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J Kaplan

Publications and source records attributed to J Kaplan.

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

Desferrioxamine-mediated iron uptake in Saccharomyces cerevisiae. Evidence for two pathways of iron uptake.

In the yeast Saccharomyces cerevisiae, uptake of iron is largely regulated by the transcription factor Aft1. cDNA microarrays were used to identify new iron and AFT1-regulated genes. Four homologous genes regulated as part of the AFT1-regulon (ARN1-4) were predicted to encode members of a subfamily of the major facilitator superfamily of transporters. These genes were predicted to encode proteins with 14 membrane spanning domains and were from 26 to 53% identical at the amino acid level. ARN3 is identical to SIT1, which is reported to encode a ferrioxamine B permease. Deletion of ARN3 did not prevent yeast from using ferrioxamine B as an iron source; however, deletion of ARN3 and FET3, a component of the high affinity ferrous iron transport system, did prevent uptake of ferrioxamine-bound iron and growth on ferrioxamine as an iron source. The siderophore-mediated transport system and the high affinity ferrous iron transport system were localized to separate cellular compartments. Epitope-tagged Arn3p was expressed in intracellular vesicles that co-sediment with the endosomal protein Pep12. In contrast, Fet3p was expressed on the plasma membrane and was digested by extracellular proteases. These data indicate that S. cerevisiae has two pathways for ferrrioxamine-mediated iron uptake, one occurring at the plasma membrane and the other occurring in an intracellular compartment.

Amino Acid Sequence↗
PubMed2000

CCC1 suppresses mitochondrial damage in the yeast model of Friedreich's ataxia by limiting mitochondrial iron accumulation.

Deletion of YFH1 in Saccharomyces cerevisiae leads to a loss of respiratory competence due to excessive mitochondrial iron accumulation. A suppressor screen identified a gene, CCC1, that maintained respiratory function in a Deltayfh1 yeast strain regardless of extracellular iron concentration. CCC1 expression prevented excessive mitochondrial iron accumulation by limiting mitochondrial iron uptake rather than by increasing mitochondrial iron egress. Expression of CCC1 did not result in sequestration of iron in membranous compartments or cellular iron export. CCC1 expression in wild type cells resulted in increased expression of the high affinity iron transport system composed of FET3 and FTR1, suggesting that intracellular iron is not sensed by the iron-dependent transcription factor Aft1p. Introduction of AFT1(up), a constitutive allele of the iron transcription factor, AFT1, that also leads to increased high affinity iron transport did not prevent Deltayfh1 cells from becoming respiratory-incompetent. Although the mechanism by which CCC1 expression affects cytosolic iron is not known, the data suggest that excessive mitochondrial iron accumulation only occurs when cytosolic free iron levels are high.

Biological Transport↗
PubMed2000

Interferon-gamma receptor polymorphisms determine strain differences in accessibility of activated lymphocyte NK-triggering antigens to recognition by self-reactive NK cells.

The "NK-triggering-antigen regulator" (Nktar) gene is a locus identified in the C57BL/6 genome which regulates the ability of unlabeled activated Con A blasts to compete for recognition of labeled syngeneic Con A blasts by BALB/c NK cells. Linkage analysis on Con A blasts from (BALB/c x CByB6F1) N2 backcross progeny for (1) relative level of competitive inhibition of BALB/c NK lysis of syngeneic Con A blasts and (2) genotypes at polymorphic microsatellite markers distributed throughout the mouse genome mapped the Nktar gene locus to a 5-cM region of chromosome 10 containing the interferon-gamma receptor (Ifngr) gene locus. N2 Con A blasts exhibited an inverse relationship between (a) their cell surface density of IFN-gammaR molecules detected by FACS with monoclonal anti-CD119 and (b) their cold target inhibition of BALB/c NK self-reactivity. Con A blasts from Ifngr(-/-) knockout mice showed a relatively high level of inhibition of BALB/c NK self-lysis and a relatively low level of class I MHC, which were both reversed by transient transfection with the Ifngr gene. Sequencing studies showed that Balb/c Ifngr encodes a Gly(69) whereas C57BL/6 Ifngr encodes Glu(69) due to a difference at nucleotide 284. Sequencing studies of N2 progeny demonstrated 100% concordance between their Nktar inhibitory phenotype and their Ifngr genotype. These findings demonstrate that the Nktar and Ifngr loci are identical. They further indicate that polymorphisms related to the Ifngr locus and affecting expression of cell surface IFN-gammaR may underlie genetic differences in the availability of NK-triggering antigens (NKTAgs) to recognition by self-reactive BALB/c NK cells by differentially affecting the ability of IFN-gammaR molecules to mediate up-regulation of NKTAg-masking class I molecules.

Animals↗
PubMed2000

Prevalence of AIPL1 mutations in inherited retinal degenerative disease.

Leber congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy and the most frequent cause of inherited blindness in children. LCA is usually inherited in an autosomal recessive fashion, although rare dominant cases have been reported. One form of LCA, LCA4, maps to chromosome 17p13 and is genetically distinct from other forms of LCA. We recently identified the gene associated with LCA4, AIPL1 (aryl-hydrocarbon interacting protein-like 1) and identified three mutations that were the cause of blindness in five families with LCA. In this study, AIPL1 was screened for mutations in 512 unrelated probands with a range of retinal degenerative diseases to determine if AIPL1 mutations cause other forms of inherited retinal degeneration and to determine the relative contribution of AIPL1 mutations to inherited retinal disorders in populations worldwide. We identified 11 LCA families whose retinal disorder is caused by homozygous or compound heterozygous AIPL1 mutations. We also identified affected individuals in two apparently dominant families, diagnosed with juvenile retinitis pigmentosa or dominant cone-rod dystrophy, respectively, who are heterozygous for a 12-bp AIPL1 deletion. Our results suggest that AIPL1 mutations cause approximately 7% of LCA worldwide and may cause dominant retinopathy.

Adaptor Proteins, Signal Transducing↗
PubMed2000

The photoreceptor cell-specific nuclear receptor gene (PNR) accounts for retinitis pigmentosa in the Crypto-Jews from Portugal (Marranos), survivors from the Spanish Inquisition.

The last Crypto-Jews (Marranos) are the survivors of Spanish Jews who were persecuted in the late fifteenth century, escaped to Portugal and were forced to convert to save their lives. Isolated groups still exist in mountainous areas such as Belmonte in the Beira-Baixa province of Portugal. We report here the genetic study of a highly consanguineous endogamic population of Crypto-Jews of Belmonte affected with autosomal recessive retinitis pigmentosa (RP). A genome-wide search for homozygosity allowed us to localize the disease gene to chromosome 15q22-q24 (Zmax=2.95 at theta=0 at the D15S131 locus). Interestingly, the photoreceptor cell-specific nuclear receptor (PNR) gene, the expression of which is restricted to the outer nuclear layer of retinal photoreceptor cells, was found to map to the YAC contig encompassing the disease locus. A search for mutations allowed us to ascribe the RP of Crypto-Jews of Belmonte to a homozygous missense mutation in the PNR gene. Preliminary haplotype studies support the view that this mutation is relatively ancient but probably occurred after the population settled in Belmonte.

Chromosomes, Human, Pair 15↗
PubMed2000

Lumpectomy margins, reexcision, and local recurrence of breast cancer.

BACKGROUND: The diagnosis of breast cancer is often made by excisional biopsy without margin assessment for mammographic findings or palpable masses. Many patients treated with breast conservation undergo reexcision to obtain clear margins although the relationship between clear margins and local recurrence remains controversial. METHODS: Patients undergoing breast conservation and adjuvant radiation therapy with complete follow-up over 5 years were studied. Factors associated with obtaining clear histopathologic margins and undergoing reexcision to obtain clear margins were studied in relation to the risk of local recurrence. RESULTS: Clear biopsy margins were associated with diagnosis by fine-needle aspiration cytology (fine-needle aspiration 42%, spot localization 11%, excisional biopsy 10%; P <0.001). Reexcision was significantly related to diagnostic method (spot localization 63%, excisional biopsy 36%, fine-needle aspiration 10%; P <0.001), first margin status (clear 0%, close 11%, positive 46%, unknown 48%; P <0.001), patient age (54 years for reexcised patients and 58 for non-reexcised patients; P <0.001), and tumor size (mean tumor size 1. 4 cm for reexcised patients and 1.7 cm for non-reexcised patients; P = 0.003). Patients undergoing reexcision were significantly more likely to be diagnosed by spot localization, have nonnegative excisional biopsy margins, be younger, and have smaller tumors than patients not undergoing reexcision. Local recurrence was not significantly related to margin status (8% with clear margins, 7% with positive margins, 19% with close margins, and 11% with unknown margins) or reexcision (10% local recurrence rate for patients with negative final margins after reexcision and 12% with positive, close or unknown first margin without reexcision). Estrogen receptor status was the only variable related to local recurrence in Cox proportional hazards model (P = 0.009). Estrogen receptor negative patients with nonnegative margins experienced a 20% rate of local recurrence compared with 10% for estrogen receptor negative patients with negative margins and 7% for estrogen receptor positive patients regardless of margin status (P = 0.021). CONCLUSIONS: Clear excision margins are facilitated by preoperative diagnosis by fine-needle cytology. For patients with nonnegative margins, reexcision was more commonly performed in young patients with small tumors diagnosed by spot localization biopsy. The relationship of local recurrence to margins and reexcision was not statistically significant. Estrogen receptor negative tumors with nonnegative margins had a significantly higher rate of local recurrence than estrogen receptor negative tumors with clear margins and estrogen receptor positive tumors regardless of margin status.

Adult↗
PubMed2000

Spinocerebellar syndrome in patients infected with human T-lymphotropic virus types I and II (HTLV-I/HTLV-II): report of 3 cases from Panama.

Cerebellar symptoms at onset are unusual in HTLV-I/II-associated tropical spastic paraparesis (TSP). A prospective study of neurological disorders in Panama (1985-1990) revealed 13 patients with TSP and 3 with HTLV-I/II-associated spinocerebellar syndrome (HSCS) presenting at onset loss of balance, wide-based stance and gait, truncal instability, and mild leg ataxia (vermian cerebellar syndrome), with absent upper limb dysmetria but with postural tremor, downbeat nystagmus, and dysarthria. In 4-5 years, spinal cord manifestations of TSP developed, including spastic paraparesis, pyramidal signs, bladder and sphincter disturbances. Two patients were infected with HTLV-I and another one, a Guaymi Amerindian woman, with HTLV-II. Magnetic resonance imaging (MRI) demonstrated cerebellar atrophy involving predominantly the superior vermis. Mild axonal peripheral neuropathy in the lower limbs, dorsal column involvement and inflammatory myopathy were found by neurophysiology studies. There are 14 similar cases reported in Japan and Canada, but to our knowledge these are the first documented cases of HSCS in the tropics. A cerebellar syndrome constitutes another form of presentation of HTLV-I/II infection of the nervous system.

Cerebellum↗
PubMed2000

Analysis of the lysosomal storage disease Chediak-Higashi syndrome.

Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disorder of human, mouse (beige) and other mammalian species. The same genetic defect was found to result in the disease in all species identified, permitting a positional cloning approach using the mouse model beige to identify the responsible gene. The CHS gene was cloned and mutations identified in affected species. This review discusses the clinical features of CHS contrasting features seen in similar syndromes. The possible functions of the protein encoded by the CHS/beige gene are discussed, along with the alterations in cellular physiology seen in mutant cells.

Animals↗
PubMed2000

Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy.

Optic atrophy type 1 (OPA1, MIM 165500) is a dominantly inherited optic neuropathy occurring in 1 in 50,000 individuals that features progressive loss in visual acuity leading, in many cases, to legal blindness. Phenotypic variations and loss of retinal ganglion cells, as found in Leber hereditary optic neuropathy (LHON), have suggested possible mitochondrial impairment. The OPA1 gene has been localized to 3q28-q29 (refs 13-19). We describe here a nuclear gene, OPA1, that maps within the candidate region and encodes a dynamin-related protein localized to mitochondria. We found four different OPA1 mutations, including frameshift and missense mutations, to segregate with the disease, demonstrating a role for mitochondria in retinal ganglion cell pathophysiology.

Amino Acid Sequence↗
PubMed2000

Spectrum of retGC1 mutations in Leber's congenital amaurosis.

Leber's congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies responsible for congenital blindness. Genetic heterogeneity of LCA has been suspected since the report by Waardenburg of normal children born to affected parents. In 1995 we localised the first disease causing gene, LCA1, to chromosome 17p13 and confirmed the genetic heterogeneity. In 1996 we ascribed LCA1 to mutations in the photoreceptor-specific guanylate cyclase gene (retGC1). Here, we report on the screening of the whole coding sequence of the retGC1 gene in 118 patients affected with LCA. We found 22 different mutations in 24 unrelated families originating from various countries of the world. It is worth noting that all retGC1 mutations consistently caused congenital cone-rod dystrophy in our series, confirming the previous genotype-phenotype correlations we were able to establish. RetGC1 is an essential protein implicated in the phototransduction cascade, especially in the recovery of the dark state after the excitation process of photoreceptor cells by light stimulation. We postulate that the retGC1 mutations hinder the restoration of the basal level of cGMP of cone and rod photoreceptor cells, leading to a situation equivalent to consistent light exposure during photoreceptor development, explaining the severity of the visual disorder at birth.

Blindness↗
PubMed2000

Reconstruction of a parotidectomy defect using a paraumbilical perforator flap without deep inferior epigastric vessels.

A 37-year-old woman who underwent a parotidectomy for acinic cell carcinoma was referred for correction of the resulting defect. As an assistant principal, the patient was often in public and, because she was somewhat self-conscious about her facial deformity, she sought reconstruction. Physical examination revealed a pre-auricular soft-tissue defect that measured approximately 5 x 5 cm. After consultation with the patient, microsurgical transfer of fat from the lower abdomen based on branches of the deep inferior epigastric vessels, rather than the deep inferior epigastric artery and vein itself, was planned. A vertical skin ellipse measuring 6 x 5 cm was raised from the right lower abdomen with a pedicle consisting of only a branch of the deep inferior epigastric artery and vein. The donor vessels were then microsurgically anastomosed to the superficial temporal artery and vein on the left side of the face. Two weeks postoperatively the flap was defatted, with removal of the skin-monitoring island. The patient continues to do well with a normal contour of the face and decreased anxiety secondary to correction of her facial deformity.

Adult↗
PubMed2000

Factor VIII inhibitors. Potential for prevention of inhibitor formation by immune tolerance.

Factor VIII inhibitory antibodies occur following treatment in more than 30% of subjects with severe factor VIII deficiency. Almost all inhibitor formation occurs in subjects with little if any circulating factor VIII. In the absence of in utero exposure to endogenous or maternal factor VIII, these subjects probably recognize factor VIII as a non-self antigen; in other words, their immune systems fail to become tolerant to factor VIII. This opens up the possibility of preventing inhibitor formation by neonatal induction of tolerance to factor VIII. The various possible approaches include prenatal or neonatal tolerance by the parenteral or oral administration of purified factor VIII protein or factor VIII-encoding DNA. The results of preliminary experiments in mice indicate that feeding newborns a series of low doses of factor VIII does not suppress induction of anti-factor VIII antibody. Whether tolerance can be achieved by feeding mice high doses of factor VIII or by intrauterine or neonatal administration of factor protein or DNA remains to be determined.

Animals↗
PubMed2000

Syntaxin 7 and VAMP-7 are soluble N-ethylmaleimide-sensitive factor attachment protein receptors required for late endosome-lysosome and homotypic lysosome fusion in alveolar macrophages.

Endocytosis in alveolar macrophages can be reversibly inhibited, permitting the isolation of endocytic vesicles at defined stages of maturation. Using an in vitro fusion assay, we determined that each isolated endosome population was capable of homotypic fusion. All vesicle populations were also capable of heterotypic fusion in a temporally specific manner; early endosomes, isolated 4 min after internalization, could fuse with endosomes isolated 8 min after internalization but not with 12-min endosomes or lysosomes. Lysosomes fuse with 12-min endosomes but not with earlier endosomes. Using homogenous populations of endosomes, we have identified Syntaxin 7 as a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) required for late endosome-lysosome and homotypic lysosome fusion in vitro. A bacterially expressed human Syntaxin 7 lacking the transmembrane domain inhibited homotypic late endosome and lysosome fusion as well as heterotypic late endosome-lysosome fusion. Affinity-purified antibodies directed against Syntaxin 7 also inhibited lysosome fusion in vitro but had no affect on homotypic early endosome fusion. Previous work suggested that human VAMP-7 (vesicle-associated membrane protein-7) was a SNARE required for late endosome-lysosome fusion. A bacterially expressed human VAMP-7 lacking the transmembrane domain inhibited both late endosome-lysosome fusion and homotypic lysosome fusion in vitro. These studies indicate that: 1) fusion along the endocytic pathway is a highly regulated process, and 2) two SNARE molecules, Syntaxin 7 and human VAMP-7, are involved in fusion of vesicles in the late endocytic pathway in alveolar macrophages.

Animals↗
PubMed2000

Correlated molecular-field theory for ising models

The critical temperature T(c) of Ising models is obtained quite accurately by simple improvements over the standard molecular-field theory. The important physical effect we include is that the effective field of neighboring spins is influenced by the spin state of the central spin. When used in combination with a self-consistency condition, this correlated molecular-field theory leads to estimates of T(c) more accurate than those obtained from the Bethe-Peierls-Weiss approximation.

Journal Article↗
PubMed2000

Static light scattering studies of OmpF porin: implications for integral membrane protein crystallization.

Integral membrane proteins carry out some of the most important functions of living cells, yet relatively few details are known about their structures. This is due, in large part, to the difficulties associated with preparing membrane protein crystals suitable for X-ray diffraction analysis. Mechanistic studies of membrane protein crystallization may provide insights that will aid in determining future membrane protein structures. Accordingly, the solution behavior of the bacterial outer membrane protein OmpF porin was studied by static light scattering under conditions favorable for crystal growth. The second osmotic virial coefficient (B22) was found to be a predictor of the crystallization behavior of porin, as has previously been found for soluble proteins. Both tetragonal and trigonal porin crystals were found to form only within a narrow window of B22 values located at approximately -0.5 to -2 X 10(-4) mol mL g(-2), which is similar to the "crystallization slot" observed for soluble proteins. The B22 behavior of protein-free detergent micelles proved very similar to that of porin-detergent complexes, suggesting that the detergent's contribution dominates the behavior of protein-detergent complexes under crystallizing conditions. This observation implies that, for any given detergent, it may be possible to construct membrane protein crystallization screens of general utility by manipulating the solution properties so as to drive detergent B22 values into the crystallization slot. Such screens would limit the screening effort to the detergent systems most likely to yield crystals, thereby minimizing protein requirements and improving productivity.

Bacterial Outer Membrane Proteins↗