Deficiency of the human mitochondrial transcription factor h-mtTFA in infantile mitochondrial myopathy is associated with mtDNA depletion

Recent studies show that patients presenting with cytochrome oxidase (COX) deficiency in infancy may have reduced mitochondrial DNA (mtDNA) in muscle. The human mitochondrial transcription factor A (h-mtTFA) may be an important regulator of both transcription and replication of mtDNA. h-mtTFA levels were investigated in cell lines which were either free of mtDNA (rho 0) or temporarily depleted by treatment with dideoxycytidine (ddC), and in tissue from three patients with mtDNA depletion and cytochrome oxidase deficiency. h-mtTFA was compared with other mitochondrial proteins such as pyruvate dehydrogenase and porin by Western blotting. The ratio of mtDNA and h-mtTFA mRNA to reference nuclear probes was measured by dual labelling of dot blots. The ratio of mtDNA to nuclear DNA in skeletal muscle was low in muscle in the three patients and in other tissues in one. h-mtTFA was low in cells depleted either permanently or transiently of mtDNA, and this reduction in h-mtTFA roughly paralleled mtDNA levels. Similarly, treatment of rho 0 cell lines with ddC induced a reduction in mtDNA as well as h-mtTFA protein. The relationship between h-mtTFA and mtDNA levels suggests that they may be causally linked. MtDNA depletion was accompanied by an increase in the level of h-mtTFA RNA in the cell lines but low levels in the patient. This suggests that either h-mtTFA regulates mtDNA levels, or that h-mtTFA expression may be regulated by a feedback mechanism initiated by MtDNA Depletion.

Epidermal growth factor antagonizes vasopressin in vivo and in vitro

Since EGF causes diuresis through a renal action and may antagonize the hydroosmotic effect of AVP in vitro we investigated the antagonistic action of EGF with AVP in vivo and the mechanism of the antagonism in vitro. Conscious ewes received i.m. injections of a selective AVP V2-receptor agonist (1-desamino, D-Arg8 vasopressin acetate, DDAVP) every 12 hours for days 5 to 16. All ewes received an i.v. isotonic saline infusion (100 ml/day) for days 1 to 8 and days 13 to 16, and i.v. EGF in 100 ml saline/day at doses of 0 (N = 8) or 10 (N = 8) micrograms/hr for days 9 to 12. DDAVP reduced both urine volume and water intake, and increased urine osmolality. In contrast, simultaneous infusion of EGF reversed the DDAVP-induced responses, resulting in a transient negative fluid balance, kaliuresis and a transient natriuresis (all P < 0.05). When EGF treatment ceased, the effects of DDAVP treatment alone gradually became apparent. From the in vitro studies, the AVP-related peptides displaced specific AVP V1- and V2-receptor antagonist radioligands from rat renal inner medullary membranes, whereas EGF had no effect. However, EGF antagonized AVP V2-stimulated cAMP production in a dose-dependent way (IC50 = 2 x 10(-7) M). Therefore, the diuretic effect of EGF is not via direct antagonism of the antidiuretic AVP V2-receptor but seems mediated by inhibition of the antidiuretic AVP V2-receptor second messenger system.

Androgen manipulation and vasopressin binding in the rat brain and peripheral organs

It is now widely recognized that there is a sexual dimorphism in the development of arginine vasopressin (AVP) immunoreactivity in certain parts of the brain, and that changes in brain AVP immunoreactivity change with manipulation of androgen status. The aim of this experiment was to determine specifically any AVP receptor changes in response to manipulation of androgen levels using a selective V1 antagonist radioligand. Following castration, plasma testosterone levels fell and AVP immunoreactivity was reduced in the lateral septum and bed nucleus of the stria terminalis. With testosterone supplementation in castrated animals, the immunoreactivity in these regions was restored to a higher degree than in sham-operated animals. Central and peripheral V1 AVP receptor binding (as determined using the selective AVP V1 antagonist radioligand [125I](d(CH2)5,sarcosine7)AVP was not changed in any of the brain regions studied or in liver or kidney membranes from the three groups. This study demonstrates that there is no change in brain AVP receptor binding despite changes in regional AVP immunoreactivity in the brain, and excludes any confounding interaction with changes in oxytocin receptors.

Involvement of the 5-HT2 receptor in the 5-HT receptor-mediated stimulation of prolactin release

The present study examined the involvement of 5-HT1C and 5-HT2 receptors in the regulation of prolactin release in the rat. Both the mixed 5-HT2/5-HT1C receptor agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), and the preferential 5-HT1C agonist, 2-chloro-6-(1-piperazinyl)pyrazine monohydrochloride (MK-212), elicited a significant increase in plasma prolactin concentration with DOI about 20 times more potent than MK-212. Treatment with DOI, but not with MK-212, induced head twitching in the rat, and this behavior was inhibited by both the mixed 5-HT2/5-HT1C receptor antagonist, ritanserin, and the selective 5-HT2 receptor antagonist, amperozide. DOI-induced prolactin release was also antagonized by ritanserin and amperozide, whereas only ritanserin affected MK-212-induced prolactin release. Furthermore, amperozide did not attenuate d-fenfluramine-elicited prolactin release, which is known to be antagonized by ritanserin. These data suggest that the pharmacological stimulation of prolactin release by DOI is mediated via the 5-HT2 receptor and that the 5-HT1C receptor may be of importance for the physiological regulation of prolactin release.

Effects of anti-emetics on water excretion in humans

1. The anti-emetic drug metoclopramide has been shown to stimulate secretion of the antidiuretic hormone arginine vasopressin. Since metoclopramide is used to treat nausea, which is another potent stimulus to vasopressin secretion, the aim of this study was to determine whether metoclopramide might limit free water excretion and so cause hyponatraemia. 2. Metoclopramide 20 mg (0.2-0.3 mg/kg), prochlorperazine 12.5 mg (0.1-0.2 mg/kg) and placebo were administered intravenously in a double blind randomized crossover way at 2 week intervals and the effects on urine flow rate, plasma osmolality, thirst ratings and plasma sodium and atrial natriuretic peptide concentrations determined in water-loaded (10 mL/kg) healthy young men. 3. There were no differential effects on any variable of either drug versus placebo. 4. These results indicate that metoclopramide is unlikely to cause any significant water retention in a clinical setting or precipitate hyponatraemia.

Living near a lead smelter: an environmental health risk assessment in Boolaroo and Argenton, New South Wales

This paper outlines a risk assessment of a lead-contaminated residential site in Lake Macquarie, New South Wales, near the Pasminco Metals-Sulphide lead and zinc smelter. The assessment includes a hazard identification and a dose-response assessment based on recent research findings; an exposure assessment based on two interrelated indicators, soil/dust lead and blood lead; a risk characterisation; and finally, a discussion of environmental and behavioural options for the management of risk. The exposure assessment showed lead concentrations of 20 to 21,460 parts per million in soil survey samples, 23 to 35,870 parts per million in household dust, and a range of mean values for blood lead concentration of 11 micrograms/dl to 17 micrograms/dl, in four study groups. The proportions of children within these groups having blood lead concentrations of 10 micrograms/dl or greater, the current level of known health effect, ranged from 57 per cent to 85 per cent. The decision by the National Health and Medical Research Council in June 1993 to set a goal for blood lead of below 10 micrograms/dl has important implications for the definition and the management of the environmental health risk from 'living with lead' in the area assessed.

Multiple binding sites for nicotine receptor antagonists in inhibiting [3H](-)-nicotine binding in rat cortex

The displacement of [3H](-)-nicotine from its binding site in rat cerebral cortex by a number of antagonists was investigated. [3H](-)-Nicotine appeared to bind to a single site with a dissociation constant (KD) of 5.5 nM; pancuronium, gallamine and trimetaphan displaced [3H](-)-nicotine with inhibition constants (KI) of 57, 99 and 621 microM, respectively, whereas mecamylamine only displaced 50% of nicotine binding in concentration > 1 mM. For hexamethonium and (+)-tubocurarine the displacement of [3H](-)-nicotine binding appeared to involve two sites; the higher affinity site comprising 30% of the total binding for hexamethonium but 76% of the sites for (+)-tubocurarine. In the presence of mecamylamine (100 microM) the displacement of [3H](-)-nicotine binding by (+)-tubocurarine appeared to involve only a single site with an affinity similar to that for the high affinity site in the absence of mecamylamine whereas that for hexamethonium still involved two sites. It is suggested that (+)-tubocurarine may act at both the binding site for [3H](-)-nicotine per se and also at an allosteric site. The failure of mecamylamine to influence the binding of hexamethonium suggests that there may be more than one allosteric site or that hexamethonium may distinguish between subtypes of nicotine receptors in the cortex.

Characterization of a novel non-peptide vasopressin V1 receptor antagonist (OPC-21268) in the rat

A non-peptide, orally effective, vasopressin (AVP) V1 receptor antagonist 1-(1-[4-(3-acetylaminopropoxy) benzoyl]-4-piperidyl)-3,4-dihydro-2(1H)-quinolinone (OPC-21268) has recently been described. This paper reports the in-vitro and in-vivo characterization of OPC-21268 binding to vasopressin receptors in rat liver and kidney. OPC-21268 caused a concentration-dependent displacement of the selective V1 receptor antagonist radioligand, 125I-labelled [d(CH2)5,sarcosine7]AVP to V1 receptors in both rat liver and kidney medulla membranes. The concentration of OPC-21268 that displaced 50% of specific AVP binding (IC50) was 40 +/- 3 nmol/l for liver V1 and 15 +/- 2 nmol/l for kidney V1 receptors (mean +/- S.E.M.; n = 3). OPC-21268 had little effect on the selective V2 antagonist radioligand [3H]desGly-NH2(9)]d(CH2)5,D-Ile2,Ile4] AVP binding to V2 receptors in renal medulla membranes (IC50 > 0.1 mmol/l). After oral administration to rats, OPC-21268 was an effective V1 antagonist in a time- and dose-dependent manner. Binding kinetic studies showed that OPC-21268 acted as a competitive antagonist at the liver V1 receptor in vitro and in vivo, in addition to its in-vitro competitive effects at the renal V1 receptor. OPC-21268 shows promise as an orally active V1 antagonist.

Familial MDS with 5q- abnormality

Abnormalities of chromosome 5 and 7 are frequently found in primary MDS. Cases with familial monosomy 7 are well recognized, but there are no reports of familial MDS with deletion of 5q. We describe two sisters, aged 38 and 36 years, both of whom had MDS and interstitial deletion of 5q. The occurrence of this chromosomal abnormality reinforces the concept of tumour suppressor gene hypothesis in some cases with familial MDS.

Effects of an orally active vasopressin V1 receptor antagonist

1. This paper reports on the in vitro and in vivo characteristics of a non-peptide vasopressin V1 receptor antagonist 1-(1-[4-(3-acetylaminopropoxy)benzoyl]-4-piperidyl)-3,4-dihydro-2( 1H)- quinolinone (OPC-21268). 2. OPC-21268 caused a concentration-dependent displacement of the selective V1 receptor antagonist radioligand, [125I]-[d(CH2)5, sarcosine7]AVP from vasopressin V1 receptors in rat liver and kidney membranes, inhibitory concentration of 50% (IC50) 4 x 10(-8), 0.3 mol/L liver and 1.5 x 10(-8), 0.2 mol/L kidney. OPC-21268 had little effect on the selective V2 antagonist radioligand [3H]desGly-NH2(9)-d(CH2)5[D-Ileu2, Ileu4]AVP binding to V2 receptors in renal membranes (IC50 > 10(-4) mol/L). 3. After oral administration to rats, OPC-21268 was an effective V1 antagonist to both liver and kidney V1 receptors, in a dose-dependent manner. 4. These studies confirm that OPC-21268 is a potent non-peptide, orally effective V1 vasopressin receptor antagonist.

Myelodysplastic syndromes: from morphology to molecular biology. Part I. Classification, natural history and cell biology of myelodysplasia

The myelodysplastic syndromes are a heterogeneous group of clonal hematopoietic disorders predominantly affecting the elderly. Patients frequently develop acute leukemia, but the majority suffer from the consequences of bone marrow failure. The underlying acquired genetic abnormality is the inadequate production of dysplastic and poorly functional cells resulting from defective differentiation and premature cell death of the abnormal hematopoietic clone. Although the pathogenesis is unknown, recent evidence suggests that a sequence of DNA lesions leads to alteration of the cellular function, emergence and consequent evolution of the premalignant clone.

Myelodysplastic syndromes: from morphology to molecular biology. Part II. The molecular genetics of myelodysplasia

Most studies of the clonal origin of the underlying lesion(s) and all investigations using X-inactivation, have concluded that the myelodysplastic syndromes arise from a multipotent stem cell. Non-random chromosomal abnormalities, particularly deletions of 5q and 7q, are common, most notably in therapy related MDS. Progression to AML is also frequently accompanied by increased genomic instability as evidenced by the emergence of multiple karyotypic abnormalities. While some evidence hints at the presence of tumour suppressor genes on chromosomes 5, 7, 20 and 12, no such genes have yet been identified. The search for point mutations in known oncogenes has concentrated on two oncogenes RAS and c-FMS. Point mutation frequency generating active forms of RAS oncogenes is approximately 40% in MDS overall, up to 80% in studies of CMML. 60% of all MDS RAS mutation involves a G to A transition, producing a substitution of aspartate for glycine at a frequency of 50% (of total ras mutants). RAS mutation is associated with progression to AML, although the presence of a RAS point mutation alone is neither necessary nor sufficient for leukaemic transformation. Mutation of c-FMS is also more common in CMML in comparison to other MDS subtypes and, as yet, point mutation potentiating the response of the receptor to CSF-1 (codon 969) has been found more frequently than point mutation resulting in permanently activated receptor (codon 301). However, recent work has identified additional mutations which produce transforming proteins, and mutation rates at these sites may be relevant in MDS.

Methylation status within exon 3 of the c-myc gene as a prognostic marker in myeloma and leukaemia

The third exon of the c-myc gene contains a CpG site which has been implicated as a regulatory region. When this site is methylated it has protein binding properties and binds a different set of proteins in normal and neoplastic cells. Recent work using myeloma cell lines indicates a correlation between hypomethylation at this site and enhanced expression of the myc protein. We investigated the methylation of this site in 10 cases of myeloma but found that there was no change from the high degree of methylation found in normal cells. Therefore, methylation status at this site is unlikely to serve as a prognosticator in myelomatosis. However, methylation changes at this site were observed in DNA from two cases of CMML, in which hypomethylation was observed and in three AML cases, which were completely methylated at this site.

Recent trends in diabetes mortality in England and Wales

Trends in diabetes-related mortality in England and Wales between 1975-6 and 1985-6, and regional and ethnic differences in diabetes-related mortality in 1985-6, have been examined. Data from death certificates mentioning diabetes in 1975-6 were compared with those for 1985-6 for different age groups. Data for 1985-6 were also analysed for different regions of England and Wales, and for country of birth. Between 1975-6 and 1985-6, the age-standardized rate of mentioning diabetes rose by 2.7% (95% confidence interval 1.4%, 4.1%) in men of all ages, and fell by 11.7% (10.6, 12.8) in women of all ages. By contrast, the rate of mentioning diabetes in those below 45 years fell by 30.7% (23.0, 37.7) in men and by 26.7% (16.5, 35.6) in women. Deaths in which the underlying cause was ischaemic heart disease (IHD), and where diabetes was also mentioned on the death certificate, rose by 14.4% (11.5, 16.8) in men and did not change significantly in women of all ages, but fell by 18.4% (-35.1, +2.6) in men, and 23.5% (-49.1, +15.2) in women below age 45. This was less favourable than the trend in the general population, where IHD mortality fell by 9.7% in men and 8.3% in women of all ages, and by 31.1% (28.6, 33.5) in men and 40.5% (35.0, 45.5) in women under 45 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of CCK binding sites in the human hippocampal formation and their alteration in schizophrenia: a post-mortem autoradiographic study

The distribution of cholecystokinin binding sites has been visualized and quantified by quantitative autoradiography in the human hippocampus from post-mortem brains of 11 controls and 11 schizophrenics. CCK receptors were localized to subiculum and parahippocampal gyrus. In the cortical areas there was a particularly dense lamination of receptors. In the schizophrenic material a similar overall pattern was seen, but there were significant losses of receptors in CA1 subiculum and cortex. These findings confirm the distribution of CCK receptors in the retrohippocampal areas in man and also provide further support for earlier homogenate studies which have also shown a loss of CCK binding sites in schizophrenia. This effect was localized primarily to parahippocampal gyrus suggesting that CCK plays some role in the genesis of developmental abnormalities in this region.

Bacteriology of acute otitis media in adults

OBJECTIVE

--The objective of this study was to determine the bacteriology of acute otitis media in adults. Although this has frequently been studied in children, no data have recently been reported from adults in the United States. Additionally, information on the prevalence of Haemophilus influenzae as a causative organism in acute otitis media in adults has not been available.

DESIGN

--Middle-ear aspirates for cultures were obtained by myringotomy from adults meeting entry criteria.

SETTING

--Emergency department, Eye and Ear Hospital of Pittsburgh, Pa.

PATIENTS

--Thirty-four patients (volunteer sample) met the eligibility requirements. Exclusion criteria included history of chronic otitis media, recent antibiotic therapy, immunosuppressive illnesses, or prior otologic surgery.

INTERVENTION

--Ten days of oral cefuroxime axetil (250 mg) was prescribed.

MAIN OUTCOME MEASURES

--Patients were followed closely for at least 6 weeks. Aerobic and anaerobic cultures were incubated and evaluated per the scheduled protocol.

RESULTS

--Haemophilus influenzae and Streptococcus pneumoniae were grown on culture of specimens from nine and seven patients (26% and 21%), respectively. Twenty-two percent (2/9) of the H influenzae isolates and the single isolate of Moraxella catarrhalis produced beta-lactamase (9% overall).

CONCLUSIONS

--The present results suggest that, as in children, amoxicillin would be an appropriate first-line agent for empiric therapy of acute otitis media in adults. Antimicrobials inactive against H influenzae (eg, penicillin V, cephalexin, erythromycin, or tetracyclines) are not appropriate for initial therapy. Antimicrobials with efficacy against organisms producing beta-lactamase, such as cefuroxime axetil, which was used to treat the study patients, do not appear to be required for routine initial therapy in adults. However, they would be appropriate when an organism producing beta-lactamase is isolated from the middle ear or when a patient fails to improve rapidly on amoxicillin therapy.

Enhanced growth hormone responses to growth hormone releasing hormone in male type I diabetic patients

In a previous paper we have demonstrated that growth hormone (GH) responses to growth hormone releasing hormone (GHRH) are higher in premenopausal normal women than in age matched healthy men. As in type I diabetes mellitus various disturbances of GH secretion have been reported, the aim of our study was to assess the effect of sex on basal and GHRH stimulated GH secretion in type I diabetes mellitus. In 21 female and 23 male type I diabetic patients and 28 female and 30 male control subjects GH levels were measured before and after stimulation with GHRH (1 microgram/kg body weight i.v.) by radioimmunoassay. GH responses to GHRH were significantly higher in female than in male control subjects (p less than 0.02), whereas the GH levels following GHRH stimulation were similar in female and male type I diabetic patients. GH responses to GHRH were significantly higher in the male type I diabetic patients than in the male control subjects (p less than 0.001); in the female type I diabetic patients and the female control subjects, however, GH responses to GHRH were not statistically different. The absence of an effect of sex on GHRH stimulated GH responses in type I diabetes mellitus provides further evidence of an abnormal GH secretion in this disorder.