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Biomedical subjects

D A Matthews

Publications and source records attributed to D A Matthews.

At least 55 records · Page 3Linked to original sources
PubMed1994

Structure of human rhinovirus 3C protease reveals a trypsin-like polypeptide fold, RNA-binding site, and means for cleaving precursor polyprotein.

The structure of human rhinovirus-14 3C protease (3Cpro) has been determined at 2.3 A resolution and refined to an R factor of 0.22. This cysteine protease folds into two topologically equivalent six-stranded beta barrels and in this sense is similar to trypsin-like serine proteases. However, there are differences in the lengths and positioning of individual beta strands as well as in loops connecting elements of secondary structure. The catalytic residues Cys-146, His-40, and Glu-71 are positioned as in serine proteases, but the oxyanion hole is moved 1-1.2 A away. Residues that bind to the 5' noncoding region of rhinovirus genomic RNA are located on the opposite side of the molecule from the active site. Interactions between individual 3Cpro molecules in the crystal lattice suggest a model for intermolecular proteolytic cleavage of the 3CD polyprotein.

3C Viral Proteases↗
PubMed1994

Structure of and kinetic channelling in bifunctional dihydrofolate reductase-thymidylate synthase.

The bifunctional enzyme dihydrofolate reductase-thymidylate synthase catalyses both the reductive methylation of 2'-deoxyuridylate and the subsequent reduction of dihydrofolate to yield 2'-deoxythymidylate and tetrahydrofolate at two spacially discrete sites situated on different protein domains. The X-ray structure of dihydrofolate reductase-thymidylate synthase from Leishmania major indicates that transfer of dihydrofolate between these sites does not occur by transient binding at both sites but rather by movement of dihydrofolate across the surface of the protein. The enzyme has an unusual surface charge distribution that could account for this channelling of dihydrofolate between active sites.

Amino Acid Sequence↗
PubMed1994

Alpha-delta sleep in patients with a chief complaint of chronic fatigue.

Our prospective, standardized cohort study was designed to assess the presence of alpha wave intrusions during non-rapid eye movement sleep (alpha-delta sleep) and its relationship to fibromyalgia, major depression, and chronic fatigue syndrome (CFS) in patients with a chief complaint of chronic fatigue. The study group comprised 30 consecutive patients seen at a university hospital referral clinic for evaluation of chronic fatigue. All patients had nocturnal polysomnography, dolorimetric tender point assessment for fibromyalgia, a comprehensive history, physical, and laboratory evaluation, and a structured psychiatric interview. Alpha-delta sleep was identified in 8 of the 30 patients (26%), major depression in 20 (67%), CFS in 15 (50%), and fibromyalgia in 4 (13%). Ten of the 30 patients (33%) had a primary sleep disorder (sleep apnea, periodic limb movements, or narcolepsy). Alpha-delta sleep was not significantly correlated with fibromyalgia, CFS, major depression, or primary sleep disorders, but was significantly more common among patients who had chronic fatigue without major depression. We conclude that primary sleep disorders are relatively common among patients with chronic fatigue and must be diligently sought and treated. Alpha-delta sleep is not a marker of fibromyalgia or CFS, but may contribute to the illness of nondepressed patients with these conditions.

Adolescent↗
PubMed1994

Adenovirus protein-protein interactions: hexon and protein VI.

A variety of mastadenoviruses were denatured, their polypeptides separated by electrophoresis on SDS-polyacrylamide gels and transferred to nitrocellulose. The immobilized polypeptides were washed, incubated with buffers containing hexons from human adenoviruses (Ad) types 2, 5 and 12 and the location of bound hexons was detected with anti-hexon antibodies. It was found that hexons from any of the three human adenovirus types bound to protein VI from all the mastadenoviruses examined. Furthermore we found that hexon-VI binding was significantly greater than the interaction between hexon and the precursor to VI, pVI. This binding was susceptible to detergents and to changes in pH or salt concentration. A rabbit polyclonal antibody was raised against a recombinant protein derived from the middle third of pVI from Ad2 and was used to quantify the difference in binding and to demonstrate the presence of a single intermediate (designated iVI) in the processing of pVI to VI. The affinity between iVI and hexon was considerably greater in our assay than that of pVI but was less than that between hexon and VI. A complementary binding of recombinant iVI to immobilized hexons was also demonstrated. This latter interaction, however, was only observed when hexon preparations were not boiled prior to electrophoresis, substantiating the proposition that the recognition motif on the hexon was conformation-dependent. These results are discussed in the context of understanding further the molecular basis of protein-protein interactions between the structural proteins of adenoviruses and the factors involved in virion maturation.

Adenoviruses, Human↗
PubMed1994

Analysis of respiratory syncytial virus strain variation in successive epidemics in one city.

The variability of respiratory syncytial virus isolates from five successive epidemics in an urban population was determined. A total of 187 isolates of respiratory syncytial virus from the southern part of Birmingham, United Kingdom, were classified into subgroups A and B and were then further assigned to genetic lineages. Allocation of isolates into lineages was achieved by reverse transcription of infected cell RNA and then PCR amplification of selected regions of the genome; PCR products were examined by restriction mapping or nucleotide sequencing of parts of the nucleoprotein gene, the small hydrophobic protein gene, and the attachment protein gene. Previous work has shown that estimations of genetic diversity by analysis of genes coding for proteins likely (attachment protein) and unlikely (nucleoprotein and small hydrophobic protein) to be under immune pressure gave concordant results. Six genetic lineages of subgroup A isolates have been defined by this procedure; these isolates differ by up to 20% in the amino acid sequences of their attachment proteins; likewise, subgroup B isolates can be divided into two categories by restriction mapping of parts of their nucleoprotein and attachment protein genes. The same genetic lineages appeared to be present worldwide during the same period. The analysis of isolates from successive epidemics showed that different lineages predominated in each epidemic and that not all lineages were present in every epidemic. Some lineages appeared to increase in numbers over several years and then decline, possibly indicating a buildup of resistance in the community to a particular genotype.

Capsid↗
PubMed1993

Making "connexions": enhancing the therapeutic potential of patient-clinician relationships.

Healers must try to understand what the illness means to the patient and create a therapeutic sense of connection in the patient-clinician relationship. A favorable climate for "connexional" experiences can be created through the use of various interviewing techniques. Attending to rapport, silencing internal talk, accessing unconscious processes, and communicating understanding can help clinicians enhance their sensitivity to the subtle clues on which issues of meaning and connection often depend. Several risks are associated with the establishment of closer patient-clinician relationships, including dependence and power issues, sexual attraction, and deeper exposure of the clinician to the patient's pain. Prepared with an awareness of these risks and techniques to address them, clinicians are encouraged to deepen their level of dialogue with patients, to compare their experiences with those of other clinicians, and to thereby develop a more systematic understanding of therapeutic relationships.

Communication Barriers↗
PubMed1993

Design of thymidylate synthase inhibitors using protein crystal structures: the synthesis and biological evaluation of a novel class of 5-substituted quinazolinones.

The design, synthesis, and biological evaluation of a new class of inhibitors of thymidylate synthase (TS) is described. The molecular design was carried out by a repetitive crystallographic analysis of protein-ligand structures. At the onset of this project, we focused on the folate cofactor binding site of a high-resolution ternary crystal complex of Escherichia coli TS, 5'-fluorodeoxyuridylate (5-FdUMP) and a classical glutamate-containing folic acid analog. A preliminary ternary crystal structure of a novel compound was successfully solved. Upon analysis of this initial complex, further structural elaborations were made, and a series of active 5-(arylthio)quinazolinones was developed. The synthetic strategy was based on the displacement of a halogen at the 5-position of a quinazolinone by various aryl thioanions. The compounds were tested for inhibition of purified E. coli and/or human TS, and were assayed for cytotoxicity against three tumor cell lines in vitro. Significant thymidine protection effects were observed with several of the inhibitors, indicating that TS was the intracellular locus of activity.

Crystallography↗
PubMed1993

Food intolerance in patients with chronic fatigue.

Intolerance to various foods is reported often by patients seeking evaluation for chronic fatigue, a common symptom in primary care practice. To assess the prevalence and significance of this phenomenon we studied 200 consecutive patients with chronic fatigue who were given a comprehensive medical and psychiatric evaluation. Intolerance to foods from at least three different groups was reported by 27 patients (13.5%). We compared these patients with 27 age- and gender-matched patients from the same cohort of fatigued patients. Physical examination and laboratory testing showed few abnormalities in either group. The two groups were similar with respect to the duration and severity of fatigue, lifetime depressive symptoms, and prevalence of current depressive disorders (67% vs. 63%) and anxiety disorders (11% vs. 15%). Patients with multiple food intolerance had more lifetime functional somatic symptoms (p < .05) and a significantly higher (33% vs. 7%) prevalence of somatization disorder (p < .025). These data suggest that intolerance to multiple foods is probably not a cause or the effect of chronic fatigue, but rather one of the manifestations of the somatization trait expressed in these patients.

Adult↗
PubMed1993

Chronic fatigue and chronic fatigue syndrome: clinical epidemiology and aetiological classification.

To determine the medical and psychiatric diagnoses that have an aetiological role in chronic fatigue we conducted a prospective study of 405 (65% women) patients who presented for evaluation with this chief complaint to an academic medical centre. The average age was 38.1 years and the average duration of fatigue at entry in the study was 6.9 years. All patients were given comprehensive physical and laboratory evaluations and were administered a highly structured psychiatric interview. Psychiatric diagnoses explaining the chronic fatigue were identified in 74% of patients and physical disorders were diagnosed in 7% of patients. The most common psychiatric conditions in this series were major depression, diagnosed in 58% of patients, panic disorder, diagnosed in 14% of patients, and somatization disorder, diagnosed in 10% of patients. Primary sleep disorders, diagnosed in 2% patients, and chronic infections, confirmed in 1.6% patients, explained the majority of cases whose chronic fatigue was attributed to a physical disorder. Thirty per cent of patients met the criteria used to define the chronic fatigue syndrome (CFS). Compared with age- and gender-matched control subjects with chronic fatigue, CFS patients had a similarly high prevalence of current psychiatric disorders (78% versus 82%), but were significantly more likely to have somatization disorder (28% versus 5%) and to attribute their illness to a viral infection (70% versus 33%). We conclude that most patients with a chief complaint of chronic fatigue, including those exhibiting the features of CFS, suffer from standard mood, anxiety and/or somatoform disorders. Careful research is still needed to determine whether CFS is a distinct entity or a variant of these psychiatric illness.

Adult↗
PubMed1993

Frequent polymerase errors observed in a restricted area of clones derived from the attachment (G) protein gene of respiratory syncytial virus.

Sequence analysis of a large number of clones derived from the carboxy-terminal one-third of the attachment (G) protein gene of subgroup A respiratory syncytial viruses revealed a region very prone to polymerase errors which resulted mainly in frameshifts because of the insertion or deletion of adenosine residues in some but not all runs of such residues. Such mutations were detected in 14% of clones derived from mRNA, 58% of clones derived from genomic-sense RNA, and 50% of clones derived from in vitro-transcribed RNA. This phenomenon appears to be dependent on the template sequence.

Adenosine↗
PubMed1992

Analysis of relatedness of subgroup A respiratory syncytial viruses isolated worldwide.

Respiratory syncytial virus strains (subgroup A) isolated from around the world during the period 1988-1991 were analysed to determine their relatedness. Analysis was by restriction mapping and nucleotide sequencing following amplification of selected regions of the virus genome by polymerase chain reaction (PCR). Twenty-three viruses of subgroup A isolated from cities in temperate regions of the Northern and Southern hemispheres and the tropics during the period 1988-1991 fell into distinct groupings closely related to four of the six lineages defined in analysis of recurrent epidemics within the same city (Birmingham, UK) during the same period. These observations confirm that multiple lineages of RS virus co-circulate locally, and show that very similar viruses are present simultaneously in widely separated countries.

Amino Acid Sequence↗
PubMed1992

Characterization and nucleotide binding properties of a mutant dihydropteridine reductase containing an aspartate 37-isoleucine replacement.

Kinetic constants for the interaction of NADH and NADPH with native rat dihydropteridine reductase (DHPR) and an Escherichia coli expressed mutant (D-37-I) have been determined. Comparison of kcat and Km values measured employing quinonoid 6,7-dimethyldihydropteridine (q-PtH2) as substrate indicate that the native enzyme has a considerable preference for NADH with an optimum kcat/Km of 12 microM-1 s-1 compared with a figure of 0.25 microM-1 s-1 for NADPH. Although the mutant enzyme still displays an apparent preference for NADH (kcat/Km = 1.2 microM-1 s-1) compared with NADPH (kcat/Km = 0.6 microM-1 s-1), kinetic analysis indicates that NADH and NADPH have comparable stickiness in the D-37-I mutant. The dihydropteridine site is less affected, since the Km for q-PtH2 and K(is) for aminopterin are unchanged and the 14-26-fold synergy seen for aminopterin binding to E.NAD(P)H versus free E is decreased by less than 2-fold in the D-37-I mutant. No significant changes in log kcat and log kcat/Km versus pH profiles for NADH and NADPH were seen for the D-37-I mutant enzyme. However, the mutant enzyme is less stable to proteolytic degradation, to elevated temperature, and to increasing concentrations of urea and salt than the wild type. NADPH provides maximal protection against inactivation in all cases for both the native and D-37-I mutant enzymes. Examination of the rat DHPR sequence shows a typical dinucleotide binding fold with Asp-37 located precisely in the position predicted for the acidic residue that participates in hydrogen bond formation with the 2'-hydroxyl moiety of all known NAD-dependent dehydrogenases. This assignment is consistent with x-ray crystallographic results that localize the aspartate 37 carboxyl within ideal hydrogen bonding distance of the 2'- and 3'-hydroxyl moieties of adenosine ribose in the binary E.NADH complex.

Amino Acid Sequence↗
PubMed1992

Crystal structure of rat liver dihydropteridine reductase.

The structure of a binary complex of dihydropteridine reductase [DHPR; NAD(P)H:6,7-dihydropteridine oxidoreductase, EC 1.6.99.7] with its cofactor, NADH, has been solved and refined to a final R factor of 15.4% by using 2.3 A diffraction data. DHPR is an alpha/beta protein with a Rossmann-type dinucleotide fold for NADH binding. Insertion of an extra threonine residue in the human enzyme is associated with severe symptoms of a variant form of phenylketonuria and maps to a tightly linked sequence of secondary-structural elements near the dimer interface. Dimerization is mediated by a four-helix bundle motif (two helices from each protomer) having an unusual right-handed twist. DHPR is structurally and mechanistically distinct from dihydrofolate reductase, appearing to more closely resemble certain nicotinamide dinucleotide-requiring flavin-dependent enzymes, such as glutathione reductase.

Animals↗
PubMed1992

Design and synthesis of novel 6,7-imidazotetrahydroquinoline inhibitors of thymidylate synthase using iterative protein crystal structure analysis.

Antifolate inhibitors of thymidylate synthase (TS) have primarily been based on the structure of folic acid. This paper describes the identification and development of novel 6,7-imidazotetrahydroquinoline TS inhibitors by iterative ligand design, synthesis, and crystallographic analysis of protein-inhibitor complexes. Beginning with a high-resolution crystal structure of E. coli TS (TS, EC 2.1.1.45), an imidazotetrahydroquinoline inhibitor was designed de novo to occupy the folate binding pocket. Structural modifications of the initial compound 1h (Ki approximately 5 microM human/E. coli TS) were then made on the basis of feedback from additional cocrystal structures and activity data. An amino group in the 2-position of the imidazole was found to increase the potency of the series by 1-2 orders of magnitude. Other substitutions on the imidazole ring (1-CH3, 2-CH3, 2-NHCH3, 2-SCH3) generally led to weaker inhibition. Additional improvements in activity were obtained by modification of the substituents on the tetrahydroquinoline nitrogen, bringing the Ki of three of the compounds below 15 nM against the human TS enzyme. The compounds were tested for cytotoxicity and were shown to inhibit the growth of three tumor cell lines in vitro.

Adenocarcinoma↗
PubMed1992

Children in hospital: II. Reading therapy and children in hospital.

Following the survey of book and library services described in the first of these two articles (Health Libraries Review, 8, 210-219), a research project funded by BNB Research Fund in 1991 investigated the theory and practice of reading therapy with children in hospital. Hospital play staff had been identified as the therapists most commonly involved and a number of them were interviewed using advance notice questionnaires and structured discussion. The following aspects were investigated: definitions of reading therapy, children in hospital, the reading therapy process, materials used, evaluation, services to facilitate and promote reading therapy, training and the role of libraries and librarians. Recommendations relate to practice, to provision and listing of materials, to evaluation procedures and to training. The final conclusions relate to the role of librarians in the processes and development of reading therapy with children in hospital.

Bibliotherapy↗
PubMed1992

Chronic fatigue syndromes in clinical practice.

Chronic fatigue is a common and difficult challenge in clinical practice. The majority of patients with this chief complaint have treatable mood or anxiety disorders, complicated by a tendency toward somatization. A minority of patients suffer from sleep disorders, endocrinologic abnormalities, or chronic inflammatory conditions. Prolonged recovery after viral infections is only rarely the cause of chronic fatigue. Specific pharmacologic interventions and cognitive-behavioral therapy are effective in an environment that is sensitive to the patient's interpretation of symptoms and avoids unproven medical investigations and therapies.

Adult↗
PubMed1992

The pathophysiology of chronic fatigue syndrome: confirmations, contradictions, and conjectures.

OBJECTIVE: To examine published data regarding patient cohorts with the recently defined chronic fatigue syndrome. METHOD: Review of thirty-two peer-assessed research publications that included full disclosure of the methodology employed; classification of the findings as confirmed, contradictory, or non-duplicated. RESULTS: Research studies have confirmed that the majority of patients with the chronic fatigue syndrome: 1) are white middle-aged women, 2) have a high prevalence of current major depression and somatization disorder, 3) have abnormal personality traits, 4) believe that their fatigue has a physical cause, and 5) show mild abnormalities of humoral immunity. Contradictory data have been presented with regard to: 1) the time of onset of depressive disorders, 2) the etiologic role of herpetic and enteroviral infections, 3) the presence of abnormal cellular immunity, and 4) the clinical utility of immunoglobulin therapy. Non-duplicated research has indicated 1) hypothalamic-pituitary-adrenal axis dysfunction, 2) abnormalities on magnetic resonance images of the brain, 3) altered cytokine production, and 4) the possibility of retroviral infection. CONCLUSIONS: As presently defined, the chronic fatigue syndrome has many of the clinical and biological features associated with depressive and somatoform disorders. A specific etiologic role for infections or immune dysfunction has not been confirmed.

Adrenocorticotropic Hormone↗