Protective effect of aminoguanidine on hypoxic-ischemic brain damage and temporal profile of brain nitric oxide in neonatal rat

Nitric oxide (NO) produced by inducible NO synthase contributes to ischemic brain damage. However, the role of inducible NO synthase-derived NO on neonatal hypoxic-ischemic encephalopathy has not been clarified. We demonstrate here that aminoguanidine, a relatively selective inhibitor of inducible NO synthase, ameliorated neonatal hypoxic-ischemic brain damage and that temporal profiles of NO correlated with the neuroprotective effect of aminoguanidine. Seven-day-old Wister rat pups were subjected to left carotid artery occlusion followed by 2.5 h of hypoxic exposure (8% oxygen). Infarct volumes (cortical and striatal) were assessed 72 h after the onset of hypoxia-ischemia by planimetric analysis of coronal brain slices stained with hematoxylin-eosin. Aminoguanidine (300 mg/kg i.p.), administered once before the onset of hypoxia-ischemia and then three times daily, significantly ameliorated infarct volume (89% reduction in the cerebral cortex and 90% in the striatum; p<0.001). NO metabolites were measured by means of chemiluminescence using an NO analyzer. In controls, there was a significant biphasic increase in NO metabolites in the ligated side at 1 h (during hypoxia) and at 72 h after the onset of hypoxia (p<0.05). Aminoguanidine did not suppress the first peak but significantly reduced the second one (p<0.05), and markedly reduced infarct size in a neonatal ischemic rat model. Suppression of NO production after reperfusion is a likely mechanism of this neuroprotection.

1Alpha-hydroxyvitamin D3 prevents the decrease of bone mineral density in lactating beagles

We assessed the change of bone mineral density (BMD) in lactating beagles with dual energy X-ray absorptiometry (DXA) and the preventive effect of 1alpha-hydroxyvitamin D3 (1alpha(OH)D3) on the BMD. Beagles, two to five years old, were used for detecting the time course change of BMD. Since the coefficient of variation (CV(%)) on detecting lumber vertebral (L2-L4) and tibial BMD by DXA was about 0.5%, DXA was useful to detect the change of BMD in beagles. There was a marked decrease in vertebral BMD during lactational period in the control group. The BMD levels after weaning were found to reverse to the initial level at mating. The same tendency was observed in tibial BMD as vertebral BMD, though the BMD changes were not marked. Beagles were administered at a dose of 0.1 microg/kg of 1alpha(OH)D3 three times in a week, and it was found to suppress the decrease in vertebral BMD during the breast feeding period. Also, the administration of 1alpha(OH)D3 promoted the prevention of decreased BMD during lactation both in vertebrae and tibiae. Significant effects of 1alpha(OH)D3 administration on tibial BMD were not observed. No adverse effects, such as hypercalcemia and hypercalciuria, were observed during the experimental period. Therefore, DXA was useful for detecting the changes of BMD in lactating beagles and the change of BMD was marked in lumber vertebrae, which are rich in trabecular bone. The preventive effect of 1alpha(OH)D3 on the decrease of BMD during the lactation period was observed in beagles.

Quantitative determination of arterial wall mechanics with pulse oximetric finger plethysmography

PURPOSE

The plethysmographic wave of pulse oximetry reflects arterial pulsation at the fingertip. Since arterial pressure and the pulsatile component of the arterial cross section represent the input and output of the fingertip arterial system, respectively, arterial wall mechanics may be delineated from their relationship. We aimed to construct a mathematical model of the fingertip arterial wall from the relationship between the plethysmographic wave and arterial pressure.

METHODS

The pulse oximetric plethysmographic signal at the forefinger and pressure at the ipsilateral radial artery were measured. Employing the data, simple mathematical models with one to four mechanical elements were tested in terms of the goodness of fit and the physiological implications. The determined model was applied to the data obtained during administration of vasoactive agents in anesthetized patients.

RESULTS

The mathematical model suited for describing arterial wall mechanics was a four-element, two-compartment model. The two compartments represent passive mechanical and active contractile properties, respectively. In the application of the model to the anesthetized patients, the vasoactive agents produced changes in the model parameters that implied mechanical alterations in the arterial wall.

CONCLUSION

These findings suggest the benefit of the four-element, two-compartment model in analyzing peripheral vascular wall mechanics influenced by various stimuli in intensive care and anesthesia.

Crystal structure of chitosanase from Bacillus circulans MH-K1 at 1.6-A resolution and its substrate recognition mechanism

Chitosanase from Bacillus circulans MH-K1 is a 29-kDa extracellular protein composed of 259 amino acids. The crystal structure of chitosanase from B. circulans MH-K1 has been determined by multiwavelength anomalous diffraction method and refined to crystallographic R = 19.2% (R(free) = 23.5%) for the diffraction data at 1.6-A resolution collected by synchrotron radiation. The enzyme has two globular upper and lower domains, which generate the active site cleft for the substrate binding. The overall molecular folding is similar to chitosanase from Streptomyces sp. N174, although there is only 20% identity at the amino acid sequence level between both chitosanases. However, there are three regions in which the topology is remarkably different. In addition, the disulfide bridge between Cys(50) and Cys(124) joins the beta1 strand and the alpha7 helix, which is not conserved among other chitosanases. The orientation of two backbone helices, which connect the two domains, is also different and is responsible for the differences in size and shape of the active site cleft in these two chitosanases. This structural difference in the active site cleft is the reason why the enzymes specifically recognize different substrates and catalyze different types of chitosan degradation.

Osteoporosis in hemiplegic stroke patients as studied with dual-energy X-ray absorptiometry

OBJECTIVES

To compare bone mineral densities (BMDs) of the affected and unaffected limbs in stroke patients at multiple sites; to study longitudinal changes during a 3-month rehabilitation program; and to relate BMDs to demographic, impairment, and disability variables.

DESIGN

Descriptive study.

SETTING

Tertiary rehabilitation center.

PATIENTS

One hundred four consecutive hemiplegic inpatients, 69 men, age 56.5 +/- 13.2 yrs, 47 with left-sided brain lesion. Median days from onset to admission and median length of stay days were 83 and 105.5, respectively.

MAIN OUTCOME MEASURES

BMDs of proximal humerus, distal radius, femoral neck, and calcaneus bilaterally, and third lumbar vertebra, measured with dual-energy x-ray absorptiometry (DXA), were compared between affected and unaffected sides at admission and discharge.

RESULTS

Stroke Impairment Assessment Set (SIAS) motor scores, Functional Independence Measure (FIM) scores, grip strength, and awake/sleep heart rate counts (activity index) improved significantly at discharge. Affected/unaffected BMD ratios were 88.3% to 98.4% at admission and 79.6% to 98.8% at discharge, lowest for the humerus. Discharge/admission ratios were 89.1% to 97.8% for the affected and 97.4% to 100% for the unaffected side. All BMDs were intercorrelated (R = .438 to .873). They correlated significantly with age, body weight, grip strength, FIM scores, and activity index. Factors selected to explain BMD with multiple regression analysis differed according to the site and timing of the measurement.

CONCLUSIONS

BMDs of the affected side were lower and most marked in the humerus. Longitudinally, not only the affected but the unaffected BMDs decreased. Age, sex, duration of stroke, anthropometric measurements, motor paralysis, muscle strength, and activity level contributed differently to bone loss according to the site and timing of the measurement.

[A case positive for the inhibitor for coagulation factor V]

We report a 71-year-old man who exhibited hepatocellular carcinoma and the inhibitor for coagulation factor V (FV). The inhibitor was found when his coagulation screening tests revealed an abnormally prolonged prothrombin time (71.1 sec) and activated partial thromboplastin time (more than 120 sec) but normal values of fibrinogen (241 mg/dl), the thrombo test (84%) and hepaplastin test (71%). In addition, FV-coagulation activity of the patient's plasma showed less than 1% of the pooled normal plasma and inhibitory activity for FV of his plasma was 32 Bethesda units. This inhibitory activity was neutralized by the addition of anti-human immunoglobulin-gamma-chain serum. The patient was treated with a fibrin sealant including human thrombin when he underwent an partial hepatectomy (32 months before onset) and received 2 doses of thrombin orally (5 months and 2 weeks before onset) to stop bleeding from phlebeurysm. Several studies have reported that the inhibitor for FV was produced after treatment with bovine thrombin containing FV as a contaminant. These findings suggest that our patient may produce an immunoglobulin specific for FV after similar stimulation of human thrombin containing FV.

Effects of sinus surgery on asthma in aspirin triad patients

The aspirin triad (nasal polyposis, asthma and sensitivity to aspirin) is a well-recognized clinical entity, also known as aspirin-induced asthma (AIA). The sinusitis associated with AIA is often difficult to treat and aggravates the asthmatic symptoms. In order to evaluate the surgical treatment of sinusitis in AIA, 22 patients who underwent sinus surgery were studied. Twenty patients (90.9%) got any relief of their asthma symptoms from sinus surgery. Postoperative pulmonary function test 1 year after surgery showed statistically significant improvement over the preoperative one. Three of 5 patients (60%) who used systemic steroids were able to eliminate or reduce their dosages. Also, 8 of 17 patients (47.1%) who were using inhaled topical steroids reduced their dosages and statistical analysis showed a significant difference in the doses of topical steroid used before and after surgery. Subjective evaluation of 20 patients (90.9%) indicated that the sinus surgery was effective for their asthma condition; showing from mild to marked improvement. For AIA patients aggravated by sinus disease, we recommend sinus surgery to improve the quality of life.

Congenital fiber type disproportion: severe form with marked improvement

A 30-month-old male exhibited marked hypotonia at birth accompanied by respiratory distress necessitating ventilator support. He subsequently demonstrated marked improvement in muscle power. He became independent of the respirator at 21 days of age and was able to sit without support at 11 months and walked alone at 24 months. Histopathologic analysis of the quadriceps femoris muscle confirmed the diagnosis of congenital fiber type of disproportion at 11 months of age. No other studies have described a patient with a severe neonatal form of congenital fiber type of disproportion who demonstrated such clear improvement. Physicians should be aware of this possibility when they interact with such patients and their families.

Crystal structure of a prokaryotic replication initiator protein bound to DNA at 2.6 A resolution

The initiator protein (RepE) of F factor, a plasmid involved in sexual conjugation in Escherichia coli, has dual functions during the initiation of DNA replication which are determined by whether it exists as a dimer or as a monomer. A RepE monomer functions as a replication initiator, but a RepE dimer functions as an autogenous repressor. We have solved the crystal structure of the RepE monomer bound to an iteron DNA sequence of the replication origin of plasmid F. The RepE monomer consists of topologically similar N- and C-terminal domains related to each other by internal pseudo 2-fold symmetry, despite the lack of amino acid similarities between the domains. Both domains bind to the two major grooves of the iteron (19 bp) with different binding affinities. The C-terminal domain plays the leading role in this binding, while the N-terminal domain has an additional role in RepE dimerization. The structure also suggests that superhelical DNA induced at the origin of plasmid F by four RepEs and one HU dimer has an essential role in the initiation of DNA replication.

Gene expression during osteoclast-like cell formation induced by antifusion regulatory protein-1/CD98/4F2 monoclonal antibodies (MAbs): c-src is selectively induced by anti-FRP-1 MAb

Human blood monocytes can differentiate into osteoclast-like cells when they are cultured in the presence of anti-FRP-1. Messenger (mRNA) expression of markers related to osteoclasts was analyzed during differentiation of osteoclasts from monocytes. As markers related to osteoclasts, we selected cathepsin-K, carbonic anhydrase (CA) II, vacuolar H(+)-ATPase (v-ATPase), vitronectin receptor (VNR), tartrate-resistant acid phosphatase (TRAP), osteopontin (OPN), galectin-3, c-src, c-fos, and c-fms. The mRNAs other than c-src mRNA were expressed in freshly isolated monocytes or monocytes incubated with control antibody or anti-FRP-1 monoclonal antibody (MAb) for 14 days. Of these mRNAs, cathepsin-K, CA II, v-ATPase, VNR, TRAP, OPN, and c-fms mRNAs were expressed at higher levels in the osteoclast-like cells than those in monocytes cultured with control antibody. On the other hand, galectin-3 mRNA was expressed at lower levels in the osteoclast-like cells, and there was no significant difference in c-fos mRNA expression between the monocytes cultured with control antibody and anti-FRP-1 MAb. c-src mRNA could not be detected in monocytes freshly isolated or incubated with control antibody. Surprisingly, expression of c-src mRNA was induced in monocytes by anti-FRP-1 MAb and was detectable as early as 3 h after anti-FRP-1 MAb treatment, indicating that c-src is selectively induced by anti-FRP-1 MAb treatment. Furthermore, the osteoclast-like cells expressed calcitonin receptor. Receptor activator of NF-kappaB (RANK) mRNA was detectable in freshly isolated monocytes or monocytes cultured with control antibody or anti-FRP-1 MAbs. Maximal expression of RANK was observed in osteoclast-like cells. On the other hand, no receptor activator of NF-KB ligand (RANKL) mRNA was detectable in any of the samples, suggesting that anti-FRP-1 mAb can induce osteoclast-like cells from blood monocytes without RANKL.

ADAM family proteins in the immune system

CD156 is a member of a family proteins characterized by a disintegrin and a metalloprotease domain (ADAM). These molecules are phylogenically conserved but have individual roles in a variety of cells. Here, Shunsuke Yamamoto and colleagues discuss data suggesting that ADAM family proteins have important roles in the immune system.

Infrared laser spectroscopic imaging based on degenerate four-wave-mixing spectroscopy combined with frequency-upconversion detection

Frequency-upconversion detection of an infrared degenerate four-wave-mixing image was proposed for infrared laser spectroscopic imaging of species in the gas phase. The operation of the imaging system has been demonstrated by observation of an expanding Cs plume generated by laser ablation.

Removal of the bridging ligand atom at the Ni-Fe active site of [NiFe] hydrogenase upon reduction with H2, as revealed by X-ray structure analysis at 1.4 A resolution

BACKGROUND

The active site of [NiFe] hydrogenase, a heterodimeric protein, is suggested to be a binuclear Ni-Fe complex having three diatomic ligands to the Fe atom and three bridging ligands between the Fe and Ni atoms in the oxidized form of the enzyme. Two of the bridging ligands are thiolate sidechains of cysteinyl residues of the large subunit, but the third bridging ligand was assigned as a non-protein monatomic sulfur species in Desulfovibrio vulgaris Miyazaki F hydrogenase.

RESULTS

The X-ray crystal structure of the reduced form of D. vulgaris Miyazaki F [NiFe] hydrogenase has been solved at 1.4 A resolution and refined to a crystallographic R factor of 21.8%. The overall structure is very similar to that of the oxidized form, with the exception that the third monatomic bridge observed at the Ni-Fe site in the oxidized enzyme is absent, leaving this site unoccupied in the reduced form.

CONCLUSIONS

The unusual ligand structure found in the oxidized form of D. vulgaris Miyazaki F [NiFe] hydrogenase was confirmed in the reduced form of the enzyme, with the exception that the electron density assigned to the monatomic sulfur bridge had almost disappeared. On the basis of this finding, as well as the observation that H2S is liberated from the oxidized enzyme under an atmosphere of H2 in the presence of its electron carrier, it was postulated that the monatomic sulfur bridge must be removed for the enzyme to be activated. A possible mechanism for the catalytic action of the hydrogenase is proposed.

Suppression of FRP-1/CD98-mediated multinucleated giant cell and osteoclast formation by an anti-FRP-1/CD98 mAb, HBJ 127, that inhibits c-src expression

When anti-CD98 mAb 6-1-13, 4-5-1, or 38-2-2 was added to the culture fluids of monocytes, extensive cell aggregation and polykaryocyte formation were induced. These multinucleated giant cells were tartrate-resistant acid phosphatase (TRAP) positive. On the other hand, when monocytes were incubated with another anti-CD98 mAb, HBJ 127, polykaryocyte formation was not detected, although extensive cell aggregation was induced. When HBJ 127 and 6-1-13 were simultaneously added to the culture fluids, anti-CD98 mAb-induced cell fusion was inhibited almost completely. HBJ 127 suppressed formation of 6-1-13-induced cell fusion in a dose-dependent manner. If, however, HBJ 127 was added after incubation of monocytes with mAb 6-1-13 for 6 h, an appreciable degree of TRAP-positive polykaryocyte formation was found. The bindings of 6-1-13 and HBJ 127 were not mutually competed. When monocytes were incubated with 6-1-13 or HBJ 127, 6-1-13 induced c-src mRNA, while HBJ 127 did not. Furthermore, when monocytes were incubated with both 6-1-13 and HBJ 127, c-src mRNA could not be detected, showing that HBJ 127 suppresses c-src expression. Therefore, CD98-mediated osteoclast formation can be regulated by modification of CD98 system.

Fibrinogen Matsumoto III: a variant with gamma275 Arg-->Cys (CGC-->TGC)--comparison of fibrin polymerization properties with those of Matsumoto I (gamma364 Asp-->His) and Matsumoto II (gamma308 Asn-->Lys)

Fibrinogen Matsumoto III (M-III) is a dysfibrinogen identified in a 66-year-old woman with rectal cancer. The fibrinogen level determined by the thrombin-time method was markedly decreased in preoperative coagulation tests of her plasma. Three fibrinogen polypeptide-chain gene fragments from the proposita were amplified by the polymerase chain reaction method, then sequenced. The triplet CGC encoding the amino acid residue gamma275 was replaced by TGC, resulting in the substitution of Arg->Cys. There have been previous reports of nine families with the same alteration, nine families with an Arg->His variant and one family with an Arg->Ser variant in this residue, which has been shown to be one of the most important amino acids in the 'D:D' interaction site. In addition, there are three silent mutations in the Aalpha-chain gene and two mutations in the intron of the Bbeta-chain and the gamma-chain gene. However, none of these mutations is thought to be the cause of the dysfunctional fibrinogen. The thrombin-catalyzed fibrin polymerization in the presence of 1 mM Ca ions was markedly delayed in purified M-III. Its lag period was longer than those of Matsumoto II (M-II; gamma308Asn->Lys) and Matsumoto I (M-I; gamma364Asp-His). gamma364Asp is one of the most important residues in the polymerization pocket of the 'D:E' interaction site and gamma308Asn is located in the vicinity of a high affinity Ca2+ binding site in the D-domain, gamma311-336. The maximum slope of the polymerization curve for M-III was about 4-fold steeper than that for M-1 but less steep than that for M-II. These results may suggest that the tertiary structure of the polymerization pocket plays a more important role in the lateral aggregation of protofibrils than that of the 'D:D' interaction site.

Crystallization and preliminary crystallographic studies of FMN-binding protein from Desulfovibrio vulgaris miyazaki F

The flavin mononucleotide binding protein from Desulfovibrio vulgaris (Miyazaki F) was crystallized using the vapour-diffusion method. The crystal belongs to the monoclinic space group P21 with unit-cell parameters a = 37.2, b = 84.6, c = 41.1 A, beta = 94.1 degrees, contains two molecules per asymmetric unit and diffracts beyond 1.2 A resolution with a synchrotron radiation X-ray source.

Crystallization and preliminary x-ray study of two crystal forms of Klebsiella oxytoca diol dehydratase-cyanocobalamin complex

Two crystal forms of Klebsiella oxytoca diol dehydratase complexed with cyanocobalamin have been obtained and preliminary crystallographic experiments have been performed. The crystals belong to two different space groups, depending on the crystallization conditions. One crystal (form I) belongs to space group P212121 with unit-cell parameters a = 76.2, b = 122.3, c = 209. 6 A, and diffracts to 2.2 A resolution using an X-ray beam from a synchrotron radiation source. The other crystal (form II) belongs to space group P21 with unit-cell parameters a = 75.4, b = 132.7, c = 298.8 A, beta = 91.9 degrees, and diffracts to 3.0 A resolution. For the purpose of structure determination, a heavy-atom derivative search was carried out and some mercuric derivatives were found to be promising. Structure analysis by the multiple isomorphous replacement method is now under way.

Effects of continuous infusion of PTH on experimental tooth movement in rats

Development of new methods for accelerating orthodontic tooth movement has been strongly desired for shortening of the treatment period. The rate of orthodontic tooth movement is dependent on the rate of bone resorption occurring in the compressed periodontium in the direction of orthodontic force applied to the tooth. In the present study, we examined the effects of continuous infusion of parathyroid hormone (PTH) on tooth movement. Male rats weighing 350-400 g were treated with subcutaneous of vehicle or hPTH(1-84) at 1-10 micrograms/100 g of body weight/day. When the upper right first molar (M1) was moved mesially for 72 h by the insertion of an elastic band between the first and second molars, M1 movement was accelerated by PTH infusion at 10 micrograms. PTH infusion caused a 2- to 3-fold increase in the number of osteoclasts in the compressed periodontium of M1, indicating that such treatment accelerated tooth movement by enhancing bone resorptive activity induced in the compressed periodontium. When M1 was moved mesially by an orthodontic coil spring ligated between upper incisors and M1 for 12 days, PTH(1-84) infusion at 10 micrograms caused a 2-fold increase in the rate of M1 movement. PTH(1-34) infusion at 4 micrograms had an effect comparable to that of PTH(1-84). However, intermittent injection of PTH(1-34) did not accelerate M1 movement. PTH infusion for 13 days did not affect either bone mineral measurements or the serum calcium level. These findings suggest that continuous administration of PTH is applicable to accelerate orthodontic tooth movement.

Close localization of mouse CD14 and CD32/16 in the cell surface of monocytic cell lines

The binding of a rat anti-mouse CD14 monoclonal antibody (mAb) (rmC5-3) was inhibited by pretreatment of a mouse monocytic cell line WEHI-3 cells with anti-mouse CD32/16 mAb (2.4G2), whereas that of 2.4G2 was not inhibited by pretreatment of WEHI-3 cells with rmC5-3. An enzyme-linked immunosorbent assay showed that rmC5-3 detected peptide 9 corresponding to amino acid position 308-322 of CD14 but 2.4G2 did not. A Western blot analysis of sera revealed that rmC5-3 and 2.4G2 detected the bands thought to be soluble CD14 and CD32/16, respectively. rmC5-3 reacted with mouse CD14-transfected CHO cells, CD14-CHO-K1 cells, but 2.4G2 did not. Lipopolysaccharide-induced tumor necrosis factor (TNF)-alpha release was enhanced when a monocyte cell line (J774) was pretreated with rmC5-3. The enhancement was abolished by pretreatment with 2.4G2. The release of TNF-alpha was observed following treatment of J774 cells with 2.4G2 followed by anti-rat IgG F(ab')2.

CD14 transgenic mice expressing membrane and soluble forms: comparisons of levels of cytokines and lethalities in response to lipopolysaccharide between transgenic and non-transgenic mice

Two different metallothionein promoter-mouse CD14 fusion genes were constructed. The membrane form of the CD14 fusion gene, designated M14M, contained the full-length CD14 cDNA sequence, whereas the soluble form of the fusion gene, designated M14S, was truncated to lack the sequence for the phosphatidylinositol-anchoring site. Expression of transgenic RNA in M14M and M14S mice on the basal diet was abundant in the liver. After maintenance with water containing ZnSO4 (50 mM) for 4 days, expression of transgenic RNA in M14M and M14S mice was strong in the small intestine. Immunohistochemical analysis demonstrated CD14 expression in these organs in M14S and M14M mice. Levels of CD14 in sera from M14S mice after zinc administration were significantly higher than these animals maintained with normal water, M14M mice after zinc administration and non-transgenic mice. Sera from M14S and M14M mice after stimulation with lipopolysaccharide LPS (LPS) demonstrated significantly lower levels of tumor necrosis factor-alpha and IL-6 than those from non-transgenic mice. Lethality in endotoxin shock produced by i.p. injection of 30-40 microg/g body wt LPS was not different between M14S, M14M and non-transgenic mice. However, survival rates in the lethal Shwartzman reaction induced by priming and challenge injections of LPS were significantly higher in M14M and M14S mice than in non-transgenic mice.

Glutathione depletion induces giant DNA and high-molecular-weight DNA fragmentation associated with apoptosis through lipid peroxidation and protein kinase C activation in C6 glioma cells

Glutathione (GSH) depletion caused by l-buthionine-(S,R)-sulfoximine (BSO) induced apoptosis that was recognized by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick endo-labeling (TUNEL), nuclear DNA staining with fluorescence dye, and internucleosomal DNA fragmentation in C6 rat glioma cells. The BSO-induced cell death was associated with caspase-3 activation. Lipid peroxidation and protein kinase C (PK-C) activation were observed during the apoptosis of C6 cells, and these events were inhibited by antioxidants and iron chelators without affecting BSO-induced GSH depletion. Furthermore, approximately 2 Mbp giant DNA fragments were observed in the BSO-treated cells. The giant DNA fragmentation were followed by approximately 30-700 kbp and then less than 100 kbp, including internucleosomal DNA fragmentations. Such serial DNA degradation was prevented by the antioxidants, the iron chelators, and the PK-C inhibitors. These results suggest that during apoptosis induced by GSH-depletion caused by BSO, reactive oxygen species endogenously produced cause lipid peroxidation and that the lipid peroxidation induced PK-C activation, processes which are thought to be involved in the giant DNA, high-molecular-weight DNA, and the internucleosomal DNA fragmentations.

Liberation of hydrogen sulfide during the catalytic action of Desulfovibrio hydrogenase under the atmosphere of hydrogen

The active site of [NiFe] hydrogenase from Desulfovibrio species is composed of a binuclear Ni-Fe complex bearing three diatomic nonprotein ligands to Fe and three bridges between the two metals, two of which are thiolate side chains of the protein moiety. The third bridging atom in the enzyme isolated from D. vulgaris Miyazaki F was suggested to be sulfur species, but was suggested to be oxygen species in D. gigas enzyme. When the hydrogenase from D. vulgaris Miyazaki F was incubated under the atmosphere of H2, H2S was liberated from the enzyme only in the presence of its electron carrier, cytochrome c3 or methylviologen. The amount of H2S liberation was little in the absence of electron carrier or essentially null when the enzyme was incubated under N2. The amount of H2S liberated was about 37% of the hydrogenase contained in the reaction vial in molar basis. These observations are in agreement with the recent observation that the third bridging site at the Ni-Fe active site is vacant in the reduced form of the enzyme revealed by X-ray crystallography.