[Analysis of the influencing factors of short-term and long-term facial nerve function after vestibular schwannoma resection via suboccipital retrosigmoid approach]

Objective: To summarize the experience of facial nerve(FN) preservation in microsurgical treatment of vestibular schwannoma (VS) resection via suboccipital retrosigmoid approach and to analyze the influencing factors of facial function prognosis in short-term and long-term period. Methods: Patients with VS who underwent microsurgery via suboccipital retrosigmoid approach by the skull base surgery team in Huashan Hospital from January 2013 to February 2018 were enrolled. A total of 308 patients were included in this study, including 132 males and 176 females. The average age was 47.9 year-old (Range: 17-79 year-old). The patient's clinical data and FN function prognosis were recorded. Univariate and multivariate analysis by SPSS 23.0 statistical software were performed to evaluate the factors affecting facial function prognosis and its recovery. Results: Gross total resection was achieved in 304 cases, and subtotal resection was in 4 cases. The facial nerve preservation rate anatomically was 99.4%. The facial nerve of 2 cases was thin due to large tumor compression and severed, and a one-stage reconstruction was performed during surgery.Of the 308 patients, 300 cases were successfully followed up, and 8 cases were lost to follow-up. The mean follow-up time was 52 months. In short-term (2 weeks after surgery), satisfactory facial nerve function (House-Brackmann (H-B) grade Ⅰ-Ⅱ) was achieved in 96 cases, and 212 cases were unsatisfactory function (H-B grade Ⅲ-Ⅵ). After 1 year, 198 were satisfactory function and 97 were unsatisfactory. After 3 years, 219 were satisfactory function and 75 were unsatisfactory. Five years later, 155 were satisfactory function and 34 were unsatisfactory. According to the results of logistic regression analysis, the impact factors of FN function in short-term were tumor size (P=0.011) and stimulation threshold (ST) of EMG monitoring (P<0.001). The impact factors in long-term were tumor size (P=0.005), ST of EMG monitoring (P=0.005) and FN rehabilitation training. Conclusions: Tumor diameter is an independent factor related to FN function, and the larger the tumor, the worse the postoperative FN function. The ST of EMG (ST≤0.05 mA) can predict short-term and long-term FN function. The systematic facial rehabilitation training can effectively promote the recovery of FN after surgery.

[Characteristics of autonomic neuropathy in patients with vestibular migraine]

Objective: To investigate the characteristics of autonomic neuropathy in patients with vestibular migraine (VM) by sympathetic skin reflex (SSR) and R-R interval variation (RRIV). Methods: Seventy-three patients with interseizure VM and 36 healthy controls in the Department of Neurology affiliated to Shanghai Fourth People's Hospital of Tongji University from November 1, 2019 to December 31, 2021 were prospectively enrolled. SSR and RRIV were performed and relevant parameters were recorded, including SSR latency, SSR amplitude, RRIV during calm breathing (R%), RRIV during deep breathing (D%), RRIV difference between deep breathing and calm breathing (D%-R%), RRIV ratio between deep breathing and calm breathing (D%/R%), and the difference and correlation of various parameters between VM patients and healthy controls were analyzed. Results: Among the 73 patients with VM, there were 12 males and 61 females, and aged (46±13) years. While among 36 healthy controls, there were 6 males and 30 females, and aged (46±7) years. Among the 73 VM patients, abnormal SSR, abnormal RRIV, abnormal SSR and RRIV, and abnormal SSR or RRIV was detected in 38 cases (52%), 17 cases (23%), 11 cases (15%) and 44 cases (60%), respectively. Compared with healthy controls, the lower extremity SSR latency [(1 719±289) ms] in VM patients was longer than that in control group [(1 500±349) ms] (P=0.001), but the upper extremity SSR amplitude [1.6 (0.8, 3.0) mV] was lower than that in control group [2.6 (1.8, 4.2) mV] (P=0.006). SSR amplitude, R% and D% were negatively correlated with age in VM patients (r_s=-0.311, P=0.007; r_s=-0.237, P=0.043; r_s=-0.263, P=0.024, respectively). SSR of lower extremity in VM patients was longer than that of upper extremity [(1 719±289) ms vs (1 244±185) ms, P<0.001], but the amplitude of lower extremity was lower than that of upper extremity [0.8 (0.3, 1.7) mV vs 1.6 (0.8, 3.0) mV, P<0.001]. SSR latency of upper limb was positively correlated with SSR latency of lower limb (r=0.436, P<0.001), the amplitude of upper limb was positively correlated with amplitude of lower limb (r_s=0.456, P<0.001), and D% was positively correlated with R% (r_s=0.357, P=0.002). Conclusion: The autonomic neuropathy during VM interphase features with imbalance between sympathetic and parasympathetic nervous system, and the sympathetic nerve function is mainly impaired.

Anti-Inflammatory and Anti-Oxidant Activity of Ultra-Short Wave Diathermy on LPS-Induced Rat Lung Injury

We studied the lung-protective effect and mechanisms of the anti-inflammatory and antioxidant effects of ultra-short-wave diathermy (USWD) in a rat model of LPS-induced acute lung injury. Histological examination of the lung tissues was performed and the levels of oxidative stress-related factors and inflammatory cytokines were measured. It was shown that the lung injury score, the lung wet-to-dry weight ratio (W/D), oxidative stress-related factors malondialdehyde and acyl-CoA synthetase long-chain family member 4 (ACSL4), and inflammatory cytokines were increased after LPS administration, while USWD treatment reduced these parameters. In addition, superoxide dismutase and glutathione peroxidase 4 were decreased in rats with LPS-induced acute lung injury, while USWD therapy up-regulated the expression of these enzymes. Thus, USWD could antagonize lung injury by inhibiting oxidative stress and inflammatory response in rats with acute lung injury. USWD can be a promising adjunctive treatment to counter oxidative stress and inflammation and a potential therapeutic candidate for the treatment of patients with this pathology.

Correction: Elevation of p11 in lateral habenula mediates depression-like behavior

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Shock-Induced Damage and Dynamic Fracture in Cylindrical Bodies Submerged in Liquid

Understanding the response of solid materials to shock loading is important for mitigating shock-induced damages and failures, as well as advancing the beneficial use of shock waves for material modifications. In this paper, we consider a representative brittle material, BegoStone, in the form of cylindrical bodies and submerged in water. We present a computational study on the causal relationship between the prescribed shock load and the resulting elastic waves and damage in the solid material. A recently developed three-dimensional computational framework, FIVER, is employed, which couples a finite volume compressible fluid solver with a finite element structural dynamics solver through the construction and solution of local, one-dimensional fluid-solid Riemann problems. The material damage and fracture are modeled and simulated using a continuum damage mechanics model and an element erosion method. The computational model is validated in the context of shock wave lithotripsy and the results are compared with experimental data. We first show that after calibrating the growth rate of microscopic damage and the threshold for macroscopic fracture, the computational framework is capable of capturing the location and shape of the shock-induced fracture observed in a laboratory experiment. Next, we introduce a new phenomenological model of shock waveform, and present a numerical parametric study on the effects of a single shock load, in which the shock waveform, magnitude, and the size of the target material are varied. In particular, we vary the waveform gradually from one that features non-monotonic decay with a tensile phase to one that exhibits monotonic decay without a tensile phase. The result suggests that when the length of the shock pulse is comparable to that of the target material, the former waveform may induce much more significant damage than the latter one, even if the two share the same magnitude, duration, and acoustic energy.

Synthetic 10FN3-based mono- and bivalent inhibitors of MDM2/X function

Engineered non-antibody scaffold proteins constitute a rapidly growing technology for diagnostics and modulation/perturbation of protein function. Here, we describe the rapid and systematic development of high-affinity 10FN3 domain inhibitors of the MDM2 and MDMX proteins. These are often overexpressed in cancer and represent attractive drug targets. Using facile in vitro expression and pull-down assay methodology, numerous design iterations addressing insertion site(s) and spacer length were screened for optimal presentation of an MDM2/X dual peptide inhibitor in the 10FN3 scaffold. Lead inhibitors demonstrated robust, on-target cellular inhibition of MDM2/X leading to activation of the p53 tumor suppressor. Significant improvement to target engagement was observed by increasing valency within a single 10FN3 domain, which has not been demonstrated previously. We further established stable reporter cell lines with tunable expression of EGFP-fused 10FN3 domain inhibitors, and showed their intracellular location to be contingent on target engagement. Importantly, competitive inhibition of MDM2/X by small molecules and cell-penetrating peptides led to a readily observable phenotype, indicating significant potential of the developed platform as a robust tool for cell-based drug screening.

Elevation of p11 in lateral habenula mediates depression-like behavior

The lateral habenula (LHb) is a key brain region involved in the pathophysiology of depression. It is activated by stimuli associated with negative experiences and is involved in encoding aversive signals. Hyperactivity of LHb is found in both rodent models of depression and human patients with depression. However, little is known about the underlying molecular mechanisms. Here we show that in LHb neurons, p11, a multifunctional protein implicated in depression, is significantly upregulated by chronic restraint stress. Knockdown of p11 expression in LHb alleviates the stress-induced depression-like behaviors. Moreover, chronic restraint stress induces bursting action potentials in LHb neurons, which are abolished by p11 knockdown. Overexpression of p11 in dopamine D2 receptor-containing LHb neurons of control mice induces depression-like behaviors. These results have identified p11 in LHb as a key molecular determinant regulating negative emotions, which may help to understand the molecular and cellular basis of depression.

[The relationship between nutritional status and oxidative stress markers, pulmonary function in patients with stable chronic obstructive pulmonary disease]

Objective: To investigate the association between the nutritional status of patients with chronic obstructive pulmonary disease (COPD) and the levels of serum oxidative stress markers protein carbonyls (PC), malondialdehyde (MDA), 8-hydroxy-2'-deoxyguanosine (8-OHdG), total antioxidant capacity (TAC) and pulmonary function. Methods: 200 patients with stable COPD (the COPD group) and 100 healthy individuals (the control group) who visited during June 2014 and August 2014 were enrolled in our study. The levels of PC, MDA, 8-OHdG and TAC in serum were detected. Pulmonary function was tested. Nutritional status was assessed by mini nutritional assessment (MNA) that classified the nutrition class. Results: The levels of PC, MDA, and 8-OHdG in serum increased significantly in the COPD group [3.82 (1.79, 6.83) μg/L, 3.89(2.77, 5.40) μmol/L and 359.18(259.25, 587.85) ng/L, respectively], and the levels of TAC in serum decreased significantly in COPD group [11.35(4.81, 20.20)U/ml], as compared with the control group [2.29(1.08, 3.26) μg/L, 3.08(2.32, 4.03) μmol/L, 311.37(265.47, 374.08) ng/L and 18.81(15.21, 23.19) U/ml, respectively, all P<0.05]. All the nutrition assessment parameters were gradually decreased as nutritional status worsen (all P<0.05). In malnourished (risk) COPD subgroup, the levels of PC and TAC in serum increased significantly [6.10(3.02, 8.18) μg/L and 13.33(6.07, 23.96) U/ml, respectively] and the FEV(1)% and FEV(1)/FVC index decreased significantly [42.90(34.68, 71.23) and 46.96(38.96, 60.63), respectively] as compared the well-nourished COPD subgroup [3.25(1.61, 5.37) μg/L, 9.99(4.41, 16.77) U/ml, 69.10(45.95, 89.23) and 53.32(42.13, 63.15), all P<0.05]. Furthermore, we had found that the upper arm muscle circumference, calf circumference and BMI were positively correlated with MNA (r=0.498, 0.587, 0.781, P<0.001), negatively correlated with PC (r=-0.209, -0.195, -0.231, P<0.05) and positively correlated with FEV(1)% (r=0.223, 0.274, 0.350, P<0.05). The upper arm muscle circumference and BMI were positively correlated with FEV(1)/FVC (r=0.166, 0.224, P<0.05). In COPD group, the level of PC in serum and FEV(1)% were important factor in MNA score, and the impacts of FEV(1)% were greater than the level of PC(β=0.367, -0.304, P<0.001). Conclusion: The protein carbonylation and airflow limitation might be closely related to malnutrition.

[The surgical management of giant intracranial vestibular schwannoma via retrosigmoid approach: a retrospective review of 657 cases]

OBJECTIVE

To discuss the surgical technique and common complications from the microsurgical treatment of giant intracranial vestibular schwannoma via suboccipital retrosigmoid approach and to propose strategies for minimizing such complications.

METHODS

Surgical outcomes and complications were evaluated in a consecutive series of 657 unilateral giant vestibular schwannomas treated in Shanghai Huashan Hospital via suboccipital retrosigmoid approach from 1999 to 2014. According to the international classification of vestibular schwannoma, giant tumor means tumor's size over 4 cm in diameter. Clinical status and complications were assessed postoperatively within 14 days and at follow-ups (range, 6-191 months; mean, 59.6 months).

RESULTS

Follow-up data were available for 566 of the 657 patients (86.1%). The most frequent clinical symptoms were hearing loss in different levels (100%), deafness (36.4%), facial numbness (68.8%). Total tumor resection was achieved in 556 patients (84.6%), subtotal resection in 99 patients (15.1%), and partial resection in 2 patients (0.3%). The common postoperative complications included new deafness (49.6%), intracranial infection (7.6%), low cranial nerve defect (7.5%) and pneumonia (6.2%). The facial nerve was preserved anatomically in 589 cases (89.6%) after operation, and the functional valuation of facial nerve according to postoperative House-Brackmann showed 216 patients (32.9%) in grade Ⅰ-Ⅱ, 308 cases (46.9%) in grade Ⅲ, 133 patients (20.2%) in grade Ⅳ-Ⅵ. Long-term followed-up results showed 428 patients (75.6%) in grade Ⅰ-Ⅲ one year after surgical treatment.

CONCLUSIONS

Many of these complications are avoidable. Surgical experiences and the clinical anatomy of the approach, accompany with using intraoperative nerve monitoring, preoperatively study the individual imaging and clinical data and multidisciplinary cooperation are the key points to avoid the complications of giant intracranial vestibular schwannoma via suboccipital retrosigmoid approach.

[Epidemic situation of imported malaria in Chengdu City from 2012 to 2016]

Objective To understand the malaria epidemic situation in Chengdu City, so as to provide the evidence for effectively carrying out the malaria elimination work. Methods The data of imported malaria in Chengdu City from 2012 to 2016 were collected from the Disease Surveillance Information Reporting System of Chinese Center for Disease Control and Prevention and analyzed respectively. Results A total of 240 imported malaria cases were reported in Chengdu City from 2012 to 2016. In detail, 68.75% of the cases were falciparum malaria cases, 20.41% were vivax malaria cases, 2.50% were quartan malaria cases, 6.25% were ovale malaria cases, and 2.08% were mixed Plasmodium infections. Among them three patients died, with a mortality of 1.25%. All of the cases were infected overseas, among which 224 patients returned from Africa and 16 patients from Southeast Asia. The annual average morbidity was 0.28/100 000, and there was a significantly difference among annual average morbidities (χ² = 23.87, P < 0.001). There were malaria cases reported in every month, and no significantly difference among seasons (χ² = 0.833, P > 0.05). Conclusion The number of overseas imported malaria in Chengdu City increases year by year. The effective measures to control the overseas imported malaria should be strengthened to consolidate the achievements of malaria elimination.

Serum total bilirubin levels are negatively correlated with metabolic syndrome in aged Chinese women: a community-based study

We evaluated serum total bilirubin levels as a predictor for metabolic syndrome (MetS) and investigated the relationship between serum total bilirubin levels and MetS prevalence. This cross-sectional study included 1728 participants over 65 years of age from Eastern China. Anthropometric data, lifestyle information, and previous medical history were collected. We then measured serum levels of fasting blood-glucose, total cholesterol, triglycerides, and total bilirubin, as well as alanine aminotransferase activity. The prevalence of MetS and each of its individual component were calculated per quartile of total bilirubin level. Logistic regression was used to assess the correlation between serum total bilirubin levels and MetS. Total bilirubin level in the women who did not have MetS was significantly higher than in those who had MetS (P<0.001). Serum total bilirubin quartiles were linearly and negatively correlated with MetS prevalence and hypertriglyceridemia (HTG) in females (P<0.005). Logistic regression showed that serum total bilirubin was an independent predictor of MetS for females (OR: 0.910, 95%CI: 0.863-0.960; P=0.001). The present study suggests that physiological levels of serum total bilirubin might be an independent risk factor for aged Chinese women, and the prevalence of MetS and HTG are negatively correlated to serum total bilirubin levels.

Direct conversion of human fibroblasts to induced serotonergic neurons

Serotonergic (5HT) neurons exert diverse and widespread functions in the brain. Dysfunction of the serotonergic system gives rise to a variety of mental illnesses including depression, anxiety, obsessive compulsive disorder, autism and eating disorders. Here we show that human primary fibroblasts were directly converted to induced serotonergic (i5HT) neurons by the expression of Ascl1, Foxa2, Lmx1b and FEV. The transdifferentiation was enhanced by p53 knockdown and appropriate culture conditions including hypoxia. The i5HT neurons expressed markers for mature serotonergic neurons, had Ca(2+)-dependent 5HT release and selective 5HT uptake, exhibited spontaneous action potentials and spontaneous excitatory postsynaptic currents. Application of serotonin significantly increased the firing rate of spontaneous action potentials, demonstrating the functional utility of i5HT neurons for studying serotonergic neurotransmission. The availability of human i5HT neurons will be very useful for research and drug discovery on many serotonin-related mental disorders.

Long-term treadmill exercise improves spatial memory of male APPswe/PS1dE9 mice by regulation of BDNF expression and microglia activation

Increasing evidence suggests that physical activity could delay or attenuate the symptoms of Alzheimer's disease (AD). But the underlying mechanisms are still not fully understood. To investigate the effect of long-term treadmill exercise on the spatial memory of AD mice and the possible role of β-amyloid, brain-derived neurotrophic factor (BDNF) and microglia in the effect, male APPswe/PS1dE9 AD mice aged 4 months were subjected to treadmill exercise for 5 months with 6 sessions per week and gradually increased load. A Morris water maze was used to evaluate the spatial memory. Expression levels of β-amyloid, BDNF and Iba-1 (a microglia marker) in brain tissue were detected by immunohistochemistry. Sedentary AD mice and wildtype C57BL/6J mice served as controls. The results showed that 5-month treadmill exercise significantly decreased the escape latencies (P < 0.01 on the 4th day) and improved the spatial memory of the AD mice in the water maze test. Meanwhile, treadmill exercise significantly increased the number of BDNF-positive cells and decreased the ratios of activated microglia in both the cerebral cortex and the hippocampus. However, treadmill exercise did not significantly alleviate the accumulation of β-amyloid in either the cerebral cortex or the hippocampus of the AD mice (P > 0.05). The study suggested that long-term treadmill exercise could improve the spatial memory of the male APPswe/PS1dE9 AD mice. The increase in BDNF-positive cells and decrease in activated microglia might underpin the beneficial effect.

Estrogen protects against the detrimental effects of repeated stress on glutamatergic transmission and cognition

Converging evidence suggests that females and males show different responses to stress; however, little is known about the mechanism underlying the sexually dimorphic effects of stress. In this study, we found that young female rats exposed to 1 week of repeated restraint stress show no negative effects on temporal order recognition memory (TORM), a cognitive process controlled by the prefrontal cortex (PFC), which was contrary to the impairment in TORM observed in stressed males. Concomitantly, normal glutamatergic transmission and glutamate receptor surface expression in PFC pyramidal neurons were found in repeatedly stressed females, in contrast to the significant reduction seen in stressed males. The detrimental effects of repeated stress on TORM and glutamate receptors were unmasked in stressed females when estrogen receptors were inhibited or knocked down in PFC, and were prevented in stressed males with the administration of estradiol. Blocking aromatase, the enzyme for the biosynthesis of estrogen, revealed the stress-induced glutamatergic deficits and memory impairment in females, and the level of aromatase was significantly higher in the PFC of females than in males. These results suggest that estrogen protects against the detrimental effects of repeated stress on glutamatergic transmission and PFC-dependent cognition, which may underlie the stress resilience of females.

Modelling single- and tandem-bubble dynamics between two parallel plates for biomedical applications

Carefully timed tandem microbubbles have been shown to produce directional and targeted membrane poration of individual cells in microfluidic systems, which could be of use in ultrasound-mediated drug and gene delivery. This study aims at contributing to the understanding of the mechanisms at play in such an interaction. The dynamics of single and tandem microbubbles between two parallel plates is studied numerically and analytically. Comparisons are then made between the numerical results and the available experimental results. Numerically, assuming a potential flow, a three-dimensional boundary element method (BEM) is used to describe complex bubble deformations, jet formation, and bubble splitting. Analytically, compressibility and viscous boundary layer effects along the channel walls, neglected in the BEM model, are considered while shape of the bubble is not considered. Comparisons show that energy losses modify the bubble dynamics when the two approaches use identical initial conditions. The initial conditions in the boundary element method can be adjusted to recover the bubble period and maximum bubble volume when in an infinite medium. Using the same conditions enables the method to recover the full dynamics of single and tandem bubbles, including large deformations and fast re-entering jet formation. This method can be used as a design tool for future tandem-bubble sonoporation experiments.

Stone comminution correlates with the average peak pressure incident on a stone during shock wave lithotripsy

To investigate the roles of lithotripter shock wave (LSW) parameters and cavitation in stone comminution, a series of in vitro fragmentation experiments have been conducted in water and 1,3-butanediol (a cavitation-suppressive fluid) at a variety of acoustic field positions of an electromagnetic shock wave lithotripter. Using field mapping data and integrated parameters averaged over a circular stone holder area (R(h)=7 mm), close logarithmic correlations between the average peak pressure (P(+(avg))) incident on the stone (D=10 mm BegoStone) and comminution efficiency after 500 and 1000 shocks have been identified. Moreover, the correlations have demonstrated distinctive thresholds in P(+(avg)) (5.3 MPa and 7.6 MPa for soft and hard stones, respectively), that are required to initiate stone fragmentation independent of surrounding fluid medium and LSW dose. These observations, should they be confirmed using other shock wave lithotripters, may provide an important field parameter (i.e., P(+(avg))) to guide appropriate application of SWL in clinics, and facilitate device comparison and design improvements in future lithotripters.

A comparison of light spot hydrophone and fiber optic probe hydrophone for lithotripter field characterization

The performance of a newly developed light spot hydrophone (LSHD) in lithotripter field characterization was compared to that of the fiber optic probe hydrophone (FOPH). Pressure waveforms produced by a stable electromagnetic shock wave source were measured by the LSHD and FOPH under identical experimental conditions. In the low energy regime, focus and field acoustic parameters matched well between the two hydrophones. At clinically relevant high energy settings for shock wave lithotripsy, the measured leading compressive pressure waveforms matched closely with each other. However, the LSHD recorded slightly larger |P_| (p < 0.05) and secondary peak compressive pressures (p < 0.01) than the FOPH, leading to about 20% increase in total acoustic pulse energy calculated in a 6 mm radius around the focus (p = 0.06). Tensile pulse durations deviated ~5% (p < 0.01) due to tensile wave shortening from cavitation activity using the LSHD. Intermittent compression spikes and laser light reflection artifacts have been correlated to bubble activity based on simultaneous high-speed imaging analysis. Altogether, both hydrophones are adequate for lithotripter field characterization as specified by the international standard IEC 61846.

Metal-assisted electrochemical etching of silicon

In this paper the metal-assisted electrochemical etching of silicon is introduced. By electrochemical measurement and sequent simulation, it is revealed that the potential of the valence band maximum at the silicon/metal interface is more negative than that of the silicon/electrolyte interface. Accordingly, holes injected from the back contact are driven preferentially to the silicon/metal interface. Consequently, silicon below metal is electrochemically etched much faster than a naked silicon surface without metal coverage. Metals such as Ag and Cu have been utilized to catalyze the electrochemical etching. Feature sizes as small as 30 nm can be achieved by metal-assisted electrochemical etching. Meanwhile, the metal-assisted electrochemical etching method enables convenient control over the etching direction of non-(100) substrates, and facilitates the fabrication of orientation-modulated silicon nanostructures.

Pulsating tandem microbubble for localized and directional single-cell membrane poration

The interaction of laser-generated tandem microbubble (maximum diameter of about 50  μm) with single (rat mammary carcinoma) cells is investigated in a 25-μm liquid layer. Antiphase and coupled oscillation of the tandem microbubble leads to the formation of alternating, directional microjets (with max microstreaming velocity of 10  m/s) and vortices (max vorticity of 350 000  s{-1}) in opposite directions. Localized and directional membrane poration (200 nm to 2  μm in pore size) can be produced by the tandem microbubble in an orientation and proximity-dependent manner, which is absent from a single oscillating microbubble of comparable size and at the same stand-off distance.

A composite kidney stone phantom with mechanical properties controllable over the range of human kidney stones

A novel composite kidney stone phantom has been developed. This stone phantom is producible with mechanical properties mimicking the range of tensile fracture strength and acoustic properties of human kidney stones and is an inorganic/organic composite material, as are natural kidney stones. Diametral compression testing was used to measure tensile fracture strength, which determines the acoustic comminution behavior of kidney stones. Ultrasound transmission tests were made to characterize the acoustic properties of these stone phantoms. Both the tensile fracture strength (controllable from 1 to approximately 5 MPa) and acoustic properties (C(L) = 2700-4400 m/s and C(T)=1600-2300m/s) of these composite phantom stones match those of a wide variety of human kidney stones. These artificial stone phantoms should have wide utility in lithotripsy research.

Activation of transgene expression in skeletal muscle by focused ultrasound

To correlate thermal dose from focused ultrasound (FUS) with gene expression and tissue injury, a temperature plateau strategy was employed. Plasmids encoding luciferase gene under the control of hsp70B promoter were transfected into the right gastrocnemius muscle in a rat via electroporation. One day after transfection, hind limbs were treated with 3.3-MHz focused ultrasound, using one of four different temperature plateaus with spatial-peak time-average focal temperatures (T(SPTA)) of 46 degrees C, 48 degrees C, 51 degrees C and 62 degrees C. The treatment duration at the plateau temperature was varied from 0 to 30s. Gene expression was analyzed in vivo one day following FUS treatment, and H&E staining was employed to assess tissue injury. Gene activation and tissue damage correlated closely with thermal dose. The highest level of gene activation was induced by FUS at T(SPTA)=51 degrees C for 20s, which was found to be statistically equivalent to that produced by water-bath hyperthermia.

Interaction between shock wave and single inertial bubbles near an elastic boundary

The interaction of laser-generated single inertial bubbles (collapse time = 121 mus) near a silicon rubber membrane with a shock wave (55 MPa in peak pressure and 1.7 mus in compressive pulse duration) is investigated. The interaction leads to directional, forced asymmetric collapse of the bubble with microjet formation toward the surface. Maximum jet penetration into the membrane is produced during the bubble collapse phase with optimal shock wave arrival time and stand-off distance. Such interaction may provide a unique acoustic means for in vivo microinjection, applicable to targeted delivery of macromolecules and gene vectors to biological tissues.

Shock wave interaction with laser-generated single bubbles

The interaction of a lithotripter shock wave (LSW) with laser-generated single vapor bubbles in water is investigated using high-speed photography and pressure measurement via a fiber-optic probe hydrophone. The interaction leads to nonspherical collapse of the bubble with secondary shock wave emission and microjet formation along the LSW propagation direction. The maximum pressure amplification is produced during the collapse phase of the bubble oscillation when the compressive pulse duration of the LSW matches with the forced collapse time of the bubble.

The Use of Chemical Treatments for Improved Comminution of Artificial Stones

PURPOSE

The acoustic and mechanical properties of various stone compositions are significantly different and thus result in varying degrees of fragility. Consequently, results to shock wave lithotripsy (SWL) are influenced accordingly. We report the results of a study of fragility of various stone compositions, and the influence on each stone's baseline physical properties and fragility when exposed to various chemolytic solutions.

MATERIALS AND METHODS

Before SWL artificial stones of differing compositions were irrigated with various chemolytic solutions. Calcium oxalate monohydrate (COM) stones were treated with ethylenediaminetetraacetic acid (EDTA), stones composed of magnesium ammonium phosphate hydrogen were treated with hemiacidrin, and stones made of uric acid (UA) were treated with tromethamine. Synthetic urine served as a control for all stone groups. Using an ultrasound transmission technique, longitudinal wave propagation speed was measured in all groups of artificial stones. Stone density was also measured by using a pycnometer (based on Archimedes' principle). Based on these measurements transverse (shear) wave speed (assuming a constant Poisson's ratio), wave impedance and dynamic mechanical properties of the artificial stones were calculated. Moreover, the microhardness of these artificial stones was measured, and fragility testing using SWL with and without pretreatment with the previously mentioned chemolytic solutions, was performed.

RESULTS

Wave speed, wave impedance, dynamic mechanical properties and microhardness of EDTA treated COM stones and tromethamine treated UA stones were found to decrease compared to untreated (synthetic urine) control groups. The suggestion that chemolytic pretreatment increases stone fragility was verified by the finding of increased stone comminution after SWL testing. Combining this medical pretreatment and SWL, the findings demonstrate a significant impact of various solvents on stone comminution, in particular EDTA treated COM stones, tromethamine treated UA stones and hemiacidrin treated magnesium ammonium phosphate hydrogen stones. These data suggest that by altering the chemical environment of the fluid surrounding the stones it is possible to increase the fragility of renal calculi in vitro.

CONCLUSIONS

These results indicate that appropriate chemical treatments may provide a useful adjunctive modality for improving the efficacy of stone comminution during shock wave lithotripsy.

Chronic antidepressant treatment alters serotonergic regulation of GABA transmission in prefrontal cortical pyramidal neurons

The serotonin system is highly involved in the pathophysiology of mood disorders such as depression and anxiety. Currently, the most widely used treatment for these illnesses is selective serotonin (5-HT)reuptake inhibitors, such as fluoxetine. Because of the multiplicity of 5-HT receptors and their different adaptive properties, the chronic effects of fluoxetine have remained unclear. In this study, we investigated the alteration of 5-HT functions by long-term antidepressant treatment in pyramidal neurons of prefrontal cortex (PFC), a brain region crucial for the control of emotion and cognition. One prominent function of serotonin in PFC is to regulate GABAergic inhibitory transmission. Application of 5-HT induced a large, desensitizing enhancement of the amplitude and frequency of spontaneous inhibitory postsynaptic currents (sIPSC), as well as a potent reduction of electrically evoked IPSC (eIPSC). Chronic fluoxetine treatment did not alter basal sIPSC, but reduced eIPSC in response to different stimulus strengths. Moreover, chronic (but not acute) fluoxetine treatment caused a much faster desensitization of the 5-HT effect on sIPSC, and significantly attenuated the 5-HT effect on eIPSC. Application of a 5-HT(2) receptor agonist produced similar effects as 5-HT on sIPSC and eIPSC, and these effects were similarly altered by long-term fluoxetine treatment. These electrophysiological results suggest that chronic antidepressant treatment resulted in a down-regulation of the synaptic function of forebrain 5-HT(2) receptors. Given the key role of GABAergic inhibitory transmission in controlling PFC functions, its altered regulation by serotonin after chronic fluoxetine treatment may provide a mechanism underlying the therapeutic action of antidepressants.

Preparation and identification of specific and high-affinity monoclonal antibodies against morphine

A C6-hemisuccinate derivative of morphine was prepared and conjugated to bovine serum albumin and ovalbumin. High titer antibody producing spleen cells were removed and fused with myeloma cells of SP2/0 origin. Using a conventional immunization protocol generated twenty-six stable murine monoclonal antibodies (MAbs) producing cell lines to morphine. The donor mouse produced antiserum with a high titer of 1/640,000. Twelve MAbs were selected for further characterization since they showed high sensitivities (53 pg/well to inhibit 50% of the tracer) in improved group-selective immunoassay (IGSI). The assay, which maintains high sensitivity, high precision, and a wide range of optical density (OD) values, was developed using the conjugate M-6-S-OVA to screen and characterize the anti-morphine MAbs. After four successive limiting dilutions, antibodies produced by 12 clones had high affinities ranging from 10(9) to 10(10) M(-1). These clones were found to be of Ig(G) class and IgM class with kappa and lambda light chain. Subclass determination showed that the clones produced IgG1, IgG2a, IgG3, and IgM types of antibody. One clone (2F8B11F2A12) was used to establish the calibration curve with a sensitivity of 400 pg/mL covering up to 25.6 ng/mL in urine.

Binding site of macrolide antibiotics on the ribosome: new resistance mutation identifies a specific interaction of ketolides with rRNA

Macrolides represent a clinically important class of antibiotics that block protein synthesis by interacting with the large ribosomal subunit. The macrolide binding site is composed primarily of rRNA. However, the mode of interaction of macrolides with rRNA and the exact location of the drug binding site have yet to be described. A new class of macrolide antibiotics, known as ketolides, show improved activity against organisms that have developed resistance to previously used macrolides. The biochemical reasons for increased potency of ketolides remain unknown. Here we describe the first mutation that confers resistance to ketolide antibiotics while leaving cells sensitive to other types of macrolides. A transition of U to C at position 2609 of 23S rRNA rendered E. coli cells resistant to two different types of ketolides, telithromycin and ABT-773, but increased slightly the sensitivity to erythromycin, azithromycin, and a cladinose-containing derivative of telithromycin. Ribosomes isolated from the mutant cells had reduced affinity for ketolides, while their affinity for erythromycin was not diminished. Possible direct interaction of ketolides with position 2609 in 23S rRNA was further confirmed by RNA footprinting. The newly isolated ketolide-resistance mutation, as well as 23S rRNA positions shown previously to be involved in interaction with macrolide antibiotics, have been modeled in the crystallographic structure of the large ribosomal subunit. The location of the macrolide binding site in the nascent peptide exit tunnel at some distance from the peptidyl transferase center agrees with the proposed model of macrolide inhibitory action and explains the dominant nature of macrolide resistance mutations. Spatial separation of the rRNA residues involved in universal contacts with macrolides from those believed to participate in structure-specific interactions with ketolides provides the structural basis for the improved activity of the broader spectrum group of macrolide antibiotics.

Suppression of large intraluminal bubble expansion in shock wave lithotripsy without compromising stone comminution: methodology and in vitro experiments

To reduce the potential of vascular injury without compromising the stone comminution capability of a Dornier HM-3 lithotripter, we have devised a method to suppress intraluminal bubble expansion via in situ pulse superposition. A thin shell ellipsoidal reflector insert was designed and fabricated to fit snugly into the original reflector of an HM-3 lithotripter. The inner surface of the reflector insert shares the same first focus with the original HM-3 reflector, but has its second focus located 5 mm proximal to the generator than that of the HM-3 reflector. With this modification, the original lithotripter shock wave is partitioned into a leading lithotripter pulse (peak positive pressure of 46 MPa and positive pulse duration of 1 micros at 24 kV) and an ensuing second compressive wave of 10 MPa peak pressure and 2 micros pulse duration, separated from each other by about 4 micros. Superposition of the two waves leads to a selective truncation of the trailing tensile component of the lithotripter shock wave, and consequently, a reduction in the maximum bubble expansion up to 41% compared to that produced by the original reflector. The pulse amplitude and -6 dB beam width of the leading lithotripter shock wave from the upgraded reflector at 24 kV are comparable to that produced by the original HM-3 reflector at 20 kV. At the lithotripter focus, while only about 30 shocks are needed to cause a rupture of a blood vessel phantom made of cellulose hollow fiber (i.d.=0.2 mm) using the original HM-3 reflector at 20 kV, no rupture could be produced after 200 shocks using the upgraded reflector at 24 kV. On the other hand, after 100 shocks the upgraded reflector at 24 kV can achieve a stone comminution efficiency of 22%, which is better than the 18% efficiency produced by the original reflector at 20 kV (p = 0.043). All together, it has been shown in vitro that the upgraded reflector can produce satisfactory stone comminution while significantly reducing the potential for vessel rupture in shock wave lithotripsy.

Novel erythromycin derivatives with aryl groups tethered to the C-6 position are potent protein synthesis inhibitors and active against multidrug-resistant respiratory pathogens

A novel series of erythromycin derivatives has been discovered with potent activity against key respiratory pathogens, including those resistant to erythromycin. These compounds are characterized by having an aryl group tethered to the C-6 position of the erythronolide skeleton. Extensive structural modification of the C-6 moiety led to the discovery of several promising compounds with potent activity against both mef- and erm-mediated resistant Streptoccoccus pneumoniae. Preliminary mechanistic studies indicated that the new macrolides are potent protein synthesis inhibitors, which interact with methylated ribosomes isolated from resistant organisms. In experimental animal models, these compounds exhibited excellent in vivo efficacy and balanced pharmacokinetic profiles.

[Effect of simulated weightlessness on the apoptosis of thymus cells in tail-suspended mice]

OBJECTIVE

To investigate the effect of simulated weightlessness on apoptosis of thymus cells in mice.

METHOD

Tail-suspended mice were used as an animal model of simulated weightlessness; chromosome breakage was measured by PI staining, and changes of cell membrane were determined by Annexin-V analysis.

RESULT

As compared with the control, there was no obvious chromosome breakage; the total number of apoptotic cells and number of early apoptotic cells increased in 1 d suspended group; the number of early apoptotic cells increased significantly and the total number of apoptotic cells increased very significantly in 2d suspended groups.

CONCLUSION

These results suggested that simulated weightlessness could promote apoptosis of thymus cells.

The emerging new generation of antibiotic: ketolides

The bacterial ribosome is a target for a variety of drug classes including macrolides. Macrolide antibiotics are primarily used for the treatment of respiratory tract infections. One of the most important features of the macrolide class is the excellent safety profile allowing the drug to be used broadly across all age groups. The emergence of macrolide resistance, especially in S. pneumoniae, threatens the long-term usefulness of macrolide antibiotics. The newly developed ketolide class, including telithromycin and ABT-773, evolved from the macrolide class and displays significant improvements over macrolides while maintaining safety profiles similar to macrolides. The key improvement in antimicrobial spectrum is the in vitro potency against macrolide resistant pathogens, especially S. pneumoniae. This review outlines the key improvements of ketolides over macrolides in terms of in vitro microbiology, as well as the pharmacokinetic and pharmacodynamic profiles and updates the current understanding of drug-ribosome interactions. The application of cutting-edge technology such as ribosome structure-based rational drug design and genetic engineering are also briefly discussed.

[Protective effects of Chinese herb-compound on cellular immunological function (correction of funcion) in tail-suspended rats]

Objective. To observe the protective effects of two kinds of Chinese herb-compounds (Dan-huang-ci compound and Shen-chuan-shu compound) on cellular immunology in tail-suspended rats. Method. The rats were divided into: 1) normal control group; 2) tail-suspended group; 3) tail-suspended + Dan-huang-ci compound; and 4) tail-suspended + Shen-chuan-shu compound. Ability of lymphocyte proliferation and production of IL-2 in rats in the four groups were compared after 21 d. Result. The immunological function of tail-suspended control group decreased significantly as compared with normal control group. Shen-chuan-shu compound could improve immunological function of tail-suspended rats obviously. Conclusion. Shen-chuan-shu compound could enhance cellular immunological function in rats under simulated weightlessness.

Dynamic photoelastic study of the transient stress field in solids during shock wave lithotripsy

Photoelastic and shadowgraph imaging techniques were used to visualize the propagation and evolution of stress waves, and the resultant transient stress fields in solids during shock wave lithotripsy. In parallel, theoretical analysis of the wavefront evolution inside the solids was performed using a ray-tracing method. Excellent agreement between the theoretical prediction and experimental results was observed. Both the sample size and geometry were found to have a significant influence on the wave evolution and associated stress field produced inside the solid. In particular, characteristic patterns of spalling damage (i.e., transverse and longitudinal crack formation) were observed using plaster-of-Paris cylindrical phantoms of rectangular and circular cross sections. It was found that the leading tensile pulse of the reflected longitudinal wave is responsible for the initiation of microcracks in regions inside the phantom where high tensile stresses are produced. In addition, the transmitted shear wave was found to play a critical role in facilitating the extension and propagation of the microcrack.

Dynamics of bubble oscillation in constrained media and mechanisms of vessel rupture in SWL

Rupture of small blood vessels is a primary feature of the vascular injury associated with shock-wave lithotripsy (SWL) and cavitation has been implicated as a potential mechanism. To understand more precisely the underlying mechanical cause of the injury, the dynamics of SWL-induced bubble dynamics in constrained media were investigated. Silicone tubing and regenerated cellulose hollow fibers of various inner diameters (0.2 to 1.5 mm) were used to fabricate vessel phantoms, which were placed in a test chamber filled with castor oil so that cavitation outside the phantom could be suppressed. Degassed water seeded with 0.2% Albunex contrast agent was circulated inside the vessel phantom, and intraluminal bubble dynamics during SWL were examined by high-speed shadowgraph imaging and passive cavitation detection via a 20-MHz focused transducer. It was observed that, in contrast to the typical large and prolonged expansion and violent inertial collapse of SWL-induced bubbles in a free field, the expansion of the bubbles inside the vessel phantom was significantly constrained, leading to asymmetric elongation of the bubbles along the vessel axis and, presumably, much weakened collapse. The severity of the constraint is vessel-size dependent, and increases dramatically when the inner diameter of the vessel becomes smaller than 300 microm. Conversely, the rapid, large intraluminal expansion of the bubbles causes a significant dilation of the vessel wall, leading to consistent rupture of the hollow fibers (i.d. = 200 microm) after less than 20 pulses of shock wave exposure in a XL-1 lithotripter. The rupture is dose-dependent, and varies with the spatial location of the vessel phantom in the lithotripter field. Further, when the large intraluminal bubble expansion was suppressed by inversion of the lithotripter pressure waveform, rupture of the hollow fiber could be avoided even after 100 shocks. Theoretical calculation of SWL-induced bubble dynamics in blood confirms that the propensity of vascular injury due to intraluminal bubble expansion increases with the tensile pressure of the lithotripter shock wave, and with the reduction of the inner diameter of the vessel. It is suggested that selective truncation of the tensile pressure of the shock wave may reduce tissue injury without compromising the fragmentation capability of the lithotripter pulse.

Molecular determinants of the functional interaction between syntaxin and N-type Ca2+ channel gating

Syntaxin is a key presynaptic protein that binds to N- and P/Q-type Ca(2+) channels in biochemical studies and affects gating of these Ca(2+) channels in expression systems and in synaptosomes. The present study was aimed at understanding the molecular basis of syntaxin modulation of N-type channel gating. Mutagenesis of either syntaxin 1A or the pore-forming alpha(1B) subunit of N-type Ca(2+) channels was combined with functional assays of N-type channel gating in a Xenopus oocyte coexpression system and in biochemical binding experiments in vitro. Our analysis showed that the transmembrane region of syntaxin and a short region within the H3 helical cytoplasmic domain of syntaxin, containing residues Ala-240 and Val-244, appeared critical for the channel modulation but not for biochemical association with the "synprint site" in the II/III loop of alpha(1B). These results suggest that syntaxin and the alpha(1B) subunit engage in two kinds of interactions: an anchoring interaction via the II/III loop synprint site and a modulatory interaction via another site located elsewhere in the channel sequence. The segment of syntaxin H3 found to be involved in the modulatory interaction would lie hidden within the four-helix structure of the SNARE complex, supporting the hypothesis that syntaxin's ability to regulate N-type Ca(2+) channels would be enabled after SNARE complex disassembly after synaptic vesicle exocytosis.

Quantification of the tip movement of lithotripsy flexible pneumatic probes

PURPOSE

We developed an optical system to quantify in vitro tip movement of the Lithoclastdouble dagger flexible probe, and correlated various physical parameters of the vibrating probe tip with resultant stone fragmentation.

MATERIALS AND METHODS

A noncontact optical measurement system was developed to quantify in vitro tip movement of the Lithoclast flexible probe. This system and an in vitro fragmentation model were used to determine the tip displacement, velocity, impact momentum, impact energy and stone fragmentation of the flexible probe at 5 deflection angles between 0 and 48 degrees, and the 2 pneumatic pressure levels of 2.0 and 2.5 bar.

RESULTS

An increase in maximum probe tip displacement, velocity, impact momentum and energy, and stone fragmentation was seen as the pneumatic pressure was increased from 2.0 to 2.5 bar. A progressive decrease in these parameters was demonstrated as the probe tip was deflected, especially at deflection angles greater than 24 degrees. Impact momentum appears to be the physical parameter most closely correlated with stone fragmentation efficiency.

CONCLUSIONS

The optical measurement system and in vitro fragmentation model developed allow one to quickly and reliably assess the performance of flexible pneumatic probes in vitro. This system can be used for general bench testing and basic research that can provide critical information for the design of more effective and efficient flexible pneumatic lithotripsy probes.

[Alteration of banked blood cholinesterase level and its significance in emergency treatment of acute organophosphorus pesticide poisoning]

OBJECTIVE

To observe the relationship between the preservation days of banked blood and the alteration level of plasma cholinesterase with the aim of making proper selection of banked blood in emergency treatment of acute organophosphorus pesticide poisoning (AOPP).

METHODS

We selected at random the banked blood that has been stored for different length of time before blood transfusion so as to determine the plasma cholinesterase value. The normal plasma cholinesterase value was determined on blood samples in the Blood Center which served as a control group. The cholinesterase value was determined with a kit of the BM Company and the Cobes-Fara II automatic analysor of the Roch Company.

RESULTS

It was found that there was no significant difference of plasma cholinesterase value between the one-day banked blood and the normal control group (P > 0.05), but the plasma cholinesterase values of the other experiment groups were all significantly lower than that of the control group (P < 0.05). As compared with the normal control group, the relative ratio with fixed base was about from 80 percent to 16 percent. It seems that the preservation days are in negative correlation with the cholinesterase value (r = -0.7929, P < 0.01). The curvilinear regression equation is Y = -1,823.3 Ln(X) +/- 6,229.4.

CONCLUSION

With the increase of the banked blood preservation days after blood sampling, the plasma cholinesterase value decreased gradually. So in the emergency treatment of severe AOPP, it is essential to use the fresh blood collected within one day, so as to avoid missing the chance of first-aid treatment. This study provides the experimental basis for emphasizing transfusion of fresh blood and ensuring transfusion of highly active cholinesterase in treating AOPP.

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.