Hilton H. Mollenhauer

Effect of Carbohydrates on Salmonella typhimurium Colonization in Broiler Chickens

The effect of carbohydrates in the drinking water of broiler chickens on Salmonella typhimurium colonization was evaluated. Results indicate that mannose and lactose (2.5%) significantly (P less than 0.05) reduced intestinal colonization of S. typhimurium by at least one-half, as compared with dextrose, maltose, and sucrose. Lactose and mannose also significantly reduced (P less than 0.01) the mean log10 number of S. typhimurium in the cecal contents. Although mannose was the most effective sugar at blocking colonization, lactose may be more practical because it is effective and costs much less than mannose. Provision of carbohydrates in the drinking water had no significant effect on weight gain.

An ultrastructural study of the leukocytes of the channel catfish, Ictalurus punctatus

Ultrastructural studies on blood leukocytes of the channel catfish, Ictalurus punctatus, show the presence of heterophils (neutrophils), small lymphocytes, monocytes, and thrombocytes. Monocytes cannot always be distinguished from large lymphocytes. Cells resembling macrophages or transitional forms between monocytes and macrophages are occasionally seen. Blood eosinophils and basophils are not found. Thrombocytes and small lymphocytes are the most abundant leukocytes, while monocytes are the least frequently encountered leukocyte. Glycogen, present in all leukocytes, is most abundant in heterophils and least abundant in monocytes. Although monocytes are similar to heterophils in size and shape, a greater amount of rough endoplasmic reticulum, free ribosomes, and fewer granules are observed in monocytes. Heterophils possess oval or elongate granules, which often contain a crystalline or striated structure; small tubules which resemble smooth endoplasmic reticulum, and cristae which traverse the long axes of the mitochondria are frequently seen. Small lymphocytes are characterized by the presence of pseudopodia, many free ribosomes, numerous large mitochondria, dictyosomes (Golgi), and long profiles of rough endoplasmic reticulum. The dictyosomes are often associated with a large zone of exclusion. Bundles of microtubules are observed near the elongated ends of thrombocytes. Deep indentations of the plasmalemma, which give the appearance of vacuoles, are also seen in thrombocytes.

Xylem morphology of Pierce's disease-infected grapevines with different levels of tolerance

Abstract Pierces disease bacteria formed aggregates in the xylem of susceptible grapevines that appeared to hinder the flow of water and mineral nutrients through the plant. Similar aggregates were present in tolerant grapevines, but in substantially lower numbers. Pierces disease iunduced the formation of tyloses and gums in the tracheary elements of infected grapevines. Thwe frequencies of tyloses and gums in tolerant muscadine and wild grapevines were 7 or 8 times those in susceptible bynch grapevines. These tyloses and gums often encapsulated the bacteria and occasionally filled the infected elements of the xylem. The results suggest that gums and tyloses restrict the spread of infecting bacteria, thus imparting tolerance to Pierces disease in certain types of grapevines.

Ultrastructural observations of maize root tips following exposure to monensin

SummaryEpidermal and outer rootcap cells of maize root tips were treated with the sodium selective ionophore, monensin, and the ultrastructural changes were studied. In the presence of 10−5 to 10−3 M monensin, dictyosomes became distorted, cisternae separated from the stack, and secretory vesicles were released. Released secretory vesicles disappeard from the cytoplasm suggesting that their transport to, and fusion with, the plasma membrane was unaffected. Monensin did not inhibit cytoplasmic streaming of the outer rootcap cells. No new secretory vesicles were formed on the remaining dictyosomes or dictyosome fragments. In contrast to results with animal cells, swelling of plant dictyosome cisternae was observed only after fixation in glutaraldehyde-osmium tetroxide and not after fixation in potassium permanganate. Other cell components were not altered structurally by monensin. The effects of monensin on the Golgi apparatus were reversible, and dictyosomes were either repaired or new dictyosomes were formed after the root tips were removed from the monensin.Dictyosomes in epidermal cells reacted in the same manner as those in the rootcap except that numerous secretory vesicles remained in the cytoplasm, mostly in association with dictyosome fragments. Some secretory vesicles increased in size but no evidence of vesicle-vesicle fusion was noted. Cell plate formation was partially inhibited or blocked by monensin.

Modulation of cell-mediated resistance to listeriosis in mice given T-2 toxin

The modulating effect of preinoculation and postinoculation treatment with a single oral 4.0 mg/kg dosage of T-2 toxin on cell-mediated resistance was studied in mice inoculated with Listeria monocytogenes. Toxin treatment caused significant decreases in thymus and spleen weights, bone marrow cellularity, and in the total number of circulating leukocytes, lymphocytes, and neutrophils. Enhancement or suppression of resistance to listeriosis was dependent on the time of toxin administration relative to the time of Listeria challenge. Preinoculation treatment on Day 2 or 4 prior to Listeria challenge significantly enhanced resistance and decreased mortality due to listeriosis by as much as 50%. In contrast, resistance was suppressed and mortality was increased by 50% in mice that were treated with toxin after Listeria challenge. Enhanced resistance to listeriosis was accompanied by a significant increase in the influx of macrophages into Listeria-elicited peritoneal exudates. In addition, in vivo phagocytosis of sheep red blood cells by peritoneal macrophages was significantly increased in toxin-treated mice that were sensitized with sheep erythrocytes. The data indicate that T-2 toxin has a modulating effect on cell-mediated resistance and that enhancement of resistance to listeriosis in mice pretreated with T-2 toxin is associated with increased migration/activation of macrophage effector cells.

Effects of dietary cobalt on testicular structure.

SummaryAdult male rats were maintained on a diet containing 265 ppm cobalt for up to 98 days. Three rats were sacrificed weekly and assayed for testicular damage by light and electron microscopy. Testicular damage was first apparent after 70 days of treatment, followed by a progressive deterioration of cell architecture and decrease in testicular volume. The degenerative changes were of a very general nature; e.g., thickening of basal lamina and basement membranes, increased packing of red blood cells in veins and arteries, formation of “giant” cells, loss of sperm tail filaments, and degeneration of sperm mitochondria. No cobalt residues could be detected by energy dispersive x-ray microanalysis. These data indicate that testicular degeneration was not a primary response to cobalt and suggest that the testes become hypoxic due both to blockage of veins and arteries by red blood cells and to changes in permeability caused by thickening of basal lamina and basement membranes.

Monensin affects the trans half ofEuglena dictyosomes

SummaryEuglena gracilis was treated in 10-5 M monensin for various times from 2 minutes to 24 hours, and then processed for electron microscopy by fixation in glutaraldehyde and osmium tetroxide or potassium permanganate. Monensin affected the mature (trans) half of the cisternae but not the forming (cis) half of the cisternae. After glutaraldehyde and osmium tetroxide fixation, the affected cisternae appeared swollen, whereas after potassium permanganate fixation, the affected cisternae were distorted but not swollen. The monensin effect was first noticeable after 5 minutes of treatment and the maximum effect was observed after only 10 minutes of treatment. No additional monensin effects were observed up to 24 hours of treatment; however, by 24 hours there was variability in dictyosome form and some dictyosomes appeared relatively normal. The first noticeable effects at the 5 minute treatment time involved either the most mature (trans) cisterna or cisternae in the middle of the stack. Thus, inEuglena, the region of the Golgi apparatus that responds to monensin by cisternal dilation is restricted to the mature (trans) half of the dictyosomes, with the initial response given by specific cisternae in the stack.

Plasma membrane transformations in spermatogenesis revealed by aldehyde fixatives containing tannic acid.

During spermatogenesis in the rat, the plasma membrane of the germ cell undergoes an abrupt change. The change appears in electron micrographs as a reduction of the electron density or as a reorganization of the outermost lamella of the unit membrane or both. The change occurs in the developmental stage between type B spermatogonia and early spermatocytes and is most clearly depicted in tissues fixed in glutaraldehyde—tannic acid followed by osmium tetroxide. The change is specific to germ cells and is not evident in Sertoli cells. The origin of the new type of germ cell plasma membrane has not been determined; however, it is noted that a population of thin-membrane cytoplasmic vesicles with asymmetrically stained membranes is present in spermatogonia before plasma membrane transformation but nearly absent in spermatocytes after plasma membrane transformation. The asymmetrical membranes of these cytoplasmic vesicles could be precursor material for the new, or transformed, type of germ cell plasma membrane. The plasma membrane changes noted above persist through spermatid development.

Some specific staining reactions of potassium ferricyanide in cells of guinea pig testes.

Guinea pig testes were processed for electron microscopy by prefixing in phosphate-buffered aldehyde and postfixing in 1% OsO 4 plus 0.05 M potassium ferricyanide [(K 3 Fe(CN) 6 )]. The K 3 Fe(CN) 6 enhanced the staining of glycogen, which was located predominantly in the Sertoli cells, and decreased the staining of ribosomes. The K 3 Fe(CN) 6 also selectively stained some of the small vesicles associated with the forming faces of spermatid Golgi apparatus, the nuclear envelope under the acrosome, and the ground substance of spermatid and spermatozoa mitochondria. This last staining reaction was subdued or absent from spermatocytes, spermatogonia, Sertoli cells, and Leydig cells.

Effects of ochratoxin a in the partially nephrectomized rat

The effects of ochratoxin A (OA), a nephrotoxic mycotoxin, were investigated in partially nephrectomized (PN) rats (approximately 70% reduction in renal mass) following compensatory hypertrophy of the renal remnant. Renal function stabilized 27 d after surgery. PN rats compensated for the initial loss of renal function except for glomerular filtration rate (GFR, inulin clearance); this remained significantly impaired. Sham-operated (SO) rats cleared inulin and p-aminohippurate (PAH) at rates of 3.84 and 7.49 ml/min, respectively, while compensated PN rats cleared inulin at 2.51 and PAH at 8.84 ml/min. Daily administration of low levels of OA produced decreased urine osmolality and body weight with a modest increase in urinary protein of PN versus SO rats. OA-treated rats cleared inulin, creatinine, and PAH at rates significantly lower than nontreated controls: 0.89 and 1.96 ml/min for inulin, 0.35 and 0.56 ml/min for creatinine, and 2.29 and 6.23 ml/min for PAH. Histopathological findings indicated a considerable increase in renal tubular necrosis and subcellular damage (i.e., loss of cytoplasmic ground substance, vacuolization, degeneration of mitochondria, and reorganization of endoplasmic reticulum) in PN animals versus controls, concurrent with alteration in renal function. These results verify that the nephrotoxic action of OA is elicited mainly in renal proximal tubules and is enhanced in the PN rat.