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Biomedical subjects

S C Roberts

Publications and source records attributed to S C Roberts.

At least 19 recordsLinked to original sources
PubMed1998

Blind analysis of denaturing high-performance liquid chromatography as a tool for mutation detection.

Denaturing high-performance liquid chromatography (DHPLC) is a novel high-capacity technique for detecting new mutations. We have evaluated the sensitivity and specificity of this method in a blind analysis of exon H of the factor IX gene and exon 16 of the neurofibromatosis type 1 gene. Under a single set of conditions for each exon, 55/55 individuals carrying 48 unique mutations were correctly identified as were 55/55 individuals with wildtype alleles. We conclude that DHPLC is a highly sensitive and specific method for mutation detection.

Chromatography, High Pressure Liquid↗
PubMed1996

Kinetics of taxol production and nutrient use in suspension cultures of Taxus cuspidata in shake flasks and a Wilson-type bioreactor.

Suspension cultures of Taxus cuspidata were grown in shake flasks and Wilson-type reactors where bubbled air provided both agitation and mixing. Taxol titers of 22 mg l-1 were achieved for both configurations in 20 days for a volumetric productivity of 1.1 mg l-1 day-1. This productivity is many-fold higher than reported for other Taxus sp. suspension cultures. Taxol was released to the extracellular medium as it was produced with little intracellular retention (< or = 10%). Taxol production occurred during the last seven days of the cultivation period and was not growth-associated. Although the same taxol titers could be obtained in both reactor types, nutrient uptake rates were faster in the Wilson-type reactor than in shake flasks. Formation of a growth ring in the Wilson-type reactor reduced measured cell mass yields.

Antineoplastic Agents, Phytogenic↗
PubMed1996

Assessment of a technology that permits individualized scan delays on helical hepatic CT: a technique to improve efficiency in use of contrast material.

OBJECTIVE: We performed this study to assess the usefulness of a computer automated scan technology (CAST) for individualizing scan delay during helical CT to improve the efficiency of hepatic enhancement. SUBJECTS AND METHODS: We prospectively evaluated 183 patients who were randomized into five groups. Control patients received 100 or 150 ml of contrast material (320 mg I/ml) with a 60-sec delay between contrast injection at 3 ml/sec and scanning. CAST patients received 100, 125, or 150 ml. In our latter groups we used an hepatic enhancement threshold of 50 H over baseline to determine the optimum delay between contrast injection and scanning. For the intergroup comparisons, we measured the liver on baseline and enhanced helical CT scans at the upper, mid, and lower levels of the liver. RESULTS: The mean enhancement in patients who received 150 ml of contrast material was 70.7 +/- 19.4 H for the control group and 81.0 +/- 17.5 H for the CAST group (p < .05). Hepatic enhancement above 50 H was achieved in 84% of the control subjects compared with 100% of CAST subjects; more than 60 H hepatic enhancement was achieved in 73% of control subjects and in 89% of CAST subjects. The use of CAST software with 125-ml contrast doses provided enhancement equivalent to that of control subjects who received 150 ml of contrast material (mean enhancement in CAST subjects, 70.3 +/- 15.4 H). Enhancement above 50 H was reached in 98% of CAST and 84% of control patients. With 100 ml of contrast material, 24% of patients failed to initiate CAST, resulting in enhancement similar to control patients (CAST, 54.2 +/- 11.4 H; controls, 56.9 +/- 15.2 H). CONCLUSION: Using a contrast dose of 150 ml, CAST provided significantly increased hepatic enhancement than that achieved in control subjects with less variability. For equivalent hepatic enhancement, contrast doses could be decreased by 25 ml using CAST technology because it provides individualized scan delays.

Adult↗
PubMed1995

Developmentally regulated expression of a novel 59-kDa product of the major surface protease (Msp or gp63) gene family of Leishmania chagasi.

All species of Leishmania express a major surface protease (Msp or gp63) that facilitates the interactions of the parasite with its environment at several steps in its life cycle. The msp gene family in Leishmania chagasi contains three classes of genes whose mRNAs are differentially expressed during parasite growth. Logarithmic phase (low infectivity) promastigotes express only 63-kDa versions of Msp, whereas stationary phase (high infectivity) promastigotes express both 63- and 59-kDa Msps. The different migrations of the 59- and 63-kDa proteins on acrylamide gels are not due to differences in N-linked glycosylation or the membrane anchor. Plasmid transfections of Leishmania demonstrate that mspS2 of the stationary gene class encodes a 59-kDa protein. Expression of the 59-kDa protein in stationary phase promastigotes ceases after about 12 weeks of in vitro cultivation when the parasites become attenuated. Attenuated parasites can be stimulated to re-express the 59-kDa Msp by passage through mice followed by several in vitro passages of recovered promastigotes. Amastigotes express yet another subset of Msp proteins. Thus, the 59-kDa product of mspS2 is expressed only in stationary phase promastigotes and only after recent exposure to environmental changes encountered in the mammalian host cell.

Amino Acid Sequence↗
PubMed1993

Sequence diversity and organization of the msp gene family encoding gp63 of Leishmania chagasi.

During in vitro growth Leishmania chagasi promastigotes differentially express 3 classes of RNAs encoding the major surface protease (MSP) gp63 that can be distinguished by their unique 3' untranslated regions. Here we show that the three classes (logarithmic-specific, stationary-specific and constitutively expressed) are encoded by a family of at least 4 tandem stationary genes (mspS2, mspS1, mspS3 and mspS5) followed by twelve or more logarithmic genes (mspL genes), one constitutive gene (mspC) and a final stationary gene (mspS4). Some of the stationary genes can be distinguished from each other by groups of nucleotide differences within the coding regions that result in localized amino acid differences. Northern blots confirm that RNAs from the individual stationary genes are present in stationary, but not logarithmic, phase promastigotes. Western blots using sera directed against synthetic peptides indicate that correspondingly heterogeneous gp63 proteins are expressed in L. chagasi promastigotes. A 200-bp region upstream of all three gp63 gene classes is conserved except for a variable number of 6-bp repeats. Downstream of the gp63 coding regions are highly conserved, class-specific sequences that include the 3' untranslated regions and extend past the polyadenylation site for 65 bp (mspL), 345 bp (mspC) or 2.8 kb (mspS). These sequence features flanking the msp coding regions are likely important in the growth phase-specific expression of the three gp63 RNA classes.

Amino Acid Sequence↗
PubMed1992

Three distinct RNAs for the surface protease gp63 are differentially expressed during development of Leishmania donovani chagasi promastigotes to an infectious form.

Leishmania sp. protozoa contain an abundant surface protease (gp63) that is important for the virulence of the parasite. We found that the average amount of gp63 expressed by Leishmania donovani chagasi promastigotes increases 6-11-fold as they develop from a less infectious form in logarithmic phase to a highly infectious form during stationary phase of cultivation in vitro. The predominant gp63 RNA switches from a 2.7 to a 3.0 kilobase (kb) RNA during the transition from log to stationary phase. Sequence analysis of gp63 cDNAs reveals that three different classes of gp63 RNAs, containing unique 3'-untranslated regions (3' UTRs), are expressed during growth to stationary phase. The predominant 2.7-(log) and 3.0-kb (stationary) class gp63 RNAs possess nearly identical coding regions, but they diverge in their 3' UTRs. A third class, consisting of 3.1- and 2.6-kb (constitutive) gp63 RNAs, is expressed at low levels throughout cultivation. This latter class encodes a gp63 with an additional 41 amino acids at its C terminus, replacing a potential signal for attachment of a glycolipid membrane anchor with a sequence that could be a transmembrane region. These findings are consistent with the regulated expression of different gp63 genes, resulting in different amounts of gp63 protein, during the promastigote's in vitro development to an infectious form.

Amino Acid Sequence↗
PubMed1991

Immunogenicity in adult males of a Neisseria meningitidis group B vaccine composed of polysaccharide complexed with outer membrane proteins.

Twenty five adult male volunteers were given a vaccine composed of the capsular B polysaccharide non-covalently complexed to serotype 6 outer membrane proteins (OMP) of Neisseria meningitidis. Subjects were divided into three dose groups receiving 50, 100 or 150 micrograms vaccine in aluminium hydroxide in each of three injections spaced 4 weeks apart. Systemic signs/symptoms considered clinically significant were recorded on 6% (4/70) of occasions and were succeeded by withdrawal of two volunteers from the study. Local injection site reactions, mostly mild to moderate, were reported after all vaccinations with one such reaction leading to a third volunteer withdrawing from the study. Geometric mean anti-B responses before immunization and 1 week after the third immunization (9 weeks) were 3.60 and 7.12 micrograms ml-1 in the 50 micrograms group (p less than 0.05) 2.05 and 12.19 micrograms ml-1 in the 100 micrograms group (p less than 0.001), and 3.68 and 14.20 micrograms ml-1 in the 150 micrograms group (p less than 0.001). The anti-B response was predominantly of the IgM isotype and persistence above prevaccination levels was evident for at least 12 months. Anti-type 6 OMP responses were also evidenced with geometric mean multiplicative increases over prevaccination levels at 9 weeks and 6 months of 7.8 and 4.2 for the 50 micrograms group, 11.6 and 5.6 for the 100 micrograms group and 6.8 and 3.4 for the 150 micrograms group. The bulk of this response was of the IgG isotype. Passive protection of mice was achieved with both pre- and post-vaccination (9 weeks; 100 and 150 micrograms groups) pools of sera.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Vaccination and cot deaths in perspective.

In 1985 twin boys simultaneously succumbed to sudden unexpected deaths two to three hours after vaccination with diphtheria, tetanus, and pertussis vaccine (DTP). This occurrence again raises the question of whether an association of sudden infant death (SID) with vaccination is other than temporal. Taking the incidence of SID in conjunction with rates of infant vaccination in the United Kingdom, nine infants would be expected to die, each year by chance alone, suddenly within 24 hours of (and within each 24 hour period succeeding) vaccination with DTP. Twins are at a greater risk of SID than single born infants and occasionally are found dead together. A number of studies into DTP vaccination as a risk factor in SID have shown that SID is less common in vaccinated than in unvaccinated infants.

Diphtheria↗