An evolutionary approach to the design of glutathione-linked enzymes

Studies of protein structure provide information about principles of protein design that have come into play in natural evolution. This information can be exploited in the redesign of enzymes for novel functions. The glutathione-binding domain of glutathione transferases has similarities with structures in other glutathione-linked proteins, such as glutathione peroxidases and thioredoxin (glutaredoxin), suggesting divergent evolution from a common ancestral protein fold. In contrast, the binding site for glutathione in human glyoxalase I is located at the interface between the two identical subunits of the protein. Comparison with the homologous, but monomeric, yeast glyoxalase I suggests that new domains have originated through gene duplications, and that the oligomeric structure of the mammalian glyoxalase I has arisen by 'domain swapping'. Recombinant DNA techniques are being used for the redesign of glutathione-linked proteins in attempts to create binding proteins with novel functions and catalysts with tailored specificities. Enzymes with desired properties are selected from libraries of variant structures by use of phage display and functional assays.

The multi-channel VEP topographies in patients with late-stage glaucoma

PURPOSE

To study the clinical application of multi-channel VEP topographies in patients with late-stage glaucoma.

METHODS

The multi-channel checkerboard reversal VEP waves of 25 normal persons and 15 patients with late-stage glaucoma were recorded and analyzed, All patients were examined using Humphrey Field Analyzer. The VEP topographies of multi-channel VEP waves were shown by computer processing system.

RESULTS

In normal subjects, the topographies showed symmetric distribution to full-field pattern stimulation. In all patients with late-stage glaucoma, even whose visual field was severely damaged, multi-channel VEP could be recorded, All channels showed simple 'NPN' wave form, N1, N2 waves were not conspicuous, even both were lost, all channels showed the reduced amplitudes of P1 waves, and longer latency. The multi-channel VEP topographies showed irregular distribution, Some showed amplitude asymmetry, other limited or widespread, lateralized.

CONCLUSIONS

Despite the severely damaged visual field, the patients with late-stage glaucoma showed special multi-channel VEPs topographies, Multi-channel VEP topographies should be useful in following up patients suffering from late-stage glaucoma and studying visual processing in human brain.

Purification and characterization of phosphatidylglycerolphosphate synthase from Schizosaccharomyces pombe

The enzyme CDP-diacylglycerol:sn-glycerol-3-phosphate 3-phosphatidyltransferase (phosphatidylglycerolphosphate synthase; PGPS4; EC 2.7.8.5) is located in the mitochondrial inner membrane and catalyzes the committed step in the cardiolipin branch of phospholipid synthesis. Previous studies revealed that PGPS is the most highly regulated enzyme in cardiolipin biosynthesis in both Saccharomyces cerevisiae and Schizosaccharomyces pombe. In this work, we report the purification to homogeneity of PGPS from S. pombe. The enzyme was solubilized from the mitochondrial membrane of S. pombe with Triton X-100. The solubilized enzyme, together with the associated detergent and intrinsic lipids, had a molecular mass of 120 kDa, as determined by gel filtration. The enzyme was further purified using salt-induced phase separation, gel filtration, and ionic exchange, hydroxylapatite, and affinity chromatographies. The procedure yielded a homogeneous protein preparation, evidenced by both SDS-polyacrylamide gel electrophoresis (PAGE) and agarose isoelectric focusing under nondenaturing conditions. The purified enzyme had an apparent molecular mass of 60 kDa as determined by SDS-PAGE. The enzyme showed a strong dependence on lipid cofactors for activity in vitro. While both phosphatidic acid and CDP-diacylglycerol appeared to be activators, the most significant activation was observed with cardiolipin. The possible physiological significance of the lipid cofactor effect is discussed. This is the first purification of a eucaryotic PGPS enzyme to date, and the first purification of a phospholipid biosynthetic enzyme from S. pombe.

Model-based, goal-oriented, individualised drug therapy. Linkage of population modelling, new 'multiple model' dosage design, bayesian feedback and individualised target goals

This article examines the use of population pharmacokinetic models to store experiences about drugs in patients and to apply that experience to the care of new patients. Population models are the Bayesian prior. For truly individualised therapy, it is necessary first to select a specific target goal, such as a desired serum or peripheral compartment concentration, and then to develop the dosage regimen individualised to best hit that target in that patient. One must monitor the behaviour of the drug by measuring serum concentrations or other responses, hopefully obtained at optimally chosen times, not only to see the raw results, but to also make an individualised (Bayesian posterior) model of how the drug is behaving in that patient. Only then can one see the relationship between the dose and the absorption, distribution, effect and elimination of the drug, and the patient's clinical sensitivity to it; one must always look at the patient. Only by looking at both the patient and the model can it be judged whether the target goal was correct or needs to be changed. The adjusted dosage regimen is again developed to hit that target most precisely starting with the very next dose, not just for some future steady state. Nonparametric population models have discrete, not continuous, parameter distributions. These lead naturally into the multiple model method of dosage design, specifically to hit a desired target with the greatest possible precision for whatever past experience and present data are available on that drug--a new feature for this goal-oriented, model-based, individualised drug therapy. As clinical versions of this new approach become available from several centers, it should lead to further improvements in patient care, especially for bacterial and viral infections, cardiovascular therapy, and cancer and transplant situations.

Role of potassium channels in the nitrergic nerve stimulation-induced vasodilatation in the guinea-pig isolated basilar artery

1. We studied the effects of various K+ channel blockers on the vasodilator responses of guinea-pig isolated basilar arteries to nitrergic nerve stimulation, the nitric oxide (NO) donor sodium nitroprusside (SNP), and the membrane permeable guanosine-3',5'-cyclic monophosphate (cyclic GMP) analogue 8-bromo-cyclic GMP (8-Br-cyclic GMP). 2. In endothelium-denuded preparations which were contracted with prostaglandin F2alpha (1 microM), electrical field stimulation (EFS, 10 Hz for 30 s) produced a vasodilatation which was totally blocked by the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester L-NAME; 100 microM) (n=3) and by the selective NO-sensitive guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ; 1 microM) (n=4). The vasodilator response to SNP (100 nM) was not reduced by L-NAME but was abolished by ODQ (1 microM) (n=4). 3. EFS-elicited vasodilatation was partly but significantly reduced by the non-selective K+ channel blockers tetraethylammonium (TEA, 1 and 3 mM) and 4-aminopyridine (4-AP, 3 mM), and by the large-conductance calcium-activated K+ channel (K(Ca) channel) blockers charybdotoxin (ChTX, 150 nM) and iberiotoxin (IbTX, 30 and 100 nM). In contrast, the ATP-sensitive K+ channel (K(ATP) channel) blocker glibenclamide (1-10 microM) and the small-conductance K(Ca) channel blocker apamin (100-500 nM) did not affect EFS-induced vasodilatation. 4. The vasodilator response elicited by SNP (10-100 nM) was significantly reduced by TEA (3 mM) and ChTX (150 nM) but not by apamin (500 nM) or glibenclamide (1 microM). The vasodilatation elicited by 8-Br-cyclic GMP (100 microM) was also reduced by TEA (3 mM) and ChTX (150 nM). 5. The results indicate that the vasodilatations induced by nitrergic nerve stimulation and the NO donor SNP in endothelium-denuded guinea-pig basilar artery depend on the formation of intracellular cyclic GMP. The increased cyclic GMP level activates large-conductance K(Ca) channels which partly mediate the vasodilator response. Neither K(ATP) channels nor apamin-sensitive small-conductance K(Ca) channels are involved in nitrergic transmitter-mediated vasodilatation.

Effect of hydroxocobalamin on vasodilatations to nitrergic transmitter, nitric oxide and endothelium-derived relaxing factor in guinea-pig basilar artery

In endothelium-denuded guinea-pig isolated basilar artery preparations, hydroxocobalamin (30, 100 and 300 microM) concentration-dependently inhibited the vasodilator responses to exogenous nitric oxide (NO), whereas the vasodilator responses to nitrergic nerve stimulation were slightly reduced by high (100 and 300 microM) but not by the low (30 microM) concentration of hydroxocobalamin. Vasodilatation in response to sodium nitroprusside (10-100 nM) was totally abolished by 300 microM hydroxocobalamin. In endothelium-intact preparations, vasodilator responses to acetylcholine (0.3-3 microM) were significantly reduced or abolished by hydroxocobalamin (30-300 microM). The mean reduction by hydroxocobalamin of relaxations to acetylcholine was significantly greater than that of the equivalent response evoked by nitrergic nerve stimulation. The findings suggest that the nitrergic transmitter in the guinea-pig basilar artery may be quantitatively less susceptible than the endothelium-derived relaxing factor to the NO scavenger hydroxocobalamin.

Electrical stimulation of the septal region of aged rats improves performance in an open-field maze

Memory deficits of age and disease may result from dysfunction of septohippocampal structures. Electrical brain stimulation might ameliorate these memory deficits. We show here that septal stimulation of very old rats leads to a marked and progressive improvement in performance in an open-field maze task. Unilateral stimulation of the perforant path is less effective. The frequency of stimulation is important: stimulation at 5 Hz and 50 Hz is effective, whereas stimulation at 0.5 Hz is less effective (though still significantly better than control). Hippocampal (dentate) EEG does not change significantly with septal stimulation frequency. These results may bear on the memory deficit of old age in humans. The results may also bear on the memory deficits seen in human disease states such as Alzheimer's disease.

[Investigation on hepatitis G virus (HGV) infection among different populations in Shenzhen]

A reverse transcription polymerase chain reaction assay with nested primers (RT-nested PCR) deduced from the 5' untranslated region of HGV genome was established to detect HGV RNA. By using this assay, we tested the serum samples of 106 paid blood donors, 80 intravenous drug users and 168 cases with viral hepatitis in Shenzhen, China. The positive rates of HGV RNA were 8.5%, 46.3% and 7.7%, respectively. The positive rates of HGV RNA in 61 cases with chronic hepatitis B and 33 cases with chronic hepatitis C were 8.2% and 21.2%. Among the 33 cases with chronic hepatitis C, the positive rate of HGV RNA in 15 cases infected with HCV by blood or blood products was 40.0%, compared with 1.7% in 18 cases without exposure to blood or blood products (P<0.05). The results of this study suggest that HGV infection is common in paid blood donors; the intravenous drug user is the population at high risk for HGV infection; the patients with post-transfusion chronic hepatitis C are often supperinfected with HGV.

Cardiolipin is not essential for the growth of Saccharomyces cerevisiae on fermentable or non-fermentable carbon sources

Cardiolipin is a unique dimeric phospholipid, which is present throughout the eukaryotic kingdom and is specifically localized in mitochondrial membranes. It is widely believed that mitochondria possess an essential requirement for this phospholipid. To determine whether cardiolipin is essential for yeast growth, we generated a cardiolipin synthase null mutant by disrupting the CLS1 gene (open reading frame YDL142c on chromosome IV) of Saccharomyces cerevisiae. Biochemical analysis of the mutant indicated that it had no cardiolipin synthase activity and no cardiolipin in its membranes. The enzyme phosphatidylglycerolphosphate synthase, which catalyses the committed step of the cardiolipin pathway, remained unaffected in the null mutant. Haploid cells containing the null allele are viable in media containing glucose, galactose or glycerol/ethanol as the sole carbon source, although growth in galactose or glycerol/ethanol is somewhat reduced in the mutant compared with the wild type. These results indicate that cardiolipin is not essential for the growth of S. cerevisiae in fermentable or non-fermentable carbon sources.

Ticks and tick-borne bovine piroplasmosis in the Southmountain pasture of Hunan Province, China

Ticks and tick-borne bovine piroplasmosis is one of the most serious diseases affecting cattle bred in the Southmountain pasture of Hunan province. An investigation carried out from 1992 to 1995 showed that Theileria sergenti was found in the blood of disease-stricken cows. Ticks were collected from cattle. The species concerned (three genera and four species of ticks: Haemaphysalis vietnamensis, Haemaphysalis longicornis, Ixodes sinensis and Boophilus microplus) were identified by microscopy and their numbers recorded every month. Because H. longicornis is a three-host tick, with the larvae, nymphs and adults all infesting cows and seasonal fluctuations in nymphs and adults correlating with theileriosis outbreaks, this tick species was a potential vector of T. sergenti. Epidemiological studies indicated that this disease usually occurred in summer or autumn. The disease attacked calves from May to August reaching a peak in June or July (as happened from 1992-1994). In cattle, the disease occurred from June to September with a peak in September. The following pathological lesions were observed: haemorrhages were seen in the subcutaneous tissues and serosa, in the intestinal mucosa and the mesenteric lymph nodes. The surface of the abomasum looked like a piece of red cloth. The liver was enlarged, its edge blunt and curled over. The gall bladder was filled with tawny coloured bile. The spleen was enlarged and dark brown. The heart was enlarged with numerous haemorrhagic foci in the auricle. The blood clotted incompletely. Sick cattle were treated with Berenil and imidocarb and the death rate was reduced from 26% to 5.9%.

[The effects of pressure on cultured bovine trabecular meshwork cells]

OBJECTIVE

To observe the effects of pressure on trabecular meshwork cells.

METHODS

Bovine trabecular meshwork cells were cultured and submitted to different amounts of hydrostatic pressure. Cellular morphology and phagocytic function were observed under inverted phase-contrast microscope, light microscope and electron microscope.

RESULTS

Compared with the control group, the cells under 2.0 kPa or 2.67 kPa for 48 hours had no remarkable difference in criteria observed. Those under 4.0 kPa for 24 hours showed slight changes in structure and a mild decrease in phagocytic function. The damage appeared more severe if the pressure was higher or lasted longer.

CONCLUSION

Trabecular meshwork cells can only bear pressure below a certain level. They may be destroyed structurally or impaired functionally by pressure over this level.

Evidence for redox regulation of the transcription factor NtcA, acting both as an activator and a repressor, in the cyanobacterium Anabaena PCC 7120

NtcA has been identified as a nitrogen-responsive regulatory protein required for nitrogen assimilation and heterocyst differentiation in cyanobacteria. It is proposed that NtcA functions through the formation of DNA-protein complexes with its specific target sequence within the promoter regions of the regulated genes. In vitro, NtcA of Anabaena PCC 7120 binds to upstream regions of the genes whose products are involved in nitrogen assimilation, but also to the upstream region of rbcLS (carbon-fixation gene), xisA (encoding a site-specific recombinase expressed during heterocyst differentiation) and ntcA (encoding NtcA itself). However, the mechanism by which NtcA serves as a critical regulator for such diverse processes is not understood. With the use of electrophoretic mobility shift assays, NtcA from Anabaena PCC 7120 was here shown to interact with the promoter sequence of the gor gene, encoding glutathione reductase, thereby providing a novel example of NtcA's acting as a repressor, previously found only for the rbcLS gene. Furthermore we demonstrate that the binding of DNA by NtcA is regulated in vitro by a redox-dependent mechanism involving cysteine residues of the NtcA protein. These findings suggest that NtcA is a transcriptional regulator that responds not only to the nitrogen status but also to the cellular redox status, a function that might be particularly significant during heterocyst differentiation.

Structure, recognition and adaptive binding in RNA aptamer complexes

Novel features of RNA structure, recognition and discrimination have been recently elucidated through the solution structural characterization of RNA aptamers that bind cofactors, aminoglycoside antibiotics, amino acids and peptides with high affinity and specificity. This review presents the solution structures of RNA aptamer complexes with adenosine monophosphate, flavin mononucleotide, arginine/citrulline and tobramycin together with an example of hydrogen exchange measurements of the base-pair kinetics for the AMP-RNA aptamer complex. A comparative analysis of the structures of these RNA aptamer complexes yields the principles, patterns and diversity associated with RNA architecture, molecular recognition and adaptive binding associated with complex formation.

Marked genetic differences between stage pTa and stage pT1 papillary bladder cancer detected by comparative genomic hybridization

Little is known about the genetic changes underlying invasive tumor growth in bladder cancer. Because alterations that are linked to invasive tumor growth may be detectable in minimally invasive (stage pT1) but not in noninvasive (stage pTa) tumors, we searched for genetic differences between 28 pTa and 28 papillary pT1 bladder tumors by comparative genomic hybridization. Losses of 9q (54%), 9p (39%), and Y (28%) and gains of 1q (14%) were most prevalent in pTa tumors. These changes may play a role in the initiation of noninvasive papillary bladder cancer. The total number of aberrations was higher in pT1 tumors (6.5 +/- 5.4) than in pTa tumors (2.3 +/- 2.1; P = 0.0003), suggesting an increased genetic instability at stage pT1. Specific alterations, which were significantly more frequent in pT1 than in pTa tumors (P < or = 0.05), included deletions at 2q (36% of pT1 tumors), 8p (32%), and 11p (21%) and gains at 1q (54%), 8q (32%), 3p, 3q, 5p, 6p, and 10p (18% each). These loci are candidates for carrying genes involved in invasive tumor growth in bladder cancer. High-level amplifications at 1q22-24, 3p24-25, 6p22, 8p12, 8q21-22, 10p12.1-14, 11q13, 12q15-21, 13q31-33, Xp11-13, and Xq21-22.2 may pinpoint the location of oncogenes with relevance for bladder cancer.

Base dynamics in a UUCG tetraloop RNA hairpin characterized by 15N spin relaxation: correlations with structure and stability

Intramolecular dynamics of guanine and uracil bases in a 14-nt RNA hairpin including the extraordinarily stable UUCG tetraloop were studied by 15N spin relaxation experiments that are sensitive to structural fluctuations occurring on a time scale of picoseconds to nanoseconds. The relaxation data were interpreted in the framework of the anisotropic model-free formalism, using assumed values for the chemical shift anisotropies of the 15N spins. The rotational diffusion tensor was determined to be symmetric with an axial ratio of 1.34 +/- 0.12, in agreement with estimates based on the ratio of the principal moments of the inertia tensor. The model-free results indicate that the bases of the G x U pair in the tetraloop are at least as rigid as the interior base pairs in the stem, whereas the 5'-terminal guanine is more flexible. The observed range of order parameters corresponds to base fluctuations of 19-22 degrees about the chi torsion angle. The results reveal dynamical consequences of the unusual structural features in the UUCG tetraloop and offer insights into the configurational entropy of hairpin formation.

Imino proton exchange and base-pair kinetics in the AMP-RNA aptamer complex

We report on the dynamics of base-pair opening in the ATP-binding asymmetric internal loop and flanking base-pairs of the AMP-RNA aptamer complex by monitoring the exchange characteristics of the extremely well resolved imino protons in the NMR spectrum of the complex. The kinetics of imino proton exchange as a function of basic pH or added ammonia catalyst are used to measure the apparent base-pair dissociation constants and lifetimes of Watson-Crick and mismatched base-pairs, as well as the solvent accessibility of the unpaired imino protons in the complex. The exchange characteristics of the imino protons identify the existence of four additional hydrogen bonds stabilizing the conformation of the asymmetric ATP-binding internal loop that were not detected by NOEs and coupling constants alone, but are readily accommodated in the previously reported solution structure of the AMP-RNA aptamer complex published from our laboratory. The hydrogen exchange kinetics of the non-Watson-Crick pairs in the asymmetric internal loop of the AMP-RNA aptamer complex have been characterized and yield apparent dissociation constants (alphaKd) that range from 10(-2) to 10(-7). Surprisingly, three of these alphaKd values are amongst the lowest measured for all base-pairs in the AMP-RNA aptamer complex. Comparative studies of hydrogen exchange of the imino protons in the free RNA aptamer and the AMP-RNA aptamer complex establish that complexation stabilizes not only the bases within the ATP-binding asymmetric internal loop, but also the flanking stem base-pairs (two pairs on either side) of the binding site. We also outline some preliminary results related to the exchange properties of a sugar 2'-hydroxyl proton of a guanosine residue involved in a novel hydrogen bond that has been shown to contribute to the immobilization of the bound AMP by the RNA aptamer, and whose resonance is narrow and downfield shifted in the spectrum.

Mechanisms of electrical field stimulation-induced vasodilatation in the guinea-pig basilar artery: the role of endothelium

1. The role of endothelium in neuronal vasodilatation elicited by electrical field stimulation (EFS) was investigated in preparations of the isolated guinea-pig basilar artery in which the tone was raised with prostaglandin F2 alpha. 2. In preparations with intact endothelium, EFS produced frequency-dependent dilatations which were not affected by guanethidine but were slightly yet significantly reduced by atropine (1 microM), and were blocked by tetrodotoxin (1 microM) and the nitric oxide synthase inhibitor L-NAME (10 microM). 3. Dilatations were elicited by acetylcholine (3 microM); these were blocked by L-NAME and atropine (1 microM). 4. Dilatations were elicited by nicotine (100 microM); these were blocked by L-NAME and hexamethonium (100 microM). 5. Dilation elicited by sodium nitroprusside (SNP, 3 microM) was not affected by L-NAME. 6. The inhibitory effects of L-NAME were partially prevented by L-arginine (1 microM). 7. Removal of the endothelium resulted in a significant reduction of dilatations elicited by EFS, elimination of the dilator action of acetylcholine, but enhancement of that to SNP. 8. The results suggest that EFS-induced vasodilatation is mediated in part by the nitrergic transmitter and in part endothelium derived relaxing factor (EDRF) activated by acetylcholine released from cholinergic nerves.

Photodynamic therapy of 9L gliosarcoma with liposome-delivered photofrin

The effect of Photofrin encapsulated in a liposome delivery vehicle for photodynamic therapy (PDT) of the 9L gliosarcoma and normal rat brain was tested. We hypothesized that the liposome vehicle enhances therapeutic efficacy, possibly by increasing tumor tissue concentration of Photofrin. Male Fisher rats bearing a 9L gliosarcoma were treated 16 days after intracerebral tumor implantation with either Photofrin in dextrose (n = 5) or Photofrin in liposome (n = 6). Nontumor-bearing animals were treated with Photofrin delivered either in dextrose (n = 4) or liposome (n = 4) vehicle. Tissue concentrations of Photofrin delivered either in dextrose (n = 4) or liposome (n = 4) vehicle were measured in tumor, brain adjacent to tumor and in normal brain tissue. Photofrin was administered (intraperitoneally) at a dose of 12.5 mg/kg and PDT (17 J/cm2 of 632 nm light at 100 mW/cm2) was performed 24 h after Photofrin administration. Brains were removed 24 h after PDT and stained with hematoxylin and eosin for analysis of cellular damage. The PDT using Photofrin in the liposome vehicle caused significantly more damage to the tumor (P < 0.001) than did PDT with Photofrin in dextrose. The PDT of tumor with Photofrin delivered in liposomes caused a 22% volume of cellular necrosis, while PDT of tumor with Photofrin delivered in dextrose caused only scattered cellular damage. Photofrin concentration in tumors was significantly higher (P = 0.021) using liposome (33.8 +/- 18.9 micrograms/g) compared to dextrose delivery (5.5 +/- 1.5 micrograms/g). Normal brain was affected similarly in both groups, with only scattered cellular necrosis. Our data suggest that the liposome vehicle enhances the therapeutic efficacy of PDT treatment of 9L tumors.

p53 protein expression but not mdm-2 protein expression is associated with rapid tumor cell proliferation and prognosis in renal cell carcinoma

The clinical course of renal cell carcinoma (RCC) is highly variable. Overexpression of the p53 protein has been suggested as a possible prognostic parameter in RCC. Overexpression of the mdm-2 oncogene product has been shown to interact with the p53 function. To investigate the immunohistochemical overexpression of mdm-2 protein in comparison with that of p53 protein in RCC, 50 nonpapillary pT3 RCCs were immunostained for p53 protein (DO-7) and mdm-2 (IF2). Tumor growth fraction (Ki-67 labeling index; MIB-1) was determined by immunohistochemistry. p53 positivity was detected in 16% of tumors. mdm-2 overexpression was seen in 30% of RCCs. There was a significant association between p53 and mdm-2 immunostaining (P = 0.0006), suggesting that mdm-2 protein may contribute to p53 protein stabilization in RCC. p53 overexpression was associated with a high Ki-67 LI (P = 0.0002), suggesting that p53 overexpression is involved in growth control in RCC. Survival analysis showed that Ki-67 LI (P = 0.04) and p53 overexpression were associated with poor prognosis (P = 0.0021), whereas mdm-2 overexpression was not related to patient outcome (P = 0.73). A Cox regression analysis revealed tumor stage (P < 0.001) and p53 overexpression (P < 0.05) to be independent prognostic parameters. It is concluded that p53 but not mdm-2 may be of practical relevance in predicting patient prognosis in RCC.

A model of orthotopic murine bladder (MBT-2) tumor implants

We produced a model of orthotopic transplantation in C3H/He mice by transplanting MBT-2 cells. A single-cell suspension of 1.0 x 10(5) MBT-2 cells/0.02 ml was successfully injected into the submucosal layer of the bladder, with an incidence of 100% after four experimental weeks. Inoculated tumor grew expansively into the bladder cavity from the bladder submucosa and invaded the serosa and the surrounding tissue. This model more closely resembled the characteristics of human bladder tumor when compared to other bladder cancer models. The results of the histological observation, electron microscopic examination and DNA content analysis by flow cytometry showed that the transplanted carcinoma maintained the biologic characteristics of the primary tumor.

DNA aberrations in urinary bladder cancer detected by flow cytometry and FISH

Detection of molecular alterations is of potential significance for diagnosis and prognosis in bladder cancer. Fluorescence in situ hybridization (FISH) allows visualization and quantitation of genes and chromosomes on a cell by cell level and can easily be applied to urinary cells. To evaluate the sensitivity of FISH for detection of DNA aberrations in bladder cancer, formalin-fixed tissues of 293 tumors were examined by FISH and flow cytometry (FCM). Centromere probes for the chromosomes X, Y, 1, 7, 9, and 17 were used for FISH analysis. FISH was more sensitive for detection of quantitative DNA aberrations than FCM. An aberration of at least one chromosome was found in 107 of 108 tumors (99%), which were tetraploid, aneuploid, or multiploid, and in 29 of 49 tumors (59%), which were diploid, by FCM. The frequency of FISH aberrations showed greater differences between pTa (47%) and pT1 tumors (85%; P < 0.0001) than between stages pT1 and pT2-4 (98%). The marked genetic difference between pTa and pT1 tumors argues against the concept of grouping pTa and pT1 tumors together as "superficial bladder cancer." The frequency of tumors with chromosomal aberrations detected by FISH increased with the number of chromosomes examined. Aneusomy was seen in 68% of grade 1 tumors examined for > or = 4 chromosomes, suggesting that the cytological diagnosis of bladder cancer recurrences could be substantially improved by FISH.

Specific labeling approaches to guanine and adenine imino and amino proton assignments in the AMP-RNA aptamer complex

The secondary structure of a recently identified ATP-binding RNA aptamer consists of a purine-rich 11-residue internal loop positioned opposite a single guanine bulge flanked on either side by helical stem segments. The ATP ligand targets the internal loop and bulge domains, inducing a structural transition in this RNA segment on complex formation. Specifically, 10 new slowly exchanging proton resonances in the imino, amino and sugar hydroxyl chemical shift range are observed on AMP-RNA aptamer complex formation. This paper outlines site-specific labeling approaches to identify slowly exchanging imino (guanine) and amino (guanine and adenine) protons in internal loop and bulge segments of compact RNA folds such as found in the AMP-RNA aptamer complex. One approach incorporates 15N-labeled guanine (N1 imino and N2 amino positions) and 15N-labeled adenine (N6 amino position), one residue at a time, in the AMP-binding RNA aptamer, with labeling incorporation through chemical synthesis facilitated by generating the aptamer from two separate strands. The unambiguous assignments deduced from the 15N labeling studies have been verified from an independent labeling strategy where individual guanines in the internal loop have been replaced, one at a time, by inosines and assignments were made on the basis of the large 2 ppm downfield shift of the guanine imino protons on inosine substitution. The strengths and limitations of the inosine-for-guanine substitution approach emerge from our studies on the AMP-RNA aptamer complex. The assignment of the internal loop and bulge imino and amino protons was critical in our efforts to define the solution structure of the AMP-RNA aptamer complex since these slowly exchanging protons exhibit a large number of long-range intramolecular NOEs within the RNA, as well as intermolecular NOEs to the AMP in the complex. The current application of specific 15N and inosine labeling approaches for exchangeable imino and imino proton assignments in the nonhelical segments of an RNA aptamer complex in our laboratory complements selective 2H and 13C approaches to assign nonexchangeable base and sugar protons in RNA and ligand-RNA complexes reported in the literature.

[A study of 5-fluorouracil on bovine trabecular meshwork cells in vitro]

OBJECTIVE

To determine whether the clinical use of 5-fluorouracil (5-FU) may have any toxic effects on trabecular meshwork cells.

METHODS

Bovine trabecular meshwork (BTM) cells were cultured in vitro. The effects of 5-FU on BTM cells concerning cellular morphology, ultrastructure, vitality and phagocytosis were observed.

RESULT

The safe dosage of 5-FU on BTM cell was 1 x 10-6g.ml-1.

CONCLUSION

Based on the pharmacokinetic data in the rabbit anterior chamber, it is suggested that the 5-FU dosage of conventional use cause no injury to human trabecular meshwork cells.

RNA folding topology and intermolecular contacts in the AMP-RNA aptamer complex

We report below on the NMR structural characterization of the complex between AMP and a 40-mer RNA aptamer in aqueous solution. Resonance assignments are based on multinuclear multidimensional NMR studies on complexes uniformly 13C, 15N-labeled with either AMP or the RNA aptamer. AMP binds to an internal loop (labeled G7-G8-A9-A10-G11-A12-A13-A14-C15-U16-G17) and bulge (G34 positioned opposite the internal loop) segment in the RNA aptamer, and our NMR study provides insights into features of the RNA folding topology and the molecular recognition events in the AMP binding pocket on the RNA. Specifically, the helical stems are extended by G-G mismatch formation from either direction into the internal loop/bulge segment of the RNA aptamer on complex formation. The internal loop adopts a unique fold with the purine ring of AMP intercalated between A10 and G11 in the complex. The G8-A9-A10-AMP segment adopts certain stacking features in common with a GNRA turn and is closed by the G7.G11 mismatch pair. The purine rings of A12 and G34 (syn) are stacked on each other and participate in stablizing the AMP intercalation site. A large number of intermolecular NOEs have been identified between the AMP ligand and the G8, A10, G11, G17, U18, and G34 residues on the RNA aptamer in the complex. The Watson-Crick edge of the AMP is oriented toward the exocyclic amino group of G8, suggestive of a hydrogen-bonding alignment between G8 and AMP in the complex. The AMP sugar ring is positioned in the minor groove of the rightward helical stem centered about the G17.G34 mismatch and U18.A33 Watson-Crick pairs. The AMP binds to one face of the folded internal loop/bulge segment of the RNA aptamer while the opposite face is capped by a stacked alignment of the A13-A14-C15-U16 segment located toward the 3'-end of the internal loop segment. Globally, the two helical stems of the RNA aptamer are aligned approximately orthogonal to each other with tertiary interactions centered about the internal loop/bulge segment generating the AMP binding site on the RNA.

Photodynamic therapy of human glioma (U87) in the nude rat

We measured the response of normal brain and the human U87 glioma implanted in the brain of rats (n = 65) to photodynamic therapy (PDT) using Photofrin as the sensitizer. Normal brain and U87 tumor implanted within brain of athymic (nude) rats were subjected to PDT (12.5 mg/kg of Photofrin) at increasing optical energy doses (35 J/cm2, 140 J/cm2, 280 J/cm2) of 632 nm light. Photofrin concentration in tumor, brain adjacent to tumor and normal brain were measured in a separate population of rats. Twenty-four hours after PDT, the brains were removed, sectioned, stained with hematoxylin and eosin (H&E), and the volumes of the PDT-induced lesion measured. Photofrin concentration in tumor greatly exceeded that of normal brain and brain adjacent to tumor (> 20x). Both normal brain and U87 tumor exhibited superficial tissue damage with PDT at 35 J/cm2. However, both normal and tumor-implanted brain exhibited tissue damage with increasing optical dose. A heterogeneous pattern of pannecrosis along with a uniform volume of pannecrosis was detected in the tumor. In contrast, normal brain exhibited a uniform sharply demarcated volume of necrosis. Our data indicate that the U87 human brain tumor model and the normal brain in the athymic rat are sensitive to PDT and Photofrin with an optical dose-dependent response to treatment.

Sensitivity of 9L gliosarcomas to photodynamic therapy

Photodynamic therapy (PDT) has been used clinically for the treatment of malignant brain gliomas. However, the efficacy of this treatment to date has remained equivocal. This study focused on determining the sensitivity of 9L glio sarcoma in Fischer 344 rats to PDT with increasing doses of 632 nm light and making a comparison of the responses of normal and tumor tissue in the brain at these doses. This sensitivity was then correlated with the concentrations of Photoforin present in these tissues at the time of treatment. Our study indicates that the level of Photofrin in the tumor was 13 times that present in normal brain 48 h after injection. However, this selective localization of the photosensitizer was not reflected in a selective tissue response to PDT. There was minimal tumor response to a dose of 35 J cm-2, which has been reported previously to cause necrosis to the normal brain. Increasing energy dose levels resulted in an increased tumor response to PDT; however, normal tissue remained more sensitive than tumor tissue at all energy dose levels examined. These data indicate that, although Photofrin is retained to a significantly higher degree in the tumor than in the normal brain tissue, the normal brain is more sensitive than the tumor to PDT under the conditions outlined in this study.

[Pharmacognostical study on the Chinese drug biejia]

The Chinese drug Biejia is taken from a variety of animals. In this paper, 3 kinds of Biejia from different genera have been studied in their pharmacognostical characteristics and microproperties. A key has been complied based on the experimental results.

Steroidal glycosides from Tribulus terrestris

In addition to hecogenin 3-O-beta-D-glucopyranosyl(1--> 4)-beta-D-galactopyranoside, two new steroidal saponins were isolated from the aerial parts of Tribulus terrestris L. On the basis of chemical and spectroscopic evidence, especially 2D NMR spectroscopic techniques, the structures of the new saponins were established as 26-O-beta-D-glucopyranosyl-3-O-[-beta-D-xylopyranosyl(1--> 3)--beta-D-galactopyranosyl(1-->2)--beta-D-glucopyranosyl (1--> 4)-beta-D-glucopyranosyl]-5 alpha-furost-20(22)-en-12-one-3 beta,26-diol and 26-O-beta-D-glucopyranosyl-3-O-[{beta-D-xylopyranosyl (1-->3)--beta-D-galactopyranosyl(1-->2)--beta-D-glucopyranosyl(1 -->4)-beta-D-glucopyranosyl]-5 alpha-furostan-12-one-3 beta,22,26-triol.

Structural basis of RNA folding and recognition in an AMP-RNA aptamer complex

The catalytic properties of RNA and its well known role in gene expression and regulation are the consequence of its unique solution structures. Identification of the structural determinants of ligand recognition by RNA molecules is of fundamental importance for understanding the biological functions of RNA, as well as for the rational design of RNA Sequences with specific catalytic activities. Towards this latter end, Szostak et al. used in vitro selection techniques to isolate RNA sequences ('aptamers') containing a high-affinity binding site for ATP, the universal currency of cellular energy, and then used this motif to engineer ribozymes with polynucleotide kinase activity. Here we present the solution structure, as determined by multidimensional NMR spectroscopy and molecular dynamics calculations, of both uniformly and specifically 13C-, 15N-labelled 40-mer RNA containing the ATP-binding motif complexed with AMP. The aptamer adopts an L-shaped structure with two nearly orthogonal stems, each capped proximally by a G x G mismatch pair, binding the AMP ligand at their junction in a GNRA-like motif.

[Comparison of the three methods for estimating the dry-weight of hemodialysis patients]

In order to find the best method for estimating the dry-weight of hemodialysis (HD) patients, we compared the three methods used, i.e. bioelectrical resistivity (rho), plasma cGMP (cGMP) and bromide (Br) methods. The results showed that the extracellular fluid volume per unit body mass (EFV/mass) determined with rho was negatively correlated with that determined with Br. (r = -0.7601 for normal controls and -0.5293 for HD patients, P < 0.05). However, plasma cGMP concentration was neither correlated with EFV/mass (r = 0.3724 for normal control and 0.2538 for HD patients, P > 0.05) nor with rho (r = 0.5210 for normal controls and 0.2106 for HD patients, P > 0.05). These results suggest that the bioelectrical resistivity dry-weight method is more accurate than cGMP method and moreover it is easier to perform than the NaBr method.

Somatostatin stimulates BKCa channels in rat pituitary tumor cells through lipoxygenase metabolites of arachidonic acid

The stimulation of large-conductance, calcium-activated (BK) potassium channels by somatostatin through protein dephosphorylation in rat pituitary tumor cells (White et al., Nature 351, 570-573, 1991) is blocked by drugs that interfere with arachidonic acid release by phospholipase A2 and metabolism by 5-lip-oxygenase. In contrast, higher concentrations of the same drugs had no effect on BK channel gating in cell-free patches, on the inhibition of adenylyl cyclase by somatostatin, or on the stimulation of BK channels by protein dephosphorylation through a cGMP-dependent pathway (White et al., Nature 361, 263-266, 1993). Exogenous arachidonic acid (1-20 muM) stimulated BK channel activity through protein dephosphorylation as effectively as somatostatin and was also blocked by inhibitors of lipoxygenases but not by inhibitors of phospholipase A2. These results support the hypothesis that lipoxygenase metabolites of arachidonic acid are second messengers linking pertussis toxin sensitive G-proteins to protein phosphatases regulating potassium channel activity (Armstrong and White, Trends Neurosci. 15, 403-408, 1992).

[Preliminary survey on the traditional Chinese drug: shell of abalone or sea-ear]

According to an on-site survey of the commercial medicinal materials in China, it is demonstrated that the shells of abalone or sea-ear consist of nine types. Their original animals are Haliotios diversicolor, H. discus hannai, H. ovina, H. asinia, H. ruber, H. laevigata, H. semistrata, H. midae and H. cracherodii. Three of these types namely, H. semistrata, H. midae and H. cracherodii are not included in the Chinese Pharmacopeia. Furthermore, most of the shells of abalone or sea-ear presently on market are Haliotios ruber and H. discus hannai.

Cloning, sequencing, and regulation of the glutathione reductase gene from the cyanobacterium Anabaena PCC 7120

Glutathione reductase (GR) was purified from the cyanobacterium Anabaena PCC 7120. A 3-kilobase genomic DNA fragment containing the coding sequence for the GR gene (gor) was identified and cloned by polymerase chain reaction based on sequences of selected peptides isolated from proteolyzed GR. The coding sequence encompassing 458 amino acid residues, as well as 360 base pairs of the 5'-flanking region and 430 base pairs of the 3'-flanking region, were determined. Genomic Southern analysis indicates that gor is a single-copy gene. A gor antisense RNA probe hybridized with a 1.4-kilobase transcript, suggesting that the gene is not part of an operon including additional genes. The deduced GR amino acid sequence shows 41 to 48% identity with those of human, Escherichia coli, Pseudomonas aeruginosa, pea, and Arabidopsis thaliana GR. The coding sequence of GR was overexpressed in a GR-deficient E. coli strain, SG5, and the recombinant protein was purified. Anabaena GR is NADPH-linked, but a Lys residue replaces an Arg residue involved in NADPH binding in GR from other species. In addition, Anabaena GR carries the GXGXXG "fingerprint" motif which otherwise characterizes NAD(H)-dependent enzymes. These differences may contribute to the lack of affinity for 2',5'-ADP-Sepharose 4B of Anabaena GR. Three E. coli-type promoter sequences and a BifA/NtcA binding motif were found upstream of the open reading frame. The middle and the proximal promoters were shown to be active. However, the use of the middle promoter was dependent on the nitrogen source in the culture medium. Both GR activity and GR protein concentration increased in ammonium grown cultures in which both the middle and proximal promoters were used for transcriptional initiation. The BifA/NtcA-binding site overlaps the middle promoter sequence and may thus be involved in regulation of differential transcription.

A new digoxin immunoassay substantially free of interference by digoxin immunoreactive factor

We have evaluated the new Roche digoxin "On Line" procedure for use in a pediatric population with particular interest in the potential for interference by digoxin-like immunoreactive factor (DLIF). An initial study comparing digoxin values obtained with the new Roche procedure with determinations on an Abbott TDx, American Dade Stratus, and COBAS-FARA using Microgenics Cedia reagents, found good correlations with these established methods. The Roche method was suitably precise and utilized either serum or plasma. Interference by DLIF was assessed by analyzing specimens from patients not receiving digoxin but likely to contain DLIF, with the argument that non-zero values represent cross-reactivity of anti-digoxin antibodies with DLIF endogenous to these specimens. When specimens from neonates, women with second/third trimester pregnancies, and patients with renal and liver failure were assayed with the Roche, Stratus, and TDx methods, all three methods measured DLIF in some specimens, but the Roche method possessed the lowest overall DLIF interference. The modest extent of DLIF interference and the requirement of a small amount of specimen make the Roche method superior in monitoring digoxin in a pediatric population.

Cu(II) coordination in arthropod and mollusk green half-methemocyanins analyzed by electron spin-echo envelope modulation spectroscopy

Hemocyanin (Hc) is a dinuclear copper protein that binds oxygen reversibly. The structure of the Cu(II) site in a derivative of hemocyanin known as green half-met (GHM) has been analyzed using the pulsed EPR technique of electron spin-echo envelope modulation (ESEEM) spectroscopy. The derivative, prepared by treating the native protein with nitrite at low pH, contains a mixed-valent binuclear copper center. It was shown through chemical assays and the ligand exchange reaction products identified by EPR spectroscopy to contain a nitrite ligand bound to Cu(II). The ESEEM spectra of green half-methemocyanins from mollusks and arthropods indicated that three imidazole ligands are coordinated to Cu(II). Therefore, a tetragonal N3O ligand structure (O is an oxygen of nitrite) is proposed. For GHM Hc from the mollusks Octopus vulgaris and Rapana thomasiana, the isotropic nitrogen nuclear hyperfine coupling constant, aiso, for the N delta (or remote) nitrogen of two imidazoles was approximately 1.4 MHz, while for the third, aiso congruent to 2.2 MHz. The difference between the two weaker nitrogens and the single, more strongly coupled nitrogen was smaller by 0.2 MHz in the GHM Hcs from the arthropods Carcinus maenas, Homarus americanus and Panulirus interruptus. The nitrogen nuclear quadrupole coupling constants and asymmetry parameters, e2Qq and eta, for the N delta nitrogens in nearly all cases were near 1.4 MHz and 0.8, respectively, although Rapana thomasiana GHM Hc exhibited a reduction in eta that may indicate weaker hydrogen bonding in the active site of this protein. The g and ACu (copper nuclear hyperfine coupling) values for the derivatives, and the finding of three similar nuclear hyperfine coupling constants for the N delta sites of imidazole ligands, when considered with the orientation-specific information obtained using angle-selection methods for simulation of ESEEM spectra, suggest a distorted tetragonal Cu(II) structure in which three imidazoles and a nitrite ligand are bound near the equatorial plane. The finding that the two molluscan GHM Hcs exhibit differences associated with the remote nitrogen of imidazoles bound to Cu(II) may be related to a structural variability in the active sites of these proteins not found in the arthropodan GHM Hcs examined.

Comparison of the induction of rat glutathione S-transferase and fatty acid ethyl ester synthase activities

Fatty acid ethyl esters (FAEE) are formed following the administration of ethanol and have previously been associated with toxicological effects in animals and humans. It has been suggested that the enzyme responsible, FAEE synthase, has both structural and catalytic properties very similar to a glutathione S-transferase (GST). Since GSTs are inducible, their induction could be associated with enhanced FAEE formation and toxicity. In the present study, rats were administered beta-naphthoflavone, phenobarbital, ethanol, or Aroclor 1254, and hepatic FAEE synthase and GST activities were measured. beta-Naphthoflavone and ethanol did not induce either activity. Phenobarbital increased GST activity in the liver but not in lung or pancreas. Only Aroclor 1254, which increased GST activity in liver and pancreas, increased FAEE synthase activity and then only in the liver. Thus, in comparison with GST activity, FAEE synthase activity is very limited in its ability to be induced.

Hippocampal stimulation of fornical-lesioned rats improves working memory

Intrinsic rhythmic electrical activity in the brain, such as the hippocampal theta rhythm, might serve important roles in normal cognition. Lesions to the medial septal nuclei, or to the fimbria/fornix, disrupt the hippocampal theta rhythm and lead to memory impairment. We have superimposed an artificial stimulating rhythm to the hippocampus of rats with prior lesion of the fornix, during testing in the Morris water maze. This intervention improves performance in a test of working memory, and lends support to the view that intrinsic rhythmic activity may play an important role in normal physiology, and in certain disease states.

Overexpression and characterization of recombinant human fusion protein IL-6/IL-2 (CH925)

An expression vector encoding the human recombinant fusion protein interleukin 6/interleukin 2 (IL-6/IL-2) was constructed. When a flexible linker had been synthesized and ligated with the IL-2 gene fragment by polymerase chain reaction (PCR) amplification, the IL-6 gene fragment was unidirectionally inserted into the upstream of the linker-IL-2 sequence. The molecule of the IL-6-linker-IL-2 fusion gene named E. coli DH5 alpha/pfIL-6/2 was cloned and identified by DNA sequencing. The expressed protein named as CH925 showed a strong band on SDS-PAGE and amounted to 32% of total cell protein, and its estimated molecular weight was about 37 kDa. The fusion protein purified by gel filtration and reversed-phase HPLC showed as almost homogeneous. CH925 possesses both IL-2 and IL-6 activities when assayed by CTLL2- and 7TD1-dependent cell lines, respectively. The specific activity of IL-2 was 2.1 x 10(6) U/mg while that of IL-6 was 2.3 x 10(8) U/mg. Our studies exhibited that CH925 exerted a significant augmentative effect on the growth of erythroid colony forming units (CFU-E), and synergized with erythropoietin (EPO) and/or IL-3 in a dose-dependent way. Our experimental results also showed CH925 at a low dose causing active lymphokine-activated killer (LAK) cell proliferation more vigorous than IL-2 and/or IL-6 (p < 0.001). CH925 is a novel fusion protein, being neither IL-6 nor IL-2, more potent than IL-2 and/or IL-6 and causing non-IL-2 and non-IL-6 functions of strong EPO-like and mild IL-3-like effects on erythroid progenitor cell growth. There is a potential for efficacious clinical application of CH925.

[Study on risk factors of 292 pregnant women infected with HCMV]

This paper is to determine the risk factors of reactivation by HCMV during pregnancy for improving child birth and bringing-up. A total of 292 paired sera were collected from mothers and their infants in Shanghai and were tested for IgG and IgM by ELISA. The positive rates of HCMV IgG and IgM were 98.97%, 96.97% and 3.77%, 1.71%, respectively in mothers and infants. The rate of IgM was 1.49% in infants whose mothers' education were above the high school level, whereas it was 4.17% whose mothers' educational degree was lower than that grade, and the relative ratio (RR) was 2.8. The number of previous pregnancies were closely associated with the positive rate of IgM. In infants born to mothers at first pregnancy, the positive rate was 1.96%, whereas in infants born to mothers at third pregnancy it increased to 3.70%, RR was 1.89. In pregnant women who were known to have postmortem or premature deliveries before the positive rate was 9.09%, whereas it was 2.53% in pregnant women at first pregnancy, the RR was 3.59. The rates of their infants were 3.03% and 1.90%, respectively, the RR was 1.59. The frequency of IgM antibody in 292 sera of mothers was correlated with that in their infants. It showed that HCMV might be transmitted from mother to fetus.

Two crystal structures of a potently sweet protein. Natural monellin at 2.75 A resolution and single-chain monellin at 1.7 A resolution

Two refined structures of the sweet-tasting protein monellin are presented. The structure of natural monellin has been refined at 2.75 A resolution. The final model consists of four monellin molecules in the asymmetric unit, encompassing 3136 non-hydrogen atoms. The crystallographic R-factor is 0.193 for the 8853 reflections between 6.0 A and 2.75 A resolution, and the root-mean-square deviations from ideality are 0.017 A for bond lengths and 3.6 degrees for bond angles. The refined structure generally confirms, with some difference in detail, the initial backbone model of monellin that was based on 3.0 A resolution data. Single-chain monellin (scm) was genetically engineered by fusing the two chains of monellin into a single 94-residue polypeptide. Using the refined monellin coordinates as a search model, the crystal structure of scm has been solved with the techniques of molecular replacement, and has been refined against data to 1.7 A resolution. The final model consists of two scm molecules per asymmetric unit, and includes 137 bound water molecules. The crystallographic R-factor for this model is 0.174 for the 15,053 reflections (magnitude of FO magnitude of > 2 sigma (FO)) between 6.0 A and 1.7 A resolution. The root-mean-square deviations from ideal bond lengths and angles are 0.015 A and 2.86 degrees, respectively, and the average coordinate error is approximately 0.2 A, as estimated from a Luzzati plot. The error in the model was also estimated by comparing the two molecules in the asymmetric unit. The most significant differences between the two molecules occur in loop regions and at the C terminus of the protein, and are generally correlated to differences in crystal packing contacts. Linking the two chains of monellin has not substantially altered the structure beyond the region immediately surrounding the new peptide bond. Like natural monellin, the conformation of scm is dominated by a 17-residue alpha-helix folded into the concave side of a twisted, five-strand anti-parallel beta-sheet. We expect that the availability of a high-resolution structure of scm, along with the convenience of producing site-specific mutants of this protein, will make scm a good model with which to probe the structural basis of sweetness.

Modified polyvinyl alcohol-benzoporphyrin derivative conjugates as phototoxic agents

Photosensitizing and biodistribution characteristics of a photosensitizer (benzoporphyrin derivative, monoacid ring A; BPD) conjugated to a macromolecule (modified polyvinyl alcohol; M-PVA, molecular weight = 10,000) were tested in vitro and in vivo. Modified PVA was loaded with BPD at molar ratios 1:12, 1:25, 1:50, 1:75 and 1:100. Most of the work was carried out with a conjugate having a 1:25 molar ratio. In vitro photosensitization was tested using A549 (human lung carcinoma), A432 (human epidermoid carcinoma) and P815 (mastocytoma of DBA/2 mice) cell lines. Photosensitization of M1 (rhabdomyosarcoma of DBA/2 mice) tumors was tested in an in vivo/in vitro assay, in which tumor-bearing mice were injected intravenously with free or conjugated 3H-BPD and 3 h later light activation of tumor cells was carried out in vitro. Biodistribution studies were carried out using M1 tumor-bearing DBA/2 mice and 3H-BPD either free or conjugated to M-PVA. The results of these studies showed that the conjugation of BPD to M-PVA resulted in the formation of a macromolecular photosensitizer that retained full photosensitizing activity of the photosensitizer molecules and at the same time gained new characteristics, advantageous for photodynamic treatment, especially in vivo. In vitro M-PVA-BPD conjugates were at least as efficient in photosensitization of tumor cells as an equivalent number of free BPD molecules, both in the presence and in the absence of serum. Although the biodistribution was in general comparable to free BPD, the conjugate (1:25) reached slightly higher levels in the blood, kidney, lung and spleen, and lower levels in the liver, brain, skin and muscle in comparison with free BPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ethanol ingestion on glucose transporter-1 protein and mRNA levels in rat brain

In the normal adult brain, glucose provides 90% of the energy requirement, as well as substrate for nucleic acid and lipid synthesis. We have previously observed that ethanol impairs hexose uptake by rat astrocytes in culture. In the present study, male Sprague-Dawley rats, 200-250 g, were fed liquid diet in which 36% of the calories were derived from ethanol (EF) for 4 weeks. Controls were fed ad libitum (AF) or pair-fed (PF) an equicaloric diet without ethanol. Blood glucose levels did not differ between the groups at the time of study. Glucose transport by brain plasma membranes was characterized by cytochalasin B binding and showed a slight increase in transporter number (mean +/- SEM of 4 experiments = 76.4 +/- 2.5 pmoles/mg protein in EF vs. 69.5 +/- 1.0 in PF) with no change in affinity (1.8 +/- 0.1 nM-1 in EF and 1.6 +/- 0.1 in PF). Glucose transporter, GLUT-1, was increased on Western blots. In contrast, Northern analysis of cortical tissue, using a rat brain glucose transporter cDNA insert (1.59 kb Bgl II fragment of pSPGT-1), showed a 23 to 35% decrease in steady-state levels of glucose transporter mRNA. GLUT-1 mRNA, localized in brain sections by in situ hybridization histochemistry, showed marked reductions in choroid plexus and hippocampus following ethanol treatment. Ethanol appears to have multiple effects on brain GLUT-1.

Visual functions and trace element metabolism in tobacco-toxic optic neuropathy

Visual functions and nutrition metabolic characteristics were studied in 8 subjects (16 eyes) with tobacco-toxic optic neuropathy (TTON). Their visual functions tested by psychophysical and electrophysiologic methods showed that 1: 1. central vision diminished in 16 eyes, 2. dyschromatopsias were found in 14 tested eyes, 3. bilateral symmetrical central or cecocentral scotomas were the visual field characteristics in all cases, 4. PVEP were severe abnormal in 3 spatial frequencies in all cases and 56.3% of 15' checkboard PVEP showed flat responses, which indicated the impairment of optic nerve dominated by the central field. However, the preserved visual responses could be obtained by FVEP test in 14 tested eyes even though their visual acuity were between the range of 0.02-0.2 and flat PVEP responses. The II and III wave latencies of primary stage were more prolonged than those of control group (P < 0.01), which further indicated the preferential demyelination corresponding to the papillomacular bundles, 5. ERG showed slightly attenuated amplitudes in 5 of 8 tested eyes, which indicated the secondary and mild retinal lesion. On the other hand, TTON occurred on a background of long-term, heavy smoking, drinking, emaciation and malnutrition bodies with low serum zinc level.