The effects of portacaval shunt upon hepatic cholesterol synthesis and cyclic AMP in dogs and baboons

Hepatic cholesterol synthesis, hepatic cyclic AMP, and portal and peripheral insulin and glucagon levels were investigated in nine dogs and three baboons after complete portacaval shunt. Cholesterol synthesis as measured with acetate incorporation was reduced in both species. Hepatic cyclic AMP increased in dogs. Changes in portal and systemic insulin were inconsistent, but hyper-glucagonemia occurred regularly. Diminished hepatic cholesterol synthesis is apparently one factor, although probably not the only one, in the antilipidemic effect of portacaval shunt. This altered cholesterol metabolism may be due to a change in the hormonal environment of the liver caused by portal diversion

The effect of splanchnic viscera removal upon canine liver regeneration

The influence of portal blood factors on canine liver regeneration was studied with graded nonhepatic splanchnic evisceration, coupled with 44 and 72 per cent hepatectomies. In one type of experiment, the pancreas was retained while the rest of the intra-abdominal gastrointestinal tract was removed. In a second variety, total pancreatectomy was performed with preservation of the intra-abdominal organs. In a third kind of experiment, total nonhepatic splanchnic evisceration was performed. Liver regeneration after hepatectomy was decreased by all three kinds of viscera removed as judged by deoxyribonucleic acid synthesis, autoradiography and mitotic index. Pancreatectomy and nonpancreatic splanchnic evisceration caused almost equal decreases in the regenerative response. Total nonhepatic splanchnic evisceration essentially halted regeneration during the first three postoperative days and intraportal infusions of insulin or glucagon, or both together, did not reverse this effect. The decrease in liver membrane bound adenyl cyclase activity and biphasic change in liver cyclic 3',5'-adenosine monophosphate concentrations normally seen partial hepatectomy was disrupted after the various eviscerations. Adenyl cyclase activity and cyclic monophosphate concentrations tended to be higher than normal in the eviscerated dogs. These observations provide more support for our previously proposed hypothesis that control of liver regeneration is by multiple factors. Pancreatic hormones are important modifiers of this response but by no means exercise exclusive control. Other substances of gastrointestinal origin, presumably including hormones and nutrient supply apparently play important specific roles. The volume of portal flow is a secondary and nonspecific, but possibly significant, factor

Intrinsic Friction of Monolayers Adsorbed on Solid Surfaces

We overview recent results on intrinsic frictional properties of adsorbed monolayers, composed of mobile hard-core particles undergoing continuous exchanges with a vapor phase. In terms of a dynamical master equation approach we determine the velocity of a biased impure molecule - the tracer particle (TP), constrained to move inside the adsorbed monolayer probing its frictional properties, define the frictional forces exerted by the monolayer on the TP, as well as the particles density distribution in the monolayer.Comment: 12 pages, 5 figures, talk at the MRS Fall 2003 Meeting, Boston, December 1-5, 200

Massless particles on supergroups and AdS3 x S3 supergravity

Firstly, we study the state space of a massless particle on a supergroup with a reparameterization invariant action. After gauge fixing the reparameterization invariance, we compute the physical state space through the BRST cohomology and show that the quadratic Casimir Hamiltonian becomes diagonalizable in cohomology. We illustrate the general mechanism in detail in the example of a supergroup target GL(1|1). The space of physical states remains an indecomposable infinite dimensional representation of the space-time supersymmetry algebra. Secondly, we show how the full string BRST cohomology in the particle limit of string theory on AdS3 x S3 renders the quadratic Casimir diagonalizable, and reduces the Hilbert space to finite dimensional representations of the space-time supersymmetry algebra (after analytic continuation). Our analysis provides an efficient way to calculate the Kaluza-Klein spectrum for supergravity on AdS3 x S3. It may also be a step towards the identification of an interesting and simpler subsector of logarithmic supergroup conformal field theories, relevant to string theory.Comment: 16 pages, 10 figure

The effect upon the liver of evisceration with or without hormone replacement

All, or nearly all, of the nonhepatic splanchnic viscera were removed in dogs. In most untreated dogs, the liver cells underwent changes similar to those caused by portacaval shunt, including structural deterioration of organelles and fatty metamorphosis. The rate of division of the hepatocytes, as measured by the mitotic index and by autoradiography, was depressed as were deoxyribonucleic acid synthesis and adenylate cyclase activity. These changes were restored to, or toward, normal with the intraportal administration of commercial or purified insulin but not with glucagon or epidermal growth factor. The results of both the pathologic and biochemical studies were consistent, except for an incongruity in some of the dogs in which the colon was retained

Intermittent exploration on a scale-free network

We study an intermittent random walk on a random network of scale-free degree distribution. The walk is a combination of simple random walks of duration $t_w$ and random long-range jumps. While the time the walker needs to cover all the nodes increases with $t_w$, the corresponding time for the edges displays a non monotonic behavior with a minimum for some nontrivial value of $t_w$. This is a heterogeneity-induced effect that is not observed in homogeneous small-world networks. The optimal $t_w$ increases with the degree of assortativity in the network. Depending on the nature of degree correlations and the elapsed time the walker finds an over/under-estimate of the degree distribution exponent.Comment: 12 pages, 3 figures, 1 table, published versio

Tolerance induction after organ transplantation, “delayed tolerance,” via the mixed chimerism approach: Planting flowers in a battle field

We have previously reported that peri-transplant conditioning leads to successful induction of renal allograft tolerance via the mixed chimerism approach in nonhuman primates (NHP) and humans. However, this strategy requires treatments beginning six days prior to transplantation, which limits its relevance only to living donor transplant recipients. To extend the clinical applicability of this approach, we developed a novel regimen “delayed tolerance,” with which the recipient initially undergoes organ transplantation with conventional immunosuppression, followed by conditioning and donor bone marrow transplantation (DBMT) at a later date. This approach might be likened to “planting flowers in a battle field.” That is, the recipient’s immunologic environment after organ transplantation is like a battlefield filled with hostile innate and adaptive immune-responses directed against donor antigeneic specificities. Implanting fragile donor hematopoietic progenitors into this environment and encouraging them to bloom in this vicious field requires special treatments