使用无线电集群通信系统应扬长避短

本文先对集群通信系统的概念作一些阐述,包括其含义、特点和一些主要功能。对集群方式的三种形式——消息集群、传输集群和准传输集群作了简要介绍。对集群系统的两种控制方式——专用控制信道方式和非专用控制信道方式也作了简单分析。在此基础上,对集群通信系统的正确使用提出了看法,对蜂窝和集群两个系统作了简要比较。     

All-trans-retinoic acid interacts synergistically with basic fibroblast growth factor and epidermal growth factor to stimulate the production of tissue inhibitor of metalloproteinases from fibroblasts

This report examines the effect of all-trans-retinoic acid in combination with basic fibroblast growth factor (bFGF) or epidermal growth factor (EGF) on collagenase and tissue inhibitor of metalloproteinases (TIMP) production from human foreskin and synovial fibroblasts. When 10(-5) M retinoic acid is applied in combination with 1, 10, and 100 ng/ml of either FGF or EGF to foreskin or synovial fibroblasts, this results in a dose-dependent synergistic increase in TIMP protein production which is greater than the additive effect of the agents by up to fourfold. These responses can be inhibited by the presence of specific neutralizing antibodies to bFGF and EGF, demonstrating that they result from the presence of the growth factors and not from an experimental artifact such as bacterial endotoxin. We have also found that retinoic acid potently inhibits bFGF- and EGF-stimulated collagenase protein production in both skin and synovial fibroblasts.     

Adsorption of botulinum toxin to activated charcoal with a mouse bioassay

STUDY OBJECTIVE: We evaluated the effectiveness of activated charcoal (AC) in adsorbing Clostridium botulinum type A toxin using a mouse bioassay. DESIGN: Prospective, blinded, randomized, controlled animal study. SETTING: Animal care facility. PARTICIPANTS: One hundred forty Swiss/Webster ND-4 strain mice. INTERVENTION: Food contaminated with type A botulinum toxin was homogenized in a phosphate/gel buffer (pH 6.2). The concentrate was diluted by factors of 1:10, 1:50, and 1:100. AC was added to aliquots of the dilutions to a 20% final concentration. The samples were centrifuged, supernatant was removed, and separate groups of mice were injected intraperitoneally with .5 mL of each dilution (those treated with AC and controls untreated with AC). The animals were then observed over 5 days for signs of botulism. RESULTS: None of the 60 animals injected intraperitoneally with dilutions treated with AC was observed to have any signs of botulism. In contrast, deaths were observed in 10 of 20, 9 of 20 and 4 of 20 mice injected with untreated dilutions of 1:100, 1:50, and 1:10, respectively (P < .004). CONCLUSION: In this model, treatment of botulinum toxin with AC before administration resulted in greatly reduced morbidity and mortality.     

Serotonin receptor 1A knockout: an animal model of anxiety-related disorder

To investigate the contribution of individual serotonin (5-hydroxytryptamine; 5-HT) receptors to mood control, we have used homologous recombination to generate mice lacking specific serotonergic receptor subtypes. In the present report, we demonstrate that mice without 5-HT1A receptors display decreased exploratory activity and increased fear of aversive environments (open or elevated spaces). 5-HT1A knockout mice also exhibited a decreased immobility in the forced swim test, an effect commonly associated with antidepressant treatment. Although 5-HT1A receptors are involved in controlling the activity of serotonergic neurons, 5-HT1A knockout mice had normal levels of 5-HT and 5-hydroxyindoleacetic acid, possibly because of an up-regulation of 5-HT1B autoreceptors. Heterozygote 5-HT1A mutants expressed approximately one-half of wild-type receptor density and displayed intermediate phenotypes in most behavioral tests. These results demonstrate that 5-HT1A receptors are involved in the modulation of exploratory and fear-related behaviors and suggest that reductions in 5-HT1A receptor density due to genetic defects or environmental stressors might result in heightened anxiety.