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M C Smith

Publications and source records attributed to M C Smith.

At least 19 recordsLinked to original sources
PubMed1992

Transcription map of the early region of the Streptomyces bacteriophage phi C31.

Streptomyces coelicolor A3(2), lysogenised by the temperature-sensitive cts1 mutant of phi C31, can be synchronously induced into the lytic cycle by heat treatment. A transcription map of 10 kb of the phi C31 early gene cluster was deduced using low-resolution S1 nuclease mapping of RNA prepared 10 min after induction. At least nine early transcripts, early (e)RNAs 1-9, were localised reading exclusively rightwards with respect to the standard physical map of phi C31. The mRNAs were extensively overlapping, frequently initiating at the same place but terminating at different sites, and vice versa. Gene expression during the lytic cycle was tightly regulated; no transcription was observed before induction. Transcription was maximal at 10 min post-induction, and at 20 min, eRNAs 5 and 6 persisted whilst eRNAs 7-9 were severely reduced or absent. The pattern of transcription of the early region is consistent with the simultaneous activation of a large number of promoters and differential termination efficiency.

Bacteriophages↗
PubMed1992

Effect of the Gulf War on infant and child mortality in Iraq.

BACKGROUND: Increased malnutrition and morbidity among Iraqi children after the onset of the Persian Gulf war have been reported by several fact-finding missions. The magnitude of the effect of the war and the economic embargo on child mortality remains uncertain, however. METHODS: We conducted a survey of 271 clusters of 25 to 30 households each, chosen as a representative sample of the Iraqi population. The households were selected and the interviews conducted by an international team of public health professionals independent of Iraqi authorities. In each household all women 15 to 49 years of age were interviewed, and the dates of birth and death of all children born on or after January 1, 1985, were recorded. RESULTS: The study population included 16,076 children, 768 of whom died during the period surveyed (January 1, 1985, to August 31, 1991). The age-adjusted relative mortality for the period after the war began, as compared with the period before the war, was 3.2 (95 percent confidence interval, 2.8 to 3.7). No material change in the relative risk was observed after adjustment for region of residence, maternal education, and maternal age. The increase in mortality after the onset of the war was higher among children 1 to less than 12 months old (relative risk, 4.1; 95 percent confidence interval, 3.3 to 5.2) and among those 12 to less than 60 months old (relative risk, 3.8; 95 percent confidence interval, 2.6 to 5.4) than among those less than 1 month old (relative risk, 1.8; 95 percent confidence interval, 1.4 to 2.4). The association between the war and mortality was stronger in northern Iraq (relative risk, 5.3) and southern Iraq (relative risk, 3.4) than in the central areas (relative risk, 1.9) or in Baghdad (relative risk, 1.7). CONCLUSIONS: These results provide strong evidence that the Gulf war and trade sanctions caused a threefold increase in mortality among Iraqi children under five years of age. We estimate that more than 46,900 children died between January and August 1991.

Child, Preschool↗
PubMed1992

Gene expression in the Streptomyces temperate phage phi C31.

The repressor gene, c, of the temperate Streptomyces phage, phi C31 was previously cloned and sequenced, and predicted to encode a 74-kDa protein. The c gene actually produces three in-frame, N-terminally different, C-terminally identical proteins of 74, 54 and 42 kDa. The repressor proteins are translated from a corresponding nest of transcripts. Genetic and biochemical evidence suggests that the transcription of the c locus is autoregulated possibly by the 42-kDa protein binding to a highly conserved 16-bp perfect inverted repeat. The 16-bp sequence is present at at least twelve loci throughout the phi C31 genome. Transcription of the 'early' region is complex, possibly involving phage-specific promoters. The phi C31 terminators display sequence conservation and may be regulated. The phi C31 gene 'k' may encode a nucleotide kinase-encoding gene.

Bacteriophages↗
PubMed1992

Purification and initial characterization of AhrC: the regulator of arginine metabolism genes in Bacillus subtilis.

The arginine-dependent repressor-activator from Bacillus subtilis, AhrC, has been overexpressed in Escherichia coli and purified to homogeneity. AhrC, expressed in E. coli, is able to repress a Bacillus promoter (argCp), which lies upstream of the argC gene. The purified protein is a hexamer with a subunit molecular mass of 16.7 kDa. Its ability to recognize DNA has been examined in vitro using argCp in both DNase I and hydroxyl radical protection assays. AhrC binds at two distinct sites within the argCp fragment. One site, argCo1, with the highest affinity for protein, is located within the 5' promoter sequences, whilst the other, argCo2, is within the coding region of argC. The data are consistent with the binding of a single hexamer of AhrC to argCo1 via four of its subunits, possibly allowing the remaining two subunits to bind at argCo2 in vivo forming a repression loop similar to those observed for the E. coli Lac repressor.

Amino Acid Sequence↗
PubMed1992

Sequence analysis of the beta-lactamase repressor from Staphylococcus aureus and hybridization studies with two beta-lactamase-producing isolates of Enterococcus faecalis.

The putative beta-lactamase (Bla) repressor gene, blaI, from the staphylococcal plasmid pI524 was isolated, and the DNA sequence was determined. The sequence of blaI was found to be identical to the blaI sequence from pI9789 (blaI blaZ seg-1), a plasmid related to pI524. A blaI probe from pI524 was hybridized with plasmid and genomic DNA from Bla+ Enterococcus faecalis isolates HH22 and PA. The Bla structural gene of HH22 has been previously shown to be of staphylococcal origin, but DNA homologous to the staphylococcal Bla repressor was not found, indicating that the constitutive production of beta-lactamase in these E. faecalis isolates may be the result of a missing repressor protein.

Base Sequence↗
PubMed1992

Comparison of enterococcal and staphylococcal beta-lactamase-encoding fragments.

A restriction map of a 13.5-kb EcoRI fragment encoding beta-lactamase from a plasmid isolated from enterococcal strain PA was prepared and found to differ markedly from the published maps of beta-lactamase-encoding EcoRI fragments of two staphylococcal plasmids and the plasmid from enterococcal strain HH22. This comparison also showed that one of two contiguous EcoRV fragments that encompass the beta-lactamase gene differs in size in the PA strain from that found in the other strains. However, restriction sites in the beta-lactamase structural gene (blaZ) were identical in all four plasmids. Further studies compared the beta-lactamase genes of four clinical enterococcal isolates from various geographic locations with those described above. Isolates from Virginia and Florida generated EcoRV fragments identical to those from the plasmid from strain PA, while isolates from Lebanon and Argentina showed EcoRV fragments analogous to those from HH22 and the staphylococci studied. Although there is evidence suggesting that some of these beta-lactamase-producing enterococcal isolates represent a single strain, this study indicates that there is significant variation in the plasmids that encode beta-lactamase.

Autoradiography↗
PubMed1992

An outbreak of hepatitis A in Gloucester, UK.

During an outbreak of hepatitis A that occurred in Gloucester, UK between September 1989 and January 1991, 162 clinical cases were identified through notifications and laboratory reports, a monthly attack rate of 1.05 per 10,000 residents. The highest attack rate was seen in 5-14-year-olds. There were significant correlations between hepatitis A attack rates in the electoral wards of Gloucester and with the Jarman UPA 8 scores for the wards and with overcrowding, unemployment, under 5-year-olds and ethnic minority. The use of human normal immune globulin prophylaxis (HNIG) for household contacts was unsuccessful in ending the outbreak, partly because only one third of cases reported a household contact with recent hepatitis A. Our experience does not support the use of HNIG in stopping community-wide outbreaks of hepatitis A. Two public health campaigns were mounted during the outbreak; both were followed by a fall in the number of cases. Greater priority should be given to the implementation and evaluation of public health campaigns in future community-wide outbreaks of hepatitis A.

Adolescent↗
PubMed1992

Parietal bone mobility in the anesthetized cat.

To quantify parietal bone motion in reference to the medial sagittal suture, a newly developed instrument was attached to the surgically exposed skull of anesthetized adult cats. The instrument differentiated between lateral and rotational parietal bone movements around the fulcrum of the suture. Bone movement was produced by external forces applied to the skull and by changes in intracranial pressure associated with induced hypercapnia, intravenous injections of norepinephrine, and controlled injections of artificial cerebrospinal fluid into the lateral cerebral ventricle. Responses varied considerably among test animals. Generally, lateral head compression caused sagittal suture closure, small inward rotation of the parietal bones, increased intraventricular pressure, transient apnea, and unstable systemic arterial blood pressure. Graded increases in intracranial volume produced stepped increases in pressure, lateral expansion at the sagittal suture, and outward rotation of the parietal bones. We attribute variations in animal response largely to differences in intracranial and suture compliance among them. Cranial suture compliance may be an important factor in defining total cranial compliance.

Animals↗
PubMed1991

Catalytic hydrogenolysis of poly-iodinated recombinant human insulin-like growth factor II (IGF-II): a potentially useful method for the tritiation of IGF-II.

A method has been developed to prepare, purify, and fully characterize poly-iodinated insulin-like growth factor II (IGF-II) which can then be catalytically deiodinated to produce IGF-II with its native disulfide bonded structure. This method can potentially be adapted to prepare tritiated IGF-II with the use of tritium gas in the hydrogenolysis step. IGF-II was iodinated at all three tyrosines using lactoperoxidase with a three-fold excess of sodium iodide. The iodinated products were purified using reversed-phase HPLC and characterized by peptide mapping. The tyrosine-containing peptides generated by pepsin digestion were characterized by amino acid sequence analysis. Mono- and di-iodinated phenylthiohydantoin tyrosine derivatives were synthesized and used to identify the iodination state of the modified tyrosine residues in the sequence analysis. Purified poly-iodinated IGF-II was deiodinated by hydrogenolysis, over a prereduced palladium (II) oxide catalyst to form IGF-II with its native disulfide bonds intact, as shown by peptide mapping.

Amino Acid Sequence↗
PubMed1991

Altered affinity of insulin-like growth factor II (IGF-II) for receptors and IGF-binding proteins, resulting from limited modifications of the IGF-II molecule.

The binding affinities of seven analogues of recombinant human insulin-like growth factor II (hIGF-II) were characterized for the IGF type-I and type-II receptors and insulin receptors, as well as for IGF-binding protein (IGFBP)-1, IGFBP-2, IGFPB-3 and human serum IGFBPs. A switch of two of the three cysteine bridges in hIGF-II, 9-47 and 46-51 to 9-46 and 47-51, severely impaired the binding of this analogue to all receptors and to the IGFBPs. The affinities for the IGF type-I receptor and the IGFBPs were decreased over 100-fold, while the binding to the insulin receptor and the IGF type-II receptor was less affected, with a 6-10-fold decrease in affinity. Slight modifications of the N-terminus had only minor effects upon the binding of hIGF-II to the IGFBPs or to the receptors. Deletion of both the N-terminal amino acid and the two C-terminal amino acids resulted in moderate decreases in affinity, with a 60% decrease in affinity for IGFBP-1 and the IGF type-I receptor. Acetylation of the N-terminus of Ala1 and the epsilon-nitrogen of Lys65 decreased the affinity, by 60-90%, of hIGF-II for all of the IGFBPs and receptors. The experiments involving acetylation of IGF-II or switching of its cysteine bridges indicated that these modifications (no substitution, deletion or addition of any of the 67 amino acids of hIGF-II) may lead to a severe impairment of the binding affinity of IGF-II for both the IGFBPs and the receptors. Acetylation of the epsilon-nitrogen of Lys65, which causes a charge change, or alteration of the three-dimensional structure, as shown by the cysteine bridge switch, lead to a severe impairment of the binding affinity for the binding proteins and for the receptors. In general, care should be taken with the synthesis of analogues and the interpretation of resulting binding data, since affinity alterations ascribed to amino acid changes may instead be caused by alterations of the charge or the three-dimensional structure of the protein.

Amino Acid Sequence↗
PubMed1991

Effects of second-codon mutations on expression of the insulin-like growth factor-II-encoding gene in Escherichia coli.

Expression plasmids encoding random sequence mutant proteins of insulin-like growth factor II (IGFII) were constructed by cassette mutagenesis, to improve the efficiency of IGFII synthesis in Escherichia coli. A pool of oligodeoxyribonucleotide linkers containing random trinucleotide sequences were used to introduce second-codon substitutions into the gene encoding Met-Xaa-Trp-IGFII in expression vectors. E. coli RV308 cells transformed with these vectors synthesized IGFII at levels varying from 0-22% of total cell protein. This variable synthesis is a function of the random second-codon sequence and its corresponding amino acid, Xaa. Our data showed that mRNA stability, protein stability and translational efficiency all contributed to variable expression levels of Met-Xaa-Trp-IGFII in E. coli. Furthermore, an efficiently synthesized IGFII mutant protein, Met-His-Trp-IGFII, was converted to natural sequence IGFII by a simple oxidative cleavage reaction.

Amino Acid Sequence↗
PubMed1991

A randomized, double-blind trial of prostaglandin E2 gel for cervical ripening and meta-analysis.

The ability of prostaglandin E2 to prepare the unripe cervix before an indicated labor induction is controversial. We therefore tested 100 pregnant women in a randomized, double-blind trial with intracervical prostaglandin E2 gel, 0.5 mg. The 53 women who received the placebo gel had an outcome similar to that of the 47 women who received the prostaglandin E2 gel. The mean change in cervical score, mean application-to-delivery interval, incidence of uncomplicated spontaneous labor, incidence of cesarean delivery for a failed induction, and the overall cesarean section rate were not significantly different for the two groups. A meta-analysis, incorporating 18 studies of 1811 patients who received a single application of at least 5 mg prostaglandin E2 gel intravaginally or 0.5 mg intracervically, demonstrated no significant decrease in the overall cesarean delivery rate (p = 0.85). We conclude that the use of single-dose intracervical prostaglandin E2 gel for cervical ripening has little effect on labor induction. Moreover, the use of single-dose intracervical or intravaginal prostaglandin E2 gel does not alter the incidence of cesarean delivery, even when large numbers of patients are analyzed by combining the results of similar reports.

Adult↗