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Biomedical subjects

A Rubenstein

Publications and source records attributed to A Rubenstein.

At least 19 recordsLinked to original sources
PubMed2002

Plexiform neurofibromas in NF1: toward biologic-based therapy.

Neurofibromatosis type 1 (NF1) is one of the most common neurogenetic diseases affecting adults and children. Neurofibromas are one of the most common of the protean manifestations of NF1. Plexiform neurofibromas, which will frequently cause cosmetic abnormalities, pain, and neurologic deficits, are composed of "neoplastic" Schwann cells accompanied by other participating cellular and noncellular components. There is increasing evidence that loss of NF1 expression in neoplastic Schwann cells is associated with elevated levels of activated RAS, supporting the notion that the NF1 gene product, neurofibromin, acts as a growth regulator by inhibiting ras growth-promoting activity. In addition, there is increasing evidence that other cooperating events, which may be under cytokine modulation, are important for neurofibroma development and growth. Treatment of plexiform neurofibromas has been empiric, with surgery being the primary option for those with progressive lesions causing a major degree of morbidity. The efficacy of alternative treatment approaches, including the use of antihistamines, maturation agents, and antiangiogenic drugs, has been questionable. More recently, biologic-based therapeutic approaches, using drugs that target the molecular genetic underpinnings of plexiform neurofibromas or cytokines believed important in tumor growth, have been initiated. Evaluation of such trials is hindered by the unpredictable natural history of plexiform neurofibromas and difficulties in determining objective response in tumors that are notoriously large and irregular in shape. Innovative neuroimaging techniques and the incorporation of quality-of-life scales may be helpful in evaluation of therapeutic interventions. The ability to design more rational therapies for NF1-associated neurofibromas is heavily predicated on an improved understanding of the molecular and cellular biology of the cells involved in neurofibroma formation and growth.

Biological Therapy↗
PubMed2000

Integrating clinician-educators into Academic Medical Centers: challenges and potential solutions.

During the last decade academic medical centers (AMCs) have hired large numbers of clinician-educators to teach and provide clinical care. However, these clinician-educators often do not advance in academic rank, since excellence in clinical care and teaching alone is not adequate justification for advancement. The authors articulate the problems with the present system of recognition for clinician-educators-i.e., the requirement for regional and national reputation, the lack of reliable measures of clinical and teaching excellence, and the lack of training opportunities for young clinician-educators. They call for solutions, including fundamental changes in promotion criteria (e.g., focus criteria for promotion on clinician-educators' accomplishments within their institutions) and the development of valid and feasible methods to measure outcomes of teaching programs. Further, they recommend the development of a new faculty position, a "clinician-educator researcher," to foster the scholarship of discovery in medical education and clinical practice. Investments in clinician-educator researchers will ultimately help AMCs to achieve their threefold mission-excellence in patient care, teaching, and research.

Academic Medical Centers↗
PubMed1997

The diagnostic evaluation and multidisciplinary management of neurofibromatosis 1 and neurofibromatosis 2.

OBJECTIVE: Neurofibromatosis 1 and neurofibromatosis 2 are autosomal dominant genetic disorders in which affected individuals develop both benign and malignant tumors at an increased frequency. Since the original National Institutes of Health Consensus Development Conference in 1987, there has been significant progress toward a more complete understanding of the molecular bases for neurofibromatosis 1 and neurofibromatosis 2. Our objective was to determine the diagnostic criteria for neurofibromatosis 1 and neurofibromatosis 2, recommendations for the care of patients and their families at diagnosis and during routine follow-up, and the role of DNA diagnostic testing in the evaluation of these disorders. DATA SOURCES: Published reports from 1966 through 1996 obtained by MEDLINE search and studies presented at national and international meetings. STUDY SELECTION: All studies were reviewed and analyzed by consensus from multiple authors. DATA EXTRACTION: Peer-reviewed published data were critically evaluated by independent extraction by multiple authors. DATA SYNTHESIS: The main results of the review were qualitative and were reviewed by neurofibromatosis clinical directors worldwide through an Internet Web site. CONCLUSIONS: On the basis of the information presented in this review, we propose a comprehensive approach to the diagnosis and treatment of individuals with neurofibromatosis 1 and neurofibromatosis 2.

Genes, Neurofibromatosis 1↗
PubMed1997

Localizing the adhesive and signaling functions of plakoglobin.

Plakoglobin (PKG) is a major component of cell-cell adhesive junctions. It is also closely related to the Drosophila segment polarity gene product armadillo and can induce a WNT-like neural axis duplication (NAD) phenotype in Xenopus [Kamovsky and Klymkowsky, 1995.] To define the regions of PKG involved in cell adhesion and inductive signaling, we examined the behavior of mutated forms of PKG in Xenopus. Deletion of amino acids 22 through 39 (in the Xenopus PKG sequence increased the apparent stability of the polypeptide within the embryo and increased its ability to induce a WNT-like, NAD phenotype when expressed in the vegetal hemisphere. The N-terminal "head" and first 6 "ARM" repeats of PKG, or the C-terminal "tail" and the last 3 "ARM" repeats, could be removed without destroying the remaining polypeptide's ability to induce a NAD phenotype. The nuclear localization of mutant PKGs, however, was not strictly correlated with the ability to induce a NAD phenotype, i.e., some inactive polypeptides still accumulate in nuclei. Removal of PKG's head and first ARM repeat, which includes its alpha-catenin binding site, resulted in a polypeptide that, when expressed in the embryo, generated alpha dramatic cell adhesion defect. Removal of the next three ARM repeats abolished this adhesion defect, suggesting that the polypeptide no longer competes effectively with endogenous catenins for binding to cadherins. Expression of a form of PKG truncated after the 5th ARM repeat produced a milder cell adhesion defect, whereas expression of a polypeptide truncated after the 8th ARM repeat had little apparent effect on cellular adhesion. Based on these observations, we conclude that functions related to stability and cellular adhesion reside in the N-terminal region of the polypeptide, whereas the ability to induce a NAD phenotype lies within repeats 6-10 of the central region. The function(s) of the C-terminal domain of PKG remain uncertain at this time.

Amino Acid Sequence↗
PubMed1997

Implementation of universal directly observed therapy at a New York City hospital and evaluation of an out-patient directly observed therapy program.

SETTING: Directly observed therapy (DOT) program for tuberculosis (TB) at a New York City hospital. OBJECTIVE: To describe a specific TB DOT program model utilizing active prospective identification of inpatients, and identify factors associated with patient acceptance of voluntary DOT and with their retention in therapy. METHODS: Recruitment for DOT by daily surveillance of in-patients. DOT was offered as the patient's choice together with concrete services and incentives. On-site DOT was offered in an out-patient clinic. Outreach efforts were initiated when a patient missed one or more DOT visit. RESULTS: During the study period, 95% of 176 in-patients with TB were evaluated for DOT. Of the 137 who were eligible for DOT, 85% (95% confidence interval [CI], 77.5% to 90%) elected to receive DOT. Illicit drug use was independently associated with a higher likelihood of acceptance of DOT (odds ratio[OR], 4.88; 95% CI, 1.5-15.7). Among the 101 patients who received onsite DOT, illicit drug use (OR, 0.21; 95% CI, 0.08-0.6) and previous TB therapy (OR, 0.27; 95% CI, 0.27-0.7) were both independently associated with lower retention in therapy. However, with intensive case management, only 1% of this cohort was lost to follow-up and the overall treatment completion index was 98%. CONCLUSION: In-patient surveillance is a highly effective DOT recruitment strategy. A DOT model which elicits patient participation in discharge plans and offers incentives can yield a high rate of voluntary acceptance. Outpatient case management is a highly effective means of ensuring treatment completion, especially in those at risk for poor retention.

Adult↗
PubMed1996

The detection of contiguous gene deletions at the neurofibromatosis 1 locus with fluorescence in situ hybridization.

Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized primarily by the development of multiple neurofibromas and pigmentary changes. The recent identification of contiguous gene deletions in NF1, a previously unrecognized molecular basis for this disorder, raises important questions regarding deletion frequency in the patient population and the role that contiguous genes may play in the physical manifestations of NF1 patients. To facilitate the identification of patients with large NF1 deletions, we have isolated clones carrying large genomic segments from the NF1 locus and tested their efficacy as probes for fluorescence in situ hybridization (FISH). Clone P1-9 spans approximately 65 kb of the NF1 gene, including exons 2-11, and clone P1-12 carries approximately 55 kb of NF1 intron 27B. FISH studies performed with P1-9, P1-12, and a set of overlapping 1F10 cosmid clones mapping telomeric to the NF1 locus identified large deletions in two new neurofibromatosis type 1 patients who, like previously characterized deletion patients, had mildly dysmorphic facial features and large numbers of cutaneous neurofibromas.

Chromosome Aberrations↗
PubMed1994

Concentration and distribution of infectivity and PrPSc following partial denaturation of a mouse-adapted and a hamster-adapted scrapie strain.

PrPSc is a specific protein marker for slow infectious diseases known as the transmissible subacute spongiform encephalopathies. Although PrPSc is closely associated with infectivity, it is not known if it is the infectious agent itself, a component of the agent or merely adventitiously associated with infectivity. In the present study we demonstrate that the resistance of PrPSc to partial denaturation and of infectivity to inactivation differs markedly for two scrapie strains. Proteinase K treatment or electrophoretic analysis of partially denatured PrPSc preparations reveal a dissociation between infectivity and demonstrable PrPSc. Our findings support other evidence that not all PrPSc is required for infectivity. Our studies combined with previous biological analyses suggest that PrPSc cannot be the sole component associated with the infectious agent.

Animals↗
PubMed1994

Deletions spanning the neurofibromatosis 1 gene: identification and phenotype of five patients.

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by marked variation in clinical severity. To investigate the contribution to variability by genes either contiguous to or contained within the NF1 gene, we screened six NF1 patients with mild facial dysmorphology, mental retardation, and/or learning disabilities, for DNA rearrangement of the NF1 region. Five of the six patients had NF1 gene deletions on the basis of quantitative densitometry, locus hemizygosity, and analysis of somatic cell hybrid lines. Analyses of hybrid lines carrying each of the patient's chromosomes 17, with 15 regional DNA markers, demonstrated that each of the five patients carried a deletion > 700 kb in size. Minimally, each of the deletions involved the entire 350-kb NF1 gene; the three genes--EVI2A, EVI2B, and OMG--that are contained within an NF1 intron; and considerable flanking DNA. For four of the patients, the deletions mapped to the same interval; the deletion in the fifth patient was larger, extending farther in both directions. The remaining NF1 allele presumably produced functional neurofibromin; no gene rearrangements were detected, and RNA-PCR demonstrated that it was transcribed. These data provide compelling evidence that the NF1 disorder results from haploid insufficiency of neurofibromin. Of the three documented de novo deletion cases, two involved the paternal NF1 allele and one the maternal allele. The parental origin of the single remaining expressed NF1 allele had no dramatic effect on patient phenotype. The deletion patients exhibited a variable number of physical anomalies that were not correlated with the extent of their deletion. All five patients with deletions were remarkable for exhibiting a large number of neurofibromas for their age, suggesting that deletion of an unknown gene in the NF1 region may affect tumor initiation or development.

Adolescent↗
PubMed1990

Primary central nervous system lymphoma in a pediatric patient with acquired immune deficiency syndrome. Treatment with radiation therapy.

Primary central nervous system (CNS) lymphoma, an otherwise rare pediatric tumor, has been reported with increasing frequency in children with acquired immune deficiency syndrome (AIDS). With current therapy, the outcome of this disease is invariably fatal. The authors present a case of primary CNS lymphoma in a 3.5-year-old girl with AIDS who received treatment with total brain irradiation. After treatment, the patient's mental status improved, the seizures resolved, and she had no further progression of her neurologic symptoms until she died of pneumonia 6 months later. The autopsy revealed a necrotic mass at the site of the original tumor. The brain stem and spinal cord, unirradiated, contained lymphomatous lesions. The patient had extensive fibrinoid necrosis and leukoencephalopathy that were consistent with radiation-induced CNS damage. Coexisting AIDS encephalopathy also contributed to the patient's CNS injury. Effective palliation of CNS lymphoma in children with AIDS may be obtained with cranial irradiation. Pediatric AIDS patients may show more severe tissue effects from irradiation than unaffected children.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Striatal tachykinin gene expression regulated by interaction of D-1 and D-2 dopamine receptors.

The involvement of D-1 and D-2 dopamine (DA) receptors in mediating the DA regulation of preprotachykinin (PPT) gene expression was investigated in rat striatal tissue. Initial experiments determined that acute treatment with the indirect DA agonist methamphetamine induces increases in total PPT messenger RNA, with a maximal effect seen within 3 hr. RNA protection studies established that acute methamphetamine treatment did not affect the relative ratios of the various PPT gene transcripts derived by alternate splicing. The methamphetamine-induced increase in total PPT messenger RNA could be blocked by either a D-1 or a D-2 selective DA antagonist (SCH 23390 and sulpiride, respectively). The D-2 agonist quinpirole, but not the D-1 agonist SKF 38393, mimicked the methamphetamine-induced increase. This D-2 agonist-induced increase was dependent upon D-1 receptor tone, as either co-administration of SCH 23390 or pretreatment with the DA synthesis inhibitor alpha-methyltyrosine blocked the quinpirole-induced increase. These studies provide biochemical evidence for an enabling role of D-1 DA receptors in striatal D-2 DA receptor function.

Animals↗
PubMed1986

The limitations to and valid use of C-peptide as a marker of the secretion of insulin.

The accuracy with which the secretion rate of insulin can be calculated from peripheral concentrations of C-peptide was investigated in conscious mongrel dogs. Biosynthetic human C-peptide and insulin were infused intraportally and their concentrations measured in the femoral artery. During steady-state infusions of C-peptide, the peripheral concentration changed in proportion to the infusion rate and the metabolic clearance rate (5.2 +/- 0.3 ml/kg/min) remained constant over a wide range of plasma concentrations. Application of a two-compartment mathematical model, in which the model parameters were estimated from analysis of C-peptide decay curves after intravenous bolus injections, allowed the intraportal infusion rate of C-peptide to be derived from peripheral C-peptide concentrations, even under non-steady-state conditions. Estimates of the intraportal infusion rate based on this model were 102.4 +/- 2.6% of the actual infusion rate as it was increasing and 102.3 +/- 5.5% of this rate as it was falling. The peripheral C-peptide: insulin molar ratio was influenced by the rate at which equimolar intraportal infusions of C-peptide and insulin were changed. The baseline C-peptide: insulin molar ratio (4.1 +/- 0.9) increased to peak values of 8.2 +/- 0.6, 10.3 +/- 2.0, and 14.9 +/- 1.3 when the infusion rate was increased and then decreased rapidly. Peak values of only 5.7 +/- 1.2 were found if the intraportal infusion rate was changed slowly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Plasma lipoprotein abnormalities associated with acquired hepatic triglyceride lipase deficiency.

Two enzymes, lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL), are released into human plasma after intravenous injection of heparin. LPL is the major enzyme responsible for initiating catabolism of chylomicrons and very-low-density lipoproteins (VLDL). The physiological role of HTGL is less certain. HTGL has been postulated to be an alternate enzyme to LPL in hydrolysis of triglyceride in VLDL and to be an important enzyme for removal of phospholipid from both low-density lipoproteins (LDL) and high-density lipoproteins (HDL). In this latter role, this enzyme would convert larger, lighter lipoprotein particles to smaller denser particles. HTGL deficiency has been found in severe liver disease and with a genetic deficiency of this enzyme. A unique patient is described with acquired hepatic triglyceride lipase deficiency and vitamin A intoxication. This patient developed hypercholesterolemia with an increase in both LDL and HDL. An increased proportion of lighter LDL (LDL1) and HDL (HDL2) was noted. In addition, after administration of heparin there was no shift in the distribution of apoE in plasma fractionated using a column containing 4% agarose. These findings are consistent with a postulated role of HTGL in metabolism of light LDL and HDL particles and some classes of apoE containing lipoproteins.

Chromatography, Agarose↗