Synthesis of methyl alpha-L-vancosaminide

The synthesis of methyl alpha-L-vancosaminide from di-O-acetyl-L-rhamnal is described. The allylic alcohol methyl 2,3,6-trideoxy-3-C-methyl-alpha-L-threo-hex-2-enopyranoside was prepared from the glycal, 1,5-anhydro-1,2,6-trideoxy-3-C-methyl-L-ribo-hex-1-enitol, and converted to its N,N-dimethylisourea derivative. The cis amino alcohol functionality in vancosamine was introduced by the electrophilic cyclization of the isourea, followed by hydrolysis of the resulting oxazoline.

Antiarrhythmic efficacy of selective blockade of the cardiac slowly activating delayed rectifier current, I(Ks), in canine models of malignant ischemic ventricular arrhythmia

BACKGROUND

To date, the lack of potent and selective inhibitors has hampered the physiological assessment of modulation of the cardiac slowly activating delayed rectifier current, I(Ks). The present study, using the I(Ks) blocker L-768,673, represents the first in vivo assessment of the cardiac electrophysiological and antiarrhythmic effects of selective I(Ks) blockade.

METHODS AND RESULTS

In an anesthetized canine model of recent (8.5+/-0.4 days) anterior myocardial infarction, 0.003 to 0.03 mg/kg L-768,673 IV significantly suppressed electrically induced ventricular tachyarrhythmias and reduced the incidence of lethal arrhythmias precipitated by acute, thrombotically induced posterolateral myocardial ischemia. Antiarrhythmic protection afforded by L-768,673 was accompanied by modest 7% to 10% increases in noninfarct zone ventricular effective refractory period, 3% to 5% increases in infarct zone ventricular effective refractory period, and 4% to 6% increases in QTc interval. In a conscious canine model of healed (3 to 4 weeks) anterior myocardial infarction, ventricular fibrillation was provoked by transient occlusion of the left circumflex coronary artery during submaximal exercise. Pretreatment with 0.03 mg/kg L-768,673 IV elicited a modest 7% increase in QTc, prevented ventricular fibrillation in 5 of 6 animals, and suppressed arrhythmias in 2 additional animals.

CONCLUSIONS

The present findings suggest that selective blockade of I(Ks) may be a potentially useful intervention for the prevention of malignant ischemic ventricular arrhythmias.

A community study of depression treatment and employment earnings

OBJECTIVE

Although treatment for major depression has been shown to reduce the costs of lost earnings resulting from lost work days, research has not demonstrated whether the reduction fully offsets the costs of treatment for the disorder.

METHODS

A statewide cohort of community residents with recent major depression, dysthymia, or substantial depressive symptoms was recruited and interviewed at baseline and at six-month and 12-month follow-ups. The cost of lost earnings was measured by lost work days multiplied by subjects' wage rates. Cost of treatment for depression was approximated using charges abstracted from provider and insurance records. Net economic cost, defined as the sum of changes in lost earnings and depression treatment costs, was examined in multiple regression analyses.

RESULTS

After the analyses controlled for sociodemographic characteristics, baseline severity of depression, and comorbidity, no statistically significant effect of depression treatment on net economic cost was found. This finding suggests that the cost of depression treatment was fully offset by savings from reduction in lost work days. Results from sensitivity analyses in multiple alternative scenarios support the same conclusion.

CONCLUSIONS

The finding of a full offset of depression treatment cost is conservative because other benefits, such as reduced pain and suffering and increased productivity while at work, were not included in the analyses. Employers who bear the cost from lost work days should encourage their employees with depressive disorders to seek treatment, even if it means paying for the entire treatment cost. Self-employed individuals with depression also will benefit even if they pay for the treatment costs themselves.

Project leadership: why project management alone doesn't work

Projects often fall short of achieving their anticipated results, not due to a lack of project management, but rather from a lack of project leadership. Because project success is a direct reflection of the project manager, it is his or her responsibility not just to manage the details and report status of a project, but to go beyond and add value through providing leadership. Project managers can no longer update task lists and issue meeting minutes if they are to succeed. This article focuses on adapting proven leadership strategies to project environments, helping to increase the probability for project success. When properly applied, they will help turn today's project manager into tomorrow's project leader.

Design and synthesis of potent, selective, and orally bioavailable tetrasubstituted imidazole inhibitors of p38 mitogen-activated protein kinase

Novel potent and selective diarylimidazole inhibitors of p38 MAP (mitogen-activated protein) kinase are described which have activity in both cell-based assays of tumor necrosis factor-alpha (TNF-alpha) release and an animal model of rheumatoid arthritis. The SAR leading to the development of selectivity against c-Raf and JNK2alpha1 kinases is presented, with key features being substitution of the 4-aryl ring with m-trifluoromethyl and substitution of the 5-heteroaryl ring with a 2-amino substituent. Cell-based activity was significantly enhanced by incorporation of a 4-piperidinyl moiety at the 2-position of the imidazole which also enhanced aqueous solubility. In general, oral bioavailability of this class of compounds was found to be poor unless the imidazole was methylated on nitrogen. This work led to identification of 48, a potent (p38 MAP kinase inhibition IC50 0.24 nM) and selective p38 MAP kinase inhibitor which inhibits lipopolysaccharide-stimulated release of TNF-alpha from human blood with an IC50 2.2 nM, shows good oral bioavailability in rat and rhesus monkey, and demonstrates significant improvement in measures of disease progression in a rat adjuvant-induced arthritis model.

Effective diffusion coefficients of K+ and Cl- ions in ion channel models

We have used molecular dynamics simulations, corresponding to a total simulation time of 11 ns, to investigate the effective short-time local diffusion coefficient of potassium and chloride ions in a series of model ion channels. These models, which include channels formed by the fungal peptide alamethicin, by a synthetic leucine-serine peptide, and by the pore-lining M2 helix bundle of the nicotinic acetylcholine receptor, have a range of different secondary structures, diameters and hydrophobicities. We find that the diffusion coefficients of both ions are appreciably reduced in the narrower channels, the extent of the reduction being similar for both the anionic and cationic species. This suggests that a difference in mobility cannot be the source of the ion selectivity exhibited by some of the channels (for example, the leucine-serine peptide). We find no evidence for a reduction in mobility of either ion in the nAChR model. These results are broadly in line with a previous similar study of Na+ ions, and may be useful in Poisson-Nernst-Planck, Eyring rate theory or Brownian dynamics calculations of channel conductance.

An extensive and diverse gene family of nicotinic acetylcholine receptor alpha subunits in Caenorhabditis elegans

Using reverse transcription-polymerase chain reactions the transcription of eight novel candidate nicotinic acetylcholine receptor (nAChR) alpha subunit genes has been demonstrated in the nematode Caenorhabditis elegans. Together with five other alpha subunit genes described elsewhere by ourselves (unc-38) and other workers (deg-3, acr-4, Ce21 and acr-6), this is now the largest known family of nAChR alpha subunit genes in a single species. By homology we have identified four groups of alpha subunits: DEG-3-like; ACR-16[Ce21]-like; UNC-38-like and ACR-8-like. Five C. elegans nAChR alpha subunits contain a modification in loop C of the ACh binding site in which the normally conserved Tyr-x-Cys-Cys, is replaced by a distinct motif (Tyr-x-x-Cys-Cys). Variation is also found in the channel lining M2 regions, including the replacement in four subunits of the highly conserved leucine at the 9' position by valine and most notably, the replacement in all ACR-8-like subunits of the highly conserved glutamic acid at the -1' position by histidine. Restrained molecular dynamics simulations have been used to generate homo-pentameric M2 helix bundle models for alpha subunits and possible functional implications examined. The calculated electrostatic potential energy profile for the M2 region of ACR-8 differs strikingly from that of ACR-16[Ce21] largely due to the presence of histidine at the -1' position, suggesting a possible perturbation of nAChR channel action permeability in the presence of this subunit type.

Regulation of homologous recombination: Chi inactivates RecBCD enzyme by disassembly of the three subunits

We report here an unusual mechanism for enzyme regulation: the disassembly of all three subunits of RecBCD enzyme after its interaction with a Chi recombination hot spot. The enzyme, which is essential for the major pathway of recombination in Escherichia coli, acts on linear double-stranded DNA bearing a Chi site to produce single-stranded DNA substrates for strand exchange by RecA protein. We show that after reaction with DNA bearing Chi sites, RecBCD enzyme is inactivated and the three subunits migrate as separate species during glycerol gradient ultracentrifugation or native gel electrophoresis. This Chi-mediated inactivation and disassembly of purified RecBCD enzyme can account for the previously reported Chi-dependent loss of Chi activity in E. coli cells containing broken DNA. Our results support a model of recombination in which Chi regulates one RecBCD enzyme molecule to make a single recombinational exchange ('one enzyme-one exchange' hypothesis).

Dynamic properties of Na+ ions in models of ion channels: a molecular dynamics study

We present simulation results for the effective diffusion coefficients of a sodium ion in a series of model ion channels of different diameters and hydrophobicities, including models of alamethicin, a leucine-serine peptide, and the M2 helix bundle of the nicotinic acetylcholine receptor. The diffusion coefficient, which in the simulations has a value of 0.15(2) A2ps-1 in bulk water, is found to be reduced to as little as 0.02(1) A2ps-1 in the narrower channels, and to about 0.10(5) A2ps-1 in wider channels such as the nicotinic acetylcholine receptor. It is anticipated that this work will be useful in connection with calculations of channel conductivity using such techniques as the Poisson-Nernst-Planck equation, Eyring rate theory, or Brownian dynamics.

Molecular characterization of Fiji disease fijivirus genome segment 9

This is the first report of sequence from Fiji disease fijivirus (FDV), the type member of the genus Fijivirus of the family Reoviridae. FDV genome segment (S9) comprised 1843 nt and contained two non-overlapping ORFs, separated by a 57 nt intergenic region. S9 ORF 1 comprised 1008 nt and encoded a 335-amino-acid polypeptide (predicted molecular mass 38.6 kDa), while ORF 2 comprised 627 nt and encoded a 208-amino-acid polypeptide (predicted molecular mass 23.8 kDa). The 5' and 3' non-coding regions were 49 and 102 nt, respectively. The S9 terminal sequences were 5' AAGUUUUU------UGUC 3', and located immediately adjacent to these sequences were 12 bp imperfect inverted repeats. The entire S9 ORF 1 and the hydrophilic regions of S9 ORF 2 were each expressed as a fusion protein with the maltose-binding protein in Escherichia coli. Antibodies produced against the ORF 1 fusion protein reacted strongly with a protein of approximately 39 kDa present in both crude extracts of FDV-infected sugarcane and partially purified FDV preparations. In contrast, antibodies raised against the modified ORF 2 fusion protein did not react with any proteins in the same samples. Further, polyclonal antibodies produced against partially purified FDV reacted with the ORF 1, but not the modified ORF 2, fusion protein. These results indicate that FDV S9 ORF 1 encodes a major structural protein, while ORF 2 probably encodes a non-structural protein.

Diagnosing depression in the medically ill: validity of a lay-administered structured diagnostic interview

Understanding the validity of structured psychiatric diagnostic interviews in medically ill patients will advance the ability to conduct research into the treatment and management of these disorders in general medical settings. We compared the University of Michigan version of the CIDI (Composite International Diagnostic Interview) for major depression to a clinical gold standard, derived through Spitzer's Longitudinal, Expert, All Data (LEAD) criteria based on the SCID-III-R. A convenience sample of medical inpatients was administered the SCID-III-R and the CIDI for major depression in random order. A physician panel reviewed the SCID interview and other pertinent data and determined whether patients had a lifetime or current (past month) diagnosis of major depression. The CIDI was scored with and without hierarchical exclusions for mania, hypomania, substance use, or medical illness. When the UM-CIDI was scored for a lifetime diagnosis of major depression without hierarchical exclusions, agreement above chance (kappa) was very good (kappa = 0.67) between the CIDI and the physician panel and good (kappa = 0.46) when the UM-CIDI was scored with exclusions. Agreement above chance for diagnosis of a recent disorder was better for UM-CIDI scoring with exclusions (kappa = 0.51) compared to scoring without exclusions (kappa = 0.43). Predictive value-positive was excellent in both scoring versions for a lifetime diagnosis (82%) and good to very good for current depression (46% and 62%). In all cases predictive value-negative was very good to excellent (77-93%). Discordant cases were almost uniformly due to difficulties in attribution of symptoms to medical illnesses. We conclude that the CIDI can perform acceptably as a research instrument to diagnose major depression in medically ill patients, potentially supplemented by clinician review of cases identified by the CIDI with current disorder.

Control of meiotic recombination in Schizosaccharomyces pombe

Homologous recombination occurs at high frequency during meiosis and is essential for the proper segregation of chromosomes and the generation of genetic diversity. Meiotic recombination is controlled in numerous ways. In the fission yeast Schizosaccharomyces pombe nutritional starvation induces meiosis and high-level expression of many genes, including numerous recombination (rec) genes, whose products are required for recombination. Accompanying the two meiotic divisions are profound changes in nuclear and chromosomal structure and movement, which may play an important role in meiotic recombination. Although recombination occurs throughout the genome, it occurs at high frequency in some intervals (hotspots) and at low frequency in others (coldspots). The well-characterized hotspot M26 is activated by the Mts1/Mts2 protein; this site and its binding proteins interact with the local chromosomal structure to enhance recombination. A coldspot between the silent mating-type loci is repressed by identified proteins, which may also alter local chromatin. We discuss in detail the rec genes and the possible functions of their products, some but not all of which share homology with other identified proteins. Although some of the rec gene products are required for recombination throughout the genome, others demonstrate regional specificity and are required in certain genomic regions but not in others. Throughout the review contrasts are made with meiotic recombination in the more thoroughly studied budding yeast Saccharomyces cerevisiae.

Electrostatics and the ion selectivity of ligand-gated channels

The nicotinic acetylcholine receptor (nAChR) is a cation-selective ion channel that opens in response to acetylcholine binding. The related glycine receptor (GlyR) is anion selective. The pore-lining domain of each protein may be modeled as a bundle of five parallel M2 helices. Models of the pore-lining domains of homopentameric nAChR and GlyR have been used in continuum electrostatics calculations to probe the origins of ion selectivity. Calculated pKA values suggest that "rings" of acidic or basic side chains at the mouths of the nAChR or GlyR M2 helix bundles, respectively, may not be fully ionized. In particular, for the nAChR the ring of glutamate side chains at the extracellular mouth of the pore is predicted to be largely protonated at neutral pH, whereas those glutamate side chains in the intracellular and intermediate rings (at the opposite mouth of the pore) are predicted to be fully ionized. Inclusion of the other domains of each protein represented as an irregular cylindrical tube in which the M2 bundles are embedded suggests that both the M2 helices and the extramembrane domains play significant roles in determining ion selectivity.

Sequence diversity in the coat protein coding region of twelve sugarcane mosaic potyvirus isolates from Australia, USA and South Africa

We have sequenced the coat protein (CP) coding region of 11 field isolates of SCMV from Australia, USA and South Africa. The differences between the nucleotide sequences of the isolates was 0.2 to 4.1% and the encoded amino acid sequences differed by 0.0 to 3.5%. Phylogenetic analysis of the CP coding sequences of the SCMV isolates and the related potyviruses SCMV-MDB, JGMV, SrMV, MDMV-A and PVY showed that the SCMV isolates formed a tightly clustered group, with SCMV-MDB forming a separate branch. This indicated that (i) the SCMV isolates are of one strain (SCMV-A) and not geographically distinct species and (ii) SCMV-MDB is clearly distinct, and may represent another potyvirus species.

Expenditures for the treatment of major depression

OBJECTIVE

Health policy makers lack accurate information about per capita spending for the treatment of major depression, the distribution of those expenditures, and the proportion of the health care dollar consumed by depression treatment.

METHOD

The authors recruited and followed a community cohort of individuals with major depression; the 298 subjects were either enrolled in fee-for-service insurance plans or self-insured. Charges for all health care services received during the year following baseline were abstracted from medical and insurance records.

RESULTS

Over the course of 1 year, 48.1% of the subjects received depression treatment. The per capita total expenditure for inpatient and outpatient depression treatment averaged $631, with a median of $152, for the treated subjects. Just 4.9% of the treated subjects consumed 45.0% of the outpatient expenditures. Depression treatment consumed only 8 cents of every health care dollar spent on the patients treated for depression.

CONCLUSIONS

Studies are needed to examine how the level and distribution of expenditures for depression treatment change under managed care and to determine whether and how any differences affect outcomes in the afflicted population. Managed care attempts to contain costs by limiting outpatient care may not affect total health care expenditures dramatically, since depression treatment consumes such a minuscule portion of the health care dollar spent on this population.

Rural-urban differences in depression treatment and suicidality

OBJECTIVES

Because there are fewer per capita providers trained to deliver mental health services in rural areas, the authors hypothesized that depressed rural individuals would receive less outpatient treatment and report higher rates of hospital admittance and suicide attempts than their urban counterparts.

METHODS

The authors recruited 74% of eligible participants (n = 470) from a 1992 telephone survey and followed up 95% of subjects for 1 year. The authors collected data from subjects on psychiatric problems and service use and from insurers/providers on treatment and expenditures.

RESULTS

Although there were no rural-urban differences in the rate, type, or quality of outpatient depression treatment, rural subjects made significantly fewer specialty care visits for depression. Depressed rural individuals had 3.05 times the odds of being admitted to the hospital for physical problems (P = 0.02) and 3.06 times the odds of being admitted for mental health problems (P = 0.08) during the year. Elevated rates of hospital admittance disappear in models controlling for number of specialty care depression visits in the previous month. Rural subjects reported significantly more suicide attempts during the period of 1 year (P = 0.05).

CONCLUSIONS

Additional work is warranted to determine how to alter barriers to outpatient specialty care if the rural health care delivery system is to provide cost-effective depression care.

Modelling and simulation of ion channels: applications to the nicotinic acetylcholine receptor

Molecular dynamics simulations with experimentally derived restraints have been used to develop atomic models of M2 helix bundles forming the pore-lining domains of the nicotinic acetylcholine receptor and related ligand-gated ion channels. M2 helix bundles have been used in microscopic simulations of the dynamics and energetics of water and ions within an ion channel. Translational and rotational motion of water are restricted within the pore, and water dipoles are aligned relative to the pore axis by the surrounding helix dipoles. Potential energy profiles for translation of a Na+ ion along the pore suggest that the protein and water components of the interaction energy exert an opposing effect on the ion, resulting in a relatively flat profile which favors cation permeation. Empirical conductance calculations based on a pore radius profile suggest that the M2 helix model is consistent with a single channel conductance of ca. 50 pS. Continuum electrostatics calculations indicate that a ring of glutamate residues at the cytoplasmic mouth of the alpha 7 nicotinic receptor M2 helix bundle may not be fully ionized. A simplified model of the remainder of the channel protein when added to the M2 helix bundle plays a significant role in enhancing the ion selectivity of the channel.