Manganese cycling in an acidic Adirondack lake

There is considerable interest in the chemistry of Mn in acidic waters because of its role in the generation of acid neutralizing capacity during reduction processes, as an adsorbent in element cycling, and as a potential toxicant to aquatic organisms. Temporal and spatial variations in the concentration of Mn were evident in acidic Dart's Lake (1.0–2.3 mol l^–1), located in the Adirondack Region of New York. Seasonal changes in pH and dissolved oxygen concentration had subtle effects on the chemistry and transport of Mn. Despite oversaturation with respect to the solubility of manganite during periods of stratification, vertical deposition of Mn was minimal. The conservative nature of Mn appears to be due to the acidic conditions in Dart's Lake.     

Purification of bovine liver histidyl-tRNA synthetase, the Jo-1 antigen of polymyositis: size of the whole enzyme and its characteristic proteolytic fragments

We have recently reported the marked increase in frequency which can be achieved in the detection of the anti-Jo-1 antibody of polymyositis in serum samples by replacing commercial mixtures of cytoplasmic and nuclear antigens with the purified antigen, histidyl-tRNA synthetase. The present paper describes a method for purifying this antigen and an investigation of its size. Molecular masses previously reported for the enzyme have varied from 85-154 kDa and subunit molecular masses varying from 40-77 kDa have been observed. Several of these fragments are of sizes similar to those of a number of other autoantigens commonly observed in connective tissue diseases. Since the clinical identification of these autoantigens often relies exclusively on size determination by Western blotting, we have characterized the commonly occurring fragments of histidyl-tRNA synthetase lest they confuse such identification. It is concluded that histidyl-tRNA synthetase, like many other aminoacyl-tRNA synthetases, is subject to severe proteolysis during extraction procedures. Several characteristic fragments (Mr = 80, 75, 61, 55, 50 and 45 kDa) result, a finding that provides a satisfactory explanation of the various values previously reported. The intact bovine enzyme is a dimer of molecular mass close to 160 kDa.     

The cis-acting DNA sequences required in vivo for bacteriophage Mu helper-mediated transposition and packaging

The 37,000 bp double-stranded DNA genome of bacteriophage Mu behaves as a plaque-forming transposable element of Escherichia coli. We have defined the cis-acting DNA sequences required in vivo for transposition and packaging of the viral genome by monitoring the transposition and maturation of Mu DNA-containing pSC101 and pBR322 plasmids with an induced helper Mu prophage to provide the trans-acting functions. We found that nucleotides 1 to 54 of the Mu left end define an essential domain for transposition, and that sequences between nucleotides 126 and 203, and between 203 and 1,699, define two auxiliary domains that stimulate transposition in vivo. At the right extremity, the essential sequences for transposition require not more than the first 62 base pairs (bp), although the presence of sequences between 63 and 117 bp from the right end increases the transposition frequency about 15-fold in our system. Finally, we have delineated the pac recognition site for DNA maturation to nucleotides 32 to 54 of the Mu left end which reside inside of the first transposase binding site (L1) located between nucleotides 1–30. Thus, the transposase binding site and packaging domains of bacteriophage Mu DNA can be separated into two well-defined regions which do not appear to overlap.Abbreviations attL attachment site left - attR attachment site right - bp base pairs - Kb kilobase pair - nt nucleotide - Pu Purine - Py pyrimidine - Tn transposable element State University of New York, Downstate Medical Center, Brooklyn, NY 11204 USA     

Keratin polypeptide expression in mouse epidermis and cultured epidermal cells

Adult mouse epidermis contains up to 11 distinct keratin polypeptides, as resolved by two-dimensional gel electrophoresis. These include both basic (Type II; 67-, 65-, 63-, 62-, and 60-kDa) and acidic (Type I; 61- to 59-, 54-, 52-, 49-, and 48-kDa) keratins that exhibit multiple isoelectric forms. Several, but not all, of these keratins, identified by immunoblotting, were found to be actively synthesized in the skin when assayed in short-term pulse-labeling experiments. When compared to the adult, newborn mouse epidermis expresses fewer keratin subunits. However, greater amounts of keratins associated with differentiated suprabasal cells and stratum corneum, which is more pronounced morphologically in the newborn, were identified. We also observed strain-specific differences in the expression of a Type I acidic keratin. This 61-kDa (pI, approx. 5.3) keratin was produced exclusively by the CF-1 mouse and, based on peptide mapping, appeared to be related to the acidic 59-kDa keratin that was identified in this strain as well as all other mouse strains. The 61-kDa keratin was not expressed in vitamin A-deficient animals, suggesting that its appearance may be related to a retinoid-dependent posttranslational modification. In comparison to keratin expression in vivo, primary mouse keratinocyte monolayer cultures maintained in low Ca2+ (less than 0.08 mM) did not express the terminal differentiation keratins of 67-kDa (basic) or 59-kDa (acidic), although enhanced synthesis of the 60-kDa (basic) and the 52-kDa and 59-kDa (acidic) keratins associated with proliferation were observed. In addition, a subpopulation of nonadherent cells was continuously produced by the primary keratinocyte cultures that expressed the 67-kDa (basic) keratin specific for terminal differentiation. When the keratinocyte cultures were induced to terminally differentiate with Ca2+, the overall pattern of keratin expression was not changed significantly. Taken together, these results provide further evidence for the variable nature of keratin expression in mouse epidermal keratinocytes under different growth conditions.     

Surface EMG recordings and pain-related disorders: A diagnostic framework

Surface electromyography provides a very valuable set of information when used diagnostically with pain-related disorders. Unfortunately, most researchers and clinicians limit their investigation to only one level of diagnostic information available concerning the neuromuscular system. This article develops and encourages the clinician/researcher to consider three levels of diagnostic information: emotional, organ-related, and postural aspects. The theoretical background and diagnostic procedures used to investigate each is presented. Differential treatment considerations, given differential diagnostic findings, are discussed.     

Persistence of community structure: what happens when you change taxonomic scale?

It is common in community ecology to use the species as the taxonomic category of interest, yet in rich tropical assemblages containing guilds of very similar species this may not be appropriate. Such assemblages may be organized at the level of guilds rather than at the finer species level. In a ten-year study of assemblages of fish at One Tree Reef, Great Barrier Reef, we found species composition and the number of fish on a given lagoonal patch reef vary greatly across time (Sale and Douglas 1984; Sale et al. in preparation). The mean average proportional similarity of a reef's assemblage to itself at different times (censuses) is usually low at a value of around 0.5. This apparent variability may be ecologically irrelevant noise if organization is at the higher guild level. We have recast our database at the guild level to test this possibility. Thirteen guilds were defined by the diets, foraging habitats and times of the individual species comprising them. Similarity of an assemblage to itself at successive censuses was re-calculated using the number of individuals in each guild instead of the numbers in each species. This analysis yielded significantly higher levels of similarity (P<0.01) among censuses. To test whether this increase in similarity was due solely to the smaller number of categories used to calculate the similarity indices, 5 sets of randomly generated guilds were constructed using a Monte Carlo approach. No significant difference (P>0.05) was found between the average similarity among censuses when assemblages were classified into these null guilds and when they were classified according to the real guilds. These results indicate that shifting to the larger taxonomic scale of guilds does not reveal a significantly more persistent assemblage structure than that revealed when analysis is at the smaller scale of species. There is no evidence of an underlying organization of these assemblages at the guild level.     

Characterization of endogenous and recombinant proviral elements of a highly tumorigenic AKR cell line

As an approach to evaluating the contribution of classes of endogenous viral sequences to leukemogenesis, a genomic library was prepared from the highly tumorigenic AKR SL12.3 cell line and screened for env-containing proviruses. An extensive battery of virus-derived probes and specific oligonucleotide probes were used to segregate 83 positive clones into related groups. The nonecotropic endogenous retroviruses were identified as members of the polytropic, modified polytropic, or xenotropic groups. At least three unique xenotropic proviruses were detected that differed from the published xenotropic sequence within a variable region of the 5' portion of env. Changes among the xenotropic proviruses included relative insertions and/or deletions that maintain an open reading frame and hence the potential to encode viable envelope gene products. Several recombinant viruses were also detected. Recombination was not random and primarily involved the formation of mink cell focus-inducing class I retroviruses via recombination between polytropic elements and ecotropic virus. One other recombinant was detected which contained ecotropic virus sequences in the 5' region encoding p15 of an otherwise xenotropic provirus. An interesting observation was the finding that certain clones contained more than one provirus within the average 20-kb cloned insert. This would not be expected if integration were totally random. The de novo recombinant proviruses identified here provide a series of potential candidates to be evaluated for their contribution to the tumorigencity of the SL12.3 cell line.     

Biologic markers in ethylene oxide-exposed workers and controls

Ethylene oxide (EtO) is an alkylating agent and a model direct-acting mutagen and carcinogen. This study has evaluated a panel of biologic markers including EtO-hemoglobin adducts (EtO-Hb), sister-chromatid exchanges (SCEs), micronuclei, chromosomal aberrations (CAs), DNA single-strand breaks (SSB) and an index of DNA repair (ratio of UDS to NA-AAF-DNA binding) in the peripheral blood cells of 34 workers at a sterilization unit of a large university hospital and 23 controls working in the university library. Comprehensive environmental histories were obtained on each subject including detailed occupational and smoking histories. Industrial hygiene data obtained prior to the study and personal monitoring during the 8 years preceding the study showed that workers were subject to low-level exposure near or below the current Occupational Safety and Health Administration (OSHA) standard of 1 ppm (TWA). Personal monitoring data obtained during 2 weeks prior to blood sampling were uniformly less than 0.3 ppm (TWA). After adjusting for smoking, EtO workplace exposure was significantly (p less than 0.001) associated with EtO-Hb (a carcinogen-protein adduct) and 2 measures of SCEs [the average number of SCEs/cell (SCE50) and the number of high frequency cells (SCEHFC)]. There was an apparent suppression of DNA repair capacity in EtO-exposed individuals as measured by the DNA repair index; i.e., the ratio of unscheduled DNA synthesis (UDS) and NA-AAF-DNA binding (p less than 0.01). No association of DNA repair index with smoking was found. Another important finding of this study is the highly significant correlation between EtO-Hb adduct levels and SCEHFC (p less than 0.01) and SCEs (p less than 0.02) which provides evidence of a direct link between a marker of biologically effective dose and markers of genotoxic response. In contrast, micronuclei, CAs and SSBs were not significantly elevated in the workers. The activity of the u-isoenzyme of glutathione-S-transferase (GT) was measured as a possible genetic marker of susceptibility and a modulator of biomarker formation. However, possibly because of confounding by age, no significant relationships were found between GT and any of the exposure-related markers by ANOVA or among other independent variables by regression. This study demonstrates significant effects of low-level EtO exposure, independent of smoking history, near or below 1 ppm on multiple biomarkers and suggests that the current OSHA standard may not be adequately protective. Previously described effects of smoking on EtO-Hb adducts, SCEs and SCEHFC were also seen in this study.(ABSTRACT TRUNCATED AT 400 WORDS)