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  • 1
    Electronic Resource
    Electronic Resource
    Thermal degradation of the structural isomers arsenazo III and palladiazo (1971)
    Springer
    Microchimica acta 59 (1971), S. 447-454 
    Details
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Wirkung hoher Temperaturen bei der vollständigen Trocknung von Arsenazo III und Palladiazo wurde mit und ohne Anwesenheit von Sulfaminsäure untersucht, um so die Bedingungen nachzuahmen, wie sie bei der Anwendung von Sulfaminsäure zur Entfernung überschüssiger salpetriger Säure gegeben sind und wie sie bei der Synthese dieser Farbstoffe als Folge der Diazotierung eintreten. Spektrophotometrische Messungen zeigen, daß das stark unterschiedliche Ausmaß des thermischen Zersetzungsvorganges von der Anwesenheit der Sulfaminsäure abhängt, wenn auch eine gewisse Zersetzung durch den Trocknungsprozeß selbst zustande kommt. Da der Zersetzungsgrad der genannten Farbstoffe mit diesen Faktoren nicht genau korreliert, wird dringend empfohlen, bei der Synthese keine Sulfaminsäure zu verwenden und die Reaktionsprodukte bei Zimmertemperatur im Vakuum zu trocknen.
    Notes: Summary The effect of heating in the total dehydration of arsenazo III and palladiazo has been investigated in the presence and absence of sulphamic acid in an attempt to simulate the conditions resulting from the use of sulphamic acid to eliminate excess of nitrous acid in the diazotisation step in the synthesis of these reagents. Spectrophotometric measurements indicate that the appearance of widely varying thermal degradation processes derives from the presence of sulphamic acid, although some degradation occurs during the desiccation process itself. Since the degree of degradation of the dyes cannot be accurately correlated with these factors, it is strongly recommended not to use sulphamie acid in the synthesis, and to dry the products at room temperature, preferably under vacuum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01219051
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  • 2
    Electronic Resource
    Electronic Resource
    Anomalous ion-exchange behaviour exhibited by aged acid-free uranyl nitrate solutions (1971)
    Springer
    Microchimica acta 59 (1971), S. 455-463 
    Details
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ein Vergleich des Ionenaustauschverhaltens frisch hergestellter und stark gealterter (7 bis 8 Jahre), säurefreier Uranylnitratlösungen gegenüber verschiedenen Kationen- und Anionenaustauschern wurde durchgeführt. Während frisch hergestellte Lösungen einem völlig normalen, stöchiometrischen Anionen- bzw. Kationenaustausch beim Durchlaufen stark saurer oder basischer Ionenaustauscherharze unterliegen, zeigen gealterte Lösungen ein deutlich anormales Kationenaustauschverhalten, da das Uranylkation scheinbar eine vierfach positive elektrische Ladung trägt. Daher muß auf die Möglichkeit beschränkter Anwendbarkeit von Kationenaustauschern für die Bestimmung freier Acidität in Uranylnitratlösungen besonders dann geachtet werden, wenn es sich um gealterte Lösungen mit geringer freier Acidität handelt.
    Notes: Summary A comparison of the ion-exchange behaviour of stoicheiometric acidfree freshly prepared and strongly aged (7–8 years) uranyl nitrate solutions has been made by means of different cation-exchange and anion-exchange resin systems. While the freshly prepared solutions undergo completely normal stoicheiometric anionic and cationic exchange when percolated through strongly acidic or basic ion-exchange resins, the aged solutions show a strikingly anomalous cation-exchange behaviour since the uranyl cation exhibits an apparent net electrical charge of about 4 +. On the basis of these findings it is concluded that proper attention should be paid to possible restrictions in the applicability of cation-exchange resins for the determination of free acidity in uranyl nitrate solutions, especially when dealing with aged solutions of very low free acidity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01219052
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  • 3
    Electronic Resource
    Electronic Resource
    A schematic overview of the historical evolution of Analytical Chemistry (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 151-161 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The historical evolution of Analytical Chemistry is briefly discussed as related to the progress of Chemistry within the 16–19th centuries under the leadership of Paracelsus, Boyle, Lavoisier and Dalton. A clear distinction is made between chemical analysis (up to the end of the 19th c.) and today’s Analytical Chemistry, paying close attention to a number of aspects and consequences related to the chemical revolution which took place at the overlap of the 18–19th c. which resulted in the quantification of Chemistry, causing increasing development and improvement of the chemical metrology which was an essential factor for Chemistry to acquire a scientific dimension and to become more specialised during the 19th century. A panoramic view of the whole development is presented by resorting to the inclusion of a number of synoptical tables outlining the stepwise progress of Chemistry, chemical analysis and Analytical Chemistry within the five last centuries taking into consideration the main protagonists involved as well as the experimental means, techniques and methodologies used and/or developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050130
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  • 4
    Electronic Resource
    Electronic Resource
    Analytical chemistry in the discovery of the elements (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 162-172 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract After a brief introduction to the evolution of the philosophy of matter over the centuries to arrive at the actual concept of chemical elements and “chemical matter” a historical overview is presented on the discovery of new elements within the 17–20th centuries, associated with the development and progress of chemical analysis and analytical chemistry. Some specific details are included in connection with imaginative theories, controversies on precedence of discovery, and spurious discoveries and their discoverers. 16 new elements were discovered in the 18th c., 51 in the 19th c. and 26 in the present c. The influence of some chemical schools, the incidence of conjunctural circumstances, the difficulties implied by some discoveries, serendipitous and fictitious discoveries, etc. are considered focusing on specially remarkable cases of historic interest. Historical and actual controversies related to naming of new elements are briefly considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050131
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  • 5
    Electronic Resource
    Electronic Resource
    Nest maintenance and stone theft in the Chinstrap penguin (Pygoscelis antarctica) (1995)
    Springer
    Polar biology 15 (1995), S. 533-540 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chinstrap penguins, Pygoscelis antarctica, after being relieved from incubation, collect stones from the ground or steal them from other nests and incorporate them into their own nests. The variation in stone-collecting behaviour after incubation reliefs, nest defence intensity and nest weights were measured in a sample of 100 nests in a large subcolony sited in the Vapour Col Chinstrap penguin colony on Deception Island, South Shetland Islands. Males collected more and larger stones, stole more stones and were more aggressive in nest defence towards potential thieves than females. Females suffered stone theft to a greater degree than males. Nests changed in weight during a period of 20 days. Initial nest size was negatively correlated with change in nest weight. The intensity of stone collection and theft by males was positively correlated with the increase in nest weight and with the final nest weight attained, while nest defence intensity by males and females was positively correlated with initial and final nest weight. Flooding after a snow storm affected 31% of nests and caused the loss of up to 14% of eggs/hatchlings. Flooded nests were significantly smaller than non-flooded nests. Results indicate that nest maintenance behaviour and stone theft in Chinstrap penguins serve to improve nest quality and thus enhance reproductive success.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239644
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  • 6
    Electronic Resource
    Electronic Resource
    Open states of nuclear envelope ion channels in cardiac myocytes (1994)
    Springer
    The journal of membrane biology 138 (1994), S. 77-89 
    Details
    ISSN: 1432-1424
    Keywords: Cardiac ; Nucleus ; Nuclear envelope ; Nuclear pore complex ; Nuclear ion channels ; Channel conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Prevalent nucleocytoplasmic transport theory views flow of monoatomic ions as completely unrestricted, resulting from the presence of large diameter pore complexes (NPCs) that perforate, but hold together, the two separate membranes of the nuclear envelope (NE). However, three lines of investigations indicate that, at least in some cell types, monoatomic ion flow is restricted. (i) Patch clamp reveals quantized, ion channel-like activity in several NE preparations; activity thought to result from nuclear ion channels (NICs) connected to NPCs. (ii) Ratiometric fluorescence microscopy demonstrates that ions, as well as small molecules relevant to signal transduction, do distribute as if there is a NE barrier. (iii) Electron microscopy shows that NPCs contain material that behaves like a plug. NICs' large conductance (up to 1,000 pS) makes them a major determinant of nuclear ion concentrations which, in turn, influence nuclear processes. Therefore, NICs are an important modulating force of gene and transcriptional activities—two major determinants of gene expression. As nuclear processes may take from seconds (e.g., signaling) to minutes (e.g., transcription), the time the channels dwell in the ion-conducting open state is relevant to understanding NICs' role in nuclear function. Consequently, dwell-times and lifetimes of open NIC states were studied in 61 patch-clamped adult mouse cardiac myocyte nuclei. Upon voltage stimulation, NICs opened to main states of large conductance (281 ± 198 pS, range = 120–490 pS, n = 55) and wide-range mean dwell-times (∼100 msec, 1–10 sec, and min). Closed states (0 pS) also had widely distributed mean dwell-times (∼100 msec, 1–10 sec, and min). Putative open substates (37 ±11 pS, range = 25–50, pS, n = 6) of high bursting frequency (〈1 msec) were observed without intervening main states (≈5% of patches). Fast (∼0.1 msec) and slow (∼10 msec) statetransitions were also detected. These observations suggest a role for NICs in mediating cytoplasmic signal control of cardiomyocyte gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211071
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  • 7
    Electronic Resource
    Electronic Resource
    Nuclear electrophysiology (1994)
    Springer
    The journal of membrane biology 138 (1994), S. 105-112 
    Details
    ISSN: 1432-1424
    Keywords: Nucleus ; Nuclear membrane ; Nuclear envelope ; Nucleocytoplasmic transport ; Nuclear pore complex ; Ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Conclusions Patch-clamp, fluorescence microscopy and high-resolution EM have yielded new data which question current concepts of ion transport across the nuclear envelope. The current challenge is to prove that NICs play an important role in nuclear function either through their identity with NPCs or parts thereof. Electrophysiological designs must incorporate cell biology approaches as done for putative protein-conducting channels of the ER (Simon & Blobel, 1991, 1992). Preliminary studies (J.O. Bustamante et al., in preparation), illustrated in Fig. 1, confirm that, as is the case of NPCs, NICs cannot function in an extracellular environment deprived of cytosolic factors. Our current efforts aim at clarifying if the lysate factors required for macromolecular transport through NPCs (e.g., Adam et al., 199la,b) are those required for NIC open-shut gating. Monoclonal antibodies to identified NPC proteins should be helpful in furthering the identification of NICs with NPCs. Our observation of blockade of NIC activity with wheat germ agglutinin, discussed above, supports the idea that NPCs are the structural foundation for NICs. Should NICs be identified with NPCs or otherwise proven essential to nucleocytoplasmic transport, NIC response to cytoplasmic signals would suggest that they are relevant to mediating gene control by transduction and other cytosolic signals (Karin, 1991; Davis, 1992). NIC influence on intranuclear free ion concentrations is potentially important to controlling gene activation, repression, as well as the efficiency and fidelity of gene expression (e.g., Kroeger, 1963; Lezzi & Gilbert, 1970; Leake et al., 1972; Morgan & Curran, 1986; Li & Rokita, 1991; Lippard, 1993). As electrophysiological and cell/molecular biology approaches merge, the prospects improve for the field of nuclear electrophysiology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232638
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  • 8
    Electronic Resource
    Electronic Resource
    Adenosine transport and nitrobenzylthioinosine binding in human placental membrane vesicles from brush-border and basal sides of the trophoblast (1991)
    Springer
    The journal of membrane biology 119 (1991), S. 151-161 
    Details
    ISSN: 1432-1424
    Keywords: nucleoside transport ; adenosine ; nitrobenzylthioinosine (NBMPR) ; microvillous and basal membrane vesicles ; photoaffinity labeling ; human placenta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The nucleoside transport activity of human placental syncytiotrophoblast brush-border and basal membrane vesicles was compared. Adenosine and uridine were taken up into an osmotically active space. Adenosine was rapidly metabolized to inosine, metabolism was blocked by preincubating vesicles with 2′-deoxycoformycin, and subsequent adenosine uptake studies were performed in the presence of 2′-deoxycoformycin. Adenosine influx by brush-border membrane vesicles was fitted to a two-component system consisting of a saturable system with apparent Michaelis-Menten kinetics (apparentK m approx. 150 μm) and a linear component. Adenosine uptake by the saturable system was blocked by nitrobenzylthioinosine (NBMPR), dilazep, dipyridamole and other nucleosides. Inhibition by NBMPR was associated with high-affinity binding of NBMPR to the brush-border membrane vesicles (apparentK d 0.98±0.21nm). Binding of NBMPR to these sites was blocked by adenosine, inosine, uridine, thymidine, dilazep and dipyridamole, and the respective apparentK i values were 0.23±0.012, 0.36±0.035, 0.78±0.1, 0.70±0.12 (mm), and 0.12 and 4.2±1.4 (nm). In contrast, adenosine influx by basal membrane vesicles was low (less than 10% of the rate observed with brush-border membrane vesicles under similar conditions), and hence no quantitative studies of adenosine uptake could be performed with these vesicles. Nevertheless, high-affinity NBMPR binding sites were demonstrated in basal membrane vesicles with similar properties to those in brushborder membrane vesicles (apparentK d 1.05±0.13nM and apparentK i values for adenosine, inosine, uridine, thymidine, dilazep and dipyridamole of 0.14±0.045, 0.54±0.046, 1.26±0.20, 1.09±0.18mm and 0.14 and 3.7±0.5nm, respectively). Exposure of both membrane vesicles to UV light in the presence of [3H]NBMPR resulted in covalent labeling of a membrane protein(s) with a broad apparentM r on SDS gel electropherograms of 77,000–45,000, similar to that previously reported for many other tissues, including human erythrocytes. We conclude that the maternal (brush-border) and fetal (basal) surface of the human placental syncytiotrophoblast posses broad-specificity, facilitated-diffusion, NBMPR-sensitive nucleoside transporters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871414
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  • 9
    Electronic Resource
    Electronic Resource
    Patch clamp detection of transcription factor translocation along the nuclear pore complex channel (1995)
    Springer
    The journal of membrane biology 146 (1995), S. 253-261 
    Details
    ISSN: 1432-1424
    Keywords: Nuclear pore complex ; Nuclear ion channels ; Gene activity ; Control of gene expression ; Transcription factors ; Oncogenes ; Proto-oncogenes ; AP-1 ; c-Jun ; NF-κB ; SP1 ; Patch clamp ; Cardiac myocytes ; Cell nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Transcription factors (TFs) are cytoplasmic proteins that play an essential role in gene expression. These proteins form multimers and this phenomenon is thought to be one of the mechanisms that regulate transcription. TF molecules reach their DNA binding sites through the large central channel of the nuclear pore complex (NPC). However, the NPC channel is known to restrict the translocation of molecules ⩾20–70 kD. Therefore, during their translocation, TF molecules and/or their multimers may plug the NPC channel and thus, interrupt ion flow through the channel, with a concomitant reduction in the ion conductance of the channel (γ). Here we show with patch clamp that γ is reduced during translocation of three major TFs: c-Jun (40 kD), NF-κB (≈50 kD), and SP1 (≈100 kD). Within a minute, femtomolar concentrations of these proteins reduced γ suggesting a purely mechanical interaction between single TF molecules and the inner wall of the NPC channel. NPCs remained plugged for 0.5–3 hr in the absence of ATP but when ATP was added, channel plugging was shortened to 〈5 min. After unplugging, channel closures were rarely observed and the number of functional channels increased. The transcription factors also stabilized the NPCs as shown by the extended duration of the preparations which allowed recordings for up to 72 hr. These observations are the first direct demonstration of the important role of NPCs in mediating nuclear translocation of TFs and, therefore, in forming part of the mechanisms regulating gene expression. The studies also demonstrate the potential of the patch clamp technique in quantifying TF translocation to the nucleus, mRNA export, and other processes governing gene expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233945
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  • 10
    Electronic Resource
    Electronic Resource
    The ion channel behavior of the nuclear pore complex (1995)
    Springer
    The journal of membrane biology 146 (1995), S. 239-251 
    Details
    ISSN: 1432-1424
    Keywords: Nuclear pore complex ; Nuclear ion channels ; Gene activity ; Control of gene expression ; Patch clamp ; Cardiac myocytes ; Cell nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Macromolecule-conducting pores have been recently recognized as a distinct class of ion channels. The poor role of macromolecules as electrical charge carriers can be used to detect their movement along electrolyte-filled pores. Because of their negligible contribution to electrical ion currents, translocating macromolecules reduce the net conductivity of the medium inside the pore, thus decreasing the measured pore ion conductance. In the extreme case, a large translocating macromolecule can interrupt ion flow along the pore lumen, reflected as a negligible pore conductance. Therefore, ion conductance serves as a measurement of macromolecular transport, with lesser values indicating greater macromolecular translocation (in size and/or number). Such is the principle of operation of the widely used Coulter counter, an instrument for counting and sizing particles. It has long been known that macromolecules translocate across the central channel of nuclear pore complexes (NPCs). Recently, large conductance ion channel activity (100–1000 pS) was recorded from the nuclear envelope (NE) of various preparations and it was suggested that NPCs may be the source of this activity. Despite its significance to understanding the regulation of transcription, replication, mRNA export, and thus gene expression of normal and pathological states, no report has appeared demonstrating that this channel activity corresponds to ion flow along the central channel of the NPC. Here we present such a demonstration in adult mouse cardiac myocyte nuclei. In agreement with concepts introduced for macromolecule-conducting channels, our patch clamp experiments showed that ion conductance is reduced, and thus that ion flow is restricted during translocation of macromolecules containing nuclear targeting signals. Ion flow was blocked by mAb414, a monoclonal antibody raised against a major NPC glycoprotein and known to localize on the NPC channel where it blocks macromolecular transport. These results also establish patch clamp as a useful technique for the measurement of macromolecular translocation along the large central channel of the NPC and provide a basis for the design of future investigations of nuclear signaling for control of gene activity, mRNA export for gene expression, as well as other processes subservient to NPC-mediated nucleocytoplasmic exchange.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233944
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