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Biomedical subjects

J Pitts

Publications and source records attributed to J Pitts.

At least 19 recordsLinked to original sources
PubMed2001

Gap junctional communication and connexin expression in cultured olfactory ensheathing cells.

The olfactory ensheathing cell (OEC) is a unique glial cell able to support neurite outgrowth in the CNS throughout life. The OEC has been described as having both Schwann cell-like and astrocyte-like characteristics. The purpose of this study was to compare gap junctional communication and connexin (Cx) expression in cultured olfactory ensheathing cells with both astrocytes and Schwann cells to establish which of these two cells types they most closely resemble. We examined the Cx mRNA profile of OECs, astrocytes, and Schwann cells using primers to Cx26, Cx32, Cx37, Cx43, Cx46, and Cx50. All connexins tested except Cx50 were expressed by all three cell types when initially cultured. However, we observed differences in the levels of expression of Cx32 and Cx26 between astrocytes, Schwann cells, and OECs that became pronounced with time. All three cell types show limited and variable gap junctional communication in culture as assessed by the transfer of microinjected Lucifer yellow. OECs had limited coupling compared with Schwann cells and astrocytes, although the extent of the dye spread through OECs was more comparable to that seen with Schwann cells than astrocytes. Thus, OECs display a profile of Cx expression that more closely resembles the Cx expression of Schwann cells rather than astrocytes.

Animals↗
PubMed2001

Structure-function studies of an IGF-I analogue that can be chemically cleaved to a two-chain mini-IGF-I.

The structure and biological activities of two disulphide isomers of a C-region deletion mutant of insulin-like growth factor-I (IGF-I) which has an Asn--Gly link engineered at the junction of the A- and B-regions were studied before and after chemical cleavage. Circular dichroism (CD) spectra and binding affinity to IGF binding protein 3 (IGFBP3) indicated that the treatment with hydroxylamine did not disrupt the overall tertiary fold of the hormones. Cleavage restored some binding affinity for the IGF-I receptor in both isomers and weakly restored the ability to stimulate incorporation of tritiated thymidine into DNA in NIH 3T3 fibroblasts transfected with the human IGF-I receptor. Cleavage also restored metabolic capacity, as measured by the ability of the isomers to promote lipogenesis in isolated rat adipocytes through the insulin receptor. These results are consistent with the theory that binding of IGF-I to the IGF-I receptor requires a conformational change similar to that involved in insulin binding the insulin receptor. The weak affinity for the IGF-I receptor after cleavage is consistent with the belief that residues in the C-region interact with the IGF-I receptor. This structural difference between insulin and IGF-I gives each a higher binding affinity for its own receptor.

3T3 Cells↗
PubMed2001

Autogenous hard palate mucosa: the ideal lower eyelid spacer?

BACKGROUND/AIMS: Raising a displaced lower eyelid frequently involves recession of the lower eyelid retractors with interposition of a "spacer," and several materials for this purpose have been described. This study reviewed the results of autogenous palatal mucosa in the treatment of lower eyelid displacement, including assessment of any donor site morbidity. METHODS: A retrospective case note review of consecutive patients treated at Moorfields Eye Hospital between 1993 and 1998. All patients underwent insertion of hard palate mucosa between the inferior border of the tarsus and the recessed conjunctiva and lower eyelid retractors. Parameters studied included the underlying diagnosis, measurements of lower lid displacement or retraction, related previous surgery, the experience of the operating surgeon, intraoperative and postoperative complications, surgical outcome, and length of follow up. The main outcome measure was the position of the lower eyelid relative to the globe in primary position of gaze. RESULTS: 102 lower eyelids of 68 patients were included and a satisfactory lid position was achieved in 87/102 (85%), with inadequate lengthening or significant recurrence of displacement occurring in 15 cases. Donor site haemorrhage requiring treatment in the early postoperative period occurred in seven patients (10%). CONCLUSION: Autogenous hard palate mucosa is an effective eyelid spacer and provides good long term support for the lower eyelid. Donor site complications are the main disadvantage, but may be minimised by attention to meticulous surgical technique and appropriate postoperative management.

Adult↗
PubMed2001

Novel expression and function of peroxisome proliferator-activated receptor gamma (PPARgamma) in human neuroblastoma cells.

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors that has been shown to play a major role in adipocyte and monocyte/macrophage differentiation. Recent work has also suggested a role for PPARgamma in cell cycle control and/or differentiation of other cell types including breast and lung cancer cells. Using reverse transcription-PCR, we now show for the first time that human neuroblastoma (nb) cells express PPARbeta and -gamma, but not -alpha. Using the LA-N-5 nb cell line, we have determined that the natural PPARgamma ligand 15-deoxy-delta prostaglandin J2, as well as the synthetic PPARgamma agonist GW1929, can stimulate the differentiation of nb cells, as evidenced by the inhibition of cell proliferation, neurite outgrowth, increased acetylcholinesterase activity, and the reduction of N-myc expression. We have also demonstrated that PPARgamma is expressed in primary nb and, furthermore, that the expression of this receptor correlates with the maturational stage of the nb cells. Taken together, these studies have implicated a role for PPARgamma in peripheral nerve cell biology and suggest that the PPARgamma signaling pathway is involved in the regulation of nb cell growth and differentiation.

Acetylcholinesterase↗
PubMed2000

PPARgamma: observations in the hematopoietic system.

Human Peroxisome Proliferator-Activated Receptor gamma (PPARgamma) was originally cloned from a human bone marrow library. What role does this ligand activated transcription factor play in hematopoiesis and the immune system? We note that: a) PPARgamma has potential to interact/interfere or synergize with retinoid biology, b) fatty acids and a prostaglandin have been identified as ligands, and c) lymphocytes, monocytes and neutrophils use fatty acids as a major source of energy production, d) PPARgamma has been shown to oppose TNFalpha and down regulate cytokine production in monocytes. Therefore, we undertook a review of the literature and an expression survey of PPARgamma in a number of major organs and cells involved in the hematopoietic system, for the purpose of building a database towards understanding the role and function of PPARgamma gene regulation in the developing blood and immune systems. PPARgamma is expressed before mesodermal induction in tissue in and around Speymann's organizer in the xenopus blastocyst, in erythroid precursors of blood islands and in the circulation of the day 10.0 murine embryo, in human 19 week fetal liver, in some but not all murine and human bone marrow erythroid, myeloid, and monocytoid progenitors, bone marrow stromal cells and adipocytes, osteoblasts, endothelial cells, some T, and B lymphocytes, monocytes, macrophages, and other monocytic derivatives. It can be found in the cells of Peyer's patches, lymphoid follicles, spleen, and thymus. It is not clear if it is ever or transiently expressed in megakaryocytes, mast cells, or neutrophils. Based on the above data and a review of the literature, PPARgamma seems to play a role during the elicitation of immune responses. We propose PPARgamma may be involved in changes in energy states required during activation and development of many cell types involved, and has additional immunologically relevant effects in erythroid, myeloid, monocytic, T and B lymphocytic, stromal, and endothelial cell function.

Amino Acid Sequence↗
PubMed2000

Associations between primary care physician satisfaction and self-reported aspects of utilization management.

OBJECTIVE: To evaluate the association between physician-reported utilization management (UM) techniques in capitated physician groups and physician satisfaction with capitated care. STUDY SETTING: 1,138 primary care physicians from 89 California capitated physician groups in 1995. STUDY DESIGN: Eighty percent of physicians (N = 910) responded to a mail survey regarding the UM policies in their groups and their satisfaction with the care they deliver. Physician-reported UM strategies measured included group-mandated preauthorization (number of referrals requiring preauthorization, referral denial rate, and referral turnaround time), group-provided explicit practice guidelines, and group-delivered educational programs regarding capitated care. We also measured two key dimensions of satisfaction with capitated care (multi-item scales): (1) satisfaction with capitated care autonomy and quality, and (2) satisfaction with administrative burden for capitated patients. EXTRACTION METHODS: We constructed two multivariate linear regression models to examine associations between physician-reported UM strategies and physician satisfaction, controlling for demographic and practice characteristics and adjusting for clustering. PRINCIPAL FINDINGS: Physician-reported denial rate and turnaround time were significantly negatively associated with capitated care satisfaction. Physicians who reported that their groups provided more guidelines were more satisfied on both dimensions, while physicians who reported that their groups sponsored more educational programs were more satisfied with administrative burden. The number of clinical decisions requiring preauthorization was not significantly associated with either dimension of satisfaction. CONCLUSIONS: Physicians who reported that their groups used UM methods that directly affected their autonomy (high denial rates and long turnaround times) were less satisfied with care for capitated patients. However, a preauthorization policy for referrals or tests was not, in and of itself, associated with satisfaction. Indirect control mechanisms such as guidelines and education were positively associated with satisfaction.

Adult↗
PubMed1999

Educational portfolios in the assessment of general practice trainers: reliability of assessors.

OBJECTIVES: This paper reports a project that assessed a series of portfolios assembled by a cohort of participants attending a course for prospective general practice trainers. DESIGN: The reliability of judgements about individual 'components', together with an overall global judgement about performance were studied. SETTING: NHSE South & West, King Alfred's College, Winchester and Institute of Community Studies, Bournemouth University. SUBJECTS: Eight experienced general practice trainers recruited from around Wessex, which incorporates Hampshire, Dorset, Wiltshire and the Isle of Wight. RESULTS: The reliability of individual assessor's judgements (i.e. their consistency) was moderate, but inter-rater reliability did not reach a level which could support making a safe summative judgement. The levels of reliability reached were similar to other subjective assessments and perhaps reflected individuality of personal agendas of both the assessed and the assessors, and variations in portfolio structure and content. CONCLUSIONS: Suggestions for approaches in future are made.

Education, Medical, Continuing↗
PubMed1999

Modelling of the disulphide-swapped isomer of human insulin-like growth factor-1: implications for receptor binding.

Insulin-like growth factor-1 (IGF-1) is a serum protein which unexpectedly folds to yield two stable tertiary structures with different disulphide connectivities; native IGF-1 [18-61,6-48,47-52] and IGF-1 swap [18-61,6-47, 48-52]. Here we demonstrate in detail the biological properties of recombinant human native IGF-1 and IGF-1 swap secreted from Saccharomyces cerevisiae. IGF-1 swap had a approximately 30 fold loss in affinity for the IGF-1 receptor overexpressed on BHK cells compared with native IGF-1. The parallel increase in dose required to induce negative cooperativity together with the parallel loss in mitogenicity in NIH 3T3 cells implies that disruption of the IGF-1 receptor binding interaction rather than restriction of a post-binding conformational change is responsible for the reduction in biological activity of IGF-1 swap. Interestingly, the affinity of IGF-1 swap for the insulin receptor was approximately 200 fold lower than that of native IGF-1 indicating that the binding surface complementary to the insulin receptor (or the ability to attain it) is disturbed to a greater extent than that to the IGF-1 receptor. A 1.0 ns high-temperature molecular dynamics study of the local energy landscape of IGF-1 swap resulted in uncoiling of the first A-region alpha-helix and a rearrangement in the relative orientation of the A- and B-regions. The model of IGF-1 swap is structurally homologous to the NMR structure of insulin swap and CD spectra consistent with the model are presented. However, in the model of IGF-1 swap the C-region has filled the space where the first A-region alpha-helix has uncoiled and this may be hindering interaction of Val44 with the second insulin receptor binding pocket.

3T3 Cells↗
PubMed1999

Comparison of dacryocystography and lacrimal scintigraphy in the diagnosis of functional nasolacrimal duct obstruction.

AIM: It appears from the literature that no standardised examination exists for patients with functional nasolacrimal duct obstruction. The role of dacryocystography and lacrimal scintigraphy was compared in the diagnosis and management of these patients. METHOD: Patients who were clinically diagnosed as having unilateral or bilateral functional nasolacrimal duct obstruction were prospectively entered into the study and data collected over 12 months in Moorfields Eye Hospital and Whipps Cross Hospital, London. All cases had, on separate occasions, a standardised dacryocystogram with delayed erect films and a lacrimal drainage scintigram. RESULTS: 45 lacrimal systems of 32 patients (mean age 62 years; 59% male) fulfilled the inclusion criteria. Abnormalities were detected with dacryocystography in 93% of systems and with lacrimal drainage scintigraphy in 95% of systems. Based on the results of previous quantitative studies, the positive scintigrams were subdivided into those demonstrating prelacrimal sac delay (13%), delay at the lacrimal sac/duct junction (35%), or delay within the duct (47%). Combining the two imaging techniques increased the sensitivity to 98%. CONCLUSIONS: Both investigations are very sensitive at detecting abnormalities in patients with a clinical diagnosis of functional nasolacrimal duct obstruction. Lacrimal drainage scintigraphy is a slightly more sensitive test, but missed an abnormality detected by dacryocystography in two (4%) systems. A combination of the two techniques gives the highest sensitivity with maximum anatomical and physiological information but, in clinical practice, it is reasonable to perform a dacryocystogram initially and proceed to scintigraphy only if contrast radiography is normal.

Adult↗
PubMed1999

'Practice professional development plans': general practitioners' perspectives on proposed changes in general practice education.

BACKGROUND: The Chief Medical Officer has presented a report proposing a change in general practitioners' education towards a 'Practice Professional Development Plan', which, in principle, is based around formal needs assessment, practice-based learning in areas identified by those involved, and with the potential for multi-professional learning. This aims to replace the present system of a financial allowance earned by attending a certain amount of educational activity. AIM: To study the opinions of a group of general practitioners attending a course that included workshops that introduced and considered this educational initiative. METHOD: Semi-structured interviews four weeks after the course. RESULTS: Educational benefits were clearly seen, while issues such as funding and time will present difficulties in implementation. CONCLUSIONS: This proposal was seen as an improvement to the existing postgraduate educational allowance system. To maintain enthusiasm, successful introduction will depend on the issues of support and resources.

Adult↗
PubMed1998

Psychometric properties of the National Eye Institute Visual Function Questionnaire (NEI-VFQ). NEI-VFQ Field Test Investigators.

OBJECTIVE: To test the reliability and validity of the 51-item Field Test Version of the National Eye Institute Visual Function Questionnaire (NEI-VFQ) across 5 common chronic eye conditions. DESIGN: Prospective observational cohort study of persons with 1 of 5 chronic eye diseases who were scheduled for nonurgent visits in ophthalmology practices or had low vision from any cause, and a reference sample of persons without eye disease. SETTING: Six university-based ophthalmology practices and the National Eye Institute Clinical Center, Bethesda, Md. PATIENTS: Eligible participants had to have 1 of the following eye conditions: age-related cataracts, age-related macular degeneration, diabetic retinopathy, primary open-angle glaucoma, cytomegalovirus retinitis, or low vision from any cause. Each of the 7 sites also enrolled persons in a reference sample. Reference sample participants had no evidence of underlying eye disease but were scheduled for either screening eye examinations or correction of refractive error. All eligible persons had to be aged 21 years or older, English speaking, and cognitively able to give informed consent and participate in a health status interview. MEASUREMENTS AND MAIN RESULTS: To provide the data needed to assess the reliability and validity of the 51-item NEI-VFQ, all subjects completed an interview that consisted of the 51-item NEI-VFQ, the Medical Outcomes Study 36-Item Short-Form Health Survey, and at least 1 measure of vision-targeted functional status. Estimates of internal consistency and test-retest reproducibility indicate that the 51-item NEI-VFQ is reliable. Tests of association with other scales and clinical variables support the construct validity of the survey. CONCLUSIONS: In this cross-sectional study, the 51-item NEI-VFQ seems to be reliable and valid and should be a useful tool for group-level comparisons of vision-targeted, health-related quality of life in clinical research. Additionally, the psychometric properties of the NEI-VFQ were not influenced by the type or severity of the underlying eye disease, suggesting that the measure will provide reproducible and valid data when used across multiple eye conditions.

Activities of Daily Living↗
PubMed1998

Experiences and career intentions of general practice registrars from The Netherlands.

For some years prospective general practitioners (GPs) from the Netherlands have come to Britain to complete their training. Not all report enjoying their time here, and many leave this country after training. The aim of this study was to examine reasons for coming to Britain, experiences, perceptions and career intentions. The sample consisted of 14 general practice registrars working in their practice year in Southern England. Data were collected through in-depth semistructured interviews and analysed by thematic qualitative analysis. The main reasons for training in this country were easier access, a quicker route to specialization and the quality of training provided. Most had positive professional and personal experiences and saw the British system of training GPs as up to date and supportive of their educational and professional needs. They highlighted some of the positive aspects of the British system, such as the emphasis on teamwork and collaboration with other primary care professionals. They did, however, point out problems and conflicts; for instance, they saw the health care system in Britain as more bureaucratic and as providing unequal access for different groups of the population. Despite their fear of litigation, which they saw as one of the drawbacks for British general practitioners, most looked favourably on the option of staying in or returning to this country if possible. All registrars valued their stay in Britain; however, personal circumstances often dictated a return to Holland. Our findings have implications for manpower planning and recruitment for general practice in both Britain and Holland.

Attitude of Health Personnel↗
PubMed1996

Solution structure of a mini IGF-1.

Mini insulin-like growth factor 1, an inactive insulin-like growth factor 1 mutant lacking the C region, was studied by 2D NMR spectroscopy. Resonances were assigned for almost all protons of the 57 amino acid residues. The 3D structure of the protein was determined by distance geometry methods. Three helical segments; Ala 8-Cys 18, Gly 42-Phe 49, and Leu 54-Cys 61, were identified, corresponding to those present in wild-type insulin-like growth factor 1 and in single-chain insulin. Their relative orientation, however, was found to be changed. This change is connected with a displacement of the Phe 23-Tyr 24-Phe 25-Asn 26 beta-strand-like segment, i.e., of aromatic side chains known to be important for receptor binding. Thus, deletion of the C region of IGF-1 results in a substantial tertiary structural rearrangement that accounts for the loss of receptor affinity.

Amino Acid Sequence↗
PubMed1996

Engineering the C-region of human insulin-like growth factor-1: implications for receptor binding.

Recombinant wild-type human IGF-1 and a C-region mutant in which residues 28-37 have been replaced by a 4-glycine bridge (4-Gly IGF-1) were secreted and purified from yeast. An IGF-1 analogue in which residues 29-41 of the C-region have been deleted (mini IGF-1) was created by site-directed mutagenesis and also expressed. All three proteins adopted the insulin-fold as determined by circular dichroism. The significantly raised expression levels of mini IGF-1 allowed the recording of two-dimensional NMR spectra. The affinity of 4-Gly IGF-1 for the IGF-1 receptor was approximately 100-fold lower than that of wild-type IGF-1 and the affinity for the insulin receptor was approximately 10-fold lower. Mini IGF-1 showed no affinity for either receptor. Not only does the C-region of IGF-1 contribute directly to the free energy of binding to the IGF-1 receptor, but also the absence of flexibility in this region eliminates binding altogether. As postulated for the binding of insulin to its own receptor, it is proposed that binding of IGF-1 to the IGF-1 receptor also involves a conformational change in which the C-terminal B-region residues detach from the body of the molecule to expose the underlying A-region residues.

Amino Acid Sequence↗