Selective increase of dATP pools upon activation of deoxycytidine kinase in lymphocytes: implications in apoptosis

Stimulation of the activity of deoxycytidine kinase (dCK), the principal deoxynucleoside salvage enzyme, has been recently considered as a protective cellular response to a wide range of agents interfering with DNA repair and apoptosis. In light of this, the potential contribution of dCK activation to apoptosis induction--presumably by supplying dATP or its analogues for the apoptosome formation--deserves consideration. Two-hour exposure of human tonsillar lymphocytes to 2-chloro-deoxyadenosine (CdA) led to a two-fold activation of dCK. This activation process was inhibited by pifithrin-alpha, a potent inhibitor of p53. When the dNTP pools were determined, both deoxypyrimidine triphosphate and dGTP pools were reduced after the treatments, while dATP levels elevated by 62%, 77% and 50% in the CdA, aphidicolin and etoposide-treated cells, respectively. We assume that dCK activation elicited by cellular damage might be a proapoptotic factor in terms of generating dATP well before the release of cytochrome c and deoxyguanosine kinase from mitochondria.     

Heparan sulfate 6-o-sulfotransferase is essential for muscle development in zebrafish

Heparan sulfate proteoglycans function in development and disease. They consist of a core protein with attached heparan sulfate chains that are altered by a series of carbohydrate-modifying enzymes and sulfotransferases. Here, we report on the identification and characterization of a gene encoding zebrafish heparan sulfate 6-O-sulfotransferase (hs6st) that shows high homology to other heparan sulfate 6-O-sulfotransferases. When expressed as a fusion protein in cultured cells, the protein shows specific 6-O-sulfotransferase activity and preferentially acts on the iduronosyl N-sulfoglycosamine. In the developing embryo, hs6st is expressed in the brain, the somites, and the fins; the same structures that were affected upon morpholino-mediated functional knockdown. Morpholino injections significantly inhibited 6-O- but not 2-O-sulfation as assessed by HPLC. Morphants display disturbed somite specification independent of the somite oscillator mechanism and have impaired muscle differentiation. In conclusion, our results show that transfer of sulfate to specific positions on glycosaminoglycans is essential for muscle development.     

Sporadic chromosome aberrations in healthy individuals studied between 1986-2001

In the second half of 2002, IARC for Central and Eastern European countries targeted studies on the relationship between chromosomal aberrations (CAs) and cancer risk. For these purposes we preliminarily investigated, under identical methodological circumstances, the base-line level of CAs in peripheral blood lymphocytes of 1414 healthy Hungarian persons between 1986 and 2001. The age and sex as biological, and smoking habit and residency (Budapest, industrial- and agricultural settlements) as environmental confounding factors were evaluated. Previously, people were not exposed to any known potential mutagens. The overall frequencies of aberrant cells (1.60+/-0.05%) were not influenced by sex, age and residency, but the smoking habits (1.84+/-0.09%) had significant impact on the elevation of aberrant cells. Aneuploidy, exchange-type dicentric chromosomes and the total of aberrations increased significantly with the age of the donors. The individual frequency of aberrant cells ranged between 0-12%. No aberrant cells were detected in 35% of individuals, and 1 aberrant cell was found in 23% of the total population, while 42% of the examined persons were characterized with aberrant cell rates between 2-12%. The initial value of 0.85% of aberrant cells doubled by the end of the examined 16-year period, following 2-4-fold fluctuations. None of the investigated biological or environmental factors was responsible for the elevation of the CAs. The causes of the elevation of CA-level can be explained more precisely when these data will be compared to cancer registry database of these persons.     

Causes of local recurrence after curative surgery for rectal cancer

The rate of local recurrence (LR) has been 20-40% after resective surgery for rectal cancer by the traditional - Miles or Dixon - operative technics. The authors performed curative resection in 358 patients with rectal cancer in a 10 year period (01.01.1990 - 31.12.2000) in the Surgical Department of Szeged University. Since 01.01.1996 the authors changed this type of surgery for the Heald technics (total mesorectal excision - TME - with sharp dissection, using the UltraCision device) for the surgical treatment of middle or lower third rectal cancer. To compare the results of the two procedures, the authors analysed their material in two periods: Period I: 01.01.1991 - 31.12.1992: 62 patients operated on with the traditional operative technics; LR 15% within 2 years after surgery. Period II: 01.01.1997 - 31.12.1998: 78 patients operated on with the Heald technics (TME with sharp dissection); LR 6.4% within 2 years after surgery. Based on their results, the authors found that the modern operative technics by Heald, used in the second period of the study, was a relevant factor decreasing LR from 15% to 6.4%, while the gender, age of the patients, ratio of the abdominoperineal extirpation versus anterior resection (APRE/AR) and the free margin of more than 3 cm proved to be irrelevant.     

Seasonal home range shift of red deer in a forest-agriculture area in southern Hungary

A long-term radiotelemetry study on red deerCervus elaphus Linnaeus, 1758 was carried out in a lowland forest-agriculture area in Hungary between 1993–2000. Previous observations suggested seasonal changes in population distribution between forested and agricultural habitat. Red deer concentrated in the forest during winter, but they appeared in the agricultural field during the vegetational period. We investigated the ranging behaviour, testing two alternative hypotheses: home range expansion and home range shift. Weekly radiotelemetry localisations revealed that 9 of 28 hinds showed a clear home range shift from the forest to the agricultural area for a prolonged time during the vegetational period. The remaining portion of the animals used a home range within the forest throughout the entire year. Diet composition analysis using indicator plant species showed that neither daily passages between habitats, nor home range expansion exists. These ranging behaviours were stable hence, if an animal shifted one year it shifted again in consecutive years andvice versa. Our results could be useful for the successful management of red deer populations in such complex habitats and to decrease agricultural damage.     

The evolution of immune defense and song complexity in birds

Abstract There are three main hypotheses that explain how the evolution of parasite virulence could be linked to the evolution of secondary sexual traits, such as bird song. First, as Hamilton and Zuk proposed a role for parasites in sexual selection, female preference for healthy males in heavily parasitized species may result in extravagant trait expression. Second, a reverse causal mechanism may act, if sexual selection affects the coevolutionary dynamics of host-parasite interactions per se by selecting for increased virulence. Third, the immuno-suppressive effects of ornamentation by testosterone or limited resources may lead to increased susceptibility to parasites in species with elaborate songs. Assuming a coevolutionary relationship between parasite virulence and host investment in immune defense we used measures of immune function and song complexity to test these hypotheses in a comparative study of passerine birds. Under the first two hypotheses we predicted avian song complexity to be positively related to immune defense among species, whereas this relationship was expected to be negative if immuno-suppression was at work. We found that adult T-cell mediated immune response and the relative size of the bursa of Fabricius were independently positively correlated with a measure of song complexity, even when potentially confounding variables were held constant. Nestling T-cell response was not related to song complexity, probably reflecting age-dependent selective pressures on host immune defense. Our results are consistent with the hypotheses that predict a positive relationship between song complexity and immune function, thus indicating a role for parasites in sexual selection. Different components of the immune system may have been independently involved in this process.     

Adenohypophysis formation in the zebrafish and its dependence on sonic hedgehog

Formation of the adenohypophysis in mammalian embryos occurs via an invagination of the oral ectoderm to form Rathke's pouch, which becomes exposed to opposing dorsoventral gradients of signaling proteins governing specification of the different hormone-producing pituitary cell types. One signal promoting pituitary cell proliferation and differentiation to ventral cell types is Sonic hedgehog (Shh) from the oral ectoderm. To study pituitary formation and patterning in zebrafish, we cloned four cDNAs encoding different pituitary hormones, prolactin (prl), proopiomelancortin (pomc), thyroid stimulating hormone (tsh), and growth hormone (gh), and analyzed their expression patterns relative to that of the pituitary marker lim3. prl and pomc start to be expressed at the lateral edges of the lim3 expression domain, before pituitary cells move into the head. This indicates that patterning of the pituitary anlage and terminal differentiation of pituitary cells starts while cells are still organized in a placodal fashion at the anterior edge of the developing brain. Following the expression pattern of prl and pomc during development, we show that no pituitary-specific invagination equivalent to Rathke's pouch formation takes place. Rather, pituitary cells move inwards together with stomodeal cells during oral cavity formation, with medial cells of the placode ending up posterior and lateral cells ending up anterior, resulting in an anterior-posterior, rather than a dorsoventral, patterning of the adenohypophysis. Carrying out loss- and gain-of-function experiments, we show that Shh from the ventral diencephalon plays a crucial role during induction, patterning, and growth of the zebrafish adenohypophysis. The phenotypes are very similar to those obtained upon pituitary-specific inactivation or overexpression of Shh in mouse embryo, suggesting that the role of Shh during pituitary development has been largely conserved between fish and mice, despite the different modes of pituitary formation in the two vertebrate classes.     

On the role of mechanosensitive mechanisms eliciting reactive hyperemia

We hypothesized that changes in hemodynamic forces such as pressure (P) and flow (F) contribute importantly to the development of reactive hyperemia. To exclude the effects of vivo factors, isolated rat skeletal muscle arterioles ( approximately 130 microm) were utilized. We found that changes in P or P + F following occlusions elicited reactive dilations (RD). The peak of RD (up to approximately 45 microm), but not the duration of RD, increased to changes in P (80 to 10, then back to 80 mmHg) as a function of the length of occlusions (30, 60, and 120 s). However, changes in P + F (80-10 -80 mmHg + 25-0-25 microl/min) increased both the peak and duration of RD (from approximately 25 to 90 s) with longer occlusions. When only P changed, inhibition of nitric oxide synthesis or endothelium removal (E-) reduced only the peak of RD, whereas when P + F were changed, both the peak and duration of RD became reduced. Inhibition of stretch-activated cation channels by gadolinium reduced the peak but enhanced the duration of RD (both to P or P + F) that was unaffected by N(G)-nitro-l-arginine methyl ester (l-NAME) or by E-. When only P changed, inhibition of tyrosine kinases by genistein reduced peak RD but did not affect the RD duration. However, when P + F changed, genistein reduced both the peak and the duration of RD, additional l-NAME reduced the peak RD, but did not affect the duration of RD. Thus in isolated arterioles an RD resembling the characteristics of reactive hyperemia can be generated that is elicited by deformation, stretch, pressure, and flow/shear stress-sensitive mechanisms and is, in part, mediated by nitric oxide.