InSAR constraints on soil moisture evolution after the March 2015 extreme precipitation event in Chile.

ABSTARCT: Constraints on soil moisture can guide agricultural practices, act as input into weather, flooding and climate models and inform water resource policies. Space-based interferometric synthetic aperture radar (InSAR) observations provide near-global coverage, even in the presence of clouds, of proxies for soil moisture derived from the amplitude and phase content of radar imagery. We describe results from a 1.5 year-long InSAR time series spanning the March, 2015 extreme precipitation event in the hyperarid Atacama desert of Chile, constraining the immediate increase in soil moisture and drying out over the following months, as well as the response to a later, smaller precipitation event. The inferred temporal evolution of soil moisture is remarkably consistent between independent, overlapping SAR tracks covering a region ~100 km in extent. The unusually large rain event, combined with the extensive spatial and temporal coverage of the SAR dataset, present an unprecedented opportunity to image the time-evolution of soil characteristics over different surface types. Constraints on the timescale of shallow water storage after precipitation events are increasingly valuable as global water resources continue to be stretched to their limits and communities continue to develop in flood-prone areas.

In vitro inhibition of coagulase-negative staphylococci by vancomycin/aminoglycoside-loaded cement spacers.

BACKGROUND: Successful treatment of allograft infections by the temporary implantation of an antibiotic-loaded polymethylmethacrylate cement spacer depends on the diffusion of antibiotics out of the cement and inhibition of bacterial growth in the surrounding tissue. We investigated with an in vitro model how long antibiotics are released by the cement and if gentamicin-resistant coagulase-negative staphylococci (CNS) are inhibited by vancomycin mixed with the gentamicin-loaded cement. MATERIALS AND METHODS: Four formulations of antibiotic-loaded cement disks, i.e. gentamicin, tobramycin, vancomycin and tobramycin combined with vancomycin, respectively, were used to test the inhibition of eight isolates of Staphylococcus epidermidis and two reference strains of Staphylococcus aureus by an agar diffusion test on Mueller-Hinton (MH) agar similar to the routine laboratory disk diffusion method. Moreover, cement spacer cylinders loaded with gentamicin alone or combined with vancomycin were submerged in MH agar for weeks and the capacity to inhibit five different isolates of S. epidermidis was measured. RESULTS: The size of the inhibition zones around the antibiotic-loaded cement disks correlated with the minimal inhibitory concentration (MIC) of the antibiotics against the tested strains. All five strains of S. epidermidis were inhibited by vancomycin-loaded cement spacers for at least 30 days. However, two gentamicin-resistant S. epidermidis strains with MICs of 4 mg/l and 16 mg/l could not be inhibited longer than 3 days by the gentamicin-loaded cement spacer. CONCLUSION: The in vitro data suggest that antibiotic-loaded cement spacers inhibit susceptible bacteria for 4-6 weeks. The addition of vancomycin to commercial aminoglycoside-loaded cements might be helpful in allograft infections in tumor patients to inhibit a broad range of bacteria including gentamicin-resistant CNS very commonly found in such infections.

Structural requirements for the biosynthesis of backbone cyclic peptide libraries.

BACKGROUND: Combinatorial methods for the production of molecular libraries are an important source of ligand diversity for chemical biology. Synthetic methods focus on the production of small molecules that must traverse the cell membrane to elicit a response. Genetic methods enable intracellular ligand production, but products must typically be large molecules in order to withstand cellular catabolism. Here we describe an intein-based approach to biosynthesis of backbone cyclic peptide libraries that combines the strengths of synthetic and genetic methods. RESULTS: Through site-directed mutagenesis we show that the DnaE intein from Synechocystis sp. PCC6803 is very promiscuous with respect to peptide substrate composition, and can generate cyclic products ranging from four to nine amino acids. Libraries with five variable amino acids and either one or four fixed residues were prepared, yielding between 10(7) and 10(8) transformants. The majority of randomly selected clones from each library gave cyclic products. CONCLUSIONS: We have developed a versatile method for producing intracellular libraries of small, stable cyclic peptides. Genetic encoding enables facile manipulation of vast numbers of compounds, while low molecular weight ensures ready pharmacophore identification. The demonstrated flexibility of the method towards both peptide length and composition makes it a valuable addition to existing methods for generating ligand diversity.

A quantitative model for allosteric control of purine reduction by murine ribonucleotide reductase.

The reduction of purine nucleoside diphosphates by murine ribonucleotide reductase requires catalytic (R1) and free radical-containing (R2) enzyme subunits and deoxynucleoside triphosphate allosteric effectors. A quantitative 16 species model is presented, in which all pertinent equilibrium constants are evaluated, that accounts for the effects of the purine substrates ADP and GDP, the deoxynucleoside triphosphate allosteric effectors dGTP and dTTP, and the dimeric murine R2 subunit on both the quaternary structure of murine R1 subunit and the dependence of holoenzyme (R1(2)R2(2)) activity on substrate and effector concentrations. R1, monomeric in the absence of ligands, dimerizes in the presence of substrate, effectors, or R2(2) because each of these ligands binds R1(2) with higher affinity than R1 monomer. This leads to apparent positive heterotropic cooperativity between substrate and allosteric effector binding that is not observed when binding to the dimeric protein itself is evaluated. Allosteric activation results from an increase in k(cat) for substrate reduction upon binding of the correct effector, rather than from heterotropic cooperativity between effector and substrate. Neither the allosteric site nor the active site displays nucleotide base specificity: dissociation constants for dGTP and dTTP are nearly equivalent and K(m) and k(cat) values for both ADP and GDP are similar. R2(2) binding to R1(2) shows negative heterotropic cooperativity vis-à-vis effectors but positive heterotropic cooperativity vis-à-vis substrates. Binding of allosteric effectors to the holoenzyme shows homotropic cooperativity, suggestive of a conformational change induced by activator binding. This is consistent with kinetic results indicating full dimer activation upon binding a single equivalent of effector per R1(2)R2(2).

Production of cyclic peptides and proteins in vivo.

Combinatorial libraries of synthetic and natural products are an important source of molecular information for the interrogation of biological targets. Methods for the intracellular production of libraries of small, stable molecules would be a valuable addition to existing library technologies by combining the discovery potential inherent in small molecules with the large library sizes that can be realized by intracellular methods. We have explored the use of split inteins (internal proteins) for the intracellular catalysis of peptide backbone cyclization as a method for generating proteins and small peptides that are stabilized against cellular catabolism. The DnaE split intein from Synechocystis sp. PCC6803 was used to cyclize the Escherichia coli enzyme dihydrofolate reductase and to produce the cyclic, eight-amino acid tyrosinase inhibitor pseudostellarin F in bacteria. Cyclic dihydrofolate reductase displayed improved in vitro thermostability, and pseudostellarin F production was readily apparent in vivo through its inhibition of melanin production catalyzed by recombinant Streptomyces antibioticus tyrosinase. The ability to generate and screen for backbone cyclic products in vivo is an important milestone toward the goal of generating intracellular cyclic peptide and protein libraries.

Effectiveness of bone cement containing tobramycin. An in vitro susceptibility study of 99 organisms found in infected joint arthroplasty.

We used 99 strains of organisms representative of orthopaedic infections to examine the effectiveness of a bone cement containing tobramycin, employing a modified in vitro Kirby-Bauer susceptibility model. The spectrum was broad, including Gram-positive and Gram-negative aerobic organisms, anaerobes and mycobacteria. Simplex P with added tobramycin was effective against most of the strains, including those which are resistant to typical systemic levels of tobramycin. Although direct correlation between in vitro and in vivo results is difficult, the study showed that tobramycin is stable to the exothermic polymerisation of the cement, and that it is released from the surface of the cement at concentrations high enough to inhibit the growth of most organisms which may be encountered after joint arthroplasty.

The 'usual care' of major depression in primary care practice.

OBJECTIVE: To determine how primary care physicians treat patients with major depression in the course of routine practice and the degree to which such practice produces outcomes anticipated with interventions recommended by the Agency for Health Care Policy and Research Depression Guideline Panel. DESIGNS: Prospective cohort study. SETTINGS: Academically affiliated ambulatory family practice centers and internal medicine clinics in urban neighborhoods of Pittsburgh, Pa. PATIENTS: Ninety-two patients who were seen in primary care practices and who met criteria for a current major depression as determined by the Diagnostic Interview Schedule and a psychiatrist's assessment. INTERVENTION: Physicians were informed of the patient's psychiatric diagnosis, and were urged to treat it in whatever manner and for whatever duration they deemed appropriate (ie, with "usual care"). MAIN OUTCOME MEASURES: The treatments that were provided, the patients' clinical course, and the relationship between the type of treatment and clinical course. RESULTS: Health center records indicated that 67 patients (73%) received a depression-specific treatment in the 8 months following study entry. A majority of the total cohort were prescribed an antidepressant drug. Of the 92 patients, 18 (20%) were asymptomatic at 8 months (Hamilton Rating Scale for Depression score, < or = 7). The treatment pattern was not clearly related to the clinical course. CONCLUSIONS: The recovery rates for the patients with major depression who were treated with usual care in routine primary care practices were lower than those anticipated from treatments consistent with the Agency for Health Care Policy and Research guidelines. Further studies of the caregiving elements that influence the effectiveness of depression-specific treatments of patients in primary care settings are needed.

Treating major depression in primary care practice. Eight-month clinical outcomes.

BACKGROUND: We studied whether standardized treatments of major depression whose efficacy was established with psychiatric patients are equally effective when provided to primary care patients, and whether standardized treatments are more effective than a primary care physician's usual care. METHODS: A randomized controlled trial was conducted, in which primary care patients meeting DSM-III-R criteria for a current major depression were assigned to nortriptyline (n = 91) or interpersonal psychotherapy (n = 93) provided within well-structured parameters, or a physician's usual care (n = 92). The main outcome measures were degree and rate of improvement in severity of depressive symptoms and proportion of patients recovered at 8 months. RESULTS: Severity of depressive symptoms was reduced more rapidly and more effectively among patients randomized to pharmacotherapy or psychotherapy than among patients assigned to a physician's usual care. Among treatment completers, approximately 70% of patients participating in the full pharmacotherapy or psychotherapy protocol but only 20% of usual care patients were judged as recovered at 8 months. CONCLUSIONS: Pharmacotherapy and psychotherapy effectively treat major depression among primary care patients when provided within specific parameters and for the full acute and continuation phases. Treatment principles recommended by the Depression Guideline Panel of the Agency for Health Care Policy and Research are supported.

Examination of the relationship between African American adolescents' condom use at sexual onset and later sexual behavior: implications for condom distribution programs.

School-based condom distribution programs have generated considerable controversy across the country. In the present study 249 sexually active African American adolescents who did (n = 119) and did not (n = 130) use a condom during their initial sexual experience were compared to assess whether condom use at the onset of sexual activity was associated with later differences in sexual behavior. The results indicated that youths who used a condom from the onset of sexual activity were more likely to have used a condom in the most recent intercourse occasion, less likely to be diagnosed with a sexually transmitted disease (STD) or to combine substance use with sexual activity, endorsed more positive attitudes toward condoms, and were older when they initiated sexual activity. The findings have implications for condom availability programs and indicate that initial condom use was not associated with earlier onset of sexual activity and was associated with higher rates of precautionary behavior among sexually active minority adolescents.

Major depression in primary care practice. Clinical characteristics and treatment implications.

Major depression is thought to be underdiagnosed and undertreated in primary medical care facilities. The authors conducted a clinical trial that included a three-phase assessment so only ambulatory medical patients judged eligible for treatment of this disorder in medical settings were recruited. In addition to administering the Center for Epidemiologic Studies-Depression scale and the Diagnostic Interview Schedule's (DIS) Depression section, the psychiatrists evaluated the DIS-positive patients. This third assessment determined that clinical characteristics of DIS-positive patients were such that 70% of the patients could be treated for major depression in a primary care setting, 13% should probably be referred to a mental health facility, and 17% were experiencing conditions other than major depression.

Applicability of clinical pharmacotherapy guidelines for major depression in primary care settings.

OBJECTIVE: To determine whether guidelines established for pharmacologic treatment of major depression are feasible in primary care. DESIGN: Prospective cohort study. SETTING: Ambulatory family health centers and internal medicine clinics. PATIENTS: Ninety-one primary care patients meeting criteria within the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition for a current major depression randomized to receive antidepressant medication after being judged by a psychiatrist as clinically eligible for pharmacotherapy in an ambulatory setting. INTERVENTION: Nortriptyline hydrochloride prescribed by primary care physicians trained in clinical guidelines specifying dosage schedules, durations, and procedures resembling those recommended by the AHCPR (Agency for Health Care Policy and Research) Depression Guideline Panel. MAIN OUTCOME MEASURES: Patient participation and continuation in medication treatment. RESULTS: Fifty-five percent of patients completed the acute phase of treatment after a mean of 6.9 visits extending over a mean of 8.1 weeks. Of those patients entering the continuation phase, 60% completed the follow-up visits for 6 months. Taken together, only 33% of patients assigned to receive antidepressant medication completed the full regimen recommended by the AHCPR guidelines. CONCLUSIONS: The treatment of depressed primary care patients within AHCPR guidelines for antidepressant medication is feasible but complex. Although primary care physicians ably adhere to these guidelines, keeping patients in treatment is difficult and possibly requires greater flexibility in treatment regimens.

Cross-cultural comparison of US and Nigerian adolescents' HIV-related knowledge, attitudes, and risk behaviour: implications for risk reduction interventions.

Attitudes towards AIDS prevention, AIDS-related knowledge, and sexual behaviour of Nigerian adolescents and their African-American counterparts in two geographic regions of the United States were compared to assess cross-cultural similarities and differences between the adolescents. This study was conducted as the first in a programmatic sequence of activities leading toward the adaptation of a risk reduction intervention that was developed in the US for implementation with Nigerian youths. Subjects (n = 511) completed self-report measures of AIDS-related knowledge, attitudes towards condoms, attitudes towards AIDS prevention, sexual behaviour over the past two months, self- and response efficacy, and perceived vulnerability. Between-group comparisons revealed that US adolescents were more knowledgeable, held more favourable attitudes towards prevention and toward condoms, reported more sex partners, engaged in higher frequencies of unprotected vaginal intercourse, and became sexually active at later age than Nigerian adolescents. The findings are discussed with respect to their implications for translating risk reduction interventions developed in the US for African-American adolescents for later cross-cultural implementation with adolescents in developing countries where such risk reduction efforts are urgently needed.

High level expression of the large subunit of mouse ribonucleotide reductase in a baculovirus system.

The large subunit of ribonucleotide reductase from mouse has been overexpressed in Spodoptera frugiperda cells infected with recombinant baculovirus. The expressed protein was purified by affinity chromatography to apparent homogeneity as determined by SDS-PAGE. The homogeneous protein is recognized in Western blot analysis by a monoclonal antibody raised to the large subunit of ribonucleotide reductase from calf thymus, has the correct N-terminal sequence, and, in the presence of the small subunit of mouse ribonucleotide reductase and nucleoside triphosphate effectors, catalyzes the reduction of both purine and pyrimidine nucleoside diphosphates.

Clinical trials of primary care treatments for major depression: issues in design, recruitment and treatment.

The objective of this article is to consider whether randomized clinical trials (RCTs) are able to determine the validity of transferring treatments for major depression from the psychiatric to the primary care sector. This clinical issue is of growing concern in the United States since both governmental and professional bodies are establishing guidelines for the treatment of medical patients with the affective disorder. The article's method involves analysis of how the competing aims of rigorous scientific methodology (internal validity) and generalization of study findings (external validity) are best balanced within the RCT. Experiences in recruiting medical patients with major depression and providing pharmacologic, psychotherapeutic, and usual care interventions compatible with the sociotechnical characteristics of ambulatory medical centers are described to illustrate the complexities of investigating transferability of treatments for major depression with RCT methodology.

Strategies for evaluating treatments for major depression in primary care patients.

Primary care physicians are being urged to provide patients experiencing a major depression treatments validated with psychiatric patients. The propriety of transferring clinical technologies from one care-giving sector to another is questionable, however, as it has little scientific support. We suggest that clinical trials be initiated so as to expand the available knowledge base. This paper analyzes the methodologic issues involved in pursuing such experimental research and urges that it be conducted despite the possible need for initial design compromises.

Some observations on the incidence of lameness in dairy cattle in Somerset.

A three year study of practice records of lame cows and meteorological data on rainfall suggests a correlation between rainfall and incidence of lameness in dairy cattle. Over a 12 month period requests to treat lameness in 1256 cattle were received by one six-person practice and were the subject of a detailed survey. The incidence on the 150 farms where lameness was recorded was 7.33 per cent, 92.2 per cent of lameness occurring in the foot. White line disease (34.9 per cent), pricked sole (20.4 per cent), foul in the foot (14.3 per cent) ulcerated sole (11.4 per cent), and foreign body (4.8 per cent) accounted for 85.8 per cent of the 927 recorded foot lesions. Hind feet lameness appeared more common in older cows, but this was not shown to be the case with front foot lameness. Lameness also appeared to be most common in early lactation and of relatively low incidence in the dry period. The seasonal distribution differed between the lesions, ulcerated sole being more common February to May, foul in the foot and white line separation in the autumn, and white line abscess and pricked sole in the autumn and winter months.