Oligomerization properties of GCN4 leucine zipper e and g position mutants

Putative intersubunit electrostatic interactions between charged amino acids on the surfaces of the dimer interfaces of leucine zippers (g-e' ion pairs) have been implicated as determinants of dimerization specificity. To evaluate the importance of these ionic interactions in determining the specificity of dimer formation, we constructed a pool of > 65,000 GCN4 leucine zipper mutants in which all the e and g positions are occupied by different combinations of alanine, glutamic acid, lysine, or threonine. The oligomerization properties of these mutants were evaluated based on the phenotypes of cells expressing lambda repressor-leucine zipper fusion proteins. About 90% of the mutants do not form stable homooligomers. Surprisingly, approximately 8% of the mutant sequences have phenotypes consistent with the formation of higher-order (> dimer) oligomers, which can be classified into three types based on sequence features. The oligomerization states of mutants from two of these types were determined by characterizing purified fusion proteins. The Type I mutant behaved as a tetramer under all tested conditions, whereas the Type III mutant formed a variety of higher-order oligomers, depending on the solution conditions. Stable homodimers comprise less than 3% of the pool; several g-e' positions in these mutants could form attractive ion pairs. Putative repulsive ion pairs are not found among the homodimeric mutants. However, patterns of charged residues at the e and g positions do not seem to be sufficient to predict either homodimer or heterodimer formation among the mutants.

The association of squamous cell carcinomas of the nasopharynx with Epstein-Barr virus shows geographical variation reminiscent of Burkitt's lymphoma

Nasopharyngeal carcinoma (NPC) is rare in most parts of the world but occurs with high incidence in certain regions, such as South-East Asia. Two major histological types of NPC are recognized, non-keratinizing carcinoma and squamous cell carcinoma. Non-keratinizing NPCs, which include undifferentiated NPC, are invariably associated with Epstein-Barr virus (EBV) infection, regardless of the geographical or ethnic origin of the patients. By contrast, conflicting results have been published concerning a possible association of squamous cell NPC with the virus. To address this question, squamous cell NPCs have been collated from an area where NPC is endemic, Hong Kong, and from two regions where NPC occurs with a lower incidence, Chengdu, PR China, and Birmingham, United Kingdom. In situ hybridization for the detection of the small EBV-encoded nuclear RNAs (EBERs) demonstrated that all 22 cases from Hong Kong were EBV-positive. By contrast, EBV was detectable in 7 of 19 cases from central China, and in 3 of 7 cases from the U.K. Expression of the virus-encoded latent membrane protein 1 (LMP1) was detected in 3 of 32 EBV-positive squamous cell NPCs. These results indicate that the association of squamous cell NPCs with EBV shows geographical variability in a manner which is reminiscent of the situation encountered in Burkitt's lymphoma. This suggests that squamous cell NPCs are a pathogenetically heterogeneous group of tumours distinct from non-keratinizing NPCs.

[Effects of different components of serum from radiation, burn and combined radiation-burn injury on L-type calcium channel of cultured myocardial cells]

The effects of different components of serum from radiation, burn and combined radiation-burn injury on the activity of L-type calcium channel in cultured myocardial cells were investigated in this study. The results revealed that the serum from different injury groups could all activate the L-type calcium channel of cultured myocardial cells. These changes altered the calcium level in cells, which might be an important cause of dysfunction in cardiovascular system. Among the components of postinjury serum, the effect of high molecular components (> 8-10 kD) was not significant, whereas low molecule (< 8-10kD) and lipid components were the major effective components. The low molecule of postinjury serum affected not only on the opening activity of L-type channel, but also on the state of molecular movement in the membrane. The effect of serum lipids from injury groups could be depressed by SOD, which suggests that there may be free radical reactions during the serum lipids effect on calcium channel. The effects of serum and its components from combined radiation-burn group were the most intensive, and those from radiation injury were the weakest. The nature of the toxic material in serum remains to be further investigated.

[The development of a multivision glare tester]

This paper presents a new kind of multivision glare tester. Its composition, function, hardware, software and application are introduced. The tester provides a practical tool for evaluating visual function change under glare-producing conditions.

Experimental study on relationship between exogenous estrogen and breast cancer risk

OBJECTIVE

To investigate the relationship between exogenous estrogen and breast cancer risk.

METHODS

Female rats were randomly divided into three groups, namely diethylstilbestrol (DES), norethindrone compositae (CoNET) and control group. The histological structure and ultrastructural changes of mammae were observed. The levels of sexual hormones in serum were determined and the AgNOR counts, DNA contents and steroid receptor contents in mammary epithelium were also detected.

RESULTS

In DES group, the level of progesterone (10.38 ng/ml) was obviously lower than that in the control group (13.37 ng/ml); the incidence of hyperplasia of mammary gland (73.33%) was significantly higher than that in the control group (7.69%); and the degree of hyperplasia was obviously more serious than that in the control group. Moreover, there were 13.33% of rats with atypical hyperplasia in DES group. The DNA contents, AgNOR counts and estrogen receptor (ER) positive rate were markedly higher in DES group (95.60, 2.43 and 71.71% respectively) than in the control group (83.07, 1.88 and 40% respectively). However, in CoNET group, there were no obvious influences on ER, AgNOR and DNA in mammary epithelium.

CONCLUSIONS

Exogenous estrogen (DES) could affect the levels of sexual hormones in serum, accelerate the DNA duplication, increase the AgNOR counts and ER contents, and induce atypical hyperplasia and ultrastructural changes of mammary gland, hence becoming a latent risk factor of breast cancer. However, the results failed to suggest that the contraceptive, CoNET, could increase the risk of breast cancer.

Buried asparagines determine the dimerization specificities of leucine zipper mutants

Regulation of gene expression by many transcription factors is controlled by specific combinations of homo- and heterodimers through a short alpha-helical coiled-coil known as a leucine zipper. The dimer interface of a leucine zipper involves side chains of the residues at the a, d, e, and g positions of the (abcdefg)n heptad repeat. To understand the basis for the specificity of dimer formation, we characterized GCN4 leucine zipper mutants with all 16 possible permutations and combinations of isoleucines and asparagines at four a positions in the dimer interface, using a genetic test for the specificity of dimer formation by lambda repressor-leucine zipper fusions. Heterodimers were detected by loss of repressor activity in the presence of a fusion to a dominant-negative mutant form of the DNA-binding domain of repressor. Reconstruction experiments using leucine zippers from GCN4, Jun, Fos, and C/EBP showed that this assay distinguishes pairs that form heterodimers from those that do not. We found that the mutants have novel dimerization specificities determined by the positioning of buried asparagine residues at the a positions. The pattern of buried polar residues could also explain the dimerization specificities of some naturally occurring leucine zippers. The altered specificity mutants described here should be useful for the construction of artificial regulatory circuitry.

Far-field radiation of planar Gaussian sources and comparison with solutions based on the parabolic approximation

Previous research on the Gaussian beam was restricted in scope because of the paraxial assumption. Based on a rigorous solution of the Helmholtz equation, the radiation properties of a Gaussian source are reexamined. The results are different from what previous paraxial theory predicted. It is shown that the commonly used concept of the Gaussian beam and the separability of the field distribution along the two transverse axes may be misleading in certain conditions. Furthermore the theoretical upper limit on the beam divergence angle is shown to be 65.5 degrees .

[Expression of metastasis-suppressor gene nm23H1 product in nasopharyngeal carcinoma]

Using the specific monoclonal antibody of nm23H1 gene product and the immunohistochemical technique, we studied the expression of DNPK/nm23H1 and its correlation with lymph-node metastasis in nasopharyngeal carchnoma (NPC). The results revealed that, in a total of 31 cases of NPC, 13 showed positive expression with a positive rate of 41.9%. Among 21 cases of NPC with no lymph-node metastasis, 11 (52.3%) showed positive expression while only 20% (2/10) of those with lymph-node metastasis were positive, and there was significant difference between them (P < 0.01). Meantime the expression was very low or not detectable in the cancerous cells of the match lymph-node metastasis and all 10 cases showed negative expression. Statistical significant difference was found between the group of NPC with no metastasis and the group of lymph-node metastasis (P < 0.01). The above results indicated that high expression of DNPK/nm23H1 existed in the group of NPC with no metastasis while low expression existed in those with metastasis and lymph-node metastasis. It suggests that the expression of nm23H1 is inversely associated with lymph-node metastasis. The DNPK/nm23H1 may play a role in polymerization of microtubulin protein and participate in the process of cancer metastasis.

Detection of tetramerization domains in vivo by cooperative DNA binding to tandem lambda operator sites

Chimeric proteins comprising the N-terminal DNA binding domain of lambda repressor fused to a fragment of a foreign protein have been used to detect oligomerization of the latter. Fusions containing dimeric and tetrameric leucine zipper domains can be distinguished based on their in vivo repressor activities on a pair of cat-lacZ reporter strains. Repressor fusions are unable to efficiently repress transcription from a synthetic promoter that overlaps a weak operator site; repression by tetrameric, but not dimeric, fusion proteins is increased by the presence of a strong, upstream operator site. To construct reporters we developed a shuttle system that allows rapid construction of single-copy operon fusions in E. coli, with both cat and lacZ as reporters.

Depression of early and late monosynaptic inhibitory postsynaptic potentials in hippocampal CA1 neurons following prolonged benzodiazepine administration: role of a reduction in Cl- driving force

GABAergic synaptic responses were studied by direct, monosynaptic activation of GABAergic interneurons in the CA1 region of in vitro hippocampal slices from rats made tolerant to the benzodiazepine, flurazepam. Monosynaptic IPSPs were elicited in CA1 pyramidal neurons, following 1 week oral flurazepam administration, by electrical stimulation at the stratum oriens/stratum pyramidale or stratum radiatum/ stratum-lacanosum border < or = 0.5 mm from the recording electrode plane. Excitatory input to pyramidal cells and interneurons was eliminated by prior superfusion of the glutamate receptor antagonists, APV (50 microM) and DNQX (10 microM). GABAA receptor-mediated early IPSPs were further isolated by perfusion of the GABAB antagonist, CGP 35348 (25 microM) or by diffusion of Cs- from the recording electrode. GABAB receptor-mediated late IPSPs were pharmacologically isolated by perfusion of the GABAA antagonist, picrotoxin (50 microM). There was a significant decrease in the amplitude of pharmacologically isolated early and late IPSPs in FZP-treated neurons without a change in passive membrane properties. A shift of the early IPSP, but not the late IPSP, reversal potential in FZP-treated neurons suggested that a change in the driving force for anions, presumably Cl, in CA1 neurons was one important factor related to the decreased early IPSP amplitude after prolonged activation of GABAA receptors by flurazepam. A decreased early IPSP amplitude accompanied by a decreased late IPSP amplitude suggested that presynaptic GABA release onto FZP-treated pyramidal cells may also be reduced. We conclude from these data that an impairment of GABAergic transmission in CA1 pyramidal neurons associated with the development of tolerance during chronic benzodiazepine treatment may be related to the regulation of both pre- and postsynaptic mechanisms at the GABA synapse.

The mammalian transcriptional repressor RBP (CBF1) regulates interleukin-6 gene expression

The cellular interleukin-6 (IL-6) gene contains a target site for the mammalian transcriptional repressor RBP. The target site is contained within the interleukin response element (ILRE), which mediates IL-6 activation by NF-kappa B. In this study, we show by using transient-expression assays that RBP represses activated transcription from the IL-6 gene. The presence and position of the RBP target site are crucial in mediating repression by RBP. While RBP binds within the ILRE, it does not target NF-kappa B alone; nonetheless, NF-kappa B binding to the ILRE is required for repression. Our results indicate that RBP represses coactivation by NF-kappa B and another cellular transcription factor, C/EBP-beta.

[A study on the setting-up a high-risk scoring system for neonatal adverse outcomes]

In order to popularize the technique of risk approach to neonates among child health care providers in rural areas, data of surveillance for risk factors of the three major adverse outcomes in 1,116 neonates in rural areas of Zhangye prefecture, Gansu Province, China were analyzed, and two comprehensive scoring method of "whole risk factors" and "significant risk factors", to identify neonates at high-risk, were established and compared with standardized partial coefficient weighting of multiple logistic regression. The "whole risk factors" method of comprehensive scoring is recommended by this study as criteria for identification of high-risk neonates.

[Cloning and identification of the Mycobacterium bovis BCG gene for signal peptide of antigen 85-B]

OBJECTIVE

To clone and identify the Mycobacterium bovis BCG gene for signal peptide of antigen 85-B.

METHODS

Using a polymerase chain reaction technique, the signal peptide sequence (position 94 to 211) of antigen 85-B was technique, which is one of the major protein secreted by Mycobacterium bovis BCG (Bacille-Calmette-Guerin). The gene of 117bp fragment was cloned into the SacI and EcoRI sites of pBluecript SK, and its sequence was determined by using T7DNA polymerase kit.

RESULTS

The sequence analysis showed that the sequence of 117bp signal peptide was not misincorporated and in 3' end understream of signal peptide the 12 multi cloning sites for foreign gene could be provided by the recombinant plasmid.

CONCLUSIONS

The signal sequence of BCG antigen 85-B was cloned into the pBluescript plasmid. The recombinant plasmid was called BCG-S01. According to the genetic information a secreted protein from M. bovis BCG could be utilized in making a useful vaccine vehicle to produce and secrete a vaccinal protein from M. bovis BCG living cells.

[Study of electrophysiological properties of large conductance K(+)-channels in outer hair cells from the guinea pig with patch-clamp technique]

The basic electrophysiological characteristics of large conductance K(+)-channels in the basolateral cell membrane of outer hair cells (OHC) from the guinea pig cochlea were studied with patch-clamp technique. Acutely isolated OHC preparations were obtained by enzymatic digestion and excised patches were made in cell-attached configuration to record single-channel currents led by patch-clamp micropipette and fed to patch-clamp amplifier. Data were sampled and analyzed on-line with a computer. The result showed that the typical properties of single channels of large conductance K(+)-channels were: 1. The channel was activated by depolarization of membrane and it showed a marked voltage-dependence. The channel had a unitary conductance of about 133 pS and the channel current reversed at about -30mV under asymmetrical K+ concentration gradient. 2. Tetraethylammonium (TEA, > 10 mmol/L), a potassium channel blocker, dose-dependently abolished the outward current. 3. The open probability (Po) and mean open time of this channel was markedly increased with elevation of cytoplasmic Ca2+ concentration. These results suggest that a population of voltage-dependent and Ca(2+)-activated K+ channel exists in the basolateral membrane of OHC of the guinea pig; it is characterized by a very high unitary conductance and high sensitivity to Ca2+ and is blocked by K+ channel blocker. This work provided valuable basic materials for further study on the regulation and drug influence of the type of single channels.

[Anorectal malignant melanoma: report of 33 cases]

33 Cases of anorectal malignant melanoma (ARMM) diagnosed pathologically were treated in Tianjin Cancer Hospital from 1996 to 1994. Some of these patients were treated with abdominoperineal resection (Mile's operation) and local resection plus chemotherapy, biotherapy and radiotherapy, others were given chemotherapy only. 25 cases were followed up from six months up to six years. The results showed that the median survival time was 23.5 months in the group of Mile's, 17.5 months of local resection and 5.5 months in chemotherapy alone respectively. The authors considered that early diagnosis and treatment are the key to raise the survival rate. For the cases diagnosed pathologically the Mile's operation should be performed and groin dissection is necessary for cases of groin lymphatic metastasis.

[The clinical efficacy of hepatic artery infusion chemotherapy and chemoembolization in the treatment of liver metastases]

The efficacy and clinical experience of transcatheter hepatic artery infusion chemotherapy alone or chemoembolization in 118 patients with hepatic metastases were reviewed. Hepatic arterial infusion chemotherapy followed by embolization with lipiodol suspension and gelatin sponge pieces was carried out in 72 cases, infusion chemotherapy followed by embolization with lipiodol suspension in 32, and arterial infusion chemotherapy alone in 14. The results showed that the clinical efficacy of the first method was the best while that of the third method was the worst. The best effect was seen in patients with the single and hypervascular metastatic focus. The overall survival rate was 86.0%, 25.0%, 3.0% in 1 year, 3 years and 5 years, respectively.

[A review of 10 patients of nephrectomy through laparoscope video]

Ten patients were subjected to nephrectomy through laparoscope video. Compared with routine nephrectomy, it has such merits as slight trauma, less bleeding and pain during the operation as well as quick recovery and short hospitalization. In 6 male patients and 4 female patients the oldest one was 75 years old, and the youngest one was 15 years old. Seven patients suffered from nephrohydrosis and 3 from polycystic kidney. Before the operation, the patients were found the loss of function of the diseased kidney. The video scope was inserted into the abdominal cavity through an operating hole under the navel making the exploration in the cavity; the other operations are as basical as routine operations. The ill kidney was cut off and put into a special pocket, then it was cut into pieces, and taken out. The abdominal membrane was enclosed by the emanometer, the drainage tube kept. In the 10 patients the operations were successful and satisfactory.

[A cohort study on the relationship between standardized mortality of pulmonary heart disease and smoking]

We explored the relationship between the standardized mortality of pulmonary heart disease (PHD) and smoking at Shifang county through a five-year follow-up study of 29,498 farmers over 35 years old. The death ratio of PHD was 30.35%, which stood first in all causes of death. The mortality of PHD for cigar/cigarette smokers regardless of sex was not significantly different from that for nonsmokers (P > 0.05). The RR was 1 or so. The analysis of data stratified by age showed that the specific mortality increased with age in spite of some inequalities smoking; the RR of PHD for cigar/cigarette smokers in all age groups were 1 or so revealing no significant differences (P > 0.05). However, the standardized mortality of PHD increased with the accumulated amount of smoking. The relationship between the mortality of PHD and short-term smoking with small dose was not significant (P > 0.05), but when the accumulated amount reached certain level, i.e. the smoker consumed cigar more than 270 kg or consumed cigarette more than 20,000 packs, the relationship between the behavior of cigar/cigarette smoking and the mortality of PHD became apparent. The RRs were 1.40-3.94 and the ARs 171-1610 per 100,000 person years (P < 0.05-0.01).

Maximum far-field divergence angle of a plane source

The far-field properties of a plane source with a constant phase distribution are presented. It is found, for the first time to our knowledge, that for any plane source the theoretical upper limit of the far-field divergence angle is shown to be 65.5°. This result is different from what previous propagation and diffraction theories predicted, and when the size of the source approaches zero, the far-field behavior of the plane source is also different from a spherical wave in half-space.

[The diagnosis and surgical management of ectopic thyroid tumour]

The diagnosis and treatment of seven patients with ectopic thyroid tumour in different position suggest that fine needle aspiration biopsy cytology be used before operation and fast freezing section be made during operation. Isotope scanning should be used as a routine method to determine whether there is normal thyroid in neck, so that we can treat it appropriately and prevent serious complications after operation.

[The effects of a single active ingredient (T4) of Tripterygium Wilfordii Hook on the production of tumor necrosis factor by the peripheral blood mononuclear cells and synovium cells of rheumatoid arthritis patients]

Encouraged by good therapeutic results of the semipurified preparations of Tripterygium Wilfordii Hook (TWH) (code name T4) a single-active ingredient of TWH with the code name of T4 was obtained. The in vitro effects of T4 on the bioactivity of TNF produced by PBMC of normal subjects (n = 10) and RA patients (n = 6) or the RA digested synovium single cells (DSSC) were studied. The results showed that under pretreatment of PBMC of healthy persons with T4 (35 ng/ml) for two hours, TNF were reduced to 36.13 +/- 1.75% in comparison with the control of 63.33 +/- 2.51% (P < 0.001), with an inhibition rate of 40.31%. Similarly, the inhibition rate for the PBMC of RA patients (P < 0.001), was 25.54%. The fact that coculture of PBMC and T4 for 6 hours instead of treatment with T4 for 2 hours caused an inhibition rate of 40.51% (P < 0.01), might indicate that time of interaction was also a factor of importance. T4 also reduced TNF secretion by RA-DSSC from 72.1 +/- 6.1% to 51.6 +/- 2.0% with an inhibition rate of 28.4%. The aformentioned indicates that T4 appears to possess suppressive actions on production of TNF by PBMC and DSSC of RA patients. Therefore, it is possible that T4 may be used clinically for RA patients.

[Inhibitory effect of tamoxifen on the breast cancer risk induced by exogenous estrogen in rat]

In order to investigate the inhibitory effect of tamoxifen (TAM) on breast cancer risk induced by exogenous estrogen, female rats were randomly allocated into three groups, namely DES (diethylstilbestrol) group, DES + TAM group and blank control group. We found that in DES + TAM group the levels of estradiol (62.14 pg/ml) and progesteron (15.02 ng/ml) in serum were obviously higher than those in DES group (52.69 pg/ml, 10.38 ng/ml) individually (P < 0.05, P < 0.01), the incidence (28.57%) of mammary hyperplasia was significantly lower than that in DES group (73.33%) (P < 0.025), the degree of hyperplasia markedly slighter than that in DES group (P < 0.025), and the AgNOR count (1.93%), DNA content (80.24%) and ER positive rate (36.46%) were obviously lower than those in DES group (2.43%, 95.60%, 71.71%) individually. The results indicated that TAM could increase the levels of estradiol and progesterone in serum, also could decrease the ER contents, AgNOR counts and DNA contents in mammary epithelium. It suggested that the TAM could interfere the effect on the breast carcinogenesis induced by exogenous estrogen.

[Chemical constituents of the fruits of Vitex trifolia L]

Five compounds were isolated from the fruits of Vitex trifolia and identified on the basis of spectral data and chemical methods to be rho-hydroxybenzoic acid, beta-sitosterol, beta-sitosterol-3-O-glucoside, casticin and, 3,6,7-trimethylquercetagetin. Except beta-sitosterol all of the compounds were obtained from the fruits of the plant for the first time.

[Dental appliances for the treatment of obstructive sleep apnea syndrome]

This study combined the use of cephalometrics and overnight polysomnographic monitoring to analyze the effects of a dental appliance on airway, sleep and respiratory conditions in 10 patients with obstructive sleep apnea. The findings indicated that horizontal and vertical mean changes in mandibular position while the appliance was worn were 1.73 mm and 9.30 mm, respectively, the mean superior airway space increased by 2.80 mm (P < 0.01), while the mean middle airway space increased by 6.75 mm (P = 0.01), the inferior airway space, however, didn't change significantly when the appliance was worn. The average Apnea Index decreased by 15.98 events per hour when the appliance was worn (P < 0.01), the average Respiratory Disturbance Index decreased from 39.43 to 6.62 events per hour in 9 of 10 patients (P < 0.01, one patient didn't have recording of hypoventilation). the lowest SaO2 value increased from 73.87% to 85.50% (P < 0.01). The reduction in the rate of airway obstructive events is attributed to the effect of appliance on the orophargneal structures. The dental appliance is a conservative, successful treatment alternative that could benefit patients with obstructive sleep apnea syndrome.

[Effects of vesnarinone on L-type single Ca2+ channel current in cultured ventricular myocytes of embryonic chick]

The effects of vesnarinone on L-type Ca2+ channel current of embryonic chick ventricular myocytes were studied with cell-attached patch clamp technique. Vesnarinone was used in the concentrations of 10(-5), 2 x 10(-5) and 10(-4) mol/L; the availability (P8) of Ca2+ channel activity was increased (P < 0.001) markedly (about 2-3 fold). The increasing of the open probability (Po) of Ca2+ channel by vesnarinone showed concentration-dependence. The increase was 2.25 (10(-5)mol/L), 3(2 x 10(-5)mol/L) and 4.3(10(-4)mol/L) fold. The open time rate constant (tau 0) and close time rate constant (tau 1 and tau 2) of Ca2+ channel were not changed in the concentrations of 10(-5) and 2 x 10(-5) mol/L, but the tau 0 was slightly decreased in the concentration of 10(-4) mol/L. The actions of vesnarinone on single Ca2+ current were compared with those of milrinone (it is known as an PDE inhibitor which had inotropic effect associated with an increase in cytoplasmic cAMP level.) The effects of milrinone on P8, tau 0 and tau 1 were similar with those of vesnarinone (10(-4) mol/L), but the increase of Po was 2 fold less than that of vesnarinone. The results showed that apart from the role of PDE inhibitor, vesnarinone has other effects on myocytes.

[A study on antibiotic abuse in 750 children with acute respiratory infection in Tongxian County of Beijing]

A study on antibiotic abuse and inappropriate use was conducted in 750 children under five years old with acute respiratory infection (ARI) in Tongxian County, Beijing, based on WHO's ARI Standard Case Management for Young Children, who sought medical care in clinics at county, township, and village levels provided by 100 physicians. Results showed 96.9% of them were defined as antibiotic abuse and 62.9% as inappropriate use. Factors that contributed to antibiotic abuse and inappropriate use were length of medical practice of physicians the ill children consulted, their education level, scores of their knowledge and attitude, their diagnostic skills, purposes for antibiotic use, whether or not to enjoy free medical care by employees' dependents, ill children's degree of fever and self-prescription by parents, and so on.

Yeast two-hybrid system demonstrates that estrogen receptor dimerization is ligand-dependent in vivo

Previous studies using in vitro procedures have not clearly established whether the estrogen receptor (ER) acts as a monomer or dimer in the cell. We have used the yeast two-hybrid system as an in vivo approach to investigate the dimerization of the estrogen receptor in the absence and presence of estrogen and anti-estrogens. This system is independent of ER binding to the estrogen response element. Two vectors, expressing GAL4 DNA binding domain-human ER and GAL4 transactivation domain-human ER, were constructed. Control experiments showed that each fusion protein had a high affinity binding site for estradiol-17 beta and could transactivate an ERE-LacZ reporter gene in yeast similar to the wild type ER. The two fusion proteins, GAL4 DB-hER and GAL 4 TA-hER, were expressed in the yeast strain, PCY2, which carries a GAL1 promoter-lacZ reporter. ER dimerization was measured via reconstitution of GAL4 through interaction of the fusion proteins, which transactivates LacZ through the GAL1 promoter. When both ER fusion proteins were expressed, beta-galactosidase activity was estradiol-17 beta-inducible. Furthermore, we showed that both tamoxifen and ICI 182,780 also induced beta-galactosidase activity, albeit lower than that induced by estradiol-17 beta. These results strongly argue that ER dimerization is ligand-dependent and the dimer can be induced by estradiol-17 beta, tamoxifen, or ICI 182,780. We also treated the yeast containing the two fusion proteins with estradiol-17 beta and tamoxifen or ICI 182,780 simultaneously to determine the effects on ER dimerization. beta-Galactosidase activity was lower when the yeast was treated with a higher ratio of tamoxifen or ICI 182,780 to estrogen than estradiol-17 beta alone. Taken together, we conclude that ER dimerization is ligand (estradiol-17 beta, tamoxifen, or ICI 182, 780)-dependent, and we suggest that estradiol-17 beta-induced dimers are destabilized when estradiol-17 beta is used with tamoxifen or ICI 182,780 simultaneously.

Double-stranded damage of DNA.RNA hybrids by neocarzinostatin chromophore: selective C-1' chemistry on the RNA strand

Glutathione-activated neocarzinostatin chromophore generates bistranded lesions in the hybrid formed by yeast tRNA(phe) and DNA complementary to its 31-mer 3' terminus. To elucidate the chemistry of the RNA cleavage reaction and to show that the lesions are double-stranded (ds), a series of shorter oligoribonucleotides containing the target sequence r(AGAAUUC).(GAATTCT) (underlining indicates major attack site) was studied as substrates. In addition to cleavage at both U residues, major damage was produced in the form of an abasic site at the U residues. Evidence for abasic site formation on the RNA strand was obtained from sequencing-gel analysis and measurement of uracil base release. Initial evidence for the ds nature of the damage came from experiments in which 2'-O-methyluridine was substituted for uridine in the RNA at one or both of the target sites. The site containing the substitution was not a target for cleavage or abasic site formation, and the particular T residue, staggered two nucleotides in the 3' direction on the complementary DNA strand, was cleaved significantly less. These studies were valuable in identifying the DNA ds partner of the RNA attack site. Direct evidence for ds lesions came from analysis of the products from a hairpin oligonucleotide construct in which the RNA and DNA strands were linked by four T residues and contained an internal 32P label at the 3' end of the RNA strand. Substitution of deuterium for hydrogen at the C-1' position of the U residues led to a substantial isotope effect (k1H/k2H = 3) upon the formation of the RNA abasic lesion and the RNA cleavage products, providing conclusive evidence for selective 1' chemistry. On the other hand, cleavage at the T residues on the complementary DNA strand involved C-5' hydrogen abstraction, as was also true for the T residue in an oligodeoxynucleotide analogue of the RNA strand. Chemical mechanisms to account for the RNA cleavage and abasic site formation via C-1' hydrogen abstraction are proposed.

[Inward rectifier potassium current in cultured embryonic chick ventricular myocytes and effect of culture time]

The single channel features of inward rectifier potassium current (IK1) in primary cultured embryonic chick ventricular myocytes and the effect of culture time on it were studied by using cell-attached patch clamp technique. The results showed that inward current fluctuation could be recorded at membrane potential negative to the potassium equilibrium potential (EK) and [K+] o = [K+]i = 140 mmol/L. The single channel current-voltage (I-V) relation was linear. The slope conductance was 35 pS (1-3 day culture). But at membrane potential positive to the EK, strong inward rectification was evident. The analysis of open and close time distribution indicated that a close-close-open three state model was appropriate to describe the gating processes of IK1 channel. No significant effect of culture time was observed. The channel density and slope conductance of IK1 were 0.64, 0.76, 0.77 channels/microns and 35, 28, 37 pS corresponding to 1-3, 4-6, and 7-11 day culture period, respectively. This result could partially explain why action potential of cardiomyocytes did not change with culture time.

Reduction of GABA-mediated inhibitory postsynaptic potentials in hippocampal CA1 pyramidal neurons following oral flurazepam administration

Oral administration of the benzodiazepine, flurazepam, for one week results in tolerance in vivo and in vitro and in a reduction in recurrent and feedforward inhibition in vitro in the CA1 pyramidal cell region of hippocampus. In the present study CA1 pyramidal cells were examined intracellularly in vitro in rat hippocampal slices (500 microns) from rats sacrificed two or seven days after cessation of oral flurazepam treatment. Following drug treatment, the membrane characteristics of CA1 pyramidal cells were not significantly different from control neurons. GABAA-mediated, early inhibitory postsynaptic potentials were significantly reduced in amplitude (60%) in pyramidal neurons from rats killed two days, but not in those killed seven days, after the end of drug administration. The decrease in early inhibitory postsynaptic potential amplitude was observed using just-subthreshold, threshold and supramaximal orthodromic stimulation as well as following antidromic activation. The magnitude of the decrease in the early inhibitory postsynaptic potential amplitude was similar in the presence of the GABAB antagonist, CGP 35348, and could not be attributed to differences in the strength of afferent stimulation between flurazepam-treated and control groups. The size of the GABAB-mediated, late inhibitory postsynaptic potentials was also significantly decreased (45%) in comparison to control cells. Reversal potentials for both the early (-72 mV) and late (-92 mV) hyperpolarizations were not significantly different between groups. Following high intensity orthodromic stimulation, in the presence of an intracellular sodium channel blocker (QX-314) which also blocks the GABAB-mediated late hyperpolarization, a bicuculline-sensitive late depolarizing potential was unmasked in neurons from FZP-treated rats, but never from control cells. Excitatory postsynaptic potential amplitude was significantly increased in flurazepam-treated neurons and the threshold for the synaptically-evoked action potential was significantly increased. Following depolarizing current injection, the duration and frequency of pyramidal cell discharges and the action potential threshold were not altered by oral flurazepam treatment. The amplitude of the fast afterhyperpolarization was also not changed. Overall, the findings indicate an impairment of transmission at GABAergic synapses onto hippocampal CA1 pyramidal cell neurons after chronic benzodiazepine treatment at a time when rats are tolerant to the anticonvulsant effects of the benzodiazepines in vivo.

[Experimental comparison of the analgesic action of Aconitum and its processed products]

This paper deals with the effects of crude Aconitum and Aconitum processed by a new method of moistening and steaming, and by method of pharmacopoeial stipulation on the analgesic action with writhing test and hot plate test in mice. The result shows that the Aconitum processed by new method No 1, which applies moistening in water for 48h and then heating with high pressure steam (68.65kPa, 115 degrees C) for 2h has an advantage over that processed according to pharmacopoeial routine (P < 0.05).

Impairment of feedforward inhibition in CA1 region of hippocampus after chronic benzodiazepine treatment

The strength of feedforward inhibition was assessed in the CA1 region of in vitro hippocampus of benzodiazepine tolerant rats 2 and 7 days after 1 week oral flurazepam (FZP) administration. Feedforward inhibition was activated with a Schaffer collateral stimulation just-subthreshold for a population spike followed at intervals of 10-100 ms by test population spikes elicited from the subicular side of the recording electrode. The amplitude of test spike was reduced to a lesser degree 2 days, but not 7 days, after FZP treatment, suggesting a decrease feedforward inhibition in treated rats coinciding with the time course for reversal of anticonvulsant tolerance in vivo.

The recombination signal sequence-binding protein RBP-2N functions as a transcriptional repressor

We have identified a cellular protein, RBP-2N, a presumed recombinase, as a repressor of transcription. Inhibition of transcription by RBP-2N was dependent on its DNA recognition site and was demonstrated in vitro and in vivo. This repression appears to be general, as transcription mediated by SP1 and Gal4/VP16 was inhibited by RBP-2N. The protein was purified to near homogeneity from human cells on the basis of its binding to a site present in the promoter of the adenovirus pIX gene. The DNA recognition sequence is 5'-TGGGAAAGAA, which is markedly different from the recombination signal sequence originally identified as the target site for this protein. The sequence of the purified protein is 97% identical with that published for the mouse RBP-2N protein. The reported homolog in Drosophila is Suppressor of Hairless. RBP-2N binding sites are present in a number of cellular and viral promoters, so RBP-2N may have a general role in transcriptional repression.

[Spiral shaped bacteria in the human gastric biopsy]

Biopsy specimens from the gastric mucosa of 149 patients who underwent gastroduodenal endoscopy for upper gastrointestinal complaints were studied by light microscopy and culture. Spiral shaped bacteria were detected in four of the specimens by smears with Gram stain. The positive rate was 2.68%, but these bacteria and HP did not grow in culture. The characteristic helical morphology of the bacteria appears to be similar to that of the bacteria found in the stomach of cats and dogs. And what of significance in these cases is the presence of spiral shaped bacteria in association with chronic gastritis.

Far-field distribution of double-heterostructure diode laser beams

Previous analytical solutions for the far-field of a double-heterostructure diode laser have been restricted in scope because of several ad hoc assumptions, which were incorporated at rather early stages of the analysis. Based on a rigorous solution of the Helmholtz equation, it is shown that the commonly used assumption of separability of the field distributions along the two transverse axes of a diode may be misleading under certain conditions. Furthermore, the theoretical upper limit on the F.W.H.M. divergence angle is shown to be 65.5°, which is more realistic than the previous estimate of this parameter.

GCR1, a transcriptional activator in Saccharomyces cerevisiae, complexes with RAP1 and can function without its DNA binding domain

In Saccharomyces cerevisiae, efficient expression of glycolytic and translational component genes requires two DNA binding proteins, RAP1 (which binds to UASRPG) and GCR1 (which binds to the CT box). We generated deletions in GCR1 to test the validity of several different models for GCR1 function. We report here that the C-terminal half of GCR1, which includes the domain required for DNA binding to the CT box in vitro, can be removed without affecting GCR1-dependent transcription of either the glycolytic gene ADH1 or the translational component genes TEF1 and TEF2. We have also identified an activation domain within a segment of the GCR1 protein (the N-terminal third) that is essential for in vivo function. RAP1 and GCR1 can be co-immunoprecipitated from whole cell extracts, suggesting that they form a complex in vivo. The data are most consistent with a model in which GCR1 is attracted to DNA through contact with RAP1.

Role of cysteines in the activation and inactivation of brewers' yeast pyruvate decarboxylase investigated with a PDC1-PDC6 fusion protein

Possible roles of the Cys side chains in the activation and inactivation mechanisms of brewers' yeast pyruvate decarboxylase were investigated by comparing the behavior of the tetrameric enzyme pdc1 containing four cysteines/subunit (positions 69, 152, 221, and 222) with that of a fusion enzyme (pdc1-6, a result of spontaneous gene fusion between PDC1 and PDC6 genes) that is 84% identical in sequence with pdc1 and has only Cys221 (the other three Cys being replaced by aliphatic side chains). The two forms of the enzyme are rather similar so far as steady-state kinetic parameters and substrate activation are considered, as tested for activation by the substrate surrogate pyruvamide. Therefore, if a cysteine is responsible for substrate activation, it must be Cys221. The inactivation of the two enzymes was tested with several inhibitors. Methylmethanethiol sulfonate, a broad spectrum sulfhydryl reagent, could substantially inactivate both enzymes, but was slightly less effective toward the fusion enzyme. (p-Nitrobenzoyl)formic acid is an excellent alternate substrate, whose decarboxylation product p-nitrobenzaldehyde inhibited both enzymes possibly at a Cys221, the only one still present in the fusion enzyme. Exposure of the fusion enzyme, just as of pdc1, to (E)-2-oxo-4-phenyl-3-butenoic acid type inhibitors/alternate substrates enabled detection of the enzyme-bound enamine intermediate at 440 nm. However, unlike pdc1, the fusion enzyme was not irreversibly inactivated by these substrates. These substrates are now known to cause inactivation of pdc1 with concomitant modification of one Cys of the four [Zeng, X.; Chung, A.; Haran, M.; Jordan, F. (1991) J. Am. Chem. Soc. 113, 5842-49].(ABSTRACT TRUNCATED AT 250 WORDS)

[Antisteatotic effects of four kinds of dietary fibers in rats fed on high cholesterol diet: a preliminary morphometric analysis]

The hypolipidaemic and antisteatotic effects of the Konnyaku Powder (KP) have been reported before. In order to evaluate further the antisteatotic role played by KP, the effects of KP on the levels of liver lipid and on the hepatic histopathology and morphometry in comparison with those of pectin, algin and agar were studied. Sixty Wistar strain rats were divided into 6 groups: a normal diet group, a high cholesterol diet group (HC), and 4 test groups, in which the animals were fed on a diet similar to that of the high cholesterol diet group with addition of KP, pectin, algin or agar at a dosage of 5%, respectively. All the animals were killed at the end of the diet treatment for 9 weeks. The results showed that relative liver weights were lower in four experimental groups than in the HC group. The levels of total and free cholesterol, and triglyceride in the liver were lower in KP group than in HC group and in the other three experimental groups. Hepatic histopathology and morphometric examination indicated that antisteatotic effects of KP appeared to be much more significant than those of the other fibers.

[Observation of T cells and T-cell subsets in mycosis fungoides]

Skin lesions from 14 patients with mycosis fungoides (MF) were studied immunohistochemically with monoclonal antibodies that identify pan T (Leu4), T-helper/inducer (TH), T-suppressor/cytotoxic (Ts) (Leu3a, Leu2a) and pan B (Leu12) cells. Lymphoid cell reactivity was diverse among these cases. Among 12 cases of MF, TH cells were predominant over Ts cells, and one case featured nonreactive Ts cells in the dermis. In one case of MF, Ts cells were predominant. One case of MF showed strong reactivity for both T cell subset markers. The intraepidermal lymphoid cellularity was Leu4-reactive in 14 cases of MF. Among these 14 cases, the intraepidermal cellularity was Leu3a-reactive in 11 and Leu2a-reactive in 4. The use of such studies of T cell subsets may demonstrate a correlation of MF with cytomorphology, clinical stage, and disease prognosis.

Regulation of 5-Aminolevulinic Acid Synthesis in Developing Chloroplasts : IV. An Endogenous Inhibitor from the Thylakoid Membranes

5-Aminolevulinic acid synthesis in isolated, intact, developing chloroplasts from greening cucumber (Cucumis sativus) cotyledons was inhibited by broken chloroplast fragments. It was shown that the inhibitory constituent was associated with the thylakoid membrane system. The inhibitor was resistant to boiling, was not a form of ribonuclease, and did not inhibit Mg-chelatase, indicating that massive organelle destruction was not involved. The inhibitor was also found in etioplast and mature chloroplasts; and it was found in barley as well as cucumber. 5-Aminolevulinate synthesis in the dark with exogenous ATP and NADPH, or in the light without added cofactors, were inhibited approximately equally. In the dark, 5-aminolevulinate synthesis and protochlorophyllide synthesis from glutamate were inhibited to about equal extent. The inhibition was decreased when the membranes were washed with aqueous acetone prior to incubation. The inhibition by the unknown factor was compared to the inhibition by gabaculine, 4-amino-5-hexynoic acid, protoheme, and glutathione. The unknown inhibitor appeared to have a number of similarities with protoheme.

[Prophylactic effect of refined amorphophallus konjac on MNNG-induced lung cancers in mice]

Three hundred and seventy LACA mice of seven weeks old were used in 2 batches for studying the prophylactic effect of Konjaku powder on MNNG-induced lung cancers. These mice (within each batch) were randomly allocated to four groups, namely positive control (MNNG), refined Amorphophallus Konjac (R.A.K.), complex (MNNG + R.A.K.), and blank control (C). In MNNG group, MNNG (250 micrograms) was injected intravenously once five days for seven times in each mouse, the total dosage of MNNG was 1.75 mg. In R.A.K. group, according to w/w, 8% R.A.K. was well mixed into 92% common diet for long-term term breeding. In complex group, MNNG was given as that in MNNG group and the mice were reared as those in R.A.K. group. The mice in MNNG group and in C group were all reared by common diet. The results of experiments showed different degrees of preventive effect of R.A.K. on MNNG-induced lung cancers in LACA mice. R.A.K. not only exerted effect on the number of induced cancer, causing a drop of the cancerous rate from 79.75% to 20.00% and the mean number of cancer in each animal, but also prolonged the survival time of animals. At the same time, the constituent ratio of the kinds of tumor denoted a decrease in malignancy (adenoma with malignant change), an absence of adenocarcinoma and relative increase in benign adenoma. The results of experiments also exhibited good duplication as well as absence of adverse reactions to Konjaku powder.

[Small-airway lesions induced by inhalation of asbestos dust in dogs--pathological and aetiological studies]

This paper presents the pathological changes of the small airways of dogs inhaling asbestos dust in the workshop of Xin Kong Asbestos Mine for 1 to 3 years. Dogs of the experimental group showed that variable degrees of dust deposition and fibrous tissue reaction were found in all the three types of the small airways-respiratory bronchioles, alveolar ducts and membranous bronchioles of both lungs. The lesions in the lung increased with the duration of exposure. These changes in the canine small airways resulting from asbestos dust were very much similar to those of the humans. In addition, deposited dust collected from the workshop of the asbestos mine, and 50 dust particles selected randomly in foci were identified in situ by energy dispersive X-ray analysis. Findings demonstrated that the majority of the dust particles in the foci was principally mixed silicate dust. Among them asbestos dust predominated absolutely, and there were more amphiboles than chrysotiles. Therefore, it is concluded that the small airway lesions induced in the dogs are mainly due to mixed asbestos dust, and that there appears to exist a dose-response relationship.

[Chemical constituents of Osbeckia chinensis L]

Five constituents, 2-furoic acid, succinic acid, ursolic acid, quercetin and daucosterol were isolated and identified from Osbeckia chinensis. All of them are reported to have been found from this plant for the first time.