Skeletal muscle index is associated with long term outcomes after lobectomy for non-small cell lung cancer.

BACKGROUND: Skeletal muscle indices have been associated with improved peri-operative outcomes after surgical resection of non-small-cell lung cancer (NSCLC). However, it is unclear if these indices can predict long term cancer specific outcomes. METHODS: NSCLC patients undergoing lobectomy at our institute between 2009-2015 were included in this analysis (N = 492). Preoperative CT scans were used to quantify skeletal muscle index (SMI) at L4 using sliceOmatic software. Cox proportional modelling was performed for overall (OS) and recurrence free survival (RFS). RESULTS: For all patients, median SMI was 45.7 cm2/m2 (IQR, 40-53.8). SMI was negatively associated with age (R = -0.2; p < 0.05) and positively associated with BMI (R = 0.46; P < 0.05). No association with either OS or RFS was seen with univariate cox modelling. However, multivariable modelling for SMI with patient age, gender, race, smoking status, DLCO and FEV1 (% predicted), American Society of Anesthesiology (ASA) score, tumor histology and stage, and postoperative neoadjuvant therapy showed improved OS (HR = 0.97; P = 0.0005) and RFS (HR = 0.97; P = 0.01) with SMI. Using sex specific median SMI as cutoff, a lower SMI was associated with poor OS (HR = 1.65, P = 0.001) and RFS (HR = 1.47, P = 0.03). CONCLUSIONS: SMI is associated with improved outcomes after resection of NSCLC. Further studies are needed to understand the biological basis of this observation. This study provides additional rationale for designing and implementation of rehabilitation trials after surgical resection, to gain durable oncologic benefit.

A vein bypass first versus a best endovascular treatment first revascularisation strategy for patients with chronic limb threatening ischaemia who required an infra-popliteal, with or without an additional more proximal infra-inguinal revascularisation procedure to restore limb perfusion (BASIL-2): an open-label, randomised, multicentre, phase 3 trial.

BACKGROUND: Chronic limb-threatening ischaemia is the severest manifestation of peripheral arterial disease and presents with ischaemic pain at rest or tissue loss (ulceration, gangrene, or both), or both. We compared the effectiveness of a vein bypass first with a best endovascular treatment first revascularisation strategy in terms of preventing major amputation and death in patients with chronic limb threatening ischaemia who required an infra-popliteal, with or without an additional more proximal infra-inguinal, revascularisation procedure to restore limb perfusion. METHODS: Bypass versus Angioplasty for Severe Ischaemia of the Leg (BASIL)-2 was an open-label, pragmatic, multicentre, phase 3, randomised trial done at 41 vascular surgery units in the UK (n=39), Sweden (n=1), and Denmark (n=1). Eligible patients were those who presented to hospital-based vascular surgery units with chronic limb-threatening ischaemia due to atherosclerotic disease and who required an infra-popliteal, with or without an additional more proximal infra-inguinal, revascularisation procedure to restore limb perfusion. Participants were randomly assigned (1:1) to receive either vein bypass (vein bypass group) or best endovascular treatment (best endovascular treatment group) as their first revascularisation procedure through a secure online randomisation system. Participants were excluded if they had ischaemic pain or tissue loss considered not to be primarily due to atherosclerotic peripheral artery disease. Most vein bypasses used the great saphenous vein and originated from the common or superficial femoral arteries. Most endovascular interventions comprised plain balloon angioplasty with selective use of plain or drug eluting stents. Participants were followed up for a minimum of 2 years. Data were collected locally at participating centres. In England, Wales, and Sweden, centralised databases were used to collect information on amputations and deaths. Data were analysed centrally at the Birmingham Clinical Trials Unit. The primary outcome was amputation-free survival defined as time to first major (above the ankle) amputation or death from any cause measured in the intention-to-treat population. Safety was assessed by monitoring serious adverse events up to 30-days after first revascularisation. The trial is registered with the ISRCTN registry, ISRCTN27728689. FINDINGS: Between July 22, 2014, and Nov 30, 2020, 345 participants (65 [19%] women and 280 [81%] men; median age 72·5 years [62·7-79·3]) with chronic limb-threatening ischaemia were enrolled in the trial and randomly assigned: 172 (50%) to the vein bypass group and 173 (50%) to the best endovascular treatment group. Major amputation or death occurred in 108 (63%) of 172 patients in the vein bypass group and 92 (53%) of 173 patients in the best endovascular treatment group (adjusted hazard ratio [HR] 1·35 [95% CI 1·02-1·80]; p=0·037). 91 (53%) of 172 patients in the vein bypass group and 77 (45%) of 173 patients in the best endovascular treatment group died (adjusted HR 1·37 [95% CI 1·00-1·87]). In both groups the most common causes of morbidity and death, including that occurring within 30 days of their first revascularisation, were cardiovascular (61 deaths in the vein bypass group and 49 in the best endovascular treatment group) and respiratory events (25 deaths in the vein bypass group and 23 in the best endovascular treatment group; number of cardiovascular and respiratory deaths were not mutually exclusive). INTERPRETATION: In the BASIL-2 trial, a best endovascular treatment first revascularisation strategy was associated with a better amputation-free survival, which was largely driven by fewer deaths in the best endovascular treatment group. These data suggest that more patients with chronic limb-threatening ischaemia who required an infra-popliteal, with or without an additional more proximal infra-inguinal, revascularisation procedure to restore limb perfusion should be considered for a best endovascular treatment first revascularisation strategy. FUNDING: UK National Institute of Health Research Health Technology Programme.

Crush techniques for percutaneous coronary intervention of bifurcation lesions.

Percutaneous coronary intervention (PCI) of coronary artery bifurcation lesions entails technical challenges and carries a higher risk of adverse events on follow-up, driven by repeat revascularisation and stent thrombosis. While most bifurcations can be tackled with a provisional (single-stent) approach, more complex lesions involving both branches (true bifurcation lesions) require a two-stent approach. In the latter context, several techniques have been proposed. Among them, the crush technique has dramatically evolved in recent years, and its more recent iterations have been shown to provide excellent and durable results, both for left main and non-left main bifurcations. The aim of the present work is to discuss the technical aspects and outcomes of the variants of the crush technique from the first description in the early 2000s to the present day.

Revealing hydrogen peroxide as an external stressor in macrophyte-dominated coastal ecosystems.

Benthic primary producers in coastal ecosystems provide important habitat for marine organisms through the provision of complex 3D habitat. Primary producers produce organic matter, while simultaneously producing reactive oxygen species, including hydrogen peroxide (H2O2), a driver of oxidative stress. Through their high biomass, productivity and effect on local hydrodynamics, benthic primary producers can potentially increase H2O2 concentrations surrounding the biogenic structures they form. The aim of this study was to identify the potential role of H2O2 produced by benthic primary producers as an external stressor in coastal ecosystems. This was achieved by measuring H2O2 concentrations within sea lettuce blooms (Ulva sp.), giant kelp forests (Macrocystis pyrifera), and seagrass meadows (Zostera muelleri); quantifying H2O2 production rates of these species; and testing heterotrophic bacterial response to relevant H2O2 concentrations. Ulva sp. produced five times more H2O2 than other species. At in situ concentrations, H2O2 inhibited bacterial production and carbon flow through the microbial loop by 75%. This study reveals H2O2 as an additional stressor in bloom-forming Ulva sp. with higher H2O2 production compared to the ecosystem engineers M. pyrifera and Z. muelleri. H2O2 production by benthic primary producers can affect carbon flow through the microbial loop, with the potential to propagate a stress signal up the food web.

Three-year results comparing platinum-chromium PROMUS element and cobalt-chromium XIENCE V everolimus-eluting stents in de novo coronary artery narrowing (from the PLATINUM Trial).

In the randomized PLATINUM trial, the PROMUS Element platinum-chromium everolimus-eluting stent (PtCr-EES; Boston Scientific, Natick, Massachusetts) was noninferior to the XIENCE V cobalt-chromium everolimus-eluting stent (CoCr-EES; Boston Scientific and Abbott Vascular, Santa Clara, California) for the primary end point of 1-year target lesion failure. This study reports the 3-year outcomes. Patients (n=1,530) with 1 or 2 de novo native coronary artery lesions (baseline vessel diameter≥2.50 mm to ≤4.25 mm and length≤24 mm) were randomized 1:1 to PtCr-EES versus CoCr-EES. Three-year follow-up was available in 93.9% (703 of 749) of patients with CoCr-EES and 96.7% (733 of 758) of patients with PtCr-EES. Comparing CoCr-EES with PtCr-EES, 3-year rates of death (4.3% vs 3.7%, hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.52 to 1.48, p=0.62), cardiac death (1.9% vs 1.2%, HR 0.63, 95% CI 0.27 to 1.45, p=0.27), myocardial infarction (2.5% vs 2.3%, HR 0.92, 95% CI 0.48 to 1.79, p=0.81), ischemia-driven target lesion revascularization (4.9% vs 3.5%, HR 0.72, 95% CI 0.43 to 1.20, p=0.21), and Academic Research Consortium definite or probable stent thrombosis (0.5% vs 0.7%, HR 1.23, 95% CI 0.33 to 4.57, p=0.76) were not significantly different. In conclusion, 3-year results of the PLATINUM randomized, controlled, clinical trial demonstrate comparable safety and efficacy outcomes of the PROMUS Element PtCr-EES and the XIENCE V CoCr-EES.

Final 5-year results of the TAXUS ATLAS, TAXUS ATLAS Small Vessel, and TAXUS ATLAS Long Lesion clinical trials of the TAXUS Liberté paclitaxel-eluting stent in de-novo coronary artery lesions.

OBJECTIVE: To report the final, cumulative, 5-year outcomes from the TAXUS ATLAS program, which studied the use of the TAXUS Liberté paclitaxel-eluting stent in de-novo coronary artery lesions. METHODS: TAXUS ATLAS Workhorse, Small Vessel, and Long Lesion are nonrandomized studies comparing TAXUS Liberté (N=871), TAXUS Liberté 2.25 mm (N=261), and TAXUS Liberté 38 mm (N=150) stents, respectively, with case-matched TAXUS Express historical controls. RESULTS: In the unadjusted analysis, TAXUS Liberté showed comparable 5-year rates of major adverse cardiac events (27.1% TAXUS Express vs. 26.2% TAXUS Liberté, P=0.70) in workhorse lesions and greater 5-year cumulative freedom from target lesion revascularization (78.4 vs. 87.3%, P=0.03) in small vessels. In addition, a lower periprocedural myocardial infarction rate (MI, 4.1 vs. 0.0%; P=0.01) was observed in long lesions versus TAXUS Express. After propensity score adjustment, no statistically significant effect of TAXUS Liberté on the 5-year rates of TLR in small vessels (17.9 vs. 13.3%, P=0.36) or MI in long lesions (9.1 vs. 7.0%, P=0.53) was found, although the rates remained numerically lower with TAXUS Liberté. CONCLUSION: Cumulative 5-year results of the TAXUS ATLAS studies suggest that the TAXUS Liberté stent provides similar safety and effectiveness in workhorse lesions, and may provide lower revascularization rates in small vessels and lower periprocedural MI rates in long lesions compared with the TAXUS Express stent, although no statistically significant differences were found following propensity adjustment.

Long-term benefit of the TAXUS Liberté stent in small vessels and long lesions. TAXUS ATLAS program.

BACKGROUND: The long-term impact of treating de novo coronary lesions in native vessels and challenging small vessel and long lesion subsets with TAXUS Liberté stents is unknown. This report examines the 3-year efficacy and safety from the TAXUS ATLAS program. METHODS AND RESULTS: TAXUS ATLAS WH, Small Vessel, and Long Lesion are non-randomized studies comparing TAXUS Liberté (n = 871), TAXUS Liberté 2.25 mm (n = 261), and TAXUS Liberté 38 mm (n = 150) stents, respectively, to case-matched TAXUS Express historical controls. TAXUS Liberté demonstrated comparable 3-year rates of major adverse cardiac events (19.0% vs. 20.2%, P = 0.51) in de novo lesions, reduced target lesion revascularization (TLR, 10.0% vs. 22.1%, P = 0.008) in small vessels, and reduced myocardial infarction (MI, 2.9% vs. 10.4%; P = 0.01) and stent thrombosis (ST, 0.0% vs. 3.9%, P = 0.03) in long lesions vs. TAXUS Express. After propensity score adjustment, no statistically significant effect of TAXUS Liberté on TLR (9.7% vs. 16.9%, P = 0.12) in small vessels or MI (2.9% vs. 7.9%, P = 0.05) in long lesions was noted, although reduced ST (0.0% vs. 2.7%, P = 0.02) remained in long lesions. Multivariate analyses demonstrated that TAXUS Liberté treatment significantly reduced TLR by 66% in small vessels, and MI by 75% in long lesions, vs. TAXUS Express. CONCLUSIONS: TAXUS Liberté suggests durable 3-year effectiveness in reducing restenosis and improved clinical outcomes in small vessels and long lesions compared with TAXUS Express.

A nonimaging catheter for measurement of coronary artery lumen area: a first in man pilot study.

OBJECTIVES: The objective of this human pilot study was to determine the safety and the level of agreement between a novel nonimaging 2.7 Fr. catheter-based system (LumenRECON, LR) that uses electrical conductance for measurement of lumen cross-sectional area (CSA) with intravascular ultrasound (IVUS) and quantitative coronary angiography (QCA). Based on previous animal studies, we hypothesized the level of agreement between LR and IVUS to be 13%. BACKGROUND: Accurate and reproducible vessel sizing is essential for optimal percutaneous coronary intervention (PCI). METHODS: A total of 12 patients were studied to evaluate the safety, accuracy, and reproducibility of the system in comparison with IVUS and QCA. The CSA of coronary arteries was determined by IVUS, QCA, and LR in the distal, proximal, and center of a lesion during standard PCI. RESULTS: A Bland-Altman plot of the LR versus IVUS and QCA show a nonsignificant mean difference between the two measurements of 0.04 and 0.07 mm in diameter, respectively. The root mean square error of LR versus IVUS and QCA was 14.3 and 25.8% of the mean IVUS or QCA diameter, respectively. The mean of the difference between two LR duplicate measurements was nearly zero (0.03 mm) and the repeatability coefficient was within 8.7% of the mean of the two measurements. There were no procedural complications nor were any device-related MACE reported within 30 days of the procedure. CONCLUSIONS: This proof of concept pilot study establishes the safety and accuracy of the conductance technology for a pivotal trial of coronary sizing.

Improved strut coverage and less late incomplete apposition with thin-strut TAXUS Liberté vs. TAXUS Express: the importance of stent platform design for drug-eluting stents.

BACKGROUND: The objective of this intravascular ultrasound (IVUS) analysis was to evaluate the vascular response of the thin-strut TAXUS Liberté stent compared with the otherwise identical TAXUS Express stent. METHODS AND MATERIALS: The TAXUS ATLAS and TAXUS ATLAS Long Lesion studies are nonrandomized trials comparing the thin-strut TAXUS Liberté stent to historical TAXUS Express controls from the TAXUS IV and TAXUS V trials. A total of 377 patients enrolled in the two TAXUS ATLAS studies were randomly selected for the IVUS subset and compared to 314 TAXUS Express IVUS controls. RESULTS: Despite increased lesion complexity in the TAXUS Liberté group, neointimal formation at 9 months was similar in both stents (TAXUS Liberté 13.8±11.0%; TAXUS Express 13.1±13.8%, P=.56). However, this neointima covered more of the overall stent in the TAXUS Liberté (67.9±32.5%) compared with the TAXUS Express (54.4±37.2%, P<.001), suggesting more uniform neointimal distribution. TAXUS Liberté also showed less pronounced negative remodeling at both stent edges and had significantly less (4.3% vs. 9.6%, P=.04) late incomplete stent apposition (ISA). CONCLUSIONS: Despite identical polymer and drug release characteristic, the thin-strut TAXUS Liberté stent demonstrates improved neointimal coverage, better edge remodeling, and less late ISA vs. TAXUS Express, hereby highlighting the importance of the platform design for drug-eluting stents.

TAXUS Liberté attenuates the risk of restenosis in patients with medically treated diabetes mellitus: results from the TAXUS ATLAS program.

OBJECTIVES: The aim of this study was to assess the relative efficacy and safety of the second-generation TAXUS Liberté paclitaxel-eluting stent (PES) in patients with and without diabetes mellitus. BACKGROUND: Diabetic patients suffer from accelerated atherosclerosis and increased risk of restenosis after coronary interventions; however, prior data suggest that PES might blunt this effect, providing equal benefit in diabetic and nondiabetic patients. METHODS: A pooled analysis of all 4 TAXUS ATLAS studies was conducted that included 413 diabetic and 1,116 nondiabetic subjects treated with the TAXUS Liberté stent for de novo coronary lesions. Angiographic and intravascular ultrasound outcomes at 9 months and clinical outcomes at 9 and 12 months were compared in patients with and without diabetes. Propensity score and multivariate adjustments were performed to correct for baseline differences. RESULTS: In-stent angiographic restenosis (13.0% vs. 9.6%, p = 0.12), late luminal loss (0.40 mm vs. 0.38 mm, p = 0.58), and intimal hyperplasia (14.8% vs. 13.4%, p = 0.29) were similar for diabetic and nondiabetic subjects. After propensity adjustment, 12-month target lesion revascularization rates were similar for diabetic and nondiabetic subjects (6.4% vs. 4.7%, p = 0.18), with no differences in mortality, myocardial infarction, or stent thrombosis. However, the rate of target vessel revascularization (TVR) was higher for diabetic subjects due to increased TVR outside the target lesion (TVR Remote). CONCLUSIONS: Similar clinical, angiographic, and intravascular ultrasound outcomes were observed for both diabetic and nondiabetic subjects treated with TAXUS Liberté, suggesting that this PES attenuates the effect of diabetes on restenosis after percutaneous coronary intervention, yielding comparable efficacy and safety in diabetic and nondiabetic patients. (TAXUS ATLAS; NCT00371709, NCT00371423, NCT00371748, and NCT00371475).

Direct stenting with the TAXUS Liberté drug-eluting stent: results from the Taxus Atlas Direct Stent Study.

OBJECTIVES: This study was conducted to determine whether direct stenting with TAXUS Liberté is noninferior to stenting after pre-dilation. BACKGROUND: Direct stenting is performed in approximately 30% of patients, but data on clinical and angiographic outcomes with drug-eluting stents are limited. METHODS: The TAXUS ATLAS DIRECT STENT is a single-arm, multicenter study that enrolled patients with de novo coronary lesions visually estimated to be 10 to 28 mm in length in vessels 2.5 to 4.0 mm in diameter. The control group is the quantitative coronary angiography (QCA) subset of the TAXUS ATLAS trial, which used identical inclusion and exclusion criteria but mandated pre-dilation. The primary end point is 9-month analysis-segment percent diameter stenosis (%DS). RESULTS: Baseline patient characteristics were similar between the groups. On QCA analysis, significantly shorter lesions with larger lumen diameter and less calcification were observed in the direct stent group. Direct stenting was successful in 97.6% of patients and was associated with a shorter procedure time and fewer complications. Follow-up %DS was noninferior for direct stent (26.41%) versus pre-dilation (29.14%) with a 1-sided 95% confidence interval of the difference between the groups (-0.34%) well below the pre-specified noninferiority margin (6.75%). Additionally, significantly lower restenosis (5.9% vs. 11.4%, p = 0.0229) and target lesion revascularization (TLR) 2.9% vs. 7.8%, p = 0.0087) rates were seen for direct stent versus pre-dilation. CONCLUSIONS: Direct stenting of TAXUS Liberté is feasible and highly successful in carefully selected lesions. Direct stenting is noninferior to stenting after pre-dilation on the basis of %DS and can significantly reduce procedural time, procedural complications, and possibly angiographic restenosis and TLR.

Reduced risk of restenosis in small vessels and reduced risk of myocardial infarction in long lesions with the new thin-strut TAXUS Liberté stent: 1-year results from the TAXUS ATLAS program.

OBJECTIVES: The TAXUS ATLAS Small Vessel (SV) and Long Lesion (LL) multicenter studies compared the performance of the thin-strut (0.0038 inch) TAXUS Liberté 2.25-mm stent (Boston Scientific; Natick, Massachusetts) and the TAXUS Liberté 38-mm long stent (Boston Scientific; Natick, Massachusetts) with the earlier paclitaxel-eluting TAXUS Express (Boston Scientific) stent that has identical polymer, drug dosage, and release kinetics but different stent geometry and thicker struts (0.0052 inch). BACKGROUND: The TAXUS Liberté stent was designed with thinner and more even strut spacing to provide more uniform drug distribution, as well as increased flexibility and conformability. Clinical benefits of the new stent design have not been evaluated. METHODS: The TAXUS ATLAS SV and LL studies are nonrandomized studies comparing outcomes of the TAXUS Liberté 2.25 mm (N = 261) and TAXUS Liberté 38 mm (N = 150) stents to TAXUS Express historical control groups derived from the TAXUS IV and V trials. Inclusion/exclusion criteria for TAXUS Express and Liberté groups were similar in both studies. RESULTS: Each study met its primary end point of noninferiority of 9-month in-segment diameter stenosis. Furthermore, TAXUS Liberté 2.25 mm, when compared with TAXUS Express, significantly reduced the rate of both 9-month angiographic restenosis (18.5% vs. 32.7%, p = 0.0219) and 12-month target lesion revascularization (6.1% vs. 16.9%, p = 0.0039). In addition, TAXUS Liberté 38 mm significantly reduced the risk of 12-month myocardial infarction compared with TAXUS Express (1.4% vs. 6.5%, p = 0.0246). CONCLUSIONS: The thinner-strut TAXUS Liberté stent improved outcomes compared with the earlier TAXUS Express stent in both SVs and LLs (A Study of the TAXUS Liberté Stent for the Treatment of de Novo Coronary Artery Lesions in Small Vessels; NCT00371748; A Study of the TAXUS Liberté Stent for the Treatment of Long De Novo Coronary Artery Lesions; NCT00371475).

Polymer-based, paclitaxel-eluting TAXUS Liberté stent in de novo lesions: the pivotal TAXUS ATLAS trial.

OBJECTIVES: The goal of this research was to assess non-inferiority of the next-generation TAXUS Liberté stent (Boston Scientific Corp., Natick, Massachusetts) versus the TAXUS Express stent (Boston Scientific Corp.). BACKGROUND: The introduction of drug-eluting stents (DES) has shifted clinical practice towards more complex lesion subsets, prompting the need for more deliverable DES. TAXUS Liberté was designed to combine the established polymer-based, paclitaxel-elution TAXUS technology with the more advanced Liberté stent platform. METHODS: The TAXUS ATLAS study is a global, prospective, single-arm trial evaluating outcomes in de novo coronary lesions visually estimated to be 10 to 28 mm in length in vessels 2.5 to 4.0 mm in diameter. The control group is an entry-criteria-matched population of TAXUS Express patients from the TAXUS IV and V trials. The primary end point is non-inferiority of TAXUS Liberté versus TAXUS Express for 9-month target vessel revascularization. RESULTS: Despite similar inclusion criteria, quantitative coronary angiography-determined baseline lesion characteristics were significantly more complex for TAXUS Liberté than TAXUS Express. The primary non-inferiority end point was met with the 1-sided 95% confidence bound of 2.98% less than the pre-specified non-inferiority margin of 3% (p = 0.0487). CONCLUSIONS: Despite the treatment of more complex lesions with TAXUS Liberté, the primary end point was met, demonstrating that TAXUS Liberté is non-inferior to TAXUS Express. The successful transfer of the proven TAXUS technology to the more advanced TAXUS Liberté platform was demonstrated. (TAXUS ATLAS: TAXUS Liberté-SR Stent for the Treatment of De Novo Coronary Artery Lesions; http://www.clinicaltrials.gov/ct/show/NCT00371709?order=1; NCT00371709).

Early renal changes in 45 degrees HDT rats.

BACKGROUND: Both microgravity and simulated microgravity models, such as the 45HDT (45 degrees head-down tilt), cause a redistribution of body fluids indicating a possible adaptive process to the microgravity stressor. Understanding the physiological processes that occur in microgravity is a first step to developing countermeasures to stop its harmful effects, i.e., (edema, motion sickness) during long-term space flights. HYPOTHESIS: Because of the kidneys' functional role in the regulation of fluid volume in the body, it plays a key role in the body's adaptation to microgravity. METHODS: Rats were injected intramuscularly with a radioactive tracer and then lightly anesthetized in order to facilitate their placement in the 45HDT position. They were then placed in the 45HDT position using a specially designed ramp (45HDT group) or prone position (control group) for an experimental time period of 1 h. During this period, the 99mTc-DTPA (technetium-labeled diethylenepentaacetate, MW=492 amu, physical half-life of 6.02 h) radioactive tracer clearance rate was determined by measuring gamma counts per minute. The kidneys were then fixed and sectioned for electron microscopy. A point counting method was used to quantitate intracellular spaces of the kidney proximal tubules. RESULTS: 45HDT animals show a significantly (p=0.0001) increased area in the interstitial space of the proximal tubules. CONCLUSIONS: There are significant changes in the kidneys during a 1 h exposure to a simulated microgravity environment that consist primarily of anatomical alterations in the kidney proximal tubules. The kidneys also appear to respond differently to the initial periods of head-down tilt.