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Biomedical subjects

A Clark

Publications and source records attributed to A Clark.

At least 127 records · Page 7Linked to original sources
PubMed1997

Spray dried powders and powder blends of recombinant human deoxyribonuclease (rhDNase) for aerosol delivery.

PURPOSE: We have used rhDNase to investigate the feasibility of developing a dry protein powder aerosol for inhalation delivery. METHODS: Powders of rhDNase alone and with sodium chloride were prepared by spray drying. Powder blends were obtained by mixing (tumbling and sieving) pure rhDNase powder with 'carrier' materials (lactose, mannitol or sodium chloride). The weight percent of drug in the blends was between 5 and 70%. The particle size distributions and crystallinity of the spray dried powders were obtained by laser diffraction and X-ray powder diffraction, respectively. Particle morphology was examined by scanning electron microscopy. The ability of the powders and powder blends to be dispersed into respirable aerosols was measured using a Rotahaler connected to a multistage liquid impinger operating at 60 L/min. RESULTS: Pure rhDNase powder was quite cohesive with a fine particle fraction (FPF or "respirable fraction': % wt. of particles < 7 microns in the aerosol cloud) of about 20%. When particles also contained NaCl, the powders were dispersed better to form aerosols. A linear relationship was observed between the NaCl content and FPF for a similar primary size (approximately 3 microns volume median diameter) of particles. The particle morphology of these powders varied systematically with the salt content. For the blends, SEM revealed a monolayer-like adhesion of the fine drug particles to the carriers at drug contents > or = 50% wt. An overall 2-fold increase in FPF of rhDNase in the aerosol cloud was obtained for all the blends compared to the pure drug aerosols. CONCLUSIONS: The aerosol properties of spray dried rhDNase powders can be controlled by incorporation of a suitable excipient, such as NaCl, and its relative proportion. Coarse carriers can also enhance the performance of rhDNase dry powder aerosols.

Aerosols↗
PubMed1997

A ubiquitin-conjugating enzyme is essential for developmental transitions in Dictyostelium.

We have identified a developmentally essential gene, UbcB, by insertional mutagenesis. The encoded protein (UBC1) shows very high amino acid sequence identity to ubiquitin-conjugating enzymes from other organisms, suggesting that UBC1 is involved in protein ubiquitination and possibly degradation during Dictyostelium development. Consistent with the homology of the UBC1 protein to UBCs, the developmental pattern of protein ubiquitination is altered in ubcB-null cells. ubcB-null cells are blocked in the ability to properly execute the developmental transition that occurs between the induction of postaggregative gene expression during mound formation and the induction of cell-type differentiation and subsequent morphogenesis. ubcB-null cells plated on agar form mounds with normal kinetics; however, they remain at this stage for approximately 10 h before forming multiple tips and fingers that then arrest. Under other conditions, some of the fingers form migrating slugs, but no culmination is observed. In ubcB-null cells, postaggregative gene transcripts accumulate to very high levels and do not decrease significantly with time as they do in wild-type cells. Expression of cell-type-specific genes is very delayed, with the level of prespore-specific gene expression being significantly reduced compared with that in wild-type cells. lacZ reporter studies using developmentally regulated and cell-type-specific promoters suggest that ubcB-null cells show an unusually elevated level of staining of lacZ reporters expressed in anterior-like cells, a regulatory cell population found scattered throughout the aggregate, and reduced staining of a prespore reporter. ubcB-null cells in a chimeric organism containing predominantly wild-type cells are able to undergo terminal differentiation but show altered spatial localization. In contrast, in chimeras containing only a small fraction of wild-type cells, the mature fruiting body is very small and composed almost exclusively of wild-type cells, with the ubcB-null cells being present as a mass of cells located in extreme posterior of the developing organism. The amino acid sequence analysis of the UbcB open reading frame (ORF) and the analysis of the developmental phenotypes suggest that tip formation and subsequent development requires specific protein ubiquitination, and possibly degradation.

Amino Acid Sequence↗
PubMed1997

A novel mechanism of vascular endothelial growth factor, leptin and transforming growth factor-beta2 sequestration in a subpopulation of human ovarian follicle cells.

This study describes the occurrence of a highly specialized subpopulation of granulosa and cumulus oophorus cells that accumulate and sequester specific growth factors by a novel mechanism. These cells are characterized by multiple balloon-like processes tethered to the cell by means of a slender stalk of plasma membrane. Time-lapse analyses demonstrate that these tethered structures (TS) form in minutes and frequently detach from the cell with the bulbous portion remaining motile on the cell surface. Serial section reconstruction of transmission electron microscopic images shows a specific and stable intracellular organization in which an apparent secretory compartment composed of densely packed vacuoles, vesicles, and cisternae is separated by a thick filamentous network from a nuclear compartment containing mitochondria, polyribosomes, lipid inclusions, and rough-surfaced endoplasmic reticulum. Immunofluorescent analysis performed during the formation of these structures showed a progressive accumulation of vascular endothelial growth factor, leptin, and transforming growth factor-beta2 in the bulbous region. TS were identified in newly aspirated masses of granulosa and cumulus oophorus, and their production persists for months in culture. Observations of TS-forming cells made over several days of culture indicates that their production is episodic and factor release from these cells may be pulsatile. The findings suggest that a novel method of growth factor storage and release by an apparent apocrine-like mechanism occurs in the human ovarian follicle. The results are discussed with respect to possible roles in pre- and post-ovulatory follicular development.

Actin Cytoskeleton↗
PubMed1997

High-performance liquid chromatography-tandem mass spectrometry as a reference for analysis of tacrolimus to assess two immunoassays in patients with liver and renal transplants.

The accuracy and imprecision of three assays used for therapeutic monitoring of tacrolimus were tested using blood-containing weighed-in amounts of the drug, an enzyme-linked immunosorbent assay (ELISA), a microparticle enzyme immunoassay (MEIA I), and a high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS2) assay. Accuracy was acceptable for the HPLC-MS2 assay at all concentrations tested (< 10% deviation) and for the ELISA at 1.0 and 4.0 microg/l. Accuracy was not acceptable for the ELISA at 15.0 and 50.0 microg/l or for the MEIA I at all concentrations tested. Imprecision was acceptable for the HPLC-MS2 assay at all concentrations tested (coefficient of variation < 10%), for the ELISA at 15.0 and 50.0 microg/l, and for the MEIA I at 15.0 and 50.0 microg/l. Imprecision was not acceptable for the ELISA at 1.0 and 4.0 microg/l or for the MEIA I at 1.0 and 4.0 microg/l. This assessment with weighed-in amounts of tacrolimus verified the HPLC-MS2 assay as a reference method. The performance of the two immunoassays with HPLC-MS2 was then compared in the clinical setting using blood from patients with liver (n = 30) and renal (n = 37) transplants. In the liver transplant group (127 samples), the range of tacrolimus concentrations measured by HPLC-MS2, ELISA, and MEIA I was 1.9 to 31.8, 2.1 to 35.0, and less than 0.1 to 36.5 mg/l, respectively. In the renal transplant group (129 samples), the ranges were 1.7 to 26.1, 1.9 to 24.4, and 0.9 to 28.5 microg/l, respectively. Compared with the HPLC-MS2, the ELISA had minimal bias (0.1 to 0.2 microg/l) but unacceptable variability in values (SD > 13%). The MEIA I had unacceptable bias (1.7-1.8 microg/l) and variability (SD > 23%). These data indicated that neither the ELISA nor MEIA I is interchangeable with HPLC-MS2. Moreover, in view of the current trend to reduce the therapeutic dose of tacrolimus, quantitative results using the MEIA I would not be obtainable during therapeutic drug monitoring in some patients in whom effective therapeutic concentrations can be less than 5.0 microg/l.

Chromatography, High Pressure Liquid↗
PubMed1997

Surgical treatment of acute manifestations of Crohn's disease during pregnancy.

When requiring surgery, acute exacerbations of Crohn's disease in pregnancy have been reported to carry high maternal and fetal mortality. We report six cases. The women presented at 30, 28, 12, 11, 31 and 25 weeks' gestation and all proved to have intraperitoneal sepsis. In three, the acute symptoms were the first indication of Crohn's disease. All the women recovered and five had healthy babies; the other had a miscarriage when a colonic anastomosis dehisced. In pregnant women with Crohn's disease, the indications for surgery are the same as in non-pregnant patients. For acute manifestations we recommend removal of the source of the sepsis and exteriorization of the bowel ends.

Acute Disease↗
PubMed1997

Community participation in determining the needs of users and carers of rural community care services. Highland Community Care Forum.

In this paper we present the methods and key outcomes of a community led needs assessment exercise. The needs assessment sought to enhance the development of rural community care services by ensuring the views of users and carers were secured and considered in joint planning processes. The research was developed by members of the North and West Sutherland Community Care Forum. A community profiling template was developed and employed in five parish areas of Sutherland. This was drawn from 45 interviews with key informants and 2 community workshops, In addition 54 users and carers were interviewed. The outcomes of the needs assessment exercise identified geographical and cultural factors which present difficulties in developing services as well as posing barriers to user involvement.

Community Health Services↗
PubMed1997

Counsellors in primary care in Southampton: a questionnaire survey of their qualifications, working arrangements, and casemix.

BACKGROUND: There has been an upsurge of interest in counselling in primary care over the past five years. This has been stimulated by a growing demand for non-drug treatment of emotional disorders and by the extension of reimbursement for the costs of counsellors. Continued calls for careful evaluation have been largely unheeded in the face of heady growth. AIM: To establish the prevalence of counselling services in the 67 general practices in the Southampton and South West Hampshire Health District, and to describe in detail their qualifications, working arrangements, and casemix. METHOD: A questionnaire enquiring about counselling services was sent to all the general practices in the district. A second questionnaire was then posted to all the counsellors identified as working in these practices. RESULTS: Twenty-six (39%) practices employed one or more counsellors. Fundholding practices were four times more likely than non-fundholders to employ a counsellor. Most of the counselling work was short term (4-20 sessions). The most common presenting complaints were relationship problems, depression, anxiety, and bereavement. CONCLUSION: This descriptive study highlights the wide variation in the qualifications and training of counsellors. Until the issue of effectiveness is resolved through further research, the best safeguard of quality is to ensure that counsellors meet the appropriate training standards laid down by the British Association of Counsellors. Monitoring standards is a legitimate task for those commissioning health care who are increasingly responsible for reimbursement of a counsellor's salary. Counsellors who meet appropriate training criteria should be encouraged to pursue accreditation with the British Association of Counsellors. Those who do not meet these criteria should be encouraged to undergo additional training.

Counseling↗
PubMed1996

Leg blood flow, metabolism and exercise capacity in chronic stable heart failure.

OBJECTIVES: To assess the metabolic state of skeletal muscle during exercise in patients with chronic heart failure (CHF) and relate this to exercise capacity. BACKGROUND: During exercise in CHF, there is little relation between exercise capacity and central haemodynamic function. Skeletal muscle and limb blood flow are abnormal in CHF. We investigated the relationship between leg blood flow, metabolism and exercise capacity and ventilation in 10 patients (average age 63.3 +/- 6.0 years; 3 female) with stable CHF. METHODS: Patients undertook maximal exercise testing. Peak oxygen consumption (VO2) and the slope of the relationship between ventilation and carbon dioxide production (VE/CO2 slope) were derived. During a supine cycle exercise test, cardiac output (CO) by Doppler echocardiography, femoral blood flow (FBF) by thermodilution, pulse and blood pressure were recorded, and radial arterial and femoral venous blood samples taken for catecholamine, lactate and potassium estimation every 3 min. RESULTS: The average peak VO2 was 19.7 (+/- 5.2; range 11.3-29.0) ml/kg/min. The proportion of CO to the right leg increased from 0.08 (+/- 0.03) to 0.22 (+/- 0.06) (P < 0.001) at 3 min, with no further significant change thereafter. There was a liner increase in leg VO2 reaching a plateau towards peak. At peak, femoral venous saturation was 22.79% +/- 7.20%. Venous lactate and potassium were higher than arterial (P < 0.001 for each comparison). There was no correlation between exercise performance and any of the measured metabolites either in absolute measurements, expressed as change from rest to peak exercise or as arterio-venous difference. The closest correlate of leg VO2 was leg hydrogen ion production, V[H+]. Change in femoral venous lactate from rest to peak exercise correlated with VE/VCO2 slope even when calculated from before the anaerobic threshold (r = -0.80; P = 0.025). CONCLUSIONS: In CHF, exercise capacity is not determined by individual haemodynamic events, and does not seem to be determined by the possible humoral signals we investigated. Ventilation is abnormal before anaerobic threshold, and predicts subsequent lactate rise, suggesting that skeletal muscle is the origin of excessive ventilation.

Aged↗
PubMed1996

Processing of pro-islet amyloid polypeptide (proIAPP) by the prohormone convertase PC2.

Islet amyloid polypeptide (IAPP), 'amylin', is the component peptide of islet amyloid formed in Type 2 diabetes. IAPP is expressed in islet beta-cells and is derived from a larger precursor, proIAPP, by proteolysis. An in vitro translation/translocation system was used to separately examine processing of human proIAPP by the beta-cell endopeptidases PC2, PC3 or furin. ProIAPP was converted to mature IAPP by PC2 but there was little conversion by furin or PC3. These data are consistent with processing of proIAPP in beta-cell secretory granules. Abnormal cellular proteolysis associated with type 2 diabetes could contribute to IAPP amyloidosis.

Amino Acid Sequence↗
PubMed1996

Apolipoprotein E is associated with islet amyloid and other amyloidoses: implications for Alzheimer's disease.

Apolipoprotein E (ApoE) has recently been proposed as an aetiological factor of Alzheimer's disease (AD): ApoE is co-localized to amyloid plaques and neurofibrillary tangles in the brain and binds to A beta-protein in vitro. An association of ApoE epsilon 4 allele with the development of AD has been reported. Islet amyloid is formed from islet amyloid polypeptide (IAPP) in pancreatic islets of 90 per cent of patients with non-insulin-dependent diabetes mellitus (NIDDM) which, like AD, is an age-dependent pathology. The relationship of ApoE to islet amyloid and other amyloidoses is largely unknown. In this study, ApoE was localized by immunocytochemistry on pancreatic specimens from non-diabetic man, monkey, and mouse, and on amyloid-containing human tissues from pancreas, heart, brain, and intestine. All types of amyloid deposits, irrespective of the constituent peptide, site of deposition, or species, showed immunoreactivity for ApoE (ApoE-IR). Quantitative morphometry showed that similar proportions of islet amyloid were labelled for IAPP and ApoE in monkey islets. ApoE-IR was observed in pancreatic islet cells of non-diabetics. These results suggest that the association of ApoE with amyloid is non-specific for AD or to the component peptide of amyloid fibrils. If ApoE promotes amyloid formation, its synthesis in pancreatic islets could be important for the initiation or the development of pancreatic amyloid in NIDDM.

Alzheimer Disease↗
PubMed1996

Evaluation of dexfenfluramine in a weight loss program for obese infertile women.

OBJECTIVE: To evaluate the usefulness of dexfenfluramine as an adjunct to a group treatment program for obese infertile women. METHOD: Twenty-one obese infertile women were referred by the Reproductive Medicine Unit. They attended a 24-week group program which included exercise and educational sessions. Dexfenfluramine and placebo were given, each for 12 weeks, in a double-blind crossover design. RESULTS: Dexfenfluramine treatment was not associated with greater loss of weight. The mean weight loss during dexfenfluramine treatment was 3.21 kg (SD 3.09) and during placebo was 3.31 kg (SD 3.15). Self-esteem, anxiety, and depression ratings all improved significantly over the 24 weeks. DISCUSSION: The group treatment program appeared to be equally effective with or without dexfenfluramine. Previous studies have found dexfenfluramine to be effective in combination with individual treatment, but it has not previously been evaluated as an adjunct to group treatment. It is unclear whether dexfenfluramine may be less effective in combination with group treatment programs, or whether its usefulness is restricted in this particular population of obese patients. No differences were found associated with the order in which active and placebo treatments were given. Patients showed improvement in self-esteem and reduction in depression and anxiety, but dexfenfluramine treatment was not associated with any difference in these measures, compared to placebo.

Adult↗
PubMed1996

Heterogeneity of the glutathione transferase genes encoding enzymes responsible for insecticide degradation in the housefly.

One of the four glutathione-S-transferases (GST) that is overproduced in the insecticide-resistant Cornell-R strain of the housefly (Musca domestica) produces an activity that degrades the insecticide dimethyl parathion and conjugates glutathione to lindane. In earlier work, it was shown that the resistant Cornell-R carries an amplification, probably a duplication, of one or more of its GST loci and that this amplification is directly related to resistance. Using polymerase chain reaction (PCR) amplification with genomic DNA, multiple copies of the gene encoding the parathion-degrading activity (called MdGst-3) were subcloned from both the ancestral, insecticide-susceptible strain BPM and from the insecticide-resistant Cornell-R. In BPM, three different MdGst-3 genes were identified while in Cornell-R, 12 different MdGst-3 sequences were found that, though closely related to ancestral genes, had diverged by a few nucleotides. This diversity in MdGst-3 genomic sequences in Cornell-R is reflected in the expressed sequences, as sampled through a cDNA bank. Population heterozygosity cannot account for these multiple GST genes. We suggest that selection for resistance to insecticides has resulted in not only amplification of the MdGst-3 genes but also in the divergence of sequence between the amplified copies.

Animals↗
PubMed1996

Improved pregnancy rates for obese, infertile women following a group treatment program. An open pilot study.

Thirty-seven women with a mean initial weight of 98.5 +/- 18.7 kg completed a group treatment program for obese, infertile women. The program lasted for 24 weeks and included regular exercise and group discussion of topics such as coping with the psychological impact of infertility, developing healthy eating patterns, and the effects of obesity on reproductive physiology. There was significant weight loss (mean weight loss 6.2 +/- 4.5 kg, p < 0.001) and improvement on measures of self-esteem, anxiety, depression, and general health. Twenty-nine women became pregnant during the follow-up period (21-36 months). Two women were avoiding pregnancy, so only six who had completed the group program and wished to become pregnant had not conceived by the end of the follow-up period. A further five women did not complete the program as they became pregnant while attending the group. Our results suggest that active measures to improve mood and self-esteem, along with better nutrition and weight reduction through diet and exercise, can produce considerable improvement in the outcome of treatment for infertility in obese women.

Adaptation, Psychological↗
PubMed1996

Islet amyloid polypeptide: actions and role in the pathogenesis of diabetes.

IAPP has been postulated to have a role as a modulating factor in glucose homoeostasis and to be involved in the pathophysiology of diabetes. However, the normal physiological functions of the peptide remain obscure: exogenous IAPP acts on many experimental systems to modulate nutrient supply and metabolism but there is no evidence to suggest that circulating IAPP has an aetiological role in the onset of Type-2 diabetes. Amyloid deposits formed from polymerized IAPP progressively accumulate in the islets of Type-2 diabetic patients. These insoluble deposits do not precipitate the onset of hyperglycaemia in Type-2 diabetes, but progressive accumulation of amyloid is associated with islet cell destruction and decreased islet function in the later stages of the disease. Although the causative factors of formation of the first IAPP fibril are unknown, continued high levels of insulin and IAPP secretion as a result of nutrient stimulation or insulin resistance will promote binding to preformed fibrils and extension of the deposits. It is important that methods to identify patients susceptible to amyloid deposition are developed and therapeutic agents are produced that can reduce or prevent polymerizatin of IAPP to form amyloid and minimize severe deterioration of islet function in Type-2 diabetes.

Amino Acid Sequence↗
PubMed1996

Islet amyloid in type 2 (non-insulin-dependent) diabetes.

Amyloid deposits are found in pancreatic islets of 90% of type 2 (non-insulin-dependent) diabetic subjects at postmortem. Islet amyloid is formed from islet amyloid polypeptide (IAPP). IAPP is a 37 amino acid peptide which is a normal constituent of beta cells and is co-secreted with insulin in animals and in man. The causative factors for fibrillogenesis of IAPP are unclear, but could be related to the sequence of IAPP and abnormal production of the peptide. The lack of islet amyloid in rodent models of diabetes is due to proline substitutions in the amyloidogenic region of IAPP. Amyloid fibrils are deposited between beta cells and islet capillaries: fibrils in invaginations of the plasma membrane may interfere with membrane signalling and insulin release. Amyloid fibrils are formed within 2 days in culture in islets isolated from transgenic mice expressing the gene for human IAPP, but not in vivo. Overexpression and decreased clearance of human IAPP from islet spaces may be important factors. Progressive deposition of IAPP fibrils combined with the associated reduction in the insulin-secreting beta cells is likely to contribute to deterioration of islet function in the course of type 2 diabetes.

Amino Acid Sequence↗
PubMed1996

The Symptom Questionnaire: British standardization data.

The Symptom Questionnaire is a simple and quick measure of emotional state; previous work has indicated that the Questionnaire has good reliability and validity. However the original sample on which it was based was small, and exclusively North American. Data from a large sample (N = 707) of British psychiatric in-patients, out-patients, day hospital attenders, and a non-patient population sample are presented. Consistent differences between the patient and non-patient samples were obtained on the scales, with a few exceptions; there were no significant differences due to sex.

Affect↗
PubMed1996

A group program for obese, infertile women: weight loss and improved psychological health.

We report on a group program for obese infertile women. Sixty-four women completed the 24-week program, which included exercise, information about healthy eating and group discussion sessions. Their mean initial weight was 101.9 +/- 18.14 kg. The mean weight loss on completion of the program was 5.2 +/- 5.11 kg (p < 0.0001). There was significant improvement on ratings of self-esteem and depression. Changes to life-style and health which are known to improve fertility may be a useful precursor to invasive, high technology infertility treatment procedures.

Anxiety↗