Air pollution and hospital admissions for respiratory and cardiovascular diseases in Hong Kong

OBJECTIVE

To investigate short term effects of concentrations of pollutants in ambient air on hospital admissions for cardiovascular and respiratory diseases in Hong Kong.

METHODS

Retrospective ecological study. A Poisson regression was performed of concentrations of daily air pollutant on daily counts of emergency hospital admissions in 12 major hospitals. The effects of time trend, season, and other cyclical factors, temperature, and humidity were accounted for. Autocorrelation and overdispersion were corrected. Daily concentrations of nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), and particulate matter < 10 microns in aerodynamic diameter (PM10) were obtained from seven air monitoring stations in Hong Kong in 1994 and 1995. Relative risks (RR) of respiratory and cardiovascular disease admissions (for an increase of 10 micrograms/m3 in concentration of air pollutant) were calculated.

RESULTS

Significant associations were found between hospital admissions for all respiratory diseases, all cardiovascular diseases, chronic obstructive pulmonary diseases, and heart failure and the concentrations of all four pollutants. Admissions for asthma, pneumonia, and influenza were significantly associated with NO2, O3, and PM10. Relative risk (RR) for admissions for respiratory disease for the four pollutants ranged from 1.013 (for SO2) to 1.022 (for O3), and for admissions for cardiovascular disease, from 1.006 (for PM10) to 1.016 (for SO2). Those aged > or = 65 years were at higher risk. Significant positive interactions were detected between NO2, O3, and PM10, and between O3 and winter months.

CONCLUSIONS

Adverse health effects are evident at current ambient concentrations of air pollutants. Further reduction in air pollution is necessary to protect the health of the community, especially that of the high risk group.

Phloem long-distance trafficking of GIBBERELLIC ACID-INSENSITIVE RNA regulates leaf development

The phloem translocation stream contains a population of RNA molecules, suggesting plants use RNA to integrate developmental processes, at the whole-plant level. In the present study, we analyzed the role of long-distance trafficking in the delivery of transcripts from two members of the GRAS family, namely CmGAIP and GAI. These two homologs were chosen because of their involvement as transcriptional regulators in GA signaling. A combination of pumpkin, tomato and Arabidopsis was employed to examine the processes involved in long-distance delivery, to sink tissues, of RNA for engineered dominant gain-of-function pumpkin (Cmgaip) and Arabidopsis (DeltaDELLA-gai) genes. Our studies demonstrate that gai RNA entry into functional sieve elements occurs via a selective process. Both engineered mutant gai transcripts were able to exit the scion phloem and traffic cell to cell into the shoot apex. Delivery of Cmgaip and DeltaDELLA-gai RNA mediated highly reproducible changes in leaf phenotype in transgenic tomato lines grown under greenhouse conditions. Phenotypic analysis indicated that tomato leaflet morphology was influenced quite late in development. In addition, tissue sink strength did not appear to dictate gai RNA delivery, suggesting complexity in the process underlying macromolecular trafficking. These results establish that the molecular properties of the Cmgaip and DeltaDELLA-gai transcripts are compatible with the tomato cell-to-cell and long-distance macromolecular trafficking systems. An important conclusion, based on our work, is that control over GAI RNA delivery, via the phloem, may be regulated by sequence motifs conserved between plant families. We propose that RNA delivery via the phloem allows for flexibility in fine tuning of developmental programs to ensure newly developing leaves are optimized for performance under the prevailing environmental conditions.

Associations between daily mortalities from respiratory and cardiovascular diseases and air pollution in Hong Kong, China

OBJECTIVE

To investigate the association between ambient concentrations of air pollutants and respiratory and cardiovascular mortalities in Hong Kong.

METHODS

Retrospective ecological study. A Poisson regression of concentrations of daily air pollutants on daily mortalities for respiratory and cardiovascular diseases in Hong Kong from 1995 to the end of 1998 was performed using the air pollution and health: the European approach (APHEA) protocol. The effects of time trend, seasonal variations, temperature, and humidity were adjusted. Autocorrelation and overdispersion were corrected. Daily concentrations of nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), and particulate matter <10 microm in aerodynamic diameter (PM10) were averaged from eight monitoring stations in Hong Kong. Relative risks (RRs) of respiratory and cardiovascular mortalities (per 10 microg/m(3) increase in air pollutant concentration) were calculated.

RESULTS

Significant associations were found between mortalities for all respiratory diseases and ischaemic heart diseases (IHD) and the concentrations of all pollutants when analysed singly. The RRs for all respiratory mortalities (for a 10 microg/m(3) increase in the concentration of a pollutant) ranged from 1.008 (for PM10) to 1.015 (for SO2) and were higher for chronic obstructive pulmonary diseases (COPD) with all pollutants except SO2, ranging from 1.017 (for PM10) to 1.034 (for O3). RRs for IHD ranged from 1.009 (for O3) to 1.028 (for SO2). In a multipollutant model, O3 and SO2 were significantly associated with all respiratory mortalities, whereas NO2 was associated with mortality from IHD. No interactions were detected between any of the pollutants or with the winter season. A dose-response effect was evident for all air pollutants. Harvesting was not found in the short term.

CONCLUSIONS

Mortality risks were detected at current ambient concentrations of air pollutants. The associations with the particulates and some gaseous pollutants when analysed singly were consistent with many reported in temperate countries. PM10 was not associated with respiratory or cardiovascular mortalities in multipollutant analyses.

The Arabidopsis sex1 mutant is defective in the R1 protein, a general regulator of starch degradation in plants, and not in the chloroplast hexose transporter

Starch is the major storage carbohydrate in higher plants and of considerable importance for the human diet and for numerous technical applications. In addition, starch can be accumulated transiently in chloroplasts as a temporary deposit of carbohydrates during ongoing photosynthesis. This transitory starch has to be mobilized during the subsequent dark period. Mutants defective in starch mobilization are characterized by high starch contents in leaves after prolonged periods of darkness and therefore are termed starch excess (sex) mutants. Here we describe the molecular characterization of the Arabidopsis sex1 mutant that has been proposed to be defective in the export of glucose resulting from hydrolytic starch breakdown. The mutated gene in sex1 was cloned using a map-based cloning approach. By complementation of the mutant, immunological analysis, and analysis of starch phosphorylation, we show that sex1 is defective in the Arabidopsis homolog of the R1 protein and not in the hexose transporter. We propose that the SEX1 protein (R1) functions as an overall regulator of starch mobilization by controlling the phosphate content of starch.

α-Amylase Is Not Required for Breakdown of Transitory Starch in Arabidopsis Leaves

The Arabidopsis thaliana genome encodes three alpha-amylase-like proteins (AtAMY1, AtAMY2, and AtAMY3). Only AtAMY3 has a predicted N-terminal transit peptide for plastidial localization. AtAMY3 is an unusually large alpha-amylase (93.5 kDa) with the C-terminal half showing similarity to other known alpha-amylases. When expressed in Escherichia coli, both the whole AtAMY3 protein and the C-terminal half alone show alpha-amylase activity. We show that AtAMY3 is localized in chloroplasts. The starch-excess mutant of Arabidopsis sex4, previously shown to have reduced plastidial alpha-amylase activity, is deficient in AtAMY3 protein. Unexpectedly, T-DNA knock-out mutants of AtAMY3 have the same diurnal pattern of transitory starch metabolism as the wild type. These results show that AtAMY3 is not required for transitory starch breakdown and that the starch-excess phenotype of the sex4 mutant is not caused simply by deficiency of AtAMY3 protein. Knock-out mutants in the predicted non-plastidial alpha-amylases AtAMY1 and AtAMY2 were also isolated, and these displayed normal starch breakdown in the dark as expected for extraplastidial amylases. Furthermore, all three AtAMY double knock-out mutant combinations and the triple knock-out degraded their leaf starch normally. We conclude that alpha-amylase is not necessary for transitory starch breakdown in Arabidopsis leaves.

Mutation of Arabidopsis plastid phosphoglucose isomerase affects leaf starch synthesis and floral initiation

We isolated pgi1-1, an Arabidopsis mutant with a decreased plastid phospho-glucose (Glc) isomerase activity. While pgi1-1 mutant has a deficiency in leaf starch synthesis, it accumulates starch in root cap cells. It has been shown that a plastid transporter for hexose phosphate transports cytosolic Glc-6-P into plastids and expresses restricted mainly to the heterotrophic tissues. The decreased starch content in leaves of the pgi1-1 mutant indicates that cytosolic Glc-6-P cannot be efficiently transported into chloroplasts to complement the mutant's deficiency in chloroplastic phospho-Glc isomerase activity for starch synthesis. We cloned the Arabidopsis PGI1 gene and showed that it encodes the plastid phospho-Glc isomerase. The pgi1-1 allele was found to have a single nucleotide substitution, causing a Ser to Phe transition. While the flowering times of the Arabidopsis starch-deficient mutants pgi1, pgm1, and adg1 were similar to that of the wild type under long-day conditions, it was significantly delayed under short-day conditions. The pleiotropic phenotype of late flowering conferred by these starch metabolic mutations suggests that carbohydrate metabolism plays an important role in floral initiation.

Arabidopsis thaliana CENTRORADIALIS homologue (ATC) acts systemically to inhibit floral initiation in Arabidopsis

Floral initiation is orchestrated by systemic floral activators and inhibitors. This remote-control system may integrate environmental cues to modulate floral initiation. Recently, FLOWERING LOCUS T (FT) was found to be a florigen. However, the identity of systemic floral inhibitor or anti-florigen remains to be elucidated. Here we show that Arabidopsis thaliana CENTRORADIALIS homologue (ATC), an Arabidopsis FT homologue, may act in a non-cell autonomous manner to inhibit floral initiation. Analysis of the ATC null mutant revealed that ATC is a short-day-induced floral inhibitor. Cell type-specific expression showed that companion cells and apex that express ATC are sufficient to inhibit floral initiation. Histochemical analysis showed that the promoter activity of ATC was mainly found in vasculature but under the detection limit in apex, a finding that suggests that ATC may move from the vasculature to the apex to influence flowering. Consistent with this notion, Arabidopsis seedling grafting experiments demonstrated that ATC moved over a long distance and that floral inhibition by ATC is graft transmissible. ATC probably antagonizes FT activity, because both ATC and FT interact with FD and affect the same downstream meristem identity genes APETALA1, in an opposite manner. Thus, photoperiodic variations may trigger functionally opposite FT homologues to systemically influence floral initiation.

Carbohydrate starvation stimulates differential expression of rice alpha-amylase genes that is modulated through complicated transcriptional and posttranscriptional processes

Expression of alpha-amylase genes in cultured rice suspension cells is induced by sucrose starvation. To study the mechanism of sugar metabolite regulation on the expression of individual alpha-amylase genes, DNA fragments specific to each of eight rice alpha-amylase genes were synthesized and used as gene-specific probes. Comparison of the relative abundance of mRNA revealed that expression of the eight alpha-amylase genes in rice cells was differentially regulated by sucrose starvation. Accumulation of all the alpha-amylase mRNAs increased in response to sucrose starvation; however, levels of the alphaAmy3 and alphaAmy8 mRNAs were distinctly higher and constituted 90% of total alpha-amylase mRNAs. RNA gel blot and nuclear run-on transcription analyses demonstrated a positive correlation between the increased transcription rates and the elevated steady-state levels of alpha-amylase mRNAs induced by sucrose starvation. The half-lives of alphaAmy3, alphaAmy7, and alphaAmy8 were prolonged by sucrose-starvation; however, the stability of the three mRNAs seems controlled by different mechanisms. The translation inhibitors cycloheximide and anisomycin preferentially blocked the sucrose-suppressed expression of alphaAmy3 but not that of alphaAmy7 and alphaAmy8. These inhibitors also enhanced the sucrose starvation-induced accumulation of alphaAmy3 mRNA but not that of alphaAmy7 or alphaAmy8 mRNAs. Cycloheximide did not significantly alter the transcription rates of alpha-amylase genes, suggesting that labile proteins may selectively stabilize the alphaAmy7 and alphaAmy8 mRNAs but destabilize the alphaAmy3 mRNA.

Prevalence of migraine and other headaches in Hong Kong

From July 1992 to March 1993, we conducted a community-based prevalence survey of migraine and other types of recurrent headache by a telephone interview of 2,240 households with 7,356 persons aged 15 and above. 311 patients with recurrent headache were successfully interviewed. Of these, 101 were clinically validated. The overall prevalence rates were 1% for migraine, 2% for tension-type headache and 1% for unclassified headache. Adjusted for misclassification and non-response, the estimated prevalence rates for the three categories were 1.5, 3 and 0.4%, respectively. Agreement between clinical method and questionnaire interview was good for migraine, fair for tension-type headache and poor for unclassified headache. For all three types of recurrent headache, there was a female preponderance with a peak in the 25-44 age group. The prevalence of migraine was much lower than in Western communities but higher than that found in mainland China [1-8]. Common predisposing and aggravating factors for all three types of headaches as reported by the patients were mental stress, physical exertion and menstruation among females. Despite the low prevalence, the overall socioeconomic impact to a populous community is considerable.

Long-distance movement of Arabidopsis FLOWERING LOCUS T RNA participates in systemic floral regulation

The finding of mRNA acting as a systemic information molecule is one of the most exciting discoveries in recent plant biology. However, evidence demonstrating the functional significance of non-cell autonomous RNA remains limited. Recent analyses of Arabidopsis and rice revealed FLOWERING LOCUS T (FT) protein as a systemic florigenic signal. However, whether the FT RNA also participates in systemic floral regulation remains controversial. By using Arabidopsis cleft-grafting experiments, we showed that the RNA of Arabidopsis FT undergoes long-distance movement from the stock to the scion apex in both FT transformants and non-transformants. In addition, the sequences of FT RNA are sufficient to target a cell-autonomous RNA for long-distance movement. Therefore, FT RNA is a bona fide non-cell autonomous RNA. To examine the systemic action of FT RNA, we uncoupled the movement of FT RNA from protein by fusing FT with RED FLUORESCENT PROTEIN (RFP). When RFP-FT protein was retained in companion cells, the detection of RFP-FT RNA correlates with floral promotion in the scion. Further depletion of the translocated RFP-FT RNA by RNAi or artificial miRNA against FT delayed the floral promotion, indicating that the translocated FT RNA acts as a part of the systemic floral signaling. Our results indicate that both FT RNA and protein move long distance and act redundantly to integrate the photoperiodic signals.

The Arabidopsis sex1 mutant is defective in the R1 protein, a general regulator of starch degradation in plants, and not in the chloroplast hexose transporter

Starch is the major storage carbohydrate in higher plants and of considerable importance for the human diet and for numerous technical applications. In addition, starch can be accumulated transiently in chloroplasts as a temporary deposit of carbohydrates during ongoing photosynthesis. This transitory starch has to be mobilized during the subsequent dark period. Mutants defective in starch mobilization are characterized by high starch contents in leaves after prolonged periods of darkness and therefore are termed starch excess (sex) mutants. Here we describe the molecular characterization of the Arabidopsis sex1 mutant that has been proposed to be defective in the export of glucose resulting from hydrolytic starch breakdown. The mutated gene in sex1 was cloned using a map-based cloning approach. By complementation of the mutant, immunological analysis, and analysis of starch phosphorylation, we show that sex1 is defective in the Arabidopsis homolog of the R1 protein and not in the hexose transporter. We propose that the SEX1 protein (R1) functions as an overall regulator of starch mobilization by controlling the phosphate content of starch.

The sequences of Arabidopsis GA-INSENSITIVE RNA constitute the motifs that are necessary and sufficient for RNA long-distance trafficking

In higher plants a number of physiological processes are regulated by systemic RNA signaling molecules. This phloem-mediated remote-control system provides specific and efficient regulation to fine-tune many plant developmental programs. However, the molecular mechanism underlying long-distance movement of RNA remains to be elucidated. To this end, we examined the long-distance movement of GA-insensitive (GAI) RNA by Arabidopsis inflorescence grafting and RT-PCR analysis. Our results demonstrated that long-distance movement of RNA only occurred in specific transcripts. In addition, the sequences of GAI RNA are necessary and sufficient to target GREEN FLUORESCENT PROTEIN (GFP) RNA for long-distance movement, which indicates that the trafficking of GAI RNA is mediated by specific RNA motifs. Further analyses revealed that the motifs at coding sequences and 3' untranslated regions of GAI RNA play important roles during RNA movement. In addition, the structure of the RNA rather than its specific sequence may also be important in GAI RNA trafficking. However, the secondary structure of GAI RNA is not the only factor to target RNA for long-distance movement, because recovery of the secondary structure of movement-defective GAI RNA only partially rescued RNA movement. Taken together, our results show that long-distance movement of non-cell autonomous RNA operates by specific RNA mobile elements.

Selective Targeting of Mobile mRNAs to Plasmodesmata for Cell-to-Cell Movement

Many plant mRNAs move from cell to cell or long distance to execute non-cell-autonomous functions. These mobile mRNAs traffic through the phloem to regulate many developmental processes, but despite the burgeoning discovery of mobile mRNAs, little is known about the mechanism underlying the intracellular sorting of these mRNAs. Here, we exploited a fluorescence-based mRNA labeling system, using the bacteriophage coat protein MS2, fused to GFP (MS2-GFP) and an MS2 recognition site in the RNA of interest, to visualize the intracellular trafficking of mobile mRNAs in living plant cells of Nicotiana benthamiana We first improved this system by using the nuclear localization sequence from FD, which substantially reduced the fluorescent background of MS2-GFP in the cytoplasm. The modified system allowed us to observe the cytoplasmic fluorescent foci dependent on MS2-binding sites. Coexpressing the MS2-GFP system with a virus movement protein, which is a plasmodesmata (PD)-localized nonspecific RNA-binding protein, targeted cytoplasmic fluorescent foci to the PD, suggesting that the cytoplasmic fluorescent foci contain mRNA and MS2-GFP. Our ex vivo RNA imaging revealed that mobile but not nonmobile mRNAs were selectively targeted to PD. Real-time images of intracellular translocation revealed that the translocation of mRNA and organelles in the transvacuolar strands may be governed by the same mechanism. Our study suggests that PD targeting of mRNA is a selective step in determining mRNA cell-to-cell movement of mRNAs.

Rice alpha-amylase transcriptional enhancers direct multiple mode regulation of promoters in transgenic rice

Expression of alpha-amylase genes in cereals is induced by both gibberellin (GA) and sugar starvation. In a transient expression assay, a 105-bp sugar response sequence (SRS) in the promoter of a sugar starvation highly inducible rice alpha-amylase gene, alphaAmy3, was shown previously to confer sugar response and to enhance the activity of the rice Act1 promoter in rice protoplasts. A 230-bp SRS-like sequence was also found in the promoter of another sugar starvation highly inducible rice alpha-amylase gene, alphaAmy8. The alphaAmy8 SRS contains a GA response sequence and was designated as alphaAmy8 SRS/GARS. In the present study, a transgenic approach was employed to characterize the function of the alpha-amylase gene SRSs in rice. We found that the alphaAmy3 SRS significantly enhances the endogenous expression pattern of the Act1 promoter in various rice tissues throughout their developmental stages. By contrast, the alphaAmy8 SRS/GARS significantly enhances Act1 promoter activity only in embryos and endosperms of germinating rice seeds. A minimal promoter fused to the alphaAmy8 SRS/GARS is specifically active in rice embryo and endosperm and is subject to sugar repression and GA induction in rice embryos. This sugar repression was found to override GA induction of alphaAmy8 SRS/GARS activity. Our study demonstrates that the alpha-amylase transcriptional enhancers contain cis-acting elements capable of enhancing endogenous expression patterns or activating sugar-sensitive, hormone-responsive, tissue-specific, and developmental stage-dependent expression of promoters in transgenic rice. These enhancers may facilitate the design of highly active and tightly regulated composite promoters for monocot transformation and gene expression. Our study also reveals the existence of cross-talk between the sugar and GA signaling pathways in cereals and provides a system for analyzing the underlying molecular mechanisms involved.

Cloning, sequencing, and tissue expression of CYP3A27, a new member of the CYP3A subfamily from embryonic and adult rainbow trout livers

Screening of lambdagt11 and lambdagt22A cDNA libraries of livers from adult females and embryos of rainbow trout (Oncorhynchus mykiss), respectively, using rabbit anti-rainbow trout cytochrome P450 LMC5 polyclonal antibodies showed that there were identical cDNAs of 1802-bp nucleotides with open reading frames coding for proteins containing 518 amino acids (59,206 Da, pI = 6.39). The cDNA was assigned CYP3A27 by the P450 Nomenclature Committee to represent the first CYP3A subfamily member reported for aquatic species. The deduced N-terminal sequence of CYP3A27 was in agreement with 8 of the first 12 confirmed amino acid residues from Edman degradation of LMC5, a P450 previously isolated from juvenile trout liver. In similarity comparisons between species by positional alignment, the deduced amino acid sequence of rainbow trout CYP3A27 was 56.4% identical with dog CYP3A12, 56.0% with monkey CYP3A8, 54.9% with human CYP3A4, 54.7% with rat CYP3A9, and 54.2% with sheep CYP3A24. Marked differences in sex, age, and tissue expression of CYP3A27 in rainbow trout were observed at the mRNA level as shown by Northern blots. The major extrahepatic expression site for CYP3A27 was upper small intestine. Females expressed considerably more CYP3A27 mRNA than male in the fish examined. Southern blot analysis of restriction enzyme-digested rainbow trout genomic DNA demonstrated that multiple CYP3A27-related genes exist in rainbow trout.

Characterization of ADG1, an Arabidopsis locus encoding for ADPG pyrophosphorylase small subunit, demonstrates that the presence of the small subunit is required for large subunit stability

Two mutants of Arabidopsis have been isolated that affect ADPG pyrophosphorylase (ADGase) activity. Previously, it has been shown that ADG2 encodes the large subunit of ADGase. This study characterizes the adg1 mutant phenotype and ADG1 gene structure. RNA blot analyses indicate that the adg1-1 mutant accumulates transcripts encoding both the large and small subunits of ADGase, while the adg1-2 mutant accumulates only large subunit transcripts. RFLP analysis and complementation of adg1 mutants with the ADGase small subunit gene demonstrate that ADG1 encodes the small subunit. Sequence analysis indicates that adg1-1 represents a missense mutation within the gene. Western blot analysis confirms that adg1 mutants contain neither the large nor the small subunit proteins, suggesting that the presence of functional small subunits is required for large subunit stability.

Mobility of Antiflorigen and PEBP mRNAs in Tomato-Tobacco Heterografts

Photoperiodic floral induction is controlled by the leaf-derived and antagonistic mobile signals florigen and antiflorigen. In response to photoperiodic variations, florigen and antiflorigen are produced in leaves and translocated through phloem to the apex, where they counteract floral initiation. Florigen and antiflorigen are encoded by a pair of homologs belonging to FLOWERING LOCUS T (FT)- or TERMINAL FLOWER1 (TFL1)-like clades in the phosphatidylethanolamine-binding domain protein (PEBP) family. The PEBP gene family contains FT-, TFL1-, and MOTHER OF FT AND TFL1 (MFT)-like clades. Evolutionary analysis suggests that FT- and TFL1-like clades arose from an ancient MFT-like clade. The protein movement of the PEBP family is an evolutionarily conserved mechanism in many plants; however, the mRNA movement of the PEBP family remains controversial. Here, we examined the mRNA movement of PEBP genes in different plant species. We identified a tobacco (Nicotiana sylvestris) CENTRORADIALIS-like1 gene, denoted NsCET1, and showed that NsCET1 is an ortholog of the Arabidopsis (Arabidopsis thaliana) antiflorigen ATC In tobacco, NsCET1 acts as a mobile molecule that non-cell-autonomously inhibits flowering. Grafting experiments showed that endogenous and ectopically expressed NsCET1 mRNAs move long distances in tobacco and Arabidopsis. Heterografts of tobacco and tomato (Solanum lycopersicum) showed that, in addition to NsCET1, multiple members of the FT-, TFL1-, and MFT-like clades of tobacco and tomato PEBP gene families are mobile mRNAs. Our results suggest that the mRNA mobility is a common feature of the three clades of PEBP-like genes among different plant species.

Chloroplast protein translocon components atToc159 and atToc33 are not essential for chloroplast biogenesis in guard cells and root cells

Protein import into chloroplasts is mediated by a protein import apparatus located in the chloroplast envelope. Previous results indicate that there may be multiple import complexes in Arabidopsis. To gain further insight into the nature of this multiplicity, we analyzed the Arabidopsis ppi1 and ppi2 mutants, which are null mutants of the atToc33 and atToc159 translocon proteins, respectively. In the ppi2 mutant, in contrast to the extremely defective plastids in mesophyll cells, chloroplasts in guard cells still contained starch granules and thylakoid membranes. The morphology of root plastids in both mutants was similar to that in wild type. After prolonged light treatments, root plastids of both mutants and the wild type differentiated into chloroplasts. Enzymatic assays indicated that the activity of a plastid enzyme was reduced only in leaves but not in roots. These results indicated that both the ppi1 and ppi2 mutants had functional root and guard cell plastids. Therefore, we propose that import complexes are cell type specific rather than substrate or plastid specific.

Household gas cooking: a risk factor for respiratory illnesses in preschool children

AIMS

To explore the association of household gas cooking and respiratory illnesses in preschool children and their relation to outdoor air pollution.

METHODS

Cross-sectional study among households that used gas stoves for cooking in two housing estates with contrasting air qualities in Hong Kong. A structured questionnaire was administered to parents of 426 children aged 0-6 years on their exposure to gas cooking and passive smoking, and the prevalence of respiratory illnesses.

RESULTS

A total of 111 children (26.1%) were reported to have one or more respiratory illnesses (allergic rhinitis, asthma, bronchitis, sinusitis, and pneumonia). Of these, 21 (18.9%), 41 (36.9%), and 49 (44.1%) children were from households that cooked once, twice, and three times a day with gas. Hierarchical logistic regression models adjusting for socioeconomic, demographic, and indoor risk factors including passive smoking showed that household gas cooking was positively associated with respiratory illnesses. There was a dose-response relation between the frequency of gas cooking and the prevalence of respiratory illnesses in the estate with lower outdoor air pollution (OR = 6.1 and 3.2 respectively, for cooking three and two meals a day, compared to one meal a day). This relation was not observed in the more polluted estate. The association between the presence of a cigarette smoker in the household and the prevalence of respiratory illnesses was not significant.

CONCLUSIONS

As gas cooking is common in urban households, the findings could have important public health implications.

adg2-1 represents a missense mutation in the ADPG pyrophosphorylase large subunit gene of Arabidopsis thaliana

Arabidopsis mutants affecting ADPG pyrophosphorylase (ADGase) activity can be divided into two complementation groups, adg1 and adg2. Previous biochemical studies of adg2-1 mutant indicated that mutant plants do not accumulate ADGase large subunit protein and that ADGase small subunits assemble as homotetramers. This suggested that the ADG2 gene may encode the large subunit of ADGase. In this paper, it is shown that adg2-1 mutant plants accumulate near wild-type levels of transcripts encoding both the large and small subunits of ADGase. However, by RFLP analysis and complementation of adg2-1 with the ADGase large subunit gene, we show that the adg2-1 mutant does represent a mutation of the ADGase large subunit gene. Sequence analysis of the adg2-1 allele revealed a missense mutation. The results therefore suggest either that the missense mutation affects the stability of the ADGase large subunit protein or that it prevents assembly of the large subunit into holoenzyme.

Changes in the gene expression of GABA(A) receptor alpha1 and alpha2 subunits and metabotropic glutamate receptor 5 in the basal ganglia of the rats with unilateral 6-hydroxydopamine lesion and embryonic mesencephalic grafts

By using an animal model of parkinsonism, we examined the expression of GABA(A) receptor (R) and metabotropic glutamate receptor (mGluR) 5 in the basal ganglia after transplantation with dopamine-rich tissue. The adult rats were unilaterally lesioned by the injection of 6-hydroxydopamine to their left medial forebrain bundles. At 5-10 weeks following the dopaminergic denervation, the levels of GABA(A)R in the left caudate-putamen and globus pallidus were about 20 and 16% lower than that of the right intact (control) sides, as shown by [3H]flunitrazepam binding autoradiography on the brain sections. However, the receptor density increased to around 132 and 130% of control levels in the entopeduncular nucleus and substantia nigra pars reticulata of the lesioned sides. Furthermore, in situ hybridization analysis exhibited parallel trends of changes in the levels of the GABA(A)R alpha1 and alpha2 subunit and mGluR5 mRNAs in the neurons of the brain regions with that of the proteins detected by the binding assay. A number of the rats 5 weeks postlesion were transplanted with the ventral mesencephalon of the embryonic rat into their left striata. Five weeks later, the changes in the [3H]flunitrazepam binding seemed to be recovered by approximately 50-63% on the grafted sides of the areas. Moreover, the transplantation appeared to produce a nearly complete reversal of the lesion-induced alterations in the levels of the mRNAs. Thus, the data indicate the mechanism of gene regulation for the modified expression of the receptors and could implicate the participation of the receptors in the pathogenesis of Parkinson's disease.

Predicted maximal oxygen uptake in normal Hong Kong Chinese schoolchildren and those with respiratory diseases

To assess the maximum oxygen uptake (V'O2 max) of Hong Kong Chinese children and to explore its association with respiratory illnesses, we conducted the Multistage Fitness Test (MFT), a 20-m shuttle run test, in 1,427 schoolchildren aged between 8-12 years. Information on respiratory symptoms in the previous year, cumulative respiratory illnesses, and habitual physical activities were collected. Spirometry was carried out to derive forced expiratory volume in 1 sec (FEV1). The V'O2max was 30.3 mL x kg( - 1) x min( - 1) for boys, and 28.6-mL x kg( - 1) x min( - 1) for girls; these values were low by Western standards. V'O2max was significantly reduced in children with asthma ( - 1.3 mL x kg( - 1) x min( - 1)) and bronchitis ( - 0.7.mL x kg( - 1) x min( - 1)) when adjusted for other covariates. A significant decrease in FEV1 was also observed in these children. The correlation between V'O2max and FEV1 was significant but weak. Habitual physical activity was an independent predictor of V'O2max, but not of FEV1. The low V'O2 max in Hong Kong children may be explained in part by ethnic differences and possibly a low level of physical activity.

Factors associated with the utilization of traditional Chinese medicine in a small town in Hong Kong

The practice of Traditional Chinese Medicine (TCM) is largely unregulated in Hong Kong. Yet, as previous studies have shown, a sizable segment of the population consults TCM practitioners for health problems. This paper uses health care utilization data from a telephone health survey of 847 adult subjects in Tai Po District who had suffered from acute illness in the past month, to examine the profile of TCM users in the District. Women, older residents, unemployed workers, low skill laborers, current smokers and subjects dissatisfied with the quality of private sector clinics were significantly more likely to consult TCM practitioners.

Adverse effects of low-level air pollution on the respiratory health of schoolchildren in Hong Kong

To evaluate the respiratory effects of long-term exposure to air pollution, schoolchildren (ages 8 to 12 years) from two districts in Hong Kong with contrasting air quality were studied. Parents of 1660 children completed questionnaires on respiratory symptoms, and 1294 children had their ventilatory function tested with a spirometer. After adjustment for relevant covariates, children living in the more polluted district had increased odds ratios for frequent cough (1.74), frequent sputum (1.87), chronic sputum (1.84), and doctor-diagnosed asthma (1.98). Children of both sexes in the more polluted district had significantly poorer lung function, and the differences among girls were more marked. The study provides additional evidence for the adverse effects of long-term exposure to relatively low-level air pollution.

Lung cancer mortality among a cohort of men in a silicotic register

To examine any association between silicosis and lung cancer, the clinic records of a cohort of 1502 silicotic workers diagnosed after 1981 were reviewed. All of the essential data, including occupational exposure, smoking habits, radiographic extent of silicosis, and vital status of each subject, were noted. The standardized mortality ratio for various causes of death was calculated. Thirty-three patients died from lung cancer, giving a standardized mortality ratio of 1.94 (95% confidence interval, 1.35 to 2.70). However, smoking accounted for most of the excess of lung cancer deaths among the silicotic workers in the cohort, and no consistent relationship between lung cancer mortality risk and either duration of exposure to silica dust or severity of silicosis was observed. There is no conclusive evidence in our data to support the hypothesis that lung cancer may be associated with silicosis.