Search PubMed⌕ Search

Biomedical subjects

S Andersson

Publications and source records attributed to S Andersson.

At least 217 records · Page 12Linked to original sources
PubMed1990

Cloning and regulation of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in bile acid biosynthesis.

The rate-limiting step in bile acid biosynthesis is catalyzed by the microsomal cytochrome P-450 cholesterol 7 alpha-hydroxylase (7 alpha-hydroxylase). The expression of this enzyme is subject to feedback regulation by sterols and is thought to be coordinately regulated with enzymes in the cholesterol supply pathways, including the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl-coenzyme A reductase and synthase. Here we report the purification of rat 7 alpha-hydroxylase and the determination of a partial amino acid sequence. Oligonucleotides derived from peptide sequence were used to clone a full-length cDNA encoding 7 alpha-hydroxylase. DNA sequence analysis of the cDNA revealed a 7 alpha-hydroxylase protein of 503 amino acids with a predicted molecular weight of 56,890 which represents a novel family of cytochrome P-450 enzymes. Transfection of a 7 alpha-hydroxylase cDNA into simian COS cells resulted in the synthesis of a functional enzyme whose activity was stimulated in vitro by the addition of rat microsomal cytochrome P-450 reductase protein. RNA blot hybridization experiments indicated that the mRNA for 7 alpha-hydroxylase is found only in the liver. The levels of this mRNA increased when bile acids were depleted by dietary cholestyramine and decreased when bile acids were consumed. Dietary cholesterol led to an increase in 7 alpha-hydroxylase mRNA levels. The enzymatic activity of 7 alpha-hydroxylase paralleled the observed changes in mRNA levels. These results suggest that bile acids and sterols are able to alter the transcription of the 7 alpha-hydroxylase gene and that this control explains the previously observed feedback regulation of bile acid synthesis.

Amino Acid Sequence↗
PubMed1990

Assessment of autonomic nerve function in myotonic dystrophy.

The function of the autonomic nervous system was studied in 23 patients with myotonic dystrophy, from a defined population in northern Sweden with an extremely high prevalence of this disease. Heart rate variability tests showed only minor signs of parasympathetic dysfunction. Blood pressure and plasma noradrenaline measurements in recumbent and upright positions showed no signs of sympathetic neuropathy. Increased plasma levels of noradrenaline was an unexpected finding. Our study does not support the hypothesis that cardiac arrhythmias, orthostatic hypotension, gastrointestinal motility disturbances and urinary bladder dysfunction in myotonic dystrophy are caused by autonomic neuropathy, and we believe that these symptoms should rather be ascribed to a defective function of the target organs.

Adolescent↗
PubMed1990

Characterization of a novel Minute-locus in Drosophila melanogaster: a putative ribosomal protein gene.

We describe a novel Minute locus, M(1)7C, on the X-chromosome of Drosophila melanogaster. Heterozygous deficient females have most, if not all, of the Minute features (short and fine bristles, rough and somewhat larger eyes, thin-textured wings, missing aristae, affected antennae, delayed development, reduced fertility, and decreased viability). Both Minute and non-Minute adult progeny from Minute mothers suffer from Minute maternal effects such as abdominal segmentation defects, fused tergites, and missing or defective legs and halteres. Using a plasmid clone from region 7C5-9, which harbours the D. melanogaster ribosomal protein gene RPS14, we have found that the accumulation of a single transcript of approximately 650 b is extremely reduced in Minute larvae in comparison with wild-type. We have localized the RPS14 gene to approximately 28 kbp distal from the singed locus. The results suggest that M(1)7C and RPS14 may be the same gene.

Animals↗
PubMed1990

Structural and biochemical properties of cloned and expressed human and rat steroid 5 alpha-reductases.

The microsomal enzyme steroid 5 alpha-reductase is responsible for the conversion of testosterone into the more potent androgen dihydrotestosterone. In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiation in the fetus and prostatic growth in men. Here we describe the isolation, structure, and expression of a cDNA encoding the human steroid 5 alpha-reductase. A rat cDNA was used as a hybridization probe to screen a human prostate cDNA library. A 2.1-kilobase cDNA was identified and DNA sequence analysis indicated that the human steroid 5 alpha-reductase was a hydrophobic protein of 259 amino acids with a predicted molecular weight of 29,462. A comparison of the human and rat protein sequences revealed a 60% identity. Transfection of expression vectors containing the human and rat cDNAs into simian COS cells resulted in the synthesis of high levels of steroid 5 alpha-reductase enzyme activity. Both enzymes expressed in COS cells showed similar substrate specificities for naturally occurring steroid hormones. However, synthetic 4-azasteroids demonstrated marked differences in their abilities to inhibit the human and rat steroid 5 alpha-reductases.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1990

Cardiac involvement in congenital myotonic dystrophy.

Seven young patients (mean age 19 years 8 months) with congenital myotonic dystrophy and with defined symptoms at birth were investigated by electrocardiography and echocardiography. None had cardiovascular symptoms. Electrocardiograms or echocardiograms or both were abnormal in all patients. Atrioventricular and intraventricular conduction defects were the most common electrocardiographic abnormalities and were seen in five patients. The echocardiographic examinations showed impaired left ventricular systolic function in one patient. Other echocardiographic findings were a small left ventricle and atrium, minor valve defects, and mitral valve prolapse. This study shows that the heart is often affected in young patients with congenital myotonic dystrophy. The specialised conduction system is often affected and so too is the myocardium, causing impaired systolic function.

Adolescent↗
PubMed1990

Correlation of patent ductus arteriosus shunting with plasma atrial natriuretic factor concentration in preterm infants with respiratory distress syndrome.

The concentration of plasma atrial natriuretic factor (ANF) and the mechanism for its secretion were investigated in 17 preterm infants with respiratory distress. Their mean gestational age was 29 wk and wt 1250 g. The infants were followed during the first week of life by sequential Doppler ultrasound studies. Ductal openness versus closure and amount of ductal flow were correlated with plasma ANF concentrations. In a subset of 10 infants, sequential Doppler color flow mapping was used to quantify the ductal flow. During the first 72 h, plasma ANF was high, 361 pg/mL; it decreased to 96 pg/mL by the end of the 1st wk. The ANF level was significantly higher when the ductus was open than closed (393 versus 123 pg/mL, p less than 0.05). In patients with open ductus and bidirectional foramen ovale shunting (n = 3) ANF was 567 pg/mL and in those with left-to-right shunt 355 pg/mL (n 15, NS). The left atrial size, i.e. the left atrial to aortic root ratio, correlated with the amount of ductal shunting (r = 0.63, p less than 0.01) and with ANF concentration (r = 0.46, p less than 0.02). The correlation of ANF values and the magnitude of left-to-right ductal shunting assessed by color flow mapping was highly significant (r = 0.66, p less than 0.001). In these patients, the elevation of ANF is reflective of ductal flow.

Age Factors↗
PubMed1990

Expression of neural 5 alpha-reductase messenger ribonucleic acid: comparison to 5 alpha-reductase activity during prenatal development in the rat.

The present study was designed to characterize the developmental pattern of 5 alpha-reductase messenger RNA (mRNA) levels and enzyme activity in intact medial basal hypothalamic (MBH) and preoptic area (POA) tissue fragments of rats during fetal development. 5 alpha-Reductase activity was determined using [3H]testosterone as the substrate and quantifying, by TLC, the radiolabeled 5 alpha-reduced metabolites (dihydrotestosterone [DHT] and 5 alpha-androstane-3 alpha,17 beta-diol). Confirmation of the identity of the [3H]5 alpha-DHT formed was demonstrated by recrystallization of the derivatized DHT to constant specific activity. Under saturating substrate conditions (1.7 microM testosterone), there were no significant sex differences (male vs. female) detected in neural 5 alpha-reductase during prenatal, perinatal, or neonatal development. 5 alpha-Reductase activity was low but detectable at gestational day (GD) 15 (approximately 10 pmol/h.mg protein), increased over 3-fold to peak levels at GD 18, and then declined to moderate levels at GD 22 (approximately 22 pmol/h.mg protein) and 4 days after birth (approximately 17 pmol/h.mg protein). In addition, the developmental pattern of 5 alpha-reductase mRNA expression in fetal MBH-POA tissue was determined, by RNA blot hybridization, using a complementary DNA encoding the rat 5 alpha-reductase enzyme. A single mRNA species was detected at 2.5 kilobase in MBH-POA tissue, which is similar in size to adult rat liver and prostate 5 alpha-reductase mRNA. At GD 15, 5 alpha-reductase mRNA was clearly detectable; the abundance increased on GD 17, remained at maximal levels at GDs 18, 19, and 20, and then decreased to moderate levels on GD 22. A correlation calculated between the normalized 5 alpha-reductase mRNA levels and enzyme activities revealed a strong correspondence between mRNA abundance and enzyme activity values during prenatal development, r = 0.80, P = 0.056. These findings indicate that neural 5 alpha-reductase activity may be developmentally regulated, and that the changes in 5 alpha-reductase activity in MBH-POA tissue during late fetal development are regulated, in part, by the levels of mRNA encoding the 5 alpha-reductase enzyme.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1989

Structure and dynamics of a fluorescent DNA oligomer containing the EcoRI recognition sequence: fluorescence, molecular dynamics, and NMR studies.

The self-complementary DNA decamer duplex d(CTGAATTCAG)2 and its modified counterpart d(CTGA[2AP]TTCAG)2, where the innermost adenine (6-aminopurine) has been replaced with the fluorescent analogue 2-aminopurine (2AP), have been studied by fluorescence and NMR spectroscopy and simulated by molecular dynamics. Both decamers are recognized and cleaved by the EcoRI restriction endonuclease. 2D NMR results show that both decamers have a standard B-type conformation below 20 degrees C, though a disturbance exists to the 5' side of the 2AP site which may originate from increased local mobility. The fluorescence and fluorescence anisotropy decays of both decamers, as well as the one containing 2AP in only one chain, were studied as a function of temperature. The data show that the 2AP base exists in a temperature-dependent distribution of states and shows rapid motions, suggesting interconversion among these states on a time scale of about 10(-10) s. The integrated fluorescence of the decamer with 2AP in both chains shows a large increase around the helix melting temperature whereas the decamer with one 2AP shows only a mild increase, showing that the mixed helix has a different structural transition as sensed by the 2AP base. The data suggest a model of conformational states which have distinct fluorescence decay times. The various states may differ in the degree of base stacking. Fluctuations in the degree of stacking of the A or 2AP base are supported by molecular dynamics simulations, which additionally show that the 2AP-T or A-T base pair hydrogen bonds remain intact during these large motions.

DNA↗
PubMed1989

Expression cloning and regulation of steroid 5 alpha-reductase, an enzyme essential for male sexual differentiation.

The conversion of testosterone into the more potent androgen, dihydrotestosterone, catalyzed by the enzyme steroid 5 alpha-reductase, is required for the differentiation of male external genitalia. Here, we report the isolation of cDNA clones encoding the rat steroid 5 alpha-reductase using expression cloning in Xenopus oocytes. DNA sequence analysis demonstrates that the liver and ventral prostate forms of steroid 5 alpha-reductases are identical hydrophobic proteins of 29 kDa. The amount of steroid 5 alpha-reductase mRNA in liver increased in response to castration, but remained unchanged in the prostate. Testosterone administration to castrates induced expression of mRNA in the prostate but had no effect on liver. The data suggest that the steroid 5 alpha-reductase gene is differentially regulated by testosterone in androgen-responsive versus non-responsive tissues.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1989

Cloning, structure, and expression of the mitochondrial cytochrome P-450 sterol 26-hydroxylase, a bile acid biosynthetic enzyme.

The conversion of cholesterol into bile acids in the liver represents the major catabolic pathway for the removal of cholesterol from the body. In this complex biosynthetic pathway, at least 10 enzymes modify both the ring structure and side chain of cholesterol, resulting in the formation of the primary bile acids, cholic acid, and chenodeoxycholic acid. To gain insight into the details and regulation of this pathway, we have used protein sequencing and molecular cloning techniques to isolate and characterize a cDNA encoding the rabbit mitochondrial sterol 26-hydroxylase. This enzyme catalyzes the first step in the oxidation of the side chain of sterol intermediates in the biosynthesis of bile acids. The structure of the sterol 26-hydroxylase, as deduced by both DNA sequence analysis of the cDNA and protein sequence analysis, reveals it to be a mitochondrial cytochrome P-450. A signal sequence of 36 residues precedes a coding region of 499 amino acids, predicting a molecular weight of 56,657 for the mature protein. The identity of the 26-hydroxylase cDNA was further confirmed by expression in monkey COS cells employing a versatile eukaryotic expression vector. Blotting experiments revealed that the mRNA for this enzyme is expressed in many tissues and that it is encoded by a low copy number gene in the rabbit genome.

Amino Acid Sequence↗
PubMed1989

Experimental ductus arteriosus: the relationships of atrial pressure, dilatation and flow with ANF secretion.

The design of the study was to determine whether an increased blood flow as seen in shunt lesions could serve as a stimulus for the secretion of atrial natriuretic factor (ANF). Since atrial pressure, flow, and dilatation are closely related, an experimental ductus arteriosus model was utilized, in which acute changes of flow are assumed not to dilate the left atrium. In six dogs, a Dacron graft was constructed between the main pulmonary artery and the innominate artery. Constricting and releasing the tape around the graft adjusted the amount of "ductal" shunting. The total pulmonary flow and the shunt flow were measured by electromagnetic-flow transducers around the aortic root and around the graft. Plasma ANF concentration was measured from both cardiac atria. The size of the left atrium was determined from echocardiographic measurements made from a short-axis view. The total pulmonary flow varied between 1.2 and 5.8 1/min. The highest measured ANF was 396 pg/ml, and this was from the left atrium when the pressure was 18 mmHg, the highest left atrial pressure recorded. The highest right atrial pressure (5 mmHg) also correlated with the highest right-atrial level of ANF (366 pg/ml). The right atrial pressure had a significant correlation with plasma ANF concentration (R = 0.43, p less than 0.05). Pulmonary flow and plasma ANF concentration did not correlate; neither did left atrial size and ANF levels in 16 flow states where the size was measured. In the absence of atrial dilatation there was minimal stimulus for ANF secretion. A transient increase of left atrial pressure, without a concomitant significant atrial dilatation, did not serve as a significant stimulus for ANF secretion.

Animals↗
PubMed1989

Cloning and characterization of variable-sized gypsy mobile elements in Drosophila melanogaster.

A cosmid genomic library from a known gypsy-induced forked mutation, f1, was screened by 32P-labeled gypsy transposable element. Of more than 250 positive clones we randomly selected 21 for in situ hybridization to wild-type polytene chromosomes. Two clones hybridized to region 15F on the X-chromosome, the cytological position of forked. A third clone hybridized to at least 17 sites on the chromosomes indicating the presence of repetitive sequences in the gypsy flanking DNA. All clones labeled the centromeric regions heavily. Ten clones, including the two hybridizing at 15F, were chosen for further analysis, and restriction mapping allowed us to place them into three groups: (1) full-length, (2) slightly diverging, and (3) highly diverging gypsy elements. Group (2) is missing the XbaI site in both their long terminal repeats (LTRs) as well as the middle HindIII site; four of these gypsy elements also have a approximately 100-bp deletion at the 5' LTR. The group (3) gypsy transposons are missing one LTR and also have highly diverging DNA sequences. The restriction analyses further imply that most of these different gypsy elements are present in more than one copy in the genome of the f1 stock used in this study. The results raise intriguing questions regarding the significance of transposable elements in evolution and biological functions.

Animals↗
PubMed1989

Continuous and stepwise cystometry through suprapubic catheters--effect of infusion pattern and infusion rate on the cystometrogram of the normal human bladder.

Continuous cystometry at two filling rates (50 and 100 ml min-1) and stepwise cystometry (successive rapid volume infusions followed by bladder wall relaxation) were performed in 12 healthy subjects. Suprapubic catheters were used for infusion and recording of perivesical and intravesical pressures. The continuous cystometrograms obtained at filling rates of 50 and 100 ml min-1, respectively, did not differ with respect to desire to void, transmural pressure increase or bladder capacity. Stepwise cystometry allowed the bladders to be filled to a slightly larger volume than during continuous cystometry, but with comparatively lower transmural pressures only at very large distension of the bladder. There was considerable inter-individual variation in transmural pressure at both continuous and stepwise cystometry. Stepwise cystometry did not appear to provide any important additional information about pressure-volume relationship in the normal human bladder than could be obtained at routine clinical cystometry.

Administration, Intravesical↗
PubMed1989

Placental alcohol metabolism in chronic alcohol abuse.

The activities of aldehyde dehydrogenase (ALDH; EC 1.2.1.3) and alcohol dehydrogenase (ADH; EC 1.1.1.1) were measured in term placentas of 13 alcoholic women and 16 matched controls. With acetaldehyde 8 mmol/l as substrate, the ALDH activity was 29.1 +/- 12.2 and 34.4 +/- 15.3 mU/g of wet weight (mean +/- SD; p greater than 0.4) for alcoholics and controls, respectively. With 50 mumol of acetaldehyde, ALDH activity was undetectable in both groups. No ADH activity could be detected in the placentas. The weights of placentas and newborns were significantly lower in the alcoholic group (placentas: 526 +/- 116 vs. 653 +/- 77 g, p less than 0.005; newborns 2,878 +/- 417 vs. 3,595 +/- 346 g, p less than 0.001). The results suggest that in chronic alcohol abuse, the placenta plays a negligible role in the metabolism of ethanol and acetaldehyde.

Acetaldehyde↗
PubMed1989

Viscoelastic properties of the normal human bladder.

Continuous and stepwise cystometry were performed through suprapubic catheters in 12 healthy young subjects in order to assess passive viscoelastic variables of the normal human bladder during the collection phase. Elastic contants increased non-linearly with bladder distension. Relative elastic modulus and relaxation time of the bladder wall increased or tended to increase with bladder distension and infusion rate. There was considerable interindividual variation in all variables suggesting that discrimination between normal and abnormal bladder wall viscoelasticity may be difficult in routine clinical practice.

Adult↗