Bimodal dose-dependence of FK506 on the rate of axonal regeneration in mouse peripheral nerve

FK506 has been shown to enhance the rate of axonal regeneration after peripheral nerve lesions. However, quite variable doses of FK506 have been used in different animal studies. We examined the dose-dependence of FK506 on the rate of axonal regeneration after crush lesion of the mouse sciatic nerve. Mice received daily subcutaneous injections of FK506 at 0.2, 0.5, 1, 2, 5, or 10 mg/kg for 7 days after lesioning. A control group was injected with saline. The distance that regenerative axons advanced from the crush site was measured by the pinch test at 2, 4, and 7 days. Regenerating axons reached greater mean distances in all FK506-treated groups compared to the control group. The fastest regeneration rate was found at 5 mg/kg (12% increase over controls), although the 0.2 and 2 mg/kg doses achieved similar regeneration rates. In contrast, intermediate doses (0.5 and 1 mg/kg) and a higher dose (10 mg/kg) were not different from controls. Calcitonin gene-related peptide immunohistochemical labeling of regenerating axons yielded similar results to those found with the pinch test. Based on our finding of a double peak in the dose-response for FK506, it is hypothesized that at least two mechanisms of action (perhaps corresponding to distinct functional binding sites) are evoked at different concentrations of the drug to accelerate nerve regeneration. These results have clinical implications for the pharmacological treatment of nerve injuries while avoiding immunosuppressive effects and for the design of related drugs with more specific activities.     

Aminopeptidase inhibitory properties and analgesic activity of (2S,3R)-3,7-diamino-2-hydroxy-heptanoic acid containing tripeptide analogues of the N-terminal tripeptide of probestin.

(2S,3R)-3,7-Diamino-2-hydroxy-heptanoyl-Leu-Pro-OH [(2S,3R)-DAHHA-Leu-Pro-OH, 4], analogue of the N-terminal tripeptide of probestin, has been synthesized, and tested as inhibitor of AP-B, Leu-AP, AP-M, and enkephalin-degrading APs, and as analgesic. In order to establish structure-activity relationships the dipeptide (2S,3R)-DAHHA-Pro-OH (5) and the tripeptide (2S,3R)-DAHHA-Ala-Pro-OH (6) were also prepared. Compounds 4 and 6 were potent and selective inhibitors of enkephalin-degrading APs and showed a prolonged antinociceptive effect.     

Inhibitory effect of c-Myc on p53-induced apoptosis in leukemia cells. Microarray analysis reveals defective induction of p53 target genes and upregulation of chaperone genes

We have previously demonstrated that c-Myc impairs p53-mediated apoptosis in K562 human leukemia cells, which lack ARF. To investigate the mechanisms by which c-Myc protects from p53-mediated apoptosis, we used K562 cells that conditionally express c-Myc and harbor a temperature-sensitive allele of p53. Gene expression profiles of cells expressing wild-type conformation p53 in the presence of either uninduced or induced c-Myc were analysed by cDNA microarrays. The results show that multiple p53 target genes are downregulated when c-Myc is present, including p21WAF1, MDM2, PERP, NOXA, GADD45, DDB2, PIR121 and p53R2. Also, a number of genes that are upregulated by c-Myc in cells expressing wild-type conformation p53 encode chaperones related to cell death protection as HSP105, HSP90 and HSP27. Both downregulation of p53 target genes and upregulation of chaperones could explain the inhibition of apoptosis observed in K562 cells with ectopic c-Myc. Myc-mediated impairment of p53 transactivation was not restricted to K562 cells, but it was reproduced in a panel of human cancer cell lines derived from different tissues. Our data suggest that elevated levels of Myc counteract p53 activity in human tumor cells that lack ARF. This mechanism could contribute to explain the c-Myc deregulation frequently found in cancer.     

Visual-spatial attention in alcoholics and illicit stimulant abusers: effects of nicotine replacement

Reports of alcohol or illicit drug-related cognitive impairments have frequently disregarded the potentially confounding effects of smoking status and nicotine withdrawal on these measures. This study addressed this issue by measuring visual-spatial attention via an adaptation of the Posner paradigm in three groups of tobacco smokers: controls without a history of alcoholism or illicit drug use (n=27; 20 male), chronic alcoholics (n=22; 18 male), and illicit stimulant abusers (n=36; 21 male). Throughout testing, nicotine levels were stabilized by the double-blind administration of a high (14 or 21 mg) or low (7 mg) dose transdermal nicotine patch. A significant effect of group was observed for number of correct responses to restriction trials (F=5.48, 2/79 df; p=.006). Performance was normalized in the illicit stimulant group, and alcoholic participants exhibited superior performance relative to both illicit stimulant abusers (p=.002) and controls (p=.01). These findings support the hypothesis that nicotine may have a compensatory or normalizing effect on attentional functions in substance abusers. Whether these results reflect the central nervous system-activating effects of nicotine or merely alleviation of nicotine withdrawal is a topic of ongoing research.     

Epidemiology and prognosis of hyperosmolar state in the elderly

OBJECTIVE: We studied elderly patients admitted for hyperosmolar state (HS) to evaluate current outcome of HS and identify prognosis factors associated with mortality. STUDY DESIGN: A clinical retrospective study in an eight bed ICU. PATIENTS AND METHODS: Eighteen over 65-year-old patients admitted with a serum osmolality greater than 325 mOsm/kg were reviewed. Age, sex, diabetes mellitus, underlying medical condition, presence of an acute precipitating factor, Apache II and Glasgow scores, systolic arterial pressure, state of hydration, core temperature, heart rate, serum osmolality, creatininemia, lactatemia, plasma urea and bicarbonate, and protidemia were collected at the admission. Amount of fluid, time course of osmolality correction, length of hospitalization and mortality were recorded. All data were analyzed to identify possible correlations with patient outcome. RESULTS: Mean age: 75 +/- 11 years; sex ratio 1/2; hyperosmolar hyperglycemic states: 13 patients; hyperosmolar hypernatremic states: five patients; mean Apache II score: 18 +/- 7; Glasgow coma score: 11 +/- 3; mean osmolality: 370 +/- 25 mOsm/kg. In nine patients, infection was the precipitating factor. Five patients died (28%). At the admission, low blood pressure and high heart rate were related to mortality. During hospitalization, the occurrence of an acute cardiocirculatory failure and/or the need of mechanical ventilation significantly worsens the outcome. CONCLUSION: Our results showed that ICU mortality of HS in the elderly was at 28%. Haemodynamic state was the only factor of prognosis at the admission. Deaths were mostly related to acute respiratory and circulatory failure.     

Functional responses to the cannabinoid agonist WIN 55,212-2 in neonatal rats of both genders: influence of weaning

We have studied behavioural, biochemical and endocrine responses to the cannabinoid agonist WIN 55,212-2 (WIN) in neonatal rats, as well as the effects of weaning on such responses. We used preweanling rats (20 days of age), 25-day-old weaned rats (weaning at Day 22) and 25-day-old nonweaned rats of both sexes. The behavioural effects of WIN were assessed in the nociceptive tail immersion test and in the open field. We also analysed the effect of weaning on corticosterone responses to WIN (radioimmunoassay) as well as on WIN-stimulated [35S] GTPgammaS binding in periaqueductal grey (PAG) and striatum. The cannabinoid agonist induced a modest increase in pain thresholds, whereas the effect of the drug on open-field activity, particularly on vertical activity, was much more marked. The weaning process appeared to reduce the baseline nociceptive latencies of the female rats. No significant effect of weaning on the behavioural responses to WIN was found. However, the group of weaned females (but not males) showed a significantly reduced WIN-stimulated [35S] GTPgammaS binding in the striatum. The cannabinoid agonist significantly increased the corticosterone levels of 25-day-old rats with the effect being more marked in weaned than in nonweaned animals. The results suggest that the weaning process might produce some sexually dimorphic developmental changes in CB1 receptor function.