Simultaneous visualization of two Citrus tristeza virus genotypes provides new insights into the structure of multi-component virus populations in a host

Complex Citrus tristeza virus (CTV) populations composed of mixtures of different strains of the virus are commonly found in citrus trees in the field. At present, little is known about how these populations are formed, maintained, and how they are structured within a host. Here we used a novel in situ hybridization approach allowing simultaneous visualization of two different RNA targets with high sensitivity and specificity to examine the distribution of two isolates, T36 and T68-1, representing phylogenetically distinct strains of CTV, in a citrus host in single and mixed infections. Remarkably, in doubly inoculated plants the two virus variants appeared to be well mixed within the infected tissue and showed no spatial segregation. In addition, both CTV variants were often found occupying the same cells. Possible mechanisms involved in shaping CTV populations and the biological significance of the observed lack of structural separation of the individual components are discussed.

The Ah receptor can bind ligand in the absence of receptor-associated heat-shock protein 90

The Ah receptor (AhR) is a soluble ligand-dependent DNA regulatory protein that mediates many of the biological responses to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) and related chemicals. In the absence of ligand, the cytosolic form of the AhR is found complexed with at least two molecules of hsp90, a heat shock protein of 90 kDa. In addition to its role in AhR protein folding and ability to repress the inherent nuclear localization, dimerization, and DNA binding activity of the AhR, it has been reported that hsp90 is absolutely required for maintaining the AhR in its high-affinity ligand binding conformation. The ability of high salt conditions (0. 4 M KCl) to dissociate the multimeric AhR complex into its monomeric form provides us with an avenue to examine the role of hsp90 in AhR ligand binding activity. In contrast to previous reports, we demonstrate that salt-dissociated "hsp90-free" AhR from several species still retains the ability to specifically bind ligand ([3H]TCDD). Although partial inactivation of ligand binding of salt-dissociated rat hepatic AhR was observed (to a maximum of 50% of total AhR binding), the presence of bound ligand protected against this inactivation. Little or no inactivation of the ligand binding ability of salt-dissociated guinea pig or rabbit AhR occurred. Our results not only indicate a significant species-difference in AhR ligand binding stability and/or activity, but also demonstrate that AhR ligand binding activity does not absolutely require the presence of receptor-bound hsp90.

Nutrition in the critically ill

When indicated, artificial feeding in critically ill patients should be instituted as early and as simply as possible. If feasible, enteral feeding is preferable but a period of intravenous nutrition is usually necessary in the critically ill. A compounded feed, administered via a sterile single lumen subclavian catheter is recommended. The volume and electrolyte composition are centrally important. High nitrogen and relatively low caloric intake are more likely requirements in stressed patients. The most important supplements are water soluble vitamins (including folate) and the trace element zinc. Safe practice requires a system of monitoring and awareness of potential complications.

Oral rehydration therapy: a Third World solution applied to intensive care

Oral rehydration therapy (ORT)--World Health Organisation formula--has reduced the mortality of severe diarrhoea tenfold but its use in Intensive Care has not been reported. ORT was administered via a nasogastric tube to 3 adult intensive care patients who developed severe diarrhoea and post-operative acute renal impairment. The median intake of ORT was 2.21/day (range 1.5-3.0) and the mean duration of therapy was 7 days (range 6-10). Renal function improved (creatinine fell from 389 to 165 mmol/l) and both haemodynamic and metabolic stability (Na, K, Mg, PO4 and urea) were maintained. While it may not reduce the volume of diarrhoea, ORT provides a cheap, effective and physiological solution to severe gastrointestinal losses in intensive care and may have wider application in both adult and paediatric practice.

A complication of cricothyroid "minitracheostomy"--oesophageal perforation

Two patients suffered perforation of the oesophagus during attempted placement of a cricothyroid minitracheostomy. We discuss the probable mechanisms and means of preventing such a recurrence.

Cerebral oedema and the fat embolism syndrome

A 19-year-old woman who sustained multiple trauma, but no head injury, developed the fat embolism syndrome. Her severe, fulminant and reversible neurological deterioration was associated with cerebral oedema. We suggest that cerebral oedema may contribute to the neurological deterioration in the fat embolism syndrome.

Hypokalaemic coma

A 55-year-old woman with renal tubular acidosis and urinary potassium wasting became comatose and subsequently fitted when her plasma potassium level fell to 0.9 mmol/l. Her neurological state resolved with potassium therapy. She had no other recognised cause for her coma. It appears that coma represents the extreme of the spectrum of neurological change that may occur in association with hypokalaemia.

Adult epiglottitis. Is there a role for the fiberoptic bronchoscope?

The "cherry red" laryngoscopic appearance of adult epiglottitis, as visualized through a fiberscope, is reproduced. The possible role of the fiberoptic bronchoscope, both as a diagnostic aid and as a means of facilitating endotracheal intubation, in this condition, is discussed.

A comparison of hyper- and isobaric solutions of bupivacaine for subarachnoid block

The comparative efficacy of two solutions of bupivacaine, 0.5% plain (isobaric-specific gravity 1.010), and 0.4% bupivacaine (hyperbaric-specific gravity 1.027) in 4% dextrose, for spinal anaesthesia was studied in 67 patients. Both solutions were clinically satisfactory (94% completely successful neural blockade). Hyperbaric bupivacaine blocks a greater number of spinal segments (p less than 0.01), causes a more rapid fall in blood pressure (p less than 0.05), and is more predictable in effect with regard to the number of segments blocked and to the lateralisation of the block. The duration of perioperative analgesia with the hyperbaric preparation is, however, shorter-3.8 hours as opposed to 5.8 hours (p less than 0.01)--but this was likely to be due to the smaller total dosage of bupivacaine used in the hyperbaric group. It is concluded that either solution may be used satisfactorily in clinical practice. The isobaric solution, however, despite its ready availability, is less satisfactory than the hyperbaric because its effect with regard to the extent of blockade is less predictable.