PubMed Health⌕ Search

Biomedical subjects

M A Levine

Publications and source records attributed to M A Levine.

At least 19 recordsLinked to original sources
PubMed1997

Olfactory dysfunction in type I pseudohypoparathyroidism: dissociation from Gs alpha protein deficiency.

The discovery of variably decreased olfactory ability in Type Ia pseudohypoparathyroidism (PHP), a syndrome in which generalized hormone resistance is associated with deficiency of the alpha chain of the stimulatory guanine nucleotide-binding protein (Gs alpha) of adenylyl cyclase, has been used to support the hypothesis that Gs alpha plays a major role in human olfactory transduction. However, only a limited number of olfactory tests have been administered to such patients, and these patients have other problems that might cause or contribute to their olfactory dysfunction, including an unusual constellation of skeletal and developmental deficits termed Albright hereditary osteodystrophy (AHO). In this study, we administered tests of odor detection, identification, and memory to (i) 13 patients with Type Ia PHP; (ii) 8 patients with Type Ib PHP; (iii) 7 patients with pseudopseudohypoparathyroidism (PPHP); and (iv) 3 sets of normal controls matched to these groups on the basis of age, gender, and smoking history. Although we confirm that PHP Type Ia patients evidence olfactory dysfunction, we also demonstrate that (i) patients with Type Ib PHP, who have no AHO, no generalized hormone resistance, and normal Gs alpha activity, also evidence olfactory dysfunction relative to matched controls; and (ii) patients with PPHP, who have AHO, no generalized hormone resistance, and deficient Gs alpha protein activity, have relatively normal olfactory function. These observations do not support the hypothesis that the olfactory dysfunction associated with PHP is the result of generalized Gs alpha protein deficiency and imply that other mechanisms (e.g. ones associated with PTH or PTHrP resistance) are responsible for the olfactory deficits of this disorder.

Adult↗
PubMed1996

Developing a Canadian prescribing practices network. Network Development Committee of the Canadian Prescribing Practices Network Project.

Expenditure on drug therapy in Canada has been growing at a faster rate than spending on any other aspect of health care. Increasing societal pressure to use scarce resources more efficiently, advances in communication technology and data indicating that there is room for improvement in drug prescribing suggest that the time has come for an organized linkage of the available drug-utilization and health-outcomes data-bases across the country. A national prescribing practices network would assist prescribers, researchers and policymakers to optimize prescribing with respect to both cost effectiveness and health outcomes. The authors outline the main concerns addressed in the 1994 report to the National Pharmaceutical Strategy and present the results of discussions by the Canadian Prescribing Practices Network Project with respect to the potential users and data sources of a national network and the communications technology on which it would rely.

Canada↗
PubMed1996

Normal parathyroid hormone responsiveness of bone-derived cells from a patient with pseudohypoparathyroidism.

Pseudohypoparathyroidism (PHP) is characterized by a lack of response to parathyroid hormone (PTH); however, normal skeletal responsiveness to PTH in some patients with PHP type Ia was previously suggested on the basis of clinical observations. To test this hypothesis, we measured cyclic adenosine monophosphate (cAMP) production in response to various agonists in bone-derived osteoblast-like (OBL) cells from trabecular explants obtained from an iliac crest biopsy of a 25-year-old woman with PHP. The patient was proved to have PHP type Ia on the basis of Albright's hereditary osteodystrophy and decreased activity of stimulatory guanine nucleotide-binding protein (Gs) in erythrocytes. Responsiveness of the patient's OBL cells was compared with OBL cells from eight subjects aged 18-39 years who had no evidence of metabolic bone disease. OBL cells from the patient responded to the following agonists (expressed in multiples of elevation of cAMP, stimulated/basal, mean +/- SE, n = 3): PTH, 3.8 +/- 0.3; forskolin, 8.2 +/- 0.2; and cholera toxin, 56.8 +/- 10.0. These responses were not significantly different from those of control OBL cells: PTH, 4.5 +/- 1.1 (range 2.4-7.5); forskolin, 7.7 +/- 1.4; and cholera toxin, 57.9 +/- 16.2. The normal cholera toxin response indicated the presence of functional Gs. Bone cells from patients with PHP type Ia may exhibit a normal PTH receptor-coupled adenylyl cyclase system in vitro despite clinical evidence of impaired hormone-responsive adenylyl cyclase in other tissues, including the kidney. Skeletal responsiveness to PTH may explain the long periods of spontaneous normocalcemia observed in this patient.

Adenylyl Cyclases↗
PubMed1996

Adenoviral infection of thyroid cells: a rationale for gene therapy for metastatic thyroid carcinoma.

BACKGROUND: Patients with thyroid carcinoma experience excellent long-term survival; however, up to 16% will die of their disease. We have transformed a rat thyroid follicular cell line (FRTL-5) with a gene (TGCT) that mimics a known mutation associated with thyroid neoplasms. These cells form subcutaneous tumors that metastasize to lung in nude mice. METHODS: In anticipation of developing gene therapy against this thyroid carcinoma model, we (1) tested whether adenovirus containing the beta-galactosidase gene could infect FRTL-5 cells and neonatal rat thyroid and (2) evaluated the ability to kill FRTL-5 cells by transfecting them with a transgene in which the thyroglobulin promoter (TG) directed the expression of herpes simplex virus type I thymidine kinase (HSV1TK) and treating TG-HSV1TK-transfected cells with 5 micrograms/ml ganciclovir. RESULTS: Nearly 100% of the TG-HSV1TK but only 5% of control cells were killed by addition of ganciclovir. Histochemical staining for beta-galactosidase activity demonstrated infection of FRTL-5 cells and neonatal rat thyroid tissue by adenovirus beta-galactosidase. CONCLUSIONS: These data demonstrate the feasibility of using adenovirus as vector to infect thyroid cells in vivo and provide a rationale for development of gene therapy for treatment of thyroid cancer.

Adenoviridae↗
PubMed1996

Analysis of lysophophatidylcholine-induced endothelial dysfunction.

Endothelial dysfunction caused by the early atherosclerotic process or by endothelial exposure to atherogenic lipids, including lysophosphatidylcholine (lysoPC), is characterized by a selective impairment of responses mediated by the pertussis toxin-sensitive Gi-2 protein. Experiments were performed to analyze the mechanisms underlying this effect. Bradykinin (BK: Gi-2 protein-independent), serotonin (5-HT: Gi-2 protein-dependent), or direct activation of the G(i-2)-protein by mastoparan increased the release of endothelium-derived nitric oxide (EDNO) from porcine arterial endothelial cells (EC). LysoPC decreased the release of EDNO caused by 5-HT, but did not affect the response to BK or mastoparan. LysoPC did not increase production of superoxide radicals detected by lucigenin-enhanced chemiluminescence. Western blot analysis showed no difference in the level of immunoreactive Gi alpha-2 between control and lysoPC-treated cells. Activation of the Gi-2 protein by serotonergic or alpha 2-adrenoceptor stimulation decreased the pertussis toxin-catalyzed ADP-ribosylation of Gi alpha-2 protein in membranes from control but not lysoPC-treated cells. However, direct activation of the Gi-2 protein by mastoparan inhibited the ADP-ribosylation in membranes from control and lysoPC-treated cells. The toxin-catalyzed reaction was reduced in lysoPC-treated cells or lysoPC-treated membranes. LysoPC reduced the ability of endothelin to increase GTP gamma S binding to the Gi-2 protein but did not affect the activity of mastoparan. These results suggest that lysoPC inhibits a pertussis toxin-sensitive signaling pathway in EC by an effect consistent with receptor:Gi-2-protein uncoupling.

Animals↗
PubMed1996

Clinical implications of genetic defects in G proteins. The molecular basis of McCune-Albright syndrome and Albright hereditary osteodystrophy.

Inactivating and activating mutations in the gene encoding G alpha s (GNAS1) are known to be the basis for 2 well-described contrasting clinical disorders, Albright hereditary osteodystrophy (AHO) and McCune-Albright syndrome (MAS). AHO is an autosomal dominant disorder due to germline mutations in GNAS1 that decrease expression or function of G alpha s protein. Loss of G alpha s function leads to tissue resistance to multiple hormones whose receptors couple to G alpha s. By contrast, MAS results from postzygotic somatic mutations in GNAS1 that lead to enhanced function of G alpha s protein. Acquisition of the activating mutation early in life leads to a more generalized distribution of the mosaicism and is associated with the classic clinical triad of polyostotic fibrous dysplasia, endocrine hyperfunction, and café au lait skin lesions described in MAS. Acquisition of a similar activating mutation in GNAS1 later in life presumably accounts for the restricted distribution of the gsp oncogene, and is associated with the development of isolated lesions (for example, fibrous dysplasia, pituitary or thyroid tumors) without other manifestations of MAS. Tissues that are affected by loss of G alpha s function in AHO are also affected by gain of G alpha s function in MAS, thus identifying specific tissues in which the second messenger cAMP plays a dominant role in cell growth, proliferation, or function. Further investigations of the functions of G alpha s and other members of the GTPase binding protein family will provide more insight into the pathogenesis and clinical manifestations of human disease.

Adolescent↗
PubMed1996

Transformation of rat thyroid follicular cells stably transfected with cholera toxin A1 fragment.

Activating mutations of the alpha subunit of the G protein G(s) (G(s)alpha) have been identified in thyroid adenomas and well-differentiated thyroid carcinomas. To examine the role of activating mutations of G(s)alpha in thyroid neoplasia, we transfected rat follicular thyroid (FRTL-5) cells with a transgene in which the cholera toxin A1 subunit (CTA1) is expressed under the control of the rat thyroglobulin gene promoter (TG). This transgene recapitulates effects of the activating mutation of G(s)alpha by its ability to ADP-ribosylate and thereby inhibit GTPase activity of endogenous G(s)alpha molecules. To assess the effect of G(s)alpha activation on cell growth, TGCTA1, or control, pM AM neotransfected FRTL-5 cells (10(4)-10(6)) were injected s.c. into nude mice. TGCTA1-transfected FRTL-5 cells grow in nude mice, whereas control cells do not. Tumor histology revealed increased mitotic activity, infiltration of skeletal muscle, perineural invasion, and plugging of lymphatic spaces. In addition, nude mice injected with TGCTA1 transfected cells or xenografted with the tumors developed metastases to lung. These results indicate that activation of G(s)alpha and constitutive production of cAMP in FRTL-5 cells can result in TSH-independent cellular proliferation and neoplastic transformation.

Adenosine Diphosphate Ribose↗
PubMed1996

Increased cyclic adenosine 3',5'-monophosphate inhibits G protein-coupled activation of phospholipase C in rat FRTL-5 thyroid cells.

Thyroid cell growth and function are regulated by several hormones and growth factors that bind to cell surface receptors coupled via G proteins, Gs and Gq, to stimulation of adenylyl cyclase and phospholipase C (PLC), respectively. We created a permanently transfected FRTL-5 cell line (TG8) in which the thyroglobulin gene promoter directs expression of the cholera toxin (CT) A1 subunit (CTA1). CTA1 catalyzes ADP ribosylation of Gs alpha, which results in persistent activation of Gs alpha. Activated Gs alpha causes constitutive stimulation of adenylyl cyclase and increases levels of intracellular cAMP. Because G protein-coupled signaling pathways exhibit cross-talk, we compared TG8 cells to FRTL-5 cells transfected with the neomycin resistance gene (TG4) to determine whether constitutive stimulation of adenylyl cyclase influences the PLC pathway. PLC activity was assessed by measuring levels of total inositol phosphates (IPs) in TG4 and TG8 cells that had been preincubated with myo-[3H]inositol for 2 days. Baseline values of [3H]IP production were similar for the two cell lines. Incubation of TG4 control cells with 10(-8) M TSH, 300 microM ATP, and 100 microM norepinephrine for 60 min stimulated 2.5-, 8.1-, and 3.4-fold increases, respectively, in [3H]IP production over the control value. By contrast, there was no [3H]IP response to any of these ligands in TG8 cells. TG8 cells exhibit a decrease in [35S]adenosine 5'-(gamma-thio)triphosphate binding to their cell surface compared to TG4 control cells counterparts, but no decrease in [125I]TSH binding. Treatment of TG4 cells with 100 ng/ml CT, 50 microM forskolin, or 1 mM 8-bromo-cAMP for 2 days reproduced the loss of ligand-stimulated [3H]IP synthesis present in TG8 cells. Although levels of immunoreactive Gq alpha and Gq alpha 11 were normal in TG8 cells, sodium fluoride-induced [3H]IP production was also inhibited. Levels of immunoreactive PLC beta 3, the dominant subtype of PLC beta in FRTL-5 cells, were not altered in TG8 cells or by CT treatment of TG4 cells. These data indicate that elevated levels of cAMP can inhibit the activity of G protein-coupled PLC. Further study of this model will elucidate our understanding of the exact mechanism responsible for this interaction.

Adenosine Triphosphate↗
PubMed1996

Midwives' network.

Explore the source record for details and available documents.

Developing Countries↗
PubMed1995

Probing the bimolecular interactions of parathyroid hormone and the human parathyroid hormone/parathyroid hormone-related protein receptor. 2. Cloning, characterization, and photoaffinity labeling of the recombinant human receptor.

Parathyroid hormone (PTH) acts to regulate calcium homeostasis by interacting with a G-protein-coupled receptor that also binds PTH-related protein (PTHrP). In this report we describe the cloning, characterization, and biological activity of the cloned human (h) PTH/PTHrP receptor (Rc) and cross-linking of a benzophenone-substituted PTH analog, [Nle8,18,Lys13(epsilon-pBZ2),L-2-Nal23,Tyr34]bPTH(1-34 )NH2(K13), to cells endogenously expressing the Rc and cells transiently or stably transfected with the human Rc. A full-length cDNA clone was isolated and fully sequenced from a human kidney cDNA library. Northern blot analysis of normal human tissues revealed a limited tissue distribution: a single transcript of approximately 2.3 kb was detected in kidney, lung, placenta, and liver. In human embryonic kidney cells (HEK-293, clone C-21) stably transfected with hPTH/PTHrP Rc, a single 85-90 kDa Rc-hormone complex was formed after photolysis in the presence of K13. This covalent cross-linking reaction was specifically inhibited by excess quantities of biologically active 1-34 analogs of bovine (b) PTH or hPTHrP but not by C-terminal and midregion PTH peptides. Photoincorporation of 125I-labeled K13 into the Rc occurred with high efficiency (60-70%), approximately an order of magnitude greater than that achieved with conventional aryl azide cross-linking reagents. These results support the feasibility of our approach for specifically cross-linking a tagged PTH analog to the Rc, as a first step in the effort to identify directly the amino acid residues that constitute the Rc binding site.

Affinity Labels↗
PubMed1995

Albright hereditary osteodystrophy and del(2) (q37.3) in four unrelated individuals.

Albright hereditary osteodystrophy (AHO) is a condition with characteristic physical findings (short stature, obesity, round face, brachydactyly) but variable biochemical changes (pseudohypoparathyroidism, pseudopseudohypoparathyroidism). Most patients with AHO have decreased activity of the guanine nucleotide-binding protein (GS protein) that stimulates adenylyl cyclase. The gene encoding the alpha subunit of the GS protein (GNAS1) has been mapped to the long arm of chromosome 20. We describe 4 unrelated individuals with apparent AHO, associated with small terminal deletions of chromosome 2. All 4 patients had normal serum calcium levels consistent with pseudopseudohypoparathyroidism. Del(2) (q37) is the first consistent karyotypic abnormality that has been documented in AHO [Phelan et al., 1993: Am J Hum Genet 53:484]. The finding of the same small terminal deletion in 4 unrelated individuals with a similar phenotype suggests that a gene locus in the 2q37 region is important in the pathogenesis of Albright syndrome. The association of Albright syndrome and the GNAS1 locus on chromosome 20 is well documented. The observation of a second potential disease locus on chromosome 2 may help explain the heterogeneity observed in this disorder.

Adolescent↗
PubMed1995

Reduced adenylyl cyclase activation with no decrease in beta-adrenergic receptors in basenji greyhound leukocytes: relevance to beta-adrenergic responses in airway smooth muscle.

Mononuclear leukocytes (MNLs) have been used as a model of beta-adrenergic responsiveness of airway smooth muscle, but the relevance of this model remains controversial. The basenji greyhound (BG) dog model of airway hyperresponsiveness shares some features with human asthma, and airway smooth muscle shows a selective impairment in isoproterenol-stimulated adenylyl cyclase activity. In this study, MNL membranes were obtained from these same dogs, and the beta-adrenergic receptor-adenylyl cyclase cascade function was compared with that in airway smooth muscle. beta-Adrenergic receptor numbers and affinities for iodine 125-cyanopindolol were similar in the two dog groups (receptor numbers [Bmax] = 441 +/- 101 and 447 +/- 61 fmol/mg protein and dissociation constant [Kd] = 269 +/- 44 and 312 +/- 60 pmol/L for mongrel and BG MNLs, respectively). Quantities of the Gs alpha protein were not different in the membranes as determined by immunoblotting. Stimulation of adenylyl cyclase by isoproterenol (100 mumol/L) was impaired in MNL membranes of BG membranes (22% +/- 4% increase over guanosine triphosphate [10 mumol/L]) compared with mongrel membranes (47% +/- 8.6% increase over guanosine triphosphate [10 mumol/L], p < 0.05). Stimulation of adenylyl cyclase by prostaglandin E1 (10 mumol/L), NaF (10 mmol/L), or forskolin (10 mumol/L) did not differ in membranes from the two groups. No difference was found in the lymphocyte subsets in the two groups as determined by flow cytometry. These findings are qualitatively similar to studies of trachealis muscle membranes from these same dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1995

Health-related quality of life in patients with major depression who are treated with moclobemide.

A total of 651 depressed patients completed self-administered health-related quality-of-life (HRQOL) questionnaires during treatment with moclobemide in order to evaluate whether general and psychopathology-specific HRQOL questionnaires could detect changes in depressed patients receiving treatment. Patients were treated with moclobemide on an outpatient basis over an 8-week period; questionnaires were completed at weeks 0, 2, 4, and 8. At each assessment, patients completed one of two HRQOL questionnaires: namely, the General Health Questionnaire (GHQ), a psychopathology-specific HRQOL questionnaire, or the Short-Form 36 (SF-36), a general HRQOL instrument. Physicians were randomized to one of the two HRQOL questionnaires for all of their patients. Because the French version of the SF-36 was not available in the public domain, the patients of all Francophone physicians completed the GHQ, whereas the patients enrolled by Anglophone physicians completed either the SF-36 or the GHQ. The GHQ provides an overall score that measures the emotional dimensions of HRQOL, whereas the SF-36 provides scores in the following eight domains: physical functioning (PF), physical role functioning (PRF), emotional role functioning (ERF), social functioning (SF), bodily pain (BP), mental health (MH), vitality (VT), and general health perceptions (GHP). The GHQ and seven domains of the SF-36 detected a statistically significant linear trend (improvement) over time (p < 0.05). The change in the BP domain of the SF-36 was not statistically significant (p = 0.29).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Expression of muscarinic receptor subtypes and M2-muscarinic inhibition of adenylyl cyclase in lung.

The relative distribution and absolute quantities of muscarinic receptor subtypes m1, m2, m3, and m4 were determined in membranes of canine trachealis muscle, bronchi, and lung parenchyma by immuno-precipitation with receptor subtype-specific rabbit polyclonal antisera. Additionally, the functional coupling of muscarinic receptors to the inhibition of adenylyl cyclase was related to the presence of m2-muscarinic receptors in each region. Immunoprecipitation identified more total muscarinic receptors in trachealis muscle than in bronchi or lung. m2-Muscarinic receptor predominated in tracheal muscle (372 +/- 85 fmol/mg protein) with fewer m3 receptors (48 +/- 5 fmol/mg protein). Bronchi contained 6.6 +/- 2.0 and 9.2 +/- 1.8 fmol/mg protein of m2 and m3 receptors, respectively. Lung parenchyma contained 13.9 +/- 3.9 fmol/mg protein of m3 receptors. Adenylyl cyclase activity increased in response to guanosine triphosphate and isoproterenol in membranes from all three lung regions, but muscarinic-mediated inhibition of adenylyl cyclase occurred only in trachealis membranes. These studies provide the first quantitative assessment of muscarinic receptor subtypes in different regions of the lung and relate the ability to measure muscarinic inhibition of adenylyl cyclase to the presence of m2 receptors.

Acetylcholine↗
PubMed1995

Basenji-greyhound dog: increased m2 muscarinic receptor expression in trachealis muscle.

Airway smooth muscle from asthmatic humans and from the Basenji-greyhound dog (BG) dog is hyporesponsive to beta-adrenergic agonist stimulation. Because adenylyl cyclase is under dual regulation in airway smooth muscle, we compared muscarinic receptor-coupled inhibition of adenylyl cyclase in airway smooth muscle from BG and mongrel dogs. Inhibition of forskolin-stimulated adenylyl cyclase activity by the muscarinic M2 agonist oxotremorine was greater in airway smooth muscle membranes from BG compared with mongrel controls. Quantitative immunoprecipitation studies showed increased numbers of m2 but not m3 muscarinic receptors in the BG airway smooth muscle. The enhanced ability of muscarinic agonists to inhibit adenylyl cyclase in BG airway smooth muscle may be due to the greater numbers of muscarinic m2 receptors, which may account in part for impaired airway smooth muscle relaxation in the BG model of airway hyperresponsiveness.

Adenylyl Cyclase Inhibitors↗
PubMed1995

Experience in the development of a postmarketing surveillance network: the pharmacy medication monitoring program.

OBJECTIVE: To describe the pilot and early implementation phase of a system for assembling and recruiting cohorts of patients taking selected prescription medications and prospectively monitoring them for new health events. DESIGN: Prospective observational study, based on telephone interviews, of 1475 patients filling prescriptions for a nonsteroidal antiinflammatory drug (NSAID). Patients were interviewed by telephone using trained interviewers at a central site. Hospitalizations and deaths were followed up and reviewed by an independently physician. SETTING: Community setting in a region of Hamilton, Ontario, Canada. PARTICIPANTS: All consenting patients filling new or repeat prescriptions for NSAIDs at participating pharmacies. MAIN OUTCOME MEASURES: The authors report on the development and assessment of systems for: (1) ongoing recruitment of patients through community pharmacies; (2) data transfer from pharmacies to the coordinating center; (3) surveying patients; (4) classifying, coding, and evaluating new health events; and (5) following up on new serious adverse events. RESULTS: Fifty-one percent of patients approached were recruited, and 83% of these provided completed interviews. For patients picking up their own medications, pharmacy workload varied from 4 to 10 minutes per patient approached. Nineteen percent of patients reported having a new health problem or unusual symptom at the initial telephone interview. Reported health-related events were similar to those described in other studies of NSAIDs. CONCLUSIONS: Most aspects of the monitoring system performed well. One limitation was the low recruitment rate for patients who did not directly drop off or pick up their own prescriptions. Even so, this method of patient accrual may complement alternative monitoring programs.

Adverse Drug Reaction Reporting Systems↗