Structural investigations on lipid nanoparticles containing high amounts of lecithin.

Solid lipid nanoparticles (SLN), an alternative colloidal drug delivery system to polymer nanoparticles, emulsions and liposomes, possess inherent low incorporation rates resulting from the crystalline structure of the solid lipid. To increase the drug loading capacity of SLN, matrix modification by incorporation of the amphiphilic lipid lecithin within the lipid matrices has been proposed as a promising alternative. The objective of this work is to investigate the effects of the lecithin on the microstructure of matrix modified SLN. In addition, these systems were checked for the existence of aggregates like mixed micelles, liposomes, etc., which could possibly be formed by lecithin leakage into the aqueous phase during the preparation process. For this purpose, laser diffraction, photon correlation spectroscopy (PCS), small angle X-ray scattering (SAXS), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) were performed to investigate the structure, mobility, and molecular environment of the compounds. Lecithin incorporation within the lipid matrices resulted in a concentration dependent decrease in particle size up to a critical concentration of 30%. Lecithin incorporation up to 50% was investigated but caused no further particle size decrease. TEM revealed anisometrical and crystalline platelets of ellipsoidal to disc-like shape. Furthermore, SAXS and TEM showed no signs of lecithin and nonionic emulsifier derived aggregates in the aqueous phase. This points in agreement with NMR measurements to a strong attachment of both substances to the SLN surfaces. The proposed structure of the particles after melt emulsification consists of two different layers: a crystalline triglyceride-rich core is covered in dependence of the lecithin content either by a monomolecular or multimolecular lecithin/Solutol HS15 (SOL) layer.     

Identity development, coping, and adjustment in emerging adults with a chronic illness: the sample case of type 1 diabetes

PURPOSE: The present study focused on identity development in emerging adults (aged 18-30 years) with type 1 diabetes. The three study aims were to examine the following: (1) whether identity development was affected by having diabetes, as compared with development in a nondiabetic sample; (2) how identity development was related to depressive symptoms, coping with diabetes, and diabetes-related problems in the diabetic sample; and (3) whether the pathways from identity development to problems with diabetes and depressive symptoms were mediated through coping strategies in the diabetic sample. METHODS: A total of 194 emerging adults with type 1 diabetes and 344 nondiabetic emerging adults participated. RESULTS: First, using analyses of variance, some mean identity differences between the diabetic and comparison samples were found, with emerging adults with diabetes scoring lower on proactive identity exploration. Using cluster analysis, we found that the same identity types or statuses emerged in both the diabetic and nondiabetic samples. Second, in emerging adults with diabetes, these identity statuses were differentially related to diabetes-related problems, depressive symptoms, and illness coping, with the identity statuses representing a strong sense of identity being accompanied by less diabetes-related problems and depressive symptoms and more adequate coping strategies. Third, using structural equation modeling, the pathways from a strong sense of identity to diabetes-related problems and depressive symptoms were mediated through adaptive and maladaptive coping. CONCLUSIONS: Clinicians should be sensitive to the normative task of identity development in emerging adults with diabetes because identity development can function as a resource in coping with and adjusting to diabetes.     

Maximum tolerated doses of methotrexate and 7-hydroxy-methotrexate in a model of acute toxicity in rats

Purpose: After more than 50 years of methotrexate (MTX) treatment of acute lymphoblastic leukaemia (ALL), it is currently believed that as long as dose escalations are followed by adequate leucovorin rescue guided by monitoring MTX serum concentrations, hydration and urinary alkalinization, high-dose MTX (HD-MTX) can be tolerated without life-threatening toxicity. However, our recent experimental animal studies of the major metabolite of MTX, 7-OH-MTX, indicate that this concept may have some limitations. Animals with levels of 7-OH-MTX of 1 mM, which is below the levels routinely found in patients on HD-MTX, demonstrate intolerable toxicity and some animals die within 8 h. Electron microscopy indicates that endothelial cell and platelet functions are perturbed. Since animal data are lacking, and interspecies differences not known, we wanted to investigate the maximum tolerated doses of MTX and 7-OH-MTX in a rat model of short-term effects. The maximum tolerated dose was chosen instead of LD₅₀ for reasons of animal welfare. Methods: We infused MTX and 7-OH-MTX into anaesthetized male Wistar rats and monitored the animals for 8 h. The drugs were given as a bolus plus continuous infusion. The dose-finding ranges were 1.8–11.3 g/kg MTX and 0.1–1.2 g/kg 7-OH-MTX. Results: The maximum tolerated dose was between 3 and 5 g/kg for MTX and lower than 0.1 g/kg for 7-OH-MTX. The mean serum concentrations of MTX and 7-OH-MTX in animals that did not survive the 8-h period were 21.9 and 1.6 mM, respectively. The animals that received the highest MTX or 7-OH-MTX doses and concentrations died after sudden reductions in heart rate and blood pressure. Conclusions: We demonstrated a lower maximum tolerated dose of 7-OH-MTX than of MTX in rats after 8 h. The 7-OH-MTX concentrations were in the therapeutic range after HD-MTX. If the rat/human interspecies differences are not large, our data may indicate that HD-MTX regimens should not be further dose intensified, due not so much to the effects of MTX as to those of 7-OH-MTX. Received: 28 July 1999 / Accepted: 25 January 2000     

Enhancement of the bacterial degradation of phenoxyalkanoate herbicides by the use of modified polyurethane foam as a support

The enhancement of the degradative behaviour of Flavobacterium sp. MH concerning the phenoxyalkanoate herbicides 2,4-D, 2,4-DP, 2,4-DB, MCPA, MCPP, and MCPB, respectively, was achieved by the use of an inert polyurethane (PU)-foam. In comparative batch-degradation experiments with and without the addition of the PU-carrier (1.25 % w/v), respectively, the advantages of the PU-supply were demonstrated. When 2,4-D, 2,4-DP, and MCPP, respectively, was used as a growth substrate by strain MH the PU-supply led to a reduced lag-phase. In the case of the stronger toxic phenoxyalkanoates 2,4-DB and MCPB, respectively, the inital substrate concentration (0.1 g/1) was significantly reduced to a minor toxic concentration due to a distinct adsorption to the PU-carrier, thus enabling the biodegradation. Finally, the total initially supplied amount of the phenoxyalkanoates was detoxified as verified by thechloride balance. After several steps of subcultivation, even a five-fold increased MCPB concentration (0.5 g/1) could be detoxified by strain MH in a PU-supplied bubble reactor within several days.     

Tibial tunnel enlargement after anterior cruciate ligament reconstruction by autogenous bone-patellar tendon-bone graft

This retrospective study was designed to evaluate changes in the diameter of the tibial tunnel over time following the reconstruction of the anterior cruciate ligament (ACL) with a bone-patellar tendon-bone autograft in 44 patients. The changes in the geometry of the bone tunnels were measured radiographically during the immediate postoperative period and at time intervals between 3 and 36 months after surgery. The dimensions at 1 year were correlated with the 1-year clinical results. The distance between the sclerotic margins of the tibial tunnel was measured at the distal tunnel exis on the medial tibial cortex, in the middle of the tunnel, and proximally at the level of the joint line. The dimensions were calculated by using a magnification factor determined by reference to the interference screw of known diameter located within the tunnel. The position of the centre of the tibial tunnel with regard to Blumensaat's line was also measured. The average tunnel diameter at the proximal tibial exit increased from 12±1.9 mm (mean ± standard deviation) postoperatively to 14±2.2 mm at 3 months. The average proximal tunnel diameter did not significantly change from 3 months to 2 years, and then decreased to 13±2.4 mm at 3 years. At 1 year, most of the patterns of osteolysis were of the cone type (57%), followed by the cavity type (40%) and line type (3%). The degree of osteolysis was not related to the tibial tunnel position with respect to Blumensaat's line. There was no correlation between the changes in tunnel diameter and either the IKDC score or the residual joint laxity measured by a KT-1000 arthrometer. The aetiology of tunnel enlargement is currently unknown. Possible factors responsible for bone resorption include micromotion of the graft relative to the tunnel wall, leading to an inflammatory response in the tunnel, or stress shielding of the tunnel wall proximal to the interference screw.     

The hScrib/Dlg apico-basal control complex is differentially targeted by HPV-16 and HPV-18 E6 proteins

The E6 proteins of the high-risk Human papillomaviruses (HPV) types have a well-documented ability to target certain cellular proteins for ubiquitin-mediated degradation via the proteasome. Previous studies have shown that E6 proteins interact differently with different target proteins, and that the viral proteins, depending upon the target, may recruit diverse cellular ubiquitin-protein ligases. In this study, we have examined the abilities of E6 proteins from HPV-16 and HPV-18 to interact with and induce the degradation of two PDZ domain-containing targets, Dlg and hScrib. We have also mapped the binding site of E6 on hScrib and shown that the interaction of E6 with hScrib is distinct from its interactions with other PDZ domain-containing targets. This is reflected in the efficiency with which the two viral E6 proteins can inhibit hScrib's suppression of cell transformation.Dlg and hScrib have complementary activities in the control of epithelial cell polarity and the fact that both are targeted by high-risk HPV E6 proteins underlines their importance. Our finding that they are each targeted differently by HPV-16 and HPV-18 E 6 s suggests that the two viruses are subjected to somewhat different constraints and provides a possible explanation for the apparent redundancy in targeting both parts of this important control mechanism.     

Formation of PAH-DNA adducts after in vivo and vitro exposure of rats and lung cells to different commercial carbon blacks

OBJECTIVE: The current study was designed to test the possible release and bioavailability of polycyclic aromatic hydrocarbons (PAHs) from a set of commercial carbon blacks (CBs) as well as the ability of these PAHs to form bulky DNA adducts. METHODS: In four commercial CBs (Printex 90, Sterling V, N330, Lampblack 101), leaching of PAH was examined through (1) release of parent PAHs in saline with or without surfactant, and (2) PAH adducts in lung epithelial cells (A549) or in rat lungs after exposure to two CBs (Printex 90, Sterling V) for 13 weeks (50 mg/m(3)). In vitro experiments were done with original and extracted particles, as well as organic extracts of CB in DMSO. As positive controls, B[a]P (0.03 microM) and a mixture of 16 PAHs (0.1 microM) were used. RESULTS: No leaching of PAHs was measured in saline or surfactant-containing saline. In vitro incubations with CB particles (30-300 microg/cm(2)) revealed no adduct spots except for Sterling V. However, the spot was not concentration dependent and remains unidentified. Lung DNA from rats after inhalation of Printex 90 or Sterling V showed no spots related to PAH-DNA adduct formation compared to sham-exposed rats. CONCLUSION: The results suggest that PAHs are very tightly bound to these CBs. Only using organic extracts or particles of low-surface Sterling V, with high PAH content, PAHs may become available to form PAH-DNA adducts. However, the in vitro conditions showing this effect will not be encountered in vivo and renders this mechanism in particle-induced lung cancer at in vivo exposures highly unlikely.     

Acute psychological stress affects glucose concentrations in patients with type 1 diabetes following food intake but not in the fasting state

OBJECTIVE: To compare the effect of acute psychosocial stress on glucose concentrations in the fasting state and following food intake in patients with type 1 diabetes. RESEARCH DESIGN AND METHODS: In study 1, 20 patients were exposed to moderate psychosocial stress by means of the Trier Social Stress Test (TSST) in the fasting state. In study 2, the TSST was applied to 20 additional patients 75 min after intake of a standard meal. Glucose concentrations (by continuous glucose monitoring system), blood pressure, and heart rate were monitored on the control day and on the stress testing day. RESULTS: In both studies, blood pressure increased in response to TSST from 122/77 +/- 14/9 mmHg at baseline to a maximum of 152/93 +/- 21/13 mmHg (P < 0.001), and heart rate increased from 80 +/- 11 to 99 +/- 19 bpm (P < 0.001). In the fasting state (study 1), glucose concentrations remained unchanged during the control day as well as during the stress testing day. In study 2, glucose concentrations were similar on both days before and up to 75 min after the intake of the standard meal. However, a significant delay (of 45 min) in the decrease of glucose concentrations was induced by psychological stress. A two-factor repeated-measures ANOVA revealed a significant difference of glucose concentrations over time (F = 646.65/P < 0.001). CONCLUSIONS: In the postprandial period, acute psychological stress induced a significantly delayed decrease of glucose concentrations, whereas in the fasting state, no effect on poststress glucose concentrations was observed.     

Moderate increase in intraabdominal pressure attenuates gastric mucosal oxygen saturation in patients undergoing laparoscopy

BACKGROUND: Perioperative disturbances of microvascular blood flow and oxygenation in the intestinal tract have been hypothesized to play an important role in development of the multiple organ dysfunction syndrome. Herein, increased intra-abdominal pressure (IAP) has been identified as a key factor in the initiation of the pathophysiologic cascade. The authors hypothesized that increasing the IAP by intraperitoneal insufflation of carbon dioxide attenuates microvascular oxygen saturation in gastric mucosa. They tested this hypothesis in a prospective, observational study in 16 patients scheduled to undergo elective diagnostic laparoscopy. METHODS: The authors continuously assessed microvascular oxygen saturation in gastric mucosa by reflectance spectrophotometry. Simultaneously systemic oxygen saturation, heart rate, arterial blood pressure, and ventilation-derived variables were measured noninvasively. During general anesthesia and controlled mechanical ventilation, baseline values were obtained. Thereafter, the IAP was increased to 8 and 12 mmHg, respectively, followed by a control period after desufflation. RESULTS: The increase in IAP from baseline to 8 mmHg decreased microvascular oxygen saturation in gastric mucosa from 69+/-7% (mean +/- SD) to 63+/-8% at 8 mmHg IAP (P <0.05), with a further significant reduction to 54+/-13% at 12 mmHg IAP (P <0.01). Microvascular oxygen saturation in gastric mucosa recovered rapidly to baseline level (66 +/- 10%) after release of increased IAP. In striking contrast to regional mucosal oxygen saturation, systemic oxygenation did not change with either of the interventions. CONCLUSIONS: The results suggest that increasing intraabdominal pressure to moderate levels, commonly applied to induce a surgical pneumoperitoneum, decreases gastric mucosal oxygen saturation.