Dislocation of the polyethylene liner in hip arthroplasty: 6 patients with dislocation within 3 years

We revised 6 patients with early destruction of the liner in a cementless press-fit acetabular cup. They had no signs of infection or evidence of trauma. The failures were probably due to rotation of the liner inside the metal shell and destruction of the polyethylene by the cutting edge of the metal. This early complication may be difficult to diagnose because of normal radiographs. We suggest that the manufacturer should provide the insert with a metal marker to make this complication easier to detect.     

Ionic radiocontrast media disrupt intercellular contacts via an extracellular calcium-independent mechanism

Direct cytotoxic effects of radiocontrast (RC) agents have been implicated in radiocontrast nephropathy (RCIN). The interaction between extracellular calcium, which plays a central role in intercellular contacts, and the in vitro toxicity of RC was tested in Madin-Darby canine kidney (MDCK) cell monolayers grown on permeable supports. Cell viability was determined by trypan blue exclusion. The function of intercellular junctions was assessed by measuring the electrical transmonolayer resistance (TMR). The cell contacts were examined with indirect immunofluorescence microscopy using antibodies against the junctional proteins E-cadherin, ZO-1 and occludin. The ionic RC agents diatrizoate and ioxaglate (74 mg iodine/ml), but not the nonionic compounds iohexol or iodixanol, decreased ionized calcium (Ca2+) in the incubation media from 1.48 +/- 0.04 mM (control) to 0.89 +/- 0.06 mM (diatrizoate), respectively to 1.05 +/- 0.08 mM (ioxaglate). Diatrizoate, and to a lesser extent ioxaglate, reduced the number of viable MDCK cells and showed a redistribution of the E-cadherin, ZO-1 and occludin immunofluorescence signal with a parallel decrease of the TMR indicating an impaired monolayer integrity. A similar reduction of extracellular Ca2+ through EGTA failed to reproduce these effects. Conversely, raising Ca2+ in diatrizoate-containing media to control levels did not abrogate its toxicity. In conclusion, the ionic RC agents diatrizoate and ioxaglate, but not the nonionic compounds iohexol or iodixanol, reduce extracellular Ca2+ in vitro. However, this reduction of Ca2+ does not explain their cytotoxic effects which could contribute to the pathogenesis of RCIN in vivo by opening intercellular junctions.     

Glomerular endothelial fenestrae in vivo are not formed from caveolae

Previous reports indicate that endothelial fenestrae in vitro can form by fusion of caveolae or caveolae-like vesicles. The principal aim of this study was to determine whether formation of glomerular endothelial cell fenestrae in vivo similarly involves caveolae and caveolin-1. Whereas caveolin-1 immunofluorescence was found around the circumference of human and mouse glomerular capillary loops, it co-localized only partially with the endothelium-specific lectin Ulex Europaeus I in human glomeruli, leaving portions of the endothelium devoid of caveolin-1. Immunogold electron microscopy, used to definitively localize caveolin-1 in glomeruli, showed that caveolin-1 was completely excluded from the fenestrated portion of the endothelium. Moreover, in caveolin-1-deficient mice, which cannot form caveolae, the ultrastructure of glomerular endothelial fenestrae appeared entirely normal. Interestingly, strong caveolin-1 immunogold labeling was observed in podocytes, where some caveolin-1 localized to filtration slits. Caveolin-1 co-immunoprecipitated with the podocyte slit diaphragm proteins nephrin and CD2AP, and dual immunofluorescence confirmed co-localization of caveolin-1 and nephrin. Nevertheless, in caveolin-1-deficient mice, podocyte ultrastructure appeared normal, and the podocyte proteins synaptopodin, nephrin, and podocin were expressed normally. In addition, blood urea nitrogen concentrations and urinary protein excretion in these mice were similar to those in wild-type mice. Thus, unlike caveolae formation, glomerular endothelial cell fenestrae formation in vivo does not require caveolin-1, ruling out the previous hypothesis that endothelial fenestrae represent fused caveolae, at least for glomerular endothelial cells. Localization of caveolin-1 to podocytes and their filtration slits is consistent with the view that the filtration slit plasma membrane represents a type of lipid raft microdomain.     

Assessment of cardiac output,intravascular volume status,and extravascular lung water by transpulmonary indicator dilution in critically ill neonates and infants

OBJECTIVE: To assess cardiac output, intrathoracic blood volume, global end-diastolic volume, and extravascular lung water in critically ill neonates and small infants using transpulmonary indicator dilution. DESIGN: Prospective, observational, clinical study. SETTING: Pediatric intensive care unit in a university hospital. PARTICIPANTS: Critically ill neonates and small infants suffering from severe heart failure, respiratory failure, or sepsis (n = 10). INTERVENTIONS: A total of 194 transpulmonary indicator dilution measurements were done. Global end-diastolic volume, intrathoracic blood volume, and stroke volume were measured and compared with standard hemodynamic parameters during the clinical course and before and after volume loading (16 +/- 3.7 mL/kg of 10% albumin solution) in 8 of 10 patients. MEASUREMENTS AND MAIN RESULTS: A positive correlation was found for stroke volume index versus global end-diastolic volume (r = 0.76, p < 0.001) and intrathoracic blood volume (r = 0.56, p < 0.001). In contrast, no correlation was observed for stroke volume index versus central venous pressure. Volume loading resulted in significant increases in stroke volume index (p < 0.01), global end-diastolic volume (p < 0.01), and intrathoracic blood volume (p < 0.01); whereas central venous pressure, heart rate, mean arterial pressure, and extravascular lung water remained unchanged. CONCLUSION: Transpulmonary indicator dilution enables measurement of cardiac output and intravascular volume status in critically ill neonates and infants at the bedside. The effects of volume loading on cardiac preload and effective change in stroke volume can be monitored by this technique, whereas central venous pressure was not indicative of changes in intravascular volume status.     

Severe head trauma in children: cranial computer tomography and clinical consequences

BACKGROUND: We investigated the prognostic and therapeutic implications of cranial computerized tomography (CCT) examinations after severe head trauma in children. MATERIALS AND METHODS: The CCT scans from 248 children (aged 0.1-14 years) during the course of treatment after severe head trauma were assessed. The initial CCT findings, the frequency of CCT examinations and the schedule as well as duration of treatment were registered. The neurological outcome was examined both 1 month and 1 year after the trauma. RESULTS: Approximately one-third (29%) of the children who suffered from severe head trauma showed no changes in the CCT. Furthermore, 40.3% of the children showed a singular finding in the CCT, whereas 30.6% of all children had a combined injury pattern. One year after trauma, we found no impairment of consciousness in children without pathological CCT findings, as well as in cases with isolated epidural and subdural haemorrhage. Children with massive generalized brain oedema had the poorest prognosis (37% died, 25% had impairment of consciousness). The outcome of children with parenchymal and ventricular bleeding was also unfavourable (23.1% and 33.3% neurological findings). Patients with focal oedema likewise had impairment of consciousness. An average number of 3.0 CCT per child was performed but numbers in single cases varied greatly (1-13 scans per individual). CONCLUSIONS: The initial CCT was of importance regarding further therapy, especially for children in need of surgical treatment. In the other cases, there was no direct impact from CCT findings on treatment procedures in the paediatric intensive care unit. The initial CCT was related to the prognosis, which can be poor even if there are only minimal changes in CCT, such as focal oedema or isolated ventricular bleeding.     

Physiological Effects of an Ultra-Cycle Ride in an Amateur Athlete - A Case Report

The physiological effects of ultraendurance exercise are poorly investigated. The present case report describes the exercise intensity of ultraendurance cycling and its physiological impacts on various organ functions in an amateur cyclist performing the Ötztal Radmarathon twice en bloque in a circuit of 2 identical laps (distance 460 km; cumulative altitude difference 11,000 m). In a pre-race laboratory test the athlete''s performance capacity was measured as the maximal aerobic power (VO_2max= 70 ml.kg^-1.min^-1), a maximal power output (5.7 W.kg^-1) and lactate threshold of 89%. The overall intensity during the ride was moderate (HR_mean = 131 b.min^-1; %HR_max = 0.71) and significantly declined during the course of the race. Extensive biochemical laboratory testing performed pre- and post-race excluded major exercise-induced organ disturbances. For further confirmation and better understanding of the physiological effects of ultra-cycle events future studies of larger athlete populations are required.Key Words: Ultraendurance event, exercise intensity, heart rate, organ functions, cycling     

Modulation of human motor cortex excitability by single doses of amantadine.

Amantadine-sulfate has been used for several decades to treat acute influenza A, Parkinson's disease (PD), and acute or chronic drug-induced dyskinesia. Several mechanisms of actions detected in vivo/in vitro including N-methyl-D-aspartate (NMDA)-receptor antagonism, blockage of potassium channels, dopamine receptor agonism, enhancement of noradrenergic release, and anticholinergic effects have been described. We used transcranial magnetic stimulation (TMS) to evaluate the effect of single doses of amantadine on human motor cortex excitability in normal subjects. Using a double-blind, placebo-controlled, crossover study design, motor thresholds, recruitment curves, cortical stimulation-induced silent period (CSP), short intracortical inhibition (ICI), intracortical facilitation (ICF), and late inhibition (L-ICI) in 14 healthy subjects were investigated after oral doses of 50 and 100 mg amantadine with single and paired pulse TMS paradigms. Spinal cord excitability was investigated by distal latencies and M-amplitudes of the abductor digiti minimi muscle. After intake of amantadine, a significant dose-dependent decrease of ICF was noticed as well as a significant increase of L-ICI as compared to placebo. The effect on ICF and L-ICI significantly correlated with amantadine serum levels. ICI was slightly increased after amantadine intake, but the effect failed to be significant. Furthermore, amantadine had no significant effects on motor thresholds, MEP recruitment curves, CSP, or peripheral excitability. In conclusion, a low dose of amantadine is sufficient in modulating human motor cortex excitability. The decrease of ICF and increase of L-ICI may reflect glutamatergic modulation or a polysynaptic interaction of glutamatergic and GABA-ergic circuits. Although amantadine has several mechanisms of action, the NMDA-receptor antagonism seems to be the most relevant effect on cortical excitability. As L-ICI can be influenced by this type of drug, it may be an interesting parameter for studies of motor learning and use-dependent plasticity.     

The distribution pattern of radioactivity across different tissues in quantitative whole-body autoradiography (QWBA) studies.

This study explored whether common rules exist for the distribution patterns across tissues in tissue distribution studies. To investigate this we tested whether tissue:plasma partition coefficients (PCs) of radioactivity are correlated with muscle:plasma PCs. The relationships between PCs of radioactivity in muscle and those in other tissues were investigated in 25 tissues for 20 structurally unrelated drug candidates. Tissue distribution data were obtained by quantitative whole-body autoradiography. Linear regression analysis was performed for each tissue. Radioactivity from basic and acidic/neutral compounds was analyzed separately. Results for acidic/neutral compounds: for the majority of the tissues investigated, the tissue:plasma PCs were well correlated with muscle:plasma PCs (R2 > 0.7). Correlations were worse (R2 < 0.7) in blood, white fat, excretory organs and tissues protected by a penetration barrier (e.g. brain). Slope factors for the regression ranged from 0.2 (blood) to 3.8 (Harderian gland) and were correlated with neutral lipid contents in tissues. Results for basic compounds: in most tissues, slope factors appeared to be higher than for acidic/neutral compounds. Correlations, however, were poorer than for acidic/neutral compounds. Overall, the present study demonstrates that muscle:plasma PCs are indicative of the overall tissue distribution of drug-related material, as they are well correlated with tissue:plasma PCs in most other tissues. Correlations for acidic/neutral compounds differ from those for basic compounds. The found PC relationships provide an explanation for the distribution pattern across tissues usually seen in tissue distribution studies.