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H Lou

Publications and source records attributed to H Lou.

At least 73 records · Page 4Linked to original sources
PubMed1993

Angiotensin II regulates insulin-like growth factor I gene expression in vascular smooth muscle cells.

The potent vasoconstrictor peptide angiotensin II (ang II) has been shown to promote growth of vascular smooth muscle cells (VSMC) in vitro and in vivo. We have previously demonstrated that VSMC synthesize insulin-like growth factor I (IGF I), an important autocrine/paracrine growth factor. Exposure of quiescent VSMC to ang II caused a marked increase in IGF I mRNA levels, peaking at 6 h (199 +/- 26% above control) and sustained for at least 24 h. This increase was completely inhibited by actinomycin D. Nuclear run-on assays indicated that ang II stimulated IGF I gene transcription 3.6-fold. Protein synthesis inhibition with cycloheximide increased basal IGF I mRNA levels but blocked ang II-induced IGF I expression. Immunoreactive IGF I levels in VSMC-conditioned medium were increased by 2.7-fold 24 h following ang II exposure. Measurements of [3H]thymidine incorporation showed that ang II caused a 117% increase in DNA synthesis at 24 h that was almost completely inhibited in the presence of an anti-IGF I antibody. Thus, ang II regulates transcription of the IGF I gene in VSMC and IGF I is required for ang II-induced DNA synthesis. These findings suggest a potentially important role for IGF I as a mediator of the vascular growth responses induced by activation of the renin-angiotensin system in vivo.

Angiotensin II↗
PubMed1993

cDNA cloning and expression of the human hepatic bile acid-binding protein. A member of the monomeric reductase gene family.

In human liver, we previously identified one isoform of dihydrodiol dehydrogenase activity that expresses high affinity bile acid binding (HBAB) with minimal 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity for bile acids. This protein may assist in the rapid intracellular transport of bile acids from the sinusoidal to the canalicular pole of the cell. We now report the cDNA cloning and bacterial expression of this novel, multifunctional protein. A 1252-base pair HBAB cDNA was cloned from a HepG2 lambda GT11 library using a rat hepatic bile acid binder cDNA probe. Bacterial expressed recombinant HBAB oxidized racemic trans dihydrodiol benzene (0.455 mumol NADPH/mg/min) with minimal 3 alpha-HSD activity for bile acids (< 0.003 mumol NADPH/mg/min). Lithocholic acid and chenodeoxycholic acid dissociation constants as determined by displacement of the fluorescent probe, bis-1-anilino-8 sulfonate, were higher than those previously reported for the native protein (1 microM versus 10 nM). Significant amino acid sequence homology was found with the human chlordecone reductase, bovine prostaglandin F synthetase, and rat hepatic-3 alpha-HSD suggesting, that HBAB is also a member of the recently identified, monomeric oxidoreductase gene family. Future studies will define the physiologic significance of this novel, multifunctional protein in bile acid transport and xenobiotic metabolism.

3-Hydroxysteroid Dehydrogenases↗
PubMed1993

Further isolation of glycosides from Cynanchum hancockianum.

Three new glycosides, neohancosides B, C, and D, have been isolated as polyacetates 2, 3, and 4 from Cynanchum hancockianum along with neohancoside A hexaacetate [1]. The new compounds were established as 9-hydroxylinalool-3-O-beta-D-xylopyranosyl-(1-->6)-beta-D-glucopyr anoside heptaacetate [2], 2-hydroxyacetophenone-2-O-beta-D-xylopyranosyl-(1-->6)-beta-D-gluc opyranoside hexaacetate [3], and 6'-O-sinapoylsucrose octaacetate [4] by means of spectroscopic and chemical tools.

Drugs, Chinese Herbal↗
PubMed1993

Expression of maize Adh1 intron mutants in tobacco nuclei.

In vivo and in vitro gene transfer experiments have suggested that the elements mediating intron recognition differ in mammalian, yeast and plant nuclei. Differences in the sequence dependencies, which also exist between dicotyledonous and monocotyledonous nuclei, have prevented some monocot introns from being spliced in dicot nuclei. To locate elements which modulate efficient recognition of introns in dicot nuclei, the maize Adh1 gene has been expressed in full-length and single intron constructs in Nicotiana benthamiana nuclei using an autonomously replicating plant expression vector. Quantitative PCR-Southern analyses indicate that the inefficient splicing of the maize Adh1 intron 1 (57% AU) in these dicot nuclei can be dramatically enhanced by increasing the degree of U1 snRNA complementarity at the 5' splice site. This indicates that the 5' splice site plays a significant role in defining the splicing efficiency of an intron in dicot nuclei and that, most importantly, the remainder of this monocot intron contains no elements which inhibit its accurate recognition in dicot nuclei. Deletions in intron 3 (66% AU) which effectively move the 3' boundary between AU-rich intron and GC-rich exon sequences strongly activate a cryptic upstream splice site; those which do not reposition this boundary activate a downstream cryptic splice site. This suggests that 3' splice site selection in dicot nuclei is extremely flexible and not dependent on strict sequence requirements but rather on the transition points between introns and exons. Our results are consistent with a model in which potential splice sites are selected if they are located upstream (5' splice site) or downstream (3' splice site) of AU transition points and not if they are embedded within AU-rich sequences.

Alcohol Dehydrogenase↗
PubMed1993

Factors affecting authentic 5' splice site selection in plant nuclei.

To define elements critical for 5' splice selection in dicot plant nuclei, wild-type and mutant transcripts containing the first intron of the pea rbcS3A gene were expressed in vivo by using an autonomously replicating plant expression vector. Mutations within the normal 5' splice site (+1) of this intron demonstrate that 5' splice sites at the normal exon-intron boundary having only limited agreement with a 5' splice site consensus sequence can be spliced quite effectively in dicot nuclei. Inactivation of the normal 5' splice site occurs only by point mutations of the G at position +1 of the intron (+1G) or +2U or by multiple mutations at other positions and results in the activation of three cryptic 5' splice sites in the adjacent exon and intron. cis competition of cryptic sites having consensus 5' splice site sequences with the normal 5' splice site demonstrates that cryptic splice sites in the exon, but not the intron, can compete to some extent with the normal site. Replacement of the sequences between the cryptic and normal 5' splice sites with heterologous exon or intron sequences demonstrates that the 5' boundary of this plant intron is defined by its position relative to the AU transition point between exon and intron. These results suggest that potential 5' splice sites upstream of the AU transition point are accessible for recognition by the plant pre-mRNA splicing machinery and that those downstream in the AU-rich intron are masked from recognition.

Base Composition↗
PubMed1993

3' splice site selection in dicot plant nuclei is position dependent.

In contrast to mammalian and yeast systems, the mechanism for intron recognition and splice site selection in plant pre-mRNAs is poorly understood. Splice site sequences and putative branchpoint sequences are loosely conserved in plant introns compared with other eukaryotes. Perhaps to compensate for these variations, plant introns are significantly richer in adenosine and uridine residues than are their adjacent exons. To define elements critical for 3' splice site selection in dicotyledonous plant nuclei, pre-mRNA transcripts containing intron 3 of the maize Adh1 gene were expressed in Nicotiana benthamiana nuclei by using an autonomously replicating plant expression vector. Using a series of intron rearrangements which reposition the 3' intron-exon border, we demonstrate that the normal 3' splice site is defined in a position-dependent manner and that cryptic 3' splice sites within the intron are masked by the presence of a functional downstream 3' splice site. Disruption of the AU-rich elements upstream from the normal 3' splice site indicates that multiple AU elements between -66 and -6 cooperatively define the 3' boundary of the intron. These results are consistent with a model for plant intron recognition in which AU-rich elements spread throughout the length of the intron roughly define the intron boundaries by generating strong AU transition points. Functional 3' splice sites located downstream from these AU-rich sequences are preferentially selected over sites embedded within them.

Alcohol Dehydrogenase↗
PubMed1993

Estimation of cerebral venous saturation in newborn infants by near infrared spectroscopy.

The purpose of the study was to evaluate the near infrared spectroscopy technique for determination of the cerebral venous oxygen saturation. By tilting the patient's head down 15 degrees, changes in OD may be caused by changes in cerebral blood volume. On the assumption that increases in cerebral blood volume consist of venous blood only, cerebral venous oxygen saturation can be calculated as the measured change in oxygenated Hb divided by the change in total Hb. Two groups of mechanically ventilated, newborn infants were investigated: 10 asphyxiated, term infants and another 22 preterm infants with respiratory distress syndrome. All were monitored by near infrared spectroscopy during tilting, and cerebral blood flow was estimated by the 133Xe clearance technique immediately before tilting. Cerebral venous oxygen saturation could not be calculated in 13 preterm infants, as the blood volume remained constant during tilting. In the remaining 19, cerebral venous oxygen saturation averaged 0.67 (SD = 0.09) in asphyxiated infants and 0.53 (SD = 0.15) in preterm infants (p = 0.03). The corresponding values of cerebral blood flow were closely and inversely related to oxygen extraction calculated from cerebral venous saturation as estimated by near infrared spectroscopy.

Asphyxia Neonatorum↗
PubMed1993

Compound heterozygosity for metachromatic leukodystrophy and arylsulfatase A pseudodeficiency alleles is not associated with progressive neurological disease.

Several allelic mutations at the arylsulfatase A (ASA) locus cause substantial deficiencies of this lysosomal enzyme. Depending on the genetically determined degree of the deficiency, the clinical outcome may be very different--either metachromatic leukodystrophy (MLD), a lethal lysosomal storage disorder affecting the nervous system, or, more frequently, the so-called pseudodeficiency (PD), which has no apparent clinical consequence. Because of compound heterozygosity for MLD and PD, 1/1,000 individuals in the population have low residual enzyme activities, which are intermediate between those of MLD patients and those of PD homozygous normal individuals. In order to assess whether PD/MLD compound heterozygotes bear a health risk, we examined clinically and biochemically 16 individuals with this genotype. Of these subjects, two had neurological symptoms and two showed lesions, without clinical symptoms, in magnetic resonance imaging of the brain. None of these symptoms was progressive, nor did they resemble those of MLD. Nerve conduction velocities were normal in these probands, and they secreted only low amounts of sulfatide in the urine. We conclude that the observed neurological symptoms are unrelated to the ASA genotype and that PD/MLD compound heterozygotes are not at an increased risk for developing progressive nervous system diseases.

Adolescent↗
PubMed1992

Multiple origins for phenylketonuria in Europe.

Phenylketonuria (PKU), a disorder of amino acid metabolism prevalent among Caucasians and other ethnic groups, is caused primarily by a deficiency of the hepatic enzyme phenylalanine hydroxylase (PAH). PKU is a highly heterogeneous disorder, with more than 60 molecular lesions identified in the PAH gene. The haplotype associations, relative frequencies, and distributions of five prevalent PAH mutations (R158Q, R261Q, IVS10nt546, R408W, and IVS12n1) were established in a comprehensive European sample population and subsequently were examined to determine the potential roles of several genetic mechanisms in explaining the present distribution of the major PKU alleles. Each of these five mutations was strongly associated with only one of the more than 70 chromosomal haplotypes defined by eight RFLPs in or near the PAH gene. These findings suggest that each of these mutations arose through a single founding event that occurred within time periods ranging from several hundred to several thousand years ago. From the significant differences observed in the relative frequencies and distributions of these five alleles throughout Europe, four of these putative founding events could be localized to specific ethnic subgroups. Together, these data suggest that there were multiple, geographically and ethnically distinct origins for PKU within the European population.

Europe↗
PubMed1991

Correlation between cerebrospinal fluid phenylalanine and beta-endorphin in patients with phenylketonuria.

Previous animal and human studies have suggested an analgesic effect of phenylalanine involving endogenous opioid peptides. Phenylalanine was measured by a HPLC method with electrochemical detection and beta-endorphin by a specific radioimmunoassay in 14 lumbar cerebrospinal fluid samples from 13 patients with phenylketonuria. Cerebrospinal fluid beta-endorphin was also determined in 6 age-matched control subjects. We found a trend towards a higher beta-endorphin level in phenylketonuria (median 26.0 pM, range 13.0-37.8) than in the control subjects (20.6 pM, 12.7-28.0), P = 0.13. Cerebrospinal fluid concentrations of phenylalanine and beta-endorphin were significantly correlated (r = 0.68, P = 0.008). The results support the hypothesis that phenylalanine modifies the central endogenous opioid system.

Adolescent↗
PubMed1991

In vivo analysis of plant pre-mRNA splicing using an autonomously replicating vector.

In this paper, we demonstrate that an autonomously replicating plant expression vector can be used for analysis of pre-mRNA splicing determinants in intact dicot cells. This vector system relies on the Agrobacterium-mediated transfection of leaf discs with the A component of the geminivirus tomato golden mosaic virus (TGMV). Insertion of intron sequences between viral promoter and terminator sequences results in the production of high levels of pre-mRNA transcripts that are effectively and accurately spliced in vivo. Introns from the soybean B-conglycinin gene are spliced at greater than 95% efficiency indicating that the high expression levels of precursor RNA do not exceed the intron splicing capacity of these cells. Introns from the pea and wheat rbcS genes are spliced at 85% and 73% efficiency, respectively, indicating that tobacco leaf disc nuclei are capable of effectively and accurately processing particular dicot and monocot introns. Inclusion of a dicot intron in an engineered construct results in a five-fold enhancement of the level of mRNA stably expressed in dicot nuclei.

Base Sequence↗
PubMed1991

Molecular basis of phenotypic heterogeneity in phenylketonuria.

BACKGROUND: Phenylketonuria is a metabolic disorder that results from a deficiency of the hepatic enzyme phenylalanine hydroxylase. Its clinical phenotype varies widely, and to date more than 10 mutations in the phenylalanine hydroxylase gene have been identified in persons with the disorder. We attempted to relate the clinical phenotype of patients to their genotype. METHODS: We studied 258 patients with phenylketonuria from Denmark and Germany for the presence of eight mutations previously found in patients from these countries. The in vitro activity of the enzymes associated with these mutations was determined by expression analysis in heterologous mammalian cells. The level of activity was then used to predict the in vivo level of phenylalanine hydroxylase activity in patients with various combinations of mutant phenylalanine hydroxylase alleles. RESULTS: The eight mutations involved 64 percent of all mutant phenylalanine hydroxylase alleles in the patients. Expression analysis showed that these mutant enzymes produced from 0 to 50 percent of normal enzyme activity. The predicted level of phenylalanine hydroxylase activity correlated strongly with the pretreatment serum level of phenylalanine (r = 0.91, P less than 0.001 in the Danish patients and r = 0.74, P less than 0.001 in the German patients), phenylalanine tolerance in the Danish patients (r = 0.84, P less than 0.001), and the serum phenylalanine level measured after standardized oral protein loading in the German patients (r = 0.84, P less than 0.001). CONCLUSIONS: Our results strongly support the hypothesis that there is a molecular basis for phenotypic heterogeneity in phenylketonuria. The establishment of genotype will therefore aid in the prediction of biochemical and clinical phenotypes in patients with this disease.

Alleles↗
PubMed1991

Cerebrospinal fluid beta-endorphin in Rett syndrome.

An hypothesis of increased endorphinergic activity has been proposed to account for the characteristic symptoms of Rett syndrome. Cerebrospinal fluid samples from eight girls with Rett syndrome were analysed for beta-endorphin (beta-EP) immunoactivity and compared with samples from a control group of 15 children with acute leukaemia in remission. Severity of symptoms was not found to be related to beta-EP level. A group of early-treated adolescents with phenylketonuria had beta-EP levels similar to the Rett syndrome patients, but no symptoms resembling theirs. Therefore it is unlikely that increased levels of beta-EP are of primary pathogenetic significance. The conflicting findings of many earlier reports may be a result of differences between control groups.

Adolescent↗
PubMed1991

Regulation of insulin-like growth factor I messenger RNA levels in vascular smooth muscle cells.

We have previously demonstrated specific insulin-like growth factor I (IGF I) messenger RNA (mRNA) transcripts in cultured rat aortic smooth muscle cells (RASM). To define the role of IGF I in the autocrine growth program of vascular smooth muscle cells, we quantitated IGF I mRNA levels in proliferating and quiescent (serum-deprived for 48 hours) RASM. IGF I mRNA levels were markedly decreased in quiescent cells, and this effect was reversible on reexposure to serum. Since platelet-derived growth factor (PDGF) acts synergistically with IGF I to stimulate vascular smooth muscle cell growth, we exposed quiescent RASM to PDGF AB or BB and quantitated IGF I transcript levels. Both PDGF dimers caused a marked, rapid increase in IGF I message levels. To determine whether induction of IGF I mRNA levels correlated with secretion of IGF I, we measured immunoreactive IGF I in RASM conditioned medium after separation of IGF I binding proteins by gel filtration chromatography. PDGF caused a significant increase in IGF I release at 24 hours. These findings indicate that IGF I mRNA levels in vitro are regulated by serum and by growth factors such as PDGF. Serum deprivation reversibly decreases IGF I transcript levels, and exposure of quiescent cells to PDGF increases IGF I mRNA levels and IGF I release. Regulation of IGF I expression by competence growth factors such as PDGF may play an important role in the control of vascular smooth muscle cell growth.

Blotting, Northern↗
PubMed1990

Immature pattern of brain activity in Rett syndrome.

Seven girls with Rett syndrome, a progressive degenerative encephalopathy affecting girls, were studied with single photon emission computed tomography and compared with an aged-matched control group of nine normal children. Global cerebral blood flow was significantly lower in Rett syndrome (54 vs 69 mL/100 g per minute), and the flows in prefrontal and temporoparietal association regions of the telencephalon were markedly reduced, whereas the primary sensorimotor regions were relatively spared. The flow distribution in Rett syndrome is very similar to the distribution of brain metabolic activity in infants of a few months of age. The abnormal regional cerebral blood flow distribution most likely reflects the widespread functional disturbances in the brain of patients with Rett syndrome, whereas computed tomographic and neuropathologic examination only reveal slight changes when compared with normal children.

Adolescent↗
PubMed1990

Cognitive development in offspring of untreated and preconceptionally treated maternal phenylketonuria.

A survey is given of literature reports on the effect of performance in offspring from 26 maternal PKU pregnancies treated prior to conception. The survey includes two women who were referred to us for genetic counselling because they had both given birth to microcephalic, mentally retarded children. The women were discovered to suffer from unrecognized maternal PKU with fasting phenylalanine concentration of 1.1-1.5 mmol/L. A strict diet was introduced prior to planned pregnancy and after some months on diet (phenylalanine concentrations less than 0.6 mmol/L) they became pregnant again. Serum phenylalanine levels were monitored weekly throughout pregnancy, and adjustments in the diet were made to keep serum phenylalanine concentration within the range of 0.18-0.42 mmol/L. The outcome of the pregnancies were healthy children who have developed normally. Their IQs are 105 and 119 at ten and four years of age, respectively and their head circumferences are normal. Our data show that the effect of preconceptional dietary treatment was children with a normal performance, contrary to their older siblings born following untreated pregnancies. These results are in agreement with the survey of ten years' promising experiences with preconceptional treatment in maternal PKU. The data may help to motivate young PKU women to accept planned pregnancies and to encourage them to return to the strict diet, which has prevented them from being retarded.

Child↗
PubMed1990

Vasoparalysis associated with brain damage in asphyxiated term infants.

The relationship of cerebral blood flow to acute changes in arterial carbon dioxide and mean arterial blood pressure (MABP) was determined during the first day of life in 19 severely asphyxiated term infants supported by mechanical ventilation. For comparison, 12 infants without perinatal asphyxia were also investigated. Global cerebral blood flow (CBF infinity) was determined by xenon 133 clearance two or three times within approximately 2 hours. During the cerebral blood flow measurement, the amplitude-integrated electroencephalogram and visual-evoked potential were recorded. Changes in arterial carbon dioxide pressure followed adjustments of the ventilator settings, whereas MABP fluctuated spontaneously. Arterial oxygen pressure and blood glucose concentration were in the normal range. Five of the asphyxiated infants had isoelectric electroencephalograms and died subsequently with severe brain damage. They had a high CBF infinity (mean 30.6 ml/100 gm/min) and abolished carbon dioxide and MABP reactivity. Lower CBF infinity (mean 14.7 ml/100 gm/min) and abolished MABP reactivity were found in another five asphyxiated infants with burst-suppression electroencephalograms in whom computed tomographic or clinical signs of brain lesions developed. The carbon dioxide reactivity was preserved in these infants. In the remaining nine asphyxiated infants without signs of central nervous system abnormality, carbon dioxide and MABP reactivity were preserved, as was also the case in the control group. We conclude that abolished autoregulation is associated with cerebral damage in asphyxiated infants and that the combination of isoelectric electroencephalograms and cerebral hyperperfusion is an early indicator of very severe brain damage.

Asphyxia Neonatorum↗