Large, rapidly evolving intergenic spacers in the mitochondrial DNA of the salamander family Ambystomatidae (Amphibia: Caudata)

We report the presence, in the mitochondrial DNA (mtDNA) of all of the sexual species of the salamander family Ambystomatidae, of a shared 240- bp intergenic spacer between tRNAThr and tRNAPro. We place the intergenic spacer in context by presenting the sequence of 1,746 bp of mtDNA from Ambystoma tigrinum tigrinum, describe the nucleotide composition of the intergenic spacer in all of the species of Ambystomatidae, and compare it to other coding and noncoding regions of Ambystoma and several other vertebrate mtDNAs. The nucleotide substitution rate of the intergenic spacer is approximately three times faster than the substitution rate of the control region, as shown by comparisons among six Ambystoma macrodactylum sequences and eight members of the Ambystoma tigrinum complex. We also found additional inserts within the intergenic spacers of five species that varied from 87-444 bp in length. The presence of the intergenic spacer in all sexual species of Ambystomatidae suggests that it arose at least 20 MYA and has been a stable component of the ambystomatid mtDNA ever since. As such, it represents one of the few examples of a large and persistent intergenic spacer in the mtDNA of any vertebrate clade.      

TNF-α is associated with loss of lean body mass only in already cachectic COPD patients

Background

Systemic inflammation may contribute to cachexia in patients with chronic obstructive pulmonary disease (COPD). In this longitudinal study we assessed the association between circulating C-reactive protein (CRP), tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-6 levels and subsequent loss of fat free mass and fat mass in more than 400 COPD patients over three years.

Methods

The patients, aged 40–76, GOLD stage II-IV, were enrolled in 2006/07, and followed annually. Fat free mass and fat mass indexes (FFMI & FMI) were calculated using bioelectrical impedance, and CRP, TNF-α, IL-1ß, and IL-6 were measured using enzyme immunoassays. Associations with mean change in FFMI and FMI of the four inflammatory plasma markers, sex, age, smoking, FEV₁, inhaled steroids, arterial hypoxemia, and Charlson comorbidity score were analyzed with linear mixed models.

Results

At baseline, only CRP was significantly (but weakly) associated with FFMI (r = 0.18, p < 0.01) and FMI (r = 0.27, p < 0.01). Univariately, higher age, lower FEV₁, and use of beta2-agonists were the only significant predictors of decline in FFMI, whereas smoking, hypoxemia, Charlson score, and use of inhaled steroids predicted increased loss in FMI. Multivariately, high levels of TNF-α (but not CRP, IL-1ß or IL-6) significantly predicted loss of FFMI, however only in patients with established cachexia at entry.

Conclusion

This study does not support the hypothesis that systemic inflammation is the cause of accelerated loss of fat free mass in COPD patients, but suggests a role for TNF-α in already cachectic COPD patients.     

Differential response of cycling and noncycling cells to inducers of DNA synthesis and mitosis

The objective of this study was to determine whether cells in G(0) phase are functionally distinct from those in G(1) with regard to their ability to respond to the inducers of DNA synthesis and to retard the cell cycle traverse of the G(2) component after fusion. Synchronized populations of HeLa cells in G(1) and human diploid fibroblasts in G(1) and G(0) phases were separately fused using UV-inactivated Sendai virus with HeLa cells prelabeled with [(3)H]ThdR and synchronized in S or G(2) phases. The kinetics of initiation of DNA synthesis in the nuclei of G(0) and G(1) cells residing in G(0)/S and G(1)/S dikaryons, respectively, were studied as a function of time after fusion. In the G(0)/G(2) and G(1)/G(2) fusions, the rate of entry into mitosis of the heterophasic binucleate cells was monitored in the presence of Colcemid. The effects of protein synthesis inhibition in the G(1) cells, and the UV irradiation of G(0) cells before fusion, on the rate of entry of the G(2) component into mitosis were also studied. The results of this study indicate that DNA synthesis can be induced in G(0)nuclei after fusion between G(0)- and S-phase cells, but G(0) nuclei are much slower than G(1) nuclei in responding to the inducers of DNA synthesis because the chromatin of G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells differ from G(1) cells with regard to their effects on the cell cycle progression of the G(2) nucleus into mitosis. This difference between G(0) and G(1) cells appears to depend on certain factors, probably nonhistone proteins, present in G(1) cells but absent in G(0) cells. These factors can be induced in G(0) cells by UV irradiation and inhibited in G(1) cells by cycloheximide treatment.     

Survival Rate and Enzyme Activities ofLactobacillus acidophilusFollowing Frozen Storage

The ability of two strains of Lactobacillus acidophilus, CRL 640 and CRL 800, to survive and retain their biological activities under frozen storage was determined. Freezing and thawing, as well as frozen storage, damaged the cell membrane, rendering the microorganisms sensitive to sodium chloride and bile salts. Both lactic acid production and proteolytic activity were depressed after 21 days at -20 degreesC, whereas beta-galactosidase activity per cell unit was increased. Cell injury was partially overcome after repair in a salt-rich medium. Copyright 1998 Academic Press.     

Viral CTL escape mutants are generated in lymph nodes and subsequently become fixed in plasma and rectal mucosa during acute SIV infection of macaques

SIV(mac239) infection of rhesus macaques (RMs) results in AIDS despite the generation of a strong antiviral cytotoxic T lymphocyte (CTL) response, possibly due to the emergence of viral escape mutants that prevent recognition of infected cells by CTLs. To determine the anatomic origin of these SIV mutants, we longitudinally assessed the presence of CTL escape variants in two MamuA*01-restricted immunodominant epitopes (Tat-SL8 and Gag-CM9) in the plasma, PBMCs, lymph nodes (LN), and rectal biopsies (RB) of fifteen SIV(mac239)-infected RMs. As expected, Gag-CM9 did not exhibit signs of escape before day 84 post infection. In contrast, Tat-SL8 escape mutants were apparent in all tissues by day 14 post infection. Interestingly LNs and plasma exhibited the highest level of escape at day 14 and day 28 post infection, respectively, with the rate of escape in the RB remaining lower throughout the acute infection. The possibility that CTL escape occurs in LNs before RBs is confirmed by the observation that the specific mutants found at high frequency in LNs at day 14 post infection became dominant at day 28 post infection in plasma, PBMC, and RB. Finally, the frequency of escape mutants in plasma at day 28 post infection correlated strongly with the level Tat-SL8-specific CD8 T cells in the LN and PBMC at day 14 post infection. These results indicate that LNs represent the primary source of CTL escape mutants during the acute phase of SIV(mac239) infection, suggesting that LNs are the main anatomic sites of virus replication and/or the tissues in which CTL pressure is most effective in selecting SIV escape variants.     

Molecular genetic diagnosis of sickle cell disease using dried blood specimens on blotters used for newborn screening

Summary The protein-based technologies used to screen newborns for sickle cell disease require confirmation with a liquid blood specimen. We have developed a strategy for rapid and specific genotypic diagnosis using DNA extracted from a dried blood spot on the filter paper blotter used to screen newborns. DNA could be microextracted from a specimen as small as a 1/8 inch diameter punched disc representing the dried equivalent of approximately 3 μl of whole blood. We utilized the DNA from a 1/4 inch diameter specimen (12 μl equivalent) for polymerase chain reaction amplification of the β-globin region spanning the sickle cell mutation with detection by allele-specific oligonucleotide probes. Molecular confirmation of genotype from the original blotter would reduce the personnel costs associated with obtaining follow-up liquid blood specimens and would provide information to the family in a more timely and less equivocal manner.     

Phytotransformation of trinitrotoluene (TNT) and distribution of metabolic products in Myriophyllum aquaticum

Dissolved [U-ring-C]2,4,6-trinitrotoluene, when exposed to Myriophyllum aquaticum plants, was transformed with approximately 30% of products recovered in the aqueous medium, regardless of incubation period. The remaining fraction was retained inside of the plant and was distributed throughout various anatomical structures. After five days of incubation the plant associated fraction became increasingly resistant to extraction with methanol. The plant associated accumulation of C was highest in roots.