Impedance of the electrogenic Cl− pump inAcetabularia: Electrical frequency entrainements,voltage-sensitivity,and reaction kinetic interpretation

Summary Reaction kinetic analysis of the electrical properties of the electrogenic Cl^– pump inAcetabularia has been extended from steady-state to nonsteady-state conditions: electrical frequency responses of theAcetabularia membrane have been measured over the range from 1 Hz to 10 kHz at transmembrane potential differences across the plasmalemma (V _m ) between –70 and –240 mV using voltage-clamp techniques. The results are well described by an electrical equivalent circuit with three parallel limbs: a conventional membrane capacitancec _m , a steadystate conductanceg _o (predominantly of the pump pathway plus a minor passive ion conductance) and a conductanceg _s in series with a capacitancec _p which are peculiar to the temporal behavior of the pump. The absolute values and voltage sensitivities of these four elements have been determined:c _m of about 8 mF m^–2 turned out to be voltage insensitive; it is considered to be normal.g _o is voltage sensitive and displays a peak of about 80 S m^–2 around –180 mV. Voltage sensitivity ofg _s could not be documented due to large scatter ofg _s (around 80 S m^–2).c _p behaved voltage sensitive with a notch of about 20 mF m^–2 around –180 mV, a peak of about 40 mF m^–2 at –120 mV and vanishing at –70 mV. When these data are compared with the predictions of nonsteady-state electrical properties of charge transport systems (U.-P. Hansen, J. Tittor, D. Gradmann, 1983,J. Membrane Biol. in press), model A (redistribution of states within the reaction cycle) consistently provides magnitude and voltage sensitivity of the elementsg _o ,g _s andc _p of the equivalent circuit, when known kinetic parameters of the pump are used for the calculations. This analysis results in a density of pump elements in theAcetabularia plasmalemma of about 50 nmol m^–2. The dominating rate constants for the redistribution of the individual states of the pump in the electric field turn out to be in the range of 500 sec^–1, under normal conditions.     

Physiological effects of an allozyme polymorphism: Glutamate-pyruvate transaminase and response to hyperosmotic stress in the copepod Tigriopus californicus

In order to regulate cell volume during hyperosmotic stress, the intertidal copepod Tigriopus californicus, like other aquatic crustaceans, rapidly accumulates high levels of intracellular alanine, proline, and glycine. Glutamate-pyruvate transaminase (GPT; EC 2.6.1.2), which catalyzes the final step of alanine synthesis, is genetically polymorphic in T. californicus populations at Santa Cruz, California. Spectrophotometric studies of homogenates derived from a homozygous isofemale line of each of the two common GPT alleles indicated that the GPT^F allozyme has a significantly higher specific activity than the GPT^S allozyme. Under conditions of hyperosmotic stress, individual adult copepods of GPT^F and GPT^F/S genotypes accumulated alanine, but not glycine or proline, more rapidly than GPT^S homozygotes. When young larvae were subjected to the same hyperosmotic conditions, GPT^S larvae suffered a significantly higher mortality than GPT^F or GPT^F/S larvae. These results suggest that the biochemical differences among GPT allozymes result in specific physiological variation among GPT genotypes and that this physiological variation is manifested in differential genotypic survivorships under some naturally occurring environmental conditions.This work was supported in part by a grant from the Lerner Fund for Marine Research of the American Museum of Natural History, an NIH Training Grant in Integrative Biology, and NIH Grants GM 28016 and GM 10452.     

Dielectric behavior of polyelectrolytes. III. The role of counterion interactions

The role of the Coulomb forces between the counterions on the surface of polyelectrolytes on the dielectric response is analyzed. An estimate of the maximum dielectric increment (as a function of the number of counterions) is found as a function of the molecular length. The minimum-energy configuration of the counterions on a cylinder is found to be a double helix, suggesting the fundamental importance of electrostatic interactions in determining structure. Solutions of the dynamical equations for a few counterions indicate that a single mode dominates the relaxation which is enhanced by the inter-ion repulsions. A lower bound is found for this mode based on analysis of the system response for short lengths. Sum rules for the rates and amplitudes of the dipolar correlation function are derived and lead to an upper bound for the rate of the dominant mode. These bounds approach one another for the parameters characteristic of restriction fragments of DNA. This permits a prediction of the magnitude and time scale of the dielectric response.     

Bionomics ofTrioxys indicus [Hym.: Aphidiidae], a parasitoid ofAphis craccivora [Hem.: Aphididae]: 31. Effect of host haemolymph on the numerical response of the parasitoid

The influence of kairomones on the numerical response of the parasitoidTrioxys indicus against its hostAphis craccivora at its varying density was studied. The kairomones (applied as aqueous extract of the host) significantly enhanced the rate of parasitisation and multiplication and the area of discovery of the parasitoid and also the K-values of mortality of the host at all parasitoid densities introduced (1, 2, 4, 8, 12 and 16 parasitoids) into troughs having about 200 hosts. The sex-ratio of F₁ offspring decreased at lower parasitoid densities and remained more or less unchanged at higher parasitoid densities after the application of kairomones. The present findings indicate that if kairomones are applied properly, the number of hosts destroyed by a stimulated parasitoid will be about 200, twice the number reported earlier, thus fewer parasitoids will be needed to regulate an estimated population of the hosts.      

应用酶联免疫吸附试验检测不同类型乙型肝炎中激活补体类HBsAg循环免疫复合物

本文以抗人C_(?)的羊IgG为包被抗体,以HRP-HBs抗体为指示抗体,建立了可检测激活补体类HBsAg循环免疫复合物(HBsAg/C3-CIC)的C_3捕捉法酶联免疫吸附试验。检测了236例六种类型临床诊断为乙型肝炎的病人血清标本,其阳性率分别为:无症状携带者(ASC)12.9％(4/31),急性肝炎(AH)36.7％(22/60),慢性迁延性肝炎(CPH)33.3％(7/21),慢性活动性肝炎(CAH)59.6％(34/57),重型肝炎(SH)77.8％(14/18),肝炎后肝硬化(PLC)67.3％(33/49),阳性率与肝损严重程度明显相关(P<0.01)。认为HBs-Ag/C3-CIC可能在乙型肝炎病毒引起的慢性活动性肝炎、重型肝炎和肝炎后肝硬化的发病过程中起重要作用,并可作为乙型肝炎的诊断、临床分型和预后判断的指标之一。     

Modulation of IL-4-induced human IgE production in vitro by IFN-gamma and IL-5: the role of soluble CD23 (s-CD23)

IL-4 specifically induced IgE production by peripheral blood lymphocytes or by tonsil or spleen cells from healthy donors. IL-4-induced IgE synthesis was dependent on CD4+ T cells and monocytes and was blocked by IFN-gamma, IFN-alpha, and prostaglandin E-2 (PGE-2). These substances also inhibited IL-4-induced CD23 expression and subsequent release of soluble CD23 (s-CD23). In addition, IgE production was blocked by F(ab')2 fragments of an mAb against CD23. In contrast, IL-5 enhanced IL-4-induced IgE production, provided IL-4 was added at nonsaturating concentrations. This increase in IgE production correlated quantitatively with an enhanced release of s-CD23. Collectively, these results indicate that there is a correlation between s-CD23 release and IgE production. However, s-CD23 fractionated from supernatants of the lymphoblastoid cell line RPMI-8866 was ineffective in inducing IgE production in the absence of IL-4, but acted synergistically with suboptimal concentrations of IL-4. In addition, it is demonstrated that alloreactive T-cell clones produced varying concentrations of IL-4, IL-2, or IFN-gamma upon stimulation. Only supernatants of 2/4 of these T-cell clones induced a low degree of IgE synthesis, but in the presence of anti-IFN-gamma antibodies, all four supernatants induced a strong induction of IgE production. This IgE synthesis was blocked specifically by anti-IL-4 antibodies, indicating that IL-4 is the sole inducer of IgE synthesis. Our findings demonstrate that IL-4-induced IgE production involves complex interactions of T cells, B cells, and monocytes and is positively modulated by IL-5 and s-CD23 but down-regulated by IFN-gamma, IFN-alpha, and PGE-2, respectively.     

Transforming growth factor-beta does not alter interleukin-1 expression in cultured human macrophages

Transforming growth factor-beta (TGF beta) is a growth modulator that stimulates the growth of fibroblastic cells but inhibits the growth of cells of epithelial origin. TGF beta also influences the production of extracellular matrix proteins, and of proteases and the type 1 plasminogen activator inhibitor (PAI-1) by cultured cells. TGF beta appears also to have various immunoregulatory effects, suppressing both T- and B-cell activities. It has been proposed that it might increase the expression of interleukin-1 (IL-1) mRNA in cultured human monocytes, thus potentiating immune functions. To analyze the role of TGF beta in IL-1 production we have now quantitated the effect of this factor on the production of biologically active IL-1 as well as IL-1 beta mRNA expression. The effect of TGF beta on IL-1 production optimally activated with bacterial lipopolysaccharide (LPS) was also studied. It was found that IL-1 activity and mRNA levels were rapidly elevated by LPS but not by TGF beta. Culture fluids from monocytes treated with TGF beta alone or with TGF beta plus LPS inhibited the proliferation of the test thymocytes. After gel filtration, the media from TGF beta-treated cultures showed no activity in the molecular weight area of IL-1 (approx. 15 kD), while the supernatants from TGF beta plus LPS-induced cells contained IL-1 activity in these fractions, the magnitude of which was, however, at the same level as in the culture fluids derived from cells stimulated with LPS alone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Roles of Escherichia coli heat shock proteins DnaK, DnaJ and GrpE in mini-F plasmid replication

Summary A subset of Escherichia coli heat shock proteins, DnaK, DnaJ and GrpE were shown to be required for replication of mini-F plasmid. Strains of E. coli K12 carrying a missense mutation or deletion in the dnaK, dnaJ, or grpE gene were virtually unable to be transformed by mini-F DNA at the temperature (30° C) that permits cell growth. When excess amounts of the replication initiator protein (repE gene product) of mini-F were provided by means of a multicopy plasmid carrying repE, these mutant bacteria became capable of supporting mini-F replication under the same conditions. However, the copy number of a high copy number mini-F plasmid was reduced in these mutant bacteria as compared with the wild type in the presence of excess RepE protein. Furthermore, mini-F plasmid mutants that produce altered initiator protein and exhibit a very high copy number were able to replicate in strains deficient in any of the above heat shock proteins. These results indicate that the subset of heat shock proteins (DnaK, DnaJ and GrpE) play essential roles that help the functioning of the RepE initiator protein in mini-F DNA replication.     

Effects of vanillin and o-vanillin on induction of DNA-repair networks: modulation of mutagenesis in Escherichia coli

Vanillin and its isomer o-vanillin have an effect on the adaptive and SOS responses, as well as mutagenesis, induced in Escherichia coli by N-methyl-N-nitrosourea (MNU) and UV irradiation, potentiating in some cases and suppressing in others. o-Vanillin markedly inhibited the MNU-induced adaptive response, while both vanillins potentiated the UV-induced SOS response. These phenomena appear to be responsible for the comutagenic or antimutagenic role of these chemicals in MNU and UV mutagenesis.