Barotrauma

Barotrauma is pressure-induced injury. The application of direct pressure to the body may cause trauma, including positive pressure from artificial ventilation. Trauma may also be caused by the effects of pressure changes on gas-containing body spaces, not in communication with the environment. This can include the external ear, the middle ear (and, indirectly, the inner ear), the para-nasal sinuses, the lungs, the gut, and abscess cavities (for example, in the teeth). Gas may penetrate tissues adjoining the affected space (such as the anterior cranial fossa, via the ethmoid sinus), or may embolise via the blood stream. The most severe expression of this is cerebral arterial gas embolism, which may present as a stroke. The management of these problems includes prevention, the use of pressure-equalizing techniques, vasoconstrictor drugs, surgery, and hyperbaric oxygen therapy.

Inpatient management of diabetes: survey in a tertiary care centre

AIMS

Good glycaemic control in hospitalised patients with diabetes mellitus improves wellbeing and aids recovery. This survey aimed to: (1) assess glycaemic control in patients with diabetes admitted to hospital for reasons other than diabetes, (2) compare the glycaemic control in patients treated in medical and surgical units, and (3) see the impact of specialists' input on glycaemic control.

METHODS

The first 150 patients admitted to hospital were identified; those with acute metabolic complications of diabetes mellitus, acute myocardial infarction, pregestational or gestational diabetes, and patients in different intensive care units were excluded. Case notes were reviewed with particular attention to glycaemic control, frequency of blood monitoring, complications, and the actions taken to improve glycaemic control.

RESULTS

Four of the 150 patients died in hospital. When subcutaneous insulin was used glycaemic control was good in 48%, suboptimal in 15%, and poor in 37% of patients. The results were not significantly different with subcutaneous or intravenous insulin. There was also no difference in glycaemic control among medical and surgical patients. Patients managed by designated specialists had better control than those managed by physicians (p<0.001). Hypoglycaemia was documented in 20% and two patients developed non-ketotic hyperosmolar coma while in hospital. In a few cases treatment at discharge was not changed despite poor control while in hospital.

CONCLUSION

More attention should be given to improving glycaemic control in patients hospitalised for reasons other than diabetes. Particular care should be taken to modify the dose of insulin needed to get good glycaemic control; control was better with specialists' input. A follow up survey will be conducted.

Human neural stem cells: a new tool for studying cortical development in Down's syndrome

The clinical characteristics of Down's syndrome (DS), or trisomy 21, are caused by errors that occur during development. In addition to mental retardation, DS individuals have craniofacial abnormalities, clinical defects of the heart, gut and immune system, as well as predisposition to certain diseases, such as leukemias and Alzheimer's disease. To explain the developmental mechanisms that cause these traits, it is necessary to look at how developmental processes in DS compare to normal development. The neurological characteristics of DS are established during the prenatal and early postnatal period in humans, when the bulk of brain development occurs. Mouse models of DS have provided a useful way of studying DS neural development. However, there are clearly significant differences between rodent and human biology that may not be reflected in mouse models. Recent advances in stem cell biology now allow the generation of human neural tissue in the culture dish (Ostenfeld & Svendsen 2003). Stem cells offer a novel model system to study alterations in neuron development in developmental disorders such as DS.

Oscillating laminar electrokinetic flow in infinitely extended rectangular microchannels

This paper has addressed analytically the problem of laminar flow in microchannels with rectangular cross-section subjected to a time-dependent sinusoidal pressure gradient and a sinusoidal electric field. The analytical solution has been determined based on the Debye-Hückel approximation of a low surface potential at the channel wall. We have demonstrated that Onsager's principle of reciprocity is valid for this problem. Parametric studies of streaming potential have shown the dependence of the electroviscous effect not only on the Debye length, but also on the oscillation frequency and the microchannel width. Parametric studies of electroosmosis demonstrate that the flow rate decreases due to an increase in frequency. The obtained solutions for both the streaming potential and electroosmotic flows become those for flow between two parallel plates in the limit of a large aspect ratio.

Oscillating laminar electrokinetic flow in infinitely extended circular microchannels

This article addresses the problem of oscillating laminar electrokinetic liquid flow in an infinitely extended circular microchannel. Based on the Debye-Huckel approximation for low surface potential at the channel wall, a complex variable approach is used to obtain an analytical solution for the flow. The complex counterparts of the flow rate and the current are linearly dependent on the pressure gradient and the external electric field. This property is used to show that Onsager's principle of reciprocity continues to be valid (involving the complex quantities) for the stated problem. During oscillating pressure-driven flow, the electroviscous effect for a given value of the normalized reciprocal electrical double-layer (EDL) thickness is observed to attain a maximum at a certain normalized frequency. In general, an increasing normalized frequency results in a reduction of EDL effects, leading to (i). a volumetric flow rate in the case of streaming potential approaching that predicted by the theory without EDL effects, and (ii). a reduction in the volumetric flow rate in the case of electroosmosis.

Magnification chromoendoscopy for the detection of intestinal metaplasia and dysplasia in Barrett's oesophagus

BACKGROUND

The presence of intestinal metaplasia (IM) in the columnar lined distal oesophagus defines Barrett's oesophagus with the risk of future malignant transformation. The distribution of both IM and dysplasia (low grade (LGD) and high grade (HGD)) within the columnar lined oesophagus is patchy and mosaic requiring random biopsies. Techniques that could help target areas of high yield within Barrett's mucosa would be helpful.

AIM

To study the utility of high magnification chromoendoscopy (MCE) in the detection of IM, LGD, and HGD in patients with Barrett's oesophagus.

METHODS

Consecutive patients detected with columnar mucosa in the distal oesophagus were studied using an Olympus magnification endoscope (GIF-Q16OZ, 115x). The distal oesophagus was sprayed with indigo carmine solution and the oesophageal columnar mucosa patterns were noted under high magnification and targeted for biopsy. All biopsies were read by pathologists blinded to the endoscopic findings.

RESULTS

Eighty patients with suspected Barrett's oesophagus (that is, columnar lined distal oesophagus) were studied: mean age 62.7 years (range 35-81). Mean length of columnar mucosa was 3.7 cm (range 0.5-17). Three types of mucosal patterns were noted within the columnar mucosa after spraying indigo carmine and using MCE: ridged/villous pattern, circular pattern, and irregular/distorted pattern. The yield of IM on target biopsies according to the patterns was: ridged/villous 57/62 (97%) and circular 2/12 (17%). Six patients had an irregular/distorted pattern and all had HGD on biopsy (6/6 (100%)). Eighteen patients had LGD on target biopsies; all had the ridged/villous pattern. All patients with long segment Barrett's were identified using MCE whereas 23/28 patients (82%) with short segment Barrett's had the ridged/villous pattern.

CONCLUSIONS

MCE helps visually identify areas with IM and HGD having specific patterns but not patients with LGD (appear similar to IM). MCE may be a useful clinical tool for the increased detection of patients with IM as well as for surveillance of patients for the detection of HGD. If these preliminary results are validated, MCE would help identify high yield areas, potentially eliminating the need for random biopsies.

In-patient management of diabetes mellitus and patient satisfaction

AIMS

To devise a system for assessing in-patient glycaemic control and care satisfaction in diabetic patients admitted to hospital for reasons other than their diabetes.

METHODS

Consecutive January to March 2001 case-notes were reviewed. Admissions with acute metabolic complications, acute myocardial infarction and pregestational or gestational diabetes were excluded. Glycaemic control, frequency of blood monitoring and management of hyperglycaemia were recorded. The diabetes treatment satisfaction questionnaire was used to assess preadmission satisfaction with care. Post-admission a 12-stem questionnaire was used to assess satisfaction with in-patient diabetes management.

RESULTS

Hypoglycaemia was common. Although none developed a hyperglycaemic emergency, high blood glucose was prevalent and, frequently, persistent hyperglycaemia or recurrent hypoglycaemia was not acted on appropriately. The overall score for in-patient satisfaction with treatment was fair (4.1 +/- 1.8 on a six-point scale; 6 = very satisfied and 1 = very dissatisfied). Scores were higher among patients on surgical wards than on medical wards (P = 0.008), but satisfaction did not vary when patients were stratified according to sex, age and mode of treatment.

CONCLUSION

Current systems are not achieving satisfactory in-patient glycaemic control and there is poor satisfaction with medical in-patient diabetes care. Following changes intended to produce improvements, this assessment system can be used recurrently to monitor in-patient care and satisfaction.

Measurement of the cosmic-ray antiproton-to-proton abundance ratio between 4 and 50 GeV

We present a new measurement of the antiproton-to-proton abundance ratio, pbar/p, in the cosmic radiation. The HEAT-pbar instrument, a balloon borne magnet spectrometer with precise rigidity and multiple energy loss measurement capability, was flown successfully in Spring 2000, at an average atmospheric depth of 7.2 g/cm(2). A total of 71 antiprotons were identified above the vertical geomagnetic cutoff rigidity of 4.2 GV. The highest measured proton energy was 81 GeV. We find that the pbar/p abundance ratio agrees with that expected from a purely secondary origin of antiprotons produced by primary protons with a standard soft energy spectrum.

Reduction in animal numbers by long-term implantation of intravenous and intra-arterial catheters in thyroparathyroidectomized rats

The thyroparathyroidectomized (TPTx) rat has been extensively used to study parathyroid hormone (PTH)-mediated bone resorption by measuring systemic Ca2+ concentrations. Animals have been traditionally used acutely; that is, they are often infused immediately after surgery and are sacrificed after a single use. To perform multiple experiments using a single group of animals we developed a system of long-term implanted intravenous/arterial catheters. Using calcitonin (CT) as a positive control, we successfully completed 12 separate controlled subexperiments documenting significant reductions in PTH-induced hypercalcemia in rats of the CT group. We then successfully completed two separate TPTx subexperiments, using a 3 x 3 Latin square experimental design. In both subexperiments, CT significantly inhibited the increase of blood Ca2+ concentration resulting from continuous PTH infusion. Our results indicate that, by combining the long-term use of catheters with the Latin square design, we can successfully reduce the number of animals used, increase the number of compounds screened, and improve the quality of the data. Although results of this study confirmed the acceptability of multiple infusions in anti-resorptive studies, investigations into the applicability of this set up to other areas of study requiring infusions and frequent blood sample collections seem appropriate.

Neurotrophins use the Erk5 pathway to mediate a retrograde survival response

Growth factors synthesized and released by target tissues promote survival and differentiation of innervating neurons. This retrograde signal begins when growth factors bind receptors at nerve terminals. Activated receptors are then endocytosed and transported through the axon to the cell body. Here we show that the mitogen-activated protein kinase (MAPK) signaling pathways used by neurotrophins during retrograde signaling differ from those used following direct stimulation of the cell soma. During retrograde signaling, endocytosed neurotrophin receptors (Trks) activate the extracellular signal-related protein kinase 5 (Erk5) pathway, leading to nuclear translocation of Erk5, phosphorylation of CREB, and enhanced neuronal survival. In contrast, Erk1/2, which mediates nuclear responses following direct cell body stimulation, does not transmit a retrograde signal. Thus, the Erk5 pathway has a unique function in retrograde signaling. Differential activation of distinct MAPK pathways may enable an individual growth factor to relay information that specifies the location and the nature of stimulation.

Potent and selective inhibition of human cathepsin K leads to inhibition of bone resorption in vivo in a nonhuman primate

Cathepsin K is a cysteine protease that plays an essential role in osteoclast-mediated degradation of the organic matrix of bone. Knockout of the enzyme in mice, as well as lack of functional enzyme in the human condition pycnodysostosis, results in osteopetrosis. These results suggests that inhibition of the human enzyme may provide protection from bone loss in states of elevated bone turnover, such as postmenopausal osteoporosis. To test this theory, we have produced a small molecule inhibitor of human cathepsin K, SB-357114, that potently and selectively inhibits this enzyme (Ki = 0.16 nM). This compound potently inhibited cathepsin activity in situ, in human osteoclasts (inhibitor concentration [IC]50 = 70 nM) as well as bone resorption mediated by human osteoclasts in vitro (IC50 = 29 nM). Using SB-357114, we evaluated the effect of inhibition of cathepsin K on bone resorption in vivo using a nonhuman primate model of postmenopausal bone loss in which the active form of cathepsin K is identical to the human orthologue. A gonadotropin-releasing hormone agonist (GnRHa) was used to render cynomolgus monkeys estrogen deficient, which led to an increase in bone turnover. Treatment with SB-357114 (12 mg/kg subcutaneously) resulted in a significant reduction in serum markers of bone resorption relative to untreated controls. The effect was observed 1.5 h after the first dose and was maintained for 24 h. After 5 days of dosing, the reductions in N-terminal telopeptides (NTx) and C-terminal telopeptides (CTx) of type I collagen were 61% and 67%, respectively. A decrease in serum osteocalcin of 22% was also observed. These data show that inhibition of cathepsin K results in a significant reduction of bone resorption in vivo and provide further evidence that this may be a viable approach to the treatment of postmenopausal osteoporosis.

A small protein-protein interaction domain common to KlcB and global regulators KorA and TrbA of promiscuous IncP plasmids

The kor regulon of broad host-range, incompatibility group P (IncP) plasmids uses the KorA, KorB, and KorC repressors to regulate expression of genes for replication, conjugation, segregation, and host range. One operon, kilC, encodes the KorC repressor and two genes of unknown function (klcA and klcB). The predicted sequences of the 51.1 kDa KlcB protein, the 11.3 kDa KorA repressor, and another small (13.5 kDa) regulatory protein, TrbA, show a highly related 35 amino acid residue segment (V-L-P domain). We found that induction of the klcB gene is toxic to Escherichia coli host cells harboring an IncP plasmid. We confirmed a model in which the V-L-P domain of KlcB interacts directly with the V-L-P domain of KorA to derepress KorA-regulated operons, thereby allowing expression of toxic genes. First, a lacZ reporter fused to the kleA promoter, which is regulated by KorA and KorC, revealed that klcB induction specifically releases KorA-repression but has no effect on KorC repression. Second, induced expression of the V-L-P domains from KorA or KlcB is sufficient to release KorA-repression at the kleA promoter. Third, purified GST-KlcB fusion protein interacts specifically with His-tagged KorA. Fourth, fusion of the V-L-P domains of KorA and TrbA and full-length KlcB polypeptide to the DNA-binding domain of bacteriophage lambda repressor leads to the formation of functional, dimeric repressors, and mutations that alter conserved residues of the V-L-P domain adversely affect dimerization. Fifth, crosslinking experiments demonstrated that the V-L-P domain of KorA is able to dimerize in solution and form heterodimers in mixtures with full-length KorA polypeptide. These findings show that the V-L-P domain is a protein-protein interaction module that is likely to be responsible for dimerization of KorA and TrbA, and important for KlcB dimerization. We speculate on the possible significance of KlcB-KorA heterodimers in IncP plasmid maintenance.