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D H Harrison

Publications and source records attributed to D H Harrison.

At least 37 records · Page 2Linked to original sources
PubMed1997

The alrestatin double-decker: binding of two inhibitor molecules to human aldose reductase reveals a new specificity determinant.

It is generally expected that only one inhibitor molecule will bind to an enzyme active site. In fact, specific drug design theories depend upon this assumption. Here, we report the binding of two molecules of an inhibitor to the same active site which we observed in the 1.8 A resolution structure of the drug Alrestatin bound to a mutant of human aldose reductase. The two molecules of Alrestatin bind to the active site in a stacked arrangement (a double-decker). This stack positions the carboxylic acid of one drug molecule near the NADP+ cofactor at a previously determined anion binding site and the carboxylic acid of the second drug molecule near the carboxy-terminal tail of the enzyme. We propose that interactions of inhibitors with the carboxy-terminal loop of aldose reductase are critical for the development of inhibitors that are able to discriminate between aldose reductase and other members of the aldo-keto reductase superfamily. This finding suggests a new direction for the introduction of specificity to aldose reductase-targeted drugs.

Aldehyde Reductase↗
PubMed1997

Urethral advancement and glanuloplasty (UGPI): a modification of the MAGPI procedure for distal hypospadias.

A modification of the meatal advancement and glanuloplasty technique (MAGPI), the urethral advancement and glanuloplasty (UGPI), is described. Forty-seven patients, who had this operation from 1985 to 1994, have been reviewed. The overall complication rate was low with a 2.1% fistula rate and a 6.4% incidence of meatal retraction. Only one patient required secondary surgery.

Child, Preschool↗
PubMed1997

The distally based ulnar artery island flap in hand reconstruction.

The distally based ulnar artery island flap is a highly versatile flap for hand reconstruction. It fulfils all the necessary criteria required for a flap to the hand providing thin pliable hairless skin. It can be used as a composite flap including tendon and bone and provides an ideal tunnel for tendons to glide in. It can be used as a fasciocutaneous flap or as a fascial flap and can easily be rotated to the dorsum of the hand by opening Guyon's canal. The palm or dorsum of the hand and even the fingertips can be reached easily. A superficial venous anastomosis should be made if marked venous congestion is noted intraoperatively. Six cases utilizing a distally based ulnar island flap in hand reconstruction are presented.

Adolescent↗
PubMed1996

Regeneration through a long nerve graft used in the correction of facial palsy. A qualitative and quantitative study.

A surgical technique has been developed for the correction of established unilateral palsy in man. A long (20 cm or more) sural nerve graft is anastomosed to a facial nerve branch on the unaffected side and its distal end left lying free in the cheek of the affected side. After regeneration times of 5.5-14.5 months, the distal end of the graft is joined to a free (pectoralis minor) muscle graft. In due course the muscle graft contracts in unison with the unaffected side giving near normal symmetry to facial movements. In 30 cases (ages 6-52 years) qualitative and quantitative examination was made of the distal end of grafts taken at the time of joining the graft to the muscle. Total axon counts, myelinated plus non-myelinated, confirmed abundant regeneration when compared with total axons in the supplying facial nerve; myelinated fibres remained small (mean diameter 2.5 micrometers) over the range of regeneration times. Quantitation included non-myelinated axons because they probably have the potential to become myelinated once the nerve is functional. Numbers of regenerating axons were not correlated with age, nor with regeneration time. Lack of a distal connection did not appear to lead to secondary degeneration of the regenerated myelinated fibres. These were maintained in an 'immature' state for many months. This observation is of practical interest since it has been suggested that delayed connection to the distal target may have a deleterious effect on the outcome of the procedure.

Adolescent↗
PubMed1996

Is permanent congenital facial palsy caused by birth trauma?

OBJECTIVE: To study the relation between traumatic birth and the development of permanent facial palsy in the newborn. DESIGN: Retrospective case control study of children with 'congenital' facial palsy. SETTING: Two tertiary referral centres for patients with facial palsy. SUBJECTS: 61 children with established facial palsy. MAIN OUTCOME MEASURES: Odds ratios of recognised factors for birth injury: maternal primiparity, high birth weight, and the use of obstetric forceps at delivery. RESULTS: 13.2% of those studied had forceps assisted delivery compared to 10.2% in the normal population (odds ratio 1.34; 95% confidence intervals 0.61 to 2.97) 39.6% were born to primiparae compared to a national rate of 36.7% (1.13; 0.65 to 1.96) and only 18.9% weighed more than 3500 g at birth (0.37; 0.19 to 0.74). CONCLUSIONS: There is no association between the development of permanent 'congenital' facial palsy and recognised risk factors for birth injury. These data suggest an intrauterine rather than a traumatic aetiology.

Birth Injuries↗
PubMed1996

Hypospadias repair: the influence of postoperative care and a patient factor on surgical morbidity.

More than 200 surgical techniques have been advocated for hypospadias repair and perfection is still eluding us. The purpose of this paper is not to comment on a surgical technique, but to highlight the importance of postoperative care on the eventual surgical outcome. Two hundred six children undergoing primary hypospadias surgery from 1984 to 1994 at Mount Vernon Hospital were analyzed. The mean age of surgery was 3.8 years (range, 8 months-17 years) and our mean follow-up was 6.1 years. Various surgical techniques were used. During 1989, we changed our postoperative regime and patients were mobilized early (within 48 hours) compared to the strict-bed rest-till-catheter-out regime before 1988. This significantly reduced our fistula rate from 22% to 9.8% (chi squared p = 0.0016). Patient factors such as pulling on the catheter, urinary obstruction/blocked catheter, erections, straining due to constipation, and interference with dressings influence surgical outcome negatively. One of these patient factors was documented in all of our 33 patients who developed fistulas. In 6 patients (3.5%), a patient factor was present without any complication. This is highly significant statistically (chi squared p < 0.0001). The type of urinary diversion, period of urinary diversion, type of dressing, catheter size, and anesthetic regime did not influence outcome significantly.

Adolescent↗
PubMed1995

All in the family.

Identification of the residues involved in the reaction catalysed by aldehyde reductase should aid in the development of drugs for the treatment of diabetic complications.

Aldehyde Reductase↗
PubMed1994

Structure of the human ADP-ribosylation factor 1 complexed with GDP.

ADP-ribosylation factors (ARFs) are essential and ubiquitous in eukaryotes, being involved in vesicular transport and functioning as an activator of phospholipase D (refs 1, 2) and cholera toxin. The functions of ARF proteins in membrane traffic and organelle integrity are intimately tied to its reversible association with membranes and specific interactions with membrane phospholipids. One common feature of these functions is their regulation by the binding and hydrolysis of GTP. Here we report the three-dimensional structure of full-length human ARF1 (M(r) 21,000) in its GDP-bound non-myristoylated form. The presence of a unique amino-terminal alpha-helix and loop, together with differences in Mg2+ ligation and the existence of a non-crystallographic dimer, set this structure apart from other GTP-binding proteins. These features provide a structural basis for the GTP-dependent modulation of membrane affinity, the lack of intrinsic GTPase activity, and the nature of effector binding surfaces.

ADP-Ribosylation Factor 1↗
PubMed1994

Structure of the regulatory domain of scallop myosin at 2.8 A resolution.

The regulatory domain of scallop myosin is a three-chain protein complex that switches on this motor in response to Ca2+ binding. This domain has been crystallized and the structure solved to 2.8 A resolution. Side-chain interactions link the two light chains in tandem to adjacent segments of the heavy chain bearing the IQ-sequence motif. The Ca(2+)-binding site is a novel EF-hand motif on the essential light chain and is stabilized by linkages involving the heavy chain and both light chains, accounting for the requirement of all three chains for Ca2+ binding and regulation in the intact myosin molecule.

Amino Acid Sequence↗
PubMed1994

An anion binding site in human aldose reductase: mechanistic implications for the binding of citrate, cacodylate, and glucose 6-phosphate.

Aldose reductase is a NADPH-dependent aldo-keto reductase involved in the pathogenesis of some diabetic and galactosemic complications. The published crystal structure of human aldose reductase [Wilson et al. (1992) Science 257, 81-84] contains a hitherto unexplained electron density positioned within the active site pocket facing the nicotinamide ring of the NADPH and other key active site residues (Tyr48, His110, and Cys298). In this paper we identify the electron density as citrate, which is present in the crystallization buffer (pH 5.0), and provide confirmatory evidence by both kinetic and crystallographic experiments. Citrate is an uncompetitive inhibitor in the forward reaction with respect to aldehyde (reduction of aldehyde), while it is a competitive inhibitor with respect to alcohol in the backward reaction (oxidation of alcohol), indicating that it interacts with the enzyme-NADP(+)-product complex. Citrate can be replaced in the crystalline enzyme complex by cacodylate or glucose 6-phosphate; the structure of each of these complexes shows the specific molecule bound in the active site. All of the structures have been determined to a nominal resolution of 1.76 A and refined to R-factors below 18%. While cacodylate can be bound within the active site under the crystallization conditions, it does not inhibit the wild-type enzyme in solution. Glucose 6-phosphate, however, is a substrate for aldose reductase. The similar location of the negative charges of citrate, cacodylate, and glucose 6-phosphate within the active site suggests an anion-binding site delineated by the C4N of nicotinamide, the OH of Tyr48, and the N epsilon of His110. The location of citrate binding in the active site leads to a plausible catalytic mechanism for aldose reductase.

Aldehyde Reductase↗
PubMed1994

Tyrosine-48 is the proton donor and histidine-110 directs substrate stereochemical selectivity in the reduction reaction of human aldose reductase: enzyme kinetics and crystal structure of the Y48H mutant enzyme.

The active site of human aldose reductase contains two residues, His110 and Tyr48, either of which could be the proton donor during catalysis. Tyr48 is a candidate since its hydroxyl group is in proximity to Lys77 and thus may have an abnormally low pKa value. To distinguish between these possibilities, we used site-directed mutagenesis to create the H110Q and H110A, the Y48F, Y48H, and Y48S, and the K77M mutant enzymes. The two His110 mutants resulted in a 1000-20,000-fold drop in kcat/Km, respectively, for the reduction of DL-glyceraldehyde at pH 7. The Y48F mutation caused total loss of activity, whereas the Y48H and Y48S mutants retained catalytic activity with kcat/Km reduced by 5 orders of magnitude. The K77M mutant is an inactive enzyme. Kinetic studies using xylose stereoisomers show that the wild-type enzyme distinguishes between D-xylose, L-xylose, and D-lyxose up to 150-fold better than the H110A or H110Q mutants. The His110 mutants do not effectively discriminate between these isomers (4-11-fold). The crystal structure of the Y48H mutant refined at 1.8-A resolution shows that the overall structure is not significantly different from the wild-type structure. Electron densities for the histidine side chain and a new water molecule fill the space occupied by Tyr48 in the wild-type enzyme. The water molecule is in hydrogen-bonding distance to the N zeta group of Lys77 and to the N epsilon of His48 and fills the space occupied by the hydroxyl group of tyrosine in the wild-type structure. These findings suggest that proton transfer is mediated in the Y48H mutant enzyme by the water molecule. The Y48H mutant shows large and equal primary deuterium isotope effects on kcat and kcat/Km (1.81 +/- 0.03), providing direct evidence for hydride transfer as the rate-determining step in this mutant. Deuterium solvent isotope effects indicate that the relative contribution of proton transfer to this step of the catalytic cascade is much less important for the Y48H mutant than for the wild-type enzyme [D2O(kcat/Km) = 1.06 +/- 0.02 and 4.73 +/- 0.23, respectively]. The kinetic and mutagenesis data, together with structural data, indicate that His 110 plays an important role in the orientation of substrates in the active site pocket, while Tyr48 is the proton donor during aldehyde reduction by aldose reductase.

Aldehyde Reductase↗
PubMed1992

The exposed total knee replacement prosthesis: a new classification and treatment algorithm.

The increased frequency of total knee replacement arthroplasty (TKRA) has been reflected in the number of patients with exposed prostheses referred to this unit. An algorithm has been developed to assist in the preoperative assessment of the wound and this has been tested on 25 patients with wound breakdown following TKRA. The grade of exposure so derived predicts the most appropriate surgical management. The algorithm, grading system and proposed management are described.

Algorithms↗
PubMed1991

Two flaps to resurface the basal flexion-crease of the finger area.

Two flaps are described which have been designed to resurface the skin around the basal flexion crease of the fingers. Their most common use is on the ulnar side of the hand but any finger can be resurfaced. Both flaps are 1 cm in width so the donor sites can be repaired directly without the use of skin grafts. Mobilisation of the fingers is therefore permissible within 24 hours and thus postoperative stiffness avoided. The one-stage cross-finger flap is of particular value in resurfacing and preventing the recurrence of Dupuytren's in the M.P. joint area. The palmar transposition flap based on the inter-digital cleft is useful for the release of volar contractures and resurfacing localised full thickness burns. They are quick to raise and very reliable, providing their nutrient vessel is retained. The donor site distortion is minimal. We have had no flap loss and no limitation of flexion.

Dupuytren Contracture↗