To thermoconform or thermoregulate? An assessment of thermoregulation opportunities for the lizard<Emphasis Type="Italic"> Zootoca vivipara</Emphasis> in the subarctic

The general model of thermoregulation of ectotherms predicts that thermally challenging environments select for evolution of thermoconformity. Studies of reptilian thermoregulation at climatic extremes are rare and, in the subarctic zone, completely lacking. Thermal characteristics of the habitat of the lizard Zootoca vivipara were studied in the subarctic zone, at the northern margin of its distribution, where lizard density was already extremely low. We found that, during the activity period, the preferred body temperatures of Z. vivipara were not available for a thermoconformer, but available for 7 h for a thermoregulator in an average day. Therefore, thermoconformity is unbeneficial and accurate thermoregulation should be the appropriate strategy. We hypothesise that the extremely low lizard abundance at our subarctic study site is caused by the short activity season and the large daily temperature fluctuations, with night temperatures occasionally falling below zero even during the activity period.     

Seasonal reproductive endocrine profile of the raccoon dog (Nyctereutes procyonoides)-effects of melatonin and food deprivation

The raccoon dog (Nyctereutes procyonoides, Canidae, Carnivora) is a middle-sized omnivore with excessive autumnal fattening and winter sleep. We studied adaptations of the species to boreal climate and photoperiod by following the plasma reproductive and thyroid hormone concentrations of farm-bred raccoon dogs (n=32) for 12 months. On August 16, 2000, and February 8, 2001, half of the raccoon dogs received continuous-release melatonin implants (the MEL group). The other half was sham-operated (the SHAM group). Between November 27, 2000, and January 25, 2001, half of the animals of both groups were fasted. The plasma testosterone concentrations of the MEL males peaked in February, a month earlier than in the SHAM males. Autumnal melatonin treatment also advanced the gestation period reflected by the plasma progesterone concentrations by seven weeks. Food deprivation in winter seems to accentuate the sex steroid response during the mating as the fasted males had higher testosterone concentrations than the fed males in February and March.     

Identification of a basolateral Cl-/HCO3- exchanger specific to gastric parietal cells

The basolateral Cl(-)/HCO(3)(-) exchanger in parietal cells plays an essential role in gastric acid secretion mediated via the apical gastric H(+)-K(+)-ATPase. Here, we report the identification of a new Cl(-)/HCO(3)(-) exchanger, which shows exclusive expression in mouse stomach and kidney, with expression in the stomach limited to the basolateral membrane of gastric parietal cells. Tissue distribution studies by RT-PCR and Northern hybridizations demonstrated the exclusive expression of this transporter, also known as SLC26A7, to stomach and kidney, with the stomach expression significantly more abundant. No expression was detected in the intestine. Cellular distribution studies by RT-PCR and Northern hybridizations demonstrated predominant localization of SLC26A7 in gastric parietal cells. Immunofluorescence labeling localized this exchanger exclusively to the basolateral membrane of gastric parietal cells, and functional studies in oocytes indicated that SLC26A7 is a DIDS-sensitive Cl(-)/HCO(3)(-) exchanger that is active in both acidic and alkaline pH(i). On the basis of its unique expression pattern and function, we propose that SLC26A7 is a basolateral Cl(-)/HCO(3)(-) exchanger in gastric parietal cells and plays a major role in gastric acid secretion.     

FGF signaling through FGFR1 is required for olfactory bulb morphogenesis

During development, the embryonic telencephalon is patterned into different areas that give rise to distinct adult brain structures. Several secreted signaling molecules are expressed at putative signaling centers in the early telencephalon. In particular, Fgf8 is expressed at the anterior end of the telencephalon and is hypothesized to pattern it along the anteroposterior (AP) axis. Using a CRE/loxP genetic approach to disrupt genes in the telencephalon, we address the role of FGF signaling directly in vivo by abolishing expression of the FGF receptor Fgfr1. In the Fgfr1-deficient telencephalon, AP patterning is largely normal. However, morphological defects are observed at the anterior end of the telencephalon. Most notably, the olfactory bulbs do not form normally. Examination of the proliferation state of anterior telencephalic cells supports a model for olfactory bulb formation in which an FGF-dependent decrease in proliferation is required for initial bulb evagination. Together the results demonstrate an essential role for Fgfr1 in patterning and morphogenesis of the telencephalon.     

Expression of transmembrane carbonic anhydrase isoenzymes IX and XII in normal human pancreas and pancreatic tumours

Carbonic anhydrase (CA) IX and XII are transmembrane isoenzymes which are expressed in several epithelia and overexpressed in some carcinomas. They have recently been linked to von Hippel-Lindau gene-mediated carcinogenesis in that both isoenzymes are downregulated by the product of the wild-type von Hippel-Lindau tumour suppressor gene. This paper describes the localisation of CA IX and XII in the normal human pancreas and pancreatic tumours. Both isoenzymes showed positive reaction in the basolateral plasma membrane of the normal acinar and ductal epithelia. The hyperplastic ductal epithelium in tumour specimens generally showed an increased staining for CA IX. Of 29 malignant tumours of exocrine pancreas, 10 showed moderate or strong immunoreaction for CA IX. The signal for CA XII remained weak in most malignant lesions. The present results show that both CA IX and XII are unevenly expressed in the ductal and acinar compartments of the human pancreas. The expression of these isoenzymes in a relatively low number of malignant tumour specimens suggests that they have a limited value in diagnostic evaluation of pancreatic carcinoma. However, the increased expression of CA IX in hyperplastic ductal epithelium may contribute to the pancreatic tumourigenesis.     

Isolation, Characterization, Molecular Gene Cloning, and Sequencing of a Novel Phytase from Bacillus subtilis

The Bacillus subtilis strain VTT E-68013 was chosen for purification and characterization of its excreted phytase. Purified enzyme had maximal phytase activity at pH 7 and 55°C. Isolated enzyme required calcium for its activity and/or stability and was readily inhibited by EDTA. The enzyme proved to be highly specific since, of the substrates tested, only phytate, ADP, and ATP were hydrolyzed (100, 75, and 50% of the relative activity, respectively). The phytase gene (phyC) was cloned from the B. subtilis VTT E-68013 genomic library. The deduced amino acid sequence (383 residues) showed no homology to the sequences of other phytases nor to those of any known phosphatases. PhyC did not have the conserved RHGXRXP sequence found in the active site of known phytases, and therefore PhyC appears not to be a member of the phytase subfamily of histidine acid phosphatases but a novel enzyme having phytase activity. Due to its pH profile and optimum, it could be an interesting candidate for feed applications.     

Mapping and cloning of FAD2 gene to develop allele-specific PCR for oleic acid in spring turnip rape (Brassica rapa ssp. oleifera)

The previously identified QTL for oleic acid content observed in an F2 population from the Brassica rapa ssp. oleifera cross Jo4002 × Jo4072 (a high-oleic-acid individual) was mapped more precisely by adding markers to the linkage group which harbours the locus. In addition, the fad2 gene, which is known to encode the 18:1 desaturase in Arabidopsis, was mapped in Brassica, too. The results are consistent with the QTL corresponding to the Arabidopsis fad2 gene. Comparison of the wild-type and high-oleic-acid allele of the locus revealed only one difference in their nucleic acid sequences leading to an amino acid change. This substitution of leucine by proline most likely affects the fold of the protein and thereby activity of the enzyme. Using this base difference, an allele-specific PCR was designed. The allele-specific markers will be very effective in selection for plants with high-oleic-acid content derived from Jo4072 because they are located exactly at the locus and can differentiate between homo- and heterozygotes.