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Biomedical subjects

H Pedersen

Publications and source records attributed to H Pedersen.

At least 55 records · Page 3Linked to original sources
PubMed1992

Diagnostic problems with meningococcal disease in general practice.

Based on general practitioners' referral letters and hospital records, we made a retrospective analysis of a cohort of 177 consecutive cases of meningococcal disease that occurred during a period of 10 years in the County of North Jutland, Denmark. The analysis concerned diagnostic problems in general practice, prognosis, pre-hospital antibiotic treatment and its effect on subsequent cultures, and degree of obligatory notification. The referring doctor suspected meningococcal disease/central nervous infection in 123 patients (69.5%). Neck stiffness and petechiae were related to a correct referral diagnosis, in contrast to the occurrence of a non-petechial rash. The presence of disseminated intravascular coagulation was associated with the mortality rate, which was 0.062. The therapeutic recommendations of the Danish Health Authorities were followed in only 25 of the 98 patients who fulfilled the criteria for pre-hospital parenteral antibiotic treatment. Pre-hospital antibiotic treatment was related to negative culture of spinal fluid or blood. Seven of the 177 patients were not notified according to the rules. Difficulties in pre-hospital diagnosis seem not to influence the lethal course of the disease.

Adolescent↗
PubMed1992

A rat model of reproducible cerebral infarction using thrombotic blood clot emboli.

The purpose of this study was the development of a model of embolic stroke with high reproducibility concerning infarct volume. In 37 male Sprague-Dawley rats, the internal carotid artery was embolized with in vitro preformed suspensions of autologous microemboli resembling arterial thrombi. With a method of continuous flow through the carotid arterial catheter, reflux of blood with uncontrolled clotting and embolization was avoided, thereby providing control animals free of ischemic damage. The embolized animals had arterial occlusions on angiograms immediately after embolization and no spontaneous recanalization on angiograms 2 h later. The cerebral blood flow measured by the intra-arterial 133Xe injection method decreased to 21-37% of baseline values. All embolized animals developed hemiparesis with spontaneous circling behavior, embolization with more than 150 microliters clot suspension resulted in hemispherical infarcts. There was a strong statistically significant correlation between amount of emboli, rate of vascular occlusion, and volume of infarcted tissue. This is the first model presented utilizing autologous in vitro microemboli imitating "white" arterial thrombi. The animals developed infarction, resembling human stroke.

Angiography↗
PubMed1992

Dose-response of rt-PA and its combination with aspirin in a rat embolic stroke model.

The efficacy and safety of thrombolysis with different dose regimens of recombinant tissue plasminogen activator (rt-PA) and its combination with aspirin was tested in an embolic stroke model. In rats the carotid territory was embolized with a single clot formed in a polyethylene tube and washed with saline. Fifteen minutes after embolization 10 animals were treated with rt-PA 10 mg kg-1; 11 with 15 mg kg-1; 12 with 20 mg kg-1 and 9 with 10 mg kg-1 + 20 mg kg-1 aspirin and 34 animals with saline. Rt-PA 10 mg kg-1 reduced median infarct volume (in percent of the ipsilateral hemisphere volume) from 19.5 to 4.8; rt-PA 15 mg kg-1 to 2.0; rt-PA 20 mg kg-1 to 0.0, while rt-PA 10 mg kg-1 + aspirin resulted in a median infarct volume of 9.5%. Thrombolytic therapy significantly and dose dependently (p = 0.001) reduced the infarct volume, improved the presacrifice clinical score and increased (p = 0.02) angiographically verified reperfusion. There was no additional benefit of coadministration of aspirin.

Animals↗
PubMed1992

Reduction of infarct volume and mortality by thrombolysis in a rat embolic stroke model.

BACKGROUND AND PURPOSE: Thrombolytic therapy with recombinant tissue plasminogen activator was tested in a rat embolic stroke model. METHODS: The rat carotid territory was embolized with arterial-like microthrombi formed under pressure. Hemispheric cerebral blood flow before and after embolization was measured by the intraarterial Xenon-133 injection method. Fifteen minutes after embolization, 24 rats were treated with 3 mg/kg or 10 mg/kg tissue plasminogen activator, and 27 were treated with saline. Carotid angiography displayed the rate of occlusion of the cerebral arterial supply before and after treatment. Brains were fixed and evaluated neuropathologically and infarct volume was measured. RESULTS: Cerebral blood flow was reduced 70-86% after embolization. The comparison of pretreatment and posttreatment angiography showed significant (p = 0.0005) reperfusion in the treated rats. Thrombolytic therapy significantly reduced the infarct volume from 55.1% to 24.4% of embolized hemisphere volume (p = 0.007) and increased the survival rate from 0.48 to 0.96 (p = 0.0004). Fifty-three percent of the embolized rats recanalized completely after thrombolytic treatment and developed almost no infarction (median volume 2.8%), and all survived. No hemorrhagic complications were observed. CONCLUSIONS: Early thrombolytic therapy induced recanalization and reduced mortality and infarct volume after embolic stroke in this model.

Animals↗
PubMed1992

Effect of ropivacaine and bupivacaine on uterine blood flow in pregnant ewes.

The effects of ropivacaine, a new amide local anesthetic, on uterine blood flow and fetal well-being were compared with those of bupivacaine in 10 chronically instrumented pregnant ewes. In random sequence, animals received two intravenous infusions of each drug. The low infusion rate regimens were chosen to result in clinically relevant maternal plasma concentrations of local anesthetics, whereas the more rapid rates of infusions were given to assess the safety of higher maternal drug concentrations. An epinephrine infusion was given to demonstrate the appropriateness of the animal model for the measurement of uterine blood flow. Maternal and fetal heart rates, arterial blood pressure, and the ewe's central venous pressure, intraamniotic pressure, and uterine blood flow were recorded continuously. Arterial blood samples were taken from mother and fetus at frequent intervals to determine acid-base status and local anesthetic concentrations. A total of 39 studies were performed. None of the infusions of either local anesthetic resulted in a significant decrease in uterine blood flow or deterioration in fetal condition. The mean maternal plasma concentrations at the end of infusions were as follows: ropivacaine low dose, 1.60 +/- 0.35 micrograms/mL; bupivacaine low dose, 1.55 +/- 0.15 micrograms/mL; ropivacaine high dose, 2.50 +/- 0.37 micrograms/mL; and bupivacaine high dose, 1.83 +/- 0.19 micrograms/mL. Epinephrine infusion resulted in a 25% decrease in uterine blood flow without adverse fetal effects. We conclude that neither ropivacaine nor bupivacaine, as administered in this study, led to any ill effects on uterine artery blood flow or fetal well-being.

Amides↗
PubMed1991

Heterologous cooperativity in Escherichia coli. The CytR repressor both contacts DNA and the cAMP receptor protein when binding to the deoP2 promoter.

Promoters in Escherichia coli that are negatively regulated by the CytR repressor are also activated by the cAMP receptor protein (CRP) complexed to cAMP; as a characteristic, these promoters encode two binding sites for the cAMP.CRP complex. Biochemical and genetic studies have shown that CytR relies on interactions with the cAMP.CRP complex in order to bind promoter DNA and repress transcription. Here we have purified CytR to near homogeneity and addressed the question of how it interacts with the deoP2 promoter. Gel retardation and DNase I footprinting analyses show that CytR is a true sequence-specific DNA-binding protein that binds to the sequence between the two CRP sites in deoP2 with a relatively low affinity. In the presence of the cAMP.CRP complex the two protein species bind cooperatively to deoP2, forming a complex in which CytR occupies the sequence between the two DNA bound cAMP.CRP complexes. Furthermore, the inducer (cytidine) does not affect independent DNA binding of CytR, rather the CytR/cAMP.CRP cooperativity is perturbed. These results indicate that CytR binding to deoP2 relies on both repressor-DNA interactions and protein-protein interactions to cAMP.CRP. This combinatorial repression mechanism, in which an activator functions as an adaptor for a repressor that is not capable of blocking transcription on its own, is unprecedented in prokaryotes; it is, however, reminiscent of repression mechanisms found in eukaryotes.

Bacterial Proteins↗
PubMed1991

Single amino acid substitutions in the cAMP receptor protein specifically abolish regulation by the CytR repressor in Escherichia coli.

Promoters in Escherichia coli that are negatively regulated by the CytR repressor are also activated by the cAMP receptor protein (CRP) complexed to cAMP; as a characteristic, these promoters encode tandem binding sites for cAMP-CRP. In one such promoter, deoP2, CytR binds to the region between the tandem CRP binding sites with a relatively low affinity; in the presence of cAMP-CRP, however, the repressor and activator bind cooperatively to the DNA. Here we have investigated this cooperativity by isolating mutants of the CRP protein that abolish CytR regulation without exhibiting a concomitant loss in their ability to activate transcription. Four different, single amino acid substitutions in CRP give rise to this phenotype. These amino acids lie in close proximity on the surface of the CRP tertiary structure in a portion of the protein that is not in contact with the DNA. In vitro analyses of one of the CRP mutants show that it interacts with the DNA in a manner indistinguishable from wild-type CRP, whereas its interaction with CytR is perturbed. These results strongly indicate that cooperative DNA binding of CytR and cAMP-CRP is achieved through protein-protein interactions.

Bacterial Proteins↗
PubMed1991

A hybrid bioreactor for high density cultivation of plant cell suspensions.

A hybrid bioreactor was developed for the production of secondary metabolites from high density cultivation of plant cell suspensions. Some of the advantages of both air-lift and cell-lift by agitation were combined. The addition of a decanting column also made it possible to run a perfusion system for high density culture or to run a two-stage culture efficiently. Cell growth and the production of berberine from Thalictrum rugosum in the hybrid bioreactor are reported in this paper. A cell density up to 31 g/l was obtained by perfusion without any problems in mixing or loss of cell viability and the specific berberine productivity was comparable to that in shake flasks. The maximum berberine concentration was 88 mg/l at 3 weeks of operation and declined thereafter.

Berberine↗
PubMed1991

Upper extremity function in spina bifida.

Poor upper extremity function is often recorded in meningomyelocele patients. Only 2 of the 25 patients we assessed, 5 to 19 years old, showed normal upper extremity function in the clinical neurological examination and a timed hand function test simulating daily activities. Slow performance with unsystematic variability was typical. Poor hand function correlated strongly with hydrocephalus. A trend towards better performance with increasing age may indicate that the difficulties are overcome in some patients. While patients without hydrocephalus showed a near-normal distribution in the seven subtests, patients with hydrocephalus needed more time than normal children. Patients with shunt-treated hydrocephalus did not cope as well as patients without a shunt. Mean age in the three groups differed and may partly explain the differences.

Adolescent↗
PubMed1991

Encapsulated epidural catheter. CT findings.

A case where an encapsulated permanent epidural catheter for continuous analgesia caused pressure on the dural sac is presented. The clinical findings and postmyelographic computerised tomography (CT) imitated an epidural metastasis, until an epidurography via the epidural catheter revealed its true nature.

Aged↗
PubMed1991

Octoclothepin enantiomers. A reinvestigation of their biochemical and pharmacological activity in relation to a new receptor-interaction model for dopamine D-2 receptor antagonists.

Octoclothepin (1) was resolved into its R and S enantiomers via the diastereomeric tartaric acid salts. The enantiomers were shown to be of high optical purity by 1H NMR with use of the chiral shift reagent (R)-(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol. Pharmacological and biochemical testing confirmed that (S)-1 is the more potent dopamine (DA) D-2 antagonist both in vitro and in vivo, although the R enantiomer still has significant D-2 antagonistic activity. In contrast, both enantiomers were equally active in test models detecting activity at D-1 receptors, serotonin-2 (5-HT2) receptors and alpha 1 adrenoceptors. Contrary to a previous prediction, it was found that norepinephrine (NE) uptake inhibition was confined solely to the S enantiomer. Overall, (S)-1 has a "classical" neuroleptic profile, while the R enantiomer has a more "atypical" profile. These pharmacological profiles seem to be in agreement with the reported clinical profiles of the two enantiomers. A previous conformational study was revised in light of the biochemical test results with enantiomers of known optical purity. Their relative D-2 receptor affinity corresponded well with the calculated conformational energy difference between their "active conformations" deduced from a previously reported new D-2 receptor model. Also the high enantioselectivity of (S)-1 at the NE uptake site could be explained after a detailed conformational analysis showing strict requirements for the orientation of the piperazine lone-pair direction at the NE uptake site.

Animals↗
PubMed1991

Systemic toxicity of ropivacaine during ovine pregnancy.

Ropivacaine is a new amide local anesthetic structurally related to bupivacaine and mepivacaine. Its potency and duration of action are similar to those of bupivacaine but its therapeutic index may be greater. Since pregnancy enhances the cardiotoxicity of bupivacaine, the current study was devised to compare the toxicity of ropivacaine in chronically instrumented nonpregnant and pregnant ewes during continuous intravenous infusion of the drug at the rate of 0.5 mg.kg-1.min-1. In all animals, symptoms of local anesthetic toxicity occurred in the usual order--convulsions, hypotension, apnea, and circulatory collapse. There were no significant differences between the two groups of animals in the doses and plasma concentrations of ropivacaine associated with each toxic manifestations. For example, circulatory collapse occurred at a mean dose of 11.3 +/- 1.1 mg.kg-1 in nonpregnant and 12.4 +/- 0.9 mg.kg-1 in pregnant animals, with corresponding plasma concentrations of 7.3 +/- 0.3 and 9.6 +/- 2.1 micrograms.ml-1 (P = not significant). Protein binding of ropivacaine in the concentration range associated with toxic manifestations was similar in sera obtained from nonpregnant and pregnant ewes. In conclusion, ovine pregnancy does not enhance the systemic toxicity of ropivacaine, possibly because of an absence of gestation-related increase in the availability of free drug.

Amides↗
PubMed1991

A novel function of the cAMP-CRP complex in Escherichia coli: cAMP-CRP functions as an adaptor for the CytR repressor in the deo operon.

Unlike classical bacterial repressors, the CytR repressor of Escherichia coli cannot independently regulate gene expression. Here we show that CytR binding to the deoP2 promoter relies on interaction with the master gene regulatory protein, CRP, and, furthermore, that cAMP-CRP and CytR bind co-operatively to deoP2. Using mutant promoters we show that tandem, properly spaced DNA-bound cAMP-CRP complexes are required for this co-operative binding. These data suggest that CytR forms a bridge between tandem cAMP-CRP complexes, and that cAMP-CRP functions as an adaptor for CytR. The implications of this new version of negative control in E. coli on bacterial gene expression and on combinatorial gene regulation in higher organisms are discussed.

Bacterial Proteins↗
PubMed1991

The cyclic AMP (cAMP)-cAMP receptor protein complex functions both as an activator and as a corepressor at the tsx-p2 promoter of Escherichia coli K-12.

The tsx-p2 promoter is one of at least seven Escherichia coli promoters that are activated by the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex and negatively regulated by the CytR repressor. DNase I footprinting assays were used to study the interactions of these regulatory proteins with the tsx-p2 promoter region and to characterize tsx-p2 regulatory mutants exhibiting an altered response to CytR. We show that the cAMP-CRP activator complex recognizes two sites in tsx-p2 that are separated by 33 bp: a high-affinity site (CRP-1) overlaps the -35 region, and a low-affinity site (CRP-2) is centered around position -74 bp. The CytR repressor protects a DNA segment that is located between the two CRP sites and partially overlaps the CRP-1 target. In combination, the cAMP-CRP and CytR proteins bind cooperatively to tsx-p2, and the nucleoprotein complex formed covers a region of 78 bp extending from the CRP-2 site close to the -10 region. The inducer for the CytR repressor, cytidine, does not prevent in vitro DNA binding of CytR, but releases the repressor from the nucleoprotein complex and leaves the cAMP-CRP activator bound to its two DNA targets. Thus, cytidine interferes with the cooperative DNA binding of cAMP-CRP and CytR to tsx-p2. We characterized four tsx-p2 mutants exhibiting a reduced response to CytR; three carried mutations in the CRP-2 site, and one carried a mutation in the region between CRP-1 and the -10 sequence. Formation of the cAMP-CRP-CytR DNA nucleoprotein complex in vitro was perturbed in each mutant. These data indicate that the CytR repressor relies on the presence of the cAMP-CRP activator complex to regulate tsx-p2 promoter activity and that the formation of an active repression complex requires the combined interactions of cAMP-CRP and CytR at tsx-p2.

Amino Acid Sequence↗
PubMed1990

[Cerebral computed tomography in infantile spasms].

A prospective investigation of 52 children with infantile spasms was carried out employing computed tomography. Normal conditions were demonstrated in 21 (40%). Among the 31 children with pathological computed tomografic findings, dilatation of the ventricular system and/or subarachnoid space was found in nine cases (17%), congenital malformations in ten (19%) and cerebrovascular changes in a similar number (19%). One patient had a tumour and one had congenital toxoplasmosis. No significant differences were found in the frequencies of normal psychomotor development between children with normal and abnormal computed tomographic findings. The reason for this is probably that a good prognosis may be anticipated in the idiopathic forms provided that ACTH treatment is initiated early in the course of the disease. Computed tomography is useful to differentiate between symptomatic and idiopathic cases of infantile spasms. It may, however, be assumed that neuronal heterotopy without other malformations in the central nervous system may be difficult to diagnose with computed tomography. Magnetic resonance scanning will probably be able to demonstrate these cases.

Adrenocorticotropic Hormone↗
PubMed1990

Two stage cultures for the production of berberine in cell suspension cultures of Thalictrum rugosum.

Two stage culture systems were examined in cell suspensions of Thalictrum rugosum which produce berberine in a growth associated manner. The utilization of indole 3-acetic acid (IAA) as a growth regulator, in place of 2,4-dichlorophenoxyacetic acid (2,4-D), at various growth phases was investigated. Although the enhancing effect was clear when it was used separately, in combination with 2,4-D effect of IAA was suppressed and medium change from 2,4-D to IAA was detrimental to product formation. The decrease of berberine production in this two stage culture may be due to the loss of conditioning factors associated with medium replacement.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1990

Thrombolytic therapy of cerebral arterial occlusion with recombinant tissue plasminogen activator.

This report describes three patients, with acute cerebral arterial occlusion, treated with recombinant tissue plasminogen activator (rt-PA). In one patient with basilar artery occlusion thrombolytic treatment was initiated 12 h after onset of the symptoms. In two patients with angiographically verified occlusion of the middle cerebral artery, the treatment was initiated approximately 4.5 h after onset of the symptoms. Recombinant tissue plasminogen activator 80-120 mg, was infused intra-arterially over 90-100 min via a catheter the tip of which was close to the occlusion. This regimen resulted in recanalization in all the patients; however, in two patients it was verified by repeat CT scan only. In two patients the thrombolytic treatment was successful (the patients improved clinically); the third patient died of massive cerebral infarct-related oedema. In none of the patients did significant bleeding or other obvious side-effects occur. From this preliminary report it is concluded that angiographically proven thrombolytic recanalization in acute cerebrovascular occlusion is possible with rt-PA. In some patients, however, the treatment is initiated too late. Further investigation of the possible indication for thrombolytic therapy in stroke is needed.

Adult↗