was maternal renal function affected irreversibly, although proteinuria increased substantially during pregnancy in six patients, and creatinine clearance fell during pregnancy, also in six patients. No 'flares' in systemic disease were seen, but all patients save five were treated with a brief period of high-dose oral corticosteroids or intravenous methylprednisolone in the postpartum period. No case of neonatal lupus or congenital heart block was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1991

Familial juvenile gouty nephropathy with renal urate hypoexcretion preceding renal disease.

This paper reports investigations in a young woman with renal disease and six other seemingly healthy young members of a new kindred (four male:two female) with familial juvenile gouty nephropathy (McKusick 16200). The family had previously been known to have a "familial" renal disease, but came to attention through an isolated episode of gout in the propositus when renal function was already impaired. A reduced GFR was found in three of the other six subjects. Hyperuricemia associated with a grossly reduced fractional uric acid clearance (Cur/Ccr x 100) was present in the propositus and five kindred members, three of whom were children. The finding of this abnormality in two subjects with normal GFR suggests that this apparent hallmark of the disease precedes the onset of renal damage. The results confirm the dominant nature of the disorder, and highlight the need to investigate all kindred members of patients with juvenile gout and renal failure. Early recognition is important, since allopurinol therapy in doses adjusted to the reduced renal function may ameliorate the progression of the renal lesion.

Adolescent↗
PubMed1990

Recombinant human erythropoietin shortens the uraemic bleeding time without causing intravascular haemostatic activation.

Blood rheology and haemostasis have been investigated in 8 haemodialysis patients during treatment with recombinant human erythropoietin (rHuEPO). The aim was to elucidate the mechanism by which rHuEPO improves haemostasis, and to determine whether rHuEPO promotes intravascular coagulation. Investigations were performed before, and after 3 months of treatment. Haemoglobin and haematocrit rose significantly after rHuEPO (p less than 0.001) and there was a concurrent shortening of the bleeding time. No significant changes were observed in platelet aggregation, thromboxane generation, or platelet nucleotide content during the treatment period. Whole blood viscosity increased following rHuEPO (p less than 0.01), but plasma viscosity and red cell deformability were unchanged, as were markers of intravascular platelet activation and plasma levels of cross-linked fibrin derivatives. No patient suffered from thrombosis during the study period, and elevation of the haematocrit in uraemic patients up to 0.35 with rHuEPO did not appear to lead to intravascular coagulation. Shortening of the prolonged bleeding time in haemodialyzed patients following rHuEPO appeared to be due to the increase in circulating red cells, rather than to changes in platelet reactivity.

Adult↗
PubMed1990

Recurrence of focal segmental glomerulosclerosis in transplanted kidneys: analysis of incidence and risk factors in 59 allografts.

Fifty-nine allografts were placed in 43 patients with renal failure from focal segmental glomerulosclerosis (FSGS): 27 allografts were put into 16 children aged less than 15 years, and 32 allografts into 27 adolescents and adults. Recurrence of FSGS was noted histologically in 13 allografts, 10 in 8 children and 3 in adults. None of the 9 children and 24 adults who never developed an allograft nephrotic syndrome showed FSGS in their allograft biopsies. The age of onset was a strong risk factor for recurrence: recurrent FSGS developed in 8 of 16 children (50%) but only in 11% of adolescents and adults (3 of 27 patients). Although the time from apparent onset to renal replacement treatment was shorter in those with recurrence than those without in the children, there was no difference in the time spent on dialysis prior to transplantation. Mesangial prominence was observed in the original biopsy in 12 of 13 patients with recurrence, and recurrence rate was similar in living and cadaver donor allografts; class I MHC matching was similar in those with and without recurrence. Three allografts treated with cyclosporin A as well as 9 with azathioprine showed recurrence. Of 9 second or subsequent allografts placed in those with recurrence in the first allograft, only 3 showed further recurrence. In 3 re-grafted after 13, 11 and 5 years, normal function was seen.

Adolescent↗
PubMed1990

The 'antiphospholipid syndrome' and the 'lupus anticoagulant'.

In recent years an association has been described between, on the one hand, an in vitro prolongation of phospholipid-dependent coagulation tests (the 'lupus anticoagulant') or the demonstration of antiphospholipid antibodies and, on the other, clinical events, particularly recurrent thrombosis (usually venous but sometimes arterial), thrombocytopenia, and also recurrent mid-term fetal loss. Other less well-documented associations with haemolytic anaemia, livedo reticularis, strokes and other neurological syndromes have been suggested. The antibodies are present temporarily in many infections, are usually of IgM isotype and thrombosis does not occur. However, they are persistently present and mainly of IgG isotype in a number of auto-immune disorders associated with thrombosis, in particular systemic lupus erythematosus, in which 50% of patients will show antibody of one isotype or another. The strongest association is with antinuclear factor-negative lupus and 'lupus-like' disorders in which a full diagnosis of classical lupus cannot be made. The clotting test abnormality and antiphospholipid antibodies may be found also in otherwise normal individuals suffering thrombosis or fetal loss--the so-called primary antiphospholipid syndrome. These data raise important questions for management, but many details are controversial despite a decade's work; this review examines the present position and outlines some of the difficulties, particularly from the point of view of nephrology and paediatrics.

Autoantibodies↗
PubMed1990

Membranous nephropathy in childhood and its treatment.

Membranous nephropathy is predominantly a disease of middle-aged and elderly individuals, and is thus rather an uncommon finding in proteinuric and nephrotic children. In children, it differs in several important respects from the disease as seen in adults: an apparent associated cause is more common, macroscopic haematuria is seen quite frequently, a relapsing course is more often noted, renal venous thrombosis is not found and evolution into renal failure is the exception. Nevertheless, a proportion of children with membranous nephropathy do evolve into renal failure, and their management is discussed with particular reference to recent papers on the treatment of membranous nephropathy in adults. An aggressive search for associated disease is worthwhile in children, and one should wait to see what the evolution or proteinuria and renal function may be. If a progressive course becomes evident, then a trial of treatment with corticosteroids is worthwhile, but if this is ineffective then a more aggressive approach involving the use of alkylating agents may be justified. It remains undetermined what the best regime in children and adolescents may be.

Alkylating Agents↗
PubMed1990

Lupus nephritis: correlation of interstitial cells with glomerular function.

Mononuclear inflammatory cells were studied using monoclonal antibodies in the interstitium and glomeruli of 35 renal biopsy specimens from patients with lupus nephritis already taking immunosuppressants. The aims of this study were to assess the composition and significance of the infiltrate, and to assess correlations with immediate glomerular function and ability to predict the future course of the disease. The majority of interstitial cells were T lymphocytes and monocytes/macrophages. The number of interstitial CD4 + ve T helper/inducer lymphocytes was greater than that of CD8 + ve T cytotoxic/suppressor cells in only 19 out of 35 biopsies, the mean CD4:CD8 ratio being only 1.5 +/- 1.2. NK cells and B lymphocytes were a minor component only. Some expression of IL-2, transferrin and C3b receptors was seen on interstitial cells, but HLA-DR expressing cells were much in excess of controls and the numbers of tubular cells expressing HLA-DR was also increased. The number of interstitial T cells, CD4 + ve cells and monocytes/macrophages was highly correlated with the extent of chronic damage judged by optical microscopy. There was also an association between glomerular function at biopsy and numbers of interstitial T cells, CD8 + ve cells, monocytes/macrophages and DR expressing cells. Subsequent decline in renal function, however, was associated only with numbers of monocytes/macrophages and the rather small number of C3b receptor-positive cells. The presence of tubulointerstitial immune aggregates of Ig and/or C in 63% of patients was associated with greater numbers of NK cells. As previously described, the degree of renal function at biopsy correlated with a chronicity index based on optical microscopy. No correlations were found between numbers or types (mostly monocyte/macrophages) of intraglomerular leukocytes and clinical or biopsy features, except that more proliferative types showed greater leukocyte numbers. One hypothesis consistent with our findings is that interstitial T cells and monocytes may be important determinants of pathogenesis and progression of lupus nephritis. While several mechanisms may play an initial role, interstitial monocytes may be the major factor in chronic injury.

Adult↗
PubMed1990

IgA affinity to ssDNA or endothelial cells and its deposition in glomerular capillary walls in IgA nephropathy.

Autoantibodies to glomerular components may be pathogenetic in IgA nephropathy. We studied sera from 32 IgA nephropathy patients, 35 normal controls and 102 patients controls with other forms of glomerulonephritis for IgA isotype affinity to endothelial cells, denatured DNA (ssDNA), murine laminin, and cardiolipin measured by ELISA. Compared to the normal controls, patients with IgA nephropathy had significantly elevated IgA with affinity to endothelial cells (P = 0.01) and ssDNA (P = 0.04), but not to murine laminin or cardiolipin. Furthermore, serum IgA with affinity to ssDNA, but not to endothelial cells, was associated with the presence of IgA deposited in the glomerular capillary walls (P = 0.011), an indicator of poor prognosis in patients with IgA nephropathy. Therefore, IgA with affinity to ssDNA may represent an autoantibody with pathogenetic significance in IgA nephropathy.

Adult↗
PubMed1990

Number of interstitial capillary cross-sections assessed by monoclonal antibodies: relation to interstitial damage.

Using thin Plexiglass sections stained with silver, the peritubular capillary area and number of capillary cross-sections can predict both interstitial damage and plasma creatinine concentrations. This technique is both difficult to perform and time-consuming. We have restudied this topic using conventional cryostat sections from 46 biopsies with chronic glomerulonephritis and tubulointerstitial nephritis and two monoclonal antibodies (MoAb) recognising capillary endothelium. Seven pretransplant biopsies acted as controls. The number of capillary cross-sections/mm2 was counted, and the degree of tubular atrophy, interstitial fibrosis and cell infiltration of the interstitium independently assessed on a semiquantitative scale using paraffin sections. These results were correlated with the plasma creatinine or 51Cr-EDTA glomerular filtration rate. Mean number of capillary cross-sections in normal interstitium was 373 +/- 50/mm2, and in the 46 biopsies studied 242 +/- 57/mm2. The number of capillary cross-sections reflected the plasma creatinine (r = 0.82, P less than or equal to 0.0001) and the glomerular filtration rate (r = 0.64, P less than or equal to 0.0001) at the time of biopsy with greater accuracy than any of the conventional gradings of interstitial damage on paraffin sections. We conclude that the use of anti-endothelial cell monoclonal antibodies makes counting capillary cross-sections easy and reliable, and that this technique can be employed to assess the extent of interstitial damage in conventional cryostat sections.

Antibodies, Monoclonal↗