bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential distribution of VGF-derived peptides in the adrenal medulla and evidence for their selective modulation
Authors: D'Amato Filomena , Noli Barbara , Brancia Carla , Cocco Cristina , Flore Giovanna , Collu Maria , Nicolussi Paola , Ferri Gian-Luca
Published: April 2008

While vg f gene knockout mice are hyperactive and hypermetabolic, surprisingly the TLQP-21 brain VGF peptide increased energy consumption, suggesting that opposing regulatory effects could be exerted by peptides alternatively cleaved from the VGF precursor. Using antisera to the VGF precursor C-terminus and three cleavage products, we revealed a distinct differential distribution in adrenal, certain peptides (VGF422–430: PGH peptides) being found throughout bovine and swine medulla, while C-terminus and TLQP peptides were confined to adrenaline cells in the above species and in rat and C-terminally shortened forms (VGF604–612: HVLL peptides) to nor-adrenaline cells. Random abattoir samples of bovine and swine adrenal contained 520±40 and 450±60 pmol/g (mean±s.e.m. respectively) of C-terminus peptides and similar or lower amounts of others. Upon gel chromatography, bona fide VGF precursor, ~7.5 and ~3.5 kDa forms were revealed by C-terminus assays, HVLL peptides being limited to small fragments. TLQP peptides included ~7.5 kDa form and peaks accounting for TLQP-21 and predicted TLQP-30 and TLQP-42. Low molecular weight (MW) PGH peptides were revealed, together with a high MW form possibly encompassing the VGF precursor N-terminus. In acutely stressed swine, a striking increase was seen for C-terminus and TLQP peptides, with no significant differences for PGH peptides. A similar response was found in rat TLQP peptides showing a major increase upon an acute swimming stress and 30 min thereafter. A differential processing of the VGF precursor encompassing many areas of its primary sequence and selective modulations of its derived peptides occur in adrenal medullary cells, possibly relevant to adaptive homeostatic responses.
Pancreatic β-cells express hepcidin, an iron-uptake regulatory peptide
Authors: Kulaksiz Hasan , Fein Evelyn , Redecker Peter , Stremmel Wolfgang , Adler Guido , Cetin Yalcin
Published: April 2008

Body iron is involved in various vital functions. Its uptake in the intestine is regulated by hepcidin, a bioactive peptide originally identified in plasma and urine and subsequently in the liver. In the present study, we provide evidence at the transcriptional and translational levels that hepcidin is also expressed in the pancreas of rat and man. Immunohistochemical studies localized the peptide exclusively to β-cells of the islets of Langerhans. Immunoelectron microscopical analyses revealed that hepcidin is confined to the insulin-storing β-cell secretory granules. As demonstrated in insulinoma-derived RINm5F cells, the expression of hepcidin in β-cells is regulated by iron. Based on the present findings we conclude that pancreatic islets are an additional source of the peptide hepcidin. The localization of this peptide to β-cells suggests that pancreatic β-cells may be involved in iron metabolism in addition to their genuine function in blood glucose regulation. In view of the various linked iron/glucose disorders in the pancreas, the present findings may provide an insight into the phenomenology of intriguing mutual relationships between iron and glucose metabolisms.
Endocrine gland-derived vascular endothelial growth factor in rat pancreas: genetic expression and testosterone regulation
Authors: Morales Angélica , Morimoto Sumiko , Díaz Lorenza , Robles Guillermo , Díaz-Sánchez Vicente
Published: April 2008

Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an endothelial cell mitogen, expressed essentially in steroidogenic cells. Recently, the expression of EG-VEGF in normal human pancreas and pancreatic adenocarcinoma has been demonstrated. Epidemiologically, pancreatic carcinogenesis is more frequent in males than females, and given that androgen receptors and testosterone biotransformation have been described in pancreas, we hypothesized that testosterone could participate in the regulation of EG-VEGF expression. In this study, we investigated the regulation of EG-VEGF gene expression by testosterone in normal rat pancreatic tissue and rat insulinoma cells (RINm5F). Total RNA was extracted from rat pancreas and cultured cells. Gene expression was studied by real-time PCR and protein detection by immunohistochemistry. Serum testosterone was quantified by RIA. Results showed that EG-VEGF is expressed predominantly in pancreatic islets and vascular endothelium, as well as in RINm5F cells. EG-VEGF gene expression was lower in the pancreas of rats with higher testosterone serum levels. A similar effect that was reverted by flutamide was observed in testosterone-treated RINm5F cells. In summary, testosterone down-regulated EG-VEGF gene expression in rat pancreatic tissue and RINm5F cells. This effect could be mediated by the androgen receptor. To our knowledge, this is the first time that a direct effect of testosterone on EG-VEGF gene expression in rat pancreas and RINm5F cells is demonstrated.
Ghrelin secretion is more closely aligned to energy balance than with feeding behaviour in the grower pig
Authors: Scrimgeour K , Gresham M J , Giles L R , Thomson P C , Wynn P C , Newman R E
Published: April 2008

Secretory characteristics of the ghrelin profile for the pig are still unknown. Our objective was to clarify the mechanisms that influence ghrelin secretion during differing feeding patterns. Pigs were initially fed a commercial pelleted diet offered ad libitum and blood samples collected for 24 h at intervals of 1 h. The pigs were then entrained for 17 days to a twice daily interval feeding regimen (0900–1000 and 1600–1700 h) and blood samples were collected for 12 h (0800–2000 h). This was followed by a similar interval feeding and blood sampling regimen with the 0900–1000 h feeding period being replaced by a sham feed where pigs were shown their usual feed but none offered. During the ad libitum feeding regimen, there was no preprandial rise or postprandial fall in circulating plasma total ghrelin concentration, which remained constant throughout the sampling period. In addition, no preprandial rise or postprandial fall in ghrelin concentrations was observed when pigs were fed either twice or once daily; however, plasma ghrelin concentration rose gradually over the 12-h sampling period during the twice daily feeding regimen and increased further when pigs were fed once per day. This increase in ghrelin levels coincided with an increase in plasma GH and non-esterified fatty acid concentrations and was not associated with either plasma glucose or insulin concentrations. These results suggest that circulating total plasma ghrelin concentrations in the pig appear to be influenced by chronic changes in energy balance rather than the feeding pattern per se.
The novel estrogen receptor G-protein-coupled receptor 30 is expressed in human bone
Authors: Heino Terhi J , Chagin Andrei S , Sävendahl Lars
Published: April 2008

Estrogens have significant impact on bone mineral metabolism. Besides the classical estrogen receptors (ERα and ERβ), a trans-membrane G-protein-coupled receptor (GPR30) has been demonstrated to mediate estrogenic effects. We aimed to study whether GPR30 is expressed in bone cells and if so, whether the level of expression is developmentally regulated. Metaphyseal bone biopsies were collected from the tibia in 14 boys and 6 girls, all at different stages of puberty. GPR30 protein expression was studied by immunohistochemistry in paraffin-embedded sections. GPR30-positive osteocytes and osteoblasts were quantified and linear regression analysis was applied. Cytoplasmic GPR30 expression was detected in osteoblasts, osteocytes, and osteoclasts. Osteocytes were more frequently positive for GPR30 than osteoblasts (58±4% vs 46±3% positive cells respectively, P<0.05). Detailed analysis demonstrated that GPR30 positivity declined during pubertal development in osteocytes (R=−0.56, P<0.01) but not in osteoblasts (R=−0.31, P>0.05). No sex difference was observed in the numbers of GPR30-positive osteoblasts or osteocytes. Furthermore, GPR30 expression did not correlate with chronological or bone age. In conclusion, the novel ER GPR30 is expressed in osteoblasts, osteocytes, and osteoclasts suggesting that non-genomic estrogen signaling via GPR30 may exist in bone. However, the functional role of GPR30 in bone tissue remains to be elucidated.
Glucocorticoids and fatty acid metabolism in humans: fuelling fat redistribution in the metabolic syndrome
Authors: Macfarlane David P , Forbes Shareen , Walker Brian R
Published: April 2008

Glucocorticoid hormones constitute an integral component of the response to stress, and many of the manifestations of glucocorticoid excess (Cushing's syndrome) are predictable on the basis of their acute effects to raise blood pressure, induce insulin resistance, increase protein catabolism and elevate plasma glucose. However, it appears to be a paradox that the acute lipolytic effect of glucocorticoids is not manifest in long-term weight loss in humans. The effects of glucocorticoids on glucose metabolism are well characterised, involving impaired peripheral glucose uptake and hepatic insulin resistance, and there is mounting evidence that subtle abnormalities in glucocorticoid concentrations in the plasma and/or in tissue sensitivity to glucocorticoids are important in metabolic syndrome. The effects of glucocorticoids on fatty acid metabolism are less well understood than their influence on glucose metabolism. In this article, we review the literature describing the effects of glucocorticoids on fatty acid metabolism, with particular reference to in vivo human studies. We consider the implications for contrasting acute versus chronic effects of glucocorticoids on fat accumulation, effects in different adipose depots and the potential role of glucocorticoid signalling in the pathogenesis and therapy of metabolic syndrome.
Chicken leptin receptor is functional in activating JAK–STATpathway in vitro
Authors: Adachi Hiromi , Takemoto Yasumasa , Bungo Takashi , Ohkubo Takeshi
Published: April 2008

Leptin is a cytokine-like hormone that regulates food intake and energy homeostasis via its interaction with the leptin receptor (LEPR) located in the target tissues. Leptin-dependent signal transduction pathways have been well characterised in mammals but less is known about them in other vertebrates. In birds, although the existence of the LEPR has been confirmed, the identity of the natural ligand for the LEPR is controversial and the signalling cascade is not fully understood either. Here, we describe the in vitro expression of chicken LEPR (chLEPR), which can mediate the leptin signal. Murine leptin specifically bound with the chLEPR, which initiated the activation of luciferase in chLEPR-expressing cells. Leptin stimulation led to phosphorylation of signal transducers and activators of transcription 3 (STAT3) via chLEPR, and Janus kinase–2 (JAK–2) inhibitor partially blocked leptin-induced luciferase activation in CHO-K1 cells stably expressing chLEPR (CHO-chLEPR). RNA interference for chLEPR reduced the induction rate of luciferase activity by leptin in CHO-chLEPR cells. Furthermore, we found that leptin phosphorylated STAT3 and increased luciferase activity in LMH cells, a chicken hepatoma cell line, transiently expressing chLEPR. These results strongly suggest that the chLEPR is functional in activating the JAK–STAT pathway, which may indicate that the LEPR expressed in chicken tissues is capable of binding endogenous ligand as well as exogenous mammalian leptin, leading to physiological actions.
Modifying a Victorian spillway to comply with current design standards
Authors: Farnell Paul
Published: April 2008

The lower reservoir in a cascade built in the mid- to late nineteenth century was reclassified to category A. This paper discusses the modifications required to enable the spillway to pass the probable maximum flood safely. It covers flood study, physical model study, design and construction phases.
Design of carbon nanotubes for large‐area electron field‐emission cathodes
Authors: Smith Richard C. , Silva S. R. P.
Published: April 2008

Abstract— Electron field‐emission displays offer a viable option for the next generation of flat‐panel screens. Boasting high‐quality images in terms of good color saturation, fast refresh rate, and high brightness, these displays have the potential to offer above and beyond what the current market leaders, LCD and plasma. However, for the realization of such a new display disrupting the incumbent LCD and plasma displays, not only does the image quality need to be better, but fabrication costs and suitable manufacturing processes need to be in place at reduced cost. Many viable cathode materials have been proposed in recent years, one of which being the use of carbon nanotubes (CNTs) in various forms (aligned growth, screen printing, and polymer matrix). In this review, a series of recent experiments investigating the field‐emission characteristics of carbon‐nanotube systems for possible use in the display industry is presented.
Growth of uniform carbon‐nanotube arrays with sandwich technology
Authors: Chen Zexiang , Zhang Qiang , Zhu Bingjin , den Engelsen Daniel , Bachmann Peter K. , Lewalter Astrid
Published: April 2008

Abstract—In this work, a novel approach to grow structured, highly oriented carbon nanotubes (CNTs), which are vertically aligned to the substrate and show large field emission is reported. Growth is performed on lithographically defined dots of catalysts, which can be deposited on metallic, semiconducting, and glass substrates. A sandwiched catalyst structure and microwave plasma chemical vapor deposition enables the formation of uniform CNT arrays of 1.6 × 1.6 μm2. The method is easily scalable to large areas. The CNT arrays exhibit a stable field emission of 20 mA and a macroscopic current density of 50 mA/cm2at a rather low electric field of 5.33 V/μm. Modeling of space charge indicates that space charge reduces the magnitude of the CNT emission at high field strength: this agrees satisfactorily with the measurements.
Toxicity of aqueous fullerene in adult and larval Fundulus heteroclitus
Authors: Blickley Twyla Michelle , McClellan-Green Patricia
Published: April 2008

Aqueous suspensions of fullerene aggregates (aqua-nC60) were used to investigate the movement of carbon-based nanomaterials in a marine water column and to determine their effects on different life stages of a marine teleost. Fullerene aggregates formed precipitates as a result of mixing in natural seawater, and levels of aqua-nC60 were significantly increased in bottom waters after 24 h. Exposure of Fundulus heteroclitus embryos, larvae, and adults to increasing concentrations of aqua-nC60 resulted in very little mortality, and no median lethal concentrations could be calculated at ≤ 10 mg/L. Aggregates of aqua-nC60 did adhere to the chorion but did not affect development of the embryos or their hatching success. Movements of aqua-nC60 through the chorion and into the embryo tended to increase with higher exposure levels; however, the concentrations were extremely low and did not differ significantly. Larvae exposed to increasing concentrations of aqua-nC60 exhibited a significant dose-dependent increase in total glutathione (GSH). This was accompanied by a decreasing trend in lipid peroxidation (LPO), but LPO was not statistically different between treatments. Adult F. heteroclitus exposed to increasing concentrations of aqua-nC60 exhibited an increase in total GSH in liver tissue but not in the gill. No significant effects on LPO were observed in either tissue. Thus, we conclude that aqua-nC60 affects the oxidative stress response of F. heteroclitus and that increased antioxidant defenses provide some physiological tolerance for these materials. Environmental factors influencing uptake, metabolism, and physiological response following exposure, however, need further investigation.
Neogene crustal shear zone along the western Gulf of Mexico margin and its implications for gravity sliding processes. Evidences from 2D and 3D multichannel seismic data
Authors: Le Roy Charlotte , Rangin Claude , Le Pichon Xavier , Thi Ngoc Hai Nguyen , Andreani Louis , Aranda-Garcia Mario
Published: April 2008

No significant crustal deformation was registered along the western Gulf of Mexico margin since the late Jurassic except the well known Cenozoic gravity tectonics. This is marked by a major extension across the platform and the upper continental slope compensated downslope by shortening across the Mexican Ridges fold belt.

Based on extensive offshore 2D and 3D industrial multichannel seismic reflection data provided to us by PEMEX, we have evidenced significant Neogene deep-rooted deformation below the main décollement level (5 to 7 s-twtt) related to these gravitational processes. The main crustal deformation is outlined by a N170° trending deep-seated reverse fault zone, which flattens downwards near the Moho and merges upwards near the main Oligo-Miocene décollement level, close to the Neogene Mexican Ridges fold belt. This deep seated fabric is interpreted as the result of a dextral strike slip fault zone rather steep and linear into the north and connecting southwards to a N150° trending dextral wrench zone east of the Trans-Mexican volcanic belt.

We consider that this Neogene transpressive dextral motion could have triggered gravity sliding along the Mexican Gulf margin. It could be located at the continent-ocean boundary and is probably linked to conjugate dextral slip related to the late Neogene N140° trending left lateral slip along the Veracruz shear zone active since the Late Miocene. We discuss whether this deep thrust wrench zone is related with the eastward migrating Laramide orogeny front dated Paleocene-Eocene.
New Metalized Polyimide Films Structure and Physical Properties
Authors: Kudaikulova Saule K. , Iskakov Rinat , Vecherkina Elena , Zhubanov Bulat A. , Prikhodko Oleg , Kurbatov Andrey , Akhmetov Tleuken , Bazhenov Sergey , Razumovskaya Irina , Perichaud Alain , Voytekunas Vanda Yu. , Lipik Vitali , Abadie Marc J.M.
Published: April 2008

The classical techniques of PI film metallization by either vapour deposition or electrochemical reduction of
metals involve necessary technological steps such as polymer surface modification via plasma or ion beam, electron
beam, or photolytic treatment, or surface sensitization by the conferment of catalytic properties, in order to enhance metal-
PI adhesion, which is the main problem to be overcome in all processes.

The technology presented differs by the use of another chemical approach yielding electro-conductive materials with high
reflectivity, but without damaging the films in the process. The metalized polyimide films have been prepared by heterogeneous
chemical modification of the polyimide surface and the suggested technology includes several chemical conversion
steps (hydrolysis, chelating by metal salts and reduction) requiring no complicated procedures and proceeding under
mild conditions, at room temperature and without aggressive agents. This new process allows the formulation of metal
phase while both simplifying the technology and making use of commercial PI films, such as Kapton®HN and Upilex®S.

In memoriam of Dr. Saule K. Kudaikulova
Barriers to Transfer Student Academic Success and Retention
Authors: Duggan Molly H. , Pickering J. Worth
Published: April 2008

The Transition to College Inventory (TCI) designed to identify patterns of noncognitive factors related to academic performance and persistence was adapted and validated for use with first-year transfer students in a university setting. In this study, 369 entering transfer students were surveyed during Transfer Preview, an orientation program for transfer students. This study confirmed that noncognitive factors can be used to predict academic success and persistence for first-year transfer students. A major finding was that the barriers differed between freshman, sophomore, and upper division (junior/senior) transfer students. The results of this study show promise in giving four-year institutions the ability to identify at-risk transfer students, pin-pointing areas of needs for intervention.
Project Northland in Croatia: Results and Lessons Learned
Authors: West Bernadette , Abatemarco Diane , Ohman-Strickland Pamela A. , Zec Vezna , Russo Andrea , Milic Ranko
Published: April 2008

As part of an international public health partnership formed in 2001 we assessed the impact of Project Northland in Croatia—an adolescent alcohol school-based prevention intervention implemented in Split—on students. The curriculum was implemented in 13 randomly selected schools with another 13 schools serving as controls. The evaluation included quantitative and qualitative methods, using pre/post-tests to compare intervention and controls and follow-up focus groups with parents and teachers. Quantitative data showed the intervention was more successful in changing attitudes in the first two years, but had less impact on older students. Qualitative data suggest benefits from the program overall. Given the intervention was successful in the earlier grades it should be initiated earlier to have a greater impact. Challenges and lessons learned are offered.
Emotional Intelligence: A Moderator of Perceived Alcohol Peer Norms and Alcohol Use
Authors: Ghee Anna Cash , Johnson Candace S.
Published: April 2008

This study investigated the roles of emotional intelligence and perceived alcohol peer norms in relation to alcohol use. Two hundred and forty-two undergraduates completed the Campus Survey of Alcohol and Other Drug Norms (Core Institute, 1997) and the Emotional Intelligence Scale (Schutte, Malouff, Hall, Haggerty, & Cooper, 1998). Contrary to emerging research findings, emotional intelligence (EI) was not directly associated with the study's alcohol-use variables. However, the moderating role of EI was supported in the relationship between perceived alcohol peer norms and students' alcohol use. Among college students with lower EI, there was a significantly stronger association between these variables, compared to students with higher EI.
Virtually Unaltered Permeability‐Surface Area Products Imply Little Capillary Recruitment in Brain with Hypoxia
Authors: Chen J.‐L. , Wei L. , Bereczki D. , Hans F.‐J. , Otsuka T. , Acuff V. , Richardson G. , Patlak C. , Fenstermacher J.
Published: April 2008

Objective: To test the capillary recruitment hypothesis for the brain with control and hypoxic rats.

Methods: Local cerebral blood flow (LCBF) was sharply raised by respiring 10% O2 (hypoxia). LCBF as well as local influx rate constants (K1) and permeability‐surface area (PS) products of 14C‐antipyrine and 14C‐3‐O‐methyl‐d‐glucose (30MG) were estimated for capillary systems in 44 brain areas.

Results: With this testing, an increase in PS product would be suggestive of capillary recruitment. In all brain areas, LCBF was increased by 30–90% by hypoxia. Hypoxia modestly raised the influx of antipyrine in brain but did not appreciably alter its PS products. With hypoxia, K1's and PS products of 30MG were significantly lowered (5–25%) throughout the brain, and the blood levels of glucose were sizeably raised. The latter increase would diminish the transfer of 30MG across the blood‐brain barrier by the hexose transporter because of increased glucose competition. By applying a glucose‐concentration correction to the data, the apparent PS product of 30MG for the hypoxic group became equal to that for the controls, which agrees with the antipyrine PS product results.

Conclusions: Hypoxia, thus, leads to virtually no increase in PS products and no capillary recruitment in brain, and elevates LCBF mainly, perhaps exclusively, by raising the velocity of flow through already perfused capillaries.
Changes in Perimicrovascular Protein Spatial Distribution due to Superfusate
Authors: Barber B. J. , Dutta S. , Parameswaran S. , Babbitt R. A.
Published: April 2008

Objective: To determine superfusate‐induced changes in the distribution of plasma proteins in the perimicrovascular interstitial matrix.

Methods: Rats were anesthetized with sodium pentobarbital and a mesenteric loop was exteriorized. Intravital video microspectrophotometry was performed using wavelengths of 280, 320, and 700 nm. The images were analyzed to give protein and collagen spatial distributions in vascular regions of rat mesenteric tissue. Perimicrovascular protein concentrations were fitted to an exponential decay model ci + cv exp (‐x/k), where ci is distal protein concentration, ci + cv is the protein concentration proximal to the vessel, x is the distance from the vessel wall, and k is the decay constant indicating protein gradient slope.

Results: Before superfusion with 0.5‐ml normal saline, ci = 1.45 ± 0.13 g/dl, ci + cv = 4.56 ± 0.23 g/dl. After the first superfusion, ci decreased (p < 0.01) to 0.53 ± 0.06 g/dl; following a second superfusion, ci decreased to 0.4 ± 0.03 g/dl; an additional final superfusion caused a further decrease to 0.33 ± 0.02 g/dl. ci + cv also decreased significantly during repeated superfusions to 2.92 ± 0.15, 2.35 ± 0.25, and 2.1 ± 0.12 g/dl, respectively.

Conclusions: Superfusion produced changes in perivascular and distal interstitial matrix protein distribution. Protein concentration proximal to the microvessel remained higher than distal concentrations. This could be due to increased gel concentrations inhibiting protein mobility.
Differential Contractile Response of Cultured Microvascular Pericytes to Vasoactive Agents
Authors: Murphy Diane D. , Wagner Roger C.
Published: April 2008

Objective: Microvascular pericytes may contract in two different ways: In the first, a circumferential or radial mechanical force applied at right angles to the long axis of the vessel may constrict the underlying vessel affecting blood flow and transmural pressure. Retraction and elongation of pericyte processes may also occur tangentially and at right angles to the vessel axis and alter microvessel permeability by changing the amount of ablumenal surface covered or the openness of interendothelial junctions. In this study, cultured pericytes were utilized as a model experimental system to determine if vasoactive stimulation changes their shape in a manner consistent with this hypothesis.

Methods: Pericytes cultured from isolated rate capillaries were subjected to angiotensin II and histamine. Their response was monitored by measuring the area of nonyielding substrate covered by the pericytes and the manner in which their shape changed. Shape changes were quantified by calculating the surface area: perimeter perimeter ratios.

Results: Histamine significantly reduced surface area covered and the surface area: perimeter ratio. The pericyte processes retracted, resulting in elongated, spindle‐shaped cells. These effects were nullified by the H1 blocker diphenhydramine suggesting a receptor‐specific response. Angiotensin II also elicited contraction and reduced surface area, but the cells contracted laterally and longitudinally. The surface area: perimeter ratios also decreased.

Conclusions: These results indicate that pericytes are capable of two types of contractile responses in culture, depending on the specific vasoactive stimulus.
Reduced Renal Microvascular Reactivity to Angiotensin II in Diabetic Rats
Authors: Inman Sharon R. , Porter James P. , Fleming John T.
Published: April 2008

Objective: Renal hyperfiltration in early diabetes is often correlated with increased renal blood flow, reflecting dilation of resistance arterioles. This loss of arteriolar tone has been associated with an impaired reactivity to angiotensin II (Ang II). This study determined if outer cortical arterioles (preglomerular and/or postglomerular) of diabetic rats exhibit a diminished reactivity to Ang II and established if renal vascular prostaglandins account for the diminished responsiveness.

Methods: The constriction of renal microvessels to Ang II (applied to the kidney bath) was quantitated in hydronephrotic kidneys of diabetic rats (7‐10 days after streptozotocin treatment) and nondiabetic rats by in vivo videomicroscopy.

Results: Interlobular, afferent, and efferent arterioles of diabetic rats were found to be less reactive to Ang II than arterioles of nondiabetic rats. Indomethacin, added to the bath to inhibit renal vascular prostaglandin synthesis, enhanced the interlobular and efferent arteriolar reactivity to the peptide among diabetic rats. Yet, after indomethacin treatment, the afferent and efferent arterioles of diabetic rats were still less reactive than control arterioles to Ang II.

Conclusions: We conclude that the blunted reactivity of afferent and efferent arterioles to Ang II among diabetic hydronephotic kidneys cannot be fully explained by the influence of renal vascular‐derived dilator prostaglandins.
Role of Endothelium‐Derived Relaxing Factors in Arteriolar Dilation During Muscle Contraction Elicited by Electrical Field Stimulation
Authors: Saito Yuichiro , Eraslan Akin , Hester Robert L.
Published: April 2008

Objective: To determine the contribution of either endothelium‐derived nitric oxide (EDNO) or prostaglandins in the functional vasodilation of first‐order arterioles of the hamster cremaster muscle.

Methods: First‐order arterioles dilated from 72 ± 3 μm to 93 ± 4 μm in response to contraction of the cremaster muscle for 1 min (n = 7). After EDNO inhibition by topical application of 10 μM Nω‐nitro‐l‐arginine methyl ester (L‐NAME), the resting diameter decreased to 66 ± 3 μm and functional dilation was attenuated to 75 ± 3 μm (P < 0.05). When the arteriolar diameter was returned to the control values by the addition of sodium nitroprusside, an NO donor, into the superfusion solution (n = 7), functional dilation was similar to that observed before EDNO inhibition (91 ± 3 μm vs. 89 ± 3 μm, P > 0.05). To evaluate whether the vasoconstrictor effect of L‐NAME on functional dilation is same as other vasoconstrictors, norepinephrine was applied on the cremaster muscle to induce a vasoconstriction (72 ± 2 to 66 ± 1 μm, n = 7) equivalent to L‐NAME.

Results: Norepinephrine treatment attenuated functional dilation to 77 ± 3 μm which was to a level similar to L‐NAME treatment (P > 0.05). Inhibition of prostaglandin synthesis by topical application of indomethacin (28 μM) resulted in no significant changes in the resting diameter but functional vasodilation was attenuated from 89 ± 2 to 81 ± 3 μm (n = 7, P < 0.05).

Conclusions: These results suggest that EDNO is important for the resting tone of arterioles and that prostaglandins are important in modulating the functional dilation of the first‐order arterioles in the hamster cremaster muscle.
A Circumferential Stress‐Growth Rule Predicts Arcade Arteriole Formation in a Network Model
Authors: PRICE RICHARD J. , SKALAK THOMAS C.
Published: April 2008

Objective: To test the hypothesis that terminal arteriolar remodeling that is stimulated by elevated levels of circumferential wall stress (σθ) will proceed in a network pattern that gives rise to new arcade arterioles.

Methods: A network model of two interconnected skeletal muscle arterio‐capillary‐venous units that incorporated diameter‐ and hematocrit‐dependent blood viscosity was constructed. After computing the control values for wall shear stresses (τij) and σθij, a stimulus was provided by dilating the arterioles and raising input pressure. Wall shear stresses and σθij were then recomputed. The diameters of transverse arteriolar segments with σθij greater than a σθ threshold were increased by an amount that was dependent on the original diameter and the difference between σθ and the σθ threshold. Capillaries with an intraluminal pressure greater than a specified threshold were converted to terminal arterioles. Separate simulations in which remodeling was stimulated by elevated levels of τij were also performed for comparison.

Results: Arterialization patterns from simulations of σθij stimulated arteriolar remodeling were representative of those seen in vivo with arterialization of back‐connection capillaries leading to arcade arteriole formation. Simulations based on similar rules for τij yielded arterio‐venous shunts, which are rarely seen in vivo, but no arcade arterioles.

Conclusion: The simulations presented here are consistent with the hypothesis that arteriolar remodeling is stimulated by increased levels of circumferential wall stress and that new arcade arteriole formation is a consequence of terminal arteriolar growth.
The H2O2‐Generating Enzyme, Xanthine Oxidase, Decreases Luminal Ca2+ Content of the IP3‐Sensitive Ca2+ Store in Vascular Endothelial Cells
Authors: WESSON DONALD E. , ELLIOTT STEPHEN J.
Published: April 2008

Objective: Xanthine oxidase inhibits agonist‐stimulated Ca2+ signaling in calf pulmonary artery endothelial cells by an H2O2‐dependent mechanism. We investigated the effect of xanthine oxidase on luminal Ca2+ content of the inositol‐1,4,5‐trisphosphate (IP3)‐sensitive Ca2+ store.

Methods: Luminal Ca2+ content was estimated from the net release of Ca2+ activated by 2,5‐di‐t‐butylhydroquinone (BHQ), an inhibitor of microsomal Ca2+ pumps.

Results: Initially, xanthine oxidase depleted the IP3‐sensitive Ca2+ store of releasable Ca2+, but with more prolonged incubation, the enzyme also depleted non‐IP3‐sensitive stores. In addition, xanthine oxidase inhibited capacitative Ca2+ influx. Similar results were observed when thapsigargin was substituted for BHQ.

Conclusions: Depletion of luminal Ca2+ content within the IP3‐sensitive Ca2+ store contributes to xanthine oxidase inhibition of Ca2+ signaling in vascular endothelial cells.
Deformation of Erythrocytes in Microvessels and Glass Capillaries: Effects of Erythrocyte Deformability
Authors: SUZUKI YOJI , TATEISHI NORIHIKO , SOUTANI MASAO , MAEDA NOBUJI
Published: April 2008

Objective: The deformation of erythrocytes in microvessels less than 15 μm in inner diameter was analyzed using a microvascular bed isolated from rabbit mesentery. The deformation was compared with that found in glass capillaries.

Methods: Human erythrocytes were perfused through two media: first, a microvascular‐bed section isolated from rabbit mesentery; and second, a set of glass capillaries. Images of deformed erythrocytes were recorded on videotape under strobe light and analyzed with an image processor. The flow velocity of the erythrocytes was determined from the difference of their positions between video frames or by a dual‐spot cross‐correlation technique. Erythrocyte deformability was modified with diamide, diazene dicarboxylic acid bis[N,N‐dimethylamide], by crosslinking spectrins.

Results: Symmetrical (parachute‐like or slipper‐like) deformation of erythrocytes was observed only in microvessels smaller than 13 μm in inner diameter. Erythrocytes in microvessels were less deformed than those in glass capillaries with corresponding diameters, and the marginal cell‐free layer was narrower. The deformation increased by increasing the flow velocity of erythrocytes, and the cell‐free layer became wider. Diamide‐treated cells in microvessels were less deformed than normal cells and showed slightly narrower cell‐free layers. Stronger stress in narrower microvessels induced further deformation of cells.

Conclusions: Erythrocyte deformation in microvessels was essentially different from that in glass capillaries, and the effect of erythrocyte deformability on the flow dynamics of erythrocytes in microvessels was properly evaluated using an isolated microvascular bed.
Ascorbate Uptake by Microvascular Endothelial Cells of Rat Skeletal Muscle
Authors: Wilson J. X. , Dixon S. J. , Yu J. , Nees S. , Tyml K.
Published: April 2008

Objective: In several systems, exogenous ascorbate (reduced vitamin C) has been shown to protect against microvascular injury induced by reactive oxygen species. Since skeletal muscle is relatively resistant to oxidative injury, it is possible that under physiological conditions endogenous ascorbate in the muscle microvasculature affords such protection. To examine the ability of microvascular endothelium to accumulate ascorbate, we aimed (1) to develop an in vitro model of microvascular endothelial cells derived from rat hindlimb skeletal muscles and (2) to investigate the uptake and steady‐state concentration of ascorbate in these cells.

Methods: Microvascular cells were enzymatically dissociated, isolated on a density gradient, and grown in serum‐supplemented medium. After passaging, they were tested for formation of tube‐like structures, coagulation factor VIII antigen expression, Griffonia simplicifolia lectin I‐isolectin B4 binding, and acetylated low‐density lipoprotein (LDL) uptake. Concentrations of reduced ascorbate were measured by high‐performance liquid chromatography (HPLC) with electrochemical detection. Transport activity was assessed on the basis of the initial rate of [14C]ascorbate uptake.

Results: The cultured cells tested positively for factor VIII antigen expression, lectin binding, LDL uptake, and tube formation. Although these cells did not synthesize ascorbate de novo, they accumulated reduced vitamin C when it was added to the culture medium. The initial rate of [14C]ascorbate uptake was 0.9 μ‐mol/g cell protein 10 min when cells were incubated with 10 μM of the radiolabeled vitamin. This uptake was Na+‐dependent and was blocked by the organic anion transport inhibitor sulfinpyrazone, but was not acutely affected by glucose. Following incubation with a physiological concentration of vitamin C (100 μM L‐ascorbate), cells accumulated a high concentration of ascorbate within 6 h (approximately 16 mM at steady‐state). Steady‐state cellular ascorbate concentration was also dependent on extracellular Na+ and sensitive to sulfinpyrazone.

Conclusions: Microvascular cells derived from rat hindlimb muscles demonstrated endothelial characteristics. These cells accumulated reduced vitamin C by means of Na+‐dependent ascorbate transporters, which are distinct from hexose carriers. The high endothelial ascorbate concentration at steady‐state is consistent with the role of ascorbate as a major antioxidant in the skeletal muscle microvasculature.
Enzymatic Isolation and Characterization of Single Vascular Smooth Muscle Cells from Cremasteric Arterioles
Authors: Jackson William F. , Huebner James M. , Rusch Nancy J.
Published: April 2008

Objective: The goal of the present study was to develop a method to isolate enzymatically viable arteriolar muscle cells from single cremasteric arterioles, which retain the contractile and electrophysiological phenotype of the donor microvessels.

Methods: Arterioles were hand‐dissected from rat and hamster cremaster muscles and dissociated by incubation in papain and didiioerythritol for 35 min followed by incubation in collagenase, elastase, and soybean trypsin inhibitor for 10 to 25 min in solutions containing 100 μM Ca2+, 10 μM sodium nitroprusside, and 1 mg/ml albumin at 37°C.

Results: Populations of single smooth muscle cells enzymatically isolated from cremasteric arterioles showed elongated fusiform morphology and intact plasmalemmal membranes as indicated by retention of calcein, by exclusion of ethidium homodimer‐1, and by high membrane resistances (11 ± 0.8 Gω, n = 36 for rat cells; 8 ± 0.6 Gω, n = 21 for hamster cells; p < 0.05). Muscle cells contracted in a concentration‐dependent fashion in response to pipette application of norepinephrine (10 nM‐100 μM). Cell shortening in response to 1 μM norepinephrine was inhibited by 10 μM phentolamine, 1 μM sodium nitroprusside, and 1 μM nifedipine or nominally Ca2+‐free media. Resting membrane potential recorded in patch‐clamped cells by perforated patch methods was −48 ± 1 mV (n = 47) for rat cells and −44 ± 2.8 mV (n = 14) for hamster cells (p > 0.05). Families of voltage‐dependent K+ currents were observed during stepwise depolarizing pulses from −60 mV to more positive potentials. Blockers of voltage‐gated and ATP‐sensitive K+ channels (4‐Aminopyridine [3 mM] and glibenclamide [1 μM], respectively) inhibited membrane K+ conductance, increased membrane resistance, and depolarized cells by 20 ± 4 mV (n = 8) and 14 ± 3 mV (n = 6), respectively.

Conclusions: The present method permits isolation of smooth muscle cells from a single cremasteric arteriole. These cells seem to retain the contractile phenotype, α‐adrenergic signaling cascade, membrane potential, and K+ conductances described for the donor arteriole. Correlating the functional and electrophysiological properties of these smooth muscle cells to in situ and in vitro studies of their donor arterioles should provide a useful extension for understanding die physiology, pathophysiology, biophysics, and cell biology of the microcirculation in skeletal muscle.
Perfusion of Single Tumor Microvessels: Application to Vascular Permeability Measurement
Authors: Lichtenbeld Hera C. , Yuan Fan , Michel C. Charles , Jain Rakesh K.
Published: April 2008

Objective: To develop a new method for determining the relative importance of convection versus diffusion in macromolecular transport across tumor microvessel walls.

Methods: The human colon adenocarcinoma LS174T was transplanted in the dorsal skinfold chamber in a severe combined immunodeficient (SCID) mouse. The vasculature at the tumor surface was exposed by carefully removing the glass window of the chamber. A tumor microvessel was randomly selected, which was ∼20–40 μm in diameter, embedded in the connective tissue 10–12 μm below the surface of the tumor. The vessel was cannulated with a micropipette and perfused with fluorescein isothiocyanate (FITC)‐labeled bovine serum albumin (BSA) at different perfusion pressures. The fluorescence intensity was recorded on videotapes via a video system attached to the fluorescence microscope for offline analysis. The apparent vascular permeability was determined based on the time‐dependence of fluorescence intensity and the vessel diameter.

Results: The apparent vascular permeability of single vessels to FITC‐labeled BSA was quantified at perfusion pressures of 20–45 cmH2O. The pressure dependence of vascular permeability in LS174T tumors was heterogeneous. On average, there was no correlation between the apparent vascular permeability and the perfusion pressure in the range of 20–35 cmH2O (p= 0.73), even though the apparent permeability increased significantly when the pressure was increased from 20 to 45 cmH2O (p= 0.008).

Conclusions: These results indicate that convection in the transvascular transport of albumin is not significant in non‐peripheral regions of solid tumors in which the pressure difference across the vessel wall is small or even negligible. In addition to the permeability studies, this preparation can be used to study cell‐cell interactions in single tumor vessels under defined flow conditions.
Myocardial Fluid Balance in Acute Hypertension
Authors: Mehlhorn Uwe , Davis Karen L. , Laine Glen A. , Geissler Hans J. , Allen Steven J.
Published: April 2008

Objectives: We hypothesized that (1) acute arterial hypertension increases myocardial microvascular fluid filtration and (2) the combination of acute arterial hypertension and coronary sinus pressure elevation may increase myocardial microvascular filtration sufficiently to estimate the osmotic reflection coefficient of the myocardial exchange vessels.

Methods: In nine mechanically ventilated dogs we cannulated the prenodal major cardiac lymph trunk. With the use of central venous phenylephrine infusion, mean arterial pressure (MAP) was raised progressively to 120, 160, and 180 mm Hg. In five dogs we additionally raised coronary sinus pressure (CSP) to 20 and 40 mm Hg. At each manipulation of MAP and/or CSP, we measured indexes of myocardial lymphatic function and lymph‐to‐plasma concentration ratios for total protein (CL(TP)/CP(TP)) and albumin (CL(alb)/CP(alb)).

Results: Myocardial lymph flow rate (QL; μL/min) increased exponentially (QL= 10.9 e0.014‐(MAP)) and myocardial lymph driving pressure (PL; mm Hg) increased linearly (PL= 2.30 + 0.20 MAP) following MAP increases, whereas CL(TP)/CP(TP) and CL(alb)/CP(alb) decreased from 0.67 ± 0.07 (SD) to 0.56 ± 0.10 and from 0.91 ± 0.05 to 0.75 ± 0.11, respectively. Adding CSP elevation increased QL up to 12 times control associated with further CL(TP)/CP(TP) and CL(alb)/CP(alb) decreases to 0.49 ± 0.05 and 0.59 ± 0.02, respectively.

Conclusions: We conclude that hypertensive arterial pressures are, at least in part, transmitted to the myocardial microvascular exchange vessels in the intact animal leading to increased microvascular fluid filtration. However, the combination of acute arterial hypertension and coronary sinus pressure elevation is not sufficient to produce filtration independence required for myocardial osmotic reflection coefficient determination.
Attenuation of Oxygen Free Radical Formation and Tissue Injury During Experimental Inflammation by P‐selectin Blockade
Authors: Delano Frank A. , Forrest Michael J. , Schmid‐Schönbein Geert W.
Published: April 2008

Objective: Neutrophilic leukocyte rolling on postcapillary endothelium requires membrane interaction between SLex‐containing ligands on neutrophils and P‐selectin on endothelial cells. The current sequence of studies was performed to explore the hypothesis that the leukocyte‐endothelial rolling interaction not only precedes leukocyte migration but also is accompanied by oxygen free radical production and interstitial cell death in the rat mesentery.

Methods: The ratio of leukocyte rolling velocity on the endothelium of postcapillary venules and centerline red cell velocity was determined after topical application of platelet activating factor (PAF; 10−8 mol/L). Superoxide formation was determined by an in situ nitroblue tetrazolium reduction to dark blue formazan crystals in the in situ mesentery preparation, and cell death was detected by nuclear staining with propidium iodide.

Results: Leukocyte rolling and subsequent adhesion was inhibited with a monoclonal antibody against P‐selectin, PB1.3. Superoxide formation, as well as parenchymal cell death, was significantly enhanced in the mesentery after stimulation with platelet activating factor, and both could be significantly attenuated by reduction of the rolling leukocyte‐endothelial interaction with PB1.3.

Conclusions: These results provide direct evidence that the interaction of leukocytes and endothelium followed by migration of leukocytes into the interstitium is accompanied by enhanced oxidative stress and parenchymal cell death. Early interruption of the interaction provides significant protection even in the presence of a proinflammatory stimulus.
Delivery of Molecular and Cellular Medicine to Solid Tumors
Authors: Jain Rakesh K.
Published: April 2008

To reach cancer cells in a tumor, a blood‐borne therapeutic molecule or cell must make its way into the blood vessels of the tumor and across the vessel wall into the interstitium and finally migrate through the interstitium. Unfortunately, tumors often develop in ways that hinder each of these steps. Our research goals are to analyze each of these steps experimentally and theoretically and then integrate the resulting information in a unified theoretical framework. This paradigm of analysis and synthesis has allowed us to obtain a better understanding of physiologic barriers in solid tumors and to develop novel strategies to exploit and/or to overcome these barriers for improved cancer detection and treatment.