The lupus phenotype in B6.NZBc1 congenic mice reflects interactions between multiple susceptibility loci and a suppressor locus.

Lupus susceptibility loci on chromosome 1 have an important role in the development of autoimmunity in the New Zealand Black (NZB) mouse. We have previously shown that C57BL/6 congenic mice with an introgressed homozygous NZB chromosome 1 interval extending from ∼35 to 106 cM develop anti-nuclear antibodies and mild glomerulonephritis. In this study, we produced subcongenic mouse strains to localize the susceptibility loci in this interval and investigate how they promote autoimmunity. Our results indicate at least four susceptibility alleles and a suppressor allele. One allele is located in the 96-100 cM region and is sufficient to breach tolerance to chromatin. Addition of a second locus in the 88-96 cM interval enhances anti-dsDNA antibody production and promotes renal disease, which together with a third susceptibility allele in the 70-88 interval results in significant mortality. We further demonstrate the presence of a suppressor locus in the 35-70 or 100-102 cM interval that abrogates these phenotypes and an additional susceptibility allele in the 102-106 cM interval that restores a milder autoimmune phenotype. Several of these loci alter T-cell function. Thus, there is substantial genetic complexity in the NZB 35-106 cM interval, with disease reflecting a balance between susceptibility and suppressor loci.

Ontogeny of the HPA axis of the CD1 mouse following 24 h maternal deprivation at pnd 3.

One of the striking characteristics of the developing neuroendocrine system of rats and mice is the stress hypo-responsive period (SHRP), i.e. low basal corticosterone secretion and the inability to increase corticosterone in response to mild stressors during the first 2 weeks of life. However, immediately after 24 h of deprivation from maternal care the response of the hypothalamic-pituitary-adrenal (HPA) axis to mild stressors is enhanced. This study examines in CD1 mouse pups the recovery pattern of markers of HPA axis (re)activity from maternal deprivation (once for 24 h from postnatal days (pnds) 3 to 4). As expected, deprivation induced a profound corticosterone response to novelty immediately after deprivation. In contrast, 1 day after reunion with the mother (pnd 5), this effect was abolished, lasting for at least 3 days. Basal corticosterone remained even below control levels. Corticotropin-releasing hormone (CRH) mRNA expression in the hypothalamic paraventricular nucleus (PVN) was suppressed for 2 days, exceeded control levels at pnds 7 and 8, and subsequently followed the gradual decline observed in controls until pnd 12. Delayed and rather short-lasting changes were found for adrenocorticotropic hormone (low at pnd 5), and glucocorticoid receptor mRNA expression (decreased in the PVN at pnd 4, and in the hippocampal CA1 area at pnd 5). Hippocampal mineralocorticoid receptor mRNA expression was unaffected. From pnds 9 to 13, both deprived and control pups gradually emerged from the SHRP in a similar temporal pattern. In conclusion, maternal deprivation at pnd 3 augments hypo-responsiveness of corticosterone secretion to mild stress for several days, but does not affect the duration of the SHRP. Whether CRH and glucocorticoid receptor changes are cause or consequence remains to be established.

Assessment of sediment toxicity using different trophic organisms.

The main aim of the present project is to study the feasibility of using different trophic organisms for evaluating the toxicity of dredged sediments arising in Hong Kong. A total of eight sediment samples (duplicate samples collected from four selected sites: Kowloon Bay, Tsing Yi,Chek Lap Kok, and Double Haven) of Hong Kong coastal waters were analyzed for the total concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, total organic carbon, acid volatile sulfides, simultaneously extracted metals, redox potential, and 12 organic micropollutants. The sediment elutriates were also analysed for the various metal concentrations, as well as contents of ammonia-N, nitrate, total sulfide, sulfate, and total organic carbon. Elutriate Sediment Toxicity Tests (ESTT) were also conducted, using two microalgae (Skeletonema costatum, a diatom and Dunaliella tertiolecta, a flagellate), juvenile shrimp (Metapenaeus ensis) and juvenile fish (Trachinotus obtaus). Two commercially available tests using bacteria (Microtox Test and Toxi-Chromotest) also were employed to test both the solid phase and elutriates of the sediments. The results of Microtox test on the solid phase, and bioassay tests using diatom on the sediment elutriate, especially the former, were correlated significantly (p < 0.05) with a number of physico-chemical properties of sediments and elutriates. It is recommended that a combination of a liquid-phase bioassay using diatom and a solid-phase bioassay using Microtox test should be used for screening a large number of sediment samples. However, the presence of ammonia in the sediments containing a high content of organic matter seemed to interfere the detection of contamination impacts.

Toxic effects of dredged sediments of Hong Kong coastal waters on clams.

The present project is an attempt to study the effects of the sediments collected from various sites on the survival of three indigenous bivalves (Circe scripta, Gafrarium fumidum and Tapes philippinarium). The preliminary trial revealed that T. philippinarium was more sensitive than the other two species in response to the dredged sediment collected from the pollution blackspot: Yau Ma Tei typhoon shelter. A subsequent experiment used T. philippinarium to assess the toxicity of sediments under different dissolved oxygen regimes (7.8, 8.0 and 8.2 mg L-1). Significant correlations (p<0.05) were noted between the mortality rates of the test animals and the total nitrogen and ammonia contents in the seawater.

Morphological changes in the gills of tilapia fed sterilized and nonsterilized sludge.

The effects of digested sludge on the ultrastructure of gills of Sarotherodon mossambicus were investigated. Samples of digested sludge were collected from the Shatin Sewage Treatment Plant in Hong Kong and they were (1) sun-dried (NS) or (2) sterilized in an autoclave (SS). They were then used as supplementary fish feed to cultivate the freshwater tilapia, S. mossambicus, for 50 days under laboratory conditions. The SS at low dosage (25%) had the lowest toxicity among different treatments. A swelling of lamellar epithelium, the enlargement of the the subepithelial space, the collapse of capillaries, and the infiltration of polymorphonuclear cells in the lamellae of fish gills were common to fish fed 50 to 100% NS and SS. The thickening of the basal lamina in the gill lamellae is a common feature found in the sludge-treated fish.

Cytotoxicity of airborne particles from roadside urban gardens.

Airborne particles were collected in two small urban gardens along the roads with heavy traffic in Hong Kong. The chemical and physical properties of the particles of a diameter about 1 micron were analysed by a scanning electron microscope incorporated with a x-ray energy dispersive microanalyzer and an atomic absorption spectrophotometer. The cytotoxicities of particles were compared using an in vitro alveolar macrophage culture assay. It was found that both particles significantly increase (p less than 0.05) the release of lactate dehydrogenase and acid phosphatase into the medium in addition to damage the surface morphology and intracellular structures of the macrophages to a variable extent after exposure to the particles.

Toxic effects of animal manures and sewage sludge as supplementary feeds for the common carp. Cyprinus carpio.

Activated sludge, chicken manure and pig manure were tested for their toxic effects as supplementary feeds for the common carp, Cyprinus carpio. The acute toxicity test showed that animal manures were more toxic than activated sludge (e.g., 96-h LC50 values for pig manure and chicken manure were 0.55% and 0.29%, respectively, while no effective value was revealed for activated sludge). This may be due to the inadequate processing of the manures which resulted in the release of harmful substances during decomposition. In general, body weights of all the fish fed the wastes decreased during the culture period. High heavy metal concentrations (Pb, Cu, Zn and Mn) were found accumulated in the flesh of the fish fed the wastes. It is suggested that waste materials should be pretreated and detoxified before using them as animal feeds.