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Biomedical subjects

J Cole

Publications and source records attributed to J Cole.

At least 127 records · Page 7Linked to original sources
PubMed1994

Effect of deoxyribonucleosides on the hypersensitivity of human peripheral blood lymphocytes to UV-B and UV-C irradiation.

We have previously shown that non-cycling (unstimulated) human lymphocytes from normal donors show extreme hypersensitivity to UV-B irradiation, and are killed by an excisable lesion which is not a pyrimidine dimer or 6-4 photoproduct. In this paper we show that addition of the 4 deoxyribonucleosides to the medium, each at 10(-5) M, substantially increased the survival of non-cycling normal human T-lymphocytes following UV-B irradiation and substantially reduced the frequency of excision-related strand breaks in human mononuclear cells. Addition of ribonucleosides to the medium did not enhance excision-break rejoining. The survival of fibroblasts, of cycling T-lymphocytes and of unstimulated xeroderma pigmentosum T-lymphocytes was not enhanced by deoxyribonucleosides. This suggests that the hypersensitivity is due to reduced rejoining of excision breaks as a consequence of low intracellular deoxyribonucleotide pools and that it can be redressed by supplementation of the medium with deoxyribonucleosides or upregulation of ribonucleotide reductase following mitogen stimulation. We suggest that UV-B forms an additional DNA lesion which is not a pyrimidine dimer or 6-4 photoproduct, which is relatively common, and at which incision is particularly efficient. In fibroblasts, repair of this lesion is completed with high efficiency, whereas in normal unstimulated T-lymphocytes, rapid incision exacerbates the effects of the reduced rate of strand rejoining and leads to cell death.

Cells, Cultured↗
PubMed1994

Dietary calcium intake in 18-year-old women: comparison with recommended daily intake and dietary energy intake.

Average dietary calcium intake and energy intake of 113 18-year-old university students in Western Australia was examined. Four-day, weighted diet records, including 1 weekend day, were completed by the subjects. A large proportion of the students (68%) had an average daily calcium consumption below the 800 mg recommended by the National Health and Medical Research Council of Australia. A strong positive association was also found between dietary calcium and dietary energy intakes. Many young women on self-imposed energy reduction diets are at risk of a dietary calcium intake deficit at a time when it should be enhanced. These findings are significant for nursing practice as they indicate the need for further health education concerning the importance of dietary calcium in young women.

Adolescent↗
PubMed1994

A seven-gene operon essential for formate-dependent nitrite reduction to ammonia by enteric bacteria.

The DNA sequence of the regulatory region and the structural gene, nrfA, for cytochrome c552 of Escherichia coli K-12 have been reported. We have now established that nrfA is the first gene in a seven-gene operon, designated the nrf operon, at least five of which are essential for formate-dependent nitrite reduction to ammonia. This operon terminates just upstream of the previously sequenced gltP gene encoding a sodium-independent, glutamate and aspartate transporter. Expression of lac fused to nrfA, nrfE or nrfG is regulated by oxygen repression, FNR-dependent anaerobic induction, nitrite induction and nitrate repression during anaerobic growth, exactly as previously reported for the nrfA promoter. In contrast, expression of the gltP-lac fusion was FNR-independent. The open reading frame immediately downstream of nrfA encodes NrfB, a hydrophilic, penta-haem cytochrome c with an M(r) of 20,714. The structure of the N-terminal region is typical of a signal peptide for a periplasmic protein: cleavage at the putative signal peptide cleavage site, Ala-26, would result in a periplasmic cytochrome with a molecular mass of 18 kDa. The NrfC polypeptide, M(r) 24,567, contains 16 cysteine residues arranged in four clusters typical of the CooF super-family of non-haem iron-sulphur proteins. The NrfD sequence predicts a 318-residue hydrophobic protein with a distribution of acidic and basic amino acids which suggests that NrfD is an integral transmembrane protein with loops in both the periplasm and the cytoplasm. Proteins most similar to NrfD include the PsrC subunit of polysulphide reductase from Wolinella, but, as seven of the 10 most similar proteins are NADH-ubiquinone oxidoreductases, we propose that NrfD participates in the transfer of electrons from the quinone pool into the terminal components of the Nrf pathway. NrfE, M(r) 60,851, is predicted to be another hydrophobic, integral membrane protein homologous to the CdI1 protein of Rhodobacter capsulatus, which has been implicated in the assembly of periplasmic c-type cytochromes. The sequence of the 127 residue NrfF polypeptide, M(r) 14,522, is strikingly similar to the CcI2 protein of R. capsulatus, especially in the putative haem-binding motif, RCPQCQNQN.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1994

Cloning efficiency and spontaneous mutant frequency in circulating T-lymphocytes in ataxia-telangiectasia patients.

The mutant frequency at the hprt locus in circulating T-lymphocytes has been determined in 16 ataxia-telangiectasia (A-T) patients, 19 A-T heterozygotes and 12 A-T sibs. Mutant frequency in the A-T patients is highly significantly elevated as a group, even when the relatively poor cloning efficiency of many of the A-T lymphocyte samples is taken into account. However, within the A-T set, considerable variation in both cloning efficiency and mutant frequency is seen. Cellular radiation sensitivity, measured by clonal survival assays and chromosome breakage, also varies, as do the clinical symptoms of the patients, including the age at which they become wheelchair bound and the severity of their telangiectasia. Here all the information available to us on this group of patients is presented in an attempt to discern if there is any relationship between those cellular characteristics we have observed and the severity of the symptoms and progression of the disease in the patients. Although we feel that it may be relevant that the adult patients in our study all have mutant frequencies that are not highly elevated, insufficient data are available at present to resolve any relationship between the heterogeneous clinical symptoms and cellular responses seen in the A-T patients as a group.

Adolescent↗
PubMed1994

Clinical heterogeneity within xeroderma pigmentosum associated with mutations in the DNA repair and transcription gene ERCC3.

The human DNA excision repair gene ERCC3 specifically corrects the nucleotide excision repair (NER) defect of xeroderma pigmentosum (XP) complementation group B. In addition to its function in NER, the ERCC3 DNA helicase was recently identified as one of the components of the human BTF2/TFIIH transcription factor complex, which is required for initiation of transcription of class II genes. To date, a single patient (XP11BE) has been assigned to this XP group B (XP-B), with ther remarkable conjunction of two autosomal recessive DNA repair deficiency disorders: XP and Cockayne syndrome (CS). The intriguing involvement of the ERCC3 protein in the vital process of transcription may provide an explanation for the rarity, severity, and wide spectrum of clinical features in this complementation group. Here we report the identification of two new XP-B patients: XPCS1BA and XPCS2BA (siblings), by microneedle injection of the cloned ERCC3 repair gene as well as by cell hybridization. Molecular analysis of the ERCC3 gene in both patients revealed a single base substitution causing a missense mutation in a region that is completely conserved in yeast, Drosophila, mouse, and human ERCC3. As in patient XP11BE, the expression of only one allele (paternal) is detected. The mutation causes a virtually complete inactivation of the NER function of the protein. Despite this severe NER defect, both patients display a late onset of neurologic impairment, mild cutaneous symptoms, and a striking absence of skin tumors even at an age of > 40 years. Analysis of the frequency of hprt- mutant T-lymphocytes in blood samples suggests a relatively low in vivo mutation frequency in these patients. Factors in addition to NER deficiency may be required for the development of cutaneous tumors.

Amino Acid Sequence↗
PubMed1993

The Escherichia coli cysG promoter belongs to the 'extended -10' class of bacterial promoters.

The Escherichia coli cysG promoter has been subcloned and shown to function constitutively in a range of different growth conditions. Point mutations identify the -10 hexamer and an important 5'-TGN-3' motif immediately upstream. The effects of different deletions suggest that specific sequences in the -35 region are not essential for the activity of this promoter in vivo. This conclusion was confirmed by in vitro run-off transcription assays. The DNAase I footprint of RNA polymerase at the cysG promoter reveals extended protection upstream of the transcript start, and studies with potassium permanganate as a probe suggest that the upstream region is distorted in open complexes. Taken together, the results show that the cysG promoter belongs to the 'extended -10' class of promoters, and the base sequence is similar to that of the P1 promoter of the E. coli galactose operon, another promoter in this class. In vivo, messenger initiated at the cysG promoter appears to be processed by cleavage at a site 41 bases downstream from the transcript start point.

Base Sequence↗
PubMed1993

Hypersensitivity of human lymphocytes to UV-B and solar irradiation.

T-lymphocytes from three normal human donors, irradiated with broad-spectrum UV-B (peak emission, 312 nm), are 20-fold more sensitive than fibroblasts from four normal donors in a clonogenic assay. We have compared the formation of thymine cyclobutane dimers and pyrimidine-(6-4)-pyrimidone photoproducts following irradiation by UV-C (254 nm) and UV-B and studied killing at doses giving equal dimer formation. UV-B killing of fibroblasts appears to be associated with dipyrimidine photoproduct formation, whereas UV-B killing of lymphocytes is mediated by nondimer damage. Strand breakage following UV-B irradiation measured using the "Comet" assay (single cell gel electrophoresis) reflects this nondimer damage and has kinetics consistent with excisable damage. Lymphocytes from three excision-deficient xeroderma pigmentosum donors show reduced strand breakage and increased killing following UV-B irradiation, compared with lymphocytes from normal donors. We therefore suggest that UV-B kills human lymphocytes by excisable nondimer damage and that xeroderma pigmentosum lymphocytes are defective in its repair. The putative nondimer damage does not appear to be associated with radical attack, and the strand breakage is not a manifestation of apoptosis. A 1-min exposure of human lymphocytes in vitro to natural sunlight is sufficient to produce damage measurable by the Comet assay.

Apoptosis↗
PubMed1993

Fluctuations in infant mortality rates in Berlin during and after the First World War.

"This paper will examine infant mortality in Berlin during and after [World War I].... We argue that the social crisis of war, defeat and postwar instability is reflected in the history of infant mortality in Berlin.... We conclude...that the history of infant mortality in Berlin between 1914 and 1923 is one in which members of marginalized groups, specifically the children of unmarried women, paid an exceptionally high price for the war." (SUMMARY IN FRE)

Demography↗
PubMed1993

An improved procedure for the in vitro expansion of human T-lymphocyte clones for mutant analysis.

Assays detecting mutants present in human peripheral blood T-lymphocytes have been developed to monitor the population for somatic mutations. In order to investigate the nature of the mutations, colonies are further expanded in vitro by repeated lectin stimulation. To characterise fully each mutant clone, sufficient cells (approximately 10(7)) must be available for several molecular and biochemical techniques to be employed. These techniques, and their importance to the assay for population monitoring, are discussed briefly. We report here that the expansion of mutant colonies to approximately 10(7) cells by repeated lectin stimulation is not effective for all T-cell clones but that an alternative "lectin free" expansion method has enabled us to expand all the clones tested from a variety of normal donors and other individuals of interest.

Cell Division↗
PubMed1993

Controlling environmental nitrogen through microbial metabolism.

The major sources of environmental nitrogen are the result of process intensification by human activities such as the chemical synthesis of nitrogenous fertilizers, internal-combustion engines, intensive farming and the use of xenobiotic chemicals in industrial processes. Recent advances in the biochemistry, genetics and ecology of nitrifying and denitrifying bacteria can now be exploited in the control of environmental pollution from these sources. However, frequently, biotreatment must be combined with physical and chemical processes to achieve satisfactory remediation.

Biodegradation, Environmental↗
PubMed1993

Molecular analysis of mutations in the hprt gene in circulating lymphocytes from normal and DNA-repair-deficient donors.

Circulating lymphocytes from patients with the DNA-repair-deficient disorders, xeroderma pigmentosum (XP) and ataxia telangiectasia (A-T) have elevated frequencies of mutants at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus. We have analysed the DNA sequence of the hprt gene in mutants from normal donors, and compared them with mutants from XP and A-T individuals. In normal donors we found a range of mutations including principally transitions (40%), transversions (32%) and small deletions (20%). In an excision-deficient XP donor from complementation group C the mutation spectrum was similar to that from normal donors, whereas in an XP variant there was a significantly higher frequency (44%) of small deletions. In the two A-T donors, there was a high frequency of large deletions (22 and 75%) compared with only 4% in normal donors.

Adult↗
PubMed1993

A new approach to probability of survival scoring for trauma quality assurance.

This study examined the application of an artificial intelligence technique, the neural network (NET), in predicting probability of survival (Ps) for patients with penetrating trauma. A NET is a computer construct that can detect complex patterns within a data set. A NET must be "trained" by supplying a series of input patterns and the corresponding expected output (e.g., survival). Once trained, the NET can recall the proper outputs for a specific set of inputs. It can also extrapolate correct outputs for patterns never before encountered. A neural network was trained on Revised Trauma Score, Injury Severity Score, age, and survival data contained in 3500 of 8300 state registry records of all patients with penetrating trauma reported in Pennsylvania from 1987 through 1990. The remaining 4800 records were analyzed by TRISS, ASCOT, and the trained NET. Sensitivity (accuracy of predicting death) and specificity (accuracy of predicting survival) were 0.840 and 0.985 for TRISS, 0.842 and 0.985 for ASCOT, and 0.904 and 0.972 for the neural network. This represents a decrease in the number of improperly classified ("unexpected") deaths, from 73 for TRISS and 72 for ASCOT, to 44 for the neural network. The increased sensitivity was statistically significant by Chi-square analysis. The NET for penetrating trauma provided a more sensitive but less specific technique for calculating Ps than did either TRISS or ASCOT. This translated into a 40% reduction in the number of deaths requiring review, and the potential for more efficient use of quality assurance resources.

Artificial Intelligence↗
PubMed1993

Identification of the formate dehydrogenases and genetic determinants of formate-dependent nitrite reduction by Escherichia coli K12.

The formate dehydrogenases of Escherichia coli involved in electron transfer from formate to nitrite (Nrf activity: nitrite reduction by formate) have been identified. No previously undescribed selenoprotein was detected in bacteria grown under conditions optimal for the expression of Nrf activity. The Nrf activities of single mutants defective in either FdhN or FdhH were between 50 and 60% that of the parental strain. A double mutant defective in both FdhN and FdhH retained less than 10% of the activity of the FdhN+ FdhH+ strain. No Nrf activity was detected in a triple mutant defective in FdhN, FdhH and FdhO or in the selC strain. It is concluded that all three of the known formate dehydrogenases of E. coli can contribute to the transfer of electrons from formate to the Nrf pathway. Mutants defective in Nrf activity and cytochrome c552 synthesis were isolated by insertion mutagenesis or identified amongst strains received from the E. coli Genetic Stock Center. The mutations were located in at least three regions of the chromosome, including the 92 to 94 minute region which includes fdhF, the gene encoding FdhH required for formate hydrogenlyase activity. Fine structure mapping by P1 transduction established that the nrf mutations in the fdhF region were due to defects in three separable loci, all of which were independent of but close to fdhF. Clones were isolated from a cosmid library that complemented a deletion extending from fdhF into a region essential for Nrf activity. From these clones, plasmids were isolated that complemented only some of the Nrf- mutations in the 92 to 94 minute region, confirming the presence of different operons essential for Nrf activity and cytochrome c552 synthesis in this region. Suggested reasons for this genetic complexity include the need for proteins involved in electron transfer from the various formate dehydrogenases to cytochrome c552, for the attachment of the haem group to the apocytochrome and for cytochrome c552 export into the periplasm.

Cloning, Molecular↗
PubMed1993

Regulation and sequence of the structural gene for cytochrome c552 from Escherichia coli: not a hexahaem but a 50 kDa tetrahaem nitrite reductase.

The structural gene, nrfA, for cytochrome c552, which is the terminal reductase of the formate-dependent pathway for nitrite reduction to ammonia, has been located at co-ordinate 4366 on the physical map of the Escherichia coli chromosome. The DNA sequence of nrfA encodes a tetrahaem c-type cytochrome with a predicted M(r) for the unprocessed product of 53,788. Cleavage of the putative signal peptide at Ala-26 would result in a mature, periplasmic cytochrome of M(r) 50,580 rather than a larger hexahaem cytochrome, as has been widely reported previously. A cytochrome of this size was detected by staining SDS-polyacrylamide gels for covalently bound haem. This cytochrome was partially purified by anion exchange chromatography and confirmed to be cytochrome c552 by difference spectroscopy. Similar cytochromes were detected in five other E. coli strains including strain ST 249, which was used previously to purify and characterize the protein. A plasmid with an in-phase deletion within nrfA directed the synthesis of a truncated haemoprotein of the predicted mass. In-phase translational fusions to lacZ were used to locate the nrfA translation start, and the transcription start site was found by S1 mapping. Expression from the FNR-dependent nrfA promoter was almost totally repressed during aerobic growth, partially induced during anaerobic growth in the absence of nitrite or in the presence of nitrate, but fully induced only during anaerobic growth in the presence of nitrite. No nitrate repression was detected in a narL mutant, but nitrite induction was unaffected, indicating that the nitrite-sensing mechanism is independent of the NarL protein. Expression from the nrfA promoter was subject to glucose repression but regulation was independent of the CRP-cAMP complex.

Aerobiosis↗
PubMed1993

Shade selection and laboratory communication.

This article reviews some of the factors involved in shade selection for prosthetic teeth and suggests simple techniques for accurately transmitting information about the desired color to the laboratory technician.

Color↗
PubMed1993

Urban firearm deaths: a five-year perspective.

Firearm violence is an ever-increasing element in the lives of the U.S. urban population. This study examined the trends in firearm violence and victims during a 5-year period in the city of Philadelphia. Medical Examiner records of all deaths in Philadelphia County in 1985 and 1990 were reviewed. Demographic, autopsy, and criminal record information was analyzed. There were 145 firearm homicide victims in 1985 versus 324 in 1990, a 123% increase. This was primarily because of deaths among young (age 15-24 years), black male victims. Handguns were involved in at least 90% of firearm homicides in both study years. The use of semiautomatic handguns increased from 24% to 39% during the study period. In 1985, 42% of revolver homicides died at the scene, versus 18% in 1990. However, 5% of victims of semiautomatic weapons fire died at the scene in 1985 versus 34% in 1990. The decrease in survival of semiautomatic weapon victims occurred despite the implementation of six trauma centers within the county, and probably reflects a shift toward high-velocity, high-caliber ammunition. Antemortem drug use and criminal history was common. A total of 54% of victims were intoxicated in 1985 and 61% were in 1990. Cocaine became the most common intoxicant in 1990, with 39% of victims using it during the antemortem period. The percentage of victims with a criminal record increased from 44% to 67%. Although the duration of criminal history decreased from 14 to 6 years, the number of patients with previous drug offenses increased from 33% to 84%..(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗