The lymphatic absorption of four water-soluble compounds with different molecular weights (MW) was determined by measuring their cumulative recovery in lymph draining from the site of s.c. administration in sheep. The cumulative recoveries (% of dose, mean +/- SD; N = 3) were 4.0 +/- 1.5 (5-fluoro-2'-deoxyuridine, MW 246.2), 21.0 +/- 7.1 (inulin, MW 5200), 38.6 +/- 6.7 (cytochrome c, MW 12,300), and 59.5 +/- 7.7 [human recombinant interferon (rIFN) alpha-2a, MW 19,000], respectively. Our data show that in the investigated MW range, there is a linear relationship between the molecular weight and the proportion of the dose absorbed lymphatically. An increase in molecular weight results in an increased lymphatic absorption. Molecules with MW greater than 16,000 are absorbed mainly by the lymphatics which drain the application site. The knowledge gained in this investigation may help to improve the mode of administration and therapeutic efficacy of endogenous proteins whose targets are lymphoid cells (e.g., interferons, interleukins). Practical implications for the clinical use of such proteins are discussed.

There is a statistically significant order in the tangential orientation of stellate cell dendrites, both spiny and smooth, in layer IV of the barrelfield of the mouse parietal cortex. Neurones situated in a barrel side have most of their dendrites oriented towards the barrel hollow; those situated in the hollow preferentially orient their dendrites parallel to the long axis of the barrel. A quantitative measure of the orientation of individual dendrites in barrelfields of 60-day old mice was obtained using a semi-automatic computer-microscope and a minicomputer. In the same manner, the dendrite orientation of layer IV stellate cells was determined in barrelfields, whose (cytoarchitectonic) pattern had been experimentally altered through lesions of the middle row of the mystacial vibrissal follicles at birth. The dendrites of these cells are oriented in harmony with the novel parcellation of the cortex. Consequently, for cells in the altered areas of the barrelfields, the dendrite orientation is different from that of cells with identical positions in a normal field (see Fig. 8). We tentatively interpret these findings as an adaptation of dendrite orientation to an altered pattern of thalamic input to layer IV that, in turn, is a consequence of the peripheral manipulation.

The binding of thiltmine pyrophosphate to apotransketolase from baker's yeast has been studied by measuring the cofactor-dependent activity after passage through a column of Sephadex G-25 or dialysis, respectively. At pH values >6.5, the cofactors Mga+ and thiamine pyrophosphate were lost upon gel filtration or dialysis, indicating reversible binding. Thiamine pyrophosphate alone was able to activate and partially reconstitute transketolase activity in the absence of divalent cations. Using activity and fluorescence-quenching measurements the reconstitution process of transketolase was studied as a function of different parameters such as pH, temperature, ionic strength, donor and acceptor substrates and various divalent cations. The rate of recombination of transketolase from its components, apotransketolase, thiamine pyrophosphate and divalent cations, increases in the order Ni < Mg < Co < Mn < Ca, whereas the catalytic activity of the enzyme does not depend on the nature of the complexing metal ion. Extensively dialyzed apotransketolase is activated by SO?-ions in 10-20 mM concentration. The binding constants for thiamine pyrophosphate determined by activity measurements were 4.8 pM in the absence and 1.0 pM in the presence of 4.4 mM Mg2+. A K , of 1.1 pM (5 mM Mg2+) was obtained from fluorescence quenching experiments. A K , of 5.5 p.M was obtained for 2'-ethylthiamine pyrophosphate. The V for the latter compound was 27O/, of that of thiamine pyrophosphate. For the following competitive inhibitors of thiamine pyrophosphate the inhibitor constants (Ki) were determined : oxythiamine pyrophosphate, 0.03 p.M ; tetrahydrothiamine pyrophosphate, 0.40 pM; thiochrome pyrophosphate, 6.3 pM; pyrithiamine pyrophosphate, 110 pM ; inorganic pyrophosphate, 4200 pM.The relevance of the charge transfer interaction between thiamine pyrophosphate and apotransketolase is discussed.Transketolase from baker's yeast requires the addition of thiamine pyrophosphate and metal ions (Me2+) for activity. Considerable progress has been made in elucidating its mechanism of action. As shown by Holzer and co-workers, transketolase reactions proceed via "active glycolaldehyde" as intermediate [I]. Up to now, only a few experiments have been carried out in order to obtain a better understanding of the nature of the binding of thiamine pyrophosphate to transketolase [2,3]. The present paper reports on the reversibility of coenzyme binding to apotransketolase and on the influence of parameters such as temperature, pH, ionic strength, divalent cations and substrates on the reconstitution of transketolase from baker's Abbreviation. CD, circular dichroism. Enzymes. Transketolase or sedoheptulose-7-phosphate : ~-glyceraldehyde-3-phosphate glycolaldehyde transferase (EC 2.2

No abstract

Aberrant activation of plasmacytoid dendritic cells (pDCs) with excessive production of interferon alpha (IFNα) represents one of the hallmarks of immune activation during chronic phase of human immunodeficiency virus (HIV) infection. A number of studies have shown that disruption of mucosal integrity in the gut is a cause of persistent immune activation. However, little is known about the role that pDCs play in this process, and our current understanding comes from the simian immunodeficiency virus macaque model. Thus, in the present study we sought to investigate the frequency and function of pDCs in peripheral blood and gut samples from HIV-infected individuals before and 6 months after initiation of antiretroviral therapy (ART). We show that circulating pDCs were depleted in ART-naive HIV+ patients, and upregulated the gut-homing receptor CD103 compared with uninfected controls. By converse, pDCs accumulated in the terminal ileum of ART-naive HIV individuals compared with controls. Baseline levels of IFNα production and markers of immune activation in gut samples of ART-naive HIV subjects were elevated. All these parameters declined after 6 months of ART. Our results suggest that in chronic HIV infection, pDCs migrate from peripheral blood to the gut-associated lymphatic tissue, where they may contribute to immune activation.