Escherichia coli purine repressor: key residues for the allosteric transition between active and inactive conformations and for interdomain signaling

The Escherichia coli purine repressor, PurR, exists in an equilibrium between open and closed conformations. Binding of a corepressor, hypoxanthine or guanine, shifts the allosteric equilibrium in favor of the closed conformation and increases the operator DNA binding affinity by 40-fold compared to aporepressor. Glu70 and Trp147 PurR mutations were isolated which perturb the allosteric equilibrium. Three lines of evidence indicate that the allosteric equilibrium of E70A and W147A aporepressors was shifted toward the closed conformation. First, compared to wild-type PurR, these mutant repressors had a 10-30-fold higher corepressor binding affinity. Second, the mutant aporepressors bound to operator DNA with an affinity that is characteristic of the wild-type PurR holorepressor. Third, binding of guanine to wild-type PurR resulted in a near-UV circular dichroism spectral change at 297-305 nm that is attributed to the closed conformation. The circular dichroism spectrum of the E70A aporepressor at 297-305 nm was that expected for the closed conformation, and it was not appreciably altered by corepressor binding. Mutational analysis was used to identify an Arg115-Ser46' interdomain intersubunit hydrogen bond that is necessary for transmitting the allosteric transition in the corepressor binding domain to the DNA binding domain. R115A and S46G PurR mutants were defective in DNA binding in vitro and repressor function in vivo although corepressor binding was identical to the wild type. These results establish that the hydrogen bond between the side chain NH2 of Arg115 and the main chain CO of Ser46' plays a critical role in interdomain signaling.

[Isolation and identification of Rhodopseudomonas acidophila from Fujian province, China]

A strain P301 of Gram negative purple nonsulfur bacterium was isolated from the ditch's mud collected in Fuzhou, Fujian. The cells are rod-shaped. Multiplication occur by budding without stalk formation. Growth optimum pH is 5.0-5.7. No growth factors required. The cells contain bacteriochlorophyll a. The photosynthetic membrane system consists of parallel lamellae. According to Bergery's Manual of Determinative Bacteriology, 8th ed. (1974) and 9th ed. (1994), the strain was identified to be Rhodopseudomonas acidophila. But on the side of enzyme activity, utilization of organic substrates and others the strain some differ from the type strain described by N Pfennig (1969). Therefore the strain P301 was identified to be Rhodopseudomonas acidophila var. fujianensis n. var.

[Longitudinal evaluation of vocal function following thyroplasty type I for the treatment of unilateral vocal paralysis]

Longitudinal changes of vocal efficiency and stability following thyroplasty type I were analysed. Fifty-three patients with unilateral vocal fold paralysis underwent vocal function evaluation preoperatively and 1, 3 and 6 months postoperatively. Vocal function assessment included videostrobolaryngoscopic examination, acoustical and aerodynamic analyses, and perceptual ratings of voice. Parameters including glottic gag size, maximum phonation time, glottic flow rate, jitter, harmonic to noise ratio, breathness, hoarseness, loudness and phrasing showed significant improvement after thyroplasty and remained stable within 1 month with only slight fluctuations over a 6 month period. Postoperative voice outcome was not affected by age, sex, duration of vocal symptoms, etiology of paralysis, or preoperative pulmonary function.

The structure of PurR mutant L54M shows an alternative route to DNA kinking

The crystal structure of the purine repressor mutant L54M bound to hypoxanthine and to the purF operator provides a stereochemical understanding of the high DNA affinity of this hinge helix mutant. Comparison of the PurR L54M-DNA complex to that of the wild type PurR-DNA complex reveals that these purine repressors bind and kink DNA similarly despite significant differences in their minor groove contacts and routes to interdigitation of the central C.G:G.C base pair step. Modeling studies, supported by genetic and biochemical data, show that the stereochemistry of the backbone atoms of the abutting hinge helices combined with the rigidity of the kinked base pair step constrain the interdigitating residue to leucine or methionine for the LacI/GalR family of transcription regulators.

[Biodegradation and biocompatibility of a chitosan film]

The biodegradability and biocompatibility of a chitosan film were investigated in mice. The results showed that chitosan films had a mild inflammatory reaction in the early days of grafting, and after 16 weeks the inflammation basically subsided. Chitosan films were easily biodegraded. Chitosan is a novel natural absorbable medical film material and has a good developmental prospect.

Structure of human endothelin-2 gene and demonstration of common expression in human right atrial tissue

The endothelins (ET) are a group of three vasoactive peptides also known to be involved in vascular remodeling. ET1 is the most extensively studied, but recent evidence has highlighted the role of the little investigated ET2 gene as a potential candidate gene in regulating blood pressure. To allow the future role of this gene to be studied the structure of human ET2 was characterized and intron/exon boundaries were determined. With this structural information and using reverse-transcriptase PCR technology we show that the ET2 gene is commonly expressed in human right atrial tissue. This work will allow a more detailed assessment of the role of this physiologically important gene in human essential hypertension.

[Studies on the oxidation reaction of octanol-2 with nitric acid by infrared spectroscopy]

In this paper, the reaction process of oxidation of octanol-2 with nitric acid has been studied by IR spectroscopy. It is found that the main components of non-sapoifiable matter are different in different oxidation degrees. The relation between oxidation products and the amount of nitric acid are investigated,the reaction mechanism has also been studied. Experimental results show that the oxidation process of octanol-2 is as follows: first, octanol-2 is oxidated to octanone-2, or to nitrate, nitrite and nitrile copmpounds, then these compounds are reoxidated to caproic acid in the meantime some by-products, such as valeric, enanthic acids are also found in oxidated products.

The DFRC Method for Lignin Analysis. 4. Lignin Dimers Isolated from DFRC-Degraded Loblolly Pine Wood

Sixteen lignin dimers were directly isolated by gel permeation and reversed-phase TLC and HPLC from loblolly pine (Pinus taeda L.) sapwood following large-scale application of the new derivatization followed by reductive cleavage (DFRC) procedure. Their structures were elucidated by GC/MS and NMR. These dimers included representatives from all of the common interunit linkages in softwood lignins (beta-1, beta-beta, 5-5, beta-5, and 5-O-4). The DFRC procedure efficiently cleaves beta-aryl ethers, the major structural unit, so beta-ethers were not found among the dimeric products. All but two of the isolated dimers were guaiacyl-guaiacyl (from coniferyl alcohol-derived units in lignin); small amounts of p-hydroxyphenyl/guaiacyl beta-5 and beta-1 dimers were characterized. Several dimers have benzaldehydes as one unit-since aldehydes are not created by the procedure, they are either present in the native lignin or are formed during the minimal preparation of the wood. The dimers isolated and identified here will eventually allow their quantitation to aid in the structural analyses of wide-ranging plant materials.

The DFRC Method for Lignin Analysis. 2. Monomers from Isolated Lignins

Monomers released from derivatization followed by reductive cleavage (DFRC degradation) of lignins have been identified by mass spectra and/or comparison of their GC retention times with authentic compounds. The primary monomers from several isolated lignins representing softwoods, hardwoods, grasses, and dicots have been quantified by GC. Sources of the minor monomeric components have been rationalized on the basis of the DFRC mechanisms; products from cinnamyl alcohol endgroups, aldehydes, arylglycerols, and alpha-carbonyl units have been identified. From isolated lignins, the DFRC method produces its diagnostic primary monomers, the hydroxycinnamyl peracetates, with yields comparable to the production of monomers from other ether-cleaving analytical methods.

Structure-based redesign of corepressor specificity of the Escherichia coli purine repressor by substitution of residue 190

Guanine or hypoxanthine, physiological corepressors of the Escherichia coli purine repressor (PurR), promote formation of the ternary PurR-corepressor-operator DNA complex that functions to repress pur operon gene expression. Structure-based predictions on the importance of Arg190 in determining 6-oxopurine specificity and corepressor binding affinity were tested by mutagenesis, analysis of in vivo function, and in vitro corepressor binding measurements. Replacements of Arg190 with Ala or Gln resulted in functional repressors in which binding of guanine and hypoxanthine was retained but specificity was relaxed to permit binding of adenine. X-ray structures were determined for ternary complexes of mutant repressors with purines (adenine, guanine, hypoxanthine, and 6-methylpurine) and operator DNA. These structures indicate that R190A binds guanine, hypoxanthine, and adenine with nearly equal, albeit reduced, affinity in large part because of a newly made compensatory hydrogen bond between the rotated hydroxyl side chain of Ser124 and the exocyclic 6 positions of the purines. Through direct and water-mediated contacts, the R190Q protein binds adenine with a nearly 75-fold higher affinity than the wild type repressor while maintaining wild type affinity for guanine and hypoxanthine. The results establish at the atomic level the basis for the critical role of Arg190 in the recognition of the exocyclic 6 position of its purine corepressors and the successful redesign of corepressor specificity.

[Effects of bilateral lesions of ventrolateral orbital cortex on the rat tail flick reflex inhibition evoked by electroacupuncture]

This study found that bilateral electrolytic lesions of the ventrolateral orbital cortex (VLO) markedly reduced the inhibitory effects of high intensity electroacupuncture (EA) at "Zusanli" point on tail flick reflex in lightly anesthetized rats, but did not influence the inhibitory effects of low intensity EA stimulation. The results show that the VLO is involved in acupuncture analgesia produced by activation of small afferent fibers with high intensity electroacupunture. Results of this study provide further support for a hypothesis that spinal cord-Sm-VLO-PAG-spinal cord may constitute a negative feedback loop of nociceptive modulation. The analgesic effects produced by high intensity electroacupuncture may be mediated by this loop leading to depression of the nociceptive inputs at the spinal cord level.

Immunolocalisation of P450(C17) in the fetal sheep adrenal gland during gestation and in response to ACTH and glucocorticoid administration

In sheep, increased output of cortisol from the fetal adrenal gland is critical to organ maturation and parturition. Cortisol synthesis is determined in part by the activity of P450(C17) enzyme. We have used immunohistochemistry and Western immunoblotting to examine the distribution of P450(C17) in the ovine fetal adrenal during gestation, and after ACTH or dexamethasone administration to fetuses between Days 125 and 130. The patterns were compared with changes in 3beta-hydroxysteroid dehydrogenase (3beta-HSD) localisation and levels. Adrenal tissue was obtained from four fetuses at each of Days 63-65, 100, 125-130 and term (>140 days). Further animals were chronically catheterised and infused with ACTH, dexamethasone or saline for 96 h beginning on Day 125. Immunohistochemistry for P450(C17), 3beta-HSD, and phenylethanolamine-N-methyl transferase (PNMT) was conducted using standard techniques. At Day 63-65 of pregnancy immunoreactive (ir-)P450(C17) was present in cords of cells throughout the adrenal gland. Ir-P450(C17) was reduced or was undetectable at Day 100, but had increased by Day 125-130, and was present throughout the zona fasciculata of the adrenal cortex of term animals. An increase in P450(C17) protein was also seen between Day 100 and 125 by Western blotting, and after ACTH treatment. Dexamethasone administration led to a marked reduction in ir-P450(C17) levels. In contrast, ir-3beta-HSD was present in the fetal adrenal cortex between Day 100 and term, and was less affected by ACTH or dexamethasone treatment. We conclude that P450(C17) in the fetal sheep adrenal is responsive to regulation by ACTH, and that changes in its levels correlate with previously reported alterations in patterns of cortisol output by the fetal adrenal gland.

[Surgical treatment of traumatic facial paralysis]

The paper reviews 27 cases of traumatic facial paralysis undergone surgical treatment. Most of the cases showed injuries to the horizontal and perigeniculate segments of the facial nerve. All cases have been followed up for 6 months to 2 years. Complete recovery occurred in 20 of the cases and partial recovery in 7 cases (II in 2, III in 5). Trans-mastoid/attic approach was used which yielded exposure of the geniculate ganglion and distal part of the labyrinthine segment of the nerve. Indications and surgical approach were discussed.

Quality of life scores: an independent prognostic variable in a general population of cancer patients receiving chemotherapy. The National Cancer Institute of Canada Clinical Trials Group

This report examines the prognostic associations between QOL scores measured by the EORTC QLQ-C30 and survival in a large heterogeneous population of cancer patients. Eight hundred and fifty-one cancer patients who were to receive chemotherapy were enrolled in two National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) antiemetic trials. All patients completed the EORTC QLQ-C30 immediately prior to their first chemotherapy. Survival data were available and obtained for 474 of 639 patients (74%). Cox's proportional hazards model was used to assess the independent impact of QOL and demographic variables on survival. Presence of metastatic disease, diagnosis of lung or ovarian cancer, ECOG performance status, global quality of life and emotional functioning were significantly associated with survival. Global QOL was predictive in all patients, in subgroups of patients with metastatic disease, with breast and lung cancer and other tumour types. In patients with low global quality of life scores, patients with low emotional functioning ratings lived longer than did patients with high emotional functioning ratings. Patients with high global QOL live significantly longer than do patients with low global QOL. The relationship between emotional functioning in patients with low global QOL and survival needs confirmation.

Planar optical waveguide in Cu-doped potassium sodium strontium barium niobate crystal formed by mega-electron-volt He-ion implantation

The first planar optical waveguide to the authors' knowledge has been formed in Cu-doped potassium sodium strontium barium niobate crystal by mega-electron-volt He(+) implantation. Both TE and TM modes are observed. The profiles of the ordinary and the extraordinary refractive indices are deduced from dark-line mode spectroscopy. The results show that the mega-electron-volt He implantation results in a decrease in refractive index in barriers for both n(o) and n(e), but for n(e) there is an obvious increase in the waveguide region. From an experiment in photorefractive two-wave mixing, it is found that the erasure time for two-wave mixing is prolonged by ion implantation.

A preliminary study on immune response to hepatitis E virus DNA vaccine in mice

OBJECTIVE

In order to elicit immune response to hepatitis E virus (HEV) with the method of direct injection of naked DNA.

METHODS

The gene encoding the structural protein of pORF3, a Chinese strain of HEV, was cloned into the eukaryotic expression plasmid pSVL. The resulted plasmid pSVL-HEV ORF3 was used as HEV DNA vaccine, to inoculate Balb/c mice intramuscularly with a dose of 100 micrograms. Mice injected with empty pSVL DNA served as control.

RESULTS

After 1-2 times inoculation, twelve of 16 mice inoculated with pSVL-HEV ORF3 had anti-HEV IgG seroconversion. pSVL-HEV ORF3 was still detectable in the muscle of the inoculated mice 18 days after the injection, by the method of PCR. None of the control group had a detectable level of anti-HEV IgG. It is also found that the humoral immune response to HEV induced by DNA vaccine could be boostered by HEV recombinant fusion protein.

CONCLUSION

Our present study demonstrated that nucleic acid vaccine is able to prime a specific humoral immune response to HEV in mice.

[Early results of CABG operation in 110 patients]

Coronary artery bypass grafting (CABG) operations were performed in 110 consecutive patients. Most of them had extensive triple-vessel disease or left main coronary artery disease. Internal mammary artery (IMA) was used as a graft in 65 patients. Valvular replacement or valvuloplasty were performed in 8 patients and ventricular aneurysmectomy in 10 patients including post infarction VSD repaired in 1 patient simultaneously. Angina pectoris was relieved in all patients except one died from acute renal failure postoperatively. The IMA could be used safely and efficiently in nearly all patients. Using very fine technique, we suggested good exposure, and hemostasis to handle IMA. The key factor of success in CABG operation was complete revascularization by passing all significant stenosis larger than 1 mm diameter in all coronary artery branches.

[Study of nitric oxide synthases, nitric oxide and tumor necrosis factor in different types of ascites]

The purpose of this study was to elucidate the clinical significance of nitric oxide synthases (NOS), nitric oxide (NO) and tumor necrosis factor (TNF) in different types of ascites. NOS, NO and TNF in ascitic transudates of 21 patients with liver cirrhosis, ascitic exudate of 32 patients with liver cirrhosis and carcinogenesic ascites of 19 patients were measured by Griess, ELISA and colorimetric methods. Compares to the value in ascitic transudate of 21 patients with liver cirrhosis, NOS (7.32 +/- 3.13 nmol.min-1.g-1), NO (15.4 +/- 7.6 mumol/L) and TNF (331.7 +/- 121.2 mumol/L) in ascitic exudate of 32 patients with liver cirrhosis were significantly higher (P < 0.01). The NO (10.7 +/- 3.2 mumol/L) and TNF (185.6 +/- 84.1 mumol/L) in carcinogenesic ascites of 19 patients were between those in ascitic exudates and those in ascitic transudates of patients with liver cirrhosis (P < 0.05 or 0.01). The NOS activity was highest in carcinogenesic ascites. The decrease of 24h urine volume in patients with cirrhosis was relative to the increase of NO level in ascites. Those suggested that measurements of NOS, NO and TNF in ascites are helpful in differential diagnosis of ascites. The separation between NO level and NOS activity in ascites indicates that the ascites is carcinogenesis.