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Biomedical subjects

M Scott

Publications and source records attributed to M Scott.

At least 199 records · Page 11Linked to original sources
PubMed1994

Primers frequently used for detecting the t(14;18) major breakpoint also amplify Epstein-Barr viral DNA.

We observed a potentially misinterpretable polymerase chain reaction (PCR) amplification product generated with standard primers used to detect the major breakpoint region (mbr) of chromosomal translocation t(14;18). This unexpected phenomenon was initially detected during attempts to transform follicular lymphomas in vitro with Epstein-Barr virus (EBV). Additional studies were performed using the EBV-producing cell line MCUV5, cell lines from EBV-transformed normal B-lymphocytes, and an excised lymph node from a patient with documented EBV-associated infectious mononucleosis. These samples consistently produced a 167-base pair product, which was indistinguishable from a t(14;18) lymphoma product when viewed on ethidium bromide-stained gels. Through DNA sequencing and gene bank analysis, the product was identified as a portion of the EBV genome. A mbr-specific 20-base oligonucleotide probe was able to discriminate between true translocations and the EBV-related amplifications. These results underscore the importance of employing a specific detection system, and comprehensively screening primers when working with PCR.

Animals↗
PubMed1994

Maternal drinking during pregnancy: attention and short-term memory in 14-year-old offspring--a longitudinal prospective study.

A large and compelling experimental literature has documented the adverse impact of prenatal alcohol exposure on the developing brain of the offspring. This is the first report of adolescent attention/memory performance and its relationship with prenatal alcohol exposure in a population-based, longitudinal, prospective study (n = 462) involving substantial covariate control and "blind" examiners. Prenatal alcohol exposure was significantly related to attention/memory deficits in a dose-dependent fashion. A latent variable reflecting 13 measures of maternal drinking was correlated 0.26 with a latent variable representing 52 scores from 6 tests measuring various components of attention and short-term memory performance. The number of drinks/occasion was the strongest alcohol predictor. Fluctuating attentional states, problems with response inhibition, and spatial learning showed the strongest association with prenatal alcohol exposure. A latent variable reflecting the pattern of attention/memory deficits observed at 14 years correlated 0.67 with a composite pattern of deficits previously detected on neurobehavioral tests administered during the first 7 years of life. The 14-year attention/memory deficits observed in the present study appear to be the adolescent sequelae of deficits observed earlier in development. As is usual in such studies, not all exposed offspring showed deficits.

Adolescent↗
PubMed1994

Intestinal varices: treatment with the transjugular intrahepatic portosystemic shunt.

PURPOSE: To perform a retrospective evaluation of transjugular intrahepatic portosystemic shunt (TIPS) placement for treatment of intestinal varices. MATERIALS AND METHODS: TIPS were placed in nine patients (six women and three men, aged 36-85 years [mean, 64 years]) with small- (n = 6) and large- (n = 3) intestinal varices. Six patients were actively bleeding at the time of shunt placement. One patient with colon cancer underwent prophylactic TIPS placement for variceal decompression before colectomy. RESULTS: The mean preprocedure portosystemic gradient of 26.8 mm Hg +/- 5.1 was reduced to 8.8 mm Hg +/- 2.9. Bleeding was controlled in all but one case, in which supplemental variceal embolization was required. Two patients died within 5 days of TIPS placement of preexisting multisystem failure. Three patients died of unrelated causes at 2, 6, and 7 months. The remaining patients were alive an average of 15 months after TIPS placement. There was no recurrent bleeding in any case. CONCLUSION: TIPS placement is an effective method of decompressing intestinal varices.

Adult↗
PubMed1994

Cellular mechanisms of captopril-induced matrix remodeling in Syrian hamster cardiomyopathy.

BACKGROUND: Although angiotensin-converting enzyme (ACE) inhibitors have become a mainstay of treatment for chronic congestive heart failure (CHF), it is not known whether the cardiac remodeling effects are a secondary phenomenon, resulting from ACE inhibitors' hemodynamic actions of afterload reduction, or occur through an independent mechanism. METHODS AND RESULTS: We used ultrasonic tissue characterization to define potentially salutary effects of treatment with ACE inhibitors on the material properties of the heart and its potential influence on cardiac remodeling at the cellular level. Ten 1-month-old, cardiomyopathic (CM) Syrian hamsters and 6 normal (NL) hamsters were treated with captopril (2 g/L water ad libitum), and 10 CM hamsters and 10 NL hamsters were maintained untreated for 3 months. Hearts were excised, and backscattered radiofrequency data were acquired from 1200 independent sites from each specimen with a high-resolution 50-MHz acoustic microscope for calculation of integrated backscatter (IB). Treatment with captopril reduced left ventricular mass, calcium concentration, and IB in CM hearts without affecting myofiber size or collagen concentration. The IB from grossly normal regions of myocardium in NL hamsters, treated CM hamsters, and untreated CM hamsters was not significantly different. The IB from the microscopic regions of scar tissue in treated CM hamsters was significantly less (P = .0004) than that from scar tissue in untreated CM hamsters. CONCLUSIONS: The reduced IB from treated scar tissue components reflects specific alterations in the material properties (elastic stiffness, density) of fibrous regions in CM hearts induced by captopril. This is the first report that defines specific cellular effects of ACE inhibitors on the material properties of isolated components of cardiac tissue in experimental cardiomyopathy. These alterations in material properties of scar tissue components represent a potential mechanism for the salutary actions of ACE inhibitors in heart failure.

Animals↗
PubMed1994

Expression pattern and partial sequence analysis of a fetal bovine myosin heavy-chain gene.

A fragment of a bovine myosin heavy-chain (MHC) gene approximately 15 kbp in size (designated MHC 67) was isolated from a bovine genomic DNA library. The direction of transcription was determined, and preliminary experiments indicated that the gene was expressed in fetal skeletal muscle. The expression pattern of this gene was, therefore, evaluated in detail using northern blots containing RNA from eleven different bovine muscle and nonmuscle tissues at three developmental ages. A restriction fragment of clone MHC 67 containing the 3' untranslated sequence (which is specific for each MHC gene) was used as a probe. This gene fragment hybridized predominantly to RNA from fetal skeletal muscles and did not hybridize to RNA from either neonatal or adult skeletal muscles (red or white), smooth muscle tissue, or nonmuscle tissue. A 7-kb EcoRI fragment containing both translated and untranslated regions surrounding the 3' end of the gene was subcloned into pBluescript II KS+ and partially sequenced. When these bovine sequences were aligned to that of the human and rat skeletal and cardiac MHC genes, we found that these sequences corresponded to exons 31, 32, and 33, and that they had homology with human perinatal and fetal MHC as high as 90% at the nucleotide level and 97% at the amino acid level. Comparison of the nucleotide sequences of isoform-specific 3' nontranslated regions from bovine, human, and rat genes further verify that the MHC 67 clone encodes the bovine fetal or perinatal MHC isoform.

Amino Acid Sequence↗
PubMed1994

Defective CD3 mediated proliferation and LPS responsiveness in multiple sclerosis.

Multiple sclerosis [MS] is a chronic inflammatory disease of the central nervous system which has been postulated to be a T cell mediated disease. We examined proliferation of mononuclear cells to OKT3 mAb, Con A, ionomycin plus PMA and human myelin basic protein in subjects with relapsing-remitting and chronic progressive multiple sclerosis. Age and sex matched controls demonstrated a good proliferation to anti-CD3 mAb whereas subjects with relapsing-remitting multiple sclerosis showed a significantly decreased anti-CD3 mAb response. There was no difference in mitogen, ionomycin plus PMA or human MBP proliferation between controls and MS subjects. There was also a trend for decreasing anti-CD3 mAb proliferation in patients with chronic progressive multiple sclerosis compared to controls. LPS significantly decreased anti-CD3 mAb proliferation in controls but not in the MS subjects. An abnormality of signal transduction via the CD3 T-cell receptor complex in T cells and responsiveness to the immunomodulatory effect of IFN inducers may exist in multiple sclerosis.

CD3 Complex↗
PubMed1994

In vitro proliferation by cells mobilized into the peripheral blood for collection and autologous transplantation.

We have investigated the properties of mobilized, cryopreserved, peripheral blood stem cells (PBSC), collected by leukapheresis over a period of 5 days, from eight myeloma patients in clinical remission. Cells were mobilized by treatment with cyclophosphamide and granulocyte colony-stimulating factor (G-CSF), and each day's collection was evaluated for its content of CD34+ cells, colony-forming units granulocyte/macrophage (CFU-GM), and plastic-adherent pre-CFU-GM. Peak values for these three parameters were observed at different times in different patients. There was no correlation between CD34+ content and CFU-GM, but there was some (r = 0.65) between CD34 numbers and colonies generated from a delta assay initiated using plastic-adherent pre-CFU-GM. In suspension cultures, the cells grew exponentially for 50 days. Thereafter, they did not divide, although they remained viable in culture for up to 1 month longer. Suspension cultures of PBSC grown with interleukin-3 (IL-3) displayed a predominantly myelomonocytic phenotype, but some megakaryocytes and erythroid cells were observed consistently. These results indicate that pre-CFU-GM in PBSC collections are capable of generating large numbers of clonogenic progeny in liquid culture and are capable of producing multiple lineages of differentiation.

Antigens, CD↗
PubMed1994

Silicone breast implant rupture: common/serious complication?

Of the potential health risks of silicone breast implants it is the concern about implant durability, life span and the possible association with connective tissue disease which has attracted most attention. A prospective study addressing these factors was therefore undertaken over an 11 month period. 51 patients presenting with significant capsular contracture, suspected prosthesis rupture or unrelieved implant-induced anxiety underwent revisional breast surgery after biochemical, haematological and immunological screening. Of these 51 patients (83 breasts), 14 (19 breasts) had ruptured implants (23% incidence). These were all smooth prostheses belonging to a cohort manufactured more than 10 years ago; their mean in situ duration being 12 years vs. 5.5 years for the intact group (p = 0.0024; Kruskal-Wallis one-way ANOVA). There were no systemic complications from implant rupture and the mean blood silicon level was normal. One patient with pre-existing pernicious anaemia had elevated autoantibodies. The mean ESR in the ruptured implant group was 6 mm/hour. It is concluded that rupture of breast implants is not as uncommon as hitherto thought and is strongly correlated with their in situ duration. In this study implant gel leakage was not associated with serious systemic effects.

Adult↗
PubMed1994

Use of pediatric physician extenders in pediatric and neonatal intensive care units.

OBJECTIVES: To determine present and future use of pediatric physician extenders in neonatal and pediatric intensive care units (ICUs). DESIGN: Descriptive, prospective, questionnaire survey. PARTICIPANTS: One hundred thirty hospitals represented by members of the Pediatric Section of the Society of Critical Care Medicine and 18 randomly selected hospitals identified as having no pediatric intensivist. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: One hundred one (68.2%) of 148 responding institutions employed physician extenders and 69 (46.7%) employed pediatric physician extenders. Eighty percent of the hospitals using pediatric physician extenders employed pediatric nurse practitioners and 25% employed physician assistants. Of the 69 hospitals that employed pediatric physician extenders, 51 (73.9%) hospitals utilized them in neonatal ICUs and 12 (17.4%) hospitals used them in the pediatric ICUs. Institutions that did or did not employ pediatric physician extenders in pediatric ICUs were comparable in all factors studied, except for the perception of childcare physician staffing shortages. Duties competently performed by pediatric physician extenders did not differ between pediatric nurse practitioners and physician assistants and were similar to those duties of a second-year pediatric resident. More than 40% of institutions expected to increase the use of pediatric physician extenders in neonatal and pediatric ICUs and they expected to provide the majority of the specialty training required. CONCLUSIONS: Pediatric physician extenders are extensively employed in pediatric and neonatal ICUs. They are perceived to perform at the level of second-year pediatric residents and are strongly supported by staff physicians and residents. It appears that more pediatric physician extenders will be employed in pediatric and neonatal ICUs in the future.

Chi-Square Distribution↗
PubMed1994

Standard polymerase chain reaction analysis does not detect t(14;18) in reactive lymphoid hyperplasia.

There are conflicting data regarding the detection of t(14;18) in reactive lymphoid hyperplasia (RLH) by the polymerase chain reaction (PCR). Although most studies have not detected t(14;18), several groups have definitively shown that a very low number of cells with this translocation (one in 10(5) to 10(6)) are present in a significant proportion of follicular hyperplasias. Review of the methods from these series reveals that modifications of the PCR assay (ie, enhanced sensitivity steps such as seminesting, lengthy autoradiographic exposure times, multiple aliquot reactions of single samples, and/or high concentrations of template DNA) are probably necessary to detect t(14;18) in RLH. We evaluated a diverse set of 111 RLH (85 lymph nodes, 22 tonsils, and four other sites) from patients of different age groups (age range, 9 months to 80 years) to determine if a standard PCR assay would amplify t(14;18). Of these, 61 (55%) specimens had a prominent follicular hyperplastic component. Fifty-seven follicular lymphomas served as a control group. Polymerase chain reaction was performed as a single-run, two-primer-based assay for major breakpoint region bcl-2 translocations (5' major breakpoint region primer and 3' immunoglobulin heavy-chain gene-joining region consensus primer). Two different types of thermocyclers were employed. A metal block thermocycler was used with 35 cycles of amplification on 500 ng to 1 micrograms of genomic DNA, and a separate air thermocycler was used with 45 cycles of amplification on 50 ng of genomic DNA. Product detection was carried out through ethidium bromide staining and UV gel illumination, along with a digoxigenin-alkaline phosphatase-based, internal major breakpoint region oligonucleotide probe system. We found no amplified t(14;18) products in any RLH. In contrast, 36 (63%) of 57 follicular lymphomas showed t(14;18) (published range for detection of major breakpoint region translocations by PCR, 31% to 74%). Moreover, the assay's sensitivity, estimated through dilution studies, was to one in 10(4) to 10(5) cells. Although theoretically possible, our data suggest that there is practically no risk of amplifying a t(14;18) from RLH when utilizing a standard PCR assay.

Adolescent↗
PubMed1994

Biosynthesis of the prion proteins in scrapie-infected cells in culture.

Prions are small proteinaceous particles that transmit scrapie and other fatal encephalopathies of humans and animals, and that appear to be devoid of nucleic acids. The only known--and perhaps the sole--component of the scrapie prion is an abnormal host-encoded protein, the scrapie prion protein PrPSc. The biosynthesis of this pathological protein in the host cell, which is thus of paramount importance to prion replication, is still poorly understood. We are studying the biosynthesis and degradation of the scrapie prion protein PrPSc and of its normal isoform PrPC in scrapie-infected rodent cells in culture. PrPC is anchored to the plasma membrane through a glycosylphosphatidylinositol (GPI) moiety. In scrapie-infected mouse neuroblastoma N2a cells, PrPSc is formed post-translationally, probably from plasma membrane PrPC, in an unknown subcellular compartment that is readily accessible from the plasma membrane. Transport along the secretory pathway is necessary for PrPSc synthesis. In contrast to PrPC, PrPSc accumulates intracellularly, primarily in secondary lysosomes. The subcellular compartment(s) in which PrPSc is formed remain to be determined.

Animals↗
PubMed1994

Antimalarial quinones: redox potential dependence of methemoglobin formation and heme release in erythrocytes.

A number of quinones have been shown to be effective antimalarials. In addition some have been shown to have oxidant effects on glucose-6-phosphate dehydrogenase-deficient red cells. To clarify the mechanism of this oxidant effect and to determine whether it is a general property of antimalarial quinones, the effects of five compounds on red cells were studied. Two, 5-hydroxy-6-demethyl pentaquine (5H6DP) and menadione, caused marked methemoglobin production and the insertion of heme into the red-cell membrane. The other three, atovaquone, daphnetin, and menoctone, did not. The insertion of heme into membranes caused diminished deformability, and this might account for the hemolytic effects. Redox potentials of all five compounds were measured. The two quinones that caused heme release, menadione and 5H6DP, had redox potentials of -141 +/- 12 and -97 +/- 25 mV, respectively, which are similar to the reported redox potentials for hemoglobin. The other three quinones had redox potentials that were either significantly higher or lower. Thus only quinones of the appropriate redox potentials are likely to be toxic to red cells.

Antimalarials↗
PubMed1993

Peptide sequences selected by BA4, a tropoelastin-specific monoclonal antibody, are ligands for the 67-kilodalton bovine elastin receptor.

A 67-kDa cell-surface elastin/laminin receptor is expressed by fetal bovine ligamentum nuchae fibroblasts and neutrophils. Two hexapeptides, VGVAPG and PGAIPG, contained within hydrophobic domains of tropoelastin are binding sites for this receptor. Studies of recombinant tropoelastin proteins and synthetic peptides demonstrated that a monoclonal antibody, BA4, recognized peptide sequences similar to those recognized by the 67-kDa receptor. Taking advantage of this similarity, an "epitope library" containing random hexapeptides was screened with BA4. Four BA4-selected peptides (VGAMPG, VGMAPG, VGSLPG, and VGLSPG) were synthesized; studies of fibroblast and neutrophil migration support the hypothesis that these peptides are ligands of the 67-kDa receptor present on ligamentum nuchae fibroblasts and neutrophils. Two additional, physically similar tropoelastin peptides,AGAIPG and PGAVGP, were also identified as peptide ligands, and hence potential binding sites within tropoelastin, of the elastin receptor. These data suggest that the 67-kDa elastin/laminin receptor may interact with a wide range of structurally similar peptides containing amino acid substitutions involving small nonpolar and uncharged amino acids.

Amino Acid Sequence↗
PubMed1993

Propagation of prions with artificial properties in transgenic mice expressing chimeric PrP genes.

Transgenic mice expressing chimeric prion protein (PrP) genes derived from Syrian hamster (SHa) and mouse (Mo) PrP genes were constructed. One SHa/MoPrP gene, designated MH2M PrP, contains five amino acid substitutions encoded by SHaPrP, while another construct, designated MHM2 PrP, has two substitutions. Transgenic (Tg) (MH2M PrP) mice were susceptible to both Syrian hamster and mouse prions, whereas three lines expressing MHM2 PrP were resistant to Syrian hamster prions. The brains of Tg(MH2M PrP) mice dying of scrapie contained chimeric PrPSc and prions with an artificial host range favoring propagation in mice that express the corresponding chimeric PrP and were also transmissible, at reduced efficiency, to nontransgenic mice and hamsters. Our findings provide genetic evidence for homophilic interactions between PrPSc in the inoculum and PrPc synthesized by the host.

Animals↗
PubMed1993

Conversion of truncated and elongated prion proteins into the scrapie isoform in cultured cells.

The only known component of the infectious prion is a posttranslationally modified protein known as the scrapie isoform of the prion protein, PrPSc. Upon limited proteolysis, a protease-resistant fragment designated PrP 27-30 is formed. Using in vitro mutagenesis, we examined the role of the N and C termini in the formation of PrPSc in persistently infected, mouse neuroblastoma (ScN2a) cells. Neither deletion of amino acids 23-88, which are also removed by proteinase K in the formation of PrP 27-30, nor deletion of the five octapeptide repeats within this region altered synthesis of PrPSc. Elongation of PrP with one, two, four, or six octapeptide repeats in addition to the five found in wild-type PrP did not alter the synthesis of PrPSc. Truncation of the C terminus was accomplished by substituting a translation stop codon for the predicted glycosylinositol phospholipid (GPI) anchor-attachment signal corresponding to amino acids 231-254. Expression of this C-terminal PrP mutant in ScN2a cells produced PrPSc that appeared to lack a GPI anchor. We conclude that neither the GPI anchor nor the N-terminal 66 amino acids are required for the synthesis of PrPSc as measured by the acquisition of limited resistance to proteinase K digestion. Whether these truncated or elongated PrP molecules are competent to participate in the formation of infectious prions remains to be established.

Amino Acid Sequence↗
PubMed1993

Crystallization and preliminary X-ray analysis of the catalytic domain of xylanase a from Pseudomonas fluorescens subspecies cellulosa.

The catalytic domain of the xylan-degrading enzyme xylanase A, from Pseudomonas fluorescens subspecies cellulosa, has been expressed in Escherichia coli and crystallized. The crystals are well ordered and diffract to 1.8 A using X-rays generated at the Photon Factory in Japan. The crystals are orthorhombic, space group P2(1)2(1)2(1) with a = 95.7 A, b = 97.1 A and c = 149.8 A (all +/- 0.2 A). The similarity of the a and b cell edges, the intensity of the reflections along c* and the self rotation function results suggest a pseudo-tetragonal arrangement of molecules in the unit cell. There are probably four molecules in the asymmetric unit.

Binding Sites↗