Semi-conducting properties of titanium dioxide surfaces on titanium implants

The properties of the TiO₂ layer on titanium implant surfaces are decisive for good contact with the surrounding tissue. The oxide properties can be deliberately changed by for example chemical etching, ion incorporation or anodisation. In the present study impedance spectroscopy was used to study the semi-conducting properties of the naturally formed oxide for different pre-treatment of the surface. A turned surface was used as a reference and both physical (blasting) and chemical (hydrofluoric acid etching) treatments were investigated. Blasting of a titanium sample introduces defects in the metal surface and the study clearly shows that also the oxide layer contains defects leading to a higher number of charge carriers (increased conductivity) compared with the oxide on the turned surface. The hydrofluoric acid etching of the blasted surface results in an oxide film with even higher conductivity. Indication of the defect oxide structure for fluoride treated samples was also seen when analysing the TiO⁺/Ti⁺ ratio from ToF-SIMS data. The lowest value of this ratio was obtained for the HF etched sample, indicating a less stoichiometric oxide compared to the other surfaces. This is a result of incorporation of fluoride ions in the oxide, as proven by adsorption studies on a TiO₂ suspension. The results were treated in the context of surface complexation and two surface complexes were identified. Our results are discussed in relation to pull-out data on rabbit. The pull-out forces depend primarily on surface roughness but the contribution from the hydrofluoric acid etching might be explained by fluoride ion incorporation and the resulting increase in oxide conductivity.     

Disruption of interleukin-18, but not interleukin-1, increases vulnerability to preterm delivery and fetal mortality after intrauterine inflammation

Preterm birth is a major contributor of adverse perinatal outcome. Clinical data suggest that an inflammatory response is important in the process leading to preterm labor. By using a recently introduced mouse model of localized intrauterine lipopolysaccharide-induced inflammation, the effect of interleukin (IL)-18 gene disruption and/or IL-18 neutralization as well as combined IL-1alpha/beta gene disruption on inflammation-induced fetal loss was investigated. The frequency of preterm fetal loss was significantly higher in IL-18 knockout mice (58.9%) and in mice administered IL-18-binding protein (59.7%) compared to wild-type controls (34.7%). The rate of fetal loss was not affected by IL-1alpha/beta gene deficiency (38.7%). Decreased IL-18 protein expression combined with elevated IL-12 protein expression in uterine tissue of IL-18 knockout mice and IL-18-binding protein-treated animals was noticed. These data demonstrate that preterm pregnancy loss in response to intrauterine inflammation was enhanced by disruption of the IL-18 gene and/or IL-18 neutralization, events that may relate to exaggerated Th1 responses because of an increased IL-12/IL-18 ratio.     

The role of illness beliefs, treatment beliefs, and perceived severity of symptoms in explaining distress in cancer patients during chemotherapy treatment

The authors investigated cancer patients' interpretations of their physical symptoms and their illness beliefs with the objective of establishing the importance of these variables in predicting distress during chemotherapy treatment. Past researchers have suggested that causal attributions of physical symptoms and beliefs about illness progression and its consequences may serve as important mediators between number and perceived severity of symptoms and psychological adjustment in cancer patients during the treatment phase. Our aim in this study was to further these findings using the Self-Regulation Model as a theoretical framework. The study was cross-sectional in design, testing 72 patients with cancer receiving intravenous chemotherapy as outpatients in the United Kingdom. The participants completed questionnaires measuring number and perceived severity of symptoms, the causal attributions of these, illness and treatment beliefs, anxiety, and depression. The results showed that consequence beliefs serve as important mediators between number of symptoms and distress, explaining 15% of the variance in anxious mood and 5% of the variance in depressed mood. The authors found perceived severity of symptoms to be an independent predictor of anxious mood, explaining 7% of the variance. Its role in predicting depressed mood was not significant.     

Down regulation of TRPC1 by shRNA reduces mechanosensitivity in mouse dorsal root ganglion neurons in vitro

Mechanosensitivity is a crucial but poorly understood property of the sensory nervous system. Transient receptor potential (TRP) channels, which have been found to be responsible for the detection of other sensory stimuli such as temperature and pungent chemicals, have been suggested to also recognize stretch or pressure to cell membranes. TRPC1 is one candidate from studies in oocytes but evidence in native sensory neurons has been lacking. Therefore, we have measured an increase in intracellular Ca²⁺ levels upon mechanical activation of native mouse dorsal root ganglion (DRG) neurons in culture using hypoosmolar buffer. Our results show that down regulation of TRPC1 with short hairpin RNA results in a 65% reduction of neurons with stretch activated responses. These results implicate a direct or indirect involvement of TRPC1 in the mechanosensitivity of DRG neurons.     

Cyp1b1 protein in the mouse eye during development: an immunohistochemical study.

We show, for the first time, the spatiotemporal appearance of Cyp1b1 protein during mouse eye ontogeny. The protein was unambiguously identified in the adult mouse eye and newborn (P0) whole mouse microsomes and was shown to be localized in inner ciliary epithelium, corneal epithelium, retinal inner nuclear cells, and ganglion cells. The enzyme protein was present in the lens epithelium adjacent to the developing ciliary body at 15.5 days postconception (E15.5) and was most strongly expressed during E17.5 to 7 days postnatally (P07). Subsequently, it declined to very low levels. The protein was also expressed in the corneal endothelial cells adjacent to the ciliary body at P07. Cyp1b1 was barely detectable in the inner ciliary epithelium before E17.5 but increased rapidly postnatally, reaching adult levels by P28. Levels of the enzyme protein in the corneal epithelium were seen from E15.5 onward, increasing sharply, and after a decrease at P07, were highest in the adult animal eye. The presence of Cyp1b1 protein in the inner nuclear layer of the retina was very low in the prenatal eye, increasing rapidly postnatally, and was highest in the adult animal eye. In the ganglion cell layer of the retina, it increased slowly from E15.5 to P07 and then rapidly reached adult levels. Interestingly, Cyp1b1 was not detected in the trabecular meshwork at any stage of development or in the adult eye. We conclude that the enzyme may play important roles in normal eye development and function in mice as in humans, and that the mouse may prove to be an excellent model for determination of the roles of CYP1B1 in human eye development and function.     

A comparative study of enzyme histochemical features in the gerbilline and human cholesteatoma

Spontaneous and experimentally induced cholesteatoma in the Mongolian gerbil has been found to exhibit histopathological similarities to human aural cholesteatoma and has been suggested as an experimental model for studies of the clinical situation. In an attempt to further characterize this model, we compared experimentally induced cholesteatomas in the external auditory canal from gerbils with those of the human ear by means of a correlated histopathologic and enzyme histochemical study. The human and gerbilline cholesteatomas revealed similar histopathologic features. Even enzyme histochemically, the human and experimentally induced cholesteatomas demonstrated similar features. Thus glucose-6-phosphate dehydrogenase activity, an indicator of oxidative metabolism, was demonstrated especially in the stratum granulosum cells of the heavily orthokeratinizing squamous epithelium adjacent to the cholesteatomas. The human ear canal skin also revealed enzyme histochemical characteristics similar to the squamous epithelium lining the human cholesteatoma. The hydrolytic enzyme activity (leucyl-aminopeptidase) was strong in the connective tissue surrounding human cholesteatoma when compared with that of ear canal skin. In the gerbilline cholesteatoma, this activity was demonstrated especially in the connective tissue adjacent to eroded bone, which possibly may facilitate cholesteatoma progression. We conclude that experimentally induced cholesteatoma has both histophatological and enzyme histochemical similarities to human aural cholesteatoma and therefore it is suggested that the gerbilline model may be used for studies on the development of human cholesteatoma. Our results support the view that cholesteatoma may originate from migrated hyperkeratinizing cells from the epidermis of the tympanic membrane or the meatus.     

Chemotherapy improves survival and quality of life in advanced pancreatic and biliary cancer

BACKGROUND:: In certain patients with pancreatic and biliary cancer, chemotherapymay relieve tumour-related symptoms, improve quality of lifeand possibly prolong survival. The extent of these improvementsis not completely known in spite of the extensive use of thistreatment modality. The aim of this study was to estimate anygain in the quantity and quality of life produced by chemotherapyin patients with pancreatic and biliary cancer. PATIENTS AND METHODS:: Between January 1991 and February 1995, 90 eligible patientswith pancreatic or biliary cancer were randomized to eitherchemotherapy in addition to best supportive care or to bestsupportive care. Chemotherapy was allowed in the latter groupif the supportive measures did not lead to palliation. Chemotherapywas either sequential 5-fluorouracil/leucovorin combined withetoposide (FELv) or, in elderly and poor performance patients,the same regimen without etoposide (FLv). Quality of life wasevaluated with the EORTC-QLQ-C30 instrument. RESULTS:: Mean scale scores in the QLQ-C30 improved more often/deterioratedless frequently in the chemotherapy group than in the best supportivecare group. More patients in the chemotherapy group (36%, 17/49)had an improved or prolonged high quality of life for a minimumperiod of months compared to those in the best supportive caregroup (10%, 4/41, p <0.01). Overall survival was significantlylonger in the chemotherapy group (median 6 vs. 2.5 months, p<0.01). Also, the quality-adjusted survival time was longerfor patients randomized to chemotherapy (median 4 vs. 1 months,p <0.01). The effects were seen both in pancreatic and biliarycancer. CONCLUSION:: The results show that chemotherapy can add to both quantityand quality of life in advanced pancreatic and biliary cancer.The number of patients who benefit from treatment is, however,still limited; for this reason careful selection before, andclose monitoring during, treatment are necessary. biliary cancer, chemotherapy, palliation, pancreatic cancer, randomized study     

Influence of nitrogen status on the bioconcentration of hydrophobic organic compounds to Selenastrum capricornutum

Changes in algal nitrogen status that increase algal lipid content also affect the bioconcentration of hydrophobic organic compounds (HOCs). Bioconcentration factors (BCFs) for several HOCs increased up to nine times as the total algal lipid content of the green algae Selenastrum carpricornutum increased from 17 to 44% of the algal dry weight as a consequence of nitrogen starvation. An increase in total lipid from 17 to 44% should theoretically increase the BCFs by a factor of 2.6. BCFs for PCB 31, PCB 49, PCB 153, and DDT increased with maximum lipid content by factors of 6.3, 8.9, 8.9, and 6.6, respectively, thus more than theoretically predicted from the lipid normalization of BCFs obtained at exponential growth phase (17% total lipid for S. carpricornutum), whereas BCFs for PCB 105, phenanthrene, and 4-chloroaniline increased at 44% lipid content, only by factors of 1.5, 1.5, and 2.5, respectively, and thus less than or equal to the theoretical prediction. Lipid-class normalization of BCFs did not reveal significant information beyond that available from normalizing to total lipid.     

A novel quantitative dual-isotope method for simultaneous ventilation and perfusion lung SPET

A quantitative dual-isotope single-photon emission tomography (SPET) technique for the assessment of lung ventilation (V) and perfusion (Q) using, respectively, technetium-99m labelled Technegas (140 keV) and indium-113m labelled macro-aggregated albumin (392 keV), is presented, validated and clinically tested in a healthy volunteer. In order to assess V, Q and V/Q distributions in quantitative terms, algorithms which correct for down scattering, photon scattering and attenuation, as well as an organ outline algorithm, were implemented. Scatter and down-scatter correction were made in the spatial domain by pixel-wise image subtraction of projection-dependent global scattering factors obtained from the energy domain. The attenuation correction was based on an iterative projection/back-projection method. All studies were made on a three-headed SPET system (Trionix) with medium-energy parallel-hole collimators. The set of input data for quantification was based on SPET acquisition of emission data in four separate energy windows, the associated cumulative energy spectra and transmission data. The attenuation correction routine as well as the edge detection algorithm utilized data from (99m)Tc transmission tomography. Attenuation data for (113m)In were obtained by linear scaling of the (99m)Tc attenuation maps. The correction algorithms were experimentally validated with a stack phantom system and applied on a healthy volunteer. The mean difference between the corrected SPET data of the dense stack lung phantom and those obtained from the corresponding scatter- and attenuation-"free" version was only 1.9% for (99m)Tc and 0.9% for (113m)In. The estimated fractional V/Q distribution in the 3-D lung phantom volume had its peak at V/Q=1, with a width (FWHM) of 0.31 due to noise, particularly in the (113m)In images, and to partial volume effects. For a healthy volunteer, the corresponding values were 0.9 and 0.35, respectively. This method allows accurate assessment of radionuclide distribution on a regional basis. For basic lung physiology and clinical practice, the method allows assessment of the global frequency functions of the V, Q and V/Q distributions.