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PubMed1977

[Alkali treatment of proteins. I. Behavior of sulfhydryl and disulfide groups in alkali-treated beta-lactoglobulin and alpha-lactalbumin].

The alkali treatment of beta-lactoglobulin and alpha-lactalbumin results in the splitting of disulphide bonds in the protein molecules. When a 0.8-10(4) M beta-lactoglobulin solution in a 0.022 N sodium hydroxide solution (pH = 12) is heated at 90 degrees C for 30 min, 0-4 M disulphide groups, 2.2 M sulfhydryl groups and 1.8 M sulphide ions/M dimeric beta-lactoglobulin are detectable of the total of 4 M disulphide groups and 2 M sulfhydryl groups/M dimeric beta-lactoglobulin. The sulphide ions can be determined directly in the form of hydrogen sulphide or by calculating the difference between the values from the amperometric-argentometric titration and those from the method of ELLMAN (reaction with DTNB). The disulphide groups are determined with the aid of DTNB after reduction with sodium borohydride. The sulfhydryl groups obtained by reduction with sodium borohydride re-oxidize, the reaction velocity being of the second order. If the disulphide groups are reduced with sodium borohydride, the argentometric-amperometric determination of the sulfhydryl groups by means of the platinum rotating-disk electrode is disturbed by the presence of boric acid.

Chemical Phenomena↗
PubMed1978

Mean activity coefficients for the simple electrolyte in aqueous mixtures of polyelectrolyte and simple electrolyte. V. Common counterion mixtures of alkali-metal dextransulfates with alkali metal chlorides.

Mean molal activity coefficients of simple electrolyte in aqueous solutions of Li, Na, K or Cs salts of dextransulfate (DS) with added LiCl, NaCl, KCl or CsCl are reported. The measurements were carried out by means of an electrochemical cell method using a cation exchange membrane as cation selective electrode and Ag/AgCl electrodes. For LiDS-LiCl, NaDS-NaCl and CsDS-CsCl systems the polymer concentration, mp, was varied from 0.0088 to 0.113 m and at a given mp the ratio X of the polymer to salt concentration was varied from 0.5 to 16. Due to the insolubility of KDS in high concentration of KCl, the measurements on KDS-KCl system were performed in the mp range of 0.0088--0.089 m and some of the smaller X values were omitted. The activity coefficient results are compared to Manning's limiting laws, the additivity rule, and to new limiting laws. The additivity rule can give an excellent representation of the data for all mp values when gammap is used as an adjustable parameter.

Chemical Phenomena↗
PubMed1978

Attainment and maintenance of normal stature with alkali therapy in infants and children with classic renal tubular acidosis.

Growth was evaluated in a group of 10 infants and children with familial or idiopathic classic renal tubular acidosis in whom alkali therapy was initiated at ages ranging from 8 days to 9.5 yr and administered at dosage schedules documented to sustain correction of acidosis in at least four prolonged observation periods on the Pediatric Clinical Research Ward. When alkali therapy was begun, six patients (four infants and two children) were stunted (height <2.5 SD below mean). Of the four who were not, two infants were too young (<2 wk of age) to have become stunted, and two children had been documented earlier to be nonacidotic. At the start of alkali therapy, the heights of the patients correlated inversely with the maximal possible duration of prior acidosis. WITH SUSTAINED ALKALI THERAPY: (a) each patient attained and maintained normal stature; (b) the mean height of the 10 patients increased from the 1.4+/-4 to the 37.0+/-33 percentile (of a normal age- and sex-matched population); (c) the mean height reached the 69th percentile in the eight patients whose heights could be analyzed according to parental prediction (Tanner technique); (d) the rate of growth increased two- to threefold, and normal heights were attained within 6 mo of initiating alkali therapy in the stunted infants and within 3 yr in the stunted children; (e) the height attained correlated inversely with the maximal possible duration of acidosis (before alkali therapy) only in those patients in whom alkali therapy was started after 6 mo of age, and not in those treated earlier. The amount of alkali required to sustain correction of acidosis increased substantially during the course of treatment in each patient. The maximal alkali requirement ranged from 4.8 to 14.1 meq/kg per day, and in each patient its amount was determined principally by the magnitude of renal bicarbonate wasting.

Acidosis, Renal Tubular↗
PubMed2026

Physiological and transcriptomic responses of sunflower to combined saline-alkali stress.

BACKGROUND: Sunflower (Helianthus annuus L.), an important oilseed crop, is often used as a pioneer species for improving saline-alkali soils. However, the molecular mechanisms underlying sunflower seedling responses to combined saline-alkali stress remain unclear. This study aimed to elucidate the molecular basis of saline-alkali tolerance at the seedling stage by comparing physiological and transcriptomic responses between tolerant and sensitive sunflower hybrids. The saline-alkali tolerant hybrid K-27 and the sensitive hybrid K-7 were used as experimental materials. Root samples were collected at 0, 3, 12, 24, 48, and 96 h after exposure to combined saline-alkali stress (0.5% NaCl + Na2CO3, adjusted to pH 9.0). Physiological parameters, including antioxidant enzyme activities, osmolyte contents, ion concentrations, membrane damage levels, and cell wall components, were measured, followed by transcriptome sequencing analysis. RESULTS: Phenotypic analysis showed that the root length inhibition rate and fresh weight loss rate of K-27 were significantly lower than those of K-7, indicating stronger tolerance. Physiological analysis revealed that K-27 exhibited an inducible antioxidant enzyme response pattern. In addition, K-27 achieved osmotic adjustment through sustained proline accumulation (peaking at 12 h and remaining significantly higher than that of K-7 at 96 h) and exhibited higher basal levels of lignin and hemicellulose. Transcriptome analysis showed that the number of upregulated genes in K-27 was consistently higher than in K-7 at all time points, with 5,283 genes upregulated as early as 3 h after stress exposure. Venn analysis identified 44 core differentially expressed genes (cDEGs) shared between the two genotypes, which were mainly enriched in auxin biosynthesis regulation, phenylpropanoid biosynthesis, and glutathione metabolism. Among them, the benzoic acid carboxyl methyltransferase gene (BAMT) was continuously upregulated in K-27 but persistently downregulated in K-7. In addition, five other genes (encoding fatty aldehyde dehydrogenase, pectin methylesterase inhibitor, glutathione S-transferase, INPP5E, and HXXXD-type acyltransferase) exhibited significantly higher expression levels in K-27. CONCLUSION: K-27 tolerates combined saline-alkali stress through coordinated multi-layered response mechanisms, including inducible antioxidant defense, maintenance of ion homeostasis, sustained osmotic adjustment, and activation of the phenylpropanoid metabolic pathway. Candidate genes such as BAMT may provide potential targets for molecular breeding of saline-alkali tolerant sunflower, although their functions require further experimental validation.

Helianthus↗
PubMed1978

Alkali-labile sites and post-irradiation effects in single-stranded DNA induced by H radicals.

Single-stranded phiX174 DNA in aqueous solutions has been irradiated in the absence of oxygen, under conditions in which only H radicals react with the DNA. It was shown that H radical reactions result in breaks, which contribute approximately 10 per cent inactivation. Further, two types of alkali-labile sites are formed. One is lethal and gives rise to single-strand breaks by alkali and is most probably identical with post-irradiation heat damage and contributes about 33 per cent to the inactivation mentioned above. The other consists of non-lethal damage, partly dihydropyrimidine derivatives, and is converted to lethal damage by alkali. This follows from experiments in which the DNA was treated with osmium-tetroxide, which oxidizes thymine to 5,6-dihydroxy-dihydrothymine. Treatment with alkali of this DNA gives the same temperature dependence as found for the non-lethal alkali-labile sites in irradiated DNA. A similar temperature dependence is found for dihydrothymine and irradiated pyrimidines with alkali.

Alkalies↗
PubMed2026

Functional study of the AfRAP2 gene in Amorpha fruticosa L. tolerance to saline-alkali and drought stress.

BACKGROUND: Amorpha fruticosa L. is a leguminous shrub with high tolerance to drought, poor soil, and saline-alkali stress conditions. As a member of the family of transcription factors in higher plants, the ethylene response factor AP2/ERF plays a crucial role in both plant adaptation to abiotic stress and in growth and development. In this study, based on genes identified from the transcriptomic sequencing of Amorpha fruticosa L. under drought stress, the upregulated gene AfRAP2 was isolated from its seedlings, with the aim of elucidating its stress-response function using molecular biological techniques. RESULTS: In this study, the AfRAP2 gene was cloned from the leaves of Amorpha fruticosa L. using RT-PCR. Bioinformatics analysis revealed that AfRAP2 contains an AP2 domain and belongs to the DREB subfamily of the AP2/ERF transcription factor family, showing close phylogenetic relationships with LaEREBP from Lathyrus albus. Real-time quantitative PCR (RT-qPCR) results indicate that AfRAP2 is expressed in various tissues of Amorpha fruticosa L., with the highest expression in leaves and the lowest in stems, furthermore, its expression is significantly upregulated in roots and leaves upon induction by NaHCO3 and PEG6000. Subcellular localization experiments confirmed that the AfRAP2 protein is localized to the nucleus, and GUS histochemical staining assay revealed that its promoter drives GUS expression in anthers. Resistance analysis of overexpressing yeast strains showed that yeast transformed with the AfRAP2 gene exhibited significantly better growth under sorbitol, mannitol, and NaHCO3 stress conditions compared to the control, indicating that this gene enhances yeast tolerance to drought and saline-alkali stress. We screened transgenic tobacco and Populus davidiana &#xd7; P. alba var. Pyramidalis. The results showed that under natural drought and saline-alkali stress treatments, the transgenic lines exhibited significantly improved growth and higher activities of the physiological indicators of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) compared with wild-type plants, indicating that the overexpression of the AfRAP2 gene plays a key role in the response to saline-alkali stress and drought stress. CONCLUSION: In summary, AfRAP2 contains an AP2 domain and belongs to the DREB subfamily of transcription factors, under abiotic stress induced by NaHCO&#x2083; and mannitol, it can induce the expression of the AfRAP2 gene in tobacco and Populus davidiana&#xd7;P. alba var. pyramidalis. AfRAP2 plays a vital role in the plant response to saline-alkali stress and drought stress and is a promising candidate gene for stress-tolerant breeding.

Plant Proteins↗
PubMed2026

Comprehensive characterization of the genes in AP2/ERF family and their involvement in salt-alkali stress response during Nelumbo nucifera seed germination.

Nelumbo nucifera Gaertn. is an economically and ecologically important aquatic plant, but its growth and productivity are severely constrained by soil salinization and alkalization. AP2/ERF transcription factors are key regulators of plant abiotic stress responses; however, their roles in salt-alkali tolerance in N. nucifera remain largely unclear. In this study, we performed a genome-wide identification and characterization of the AP2/ERF gene family in N. nucifera, followed by phylogenetic, structural, and physicochemical analyses. A total of 101 AP2/ERF genes were identified and classified into five subfamilies, showing both evolutionary conservation and species-specific divergence compared with Arabidopsis thaliana. Physiological analyses during seed germination under salt-alkali stress revealed significant changes in malondialdehyde content, proline accumulation, and antioxidant enzyme activities, suggesting activation of oxidative stress defense and osmotic adjustment mechanisms. Transcriptome profiling of seedlings treated with 150 mM salt-alkali solution for 5 and 10 days identified 7,350 differentially expressed genes, including 29 AP2/ERF members responsive to stress. Among them, 13 genes, including AP2-9, ERF23, ERF15, ERF31, ERF34, and DREB21, were consistently upregulated under both treatments, indicating their potential roles in stress adaptation. qRT-PCR validation further confirmed the sustained upregulation of key genes AP2-9, ERF23, ERF34, and DREB21, consistent with transcriptome data. Overall, this study provides the first comprehensive overview of the AP2/ERF gene family in N. nucifera and identifies candidate regulators involved in salt-alkali stress responses, offering valuable insights into the molecular mechanisms of stress adaptation and potential genetic resources for breeding salt-alkali tolerant aquatic plants.

AP2/ERF transcription factors↗
PubMed1975

The modifications of the final stages of the complement reaction by alkali metal cations.

We studied the effects of alkali metal cations on the terminal stages of complement lysis of human and sheep HK erythrocytes. Sensitized erythrocytes (EA) were reacted with limited amounts of complement for 1 hr at 37 degrees C in buffer containing 147 mM NaCl (Na buffer), which resulted in 10-40% lysis. The unlysed cells were washed with Na buffer at 0-2 degrees C and incubated for 1 hr at 37 degrees C in buffers containing 147 mM of the various alkali metal cations. Although additional lysis (25 to 65%) occurred with K, Rb, or Cs buffer, only minor degrees developed with Na or Li buffer, only minor degrees developed with Na or Li buffer. Intermediate levels occurred with 100 mM of the divalent alkali cations. Halogen ions and SCN-(147 MM), Ca++ (0.15mM), and Mg++ (0.5 mM) did not alter the effect of the alkali metal cations. Lysis occurring in K+, Rb+ or Cs+ proceeded without lag, was temperature dependent with an optimum of 43 degrees C, and had a pH optimum of 6.5. Lysis in K and Na buffers was unaffected by 10(-3) to 10(-5) M ouabain. Experiments with mixtures of cations indicated that Na+ had a mild inhibitory effect that could be totally overcome by K+, partially by Rb+, and not at all by Cs+. Li+ had a strong inhibitory effect, 6 X 10(-5) M causing 50% inhibition in buffers containing 147 mM K+, Rb+, or Cs+. By using intermediate complexes of EA and purified complement components we demonstrated that K+ enhances the lytic action of C8 on EAC1-7 as well as that of C9 on EAC1-8. It was known that Li+ facilitates lysis when acting on the entire complement reaction. We found that Li+ enhanced the lytic action of C8 on EAC1-7, with a kinetic that differed from that of the K+ effect. In addition, Li+ inhibited the enhancing effect of K+ upon lysis of EAC1-8 by C9. This occurred at concentration of Li+ similar to those which inhibited the additional lysis by K+, Rb+, and Cs+ of cells that were pretreated in Na buffer with the entire complement sequence. We propose that the major effects of alkali metal cations on complement lysis are due to their interaction with C8 and/or membrane constitutes.

Adenosine Triphosphate↗
PubMed1977

Biological effects of alkali-treated protein and lysinoalanine: an overview.

The renal alterations induced by alkali-treated protein and lysinoalanine are reviewed and their biological implications discussed. Alkali-treated proteins and lysinoalanine, an unusual amino acid formed in proteins during alkali treatment, have been shown to produce a renal alteration characterized by nuclear and cytoplasmic enlargement, with alterations in DNA synthesis, mitotsis and nucleoprotein. These changes are localized in the straight portion of the proximal renal tubule and have been observed in rats but not in several other species. The nephrotoxic effect of synthetic lysinoalanine has been consistently demonstrated, but the ability of alkali-treated protein to induce renal alterations is apparently modified by factors other than lysinoalanine content. Factors which may influence the development of the kidney lesions in animals fed alkali-treatment protein are discussed, including nutritional factors, the chemical form of lysinoalanine in the protein, species differences, and metabolic fate. Other clinical and experimental conditions that result in similar renal alterations are presented for comparison with the lysinoalanine induced lesion, and possible functional consequences are considred.

Alanine↗
PubMed1979

Site specificity of bleomycin-mediated single-strand scissions and alkali-labile damage in duplex DNA.

Form II PM2 DNA, which contained bleomycin-mediated single-strand breaks, was purified and treated with the extracellular endonuclease from Alteromonas BAL 31. This enzyme cleaves the phosphodiester backbone opposite a single-strand break to yield a double-strand break. The locations of these double-strand breaks were determined relative to the cleavage sites produced by the restriction enzyme HindIII. The experimental procedure was as follows. Form I PM2 DNA was treated with bleomycin to produce alkali-labile bonds. These were hydrolyzed by alkali treatment and the DNA, now containing single-strand breaks, was purified and treated with the BAL 31 enzyme and the HindIII enzyme to determine the positions of the original alkali-labile bonds. It was found that the single-strand breaks and alkali-labile bonds were introduced at preferred sites on the PM2 genome, since electrophoretic analyses of the DNA after the HindIII digestion revealed DNA bands of discrete sizes. The molecular weights of the DNA fragments produced by these treatments indicate that single-strand breaks and alkali-labile bonds occur at the same sites as those previously determined for direct double-strand scissions introduced by bleomycin at neutral pH. Some of the specific sites of double-strand scissions mediated by bleomycin at neutral pH (Lloyd et al., 1978b) are also shown here to be relatively more reactive than other sites when the DNA contains superhelical turns.

Bacteriophages↗
PubMed1978

Treating heartburn in pregnancy: comparison of acid and alkali mixtures.

A randomised crossover trial was performed in 55 pregnant women who complained of heartburn to see whether alkali or acid treatment alleviated it. Each woman was given a week's treatment with an acid mixture, an alkali mixture, and a placebo in randomised order. Both acid and alkali mixtures were better than placebo, but there was no significant difference between the acid and alkali treatments. Together with the inconsistent reports of some patients, these findings suggest that both acid reflux and bile regurgitation may cause heartburn in pregnant women and that other factors may also play a part. Because the cause of heartburn may be difficult to determine, treatment should be empirical. If the patient does not respond to seven days' acid treatment an alkali mixture should be prescribed; there is a 98% chance that one of these treatments will relieve symptoms.

Bicarbonates↗
PubMed1975

Membrane potential and conductance during pinocytosis induced in Amoeba proteus with alkali metal ions.

An investigation of the relationship between the polarized state of the membrane and the onset and the intensity of pinocytosis was made in Amoeba proteus. Membrane potential and input resistance was in all instances found to decrease in approximate proportion to the number of channels when pinocytosis was induced by a variety of alkali metal ions at varying pH. Channels began to appear when the membrane was depolarized to -30 mV by the inducer of pinocytosis. With all inducers the maximum pinocytosis was encountered at membrane potentials close to zero. No positive potentials were recorded when the chloride salts of the inducing cations were used. At high concentrations of alkali ions a transient increase of the chloride permeability caused short-lasting hyperolarizations of the membrane. Inhibition of pinocytosis by Ca++ was accompanied by an increase of input resistance and membrane potential. The selectivity of the membrane to different alkali metal ions observed as changes in pinocytosis intensity, membrane potential and input resistance was found to vary with the concentration of the inducer and with the Ca++ concentration of the extracellular solution. Displacement of membrane bound Ca++ appeared to decrease the field strength of charged groups in the membrane altering its selectivity among alkali cations. The formation of pinocytotic channels is suggested to require translocation of Ca++ from the membrane into the cell and would therefore be closely related to the electrical properties of the amoeba.

Alkalies↗
PubMed1979

Pepsin 5 in gastric juice: determination and relationship to the alkali-stable peptic activity.

Pure human pepsins 1 and 3 are inactivated by incubation at pH 7.1-7.3 for 30 minutes, losing 90% or more of activity. Pepsin 5 is alkali-stable, retaining 100% of activity. Mixtures of pure pepsins 1 and/or 3 with pepsin 5 were found to have greater alkali-stable activity than predicted. Two published methods for determining the alkali-stable fraction of the peptic activity of gastric juice gave, respectively, in our hands values of 45.4-80.0% and 27.5-43.9% of the total activity. These values seemed too high to be attributable only to pepsin 5 in gastric juice, as agar gel electrophoresis shows pepsin 3 to have the principal activity. Electrophoretograms of alkaline incubated gastric juice revealed that large amounts of pepsin 3 retained activity as well as pepsin 5, and a proteolytic zone "4" appeared between them. Alkali inactivation thus does not allow the estimation of pepsin 5 individually in gastric juice. Pepstatin, at a final concentration of 100 to 170 pmol/ml, may be used to estimate pepsin 5 in gastric juice and gave values of 18.0 to 27.6% of the total peptic activity. Pepsin 5, in gastric juice and in mixtures of pepsins, appears to protect pepsin 3 from alkaline-inactivation, and to a lesser extent from pepstatin inhibition.

Alkalies↗
PubMed2026

Characterization of oxidative status in maize protoplasts under temperature and saline-alkali stresses.

BACKGROUND: Protoplasts have emerged as a powerful model system in plant functional genomics, offering significant utility in functional gene analysis, protein interaction studies, and transient expression platforms for gene editing. Despite their versatility, inherent limitations restrict their broader application, highlighting the need for systematic investigations into their responses to abiotic stressors, such as temperature fluctuations and saline-alkali conditions (200 mM saline mixture: 170mM NaCl and 30mM Na2CO3, pH&#x2009;=&#x2009;9.1). RESULTS: In this study, we comprehensively examined the effects of varying temperatures and saline-alkali stress on the integrity, viability, and reactive oxygen species (ROS) metabolism of maize protoplasts. Key markers of oxidative stress-including ROS accumulation, lipid peroxidation (measured as malondialdehyde, MDA), antioxidant enzyme activity (superoxide dismutase, SOD), and hydrogen peroxide (H2O2) levels-were quantified to assess the oxidative stress response. Protoplasts maintained at 4&#xa0;&#xb0;C demonstrated enhanced stability and antioxidant capacity, preserving cell viability and endogenous protein integrity for up to 16&#xa0;h. Conversely, exposure to 37&#xa0;&#xb0;C significantly compromised protoplast viability, while incubation at 28&#xa0;&#xb0;C exerted minimal effects within 16&#xa0;h. CONCLUSIONS: Our study investigated the effects of various temperature stresses and salt-alkali stress on maize protoplasts. The results demonstrated that both temperature and salt-alkali stress significantly impacted protoplast production, viability, and the expression of endogenous proteins. These findings not only characterize the redox response of maize protoplasts, but also provide guidance for protoplast isolation and other procedures: 4&#xa0;&#xb0;C is suitable for short-term maintenance, 25-28&#xa0;&#xb0;C for routine functional assays, and 37&#xa0;&#xb0;C should be avoided. These findings provide valuable insights into the stress responses of protoplasts and establish a foundation for future research aimed at improving plant stress tolerance through protoplast-based techniques.

Zea mays↗
PubMed1976

Effects of alkali-treated proteins: feeding studies with free and protein-bound lysinoalanine in rats and other animals.

To find out whether alkali-treated proteins posses nephrotoxic properties, feeding studies were conducted with drastically treated soybean protein and casein, and also with lysinoalanine (LAL), the amino acid known to be formed in protein subjected to high pH at elevated temperature. The feeding of synthesized LAL to rats at dietary levels of 100 ppm and above induced typical renal changes, called nephrocytomegalia. No such changes or any other indications of toxicity were observed, however, upon feeding much higher levels of LAL (up to 6,000 ppm) when provided as the protein-bound compound in alkali-treated casein or soybean protein. When set free by complete acid hydrolysis, LAL induced considerable renal activity, comparable to that of the synthetic compound. These results indicate that alkali treatment of proteins does not induce nephrotoxic properties provided that the compound remains protein-bound. Some nephrotoxic activity was observed, however, with peptide-boound LAL in break-down products (molecular weight less than 5,000) of alkali-treated casein, but considerably less than that of the free compound. LAL-analyses in blood, urine, and feces of rats fed free or protein-bound LAL indicated a positive correlation between intestinal absorption and nephrotoxic potential. No renal changes were encountered upon feeding diets with 1,000 ppm synthetic LAL to mice, hamsters, rabbits, quail, dogs or monkeys, which suggest a species specificity of LAL-induced renal changes in rats.

Animals↗
PubMed1977

Molecular architecture of cytochrome oxidase and its transition on treatment with alkali or sodium dodecyl sulfate.

In dimeric cytochrome oxidase [EC 1.9.3.1], one of the two heme a molecules of one monomeric unit has been proposed to be converted by the other unit, thus becoming latent in terms of catalytic functions (1). As the dimer was split into two monomers by treatment with alkali or sodium dodecyl sulfate (SDS), it was shown that the intensity of circular dichroism (CD) in the Soret region due to heme a decreased, probably reflecting release of the strain on the latent heme. On the other hand, the profile of magnetic circular dichroism (MCD) was nearly unchanged during this conversion, except for a weakening of the signal due to deprotonation of the heme during the alkali treatment. When the monomer was further dissociated into constituent subunits in strong alkali or at high concentrations of SDS, the CD spectrum disappeared almost completely, indicating loss of the asymmetric interactions of the chromophoric heme a with its immediate environments, consisting of the subunit assembly. The MCD pattern also suffered a small change as the dissociation proceeded, and a specific pattern appeared as the Schiff base was finally formed. The Schiff base formation of cytochrome oxidase in strong alkali proceeded in two steps whether the heme iron was in the oxidized or reduced state. As a consequence of the initial rapid reaction, the enzyme was suggested to have been disintegrated into constituent subunits with heme a being attached nonspecifically to either one, and structural characteristics dependent on the redox state were completely lost. The Arrehenius plot for this rapid change showed a break, indicating a transition in the structure of the cytochrome oxidase assembly, although no such phenomenon was observed during the slow reaction. Activation parameters in the rapid and slow reactions for the oxidized and reduced oxidase are given. Based on these findings, as well as other considerations, a molecular architecture of this enzyme is proposed; the role of heme a in anchoring four 14,000-dalton polypeptides into the minimal functional unit catalyzing the aerobic oxidation of ferrocytochrome c is emphasized.

Circular Dichroism↗
PubMed1976

Myocardial ischemia and cell acidosis: Modification by alkali and the effects on ventricular function and cation composition.

Myocardial cell pH was measured with 5, 5 dimethyl-2, 4-oxazolidinedione (DMO) in intact anesthetized dogs by a transient indicator dilution technique. Bolus injections of labeled DMO, vascular, extracellular and water indicators were made into the left anterior descending coronary artery, and blood samples were collected from the great cardiac vein. The steady state distribution of DMO between cells and plasma was calculated from the mean transit times of the indicator. Normal myocardial cell pH averaged 6.94 and changed by 58% of the concomitant alterations in plasma pH after infusions of acid or alkali. Myocardial ischemia induced by inflation of a balloon tip catheter in the left anterior descending coronary artery resulted in progressive decreases in cell pH to 6.59 by 1 hour. Infusions of sodium carbonate diminished intracellular acidosis. Hemodynamic studies during 4 hours of ischemia with blood pH at 7.55 to 7.60 indicated a significantly reduced left ventricular end-diastolic pressure and increased stroke volume by comparison with findings in animals given infusions of saline solution. Ventriculograms revealed improved wall motion in the ischemic segment after infusion of alkali. Precordial mapping showed a significant reduction in the number of leads with S-T segment elevation as well as in the sum of S-T segment elevations, but R wave amplitudes did not differ from those in control studies. Calculations of extracellular space, tissue water and cation content revealed a reduced gain of cell sodium ion and loss of cell potassium ion during ischemia after alkali treatment. The latter may account for the S-T segment responses, whereas enhanced ventricular performance may be related to reduced competition of hydrogen ion with calcium ion for binding sites on contractile protein.

Acidosis↗