Subacute hemicorporal parkinsonism in 5 patients with infarcts of the basal ganglia

In 1929, Critchley introduced the term "vascular parkinsonism" (VP), which has been the subject of considerable controversy in neurology. Parkinsonism does not appear to be a frequent consequence of striatal infarcts, although unilateral parkinsonism has been reported as an acute or subacute onset syndrome following strategic infarcts in the striatum. Previous 123-I ioflupane SPECT (DaTSCAN) studies involving radioisotope labeling of the dopamine transporter protein at presynaptic level in patients with IPD (idiopathic Parkinson's disease) have found this technique to be highly sensitive in exploring the nigrostriatal pathway. Previous studies of VP with DatSCAN have been inconclusive. The present study correlates clinical data (unilateral parkinsonism following contralateral lenticular infarction), and radiological (CT/MRI) and functional neuroimaging findings (DatSCAN) in 5 patients with CT/MRI criteria for striatal infarcts. Finally, in 2 of these patients a diagnosis of IPD was made because of the follow-up of clinical signs and pathological DaTSCAN findings not concordant with the size and location of the vascular lesion.

Delayed ageing through damage protection by the Arf/p53 pathway

The tumour-suppressor pathway formed by the alternative reading frame protein of the Cdkn2a locus (Arf) and by p53 (also called Trp53) plays a central part in the detection and elimination of cellular damage, and this constitutes the basis of its potent cancer protection activity. Similar to cancer, ageing also results from the accumulation of damage and, therefore, we have reasoned that Arf/p53 could have anti-ageing activity by alleviating the load of age-associated damage. Here we show that genetically manipulated mice with increased, but otherwise normally regulated, levels of Arf and p53 present strong cancer resistance and have decreased levels of ageing-associated damage. These observations extend the protective role of Arf/p53 to ageing, revealing a previously unknown anti-ageing mechanism and providing a rationale for the co-evolution of cancer resistance and longevity.

Three Gaussian beam interferometric profilometer applied to the characterization of an optical flat

A three-beam scanning optical interferometric microscopic technique applied to roughness characterization of optical flats is described. The technique is based on the heterodinization of three coherent optical beams. One of the beams, the probe beam, is focused on the surface under test. A second beam is obtained after being reflected by a reference surface. Finally, the last beam consists of one of the first orders of diffraction that emerges of a Bragg-cell. The three beams are coherently added at the sensitive surface of a photodetector that integrates the overall intensity of the beams. We show analytically that, the electrical signal at the output of the photodetector, is a time-varying signal whose amplitude is proportional to the surface local vertical height. We characterize experimentally the frequency response of the system by measuring the profile of three different gratings. We show measurements of the roughness of an optical flat processed by means of the frequency response of the system.

Telomerase abrogation dramatically accelerates TRF2-induced epithelial carcinogenesis

TRF2 is a telomere-binding protein with roles in telomere protection and telomere-length regulation. The fact that TRF2 is up-regulated in some human tumors suggests a role of TRF2 in cancer. Mice that overexpress TRF2 in the skin, K5TRF2 mice, show critically short telomeres and are susceptible to UV-induced carcinogenesis as a result of deregulated XPF/ERCC1 activity, a nuclease involved in UV damage repair. Here we demonstrate that, when in combination with telomerase deficiency, TRF2 acts as a very potent oncogene in vivo. In particular, we show that telomerase deficiency dramatically accelerates TRF2-induced epithelial carcinogenesis in K5TRF2/Terc-/- mice, coinciding with increased chromosomal instability and DNA damage. Telomere recombination is also increased in these mice, suggesting that TRF2 favors the activation of alternative telomere maintenance mechanisms. Together, these results demonstrate that TRF2 increased expression is a potent oncogenic event that along with telomerase deficiency accelerates carcinogenesis, coincidental with a derepression of telomere recombination. These results are of particular relevance given that TRF2 is up-regulated in some human cancers. Furthermore, these data suggest that telomerase inhibition might not be effective to cease the growth of TRF2-overexpressing tumors.

p21CIP1/WAF1 Controls Proliferation of Activated/Memory T Cells and Affects Homeostasis and Memory T Cell Responses

Development of autoantibodies and lupus-like autoimmunity by 129/Sv x C57BL/6 p21(-/-) mice has established that cell cycle deregulation is one the defective pathways leading to break of tolerance. Memory T cell accumulation is thought to be related to tolerance loss in murine lupus models. We studied T cell memory responses in C57BL/6 p21(-/-) mice that develop lupus-like disease manifestations. p21 did not affect primary proliferation of naive T cells, and was required for cycling control, but not for apoptosis of activated/memory T cells. When we induced apoptosis by secondary TCR challenge, surviving memory T cells depended on p21 for proliferation control. Under conditions of secondary T cell stimulation that did not cause apoptosis, p21 was also needed for regulation of activated/memory T cell expansion. The requirement for p21 in the control of T cell proliferation of activated/memory T cells suggests that in addition to apoptosis, cycling regulation by p21 constitutes a new pathway for T cell homeostasis. Concurring with this view, we found accumulation in p21(-/-) mice of memory CD4(+) T cells that showed increased proliferative potential after TCR stimulation. Furthermore, OVA immunization of p21(-/-) mice generated hyperresponsive OVA-specific T cells. Overall, the data show that p21 controls the proliferation of only activated/memory T cells, and suggest that p21 forms part of the memory T cell homeostasis mechanism, contributing to maintenance of tolerance.

Normal cellular senescence and cancer susceptibility in mice genetically deficient in Ras-induced senescence-1 (Ris1)

Oncogenic Ras triggers a permanent cell-cycle arrest known as oncogene-induced senescence (OIS) that constitutes a relevant tumor suppressor mechanism. Ris1 (Ras-induced senescence-1) is a novel gene that was identified in a screen as specifically upregulated during Ras-induced senescence, and that is located at a chromosomal region, 3p21.3, frequently lost in human cancer. Moreover, Ris1 is highly conserved in vertebrates, does not present paralogs, and its sequence does not reveal similarities with other proteins or domains. To analyse the physiological function of Ris1 and test its putative role as a tumor suppressor gene, we have generated mutant mice deficient for this gene. Ris1-null mice are viable, fertile, develop normally and do not display any obvious abnormalities. Of relevance, Ris1-deficient mice had a normal lifespan and did not exhibit predisposition to spontaneous tumors or to tumors induced by chemical carcinogens. Finally, Ris1-deficient embryonic fibroblasts were indistinguishable from wild-type cells regarding their proliferation properties, immortalization, senescence and oncogenic transformation. These findings do not support a role of Ris1 in tumor suppression or in OIS.

The role of pollen in chalkbrood disease in Apis mellifera: transmission and predisposing conditions

Chalkbrood in honeybees (Apis mellifera L. Himenoptera: Apidae) is a fungal disease caused by Ascosphaera apis (Maassen ex Claussen) Olive and Spiltoir. This disease requires the presence of fungal spores and a predisposing condition in the susceptible brood for the disease to develop. In this study we examined the role of pollen in the development of chalkbrood disease under two experimental conditions: (i) pollen combs were transferred from infected to uninfected beehives and (ii) colonies were deprived of adequate pollen supplies to feed the brood. The results of both treatments confirmed that pollen is an element that should be taken into account when controlling this honeybee disease.

Increased p53 activity does not accelerate telomere-driven ageing

There is a great interest in determining the impact of p53 on ageing and, for this, it is important to discriminate among the known causes of ageing. Telomere loss is a well-established source of age-associated damage, which by itself can recapitulate ageing in mouse models. Here, we have used a genetic approach to interrogate whether p53 contributes to the elimination of telomere-damaged cells and its impact on telomere-driven ageing. We have generated compound mice carrying three functional copies of the p53 gene (super-p53) in a telomerase-deficient background and we have measured the presence of chromosomal abnormalities and DNA damage in several tissues. We have found that the in vivo load of telomere-derived chromosomal damage is significantly decreased in super-p53/telomerase-null mice compared with normal-p53/telomerase-null mice. Interestingly, the presence of extra p53 activity neither accelerates nor delays telomere-driven ageing. From these observations, we conclude that p53 has an active role in eliminating telomere-damaged cells, and we exclude the possibility of an age-promoting effect of p53 on telomere-driven ageing.

Sex steroid receptor expression in the oviduct and uterus of sheep with estrus synchronized with progestagen or prostaglandin analogues

The objective of this study was to investigate differences in the expression of estrogen receptor-alpha (ERalpha), progesterone receptor (PR) and the proliferative indexes (Ki-67), in the uterus and oviduct of sheep with estrus synchronized either by prostaglandin analogues (Group PA, n=27) or by treatment with progestagens (Group P, n=29) on days 4 and 7 (day 0=estrus), when the embryos were collected. Immunohistochemical methods were used to quantify ERalpha, PR and Ki-67 in six superficial and deep compartments in the uterus and oviduct. The expression of ERalpha was significantly (P<0.01) lower in progestagen treated ewes than in prostaglandin analogues treated group in the luminal epithelium, superficial glands and superficial stroma in the uterus on day 4. The expression of PR was significantly lower in progesterone treated ewes than in the PA Group in the superficial gland (P<0.05) in both days studied. The lowest expression of PR was observed in the luminal caruncular epithelium and superficial glands in both treatments, obtaining the lowest levels on day 4 (P<0.05). There were significant differences between days 4 and 7 in the Ki-67 immunostaining in the luminal epithelium (P<0.01) and superficial glands (P<0.05). A higher cell proliferation was observed in the uterine epithelium (P<0.05) on day 4 in the animals treated with progestagens. Results indicate that sheep with synchronization of estrus with progestagens showed a reduction of ERalpha and PR protein expression in most of oviductal and uterine cells.

Tumorigenic activity of p21Waf1/Cip1 in thymic lymphoma

The cell cycle inhibitor p21Waf1/Cip1 is among the most important mediators of the tumor suppressor p53. However, there is increasing evidence indicating that p21 could favor tumorigenesis in specific cell types. In particular, the absence of p21 delays the development of thymic lymphomas induced either by ataxia-telangiectasia mutated deficiency or by ionizing irradiation. Here, we extend these observations to the context of p53-deficient mice. The absence of p21 results in a significant extension of the lifespan of p53-null and p53-haploinsufficient mice, and this effect can be attributed exclusively to a decrease in the incidence of spontaneous thymic lymphomas. Specifically, despite the occurrence of a variety of tumor types in the context of p53 deficiency, the only tumors that were significantly impaired by the absence of p21 were thymic lymphomas. Moreover, the absence of p21 also delays the incidence of radiation-induced thymic lymphomas in p53-deficient mice. Interestingly, p21-deficient lymphomas have a higher apoptotic rate than p21-proficient lymphomas, and this could be on the basis of the delayed incidence of thymic lymphomas in the absence of p21. Together, our results indicate that p21 plays an oncogenic role restricted to thymic lymphomas that is mechanistically independent of p53 and associated to a lower tumor apoptotic rate.

[Study of presynaptic nigrostriatal pathway by 123-I-FD-CIT-SPECT (DatSCAN SPECT) in primary orthostatic tremor]

INTRODUCTION

Primary orthostatic tremor (OT) is defined as a clinical syndrome with high frequency (13-18 Hz) tremor when standing predominantly involving legs and trunk. OT is thought to be driven by an unique supraspinal tremor generator. Previous studies suggest that the nigrostriatal dopaminergic transmission is impaired in patients with OT.

CLINICAL CASE

All three patients at an age of 56, 45 and 72 years fulfilled the diagnosis criteria of primary OT. The duration of illness amounted to 4, 3 and 1 year, respectively. The three patients had single-photon emission computed tomography (SPECT) using 123-I-FP-CIT as dopamine transporter tracer (DatSCAN).

RESULTS

DatSCAN was normal in every patient.

CONCLUSIONS

OT is considered to be caused by a central oscillator because high-frequency tremor bursts are time locked in arm, leg, trunk, and even facial muscles and peripheral stimulation does not reset the tremor. Some reports suggest that the central generator may be located in the posterior fossa. In our patients presynaptic nigrostriatal pathway was normal.

Class IB-Phosphatidylinositol 3-Kinase (PI3K) Deficiency Ameliorates IA-PI3K-Induced Systemic Lupus but Not T Cell Invasion

Class I PI3K catalyzes formation of 3-poly-phosphoinositides. The family is divided into IA isoforms, activated by Tyr kinases and the IB isoform (PI3Kgamma), activated by G protein-coupled receptors. Mutations that affect PI3K are implicated in chronic inflammation, although the differential contribution of each isoform to pathology has not been elucidated. Enhanced activation of class IA-PI3K in T cells extends CD4+ memory cell survival, triggering an invasive lymphoproliferative disorder and systemic lupus. As both IA- and IB-PI3K isoforms regulate T cell activation, and activated pathogenic CD4+ memory cells are involved in triggering systemic lupus, we examined whether deletion of IB could reduce the pathological consequences of increased IA-PI3K activity. IB-PI3Kgamma deficiency did not abolish invasion or lymphoproliferation, but reduced CD4+ memory cell survival, autoantibody production, glomerulonephritis, and systemic lupus. Deletion of the IB-PI3Kgamma isoform thus decreased survival of pathogenic CD4+ memory cells, selectively inhibiting systemic lupus development. These results validate the PI3Kgamma isoform as a target for systemic lupus erythematosus treatment.

XPF nuclease-dependent telomere loss and increased DNA damage in mice overexpressing TRF2 result in premature aging and cancer

TRF2 is a telomere-binding protein that has a role in telomere protection. We generated mice that overexpress TRF2 in the skin. These mice had a severe phenotype in the skin in response to light, consisting of premature skin deterioration, hyperpigmentation and increased skin cancer, which resembles the human syndrome xeroderma pigmentosum. Keratinocytes from these mice were hypersensitive to ultraviolet irradiation and DNA crosslinking agents. The skin cells of these mice had marked telomere shortening, loss of the telomeric G-strand overhang and increased chromosomal instability. Telomere loss in these mice was mediated by XPF, a structure-specific nuclease involved in ultraviolet-induced damage repair and mutated in individuals with xeroderma pigmentosum. These findings suggest that TRF2 provides a crucial link between telomere function and ultraviolet-induced damage repair, whose alteration underlies genomic instability, cancer and aging. Finally, we show that a number of human skin tumors have increased expression of TRF2, further highlighting a role for TRF2 in skin cancer.

PI3Kgamma inhibition blocks glomerulonephritis and extends lifespan in a mouse model of systemic lupus

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease generated by deregulation of T cell-mediated B-cell activation, which results in glomerulonephritis and renal failure. Disease is treated with immunosuppressants and cytostatic agents that have numerous side effects. Here we examine the use of inhibitors of phosphoinositide 3-kinase (PI3K) gamma, a lipid kinase that regulates inflammation, in the MRL-lpr mouse model of SLE. Treatment reduced glomerulonephritis and prolonged lifespan, suggesting that P13Kgamma may be a useful target in the treatment of chronic inflammation.

Dido gene expression alterations are implicated in the induction of hematological myeloid neoplasms

The myelodysplastic/myeloproliferative diseases (MDS/MPDs) are a heterogeneous group of myeloid neoplasms that share characteristics with chronic myeloproliferative diseases and myelodysplastic syndromes. The broad spectrum of clinical manifestations makes MDS/MPDs extremely difficult to diagnose and treat, with a median survival time of 1-5 years. No single gene defect has been firmly associated with MDS/MPDs, and no animal models have been developed for these diseases. The association of deletions on chromosome 20q with myeloid malignancies suggests the presence of unidentified tumor suppressor genes in this region. Here we show that the recently identified death inducer-obliterator (Dido) gene gives rise to at least 3 polypeptides (Dido1, Dido2, and Dido3) through alternative splicing, and we map the human gene to the long arm of chromosome 20. We found that targeting of murine Dido caused a transplantable disease whose symptoms and signs suggested MDS/MPDs. Furthermore, 100% of human MDS/MPD patients analyzed showed Dido expression abnormalities, which we also found in other myeloid but not lymphoid neoplasms or in healthy donors. Our findings suggest that Dido might be one of the tumor suppressor genes at chromosome 20q and that the Dido-targeted mouse may be a suitable model for studying MDS/MPD diseases and testing new approaches to their diagnosis and treatment.

Tumour biology: senescence in premalignant tumours

Oncogene-induced senescence is a cellular response that may be crucial for protection against cancer development, but its investigation has so far been restricted to cultured cells that have been manipulated to overexpress an oncogene. Here we analyse tumours initiated by an endogenous oncogene, ras, and show that senescent cells exist in premalignant tumours but not in malignant ones. Senescence is therefore a defining feature of premalignant tumours that could prove valuable in the diagnosis and prognosis of cancer.

Tumour-suppression activity of the proapoptotic regulator Par4

The proapoptotic protein encoded by Par4 (prostate apoptosis response 4) has been implicated in tumour suppression, particularly in the prostate. We report here that Par4-null mice are prone to develop tumours, both spontaneously and on carcinogenic treatment. The endometrium and prostate of Par4-null mice were particularly sensitive to the development of proliferative lesions. Most (80%) Par4-null females presented endometrial hyperplasia by 9 months of age, and a significant proportion (36%) developed endometrial adenocarcinomas after 1 year of age. Similarly, Par4-null males showed a high incidence of prostate hyperplasia and prostatic intraepithelial neoplasias, and were extraordinarily sensitive to testosterone-induced prostate hyperplasia. Finally, the uterus and prostate of young Par4-null mice have increased levels of the apoptosis inhibitor XIAP (X-chromosome-linked inhibitor of apoptosis), supporting the previously proposed function of Par4 as an inhibitor of the (zeta)PKC (atypical protein kinase)-NF-(kappa)B (nuclear factor-(kappa)B)-XIAP pathway. These data show that Par4 has an important role in tumour suppression, with a particular relevance in the endometrium and prostate.

The telomerase RNA component Terc is required for the tumour-promoting effects of Tert overexpression

A role for the telomerase reverse transcriptase subunit (Tert) in tumorigenesis independent of telomere length is emerging. K5-Tert mice, which overexpress Tert in the skin, show increased tumorigenesis and faster wound healing than wild-type controls. Here, we demonstrate that the telomerase RNA component Terc is necessary to mediate these effects of Tert overexpression. In contrast to K5-Tert mice, K5-Tert mice in a Terc-deficient background, K5-Tert/Terc-/-, do not show increased tumorigenesis or increased wound healing compared with wild-type controls. Indeed, K5-Tert/Terc-/- mice show a reduction in tumour growth compared with Terc-/- controls, indicating an inhibitory effect of Tert overexpression in the absence of Terc. These results indicate that the tumour-promoting effects of Tert overexpression require the formation of Tert-Terc complexes. In addition, we show that the increased expression of Tert in the absence of Terc has an inhibitory effect on tumorigenesis, independently of telomere length and telomerase activity. These findings highlight Terc as a target for telomerase-based anticancer therapies.

Spores of Ascosphaera apis contained in wax foundation can infect honeybee brood

Chalkbrood disease in honeybees (Apis mellifera L.) is caused by an infection with Ascosphaera apis. Disease expression requires the consumption of fungal spores and a predisposing condition in the susceptible brood. A. apis spores within sheets of wax foundation could be a source of inoculum leading to chalkbrood, but it is also possible that these spores remain confined in the wax and do not contribute to disease. We have resolved this topic by chilling susceptible brood within wax combs built on contaminated foundation (using treatments of spores from 1 mummy and spores from 10 mummies) versus uncontaminated foundation. We found significantly higher levels of chalkbrood in brood exposed to the higher dosage. Our results demonstrate that foundation wax contaminated with spores of A. apis spores may be a source of chalkbrood in honeybee colonies.

Effects of progestagens and prostaglandin analogues on ovarian function and embryo viability in sheep

Current study assessed differences in the response of sheep to estrus synchronization either by the administration of two doses of prostaglandin or by the insertion of an intravaginal progestagen sponge. The preovulatory follicular dynamics and estradiol secretion, the ovulatory response and progesterone secretion and the number and quality of embryos were studied in 27 ewes treated with two doses of 100 microg of cloprostenol, 10 days apart, and in 29 sheep treated with progestagen sponges for 14 days. Percentage of sheep responding to the synchronization treatments with signs of estrus behaviour was similar between both groups (81.5% versus 72.4%, respectively). The use of progestagen resulted in a higher diameter of the largest follicle (6.6+/-0.2 versus 5.9+/-0.2, P<0.05), and a lower number of small (6.7+/-0.3 versus 9.6+/-0.4, P<0.005) and total follicles (10.3+/-0.3 versus 12.9+/-0.4, P<0.005). However, mean plasma estradiol concentration during the follicular phase was higher in cloprostenol treated sheep (P<0.005). The mean ovulation rate was similar in both treatments (1.7+/-0.2 versus 1.7+/-0.3), but progesterone concentration during the early luteal phase was again higher in sheep treated with cloprostenol (P<0.05). The mean number of retrieved oocytes/embryos was very similar in both treatments (1.2+/-0.2 versus 1.4+/-0.2) and showed similar fertilization rates (70.6% versus 66.7%), but, although differences did not reach statistical significance, final viability rate was higher in cloprostenol than in progestagen treated ewes (58.9% versus 46.1%, P=0.07). Current results give new evidences supporting the negative effects of progestagens on the functionality of ovulatory follicles and support the development of new protocols for assisted reproduction including the use of prostaglandin analogues.

Antagonistic effects of telomerase on cancer and aging in K5-mTert transgenic mice

Many degenerative diseases that occur with aging, as well as premature aging syndromes, are characterized by presenting cells with critically short telomeres. Telomerase reintroduction is envisioned as a putative therapy for diseases characterized by telomere exhaustion. K5-mTert transgenic mice overexpress telomerase in a wide spectrum of tissues. These mice have a higher incidence of both induced and spontaneous tumors, resulting in increased mortality during the first year of life. Here, we show that in spite of this elevated tumor incidence and the initial lower survival, K5-mTert mice show an extension of the maximum lifespan from 1.5 to 3 months, depending on the transgenic line, which represents up to a 10% increase in the mean lifespan compared to wild-type littermates. This longer lifespan is coincidental with a lower incidence of certain age-related degenerative diseases, mainly those related to kidney function and germline integrity. Importantly, these effects of telomerase overexpression cannot be attributed to dramatic differences in telomere length in aged K5-Tert mice compared to wild-type mice, as shown by quantitative telomeric FISH. These findings indicate that telomerase overexpression extends the maximum lifespan of mice.

Epithelioid malignant peripheral nerve sheath tumour in a dog

An unusual morphological variant of malignant peripheral nerve sheath tumour, in which the cells exhibited a predominantly epithelial morphology, was diagnosed in a dog. The animal had a history of progressive ataxia. Post-mortem examination revealed an infiltrative growth in the sublumbar region, encroaching on the L1 and L2 vertebral bodies; additional masses were observed in the kidneys, liver and lungs. Histologically, the subcutaneous mass was composed of a dense population of spindle-shaped cells arranged in fascicles. The internal masses were composed of epithelioid cells arranged in a nodular pattern. Immunohistochemically, the spindle-shaped cells of the subcutaneous mass were positive for S-100, and the epithelioid cells of the internal growths exhibited weak S-100 immunoreactivity.

Different cooperating effect of p21 or p27 deficiency in combination with INK4a/ARF deletion in mice

The control exerted by the INK4a/ARF locus on cellular proliferation is crucial to restrict tumor development. In agreement with this, mice with defects in this locus are highly tumor prone. However, the potential contribution of other pathways in modulating tumorigenesis in the absence of INK4a/ARF is largely unexplored. In the present study, we investigated the consequences of the combined loss of either of two cyclin-dependent kinase inhibitors, p21 and p27, in cooperation with deletion of the INK4a/ARF locus. Our results show a clear differential effect in tumorigenesis depending on the CKI that is absent. The absence of p21 produced no overt alteration of the lifespan of the INK4a/ARF-null mice, although it modified their tumor spectrum, causing a significant increase in the incidence of fibrosarcomas and the appearance of a small number of rhabdomyosarcomas. In contrast, deficiency of p27 resulted in a significant increase in lethality due to accelerated tumor development, especially in the case of T-cell lymphomas. Finally, combined deficiency of INK4a/ARF and p27 resulted in a significant increase in the number of metastatic tumors. These results demonstrate genetically the oncogenic cooperation between defects on INK4a/ARF and p27, which are common alterations in human cancer.

Antitumor effectiveness of different amounts of electrical charge in Ehrlich and fibrosarcoma Sa-37 tumors

Background

In vivo studies were conducted to quantify the effectiveness of low-level direct electric current for different amounts of electrical charge and the survival rate in fibrosarcoma Sa-37 and Ehrlich tumors, also the effect of direct electric in Ehrlich tumor was evaluate through the measurements of tumor volume and the peritumoral and tumoral findings.

Methods

BALB/c male mice, 7–8 week old and 20–22 g weight were used. Ehrlich and fibrosarcoma Sa-37 cell lines, growing in BALB/c mice. Solid and subcutaneous Ehrlich and fibrosarcoma Sa-37 tumors, located dorsolaterally in animals, were initiated by the inoculation of 5 × 10⁶ and 1 × 10⁵ viable tumor cells, respectively. For each type of tumor four groups (one control group and three treated groups) consisting of 10 mice randomly divided were formed. When the tumors reached approximately 0.5 cm³, four platinum electrodes were inserted into their bases. The electric charge delivered to the tumors was varied in the range of 5.5 to 110 C/cm³ for a constant time of 45 minutes. An additional experiment was performed in BALB/c male mice bearing Ehrlich tumor to examine from a histolological point of view the effects of direct electric current. A control group and a treated group with 77 C/cm³ (27.0 C in 0.35 cm³) and 10 mA for 45 min were formed. In this experiment when the tumor volumes reached 0.35 cm³, two anodes and two cathodes were inserted into the base perpendicular to the tumor long axis.

Results

Significant tumor growth delay and survival rate were achieved after electrotherapy and both were dependent on direct electric current intensity, being more marked in fibrosarcoma Sa-37 tumor. Complete regressions for fibrosarcoma Sa-37 and Ehrlich tumors were observed for electrical charges of 80 and 92 C/cm³, respectively.

Histopathological and peritumoral findings in Ehrlich tumor revealed in the treated group marked tumor necrosis, vascular congestion, peritumoral neutrophil infiltration, an acute inflammatory response, and a moderate peritumoral monocyte infiltration. The morphologic pattern of necrotic cell mass after direct electric current treatment is the coagulative necrosis. These findings were not observed in any of the untreated tumors.

Conclusion

The data presented indicate that electrotherapy with low-level DEC is feasible and effective in the treatment of the Ehrlich and fibrosarcoma Sa-37 tumors. Our results demonstrate that the sensitivity of these tumors to direct electric current and survival rates of the mice depended on both the amount of electrical charge and the type of tumor. Also the complete regression of each type of tumor is obtained for a threshold amount of electrical charge.

Impact of telomerase ablation on organismal viability, aging, and tumorigenesis in mice lacking the DNA repair proteins PARP-1, Ku86, or DNA-PKcs

The DNA repair proteins poly(ADP-ribose) polymerase-1 (PARP-1), Ku86, and catalytic subunit of DNA-PK (DNA-PKcs) have been involved in telomere metabolism. To genetically dissect the impact of these activities on telomere function, as well as organismal cancer and aging, we have generated mice doubly deficient for both telomerase and any of the mentioned DNA repair proteins, PARP-1, Ku86, or DNA-PKcs. First, we show that abrogation of PARP-1 in the absence of telomerase does not affect the rate of telomere shortening, telomere capping, or organismal viability compared with single telomerase-deficient controls. Thus, PARP-1 does not have a major role in telomere metabolism, not even in the context of telomerase deficiency. In contrast, mice doubly deficient for telomerase and either Ku86 or DNA-PKcs manifest accelerated loss of organismal viability compared with single telomerase-deficient mice. Interestingly, this loss of organismal viability correlates with proliferative defects and age-related pathologies, but not with increased incidence of cancer. These results support the notion that absence of telomerase and short telomeres in combination with DNA repair deficiencies accelerate the aging process without impacting on tumorigenesis.

Increased gene dosage of Ink4a/Arf results in cancer resistance and normal aging

Mammalian genes frequently present allelic variants that differ in their expression levels and that, in the case of tumor suppressor genes, can be of relevance for cancer susceptibility and aging. We report here the characterization of a novel mouse model with increased activity for the Ink4a and Arf tumor suppressors. We have generated a "super Ink4a/Arf" mouse strain carrying a transgenic copy of the entire Ink4a/Arf locus. Cells derived from super Ink4a/Arf mice have increased resistance to in vitro immortalization and oncogenic transformation. Importantly, super Ink4a/Arf mice manifest higher resistance to cancer compared to normal, nontransgenic, mice. Finally, super Ink4a/Arf mice have normal aging and lifespan. Together, these results indicate that modest increases in the activity of the Ink4a/Arf tumor suppressor result in a beneficial cancer-resistant phenotype without affecting normal viability or aging.

Oxytetracycline as a predisposing condition for chalkbrood in honeybee

Antibiotics, particularly oxytetracycline, have been discussed as a possible predisposing condition in the appearance of chalkbrood in the honeybee (Apis mellifera L.). Nevertheless, the scientific data to support this belief have been insufficient. We have developed a method to study the effects of this antibiotic as a predisposing factor under different circumstances. We conclude that oxytetracycline does not increase the risk of chalkbrood in susceptible worker brood in the short or mid-term.

Constitutive expression of tert in thymocytes leads to increased incidence and dissemination of T-cell lymphoma in Lck-Tert mice

Here we describe a new mouse model with constitutive expression of the catalytic subunit of telomerase (Tert) targeted to thymocytes and peripheral T cells (Lck-Tert mice). Two independent Lck-Tert mouse lines showed higher incidences of spontaneous T-cell lymphoma than the corresponding age-matched wild-type controls, indicating that constitutive expression of Tert promotes lymphoma. Interestingly, T-cell lymphomas in Lck-Tert mice were more disseminated than those in wild-type controls and affected both lymphoid and nonlymphoid tissues, while nonlymphoid tissues were never affected with lymphoma in age-matched wild-type controls. Importantly, these roles of Tert constitutive expression in promoting tumor progression and dissemination were independent of the role of telomerase in telomere length maintenance, since telomere length distributions on a single-cell basis were identical in Lck-Tert and wild-type thymocytes. Finally, Tert constitutive expression did not interfere with telomere capping in Lck-Tert primary thymocytes, although it resulted in greater chromosomal instability upon gamma irradiation in Lck-Tert primary lymphocytes than in controls, suggesting that Tert overexpression may interfere with the cellular response to DNA damage.

Shorter telomeres, accelerated ageing and increased lymphoma in DNA-PKcs-deficient mice

Non-homologous end joining (NHEJ) is the principal repair mechanism used by mammalian cells to cope with double-strand breaks (DSBs) that continually occur in the genome. One of the key components of the mammalian NHEJ machinery is the DNA-PK complex, formed by the Ku86/70 heterodimer and the DNA-PK catalytic subunit (DNA-PKcs). Here, we report on the detailed life-long follow-up of DNA-PKcs-defective mice. Apart from defining a role of DNA-PKcs in telomere length maintenance in the context of the ageing organism, we observed that DNA-PKcs-defective mice had a shorter life span and showed an earlier onset of ageing-related pathologies than the corresponding wild-type littermates. In addition, DNA-PKcs ablation was associated with a markedly higher incidence of T lymphomas and infections. In conclusion, these data link the dual role of DNA-PKcs in DNA repair and telomere length maintenance to organismal ageing and cancer.

Leukocyte attraction through the CCR5 receptor controls progress from insulitis to diabetes in non-obese diabetic mice

Lymphocyte infiltration to pancreatic islets is associated to chemoattraction, as are other inflammatory autoimmune processes. We examined whether development of insulitis and diabetes depends on chemoattraction of lymphocytes via the CCR5 chemokine receptor. In non-obese diabetic (NOD) mice, a substantial fraction of peripheral T cells and virtually all B cells expressed high CCR5 levels. CCR5 expression characterized the effector T cell phenotype, suggesting their potential involvement in disease development. In view of these findings and the CCL5 (RANTES, the CCR5 ligand) expression by pancreatic islets, we treated NOD mice with a neutralizing anti-CCR5 antibody. This did not influence peri-insulitis advancement, but inhibited beta-cell destruction and diabetes. These data demonstrate a role of CCR5-dependent chemoattraction in insulitis progression to islet destruction, suggesting the potential value of therapeutic intervention by CCR5 targeting.

The atypical PKC-interacting protein p62 is an important mediator of RANK-activated osteoclastogenesis

The atypical PKCs (aPKCs) have been implicated genetically in at least two independent signaling cascades that control NF-kappa B and cell polarity, through the interaction with the adapters p62 and Par-6, respectively. P62 binds TRAF6, which plays an essential role in osteoclastogenesis and bone remodeling. Recently, p62 mutations have been shown to be the cause of the 5q35-linked Paget's disease of bone, a genetic disorder characterized by aberrant osteoclastic activity. Here we show that p62, like TRAF6, is upregulated during RANK-L-induced osteoclastogenesis and that the genetic inactivation of p62 in mice leads to impaired osteoclastogenesis in vitro and in vivo, as well as inhibition of IKK activation and NF-kappa B nuclear translocation. In addition, RANK-L stimulation leads to the inducible formation of a ternary complex involving TRAF6, p62, and the aPKCs. These observations demonstrate that p62 is an important mediator during osteoclastogenesis and induced bone remodeling.

Expression of αv, α4, α5 and β3 integrin subunits, fibronectin and vitronectin in goat peri-implantation

Integrins are glycoprotein heterodimers located in the cell membranes that stimulate intercellular adhesion and act as extracellular matrix (ECM) protein receptors. Although integrins have been detected in the implantation sites of various species, little is known about their participation in ruminant non-invasive placentation. The objective of this study was the detection of alphav, alpha4, alpha5, beta1 and beta3 integrin subunits and of two of their ligands, fibronectin and vitronectin, to determine their participation in the caprine peri-implantation process. On Day 21 post-coitum (pc), endometrial epithelium and trophoblastic cells showed an intense alphav and beta3 integrin subunits expression and moderate staining for alpha4 and alpha5. On Day 23 pc, integrin expression decreased noticeably and only a weak staining of alpha4 and beta3 integrin subunits were observed. No beta1 integrin subunit expression was detected on either of the days studied. Fibronectin (FN) expression in trophectodermic and endometrial epithelium was weak or moderate on the days studied while vitronectin (VN) expression in the same tissues was moderate or strong on Day 21 pc but decreased on Day 23 pc. These results suggest that alphavbeta3 integrin, alpha4 and alpha5 subunits, VN and FN are expressed in caprine endometrium and blastocyst and may play a role in the cascade of the implantation process.

Telomere dysfunction results in enhanced organismal sensitivity to the alkylating agent N-methyl-N-nitrosourea

Here, we use telomerase-deficient mice, Terc(-/-), to study the impact of telomerase abrogation in response to treatment with the alkylating agent N-Methyl-N-Nitrosourea (MNU), a potent carcinogen in the mouse. Wild-type mice treated with MNU developed lymphomas and carcinomas. In contrast, similarly treated G5 Terc(-/-) mice with critically short telomeres did not develop tumors and died of acute toxicity to the small intestine. G2 Terc(-/-) mice, which have long telomeres, were less susceptible to MNU-induced tumors than wild-type mice, as well as less sensitive to MNU toxicity than G5 Terc(-/-) mice. The results indicate that short telomeres suppress tumor growth and that lack of telomerase retards tumor progression, even in the presence of long telomeres. Finally, G5 Terc(-/-) hypersensitivity to MNU supports the notion that short telomeres interfere with proper DNA damage repair.

"Super p53" mice exhibit enhanced DNA damage response, are tumor resistant and age normally

The tumor suppressor p53 is critical in preventing cancer due to its ability to trigger proliferation arrest and cell death upon the occurrence of a variety of stresses, most notably, DNA damage and oncogenic stress. Here, we report the generation and characterization of mice carrying supernumerary copies of the p53 gene in the form of large genomic transgenes. Prior to this, we demonstrate that the p53 transgenic allele (p53-tg), when present in a p53-null genetic background, behaves as a functional replica of the endogenous gene. "Super p53" mice, carrying p53-tg alleles in addition to the two endogenous alleles, exhibit an enhanced response to DNA damage. Importantly, "super p53" mice are significantly protected from cancer when compared with normal mice. Finally, in contrast to previously reported mice with constitutively active p53, "super p53" mice do not show any indication of premature aging, probably reflecting the fact that p53 is under normal regulatory control. Together, our results prove that cancer resistance can be enhanced by a simple genetic modification and in the absence of undesirable effects.

Cooperation between p53 mutation and high telomerase transgenic expression in spontaneous cancer development

Telomerase reintroduction in adult somatic tissues is envisioned as a way to extend their proliferative capacity. It is still a question, however, whether constitutive telomerase expression in adult tissues impacts the normal aging and spontaneous cancer incidence of an organism. Here, we studied the aging and spontaneous cancer incidence of mice with transgenic telomerase expression in a wide range of adult tissues, K5-Tert mice. For this, we maintained large colonies of K5-Tert mice for more than 2 years. K5-Tert mice showed a decreased life span compared to wild-type cohorts associated with a higher incidence of preneoplastic and neoplastic lesions in various tissue types. Neoplasias in K5-Tert mice were coincident with transgene expression in the affected tissues. These observations suggest that high telomerase activity may cooperate with genetic alterations that occur with age to promote tumorigenesis. Indeed, we demonstrate here that increased cancer incidence and the reduced viability of K5-Tert mice are aggravated in a p53(+/-) genetic background, indicating that telomerase cooperates with loss of p53 function in inducing tumorigenesis. Altogether, these results demonstrate that constitutive high levels of telomerase activity result in a decreased life span associated with an increased incidence of neoplasias as the organism ages.

Outbreak of avian tuberculosis in 48-week-old commercial layer hen flock

This report describes an outbreak of tuberculosis in a flock of 38,500 48-wk-old layer hens. Clinical characteristics of the process included a gradual drop in egg production and feed intake, as well as an increased mortality rate. Two well-defined clinical features were observed. On the one hand, a number of birds displayed good body condition and continued to lay but presented granulomatous nodular lesions, particularly in the infraorbital sinus, liver, and intestine. In contrast, other hens were emaciated and presented granulomatous lesions of various sizes throughout the internal organs. The lesions observed in the various organs of all the affected birds consisted of granulomas containing acid/alcohol-fast bacilli. The presence of Mycobacterium avium was confirmed through polymerase chain reaction techniques. This report describes the epidemiologic and histopathologic characteristics of the outbreak.

Fibroblastic growth factor receptor (FGF-R) expression during uterine involution in goat

To investigate the possible participation of fibroblastic growth factors (FGFs) in endometrial involution, 20 multiparous goats, slaughtered on days 0, 1, 4, 10, 16 and 22 postpartum (pp), were used. Samples of different parts of the previous pregnant horns were taken and processed using streptoavidin-biotin-peroxidase complex method to analyse FGF receptor (FGF-R) expression. The percentage of positive cells in luminal epithelium, superficial and deep glands and stroma was evaluated. Epithelial, glandular and stromal cells exhibited FGF-R immunoreactivity. No differences between caruncular and inter-caruncular epithelium were observed and staining was most evident in the superficial glands. The greatest degree of FGF-R expression was seen on days 10 and 16 pp, coinciding with epithelial and stromal cellular regeneration. These results suggest that caprine uterine involution is associated with variations in the expression of FGF-R.

[Efficacy of the APimicos-B to control and prevent chalkbrood disease in honey bees]

Chalkbrood disease in Apis mellifera is a fungal disease affecting developing brood, infested larvae become mummified. As it is a factorial disease, studies on this pathology are obstructed by the need of some predisposing conditions which must occur for such disease to develop. Thus, many questions are yet to be answered about which treatments to apply. The aim of this work is to evaluate the efficacy of the Apimicos-B, a treatment against chalk brood. To induce the disease, some pieces of combs containing susceptible worker brood both from infected and treated colonies and from infected and untreated colonies were cooled. No significant differences were registered (53.12% and 59.58% of mummification respectively).

Restoration of telomerase activity rescues chromosomal instability and premature aging in Terc-/- mice with short telomeres

Reconstitution of telomerase activity is proposed as a potential gene therapy to prevent, or rescue, age-related diseases produced by critical telomere shortening. However, it is not known whether or not short telomeres are irreversibly damaged. We addressed this by re-introducing telomerase in late generation telomerase-deficient mice, Terc-/-, which have short telomeres and show severe proliferative defects. For this, we have crossed these mice with Terc+/- mice and analyzed telomere length, chromosomal instability and premature aging of the progeny. The Terc-/- progeny had one set of chromosomes with normal telomeres, whereas the other set remained with critically short telomeres; these mice presented chromosomal instability and premature aging. In contrast, Terc+/- progeny showed all chromosomes with detectable telomeres, and did not show chromosomal instability or premature aging. These results prove that critically short telomeres can be rescued by telomerase, and become fully functional, thus rescuing premature aging. This has important implications for the future design of telomerase-based gene therapy of age-related diseases.

Tumor susceptibility of p21(Waf1/Cip1)-deficient mice

The cell cycle regulator p21 mediates the ability of the tumor suppressor p53 to arrest cellular proliferation. We have examined the involvement of p21 in tumor suppression by following a large cohort of p21-deficient mice for an extended period of time. We report that p21-deficient mice develop spontaneous tumors at an average age of 16 months, whereas wild-type mice are tumor-free beyond 2 years of age. The tumors arising in p21-null mice derive from a variety of cell types and include hematopoietic ( approximately 65% of the tumors), endothelial ( approximately 20%), and epithelial ( approximately 10%) tumors. We have also studied radiation-induced carcinogenesis to test whether, in this setting, p53 exerts its tumor suppressor activity mainly through apoptosis, rather than through p21-mediated cell-cycle arrest. Concurring with this, p21-deficient mice did not show increased susceptibility to radiation-induced carcinogenesis. On the contrary, they were protected relative to wild-type mice. We conclude that p21, by mediating p53-dependent cell-cycle arrest, plays a significant role in tumor suppression.

Detection of estrogen alpha and progesterone receptors and cell proliferation in the uterus during early pregnancy in the goat

The objectives of this study were to investigate in the goat uterus the expression of estrogen-alpha (ER alpha) and progesterone receptors (PR) and their relationship to proliferation indices (Ki-67) during peri-implantation on Days 22 to 30 post coitum (pc). Immunohistochemical methods were used to quantify ER alpha and PR for luminal and deep regions of the endometrium and of the myometrium. On Day 22 pc cell proliferation was only observed in the luminal epithelium. On Day 24 pc, high cell proliferation indices were seen in luminal epithelium and proliferation began in the luminal stroma and glands. There was a positive correlation between Ki-67 and total ER alpha score in the luminal epithelium (r = 0.53, P < 0.01). Levels of PR scores were highly correlated with Ki-67 indices in luminal epithelium (r = 0.74, P < 0.01) and stroma (r = 0.70, P < 0.01). No Ki-67 expression was observed in deep glands, stroma or myometrium on any of the days studied. Results indicate that patterns of ER alpha and PR expression differ markedly, and that there was a high correlation between PR expression and cell proliferation in the caprine uterus during the peri-implantation period.

Increased epidermal tumors and increased skin wound healing in transgenic mice overexpressing the catalytic subunit of telomerase, mTERT, in basal keratinocytes

Telomerase transgenics are an important tool to assess the role of telomerase in cancer, as well as to evaluate the potential use of telomerase for gene therapy of age-associated diseases. Here, we have targeted the expression of the catalytic component of mouse telomerase, mTERT, to basal keratinocytes using the bovine keratin 5 promoter. These telomerase-transgenic mice are viable and show histologically normal stratified epithelia with high levels of telomerase activity and normal telomere length. Interestingly, the epidermis of these mice is highly responsive to the mitogenic effects of phorbol esters, and it is more susceptible than that of wild-type littermates to the development skin tumors upon chemical carcinogenesis. The epidermis of telomerase-transgenic mice also shows an increased wound-healing rate compared with wild-type littermates. These results suggest that, contrary to the general assumption, telomerase actively promotes proliferation in cells that have sufficiently long telomeres and unravel potential risks of gene therapy for age-associated diseases based on telomerase upregulation.

Cellular immune responses in mice immunized with Anisakis simplex larval antigens

Cellular immune responses to Anisakis simplex L3 antigens were investigated in BALB/c mice injected subcutaneously with a homologous crude extract (CE). Popliteal lymph nodes (PLN) were found to be increased in size and weight after A. simplex CE footpad injection. The effects of A. simplex CE in vitro proliferation were assayed with non-fractionated PLN cells or nylon-wool purified T cells derived from pooled lymph node cells of mice subcutaneously injected with CE. Spleen cells from immunized animals (antigen alone, or larva alone, or antigen plus larva) were studied by flow cytometry. The immunization induced a high proportion of CD4 + and TCRalphabeta + T cells. The number of B cells (CD45 + and TCRalphabeta-) in pre-immunized and infected mice was lower than that observed in animals subjected to infection only. The number of CD4+ T cells increased in the infected and in the pre-immunized and infected mice. In the latter, a decrease of CD8a + T cells was noted. The greatest increase in CD8a+ and TCRalphabeta- T cells was found in mice that had been subjected to infection only. Histological analysis showed that the most prominent lesions were gastric and intestinal in animals infected orally with one larva.

[C reactive protein as marker of infection among patients with severe closed trauma]

BACKGROUND

Injury and infection are characterized by the activation of the acute phase proteins response. C-reactive protein (CRP), an acute phase protein, has been mentioned as an useful indicator of infection and sepsis in critically ill patients.

OBJECTIVE

To study the evolution of serum CRP in patients with severe blunt trauma and to ascertain its ability as a biological marker of infection during the first seven days after injury.

METHODS

We prospectively studied 54 patients with blunt trauma (injury severity score>=16) age>14 years and length of the Intensive Care Unit (ICU) estay>= 7 days, over a 4-month period. Culture-proven infections were collected and serum CRP was determinated every day, during the first week after ICU admission.

RESULTS

Twenty-eight patients (51.8%) developed an infection during the first week, and the median day of diagnosis of infection was day 6. Pneumonia was the most common infection (50%) and Gram-negative bacilli (63.3%) were the most common microorganisms recovered. Serum CRP levels were significantly higher in the infected patients group after day 4, showing a median value higher than 170 mg/l. Based on the receiver operating characteristic (ROC) curve analysis, a cutoff value of 109.5 mg/l for CRP gives a sensitivity of 78.6% and a specifity of 73.1% in predicting the presence of infection.

CONCLUSIONS

The course of serum CRP levels is different in the group of patients with severe blunt trauma and infection, compared with the non-infected group during the first week after injury and it could be an useful supplementary marker for infection after postinjury day 4. A value of 110 mg/l or higher for CRP should suggest an underlying infectious complication.

Effect of dietary linoleic acid concentration and vitamin E supplementation on cell desquamation and susceptibility to oxidative damage of pig jejunal mucosa

Sixty Large White x Great York pigs weighing approximately 60 kg were individually fed on six experimental diets. The experiment was organized in a 3 x 2 factorial arrangement design with three different fat sources and a basal or supplemented (200 mg/kg diet) level of alpha-tocopheryl acetate. All diets contained the same concentration of saturated fatty acids (15 +/- 0.2 g/kg dry matter) but differed in the concentration of C18 : 2 (14 +/- 0.5, 18 +/- 0.4 and 21 +/- 0.6 g/kg) and monounsaturated fatty acids (19 +/- 0.2, 15 +/- 1.2 and 10 +/- 1.3 g/kg). No effect of dietary treatment was observed on weight gain and feed consumption. A histological study of the jejunal mucosa showed lower cell desquamation in groups containing a supplemental level of alpha-tocopheryl acetate (p=0.080). A higher cell desquamation was found in the groups fed diets containing the higher concentration of C18 : 2 (p=0.087). We also observed an interaction effect (p < 0.001) of dietary fat source and vitamin E supplementation on jejunal cell desquamation in which the effect of dietary vitamin E was lower when diets with a low concentration of C18 : 2 were administered. In vitro-induced oxidation of jejunal mucosa homogenates was lower in pigs fed diets supplemented with alpha-tocopheryl acetate (p < 0.002). The dietary concentration of C18 : 2 significantly affected oxidation of pig jejunal mucosa (p < 0.002).

Early risk factors for sepsis in patients with severe blunt trauma

We studied 43 patients with blunt trauma (injury severity score, > or =25), age >14 years and length of the intensive care unit (ICU) stay >48 h in order to estimate the frequency of sepsis and to identify early risk factors related to its development. Clinical data were collected during the first 24 h and several inflammatory mediators were determined from serum samples of the first 2 days after injury.Twenty-one patients (48.8%) met sepsis criteria during their ICU stay, 9 (20.9%) fulfilled only criteria for sepsis; 6 (13.9%) fulfilled criteria for severe sepsis and another 6 (13.9%) criteria for septic shock. An APACHE II score > or =14, the presence of hypovolemic shock, the need for three or more units of blood to be transfused and the administration of a total volume of fluids > or =10 l were all factors associated significantly with the development of sepsis. In the multivariant analysis, the need for a total volume of fluids > or =10 l was the only independent risk factor (adjusted odds ratio=10.49, 95% CI, 2.34-47.02; P=0.002). No significant differences were documented in relation to the behaviour of the serum markers.

Short telomeres result in organismal hypersensitivity to ionizing radiation in mammals

Here we show a correlation between telomere length and organismal sensitivity to ionizing radiation (IR) in mammals. In particular, fifth generation (G5) mouse telomerase RNA (mTR)(-/)- mice, with telomeres 40% shorter than in wild-type mice, are hypersensitive to cumulative doses of gamma rays. 60% of the irradiated G5 mTR(-/)- mice die of acute radiation toxicity in the gastrointestinal tract, lymphoid organs, and kidney. The affected G5 mTR(-/)- mice show higher chromosomal damage and greater apoptosis than similarly irradiated wild-type controls. Furthermore, we show that G5 mTR(-/)- mice show normal frequencies of sister chromatid exchange and normal V(D)J recombination, suggesting that short telomeres do not significantly affect the efficiency of DNA double strand break repair in mammals. The IR-sensitive phenotype of G5 mTR(-/)- mice suggests that telomere function is one of the determinants of radiation sensitivity of whole animals.

Telomerase-deficient mice with short telomeres are resistant to skin tumorigenesis

Inhibition of telomerase is proposed to limit the growth of cancer cells by triggering telomere shortening and cell death. Telomere maintenance by telomerase is sufficient, in some cell types, to allow immortal growth. Telomerase has been shown to cooperate with oncogenes in transforming cultured primary human cells into neoplastic cells, suggesting that telomerase activation contributes to malignant transformation. Moreover, telomerase inhibition in human tumour cell lines using dominant-negative versions of TERT leads to telomere shortening and cell death. These findings have led to the proposition that telomerase inhibition may result in cessation of tumour growth. The absence of telomerase from most normal cells supports the potential efficacy of anti-telomerase drugs for tumour therapy, as its inhibition is unlikely to have toxic effects. Mice deficient for Terc RNA (encoding telomerase) lack telomerase activity, and constitute a model for evaluating the role of telomerase and telomeres in tumourigenesis. Late-generation Terc-/- mice show defects in proliferative tissues and a moderate increase in the incidence of spontaneous tumours in highly proliferative cell types (lymphomas, teratocarcinomas). The appearance of these tumours is thought to be a consequence of chromosomal instability in these mice. These observations have challenged the expected effectiveness of anti-telomerase-based cancer therapies. Different cell types may nonetheless vary in their sensitivity to the chromosomal instability produced by telomere loss or to the activation of telomere-rescue mechanisms. Here we show that late-generation Terc-/- mice, which have short telomeres and are telomerase-deficient, are resistant to tumour development in multi-stage skin carcinogenesis. Our results predict that an anti-telomerase-based tumour therapy may be effective in epithelial tumours.