End-of-life cell cycle arrest contributes to stochasticity of yeast replicative aging

There is growing evidence that stochastic events play an important role in determining individual longevity. Studies in model organisms have demonstrated that genetically identical populations maintained under apparently equivalent environmental conditions display individual variation in life span that can be modeled by the Gompertz-Makeham law of mortality. Here, we report that within genetically identical haploid and diploid wild-type populations, shorter-lived cells tend to arrest in a budded state, while cells that arrest in an unbudded state are significantly longer-lived. This relationship is particularly notable in diploid BY4743 cells, where mother cells that arrest in a budded state have a shorter mean life span (25.6 vs. 35.6) and larger coefficient of variance with respect to individual life span (0.42 vs. 0.32) than cells that arrest in an unbudded state. Mutations that cause genomic instability tend to shorten life span and increase the proportion of the population that arrest in a budded state. These observations suggest that randomly occurring damage may contribute to stochasticity during replicative aging by causing a subset of the population to terminally arrest prematurely in the S or G2 phase of the cell cycle.

Dietary restriction and mitochondrial function link replicative and chronological aging in Saccharomyces cerevisiae

Chronological aging of budding yeast cells results in a reduction in subsequent replicative life span through unknown mechanisms. Here we show that dietary restriction during chronological aging delays the reduction in subsequent replicative life span up to at least 23days of chronological age. We further show that among the viable portion of the control population aged 26days, individual cells with the lowest mitochondrial membrane potential have the longest subsequent replicative lifespan. These observations demonstrate that dietary restriction modulates a common molecular mechanism linking chronological and replicative aging in yeast and indicate a critical role for mitochondrial function in this process.

pH neutralization protects against reduction in replicative lifespan following chronological aging in yeast

Chronological and replicative aging have been studied in yeast as alternative paradigms for post-mitotic and mitotic aging, respectively. It has been known for more than a decade that cells of the S288C background aged chronologically in rich medium have reduced replicative lifespan relative to chronologically young cells. Here we report replication of this observation in the diploid BY4743 strain background. We further show that the reduction in replicative lifespan from chronological aging is accelerated when cells are chronologically aged under standard conditions in synthetic complete medium rather than rich medium. The loss of replicative potential with chronological age is attenuated by buffering the pH of the chronological aging medium to 6.0, an intervention that we have previously shown can extend chronological lifespan. These data demonstrate that extracellular acidification of the culture medium can cause intracellular damage in the chronologically aging population that is asymmetrically segregated by the mother cell to limit subsequent replicative lifespan.

Expression of erythropoietin and angiogenic growth factors following inner ear injury of newborn rats

Recently we have demonstrated that recombinant human erythropoietin (EPO) protects neurosensory hair cells in the organotypic culture of the organ of Corti by reducing apoptosis and necrosis. In the present study, we tested the hypothesis that EPO may be involved in reparative angiogenesis. We analyzed in parallel the endogenous erythropoietin (Epo) mRNA expression and that of Epo receptor (Epor) and of genes associated with angiogenesis in the organ of Corti, the modiolus and the stria vascularis using real time reverse transcription polymerase chain reaction and microarray. We compared the expression levels of freshly prepared tissue (control) and tissue cultured for 24 h under normoxia or hypoxia. The basal expression of Epo- and Epor mRNA in controls of all regions was very low. However, after 24 h in culture, a 20-100 fold increase of these two transcripts was measured. In culture, the vascular endothelial growth factor and the Cxcr4 (the receptor for the stromal cell-derived factor-1, Sdf-1) mRNA levels, were found to be increased and the Sdf-1 mRNA level to be decreased. Changes in mRNA expression occurred in all pathways activated in non-erythroid cells by the application of EPO (phosphoinositide 3-kinase/serine-threonine protein kinase B, Janus-type protein tyrosine kinase 2/signal transducer and activator of transcription 3, and the mitogen activated protein kinase). These data suggest that the neuroprotective effect of EPO may include at least two molecular events, the decrease of hair cell death rate and the induction of angiogenic genes.

Development and evaluation of a new ELISA for the detection and quantification of antierythropoietin antibodies in human sera

Assays for the analysis of antierythropoietin antibodies (anti-EPO Abs) currently suffer from a high degree of nonspecificity or are cumbersome and time consuming to perform. They are therefore not well suited for the analysis of large numbers of human sera samples, a task that has become increasingly important due to an increase in the number of patients developing anti-EPO Abs. The objective of this study was to develop and validate a sensitive and specific ELISA for the determination of anti-EPO Abs that would suit these purposes. In this new double antigen bridging ELISA, anti-EPO Abs bind via one site to recombinant human erythropoietin (rhEPO)-biotin immobilized to streptavidin-coated microtiter plates (MTPs) and by a second site to rhEPO labelled with digoxigenin (DIG). The amount of bound antibody is determined using an anti-DIG antibody coupled to peroxidase. A rabbit polyclonal anti-EPO Ab purified by immunoadsorption is used as reference antibody preparation. The dynamic range of this ELISA was 1-75 ng/ml per assay calibrated with the reference antibody preparation. The assay was specific for anti-EPO Abs and did not react with other immunoglobulins (Ig) present in human serum. The lower limit of detection (LLD) of the assay was 0.5 ng/ml, and the lower limit of quantitation (LLQ) was 1.0 ng/ml. Anti-EPO Abs could be detected in the sera of pure red cell aplasia (PRCA) patients. In contrast to previous reports, no anti-EPO Abs could be detected in the sera of patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjogren's syndrome (SS), or in the sera of dialysis patients.

Effect of a high fat diet on phospholipid class distribution and fatty acid composition in rat liver

1. Long term consumption (20 weeks) of a high fat diet (65% of the energy content as fat) rich in either saturated [30% (w/w) coconut oil] or unsaturated [30% (w/w) sunflower oil] fatty acids resulted in strikingly similar alterations in the phospholipid class distribution and fatty acid composition in the liver of male Wistar rats. 2. The effect of these two diets was compared to a control group maintained on a 2% fat diet (w/w) for the same time interval. 3. In spite of the difference in the PUFA/SFA (polyunsaturated fatty acid/saturated fatty acid) ratio between the two high fat diets (0.1, saturated fatty acid diet; 5.4, unsaturated fatty acid diet), both diets resulted in a similar PUFA/SFA ratio in liver phospholipids, a similar reduction in palmitic acid (16:0), oleic acid (18:1, n-9) and arachidonic acid (20:4, n-6) and an elevation in stearic acid (18:0), linoleic acid (18:2, n-6) and docosahexaenoic acid (22:6, n-3). 4. Further, changes in the phospholipid classes were also similarly affected by both high fat diets.

Cardiac electrophysiologic properties of bupivacaine and lidocaine compared with those of ropivacaine, a new amide local anesthetic

Ropivacaine is a new amino-amide local anesthetic whose anesthetic profile appears similar to that of bupivacaine. Moreover, in intact animals ropivacaine was reportedly less arrhythmogenic than bupivacaine. These experiments evaluated the cardiac transmembrane electrophysiologic effects of ropivacaine compared with those of lidocaine and bupivacaine in an isolated rabbit Purkinje fiberventricular muscle preparation. Only bupivacaine (3-5 micrograms/ml, 0.92-1.5 x 10(-5) m) significantly decreased Purkinje fiber maximum diastolic potential. Action potential amplitude and maximal rate of depolarization (Vmax) were significantly decreased by all agents in the following order: bupivacaine, ropivacaine, lidocaine. High concentrations of bupivacaine and ropivacaine caused premature depolarizations during phase 3 in some preparations. In addition, bupivacaine altered the action potential configuration by producing "notching" not seen with either ropivacaine or lidocaine. This may reflect effects caused by changes in Ca2+, K+, or electrotonic effects. Ropivacaine and bupivacaine (30 micrograms/ml, 9.2 x 10(-5) m) and lidocaine (100 micrograms/ml, 3.74 x 10(-4) m) caused Purkinje fiber inexcitability and Purkinje fiber-ventricular muscle conduction block. However, the duration of PF inexcitability following exposure to ropivacaine and lidocaine was significantly shorter than in bupivacaine-treated preparation. Duration of PF-VM conduction block also tended to be shorter for ropivacaine than bupivacaine, but significantly longer than lidocaine. In general, ropivacaine is less potent than bupivacaine but more potent than lidocaine in terms of its depressant effect on cardiac excitation and conduction.

Symptomatic radiation-induced pericarditis in Hodgkin's disease

This is a retrospective review of 193 evaluable patients treated with radiation therapy to the mediastinum for Stages I, II and III-A Hodgkin's disease. Eligible patients were those receiving 3000 rad or more to the mediastinum and no chemotherapy prior to the radiation. During the study period, 13 patients developed symptomatic pericarditis. The interval post treatment to the development of symptoms was six to 34 months. The incidence of pericarditis was studied as a function of: (1) the dose of radiation at a depth of 2 cm, 5 cm and the midplane of the mediastinum; (2) the ratio of anterior to posterior weighting of dose; (3) the presence or absence of intrathoracic tumor; (4) the size of the tumor when present; and (5) the fraction of the heart exposed to the radiation beam. There was a significant increase in the incidence of pericarditis with an increased dose of radiation at 2 cm, 5 cm and midplane depths and also with the presence of a large intrathoracic tumor. A reduction in mediastinal dose is recommended.

Antiarrhythmic effects of tocainide and lidocaine in dogs

To compare the antiarrhythmic activities of tocainide and lidocaine in dogs, a protocol was designed where the drug plasma levels were increased stepwise. This was achieved by computerizing bolus doses and infusion rates, using pharmacokinetic equations with constants, derived from previous experiments in similar animals. In conscious coronary-ligated dogs with ischaemic arrhythmias both compounds were active, causing a 50% reduction in VPB's at plasma concentrations of 5.0 micrograms/ml (tocainide) and 3.5 micrograms/ml (lidocaine). "Clearing" of catecholamine-induced arrhythmias was not obtained in any of six dogs given tocainide and only in two out of six dogs given lidocaine.

Influence of drugs on the bilirubin UDP-glucuronyltransferase activity and the concentration of Y and Z acceptor proteins in rat liver

The aim of this paper is to report on the influence of phenobarbital, the combination of phenobarbital/nikethamide, the racemate and (+) isomer of methylphenobarbital on the activity of bilirubin UDP-glucuronyltransferase and the concentration of intrahepatic Y and Z protein in rats. The activity of bilirubin DP-glucuronyltransferase increased after the treatment in all groups. Pretreatment with phenobarbital/nikethamide resulted in the highest enzyme activity, using wet weight as reference. (+) Methylphenobarbital isomer as well as the racemate showed effects similar to those of phenobarbital. The concentration of hepatic Y acceptor protein increased in all pretreated groups by about 30%. The drugs did not increase the concentration of Z protein. The (+) isomer of methylphenobarbital seems better suited as an inductive drug in the prophylaxis of hyperbilirubinemia and in the treatment of nonconjugated hyperbilirubinemia than phenobarbital or phenobarbital/nikethamide since it has no sedative effect.

Relationship between arsenic intake and internal malignant neoplasms

An attempt has been made to assess the carcinogenic effect of arsenic intake by analyzing a group of patients who were treated with arsenic for various skin diseases in the 1930s. When compared with the expected incidence of malignant internal neoplasms, based on figures obtained from the Danish Cancer Registry, a significant increase in the incidence of internal malignant neoplasms was observed in females with multiple basal cell carcinomas. A group comprising 53 patients with arsenic keratoses presented a considerable increase in the incidence of internal malignant neoplasms. However, these patients were so specifically selected that no regular statistical analysis can be made of this group. It may be said that arsenic has a carcinogenic effect even in the relatively small doses applied in dermatological therapy.

Gentamicin-induced nephropathy

162 consecutive gentamicin courses have been evaluated retrospectively with respect to nephrotoxicity of gentamicin (GM). Of these, 120 courses were administered in 106 patients for more than 2 days and under adequate control of plasma creatinine (PCr). In 62 of these 120 courses, PCr concentrations increased. In 17 courses (14%), GM therapy was found to be the only demonstrable etiology to the rise in PCr. The 17 courses with GM-induced reduction in kidney function were characterized by a prolonged duration of treatment, a high total dose of GM and a somewhat higher level of serum GM than the 58 courses of GM treatment in which PCr remained unchanged. No significant differences were found with regard to age, average daily dose of GM, average daily dose per kg and average daily dose in proportion to average diuresis. Additional administration of other nephrotoxic drugs did not increase the incidence of GM-induced nephropathy. When GM was the only demonstrable cause of nephropathy, the elevation in PCr concentrations were generally mild and transient, while the nephropathy when other factors were involved more often became severe and occasionally irreversible.