Interaction of heme with a synthetic peptide mimicking the putative heme-binding site of histidine-rich glycoprotein

We synthesized a hexapeptide, Gly-His-His-Pro-His-Gly, previously identified as a tandem motif in the histidine-rich glycoprotein (HRG) which has multiple heme-binding sites. Binding of heme to the peptide was demonstrated by the characteristic difference spectrum showing a close resemblance to that of HRG, implying that the peptide binds heme through biaxial coordination with histidine imidazoles. Furthermore, the EPR spectra of the heme-peptide and heme-HRG complexes were almost completely identical in pattern, showing signals characteristic of the low spin iron. The results suggest that the synthetic peptide simulates the heme-binding properties of HRG and that each tandem motif in HRG serves as a unitary binding site for heme.

Hemin inhibits virion-associated reverse transcriptase of murine leukemia virus

The virion-associated reverse transcriptase activity of Rauscher murine leukemia virus was inhibited by freshly prepared hemin at a concentration of 10(-4) M. When the hemin solution was aged at room temperature for 5 days, the concentration of 50% inhibition decreased to as low as 10(-7) M. Removal of O2 from the solution partially prevented the aging. The hemin inhibition was reversible and appears to be directed against the enzyme rather than the template. Hemin did not inhibit the activity of reverse transcriptase purified from avian myeloblastosis virus.

Properties of the binding of follicle-stimulating hormone to the fetal rat testis

Basic properties of the binding of [131I]-labeled rat FSH ([131I]rFSH) to the testicular homogenates of fetal rats were analyzed by micro-radioreceptor assay. Specific binding of FSH was detectable in the testicular preparations from 15.5-day fetuses, but it was very low. After 17.5 days of gestation, specific FSH binding was apparent in the testis and was effectively displaced by rat FSH but not by rat LH. The Scatchard plot analyses of the binding of FSH to the testicular preparations of fetuses showed straight lines similar to those of postnatal rats, suggesting the presence of a single class of binding sites. The mean dissociation constant (Kd) for FSH receptors in 17.5-day fetuses was 0.413 +/- 0.043 nM, which was significantly greater than that in postnatal rats at 50 days of age. However, the Kd in 19.5-day fetuses was not significantly different from those in 17.5-day fetuses and postnatal rats due to its considerable variance. The capacity of FSH binding sites was 0.51 +/- 0.01 fmol/testis in 17.5-day fetuses, which was significantly less than those of 19.5-day fetuses and postnatal rats.

[Present status of hypoxic cell sensitizers and PLDR inhibitors]

Clinical and basic studies in hypoxic cell radiosensitizers and potentially lethal damage (PLD) repair inhibitors were reviewed. Most clinical trails on misonidazole (MISO) show that the toxicity of MISO is a major reason for failure in the trials and an adequate selection of tumors is needed for the success. Phase III studies on SR-2508 and RO 03-8799, less toxic and more effective sensitizers, are in progress. AK-2123 and RK-28 developed in Japan are drugs with similar clinical applicability of MISO. Thiol depletion of tumors is one of the way to increase the radiosensitization. The measurement of intercapillary distance on histopathological microslide is a valuable method to select the tumors containing much hypoxic cell fractions. Stable and effective chemicals as MISO in hypoxic cell sensitization must be developed to investigate the clinical applicability of PLD repair inhibitors.

Autoradiographic study of binding and internalization of follicle-stimulating hormone in the mouse testis minces in vitro

The internalization of FSH-receptor complexes was demonstrated in mouse testis by means of light and electron microscopic autoradiography. Chopped testicular pieces were incubated with radioiodinated FSH (131I-NIADDK-rat FSH-I-4) for 10, 20, 60 and 180 min. After incubation the pieces were fixed with glutaraldehyde containing tannic acid, and embedded in Spurr's resin. Semithin and ultrathin sections were cut for light and electron microscopic autoradiography, respectively. In light microscopic autoradiographs, silver grains were preferentially localized over Sertoli cells, regardless of incubation time. Sixty to 70% of the total number of grains were located over Sertoli cells which account for only about 4% of the total cell population of the seminiferous tubules. The majority of these grains correspond to the specific FSH binding sites, because few grains remained after incubation with an excess amount of unlabeled FSH. In electron microscopic autoradiographs, the half-distance (HD) value for the 131I-labeled line source was about 216 nm in the present study. After 10 min of incubation, 56.6% of the total number of silver grains were located over the plasma membrane of Sertoli cells. In testicular pieces incubated for longer periods (20, 60 and 180 min), both the percentage and relative concentration of grains increased in the Golgi apparatus and lysosomes and decreased in the plasma membrane. These results suggest that [131I]iodo-FSH first binds to FSH receptors on the plasma membrane of Sertoli cells, then FSH-receptor complexes are internalized. The increase in the number of grains over the lysosomes following longer incubation, indicates that internalized [131I]iodo-FSH or FSH-receptor complexes are subjected to degradation.

[Fundamental studies on thyroid stimulating hormone immunoradiometric assay kit (TSH RIABEAD II)]

We have reported fundamental studies on the TSH immunoradiometric assay, using TSH RIABEAD II kit (Dainabot). The sensitivity of the assay was 0.03 mu IU/ml and its C.V. was 27.2%. Intra- and inter-assay C.V. were less than 5%. Dilution test and recovery test were good. Serum TSH level was 0.3-4.0 mu IU/ml in normal subjects, less than 0.03 mu IU/ml in untreated Graves' disease and subacute thyroiditis. Therefore, it was found that the clear difference exist in serum TSH levels between normal subjects and patients with untreated Graves' disease. There was a well correlation on the serum TSH levels between this method and TSH radioimmunoassay kit (Amerlex TSH, r = 0.983). Especially, the measurement of serum TSH levels, using immunoradiometric assay kit, was useful for the diagnosis of patients with Graves' disease.

Combined effect of buthionine sulfoximine and cyclophosphamide upon murine tumours and bone marrow

Two and four treatments of 5 mmol kg-1 of buthionine sulfoximine (BSO) at an interval of 12 h depleted the glutathione (GSH) content in NFSa tumours of C3H/He mice, respectively, to 24.0 and 1.78 percent of the untreated controls. BSO pre-treatments every 12 h enhanced the cytotoxicity of cyclophosphamide (CYC) towards artificial lung micrometastases of NFSa tumours giving enhancement ratios (ERs) ranging from 1.75 to 1.83 and from 2.41 to 2.73, for two and four BSO pretreatments respectively. Large ERs were obtained at low CYC doses (high cell survival). Four BSO pre-treatments at an interval of 12 h did not increase the cytotoxicity of CYC to bone marrow stem cells. Our results suggest a clinical applicability of the combination of BSO and CYC.

Variation in the hypoxic fraction among mouse tumors of different types, sizes, and sites

Radiobiologically hypoxic fractions of 4 experimental tumors (RIF1, B16, EMT6/KU, SCCVII) of various sizes implanted subcutaneously (sc) or intradermally (id) were compared under identical conditions by using the paired survival curve assay method. The two survival curves for tumors in air-breathing and asphyxiated mice were almost parallel for EMT6/KU and SCCVII tumors, but not for RIF1 and B16 tumors. Therefore, hypoxic fractions were estimated by fitting the best parallel lines to the two sets of survival data. The values for 10 mm-diameter sc tumors in the hind legs of syngeneic mice were 4.7% for RIF1, 4.5% for B16, 14% for EMT6/KU, and 8.5% for SCCVII. The variation of the values is quite small in spite of the variety of biological characteristics of these tumors. Histological examination revealed that EMT6/KU and B16 tumors contained large necrotic areas, while SCCVII and RIF1 had small areas of necrosis. Thus, the hypoxic fraction and the proportion of necrosis in the histological specimens were not clearly correlated. The values for 6 mm and 16 mm sc EMT6/KU tumors were 5.9 and 22%, respectively, while that for 6 mm id tumors was 16%. The values for 5 mm and 18 mm sc SCCVII tumors were 0.86 and 8.4%, respectively. These results indicated that: (1) id EMT6/KU tumors had a higher hypoxic fraction than sc ones of the same size; (2) the hypoxic fraction increased with increase in tumor size in EMT6/KU tumors, while it reached a plateau at a certain size in SCVII tumors.

Radiosensitizing effect of misonidazole in combination with an inhibitor of glutathione synthesis in murine tumors

The radiosensitizing effects of misonidazole (MISO) in combination with D,L-buthionine-S, R-sulfoximine (BSO), an inhibitor of glutathione (GSH) biosynthesis, were studied in NFSa tumors of C3H/He mice. The radiation response of tumors was assayed by the tumor growth delay time. The GSH contents in tissues were assayed by high performance liquid chromatography (HPLC). GSH content in the tumors decreased to the minimum level (45% of the control), and then gradually recovered to 75% of the control, respectively, 12 and 24 hr after the intraperitoneal injection of 5 mmole/kg BSO. On the other hand, the maximum non-protein sulfhydryl (NPSH) depletion (29% of the control) in the liver of tumor bearing mice was achieved 6 hr after the administration of the same dose of BSO, but fully recovered 24 hr later. When 5 mmole/kg BSO was injected repeatedly 4 times at an interval of 6 hr, GSH content in the tumors decreased to 19% of the control 24 hr after the first injection of BSO. The radiosensitizing effect of 0.5 mmole/kg MISO was markedly increased by this BSO treatment. The enhancement ratio (ER) of this combined treatment was 1.93. On the other hand, ERs of 1.44 and 1.16 were obtained for MISO (0.5 mmole/kg) and for 4 injections of BSO (5 mmole/kg) in combination with radiation, respectively. Although a considerable increase in the radiosensitizing efficiency of MISO in vivo by the treatment with BSO was found without any notable side effects of the combination, more studies on toxicities are needed to get a definite conclusion on the clinical applicability of the combination.

Levels of topoisomerase II and DNA polymerase alpha are regulated independently in developing neuronal nuclei

A possible correlation between activity levels of topoisomerase II and DNA polymerase alpha was studied in neuronal nuclei from developing rat brain. A high level of canonical topoisomerase II activity was detected in neuronal nuclei throughout the development even at a late stage (28 days after birth) when the activity of DNA polymerase alpha decreased to less than 2% of the fetal level. Thus, in contrast to other systems, topoisomerase II does not change in parallel with DNA polymerase alpha during neuronal development. Our results suggest that topoisomerase II is required to maintain some fundamental processes in differentiated cells, including transcription.

Chemosensitization by buthionine sulfoximine in vivo

The in vivo effects of buthionine sulfoximine (BSO), an inhibitor of glutathione (GSH) biosynthesis, on the cytotoxicity of cyclophosphamide (CYM), cisplatin (CDDP) and bleomycin (BLM), were examined by monitoring the changes of non-protein thiols (NPSH) in normal tissues and in the NFSa fibrosarcoma. We used the lung colony assay as a measure of tumor response and the spleen colony assay as a measure of normal tissue response to CYM. In this study, 5 mmol/kg of BSO was subcutaneously injected four times every 12 hr before administration of the above anti-neoplastic drugs. GSH levels in subcutaneous NFSa tumors decreased to 2% of the control 12 hr after the last administration of BSO, but in the bone marrow, had recovered to 41%. In the colony assays, BSO increased the anti-cancer effects of the three chemotherapeutic agents, but did not modify the bone marrow suppression by CYM. This finding was a result of the differential response of GSH depletion in the tumor and in the bone marrow. Our study demonstrates that BSO is an effective chemosensitizer of these drugs and may be of therapeutic value when used at an optimal interval.

Effect of vasopressin antagonist on water excretion in inferior vena cava constriction

Elevated levels of plasma arginine vasopressin (AVP) have been suggested to impair water excretion in congestive heart failure. In the present study, to determine a role for AVP in the impaired water excretion in rats with the inferior vena cava constriction (IVC), two AVP antagonists were used in the IVC rats at the proximal portion of the hepatic vein under the diaphragm and in sham-operated (control) rats. After surgery, 48 hrs were allowed before the experiments were started. A mean cardiac index of 260.0 +/- 12.3 ml/min/kg in the IVC rats was significantly lower than that in the control rats, 323.6 +/- 13.2 ml/min/kg (P less than 0.01). The rats were given an antidiuretic antagonist, [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid), 2-(O-ethyl)-D-tyrosine, 4-valine] AVP (30 micrograms/kg) or the antagonist vehicle, i.p., and 20 min later they were administered 30 ml/kg of water orally. Minimal urinary osmolality (Uosm) in the IVC rats receiving the vehicle was significantly greater than the control rats (292.7 +/- 53.1 vs. 97.8 +/- 10.6 mOsm/kg H2O, P less than 0.01). The administration of the antidiuretic antagonist in the IVC rats decreased minimal Uosm to 90.0 +/- 3.6 mOsm/kg H2O. This value was significantly lower than the vehicle rats (P less than 0.01), and was a comparable level to minimal Uosm of 82.1 +/- 3.7 mOsm/kg H2O in the control rats receiving the antidiuretic antagonist. The IVC rats excreted 51.4 +/- 5.9% of the water load in three hr, a value significantly less than that excreted by the control rats, 95.1 +/- 6.0% (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor vessels and contrast enhancement of hepatocellular carcinoma demonstrated by percutaneous transhepatic portography. Report of a case

A patient with an Edmondson type I-II hepatocellular carcinoma had, at celiac angiography, a poor arterial supply but a rich portal supply as observed at percutaneous transhepatic portography, an observation not previously reported in this disease. The importance of demonstrating the vascular supply of the tumor previous to planned intravascular treatment is obvious.

Radiation therapy for nasopharyngeal carcinoma. Retrospective review of 105 patients based on a survey of Kansai Cancer Therapist Group

One hundred five patients with nasopharyngeal carcinoma were treated with radiation therapy combined with or without chemotherapy at 16 of the participating institutes in Kansai Cancer Therapist Group, Japan, from January 1978 to December 1980. The study comprised 77 males and 28 females; their ages ranged from 15 to 80 years (mean, 53 years). Five-year survival rates according to stage were as follows: Stage I, 100%; Stage II, 67%; Stage III, 44%; and Stage IV, 34%. As far as Stage IV disease was concerned, the radiation therapy only group showed significantly poorer prognosis than the combined radiation and chemotherapy group (P less than 0.05). Concerning the N stage and treatment method, the radiation therapy only group showed a higher metastatic rate than the chemotherapy combined group (35% versus 14%, P less than 0.05).

Tripolyphosphate is an alternative phosphodonor of the selective protein phosphorylation of liver microsomal membrane

Two proteins (Mr = 145,000 and Mr = 130,000) of rat liver microsomal membrane are selectively phosphorylated in a characteristic biphasic time course by incubating the membrane with [gamma-32P]ATP in the absence of exogenously added Mg2+ (Lam, K. S., and Kasper, C. B. (1980) J. Biol. Chem. 255, 259-266). This endogenous phosphorylation system was solubilized with Triton X-100 and fractionated by chromatography with DEAE-cellulose and Sepharose 4B. The resulting preparation lacked both ATPase and inorganic pyrophosphatase activity, but retained its original character: the first phase occurred in the presence of ATP but the second phase was initiated after its depletion, implying the presence of a phosphodonor other than ATP. The putative phosphoryl donors were demonstrated to be ATP in the first phase and in the second phase tripolyphosphate, which is present in [gamma-32P]ATP preparations as a radioactive impurity. The latter conclusion was corroborated by results showing that tripolyphosphate purified from a commercial [gamma-32P]ATP and chemically synthesized [32P] tripolyphosphate were both capable of phosphorylating the two proteins and that the unlabeled tripolyphosphate competed effectively against the phosphodonor. A rapid dephosphorylation was observed in both phases upon removal of substrates during the reaction, indicating that there is a continuous turnover of the phosphoryl groups being transferred to the proteins. The second phase of phosphorylation maintained by the tripolyphosphate was shown to be reversibly inhibited by micromolar levels of ATP, ADP, and nonhydrolyzable analogues of these compounds. The implications of this unique phosphorylation system are discussed.

Developmental changes in the binding of follicle-stimulating hormone (FSH) to testicular preparations of mice and the effects of hypophysectomy and administration of FSH on the binding

Changes with age in testicular FSH binding and the effects of hypophysectomy and administration of FSH on FSH binding were studied in mice. The binding per unit testicular weight reached a peak at 10-20 days of age and it rapidly decreased during 20-37 days. The total binding per two testes increased from 4 days of age, reaching a peak at 31 days, and decreased thereafter when the testis still continued growing. Scatchard plot analyses of the binding showed that the equilibrium constant of dissociation (Kd) was about 3 X 10(-10) M regardless of age, and the changes in FSH binding were due to changes in the number of binding sites. Hypophysectomy at 90 days of age induced a significant decrease in the testicular weight, but the concentration of FSH binding sites markedly increased 16 days after the operation. In hypophysectomized mice the total number of FSH binding sites was increased 1.8-fold as compared with intact mice. In contrast, hypophysectomy induced a decrease in the total number of LH-binding sites. Injections of 100 micrograms NIH-FSH-P-2 for 10 days to hypophysectomized mice significantly decreased the concentration and the total number of FSH binding sites as compared with those in saline-injected hypophysectomized mice. These results suggest that FSH reduces its own receptors in the testis of mice.

Silver staining for selective detection of histones in polyacrylamide gels

A simple silver-staining technique was developed for selective visualization of histones in polyacrylamide gels. The specificity of the stain was confirmed using a variety of protein mixtures and isolated histones. The staining procedure requires a relatively short time to perform (2.5-3 h), and the sensitivity to lysine-rich histones is comparable to that of the conventional Coomassie blue stain (about 0.1 microgram per band). A possible mechanism for the selective staining was deduced from a comparison with the widely used ultrasensitive silver staining.

Difference in the homology of two nuclear nonhistone protein fractions as compared by polyacrylamide gel electrophoresis

The extent of homology between two protein fractions was compared by simple electrophoretic analysis. Nuclear proteins of several rodent cells of different origins were fractionated into acid-soluble and acid-insoluble fractions. The two protein fractions were subjected to polyacrylamide gel electrophoresis in separate gel systems, and protein bands with identical mobilities were sought either in all possible combinational pairs of cell types or in all cell types. The paired and overall homology indices calculated from these data and chi-square testing of the results indicated that acid-soluble nuclear nonhistone proteins are more homologous than acid-insoluble nuclear proteins. Several factors which might have affected the results were discussed.

Mechanism of silver staining of histones: evidence for involvement of clustered lysine residues

Pretreatment of histones with formaldehyde markedly enhances the formation of metalic silver from ammoniacal silver ion. The rate of silver reduction was determined with different histones by spectrophotometric measurement of colloidal silver stabilized in solution, and the apparent reactivity thus determined was found to be in the decreasing order of H1 greater than H2B greater than H2A greater than H3 greater than H4. Involvement of lysine residues was suggested since this order coincides with that of lysine content of these histones. However, the exceptionally high reactivity of histone H1 can be explained only when greater contribution of clustered lysine residues is assumed. Amino group modification and tryptic digestion studies of H1 corroborated this assumption.

Cross-linking of proteins to DNA in newly synthesized chromatin by diisopropylfluorophosphate, a serine protease inhibitor

When nascent DNA of SV40 pulse labeled with [alpha-32p]dCTP in a permeable cell system was treated in situ with diisopropylfluorophosphate (DFP), a significant fraction of radioactivity was found to be covalently complexed with proteins. The adduct formation was demonstrated by density separation in CsCl, selective precipitation of the complexed DNA with SDS-KC1, and visualization of cross-linked proteins after SDS-PAGE. No cross-linking occurred with mature SV40 chromatin labeled in vivo and extracted from nuclei of infected cells. The DFP-induced DNA-protein cross-linking reaction appears to involve the protein's sulfhydryl groups since pretreatment with some sulfhydryl reagents completely inhibited the reaction.

Partial purification of Simian virus 40 large T antigen by immunoaffinity chromatography and its detection by enzyme-linked immunosorbent assay

Simian virus 40 (SV40) large T antigen was partially purified from small amounts of SV40-infected and SV40-transformed cells by immunoaffinity chromatography with high recovery. T antigen, in both crude and partially purified states, was detected rapidly by a sensitive and quantitative enzyme-linked immunosorbent assay (ELISA). Stability of the partially purified T antigen was found to increase by addition of 0.01% bovine serum albumin (BSA).

[Changes in meal patterns and endogenous chemical determinants related to food intake following intra-ventricle III infusion of mazindol]

To clarify suppressive effects of mazindol on food intake in rats, changes in body weight, meal patterns as well as 24-hr food intake, and endogenous chemical substances were investigated following the intra-ventricle III infusion of 0.03 mumole mazindol. Experiments were carried out under the condition of a 12: 12 light-dark cycle (light: 0800-2000 hr). Mazindol decreased food intake as well as body weight after a 12 hr starvation. Reduced food consumption was observed during 12 hr following the injection. Weight reduction, however, lasted over all 3-tested days. When food was available ad. lib., mazindol decreased meal size during the 4 hr after injection and prolonged postprandial intermeal interval during the 4 hr period starting 2 hr after the injection. The infusion of mazindol also produced relative hyperglycemia and decreased free fatty acids, which was not accompanied with hyperinsulinemia. These findings, together with other reports, indicates that mazindol, unlike amphetamine and fenfluramine, possesses inhibitory actions on the hypothalamic feeding center.

Development of "granulosa" cell tumors from intrasplenic testicular transplants in castrated ACI rats

A day-old testis was transplanted into the spleen of one-month-old castrated ACI male rats. For the first six months, diffuse hyperplasia of the interstitial cells was conspicuous with progressive deletion of spermatogenic cells in the seminiferous tubules. Then multiple foci of hyperplastic nodules started to appear, mainly near the tunica albuginea, in all castrated rats, but never in noncastrated rats. These nodular tissues gradually fused together (so-called Leydig cell tumors) and at about 12 months, other distinct tumor foci, morphologically indistinguishable from ovarian granulosa cell tumors, developed in and replaced the nodular tissues. The specific binding of follicle stimulating hormone to the "granulosa" cell tumor tissues was demonstrated. The hypothesis is presented that Sertoli cells were involved in the hyperplastic nodules and ultimately gave rise to the "granulosa" cell tumors.

Study on subacute toxicity of intravenous sorbitan trioleate (STO) in Wistar rats

Subacute toxicity of STO was carried out using Wistar rats. STO was administered intravenously at dose levels of 12.5, 50.0 and 200.0 mg/kg for 35 days. No influence on general symptom, body weight, food and water consumption and urinalysis were observed. In 200.0 mg/kg group, the hematological examination revealed anemia corresponding to the histological findings of the bone marrow. Biochemical analysis displayed the significant increase and/or decrease of enzyme values in 200.0 mg/kg group. Morphology showed the swelling, vacuolization and granuloma of the spleen, hepatic granuloma, the increase of reticulum cells and granuloma in the bone marrow. Embolism and thrombus were also found in the pulmonary and tail veins probably due to an artifact caused by the i.v. injection. The toxicity of the STO were observed only in 200.0 mg/kg group of both sexes and any remarkable change other than physical effects were found in other groups under the above dosage. Accordingly, the maximal no-effect level of the STO in Wistar rats was considered to be 50.0 mg/kg.

Feeding suppression induced by intra-ventricle III infusion of 1,5-anhydroglucitol

1,5-Anhydroglucitol (1-DG) has been known as an antimetabolic glucose analogue. Using gas chromatography, 1-DG was found to be physiologically present in rat serum. In order to investigate its direct and long-term effects on feeding, 1-DG was infused during the light period into the rat third ventricle in doses of 3.0, 6.0 and 12.0 mumol/rat. Its effects were then compared to those of similarly applied 2-deoxy-D-glucose (2-DG). Following initial hyperphagia, both of these glucose-analogues produced suppressive effects on feeding during the subsequent day throughout the light and dark periods. On the third day after 2-DG injection reduction of feeding did not recover completely to the pretreatment baseline levels, but it did recover after 1-DG. Both 1-DG and 2-DG caused linear dose-related hypophagia, with the slope for 1-DG being about half of that for 2-DG. It is suggested that the delayed hypophagia which followed the initial hyperphagia produced by deoxyglucose was a result of sustained inactivation of the Na-pump due to intracellular ATP deficiency caused by accumulation of deoxy-glucose-6-phosphate.

Electron microscopic study on vaccinia virus release

FL cells infected with the IHD-W strain of vaccinia virus were studied by scanning and transmission electron microscopy. A large number of naked virus particles were found to accumulate beneath the host cell plasma membrane and to protrude from the cell surface. It was seen in some cases that naked viral particles were released by budding not only from the cell surface but also from the surface of cytoplasmic packets which were seen along the cell periphery.

Susceptibility of Rous sarcoma virus-specific sequences integrated into SR-C3H/He mouse ascites sarcoma cell chromatin to DNase I and DNase II

The susceptibility of Rous sarcoma virus (RSV) genomes integrated in mouse ascites sarcoma cells (SR-C3H/He cells) to DNase I and DNase II was investigated. Approximately half of the viral sequences were sensitive to DNase I and DNase II when 17% and 7.4% of the chromatin DNA was rendered acid soluble, respectively. The results suggest that newly acquired exogenous proviral sequences are integrated into both transcriptionally active and inactive regions of chromatin in cells lacking related endogenous viral sequences.

Identification of proteins interacting with newly replicated DNA in SV40-infected cells by UV-induced DNA-protein cross-linking

Protein species interacting with newly replicated DNA were analyzed using a photo cross-linking technique. Nascent DNA was labeled in vitro with [alpha-32P]dCTP and BrdUTP in SV40-infected CV-1 cells made permeable with saponin. The labeled cells were then irradiated with UV light (254 nm) and were treated extensively with DNase I. Proteins with radioactive DNA tags were separated by SDS-PAGE and visualized by autoradiography. Among 10-15 proteins which were cross-linked, the proteins with apparent molecular weights of 16.5 K, 44 K, 82 K and those in the 94-140 K region appeared to be associated with newly replicated SV40 DNA. A pulse-chase experiment showed that the 82 K and 94-140 K proteins interacted with new DNA in a relatively localized region close to the replication fork. The 44 K protein was identified as the major viral capsid protein, VP1, using antiserum to SV40 capsid proteins. It was suggested that VP1 binds to nascent DNA shortly after DNA synthesis and migrates into chromatin maturation regions.

A protein with multiple heme-binding sites from rabbit serum

A 93,000 molecular weight protein (HBP.93) which binds hemin and protoporphyrin IX with high affinity has been isolated from rabbit serum using affinity chromatography on hemin-conjugated agarose. The amino acid composition of this protein is unique in that the proline and histidine contents are remarkably high (16.6 and 9.9 mol %, respectively). A large increase in the absorbance of the Soret region arises from the heme-protein interaction. The spectrophotometric titration showed that the protein can bind 25-35 mol of hemin/mol of protein. The apparent dissociation constant was estimated to be 1-4 X 10(-7) M for hemin at pH 7.4 and approximately 10(-6) M for protoporphyrin IX at pH 9.2. The similarity of the difference spectrum of heme-HBP.93 complex to that of heme-hemopexin complex suggests that a bisimidazol-type coordination of heme iron is involved in the binding. The extremely high capacity of HBP.93 to bind heme is also demonstrated by a large increase in the sedimentation velocity of the protein upon heme binding. The native heme-protein complex migrates faster than the heme-free protein in a polyacrylamide gel at pH 8.8; the increased mobility appears to be due to the charge on the carboxyl groups of the bound heme. Although the use of a hemin-agarose column has failed to reveal a protein of similar size and heme affinity in the sera of a number of other species, including man, the heme-binding properties and high histidine level of the human alpha 2-histidine-rich glycoprotein raise the possibility that the two proteins are related.

Theophylline disrupts diurnal rhythms of humoral factors with loss of meal cyclicity

To test the possibility that theophylline induced circadian disappearance of food intake might depend upon rhythmic disruption of blood glucose, insulin and free fatty acids (FFA), theophylline was administered chronically. This markedly lengthened postprandial intermeal intervals during the dark, and induced approximately identical intermeal intervals and identical meal sizes in the light and dark periods. In contrast to the clear light-dark dependent oscillations of serum glucose, insulin and FFA in the controls, the theophyllinized rats lost circadian fluctuation of each of these three chemical substances. Further, theophyllinized rats, unlike controls, had no time-dependent fluctuation in the levels of these substances at -120, -60 or -15 min preceding the onset of the first meal before the dark. These findings, together with previous reports, explain the disappearance of nocturnal feeding rhythm in theophyllinized rats in terms of functional destruction of circadian regulation in the hypothalamus which modulate the production of chemical determinants of food intake.

The turnover of molecular species of phosphatidylinositol in Ehrlich ascites tumor cells

It has been shown previously the 32Pi is incorporated into phosphatidylinositol 30 times faster than into the other phospholipids classes in Ehrlich ascites tumor cells, whereas [1-14C] glycerol is incorporated at almost the same rate (Waku, K., Nakazawa, Y. and MOri, W. (1976) J. Biochem. 79, 407-411). It was therefore suggested that there is a recirculating system (phosphatidylinositol leads to diacylglycerol leads to phosphatidic acid leads to CDP diacylglycerol leads to phosphatidylinositol) of phosphatidylinositol in Ehrlich ascites tumor cells. In this work, 32Pi or [1-3H] glycerol was injected into the peritoneal cavity of mice bearing Ehrlich ascites tumor cells from which the lipids were extracted after selected periods. Phosphatidylinositol was prepared and fractionated in the form of dimethylphosphatidic acid into six molecular species by AgNO3-impregnated TLC. The specific radioactivities of the fractionated species were determined. 32Pi was incorporated into diene molecular species and [1-3H] glycerol into monoene species with a higher rate than the other species and both precursors were incorporated into tetraene species rather slowly. 32P/3H values appeared to be at almost the same for each molecular species, although monoene species showed slightly lower values. These results suggest that there could be a recirculating of the phosphorylinositol moiety in each of the molecular species of phosphatidylinositol.

[The correlation between serum angiotensin I-converting enzyme activity and the renin-angiotensin-aldosterone system in hypertensive patients (author's transl)]

In order to investigate the role and origin of serum angiotensin I-converting enzyme activity (ACEA) in hypertension, the correlation between serum ACEA and the renin-angiotensin-aldosterone system was evaluated in hypertensive patients of whom 36 had essential hypertension, five had hypertension associated with chronic renal failure, three had renovascular hypertension, and one had primary aldosteronism. Serum ACEA was 17.0 +/- 3.3 U (mean +/- sd) in the normotensive control, 20.1 +/- 7.1 U in patients with essential hypertension, 11.6 +/- 3.4 U in patients with chronic renal failure, 31.7 +/- 1.1 U in patients with renovascular hypertension, and 9.7 U in primary aldosteronism in a recumbent state. There was a significant correlation between serum ACEA and plasma renin activity (PRA) (r = 0.615, p less than 0.001, n = 45) and plasma aldosterone concentration (PAC) (r = 0.599, p less than 0.001, n = 34) in a recumbent state. However, there was no significant correlation between serum ACEA and mean blood pressure. Serum ACEA elevated with furosemide and an upright posture significantly correlated with elevation in PRA (r = 0.369, p less than 0.05, n = 32) but did not significantly correlate with elevation in PAC. It is suggested, therefore, that the kidney is the suspected source of the plasma activity of the enzyme and that serum ACEA plays a possible role in the regulations of blood pressure and electrolyte metabolism modulating the renin-angiotensin-aldosterone system.