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S Werner

Publications and source records attributed to S Werner.

At least 253 records · Page 14Linked to original sources
PubMed1986

Mitochondrial gene URFN of Neurospora crassa codes for a long polypeptide with highly repetitive structure.

The mitochondrial DNA of Neurospora crassa contains a long potential gene, designated URFN, which is located immediately downstream from the CO1 gene. These two genes are encoded in different reading frames and overlap by 13 codons. URFN is 633 triplets long and terminates at a UAG stop codon. Its codon usage is atypical for N. crassa mitochondrial exons and introns, and resembles that of the long open reading frame (ORF) of the mitochondrial plasmid present in N. crassa strain Mauriceville. Multiple sequence repetitions occur in the presumptive URFN polypeptide, most notably a seven-times reiterated motif of 16 to 18 amino acid residues length. The hydropathy pattern shows that the N-terminal third of the URFN polypeptide is predominantly apolar and includes several potentially membrane-spanning stretches; the remaining part is hydrophilic. Calculation of the secondary structure predicts a high proportion (47%) of alpha-helix conformation. The longest alpha-helix contains 40 residues. No similarities to other mitochondrial genes or reading frames have been found, except a significant homology over a stretch of 16 amino acid residues between the N-terminal part of URFN and a well-conserved sequence in the C-terminal region of CO1. The repetitive region in URFN resembles a similarly repetitive stretch in an unassigned reading frame from bacteriophage lambda. Three arguments support the view that URFN is translated. The open reading frame has a considerable length; URFN is transcribed into a mRNA including the overlapping CO1 gene; URFN is most probably conserved among all the various Neurospora species examined thus far, strongly suggesting that it codes for an essential protein.

Amino Acid Sequence↗
PubMed1986

Nuclear genes for cytochrome c oxidase subunits of Neurospora crassa. Isolation and characterization of cDNA clones for subunits IV, V, VI, and possibly VII.

We obtained cDNA clones for cytochrome oxidase subunits IV, V, VI, and possibly VII by constructing a lambda gt11 library of Neurospora crassa cDNA and probing it with antiserum directed against Neurospora cytochrome oxidase holoenzyme. Positive clones were further characterized with antisera directed against individual cytochrome oxidase subunits and subsequently by DNA sequencing. The clones for subunits IV and V encode proteins with regions matching the known N-terminal amino acid sequences of purified Neurospora cytochrome oxidase subunits IV and V, respectively. The sequences of these clones provide the first evidence that cytochrome oxidase subunits IV and V are made as precursors with N-terminal extensions in Neurospora. The N-terminal extensions encoded by these clones share homology, and are rich in arginine, as are signal sequences of other mitochondrially destined proteins. The subunit VI clone codes for the carboxyl terminus of a protein homologous to the carboxy termini of yeast cytochrome oxidase subunit VI and bovine cytochrome oxidase subunit Va. The subunit VII clone contains an open reading frame for a 47-residue protein, the expected size for subunit VII. However, the protein coded by this clone has an unusual amino acid composition. Whether this clone represents an authentic cytochrome oxidase subunit is not established.

Amino Acid Sequence↗
PubMed1986

Cortisol insufficiency caused by electroconvulsive therapy? A case report.

A 30-year-old woman was treated with a series of electroconvulsive therapy (ECT) due to a personality disorder with depressive symptoms. Three days after the last ECT, anisocoria was noticed. It subsided after 2 days, and attacks of syncope, vertigo, anorexia and weight loss started. These symptoms ceased by administration of cortisone acetate and fluoro-cortisone. During an observation time of five years, repeated attempts to omit the cortico-steroids or reduce the cortisone dose to less than 20 mg/day have resulted in immediate symptoms of cortisol deficiency. Plasma adrenocorticotrophin (ACTH) and cortisol and urinary cortisol were low during cortisol withdrawal. Cortisol response to ACTH stimulation and cortisol and ACTH response to hypoglycemia were normal. The cortisol deficiency was considered to be due to a defect in the central nervous regulation of ACTH secretion. As it occurred in close connection to ECT, it seems likely that the treatment induced a defect, or aggravated a preexisting one, in neural pathways controlling corticotrophin-releasing factor and ACTH secretion.

Adrenocorticotropic Hormone↗
PubMed1986

Insulin action in human adipose tissue in acromegaly.

The mechanisms underlying insulin resistance in acromegaly were investigated. Adipose tissue was obtained from nine patients with acromegaly who had in vivo insulin resistance and from 14 matched healthy control subjects. Receptor binding and the antilipolytic effect of insulin were determined in isolated fat cells. Insulin-induced glucose oxidation at a physiological hexose concentration was investigated in fat segments. In fat cells obtained from acromegaly patients after an overnight fast, insulin binding at low hormone concentrations was significantly reduced by 20-30%, insulin-induced antilipolysis was unchanged, but glucose oxidation was unresponsive to insulin. Since it has recently been observed that glucose feeding may rapidly modify insulin action in human adipocytes, fat cells were also obtained 60 min after an 100-g oral glucose load. In this situation, insulin binding at low hormone concentrations was further reduced to one-half of that in the control group, and the sensitivity of insulin-induced antilipolysis was markedly decreased in acromegaly. It is concluded that, in the fasting state, the action of insulin on glucose utilization but not on lipolysis is impaired in adipose tissue of acromegalic patients because of a postreceptor defect. After glucose ingestion, the resistance to insulin in acromegaly is further enhanced and antilipolysis is also impaired. Altered coupling between receptor and effector alone or in combination with an additional decrease in receptor binding may explain the enhancement of insulin resistance. These mechanisms may be essential factors in the pathogenesis of insulin resistance in acromegaly.

Acromegaly↗
PubMed1986

Primary cortisol resistance associated with a thermolabile glucocorticoid receptor in a patient with fatigue as the only symptom.

We have studied a woman with an apparent receptor-mediated resistance to cortisol on the basis of elevated 24-h mean plasma cortisol levels and increased urinary free cortisol. Plasma ACTH concentrations were normal but she was resistant to adrenal suppression by dexamethasone. No stigmata of Cushing's syndrome were seen. To study the proposed end-organ resistance to cortisol, we examined the glucocorticoid receptor (GR) in lymphocytes and in fibroblasts from this patient and from her son. Several molecular properties of the GR of lymphocytes from the patient were indistinguishable from that of normal control subjects. In thermolability assays, however, the patient's GR as well as her son's GR showed a striking heat sensitivity at 40 degrees and 45 degrees C when compared with GR from normal persons. In addition, data from the thermolability assays correlated well with the lack at 45 degrees C of dexamethasone-induced decrease in in vitro [3H]thymidine incorporation into lymphocytes derived from both patients.

Cells, Cultured↗
PubMed1986

Women with prolactinoma--effect of pregnancy and lactation on serum prolactin and on tumour growth.

Thirty-five women with prolactinoma have been investigated during 41 pregnancies and 35 lactation periods. Nine of the women had a macroadenoma; 4 of them underwent transsphenoidal microsurgery and one was treated with external pituitary irradiation before pregnancy. All nine were given bromocriptine to induce ovulation. Four women with a microadenoma became pregnant without medical treatment, one shortly after pituitary microsurgery. The other 22 women were treated with bromocriptine only for varying periods before conception. Tumour complications developed in 7 women (20%); 3 had signs of optical nerve compression and 4 showed increased sella volume after pregnancy. All women with tumour complications had been treated with bromocriptine for less than 12 months before conception. Serum prolactin (Prl) was measured every four weeks during pregnancy and after cessation of lactation. In contrast to normal pregnancy, the mean serum Prl did not increase during the second and third trimester of pregnancy in women with pretreatment serum Prl levels above 60 micrograms/l. The lactation period did not have any harmful influence on tumour development. It is concluded that neither pretreatment serum Prl nor radiological changes of the sella turcica can predict tumour development during pregnancy. Treatment with bromocriptine for more than 12 months before conception seems to reduce the risk of tumour progress.

Adenoma↗
PubMed1985

The mitochondrial URF1 gene in Neurospora crassa has an intron that contains a novel type of URF.

In Neurospora crassa, a 2670 base-pair segment of the mitochondrial DNA was sequenced including a gene homologous to the mammalian URF1 that was recently shown to encode a subunit of the respiratory chain NADH dehydrogenase complex. URF1 of N. crassa is interrupted by an intron of 1118 base-pairs that divides the protein-coding sequence into two exons of 636 and 480 base-pairs length, respectively. The deduced URF1 polypeptide of 371 residues was aligned with that of other eukaryotes, revealing a degree of conservation similar to that of ubiquitous mitochondrial genes. The two highly conserved stretches coincide with the most polar regions of the otherwise hydrophobic URF1 polypeptides and may constitute functional domains of the complex I subunit. In the exon sequences of URF1, 17 codons occur that are infrequently utilized in other mitochondrial genes of N. crassa, indicating a low translational efficiency or a foreign origin of URF1. The URF1 intron is inserted in the most conserved region. It belongs to group I and contains an open reading frame of 305 codons not continuous with the upstream exon. Sequences convincingly homologous to conserved group I decapeptide motifs were not found in the URF1 intronic unassigned reading frame (URF). However, significant homology was detected to intronic URFs of the respective gene from Podospora anserina, suggesting that these reading frames constitute a novel type of group I intronic URFs. Three species of URF1 transcripts were identified. They arise most probably by subsequent removal of the intron and leader sequences from an URF1 precursor transcript.

Amino Acid Sequence↗
PubMed1985

Identification of the polypeptide encoded by the URF-1 gene of Neurospora crassa mtDNA.

Two peptides, potentially representing antigenic determinants of a proposed gene product, were synthesized. The peptide sequences were deduced from the nucleotide sequence of the unidentified reading frame (URF)1 of the Neurospora crassa mitochondrial genome. Specific antisera to the synthetic peptides were produced. The antibodies recognized a single polypeptide species with an apparent relative molecular mass of about 30 000. The mitochondrial origin of this polypeptide was verified by in vivo labelling experiments in the presence of cycloheximide, as well as by in vitro translation using isolated mitochondria. The chemical identification of the protein was performed by partial radiosequencing of the N-terminal portion of the immunoprecipitated URF-1 product. The amount of URF-1 polypeptide present in N. crassa mitochondria is in the range of 1-2%. The protein is a constituent of the inner envelope of the organelle and probably part of a more complex membrane unit.

Amino Acid Sequence↗
PubMed1985

RNA processing in Neurospora crassa mitochondria: transfer RNAs punctuate a large precursor transcript.

The pattern of transcripts arising from a large contiguous portion of the Neurospora crassa mitochondrial genome and the processing of these transcripts have been investigated. Evidence is presented for the transcription of a single, at least 12.5 kb, precursor RNA that contains sequences corresponding to the apocytochrome b (cob), tRNACys, cytochrome oxidase subunit 1 (CO I), tRNAArg and unidentified reading frame (URF) 1 genes. The two tRNA sequences serve as punctuation signals for the cleavage of this large transcript. Processing at the tRNACys and tRNAArg sequences directly generates the proposed CO I mRNA, as well as the mature 3' end of the cob transcripts. Moreover, three other sites have been identified that are specifically involved in further 5' end processing events. One of the two 5' end processing sites of the cob transcript shares homology with the 5' end processing sites of the mitochondrial 19S and 25S rRNA precursors. PstI palindromes do not act as processing signals because six of these palindromic sequences are present in the cob and CO I mRNAs.

Base Sequence↗
PubMed1985

Metyrapone: an agent for melatonin as well as ACTH and cortisol secretion.

The metyrapone-test was used to study the influence of pituitary-adrenal activity on the pineal function in man. We recorded in blood the circadian rhythmicity of melatonin, ACTH and cortisol and the excretion of melatonin, cortisol and Porter-Silber chromogens in urine before, during and after the administration of 750 mg metyrapone every 4 h during 24 h in two healthy volunteers and in two patients with asymptomatic, moderate hyperparathyroidism and a prolactin-secreting microadenoma, respectively. The present study confirmed our previous report on an increased excretion of melatonin per 24 h and per mmol creatinine during the administration of metyrapone. The excretory maximum preceded the maximal ACTH-adrenal response. Serum melatonin remained unchanged during the administration of metyrapone. A second finding was depressed serum melatonin the night after the test in the subjects with the most marked ACTH-cortisol response following the metyrapone-test indicating suppression of melatonin secretion when ACTH-cortisol secretions were increased. A third finding was a late increase in diuresis appearing the day after metyrapone-administration while glomerular filtration rates did not show significant alterations. Thus, it is shown that the metyrapone-induced cortisol inhibition stimulates both ACTH and melatonin secretion, while high ACTH and cortisol levels are accompanied by reduced S-melatonin levels.

17-Hydroxycorticosteroids↗
PubMed1985

Growth hormone producing pituitary adenomas with concomitant hypersecretion of prolactin are particularly sensitive to photon irradiation.

The effect of photon irradiation (50 Gy with a 3-field technique in fractionated doses) on growth hormone (GH), prolactin (PRL), and somatomedin A (SMA) was studied in 25 patients with acromegaly after previous unsuccessful surgery. In patients with concomitant hypersecretion of PRL, the GH reduction was 70 +/- 22% 1 year and 88 +/- 10% 3 years after radiotherapy. The corresponding reductions in patients with isolated GH hypersecretion were 42 +/- 25% and 60 +/- 22%. The reduction of GH levels was most notable the first year after radiotherapy in 16 patients and during the second year in 7 patients. Serum PRL decreased after radiotherapy in all patients with hyperprolactinemia, whereas PRL in normoprolactinemic patients showed inconsistent changes, including PRL increments in 8/12 patients. The effect of radiotherapy on GH and PRL was not correlated to the irradiation target volume or the cumulative radiation effect. SMA levels decreased after radiotherapy, but became normal only in 3 patients, all with pretreatment GH less than 5 micrograms/l. Radiotherapy, 3 years after treatment, appeared to be equivalent to the primary surgical intervention in reducing GH and SMA in patients with acromegaly due to advanced macroadenomas. Patients with concomitant hyperprolactinemia showed increased sensitivity to radiation compared to normoprolactinemic patients with acromegaly.

Acromegaly↗
PubMed1985

Leukotriene C4 as a mediator of luteinizing hormone release from rat anterior pituitary cells.

This study demonstrates that leukotriene C4, at concentrations in the picomolar range, released luteinizing hormone (LH) but not growth hormone (GH) from dispersed rat anterior pituitary cells. Leukotriene B4, another lipoxygenase pathway product of arachidonic acid, had no effect on LH or GH release. The stimulatory effect of leukotriene C4 could be seen after 0.5 but not after 3 hr of incubation. This was in contrast to the dose-dependent LH-releasing hormone (LHRH)-induced LH release that was not measurable after 0.5 hr but was fully established after incubation for 3 hr. Furthermore, the LH-releasing ability of leukotriene C4 was blocked in the presence of high doses of LHRH. The immunohistochemical analysis revealed leukotriene C4-immunoreactive fibers at all levels of the median eminence, mainly in the lateral parts. These fibers exhibited a marked overlap distribution with LHRH-immunoreactive fibers and elution-restaining experiments revealed identity of at least a large proportion of the leukotriene C4- and LHRH-immunoreactive fibers. Furthermore, cell bodies in the preoptic area contained both leukotriene C4- and LHRH-like immunoreactivities, suggesting localization of these two compounds in the same neurons.

Animals↗
PubMed1985

Prolactinomas in men: clinical characteristics and the effect of bromocriptine treatment.

Thirty-seven men with prolactin (PRL) producing pituitary adenomas were studied to elucidate if patient's delay might cause the predominance of large tumours in men as compared to women in whom microadenomas predominate. We found two clinical subgroups; one presented with short duration of symptoms, dominated by local signs from the growth of notably large tumours, the other exhibited a long history of disease with hypogonadism as the dominating symptom. There was a correlation between tumour size and PRL levels. The age at the time of diagnosis showed no correlation to duration of symptoms, size of adenoma or PRL levels. Four patients with small adenomas, moderate hyperprolactinemia and short duration of symptoms showed signs of hypergonadotropic hypogonadism. Surgery or irradiation, performed in 14 patients, did not normalize PRL levels. Bromocriptine was equally beneficial in the two clinical subgroups, improving clinical symptoms and normalizing PRL levels in all but three patients. The study shows that the predominance of large tumours in men does not depend on patient's or doctor's delay, but on a high frequency of presumably rapidly growing PRL producing tumours. In the majority of patients, these tumours do not give signs of hypogonadism before the tumour is revealed by local signs of tumour growth.

Adult↗
PubMed1985

Cushing's syndrome due to an ACTH-producing neuroendocrine tumour in the nasal roof.

A patient with ectopic adrenocorticotrophic hormone (ACTH) production from a neuroendocrine tumour of the nasal roof is presented. By indirect immunoperoxidase techniques the tumour cells were shown to be distinctly positive for ACTH and beta-endorphin but negative for other peptides derived from pro-opiomelanocortin. Neither corticotropin releasing hormone (CRF) found in some tumours associated with ectopic Cushing's syndrome, nor gastrin immunoreactivity, which coexists with ACTH in normal rat pituitary and in rat and human gastrointestinal cells, were demonstrable in the tumour. A review of other, previously recognized locations of CRF/ACTH producing tumours is given to increase the awareness of the ectopic Cushing's syndrome, which may lack the classical features and is characterized by fulminant clinical course, extreme fatigue, weakness, pale facial swelling, oedema and hypokalaemic alkalosis.

ACTH Syndrome, Ectopic↗