Biomedical subjects

J A Smith

Publications and source records attributed to J A Smith.

At least 55 records · Page 3Linked to original sources

PubMed2001

Rsk2 allosterically activates estrogen receptor alpha by docking to the hormone-binding domain.

We describe a novel mechanism for transcriptional regulation, in which docking of p90 ribosomal S6 kinase 2 (Rsk2) to the hormone-binding domain (HBD) of estrogen receptor alpha (ERalpha) induces a conformational change that enhances the transcriptional activation function contained in the HBD. A constitutively active mutant of Rsk2 specifically enhances ERalpha-mediated transcription by phosphorylation of Ser167 in ERalpha and by physically associating with residues 326-394 of the ERalpha HBD. The anti-estrogen 4-hydroxytamoxifen blocks Rsk2-mediated activation of ERalpha, by inducing a conformation of ERalpha in which the Rsk2 docking site is masked. Transcriptional activation and docking are specific for ERalpha and do not occur with the related isoform, ERbeta. ERalpha phosphorylation, docking and transcriptional activation are regulated by the Rsk2 N-terminal kinase domain. The allosteric regulation of a target protein, independent of phosphorylation, may be paradigmatic of a general function for protein kinase docking sites.

Allosteric Regulation↗

PubMed2001

Activation of Toll-like receptor-2 by glycosylphosphatidylinositol anchors from a protozoan parasite.

Glycosylphosphatidylinositol (GPI) anchors and glycoinositolphospholipids (GIPLs) from parasitic protozoa have been shown to exert a wide variety of effects on cells of the host innate immune system. However, the receptor(s) that are triggered by these protozoan glycolipids has not been identified. Here we present evidence that Trypanosoma cruzi-derived GPI anchors and GIPLs trigger CD25 expression on Chinese hamster ovary-K1 cells transfected with CD14 and Toll-like receptor-2 (TLR-2), but not wild-type (TLR-2-deficient) Chinese hamster ovary cells. The protozoan-derived GPI anchors and GIPLs containing alkylacylglycerol and saturated fatty acid chains or ceramide were found to be active in a concentration range of 100 nM to 1 microM. More importantly, the GPI anchors purified from T. cruzi trypomastigotes, which contain a longer glycan core and unsaturated fatty acids in the sn-2 position of the alkylacylglycerolipid component, triggered TLR-2 at subnanomolar concentrations. We performed experiments with macrophages from TLR-2 knockout and TLR-4 knockout mice, and found that TLR-2 expression appears to be essential for induction of IL-12, TNF-alpha, and NO by GPI anchors derived from T. cruzi trypomastigotes. Thus, highly purified GPI anchors from T. cruzi parasites are potent activators of TLR-2 from both mouse and human origin. The activation of TLR-2 may initiate host innate defense mechanisms and inflammatory response during protozoan infection, and may provide new strategies for immune intervention during protozoan infections.

Animals↗

PubMed2001

Neuroprotective effects of pramipexole in young and aged MPTP-treated mice.

This study examined the effect of pramipexole (PPX), a selective dopamine (DA) D(3)/D(2) agonist, on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced damage to the nigrostriatal dopamine system in young (8-week-old) and aged (12-month-old) mice. Co-administration of PPX and MPTP to young or aged mice, followed by 2 or 14 days of additional PPX treatment, significantly attenuated MPTP-induced striatal DA loss. Pramipexole treatment also significantly attenuated the loss of tyrosine hydroxylase immunoreactive neurons (TH-IR) within the substantia nigra pars compacta (SNc) in both young and aged animals. Effects of PPX administration on dopaminergic cell survival were confirmed in Nissl-stained sections and by quantitation of retrogradely labeled Fluorogold-positive SNc neurons. Protective effects of PPX on striatal DA levels and SNc DA neuron survival were similar in young and aged animals, although the magnitude of these effects was significantly less in aged animals. These findings support the early initiation of PPX therapy in Parkinson's disease patients.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed2001

Observation of exotic meson production in the reaction pi- p --> eta'pi- p at 18 GeV/c.

An amplitude analysis of an exclusive sample of 5765 events from the reaction pi- p-->eta'pi- p at 18 GeV/c is described. The eta'pi- production is dominated by natural parity exchange and by three partial waves: those with J(PC) = 1(-+), 2(++), and 4(++). A mass-dependent analysis of the partial-wave amplitudes indicates the production of the a2(1320) meson as well as the a4(2040) meson, observed for the first time decaying to eta'pi-. The dominant, exotic (non- qq) 1(-+) partial wave is shown to be resonant with a mass of 1.597+/-0.010(+0.045)(-0.010) GeV/c2 and a width of 0.340+/-0.040+/-0.050 GeV/c2. This exotic state, the pi1(1600), is produced with a t dependence which is different from that of the a2(1320) meson, indicating differences between the production mechanisms for the two states.

Journal Article↗

PubMed2001

Differential effects of a Toll-like receptor antagonist on Mycobacterium tuberculosis-induced macrophage responses.

We previously showed that viable Mycobacterium tuberculosis (Mtb) bacilli contain distinct ligands that activate cells via the mammalian Toll-like receptor (TLR) proteins TLR2 and TLR4. We now demonstrate that expression of a dominant negative TLR2 or TLR4 proteins in RAW 264.7 macrophages partially blocked Mtb-induced NF-kappa B activation. Coexpression of both dominant negative proteins blocked virtually all Mtb-induced NF-kappa B activation. The role of the TLR4 coreceptor MD-2 was also examined. Unlike LPS, Mtb-induced macrophage activation was not augmented by overexpression of ectopic MD-2. Moreover, cells expressing an LPS-unresponsive MD-2 mutant responded normally to Mtb. We also observed that the lipid A-like antagonist E5531 specifically inhibited TLR4-dependent Mtb-induced cellular responses. E5531 could substantially block LPS- and Mtb-induced TNF-alpha production in both RAW 264.7 cells and primary human alveolar macrophages (AM phi). E5531 inhibited Mtb-induced AM phi apoptosis in vitro, an effect that was a consequence of the inhibition of TNF-alpha production by E5531. In contrast, E5531 did not inhibit Mtb-induced NO production in RAW 264.7 cells and AM phi. Mtb-stimulated peritoneal macrophages from TLR2- and TLR4-deficient animals produced similar amounts of NO compared with control animals, demonstrating that these TLR proteins are not required for Mtb-induced NO production. Lastly, we demonstrated that a dominant negative MyD88 mutant could block Mtb-induced activation of the TNF-alpha promoter, but not the inducible NO synthase promoter, in murine macrophages. Together, these data suggest that Mtb-induced TNF-alpha production is largely dependent on TLR signaling. In contrast, Mtb-induced NO production may be either TLR independent or mediated by TLR proteins in a MyD88-independent manner.

Animals↗

PubMed2001

Immunolocalisation of adenosine A(1) receptors in the rat kidney.

The location of adenosine A(1) receptors in the rat kidney was investigated using immunolabelling with antibodies raised to a 15-amino-acid sequence near the C-terminus of the receptor (antibody I) and to a 14-amino-acid sequence in the second extracellular loop (antibody II). In the cortex, antibody I bound to adenosine A(1) receptors in mesangial cells and afferent arterioles, whilst antibody II bound to receptors in proximal convoluted tubules. In the medulla, both antibodies bound to receptors in collecting ducts and the papillary surface epithelium. These observations provide support for the diverse functional roles previously proposed for the adenosine A(1) receptor in the kidney. The labelling of distinct but different structures in the cortex by antibodies raised to different amino acid sequences on the A(1) receptor protein suggests that differing forms of the receptor are present in this region of the kidney.

Animals↗

PubMed2001

A phase I and pharmacologic study of 9-aminocamptothecin administered as a 120-h infusion weekly to adult cancer patients.

PURPOSE: To define the toxicity profile and the recommended phase II doses of 9-aminocamptothecin (9-AC) administered as a weekly 120-h infusion. METHODS: 9-AC was administered over 120 h weekly to 55 adult cancer patients with solid tumors over doses ranging from 0.41 to 0.77 mg/m2 per day in a phase I and pharmacologic study. 9-AC formulated in dimethylacetamide/polyethylene glycol (DMA) was administered on a 3 of 4-week schedule, and the newer colloidal dispersion (CD) formulation was given on a 2 of 3-week schedule. RESULTS: Overall, 193 courses of therapy were administered over 122 dose levels. On the 3 of 4-week schedule, 9-AC DMA infused at > or = 0.6 mg/m2 per day for 120 h weekly produced dose-limiting neutropenia, thrombocytopenia, and diarrhea, or resulted in 1-2-week treatment delays. Shortening treatments to 2 of 3 weeks resulted in dose-limiting neutropenia and fatigue at infusion rates > 0.72 mg/m2 per day. The ratio of 9-AC lactone to total (carboxylate + lactone) drug plasma concentrations at steady-state was 0.15 +/- 0.07. Clinical toxicities and drug pharmacokinetics were not substantially different between the DMA and CD formulations. One objective response was observed in a patient with bladder cancer and minor responses were observed in patients with lung and colon cancers. Plasma area under the concentration versus time curve for 9-AC lactone modestly correlated with the degree of thrombocytopenia (r=0.51) using a sigmoid Emax pharmacodynamic model. CONCLUSION: The recommended phase II dose for the 9-AC DMA formulation is 0.48 mg/m2 per h over 120 h for 3 of 4 weeks and for the 9-AC CD formulation is 0.6 mg/m2 per day over 120 h for 2 of 3 weeks. Both regimens were well tolerated and feasible to administer.

Adult↗

PubMed2001

Frosted branch angiitis in a child with HIV infection.

PURPOSE: In adults with human immunodeficiency virus (HIV) infection, frosted branch angiitis is commonly associated with cytomegalovirus retinitis and responds to anti-cytomegalovirus therapy. We describe the first pediatric case of HIV-associated frosted branch angiitis. METHODS: Case report. RESULTS: A 7-year-old HIV-infected male with frosted branch angiitis was refractory to induction doses of intravenous ganciclovir and foscarnet over a 2-month period. Although cytomegalovirus antigenemia resolved, the angiitis only improved after subsequent treatment with systemic corticosteroids. CONCLUSION: Frosted branch angiitis in this patient was not attributed to cytomegalovirus. The pathogenesis of HIV-associated frosted branch angiitis may differ between children and adults.

Antiviral Agents↗

PubMed2001

Conjunctival T-cell lymphoma caused by human T-cell lymphotrophic virus infection.

PURPOSE: To examine the cause of adult T-cell leukemia/lymphoma. METHODS: We examined a conjunctival biopsy from a 29-year-old Jamaican man who developed bilateral conjunctival masses. Adult T-cell leukemia/lymphoma was diagnosed using routine histology, immunohistochemistry, electron microscopy, microdissection, and the polymerase chain reaction. RESULTS: Histopathologic examination revealed a conjunctival lymphoma. Clonality of the T-cell receptor gamma gene and human T-cell lymphotrophic virus gag gene were detected in the malignant cells. The demonstration of the human T-cell lymphotrophic virus gene and the rearrangement of the T-cell receptor gene in this neoplasm provide proof that human T-cell lymphotrophic virus is the cause of this conjunctival T-cell lymphoma. CONCLUSION: Human T-cell lymphotrophic virus is the cause of adult T-cell leukemia/lymphoma, an aggressive malignancy of CD4+ lymphocytes.

Adult↗

PubMed2001

New corneal findings in human T-cell lymphotrophic virus type 1 infection.

PURPOSE: Human T-cell lymphotrophic virus type 1 is a RNA retrovirus that primarily affects CD4+ T-cells. Human T-cell lymphotrophic virus type 1 infection is the established cause of adult T-cell leukemia/lymphoma, an aggressive malignancy of CD4+ T-cells, and two nonneoplastic conditions: human T-cell lymphotrophic virus type 1-associated myelopathy/tropical spastic paraparesis and human T-cell lymphotrophic virus type 1 uveitis. Other reported ophthalmic manifestations of human T-cell lymphotrophic virus type 1 infection include lymphomatous and leukemic infiltrates in the eye and ocular adnexa in patients with adult T-cell leukemia/lymphoma, retinal pigmentary degeneration, and neuro-ophthalmic disorders in patients with human T-cell lymphotrophic virus type 1-associated myelopathy/tropical spastic paraparesis and keratoconjunctivitis sicca, episcleritis, and sclerouveitis in asymptomatic human T-cell lymphotrophic virus type 1 carriers. This report describes the ocular findings in three Jamaican patients with human T-cell lymphotrophic virus type 1 infection and adult T-cell leukemia/lymphoma. METHODS: The clinical records of three patients with human T-cell lymphotrophic virus type 1 infection and adult T-cell leukemia/lymphoma examined at the National Eye Institute were reviewed. Each patient had one or more complete ophthalmic evaluations. RESULTS: All three patients had corneal abnormalities, including corneal haze and central opacities with thinning; bilateral immunoprotein keratopathy; and peripheral corneal thinning, scarring, and neovascularization. All three patients had elevated serum immunoglobulin levels. CONCLUSIONS: We believe that the novel corneal findings in these patients are most likely a consequence of the hypergammaglobulinemia induced by the human T-cell lymphotrophic virus type 1 infection or the T-cell malignancy.

Adult↗

PubMed2001

Keratitis caused by Candida glabrata in a patient with chronic granulomatous disease.

PURPOSE: To report an unusual ocular presentation of Candida glabrata in a patient with chronic granulomatous disease. METHODS: Interventional case report. A 15-year-old boy with chronic granulomatous disease presented with bilateral limbal infiltrates. He had been receiving broad-spectrum systemic antibiotics for recurrent liver abscesses. The keratitis did not respond to antibiotics and did not resolve after a course of topical steroids. RESULTS: Corneal cultures revealed Candida glabrata. The same species was simultaneously isolated from the surgical drainage of the liver abscesses. The ocular and hepatic findings resolved on intravenous amphotericin B. CONCLUSION: Candida glabrata has recently emerged as an important nosocomial pathogen. It may present as a limbal keratitis in the setting of systemic infection.

Adolescent↗

PubMed2001

Lung volume reduction surgery in emphysema: a systematic review.

The aim of this study was to systematically review the literature regarding the safety and efficacy of lung volume reduction surgery (LVRS) in patients with emphysema. Studies on LVRS to August 2000 were identified using MEDLINE, Embase, Current Contents, and the Cochrane Library. Human studies of patients with upper, lower or diffuse distributions of emphysema were included. All types of bullous emphysema were excluded. A surgeon and researcher independently assessed the retrieved articles for their inclusion in the review. When LVRS was compared with medical management, at 2 years LVRS was associated with a higher FEV1 and at least equivalent survival. The use of staple excision of selected areas of lung appeared to be more efficacious than laser ablation. There is insufficient evidence to show preference for median sternotomy or videoscopically assisted thoracotomy, as the more safe and efficacious procedure. In highly selected patients with emphysema LVRS is deemed an acceptable treatment. To fully evaluate the safety and efficacy of LVRS, outcomes beyond 2 years must be included. The results of prospective randomized trials between medical management and LVRS, now in progress, are essential before a final assessment can be made.

Hospital Mortality↗

PubMed2001

Intrarectal lidocaine during transrectal prostate biopsy: results of a prospective double-blind randomized trial.

PURPOSE: Recent reports have indicated the benefit of anesthesia during prostate biopsy. To assess this finding objectively we performed a prospective randomized double-blind study to compare patient pain with and without local anesthesia during transrectal ultrasound guided prostate biopsies. MATERIALS AND METHODS: Between August 2000 and March 2001, 108 men undergoing transrectal ultrasound guided biopsy of the prostate were randomized in double-blind fashion to receive intrarectal 2% lidocaine gel or intrarectal lubricant alone. No patient received pre-procedure narcotics or sedation. Pain associated with biopsy was determined using a horizontal linear visual analog pain scale. Pain scores in the 2 treatment groups were compared and possible predictors of increased pain were examined. RESULTS: The 2 groups were similar in demographic characteristics. There was no significant difference in pain score in the 2% lidocaine and lubricant alone groups (28.3 versus 28.9 mm., p = 0.88). Previous biopsy, time since previous biopsy, physician, number of biopsies and prostate volume did not correlate with pain score, while age correlated negatively with the score (r = -0.27, p = 0.005). A single complication involving a vasovagal episode resolved spontaneously. CONCLUSIONS: Intrarectal lidocaine gel provides no significant therapeutic or analgesic benefit compared with lubricant alone for transrectal ultrasound guided biopsy of the prostate. In younger patients more discomfort is associated with this procedure.

Administration, Rectal↗

PubMed2001

Intraoperative nerve stimulation predicts postoperative potency.

OBJECTIVES: Intraoperative nerve stimulation has been used to map the course of cavernosal nerve bundles to aid in nerve-sparing radical prostatectomy (RP). We sought to determine whether the intraoperative nerve stimulation response after removal of the prostate specimen predicts postoperative potency. METHODS: We prospectively evaluated 63 consecutive patients undergoing RP. Among these 63 patients, 41 patients had a bilateral nerve-sparing procedure, and 22 underwent bilateral wide resection of the neurovascular bundles. Potency was determined at 1 year by direct patient interview. RESULTS: Of the 22 patients with wide resection, 16 (73%) had no observed stimulated response, 4 (18%) had a measurable tumescence response, and 2 (9%) had detumescence. All 22 patients were impotent postoperatively. At a minimum follow-up of 1 year, of the 41 patients who underwent nerve-sparing RP, 27 (66%) had postoperative erections sufficient for penetration. Of the 30 men with an intraoperative stimulated tumescence response, 24 (80%) were potent; of the 6 with a detumescence response, 2 (33%) were potent; and of the 5 with no stimulated nerve response, 1 (20%) was potent. A tumescence response was significantly more predictive of postoperative potency than no intraoperative response (P = 0.017). CONCLUSIONS: An intraoperative tumescence response with stimulation of the neurovascular bundles after prostate specimen removal is more likely to correspond to successful postoperative sexual function after nerve-sparing RP than is no response.

Adenocarcinoma↗

PubMed2001

Vascular response of the meniscus to injury: effects of immobilization.

Failed meniscal healing may lead to degenerative osteoarthritis of the knee. Healing is thought to be dependent upon an adequate blood supply, yet "normal" vascular changes during healing are not well understood. In this study we have quantified vasoactive and angiogenic responses to medial meniscal injury in a rabbit model under clinically relevant conditions, and related these to histological criteria of healing. Twenty-six adult rabbits were given a standardized meniscal injury; 12 of these had the hind limb immobilized by pinning. Eight normal controls and 12 sham-operated animals were also studied. After 4 weeks, animals underwent either vascular volume (vascular index) determination, or blood flow measurement using coloured microspheres. Histological analysis was also performed to assess meniscal healing. In injured animals, blood flow to the menisci was increased fivefold 4 weeks post-operative; this increase was prevented by immobilization. The vascular index of the menisci was also increased threefold by injury, but not significantly reduced by immobilization. Histological examination of injured menisci showed examples of healing and non-healing tears in both mobile and immobile groups. Meniscal injuries are associated with characteristic changes in vascularity and perfusion, and these changes likely play a significant role in the healing process. Characterization of the vascular responses to meniscal injury may lead to techniques that can promote reliable healing of meniscal tears and thereby improve clinical outcomes.

Animals↗

PubMed2001

Once-daily budesonide inhalation suspension in infants and children < 4 and > or = 4 years of age with persistent asthma.

BACKGROUND: Budesonide inhalation suspension (Pulmicort Respules; AstraZeneca LP, Wilmington, DE), a nebulized corticosteroid, was developed for use in infants and young children with persistent asthma. OBJECTIVE: To compare the efficacy and safety of once-daily budesonide inhalation suspension in children < 4 years of age and in those > or = 4 years of age with persistent asthma. METHODS: A retrospective analysis stratified by age group was performed on data from two randomized, double-blind, placebo-controlled, parallel-group studies that evaluated the efficacy and safety of budesonide inhalation suspension 0.25 mg, 0.5 mg, or 1.0 mg once daily for 12 weeks in children 6 months to 8 years of age with persistent asthma. Clinical assessments included nighttime and daytime asthma symptoms, breakthrough medication use, adverse events, and hypothalamic-pituitary-adrenal-axis function. RESULTS: In both randomized studies, budesonide inhalation suspension demonstrated statistically significant improvement in nighttime and daytime asthma symptom scores compared with placebo. In the retrospective analysis of pooled data from these studies, the efficacy of budesonide was maintained when children were stratified by age group. Clinical improvements from baseline in nighttime and daytime asthma symptom scores were observed in both age groups at all budesonide inhalation suspension dose levels. No significant differences were observed between age groups in breakthrough medication use in any of the treatment groups. No differences were observed in the incidence of adverse events between the two age groups, and significant (P < 0.01) effect on hypothalamic-pituitary-adrenal-axis function was apparent only in children < 4 years of age at the 0.25-mg dose level. CONCLUSIONS: Once-daily budesonide inhalation suspension is effective in the treatment of persistent asthma in children aged < 4 and > or = 4 years of age.

Administration, Inhalation↗

PubMed2001

Relations between medical history, clinical findings and plasma N-terminal proatrial natriuretic peptide in patients in primary health care.

BACKGROUND: recent studies indicate that measurement of natriuretic peptides may be a valuable tool to improve the quality of the diagnosis of heart failure in general practice. AIM: the aim of the present study was to examine the relationship between the plasma level of the natriuretic peptide N-terminal proANP and symptoms and signs of heart failure in patients from general practice in the Oslo area. METHODS AND RESULTS: we undertook a survey of 499 patients consecutively enrolled from the practice of 27 practitioners. One hundred and twenty-nine patients were classified as having possible or some degree of heart failure. The plasma concentration of N-terminal proANP increased with severity of heart failure as judged from clinical examination. In multivariate analysis age, history of heart disease, plasma creatinine, use of beta-blockers and digitalis, oedemas and atrial fibrillation were the main determinants of plasma N-terminal proANP. CONCLUSION: while there was an overall increase in N-terminal proANP values with increasing symptoms and degree of heart failure, no single finding was closely related to N-terminal proANP. Treatment effects and diagnostic errors may both influence the relationship between N-terminal proANP and clinical findings. The current study has demonstrated the feasibility of using N-terminal proANP by general practitioners for the potentially improved diagnosis of heart failure. Further research is required to determine the precise role of this assay in clinical practice.

Aged↗

PubMed2001

Bone-targeted Src SH2 inhibitors block Src cellular activity and osteoclast-mediated resorption.

Src, a nonreceptor tyrosine kinase, is an important regulator of osteoclast-mediated resorption. We have investigated whether compounds that bind to the Src SH2 domain inhibit Src activity in cells and decrease osteoclast-mediated resorption. Compounds were examined for binding to the Src SH2 domain in vitro using a fluorescence polarization binding assay. Experiments were carried out with compounds demonstrating in vitro binding activity (nmol/L range) to determine if they inhibit Src SH2 binding and Src function in cells, demonstrate blockade of Src signaling, and lack cellular toxicity. Cell-based assays included: (1) a mammalian two-hybrid assay; (2) morphological reversion and growth inhibition of cSrcY527F-transformed cells; and (3) inhibition of cortactin phosphorylation in csk-/- cells. The Src SH2 binding compounds inhibit Src activity in all three of these mechanism-based assays. The compounds described were synthesized to contain nonhydrolyzable phosphotyrosine mimics that bind to bone. These compounds were further tested and found to inhibit rabbit osteoclast-mediated resorption of dentine. These results indicate that compounds that bind to the Src SH2 domain can inhibit Src activity in cells and inhibit osteoclast-mediated resorption.

Actins↗