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Biomedical subjects

R Davis

Publications and source records attributed to R Davis.

At least 37 records · Page 2Linked to original sources
PubMed1994

1H NMR studies of mouse ribonucleotide reductase: the R2 protein carboxyl-terminal tail, essential for subunit interaction, is highly flexible but becomes rigid in the presence of protein R1.

Mouse ribonucleotide reductase consists of two nonidentical subunits, proteins R1 and R2, each inactive alone. It has earlier been shown that the carboxyl-terminal part of the R2 protein is essential for subunit association to form the active enzyme complex. We now demonstrate that protein R2 gives rise to a number of sharp 1H NMR resonances, significantly narrower than the major part of the resonances. This line narrowing of certain resonances indicates segmental mobility in the molecule. In two-dimensional 1H TOCSY spectra of protein R2, cross-peak patterns from about 25 amino acid residues are visible. Most of these were assigned to the carboxyl-terminal part of the protein by comparisons with cross-peak patterns of oligopeptides corresponding to the carboxyl terminus of mouse R2 and to the patterns of a seven amino acid residue carboxyl-terminal truncated form of protein R2. These results and the magnitude of the chemical shifts of the assigned residues demonstrate that the carboxyl-terminal part of mouse R2 protein is highly mobile compared to the rest of the protein and essentially unstructured. When protein R1 is added to a solution of protein R2, the sharp resonances are broadened, suggesting that the mobility of the carboxyl-terminal tail of protein R2 is reduced. The possibility of making direct observations of subunit interaction in native and mutagenized R1/R2 proteins should allow discrimination between effects of amino acid replacements on the catalytic mechanism and effects on subunit interaction.

Amino Acid Sequence↗
PubMed1994

DNA sequence confidence estimation.

A significant bottleneck in the current DNA sequencing process is the manual editing of trace data generated by automated DNA sequencers. This step is used to correct base calls and to associate to each base call a confidence level. The confidence levels are used in the assembly process to determine overlaps and to resolve discrepancies in determining the consensus sequence. This single step may cost as much as 4 to 8 cents per finished base. We report an approach to automated trace editing using classification trees to detect and exploit context-based patterns in trace peak heights. Local base composition and nearby peak heights account for 80% of the variations in peak heights. Classification algorithms were developed to identify 37% of automated base calls that differ from the consensus sequence. With these algorithms, 12% of the base calls had confidence levels less than 90%.

Algorithms↗
PubMed1994

Trimetrexate with leucovorin versus trimethoprim-sulfamethoxazole for moderate to severe episodes of Pneumocystis carinii pneumonia in patients with AIDS: a prospective, controlled multicenter investigation of the AIDS Clinical Trials Group Protocol 029/031.

Trimetrexate is a powerful inhibitor of the dihydrofolate reductase of Pneumocystis carinii. AIDS patients (n = 215) with moderate to severe P. carinii pneumonia were enrolled in a double-blind study of trimetrexate plus leucovorin versus trimethoprim-sulfamethoxazole (TMP-SMZ) for 21 days. By study day 10, study therapy failed because of lack of efficacy in 16% of patients assigned to TMP-SMZ and 27% assigned to trimetrexate (P = .064), and the PAO2-PaO2 improved significantly faster with TMP-SMZ. By study day 21, failure rates were 20% with TMP-SMZ and 38% with trimetrexate (P = .008), with respective mortality rates of 12% and 20% (P = .088). By study day 49, the difference in mortality (16% vs. 31%) was significant (P = .028). The cumulative incidence of serious and treatment-terminating adverse events including hematologic toxicities was less with trimetrexate (P < .001). Thus, trimetrexate plus leucovorin was effective, albeit inferior to TMP-SMZ, for moderately severe P. carinii pneumonia but was better tolerated than TMP-SMZ.

AIDS-Related Opportunistic Infections↗
PubMed1994

Phase II dose-ranging trial of foscarnet salvage therapy for cytomegalovirus retinitis in AIDS patients intolerant of or resistant to ganciclovir (ACTG protocol 093). AIDS Clinical Trials Group of the National Institute of Allergy and Infectious Diseases.

OBJECTIVE: To document response to foscarnet salvage therapy in patients with cytomegalovirus (CMV) retinitis who are intolerant of or resistant to ganciclovir. METHODS: Patients with AIDS and CMV retinitis who had documented hematologic intolerance or resistance to ganciclovir therapy received an induction course of foscarnet, 60 mg/kg every 8 h for 14 days, and subsequent chronic maintenance foscarnet therapy at a daily dose of 60, 90 or 120 mg/kg/day. The first 87 patients were randomly assigned to receive maintenance foscarnet at a dose of 60 or 90 mg/kg/day; all subsequent patients were assigned a maintenance dose of 120 mg/kg/day. RESULTS: A total of 156 evaluable patients were enrolled. Median time to retinitis progression and survival did not differ significantly among groups assigned to different maintenance foscarnet doses. Among patients with retinitis progression documented ophthalmologically occurring at < or = 2 week intervals, despite optimal doses of ganciclovir, time to progression on foscarnet therapy was a median 8 weeks at all doses studied. By dose assignment, there were no significant differences in serious drug-associated toxicity, although trends toward increased renal and hypocalcemic adverse events were observed at higher maintenance doses. CONCLUSION: In patients intolerant of ganciclovir, salvage foscarnet therapy resulted in a longer time to retinitis progression than reported previously in historic controls who terminated ganciclovir therapy. In patients who exhibited clinical resistance to ganciclovir, foscarnet appeared to have efficacy in controlling retinitis. No significant differences in either efficacy or toxicity were observed in the range of foscarnet maintenance doses studied.

AIDS-Related Opportunistic Infections↗
PubMed1994

Pharmacodynamic relationship of pharmacokinetic parameters of maintenance doses of foscarnet and clinical outcome of cytomegalovirus retinitis.

The pharmacodynamic relationship between a range of foscarnet exposure measurements obtained from studying nine patients receiving ongoing maintenance therapy for cytomegalovirus retinitis and a range of efficacy values (days to retinitis progression) obtained by independent examination of serial retinal photographs from the same nine patients was analyzed. In the resulting proportional hazards models, the foscarnet area under the concentration-time curve approached statistical significance (P = 0.11) as a predictor of decreased risk of retinitis progression.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Serotypes of Streptococcus pneumoniae blood culture isolates from adults in Franklin County, Ohio.

Isolates of Streptococcus pneumoniae in cultures of blood from 258 adults seen in 10 Franklin County, Ohio, hospitals from 1991 and 1992 were serotyped. Most strains (230 [89.2%]) belonged to serotypes that are included in the current pneumococcal vaccine. An additional 16 isolates (6.2%) were immunologically related to strains with serotypes that are included in the vaccine. Only 12 isolates (4.6%) were not covered by the vaccine. The rate of mortality from pneumococcal bacteremia in adults remains high (20%). While recent studies have documented the efficacy of the pneumococcal vaccine for preventing pneumococcal bacteremia (56 to 70%), use of the pneumococcal vaccine in susceptible patients by physicians remains low (19% in Franklin County). Additional efforts need to be expended to increase the use of the pneumococcal vaccine.

Adult↗
PubMed1994

c-Jun N-terminal phosphorylation correlates with activation of the JNK subgroup but not the ERK subgroup of mitogen-activated protein kinases.

c-Jun transcriptional activity is stimulated by phosphorylation at two N-terminal sites: Ser-63 and -73. Phosphorylation of these sites is enhanced in response to a variety of extracellular stimuli, including growth factors, cytokines, and UV irradiation. New members of the mitogen-activated protein (MAP) kinase group of signal-transducing enzymes, termed JNKs, bind to the activation domain of c-Jun and specifically phosphorylate these sites. However, the N-terminal sites of c-Jun were also suggested to be phosphorylated by two other MAP kinases, ERK1 and ERK2. Despite these reports, we find that unlike the JNKs, ERK1 and ERK2 do not phosphorylate the N-terminal sites of c-Jun in vitro; instead they phosphorylate an inhibitory C-terminal site. Furthermore, the phosphorylation of c-Jun in vivo at the N-terminal sites correlates with activation of the JNKs but not the ERKs. The ERKs are probably involved in the induction of c-fos expression and thereby contribute to the stimulation of AP-1 activity. Our study suggests that two different branches of the MAP kinase group are involved in the stimulation of AP-1 activity through two different mechanisms.

Animals↗
PubMed1994

Initial results of the nucleus FES-22-implanted system for limb movement in paraplegia.

The Nucleus 'FES-22' channel stimulation system has been developed for partial restoration of lower limb function in paraplegic individuals. One FES-22 stimulator has been implanted in a 25-year-old paraplegic subject in November 1991. Of the twenty 2.5-mm disc electrodes attached epineurally onto motor nerves, fifteen are capable of producing observable threshold and maximal muscle contractions with joint movements.

Adult↗
PubMed1994

Prevalence of postnatal psychiatric morbidity in mothers and fathers.

In the first study to systematically examine postnatal depression in fathers, we examined depression in 200 postnatal couples, using a two-stage design. The prevalence of depression ascertained by the 13-item Edinburgh Postnatal Depression Scale (EPDS), using a cut-off score for 'caseness' of 13 or more in an unselected postnatal sample, was 27.5% in mothers at six weeks postpartum, 25.7% in mothers at six months postpartum, 9.0% in fathers at six weeks postpartum, and 5.4% in fathers at six months postpartum. The prevalence did not differ significantly in either mothers or fathers from a control group of parents with children between three and five years of age. As expected, mothers had a significantly higher prevalence of psychiatric 'caseness' at both six weeks and six months postpartum than fathers. Fathers were significantly more likely to be cases if their partners were also cases. The hypothesis that different aetiological factors would be important in brief and persistent disorders in mothers was upheld.

Adult↗
PubMed1994

Levofloxacin. A review of its antibacterial activity, pharmacokinetics and therapeutic efficacy.

Levofloxacin, an oral fluoroquinolone antibacterial agent, is the optical S-(-) isomer of ofloxacin. In vitro it is generally twice as potent as ofloxacin. Levofloxacin is active against most aerobic Gram-positive and Gram-negative organisms and demonstrates moderate activity against anaerobes. Drug penetration into body tissues and fluids is rapid and widespread after oral administration. In clinical trials conducted in Japan, oral levofloxacin has demonstrated antibacterial efficacy against a variety of infections, including upper and lower respiratory tract, genitourinary, obstetric, gynaecological and skin and soft tissues. In comparative trials with ofloxacin, levofloxacin, at half the daily dosage of ofloxacin, showed equivalent efficacy and a reduced incidence of adverse effects in the treatment of lower respiratory tract and complicated urinary tract infections. Levofloxacin has a tolerability profile similar to that of other oral fluoroquinolones, with gastrointestinal and central nervous system effects reported most commonly. Theophylline dosage adjustment does not appear to be necessary in patients receiving concomitant levofloxacin. Coadministration with antacids or with other drugs containing divalent or trivalent cations reduces levofloxacin absorption. Thus, levofloxacin has potential as a broad spectrum antibacterial drug in the treatment of a variety of infections. However, clinical trials recruiting non-Japanese patients are in progress and these results will form a basis on which future recommendations for the broader use of levofloxacin can be made.

Administration, Oral↗
PubMed1994

Nimesulide. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy.

Nimesulide is a nonsteroidal anti-inflammatory drug (NSAID) administered orally or rectally twice daily for a variety of inflammatory and pain states. In mostly short term studies (up to 4 weeks), it was effective in reducing pain associated with osteoarthritis, cancer, thrombophlebitis, oral surgery and dysmenorrhoea in adults, reducing pain associated with general surgery in adults and children, and pain, fever and inflammation accompanying respiratory tract infections, otorhinolaryngological diseases and traumatic injury in adults and children. Nimesulide appeared to be at least as effective as other NSAIDs in all of these indications. Nimesulide has been well tolerated by adult, elderly and paediatric patients in clinical trials and large postmarketing surveillance studies. In general qualitative terms nimesulide exhibits the usual adverse events associated with NSAIDs (gastrointestinal, dermatological and neurological). However, it has a pharmacodynamic profile suggestive of a possibly reduced propensity to cause adverse gastrointestinal effects, although this has not been conclusively demonstrated in comparative clinical trials, many of which showed a similar incidence of such effects for nimesulide and the comparator agent. Additionally, nimesulide has been well tolerated by most aspirin (acetylsalicylic acid)- and/or NSAID-intolerant patients and in patients with asthma. Thus, available evidence indicates that nimesulide is an effective and well tolerated alternative to other NSAIDs in the short term treatment of pain and inflammation of osteoarthritis and various other causes.

Animals↗
PubMed1994

Valproic acid. A reappraisal of its pharmacological properties and clinical efficacy in epilepsy.

Valproic acid is a branched-chained fatty acid, structurally unrelated to any other antiepileptic drug. Since publication of the original review in the Journal in 1977, several clinical trials have documented its efficacy and safety in adults and children for the treatment of generalised seizures (absence, tonic-clonic, myoclonic), partial seizures (simple, complex, secondarily generalised) and compound/combination seizures (including those refractory to treatment with other antiepileptic drugs). Valproic acid monotherapy has demonstrated efficacy equivalent to that of carbamazepine, phenytoin, and phenobarbital in the treatment of both generalised and partial seizures and ethosuximide in the treatment of absence seizures. Adverse effects associated with the drug are primarily gastrointestinal (nausea, vomiting, dyspepsia) in nature, although the use of enteric-coated formulations has reduced the incidence of abdominal discomfort. Weight gain, tremor and transient hair loss are commonly reported. Importantly, valproic acid has minimal neurological adverse effects (sedation, ataxia, impairment of cognitive function) compared with other antiepileptic drugs, a finding that may be of particular relevance in many patients with epilepsy. The incidence of rare, fatal liver failure has been greatly reduced by identifying and avoiding administration of valproic acid to high risk patient populations. An estimated risk of 1 to 2% for neural tube defects, predominantly spina bifida aperta, with maternal use of valproic acid therapy has been reported. Valproic acid inhibits hepatic drug metabolism and displaces other highly bound drugs from their plasma protein binding sites. Therefore, coadministered drugs which are highly protein bound or hepatically metabolised may require dosage adjustment. Enzyme-inducing antiepileptic drugs may increase valproic acid metabolism and necessitate increasing its dosage. Thus, comparative trials and extensive clinical experience have demonstrated the efficacy and tolerability of valproic acid and support its role as a valuable and well established first-line treatment for patients with a broad range of seizure types.

Adult↗
PubMed1994

3-D reconstruction of an ancient Egyptian mummy using X-ray computer tomography.

Computer tomography has been used to image and reconstruct in 3-D an Egyptian mummy from the collection of the British Museum. This study of Tjentmutengebtiu, a priestess from the 22nd dynasty (945-715 BC) revealed invaluable information of a scientific, Egyptological and palaeopathological nature without mutilation and destruction of the painted cartonnage case or linen wrappings. Precise details on the removal of the brain through the nasal cavity and the viscera from the abdominal cavity were obtained. The nature and composition of the false eyes were investigated. The detailed analysis of the teeth provided a much closer approximation of age at death. The identification of materials used for the various amulets including that of the figures placed in the viscera was graphically demonstrated using this technique.

Humans↗