The temperature dependence of some kinetic and conductance properties of acetylcholine receptor channels

We examined the temperature dependence of single-channel properties of the nicotinic acetylcholine receptor channel from clonal BC3H-1 cells over a range of 10-40 degrees C. We found temperature sensitivities (Q10 values) of 2-4 for the mean channel open time. The Q10 did not depend strongly on voltage and the voltage dependence of the mean open time was temperature-independent. The Q10 of closing rate of the long-lived open state was 3-4 but the Q10 of closing rate of the brief open state was independent of temperature. The duration of brief closures could be measured only between 10 and 25 degrees C. Since this approached the limit of the experimental time resolution, an accurate determination of the Q10 could not be made. The current decay due to desensitization after rapid application of high concentrations of agonist varied with a Q10 of about 2. The conductance of single channels (the inverse of the ion translocation rate) had a Q10 of 1.3-1.5. We found no obvious nonlinearities in the Arrhenius curves for any of the measured properties.

[Anti-oxidation of Paecilomyces Sinensis (S. Pnov.)]

This paper indicates that Paecilomyces sinensis ig 3g/kg/dx14 increases the amount of superoxide dismutase in the liver tissues of mice; that Paecilomyces sinensis is similar to natural Cordyceps sinensis in inhibiting the production of Lpo and increasing the amount of superoxide dismutase in the liver homogenates of mice in vitro. In addition Paecilomyces sinensis can also increase the amount of glutathione peroxidase in the liver homogenates of mice in vitro.

Microbial induction of co-stimulatory activity for CD4 T-cell growth

The activation of naive CD4 T cells by antigen is a critical step in the initiation of an immune response; it requires both ligation of the T-cell receptor (TCR) and the delivery of co-stimulatory factors by accessory cells. We have examined the role of syngeneic accessory cells in the response of purified normal CD4 T cells to anti-CD3 antibody as ligand. We show that the ability to deliver co-stimulatory signals is inducible in B cells by microbial products such as bacterial lipopolysaccharide (LPS), mitogenic influenza viruses, and synthetic polyinosinic-polycytidylic acid (poly-I:C) as a mimic of viral infection. LPS stimulation for 16 h allows the co-stimulatory activity of B cells to become resistant to paraformaldehyde fixation. LPS induction of fixation-resistant co-stimulator activity requires new protein synthesis, as it is inhibited by cycloheximide. Using the anti-CD45RB mAb 16A as marker for naive and memory CD4 T cells, we show that B cells activated by LPS and by poly-I:C can provide co-stimulatory signal to both naive and memory CD4 T cells. By contrast, zymosan particles, which are known to activate macrophages in a variety of assays, do not activate B cells to become co-stimulatory, but do induce this activity in macrophages. These data demonstrate that a variety of infectious agents or their constituents can induce accessory cells to become co-stimulatory for CD4 T cells. They are interpreted in light of a proposed role for two classes of recognition in the induction of the immune responses, specific recognition of antigens and non-specific recognition of infectious agents. These data support the contention that the immune system uses this mechanism to discriminate infectious non-self from non-infectious self.

Ganglioside-binding proteins in skeletal and cardiac muscle

Several ganglioside-binding proteins have been identified in guinea pig skeletal and cardiac muscle. In the cytosolic fractions of both tissues, a 130-kD protein was found to have the highest propensity to bind lucifer yellow CH-labelled GM1. This binding could be abolished by prior incubation of the protein with GM2. Polysialogangliosides including GD1a, GD1b, GT1b, and GQ1b were less effective. The 130-kD protein migrated as a doublet with apparent isoelectric points (pI) of 6.3 and 6.5, respectively, in isoelectric focusing gel, but as a single species with an apparent Mr of 43,000 in SDS-polyacrylamide gel. Both the ganglioside-binding and the immunological properties of the 43-kD subunit protein were different from those of rabbit skeletal muscle actin. Cardiac muscle extract also contained a 77-kD minor ganglioside-binding protein that was absent in skeletal muscle. This protein had an apparent pI of 5.4 and migrated as a 39-kD species in SDS gels. By contrast, only the particulate fraction of skeletal muscle was found to contain a 180-kD major ganglioside-binding protein. Binding of fluorescent GM1 to this protein was blocked by pre-incubation of the protein with GM1 or GM2. The 180-kD protein migrated as a 98-kD species in SDS gels. However, its propensity to bind lucifer yellow CH-GM1 was at least 10 times greater than that of rabbit skeletal muscle phosphorylase b (Mr = 97,400). The apparent pI (6.5) of the 180-kD protein also was slightly higher than that of rabbit phosphorylase. Tissue distribution studies revealed that both the 130-kD and the 180-kD major ganglioside-binding proteins were muscle specific. It is, therefore, possible that these two proteins may play some unique roles in ganglioside-related functions in muscle tissues.

Iris nevus syndrome (report of 9 cases)

This paper reports on 9 cases of iris nevus syndrome diagnosed clinically, eight of which were confirmed by microscopy. The clinicopathologic features, etiology and pathogenesis of iris nevus syndrome are discussed. It was verified that iris nevus syndrome and other clinical variations of iridocorneal endothelial (ICE) syndrome had the same characteristic corneal endothelial defect. Also this syndrome was considered to be related to Chandler's syndrome Clinically.

Complex formation between the protein components of methane monooxygenase from Methylosinus trichosporium OB3b. Identification of sites of component interaction

Kinetic, spectroscopic, and chemical evidence for the formation of specific catalytically essential complexes between the three protein components of the soluble form of methane monooxygenase from Methylosinus trichosporium OB3b is reported. The effects of the concentrations of the reductase and component B on the hydroxylation activity of the reconstituted enzyme system has been numerically simulated based on a kinetic model which assumes formation of multiple high affinity complexes with the hydroxylase component during catalysis. The formation of several of these complexes has been directly demonstrated. By using EPR spectroscopy, the binding of approximately 2 mol of component B/mol of hydroxylase (subunit structure (alpha beta gamma)2) is shown to significantly change the electronic environment of the mu-(H/R)-oxo-bridged binuclear iron cluster of the hydroxylase in both the mixed valent (Fe(II).Fe(III)) and fully reduced (Fe(II).Fe(II)) states. Protein-protein complexes between the reductase and component B as well as between the reductase and hydroxylase have been shown to form by monitoring quenching of the tryptophan fluorescence spectrum of either the component B (KD approximately 0.4 microM) or hydroxylase (two binding sites, KDa approximately 10 nM, KDb approximately 8 microM). The observed KD values are in agreement with the best fit values from the kinetic simulation. Through the use of the covalent zero length cross-linking reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC), the binding sites of the component B and reductase were shown to be on the hydroxylase alpha and beta subunits, respectively. The alpha and beta subunits of the hydroxylase are cross-linked by EDC suggesting that they are juxtaposed. EDC also caused the rapid loss of the ability of the monomeric component B to stimulate the hydroxylation reaction suggesting that cross-linking of reactive groups on the protein surface had occurred. This effect was inhibited by the presence of hydroxylase and was accompanied by a loss of the ability of the component B to bind to the hydroxylase. Thus, formation of a component B-hydroxylase complex is apparently required for effective catalysis linked to NADH oxidation. When present in concentrations greater than required to saturate the initial hydroxylase complex, component B inhibited both the rate of the enzymic reaction and the cross-linking of the reductase to the hydroxylase. This suggests that a second complex involving component B can form that negatively regulates catalysis by preventing formation of the reductase-hydroxylase complex.

Serum-free growth and karyotype analyses of cultured normal and tumorous (SqCC/Y1) human buccal epithelial cells

Epithelial cell cultures were obtained following tryptic digestion of normal human buccal mucosa. Primary cultures exhibited markedly higher colony-forming efficiencies and growth rates using fibronectin/collagen-coated, as compared to non-coated culture dishes and a serum-free MCDB 153 medium developed for epidermal epithelial cells than a similar medium previously developed for buccal explant outgrowth cultures. At the preferred conditions, the cells could be transferred at least 5-fold, divided at about one population doubling per day, and commonly underwent 60 population doublings resulting in yields of 10(8) to 10(11) cells per cm2 mucosal specimen. Moreover, these conditions successfully cultivated a buccal carcinoma cell line (SqCC/Y1) for several months. The carcinoma cells were resistant to factors that inhibited growth or induced differentiation of normal cells, i.e., transforming growth factor type beta 1, Ca2+, or serum. Karyotype analyses of SqCC/Y1 cells showed 63 to 83 chromosomes per metaphase and consistent occurrences of monosomy 1, tetrasomy 19 and 20, as well as trisomy 22, and at least 7 marker chromosomes, whereas cells obtained from non-cancerous donors were diploid. It is concluded that the similarly defined culture conditions may now be applied to study characteristics of both normal and tumorous buccal epithelial cells.

Monoclonal antibodies against T cell receptor/CD3 complex induce cell death of Th1 clones in the absence of accessory cells

We have used anti-T cell mAbs as mimic ligands to study the effects of TCR/CD3 ligation of Th1 clones in the presence or absence of accessory cells. Our results demonstrated that ligation of TCR/CD3 in the presence of accessory cells induces proliferation of Th1 clone, while the same ligation in the absence of accessory cells results in death. This effect is inhibited by cyclosporin A and by anti-IFN-gamma mAbs and is restored by adding exogenous recombinant IFN-gamma tb CsA treated cells. We propose a model which could provide a general framework to explain activation, clonal anergy as well as clonal deletion of T lymphocytes during thymic development and in the peripheral.

Influence of high cholesterol feeding on the pattern and progression of experimental cerebral ischemia

The aim of our research was to study if cholesterol feeding might affect the ischemic changes in the vessels surrounding infarction foci in Sephadex G-75-induced cerebral ischemia model (SG-75). One hundred-twenty-four rabbits were divided as follows: group I was given standard food for 5 weeks; group II: as group I and then injected with SG-75; group III: standard food plus 1% cholesterol for 5 weeks; and group IV: as group III and then injected with SG-75. Rabbits were sacrificed 3 h, 6 h and 2, 5 and 7 days after ischemia had occurred. Vessels surrounding infarction foci (SIF) were identified by using a 6% carbon perfusion. Samples were examined by light microscopy and transmission electron microscopy (TEM). The occurrence of hemorrhagic infarction (HI) showed a clear time/course increase in group II whereas a decrease after 2 days in group IV was observed. The rate of HI was 40% and 20% in group II and IV, respectively. SIF vessels showed red blood cells leakage in group II, whereas multiple platelet thrombi appeared in group IV. This phenomenon caused a more extensive ischemic damage, when compared to group II. By making use of a widely employed model of high cholesterol diet and of a more physiological model of cerebral ischemia devised by us, we have provided the evidence that the hypercholesterolemia-induced changes in the SIF vessels strongly affect the pattern and progression of cerebral ischemia.

The Kangmar Dome: A Metamorphic Core Complex in Southern Xizang (Tibet)

The Kangmar metamorphic-igneous complex is one of the most accessible examples of an enigmatic group of gneiss domes (the North Himalayan belt) that lies midway between the Greater Himalaya and the Indus-Tsangpo suture in southern Tibet. Structural analysis suggests that the domal structure formed as a consequence of extensional deformation, much like the Tertiary metamorphic core complexes in the North American Cordillera. Unlike its North American counterparts, the Kangmar dome developed in an entirely convergent tectonic setting. The documentation of metamorphic core complexes in the Himalayan orogen supports the emerging concept that extensional processes may play an important role in the evolution of compressional mountain belts.

Development and distribution of opsin-like immunoreactivity in the dystrophic retinas of rdle mutant mice

The opsin-like immunoreactivity in the retinas of C57BL/6J rdle mutant mice has been studied by light-microscopic immunocytochemistry. Positively labeled cells were found in the normal heterozygous and homozygous mutant mouse outer nuclear layer (ONL) as early as postnatal day 3 (PN3). Beginning at PN10, in the retinas of the homozygous mutant mice, labeled photoreceptor cells rapidly decreased in number and disappeared after PN42. In the decreased ONL, remaining opsin-positive cells were labeled at higher density than those of controls. The retinal pigment epithelium was also moderately labeled during the loss of opsin-positive photoreceptor cells. In addition, sparse opsin-immunoreactive cells were demonstrated in the inner nuclear layer (INL) in the retinas of both the mutant and non-dystrophic mice as early as PN10 and are presumed to be ectopic photoreceptor cells. However, these displaced photoreceptor cells disappeared by PN28 in mutants along the same time course as those in the ONL but were still present in the PN28 retina of controls and seemed to be more abundant at later adult ages. There was no difference in the developmental regulation of opsin in the heterozygous and normal controls.

[Circadian rhythms of mice to the catharsis of radix et rhizoma Rhei]

Circadian rhythms have been observed obviously for both normal and pathological mice when Radix et Rhizoma Rhei is given. As a rule, the catharsis becomes stronger when Radix et Rhizoma Rhei is given at night than during the day. The rhythms vary with different pathological models. Compared with the normal mice, the circadian rhythms tend to be clearer for those mice excited by thyroidization. However, thyroidization makes the mice less sensitive to the dosage change of Radix et Rhizoma Rhei, while the mice weakened by tabazole administration show the reverse reaction.

Interferon gamma plays a critical role in induced cell death of effector T cell: a possible third mechanism of self-tolerance

We have used anti-T cell monoclonal antibodies (mAbs) as mimic ligands to study the effects of T cell receptor (TCR) ligation of cloned T helper type 1 cells in the presence or absence of accessory cells. Our results demonstrate that ligation of the TCR in the absence of accessory cells rapidly induces cell death. Cell death can be prevented by addition of spleen adherent cells, leading to strong clonal expansion. Induced cell death is inhibited by cyclosporin A and by anti-interferon gamma (IFN-gamma), and is restored by adding exogenous recombinant IFN-gamma to cyclosporin A-treated cells. These results demonstrate that IFN-gamma plays a critical role in cell death induced by anti-TCR mAbs in the absence of costimulatory cells. We propose that induced cell death of active effector T cells provides a third mechanism of tolerance in addition to intrathymic deletion of developing autoreactive T cells and peripheral inactivation of mature, naive T cells.

Preliminary study on antiamnestic mechanism of ginsenoside Rg1 and Rb1

The effect of ginsenoside Rg1 and Rb1 on memory in mice and rats were studied using one trial avoidance learning method. The results showed that Rg1 and Rb1 improved acquisition, consolidation and retrieval of memory improved by amnestic agents. For the elucidation of the antiamnestic mechanism of Rg1 and Rb1, HPLC-ECD, isotope labelling technique, radioligand binding assay, RIA and oxygen radical generating systems were employed in experiments. Rg1 and Rb1 were shown to increase protein bisynthesis of brain and ACTH level of plasma and decrease 5-HT level or slow down the 5-HT turnover rate in rats. No specific binding of Rg1 and Rb1 to alpha 1, alpha 2 and beta-adrenoceptors, or to DA, 5-HT, GABA and M-cholinergic receptors was detectable. However, 5 days after ip Rg1 and Rb1, higher Bmas values were obtained for the brain membranes from treated mice than those from control mice. In the mean time, Rg1 and Rb1 did not lower and might even increase the contents of acetylcholine in the brain. Besides, Rb1 could antagonize lipid peroxidation in the brain. Besides, Rb1 could antagonize lipid peroxidation and scavenge oxygen free radicals as well as increase catalase and GSH-PX activities. Clearly, these data may serve as the basis for the elucidation of the antiamnestic mechanism of Rg1 and Rb1.

[Scanning electron microscopic study of the reaction of ceramics implant in middle ear]

In this article, the reaction of ceramics implanted in cat's middle ear was observed and compared with autologous cortex bone and Teflon. The three types of graft were implanted in cat's middle ear. Then the cats were killed at one, two and four months after operation. The grafts were taken out and observed under scanning electron microscope. We found that the ceramics were coated by a continuous epithelium. Beneath this there were fibers and capillaries. These results indicated that Al2O3 ceramics are better than Teflon and is a good ossicular prosthesis.