[Coronary heart disease in patients with obstructive sleep apnea]

OBJECTIVE

As patients with severe obstructive sleep apnoea (OSA) have increased cardiovascular morbidity and mortality rates, the prevalence of coronary heart disease (CHD) was investigated in patients with OSA proven by polysomnography (apnoea/hypopnea index > or = 10/h).

PATIENTS AND METHODS

In 440 patients (400 men, 40 women; mean age 55.3 [16-80] years) with OSA proven by polysomnography, the possible diagnosis of CHD was assessed by history, physical examination, ECG at rest and on exercise, one- and two-dimensional echocardiography and, where indicated, myocardial scintigraphy and coronary angiography.

RESULTS

CHD was demonstrated by angiography in 24.6% (men: 26.4%; women: 7.5%). Adding patients with CHD diagnosed noninvasively, but unconfirmed by angiography, positive correlation was found in 33.2% (men: 34.8%; women: 17.5%).

CONCLUSION

There was a high prevalence of CHD in patients with OSA. This underlines the importance of careful cardiac diagnosis in patients with OSA.

[Treatment of radiotherapy-induced gastroparesis with erythromycin]

HISTORY

A 75-year-old woman who had undergone a hysterectomy with adnexectomy followed by radiotherapy for endometrial carcinoma complained of postprandial nausea with vomiting after eating solid foods and of cramp-like abdominal pain, but her appetite was good. She had lost 25 kg in weight over 13 months.

EXAMINATION

Physical examination, laboratory tests, radiology and gastroscopy were unremarkable. Gastric scintigraphy showed abnormally prolonged emptying.

TREATMENT AND COURSE

Nausea and vomiting stopped at once after erythromycin (a motilin agonist) had been administered. It was at first given intravenously after meals (50 mg three times daily for 5 days), then orally for 10 weeks (250 mg three times daily before meals). Subsequent examination revealed normal gastric emptying. The symptoms did not recur after erythromycin had been discontinued.

CONCLUSION

Erythromycin is an effective drug against gastroparesis caused by radiotherapy, because it acts even when the enteric nerves are damaged.

[Obstructive sleep apnea in patients with coronary heart disease]

Patients with obstructive sleep apnea have an increased cardiovascular morbidity and mortality, those with co-existent coronary artery disease being particularly at risk. The object of our study was to evaluate the prevalence of obstructive sleep apnea in patients with coronary artery disease. 153 patients (117 men, 36 women) with verified coronary artery disease were given a highly sensitive standardized questionnaire. The 59 patients with pathological results were then checked with a 6-channel non-laboratory monitoring system. 22.2% of all patients had a respiratory disturbance index (RDI) above 5/h. and 14.4% above 10/h. 13.3% had a pathological RDI and additionally suffered from excessive daytime sleepiness. Patients with coronary artery disease have a high prevalence of obstructive sleep apnea and should consequently be screened for this sleep-related breathing disorder.

Cloning and characterization of a glutathione S-transferase that can be photolabeled with 5-azido-indole-3-acetic acid

Previously, we identified a soluble protein from Hyoscyamus muticus that was photolabeled by 5-azido-indole-3-acetic acid. This protein was determined to be a glutathione S-transferase (GST; J. Bilang, H. Macdonald, P.J. King, and A. Sturm [1993] Plant Physiol 102: 29-34). We have examined the effect of auxin on the activity of this H. muticus GST. Auxins reduced enzyme activity only at high concentrations, with 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid being more effective than indole-3-acetic acid (IAA) and naphthylacetic acid. IAA was a noncompetitive inhibitor, whereas inhibition by 2,4-D was competitive with respect to 1-chloro-2,4-dinitro-benzene. We also present the sequence of a full-length cDNA clone that codes for a GST and contains all partial amino acid sequences of the purified protein. The auxin-binding GST was found in high amounts in roots and stems and low amounts in leaves and flower buds. The steady-state mRNA level was not regulated by IAA or naphthylacetic acid, whereas 2,4-D and 2,3-dichlorophenoxyacetic acid increased mRNA levels. We propose a model in which 2,4-D is a substrate for GST, whereas IAA binds at a second site, known as a ligandin-binding site for the purpose of intracellular transport.

Biochemical, physiological, and molecular characterization of sucrose synthase from Daucus carota

Sucrose synthase (EC 2.4.1.13) from carrot (Daucus carota) is a tetramer with a molecular mass of 320 kD and subunits of 80 kD. The enzyme has a pH optimum of 7.0 (cleavage direction). Maximal activities were measured at 55 degrees C. The Km for Suc was estimated as 87 mM and for UDP as 0.39 mM. Fructose acts as a noncompetitive inhibitor with an inhibition constant of 17.2 mM. In contrast, glucose inhibits carrot sucrose synthase uncompetitively with an inhibition constant of 4.3 mM. cDNA clones encoding a single class of sucrose synthase polypeptide were isolated and sequenced. DNA gel blot analysis also indicated the occurrence of only one to two genes. The deduced amino acid sequence of the carrot enzyme is highly homologous to the sucrose synthase sequences of tomato, potato, and bean. A comparison of the cDNA-derived amino acid sequence with the SS1- and SS2-type sucrose synthase sequences of the monocot plants maize, rice, and barley showed that the carrot enzyme is neither of the SS1 nor of the SS2 type. High enzyme activity was found in roots and petioles of developing carrot plants, with maximal activity in roots at the transition of primary roots to tap roots. Enzyme activity was highly correlated with both polypeptide and transcript levels, indicating that gene expression is regulated mainly at the mRNA level in the different tissues and organs of developing carrot plants.

[Structural cardiac changes in patients with obstructive sleep apnea]

Important pathophysiological mechanisms in obstructive sleep apnea at night are increasing pleural pressure swings, hypoxia and hypercapnia, as well as central nervous arousals with consecutive fragmentation of regular sleep structure. They influence the cardiovascular system, at first only at night and at a later stage also during the day. This might result in cardiac structural changes: dilation and hypertrophy of the right ventricle, hypertrophy of the left ventricle, (especially of the muscular ventricular septum), dilation of right and left atrium. It is suggested that these cardiac structural changes are characteristic for obstructive sleep apnea and therefore define the "sleep apnea heart".

Structural organization and differential expression of carrot beta-fructofuranosidase genes: identification of a gene coding for a flower bud-specific isozyme

Three genomic clones (Inv*Dc1, Inv*Dc2 and Inv*Dc3) were isolated by using the cDNA for carrot cell wall beta-fructofuranosidase as a probe. The expression patterns of the three genes differed markedly. High levels of Inv*Dc1 transcripts were found in leaves and roots of young carrot, whereas in plants with developing tap roots no transcripts were detected. A high level of mRNA of Inv*Dc1 was also present in suspension-cultured cells. In developing reproductive organs, only low levels of transcripts of Inv*Dc1 were found in flower buds and flowers and none at later stages of development. In contrast, Inv*Dc2 and Inv*Dc3 were not expressed in vegetative plant organs. Invb1*Dc1 was exclusively and strongly expressed in flower buds, and Inv*Dc3 at a very low level in suspension-cultured cells.

[Sleep disorders in patients with dialysis-dependent renal failure]

A questionnaire was performed in order to classify the prevalence of sleep disorders in patients with end-stage renal disease treated with hemodialysis. 69 patients (41 male, 28 female) with a median age of 57 years completed the questionnaire. 67% of these patients complained of sleep disorders. 31 patients (45%) had evidence of periodic leg movement syndrome, 22 patients (32%) of restless legs syndrome. 29 patients (42%) had difficulties in falling asleep, 27 patients (39%) in maintaining sleep and 17 (25%) experienced both. Snoring was found in 25 patients (36%), 13 patients (19%) seemed to have sleep apnea. These data show an increased prevalence of sleep disorders in patients with end-stage renal disease on hemodialysis treatment. We conclude that these patients should consequently be asked for sleep disorders, as a specific diagnostic and therapeutic regime could improve quality of life and life expectancy. Especially sleep apnea is a disease that has a high prevalence in this patient group and which can be treated successfully.

Relaxation of trabecular meshwork and ciliary muscle by release of nitric oxide

PURPOSE

Recent evidence suggests that nitric oxide (NO) is a major messenger molecule regulating smooth muscle contractility. A role for NO in aqueous humor dynamics, and thus regulation of intraocular pressure, has been postulated. Recently, we described contractile properties of isolated bovine trabecular meshwork and ciliary muscle strips. To assess whether vasodilators contribute to the regulation of trabecular meshwork and ciliary muscle contractility, we measured the effect of various substances known to induce vasodilation by increasing intracellular cGMP production.

METHODS

Measurements of isometric tension were performed on isolated bovine ciliary muscle and trabecular meshwork strips using a custom-built electromagnetic force-length transducer. The effects of a membrane-permeable cGMP and an inhibitor of nitric oxide formation (L-nitroarginine = L-NAG) were investigated. Organic nitrate (isosorbide dinitrate = ISDN, isosorbide-5-mononitrate = 5-ISMN) and non-nitrate (sodium nitroprusside = SNP, S-nitroso-N-acetyl penicillamine = SNAP) vasodilators were tested.

RESULTS

Isolated strips were precontracted by carbachol 10(-6) mol/l for 30 minutes (100% carbachol maximal contraction). 8-bromo-cGMP 10(-4) mol/l evoked a relaxation to 86.7% +/- 1.4% (n = 8) in ciliary muscle and 58.6% +/- 5.4% (n = 7) in trabecular meshwork. Inhibition of NO-synthase by L-NAG increased the carbachol-induced contraction. The organic nitrovasodilators ISDN and 5-ISMN produced significant relaxations. The non-nitrates SNP and SNAP were the most potent relaxants. SNP 10(-4) mol/l relaxed the isolated ciliary muscle to 55.5% +/- 3.5% and the trabecular meshwork to 38.6% +/- 3.6%. ISDN and SNP were also tested on isolated strips without carbachol-induced precontraction. Both vasodilators had significant relaxing activity under these conditions.

CONCLUSION

The data indicate that an increase of intracellular cGMP by application of cGMP and organic nitrate or non-nitrate vasodilators induces relaxation of the bovine trabecular meshwork and ciliary muscle. Thus, nitric oxide is a cotransmitter of smooth muscle relaxation in the chamber angle and may be involved in the regulation of aqueous humor dynamics.

cDNA cloning of carrot (Daucus carota) soluble acid beta-fructofuranosidases and comparison with the cell wall isoenzyme

Carrot (Daucus carota), like most other plants, contains various isoenzymes of acid beta-fructofuranosidase (beta F) (invertase), which either accumulate as soluble polypeptides in the vacuole (isoenzymes I and II) or are ionically bound to the cell wall (extracellular beta F). Using antibodies against isoenzyme I of carrot soluble beta F, we isolated several cDNA clones encoding polypeptides with sequences characteristic of beta Fs, from bacteria, yeast, and plants. The cDNA-derived polypeptide of one of the clones contains all partial peptide sequences of the purified isoenzyme I and thus codes for soluble acid beta F isoenzyme I. A second clone codes for a related polypeptide (63% identity and 77% similarity) with characteristics of isoenzyme II. These two soluble beta Fs, have acidic isoelectric points (3.8 and 5.7, respectively) clearly different from the extracellular enzyme, which has a basic isoelectric point of 9.9. Marked differences among the three nucleotide sequences as well as different hybridization patterns on genomic DNA gel blots prove that these three isoenzymes of carrot acid beta F are encoded by different genes and do not originate from differential splicing of a common gene, as is the case in the yeast Saccharomyces cerevisiae. All three carrot acid beta Fs, are preproenzymes with signal peptides and N-terminal propeptides. A comparison of the sequences of the soluble enzymes with the sequence of the extracellular protein identified C-terminal extensions with short hydrophobic amino acid stretches that may contain the information for vacuolar targeting.

The carrot secreted glycoprotein gene EP1 is expressed in the epidermis and has sequence homology to Brassica S-locus glycoproteins

Non-embryogenic carrot suspension cells secrete the EP1 glycoprotein. A cDNA clone encoding EP1 was isolated and sequenced. The EP1 sequence revealed a region of homology with Brassica S-locus glycoprotein genes, an Arabidopsis S-like gene and putative S-like receptor protein kinases from maize and Arabidopsis. EP1 gene expression, analysed by in situ mRNA localization, was detected in cells located at the surface of the seedling: in the epidermis of the root, the hypocotyl and the cotyledons, in the root cap, and in a crescent of cells in the apical dome of the shoot. In developing seeds, expression was most pronounced in both the inner and outer integument epidermis.

Molecular characterization of the gene for carrot cell wall beta-fructosidase

Carrot cell wall beta-fructosidase, previously purified and cloned, is encoded by a single, wound- and pathogen-inducible gene. The developmental regulation of the gene was studied by determining the steady-state mRNA levels in different organs during carrot development: cell wall beta-fructosidase mRNA was detected in roots and leaves of young plants but not during tap root development. A genomic clone was isolated and characterized. The transcription start site was determined by primer extension analysis. Inspection of the promoter sequence (1488 bp) revealed the presence of sequences with high homology to cis-acting elements for the regulation of plant genes by wounding and infection. The 5'-regulatory sequence was fused to the reporter gene beta-glucuronidase (GUS) and tested in a transient expression assay with carrot suspension cells and wounded carrot root tissue (aged disks of carrot roots). The expression of the GUS gene in the transfected cells proved that the isolated promoter was functional. In transgenic tobacco plants containing the cell wall beta-fructosidase promoter fused to GUS, the reporter gene was predominantly expressed in the shoot and root meristems of young seedlings. No GUS expression was detected in mature tobacco plants, showing that the development-specific regulation of the cell wall beta-fructosidase promoter seen in carrot was maintained in tobacco plants. In contrast, expression of the GUS reporter gene in transgenic tobacco was not wound inducible. To analyze the functional organization of the cell wall beta-fructosidase promoter, a 5'-deletion series was generated and tested in a transient expression assay in protoplasts of Nicotiana plumbaginifolia. Two regions containing putative silencer elements were identified. A comparison of these regions with known silencer elements identified in both regions one copy of the negative dominant cis-acting element found in a chalcone synthase promoter of petunia.

Isolation of a mutant Arabidopsis plant that lacks N-acetyl glucosaminyl transferase I and is unable to synthesize Golgi-modified complex N-linked glycans

The complex asparagine-linked glycans of plant glycoproteins, characterized by the presence of beta 1-->2 xylose and alpha 1-->3 fucose residues, are derived from typical mannose9(N-acetylglucosamine)2 (Man9GlcNAc2) N-linked glycans through the activity of a series of glycosidases and glycosyl transferases in the Golgi apparatus. By screening leaf extracts with an antiserum against complex glycans, we isolated a mutant of Arabidopsis thaliana that is blocked in the conversion of high-manne to complex glycans. In callus tissues derived from the mutant plants, all glycans bind to concanavalin A. These glycans can be released by treatment with endoglycosidase H, and the majority has the same size as Man5GlcNAc1 glycans. In the presence of deoxymannojirimycin, an inhibitor of mannosidase I, the mutant cells synthesize Man9GlcNAc2 and Man8GlcNAc2 glycans, suggesting that the biochemical lesion in the mutant is not in the biosynthesis of high-mannose glycans in the endoplasmic reticulum but in their modification in the Golgi. Direct enzyme assays of cell extracts show that the mutant cells lack N-acetyl glucosaminyl transferase I, the first enzyme in the pathway of complex glycan biosynthesis. The mutant plants are able to complete their development normally under several environmental conditions, suggesting that complex glycans are not essential for normal developmental processes. By crossing the complex-glycan-deficient strain of A. thaliana with a transgenic strain that expresses the glycoprotein phytohemagglutinin, we obtained a unique strain that synthesizes phytohemagglutinin with two high-mannose glycans, instead of one high-mannose and one complex glycan.

A soluble auxin-binding protein from Hyoscyamus muticus is a glutathione S-transferase

We have used the photoaffinity label azido-[3H]IAA (5-N3-[7-3H]indole-3-acetic acid), a biologically active analog of indole-3-acetic acid, to identify auxin-binding proteins (ABPs) in the soluble fraction of Hyoscyamus muticus. A 25-kD polypeptide previously described (H. Macdonald, A. M. Jones, P. J. King [1991] J Biol Chem 266: 7393-7399) has now been purified to homogeneity by conventional methods. Binding of azido-[3H]IAA to the purified protein was reduced by active auxins but not by inactive indoles. Partial amino acid sequences of the purified protein showed high homology to glutathione S-transferase (GST) from tobacco (ParB) and from maize (GT32). The conclusion that the 25-kD ABP is a GST is further supported by high GST activity in fractions highly enriched in the 25-kD polypeptide and recognition of the ABP by antibodies against GST from wheat and maize. Furthermore, purification of a protein from a soluble protein extract from H. muticus by affinity chromatography on glutathione-agarose also yielded a 25-kD polypeptide that was indistinguishable in its N-terminal amino acid sequence and biochemical characteristics from the protein purified by conventional methods. Possible functions of GST in auxin action are discussed.

cDNA cloning of an extracellular dermal glycoprotein of carrot and its expression in response to wounding

Suspension-cultured cells of carrot (Daucus carota L.) synthesize and secrete a glycoprotein that is normally found only in dermal tissues (epidermis, endodermis and periderm). This protein, previously called GP57, is now referred to as EDGP (E xtracellular D ermal G lyco P rotein). We purified sufficient quantities of EDGP to obtain amino-acid sequences on two internal tryptic peptides and screened a cDNA library of young carrot roots with antiserum to EDGP and with oligonucleotides corresponding to the peptides. Here we report the derived amino-acid sequence of EDGP. Sequence comparisons show that it has 40% amino-acid sequence identity with 7S basic globulin, a protein that is released when soybean seeds are soaked in hot water for a few hours. We suggest that these two proteins belong to a new family of dermal proteins. As far as we know, this is the first reported derived amino-acid sequence for protein that is specific to the epidermis and other dermal tissues. The level of EDGP mRNA is low in dry seeds, but increases rapidly in growing seedlings as they develop dermal tissues. The level of mRNA is low in storage roots, but increases rapidly in response to wounding. The presence of EDGP in dermal tissues and its up-regulation in response to wounding indicate a role in the response of plants to biotic and-or abiotic stresses. An unusual feature of the amino-acid sequence of EDGP is that it contains a short motif, which is present at the active site of aspartyl proteases such as pepsin and chymosin.

A Wound-Inducible Glycine-Rich Protein from Daucus carota with Homology to Single-Stranded Nucleic Acid-Binding Proteins

A cDNA clone was isolated that encodes a wound-inducible glycine-rich protein. The homology of the carrot (Daucus carota) protein with the A1 protein of the heterogeneous ribonucleoprotein complex suggests that the polypeptide plays a role in the biosynthesis and processing of heterogeneous nuclear RNA and in the maturation of specific mRNAs in response to wounding.

Purification and characterization of a soluble beta-fructofuranosidase from Daucus carota

Soluble beta-fructofuranosidase with an intracellular location and an isoelectric point of 3.8 (isoenzyme I) was purified and characterized from dry seeds and seedlings of carrot (Daucus carota). The enzyme hydrolyzed sucrose with a Km of 5 mM and a broad pH optimum around 5.0. The purified protein, which was N-glycosylated with high-mannose-containing and high-xylose-containing complex glycans, eluted as a monomeric polypeptide with a molecular mass of 68,000 from a gel-filtration column. On SDS/PAGE, the protein separated in the presence of SDS and 2-mercaptoethanol into three polypeptides with molecular masses of 68, 43 and 25 kDa. The amount of the 68-kDa polypeptide was highest in dry seeds and decreased with increasing age of carrot seedlings. Amino acid sequence analysis and immunological studies showed that the 43-kDa and 25-kDa polypeptides were N-terminal and C-terminal proteolytic fragments of the 68-kDa polypeptide. A comparison of partial amino acid sequences of the soluble beta-fructofuranosidase with the complete sequence of carrot cell-wall beta-fructofuranosidase showed that their N-terminal sequences were different, whereas some of the internal tryptic peptide sequences were up to 70% identical.

1H-NMR structural determination of the N-linked carbohydrate chains on glycopeptides obtained from the bean lectin phytohemagglutinin

Phytohemagglutinin, the lectin of the common bean Phaseolus vulgaris, is a N-linked glycoprotein with one high-mannose-type and one xylose-containing oligosaccharide side chain per polypeptide. The high-mannose-type glycan is attached to Asn12 and the complex-type glycan to Asn60 [Sturm, A. & Chrispeels, M. J. (1986) Plant Physiol. 81, 320-322]. The structures of the oligosaccharides were elucidated from two glycopeptides obtained from the lectin by Pronase digestion, affinity chromatography on concanavalin-A--Sepharose and gel-filtration chromatography on a column of BioGel P-4. The N-linked glycan structures were investigated by 500-MHz 1H-NMR spectroscopy and were established to be: [formula; see text]