Cell cycle features of primate embryonic stem cells

Using flow cytometry measurements combined with quantitative analysis of cell cycle kinetics, we show that rhesus monkey embryonic stem cells (ESCs) are characterized by an extremely rapid transit through the G1 phase, which accounts for 15% of the total cell cycle duration. Monkey ESCs exhibit a non-phasic expression of cyclin E, which is detected during all phases of the cell cycle, and do not growth-arrest in G1 after gamma-irradiation, reflecting the absence of a G1 checkpoint. Serum deprivation or pharmacological inhibition of mitogen-activated protein kinase kinase (MEK) did not result in any alteration in the cell cycle distribution, indicating that ESC growth does not rely on mitogenic signals transduced by the Ras/Raf/MEK pathway. Taken together, these data indicate that rhesus monkey ESCs, like their murine counterparts, exhibit unusual cell cycle features in which cell cycle control mechanisms operating during the G1 phase are reduced or absent.     

Synergetic interactions between rehabilitation and pharmacotherapy in COPD

BACKGROUND: Once viewed as an irreversible condition, chronic obstructive pulmonary disease (COPD) is now considered as a preventable and treatable disease. The past ten years of research have clearly indicate that dyspnea, exercise tolerance and quality of life can be improved considerably with appropriate therapeutic interventions that include pharmacological and non-pharmacological components. It is also becoming evident that it is the concomitant use of appropriate pharmacotherapy and non-pharmacological approaches, such as exercise training and pulmonary rehabilitation, that offers the best hope for an optimal status. PURPOSE: The objective of this short paper is to review the rationale of combining pharmacological and non-pharmacological therapeutic approaches to optimize functional status and quality of life in patients with COPD. PRINCIPAL FINDINGS: Optimal bronchodilation is the mainstay of treatment. Leg fatigue will prevent patients with COPD from obtaining full advantage of bronchodilation. Quadriceps fatigue during cycling exercise is linked to events taking place within the muscle providing a muscular and metabolic basis to explain the observation that some patients with COPD develop contractile fatigue after exercise. Muscle fatigue can be improved with exercise training. Pharmacotherapy and exercise training offer the best hope for an optimal status in COPD. CONCLUSION: Our goals are to stimulate interest in COPD, provide a strong case against the nihilistic approach to this disease to ultimately raise the standard of care to the benefit of the numerous patients afflicted by this condition.     

High redox thioredoxin but low thioredoxin reductase activities in the serum of patients with rheumatoid arthritis

BACKGROUND: Thioredoxin (Trx)/thioredoxin reductase (TrxR) is a redox-active system induced by oxidative stress. We investigated its status as a function of RA disease activity. METHODS: 64 consecutive RA patients and 27 healthy subjects were enrolled in the study. Serum Trx protein levels were evaluated using an immunoassay and immunoblot, while redox Trx and TrxR activities and oxidative stress markers (carbonyl groups, thiols), were determined using spectrophotometric methods. RESULTS: Redox Trx activity and Trx protein concentrations were significantly higher in RA patients than in controls (redox Trx activity: 37.7+/-22.6 versus 21.1+/-7.9 ng/mL, p<0.01; Trx protein: 25.5+/-12.0 versus 12.3+/-5.1 ng/mL, p<0.0001). Redox Trx activity correlated with the DAS score (r=0.45, p=0.004) and with the tender joint count (r=0.49, p=0.002) whereas there was no correlation with Trx protein concentrations. Immunoblot analysis showed that circulating Trx was partially aggregated. TrxR activity was lower in the serum of RA patients than in healthy subjects (197+/-70 versus 263+/-56 U/L, p=0.002). TrxR activity was correlated with the DAS score (r=0.53, p<0.001) and with the tender joint count (r=0.36, p<0.01). There were no correlations between oxidative stress marker levels and redox Trx activity, Trx protein concentrations or TrxR activity. CONCLUSION: Redox Trx and TrxR activities correlated with the disease activity of RA patients consistent with the hypothesis that Trx/TrxR activities may contribute to disease activity in RA.     

Autologous myoblast transplantation after myocardial infarction increases the inducibility of ventricular arrhythmias

BACKGROUND: Small scale clinical trials suggested the feasibility and the efficacy of autologous myoblast transplantation to improve ventricular function after myocardial infarction. However, these trials were hampered by unexpected episodes of life-threatening ventricular tachyarrhythmias (VT). We investigated cardiac electrical stability after myoblast transplantation to the myocardium. METHODS AND RESULTS: Seven days after coronary ligation, Wistar rats were randomized into 3 groups: a control group receiving no further treatment, a vehicle group injected with culture medium into the infarcted myocardium, and a myoblast group injected with autologous myoblasts. Holter monitoring did not discriminate the myoblast from the vehicle groups. Programmed Electrical Stimulation (PES) was performed to evaluate further a cardiac substrate for arrhythmia susceptibility. The occurrence of sustained VT during PES was similar in control and vehicle groups (5/17 and 4/19 rats, respectively; p=0.50). In contrast, 13/20 rats (65%) from the myoblast group showed at least one episode of sustained VT during PES (p<0.05 and p<0.005 versus control and vehicle groups). As a further control group, rats injected with autologous bone marrow mononuclear cells into the infarcted myocardium did not show increased susceptibility to PES. CONCLUSIONS: In an infarcted rat model, myoblast transplantation but not bone marrow mononuclear cells or myocardial injection per se induces electrical ventricular instability. Because ventricular arrhythmias are life-threatening disorders, we suggest that such preclinical evaluation should be conducted for any new source of cells to be injected into the myocardium.     

Characterization of insulin secretion and resistance in type 2 diabetes of adolescents

CONTEXT: Type 2 diabetes (T2D) in obese children is an emerging problem, including in Europe. Its presentation at diagnosis very often differs from that in adults. OBJECTIVE: The objective of this study was to investigate the relative contributions of the two components of T2D, insulin resistance and insulin secretion, early in the history of the disease in adolescents. PATIENTS AND METHODS: Six obese adolescents with T2D were included 2 months to 4.3 yr after diagnosis (five girls and one boy; median age, 15.4 yr; median body mass index, 4.4 sd). Peripheral and hepatic insulin sensitivity was evaluated with euglycemic hyperinsulinemic (40 mU/m(2).min) clamp. First-phase insulin release was evaluated after iv glucose stimulation. A graded iv glucose infusion and an arginine test were performed to measure insulin secretion. RESULTS: All patients showed decreased peripheral glucose uptake to the same extent. Five patients showed hepatic insulin resistance. First-phase insulin release was very low in two patients. Three patients showed an exaggerated insulin response under graded glucose infusion and preserved secretion under arginine stimulation. Three other patients, with elevated fasting plasma glucose levels, demonstrated a very low insulin response under glucose stimulation and a low insulin response under arginine stimulation. CONCLUSIONS: These data emphasize that together with marked insulin resistance, the failure of beta-cell function is a major component in the course of T2D in childhood.     

Experimentally infected human body lice (pediculus humanus humanus) as vectors of Rickettsia rickettsii and Rickettsia conorii in a rabbit model

The human body louse, the natural vector of Rickettsia prowazekii, is able to experimentally transmit the normally flea-borne rickettsia R. typhi, suggesting that the relationships between the body louse and rickettsiae are not specific. We used our experimental infection model to test the ability of body lice to transmit two prevalent tick-borne rickettsiae. Each of two rabbits was made bacteremic by injecting intravenously 2 x 10(6) plaque-forming units of either R. rickettsii or R. conorii. Four hundred body lice were infected by feeding on the bacteremic rabbit and were compared with 400 uninfected lice. Each louse group was fed once a day on a separate seronegative rabbit. The survival of infected lice was not different from that of uninfected controls. Lice remained infected for their lifespan, excreted R. rickettsii and R. conorii in their feces, but did not transmit the infection to their progeny. The nurse rabbit of uninfected lice remained asymptomatic and seronegative. Those rabbits used to feed infected lice developed bacteremia and seroconverted. Although the body louse is not a known vector of spotted fevers, it was able in our study to acquire, maintain, and transmit both R. rickettsii and R. conorii.     

Thyrotropin stimulates the generation of inositol 1,4,5-trisphosphate in human thyroid cells

CONTEXT: Dual activation by TSH of the phospholipase C and cAMP cascades has been reported in human thyroid cells. In contrast, Singh et al. reported convincing data in FRTL-5 thyrocytes arguing against such an effect in this model. Their data in FRTL-5 cells indicated no increase in inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] in response to TSH. Therefore, the authors questioned results previously obtained on human cells by cruder methodology. OBJECTIVE: We investigated the formation of inositol phosphates by HPLC techniques in human thyroid slices to separate the inositol phosphate isomers. RESULTS: Ins(1,4,5)P3, inositol 1,3,4-trisphosphate, and inositol 1,3,4,5-tetrakisphosphate were increased after TSH stimulation. The effect of TSH in human thyroid cells was reproduced by recombinant TSH and prevented by antibodies blocking the TSH receptor. Thyroid-stimulating antibodies at concentrations eliciting a cAMP response equivalent to TSH failed to stimulate inositol phosphate generation. CONCLUSIONS: TSH, but not thyroid-stimulating antibodies, activates both cAMP and the phospholipase C cascade in human thyroid as now demonstrated by an increase in Ins(1,4,5)P3 and its inositol phosphate metabolites. Therefore, this effect cannot be extrapolated to the FRTL-5 cell line. The apparent discrepancy may be due to a difference between species (human vs. rat) or to the loss of the fresh tissue properties in a cell line. The dual effect of TSH in human cells, through cAMP on secretion of thyroid hormones and through the diacylglycerol, Ins(1,4,5)P3 Ca2+ pathway on thyroid hormone synthesis, implies the possible separation of these effects in thyroid disease.     

Antiangiogenic effect of erythromycin: an in vitro model of Bartonella quintana infection

BACKGROUND: Bartonella quintana, the etiological agent of bacillary angiomatosis (BA), causes endothelial cell proliferation. Erythromycin has dramatic effects on BA, and the effects are largely unexplained by the compound's bacteriostatic properties. Our aim here was to evaluate the possibility that erythromycin alters angiogenesis. METHODS: The effect of erythromycin on B. quintana-induced endothelial cell proliferation was studied using a wild-type strain and an erythromycin-resistant B. quintana mutant. The latter was generated by serial subcultures on blood agar plates. RESULTS: We show that erythromycin significantly inhibits the proliferation of dermal microvascular endothelial cells induced either by wild-type B. quintana or by our erythromycin-resistant mutant. Doxycycline and gentamycin failed to exert such an effect. Finally, we found that the resistant strain harbored a 27-bp insertion in the highly conserved region of the gene encoding the ribosomal protein L4; this insertion may explain the existence of the resistance to erythromycin. CONCLUSION: The data presented here indicate that erythromycin profoundly down-modulates endothelial cell proliferation irrespective of its bacteriostatic effects and suggest that this may be a key component of the efficacy of the compound in the treatment of patients with BA.     

Oral ivermectin in the treatment of body lice

The mainstays of treatment of body-louse infestation in humans in a community setting are insecticides and the removal of infested clothing. We report here the dramatic effect that 3 doses of oral ivermectin (12 mg each), administered at 7-day intervals, have in reducing the total number of body lice in a cohort of homeless men from a shelter in Marseilles, France. We identified a baseline total of 1898 lice in the cohort. Over a 14-day period, this number fell to 6 lice; the prevalence of infested individuals fell from 84.9% to 18.5%. Although this effect was not sustained at day 45, it establishes that ivermectin plays a novel role in the control of body-louse infestation in humans.     

Psychophysical study of the effects of topical application of menthol in healthy volunteers

Cold hyperalgesia is a major clinical phenomenon, but validated experimental models are still lacking for humans. Topical menthol application has recently been proposed as a possible model for the study of cold pain. We characterized the psychophysical effects of 30% l-menthol in ethanol on glabrous skin in 39 healthy subjects, using a double-blind, randomized, crossover design, with ethanol as a control. Psychophysical testing included an assessment of pain thresholds and detection of mechanical, cold, and heat stimuli, and of the sensations induced by suprathreshold stimuli. Most subjects (90%) perceived a cooling sensation with menthol. Menthol decreased cold pain thresholds and enhanced pain responses to suprathreshold noxious cold stimuli, without affecting responses to other stimuli. Menthol therefore has selective effects on noxious cold processing. No subject displayed signs of skin irritation or redness. These data suggest that 30% menthol application may be a useful experimental model for studies of cold hyperalgesia in humans. The absence of local skin reactions also makes this test potentially suitable for use in patients.