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1.
Antidepressants, such as traditional tricyclic antidepressants (TCAs), are the first-line treatment for various pain syndromes.
Available evidence indicates that TCAs may target Na+ channels for their analgesic action. In this report, we examined the effects of contemporary antidepressants sertraline and
paroxetine on (1) neuronal Na+ channels expressed in GH3 cells and (2) muscle rNav1.4 Na+ channels heterologously expressed in Hek293t cells. Our results showed that both antidepressants blocked Na+ channels in a highly state-dependent manner. The 50% inhibitory concentrations (IC50) for sertraline and paroxetine ranged ∼18–28 μm for resting block and ∼2–8 μm for inactivated block of neuronal and rNav1.4 Na+ channels. Surprisingly, the IC50 values for both drugs were about 0.6–0.7 μm for the open channel block of persistent late Na+ currents generated through inactivation-deficient rNav1.4 mutant Na+ channels. For comparison, the open channel block in neuronal hNav1.7 counterparts yielded IC50 values around 0.3–0.4 μm for both drugs. Receptor mapping using fast inactivation-deficient rNav1.4-F1579A/K mutants with reduced affinities toward
local anesthetics (LAs) and TCAs indicated that the F1579 residue is not involved in the binding of sertraline and paroxetine.
Thus, sertraline and paroxetine are potent open channel blockers that target persistent late Na+ currents preferentially, but their block is not mediated via the phenylalanine residue at the known LA/TCA receptor site. 相似文献
2.
J. N. Harney E. E. Grossman B. M. Richmond C. H. Fletcher III 《Coral reefs (Online)》2000,19(2):141-154
The origin, age, and dynamics of carbonate sediments in Kailua Bay on Oahu, Hawaii, are described. The shoreface (from shoreline
to 4 km offshore) consists of a broad (5 km2) fringing coral reef ecosystem bisected by a sinuous, shore-normal, sand-filled paleostream channel 200–300 m wide. The median
grain diameter of surface sands is finest on the beach face (<0.3 mm) and increases offshore along the channel axis. Kailua
sands are >90% biogenic carbonate, dominated by skeletal fragments of coralline algae (e.g. Porolithon, up to 50%) followed by the calcareous green alga Halimeda (up to 32%), coral fragments (1–24%), mollusc fragments (6–21%), and benthic foraminifera (1–10%). Sand composition and age
across the shoreface are correlated to carbonate production. Corals and coralline algae, principal builders of the reef framework,
are younger and more abundant in sands along the channel axis and in offshore reefal areas, while Halimeda, molluscs, and foraminifera are younger and more dominant in nearshore waters shoreward of the main region of framework building.
Shoreface sediments are relatively old. Of 20 calibrated radiocarbon dates on skeletal constituents of sand, only three are
younger than 500 years b.p.; six are 500–1000 years b.p.; six are 1000–2000 years b.p.; and five are 2000–5000 years b.p. Dated fine sands are older than medium to coarse sands and hence may constitute a reservoir of fossil carbonate that is
distributed over the entire shoreface. Dominance of fossiliferous sand indicates long storage times for carbonate grains,
which tend to decrease in size with age, such that the entire period of relative sea-level inundation (∼5000 years) is represented
in the sediment. Despite an apparently healthy modern coral ecosystem, the surficial sand pool of Kailua Bay is dominated
by sand reflecting an antecedent system, possibly one that existed under a +1–2 m sea-level high stand during the mid- to
late Holocene.
Accepted: 20 December 1999 相似文献
3.
Yu. V. Kirichok Ya. A. Boychuk M. V. Kopanitsa T. Sh. Tsintsadze N. A. Lozovaya O. A. Krishtal 《Neurophysiology》2000,32(1):12-16
The effects of a novel anti-hypertensive drug, mibefradil, on voltage-dependent currents in isolated thalamic and hippocampal
neurons, as well as on synaptic transmission in the hippocampus have been studied. Mibefradil exerted a potent inhibitory
action on low-threshold calcium currents in thalamic neurons (IC50=160 nM). In higher concentrations (1–20 μM), this drug blocked not only low-threshold calcium current but also voltage-dependent
sodium and delayed potassium currents in pyramidal hippocampal neurons. The amplitude of population action potentials in hippocampal
slices decreased by 55% in the presence of 20μM mibefradil. All of the effects of mibefradil were almost completely reversible.
In our experiments, the sensitivity of low-threshold calcium channels in thalamic neurons to mibefradil was higher than that
observed on other objects. The ability of mibefradil to block not only calcium currents but also other types of voltage-dependent
ion conductances in hippocampal neurons may be considered an essential factor that determines the specificity of the pharmacological
profile of this drug. 相似文献
4.
Kumaran S Panneerselvam KS Shila S Sivarajan K Panneerselvam C 《Molecular and cellular biochemistry》2005,280(1-2):83-89
Mitochondrial damage has implicated a major contributor for ageing process. In the present study, we measured mitochondrial
membrane swelling, mitochondrial respiration (state 3 and 4) by using oxygen electrode in skeletal muscle of young (3–4 months
old) and aged rats (above 24 months old) with supplementation of l-carnitine and dl-α-lipoic acid. Our results shows that the mitochondrial membrane swelling and state 4 respiration were increased more in
skeletal muscle mitochondria of aged rats than in young control rats, whereas the state 3 respiration, respiratory control
ratio (RCR) and ADP:O ratio decreased more in aged rats than in young rats. After supplementation of carnitine and lipoic
acid to aged rats for 30 days, the state 3 respiration and RCR were increased, whereas the state 4 and mitochondrial membrane
swelling were decreased to near normal rats. From our results, we conclude that combined supplementation of carnitine and
lipoic acids to aged rats increases the skeletal muscle mitochondrial respiration, thereby increasing the level of ATP. (Mol
Cell Biochem xxx: 83–89, 2005) 相似文献
5.
Sørensen HR Jørgensen CT Hansen CH Jørgensen CI Pedersen S Meyer AS 《Applied microbiology and biotechnology》2006,73(4):850-861
A novel α-l-arabinofuranosidase (α-AraF) belonging to glycoside hydrolase (GH) family 43 was cloned from Humicola insolens and expressed in Aspergillus oryzae. 1H-NMR analysis revealed that the novel GH43 enzyme selectively hydrolysed (1→3)-α-l-arabinofuranosyl residues of doubly substituted xylopyranosyl residues in arabinoxylan and in arabinoxylan-derived oligosaccharides. The optimal activity of the cloned enzyme was at pH 6.7 and 53 °C. Two other novel α-l-arabinofuranosidases (α-AraFs), both belonging to GH family 51, were cloned from H. insolens and from the white-rot basidiomycete Meripilus giganteus. Both GH51 enzymes catalysed removal of (1→2) and (1→3)-α-l-arabinofuranosyl residues from singly substituted xylopyranosyls in arabinoxylan; the highest arabinose yields were obtained with the M. giganteus enzyme. Combinations (50:50) of the GH43 α-AraF from H. insolens and the GH51 α-AraFs from either M. giganteus or H. insolens resulted in a synergistic increase in arabinose release from water-soluble wheat arabinoxylan in extended reactions at pH 6 and 40 °C. This synergistic interaction between GH43 and GH51 α-AraFs was also evident when a GH43 α-AraF from a Bifidobacterium sp. was supplemented in combination with either of the GH51 enzymes. The synergistic effect is presumed to be a result of the GH51 α-AraFs being able to catalyse the removal of single-sitting (1→2)–α-l-arabinofuranosyls that resulted after the GH43 enzyme had catalysed the removal of (1→3)–α-l-arabinofuranosyl residues on doubly substituted xylopyranosyls in the wheat arabinoxylan. 相似文献
6.
This study investigated the enolization and racemization reactions of glucose and fructose on heating with amino acid enantiomers
and the formation of melanoidins as a result of the Maillard reaction. The study measured reducing sugars and L- and D- amino acids using HPLC as an index for the amount of enolization of the sugars and isomerization of the amino acids. Additionally,
the absorption of melanoidins was measured at different wavelengths (420, 450, 470, 490 nm); the UV–Vis spectra and the extinction
coefficient were determined for the formation of melanoidins. Melanoidins were, rather arbitrarily, defined by a high-molecular-weight
(HMW) if it was above a lower limit of 12.4 kDa, which was the nominal cut-off value in the dialysis system used. A remarkable
enolization reaction of the sugars was observed in the course of the Maillard reaction. Especially, in the Fru/D-Asn model system, the degree of sugar enolization was more than in the other model systems. All of the FDAA (1-fluoro-2,
4-dinitrophenyl-5-L-alanine amide) amino acids were separated by TLC. The racemization of the amino acids was higher in the fructose-amino acids
systems. Isomer formation was the highest in the Fru/D-Asn system. The L- and D- isomers showed different absorptions in the UV–Vis spectra, although these had similar shapes. The absorption of the melanoidins
formed from glucose was higher than that formed from fructose. In particular, the sugar–asparagine system showed different
characteristics according to the L- and D-isomers. The differences in the extinction coefficients of the melanoidins was significant (P < 0.05), except for the sugar–lysine system. 相似文献
7.
In the present investigation, nutritional requirements for induction of a high frequency of well formed somatic embryos (SEs)
from zygotic embryos (ZEs) of sunflower were assessed. Variables like genotype, embryo size (0.5–10 mm), sucrose concentration
(30–240 g l−1), carbohydrate source (sucrose, glucose, maltose), agar strength (0.2–1.0%), basal media (MS, Gamborg, Nitsch, White), photoperiod
(light/dark) and temperature (20–36°C) were tested. All these variables except photoperiod had significant effect on the frequency
of embryogenesis. Highest frequency of embryogenesis was facilitated by Gamborg basal salt media, 120–210 g l−1 sucrose, 0.8–1.0% agar, smaller sized embryos (0.5–2 mm) and incubation temperature of 28–32°C. In addition to these, growth
regulator combinations (2,4-D, 2,4-D+kinetin, BA+NAA) in varying concentrations were tried. Media supplemented with 2,4-D promoted direct embryogenesis, BA+NAA facilitated formation of single/multiple shoots while there was no response on 2,4-D+kinetin supplemented media. Zygotic embryos with well differentiated embryos were transferred to growth regulator free half
strength MS medium for whole plantlet development.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Temporal and Spatial Distribution of the nifH Gene of N2 Fixing Bacteria in Forests and Clearcuts in Western Oregon 总被引:1,自引:0,他引:1
Abstract
Decomposition of plant litter is a primary mechanism of nutrient recycling and redistribution in most terrestrial ecosystems.
Previously we demonstrated by a nested PCR protocol that 20 distinctive nifH (the gene encoding nitrogenase reductase) HaeIII restriction fragment length polymorphism (RFLP) patterns were derived from bulk DNA associated with samples of plant litter
and soil collected at one Douglas Fir (DF) forest [33]. Five of the nifH DNA patterns (II–VI) were dominant types in DF litter with characteristic fragments of 237–303 bp length, whereas samples
from soil contained primarily seven other patterns 131–188 bp length (IX–XV). Here we report that the 237–303 bp fragments
characteristic for forest litter could generally not be detected in plant litter or soil samples collected in clearcuts that
adjoin the forest sites. The same fragments (237–303 bp) were also found in the litter at this DF forest site over 16 months
and were consistently found in litter at 12 other DF forest or recent (<2 yrs) clearcut sites. However, trace to none of these
fragments were detected in 6 clearcut (5–10 yrs) or different forest types (oak, alder) collected over a 200 km east–west
direction in western Oregon, USA. Data suggest that the logging practice in DF forests that creates a clearcut removes a unique
gene pool of nitrogen-fixing microorganisms. These organisms could potentially contribute more to nitrogen fixation in forest
litter than litter from natural or invasive plants that grow in clearcuts [26].
Received: 1 June 1999; Accepted: 7 October 1999; Online Publication: 23 February 2000 相似文献
9.
Regeneration and large-scale propagation of bamboo (Dendrocalamus strictus Nees) through somatic embryogenesis 总被引:1,自引:0,他引:1
A complete protocol for large-scale propagation of Dendrocalamus strictus Nees by somatic embryogenesis has been developed. Seeds cultured on agar-solidified Murashige and Skoog (MS) medium supplemented
with 2,4-dichlorophenoxyacetic acid (2,4-D; 3×10–5
m) produced embryogenic callus from proliferation of the embryo. Somatic embryos formed in vitro multiplied rapidly (two- to
five fold every 5 weeks) on semi-solid MS medium containing 2,4-D (1×10–5
m), kinetin (Kn) (5×10–6
m), 1-indolebutyric acid (IBA) (2×10–6
m) and soluble polyvinylpyrrolidone (PVP) (250 mg l–1), or MS with 2,4-D (1×10–5
m), 6-benzylaminopurine (BAP) (1×10–5
m), and soluble PVP (250 mg l–1). Upon transfer to MS containing 1-naphthaleneacetic acid (NAA) (5×10–6
m), Kn (5×10–6
m) and soluble PVP (250 mg l–1), the dark-green embryos developed into healthy plantlets. Unrooted shoots, if any, obtained on the multiplication media
were rooted on MS major salts reduced to half strength supplemented with NAA (3×10–6
m) and IBA (2.5×10–6
m). The rooted plants were successfully transferred to soil in polythene bags with over 80% survival. Using this methodology,
more than 100,000 plants have been produced.
Received: 16 April 1998 / Revision received: 25 September 1998 / Accepted: 10 October 1998 相似文献
10.
Kawai R Igarashi K Yoshida M Kitaoka M Samejima M 《Applied microbiology and biotechnology》2006,71(6):898-906
When Phanerochaete chrysosporium was grown with laminarin (a β-1,3/1,6-glucan) as the sole carbon source, a β-1,3-glucanase with a molecular mass of 36 kDa was produced as a major extracellular protein. The cDNA encoding this enzyme was cloned, and the deduced amino acid sequence revealed that this enzyme belongs to glycoside hydrolase family 16; it was named Lam16A. Recombinant Lam16A, expressed in the methylotrophic yeast Pichia pastoris, randomly hydrolyzes linear β-1,3-glucan, branched β-1,3/1,6-glucan, and β-1,3-1,4-glucan, suggesting that the enzyme is a typical endo-1,3(4)-β-glucanase (EC 3.2.1.6) with broad substrate specificity for β-1,3-glucans. When laminarin and lichenan were used as substrates, Lam16A produced 6-O-glucosyl-laminaritriose (β-d-Glcp-(1–>6)-β-d-Glcp-(1–>3)-β-d-Glcp-(1–>3)-d-Glc) and 4-O-glucosyl-laminaribiose (β-d-Glcp-(1–>4)-β-d-Glcp-(1–>3)-d-Glc), respectively, as one of the major products. These results suggested that the enzyme strictly recognizes β-d-Glcp-(1–>3)-d-Glcp at subsites −2 and −1, whereas it permits 6-O-glucosyl substitution at subsite +1 and a β-1,4-glucosidic linkage at the catalytic site. Consequently, Lam16A generates non-branched oligosaccharide from branched β-1,3/1,6-glucan and, thus, may contribute to the effective degradation of such molecules in combination with other extracellular β-1,3-glucanases. 相似文献
11.
Morphogenesis from several explant types excised from in-vitro-grown plantlets of a Brazilian eggplant (Solanum melongena L.) variety (F-100) was evaluated in response to thidiazuron (TDZ). Leaves and cotyledons were found to be the most responsive
explants. Optimal shoot bud induction rates (75–100 buds/explant) were achieved in the presence of 0.2 μm TDZ. Organogenic calli were transferred to growth regulator free MS medium before shoot excision. Rooting was induced on
half-strength MS medium supplemented with 0.6 μm IAA.
Received: 1 March 1997 / Revision received: 29 October 1997 / Accepted: 15 November 1997 相似文献
12.
Peter C. Hubbard Eduardo N. Barata Rodrigo O. A. Ozório Luisa M. P. Valente Adelino V. M. Canário 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(8):839-849
The current study investigated the olfactory sensitivity of the blackspot sea bream to amino acids, odorants associated with
food detection in fish, and compared the efficacy of two different experimental methods: multi-unit recording from the olfactory
nerve and the electro-olfactogram (EOG). Twenty essential amino acids plus l-DOPA evoked clear, concentration-dependent olfactory responses using both methods, with estimated thresholds of 10−8.5–10−6.2 M (nerve recording) and 10−7.5–10−4.8 M (EOG). The most potent amino acids were l-cysteine, l-methionine (both sulphur-containing), l-alanine, l-leucine (both neutral), l-glutamine (amide-containing) and l-serine (hydroxyl-containing). The least potent were l-proline (secondary α-amino group), the aromatic amino acids and glycine (simplest). Although the rank order of olfactory
potency was similar for the two methods used, and the calculated thresholds given by the two methods were positively correlated,
the sensitivity of the EOG was consistently lower than multi-unit recording by approximately one order of magnitude, presumably
due to the electrical shunting effect of seawater. As in freshwater, the EOG could be a valid method for comparing olfactory
potency of different odorants in stenohaline marine fish; however, for absolute ‘biological’ thresholds, a more invasive recording
technique, such as multi-unit recording from the olfactory nerve, should be used. 相似文献
13.
Yi-Guang Chen Shu-Kun Tang Yu-Qin Zhang Zhu-Xiang Liu Qi-Hui Chen Jian-Wu He Xiao-Long Cui Wen-Jun Li 《Extremophiles : life under extreme conditions》2010,14(4):397-402
A novel moderately halophilic, alkaliphilic, non-motile, non-sporulating, catalase-positive, oxidase-negative, aerobic, coccus-shaped,
Gram-positive bacterium, designated strain JSM 071043T, was isolated from a subterranean brine sample collected from a salt mine in Hunan Province, China. Growth occurred with
0.5–20% (w/v) NaCl (optimum 5–10%) at pH 6.5–10.5 (optimum pH 8.5) and at 10–40°C (optimum 25–30°C). Good growth also occurred
in the presence of 0.5–20% (w/v) KCl (optimum 5–8%) or 0.5–25% (w/v) MgCl2·6H2O (optimum 5–10%). The peptidoglycan type was A4α (l-Lys–l-Ala–l-Glu) and major cell-wall sugars were tyvelose and mannose. The major cellular fatty acids were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. Strain JSM 071043T contained MK-9 and MK-8 as the predominant menaquinones and diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol
as the major polar lipids. The DNA G + C content was 67.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed
that strain JSM 071043T was a member of the suborder Micrococcineae, and was most closely related to Zhihengliuella halotolerans YIM 70185T (sequence similarity 98.9%) and Zhihengliuella alba YIM 90734T (98.2%), and the three strains formed a distinct branch in the phylogenetic tree. The combination of phylogenetic analysis,
DNA–DNA relatedness values, phenotypic characteristics and chemotaxonomic data supports the proposal that strain JSM 071043T represents a novel species of the genus Zhihengliuella, for which the name Z. salsuginis sp. nov. is proposed. The type strain is JSM 071043T (= DSM 21149T = KCTC 19466T). 相似文献
14.
Proteins have been considered to consist exclusively of l-amino acids in living tissues. However, our previous studies showed that two specific aspartyl (Asp) residues in αA- and
αB-crystallins from human eye lenses invert to the d-isomers to a high degree during aging. The reaction is also accompanied by isomerization into a form containing β-Asp (isoaspartate)
residues. The appearance of d- and β-Asp in a protein potentially induces large changes to the higher order structure of the protein as well as to its
function. However, it remains unclear whether the formation of the Asp isomer is the direct trigger of the change to the higher
order structure and function. In this study, in order to clarify the effect of the inversion to d-isomers in a protein, we synthesized peptides corresponding to the 70–88 (KFVIFLDVKHFSPEDLTVK) fragment of human αA-crystallin
and its corresponding diastereoisomers in which lα-Asp was replaced with lβ-Asp, dα-Asp, and dβ-Asp at position 76 and compared their biochemical properties with that of normal peptide. The peptides containing abnormal
isomers (lβ-Asp, dα-Asp, and dβ-Asp residues, respectively) were more hydrophilic than the normal peptide (containing lα-Asp), lost β-sheet structure and changed to random structures. The normal peptide promoted the aggregation of insulin while
the other three isomers suppressed the aggregation of insulin. This is the first evidence that a single substitution of an
Asp isomer in a peptide induces a large change to the properties of the peptide. 相似文献
15.
A rapid and reliable micropropagation method was established for Spathoglottis plicata. Nodal and leaf explants dissected from 8-month-old pot-grown seedlings were cultured on charcoal-amended Murashige and Skoog
medium supplemented with 16 combinations of α-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BA) at concentrations
of 0.54–10.74 μm. Regeneration of protocorm-like bodies (PLBs) and subsequent plantlet development were observed from 98.5% of the nodal explants.
Only 6.5% of leaf explants and occasionally some root segments (dissected from regenerated plantlets) were able to produce
PLBs and then plantlets. The optimum plant growth regulator (PGR) combination for maximal PLB regeneration was 5.37 μm NAA and 0.44 μm BA. The best combination of PGR for plantlet development was 2.69–10.74 μm NAA and 8.88 μm BA. The NAA to BA ratios for maximal PLB induction and plantlet development were 12.2 and 0.3–1.2, respectively. Regenerated
PLBs and plantlets, when cut into pieces of less than 1 mm and subcultured onto the above media, regenerated new PLBs and
plantlets in another 3 months.
Received: 20 February 1997 / Revision received: 27 May 1997 / Accepted: 16 June 1997 相似文献
16.
Richard Tipping Patrick Ashmore Althea L. Davies B. Andrew Haggart Andrew Moir Anthony Newton Robert Sands Theo Skinner Eileen Tisdall 《Vegetation History and Archaeobotany》2008,17(3):251-267
Pollen, microscopic charcoal, palaeohydrological and dendrochronological analyses are applied to a radiocarbon and tephrochronologically
dated mid Holocene (ca. 8500–3000 cal b.p.) peat sequence with abundant fossil Pinus (pine) wood. The Pinus populations on peat fluctuated considerably over the period in question. Colonisation by Pinus from ca. 7900–7600 cal b.p. appears to have had no specific environmental trigger; it was probably determined by the rate of migration from particular
populations. The second phase, at ca. 5000–4400 cal b.p., was facilitated by anthropogenic interference that reduced competition from other trees. The pollen record shows two Pinus declines. The first at ca. 6200–5500 cal b.p. was caused by a series of rapid and frequent climatic shifts. The second, the so-called pine decline, was very gradual (ca.
4200–3300 cal b.p.) at Loch Farlary and may not have been related to climate change as is often supposed. Low intensity but sustained grazing
pressures were more important. Throughout the mid Holocene, the frequency and intensity of burning in these open Pinus–Calluna woods were probably highly sensitive to hydrological (climatic) change. Axe marks on several trees are related to the mid
to late Bronze Age, i.e., long after the trees had died. 相似文献
17.
Jiro Arima Masanori Chiba Tsuyoshi Ichiyanagi Yukinori Yabuta Nobuhiro Mori Tadanori Aimi 《Applied microbiology and biotechnology》2010,87(5):1791-1801
An aminopeptidase that has peptide bond formation activity was identified in the cell-free extract of carpophore of Pleurotus eryngii. The enzyme, redesignated as eryngase, was purified for homogeneity and characterized. Eryngase had a molecular mass of approximately
79 kDa. It showed somewhat high stability with respect to temperature and pH; it was inhibited by iodoacetate. Among hydrolytic
activities toward aminoacyl-p-nitroanilides (aminoacyl-pNAs), eryngase mainly hydrolyzed hydrophobic l-aminoacyl-pNAs and exhibited little activity toward d-Ala-pNA and d-Leu-pNA. In terms of peptide bond formation activity, eryngase used various aminoacyl derivatives as acyl donors and acceptors.
The products were all dipeptidyl derivatives. Investigation of time dependence on peptide synthesis revealed that some peptides
that are not recognized as substrates for hydrolytic activity of eryngase could become good targets for synthesis. Furthermore,
eryngase has produced opioid dipeptides––l-kyotorphin (l-Tyr-l-Arg) and d-kyotorphin (l-Tyr-d-Arg)––using l-Tyr-NH2 and d- and l-Arg-methyl ester respectively as an acyl donor and acceptor. Yield evaluation of kyotorphin synthesis indicated that the
conversion ratio of substrate to kyotorphin was moderate: the value was estimated as greater than 20%. 相似文献
18.
Akira Hisanaga Yukuo Eguchi Miyuki Hirata Noburu Ishinishi 《Biological trace element research》1988,16(1):77-85
During the past few centuries, lead production, consumption and emissions, to our total environment have increased remarkably.
We have determined the concentrations of lead in 41 well-preserved ancient and 11 contemporary rib bones of a mature age (40–60
y), with a view to historically evaluating lead exposure in humans. The oldest Japanese bones (1000–300b.c.) were found to contain a mean of 0.58 μg Pb/g dry wt and a mean molar ratio of lead to calcium of 0.6×10−6, compared with 4.7–5.2×10−6 in the bones of the Edo era (1600–1867a.d.) and contemporary residents in Japan. The mean molar ratios of female bones were always higher than those of male bones for
each era. From this fact we may assume that facial cosmetics were one of the main routes of lead exposure among the ancient
Japanese, especially those who lived during the Edo era. 相似文献
19.
Primary cultures containing a high percentage of lactotrophs were obtained by dissociating the pituitary of rats following
14–18 days of lactation. Lactotrophs with a distinctive appearance were recorded after 1–35 days in vitro and identified by
immunocytochemical staining for prolactin. Whole-cell voltage clamp measurements in isotonic KCl solution from a holding potential
of −40 mV revealed the presence of inward-rectifying K currents with a time-dependent, Na+-independent inactivation at potentials negative to −60 mV. The time for complete inactivation was strikingly different between
lactotrophs, varying between 1 sec and more than 5 sec at −120 mV, and was not related to time in culture. The reversal potential
shifted 59 mV (25°C) for a tenfold change in external K+ concentration, demonstrating the selectivity of the channel for K+ over Na+. The inward-rectifying K current was blocked by 5 mm Ba2+ and partially blocked by 10 mm TEA. Chloramine-T (1 and 2 mm) produced a total block of the inward-rectifying K current in lactotrophs. Thyrotropin-releasing hormone (500 nm) significantly reduced the inward-rectifying K current in about half of the lactotrophs. This current is similar to the inward-rectifying
K current previously characterized in clonal somatomammotrophic pituitary cells (GH3B6). The variability of the rate of inactivation of this current in lactotrophs and its responsiveness to TRH is discussed.
Received: 28 September 1995/Revised: 11 December 1995 相似文献
20.
Abstract
The dominant members of the bacterioplankton community in a set of 10 small, thermally stratified lakes in northeastern Indiana
were determined by denaturing gradient gel electrophoresis (DGGE) of a polymerase chain reaction amplified fragment of 16S
rDNA. The variability in community composition was analyzed as function of vertical stratification (epilimnion vs metalimnion),
time (July vs August samples), and geographical location. In 58 discrete samples, a range of 8–23 bands were detected (mean
= 14, s.d. = 4). For all variables, sample pairs shared about 40–70% of bands. In comparisons between depth strata, pairs
of oxic samples shared more bands than an oxic–anoxic pair. There was no obvious relationship between the geographical location
of lakes (or their physical connection) and band sharing.
Received: 4 March 1999; Accepted: 11 May 1999 相似文献