Complex structure and regulation of the P16 (MTS1) locus

The p16 gene (P16, MTS1, CDKN2) encodes a negative regulator of the cell cycle. Molecular genetic techniques have been used to explore the role of p16 in normal development and cancer. Two transcripts derived from the p16 gene with distinct protein coding potentials are described. The previously undescribed transcript form has the same exons 2 and 3 as the p16-encoding mRNA but contains a different exon 1. The human p16 transcripts are detected in various tissues, and the ratio of the transcripts is regulated in both a tissue-specific and cell cycle-specific manner. The P16-derived mRNAs are probably generated from separate promoters, and transcription from one of the promoters appears to be regulated, at least in part, by the retinoblastoma gene product.

[Effect of glucocorticoids and other steroids on arginine vasopressin release from rat hypothalamic slices]

Rat hypothalamic slices sectioned with vibratome (containing paraventricular and supraoptic nuclei) were incubated in static microchamber and the Arginine vasopressin (AVP) released from the slices was measured by radioimmunoassay. The effect of glucocorticoids (GC) and other steroids on AVP release was investigated. The results were as follows: (1) AVP was steadily released at a rate of 9.06 +/- 1.23 pg/min for as long as 6 h (not including the 90 min for recovery of slices). (2) Corticosterone (B) inhibited AVP release within 20 min in a dose-dependent manner from 10(-7) to 10(-4) mol/L. (3) Cortisol, 17 beta-estradiol, or testosterone (10(-6) mol/L) also inhibited AVP release within 20 min, but dexamethasone, aldosterone, progesterone, RU486, or cholesterol had no significant effect. (4) RU486 (10(-5)-10(-3) mol/L) could partially block the rapid inhibitory effect of corticosterone. These results suggested that GC might exert in situ a regulatory negative feedback action on the AVP release from hypothalamus of rat through a non-genomic rather than a genomic mechanism.

The effect of hypothermia on transient focal ischemia in rat brain evaluated by diffusion- and perfusion-weighted NMR imaging

The effect of moderate whole-body hypothermia (30 degrees C) on transient middle cerebral artery (MCA) occlusion in the rat was evaluated using diffusion- and perfusion-weighted magnetic resonance imaging. Two hours of transient MCA occlusion was induced by intracarotid insertion of a nylon filament under normothermic (n = 14) and hypothermic (n = 7) conditions. Diffusion- and perfusion-weighted imaging were performed before, during, and after focal ischemia from 30 min up to 7 days. In hypothermic animals, scattered neuronal necrosis was localized to select areas of the caudate putamen and the parietal and insular cortex. In contrast, the normothermic ischemic animals exhibited pan-necrosis and infarct encompassing the damaged area. The diffusion and perfusion data measured from caudate putamen indicate that hypothermia causes a significant reduction in the apparent diffusion coefficient of water (ADCw) and CBF values from normothermic control values (p < 0.01). In both normothermic and hypothermic animals after onset of MCA occlusion, ADCw and CBF values in the core of the ischemic region (striatum) significantly declined from the preischemic and homologous contralateral control ADCw and CBF values (p < 0.05). However, ADCw and CBF in the hypothermic group returned toward control more rapidly than in the normothermic group. These results suggest that the protective effect of hypothermia on ischemic cell damage is reflected in the early return of ADCw during reperfusion and the reduction of ischemic cell damage by hypothermia may be mediated by the improved CBF during acute reperfusion.

Inhibition of fatty acid synthesis in Escherichia coli in the absence of phospholipid synthesis and release of inhibition by thioesterase action

The effects of inhibition of Escherichia coli phospholipid synthesis on the accumulation of intermediates of the fatty acid synthetic pathway have been previously investigated with conflicting results. We report construction of an E. coli strain that allows valid [14C]acetate labeling of fatty acids under these conditions. In this strain, acetate is a specific precursor of fatty acid synthesis and the intracellular acetate pools are not altered by blockage of phospholipid synthesis. By use of this strain, we show that significant pools of fatty acid synthetic intermediates and free fatty acids accumulate during inhibition of phospholipid synthesis and that the rate of synthesis of these intermediates is 10 to 20% of the rate at which fatty acids are synthesized during normal growth. Free fatty acids of abnormal chain length (e.g., cis-13-eicosenoic acid) were found to accumulate in glycerol-starved cultures. Analysis of extracts of [35S]methionine-labeled cells showed that glycerol starvation resulted in the accumulation of several long-chain acyl-acyl carrier protein (ACP) species, with the major species being ACP acylated with cis-13-eicosenoic acid. Upon the restoration of phospholipid biosynthesis, the abnormally long-chain acyl-ACPs decreased, consistent with transfer of the acyl groups to phospholipid. The introduction of multicopy plasmids that greatly overproduced either E. coli thioesterase I or E. coli thioesterase II fully relieved the inhibition of fatty acid synthesis seen upon glycerol starvation, whereas overexpression of ACP had no effect. Thioesterase I overproduction also resulted in disappearance of the long-chain acyl-ACP species. The release of inhibition by thiosterase overproduction, together with the correlation between the inhibition of fatty acid synthesis and the presence of abnormally long-chain acyl-ACPs, suggests with that these acyl-ACP species may act as feedback inhibitors of a key fatty acid synthetic enzyme(s).

Developmental and glucocorticoid modulation of the expression of mRNAs for Gs alpha and G beta subunits in neonatal liver

The mRNA levels for Gs alpha and G beta in liver from various age groups of rabbits were assessed by Northern and dot-blot hybridization assays using cDNA and oligonucleotide probes. The mRNA levels for both Gs alpha and G beta exhibited a transient 30-35% decrease at 3-6 h after birth, followed by a 3- to 3.5-fold increase which peaked at 2 days after birth, then gradually declined to adult levels at 4-6 weeks. The changes in mRNA levels paralleled the changes in protein levels [previously measured by immunoblotting (Kawai and Arinze, 1991)] in the first 2 days after birth, but not in the later periods of development. Beyond day 3, the increase in protein levels persists, reaching maximal levels at 4 weeks and equalling adult levels while their mRNA levels decrease to about 50% of the levels at day 2. In vivo administration of dexamethasone to neonatal rabbits increased hepatic mRNA levels for both Gs alpha and G beta by about 50%; the effect was moderate compared to the 2- to 3-fold increase in corresponding protein levels. The transcription rate for the Gs alpha gene increased by only 32% at day 2 after birth compared to term. A 68% increase in transcription rate for this gene was observed after the dexamethasone treatment. Taken together, these data indicate that the developmental and glucocorticoid-regulated expression of Gs alpha- and G beta-subunits in neonatal liver is modulated at the transcriptional level.

Method for determining the reliable prediction(s) of compositions of tissue phantoms

In a previous paper, we showed that mixture laws can be used to predict the compositions of tissue phantoms. Due to the variation in the performance of the mixture laws when they are applied to phantoms, however, it is difficult to determine which predictions of the composition are most reliable. In this paper, we study the causes of the variation in the performances of different sets of mixture laws, and propose a criterion for choosing a reliable predictor. The predictions selected with the proposed criterion agree very well with the known compositions of phantoms. The potential uses of the mixture methodology and the criterion to tissue characterization are discussed.

Genetic analysis of the agrocinopine catabolic region of Agrobacterium tumefaciens Ti plasmid pTiC58, which encodes genes required for opine and agrocin 84 transport

The acc region, subcloned from pTiC58 of classical nopaline and agrocinopine A and B Agrobacterium tumefaciens C58, allowed agrobacteria to grow using agrocinopine B as the sole source of carbon and energy. acc is approximately 6 kb in size. It consists of at least five genes, accA through accE, as defined by complementation analysis using subcloned fragments and transposon insertion mutations of acc carried on different plasmids within the same cell. All five regions are required for agrocin 84 sensitivity, and at least four are required for agrocinopine and agrocin 84 uptake. The complementation results are consistent with the hypothesis that each of the five regions is separately transcribed. Maxicell experiments showed that the first of these genes, accA, encodes a 60-kDa protein. Analysis of osmotic shock fractions showed this protein to be located in the periplasm. The DNA sequence of the accA region revealed an open reading frame encoding a predicted polypeptide of 59,147 Da. The amino acid sequence encoded by this open reading frame is similar to the periplasmic binding proteins OppA and DppA of Escherichia coli and Salmonella typhimurium and OppA of Bacillus subtilis.

The acquisition of lysophosphatidylcholine by African trypanosomes

Bloodstream forms of the African trypanosome, Trypanosoma brucei, can acquire substantial amounts of exogenous lysophospholipid. Lysophosphatidylcholine uptake is through a pathway consisting of three enzymes, phospholipase A1, acyl-CoA ligase, and lysophosphatidylcholine:acyl-CoA acyltransferase. The pathway enables the organism to acquire fatty acids and phospholipid head groups such as choline. Radiolabeling and 13C NMR studies show that two molecules of lysophosphatidylcholine are used to generate one molecule of cellular phosphatidylcholine. The three enzymes are associated with the trypanosomal plasma membrane and are accessible to exogenous substrates. The first enzyme, phospholipase A1, generates free fatty acid from exogenous lysophospholipid, which the second enzyme, a ligase, uses to form acyl-CoA. The fatty acyl-CoA formed by this route is in a separate pool from that derived from exogenous free fatty acid and is used by the third enzyme, acyltransferase, to acylate a second molecule of exogenous lysophospholipid. Acyltransferase is accessible to exogenous and endogenous acyl-CoA. The high activity of this pathway in bloodstream forms, compared with procyclic culture form trypanosomes, suggests that it may play a role in the acquisition of fatty acids for synthesis of the membrane form of the variant surface glycoprotein. Extracellular myristoyllysophosphatidylcholine can be used by trypanosomes as a source of myristate in remodeling the lipid anchor of the variant surface glycoprotein.

Spectral measurements of NH(3) absorption lines by a 1.5-microm grating-external-cavity semiconductor laser

Forty-four NH(3) absorption spectral lines of the combination tones of the vibration-rotation transitions were observed at 1.4988-1.5520 microm with a 1.5-microm grating-external-cavity semiconductor laser. The linewidth and absorption rate of NH(3) absorption spectral lines were measured. Also, the changes of center frequency and linewidth of the NH(3) absorption spectral line with the our knowledge the first time.

Treatment of ovarian malignant germ cell tumors with preservation of fertility

Conservative operation and postoperative chemotherapy were given to 15 patients with malignant germ cell tumors of the ovary with the preservation of fertility and ovarian functions. Four patients, one with endodermal sinus tumor and three immature teratoma, had full term deliveries after the operation. The possibility was discussed to preserve young women's fertility and ovarian function in treating their malignant germ cell tumors.

Conformation of a synthetic hexapeptide substrate of collagen lysyl hydroxylase

The hexapeptide Hyp-Gly-Pro-Lys-Gly-Glu was synthesized as a potential substrate for collagen lysyl hydroxylase. Kinetic data on the interaction of this peptide with purified chicken embryo lysyl hydroxylase showed that the hexapeptide is a moderately good substrate having Km, Vmax, and Kcat/Km values comparable to those of synthetic peptide substrates having longer chain lengths. Circular dichroism spectral data suggested a consecutive beta turn or 3(10) helical conformation for the peptide in trifluoroethanol. The two-dimensional 1H-TOCSY spectrum of the peptide in dimethylsulfoxide permitted complete assignment of all the protons in the hexapeptide. Through-space connectivities between protons in the peptide molecule were obtained from two-dimensional 1H-NOESY spectral data on the peptide. Using the distances calculated from these data as input constraints, the minimum-energy conformation of the peptide was computed. These calculations and an unconstrained Monte Carlo molecular simulation both led to a folded conformation for the hexapeptide with dihedral angles close to a set of consecutive beta turns as the lowest-energy conformer. This structure is stabilized further by a salt bridge between the side chains of Lys4 and Glu6. Several other conformers energetically close to the minimum-energy conformer exhibited the structural features of the latter except for variations at the N-terminal end and in the side chains. In conjunction with data obtained earlier on lysyl hydroxylase (P. Jiang and V. S. Ananthanarayanan, 1991, J. Biol. Chem. 266, 22960-22967) and the functionally related prolyl hydroxylase (P. L. Atreya and V. S. Ananthanarayanan, 1991, J. Biol. Chem. 266, 2852-2858), the present results suggest that the folded beta turn in the respective peptide substrate may be the structural determinant at the catalytic sites of these enzymes. Additional structural features may govern the effective binding of the peptide at the enzymes' active sites.

[Chemical constituents of Eupolyphaga sinensis Walker]

Five compounds were isolated from the n-hexane extract and n-butanol of extract Eupolyphaga sinensis. These compounds were identified as octacosanol, beta-sitosterol, batyl alcohol, 2,4-pyrimidinedione and allantoin.

Conformational requirement for lysine hydroxylation in collagen. Structural studies on synthetic peptide substrates of lysyl hydroxylase

An attempt has been made to understand the conformational determinants that govern the hydroxylation of selected lysyl residues in the nascent collagen molecule by lysyl hydroxylase (EC 1.14.11.4). A series of peptide substrates of the enzyme, ranging in length from 3 to 12 residues, were synthesized. These included: tert-butyloxylcarbonyl (t-Boc)-Ile-Lys-Gly; Boc-Ala-Lys-Gly; N-acetyl-Ala-Lys-Gly-Ser; Hyp-Gly-Pro-Lys-Gly-Glu; Leu-Hyp-Gly-Ala-Lys-Gly-Glu; Gly-Phe-Hyp-Gly-Leu-Hyp-Gly-Ala-Lys-Gly-Glu; (Hyp-Gly-Pro-Lys-Gly-Glu)2; and Ala-Arg-Gly-Ile-Lys-Gly-Ile-Arg-Gly-Phe-Ser-Gly. The conformational features of these peptides were studied by spectroscopic methods so as to relate this information with the kinetic parameters for the interaction of these peptides with purified lysyl hydroxylase. Spectroscopic data, supported by conformational energy calculations, indicated that the tripeptides t-Boc-Ile-Lys-Gly and t-Boc-Ala-Lys-Gly adopt a gamma-turn structure in water and trifluoroethanol with Lys in the second position of the turn. In the tetra- and larger peptides two structures, the beta-turn and a polyproline-II (PP-II) type extended conformation, were identified. The proportions of these two structures in a given peptide depended on the polarity of the solvent. All of the peptides were hydroxylated by lysyl hydroxylase isolated from chicken embryos. In contrast, a control peptide, t-Boc-Ala-Gly-Lys which adopted a beta-turn with Lys at the end of the turn, was not hydroxylated. Competitive inhibition of the hydroxylation of protocollagen by some of the peptides showed a common binding site for these substrates in the enzyme's active site. Kinetic data on the peptides indicated improved hydroxylation rate (higher Vmax) in peptides having relatively higher beta-turn content and improved binding (lower Km) in peptides with higher content of the PP-II structure. The efficacy of the substrate was also governed by its chain length. These data suggest that the conformational criterion for lysine hydroxylation in collagen-related peptides is the presence of a "bent" structure, such as the gamma- or beta-turn at the catalytic site of lysyl hydroxylase and an "extended" PP-II type structure at the binding site(s) of the enzyme's active site. This suggestion also provides a conformational rationale for earlier observations on the substrate specificity of lysyl hydroxylase.

[On the skinning of radix Adenophorae]

Traditional experience calls for the skinning of Radix Adenophorae. Depending on the chemical compositions, this paper presents a comparative study on the skin, the radix with skin and the skinned radix. The experimental results show that the contents of beta-sitosterol, saponins, amino acids and trace elements are highest in the radix with skin, and that the radix with skin and the skinned radix are similar in the contents of polysaccharides.

[Chemical constituents of Adenophora stricta Miq]

Four compounds were isolated from the roots of Adenophora stricta. On the basis of spectrometric analysis and physicochemical constants, they were identified as beta-sitosterol, beta-sitosterol-O-beta-D-glucopyranoside, taraxerone and octacasanoic acid respectively. Taraxerone and octacasanoic acid were isolated from the plants of Adenophora for the first time.

[Electron microscopic observation of the effects of Rhodiola kirilowii (Regel.) Maxim. in preventing damage of the rat viscera by a hypoxic high altitude environment]

This paper has shown that the pathologic damages done to rat's viscera due to hypoxic environment of altitude can be reduced significantly by oral administrations of Shengmaiyin, Danshen-Chuanxiong mixture and Rhodiola kirilowii. Shengmaiyin that maintains interior substances in the plate layer bodies proves more effective than Danshen-Chuanxiong mixture, while the latter excels in preventing capillary contraction, thus improving blood circulation. Rhodiola kirilowii has the effects of both Shengmaiyin and Danshen-Chuanxiong mixtures.

[Determination of calcium carbonate, trace elements and amino acids in Os Sepiae]

This paper reports the determination methods for calcium carbonate, trace elements and amino acids in the traditional Chinese medicine Os Sepiae. The data provide a reference for the quality control of the drug.

Characteristics of immobilized aminoacylase from Aspergillus oryzae on macroporous copolymers

Aminoacylase from Aspergillus oryzae was adsorbed on functionallized macroporous copolymers where the enzyme showed excellent catalyzing activity and operation stability. Various factors which effect the activity of the immobilized aminoacylase such as temperature, pH and ionic strength were investigated. The continuous operation of the enzyme immobilized on macroporous copolymers was compared with that of the enzyme immobilized on DEAE-Sephadex.