Synthesis and structure-activity studies of antibacterial oxazolidinones containing dihydrothiopyran or dihydrothiazine C-rings

A new series of antimicrobial oxazolidinones bearing unsaturated heterocyclic C-rings is described. Dihydrothiopyran derivatives were prepared from the saturated tetrahydrothiopyran sulfoxides via a Pummerer-rearrangement/elimination sequence. Two new synthetic approaches to the dihydrothiazine ring system were explored, the first involving a novel trifluoroacetylative-detrifluoroacetylative Pummerer-type reaction sequence and the second involving direct dehydrogenation of tetrahydrothiopyran S,S-dioxide intermediates. Final analogs such as 4 and 13 represent oxidized congeners of recent pre-clinical and clinical oxazolidinones.     

Genotypic diversity of Borrelia burgdorferi strains detected in Ixodes scapularis larvae collected from North American songbirds

We genotyped Borrelia burgdorferi strains detected in larvae of Ixodes scapularis removed from songbirds and compared them with those found in host-seeking I. scapularis nymphs sampled throughout the eastern United States. Birds are capable of transmitting most known genotypes, albeit at different frequencies than expected based on genotypes found among host-seeking nymphs.     

Extinction deficits in male rhesus macaques with a history of self-injurious behavior

Self-injurious behavior (SIB) occurs in both human and nonhuman primate populations. Despite the potential for harm, SIB may persist in part because of an inability to inhibit behavior that results in wounding. A lever-pressing task was used to test the prediction that monkeys with SIB would show greater persistence in lever-pressing on extinction trials than monkeys without the disorder. The subjects were 15 individually-housed adult male rhesus macaques, 10 of which (the SIB group) had a veterinary record of self-inflicted wounding. All of the monkeys were trained to lever-press for food rewards to a criterion of 400 total responses. The test procedures consisted of five daily 30-min sessions divided into six 5-min intervals. On day 1, the subjects received continuous reinforcement. On days 2-4, testing consisted of alternating reinforced/unreinforced 5-min intervals, beginning with reinforcement. Reinforced intervals were cued with a buzzer. On day 5, the subjects received no reinforcement. The number of lever-presses and behavioral responses were recorded during each session. Saliva samples were collected for cortisol measurement before and after test sessions on days 1, 2, and 5. As predicted, monkeys with SIB lever-pressed more than controls during extinction intervals on days 2-4. There was no difference on day 1 or day 5. The frequency of scratching, yawning, and abnormal behavior increased when reinforcement was intermittent (days 2-4) or absent (day 5). Cortisol levels were highest with continuous reinforcement (day 1), and may reflect differential levels of food intake rather than stress. The presence of extinction deficits suggests that SIB may persist in some monkeys because they lack the ability to regulate the intensity of their biting behavior.     

Nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF) regulate substance P release in adult spinal sensory neurons

NGF increases expression and content of substance P in developing and mature spinal sensory neurons. The role this neurotrophin plays in peptide release, however, is less clear. Accordingly, we examined substance P release from cultures of mature rat sensory neurons, which do not require NGF for survival. Neurons grown without NGF have a low but detectable basal release, which increases with depolarization by KCl (50 mM) but never achieves statistical significance. In contrast, basal release is 3 times higher from neurons that have been cultured in the presence of NGF, and KCl depolarization triples the amount of SP released. Stimulation with capsaicin (10^–7 M) yields similar results. Residual peptide remaining after capsaicin stimulation is refractory to release for up to 24 h. Bradykinin does not induce SP secretion from mature neurons nor does it potentiate the action of capsaicin. GDNF, which also increases SP content, mimics NGF. Addition of NGF to the bath during release does not directly induce SP secretion, nor does it alter the effects of KCl, capsaicin, or bradykinin. It appears therefore that NGF increases SP release indirectly by increasing intracellular stores.     

Microsatellite typing of the rhesus macaque MHC region

To improve the results gained by serotyping rhesus macaque major histocompatibility complex (MHC) antigens, molecular typing techniques have been established for class I and II genes. Like the rhesus macaque Mamu-DRB loci, the Mamu-A and -B are not only polymorphic but also polygenic. As a consequence, sequence-based typing of these genes is time-consuming. Therefore, eight MHC-linked microsatellites, or short tandem repeats (STRs), were evaluated for their use in haplotype characterization. Polymorphism analyses in rhesus macaques of Indian and Chinese origin showed high STR allelic diversity in both populations but different patterns of allele frequency distribution between the groups. Pedigree data for class I and II loci and the eight STRs allowed us to determine extended MHC haplotypes in rhesus macaque breeding groups. STR sequencing and comparisons with the complete rhesus macaque MHC genomic map allowed the exact positioning of the markers. Strong linkage disequilibria were observed between Mamu-DR and -DQ loci and adjacent STRs. Microsatellite typing provides an efficient, robust, and quick method of genotyping and deriving MHC haplotypes for rhesus macaques regardless of their geographical origin. The incorporation of MHC-linked STRs into routine genetic tests will contribute to efforts to improve the genetic characterization of the rhesus macaque for biomedical research and can provide comparative information about the evolution of the MHC region.     

Characterization of the Citrobacter freundii phoE gene and development of C. freundii-specific oligonucleotides

The phoE gene of Citrobacter freundii, encoding a pore-forming outer membrane protein, was cloned and its nucleotide sequence was determined. The homologies in terms of identical amino acids between the C. freundii PhoE protein and those of Escherichia coli, E. cloacae and Klebsiella pneumoniae were 90%, 86% and 84%, respectively. Two synthetic oligonucleotides, corresponding to hypervariable, cell surface-exposed regions of the protein, were tested for their specificity in polymerase chain reactions. They were specific for the species C. freundii, i.e., no reaction was detected with 35 non-C. freundii strains tested, including 17 Salmonella, two C. amalonaticus and three C. diversus strains, whereas all five C. freundii strains tested were correctly recognized.     

Avian Host-Selection by Culex pipiens in Experimental Trials

Evidence from field studies suggests that Culex pipiens, the primary mosquito vector of West Nile virus (WNV) in the northeastern and north central United States, feeds preferentially on American robins (Turdus migratorius). To determine the contribution of innate preferences to observed preference patterns in the field, we conducted host preference trials with a known number of adult female C. pipiens in outdoor cages comparing the relative attractiveness of American robins with two common sympatric bird species, European starling, Sternus vulgaris and house sparrow, Passer domesticus. Host seeking C. pipiens were three times more likely to enter robin-baited traps when with the alternate host was a European starling (n = 4 trials; OR = 3.06; CI [1.42–6.46]) and almost twice more likely when the alternative was a house sparrow (n = 8 trials; OR = 1.80; CI = [1.22–2.90]). There was no difference in the probability of trap entry when two robins were offered (n = 8 trials). Logistic regression analysis determined that the age, sex and weight of the birds, the date of the trial, starting-time, temperature, humidity, wind-speed and age of the mosquitoes had no effect on the probability of a choosing a robin over an alternate bird. Findings indicate that preferential feeding by C. pipiens mosquitoes on certain avian hosts is likely to be inherent, and we discuss the implications innate host preferences may have on enzootic WNV transmission.