Design and Application of Compliant Mechanisms for Surgical Tools

This paper introduces the benefits of exploiting elasticity in the engineering design of surgical tools, in general, and of minimally invasive procedures, in particular. Compliant mechanisms are jointless mechanisms that rely on elastic deformation to transmit forces and motion. The lack of traditional joints in these single-piece flexible structures offers many benefits, including the absence of wear debris, pinch points, crevices, and lubrication. Such systems are particularly amenable to embedded sensing for haptic feedback and embedded actuation with active-material actuators. The paper provides an overview of design synthesis methods developed at the Compliant Systems Design Laboratory and focuses specifically on surgical applications. Compliant systems have potential to integrate well within the constraints of laparoscopic procedures and telerobotic surgery. A load-path representation is used within a genetic algorithm to solve two gripper example problems. In addition, the paper illustrates the design and construction of an organ (kidney) manipulator for use in minimally invasive procedures.

Novel mechanism of anomalous electron heat conductivity and thermal crashes during Alfvénic activity in the Wendelstein 7-AS stellarator

Enhanced plasma heat conductivity in the presence of kinetic Alfvén waves (KAW) is predicted theoretically. The enhancement is shown to be strongest when the electron collision frequency exceeds the particle transit frequency in the wave field. Alfvén waves (both KAW and ideal MHD Alfvén eigenmodes generating the KAW) are studied in a shot of the Wendelstein 7-AS stellarator. On the basis of these results, strong thermal crashes observed during bursting Alfvénic activity in the mentioned shot are explained.

[Esophageal stents]

The method of oesophageal stents application using a surgical procedure via gastrotomy for otherwise surgically unmanageable malignant stenoses of the oesophagus and the gastric cardia, has been used for several decades. Once the self-expandible endoprostheses, applied under either the endoscopical or radiological (RTG) control, or both, and following a change in the oesophageal malignities treatment strategy, the spectrum of indication groups of the patients, who would undergo the stent implantation, have enlarged. Recently, thank to the endoscopically removable endoprostheses, the authors broaden the spectrum of use to benign findings of the oesophageus and the gastric cardia (strictures, perforations, insuficiency of anastomoses), as well. In their work, the authors present a group of patients who have had the oesophageal stent, using the endoscopic method, implanted at the Surgical Clinic of the Faculty Hospital in Plzen since 1992.

Evaluation of disinfectant efficacy against biofilm and suspended bacteria in a laboratory swimming pool model

Laboratory reactor systems designed to model specific environments enable researchers to explore environmental dynamics in a more controlled manner. This paper describes the design and operation of a reactor system built to model a swimming pool in the laboratory. The model included relevant engineering parameters such as filter loading and turn-overs per day. The water chemistry in the system's bulk water was balanced according to standard recommendations and the system was challenged with a bacterial load and synthetic bather insult, formulated to represent urine and perspiration. The laboratory model was then used to evaluate the efficacy of six chemical treatments against biofilm and planktonic bacteria. Results showed that the biofilm was able to accumulate on coupons and in the filter systems of reactors treated with either 1-3 mg/L free chlorine or 10 mg/L polyhexamethylene biguanide (PHMB). All the treatments tested resulted in at least a 4 log reduction in biofilm density when compared to the control, but shock treatments were the most effective at controlling biofilm accumulation. A once weekly shock dose of 10 mg/L free chlorine resulted in the greatest log reduction in biofilm density. The research demonstrated the importance of studying a biofilm in addition to the planktonic bacteria to assess the microbial dynamics that exist in a swimming pool model.

Oxidative stress in HIV demented patients and protection ex vivo with novel antioxidants

OBJECTIVE

To determine the role of oxidative stress in mediating HIV dementia and to identify novel therapeutic compounds that may block this oxidative stress.

METHODS

Brain tissue from patients with HIV encephalitis and macaques with simian immune deficiency virus encephalitis was immunostained for lipid peroxidation. Oxidized proteins in CSF of patients with various stages of HIV dementia were quantitated and we determined whether CSF from these patients could alter mitochondrial function. Several novel compounds with antioxidant effects were screened to determine their relative efficacy in protecting against CSF-induced neurotoxicity.

RESULTS

Evidence for oxidative stress was present both in brain and in CSF. The presence of oxidized proteins in the CSF and CSF-induced progressive decrease in mitochondrial activity correlated with the severity of cognitive impairment, but only the group of patients with moderate to severe dementia reached statistical significance. L-deprenyl, didox, imidate, diosgenin, and ebselen blocked the CSF-induced toxicity. No effect of trimidox, ruthenium red, or Quercetin was seen.

CONCLUSIONS

Increased oxidative stress is present in brain and CSF of HIV-infected patients. There is also an accumulation of toxic substances in the CSF that are capable of inducing oxidative stress. The authors have identified several novel compounds that are capable of blocking the CSF-induced toxicity, the therapeutic potential of which is worthy of further exploration.

[Conversion of laparoscopic cholecystectomy]

Laparoscopic cholecystectomy is nowadays the method of choice in treatment of symptomatic cholecystolithiasis, despite the fact that some operations cannot be completed laparoscopically and are converted. In a group of 431 patients operated during the last two years the authors evaluate the causes and predispositions of conversion which was performed in 7.4%. A significantly higher risk was found in subjects above 65 years of age, in those with ultrasonographic signs of thickening of the gallbladder wall and patients with acute cholecystitis. The risk of conversion is not significantly influenced by the patient's sex, obesity, the condition after endoscopic retrograde cholangiopancreaticography, pancreatitis and a previous abdominal operation.

Development of a simple gradient LC-IR interface for the detection of terpenoids from the alpha-pinene-ozone reaction

The development of a simple interface between liquid chromatography and infrared spectroscopy (LC-IR) using a coaxial sprayer is described for less volatile analytes. The system consists of a transfer capillary, in which the analytes are transported from the separation column of the gradient-LC to the outlet of the sprayer. This transfer capillary is coaxially surrounded at the outlet by a stainless steel sprayer capillary, which is resistively heated and flushed with nitrogen gas. The samples are sprayed in the manner that the eluent is vaporized by the heated nitrogen when exiting the capillary, while the analytes are deposited on a moving slide made of infrared transparent material (ZnSe or CaF2). Afterwards the deposited compounds are analyzed with an infrared microscope in transmission. First results from reaction products of the gas phase reaction of alpha-pinene with ozone are presented.

Degradation of alpha-pinene on Tenax during sample storage: effects of daylight radiation and temperature

The behavior of alpha-pinene sampled on adsorption cartridges filled with Tenax TA has been investigated in relation to different storage conditions, focusing on daylight radiation and temperature. After sampling, the respective cartridges containing the terpene were placed in sunlight on the windowsill for up to 1 month. Corresponding samples have been wrapped in aluminum foil to prevent the influence of daylight radiation. Additional sample cartridges with alpha-pinene were stored in the refrigerator at 4 degrees C and a freezer at -18 degrees C. All cartridges were analyzed using thermodesorption injection onto a gas chromatograph, and the compounds were detected using either a cryocondensation-interface to a Fourier transform infrared-spectrometer (GC/FT-IR) or the flame ionization detector (FID). In summary, 12 compounds were detected and identified, from which eight were products that were formed on Tenax through different mechanisms. Two compounds seemed to be formed under the influence of daylight radiation, while the others appear to be mainly autoxidation products. Estimates after 1 month of storage showed recoveries of over 99% for wrapped samples, while for unwrapped cartridges only about 88% of alpha-pinene was found. A pattern of up to five compounds was found that can be used as an indicator for storage reactions.

Inhibitors of platelet signal transduction as anti-aggregatory drugs

In the treatment and prevention of cardiovascular diseases, inhibition of platelet aggregation is of fundamental importance. Inhibition of platelet aggregation can be achieved by either inhibition of membrane receptors or by interception of signalling pathways. While receptor antagonism provides high specificity, the inhibition of platelet signal transduction is more effective. The effectiveness results from the inhibition of platelets, regardless of the cause of activation. These common pathway inhibitors are either intercepting platelet activating mechanisms or amplifying the action of endogenous platelet inhibitors. The physiological anti-aggregants are the endothelial factors NO and prostacyclin, which elevate intracellular cGMP or cAMP content, respectively. By administration of NO-releasing agents, prostacyclin analogues or other cyclic nucleotide elevating drugs the platelet anti-aggregatory action of endothelial factors can be effectively mimicked. Besides antiplatelet activity these drugs also act on vascular smooth muscle causing relaxation and therefore vasodilation, an additional beneficial effect. Inhibition of phosphodiesterases causes elevation of platelet cyclic nucleotide content and thus inhibits platelet aggregation and causes vasodilation. Another relevant target for anti-aggregatory treatment is the arachidonic acid metabolic pathway. This pathway can be intercepted by blockade of either cyclooxygenase-1 (COX-1) or thromboxane synthase. Inhibition of these enzymes may be further amplified by additional antagonism of the thromboxane receptor thus not only preventing formation of thromboxane but also activation of thromboxane receptor by thromboxane precursors, which were particularly effective in clinical trials. In vivo these precursors may be metabolised to prostacyclin in the endothelium and consequently provide additional platelet anti-aggregatory activity. A rather new target for platelet anti-aggregatory treatment is the ecto-nucleotidase CD-39 which limits the plasma level of nucleotides. While several of the novel anti-aggregatory drugs were disappointing in clinical studies combinations of drugs with different effector enzymes showed potent antithrombotic efficacy.

The mycobiota of speck, a traditional Tyrolean smoked and cured ham

Speck is a ham specialty product traditionally produced in South Tyrol (Italy) and North Tyrol (Austria) by farmers, butcheries, and meat industries. To date, nothing has been learned about fungi associated with this smoked and cured meat. Therefore, it was the main objective of this study to assess the typical mycobiota of Speck in relation to the different production types and the geographic provenance. A total of 121 Speck samples from North Tyrol and South Tyrol was analyzed. From 63 isolated fungal species, only a few can be regarded as typical colonizers: Eurotium rubrum and Penicillium solitum were the dominating species in all types and parts of Speck (crust, meat, and fat). Eight other Penicillium spp. were relatively frequent. The species diversity increased from industrially produced Speck to products from butcheries and farmers, and it was higher in all types of South Tyrolean products. Among the typical mycobiota, Penicillium verrucosum, Penicillium canescens, and Penicillium commune are known as potentially mycotoxigenic.

Treatment of solid tumours in children with tumour-lysate-pulsed dendritic cells

Dendritic cells are potent stimulators of antigen-specific immune responses, including antitumour responses. We explored the use of tumour-lysate-pulsed dendritic cells in children with relapsed solid tumours. Dendritic cell treatment in children was feasible and apparently not toxic. The treatment was able to produce significant tumour regression in a child with metastatic fibrosarcoma.

Inhibition of cADP-ribose formation produces vasodilation in bovine coronary arteries

cADP-ribose (cADPR) induces the release of Ca(2+) from the intracellular stores of coronary artery smooth muscle cells. However, little is known about the role of cADPR-mediated intracellular Ca(2+) release in the control of vascular tone. The present study examined the effects of nicotinamide, a specific inhibitor of ADP-ribosylcyclase, on the vascular tone of bovine coronary arteries. A bovine coronary artery homogenate stimulated the conversion of nicotinamide guanine dinucleotide into cGDP-ribose, which is a measure of ADP-ribosylcyclase activity. Nicotinamide significantly inhibited the formation of cGDP-ribose in a concentration-dependent manner: at a concentration of 10 mmol/L, it reduced the conversion rate from 3.34+/-0.11 nmol. min(-1). mg(-1) of protein in control cells to 1.42+/-0.11 nmol. min(-1). mg(-1) of protein in treated cells, a 58% reduction. In U46619-precontracted coronary artery rings, nicotinamide produced concentration-dependent relaxation. Complete relaxation with nicotinamide occurred at a dose of 8 mmol/L; the median inhibitory concentration (IC(50)) was 1.7 mmol/L. In the presence of a cell membrane-permeant cADPR antagonist, 8-bromo-cADPR, nicotinamide-induced vasorelaxation was markedly attenuated. Pretreatment of the arterial rings with ryanodine (50 micromol/L) significantly blunted the vasorelaxation response to nicotinamide. However, iloprost- and adenosine-induced vasorelaxation was not altered by 8-bromo-cADPR. Moreover, nicotinamide significantly attenuated KCl- or Bay K8644-induced vasoconstriction by 60% and 70%, respectively. These results suggest that the inhibition of cADPR formation by nicotinamide produces vasorelaxation and blunts KCl- and Bay K8644-induced vasoconstriction in coronary arteries and that the cADPR-mediated Ca(2+) signaling pathway plays a role in the control of vascular tone in coronary circulation.

Application of gas chromatography-cryocondensation-Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry to the identification of gas phase reaction products from the alpha-pinene/ozone reaction

The gas phase reaction of alpha-pinene with the atmospheric oxidant ozone was investigated by using the capabilities of both gas chromatography-cryocondensation-Fourier transform infrared spectroscopy (GC-FT-IR) and gas chromatography-mass spectrometry (GC-MS), for the identification of the reaction products formed. The reaction was carried out in a flow reaction chamber from where the compounds were sampled on Tenax-containing adsorption cartridges. The reaction mixture was injected onto the column after thermodesorption and analyzed using both GC-IR and GC-MS. Twenty compounds could be detected, including the reactant alpha-pinene and it's impurities tricyclene and camphene. Eleven compounds were identified by spectra comparison with either reference data or spectra obtained from commercial standards. Four compounds were tentatively identified from their IR and MS spectra, while from the remaining two compounds the nature of basic functional groups could be established.

Flow cytometry analysis of intracellular VASP phosphorylation for the assessment of activating and inhibitory signal transduction pathways in human platelets--definition and detection of ticlopidine/clopidogrel effects

Increased platelet adhesion or aggregation are key events in the pathogenesis of cardiovascular diseases. Exact determination of the platelet activation state is essential to recognize, prevent, and treat cardiovascular complications due to platelet dysfunction. Initial phases of platelet activation and inhibition are characterized by phosphorylation of specific intracellular proteins. However, methodological problems often prevent analysis of platelet protein phosphorylation under clinical conditions. A novel flow cytometry-based method using a phosphorylation-specific antibody was developed for fast and easy quantification of the phosphorylation state of a specific intracellular platelet protein. This method was used to analyze various platelet receptors and their intracellular signaling which may be impaired in genetic or acquired disorders or altered due to therapeutic interventions. In a first clinical application, the inhibitory effects of ticlopidine and clopidogrel on the platelet P2YAC ADP receptor were monitored.

Specific impairment of human platelet P2Y(AC) ADP receptor-mediated signaling by the antiplatelet drug clopidogrel

Clopidogrel is an effective new antiplatelet agent useful for the treatment of ischemic cerebrovascular, cardiac, and peripheral arterial disease. However, the mechanism of clopidogrel action is not well understood, although it is known to inhibit ADP-evoked platelet aggregation. In the current study, the effect of clopidogrel on recently identified human platelet ADP receptors and their signaling pathways was investigated by using platelets from clopidogrel-treated subjects, 6 healthy volunteers (2 females and 4 males) who received 75 mg of clopidogrel daily for 7 days. Blood was taken and various platelet receptor signaling pathways were analyzed before treatment, after 7 days of medication, and 4 weeks after treatment had ceased. Platelet tests included the analysis of aggregation, rapid calcium influx, calcium mobilization from intracellular stores, adenylyl cyclase, and phosphorylation of vasodilator-stimulated phosphoprotein (VASP). The data indicate that clopidogrel does not affect those platelet ADP receptors coupled to cation influx (P2X1 ADP receptors) or calcium mobilization (P2Y1 ADP receptors). In contrast, clopidogrel treatment specifically impairs the ADP receptor coupled to G(i)/adenylyl cyclase (P2Y(AC) ADP receptors). Clopidogrel abolishes the inhibitory P2Y(AC) receptor-mediated ADP effects on prostaglandin E(1)-stimulated, cAMP-dependent phosphorylation of VASP without affecting epinephrine, thrombin, and thromboxane signaling. VASP phosphorylation is known to be closely correlated with the inhibition of platelet and fibrinogen receptor (glycoprotein IIb/IIIa) activation. Therefore, inhibition of the platelet P2Y(AC) ADP receptor and its intracellular signaling, including decreased VASP phosphorylation, is suggested as a molecular mechanism of clopidogrel action.