Gridless adult cervical spine radiography and its' effect on image quality and radiation dose: A phantom study.

INTRODUCTION: Imaging of the cervical spine in general radiography is most frequently performed using an anti-scatter grid. The purpose of this study was to investigate the effects of a gridless setting on image quality and radiation dose during digital radiography of the anteroposterior (AP) and lateral (LAT) cervical spine. METHODS: A phantom study was performed with a variety of tube voltages (63-75 kV) with and without an anti-scatter grid. The tube current time product (mAs) and dose area product (DAP) were recorded and used to calculate effective dose (ED) and individual organ dose using PCXMC 2.0 software, as well as entrance surface dose (ESD) and objective image quality: signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective visual image quality grading characteristics (VGC) was performed by five qualified radiographers. RESULTS: In a gridless setting, the AP and LAT positions showed significantly lower DAP (1.6 µGym2; 61.3 % and 1.6 µGym2; 51.2%), ESD (27.6 µGy; 57.3% and 77.2 µGy; 47.2%) and ED (4.2 µSv; 61.3% and 2.3 µSv; 48.9%). In a gridless setting in the AP position, there is a slight significant deterioration in image quality. In the lateral projection, on the other hand, the image quality without the use of grid was only significantly reduced in three of six criteria and there was no difference in the objective image quality between the two settings examined. CONCLUSION: The results of this study show that gridless setting significantly decreases radiation dose and image quality, but the quality in the lateral projection is still acceptable for diagnostic purpose. IMPLICATIONS FOR PRACTICE: The protocol without the use of the anti-scatter grid in cervical spine radiography leads to a reduction in the radiation dose in both projections, but the image quality in the AP is significantly reduced for all criteria examined, with a slight deterioration in image quality in the lateral projection.

Neurotrophin and GDNF expression increases in rat adrenal glands during experimental colitis.

OBJECTIVES: Neurotrophins and GDNF have been recently recognized as important local regulators of inflammatory processes of the gut. RESULTS: We now demonstrate that experimental TNBS-colitis is associated with the increased expression of neurotrophins and GDNF in the adrenal glands. In histological sections of the adrenals from untreated control animals, faint immunolabeling for BDNF, NT-3 and NGF was detectable in the adrenal cortex, with some additional labeling for NGF over the adrenal medulla, whereas GDNF immunolabeling was confined to the adrenal medulla. Induction of TNBS-colitis markedly increased NGF, BDNF, and NT-3 expression within the adrenal cortex after 8 h. NGF declined to basal levels after 7 days. In case of BDNF and NT-3 basal expression levels were reached after 14 days. GDNF expression was robustly upregulated in the adrenal medulla 8 h after induction of colitis and stayed elevated for up to 14 days. CONCLUSION: Together these observations suggest that neurotrophins and GDNF might act as local modulators of components of the HPA-axis during peripheral inflammation.

Protective role of neurotrophins in experimental inflammation of the rat gut.

BACKGROUND & AIMS: Sensory neuropeptides modulate the mucosal response to inflammation in experimental colitis. Because nerve growth factor (NGF) regulates the expression of neuropeptides such as substance P and calcitonin gene-related peptide (CGRP) and is implicated as a link between the nervous system and the immune system in the inflammatory process, we investigated the functional role of NGF and neurotrophin-3 during experimental colitis. METHODS: Immunoneutralizing antibodies specific for NGF and neurotrophin (NT)-3 were used to block their endogenous activity. Mild trinitrobenzene sulfonic acid (TNBS) colitis was induced, and damage scores were assessed after 1 week. Neuropeptide content in the colon and NT messenger RNA (mRNA) expression were determined. RESULTS: The pretreatment with anti-NGF or anti-NT-3 caused a significant 2-3-fold increase in the severity of the experimental inflammation as assessed by a macroscopic damage score, histologic ulceration score, and myeloperoxidase activity in the tissue. CGRP, but not substance P, contents in the colon were significantly reduced by NGF immunoneutralization. NGF mRNA was slightly up-regulated after NGF immunoneutralization, but NT-3 mRNA was unchanged by NT-3 immunoneutralization. CGRP mRNA was not significantly changed after 1 week of colitis by NGF or NT-3 immunoneutralization, whereas beta-preprotachykinin mRNA was up-regulated after immunoneutralization. CONCLUSIONS: These findings suggest a regulatory role for NGF and NT-3 in experimental inflammation of the gut. This effect may be partly caused by the reduction of mucosal CGRP content caused by the NGF blockade.

Commercial recombinant human beta-nerve growth factor and adult rat dorsal root ganglia contain an identical molecular species of nerve growth factor prohormone.

Examination of commercial recombinant human beta-nerve growth factor (rh-beta-NGF) preparations with polyclonal antibodies specific to 13-kDa NGF and pro-NGF-specific domains revealed the presence of high-molecular-mass immunoreactive proteins, including a 60-kDa NGF prohormone. On incubation with a mixture of N- and O-specific glycosidases, the 60-kDa NGF pro-hormone generated a 32-kDa protein corresponding to the molecular size of NGF precursor predicted by the cloned human NGF cDNA. Highly sensitive chemiluminescence immunoblot analysis of adult rat dorsal root ganglia, spinal cord, and colon tissues with NGF- and pro-NGF domain-specific antibodies also revealed the presence of high-molecular-mass proteins, including the 60-kDa NGF prohormone. Based on the presence of the 60-kDa NGF prohormone in dorsal root ganglia and its efferent tissues, we suggest that proteolytically unprocessed, glycosylated NGF prohormone may mediate interactions between neurons and the tissues they innervate.

Transforming growth factor-beta-induced upregulation of transforming growth factor-beta receptor expression in pancreatic regeneration.

The transforming growth factor-beta (TGFbeta) signaling pathway is one important player in the regulation of extracellular matrix turnover and cell proliferation in epithelial regeneration. We used cerulein-induced pancreatitis in rats as a model to investigate the regulation of TGFbeta receptor type I and type II expression on protein and messenger RNA level during regeneration. In the regenerating pancreas, mRNA levels of TGFbeta receptor I and II were significantly increased with a maximum after 2 days. On protein level, expression of TGFbeta receptor II was significantly increased after three to 3-5 days. This elevated expression could be inhibited by neutralizing the endogenous biological activity of TGFbeta1 with a specific antibody. In cultured pancreatic epithelial cells, TGFbeta1 reduced cell proliferation as measured by [3H]thymidine incorporation. Furthermore the transcript levels of TGFbeta1 as well as mRNA and protein concentrations of type I and type II receptor increased during TGFbeta stimulation in vitro. These results indicate that epithelial pancreatic cells contribute to the enhanced TGFbeta1 synthesis during pancreatic regeneration by an autocrine mechanism. TGFbeta1, furthermore, upregulates the expression of its own receptors during the regenerative process, thereby contributing to the increase of the TGFbeta-induced cellular responses.

Calcitonin gene-related peptide mediates the protective effect of sensory nerves in a model of colonic injury.

Recently we demonstrated that sensory denervation with the neurotoxin capsaicin worsened the inflammation in an acute and chronic model of experimental colitis, which suggests a protective role of sensory nerve fibers during gut inflammation. Because we could demonstrate that sensory neuropeptides like Calcitonin gene-related peptide (CGRP) and substance P (SP) are released from sensory nerve fibers during intestinal inflammation, both are strong candidates as mediators for the protective effect of sensory neurons. In this study we investigate the role of CGRP and SP during experimental colitis in the rat by use of receptor antagonists against CGRP (CGRP 8-37, 1 microg/h continuous subcutaneous infusion), SP (RP67580, a NK-1 receptor antagonist, 3 mg/kg i.p.) and an immunoneutralizing CGRP-antibody. A mild colitis was induced by a rectal enema containing trinitrobenzenesulfonic acid. The severity of inflammation increased markedly after 7 days in the CGRP receptor antagonist and CGRP-antibody group compared with the vehicle group as determined by a macroscopic damage score (10.4 +/- 1.2 and 9.6 +/- 1.6 vs. 6.2 +/- 2.1) by a histologic ulceration score (82 +/- 8% and 73 +/- 6% vs. 42 +/- 23%) and by myeloperoxidase activity (19.2 +/- 6.8 and 18.1 +/- 5.9 vs. 8.6 +/- 5.3 U/mg tissue protein), respectively. Treatment with the specific SP receptor antagonist did not significantly alter the severity of colitis at 7 days compared with the control group. These data suggest that CGRP exerts mucosal protection during chronic experimental colitis.

Commercial mouse and human nerve growth factors contain nerve growth factor prohormone isoforms.

Highly sensitive chemiluminescence immunoblot analysis was utilized to examine the purity of mouse 2.5S-, beta- and 7S nerve growth factors as well as that of recombinant human beta-nerve growth factor obtained from commercial vendors. Three polyclonal antisera and two monoclonal antibodies to 13 kDa nerve growth factor (2.5S NGF and beta-NGF) were employed for assessing the purity of each preparation. In addition, polyclonal antisera against two prepro-NGF specific domains were used for immunoblotting analysis to ascertain the identity of high molecular weight nerve growth factor immunoreactive proteins as prohormones. Both the mouse and human NGF preparations contained 53 and 60 kDa immunoreactive proteins. Of these, the mouse 60 kDa and the human 53 kDa proteins strongly immunoreacted with both prepro-nerve growth factor specific domain antibodies suggesting that they are two NGF prohormone isoforms. In addition, both the mouse and human nerve growth factor preparations contained proteins that were immunoreactive to polyclonal antisera and monoclonal antibodies to mouse 2.5S and/or beta-NGF. High molecular weight aggregates of prohormones were also observed in mouse and human nerve growth factor samples. In summary, none of the ten NGF samples examined were pure as stated. Our study cautions investigators in the field to be aware of the presence of nerve growth factor prohormones and other proteins in various mouse and human nerve growth factors sold commercially.

Influence of cholesterol supply on cell growth and differentiation in cultured enterocytes (CaCo-2).

When used as treatment for hypercholesterolemia HMG-CoA reductase inhibitors will first pass through and act upon the gut mucosa. Although cholesterol availability is essential for cell growth of the intestinal mucosa adverse intestinal events are rare which is possibly due to hitherto undefined compensatory mechanisms. In the present work we therefore studied the long-term influence of mevinolin on proliferation and differentiation of CaCo-2 cells as an enterocyte model and their response upon the cholesterol supply of different origin. Mevinolin caused a marked and dose-dependent inhibition of cell proliferation, microvilli length and alkaline phosphatase. This parallel suppression was reversed by the addition of either exogenous free cholesterol, endogenous cholesterol from mevalonolactone or LDL but not HDL3. Surprisingly, sucrase activity reacted in an inverse fashion to alkaline phosphatase activity. Mevinolin induced enzyme activity and this was further enhanced by mevalonolactone supply, while cholesterol and LDL normalized sucrase to controls. In conclusion, the presence of luminal cholesterol as well as plasma LDL as the cholesterol source for the enterocyte may prevent mevinolin toxicity.

HDL3-mediated cholesterol efflux from cultured enterocytes: the role of apoproteins A-I and A-II.

High density lipoproteins (HDL) were recently demonstrated in an enterocyte model (CaCo-2 cells) to mediate reverse cholesterol transport by retroendocytosis. The present study was carried out to define the role of the major HDL apoproteins (apo) A-I and apo A-II in this pathway. HDL3 was fractionated by heparin affinity chromatography into the two main fractions containing either apo A-I only (fraction A) or both apo A-I and apo A-II (fraction B). In addition, liposomes were reconstituted from purified apo A-I or apo A-II and dimyristoyl phosphatidylcholine. The cell binding properties and cholesterol efflux potential were studied in the lipoprotein fractions and the liposomes. Both fractions exhibited similar maximal binding capacities of 4427 (A) and 5041 (B) ng/mg cell protein, but their dissociation constants differed (40.5 and 167.7 micrograms/mL, respectively). Fraction A induced cholesterol efflux and stimulated cholesterol synthesis more than did fraction B. Fraction A mobilized both cellular free and esterified cholesterol, whereas fraction B preferentially mobilized cholesteryl esters. Liposomes, containing either apo A-I or apo A-II, showed specific binding, endocytosis and endosomal transport, and were released as intact particles. Apo A-I liposomes also mediated cholesterol efflux. In conclusion, there is evidence that the HDL3 subfractions A and B, as well as reconstituted liposomes containing either apo A-I or apo A-II, were specifically bound and entered a retroendocytosis pathway which was directly linked to cholesterol efflux. Quantitatively, the apo A-I subfraction appeared to play the dominant role in normal enterocytes. The apo A-II content of fraction B was related to the mobilization of cholesteryl esters.

Effects of insulin, glucagon and dexamethasone on pyruvate kinase in cultured hepatocytes.

Long-term (24-48 h) and short-term (10-30 min) regulation by hormones of hepatic pyruvate kinase activity was investigated in adult rat hepatocytes cultured under serum-free conditions. In the absence of hormones, pyruvate kinase total activity decreased to 83%, 67% and 39% of the initial level at 24, 48 and 72 h of culture. Insulin (100 nM) maintained total activity significantly above control levels throughout this period. In contrast, glucagon (100 nM) and dexamethasone (100 nM) accelerated the gradual decrease within 24 h (glucagon) or 48 h (dexamethasone) of culture. In these long-term experiments, activity at non-saturating concentrations of phosphoenolpyruvate was decreased by glucagon and dexamethasone but not directly modulated by insulin. However, insulin increased the cellular content of the pyruvate kinase activator fructose-1,6-diphosphate. In short-term experiments on cells cultured under serum- and hormone-free conditions for 48 h, both glucagon and dexamethasone independently caused a rapid, dose-dependent increase of the K0.5 for phosphoenolpyruvate within 10 min, while Vmax was not affected. Insulin inhibited this action of glucagon and dexamethasone and, in their absence, significantly increased substrate affinity for phosphoenolpyruvate within 30 min. Cellular fructose-1,6-diphosphate contents remained unchanged under these conditions. The data identify glucocorticoids and insulin - in addition to glucagon - as short-term regulators of the catalytic properties of pyruvate kinase. All three hormones are effective in the long-term control of total enzyme activity.