Microdialysis assessment of shock wave lithotripsy-induced renal injury

OBJECTIVES

Shock wave lithotripsy (SWL) is the primary treatment modality for managing the majority of symptomatic renal calculi. However, the fundamental mechanisms for stone fragmentation and the resultant morphologic changes that occur are not fully understood. Furthermore, a thorough understanding of the complex biologic pathways involved in SWL-induced renal injury does not exist at present. To elucidate the biologic processes involved in tissue injury after SWL, an animal model was designed to mimic the pathogenesis of high-energy SWL in humans.

METHODS

Juvenile female swine were anesthetized, and a midline laparotomy incision was performed to expose the right kidney. Using an introducer apparatus, a microdialysis probe was placed into the renal parenchyma of the right kidney lower pole and a tunnel was generated to exit the distal ends of the inlet and outlet tubing outside the body. After a 72-hour postoperative recovery period, SWL was performed to the lower pole renal region of the kidney, as a microdialysis pump continuously infused dialysate through the inlet tubing. Microdialysis fluids were collected during SWL, and lipid peroxidation, as measured by conjugated diene concentrations, was monitored.

RESULTS

All microdialysis probes remained patent for a total of 2000 shock waves. A significant elevation in conjugated diene levels was observed in the SWL versus untreated kidneys after 1000 shock waves were administered (P <0.02).

CONCLUSIONS

This animal model is unique in that it represents the first system for the real-time collection of renal interstitial fluids during SWL. Analysis of this fluid may provide insight into the physiologic mechanisms responsible for shock wave-induced renal injury.

[Preparation of monoclonal antibodies against malaria through immunization of mice with recombinant plasmid DNA]

BALB/c mice were immunized by injection of recombinant plasmid DNA carrying MSP1-31 fragment of Plasmodium falciparum. After antiserum was induced, McAbs were prepared by fusing SP2/0 myeloma cells with spleen cells. Specific McAbs were detected in hybridoma culture supernatant and mouse ascites by ELISA, positive hybridomas were cloned by technique of limiting dilutions. Two McAbs, 9H9 and 8A2, against the malaria protein were produced and characterized. The titers of the two McAbs in acites were 1:10,000 and 1:2500 respectively. The Ig subclass of these McAbs was IgG1. Western blot test showed that the McAb specifically reacted with MSP1-31 antigen. These results proved that monoclonal antibodies could be produced by use of immunization of mice with plasmid DNA or DNA vaccine.

Acoustic and mechanical properties of artificial stones in comparison to natural kidney stones

PURPOSE

Standardized and reproducible artificial kidney stone models are important for performing comparative studies of different lithotripsy modalities. The acoustic and mechanical properties of renal calculi dictate the manner by which stones interact with the mechanical stresses produced by shock wave lithotripsy (SWL) or intracorporeal lithotripsy modalities. We have developed a novel artificial kidney stone model that is made of natural substances found in real kidney stones. These stone models appear to be much closer in physical properties to natural kidney stones than previously used stone models.

MATERIALS AND METHODS

The acoustic and mechanical properties of six groups of artificial stone models were compared to corresponding natural stones of similar compositions. Moreover, three groups of artificial stone models made of plaster-of-Paris were compared to their natural counterparts. In terms of acoustic properties, stone density was measured using a pycnometer based on Archimedes' principle, whereas longitudinal and transverse (or shear) wave propagation speeds were measured using an ultrasound pulse transmission technique. These values were used to calculate wave impedance and dynamic mechanical properties (bulk modulus, Young's modulus, and shear modulus) of the stones. The microhardness of the stones was measured and the effect of composition on stone fragility was evaluated.

RESULTS

Artificial stones, when compared to natural stones of similar composition, showed similar trends in longitudinal and transverse wave speeds, wave impedance, and dynamic elastic moduli. However, values for the artificial stones were uniformly low compared to those of natural stones, suggesting that these artificial stones may be more amenable to shock wave fragmentation. The results of SWL on stone fragmentation of artificial and natural stones also revealed similar trends with the exception of artificial cystine stones which were found to be the most resistant to shock wave fragmentation.

CONCLUSIONS

The results indicate that the physical properties of artificial stones made of natural stone materials are comparable to renal calculi of the same chemical composition. The data suggests that these stone phantoms are suitable for performing standardized and reproducible in vitro investigations, especially with regards to fragility of kidney stones of different chemical compositions during SWL.

Studies of the novel ketolide ABT-773: transport, binding to ribosomes, and inhibition of protein synthesis in Streptococcus pneumoniae

Macrolide resistance in Streptococcus pneumoniae has been associated with two main mechanisms: target modification by Erm methyltransferases and efflux by macrolide pumps. The ketolide ABT-773, which has a 3-keto group and no L-cladinose sugar, represents a new class of drugs with in vitro activity against a variety of resistant bacteria. Several approaches were undertaken to understand how ABT-773 was able to defeat resistance mechanisms. We demonstrated tighter ribosome binding of ABT-773 than erythromycin. We also showed that ABT-773 (i) accumulated in macrolide-sensitive S. pneumoniae at a higher rate than erythromycin, (ii) was able to bind with methylated ribosomes, though at lower affinities than with wild-type ribosomes, and (iii) accumulated in S. pneumoniae strains with the efflux-resistant phenotype.

Induction of ribosome methylation in MLS-resistant Streptococcus pneumoniae by macrolides and ketolides

One major mechanism for resistance to macrolide antibiotics in Streptococcus pneumoniae is MLS (macrolide, lincosamide, and streptogramin B) resistance, manifested when the 23S rRNA is methylated by the product of an erm gene. This modification results in the decreased binding of all known macrolide, lincosamide, and streptogramin B antibiotics to the ribosome. More than 30 ermAM-containing clinical isolates of S. pneumoniae were examined in our lab and showed high-level resistance (MIC > or =128 microg/ml) to erythromycin, azithromycin, tylosin, clindamycin, and ketolide (macrolides that lack the cladinose sugar) TE-802. We found that the new generation of ketolides A965 and A088 displayed variable activity against the same group of resistant S. pneumoniae strains. To understand the basis of variability of the minimal inhibitory concentration (MIC) values of A965 and A088, we examined the effects of a series of macrolides and ketolides on the level of 23S rRNA methylation in five ermAM-containing resistant S. pneumoniae isolates. We show here that the basal levels of ribosomal methylation vary from strain to strain. The level of rRNA methylation can be strongly induced by erythromycin, azithromycin, and TE-802, resulting in high-level of resistance to these compounds. Ketolide A965 and A088, however, are weak inducers at sub-MIC drug concentrations, therefore showing variable activities in strains with differential methylation levels.

The HIV-2 genotype and the HIV-1 syncytium-inducing phenotype are associated with a lower virus replication in dendritic cells

During sexual transmission, HIV infects the mucosal dendritic cells and is transferred to CD4 T cells. Whether HIV variants of a particular genetic (sub)type or phenotype selectively infect dendritic cells (DC) or are preferentially transferred to T cells remains highly controversial. To avoid the cumbersome use of primary dendritic cells, in vitro dendritic cell models were generated from precursors, either hematopoietic progenitor cells (HPC) or monocytes (MO). Productive infection in the dendritic cells and transfer of the virus to T cells was assessed for a range of HIV variants. HPC-derived dendritic cells (HPC-DC) were more susceptible to HIV-1 than to HIV-2 isolates. The HIV-1 group O strains were more productive in HPC-DC than group M, but amongst the latter, no subtype-related difference was observed. Both non-syncytium-inducing (NSI) and SI HIV isolates and lab strains could productively infect HPC-DC, albeit with a different efficiency. Adding blocking antibodies confirmed that both CCR-5 and CXCR-4 co-receptors were functional. Biological HIV-1 clones of the NSI/R5 phenotype infected more readily HPC-DC than SI/X4 clones. MO-derived dendritic cells were, however, more exclusive in their preference for NSI/R5 clones. Some HIV variants, that did not grow readily in HPC-DC alone, could be rescued by adding resting or pre-activated T cells. The present data show that HIV-2 isolates and SI clones replicate less in model-DC, but no preference for a particular HIV-1 subtype was evident. Co-culture with T cells could "correct" a limited growth in dendritic cells. Clearly, both intrinsic dendritic cell susceptibility and enhancement by T cells are explained only partly by HIV genotype and phenotype. The in vitro dendritic cell models seem useful tools to further unravel interactions between HIV, DC, and T cells.

Improvement of stone fragmentation during shock-wave lithotripsy using a combined EH/PEAA shock-wave generator-in vitro experiments

To control the collapse of cavitation bubbles induced during shock-wave lithotripsy (SWL), a piezoelectric annular array (PEAA) shock-wave generator was fabricated and combined with an experimental electrohydraulic (EH) shock-wave lithotripter with a truncated HM-3 reflector. The PEAA generator consists of eight individual transducers of 200-kHz resonant frequency. At a discharge voltage of 15 kV, the PEAA generator produces a shock wave with a peak positive pressure of 8.2 MPa, a positive half cycle duration of 2.9 micros, and a -6-dB beam width of 5 mm. The trigger of the PEAA generator was controlled via fiberoptic link with reference to the spark discharge of the EH generator. Hence, the PEAA-generated shock wave could be used to interact with cavitation bubbles induced by the EH source at various stages of their oscillation. The duration of bubble oscillation during SWL was monitored by a 2.25-MHz focused hydrophone, and this information was used to control the release timing of the PEAA generator. Stone fragmentation tests in vitro were carried out, and demonstrated that stone comminution could be significantly enhanced when the shock wave-bubble interaction occurred during the collapsing phase of the bubbles. A maximum increment of 60% to 80% in stone fragmentation was achieved when the PEAA-generated shock wave arrives near the collapse of the bubbles. Under these conditions, much intensified collapse of the bubbles near the surface of the stone, with strong secondary shock-wave emission and increased stress concentration at the impact site of the solid boundary, was observed using high-speed shadowgraph and photoelastic imaging.

Shock wave-inertial microbubble interaction: a theoretical study based on the Gilmore formulation for bubble dynamics

The Gilmore formulation for bubble dynamics coupled with zeroth-order gas diffusion were used to investigate theoretically the cavitation activity produced by a modified XL-1 lithotripter [J. Acoust. Soc. Am. 105, 1997-2009 (1999)]. The model calculation confirms many of the basic features in bubble dynamics observed experimentally, in particular the strong secondary shock wave emission generated by in situ lithotripter shock wave-inertial microbubble interaction. In addition, shock wave-inertial microbubble interaction produced by a Dornier HM-3, the most commonly used clinical lithotripter, was evaluated. It was shown that the forced collapse of inertial microbubbles with strong secondary shock wave emission could be produced consistently, provided that an appropriate preceding shock wave and interpulse delay were used. Further, it was demonstrated that truncation of the tensile stress of the lithotripter shock wave could significantly reduce the large expansion of the bubble following shock wave-inertial microbubble interaction, which may alleviate the risk for vascular injury during shock wave exposure.

Recent developments in SWL physics research

Two projects in our laboratory highlight some recent developments in shockwave lithotripsy (SWL) physics research. In the first project, we developed a prototype of a piezoelectric annular array (PEAA) shockwave generator that can be retrofitted on a Dornier HM-3 lithotripter for active control of cavitation during SWL. The PEAA generator, operating at 15 kV, produces a peak positive pressure of approximately 8 MPa with a -6-dB beam diameter of 5 mm. The shockwave generated by the PEAA was used to control and force the collapse of cavitation bubbles induced by a laboratory electrohydraulic shockwave lithotripter with a truncated HM-3 reflector. With optimal time delay between the lithotripter pulse and the PEAA-generated shockwave, the collapse of cavitation bubbles near the stone surface could be intensified, and the resultant stone fragmentation in vitro could be significantly improved. In the second project, high-speed shadowgraph imaging was used to visualize the dynamics of lithotripter-induced bubble oscillation in a vascular phantom. Compared with the free bubble oscillation in water, the expansion of cavitation bubble(s) produced in silicone tubes and a 200-microm cellulose hollow fiber by either a Nortech EHL or a Dornier XL-1 lithotripter was found to be significantly constrained. Rupture of the cellulose hollow fiber was observed consistently after about 20 shocks from the XL-1 lithotripter at an output voltage of 20 kV. These results confirm experimentally that SWL-induced cavitation in vivo can be significantly constrained by the surrounding tissue, and large intraluminal bubble expansions could cause rupture of capillaries and small blood vessels.

Novel inhibitors of Erm methyltransferases from NMR and parallel synthesis

The Erm family of methyltransferases confers resistance to the macrolide-lincosamide-streptogramin type B (MLS) antibiotics through the methylation of 23S ribosomal RNA. Upon the methylation of RNA, the MLS antibiotics lose their ability to bind to the ribosome and exhibit their antibiotic activity. Using an NMR-based screen, we identified a series of triazine-containing compounds that bind weakly to ErmAM. These initial lead compounds were optimized by the parallel synthesis of a large number of analogues, resulting in compounds which inhibit the Erm-mediated methylation of rRNA in the low micromolar range. NMR and X-ray structures of enzyme/inhibitor complexes reveal that the inhibitors bind to the S-adenosylmethionine binding site on the Erm protein. These compounds represent novel methyltransferase inhibitors that serve as new leads for the reversal of Erm-mediated MLS antibiotic resistance.

How to improve lithotripsy and chemolitholysis of brushite-stones: an in vitro study

Because of their resistance to fragmentation, treatment of brushite stones is a big problem. This study was performed to look for an improvement in therapeutic strategies by using artificial stones made of brushite (Bon(n)-stones), which are comparable to their natural counterparts. Using an ultrasound transmission technique, longitudinal wave propagation speeds were measured at different time intervals during treatment with hemiacidrin. From these and density measurements, transverse wave speed, wave impedance and dynamic mechanical properties of the artificial stones were calculated. Moreover, the microhardness of artificial stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of brushite stones through treatment with hemiacidrin. Additionally, we demonstrated the efficacy of Suby G in dissolving artificial brushite stones using an experimental arrangement simulating the physiological conditions in the upper urinary tract. Moreover, the efficacy of four different intracorporeal lithotripsy devices (electrohydraulic, pneumatic, laser and ultrasound) was tested and it was shown that electrohydraulic lithotripsy seems to be the best system for comminution of brushite stones.

The 2.2 A structure of the rRNA methyltransferase ErmC' and its complexes with cofactor and cofactor analogs: implications for the reaction mechanism

The rRNA methyltransferase ErmC' transfers methyl groups from S -adenosyl-l-methionine to atom N6 of an adenine base within the peptidyltransferase loop of 23 S rRNA, thus conferring antibiotic resistance against a number of macrolide antibiotics. The crystal structures of ErmC' and of its complexes with the cofactor S -adenosyl-l-methionine, the reaction product S-adenosyl-l-homocysteine and the methyltransferase inhibitor Sinefungin, respectively, show that the enzyme undergoes small conformational changes upon ligand binding. Overall, the ligand molecules bind to the protein in a similar mode as observed for other methyltransferases. Small differences between the binding of the amino acid parts of the different ligands are correlated with differences in their chemical structure. A model for the transition-state based on the atomic details of the active site is consistent with a one-step methyl-transfer mechanism and might serve as a first step towards the design of potent Erm inhibitors.

Shock wave-inertial microbubble interaction: methodology, physical characterization, and bioeffect study

A method of generating in situ shock wave-inertial microbubble interaction by a modified electrohydraulic shock wave lithotripter is proposed and tested in vitro. An annular brass ellipsoidal reflector (thickness = 28 mm) that can be mounted on the aperture rim of a Dornier XL-1 lithotripter was designed and fabricated. This ring reflector shares the same foci with the XL-1 reflector, but is 15 mm short in major axis. Thus, a small portion of the spherical shock wave, generated by a spark discharge at the first focus (F1) of the reflector, is reflected and diffracted by the ring reflector, producing a weak shock wave approximately 8.5 microseconds in front of the lithotripter pulse. Based on the configuration of the ring reflector (different combinations of six identical segments), the peak negative pressure of the preceding weak shock wave at the second focus (F2) can be adjusted from -0.96 to -1.91 MPa, at an output voltage of 25 kV. The preceding shock wave induces inertial microbubbles, most of which expand to a maximum size of 100-200 microns, with a few expanding up to 400 microns before being collapsed in situ by the ensuing lithotripter pulse. Physical characterizations utilizing polyvinylidene difluoride (PVDF) membrane hydrophone, high-speed shadowgraph imaging, and passive cavitation detection have shown strong secondary shock wave emission immediately following the propagating lithotripter shock front, and microjet formation along the wave propagation direction. Using the modified reflector, injury to mouse lymphoid cells is significantly increased at high exposure (up to 50% with shock number > 100). With optimal pulse combination, the maximum efficiency of shock wave-induced membrane permeabilization can be enhanced substantially (up to 91%), achieved at a low exposure of 50 shocks. These results suggest that shock wave-inertial microbubble interaction may be used selectively to either enhance the efficiency of shock wave-mediated macromolecule delivery at low exposure or tissue destruction at high exposure.

Impact of holmium laser settings and fiber diameter on stone fragmentation and endoscope deflection

We compared the impact of various energy settings, frequency, and fiber diameters on the stone fragmentation capabilities of the holmium laser. Stone phantoms, made from plaster of Paris and uniform in weight, were treated with one of two laser fiber sizes: small (200 and 365 microm) and large (550 and 1000 microm). Stones were immersed in water and fragmented for 3 minutes at 0.5, 1.0, or 2.0 J and 5, 10, or 15 Hz. The mean percentage decrease in weight in the two groups was compared using one-way ANOVA. The effect on flexible ureterorenoscope deflection of the small fibers was tested in two different ureterorenoscopes. Raising the energy level when using the small fibers resulted in more weight loss (P < 0.05). Increasing the frequency up to 10 Hz also resulted in a significant increase in weight loss (P < 0.05), yet above 10 Hz, there was no significant additional weight loss noted for either small fiber. There was no significant difference in the weight loss produced by the two fibers unless the energy setting was >1.0 J. Studies with the large fibers demonstrated similar results, with significant increments of weight loss occurring with increased energy (P < 0.05), while nonsignificant differences were seen for the two fiber diameters. Increasing laser frequency up to 15 Hz resulted in a significant increase in weight loss for the large fibers. Loss of ureterorenoscope deflection ranged from 7% to 16% and 18% to 37% for the 200-microm and 365-microm fibers, respectively. Small-diameter fibers, in combination with semirigid or flexible ureteroscopes, should be used to treat upper urinary tract stones. The 365-microm fiber should be utilized for the management of ureteral stones, as minimal endoscopic deflection is required to access these calculi. Because the 200-microm fibers are considerably more expensive, their use should be reserved for fragmentation of intrarenal calculi, where maximum deflection is required during flexible ureterorenoscopy. The ideal energy and frequency settings for the small fibers are <1.0 J and 5 to 10 Hz. Larger fibers can be used for managing bladder or renal calculi, as there is no need for significant fiber deflection. The 550-microm fiber is preferred, as it is comparable in efficacy to the 1000-microm fiber and is less expensive. Energy and frequency can be maximized to 2.0 J and 15 Hz without damage to the fiber, but visibility can be affected by high frequencies. Appropriate fiber selection and energy/frequency settings will allow access to most stones throughout the urinary tract, maximize fiber life, and minimize fiber expense.

Transient cavitation and acoustic emission produced by different laser lithotripters

Transient cavitation and shockwave generation produced by pulsed-dye and holmium:YAG laser lithotripters were studied using high-speed photography and acoustic emission measurements. In addition, stone phantoms were used to compare the fragmentation efficiency of various laser and electrohydraulic lithotripters. The pulsed-dye laser, with a wavelength (504 nm) strongly absorbed by most stone materials but not by water, and a short pulse duration of approximately 1 microsec, induces plasma formation on the surface of the target calculi. Subsequently, the rapid expansion of the plasma forms a cavitation bubble, which expands spherically to a maximum size and then collapses violently, leading to strong shockwave generation and microjet impingement, which comprises the primary mechanism for stone fragmentation with short-pulse lasers. In contrast, the holmium laser, with a wavelength (2100 nm) most strongly absorbed by water as well as by all stone materials and a long pulse duration of 250 to 350 microsec, produces an elongated, pear-shaped cavitation bubble at the tip of the optical fiber that forms a vapor channel to conduct the ensuing laser energy to the target stone (Moss effect). The expansion and subsequent collapse of the elongated bubble is asymmetric, resulting in weak shockwave generation and microjet impingement. Thus, stone fragmentation in holmium laser lithotripsy is caused primarily by thermal ablation (drilling effect).

Design and evaluation of an in-house HIV-1 (group M and O), SIVmnd and SIVcpz antigen capture assay

An enzyme-linked immuno-sorbent assay (ELISA) for the detection of human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIVcpz/SIVmnd) antigens was designed using immunoreagents from naturally infected individuals, and compared to the commercially available Vironostika HIV-1 Antigen Microelisa System (Organon Teknika). The in-house assay proved to be specific for HIV-1 isolates belonging to group M (A-H) and group O and for SIVcpz and SIVmnd isolates, but was less sensitive than the Vironostika HIV-1 Antigen Microelisa System, except for SIVmnd. For the strains belonging to HIV-2, SIVmac and SIVagm, the in-house assay could not detect antigen to an appreciable degree. This study shows that a considerably less expensive but sufficiently accurate HIV-1 antigen capture assay can be developed to monitor HIV-1 (group M and O), SIVcpv and SIVmnd antigen in the supernatants of virus cultures.

Laboratory and clinical assessment of pneumatically driven intracorporeal lithotripsy

A pneumatically driven intracorporeal lithotripter (the Swiss Lithoclast) has recently been approved for use in the United States. We compared its performance in vitro with ultrasonic, electrohydraulic and laser lithotripsy devices using a standard plaster-of-Paris stone phantom. The probe sizes and output settings were identical to those used during clinical treatment. The fragmentation efficiency index (measured as the lithotripsy time needed to reduce the stone phantom to particles <2 mm divided by the initial stone weight) ranged from 5.0 to 8.5 min/g of stone mass, with this value increasing from pneumatic to electrohydraulic to laser and to ultrasonic lithotripsy. We also performed an objective study in a swine model, which showed no adverse consequence of pneumatic lithotripsy. Finally, we evaluated our initial 41 patients who had undergone pneumatic stone fragmentation. We treated 8 patients having 11 renal calculi, 30 patients having 37 ureteral calculi, and 3 patients having 6 bladder calculi employing pneumatic probes ranging in size from 0.8 to 2.0 mm. Stone fragmentation was successful in a single session in 95% of the ureteral calculi and 100% of both renal and bladder calculi. Stone analysis in 23 patients revealed 17 (74%) calcium oxalate monohydrate and 1 (4%) cystine calculi. Our clinical and laboratory assessment of this newly developed pneumatic lithotripsy device further validates its efficacy in fragmenting stone of all compositions and its overall safety associated with clinical application.

[Peripheral corneal edema after cataract extraction]

OBJECTIVE

To report a rare type of corneal edema, i.e. peripheral corneal edema after cataract extraction---Brown-Mclean syndrome.

METHODS

Clinical charts of 8 affected eyes in 5 patients were reviewed. Ultrasound pachymetry was used to determine central corneal thickness. Cell densities were measured by specular microscopy. The clinical characteristics and pathogenesis were discussed.

RESULTS

The average time from operation to initial diagnosis was 10.5 years. The typical edema started inferiorly and progressed circumferentially, but central portion of the cornea was clear. The corneal thickness at edematous area was increased. The cell counts of endothelium was decreased in our patients. Additionally, the edema was associated with a punctate orange-brown pigmentation on the endothelium.

CONCLUSIONS

So far this new syndrome of corneal edema has not been reported in china. Its clinical characteristics are not similar to that of conventional edema after intracapsular cataract extraction. The pathogenesis of this curious condition is still unknown. It may be associated with an aphakic eye, chronic uveitis and hereditary factors.

[A long-term evaluation for opticfull-thickness lamellar keratoplasty]

OBJECTIVE

To investigate the long-term optic effects of optic full thickness lamellar keratoplasty (OFLK) and penetrating keratoplasty (PKP) and compare their effects.

METHODS

44 cases (48 eyes) with stromal disorder with normal endothelial function were treated by OFLK (25 eyes) or PKP (23 eyes). The optic effect of OFLK group was compared with that of the PKP group, and the endothelial density in partial cases was observed.

RESULTS

The rate of transparent graft of OFLK group was 84.0%, and that of PKP group was 69.6% at postoperative 2 - 3 years, the rate of escaping blindness being 80% and 78.3% respectively. The rate of obtaining more than 0.3 vision in OFLK group was 40.0%, and in PKP group was 21.7%. Postoperatively, the endothelial cell density tended to decrease with time in PKP group, but was relatively stable in OFLK group.

CONCLUSION

The results show that the optic effect of OFLK group is similar to that of PKP group, and the safety, less complications of OFLK group are the same as that of lamellar keratoplasty. It is considered that OFLK might have a bright future and the operative technique should be further studied.

[Effects of electroacupuncture at du meridian on contents of nitric oxide and endothelin in rats with acute cerebral ischemia]

Thirty rats were randomly assigned to three groups, control group (10 cases), acute cerebral ischemia group (10 cases) and electroacupuncture (EA) group (10 cases). The bilateral common carotid arteries were occluded, which caused sharp drop of regional cerebral bloodflow and led acute cerebral ischemia. Contents of nitric oxide (NO) and endothalin (ET) in the cerebral cortex and boold were determined in normal, during occluding and after EA of Du meridian (GV 20, GV 14) point in rats. It was found that in acute cerebral ischemia, the brain contents of NO and ET increased, the plasme level of ET elevated and serum level of NO decreased. After EA of Du meridian point, the levels of ET and NO in the brain and blood were returned significantly to normal. It is suggested that EA at Du meridian have protective effect on neural damage induced by brain ischemia. NO and ET are possibly involved in the regulative effect of EA.

Controlled, forced collapse of cavitation bubbles for improved stone fragmentation during shock wave lithotripsy

The feasibility of using controlled, forced collapse of cavitation bubbles for improved stone fragmentation during shock wave lithotripsy was demonstrated using microsecond tandem shockwave pulses. High-speed photography revealed that a secondary shock wave, released in less than 500 microseconds (microsec.) following a lithotripter-generated shock wave, can be used to control and force the collapse of cavitation bubbles toward target concretions. This timely enforced shockwave-bubble interaction was found to greatly enhance the cavitational activity near the stone surface, with a resultant up to 43% increment in stone fragmentation. Since most of the cavitation energy is directed and concentrated toward the target stones and fewer shock waves are needed for successful stone comminution, tissue injury associated with this new lithotripsy procedure may also be reduced. This novel concept of shock wave lithotripsy may be used to improve the treatment efficiency and safety of existing clinical lithotripters, as well as in the design of new shock wave lithotripters.

[Effect of yuxintong on ECE, NOS gene expression and immunohistochemical studies on cooper-zinc-SOD in ischemic myocardium in experimental dogs]

OBJECTIVE

To explore the effect of Yuxintong (YXT) on the endothelin converting enzyme (ECE) and the nitric oxide synthase (NOS) gene expression levels and cooper-zinc-superoxide dismutase (SOD) activity.

METHODS

The acute myocardial ischemia models were reproduced in anesthetized dogs by ligating the left coronary artery at the middle of anterior descending branch. The ECE and NOS gene expressions were observed by in situ hybridization and the cooper-zinc-SOD was studied by immunohistochemical and image analysis.

RESULTS

It was found that the transfer of ECE mRNA was greatly increased, while that of NOS mRNA was greatly decreased in ischemic my ocardium, but the YXT could enhance the expression levels of NOS mRNA and inhibit the over expression of ECE mRNA in ischemic myocardium in dog. Meanwhile, the cooper-zinc-SOD immunohistochemistry was significantly weakened in ischemic myocardium, but the YXT could evidently increase SOD activity in experimental ischemic myocardium.

CONCLUSIONS

It suggested that YXT had notable protection on experimental ischemic myocardium and was definitely valuable on prevention and treatment of coronary heart disease.

Solution structure of an rRNA methyltransferase (ErmAM) that confers macrolide-lincosamide-streptogramin antibiotic resistance

The Erm family of methyltransferases is responsible for the development of resistance to the macrolide-lincosamide-streptogramin type B (MLS) antibiotics. These enzymes methylate an adenine of 23S ribosomal RNA that prevents the MLS antibiotics from binding to the ribosome and exhibiting their antibacterial activity. Here we describe the three-dimensional structure of an Erm family member, ErmAM, as determined by NMR spectroscopy. The catalytic domain of ErmAM is structurally similar to that found in other methyltransferases and consists of a seven-stranded beta-sheet flanked by alpha-helices and a small two-stranded beta-sheet. In contrast to the catalytic domain, the substrate binding domain is different from other methyltransferases and adopts a novel fold that consists of four alpha-helices.

Inertial cavitation and associated acoustic emission produced during electrohydraulic shock wave lithotripsy

The inertial cavitation and associated acoustic emission generated during electrohydraulic shock wave lithotripsy were studied using high-speed photography and acoustic pressure measurements. The dynamics of cavitation bubble clusters, induced in vitro by an experimental laboratory lithotripter, were recorded using a high-speed rotating drum camera at 20,000 frames/s. The acoustic emission, generated by the rapid initial expansion and subsequent violent collapse of the cavitation bubbles, was measured simultaneously using a 1-MHz focused hydrophone, The expansion duration of the cavitation bubble cluster was found to correlate closely with the time delay between the first two groups of pressure spikes in the acoustic emission signal. This correlation provides an essential physical basis to assess the inertial cavitation produced by a clinical Dornier HM-3 shock wave lithotripter, both in water and in renal parenchyma of a swine model. In the clinical output voltage range (16-24 kV), the expansion duration of the primary cavitation bubble cluster generated by the HM-3 lithotripter in water increases from 158 to 254 microseconds, whereas the corresponding values in renal parenchyma are much smaller and remain almost unchanged (from 71 to 72 microseconds). In contrast, subsequent oscillation of the bubble following its primary collapse is significantly prolonged (from 158-235 microseconds in water to 1364-1373 microseconds in renal parenchyma). These distinctive differences between lithotripsy-induced inertial cavitation in vitro and that in vivo are presumably due to the constraining effect of renal tissue on bubble expansion.

An alpha-helical minimal binding domain within the H3 domain of syntaxin is required for SNAP-25 binding

The interaction between the proteins syntaxin 1A and SNAP-25 is a key step in synaptic vesicle docking and fusion. To define the SNAP-25 binding domain on syntaxin, we have prepared peptides that span the syntaxin H3 domain (residues 191-266), the region previously shown to be important for binding to SNAP-25, and then determined the affinities of these peptides for binding to SNAP-25. A minimal binding domain was identified within a region of 32 amino acids (residues 189-220). Its affinity for SNAP-25 is substantially enhanced by C-terminal extension (residues 221-266). Circular dichroism revealed the presence of substantial alpha-helicity in the H3 domain and in the 32-mer minimal binding domain, but not in H3 peptides that do not bind to SNAP-25. At temperatures that denature the alpha-helix of the minimal binding domain peptide, SNAP-25 binding is lost. Selected mutations in evolutionarily conserved residues of the amphiphilic alpha-helix within the minimal binding domain (e.g., residues 205 and 209) greatly reduce the affinity for SNAP-25 but have no major effect on secondary structure, suggesting that these residues may interact directly with SNAP-25. The H3 domain peptide and the minimal binding domain peptide inhibit norepinephrine release from PC12 cells. These results suggest that specific amino acid residues in the H3 domain, positioned by the underlying alpha-helical structure, are important for its binding to SNAP-25 and support the notion that this interaction is important for presynaptic vesicular exocytosis.

Transient oscillation of cavitation bubbles near stone surface during electrohydraulic lithotripsy

Using high-speed photography and acoustic emission measurements, we studied the dynamics of a transient cavitation bubble near a stone surface and the concomitant shockwaves generated during electrohydraulic lithotripsy (EHL). At each spark discharge, a vapor plasma and subsequently a cavitation bubble oscillating around the tip of an EHL probe are produced. Simultaneously, three distinctive shockwave pulses are generated. The first shockwave is produced by the rapid expansion of the vapor plasma, while the second and third waves are produced by rebounds of the cavitation bubble. Depending on the proximity of the probe to the stone surface, the collapse of the cavitation bubble may be symmetric, resulting in a strong shockwave emission; or asymmetric, leading to the formation of a liquid jet. For the Nortech AUTOLITH lithotripter with a 1.9F probe that was used in this study, maximum shockwave emission is produced when the probe is about 1 mm from the stone surface, whereas the maximum jet velocity is produced when the probe tip is at distance equivalent to the maximum bubble radius of about 3 mm. These findings are consistent with clinical experience, which suggests that for optimal treatment results, the EHL probe should be placed close to the stone surface.

[An analysis of the cause of misdiagnosis with ocular opportunistic infection]

OBJECTIVE

To evaluate the causes of misdiagnosis with ocular opportunistic infection.

METHOD

The causes of misdiagnosis on 4 cases (6 eyes) with ocular opportunistic infection were analyzed.

RESULTS

Acanthoamoeba keratitis was misdiagnosed as herpes simplex keratitis and fungal keratitis in 1 case (1 eye). Propionibacterium acne endophthalmitis was misdiagnosed as exogenous fungal keratitis in 1 case (1 eye). Endogenous fungal endophthalmitis was misdiagnosed as metastatic choroid cancer from lung in 1 case (2 eyes). Cytomegalovirus retinitis was misdiagnosed as endogenous fungal endophthalmitis in 1 case (2 eyes).

CONCLUSION

If common therapies are of no effect with some ocular infections and the causative organisms responsible for the infection could not be found out after repeated tests, the rare ocular opportunistic infection should be considered. Special examinations (such as acanthoamoeba culture, anaerobic culture, fungus blood culture, cytomegalovirus serological assays, etc.) should be made for a definite diagnosis.

Biological phenotypes of HIV-1 subtypes A and B strains of diverse origins

The identification of specific biologic phenotypic traits that can be correlated with different HIV-1 genetic subtypes was sought. The genetic subtypes were determined by either sequencing (Cameroonian strains, n = 18) or by the heteroduplex mobility assay (HMA) (Belgian strains, n = 21 and Ivorian strains, n = 25). Seventeen (81%) of the 21 Belgian isolates belonged to subtype B and 4 (17%) were subtype A strains. Subtype A variants were predominant in the two African countries studied; 11 (61%) of 18 strains from Cameroon and 23 (92%) of 25 strains from the Ivory Coast. Of the 64 isolates, 38 (58%) and 19 (29%) belonged to subtypes A and B, respectively. No significant difference was observed for biological phenotypes (slow/low and rapid/high) of both genetic subtypes. In symptomatic individuals, however, a significantly higher number of subtype B isolates were of rapid/high phenotype, compared with subtype A (5 of 10; 50%) vs. 2 of 22; 9%), respectively; X2 = 6.7, P = 0.02). The findings suggest that overall HIV-1 isolates belonging to genetic subtype B are not distinguishable from subtype A variants on the basis of their biological phenotypes. Syncytium-inducing variants were less prevalent regardless of the geographic origin of the isolates.

Substrate requirements for ErmC' methyltransferase activity

ErmC' is a methyltransferase that confers resistance to the macrolide-lincosamide-streptogramin B group of antibiotics by catalyzing the methylation of 23S rRNA at a specific adenine residue (A-2085 in Bacillus subtilis; A-2058 in Escherichia coli). The gene for ErmC' was cloned and expressed to a high level in E. coli, and the protein was purified to virtual homogeneity. Studies of substrate requirements of ErmC' have shown that a 262-nucleotide RNA fragment within domain V of B. subtilis 23S rRNA can be utilized efficiently as a substrate for methylation at A-2085. Kinetic studies of the monomethylation reaction showed that the apparent Km of this 262-nucleotide RNA oligonucleotide was 26-fold greater than the value determined for full-size and domain V 23S rRNA. In addition, the Vmax for this fragment also rose sevenfold. A model of RNA-ErmC' interaction involving multiple binding sites is proposed from the kinetic data presented.

Transcriptional regulation of hippocampal 5-HT1a receptors by corticosteroid hormones

5-HT1a receptors in the hippocampus play a critical role in modulating limbic system output. The activity and level of 5-HT1a receptors are modulated by glucocorticoid levels. The present study was undertaken to test the hypothesis that glucocorticoids attenuate the transcriptional activity of the 5-HT1a receptor gene. Using in situ hybridization and RNase protection assays, we observed a substantial increase in 5-HT1a mRNA expression after adrenalectomy in the same hippocampal regions in which 5-HT1a binding sites are increased. This increase in 5-HT1a mRNA expression occurs as early as 1 h after adrenalectomy and precedes the increase in receptor binding sites. Further in situ hybridization analysis showed that 5-HT1a mRNA is increased within individual hippocampal cells after adrenalectomy. Administration of dexamethasone completely prevents the adrenalectomy-induced elevation in hippocampal 5-HT1a receptor mRNA. Nuclear run-on assays showed that the rate of transcription of 5-HT1a mRNA after adrenalectomy increased 70% above the rate from control preparations and could be reduced to basal levels by the administration of dexamethasone. Adrenalectomy did not cause an increase in functional coupling of 5-HT1a receptors to adenylyl cyclase or phospholipase C. These results suggest that transcription of hippocampal 5-HT1a receptor mRNA is under negative regulation by corticosteroid hormones.

Correlation between genetic and biological properties of biologically cloned HIV type 1 viruses representing subtypes A, B, and D

The relationship between the genetic variability in the V3 loop and the biological characteristics of 38 biological clones from 5 European and 7 African HIV-1 isolates belonging to 3 different subtypes (subtype A, B, and D) was investigated. Seventeen of 19 clones displaying a syncytium-inducing (SI) capacity had a positively charged amino acid located at position 11 and/or 25 in the V3 loop sequence. All 19 non-syncytium-inducing (NSI) virus clones lacked such a positive charge at the same positions (p < 0.001). The mean of net charge in the overall V3 loop sequences of the SI clones was higher than that of the NSI clones (p < 0.001). Within the same strains, the SI clones replicated faster/higher than the NSI clones in peripheral blood mononuclear cells (p < 0.01), but not in CD4+ T cell cultures (p > 0.1). All SI clones but only 5 of 19 NSI clones could replicate in human continuous T cell and monocytic cell lines (p < 0.001). A higher number of positively charged amino acid substitutions was found among the subtype D SI clones. Only one of eight autologous sera tested had the ability to neutralize the contemporaneously isolated NSI clones, but not the SI clones. This study indicates that the V3 loop amino acid sequences of HIV-1 biological clones from different origins belonging to different genetic subtypes are clearly correlated with viral syncytium-inducing capacity, cell tropism, and replication rate.

Design and evaluation of new, highly sensitive and specific primers for polymerase chain reaction detection of HIV-1 infected primary lymphocytes

Primer pairs in the HIV-1 POL and ENV genes were evaluated by performing a PCR on lysed peripheral blood mononuclear cells (PBMCs) from 96 HIV-1 seropositive and 40 seronegative individuals originating from 16 different geographical localities in Africa, Europe and Haiti. A single PCR using primer pairs to the LTR, GAG and ENV regions and detection by radioactively labelled oligonucleotide probes was compared to a nested PCR scheme using newly designed POL and ENV primers which used ethidium-bromide staining of the amplified product on agarose gel. The newly designed POL nested primer pair was shown to be highly sensitive (93%) and specific (100%) for the detection of HIV-1 proviral DNA of very diverse geographical and genetic origin, including highly aberrant HIV-1 isolates. The sensitivity of the newly designed ENV primers was 68.7%, which does not differ significantly from the sensitivity of the classical primers, SK 68/69. Both ENV primers were unable to amplify two SIVcpz isolates from naturally infected chimpanzees.

Mechanisms of differing stone fragility in extracorporeal shockwave lithotripsy

Clinical experience with extracorporeal shockwave lithotripsy (SWL) has demonstrated significant variations in stone fragility. To understand the physical mechanisms of the differences, we quantitatively determined shockwave-stone interaction under clinically relevant SWL conditions for six stone compositions: calcium oxalate monohydrate (COM), struvite (MAPH), calcium apatite (CA), uric acid (UA), brushite, and cystine. We also characterized the acoustic and mechanical properties of the stones using ultrasound and microindentation techniques. Our results show that renal calculi have distinctly different acoustic and mechanical properties. Higher wave speed, Young's modulus, and fracture toughness were measured from COM and cystine stones, whereas lower values of the corresponding properties were found in CA and MAPH, and the values for brushite and UA stones were in between. Computer modeling of shockwave propagation revealed that under the same shockwave intensity, larger deformation was induced in CA and MAPH stones than in COM and cystine stones. In addition, multiple reflected tensile waves were predicted for stones with concentric layer structure, indicating their susceptibility to shockwave fragmentation. These findings elucidate the mechanisms of the differences in stone fragility observed clinically. Their implications to SWL are discussed.

Agonist-induced desensitization and loss of high-affinity binding sites of stably expressed human 5-HT1A receptors

Exposure of HeLa cells stably expressing cloned human 5-hydroxytryptamine (5-HT)1A receptors (HA7 cells) to the agonist 8-hydroxy-2-(di-N-propylamino)-tetralin (8-OH-DPAT) results in a loss of high-affinity binding sites and a desensitization of receptor-adenylate cyclase coupling, as measured by 5-HT1A-mediated inhibition of forskolin-stimulated adenylate cyclase activity. These responses can also be observed after exposure to forskolin, which activates cyclic AMP-dependent protein kinase A or after treatment with known activators of protein kinase C (PKC) such as phorbol-12-myristate 13-acetate (PMA). The responses elicited by exposure to 8-OH-DPAT or PMA can be blocked completely by inhibitors of PKC and also by 24-hr exposure to PMA. Preincubation of HA7 cells with 8-OH-DPAT also stimulates hydrolysis of inositol phospholipids and the production of arachidonic acid. Inhibition of phospholipase A2 with quinacrine or by removal of extracellular Ca++ blocks the agonist-mediated loss of 5-HT1A receptor binding sites. These data demonstrate that agonist-induced down regulation of the 5-HT1A receptor occurs after stimulation of both the PKC and phospholipase A2 signaling pathways, both of which may activate PKC. The subsequent response is a loss of high-affinity ligand binding sites and functional receptor coupling to adenylate cyclase.

Importance of receptor occupancy, concentration differences, and ligand exchange in the insulin-like growth factor I receptor system

We have investigated by use of placental membranes the mechanisms through which insulin-like growth factor I (IGF-I) comes to be associated with its alpha 2 beta 2 receptor heterotetramer. Our results suggest that (i) at low ligand concentrations, the formation and disruption of IGF-I--receptor complexes are consistent with ligand binding de novo to empty receptors but not with equilibria involving ligand dissociation; (ii) at higher ligand concentrations, rapid exchange arising from the formation and collapse of bis-liganded receptors leads to a transiently perturbed receptor state; (iii) these nonclassical IGF-I receptor interactions depend on close communication between the alpha beta halves of the alpha 2 beta 2 holo-IGF-I receptor; and (iv) related processes based on ligand exchange have the potential for serving as biological sensors of changes in ligand concentration, while ordinary binding processes serve as sensors of ligand concentrations themselves. A model is presented in which one or two molecules of ligand can be bound to an alpha 2 beta 2 IGF-I receptor heterotetramer, new ligand becomes associated with receptor by exchanging for a previously bound molecule of IGF-I, and fluctuating changes in free-ligand concentration might lead to enhanced IGF-I function.

Acoustic and mechanical properties of renal calculi: implications in shock wave lithotripsy

The acoustic and mechanical properties of renal calculi dictate how a stone interacts with the mechanical forces produced by shock wave lithotripsy; thus, these properties are directly related to the success of the treatment. Using an ultrasound pulse transmission technique, we measured both longitudinal and transverse (or shear) wave propagation speeds in nine groups of renal calculi with different chemical compositions. We also measured stone density using a pycnometer based on Archimedes' principle. From these measurements, we calculated wave impedance and dynamic mechanical properties of the renal stones. Calcium oxalate monohydrate and cystine stones had higher longitudinal and transverse wave speeds, wave impedances, and dynamic moduli (bulk modulus, Young's modulus, and shear modulus), suggesting that these stones are more difficult to fragment. Phosphate stones (carbonate apatite and magnesium ammonium phosphate hydrogen) were found to have lower values of these properties, suggesting they are more amenable to shock wave fragmentation. These data provide a physical explanation for the significant differences in stone fragility observed clinically.

Propagation of shock waves in elastic solids caused by cavitation microjet impact. II: Application in extracorporeal shock wave lithotripsy

To better understand the mechanism of stone fragmentation during extracorporeal shock wave lithotripsy (ESWL), the model developed in Part I [P. Zhong and C.J. Chuong, J. Acoust. Soc. Am. 94, 19-28 (1993)] is applied to study cavitation microjet impingement and its resultant shock wave propagation in renal calculi. Impact pressure at the stone boundary and stress, strain at the propagating shock fronts in the stone were calculated for typical ESWL loading conditions. At the anterior surface of the stone, the jet induced compressive stress can vary from 0.82 approximately 4 times that of the water hammer pressure depending on the contact angles; whereas the jet-induced shear stress can achieve its maximum, with a magnitude of 30% approximately 54% of the water hammer pressure, near the detachment of the longitudinal (or P) wave in the solid. Comparison of model predictions with material failure strengths of renal calculi suggests that jet impact can lead to stone surface erosion by combined compressive and shear loadings at the jet impacting surface, and spalling failure by tensile forces at the distal surface of the stone. Comparing responses from four different stone types suggests that cystine is the most difficult stone to fragment in ESWL, as observed from clinical experience.

Propagation of shock waves in elastic solids caused by cavitation microjet impact. I: Theoretical formulation

To understand the physical process of the impingement of cavitation microjet and the resultant shock wave propagation in an elastic solid, a theoretical model using geometrical acoustics was developed. Shock waves induced in both the jet head (water) and the solid were analyzed during a tri-supersonic impact configuration when the contact edge between the jet head and the elastic boundary expands faster than the longitudinal wave speed in the solid. Impact pressure at the boundary was solved using continuity conditions along the boundary normal. Reflection and refraction of shock waves from a solid-water interface were also included in the model. With this model, the impact pressure at the solid boundary and the stress, strain as well as velocity discontinuities at the propagating shock fronts were calculated. A comparison with results from previous studies shows that this model provides a more complete and general solution for the jet impact problem.

Molecular biology of serotonin receptors

The past decade has seen an explosive growth in our understanding of neurotransmitter receptors and the roles they play in neurotransmission. This is particularly true of the serotonin receptors where a synergy of basic science and clinical research has not only produced a deeper understanding of serotonin receptors and their actions but also resulted in the availability of new therapeutic agents useful for treating a number of psychiatric illnesses. This chapter details our current knowledge of the major subtypes of the serotonin receptor, including recent advances in the molecular biology, pharmacology, biochemistry, and clinical correlates of these receptors.

Microhardness measurements of renal calculi: regional differences and effects of microstructure

Microhardnesses of five types of renal calculi: calcium apatite (82.5%)/magnesium ammonium phosphate hydrogen (10%)/calcium oxalate monohydrate (7.5%); calcium apatite (95%)/calcium oxalate monohydrate (5%); magnesium ammonium phosphate hydrogen (90%)/calcium apatite (10%); calcium oxalate monohydrate (85%)/calcium apatite (15%); and cystine (100%) were measured. Using Knoop and Vickers indenters the effects of chemical composition and microstructure on the microhardness measurement were assessed. Calcium oxalate monohydrate, magnesium ammonium phosphate hydrogen, and cystine stones, without apparent structure pattern, showed neither regional nor directional differences in their microhardness. In contrast, calcium apatite stones, with distinctly concentric laminae structure, showed regional variations which were correlated with the chemical composition of stone constituents. Scanning electron microscopy of the indenter impressions were taken to help in interpreting the directional dependence in Knoop hardness measurements with respect to the microstructure of the calculi. Vickers measurements showed the crystalline stones were isotropic within a layer. Combined results of Knoop and Vickers measurements indicate that the anisotropic Knoop hardness readings seen in the laminated regions were structural but not material-based. Implications of the results for the fragmentation of renal calculi in extracorporeal shock wave lithotripsy are discussed.

Metabolic thermotolerance: magnetic resonance detected protection of glutamate synthase

Metabolism in maize meristem cultures exposed to different heat treatments has been analyzed by 13C-NMR spectroscopy of tissue extracts. The effects of a 40 degrees C permissive stress were compared with a 45 degrees C lethal stress, and the metabolism of glutamate and glutamine were markedly altered by both temperatures. Changes in the incorporation of labeled precursors, alterations due to the in vivo application of enzyme inhibitors, and differences in the activity of enzymes in cell free extracts have confirmed that glutamate synthase (GluS) is partially inactivated by the lethal thermal exposure. This enzyme is quantitatively protected by the induction of thermotolerance. The time dependence for the protection correlates with the appearance of a set of late-arising heat shock proteins (hsps). The function of these late-arising proteins is not yet known, but only one of them, a 67-kDa protein, is spatially correlated with GluS protection. Therefore, the quantitative protection of a key metabolic enzyme has been correlated with the in vivo function of a specific hsp.

A comparison of stone damage caused by different modes of shock wave generation

A standard stone phantom was used to compare stone damage after extracorporeal shock wave administration from electrohydraulic, electromagnetic and piezoelectric lithotripters. For each machine, a low and high shock wave intensity setting was chosen: 18 & 24 kV for electrohydraulic; 16 & 19 kV for electromagnetic; power levels 1 and 4 for piezoelectric. The shock wave was focused either at the front (surface facing the wave source) or back surface of the stone and 50, 100, 200 or 400 shocks were delivered to different stone groups. Effects of varying physical properties in the stone phantom were also investigated. Stone damage was described in terms of volume loss and both depth and width of the resulting damage crater. At the lower intensity settings, all three machines produced stone volume loss which was linearly related to the number of shock delivered. At higher intensity settings, volume loss increased rapidly as the number of shocks increased. With the same number of shocks, stone volume loss was greatest with the electrohydraulic machine, followed by electromagnetic and piezoelectric lithotripters for both low and high intensity settings. Damage craters from the piezoelectric device were narrow and deep; those from the electromagnetic machine were of the shape of a right angle circular cone; whereas those from the electrohydraulic lithotripter were shallow and wide. At the high intensity settings, damage from the piezoelectric and electrohydraulic lithotripters appeared to depend upon the position of the focal point with a higher volume loss when the shock waves were targeted at the front surface of the stone. For the electromagnetic device, a higher volume loss was found when we positioned the focal point at the back surface of the stone phantom. Stone phantoms with lower mechanical strength and acoustic impedance were more easily damaged than those with higher values. Finally, a computer regression model was developed to express volume loss in terms of the intensity setting, focal position and number of shocks for each lithotripter.