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Biomedical subjects

D J Matthews

Publications and source records attributed to D J Matthews.

35 records · Page 2Linked to original sources
PubMed1995

Interfacial metal-binding site design.

In recent years, much attention has focused on the characterization of metal-binding sites in natural metalloproteins and the design of novel metal-binding motifs. As a result, it is now possible to harness the high specificity and potency of metal-ion binding to modulate intermolecular interactions. Some encouraging results have been obtained using designed metal-binding sites in such diverse applications as the stabilization of artificial peptide assembly, regulation of membrane channels, control of enzyme activity and enhancement of hormone-receptor interactions.

Binding Sites↗
PubMed1995

Proliferation of MIELIKI a novel t(7;9) early pre-B acute lymphoblastic leukemia cell line is inhibited concomitantly by IL-4 and IL-7.

The present study describes a novel cell line, MIELIKI, established from bone marrow of a pediatric patient with B lineage acute lymphoblastic leukemia (ALL) at diagnosis. The MIELIKI cell line displays an early pre-B cell phenotype (CD10+, CD19+, CD20+, CD34-, Cmu-, sIg-) with rearrangements on both Ig heavy chain and k light chain alleles, and carries an unfrequent t(7;9) chromosomal translocation identical to the freshly isolated leukemic blasts. The proliferation of MIELIKI cells was abrogated by IL-4 and by IL-7, as measured by DNA replication and viable cell recovery. The effects of IL-4 and IL-7 were mediated, respectively, through the CDw124 and CDw127 IL-4 and IL-7 receptor components. Growth inhibition by IL-4 was not mediated by soluble factors released by MIELIKI cells in response to IL-4, suggesting the existence of an intrinsic negative signaling pathway. Finally, neither IL-4 nor IL-7 were found to induce maturation of MIELIKI into cells expressing cytoplasmic or surface membrane mu chain. The present cell line should constitute a useful model of t(7;9) early pre-B ALL and allow investigation of the relationship between IL-4 and IL-7 negative signaling in leukemic B cell ontogeny.

Antigens, CD↗
PubMed1994

A survey of furin substrate specificity using substrate phage display.

The substrate specificity of furin, a mammalian enzyme involved in the cleavage of many constitutively expressed protein precursors, was studied using substrate phage display. In this method, a multitude of substrate sequences are displayed as fusion proteins on filamentous phage particles and ones that are cleaved can be purified by affinity chromatography. The cleaved phage are propagated and submitted to additional rounds of protease selection to further enrich for good substrates. DNA sequencing of the cleaved phage is used to identify the substrate sequence. After 6 rounds of sorting a substrate phage library comprising 5 randomized amino acids (xxxxx), virtually all clones had an RxxR motif and many had Lys, Arg, or Pro before the second Arg. Nine of the selected sequences were assayed using a substrate-alkaline phosphatase fusion protein system. All were cleaved after the RxxR, and some substrates with Pro or Thr in P2 were also found to be cleaved as efficiently as RxKR or RxRR. To further elaborate surrounding determinants, we constructed 2 secondary libraries (xxRx(K/R)Rx and xxRxPRx). Although no consensus developed for the latter library, many of the sequences in the the former library had the 7-residue motif (L/P)RRF(K/R)RP, suggesting that the furin recognition sequence may extend over more than 4 residues. These studies further clarify the substrate specificity of furin and suggest the substrate phage method may be useful for identifying consensus substrate motifs in other protein processing enzymes.

Amino Acid Sequence↗
PubMed1994

Engineering an interfacial zinc site to increase hormone-receptor affinity.

BACKGROUND: Human growth hormone (hGH) binds to both the hGH and human prolactin (hPRL) receptors. Binding to the hPRL receptor, however, is approximately 50-fold tighter and requires a single Zn2+ cation, unlike binding of hGH to the hGH receptor. Previous mutational studies have identified putative ligands from hGH and the hPRL receptor responsible for coordinating the interfacial Zn2+. RESULTS: One of these ligands was introduced at a structurally analogous site in the extracellular domain of the hGH receptor by mutating Asn218 to His, and the resulting mutant protein showed a 20-fold increase in hGH binding in the presence of ZnCl2. Alanine-scanning mutagenesis showed that the binding site on hGH for the Asn218-->His hGH receptor in the presence of Zn2+ resembled that for the hPRL receptor. CONCLUSIONS: It is possible to introduce the metal-binding site from the hPRL receptor into the homologous hGH receptor. More generally, these studies indicate that affinity between two proteins may be enhanced by design of an interfacial metal-binding site.

Binding Sites↗
PubMed1993

Substrate phage: selection of protease substrates by monovalent phage display.

A method is described here for identifying good protease substrates among approximately 10(7) possible sequences. A library of fusion proteins was constructed containing an amino-terminal domain used to bind to an affinity support, followed by a randomized protease substrate sequence and the carboxyl-terminal domain of M13 gene III. Each fusion protein was displayed as a single copy on filamentous phagemid particles (substrate phage). Phage were then bound to an affinity support and treated with the protease of interest. Phage with good protease substrates were released, whereas phage with substrates that resisted proteolysis remained bound. After several rounds of binding, proteolysis, and phagemid propagation, sensitive and resistant substrate sequences were identified for two different proteases, a variant of subtilisin and factor Xa. The technique may also be useful for studying the sequence specificity of a variety of posttranslational modifications.

Amino Acid Sequence↗
PubMed1992

Binding of the Kunitz-type trypsin inhibitor DE-3 from Erythrina caffra seeds to serine proteinases: a comparative study.

The effect of pH and temperature on kinetic and thermodynamic parameters (i.e., k(on),k(off),Ka,delta G0, delta H0 and delta S0 values) for the binding of the Kunitz-type trypsin inhibitor DE-3 from Erythrina caffra seeds (ETI) to bovine beta-trypsin, bovine alpha-chymotrypsin, the human tissue plasminogen activator, human alpha-, beta- and gamma-thrombin, as well as the M(r) 33,000 and M(r) 54,000 species of the human urinary plasminogen activator (also named urokinase) has been investigated. At pH 8.0 and 21.0 degrees C: (i) values of the second-order rate constant (K(on)) for the proteinase:ETI complex formation vary between 8.7 x 10(5) and 1.4 x 10(7)/M/s; (ii) values of the dissociation rate constant (k(off)) for the proteinase: ETI complex destabilization range from 3.7 x 10(-5) to 1.4 x 10(-1)/s; and (iii) values of the association equilibrium constant (Ka) for the proteinase:ETI complexation change from < 1.0 x 10(4) to 3.8 x 10(11)/M. Thus, differences in k(off) values account mostly for the large changes in Ka values for ETI binding. The affinity of ETI for the serine proteinases considered can be arranged as follows: bovine beta-trypsin > human tissue plasminogen activator > bovine alpha-chymotrypsin >> human alpha-, beta- and gamma-thrombin approximately M(r) 33,000 and M(r) 54,000 species of the human urinary plasminogen activator. Moreover, the serine proteinase:ETI complex formation is an endothermic, entropy-driven, process.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Assignment of the polymorphic intestinal mucin gene (MUC2) to chromosome 11p15.

A cDNA coding for a mucin expressed in intestine has recently been cloned (Gum et al. 1989). We describe here the use of this cDNA to map the gene (MUC2) to human chromosome 11 using somatic cell hybrids, and to make the regional localization to 11p15 by in situ hybridization. Analysis of the CEPH (Centre d'Etude du Polymorphisme Humain) families revealed that MUC2 forms part of the tight linkage group on 11p15 which contains HRAS, INS, TH and HBBC.

Animals↗
PubMed1990

Ethical issues encountered in pediatric rehabilitation.

Ethical issues in pediatric rehabilitation should be viewed within the framework of the understanding of the terms of autonomy, nonmaleficence, beneficence and justice. In dealing with the pediatric patient, health professionals are most frequently treating the parents who have the decision-making authority. Normalization which underlies the concept of mainstreaming has become an important issue in pediatric rehabilitation. Normalization is based on the provision of opportunities for choosing, for independent decision making, and for autonomy. The right of the disabled child to have sexual information and to be acknowledged as a sexual individual is essential to the child's autonomy. More children are surviving catastrophic injuries and living with severe disabilities. Birth defects such as myelodysplasias point to the issues of treatment selection involving ethical, moral, philosophical, religious, financial and social values. The phrase 'quality of life' is often applied in these situations and is frequently understood as the 'best interests of the child' which should result in child-centered decisions. In this way, a decision to begin or to withhold treatment can be made in a more ethically considered manner. Resource allocation is of special concern in disabled children since they may consume significant resources in medical and rehabilitation costs spent throughout a lifetime. However, these costs may be justifiable when a disabled child matures into a productive adult. If maximum benefit of limited resources is to be achieved, these children should receive their care from rehabilitation professionals in established centers of rehabilitation expertise. However, we may soon need to accept the responsibility for rationing rehabilitative care as the number of disabled children grows beyond the dollars available to be spent.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Pediatric rehabilitation. 1. General principles and special considerations.

This self-directed learning module addresses core concepts in the assessment of any child with disability, including physical growth and development, evolution of reflexes, and cognitive and personality development. It is a section of the chapter on pediatric rehabilitation for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. The rehabilitation perspective is emphasized, especially as it changes to accommodate the developing child, with a focus on specific chronic disorders such as respiratory disease, congenital heart disease, and malignancy. These types of disorders serve as a model for the management of problems that require special medical, rehabilitative, and psychosocial consideration.

Child↗
PubMed1989

Pediatric rehabilitation. 2. Brain damage causing disability.

This self-directed learning module addresses rehabilitation issues in the child with brain damage. It is a section of the chapter on pediatric rehabilitation for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. In addition to the motor manifestations, intellectual, social, and emotional impairment are addressed. Problems vary with developmental stage. Emphasis is on the etiology, severity, and combination of deficits in order to develop a plan of management, including physical, occupational, and speech therapy, recreational and social milieu, and family and community resources.

Brain Damage, Chronic↗
PubMed1989

Pediatric rehabilitation. 3. Disorders of the spinal cord: spinal cord injury, myelodysplasia.

This self-directed learning module provides review and references for the basic concepts of, and highlights new advances in, disorders of the spinal cord in children. It is a section of the chapter on pediatric rehabilitation for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. For spinal cord injury, only data pertinent to the pediatric age group are discussed. Myelodysplasia is presented in detail to include genetic implications, early intervention, long-term management planning, psychosocial impact, and quality-of-life considerations.

Child↗
PubMed1989

Pediatric rehabilitation. 4. Disorders of the motor unit.

This self-directed learning module addresses diagnostic and rehabilitation issues in children with the most common disorders of the motor unit. It is a section of the chapter on pediatric rehabilitation for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. Conditions occurring only in infancy or childhood and differences in diagnostic and rehabilitation approaches as compared with those used in adults are highlighted.

Child↗
PubMed1989

Pediatric rehabilitation. 5. Joint and connective tissue diseases.

This self-directed learning module presents pertinent information about rehabilitation management of specific joint and connective tissue diseases affecting children. This section highlights juvenile rheumatoid arthritis, Lyme disease, rheumatic fever, hemophilia, dermatomyositis, polymyositis, systemic lupus erythematosus, and other forms of arthritis. It is a section of the chapter of pediatric rehabilitation for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation.

Child↗
PubMed1989

Pediatric rehabilitation. 6. Musculoskeletal and soft tissue disorders.

This self-directed learning module highlights advances in evaluation and treatment of congenital and acquired musculoskeletal disorders in the child. It is a section of the chapter on pediatric rehabilitation for the Self-Directed Medical Knowledge Program Study Guide for practitioners and trainees in physical medicine and rehabilitation. This section contains information on alterations of limb structure and gait, scoliosis, torticollis, sports injuries and overuse syndromes, and unexplained pain in children.

Arm Injuries↗
PubMed1984

Functional outcome of closed head injury in children and young adults.

A comprehensive questionnaire which measured gross and fine motor function in the area of cognition, communication, and social development was completed by parents of children and young adults who had suffered severe closed head injuries between the years 1967 and 1978. The final sample included 42 returned questionnaires. Of these patients, 15 (37%) were considered independent, 20 (49%) dependent, and 6 (14%) had died. The area of cognition and communication dysfunction seemed to contribute most to dependency. The younger age group and the patients who were comatose for a shorter period of time tended to do the best functionally. While severe closed head injury can result in significant disability, many patients can achieve functional independence.

Adolescent↗