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Biomedical subjects

T Evans

Publications and source records attributed to T Evans.

At least 55 records · Page 3Linked to original sources
PubMed2000

Endothelins, their receptors, and retinal vascular dysfunction in galactose-fed rats.

PURPOSE: Endothelins are potent vasoactive factors that have been implicated in the pathogenesis of several vascular disorders. This study was conducted to determine the role that endothelins play in the development of retinal microangiopathy under hyperhexosemic conditions induced by galactose feeding. METHODS: Retinal blood flow was determined using Doppler sonography in galactose fed rats with or without an endothelin receptor antagonist (Bosentan) treatment and were compared to control rats after 1 and 6 months of follow-up. Levels of endothelin-1, endothelin-3, (ET-1, ET3) and receptors endothelin A, endothelin B, (ET(A), ET(B)) mRNA expression were determined by semiquantitative RT-PCR. Immunohistochemical distribution of ET-1 and ET-3, ligand binding, and autoradiography to determine ET receptor distribution were carried out. RESULTS: Retinal vasoconstriction measured by an increase in resistivity index (RI) was present in 1 month galactose feeding compared to controls, which was prevented by Bosentan treatment. After 6 months of follow up all animal groups exhibited higher RI compared to their 1 month counterpart, although they were not different from each other. Compared to the controls, after 1 month levels of mRNA for ET-1, ET-3, and ET(A) were increased in galactose-fed rats, whereas ET(B) mRNA production remained similar to controls. After 6 months, all four genes exhibited increased levels compared to the controls, and no effect of Bosentan treatment on gene expression was evident. Increased immunoreactivity of ET-1 and ET-3 was determined, as well as increased ET receptor concentration was further present in the retina of galactose-fed animals. CONCLUSION: The data suggests that endothelin production is increased under hyperhexosemic conditions and that the endothelins play an important role in regulating the hemodynamics of retinal blood flow.

Animals↗
PubMed2000

Chronic paronychia, osteomyelitis, and paravertebral abscess in a child with blastomycosis.

Blastomycosis is an unusual fungal infection in children. It is often a chronic infection characterized by granulomatous and suppurative lesions. Clinical manifestations include either pulmonary findings or disseminated disease. Disseminated blastomycosis usually begins with a lung infection that spreads to the skin, bones, and central nervous system. This is a case report of a child with chronic blastomycosis presenting with chronic paronychia, fever, cough, malaise, and back pain. The child underwent surgical drainage of a paravertebral abscess and administration of intravenous amphotericin B. He was discharged in good condition on oral therapy with ketoconazole. The literature on blastomycosis, with particular emphasis on clinical presentations and management, is reviewed. When the history and physical examination suggest a chronic granulomatous or disseminated disease, such as tuberculosis, the physician must include blastomycosis in the differential.

Abscess↗
PubMed2000

Mental health consultation in a nursing home.

As the world's population ages, increasing numbers of people can anticipate spending their latter years in long-term care settings. Many of these nursing home residents will also present psychiatric illnesses as primary or secondary diagnoses. The resulting behavioral problems may present challenges to nursing staff that they are ill-prepared to meet. This article illustrates the application of the Blake and Mouton consultation model to a Veterans Administration (VA) nursing home situation by a team of psychiatric mental health nurse specialists. The consultation is described and interpreted in terms of the Blake and Mouton model. The focal conflicts addressed in the consultation included issues of morale/cohesion, power/authority, and norms/standards. Interventions used were acceptant, prescriptive, confrontation, and theories/principles. The model provided a useful structure for conceptualizing and organizing assessment and intervention in the consultation situation.

Absenteeism↗
PubMed2000

Endothelin receptor blockade prevents augmented extracellular matrix component mRNA expression and capillary basement membrane thickening in the retina of diabetic and galactose-fed rats.

Endothelins (ETs) are a family of vasoactive peptides that have mitogenic properties and have also been associated with altered long-term nuclear signaling. We have previously shown that mRNA levels for ET-1, ET-3, and their receptors are upregulated under hyperhexosemic conditions. In this study, an endothelin antagonist was used to assess the effects of endothelin blockage on the production of two basement membrane transcripts, fibronectin and collagen alpha1 (IV). The microvascular basement membranes were analyzed using ultrastructural morphometry. Streptozotocin-induced diabetic rats, galactose-fed rats (30% galactose in diet), and nondiabetic, non-galactose-fed control rats were studied after 1-month and 6-month follow-up. Simultaneously, similar animal groups were treated with a general ET receptor blocker (bosentan, 100 mg x kg(-1) x day(-1)) and investigated. Semiquantitative reverse transcription-polymerase chain reaction for fibronectin and collagen alpha1 (IV) was conducted after 1 month of follow-up with comparison to beta-actin housekeeping gene using slot blot hybridization and densitometry. Basement membrane thickness was assessed after 6 months of follow-up in diabetic rats, using the orthogonal intercept method. After 1 month of follow-up, increased fibronectin and collagen alpha1 (IV) mRNA were present in the retina of diabetic and galactosemic animals, and the bosentan-treated groups exhibited mRNA levels similar to the control animals. After 6 months of follow-up, diabetes and galactose feeding induced basement membrane thickening, which was partially prevented by bosentan treatment. The above findings indicate that increased production of extracellular matrix proteins leading to thickening of microvascular basement membrane, secondary to hyperhexosemia, may be mediated via augmented ET production.

Animals↗
PubMed1999

A role for GATA-4/5/6 in the regulation of Nkx2.5 expression with implications for patterning of the precardiac field.

Interactions between the key regulatory genes of the cardiogenic pathway, including those from the GATA and Nkx2 transcription factor families, are not well defined. Treating neurula-stage Xenopus embryos with retinoic acid (RA) causes a specific block in cardiomyocyte development that correlates with a progressive reduction in the region of the presumptive heart-forming region expressing Nkx2.5. In contrast, RA does not block expression of the GATA-4/5/6 genes, which are transcribed normally in an overlapping pattern with Nkx2.5 throughout cardiogenesis. Instead, GATA-4/5/6 transcription levels are increased, including an expansion of the expression domain corresponding to lateral plate mesoderm that is part of the early heart field, but that normally is progressively restricted in its ability to contribute to the myocardium. GATA-dependent regulatory sequences of the Nkx2.5 gene that implicate GATA-4/5/6 as upstream positive regulators were described recently. However, our experiments also indicate that GATA factors might normally antagonize transcription of Nkx2.5. To test this hypothesis we generated a dominant negative isoform of GATA-4 (SRG4) capable of inhibiting transcription of GATA-dependent target genes. Ectopic expression of SRG4 results in a transient expansion of the Nkx2.5 transcript pattern, indicating that a normal function of GATA factors is to limit the boundary of the Nkx2.5 expression domain to the most anterior ventral region of the heart field. Regulatory mechanisms altered by excess RA must function normally to limit GATA-4/5/6 expression levels, to define the region of Nkx2.5 expression and regulate myocardial differentiation.

Animals↗
PubMed1999

Direct interaction of hematopoietic transcription factors PU.1 and GATA-1: functional antagonism in erythroid cells.

Malignant transformation usually inhibits terminal cell differentiation but the precise mechanisms involved are not understood. PU.1 is a hematopoietic-specific Ets family transcription factor that is required for development of some lymphoid and myeloid lineages. PU.1 can also act as an oncoprotein as activation of its expression in erythroid precursors by proviral insertion or transgenesis causes erythroleukemias in mice. Restoration of terminal differentiation in the mouse erythroleukemia (MEL) cells requires a decline in the level of PU.1, indicating that PU.1 can block erythroid differentiation. Here we investigate the mechanism by which PU.1 interferes with erythroid differentiation. We find that PU.1 interacts directly with GATA-1, a zinc finger transcription factor required for erythroid differentiation. Interaction between PU.1 and GATA-1 requires intact DNA-binding domains in both proteins. PU.1 represses GATA-1-mediated transcriptional activation. Both the DNA binding and transactivation domains of PU.1 are required for repression and both domains are also needed to block terminal differentiation in MEL cells. We also show that ectopic expression of PU.1 in Xenopus embryos is sufficient to block erythropoiesis during normal development. Furthermore, introduction of exogenous GATA-1 in both MEL cells and Xenopus embryos and explants relieves the block to erythroid differentiation imposed by PU.1. Our results indicate that the stoichiometry of directly interacting but opposing transcription factors may be a crucial determinant governing processes of normal differentiation and malignant transformation.

3T3 Cells↗
PubMed1999

Reversal of GATA-6 downregulation promotes smooth muscle differentiation and inhibits intimal hyperplasia in balloon-injured rat carotid artery.

The GATA-6 transcription factor is expressed in quiescent vascular smooth muscle cells (VSMCs) in culture, and levels of its transcript are rapidly downregulated on mitogen stimulation. In this study, we demonstrate that the GATA-6 transcript, protein, and DNA-binding activity are downregulated in rat carotid arteries on balloon injury. Downregulation was detected at 1 and 3 days after injury and recovered by 7 days. To assess the role of GATA-6 downregulation in injury-induced vascular lesion formation, adenoviral vectors were used to express wild-type human GATA-6 cDNA (Ad-GATA6) or an inactive mutant cDNA that lacks a portion of the zinc-finger domain (Ad-GATA6DeltaZF). Adenovirus-mediated GATA-6 gene transfer to the vessel wall after balloon injury partially restored the levels of GATA-6 protein and DNA-binding activity to before injury levels. The local delivery of Ad-GATA6 but not Ad-GATA6DeltaZF inhibited lesion formation by 46% relative to saline control and 50% relative to a control adenovirus that expressed lacZ. Local delivery of Ad-GATA6 also reversed changes in the expression patterns of smooth muscle myosin heavy chain, smooth muscle alpha-actin, calponin, vinculin, metavinculin, and proliferating cell nuclear antigen that are associated with injury-induced VSMC phenotypic modulation. These data indicate that the injury-induced downregulation of GATA-6 is an essential feature of VSMC phenotypic modulation that contributes to vessel lesion formation.

Adenoviridae↗
PubMed1999

Retinoid signaling required for normal heart development regulates GATA-4 in a pathway distinct from cardiomyocyte differentiation.

Vitamin A is essential for normal embryonic cardiogenesis. The vitamin A-deficient phenotype in the avian embryo includes an abnormal heart tube closed at the sinus venosus and the absence of large vessels that normally connect the embryonic heart to the developing circulatory system. In vitamin A-deficient embryos the expression of cardiomyocyte differentiation genes, including atrial-specific myosin heavy chain, ventricular-specific myosin, and sarcomeric myosins as well as the putative cardiomyocyte specification gene Nkx-2.5, is not altered. However, the expression of transcription factor GATA-4 is severely decreased in the heart-forming regions of vitamin A-deficient stage 7-10 embryos. Significantly, GATA-4 transcripts are completely lacking in the lateral mesoderm posterior to the heart, in the area of the developing cardiac inflow tract that later displays prominent morphological defects, including a closed nonseptated heart lacking a sinus venosus. The administration of retinol to the vitamin A-deficient embryo restores GATA-4 expression and completely rescues the vitamin A-deficient phenotype. Our results indicate that GATA-4 is a component of the retinoid-mediated cardiogenic pathway unlinked to cardiomyocyte differentiation, but involved in the morphogenesis of the posterior heart tube and the development of the cardiac inflow tract.

Animals↗
PubMed1999

Diabetes-induced vascular dysfunction in the retina: role of endothelins.

AIMS/HYPOTHESIS: Vasoactive factors like endothelins, by virtue of the microvascular regulation as well as by other effects, possibly play important parts in the pathogenesis of diabetic retinal microangiopathy. We investigated retinal vascular dysfunction in streptozotocin-induced diabetes and its relation with endothelins in short- and long-term diabetes. METHODS: Diabetic rats with or without an endothelin receptor antagonist (bosentan) treatment were investigated after 1 month and 6 months of follow-up. Retinal blood flow was measured and compared with age- and sex-matched non-diabetic control animals. Retinal tissues were analysed for endothelin-1, endothelin-3, endothelin A and endothelin B mRNA. Distribution of endothelin-1 and endothelin-3 was investigated by immunocytochemistry and that for endothelin receptors by ligand binding and autoradiography. RESULTS: Diabetic animals showed hyperglycaemia, glycosuria, elevated glycated haemoglobin values and reduced body weight gain. Retinal blood flow showed an increased resistivity index, an indicator of vasoconstriction, after 1 month of diabetes which was prevented by treatment with bosentan. This functional change in diabetes was eliminated after 6 months of follow-up. The retina from the diabetic animals showed increased mRNA expression for endothelin-1, endothelin-3 and endothelin A after one month. In addition, endothelin B mRNA expression was increased after 6 months. Furthermore, endothelin-1 and endothelin-3 immunoreactivity and endothelin receptor concentrations were increased in the retina of diabetic rats. CONCLUSION/INTERPRETATION: The results from this study indicate that the endothelin system is of importance in mediating retinal changes in diabetes although mechanisms of the endothelin system alteration as well as their effects might vary depending on the duration of diabetes. [Diabetologia (1999) 42: 1228-1234]

Animals↗
PubMed1999

Acute varicella zoster with postherpetic hyperhidrosis as the initial presentation of HIV infection.

A 31-year-old man presented with acute pain in his left arm and hemorrhagic vesicles that followed his left 8th cervical nerve. A diagnosis of herpes zoster was made, and the patient was treated with valacyclovir. He refused testing for antibodies to HIV because he denied being at risk. Two months later he returned with postherpetic neuralgia and postherpetic hyperhidrosis in the distribution of the vesicles, which had since resolved. Serology for HIV at this visit was positive, and the patient admitted to having sexual relations with prostitutes. Six months later the patient was being treated with triple antiretroviral therapy, and all signs and symptoms of postherpetic zoster had resolved. This case report documents the need for HIV testing in patients with unusual presentations of herpes zoster even if they initially deny being at risk.

AIDS-Related Opportunistic Infections↗
PubMed1999

Trends in transition from pediatric to adult health care services for young adults with chronic conditions.

PURPOSE: The rationale underlying this study was the need to move the transition health services model from a theoretical framework to an empirically-based investigation. Thus, it was necessary to identify programs for youth with chronic or disabling conditions that assist in transitioning from child- to adult-focused health services by (a) discrete types, (b) functional categories, and (c) problems and issues faced by these programs. METHODS: Nominations for transition health services programs were solicited from 1025 organizational agencies at the local, state, regional, and national levels. Two solicitations yielded 277 nominees. After pilot testing, a survey of 163 forced responses and open-ended questions was mailed to each nominated transition health services program. A total of 122 programs returned completed surveys. RESULTS: Program services were categorized as adolescent-focused (38%), condition-focused (36%), and specialty-specific programs (26%). Few programs were primary care-based. Categories were subsequently collapsed into two types: adolescent-focused and condition-focused. No significant differences were noted between adolescent- and condition-focused programs regarding provision of mental health services, vocational counseling, self-efficacy training, or health education. The primary barriers to transition health services were identified as funding and access to key staff, rather than family and adolescent resistance. CONCLUSION: In general, self-identified transition health care programs do not achieve the goal of collaborative, coordinated, and integrative services to adolescents with chronic or disabling conditions. Furthermore, the barriers to attaining the goal are the limitations of the health care system itself.

Adolescent↗
PubMed1999

Early pregnancy assessment; a role for the gynaecology nurse-practitioner.

Recent improvements in the investigation of bleeding and pain in early pregnancy has led to simplified clinical guidelines. These in turn have created the opportunity for nurse-led early pregnancy assessment. We arranged for a gynaecology nurse-practitioner with experience to undergo additional training in early pregnancy care. She then took over the daily running of the Early pregnancy assessment centre (EPAC). A review of 200 consecutive cases showed that the nurse followed the guidelines extremely closely in terms of categorisation of patients, referral to the medical team for further investigation and selection of women who required anti-Rh(D) immunoglobulin. In addition, in the first 6 months of the clinic no cases of ectopic pregnancy were overlooked by the nurse-practitioner. Sixty-one per cent of the women attending the clinic did not need to see a doctor.

Journal Article↗
PubMed1999

Isolation and characterization of human patched 2 (PTCH2), a putative tumour suppressor gene inbasal cell carcinoma and medulloblastoma on chromosome 1p32.

Mutations of the human Patched gene ( PTCH ) have been identified in individuals with the nevoid basal cell carcinoma syndrome (NBCCS) as well as in sporadic basal cell carcinomas and medulloblastomas. We have isolated a homologue of this tumour suppressor gene and localized it to the short arm of chromosome 1 (1p32.1-32.3). Patched 2 ( PTCH2 ) comprises 22 coding exons and spans approximately 15 kb of genomic DNA. The gene encodes a 1203 amino acid putative transmembrane protein which is highly homologous to the PTCH product. We have characterized the genomic structure of PTCH2 and have used single-stranded conformational polymorphism analysis to search for mutations in PTCH2 in NBCCS patients, basal cell carcinomas and in medulloblastomas. To date, we have identified one truncating mutation in a medulloblastoma and a change in a splice donor site in a basal cell carcinoma, suggesting that the gene plays a role in the development of some tumours.

Amino Acid Sequence↗