Search PubMed⌕ Search

Biomedical subjects

J Cunningham

Publications and source records attributed to J Cunningham.

At least 127 records · Page 7Linked to original sources
PubMed1993

Cyclosporine and cremaphor modulate von Willebrand factor release from cultured human endothelial cells.

Cyclosporine has been associated with microangiopathic hemolysis (MAHA) and other thrombotic complications of bone marrow and renal transplantation. MAHA is characterized by intravascular platelet aggregation, which, in some situations, is thought to be mediated by hyperactive high molecular weight von Willebrand factor (vWF). We have hypothesized that transplant-related MAHA may be caused by CsA-mediated release of von Willebrand factor from endothelial cells. This hypothesis was tested by studying vWF release from human umbilical vein endothelial cells primed with either CsA or cremophor EL. CsA and cremophor alone did not increase vWF release until toxic concentrations were reached (50-100 micrograms/ml). However, at therapeutic concentrations (0.1-5 micrograms/ml) vWF release by cells stimulated with thrombin, histamine, PMA, and the calcium ionophore A23187 was enhanced by both CsA and cremophor in a concentration-dependent manner. In single isolated endothelial cells, the thrombin-induced increase in cytosolic free calcium was enhanced by both CsA and cremophor. Preincubation for 24 hr with CsA but not cremophor suppressed vWF release after thrombin stimulation. These observations were mirrored by a concentration-dependent suppression of [3H]thymidine uptake by CsA. We conclude that CsA vehicle, cremophor, enhances stimulated vWF release in vitro, probably by processes dependent upon increased cytosolic free calcium. This suggests a possible mechanism for thrombotic transplant complications.

Calcium↗
PubMed1993

The prevention of secondary hyperparathyroidism.

It has become increasingly evident that clear-cut disturbances of bone and mineral metabolism develop early in renal failure. Among these disturbances, hyperparathyroidism is well documented and is usually asymptomatic at that early stage. It is now accepted that early therapy using phosphate restriction, through diet and calcium-containing phosphate binders, and 1 alpha-hydroxylated vitamin D analogues is an effective means of preventing or even reversing hyperparathyroidism in early renal failure. The response to these therapies is both functional (reduced parathyroid hormone secretion) and structural (prevention of parathyroid gland hyperplasia). Parathyroid hyperplasia is largely irreversible; prevention is therefore important and can be achieved initially by a combination of diet and calcium-containing phosphate binders, with later addition of calcitriol or alfacalcidol if parathyroid hormone control cannot be achieved or sustained.

Humans↗
PubMed1993

A comparison of rat brain amino acid and monoamine content in diazepam withdrawal and after exposure to a phobic stimulus.

1. The content of amino acids (taurine, glycine, glutamic acid, gamma-aminobutyric acid (GABA) and aspartic acid) and monoamines (5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and noradrenaline) in homogenates of rat cortical and hippocampal tissue were measured by high performance liquid chromatography (h.p.l.c.) with fluorescent and electrochemical detection respectively, after two anxiogenic treatments: exposure to a phobic stimulus (cat odour) and withdrawal from chronic diazepam treatment. 2. In neither of the two anxiogenic situations was there a significant change in any amino acid content, in either brain area. 3. In the group withdrawn from chronic diazepam, cortical 5-HT and 5-HIAA levels and hippocampal 5-HT levels were significantly increased. Noradrenaline content was significantly decreased in the hippocampus. 4. The changes in 5-HT and 5-HIAA levels following cat odour exposure were area-specific in that they decreased in the hippocampus, but increased in the cortex. 5. Following cat odour exposure, noradrenaline levels appeared not to change in either area studied. However during exposure to cat odour, it was found that half the animals avoided the odour source and half were indifferent. The animals showing marked avoidance had significantly higher cortical noradrenaline content and this was significantly different from control, whereas hippocampal noradrenaline levels were not dependent upon the differences in avoidance of the odour source. 6. The results show clearly different neurochemical changes in the rat following exposure to a phobic stimulus and withdrawal from diazepam. It is hoped comparative studies such as this will enable better understanding of anxiety states in the rat which could parallel the different classes of anxiety recognised in the clinic

Amino Acids↗
PubMed1993

Dual energy X-ray absorptiometry versus skinfold measurements in the assessment of total body fat in renal transplant recipients.

Traditional methods for estimating total body fat rely on the assumption that body fat distribution and bone mineral content are constant. However, in patients undergoing renal transplantation rapid changes in body composition occur, with variations in fat distribution and bone mineral content. In order to determine the reliability of skinfold measurement (SFM) in these patients, we compared it with dual energy X-ray absorptiometry (DEXA), which estimates body composition without reliance on assumptions of constant fat distribution and bone mineral content. Thirty-four adult renal transplant recipients were studied at the time of transplantation and again after 3 and 6 months. The correlation coefficients of DEXA vs SFM at the three time points were 0.84, 0.78, 0.85, respectively (P = 0.0001). In 34 healthy adults serving as controls, the correlation coefficient was 0.95 (P = 0.0001). Total body fat increased progressively following renal transplantation (P < 0.03 by 6 months) with SFM showing considerable disagreement with DEXA measurements of percentage total body fat. Thus skinfold measurements underestimated changes in total body fat following renal transplantation, especially in those gaining substantial amounts of body fat, and DEXA appeared to be a more appropriate technique.

Absorptiometry, Photon↗
PubMed1992

Current status of adjuvant chemotherapy for colorectal cancer. Can molecular markers play a role in predicting prognosis?

BACKGROUND: Recent clinical trials establish a beneficial effect for adjuvant chemotherapy after surgical resection of the primary tumor (1) as single treatment for patients with colonic cancer and (2) combined with radiation therapy for patients with rectal cancer. Because adjuvant chemotherapy is not universally effective and is associated with toxicity and some degree of risk, it would be desirable to supplement standard pathologic staging criteria to define more precisely the subset of patients at high risk for tumor recurrence who would benefit most from adjuvant therapy. Tumor cell DNA content and cell proliferation measured by flow cytometry were identified as important and independent prognostic factors for patients undergoing curative resection of colorectal cancer. Basic laboratory investigations show a series of more specific molecular and genetic abnormalities that might provide better prognostic discrimination. Recent molecular studies suggest that the process of tumorigenesis in colorectal cancer proceeds through a series of genetic alterations that include both dominant and recessive protooncogenes. Characterization of these molecular genetic abnormalities may provide valuable prognostic information for use in patient management. METHODS: Allelic loss was studied for chromosomes 5, 17, and 18, and immunohistochemical analysis was done of the p53 protein product in tumors from 91 patients with colorectal cancer. RESULTS: Preliminary analysis of disease-free survival after surgical resection in 60 patients with Dukes' B or C tumors suggests a poorer prognosis associated with allelic loss on chromosome 18q (P = 0.08). CONCLUSIONS: Additional studies involving a much larger population of patients with Dukes' B and C colorectal cancer are needed to define the true prognostic significance of these molecular markers.

Aged↗
PubMed1992

Expression of p53 and 17p allelic loss in colorectal carcinoma.

Mutations in the p53 gene are the most common genetic changes in cancer thus far. Many p53 mutations result in a protein product having a prolonged half-life compared to wild-type p53. The mutant protein is frequently detectable immunohistochemically, whereas the wild-type p53 present in normal cells is not. We examined 90 colorectal carcinomas for increased expression of p53 using 3 p53 specific monoclonal antibodies, PAb1801, PAb421, and PAb240. Overall, 70% of the colorectal carcinomas stained for p53. Each tumor's DNA was also assessed for loss of heterozygosity on chromosome 17p, the location of the p53 gene. Of those tumors that reacted with the anti-p53 antibodies, 76% showed loss on chromosome 17p. Tumors with loss of heterozygosity on 17p generally stained with all 3 antibodies, whereas those without loss tended to stain with just one antibody, typically PAb240. Fifteen tumors were examined for the presence of specific p53 mutations. A total of 10 mutations were found, 6 were missense and 2 were deletions, and all but one of the tumors with missense mutations stained for p53.

Alleles↗
PubMed1992

Pattern of p53 gene mutations in breast cancers of women of the midwestern United States.

BACKGROUND: Mutation in the p53 gene is the most common genetic lesion in human cancers. The pattern of mutation in the p53 gene differs among cancers and may be a useful epidemiological tool for identification of factors contributing to carcinogenesis. PURPOSE: Our purpose was to determine if the pattern of p53 mutation in breast carcinomas in our population of women residing in the midwestern region of the United States is similar to the pattern of p53 mutation in breast cancers in patients from other regions of the United States and Europe and in other epithelial tumors. METHODS: With a technique we recently developed for the analysis of p53 mutations in genomic DNA from tumor cell clusters in touch preparations of solid tumors, we sequenced exons 5-9 and adjacent splice junctions of the gene in 44 breast cancers. Cells from each tumor were also stained with three monoclonal antibodies which recognize different epitopes of the p53 protein. RESULTS: We detected p53 mutations in 14 (32.6%) of 44 breast carcinomas. Only half of the mutations were missense changes. The other half included five microdeletions (three producing frame-shifts), one single-base substitution generating a stop codon, and one single-base substitution generating a splice junction abnormality. Nuclear expression of p53 antigen was present in eight of 44 cancers, including six with hemizygous missense mutations in the p53 gene. CONCLUSIONS: The pattern of p53 mutations in our breast cancer population differs from that reported in breast cancer populations by other investigators in which most p53 mutations were missense. Among 14 mutations in our population, at least five drastically altered the structure of p53, suggesting that a recessive mechanism of inactivation of the p53 gene may be more common than in other populations. IMPLICATIONS: Differences in the pattern of p53 mutation in breast cancers in Midwestern women and in breast cancers in other populations may reflect selection bias or small sample sizes currently available. However, our data are compatible with the possibility that an endogenous or exogenous factor influences p53 carcinogenesis in some women with breast cancer in the Midwest to a greater extent than in other regions of the United States and Europe.

Adult↗
PubMed1992

Phase I trial of murine monoclonal antibody L6 in combination with subcutaneous interleukin-2 in patients with advanced carcinoma of the breast, colorectum, and lung.

PURPOSE: A phase I trial was undertaken to determine the toxicity and biologic effects of a combination of murine monoclonal antibody L6 (MoAb L6) plus subcutaneous (SC) interleukin-2 (IL-2). PATIENTS AND METHODS: Fifteen patients with refractory adenocarcinoma (five breast, five lung, five colorectal), received L6 at 200 mg/m2 intravenously (IV) daily on days 1 to 7, followed by a 1-week rest period. IL-2 was given at either 2, 3, or 4.5 x 10(6) U/m2 daily doses times 4 days for a total duration of 3 weeks. RESULTS: Side effects of L6 consisted of mild fever and chills along with a rash and serum sickness in one patient. One patient developed dyspnea and urticaria, that resolved with antihistamines. Maximum-tolerated dose (MTD) of SC IL-2 was 3 x 10(6) U/m2, with dose-limiting toxicities that consisted of grade 4 fatigue and dyspnea. Significant decreases in complement levels along with increases in absolute lymphocyte count and eosinophil count were observed. Mean antibody-dependent cellular cytotoxicity from mononuclear cells taken from patients who received IL-2 was elevated significantly compared with baseline in all patients independent of IL-2 dose (P less than .05). Serum IL-2 levels were elevated in 13 of 14 patients (range, 0.9 to 100 U/mL). Human antimouse antibody (HAMA) titers were elevated in nine of 14 (64%) patients who were tested between 3 and 8 weeks after L6 infusion. One patient with breast cancer had a transient mixed response, and one patient with colorectal cancer had a partial response. CONCLUSIONS: L6 and SC IL-2 were well tolerated in the majority of patients when given in the outpatient setting. In view of the clinical efficacy of this combination, more phase II trials are warranted.

Adult↗
PubMed1992

Dialysate calcium reduction in CAPD patients treated with calcium carbonate and alfacalcidol.

The use of oral calcium carbonate as a phosphate binder is often complicated by hypercalcaemia, particularly with concomitant use of vitamin D analogues. We previously found that stepwise reduction of dialysate calcium effectively countered this complication in haemodialysis patients, and have now assessed the strategy in CAPD patients. Seventeen patients underwent conversion from aluminium hydroxide to calcium carbonate and were followed for 5 months, with subsequent addition of alfacalcidol for a further 5 months. Standard CAPD dialysate (1.75 mM calcium) was used, reducing to 1.45 mM and, if necessary, to 1.00 mM in patients who became hypercalcaemic. While receiving calcium carbonate alone, 12 of the 17 patients became hypercalcaemic, this responding in four to dialysate calcium reduction to 1.45 mM. In the remaining eight patients, further reduction to 1.00 mM was required and in two patients even this failed to control hypercalcaemia adequately, necessitating reversion to aluminium hydroxide. Phosphate control remained unchanged, as did calcium x phosphorus product. There were transient increases of blood ionised calcium, and decreases of parathyroid hormone, with progressive reduction of serum aluminium and alkaline phosphatase. The addition of alfacalcidol (0.25 microgram/day) led to hypercalcaemia in six subjects, successfully countered by dialysate calcium reduction in four. The results show that standard CAPD dialysate calcium at 1.75 mM is too high for the majority of calcium carbonate treated patients and that substantial reductions of the dialysate calcium concentration are required if calcium carbonate is to be used effectively.

Aluminum Hydroxide↗
PubMed1992

'Pulse' oral calcitriol in uraemic patients: rapid modification of parathyroid response to calcium.

We performed dynamic parathyroid function tests, with generation of parathyroid hormone/ionized calcium (PTH/iCa) response curves, obtained during sequential hypercalcaemic and hypocalcaemic dialysis, on six haemodialysis patients before and after 4-weekly 'pulse' doses of oral calcitriol. There were no significant changes in the pretreatment, 2-week and 4-week values of blood ionized calcium, serum total calcium, phosphate, and alkaline phosphatase. PTH decreased significantly after 4 weeks of treatment with calcitriol (P less than 0.03), and the post-treatment PTH/iCa curves were all displaced leftwards and downwards, indicating a marked inhibitory effect of calcitriol on parathyroid responsiveness across and beyond the physiological range of calcaemia. The mean shift of the PTH/iCa relationship was equivalent to a reduction of iCa of 0.2 mM for any given concentration of PTH, and conversely to a 70% reduction of PTH for any given blood iCa. The results suggest that wide spacing of oral 'pulse' doses of calcitriol can achieve favourable modification of the PTH/iCa relationship, and that dosing interval and dose size, rather than route of administration, may be the major determinants of the previously reported superiority of intravenous over daily oral calcitriol regimens.

Administration, Oral↗
PubMed1992

Does the arteriovenous fistula in chronic haemodialysis patients stimulate endothelin-1 release?

Plasma endothelin-1 (ET-1)-like immunoreactivity was measured by radioimmune assay in predialysis plasma samples from 16 chronic haemodialysis patients (7 dialysing through arteriovenous (AV) fistulae and 9 using central venous cannulae for access), from 10 patients with functioning renal transplants (5 with AV fistulae and 5 without), and from 6 healthy subjects as controls. Among dialysis patients, ET-1 was greater in those with AV fistulae than in those using cannulae for dialysis (median (range), 5.5 (3.1) pM versus 3.7 (2.0) pM, P = 0.02), and in all haemodialysis patients ET-1 values were substantially greater than in normal controls (3.9 (3.2) pM versus 0.5 (0.1) pM; P = 0.001). In patients with functioning AV fistulae, ET-1 concentrations obtained directly from the AV anastomosis of the fistula (4.4 (3.0) pM) were less than those taken simultaneously from the contralateral arm (5.5 (3.1) pM; P = 0.04), while samples drawn from the venous side of the fistula were intermediate (4.6 (3.4) pM). In renal transplant recipients, ET-1 values did not differ significantly from those in control subjects (0.7 (1.9) pM versus 0.5 (0.1) pM, n.s.), but in these patients there was a significant difference between peripheral venous ET-1 in transplant patients with and without AV fistulae (0.8 (1.9) pM versus 0.6 (1.1) pM respectively, P = 0.04). The results suggest that the increased blood flow rate through the arterialized venous circulation in the fistula arm stimulates increased ET-1 release in these patients, and that this accounts, at least in part, for the increased ET-1 found in the patients with functioning AV fistulae.

Adult↗