An economic analysis of leachate purification through willow-coppice vegetation filters

In this study an economic analysis of the purification of integrated solid waste treatment facility leachates through a willow-coppice (Salix) vegetation filter in southern Sweden was carried out. Calculations were based on the use of two computer models that were initially used in estimating a pump-and-pipe irrigation system for a 36-ha willow-coppice plantation to purify an average annual quantity of 195,000 m(3) of leachate with an average nitrogen content of 24 g/m(3). Results showed that facility leachates could be purified at US dollars 0.34/m(3) compared with US dollars 0.62/m(3) for that of conventional leachate treatment at a wastewater treatment plant. Furthermore, results revealed that the increased income from willow growing and sale of the biomass chips represented only a small factor in the overall cost of the purification technique--decreasing purification costs to US dollars 0.326/m(3). Sensitivity analyses also demonstrated that, because of the large leachate holding pond expense, only a fraction of facility leachate should be treated through a vegetation filter.     

Increased sensitivity to dietary cholesterol in diabetic and hypothyroid rats associated with low levels of hepatic HMG-CoA reductase expression

We recently postulated that hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase functions as a cholesterol buffer to protect against the serum and tissue cholesterol raising action of dietary cholesterol. This postulate predicts that diminished basal expression of hepatic HMG-CoA reductase results in increased sensitivity to dietary cholesterol. Because diabetic and hypothyroid animals are known to have markedly reduced hepatic HMG-CoA reductase, these animals were selected as models to test our postulate. When rats were rendered diabetic with streptozotocin, their hepatic HMG-CoA reductase activity decreased from 314 to 22 pmol. min(-1). mg(-1), and their serum cholesterol levels increased slightly. When the diabetic animals were challenged with a diet containing 1% cholesterol, their serum cholesterol levels doubled, and their hepatic reductase activity decreased further to 0.9 pmol. min(-1). mg(-1). Hepatic low-density lipoprotein (LDL) receptor immunoreactive protein levels were unaffected in the diabetic rats whether fed cholesterol-supplemented diets or not. In rats rendered hypothyroid by thyroparathyroidectomy, serum cholesterol levels rose from 100 to 386 mg/dl in response to the 1% cholesterol challenge, whereas HMG-CoA reductase activity dropped from 33.8 to 3.4 pmol. min(-1). mg(-1). Hepatic LDL receptor immunoreactive protein levels decreased only slightly in the hypothyroid rats fed cholesterol-supplemented diets. Taken together, these results show that rats deficient in either insulin or thyroid hormone are extremely sensitive to dietary cholesterol largely due to low basal expression of hepatic HMG-CoA reductase.     

Systematic variation of amino acid substitutions for stringent assessment of pairwise covariation

During protein evolution, amino acids change due to a combination of functional constraints and genetic drift. Proteins frequently contain pairs of amino acids that appear to change together (covariation). Analysis of covariation from naturally occurring sets of orthologs cannot distinguish between residue pairs retained by functional requirements of the protein and those pairs existing due to changes along a common evolutionary path. Here, we have separated the two types of covariation by independently recombining every naturally occurring amino acid variant within a set of 15 subtilisin orthologs. Our analysis shows that in this family of subtilisin orthologs, almost all possible pairwise combinations of amino acids can coexist. This suggests that amino acid covariation found in the subtilisin orthologs is almost entirely due to common ancestral origin of the changes rather than functional constraints. We conclude that naturally occurring sequence diversity can be used to identify positions that can vary independently without destroying protein function.     

Association of the low-density lipoprotein receptor with caveolae in hamster and rat liver

The association of the low-density lipoprotein (LDL) receptor with detergent resistant hepatic membranes was investigated using discontinuous sucrose gradients. In liver homogenates from both hamsters and rats, the fractions with the highest concentrations of LDL receptor coincided with the location of caveolin-1, a marker of the cholesterol-rich caveolae. Feeding the animals diets enriched in cholesterol slightly shifted both LDL receptor and caveolin-1 to positions of lower density. The cholesterol content of the caveolae fractions was increased 2-fold in animals fed cholesterol-supplemented diets. In homogenates of CHO cells, fractionated in the same manner, the LDL receptor was absent from the caveolae fractions but was present in denser fractions near the bottom of the gradient. Addition of caveolin-1 antibody to solubilized caveolae from liver coimmunoprecipitated the LDL receptor. These observations suggest that in liver, the LDL receptor is mainly located in caveolae. This location contrasts with the clathrin-coated pit location observed in fibroblasts and CHO cells.     

Evolutionary potential of (beta/alpha)8-barrels: functional promiscuity produced by single substitutions in the enolase superfamily

The members of the mechanistically diverse, (beta/alpha)(8)-barrel fold-containing enolase superfamily evolved from a common progenitor but catalyze different reactions using a conserved partial reaction. The molecular pathway for natural divergent evolution of function in the superfamily is unknown. We have identified single-site mutants of the (beta/alpha)(8)-barrel domains in both the l-Ala-d/l-Glu epimerase from Escherichia coli (AEE) and the muconate lactonizing enzyme II from Pseudomonas sp. P51 (MLE II) that catalyze the o-succinylbenzoate synthase (OSBS) reaction as well as the wild-type reaction. These enzymes are members of the MLE subgroup of the superfamily, share conserved lysines on opposite sides of their active sites, but catalyze acid- and base-mediated reactions with different mechanisms. A comparison of the structures of AEE and the OSBS from E. coli was used to design the D297G mutant of AEE; the E323G mutant of MLE II was isolated from directed evolution experiments. Although neither wild-type enzyme catalyzes the OSBS reaction, both mutants complement an E. coli OSBS auxotroph and have measurable levels of OSBS activity. The analogous mutations in the D297G mutant of AEE and the E323G mutant of MLE II are each located at the end of the eighth beta-strand of the (beta/alpha)(8)-barrel and alter the ability of AEE and MLE II to bind the substrate of the OSBS reaction. The substitutions relax the substrate specificity, thereby allowing catalysis of the mechanistically diverse OSBS reaction with the assistance of the active site lysines. The generation of functionally promiscuous and mechanistically diverse enzymes via single-amino acid substitutions likely mimics the natural divergent evolution of enzymatic activities and also highlights the utility of the (beta/alpha)(8)-barrel as a scaffold for new function.     

The MHC class II-associated chicken invariant chain shares functional properties with its mammalian homologs

The nucleotide sequence of chicken invariant chain (Ii) was determined, and the amino acid sequence similarity with human Ii is 61%. Certain regions important for the biological function of human Ii are highly conserved between chicken and mammals. The cytoplasmic tail of chicken Ii fused to the plasma membrane reporter molecule neuraminidase relocated the protein to endosomes. Moreover, like the mammalian orthologs, the cytoplasmic tail was found to contain two independent leucine-based endosomal sorting signals. Chicken Ii was found to interact with human Ii and crosslinking studies also indicate that chicken Ii assembles as a trimer. The chicken Ii can furthermore bind the human MHC class II (HLA-DR1). Many of the functional properties between the chicken Ii and its mammalian orthologs are thus maintained in spite of their sequence differences.     

Sterol Uptake in Saccharomyces cerevisiae Heme Auxotrophic Mutants Is Affected by Ergosterol and Oleate but Not by Palmitoleate or by Sterol Esterification

The relationship between sterol uptake and heme competence in two yeast strains impaired in heme synthesis, namely, G204 and H12-6A, was analyzed. To evaluate heme availability, a heterologous 17α-hydroxylase cytochrome P-450 cDNA (P-450c17) was expressed in these strains, and its activity was measured in vivo. Heme deficiency in G204 led to accumulation of squalene and lethality. The heterologous cytochrome P-450 was inactive in this strain. The leaky H12-6A strain presented a slightly modified sterol content compared to that for the wild type, and the P-450c17 recovered partial activity. By analyzing sterol transfer on nongrowing cells, it was shown that the cells were permeable toward exogenous cholesterol when they were depleted of endogenous sterols, which was the case for G204 but not for H12-6A. It was concluded that the fully blocked heme mutant (G204) replenishes its diminishing endogenous sterol levels during growth by replacement with sterol from the outside medium. Endogenous sterol biosynthesis appears to be the primary factor capable of excluding exogenous sterol. Oleate but not palmitoleate was identified as a component that reduced but did not prevent sterol transfer. Sterol transfer was only slightly affected by a lack of esterification. It is described herein how avoidance of the potential cytotoxicity of the early intermediates of the mevalonate pathway could be achieved by a secondary heme mutation in erg auxotrophs.     

Birth Prevalence of Neural Tube Defects and Orofacial Clefts in India: A Systematic Review and Meta-Analysis

Background

In the last two decades, India has witnessed a substantial decrease in infant mortality attributed to infectious disease and malnutrition. However, the mortality attributed to birth defects remains constant. Studies on the prevalence of birth defects such as neural tube defects and orofacial clefts in India have reported inconsistent results. Therefore, we conducted a systematic review of observational studies to document the birth prevalence of neural tube defects and orofacial clefts.

Methods

A comprehensive literature search for observational studies was conducted in MEDLINE and EMBASE databases using key MeSH terms (neural tube defects OR cleft lip OR cleft palate AND Prevalence AND India). Two reviewers independently reviewed the retrieved studies, and studies satisfying the eligibility were included. The quality of included studies was assessed using selected criteria from STROBE statement.

Results

The overall pooled birth prevalence (random effect) of neural tube defects in India is 4.5 per 1000 total births (95% CI 4.2 to 4.9). The overall pooled birth prevalence (random effect) of orofacial clefts is 1.3 per 1000 total births (95% CI 1.1 to 1.5). Subgroup analyses were performed by region, time period, consanguinity, and gender of newborn.

Conclusion

The overall prevalence of neural tube defects from India is high compared to other regions of the world, while that of orofacial clefts is similar to other countries. The majority of studies included in the review were hospital based. The quality of these studies ranged from low to moderate. Further well-designed, high quality community-based observational studies are needed to accurately estimate the burden of neural tube defects and orofacial clefts in India.     

SPONTANEOUS MUTATION ACCUMULATION IN MULTIPLE STRAINS OF THE GREEN ALGA,CHLAMYDOMONAS REINHARDTII

Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown. We maintained multiple strains of the unicellular eukaryote Chlamydomonas reinhardtii, for approximately 1000 generations under relaxed selection by transferring a single cell every ～10 generations. Mean fitness of the lines tended to decline with generations of mutation accumulation whereas mutational variance increased. We did not find any evidence for differences among strains in any of the mutational parameters estimated. The overall change in mean fitness per cell division and rate of input of mutational variance per cell division were more similar to values observed in multicellular organisms than to those in other single‐celled microbes. However, after taking into account differences in genome size among species, estimates from multicellular organisms and microbes, including our new estimates from C. reinhardtii, become substantially more similar. Thus, we suggest that variation in genome size is an important determinant of interspecific variation in mutational parameters.