Regulation of mitogen-activated protein kinases in cardiac myocytes through the small G protein Rac1

Small guanine nucleotide-binding proteins of the Ras and Rho (Rac, Cdc42, and Rho) families have been implicated in cardiac myocyte hypertrophy, and this may involve the extracellular signal-related kinase (ERK), c-Jun N-terminal kinase (JNK), and/or p38 mitogen-activated protein kinase (MAPK) cascades. In other systems, Rac and Cdc42 have been particularly implicated in the activation of JNKs and p38-MAPKs. We examined the activation of Rho family small G proteins and the regulation of MAPKs through Rac1 in cardiac myocytes. Endothelin 1 and phenylephrine (both hypertrophic agonists) induced rapid activation of endogenous Rac1, and endothelin 1 also promoted significant activation of RhoA. Toxin B (which inactivates Rho family proteins) attenuated the activation of JNKs by hyperosmotic shock or endothelin 1 but had no effect on p38-MAPK activation. Toxin B also inhibited the activation of the ERK cascade by these stimuli. In transfection experiments, dominant-negative N17Rac1 inhibited activation of ERK by endothelin 1, whereas activated V12Rac1 cooperated with c-Raf to activate ERK. Rac1 may stimulate the ERK cascade either by promoting the phosphorylation of c-Raf or by increasing MEK1 and/or -2 association with c-Raf to facilitate MEK1 and/or -2 activation. In cardiac myocytes, toxin B attenuated c-Raf(Ser-338) phosphorylation (50 to 70% inhibition), but this had no effect on c-Raf activity. However, toxin B decreased both the association of MEK1 and/or -2 with c-Raf and c-Raf-associated ERK-activating activity. V12Rac1 cooperated with c-Raf to increase expression of atrial natriuretic factor (ANF), whereas N17Rac1 inhibited endothelin 1-stimulated ANF expression, indicating that the synergy between Rac1 and c-Raf is potentially physiologically important. We conclude that activation of Rac1 by hypertrophic stimuli contributes to the hypertrophic response by modulating the ERK and/or possibly the JNK (but not the p38-MAPK) cascades.

Radiation protection consequences of the care of a terminally ill patient having received a thyroid ablation dose of 131I-sodium iodide

The death of a patient soon after an ablation dose of 131I-sodium iodide is a rare occurrence. We report a case of a patient who died, following emergency surgery to treat gastric bleeding, whilst still radioactive. The doses received by clinical staff involved in management of the patient were measured and were found to be within acceptable limits. However, there was an appreciable level of unsealed radioactivity in the Intensive Care Unit. The issues raised by this case are discussed in the context of legislative requirements and the worst case scenario. The event highlights the need for close liaison between the different specialities to ensure that clinical staff are properly advised and that necessary safety precautions are taken to avoid compromising the safety of staff or the care of the patient.

Angiogenesis in necrotic ulcers treated with hyperbaric oxygen

Necrotic/gangrenous wounds lack adequate blood supply and develop further vascular damage from either reperfusion injury or oxygen toxicity when exposed to oxygen at the wrong pressures. A prospective randomized study was performed to confirm the efficacy of topical hyperbaric oxygen at 1.004 to 1.013 atmospheres (THOT) in stimulating angiogenesis and healing of necrotic/gangrenous wounds. Participants included 40 inpatients (79 ulcers) recruited over 12 months who were assigned to treatment by either THOT or standard wound care (SWC). The results showed that 90% of the wounds healed in the THOT group compared to 22% in the SWC controls. Repeated measures ANOVA on log (ulcer size at 4 weeks) showed a significant group by time interaction, F(1,55) = 68.2, P < 0.0001. The size of ulcers (at 4 weeks) was significantly smaller with THOT, but larger with SWC. Capillary density/hpf (high power field) was significantly higher in THOT wounds than in SWC wounds (P < 0.001). It was concluded that THOT is effective in stimulating angiogenesis with enhanced healing of necrotic wounds.

Hippocampal volume and everyday memory in children of very low birth weight

Children born preterm and of very low birth weight have an increased incidence of learning difficulties, but little is known about the specific nature of their cognitive deficits and the underlying neuropathology. We hypothesized that their vulnerability to hypoxic, metabolic, and nutritional insults would lead to reduced hippocampal volumes and to deficits in memory because of the role of the hippocampus in this domain of cognition. Neuropsychological and magnetic resonance imaging methods were used to investigate this hypothesis in adolescents born preterm (< or = 30 wk gestation, n = 11) or full-term (n = 8). The preterm group had significantly smaller hippocampal volumes bilaterally, despite equivalent head size, and showed specific deficits in certain aspects of everyday memory, both on objective testing and as indicated by parental questionnaires. The preterm group also had a specific deficit in numeracy. The reduced hippocampal volumes and deficits in everyday memory have previously been unrecognized, but their prevalence in a group of neurologically normal children is striking.

PI-3-kinase is an essential anti-apoptotic effector in the proliferative response of primary human epithelial cells to mutant RAS

In contrast to its growth-inhibitory effect on primary mesenchymal cells, RAS oncogene activation induces a proliferative phenotype in normal human thyroid epithelial cells in vitro, consistent with its putative role in tumour initiation. Using this model, we previously showed that activation of the MAP kinase (MAPK) pathway is necessary, but not sufficient for the proliferative response to mutant (V12) H-RAS. Here we extend this work to show that another major RAS effector-- phosphatidylinositol-3-kinase (PI-3-K)--while also insufficient alone, is able to synergize with MAPK activation to mimic the effect of mutant RAS, albeit at reduced efficiency. Furthermore we show that PI-3-K is an absolute requirement for the proliferative response to RAS in these cells, acting via suppression of RAS-induced apoptosis. These data extend our understanding of RAS signalling in a clinically-relevant cell context and point to the use of PI-3-K inhibitors as potential therapeutic agents for targetting human cancers induced by RAS mutation.

Epidemiology and molecular typing of an outbreak of tuberculosis in a hostel for homeless men

AIM

To investigate a possible outbreak of tuberculosis in a hostel for homeless men using IS6110 profiling, a polymerase chain reaction (PCR) based fingerprinting technique.

METHODS

Eight cases of tuberculosis were diagnosed in residents of the hostel over a period of 28 months. To provide epidemiological data, a heminested inverse PCR (HIP) assay targeting the insertion sequence IS6110 together with its upstream flanking region was used to fingerprint the eight isolates of M tuberculosis under investigation.

RESULTS

The HIP technique gave IS6110 profiles which showed that while three isolates were clearly distinct, the remaining five strains were indistinguishable, suggesting the latter were representatives of a single outbreak strain.

CONCLUSIONS

The HIP assay proved discriminatory and facilitated repeated testing for the direct comparison of strains as more patients presented over the protracted course of this outbreak.

How do small GTPase signal transduction pathways regulate cell cycle entry?

A variety of studies have shown that activation of the cell cycle machinery requires the participation of multiple signalling pathways. These pathways include Ras-dependent effectors such as the extracellular-signal related kinases, otherwise known as mitogen-activated protein kinases (ERKs, MAPKs), phosphatidylinositol 3 (PI3)-kinase and p21Ral pathways, as well as other signalling pathways regulated by the small GTPases p21Rho, p21Rac and p21Cdc42.

Emergency physicians versus laboratory technicians: are the urinalysis and microscopy results comparable? A pilot study

In the literature to date, there are no studies that directly evaluate microscopic urine examination results obtained by a physician compared to those of a trained laboratory technician. Our purpose in undertaking this study was to determine whether there would be comparable results obtained by these two groups. The study took place in an Emergency Medicine Department with 45,000 visits annually. Each urine sample obtained on patients presenting to the Emergency Department was divided into two lots: one was sent to the laboratory and the other was analyzed by the emergency physician. A comparison of both dipstick and microscopic results by physician and laboratory staff was then made using sensitivity, specificity, and Kappa analysis. Statistical analysis of the data revealed close agreement between the emergency physician and laboratory technician with respect to the following components of urinalysis: red blood cell urinalysis and microscopy, leukocyte esterase, and nitrite testing. Microscopy for white cells and bacteria and testing for proteinuria were not in close agreement. Urinalysis by emergency physicians is comparable to laboratory technicians for a number of the testing components. However, in this limited pilot study, emergency physicians were not able to consistently perform urinalysis for the laboratory standard.

Endothelin-1 is elevated in monocrotaline pulmonary hypertension

These studies document striking pulmonary vasoconstrictor response to nitric oxide synthase (NOS) inhibition in monocrotaline (MCT) pulmonary hypertension in rats. This constriction is caused by elevated endothelin (ET)-1 production acting on ETA receptors. Isolated, red blood cell plus buffer-perfused lungs from rats were studied 3 wk after MCT (60 mg/kg) or saline injection. MCT-injected rats developed pulmonary hypertension, right ventricular hypertrophy, and heightened pulmonary vasoconstriction to ANG II and the NOS inhibitor NG-monomethyl-L-arginine (L-NMMA). In MCT-injected lungs, the magnitude of the pulmonary pressor response to NOS inhibition correlated strongly with the extent of pulmonary hypertension. Pretreatment of isolated MCT-injected lungs with combined ETA (BQ-123) plus ETB (BQ-788) antagonists or ETA antagonist alone prevented the L-NMMA-induced constriction. Addition of ETA antagonist reversed established L-NMMA-induced constriction; ETB antagonist did not. ET-1 concentrations were elevated in MCT-injected lung perfusate compared with sham-injected lung perfusate, but ET-1 levels did not differ before and after NOS inhibition. NOS inhibition enhanced hypoxic pulmonary vasoconstriction in both sham- and MCT-injected lungs, but the enhancement was greater in MCT-injected lungs. Results suggest that in MCT pulmonary hypertension, elevated endogenous ET-1 production acting through ETA receptors causes pulmonary vasoconstriction that is normally masked by endogenous NO production.

Collaborative prototyping approaches for ICU decision aid design

When computer-based aids do not support the human users' decision-making strategies or anticipate the organizational impacts of technological change, advances in information technology may degrade rather than enhance decision-making performance. Such failures suggest the design of human-computer cooperation for problem solving and decision-making must be driven by human cognitive and organizational process requirements rather than computer technology. Decision- and user-centered development techniques involve domain experts and end-users in the earliest phases of design to evolve an understanding of requirements through iterative prototyping. This paper presents a collaborative approach to cognitive systems engineering applied to developing a clinical aid to assist respiratory care in the surgical ICU.

Evaluation of a protocol for the non-operative management of perforated peptic ulcer

BACKGROUND

The non-operative management of perforated peptic ulcer has previously been shown to be both safe and effective although it remains controversial. A protocol for non-operative management was set up in this hospital in 1989. Adherence to the guidelines in the protocol has been audited over a 6-year period with a review of outcome.

METHODS

The case-notes of patients with a diagnosis of perforated peptic ulcer were reviewed. Twelve guidelines from the protocol were selected for evaluation of compliance to the protocol.

RESULTS

Forty-nine patients underwent non-operative treatment initially. Eight patients failed to respond and underwent operation. Complications included abscess formation (seven patients), renal failure (one), gastric ileus (one), chest infection (two), and cardiac failure and stroke (one). Four deaths occurred in this group. Adherence to certain protocol guidelines was poor, notably those concerning prevention of thromboembolism, use of antibiotics, use of contrast examination to confirm the diagnosis and referral for follow-up endoscopy. Two gastric cancers were detected on subsequent endoscopy.

CONCLUSION

This experience demonstrates that non-operative treatment can be used successfully in a general hospital. Adherence to protocol guidelines was found to be variable and the protocol has therefore been simplified. This study highlights the need for an accurate diagnosis and the importance of follow-up endoscopy.

Role of wall tension in hypoxic responses of isolated rat pulmonary arteries

The changes in force developed during 40-min exposures to hypoxia (37 +/- 1 mmHg) were recorded in large (0.84 +/- 0.02-mm-diameter) and small (0.39 +/- 0.01-mm-diameter) intrapulmonary arteries during combinations of mechanical wall stretch tensions (passive + active myogenic components), equivalent to transmural vascular pressures of 5, 15, 30, 50, and 100 mmHg, and active (vasoconstriction) tensions, stimulated by PGF2alpha in doses of 0, 25, 50, and 75% effective concentrations. Constriction was observed in all arteries during the first minute; however, at any active tension, the pattern of the subsequent response was a function of the stretch tension. At 5, 15, and 30 mmHg, the constriction decreased slightly at 5 min and then increased again to remain constrictor throughout. At 50 and 100 mmHg, the initial constriction was followed by persistent dilation. Hypoxic constrictor responses, most resembling those observed in lungs in vivo and in vitro, were observed when the mechanical stretch wall tension was equivalent to 15 or 30 mmHg and the dose of PGF2alpha was 25 or 50% effective concentration. These observations reconcile many apparently contradictory results reported previously.

Glycopeptide-induced vasculitis--cross-reactivity between vancomycin and teicoplanin

Teicoplanin has been suggested for use in patients suffering complications from vancomycin. We describe two patients who developed a vasculitic rash whilst on vancomycin with recrudescence of the rash with subsequent teicoplanin therapy.

Single- versus multiple-dose antimicrobial prophylaxis for major surgery: a systematic review

BACKGROUND

Single-dose antimicrobial prophylaxis for major surgery is a widely accepted principle; recommendations have been based on laboratory studies and numerous clinical trials published in the last 25 years. In practice, single-dose prophylaxis has not been universally accepted and multiple-dose regimens are still used in some centres. Moreover, the principle has recently been challenged by the results of an Australian study of vascular surgery. The aim of this current systematic review is to determine the overall efficacy of single versus multiple-dose antimicrobial prophylaxis for major surgery and across surgical disciplines.

METHODS

Relevant studies were identified in the medical literature using the MEDLINE database and other search strategies. Trials included in the review were prospective and randomized, had the same antimicrobial in each treatment arm and were published in English. Rates of postoperative surgical site infections (SSI) were extracted, 2 x 2 tables prepared and odds ratios (OR) [with 95% confidence intervals (95% CI)] calculated. Data were then combined using fixed and random effects models to provide an overall figure. In this context, a high value for the combined OR, with 95% CI > 1.0, indicates superiority of multiple-dose regimens and a low OR, with 95% CI < 1.0, suggests the opposite. A combined OR close to 1.0, with narrow 95% CI straddling 1.0, indicates no clear advantage of one regimen over another. Further subgroup analyses were also performed.

RESULTS

Combined OR by both fixed (1.06, 95% CI, 0.89-1.25) and random effects (1.04, 95% CI, 0.86-1.25) models indicated no clear advantage of either single or multiple-dose regimens in preventing SSI. Likewise, subgroup analysis showed no statistically significant differences associated with type of antimicrobial used (beta-lactam vs other), blinded wound assessment, length of the multiple-dose arm (> 24 h vs 24 h or less) or type of surgery (obstetric and gynaecological vs other).

CONCLUSIONS

Continued use of single-dose antimicrobial prophylaxis for major surgery is recommended. Further studies are required, especially in previously neglected surgical disciplines.