UCL University College London Eprints
UCL Eprints collects the work of UCL researchers and makes it freely available over the web, helping the worldwide scholarly community to discover UCL research. Institutional repositories like UCL Eprints complement the traditional academic publishing and scholarly communications processes. They raise the visibility of research and help to maximise its impact. UCL researchers are encouraged to deposit a copy of each journal article, conference paper, working paper, and any other research output, in the UCL Eprints at the earliest opportunity, ensuring that their research reaches as wide an audience as possible.
Mostrando recursos 181 - 200 de 343,367
Regulation of pancreatic exocrine function: a role for cell-to-cell communication? - Bruzzone, R; Trimble, ER; Gjinovci, A; Traub, O; Willecke, K; Meda, P
The effect of heptanol, an alkanol which decreases gap junctional permeability, was investigated in the perfused rat pancreas. Under basal conditions, heptanol (3.5 mM) caused a three- to fourfold increase of pancreatic juice, protein, and amylase outputs. The effect on enzyme secretion was fully reversible upon removal of the alkanol and was not secondary to the release of acetylcholine from nerve endings, since it was not prevented by addition of atropine (10(-6) M) to the perfusate. By contrast, another alkanol, hexanol (3 mM), which does not decrease coupling between acinar cells in spite of anesthetic properties analogous to those of...
Differences in pancreatic enzyme release from ventral and dorsal areas of the rat pancreas. - Bruzzone, R; Trimble, ER; Gjinovci, A; Renold, AE
The exocrine secretory function of the ventral and dorsal areas of the rat pancreas was investigated separately. In the isolated perfused rat pancreas, caerulein (10(-12), 10(-11), and 10(-10) M) and carbachol (10(-7) and 10(-6) M) caused a greaterfold increase in pancreatic secretion from the dorsal than the ventral area. Caerulein (10(-9) M) and carbachol (10(-5) M) were supramaximal concentrations with respect to secretion from the dorsal area, but this was not the case in the ventral area. Similar findings were also observed when ventral and dorsal secretions were studied in vivo in anesthetized animals. By contrast, in dispersed acini the...
Activity of the insulo-acinar axis in the isolated perfused rat pancreas. - Trimble, ER; Bruzzone, R; Gjinovci, A; Renold, AE
The object of the present investigation was to determine whether insulin secreted by the endocrine pancreas and carried in the insulo-acinar portal system has a direct effect on pancreatic enzyme secretion. For this purpose, the isolated rat pancreas was perfused in a nonrecirculating system. The perfusate contained 3 mM glucose, and either caerulein or vaso-active intestinal polypeptide was used to stimulate exocrine secretion. The amount of insulin reaching the exocrine pancreas was reduced by two different experimental procedures. In the first, use was made of streptozotocin-diabetic rats treated with insulin in vivo. Treatment was such that the contents of amylase...
A new, rapid, method for preparation of dispersed pancreatic acini. - Bruzzone, R; Halban, PA; Gjinovci, A; Trimble, ER
A new method for the preparation of pancreatic acini is described. The method is simple and much more rapid than previously described techniques, the time required for preparation of pancreatic acini being 20 min from removal of the pancreas. Acini prepared with this method perform in a superior manner when stimulated by either caerulein or secretin. Thus this new technique would be ideal for use in binding and secretion studies.
Glucose-insulin interactions on exocrine secretion from the perfused rat pancreas. - Bruzzone, R; Trimble, ER; Gjinovci, A; Renold, AE
The effects of glucose and insulin on pancreatic enzyme release have been investigated using the isolated perfused rat pancreas. Basal and caerulein-stimulated secretion was significantly less in the presence of 15 mM glucose than with 5 mM glucose, except at a supramaximal concentration of caerulein (10(-9) M) where secretion was similar in both groups. Addition of exogenous insulin also caused a reduction in enzyme secretion, but the time of onset of the inhibitory action was delayed compared to that observed with glucose. Furthermore, it was found that the effects of 15 mM glucose and exogenous insulin were not additive at...
Increased insulin responsiveness in vivo and in vitro consequent to induced hyperinsulinemia in the rat. - Trimble, ER; Weir, GC; Gjinovci, A; Assimacopoulos-Jeannet, F; Benzi, R; Renold, AE
The effect of constant, controlled hyperinsulinemia on in vivo and in vitro insulin responsiveness has been investigated in rats that have received insulin infusions through chronically implanted jugular vein catheters. Constant rates of insulin infusion during days 1-4 resulted in stable plasma insulin concentrations. The plasma glucose initially fell from 122 +/- 3 to 53 +/- 4 mg/dl. While the infusion rate was maintained constant, the plasma glucose continued to fall over the subsequent days so that on day 4 the plasma glucose, 40 +/- 2 mg/dl, was significantly lower than that in the same animals on day 1 (P...
Changes in content and secretion of pancreatic enzymes in the obese Zucker rat. - Bruzzone, R; Trimble, ER; Gjinovci, A; Renold, AE
The contents of three major digestive enzymes (amylase, lipase and chymotrypsinogen) were measured in the obese Zucker rat. Only minimal changes were found in 7-week-old rats, but in adult obese rats (14-16 weeks) the amylase content was decreased by 50%, whereas the lipase and chymotrypsinogen contents were increased by 45% and 20%, respectively, compared with lean controls. Abnormalities of enzyme secretion were also found. Since the changes observed in enzyme proportions in adult obese Zucker rats are qualitatively similar to those observed in insulinopenic diabetes and other states associated with decreased glucose metabolism, it is speculated that the abnormalities found...
Stimulation of insulin release by glucose in a transplantable rat islet cell tumor. - Masiello, P; Wollheim, CB; Janjic, D; Gjinovci, A; Blondel, B; Praz, GA; Renold, AE
A subline of an x-ray-induced transplantable rat insulinoma has been studied in vivo and in vitro. Tumors grew rapidly after sc transplantation and were rich in insulin, but contained only small amounts of glucagon and somatostatin. Despite marked basal hyperinsulinemia, iv glucose administration caused a further increase in plasma insulin in tumor-bearing rats. When the pancreas was functionally excluded by ligation of supplying arteries, glucose still elicited a clear insulin response. In vitro, insulin release from perifused tumor fragments was stimulated by the combination of glucose and 3-isobutyl-1-methylxanthine, but not by glucose alone. In contrast, there was a clear stimulation...
Biologic activity and pharmacokinetics of biosynthetic human insulin in the rat. - Halban, PA; Berger, M; Gjinovci, A; Renold, AE
The biologic potency (plasma glucose depression) of pancreatic human insulin was compared with that of biosynthetic human insulin (BHI), manufactured by recombinant DNA techniques in bacteria, following intravenous injection in rats. The specific activity of the pancreatic human insulin was 32 U/mg, while that for BHI was 27 U/mg. These values were not significantly difference, but were higher than the value for pancreatic pork insulin (25 U/mg). The pharmacokinetics of i.v. injected A14-mono-125I-insulin (pork) were found to be similar to those observed for semisynthetic [3H]insulin (pork), the respective metabolic clearance rates (MCR) being 20.8 +/- 0.8 ml/min/kg (N = 4)...
Increased clearance and degradation of [3H]insulin in streptozotocin diabetic rats. - Philippe, J; Halban, PA; Gjinovci, A; Duckworth, WC; Estreicher, J; Renold, AE
The role of the insulin-receptor compartment in the pharmacokinetics of intravenously injected insulin in rats was studied. Since streptozotocin-diabetes in rats results in increased insulin binding to tissues in vitro, insulin pharmacokinetics in streptozotocin-diabetic rats were compared to controls, using semisynthetic [(3)H]insulin as the tracer. The initial distribution volume for [(3)H]insulin was elevated by 60% in diabetic rats. By contrast, no difference in initial distribution volume for [(14)C]inulin was observed, and the absolute values were lower than those found for [(3)H]insulin. The metabolic clearance rate of [(3)H]insulin was elevated by 44% in diabetic rats. That these differences were the result...
The neural representation of interaural time differences in gerbils is transformed from midbrain to cortex - Belliveau, L; Lyamzin, DR; Lesica, NA
Interaural time differences (ITDs) are the dominant cue for the localization of low-frequency sounds. While much is known about the processing of ITDs in the auditory brainstem and midbrain, there have been relatively few studies of ITD processing in auditory cortex. In this study, we compared the neural representation of ITDs in the inferior colliculus (IC) and primary auditory cortex (A1) of gerbils. Our IC results were largely consistent with previous studies, with most cells responding maximally to ITDs that correspond to the contralateral edge of the physiological range. In A1, however, we found that preferred ITDs were distributed evenly...
Core-Liquid-Induced Transition from Coaxial Electrospray to Electrospinning of Low-Viscosity Poly(lactide- -glycolide) Sheath Solution - Luo, CJ; Edirisinghe, M
Co-electrospinning has demonstrated that polymer solutions below the entanglement concentration can be made into fibers as an encapsulated core in an electrospinnable sheath solution containing a carrier/template polymer. The carrier polymer may require removal at a later stage. This work shows for the first time that without increasing the polymer concentration/molecular weight or needing a template polymer, simply infusing a liquid in the core nozzle can cause the sheath polymer solution (viscosity <20 mPa s) to electrospin instead of electrospray in a coaxial electrified jet. Different from coelectrospinning, the core liquid can be a common solvent such as water and...
Towards a regulatory framework for microgrids — the Singapore experience - Wouters, C
Microgrids are increasingly put forward as key concepts of future energy supply complementing the conventional centralised energy system. This paper describes operational and regulatory microgrid challenges and makes suggestions regarding how to overcome them. Motivated by its unique liberalisation process, state guided growth processes and technology focused economic and sustainable growth ambitions, Singapore is put forward as a case study. An analysis of its legislative framework identified that advanced legislation is already in place regarding the distribution of locally generated cooling. However, a regulatory framework for full energy integrated modern microgrids is still in its infancy. Global lessons learned from...
Encore for the enclave: the changing nature of the industry enclave with illustrations from the mining industry in Chile - Phelps, NA; Atienza, M; Arias, M
Conceptual innovation with respect to the enclave concept has been virtually absent compared with that on industry agglomerations. This is despite the fact that some varieties of agglomeration distinguished in the literature appear to come close to what previously were regarded as industrial enclaves and despite frequent allusions to the enclave nature of economic spaces produced by contemporary processes of globalization. Bringing the literature on agglomeration and enclaves into dialogue, we revisit the concept of the enclave - a concept that has been largely neglected since it enjoyed a popularity in connection with the study of particular (notably extractive) industries...
Spectral Non-local Restoration of Hyperspectral Images with Low-rank Property - Zhu, R; Dong, M; Xue, J
Restoration is important in pre-processing hyperspectral images (HSI) to improve their visual quality and the accuracy in target detection or classification. In this paper, we propose a new low-rank spectral non-local approach (LRSNL) to the simultaneous removal of a mixture of different types of noises, such as Gaussian noises, salt and pepper impulse noises and fixed-pattern noises including stripes and dead pixel lines. The low-rank (LR) property is exploited to obtain pre-cleaned patches, which can then be better clustered in our spectral nonlocal method (SNL). The SNL method takes both spectral and spatial information into consideration to remove mixed noises...
Synchrotron Studies of Technologically Important Metal Oxide Surfaces - Mackenzie Dover, CM
This thesis probes three technologically important metal-oxide systems; Pd nanoparticles supported on the TiO2(110) surface, acetate on TiO2(110) and Fe3O4(111). The orientation of CO adsorbed to a Pd/TiO2(110) model catalyst system was probed using X-ray photoemission electron microscopy (XPEEM) and near-edge X-ray absorption fine structure (NEXAFS). The absorbed CO molecules were found to have an off-normal polar orientation, relative to the basal plane of the substrate. The result was interpreted as an average of several sets of CO molecules absorbed and oriented orthogonally to various facets of the Pd nanoparticles, some of the facets themselves orientated with an angular separation...
Dental implants in patients affected by systemic diseases. - Donos, N; Calciolari, E
Several systemic diseases (and relative medications) have been reported to impair or in some cases complicate dental implant surgery. In broader terms, when dealing with patients suffering from systemic diseases, the monitoring of the medical condition and of the related post-operative complications is of great importance in order to avoid risks which could jeopardise the health of the patient. In this review, the available evidence on implant survival/success, as well as relevant surgical recommendations in patients affected by systemic diseases, are evaluated and when possible, practical suggestions for the clinician are provided.