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991.
Continuous pollen monitoring of an urban network consisting of three stations has been undertaken for a period of 2 years
in Perugia, central Italy. The aim has been to establish whether the Perugia pollen trap, active since 1983, is still representative
of the area following recent urbanisation. Quantitative differences were found between the stations, reflecting different
vegetational areas, but only slight differences were detected in relation to the timing of the principal period of pollination.
Therefore, although individual pollen traps are necessary to characterize fully the different areas, one trap is sufficient
to determine the key allergenic thresholds in the studied area. 相似文献
992.
Continuous pollen monitoring of an urban network consisting of three stations has been undertaken for a period of 2 years in Perugia, central Italy. The aim has been to establish whether the Perugia pollen trap, active since 1983, is still representative of the area following recent urbanisation. Quantitative differences were found between the stations, reflecting different vegetational areas, but only slight differences were detected in relation to the timing of the principal period of pollination. Therefore, although individual pollen traps are necessary to characterize fully the different areas, one trap is sufficient to determine the key allergenic thresholds in the studied area. 相似文献
993.
B. M. Culik K. Pütz R. P. Wilson C. A. Bost Y. Le Maho J. -L. Verselin 《Polar Biology》1996,16(5):371-378
Core temperature was determined in two king penguins living in the wild at Ile de la Possession, Crozel Archipelago, using
implantable four-channel temperature loggers. Core temperatures derived from bird no. 1 (sensor placed under the sternum,
in the vicinity of the liver and upper stomach) were closely correlated with diving activity (as determined by an external
light recorder), and ranged from 38.3°C, (on land) to a minimum of 37.2°C during a dive. Core temperatures measured in bird
no. 2 showed that temperatures near the heart were generally 1°C lower than those under the sternum or in the lower abdomen.
Core temperatures declined continuously during dives (by 0.8, 1.2 and 2.7°C in the lower abdomen, under the sternum and near
the heart, respectively) and showed precipitous drops to 35°C, probably associated with ingestion of food. Temperatures measured
near the heart fluctuated over a period of 288 s, corresponding to the duration (from the literature) of the surface/dive
cycle. The relevance of these findings with respect to diving physiology, blood perfusion of tissues, tissue metabolism and
aerobic dive limits is discussed. 相似文献
994.
H. Sztajer W. Wang H. Lünsdorf A. Stocker R. D. Schmid 《Applied microbiology and biotechnology》1996,45(5):600-606
Geotrichum candidum was found to produce a lactate oxidase. The enzyme was purified by gel filtration and ion-exchange chromatography. The purified
lactate oxidase showed a molecular mass of 50 kDa under denaturing and about 400 kDa under non-denaturing conditions. Transmission
electron micro-scopy analysis confirmed an octameric structure. FMN was found to be a cofactor for this enzyme. Polarographic
studies confirmed an oxygen uptake by the lactate oxidase. The enzyme showed specificity towards the L isomer of lactate and
did not oxidise pyruvate, fumarate, succinate, maleate and ascorbate. It was stable at alkaline pH and also for 15 min at
45°C. The addition of glycerol and dextran 500 000 to the enzyme sample enhanced storage stability.
Received: 28 September 1995/Received revision: 10 January 1996/Accepted: 15 January 1996 相似文献
995.
H. E. Valentin A. Schönebaum A. Steinbüchel 《Applied microbiology and biotechnology》1996,46(3):261-267
A recombinant strain of Pseudomonas putida GPp104 (pHP1014::E146), which expressed the polyhydroxyalkanoic acid (PHA) synthase of Thiocapsa pfennigii exhibiting an unusual substrate specificity at a high level was incubated in two-stage batch or fed-batch accumulation experiments
with 5-hydroxyhexanoic acid (5HHx) as carbon source in the second cultivation phase, copolyesters of 3-hydroxybutyric acid
(3HB) plus 5HHx, or of 3HB, 3-hydroxyhexanoic acid (3HHx) plus 5HHx were accumulated as revealed by gas-chromatographic and
13C-NMR spectroscopic analysis. When the recombinant P. putida GPp104 was incubated with 4-hydroxyheptanoic acid (4HHp) as carbon source in the second cultivation phase, a copolyester
consisting of 3HB, 3-hydroxyvaleric acid and 3- and 4-hydroxyheptanoic acid accumulated. Providing 4-hydroxyoctanoic acid
as carbon source in the second cultivation phase led to the accumulation of a polyester that contained 1–2 mol% 4-hydroxyoctanoic
acid besides 3-hydroxyoctanoic acid, 3HHx, 3-hydroxyvaleric acid and 3HB. In addition to PHA containing these new constituents,
PHA with 4-hydroxyvaleric acid was accumulated from laevulinic acid. Eleven strains from five genera have been also analysed
for their ability to utilize different carbon sources for colony growth, which might serve as potential precursors for the
biosynthesis of PHA with unusual constituents. Although most of the carbon sources were utilized by some strains for colony
growth, accumulation experiments gave no evidence for the accumulation of new PHA by these wild-type strains.
Received: 22 April/Received revision: 23 May 1996/Accepted: 2 June 1996 相似文献
996.
Eberhard Fuchs Jan-Christian Wasmuth Gabriele Flügge Gerald Huether Raphael Troost Jürgen Beyer 《Cellular and molecular neurobiology》1996,16(1):21-37
Summary 1. Corticotropin-releasing factor (CRF) is thought to be involved in the regulation of the diurnal activity of the hypothalamus-pituitary-adrenal
(HPA) axis and to act as a neurotransmitter in the brain. To date it is unknown whether the binding sites of the central CRF
system are subject to diurnal variations.
2. We measured the number of CRF binding sites over the course of a complete 24-hr light-dark cycle in the pituitary, amygdala,
bed nucleus of the stria terminalis (BNST), cingulate cortex, visceral cortex, paraventricular nucleus of the hypothalamus,
hippocampus, and locus ceruleus of rats byin vitro receptor autoradiography with iodinated ovine CRF. A 24-hr time course was also established for plasma CRF and corticosterone.
3. The diurnal pattern of plasma CRF does not correlate with the pattern of plasma corticosterone. Within the brain, CRF binding
in the basolateral nucleus of the amygdala showed a U-shaped curve with maximum levels in the morning and a wide hallow between
1500 and 0100. A biphasic profile with a small depression in the afternoon and a more pronounced depression in the second
half of the activity period is characteristic for the other brain areas and the pituitary. The profile for the pituitary correlates
with those for the BNST and the area of the locus ceruleus. Furthermore, the diurnal pattern of CRF binding sites in the BNST
correlates with that of the hippocampus, and the daytime pattern of the visceral cortex is similar to that of both the hippocampus
and the BNST.
4. Since the CRF-binding profiles in the brain and the pituitary clearly differ from the profiles of both plasma CRF and corticosterone,
one may assume that the diurnal pattern of central CRF binding sites is not directly coupled to the activity of the HPA axis. 相似文献
997.
High-conductance calcium-activated potassium channels; Structure,pharmacology, and function 总被引:19,自引:0,他引:19
Gregory J. Kaczorowski Hans -Günther Knaus Reid J. Leonard Owen B. McManus Maria L. Garcia 《Journal of bioenergetics and biomembranes》1996,28(3):255-267
High-conductance calcium-activated potassium (maxi-K) channels comprise a specialized family of K+ channels. They are unique in their dual requirement for depolarization and Ca2+ binding for transition to the open, or conducting, state. Ion conduction through maxi-K channels is blocked by a family of venom-derived peptides, such as charybdotoxin and iberiotoxin. These peptides have been used to study function and structure of maxi-K channels, to identify novel channel modulators, and to follow the purification of functional maxi-K channels from smooth muscle. The channel consists of two dissimilar subunits, and . The subunit is a member of theslo Ca2+-activated K+ channel gene family and forms the ion conduction pore. The subunit is a structurally unique, membrane-spanning protein that contributes to channel gating and pharmacology. Potent, selective maxi-K channel effectors (both agonists and blockers) of low molecular weight have been identified from natural product sources. These agents, together with peptidyl inhibitors and site-directed antibodies raised against and subunit sequences, can be used to anatomically map maxi-K channel expression, and to study the physiologic role of maxi-K channels in various tissues. One goal of such investigations is to determine whether maxi-K channels represent novel therapeutic targets. 相似文献
998.
Since the exact mechanism of manganese (Mn)-induced learning disability is not known, we investigated the role of elevated
cholesterol in rats exposed daily to 357 and 714 μg Mn/kg for 30 d. Significant Mn accumulation was accompanied by increased
cholesterol content in the hippocampal region of Mn-treated rats. The learning, which is based on the time needed to reach
food placed at the exit of a T-maze after a 1-d training period, was significantly slower in exposed rats than in unexposed
rats. The rats receiving 357 and 714 μg Mn/kg reached the food in 104.5±13.8 and 113.3±25.7 s, respectively, on d 30, whereas
their untreated counterparts reached the food in 28.7±11.4 s. This delay was completely corrected to 29.3±7.8 and 30.7±6.0
s in rats with coadministration of an inhibitor of cholesterol biosynthesis with 357 and 714 μg/kg of Mn. The correction of
impaired learning was associated with the normalization of hippocampal cholesterol, but the Mn level in this region of the
brain was not influenced in rats treated with a drug that inhibits cholesterol biosynthesis. These results suggested that
Mn-induced hypercholesterolemia is involved in Mn-dependent learning disability. 相似文献
999.
1000.