A murine model for the study of the impact ofAspergillus fumigatus inoculation on the foeto-placental unit

The mycotoxin cyclopiazonic acid (CPA) is a potential contaminant of processed foods, grain and poultry. Twelve male Sprague-Dawley rats were given oral doses of 0, 0.2, 0.6, 2.0 or 4.0 mg CPA/kg body weight/day for 13 consecutive weeks to study its potential subchronic toxicity. No dose-related mortality or morbidity occurred. General appearance, behavior, body weight gain and food consumption of all groups were similar. CPA had no definite adverse hematologic or serum chemistry effects, although serum creatinine concentrations of rats given 2.0 and 4.0 mg CPA/kg BW were increased after seven and 13 weeks. Mild to focally moderate acute inflammation of the lamina propria and submucosa of the gastric epithelium was found in animals given 0.6 mg CPA/kg BW. No other dose-related microscopic lesions were found. Ultrastructural examination of the livers revealed subtle disruption of the cisternal pattern of the endoplasmic reticulum with ribosomal detachment in animals receiving 4.0, but not 2.0, mg CPA/kg BW. These data suggest that the toxic effects in rats of repeated, daily oral exposure to CPA may be less than previously reported. The possible relationship between toxicity and CPA epimerization is considered.     

Synthesis and physicochemical properties of oligonucleotides built with either alpha-L or beta-L nucleotides units and covalently linked to an acridine derivative.

Modified deoxynucleosides 2'-deoxy-beta-L-uridine, beta-L-thymidine, alpha-L-thymidine, 2'-deoxy-beta-L-adenosine and 2'-deoxy-alpha-L-adenosine were synthesized and assembled as homooligomers, respectively: octa-beta-L-deoxyuridylates, octa beta-L and alpha-L-thymidylates and tetra beta-L and alpha-L-deoxyadenylates. These unnatural oligomers were then substituted with an acridine derivative. The binding studies of these modified oligonucleotides with D-ribo- and D-deoxyribopolynucleotides were carried out by absorption spectroscopy. While beta-L-d(Up)8m5Acr, beta-L-(Tp)8m5Acr, alpha-L-(Tp)8m5Acr did not interact with poly(rA) and poly(dA), beta-L-d(Ap)4m5Acr and alpha-L-d(Ap)4m5Acr did form double and triple helices with poly(rU) and poly(dT), respectively. Their stability towards nuclease digestion was studied through comparison with that of octa-beta-D-thymidylate and tetra beta-D-deoxyadenylate covalently linked to an acridine derivative. One endonuclease (nuclease P1 from Penicillium citrinum) and two exonucleases (a 3'-exonuclease from Crotalus durissus venom and a 5'-exonuclease extracted from calf thymus) were employed. beta-L- and alpha-L-oligomers demonstrate a high resistance toward nuclease digestion.     

Induction of pregnancy-associated murine protein-1 in dwarf mice by human growth hormone

Pregnancy-associated murine protein-1 (PAMP-1) could not be detected in peripheral blood of female dwarf mice (genotype dw/dw of the DW strain). By contrast the normal size females of the DW strain (genotypes +/+ and +/dw) had PAMP-1 serum levels of 18.9 AU +/- 15.7 AU/ml. Following administration of biosynthetic human growth hormone (hGH) every 2 h for 52 h PAMP-1 was detected in all dwarf females at concentrations of 16.0 AU +/- 3.3 AU/ml. The albumin levels in the circulation of DW females of normal size were significantly higher (P less than 0.05) than those of DW dwarfs, and the hGH administration did not change the serum albumin levels. The present experiment adds weight to the suggestion that the PAMP-1 serum level is regulated by GH.     

Conservation evaluation of nine Hong Kong mangals

A comparative analysis of the conservation value of nine Hong Kong mangals spread across Hong Kong has been undertaken. The analysis is based on both biological and socio-economic attributes. Biological attributes used in the analysis include plant species richness, benthic and arboreal gastropod species richness, occurrence of rare species within each site, and site representativeness. A review of the past and present development and development plans around and within each site has been undertaken to assess the comparative degree of hazard to each mangal. The drastic decline of mangal habitats throughout Hong Kong highlights the need for conservation of what remains today. Priorities and strategies for conservation of these nine mangals are discussed with particular emphasis on the preservation of biodiversity and the management of these habitats as education and research sites.Department of Applied Biology & Chemical Technology, Hong Kong Polytechnic     

Plasmin and the regulation of tissue-type plasminogen activator biosynthesis in human endothelial cells.

Plasmin inhibited the biosynthesis of tissue-type plasminogen activator (tPA) antigen by human umbilical vein endothelial cells (HUVEC) in a dose-dependent manner. The amount of tPA antigen found in the 24-h conditioned medium of cells treated with 100 nM plasmin for 1 h was 20-30% of that in the control group. However, in contrast to tPA, such treatment led to a 3-fold increase in plasminogen activator inhibitor (PAI) activity, whereas the amount of PAI type 1 antigen was unchanged. The effects of plasmin on HUVEC were binding- and catalytic activity-dependent and were specifically blocked by epsilon-aminocaproic acid. Microplasmin, which has no kringle domains, was less effective in reducing tPA antigen biosynthesis or enhancing PAI activity in HUVEC. Kringle domains of plasmin affected neither tPA antigen nor PAI activity of the cells. Other proteases including chymotrypsin, trypsin, and collagenase at comparable concentrations did not have a significant effect on the biosynthesis of tPA antigen or PAI activity of HUVEC. Thrombin stimulated the biosynthesis of tPA and PAI-1 antigens by HUVEC. Thrombin also stimulated an increase in the protein kinase activity in HUVEC, whereas plasmin inhibited the protein kinase activity of the cells. It is possible that plasmin regulates the biosynthesis of tPA in HUVEC through the signal transduction pathway involving protein kinase.     

Pregnancy-associated murine protein-1 (PAMP-1) in wild rodents.

The presence of pregnancy-associated murine protein-1 (PAMP-1) in a number of wild rodent species was examined using tandem crossed immunoelectrophoresis and anti PAMP-1 antisera raised in rabbits. PAMP-1 is a protein present in female laboratory mice and rats; analogues were readily detected in the following species: Musculus domesticus, M. musculus, Apodemus sylvaticus, A. agrarius, A. flavicollis, and Microtus arvalus. Immunologically, cross-reacting proteins could not be detected in the laboratory hamster and laboratory guinea pig. Maternal PAMP-1 serum levels were recorded throughout pregnancy in the two species of house mouse: M. domesticus and M. musculus. Both proteins exhibited maximum concentration at day 11 of gestation. During early pregnancy, M. domesticus females had significantly higher serum levels than those of M. musculus females.     

香港的生物多样性及其保育工作

香港位于热带,属海洋性气候。地势崎岖多山,山地约占全港总面积的3/4。城市发展多集中在沿海平坦地带。目前香港的城市和乡镇面积约占总面积的20%,农地约占5%(当中大部份已遭荒废),余下的均为郊野地区,这包括天然林和人工林(约占14%)、灌丛(约占36%)及草地(约占17%)。由于良好的气候和地理条件,形成了众多不同的生态环境,使总面积仅1090 km²的弹丸之地孕育出种类多样的动植物,生物多样性十分丰富。香港约有2500种原生植物,包括被子植物约1900种,裸子植物7种,蕨类植物220多种及苔藓植物300多种。动物方面,已记录的野生哺乳类动物有40多种,鸟类超过459种,两栖类23种,爬行类70多种。昆虫种类繁多,其中蜻蜓目100多种,鳞翅目2200多种(蝴蝶200多种,蛾类2000多种)。有很多是国家保护物种和特有种。植物方面属国家一级保护的有1种——刺桫椤(Alsophila spinulosa);国家二级保护的有6种,如四药门花(Tetrathryrium subcordatum);国家三级保护的有8种,如穗花杉(Amentotaxus argotaenia)。此外,香港特有种有16种,例如紫萁科(Osmundaceae)的粤紫萁(Osmunda mildei)、马兜铃科(Aristolochiaceae)的香港细辛(Asarum hongkongense)和兰科(Orchidaceae)的谢氏卷瓣兰(Bulbophyllum tseanum)。动物方面有9种属国家一级保护,例如中华白海豚(Sousa chinensis);79种属国家二级保护。特有种则有卢氏小树蛙(Philautus romeri)、包氏双足蜥(Dibamus bogadeki)及多种昆虫。为了保护丰富的野生动植物及其栖息的环境,香港特别行政区政府制定了一些法例并推行了不少保护措施,例如设立了21个郊野公园和14个特别地区,占全港陆地总面积约38%。此外,还成立了2个禁区、3个海岸公园和1个海洋保护区。另一方面,政府还设立了59个“具特殊科学价值地点”,以保护及研究各种动植物、生态系统和特殊的地质地貌。香港地少人多,总人口超过600万,是世界上人口最稠密的地区之一。多年来香港这个生物宝库不断地遭受人类活动的威胁,近年来由于人口急剧上升,对土地需求迫切,不少郊野地区被开发利用,环境污染亦日益严重。此外,一些野生植物因具有药用价值、观赏价值或其他用途而遭盗伐或采集。上述种种因素已使香港野生动植物及其生境受到严重损害,一些物种更濒于灭绝,进行生物多样性的保育工作刻不容缓。因此,香港确实需要制定整体的生物多样性保护策略。有鉴于此,香港大学生态及分类学系于1996年展开了一项为期3年的香港生物多样性调查,以增加对动植物资源现况的了解,为保护香港的珍稀濒危物种和日益恶化的自然环境提出补救方案,并为制订长远的保育策略奠定基础。     

Epstein-Barr virus-encoded latent membrane protein 1 impairs G2 checkpoint in human nasopharyngeal epithelial cells through defective Chk1 activation

Nasopharyngeal carcinoma (NPC) is a common cancer in Southeast Asia, particularly in southern regions of China. EBV infection is closely associated with NPC and has long been postulated to play an etiological role in the development of NPC. However, the role of EBV in malignant transformation of nasopharyngeal epithelial cells remains enigmatic. The current hypothesis of NPC development is that premalignant nasopharyngeal epithelial cells harboring genetic alterations support EBV infection and expression of EBV genes induces further genomic instability to facilitate the development of NPC. The latent membrane protein 1 (LMP1) is a well-documented EBV-encoded oncogene. The involvement of LMP1 in human epithelial malignancies has been implicated, but the mechanisms of oncogenic actions of LMP1, particularly in nasopharyngeal cells, are unclear. Here we observed that LMP1 expression in nasopharyngeal epithelial cells impaired G2 checkpoint, leading to formation of unrepaired chromatid breaks in metaphases after γ-ray irradiation. We further found that defective Chk1 activation was involved in the induction of G2 checkpoint defect in LMP1-expressing nasopharyngeal epithelial cells. Impairment of G2 checkpoint could result in loss of the acentrically broken chromatids and propagation of broken centric chromatids in daughter cells exiting mitosis, which facilitates chromosome instability. Our findings suggest that LMP1 expression facilitates genomic instability in cells under genotoxic stress. Elucidation of the mechanisms involved in LMP1-induced genomic instability in nasopharyngeal epithelial cells will shed lights on the understanding of role of EBV infection in NPC development.     

Id1 interacts and stabilizes the Epstein-Barr virus latent membrane protein 1 (LMP1) in nasopharyngeal epithelial cells

The EBV-encoded latent membrane protein 1 (LMP1) functions as a constitutive active form of tumor necrosis factor receptor (TNFR) and activates multiple downstream signaling pathways similar to CD40 signaling in a ligand-independent manner. LMP1 expression in EBV-infected cells has been postulated to play an important role in pathogenesis of nasopharyngeal carcinoma. However, variable levels of LMP1 expression were detected in nasopharyngeal carcinoma. At present, the regulation of LMP1 levels in nasopharyngeal carcinoma is poorly understood. Here we show that LMP1 mRNAs are transcribed in an EBV-positive nasopharyngeal carcinoma (NPC) cell line (C666-1) and other EBV-negative nasopharyngeal carcinoma cells stably re-infected with EBV. The protein levels of LMP1 could readily be detected after incubation with proteasome inhibitor, MG132 suggesting that LMP1 protein is rapidly degraded via proteasome-mediated proteolysis. Interestingly, we observed that Id1 overexpression could stabilize LMP1 protein in EBV-infected cells. In contrary, Id1 knockdown significantly reduced LMP1 levels in cells. Co-immunoprecipitation studies revealed that Id1 interacts with LMP1 by binding to the CTAR1 domain of LMP1. N-terminal region of Id1 is required for the interaction with LMP1. Furthermore, binding of Id1 to LMP1 suppressed polyubiquitination of LMP1 and may be involved in stabilization of LMP1 in EBV-infected nasopharyngeal epithelial cells.     

Characterization of Polar and Non‐Polar Compounds of House Edible Bird's Nest (EBN) from Johor,Malaysia

This work investigated the polar (PC: protein, amino acid and metabolite) and non‐polar (NPC: fatty acid) compounds and bioactivity characteristics of the EBN harvested from the state of Johor in Malaysia. The electrophoretic gels exhibited 15 protein bands (16–173 kD) with unique protein profile. Amino acids analysis by AccQ?Tag method revealed 18 types of amino acids in EBN. Metabolite profiling was performed using High‐Performance Liquid Chromatography coupled with Quadrupole Time‐of‐Flight Mass Spectrometer (HPLC‐QTOF/MS) technique and a total of 54 compounds belonging to different groups were detected and identified. These findings help to uncover the relation of therapeutic activity of EBN. The EBN was further extracted with AcOEt and BuOH. The AcOEt extract was fractionated into three fractions (F₁?F₃), and the high triglyceride content in F₂ was verified by gC‐FID. The three groups of fatty acids discovered in EBN are 48.43 % of poly‐unsaturated (PUFA), 25.35 % of saturated fatty acids (SFA) and 24.74 % of mono‐unsaturated fat (MUFA). This is the first time to report results ofEBN, BuOH, and AcOEt extracts and of fraction F₂ (TEBN) on their analysis for their antioxidant activities by DPPH, ABTS and catalase assay and for their paraoxonase and anti‐tyrosinase activities. The results showed that TEBN exhibited the significant bioactivity in all assays. These findings suggest that TEBN is a good source for natural bioactive compounds in promoting body vigor. Current work widened the content of EBN especially on the triglyceride and also marked the content of specific location (Johor, Malaysia) of EBN origin.