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PubMed1988

Reduced amounts of S-adenosylmethionine decarboxylase in the adrenal glands of rats following administration of piribedil or 2-deoxyglucose.

The activity of S-adenosylmethionine decarboxylase (SAM-DC) is decreased in the adrenal gland of the rat following physical stress, metabolic stress or administration of dopamine agonists [M. Ekker and T. L. Sourkes, Endocrinology 120, 1299 (1987)]. Immunotitration studies with a serum directed against purified rat liver SAM-DC show that the reduction in activity of the enzyme following administration of 2-deoxyglucose or piribedil was paralleled by a decrease in the amount of immuno-reactive protein. There was no difference in the half-life of SAM-DC activity between piribedil-treated rats and controls. The properties of an extensively purified preparation of the adrenal enzyme resembled those of SAM-DC obtained from rat liver. It is suggested that the reduction in adrenal SAM-DC activity and protein content caused by stress is due to a reduction in the rate of synthesis of the enzyme.

Adenosylmethionine Decarboxylase↗
PubMed1984

Initiation of meiosis and sporulation of Saccharomyces cerevisiae by sulfur or guanine deprivation.

Homothallic Saccharomyces cerevisiae, growing exponentially in a synthetic acetate medium, could be initiated to undergo meiosis and subsequent sporulation by removal of sulfur from the medium or by partial purine deprivation of purine auxotrophs or, most efficiently, by guanine deprivation of a guanine auxotroph. In contrast, partial uracil deprivation of uracil auxotrophs did not cause sporulation. Under any of the above and other sporulation conditions, the intracellular concentrations of GTP and, usually at some time later, S-adenosylmethionine (SAM) decreased; the concentrations of the other nucleoside triphosphates decreased under some but increased under other sporulation conditions. The addition of 1 mM methionine or, more effectively, of SAM or the combination of adenine plus methionine greatly increased the intracellular concentration of SAM and reduced or prevented sporulation, even when GTP decreased. However, differentiation can be inhibited by an excess of many metabolites which do not specifically control the initiation process; in particular, SAM is known to inhibit yeast metabolism (e.g., transamination). Therefore, we cannot yet decide whether the deficiency of GTP or SAM (or related compounds) serves as a signal for the initiation of meiosis/sporulation.

Culture Media↗
PubMed1990

Alteration of cellular adhesion by heat shock.

Chinese hamster ovary (CHO) cells were analyzed for their ability to reassemble microfilament bundles, to remain attached to a tissue culture surface, or to initiate and complete attachment onto a substrate after heat shock (45 degrees C/10 min). The cells remained attached to the tissue culture surface during and after the heat shock while the actin microfilament bundles were reversibly disrupted. Heat shock inhibited the ability of the cells to initiate and complete attachment onto a new tissue culture surface or onto a plastic surface coated with vitronectin. An inspection of the proteins present in substrate-attached material (SAM) revealed 11 major proteins containing glucosamine whose apparent Mr values were 250,000, 200,000, 150,000, 140,000, 90,000, 86,000, 82,000, 68,000, 54,000, 47,000, and 46,000. Three of the proteins (p200, p150, and p46) bound to wheat germ agglutinin while p150 and p140 bound to concanavalin A. The composition of the 11 proteins of the SAM fraction synthesized previous to the heat shock was not altered during heat shock. However, the appearance of the newly synthesized proteins in the SAM fraction was delayed by heat shock (0.5 h for p150 and 6 h for p82). The ability of heat-shocked cells to reattach onto a vitronectin-coated surface correlated with the appearance of newly synthesized p150 and p82 in the SAM fraction. Our results suggest that in addition to the microfilament bundles, heat shock may reversibly disrupt the cellular adhesion site. Further, p150 and p82, proteins whose appearance in the SAM fraction is delayed by heat shock, may be involved in the cellular attachment onto substrates, including vitronectin.

Actin Cytoskeleton↗
PubMed1987

Effects of the transmethylation inhibitor S-adenosyl-homocysteine and of the methyl donor S-adenosyl-methionine on rat Leydig cell function in vitro.

In purified rat Leydig cells, the methyl donor S-adenosyl-methionine (SAM), increases significantly in a dose dependent manner the [125I]hCG binding as well as the productions of cAMP and of testosterone; the competitive inhibitor of methylations S-adenosyl-homocysteine (SAH), has an opposite effect. Associated to oLH, SAM further enhances the cAMP synthesis while SAH inhibits significantly the adenylate cyclase activity. With regard to testosterone synthesis, SAM potentiates the stimulating roles of oLH and dbcAMP (27 and 38% increases, respectively) although SAH diminishes testosterone productions (48 and 35%, respectively under oLH and dbcAMP stimulations). Scatchard analysis has shown that SAM (1.4 mM) increases the number of LH/hCG binding sites on Leydig cells while SAH (1.4 mM) decreases it; LH/hCG Ka values are not modified neither by SAM nor by SAH. These data suggest that the in vitro regulation of steroidogenesis in purified rat Leydig cells may involve methylation processes (presumably phospholipids are the potential substrates of these reactions) which modulates the transmission of the hormonal signal through the membrane and affects the testosterone synthesis at a step beyond the adenylate cyclase.

Animals↗
PubMed1985

Glycosaminoglycan distribution in substratum adhesion sites of aging human skin fibroblasts, including papillary and reticular subpopulations.

Glycosaminoglycan (GAG) distribution has been analyzed in the adhesion sites, left substratum-bound after EGTA-mediated detachment, of various human skin fibroblast populations grown in vitro in the presence (asc+) or absence (asc-) of ascorbate. Examination of these skin fibroblasts during the EGTA treatment by scanning electron microscopy reveals that (a) asc+ cells detach much more rapidly than asc- cells, but (b) asc- or asc+ cells leave the same two types of structures in longterm culture-generated substratum-attached material (L-SAM)--long linear retraction fibers and "footpad-like" structures. Most of the [3H]glucosamine-radiolabeled polysaccharides in L-SAM were shown to be GAGs. Fibroblasts from a full-thickness skin sample from a very young patient (AG4449) have similar distributions of the GAGs in both the EGTA-suspended cell and L-SAM fractions; however, asc+ cell and L-SAM fractions contain relatively more heparan sulfate than the asc- fractions. In contrast, full-thickness skin fibroblasts from an elderly patient (AG2261) generate GAG distributions in their L-SAMs (with greatly elevated levels of hyaluronate and chondroitin sulfate) that are very different from those of the cell fractions and from those of AG4449; furthermore, these distributions in AG2261 fractions do not change when shifted from asc- to asc+ medium. These studies led to analyses of the two major fibroblast subsets--papillary (PAP) or reticular (RET)--that can be isolated from the dermis of a newborn infant (patient 5). The GAG distributions in the RET fractions were different from those in PAP fractions; of special note was the greater length of heparan sulfate chains from all RET fractions examined when compared to PAP fractions. There was a remarkable similarity in the GAG distributions of asc+ RET fractions when compared to the full-thickness AG2261 cell fractions. In summary, these studies demonstrate that asc- or asc+ "young" cells generate different GAG distributions in their substratum adhesion sites, whereas "old" cells from a full-thickness skin sample do not alter their distribution when shifted from asc- to asc+ (this distribution is different from that of "young" cells). Furthermore, analyses of GAGs in papillary and reticular cell fractions reveal significant differences between the two, with considerable similarity of asc+ reticular fractions to the full-thickness AG2261 fibroblasts, which is consistent with the enrichment of reticular fibroblasts in the skin of aging individuals.

Aging↗
PubMed1990

Effects of a new TRH analogue, YM-14673, on disturbance of passive avoidance learning in senescence-accelerated mice.

Effects of a new TRH analogue, YM-14673 (N alpha-[[(S)-4-oxo-2-azetidinyl]carbonyl]-L-histidyl-L-prolinamide dihydrate), on disturbance of passive avoidance behavior were observed in senescence-accelerated mice (SAM). Latency of step-through in SAM-P/8/Ta (SAM-P/8, senescence-prone substrain) was significantly shorter than that in SAM-R/1/Ta (SAM-R/1, senescence-resistant substrain). Successive oral administration of YM-14673 (1 and 10 mg/kg) and TRH (10 mg/kg) for 3 weeks prolonged the shortened latency of step-through. These results suggest that YM-14673 is more potent than TRH in antiamnesic activities.

Aging↗
PubMed1994

Nicotine improves cognitive disturbance in senescence-accelerated mice.

Senescence-accelerated mice (SAM), a murine model of age-related deterioration in learning ability, were studied as to the acetylcholine (ACh) contents in the brain tissues and the effect of nicotine administration. We found that the ACh content of SAM-P/8 (accelerated senescence-prone) mice was lower than that of SAM-R/1 (accelerated senescence-resistant) mice in the midbrain thalamus and the hypothalamus. In addition, an IP administration of nicotine was found to improve learning ability of SAM-P/8 as shown by performance of a passive avoidance task. Nicotine may potentiate cognitive function in SAM-P/8.

Acetylcholine↗
PubMed1992

Characterization of membrane fraction lipid composition and function of cirrhotic rat liver. Role of S-adenosyl-L-methionine.

The effect of S-adenosyl-L-methionine (SAM) administration on the lipid composition of the membrane fraction obtained from livers of cirrhotic rats was studied. Four groups of animals were used: group 1 received CCl4 for 8 weeks to induce cirrhosis. Animals in group 2 received 3 daily i.m. injections of SAM 20 mg/kg in addition to CCl4. Groups 3 and 4 were control groups of SAM and vehicles. Seventy-two h after the end of treatment all animals were killed and livers were studied to measure glycogen, cAMP contents and to isolate membrane fractions. The membrane activity of Na+,K(+)- and Ca(2+)-ATPases was measured and the lipid content was analyzed in extracts. Phospholipids were determined by thin-layer chromatography and fatty acids by gas chromatography. Chronic CCl4 treatment led to increases in cholesterol and in the cholesterol/phospholipid ratio. Analysis of phospholipids revealed an increase in phosphatidylserines. Saturated fatty acids increased, while unsaturated decreased significantly. The CCl4-treated group showed a decrease in glycogen and an increase in cAMP contents. Na+,K(+)- and Ca(2+)-ATPases activity were highly reduced in cirrhotic membranes. In the group receiving CCl4 + SAM the lipid composition and the function of liver membrane fraction showed no difference compared to normal controls, except for fatty acid composition which was similar to concentrations in the CCl4-treated group. Glycogen depletion was only partially prevented whereas cAMP levels were normalized in the CCl4 + SAM group. Our results showed that membrane lipid alterations were accompanied by changes in the activity of enzymes embedded in the membrane fraction derived from CCl4-cirrhotic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1987

A review of Society for Adolescent Medicine abstracts and Journal of Adolescent Health Care articles.

Adolescent medicine research has dramatically increased over the past 20 years. The object of this study was to assess the status of design in adolescent health care research. All abstracts of presentations at the 1978-1985 Society for Adolescent Medicine (SAM) Meetings are included as well as all articles from the Journal of Adolescent Health Care (JAHC) from 1980 through September of 1985. The abstracts were analyzed for basic design, subject, sample size, study site, number of authors, and type of statistical analysis. A descriptive design comprised 32.8% of the SAM abstracts and 62.9% of the JAHC articles. An observational design comprised 57.8% of the SAM abstracts and 35.5% of the JAHC articles. An experimental design comprised 9.3% of the SAM abstracts and 1.6% of the JAHC articles. Of the 203 abstracts, 46% involved medical and 45.6% psychosocial topics. The JAHC articles were also fairly equally divided. Descriptive studies have decreased from 1978 to 1985 whereas observational studies have increased. The medium sample size of SAM abstracts increased from 1978 (83) to 1985 (100). Statistical methods were only analyzed for JAHC articles. Sixty-one percent used either no methods or used descriptive statistics only. The major statistical tests used were contingency tables, t-tests, analyses of variance, and Pearson correlations. Adolescent medicine research from these two sources usually involves descriptive and observational designs. The few clinical trials conducted involved small sample sizes. An increase in experimental and collaborative projects is needed.

Adolescent↗
PubMed1988

The reduction of intracellular polyamines by sequential inhibition of the synthesis of decarboxylated S-adenosylmethionine: effects on rat leukemia.

Decarboxylated S-adenosylmethionine (SAM) is an aminopropyl donor in the synthesis of the polyamines, spermidine and spermine. The decarboxylation of SAM is inhibited by the toxic cytostatic drug methylglyoxalbis-(guanylhydrazone) (MGBG). To achieve more specific and less toxic effects of MGBG, this drug was combined with cycloleucine, which inhibits SAM synthesis, and with nitrous oxide, which inhibits methionine synthetase. This treatment thus aimed at sequential inhibition of the synthesis of decarboxylated SAM, and was studied in a rat leukemia model (BNML). Combined treatment further decreased the level of spermine, but not of spermidine, in leukemic cells, compared to the effects of MGBG alone. The therapeutic effects of this combination were additive or less than additive, however. MGBG was not very effective in reducing leukemic growth and severely toxic, although less with combined treatment. Another inhibitor of SAM decarboxylase, berenil, was also used, and although this drug was about equally active in inhibition of leukemic growth, alterations in intracellular polyamines were not observed. The combination of nitrous oxide and cycloleucine, which effectively reduced leukemic growth at non-toxic dosages, selectively inhibited spermine synthesis, and therefore may be used to interfere with polyamine metabolism. The relevance of this polyamine deprivation to the treatment of leukemia could not be demonstrated.

Adenosylmethionine Decarboxylase↗
PubMedDate not supplied

S-adenosylmethionine generation and prevention of alcoholic fatty liver by betaine.

Earlier studies by other investigators have shown that S-adenosylmethionine (SAM) has the capacity to attenuate liver injury in experimental animals. In a recent study in this laboratory, it was shown that when supplemental dietary betaine was given to control and ethanol-fed rats at the level of 0.50% (W/V), SAM levels were doubled in the livers of control animals and increased fivefold in livers of ethanol-fed rats. The increased levels of SAM in the livers of ethanol-fed animals protected the livers from fatty infiltration due to ethanol feeding. In this study, an attempt was made to determine the minimum level of dietary betaine that protects against the fatty infiltration. Levels of betaine at 0.05%, 0.10%, 0.25%, and 0.50% in semiliquid control and alcohol diets were tested in rats for 30 days. When hepatic betaine, SAM, and triglyceride levels were determined, it was demonstrated that only the dietary level of betaine at 0.50% supplied enough hepatic betaine to generate the level of SAM that was required to protect against the alcoholic steatosis resulting from the dietary ethanol. These results suggest that betaine, when given in sufficient amounts, may be a promising therapeutic agent in the treatment of liver disease.

Animals↗
PubMed2004

Self-assembled monolayers with different terminating groups as model substrates for cell adhesion studies.

Cell shapes induced by cell-substratum interactions are linked with proliferation, differentiation or apoptosis of cells. To clarify the relevance of specific surface characteristics, we applied self-assembled monolayers (SAM) of alkyl silanes exhibiting a variety of terminating functional groups. We first characterised the SAMs on glass or silicon wafers by measuring wettability, layer thickness and roughness. Water contact angle data revealed that methyl (CH(3)), bromine (Br), and vinyl (CH=CH(2)) groups lead to hydrophobic surfaces, while amine (NH(2)) and carboxyl (COOH) functions lead to moderately wettable surfaces, and polyethylene glycol (PEG) and hydroxyl (OH) groups created wettable substrata. The surfaces were found to be molecular smooth except for one type of NH(2) surface. The SDS-PAGE analysis of proteins adsorbed from bovine serum to the SAMs showed less protein adsorption to PEG and OH than to CH(3), NH(2) and COOH. Immunoblotting revealed that a key component of adsorbed proteins is vitronectin while fibronectin was not detectable. The interaction of human fibroblasts with CH(3), PEG and OH terminated SAMs was similarly weak while strong attachment, spreading, fibronectin matrix formation and growth were observed on COOH and NH(2). The strong interaction of fibroblasts with the latter SAMs was linked to an enhanced activity of integrins as observed after antibody-tagging of living cells.

Adsorption↗
PubMed2005

Nucleation and growth of calcium phosphate on amine-, carboxyl- and hydroxyl-silane self-assembled monolayers.

Upon implantation, calcium phosphate (Ca-P) surfaces form on materials that are bone bioactive. In this study, the evolving surface characteristics associated with calcium phosphate precipitation are modeled using self-assembled monolayers (SAMs), in a one-step nucleation process. SAMs were used to create amine (-NH2), carboxyl (-COOH) and hydroxyl (-OH) functionalized surfaces by grafting 3-aminopropyltriethoxysilane, 3-triethoxysilylpropyl succinic anhydride and glycidoxypropyl tri-methoxysilane, respectively, onto oxidized silicon wafers. The SAM surfaces were characterized using ellipsometry to establish the presence of grafted molecules. On the surfaces incubated in simulated physiological fluids for 7 days, the thickness of Ca-P layer grew slowly over the first few hours, increasing strongly between 1 and 5 days and then slowed down again. FTIR showed the dependence of calcium phosphate morphology on the type of surface groups, with stronger P-O bands seen on the OH-terminated surface. SEM analysis showed dispersed Ca-P precipitates on the -COOH and -OH terminated surfaces after 1 day immersion. After 7 days, all SAM surfaces were covered with uniformly dispersed and denser Ca-P precipitates. The underlying Ca-P layer showed cracks on the -NH2-terminated surface. Rutherford backscattering spectrometry (RBS) data analysis confirmed that Ca/P ratio is in excellent agreement with the theoretical value of 1.67 for hydroxyapatite. X-ray diffraction (XRD) analysis also showed evidence of apatite formation on all the surfaces, with stronger evidence on the -OH-terminated surface. Highly porous Ca-P precipitates were observed on the SAM surfaces portrayed by the AFM scans with nanoscale RMS roughness. Thus, using highly controlled surface chemistry, under physiological conditions, in vitro, this study demonstrates that a hydroxylated surface enhances Ca-P nucleation and growth relative to other surfaces, thereby supporting the concept of its beneficial effect on bone tissue formation and growth.

Amines↗
PubMed2004

S-adenosylmethionine radical enzymes.

The role of S-adenosylmethionine (SAM) as a precursor to organic radicals, generated by one-electron reduction of SAM and subsequent fission to form 5'-deoxyadenosyl radical and methionine, has been known for some time. Only recently, however, has it become apparent how widespread such enzymes are, and what a wide range of chemical reactions they catalyze. In the last few years several new SAM radical enzymes have been identified. Spectroscopic and kinetic investigations have begun to uncover the mechanism by which an iron sulfur cluster unique to these enzymes reduces SAM to generate adenosyl radical. Most recently, the first X-ray structures of SAM radical enzymes, coproporphyrinogen-III oxidase, and biotin synthase have been solved, providing a structural framework within which to interpret mechanistic studies.

Coproporphyrinogen Oxidase↗
PubMed2004

Rectified photocurrent in a protein based molecular photo-diode consisting of a cytochrome b562-green fluorescent protein chimera self-assembled monolayer.

We fabricated a self-assembled monolayer (SAM) of a chimeric protein created as a novel model protein for an artificial light-harvesting complex (LHC) composed of two proteins, cytochrome b(562) (cytb(562)) mutated for SAM fabrication (cytb(562), N22C, G82C) and enhanced green fluorescent protein (EGFP). The SAM formation of chimeric protein on a single-crystalline Au(111) substrate was confirmed by atomic force microscopy (AFM) measurement. The rectified photocurrent of the chimeric protein SAM on a gold substrate was detected by light-illumination scanning tunneling microscopy (LI-STM) co-operated with a lock-in technique. The photocurrent generation of the chimeric protein SAM was wavelength-specific to the light-illumination (488 nm), which indicated that the EGFP part of the chimera plays a role as a sensitizer in the photo-induced electron transfer process.

Biosensing Techniques↗
PubMed2004

Enhanced performance of a surface plasmon resonance immunosensor for detecting Ab-GAD antibody based on the modified self-assembled monolayers.

To enhance the feasibility of surface plasmon resonance (SPR) immunosensor as a tool for diagnosing type I diabetes, we enhanced the sensitivity of immunoresponse for detecting the monoclonal anti-glutamic acid decarboxylase (GAD) antibody by modification of mixed self-assembled monolayers (SAMs). The effects of the different mixed SAMs were evaluated with respect to the degree of streptavidin immobilization, the degree of biotin-GAD immobilization, and the immunoresponse sensitivity. Consequently, the sensitivity of the immunoresponse for the detection of anti-GAD antibody was enhanced as a result of the reduction in steric hindrance brought about by using SAMs of heterogeneous lengths. The immunoresponse for detecting the monoclonal anti-GAD antibody was also enhanced with the reduction of the excess immobilization of biotin-GAD and the minimization of non-specific binding that resulted from the simple substitution of the spacer from a carboxylic-terminated SAM for the hydroxyl-terminated SAM.

Antibodies↗
PubMed2005

KNOX action in Arabidopsis is mediated by coordinate regulation of cytokinin and gibberellin activities.

The shoot apical meristem (SAM) is a pluripotent group of cells that gives rise to the aerial parts of higher plants. Class-I KNOTTED1-like homeobox (KNOX) transcription factors promote meristem function partly through repression of biosynthesis of the growth regulator gibberellin (GA). However, regulation of GA activity cannot fully account for KNOX action. Here, we show that KNOX function is also mediated by cytokinin (CK), a growth regulator that promotes cell division and meristem function. We demonstrate that KNOX activity is sufficient to rapidly activate both CK biosynthetic gene expression and a SAM-localized CK-response regulator. We also show that CK signaling is necessary for SAM function in a weak hypomorphic allele of the KNOX gene SHOOTMERISTEMLESS (STM). Additionally, we provide evidence that a combination of constitutive GA signaling and reduced CK levels is detrimental to SAM function. Our results indicate that CK activity is both necessary and sufficient for stimulating GA catabolic gene expression, thus reinforcing the low-GA regime established by KNOX proteins in the SAM. We propose that KNOX proteins may act as general orchestrators of growth-regulator homeostasis at the shoot apex of Arabidopsis by simultaneously activating CK and repressing GA biosynthesis, thus promoting meristem activity.

Arabidopsis↗
PubMed2004

Formation and stability of rare earth metalloporphyrin monolayer films on amino-terminated silanized quartz surfaces studied by ultraviolet-visible and X-ray photoelectron spectroscopy.

We investigated the fabrication of self-assembled monolayers of 5,10,15,20-tetra-(p-chlorophenyl)-porphyrin metal hydroxyl compounds (MOH; M=Gd, Tb, Er, Lu) on amino-terminated silanized quartz surfaces using ultraviolet-visible (UV-vis) and X-ray photoelectron spectroscopy (XPS). The orientation of MOH molecules in the films, the kinetics of the adsorption of MOH from a chloroform solution on an amino-terminated quartz substrate, and the stability of the metalloporphyrin films under natural light, UV light, and acidic and basic conditions were studied by UV-vis spectroscopy. The results indicate that the central metal is crucial in the formation of self-assembled porphyrin films and that the stability of the MOH SAMs also depends on the central metal. Under natural and UV light irradiation conditions, the stability of the MOH SAMs depends on the strength of the M-N bonds between the central metal and pyrrole nitrogens or between the central metal and the axial ligand. In the acidic conditions, the UV-vis spectra of the MOH SAMs show decreases in the absorbance and blue shifts. These spectral changes lead us to suggest that the four M-N bonds between the central metal and the pyrrole nitrogens of the porphyrins are cleaved and the resulted porphyrins are protonated under acidic conditions. Thus, it is likely that the protonated porphyrins and MOH form pi-pi complexes with a parallel stacking of the macrocycles through the electrostatic attractive interaction in the SAMs, resulting in the blue shifts of the Soret bands of the SAMs.

Journal Article↗