Degradation pathway of bisphenol A: does ipso substitution apply to phenols containing a quaternary alpha-carbon structure in the para position?

The degradation of bisphenol A and nonylphenol involves the unusual rearrangement of stable carbon-carbon bonds. Some nonylphenol isomers and bisphenol A possess a quaternary alpha-carbon atom as a common structural feature. The degradation of nonylphenol in Sphingomonas sp. strain TTNP3 occurs via a type II ipso substitution with the presence of a quaternary alpha-carbon as a prerequisite. We report here a new degradation pathway of bisphenol A. Consequent to the hydroxylation at position C-4, according to a type II ipso substitution mechanism, the C-C bond between the phenolic moiety and the isopropyl group of bisphenol A is broken. Besides the formation of hydroquinone and 4-(2-hydroxypropan-2-yl)phenol as the main metabolites, further compounds resulting from molecular rearrangements consistent with a carbocationic intermediate were identified. Assays with resting cells or cell extracts of Sphingomonas sp. strain TTNP3 under an (18)O(2) atmosphere were performed. One atom of (18)O(2) was present in hydroquinone, resulting from the monooxygenation of bisphenol A and nonylphenol. The monooxygenase activity was dependent on both NADPH and flavin adenine dinucleotide. Various cytochrome P450 inhibitors had identical inhibition effects on the conversion of both xenobiotics. Using a mutant of Sphingomonas sp. strain TTNP3, which is defective for growth on nonylphenol, we demonstrated that the reaction is catalyzed by the same enzymatic system. In conclusion, the degradation of bisphenol A and nonylphenol is initiated by the same monooxygenase, which may also lead to ipso substitution in other xenobiotics containing phenol with a quaternary alpha-carbon.

[Neuromuscular blockade with cisatracurium in infants andchildren. Its course under sevoflurane anesthesia]

OBJECTIVE

To compare the onset, duration and maximum effect of 0.1 mg/kg cisatracurium during balanced anesthesia with sevoflurane and remifentanil between infants and children.

METHODS

We measured the time course of the neuromuscular blockade in 15 infants and 15 children by electromyography. Anesthesia was induced with propofol/remifentanil and maintained with sevoflurane (constant 2% endtidal) and remifentanil according to the patients individual requirements. After injection of 0.1 mg/kg cisatracurium we measured the following parameters: onset time: time between the beginning of injection of cisatracurium and maximum T1 depression, clinical duration: time between injection of the drug and recovery of T1 to 25%, recovery index: time between recovery of T1 from 25% to 75%. TOFR 0.9: time between injection of cisatracurium and recovery of the train-of-four ratio to 90%. In addition, we determined the maximum neuromuscular blockade Tmax after 0.1 mg/kg cistracurium.

RESULTS

Both groups differed significantly with regard to onset time and clinical duration. In the infants, the onset time was shorter (74 s vs. 198 s) and the clinical duration longer (55 min vs. 41 min) compared to the older children. The TOFR 0.9 was 73 min (range 56-86 min) in the group of the infants and 59 min (range 43-72 min) in the group of the older children (p < 0.001). Tmax was 100% (range 97-100%) in the infants and 98% (range 92-100%) in the children (p < 0.01). However, the recovery index was comparable in both groups (21 vs. 16 min).

CONCLUSIONS

Infants are substantially more sensitive to cisatracurium than children, which can be demonstrated in a significantly shorter onset time, a prolonged clinical duration and a delayed neuromuscular recovery. As there exist large interindividual differences, we recommend the use of neuromuscular monitoring in the routine practice of pediatric anesthesia.

Recovery and neurological examination after remifentanil-desflurane or fentanyl-desflurane anaesthesia for carotid artery surgery

We studied 44 patients undergoing carotid endarterectomy (CEA) to compare recovery after general anaesthesia with desflurane supplemented with either remifentanil or fentanyl. Remifentanil was infused at 0.1 microg kg(-1) min(-1) and desflurane was adjusted at 2 vol% end-tidal. Fentanyl was given as a bolus dose of 2 microg kg(-1) before induction and repeated at skin incision; desflurane was adjusted as needed. Times for early recovery and response to simple neurological tests (digit symbol substitution test (DSST) and Trieger dot test (TDT)) were measured 30, 60 and 90 min after operation. Emergence from remifentanil-desflurane anaesthesia was significantly quicker than that from fentanyl-desflurane anaesthesia: mean times to extubation were 4.1 (SD 1.7) and 8.2 (4.9) min, respectively; mean times for patients to state their name correctly were 6.0 (2.8) and 13.8 (9.0) min, respectively. Patients in the remifentanil-desflurane group successfully performed neurological tests significantly earlier than those in the fentanyl-desflurane group; for example, patients in the former group completed the arm holding test at 7.9 (3.0) min, while those in the latter group did this at 20.6 (19.7) min (P < or = 0.01). Intermediate recovery was less impaired at 30 min (DSST, TDT) and at 60 min (DSST). More rapid awakening and an earlier opportunity for neurological examination suggest that remifentanil-desflurane is a suitable alternative to a standard fentanyl-based general anaesthetic technique in patients undergoing CEA.

[Time course of neuromuscular blockade after rocuronium. A comparison between women and men]

BACKGROUND

We studied 40 patients (20 female and 20 male) undergoing elective surgery under general anaesthesia to evaluate the effect of gender on the pharmacodynamics of rocuronium.

METHODS

Using electromyography (EMG) we determined the maximal neuromuscular block and time course of action of 0.45 mg/kg rocuronium (1.5 x ED95).

RESULTS

Age and body mass index were comparable between females and males (38 (+/- 8) vs. 37 (+/- 10) years and 24.2 (+/- 2.9) vs. 25.2 (+/- 1.7) kg/m2. However, significant differences in weight and height were found between females and males (65.7 +/- 9.3 kg vs. 77.5 +/- 5.5 kg; p < 0.01 and 178 +/- 6.8 cm vs. 164 +/- 6.7 cm; p < 0.01). Onset time was shorter in females (168 +/- 65 s vs. 211 +/- 56 s; p < 0.05). Maximal neuromuscular blockade after 0.45 mg/kg rocuronium was 94 (+/- 3) % in females and 89 (+/- 6) % in males; p < 0.01. Clinical duration was increased in females (23 +/- 5 min vs. 17 +/- 5 min; p < 0.05), while the recovery index was comparable between both groups (9 +/- 4 min in females and 9 +/- 3 min in males; n.s.).

CONCLUSION

Compared to men neuromuscular blockade after 0.45 mg/kg rocuronium was more pronounced in women. The onset time was shortened and the clinical duration increased in female patients.

Remifentanil and propofol without muscle relaxants or with different doses of rocuronium for tracheal intubation in outpatient anaesthesia

BACKGROUND

The use of muscle relaxants in outpatient anaesthesia is controversial; some authors recommend an induction regimen including propofol and opioids without muscle relaxants. This study evaluated the requirements for rocuronium after remifentanil/propofol.

METHODS

We examined in four groups of ASA I-II patients (n= 30 for each) the intubating conditions three minutes after induction of anaesthesia with remifentanil 0.5 microg kg(-1) min(-1), propofol 2 mg kg(-1) without muscle relaxants or with different doses of rocuronium (0.6 mg kg(-1), 0.45 mg kg(-1), 0.3 mg kg(-1)) applying the criteria proposed by the Copenhagen Consensus Conference. In the second part of the study the time course of neuromuscular block was determined by electromyography using train-of-four (TOF) stimulation. To this end, another 60 ASA I-II patients were randomly assigned to receive remifentanil 0.5 microg kg(-1) min(-1), propofol 2 mg kg(-1) and either rocuronium 0.6 mg kg(-1), 0.45 mg kg(-1), 0.3 mg kg(-1), or 0.3 mg kg(-1) followed by neostigmine 40 microg kg(-1) and atropine 20 microg kg(-1) at a T1 recovery of 10% (n=15 for each).

RESULTS

Intubating conditions were good or excellent in 30 patients after rocuronium 0.6 mg kg(-1) and in 18 patients when rocuronium was omitted (P<0.01). After 0.45 mg kg(-1) and 0.3 mg kg(-1) rocuronium the numbers were 29 and 30 patients, respectively. Reducing rocuronium from 0.6 mg kg(-1) to 0.45 mg kg(-1) or 0.3 mg kg(-1) increased the onset time from 136 (35) s to 199 (34) s and 249 (52) s (mean (SD)), (P<0.01); the clinical duration decreased from 38 (10) min to 24 (8) min and 16 (5) min, respectively (P<0.01); and the duration to a TOF-ratio of 0.8 decreased from 60 (11) min to 45 (9) min and 34 (7) min (P<0.01). After rocuronium 0.3 mg kg(-1) this time interval further decreased to 22 (3) min when neostigmine was given at a T1 of 10% (P<0.01 compared with spontaneous recovery after rocuronium 0.3 mg kg(-1)).

CONCLUSION

After remifentanil/propofol intubation conditions were poor in 40% of patients without muscle relaxants; adding reduced doses of rocuronium to this regimen improved the intubation conditions significantly. In addition, reducing the initial dose of rocuronium markedly shortened its time course of action.

Mex67p mediates nuclear export of a variety of RNA polymerase II transcripts

Mex67p is essential for nuclear poly(A)(+) RNA export in yeast, but which specific transcripts are transported by Mex67p is not known. We observed that thermosensitive mex67-5 cells do not produce a heat shock response at 37 degrees C but will induce heat shock proteins (Hsp) (e.g. Hsp104p and Hsp70p) when shifted back from the restrictive to permissive temperature (30 degrees C). This memory of a previous heat stress in mex67-5 cells could be explained if HSP mRNAs accumulated inside the nucleus during heat shock and were exported and translated in the cytoplasm on return to the permissive temperature. To test this hypothesis, nuclear export of heat shock mRNAs was directly analyzed by in situ hybridization using fluorescent-labeled oligonucleotide probes specific for SSA transcripts. This revealed that Mex67p is required for nuclear export of heat shock mRNAs. Furthermore, other polymerase II transcripts encoding the transcriptional repressor ASH1 and the glycolytic enzyme PGK1 are shown to require Mex67p for their export into the cytoplasm. Thus, Mex67p is an mRNA export factor for a broad range of polymerase II transcripts.

[The use of remifentanil in critically ill patients. Clinical findings and early experience]

OBJECTIVES

It was the aim of this investigation to report our initial clinical experience on the use of remifentanil in critically ill patients undergoing mechanical ventilation. Additionally, we hypothesized that even under intensive care conditions remifentanil might facilitate a temporally predictable and "programmed" tracheal extubation.

METHODS

Remifentanil was used for analgesia and sedation of mechanically ventilated patients who were admitted to the ICU following major noncardiac surgery or who had to be ventilated due to respiratory failure. The infusion was started with 0.15 microg/kg/min and then adapted in steps of 0.05 microg/kg/min according to clinical needs. After admission to the ICU the depth of sedation was adjusted to a Ramsay score level of 4 (sleeping patient, immediately arousable) and then targeted at a level of 2-3 (patient awake, co-operative and tranquil or responding to command only). In case of sufficient pain relief but inadequate sedation patients could receive bolus doses of midazolam (1-3 mg) or an infusion of clonidine (0.5 microg/kg/h), the latter especially in case of shivering or hypertension. Prior to extubation bolus doses of piritramide (3-5 mg) and a non-opioid analgesic (metamizol or propacetamol) could be used for postoperative pain relief. Data are presented as mean+/-SD.

RESULTS

A total of 46 patients were studied, aged 62.8+/-15.4 yr with a mean APACHE II score of 19.2 points. The duration of remifentanil infusion ranged up to 78 h with a mean of 9. 8 h. The mean infusion rate was 0.14+/-0.08 microg/kg/min during ongoing analgesia and sedation and 0.10+/-0.08 microg/kg/min immediately before its discontinuance. Additional sedatives were necessary in 63% of all patients. Emergence was rapid in the majority of cases: 67% of all patients could safely be extubated within 15 min after termination of remifentanil, and a total of 87% were extubated within 45 min. A development of tolerance was not observed during the study period.

CONCLUSIONS

Remifentanil appeared to be suitable for analgesia and sedation of critically ill patients undergoing mechanical ventilation: Even under intensive care conditions recovery was rapid in the majority of cases, and in two thirds of all patients tracheal extubation was temporally predictable and could be timed within 15 min. These results are best explained by the metabolism and offset of action of remifentanil obviously unaffected in the ICU area. However, for fast emergence the cautious use of additional sedatives is crucial.

[Rocuronium for anesthesia induction in elective procedures. Time course of muscular blockade and intubation after administration of 2-compartment ED95 (0.6 mg/kg) and dose reduction (0.4 mg/kg)]

BACKGROUND

Rocuronium is a non-depolarising neuromuscular blocking agent structurally related to vecuronium. The compound has a rapid onset and an intermediate duration of action. The rapid onset is of importance in patients at risk for pulmonary aspiration, for elective induction of anaesthesia slower onset properties generally are accepted. In this context, we asked whether the induction dose of rocuronium may be reduced to doses smaller than 2 x ED95 in situations in which slower onset properties may be acceptable.

METHODS

The time course of neuromuscular block and intubating conditions of two different doses rocuronium, 2 x ED95 (0.6 mg/kg) and 1.3 x ED95 (0.4 mg/kg), were investigated in 90 patients. We first determined the time course of neuromuscular block using electromyography (EMG), n = 15 for each group. In the second part the intubating conditions 3 min after injection of either rocuronium 0.6 mg/kg or rocuronium 0.4 mg/kg were evaluated, n = 30 for each group.

RESULTS

In the present study reduction of the dose of rocuronium led to a slower onset (148 +/- 32 s vs. 220 +/- 30 s; P < 0.05) and a shorter clinical duration (21 min +/- 4 vs. 36 +/- 7 min; P < 0.05). The recovery index was modified by the dose reduction: 11 +/- 3 min after 0.6 mg/kg rocuronium and 9 +/- 2 min after 0.4 mg/kg. After both doses of rocuronium the intubating conditions were good to excellent, no difference between both rocuronium groups were found.

CONCLUSION

In the present study dose reduction from 0.6 mg/kg rocuronium to 0.4 mg/kg rocuronium led to a slower onset and reduced clinical duration. However, the intubating conditions, evaluated 3 min after injection of the muscle relaxant were comparable. This offers new possibilities for muscle relaxation for surgical or diagnostic procedures of short duration and may reduce costs.

Functional interaction of Nic96p with a core nucleoporin complex consisting of Nsp1p, Nup49p and a novel protein Nup57p

Nic96p has been isolated previously in a complex together with the nuclear pore proteins Nsp1p, Nup49p and a p54 polypeptide. In a genetic screen for Nsp1p-interacting components, we now find NIC96, as well as a novel gene NUP57 which encodes the p54 protein (called Nup57p). Nup57p which is essential for cell growth contains GLFG repeats in the N-terminal half and heptad repeats in the C-terminal half. The domain organization of Nic96p is more complex: N-terminally located heptad repeats mediate binding to a trimeric Nsp1p-Nup49p-Nup57p complex, but are not required for the formation of this core complex; single amino acid substitutions in the central domain yield thermosensitive mutants, which do not impair interaction with the Nsp1 complex; the C-terminal domain is neither essential nor required for binding to the nucleoporin complex, but strikingly mutations in this part cause synthetic lethality with nsp1 and nup57 mutant alleles. Since a strain in which the Nic96p heptad repeats were deleted shows, similar to nsp1 and nup49 mutants, cytoplasmic mislocalization of a nuclear reporter protein, we propose that the interaction of the heterotrimeric Nsp1p-Nup49p-Nup57p core complex with Nic96p is required for protein transport into the nucleus.