Laser lithotripsy in the treatment of ureteral calculi.

We examined the effectiveness of laser lithotripsy with a flash-lamp-pumped tunable dye laser in the treatment of ureteral calculi that were too large for direct extraction and that could not be treated with or had not responded to extracorporeal shock-wave lithotripsy (ESWL) or forms of ureteroscopic lithotripsy other than laser lithotripsy. In 20 (74%) of the 27 patients the laser alone successfully fragmented the calculi into pieces small enough to pass spontaneously or to be easily extracted with a basket. In five (19%) laser lithotripsy was partially successful: another procedure (ESWL in three and fragment extraction with a basket in two) was needed. In two patients (7%) the stones could not be fragmented with the laser, and either ESWL or percutaneous antegrade extraction was performed. At follow-up 3 months after treatment there was no sign of stone fragments in 26 (96%) of the patients. We believe that laser lithotripsy is a safe and effective method of ureteral stone fragmentation.     

ESWL treatment of urinary stones in children--the overview of 14 years of experience

Extracorporeal shock wave lithotripsy (ESWL) treatment has been used at Department of Urology, University Hospital "Osijek", Croatia, since July 1988. Until December 2001 seven thousand and eight hundred patients underwent ESWL for urinary stones, 68 of them were children (0.87%). Sixty-eight children aged 4 to 15 years (average 10.14 years) underwent ESWL. They were treated for the total of 91 stones: 35 (38.46%) caliceal, 23 (25.27%) in pyelon, 7 (7.69%) in pyeloureteric segment and 14 (15.38%) ureteral. Staghorn calculi were found in 6 (6.59%) patients and multiple stones (four or more stones in the same kidney) in 6 (6.59%). There was total of 95 ESWL sessions performed in 68 patients (1.39 session per patient). Fifty-six patients (82.35%) without residual stones found at the control plain film and sonography of urinary tract were considered "stone free". Addition of 5 patients with clinically insignificant residual fragments (less than 4 mm) increases overall success rate to 89.70%. ESWL is a simple, safe and effective procedure in the management of urolithiasis in childhood. Clinical experience of our institution confirms ESWL as the first line treatment for kidney stones in the pediatric age patients.     

Extracorporeal shock wave lithotripsy: the first 50 patients treated in Britain.

Fifty patients have been treated for upper tract urinary calculi by extracorporeal shock wave lithotripsy (ESWL) at the Devonshire Hospital lithotripter centre since November 1984. The average stay for an inpatient was 3 X 7 days. All patients suffered minimal postoperative discomfort and nearly all resumed normal activity within one day after discharge. Complications requiring auxiliary procedures were few. The procedure was found to be safe, cost effective, extremely well received by patients, and superior to all other methods of removing renal stones. This study confirms that treatment by ESWL is a specialised urological procedure that requires operators who are also trained in open, percutaneous, and ureteroscopic surgery and with a back up of a radiological team skilled in percutaneous renal puncture.     

排石汤联合盐酸坦洛新辅助体外冲击波碎石术治疗上尿路结石的临床疗效分析

目的:探讨排石汤联合盐酸坦洛新辅助体外冲击波碎石术(ESWL)治疗上尿路结石的临床疗效。方法:选择我院2015年1月~2016年9月收治的120例上尿路结石患者,采取随机数字表将其分成两组,每组60例。两组患者均行ESWL治疗,并于术后辅助使用盐酸坦洛新,观察组在上述治疗基础上联合排石汤治疗,对比两组的临床疗效以及治疗前后血清肌酐(Scr)、中性粒细胞明胶酶相关载脂蛋白(NGAL)、半胱氨酸蛋白酶抑制剂C(Cys-C)、肾小球滤过率(GFR)水平的变化情况。结果:观察组总有效率为96.60%,对照组为86.67%,观察组总有效率明显高于对照组(P0.05)。观察组结石排净率为95.00%,明显高于对照组(P0.05);肾绞痛发生率为6.67%,明显低于对照组(P0.05),结石排出时间、血尿持续时间均显著短于对照组(P0.01)。两组1年复发率对比差异无统计学意义(P0.05)。两组患者术后2 h、1 d血清NGAL、Cys-C水平逐渐升高,GFR逐渐下降,术后3 d上述指标逐渐恢复。观察组术后1 d、3 d NGAL、Cys-C水平明显低于对照组,GFR明显高于对照组(P0.01)。两组术前术后各时点Scr比较差异均无明显统计学意义(P0.05)。结论:排石汤联合盐酸坦洛新辅助ESWL治疗上尿路结石的临床疗效显著,并可有效改善ESWL引起的肾损伤。     

净石灵胶囊联合体外冲击波碎石术治疗复杂性肾结石临床疗效分析

目的:探讨净石灵胶囊联合体外冲击波碎石术治疗复杂性肾结石临床疗效。方法:选取2010年1月-2011年12月在我院就诊的复杂性肾结石患者83例,随机分为体外冲击波碎石术组、经皮肾镜碎石取石组、净石灵胶囊联合体外冲击波碎石术组。观察两组间的手术时间、碎石率、疗效以及组内之间不同直径的结石的碎石率。结果:ESWL组碎石成功率85.3%,PCNL组碎石成功率90.0%,净石灵胶囊联合体外冲击波碎石术组碎石成功率89.7%,三组比较无统计学意义(P>0.05);ESWL组手术时间(40.2±6.3)min,PCNL组手术时间(46.6±4.1)min,净石灵胶囊联合体外冲击波碎石术组手术时间(42.2±5.7)min,三组比较无统计学意义(P>0.05);ESWL组、PCNL组、净石灵胶囊联合体外冲击波碎石术组治疗复杂性肾结石的有效率依次为75.0%、80.0%、97.4%,组间比较,差异具有统计学意义(P<0.05);ESWL组5<10mm、10<15mm、15<20mm直径的肾结石的粉碎率依为100%、85.7%、40%,组内比较具有统计学意义(P<0.01),PCNL组5<10mm、10<15mm、15<20mm直径的肾结石的粉碎率依次为100%、83.3%、75%,组内比较具有统计学意义(P<0.05),净石灵胶囊联合体外冲击波碎石术组5<10mm、10<15mm、15<20mm直径的肾结石的粉碎率依次为100%、88.9%、57.1%,组内比较具有统计学意义(P<0.01)。结论:体净石灵胶囊联合体外冲击波碎石术治疗复杂性肾结石的临床疗效优于单纯运用体外冲击波碎石术或经皮肾镜碎石取石术。     

Percutaneous Renal Stone Manipulation—A Nonoperative Alternative

Nephrostomy tube tracts, established operatively or percutaneously, can provide access to stones in the upper urinary tract. A variety of rigid or flexible urologic instruments can be used to percutaneously disintegrate or extract calculi, thus sparing a patient an operative procedure. This is most important in the case of high-risk patients, those previously operated upon or those who have active nephrolithiasis, in whom recurrent stones are prone to form. Our early experience in percutaneous renal stone disintegration and stone manipulation enabled us to remove most (in four patients) or all (again in four patients) calculi in nine patients. The procedure offers lower morbidity, shorter hospital stay and earlier return to employment than conventional operative stone procedures.     

输尿管单发结石患者体外冲击波碎石术的冲击波频率研究及碎石效果的影响因素探讨

摘要 目的：探讨输尿管单发结石患者体外冲击波碎石术（ESWL）的最佳冲击波频率,并分析碎石效果的影响因素。方法：选取2020年4月~2022年4月期间来空军第九八六医院接受治疗的输尿管单发结石患者148例作为研究对象,按照不同治疗频率将患者分为低频组（48例,频率为60~70次/min）、中频组（51例,频率为80~90次/min）和高频组（49例,频率为100~120次/min）,观察三组患者的碎石结局、肾功能指标以及并发症发生情况。统计三组患者的碎石结局,按照碎石结局的不同分为成功组和失败组。收集所有患者的一般资料,采用多因素Logistic回归分析输尿管单发结石患者碎石效果的影响因素。结果：三组碎石成功率组间对比无统计学差异（P>0.05）。三组术后1 d、术后14 d尿素氮（BUN）、血肌酐（Scr）均升高后下降（P<0.05）。高频组、中频组术后1 d BUN、Scr均高于低频组,且高频组高于中频组（P<0.05）。高频组、中频组的并发症总发生率高于低频组（P<0.05）。单因素分析显示,输尿管单发结石患者ESWL术后碎石失败与病程、结石位置、结石直径、肾绞痛、结石嵌顿、服用坦索罗辛有关（P<0.05）。多因素Logistic回归分析显示,病程偏长、结石位置中下段、结石直径偏大、结石嵌顿、未服用坦索罗辛是碎石失败的危险因素（P＜0.05）。结论：低、中、高三种频率下的ESWL用于输尿管单发结石患者,均有较好的碎石效果。但随着频率的增加,患者一过性肾功能损伤增大,且并发症发生风险也相应增加。此外,病程偏长、结石位置中下段、结石直径偏大、结石嵌顿、未服用坦索罗辛是碎石失败的危险因素,可考虑结合上述因素进行综合评估选择最佳治疗方式。     

How has extracorporeal shock-wave lithotripsy changed the treatment of urinary stones in Quebec?

OBJECTIVES: To determine the number of people who underwent treatment of urinary stones in Quebec before and after the introduction of extracorporeal shock-wave lithotripsy (ESWL) and to determine how the introduction of ESWL influenced resource utilization. DESIGN: Before-after study; data were obtained from administrative databases and hospital-based cost estimates. SETTING: The 68 acute care hospitals in Quebec in which treatment of urinary stones is undertaken. PATIENTS: Quebec residents admitted to hospital for treatment of urinary stones between the fiscal years 1984 and 1992. OUTCOME MEASURES: Number of people treated for urinary stones per year, total number of procedures per year (including open surgery, percutaneous procedures, retrograde procedures and ESWL), and annual resources (including number of hospital bed-days and direct costs) for treatment of urinary stones used overall and in hospitals with and without ESWL services. RESULTS: Over the study period the number of people treated for urinary stones increased by 59%. As well, the combined frequency of ESWL and surgery (the two main treatment methods) increased by 107%. These increases were largely due to rates of treatment that grew by 52% among women and by 34% among men. The total number of hospital bed-days decreased by 28%, which reflected shorter hospital stays for ESWL. However, despite this decrease, the total direct annual costs were 7% higher in 1992 than in 1984 because of the increased numbers of people treated and procedures performed. In the three hospitals that offered ESWL the number of hospital bed-days and the direct costs of treating urinary stones increased by 49% and $2.5 million respectively. In the 65 other hospitals these figures decreased by 41% and about $2.9 million respectively. CONCLUSIONS: Because of increased intervention rates the total cost of treating urinary stones has risen since the introduction of ESWL. The introduction of ESWL has also been associated with a shift in the use of resources for treating urinary stones to hospitals with a lithotriptor. The reasons for the increased intervention rates are unknown. However, given the possibility of negative health effects and the increased costs, studies to determine whether the increased rates improve health outcomes are warranted.     

Adjunctive Medical Therapy with α-Blocker after Extracorporeal Shock Wave Lithotripsy of Renal and Ureteral Stones: A Meta-Analysis

Background

Although some trials assessed the efficacy and safety of the α-blocker in facilitating renal and ureteral stones expulsion after extracorporeal shock wave lithotripsy (ESWL), the role of the α-blocker in facilitating upper urinary calculi expulsion after ESWL remain controversial.

Aims

To determine the efficacy and safety of the α-blocker in facilitating renal and ureteral stones expulsion after ESWL.

Methods

A literature search was carried out using the PubMed database, EMBASE and the Cochrane Library database to identify relevant studies. Two reviewers independently extracted data and assessed methodological quality. Pooled effect estimates were obtained using a fixed- and random-effects meta-analysis.

Results

The meta-analysis included 23 RCTs, α-blocker significantly enhanced expulsion rate of upper urinary tract calculi after ESWL (P<0.00001; RR 1.21; 95% CI 1.12–1.31), significantly promoted steinstrasse expulsion (P=0.03; RR 1.25; 95% CI 1.03–1.53), significantly shortened the discharge time of upper urinary tract calculi (P=0.0001; MD -2.12; 95% CI -3.20–-1.04), significantly reduced the patient''s pain VAS score (P=0.001; RR -1.0; 95% CI -1.61–-0.39). Compared with the control group, dizziness (P=0.002; RR 5.48; 95% CI 1.91–15.77), anejaculation (P=0.02; RR 12.17; 95% CI 1.61–91.99) and headache (P=0.04; RR 4.03; 95% CI 1.04–15.72) in the α-blocker group was associated with a higher incidence.

Conclusions

Treatment with α-blocker after ESWL appears to be effective in enhancing expulsion rate of upper urinary tract calculi, shortening the discharge time of upper urinary tract calculi, reducing the patient''s pain. The side effects of α-blocker were light and few.     

坦洛新对输尿管下段结石患者体外冲击波碎石术后排石及血清IL-6，IL-10和CRP水平的影响

目的:探讨输尿管下段结石行体外冲击波碎石术(ESWL)后应用坦洛新辅助排石的临床效果及对患者血清白细胞介素-6(IL-6)、白细胞介素-10(IL-10)、C反应蛋白(CRP)水平的影响。方法:选取我院2015年1月～2016年12月收治的122例输尿管下段结石患者,采用随机数字表法均分为两组。于ESWL术后,对照组给予硝苯地平治疗,观察组予以坦洛新治疗。记录比较两组术后排石效果、疼痛情况,治疗前后血清IL-6、IL-10和CRP水平的变化及不良反应的发生情况。结果:治疗后,观察组无石率(91.8%)明显高于对照组(78.7%)(P0.05);观察组排石时间短于对照组,排石直径大于对照组(P0.05);观察组患者血清IL-6,IL-10及CRP水平均显著低于对照组(P0.05)。与对照组相比,观察组肾绞痛发生率、镇痛剂使用率及VAS评分均较低(P0.01)。用药期间,两组均未发生明显不良反应(P0.05)。结论:坦洛新能有效提高输尿管下段结石患者体外冲击波碎石术的排石效果,减轻机体损伤,缓解术后疼痛,并且安全性较高。     

Uniaxial compression measurement device for investigation of the mechanical stability of biofilms.

The mechanical stability of biofilms is important for biotechnology, as sloughing of the biomass due to mechanical failure of the biofilm matrix can lead to severe interferences with biofilm processes. In cases of biofouling, biofilms have to be removed, in which case their mechanical stability must be overcome. The apparent modulus of elasticity and the yield strength as obtained from uniaxial compression experiments can be taken as parameters indicative for the mechanical stability of a biofilm. A film rheometer is presented which allows for the determination of these quantities, using model biofilms of Pseudomonas aeruginosa grown on membrane filters. The compressive stress-strain behaviour up to the point of failure is recorded at a compression speed of 1 microm s(-1). In accordance with the stress-strain curve, the investigated biofilm can be described as viscoelastic material, which demonstrates plastic flow properties. The extracellular polymeric substances (EPS), which keep biofilms together, form a temporary network of fluctuating junction points. Above the yield point, the gel structure fails and the system behaves as a highly viscous fluid. The apparent modulus of elasticity and the yield point are considered to be useful parameters for characterizing the mechanical properties of biofilms.     

Stress-strain experiments on individual collagen fibrils

Collagen, a molecule consisting of three braided protein helices, is the primary building block of many biological tissues including bone, tendon, cartilage, and skin. Staggered arrays of collagen molecules form fibrils, which arrange into higher-ordered structures such as fibers and fascicles. Because collagen plays a crucial role in determining the mechanical properties of these tissues, significant theoretical research is directed toward developing models of the stiffness, strength, and toughness of collagen molecules and fibrils. Experimental data to guide the development of these models, however, are sparse and limited to small strain response. Using a microelectromechanical systems platform to test partially hydrated collagen fibrils under uniaxial tension, we obtained quantitative, reproducible mechanical measurements of the stress-strain curve of type I collagen fibrils, with diameters ranging from 150-470 nm. The fibrils showed a small strain (epsilon < 0.09) modulus of 0.86 +/- 0.45 GPa. Fibrils tested to strains as high as 100% demonstrated strain softening (sigma(yield) = 0.22 +/- 0.14 GPa; epsilon(yield) = 0.21 +/- 0.13) and strain hardening, time-dependent recoverable residual strain, dehydration-induced embrittlement, and susceptibility to cyclic fatigue. The results suggest that the stress-strain behavior of collagen fibrils is dictated by global characteristic dimensions as well as internal structure.     

Evaluation of filler materials used for uniform load distribution at boundaries during structural biomechanical testing of whole vertebrae

This study was designed to compare the compressive mechanical properties of filler materials, Wood's metal, dental stone, and polymethylmethacrylate (PMMA), which are widely used for performing structural testing of whole vertebrae. The effect of strain rate and specimen size on the mechanical properties of the filler materials was examined using standardized specimens and mechanical testing. Because Wood's metal can be reused after remelting, the effect of remelting on the mechanical properties was tested by comparing them before and after remelting. Finite element (FE) models were built to simulate the effect of filler material size and properties on the stiffness of vertebral body construct in compression. Modulus, yield strain, and yield strength were not different between batches (melt-remelt) of Wood's metal. Strain rate had no effect on the modulus of Wood's metal, however, Young's modulus decreased with increasing strain rate in dental stone whereas increased in PMMA. Both Wood's metal and dental stone were significantly stiffer than PMMA (12.7 +/- 1.8 GPa, 10.4 +/- 3.4 GPa, and 2.9 +/- 0.4 GPa, respectively). PMMA had greater yield strength than Wood's metal (62.9 +/- 8.7 MPa and 26.2 +/- 2.6 MPa). All materials exhibited size-dependent modulus values. The FE results indicated that filler materials, if not accounted for, could cause more than 9% variation in vertebral body stiffness. We conclude that Wood's metal is a superior moldable bonding material for biomechanical testing of whole bones, especially whole vertebrae, compared to the other candidate materials.     

Modeling of mechanical properties and structural design of spider web

With a unique combination of strength and toughness among materials, spider silk is the model for engineering materials. This paper presents the stress-strain behavior of Nephila clavipes spider silk under tension, transverse compression, and torsional deformation obtained by a battery of micro testing equipment. The experimental results showed significantly higher toughness than the state-of-the-art fibers in tension and in transverse compression. Higher shear modulus was also observed for the spider silk comparing to other liquid crystalline fibers such as aramid fibers. On the basis of the experimental results finite element analysis is used to simulate static and dynamic properties of spider web and to explore the role of both material properties and architectural design in its structural integrity and mechanical performance.     

Analysis of purines in urinary calculi by high-performance liquid chromatography

A high-pressure liquid chromatography method has been developed for the analysis in urinary calculi of six purines: uric acid, 2, 8-dihydroxyadenine, xanthine, hypoxanthine, allopurinol, and oxypurinol. Separation was conducted isocratically on a reversed-phase column, using 50 mM phosphate buffer (pH 5.5) / methanol (97/3, v/v) as mobile phase. Limits of detection, depending on compound, ranged from 7 to 28 microg/g stone weight. Hitherto, no reports have appeared on other purines present with uric acid in stones, due to lack of a sensitive and specific analytical method. We have now found that all calculi with more than 4% uric acid also contained 1-methyluric and 7-methyluric acids and trace amounts of hypoxanthine, xanthine, and 2,8-dihydroxyadenine. Accurate identification and quantitation of purines in urinary calculi are important for the diagnosis of rare metabolic diseases leading to urolithiasis (xanthinuria, dihydroxyadeninuria), as well as for prevention of iatrogenic complications during treatment with allopurinol of uric acid urolithiasis. The method may be used for reference purposes in clinical laboratories and for research on the pathogenesis of urolithiasis in disorders of purine metabolism.     

侧卧体位下经皮肾穿刺取石术联合经尿道输尿管镜取石术治疗复杂上尿路结石的临床应用价值

目的：探讨侧卧体位下经皮肾穿刺取石术联合经尿道输尿管镜取石术治疗复杂上尿路结石的可行性及临床应用价值。方法：回顾性分析2009年8月至2011年9月我院采用侧卧体住下经皮肾穿刺取石术联合经尿道输尿管镜取石术治疗复杂上尿路结石患者52例的临床资料：患者同时存在肾脏铸型结石或多发结石和或输尿管上段结石,单个结石最大径8-30mm。结果：平均手术时间60分钟（50—120分钟）;术前血红蛋白116±30g／L,术后第一天复查105±26g／L,无大出血需要输血病例;一次结石取净率为86．5％（45／52）,总取净率为92．3％（48／52）。结论：侧卧体位下经皮肾穿刺取石术及经尿道输尿管镜取石术两种术式联合应用具有可行性及互补性,在预防及减少术中出血、获得清晰的手术视野、减少灌注液外渗、增加结石清除速度及碎石成功率、缩短手术时间、减少术后发热等方面疗效显著,为治疗复杂上尿路结石提供了一个可行的新方法。     

Kidney Stones in Primary Hyperoxaluria: New Lessons Learnt

To investigate potential differences in stone composition with regard to the type of Primary Hyperoxaluria (PH), and in relation to the patient’s medical therapy (treatment naïve patients versus those on preventive medication) we examined twelve kidney stones from ten PH I and six stones from four PH III patients. Unfortunately, no PH II stones were available for analysis. The study on this set of stones indicates a more diverse composition of PH stones than previously reported and a potential dynamic response of morphology and composition of calculi to treatment with crystallization inhibitors (citrate, magnesium) in PH I. Stones formed by PH I patients under treatment are more compact and consist predominantly of calcium-oxalate monohydrate (COM, whewellite), while calcium-oxalate dihydrate (COD, weddellite) is only rarely present. In contrast, the single stone available from a treatment naïve PH I patient as well as stones from PH III patients prior to and under treatment with alkali citrate contained a wide size range of aggregated COD crystals. No significant effects of the treatment were noted in PH III stones. In disagreement with findings from previous studies, stones from patients with primary hyperoxaluria did not exclusively consist of COM. Progressive replacement of COD by small COM crystals could be caused by prolonged stone growth and residence times in the urinary tract, eventually resulting in complete replacement of calcium-oxalate dihydrate by the monohydrate form. The noted difference to the naïve PH I stone may reflect a reduced growth rate in response to treatment. This pilot study highlights the importance of detailed stone diagnostics and could be of therapeutic relevance in calcium-oxalates urolithiasis, provided that the effects of treatment can be reproduced in subsequent larger studies.     

Shear strength and toughness of trabecular bone are more sensitive to density than damage

Microdamage occurs in trabecular bone under normal loading, which impairs the mechanical properties. Architectural degradation associated with osteoporosis increases damage susceptibility, resulting in a cumulative negative effect on the mechanical properties. Treatments for osteoporosis could be targeted toward increased bone mineral density, improved architecture, or repair and prevention of microdamage. Delineating the relative roles of damage and architectural degradation on trabecular bone strength will provide insight into the most beneficial targets. In this study, damage was induced in bovine trabecular bone samples by axial compression, and the effects on the mechanical properties in shear were assessed. The damaged shear modulus, shear yield stress, ultimate shear stress, and energy to failure all depended on induced damage and decreased as the architecture became more rod-like. The changes in ultimate shear strength and toughness were proportional to the decrease in shear modulus, consistent with an effective decrease in the cross-section of trabeculae based on cellular solid analysis. For typical ranges of bone volume fraction in human bone, the strength and toughness were much more sensitive to decreased volume fraction than to induced mechanical damage. While ultimately repairing or avoiding damage to the bone structure and increasing bone density both improve mechanical properties, increasing bone density is the more important contributor to bone strength.     

体外冲击波碎石焦点附近声压分布的时域有限差分法数值解析

泌尿系统结石症是一种多发病。体外冲击波碎石(Extracorporealshockwavelithotropisy,ESWL)法是应用人体外发射的高强度脉冲超声波在人体内的焦点附近形成的冲击波破碎结石,被破碎的结石碎片随尿液排出体外的治疗泌尿系统结石症方法。由于这种治疗方法具有非创伤等优点而被广泛地应用于泌尿系统结石症的治疗。但是,ESWL治疗过程中有时会引发尿血、肾血肿等并发症,影响其治疗效果的主要因素之一为ESWL焦点附近形成的声压分布。在这里,利用作者等以前提出的时域有限差分(finitedifferencetimedomain,FDTD)超声波非线性传播的仿真方法,数值仿真ESWL超声波非线性传播过程,研究ESWL焦点附近声压的分布、焦点区域(焦区)的大小形状、高强度超声波形成的实际焦点位置。     

Inexpensive, semi-automated system for measuring mechanical properties of soft tissues.

Stiffness and strength are important properties of many tissues, but standard material-testing equipment is expensive, often ill-suited for testing soft tissues, and rarely accessible to biologists. We describe a system built around a microcomputer and an electronic balance which is particularly well-suited for measuring stress and strain in small samples of soft tissue. We use a discarded floppy disk drive as a linear actuator to strain the sample, while an electronic balance measures the tension (used to calculate stress). We give an algorithm for a program to drive a microcomputer which controls the floppy disk drive via its parallel port and records the balance measurements via its serial port. We used this system to obtain stress-strain curves from a sample of latex rubber and a sample of soft insect cuticle. Three tests of the rubber sample gave nearly identical results, with smooth, J-shaped stress-strain curves. The stress-strain curves gave a modulus elasticity value of 1.72 Mpa over the steep, straight region, well within the range for natural latex rubber. We also tested a sample of abdominal cuticle from a caterpillar (Manduca sexta). The caterpillar cuticle had a J-shaped stress-strain curve with a modulus of elasticity of 2.11 Mpa over the steep part of the curve. J. Exp. Zool. 284:374-378, 1999.