Reduction In Succinate Dehydrogenase Activity Research Articles

Hesperidin Protects Alcohol-Induced Mitochondrial Abnormalities via the Inhibition of Oxidative Stress and MPT Pore Opening in Newborn Male Rats as a Fetal Alcohol Syndrome Model.

Prenatal alcohol exposure causes fetal developmental abnormalities via mitochondrial dysfunction, reactive oxygen species (ROS) formation, and oxidative stress. Therefore, we aimed to investigate the potential of hesperidin as a mitochondrial protective and antioxidative agent in newborn male rats as a model for fetal alcohol syndrome (FAS). Newborn male rats were divided randomly into five groups: a sham group (receiving 27.8 ml/ kg milk solution, orally), an ethanol group (5.25 g/kg in milk solution, orally, 2-10 days after birth), an ethanol + hesperidin group (25 mg/kg/ day orally), an ethanol + hesperidin group (50 mg/kg/day orally), and an ethanol + hesperidin group (100 mg/kg/day orally). Thirty-six days after birth, newborn male rats were sacrificed and brain mitochondria were isolated using differential centrifugation. Mitochondrial toxicity biomarkers of succinate dehydrogenase (SDH) activity, mitochondrial swelling, mitochondrial membrane potential (MMP), and ROS were measured. Offspring neonatally exposed to ethanol showed a significant reduction in SDH activity, mitochondrial swelling, MMP collapse, induction of ROS formation, and lipid peroxidation in isolated mitochondria. Oral administration of hesperidin restored SDH activity, improved MMP collapse and mitochondrial swelling, and reduced ROS formation. This study demonstrates that hesperidin exerts a potent protective effect against alcohol-induced mitochondrial toxicity in the FAS model. Moreover, these findings indicate that hesperidin might be a useful compound for prevention of alcohol-induced fetal developmental abnormalities during pregnancy.

Serum starvation affects mitochondrial metabolism of adipose-derived stem/stromal cells

Background aimsA large part of mesenchymal stromal cell (MSC) regenerative and immunomodulatory action is mediated by paracrine signaling. Hence, an increasing body of evidence acknowledges the potential of MSC secretome in a variety of preclinical and clinical scenarios. Mid-term serum deprivation is a common approach in the pipeline of MSC secretome production. Nevertheless, up to now, little is known about the impact of this procedure on the metabolic status of donor cells. MethodsHere, through untargeted differential metabolomics, we revealed an impairment of mitochondrial metabolism in adipose-derived MSCs exposed for 72 h to serum deprivation. ResultsThis evidence was further confirmed by the significant accumulation of reactive oxygen species and the reduction of succinate dehydrogenase activity. Probably as a repair mechanism, an upregulation of mitochondrial superoxide dismutase was also induced. ConclusionsOf note, the analysis of mitochondrial functionality indicated that, despite a significant reduction of basal respiration and ATP production, serum-starved MSCs still responded to changes in energy demand. This metabolic phenotype correlates with the obtained evidence of mitochondrial elongation and branching upon starvation.

Features of the Functioning of Succinate Dehydrogenase and Malate Dehydrogenase in Leaves of Spinach (Chenopodium foliosum L.) and Amaranth (Amaranthus caudatus L.) under Salt Stress Conditions

Salt stress was shown to cause changes in the activity and isozyme composition of mitochondrial malate dehydrogenase (MDH) in leaves of amaranth (C4-type); these changes were manifested in the induction of an additional MDH isoform. Exposure of spinach plants (C3-type) to a NaCl solution did not cause significant changes in the isozyme composition and activity of the enzymes studied. Succinate dehydrogenase (SDH) activity in amaranth leaves under salt stress conditions increased several times, while the isoenzyme composition of SDH remained unchanged. The levels of gene transcripts in leaves of amaranth and spinach clearly correlated with changes in the MDH and SDH activity. Salt stress enhanced expression of the mdh-mtx (mitochondrial) and mdh-cyt (cytoplasmic) genes in amaranth leaves during the whole experiment. In the case of the sdha gene, a decrease in the content of transcripts was observed that clearly correlated with the reduction in SDH activity.

Impact of Profenofos and Carbosulfan on Dehydrogenase activity of Freshwater fish, Labeo rohita (Hamilton)

Experiments were intended to study effects of profenofos and carbosulfan on the activities of dehydrogenase of freshwater fish, Labeo rohita. Healthy freshwater fish, Labeo rohita (Hamilton) were collected from the Nandivelugu fishfarm, India. Profenofos and carbosulfan pesticides were purchased from local pesticide store in Guntur, India, based on the preliminary lethal toxicity tests (96 hr LC50 i.e. 100 μg l-1; 1.2 mg l-1 and 1/10th 96 hr LC50 i.e.10 μg l-1; 0.12mg l-1 and) were selected as lethal and sublethal concentrations. After the acclimation, fish were exposed to lethal and sublethal concentrations in groups of 10 fish in 15 L of the test water in test chambers for 1 and 8 days. Fluctuations in succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) were observed in different tissues of the experimental animal. The activity of LDH was highly elevated following profenofos and carbosulfan exposure indicating increased anaerobic respiration to meet the energy demands where aerobic oxidation is lowered. Rapid depletion of SDH activity in all tissues of fish, L. rohita treated with sublethal and lethal concentrations of profenofos and carbosulfan. When compared to their respective controls. The general reduction in SDH activity due to pesticidal stress was associated with the inhibition of mitochondrial respiratory mechanism of dearrangement on ultra-structure, architectural integrity and permeability of mitochondria. Decreased MDH activity levels due to the inhibition exerted by oxaloacetate; maybe decrease in the activity of TCA cycle dehydrogenase is consistent with the disintegration of mitochondria of CO2 formation from acetate. Both profenofos and carbosulfan intoxication exerted a profound influence on the dehydrogenase enzymes of fish L. rohita but comparatively profenofos treated fish tissues showed more deterioration when compared to carbosulfan treated fish.

Functional and cellular consequences of covalent target protein modification by furan in rat liver.

Furan hepatotoxicity is thought to be linked to covalent binding of its reactive metabolite, cis-2-butene-1,4-dial, to hepatic proteins critical for cell homeostasis and survival. We previously identified 61 putative furan target proteins, which participate in various cellular processes including carbohydrate metabolism, fatty acid β-oxidation, adenosine triphosphate (ATP) synthesis, protein folding and maintenance of redox homeostasis. To further investigate the biological significance of target protein modification, this study was designed to determine the impact of furan on the activity of key target enzymes involved in glycolysis, β-oxidation, ATP synthesis, and redox regulation in rat liver, and to link these functional changes to alterations in cellular processes. While cis-2-butene-1,4-dial inhibited thioredoxin 1 (Txn1) in a cell-free assay, in livers of rats treated with a single high dose of furan Txn1 activity was markedly increased due to rapid up-regulation of Txn1 mRNA expression. Significant inhibition of glyceraldehyde-3-phosphate dehydrogenase and metabolic changes consistent with blocked glycolytic breakdown of glucose were observed in rat liver in response to a single high dose of furan. In contrast, furan treatment resulted in increased activity of enoyl-CoA hydratase and enhanced production of ketone bodies, indicative of increased utilization of fatty acids as energy source. Consistent with changes in TCA cycle metabolites, furan treatment resulted in a reduction of succinate dehydrogenase activity, supporting mitochondrial dysfunction as a critical event in furan toxicity. No significant changes in target protein function were observed following repeated administration of furan at lower dose (0.1 and 0.5mg/kg bw for 4 weeks) closer to estimated human exposure to furan via food. Although the relative contribution of furan mediated alterations in metabolic pathways and antioxidant defense to the overall toxic response to furan, including considerations of dose and time, remains to be established, our work contributes to mapping biological processes and toxicity pathways modulated by reactive electrophiles.

Effects of static interventions on disuse atrophy of the rat soleus muscle at different sites along its longitudinal axis.

[Purpose] The purpose of our study was to verify the inhibitory effects of static intervention (heat load and muscle stretching) on disuse-related adaptation changes in the soleus muscle and to compare these effects across different sites along its longitudinal axis. [Subjects] Forty 8-week-old male Wistar rats. [Methods] The effects of heat load and/or muscle stretching in the rat soleus during hindlimb suspension were evaluated by measuring the cross-sectional area of the muscle fibers, succinate dehydrogenase activity, and number of capillaries in the proximal, middle, and distal regions. [Results] With no intervention the proximal region showed the highest reduction in the cross-sectional area, whereas the distal region showed the highest reduction in succinate dehydrogenase activity and the number of capillaries due to hindlimb suspension. These differences between the proximal and distal regions decreased with both interventions, and the effects were most pronounced with a combination of heat load and muscle stretching. [Conclusion] Differences in the muscle structure between the proximal and distal regions increased due to hindlimb suspension, and this heterogeneity associated with muscle disuse was inhibited by static intervention including heat load and muscle stretching. Furthermore, the combination of heat load and muscle stretching most reduced the heterogeneity.

Death mode-dependent reduction in succinate dehydrogenase activity in hair cells of aging rat cochleae

Background Our previous studies have shown that both apoptosis and necrosis are involved in hair cell (HC) pathogenesis in aging cochleae. To better understand the biological mechanisms responsible for the regulation of HC death, we examined the activity of succinate dehydrogenase (SDH), a mitochondrial bioenergetic enzyme, in the HCs of aging cochleae. Methods The auditory brainstem response thresholds elicited by tone bursts at 4, 10 and 20 kHz were measured in both young (2–3 months) and aging (22–23 months) Wistar rats. SDH activity was evaluated with a colorimetric assay using nitroblue tetrazolium monosodium salt. The SDH-labeled organs of Corti were double stained with propidium iodide, a DNA intercalating fluorescent probe for illustration of HC nuclei. All the specimens were examined with fluorescence microscopy and confocal microscopy. Results Aging rats exhibited a significant elevation of ABR thresholds with threshold shifts being 34 dB at 20 kHz, 28 dB at 10 kHz, and 25 dB at 4 kHz. Consistent with the reduction in the cochlear function, aging cochleae exhibited the reduction of SDH staining intensity in the apical and the basal ends of the cochleae, where a large number of apoptotic, necrotic, and missing HCs were evident. The reduction in SDH staining appeared in a cell-death-mode dependent fashion. Specifically, SDH labeling remained in apoptotic HCs. In contrast, SDH staining was markedly reduced or absent in necrotic HCs. Conclusions In the aging cochlea, SDH activity is preserved in HCs undergoing apoptosis, but is substantially reduced in necrosis. These results suggest that mitochondrial energetic function is involved in the regulation of cell death pathways in the pathogenesis of aging cochleae.

Oxidative stress associated with nematode infections in sheep: a preliminary study

A hundred and seven sheep slaughtered at the Cold Storage Company (CSC) in Bulawayo, were examined for nematode parasite infections using coporological methods. Direct smear and salt floatation methods were used to observe nematode parasite eggs. Nine sheep were found to be infested with nematode eggs only. Nine uninfected sheep were used as controls. Liver samples collected from the infected and noninfected sheep were used for assays of the antioxidant enzymes, glutathione peroxidase (GPX) and diphosphotriphosho-diaphorase (DTD) as well as the intermediary metabolic enzyme, succinate dehydrogenase (SDH). Lipid peroxidation was assayed by determining malondialdehyde (MDA) levels. Significantly higher GPX activities were observed in infected sheep when compared with non- infected sheep (p 0.05). Parasitic infection resulted in significant reduction in SDH activity (p © 2010 International Formulae Group. All rights reserved. Keywords: Glutathione peroxidase, malondialdehyde, succinate dehydrogenase, nematode diphosphotriphospho-diaphorase, lipid peroxidation

Adaptation of Skeletal Muscle O2 Transport and Utilization in Rats with Right Heart Failure

Exercise intolerance is a cardinal symptom in patients with heart failure (HF), resulting from energetic failure in both cardiac and skeletal muscles. HF is known to be associated with skeletal muscle atrophy and a shift towards fast fatigable fibers (Vescovo et al. Int J Cardiol 104:298-, 2005). Additionally, right HF is associated with peripheral edema which may impair convective and diffusive O2 transport. However, structural changes in the pathways determining diffusive O2 transport and utilization are not well understood in right HF. PURPOSE: We therefore determined capillarization, oxidative enzyme activity, fiber area and type in skeletal muscle from rats with right HF. METHODS: Right ventricle hypertrophy was induced by monocrotaline treatment (MCT; 60 mg/kg) in 6 rats, compared to saline control (CON; n=6). After 23±1 (mean, SD) days decompensated HF was verified by weight loss and clinical symptoms. Serial sections (10 μm) of the plantaris muscle were stained for ATPase activity (fiber type), succinate dehydrogenase (SDH) activity (oxidative capacity) and capillaries. Glycolytic and oxidative regions were analyzed separately and compared between conditions by two-way ANOVA. RESULTS: In MCT whole body and liver weights were less (p<0.01), and right ventricle and lung weights were greater (p<0.01) than CON. The plantaris was heavier in CON than MCT: 273±19 vs. 242±5 mg (p<0.05); but mean fiber cross-sectional area was not different: 2143±405 vs. 2045±287 μm2. The area occupied by type IIa fibers tended to be lower and the area of hybrid (IIa/x) fibers was significantly greater (p<0.05) in MCT. SDH activity was 15% lower in MCT independent of region and fiber type (p=0.06) and capillary to fiber ratio was greater in CON than MCT: 2.3±0.3 vs. 1.9±0.2 (p<0.05). CONCLUSIONS: As expected, there was a shift towards fast fatigable fibers in MCT treated rats. However, there was a similar reduction in SDH activity in both oxidative and glycolytic regions independent of fiber type, suggesting different remodeling pathways. The lower oxidative capacity in MCT was concurrent with a lower potential for diffusive O2 transport, as evidenced by fewer capillaries per fiber, but without fiber atrophy. These reductions in diffusive O2 transport and utilization may contribute to the energetic failure of skeletal muscles in right HF.

Progressive myopathy with a combined respiratory chain defect including Complex II

Biochemical defects in the respiratory chain are mostly associated with deficiencies in Complexes I, III and IV, caused by nuclear or mitochondrial DNA mutations. Combined defects including Complex II have been reported very rarely and have muscular symptoms as the main manifestation, including muscle weakness, exercise intolerance and myoglobinuria. We report a patient with a fatal progressive myopathy and muscle biopsy showing diffuse reduction in succinate dehydrogenase activity, ragged red fibers and intense lipid accumulation. Cytochrome c oxidase (COX) histochemistry demonstrated 30% of fibers with increased subsarcolemmal staining while 27% were COX negative. Western blotting analysis showed reduction in the expression of the 39 kDa subunit of Complex I, subunit II of Complex IV and the 70 kDa subunit of Complex II. Our findings suggest that the patient had a complex pattern of mitochondrial dysfunction affecting multiple respiratory chain complexes (I, II and IV) and fatty acid metabolism. This report adds a new histological pattern associated to combined deficiencies of respiratory chain with involvement of Complex II and shows that this disease may be fatal with a rapid progression.

Mitochondrial Toxin 3-Nitropropionic Acid Induces Cardiac and Neurotoxicity Differentially in Mice

We investigated the effects of 3-nitropropionic acid (3NPA), a previously characterized neurotoxin, in four strains of mice to better understand the molecular basis of variable host responses to this agent. Unexpectedly, we found significant cardiac toxicity that always accompanied the neurotoxicity in all strains of mice in acute and subacute/chronic toxicity testing. Caudate putamen infarction never occurred without cardiac toxicity. All mouse strains tested are sensitive to 3NPA although the C57BL/6 and BALB/c mice require more exposure than 129SVEMS and FVB/n mice. Cardiac toxicity alone was found in 50% of symptomatic mice tested and morphologically, the cardiac toxicity is characterized by diffuse swelling of cardiomyocytes and multifocal coagulative contraction band necrosis. In subacute to chronic exposure, atrial thrombosis, cardiac mineralization, cell loss, and fibrosis are combined with cardiomyocyte swelling and necrosis. Ultrastructurally, mitochondrial swelling occurs initially, followed by disruption of myofilaments. Biochemically, isolated heart mitochondria from the highly sensitive 129SVEMS mice have a significant reduction of succinate dehydrogenase activity, succinate oxygen consumption rates, and heart adenosine triphosphate after 3NPA treatment. The severity of morphological changes parallels the biochemical alterations caused by 3NPA, consistent with cardiac toxicity being a consequence of the effects of 3NPA on succinate dehydrogenase. These experiments show, for the first time, that 3NPA has important cardiotoxic effects as well as neurotoxic effects, and that cardiac toxicity possibly resulting from inhibition of the succinate dehydrogenase in heart mitochondria, contributes to the cause of death in 3NPA poisoning in acute and subacute/chronic studies in mice.

Cerebellar activities during visuo-motor learning: A functional MRI study

The hippocampus provides a suitable area in the brain for the analysis of neuronal plasticity after application of a selective lesioning technique. Using histochemistry and autoradiography, we studied synaptic reorganization in the rat hippocampus with selective CA1 pyramidal cell lesioning caused by transient forebrain ischemia after long-term survival. An autoradiographic study was performed on second messenger systems (3H]inositol 1,4,5-trisphosphate, [3H]forskolin and [3H]phorbol 12,13-dibutyrate binding). One-hundred days after ischemia, depletion of CA1 pyramidal cells and marked shrinkage of the CA1 subfield was noted in spite of unaltered thickness of the CA3 band and of the dentate molecular layers. Although neuronal density in the CA3 region of animals killed seven days after ischemia was not different from the normal group, 78% of animals showed neuronal loss of 30–50% in the stratum pyramidale of the CA3b 100 days after recirculation. Sixty-seven per cent of animals exhibited supragranular mossy fiber sprouting in the dentate gyrus. However, CA3 neuronal loss did not correlate with mossy fiber sprouting. Succinic dehydrogenase was depleted in the CA1 100 days after ischemia, and animals with CA3 damage showed a reduction of succinic dehydrogenase activity in the CA3. In contrast to the unaltered acetylcholinesterase in the animals killed seven days after ischemia, high density bands of acetylcholinesterase activity in the stratum pyramidale of the CA1 were found to be broadened 100 days after ischemia. In the CA1 subfield, subnormal activity of [3H]phorbol 12,13-ditutyrate and [3H]forskolin binding were observed in spite of the depleted [3H]inositol 1,4,5-triphosphate binding. [3H]Forskolin binding in the hilus had increased by 62% 100 days after ischemia, although binding in the stratum lucidum of the CA3 and in the stratum moleculare of the dentate gyrus was unaltered. However, no visible supragranular increase in [3H]forskolin binding was observed.These results indicate that long-term survival after CA1 pyramidal cell depletion caused by transient forebrain ischemia induced the modulation of neuronal activity and synaptic rearrangements in the whole hippocampal formation.

Heterogeneous distribution of early energy failure in experimental focal ischemia of the cat brain.

The distribution of succinate dehydrogenase (SDH) activity and the corresponding changes in specific gravity were studied in cats with experimental focal ischemia. Two hours of tandem occlusion of the middle cerebral artery (MCA) and the conunon carotid artery produced a scattered reduction of SDH activity and corresponding brain edema in the cortex. Recirculation ameliorated the SDH reduction and the scattered pattern disappeared, although the brain edema increased further. Four hours of focal ischemia resulted in diffuse reduction of SDH activity in the MCA-perfused area. The scattered area of SDH reduction after 2 hours of focal cerebral ischemia indicates that the ischemic core is multicentric in the early phase, and that these areas fuse together to form a well demarcated infarction, if the blood flow is not reestablished. A short period of cerebral ischemia produces multicentric small infarcts in the cortex, which resemble granular atrophy.

Variation and limitations in fiber enzymatic and size responses in hypertrophied muscle.

The present study was designed to determine whether the degree and kind of adaptation of a muscle fiber to a functional overload (FO) are determined by properties that are intrinsic to that fiber. The study also addresses the question of the capability of fibers to maintain a normal level of coordination of proteins per fiber as fiber volume changes dramatically. The plantaris muscle of six adult female cats was overloaded for 12 wk by bilateral synergist removal. Plantaris muscle fiber mean size doubled after FO, although some very small fibers that stained dark for adenosinetriphosphatase (ATPase) were observed in some of the FO muscles. There appeared to be no change in total succinate dehydrogenase activity per fiber. A reduction in succinate dehydrogenase activity per unit volume was observed in a substantial number of fibers, reflecting a disproportionate increase in fiber volume relative to mitochondrial volume. In contrast, total alpha-glycerophosphate dehydrogenase activity and actomyosin ATPase activity increased as fiber size increased, whereas there was no change in alpha-glycerophosphate dehydrogenase and ATPase activities per unit volume. Control and FO muscle fibers generally expressed either a fast or slow myosin heavy chain type, but in some cases FO muscle fibers expressed both fast and slow myosin heavy chains. The persistence of variability in fiber sizes and enzyme activities in fibers of overloaded muscles suggests a wide range in the adaptive potential of individual fibers to FO. These data indicate that a severalfold increase in cell size may occur without significant qualitative changes in the coordination of protein regulation associated with metabolic pathways and ATP utilization.

Lung adenocarcinoma is more sensitive than gastric adenocarcinoma to anticancer drugs in vitro : Kohnoe S, Moriguchi S, Emi Y, Sakaguchi Y, Maehara Y, Ishida T et al. Cancer Center, Kyushu University Hospital, Faculty of Medicine, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812. Eur J Surg Oncol 1991;17:47–50

The chemosensitivities of 26 lung adenocarcinoma tissues were compared to those of 110 gastric adenocarcinoma tissues, using the in vitro succinate dehydrogenase inhibition (SDI) test. Tumour tissues obtained at surgery were exposed to five different anticancer drugs: carboquone (CQ), adriamycin (ADM), mitomycin C (MMC), cisplatin (DDP) and 5-fluorouracil (5-FU). The lung adenocarcinomas showed a statistically significant reduction in succinate dehydrogenase (SD) activity, compared to the gastric adenocarcinomas, after exposure to each drug. The chemosensitivity was defined as a reduction in SD activity to 50% of control or less. Lesser degrees of reduction in SD activity were defined as drug resistance. The sensitivity rates to ADM, MMC and DDP, respectively, were significantly higher in the lung than in the gastric adenocarcinomas. Tumour cells from 22 (84.6%) of the 26 lung adenocarcinoma tissues showed a sensitivity to more than three drugs, whereas the rate was only 46.4% (51/110) for the gastric adenocarcinomas. The rate of resistance to all the drugs tested was 3.8% (1/26) for the lung adenocarcinomas, in contrast to the 20.9% (23/110) seen with the gastric adenocarcinomas. Thus, while adenocarcinomas of the lung and stomach both show clinical resistance to anticancer agents, the chemosensitivity of the lung tissues is greater. In the light of these observations, attention must be directed to improving specific drug delivery systems.

Post-ischemic synaptic plasticity in the rat hippocampus after long-term survival: Histochemical and autoradiographic study

The hippocampus provides a suitable area in the brain for the analysis of neuronal plasticity after application of a selective lesioning technique. Using histochemistry and autoradiography, we studied synaptic reorganization in the rat hippocampus with selective CA1 pyramidal cell lesioning caused by transient forebrain ischemia after long-term survival. An autoradiographic study was performed on second messenger systems ( 3H]inositol 1,4,5-trisphosphate, [ 3H]forskolin and [ 3H]phorbol 12,13-dibutyrate binding). One-hundred days after ischemia, depletion of CA1 pyramidal cells and marked shrinkage of the CA1 subfield was noted in spite of unaltered thickness of the CA3 band and of the dentate molecular layers. Although neuronal density in the CA3 region of animals killed seven days after ischemia was not different from the normal group, 78% of animals showed neuronal loss of 30–50% in the stratum pyramidale of the CA3b 100 days after recirculation. Sixty-seven per cent of animals exhibited supragranular mossy fiber sprouting in the dentate gyrus. However, CA3 neuronal loss did not correlate with mossy fiber sprouting. Succinic dehydrogenase was depleted in the CA1 100 days after ischemia, and animals with CA3 damage showed a reduction of succinic dehydrogenase activity in the CA3. In contrast to the unaltered acetylcholinesterase in the animals killed seven days after ischemia, high density bands of acetylcholinesterase activity in the stratum pyramidale of the CA1 were found to be broadened 100 days after ischemia. In the CA1 subfield, subnormal activity of [ 3H]phorbol 12,13-ditutyrate and [ 3H]forskolin binding were observed in spite of the depleted [ 3H]inositol 1,4,5-triphosphate binding. [ 3H]Forskolin binding in the hilus had increased by 62% 100 days after ischemia, although binding in the stratum lucidum of the CA3 and in the stratum moleculare of the dentate gyrus was unaltered. However, no visible supragranular increase in [ 3H]forskolin binding was observed. These results indicate that long-term survival after CA1 pyramidal cell depletion caused by transient forebrain ischemia induced the modulation of neuronal activity and synaptic rearrangements in the whole hippocampal formation.

Dose-effect of inorganic tin on biochemical indices in rats

The dose-effect of stannous chloride on biochemical indices was examined in weanling male rats given oral doses of 0.3, 1.0 and 3.0 mg/kg at 12-h intervals for 90 days. The 3.0 mg/kg dose caused significant decreases of the relative weights of the femur, calcium concentration, lactic dehydrogenase and alkaline phosphatase activities in the serum, succinate dehydrogenase activity in the liver, and calcium content and acid phosphatase activity in the femoral diaphysis and epiphysis. Of the above indices, the 1.0 mg/kg dose produced significant reduction of succinate dehydrogenase activity in the liver, and calcium content and acid phosphatase activity in the femoral epiphysis. Those significant decreases were not observed with the 0.3 mg/kg dose, although a slight but not significant decrease of calcium content in the femoral epiphysis was observed. These results suggest that the no-effect level of inorganic tin orally administered would be lower than 0.6 mg/kg/day.

Hyperbaric oxygen and succinic dehydrogenase in tubularian development.

1. Hyperbaric oxygen reduced deaths of tubularian embryos and larvae in standing seawater.2. Hyperbaric oxygen blocked differentiation at pressures of 2, 2½, 3 and 4 atmospheres absolute. At 1½ atmospheres it had little or no effect.3. The blockade occurred between 24 and 48 hours after early actinula or late basket stages were introduced into the chamber. The blocked embryos were unable to secrete holdfast material or produce perisarc.4. After 48 hours at 4 atmospheres the block was usually completely reversible during 24 to 36 hours after removal. Even after 72 hours a few blocked larvae attached and transformed into polyps when removed from the hyperbaric chamber.5. Histochemical visualization showed an overall reduction of succinic dehydrogenase activity in all embryos subjected to hyperbaric oxygen. Localized zones of high activity, which in controls were associated with the differentiation of tentacles, gonophore buds, perisarc-secreting region and adhesive organ, failed to develop.6. Since hyperbaric oxygen reversibly blocks certain enzyme systems but has no effect upon others, this method can prove useful in the biochemical analysis of developmental processes.

Use of a riboflavin homolog in the reduction of succinic dehydrogenase activity in tissues of healthy rats

Administration of 7-ethyl-8-methyl-10-(1- d-ribityl)isoalloxazine to weanling rats as their only source of flavin permits a normal rate of growth and development. A concomitant rapid and extensive loss of succinic acid dehydrogenase activity from the liver has been observed without any apparent influence on the animals' health. The loss of enzyme activity in the heart and kidney is not as rapid or as extensive as that in the liver. The livers of rats maintained on a riboflavin-deficient diet until they are near death also show a loss of enzyme activity, but no loss is observed for the hearts and kidneys. The administration of a mixture of flavins consisting of 93% of the homolog and 7% of riboflavin maintains the enzyme activity at higher levels than is found in animals receiving the homolog alone. The health of the animals receiving the homolog is indistinguishable from that of the animals receiving equivalent amounts of riboflavin.