Abstract. The ultrastructure of hepatic, pulmonary, and renal lesions was evaluated in rats injected intraperitoneally with a lethal dose of microcystin-LR (MCLR, 160 wg/kg), a cyclic heptapeptide hepatotoxin produced by the blue-green algae, Microcystis aeruginosa. Hepatic lesions were first seen at 10 minutes post-dosing and consisted of mild widening of hepatocyte intercellular spaces centrilobularly. At 20 minutes post-dosing, hepatocyte plasma membrane alterations were more pronounced, consisting of plasma membrane invagination with formation of variably sized and shaped intracytoplasmic vacuoles, loss of microvilli along the sinusoidal face, and widespread, pronounced hepatocyte separation. By 30 minutes, the space of Disse was markedly widened. At 60 minutes post-dosing, centrilobular areas contained necrotic cells and apparently intact, isolated, organelles intermingled with erythrocytes and platelets. In less severely affected regions there was prominent hepatocyte rounding, and erythrocytes and platelets were present in the widened space of Disse. Large amounts of hepatocellular debris and intact hepatocytes were present in the pulmonary vasculature, while smaller amounts of debris were also seen in the glomerular and peritubular capillaries of the renal cortex. This study shows that initial lesions are confined to shape changes in the plasma membrane of hepatocytes. These changes are consistent with the hypothesis that microcystin-LR induces alterations in the hepatocyte cytoskeleton. Later changes consist of hepatocyte disassociation and necrosis, as well as endothelial damage, which allow release of hepatocytes and debris into the circulation with microembolism in lungs and kidneys.Key words: Kidney; liver; lung; Microcystis aeruginosa; microcystin LR; ultrastructure.Microcystin LR (MCLR, formerly microcystin A or cyanoginosin LR) is a cyclic heptapeptide hepatotoxin produced by the cyanobacterium, Microcystis aeruginosa. Deaths in livestock and wildlife, as well as human illness, have resulted from ingestion of water containing Microcystis aeruginosa. [2][3][4][5][6][7][8][9][10]16 In all of these species, the liver is the target organ, and the lesion consists of severe hepatic necrosis. Following administration of a lethal dose of MCLR, mice die within 60 to 90 minutes. Rats, however, survive 20 to 32 hours, which is similar to survival times reported in livestock. Because of this similarity, we chose to examine the development of MCLR-induced lesions in the rat.We have shown that lethal doses (LD,o = approximately 120 pg/kg) of purified hepatotoxin injected intraperitoneally in rats cause histologic lesions that begin 20 to 30 minutes post-admini~tration.~ Initially, there is disassociation and rounding of centrilobular hepatocytes rapidly followed by severe degeneration and necrosis. By 60 minutes, these changes have progressed to midzonal and periportal regions. In addition, there is a breakdown of sinusoidal endothelium and a loss of central veins with severe centrilobular hemorrhage. At this ...

Marinades of different pH were prepared from O.lM phosphate buffers ranging in pH from 3.25 to 10.15, O.lM sodium chloride, 0.4M phosphoric acid or 0.7M acetic acid. Beef cores were marinated and composition, texture, and structural properties were evaluated. Low and high muscle pH after marinating had positive effects on texture and resulted in increased water-binding capacity, moisture content and decreased cooking losses. Electron microscopy indicated a loss of the M-line at low pH and a loss of Z-line material at high pH. Overall, both high and low marinade pH altered the textural properties of meat although, more rapid changes occurred at lower pH.

Abstract. Erythrocytes from pigs with experimental porcine eperythrozoonosis were examined using light microscopy and scanning and transmission electron microscopy. Three distinct forms of Eperythrozoon suis were attached to the plasma surface of erythrocyte membrane. Erythrocytes were initially parasitized by one or several immature forms. Immature forms enlarged and developed into juvenile and mature forms. The parasite replicated by budding of small immature forms from larger immature forms, juvenile forms, and mature forms. Small immature forms attached to adjacent membrane of the same erythrocyte or a nonparasitized erythrocyte. E. suis organisms were intimately associated with, but distinctly separated from erythrocyte membrane by a 30-nm electron lucent zone. Cell membrane in this area was denser than adjacent nonparasitized membrane. Early interaction between erythrocyte membrane and small immature forms resulted in no membrane deformation, but as this form enlarged, it later became embedded in a deep cup-like membrane invagination. As the immature form developed into the juvenile form a shallow, broad-based depression was observed in the membrane. A similar depression that covered a greater surface area was observed in the membrane parasitized by the mature form. The interaction between the parasitic forms and erythrocyte membrane resulted ultimately in severe membrane deformation. Parasite-membrane interactions may play an important role in the development of misdirected immune responses in experimental porcine eperythrozoonosis.Experimental porcine eperythrozoonosis is a unique system to study parasitic Materials and MethodsTen four-week-old crossbred pigs from the same litter were splenectomized and divided equally at random into control and experimental groups. Pigs were acclimated for two weeks following surgery. Control and expenmental pigs were housed in identical adjacent isolation rooms and were provided food and water ad libitum. Control pigs were bled before experimental pigs to prevent cross infection.Control and experimental group inocula were produced in a three-month-old crossbred splenectomized pig. Blood was obtained prior to inoculation with E. suis from the anterior vena cava, mixed with a glycerine-polyvinylpyrrolidone solution, stored in 4 ml aliquots at -70"C, and labeled as control group inoculum. This pig was then inoculated intramuscularly with 2 ml of E. suis-infected blood (> 90% parasitemia), and at the peak of parasitemia six days later blood was collected and processed as described previously for control inoculum. The number of parasitized erythrocytes was greater than 90% and this blood was labeled as expenmental inoculum. Control pigs were inoculated intramuscularly with 2 ml of E. suis-free blood and experimental pigs intramuscularly with 2 ml of E. suis-infected blood. All pigs were bled at the time of inoculation, at the peak of parasitemia one week later, I64