Significant enhancement in thermoelectric performance of nanostructured higher manganese silicides synthesized employing a melt spinning technique.

The limited thermoelectric performance of p-type Higher Manganese Silicides (HMS) in terms of their low figure-of-merit (ZT), which is far below unity, is the main bottle-neck for realising an efficient HMS based thermoelectric generator, which has been recognized as the most promising material for harnessing waste-heat in the mid-temperature range, owing to its thermal stability, earth-abundant and environmentally friendly nature of its constituent elements. We report a significant enhancement in the thermoelectric performance of nanostructured HMS synthesized using rapid solidification by optimizing the cooling rates during melt-spinning followed by spark plasma sintering of the resulting melt-spun ribbons. By employing this experimental strategy, an unprecedented ZT ∼ 0.82 at 800 K was realized in spark plasma sintered 5 at% Al-doped MnSi1.73 HMS, melt spun at an optimized high cooling rate of ∼2 × 107 K s-1. This enhancement in ZT represents a ∼25% increase over the best reported values thus far for HMS and primarily originates from a nano-crystalline microstructure consisting of a HMS matrix (20-40 nm) with excess Si (3-9 nm) uniformly distributed in it. This nanostructure, resulting from the high cooling rates employed during the melt-spinning of HMS, introduces a high density of nano-crystallite boundaries in a wide spectrum of nano-scale dimensions, which scatter the low-to-mid-wavelength heat-carrying phonons. This abundant phonon scattering results in a significantly reduced thermal conductivity of ∼1.5 W m-1 K-1 at 800 K, which primarily contributes to the enhancement in ZT.

Exploiting Le Chatelier's principle for a one-pot synthesis of nontoxic HHogGNPs with the sharpest nanoscopic features suitable for tunable plasmon spectroscopy and high throughput SERS sensing.

Applying Le Chatelier's principle, a one-pot synthesis method is reported that generates highly anisotropic hedgehog gold nanoparticles (HHogGNPs), undemanding of a preformed seed or surfactant. These non-toxic HHogGNPs are potent candidates for nanomedicinal applications owing to their broad-band plasmon tunability, gigantic Raman enhancement and remarkable retention in a highly salted physiological environment.

Inhibition of Escherichia coli ribosome subunit dissociation by chloramphenicol and Blasticidin: a new mode of action of the antibiotics.

The ability of the ribosome to assist in folding of proteins both in vitro and in vivo is well documented and is a nontranslational function of the ribosome. The interaction of the unfolded protein with the peptidyl transferase centre (PTC) of the bacterial large ribosomal subunit is followed by release of the protein in the folding competent state and rapid dissociation of ribosomal subunits. Our study demonstrates that the PTC-specific antibiotics, chloramphenicol and blasticidin S inhibit unfolded protein-mediated subunit dissociation. During post-termination stage of translation in bacteria, ribosome recycling factor (RRF) is used together with elongation factor G to recycle the 30S and 50S ribosomal subunits for the next round of translation. Ribosome dissociation mediated by RRF and induced at low magnesium concentration was also inhibited by the antibiotics indicating that the PTC antibiotics exert an associative effect on ribosomal subunits. In vivo, the antibiotics can also reduce the ribosomal degradation during carbon starvation, a process requiring ribosome subunit dissociation. This study reveals a new mode of action of the broad-spectrum antibiotics chloramphenicol and blasticidin. SIGNIFICANCE AND IMPACT OF THE STUDY: Ribosome synthesizes protein in all organisms and is the target for multiple antimicrobial agents. Our study demonstrates that chloramphenicol and blasticidin S that target the peptidyl transferase centre of the bacterial ribosome can then inhibit dissociation of 70S ribosome mediated by (i) unfolded protein, (ii) translation factors or (iii) low Mg+2 concentrations in vitro and thereby suppresses ribosomal degradation during carbon starvation in vivo. The demonstration of this new mode of action furthers the understanding of these broad-spectrum antibiotics that differentially inhibit protein synthesis in prokaryotic and eukaryotic cells.

Sequence, genomic organization, and chromosomal location of the mouse Müllerian-inhibiting substance type II receptor gene.

We have determined the sequence and structure of the mouse Müllerian-inhibiting substance (MIS) type II receptor gene. Sequence comparisons demonstrate that the mouse, rat, rabbit, and human MIS type II receptors are highly conserved. The mouse MIS type II receptor gene is encoded by 11 exons and spans approximately 9-kb. Only half of the intron/exon boundaries of its kinase domain are conserved in comparison to the kinase domain of the related activin type II receptor. Whereas the activin type II receptor gene contains large introns (> 40-kb), the largest intron of the MIS type II receptor gene is only 4.3-kb. The MIS type II receptor gene (Amhr) is closely linked to Hoxc on mouse chromosome 15. Knowledge of the sequence and genomic structure of Amhr provides important information for the genetic manipulation of the Amhr locus.

Mouse chromosomal location of three epithelial sodium channel subunit genes and an apical sodium chloride cotransporter gene.

The amiloride-sensitive epithelial sodium channel alpha, beta, and gamma subunit genes, Scnn1a, Scnn1b, and Scnn1g, and the thiazide-sensitive sodium chloride cotransporter gene, Slc12a1, have been mapped in the mouse using an interspecific backcross panel. These loci map to previously defined homologous regions between human and mouse chromosomes and provide additional information regarding human/mouse comparative mapping.

Mouse chromosomal location of four Na/H exchanger isoform genes.

The Na/H exchanger genes Slc9a1, Slc9a2, Slc9a3, and Slc9a4 have been mapped in the mouse using an interspecific backcross panel. These loci map to previously defined homologous regions between human and mouse chromosomes and provide additional information regarding human/mouse comparative mapping.

Mouse chromosomal location of three EGF receptor ligands: amphiregulin (Areg), betacellulin (Btc), and heparin-binding EGF (Hegfl).

The products of five distinct loci, Egf, Tgfa, Areg, Btc, and Hegfl act as ligands for the epidermal growth factor receptor. Egf and Tgfa have previously been mapped to mouse chromosomes 3 and 6, respectively, but the mouse chromosomal locations of Areg, Btc, and Hegfl have not been reported. Here, we show that Areg and Btc are tightly linked on mouse chromosome 5, while Hegfl maps to mouse chromosome 18. We also provide evidence that a putative sixth family member, Sdgf, is in fact a species variant of Areg. These results confirm and extend known relationships between mouse and human chromosomes, and they also provide new information regarding the evolution of this important gene family.

The presence of both negative and positive elements in the 5'-flanking sequence of the rat Na,K-ATPase alpha 3 subunit gene are required for brain expression in transgenic mice.

The Na,K-ATPase is an integral plasma membrane protein consisting of alpha and beta subunits, each of which has discrete isoforms expressed in a tissue-specific manner. Of the three functional alpha isoform genes, the one encoding the alpha 3 isoform is the most tissue-restricted in its expression, being found primarily in the brain. To identify regions of the alpha 3 isoform gene that are involved in directing expression in the brain, a 1.6 kb 5'-flanking sequence was attached to a reporter gene, chloramphenicol acetyltransferase (CAT). The alpha 3-CAT chimeric gene construct was microinjected into fertilized mouse eggs, and transgenic mice were produced. Analysis of adult transgenic mice from different lines revealed that the transgene is expressed primarily in the brain. To further delineate regions that are needed for conferring expression in this tissue, systematic deletions of the 5'-flanking sequence of the alpha 3-CAT fusion constructs were made and analyzed, again using transgenic mice. The results from these analyses indicate that DNA sequences required for mediating brain-specific expression of the alpha 3 isoform gene are present within 210 bp upstream of the transcription initiation site. alpha 3-CAT promoter constructs containing scanning mutations in this region were also assayed in transgenic mice. These studies have identified both a functional neural-restrictive silencer element as well as a positively acting cis element.

Isoflurane partially preserves energy balance in isolated hepatocytes during in vitro anoxia.

We investigated whether a volatile anesthetic (1.5% isoflurane or 1.0% halothane) or an added anaerobic energy source (10 mM glucose or fructose) could act directly on liver cells to protect energy status during 20-30 min of anoxia. We used hepatocytes freshly isolated from fed rats or rats that had fasted, suspended them in Krebs' buffer, and incubated them in sealed flasks under O2/CO2 or N2/CO2 (95%:5%). The adenosine triphosphate (ATP) to adenosine diphosphate (ADP) ratio (ATP/ADP) measured cellular energy balance--the balance between overall ATP supply and demand. Lactate levels measured the extent to which ATP was supplied by the nonmitochondrial pathway, (anaerobic) glycolysis. Maximum values of energy balance were seen in cells from fed rats incubated in the presence of glucose and O2. When glucose was replaced by fructose, ATP/ADP decreased and lactate increased. During anoxia (O2 replaced by N2), increases in lactate were also seen with glucose; and ATP/ADP decreased to similarly low values with both substrates. In cells from fasted rats, ATP/ADP decreased significantly below the value for cells from fed rats only in the presence of glucose and O2. Compared with cells from fed rats, cells from fasted rats showed decreased lactate in the face of decreased ATP/ADP, suggesting that glycolysis was impaired. Isoflurane partially prevented anoxia-induced decreases in ATP/ADP. This protective effect on energy balance occurred equally with glucose and fructose, but was not seen in cells from fasted rats or with halothane. Thus, 1 MAC isoflurane and some factor(s) related to the fed state combined to protect partially the energy balance in anoxic liver cells through action(s) at the cellular level.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the 5'-flanking region of the human and rat Na,K-ATPase alpha 3 gene.

Genomic clones containing the 5'-flanking region and exon 1 of the human and rat Na,K-ATPase alpha 3 isoform gene have been isolated and characterized. The nucleotide sequences of 1.6 kb of the rat gene and 2.8 kb of the human gene in the 5'-flanking region were determined. Mapping of transcription initiation sites by primer extension and S1 nuclease protection analyses indicates that transcription is initiated in the same region in both genes although the rat gene has a greater number of initiation sites. Neither gene has a canonical TATA box, having instead a ATAT sequence preceding the transcription initiation sites. There is a perfect CCAAT sequence, in the reverse orientation, approximately 30 bp upstream of the potential TATA box in both genes. We have identified potential binding sites for transcription factors Sp-1, AP-1, AP-2, and AP-4, as well as for glucocorticoid and thyroid hormone receptors in the 5'-flanking regions. These are conserved in both human and rat alpha 3 isoform genes.

Toxicity studies of metabolites of some fungal isolates in albino mice.

Crude metabolites of 21 of 60 fungal cultures isolated from some of the common cereals collected from different parts of India were found to be toxic. Of these toxin-producing fungi, 79% caused hepatic pathology of varying severity in mice. Serum glutamate pyruvate transaminase values and blood urea nitrogen were found to be high in such experimental animals.

Histopathology of Mycotoxicosis produced in Swiss albino mice by metabolites of some fungal isolates.

Of 199 fungal cultures isolated from some of the common cereals collected from different parts of Uttar Pradesh and Madhya Pradesh, 70 produced toxic metabolites. Of the 70 fungi isolated, 59 produced toxins which caused visible lesions in livers, kidneys, and spleens but did not cause mortality. Toxicity, graded in terms of the mortality rate and the extent of lesions in livers, kidneys, and spleens, was found to be highest in various species of Aspergillus (40%), followed by Chaetomium spp. (31%).