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Y Xiong

Publications and source records attributed to Y Xiong.

At least 199 records · Page 11Linked to original sources
PubMed1991

Density of steam-flaked sorghum grain, roughage level, and feeding regimen for feedlot steers.

Two hundred fifty-two steers (366 kg) were assigned to a 3 x 2 x 2 factorial arrangement of three densities of steam-flaked sorghum grain (bulk [flake] density of 437, 360, and 283 g/liter, B34, B28, and B22, respectively), two roughage levels (9 [R9] and 18% [R18]) and two feeding strategies (ad libitum [AD] or multiple of maintenance [MM], 2.3, 2.5, and 2.7 MM for wk 1, 2, and 3, and 2.9 MM thereafter). Steers fed R18-AD gained faster than steers fed R18-MM (1.59 vs 1.52 kg/d, P = .10); for R9 diets, no difference (P greater than .25) was found between steers fed AD and MM (interaction, P = .07). Flake density did not affect ADG (1.53 kg, P greater than .2). Dry matter intake decreased (9.8, 9.3, and 9.0 kg/d, linear, P less than .001) and gain efficiency (G/DMI, kg of gain/100 kg of DMI) increased (15.7, 16.5, and 16.9, linear, P less than .001; quadratic, P = .19) as processing degree increased (B34 to B22). Percentage of choice carcasses for B34 (67.0%) was higher (linear, P = .05) than for B28 (51.9%) and B22 (52.3%). Fecal starch and pH were 10.8, 5.7, and 4.0%, and 6.11, 6.23, and 6.37 for B34, B28, and B22, respectively (linear, P less than .001). The correlation between fecal starch and pH was -.51 (P less than .001, n = 252). Enzymatic glucose release, in vitro 6-h gas production, microbial protein synthesis, and protein degradability were 375, 483, and 559 mg/g; 24.7, 28.2, and 31.1 ml/.2 g; 6.15, 6.88, and 7.84 g/100g; and 61.4, 56.6, and 42.2% for B34, B28, and B22, respectively (linear, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1990

Type I (R1) and type II (R2) ribosomal DNA insertions of Drosophila melanogaster are retrotransposable elements closely related to those of Bombyx mori.

Approximately 50% of the ribosomal DNA (rDNA) units of Drosophila melanogaster are inactivated by two different 28 S RNA ribosomal gene insertions (type I and type II). We present here the nucleotide sequence of complete type I and type II elements. Conceptual translation of these sequences revealed open reading frames (ORFs) encoding amino acid residues conserved in all retrotransposable elements. Full-length type I elements are 5.35 x 10(3) base-pairs in length and contain two overlapping ORFs. The smaller ORF (471 amino acid residues) has similarity to gag genes, while the larger ORF (1021 residues) has similarity to pol genes. Full-length type II elements are 3.6 x 10(3) base-pairs and contain one large ORF (1056 residues) that appears to represent a gag-pol fusion. Type I and type II elements are similar in structure, in the proteins they encode, and in insertion specificity to the R1Bm and R2Bm retrotransposable elements of Bombyx mori. We suggest that the D. melanogaster elements be called R1Dm and R2Dm, to reflect their structure as retrotransposons. Comparison of the R1 and R2 elements from these two widely different species revealed regions of the ORF that are likely to play an important role in the propagation of the elements. Four distinct regions of sequence conservation separated by regions of little or no sequence similarity were detected for both the R1 and R2 elements: (1) cysteine motifs of the gag gene, with three such motifs for R1 and one motif for R2; (2) a reverse transcriptase domain; (3) an integrase domain located carboxyl terminal to the reverse transcriptase region; and (4) a small region amino terminal to the reverse transcriptase domain, whose function is not known. The level of identity of the amino acid residues for these segments is 28 to 34% between the R1 elements, and 34 to 39% for the R2 elements. Finally, it may be predicted that the mechanism of unequal crossover might eventually eliminate R1 and R2 from the rDNA locus. The long history of selection at the protein level exhibited by these elements indicates that it is their active transposition that maintains them in the locus. The high level of sequence homogeneity between copies of each element within the same species is consistent with the high turnover rate expected to result from these processes.

Amino Acid Sequence↗
PubMed1990

Origin and evolution of retroelements based upon their reverse transcriptase sequences.

To study the evolutionary relationship of reverse transcriptase (RT) containing genetic elements, a phylogenetic tree of 82 retroelements from animals, plants, protozoans and bacteria was constructed. The tree was based on seven amino acid domains totalling 178 residues identified in all RTs. We have also identified these seven domains in the RNA-directed RNA polymerases from various plus-strand RNA viruses. The sequence similarity of these RNA polymerases to RT suggests that these two enzymes evolved from a common ancestor, and thus RNA polymerase can be used as an outgroup to root the RT tree. A comparison of the genetic organization of the various RT containing elements and their position on the tree allows several inferences concerning the origin and evolution of these elements. The most probable ancestor of current retroelements was a retrotransposable element with both gag-like and pol-like genes. On one major branch of the tree, organelle and bacterial sequences (e.g. group II introns and bacterial msDNA) appear to have captured the RT sequences from retrotransposons which lack long terminal repeats (LTRs). On the other major branch, acquisition of LTRs gave rise to two distinct groups of LTR retrotransposons and three groups of viruses: retroviruses, hepadnaviruses and caulimoviruses.

Amino Acid Sequence↗
PubMed1990

Improved enzymatic method to measure processing effects and starch availability in sorghum grain.

A modified enzymatic method to measure processing effects and starch availability in steam-flaked sorghum grain (SFSG) was developed. To establish the method, experiments were conducted to determine the required enzyme concentration, color reagents, precipitants, sample particle size, shaking frequency and buffer pH. Glucose release at different incubation times (0 to 48 h) from uncooked (UNC) or fully cooked (CK, 100% gelatinized) ground sorghum grain, a 50:50 mixture of UNC and CK (C50) and SFSG was determined. Glucose release from UNC, CK and SFSG was expressed as one-component equations with rate constant k and r2 of .119 and .98, 1.781 and .98, and .368 and .99, respectively; C50 was characterized by having two starch components, one with a fast rate constant, 2.624/h, and one with a slow rate constant, .066/h (R2 = .99). Different degrees of gelatinization were obtained by mixing different proportions of CK and UNC. Glucose release from these samples was highly correlated with starch gelatinization (r2 = .99). By adjusting the tension between mill rollers, five SFSG samples with bulk densities ranging from 476 to 283 g/liter (37 to 22 lb/bu) were produced; respective roller mill electrical load ranged from 21 to 51.5 amps. Enzymatic determination of glucose release resulted in values of 422, 512, 588, 618 and 678 mg/g, which were more closely related to bulk density than birefringence measurements. The modified method for starch availability determination was found to be relatively simple, fast and sensitive, and is recommended.

Animal Feed↗
PubMed1990

Estimating starch availability and protein degradation of steam-flaked and reconstituted sorghum grain through a gas production technique.

Five steam-flaked sorghum grain (SFSG) samples with bulk densities of 476, 412, 347, 309 and 283 g/liter made by adjusting tension between mill rollers and three reconstituted sorghum grain (RSG) samples with reconstitution times of 10, 20 and 30 d and a control sample were analyzed for gas production kinetics (rumen liquor fermentation) and enzymatic glucose release (amyloglucosidase). Protein degradation was estimated from 6-h gas production and residual ammonia in the liquid. Gas production followed first-order kinetics (r2 greater than .98; P less than .01) and was used to describe rate and extent of digestion kinetics. Rate of gas production increased as processing degree increased. The magnitude of increase in gas production, however, was much less for RSG than for SFSG. Linear relationships were observed between enzymatic glucose release and the gas production rate constant k as well as gas production at 4,6 and 8 h (r2 greater than .98; P less than .01). Protein degradation decreased with processing degree of SFSG but increased with reconstitution time. A technique based on 6-h gas production and residual ammonia in the liquid is proposed to estimate both ruminal starch availability and ruminal protein degradability for processed sorghum grain.

Animal Feed↗
PubMed1990

[Mosquito-net spraying with deltamethrin for malaria control].

Mosquito-nets were sprayed with 9.6mg deltamethrin per square meter for control of malaria vectors in Yibin County, Sichuan Province in 1986. In the study area, the relative population indices of Anopheles anthropophagus and An. sinensis in 35 mosquito-nets were 0.6 and 1.4 respectively; the man biting rates of these two vectors dropped by 97.8 and 90.8% respectively. The residual toxic effect of sprayed mosquito-nets, up to 104 days after spray, caused a mortality of 93.1-100% of An. anthropophagus and 87.1-100% of An. sinensis. The multiparous mosquito rate dropped by 48.4 and 51.3%. Indoor-intruding An. anthropophagus and An. sinensis were reduced by 76% and 78.3% respectively. The incidence of malaria decreased by 94.4%, the positive rate in school children declined by 77.5%. Both entomological and epidemiological indices indicated that mosquito-nets sprayed with deltamethrin could effectively control the malaria prevalence. This measure is economical and practical for control of malaria.

Animals↗
PubMed1989

Nuptial and childbearing customs of the ethnic minorities in China.

The current nuptial customs of the ethnic minorities in China are examined. "Although monogamous marriage has now been adopted by all but a few ethnic communities, variations still exist between different nationalities in the specific forms of marriage and range of intermarriage owing to the uneven nature of historical development. Such variations are shaped by various factors of the given locality and given time such as the socioeconomy, religion, culture and education, and exert direct influence on the childbearing behavior and reproduction of the ethnic population."

Asia↗
PubMed1988

Ribosomal DNA insertion elements R1Bm and R2Bm can transpose in a sequence specific manner to locations outside the 28S genes.

A fraction of the ribosomal 28S genes in some insects are interrupted at specific sites by insertion elements R1 and R2 (also called Type I and II). These elements contain long open-reading frames with homology to reverse transcriptase. We have identified in the silkmoth, Bombyx mori, copies of these elements which have inserted into sites outside the ribosomal DNA (rDNA) units. The 3' ends of all "non-rDNA" elements are identical to the elements within the 28S genes; however their 5' ends are often truncated. Each non-rDNA copy has inserted into sequences that exhibit similarity to their target sites in the 28S gene. We also demonstrate by genomic blot analysis of different strains of B. mori that insertions of R1 and R2 outside the rDNA units have been infrequent, while considerable turnover of elements has occurred within the rDNA locus. One race of B. mori has lost all copies of R1 from its rDNA units, while retaining normal levels of R2. The level of both R1 and R2 have significantly increased in a tissue culture line. These findings add considerable support to the model that R1 and R2 are retrotransposable elements that utilize sequence specific endonucleases in their integration into the genome.

Animals↗
PubMed1988

Similarity of reverse transcriptase-like sequences of viruses, transposable elements, and mitochondrial introns.

Sequences similar to reverse transcriptase (RT) of retroviruses have been found in certain DNA viruses, mitochondrial intron sequences, and a wide variety of transposable elements. While total amino acid similarity between these diverse elements is quite low, we have identified seven regions, consisting of 182 amino acids, that are common to all elements. Highly conserved residues identified in each of these regions are diagnostic for the identification and alignment of these and for future RT-like sequences. Using both the neighbor-joining and the unweighted-pair-group methods, we have derived a probable phylogenetic tree for all RT-containing elements. These elements can be divided into two major groups. Retroviruses and DNA viruses whose propagation involves an RNA intermediate are grouped with a series of transposable elements containing long terminal repeats (LTRs). The second group is made up of RT-containing sequences of fungal mitochondrial introns and a series of transposable elements that lack LTRs. The transposable elements, copia and Ty, were found to be the most difficult to position on the phylogenetic tree, as a result of their higher rate of sequence divergence. The data are most consistent with their being distant members of the LTR group (retroviruses/LTR retrotransposons).

Amino Acid Sequence↗
PubMed1988

The site-specific ribosomal DNA insertion element R1Bm belongs to a class of non-long-terminal-repeat retrotransposons.

Two types of insertion elements, R1 and R2 (previously called type I and type II), are known to interrupt the 28S ribosomal genes of several insect species. In the silkmoth, Bombyx mori, each element occupies approximately 10% of the estimated 240 ribosomal DNA units, while at most only a few copies are located outside the ribosomal DNA units. We present here the complete nucleotide sequence of an R1 insertion from B. mori (R1Bm). This 5.1-kilobase element contains two overlapping open reading frames (ORFs) which together occupy 88% of its length. ORF1 is 461 amino acids in length and exhibits characteristics of retroviral gag genes. ORF2 is 1,051 amino acids in length and contains homology to reverse transcriptase-like enzymes. The analysis of 3' and 5' ends of independent isolates from the ribosomal locus supports the suggestion that R1 is still functioning as a transposable element. The precise location of the element within the genome implies that its transposition must occur with remarkable insertion sequence specificity. Comparison of the deduced amino acid sequences from six retrotransposons, R1 and R2 of B. mori, I factor and F element of Drosophila melanogaster, L1 of Mus domesticus, and Ingi of Trypanosoma brucei, reveals a relatively high level of sequence homology in the reverse transcriptase region. Like R1, these elements lack long terminal repeats. We have therefore named this class of related elements the non-long-terminal-repeat (non-LTR) retrotransposons.

Amino Acid Sequence↗
PubMed1985

Mutational analysis of the Klebsiella pneumoniae nitrogenase promoter: sequences essential for positive control by nifA and ntrC (glnG) products.

ntr (nitrogen regulated) and nif (nitrogen fixation) promoters are structurally similar to each other but bear no resemblance to canonic Escherichia coli promoters. ntr promoters are normally activated by the ntrC (glnG) product, but they can also be activated by the ntrC-related Klebsiella pneumoniae nifA product. In contrast, nif promoters of K. pneumoniae such as the nitrogenase (nifH) promoter can only be nifA activated. In this paper, we report the isolation and characterization of 28 mutants of the K. pneumoniae nifH promoter. Class A mutants no longer respond to nifA-mediated transcription, and class B mutants can now respond to ntrC-mediated activation. These two classes of mutants define sequences important to nifA- and ntrC-mediated transcription. Most surprising is that a single base change is sufficient to convert a nifA-activated promoter into an ntrC-activated one.

Base Sequence↗