Identification of channel-lining residues in the M2 membrane-spanning segment of the GABA(A) receptor alpha1 subunit

The gamma-aminobutyric acid type A (GABA(A)) receptors are the major inhibitory, postsynaptic, neurotransmitter receptors in the central nervous system. The binding of gamma-aminobutyric acid (GABA) to the GABA(A) receptors induces the opening of an anion-selective channel that remains open for tens of milliseconds before it closes. To understand how the structure of the GABA(A) receptor determines the functional properties such as ion conduction, ion selectivity and gating we sought to identify the amino acid residues that line the ion conducting channel. To accomplish this we mutated 26 consecutive residues (250-275), one at a time, in and flanking the M2 membrane-spanning segment of the rat alpha1 subunit to cysteine. We expressed the mutant alpha1 subunit with wild-type beta1 and gamma2 subunits in Xenopus oocytes. We probed the accessibility of the engineered cysteine to covalent modification by charged, sulfhydryl-specific reagents added extracellularly. We assume that among residues in membrane-spanning segments, only those lining the channel would be susceptible to modification by polar reagents and that such modification would irreversibly alter conduction through the channel. We infer that nine of the residues, alpha1 Val257, alpha1 Thr26l, alpha1 Thr262, alpha1 Leu264, alpha1 Thr265, alpha1 Thr268, alpha1 Ile27l, alpha1 Ser272 and alpha1 Asn275 are exposed in the channel. On a helical wheel plot, the exposed residues, except alpha1 Thr262, lie on one side of the helix in an arc of 120 degrees. We infer that the M2 segment forms an alpha helix that is interrupted in the region of alpha1 Thr262. The modification of residues as cytoplasmic as alpha1 Val257 in the closed state of the channel suggests that the gate is at least as cytoplasmic as alpha1 Val257. The ability of the positively charged reagent methanethiosulfonate ethylammonium to reach the level of alpha1 Thr261 suggests that the charge-selectivity filter is at least as cytoplasmic as this residue.

Importance of the form of topical vitamin E for prevention of photocarcinogenesis

With increasing solar ultraviolet (UV)-B radiation reaching the Earth's surface and the incidence of skin cancer rising steadily, there is an ever-increasing need to determine agents that modulate photocarcinogenesis and to understand the mechanisms underlying this modulation. Our laboratory has demonstrated that topical application of the dl-alpha-tocopherol form of vitamin E to mice prevents skin cancer and the immunosuppression induced by UVB irradiation. However, dl-alpha-tocopherol has limited stability at room temperature. The current study was designed to ask whether the thermostable esters of vitamin E, alpha-tocopheryl acetate, or alpha-tocopheryl succinate prevent skin cancer and immunosuppression induced in mice by UV radiation. In the alpha-tocopheryl acetate study, skin cancers developed in 70% of UVB-irradiated control mice and in 90%, 73%, and 90% of mice receiving topical applications of 12.5, 25, and 50 mg of dl-alpha-tocopheryl acetate, respectively. In the alpha-tocopheryl succinate study, skin cancer developed in 59.3% of control UVB-irradiated mice and in 82%, 100%, and 81.5% of mice treated with 2.5, 12.5, and 25 mg d-alpha-tocopheryl succinate, respectively. Thus neither alpha-tocopheryl acetate nor alpha-tocopheryl succinate prevented photocarcinogenesis. At 12.5 and 25 mg/treatment, alpha-tocopheryl acetate and alpha-tocopheryl succinate, respectively, enhanced photocarcinogenesis (p = 0.0114 and 0.0262, respectively, log rank test). On the basis of high-performance liquid chromatography analysis at 16-17 weeks after the first vitamin E treatment, the esterified forms of vitamin E applied epicutaneously accumulated in the skin, but the levels of free alpha-tocopherol remained low. Neither alpha-tocopheryl acetate nor alpha-tocopheryl succinate prevented the induction by UV radiation of immunosusceptibility to implanted syngeneic antigenic UV-induced tumor cells. Thus alpha-tocopheryl acetate or alpha-tocopheryl succinate not only failed to prevent photocarcinogenesis, but may have enhanced to process. Considering that alpha-tocopherol esters are included in many skin lotions, cosmetics, and sunscreens, further studies are needed to determine the conditions under which topical alpha-tocopheryl acetate and alpha-tocopheryl succinate enhance photocarcinogenesis.

Differential expression and co-assembly of NMDA zeta 1 and epsilon subunits in the mouse cerebellum during postnatal development

The differential distribution of NMDA receptor subunit mRNAs in the developing mammalian cerebellum has been previously described. In this study, we investigated the temporal expression of NMDA receptor proteins in the postnatal murine cerebellum using antibodies specific for the NMDA zeta 1 and NMDA epsilon subunits. Our results showed a gradual increase during the first three weeks of life in the relative amount of NMDA zeta 1 and NMDA epsilon 1 proteins. In contrast, NMDA epsilon 2 increased transiently during this period, reaching a maximum around postnatal day 9 and decreasing thereafter to nearly undetectable levels by the end of the third week of life. The level of NMDA epsilon 3 increased dramatically between postnatal days 9 and 15 and thereafter remained constant. Immunoprecipitation of native proteins revealed that a large fraction of NMDA epsilon 2 was associated with NMDA zeta 1 and epsilon 1. At later developmental stages, NMDA epsilon 3 was predominantly assembled with NMDA zeta 1 but not with NMDA epsilon 1 or NMDA epsilon 2. These results demonstrate that NMDA receptor subtypes, formed by the assembly of different NMDA epsilon subunits with NMDA zeta 1, are sequentially expressed in the developing mouse cerebellum. The time course of their expression suggest, that these NMDA receptor subtypes may contribute to specific aspects of granule cell differentiation in the cerebellum.

Interaction of picrotoxin with GABAA receptor channel-lining residues probed in cysteine mutants

We used the substituted-cysteine-accessibility method to identify the channel-lining residues in a region (257-261) near the putative cytoplasmic end of the M2 membrane-spanning segment of the rat gamma-aminobutyric acid type A (GABAA) receptor alpha 1 subunit. The residues alpha 1Val257 and alpha 1Thr261 were accessible to charged, sulfhydryl-specific reagents applied extracellularly in both the open and closed states. The accessibility of alpha 1V257C and alpha 1T261C in the closed state implies that the gate must be at least as close to the cytoplasmic end of the channel as alpha 1Val257. Also, the positively charged reagent methanethiosulfonate ethylammonium penetrated from the extracellular end of the channel to alpha 1T261C, with which it reacted, indicating that the anion-selectivity filter is closer to the cytoplasmic end of the channel than this residue is. Co-application of picrotoxin prevented the sulfhydryl reagents from reacting with alpha 1V257C but did not prevent reaction with the more extracellular residue alpha 1T261C. Picrotoxin protection of alpha 1V257C may be due to steric block by picrotoxin bound in the channel at the level of alpha 1Val257; however, if this protection is allosteric, it is not due to the induction of the resting closed state in which alpha 1V257C was accessible to sulfhydryl reagent.

Phenotypical and functional analyses of natural killer cells from low NK activity individuals among healthy and patient populations

We investigated the deficiency of natural killer (NK) activity by contrasting healthy individuals with patients. Human NK activities of 125 individuals consisting of 68 healthy donors and 57 patients (36 autoimmune disease and 21 cancer patients) were measured by Eu-DTPA release assay in which the target cells were labeled by nonradioactive materials-Eu-DTPA, and they were phenotypically analyzed with three-color flow cytometry. Furthermore, a part of these donors was functionally studied on NK cells sorted out from PBL. 23.3% of healthy donors and approximately 70% of patients had low NK activity (LNK). In these healthy LNK and patient LNK, the population of CD3-CD16+CD56+ subset in PBL was significantly lower than that of the same subset in healthy individuals with high and medium NK activity (HMNK). The cytotoxicity of CD3-CD16+CD56+ cells sorted out from PBL in healthy LNK and patient LNK were approximately the same with or higher than that in healthy HMNK. No differences were found either in the expression of CD2 and LFA-1 antigens on the CD3-CD56+ NK cells or in the amount of granulous proteins such as perforin and granzyme A in these cells among healthy HMNK, healthy LNK and patient LNK. These results suggested that low NK activity of healthy LNK and patient LNK was more reflected by the diminution of the population of CD3-CD16+CD56+ subset in PBL rather than the functional defects of NK cells. A phenotypical and functional study on healthy LNK has not been reported extensively, and we found several differences between healthy LNK and patient LNK in this study. By stimulation with IL-2, the cytotoxicity of healthy LNK increased more rapidly than that of patient LNK, and at high effector:target cell ratio (> or = 40) it was significantly higher than that of patient LNK. The population of CD3+CD16+/CD56+ subset in PBL of healthy LNK was higher than that of patient LNK, but on the other hand it was about the same as that of healthy HMNK.

Hearing loss and trace elements Fe2+ and Zn2+ in the perilymph

Fe2+ and Zn2+ levels in perilymph of guinea pigs injected with gentamicin (GM) were examined and compared with the corresponding concentrations in CSF, serum and hairs. We observed a preventive and therapeutic action of sea buckthorn oil and injectio gastrodini to hearing loss. The results showed that: (1) the Fe2+ content in GM-injected guinea pigs was increased in perilymph and hairs; it was decreased after prevention and treatment, but there was no obvious change in CSF and serum; (2) the Zn2+ content in perilymph and CSF was increased in GM-injected guinea pigs. It rose further after prevention, but in serum and hairs it decreased. The results indicate that the ototoxic reaction to GM is related to the rise of the Fe2+ content in perilymph. The elevation of Zn2+ is a compensatory reaction. The changes in the chemical composition of perilymph are more important than those in CSF, serum and hairs for pathological changes of the cochlea. Sea buckthorn oil can prevent GM ototoxicity.

[Synthesis and positive inotropic activity of 3,4-dimethoxybenzoyl-piperazine derivatives]

We designed and synthesized twelve new 3,4-dimethoxybenzoyl-piperazine derivatives. These chemical structures (TM-1-TM-12) were confirmed by means of IR, MS, H-NMR and elemental analysis. Compounds (OPC-8212 TM-1, TM-2, VPA) were tested for positive inotropic activity. The results showed that compounds OPC-8212 and VPA possessed positive inotropic activity (P < 0.05). Further pharmacological studies will be made.

Differential recognition of microfilarial chitinase, a transmission-blocking vaccine candidate antigen, by sera from patients with Brugian and Bancroftian filariasis

We examined the reactivity of human sera with recombinant microfilarial chitinase and with the antigenic determinant on the native parasite molecule identified by monoclonal antibody (MAb) MF1. In Brugian filariasis, the MF1 epitope is preferentially recognized by residents of endemic areas who remain amicrofilaremic and asymptomatic despite lifelong exposure to filarial worms. Reactivity with filarial chitinase and its MF1 epitope inversely correlates with microfilaremia levels in Bancroftian filariasis and is associated with a prolonged amicrofilaremic state following a single course of treatment with diethylcarbamazine. Chitinase does not appear to be a target of human antibodies that promote the adherence of cells to microfilariae, even though MAb MF1 itself promotes antibody-dependent, cell-mediated cytotoxic (ADCC) reactions that kill microfilariae in vitro. Such ADCC reactions are most often mediated by sera from amicrofilaremic patients with chronic elephantiasis that contain low or undetectable levels of IgG antibodies to chitinase. In contrast, antibodies to the MF1 epitope on this microfilarial stage-specific antigen are mostly present in amicrofilaremic donors without clinical lymphatic disease. These observations indicate that antibodies to the MF1 epitope of microfilarial chitinase reflect some degree of immune resistance to microfilaremia in a subgroup of patients with asymptomatic lymphatic filariasis. The amicrofilaremic state of individuals with chronic lymphatic disease appears to be mediated by reactivity to a different parasite antigen(s).

Electroporation of influenza virus ribonucleoprotein complexes for rescue of the nucleoprotein and matrix genes

Reverse genetics has been successfully used for the generation of recombinant influenza virus with altered biological properties. The standard method is based on DEAE-dextran transfection of in vitro reconstituted influenza virus ribonucleoprotein complex (RNP) into helper virus infected cells with subsequent selection of the recombinant viruses. Here we report the utilization of electroporation for reverse genetics of influenza virus as an improvement over the standard method. In a neuraminidase (NA) gene rescue system, we were able to demonstrate that electroporation of in vitro reconstituted NA RNP of influenza A/WSN/33 (H1N1) virus into WSN/HK virus infected cells allows the rescue of the transfectant WSN virus. The titer of transfectant virus obtained using electroporation is comparable to that generated using the DEAE-dextran transfection method. More significantly, the ratio of transfectant virus to helper virus is as much as 20-fold greater than that achieved using the DEAE-dextran system. We have also used electroporation to generate recombinant influenza virus carrying cDNA-derived matrix (M) gene or nucleoprotein (NP) gene of the WSN virus by using the temperature-sensitive (ts) mutants ts51 and ts56 as helper viruses. In the case of electroporation of M gene RNP, 88% of the viruses isolated after selection at 39 degrees C were transfectants. In contrast, the majority of viruses obtained using the DEAE-dextran transfection method were revertants of the helper virus. The NP-gene transfectant was only generated by the electroporation method. Our results suggest that electroporation of influenza virus RNP may be a useful method for generation of recombinant influenza viruses, especially in a system in which a ts mutant is used as helper virus.

[High efficiency expression of IL-4 using modified cDNA expression vector in mammalian cells]

In order to express eukaryotic gene in eukaryotic cells, a cDNA library was constructed and screened with synthesized probe of IL-4 cDNA. The obtained cDNA fragment 739 bp in length was inserted into pi H3M plasmid and expressed (8 x 10(3) IU/ml) in COS cells. A pdB-HhIL-4 expression plasmid was constructed using pdKCR and pdBPV-1 plasmid and transfected into mouse C127 cells by calcium phosphate coprecipitation. Transfected cells exhibited altered cell morphology, could be continuously cultured in DMEM essential medium and secreted IL-4 lymphokine into 1% FCS condition culture medium. High biological activity (2 x 10(4)/ml) from the culture supernatant was obtained by FACS analysis of Fc epsilon receptor expression on B cell surface.

[A preliminary study on metastasis-associated gene screened by monoclonal antibodies HIL]

The cDNA expression libraries derived from a highly metastatic cell subline Anip[973] and from the poorly metastatic, parental cell line, AGZY-83a were screened by monoclonal antibodies HIL. A positive clone (H4-D) from the Anip[973] cDNA library was isolated and its nucleotide sequence was determined. This clone contained 978 bp with an open reading frame of 318 bp encoding a polypeptide consisting of 106 amino acids. The H4-D cDNA sequence showed 85% homology with a human propionyl-CoA carboxylase alpha-chain. In western blotting analysis, the MoAb H4 recognized 2 bands (15KD and 27KD) of Anip[973] cell membrane proteins. The mRNA expression of H4-D was higher in Anip[973] cells than in AGZY-83a cells. The metastatic potential of Anip[973] cells was markedly decreased after being pretreated with MoAb H4. The above findings indicate that H4-D has a certain relationship with the metastatic phenotype of Anip[973] cells.

Progress in surgical treatment of hydatid diseases in China. A clinical analysis of 22,005 surgical cases

Altogether 27,716 cystic hydatid cases and 445 alveolar hydatid cases clinically diagnosed and surgically treated in China were retrospectively studied. In accordance with the parasitic sites of the hydatid cysts and the various pathological types, different surgical procedures were adopted. In an attempt to prevent intraoperative accidents and postoperative complications, continued improvements in operational techniques have been made. Different surgical procedures were evaluated for their advantages and disadvantages as well as their indications. According to the pathological changes of the residual cavities of ectocysts, different measures were adopted. In screening operations, injection of antihydatid drug into hydatid cysts followed by oral administration of this drug was used to prevent relapses. The therapeutic effect of all these measures has been proved satisfactory by follow-up studies. This indicates that the progress in surgical treatment of cystic hydatid disease during the recent 10 years has been attaining to the objectives of shortening the duration of treatment, decreasing the postoperative recurrence rate and increasing the cure rate. In some hospitals, no operative death and relapse of cyst growth have been reported in nearly 1,000 surgical cases of cystic hydatid disease. Only 10.8% of the 445 alveolar hydatid cases underwent radical operations and the prognoses were unfavourable. This was due to the absence of symptoms in early stages of the disease which often made the patients miss the chance for radical operation in hospitals.

PDI-, PPI- and chaperone-catalyzed refolding of recombinant human IL-2 and GM-CSF

The studies on PDI-, PPI- and chaperone-catalyzed refolding of recombinant human IL-2 and GM-CSF show that PDI can prevent the mismatch of disulfide bonds and formation of aggregates by interchains linkage; furthermore, PDI can correct the mismatching of disulfide bonds in IL-2 isomers. PPI can increase the rate of folding reaction while chaperone can prevent the aggregation during the folding process. In addition, there is a synergistic effect between them.

[Apolipoprotein A-IV and transportation of cholesterol from smooth muscle cells in experimental hyperlipidemia]

The effects of apolipoprotein (apo) A-IV and apoA-IV/phosphatidylcholine (PC) liposome on cholesterol efflux from the smooth muscle cells originating from the aorta of hypercholesterolemic rabbit model and control rabbits, and on the activation of lecithin cholesterol acyltransferase (LCAT) were studied respectively. Both apoA-IV/PC and apoA-I/PC liposomes have similar efficiency as the HDL's, i.e. a strong ability to clear intracellular cholesterol and the ability to activate LCAT. There were no differences noticed on the clearance ability between apoA-IV and apoA-I or between apoA-IV/PC and apoA-I/PC liposomes. These results suggest that apoA-IV may play an important role in the process of reverse cholesterol transport and apoA-IV/PC liposome may be effectively used instead of natural HDL to prevent the development of atherosclerosis.

Elimination of cocaine-induced hyperactivity and dopamine-mediated neurophysiological effects in dopamine D1 receptor mutant mice

The brain mesoaccumbens dopamine system is intricately involved in the psychomotor stimulant activities of cocaine. However, the extent to which different dopamine receptors mediate these effects has not yet been firmly established. The present study used dopamine D1 receptor mutant mice produced by gene targeting to investigate the role of this receptor in the effects induced by cocaine. In contrast with wild-type mice, which showed a dose-dependent increase in locomotion, D1 mutant mice exhibited a dose-dependent decrease. Electrophysiological studies of dopamine-sensitive nucleus accumbens neurons demonstrated a marked reduction in the inhibitory effects of cocaine on the generation of action potentials. In addition, the inhibitory effects of dopamine as well as D1 and D2 agonists were almost completely abolished, whereas those of serotonin were unaffected. D2-like dopamine receptor binding was also normal. These results demonstrate the essential role of the D1 receptor in the locomotor stimulant effects of cocaine and in dopamine-mediated neurophysiological effects within the nucleus accumbens.