Biomedical subjects

A Forster

Publications and source records attributed to A Forster.

At least 37 records · Page 2Linked to original sources

PubMed1995

Quantitative evaluation of tourniquet leak during i.v. regional anaesthesia of the upper and lower limbs in human volunteers.

Although it is accepted that during i.v. regional anaesthesia (IVRA) local anaesthetic can leak under the tourniquet into the systemic circulation, no published study has evaluated this leak quantitatively. In volunteers, during two random sessions, we have simulated IVRA using standard techniques with a radiolabelled compound which is chemically similar to lignocaine and has comparable tissue distribution (0.1 mg of HIDA labelled with 100 muCi of 99mTc in 40 ml of saline). The decrease in radioactivity was measured with a gamma camera for the 20 min of tourniquet inflation and for the 20 min of washout after cuff deflation. While the tourniquet was inflated, the leak for the lower limb (mean 29 (SD 8) %) was significantly greater (P < 0.004) than the leak for the upper limb (15 (5) %). Moreover, in each of 10 volunteers, the leak was always greater for the lower than the upper limb. During the first 3 min after tourniquet deflation the loss of radioactivity was 58 (8) % of the maximal amount for the upper limb and 39 (8) % for the lower limb (P < 0.001). As the leak under the tourniquet was significantly greater for the lower than the upper limb, we conclude that IVRA for the lower limb can be associated more frequently with a shorter duration of successful anaesthesia and/or failure.

Adult↗

PubMed1995

A prospective study of the feasibility of continuous spinal anesthesia in a university hospital.

A prospective study was undertaken in an elderly population undergoing orthopedic surgery to specifically study the feasibility of continuous spinal anesthesia (CSA). In a university hospital, 14 residents and 5 junior staff, using an 18-gauge needle and a 20-gauge catheter, performed 76 and 24 consecutive CSAs, respectively. There was an overall failure rate of 6%, all occurring in the residents' group. The causes affecting the success of CSA were inability to identify the subarachnoid space in 5/6 cases (all lumbar punctures were performed using the midline approach) and, in one case, inability to thread the catheter. The six failed CSAs were ultimately performed successfully by one of the senior authors. All surgeries were successfully performed with CSA, without requiring general anesthesia or intravenous narcotic supplementation. Anesthesia was initiated with isobaric bupivacaine in 94/100 cases. In 18% of patients, inadequate anesthesia prompted modifications of the local anesthetic solutions (i.e., type, baricity, total dosage) before surgery. One case of minor neurologic complication was observed, but no postspinal headache occurred. In conclusion, our findings led us to pursue CSA with large-bore equipment in an elderly population; furthermore, we believe that teaching the earlier use of alternative approaches other than the midline approach could further reduce our failure rate.

Aged↗

PubMed1995

Prevalence and associated features of the cold hemiplegic arm.

BACKGROUND AND PURPOSE: Some stroke patients complain of an unpleasant sensation of coldness in the hemiplegic arm. This study aimed to determine the prevalence of this symptom and any associated features. METHODS: A questionnaire about symptoms in the arms was sent to patients at least 12 months after stroke. Reflex sympathetic dystrophy (RSD) was diagnosed if four typical symptoms were present in the arm. RESULTS: One hundred patients were recruited and 75 complete replies received. The mean age of the patients was 74 years, and the mean time since the stroke was 19 months. Forty patients (53%) experienced unilateral coldness in the hemiplegic arm. In 14 this sensation was constant, and 10 rated the symptom as troublesome. The symptom developed at a median time of 1 month after stroke, but only 13 patients (32%) sought advice from a doctor. Sensory symptoms and arm and shoulder pain were common, but the only symptoms associated with coldness were numbness (P < .001) and color change (P < .05). Fifteen patients fulfilled the diagnostic criteria for RSD, 13 of whom had coldness only in the hemiplegic arm. CONCLUSIONS: A sensation of coldness in the hemiplegic arm is common and distressing. It is associated with numbness and color changes in the arm. Some cases are caused by RSD, but other patients have coldness that may be due to other causes such as a vasomotor abnormality.

Aged↗

PubMed1994

Specific in vivo association between the bHLH and LIM proteins implicated in human T cell leukemia.

The protein products of proto-oncogenes implicated in T cell acute lymphoblastic leukemia include two distinct families of presumptive transcription factors. RBTN1 and RBTN2 encode highly related proteins that possess cysteine-rich LIM motifs. TAL1, TAL2 and LYL1 encode a unique subgroup of basic helix-loop-helix (bHLH) proteins that share exceptional homology in their bHLH sequences. We have found that RBTN1 and RBTN2 have the ability to interact with each of the leukemogenic bHLH proteins (TAL1, TAL2 and LYL1). These interactions occur in vivo and appear to be mediated by sequences within the LIM and bHLH domains. The LIM-bHLH interactions are highly specific in that RBTN1 and RBTN2 will associate with TAL1, TAL2 and LYL1, but not with other bHLH proteins, including E12, E47, Id1, NHLH1, AP4, MAX, MYC and MyoD1. Moreover, RBTN1 and RBTN2 can interact with TAL1 polypeptides that exist in assembled bHLH heterodimers (e.g. TAL1-E47), suggesting that the RBTN proteins can influence the functional properties of TAL1. Finally, we have identified a subset of leukemia patients that harbor tumor-specific rearrangements of both their RBTN2 and TAL1 genes. Thus, the activated alleles of these genes may promote leukemia cooperatively, perhaps as a result of bHLH-LIM interactions between their protein products.

Amino Acid Sequence↗

PubMed1994

The LIM protein RBTN2 and the basic helix-loop-helix protein TAL1 are present in a complex in erythroid cells.

Chromosomal translocations in T-cell acute leukemias can activate genes encoding putative transcription factors such as the LIM proteins RBTN1 and RBTN2 and the DNA-binding basic helix-loop-helix transcription factor TAL1 associated with T-cell acute lymphocytic leukemia. While not expressed in normal T cells, RBTN2 and TAL1 are coexpressed in erythroid cells and are both important for erythroid differentiation. We demonstrate, using anti-RBTN2 and anti-TAL1 antisera, that the LIM protein RBTN2 is not phosphorylated and is complexed with the TAL1 phosphoprotein in the nucleus of erythroid cells. A complex containing both RBTN1 and TAL1 also occurs in a T-cell acute leukemia cell line. Since both RBTN2 and TAL1 are crucial for normal erythropoiesis, these data have important implications for transcription networks therein. Further, since both proteins can be involved in leukemogenesis, these data provide a direct link between proteins activated by chromosomal translocations in T-cell acute leukemia.

Adaptor Proteins, Signal Transducing↗

PubMed1994

Glucuronidation and isomerization of all-trans- and 13-cis-retinoic acid by liver microsomes of phenobarbital- or 3-methylcholanthrene-treated rats.

Glucuronidation and isomerization of all-trans-retinoic acid (tr-RA) and 13-cis-retinoic acid (13-cis-RA) were investigated in an in vitro system using liver microsomes of differently pretreated rats. In agreement with their thermodynamic stability, more retinoic acid was isomerized from the 13-cis form to the all-trans form than vice versa. Also some 9-cis-retinoic acid (9-cis-RA) could be found. Isomerization was reduced, but in contrast to glucuronidation was still important if boiled microsomes were used. This supports the view that isomerization can proceed as a non-enzymatic process. 3-Methylcholanthrene (MC) pretreatment of the rats increased the microsomal glucuronidation of 13-cis-RA and tr-RA and the formation of 13-cis-retinoyl-beta-glucuronide was enhanced up to 7-fold by MC-induced rat microsomes. The rates of glucuronidation by uninduced and phenobarbital-induced rat microsomes differed only slightly. In addition to glucuronides of the applied retinoic acid isomers (13-cis-RA and tr-RA), 9-cis-RA and its glucuronide were found. Induction of retinoid glucuronidation by pretreatment with MC indicates that this metabolic reaction is catalysed by a MC-inducible UGT isozyme. After two recently described pathways (conversions of retinol to retinal and of retinyl methyl ether to retinol) this is a third step of retinoid metabolism, induced by pretreatment with MC. With human microsomes no more than traces of glucuronides were detected; also, incubations with human microsomes resulted in a lower degree of isomerization than with rat microsomal fractions.

Animals↗

PubMed1994

Cysteine-rich LIM domains of LIM-homeodomain and LIM-only proteins contain zinc but not iron.

The structure of LIM domains has major implications for transcription because proteins such as Is1-1 contain two LIM domains associated with a homeodomain, and RBTN1/Ttg-1 and RBTN2/Ttg-2 contain two LIM domains but no homeodomain. Conserved cysteine and histidine residues in the LIM domains suggest a metal-binding role. RBTN and Is1-1 LIM proteins have been made in Escherichia coli and insect cell expression systems and their metal content has been determined using atomic absorption spectroscopy and electron paramagnetic resonance spectroscopy. LIM proteins expressed in soluble form contain zinc atoms, whereas bacterial inclusion bodies invariably also have Fe-S clusters. The latter are identified as linear [Fe3S4]+ clusters and appear to result from incorrect metal coordination by E. coli. These studies show that RBTN1, RBTN2, and Is1-1 are metalloproteins that contain zinc but not iron and, therefore, that the LIM domain represents a zinc-binding domain.

Cysteine↗

PubMed1994

Intrathecal midazolam reduces isoflurane MAC and increases the apnoeic threshold in rats.

The purpose of this study was to examine the anaesthetic requirement of intrathecal midazolam in a dose-response fashion in isoflurane-anaesthetized, tracheostomized rats, and to evaluate the apnoeic threshold after each intrathecal midazolam dose. Intrathecal midazolam, 5, 10, 20, and 30 micrograms, was administered to 25 anaesthetized tracheotomized rats. Isoflurane MAC was determined by the tail-clamp method. The effect of intrathecal midazolam on the apnoeic threshold was evaluated, and light and electron microscopy studies were performed on cervical, thoracic and lumbar sections of the spinal cord to investigate possible midazolam-induced neurotoxic effects. Intrathecal midazolam 5, 10, 20 and 30 micrograms decreased isoflurane MAC by 16%, 31%, 42%, and 53% respectively (P < 0.05). The apnoeic threshold was increased by midazolam 5 micrograms (from a PaCO2 of 4.25 +/- 0.55 to 5.28 +/- 0.76 kPa, P < 0.05) when compared with baseline values, but not further by additional doses. Light and electron microscopy studies on sections taken from the spinal cord of four animals did not show any morphological changes suggestive of midazolam-induced neurotoxicity when compared with similar preparations obtained from controls. These data suggest that intrathecal midazolam possesses dose-dependent antinociceptive properties which, associated with the ceiling effect of the apnoeic threshold obtained at the lowest midazolam dose and the lack of neurotoxic effects, may potentiate inhalational anaesthesia without producing marked respiratory depression.

Anesthesia, Spinal↗

PubMed1994

Flumazenil antagonizes the central effects of zolpidem, an imidazopyridine hypnotic.

Zolpidem is a new imidazopyridine-hypnotic that selectively binds to the central omega 1-receptor subtype. A double-blind, randomized, three-way, crossover placebo-controlled study was carried out in nine healthy male volunteers to assess the possible antagonism of central nervous system--depressant effects of zolpidem by flumazenil. Subjects received zolpidem (0.21 mg/kg) or placebo, intravenously, followed 17 minutes later by flumazenil (0.04 mg/kg) or placebo. Vigilance and performance were assessed by a trained anesthetist with use of ciliary reflex, response to a verbal instruction, subjective sedation, a tracking task, and a free recall task. Zolpidem produced a clinically relevant hypnotic effect in five subjects and significantly impaired performance in all nine subjects up to 90 minutes after dosing. Flumazenil rapidly antagonized clinical sedation in the five subjects who were asleep and significantly reversed the performance decrement within 3 minutes, without any escape phenomenon. Flumazenil did not change zolpidem plasma concentrations, confirming the pharmacodynamic nature of the interaction. Flumazenil may thus be a safe and effective antidote in patients with zolpidem overdosage.

Adult↗

PubMed1994

The influence of environmental and genetic factors on CYP2D6, CYP1A2 and UDP-glucuronosyltransferases in man using sparteine, caffeine, and paracetamol as probes.

The impact of gender, use of oral contraceptive steroids (OCS), coffee consumption and of smoking on the metabolism of sparteine, caffeine, and paracetamol was studied in 194 randomly selected subjects (98 male and 95 female). Thirty-eight of the male volunteers were cigarette smokers, 40 of the female subjects were smokers and/or users of OCS. The metabolic ratio of sparteine oxidation (MRs) showed a trimodal distribution. 7.7% of the subjects had a MRs > 20 and thus were poor metabolizers (PMs). Within the extensive metabolizer (EM) subjects, a distinct subgroup accounting for 11% was observed with 20 > MRs > 1.2. Six of the 15 phenotypical PMs were heterozygous EMs by genotyping. This indicates the existence of one or several CYP2D6 mutations which cannot be identified by the currently employed genotyping methods. In each subgroup, i.e. smokers/OCS and non-smokers/non-OCS, the cumulative frequency distribution of the heterozygous (wt/B) phenotype caused a shift to higher MRs compared with the wild-type homozygotes (wt/wt). Thus, for the in vivo activity of CYP2D6, genetic determinants prevail over environmental factors. Smoking, use of oral contraceptive steroids, caffeine consumption, or gender had no influence on sparteine metabolism. The distribution of the paracetamol glucuronide/paracetamol metabolic ratio appeared to be unimodal although skewed. Glucuronidation capacity was clearly affected by gender, OCS use and smoking. It was higher in male than in female subjects. Male smokers had the highest, and female non-smokers/non-OCS users the lowest metabolic ratio. CYP1A2 activity, as determined by a caffeine metabolic ratio ((AFMU + 1X + 1U)/1, 7U), was multimodally distributed and was clearly increased in smokers. It was significantly correlated to paracetamol glucoronidation in male heavy smokers (r=0.85), suggesting an element of co-regulation of CYP1A2 and of paracetamol conjugating UDP-glucuronosyltransferase isozymes, including UGTI.6.

Acetaminophen↗

PubMed1994

Influence of duration of lateral decubitus on the spread of hyperbaric tetracaine during spinal anesthesia: a prospective time-response study.

Searching for a differential spinal block between dependent and nondependent sides, we evaluated a prospective randomized time-response study of the influence of the duration of lateral decubitus on the spread of hyperbaric local anesthetic solution during spinal anesthesia in 60 patients undergoing lower limb surgery. In a lateral position with the operated side dependent, all patients received 12 mg of lyophilized tetracaine with 0.2 mg epinephrine in 2.5 mL 10% dextrose and were randomized into four groups according to the duration of lateral decubitus after spinal injection: Group 0, patients immediately turned supine after spinal injection; Group 6, 6 min in lateral decubitus then supine; Group 12, 12 min in lateral decubitus then supine; Group 18, 18 min in lateral decubitus then supine. There was no difference in maximum sensory level between both sides in the same group nor between the four groups. In all four groups a comparable number of patients had a Grade 4 motor block on the dependent as well as on the nondependent side. A positive correlation found between duration of lateral decubitus and duration of sensory block on the dependent side suggested a preferential spread of hyperbaric local anesthetics. This differential spread was confirmed by the positive correlation between the duration of lateral decubitus and the difference in duration between dependent and nondependent sides of both sensory and motor blocks. However, because of the minimal differences between groups, we believe there is no reason to routinely maintain patients in the lateral position after performing spinal anesthesia.

Adult↗

PubMed1993

Acute leukemias of different lineages have similar MLL gene fusions encoding related chimeric proteins resulting from chromosomal translocation.

The MLL gene, on human chromosome 11q23, undergoes chromosomal translocation in acute leukemias, resulting in gene fusion with AF4 (chromosome 4) and ENL (chromosome 19). We report here translocation of MLL with nine different chromosomes and two paracentric chromosome 11 deletions in early B cell, B- or T-cell lineage, or nonlymphocytic acute leukemias. The mRNA translocation junction from 22 t(4;11) patients, including six adult leukemias, and nine t(11;19) tumors reveals a remarkable conservation of breakpoints within MLL, AF4, or ENL genes, irrespective of tumor phenotype. Typically, the breakpoints are upstream of the zinc-finger region of MLL, and deletion of this region can accompany translocation, supporting the der(11) chromosome as the important component in leukemogenesis. Partial sequence of a fusion between MLL and the AFX1 gene from chromosome X shows the latter to be rich in Ser/Pro codons, like the ENL mRNA. These data suggest that the heterogeneous 11q23 abnormalities might cause attachment of Ser/Pro-rich segments to the NH2 terminus of MLL, lacking the zinc-finger region, and that translocations occur in early hematopoietic cells, before commitment to distinct lineages.

Acute Disease↗

PubMed1993

Paracetamol glucuronidation by recombinant rat and human phenol UDP-glucuronosyltransferases.

Stably expressed human and rat phenol UDP-glucuronosyltransferases (UGTs) of the UGT1 complex (HlugP1, HlugP4 and 3-methylcholanthrene-inducible rat UGT1A1, the latter considered to be an orthologous enzyme to HlugP1) have been used to investigate the role of UGTs in paracetamol glucuronidation. Kinetic analysis of recombinant UGTs was compared to that of total UGT activities in liver microsomes. Paracetamol was found to be an overlapping substrate of several UGTs. It shows higher affinity for HlugP1 and rat UGT1A1 (apparent Km values of 2 and 3 mM, respectively) than for HlugP4 (Km = 50 mM) and other UGTs present in liver microsomes (Km values of > 12 mM). Glucuronidation of paracetamol with HlugP1 contrasts with that of 6-hydroxychrysene and of 4-methylumbelliferone, which are conjugated with higher affinity by HlugP4 than by HlugP1. Due to the wide tissue distribution of rat UGT1A1, paracetamol glucuronidation was also investigated in extrahepatic rat and human tissues. Paracetamol UGT activity was present and inducible by 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat kidney, lung and spleen. It was also detected in human kidney. A selective cDNA probe for exon 1 of HlugP1 cross-reacted with mRNA from both human liver and kidney. The results demonstrate that paracetamol is conjugated by HlugP1 and its rat orthologue UGT1A1 with higher affinity than by HlugP4 and other UGTs.

Acetaminophen↗

PubMed1993

The cysteine-rich LIM domains inhibit DNA binding by the associated homeodomain in Isl-1.

Recently, a new class of homeobox genes has been identified, called LIM-homeobox genes. These genes encode proteins which have two tandemly repeated cysteine motifs, referred to as LIM domains, in addition to a homeodomain. In addition, proteins with only LIM domains have been described but the function of the LIM domain is unknown. We have analysed the function of LIM domains using Isl-1 as a representative LIM-homeodomain protein. Employing protein prepared in bacterial cells, we show that the presence of the LIM domain in Isl-1 inhibits binding of the homeodomain to its DNA target. This in vitro inhibition can be released either by denaturation/renaturation of the protein or by truncation of the LIM domains. A similar inhibition is observed in vivo using reporter constructs. In addition we show that LIM domains in a chimeric protein can inhibit binding of the Ubx homeodomain to its target. The ability of LIM domains to inhibit DNA binding by the homeodomain provides a possible basis for negative regulation of LIM-homeodomain proteins in vivo.

Base Sequence↗

PubMed1993

Fusion of the dominant negative transcription regulator CHOP with a novel gene FUS by translocation t(12;16) in malignant liposarcoma.

The search for tumour-specific markers is one of the chief goals in cancer biology. We show that the translocation t(12;16)(q13:p11) in malignant myxoid liposarcoma can be a fusion of the CHOP dominant negative transcription factor gene with a novel gene, FUS, which can result in fusion of the FUS glycine-rich protein with the whole CHOP coding region. The data support the concept that protein fusion may commonly occur in solid tumours resulting in tumour-specific markers of potential clinical importance. The data also indicate the importance of transcription disruption in the pathogenesis of solid tumours.

Amino Acid Sequence↗

PubMed1993

Comparison of 5 mg tetracaine diluted in 1 ml, 2 ml and 4 ml of 10% glucose for spinal anesthesia.

The influence of variations in the volume of injectate when maintaining an identical dose of a hyperbaric local anesthetic has not previously been investigated when performing spinal anesthesia. This study compares spinal anesthesia of 5 mg of lyophilized tetracaine diluted in 1 ml, 2 ml or 4 ml of 10% glucose in 45 elderly patients undergoing elective hip surgery. While supine and horizontal, each patient received double-blind one of the three solutions through a catheter inserted 4 cm into the intrathecal space at the L2-L3 or L3-L4 interspace. No difference in the anesthetic effects was found between the three groups. The median value of the maximal sensory level was T6 (range T3-L2), T4 (range T3-T9) and T5 (range T3-T11) in the 1-ml, 2-ml, and 4-ml groups, respectively. The number of patients with a motor blockade of grade 2 or 3 was 12/15, 14/15 and 13/15, and the time from the initial dose to the need for the first top-up dose (mean +/- s.d.) was 88 +/- 35 min, 75 +/- 15 min and 68 +/- 15 min for the 1-ml, 2-ml and 4-ml groups, respectively. Hemodynamic changes were also comparable between the three groups. The authors conclude that in elderly patients, undergoing spinal anesthesia while supine and horizontal, variations in volume from 1 to 4 ml do not influence the characteristics of hyperbaric spinal anesthesia while injecting an identical dose of local anesthetic.

Aged↗

PubMed1993

Continuous spinal anesthesia: where do spinal catheters go?

The purpose of this study was to investigate the incidence of technical problems encountered when performing continuous spinal anesthesia and the influence of catheter tip position on block height following injection of a hypobaric spinal anesthetic. Twenty-nine elderly patients undergoing hip surgery were studied. Lumbar puncture was performed with an 18-gauge Tuohy needle at the L3-4 (or L2-3) interspace. Threading was defined as easy if a 20-gauge catheter was inserted on the first try, 3-4 cm cephalad. Threading was considered difficult if cephalad insertion of the catheter was impossible on the first try; the Tuohy needle was then rotated with its bevel facing caudally, the catheter inserted for 1-2 mm, and the needle turned back cephalad together with the catheter partially threaded, for further cephalad insertion up to 4 cm. All patients received 7.5 mg of hypobaric bupivacaine or tetracaine in the lateral decubitus position and sensory levels were determined by pinprick. After surgery all catheters were injected with radiographic dye and examined by radiograph for verification of position. The determination of the level of lumbar puncture was falsely judged in 59% of cases, the puncture being performed 1 or 2 spaces higher than assumed. Although threading difficulties were encountered in 4/28 cases, there was a 100% success rate in catheter insertion. One catheter displacement into the epidural space was noted. Twenty of twenty-eight catheters took a cephalad direction, 6 remained coiled in a horizontal position, and 2 took a caudal direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1993

Influence of injection speed on the subarachnoid distribution of isobaric bupivacaine 0.5%.

The purpose of this study was to compare the anesthetic characteristics after two radically different speeds of intrathecal injection of isobaric 0.5% bupivacaine during continuous spinal anesthesia. Forty consenting patients, undergoing hip surgery using continuous spinal anesthesia, were allocated randomly to two groups of 20 each according to the rate of injection of 2 mL (10 mg) of isobaric 0.5% bupivacaine: FI (fast injection = 2 mL during 2 to 3 s or approximately 0.75 mL/s) or SI (slow injection = 1 mL/min). No difference was observed between the two groups in terms of sensory and motor block or hemodynamic changes. However, the onset time to maximal sensory level was significantly shorter in the SI group (16 +/- 9 min vs. 24 +/- 6 min; P < 0.05). Those patients requiring reinjection entered the second part of the study (n = 23; 15 in the FI group and 8 in the SI group). Each of these remaining patients was used as his or her own proper control. Those in the FI group received a slow reinjection and those in the SI group received a fast reinjection which consisted in all cases of 10 mg (2 mL) of isobaric 0.5% bupivacaine. When looking at the anesthetic characteristics after reinjection, maximal sensory levels, as well as onset times, were very similar in both groups. At all times, the maximal sensory level obtained after reinjection was two dermatomes higher than after the initial injection. Duration of sensory block, which was calculated only in these 23 patients, was also comparable (126 +/- 44 min for FI and slow reinjection group vs 146 +/- 25 min for SI and fast reinjection group). In conclusion, regardless of the speed of injection, there are no differences in anesthetic characteristics of spinal anesthesia using isobaric 0.5% bupivacaine.

Aged↗