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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of tyrosinase in Streptomyces requires functional MelC1 protein, which is postulated to transfer copper to apotyrosinase. We have previously isolated a mutant of Streptomyces lividans, HT32, that phenotypically suppressed mutations in cloned melC1 (H.-C. Tseng and C. W. Chen, in preparation). Plasmid pLUS132, containing an ATG to ATA transition at the initiation codon of melC1, was used for cloning the suppressor gene from HT32. A 1687bp suppressor DNA was isolated that contained two characteristic Streptomyces coding sequences: a 217-amino-acid open reading frame (cutR) and a truncated open reading frame (cutR) downstream. Subcloning analysis attributed the phenotypic suppression activity to the putative cutR gene from HT32. The putative CutR exhibited similarity to the response regulator OmpR of the osmoregulatory signal-transduction system in Escherichia coli. The truncated CutS resembled, to a lesser degree, the N-terminus of EnvZ, the histidine protein kinase counterpart of OmpR. DNA hybridizing to the cloned cutR-cutS sequence was detected in 16 other Streptomyces species. We postulate that the putative cutR-cutS operon regulates copper metabolism in Streptomyces.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: An extracellular protein was isolated from a species of soil-borne fungi (Trichoderma viride) and its amino acid composition has been determined. The protein is acidic with a molecular mass of 14 200 daltons and is given the trivial name tricholin. Tricholin is a potent inhibitor of cell-free protein synthesis. When rabbit reticulocyte lysate was incubated with tricholin at a concentration of 6.3 × 10−7 M, it completely abolished the capacity of the lysate to support protein synthesis. The inhibition appears to be due to its reaction to ribosomes, since it generates a specific cleavage product, an α-sarcin RNA fragment, from reticulocyte ribosomal RNA. This reaction to ribosomes mimics that of α-sarcin. The antibody of α-sarcin strongly cross-reacts with tricholin, while the antibody of tricholin shows a weak reaction with α-sarcin.
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Addition of endothelins (ETs) to neuroblastomaglioma hybrid cells (NG108-15) induced increases in cytosolic free Ca2+ ([Ca2+]i) levels of labeled inositol monophosphates and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. The increases in [Ca2+]i elicited by the three ETs (ET-1, ET-2, and ET-3) were transient and did not show a sustained phase. Chelating extracellular Ca2+ in the medium by adding excess EGTA decreased the ET-mediated Ca2+ response by 40-50%. This result indicates that a substantial portion of the increase in [Ca2+]i was due to influx from an extracellular source. However, the increase in [Ca2+]i was not affected by verapamil or nifedipine (10−5M). A rank order potency of ET-1 ET-2 ET-3 is shown for the stimulated increase in [Ca2+]i, as well as labeled inositol phosphates, in these cells. ATP (10−4M) and bradykinin (10−7M) also induced the increases in [Ca2+]i and Ins(1,4,5)P3 in NG108-15 cells, albeit to a different extent. When compared at 10−7M, bradykinin elicited a five- to sixfold higher increase in the level of Ins(1,4,5)P3, but less than a twofold higher increase in [Ca2+]i than those induced by ET-1. Additive increases in both Ins(1,4,5)P3 and [Ca2+]i were observed when ET-1, ATP, and bradykinin were added to the cells in different combinations, suggesting that each receptor agonist is responsible for the hydrolysis of a pool of polyphosphoinositide within the membrane. ET-1 exhibited homologous desensitization of the Ca2+ response, but partial heterologous desensitization to the Ca2+ response elicited by ATP. On the contrary, ET-1 did not desensitize the response elicited by bradykinin, although bradykinin exhibited complete heterologous desensitization to the response elicited by ET-1. Taken together, these results illustrate that, in NG108-15 cells, a considerable amount of receptor cross talk occurs between ET and other receptors that transmit signals through the polyphosphoinositide pathway.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The neurotransmitter acetylcholine regulates cAMP concentrations in mouse neuroblastoma cells (clone NS20). In these cells, the action of acetylcholine appears to be specific: it does not alter basal concentrations of cAMP, but prevents the elevation of cAMP which is mediated by either adenosine or prostaglandin E1. The receptor for acetylcholine which is involved in this phenomenon has been identified as muscarinic. Pilocarpine and carbamylcholine, but not acetate or choline, will substitute for acetylcholine. Furthermore, the action of 10 μM-carbbamylcholine is blocked by ≥ nM concentrations of atropine, isopropamide or 3-quinuclidinylbenzilate, but not by mM concentrations of d-tubocurarine or hexamethonium.Of eight cholinergic antagonists tested, decamethonium and succinylcholine were the only two which were able to substitute for acetylcholine. These two antagonists are known to cause depolarization of post-synaptic cells. Decamethonium and succinylcholine appear to interact with the same muscarinic receptor, as their actions are also blockèd by low concentrations of 3-quinuclidinylbenzilate. In addition to these two depolarizing antagonists, the ionophores, valinomycin, A23187 and X537A, were also found to prevent elevation of cAMP concentrations. The involvement of specific membrane depolarization as being the active agent by which acetylcholine inhibits elevation of cAMP concentrations is discussed.
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  • 5
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The direct renal effects of endothelin (ET) were studied in eight chronic hypoxic rats (HA) and eight sea level (SL) spontaneously hypertensive rats (SHR).2. After 4 weeks of exposure to simulated 5486 m (18000 ft) hypoxia, all HA rats were in apparently good health, and baseline renal function, except effective renal blood flow, was not significantly different from SL rats.3. Intrarenal arterial administration of ET (600 ng/ kg per h) reduced ipsilateral renal excretion of water, sodium and potassium, glomerular filtration rate and effective renal plasma flow in both SL and HA rats to almost the same extent.4. Administration of ET antiserum, however, increased the renal excretion of water in HA rats.5. It is concluded that ET may play a role in the renal regulation of chronic hypoxic SHR.
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  • 6
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Contractions and electrical activity were recorded from isolated segments of longitudinal (L) and circular (C) myometrium from rats on gestation days 16–17 and 21 before and during parturition.2. The segments were arranged so that the activity of the two layers could be monitored simultaneously and independently.3. Out of the 15 preparations from days 16–17, 13 showed no co-ordination of activity between the layers. In the other two preparations a large contraction of C occasionally initiated a contraction of L. Surgical separation of the layers disrupted the co-ordination and L then developed its independent rhythm.4. On day 21 before delivery, eight of 10 preparations exhibited 1:1 co-ordination of activity between the two layers, but C did not consistently pace L. The pacing shifted from one layer to the other several times during an experiment.5. During parturition there was a 1:1 co-ordination of activity in all 10 preparations examined. In nine of these L initiated the activity of the C. Surgical separation of the layers disrupted the co-ordination and C developed its independent rhythm. In one the pacing shifted from one layer to the other several times during the experiment.6. In all cases where co-ordination between the layers was observed it was myogenic and apparently related to the spread of action potentials between the two muscles.
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  • 7
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Rats were prepared with chronic cannulae in the carotid artery, jugular vein and urinary bladder; they were then kept 2 days to allow recovery from surgery.2. A steady-state continuous saline diuresis was established, then various anaesthetic agents were injected and changes in the urine flow, sodium and potassium excretion rates, GFR, ERPF, ERBF and blood pressure were measured.3. Five groups of rats were studied: (1) control animals given saline in place of any anaesthetic agent, all parameters measured remained constant; (2) althesin (1.2 mg/kg), all parameters remained constant except for the blood pressure which decreased slightly for 5 min; (3) althesin (12 mg/kg); (4) ketamine (50 mg/kg); (5) pentothal (50 mg/kg). The above anaesthetics altered all of the measured parameters except urine output.4. Various mechanisms for these anaesthetic agents are discussed.5. In althesin anaesthetized rats, all the retarded renal parameters recovered within 30 min. It is concluded that for the study of renal function, if a brief anaesthesia is needed, althesin is a more suitable anaesthetic agent.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Due to the difference in open circuit potential (OCP) versus SCE for Aristaloy* amalgam (-969 mV) and Dispersalloy† amalgam (-549 mV) in Ringer's solution at 25°C, a galvanic cell was created with Dispersalloy amalgam as cathode and Aristaloy amalgam as anode.The galvanic corrosion current was studied as a function of time for the above cell as well as for a cell of type III dental gold
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  • 9
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report the rare occurrence of a progressive fetal axillary cystic lymphangioma coexistent with an overlying naevus flammeus. The fetus at 22 weeks gestation was found to have a 37 × 35 mm left axillary multiloculated mass without colour-flow imaging. Amniocentesis showed a normal 46.XX karyotype. Multiple fine-needle aspirations of the mass in the second and third trimesters obtained blood-stained chocolate-coloured fluid containing numerous erythrocytes and lymphocytes but proved ineffective in lessening the progressive growth of the mass. The mother underwent caesarean delivery and a healthy neonate was born with a 141 × 81 mm left axillary cystic lymphangioma and a 50 × 35 mm coexistent naevus flammeus. The neonate was well after simple excision of the lesions. Although cystic lymphangiomas arising in the axilla enlarge progressively during fetal life. our case suggests a good prognosis and except for genetic evaluation. no prenatal intervention is required.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effect of corrosion upon dental amalgam was studied by measuring the effect of anodic polarization on its tensile strength. A conventional tensile testing method using dumb-bell shaped specimens deformed along the long axis was employed. The results showed a significant reduction (27%) in the mean tensile strength, due to the anodic polarization of conventional amalgam, whereas the strength of the high Cu-containing Dispersalloy amalgam was unaffected by polarization. When the diametral tensile strengths of polarized and unpolarized conventional amalgam and Dispersalloy specimens were compared (ADA Specification No. 1), no significant difference in strength was observed.These results indicate that the anodic corrosion of γ2 phase network in the conventional amalgam fillings can be directly attributed to a reduction of tensile strength which would be manifested clinically as marginal breakdown. It appears also that the diametral tensile test is not sufficiently discriminating to allow for an in vitro simulation of clinical properties.
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