Fluoxetine and 8-OH-DPAT in the lateral septum enhances and impairs retention of an inhibitory avoidance response in rats.

The present study investigated the role of lateral septal serotonin (5HT) in memory consolidation and the subtype of 5HT receptors involved in this process. Rats with cannulae implanted bilaterally into the lateral septum were trained in an inhibitory avoidance task. Immediately after training, the septal serotonergic function was manipulated by pharmacological agents selectively blocking 5HT reuptake (fluoxetine and zimelidine), antagonizing 5HT2 receptors (ketanserin and ritanserin), or activating 5HT1A receptors, respectively. Results indicated that direct fluoxetine infusions into the lateral septum at a dose of 6 micrograms/0.5 microliter and zimelidine at a dose of 5 micrograms/0.5 microliter both markedly enhanced memory. Intralateral septal injections of ketanserin (0.3 microgram/0.5 microliter and 0.5 microgram/0.5 microliter) and ritanserin (0.3 microgram/0.5 microliter and 0.6 microgram/0.5 microliter) did not have a significant effect by themselves on memory, and neither did they attenuate the memory-facilitating effect of fluoxetine in the same area. Intralateral septal infusions of 8-hydroxy-2-(di-n-propylamino)tetralin at 5 micrograms/0.5 microliter significantly impaired memory retention. These findings altogether support the notion that the lateral septal nuclei of rats are involved in the memory processes of inhibitory avoidance learning. Furthermore, postsynaptic 5HT receptor activation (not the 5HT2 receptor subtype) probably exerts a facilitatory effect while presynaptic 5HT1A receptor activation exerts an impairing effect on the memory consolidation process, probably due to autoreceptor inhibition of 5HT release.     

E(f)-current contributes to whole-cell calcium current in low calcium in frog sympathetic neurons

Because Ca(2+) plays diverse roles in intracellular signaling in neurons, several types of calcium channels are employed to control Ca(2+) influx in these cells. Our experiments focus on resolving the paradox of why whole-cell current has not been observed under typical recording conditions for one type of calcium channel that is highly expressed in frog sympathetic neurons. These channels, referred to as E(f)-channels, are present in the membrane at a density greater than the channels that carry approximately 90% of whole-cell current in low Ba(2+); but, E(f)-current has not been detected in low Ba(2+). Using Ca(2+) instead of Ba(2+) as the charge carrier, we recorded a possible E-type current in frog sympathetic neurons. The current was resistant to specific blockers of N-, L-, and P/Q-type calcium channels but was more sensitive to Ni(2+) block than was N- or L-current. Current amplitude in Ca(2+) is slightly greater than that in Ba(2+). In 3 mM Ca(2+), the current contributed approximately 12% of total current at peak voltage and increased at voltages more hyperpolarized to the peak, reaching approximately 40% at -30 mV, where whole-cell current starts to activate. The presence of E(f)-current in 3 mM Ca(2+) suggests a potential role for E(f)-channels in regulating calcium influx into sympathetic neurons.     

Detection and deletion of motion artifacts in electrogastrogram using feature analysis and neural networks

Electrogastrogram is a surface measurement of gastric myoelectrical activity, and electrogastrography has been an attractive method for physiological and pathophysiological studies of the stomach due to its nonivasive nature. Motion artifacts, however, ruin the electrogastrogram (EGG), and make the analysis very difficult and sometimes even impossible. They must be eliminated from EGG signals before analysis. Up to now, this can only be done by visual inspection, which is not only time-consuming but also subjective. In this study, a method using feature analysis and neural networks has been developed to realize automatic detection and elimination of the motion artifacts in EGG recordings by computer. Experiments were conducted to investigate the characteristics of different motion artifacts. Useful features were extracted, and different combinations of the features used as the input of the neural network were compared to obtain the optimal performance for the detection of motion artifacts using the artificial neural network.     

Changes in HIV-1 incidence in heroin users in Guangxi Province, China

Guangxi Province, China recently experienced an outbreak of HIV-1 infection among heroin users. We studied HIV-1 incidence rates and associated risk factors for HIV-1 infection among heroin users residing in Pingxiang City. A total of 318 heroin users were followed from February 1998 through January 1999 (median follow-up: 8.1 months). Of these, 130 were prospectively followed from January through September 1999 (median follow-up: 8.3 months). HIV-1 and hepatitis C virus (HCV) incidence rates for each period were calculated. A generalized estimating equation approach was implemented to identify independent risk factors associated with HIV-1 infection across both periods. Among 318 study participants, 97.2% were men. The median age was 22 years. Approximately 60% reported sharing needles. HIV-1 prevalence at baseline was 15.4%. During the first follow-up period, HIV-1 incidence was 2.38 per 100 person years (py), and HCV incidence was 26.8 per 100 py. During the second follow-up period, HIV-1 incidence was 6.86 per 100 py, and HCV incidence was 28.9 per 100 py. After controlling for age and other factors, HCV seropositivity, history of sexually transmitted diseases, and sharing needles were independently associated with HIV-1 infection. These data suggest that HIV-1 incidence was rising over time in Pingxiang City, Guangxi Province. The high incidence of HCV heightens the importance of enhanced prevention programs to reduce injection and needle sharing among heroin users.     

Molecular and biochemical mechanisms ofPasteurella haemolyticaleukotoxin-induced cell death

Pasteurella haemolyticaleukotoxin (LKT) is a member of the RTX family of pore-forming toxins that kill bovine immune cells. Several studies have suggested that RTX toxins kill target cells by the induction of apoptosis. In the present study, BL3 bovine leukaemia cells were exposed to LKT and assessed by molecular and flow cytometric techniques that measure different aspects of apoptotic cell death. The intoxicated cells demonstrated morphological, light scatter and Hoechst 33258 staining characteristics consistent with cells undergoing apoptosis. The cells also exhibited internucleosomal DNA fragmentation and poly (ADP-ribose) polymerase (PARP) cleavage, both indicators of apoptosis. LKT-treated cells bound annexin-V-FITC indicating that phosphatidylserine groups were translocated from the inner to the outer leaflet of the cell membrane. The effect of LKT on cells was dose dependent and inhibitable by incubation with anti-LKT monoclonal antibody. Finally, an early step for induction of apoptosis appears to be the binding of LKT to a β2 integrin since pre-incubating cells with anti-β2 integrin antibodies inhibited LKT-induced apoptosis. This study provides new insights into understanding the pathogenesis of bovine pasteurellosis and could lead to the development of both preventative and therapeutic strategies for disease management.     

聚醚型聚氨酯材料表面纤维蛋白原的吸附性研究

本文采用放射性同位素标记的方法研究了嵌段聚醚型聚氨酯在纯纤维蛋白原溶液中和稀释血浆中的表面纤维蛋白原吸附性规律，考察了聚醚型聚氨酯的特性粘数及溶液体系中的ＮａＣｌ浓度对材料表面纤维蛋白原吸附性的影响，结果表明，随着聚合物特性粘数的增大，材料表面的纤维蛋白原吸附量呈降低的趋势；溶液体系中盐浓度的降低导致纤维蛋白原凝固性增强，在纯纤维蛋白原溶液中，材料表面纤维蛋白原的吸附量相应增多，而在稀释血浆中，纤维蛋白原的吸附量相应减少，在达到最低值后又有上升的趋向，表明纤维蛋白原在材料表面的吸附还受血浆中其它大分子的影响。     

Neonatal sepsis in the neonatal intensive care unit: characteristics of early versus late onset.

Neonatal sepsis is a major cause of death in newborns despite sophisticated neonatal intensive care. This retrospective study reviewed the clinical characteristics of cases of culture-proven sepsis in a neonatal intensive care unit from January 1992 to December 2001. Patients were divided into those with onset of sepsis in the first 7 days of life (early-onset group) and those with onset after the seventh day of life (late-onset group). A total of 270 cases with 325 episodes of sepsis and 353 isolated pathogens were identified and included in the study. The male-to-female ratio was 1.4. The majority of cases of sepsis occurred in low birth weight (75.9%) and premature babies (76.7%). Late onset occurred in 71.9% of cases. Patients with late onset had a lower mortality rate than those with early onset (11.3% vs 28.9%). Coagulase-negative staphylococci (20.1%) was the most common organism isolated, but infection with Pseudomonas aeruginosa was associated with the highest morality rate (55.0%). Late-onset sepsis was significantly more common in very low birth weight and premature infants. The most frequently encountered pathogens in the early-onset group were group B streptococci (GBS) and Escherichia coli, while in the late-onset group, the organisms were coagulase-negative staphylococci and Enterobacteriaceae, including E. coli, Klebsiella pneumoniae, and Acinetobacter baumannii. GBS infection resulted in the highest mortality when the onset of sepsis was within the first 24 hours of life.     

Lack of FasL expression in cultured human retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells have been proposed to play a part in maintaining the eye as an immune privileged organ. However, our knowledge of the implicated mechanism is still sparse. Fas ligand (FasL) expression of RPE cells is generally recognized to be essential for the immune privilege of the eye, but due to contradictory published results, it is unclear whether RPE cells express this molecule. The purpose of this study was to investigate the expression of FasL in RPE cells in vitro and in vivo. Cultured human fetal and adult RPE cells were examined by flow cytometry, Western blotting, RT-PCR and RNase Protection assay for FasL expression. Additionally, sections of ocular tissue were stained for FasL by immunohistochemistry. None of the used methods indicated FasL expression in cultured fetal or adult RPE cells of various passages. However, RPE cells in vivo, as judged from tissue sections, were positive for FasL, indicating a discrepancy between RPE cells in vitro and in vivo with regard to this molecule.