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Biomedical subjects

S Merchant

Publications and source records attributed to S Merchant.

At least 19 recordsLinked to original sources
PubMed2006

A vascular ring variant: an unusual case of vocal cord palsy due to an anomalous left carotid artery arising from a retrotracheal arch of the aorta.

We present the case of an unusual vascular ring in a 23-year-old male patient who presented for CT examination of the chest for diagnostic work up for unilateral vocal cord palsy. Contrast-enhanced CT revealed the left common carotid artery to be arising from the ascending part of a retrotracheal arch of aorta and traversing anterior to the trachea in the retromanubrial space.

Adult↗
PubMed2005

Widened clinical spectrum of the Q128P MECP2 mutation in Rett syndrome.

CASE REPORT: We describe a female patient with Arnold Chiari type I malformation, atypical Rett syndrome characterized by postnatal onset microcephaly, stereotypic hand movements, ataxia, severe developmental delay, intractable tonic-clonic seizures, and a MECP2 mutation with a unique set of clinical findings. Implementation of a ketogenic diet resulted in decreased seizure activity and an improvement in the patient's degree of social relatedness with her family members. DISCUSSION: An early diagnosis of Rett syndrome allows families to maximize utilization of existing treatment modalities and seek appropriate genetic counseling and prenatal diagnoses. This case also provides further evidence for the treatment benefit of ketogenic diets for seizures in patients with Rett syndrome.

Arnold-Chiari Malformation↗
PubMed2005

An analysis of PAX1 in the development of vertebral malformations.

An analysis of PAX1 in the development of vertebral malformations. Due to the sporadic occurrence of congenital vertebral malformations, traditional linkage approaches to identify genes associated with human vertebral development are not possible. We therefore identified PAX1 as a candidate gene in vertebral malformations and congenital scoliosis due to its mutation in the undulated mouse. We performed DNA sequence analysis of the PAX1 gene in a series of 48 patients with congenital vertebral malformations, collectively spanning the entire vertebral column length. DNA sequence coding variants were identified in the heterozygous state in exon 4 in two male patients with thoracic vertebral malformations. One patient had T9 hypoplasia, T12 hemivertebrae and absent T10 pedicle, incomplete fusion of T7 posterior elements, ventricular septal defect, and polydactyly. This patient had a CCC (Pro)-->CTC (Leu) change at amino acid 410. This variant was not observed in 180 chromosomes tested in the National Institute of Environmental Health Sciences (NIEHS) single nucleotide polymorphism (SNP) database and occurred at a frequency of 0.3% in a diversity panel of 1066 human samples. The second patient had a T11 wedge vertebra and a missense mutation at amino acid 413 corresponding to CCA (Pro)-->CTA (Leu). This particular variant has been reported to occur in one of 164 chromosomes in the NIEHS SNP database and was found to occur with a similar frequency of 0.8% in a diversity panel of 1066 human samples. Although each patient's mother was clinically asymptomatic and heterozygous for the respective variant allele, the possibility that these sequence variants have clinical significance is not excluded.

Base Sequence↗
PubMed2002

Vessels within vessels in the myometrium.

We have encountered a peculiar vascular architecture in the myometrium wherein arteries are found free-floating within cleft-like spaces. Using different colored dye injections in the uterine arteries and veins, we demonstrated that these spaces are venous channels. This was confirmed by immunoperoxidase staining for CD34, which enhanced the cells lining these spaces. A review of 81 hysterectomy specimens showed that this vascular architecture was present in 42 cases (52%), while it was identified in the parenchyma of only two mastectomy specimens among the 45 specimens from different organs studied. A strong association existed between the presence of this architecture and history of menorrhagia (p = 0.0116). This peculiar vascular architecture might be important in the pathogenesis of menorrhagia and the development of intravenous leiomyomatosis. Pathologists should also be able to recognize these spaces as vascular channels in the event that malignant cells are identified within them.

Adult↗
PubMed2001

The direct medical costs of alpha(1)-antitrypsin deficiency.

BACKGROUND: For individuals with emphysema because of severe alpha(1)-antitrypsin deficiency, specific therapy called IV augmentation therapy has been available since 1989. Such therapy consists of IV infusion of pooled human plasma alpha(1)-antiprotease. METHODS: To assess the direct medical costs of having alpha(1)-antitrypsin deficiency, the current study surveyed members of the Alpha One Foundation Registry for Individuals With alpha(1)-Antitrypsin Deficiency regarding their annual expenditures for treatment of this disease. Data regarding demographic features, alpha(1)-antitrypsin status, and health-resource utilization were collected from a self-administered questionnaire. Respondents were asked to provide total health-care expenditures, but costs by specific items of care (eg, drugs, physician visits, etc) were not available. RESULTS: Mean annual cost estimates were higher for PI*ZZ-phenotype individuals ($30,948, n = 292) than for non-PI*ZZ-phenotype individuals ($20,673, n = 53; p = 0.049). Among PI*ZZ-phenotype individuals, self-reported costs of health-care services were further analyzed for those 288 individuals whose alpha(1)-antiprotease use status was reported. For the 185 current alpha(1)-antiprotease users, the mean annual cost was $40,123 (median, $36,000). CONCLUSIONS: Annual health-care expenditures by individuals with alpha(1)-antitrypsin deficiency are very high, whether or not they are currently receiving augmentation therapy. Augmentation therapy adds substantial costs, especially for heavier individuals who are receiving weekly infusions.

Direct Service Costs↗
PubMed2000

The Crd1 gene encodes a putative di-iron enzyme required for photosystem I accumulation in copper deficiency and hypoxia in Chlamydomonas reinhardtii.

Chlamydomonas reinhardtii adapts to copper deficiency by degrading apoplastocyanin and inducing Cyc6 and Cpx1 encoding cytochrome c(6) and coproporphyrinogen oxidase, respectively. To identify other components in this pathway, colonies resulting from insertional mutagenesis were screened for copper- conditional phenotypes. Twelve crd (copper response defect) strains were identified. In copper-deficient conditions, the crd strains fail to accumulate photosystem I and light-harvesting complex I, and they contain reduced amounts of light-harvesting complex II. Cyc6, Cpx1 expression and plastocyanin accumulation remain copper responsive. The crd phenotype is rescued by a similar amount of copper as is required for repression of Cyc6 and Cpx1 and for maintenance of plastocyanin at its usual stoichiometry, suggesting that the affected gene is a target of the same signal transduction pathway. The crd strains represent alleles at a single locus, CRD1, which encodes a 47 kDa, hydrophilic protein with a consensus carboxylate-bridged di-iron binding site. Crd1 homologs are present in the genomes of photosynthetic organisms. In Chlamydomonas, Crd1 expression is activated in copper- or oxygen-deficient cells, and Crd1 function is required for adaptation to these conditions.

Amino Acid Sequence↗
PubMed2000

The p24 proteins are not essential for vesicular transport in Saccharomyces cerevisiae.

To investigate the factors involved in the sorting of cargo proteins into COPII endoplasmic reticulum (ER) to Golgi apparatus transport vesicles, we have created a strain of S. cerevisiae (p24Delta8) that lacks all eight members of the p24 family of transmembrane proteins (Emp24p, Erv25p, and Erp1p to Erp6p). The p24 proteins have been implicated in COPI and COPII vesicle formation, cargo protein sorting, and regulation of vesicular transport in eukaryotic cells. We find that p24Delta8 cells grow identically to wild type and show delays of invertase and Gas1p ER-to-Golgi transport identical to those seen in a single Deltaemp24 deletion strain. Thus, p24 proteins do not have an essential function in the secretory pathway. Instead, they may serve as quality control factors to restrict the entry of proteins into COPII vesicles.

Base Sequence↗
PubMed2000

Coordinate copper- and oxygen-responsive Cyc6 and Cpx1 expression in Chlamydomonas is mediated by the same element.

Chlamydomonas reinhardtii activates the transcription of the Cyc6 and the Cpx1 genes (encoding cytochrome c(6) and coprogen oxidase) in response to copper deficiency. Mutational analysis of promoter regions of the Cyc6 and Cpx1 genes revealed a four nucleotide sequence, GTAC, which was absolutely essential for copper responsiveness. The Cyc6 promoter contains two copper response elements, each with a functionally important GTAC sequence, whereas the Cpx1 promoter contains only one. This may contribute to the stronger and more tightly regulated expression of the Cyc6 gene. Mutation or deletion of sequences flanking the GTACs implicates additional nucleotides contributing to copper-responsive expression, but none are absolutely essential. Metal ion selectivity of Cpx1 expression is identical to that described previously for Cyc6 and is restricted to the copper deficiency-induced Cpx1 transcript. The Cyc6 and Cpx1 genes are also induced by oxygen deficiency. Reporter gene constructs indicate that the induction occurs at the level of transcription and requires the same GTAC sequence that is critical for copper responsiveness. We suggest that components of the copper-responsive signal transduction pathway are used for some of the changes in gene expression in hypoxic cells.

Animals↗
PubMed2000

Validation of outcomes survey for adults with chronic suppurative otitis media.

Currently, there is no valid, disease-specific outcomes measure to evaluate health impact and treatment effectiveness for patients with chronic suppurative otitis media (CSOM). The Chronic Ear Survey (CES) is a new, disease-specific outcomes measure for CSOM that was administered in a prospective manner to 91 patients with CSOM. It was then validated according to established criteria for reliability, validity, and sensitivity to clinical change by correlation with objective data and self-assessment questionnaires such as the Hearing Handicap Inventory for Adults (HHIA) and the generic 36-Item Short-Form Health Survey (SF-36). Significant correlations between subscale scores of the CES and audiometric data and between subscale scores of the HHIA and SF-36 were found. The standardized response mean for the CES total score was 0.42, indicating moderate sensitivity to clinical change. Overall, results demonstrated that the CES is a reliable and valid instrument for investigation of health status and health-related quality-of-life outcomes.

Adult↗
PubMed1999

Induction of coproporphyrinogen oxidase in Chlamydomonas chloroplasts occurs via transcriptional regulation of Cpx1 mediated by copper response elements and increased translation from a copper deficiency-specific form of the transcript.

Coproporphyrinogen III oxidase, encoded by a single nuclear gene in Chlamydomonas reinhardtii, produces three distinct transcripts. One of these transcripts is greatly induced in copper-deficient cells by transcriptional activation, whereas the other forms are copper-insensitive. The induced form of the transcript was expressed coordinately with the cytochrome c6-encoding (Cyc6) gene, which is known to be transcriptionally regulated in copper-deficient cells. The sequence GTAC, which forms the core of a copper response element associated with the Cyc6 gene, is also essential for induction of the Cpx1 gene, suggesting that both are targets of the same signal transduction pathway. The constitutive and induced Cpx1 transcripts have the same half-lives in vivo, and all encode the same polypeptide with a chloroplast-targeting transit sequence, but the shortest one representing the induced form is a 2-4-fold better template for translation than are either of the constitutive forms. The enzyme remains localized to a soluble compartment in the chloroplast even in induced cells, and its abundance is not affected when the tetrapyrrole pathway is manipulated either genetically or by gabaculine treatment.

Amino Acid Sequence↗
PubMed1999

Human deafness dystonia syndrome is a mitochondrial disease.

The human deafness dystonia syndrome results from the mutation of a protein (DDP) of unknown function. We show now that DDP is a mitochondrial protein and similar to five small proteins (Tim8p, Tim9p, Tim10p, Tim12p, and Tim13p) of the yeast mitochondrial intermembrane space. Tim9p, Tim10p, and Tim12p mediate the import of metabolite transporters from the cytoplasm into the mitochondrial inner membrane and interact structurally and functionally with Tim8p and Tim13p. DDP is most similar to Tim8p. Tim8p exists as a soluble 70-kDa complex with Tim13p and Tim9p, and deletion of Tim8p is synthetically lethal with a conditional mutation in Tim10p. The deafness dystonia syndrome thus is a novel type of mitochondrial disease that probably is caused by a defective mitochondrial protein-import system.

Amino Acid Sequence↗
PubMed1999

How membrane proteins travel across the mitochondrial intermembrane space.

A newly discovered family of small proteins in the yeast mitochondrial intermembrane space mediates import of hydrophobic proteins from the cytoplasm into the inner membrane. Loss of one of these chaperone-like proteins from human mitochondria results in a disease that causes deafness, muscle weakness and blindness.

Amino Acid Sequence↗
PubMed1998

Tim9p, an essential partner subunit of Tim10p for the import of mitochondrial carrier proteins.

Tim10p, a protein of the yeast mitochondrial intermembrane space, was shown previously to be essential for the import of multispanning carrier proteins from the cytoplasm into the inner membrane. We now identify Tim9p, another essential component of this import pathway. Most of Tim9p is associated with Tim10p in a soluble 70 kDa complex. Tim9p and Tim10p co-purify in successive chromatographic fractionations and co-immunoprecipitated with each other. Tim9p can be cross-linked to a partly translocated carrier protein. A small fraction of Tim9p is bound to the outer face of the inner membrane in a 300 kDa complex whose other subunits include Tim54p, Tim22p, Tim12p and Tim10p. The sequence of Tim9p is 25% identical to that of Tim10p and Tim12p. A Ser67-->Cys67 mutation in Tim9p suppresses the temperature-sensitive growth defect of tim10-1 and tim12-1 mutants. Tim9p is a new subunit of the TIM machinery that guides hydrophobic inner membrane proteins across the aqueous intermembrane space.

Amino Acid Sequence↗
PubMed1998

A novel pathway for cytochromes c biogenesis in chloroplasts.

The cytochromes c are a useful model for the study of the pathways and mechanisms of assembly of the cofactor-containing components of energy transducing membranes. Genetic analyses have identified proteins that are required for the assembly of c-type cytochromes in mitochondria, bacteria and chloroplasts. The components of the pathway operating in fungal and animal mitochondria, i.e. the cytochrome (cyt) c and c1 heme lyases in the intermembrane space, were identified over a decade ago through the study of cytochrome deficiencies in Neurospora crassa and Saccharomyces cerevisiae. More recently, a large number of membrane or membrane-associated components were identified in various alpha- and gamma-proteobacteria as c-type cytochrome assembly factors; they comprise an assembly pathway that is evolutionarily and mechanistically distinct from that in fungal and animal mitochondria. The components function not only in the lyase reaction but also in the delivery and maintenance of the substrates in a state that is suitable for reaction in the bacterial periplasm. Yet a third pathway is required for cytochrome maturation in chloroplasts. Genetic analyses of Chlamydomonas reinhardtii ccs mutants, which are pleiotropically deficient in both the membrane-anchored cytochrome f and the soluble cytochrome c6, revealed a minimum of six loci, plastid ccsA and nuclear CCS1 through CCS5, that are required for the conversion of the chloroplast apocytochromes to their respective holo forms. Sequence analysis of the cloned ccsA and Ccs1 genes indicates that the predicted protein products are integral membrane proteins with homologues in cyanobacteria, some gram-positive bacteria (Bacillus subtilis, Mycobacterium spp.), beta-proteobacteria (Neisseria spp.) and an epsilon-proteobacterium (Helicobacter pylori). CcsA and Ccs1 require each other for accumulation in vivo and are therefore proposed to function in a complex, possibly with the products of some of the other CCS loci. A tryptophan-rich motif, which has been proposed to represent a heme binding site in bacterial cytochrome biogenesis proteins (CcmC and CcmF), is functionally important in plastid CcsA. As is the case for CcmC and CcmF, the tryptophan-rich sequence is predicted to occur in a loop on the p-side of the membrane, where the heme attachment reaction occurs. Conserved histidine residues in the CcsA and Ccs1 may serve as ligands to the heme iron. A multiple alignment of the tryptophan-rich regions of the CcsA-, CcmC- and CcmF-like sequences in the genome databases indicates that they represent three different families.

Amino Acid Sequence↗
PubMed1998

Laparoscopic surgery for abdominal aortic aneurysms. Technical elements of the procedure and a preliminary report of the first 22 patients.

BACKGROUND: Laparoscopic surgery for infrarenal aortic aneurysms is based on the principle of retropertoneal exclusion of the aneurysms sac with aortofemoral or aortoiliac bypass. METHODS: Of 22 patients who met the selection criteria, 20 successfully underwent laparoscopic aortic surgery at Morristown Memorial Hospital between February and October 1997. Technical elements and steps of this operation are described and illustrated. RESULTS: Within 30 days of surgery, 2 patients died and 9 had various major and minor perioperative complications. As a group, the laparoscopic patients had less postoperative pain, needed fewer hours of ventilator support, had shorter intensive care unit (ICU) and hospital lengths of stay, and resumed diet and normal activity earlier than the historical norms of patients undergoing transabdominal or retroperitoneal aortic resections at the same institution. CONCLUSIONS: These early observations suggest that the laparoscopic treatment of infrarenal abdominal aneurysms may have several significant potential benefits. Long-term results and randomized prospective studies with patients matched by risk stratification will be needed to confirm these impressions.

Aged↗