Showing papers by "University of Cologne published in 1990"
TL;DR: A flexible, fast and simple magnetic cell sorting system for separation of large numbers of cells according to specific cell surface markers was developed and tested and makes this system an ideal complement to flow cytometry.
Abstract: A flexible, fast and simple magnetic cell sorting system for separation of large numbers of cells according to specific cell surface markers was developed and tested Cells stained sequentially with biotinylated antibodies, fluorochrome-conjugated avidin, and superparamagnetic biotinylated-microparticles (about 100 nm diameter) are separated on high gradient magnetic (HGM) columns Unlabelled cells pass through the column, while labelled cells are retained The retained cells can be easily eluted More than 10(9) cells can be processed in about 15 min Enrichment rates of more than 100-fold and depletion rates of several 1,000-fold can be achieved The simultaneous tagging of cells with fluorochromes and very small, invisible magnetic beads makes this system an ideal complement to flow cytometry Light scatter and fluorescent parameters of the cells are not changed by the bound particles Magnetically separated cells can be analysed by fluorescence microscopy or flow cytometry or sorted by fluorescence-activated cell sorting without further treatment Magnetic tagging and separation does not affect cell viability and proliferation
1,728 citations
TL;DR: The structure and the expression pattern of the protein and the phenotype of mutations indicate a function of crumbs during the development of epithelia, possibly for the establishment and/or maintenance of cell polarity.
693 citations
TL;DR: The results of the studies that permit some generalizations on the catalytic mechanism of glycoside hydrolases from widely differing sources and with different sugar and aglycon specificities and that have become available over the past 15 years are discussed.
Abstract: Publisher Summary This chapter discusses the results of the studies that permit some generalizations on the catalytic mechanism of glycoside hydrolases from widely differing sources and with different sugar and aglycon specificities and that have become available over the past 15 years. The strong inhibition of glycosidases by aldonolactones was first mentioned in 1940 by Japanese workers who studied β- D -glucosidases from Aspergillus (Taka-diastase) and almonds. Even though both of these groups of compounds are derived from normal substrates by only a minor modification of the glycon moiety, they are discussed together with pseudosubstrates because their reactions with glycosidases show, in many cases, unusual kinetic features. The information relevant to the mechanism of an enzyme-catalyzed reaction can, in general, only be obtained from irreversible inhibitors that react specifically at the active site, and thereby inactivate the enzyme. In many cases, inhibition studies were not carried out to obtain information on the reaction mechanism, but for other purposes. Thus, only inhibitors were tested that were considered suitable for the particular project, for example, studies on the biological function of the enzyme where glycosylamines and aldonolactones are unsuitable.
506 citations
TL;DR: Under conditions where loop formation is impossible, occupation of O3 but not of O2 may lead to weak repression, which suggests that under these conditions CAP activation may be inhibited and that stopping transcription at O2 does not significantly contribute to repression.
Abstract: We tested the effect of systematic destruction of all three lac operators of the chromosomal lac operon of Escherichia coli on repression by Lac repressor. Absence of just one 'pseudo-operator' O2 or O3 decreases repression by wild-type tetrameric Lac repressor approximately 2- to 3-fold; absence of both 'pseudo-operators' decreases repression greater than 50-fold. O1 alone represses under these conditions only approximately 20-fold. Dimeric active Lac repressor (iadi) represses the wild-type lac operon to about the same low extent. This indicates that cooperative interaction between lac operators is due to DNA loop formation mediated by tetrameric Lac repressor. Under conditions where loop formation is impossible, occupation of O3 but not of O2 may lead to weak repression. This suggests that under these conditions CAP activation may be inhibited and that stopping transcription at O2 does not significantly contribute to repression.
490 citations
TL;DR: In this paper, determinants of political violence at the cross-national level are derived from rational action theory and tested across the entire population of independent states in the mid-1940s.
Abstract: Propositions about determinants of political violence at the cross-national level are derived from rational action theory and tested across the entire population of independent states in the mid-19...
446 citations
TL;DR: The present data show that the cells of the Ly1 B cell subset are generated not only neonatally but also beyond the first weeks of life, suggesting that these cells have already undergone a transforming event at this early developmental stage.
Abstract: Sequence analysis of rearranged VHDJH genes of B lineage cells from various stages of ontogeny indicates that short sequence homologies at the breakpoints of recombination contribute to V region gene assembly. Such homologies are regularly seen at DJH junctions of neonatal pre-B cells, most of which do not contain N sequences. In the same cells, but not at later developmental stages, preferential usage of the JH1 element is observed. After birth, N sequence insertion increases with time and is always more prominent at the VHD border than the DJH border. In pre-B cells from adult animals and in mature B cells, in cases where N sequences were not detectable, sequence homologies at the DJH border were found in only half of the instances. This lower incidence could be due to N sequence addition to one of the recombining DNA ends and/or cellular selection. Inspection of VHDJH junctions for N sequence insertion, sequence homologies at the DJH border and JH1 usage allows the estimation of the timepoint in ontogeny at which particular B cell subsets are seeded into the immune system. Specifically, the present data show that the cells of the Ly1 B cell subset are generated not only neonatally but also beyond the first weeks of life. However, the DJH junctions of the progenitors of chronic B cell leukemias which originate from the same B cell subset resemble those of neonatal pre-B cells, suggesting that these cells have already undergone a transforming event at this early developmental stage.
380 citations
TL;DR: It is shown that after an initial phase of extensive proliferation after primary immunization, memory cells can persist in the organism for extended periods of time in the absence of cell division.
Abstract: A basic feature of T-cell dependent antibody responses is the generation of memory: on a second contact with an antigen a secondary response is produced in which somatically mutated antibodies with increased affinity are synthesized. Memory can persist for long periods of time. This has classically been ascribed to the generation of long-lived memory B cells. However, it is also possible that persisting antigen, on which memory may depend, maintains a population of cycling memory cells under continuous selection or continuously recruits newly generated B cells into the memory B-cell compartment. To discriminate between these mechanisms we have now directly analysed the proliferative activity in the memory B-cell compartment of the mouse by measuring bromodeoxyuridine incorporation in vivo. We show that after an initial phase of extensive proliferation after primary immunization, memory cells can persist in the organism for extended periods of time in the absence of cell division.
326 citations
TL;DR: The binary vectors pBIG and pBIB allow for divergent transcription of the selectable marker gene and of promoter/reporter gene fusions and were effective in producing resistant plants which produce shoots and roots on MSmedium containing the appropriate antibiotics.
Abstract: With the binary vectors pBIG and pBIB it is possible to: i) exchange the plant selectable marker/promoter fusion and the reporter gene, ii) use one vector and Agrobacterium strain system, thus reducing variables associated with using different vectors and strains, iii) allow for divergent transcription of the selectable marker gene and of promoter/reporter gene fusions. The two plasmids are derivatives of the binary vectors pBI 101 and pBIN 19 (1, 2). DNA fragments can be inserted into the T-DNA by the unique restriction sites of a pUC 19 polylinker. The RK2 functions of the plasmids allow the stable maintenance both in E. coli and A. tumefaciens. The two plasmids were constructed by removing the Bam HI site in pBI 101 (1) by filling in with Klenow-polymerase. The resulting plasmid was partially digested with Sst II, blunt ended and subsequently digested with Hind III and isolated on a low melting agarose gel. An Eco RI blunt ended/Bam HI fragment containing the polyadenylation site of gene 7 (3) and a Hind IWBam HI fragment which contains a Nos-promoter/kanamycin and a Nos-promoter/hygromycin gene fusion, respectively, were inserted into the vector, thus producing the vectors pBIG-KAN and pBIG-HYG. The Nos-promoter was taken from pPCV5013 Hyg (4), the neomycin-phosphotransferase (NPT II) gene from pBI 101 (1), and a modified hygromycin B phosphotransferase (HPT) gene was taken from pGDW 11 (5). Subsequently, the GUS-gene was exchanged by the pUC 19 polylinker {Hind WSst I) without a Bam HI site to create pBEB-KAN and pBIB-HYG, respectively. The vectors have been tested by leaf disk transformation of Nicotiana tabacum cv. Petit Havana SRI and were effective in producing resistant plants which produce shoots and roots on MSmedium containing the appropriate antibiotics (kanamycin sulfate 200 /tg/ml; hygromycin B 45 /ig/ml).
271 citations
266 citations
TL;DR: The data consistently show that more than two-thirds of splenic B cells in adult mice have a lifetime of several weeks or months, whereas a more rapid turnover takes place in young mice, indicating that the peripheral B-cell pool is only slowly renewed after it has been initially built up early in life.
Abstract: We have reevaluated the in vivo lifespan of B lymphocytes based on incorporation of the thymidine analogue 5-bromo-2'-deoxyuridine into the DNA of dividing cells. To exclude potential alterations in the turnover of B-lineage cells due to the bromodeoxyuridine incorporation, we performed pulse-chase experiments comparing the appearance and disappearance of bromodeoxyuridine-labeled cells over long periods of time. The data consistently show that more than two-thirds of splenic B cells in adult (greater than 2 months old) mice have a lifetime of several weeks or months, whereas a more rapid turnover takes place in young (4 week old) mice. Thus, the peripheral B-cell pool is only slowly renewed after it has been initially built up early in life.
247 citations
TL;DR: An article de synthese sur la comprehension and les concepts actuels de l'induction de la regulation and des mecanismes moleculaires de la commutation de classe des immunoglobulines.
Abstract: Article de synthese sur la comprehension et les concepts actuels de l'induction de la regulation et des mecanismes moleculaires de la commutation de classe des immunoglobulines
TL;DR: The data indicate that the rate of glutathione synthesis in vivo may be influenced substantially by the concentration of cysteine and glutamate and may be further regulated by feedback inhibition of λ-glutamylcysteine synthetase by glutathion itself.
Abstract: λ-Glutamylcysteine synthetase activity (EC 6.3.2.2) was analysed in Sephacryl S-200 eluents of extracts from cell suspension cultures ofNicotiana tabacum L. cv. Samsun by determination of λ-glutamylcysteine as its monobromobimane derivative. The enzyme has a relative molecular mass (Mr) of 60000 and exhibits maximal activity at pH 8 (50% at pH 7.0 and pH9.0) and an absolute requirement for Mg2+. With 0.2mM Cd2+ or Zn2+, enzyme activity was reduced by 35% and 19%, respectively. Treatment with 5 mM dithioerythritol led to a heavy loss of activity and to dissociation into subunits (Mr 34000). Buthionine sulfoximine andl-methionine-sulfoximine, known as potent inhibitors of λ-glutamylcysteine synthetase from mammalian cells, were found to be effective inhibitors of the plant enzyme too. The apparent Km values forl-glutamate,l-cysteine, and α-aminobutyrate were, respectively, 10.4mM, 0.19 mM, and 6.36 mM. The enzyme was completely inhibited by glutathione (Ki=0.42 mM). The data indicate that the rate of glutathione synthesis in vivo may be influenced substantially by the concentration of cysteine and glutamate and may be further regulated by feedback inhibition of λ-glutamylcysteine synthetase by glutathione itself. λ-Glutamylcysteine synthetase is, like glutathione synthetase, localized in chloroplasts as well as in the cytoplasm. Chloroplasts fromPisum sativum L. isolated on a Percoll gradient contained about 72% of the λ-glutamylcysteine synthetase activity in leaf cells and 48% of the total glutathione synthetase activity. In chloroplasts ofSpinacia oleracea L. about 61% of the total λ-glutamylcysteine synthetase activity of the cells were found and 58% of the total glutathione synthetase activity. These results indicate that glutathione synthesis can take place in at least two compartments of the plant cell.
TL;DR: Oral drug therapy following World Health Organization guidelines led to sufficient pain control in most patients over the whole study period (7,400 days); only 11% of the patients required other methods of pain management.
TL;DR: It is suggested that placental CRH has little influence on baseline maternal adrenocortical function in pregnancy, and the elevated salivary cortisol levels in pregnancy may be explained by glucocorticoid resistance owing to the antiglucoc Corticoid action of high progesterone concentrations.
Abstract: The circadian rhythm of salivary cortisol was studied in 10 healthy women every 4 weeks throughout pregnancy. In addition, in 12 women the diurnal patterns of salivary cortisol, serum cortisol, plasma ACTH, plasma CRH and serum progesterone were analysed in late third trimester pregnancy and again 3-5 days after delivery. Salivary cortisol profiles exhibited a clear circadian rhythm during pregnancy with an increase in mean salivary cortisol from the 25th to 28th week onwards reaching concentrations in late pregnancy more than twice as high as in non-pregnant controls, rapidly returning to normal concentrations after delivery. The coefficient of variation of salivary cortisol profiles decreased in third trimester pregnancy due to a parallel upward shift of cortisol concentrations (40.2 +/- 3.4% vs 77.6 +/- 6.6% after delivery, P less than 0.01). A diurnal pattern was also found for plasma ACTH and serum cortisol before and after delivery with lower concentrations post-partum (P less than 0.01). In late pregnancy, progesterone concentrations were significantly higher in the evening (930 +/- 85 nmol/l vs 813 +/- 74 nmol/l at 0900 h, P less than 0.01) but showed no diurnal variation post-partum. Plasma CRH was significantly elevated in late third trimester pregnancy (1.22 +/- 0.23 micrograms/l at 0900 h) but showed no diurnal change (1.30 +/- 0.28 micrograms/l at 1900 h). Moreover, no correlation between the free cortisol increase in late pregnancy and plasma CRH was noted despite a wide range of CRH levels (0.13-3.60 micrograms/l). In contrast, a significant correlation was observed between the serum progesterone increase and the salivary cortisol increase in late pregnancy (r = 0.70, P less than 0.05). These findings demonstrate that placental CRH is not the only regulator of maternal ACTH and cortisol release. Instead, our study suggests that placental CRH has little influence on baseline maternal adrenocortical function in pregnancy. The elevated salivary cortisol levels in pregnancy may be explained by glucocorticoid resistance owing to the antiglucocorticoid action of high progesterone concentrations.
TL;DR: Evidence is presented that occupation of the muscarinic receptor by ACh couples to channel activation via a G protein; the coupling can be blocked by pertussis toxin or by intracellular guanosine 5'-O-(2-thio-diphosphate) (GDP beta S), whereas intrACEllular guanoine 5-thiotriphosphate (GTP gamma S) activates the channel in the absence of ACh.
Abstract: Acetylcholine (ACh) depolarizes the membrane of mammalian intestinal myocytes by activating a nonselective cation channel (G. D. Benham, T. B. Bolton, and R. J. Lang. Nature Lond. 316: 345-347, 1985; R. Inoue, K. Kitamura, and H. Kuriyama. Pfluegers Arch. 410: 69-74, 1987). Here, we present evidence that occupation of the muscarinic receptor by ACh couples to channel activation via a G protein; the coupling can be blocked by pertussis toxin or by intracellular guanosine 5'-O-(2-thio-diphosphate) (GDP beta S), whereas intracellular guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) activates the channel in the absence of ACh. The currents, activated by either ACh or GTP gamma S, are nonadditive, conduct sodium ions, and are similar in their voltage dependence and facilitation by submicromolar calcium ions in the cytosol.
TL;DR: Endoscopic guidance appears to increase the safety of this procedure and may prevent complications of pneumothorax, subcutaneous emphysema, and paratracheal false passage previously reported with blinded percutaneous methods.
Abstract: Percutaneous tracheostomy is increasingly being used for patients needing prolonged ventilatory support. The purpose of this study was to assess the feasibility of widespread application of endoscopic guided percutaneous tracheostomy. Sixty-one consecutive ICU patients requiring prolonged mechanical
TL;DR: The hemagglutinin of fowl plague virus has been expressed in Spodoptera frugiperda (SF) cell cultures using a baculovirus vector and results indicate that SF cells have the capacity to trim N-glycans to trimannosyl cores and to further process these by the addition of fucose.
TL;DR: It is demonstrated that somatic antibody mutants are largely restricted to a small compartment of peripheral B cells, namely, that of memory cells, and that the memory compartment is strongly selected for high affinity precursors and largely purged from antigen-binding loss mutants.
Abstract: The anti-(4-hydroxy-3-nitro-phenyl)acetyl (NP) response is dominated by lambda 1 chain-bearing antibodies expressing the VH gene V186.2 in combination with the D element DFL16.1. lambda 1-positive B cells were isolated from the spleens of mice immunized with NP-chicken gamma globulin 6 wk earlier. Rearranged V186.2 genes were amplified from the genomic DNA of these cells and sequenced. In cases where the rearrangement was typical for secondary anti-NP antibodies, the VHDJH sequences were generally heavily mutated. The frequency and the nature of the nucleotide exchanges mirrored those of secondary response antibodies. V186.2 genes with other rearrangements and V186.2-related genes isolated concomitantly were essentially unmutated. These results demonstrate: (a) that somatic antibody mutants are largely restricted to a small compartment of peripheral B cells, namely, that of memory cells; (b) that the memory compartment is strongly selected for high affinity precursors and largely purged from antigen-binding loss mutants; and (c) that the repertoire of binding specificities expressed in the secondary response is established in its final form before secondary immunization.
TL;DR: It is shown that fill-in of 3' PSS termini precedes ligation and can even be primed in the absence of any ligation, and postulate that this is achieved by unique DNA binding proteins that align ends in various types of joining reactions.
TL;DR: Tramadol proved to be about 1/6 to 1/10 as potent an analgesic as morphine when both intensity and duration of effect were considered and could be best described by a log-normal distribution.
Abstract: Forty patients (ASA status I-III) recovering from major orthopedic or gynecological operations were investigated to evaluate analgesic efficacy and threshold concentrations of tramadol and its main metabolite O-demethyltramadol (M1) in serum during the early postoperative period, using patie
TL;DR: It is shown that in all tissues except the brain the PreA4(695) mRNA is less abundant than the other types of mRNAs; in the brain, however, the Pre a4(694) mRNA predominates by far; the same observations hold true for human tissues.
TL;DR: The prognosis of patients with primary sarcomas of the pulmonary artery must be regarded extremely poor and the significance of adjuvant chemotherapy and/or radiotherapy cannot be appraised at present.
Abstract: Primary sarcoma of the pulmonary artery is a rare tumor which must be considered in differential diagnosis of pulmonary embolism. The data of the 93 cases published up to now is evaluated synoptically after a report on a primary sarcoma of the pulmonary artery. Modern diagnostic imaging methods (pulmonary DSA, perfusion scintigraphy, echocardiography, computer tomography, nuclear magnetic resonance tomography) may corroborate the suspicion of a sarcoma of the pulmonary artery. With a median survival time of 1.5 months, the prognosis of patients with primary sarcomas of the pulmonary artery must be regarded extremely poor. After tumor excision, the median survival time of the patients could be prolonged (statistically significant; p less than 0.01) to ten months. The significance of adjuvant chemotherapy and/or radiotherapy cannot be appraised at present.
TL;DR: The results show that the activity of Ins, ACh is very sensitive to the intracellular Ca2+ concentration in the physiological range.
Abstract: 1. The modulatory effect of internal Ca2+ on the current through the ACh-activated non-selective cation channels (Ins, ACh) was investigated by the whole-cell patch clamp technique in single isolated cells of guinea-pig ileum. 2. Ins, ACh was isolated with caesium aspartate internal solution of low Ca2(+)-buffering capacity (10 microM-EGTA). With preceding depolarizations which evoked voltage-operated Ca2+ currents (ICa), Ins, ACh increased in amplitude and decayed more rapidly. The extent of this 'facilitating' effect depended on the number and duration of the depolarizations. 3. When depolarizing pulses were applied during the sustained phase of Ins, ACh, they were followed by large inward tail currents. These tail currents (tail Ins, ACh) resembled the non-facilitated Ins, ACh recorded without the depolarizing pulse, in regard to voltage-dependent gating and dependence on the extracellular Na+ concentration, thus suggesting that the currents are flowing through the same class of channels. 4. The tail Ins, ACh was apparently composed of two components distinguished by the insensitivity to organic Ca2+ antagonists. The minor component (about 20% of tail Ins, ACh) showed a rapid decay (about 150 ms at -60 mV) which could be attributed to voltage-dependent kinetics. The major component decayed slowly within 5 s and appeared to be related to changes in the intracellular Ca2+ concentration. The latter component was not recorded when Ba2+ or Sr2+ were used as a charge carrier for ICa and was blocked by 10 microM-D600 or nitrendipine, or Cd2+ 0.2-0.5 mM). 5. The tail Ins, ACh increased in proportion to Ca2+ influx when the duration of depolarizing pulses were prolonged from 15 to 200 ms, but this 'facilitating' effect was greatly suppressed when the cell was perfused with 40 mM-EGTA. 6. When the pCa in the pipette was varied using 40 mM-Ca-EGTA, the conductance through Ins, ACh increased in a manner dependent on intracellular Ca2+ concentration. Half-maximal and submaximal activation occurred at about 200 nM and 1 microM, respectively. 7. These results show that the activity of Ins, ACh is very sensitive to the intracellular Ca2+ concentration in the physiological range.
TL;DR: In this article, a theoretischen Fassung wird dann erklärbar, warum Institutionen gegenüber Änderungen in der „Umwelt“ oft sehr resistent sind: weil the Akteure mit ihrer „bounded rationality“ rational umzugehen verstehen.
Abstract: Zusammenfassung „Rational-Choice“-Erklärungen sozialer Prozesse sind (in den Sozialwissenschaften) häufig mit dem Hinweis kritisiert worden, sie setzten einen perfekt informierten und „kalkulierenden“ Akteur voraus. „Traditionales Handeln“ und Phänomene der „Definition der Situation“ seien daher mit diesem Ansatz prinzipiell nicht zu erfassen. Der Beitrag zeigt, daß die Orientierung des Handelns an Routinen („habits“) bzw. die Situationelle Dominanz bestimmter Ziele und „Codes“ („frames“) als Spezialfälle der Theorie der rationalen Wahl konzipierbar sind. In dieser theoretischen Fassung wird dann auch erklärbar, warum Institutionen gegenüber Änderungen in der „Umwelt“ oft sehr resistent sind: weil die Akteure mit ihrer „bounded rationality“ rational umzugehen verstehen. Die theoretische Rekonstruktion wird am Beispiel des Befragtenverhaltens im Interview empirisch erläutert und untermauert.
TL;DR: The results suggest that the "incidentaloma" of the pituitary gland is a benign condition that does not necessarily require neurosurgical intervention.
Abstract: We describe a series of 18 patients with an intrasellar mass incidentally discovered by computed tomography or magnetic resonance imaging. The average size of the mass was 13 mm, with a range from 5 to 25 mm. Initial ophthalmologic examination revealed bitemporal hemianopia in 2 patients. Results of routine endocrine testing showed partial hypopituitarism in 5 patients and growth hormone hypersecretion without signs and symptoms of acromegaly in 1 patient. Four patients underwent neurosurgery. Histologically, one chondroid chordoma and three pituitary adenomas were found. In the remaining 14 patients treated conservatively, repeated computed tomography and magnetic resonance imaging revealed no significant change in tumor size at the time of follow-up (median, 22 months). Our results suggest that the "incidentaloma" of the pituitary gland is a benign condition that does not necessarily require neurosurgical intervention.
TL;DR: The data suggest divergent lateral asymmetries in the posterior intrasylvian region with excesses of superior temporal cortex in left hemispheres and of supramarginal cortex in right hemisphere.
TL;DR: This approach measures the grey level index (GLI) with a TV‐based image analysing system from routine histological sections, which is a biased estimate of the local volume density of Nissl‐positive structures (cell bodies) in order to localize areal or laminar boundaries.
Abstract: Cytoarchitectonic investigations are based on the analysis of structural inhomogeneities in the neuronal composition of nervous tissue. Boundaries of brain regions are established at locations where local structural properties, such as density, shape, orientation or arrangement of the nerve cells, change. A quantitative approach requires a complete scanning of histological sections and the measurement of at least one of these properties using an automatic device. In contrast to recently developed stereological methods which result in unbiased estimates of parameters and which are based on efficient sampling procedures, measurements with automatic devices are biased due to section thickness and problems in the segmentation of nerve cell bodies. Automatic measurements are necessary, however, if a complete scanning of histological sections is required in order to localize areal or laminar boundaries. In this approach, the grey level index (GLI) is measured with a TV-based image analysing system from routine histological sections. Using Nissl-staining, this parameter is a biased estimate of the local volume density of Nissl-positive structures (cell bodies). The histological section is digitized into a GLI image by a scanning procedure. The GLI image is processed by image enhancement procedures in order to visualize the laminar pattern. Areal boundaries are localized at positions where this laminar pattern changes. GLI statistics of single brain regions can easily be evaluated by delineating these regions with a cursor in the GLI images of the sections. Information from a series of sections is compiled by specific application programs.
TL;DR: In the Munchberg Massif in southern Germany two varieties of eclogite are known which are intercalated with amphibolite-facies meta-igneous and meta-sedimentary rocks as discussed by the authors.
TL;DR: A structural model of the B cell antigen receptor of class IgM is developed which is compared with that of the T cell antigen receptors and it is demonstrated that expression of the mb‐1 and B29 genes can influence the surface expression of IgM in μm‐transfected myeloma cells.
Abstract: Beside the immunoglobulin (Ig) heavy and light chains the murine B cell receptor of the IgM class contains a heterodimer of two transmembrane proteins (IgM-alpha and Ig-beta). By N-terminal sequencing of IgM-alpha and Ig-beta we have identified the genes encoding these proteins as mb-1 and B29, respectively. Both genes are B cell specific and have been previously cloned from B minus T cell subtractive cDNA libraries. We have constructed expression vectors of the two genes and demonstrate that expression of the mb-1 and B29 genes can influence the surface expression of IgM in micron-transfected myeloma cells. From the known sequences of the IgM-alpha and Ig-beta proteins and from the results of previous transfection experiments with various vectors expressing the mu chain we have developed a structural model of the B cell antigen receptor of class IgM which we compare with that of the T cell antigen receptor.
TL;DR: The results show that ACh‐induced depolarization is controlled by the membrane potential, which is explained by the voltage‐dependent gating of Ins, Ach.
Abstract: 1. The whole-cell patch clamp technique with caesium aspartate internal solution was used with single isolated cells from the longitudinal muscle layer of guinea-pig ileum, to investigate the voltage-dependent gating of ACh-induced inward current. 2. In voltage clamp experiments, at holding potentials ranging from -80 to -30 mV, ACh (300 microM) produced a slow sustained inward current in physiological salt bath solution (PSS). The measurements of the reversal potentials on substituting Na+ by other monovalent and divalent cations showed that this current is through non-selective cation channels (Ins, ACh). 3. During hyperpolarizations, Ins, ACh instantaneously increased in amplitude and then relaxed to a new steady-state level. The I-V relationship of the instantaneous peak was linear with a reversal potential of 0 mV, while that of the steady state was bell-shaped. The time course of relaxation appeared to be monoexponential and its time constants were reduced by stronger hyperpolarizations. 4. These results were not affected by the organic Ca2+ antagonists D600 or nitrendipine (10 microM). Under this condition, maximal chord conductance of Ins, Ach which was observed at 0 mV was about 1.5 nS. The steady-state activation relationship was well fitted by Boltzmann's equation with a half-maximal activation (Vh) of -50 mV and a slope factor (k) of -15 mV at membrane potentials negative to 0 mV, but over 0 mV the degree of activation was again decreased. The time constants for relaxation also appeared to follow a sigmoid curve. 5. In current clamp experiments, superfusion of ACh (300 microM) depolarized the membrane up to -10 to 0 mV. Inward current injection resulting in the moderate hyperpolarization of the membrane (-70 to -80 mV) attenuated ACh-induced depolarization and stronger hyperpolarization (less than -80 mV) abolished it. 6. These results show that ACh-induced depolarization is controlled by the membrane potential, which is explained by the voltage-dependent gating of Ins, Ach.