Effects of High Concentrations of KC1 and NaCl on Responses of Malate Dehydrogenase (Decarboxylating) to Malate and Various Inhibitors

1974 ◽  
Vol 1 (1) ◽  
pp. 15 ◽  
Author(s):  
H Greenway ◽  
AP Sims
Keyword(s):  
Malate Dehydrogenase ◽  
Active Sites ◽  
Substrate Inhibition ◽  
Maximum Velocity ◽  
Inhibitory Effect ◽  
The Other ◽  
Appreciable Change ◽  
Other Hand ◽  
The Hill ◽  
Hill Number

The effects of KC1 on catalytic and allosteric properties of malate dehydrogenase (decarboxylating) were studied. Chloride salts (50 mM and higher) strongly inhibited enzyme activity at low malate concentrations. At high malate (4 mM) , on the other hand, the degree of inhibition induced by chloride was very small. The s0.5 value (i.e. the malate concentration required for half maximum velocity) was about 0.4 mM in the absence of KC1 and increased to 0.75 and 1.5 mM at 50 and 100 mM KC1 respectively. High chloride concentrations also removed a small degree of substrate inhibition, which in the absence of KC1 occurred at 8 mM malate. At low malate concentrations (< 0 . 5 mM) 50 mM KC1 increased the Hill number from 1.3 to 1.9. Thus chloride treatment revealed a strong degree of cooperativity for the enzyme. This potential for homotropic effects was much less realized in MES buffer (potassium salt), presumably because affinity of malate for individual active sites was already very high. These effects of KC1 were readily reversible and the enzyme showed no appreciable change in molecular weight in the presence of 200 mM KCl. At malate concentrations between 1 and 12 mM, inhibitions of malate dehydrogenase (decarboxylating) activity induced by oxaloacetate, D-malate, and phosphoglycerate were reduced by KCl. At low malate concentrations, on the other hand, the inhibitory effect induced by oxaloacetate changed to a strong stimulatory effect in the presence of KCl. The inhibitory effect due to oxaloacetate was greatly diminished in malate dehydrogenase (decarboxylating) which was eluted from a DE52 cellulose column, but the inhibitory effect due to KC1 was retained. Elution from DE52 cellulose also reduced the Hill number to 1 and increased the s0.5 value. The above results suggest that KC1 reduced the affinity of both substrate and some allosteric inhibitors of malate dehydrogenase (decarboxylating).

II.—Physiographical Studies in Lakeland

1894 ◽  
Vol 1 (11) ◽  
pp. 489-492 ◽  
Author(s):  
J. E. Makk
Keyword(s):  
The Other ◽  
Alluvial Valley ◽  
Other Hand ◽  
The Hill

When working amongst the rocks of Lakeland, one is often confronted with problems connected with the superficial features of the country, and as some of these are of more than local interest I propose to notice them from time to time.Church Beck, flowing in a south-easterly direction from the eastern slopes of the Old Man range, passes through Coniston Valley to discharge its waters into the head of Coniston Lake, not far from the point of entrance of the more important Yewdale Beck, which flows through the wide valley of Yewdale in a southerly direction. Church Beck, on the other hand, flows through, an upland valley, and is joined by the union of Low Water, Lever's Water, and the Red Dell Becks. Walking up its banks from Coniston Village, one presently comes upon an exposure of the Skelgill graptolitic shales at a height of about 225 feet above sealevel. Above this, one rapidly mounts the hill, and passing a considerable waterfall, reaches Gill Head Bridge at a height of about 540 feet. Above this is an alluvial flat extending to the Coniston copper works at the junction of the Red Dell Beck with that formed by the union of Lever's Water and Low Water Becks. The bottom of this alluvial valley is occupied by stratified deposits, formed by the washings of the copper works, which will, of course, not be confused with the much older deposits about to be described.

COMPARISON OF THE ANTI-FERTILITY AND SEX HORMONAL ACTIVITIES OF SEX HORMONES AND THEIR DERIVATIVES

1964 ◽  
Vol 47 (3) ◽  
pp. 444-456 ◽  
Author(s):  
P. A. Desaulles ◽  
C. Krähenbühl
Keyword(s):  
Sex Hormones ◽  
Relative Intensity ◽  
Sex Steroids ◽  
Inhibitory Action ◽  
Inhibitory Effect ◽  
The Other ◽  
Potent Effect ◽  
Other Hand ◽  
Activity Ratios ◽  
Blastocyst Implantation

ABSTRACT The following effects exerted by sex steroids were measured: androgenic, oestrogenic, and progestational effects; the inhibition action on gonadotrophic function in castrated animals; and the inhibitory action on ovulation and blastocyst implantation in intact animals. The steroids investigated consisted of oestradiol and its ethinyl and methoxyethinyl derivatives, oestrone, oestriol, testosterone, progesterone, and certain synthetic gestagens derived from nortestosterone, i. e. norethisterone, norethynodrel, and ethinyl-oestrenol. Oestradiol and its derivatives show potent anti-gonadotrophic activity, a relatively less potent anti-ovulatory effect, and a marked inhibitory action on implantation. Progesterone, on the other hand, which has only a very weak inhibitory effect on gonadotrophic function, shows an anti-ovulatory activity which, though inferior in absolute terms to that of oestradiol, is still appreciable, whereas it exerts almost no effect at all on implantation. With regard to its activity ratios, testosterone occupies a position mid-way between the two female hormones. Norethisterone, norethynodrel, and ethinyl-oestrenol have a more potent effect on gonadotrophic function than progesterone. The activity ratios for the effects of these three compounds on ovulation and implantation are comparable to those of oestradiol or progesterone, depending on the relative intensity of their oestrogenic and progestational action. The nature of the endocrine changes produced by these compounds are discussed with reference to the inhibition of ovulation and implantation.

Cooperative Binding of the Organophosphate Paraoxon to the (Na+ + K+)-ATPase

1995 ◽  
Vol 50 (9-10) ◽  
pp. 660-663 ◽  
Author(s):  
Janusz Blasiak
Keyword(s):  
Active Sites ◽  
Microsomal Fraction ◽  
Inhibitory Effect ◽  
Hill Coefficient ◽  
Cooperative Binding ◽  
Enzyme Protein ◽  
The Hill ◽  
The Relationship ◽  
Dose Dependent ◽  
Substrate Kinetics

Abstract Paraoxon. the main active metabolite of the organophosphorus insecticide parathion. exerted a dose-dependent inhibitory effect on the activity of pig kidney (Na+ + K+)-ATPase contained in microsomal fraction and purified from it. Substrate kinetics studies revealed the existence of two active sites with high and low affinity to ATP. The Dixon analysis of the mode of the inhibition indicated its noncompetitive character. The purified enzyme was more affected than enzyme contained in the microsomal fraction. The inhibition constant K, ranged from 73 to 246 μm depending on the type of preparation. The Hill coefficient (n) fulfilled the relationship 1<n<3. These properties of the interaction suggest the cooperative binding of paraoxon to the enzyme. An indirect mechanism of the interaction was proposed: paraoxon could inhibit the activity of the (N a+ + K+)-ATPase by excluding the enzyme protein from its normal lipid milieu

Malate dehydrogenase from thermophilic Humicola lanuginosa and Mucor pusillus: purification and comparative properties of the enzymes with differing thermostabilities

1984 ◽  
Vol 62 (7) ◽  
pp. 559-565 ◽  
Author(s):  
Anupam S. Wali ◽  
Autar K. Mattoo
Keyword(s):  
Malate Dehydrogenase ◽  
Conformational Changes ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
The Other ◽  
Heat Inactivation ◽  
Ph Optimum ◽  
Molecular Weights ◽  
Other Hand ◽  
Humicola Lanuginosa

Malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37) was purified from the thermophiles Humicola lanuginosa and Mucor pusillus. The H. lanuginosa enzyme was homogeneous on sodium dodecyl sulphate – polyacrylamide gels, while the M. pusillus enzyme was more than 95% pure. The two enzymes appeared to be composed of two subunits of equal size, each of 36 000 daltons (H. lanuginosa) or 33 000 daltons (M. pusillus). The native enzymes revealed molecular weights of 68 000 as determined by gel filtration. The isoelectric points of malate dehydrogenase from H. lanuginosa and M. pusillus were 3.9 and 4.2, respectively. The reduction of oxaloacetate by the H. lanuginosa enzyme was optimum at pH 8.5–9 with apparent Km's of 0.12 mM for oxaloacetate and 0.027 mM for NADH. On the other hand, M. pusillus enzyme snowed a pH optimum of 7.8–8.5 with apparent Km's of 0.075 mM for oxaloacetate and 0.1 mM for NADH. The L-malate oxidation reaction was catalyzed optimally at pH 10 by the H. lanuginosa enzyme with apparent Km's of 5.8 mM for malate and 0.1 mM for NAD, while the M. pusillus enzyme catalyzed it optimally between pH 9.5 and 10 with apparent Km's of 4.44 mM for malate and 0.16 mM for NAD. The optimum temperature for reduction of oxaloacetate was 50 °C for both the enzymes. The H. lanuginosa enzyme was resistant to heat inactivation at 40 °C, but lost 60% of its activity after 15 min at 50 °C. Mucor pusillus enzyme, on the other hand, retained 90% activity at 60 °C after 10 min. The two enzymes were protected from heat inactivation by monovalent cations (viz Na+, K+, and NH4+), as well as citrate, which may possibly involve conformational changes.

Specific Inhibition of Platelet Agglutination and Aggregation by Aromatic Amidino Compounds

1978 ◽  
Vol 39 (02) ◽  
pp. 411-425 ◽  
Author(s):  
J D Geratz ◽  
R R Tidwell ◽  
K M Brinkhous ◽  
S F Mohammad ◽  
O Dann ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Human Plasma ◽  
Inhibitory Effect ◽  
The Other ◽  
Specific Inhibition ◽  
Test Systems ◽  
Other Hand ◽  
Bovine Plasma ◽  
Inhibitory Activities ◽  
High Concentrations

SummaryA series of aromatic amidino compounds were investigated for their inhibitory effect on platelet agglutination and platelet aggregation. Agglutination of fresh or fixed platelets was produced by bovine plasma or by human plasma in combination with ristocetin, while aggregation of fresh platelets was induced by ADP, thrombin or collagen. Highly effective inhibitors were found for both types of platelet clumping, but there was no parallelism between the inhibitory activities in the two test systems. 5-(5-amidino-2-benzimidazolyl)-2-(4-hydroxyben-zene)benzimidazole suppressed agglutination exclusively. Pentamidine, on the other hand, strongly blocked the aggregation reactions, but did not interfere with agglutination, even at high concentrations. Compounds which inhibited aggregation also prevented the liberation of serotonin from the platelets.

Anticoagulant Factors from Viperidae Venoms

1972 ◽  
Vol 28 (03) ◽  
pp. 509-523 ◽  
Author(s):  
Marie Claire Boffa ◽  
P Delori ◽  
J. P Soulier
Keyword(s):  
Active Sites ◽  
Inhibitory Effect ◽  
The Other ◽  
Clot Formation ◽  
Phospholipase Activity ◽  
Vipera Berus ◽  
Anticoagulant Action ◽  
Vipera Aspis

SummaryTwo proteins presenting anticoagulant activities were isolated from Viperidae venoms : one from Vipera aspis, the other from Vipera berus. They interfere with the formation of prothrombinase. Their inhibitory effect results from a specific action of a complex which blocks the active sites of phospholipids. This complex is easily dissociated by antivenoms allowing normal clot formation.Berus inhibitor possesses a high phospholipase activity while aspis inhibitor is completely devoid of this activity. The anticoagulant action of these venom factors does not appear to be enzymatic.The affinity of both inhibitors for phospholipids seems similar though aspis inhibitor shows a more marked anticoagulant action which is neutralized by the addition of a greater amount of phospholipid.The study of these venom inhibitors confirms the fact that, in the absence of platelet phospholipids, clot formation is not possible.

Potentiating Effect of Adenosine on Other Inhibitors of Platelet Aggregation

1972 ◽  
Vol 27 (02) ◽  
pp. 252-262 ◽  
Author(s):  
M. Murakami ◽  
K. Odake ◽  
M. Takase ◽  
K. Yoshino
Keyword(s):  
Platelet Aggregation ◽  
Inhibitory Action ◽  
Prostaglandin E1 ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
The Other ◽  
Other Hand ◽  
Adp Release

SummaryAdenosine was rapidly incorporated into human platelets, and the inhibitory effect of adenosine on platelet aggregation was correlated with the incorporation process. Adenosine potentiated the inhibitory action of other inhibitors, such as dipyridamole, prostaglandin E1 and Y-3642. The inhibition of aggregation was associated with the preservation of platelet adenine nucleotides and the prevention of ADP release. On the other hand, the radioactive adenine nucleotide pattern of platelets was not substantially affected by inhibitors. The relation of inhibition of aggregation with ADP release was discussed.

Rates of Evolution

1999 ◽  
Vol 9 ◽  
pp. 319-328
Author(s):  
Steven M. Stanley
Keyword(s):  
New Species ◽  
The Other ◽  
Appreciable Change ◽  
Rate Of Evolution ◽  
Geologic Time ◽  
Other Hand ◽  
Rates Of Evolution ◽  
Or Groups

Any two biologic groups — populations, species, or groups of species — that are separated in time but connected by evolution provide us with the opportunity to measure a rate of evolution.Rates are interesting because they vary greatly. Some species have survived for millions of years without appreciable change. On the other hand, some species have arisen from other, quite different species within just a few thousands or tens of thousands of years: very brief intervals of time. Similarly, some groups of organisms have diversified rapidly, producing many new species during brief intervals of geologic time, whereas others have added new species very slowly.

Inhibitory effects of calcium ionophore pretreatment of porcine oocytes on polyspermic fertilization

Zygote ◽  
2006 ◽  
Vol 14 (1) ◽  
pp. 17-22 ◽  
Author(s):  
T. Hayashi ◽  
H. Sato ◽  
H. Iwata ◽  
T. Kuwayama ◽  
Y. Monji
Keyword(s):  
Calcium Ionophore ◽  
Inhibitory Effect ◽  
Calcium Ionophore A23187 ◽  
The Other ◽  
Ionophore A23187 ◽  
Inhibitory Effects ◽  
High Concentration ◽  
Maturation Period ◽  
Low Concentration ◽  
Other Hand

The present study examined the inhibitory effects of various pretreatment concentrations (0–100 μM) of the calcium ionophore A23187 on polyspermic fertilization and then examined the effect of the maturation period and the time between calcium ionophore treatment and fertilization on the inhibitory effect of calcium ionophore on polyspermic fertilization. In experiment 1, a high concentration of calcium ionophore (100 μM) increased the rate of activated oocytes, but the rate of fertilization declined. On the other hand, when oocytes were treated with a low concentration of calcium ionophore (10 μM), monospermic fertilization was significantly increased (10 μM; 31.3%) (p < 0.05). In experiment 2, oocytes were cultured for various times (0, 0.5, 3, 6 h) after calcium ionophore treatment (10 μM) before fertilization. The highest rate of monospermic fertilization was detected in the oocytes cultured for 6 h after calcium ionophore treatment before fertilization. In experiments 3 and 4, we examined the effect of the maturation period (40 h or 44 h) on the rate of fertilization and blastulation of oocytes pretreated with calcium ionophore. The treatment of oocytes with calcium ionophore significantly decreased the rate of polyspermic fertilization regardless of the maturation period (44 h: with calcium ionophore 26.25% vs without 78.8%; 40 h: with calcium ionophore 37.5% vs without 77.5%); however, calcium ionophore treatment increased the rates of monospermic fertilization and blastulation of the oocytes matured for 44 h, but not those matured for 40 h. In conclusion, activation with a low concentration of calcium ionophore (10 μM) and a further 6 h of culture before fertilization improved the rate of monospermic fertilization and blastulation.

Jack Went up the Hill … but Where Was Jill?

1979 ◽  
Vol 4 (2) ◽  
pp. 256-260 ◽  
Author(s):  
Shirley St. Peter
Keyword(s):  
Young Children ◽  
Picture Books ◽  
Women's Movement ◽  
Sex Role ◽  
The Other ◽  
Female Characters ◽  
The Third ◽  
Other Hand ◽  
The Hill

To assess the premise that picture books are important transmitters of sex-role information, 206 picture books for children, ages 3 to 6, were analyzed. Three groups were formed: (1) titles published before the women's movement (1903–1965); (2) titles published after the women's movement (1966–1975); (3) titles chosen from a specialized nonsexist list of books about girls (1882–1973). Analyses indicated that children are presented with sex-typed book models: females, underrepresented in titles, central roles, and illustrations; males, overrepresented in instrumental pursuits and underrepresented in expressive activities. On the other hand, the third group of books featured mostly female characters and contained a predominance of instrumental models with a minimum of expressive activities. The data revealed that picture books today provide stereotyped models for young children to emulate.

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