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The size of a lymphocyte population is primarily determined by a dynamic equilibrium between cell proliferation and death. Hence, lymphocyte recirculation between the peripheral blood and lymphoid tissues is a key determinant in the maintenance of cell homeostasis. Insights into these mechanisms can be gathered from large-animal models, where lymphatic cannulation from individual lymph nodes is possible. In this study, we assessed in vivo lymphocyte trafficking in bovine leukemia virus (BLV)-infected sheep. With a carboxyfluorescein diacetate succinimidyl ester labeling technique, we demonstrate that the dynamics of lymphocyte recirculation is unaltered but that accelerated proliferation in the lymphoid tissues is compensated for by increased death in the peripheral blood cell population. Lymphocyte homeostasis is thus maintained by biphasic kinetics in two distinct tissues, emphasizing a very dynamic process during BLV infection.In vertebrates, continuous recirculation of lymphocytes from blood through tissues and lymph nodes is critical for protection of the host during pathological inflammatory processes, as well as physiological emigration of lymphocytes that participate in immune surveillance (1,4,6,11,16,33). The network of exchange between blood and lymph through the lymph node is absolutely required to maintain normal cell homeostasis. The presence of homeostatic control of lymphocyte numbers ensures an equilibrium where cell production equals cell loss. In an immune system where lymphocyte production is continuous and the total number of cells is constant, each newly produced lymphocyte can only survive if another one dies; i.e., the rate of peripheral cell renewal depends on the life span of peripheral cells. However, the life expectancy of a lymphocyte is not an intrinsic property of the cell but is determined by factors such as the environment, viral infections, and the presence or absence of another, competing, cell population. We previously studied lymphocyte homeostasis, more particularly, lymphocyte proliferation and death, in different animal models of chronic leukemia, including sheep infected by the bovine leukemia virus (BLV) (7-9). In this model, proliferation was estimated by intravenous injection of bromodeoxyuridine (BrdU), a thymidine analog which is incorporated into the newly synthesized DNA via the pyrimidine salvage pathway. Although BrdU uptake by cells might occur in blood, its incorporation is thought to occur mainly, if not exclusively, in lymphoid tissues such as the lymph nodes, the spleen, or the bone marrow (7). By this approach, the estimated B-cell proliferation rates in infected and control sheep were 0.020 day Ϫ1 and 0.011 day Ϫ1 , respectively, meaning that 2.0 and 1.1% of the cells were produced by proliferation in 1 day. In contrast, the death rates of BrdU-labeled cells were not significantly different between the two categories of animals (average death rate, 0.089 day Ϫ1 versus 0.094 day Ϫ1 , respectively). The imbalance created by the net increase in proliferation ...

Thin p-clad InGaAs ridge waveguide quantum-well lasers having an asymmetric structure design were fabricated. The internal absorption coefficient is as low as 2.5 cm 1 , due to the restricted field extension in the 0.3m-thick p-type top AlGaAs cladding layer. Ti-Pt-Au metallization is used outside the ridge to provide adherence on the oxide while Au directly contacts the ridge region. It is shown that the most likely source of loss in these thin p-clad devices is scattering at the rough interface between Au and the ++ top GaAs layer, after ohmic contact heat treatment.

1. Ribitol teichoic acids prepared by fractional precipitation of trichloroacetic acid extracts of bacterial cell walls are essentially undegraded and have similar chain length to the teichoic acid originally present in the walls. 2. The chain length of teichoic acid can be determined directly, without prior extraction from the wall. Accurate values have been obtained by measurement of the formaldehyde produced by oxidation of walls with periodate. Less accurate values have been derived from the amount of inorganic phosphate formed by heating walls at pH4. 3. The relative amounts of N-acetylglucosaminylribitol and its mono- and di-phosphates produced by heating walls of Staphylococcus aureus with alkali agree with the amounts calculated for the hydrolysis of teichoic acid having the chain length determined by other methods. 4. Chemical considerations indicate that the linkage between teichoic acid and the wall may involve a phosphoramidate bond between the terminal phosphate of the teichoic acid and one of the amino groups in the glycosaminopeptide.

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The tuberculin reaction in the skin of sheep was accompanied by greatly increased traffic of mononuclear cells through both the lesion and through regional lymph nodes, as well as the appearance of basophilic cells in the lymph. Changes in vascular permeability were also evident and two, apparently distinct, biologically active materials appeared in the lymph plasma. The first of these materials inhibited the migration of guinea pig macrophages in a conventional migration inhibition factor (MIF) test. This material was evident within a few hours; the strongest activity appeared at about 24 h. Normal lymph and serum or lymph and serum from BCG-sensitive sheep did not contain this material in detectable amounts. The second material that appeared in the lymph increased the DNA synthesis of normal lymphocyte cultures.

Lymphatic drainage of the peritoneal cavity may reduce ultrafiltration in continuous ambulatory peritoneal dialysis. We assessed lymphatic drainage of the peritoneal cavity in sheep under dialysis conditions by cannulation of the relevant lymphatic vessels and compared lymphatic drainage in anesthetized and conscious animals. Lymph was collected from the caudal mediastinal lymph node and the thoracic duct, both of which are involved in the lymphatic drainage of the ovine peritoneal cavity. Volumes of a hypertonic dialysis solution (50 ml/kg 4.25% Dianeal) containing 25 microCi 125I-human serum albumin were instilled into the peritoneal cavity, and lymph flows and the appearance of labeled protein in the lymphatic and vascular compartments were monitored for 6 h. Intraperitoneal pressures increased 4-5 cmH2O above resting levels after infusion of dialysate. On the basis of the appearance of tracer in the lymph, drainage of peritoneal fluid into the caudal lymphatic was calculated to be 3.09 +/- 0.69 and 14.14 +/- 2.86 ml/h in anesthetized and conscious sheep, respectively. Drainage of peritoneal fluid into the thoracic duct preparations was calculated to be 1.32 +/- 0.33 and 14.69 +/- 5.73 ml/h in anesthetized and conscious sheep, respectively. Significant radioactivity was found in the bloodstream, and at least a portion of this was likely contributed by the right lymph duct, which was not cannulated in our experiments.(ABSTRACT TRUNCATED AT 250 WORDS)