SEARCH · PubMed Health

Results for “complexity”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1975

Immune complexes in the spleen. Replacement of immune complexes trapped in spleen follicles by new immune complexes from the circulation.

The fate of intravenously injected 125I-BGG-anti-BGG in the spleen of mice was studied using autoradiography. Part of the labelled immune complexes was trapped in the follicles of the spleen as could be expected. In a first experiment it was found that injections with unlabelled immune complexes were followed by a partial release of the labelled immune complexes from the follicles. In a second experiment unlabelled immune complexes retained in spleen follicles appeared to inhibit the trapping of intravenously injected labelled immune complexes to some degree and for some time. The conclusion was drawn from these experiments that immune complexes, which normally remain in part of the lymphoid follicles for a long period, may be replaced by new immune complexes from the circulation. This seems important since trapping in lymphoid follicles of antigen complexed by antibody is the only known mechanism by which small amounts of antigen may be preserved in the body for a long time after the initiation of antibody production. The bulk of antigen and antigen-antibody complexes is removed by phagocytosis followed by destruction. It appeared also that, although all spleen follicles in the mouse spleen is able to retain the complexes for a longer time. Possible explanations for these individual differences between the follicles of one spleen are discussed.

Animals↗

PubMed1979

Studies on the nuclear binding of steroid hormone-receptor complex; binding of liver and thymus dexamethasone-receptor complex and prostate dihydrotestosterone-receptor complex to nuclei from various tissues.

To examine the binding specificity of steroid hormone-cytoplasmic receptor complexes to nuclei, binding of 3H-dexamethasone (Dex)-liver, 3H-Dex-thymus and 3H-dihydrotestosterone (DHT)-prostate receptor complexes to nuclei from liver, prostate, thymus, spleen and kidney was studied. It was observed that a significant amount of steroid-receptor complexes was bound to any nuclei used in the present study and the extent of the binding of receptor complexes to nuclei from homologous tissues was not always greater than that to nuclei from heterogenous tissues. However, a significant portion of the 3H-Dex-liver and 3H-DHT-prostate receptor complexes was not absorbed by nuclei from kidney, spleem, and thymus, and the unabsorbed complexes were efficiently bound to liver and prostate nuclei. The results obtained indicate that two types of receptor complex with regard to nuclear binding were present in cytosols of liver and prostate; one binds to nuclei from kidney, spleen, thymus, liver and prostate and the other does not bind to nuclei from kidney, spleen and thymus but does bind to nuclei of liver and prostate. The latter type of receptor complex was not observed in the cytosol from the thymus.

Animals↗

PubMed1979

Purification of soluble immune complexes from serum using polymethylmetacrylate beads coated with conglutinin or C1q. Application to the analysis of the components of in vitro formed immune complexes and of immune complexes occurring in vivo during leishmaniasis.

A procedure for the isolation of immune complexes from human sera has been developed. Two steps are involved: (1) lipid-free serum is precipitated by polyethylene glycol; (2) the solubilized precipitate is absorbed on a column of polymethylmethacrylate beads coated with conglutinin (K) or C1q; the column is washed, the complexes are then eluted, using 0.02 M EDTA (for K column) or 0.5 M NaCl (for C1q column). This procedure permitted the purification and the characterization of soluble 125I-BSA-anti-BSA, 125 I-tetanus toxoid-anti-tetanus toxoid, and 125-I-HBsAg-anti-HBsAg complexes made in vitro in the presence of fresh human serum. The isolated complexes were shown to contain antigen, antibody, C1q, C1r, C1s and C3. When normal human serum was submitted to such a procedure, no detectable amount of protein was present in the final eluted fraction. Immune complexes formed in vivo were also purified by conglutinin column from the serum of a patient with disseminated leishmaniasis. The isolated material was found to contain IgM, IgG, C1q, C1r, C1s, C3c and C3d. The purified complexes dissociated at acid pH were found to contain anti-IgG and anti-leishmania antibodies.

Adult↗

PubMed1978

Conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active complex by the phosphate reaction in heart mitochondria is inhibited by alloxan-diabetes or starvation in the rat.

1. The conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active (dephosphorylated) complex by pyruvate dehydrogenase phosphate phosphatase is inhibited in heart mitochondria prepared from alloxan-diabetic or 48h-starved rats, in mitochondria prepared from acetate-perfused rat hearts and in mitochondria prepared from normal rat hearts incubated with respiratory substrates for 6 min (as compared with 1 min). 2. This conclusion is based on experiments with isolated intact mitochondria in which the pyruvate dehydrogenase kinase reaction was inhibited by pyruvate or ATP depletion (by using oligomycin and carbonyl cyanide m-chlorophenylhydrazone), and in experiments in which the rate of conversion of inactive complex into active complex by the phosphatase was measured in extracts of mitochondria. The inhibition of the phosphatase reaction was seen with constant concentrations of Ca2+ and Mg2+ (activators of the phosphatase). The phosphatase reaction in these mitochondrial extracts was not inhibited when an excess of exogenous pig heart pyruvate dehydrogenase phosphate was used as substrate. It is concluded that this inhibition is due to some factor(s) associated with the substrate (pyruvate dehydrogenase phosphate complex) and not to inhibition of the phosphatase as such. 3. This conclusion was verified by isolating pyruvate dehydrogenase phosphate complex, free of phosphatase, from hearts of control and diabetic rats an from heart mitochondria incubed for 1min (control) or 6min with respiratory substrates. The rates of re-activation of the inactive complexes were then measured with preparations of ox heart or rat heart phosphatase. The rates were lower (relative to controls) with inactive complex from hearts of diabetic rats or from heart mitochondria incubated for 6min with respiratory substrates. 4. The incorporation of 32Pi into inactive complex took 6min to complete in rat heart mitocondria. The extent of incorporation was consistent with three or four sites of phosphorylation in rat heart pyruvate dehydrogenase complex. 5. It is suggested that phosphorylation of sites additional to an inactivating site may inhibit the conversion of inactive complex into active complex by the phosphatase in heart mitochondria from alloxan-diabetic or 48h-starved rats or in mitochondria incubated for 6min with respiratory substrates.

Animals↗

PubMed1977

Experimental immune complex glomerulonephritis in the mouse with two types of immune complexes.

Immune complex glomerulonephritis was induced in three groups of mice by long-term immunization. Two antigens of similar molecular weight were used. The first group was immunized with ferritin (mol wt 480,000). In altered glomeruli deposits of immune complexes were seen in the subendothelial and subepithelial spaces of the glomerular basement membrane (GBM) and in the mesangium. The immune complex deposits were formed by amorphous matrix with marked dense molecules of ferritin. The second group was immunized with human fibrinogen (mol wt 450,000). The immune complex deposits were present in the intramembranous, subepithelial and subendothelial spaces of the GBM and in the mesangium. These deposits were relatively less electron-dense and had a fine granular structure. The third group of mice were immunized with both ferritin and fibrinogen simultaneously. Two types of deposits situated subendothelially in the GBM and in the mesangium were seen in one animal of this group. One type of deposit resembled structurally the ferritin-antiferritin complex deposits, the other resembled the fibrinogen-antifibrinogen complex deposits. The individual deposits in the GBM and in the mesangium formed discrete homogeneous masses. The two types of deposit were occassionally in direct contact with one another, but were more often completely separate and were never mixed. It can be assumed that in at least some phase of the experiment both types of complex were present in the circulating blood simultaneously. However, since none of the complexes deposited in the GBM or in the mesangium were mixed, it seems probable that each type of complex is deposited separately in the form of "clusters" composed of a single type of complex. The phagocytic activity of mesangial cells of animals with complex glomerulonephritis was not increased when compared with control animals.

Animals↗

PubMed1979

Soluble oligovalent antigen--antibody complexes. II. The effect of various selective forces upon relative stability of isolated complexes.

Soluble oligovalent antigen--antibody complexes were isolated and analysed by ultracentrifugation to assess the effect of several forces upon the composition and stability of soluble complexes. Complexes were prepared with fluorescein (F) conjugates of rabbit serum albumin (RSA) or thyroglobulin (RTg) and high affinity rabbit anti-F antibodies. Isolated complexes containing two antigen molecules (Ag2 complexes) tended to dissociate and form an equilibrium with complexes containing one antigen molecule (Ag1 complexes). This equilibrium was thermolabile, concentration dependent and affected by the original combining ratio and the area in the gradient from which complexes were harvested. Small amounts of free antibody dissociated from soluble complexes also to form a dynamic equilibrium; this equilibrium was much less affected by the above parameters. The data support the concept that complexes grow in size by a process analogous to polymerization of simple subunits and that the driving forces for polymerization are of a lower order of magnitude and more affected by physical variables than the primary reaction between antibody and its antigen.

Antibody Affinity↗

PubMedDate not supplied

Chlorophyll-protein complexes of brown algae: P700 reaction centre and light-harvesting complexes.

Thylakoid membranes from several brown algae have been fragmented with the non-ionic detergent, Triton X-100. Three intrinsic chlorophyll-protein complexes with different pigment compositions have been isolated by sucrose density gradient centrifugation. Brown algae contain the photosystem 1 reaction-centre complex, a P700-chlorophyll a-protein which has similar spectroscopic and chemical properties to those of higher plants. This complex represents about 10--20% of the total chlorophyll in all species; the Acrocarpia paniculata complex has a chlorophyll/P700 ratio of 38. Two main light-harvesting complexes have also been isolated, which have properties unique to brown algae. The heavier of these, an orange fraction, is a fucoxanthin-chlorophyll a/c-protein; this complex contains most of the fucoxanthin and has only chlorophyll c2. The other, a green fraction, is a chlorophyll a/c-protein enriched in violaxanthin. Neither of these complexes possesses detectable photosystem 1 or photosystem 2 activities. Both of these complexes efficiently transfer light energy to chlorophyll a, indicating that the molecular arrangement of their pigments is similar to that in vivo. Differential extraction of thylakoid membranes indicates that the P700-chlorophyll a-protein is the complex most firmly embedded in the membrane, but the fucoxanthin-chlorophyll a/c-protein is the least firmly bound. We suggest that the fucoxanthin complex is the most variable component of the photosynthetic unit of brown algal chloroplasts.

Cell Membrane↗

PubMed1979

Passive immune complex glomerulonephritis in mice: models for various lesions found in human disease. II. Low avidity complexes and diffuse proliferative glomerulonephritis with subepithelial deposits.

Intravenous injections of mice three times a day for 3 days with soluble complexes of 3 mg. of moderately avid rabbit antibody to chicken egg albumin prepared by dissolution of equivalence precipitates in 80 times the equivalence amount of antigen resulted in a combined mesangial and loop localization of immune complexes. With complexes formed from antibody of low avidity, injected four times a day for 3 days, a predominately subepithelial loop deposition of complexes was observed. Complexes formed from moderately avid antibody gave rise to a mainly mesangiopathic glomerulonephritis, whereas low avidity complexes were associated with a diffuse glomerulonephritis. These results, in combination with those of the previous paper, successfully reproduce the basic form of the lesions seen in active immune complex disease by passive means and suggest that antibody avidity is a major determinant of the site of localization of immune complexes and therefore of the morphologic form of the resulting glomerulonephritis. The importance of these observations for our understanding of the pathogenesis of human immune complex disease is considered.

Animals↗

PubMed1979

Soluble oligovalent antigen-antibody complexes. I. The effect of antigen valence and combining ratio on the composition of fluorescein-carrier anti-fluorescein complexes.

Soluble oligovalent antigen--antibody complexes were prepared and analysed by ultracentrifugation in order to study the effect of the combining ratio, antigen valence and concentration upon the size and molecular composition of the composition of the complexes. Fluorescein (F) conjugates of rabbit serum albumin (RSA) and thyroglobulin (RTg) were combined with high affinity rabbit anti-F antibodies to form soluble complexes. The effect of the combining ratio paralleled findings in precipitating systems in that the largest soluble complexes were found at equimolarity and mild molar antibody excess. Tetravalent antigen formed precipitates at combining ratios near equimolarity, whereas trivalent antigens failed to precipitate at similar concentrations. Complexes prepared near equimolarity were most sensitive to changes in concentration, higher concentrations leading to larger complexes. The Ab/Ag ratios of different-size complexes in the same preparation were remarkably similar. This ratio was dependent on the antibody--antigen combining ratio, was limited by antigen valence and was not affected by concentration differences. The data support the hypothesis that soluble complexes are formed in two steps. First, antigen and antibody combine to form subunits whose Ab/Ag ratio is determined by the combining ratio and antigen valence. These subunits then combine to form larger complexes in a manner analogous to polymerization.

Antibodies↗

PubMed1979

CO and O2 complexes of soybean leghemoglobins: pH effects upon infrared and visible spectra. Comparisons with CO and O2 complexes of myoglobin and hemoglobin.

The effects of pH upon infrared spectra [CO stretching frequency (vco) region] and visible spectra of the CO complexes of soybean leghemoglobins a, c1, and c2, sperm whale myoglobin, and human hemoglobin A are reported. The vco for leghemoglobin--CO complexes was 1947.5 cm-1 at neutral pH. At acid pH myoglobin-- and hemoglobin--CO complexes developed vco bands at 1966--1968 cm-1, whereas leghemoglobin--CO complexes developed vco bands at approximately 1957 cm-1. All pKapp co values determined by pH-dependent variation of vco fell in the range 4.0--4.6. The pKapp co values determined from visible spectra were consistent with vco-determined values except for that of myoglobin--CO (visible pKapp co = 5.8). The pKapp co values in the 4.0--4.6 range appear to be pK values of the distal histidines, while the visible pKapp co of myoglobin--CO appears to be the pK of a group other than the distal and proximal histidines. The data are consistent with a model in which protonation of the distal histidine permits protein-free heme FeCO geometry in leghemoglobin--CO complexes but not in myoglobin-- or hemoglobin--CO complexes. Thus the heme pockets of leghemoglobins appear to be more flexible than the heme pockets of myoglobin and hemoglobin. The effects of pH upon visible spectra of the O2 complexes of soybean leghemoglobins a, c1, and c2, sperm whale myoglobin, and human hemoglobin A also are reported. pKapp o2 values of approximately 5.5 (leghemoglobins) and 4.4 (hemoglobin) are probably the pK values of the distal histidines. Comparisons of pKapp o2 values with pKapp co values indicate a more flexible heme pocket in leghemoglobins than in hemoglobin. The O2 complex of leghemoglobin c2 differed significantly from the O2 complexes of leghemoglobins a and c1 in visible spectra and titration behavior. These differences might be associated with the small structural differences in the region between the E and F helixes of leghemoglobins.

Animals↗

PubMedDate not supplied

[Formation of nitrosyl complexes of nonheme iron (2.03 complexes) in animal tissues in vivo].

Formation or dinitrozyl non-haem iron complexes (2.03 complexes) in white rats' tissues in vivo has been studied. The formation of these complexes has been examined in the liver kidneys and small intestines when injecting p/o NaNO2 to the rats. Most of the complexes have been found in the liver. They have not been detected in the heart, spleen, muscle, cerebrum and marrow in vivo. 3-4-fold content of 2.03 complexes has been determined while introducing iron and NaNO2 in running water. This effect has not been found when introducing iron and NaNO2 simultaneously. The mechanism of 2.03 complex formation in the animal tissues in vivo has been proposed. According to this mechanism these complexes are formed in the tissues when Fe-NO from nitrozyl non-haem from complexes originating in blood passes into SH-group of protein in tissues. The formation of 2.03 complexes in vivo has been found in blood uniform elements.

Administration, Oral↗

PubMed1978

Studies on the ATPase complex from beef-heart mitochondria. I. Isolation and characterization of an oligomycin-sensitive and an olgiomycin-insensitive ATPase complex from beef-heart mitochondria.

1. A new method for the isolation of the oliogomycin-sensitive ATPase from beef-heart mitochondria is described. 2. A Triton-soluble ATPase complex was isolated as a by-product of the standard procedure, or as the main product when the submitochondrial particles were pretreated with 1% Triton. The ATPase activity of this complex is sensitive neither to oligomycin nor to dicyclohexylcarbodiimide. 3. The ATPase activity of the oligomycin-sensitive ATPase complex is nearly completely dependent on added phospholipids. The highest activation was found with asolectin. 4. The oligomycin-sensitive complex can be integrated into phospholipid vesicles resulting in an ATP- and Mg2+-dependent energization of the vesicles as monitored with the fluorescent dye 9-amino-6-chloro-2-methoxyacridine. 5. Aurovertin-binding studies based on fluorescence measurement reveal the presence of 1.5 mumol aurovertin-binding sites per g protein for the oligomycin-sensitive complex and about 2.2 mumol for the oligomycin-insensitive complex. 6. The preparation of the oligomycin-sensitive complex contains at least 6--7 polypeptides in addition to those derived from F1. One of these polypeptides, with an apparent molecular weight of 31 000, is virtually absent from the oligomycin-insensitive complex. 7. Some of these polypeptides have been identified and isolated.

Adenosine Triphosphatases↗

PubMed1977

Pulmonary and extrapulmonary sarcoidosis in relation to circulating immune complexes: a quantification of immune complexes by two radioimmunoassays.

Serum specimens from 53 patients with pulmonary sarcoidosis were examined for the presence of immune complexes by 2 methods, the Raji cell and the monoclonal rheumatoid factor radioimmunoassays. We found increased concentrations of immune complexes in the sera of 27 patients by one or both techniques. A significant association was found between increased concentrations of immune complexes and stage III sarcoidosis. Seventeen of 23 patients with stage III sarcoidosis and 10 of 50 with stage I or II disease had increased concentrations of immune complexes. Eight of the 10 patients with stage I or II sarcoidosis and increased concentrations of immune complexes had extrapulmonary sarcoid features, such as erythema nodosum, synovitis, or salivary gland enlargements. The size of the immune complex was 15S in one of the patients examined. Concentrations of C4 were normal. The data suggest a possible role of immune complexes in the pathogenesis of pulmonary and extrapulmonary features of sarcoidosis.

Adult↗

PubMed1978

Effect of aminonucleoside nephrosis on immune complex localization in autologous immune complex nephropathy in rats.

The effect of increased capillary permeability on glomerular immune complex localization was studied in rats immunized with proximal tubular antigen (Fx1A) to induce autologous immune complex nephropathy (AICN). AICN rats were made proteinuric by injection or unilateral renal perfusion with aminonucleoside of puromycin (PA) before developing subepithelial complex deposits. Control AICN kidneys developed diffuse granular deposits of IgG and Fx1A on the subepithelial surface of the glomerular basement membrane (GBM) at 3 wk by immunofluorescence and electron microscopy, and deposits increased in subsequent weekly biopsies. In contrast, PA-nephrotic AICN kidneys developed few or no GBM deposits and a significant increase in mesangial localization of IgG and Fx1A during the period of PA-induced proteinuria. These alterations in complex localization were documented both in rats with PA nephrosis and in unilaterally PA-nephrotic kidneys compared with contralateral controls in the same animals, thus excluding any effect of PA on the immunopathogenetic mechanism in AICN as an explanation for these findings. The absence of GBM deposits closely correlated with reduced staining for polyanionic glomerular sialoprotein in proteinuric kidneys, since PA-perfused kidneys studied 2 wk after resolution of proteinuria demonstrated return of normal staining for sialoprotein and development of subepithelial complex deposits similar to those in contralateral control kidneys. These studies demonstrate that properties of the glomerulus itself play an important role in determining the site of complex deposition in experimental AICN and suggest that electrophysical characteristics of the glomerular capillary wall may influence complex localization on the GBM.

Animals↗

PubMed1975

Intermolecular complexes between N-methyl-1,4-dihydronicotinamide and flavines. The influence of steric and electronic factors on complex formation and the rate of flavine-dependent dihydronicotinamide dehydrogenation.

The reaction of N-methyldihydronicotinamide (NMNH) with flavine analogs saturates at high dihydronicotinamide concentrations. Complex formation between the reactants depends mainly on steric but not on electronic factors. Thus flavine analogs that differ up to 243 mV in their oxidation-reduction potential vary only between 0.09 and 0.17 M in Kd. When the flavine plane becomes blocked by bulky substituents, however, complex stability decreases by more than an order of magnitude. NMNH-flavine complexes show long wave optical absorption. The energy of the long wave transition decreases with increasing oxidation-reduction potential of the flavine as expected for charge transfer complexes. The first-order rate constants of flavine-dependent dihydronicotinamide dehydrogenation increase with increasing oxidation-reduction potential of the flavine but they are almost independent of Kd. The reaction is not subject to general acid-base catalysis. Thus flavine-dependent dihydronicotinamide dehydrogenation may be interpreted to proceed via a charge transfer complex between oxidized flavine and reduced nicotinamide. In the rate-limiting conversion of the charge transfer complex into products hydrogen is transferred directly, the rate being governed by the difference in oxidation-reduction potential between flavine and dihydronicotinamide. An alternative mechanism where the observed charge transfer complex is not on the reaction pathway appears to be improbable but cannot be eliminated.

Binding Sites↗

PubMedDate not supplied

Metal complexes of poly(alpha-amino acids). A potentiometric and circular dichroism investigation of Cu(II) complexes of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid).

The conformational properties of cupric complexes of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid) have been investigated by potentiometric, visible and UV absorption, and circular dichroism (CD) techniques. The three polymers form two kinds of complexes stable at pH less than 8.5 (type I complexes) and at pH less than 8.5 (type II complexes). It has been found that in the low pH complexes of poly(L-diaminobutyric acid) at least one deprotonated amido nitrogen is coordinated to cupric ions. Type II complexes involve always amide nitrogens in the coordination sphere of Cu(II). Evidence is presented that the structure of such complexes is not compatible with the alpha-helical conformation of the peptide backbone.

Aminobutyrates↗

PubMed1976

Complex of D-glyceraldehyde-3-phosphate dehydrogenase with Cu2+ ion. The properties of ternary Cu-enzyme-coenzyme complex.

The formation of ternary Cu-enzyme-coenzyme complex from cupric ion and D-glyceraldehyde-3-phosphate dehydrogenase holoenzyme results in similar spectral changes as the formation of binary Cu-apoenzyme complex, which indicates that the complex bonds between cupric ion and the holoenzyme, and cupric ion and the apoenzyme are similar. Spectrophotometric titration, chemical modification experiments and inhibition studies with cupric ion gave evidence that cupric ion is selectively bound on Cys-149 residue also in the Cu-GAPD-NAD complex. The charge transfer interaction between the coenzyme and Cu-GAPD, i.e. the difference spectrum of the combination of NAD with Cu-GAPD complex, is different from that of the enzyme-coenzyme complex in the absence of cupric ion. The shape of this "modified enzyme-coenzyme charge transfer spectrum" is influenced by various anions. The difference absorption does not depend on the pH in the range of 5.5 to 9. This indicates that the bound cupric ion abolishes the effect of deprotonation of a functional group in the protein on the charge transfer interaction. It is suggested that this functional group is a histidine imidazole, which activates the Cys-149 thiol group in the native enzyme and binds the metal ion in the cupric complex in a Cys-Cu-His chelate structure.

Animals↗

PubMed1979

The formation of binary and ternary complexes of cytochrome P-450scc with adrenodoxin and adrenodoxin reductase.adrenodoxin complex. The implication in ACTH function.

Binary and ternary complexes of bovine adrenocortical mitochondrial cytochrome P-450scc with adrenodoxin and adrenodoxin reductase.adrenodoxin complex are formed in the presence of cholesterol and Emulgen 913. Both cholesterol and Emulgen 913 are required for the binding of cytochrome P-450scc with adrenodoxin. Since phospholipids are able to replace Emulgen 913 in this reaction, in vivo phospholipids of the mitochondrial inner membrane appear to play the function of the detergent. The dissociation constants of the cytochrome.adrenodoxin complex are 0.3 to 0.4 microM at 130 microM dimyristoylphosphatidylcholine and 0.9 microM at 120 microM Emulgen 913, whereas the dissociation constant for the ternary complex of cytochrome P-450scc with adrenodoxin reductase and adrenodoxin is 4.0 microM at 150 microM Emulgen 913. The stoichiometry of binary and ternary complexes reveals the 1:1 and 1:1:1 molar ratios, respectively, judging from chemical analyses after the fractionation of the complexes by gel filtration. Emulgen 913, Tween 20, ethylene glycol, myristoyllysophosphatidylcholine, dimyristoylphosphatidylcholine, and phosphatidylethanolamine show the enhanced activity of cholesterol side chain cleavage reaction with cytochrome P-450scc, adrenodoxin, adrenodoxin reductase, and NADPH. These results, in conjunction with earlier experiments, lead us to the proposal on the structure of the hydroxylase complex in the membrane and to the hypothesis on the regulation of the enzymatic activity by the availability of substrate cholesterol to the cytochrome. Hence, we propose a mobile P-450scc hypothesis for the response of the mitochondrion to adrenocorticotropic hormone stimuli.

Adrenal Cortex↗