Biomedical subjects

B Schmitz

Publications and source records attributed to B Schmitz.

At least 91 records · Page 5Linked to original sources

PubMed1997

Imprinted segments in the human genome: different DNA methylation patterns in the Prader-Willi/Angelman syndrome region as determined by the genomic sequencing method.

A deletion of 15q11-q13 and uniparental disomy 15 lead to Prader-Labhart-Willi syndrome (PWS) or Angelman syndrome (AS) because this region contains genes expressed exclusively from the paternal (PWS) or maternal (AS) chromosome, respectively. DNA methylation plays a role in the control of imprinted gene expression, but so far only a few 5'-CG-3' dinucleotides within the recognition sites of the methylation sensitive enzymes have been studied. As part of a study on DNA methylation patterns in the human genome, we have applied the bisulfite protocol of genomic sequencing to study all 5'-CG-3' dinucleotides around exon 1 of SNRPN and at the D15S63 locus, which contains a start site for alternative SNRPN transcripts possibly involved in imprint switching during gametogenesis. At least 17 PCR products derived from single chromosomes of normal individuals as well as PWS and AS patients have been sequenced. We have found that cytosine residues outside 5'-CG-3' dinucleotides are always unmethylated. However, > 96% of all of the 23 5'-CG-3' dinucleotides around SNRPN exon 1 are methylated on the maternal chromosome and completely devoid of methylation on the paternal chromosome. This finding is in contrast to the D15S63 locus, where only the two Cfol/Hhal sites are methylated on the maternal chromosome at the same frequency as seen for the SNRPN segment. At the other five 5'-CG-3' dinucleotides, differential methylation is less pronounced, i.e. 45-70% on the maternal chromosome and 5-14% on the paternal chromosome. The differences between SNRPN and D15S63 methylation may reflect different biological functions of the alternative SNRPN transcripts. The systematic investigation of 5'-CG-3' methylation patterns as reported here will provide the basis for a PCR-based methylation test to diagnose PWS and AS.

5-Methylcytosine↗

PubMed1997

Inhibition of nonselective cation channels reduces focal ischemic injury of rat brain.

The effect of the novel inhibitor of receptor-activated and calcium store-operated nonselective cation channels, (RS)-(3,4-dihydro-6,7-dimethoxyisoquinoline-1-gamma 1)-2-phenyl-N, N-di-[2(2,3,4-trimethoxyphenyl) ethyl]acetamide (LOE 908 MS), on focal cerebral ischemia was studied in halothane-anesthetized rats submitted to permanent suture occlusion of the right middle cerebral artery (MCA). The treated group (n = 7) received subcutaneous injections of 30 mg/kg LOE 908 MS (in 1 ml saline) 10 min after vascular occlusion and again after 3 h. The untreated group (n = 11) was injected subcutaneously with 1 ml saline at the same times. Evolution of infarct was monitored by electrophysiological recording of EEG and cortical steady potential and by diffusion-weighted magnetic resonance imaging during the initial 6 h of vascular occlusion. The hemodynamic, biochemical, and morphological changes were studied after 6 h by combining autoradiographic measurement of blood flow with histological stainings and pictorial measurements of ATP, glucose, and tissue pH. In the untreated animals, the ischemic lesion volume [defined as the region in which the apparent diffusion coefficient (ADC) of water declined to below 80% of control] steadily increased by approximately 50% during the initial 6 h of vascular occlusion relative to the first set of data 10 min postocclusion. In the treated animals, in contrast, the ADC lesion volume declined by approximately 20% during the same interval. Treatment also led to a significant reduction in the number of periinfarct depolarizations. After 6 h of vascular occlusion, blood flow was significantly higher in the treated animals, and the volume of ATP-depleted and morphologically injured tissue representing the infarct core was 60-70% smaller. The volume of severely acidic tissue, in contrast, did not differ, indicating that LOE 908 MS does not reduce the size of ischemic penumbra. These findings demonstrate that postocclusion treatment of permanent focal ischemia with LOE 908 MS delays the expansion of the infarct core into the penumbra for a duration of at least 6 h and therefore substantially prolongs the window of opportunity for the reversal of the ischemic impact in the peripheral parts of the evolving infarct.

Acetamides↗

PubMed1997

Functional activation of cerebral blood flow after cardiac arrest in rat.

After a period of global cerebral ischemia, CO2 reactivity and the hemodynamic-metabolic activation to functional stimulation are transiently suppressed. This raises the question of whether the impaired functional coupling reflects disturbances of functional integrity of the brain or an impaired cerebrovascular reactivity. We, therefore, compared the recovery of CO2 reactivity with that of somatosensory evoked potentials, functional flow activation and neurologic deficits in a rodent model of cardiac arrest-induced cerebral ischemia, followed by up to 7 days of reperfusion. Cardiac arrest of 10 minutes' duration was produced in 24 animals by electrical fibrillation of the heart. Five animals were sham-operated controls. Resuscitation was performed by external cardiac massage, using standard resuscitation procedures. Functional activation was carried out under chloralose anesthesia by electrical stimulation of forepaws. CO2 reactivity was tested by ventilation of animals with 6% CO2. During functional and hypercapnic stimulation CBF was measured in the somatosensory cortex using laser-Doppler flowmetry, and at the end of the experiment by 14C-iodoantipyrine autoradiography. Neurologic deficits were scored by evaluating consciousness and various sensory and motor functions. In control animals 6% CO2 increased CBF measured by laser-Doppler flowmetry by 28.8% +/- 8.7%. Forepaw stimulation generated somatosensory evoked potentials with an amplitude of 750 +/- 217 microV and increased CBF measured by laser-Doppler flowmetry by 86.0% +/- 18.1%. After return of spontaneous circulation, CO2 reactivity was transiently reduced to about 30% of control at 1 hour of reperfusion (P < 0.05) but returned to near control at 5 hours. Somatosensory evoked potential amplitudes were reduced to 15% of control at 45 minutes of reperfusion and returned to only 50% to 60% at 3 and 7 days after return of spontaneous circulation (P < 0.05). Functional activation of blood flow was completely suppressed during the first hour after return of spontaneous circulation but also recovered to 50% to 60% of control at 3 days after return of spontaneous circulation (P < 0.05). Linear regression analysis revealed a significant correlation between recovery of functional activation of blood flow and both recovery of the amplitude of somatosensory evoked potentials (P = 0.03) and the neurologic deficit score (P = 0.02), but not between neurologic deficit score and recovery of CO2 reactivity or somatosensory evoked potential amplitudes. These data demonstrate that the suppression of functional activation of blood flow after 10 minutes cardiac arrest is not related to impairment of coupling mechanisms but reflects ongoing disturbances of the functional integrity of the brain. Assessment of functional flow coupling is a reliable way to study postischemic recovery of the brain.

Animals↗

PubMed1997

Refined mapping of the epilepsy susceptibility locus EJM1 on chromosome 6.

Juvenile myoclonic epilepsy (JME) is a genetically determined common subtype of idiopathic generalized epilepsy. Linkage to the HLA complex on chromosome 6p21.3 and an allelic association with HLA-DR13 and -DQB1 alleles suggest that a susceptibility locus for JME, designated as "EJM1," is located within or near the HLA region. However, further studies revealed controversial results, and genetic heterogeneity has been suspected. The present study was designed to evaluate the validity of the association and linkage findings and to refine the map position of EJM1. Our association analysis showed no significant difference of the frequency of HLA-DR13 carriers in 62 German JME patients compared with that in 77 German controls (X2 = 0.98, df = 1, p = 0.161, one-tailed). Multipoint linkage analysis with use of microsatellite markers from the chromosomal region 6p25-q13 in 29 German families of JME patients provided significant evidence that an epilepsy locus (EJM1) close to the HLA locus confers susceptibility to "idiopathic" generalized seizures (Zmax = 3.27 at theta max = 0.033 centromeric to the HLA-DQ locus), assuming an autosomal dominant mode of inheritance with 70% penetrance. Haplotype analyses revealed key recombinations in five families, which locate EJM1 to the centromeric side of the HLA-DQ locus. This study confirms a causative role of EJM1 in the pathogenesis of idiopathic generalized seizures in the majority of German families of JME patients and refines a candidate region of 10.1 cM in the chromosomal region 6p21 between the flanking loci HLA-DQ and D6S1019. A possible explanation for the current controversial results in families of different populations might be ethnic variation of interfering polygenic effects that could be permissive for heterogeneous susceptibility alleles.

Alleles↗

PubMed1997

Linkage analysis between idiopathic generalized epilepsies and the GABA(A) receptor alpha5, beta3 and gamma3 subunit gene cluster on chromosome 15.

INTRODUCTION: We tested the hypothesis that genetic variants within the GABA(A) alpha5, beta3 and gamma3 subunit gene cluster on chromosome 15q11-q13 confer genetic susceptibility to common subtypes of idiopathic generalized epilepsy (IGE). MATERIAL AND METHODS: Ninety-four families were selected from IGE patients with either juvenile myoclonic epilepsy (JME), juvenile (JAE) or childhood absence epilepsy (CAE). Cosegregation was tested between dinucleotide polymorphisms associated with the human GABA(A) alpha5, beta3 and gamma3 subunit gene cluster and three different IGE trait models. RESULTS: Evidence against linkage to the GABA(A) alpha5, beta3 and gamma3 subunit gene cluster was found in the entire family set and subsets selected from either CAE or JAE. In 61 families of JME patients, a maximum lod score (Zmax=1.40 at Theta(max)=0.00) was obtained for a broad IGE spectrum ("idiopathic" generalized seizure or generalized spike and wave discharges in the electroencephalogram) assuming genetic heterogeneity (alpha=0.37; P=0.06) and an autosomal recessive mode of inheritance. CONCLUSION: The possible hint of linkage in families of JME patients emphasizes the need for further studies to determine whether a recessively inherited gene variant within the GABA(A) alpha5, beta3 and gamma3 subunit gene cluster contributes to the pathogenesis of "idiopathic" generalized seizures and associated EEG abnormalities in a proportion of families.

Chromosomes, Human, Pair 15↗

PubMed1996

The neural adhesion molecule L1 is phosphorylated on tyrosine and serine residues.

The neural cell adhesion molecule L1 is highly homologous in its extracellular domain between species and completely identical in its cytoplasmic domain. We report here that tyrosine residues of L1 are phosphorylated in addition to serine residues, as determined by monoclonal phosphotyrosine antibodies and phosphoamino acid analysis. This result supports the suggestion that the cytoplasmic domain of L1 might be involved in signal transduction.

Animals↗

PubMed1996

Common subtypes of idiopathic generalized epilepsies: lack of linkage to D20S19 close to candidate loci (EBN1, EEGV1) on chromosome 20.

Hereditary factors play a major role in the etiology of idiopathic generalized epilepsies (IGEs). A trait locus (EBN1) for a rare subtype of IGEs, the benign neonatal familial convulsions, and a susceptibility gene (EEGV1) for the common human low-voltage electroencephalogram have been mapped close together with D20S19 to the chromosomal region 20q13.2. Both loci are potential candidates for the susceptibility to IGE spectra with age-related onset beyond the neonatal period. The present study tested the hypothesis that a putative susceptibility locus linked to D20S19 predisposes to spectra of IGEs with age-related onset from childhood to adolescence. Linkage analyses were conducted in 60 families ascertained through IGE patients with juvenile myoclonic epilepsy, juvenile absence epilepsy or childhood absence epilepsy. Our results provide evidence against linkage of a putative susceptibility gene for four hierarchically broadened IGE spectra with D20S19 assuming tentative single-locus genetic models. The extent of an "exclusion region" (lod scores below-2) varied from 0.5 cM up to 22 cM on either side of D20S19 depending on the trait assumed. These results are contrary to the expectation that a susceptibility gene in vicinity to D20S19 confers a common major gene effect to the expression of IGE spectra with age-related onset from childhood to adolescence.

Chromosome Mapping↗

PubMed1996

CD9 of mouse brain is implicated in neurite outgrowth and cell migration in vitro and is associated with the alpha 6/beta 1 integrin and the neural adhesion molecule L1.

We describe here a novel monoclonal antibody (mab H6) which recognizes CD9, an integral cell surface constituent previously described in cells of the hematopoietic lineage and involved in the aggregation of platelets. Mab H6 was raised against membranes of immature mouse astrocytes and reacted with a protein of 25-27 kD in detergent extracts of adult mouse brain membranes. Sequence analysis of the N-terminal amino acids revealed an identity of 96% with CD9 from mouse kidney. CD9 was localized in the central and peripheral mouse nervous systems: in the spinal cord of 11-day-old mouse embryos, CD9 was strongly expressed in the floor and roof plates. In the adult mouse sciatic nerve, myelin sheaths were highly CD9-immunoreactive. Mab H6 reacted with the cell surfaces of both glial cells and neurons in culture and inhibited migration of neuronal cell bodies, neurite fasciculation and outgrowth of astrocytic processes from cerebellar microexplants. Neurite outgrowth from isolated small cerebellar neurons was increased in the presence of mab H6 on substrate-coated laminin, but not on substrate-coated poly-L-lysine. Addition of mab H6 elicited an increase in intracellular Ca2+ concentration in these cells on substrate-coated laminin. Immunoprecipitates of CD9 from cultured mouse neuroblastoma N2A cells contained the alpha 6/beta 1 integrin. Moreover, preparations of CD9 immunoaffinity-purified from adult mouse brain using a mab H6 column contained the neural adhesion molecule L1, but not other neural adhesion molecules. CD9 bound to L1, but not to NCAM or MAG. Both the alpha 6/beta 1 integrin and L1 could be induced to coredistribute with CD9 on the surface of cultured neuroblastoma N2A cells. The combined observations suggest that CD9 can associate with L1 and alpha 6/beta 1 integrin to influence neural cell interactions in vitro.

Amino Acid Sequence↗

PubMed1996

Comparison of passive and active perfusion catheters: an in vitro study in a pulsatile coronary flow model.

Perfusion balloon catheters are designed to provide continuous transcatheter blood flow and thereby reduce myocardial ischemia during coronary angioplasty. To compare the transcatheter flow rates of active and passive (auto-) perfusion catheters, a well-controlled experimental study was performed in a circulation model that duplicates the phasic, predominantly diastolic flow pattern of the left coronary artery. Mean diastolic coronary driving pressure varied between 20 and 100 mm Hg. For the autoperfusion catheters, a strong relationship between transcatheter flow and diastolic coronary driving pressure was found. For example, a coronary driving pressure of 80 mm Hg provided a coronary flow of 30 ml/min (RX-Perfusion [RP], ACS), 28 ml/min (Speedflow [SF], Schneider), 20 ml/min (Lifestream [LS], ACS), and 19 ml/min (Flowtrack [FT], ACS). Reduction of driving pressure to 40 mm Hg decreased the absolute transcatheter flow, which was now 16 ml/min (RP), 13 ml/min (SF), and 10 ml/min (LS and FT). The relative catheter flow (the ratio of absolute flow to baseline coronary flow rate without a catheter in place), was independent of actual coronary driving pressure and ranged between 21% +/- 1% (RP) and 14% +/- 1% (FT and LS). For the active perfusion system (Coreflo, Leocor, a maximal transcatheter flow of 82 ml/min was found. Using this active perfusion system, the relative catheter flow increased with decreasing coronary driving pressure:80 --> 40 mm Hg: 56% --> 107%. For all catheters, the distal perfusion decreased between 30% (3.0 mm RP) and 50% (3.0 mm LS) by a 0.014-inch guidewire placed through the inner channel of the catheter. Because of the strong relationship between coronary driving pressure and transcatheter flow, the residual flow through all autoperfusion catheters becomes critical (<20 ml/min), when the coronary driving pressure drops below 50 mm Hg. By contrast, active perfusion systems are independent of the actual coronary driving pressure and are therefore advantageous for prolonged dilation in patients with low aortic pressure.

Angioplasty, Balloon, Coronary↗

PubMed1996

Ultrafast perfusion-weighted MRI of functional brain activation in rats during forepaw stimulation: comparison with T2 -weighted MRI.

A fast version of the arterial spin tagging technique for the detection of cerebral perfusion is presented. Based on adiabatic spin inversion in combination with snapshot FLASH imaging, our technique allows the recording of perfusion changes with a temporal resolution of about 3 s. Differences of cerebral perfusion dependent on the choice of anesthesia were observed in rat brain. Furthermore, with this arterial spin tagging method we demonstrated perfusion increases in the somatosensory cortex of anaesthetized rats during forepaw stimulation. Comparison of the activated areas in the T2 -weighted BOLD images and the perfusion-weighted images showed good spatial correspondence, but the sensitivity to the functional activation was more than ten times higher in the perfusion technique.

Anesthesia↗

PubMed1996

Variation of functional MRI signal in response to frequency of somatosensory stimulation in alpha-chloralose anesthetized rats.

The dependence of functional MRI contrast on the repetition rate (1.5-9 Hz) of a sensory stimulus was investigated with a T2*-weighted gradient echo method during forepaw stimulation of alpha-chloralose anesthetized rats (n = 5). An activation area was observed in the left or right somatosensory cortex dependent on the stimulation of the right or left forepaw, respectively. The activation intensity decreased for stimulation frequencies above 3 Hz, and was negligible at 9 Hz. The interpretation is that at low stimulation rates the neurons can respond to each stimulus, but at higher rates there is insufficient recovery time so that the response is progressively occluded.

Anesthesia, Intravenous↗

PubMed1996

Stability of transgene methylation patterns in mice: position effects, strain specificity and cellular mosaicism.

The methylation status of a transgene, which carried the adenovirus type 2 E2A late promoter linked to the chloramphenicol acetyltransferase gene, was studied in three transgenic mouse lines (5-8, 7-1 and 8-1). These lines were analysed over a large number of offspring generations beyond the founder animal. In mating experiments, the influence of the parent-of-origin and strain-specific backgrounds on the transgene methylation patterns were assessed and found to have no effect on the pre-established methylation patterns in mouse lines 5-8 and 8-1. The founder animal 7-1 carried two groups of a total of ten transgenes, which were located on two different chromosomes. These arrays of transgenes could be segregated into separate mouse lines 7-1A and 7-1B. The transgenes of 7-1A animals exhibited cellular mosaic methylation patterns that were demethylated in approximately 10% of the offspring in a mixed genetic background. Upon further transmission of these transgenes in a mixed genetic background, the grandparental methylation patterns were reestablished in most progeny. Mating to inbred DBA/2 mice resulted in maintenance of the demethylated pattern or in further demethylation of the transgenes in approximately 50% of the offspring. In contrast, an equal number of transgenic siblings from matings to C57BL/6 mice showed a return to the original methylation pattern. The mosaic methylation status of this locus was apparently controlled by mouse-strain-specific factors. The methylation patterns of the 7-1B transgenes were not cellular mosaic and remained stable in all offspring, as with lines 5-8 and 8-1. Hence, the strain-dependent and cellular mosaic transgene methylation patterns of 7-1A animals were probably a consequence of the chromosomal integration site of the transgenes (position effect).

Adenoviridae↗

PubMed1996

[Value of CT-angiography in diagnosis of cerebral sinus and venous thromboses].

Dural sinus thrombosis is not uncommon. Due to the nonspecific symptomatology, as well as the manifold etiology, clinical diagnosis may be difficult. In these cases imaging procedures are frequently crucial in deciding how to proceed and how to treat. The aim of our study was to evaluate the diagnostic utility of helical CT in the detection of dural sinus thrombosis. In 20 patients with clinically suspected thrombosis CT angiography was performed. In 6 patients dural sinus thrombosis was diagnosed. In order to acquire also arterial vessels, a short delay of about 22 s after the onset of the application of contrast medium was selected. By this method we found an occlusion of the MCA in two patients with clinically suspected sinus thrombosis. In all patients the transverse slices and the multiplanar reconstructions showed filling defects or an "empty delta" sign. With irregular outlines the thrombus could be depicted over the complete course of the sinus. The MIP reconstructions were particularly helpful in the evaluation of the vessel anatomy and the pathological collateral venous drainage. In three patients MR angiograms were available for comparison. The smaller veins, such as the v. vermis inferior, were less clearly depicted than in CT angiography. CT angiography is a fast and reliable method to exclude or verify a sinus thrombosis. It can be performed immediately after non-enhanced CT. According to our present experience CT angiography is sufficient for the diagnosis of a sinus thrombosis.

Adolescent↗

PubMed1996

Exclusion of linkage between idiopathic generalized epilepsies and the GABAA receptor alpha 1 and gamma 2 subunit gene cluster on chromosome 5.

Hereditary factors play a major role in the etiology of idiopathic generalized epilepsies (IGEs). The pivotal function of ionotropic gamma-aminobutyric acid type A receptors (GABRs) in inhibitory neurotransmission in the mammalian central nervous system suggests that they may be involved in epileptogenesis and genetic predisposition to IGEs. Dinucleotide repeat polymorphisms associated with the human GABAA receptor alpha 1 (GABRA1) and gamma 2 subunit (GABRG2) gene cluster on chromosome 5q32-q35 offer the opportunity to test whether these candidate genes confer susceptibility to IGEs. Our linkage analyses in 63 families ascertained through IGE patients with either juvenile myoclonic epilepsy, juvenile absence epilepsy or childhood absence epilepsy do not support the hypothesis that variants within the GABRA1 and GABRG2 gene cluster contribute a frequent major gene effect to the expression of the common familial IGEs.

Base Sequence↗

PubMed1996

Vigabatrin and behaviour disorders: a retrospective survey.

Vigabatrin is an anticonvulsant drug with a relatively favourable side-effect profile. However, in clinical trials behaviour disorders have been reported, including agitation, depression and psychoses. In this study, 136 cases of behavioural problems that had been reported to the manufacturers, or the authors, were followed up. Satisfactory clinical information could be obtained on 81 patients. Of these, 50 cases met the criteria for either a psychosis (n = 28) or depression (n = 22). These were compared with a group of Queen Square patients, with epilepsy and psychosis, who had never taken vigabatrin (n = 21) and another group, who received vigabatrin without experiencing any behavioural problems (n = 28). The main results from this study suggest that: (1) Psychosis as a treatment emergent effect of vigabatrin is seen in patients with more severe epilepsy, compared with those patients who never develop psychopathology, and those developing an affective disorder. The psychosis is related to a right-sided EEG focus, and suppression of seizures (64% became seizure free). (2) Depression as a treatment emergent effect of vigabatrin is associated with a past history of depressive illness. There was little or no change in seizure frequency is this group. Some suggestions for managing patients who may develop these behaviour disorders are given.

Anticonvulsants↗

PubMed1996

The Le(x) carbohydrate sequence is recognized by antibody to L5, a functional antigen in early neural development.

The L5 antigenic determinant was previously suggested to be a carbohydrate epitope present on murine cell recognition molecules in the developing brain and to be an early neural marker in the chick embryo. Here, we show that L5 immunoreactivity is associated with complex-type N-glycosidic oligosaccharides. To identify the carbohydrate structure recognized by the L5 antibody, we investigate its binding to N-linked oligosaccharides derived from L5 glycoproteins and to known glycans. Results of mass spectrometric analyses of L5-positive neoglycolipids prepared from L5 glycoproteins are consistent with those for N-glycans containing a 3-fucosyl N-acetyllactosamine sequence. We also investigate L5 binding to structurally defined, lipid-linked oligosaccharides based on the blood group type I and II backbones. Chromatogram binding assays, ELISA, and inhibition studies show that the antibody reacts strongly with carbohydrate chains presenting the 3-fucosyl N-acetyllactosamine sequence [Lewisx (Le(x)) or X-hapten] also recognized by anti-SSEA-1 and anti-CD15. Histochemical studies with different antibodies recognizing the Lex sequence show partially overlapping patterns of immunoreactivity during early neural development in the chick embryo. Therefore, we suggest that the epitope recognized by L5 antibody is closely related to those for anti-SSEA-1 and anti-CD15.

Animals↗

PubMed1996

Brief hypercapnia enhances somatosensory activation of blood flow in rat.

Activation of CBF by hypercapnia or functional stimulation has been attributed to multiple mediators, most of which are thought to interfere with cerebrovascular reactivity in a closely time-related manner. Here we describe that brief hypercapnia produces marked up-regulation of somatosensory activation of blood flow that outlasts carbon dioxide exposure for at least 60 min. In chloralose-anesthetized, mechanically ventilated rats, somatosensory activation was carried out by electrical stimulation of the forepaw. Blood flow was measured in the contralateral primary somatosensory cortex by laser-Doppler flowmetry (LDF). Under control conditions, somatosensory stimulation increased LDF by 38.8 +/- 11.0%. Ventilation with 6% CO2 for 3 min caused a rise of LDF by 28.0 +/- 8.7%. Baseline CBF and PaCo2 returned to control values within 20 min. Repetition of somatosensory stimulation after hypercapnia revealed a long-lasting up-regulation of the flow response: 25 min after hypercapnia, functional stimulation increased LDF by 86.0 +/- 18.1%, and 60 min after hypercapnia even by 96.0 +/- 26.0%. This is the first demonstration of CO2-induced up-regulation of functional activation of blood flow and an example of the importance of general physiological variables for the modulation of the coupling process.

Animals↗

PubMed1996

The structure of adenovirus type 12 DNA integration sites in the hamster cell genome.

Foreign DNA can integrate into the genomes of mammalian cells, and this process plays major roles in viral oncogenesis and in the generation of transgenic organisms and will be important in evolving regimens for human somatic gene therapy. In the present study, the insertion sites of adenovirus type 12 (Ad12) DNA genomes have been analyzed in detail in the Ad12-transformed hamster cell line T637, its revertants, which have lost most of the >20 Ad12 genome equivalents integrated chromosomally in cell line T637, and in the Ad12-induced tumor T191. Some of these junction sites have been molecularly cloned, and the nucleotide sequences at the sites of transition between viral and cellular DNAs have been determined. The sites of linkage between the hamster cellular and the foreign (viral) DNA are characterized by the frequent occurrence of patch homologies between the recombination partners. The cellular junction sites investigated here are not transcriptionally active. One of the cellular DNA sequences abutting the right Ad12 DNA terminus in cell line T637 (os2) is represented only once in the hamster genome and has a strikingly low abundance of 5'-CG-3' dinucleotide sequences. One 5'-GCGC-3' sequence close to the Ad12 DNA integration site is heavily methylated in normal cells, Ad12-transformed cells, and Ad12-induced tumor cells. The second such sequence is more remote from the junction site, is partly methylated in BHK21 hamster cells, and shows differences in methylation in different Ad12-transformed cell lines. This site is unmethylated in liver DNA. The cellular DNA sequence at the site of Ad12 linkage in the tumor T191 exhibits homologies to highly repetitive sequences of the Alu family and to an origin of hamster DNA replication containing an Alu element. A number of junction sites between Ad12 DNA and hamster or mouse DNA in Ad12-transformed cell lines or Ad12-induced tumor cell lines, investigated here and previously, are characterized by stem-loop structures encompassing the junction sites.

Adenoviridae↗