Distribution and subcellular localization of a hepatic proliferation inhibitor in rat liver

The subcellular and intralobular distributions of a protein which specifically inhibits the proliferation of normal liver cells were determined in rat liver, using a combination of immunological and biochemical techniques. The IgG fraction from an antiserum raised against the hepatic proliferation inhibitor was isolated by protein A-Sepharose CL-4B chromatography and shown to be highly specific for the antigen using electroimmunodiffusion and affinity chromatography. To determine the intracellular location of the inhibitor, subcellular fractions were prepared from adult rat livers by differential centrifugation. The cytoplasmic fraction contained the biologically active cytostatic inhibitor, whereas the nuclear and mitochondrial fractions were inactive. Cytoplasmic localization of the hepatic proliferation inhibitor was further confirmed by anion exchange high performance liquid chromatography and by double immunodiffusion with the anti-hepatic proliferation inhibitor IgG. When liver sections were subjected to histochemical staining mediated through the immune IgG and an avidin-biotinylated horseradish peroxidase complex, the parenchymal liver cells were stained, but endothelial and connective tissue cells were not. Although some staining was evident throughout the liver parenchyma, the most intensely stained cells were located in the centrilobular region. Moreover, an age-dependent increase in the staining intensity and/or in the number of cells containing the proliferation inhibitor was observed. Preliminary experiments showed that little, if any, staining occurred in hepatocellular carcinoma cells. This highly specific IgG can be used to monitor alterations in the content and location of hepatic proliferation inhibitor in proliferative disorders of the liver.

The protective effects of D-600 and propranolol on reperfusion injury in the anaesthetized rabbit

The ability of a calcium channel blocker (D-600) and a beta-adrenergic antagonist (propranolol) to modify the chemical, biochemical, functional, and ultrastructural manifestations of reperfusion injury following circumflex coronary artery ligation has been examined using an open chest, anaesthetized rabbit model of acute myocardial ischaemia. A 40-min ligation period followed by 60 min of reperfusion produced a decrease in mitochondrial azide-sensitive ATPase activity which could be prevented by pretreatment with either agent. While both drugs caused an equivalent (approximately 50%) reduction in myocardial Ca2+ accumulation associated with reperfusion, only D-600 preserved Mg2+ and Na+ levels. The greater protective effects of D-600 on sarcolemmal integrity were also apparent from its superior ability (when compared with propranolol) to offer protection against the loss of sarcolemmal Na+-K+ ATPase activity which we have previously suggested may parallel the development of irreversible ischaemic injury. Further support for these biochemical data came from ultrastructural studies in which we demonstrated significant improvement in subcellular membrane integrity by both of the drugs. In contrast to the foregoing protective actions, D-600 and propranolol failed to prevent the marked decrease in myocardial contractile function and in cellular ATP content associated with reperfusion. The superior effectiveness of D-600 in our system cannot be explained on the basis of Ca2+ antagonism alone, but is more likely a result of its greater negative inotropism.

Comparative studies on the role of calcium in triggering subcellular damage in cardiac muscle

Isolated cardiac muscle strips from amphibians and mammals, together with isolated frog hearts, have been used as model systems for studying the action of elevated [Ca2+]i in promoting severe damage. A23187 and caffeine are believed to cause a rise in [Ca2+]i. Elevated [Ca2+]i causes characteristic damage which has been categorized and includes hypercontraction, Z-line damage and myofilament dissolution. The damage closely resembles that described in the isolated mammalian heart and in skeletal muscle preparations when [Ca2+]i is raised dramatically. Damage can therefore be triggered by releasing Ca2+ from intracellular sites, as distinct from increasing Ca2+ entry (as in the Ca2+-paradox). DNP and ruthenium red also cause identical damage and the results suggest that whilst the fall in pHi associated with ischaemia is probably the consequence of Ca2+/2H+ exchange at the mitochondria, coupled with ATP hydrolysis, lowered pHi by mitochondrial action is probably not the only cause of myofilament dissolution. Damage is not prevented by pretreatment with leupeptin, an inhibitor of Ca2+-activated neutral proteases, and it is concluded that the latter are probably not implicated in rapid and dramatic damage. The possible involvement of lysosomal enzymes in damage triggered by high [Ca2+]i is discussed.

Defective acidification of endosomes in Chinese hamster ovary cell mutants "cross-resistant" to toxins and viruses

Like many physiological ligands, several viruses and toxins enter mammalian cells through receptor-mediated endocytosis. Once internalized, the nucleic acids of several viruses and the toxic subunit of diphtheria toxin gain access to the cytosol of the host cell through an acidic intracellular compartment. In this report, we present evidence that one class of mutants of Chinese hamster ovary (CHO)-K1 cells, which is "cross-resistant" to Pseudomonas exotoxin A, diphtheria toxin, and several animal viruses, has a defect in acidification of the endosome. Cells were allowed to internalize fluorescein isothiocyanate-conjugated dextran before subcellular fractionation. Fluorescence measurements on subcellular fractions permitted measurement of the internal pH of the isolated endosomes and lysosomes. Our results show that (i) endosomes and lysosomes from CHO-K1 cells maintain an acidic pH, (ii) acidification of both endosomes and lysosomes is mediated by a Mg2+/ATP-dependent process, (iii) GTP can satisfy the ATP requirement for acidification of lysosomes but not of endosomes, and (iv) at least one class of mutants that is cross-resistant to toxins and animal viruses has a defect in the ATP-dependent acidification of their endosomes. These studies provide biochemical and genetic evidence that the mechanisms of acidification of endosomes and lysosomes are distinct and that a defect in acidification of endosomes is one biochemical basis for cross-resistance to toxins and viruses.

Mitogenic effect of cytoplasmic membranes and a cytoplasmic fraction of Staphylococcus aureus L-forms on human peripheral blood lymphocytes

The cytoplasmic membranes and a cytoplasmic fraction of Staphylococcus aureus L-forms increased the incorporation of [3H]thymidine by human lymphocytes in the presence of fetal bovine serum. Both fractions stimulated cord blood lymphocytes as well as adult peripheral lymphocytes, suggesting the possibility that the observed effect was not due to an antigen-specific reaction, but to an immunologically nonspecific action. The membrane mitogen(s) was resistant to trypsin, although it was partially solubilized by trypsin treatment. The mitogen(s) could not be extracted with a chloroform-methanol mixture (2:1, v/v), although the chloroform-methanol soluble fraction was strongly mitogenic to murine splenocytes. Human serum which was added to the assay system in place of fetal bovine serum definitely suppressed the mitogenic effect of both cytoplasmic membranes and the cytoplasmic fraction, especially the latter.

Use of rat/hamster S-9 mixture in the Ames mutagenicity assay

Based on the findings of Nagao et al [1978] that phenacetin is negative in the standard Ames test with Aroclor induced rat S-9 and positive with hamster S-9, the test was performed with a mixture of rat/hamster S-9. Phenacetin was mutagenic with the mixture. The activity of the mixture was compared to the rat S-9 alone with low concentrations of 2-aminoanthracene (a strong promutagen for Salmonella typhimurium TA 1535, TA 100, TA 1537, and TA 98), nitrosopiperidine (a weak promutagen), and 1,2 epoxybutane (a weak, direct-acting mutagen). Except for an increased mutagenic activation by the mixture with nitrosopiperidine the mixture was comparable to the rat S-9 alone, indicating that replacing rat S-9 with a rat/hamster S9 mixture in the standard Ames test could increase the sensitivity of the test without interfering with rat S-9 activity.

[The ultrastructural morphogenetic bases of the adult respiratory distress syndrome]

Sequential study of the submicroscopic pathological events characterising the natural history of the adult respiratory distress syndrome has pinpointed three different development stages related to clinical course and prognosis. In the first stage, the decisive biological element is represented by the increase in capillary permeability, whose morphological substrate consists of the distension of intercellular junctions. The result is the formation of interstitial oedema with the characteristics of the exudate. In the second stage, when reversibility is still possible, fluid and proteins pass into the alveolus. Finally, in the third stage, the persisting stimulus of pulmonary capillaries leads on the one hand to the formation of hyaline membranes and, on the other, to a reactive lung response in the form of interstitial fibrinogenesis and hyperplasia of granular pneumocytes.

The suppressive effect of hepatic 9,000 x G supernatant fraction from 3-methylcholanthrene-treated rats on the mutagenic activity of 2-acetylaminofluorene

Hepatic 9,000 x g supernatant (S9) fraction from 3-methylcholanthrene (MC)-treated rats showed a significantly low activity in the in vitro conversion of 2-acetylaminofluorene (AAF) to mutagen(s), while S9 fraction from untreated or phenobarbital (PB)-treated rats showed a remarkable activity. The S9 fraction from MC-treated rats actually suppressed the PB-S9 mediated AAF mutagenicity. Since the suppressive effect of MC-S9 was lost by the addition of 10(-4) M alpha-naphthoflavone (alpha-NF), rat specific cytochrome P-448 may be responsible for this suppressive effect.

Inhibition of testicular organization in vitro by newborn rat ovarian cell supernatants

Cell reorganization experiments performed with newborn rat gonadal single cell suspensions resulted in organ-like reorganization after 18 h of rotation culture. When, however, testicular cells were incubated in supernatants of newborn rat ovarian cells, testicular organization was suppressed and the architecture of the reorganized gonad was rather feminine. Supernatants of adult rat ovarian cells did not inhibit testicular organization. The possible mechanisms responsible for the failure of the function of H-Y antigen by the presence of ovarian cell supernatants of newborn rats are discussed.

Ultrastructure of neurosecretosomes sedimented in the nuclear fraction from the posterior pituitary of the rat

Subcellular fractions of the posterior pituitary of the rat were isolated by differential and density gradient centrifugation, and microsamples prepared for electron miscroscopy by KMnO4 or glutaraldehyde-OsO4 fixation. The nuclear fraction, P1 (1000 g x 7 min), was the main neurosecretosome (NSS) fraction and contained nuclei and mitochondria in addition to NSS (60%). The crude mitochondrial fraction, P2 (10,000 g x 20 min), contained free mitochondria (70%), NSS, unidentified membrane particles, fat droplets derived from pituicytes, neurosecretory granules (NSG) and synaptosomes, identified by the presence of synaptic membrane thickenings. Fraction P3 (32,900 g x 20 min) contained mainly free NSG, while fraction P4 (118,000 g x 30 min) had a high microsome content.

Stimulatory effect of soluble supernatant on hydroxylase activity of rat testis microsomes

Addition of soluble supernatant to testis microsomes results in 42% increase in steroid 17,20-lyase activity and a 65% increase in 17alpha-hydroxylase activity. This stimulatory activity could be partially purified by salt fractionation. The activating factor(s) was not removed by dialysis nor did it appear to be lipid. It was destroyed by trypsin. Differential effects of heat were observed with the hydroxylase and lyase activators. The activation did not affect Km but only increased Vmax. The supernatant could be added to each enzyme to the point of maturation. No binding of steroids by the supernatant could be detected. Corpus luteum and placental supernatant did not stimulate enzymic activity, but supernatant from an adrenal adenoma was active.

In vitro HeLa cell DNA synthesis. II. Partial characterization of soluble factors stimulating nuclear dna synthesis

When HeLa cells are lysed in hypotonic buffer and the lysate is fractionated by centrifugation into particulate and soluble components, the particulate component (nuclei) is deficient compared to unfractionated lysate in the extent to which it can carry out in vitro DNA synthesis. In addition, rapidly labeled short DNA chains (Okazaki pieces) accumulate in purified nuclei, and are chased into higher molecular weight DNA to a lesser degree than in unfractinated lysate. When purified nuclei were reconstituted with soluble component, the capacity of the nuclei for in vitro DNA synthesis was fully restored, as was the capacity of the nuclei for conversion of Okazaki pieces to higher molecular weight DNA. This suggests that the soluble component contains a factor or factors necessary for normal DNA replication. The major incorporation-stimulating activity was partially characterized and partially purified from the soluble component. It is heat labile, non-dialyzable, partially recoverable in the supernatant after pH 5 precipitation, found mainly in a 55--85% saturated (NH4)2SO4 fraction, and is included on Sephadex G-100. After passage through Sephadex G-100, the activity displays increased instability to storage at either 4 degrees C or --70 degrees C. Part of the activity does not bind to phosphocellulose at pH 7.2 and low salt; no additional activity can be recovered in a 0.5 M KC1 wash of the phosphocellulose column. The Okazaki-piece-joining activity was found, along with the bulk of the incorporation-stimulating activity, in the 55--85% (NH4)2SO4 fraction. These findings provide some of the groundwork for future attempts to completely purify and characterize those activities in the soluble component of cell lysates which are involved in DNA replication.

Theoretical and practical considerations on the problem of metal--metal interaction

The interaction between two metals, which can be either synergistic or antagonistic, implies that the behavior of one is changed by the presence of the other. Possible mechanisms of these interactions, which include chemical association, competition for carriers, metabolic changes, induction of binding proteins, membrane alterations are discussed.

Subcellular distribution of a factor inactivating tyrosine aminotransferase. Study of its mechanism and relationship to different forms of the enzyme

The subcellular distribution of a tyrosine aminotransferase inactivating factor in rat liver has been investigated. Most of its activity is associated with plasma membranes, with minor amounts in mitochondria and endoplasmatic reticulum. The factor is also found in kidney and inactivates the enzyme reversibly in presence of cysteine, most likely by modification of -SH groups. ATP counteracts this inactivation only, when crude enzyme extracts are inactivated by purified subcellular fractions or when the purified enzyme is inactivated in presence of liver or kidney cortex homogenates. The relationship of this inactivation to reported different forms of the enzyme has been investigated. Form I of three different forms, that can be obtained by hydroxyl-apatite chromatography, is readily inactivated, form III can be partly converted to form I by incubation in presence of purified plasma membranes. The relationship of these findings to a possible multistep mechanism in the turnover of the enzyme discussed.

A polyvalent proteinase inhibitor from horse-blood-leucocyte cytosol. Isolation, purification and some molecular parameters

Cytosol of horse blood polymorphonuclear leucocytes contains an inhibitor active against neutral proteinases from the granules of these cells and against chymotrypsin, elastases I and II from pig pancreas, but not against trypsin. A method has been elaborated to isolate and purify this inhibitor by means of salting out with ammonium sulphate (45---70% saturation), followed by chromatography and rechromatography on a column of DEAE-Sephadex A-50. The preparation obtained is homogeneous during polyacrylamide gel electrophoresis in the presence of 0.1% sodium dodecylsulphate after reduction with 2-mercaptoethanol. It is a thermolabile protein soluble at its isoelectric point (pH 5.38) and having a molecular weight of 35200 but aggregating in solutions of low ionic strength and irreversibly precipitating during dialysis at pH 4.0. The results obtained show the similarity of this inhibitor isolated from horse blood leucocyte cytosol to other inhibitors isolated from human or pig blood leucocytes.

Negative inotropic effect of cyclic GMP in cardiac fiber fragments

The force of spontaneously beating cardiac cellular fragments obtained from mice heart by homogenization was recorded in presence of cyclic guanosine -3'.5'-monophosphate (cGMP) and cyclic 8-bromguanosine -3'.5'-monophosphate in concentrations of 3 X 10(-6) M - 33 X 10(-6) M. The nucleotide decreased the force and reduced the rate of spontaneity. Eventually the preparation became quiescent. It is thought that this nucleotide either reduces the capacity to sequester calcium or affects its release from the sarcotubular system.

[Potential difference across subcellular particle membranes. II. Compensation method of measurement]

"Zero-loop" of the molecular potential transformer of submitochondrial particles (SMP) is separated from the remaining electron transfer chain by rotenone, and its e.m.f. ET=0,003+RT/2F in [NADP X H] [NAD+]/[NADP+] [NAD X H] volts is used in the compensative method of measurement of the potential difference across the SMP membrane (delta USMP). The phospholipid membrane, measuring the concentration of the penetrating anions in the solution contained SMP, is used as "zero-indicators". This concentration drops monotonically with increase in delta USMP. Delta USMP is equal to ET when the addition of substrates of transhydrogenase reaction with definite ET does not change the potential across phospholipid membrane.

[Potential difference across subcellular particle membranes. I. Chemiosmotic and chemielectric mechanism of generation]

Transformation of light energy, of substrate oxidation and ATP hydrolysis energy into electric form during both oxidative and photo-phosphorylation can be described not only by means of chemiosmotic but also by chemielectric hypothesis. The latter hypothesis supposes, that dehydrated protons are taken up by electrostatic forces into the inner part of the membrane. Protons move into the input channels following electrons driven by chemical forces. Inside the membrane H+-ions are released into the output channels when electrons are transferred to the next electron carriers. Output H+-channels eject protons towards the other side of the membrane along the gradient of rising polarization of the channels. The inner resistance of chemielectric potential generators is lower than that of chemiosmotic one. A model of chemielectric mechanism is proposed. According to this mechanism electrons driving protons move along nonheme iron proteins and H+-ions are released into the output channels from semiquinones and hydroquinones.

Characterization of human dialyzable transfer factor from normal and chronic lymphoid leukemia sources

Dialysates of lymphomonocytes can be roughly quantified through the use of optical density and measurements of RNA and protein contents. Dialysates of normal lymphocytes (N-TFd) contain about 224 +/- 67 mug of RNA-like material per 10(8) cells, 75 to 90% of which is eluted in fractions II and III on Biogel P10 chromatography. In contrast, dialysates of lymphocytes from patients suffering chronic lymphoid leukemia (CLL-TFd) contain approximately 12 times less RNA-like material (about 27 +/- 11 mug per 10(8) lymphocytes) and have a different characteristic chromatographic pattern. Bioassays with crude dialysates confirm (a) that N-TFd increases 3H-thymidine incorporation by nonsenstitized lymphocytes "in vitro" in the presence of PPD, and (b) that inbred Lewis rats develop positive skin tests (systemic transfer) after receiving injections of N-TFd or of fractions II and III from Biogel fractionation of N-TFd. Neither test gives positive results when CLL-TFd is used.

Explanation of the stimulation of microsomal N-demethylation reactions by soluble supernatant fraction

Addition of the cell soluble supernatant fraction to an assay medium containing NADPH generating system, mixed function oxidase substrate and microsomes, resulted in a stimulation of drug metabolism ranging from 12-75%. This stimulation was observed only when the supply of DADPH generating system (isocitric dehydrogenase or glucose 6 phosphate dehydrogenase) was insufficient, leading to a NADPH oxidation rate which was greater than the rate of reduction of NADP+ during the oxidation of a drug. Hence, under our assay conditions, the soluble supernate (SS) is only providing sufficient NADPH generator, and possibly relieving inhibition by the generated NADP+. Finally, microsomal lipid peroxidation measurements under these same conditions indicate negligible to no peroxidation activity in the absence of SS.

Intracellular distribution of neutral proteinases and inhibitors in pig leucocytes. Isolation of two inhibitors of neutral proteinases

Granule and post-granular-supernatant fractions were obtained from pig leucocyte cells by differential centrifugation in 0.34 M sucrose. Granule extract possesses proteinase activity at acid and at neutral pH. Three groups of neutral and a group of acid proteinases were isolated from granule extracts by chromatography on DEAE-cellulose. In the first group are present elastase-like and plasminogen-activator proteinases, that are inhibited by diisopropylphosphorofluoridate, alpha1-antitrypsin, intracellular leucocyte inhibitor and partly with p-aminomethylbenzoic acid and Trasylol. The second group of neutral proteinases is unstable under the conditions of isolation used the third group of neutral proteinases comprises collagenases that are inhibited by ethylenediamine tetraacetic acid disodium salt, alpha1-antitrypsin and leucocyte inhibitor. The acid proteinases are inhibited only with pepstatin, up to 90%. In the post-granular supernatant was found the acid proteinase activity towards hemoglobin and casein, and non-stable neutral proteolytic activity towards bovine serum albumin and serum gamma globulin. In the post-granular supernatant also the inhibitors of neutral proteinases were found. By gel filtration on Sephadex G-100 and ion-exchange chromatography on CM-cellulose two inhibitors of neutral proteinases were isolated. The majority of the inhibitor capacity (about 80%) of post-granular supernatant was eluted together with ovalbumin (Mr 43000) and the remainder with cytochrome c (12300). These inhibitors inhibit the granule neutral proteinases, acting on all substrates used, but do not inhibit granule acid proteinase. Inhibition effects of post-granular-supernatant inhibitors on trypsin and chymotrypsin were obtained only when bovine serum albumin was used as substrate. Inhibitors of post-granular supernatant are stable at pH 6-8, but unstable in the pH rnage 2-5 and are thermolabile.

A morphometric study of cellular autophagy including diurnal variations in kidney tubules of normal rats

Cellular autophagy in convoluted tubules of kidney was studied in 24 rats, killed in pairs at constant time intervals during one diurnal cycle, by (a) morphometric evaluation of tubular cells by the point-counting method in randomly sampled micrographs, and (b) selective search for autophagic vacuoles (AV) directly on the electron microscopy screen. The total area of tubular cells recorded in the electron microscopy sections was 93 X 10(-4) mum2. Since the distal convoluted tubules, covering about 12% of the whole tubulocellular area, contained only 3-4% of all AV, they were omitted from the main calculations. The number of AV per area unit and the total amount of segregated material showed a distinct diurnal rhythm, synchronous for the different types of AV which were distinguished from each other according to their contents. The minimum was found during the night, the maximum during the day. This rhythm appears similar to that described elsewhere in liver cells. The mean segregated fractions were calculated from the relation of segregated to nonsegregated material in proximal convoluted tubular cells. The segregated fraction of the mitochondria was 4.4 X 10(-4). This value could account for the degradation of all mitochondria in a cell within 15 days, i.e., the upper limit of the lifetime of mitochondrial DNA in the cortex of the kidney, if one assumes that a mitochondrion is destroyed within 10 min after being segregated. The degregated fraction of microbodies was 11.7 X 10(-4). This suggests a shorter lifetime of these organelles. It is concluded that cellular autophagy plays a significant role in the turnover of cytoplasmic constituents, including the membranes of the endoplasmic reticulum.