[Chemical constituents of Ipomola batatas Lam]

Three chemical compounds isolated from the leaves and stems of Ipomoea batatas were identified as fumaric acid, succinic acid and 7,3',4'-trimethylquercetin by chemical and spectroscopic analysis. In this paper, an analysis of the amino-acids of Ipomoea batatas is also reported.

Imaging through a scattering wall using absorption

An object hidden behind a cloudy wall is shown to become visible when the wall is made absorbing. The underlying principle is that the absorption in a random medium preferentially reduces the intensity of the multiple scattered light (noise) over the ballistic signal (image). The intensity of the noise can be reduced below the ballistic signal intensity when the medium is made sufficiently absorbing, thus allowing us to see through an otherwise opaque random scattering wall.

Evidence for an arginine residue at the substrate binding site of Escherichia coli adenylosuccinate synthetase as studied by chemical modification and site-directed mutagenesis

Chemical modification of adenylosuccinate synthetase from Escherichia coli with phenylglyoxal resulted in an inhibition of enzyme activity with a second-order rate constant of 13.6 M-1 min-1. The substrates, GTP or IMP, partially protected the enzyme against inactivation by the chemical modification. The other substrate, aspartate, had no such effect even at a high concentration. In the presence of both IMP and GTP during the modification, nearly complete protection of the enzyme against inactivation was observed. Stoichiometry studies with [7-14C]phenylglyoxal showed that only 1 reactive arginine residue was modified by the chemical reagent and that this arginine residue could be shielded by GTP and IMP. Sequence analysis of tryptic peptides indicated that Arg147 is the site of phenylglyoxal chemical modification. This arginine has been changed to leucine by site-directed mutagenesis. The mutant enzyme (R147L) showed increased Michaelis constants for IMP and GTP relative to the wild-type system, whereas the Km for aspartate exhibited a modest decrease as compared with the native enzyme. In addition, kcat of the R147L mutant decreased by a factor of 1.3 x 10(4). On the bases of these observations, it is suggested that Arg147 is critical for enzyme catalysis.

31P nuclear magnetic resonance spectroscopy studies of substrate and product binding to fructose-1,6-bisphosphatase

The enzymatic hydrolysis of fructose 1,6-bisphosphate (Fru-1,6-P2) to fructose 6-phosphate (Fru-6-P) and inorganic phosphate (Pi), which is catalyzed by fructose-1,6-bisphosphatase, has been studied by 31P nuclear magnetic resonance spectroscopy (NMR). At pH 7.5 and 15 degrees C, the equilibrium constant for the central complex K'eq = [E.Fru-6-P.Pi]/[E.Fru-1,6-P2.H2O] is about 2. This observation is in harmony with results obtained with a number of Bi Bi enzyme systems for the determination of K'eq in which a variety of experimental techniques were used (Knowles, J.R. (1980) Annu. Rev. Biochem. 49, 877-919). Significant changes in 31P NMR chemical shifts were observed for both the substrate, Fru-1,6-P2, and the product, Fru-6-P, when bound to the enzyme relative to ligand free in solution. The chemical shifts of the substrate and product were altered further in the presence of Mg2+, the catalytic divalent metal ion. The chemical shifts caused by the addition of metal ion can be reversed in the presence of trans-1,2-diaminocyclohexane- N,N,N',N'-tetraacetic acid (CDTA) or AMP. In the presence of the metal ion chelator or the nucleotide, the substrate had a chemical shift that was about the same as that observed in the absence of metal ion. On the basis of these observations we suggest that AMP and CDTA exhibit similar effects, i.e. they both remove the catalytic metal ion from the enzyme. This finding is supportive of the suggestion (Scheffler, J. E., and Fromm, H.J. (1986) Biochemistry 25, 6659-6665; Liu, F., and Fromm, H.J. (1990) J. Biol. Chem. 265, 7401-7406) that the role of AMP in the regulation of fructose-1,6-bisphosphatase is to prevent binding of the divalent metal activator to the enzyme.

Expression of human brain hexokinase in Escherichia coli: purification and characterization of the expressed enzyme

Human brain hexokinase (hexokinase I) was produced in Escherichia coli from a synthetic gene under control of the bacteriophage T7 promoter. The expressed coding region derives from a human cDNA clone thought to specify hexokinase I based on amino acid sequence identity between the predicted translation product and hexokinase I from rat brain. The open reading frame from this cDNA was fused to the promoter and 5' flanking region of T7 gene 10, and expressed in E. coli by induction of T7 RNA polymerase. Induced cells contained a hexokinase activity and an abundant protein of apparent molecular weight 100,000, neither of which was present in cells lacking T7 RNA polymerase. Enzyme purified to near homogeneity consisted of a 100,000 Da protein, the size predicted from the nucleotide sequence of the expressed cDNA. The purified enzyme had Michaelis constants of 32 microM and 0.3 mM for glucose and ATP, respectively, and bound to rat liver mitochondria in the presence of MgCl2. Enzymatic activity was inhibited by glucose-6-P and this inhibition was relieved by inorganic phosphate. Deinhibition by phosphate is a property specific to brain hexokinase.

Further characterization of insulin-like-growth factor binding proteins in rat osteoblast-like cell cultures: modulation by 17 beta-estradiol and human growth hormone

Insulin-like growth factors (IGF-I and IGF-II) are endocrine and autocrine factors affecting bone growth and metabolism. Binding proteins for IGFs (IGFBPs) are synthesized by the target tissues of IGF actions. Thus, IGFBPs may act as modulators for the biological functions of IGFs. We have characterized the rat IGFBPs (rIGFBPs) and studied their regulation by 17 beta-estradiol (beta E2) and human GH (hGH) in rat osteoblast-like (ROB) cell cultures. ROB cells were prepared from 19- to 20-day fetal rat calvariae by sequential collagenase digestion and studies were performed on the serum and phenol red-free conditioned medium of confluent cultures. [125I]IGF-I ligand blots showed that the major rIGFBP in the ROB is a nonglycosylated protein of 31 kilodaltons. This protein was immunoprecipitated by a specific antibody to rIGFBP-2 and messenger RNA for rIGFBP-2 was detected by RNA hybridization indicating that the rIGFBP-2 is the major rIGFBP of ROB. A minor band at 24 kilodaltons is likely to be the rat homologue of the newly isolated inhibitory IGFBP-4. The predominant glycosylated adult form of rIGFBPs of rat serum, rIGFBP-3, was undetectable. When cultures were treated with beta E2 for 2 days, there was a dose-dependent biphasic response which showed an inhibition of the rIGFBP-2 at low doses of 10(-11) to 10(-9) M and a stimulation at 10(-6) M. These changes in rIGFBP-2 parallel the changes in the endogenous IGF-I level. rIGFBP-2 level was not affected by 17 alpha-estradiol at the same concentration range. hGH, on the other hand stimulated the levels of rIGFBP-2 and rIGFBP-4 at doses ranging from 10(-11) to 10(-9) M without changing the IGF-I secretion. The alteration of the rIGFBPs by beta E2 and hGH suggests a role for these hormones in bone by modulating the biological functions of IGFs via their binding proteins.

Excitatory amino acids are released from rat primary afferent neurons in vitro

Multiple lines of evidence implicate the excitatory amino acids (EAAs) (L-aspartate (L-Asp) and L-glutamate (L-Glu) as excitatory transmitters in the spinal cord. The specific objective of this study was to determine whether the EAAs are released from primary afferents. Dorsal root ganglia (DRG) from 2 to 18-day-old rats dissected and cultured for 1-2 weeks were washed in modified Ringers recording solution for a period of 1 h to allow equilibration. The mean +/- S.E.M. baseline concentrations of EAAs recovered during a 5 min interval were 533.29 +/- 65.59 nmol for L-Glu and 106.67 +/- 14.05 nmol for L-Asp. Stimulation of DRG organotypic cultures with potassium resulted in a significant concentration-dependent increase in the release of both EAAs. The concentration of Asp increased to 166 +/- 17% and 203 +/- 13% in response to 5 min exposure of the culture to 25 and 50 mM potassium, respectively. The concentration of Glu increased to 155 +/- 12% and 226 +/- 18% of control in response to the same stimuli. In response to application of 50 mM potassium for 25 min, peak concentrations increased to 465 +/- 53% for Asp and 312 +/- 51% for Glu of the basal concentration. Exposure of the cultures to 1 or 10 microM capsaicin also caused release of both EAAs. The concentrations of Asp and Glu significantly increased to 204 +/- 11% and 165 +/- 15% of basal concentrations, respectively, in response to a 5 min exposure to 1 microM capsaicin. High [K+]e failed to increase the release of EAAs from cultures where DRG cell bodies were removed 72 h prior to release experiments. These results confirm results demonstrating release of EAA from mammalian spinal cord tissues and directly demonstrate for the first time that primary afferent fibers are specifically involved in this release.

Insulin-like growth factors (IGFs) and IGF-binding proteins in the developing rhesus monkey

Rhesus monkeys follow a developmental pattern of serum insulin-like growth factor-I (IGF-I) levels similar to that found in humans. In these monkeys, serum IGF-I levels peak during puberty (2.5-4.5 yr of age in males). We have examined the developmental pattern of IGF-binding protein-1 (IGFBP-1), -2, and -3 in serum by Western ligand blotting, the levels of IGFBP-3, IGF-I, and IGF-II in serum by RIA, and the IGFBP mRNA levels of IGFBP-1, -2, and -3 in the livers of rhesus monkeys from fetal life through adulthood by Northern analysis. The pattern of the serum levels of the IGFBPs reflected the liver mRNA levels of the IGFBPs. The IGFBP-1 and IGFBP-2 liver mRNA and serum levels were highest in the fetus and first year of life and were very low after 4 yr of age. Conversely, the IGFBP-3 liver mRNA and serum levels were relatively low early in life and peaked during puberty. The serum levels of IGF-I and IGF-II were strongly correlated with the level of IGFBP-3. We conclude that the developmental pattern of IGFBPs in the rhesus monkey is similar to that in the human, and that serum IGFBP levels are probably regulated by the rate of IGFBP mRNA synthesis.

Regulation of insulin-like growth factor-binding protein messenger ribonucleic acid levels in sheep thyroid cells

The insulin-like growth factors (IGFs) exist primarily bound to cell surface receptors or complexed to specific binding proteins (IGFBPs). The IGFBPs modulate the bioavailability of the IGFs and may enhance or inhibit IGF actions. Several distinct forms of IGFBPs have been described on the basis of size, immunological determinants, and distribution in biological fluids; the IGFBPs may differ as well in their biological function. Sheep thyroid cells produce IGFBPs under hormonal regulation. Cells grown in basal medium or with six-hormone (6H) medium supplements (transferrin, glycyl-histidyl-lysine, hydrocortisone, somatostatin, insulin, and TSH) release nonglycosylated BPs that migrate at 24, 27, 29, and 32 kDa on Western ligand blot. Cells cultured with the thyroid mitogens epidermal growth factor and phorbol ester release additional glycosylated IGFBPs of 40-44 kDa. Immunoprecipitation experiments indicate that 29- and 32-kDa IGFBPs are antigenically related to IGFBP-2, and the 40- to 44-kDa proteins are related to IGFBP-3. Using specific cDNA probes IGFBP-1, -2, and -3, we examined the regulation of IGFBP mRNA levels in sheep thyroid cultures. The rat IGFBP-2 cDNA probe hybridized to an approximately 1.6-kilobase mRNA species in cells under all culture conditions. However, IGFBP-3 mRNA was detectable only in epidermal growth factor- or phorbol ester-treated cells and appeared within 4 h, preceding the release of IGFBP-3 protein into the medium. The 6H additives, which stimulate differentiated function in thyroid cells, inhibited the mRNA levels of both IGFBP-2 and IGFBP-3. IGFBP-1 mRNA was not detectable. The distinct regulation of these IGFBPs suggest that they may play different biological roles in modulating thyroid physiology.

Speed of the coherent component of femtosecond laser pulses propagating through random scattering media

The pulse profile and the speed of the coherent component of 85-fs laser pulses propagating through a slab of a random scattering medium were measured. The pulse profile was found to remain essentially the same, while the speed was reduced proportionally to the thickness of the slab and the concentration of the scatterers. The reduction in speed can be accounted for by an effective index of refraction that is described either by the volume fractional combination of the indices of refraction of the scatterers and the water or by the coherent interference between the scattered waves and the primary wave.

Cystic echinococcosis in the Xinjiang/Uygur Autonomous Region, People's Republic of China. II. Comparison of three levels of a local preventive and control program

A project to compare different levels of a hydatid disease control program was instigated and evaluated in 16 randomly selected villages in the Xinjiang/Uygur Autonomous Region, PRC (China). Factors tested included the effect of: 1) the role of a village hydatid disease control officer, 2) the use of praziquantel-medicated "bait" tablets for treatment of Echinococcus granulosus tapeworms in dogs, and 3) the use of educational materials for children and adults. Evaluation of contrasting treatment levels was done by determining infection rates of E. granulosus in about 25 dogs examined from each of the 16 villages before and after the trial period, and by use of pre- and post-treatment questionnaires distributed to 40 randomly selected households in each village. Optimum results were obtained in those villages which received medicated tablets and support visits from a control officer on a monthly basis (so-called "moderate intervention level").

A modified electrode plate for low energy electric conversion of atrial fibrillation

Fifty-six patients with atrial fibrillation associated with heart disease were treated with a modified electrode plate for low energy electric conversion. Fifty-four (96%) of these cases were successfully converted into sinus rhythm using the modified electrode plates, a new site and low energy discharge (an average of about 50 J). To construct the new-style electrode plates, a 2 cm arc segment was cut from each of two electrodes (10 cm in diameter each). As for the site of application, the cut-edge of the anterior chest electrode, which has a concave diameter of 150 cm, is placed close to the right of the sterum over the fourth to sixth intercostal spaces, and the cut-edge of the other electrode is placed to the left of the spinal column at the level of the seventh to ninth thoracic vertebrae. The safe-effective period for the appearance of the first post-discharge QRS complex was found to be 1.4-5.0 s.

[Hereditary mechanism of systemic lupus erythematosus]

The rates of Sister Chromatid Exchange (SCE) were scored in short-term cultivated peripheral lymphocytes taken from 49 SLE patients and 22 of their first degree relatives. Higher SCEs were found in these two groups as compared with the normal controls. The patients' serum levels of Superoxide Dismutase (SOD) were lower while those of their relatives were normal. Addition of SOD was able to induce marked SCE decrease. Our results indicate that SLE is associated with primary DNA repair defect and that the reduction of SOD might play an important role in the development of SLE. and exogenic SOD has certain protective effect on the human body.

Pulmonary artery involvement in aorto-arteritis. An analysis of DSA

Angiographic features of the pulmonary artery were studied in 24 patients with aortoarteritis (Takayasu's arteritis) by digital subtraction angiography. The pulmonary artery involvement was found in nine cases (37.5%). The right side was involved in eight and the left side in five cases. The right pulmonary artery was involved in two cases, the lobar artery in six, the segmental artery in six, and subsegmental as well as peripheral branches in four. The angiographic features were stenosis and/or occlusion as were the changes of the systemic arteries in aorto-arteritis. The aorta and its main branches were involved in all nine patients, but the severity of pulmonary vascular changes was not always related to the systemic vascular changes. Bronchial angiography demonstrated enlarged and tortuous bronchial arteries in four cases. Lung ECT revealed abnormalities in four cases.

A specific member of the ATF transcription factor family can mediate transcription activation by the adenovirus E1a protein

The adenovirus E1a protein stimulates transcription of viral early genes. Recent experiments indicate that E1a contains a transcriptional activating region, which functions when directed to a promoter. Because E1a is not a sequence-specific DNA binding protein, how it targets to viral promoters has been a question. Several of the viral early promoters contain one or more binding sites for ATFs, a family of cellular transcription factors. Here we show that E1a can function through a specific ATF protein, designated ATF-2. We provide evidence that E1a interacts with a discrete region of promoter-bound ATF-2, thereby positioning the E1a activating region at a viral promoter.

Cystic echinococcosis in the Xinjiang/Uygur Autonomous Region, People's Republic of China. I. Demographic and epidemiologic data

Demographic and epidemiologic data on those factors potentially related to the prevalence and transmission of hydatid disease caused by Echinococcus granulosus were collected in 1987 from each household in 85 villages in the two communities of Yuanhucun and Ershilidian within Hutubi County in the Xinjiang/Uygur Autonomous Region, PRC, with additional questionnaire data collected from approximately 40 households randomly selected from each of 16 villages within those communities. Yuanhucun and Ershilidian represent a combined area of 522.7 square km, and have 4,853 households with 25,684 inhabitants. Of those households, 69.9% are of the Han ethnic group, 22.1% Hui, 5.3% Uygur, and 2.7% Kazak. The total number of animals censused included 4,169 dogs, 41,369 sheep, 3,673 goats, 2,639 cattle, 5,400 pigs, 1,472 horses, and 59 donkeys. Levels of infection of the causative organism of cystic hydatid disease in various hosts were: dogs harboring Echinococcus granulosus tapeworms - 63 (16.2%) positive of 390 examined in 16 villages; domestic animals with hydatid cysts - 1,593 (88.6%) sheep of 1,797 examined, 69 (56.1%) of 123 goats, and 47 (94.0%) of 50 cattle; and 15 surgeries in inhabitants from 85 villages during the last 16 months prior to completion of the survey (annual case rate of 43.8/100,000). Questionnaire data collected from inhabitants in 16 villages showed that about 82% of the families owned at least one dog and 78% owned sheep. Of those families with sheep, most (84%) killed sheep for meat at least periodically, 76% had seen hydatid cysts in liver or lungs of butchered animals, and 77% routinely gave raw offal to their dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetic studies on the mechanism and regulation of rabbit liver fructose-1,6-bisphosphatase

The interaction of Mg2+, AMP, and fructose 2,6-bisphosphate with respect to rabbit liver fructose-1,6-bisphosphatase was investigated by studying initial-rate kinetics of the system at pH 9.5. A rapid-equilibrium Random Bi Bi mechanism is suggested for the rabbit liver enzyme from the kinetic data. Our kinetic findings indicate that Mg2+ and the inhibitor AMP are mutually exclusive in their binding to fructose-1,6-bisphosphatase. This probably is the mechanism for AMP regulation of fructose-1,6-bisphosphatase and thus, to some extent, gluconeogenesis. A kinetic model for the interaction of these ligands with respect to rabbit liver fructose-1,6-bisphosphatase is presented.

[Anti-inflammatory effects of verapamil, nifedipine and nicardipine]

Anti-inflammatory effects of calcium antagonists verapamil (Ver), nifedipine (Nif) and nicardipine (Nic) were compared. They all produced significant inhibitions in acute and chronic inflammatory models in a dose-dependent manner. The ED30 in the capillary permeability were: Ver 18, Nif 12 and Nic 8 mg/kg, respectively. In the xylene-induced swelling of mouse ears, the ED30 were: Ver 39, Nif 14, and Nic 25 mg/kg, respectively. In the carrageenan paw edema of mice, and in the acetic acid-induced pleurisy and cotton granuloma of rats these drugs inhibited inflammatory responses at 5 or 10 mg/kg. Nif showed a greater effect than Ver and Nic on the paw edema, and Ver showed greater effects than NIf and Nic on the pleurisy and granuloma. At 10 mg/kg they depressed the PGE2 content measured by radioimmunoassay in inflammatory tissues of carrageenan paw edema of mice.

[Chemical constituents of the seed oil of Astragalus complanatus R. Brown]

beta-sitosterol and fatty acids were obtained from the oil of seeds of Astragalus complanatus. The fatty acids were separated and their molecular weights determined by GC-MS. Fourteen of them were identified as heptenoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, octadecenoic acid, octadecanoic acid, octadecadienoic acid, linolenic acid, eicosanoic acid, eicosenoic acid and docosanoic acid, etc.

Characterization of insulin-like growth factor-binding proteins in human serum from patients with chronic renal failure

Western ligand blotting of human serum reveals proteins of 41.5, 38, 33, 28, and 23 kD which will specifically bind [125I]insulin-like growth factor-I [( 125I]IGF-I). The relationship of these binding proteins (BPs) to the two serum BP-IGF complexes of 150 and 40 kD and their relationship to the two purified and well characterized IGF-BPs, BP-25 and BP-53, are not clear. The studies reported here used gel filtration, Western ligand blotting, deglycosylation, affinity cross-linking, and immunoprecipitation with antisera against BP-25 and BP-53 to explore the relationship among these IGF-BP forms. Serum from children with chronic renal failure was used for this study, since, by Western ligand blot, it was rich in all five IGF-BPs. The 28- and 33-kD BPs, which were hard to detect in normal serum, were elevated in chronic renal failure serum. Using this serum in each experiment, it was found that the large (150-kD) BP-IGF complex contained only the 41.5- and 38-kD BPs. Both of these BPs were precipitated by anti-BP-53 antiserum, but not by anti-BP-25 antisera, and both BPs were deglycosylated by endoglycosidase-F to a single 31-kD protein which retained the ability to bind IGF-I. This molecular mass of 31 kD is similar to the 28.7-kD mass for nonglycosylated BP-53 predicted by cDNA sequence analysis. In contrast, the 33-, 28-, and 23-kD BPs were only detected in the small (40-kD) BP-IGF complex. None of the three BPs was precipitated by anti-BP-53 antiserum, and none was digested by endoglycosidase-F. The 28-kD BP comigrated with pure BP-25 under all conditions and was precipitated by two independent anti-BP-25 antisera. The 33-kD BP was also precipitated by both anti-BP-25 antisera, while the 23-kD BP was not precipitated by any of the antisera tested. Thus, BP-53 consists of a core protein of 28.7 kD which is differentially glycosylated in serum to form two BPs of 41.5 and 38 kD; these BPs circulate exclusively as part of the large BP-IGF complex. BP-25 circulates in the small BP-IGF complex as a nonglycosylated protein with an apparent mol wt of 28 kD.(ABSTRACT TRUNCATED AT 400 WORDS)

Application of traditional Chinese drugs in comprehensive treatment of primary liver cancer

The present paper is a summary for treating 50 cases of Stage II primary liver cancer by the Integrated method of traditional Chinese and Western medicine. It was found by comparative observation that the average survival time of the Spleen-Deficiency (SD) type patients was markedly longer than that of Phlegm-Dampness-Stagnancy (PDS), Qi- and Blood-Stagnancy (QBS) and Liver-Kidney-Yin-Deficiency (LKYD) types, indicating that the SD type patients might have a better prognosis, and that the Chinese herbal medicine was an alternative for treating intermediate and late carcinoma.

Identification of different classes of nonessential sulfhydryl groups in Escherichia coli adenylosuccinate synthetase

Reaction of Escherichia coli adenylosuccinate synthetase with the thiol reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) or N-ethylmaleimide (NEM) leads to modification of one cysteine residue per enzyme monomer without significant loss of enzyme activity. Modification of a second cysteine residue occurs under mild denaturing conditions (3.5 M urea), and derivatization of this thiol followed by dialysis results in complete loss of enzyme activity. The remaining two cysteine residues react with DTNB only after treatment with 8 M urea. The location of the various cysteine residues in the enzyme was established by using [14C]NEM followed by tryptic digestion and radiopeptide isolation. The reactive cysteine has been identified as Cys291, and the thiol exposed with 3.5 M urea is Cys344. When Cys344 was replaced by either serine or alanine, the mutant enzymes were found to be as active as the wild-type enzyme. These findings point to the nonessential role of Cys344 in adenylosuccinate synthetase.

Transcription factor ATF cDNA clones: an extensive family of leucine zipper proteins able to selectively form DNA-binding heterodimers

An activating transcription factor (ATF)-binding site (consensus sequence 5'-GTGACGTACAG-3') is a promoter element present in a wide variety of viral and cellular genes. The two best-characterized classes of genes that contain ATF sites are E1A-inducible adenoviral genes and cAMP-inducible cellular genes. Here, we report the isolation of eight ATF cDNA clones, each of which is derived from a separate gene. All ATF cDNA clones examined contain a leucine zipper motif and are significantly similar to one another only within this region. The leucine zipper region of ATF proteins is also similar to that of the AP-1/c-jun family of transcription factors, whose DNA-binding site differs from the ATF-binding site at a single position. DNA binding studies reveal two mechanisms for generating further diversity from the ATF proteins. First, some, but not all, combinations of ATF proteins form heterodimers that efficiently bind to DNA. Second, although all ATF proteins bind to the ATF site, their precise interactions with DNA differ from one another, as evidenced by methylation interference analysis. Our results help to explain how a single promoter element, an ATF site, can be present in a wide variety of promoters.

Investigation of the relationship between tyrosyl residues and the adenosine 5'-monophosphate binding site of rabbit liver fructose-1,6-biphosphatase as studied by chemical modification and nuclear magnetic resonance spectroscopy

The effects of AMP, fructose 6-phosphate (Fru-6-P), fructose 2,6-bisphosphate (Fru-2,6-P2), and paramagnetic ions on the aromatic region of the proton nuclear magnetic resonance (NMR) spectrum of rabbit liver fructose-1,6-bisphosphatase have been investigated at 300 MHz. Two well resolved peaks in this region of the NMR spectrum are assigned to the protons from the aromatic ring of a tyrosyl residue of the enzyme by chemical modification with tetranitromethane and by nuclear Overhauser effects. Nitration of the tyrosyl residue causes desensitization of the enzyme to AMP inhibition as well as the loss of activity. In the presence of AMP during the modifications, 1 tyrosyl residue could be protected, presumably the one observed by NMR. Binding of AMP, an allosteric inhibitor of the enzyme, to rabbit liver fructose-1,6-bisphosphatase leads to an upfield shift of the tyrosyl proton signals in the NMR spectrum. No chemical shift or line broadening could be detected in the presence of the paramagnetic manganous ion, Fru-2,6-P2, or Fru-6-P. The negative intramolecular nuclear Overhauser effect from the ribose H2' proton to the adenine H8 proton of AMP suggested that AMP binds to the enzyme with an anti conformation about the glycosidic bond. The failure to observe intermolecular nuclear Overhauser effects between the tyrosyl residue and the protons of AMP indicates that the distances between them are greater than 4 A. On the basis of these observations, it is suggested that the AMP-related tyrosyl residue may be close to the AMP binding site, but it is not directly involved in ligand binding. Rather, the protection of this tyrosyl residue by AMP as observed by chemical modification experiments may well be due to a conformational change that results from covalent modification of the enzyme.

[Influence of aminophylline on immune function of mice]

The effects of aminophylline (Ami) on immune systems in normal NIH mice were studied. Ami ig 25, 50 and 100 mg/(kg.d) x 8-10 d increased hemolytic ability of plaque forming cells and antibody concentration while it decreased the delayed type hypersensitivity (DTH) reaction and peripheral white blood cells phagocytosing function. Ami 1, 5, 10 micrograms/ml also promoted lymphocyte transformation of [methyl-3H] TdR incorporation induced by PHA in vitro.