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Biomedical subjects

J R Scott

Publications and source records attributed to J R Scott.

At least 217 records · Page 12Linked to original sources
PubMed1985

Relationship of M protein genes in group A streptococci.

The M protein of group A streptococci is considered one of the primary virulence determinants of this organism because it prevents phagocytosis. All of the 56 different M protein types of group A streptococci tested contain a DNA region that hybridizes with a labeled probe consisting of DNA encoding the type 6 M protein (emm6 gene). In addition, 2 of 3 functionally M- group A strains (strains that are successfully phagocytized) also contain this gene, but this DNA is not present in 1 M- strain. Of the other streptococcal groups, only groups C and G, which are closely related to group A, contain DNA that hybridizes with emm6. None of the non-streptococcal Gram-positive bacteria tested contains emm6-related DNA. In the strain from which emm6 was cloned, there appears to be only a single copy of this gene.

Antigens, Bacterial↗
PubMed1984

Changes in the management of severely Rh-immunized patients.

Since July 1, 1978, we have instituted the following changes in the management of severely Rh-immunized patients: (1) serial amniotic fluid optical density (delta OD450 ) values and real-time ultrasound scanning beginning at 21 weeks' gestation, (2) fetal transfusions as early as the twenty-third week, (3) ultrasound surveillance during and after intrauterine transfusions, and (4) planned premature delivery with neonatal exchange transfusions for selected cases between 29 to 32 weeks and for all patients after 32 weeks' gestation. The perinatal survival rate (83.8%) in 37 isoimmunized pregnancies managed with this regimen was significantly higher (p less than 0.05) than in 34 such pregnancies (55.9%) managed according to the protocol utilized during the previous four years.

Adult↗
PubMed1984

Streptococcal M6 protein expressed in Escherichia coli. Localization, purification, and comparison with streptococcal-derived M protein.

Type 6 streptococcal M protein produced by E. coli bearing plasmid pJRS42.13 (ColiM6) accumulates in the periplasmic space of this new host. No immunoreactive M protein was found either on the surface of the organism or in the culture medium. The ColiM6 protein was purified from the periplasm and the final preparation consisted of three protein bands of apparent molecular weight 55,000, 57,000, and 59,000. These three bands were identical in migration in SDS PAGE to that of the M protein present in freshly prepared crude periplasm. The amino acid composition of the ColiM6 protein was nearly identical to that of M protein isolated from streptococci with phage lysin (LysM6). Furthermore, except for the amino terminal residue of the LysM6 molecule, the amino terminal sequence of the ColiM6 molecule was identical to those of both LysM6 and M protein released from the streptococcus by limited peptic digestion (PepM6). These results reveal that the molecule produced in the E. coli and transported into the periplasm may be the complete M protein as it exists on the streptococcus. The results also indicate that the systems that process M protein for transport through the cytoplasmic membrane are similar in the streptococcus and E. coli. The purified ColiM6 protein was able to remove opsonic antibodies from both human and rabbit serum, as well as to stimulate the production of opsonic antibodies in rabbits, indicating that the immunodeterminants on this molecule are the same as those found on streptococcal-derived M molecules.

Amino Acid Sequence↗
PubMed1984

Location by DNA sequence analysis of cop mutations affecting the number of plasmid copies of prophage P1.

The DNA sequence of six P1 cop mutants, which are altered in the control of copy number of the plasmid prophage, was compared to that of P1 wild type. Each cop mutant differs from the wild type by a single base substitution. All of these substitutions are located within a 400 base pair region of P1 DNA that also encodes rep, a gene whose product is required for P1 replication.

Amino Acid Sequence↗
PubMed1984

Degenerative hippocampal pathology in mice infected with scrapie.

The lesions of scrapie are confined to the CNS, and the most characteristic histopathological change in mice terminally infected with scrapie is vacuolation. With most laboratory strains of scrapie, one of the regions affected by this lesion is the cerebral cortex, including the hippocampus. Under some circumstances, however, a more destructive degeneration occurs in the hippocampus, with pyramidal cell necrosis accompanied by glial reactions, which can extend to a severe hippocampal sclerosis especially when an intracerebral route of infection has been used. The purpose of this paper is to identify some of the factors involved in these differences in the pathology of the hippocampus and their interdependence; this has necessitated the development and use of a scoring system for sclerosis in the hippocampus, in conjunction with an already established scoring system for vacuolation. Comparison of average hippocampal sclerosis scores and the vacuolation index (an estimate of the severity of grey matter vacuolation throughout the brain) reveals that hippocampal sclerosis is generally associated with scrapie models which produce intense vacuolation in the hippocampus, and also in the brain as a whole. Scrapie-induced hippocampal sclerosis provides an experimental system for investigating the basis for similar lesions, which occur in a variety of conditions, such as Alzheimer's disease and epilepsy.

Animals↗
PubMed1984

Surgical treatment of congenital esophageal atresia.

Severe gastroesophageal reflux was found in 9 out of 18 infants with congenital esophageal atresia studied radiographically shortly after primary reconstruction. Pulmonary complications were recorded in 18 out of 32 similar patients in long-term follow-up. Strictures at the level of the anastomosis were detectable in 18 out of 32 patients; eleven strictures were severe enough to require dilation or surgical revision. These findings suggest that early evaluation for gastroesophageal reflux may be useful in management of infants with esophageal atresia. The precautions taken preoperatively to prevent complications of gastroesophageal reflux should be continued in the postoperative interval unless a competent lower esophageal sphincter is demonstrated.

Esophageal Atresia↗
PubMed1983

Expression of streptococcal M protein in Escherichia coli.

The structural gene for group A streptococcal M protein, the fibrillar surface molecule enabling the organism to resist phagocytosis, has been cloned into Escherichia coli. The molecule produced by Escherichia coli is slightly larger than the M protein isolated by solubilization of the streptococcal cell wall, but is similar in size to that secreted by streptococcal protoplast and L forms. Immunologically, the molecule synthesized by Escherichia coli has the same type-specific determinants as the streptococcal M protein.

Antigens, Bacterial↗
PubMed1983

Antiplatelet antibodies and platelet counts in pregnancies complicated by autoimmune thrombocytopenic purpura.

In 48 pregnant women with autoimmune thrombocytopenic purpura, no consistent correlation was found between the infant platelet count and either the maternal platelet count, a previous maternal splenectomy, or maternal treatment with corticosteroids. Although the concentration of antiplatelet antibody in maternal serum frequently reflected the severity of neonatal thrombocytopenia, a number of exceptions to this observation limited the clinical usefulness of the test for individual patients. Antiplatelet antibody levels in the amniotic fluid were always low. A twin gestation in this series of patients in which one infant was thrombocytopenic and the other was not also showed that no antepartum maternal clinical characteristic or laboratory test can accurately predict the fetal platelet count. Only fetal platelet counts from scalp samples obtained prior to or early in labor from 25 patients with autoimmune thrombocytopenic purpura proved to be reliable in assessing the degree of fetal thrombocytopenia and selecting the appropriate route of delivery.

Adrenal Cortex Hormones↗
PubMed1983

Histocompatibility in couples with recurrent spontaneous abortion and normal fertility.

Histocompatibility between husband and wife at the HLA locus has been suggested as a determinant of recurrent spontaneous abortion. We measured the incidence of HLA antigen sharing within 12 couples with histories of unexplained recurrent abortion and in a fertile control population of 77 couples. In the recurrent abortion group, 6 of 12 (50%) of the couples shared no HLA antigens, whereas only 3 of 12 (25%) shared one antigen, 1 of 12 (8.3%) shared two antigens, and 2 of 12 (17%) shared three antigens. In the fertile group, 27 of 77 (35.1%) shared no antigens, 33 of 77 (42.8%) shared one antigen, 14 of 77 (18.2%) shared two antigens, 2 of 77 (2.6%) shared three antigens, and 1 of 77 (1.3%) shared four antigens. In 50 of these control couples who were available for complete reproductive histories, there were no significant correlations between the incidence of antigen sharing and the numbers of offspring, the incidence of spontaneous abortion, or infertility problems. Six of the women in the recurrent abortion group became pregnant during the study. Three of these (50%) delivered live infants independent of the degree of antigen sharing and without the benefit of immunologic treatment. Therefore, the degree of HLA antigen sharing did not define a population with increased pregnancy wastage or predict subsequent pregnancy outcome.

Abortion, Habitual↗
PubMed1983

Studies by enzyme-linked immunosorbent assay (ELISA) of antiplatelet antibody and transient neonatal thrombocytopenic purpura.

Autoimmune thrombocytopenic purpura (ATP) is an antibody-mediated autoimmune disease of platelets. Transplacental passage of the antibody during pregnancy can result in transient neonatal thrombocytopenia, but it is not known why some infants of antibody-positive, thrombocytopenic mothers are not affected. We have developed a competitive enzyme-linked immunosorbent assay (ELISA) to measure circulating antiplatelet antibody and have used this technique to investigate the influence of maternal titers on the occurrence of neonatal thrombocytopenia. The assay is sensitive over a range of 12.5 to 800 ng of immunoglobulin G (IgG) per microtiter well and closely correlates with the complement lysis inhibition assay (CLIA) for antiplatelet antibody (correlation coefficient = 0.726). In many instances, the level of circulating antiplatelet antibody in maternal and cord bloods reflected the degree of maternal and neonatal thrombocytopenia, but several important exceptions were observed. We suggest that levels of antiplatelet antibody in the maternal blood and cord blood are not always predictive of the degree of neonatal thrombocytopenia.

Autoantibodies↗
PubMed1983

SOS induction by P1 Km miniplasmids.

We have constructed (in vitro) a set of P1 miniplasmids. The smallest of these that could function as an independent replicon contained the right side of EcoRI-5 plus all of EcoRI-8. Those miniplasmids that lack EcoRI-6 induce the SOS pathway of the cell as shown by (i) increased expression of the recA operon, (ii) excision of the cryptic genetic element e14, (iii) spontaneous induction of lambda, and (iv) dependence of e14 excision on recA+ function. This induction was contingent upon the replication of the P1 Km miniplasmids from their P1 origin and, thus, was apparently caused by an aberrant initiation of DNA replication. When P1 EcoRI-6 was present in cis or trans with a P1 Km miniplasmid, neither e14 nor lambda was excised, but the expression of the recA operon was still induced. These results suggest that P1 EcoRI fragments 5 and 8 are insufficient for normal replication, and thus our P1 Km miniplasmids induced SOS functions. A product of EcoRI-6 may partially restore normal replication.

Bacterial Proteins↗
PubMed1983

Evidence for positive regulation of plasmid prophage P1 replication: integrative suppression by copy mutants.

Like low-copy-number plasmids including P1 wild type, multicopy P1 mutants (P1 cop, maintained at five to eight copies per chromosome) can suppress the thermosensitive phenotype of an Escherichia coli dnaA host by forming a cointegrate. At 40 degrees C in a dnaA host suppressed by P1 cop, the only copy of P1 is the one in the host chromosome. Trivial explanations of the lack of extrachromosomal copies of P1 cop have been eliminated: (i) during integrative suppression, the P1 cop plasmid does not revert to cop+; (ii) the dnaA+ function of the host is not required to maintain P1 cop at a high copy number; and (iii) integrative recombination does not occur within the region of the plasmid involved in regulation of copy number. Since there are no more copies of the chromosomal origin (now located within the integrated P1 plasmid) than in a P1 cop+-suppressed strain, the extra initiation potential of the P1 cop is not used to provide multiple initiations of the chromosome. When a P1 cop-suppressed dnaA strain was grown at 30 degrees C so that replication could initiate from the chromosomal origin as well as from the P1 origin, multicopy supercoiled P1 DNA was found in the cells. This plasmid DNA was lost again when the temperature was shifted back to 40 degrees C.

Chromosomes, Bacterial↗
PubMed1983

In vitro immunization to KLH. II. Limiting dilution analysis of antigen-reactive cells in primary and secondary culture.

Limiting dilution analysis was used to estimate the frequency of human peripheral blood T lymphocytes that proliferate in response to in vitro immunization with keyhole limpet hemocyanin (KLH). Antigen-reactive cells (ARC) were estimated 9 days after primary immunization with KLH. The ARC frequency of lymphocytes from 12 subjects ranged from 1:23,800 to 1:52,631. Lymphocytes from five of these subjects were also primed for 12 days with KLH, rechallenged in secondary culture with fresh adherent cells and KLH, and assayed 4 days later. The ARC frequency increased to 1:1,123 to 1:7,247, indicating that T cell clones responsive to KLH had expanded during primary culture. In addition, we observed that the proliferative response of lymphocytes from 5 of the 12 subjects were inhibited at high cell concentrations. Depletion of OKT8+ T cells before culturing with KLH however did not alter the inhibitory effect of high concentrations of T cells.

Cells, Cultured↗