Biomedical subjects

M Keller

Publications and source records attributed to M Keller.

At least 19 recordsLinked to original sources

PubMed1992

The Euglena gracilis rbcS gene contains introns with unusual borders.

We have recently shown that, in Euglena gracilis, leader sequences are transferred by trans-splicing to the vast majority of cytoplasmic mRNAs. Trans-splicing is involved in the maturation of the rbcS transcript, which encodes eight small subunits of the ribulose 1,5 bisphosphate carboxylase/oxygenase. In this report, we show that the Euglena rbcS gene introns are different from introns found in plant rbcS genes. In addition these introns do not have the conserved 5' and 3' border sequences found in introns of eucaryotic nuclear-encoded pre-mRNAs, and they do not present any homology with self-splicing introns of groups I and II. Secondary structure analyses show that the 5' and 3' ends of Euglena introns can base-pair, suggesting that an unusual splicing mechanism exists in Euglena.

Amino Acid Sequence↗

PubMed1992

In Euglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated.

In Euglena gracilis, a 26 nucleotide leader sequence (spliced leader sequence = SL) is transferred by trans-splicing to the 5' end of a vast majority of cytoplasmic mRNAs (8). The SL originates from the 5' extremity of a family of closely related snRNAs (SL-RNAs) which are about 100 nucleotide long. In this paper we present the nucleotide sequences of two SL-RNA genes, confirming the sequences previously established by sequencing purified SL-RNAs. Although some SL-RNA genes are dispersed throughout the genome, we show that the majority of SL-RNA genes are located on 0.6 kb repeated units which also encode the cytoplasmic 5S rRNA. We estimate that the copy number of these repeated units is about 300 per haploid genome. The association of SL-RNA and 5S rRNA genes in tandemly repeated units is also found in nematodes but paradoxically does not exist in trypanosomes which are phylogenically much closer to Euglena. We also show that a high number of sequences analogous to the 26 nucleotide SL are dispersed throughout the genome and are not associated with SL-RNAs.

Animals↗

PubMed1992

The role of the mitochondrial creatine kinase system for myocardial function during ischemia and reperfusion.

The subcellular distribution of ATP, ADP, creatine phosphate and creatine was studied in normoxic control, isoprenaline-stimulated and potassium-arrested guinea-pig hearts as well as during ischemia and after reperfusion. The mitochondrial creatine phosphate/creatine ratio was closely correlated to the oxidative activity of the hearts. This was interpreted as an indication of a close coupling of mitochondrial creatine kinase to oxidative phosphorylation. To further investigate the functional coupling of mitochondrial creatine kinase to oxidative phosphorylation, rat or guinea-pig heart mitochondria were isolated and the mass action ratio of creatine kinase determined at active or inhibited oxidative phosphorylation or in the presence of high phosphate, conditions which are known to change the functional state of the mitochondrial enzyme. At active oxidative phosphorylation the mass action ratio was one-third of the equilibrium value whereas at inhibited oxidative phosphorylation (N2, oligomycin, carboxyatractyloside) or in the presence of high phosphate, the mass action ratio reached equilibrium values. These findings show that oxidative phosphorylation is essential for the regulation of the functional state of mitochondrial creatine kinase. The functional coupling of the mitochondrial creatine kinase and oxidative phosphorylation indicated from the correlation of mitochondrial creatine phosphate/creatine ratios with the oxidative activity of the heart in situ as well as from the deviation of the mass action ratio of the mitochondrial enzyme from creatine kinase equilibrium at active oxidative phosphorylation in isolated mitochondria is in accordance with the proposed operation of a creatine shuttle in heart tissue.

Animals↗

PubMed1992

Major depression in a nonclinical sample. Demographic and clinical risk factors for first onset.

The relatives, controls, and spouses of affectively ill probands underwent diagnostic examinations on two occasions, 6 years apart. Of 965 subjects who had never been mentally ill when first examined, 11.8% had development of at least one episode of major depression as defined by the Research Diagnostic Criteria during the ensuing 6 years. Subjects younger than 40 years were three times more likely than older subjects to develop depression and women were approximately twice as likely as men to develop depression regardless of age. Marital disruption, a farm setting, and high educational achievement substantially increased the risk of depression among female subjects. Of 214 never-depressed subjects with a history of nonaffective mental disorder, 62 (29.0%) developed major depression. Age and sex were again powerful determinants. The course of prospectively observed secondary depression was more severe than that for primary depression.

Adult↗

PubMed1992

Rapidly cycling affective disorder. Demographics, diagnosis, family history, and course.

Of 919 patients with major affective disorders who completed at least 1 year of a 5-year, semiannual follow-up, 45 developed a rapidly cycling bipolar course during the first year, but only one developed a rapidly cycling unipolar course. In comparison with patients who showed a non-rapidly cycling bipolar course, those who became rapid cyclers were more likely to be female and to have exhibited depression, hypomania, or cycling between depression and hypomania within the index episode. Family study data revealed no evidence that high cycle frequencies breed true. Rapid cycling was associated with a significantly lower likelihood of recovery in the second year of follow-up but not in the third, fourth, or fifth. These data suggest that rapid cycling is, in the large majority of cases, a transient, nonfamilial manifestation of bipolar affective disorder.

Adult↗

PubMed1992

Alcoholism and primary major depression: a family study approach to co-existing disorders.

Alcoholism and major depression appear together at much higher than chance rates, but reasons for this are obscure. We used the direct diagnostic assessment of 177 probands with primary, unipolar depression and 619 of their first degree relatives to explore the significance of concomitant alcoholism. The male relatives of alcoholic probands of both sexes had substantially higher rates of alcoholism than did the male relatives of non-alcoholic probands. Among female probands, but not among male probands, alcoholism was associated with markedly higher familial rates of primary depression, particularly among female relatives. These data contained no evidence that comorbidity itself was familial. The appearance of alcoholism in depressed women may indicate depression spectrum disease, a disorder which manifests as depression in women and alcoholism in men. In contrast, men with both primary depression and alcoholism may be exhibiting two distinct illnesses.

Adolescent↗

PubMed1992

Effects of advancing age on the efficacy and side effects of antiarrhythmic drugs in post-myocardial infarction patients with ventricular arrhythmias. The CAST Investigators.

OBJECTIVE: To determine the effect of age on the response to anti-arrhythmic drugs. DESIGN: Randomized controlled trial comparing particular drugs. SETTING: Multi-institutional (The Cardiac Arrhythmia Suppression Trial, CAST). PARTICIPANTS: 2,371 patients, age less than 80, with ventricular arrhythmias after a recent myocardial infarction. Subjects classified by age as less than or equal to 55, 56-65, and 66-79 years. INTERVENTION: Upwardly titrated doses of encainide, flecainide or moricizine. After identification of a tolerated and effective dose of one of the drugs, participants were randomized to that drug and dose versus its placebo for up to 10 months. MAIN OUTCOME MEASURES: Efficacy of drug (suppression of ventricular premature depolarizations and/or non-sustained ventricular tachycardia), side effects and mortality. RESULTS: Older patients had more previous MIs, congestive heart failure (CHF), hypertension, NSVT, repolarization abnormalities, digitalis use, and diuretic use. They had less pathologic Q-waves or electrocardiographic injury pattern, and their left ventricular ejection fraction (LVEF) was lower. First dose VPD suppression with the first drug averaged 53% and is not associated with age (P = 0.29). Adverse events including death are more frequent in older patients taking study drugs (P less than 0.001). This trend is consistent in all three study drugs and at varying LVEFs. History of prior MI, low LVEF, VPD (in log scale), and digitalis therapy also correlates with adverse events (all P less than 0.05). Following adjustment for these factors, older age is an independent predictor of adverse events (relative risk 1.30 per decade of age, P less than 0.001). CONCLUSIONS: Older age increases the susceptibility to adverse cardiac events from a class of relatively toxic antiarrhythmic agents.

Adult↗

PubMed1991

A homeodomain protein binds to gamma-globin gene regulatory sequences.

Developmental regulation of gamma-globin gene expression probably occurs through developmental-stage-specific trans-acting factors able to promote the interaction of enhancer elements located in the far upstream locus control region with regulatory elements in the gamma gene promoters and 3' A gamma enhancer located in close proximity to the genes. We have detected a nuclear protein in K562 and baboon fetal bone marrow nuclear extracts capable of binding to A+T-rich sequences in the locus control region, gamma gene promoter, and 3' A gamma enhancer. SDS/polyacrylamide gel analysis of the purified K562 binding activity revealed a single protein of 87 kDa. A K562 cDNA clone was isolated encoding a beta-galactosidase fusion protein with a DNA binding specificity identical to that of the K562/fetal bone marrow nuclear protein. The cDNA clone encodes a homeodomain homologous to the Drosophila antennapedia protein.

Animals↗

PubMed1991

Short leader sequences may be transferred from small RNAs to pre-mature mRNAs by trans-splicing in Euglena.

Very closely related short sequences are present at the 5' end of cytoplasmic mRNAs in Euglena as evidenced by comparison of cDNA sequences and hybrid-arrested translation experiments. By cloning Euglena gracilis nuclear DNA and isolating the rbcS gene (encoding the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase), we have shown that the short leader sequence does not flank the nuclear gene sequence. The leader sequences were found to constitute the 5' extremities of a family of small RNAs. Sequencing six members of this family revealed a striking similarity to vertebrate U snRNAs. We propose that a trans-splicing mechanism transfers the spliced leader (SL) sequence from these small RNAs (SL RNAs) to pre-mature mRNAs. Transfer of leader sequences to mRNAs by trans-splicing has been shown only in trypanosomes where cis-splicing is unknown, and in nematodes where not more than 10% of the mRNAs have leader sequences. Our results strongly suggest that Euglena is a unique organism in which both a widespread trans-splicing and a cis-splicing mechanism co-exist.

Animals↗

PubMed1991

Post-transcriptional regulation by light of the biosynthesis of Euglena ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit.

In Euglena gracilis, the amounts of the mature small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) increase during cell greening, while an analysis of the transcripts, performed at different stages of chloroplast development, shows no difference in the amounts of the corresponding mRNA. Pulse-chase experiments followed by immunoprecipitation show a significant increase in the rate of synthesis of the large molecular weight precursor (which consists of a transit peptide followed by eight small subunits) beginning after 12 h of illumination. Nevertheless, its half life does not change significantly during the chloroplast development. The results presented strongly suggest that the regulation of the expression of the Rubisco small subunit occurs at the translational level.

Animals↗

PubMed1991

Follow-up and family study of anxious depression.

OBJECTIVE: The failure of the concept of anxious depression to find its way into DSM-III-R led the authors to conclude that a further report on the occurrence of anxiety symptoms in depressed subjects is indicated. METHOD: The subjects were 327 consecutively evaluated inpatients and outpatients with primary unipolar depressive disorder at five university medical centers participating in the National Institute of Mental Health Collaborative Program on the Psychobiology of Depression--Clinical Studies. The authors restricted their sample selection to patients with primary depressive disorder so that patients with other preexisting psychiatric disorders, especially anxiety disorders, would not contaminate the symptom picture, family studies, or follow-up. The examined six anxiety symptoms and derived a new anxiety summary score to show the effect of anxiety in depression on family data and 5-year outcome. RESULTS: Depressed subjects with higher ratings for anxiety took longer to recover. There was also a significant relationship between anxiety in depressed probands and the risk for primary unipolar depressive disorder, but not anxiety disorders or alcoholism, among 832 blindly interviewed first-degree relatives. CONCLUSIONS: These data confirm the usefulness of subdividing depressed patients according to anxiety symptoms: psychic and somatic symptoms of anxiety, taken together, significantly predict family illness and course. The data also emphasize the wisdom of requiring that generalized anxiety disorder not be diagnosed in the presence of a mood disorder. Clearly, symptoms of anxiety coexist with depression and need to be recognized for the effective treatment of the underlying depressive disorder.

Ambulatory Care↗

PubMed1991

Rapid increase in LHRH mRNA levels following NMDA.

To test the hypothesis that changes in LHRH mRNA levels are tightly linked to changes in LHRH secretion, intact male rats were infused with NMDA, a substance which increases LH release by a hypothalamic action. NMDA significantly elevated cellular levels of LHRH mRNA at 15 and 60 min. Similar changes in LH levels were induced by NMDA. These effects of NMDA on LHRH mRNA levels were not due to a generalized excitatory effect in the brain because levels of mRNAs encoding proopiomelanocortin (POMC) and tyrosine hydroxylase (TH) in the arcuate-periarcuate region were not altered by NMDA and levels of TH mRNA were decreased significantly at 15 and 60 min in neurons of the zona incerta. These data strongly support the hypothesis that changes in cellular levels of LHRH mRNA are tightly linked temporally to changes in LHRH secretion.

Animals↗

PubMed1991

[Adenoma of the pigmented epithelium of the iris with endothelialization and descemetization in the horse].

The authors describe peculiar tumors with brown-white piebald anterior surface, which had grown bilaterally from the corpora nigra (C.N.) of an adult horse and occluded the pupils. The surgical procedure for removing the larger tumor and the postoperative treatment are described. The findings by light and electron microscopy suggest that the tumor represent a so-called adenoma of the iris pigment epithelium. The white patches on its surface consist of newly formed Descemet-like material produced by displaced corneal endothelial cells, which have probably grown on the tumor after contact with the posterior face of the cornea.

Adenoma↗

PubMed1990

Glycosphingolipids in insects. Chemical structures of two variants of a glucuronic-acid-containing ceramide hexasaccharide from a pupae of Calliphora vicina (Insecta: Diptera), distinguished by a N-acetylglucosamine-bound phosphoethanolamine sidechain.

The two major components of the acidic glycolipid fraction from the pupae of Calliphora vicina were isolated using high-performance liquid chromatography. The acidic moiety was identified as glucuronic acid by beta-glucuronidase cleavage and gas chromatographic analysis as the pentafluoropropionyl derivative. The structures of the carbohydrate moiety were elucidated by peracetylation, methylation, exoglycosidase cleavage, fast-atom-bombardment mass spectrometric and 1H-nuclear magnetic resonance spectroscopic analysis. The only difference between the two hexasaccharide variants was the presence, in one of them, of a between the two hexasaccharide variants was the presence, in one of them, of a phosphoethanolamine (AeP) sidechain on the third sugar of the sequence, i.e. N-acetylglucosamine. The composition of the ceramide moiety was dominated by a C20:0 fatty acid (arachidic acid) and a C14:1 sphingoid base (tetradecasphing-4-enine). The chemical structures of the two insect acidic glycosphingolipids were determined to be: GlcA(beta 1-3)Gal-(beta 1-3)GalNAc(beta 1-4)GlcNAc(beta 1-3)Man (beta 1-4)Glc(beta 1-1)Cer; GlcA(beta 1-3)Gal(beta 1-3)GalNAc(beta 1-4)[2AeP-6]-GlcNAc(beta 1-3) Man(beta 1-4)Glc(beta 1-1)Cer. Such glucuronic-acid-containing insect glycosphingolipids have been given the generic name arthrosides, with the implied synonymity to the gangliosides.

Acetylglucosamine↗

PubMed1990

Evidence for the expression of a glucuronic acid-containing epitope in the central nervous system of two insects (Calliphora vicina, Diptera; Tenebrio molitor, Coleoptera).

The monoclonal antibody CAF-I recognises a glucuronic acid-containing epitope present on various acidic glycosphingolipids of Calliphora vicina. Immunohistochemistry was performed on CAF-I-labelled whole-mount preparations of the central nervous system, visualised by peroxidase-conjugated second antibody. A differential, temporal and spatial expression of this epitope in metamorphosing nervous tissue was outlined, that apparently characterises homologous neuronal populations in two phylogenetically distinct holometabolous insects, i.e. Calliphora vicina and Tenebrio molitor. Implications for a functional interpretation of insect glyco(sphingo)lipids in tissue development are discussed.

Animals↗

PubMed1990

Affective syndromes, psychotic features, and prognosis. I. Depression.

Prognosis is an important issue among patients who have psychotic features and a depressive syndrome; some have outcomes that suggest diagnostic revisions to schizophrenia, and this has far-reaching implications for treatment. To explore this issue, we used biannual evaluations to follow up 103 such individuals for 5 years. Patients with Research Diagnostic Criteria schizoaffective disorder experienced substantially more morbidity of various sorts than did patients with Research Diagnostic Criteria psychotic major depression. Within the group with schizoaffective disorder, patients with the chronic subtype experienced more morbidity than did those with nonchronic schizoaffective disorder; the mainly affective--mainly schizophrenic distinction had less prognostic significance. Factors that predicted sustained delusions at the end of follow-up were exclusively historical and suggested a poor-outcome prototype patient who is single, was socially impaired as an adolescent, and has a history of schizophrenialike psychotic features temporarily dissociated from affective symptoms.

Adult↗

PubMed1990

Affective syndromes, psychotic features, and prognosis. II. Mania.

Fifty-six patients with mania and psychotic features and 14 with schizoaffective disorder, manic type, were followed up with biannual assessments during a 5-year period. Results were treated as they were in an analogous follow-up of patients with psychotic major depression or schizoaffective disorder, depressed type. Patients with schizoaffective mania experienced more morbidity during follow-up than did patients with psychotic mania. Among patients with schizoaffective mania, those with a chronic subtype did far worse than did the others, while the mainly schizophrenic--mainly affective distinction was not predictive. When depressed and manic groups were combined (n = 173), the following baseline variables were significant independent predictors of a sustained delusional outcome: longer duration of the index episode, temporal dissociation between psychotic features and affective symptoms, and impaired adolescent friendship pattern.

Adult↗

PubMed1990

Eight small subunits of Euglena ribulose 1-5 bisphosphate carboxylase/oxygenase are translated from a large mRNA as a polyprotein.

The small subunit (SSU) of ribulose 1-5 bisphosphate carboxylase/oxygenase is a 15 kd protein in Euglena gracilis. The protein is synthesized as a 130 kd precursor as shown by immunoprecipitation of in vitro translation products and confirmed by immunoprecipitation of in vivo pulse-labeled Euglena proteins. From the published SSU amino acid sequence, an oligonucleotide was synthesized that specifically hybridizes to a large mRNA whose length (approximately 4.3 kb) is consistent with the precursor size. The complete nucleotide sequence of the SSU mRNA was obtained by sequencing a cDNA clone from a lambda gt11 library and completed by direct mRNA sequencing. We report for the first time the complete sequence of a large mRNA and show that it encodes eight consecutive SSU mature molecules. The deduced precursor amino acid sequence shows that the amino terminus of the first SSU molecule is preceded by a 134 amino acid peptide which is cleaved during the maturation process. This long transit peptide exhibits features characteristic of signal peptides involved in the secretion of proteins through the endoplasmic reticulum. This is in agreement with the idea that the third (outer) membrane of the Euglena chloroplast envelope is of endoplasmic reticulum origin.

Amino Acid Sequence↗