In vitro platelet release by rat megakaryocytes: effect of metabolic inhibitors and cytoskeletal disrupting agents

Development of an in vitro visual assay facilitated the study of large numbers of megakaryocytes undergoing proplatelet formation in short-term cultures. Approximately 9% of megakaryocytes formed platelets during a 24-hour period. In the presence of an inhibitor of anaerobic glycolysis (NaF), proplatelet formation was inhibited, whereas inhibitors of respiration (NaCN) did not significantly (P greater than 0.05) decrease proplatelet formation. Presence of the microtubule-disrupting agents colchicine and vincristine sulfate in culture medium inhibited proplatelet formation, whereas the microfilament-disrupting agent cytochalasin B had a less pronounced inhibition.     

In vitro platelet release by rat megakaryocytes: effect of heterologous antiplatelet serum

A visual assay to study megakaryocyte platelet release via proplatelet formation in vitro was established. Samples of megakaryocyte-enriched rat bone marrow were incubated (37 C) in RPMI-1640 medium with 15% autologous serum in specially prepared chambers. In the culture system, approximately 6% of megakaryocytes formed proplatelet processes within 24 hours. Inclusion of a heterologous antiplatelet antibody in the culture system inhibited proplatelet formation, compared with that in controls.     

Intravascular Leukostasis and Systemic Aspergillosis in a Horse With Subleukemic Acute Myelomonocytic Leukemia

Leukemia is a neoplastic disease of one or more of the cell types of the hemopoietic system and is rarely diagnosed in the horse. This report describes a case of subleukemic acute myelomonocytic leukemia in an 11 -year-old gelding. Preliminary cytological diagnosis was supported by two types of laboratory investigations. Cytochemical characterization of blood and bone marrow neoplastic cells was consistent with a myelomonocytic origin. Neoplastic blast cells in peripheral blood were labeled by monoclonal antibodies specific for cell surface molecules of horse granulocytes, but they were not labeled by antibodies to T- or B-lymphocytes or macrophages. Treatment was attempted but was unsuccessful. At necropsy, intravascular leukostasis was present in all tissues examined. Fungal hyphae were also found in lung interstitium and colonic submucosa, suggesting the presence of a systemic mycosis. Nucleated cells were isolated from peripheral blood and cultured in vitro; they survived for up to 2 weeks and had evidence of cell division that was not sustained. Frozenthawed cells stored in liquid nitrogen were also successfully cultured in vitro, but no permanent cell lines could be established.     

Effects of various treatments on induced chronic aflatoxicosis in rabbits

Male New Zealand White rabbits were orally given 0.05 mg of aflatoxin B1 (AFB1)/kg of body weight daily for 10 days and were treated with glutathione-precursors and depletor, antibacterial agents, or sodium thiosulfate. The drug administered, the mortality, and the mean survival time were as follows: corn-oil controls (0), euthanatized at 25 days; AFB1-controls (2), 21 days; AFB1 and saline controls (2), 22 days; cysteine and AFB1 (5), 13 days; methionine and AFB1 (5), 12 days; sodium thiosulfate and AFB1 (2), 21 days; sulfadimethoxine and AFB1 (1), 24 days; oxytetracycline and AFB1 (0), euthanatized at 25 days; and ethyl maleate and AFB1 (3), 21 days. Clinical signs of toxicosis included decreased feed consumption during AFB1 administration, loss of body weight or failure to gain, and death. Clinicopathologic changes included increases in serum bilirubin concentration and alanine aminotransferase and aspartate aminotransferase activities. Prothrombin and activated partial thromboplastin times were lengthened. Plasma fibrinogen concentration was decreased. Changes in PCV, hemoglobin concentration, and serum alkaline phosphatase were unremarkable. Oxytetracycline had protective effects against chronic aflatoxicosis in rabbits. Cysteine and methionine enhanced chronic aflatoxicosis.     

Actin Polymerization: An Event Regulated by Tyrosine Phosphorylation During Buffalo Sperm Capacitation

In the female reproductive tract, the spermatozoa undergo a series of physiological and biochemical changes, prior to gaining the ability to fertilize, that result to capacitation. However, the actin polymerization and protein tyrosine phosphorylation are the two necessary steps for capacitation. In this study, we have demonstrated the actin polymerization and established the correlation between protein tyrosine phosphorylation and actin reorganization during in vitro capacitation in buffalo (Bubalus bubalis) spermatozoa. Indirect immunofluorescence and Western blot techniques were used to detect actin polymerization and tyrosine phosphorylation. The time‐dependent fluorimetric studies revealed that the actin polymerization starts from the tail region and progressed towards the head region of spermatozoa during capacitation. The lysophosphatidyl choline (LPC)‐induced acrosome reaction (AR) stimulated quick actin depolymerization. The inhibitor cytochalasin D (CD) blocked the in vitro capacitation by inhibiting the actin polymerization. In addition, we also performed different inhibitor (Genistein, H‐89, PD9809 and GF‐109) and enhancer (dbcAMP, H₂O₂ and vanadate) studies on actin tyrosine phosphorylation and actin polymerization. The inhibitors of tyrosine phosphorylation inhibit actin tyrosine phosphorylation and polymerization, whereas enhancers of tyrosine phosphorylation stimulate F‐actin formation and tyrosine phosphorylation. These observations suggest that the tyrosine phosphorylation regulates the actin polymerization, and both are coupled processes during capacitation of buffalo spermatozoa.     

Climate sensitivity uncertainty and the need for energy without CO2 emission

The UN Framework Convention on Climate Change calls for "stabilization of greenhouse gas concentrations at a level that would prevent dangerous anthropogenic interference with the climate system." Even if we could determine a "safe" level of interference in the climate system, the sensitivity of global mean temperature to increasing atmospheric CO2 is known perhaps only to a factor of three or less. Here we show how a factor of three uncertainty in climate sensitivity introduces even greater uncertainty in allowable increases in atmospheric CO2 concentration and allowable CO2 emissions. Nevertheless, unless climate sensitivity is low and acceptable amounts of climate change are high, climate stabilization will require a massive transition to CO2 emission-free energy technologies.