Evaluation of loop-mediated isothermal amplification for the rapid identification of bacteria and resistance determinants in positive blood cultures.

The use of molecular assays to rapidly identify pathogens and resistance genes directly from positive blood cultures (BCs) contribute to shortening the time required for the diagnosis of bloodstream infections. In this work, loop-mediated isothermal amplification (LAMP) assays have been examined for their potential use in BC diagnosis. Three different assays were applied. The commercially available eazyplex® MRSA test detects Staphylococcus aureus, S. epidermidis, mecA, and mecC. Two in-house assays [Gram-positive (GP) and Gram-negative (GN)] have been developed for the detection of streptococci, enterococci, vanA, vanB, Pseudomonas spp., Enterobacteriaceae, and the bla CTX-M family. A total of 370 positive BCs were analyzed. LAMP test results were obtained within 30 min, including sample preparation. Amplification was measured by real-time fluorescence detection. The threshold time for fluorescence intensity values ranged from 6.25 to 13.75 min. The specificity and sensitivity of the assays varied depending on the target. Overall, from 87.7% of BCs, true-positive results were obtained, compared to routine standard diagnosis. Twenty-one tests were true-negative because of the lack of an appropriate target (5.7%). The concordance of positive test results for resistance genes with subsequent antibiotic susceptibility testing was 100%. From 15 BC bottles with mixed cultures, eazyplex® assays produced correct results in 73% of the cases. This study shows that LAMP assays are fast and cost-saving tools for rapid BC testing in order to expedite the diagnostic report and improve the antibiotic stewardship for sepsis patients.

Psoriasin (S100A7) promotes stress-induced angiogenesis.

BACKGROUND: Vascular modifications occur early in the development of psoriasis, and angiogenesis is one of the key features in the pathogenesis of the disease. OBJECTIVES: To identify the role of the S100 protein psoriasin in psoriasis-associated angiogenesis. METHODS: The role of psoriasin in mediating angiogenesis was investigated by silencing psoriasin with small interfering RNA (siRNA) and measuring psoriasis-associated angiogenic factors in human epidermal keratinocytes. The secretion of psoriasin and the effect of psoriasin on general regulators of angiogenesis in keratinocytes, and on endothelial cell migration, proliferation, tube formation and production of angiogenic mediators, was evaluated. RESULTS: Reactive oxygen species (ROS) and hypoxia induced the expression of psoriasin. Downregulation of psoriasin in keratinocytes using siRNA altered the ROS-induced expression of the psoriasis-associated angiogenic factors vascular endothelial growth factor (VEGF), heparin-binding epidermal growth factor-like growth factor, matrix metalloproteinase 1 and thrombospondin 1. Overexpression of psoriasin altered several regulators of angiogenesis and led to the secretion of psoriasin. Treatment with extracellular psoriasin induced proliferation, migration and tube formation in dermal-derived endothelial cells to a similar extent as VEGF and interleukin-17, and induced the expression and release of proangiogenic mediators. These effects were suggested to be mediated by the PI3K and nuclear factor kappa B pathways. CONCLUSIONS: These findings suggest that psoriasin expression is promoted by oxidative stress in keratinocytes and amplifies the ROS-induced expression of angiogenic factors relevant to psoriasis. Moreover, extracellularly secreted psoriasin may act on dermal endothelial cells to contribute to key features angiogenesis.

Effect of wave exposure dynamics on gut content mass and growth of young-of-the-year fishes in the littoral zone of lakes.

Total length, body mass and gut content mass of young-of-the-year (YOY) perch Perca fluviatilis, dace Leuciscus leuciscus and bleak Alburnus alburnus were recorded over the summer of 2006 at three littoral sites at Upper Lake Constance. In P. fluviatilis and L. leuciscus, gut content mass correlated positively with wave-induced energy flux (E(F)) of the respective site and sampling day, while no correlation of gut content mass with E(F) was found in A. alburnus. It was assumed that benthivorous P. fluviatilis and L. leuciscus profited from suspended or uncovered benthic food items generated by wave action at sites and periods with high E(F). Alburnus alburnus, in contrast, feeding mainly on zooplankton in upper parts of the water column, could not profit from increased E(F). In P. fluviatilis, increased gut content mass during periods of high E(F) resulted in higher growth rates. For L. leuciscus, no real growth rates in local fish populations could be determined, as individuals were less sedentary, and when increased growth occurred at sites during the periods of high E(F), migration of fish levelled out the resulting size differences within few days. The results of this study show that dynamic habitat variables affect site profitability in the littoral zone of lakes, especially in benthivorous fishes. Therefore, dynamic habitat variables should be considered in addition to fixed habitat properties in analyses of habitat choice of fishes in the littoral zone of lakes.

5- and 6-pulse electron spin echo envelope modulation (ESEEM) of multi-nuclear spin systems.

In 3-pulse ESEEM and the original 4-pulse HYSCORE, nuclei with large modulation depth (k approximately 1) suppress spectral peaks from nuclei with weak modulations (k approximately 0). This cross suppression can impede the detection of the latter nuclei, which are often the ones of interest. We show that two extended pulse sequences, 5-pulse ESEEM and 6-pulse HYSCORE, can be used as experimental alternatives that suffer less strongly from the cross suppression and allow to recover signals of k approximately 0 nuclei in the presence of k approximately 1 nuclei. In the extended sequences, modulations from k approximately 0 nuclei are strongly enhanced. In addition, multi-quantum transitions are absent which simplifies the spectra. General analytical expressions for the modulation signals in these sequences are derived and discussed. Numerical simulations and experimental spectra that demonstrate the higher sensitivity of the extended pulse sequences are presented.

Heparin-binding ligands mediate autocrine epidermal growth factor receptor activation In skin organ culture.

Exogenous EGF and TGF-alpha accelerate wound healing, but treatment effects are often modest. Using short-term human skin organ culture, we found that autocrine EGF receptor activation could account for this observation. Amphiregulin and heparin-binding EGF-like growth factor (HB-EGF) transcripts were rapidly and markedly induced, whereas EGF and TGF-alpha mRNAs were undetectable or only slightly increased. Vascular permeability factor and keratin 6 transcripts were also strongly induced, albeit with a >/= 3 h delay relative to HB-EGF and amphiregulin. All four transcripts were upregulated in actual healing skin wounds, HB-EGF and keratin 6 being the most prominent. The highly EGF receptor-specific tyrosine kinase inhibitor PD153035 strongly inhibited induction of all four transcripts in organ culture, as well as release of immunoreactive HB-EGF into the medium. These effects were confirmed using the anti-EGF receptor mAb 225 IgG. Neither PD153035 nor 225 IgG was toxic to keratinocytes, as judged by calcein-AM uptake. PD153035 completely abrogated the proliferative phase of keratinocyte outgrowth in skin explant cultures, whereas it had no effect on the antecedent migratory phase. Based on these results, we conclude that EGF receptor activation by highly inducible, keratinocyte-derived heparin-binding ligands is an important mechanism for amplification and transmission of the cutaneous wound healing signal.

Extracellular adenosine triphosphate activates calcium mobilization in human phagocytic leukocytes and neutrophil/monocyte progenitor cells.

We have examined the ability of extracellular ATP to elicit intracellular Ca2+ mobilization in a broad range of human leukocytes at particular stages of hematopoietic differentiation. The average cytosolic [Ca2+] in various leukocyte populations was measured in Fura 2-loaded cell suspensions while the cytosolic [Ca2+] in individual, Indo 1-loaded leukocytes was assayed by flow cytometric methods. Utilizing normal blood- and marrow-derived cells, human leukemic cell lines, and mononuclear cell fractions derived from the blood of patients with various leukemias, we have found that ATP-induced Ca2+ mobilization appears restricted to leukocytes of neutrophil/monocyte ontogeny. Significant ATP-induced increases in cytosolic [Ca2+] were observed in neutrophils, monocytes, and myeloid progenitor cells as immature as myeloblasts, but not in lymphocytes. Extensive characterization of the ATP-induced changes in [Ca2+] observed in the HL-60 promyelocytic cell line have indicated these Ca2+-mobilizing effects of ATP can be correlated with an activation of inositol phospholipid breakdown via the occupation of P2-purinergic receptors Significantly, of the various agonists (FMLP, platelet-activating factor, LTB4, and ATP) which elicit equivalent and maximal Ca2+ mobilization in mature neutrophils and monocytes, ATP was the most efficacious stimulant of Ca2+ mobilization in immature neutrophil/monocyte precursors. Thus, expression of putative P2-purinergic receptors for ATP appears to precede expression of other receptor types known to activate the inositol phospholipid signaling cascades in terminally differentiated phagocytes.

FOXM1 allows human keratinocytes to bypass the oncogene-induced differentiation checkpoint in response to gain of MYC or loss of p53.

Tumour suppressor p53 or proto-oncogene MYC is frequently altered in squamous carcinomas, but this is insufficient to drive carcinogenesis. We have shown that overactivation of MYC or loss of p53 via DNA damage triggers an anti-oncogenic differentiation-mitosis checkpoint in human epidermal keratinocytes, resulting in impaired cell division and squamous differentiation. Forkhead box M1 (FOXM1) is a transcription factor recently proposed to govern the expression of a set of mitotic genes. Deregulation of FOXM1 occurs in a wide variety of epithelial malignancies. We have ectopically expressed FOXM1 in keratinocytes of the skin after overexpression of MYC or inactivation of endogenous p53. Ectopic FOXM1 rescues the proliferative capacity of MYC- or p53-mutant cells in spite of higher genetic damage and a larger cell size typical of differentiation. As a consequence, differentiation induced by loss of p53 or MYC is converted into increased proliferation and keratinocytes displaying genomic instability are maintained within the proliferative compartment. The results demonstrate that keratinocyte oncogene-induced differentiation is caused by mitosis control and provide new insight into the mechanisms driving malignant progression in squamous cancer.

CaN19 expression in benign and malignant hyperplasias of the skin and oral mucosa: evidence for a role in regenerative differentiation.

CaN19, a member of the S100 family of calcium-binding proteins, is known to be "underexpressed" in cultured breast carcinoma-derived cell lines relative to their normal counterparts. By Northern blotting, we confirm these results and find that CaN19 is also markedly "underexpressed" in several carcinoma-derived cell lines of the skin, oral mucosa, and urogenital tract. However, exceptions to the inverse correlation between CaN19 expression and malignancy have been identified, bringing into question the hypothesis that CaN19 functions as a tumor suppressor gene. Unexpectedly, CaN19 mRNA was strongly expressed in bulk specimens of basal and squamous cell carcinomas of the skin and oral cavity. However, in situ hybridization revealed only limited CaN19 expression in tumor cells themselves; the bulk of expression is localized to hyperplastic perilesional epidermis. Tumor cell expression of CaN19 was similar in primary and locally metastatic tumors, indicating that this gene is not necessarily down-regulated during tumor progression. Coordinate overexpression of CaN19 and the "hyperproliferalive" keratin K6a was observed only in tissues undergoing squamous differentiation. Taken together with other recent results from our laboratory, these findings suggest the hypothesis that CaN19 participates in an epidermal growth factor receptor-dependent pathway of regenerative squamous differentiation.

The EGF receptor ligand amphiregulin controls cell division via FoxM1.

Epidermal growth factor receptor (EGFR) is central to epithelial cell physiology, and deregulated EGFR signaling has an important role in a variety of human carcinomas. Here we show that silencing of the EGF-related factor amphiregulin (AREG) markedly inhibits the expansion of human keratinocytes through mitotic failure and accumulation of cells with ⩾ 4n DNA content. RNA-sequencing-based transcriptome analysis revealed that tetracycline-mediated AREG silencing significantly altered the expression of 2331 genes, 623 of which were not normalized by treatment with EGF. Interestingly, genes irreversibly upregulated by suppression of AREG overlapped with genes involved in keratinocyte differentiation. Moreover, a significant proportion of the irreversibly downregulated genes featured upstream binding sites recognized by forkhead box protein M1 (FoxM1), a key transcription factor in the control of mitosis that is widely dysregulated in cancer. The downregulation of FoxM1 and its target genes preceded mitotic arrest. Constitutive expression of FoxM1 in AREG knockdown cells normalized cell proliferation, reduced the number of cells with ⩾ 4n DNA content and rescued expression of FoxM1 target genes. These results demonstrate that AREG controls G2/M progression and cytokinesis in keratinocytes via activation of a FoxM1-dependent transcriptional program, suggesting new avenues for treatment of epithelial cancer.

EGF receptor signaling inhibits keratinocyte apoptosis: evidence for mediation by Bcl-XL.

Signaling through the epidermal growth factor receptor (EGFR) has been primarily implicated in the growth of epithelial cells including keratinocytes. However, the mechanism by which EGFR stimulation promotes keratinocyte cell growth is poorly understood. Here we report that human keratinocytes undergo apoptosis when incubated with the blocking EGFR monoclonal antibody 225 IgG, or PD153035, a highly specific EGFR tyrosine kinase inhibitor. Endogenous mRNA and protein levels of Bcl-XL, a member the Bcl-2 family which suppresses apoptosis, were specifically inhibited by EGFR blockade. Furthermore, stimulation of EGFR signaling through two natural ligands, transforming growth factor (TGF)-alpha and epidermal growth factor (EGF), increased the expression of Bcl-XL in quiescent keratinocytes and HaCaT cells. Finally, ectopic expression of Bcl-XL in HaCaT cells increased survival after EGFR blockade when compared to untransfected cells or HaCaT keratinocytes transfected with empty vector. These results suggest that the anti-apoptotic protein Bcl-XL plays an important role in the maintenance of keratinocyte survival in response to EGFR signaling.

Off-lattice Monte Carlo simulations of irreversible and reversible aggregation processes.

Monte Carlo simulations are used to get an insight into the formation of fractal aggregates from diluted to concentrated colloidal particle dispersions. Using irreversible conditions, we investigate the aggregation size distribution, architecture of the resulting fractal aggregates, possible transitions from simple aggregation to percolation and from percolation to the homogeneous aggregation regime, and discuss the fractal dimension determination from the radial distribution function. In particular the effects of the particle concentration on the aggregate fractal dimensions are considered. Reversibility is also introduced in the model so as to consider more realistic systems. The effects of aggregate fragmentation and internal reorganization are then investigated by adjusting the interparticle interaction potential. Important results dealing with the concomitant effect of aggregate break-up and internal reorganization on the aggregate local structure and stability with regards to phase separation are discussed.

Anti-interleukin 2 receptor antibodies and mycophenolate mofetil for treatment of steroid-resistant rejection in adult liver transplantation.

BACKGROUND: Steroid-resistant rejection (SRR) results in significant morbidity and mortality from the adverse effects of rescue therapy and in graft loss from chronic rejection. In our knowledge, the efficacy and safety of anti-interleukin (IL) 2r antibodies (daclizumab and basiliximab) for the treatment of SRR in adult liver transplantation has not previously been evaluated. METHODS: Twenty-five patients received either daclizumab or basiliximab as rescue therapy for SRR. Outcome and biochemical parameters were recorded before and after treatment with an anti-IL-2r antibody. RESULTS: The median time from transplantation to SRR was 25 days. Secondary immunosuppression included mycophenolate mofetil in 18 patients. Twelve patients (48%) had complete resolution of SRR. Aspartate transaminase levels normalized at a median of 37 days (range, 1-168 days). In 13 patients (52%) progressive hepatic dysfunction developed. Four of these patients received another transplant, and 6 patients had chronic rejection. Three patients died with graft failure. Of 16 patients with acute cellular rejection, 12 (75%) had resolution, 2 had chronic rejection, 1 required a repeat transplantation, and 1 died with graft failure. In contrast, all 9 patients with established chronic rejection in their pretreatment biopsy continued to have significant graft dysfunction, with 4 having persistent chronic graft dysfunction, 3 requiring repeat transplantation, and 2 dying with graft failure. CONCLUSION: Twelve (48%) of 25 patients who received an anti-IL-2r antibody because of SRR were successfully treated. All successfully treated patients had ongoing acute cellular rejection at liver biopsy (75%), whereas patients with histologic evidence of chronic rejection responded poorly.

Differential utilization and localization of ErbB receptor tyrosine kinases in skin compared to normal and malignant keratinocytes.

Induction of heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA in mouse skin organ culture was blocked by two pan-ErbB receptor tyrosine kinase (RTK) inhibitors but not by genetic ablation of ErbB1, suggesting involvement of multiple ErbB species in skin physiology. Human skin, cultured normal keratinocytes, and A431 skin carcinoma cells expressed ErbB1, ErbB2, and ErbB3, but not ErbB4. Skin and A431 cells expressed more ErbB3 than did keratinocytes. Despite strong expression of ErbB2 and ErbB3, heregulin was inactive in stimulating tyrosine phosphorylation in A431 cells. In contrast, it was highly active in MDA-MB-453 breast carcinoma cells. ErbB2 displayed punctate cytoplasmic staining in A431 and keratinocytes, compared to strong cell surface staining in MDA-MB-453. In skin, ErbB2 was cytoplasmic in basal keratinocytes, assuming a cell surface pattern in the upper suprabasal layers. In contrast, ErbB1 retained a cell surface distribution in all epidermal layers. Keratinocyte proliferation in culture was found to be ErbB1-RTK-dependent, using a selective inhibitor. These results suggest that in skin keratinocytes, ErbB2 transduces ligand-dependent differentiation signals, whereas ErbB1 transduces ligand-dependent proliferation/survival signals. Intracellular sequestration of ErbB2 may contribute to the malignant phenotype of A431 cells, by allowing them to respond to ErbB1-dependent growth/survival signals, while evading ErbB2-dependent differentiation signals.

EGF stimulates transcription of CaN19 (S100A2) in HaCaT keratinocytes.

CaN19 (S100A2), a member of the S100 family of calcium-binding proteins, was originally isolated in a screen for tumor suppressor genes. Recent work from our laboratory suggests that CaN19 is likely to be an effector of the regenerative hyperplasia pathway of epidermal differentiation. As other work from our laboratory in a human skin organ culture model suggests that this response is mediated by activation of the epidermal growth factor (EGF) receptor and/or related receptors of the ErbB family, we asked whether CaN19 expression could be increased by organ culture and by EGF treatment of human keratinocytes. CaN19 was strongly induced after 24 h of organ culture, and its induction could be blocked by PD153035, a specific inhibitor of EGF receptor tyrosine kinase activity. EGF treatment of immortalized human keratinocytes (HaCaT cells) increased CaN19 mRNA levels by 4.5-fold within 8 h, and a corresponding increase in CaN19 protein was observed by western blotting. EGF treatment had no effect on the expression of five other members of the S100A gene cluster. As assessed by nuclear run-off assay, CaN19 transcription increased rapidly in response to EGF, reaching a maximum induction of 16-fold after 2 h. In contrast, EGF treatment had no detectable effects on the decay of CaN19 transcripts, which were long lived (t1/2 > 6 h) in the presence or absence of EGF. PD153035 also blocked CaN19 transcription and the accumulation of CaN19 mRNA and protein in HaCaT cells. These results demonstrate that EGF receptor activation selectively stimulates CaN19 gene expression at the transcriptional level in human keratinocytes, and support the hypothesis that CaN19 is an important mediator of regenerative epidermal hyperplasia.

Biochemical characterization of S100A2 in human keratinocytes: subcellular localization, dimerization, and oxidative cross-linking.

S100A2 is a calmodulin-like protein of unknown function, whose transcription is positively regulated in response to ErbB and p53 signaling. Expression of S100A2 is markedly increased in the context of ErbB-driven reactive epidermal hyperplasia, and decreased in the context of hypofunctional p53 mutations in carcinoma cell lines and tumors. This bimodal pattern of regulation suggests an important function for S100A2 in keratinocyte differentiation and carcinogenesis. Taking the biochemical approach to the determination of S100A2 function, we have characterized its physical state and subcellular localization in normal human keratinocytes. S100A2 in hypotonic lysates remained soluble after centrifugation at 100 000 x g, indicating that it is not associated with cell membranes. Permeabilization experiments confirmed the lack of membrane association and revealed a digitonin-insoluble nuclear fraction of S100A2, which was confirmed by immunofluorescence microscopy. Pulldown assays of epitope-tagged S100A2 and yeast two-hybrid screening revealed that S100A2 displays a strong propensity to homodimerize. Naturally expressed S100A2 dimers in normal human keratinocytes readily underwent intermolecular disulfide cross-linking unless a strong denaturant was present during cell lysis. Treatment of intact normal human keratinocytes with hydrogen peroxide strongly promoted S100A2 cross-linking. These results demonstrate that native S100A2 is a homodimer that does not depend on disulfide cross-linking for stability, but undergoes intermolecular cross-linking at cysteine residues in response to oxidative stress. Based on these findings, we propose that S100A2 may protect normal keratinocytes against carcinogens by participating in the cellular proof-reading response to oxidative stress.

Assignment of psoriasin to human chromosomal band 1q21: coordinate overexpression of clustered genes in psoriasis.

Psoriasin is an abundant low molecular weight protein in keratinocytes from psoriatic lesions. Because of similarities in gene structure and expression to other genes on human chromosomal band 1q21, we hypothesized that psoriasin might also map to this region. To test this hypothesis, we identified and used a genomic lambda clone (lambda 9.2) as a probe for fluorescent in situ hybridization. lambda 9.2 detected the 1q21 region in 81% of 52 chromosomes 1 examined, although it also hybridized to acrocentric chromosomes. lambda 9.2 DNA yielded polymerase chain reaction amplification of 121-bp sequence colinear with psoriasin cDNA, as did genomic DNA from hybrid cell lines containing all or part of chromosome 1. The psoriasin gene was present on a 380-kb yeast artificial chromosome clone that was previously mapped to 1q21 and shown to contain calcyclin; here it is also shown to contain MRP8 and CaN19. Psoriasin and several other tightly linked 1q21 genes were markedly overexpressed in psoriatic lesions, suggesting a role for these clustered genes in the regulation of epidermal proliferation.

Heparin-binding epidermal-growth-factor-like growth factor activation of keratinocyte ErbB receptors Mediates epidermal hyperplasia, a prominent side-effect of retinoid therapy.

Sun-protected human skin was maintained in organ culture and treated with all-trans retinoic acid in the presence or absence of reversible or irreversible pharmacologic antagonists of c-erbB receptor tyrosine kinase activity. In the absence of these inhibitors, all-trans retinoic acid induced epidermal hyperplasia comparable to that induced in intact skin by all-trans retinol or all-trans retinoic acid itself. There was a strong correlation between inhibition of epidermal hyperplasia in organ culture and inhibition of epidermal-growth-factor-dependent keratinocyte growth in monolayer culture. In additional studies it was shown that all-trans retinoic acid could overcome the known inhibitory effects of calcium on expression of HB-EGF-like growth factor mRNA in organ-cultured skin. Further, it was shown that an antibody to HB-EGF-like growth factor inhibited retinoid-stimulated epidermal hyperplasia in organ culture and reduced proliferation in cultured keratinocytes. In contrast, the c-erbB receptor tyrosine kinase antagonists and the neutralizing HB-EGF-like growth factor antibody were ineffective in inhibiting all-trans-retinoic-acid-dependent survival and proliferation of human dermal fibroblasts. Taken together, these data indicate (i) that retinoid-induced epidermal hyperplasia in human skin proceeds through c-erbB, and (ii) that HB-EGF-like growth factor is one of the c-erbB ligands mediating this effect.

Growth hormone response to growth hormone-releasing hormone and clonidine in depression.

Growth hormone (GH) responses to the alpha 2-adrenoceptor agonist clonidine and to GH-releasing hormone (GHRH) were measured in 12 patients fulfilling DSM-III-R criteria for major depressive disorder and in 12 age- and sex-matched controls. GH responses to clonidine correlated significantly with the GH responses to GHRH in the depressed patients as well as in the controls. Neither the responses to clonidine nor the responses to GHRH were significantly lower in depressed patients than in controls. Similarly, somatomedin-C (Sm-C) plasma concentrations and baseline GH concentrations were not different between the two groups. The data do not suggest that blunted GH responses to clonidine and/or GHRH represent specific features of depression.

Chronic treatment of Syrian hamsters with low-dose selegiline increases life span in females but not males.

The only intervention conclusively shown to prolong life span in mammals is caloric restriction. Selegiline, a selective, irreversible inhibitor of monoamine oxidase B (MAO-B), is the first drug reported to reproducibly increase mean and maximum life span in animals, although this has only been demonstrated in male rats and mice. The effect on life span is commonly assumed to depend on MAO-B inhibition, but final experimental proof is missing. Therefore, we investigated the possible relationship between selegiline's effect on life span and MAO-B by monitoring survival data and MAO activity in Syrian hamsters of both sexes. Selegiline (0.05 mg/kg) significantly increased life span in female Syrian hamsters, but not in males. In contrast, MAO-B was inhibited equally in both sexes by about 40%, although females had a higher baseline MAO-B activity. No increase in MAO-B with age was observed. Female control hamsters had a shorter life span than male controls. Interestingly, this sex difference disappeared in the selegiline-treated animals. These findings suggest that the increase of life span by selegiline might be independent of MAO-B inhibition, but is possibly related to mechanisms determining sex differences of life span.