Plastocyanin is encoded by an uninterrupted nuclear gene in spinach

Plastocyanin is a member of photosynthetic electron transport chains that transfers electrons from cytochrome f to the oxidized P700 chlorophyll a pigment of the photosystem I reaction center. We have isolated and characterized cDNA- and genomic clones from spinach (Spinacia oleracea) encoding the complete plastocyanin-precursor polypeptide. The amino acid sequence derived from the nucleotide sequence shows that the precursor consists of 168 amino acid residues including a transit sequence of 69 residues. The precursor polypeptide has a predicted Mr of 16,917, the mature protein of 10,413. The available data indicate that plastocyanin derives probably from a single-copy gene. The coding region contains no intron. The size of the mRNA as determined by S1 nuclease protection experiments is approximately 660 nucleotides, although analysis of different cDNA clones suggests that longer RNA species do exist, approaching the size of the mRNA (850 bases) estimated by Northern blot techniques.

Cerebral phaeohyphomycosis caused by Fonsecaea monophora

We report a case of cerebral phaeohyphomycosis in a 53-year-old immunocompetent diabetic male, caused by Fonsecaea monophora. Computerized tomography of the brain revealed an abscess, which yielded F. monophora in pure culture. The patient's condition deteriorated on treatment with voriconazole and 5-fluorocytosine, and improved subsequently with high-dose itraconazole. The genus Fonsecaea has recently been revised and the new species F. monophora generated from molecular analysis of isolates, most of which were originally identified as Fonsecaea pedrosoi. This is the fourth case of cerebral infection known to have been caused by F. monophora, although only the first reported as such. These cases suggest that the clinical potential of F. monophora differs from that of F. pedrosoi, one of the main agents of chromoblastomycosis, with F. monophora being predominantly neurotropic in the human host.

Safe pre-operative fasting times after milk or clear fluid in children. A preliminary study using real-time ultrasound

Gastric emptying of orange-flavoured glucose (group I), low-fat milk (group II) and breast milk (group III) was evaluated in 45 ASA grade I children of < or = 5 years of age by using real-time ultrasonography and residual gastric volume and pH was then measured. In 15 more children, residual gastric volume and pH was measured after a midnight fast (group IV). Mean (SD) gastric emptying time in group I was 1.53 (0.25) h (range 1.00-1.75), group II 2.32 (0.31) h (range 1.75-2.75) and group III 2.43 (0.27) h (range 2.00-2.75). According to Robert and Shirley's criteria, no children of group I and II were found to be 'at risk' at 2 h and 3 h, respectively, but 13.3% of group III children were labelled as 'at risk' at 3 h. The incidence of 'at risk' children in group IV was 33.3%. It was concluded that 3% fat milk or 17.5% glucose in a volume of 10 ml.kg-1 (maximum volume of 100 ml) can be given in children safely 3 h and 2 h, respectively, before anaesthesia. More real-time studies are required on breast milk to establish guidelines for its potential use as a pre-operative feed 3 h before anaesthesia.

Randomised trial of intravenous infusion of ephedrine or mephentermine for management of hypotension during spinal anaesthesia for Caesarean section

This study compared the effects of intravenous infusions of ephedrine and mephentermine for maintenance of maternal arterial pressure and neonatal outcome in pregnant women receiving subarachnoid block for lower segment Caesarean section. Sixty patients who developed hypotension following subarachnoid block for Caesarean section were randomly divided into two groups of 30 each to receive an intravenous infusion of ephedrine or mephentermine. Hypotension was defined as a decrease in systolic blood pressure of > or = 20% from the baseline value or an absolute value of <100 mmHg, whichever was higher. The vasopressor infusion was titrated to maintain systolic blood pressure between 'hypotension' and baseline values. Baseline haemodynamic parameters, haemodynamic changes subsequent to the start of vasopressor infusion, duration of hypotension and amount of vasopressor required were statistically similar for both groups. Neonatal APGAR scores and acid-base profiles were also comparable. To conclude, mephentermine can be used as safely and effectively as ephedrine for the management of hypotension during spinal anaesthesia in patients undergoing elective Caesarean section.

Cytochrome b-559 genes from Oenothera hookeri and Nicotiana tabacum show a remarkably high degree of conservation as compared to spinach. The enigma of cytochrome b-559: highly conserved genes and proteins but no known function

Recent data suggest that cytochrome b-559, an intrinsic membrane protein of the oxygen-evolving photosystem II in chloroplasts, is a heme cross-linked heteromeric polypeptide unit (Herrmann et al. 1984, FEBS Lett 176:239-244). The genes for this cytochrome, designated psbE and psbF, have been located on the chloroplast chromosome of Oenothera hookeri and Nicotiana tabacum by hybridization with fragments of the corresponding spinach genes, and characterized. In both cases, the nucleotide sequence discloses 2 uninterrupted reading frames of 83 and 39 codons separated by a few nucleotides, as in spinach. The amber translation stop codon of psbE overlaps the putative ribosome-binding site for psbF in all cases. The predicted molecular weights of the proteins are 9.2 and 4.3 kd, respectively. In each of the three plant species, and the direction of transcription is opposite to that of the gene for cytochrome f which is located distal to the b-559 genes. Comparison of the deduced amino acid sequences with those from the corresponding spinach genes shows 97% homology. The ubiquitous presence and remarkably high degree of structural and functional conservation of this gene cluster supports the hypothesis of a heteromeric assembly and an important functional role for cytochrome b-559.

Subdural Block and the Anaesthetist

There are a number of case reports describing accidental subdural block during the performance of subarachnoid or epidural anaesthesia. However, it appears that subdural drug deposition remains a poorly understood complication of neuraxial anaesthesia. The clinical presentation may often be attributed to other causes. Subdural injection of local anaesthetic can present as high sensory block, sometimes even involving the cranial nerves due to extension of the subdural space into the cranium. The block is disproportionate to the amount of drug injected, often with sparing of sympathetic and motor fibres. On the other hand, the subdural deposition can also lead to failure of the intended block. The variable presentation can be explained by the anatomy of this space. High suspicion in the presence of predisposing factors and early detection could prevent further complications. This review aims at increasing awareness amongst anaesthetists about inadvertent subdural block. It reviews the relevant anatomy, incidence, predisposing factors, presentation, diagnosis and management of unintentional subdural block during the performance of neuraxial anaesthesia.

Sub-galeal coiling of the proximal and distal components of a ventriculo-peritoneal shunt. An unusual complication and proposed mechanism

We describe the case of a child in whom proximal migration of the peritoneal catheter and extrusion of the ventricular catheter resulted in the entire ventriculo-peritoneal shunt along with the shunt chamber (Orbis Sigma II valve) lying in a sub-galeal pocket in the occipital region in a tightly coiled fashion. This coiling was very similar in appearance to that of the pre-insertion shunt in the packaging when it is supplied; hence it is postulated that the migration was secondary to retained 'memory' of the shunt tubing. This is a rare complication of ventriculo-peritoneal shunt, which has not been described before.

Comparison of phenylephrine hydrochloride and mephentermine sulphate for prevention of post spinal hypotension

This study compared the effects of intravenous infusions of phenylephrine and mephentermine on the prevention of maternal hypotension and neonatal outcome in patients receiving spinal anaesthesia for caesarean section. Sixty ASA 1-2 patients with term, uncomplicated singleton pregnancy undergoing caesarean section under spinal anaesthesia were randomly divided into two groups of 30 each, to receive a prophylactic intravenous infusion of either phenylephrine or mephentermine. The incidence of hypotension was statistically similar in the two groups. However, in patients receiving phenylephrine, 7 (23%) developed bradycardia and 6 (20%), reactive hypertension. Neonatal outcome, in terms of Apgar scores and umbilical artery pH, was similar in both the groups. To conclude, phenylephrine and mephentermine infusions are equally effective in preventing post spinal hypotension in patients undergoing caesarean section and are associated with a similar neonatal outcome.

A comparison of pressure-controlled and volume-controlled ventilation for laparoscopic cholecystectomy

The potential advantages of pressure-controlled over volume-controlled ventilation during laparoscopic surgery have yet to be proven. We randomly assigned 42 patients with BMI <30 kg.m(-2) scheduled for laparoscopic cholecystectomy to receive either pressure- or volume-controlled ventilation. Compared with volume-controlled ventilation, pressure-controlled ventilation resulted in a significant decrease in mean (SD) peak airway pressure at 10 min (20.4 (2.7) vs 24.0 (4.7)cmH₂O, p=0.004) and 30 min (20.7 (3.0) vs 23.9 (4.9)cmH₂O, p=0.015) and an increase in mean airway pressure at 10 min (10.5 (0.9) vs 9.6 (1.1)cmH₂O, p=0.007) and 30 min (10.5 (1.1) vs 9.6 (1.2)cmH₂O, p=0.016) after the start of surgery. Gas exchange and haemodynamic stability were similar. We conclude that pressure-controlled ventilation is a safe alternative and offers some advantages to volume-controlled ventilation during laparoscopic cholecystectomy in non-obese patients.

Construction of titanium cranioplasty plate using craniectomy bone flap as template

In recent times a steady rise in cranioplasty operations has been noted because of increasing utilisation of decompressive craniectomy for trauma as well as stroke patients. A variety of techniques have been utilised for cranioplasty, with their own benefits and limitations. Titanium cranioplasty is one of the well-established and widely used techniques, with most centres utilising computer-assisted reconstruction for manufacture of titanium plates. In this paper we present a novel method for making titanium cranioplasty plates using the craniectomy bone flap as a template and the results of our experience. To date we have performed 51 cranioplasties using this method. The surgical results have been comparable to those obtained using the computer-assisted model technique. The construction cost for titanium cranioplasty plates using this method has been pound 360 cheaper per plate compared with the computer-assisted method. In addition, the CT workload and radiation exposure have been reduced.

The role of ophthalmic triage and the nurse practitioner in an eye-dedicated casualty department

PURPOSE

To evaluate the appropriateness of triage decisions in a busy ophthalmic casualty department and to assess the diagnostic and management skills of eye-dedicated nurse practitioners.

METHODS

Three hundred and one consecutive patients attending the Birmingham and Midland Eye Centre (BMEC) accident and emergency (A&E) department over a 2 week period were included in this prospective study. Patients were categorised in terms of urgency in concordance with strict guidelines, and the agreement between the final diagnosis and this system of prioritisation was then investigated. To evaluate nurse practitioner (NP) skills, all patients seen and managed by a NP were also assessed by the most senior doctor in casualty at the time in a masked fashion. Waiting times and a breakdown of waiting times were also calculated.

RESULTS

Upon establishment of a diagnosis, triage category allocation was found to be appropriate in all 301 cases. Fifty patients (16.67%) were seen by the NP. Of these the supervising doctor concurred with the NP diagnosis in all cases and with the proposed management in 96% of cases. The mean waiting time (+/- SD) was 83.43 +/- 45.84 min, with a range of 5-335 min. The delay before being attended to was greater for less urgent cases as categorised by the triage system.

CONCLUSION

This study confirms the high standard of diagnostic and management skills of the ophthalmic NP and indicates that the triage system of patient prioritisation is accurate. Waiting times in the A&E department remain unacceptable and ways of addressing this include improved ophthalmic training of general practitioners, diverting a greater proportion of non-acute cases to the primary care clinic and expanding the role of the NP.

Extrusion of BOP-B graft orally following anterior cervical discectomy and fusion

Graft extrusion following anterior cervical discectomy and fusion is a recognized complication. We report a case of oral extrusion of a synthetic graft (BOP B, Biocompatible Orthopaedic Polymer).

Photophysical characterisation and photo-cycle dynamics of LOV1-His domain of phototropin from Chlamydomonas reinhardtii with roseoflavin monophosphate cofactor

The wild-type phototropin protein phot from the green alga Chlamydomonas reinhardtii with the blue-light photoreceptor domains LOV1 and LOV2 has flavin mononucleotide (FMN) as cofactor. For the LOV1-His domain from phot of C. reinhardtii studied here, the FMN chromophore was replaced by roseoflavin monophosphate (8-dimethylamino-8-demethyl-FMN, RoFMN) during heterologous expression in a riboflavin auxotropic Escherichia coli strain. An absorption and emission spectroscopic characterisation of the cofactor exchanged-LOV1-His (RoLOV1) domain was carried out in aqueous pH 8 phosphate buffer. The fluorescence of RoLOV1 is quenched by photo-induced charge transfer at room temperature. The photo-cyclic dynamics of RoLOV1 was observed by blue-light induced hypochromic and bathochromic absorption changes which recover on a minute timescale in the dark. Photo-excited RoFMN is thought to cause reversible protein and cofactor structural changes. Prolonged intense blue-light exposure caused photo-degradation of RoFMN in RoLOV1 to fully reduced flavin and lumichrome derivatives. Photo-cycle schemes of RoLOV1 and LOV1 are presented, and the photo-degradation dynamics of RoLOV1 is discussed.

Epidural volume extension: a review

Epidural volume extension is a technical modification of the combined spinal epidural block. It involves the epidural injection of normal saline or a small volume of local anaesthetic after an intrathecal injection, aiming to augment the post-spinal sensory level. Although the consequent sensory block augmentation has been adequately documented, the probable factors influencing epidural volume extension and its implications for clinical practice are not well defined. This article reviews published literature relating to the probable factors affecting epidural volume extension, its clinical implications, case reports of its successful clinical application and summarises its unexplored effects.