Role of tryptophan 161 in catalysis by human manganese superoxide dismutase

Tryptophan 161 is a highly conserved residue that forms a hydrophobic side of the active site cavity of manganese superoxide dismutase (MnSOD), with its indole ring adjacent to and about 5 A from the manganese. We have made a mutant containing the conservative replacement Trp 161 --> Phe in human MnSOD (W161F MnSOD), determined its crystal structure, and measured the catalysis of the resulting mutant using pulse radiolysis to produce O(2)(*)(-). In the structure of W161F MnSOD the phenyl side chain of Phe 161 superimposes on the indole ring of Trp 161 in the wild type. However, in the mutant, the hydroxyl side chain of Tyr 34 is 3.9 A from the manganese, closer by 1.2 A than in the wild type. The tryptophan in MnSOD is not essential for the half-cycle of catalytic activity involving reduction of the manganese; the mutant W161F MnSOD had k(cat)/K(m) at 2.5 x 10(8) M(-)(1) s(-)(1), reduced only 3-fold compared with wild type. However, this mutant exhibited a strong product inhibition with a zero-order region of superoxide decay slower by 10-fold compared with wild type. The visible absorption spectrum of W161F MnSOD in the inhibited state was very similar to that observed for the inhibited wild-type enzyme. The appearance of the inhibited form required reaction of 2 molar equiv of O(2)(*)(-) with W161F Mn(III)SOD, one to form the reduced state of the metal and the second to form the inhibited complex, confirming that the inhibited complex requires reaction of O(2)(*)(-) with the reduced form of the enzyme. This work suggests that a significant role of Trp 161 in the active site is to promote the dissociation of product peroxide, perhaps in part through its effect on the orientation of Tyr 34.

Expression in normal human tissues of five nucleotide excision repair genes measured simultaneously by multiplex reverse transcription-polymerase chain reaction

DNA repair is central to the integrity of the human genome. Reduced DNA repair capacity has been linked to genetic susceptibility to cancer. An adequate expression level of DNA repair genes is essential for normal DNA repair activities. Although there is tissue specificity in the expression, searching for a surrogate tissue is needed for molecular epidemiological studies. In this study, the relative expression levels of five selected human nucleotide excision repair (NER) genes (ERCC1, XPB/ERCC3, XPG/ERCC5, CSB/ERCC6, and XPC) in 20 different types of human normal tissue were simultaneously measured by a new multiplex reverse transcription (RT)-PCR assay using the expression level of the beta-actin gene as an internal control. Transcripts of each of the five NER genes were detectable, but the levels varied in these normal tissues. Both mitogen (phytohemagglutinin)-stimulated and unstimulated human peripheral lymphocytes showed similar expression patterns for the five NER genes. In general, the expression levels of stimulated lymphocytes were also similar to most of the rapidly proliferating tissues, such as the skin, breast, intestine, liver, testis, ovary, placenta, or prostate, but was relatively higher than that of the slowly proliferating or nonproliferating tissues such as adipose, brain, hippocampus, muscle, spleen, or lung. The data suggested that although the five NER genes were expressed at different levels in the normal tissues examined, PHA-stimulated peripheral lymphocytes may be used as a surrogate tissue for estimating expression levels of these genes in proliferating tissues. This new multiplex RT-PCR assay may help detect aberrant expression of these NER genes in both normal and tumor tissues.

Selective targeting of cyclooxygenase-2 reveals its role in renal medullary interstitial cell survival

Renal medullary interstitial cells (MICs) are a major site of cyclooxygenase (COX)-mediated PG synthesis. These studies examined the role of COX in MIC survival. Immunoblot and nuclease protection demonstrate that cultured MICs constitutively express COX2, with little constitutive COX1 expression. SC-58236, a COX2-selective inhibitor, but not SC-58560, a COX1 inhibitor, preferentially blocks PGE2 synthesis in MICs. Transduction with a COX2 antisense adenovirus reduced MIC COX2 protein expression and also decreased PGE2 production. Antisense downregulation of COX2 was associated with MIC death, whereas a control adenovirus was without effect. Similarly, the COX2-selective inhibitor SC-58236 (30 microM) and several nonselective COX-inhibiting nonsteroidal anti-inflammatory drugs (NSAIDs), including sulindac, ibuprofen, and indomethacin, all caused MIC death. In contrast, SC-58560, a COX1-selective inhibitor, was 100-fold less potent for inducing MIC death than its structural congener SC-58236. NSAID-induced MIC death was associated with DNA laddering and nuclear fragmentation, consistent with apoptosis. These results suggest that COX2 plays an important role in MIC survival. COX2 inhibition may contribute to NSAID-associated injury of the renal medulla.

Apical and basolateral CO2-HCO3- permeability in cultured bovine corneal endothelial cells

Corneal endothelial function is dependent on HCO3- transport. However, the relative HCO3- permeabilities of the apical and basolateral membranes are unknown. Using changes in intracellular pH secondary to removing CO2-HCO3- (at constant pH) or removing HCO3- alone (at constant CO2) from apical or basolateral compartments, we determined the relative apical and basolateral HCO3- permeabilities and their dependencies on Na+ and Cl-. Removal of CO2-HCO3- from the apical side caused a steady-state alkalinization (+0.08 pH units), and removal from the basolateral side caused an acidification (-0.05 pH units). Removal of HCO3- at constant CO(2) indicated that the basolateral HCO3- fluxes were about three to four times the apical fluxes. Reducing perfusate Na+ concentration to 10 mM had no effect on apical flux but slowed basolateral HCO3- flux by one-half. In the absence of Cl-, there was an apparent increase in apical HCO3- flux under constant-pH conditions; however, no net change could be measured under constant-CO2 conditions. Basolateral flux was slowed approximately 30% in the absence of Cl-, but the net flux was unchanged. The steady-state alkalinization after removal of CO2-HCO3- apically suggests that CO2 diffusion may contribute to apical HCO3- flux through the action of a membrane-associated carbonic anhydrase. Indeed, apical CO2 fluxes were inhibited by the extracellular carbonic anhydrase inhibitor benzolamide and partially restored by exogenous carbonic anhydrase. The presence of membrane-bound carbonic anhydrase (CAIV) was confirmed by immunoblotting. We conclude that the Na+-dependent basolateral HCO3- permeability is consistent with Na+-nHCO3- cotransport. Changes in HCO3- flux in the absence of Cl- are most likely due to Na+-nHCO3- cotransport-induced membrane potential changes that cannot be dissipated. Apical HCO3- permeability is relatively low, but may be augmented by CO2 diffusion in conjunction with a CAIV.

Structure of the DNA repair enzyme endonuclease IV and its DNA complex: double-nucleotide flipping at abasic sites and three-metal-ion catalysis

Endonuclease IV is the archetype for a conserved apurinic/apyrimidinic (AP) endonuclease family that primes DNA repair synthesis by cleaving the DNA backbone 5' of AP sites. The crystal structures of Endonuclease IV and its AP-DNA complex at 1.02 and 1.55 A resolution reveal how an alpha8beta8 TIM barrel fold can bind dsDNA. Enzyme loops intercalate side chains at the abasic site, compress the DNA backbone, bend the DNA approximately 90 degrees, and promote double-nucleotide flipping to sequester the extrahelical AP site in an enzyme pocket that excludes undamaged nucleotides. These structures suggest three Zn2+ ions directly participate in phosphodiester bond cleavage and prompt hypotheses that double-nucleotide flipping and sharp bending by AP endonucleases provide exquisite damage specificity while aiding subsequent base excision repair pathway progression.

Molecular characterization of H9N2 influenza viruses: were they the donors of the "internal" genes of H5N1 viruses in Hong Kong?

The origin of the H5N1 influenza viruses that killed six of eighteen infected humans in 1997 and were highly pathogenic in chickens has not been resolved. These H5N1 viruses transmitted directly to humans from infected poultry. In the poultry markets in Hong Kong, both H5N1 and H9N2 influenza viruses were cocirculating, raising the possibility of genetic reassortment. Here we analyze the antigenic and genetic features of H9N2 influenza viruses with different epidemiological backgrounds. The results suggest that the H9N2 influenza viruses of domestic ducks have become established in the domestic poultry of Asia. Phylogenetic and antigenic analyses of the H9N2 viruses isolated from Hong Kong markets suggest three distinct sublineages. Among the chicken H9N2 viruses, six of the gene segments were apparently derived from an earlier chicken H9N2 virus isolated in China, whereas the PB1 and PB2 genes are closely related to those of the H5N1 viruses and a quail H9N2 virus-A/quail/Hong Kong/G1/97 (Qa/HK/G1/97)-suggesting that many of the 1997 chicken H9 isolates in the markets were reassortants. The similarity of the internal genes of Qa/HK/G1/97 virus to those of the H5N1 influenza viruses suggests that the quail virus may have been the internal gene donor. Our findings indicate that the human and poultry H5N1 influenza viruses in Hong Kong in 1997 were reassortants that obtained internal gene segments from Qa/HK/G1/97. However, we cannot be certain whether the replicate complex of H5N1 originated from Qa/HK/G1/97 or whether the reverse transfer occurred; the available evidence supports the former proposal.

PCR assay for the inversion causing severe Hemophilia A and its application

OBJECTIVE

To develop a new technique based on long distance polymerase chain reaction (LD-PCR) to replace Southern blotting method to detect Factor VIII (FVIII) gene inversion leading to severe Hemophilia A (HA) and carrier.

METHODS

Four primers P, Q, A&B were designed and synthesized. P&Q is specific for 5' and 3' flanking regions of F8A1 respectively. A&B is specific for 5' and 3' flanking regions of F8A2/F8A3 respectively. LD-PCR with 3 primers and 3 temprature was set up, optimized and used to detect the inversion.

RESULTS

The LD-PCR with primers P, Q, A&B, P, Q&B and P, Q&A can be used to detect the gene inversion and discriminate carrier from wild type. A blind analysis of 53 DNA samples from HA families was carried out by the LD-PCR and Southern blotting respectively. Two sets of the results were completely identical. They were 23 cases of inversion, 27 cases of wild type and 3 cases of carriers. The sensitivity and specificity of LD-PCR are both 100%. Three inversion hemizygotes and 4 female carriers were identified from 5 HA families by the LD-PCR technology.

CONCLUSIONS

The LD-PCR with primer P, Q&B or P, Q, A&B can be used to detect the gene inversion and the carrier of inversion. Compared with Southern blotting, this technique is simple, rapid, inexpensive, more sensitive, accurate and non-isotopic.

Swelling activated chloride channels in cultured bovine corneal endothelial cells

Swelling induced enhancement of anion permeability was investigated using the halide-sensitive fluorescent dye SPQ in cultured bovine corneal endothelial cells (BCEC). Rates of anion influx were quantified in terms of the rate of change of SPQ fluorescence during exposure to short duration pulses of Cl-, I-or NO3-while the cells were being perfused with I-, NO3-or Cl-Ringer, respectively. Since SPQ fluorescence is quenched to different extents by these anions, their influx or efflux causes significant changes in fluorescence. The ratio of the maximum rate of change of fluorescence during the pulse period under hyposmotic conditions to that under isosmotic conditions, referred to as the enhancement ratio (ER), was calculated as a measure of the increase in anion permeability. When cells were perfused with NO3-Ringer, exposure to I-pulses yielded an ER=9.0+/-2.6 for 110+/-5 mosmhyposmotic shock. This was higher than with Cl-/I-(6.4+/-0.7) or NO3-/Cl-(3.2+/-0.8) anion-pairs for the same level of shocks. In all cases, the enhancement occurred within approximately 100 seconds after swelling but decreased with continued progress of regulatory volume decrease (RVD). ER returned to approximately 1 within 4 minutes after returning to isosmotic conditions. The membrane potential (Em) depolarized immediately after hyposmotic shock. When cells were depolarized prior to the shocks by high [K+], changes in Emwere relatively small. ER, for the NO3-/I-anion-pair, was significantly reduced by DIDS (100% at 500 microm), NPPB ( approximately 80% at 100 microm) and tamoxifen (approximately 85% at 12 microm). Tamoxifen and NPPB also inhibited swelling induced depolarization. Increasing cationic conductance with Gramicidin D at approximately 2 minutes following hyposmotic shock induced NPPB-inhibitable secondary swelling or accelerated RVD under normal or low Na+conditions, respectively. These results demonstrate that BCEC express swelling activated Cl-channels, which facilitate RVD by enhancing anionic permeability and also by providing a favorable electrical gradient for K+efflux.

Salt-sensitive hypertension and reduced fertility in mice lacking the prostaglandin EP2 receptor

Prostaglandins (PGs) are ubiquitous lipid mediators derived from cyclooxygenase metabolism of arachidonic acid that exert a broad range of physiologic activities, including modulation of inflammation, ovulation and arterial blood pressure. PGE2, a chief cyclooxygenase product, modulates blood pressure and fertility, although the specific G protein-coupled receptors mediating these effects remain poorly defined. To evaluate the physiologic role of the PGE2 EP2 receptor subtype, we created mice with targeted disruption of this gene (EP2-/-). EP2-/- mice develop normally but produce small litters and have slightly elevated baseline systolic blood pressure. In EP2-/- mice, the characteristic hypotensive effect of intravenous PGE2 infusion was absent; PGE2 infusion instead produced hypertension. When fed a diet high in salt, the EP2-/- mice developed profound systolic hypertension, whereas wild-type mice showed no change in systolic blood pressure. Analysis of wild-type and EP2-/- mice on day 5 of pregnancy indicated that the reduced litter size of EP2-/- mice is due to a pre-implantation defect. This reduction of implanted embryos could be accounted for by impaired ovulation and dramatic reductions in fertilization observed on day 2 of pregnancy. These data demonstrate that the EP2 receptor mediates arterial dilatation, salt-sensitive hypertension, and also plays an essential part in female fertility.

DNA repair in lymphoblastoid cell lines from patients with head and neck cancer

OBJECTIVE

To analyze and compare components of the 3 primary DNA repair pathways of Epstein-Barr virus-transformed lymphocyte (lymphoblastoid) cell lines derived from 9 patients with squamous cell carcinoma of the head and neck and 11 cancer-free controls. These cell lines were previously characterized by using an established cytogenetic marker of cancer susceptibility (mutagen sensitivity assay).

DESIGN

To evaluate nucleotide excision repair (NER), we measured the reactivation level of a tobacco carcinogen-damaged plasmid containing a bacterial reporter gene transfected into these cells. To assess mismatch repair (MMR) and recombinational repair, selected gene transcript levels were quantified by using a multiplex reverse transcriptase-polymerase chain reaction assay. The results of these DNA repair assays were correlated with the previously measured mutagen sensitivity values.

RESULTS

The NER capacities of the 2 groups were similar: 25.1% (range, 14.3%-33.3%) for the patient cell lines and 26.0% (range, 9.4%-47.7%) for the control lines. Transcriptase levels for 6 MMR genes (hMSH3, hMSH2, hPMS2, GTBP, hMLH1 and hPMS1) did not differ in the 2 groups. Transcript levels for 4 of 6 recombinational repair genes (XRCC7, XRCC6, XRCC1, and RAD51) were higher in the patient cell lines, though this difference was significant only for XRCC7 (P = .003). The mutagen sensitivity values correlated with the NER capacity (P = .05) and the expression of XRCC4 (P = .01) and RAD51 (P = .06) genes.

CONCLUSIONS

As revealed by the above-named assays, these lymphoblastoid cell lines derived from patients with head and neck cancer had minor alterations in DNA repair function. However, these differences in DNA repair do appear to affect the cytogenetic marker of cancer susceptibility, mutagen sensitivity.

Characterization of avian H5N1 influenza viruses from poultry in Hong Kong

The transmission of avian H5N1 influenza viruses to 18 humans in Hong Kong in 1997 with six deaths established that avian influenza viruses can transmit to and cause lethal infection in humans. This report characterizes the antigenic and biological properties of the H5N1 influenza viruses isolated from chickens, ducks, and geese from farms and poultry markets in Hong Kong during 1997 and compares them with those of virus isolated from the index human case. Each of the H5N1 viruses from Hong Kong poultry markets that were tested were lethal in chickens, possessed polybasic amino acids at the carboxy-terminus of HA1, and by definition were highly pathogenic in poultry. The available nonpathogenic H5 influenza viruses and the pathogenic H5N1 virus from Hong Kong were analyzed with monoclonal antibodies prepared to A/chicken/Pennsylvania/1370/83 (H5N2). The analysis revealed limited antigenic drift in 15 years and established that monoclonal antibodies are useful reagents for identification and antigenic analysis of avian strains that may transmit to humans in the future. One of the monoclonal antibodies permitted separation of the H5N1 influenza viruses from poultry into two groups that correlated with the presence or absence of a carbohydrate at residue 158 adjacent to the receptor binding site on HA. The H5N1 viruses examined replicated in geese, pigs, rats, and mice, but to only a very limited extent in ducks. It is noteworthy that all infected geese shed virus and that the H5N1 viruses caused disease signs and death in a portion (3 of 16) of the geese, with evidence of systemic spread to the brain. The tropism for geese is unusual and may provide insight into the origin of these viruses. In mice, the H5N1 virus caused lethal pneumonia and spread systemically to the brain. Mice would thus provide an ideal model system for studying immune responses and pathogenesis. Transmission experiments in chickens revealed that the H5N1 viruses are spread by fecal-oral transmission rather than by aerosol, and that the viruses are inactivated by drying of feces at ambient temperature. However, infectivity is maintained for at least 4 days in wet feces at 25 degreesC. There were differences in the morphology of the H5N1 viruses isolated from birds and humans. The perpetuation of H5N1 influenza viruses in the poultry markets in Hong Kong and the transmission of these viruses to humans emphasize the importance of these markets in the epidemiology of influenza. The poultry markets are of critical importance in the perpetuation and transmission of influenza viruses to other avian species and to mammals, including humans.

MutY catalytic core, mutant and bound adenine structures define specificity for DNA repair enzyme superfamily

The DNA glycosylase MutY, which is a member of the Helix-hairpin-Helix (HhH) DNA glycosylase superfamily, excises adenine from mispairs with 8-oxoguanine and guanine. High-resolution crystal structures of the MutY catalytic core (cMutY), the complex with bound adenine, and designed mutants reveal the basis for adenine specificity and glycosyl bond cleavage chemistry. The two cMutY helical domains form a positively-charged groove with the adenine-specific pocket at their interface. The Watson-Crick hydrogen bond partners of the bound adenine are substituted by protein atoms, confirming a nucleotide flipping mechanism, and supporting a specific DNA binding orientation by MutY and structurally related DNA glycosylases.

Chemotherapy using 5-fluorouracil and nitrocaphanum in malignant trophoblastic tumor

OBJECTIVE

The aim of this study was to investigate the efficacy of nitrocaphanum (AT 1258) in combination with 5-fluorouracil (5-FU) in patients with gestational trophoblastic tumors (GTT).

METHOD

From 1979 to 1988, 152 patients with trophoblastic tumor were treated with combination chemotherapy using nitrocaphanum and 5-FU. Seventy patients had nonmetastatic disease, 61 with single organ metastasis and 9 with involvement of two or more organs. Fifty patients had received previous chemotherapy. The dose of 5-FU was 26 mg/kg and that of nitrocaphanum 0.6 mg/kg each daily for 8 days, repeated every 29 days.

RESULTS

Among patients who received nitrocaphanum with 5-FU, 134 of 152 patients (88%) achieved remission. By World Health Organization risk groups, the response to nitrocaphanum was as follows: 5-FU was 93.6% of 94 low-risk patients, 81.4% of 46 medium-risk patients, and 73.3% of 15 high-risk patients. Eighteen patients had to be given a second-line protocol because of resistance to nitrocaphanum and 5-FU. Fourteen of the 18 were cured while 4 patients died. There were 7 late recurrences more than 3 months after completion of therapy and 6 of these were cured by hysterectomy and chemotherapy.

CONCLUSION

Nitrocaphanum is an active chemotherapy agent in GTT and deserves further study for possible use in high-risk, chemotherapy-resistant patients.

[An in vitro study on toxic effect of vanadium-titanium-magnetite dust on alveolar macrophage in rabbits]

OBJECTIVE

To study the toxic effect of vanadium-titanium-magnetite (VTM) dust on alveolar macrophage (AM) and its hazardous extent.

METHODS

Survival rates, morphology and function of AM were compared in rabbits exposed to dust of VTM, vanadium oxide, titanium dioxide and silica in various doses and length of time with in vitro cell culture and putamen membrane cover glass transmission electron microscopy, and changes in activities of lactic dehydrogenase (LDH) and acid phosphatase (ACP) in cell culture were measured.

RESULTS

Exposure to all the four kinds of dust could lead to decrease in survival rate of AM, increase in activities of LDH and ACP in the cell culture, and changes in their morphology and function to the extent dependent on the nature of dust.

CONCLUSION

Toxic effect of exposure to VTM dust was lower than that to vanadium oxide and silica, but higher than that to titanium dioxide, which had slight toxic effect.

Structural polymorphism and raman conformation markers of cyclic deoxytriadenylic acid

X-ray analysis of two different trigonal crystal forms (space groups R32 and P3 ) of cyclic deoxytriadenylic acid [c(dAp)3] indicates for each an asymmetric unit consisting of two conformationally similar c(dAp)3molecules. Raman spectroscopy supports the X-ray interpretation for the R32 crystal, but identifies another c(dAp)3conformation not revealed in the P3 X-ray structure. The results for the P3 crystal can be explained if an additional c(dAp)3conformer is present but not sufficiently ordered within the lattice to contribute to X-ray diffraction. The Raman signature of aqueous c(dAp)3, which differs from signatures of both the R32 and P3 crystals, exhibits backbone markers similar to those of thermally denatured DNA and indicates that c(dAp)3molecules in solution populate a wider range of phosphoester ring conformations than in R32 and P3 crystals. Thus, polymorphism is observed for both crystal and solution structures of c(dAp)3. The results imply a highly flexible phosphoester ring that may be relevant to the function of cyclic oligonucleotides as biological effectors. A novel Raman marker at 821 cm-1is demonstrated as diagnostic of phosphoester torsions alpha and zeta in the gauche+ range. Specific Raman markers are also identified for the S -type (C2'- endo) deoxyadenosine conformations that occur in R32 and P3 crystal structures of c(dAp)3.

Molecular structure of two crystal forms of cyclic triadenylic acid at 1A resolution

The three dimensional structures of cyclic deoxytriadenylic acid, c-d(ApApAp), from two different trigonal crystal forms (space groups P3 and R32) have been determined by x-ray diffraction analysis at 1A resolution. Both structures were solved by direct methods and refined by anisotropic least squares refinement to R-factors of 0.109 and 0.137 for the P3 and R32 forms, respectively. In both crystal forms, each of the two independent c-d(ApApAp) molecules sits on the crystallographic 3-fold axis. All four independent c-d(ApApAp) molecules have similar backbone conformations. The deoxyriboses are in the S-type pucker with pseudorotation angles ranging from 156.7 degrees to 168.6 degrees and the bases have anti glycosyl torsion angles (chi falling in two ranges, one at -104.3 degrees and the other ranging from -141.0 degrees to -143.8 degrees). In the R32 form, a hexahydrated cobalt(II) ion is found to coordinate through bridging water molecules to N1, N3, and N7 atoms of three adjacent adenines and oxygen atoms of phosphates. Comparison with other structures of cyclic oligonucleotides indicates that the sugar adopts N-type pucker in cyclic dinucleotides and S-type pucker in cyclic trinucleotides, regardless whether the sugar is a ribose or a deoxyribose.

Prostaglandin E2 inhibits renal collecting duct Na+ absorption by activating the EP1 receptor

PGE2 exerts potent diuretic and natriuretic effects on the kidney. This action is mediated in part by direct inhibition of collecting duct Na+ absorption via a Ca++-coupled mechanism. These studies examine the role the Ca++-coupled PGE-E EP1 receptor plays in mediating these effects of PGE2 on Na+ transport. Rabbit EP1 receptor cDNA was amplified from rabbit kidney RNA. Nuclease protection assays demonstrated highest expression of EP1 mRNA in kidney, followed by stomach, adrenal, and ileum. In situ hybridization, demonstrated renal expression of EP1 mRNA was exclusively over the collecting duct. In fura-2-loaded microperfused rabbit cortical collecting duct, EP1 active PGE analogs were 10-1, 000-fold more potent in raising intracellular Ca++ than EP2, EP3, or EP4-selective compounds. Two different EP1 antagonists, AH6809 and SC19220, completely blocked the PGE2-stimulated intracellular calcium increase. AH6809 also completely blocked the inhibitory effect of PGE2 on Na+ absorption in microperfused rabbit cortical collecting ducts. These studies suggest that EP1 receptor activation mediates PGE2-dependent inhibition of Na+ absorption in the collecting duct, thereby contributing to its natriuretic effects.

Specific heat flow rate: an on-line monitor and potential control variable of specific metabolic rate in animal cell culture that combines microcalorimetry with dielectric spectroscopy

One of the requirements for enhanced productivity by the animal culture systems used in biotechnology is the direct assessment of the metabolic rate by on-line biosensors. Based on the fact that cell growth is associated with an enthalpy change, it is shown that the specific heat flow rate is stoichiometrically related to the net specific rates of substrates, products, and indeed to specific growth rate, and therefore a direct reflection of metabolic rate. Heat flow rate measured by conduction calorimetry has a technical advantage over estimates for many material flows which require assays at a minimum of two discrete times to give the rate. In order to make heat flow rate specific to the amount of the living cellular system, it would be advantageous to divide it by viable biomass. This requirement has been fulfilled by combining a continuous flow microcalorimeter ex situ with a dielectric spectroscope in situ, the latter measuring the viable cell mass volume fraction. The quality of the resulting biosensor for specific heat flow rate was illustrated using batch cultures of Chinese hamster ovary cells (CHO 320) producing recombinant human interferon-gamma (IFN-gamma) during growth in a stirred tank bioreactor under fully aerobic conditions. The measuring scatter of the probe was decreased significantly by applying the moving average technique to the two participant signals. It was demonstrated that the total metabolic rate of the cells, as indicated by the specific heat flow rate sensor, decreased with increasing time in batch culture, coincident with the decline in the two major substrates, glucose and glutamine, and the accumulation of the by-products, ammonia and lactate. Furthermore, the specific heat flow rate was an earlier indicator of substrate depletion than the flow rate alone. The calorimetric-respirometric ratio showed the intensive participation of anaerobic processes during growth and the related IFN-gamma production. Specific heat flow rate was monotonically related to specific cell growth rate and associated with specific IFN-gamma production. Specific heat flow rate is potentially a valid control variable for the growth of genetically engineered cell lines producing target proteins.

Reduced expression of mismatch repair genes in colorectal cancer patients in Egypt

An Egyptian hospital-based pilot case-control study was conducted to investigate the relationship between the expression level of mismatch repair (MMR) genes and the risk of colorectal cancer. The relative expression of five known MMR genes, i.e., hMSH2, hMLH1, hPMS1, hPMS2, and GTBP/hMSH6, was measured by a multiplex reverse transcriptase (RT)-polymerase chain reaction (PCR) in peripheral blood lymphocytes from 31 colorectal cancer patients and 47 age- and-sex matched controls. The expression of hMSH2, GTBP/hMSH6, hPMS1 and hPMS2 tended to be lower in patients than controls, but only the difference in hPMS2 expression was statistically significant (p<0. 01). Although 50% of the cases had chemotherapy or radiotherapy within the last six months before the blood was drawn, their gene expression was not statistically different from those who had not undergone such therapies. After adjustment for age and sex, the odds ratios (OR) calculated from a logistical regression model, using the median levels of gene expression of controls as cut-off values, indicated that increased risk was associated with reduced expressions of both hPMS1 (OR = 3.97, 95% confidence interval (CI) = 1.04 to 7.65) and hPMS2 (OR = 2.86, 95% CI = 1.05 to 7.76). Although the results of this study were inconclusive because of the small sample size and use of prevalent cases, it is biologically plausible that patients with colorectal cancers may have a lower expression of MMR genes than healthy controls because malfunction of these genes has been shown in hereditary nonpolyposis colon cancer. The involvement of low hPMS2 expression in colon cancer risk seems to be unique in the Egyptian population. Further studies with newly diagnosed patients before they begin therapy will provide more convincing data about the role of MMR gene expression in the etiology of colorectal cancers in Egypt.

Crystal structure of Y34F mutant human mitochondrial manganese superoxide dismutase and the functional role of tyrosine 34

Tyrosine 34 is a prominent and conserved residue in the active site of the manganese superoxide dismutases in organisms from bacteria to man. We have prepared the mutant containing the replacement Tyr 34 --> Phe (Y34F) in human manganese superoxide dismutase (hMnSOD) and crystallized it in two different crystal forms, orthorhombic and hexagonal. Crystal structures of hMnSOD Y34F have been solved to 1.9 A resolution in a hexagonal crystal form, denoted as Y34Fhex, and to 2.2 A resolution in an orthorhombic crystal form, denoted as Y34Fortho. Both crystal forms give structures that are closely superimposable with that of wild-type hMnSOD, with the phenyl rings of Tyr 34 in the wild type and Phe 34 in the mutant very similar in orientation. Therefore, in Y34F, a hydrogen-bonded relay that links the metal-bound hydroxyl to ordered solvent (Mn-OH to Gln 143 to Tyr 34 to H2O to His 30) is broken. Surprisingly, the loss of the Tyr 34 hydrogen bonds resulted in large increases in stability (measured by Tm), suggesting that the Tyr 34 hydroxyl does not play a role in stabilizing active-site architecture. The functional role of the side chain hydroxyl of Tyr 34 can be evaluated by comparison of the Y34F mutant with the wild-type hMnSOD. Both wild-type and Y34F had kcat/Km near 10(9) M-1 s-1, close to diffusion-controlled; however, Y34F showed kcat for maximal catalysis smaller by 10-fold than the wild type. In addition, the mutant Y34F was more susceptible to product inhibition by peroxide than the wild-type enzyme. This activity profile and the breaking of the hydrogen-bonding chain at the active site caused by the replacement Tyr 34 --> Phe suggest that Tyr 34 is a proton donor for O2* - reduction to H2O2 or is involved indirectly by orienting solvent or other residues for proton transfer. Up to 100 mM buffers in solution failed to enhance catalysis by either Y34F or the wild-type hMnSOD, suggesting that protonation from solution cannot enhance the release of the inhibiting bound peroxide ion, likely reflecting the enclosure of the active site by conserved residues as shown by the X-ray structures. The increased thermostability of the mutant Y34F and equal diffusion-controlled activity of Y34F and wild-type enzymes with normal superoxide levels suggest that evolutionary conservation of active-site residues in metalloenzymes reflects constraints from extreme rather than average cellular conditions. This new hypothesis that extreme rather than normal substrate concentrations are a powerful constraint on residue conservation may apply most strongly to enzyme defenses where the ability to meet extreme conditions directly affects cell survival.

Probing the active site of human manganese superoxide dismutase: the role of glutamine 143

Structural and biochemical characterization of the nonliganding residue glutamine 143 near the manganese of human Mn superoxide dismutase (hMnSOD), a homotetramer of 22 kDa, reveals a functional role for this residue. In the wild-type protein, the side-chain amide group of Gln 143 is about 5 A from the metal and is hydrogen-bonded to Tyr 34, which is a second prominent side chain adjacent to the metal. We have prepared the site-specific mutant of hMnSOD with the conservative replacement of Gln 143 --> Asn (Q143N). The crystal structure of Q143N shows that the side-chain amide nitrogen of residue 143 is 1.7 A more distant from the manganese than in the wild-type enzyme. The Tyr 34 side-chain hydroxyl in Q143N is also moved to become 0.6 A more distant from the metal due to an additional water molecule. Differential scanning calorimetry showed that Q143N is slightly more stable than the wild-type enzyme with Tm for the main unfolding transition increased by 2 degrees C to 90.7 degrees C. Pulse radiolysis and stopped-flow spectrophotometry reveal that unlike wild-type hMnSOD, which is strongly inhibited by peroxide, Q143N MnSOD exhibits no product inhibition even at concentrations of O2. - in the millimolar range, and its catalysis follows Michaelis kinetics with no evidence of cooperativity. However, the overall catalytic activity of this mutant was decreased 2-3 orders of magnitude compared with the wild-type MnSOD, which can account for its lack of product inhibition. Q143N MnSOD lacked the visible absorption spectrum typical of wild-type Mn(III)SOD. Also, unlike the wild-type Mn(III)SOD, which is electron paramagnetic resonance (EPR) silent, Q143N MnSOD has a complex EPR spectrum with many resonances in the region below 2250 G. We conclude that the Gln 143 --> Asn mutation has increased the reduction potential of manganese to stabilize Mn(II), indicating that Gln 143 has a substantial role in maintaining a reduction potential favorable for the oxidation and reduction cycles in the catalytic disproportionation of superoxide. A solvent hydrogen isotope effect near 2 for kcat in catalysis by Q143N hMnSOD indicates rate-contributing proton transfers to form product hydroperoxide anion or hydrogen peroxide. The data demonstrate a prominent role for Gln 143 in maintaining the microenvironment of the manganese and in efficient catalysis of superoxide dismutation to oxygen and hydrogen peroxide.

Reduced expression of hMLH1 and hGTBP/hMSH6: a risk factor for head and neck cancer

Head and neck cancer, like lung cancer, is considered a paradigm of an environmentally induced disease. Genetically determined variation in DNA repair capacity is thought to contribute to susceptibility to tobacco-related cancers. In this molecular epidemiology study, we investigated the association between DNA mismatch-repair (MMR) gene expression and the risk of head and neck cancer. Using our newly developed multiplex reverse transcription-PCR assay, we simultaneously evaluated the relative expression levels of five MMR genes (hMSH2, hMLH1, hPMS1, hPMS2, and hGTBP/hMSH6) in the peripheral blood lymphocytes of 78 patients (mean age = 59.6 +/- 12.4 years) with newly diagnosed head and neck cancer and 86 healthy controls (mean age = 58.2 +/- 12.9 years). The relative MMR gene expression was not correlated with disease stage or tumor site in the cases or with smoking and alcohol use in the controls. The expression levels increased with age in both cases and controls, but the mean expression of hMLH1, hPMS1, and hGTBP/hMSH6 was significantly lower in the cases than in the controls (P < 0.05). Using the median expression level in controls as the cutoff value, significantly increased odds ratios (ORs) were associated only with low expression of hMLH1 (OR = 4.4; 95% confidence interval = 2.1-9.1) and hGTBP/hMSH6 (OR = 2.1; 95% confidence interval = 1.1-4.1) after adjustment for age, sex, ethnicity, smoking status, and alcohol use. The results suggest that low hMLH1 and hGTBP/hMSH6 expression is associated with an increased risk of head and neck cancer. Additional studies with a larger number of subjects are warranted to confirm these findings.

Expression of five selected human mismatch repair genes simultaneously detected in normal and cancer cell lines by a nonradioactive multiplex reverse transcription-polymerase chain reaction

Abnormalities in at least 1 of 5 mismatch repair (MMR) genes (hMSH2, hMLH1, hPMS1, hPMS2 and GTBP/hMSH6) are found in hereditary nonpolyposis colon cancer and sporadic colon cancers. We used a single-reaction multiplex reverse transcription (RT)-polymerase chain reaction (PCR), with the beta-actin gene as an internal control, to simultaneously evaluate expression of these 5 known human MMR genes in normal and tumor cell lines with known or uncharacterized mutations in MMR genes. The relative quantitation of the transcripts is demonstrated by controlling the number of PCR cycles and titrating cDNA with a dose-curve. The 13 normal cell lines tested were derived from normal lymphocytes, skin, thymus, breast, lung, colon, liver and kidney. The 26 cancer cell lines were derived from melanoma and cancers of the brain, breast, lung, colon, pancreas and prostate. All 5 MMR genes were ubiquitously expressed in all normal cell lines tested, suggesting their housekeeping roles. Aberrant MMR gene expression was only observed in the colon cancer cell lines. Two previously uncharacterized colon cancer cell lines did not express hMLH1. These data suggest that this nonradioactive multiplex RT-PCR assay for MMR gene expression may be useful for fast screening for genetic alterations that may affect gene expression and so may aid molecular analysis of MMR-related colon cancer.

[A study on processing of the root of Astragalus membranaceus Bge. by HPLC]

The paper presents a study on the drug-processing of the root of Astragalus membranaceus. A HPLC method for the determination of astragaloside IV in its processed products has been established. The recovery is 96.1% and the RSD is 2.15%.

[The orthogonal design study on tumor-inhibition and cancer-block role of Chinese medicinal 1023 co]

OBJECTIVE

To study the effect of Chinese herb medicine on the inhibition of tumor formation and block of malignant transformation.

METHODS

The Chinese medicine 1023 co. was given by intubation feeding started simultaneously with the painting of 0.5% DMBA on the hamster's cheek mucosa.

RESULTS

The tumor formation in 1023 co. group was delayed for 12 days comparing with the control group and the incidence of dysplasia and cancer in 1023 co. group was lower significantly than that of the control group (P < 0.01).

CONCLUSION

The 1023 co. is effective in inhibiting tumor formation and blocking cancerous transformation. By orthogonal design we find the proper prescription is A2 B2 C2 D1.

Expression of peroxisome proliferator-activated receptors in urinary tract of rabbits and humans

Peroxisome proliferator-activated receptors (PPARs, alpha, beta/delta, and gamma) are members of the nuclear receptor superfamily of ligand-activated transcription factors. PPARs regulate the expression of genes involved in lipid metabolism. 8(S)-hydroxyeicosatetraenoic acid (8-S-HETE), leukotriene B4 (LTB4), and hypolipidemic fibrates activate PPAR alpha, whereas PPAR gamma is activated by prostaglandin metabolites. The present studies examined the intrarenal and tissue distribution of rabbit and human PPAR alpha, -beta/delta, and -gamma mRNAs. Nuclease protection showed PPAR alpha predominated in liver, heart, and kidney, whereas PPAR gamma, a putative adipose-specific transcription factor, was in white adipose tissue, bladder, and ileum, followed by kidney and spleen. Lower expression levels of PPAR beta/delta were observed in several tissues. In situ hybridization of kidney showed PPAR alpha mRNA predominated in proximal tubules and medullary thick ascending limbs of both rabbit and human. PPAR gamma was exclusively expressed in medullary collecting duct and papillary urothelium. Immunoblot confirmed the expression of PPAR gamma protein in freshly isolated inner medullary collecting ducts. mRNAs for all the PPARs were expressed in the ureter and bladder in both rabbit and human, but PPAR gamma expression was greatest. This distinct distribution of PPAR isoforms has important implications for lipid-activated gene transcription in urinary epithelia.

[Experimental study on prevention of pneumoconiosis complicating with tuberculosis by Mycobacterium vaccae]

OBJECTIVE

To explore the role of Mycobacterium vaccae in prevention of pneumoconiosis complicating with tuberculosis.

METHOD

Mycobacterium vaccae was injected into rats which had been exposed to quartz for 2 weeks, and H37Rv was injected into their tail veins 1 month later. All the rats were killed 3 months later. Indexes for evaluation in the study included tuberculous lesion pathological change index, Mycobacterium tuberculosis culture in a fixed amount in lung tissues, count of Mycobacterium tuberculosis and histopathological changes in alveolar macrophages.

RESULT

Tuberculous lesion pathological change index, Mycobacterium tuberculosis culture in a fixed amount in lung tissues and count of Mycobacterium tuberculosis in alveolar macrophages were 2.6 +/- 0.5, (4.40 +/- 4.00) x 10(4) CFU and 7.2 +/- 3.2 respectively in pneumoconiosis complicated with tuberculosis and injecting Mycobacterium vaccae group, while 3.1 +/- 0.3, (18.9 +/- 18.2) x 10(4) CFU and 12.5 +/- 6.3 respectively in the control group. And statistically significant differences were found between the two groups (P < 0.05, 0.01, 0.05 respectively). The histopathological analysis revealed that proliferative and lymphoid nodules were predominant in the pneumoconiosis complicated with tuberculosis and injecting Mycobacterium vaccae group, while necrotic nodules in the control group.

CONCLUSION

Mycobacterium vaccae might play a role in prevention of pneumoconiosis complicating with tuberculosis.

[Lecture of principles and applications of capillary electrophoresis (V) Applications of capillary electrophoresis in pharmaceutical analysis and clinical chemistry]

A review with 68 references is presented on the application and new developments of CE in pharmaceutical analysis, clinical chemistry and single cell analysis etc. The pharmaceutical analysis includes main component assay, determination of drug-related impurities, stoichiometric determination and quantitative determinations. The Chinese herb analysis includes determinations of main components and prescriptions of Chinese herb. The chiral separation includes separation mechanism and some new chiral selectors. The application of CE in clinical chemistry includes determinations of serum and protein, monitoring of drug metabolism, etc. Single cell analysis includes determinations of component in neurocells and human erythrocyte.

Experimental polyneuropathy produced in guinea-pigs immunized against sulfatide

Antibodies to sulfatide are associated with polyneuropathy. To investigate the role of anti-sulfatide antibodies in this neurological disorder, guinea-pigs were immunized with sulfatide, and their behavior, serology and pathology were compared with animals injected with simple Freund's adjuvant. Eleven of 13 guinea-pigs that developed raised serum anti-sulfatide antibodies after five injections of sulfatide showed definite motor weakness. Demyelination of peripheral nerves and immunoglobulin deposits at peripheral nerve myelin sheath were found in symptomatic animals only. Functional impairment of the animals was significantly correlated with serum anti-sulfatide IgG levels and pathological findings in nerve fiber studies. Control animals and animals that received 1-3 injections of sulfatide were behaviorally and pathologically normal.

Cloning, expression, and regulation of rabbit cyclooxygenase-2 in renal medullary interstitial cells

Prostaglandin synthesis requires cyclooxygenase-1 (COX1) or -2 (COX2), which mediate the conversion of arachidonate to prostaglandin H2. COX1 is the predominant constitutive isoform, whereas COX2 expression is typically low. In the present studies we cloned rabbit COX2 and determined its distribution in unstimulated tissues. Screening rabbit eye and uterine libraries yielded two cDNAs containing identical inserts with a 1,812-nucleotide open-reading frame. This encoded a 604-amino acid polypeptide, 90% identical to human, rat, and mouse COX2. Expression of the rabbit COX2 in HEK-293 cells enhanced prostanoid synthesis. Constitutive COX2 mRNA expression was highest in kidney and urinary bladder. COX2 expression was primarily in renal outer medullary interstitial cells with cortical expression in macula densa. In cultured medullary interstitial cells, COX2 mRNA predominated, with little COX1 expression. Interstitial cell COX2 mRNA but not COX1 was induced by phorbol ester and epidermal growth factor but suppressed by dexamethasone. Phorbol ester also upregulated immunoreactive COX2. Constitutive COX2 in these tissues has important implications for side effects of COX2-selective inhibitors.

[Preliminary study on planar two-dimensional capillary electrophoresis]

Capillary Electrophoresis (CE) system with rectangular cross section columns is integrated on quartz monocrystal plate. Because of its high surface-to-volume ratio and excellent heat conductivity of quartz, rectangular capillary is extremely efficient in dissipating heat compared to conventional circular capillaries. Comparative study showed that much higher electric field strength can be applied to this system without bubble formation. Another advantage of rectangular geometry channel is better detection ability because of the elimination of optical path distortion. The effectiveness of the planar CE has been demonstrated by comparing the separation of two solutes in phosphate buffer between rectangular and circular cross section column with same area. We also found that the separation efficiency can be improved dramatically by decreasing the channel dimension, which underlies the miniaturization of planar CE. In addition, injection by micro injector eliminate sample biasing and increase reproductivity. A simple manifold of rectangular flow channels are fabricated on quartz substrate. By use of electroosmotic pumping it is possible to control the direction of fluid flow in the manifold of intersecting channels without the use of valves. The experimental results proved that the band dispersion after the valveless switching is almost negligible, showing that the two dimensional separation is possible. The main contribution to band-broadening in our capillary electrophoresis is longitudinal diffusion, injection delay time and wall adsorption. In some cases the wall adsorption make the most contribution. Optimum efficiency depends on minimization of these unavoidable sources causing band broadening.

[Subtype and sequence analysis of the C2-V3 region of gp120 genes among human immunodeficiency virus infected IDUs in Ruili epidemic area of Yunnan Province of China]

DNA fragments of HIV-1 env gene were amplified by nested-PCR from 17 uncultured peripheral blood mononuclear cells (PBMCs) obtained from HIV-1 seropositive intravenous drug users (IDUs) in Ruili city of Yunnan Province. The C2-V3 region (about 450 bp) of them were sequenced. Sequence analysis showed that there exists two HIV-1 subtypes, B and C, with 5.8% and 2.2% gene divergence inside each subtype. The 12 subtype B strains, were closely related to those found in Thailand, Myanma and Ruili city of Yunnan, and the nucleotide sequence divergence between them ranged from 4.4% to 4.9%; meanwhile, the 5 subtype C strains were most close to those found in India as well as Ruili city, all with a genetic distance of 1.9%. The small divergence among Ruili HIV-1 subtype C strains suggests a recent epidemic. The analysis of V3 loop amino sequence of 12 subtype B HIV-1 reveals that V3-tip motif of 6 samples (50%) is GPGQ and that of 3 samples (25%) is GPGR. In addition, the codon of arginine (R) of all the strains is CGA instead of AGA. This result is in accordance with our previous hypothesis that there is a drift in vivo from GPGR to GPGQ motif on the tipof V3-loop of HIV-1 subtype B strain in this arm with the elapse of time.

Vibrational analysis of nucleic acids. IV. Normal modes of the DNA phosphodiester structure modeled by diethyl phosphate

Raman and ir spectra are reported for diethyl phosphate [(CH3CH2O)2PO2-] and diethyl phosphate isotopomers incorporating carbon-13 at methylene group sites [(CH313CH2O)2PO2-] and deuterium substituents on methyl and methylene carbons [(CH3CD2O)2PO2-, (CD3CH2O)2PO2-, (CD3CD2O)2PO2-]. The vibrational spectra are analyzed to develop a consistent set of assignments for the C-C-O-P(O2-)-O-C-C network, which serves as a model for the nucleic acid phosphodiester backbone. The present study resolves previously conflicting vibrational assignments for the phosphodiester skeleton and provides a firm empirical basis for interpreting conformationally sensitive modes of DNA and RNA. Ab initio vibrational analyses have also been conducted on the above isotopomers of diethyl phosphate in the trans-gauche-gauche-trans conformation, optimized using the 3-21+G* basis set at the restricted Hartree-Fock level. The ab initio calculations are in good agreement with the empirical results, thus strengthening the proposed assignment scheme for Raman and infrared spectra. The present study provides a basis for improvement of empirical force fields utilized in previous normal coordinate analyses of the nucleic acid phosphodiester group.

Vibrational analysis of nucleic acids. IV. Normal modes of the DNA phosphodiester structure modeled by diethyl phosphate

Raman and ir spectra are reported for diethyl phosphate [(CH3CH2O)2PO2-] and diethyl phosphate isotopomers incorporating carbon-13 at methylene group sites [(CH313CH2O)2PO2-] and deuterium substituents on methyl and methylene carbons [(CH3CD2O)2PO2-, (CD3CH2O)2PO2-, (CD3CD2O)2PO2-]. The vibrational spectra are analyzed to develop a consistent set of assignments for the C-C-O-P(O2-)-O-C-C network, which serves as a model for the nucleic acid phosphodiester backbone. The present study resolves previously conflicting vibrational assignments for the phosphodiester skeleton and provides a firm empirical basis for interpreting conformationally sensitive modes of DNA and RNA. Ab initio vibrational analyses have also been conducted on the above isotopomers of diethyl phosphate in the trans-gauche-gauche-trans conformation, optimized using the 3-21+G* basis set at the restricted Hartree-Fock level. The ab initio calculations are in good agreement with the empirical results, thus strengthening the proposed assignment scheme for Raman and infrared spectra. The present study provides a basis for improvement of empirical force fields utilized in previous normal coordinate analyses of the nucleic acid phosphodiester group.

Drosophila rosA gene, which when mutant causes aberrant photoreceptor oscillation, encodes a novel neurotransmitter transporter homologue

The Drosophila receptor oscillation A (rosA) mutations, which cause electroretinogram (ERG) defects, including oscillations, were localized to the 24F4-25A2 region of chromosome 2L. Genomic fragments from this region, isolated from bacteriophage P1 clones, included those that detect transcriptional defects in rosA mutants in RNA blot experiments. One of these genomic fragments was used to screen a head cDNA library. The largest cDNA clone (3.6 kb) isolated was shown to rescue a rosA mutant in P element-germline transformation experiments. The ROSA protein deduced from the open reading frame in the 3.6 kb rosA cDNA is 943 amino acids long and is 36-41% identical to members of the superfamily of Na+/Cl(-)-dependent neurotransmitter transporters, with no indication of higher sequence identity to any one subgroup within the superfamily. RNA blot experiments revealed multiple transcripts in various developmental stages, the most abundant one being a 3.7 kb transcript, particularly in the adult head. Tissue in situ experiments identified the rosA transcript to be localized to many tissues, with higher levels of hybridization in the nervous system and digestive tract. The results demonstrate that the rosA gene encodes a novel Na+/Cl(-)-dependent transporter important for normal response properties of the photoreceptor.

Emergence of avian H1N1 influenza viruses in pigs in China

Avian influenza A viruses from Asia are recognized as the source of genes that reassorted with human viral genes to generate the Asian/57 (H2N2) and Hong Kong/68 (H3N2) pandemic strains earlier in this century. Here we report the genetic analysis of avian influenza A H1N1 viruses recently isolated from pigs in southern China, a host suspected to generate new pandemic strains through gene reassortment events. Each of the eight gene segments was of avian origin. Phylogenetic analysis indicates that these genes form an Asian sublineage of the Eurasian avian lineage, suggesting that these viruses are an independent introduction into pigs in Asia. The presence of avian influenza viruses in pigs in China places them in an optimal position for transmission to humans and may serve as an early warning of the emergence of the next human influenza virus pandemic.

Vibrational analysis of nucleic acids. V. Force field and conformation-dependent modes of the phosphodiester backbone modeled by diethyl phosphate

A generalized valence force field is derived for the diethyl phosphate anion [(CH3CH2O)2PO2-] and its deuterium [(CH3CD2O)2PO2-, (CD3CH2O)2PO2- and (CD3CD2O)2PO2-] and carbon-13 [(CH3 13CH2O)2PO2-] derivatives in the stable trans-gauche-gauche-trans conformation. Normal coordinate analysis of the trans-gauche-gauche-trans conformer, which serves as a structural analog of the nucleic acid phosphodiester group, is based on comprehensive infrared and Raman spectroscopic data and vibrational assignments obtained for the diethyl phosphate anion. The generalized valence force field is in good agreement with the scaled ab initio force field of diethyl phosphate and represents significant improvement over earlier modeling of the phosphodiester moiety with dimethyl phosphate. The conformational dependence of skeletal C-C-O-P(O2-)-O-C-C stretching vibrations is also explored. Starting with the trans-gauche-gauche-trans conformation, the frequency dependence of skeletal stretching modes has been obtained by stepwise rotation of the torsion angles of the P-O and C-O bonds corresponding to nucleic acid torsions alpha (P-O5'), beta (O5'-C5'), epsilon (C3'-O3'), and zeta (O3'-P). Both symmetric and antisymmetric phosphoester stretching modes are highly sensitive to P-O and C-O torsions, whereas symmetric and antisymmetric phosphodioxy (PO2-) stretching modes are less sensitive. The present results provide an improved structural basis for understanding previously developed empirical correlations between vibrational marker bands and nucleic acid backbone conformation.

[Study of an ancient corpse of the Warring States period unearthed from Tomb No. 1 at Guo-Jia Gang in Jingmen City (A comprehensive study)]

An ancient female corpse excavated from the robbed tomb No. 1 at Guo-Jia-Gang in Jingmen city of Hubei Province was studied. It was confirmed that the corpse was buried more than 2,300 years ago, namely at the middle stage of the Warring States period and is the earliest one of the ancient coffin corpses unearthed in China so far. It is of the same type as the ancient corpses of Weatern Han Dynasty excavated from tomb No. 1 at Ma-Wang-Dui in Changsha City and from the tomb No. 168 at Phoenix Hill in Jinagling City respectively. The collagenous fibers of connective tissue from all parts in the corpse were well preserved, showing fine ultrastructure with clear periodical cross banding, and a lot of bacterial spores were found between them. In addition, a large number of eggs of clonorchis sinensis and trichuris trichiura were found in the content of the bowel. The level and the cause of good preservation were discussed and it was believed that the good preservation may result from the combined effect of the internal and external environmental factors around the corpse.

Clonal stability of blood cell lineages indicated by X-chromosomal transcriptional polymorphism

The idea that stem cells oscillate between a state of activity and dormancy, thereby giving rise to differentiating progeny either randomly or in orderly clonal succession, has important implications for understanding normal hematopoiesis and blood cell dyscrasias. The degree of clonal stability in individuals also has practical implications for the evaluation of clonal lymphomyeloproliferative diseases. To evaluate the clonality pattern of the different types of blood cells as a function of time we have validated the applicability, sensitivity, and reproducibility of a thermostable ligase reaction to detect transcripts of the G6PD allele on the active X-chromosome in normal heterozygous females. While the ratio of the two X-chromosome-derived allelic transcripts varied widely among hemopoietic tissues in a given individual, this allelic ratio was virtually identical in all types of mature myeloid and lymphoid cells. Longitudinal studies indicated constancy of the G6PD allelic ratio in blood cells over a 912-d period of observation in healthy females. The individual variability observed in this allelic ratio suggests that the progeny of a relatively small number of original embryonic hemopoietic stem cells, approximately eight, contribute to the sustained production of all types of blood cells in healthy individuals.

[Correction of the secondary nasal deformity in bilateral cleft lip with a new technique]

Bilateral cleft lip often has nasal deformities of various degrees. It is not enough to elongate the nasal columella for such deformities. Based on the thoughts that secondary deformities of the nose and lip should be treated as a whole, the authors introduced a new technique, in which five aspects of the deformities were considered and treated at the same time. Thirteen patients have undergone surgical correction with satisfactory results.

Yishou jiangzhi (de-blood-lipid) tablets in the treatment of hyperlipemia

The Yishoujiangzhi (de-blood-lipid) tablets (composed of Radix Polygori Multiflori, Rhizoma Polygonati, Fructus Lycii, Crataegus Pinnatifida and Cassia Tora) were used in the treatment of 130 cases of hyperlipemia, achieving an effective rate of 87.0% in lowering serum cholesterol and 80.8% in lowering triglyceride.

[Correction of unilateral cleft lip nasal deformity with modified Bardach's technique]

Twenty-nine cases of unilateral cleft lip nasal deformities were corrected with modified Bardach's technique. Overall results were satisfactory. The key to a successful and stable correction of the nasal deformity is to lengthen the columella on the cleft side and to mobilize alar cartilage from its surrounding tissue, creating a symmetric shape and length. The major advantages of the technique are lengthening of the cleft columella and creation of a symmetric and well-projected nasal tip. The surgical technique is described in details. Some considerations before and during operation were discussed.

Primary familial polycythemia: a frameshift mutation in the erythropoietin receptor gene and increased sensitivity of erythroid progenitors to erythropoietin

Primary familial and congenital polycythemia (PFCP) is characterized by erythrocytosis with normal arterial PO2, blood P50, and serum erythropoietin (EPO) levels. In two PFCP families EPO receptor (EPOR) polymorphisms cosegregated with PFCP. A heterozygous insertion of G at EPOR nucleotide 5975 was identified in genomic DNA from polycythemic members of family no. 2. 5974insG shifts the reading frame at codon 430, predicting amino acid substitutions and truncation of the last 64 amino acids. Wild-type and mutant EPOR transcripts were detected in erythroid progenitors from affected individuals. Burst-forming units-erythroid from patients exhibited increased colony size and sensitivity to EPO. Transfected Ba/F3 cells expressing EPOR 5974insG exhibited increased EPO sensitivity compared with cells expressing wild-type EPOR. The functional effect of this EPOR mutation was directly compared with the other C-terminal mutations reported in unrelated PFCP families by expression in Ba/F3 cells. The transfected cells with another primary polycythemia associated EPOR mutant construct (G6002A) also exhibited increased sensitivity to EPO.

Cloning and characterization of a dihydrolipoamide acetyltransferase (E2) subunit of the pyruvate dehydrogenase complex from Arabidopsis thaliana

A cDNA encoding a dihydrolipoamide acetyltransferase (E2) subunit of the pyruvate dehydrogenase complex has been isolated from Arabidopsis thaliana. A cell culture cDNA expression library was screened with a monoclonal antibody (JIM 63) raised against nuclear matrix proteins, and four clones were isolated. One of these was 2175 base pairs in length, and it contained an open reading frame with an amino acid sequence and domain structure with strong similarity to the E2s of other eukaryotic and prokaryotic organisms. The organization and number of functional domains within the Arabidopsis protein are identical to those of the human E2, although the amino acid sequences within these domains are equally similar to those of the yeast and human proteins. The predicted amino acid sequence reveals the presence of a putative amino-terminal leader sequence with characteristics similar to those of other proteins, which are targeted to the plant mitochondrial matrix. The cross-reactivities of plant mitochondrial matrix proteins with JIM 63 and antibodies raised against the E2 and protein X components of eukaryotic pyruvate dehydrogenase complexes are consistent with the clone encoding a mitochondrial form of E2 and not the smaller protein X. The E2 mRNA of 2.2 kilobases was expressed in a range of Arabidopsis and Brassica napus tissues.

Electrostatic potential distribution of the gene V protein from Ff phage facilitates cooperative DNA binding: a model of the GVP-ssDNA complex

The crystal structure of the gene V protein (GVP) from the Ff filamentous phages (M13, fl, fd) has been solved for the wild-type and two mutant (Y41F and Y41H) proteins at high resolution. The Y41H mutant crystal structure revealed crystal packing interactions, which suggested a plausible scheme for constructing the polymeric protein shell of the GVP-single-stranded DNA (ssDNA) complex (Guan Y, et al., 1994, Biochemistry 33:7768-7778). The electrostatic potentials of the isolated and the cooperatively formed protein shell have been calculated using the program GRASP and they revealed a highly asymmetric pattern of the electrostatic charge distribution. The inner surface of the putative DNA-binding channel is positively charged, whereas the opposite outer surface is nearly neutral. The electrostatic calculation further demonstrated that the formation of the helical protein shell enhanced the asymmetry of the electrostatic distribution. A model of the GVP-ssDNA complex with the n = 4 DNA-binding mode could be built with only minor conformational perturbation to the GVP protein shell. The model is consistent with existing biochemical and biophysical data and provides clues to the properties of GVP, including the high cooperatively of the protein binding to ssDNA. The two antiparallel ssDNA strands form a helical ribbon with the sugar-phosphate backbones at the middle and the bases pointing away from each other. The bases are stacked and the Phe 73 residue is intercalated between two bases. The optimum binding to a tetranucleotide unit requires the participation of four GVP dimers, which may explain the cooperativity of the GVP binding to DNA.

Crystal structures of Y41H and Y41F mutants of gene V protein from Ff phage suggest possible protein-protein interactions in the GVP-ssDNA complex

Gene V protein (GVP) encoded by the filamentous phage Ff (M13, fl, fd) is a homodimeric protein of 87 amino acids that binds to single-stranded DNA (ssDNA) nonspecifically and cooperatively. The structure (monoclinic C2 form) of the wild-type protein has been determined and refined at 1.8-A resolution [Skinner et al. (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 2071-2075]. The monomer structure consists of a somewhat distorted five-stranded beta-barrel core with three prominent loops: a DNA-binding loop, a dyad loop, and a dimer contact loop. The amino acid residue at position 41 plays an important role in the dimer-dimer interactions of the protein-ssDNA complex. Two Y41 mutant structures have been studied by X-ray crystallography. The Y41F GVP structure has been refined to an R-factor of 0.180 at 2.2-A resolution and is very similar to the wild-type (wt) structure (rmsd of all C alpha atoms = 0.30 A). In contrast, Y41H GVP forms a new crystal lattice in the space group P2(1)2(1)2(1) with a = 77.18 A, b = 84.17 A, and c = 28.62 A. Its structure has been solved by the molecular replacement method and refined to an R-factor of 0.170 at 2.5-A resolution. The two monomers of Y41H are crystallographically independent, and their structures remain similar to wt-GVP but with significant differences, particularly in the DNA-binding hairpin region. In both crystals, the loop (residues 36-43) that contains the Y41 residue is involved in the crystal dimer packings but in a different manner. The dimer-dimer contacts found in the wt-GVP crystal may be important for GVP aggregation in the absence of DNA. In the presence of DNA, the dimer-dimer contacts may switch to the type found in the Y41H crystal, allowing the GVP-ssDNA complex to form cooperatively. A model of the complex, consistent with existing biochemical and biophysical data, has been constructed from those crystal packing data.

E. coli penicillin acylase isolation by selective release, aqueous two-phase partitioning and ultrafiltration

A procedure has been developed for the purification of penicillin acylase from E. coli fermentation broths. The method described is based primarily on selective release from biomass, charge-directed partitioning in an aqueous two-phase system, and the use of ultrafiltration membranes to recycle the modified polyethylene glycol required and to further purify the enzyme. Each step has been discussed and comparisons have been made with other approaches, where possible. Suggestions have been made for optimisation in process engineering. The approach developed may be applicable to other beta-lactam antibiotic acylases or more generally to some of the other E. coli periplasmic proteins.