Physiological characterization of a cadmium-resistant mutant in the fission yeast Schizosaccharomyces pombe

After treatment of the wild-type strain 975 h+ with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) mutants able to grow on YEP-medium containing 15 mM CdCl2 were isolated. Mutant R17 showed a specific resistance to Cd, but no increased tolerance to Pb(NO3)2, CuSO4 or ZnCl2. No higher content of Cd-binding phytochelatins could be detected, but the mutant accumulated lower levels of Cd than the corresponding wild-type. No change, however, was observed in the accumulation of Cu. Under the influence of Cd, the respiratory activity of mutant R 17 is reduced less than in the wild-type. The mechanism of resistance could be an increased secretion or a decreased uptake of Cd.

Sequences within the parvovirus minute virus of mice NS2-specific exon are required for inclusion of this exon into spliced steady-state RNA

When the minute virus of mice NS2-specific exon was modified by either substitution or deletion, most P4-generated pre-mRNA was spliced from the large-intron donor at nucleotide 514 to the small-intron acceptor at nucleotide 2377. Improvement to consensus of large-intron splice sites in such mutants did not suppress exon skipping or restore large-intron excision. Therefore, sequences within the NS2-specific exon are required for inclusion of this exon into spliced, steady-state minute virus of mice RNA.

Using Qualitative Hypotheses to Identify Inaccurate Data

Identifying inaccurate data has long been regarded as a significant and difficult problem in AI. In this paper, we present a new method for identifying inaccurate data on the basis of qualitative correlations among related data. First, we introduce the definitions of related data and qualitative correlations among related data. Then we put forward a new concept called support coefficient function (SCF). SCF can be used to extract, represent, and calculate qualitative correlations among related data within a dataset. We propose an approach to determining dynamic shift intervals of inaccurate data, and an approach to calculating possibility of identifying inaccurate data, respectively. Both of the approaches are based on SCF. Finally we present an algorithm for identifying inaccurate data by using qualitative correlations among related data as confirmatory or disconfirmatory evidence. We have developed a practical system for interpreting infrared spectra by applying the method, and have fully tested the system against several hundred real spectra. The experimental results show that the method is significantly better than the conventional methods used in many similar systems.

Synthesis, hybridization properties, nuclease stability, and cellular uptake of the oligonucleotide--amino-beta-cyclodextrins and adamantane conjugates

Synthesis of the oligonucleotides conjugated with amino derivatives of beta-cyclodextrin and adamantane, at the 3'-end of host oligonucleotide, has been described. The oligonucleotide conjugates were examined for their nuclease stability, hybridization properties, and cellular uptake. The oligonucleotide conjugates had increased nuclease resistance compared to their parent oligonucleotides. Conjugation of adamantane to the oligonucleotides did not adversely affect the ability of the oligonucleotides to hybridize with their complementary RNA. Conjugation with amino derivatives of beta-cyclodextrin, however, significantly destabilized the duplex formation. In the cellular uptake studies, we found that amino derivatives of beta-cyclodextrin attached at 3'-end of the oligonucleotides did not help to increase the uptake by cells. Cellular uptake of oligonucleotide-adamantane conjugates in association with 2-(hydroxypropyl)-beta-cyclodextrin (HPCD) as a "carrier" was significantly higher than that of control oligonucleotides.

An experimental study of spinal cord evoked potential

The characteristics of spinal cord-evoked potentials were investigated by using an in vitro spinal cord preparation. The spinal cord isolated from adult rats was immersed in a bathing chamber filled with oxygenated artificial cerebrospinal fluid (aCSF). The spinal cord-evoked potentials elicited by the stimulation of the spinal cord were recorded by using bipolar platinum electrodes. The potentials recorded consisted of early and late negative components (N1, N2). The inhibitory effect of lowered temperature on the N1 potential was clearly demonstrated. The oxygen deprivation of aCSF showed the higher sensitivity of N2 potential to hypoxia than that of N1. It was also possible to analyze the effects of potassium and magnesium ion concentration and pH on the evoked potentials. These results showed that the pure effects of various physiological and chemical factors on the spinal cord-evoked potentials can be analyzed by this experimental model.

Multiple subpial transection for treatment of intractable epilepsy

On the basis of experimental study, we applied multiple subpial transection (MST) to treat 50 patients with intractable epilepsy in which epileptigenic lesion involved functional areas such as pericentral gyrus, postcentral gyrus, Broca's area, Wernicke's area, visual cortex, etc. They were followed up for 6 to 40 months. Complete control of seizures was obtained in 32 patients, significant reduction of seizure (more than 50%) in 13, reduction (less than 50%) in 3, and no effect in 2. The total effective rate was 96%. No functional defect was found in all patients. The mechanism of the disease and surgical technique were discussed in detail. We consider that MST could replace some standard excisional therapy for local epilepsy.

Predegeneration enhances regeneration into acellular nerve grafts

In the present study, we determined the regeneration rate and the initial delay in rat sciatic nerve grafts first made hypercellular by predegeneration then acellular by freeze-thawing. 7-day predegenerated nerve pieces from the distal nerve stump on the right side were made acellular by repeated freeze-thawing and inserted as grafts into a 10-mm long freshly created defect on the left contralateral side. Freshly made (no predegeneration period) acellular nerve grafts were used as controls. Both types of grafts supported outgrowth of regenerating axons as demonstrated by the sensory pinch test. However, the predegenerated acellular nerve grafts had a significantly shorter initial delay period (2.7 days) as compared with freshly made acellular nerve grafts (9.5 days). The initial delay period for predegenerated acellular nerve grafts was similar to that for fresh cellular nerve grafts but significantly longer than that for predegenerated cellular nerve grafts [24]. The rate of regeneration appeared independent of the type of grafts used. We suggest that modifications of the basal lamina and/or factors produced during the predegeneration period by non-neuronal cells survive the freeze-thawing cycle and account for the decrease in the initial delay period.

N-tert-butyl-alpha-phenylnitrone improves recovery of brain energy state in rats following transient focal ischemia

Recent results have demonstrated that the spin trapping agent N-tert-butyl-alpha-phenylnitrone (PBN) reduces infarct size due to middle cerebral artery occlusion (MCAO), even when given after ischemia. The objective of the present study was to explore whether PBN influences recovery of energy metabolism. MCAO of 2-hr duration was induced in rats by an intraluminal filament technique. Brains were frozen in situ at the end of ischemia and after 1, 2, and 4 hr of recirculation. PBN was given 1 hr after recirculation. Neocortical focal and perifocal ("penumbra") areas were sampled for analyses of phosphocreatine (PCr), creatine, ATP, ADP, AMP, glycogen, glucose, and lactate. The penumbra showed a moderate-to-marked decrease and the focus showed a marked decrease in PCr and ATP concentrations, a decline in the sum of adenine nucleotides, near-depletion of glycogen, and an increase in lactate concentration after 2 hr of ischemia. Recirculation for 1 hr led to only a partial recovery of energy state, with little further improvement after 2 hr and signs of secondary deterioration after 4 hr, particularly in the focus. After 4 hr of recirculation, PBN-treated animals showed pronounced recovery of energy state, with ATP and lactate contents in both focus and penumbra approaching normal values. Although an effect of PBN on mitochondria cannot be excluded, the results suggest that PBN acts by preventing a gradual compromise of microcirculation. The results justify a reevaluation of current views on the pathophysiology of focal ischemic damage and suggest that a therapeutic window of many hours exists in stroke.

Ultraviolet spectroscopic evidence for decreased motion of the active site tyrosine residue of delta 5-3-ketosteroid isomerase by steroid binding

delta 5-3-Ketosteroid isomerase (EC 5.3.3.1) from Pseudomonas testosteroni catalyzes the highly efficient conversion of delta 5-3-ketosteroids to delta 4-3-ketosteroids by a stereoselective and intramolecular transfer of the 4 beta-proton to the 6 beta-position. Tyr-14 is the critical general acid and Asp-38 is the general base involved in catalysis. The UV absorption bandwidths of Tyr-14 were much narrower than those of the other two tyrosines (Tyr-55 and Tyr-88) of isomerase or of the N-acetyltyrosine ethyl ester in aqueous solution, suggesting that Tyr-14 is restricted in its mobility. Further immobilization of this residue occurs upon steroid binding. Thus, 5 alpha-estrane-3,17-dione, an A-ring saturated steroid, induces significant narrowing of the tyrosine absorption bands (pi-->pi*) of the main peak (279.5 nm) and the shoulder (285.5 nm) of Tyr-14, with no significant changes in lambda max. No effects of steroid binding were found on the absorption bandwidths of Tyr-55, Tyr-88, or the phenylalanine residues. The ratio of the absorbance (Amax) at the absorption maximum (lambda max) to that at lambda max plus 4 nm (Amax +4) was used as a measure of peak sharpness. Specifically, the ratios of A279.5/A283.5 (main peak) and A285.5/A289.5 (shoulder) of Tyr-14 of the free enzyme at 25 degrees C were 1.25 and 1.89, respectively, and they increased to 1.41 and 2.70, respectively, in the complex. A more precise measurement of the band narrowing from 4.2 to 3.1 nm between the inflection points was obtained from the derivative spectra. The absorption bands of free and steroid-bound isomerase were narrowed significantly by lowering the temperature and were broadened by denaturation, suggesting that the unusual peak-sharpening effects induced by steroid binding arise from the restricted motion of Tyr-14, as well as from more directional hydrogen bonding resulting from the displacement of water molecules from the active site and decreased flexibility of the protein. Larger enthalpy of the sharpening effects was observed for the steroid-bound enzyme (-0.527 +/- 0.016 kcal/mol) than for the free enzyme (-0.250 +/- 0.018 kcal/mol) by lowering the temperature, indicating that interactions of Tyr-14 with its environment, which restrain its motion, are stronger in the steroid-bound enzyme than in the free enzyme. Hydrogen-bonding modes of Tyr-14, mobility of the active site, and protein flexibility are the environmental factors determining the absorption bandwidths of the critical Tyr-14 residue.

Glutamate, calcium, and free radicals as mediators of ischemic brain damage

Calcium is considered a mediator of ischemic brain damage whether this is due to global or forebrain ischemia or to focal ischemia. Supporting evidence is the translocation of extracellular calcium into cells during ischemia, the precipitous rise in the free cytosolic calcium concentration, and the role of calcium in activating lipases, proteases, kinases, phosphatases, and endonucleases in potentially harmful metabolic cascades. In vitro and in vivo experiments suggest that the main route of entry is through channels gated by glutamate receptors. These experiments led to the excitotoxic hypothesis of cell death. The in vitro experiments further support the role of calcium as a mediator of cell death. Both cell calcium overload and acidosis enhance the production of partially reduced oxygen species, thus predisposing to free radical-related damage. In transient global or forebrain ischemia, free radicals formed during reperfusion may contribute to a perturbed membrane function, leading to a sustained alteration of cell calcium metabolism with ultimate mitochondrial calcium overload. In focal ischemia (stroke), free radicals may be important mediators of the infarction process. Infarction can be regarded as a form of secondary damage, which is probably caused by microvascular dysfunction. Very likely, such dysfunction is triggered by upregulation of adhesion molecules such as ICAM-1, microvascular "plugging," and an inflammatory response at the blood-endothelial cell interface. The involvement of free radicals in this type of secondary damage is supported by results showing that nitrones that act as free radical spin-traps ameliorate focal ischemic damage with a therapeutic window of many hours.

Ultraviolet resonance Raman spectroscopy of delta 5-3-ketosteroid isomerase revisited: substrate polarization by active-site residues

The delta 5-3-ketosteroid isomerase (EC 5.3.3.1) of Pseudomonas testosteroni promotes extremely rapid conversion of delta 5- to delta 4-3-ketosteroids by a conservative intramolecular proton transfer via an enolic intermediate. The competitive inhibitor 19-nortestosterone displays marked spectroscopic changes upon binding to the enzyme, but the mechanisms responsible for these changes have not been unequivocally established. Ultraviolet resonance Raman (UVRR) spectra are reported for 19-nortestosterone in acid solutions and for this ligand when bound to delta 5-3-ketosteroid isomerase, as well as to its D38N and Y14F/D38N mutants. The frequencies of UVRR bands associated with C = O and C = C stretching can be used to monitor the state of polarization of the enone fragment of the steroid and the effects of the catalytic side chains, Tyr-14 and Asp-38, on these polarizations. Strong polarization is indicated by marked frequency downshifts of the C = O and C = C bands in the native protein; the downshifts are diminished by the mutations of these catalytic residues. The lower polarizing effects of the Y14F and D38N single mutants and the Y14F/D38N double mutant indicate that most of the polarization of the conjugated ketone is attributable to hydrogen-bond donation by the hydroxyl group of Tyr-14. A smaller contribution of Asp-38 is detected which is, in part, cooperative with that of Tyr-14. Reference spectra of hydrogen-bonded and protonated forms of 19-nortestosterone are reassigned, on the basis of the species identification of D. C. Hawkinson and R. M. Pollack [(1993) Biochemistry 32, 694-698].(ABSTRACT TRUNCATED AT 250 WORDS)

VV-hemorphin-7 and LVV-hemorphin-7 released during in vitro peptic hemoglobin hydrolysis are morphinomimetic peptides

Two opioid peptides were generated by in vitro pepsin treatment of bovine hemoglobin. These peptides were identified using a GPI test and purified using HPLC chromatographic techniques. They correspond to fragments 31-40 (LVV-hemorphin-7) and 32-40 (VV-hemorphin-7) of the beta-chain of bovine hemoglobin. Binding experiments strongly confirm that VV-hemorphin-7 and LVV-hemorphin-7 are opioid peptides since they inhibited [3H]naloxone binding to rat brain membranes. Our results indicate that VV-hemorphin-7 and LVV-hemorphin-7 exhibit a lesser potency both in GPI and binding tests. Selectivity and affinity of these purified peptides and synthetic hemorphin-7 for opioid receptors is discussed.

Glass wool-H2O2/CoCl2 test system for in vitro evaluation of biodegradative stress cracking in polyurethane elastomers

Environmental stress cracking (ESC) in polyetherurethanes has been demonstrated in animal models. However, duplication of this phenomenon in vitro has been a challenge. The glass wool-H2O2/CoCl2 test system was designed to provide oxidation components found in vivo, i.e., hydroxyl radical (HO.), molecular oxygen (O2), and superoxide (O2-.) required for auto-oxidation of polyetherurethanes. The in vitro test is not only reliable in duplicating the characteristics of in vivo stress cracking in polyetherurethanes at 37 degrees C, but also accelerates ESC as much as seven times. The test results on several types of polyurethanes showed that Tecothane 80A was as vulnerable to biodegradative stress cracking in vitro as Pellethane 2363-80A, while the new generation of polyurethanes, Corethane, demonstrated great resistance against stress cracking.

[Isolation, purification and characterization of human proteinase inhibitor, alpha 2-macroglobulin]

A study of the isolation, purification and characterization of human proteinase inhibitor, alpha 2-macroglobulin (alpha 2-M) is presented. The alpha 2-M, with a purity of more than 90% and subunit molecular weight of 185kDa, was isolated by ammonium sulfate fractionated precipitation from human blood plasma and purified by DEAE cellulose DE52 column chromatography. It was found to be the same as the standard counterpart provided by sigma company. This purification procedure of alpha 2-M can be done with low cost, high efficiency and in large scale preparation.

Peptic hemoglobin hydrolysis in an ultrafiltration reactor at pilot plant scale generates opioid peptides

Two hemorphins, peptides with opioid activity, have been isolated from a pepsin hydrolysate of bovine hemoglobin, by use of gel permeation (GP) and reverse phase (RP) high-performance liquid chromatography (HPLC). Their primary structure and accurate molecular weights, determined by amino acid analysis and fast atom bombardment (FAB) mass spectrometry, were identical to fragments 31-40 (LVV-hemorphin-7) and 32-40 (VV-hemorphin 7) of the beta-chain of bovine hemoglobin. Two other peptides, 34-40 (hemorphin-7) and 34-41 (hemorphin-8) of the beta-chain of bovine hemoglobin, have been synthesized and studied. The opioid potency of these peptides, exhibited by the use of electrically stimulated muscle of isolated guinea pig ileum (GPI), were significant and comparable with some others previously described. Studies of opioid activities and primary structure of hemorphins led us to postulate the important role of arginine and phenylalanine in opioid potency.

Airway epithelial cell responses to ozone injury

The airway epithelial cells is an important target in ozone injury. Once activated, the airway epithelium responds in three phases. The initial, or immediate phase, involves activation of constitutive cells, often through direct covalent interactions including the formation of secondary ozonolysis products--hydroxyhydroperoxides, aldehydes, and hydrogen peroxide. Recently, we found hydroxyhydroperoxides to be potent agonists of bioactive eicosanoid formation by human airway epithelial cells in culture. Other probable immediate events include activation and inactivation of enzymes present on the epithelial surface (e.g., neutral endopeptidase). During the next 2 to 24 hr, or early phase, epithelial cells respond by synthesis and release of chemotactic factors, including chemokines--macrophage inflammatory protein-2, RANTES, and interleukin-8. Infiltrating leukocytes during this period also release elastase, an important agonist of epithelial cell mucus secretion and additional chemokine formation. The third (late) phase of ozone injury is characterized by eosinophil or monocyte infiltration. Cytokine expression leads to alteration of structural protein synthesis, with increases in fibronectin evident by in situ hybridization. Synthesis of epithelial antiproteases, e.g., secretory leukocyte protease inhibitor, may also increase locally 24 to 48 hr after elastase concentrations become excessive. Thus, the epithelium is not merely a passive barrier to ozone injury but has a dynamic role in directing the migration, activating, and then counteracting inflammatory cells. Through these complex interactions, epithelial cells can be viewed as the initiators (alpha) and the receptors (omega) of ozone-induced airway disease.

[Modifications of gene expression by tumor promoters]

The modifications of gene expression by tumor promoters were analyzed in vitro and in vivo. The results of slot blot hybridizations showed that tumor promoter TPA induced c-fos and c-myc expressions in mouse fibroblast cell line BALB/3T3 and rat liver, decreased the levels of Rb RNA in BALB/3T3 cell line and of alpha 1-I3 RNA in rat liver. It was also demonstrated that tumor promoter phenobarbital influenced c-fos and c-myc expressions and decreased alpha 1I3 mRNA level in rat liver during a long term experiment. Phenobarbital was found to have no effect on c-fos and c-myc expressions in rat liver during a short experiment. Tumor promoters induced the expressions of c-fos and c-myc which were positively-related to cancer formation and inhibited the expressions of Rb and alpha 1-I3 which were negatively-related to cancer formation. This implied that tumor promotion played an important role in cancer development and tumor promoters exerted their effects selectively according to the attributes of different genes.

Hyperthermia nullifies the ameliorating effect of dizocilpine maleate (MK-801) in focal cerebral ischemia

The present study was inspired by two previous findings from the laboratory. The first was that dizocilpine maleate (MK-801) fails to reduce infarct size when the middle cerebral artery (MCA) is permanently occluded by an intraluminal filament technique in rats. In seeking the reasons for this we measured temperature and found that the body temperature of occluded animals increases to 39.0-39.5 degrees C during the first 2-3 h. In order to explore whether the rise in temperature was responsible for the lack of effect of MK-801, two groups of animals were studied, both containing animals which were subjected to 2 h of transient MCA occlusion and given MK-801 15 min before, as well as 6 and 24 h after ischemia. In one group, temperature was allowed to rise spontaneously during ischemia (39.0-39.5 degrees C). In the other, body temperature was maintained close to normal during ischemia, and for the first 6 h postischemically, by cooling of the ambient air. Infarct volume was assessed by triphenyltetrazolium chloride staining after 48 h of recovery. The results showed that MK-801 failed to reduce infarct size in animals whose body temperature rose during ischemia. In contrast, the drug markedly reduced infarct volume in temperature-controlled animals; in fact, 5/8 animals had no infarcts but selective neuronal damage only. The results suggest that amelioration of focal ischemic damage cannot be expected if body and brain temperature is allowed to rise above normal.

Enzymatic and nonenzymatic polarizations of alpha,beta-unsaturated ketosteroids and phenolic steroids. Implications for the roles of hydrogen bonding in the catalytic mechanism of delta 5-3-ketosteroid isomerase

Ketosteroids (e.g., 19-nortestosterone) and phenolic steroids (e.g., 17 beta-estradiol and 17 beta-dihydroequilenin), which are potent competitive inhibitors of delta 5-3-ketosteroid isomerase (isomerase, EC 5.3.3.1) of Pseudomonas testosteroni, undergo significant polarization upon binding to the active site of the enzyme. The 10 nm red shift of the UV absorption maximum of the enone chromophore of 19-nortestosterone, which occurs in the enzyme-steroid complex, resembles that observed when this steroid is exposed to strong acid. The UV and fluorescence spectral changes of 17 beta-estradiol and 17 beta-dihydroequilenin in the enzyme-bound complex resemble the spectra of ionized phenolate species in aqueous basic solutions. Since most enzymes bind their substrates and competitive inhibitors in a solvent-inaccessible hydrophobic environment, and the generation of charges in such nonpolar environments is unfavorable, we investigated the possibility that the spectral perturbations of the steroids might arise from strong hydrogen bonding in nonpolar environments. For this purpose, the spectral properties of model compounds capable of forming intramolecular hydrogen bonds were studied in nonpolar solvents. Thus, 4-hydroxyandrost-4-ene-3,17-dione, in which the 4-hydroxyl group is intramolecularly hydrogen-bonded to the 3-carbonyl group through a five-membered ring, exhibits a lambda max of 276.0 nm, while the corresponding 4-methyl ether, 4-methoxyandrost-4-ene-3,17-dione, which cannot form an internal hydrogen bond, shows a lambda max of 258.5 nm in aqueous solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of cyclodextrin and its derivatives as carriers for oligonucleotide delivery

The use of antisense phosphorothioate oligodeoxynucleotides as tools for modulating gene expression represents a novel strategy for designing drugs to treat a variety of diseases. Several factors, including cellular uptake and internalization of the phosphorothioate oligodeoxynucleotide, are important parameters in determining the effectiveness of antisense agents as therapies. We have used cyclodextrin and its analogs as carriers to increase cellular uptake of phosphorothioate oligodeoxynucleotides. The studies were carried out using 35S-labeled and fluorescent-labeled phosphorothioate oligodeoxynucleotide in human T cell leukemia H9 cell line. Cellular uptake of phosphorothioate oligodeoxynucleotide in the presence of cyclodextrin was found to be concentration and time dependent. Using various cyclodextrin analogs, e.g., 2-hydroxypropyl beta-cyclodextrin (HPCD), hydroxyethyl beta-cyclodextrin (HECD), and a mixture of various hydroxypropyl beta-cyclodextrins (Encapsin), we observed increases in phosphorothioate oligodeoxynucleotide uptake, up to twofold to threefold in 48 hours. Confocal microscopy studies confirmed that oligonucleotide was present intracellularly. Cyclodextrin itself was not toxic at the concentration used. Cyclodextrins did not seem to affect the efflux of phosphorothioate oligodeoxynucleotide from cells. Stability of phosphorothioate oligodeoxynucleotide against endogenous cellular nucleases remained unchanged in the presence of cyclodextrins. These studies suggest that cyclodextrin and its analogs might be used successfully as carriers for oligonucleotide and analogs.

Pre-degenerated nerve grafts enhance regeneration by shortening the initial delay period

In the present study we tested how nerve grafts with different pre-degeneration periods (1-28 days) influenced the early regenerative response in the rat sciatic nerve. The sciatic nerve on the right side was crushed and after 1-28 days of pre-degeneration, a 10 mm segment was used as an autologous nerve graft and transposed to a freshly made 10 mm long nerve defect on the left side. The regeneration distance was measured by the sensory pinch test 2-10 days after nerve repair. A newly developed mathematical model was used to calculate regeneration rates and initial delay periods from the measured regeneration distances. Pre-degenerated nerve grafts improved nerve regeneration by decreasing the initial delay period as compared to fresh nerve grafts without affecting the regeneration rate. Only one day of pre-degeneration was sufficient to reduce the initial delay period from 3.6 days to 1.7 days. The maximal effect on the initial delay period was achieved after 3 days of pre-degeneration. The initial delay period at later pre-degeneration intervals (7-14 days) was about 1 day. The effect persisted for at least 28 days of pre-degeneration. The regeneration rate was 1.5 mm/day for fresh nerve grafts and between 1.8-2.1 mm/day for pre-degenerated grafts. The results suggest that the effects of pre-degeneration are not only due to the increased cell proliferation in the graft, but that also trophic and/or inflammatory mechanisms may be of importance. Grafts pre-degenerated by crush may have clinical implications since they are easy to perform if an elective nerve grafting procedure is planned.