Land-use history of the Axlarp area in the Småland uplands,southern Sweden: palaeoecological and archaeological investigations

The results of pollen analysis, magnetic measurements (SIRM), and archaeological and historical investigations, in the Axlarp area are presented. With respect to natural conditions and the distribution of prehistoric features, this area is typical of the higher parts of the Småland uplands, which, agriculturally, is a marginal region of southern Sweden. The study shows that farming in the Axlarp area began at ca. 700 B.C. (dates in calibrated/calendar years). The period 700 B.C.-A.D. 500 was characterized by shifting cultivation of Hordeum and Triticum and much pasture. Between A.D. 500 and A.D. 1200 farming declined but some pasturage was still practised, possibly on a seasonal basis. Two farms were established in the Middle Ages, probably between A.D. 1200–1300. Cereals were sown in stone-cleared fields and pastoral farming and hay making was carried out. One farm was deserted during the 15th or early 16th century and the other developed into the hamlet Axlarp whose farmers practised a three-course cropping system. Land-use history as recorded in the pollen diagram can be related to activities associated with these farms. Cereals grown after A.D. 1200 included Hordeum and Avena, and possibly Triticum and Secale. There are no indications of slash-and-burn cultivation in the area.     

Filtration rate capacities in 6 species of European freshwater bivalves

Summary Filtration rate capacities in undisturbed freshwater bivalves were determined by means of two different methods (indirect clearance and suction methods) in Anodonta anatina (L.), Unio tumidus Philipsson, Unio pictorum (L.), Unio crassus Philipsson, Dreissena polymorpha (Pallas) and Sphaerium corneum (L.). In A. anatina, D. polymorpha, and S. corneum the filtration rate (FR, 1 h^-1) at 19–20°C as a function of dry tissue weight (DW, g) or ash-free dry weight (AFDW, g) could be expressed by the equations: 1.10 DW^0.78, 6.82 DW^0.88, and 2.14 AFDW^0.92, respectively. In U. tumidus, U. pictorum, and U. crassus filtration rates were comparable with those of A. anatina. In D. polymorpha the b value of the corresponding regression of gill area on dry weight was 0.87. The rates of water transport in freshwater bivalves are 2–8 times lower than in marine bivalves of comparable size. A corresponding difference in the filtration rate per gill area unit is found. The measured filtration rates in undisturbed bivalves are substantially higher (at least 4 times) than previously reported. This indicates that the impact of bivalve water processing on freshwater ecosystems is greater than hitherto suggested.     

What causes extended lows in microtine cycles?

Summary Synchronous declines of sympatric shrew and microtine populations in boreal regions of Fennoscandia have been claimed as evidence that predation deepens and extends the low phase of the microtine population cycles. Assuming that shrews and microtines have the same maximum intrinsic rate of increase, and that the predators kill the shrews and microtines that they encounter unselectively, this hypothesis predicts that sympatric shrew and microtine populations will decline and increase simultaneously. In this study conducted at 60°56N in southeast Norway, as well as in 13 of 15 other studies at sites in Fennoscandia, the shrew populations declined simultaneously with the sympatric microtine populations, but recovered sooner. The shrew-microtine ratio among animals trapped peaked about 2 years after the peak in the microtine population. The same pattern was found in the diet of raptors in Fennoscandia. Since the maximum intrinsic rate of increase does not seem to be higher in shrews than in microtines, the pattern suggests that either predation is not causing the extended lows in the microtine populations, or that the proportion of predators that selectively kill microtines fluctuates during the microtine cycle. The most likely candidates for selective killers are weasels.     

Girdling interruption between source and sink in Quercus pubescens does not trigger leaf senescence

Metabolite changes and senescence behaviour after mechanical phloem girdling were studied in leaf tissue of Quercus pubescens. Sugar accumulation is not only considered to be an important part of several developmental signalling pathways, but is also seen as one of the basic triggers for senescence induction, or at least an obligatory accessory phenomenon. Our survey showed that an accumulation of the soluble sugars, glucose and fructose, was not on its own obligatorily connected with the induction of leaf senescence, since no indication or even an onset of senescence could be observed during the course of the experiment. Instead, we observed an inhibition of leaf development with a decrease of photosynthesis and a slow-down of development in nearly all chlorophyll a fluorescence analysis parameters using the JIP-test. We detected a change of metabolites linked to oxidative stress, possibly due to an overexcitation of the developmentally inhibited photosynthetic apparatus.     

Neuropeptide Y: presence in sympathetic and parasympathetic innervation of the nasal mucosa

Summary The occurrence of neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) in the sympathetic and parasympathetic innervation of the nasal mucosa was studied in various species including man. A dense network of NPY-immunoreactive (IR) fibres was present around arteries and arterioles in the nasal mucosa of all species studied. NPY was also located in nerves around seromucous glands in pig and guinea-pig, but not in rat, cat and man. The NPY-IR glandular innervation corresponded to about 20% of the NPY content of the nasal mucosa as revealed by remaining NPY content determined by radioimmunoassay after sympathectomy. These periglandular NPY-positive fibres had a distribution similar to the VIP-IR and PHI-IR nerves but not to the noradrenergic markers tyrosine hydroxylase (TH) or dopamine--hydroxylase (DBH). The NPY nerves around glands and some perivascular fibres were not influenced by sympathectomy and probably originated in the sphenopalatine ganglion where NPY-IR and VIP-IR ganglion cells were present. The venous sinusoids were innervated by NPY-positive fibres in all species except the cat. Dense NPY and DBH-positive innervation was seen around thick-walled vessels in the pig nasal mucosa; the latter may represent arterio-venous shunts. Double-labelling experiments using TH and DBH, and surgical sympathectomy revealed that the majority of NPY-IR fibres around blood vessels were probably noradrenergic. The NPY-positive perivascular nerves that remained after sympathectomy in the pig nasal mucosa also contained VIP/PHI-IR. The major nasal blood vessels, i.e. sphenopalatine artery and vein, were also densely innervated by NPY-IR fibres of sympathetic origin. Perivascular VIP-IR fibres were present around small arteries, arterioles, venous sinusoids and arterio-venous shunt vessels of the nasal mucosa whereas major nasal vessels received only single VIP-positive nerves. The trigeminal ganglion of the species studied contained only single TH-IR or VIP-IR but no NPY-positive ganglion cells. It is concluded that NPY in the nasal mucosa is mainly present in perivascular nerves of sympathetic origin. In some species, such as pig, glandular and perivascular parasympathetic nerves, probably of VIP/PHI nature, also contain NPY.     

Action of rat liver cathepsin B on bradykinin and on the oxidized insulin A-chain

Rat liver cathepsin B was tested for its peptide-bond specificity against bradykinin and the oxidized insulin A-chain. Bradykinin was shown to be resistant to the action of cathepsin B. One possible reason for this resistance is the proline content of the peptide and the discrimination against proline residues at three or four subsites of cathepsin B. Oxidized insulin A-chain was degraded by a peptidyl dipeptidase activity. Three dipeptides were cleaved from the C-terminal part of the insulin A-chain after having been incubated for 2 h (molar ration E:S = 1:2800) and six dipeptides were released after a longer digestion (10 h, E:S = 1:575).     

Methylotrophic yeast Pichia pastoris as a host for production of ATP-diphosphohydrolase (apyrase) from potato tubers (Solanum tuberosum)

ATP-diphosphohydrolase (apyrase) catalyzes the hydrolysis of phosphoanhydride bonds of nucleoside tri- and di-phosphates in the presence of divalent cations. This enzyme has broad substrate specificity for nucleotides, which makes it an ideal enzyme for different biotechnical applications, such as DNA sequencing and platelet-aggregation inhibition. The only commercially available apyrase is isolated from potato tubers. To avoid batch-to-batch variations in activity and quality, we decided to produce a recombinant enzyme. The methylotrophic yeast Pichia pastoris was chosen as an eukaryotic expression host. The coding sequence of potato apyrase, without the signal peptide, was cloned into the YpDC541 vector to create a fusion with the alpha-mating secretion signal of Saccharomyces cerevisiae. The gene was placed under the control of the methanol-inducible alcohol oxidase promoter. The YpDC541-apyrase construct was integrated into P. pastoris strain SMD1168. Methanol induction resulted in secretion of apyrase to a level of 1mg/L. The biologically active recombinant apyrase was purified by hydrophobic interaction and ion exchange chromatography. According to SDS-PAGE and Western blot analysis, the purified enzyme showed to be hyperglycosylated. By enzymatic removal of N-glycans, a single band corresponding to a molecular mass of 48kDa was detected. The recombinant apyrase was found to function well when it was used in combination with the Pyrosequencing technology.     

Modulation of prolactin but not corticosterone responses to stress in relation to parental effort in a long-lived bird

We tested the hypothesis that parental effort modulates the magnitude of corticosterone and prolactin responses to stress in a long-lived bird, the Black-legged kittiwake (Rissa tridactyla). To do so, we compared corticosterone and prolactin responses to capture/restraint stress between chick-rearing birds and failed breeders (no parental effort). We predicted that (1) the increase in plasma corticosterone levels in response to stress should be lower in chick-rearing birds, (2) the decrease in plasma prolactin levels in response to stress should be lower in chick-rearing birds, and (3) as both sexes care for the chick, there should be no sex difference in the hormonal response to stress. Baseline plasma corticosterone and prolactin levels were higher in chick-rearing birds and were not influenced by body condition. Failed breeders were in better condition than chick-rearing individuals. Corticosterone response to stress was unaffected by parental effort as both chick-rearing and failed birds exhibited a robust corticosterone increase. Prolactin response to stress was however clearly influenced by parental effort: chick-rearing birds showed a modest 9% prolactin decrease whereas in failed birds prolactin concentrations fell by 41%. Body condition did not influence hormonal responses to stress. When facing stressful condition, breeding kittiwakes attenuate their prolactin response to stress while enhancing their secretion of corticosterone. Increasing corticosterone secretion triggers foraging efforts and diminishes nest attendance whereas an attenuation of prolactin response to stress maintains parental behavior. We suggest that this hormonal mechanism facilitates a flexible time-budget that has been interpreted as a buffer against environmental variability.     

Study of possible interactions of tubulin, microtubular network, and STOP protein with mitochondria in muscle cells

We studied possible connections of tubulin, microtubular system, and microtubular network stabilizing STOP protein with mitochondria in rat and mouse cardiac and skeletal muscles by confocal microscopy and oxygraphy. Intracellular localization and content of tubulin was found to be muscle type-specific, with high amounts in oxidative muscles, and much lower in glycolytic skeletal muscle. STOP protein localization and content in muscle cells was also muscle type-specific. In isolated heart mitochondria, addition of 1 μM tubulin heterodimer increased apparent K _m for ADP significantly. Dissociation of microtubular system into free tubulin by colchicine treatment only slightly decreased initially high apparent K _m for ADP in permeabilized cells, and diffusely distributed free tubulin stayed inside the cells, obviously connected to the intracellular structures. To identify the genes that are specific for oxidative muscle, we developed and applied a method of kindred DNA. The results of sequencing and bioinformatic analysis of isolated cDNA pool common for heart and m. soleus showed that in adult mice the β-tubulin gene is expressed predominantly in oxidative muscle cells. It is concluded that whereas dimeric tubulin may play a significant role in regulation of mitochondrial outer membrane permeability in the cells in vivo, its organization into microtubular network has a minor significance on that process.     

Absence of carbon transfer between Medicago truncatula plants linked by a mycorrhizal network, demonstrated in an experimental microcosm

Carbon transfer between plants via a common extraradical network of arbuscular mycorrhizal (AM) fungal hyphae has been investigated abundantly, but the results remain equivocal. We studied the transfer of carbon through this fungal network, from a Medicago truncatula donor plant to a receiver (1) M. truncatula plant growing under decreased light conditions and (2) M. truncatula seedling. Autotrophic plants were grown in bicompartmented Petri plates, with their root systems physically separated, but linked by the extraradical network of Glomus intraradices. A control Myc-/Nod- M. truncatula plant was inserted in the same compartment as the receiver plant. Following labeling of the donor plant with 13CO2, 13C was recovered in the donor plant shoots and roots, in the extraradical mycelium and in the receiver plant roots. Fatty acid analysis of the receiver's roots further demonstrated 13C enrichment in the fungal-specific lipids, while almost no label was detected in the plant-specific compounds. We conclude that carbon was transferred from the donor to the receiver plant via the AM fungal network, but that the transferred carbon remained within the intraradical AM fungal structures of the receiver's root and was not transferred to the receiver's plant tissues.