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G Chisholm

Publications and source records attributed to G Chisholm.

18 recordsLinked to original sources
PubMed2001

Production of human type I collagen in yeast reveals unexpected new insights into the molecular assembly of collagen trimers.

Substantial evidence supports the role of the procollagen C-propeptide in the initial association of procollagen polypeptides and for triple helix formation. To evaluate the role of the propeptide domains on triple helix formation, human recombinant type I procollagen, pN-collagen (procollagen without the C-propeptides), pC-collagen (procollagen without the N-propeptides), and collagen (minus both propeptide domains) heterotrimers were expressed in Saccharomyces cerevisiae. Deletion of the N- or C-propeptide, or both propeptide domains, from both proalpha-chains resulted in correctly aligned triple helical type I collagen. Protease digestion assays demonstrated folding of the triple helix in the absence of the N- and C-propeptides from both proalpha-chains. This result suggests that sequences required for folding of the triple helix are located in the helical/telopeptide domains of the collagen molecule. Using a strain that does not contain prolyl hydroxylase, the same folding mechanism was shown to be operative in the absence of prolyl hydroxylase. Normal collagen fibrils were generated showing the characteristic banding pattern using this recombinant collagen. This system offers new opportunities for the study of collagen expression and maturation.

Circular Dichroism↗
PubMed2000

Malpractice.

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Family Practice↗
PubMed2000

Production of recombinant human type I procollagen trimers using a four-gene expression system in the yeast Saccharomyces cerevisiae.

The expression of stable recombinant human collagen requires an expression system capable of post-translational modifications and assembly of the procollagen polypeptides. Two genes were expressed in the yeast Saccharomyces cerevisiae to produce both propeptide chains that constitute human type I procollagen. Two additional genes were expressed coding for the subunits of prolyl hydroxylase, an enzyme that post-translationally modifies procollagen and that confers heat (thermal) stability to the triple helical conformation of the collagen molecule. Type I procollagen was produced as a stable heterotrimeric helix similar to type I procollagen produced in tissue culture. A key requirement for glutamate was identified as a medium supplement to obtain high expression levels of type I procollagen as heat-stable heterotrimers in Saccharomyces. Expression of these four genes was sufficient for correct assembly and processing of type I procollagen in a eucaryotic system that does not produce collagen.

Biopolymers↗
PubMed2000

The First Red Azo Lake Pigment whose Structure is Characterized by Single Crystal Diffraction.

A model for red azo pigment Ca4B was characterized structurally using synchrotron radiation. This highly anisotropic ladder structure represents a new structural class in azo pigment chemistry. The picture shows that the calcium atoms coordinate in a complex manner to three azo ligands (one terdentate, one bidentate, and one monodentate) and two water molecules simultaneously.

Journal Article↗
PubMed2000

Comparison of the structural motifs of acetoacetanilides and related azo pigments

The structures of three methyl-substituted acetoacetanilides and of an azo pigment derived from one of them are presented and discussed together with a review of related known crystal structures. By considering the position of any aromatic substituents it is possible to predict whether the simple acetoacetanilides adopt planar structures with intramolecular hydrogen bonding or twisted structures featuring intermolecular hydrogen bonding. However, we find that the same crystal engineering rules cannot be applied to the related azo pigments: this is apparently due to the presence of an sp(2) atom which facilitates the adoption of planar conformations. The thermal properties of the acetoacetanilides were measured by DSC and are discussed with reference to their crystal structures.

Journal Article↗
PubMed2000

Complete non-puerperial uterine inversion as a result of a uterine sarcoma.

Complete non-puerperial uterine inversion is rare and when present is usually associated with a prolapsed submucous fibroid. The inversion in this case was associated with a uterine sarcoma in an 88 year old diabetic patient, gravida 13, who presented with a four month history of intermittent vaginal bleeding. She was successfully managed with a total abdominal hysterectomy and some of the difficulties with diagnosis and management are highlighted.

Aged↗
PubMed1995

Shared care between general practitioners and urologists in the management of benign prostatic hyperplasia: a survey of attitudes among clinicians.

Recent community-based population surveys have revealed a much greater prevalence of benign prostatic hyperplasia than previously suspected. From these data it has been projected that there may be more than 2 million men in the UK whose quality of life is to some extent impaired by this disorder. Since there are only 330 fully trained urologists in this country it will not be feasible for every individual presenting with prostatism to be assessed by a specialist. In an attempt to provide a more rational basis from which family practitioners can decide whether or not to refer a patient for a specialist opinion a 'shared care' flow diagram was developed and assumptions contained within field tested by means of a postal questionnaire which was sent to 2020 urologists, family practitioners and other interested clinicians. There was general agreement with most of the precepts set out in the flow diagram, the main exception was a rejection of the suggestion that every patient with prostatism should have a prostate-specific antigen level determined before referral. We conclude that there seems a consensus among respondents that a shared care approach to the management of BPH may both improve the standard of care provided in this area by family practitioners and allow hard pressed urologists to focus greater attention on those patients whose conditions require surgical expertise to resolve.

Attitude of Health Personnel↗
PubMed1993

The immunomodulatory effects of urine from patients with superficial bladder cancer receiving intravesical evans BCG therapy.

Bladder cancer cells were stimulated with urine obtained from patients with superficial bladder cancer who had received treatment using intravesical bacillus Calmette-Guérin (BCG). The urine from the first 12 h following each of six BCG instillations was collected and examined for its biological effect. We evaluated effects that had previously been attributed to cytokines detected in the urine of such patients. The modulation of MHC class II antigen and intercellular adhesion molecule-1 (ICAM-1) expression were studied. Using neutralizing polyclonal antibodies to interferon gamma and tumour factor alpha the relative contribution of these molecules to the effects investigated were determined. When cells were stimulated for up to 48 h with first-instillation urine, little effect was seen in any of the parameters investigated. Urine from the sixth instillation, however, proved to be a potent immunomodulatory agent, inducing MHC class II molecule and ICAM-1 expression. Urine from instillations two to five mediated increasing immunomodulatory effects. When sixth-instillation urine samples were treated with neutralizing antibodies to interferon gamma prior to their addition to the bladder cancer cells, a marked and significant decrease in their potency was observed. Only in urine from one patient did any immunomodulatory capability remain after antibody treatment. Neutralizing antibodies to tumour necrosis factor alpha, however, failed to reduce the ability of any patient's urine to induce ICAM-1 expression. When both antibodies were used simultaneously no further decrease in potency was observed. These studies demonstrate for the first time the potential immunomodulatory and cytotoxic effects of urine produced by patients receiving intravesical BCG. Furthermore, in all samples tested, the major immunomodulatory component was shown to be interferon gamma. Although tumour necrosis factor alpha is produced as a result of BCG therapy, this cytokine did not appear to contribute to the parameters investigated, namely the induction of HLA class II antigens, and cell-surface ICAM-1.

BCG Vaccine↗
PubMed1993

Orchiectomy and nilutamide or placebo as treatment of metastatic prostatic cancer in a multinational double-blind randomized trial.

The efficacy and tolerance of the nonsteroidal antiandrogen nilutamide in the treatment of prostatic cancer were studied in a large double-blind clinical trial initiated in 1986. Patients with metastatic prostatic cancer without prior endocrine manipulation underwent orchiectomy and were randomized to 1 of 2 groups receiving nilutamide (225 patients) or placebo (232). Nilutamide and placebo were evaluated for efficacy in 207 and 216 patients, respectively. Progression-free survival was significantly longer in the nilutamide group (median time to progression 20.8 months on nilutamide and 14.9 months on placebo, p = 0.005). Median time to death from prostatic cancer was 30.0 months in the placebo group and 37 months in the nilutamide group. Objective regressions were higher in the nilutamide group (41%) than in the placebo group (24%). Significant differences in favor of the nilutamide group were found at several intervals for bone pain, prostatic acid phosphatase, prostate specific antigen, alkaline phosphatase and bone scan isotope uptake. Nilutamide and orchiectomy constitute a more effective treatment for metastatic prostatic cancer than orchiectomy alone, and the adverse effects of nilutamide, usually minor, are outweighed by the significant improvements in most disease measures and progression-free survival.

Acid Phosphatase↗
PubMed1992

Prostate cancer.

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Aged↗
PubMed1991

Emotional determinants of infant-mother attachment.

The present study examined the assumption that emotion-related characteristics of mothers and infants contribute to the development of infant-mother attachment in the first year of life. Mothers' emotion and personality characteristics were assessed with expressive-behavior ratings and self-report scales. Infant characteristics were measured by emotion and temperament questionnaires (mother report) and objective coding of facial expressions of emotions. Attachment classifications were determined by means of the Strange Situation procedure, and a continuous-variable index of attachment security was derived by a discriminant function procedure. Mothers' emotion experiences, expressive behaviors, and personality traits were significant predictors of the level of security of the infant-mother attachment. Infants' expressive and temperamental characteristics as rated by their mothers were also significant predictors of attachment security.

Child, Preschool↗
PubMed1990

Premenstrual anxiety and depression: comparison of objective psychological tests with a retrospective questionnaire.

Increased anxiety and depression are among the most frequently reported psychological problems in women seeking help for severe symptomatic premenstrual change, but there has been little objective evaluation of these symptoms. We therefore examined the results of objective psychological testing in 40 women with no apparent psychiatric or psychological disorder who had reported moderate to extreme increased anxiety and depression on a retrospective assessment form. Scores on the State-Trait Anxiety Inventory and Institute of Personality and Ability Testing (IPAT) Depression Scale increased from the low symptom intermenstrual phase of the cycle (days 5-10) to the premenstrual phase (within the last 6 days of the cycle), suggesting that retrospective complaints of increased premenstrual anxiety and depression can be confirmed on objective psychological assessment. However, it was observed that the distribution of intermenstrual IPAT depression scores was bimodal. Cyclic changes varied among the tests depending upon the IPAT depression score. The study suggests that 2 populations may exist in this screened sample; one population appears to have "pure PMS" and the second groups manifests a premenstrual exacerbation of subclinical depression.

Adult↗
PubMed1984

Location of the genes that control induction of the allantoin-degrading enzymes in Saccharomyces cerevisiae.

In an effort to understand the regulation of allantoin degradation in Saccharomyces cerevisiae, we isolated two classes of mutants, each defective in the induction process associated with production of the pathway enzymes. Mutation at one locus (DAL80) results in constitutive expression of the genes involved in allantoin catabolism. Mutation at the second locus (DAL-81) results in the loss of ability to induce these enzymes. This report describes genetic data indicating that the DAL80 and DAL81 loci are situated approximately 13 cM from the centromere on the right arm of chromosome XI and 9 cM proximal to the DAL1 locus on chromosome IX, respectively.

Allantoin↗
PubMed1984

cis-Dominant mutations which dramatically enhance DUR1,2 gene expression without affecting its normal regulation.

We have isolated three cis-dominant mutations which dramatically enhance DUR1 ,2 gene expression in Saccharomyces cerevisiae. The mutant phenotype, which is expressed both in haploid and MATa/MAT alpha diploid strains, does not appear to be an alteration of the normal control system for this gene because its expression remained fully inducible and sensitive to nitrogen catabolite repression. Instead, we found much higher levels of DUR1 ,2-specific RNA under both uninduced and induced conditions, i.e., the overproduction trait was superimposed on normal regulation of the gene. The mutations seemed to affect gene expression in a unidirectional manner or to be specific for DUR1 ,2 gene expression, because other genes in proximity to the mutations were not affected. We feel that these mutations may alter the chromatin structure in the vicinity of the DUR1 ,2 upstream control sequences or, alternatively, may be Ty insertions which no longer possess the ROAM characteristics reported by others and ourselves.

Base Sequence↗
PubMed1982

Post-translational processing of urea amidolyase in Saccharomyces cerevisiae.

Urea amidolyase catalyzes the two reactions (urea carboxylase and a allophanate hydrolase) associated with urea degradation in Saccharomyces cerevisiae. Past work has shown that both reactions are catalyzed by a 204-kilodalton, multifunctional protein. In view of these observations, it was surprising to find that on induction at 22 degrees C, approximately 2 to 6 min elapsed between the appearance of allophanate hydrolase and urea carboxylase activities. In search of an explanation for this apparent paradox, we determined whether or not a detectable period of time elapsed between the appearance of allophanate hydrolase activity and activation of the urea carboxylase domain by the addition of biotin. We found that a significant portion of the protein produced immediately after the onset of induction lacked the prosthetic group. A steady-state level of biotin-free enzyme was reached 16 min after induction and persisted indefinitely thereafter. These data are consistent with the suggestion that sequential induction of allophanate hydrolase and urea carboxylase activities results from the time required to covalently bind biotin to the latter domain of the protein.

Allophanate Hydrolase↗
PubMed1982

Isolation and characterization of mutants that produce the allantoin-degrading enzymes constitutively in Saccharomyces cerevisiae.

Degradation of allantoin, allantoate, or urea by Saccharomyces cerevisiae requires the participation of four enzymes and four transport systems. Production of the four enzymes and one of the active transport systems is inducible; allophanate, the last intermediate of the pathway, functions as the inducer. The involvement of allophanate in the expression of five distinct genes suggested that they might be regulated by a common element. This suggestion is now supported by the isolation of a new class of mutants (dal80). Strains possessing lesions in the DAL80 locus produce the five inducible activities at high, constitutive levels. Comparable constitutive levels of activity were also observed in doubly mutant strains (durl dal80) which are unable to synthesize allophanate. This, with the observation that arginase activity remained at its uninduced, basal level in strains mutated at the DAL80 locus, eliminates internal induction as the basis for constitutive enzyme synthesis. Mutations in dal80 are recessive to wild-type alleles. The DAL80 locus has been located and is not linked to any of the structural genes of the allantoin pathway. Synthesis of the five enzymes produced constitutively in dal80-1-containing mutants remains normally sensitive to nitrogen repression even though the dal80-1 mutation is present. From these observations we conclude that production of the allantoin-degrading enzymes is regulated by the DAL80 gene product and that induction and repression of enzyme synthesis can be cleanly separated mutationally.

Allantoin↗