Structure elucidation of three triterpene glycosides from the trunk of Argania spinosa

Drs. John Elce and Peter Davies, biochemists at Queen's University, Kingston, Ont., are investigating the molecular structure of calpain, an enzyme that has been implicated in the cellular damage that occurs after such events as myocardial infarction and stroke. This damage is precipitated by an imbalance in the regulation of calpain that arises as an indirect result of ischemia. Elce and Davies hope that their research, which involves techniques such as recombinant DNA technology and x-ray crystallography, will lead to the development of a calpain inhibitor that will prevent such damage from occurring and enhance recovery.     

HIV-1 seroconversion in a prospective study of female sex workers in northern Thailand: continued high incidence among brothel-based women

OBJECTIVES: To determine the incidence of HIV-1 infection, temporal trends in incidence, and risk factors for seroconversion in a cohort of female commercial sex workers (CSW) in upper northern Thailand, the region of Thailand with the highest rates of HIV-1 infection. METHODS: CSW were enrolled from 1991 through 1994 and evaluated prospectively with interviews, physical examination, testing for sexually transmitted diseases (STD), and serologic testing for HIV-1 infection. RESULTS: The incidence of HIV-1 seroconversion in the first year of follow-up was 20.3 per 100 person-years among 126 brothel-based CSW and 0.7 per 100 person-years among 159 other CSW who worked in other venues such as bars or massage parlors. Incidence remained elevated among brothel-based CSW who were enrolled later in the study compared with those who enrolled earlier. Through 1996, 30 women seroconverted. In a multivariable proportional hazards model, seroconversion was significantly associated (P < 0.05) with brothel-based sex work (adjusted risk ratio, 7.3) and Chlamydia trachomatis cervical infection (adjusted risk ratio, 3.3). CONCLUSION: Despite national HIV control efforts and declining rates of infection among young men in Thailand, brothel-based CSW may continue to be at high risk for HIV-1 infection. Additional efforts are needed to provide alternative economic choices for young women, to ensure universal condom use during commercial sex, and to develop new prevention technologies.     

PACMAN: passive autoconfiguration for mobile ad hoc networks

Mobile ad hoc networks (MANETs) enable the communication between mobile nodes via multihop wireless routes without depending on a communication infrastructure. In contrast to infrastructure-based networks, MANET's support autonomous and spontaneous networking and, thus, should be capable of self-organization and -configuration. This paper presents passive autoconfiguration for mobile ad hoc network (PACMAN), a novel approach for the efficient distributed address autoconfiguration of mobile ad hoc networks. Special features of PACMAN are the support for frequent network partitioning and merging, and very low protocol overhead. This is accomplished by using cross-layer information derived from ongoing routing protocol traffic, e.g., address conflicts are detected in a passive manner based on anomalies in routing protocol traffic. Furthermore, PACMAN assigns Internet protocol (IP) addresses in a way that enables their compression, which can significantly reduce the routing protocol overhead. The performance of PACMAN is analyzed in detail based on various simulation results.     

Maternal virus load and perinatal human immunodeficiency virus type 1 subtype E transmission, Thailand. Bangkok Collaborative Perinatal HIV Transmission Study Group

To determine the rate and risk factors for human immunodeficiency virus (HIV)-1 subtype E perinatal transmission, with focus on virus load, pregnant HIV-infected women and their formula-fed infants were followed prospectively in Bangkok. Of 281 infants with known outcome, 68 were infected (transmission rate, 24.2%; 95% confidence interval, 19.3%-29.6%). Transmitting mothers had a 4.3-fold higher median plasma HIV RNA level at delivery than did nontransmitters (P<.001). No transmission occurred at <2000 copies/mL. On multivariate analysis, prematurity (adjusted odds ratio [AOR], 4.5), vaginal delivery (AOR, 2.9), low NK cell percentage (AOR, 2.4), and maternal virus load were associated with transmission. As RNA quintiles increased, the AOR for transmission increased linearly from 4.5 to 24.8. Two-thirds of transmission was attributed to virus load>10,000 copies/mL. Although risk is multifactorial, high maternal virus load at delivery strongly predicts transmission. This may have important implications for interventions designed to reduce perinatal transmission.     

Obsessive-compulsive disorder and ventromedial frontal lesions: clinical and neuropsychological findings

Using whole cell recording techniques, we distinguished immature from mature stages of development in auditory thalamic neurons of rats at ages P5 to P21. We compared voltage responses to injected currents and firing patterns of neurons in ventral partition of medial geniculate body (MGBv) in slices. Resting potential, input resistance and membrane time constant diminished to mature values between P5 and P14. Responses of young neurons to hyperpolarizing pulses showed delayed inward rectification; after P13, this was obscured by a rapid onset of another inward rectifier. All neurons possessed tetrodotoxin (TTX)-sensitive, depolarization-activated rectification, implying persistent Na+-current involvement. Despite a slightly higher voltage threshold for spiking, the current threshold was lower in younger neurons. Young neurons fired a short latency spike with afterhyperpolarization whereas older neurons exhibited a slow ramplike depolarization before tonic firing. Large currents caused continuous firing in all neurons. Before day P13, a high threshold Ca2+ spike (HTS) often was appended to action potentials. The low threshold Ca2+-spike (LTS) was too small in amplitude to evoke action potentials before P11 but produced a single spike at P12 and P13 and burst firing with HTS after P13. MGBv neurons have mature properties after P14, relevant for reactions to sound and the oscillations of slow-wave sleep.     

A sample holder for soft x-ray absorption spectroscopy of liquids in transmission mode

A novel sample holder for soft x-ray absorption spectroscopy of liquids in transmission mode based on sample cells with x-ray transparent silicon nitride membranes is introduced. The sample holder allows for a reliable preparation of ultrathin liquid films with an adjustable thickness in the nm-μm range. This enables measurements of high quality x-ray absorption spectra of liquids in transmission mode, as will be shown for the example of liquid H(2)O, aqueous solutions of 3d-transition metal ions and alcohol-water mixtures. The fine structure of the x-ray absorption spectra is not affected by the sample thickness. No effects of the silicon nitride membranes were observed in the spectra. It is shown how an inhomogeneous thickness of the sample affects the spectra and how this can be avoided.