Effect of epibiosis on the fitness of the sandy shore snail<Emphasis Type="Italic"> Batillaria zonalis</Emphasis> in Hong Kong

Batillaria zonalis is a common snail on Hong Kong sandy shores, occupying the low-mid shore. Shells of B. zonalis (basibiont) are often fouled with the rock oyster Saccostrea cucullata and the barnacle Balanus reticulatus (epibiont). This epibiotic interaction has a negative impact on the fitness of B. zonalis in terms of impairing fecundity, mobility and metabolism of fouled individuals. During the reproductive season, fouled snails had lower Gonadosomatic Index and fewer egg-bearing individuals than non-fouled snails. Fouled snails crawled in a more tortuous pathway and with lower speed when compared with non-fouled snails. Reduction in oxygen consumption and metabolic rate in fouled snails further suggested the restriction in mobility of B. zonalis by the epibionts. Glycogen content in the foot muscle tissues and hepatopancreas of fouled and non-fouled snails was, however, similar, revealing epibiosis does not influence the energy storage of B. zonalis. Mortality of fouled and non-fouled snails was similar under laboratory conditions, suggesting epibiosis does not influence the survivorship of B. zonalis in Hong Kong. Impairment in the fitness of fouled B. zonalis indicates that epibiosis can influence the population dynamics of B. zonalis in Hong Kong.Communicated by T. Ikeda, Hakodate     

Some aspects of toxic contaminants in herbal medicines

A World Health Organisation survey indicated that about 70-80% of the world populations rely on non-conventional medicine mainly of herbal sources in their primary healthcare. In recent years, we have witnessed the increasing growth in popularity of over-the-counter (OTC) health foods, nutraceuticals, and medicinal products from plants or other natural sources in developed countries. This indirectly indicates that the public is not satisfied with their orthodox medical (OM) treatment. Such increase in popularity has also brought concerns and fears over the professionalism of practitioners, and quality, efficacy and safety of their treatment methods and products from herbal and natural sources available in the market. Over the past decade several news-catching episodes in developed communities indicated adverse effects, sometimes life threatening, allegedly arisen consequential to taking of OTC herbal products or traditional medicines from various ethnic groups. These OTC products may be contaminated with excessive or banned pesticides, microbial contaminants, heavy metals, chemical toxins, and for adulterated with orthodox drugs. Excessive or banned pesticides, heavy metals and microbial contaminants may be related to the source of these herbal materials, if they are grown under contaminated environment or during collection of these plant materials. Chemical toxins may come from unfavourable or wrong storage conditions or chemical treatment due to storage. The presence of orthodox drugs can be related to unprofessional practice of manufacturers. Some of these environment related factors can be controlled by implementing standard operating procedures (SOP) leading to Good Agricultural Practice (GAP), Good Laboratory Practice (GLP), Good Supply Practice (GSP) and Good Manufacturing Practice (GMP) for producing these medicinal products from herbal or natural sources. The public's belief that herbal and natural products are safer than synthetic medicines can only be ascertained by imposing regulatory standards on these products that should be manufactured using these Good Practices. Using Chinese medicines, as examples, this paper illustrate how advances in chemical and biomedical analysis would help to detect intentional and unintentional toxic contaminants in herbal substances. The paper also summarises how modernization and progress are being carried out to get the best out of Chinese medicines for public healthcare.     

Lymphatic transport of inhaled diesel particles in the lungs of rats and guinea pigs exposed to diluted diesel exhaust

Factors influencing the disposition of the inhaled diesel particles were studied by analyzing the deposition of radioactively labelled diesel particles in the respiratory system, by determining the specific function of alveolar cellular mechanisms in the primary defense against inhaled particles and by identifying the important role of the lymphatic system in the lung clearance of experimental animals exposed to diluted emissions from a diesel engine. Radioactive ¹³¹Barium was used as a tracer of diesel particles and the deposition efficiency was determined to be 15%±6% of the inhaled dose in the Fischer 344 rat strain. The number of cells obtained by bronchial lavage increased significantly after a prolonged exposure to a concentration of 1500 μg/m³ of diesel particles. The increased cell number was more than twofold, contained two distinct cell populations (alveolar macrophages and neutrophils) and represented a reactive mobilization of the defense mechanisms in the organism. Light microscopy studies investigated the role of lymphatic transport of the particulate matter and revealed that the peribrochial and perivascular aggregates of lymphoid tissue contained diesel particles even after short exposure periods at low dose levels. With the increasing burden of particles in the respiratory system, the coloration of hilar and mediastinal lymph nodes continuously changed to gray and finally to dark black, depending upon the dose level and exposure. However, at all exposure levels, most of the diesel particles in the alveoli were phagocytized by an increased alveolar cellular defence and particle-containing macrophages were actively moving towards the mucociliary escalator or towards lymphatic channels leading to peribronchial lymphoid aggregates and bronchial or mediastinal lymph nodes. In the lymph nodes, alveolar macrophages containing diesel particles were found mostly in the afferent subcapsular lymphatic vessels and marginal sinuses. In the later stages, cellular structure disintegrated and large aggregates of particulate matter were dispersed throughout the medullary cords with increasing accumulation towards the hilus. It is concluded that the lymphoid aggregates and lymphatic nodes play an important role in sequestering diesel particles or particle-containing phagocytizing cells and provide a pathway, in addition to the mocociliary clearance for particulate removal from the deep pulmonary region.     

Introduction to and experimental conditions during the first year of the GMR chronic inhalation studies of diesel exhaust

A chronic exposure study was initiated to determine the effects of diesel exhaust on the health of experimental animals. For this purpose, test atmospheres of clean air (control) or freshly diluted diesel exhaust at concentrations of 250, 750, and 1500 μg/m³ were supplied to four 12.6 m³ inhalation chambers which housed rats and guinea pigs. Diesel aerosol size and concentration, as well as chamber temperature and relative humidity, were continually monitored and controlled to maintain the exposure dose levels and an environment of 22±2°C and 50%±20% relative humidity. The concentrations of CO and NO_x were found to be 5.8±1.0 mg/m³ and 7.9±1.0 mg/m³ above ambient in the chamber containing 1500 μg/m³ of particulate. Animals were supplied from the chambers, on a random basis, for both intramural and extramural studies throughout the exposure period. The experiment ran uninterrupted for over twelve months with mean diesel particle mass concentrations within 2% of the target values.     

The environmental awareness of environmental protection bureaucrats in the People's Republic of China

Summary Over 180 environmental protection bureaucrats in the People's Republic of China were individually interviewed to determine their environmental awareness and their attitudes towards the environment. The study indicates that environmental protection bureaucrats in China have conflicting attitudes towards the relationship between man and nature, and between economic growth and environmental protection. However, they show a strong faith in science and technology's ability to solve environmental problems. The perception that too-harsh environmental protection regulations would reduce the growth potential of the economy is so predominant that it poses a serious threat to the environment of the three municipalities under investigation. It is argued that environmental management is a matter of managing human beings. To understand people, it is imperative to gain a thorough understanding of their worldview.Dr Koon-Kwai Wong is an Associate Professor in the Department of Geography and the Geography option co-ordinator on the China Studies course at Hong Kong Baptist University. Dr Hon S. Chan is an Associate Professor in the Department of Public and Social Administration at the City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong.     

Fetal methylmercury exposure as measured by cord blood mercury concentrations in a mother-infant cohort in Hong Kong

This study was designed to examine newborn infants in Hong Kong prenatally exposed to levels of methylmercury considered to increase risk of neurotoxic effects and to examine subject characteristics that modify the degree of prenatal mercury exposure. Mercury concentrations in 1057 sets of maternal and cord blood samples and 96 randomly selected maternal hair samples were measured. Subject characteristics were measured or collected by questionnaire. Of the 1057 cord blood samples collected only 21.6% had mercury concentrations less than 29 nmol/L (5.8 micro g/L). Median maternal hair mercury concentration was 1.7 ppm. The geometric mean cord to maternal blood mercury ratio was 1.79 to 1. Increasing maternal fish consumption and maternal age were found to be associated with increased cord blood mercury concentrations. Marine fish consumption increased cord blood mercury concentrations more than freshwater fish (5.09%/kg vs 2.86%/kg). Female babies, maternal alcohol consumption and increasing maternal height were associated with decreased cord blood mercury concentrations. Pregnant women in Hong Kong consume large amounts of fish and as a result, most of their offspring have been prenatally exposed to moderately high levels of mercury. In this population, pregnant women should choose freshwater over marine fish and limit fish consumption.     

Nutrient release and sediment oxygen demand in a eutrophic land-locked embayment in Hong Kong

Tolo Harbour is a large eutrophic land-locked estuarine embayment in Hong Kong. The rapid urbanization, commercio-industrial activities and lack of legislative control around the Tolo catchment produced large quantities of untreated or partially treated municipal sewage, agricultural wastes and cottage industrial effluents which were discharged into Tolo Harbour via rivers and watercourses. Control measures were implemented to reduce the external nutrient loading into the harbour since the early 1980s. Nutrient data for the period 1982 to 1997 were analyzed for temporal trends. Over the period of observation, the total inorganic nitrogen and total phosphorus both show an increasing trend, despite a decade of efforts in reducing nutrient loading. The release rates of potentially mobile nitrogen (N) and phosphorus (P) from the sediments collected from Tolo Harbour were determined by N and P release experiments under oxic conditions. The experimental results showed that the sediment released significant amount of nutrients, especially orthophosphates and ammonia nitrogen. The maximum release rates were 15.0 and 206.0 mg/m2/day, respectively. Although the external nutrient loading has been reduced, nutrients could gradually be released back into the water column from the contaminated sediments and delay improvement of the water quality.