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Biomedical subjects

M S Bennett

Publications and source records attributed to M S Bennett.

18 recordsLinked to original sources
PubMed2001

Bacillus subtilis arsenate reductase is structurally and functionally similar to low molecular weight protein tyrosine phosphatases.

Arsenate is an abundant oxyanion that, because of its ability to mimic the phosphate group, is toxic to cells. Arsenate reductase (EC; encoded by the arsC gene in bacteria) participates to achieve arsenate resistance in both prokaryotes and yeast by reducing arsenate to arsenite; the arsenite is then exported by a specific transporter. The crystal structure of Bacillus subtilis arsenate reductase in the reduced form with a bound sulfate ion in its active site is solved at 1.6-A resolution. Significant structural similarity is seen between arsenate reductase and bovine low molecular weight protein tyrosine phosphatase, despite very low sequence identity. The similarity is especially high between their active sites. It is further confirmed that this structural homology is relevant functionally by showing the phosphatase activity of the arsenate reductase in vitro. Thus, we can understand the arsenate reduction in the light of low molecular weight protein tyrosine phosphatase mechanism and also explain the catalytic roles of essential residues such as Cys-10, Cys-82, Cys-89, Arg-16, and Asp-105. A "triple cysteine redox relay" is proposed for the arsenate reduction mechanism.

Amino Acid Sequence↗
PubMed1999

Structure to 1.9 A resolution of a complex with herpes simplex virus type-1 thymidine kinase of a novel, non-substrate inhibitor: X-ray crystallographic comparison with binding of aciclovir.

Treatment of herpes infections with nucleoside analogues requires as an initial step the activation of the compounds by thymidine kinase. As an aid to developing more effective chemotherapy, both for treatment of recurrent herpes infection and in gene therapy systems where thymidine kinase is expressed, two high-resolution X-ray structures of thymidine kinase have been compared: one with the relatively poor substrate aciclovir (Zovirax), the other with a synthetic inhibitor having an N2-substituted guanine. Both compounds have similar binding modes in spite of their size difference and apparently distinct ligand properties.

Acyclovir↗
PubMed1998

5-Substituted pyrimidines with a 1,5-anhydro-2, 3-dideoxy-D-arabino-hexitol moiety at N-1: synthesis, antiviral activity, conformational analysis, and interaction with viral thymidine kinase.

A new series of anhydrohexitol nucleosides are described. These compounds have a pyrimidine base moiety substituted in the 5-position with a chloro (1b), trifluoromethyl (1c), vinyl (1d), 2-thienyl (1e), ethynyl (1f) or propynyl (1g) substituent. The vinyl, propynyl, and, in particular, the 5-trifluoromethyl analogue showed potent activity against herpes simplex virus (HSV), 1c with a selectivity index of >16000 against HSV-1 and >1000 against HSV-2. Conformational analysis of anhydrohexitol nucleosides using computational methods indicates that these nucleosides occur in an equilibrium between the C1 and 1C form with a DeltaE of 5.9 kJ/mol. When the anhydrohexitol nucleoside is cocrystallized with the HSV-1 thymidine kinase it adopts a 1C conformation, which is opposite to the conformation found for the small molecule alone. The enzyme, apparently, induces a conformational change, and conformational flexibility of an anhydrohexitol nucleoside may be advantageous for recognition by viral enzymes.

Antiviral Agents↗
PubMed1998

Exploring the active site of herpes simplex virus type-1 thymidine kinase by X-ray crystallography of complexes with aciclovir and other ligands.

Antiherpes therapies are principally targeted at viral thymidine kinases and utilize nucleoside analogs, the triphosphates of which are inhibitors of viral DNA polymerase or result in toxic effects when incorporated into DNA. The most frequently used drug, aciclovir (Zovirax), is a relatively poor substrate for thymidine kinase and high-resolution structural information on drugs and other molecules binding to the target is therefore important for the design of novel and more potent chemotherapy, both in antiherpes treatment and in gene therapy systems where thymidine kinase is expressed. Here, we report for the first time the binary complexes of HSV-1 thymidine kinase (TK) with the drug molecules aciclovir and penciclovir, determined by X-ray crystallography at 2.37 A resolution. Moreover, from new data at 2.14 A resolution, the refined structure of the complex of TK with its substrate deoxythymidine (R = 0.209 for 96% of all data) now reveals much detail concerning substrate and solvent interactions with the enzyme. Structures of the complexes of TK with four halogen-containing substrate analogs have also been solved, to resolutions better than 2.4 A. The various TK inhibitors broadly fall into three groups which together probe the space of the enzyme active site in a manner that no one molecule does alone, so giving a composite picture of active site interactions that can be exploited in the design of novel compounds.

Acyclovir↗
PubMed1995

FISH analysis on spontaneously arising micronuclei in the ICF syndrome.

The ICF syndrome is a rare disorder where patients show undercondensation of the heterochromatic blocks of chromosomes 1, 9, and 16 along with variable immunodeficiency. The undercondensation of the heterochromatic block appears to be restricted to a portion of PHA stimulated T cells. Patients with this syndrome also show an increase in micronuclei formation. We have used dual colour FISH to investigate the chromosomal content of these micronuclei in PHA stimulated peripheral blood cultures, an EBV transformed B cell line, and also micronuclei observed in vivo from peripheral blood smears. Chromosome 1 appears to be present in a higher proportion of micronuclei compared to chromosomes 9 and 16 in both a PHA stimulated culture and an EBV transformed cell line. An 18 centromeric probe, not associated with the ICF syndrome, showed no signal in any of the micronuclei observed. The implications from these observations are that the heterochromatic instability in the ICF syndrome is manifested not only in T but also in B cells and that it is present in vivo.

B-Lymphocytes↗
PubMed1992

Influence of amantadine resistance mutations on the pH regulatory function of the M2 protein of influenza A viruses.

Mutations in the influenza M2 membrane protein which confer resistance to the antiviral drug amantadine are exclusively located within the transmembrane region of the molecule. The influence of specific amino acid substitutions on the activity of the M2 protein in influenza A virus-infected cells is assessed in this report by their effects upon haemagglutinin (HA) stability and virus growth. A number of amino acid substitutions, e.g., L26H, A30T, S31N and G34E reduced the activity of the M2 protein of A/chicken/Germany/34 (Rostock) and caused a substantial increase in expression of the low-pH form of HA. The adverse effects of the mutations on virus replication were evident from changes selected during subsequent passage of the mutant viruses in the presence or absence of amantadine: reversion to wt, the acquisition of a second suppressor mutation in M2, or the appearance of a complementary mutation in HA which increased its pH stability. In contrast, 127T and 127S, mutations which were most readily selected following passage of the wt virus in the presence of drug, caused an increase in M2 activity. Furthermore, in double mutants the 127T mutation suppressed the attenuating effects of the A30T and S31N mutations on M2 activity. The influence of primary structure on the consequences of particular amino acid changes was further emphasized by the contrasting effects of the G34E mutation on the activities of two closely related proteins, causing an increase in the activity of the M2 of A/chicken/Germany/27 (Weybridge) as opposed to the decrease in activity of the Rostock protein. Estimates of differences in trans Golgi pH based on the degree of conversion of HA to the low-pH form, or complementation of differences in pH stability of mutant HAs, indicate that changes in M2 may influence pH within the transport pathway by as much as 0.6. The results thus provide further evidence that M2 regulates transmembrane pH gradients in the trans Golgi. Incompatibility between particular HA and M2 components and the selection of M2 mutants with suboptimal activity stresses the essential relationship between the structures and functions of these two virus proteins.

Amantadine↗
PubMed1990

Recidivism in the management of medical back pain.

One Ohio hospital underwent three years of 100% focused review of admissions for medical back problems (DRG 243) due to excessive numbers of admissions previously noted. On cessation of the focused review, the volume of admissions rose at this hospital, and the admission denial rate increased. Reinstitution of focused review appeared to decrease the number of admissions, but did not affect the rate of admission denials.

Back Pain↗
PubMedDate not supplied

Strategies to improve compensation for pharmaceutical care services.

In the past decade, the pharmacy profession has made remarkable strides in implementing a wide range of pharmacy-based patient care services. To foster greater awareness of the value of these services among payers and to ensure the long-term success of pharmaceutical care, pharmacists need to focus more attention on obtaining compensation for these services. In the long run, pharmacists are likely to receive greater net profits from pharmaceutical care than from dispensing. As Norwood et al. noted, pharmacies keep all the revenues they receive from pharmaceutical care as profits and to cover operating expenses, whereas they keep only about 29% of the revenues from the sale of products. By exploring innovative markets for pharmaceutical care services and continuing to improve rates of reimbursement from third party payers, pharmacists can further enhance the revenues they obtain from their growing array of patient care services.

Humans↗
PubMedDate not supplied

A reimbursable education service for patients with hepatitis C.

OBJECTIVE: To describe a pharmacy's subcutaneous injection education service for patients with hepatitis C. PRACTICE PROBLEM: Obstacles identified in the delivery of the service included the need to increase the pharmacists' level of knowledge regarding hepatitis C, establish methods for consistent education and documentation of patient education sessions, and improve coordination of scheduling appointments, pharmacy workflow, and obtaining documentation from physicians for reimbursement. PRACTICE INNOVATION: In this pharmacist-coordinated hepatitis C education service, policies and procedures were developed and implemented to ensure uniform standards of patient care and to improve pharmacists' knowledge base, patient education, and documentation of services. A one-page, faxable treatment order form was designed to help streamline physician office documentation and workflow. A task flow sheet for each patient case was used to address additional scheduling and workflow issues. Third party payers were billed for every teaching session. RESULTS: After evaluating the service and implementing several improvements, coordination of patient care became more streamlined. From March 1997 through February 2000, 94 patients received care, with appointments lasting between 45 and 90 minutes. Reimbursement was obtained from third party payers for 19% (18/94) of the teaching sessions. When claims were rejected, patients were billed for the education service. CONCLUSION: Pharmacists have an opportunity to provide a reimbursable education service to patients with hepatitis C.

Community Pharmacy Services↗
PubMedDate not supplied

Lower extremity management in patients with diabetes.

Foot ulcers are a major cause of disability, morbidity, and mortality in people with diabetes. The three major etiological factors for diabetic foot ulcers are peripheral neuropathy, peripheral vascular disease, and infection. Tight control of blood glucose and proper foot care are essential for prevention of foot ulcers and lower extremity amputations. Treatment of lower extremity diabetic ulcers typically includes surgical debridement of the wound and appropriate oral or intravenous antibiotics. Becaplermin gel, a prescription, recombinant wound-healing therapy, may be used to promote healing of diabetic foot ulcers in select patients. Pharmacists can make a significant contribution to the prevention of diabetic foot ulcers and lower extremity amputations.

Amputation, Surgical↗