Ca2+ -Calmodulin Regulates Nuclear Translocation of the Rice Seed-specific MADS-box Transcription Factor OsMADS29

OsMADS29 (M29) is a crucial regulator of seed development in rice. The expression of M29 is strictly regulated at transcriptional as well as post-transcriptional levels. The MADS-box proteins are known to bind to DNA as dimers. However, in the case of M29, the dimerization also plays a vital role in its localization into the nucleus. The factor(s) that affect oligomerization and nuclear transport of MADS proteins have not yet been characterized. By using BiFC in transgenic BY-2 cell lines and Yeast-2-hybrid assay (Y2H), we show that calmodulin (CaM) interacts with M29 in a Ca²⁺ dependent manner. This interaction specifically takes place in the cytoplasm, probably in association with the endoplasmic reticulum. By generating domain-specific deletions, we show that both sites in M29 are involved in this interaction. Further, by using BiFC-FRET-FLIM, we demonstrate that CaM may also help in the dimerization of two M29 monomers. Since most MADS proteins have CaM binding domains, the interaction between these proteins could be a general regulatory mechanism for oligomerization and nuclear transport.

Maladaptive autophagy in the pathogenesis of autoimmune epithelitis in Sjӧgren's Syndrome

OBJECTIVE

Salivary gland epithelial cells (SGECs) are key cellular drivers in the pathogenesis of primary Sjӧgren's Syndrome (pSS); however, the mechanisms sustaining SGECs activation in pSS remain undetermined. The aim of this study is to determine the role of autophagy in the survival and activation of SGECs in pSS.

METHODS

Primary SGECs isolated from minor salivary glands (SG) of patients with pSS or sicca syndrome were evaluated by flow-cytometry, immunoblotting, and immunofluorescence to assess autophagy (autophagic-flux, LC3IIB, p62, LC3B+/LAMP1+ staining), apoptosis (annexin V/PI, Caspase-3) and activation (ICAM, VCAM). Focus score and germinal centers presence was assessed in SG from the same patients to correlate with histological severity. Human salivary gland (HSG) cells were stimulated in vitro with PBMCs and serum from pSS patients in the presence or absence of autophagy inhibitors to determine changes in autophagy and epithelial cell activation.

RESULTS

SGECs from pSS patients (n=24) exhibited increased autophagy (autophagic-flux p=0.001; LC3IIB p=0.02; p62 p=0.064; LC3IIB/LAMP1+ staining), increased expression of anti-apoptotic molecules (Bcl2 p=0.006), and reduced apoptosis (Annexin-V/PI p=0.002, Caspase-3 p=0.057) compared to sicca (n=16). Autophagy correlated with histologic disease severity. In vitro experiments on HSG cells stimulated with serum and PBMCs from pSS patients confirmed activation of autophagy and expression of adhesion molecules, which was reverted upon pharmacologic inhibition of autophagy.

CONCLUSIONS

In pSS SGECs, inflammation induces autophagy and pro-survival mechanisms, which promote SGEC activation and mirror histological severity. These findings indicate that autophagy is a central contributor to the pathogenesis of pSS and a new therapeutic target.

CsubMADS1, a lag phase transcription factor, controls development of polar eukaryotic microalga Coccomyxa subellipsoidea C-169

MADS-box transcription factors (TFs) have not been functionally delineated in microalgae. In this study, the role of CsubMADS1 from microalga Coccomyxa subellipsoidea C-169 has been explored. Unlike Type II MADS-box proteins of seed plants with MADS, Intervening, K-box, and C domains, CsubMADS1 only has MADS and Intervening domains. It forms a group with MADS TFs from algae in the phylogenetic tree within the Type II MIKC^C clade. CsubMADS1 is expressed strongly in the lag phase of growth. The CsubMADS1 monomer does not have a specific localization in the nucleus, and it forms homodimers to localize exclusively in the nucleus. The monomer has two nuclear localization signals (NLSs): an N-terminal NLS and an internal NLS. The internal NLS is functional, and the homodimer requires two NLSs for specific nuclear localization. Overexpression (OX) of CsubMADS1 slows down the growth of the culture and leads to the creation of giant polyploid multinucleate cells, resembling autospore mother cells. This implies that the release of autospores from autospore mother cells may be delayed. Thus, in wild-type (WT) cells, CsubMADS1 may play a crucial role in slowing down growth during the lag phase. Due to starvation in 2-month-old colonies on solid media, the WT colonies produce mucilage, whereas OX colonies produce significantly less mucilage. Thus, CsubMADS1 also negatively regulates stress-induced mucilage production and probably plays a role in stress tolerance during the lag phase. Taken together, our results reveal that CsubMADS1 is a key TF involved in the development and stress tolerance of this polar microalga.

927 Efficacy of Surgical Helmet Systems for Protection Against COVID-19: A Double-Blinded Randomised Control Study

Introduction

This study assesses whether sterile surgical helmet systems (SSHS) provide additional protection from aerosol pathogens alongside protecting against splash. There has been debate on whether to use such systems in orthopaedic surgery during the COVID-19 pandemic.

Method

Thirty-five participants were enrolled in a double-blinded randomised controlled study investigating efficacy of the Stryker Flyte Surgical Helmet (Stryker Corporation, Kalamazoo, MI, USA) as protection against respiratory droplets. Wearing the SSHS in a fit testing hood, subjects were randomised to nebulised saccharin solution or placebo. Twenty were allocated to the saccharin group with 15 to placebo. Positive sweet taste represented test failure. Taste tests were performed with the helmet fan turned on and off.

Results

SSHS did not prevent saccharin taste (p < 0.0001). Within the saccharin cohort, 40% recorded a positive taste with the fan on and 100% with the fan off. There was a statistically significant difference in mean time-to-taste saccharin (p = 0.049) comparing fan on (123.5 s) vs. off (62.6 s).

Conclusions

SSHS do not protect against aerosol particulate and therefore are not efficacious in protection against COVID-19. The fan system employed may even increase risk by drawing in particulates and delaying recognition of intraoperative cues that point to respirator mask leak.

Exploring the Role of a Cytokinin-Activating Enzyme LONELY GUY in Unicellular Microalga Chlorella variabilis

LONELY GUY has been previously characterized in flowering plants to be involved in the direct activation of cytokinins. In this study, the function of the only LONELY GUY gene (CvarLOG1) from unicellular green microalga Chlorella variabilis NC64A has been investigated. CvarLOG1 expressed mainly in the lag and log phases of growth and was confirmed to be a cytokinin-activating enzyme. Overexpression of CvarLOG1 in Chlorella led to extended life in culture by almost 10-20 days, creating a "stay-green" phenotype. In the transformed alga, the cell cycle was lengthened due to delayed entry into the G2/M phase contrary to the known role of cytokinins in stimulating G2/M transition possibly due to excessive levels of this hormone. However, due to the sustained growth and delayed senescence, there was an increase in cell number by 11% and in biomass by 46% at the stationary phase, indicating a potential application for the biofuel industry. The total carbohydrate and lipid yield increased by approximately 30 and 20%, respectively. RNA-Seq-based transcriptomic analysis revealed that the genes associated with light and dark reactions of photosynthesis were upregulated, which may be the reason for the increased biomass. These data show that LOG plays an essential role during the cell cycle and in the functioning of the chloroplast and that the pathway leading to direct activation of cytokinins via LOG is functional in algae.

THU0220 AUTOPHAGY IN SJOGREN’S SYNDROME SALIVARY GLAND EPITHELIAL CELLS (SGECS) IS ASSOCIATED WITH THE SEVERITY OF INFLAMMATION AND EPITHELIAL CELLS ACTIVATION

Background:

Sjögren’s Syndrome (SS) is characterized by chronic inflammation supported by intrinsic activation of salivary gland epithelial cells (SGECs). Eventually, apoptosis of SGECs ensues, which leads to salivary gland dysfunction and exposition of autoantigens. Autophagy is a stress coping mechanisms of cells implicated in both survival and exposition of autoantigens, and is thereby plausibly implicated in the pathogenesis of SS. At present, the exact relationship between apoptosis and autophagy in SS SGECs is unclear, as is the link between these mechanisms and SGECs activation.

Objectives:

To explore autophagy in SGECs from patients with SS and to evaluate its relationship with apoptosis and SGECs activation.

Methods:

Consecutive patients with suspected SS referring to our “Sjogren Clinic” were enrolled, and minor salivary gland (MSG) biopsies were collected for: (1) SGECs culture, (2) PCR analysis, (3) IFI analysis. In SGECs cultures, the expression of autophagy (LC3II), apoptosis (annexin V/PI) and adhesion molecules (ICAM) was investigated by flow cytometry (results expressed as mean % ± SD). The expression of the autophagy gene MAP1LC3II was evaluated by PCR (expressed as 2^deltaCT normalized to GADPH) on both MSG sections and MSG acinar and ductal epithelium samples obtained by laser capture microdissection. Tissue expression of LC3II was evaluated by IFI on SS MSG.

Results:

Primary SGECs cultures were established from 14 MSG obtained for diagnostic purposes (SS n=8, Sicca n=6). These cells exhibited an inverse correlation between apoptosis and autophagy (p=0.007, r=-0.784), with lower levels of apoptosis (19.7±6.5 vs 24.5±8.5, p=ns) and higher levels of autophagy (59.7±13.1 vs 54.19±19.4, p=ns) in SS compared to Sicca. In SS, MAP1LC3 was positively correlated with Focus Score (p=0.021 r=0.478); however, PCR studies did not reveal significant differences in MAP1LC3 expression between SS (n=26) and Sicca (n=15) (0.024±0.010 vs 0.022±0.008, p=ns). Ductal SGECs (n=4) isolated by laser microdissection of MSG revealed a higher expression of MAP1LC3 (0.005±0.0005 vs 0.003±0.0008; p=0.057) compared to normal acinar epithelium (n=5); a major expression of LC3II in ducts was confirmed by IFI (Image).

In SS, a higher expression of ICAM compared to sicca was observed (11.1±3.8 vs 6.9±6.9, p=0.006) and autophagy and apoptosis showed a trend of positive and negative correlation with this molecule, respectively (p=0.683 r=0.118 and p=0.106 r=-0.446).

Figure.

LC3-II staining in SS MSG [LC3-II+ (green) and Hoechst stain (blue); 60x magnification].

Conclusion:

In SS, autophagy is upregulated in SGECs and inversely correlated with apoptosis, thus supporting a role of this process in cells’ death prevention during inflammatory process. Indeed, the degree of msg inflammation is correlated more with the activation of autophagy than apoptosis. Interesting, in SS, SGECs autophagy is mainly observed at ductal level and is correlated with higher expression of adhesion molecules suggesting a link between this pathway and changes in SGECs immune phenotype.

Disclosure of Interests: :

Serena Colafrancesco: None declared, cristiana barbati: None declared, Valentina Iannizzotto: None declared, Linda Mastromanno: None declared, Saba Nayar: None declared, Elena Pipi: None declared, angelica gattamelata: None declared, francesco ciccia Grant/research support from: pfizer, novartis, roche, Consultant of: pfizer, novartis, lilly, abbvie, Speakers bureau: pfizer, novartis, lilly, abbvie, cristiano alessandri Grant/research support from: Pfizer, Francesca Barone: None declared, fabrizio conti Speakers bureau: BMS, Lilly, Abbvie, Pfizer, Sanofi, Roberta Priori: None declared

An Unusual Case of Pulmonary Mucormycosis

Invasive fungal infections in solid organ transplant recipients are associated with significant morbidity and mortality. Of these fungal infections, mucormycosis presents as an aggressive, frequently fatal angioinvasive infection. Immunocompromised hosts and diabetes are important risk factors. These infections are frequently difficult to diagnose. A high index of suspicion in the appropriate setting and early, aggressive treatment with the newer antifungal agents have altered the previously grave prognosis. We present the first reported case of cavitating pulmonary mucormycosis in a renal transplant recipient caused by an unusual species of Mucorales. The patient was treated with a combination of lobectomy and antifungal treatment comprising of amphotericin B and posaconazole. He remains free of disease recurrence on monotherapy with posaconazole.

Isolated Neurogenic Bladder Associated With Human T-Lymphotropic Virus Type 1 Infection in a Renal Transplant Patient From Central Australia: A Case Report

BACKGROUND

Human T-lymphotropic virus type 1 (HTLV-1) is endemic amongst the Aborigines of the Northern Territory of Australia. HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) has been associated with this infection. In general population, isolated neurogenic bladder dysfunction in HTLV-1-infected individuals without HAM/TSP has been reported, and the HTLV-1 proviral load has been found to be higher in such patients compared with asymptomatic carriers. In solid organ transplantation, few cases of HAM/TSP have been reported worldwide, but not an isolated neurogenic bladder.

CASE

A 50-year-old indigenous women from Alice Springs with end stage renal disease secondary to diabetic nephropathy with no prior history of bladder dysfunction received a cadaveric renal allograft following which she developed recurrent urinary tract infections. The recipient was seropositive for HTLV-1 infection. HTLV-1 status of donor was not checked. Urodynamic studies revealed stress incontinence and detrusor overactivity without urethral intrinsic sphincter deficiency. She had no features of myelopathy. There was elevation of the serum and cerebrospinal fluid HTLV-1 proviral load. The magnetic resonance imaging myelogram was normal. Pyelonephritis was diagnosed based on clinical features, positive cultures, and renal allograft biopsy. Continuous suprapubic catheter drainage helped preventing further episodes of allograft pyelonephritis in spite of chronic colonization of the urinary tract.

CONCLUSION

Isolated bladder dysfunction is a rare manifestation of HTLV-1 infection and is probably associated with high proviral loads. This may adversely affect renal allograft and patient outcomes.

A Survey of MIKC Type MADS-Box Genes in Non-seed Plants: Algae, Bryophytes, Lycophytes and Ferns

MADS box transcription factors have been studied extensively in flowering plants but remain less studied in non-seed plants. MADS box is one such example of a gene which is prevalent across many classes of plants ranging from chlorophyta to embryophyta as well as fungi and animals. MADS box transcription factors are of two types, Type I and Type II. Type II transcription factors (TF) that consist of a MADS domain, I region, K domain, and C terminal domain are discussed in this review. The Type II/ MIKC class is widespread across charophytes and all major lineages of land plants but unknown in green and red algae. These transcription factors have been implicated in floral development in seed plants and thus the question arises, "What is their role in non-seed plants?" From the studies reviewed here it can be gathered that unlike seed plants, MIKC^C genes in non-seed plants have roles in both gametophytic and sporophytic generations and contribute to the development of both vegetative and reproductive structures. On the other hand as previously observed in seed plants, MIKC^* genes of non-seed plants have a conserved role during gametophyte development. With respect to evolution of MIKC genes in non-seed plants, the number of common ancestors is probably very few at each branch. The expansion of this gene family in seed plants and increased plant complexity seem to be correlated. As gradually the genomes of non-seed plants are becoming available it is worthwhile to gather the existing information about MADS box genes in non-seed plants. This review highlights various MIKC MADS box genes discovered so far in non-seed plants, their possible roles and an insight into their evolution.

Molecular and Cellular Requirements for the Assembly of Tertiary Lymphoid Structures

At sites of chronic inflammation, recruited immune cells form structures that resemble secondary lymphoid organs (SLOs). Those are characterized by segregated areas of prevalent T- or B-cell aggregation, differentiation of high endothelial venules (HEVs) and local activation of resident stromal cells. B-cell proliferation and affinity maturation towards locally displayed autoantigens have been demonstrated at those sites, known as tertiary lymphoid structures (TLSs). TLS formation has been associated with local disease persistence and progression as well as increased systemic manifestations. While bearing a similar histological structure to SLO, the signals that regulate TLS and SLO formation can diverge, and a series of pro-inflammatory cytokines has been ascribed as responsible for TLS formation at different anatomical sites. Here we review the structural elements as well as the signals responsible for TLS aggregation, aiming to provide an overview to this complex immunological phenomenon.

Uptake of inorganic phosphorus by temperate seagrass beds of Posidonia and Amphibolis in Southern Australia

Seagrasses occupy a narrow band of sandy seabed close to the coast and are therefore vulnerable to anthropogenic influences, particularly meadows near large population centres. Over 5000 ha of seagrasses have been lost from Adelaide coastal waters (South Australia) over the past 70 years and much of this loss has been attributed to nutrient inputs from wastewater, industrial and stormwater discharges. This led to the Adelaide Coastal Waters Study to understand processes along the Adelaide metropolitan coast that led to seagrass loss. This study, a subset of the larger ACWS study, used in situ nutrient spike approach to obtain ecologically relevant estimates of seasonal variability in phosphorus uptake in two species of temperate seagrass common to this coast (Amphibolis antarctica and Posidonia angustifolia). Total uptake of phosphorus by biological components in the seagrass beds, viz., seagrass, epiphytes and phytoplankton, was negligible, never exceeding 0.5% of the total resource. Phosphorus uptake rate varied seasonally with higher rates in winter (1.49 μmol P.g(-1) DW.h(-1)) and lower rates in spring (0.70 μmol P.g(-1) DW.h(-1)) for Amphibolis and highest in winter (2.09 μmol P.g(-1) DW.h(-1)) and least in spring (0.14 μmol P.g(-1) DW.h(-1)) for Posidonia. Low biological uptake rates of inorganic phosphorus could be attributed to carbonate sediments and particulates in the water column binding inorganic phosphorus, limiting its availability for biological uptake. From an environmental perspective, seagrass beds in the Adelaide coastal waters account for the assimilation of only 5.4% (19.53 t yr(-1)) of the total anthropogenic inputs of phosphorus.

Post-translational regulation of rice MADS29 function: homodimerization or binary interactions with other seed-expressed MADS proteins modulate its translocation into the nucleus

OsMADS29 is a seed-specific MADS-box transcription factor that affects embryo development and grain filling by maintaining hormone homeostasis and degradation of cells in the nucellus and nucellar projection. Although it has a bipartite nuclear localization signal (NLS) sequence, the transiently expressed OsMADS29 monomer does not localize specifically in the nucleus. Dimerization of the monomers alters the intracellular localization fate of the resulting OsMADS29 homodimer, which then translocates into the nucleus. By generating domain-specific deletions/mutations, we show that two conserved amino acids (lysine(23) and arginine(24)) in the NLS are important for nuclear localization of the OsMADS29 homodimer. Furthermore, the analyses involving interaction of OsMADS29 with 30 seed-expressed rice MADS proteins revealed 19 more MADS-box proteins, including five E-class proteins, which interacted with OsMADS29. Eleven of these complexes were observed to be localized in the nucleus. Deletion analysis revealed that the KC region (K-box and C-terminal domain) plays a pivotal role in homodimerization. These data suggest that the biological function of OsMADS29 may not only be regulated at the level of transcription and translation as reported earlier, but also at the post-translational level by way of the interaction between OsMADS29 monomers, and between OsMADS29 and other MADS-box proteins.

Functional delineation of rice MADS29 reveals its role in embryo and endosperm development by affecting hormone homeostasis

Rice MADS29 has recently been reported to cause programmed cell death of maternal tissues, the nucellus, and the nucellar projection during early stages of seed development. However, analyses involving OsMADS29 protein expression domains and characterization of OsMADS29 gain-of-function and knockdown phenotypes revealed novel aspects of its function in maintaining hormone homeostasis, which may have a role in the development of embryo and plastid differentiation and starch filling in endosperm cells. The MADS29 transcripts accumulated to high levels soon after fertilization; however, protein accumulation was found to be delayed by at least 4 days. Immunolocalization studies revealed that the protein accumulated initially in the dorsal-vascular trace and the outer layers of endosperm, and subsequently in the embryo and aleurone and subaleurone layers of the endosperm. Ectopic expression of MADS29 resulted in a severely dwarfed phenotype, exhibiting elevated levels of cytokinin, thereby suggesting that cytokinin biosynthesis pathway could be one of the major targets of OsMADS29. Overexpression of OsMADS29 in heterologous BY2 cells was found to mimic the effects of exogenous application of cytokinins that causes differentiation of proplastids to starch-containing amyloplasts and activation of genes involved in the starch biosynthesis pathway. Suppression of MADS29 expression by RNAi severely affected seed set. The surviving seeds were smaller in size, with developmental abnormalities in the embryo and reduced size of endosperm cells, which also contained loosely packed starch granules. Microarray analysis of overexpression and knockdown lines exhibited altered expression of genes involved in plastid biogenesis, starch biosynthesis, cytokinin signalling and biosynthesis.

Managing nitrogen inputs into seagrass meadows near a coastal city: flow-on from research to environmental improvement plans

Increased human habitation has led to a 30 to 50-fold increase in nutrient loads to the coastal waters of Adelaide, resulting in the loss of over 5000 ha of seagrass meadows. The rate of loss since the 1940s has been irregular, averaging 85 ha yr(-1), marked by a substantial peak between 1971 and 1977. A modelling approach allowed comparison of the annual input with the annual uptake rates for the different biotic components in the seagrass bed. In 2005, the estimated uptake of ammonium (465 t yr(-1)) and nitrate (3.04 t yr(-1)) by the seagrass and associated epiphytes in the Adelaide region accounted for 31% of the ammonium and <1% of the nitrate that is currently discharged into the coastal waters. Environment Improvement Programs, such as the one implemented in 1996, may reduce the total nitrogen loads to 700 t yr(-1), possibly stemming further losses and facilitating recolonisation of new seagrass.

Uptake and resource allocation of ammonium and nitrate in temperate seagrasses Posidonia and Amphibolis

Ecologically relevant estimates of seasonal variability in nitrogen uptake and allocation in two species of temperate seagrasses were obtained using in situ isotope-labelling approach. Significantly higher uptake rates of ammonium by leaves, roots and epiphytes of Amphibolis than Posidonia were observed. Overall, root uptake rates were lower than other components. Effect of season was not significant for leaves, roots or epiphytes of the two species. However, plankton uptake varied seasonally with higher rates in winter (0.98 mg N g(-1)D Wh(-1)). In contrast, nitrate uptake rates for various components were significantly affected by seasons. Uptake rates by plankton were highest ranging from 0.003 mg N g(-1)D Wh(-1) (summer, Amphibolis) to 0.69 mg N g(-1)DWh(-1) (winter, Posidonia). Uptake of nitrate by roots was negligible. Biotic uptake rates for nitrate were an order of magnitude slower than ammonium, demonstrating an affinity for ammonium over nitrate as a preferred inorganic nitrogen source. Adelaide coastal waters have lost over 5000 ha of seagrasses, much of this attributed to nutrient inputs from wastewater, industrial and stormwater. Managing these inputs into future requires better understanding of the fate of nutrients, particularly biological uptake. This study attempts to quantify uptake rates of nitrogen by seagrasses.

Extramedullary paraspinal hematopoiesis in hereditary spherocytosis

Hereditary spherocytosis (HS) is a common inherited hemolytic anemia due to red cell membrane defects. Extramedullary hematopoiesis is a compensatory response to insufficient bone marrow blood cell production. The preferred sites of extramedullary hematopoietic involvement are the spleen, liver and lymph nodes; but in HS, the posterior paravertebral mediastinum is also commonly involved. We report a case of a 50-year-old male who presented to us in respiratory distress and with bilateral paravertebral posterior mediastinal masses, which on trucut biopsy were found to be extra-hematopoietic masses; and the patient was found to have hereditary spherocytosis.

Environmental effects of dredging on sediment nutrients, carbon and granulometry in a tropical estuary

This monitoring study encompassed a period prior to dredging, during dredging and post dredging between July 1999 to June 2000 in Ponggol estuary located along the northeastern coast of Singapore. Mean concentrations of sediment nutrients in mg x Kg(-1) (+/- standard error of means) prior to dredging, during dredging and post dredging were 9.75 +/- 4.24, 8.18 +/- 4.29 and 11.46 +/- 4.74 for ammonium, 0.08 +/- 0.05, 0.06 +/- 0.02 and 0.09 +/- 0.01 for nitrite, 0.04 +/- 0.04, 0.11 +/- 0.17 and 0.25 +/- 0.30 for nitrate, 4.83 +/- 3.48, 0.77 +/- 0.48 and 8.33 +/- 9.73 for phosphate respectively. Pre dredge, dredge and post dredge levels of total carbon (TC) were 18.5 +/- 3.7, 20.2 +/- 3.5 and 34.6 +/- 12.0, of total organic carbon (TOC) were 10.5 +/- 2.9, 19.5 +/- 3.6 and 34.6 +/- 12.0 and of total inorganic carbon (TIC) were 7.9 +/- 1.0, 0.7 +/- 0.4 and non detectable in the sediments, respectively. Both, sediment nutrients and carbon registered lower concentrations with onset of dredging, with the exception of nitrate and TOC. A shift in sedimentary carbon from inorganic carbon to organic carbon was also observed with the onset of the dredging activities when the organically enriched historically contaminated layer was exposed. Sediment granulometry showed that the sediments in the estuary were predominantly silt and clay prior to dredging, which changed to sand with onset of dredging. Silt load in the sediments was highest post-dredge. Sediment nutrients and sediment organic carbon were observed to associate with the finer fractions (silt and clay) of sediments. Finer fractions of sediments get resuspended during a dredging event and are dispersed spatially as the result of tides and water movements. Prior to this study, the potential for nutrient release and sediment granulometry due to dredging have been suggested, but there have been few studies of it, especially in the tropics. The baseline information gathered from this study could be used to work out effective management strategies to protect similar tropical ecosystems elsewhere, should there be no other alternative to dredging.

Spatio-temporal fluxes in particulate organic carbon in a tropical coastal lagoon

Temporal and spatial variations in particulate organic carbon (POC) in relation to primary production, chlorophyll a, phaeophytin, plankton abundance, secondary production and suspended particulate matter (SPM) were studied monthly for 1 year from April 1996 to March 1997 in a shallow tropical coastal lagoon on the southwest coast of India. Though temporal variations in all components were significant, spatial variabilities were not statistically significant. POC values range from 200 to 5690 mg C m(3) h(-1), while primary production, chlorophyll a, and phaeophytin varied between 0.02 and 14.53 mg C m(-3) h(-1), 0.87 and 23.11 mg m(-3) and 3.02 and 30.581 mg m(-3), respectively. Phytoplankton and zooplankton abundance varied from 0.01 to 655.5 x 10(5) no m(-3) and negligible to 7.08 x 10(5) no m(-3) respectively; secondary production from 10 to 490 mg C m(-3) and SPM between 0.38 and 74.43 x 10(4) mg m(-3) during this study. Temporally, postmonsoon months were observed to have the highest concentrations of POC in the lagoon waters. The bulk of the POC pool in the lagoon was composed of secondary producers (72%), followed by chlorophyll a (21%), phaeophytin (7%) and suspended particulate matter of inorganic origin (< 0.1%).

Environmental impacts of diesel fuel on bacteria and phytoplankton in a tropical estuary assessed using in situ mesocosms

Dissolved or dispersed petroleum hydrocarbon concentrations (DDPH) were monitored in Ponggol estuary, Singapore, fortnightly from July 1999 to June 2000. DDPH concentrations ranged from 4.4 to 248.9 microg l(-1) and 0.4 to 1099.7 microg l(-1) for surface and subsurface waters, respectively and with mean concentrations of 41.01 microg l(-1) in the water column. Absorbed or adsorbed petroleum hydrocarbon (AAPH) concentrations measured in sediments ranged from 20.6 to 541.0 mg kg(-1), with mean concentrations of 148.23 mg kg(-1). In situ mesocosm studies of bacteria and phytoplankton were based on field monitoring of environmentally measured concentrations of petroleum hydrocarbons, using diesel fuel as the source of contaminant. The mesocosm comprised of 25 L clear polycarbonate carboys incubated in situ for 6 days. Water and sediments from a clean site with undetectable levels of petroleum hydrocarbons were used in controls. The treatment mesocosms comprised of mean and highest concentrations of DDPH and AAPH. The study revealed signs of acute toxicity to autotrophs viz., phytoplankton and autotrophic bacteria in treatments simulating concentrations of diesel fuel found in the sediments. A stimulatory effect was seen at lower concentrations. Bacterial heterotrophs responded positively to all concentrations of diesel fuel because of the abundance of a carbon source, reduced grazing pressure and reduced competition for nutrients from phytoplankton.

Environmental impact of heavy metals from dredged and resuspended sediments on phytoplankton and bacteria assessed in in situ mesocosms

Past and on-going reclamation, dredging, construction and shipping activities impact Ponggol Estuary, located on the northeastern coast of Singapore. Tin, lead, nickel, cadmium, and copper in particulate and dissolved fractions and sediments ranged from ND (undetectable)-92 ppm, ND-303.2 ppm, ND-2818.4 ppm, ND-74.4 ppm and ND-1117.7 ppm, respectively. Intensive dredging activity during the monitoring period may have led to the resuspension and bioavailability of particulate metals. This was tested by the exposure of phytoplankton and bacteria in mesocosms to previously measured environmental levels of heavy metals and the contaminated sediments with the highest heavy metal concentrations from one of the impacted sites. The results showed significant copper toxicity to phytoplankton and autotrophic bacteria, followed by nickel and lead at all concentrations tested. Enhanced rates of heterotrophic bacterial production and total bacterial abundance were observed in treatments with higher metal concentrations. Among the various treatments, particulate and sediment metal concentrations were significantly different from those of the control. Mesocosms using contaminated sediments with the highest metal concentrations compared with the control showed a bioavailability of metals that resulted in the inhibition of phytoplankton and autotrophic bacteria. High concentrations of copper (5.52-11.35 mg L(-1)) and nickel (2.42-2.71 mg L(-1)) observed in the aqueous phase of treatment mesocosms, and attributed to release from the contaminated sediments could account for the toxicity to phytoplankton and autotrophic bacteria.

In situ microcosms to study the impact of heavy metals resuspended by dredging on periphyton in a tropical estuary

Ponggol estuary, located on the northeastern coast of Singapore, is heavily impacted by reclamation, dredging, construction and shipping. Tin, lead, nickel, cadmium, copper and zinc in the particulate and dissolved fraction and in sediments were monitored biweekly in the estuary from July 1999 to June 2000. The concentrations of tin, lead, nickel, cadmium, copper and zinc were observed to range from ND-92 ppm, ND-303 ppm, ND-2818 ppm, ND-74 ppm, ND-1117 ppm and ND-137000 ppm, respectively, in the dissolved, particulate and sediments fractions. Intensive dredging activity occurred during the monitoring period, and this may have led to the resuspension and increased bioavailability of particulate metals. Periphytic algae were established on glass slides and exposed to previously measured environmental levels of heavy metals using in situ estuarine microcosms. The toxicity of heavy metals in various fractions to periphytic algae was assessed from the changes in their chlorophyll a content. Cadmium had the least significant effect followed by lead, zinc, nickel, tin and copper at all concentrations tested. A reduction in periphyton biomass (with respect to controls) of 95-100% was observed for treatments with metals in particulate form. In addition, exposure to contaminated sediments for 3 days significantly decreased chlorophyll a by 90-99% compared to controls. High concentrations of zinc (9893-17240 mg l(-1)), copper (5-11 mg l(-1)) and cadmium (1-1.8 mg l(-1)) recorded in the aqueous phase of treatment microcosms, and attributed to release from the contaminated sediments, could account for the toxicity to periphyton.

UDP-galactose 4-epimerase from Escherichia coli: equilibrium unfolding studies

UDP-galactose 4-epimerase from Escherichia coli is a homodimer of 39 kDa subunit with non-covalently bound NAD acting as cofactor. The enzyme can be reversibly reactivated after denaturation and dissociation using 8 M urea at pH 7.0. There is a strong affinity between the cofactor and the refolded molecule as no extraneous NAD is required for its reactivation. Results from equilibrium denaturation using parameters like catalytic activity, circular-dichroism, fluorescence emission (both intrinsic and with extraneous fluorophore 1-aniline 8-naphthalene sulphonic acid), 'reductive inhibition' (associated with orientation of NAD on the native enzyme surface), elution profile from size-exclusion HPLC and light scattering have been compiled here. These show that inactivation, integrity of secondary, tertiary and quaternary structures have different transition mid-points suggestive of non-cooperative transition. The unfolding process may be broadly resolved into three parts: an active dimeric holoenzyme with 50% of its original secondary structure at 2.5 M urea; an active monomeric holoenzyme at 3 M urea with only 40% of secondary structure and finally further denaturation by 6 M urea leads to an inactive equilibrium unfolded state with only 20% of residual secondary structure. Thermodynamical parameters associated with some transitions have been quantitated. The results have been discussed with the X-ray crystallographic structure of the enzyme.

Prevalence of sputum-positive pulmonary tuberculosis in tribal and non-tribal populations of the Ashti and Karanja tahsils in Wardha district, Maharashtra State, India

SETTING

Ashti and Karanja tahsils, Wardha district, Maharashtra State, Central India.

OBJECTIVE

To find and compare the prevalence of bacillary positive pulmonary tuberculosis amongst the different tribes and in the non-tribal population.

DESIGN

Prevalence study of pulmonary tuberculosis by house-to-house survey of symptoms among tribal (n = 20596) and non-tribal (n = 93 670) populations aged 5 years and over, between September 1989 and November 1990.

RESULTS

The prevalence of smear and/or culture-positive tuberculosis/100000 population was 133 in the tribal and 144 in the non-tribal population. The difference in prevalence of symptomatic individuals and sputum-positive cases among the tribal and the non-tribal populations was statistically significant only in the symptomatic individuals/100000 (P = 0.01). The prevalence of cases in both groups was higher in males than females; however this difference was significant only in the tribal group (P = 0.05). Only two of the 46 tribes encountered, the Mana and Pawara tribes, showed a high prevalence, of 730 and 612/100000, respectively. The three other tribes with positive cases (the Gond group) had prevalences comparable to that of the nontribal population.

CONCLUSION

The prevalence of tuberculosis in tribal people was comparable to that of the non-tribal population.