Enhancement of fibrinolysis with 40-kHz ultrasound

BACKGROUND: Ultrasound at frequencies of 0.5 to 1 MHz and intensities of > or =0.5 W/cm2 accelerates enzymatic fibrinolysis in vitro and in some animal models, but unacceptable tissue heating can occur, and limited penetration would restrict application to superficial vessels. Tissue heating is less and penetration better at lower frequencies, but little information is available regarding the effect of lower-frequency ultrasound on enzymatic fibrinolysis. We therefore examined the effect of 40-kHz ultrasound on fibrinolysis, tissue penetration, and heating. METHODS AND RESULTS: 125I-fibrin-radiolabeled plasma clots in thin-walled tubes were overlaid with plasma containing tissue plasminogen activator (tPA) and exposed to ultrasound. Enzymatic fibrinolysis was measured as solubilization of radiolabel. Tissue attenuation and heating were examined in samples of porcine rib cage. Fibrinolysis was increased significantly in the presence of 40-kHz ultrasound at 0.25 W/cm2, reaching 39+/-7% and 93+/-11% at 60 minutes and 120 minutes, compared with 13+/-8% and 37+/-4% in the absence of ultrasound (P<0.0001). The acceleration of fibrinolysis increased at higher intensities. Attenuation of the ultrasound field was only 1.7+/-0.5 dB/cm through the intercostal space and 3.4+/-0.9 dB/cm through rib. Temperature increments in rib were <1 C/(W/cm2). CONCLUSIONS: These findings indicate that 40-kHz ultrasound significantly accelerates enzymatic fibrinolysis at intensities of > or =0.25 W/cm2 with excellent tissue penetration and minimal heating. Externally applied 40-kHz ultrasound at low intensities is a potentially useful therapeutic adjunct to enzymatic fibrinolysis with sufficient tissue penetration for both peripheral vascular and coronary applications.     

Role of zinc in the structure and toxic activity of botulinum neurotoxin

Zn2+-protease activity of botulinum neurotoxin causes the blockage of neurotransmitter release resulting in botulism disease. We have investigated the role of Zn2+ in the biological activity of type A botulinum neurotoxin by removing the bound Zn2+ by EDTA treatment, followed by monitoring its structure in terms of secondary and tertiary folding (second derivative UV, FT-IR, and circular dichroism spectroscopy) and function in terms of its effect on the release of norepinephrine from PC12 cells. The single Zn2+ bound to each neurotoxin molecule was reversibly removed by EDTA treatment, whereas the biological activity of the neurotoxin was irreversibly lost. Based on the Amide III IR spectral analysis, the alpha-helical content of neurotoxin increased from 29% to 42% upon removal of Zn2+, which reverted to 31% upon treatment with 1:5 molar excess of exogenous Zn2+. Second derivative UV spectroscopy revealed no change in surface topography of Tyr residues with removal of Zn2+. However, near-UV circular dichroism signals suggested significant alterations in the topography of Phe and Tyr residues that could be buried in the protein matrix. Thermal unfolding experiments suggested that removal of Zn2+ results in the formation of the molten globule-like structure of type A botulinum neurotoxin. Tertiary structural changes introduced by Zn2+ removal were irreversible, which correlated well with the irreversibility of the biological activity of the neurotoxin. On the basis of these results, we suggest that Zn2+ plays a significant structural role in addition to its catalytic role in Zn2+-protease activity of type A botulinum neurotoxin.     

Simulation techniques in operator and maintenance training,performance assessment,and personnel selection

Recent military research has examined the use of synthetic simulators employing new digital technologies for training personnel who operate and maintain electronic and other systems. Compared with the traditional approach using actual equipment for training, such simulators are safer for trainees and equipment, more reliable, more flexible, and far less costly. These synthetic trainers can be self-pace and combine two-dimensional presentation for teaching conceptual skills with full-scale 3-dimensional simulation for teaching hands-on skills. The synthetic training approach is directly applicable to the industrial marketplace, and can offer improvements in personnel selection and performance assessment as well as better training.     

IgE antibody during infection with the ovine abomasal nematode, Teladorsagia circumcincta: primary and secondary responses in serum and gastric lymph of sheep

A monoclonal antibody to ovine IgE was employed in an ELISA to investigate the IgE antibody responses in serum and gastric lymph to a primary infection of Teladorsagia circumcincta, and following challenge in previously infected sheep. During a primary response, IgE antibody to antigens derived from the infective third stage (L3) and adult (L5) worms were negligible, with low levels of IgE antibody detected in serum and lymph. In contrast, there was a pronounced IgE antibody response in 2/4 sheep to L3 antigens during 2-8 days after challenge of previously infected animals but low levels of IgE antibody to L5 antigens. This response was confirmed in a second but similar experiment, where relatively high levels of IgE antibody was detected to antigens from L3. Antibody levels were higher in lymph than in serum from the same animals, and Western blots of L3 antigen following SDS-PAGE under reducing conditions revealed several bands of MW26-96KD which reacted with the IgE antibody from gastric lymph. Immunohistochemical staining indicated that these IgE antibodies may be reacting with allergens associated with the surface cuticle of the worms.     

Uterine exteriorisation at caesarean section: influence on maternal morbidity

OBJECTIVE: To compare the influence on caesarean section morbidity of uterine exteriorisation or in situ repair. DESIGN: Randomised controlled trial. SETTING: Princess Anne Maternity Unit of the Royal Bolton Hospital, UK. POPULATION: One hundred and ninety-four women undergoing delivery by caesarean section. METHODS: Two intra-operative readings of arterial pulse rate, mean arterial blood pressure, and arterial haemoglobin oxygen saturation were obtained. Pre-operative and day-3 haemoglobin concentrations were determined. Intra- and post-operative complications, puerperal pain scores, and febrile and infectious morbidity were assessed. A postal questionnaire was used to assess morbidity six weeks after delivery. MAIN OUTCOME MEASURES: Intra-operative changes in pulse rate, mean arterial blood pressure and oxygen saturation; peri-operative changes in haemoglobin concentration; incidence of intraoperative vomiting, pain, intra- and post-operative complications, and febrile and infectious morbidity; immediate and late puerperal pain scores; satisfaction with the operation. RESULTS: No clinically significant differences between uterine exteriorisation and in situ repair were found in pulse rate, mean arterial pressure, oxygen saturation and haemoglobin changes. Likewise, the incidence of vomiting and pain was similar. Vomiting occurred in 10% of all the women, and 57% of all pain complaints occurred at the initial skin incision. There was a trend towards higher immediate and late pain scores in the exteriorisation group, reaching statistical significance on day 3. Overall, pain scores averaged 6/10 on day 1 despite patient-controlled analgesia, and three-quarters of all women reported persisting pain on day 42. Intra- and post-operative complications, febrile and infectious morbidity, and duration of hospital stay were similar in both groups. CONCLUSIONS: We have demonstrated that uterine exteriorisation and in situ repair have similar effects on peri-operative caesarean section morbidity. Intra-operative pain reflected adequacy of anaesthesia, while vomiting reflected adequacy of pre-operative preparation of patients. Exteriorising the uterus at caesarean section is a valid option.     

Quinolone-resistant Neisseria gonorrhoeae: the beginning of the end? Report of quinolone-resistant isolates and surveillance in the southwestern United States, 1989 to 1997

BACKGROUND: Fluoroquinolones are one of the most widely used treatments for gonorrhoeae. Changes in the susceptibility of Neisseria gonorrhoeae to these agents may threaten their use. GOAL OF THIS STUDY: To report several resistant strains (>1 mcg/ml) isolated in the western United States and to evaluate the prevalence of strains with reduced susceptibility (ofloxacin 0.25 mcg/ml, ciprofloxacin 0.06 mcg/ml). STUDY DESIGN: The microbiology and epidemiology of three resistant strains were characterized and 12,761 other strains were evaluated for fluoroquinolone susceptibility as part of the Gonococcal Isolate Surveillance Project of the Centers for Disease Control and Prevention. RESULTS: Fluoroquinolone-resistant strains may appear sporadically. The prevalence of isolates with reduced susceptibility to fluoroquinolones remains low in the Southwest region of the United States. CONCLUSIONS: Continued active surveillance is needed to detect and control the spread of quinolone-resistant Neisseria gonorrhoeae.     

Superior vena cava syndrome: case report. A complication of permanent transvenous endocardial cardiac pacing requiring surgical correction

Superior vena cava syndrome developed in a patient in whom an endocardial transvenous pacemaker had been inserted five years previously. Venography demonstrated an obstructing lesion at the junction of the superior vena cava and right atrium. Balloon catheter dilatation failed to afford any relief from her progressive symptoms. Exploration of the area revealed a benign fibrotic lesion encircling the pacemaker lead within the right atrium. Excision of the lesion, removal of the lead, and patching the right atrium with pericardium resulted in rapid cure.