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Biomedical subjects

G Scott

Publications and source records attributed to G Scott.

At least 91 records · Page 5Linked to original sources
PubMed2000

Inactivation of isocitrate lyase leads to increased production of medium-chain-length poly(3-hydroxyalkanoates) in Pseudomonas putida.

Medium-chain-length (mcl) poly(3-hydroxyalkanoates) (PHAs) are storage polymers that are produced from various substrates and accumulate in Pseudomonas strains belonging to rRNA homology group I. In experiments aimed at increasing PHA production in Pseudomonas strains, we generated an mcl PHA-overproducing mutant of Pseudomonas putida KT2442 by transposon mutagenesis, in which the aceA gene was knocked out. This mutation inactivated the glyoxylate shunt and reduced the in vitro activity of isocitrate dehydrogenase, a rate-limiting enzyme of the citric acid cycle. The genotype of the mutant was confirmed by DNA sequencing, and the phenotype was confirmed by biochemical experiments. The aceA mutant was not able to grow on acetate as a sole carbon source due to disruption of the glyoxylate bypass and exhibited two- to fivefold lower isocitrate dehydrogenase activity than the wild type. During growth on gluconate, the difference between the mean PHA accumulation in the mutant and the mean PHA accumulation in the wild-type strain was 52%, which resulted in a significant increase in the amount of mcl PHA at the end of the exponential phase in the mutant P. putida KT217. On the basis of a stoichiometric flux analysis we predicted that knockout of the glyoxylate pathway in addition to reduced flux through isocitrate dehydrogenase should lead to increased flux into the fatty acid synthesis pathway. Therefore, enhanced carbon flow towards the fatty acid synthesis pathway increased the amount of mcl PHA that could be accumulated by the mutant.

Gluconates↗
PubMed1999

5-methylcytosine at HpaII sites in p53 is not hypermutable after UVC irradiation.

Using a yeast based p53 functional assay we previously demonstrated that the UVC-induced p53 mutation spectrum appears to be indistinguishable from the one observed in Non Melanoma Skin Cancer (NMSC). However, position 742 (codon 248, CpG site) represented the major hot spot in NMSC but was not found mutated in the yeast system. In order to determine whether UVC-induced mutagenic events may be facilitated at methylated cytosine (5mC), a yeast expression vector harbouring a human wild-type p53 cDNA (pLS76) was methylated in vitro by HpaII methylase. Methylation induced 98% protection to HpaII endonuclease. Unmethylated and methylated pLS76 vectors were then UVC irradiated (lambda(max): 254 nm) and transfected into a yeast strain containing the ADE2 gene regulated by a p53-responsive promoter. The results revealed that: (i) 5mC at HpaII sites did not cause any difference in the UVC-induced survival and/or mutagenicity; (ii) none of the 20 mutants derived from methylated pLS76 showed p53 mutations targeted at HpaII sites; (iii) the UVC-induced p53 mutation spectra derived from methylated and unmethylated pLS76 were indistinguishable not only when classes of mutations and hot spots were concerned, but also when compared through a rigorous statistical test to estimate their relatedness (P = 0.85); (iv) the presence of 5mC did not increase the formation of photo-lesions at codon 248, as determined by using a stop polymerase assay. Although based on a limited number of mutants, these results suggest that the mere presence of 5mC at position 742 does not cause a dramatic increase of its mutability after UVC irradiation. We propose that position 742 is a hot spot in NMSC either because of mutagenic events at 5mC caused by other UV components of solarlight and/or because not all the NMSC are directly correlated with UV mutagenesis but may have a "spontaneous" origin.

5-Methylcytosine↗
PubMed1999

The burden of pneumococcal disease among adults in developed and developing countries: what is and is not known.

The burden of pneumococcal disease among adults in developed countries is neither widely known nor appreciated. The incidence of pneumococcal pneumonia is uncertain because a precise diagnosis cannot be obtained for most patients. Population-based data on invasive pneumococcal disease (e.g., bacteraemia and meningitis) suggest an annual incidence in all developed countries of > or =15-20 cases per 100,000 persons of all ages and > or =50 cases per 100,000 elderly adults (> or =65 years). In developing countries there are no population-based data on the burden of pneumococcal disease among adults. Studies of high risk groups, hospital-based studies, vaccine efficacy trials, extrapolations from surveillance of "native populations" in developed countries, and demographic studies in developing regions all suggest a high burden of disease. The broad variation in these estimates, however, indicates that better studies are needed. Increased use of pneumococcal vaccines among adults in all countries will depend on better scientific and public understanding of the burden of pneumococcal disease. In developing countries, intensive community-based studies of the impact of pneumococcal disease, or, alternatively, a "vaccine probe" approach, in which a population is vaccinated and the reduction in pneumonia is compared with that in a control population, could give more accurate estimates of the burden of disease and of the potential effectiveness of pneumococcal vaccination among adults.

Adult↗
PubMed1999

Relationship between DNA methylation and mutational patterns induced by a sequence selective minor groove methylating agent.

Me-lex, a methyl sulfonate ester appended to a neutral N-methylpyrrolecarboxamide-based dipeptide, was synthesized to preferentially generate N3-methyladenine (3-MeA) adducts which are expected to be cytotoxic rather than mutagenic DNA lesions. In the present study, the sequence specificity for DNA alkylation by Me-lex was determined in the p53 cDNA through the conversion of the adducted sites into single strand breaks and sequencing gel analysis. In order to establish the mutagenic and lethal properties of Me-lex lesions, a yeast expression vector harboring the human wild-type p53 cDNA was treated in vitro with Me-lex, and transfected into a yeast strain containing the ADE2 gene regulated by a p53-responsive promoter. The results showed that: 1) more than 99% of the lesions induced by Me-lex are 3-MeA; 2) the co-addition of distamycin quantitatively inhibited methylation at all minor groove sites; 3) Me-lex selectively methylated A's that are in, or immediately adjacent to, the lex equilibrium binding sites; 4) all but 6 of the 33 independent mutations were base pair substitutions, the majority of which (17/33; 52%) were AT-targeted; 5) AT --> TA transversions were the predominant mutations observed (13/33; 39%); 6) 13 out of 33 (39%) independent mutations involved a single lex-binding site encompassing positions A600-602 and 9 occurred at position 602 which is a real Me-lex mutation hotspot (n = 9, p < 10(-6), Poisson's normal distribution). A hypothetical model for the interpretation of mutational events at this site is proposed. The present work is the first report on mutational properties of Me-lex. Our results suggest that 3-MeA is not only a cytotoxic but also a premutagenic lesion which exerts this unexpected property in a strict sequence-dependent manner.

Adenine↗
PubMed1999

Lack of long-term effects of in utero exposure to zidovudine among uninfected children born to HIV-infected women. Pediatric AIDS Clinical Trials Group Protocol 219/076 Teams.

CONTEXT: With the success of zidovudine chemoprophylaxis for prevention of perinatal transmission of the human immunodeficiency virus (HIV), an increasing number of HIV-exposed but uninfected children will have in utero exposure to zidovudine and other antiretroviral drugs. OBJECTIVE: To evaluate the long-term effects of in utero exposure to zidovudine vs placebo among a randomized cohort of uninfected children. DESIGN: Prospective cohort study based on data collected during Pediatric AIDS Clinical Trials Group Protocol 076, a perinatal zidovudine HIV prevention trial, and Protocol 219, a long-term observational protocol. SETTING: Pediatric research clinics in the United States. PATIENTS: Two hundred thirty-four uninfected children born to 230 HIV-infected women enrolled in Protocol 076 and followed up through February 28, 1997, in Protocol 219 (122 in the zidovudine group and 112 in the placebo group). MAIN OUTCOME MEASURES: Physical growth measurements, immunologic parameters, cognitive/developmental function, occurrence of neoplasms, and mortality data assessed every 6 months for children younger than 24 months and yearly thereafter or as clinically indicated. Baseline echocardiogram and funduscopic evaluations were collected before 36 months of age. RESULTS: Median age of children at time of last follow-up visit was 4.2 years (range, 3.2-5.6 years). There were no significant differences between children exposed to zidovudine and those who received placebo in terms of sequential data on lymphocyte subsets; weight, height, and head circumference z scores; and cognitive/developmental function. No deaths or malignancies occurred. Two children (both exposed to zidovudine) are being followed up for abnormal, unexplained ophthalmic findings. One child exposed to zidovudine had a mild cardiomyopathy on echocardiogram at the age of 48 months; the child is clinically asymptomatic. CONCLUSIONS: No adverse effects were observed in HIV-uninfected children with in utero and neonatal exposure to zidovudine followed up for as long as 5.6 years. Continued prospective evaluations of children born to HIV-infected women who are exposed to antiretroviral or immunotherapeutic agents are critical to assess the long-term safety of interventions that prevent perinatal HIV transmission.

Anti-HIV Agents↗
PubMed1999

Use of corticosteroids to suppress drug toxicity in complicated tuberculosis.

Four cases of tuberculosis complicated by allergic or toxic reactions to antibiotic treatment are presented. In each, it was considered essential to suppress the reactions in order to give effective chemotherapy. This was achieved by using prednisolone generally in a dose of 40 mg/day or less during the continuation phase of therapy. Reactions to essential treatment are an important indication for corticosteroid treatment in tuberculosis.

Adult↗
PubMed1999

A novel mutation in the 1A domain of keratin 2e in ichthyosis bullosa of Siemens.

Ichthyosis bullosa of Siemens (IBS) is a rare autosomal dominant skin disorder with clinical features similar to epidermolytic hyperkeratosis (EHK). Both diseases have been linked to the type II keratin cluster on chromosome 12q. Hyperkeratosis and blister formation are relatively mild in IBS compared with EHK, and the lysis of keratinocytes is restricted to the upper spinous and granular layers of the epidermis of IBS patients, whereas in EHK lysis occurs in the lower spinous layer. Recently, mutations in the helix initiation and termination motifs of keratin 2e (K2e) have been described in IBS patients. The majority of the mutations reported to date lie in the 2B region. In this report, we have examined a large kindred in which the disease was originally diagnosed as EHK and mapped to the type II keratin cluster on chromosome 12q. Molecular analysis revealed a novel amino acid substitution at the beginning of the conserved 1A region of the rod domain (I4N) of K2e, resulting from a T to A transversion in codon 188.

Amino Acid Sequence↗
PubMed1999

Efficacy of zidovudine and human immunodeficiency virus (HIV) hyperimmune immunoglobulin for reducing perinatal HIV transmission from HIV-infected women with advanced disease: results of Pediatric AIDS Clinical Trials Group protocol 185.

Pediatric AIDS Clinical Trials Group protocol 185 evaluated whether zidovudine combined with human immunodeficiency virus (HIV) hyperimmune immunoglobulin (HIVIG) infusions administered monthly during pregnancy and to the neonate at birth would significantly lower perinatal HIV transmission compared with treatment with zidovudine and intravenous immunoglobulin (IVIG) without HIV antibody. Subjects had baseline CD4 cell counts </=500/microL (22% had counts <200/microL) and required zidovudine for maternal health (24% received zidovudine before pregnancy). Transmission was associated with lower maternal baseline CD4 cell count (odds ratio, 1.58 per 100-cell decrement; P=.005; 10.0% vs. 3.6% transmission for count <200 vs. >/=200/microL) but not with time of zidovudine initiation (5.6% vs. 4.8% if started before vs. during pregnancy; P=. 75). The Kaplan-Meier transmission rate for HIVIG recipients was 4. 1% (95% confidence interval, 1.5%-6.7%) and for IVIG recipients was 6.0% (2.8%-9.1%) (P=.36). The unexpectedly low transmission confirmed that zidovudine prophylaxis is highly effective, even for women with advanced HIV disease and prior zidovudine therapy, although it limited the study's ability to address whether passive immunization diminishes perinatal transmission.

Adult↗
PubMed1999

PGP9.5: a marker for cellular neurothekeoma.

Neurothekeomas are benign, predominantly cutaneous neoplasms that are divided histologically into myxoid, intermediate, and cellular types. Although it is generally agreed that the myxoid type of neurothekeoma has a neural origin, the lack of consistent immunoreactivity to neural markers and insufficient ultrastructural evidence of neural differentiation in cellular neurothekeoma have brought the origin of cellular neurothekeoma into question. In this report the authors show that immunoreactivity to protein gene product 9.5 (PGP9.5)--a broad neural marker--is positive in 100% of cases of cellular neurothekeoma using microwave antigen retrieval, as well as in all cases of myxoid and intermediate neurothekeoma. In contrast, immunoreactivity to S-100 protein is only positive in 3 of 12 cases of cellular neurothekeoma. These results show that PGP9.5 is a useful marker for identifying cellular neurothekeoma, as well as other types of neurothekeomas using the antigen retrieval method. The results are consistent with the notion that cellular neurothekeoma has a neural differentiation.

Adolescent↗
PubMed1999

Constitutive expression of Heregulin induces apoptosis in an erbB-2 overexpressing breast cancer cell line SKBr-3.

We have previously reported that Heregulin (HRG)/neu differentiation factor (NDF) induced growth arrest and cellular differentiation in breast cancer cells overexpressing erbB-2 receptor. To elucidate the cellular mechanisms underlying the growth inhibition by HRG, we developed an in vitro model by transfection of HRG cDNA into the erbB-2 overexpressing breast cancer cell line, SKBr-3. We showed that the enforced expression of HRG in SKBr-3 cells induces dramatic morphological changes and pronounced inhibition of anchorage-dependent and -independent growth. Most SKBr-3/HRG-transfected (SK/HRG) cells exhibited about 15-fold increase in size and persisted as multinucleated cells with extended flattened vacuole-filled cytoplasm with reduced cell attachment. The growth suppression of SK/HRG cells was accompanied by a reduction in S phase, the presence of a G2-M cell cycle delay, and an increase in DNA aneuploid components. In addition, DNA fragmentation assays showed that HRG induced apoptosis of SKBr-3 cells. In contrast, while HRG treatment of other erbB-2 overexpressing breast cancer cell lines led to growth arrest and cell detachment, it did not induce apoptotic features. Thus, this study demonstrates that while growth arrest and cell detachment are general effects of HRG towards erbB-2 overexpressing cells, the ability of HRG to induce apoptosis is a phenomenon confined to selective cells including SKBr-3 cells.

Apoptosis↗