Efficient heterocyclisation by (di)terpene synthases.

While cyclic ether forming terpene synthases are known, the basis for such heterocyclisation is unclear. Here it is reported that numerous (di)terpene synthases, particularly including the ancestral ent-kaurene synthase, efficiently produce isomers of manoyl oxide from the stereochemically appropriate substrate. Accordingly, such heterocyclisation is easily accomplished by terpene synthases. Indeed, the use of single residue changes to induce production of the appropriate substrate in the upstream active site leads to efficient bifunctional enzymes producing isomers of manoyl oxide, representing novel enzymatic activity.

Patient-controlled sedation with propofol and alfentanil during colonoscopy: a pilot study.

BACKGROUND AND STUDY AIMS: Patient controlled sedation (PCS) is becoming increasingly popular in day-case surgery and has the potential for use during endoscopy. We aimed to examine its safety and acceptability during colonoscopy in a pilot study using alfentanil and propofol and assess its influence on the patient's recovery time. PATIENTS AND METHODS: Sixteen otherwise healthy patients undergoing colonoscopy were attached to a Graseby 3300 PCA pump containing propofol 400 mg and alfentanil 1 mg (total volume 42 ml) and gave themselves bolus of 0.5 ml whenever they became uncomfortable. RESULTS: All patients tolerated the procedure well and found the PCS easy to use. There were no serious haemodynamic or respiratory complications and patients recovered quickly after the procedure, irrespective of the dose of drug given. CONCLUSIONS: PCS with propofol and alfentanil is an effective, short-acting form of sedation for patients undergoing colonoscopy and may be an alternative to benzodiazepines.

Patient-controlled sedation and analgesia, using propofol and alfentanil, during colonoscopy: a prospective randomized controlled trial.

BACKGROUND AND STUDY AIMS: Patient-controlled sedation (PCS) enables titration of dosage to an individual's requirements and is potentially useful in colonoscopy. The aim was to compare the value of patient-controlled sedation, using propofol and alfentanil, with that of intravenous diazemuls and pethidine during colonoscopy. PATIENTS AND METHODS: Following randomization, 66 patients undergoing colonoscopy received either an intravenous bolus of pethidine (50 mg) and diazemuls (10-20 mg) prior to colonoscopy or were connected to an infusion pump containing propofol (10 mg/ml) and alfentanil (25 microg/ml). Patients self-administered 0.5 ml boluses as often as they required. Pain and sedation score were recorded by a nurse specialist and on a patient questionnaire. An anaesthetist was present throughout the procedure. RESULTS: PCS provided lighter sedation (median sedation score, 3 versus 4; P=0.0001), less analgesia (median pain score, 1 versus 0; P=0.004), a smaller maximum fall in systolic blood pressure (23 mmHg versus 33 mmHg; P=0.02) and a faster recovery time (median 10 min versus 40 min; P=0.0001), irrespective of the dose administered, compared with a diazemuls-pethidine combination. The duration of the procedure was unaffected. All patients were satisfied with their level of sedation. CONCLUSIONS: Patient-controlled sedation is an effective alternative to premedication with narcotic/benzodiazepine combinations during colonoscopy.

Emergency airway management in patients with cervical spine injuries.

A retrospective study of admissions to a Level 1 Trauma Centre, revealed 393 patients with traumatic cervical spine injuries. All 36 patients intubated urgently and 37 and 68 patients intubated between 30 min and 24 h of admission, were intubated orally, following a rapid sequence induction with the application of cricoid pressure and manual in-line stabilisation of the head and neck. There were no neurological sequelae in these 73 patients (95% confidence interval 0-4%). This technique for airway management is described in detail. It is a safe, familiar, and effective method for securing the airway in patients with cervical spine injury.

Pain on intradermal injection with lignocaine. The effect of concentration.

Twenty ASA 1 volunteers were each injected intradermally with four solutions containing 0.2 ml of 0.5%, 1%, and 2% lignocaine and 0.9% saline to determine whether the pain experienced on injection was related to the concentration of local anaesthetic. A 10 cm linear analogue pain scoring system was used, and the solutions were ranked from most painful to least painful. There were no differences between the different concentrations of lignocaine and 0.9% saline in the severity of pain experienced. We conclude that any concentration of lignocaine may be used intradermally before inserting intravenous catheters without affecting the degree of pain experienced by that injection.

The Bain, ADE, and Enclosed Magill breathing systems. A comparative study during controlled ventilation.

The Enclosed Magill, Humphrey ADE and the Bain breathing systems are all used for controlled ventilation of the lungs. This study compares the three systems in vitro with a lung model and in clinical practice. No difference was observed, with ventilatory variables commonly used in clinical practice, between the Bain and the ADE, while significantly lower end-tidal carbon dioxide values were observed with the Enclosed Magill (about 7%). Lower fresh gas flows can be used under these circumstances to maintain normocapnia with the Enclosed Magill than either the Bain or the Humphrey ADE.

Teaching coin equivalence to the mentally retarded.

A program was designed to teach coin equivalence to mentally retarded adolescents. Coin equivalence was defined as choosing several different combinations of coins to equal specified target values. A pretest-posttest matched-groups design was employed with an experimental group receiving the monetary training, and a no-training control group. A multiple baseline across coin-counting responses was also incorporated in the experimental group. Training was divided into six stages, each teaching one specific method of combining coins to equal 10 target values from 5 cents through 50 cents. A three-component response chain was used, requiring (a) naming, (b) selecting and counting, and (c) depositing target monetary values into a coin machine. Experimental subjects improved significantly in coin equivalence performance and maintained their skill on follow up tests; control subjects did not.

Adaptation of Nitrogen Fixation by Intact Soybean Nodules to Altered Rhizosphere pO(2).

The N(2)-fixing legume nodule requires O(2) for ATP production; however, the O(2) sensitivity of nitrogenase dictates a requirement for a low pO(2) inside the nodule. The effects of long term exposures to various pO(2)s on N(2)[C(2)H(2)] fixation were evaluated with intact soybean (Glycine max [L.] Merr., var. Wye) plants. Continuous exposure of their rhizosphere to a pO(2) of 0.06 atmospheres initially reduced nitrogenase activity by 37 to 45% with restoration of original activity in 4 to 24 hours and with no further change in tests up to 95 hours; continuous exposure to 0.02 atmosphere of O(2) initially reduced nitrogenase activity 72%, with only partial recovery by 95 hours. Similar exposures to a pO(2) of 0.32 atmospheres had little effect on N(2)[C(2)H(2)] fixation; a pO(2) of 0.89 atmospheres initially reduced nitrogenase activity by 98% with restoration to only 14 to 24% of that of the ambient O(2) controls by 95 hours. Re-exposure to ambient pO(2) of plants adapted to nonambient pO(2)s reduced N(2)[C(2)H(2)] fixation to similar magnitudes as the reductions which occurred upon initial exposure to variant pO(2) conditions, and a time period was required to readapt to ambient O(2). It is concluded that the N(2)[C(2)H(2)]-fixing system of intact soybean plants is able to adapt to a wide range of external pO(2)s as probably occur in soil. We postulate that this occurs through an undefined mechanism which enables the nodule to maintain an internal pO(2) optimal for nitrogenase activity.