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Biomedical subjects

A M Jennings

Publications and source records attributed to A M Jennings.

At least 19 recordsLinked to original sources
PubMed1999

Estramustine reversal of resistance to intravesical epirubicin chemotherapy.

OBJECTIVE: Failure of epirubicin treatment of superficial bladder cancer implies multidrug resistance (MDR) which is common. MDR is characterised by decreased cellular levels of drug. TCC cell lines sensitive to epirubicin and resistant to both epirubicin and mitomycin C were used to investigate augmented therapy by adding the MDR reversing agent estramustine to an in vitro model. METHODS: Cells were cultured as monolayers. Fluorescence analysis was performed by flow cytometry and confocal microscopy. Cells were exposed to epirubicin 20 microg/ml for 2 h and increasing amounts of estramustine. Cytotoxicity was determined under similar exposure conditions and MTT culture (dye reduction by live cells) allowed viable biomass to be read optically. RESULTS: Resistant cells accumulated eight times less epirubicin than sensitive cells. Confocal microscopy confirmed this for nuclear uptake. Accumulation in resistant cells can be increased to near-sensitive cell levels using 40 microg/ml estramustine. Image analysis of confocal fluorescence showed a shift from cytoplasm to nucleus. This correlated with increased cytotoxicity. CONCLUSION: Estramustine plus epirubicin chemotherapy can overcome MDR and may achieve more successful tumour killing in vivo. It may also prevent emergence of resistance. Primary TCC culture examination permits detection of sensitive and resistant cells and may predict outcome allowing a more logical treatment selection.

Administration, Intravesical↗
PubMed1998

Is gamma-linolenic acid an effective intravesical agent for superficial bladder cancer? In vitro cytotoxicity and in vivo tolerance studies.

The essential fatty acid gamma-linolenic acid (GLA) is an effective cytotoxic agent when applied topically and for prolonged periods to tumour cells. Topical application, by intravesical therapy, is firmly established in the treatment of superficial bladder cancer. However, this form of therapy is limited to a maximum duration of 2 h. At such a short drug exposure time, does GLA retain its cytotoxicity? We have examined this question by exposing the superficial bladder cancer cell lines MGH-U1 and RT112 to meglumine-GLA (MeGLA) for time intervals ranging from 30 min to 2 h, at drug concentrations ranging from 1000 to 1.95 microg/ml. The MTT viable biomass assay was used to assess cell kill. Greater than 90% inhibition was observed at a concentration of 125 microg/ml (IC > 90), at 2 h drug exposure. At shorter drug exposure times, higher drug concentrations were needed to induce the same effect. At 1 h drug exposure, the IC > 90 was recorded at 500 microg/ml. In vivo intravesical tolerance studies were conducted in rats. Rats exposed to 2.5 mg/ml MeGLA intravesically for 2 h or less remained well and bladder histology showed minimal changes. This study confirms that GLA retains its cytotoxicity at short drug exposure times and is well tolerated by normal bladder mucosa in vivo. Bladder mucosa tolerated > 10x the concentration required for the IC > 90 in vitro. MeGLA is therefore a feasible intravesical agent for superficial bladder cancer.

Administration, Intravesical↗
PubMed1998

Effects of short-chain fatty acids on primary urothelial cells in culture: implications for intravesical use in enterocystoplasties.

The presence of inflammatory changes and mucopus production in an enterocystoplasty may be similar to the condition of diversion colitis and starvation diarrhea caused by a lack of luminal short-chain fatty acids (SCFAs). We postulate a therapeutic role for intravesical SCFA. Because this treatment will also contact the urothelium, we have assessed the effect on cellular proliferation by utilizing primary urothelial cells in culture. Primary urothelial cells were grown from biopsy samples of normal urothelium obtained intraoperatively. A cocktail of SCFA used in the treatment of diversion colitis was incubated with these cells for time intervals ranging from 30 minutes to 72 hours at drug concentrations ranging from 0.04 to 20 mmol/L butyrate equivalent (BE). The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to measure the residual viable biomass to assess growth inhibition. These experiments were repeated on cells grown on matrigel substrate. The human urothelial cancer line RT112 was likewise exposed to SCFAs to assess selectivity between primary and transformed cells. Primary urothelial cells in culture undergo growth inhibition when exposed to SCFAs. The concentration of SCFAs required to reduce the general biomass by 50% or more (IC> or =50) was 20 mmol/L BE when exposure was for 2 hours or less. When drug exposure was prolonged for 72 hours, the IC> or =50 was 2.5 mmol/L BE. Cells grown on matrigel had their growth similarly inhibited. The IC > or = 50 for the RT112 cell line was 2.5 mmol/L BE after 72 hours of drug incubation. Primary urothelial cells in culture undergo a time- and dose-dependent growth inhibition when exposed to SCFAs. This inhibition is particularly apparent at the higher doses similar to those in use in clinical practice. Cells grown on a matrigel substrate suffer growth attenuation similar to that affecting cells grown on polystyrene plates. In vivo assessment in a rodent intravesical model is advisable before considering instillations in patients.

Cell Division↗
PubMed1998

Bladder cancer recurrence by implantation of exfoliated cells: is gamma-linolenic acid an effective tumoricidal agent?

OBJECTIVE: To compare the tumoricidal efficacy of meglumine gamma-linolenic acid (MeGLA), mitomycin C, epirubicin and water on two urothelial cell lines, and to establish the effect of serum protein levels derived from bladder cancer resection craters on the action of these agents. MATERIALS AND METHODS: The human urothelial cell lines MGHU-1 and RT112 and their drug-resistant variants were exposed to short pulses of aqueous MeGLA, mitomycin, epirubicin and water. Both adherent and suspended cells were exposed to these agents. The MTT viable biomass assay and a clonogenic assay were used to establish tumoricidal efficacy. These experiments were then repeated to assess the effect of added serum proteins on the test results. Estimates of protein in the waste irrigation fluid from 10 patients undergoing transurethral resection of bladder tumour (TURBT) were used to select the quantity of protein used in the study, to establish the clinical relevance. RESULTS: MeGLA caused > 95% reduction in the residual viable biomass of adherent cells, compared with < 50% reduction with any other agent. Both epirubicin and mitomycin were as effective as MeGLA in preventing colony formation from suspended drug-sensitive (parental) cells. However, using multidrug-resistant (MDR) cell lines, only MeGLA prevented any colony formation, although counts were greatly reduced by mitomycin and epirubicin. Water was least effective as a tumoricidal agent on both adherent and suspended cells. On the latter, water was markedly inactivated by adding 5% serum. TURBT waste irrigation fluid was found frequently to contain such quantities of serous fluid contamination, as shown by albumin estimates in waste fluid from 10 consecutive patients undergoing this procedure. CONCLUSION: MeGLA is an effective tumoricidal agent against both parental and MDR cell lines. Its efficacy is maintained in the presence of clinically relevant serum contamination.

Antibiotics, Antineoplastic↗
PubMed1998

Intravesical chemotherapy with gamma linolenic acid becomes a realistic prospect in serum-free applications: in vitro cytotoxicity and systemic absorption studies.

PURPOSE: To assess the cytotoxicity of Meglumine gamma linolenic acid (MeGLA) in serum-free application on 2 urothelial cancer cell lines, to examine whether the instant kill action of MeGLA is retained in a serum free environment, and to study the pharmacokinetics of intravesical instillation of gamma linolenic acid (GLA). MATERIALS AND METHODS: The 2 human urothelial cancer cell lines (MGH-U1 & RT112) were utilized in classical cytotoxicity assays in which drug exposure lasted 2 hours in serum or in serum-free application. The thiozolyl blue (MTT) assay was used to quantify the residual viable biomass 5 days later. Immediate cytotoxicity was also compared in serum and serum-free application. Four Wistar rats were used to study the intravesical absorption profile of tritiated GLA (3H-GLA). RESULTS: There was a 10-fold enhancement of the lytic efficacy of MeGLA in serum-free application and this enhancement was also observed in experiments assessing instant kill. There was a similar enhancement of efficacy seen in the multi-drug resistant (MDR) clone of cells. The absorption profile showed < 2% of instilled counts were absorbed and the commonest destination for the absorbed GLA was the liver. CONCLUSIONS: The cytotoxic action of MeGLA was enhanced in serum free application. This enhancement was maintained when cells expressed the MDR phenotype. There was limited absorption from the bladder. MeGLA is a feasible intravesical agent for use in superficial bladder cancer.

Administration, Intravesical↗
PubMed1996

Impaired processing of proopiomelanocortin in corticotroph macroadenomas.

The regulation and secretion of the ACTH precursors POMC and pro-ACTH were assessed directly using a 2-site immunoradiometric assay in six patients with pituitary macroadenomas (> or = 1.2 cm in diameter) and 27 patients with Cushing's disease due to a microadenoma. ACTH precursor levels were elevated in patients with macroadenomas (150-3690 pmol/L; normal range, < 5-40 pmol/L) and significantly higher than those in microadenoma patients (median, 29 pmol/L; range, 9-104 pmol/L; P < 0.001). Patients with macroadenomas also had increased ACTH precursor/ACTH ratios (15-181:1) compared with microadenoma patients (median, 5:1, range, 0.7-18.5:1; P < 0.001). ACTH precursors were unresponsive to high dose dexamethasone in patients with macroadenomas, whereas ACTH and cortisol responses varied. After CRH administration, ACTH precursors were unchanged, whereas cortisol increased significantly, suggesting the release of biologically active ACTH. This study clearly demonstrates reduced processing of POMC to ACTH in large pituitary tumors, a characteristic usually associated with tumors causing the ectopic ACTH syndrome, and provides evidence for differential regulation of ACTH precursors and ACTH by glucocorticoid and CRH. Variation in the clinical symptoms of patients with corticotroph macroadenomas may be attributable to differences in biological potency between the ACTH precursors and ACTH.

Adenoma↗
PubMed1995

Pharmacoeconomics of intravenous antibiotic use in serious infection.

A pharmacoeconomic study of 15 antibiotics available in Barbados was performed. The antibiotics studied were amoxycillin/clavulanate, ampicillin, ampicillin/sulbactam, cefazolin, cefotaxime, ceftazidime, ceftriaxone, clindamycin, cloxacillin, cotrimoxazole, gentamicin, imipenem, metronidazole, piperacillin, piperacillin/tazobactam, and vancomycin. The costs of use of these compounds were calculated for a five-day course using a formula comprising eight categories: antibiotic purchase cost, maintenance of intravenous access, drug delivery cost, drug monitoring cost, dose readjustment, general monitoring cost, 'sharps' disposal cost and adverse effects. The costs of adverse effects were not included in this study due to lack of accurate data. The total cost of antibiotic use (in U.S. dollars) ranged from $42.52 to $463.73 per five-day course. Generic compounds were less expensive ($45.52 - $98.23) than brand-name compounds ($106.18 - $106.18 - $463.73). Antibiotic purchase costs accounted for proportions of total costs ranging from 7 to 93%. Non-drug costs represented a much greater proportion of total costs of generic compounds. For most compounds the non-drug costs were related to the frequency of dosing, but for gentamicin the non-drug costs were relatively higher because of the need for monitoring of serum gentamicin levels. Efficacy and freedom from side-effects will remain the most important determinants in the choice of antibiotic therapy. However, pharmacoeconomic analyses can provide prescribers with the information required to make cost-effective choices for treatment of their patients.

Anti-Bacterial Agents↗
PubMed1994

Differential release of proopiomelanocortin-derived peptides from the human pituitary: evidence from a panel of two-site immunoradiometric assays.

In humans, proopiomelanocortin (POMC) and the peptides derived from it have been individually identified in plasma under differing conditions. However, direct quantitative comparison has proved difficult because of the limitations of RIAs. Using a panel of monoclonal antibodies recognizing different regions of POMC, we have developed specific two-site immunoradiometric assays (IRMAs) for the ACTH precursors (POMC and pro-ACTH), ACTH, beta-lipotropin (beta LPH), beta-endorphin (beta EP), and the N-terminal POMC fragment (N-POC). We have quantified these peptides directly in plasma from normal subjects under basal conditions and in response to different regulatory factors. Basal levels of ACTH precursors, 5-40 pmol/L, were greater than or equal to ACTH, less than 0.9-11.3 pmol/L; N-POC, 5.6-16.8 pmol/L; beta LPH, 2.5-6.7 pmol/L; and beta EP less than or equal to 1.7 pmol/L. ACTH, N-POC, beta LPH, and beta EP levels increased in parallel in response to metyrapone (n = 8) and decreased in response to dexamethasone (n = 8), whereas ACTH precursor concentrations did not respond. After human CRH administration, peripheral concentrations of ACTH, N-POC, and beta LPH showed similar increments (median increment, 163%, 145%, and 172%, respectively; n = 6). POMC peptide responses to human CRH were also assessed in inferior petrosal sinuses draining the pituitary in 20 patients with pituitary-dependent Cushing's disease. In these patients, the increment in ACTH after CRH exceeded that in ACTH precursors by 4-fold (median, 459% and 96%). An increase in the ratios of ACTH/N-POC and ACTH/beta LPH was also apparent after CRH stimulation. The increment in beta EP after CRH always exceeded the increments in POMC and beta LPH. In summary, these data suggest that significant concentrations of ACTH precursors are present in the circulation of normal subjects, that ACTH precursors are not regulated in the same way as the processed POMC peptides, and that ACTH and beta EP are preferentially released from the pituitary in response to CRH.

Adrenocorticotropic Hormone↗
PubMed1993

A neural network approach to automatic chromosome classification.

Classification of banded metaphase chromosomes is an important step in automated clinical chromosome analysis. We have conducted a preliminary investigation of the application of artificial neural networks to this process, making use of a natural representation of the banding pattern. Two different network architectures have been compared: the Kohonen self-organizing feature map and the multi-layer perception (MLP). For each of these a search of their respective parameter spaces over a limited range has resulted in configurations of modest dimension which achieve creditable classification rates. The MLP in particular shows promise of being a useful classifier. When size and shape features are supplied as inputs to the MLP in addition to a low-resolution banding profile, misclassification rates are obtained which are comparable with those of a well developed statistical classifier.

Chromosomes↗
PubMed1993

Severe peripheral neuropathy and elevated plantar pressures causing foot ulceration in pituitary gigantism.

We report two patients with treated pituitary gigantism and peripheral neuropathy, one of whom has chronic foot ulceration. Detailed neurophysiological assessment was performed on both patients. The patient with foot ulceration had clinical and neurophysiological evidence of severe neuropathy, whereas the patient without ulceration had only neurophysiological abnormalities. The sweating response to acetylcholine was markedly impaired in the feet of both patients, suggesting pedal autonomic denervation. Neither patient had evidence of diabetes mellitus and detailed investigation failed to reveal an alternative cause of peripheral neuropathy. Optical pedobarography revealed abnormally high pressure (> 10 kg/cm2) under the metatarsal heads of both patients, one such area coinciding with the area of ulceration. Thus in pituitary gigantism elevated plantar pressures may contribute to the development of foot ulceration when severe peripheral neuropathy is present. Furthermore, as in diabetes mellitus, impaired sweating may also increase the risk of ulceration as the resultant dry skin may develop fissures.

Adult↗
PubMed1991

The effects of diet and insulin therapy on coagulation factor VII, blood viscosity, and platelet release proteins in diabetic patients with secondary sulphonylurea failure.

The effect of intensified dietary measures and subsequently insulin therapy upon haemorheological measures were studied in Type 2 diabetic patients with secondary sulphonylurea failure. Coagulation factors VIIc and VIIIc, fibrinogen, plasma viscosity, whole blood viscosity, beta-thromboglobulin, platelet factor 4, von Willebrand factor, and euglobulin clot lysis time were measured at baseline, after 3 months intensified dietary therapy and after 4 months insulin therapy. During intensified dietary therapy there was a significant fall in serum cholesterol (p less than 0.05) and a small decrease in weight, but no significant change in blood glucose control. Factor VIIc levels fell significantly (1.22 (SE 0.07) vs 1.42 (0.08) u ml-1, p less than 0.01), and plasma viscosity and whole blood viscosity (23 s-1) also improved (both p less than 0.05). Insulin therapy was instituted with either continuous subcutaneous insulin therapy or twice daily injections of soluble and isophane (NPH) insulin. During this period glycosylated haemoglobin improved (mean (SE) 49.5 (1.4) vs 65.0 (2.1) mmol-HMF mol-Hb-1, p less than 0.001; normal range 29-39 mmol-HMF mol-Hb-1) as did serum triglyceride (p less than 0.01), but weight increased (p less than 0.001). The only haemorheological changes with insulin were increased levels of the platelet release proteins beta-thromboglobulin (37 (3) vs 28 (2) micrograms l-1, p less than 0.01) and platelet factor 4 (median 7.5 (range 3.0-18.0) vs 4.5 (2.0-10.5) micrograms l-1, p less than 0.01).

Adult↗
PubMed1991

Randomized trial comparing continuous subcutaneous insulin infusion and conventional insulin therapy in type II diabetic patients poorly controlled with sulfonylureas.

OBJECTIVE: To compare the effects of continuous subcutaneous insulin infusion (CSII) and conventional insulin therapy (CIT) in patients with poorly controlled sulfonylurea-treated diabetes mellitus. RESEARCH DESIGN AND METHODS: Twenty-five patients aged 40-65 yr and poorly controlled with sulfonylureas and without severe diabetic complications comprised the study group. Five patients left the study (3 achieved satisfactory glycemic control without insulin, 1 defaulted, 1 developed ketonuria). Ten patients were treated with CSII and 10 with CIT. Outpatient treatment consisted of CIT (twice-daily injections of regular and NPH insulin) or CSII (basal infusion and prandial boluses of regular insulin). RESULTS: Glycosylated hemoglobin improved with both methods of insulin delivery (P less than 0.01), but 8 of 10 CSII-treated patients achieved satisfactory glycemic control (HbA1 less than 50 mmol hydroxymethylfurfural/mol Hb), whereas only 3 of 10 CIT-treated patients achieved this (P less than 0.05). Weight gain, insulin dosage, and prevalence of hypoglycemia were similar in the two groups. Retinal deterioration occurred in one CSII-treated patient and three CIT-treated patients, but there were no episodes of infusion site infection or metabolic decompensation. Patients' satisfaction with treatment improved during insulin therapy (P less than 0.02), and significant changes in beliefs about diabetes and its treatment were observed in CSII-treated patients (P less than 0.05). CONCLUSIONS: Glycemic control improved with both methods of insulin treated patients achieved satisfactory glycemic control (HbA1 less than 50 mmol hydroxymethylfurfural/mol Hb), whereas only 3 of 10 CIT-treated patients achieved this CSII. Patients' satisfaction with treatment improved during insulin therapy.

Adult↗
PubMed1990

Health belief scales developed specifically for people with tablet-treated type 2 diabetes.

The design and development of scales to measure diabetes-specific health beliefs of patients treated with oral hypoglycaemic agents and diet are described. The scales, which were developed from the responses of 187 tablet-treated patients, measure perceived Benefits of, and Barriers to Treatment, and perceived Severity of, and Vulnerability to Complications of diabetes and other disorders unrelated to diabetes. Cronbach's alpha indicated that each scale was internally reliable (alpha = 0.67 to 0.89) and construct validity was indicated by expected correlations between the scales and other variables including measures of blood glucose control, body weight, and psychological well-being. Thus, patients who were overweight and/or had higher glycosylated haemoglobin (HbA1) levels perceived their treatment to be less 'Cost-effective' (Benefits less Barriers), rated Complications as being more severe, and reported greater Vulnerability for themselves and the 'average person' with diabetes to these Complications (p less than 0.05 to p less than 0.01). Furthermore, respondents with higher Depression and Anxiety scores and lower Positive Well-being and Treatment Satisfaction scores reported greater Vulnerability to Complications for themselves and the 'average person', and also felt that their treatment was less 'Cost-effective' (p less than 0.01 to p less than 0.001). The measures are likely to be particularly useful in studies which assess the efficacy of interventions in modifying health beliefs with a view to achieving desired behaviours. They may also be useful as an instrument of audit if indicators about the suitability of possible interventions are sought.

Adult↗
PubMed1989

Islet cell antibodies and insulin autoantibodies in patients treated with oral hypoglycaemic agents.

Clinical and immunological features suggesting Type 1 diabetes were assessed in 202 patients treated with oral hypoglycaemic agents for presumed Type 2 diabetes. Islet cell antibodies (ICA) were detected at a level exceeding 5 JDF units in 5.9% of patients, and complement-fixing ICA were detected in 3.4%. IgG insulin autoantibodies were detected in 8.8% of insulin-naive patients, none of whom were ICA positive. ICA were detected more frequently in patients with shorter duration of diabetes (p = 0.02). Age and relative body weight were similar in ICA positive and negative groups. ICA positive patients were more likely to have lost weight (p less than 0.02) than ICA negative patients, although this may have been attributable to the differing duration of diabetes in the two groups. Other individual clinical features suggesting Type 1 diabetes were not significantly more frequent in ICA positive patients. However, a higher proportion of ICA positive than ICA negative patients had one or more features suggestive of Type 1 diabetes irrespective of the duration of diabetes. Clinical features suggesting Type 2 diabetes were present in a similar proportion of ICA positive and ICA negative patients. Fasting and glucagon stimulated C-peptide levels were similar in ICA positive and matched ICA negative patients.

Adult↗
PubMed1989

Comparison of insulin autoantibodies in diabetes-related and healthy populations by precise displacement ELISA.

The second international workshop on insulin autoantibodies (IAAs) demonstrated improved concordance among laboratories with both radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) when measurements were based on signals displaceable by preincubation with excess insulin. This feature has been incorporated into our original ELISA for IAAs, and the assay was used to compare IAAs in diabetes-related and healthy populations. The serum from a healthy islet cell antibody (ICA)+ and IAA+ subject was used to construct standard curves with and without preincubation with 1 U/ml human insulin. Reporting results in arbitrary displacement (delta +/- IAA) units derived from the standard curve improved precision and increased the specificity of the assay. Frequency analysis of the results from 200 control adults did not show a normal distribution, and cumulative frequency analysis demonstrated two populations: 10 of 200 (5%) control adults, 8 of 241 (3.3%) healthy schoolchildren, and 18 of 229 (7.9%) non-insulin-dependent diabetes mellitus (NIDDM) patients had IAAs greater than 12 delta +/- IAA units. On the same basis, we tested samples from 89 individuals in the prospective Bart's Windsor Family Study for insulin-dependent diabetes mellitus (IDDM), 31 of whom had ICAs greater than 5 Juvenile Diabetes Foundation (JDF) units. Of those with ICAs greater than 5 JDF units, 12 developed IDDM and 1 developed NIDDM in 10 yr of study. IAAs greater than 12 delta +/- IAA units were found in 6 of 12 (50%) who became diabetic and in 4 of 18 (22%) who remain healthy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Symptomatic hypoglycemia in NIDDM patients treated with oral hypoglycemic agents.

We assessed the prevalence of hypoglycemic symptoms in patients (aged 40-65 yr) treated with oral hypoglycemic agents (OHAs) attending routine diabetes clinics at our hospital. Symptoms were experienced during the previous 6 mo in 41 of 203 (20.2%) patients treated with sulfonylureas but in none of the 16 patients treated with metformin alone. Hypoglycemic symptoms were experienced at least monthly in 5.9% and less frequently in 14.3% of patients. The prevalence of symptoms decreased with increasing duration of sulfonylurea administration (P less than .01). Mean glycosylated hemoglobin and postprandial plasma glucose were significantly lower in patients reporting hypoglycemic symptoms than in those without symptoms (P less than .001). The prevalence of hypoglycemic symptoms was significantly higher in patients treated with glyburide than in patients treated with gliclazide (P less than .01) or chlorpropamide (P less than .05). The prevalence of symptoms was higher in patients taking medications in addition to OHAs (P less than .01). Ten (24%) of the patients who experienced hypoglycemic symptoms were taking drugs that may potentiate sulfonylureas.

Adult↗