Effects of age,replicative lifespan and growth rate of human nucleus pulposus cells on selecting age range for cell-based biological therapies for degenerative disc diseases

Autologous disc cell implantation, growth factors and gene therapy appear to be promising therapies for disc regeneration. Unfortunately, the replicative lifespan and growth kinetics of human nucleus pulposus (NP) cells related to host age are unclear. We investigated the potential relations among age, replicative lifespan and growth rate of NP cells, and determined the age range that is suitable for cell-based biological therapies for degenerative disc diseases. We used NP tissues classified by decade into five age groups: 30s, 40s, 50s, 60s and 70s. The mean cumulative population doubling level (PDL) and population doubling rate (PDR) of NP cells were assessed by decade. We also investigated correlations between cumulative PDL and age, and between PDR and age. The mean cumulative PDL and PDR decreased significantly in patients in their 60s. The mean cumulative PDL and PDR in the younger groups (30s, 40s and 50s) were significantly higher than those in the older groups (60s and 70s). There also were significant negative correlations between cumulative PDL and age, and between PDR and age. We found that the replicative lifespan and growth rate of human NP cells decreased with age. The replicative potential of NP cells decreased significantly in patients 60 years old and older. Young individuals less than 60 years old may be suitable candidates for NP cell-based biological therapies for treating degenerative disc diseases.     

Expression of ATP6V1C1 during oral carcinogenesis

We investigated the gene and protein expressions of V-type ATPase protein subunit C1 (ATP6V1C1) in cases of oral squamous cell carcinoma (OSCC) and contralateral normal mucosa in smokers, nonsmokers and former smokers. Subjects were separated into five groups of 15: group 1, smokers with OSCC; group 2, normal contralateral mucosa of OSCC patients; group 3, chronic smokers; group 4, former smokers who had stopped smoking 1 year earlier; group 5, individuals who had never smoked. Exfoliative cytology specimens from oral mucosa of smokers, former smokers and nonsmokers showed normal gene and protein expression. We found significantly greater gene expression in the OSCC group than in the nonsmoker groups. No difference in gene expression was observed between normal contralateral mucosa and nonsmoker groups, smoker and nonsmoker groups or former smoker and nonsmoker groups. We observed intense immunostaining for ATP6V1C1 protein in all cases of OSCC and weak or no staining in smoker, former smoker and nonsmoker groups. Significantly greater expression of ATP6V1C1 protein was observed in the OSCC group compared to the other groups, which supports the role of ATP6V1C1 in effecting changes associated with oral cancer. Analysis of the mucosae of chronic smokers, former smokers and the normal contralateral mucosa of patients with OSCC showed unaltered ATP6V1C1 gene and protein expression. Early stages of carcinogenesis, represented by altered epithelium of chronic smokers, had neither gene nor protein alterations as seen in OSCC. Therefore, we infer that the changes in ATP6V1C1 occur during later stages of carcinogenesis. Our preliminary study provides a basis for future studies of using ATP6V1C1 levels for detecting early stage OSCC.     

The phosphoenolpyruvate-dependent fructose-specific phosphotransferase system in Rhodopseudomonas sphaeroides. EIIFru possesses a Zn2+-binding site and a dithiol/disulfide redox centre

Two interrelated sites have been detected on the fructose carrier in Rhodopseudomonas sphaeroides: an activity-linked dithiol and a Zn2+-binding site. Binding of Zn2+ brings EIIFru into a new conformation that to some extent mimics the conformation of phosphorylated EIIFru, an essential intermediate in the turnover of the enzyme. Binding of zinc to EIIFru or phosphorylating the enzyme protects it against trypsin inactivation relative to the dephosphorylated zinc-free enzyme. A dithiol is essential for activity. Interchanges between the redox states of the enzyme can be brought about by dithiothreitol and ferricyanide, but not, or very slowly, by molecular oxygen. The dithiol is protected, in the EIIFru-Zn2+ complex, against alkylation by MalNEt, reversible oxidation by Fe(CN)6(3-) and Cu2+, irreversible oxidation by Cu2+. The pK value of the activity linked thiol is 7.8. Protection experiments show that the dithiol is not located in any of the substrate-binding sites. The redox state of the enzyme does not influence the rate of inactivation of EIIFru by trypsin.     

Evidence from nuclear sequences that invariable sites should be considered when sequence divergence is calculated

It has long been known, from the distribution of multiple amino acid replacements, that not all amino acids of a sequence are replaceable. More recently, the phenomenon was observed at the nucleotide level in mitochondrial DNA even after allowing for different rates of transition and transversion substitutions. We have extended the search to globin gene sequences from various organisms, with the following results: (1) Nearly every data set showed evidence of invariable nucleotide positions. (2) In all data sets, substitution rates of transversions and transitions were never in the ratio of 2/1, and rarely was the ratio even constant. (3) Only rarely (e.g., the third codon position of beta hemoglobins) was it possible to fit the data set solely by making allowance for the number of invariable positions and for the relative rates of transversion and transition substitutions. (4) For one data set (the second codon position of beta hemoglobins) we were able to simulate the observed data by making the allowance in (3) and having the set of covariotides (concomitantly variable nucleotides) be small in number and be turned over in a stochastic manner with a probability that was appreciable. (5) The fit in the latter case suggests, if the assumptions are correct and at all common, that current procedures for estimating the total number of nucleotide substitutions in two genes since their divergence from their common ancestor could be low by as much as an order of magnitude. (6) The fact that only a small fraction of the nucleotide positions differ is no guarantee that one is not seriously underestimating the total amount of divergence (substitutions). (7) Most data sets are so heterogeneous in their number of transition and transversion differences that none of the current models of nucleotide substitution seem to fit them even after (a) segregation of coding from noncoding sequences and (b) splitting of the codon into three subsets by codon position. (8) These frequently occurring problems cannot be seen unless several reasonably divergent orthologous genes are examined together.      

Enzyme Basis for pH Regulation of Citrate and Pyruvate Metabolism by Leuconostoc oenos

Citrate and pyruvate metabolism by nongrowing cells of Leuconostoc oenos was investigated. (sup13)C nuclear magnetic resonance (NMR) spectroscopy was used to elucidate the pathway of citrate breakdown and to probe citrate or pyruvate utilization, noninvasively, in living cell suspensions. The utilization of isotopically enriched substrates allowed us to account for the end products derived from the metabolism of endogenous reserves. The effect of environmental parameters, e.g., pH, gas atmosphere, and presence of malate, on the end products of citrate utilization was studied. Approximately 10% of the citrate supplied was converted to aspartate which remained inside the cells. A metabolic shift with pH was observed, with acetoin production being favored at pH 4, whereas lactate and acetate production increased significantly at higher pH values. The information obtained with NMR was complemented with studies on the relevant enzyme activities in the metabolic pathway of citrate breakdown. The intracellular pH of the cells was strongly dependent on the external pH; this result, together with the determination of the pH profile of the enzymic activities, allowed us to establish the basis for pH regulation; lactate dehydrogenase activity was optimal at pH 7, whereas the acetoin-forming enzymes displayed maximal activities below pH 5. Citrate utilization was also monitored in dilute cell suspensions for comparison with NMR experiments performed with dense suspensions.     

Secondary transporters for citrate and the Mg(2+)-citrate complex in Bacillus subtilis are homologous proteins.

Citrate uptake in Bacillus subtilis is mediated by a secondary transporter that transports the complex of citrate and divalent metal ions. The gene coding for the transporter termed CitM was cloned, sequenced, and functionally expressed in Escherichia coli. Translation of the base sequence to the primary sequence revealed a transporter that is not homologous to any known secondary transporter. However, CitM shares 60% sequence identity with the gene product of open reading frame N15CR that is on the genome of B. subtilis and for which no function is known. The hydropathy profiles of the primary sequences of CitM and the unknown gene product are very similar, and secondary structure prediction algorithms predict 12 transmembrane-spanning segments for both proteins. Open reading frame N15CR was cloned and expressed in E. coli and was shown to be a citrate transporter as well. The transporter is termed CitH. A remarkable difference between the two transporters is that citrate uptake by CitM is stimulated by the presence of Mg2+ ions, while citrate uptake by CitH is inhibited by Mg2+. It is concluded that the substrate of CitM is the Mg(2+)-citrate complex and that CitH transports the free citrate anion. Uptake experiments in right-side-out membrane vesicles derived from E. coli cells expressing either CitM or CitH showed that both transporters catalyze electrogenic proton/substrate symport.     

Interaction between a copper-tolerant and a copper-sensitive population of Silene cucubalus

Interactions between copper-tolerant and copper-sensitive plants of Silene cucubalus (L.) Wib. were absent when grown in mixed culture in a nutrient solution with a normal Cu²⁺ concentration (0.5 μ M ). When grown in mixed culture in a nutrient solution with 40.5 μ M CuSO₄, however, the biomass production of the sensitive plants was less affected than when grown in monoculture. At 40.5 μ M Cu²⁺, in the presence of tolerant plants, the concentration of copper in both roots and shoots of sensitive plants was significantly diminished in comparison to a monoculture without tolerant plants. At the same time the copper concentration in the roots of the tolerant plants was higher in the presence of sensitive plants. The possibility of external detoxification of the copper by tolerant plants as a mechanism of heavy metal resistance is discussed.     

Bayesian adaptive sequence alignment algorithms

The selection of a scoring matrix and gap penalty parameters continues to be an important problem in sequence alignment. We describe here an algorithm, the 'Bayes block aligner, which bypasses this requirement. Instead of requiring a fixed set of parameter settings, this algorithm returns the Bayesian posterior probability for the number of gaps and for the scoring matrices in any series of interest. Furthermore, instead of returning the single best alignment for the chosen parameter settings, this algorithm returns the posterior distribution of all alignments considering the full range of gapping and scoring matrices selected, weighing each in proportion to its probability based on the data. We compared the Bayes aligner with the popular Smith-Waterman algorithm with parameter settings from the literature which had been optimized for the identification of structural neighbors, and found that the Bayes aligner correctly identified more structural neighbors. In a detailed examination of the alignment of a pair of kinase and a pair of GTPase sequences, we illustrate the algorithm's potential to identify subsequences that are conserved to different degrees. In addition, this example shows that the Bayes aligner returns an alignment-free assessment of the distance between a pair of sequences.      

Histamine-Producing Pathway Encoded on an Unstable Plasmid in Lactobacillus hilgardii 0006

Histamine production from histidine in fermented food products by lactic acid bacteria results in food spoilage and is harmful to consumers. We have isolated a histamine-producing lactic acid bacterium, Lactobacillus hilgardii strain IOEB 0006, which could retain or lose the ability to produce histamine depending on culture conditions. The hdcA gene, coding for the histidine decarboxylase of L. hilgardii IOEB 0006, was located on an 80-kb plasmid that proved to be unstable. Sequencing of the hdcA locus disclosed a four-gene cluster encoding the histidine decarboxylase, a protein of unknown function, a histidyl-tRNA synthetase, and a protein, which we named HdcP, showing similarities to integral membrane transporters driving substrate/product exchange. The gene coding for HdcP was cloned downstream of a sequence specifying a histidine tag and expressed in Lactococcus lactis. The recombinant HdcP could drive the uptake of histidine into the cell and the exchange of histidine and histamine. The combination of HdcP and the histidine decarboxylase forms a typical bacterial decarboxylation pathway that may generate metabolic energy or be involved in the acid stress response. Analyses of sequences present in databases suggest that the other two proteins have dispensable functions. These results describe for the first time the genes encoding a histamine-producing pathway and provide clues to the parsimonious distribution and the instability of histamine-producing lactic acid bacteria.