Bioavailability of insulin detemir and human insulin at the level of peripheral interstitial fluid in humans, assessed by open-flow microperfusion.

AIMS: To find an explanation for the lower potency of insulin detemir observed in humans compared with unmodified human insulin by investigating insulin detemir and human insulin concentrations directly at the level of peripheral insulin-sensitive tissues in humans in vivo. METHODS: Euglycaemic-hyperinsulinaemic clamp experiments were performed in healthy volunteers. Human insulin was administered i.v. at 6 pmol/kg/min and insulin detemir at 60 pmol/kg/min, achieving a comparable steady-state pharmacodynamic action. In addition, insulin detemir was doubled to 120 pmol/kg/min. Minimally invasive open-flow microperfusion (OFM) sampling methodology was combined with inulin calibration to quantify human insulin and insulin detemir in the interstitial fluid (ISF) of subcutaneous adipose and skeletal muscle tissue. RESULTS: The human insulin concentration in the ISF was ∼115 pmol/l or ∼30% of the serum concentration, whereas the insulin detemir concentration in the ISF was ∼680 pmol/l or ∼2% of the serum concentration. The molar insulin detemir interstitial concentration was five to six times higher than the human insulin interstitial concentration and metabolic clearance of insulin detemir from serum was substantially reduced compared with human insulin. CONCLUSIONS: OFM proved useful for target tissue measurements of human insulin and the analogue insulin detemir. Our tissue data confirm a highly effective retention of insulin detemir in the vascular compartment. The higher insulin detemir relative to human insulin tissue concentrations at comparable pharmacodynamics, however, indicate that the lower potency of insulin detemir in humans is attributable to a reduced effect in peripheral insulin-sensitive tissues and is consistent with the reduced in vitro receptor affinity.

Intermuscular and perimuscular fat expansion in obesity correlates with skeletal muscle T cell and macrophage infiltration and insulin resistance.

BACKGROUND/OBJECTIVES: Limited numbers of studies demonstrated obesity-induced macrophage infiltration in skeletal muscle (SM), but dynamics of immune cell accumulation and contribution of T cells to SM insulin resistance are understudied. SUBJECTS/METHODS: T cells and macrophage markers were examined in SM of obese humans by reverse transcription-PCR (RT-PCR). Mice were fed high-fat diet (HFD) for 2-24 weeks, and time course of macrophage and T-cell accumulation was assessed by flow cytometry and quantitative RT-PCR. Extramyocellular adipose tissue (EMAT) was quantified by high-resolution micro-computed tomography (CT), and correlation to T-cell number in SM was examined. CD11a-/- mice and C57BL/6 mice were treated with CD11a-neutralizing antibody to determine the role of CD11a in T-cell accumulation in SM. To investigate the involvement of Janus kinase/signal transducer and activator of transcription (JAK/STAT), the major pathway for T helper I (TH1) cytokine interferon-γ, in SM and adipose tissue inflammation and insulin resistance, mice were treated with a JAK1/JAK2 inhibitor, baricitinib. RESULTS: Macrophage and T-cell markers were upregulated in SM of obese compared with lean humans. SM of obese mice had higher expression of inflammatory cytokines, with macrophages increasing by 2 weeks on HFD and T cells increasing by 8 weeks. The immune cells were localized in EMAT. Micro-CT revealed that EMAT expansion in obese mice correlated with T-cell infiltration and insulin resistance. Deficiency or neutralization of CD11a reduced T-cell accumulation in SM of obese mice. T cells polarized into a proinflammatory TH1 phenotype, with increased STAT1 phosphorylation in SM of obese mice. In vivo inhibition of JAK/STAT pathway with baricitinib reduced T-cell numbers and activation markers in SM and adipose tissue and improved insulin resistance in obese mice. CONCLUSIONS: Obesity-induced expansion of EMAT in SM was associated with accumulation and proinflammatory polarization of T cells, which may regulate SM metabolic functions through paracrine mechanisms. Obesity-associated SM 'adiposopathy' may thus have an important role in the development of insulin resistance and inflammation.

GAB2 induces tumor angiogenesis in NRAS-driven melanoma.

GAB2 is a scaffold protein with diverse upstream and downstream effectors. MAPK and PI3K signaling pathways are known effectors of GAB2. It is amplified and overexpressed in a variety of human tumors including melanoma. Here we show a previously undescribed role for GAB2 in NRAS-driven melanoma. Specifically, we found that GAB2 is co-expressed with mutant NRAS in melanoma cell lines and tumor samples and its expression correlated with metastatic potential. Co-expression of GAB2(WT) and NRAS(G12D) in melanocytes and in melanoma cells increased anchorage-independent growth by providing GAB2-expressing cells a survival advantage through upregulation of BCL-2 family of anti-apoptotic factors. Of note, collaboration of GAB2 with mutant NRAS enhanced tumorigenesis in vivo and led to an increased vessel density with strong CD34 and VEGFR2 activity. We found that GAB2 facilitiated an angiogenic switch by upregulating HIF-1α and VEGF levels. This angiogenic response was significantly suppressed with the MEK inhibitor PD325901. These data suggest that GAB2-mediated signaling cascades collaborate with NRAS-driven downstream activation for conferring an aggressive phenotype in melanoma. Second, we show that GAB2/NRAS signaling axis is non-linear and non-redundant in melanocytes and melanoma, and thus are acting independent of each other. Finally, we establish a link between GAB2 and angiogenesis in melanoma for the first time. In conclusion, our findings provide evidence that GAB2 is a novel regulator of tumor angiogenesis in NRAS-driven melanoma through regulation of HIF-1α and VEGF expressions mediated by RAS-RAF-MEK-ERK signaling.

A nine-gene signature predicting clinical outcome in cutaneous melanoma.

PURPOSE: Current histopathological staging of cutaneous melanoma is limited in predicting outcome, and complementary molecular markers are not available for prognostic assessment. The purpose of this study was to identify a quantitative gene expression score in primary melanoma and adjacent stroma that can be used in clinical routine to define, at the time of diagnosis, patient risk and need for therapy. METHODS: Expression of 92 candidate genes was quantified by RT-PCR in a training subset of 38 fresh-frozen melanomas. Correlation of gene expression with overall survival (OS) was evaluated using univariate regression analysis. Expression analysis of 11 prognostically significant genes in the complete training cohort of 91 melanomas yielded nine genes predicting outcome. Results were confirmed in a validation cohort of 44 melanomas. RESULTS: We identified a nine-gene signature associated with OS and distant metastasis-free survival. The signature comprised risk and protective genes and was applicable to melanoma samples across all AJCC stages in the presence of adjacent stroma. A signature-based risk score predicted OS in both the training cohort (multivariate regression analysis: p = 0.0004, hazard ratio 3.83) and the validation cohort, independently of AJCC staging. Consequently, when combining risk score and AJCC staging, patients in the AJCC intermediate-risk stages, IIA/B or IIIA, were re-classified either to low or high risk. CONCLUSIONS: Our gene score defines patient risk and need for therapy in melanoma. The score has the potential to be utilized in clinical routine, since it is quantitative, robust, simple, and independent of AJCC stage and sample purity.

Long-term, open-label trial: safety and efficacy of continuous maintenance treatment with pantoprazole for up to 15 years in severe acid-peptic disease.

BACKGROUND: To date, the safety and tolerability of proton pump inhibitors (PPIs) have been demonstrated in studies of up to 10 years. AIM: To report on the tolerability, safety and efficacy of up to 15 years' continuous treatment with pantoprazole in patients with severe acid-peptic disease. METHODS: Following healing of endoscopically confirmed peptic ulcer or reflux oesophagitis during 4-12 weeks' treatment with pantoprazole (40-80 mg/day), adult patients received open-label maintenance treatment with pantoprazole (40-160 mg/day) for up to 15 years in a single centre combined study (10-year initial study; 5-year extension study). Safety assessments were carried out using endoscopy, clinical examination, clinical laboratory investigations, serum gastrin determination, gastric mucosal histology and mucosal endocrine cell quantification. RESULTS: The safety set comprised 142 patients. At 12 weeks, healing rates were 95.8%. During long-term treatment, mean fasting gastrin levels rose from baseline to moderate levels throughout the study. Mean enterochromaffin-like cell density showed a moderate initial increase during the first 3 years, remaining stable thereafter. These changes were not associated with any clinically relevant changes of the gastric mucosa. Patients with successful Helicobacter pylori eradication showed long-term regression of antral and corpus gastritis during continued pantoprazole treatment. CONCLUSIONS: Daily pantoprazole maintenance therapy for up to 15 years for severe acid-peptic disease is effective and well tolerated, with no identified safety concerns. The longest study to date, these data provide reassuring evidence for the long-term safety of pantoprazole.

Benefits and costs of improved IEQ in U.S. offices.

UNLABELLED: This study estimates some of the benefits and costs of implementing scenarios that improve indoor environmental quality (IEQ) in the stock of U.S. office buildings. The scenarios include increasing ventilation rates when they are below 10 or 15 l/s per person, adding outdoor air economizers and controls when absent, eliminating winter indoor temperatures >23°C, and reducing dampness and mold problems. The estimated benefits of the scenarios analyzed are substantial in magnitude, including increased work performance, reduced Sick Building Syndrome symptoms, reduced absence, and improved thermal comfort for millions of office workers. The combined potential annual economic benefit of a set of nonoverlapping scenarios is approximately $20 billion. While the quantitative estimates have a high uncertainty, the opportunity for substantial benefits is clear. Some IEQ improvement measures will save energy while improving health or productivity, and implementing these measures should be the highest priority. PRACTICAL IMPLICATIONS: Owners, designers, and operators of office buildings have an opportunity to improve IEQ, health, work performance, and comfort of building occupants and to obtain economic benefits by improving IEQ. These benefits can be achieved with simultaneous energy savings or with only small increases in energy costs.

Toward unsupervised classification of calcified arterial lesions.

There is growing evidence that calcified arterial deposits play a crucial role in the pathogenesis of cardiovascular disease. This paper investigates the challenging problem of unsupervised calcified lesion classification. We propose an algorithm, US-CALC (UnSupervised Calcified Arterial Lesion Classification), that discriminates arterial lesions from non-arterial lesions. The proposed method first mines the characteristics of calcified lesions using a novel optimization criterion and then identifies a subset of lesion features which is optimal for classification. Second, a two stage clustering is deployed to discriminate between arterial and non-arterial lesions. A histogram intersection distance measure is incorporated to determine cluster proximity. The clustering hierarchies are carefully validated and the final clusters are determined by a new intracluster compactness measure. Experimental results indicate an average accuracy of approximately 80% on a database of electron beam CT heart scans.

Risk factors in heating, ventilating, and air-conditioning systems for occupant symptoms in US office buildings: the US EPA BASE study.

UNLABELLED: Building-related symptoms in office workers worldwide are common, but of uncertain etiology. One cause may be contaminants related to characteristics of heating, ventilating, and air-conditioning (HVAC) systems. We analyzed data from 97 representative air-conditioned US office buildings in the Building Assessment and Survey Evaluation (BASE) study. Using logistic regression models with generalized estimating equations, we estimated odds ratios (OR) and 95% confidence intervals for associations between building-related symptom outcomes and HVAC characteristics. Outdoor air intakes less than 60 m above ground level were associated with significant increases in most symptoms: e.g. for upper respiratory symptoms, OR for intake heights 30 to 60 m, 0 to <30 m, and below ground level were 2.7, 2.0, and 2.1. Humidification systems with poor condition/maintenance were associated with significantly increased upper respiratory symptoms, eye symptoms, fatigue/difficulty concentrating, and skin symptoms, with OR = 1.5, 1.5, 1.7, and 1.6. Less frequent cleaning of cooling coils and drain pans was associated with significantly increased eye symptoms and headache, with OR = 1.7 and 1.6. Symptoms may be due to microbial exposures from poorly maintained ventilation systems and to greater levels of vehicular pollutants at air intakes nearer the ground level. Replication and explanation of these findings is needed. PRACTICAL IMPLICATIONS: These findings support current beliefs that moisture-related HVAC components such as cooling coils and humidification systems, when poorly maintained, may be sources of contaminants that cause adverse health effects in occupants, even if we cannot yet identify or measure the causal exposures. While finding substantially elevated risks for poorly maintained humidification systems, relative to no humidification systems, the findings do not identify important (symptom) benefits from well-maintained humidification systems. Findings also provide an initial suggestion, needing corroboration, that outdoor air intakes lower than 18 stories in office buildings may be associated with substantial increases in many symptoms. If this is corroborated and linked to ground-level vehicle emissions, urban ventilation air intakes may need to be located as far above ground level as possible or to incorporate air cleaners that remove gaseous pollutants.

[Arthroscopic menisectomy in older patients: assessing health-related quality of life]. / Die arthroskopische Teilmenisektomie bei älteren Patienten: Erfassung der gesundheitsbezogenen Lebensqualität.

AIM: Little information is available on partial arthroscopic menisectomy in patients 60 years of age or older. Due to the co-morbidity of meniscal tears and osteoarthritis in this age group, the effectiveness of this procedure is controversial. The purpose of this study was to evaluate the outcome of this procedure in terms of function and mobility in patients 60 years of age or older. METHOD: Between 1990 and 1999, 1920 arthroscopies of the knee were performed in a single primary care institution, and 51 patients, 60 years of age or older, had a partial arthroscopic menisectomy done. Outcomes were rated using the SF-36 Health Survey and a specially designed questionnaire including items of published scores. RESULTS: The mean age at surgery was 67 years (range: 60.3 - 78.9) and the mean follow-up was 5 years (range: 2 - 12). Due to persistent pain, 4 patients underwent a second operation including knee replacement in 3 cases and a high tibial osteotomy in 1 case. 41 patients (87.1 %) stated the arthroscopy had improved their quality of life. In terms of pain and daily life activities, the majority of the subjects showed an improvement after surgery. The SF-36 showed no clinically relevant difference compared to the control in all but one subscale. CONCLUSION: Despite of the presence of osteoarthritis in this age group, arthroscopic partial menisectomy can improve pain, function and mobility in the mid-term course.

Release of bioactive transforming growth factor beta(3) from microtextured polymer surfaces in vitro and in vivo.

Transforming growth factor beta(3) (TGF-beta(3)) has been under investigation with the objective of improving wound healing. Yet, little experimental knowledge exists about applications of TGF-beta(3) in implantology and tissue engineering. The aims of this study were to determine the release kinetics and bioactivity of TGF-beta(3) released from microtextured silicone and poly-L-lactic acid (PLA) surfaces in vitro and in vivo. We loaded surfaces with 100 ng of TGF-beta(3). An in vitro assay showed that TGF-beta(3) was released in a burstlike manner. Released TGF-beta(3) was capable of inhibiting the proliferation of mink lung epithelial cells, indicating that released TGF-beta(3) had remained at least partly active. Subsequently, an in vivo experiment (1 h-3 days) was performed with implants loaded with TGF-beta(3). In cryosections, TGF-beta(3) activity was assessed by an in situ bioassay. We found that active TGF-beta(3) was released for up to 24 h. Furthermore, released TGF-beta(3) could be detected up to 320 microm from the implant. On the basis of these observations, we conclude that TGF-beta(3) loaded onto microtextured polymer membranes remains functional when released in vitro and in vivo and, therefore, may represent an alternative for introducing a growth factor into a wound to achieve long-term and long-range biological effects.

Extraction of methylxanthines from guaraná seeds, maté leaves, and cocoa beans using supercritical carbon dioxide and ethanol.

New experimental data on the extraction of caffeine from guaraná seeds and maté tea leaves, and theobromine from cocoa beans, with supercritical CO2 were obtained using a high-pressure extraction apparatus. The effect of the addition of ethanol to carbon dioxide on the extraction efficiency was also investigated. Caffeine extraction yields of 98% of the initial caffeine content in both wet ground guaraná seeds and maté tea leaves were obtained. Extractions of caffeine from guaraná seeds and maté tea leaves also exhibited a retrograde behavior for the two temperatures considered in this work. In the removal of theobromine from cocoa beans, a much smaller extraction yield was obtained with longer extraction periods and consequently larger solvent requirements. The results of this study confirm the higher selectivity of CO2 for caffeine in comparison with that for theobromine, and also the influence of other components in each particular natural product on the extraction of methylxanthines. The effect of the addition of ethanol to carbon dioxide on the extraction of methylxanthines was significant, particularly in the extraction of theobromine from cocoa beans. In general, the use of ethanol results in lower solvent and energy requirements and thereby improved extraction efficiency.

Aborted sudden death in a patient with a structurally normal heart: the Brugada syndrome.

We report a 37-year-old man with documented aborted sudden death. After resuscitation, the patient showed no structural heart disease but the ECG showed a right bundle-branch block with a descending ST segment elevation in leads V(1) and V(2). After transient normalization of the ECG, the administration of ajmaline led to spontaneous development of the distinct descending ST segment elevation in the right precordial leads and therefore to the diagnosis of Brugada syndrome. The incidence of sudden cardiac death among these patients is high. The only treatment is an implantable cardioverter-defibrillator (ICD). The Brugada syndrome should therefore be borne in mind in the differential diagnosis of sudden death.

A case of lung transplantation following Mycoplasma pneumoniae infection.

Reported here is a case of severe necrotizing pneumonia following Mycoplasma pneumoniae infection that occurred in a 55-year-old man. The histological changes of lung parenchyma included granulomas and bronchiolitis obliterans. Mycoplasma infection was diagnosed by repeated antibody determination (complement fixation test) and confirmed using the polymerase chain reaction to detect the pathogen from a tracheal aspirate. Prior to this episode of pneumonia, the patient had been healthy, except for Reiter's disease that had been diagnosed 18 years previously. In addition to severe pulmonary involvement, the patient developed rhabdomyolysis with subsequent acute renal failure, Stevens-Johnson syndrome, biochemical pancreatitis, severe anemia, and an effusion of the right knee. Contrary to the symptoms of pulmonary disease, all of the extrapulmonary manifestations except anemia were transient. Due to persistent respiratory insufficiency and long-term failure to wean the patient from a respirator, a lung transplantation was performed. Five weeks after transplantation the patient died as a result of intrapulmonary hemorrhage. To the best of our knowledge, this is the first report of pneumonia due to Mycoplasma pneumoniae leading to lung transplantation. Furthermore, the multiple extrapulmonary manifestations in this case make it exceptional.

Reversible pheripheral edema in female patients taking proton pump inhibitors for peptic acid diseases.

Pheripheral edema was observed in five female patients after taking proton pump inhibitors omeprazole, lansoprazole, or pantoprazole for 7-15 days for peptic acid diseases in recommended standard doses. Edema disappeared two to three days after stopping therapy but reappeared in all five patients after being reexposed to the drugs. In three of the patients drug kinetic investigations were performed and revealed a slow metabolizer status. During dose-finding studies for intravenous proton pump inhibitors omeprazole and pantoprazole, three of six young female volunteers receiving omeprazole and two young female volunteers receiving pantoprazole developed peripheral edema within 8 hr when high doses of the proton pump inhibitors were applied by continuous infusion together with large volumes of fluid. The edema disappeared within 24 hr after stopping the infusion therapy. Serum hormone concentrations in these patients did not change during therapy, neither did the edema factor C1-esterase inhibitor. As a possible mechanism, a competitive inhibition at the receptor site of female hormones involved in water regulation is suspected.

Dose-response relation of liquid aerosol inhaled insulin in type I diabetic patients.

AIMS/HYPOTHESIS: The AERx insulin Diabetes Management system (AERx iDMS) is a liquid aerosol device that enables insulin to be administered to the peripheral parts of the lung. This study aimed to compare the pharmacokinetic and pharmacodynamic properties of insulin which is inhaled using AERx iDMS with insulin which is subcutaneously administered. METHODS: In total, 18 C-peptide negative patients with Type I (insulin-dependent) diabetes mellitus participated in this randomised, open-label, 5-period crossover trial. Human regular insulin was administered subcutaneously (0.12 U/kg body weight) or inhaled by means of the AERx iDMS (dosages 0.3, 0.6, 1.2, and 1.8 U/kg body weight). Thereafter plasma glucose was kept constant at 7.2 mmol/l for a 10-h period (glucose clamp technique). RESULTS: Inhaled insulin provided a dose-response relation that was close to linear for both pharmacokinetic (AUC-Ins(0-10 h); Cmax-Ins) and pharmacodynamic (AUC-GIR(0-10 h); GIRmax) parameters. Time to maximum insulin concentration (Tmax-Ins) and time to maximum glucose infusion rate (TGIRmax) were shorter with inhaled insulin than with subcutaneous administration. The pharmacodynamic system efficiency of inhaled insulin (AUC-GIR(0-6 h) was 12.7% (95% C.I.: 10.2-15.6). CONCLUSION/INTERPRETATION: The inhalation of soluble human insulin using the AERx iDMS is feasible and provides a clear dose response. Further long-term studies are required to investigate safety aspects, HbA1c values, incidence of hypoglycaemic events and the quality of life.

Effects of very long (up to 10 years) proton pump blockade on human gastric mucosa.

BACKGROUND: Long-term use of proton pump inhibitors (PPI) has been reported to worsen oxyntic mucosa gastritis and the resulting gland atrophy has been considered a potential risk factor for neoplastic changes in the gastric mucosa. AIMS: The present study examines the effect of extended continuous PPI treatment for up to 10 years on the exocrine and endocrine stomach of patients with acid-related diseases of the upper GI tract. METHODS: Biopsies from the antral and oxyntic mucosa taken at regular time intervals were examined for gastritis, atrophy, intestinal metaplasia, Helicobacter pylori and argyrophil cells and correlated to serum gastrin levels. RESULTS: A general amelioration of antral gastritis without relevant changes of atrophy or intestinal metaplasia, contrasted with the worsening of gastritis and gland atrophy seen in the oxyntic mucosa of reflux esophagitis (but not gastric or duodenal ulcer) patients in the presence of H. pylori infection. In association with PPI- induced hypergastrinemia, argyrophil cell hyperplasia (but not dysplasia or neoplasia) developed in the oxyntic mucosa. CONCLUSION: The present results outline the milder pretreatment pattern and higher proneness to PPI-related, H. pylori-restricted worsening of oxyntic mucosa gastritis in reflux esophagitis compared to gastric ulcer or duodenal ulcer patients. In addition, they confirm a substantial safety of long-term PPI therapy as concerns neoplastic changes in the exocrine and endocrine human stomach.

Post-prandial administration of the insulin analogue insulin aspart in patients with Type 1 diabetes mellitus.

AIMS: In intensified insulin therapy, the recent development of short-acting insulin analogues with a very rapid onset of action forces a new discussion in terms of the optimal injection-meal interval. This study evaluated prandial glycaemia in patients with Type 1 diabetes following the subcutaneous injection of soluble human insulin (HI) and the insulin analogue insulin aspart (IAsp) at different injection-meal intervals and investigated whether administration of IAsp after the meal might provide satisfactory metabolic control. METHODS: In a randomized, double-blind, double-dummy, four-period crossover study, 20 Type 1 diabetic patients were investigated. Prandial insulin was administered 15 min before the start of the meal (HI(-15min)), immediately before the meal (HI(0min); IAsp(0min)) and 15 min after the start of the meal (IAsp(+15min)). RESULTS: Plasma glucose excursions from baseline levels during the 4 h (PGexc) were highest with HI(0min) (17.9 mmol.l(-1).h; P < 0.05 vs. other treatments) and were not statistically different for HI(-15min), IAsp(0min) and IAsp(15min) (13.6, 11.9 and 14.2 mmol.l(-1).h, respectively). Maximum concentration of plasma glucose (PGmax) was lowest with IAsp(0min) (11.2 mmol/l; P < 0.05 vs. other treatments). PGmax was comparable with HI(-15min), HI(0min) and IAsp(+15min) (13.3, 14.1 and 13.2 mmol/l, respectively). CONCLUSIONS: With regard to prandial glycaemia IAsp(+15min) is as effective as HI(-5min) and superior to HI(0min). Thus, post-prandial dosing of the insulin analogue IAsp offers an attractive and feasible therapeutic option for well-controlled patients with Type 1 diabetes mellitus.

Activation of platelet-transforming growth factor beta-1 in the absence of thrombospondin-1.

Thrombospondin-1 (TSP-1) has been shown to bind and activate transforming growth factor-beta1 (TGF-beta1). This observation raises the possibility that TSP-1 helps to sequester TGF-beta1 in platelet alpha granules and activates TGF-beta1 once both proteins are secreted. Herein, we evaluated the level of active and latent TGF-beta1 in the plasma and in the supernatant of thrombin-treated platelets from TSP-1 null and wild-type mice on two genetic backgrounds (C57BL/6 and 129Sv). The plasminogen activator inhibitor-1/luciferase bioassay and an immunological assay were used to determine active and latent TGF-beta1. No significant differences were observed in the levels of active and latent TGF-beta1 in the supernatant of thrombin-treated platelets from TSP-1 null and wild-type mice. Active and latent TGF-beta1 were significantly increased in the plasma and platelets of C57BL/6 mice as compared with 129Sv mice. In addition, there was an increase of plasma level of latent TGF-beta1 in TSP-1 null mice as compared with wild-type mice on the C57BL/6 background but not on the 129Sv background. No active TGF-beta1 was observed in the plasma of either TSP-1 null and wild-type mice. These data indicate that TSP-1 does not function as a chaperon for TGF-beta1 during platelet production and does not activate significant quantities of secreted TGF-beta1 despite a vast excess in the number of TSP-1 molecules as compared with TGF-beta1 molecules. Because platelet releasates from TSP-1 null mice contain active TGF-beta1, we suggest that other important mechanisms of physiological activation of TGF-beta1 probably exist in platelets.