Biomedical subjects

B Morse

Publications and source records attributed to B Morse.

At least 19 recordsLinked to original sources

PubMed2001

Human casein kinase Idelta phosphorylation of human circadian clock proteins period 1 and 2.

Casein kinase Iepsilon (CKIepsilon), a central component of the circadian clock, interacts with and phosphorylates human period protein 1 (hPER1) [Keesler, G.A. et al. (2000) NeuroReport 5, 951-955]. A mutation in CKIepsilon causes a shortened circadian period in Syrian Golden hamster. We have now extended our previous studies to show that human casein kinase Idelta (hCKIdelta), the closest homologue to hCKIepsilon, associates with and phosphorylates hPER1 and causes protein instability. Furthermore, we observed that both hCKIdelta and hCKIepsilon phosphorylated and caused protein instability of human period 2 protein (hPER2). Immunohistochemical staining of rat brains demonstrates that CKIdelta protein is localized in the suprachiasmatic nuclei, the central location of the master clock. These results indicate that CKIdelta may play a role similar to CKIepsilon, suggesting that it may also be involved in regulating circadian rhythmicity by post-translation modification of mammalian clock proteins hPER1 and 2.

Animals↗

PubMed2001

Anatomic modeling from unstructured samples using variational implicit surfaces.

We describe the use of variational implicit surfaces (level sets of an embedded generating function modeled using radial basis interpolants) in anatomic modeling. This technique allows the practitioner to employ sparsely and unevenly sampled data to represent complex biological surfaces, including data acquired as a series of non-parallel image slices. The method inherently accommodates interpolation across irregular spans. In addition, shapes with arbitrary topology are easily represented without interpolation or aliasing errors arising from discrete sampling. To demonstrate the medical use of variational implicit surfaces, we present the reconstruction of the inner surfaces of blood vessels from a series of endovascular ultrasound images.

Animals↗

PubMed1999

Nickel subsulfide is similar to potassium dichromate in protecting normal human fibroblasts from the mutagenic effects of benzo[a]pyrene diolepoxide.

The cellular response to multiple carcinogen treatment has not been extensively studied, even though the effect of individual carcinogens is, in many cases, well known. We have previously shown that potassium dichromate can protect normal human fibroblasts from the mutagenic effects of benzo[a]pyrene diolepoxide (BPDE), and that this effect may be via an oxidative stress mechanism [Tesfai et al. (1998) Mutat Res 416:159-168]. Here, we extend our previous work by showing that nickel subsulfide can produce the some effect. Normal human fibroblasts, preincubated with nickel subsulfide for 46 hr followed by a coincubation of nickel subsulfide and BPDE for 2 hr, showed a dramatic reduction in the mutant frequency of the hypoxanthine (guanine)phosphoribosyl-transferase (HPRT) gene when compared to cells treated only with BPDE. The preincubation period with nickel subsulfide was necessary to see the antagonistic effect, since it was not observed if the cells were simply incubated with both carcinogens for 2 hr. The extent of the antagonistic effect was nickel subsulfide dose-dependent and also appeared to be species-specific, since the effect was not observed when Chinese hamster fibroblasts were tested. Finally, the antagonistic effect of the nickel subsulfide was eliminated by vitamin E, suggesting that production of reactive oxygen species by the nickel may be required. This data, along with our previous work, suggest that the antagonistic effect we observe is not chromium-specific, and that it could be species-specific.

Animals↗

PubMed1996

Cloning and sequencing of human gp330, a Ca(2+)-binding receptor with potential intracellular signaling properties.

We present here the complete primary structure of human gp330, the human variant of the principal kidney autoantigen causing Heymann membranous glomerulonephritis in rats. The deduced 4655 amino acid residues give a calculated molecular mass of 519636 Da for the mature protein and consists of a probable 25-amino-acid N-terminal signal peptide sequence, an extracellular region of 4398 amino acids, a single transmembrane-spanning domain of 23 amino acids, and an intracellular C-terminal region of 209 amino acid residues. Three types of cysteine-rich repeats characteristic of the low density lipoprotein receptor (LDLR) superfamily are present in human gp330. In the extracellular region, there are a total of 36 LDLR ligand-binding repeats, comprising four distinct domains, 16 growth factor repeats separated by eight YWTD spacer regions, and one epidermal growth factor-like repeat. No consensus cleavage sequence for the processing endoprotease furin is detected in human gp330. The intracellular tail contains not only two copies of the F(X)NPXY coated-pit mediated internalization signal characteristic of LDLR superfamily members, but also intriguing and potentially functional motifs including several Src-homology 3 recognition motifs, one Src-homology 2 recognition motif for the p85 regulatory subunit of phosphatidylinositol 3-kinase, and additional sites for protein kinase C, casein kinase II and cAMP-/cGMP-dependent protein kinase. There is approximately 77% amino acid identity between human and rat gp330 with minor differences between the extracellular and intracellular regions. Recently gp330 has been implicated in Ca2+ regulation in the parathyroid, the placenta, and the renal tubule, but its overall physiological and pathological role still remains uncertain.

Amino Acid Sequence↗

PubMed1993

The cloning of a receptor-type protein tyrosine phosphatase expressed in the central nervous system.

We have isolated cDNA clones and deduced the complete amino acid sequence of a large receptor-type protein tyrosine phosphatase containing 2307 amino acids. The human gene encoding this phosphatase, denoted RPTP beta (or PTP zeta), has been localized to chromosome 7q31-33. RPTP beta is composed of a large extracellular domain, a single transmembrane domain, and a cytoplasmic portion with two tandem catalytic domains. We have also cloned a variant of RPTP beta lacking 859 amino acids from the extracellular domain but with intact transmembrane and cytoplasmic domains. Interestingly, the amino-terminal region of the extracellular domain of RPTP beta contains a stretch of 266 amino acids with striking homology to the enzyme carbonic anhydrase. Immunoprecipitation experiments from a human neuroblastoma cell line indicate that the apparent molecular mass of the core and glycosylated forms of RPTP beta are approximately 250 and 300 kDa, respectively. Northern blot analysis shows that RPTP beta is strictly expressed in the central nervous system. In situ hybridization was used to further localize the expression to different regions of the adult brain including the Purkinje cell layer of the cerebellum, the dentate gyrus, and the subependymal layer of the anterior horn of the lateral ventricle. Hence, RPTP beta represents the first mammalian tyrosine phosphatase whose expression is restricted to the nervous system. The high level of expression of RPTP beta transcripts in the ventricular and subventricular zones of the embryonic mouse brain suggests the importance of this tyrosine phosphatase in the development of the central nervous system.

Adult↗

PubMed1993

Modulation of mdr-1 expression by a H-ras oncogene in a human colon carcinoma cell line.

In an established colon differentiation model, introduction of a c-H-ras-1 oncogene into a poorly differentiated human colon carcinoma cell line (Clone A) results in changes associated with the acquisition of a more differentiated phenotype. Down-regulation of mdr-1 mRNA was shown to accompany ras-related differentiation events resulting in decreased Pgp synthesis and a significant reduction in membrane Pgp as detected by immunoprecipitation, Western-blot and FACS analysis. Consistent with these observations was a reduction in Pgp-mediated drug resistance associated with Clone-A ras transfectants, with no alteration in drug sensitivity being observed with non-MDR drugs in these cells. An alternative differentiation model involves exposure of Clone-A cells to sodium butyrate. Under these conditions, differentiation-related changes resulted in up-regulation of mdr-1 mRNA and Pgp synthesis, although no alteration in drug sensitivity was recorded. In agreement with this observation, the levels of membrane-associated Pgp remained unchanged throughout the period of exposure to sodium butyrate. This study shows that modulation of Pgp expression in colon differentiation is dependent upon the differentiation induction agent used.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Constitutive expression of multidrug resistance in human colorectal tumours and cell lines.

In this study we report detection of mdr1 gene expression in the liver metastases of 7/11 patients with colon carcinoma and characterise the MDR phenotype associated with a panel of 19 human colon carcinoma cell lines. Within this panel, mdr1 mRNA biosynthesis and surface localisation of Pgp were assessed with respect to MDR functionality where the cell lines are representative of different clinical stages of tumour progression, metastatic potential and differentiation. The data indicates that constitutive levels of mdr1 mRNA/Pgp expression may not necessarily result in the functional expression of the MDR phenotype. While low levels of mdr1 mRNA/Pgp were detected in 5/8 well differentiated colon cell lines, only 2/8 were functionally MDR. In contrast, 10/11 moderate and poorly differentiated lines expressed mdr1 mRNA/Pgp and of these, 9/11 were functionally MDR. The phosphorylation status of the mature 170 kD P-glycoprotein and the surface localisation of this glycoprotein showed the strongest correlation with functionality. Analysis of cell lines for cross-resistance and chemosensitivity profiles against a battery of chemotherapeutic drugs suggests multiple mechanisms, in addition to Pgp, contribute to the overall resistance of colorectal cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1993

Identification of a carbonic anhydrase-like domain in the extracellular region of RPTP gamma defines a new subfamily of receptor tyrosine phosphatases.

The tyrosine phosphatase RPTP gamma is a candidate tumor suppressor gene since it is located on human chromosome 3p14.2-p21 in a region frequently deleted in certain types of renal and lung carcinomas. In order to evaluate its oncogenic potential and to explore its normal in vivo functions, we have isolated cDNAs and deduced the complete sequences of both human and murine RPTP gamma. The murine RPTP gamma gene has been localized to chromosome 14 to a region syntenic to the location of the human gene. Northern (RNA) blot analysis reveals the presence of two major transcripts of 5.5 and 8.5 kb in a variety of murine tissues. In situ hybridization analysis reveals that RPTP gamma mRNA is expressed in specific regions of the brain and that the localization of RPTP gamma changes during brain development. RPTP gamma is composed of a putative extracellular domain, a single transmembrane domain, and a cytoplasmic portion with two tandem catalytic tyrosine phosphatase domains. The extracellular domain contains a stretch of 266 amino acids with striking homology to the zinc-containing enzyme carbonic anhydrase (CAH), indicating that RPTP gamma and RPTP beta (HPTP zeta) represent a subfamily of receptor tyrosine phosphatases. We have constructed a model for the CAH-like domain of RPTP gamma based upon the crystal structure of CAH. It appears that 11 of the 19 residues that form the active site of CAH are conserved in RPTP gamma. Yet only one of the three His residues that ligate the zinc atom and are required for catalytic activity is conserved. On the basis of this model we propose that the CAH-like domain of RPTP gamma may have a function other than catalysis of hydration of metabolic CO2.

Amino Acid Sequence↗

PubMed1991

Cloning of the human serotonin 5-HT2 and 5-HT1C receptor subtypes.

We report the cloning and the deduced amino acid sequence of cDNAs encoding both the human serotonin 5-HT2 and 5-HT1C receptors. The human 5-HT2 and 5-HT1C receptors shared 87% and 90% amino acid homology, respectively, with their rat counterparts. The most divergent regions of the 5-HT2 receptor between human and rat were the N-terminal extracellular domain (75% homology) and the C-terminal intracellular domain (67% homology between amino acids 426-474). The greatest variability between the human and rat 5-HT1C receptors were at the N-terminal extracellular domain (78% homology) and the third cytoplasmic loop (71% homology). The availability of the cloned human 5-HT2 and 5-HT1C receptors will help facilitate the further understanding of the molecular pharmacology and physiology of these receptors.

Amino Acid Sequence↗

PubMed1991

Characterization of a human recombinant receptor-linked protein tyrosine phosphatase.

The receptor-linked tyrosine phosphatase RPTP alpha from human brain (Kaplan, R., Morse, B., Huebner, K., Croce, C., Howk, R., Ravera, M., Ricca, G., Jaye, M., and Schlessinger, J. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 7000-7004) was expressed in insect cells following infection with recombinant baculovirus. Two major forms of the enzyme, with molecular sizes of 98 kDa and 114 kDa, were detected by immunoblot analysis. This heterogeneity could be ascribed to N-linked glycosylation on the basis of two lines of evidence; namely, blockage of glycosylation with tunicamycin in vivo and removal of carbohydrates by endoglycosidase F in vitro. The 114-kDa form was purified to homogeneity by chromatography on Superose 12 and Mono Q. Compared to the low Mr placenta and T-cell tyrosine phosphatases, RPTP alpha displayed a low optimum pH of 6 and a high Km in the micromolar range toward two artificial substrates (tyrosyl-phosphorylated myelin basic protein and modified lysozyme, respectively). Most effectors had a different and often an opposite influence on phosphatase activity depending on the nature of the substrate and the pH at which the assays were performed. Determination of Km and Vmax values for RPTP alpha suggests that the enzyme could exist in low and high substrate affinity states.

Baculoviridae↗

PubMed1991

Receptor protein-tyrosine phosphatase gamma is a candidate tumor suppressor gene at human chromosome region 3p21.

PTPG, the gene for protein-tyrosine phosphatase gamma (PTP gamma), maps to a region of human chromosome 3, 3p21, that is frequently deleted in renal cell carcinoma and lung carcinoma. One of the functions of protein-tyrosine phosphatases is to reverse the effect of protein-tyrosine kinases, many of which are oncogenes, suggesting that some protein-tyrosine phosphatase genes may act as tumor suppressor genes. A hallmark of tumor suppressor genes is that they are deleted in tumors in which their inactivation contributes to the malignant phenotype. In this study, one PTP gamma allele was lost in 3 of 5 renal carcinoma cell lines and 5 of 10 lung carcinoma tumor samples tested. Importantly, one PTP gamma allele was lost in three lung tumors that had not lost flanking loci. PTP gamma mRNA was expressed in kidney cell lines and lung cell lines but not expressed in several hematopoietic cell lines tested. Thus, the PTP gamma gene has characteristics that suggest it as a candidate tumor suppressor gene at 3p21.

Animals↗

PubMed1991

Comparison of EGF receptor sequences as a guide to study the ligand binding site.

While murine and human EGF-receptor (EGF-R) bind mammalian EGF with high affinity their chicken counterpart has approximately 300 fold reduced binding affinity towards mammalian EGF. We now cloned and sequenced the extracellular ligand binding domain of murine EGF-R in order to define the amino-acids which comprise the binding site for EGF. Comparison of human, murine and chicken EGF-R allows the identification of amino acid substitutions which are conservative and would not affect EGF binding, substitutions which are responsible for the low affinity binding of EGF to chicken EGF-R and those responsible for the high affinity binding of EGF to mammalian EGF-R. This analysis will enable future design of point mutations in the EGF-R which will restore the high affinity binding for EFG typical of human or murine EGF-R.

Amino Acid Sequence↗

PubMed1990

Cloning of three human tyrosine phosphatases reveals a multigene family of receptor-linked protein-tyrosine-phosphatases expressed in brain.

A human brainstem cDNA library in bacteriophage lambda gt11 was screened under conditions of reduced hybridization stringency with a leukocyte common antigen (LCA) probe that spanned both conserved cytoplasmic domains. cDNA encoding a receptor-linked protein-tyrosine-phosphatase (protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48), RPTPase alpha, has been cloned and sequenced. Human RPTPase alpha consists of 802 amino acids. The extracellular domain of 150 residues includes a hydrophobic signal peptide and eight potential N-glycosylation sites. This is followed by a transmembrane region and two tandemly repeated conserved domains characteristic of all RPTPases identified thus far. The gene for RPTPase alpha has been localized to human chromosome region 20pter-20q12 by analysis of its segregation pattern in rodent-human somatic cell hybrids. Northern blot analysis revealed the presence of two major transcripts of 4.3 and 6.3 kilobases. In addition to RPTPase alpha, two other RPTPases (beta and gamma), identified in the same screen, have been partially cloned and sequenced. Analysis of sequence comparisons among LCA, the LCA-related protein LAR, and RPTPases alpha, beta, and gamma reveals the existence of a multigene family encoding different RPTPases, each containing a distinct extracellular domain, a single hydrophobic transmembrane region, and two tandemly repeated conserved cytoplasmic domains.

Amino Acid Sequence↗

PubMed1989

Somatic mutation and transcriptional deregulation of myc in endemic Burkitt's lymphoma disease: heptamer-nonamer recognition mistakes?

We examined the structure and expression of the myc protooncogene in DNA extracted from a primary (uncultured) endemic Burkitt's lymphoma sample designated eBL3. Dot and Northern (RNA) blot analyses demonstrated extreme levels of myc RNA in the eBL3 sample. Nearly complete sequence data of the altered myc locus isolated from eBL3 DNA demonstrated extensive mutations (duplications, insertions, and deletions) in critical myc regulatory regions. Taken together, the data support the idea that myc transcriptional deregulation in Burkitt's lymphoma disease may be a consequence of the position and number of mutations produced within and around the myc locus. Furthermore, the myc exon-1-intron-1 hypermutable PvuII site is part of a potential heptamer-nonamer recognition sequence, suggesting a mechanism for mutation in endemic Burkitt's lymphoma disease.

Animals↗

PubMed1988

Insertional mutagenesis of the myc locus by a LINE-1 sequence in a human breast carcinoma.

The proto-oncogene c-myc is the cellular homologue of the transforming sequence carried by the avian myelocytomastosis virus MC29. A growing body of evidence implicates structural and functional alterations in and around proto-oncogenes such as c-myc in tumorogenesis. Here we report that comparison of the structure of myc from a ductal adenocarcinoma of the breast and from normal breast tissue of the same patient (Sc) revealed a tumour-specific rearrangement of one myc locus and amplification of the other myc locus. (For myc reviews see refs 1-4; for myc involvement in breast neoplasia see refs 5-7.) Within the second intron of the rearranged locus was a non-myc sequence with nearly complete homology to a long interspersed repetitive element (a LINE-1 sequence or L1). In this case, the L1 sequence has functioned as a mobile genetic element to produce a somatic mutation.

Base Sequence↗

PubMed1985

Homologous recombination between autonomously replicating plasmids in mammalian cells.

The ability of autonomously replicating plasmids to recombine in mammalian cells was investigated. Two deletion plasmids of the eukaryotic-prokaryotic shuttle vector pSV2neo were cotransfected into transformed monkey COS cells. Examination of the low molecular weight DNA isolated after 48 hr of incubation revealed that recombination between the plasmids had occurred. The DNA was also used to transform recA- E. coli. Yield of neoR colonies signified homologous recombination. Examination of the plasmid DNA from these colonies confirmed this view. Double-strand breaks in one or both of the input plasmids at the sites of deletion resulted in an enhancement of recombination frequency. The recombination process yielded monomeric and dimeric molecules. Examination of these molecules revealed that reciprocal recombination as well as gene conversion events were involved in the generation of plasmids bearing an intact neo gene. The COS cell system we describe is analogous to study of bacteriophage recombination and yeast random-spore analysis.

Animals↗

PubMed1984

In-utero gunshot wound to the head. Use of intraoperative ultrasonography for localization of an intracerebral projectile.

Approaching full gestational age, a 1700-g male fetus sustained a penetrating gunshot wound to the left parietal region of the head while in utero. The child was delivered by emergency caesarean section. Initially in profound fetal shock and with almost no neurological function, the child was eventually stabilized. A posttraumatic intracerebral porencephalic cyst developed, with the projectile moving freely within the confines of the cyst cavity. Six weeks after the initial injury, the patient underwent an operation for extraction of the projectile. The Neuro SectOR ATL ultrasound probe was used intraoperatively and was instrumental in determining the exact position of the intracerebral projectile.

Brain Injuries↗

PubMed1983

Abdominal aspiration biopsies. Sonographic v computed tomographic guidance.

One hundred eighty-four diagnostic aspirations performed on 169 patients were reviewed (1) to define the decision process regarding which guidance method (sonography v computed tomography) should be used on any given patient, and (2) to determine, once a guidance method was chosen, its accuracy and complication rate. Sonographic guidance (84%) proved to be an effective method for obtaining a correct diagnosis in 98% (110/112) of cystic masses and 79% (34/43) of solid masses. Computed tomography (16%) was used when sonography could not identify the mass or when the mass was small, deeply located, and often solid. Computed tomographic guidance provided a correct diagnosis in 100% (13/13) of cystic masses and 81% (13/16) of solid masses.

Abdomen↗