Factors determining the sward utilisation of winter pasture in cattle feeding.

In this review article, factors determining the sward utilisation of winter pasture in cattle feeding were defined and analyzed. The results from literature and own investigations have shown that yield and quality of autumn-saved herbage on winter pasture are determined by pratotechnical measures such as harvest date in winter and pre-utilisation date in summer, botanical composition of sward, and particularly the dominated grass species or community, nitrogen fertilisation and weather conditions in winter. The date of winter harvest as a dominating factor affects the development of dry matter yield as well as the digestibility of organic matter and nutrients concentration in herbage during winter. For the management of winter grazing systems it could be obtained that crude protein and energy concentration of the tested autumn-saved herbage met the requirements of suckler cows or beef cattle until the end of the year if they were pre-utilised in July. The weather conditions during autumn-winter period are important factor determining the accumulation of secondary metabolites formed by field fungi in herbage of winter pasture.

Accumulation of mycotoxins in forage of winter pasture during prolonged utilisation of sward.

The concentration of mycotoxins in sward depending on time of pre-utilisation in summer and date of harvest in winter was analysed during the 2000-2002 vegetation seasons. Additionally, the yield of pasture sward was estimated. Higher concentrations of ochratoxin A--respectively: 0.55 and 050 ng/g DM--were found in the pasture sward harvested in December and January when compared to the sward collected in November (0.36 ng/g DM). The average concentration of zearalenone varied from 2.74 ng/g DM in December, to 6.00 ng/g DM in November and 9.77 ng/g DM in January. The highest concentration of ochratoxin A was 1.82 ng/g DM and zearalenone 47.89 ng/g DM. The highest number of samples in which ochratoxin A exceeded the level of 0.3 ng/g DM was noted in sward harvested in January (61.1%), while in the case of zearalenone, the number of samples containing this mycotoxin at a level exceeding 3.0 ng/g DM varied from 55.6% in December to 66.7% in November and January. It seems that the percentage of ochratoxin A positive samples and the toxin concentration level in the sward of winter pastures increased during the time of sward regrowth.

Lectin staining of peritoneal mesothelial cells in vitro.

A survey of lectin-binding specificities present on rodent and human mesothelial cells propagated and maintained in tissue culture was made using fluorescein isothiocynate conjugated (FITC) lectins. Rodent and human cells exhibited cell-associated fluorescence following exposure to the FITC-lectins from C. ensiformis, T. vulgaris, A. hypogaea, E. cristagalli and B. simplicifolia, but not with lectins from G. max and D. biflorus. Rodent cells were also positive for FITC-M. pomifera lectin binding. Human, but not rodent, cells were positive for FITC-T. purpureas lectin binding. Exposure of rabbit mesothelial cells in vitro to FITC-lectins that bound to the cell surface resulted in the appearance of discrete loci of putatively intracellular fluorescence. Exposure of cells to ferritin-labelled T. vulgaris lectin at 37 degrees C for as little as 7.5 minutes resulted in the appearance of ferritin-size particles in intracellular vesicles. These results demonstrate 1. the presence of lectin-binding sites in and on peritoneal mesothelial cells from rodents and humans and 2. a possible role of such sites in mediating the entry of lectin-like endogenous molecules into the vacuolar apparatus of these cells.

In vivo and in vitro characterization of mesothelial lipid inclusions.

The nature of intracytoplasmic lipid inclusions found in cultured rabbit and rat peritoneal mesothelial cells was examined by ultrastructural and biochemical techniques. Transmission electron microscopy also demonstrated extracellular release of these lipid bodies. Differential fixation with tannic acid revealed 2 types of inclusions, lamellated (lamellar bodies) and nonlamellated (homogeneous). The lamellar bodies were found near or in the Golgi apparatus and on the cell surface where occasionally they were observed in exocytotic pouches. The homogeneous inclusions were the predominant species being found primarily intracellularly. Lipid bodies obtained from the culture media over the cells displayed on electron microscopy the same morphological characteristics as those seen intracellularly. Exposure of confluent cultures of mesothelial cells to the vital lipid stain Nile Red caused the appearance of intensely fluorescent droplets in or on the cells at wave lengths consistent with staining for phosphatidylcholine-rich vesicles. Incubation of the cells with (14C)-choline and subsequent analysis of phospholipid formation revealed high rates of (14C)-phosphatidylcholine addition to both intra- and extracellular lipid pools. Taken together, mesothelial cells exhibit lipid bodies similar in ultrastructure to the surfactant containing organelles of Type II pneumocytes.

Autosomal recessive polycystic kidney disease: characterization of human peritoneal and cystic kidney cells in vitro.

Renal cystic epithelia and peritoneal mesothelia from two humans with autosomal recessive polycystic kidney disease (ARPKD) were grown in culture. Cystic epithelial and mesothelial cells formed continuous monolayers in vitro. By electron microscopy, cystic renal cells exhibited a single apical cilium and numerous short, stubby microvilli, both in situ and in vitro. Mesothelial cells exhibited intra- and extracellular membrane-limited, lipid-filled vesicles and surface microvilli. Cystic kidney cells in vitro stained positive for lectins from Cancanavalia ensiformis (concanavalin A), Triticum vulgaris, Erythrina cristagalli, Ulex europeaus, and Arachis hypogaea. Immunocytochemical and lectin staining revealed the renal and peritoneal cells to be of collecting tubule and mesothelial origin, respectively. Both cell types showed large depositions of glycogen granules in the cytoplasm during propagation in certain culture media; in kidney cells, dibutyryl cyclic adenosine monophosphate (cAMP) abolished glycogen depositions. Glycogen deposition also was observed in liver tissue obtained by needle biopsy from one patient. No bacteria were cultured from nor endotoxin detected in the renal cyst fluid. Relative to serum, the cyst fluids contained low sodium, potassium, and chloride levels. Thus, cultured ARPKD cells demonstrate a number of characteristics that are different from cells derived from the autosomal dominant form of renal cystic disease (ADPKD).

Isolation and propagation in vitro of peritoneal mesothelial cells.

Mesothelial cells lining the peritoneal cavity are the primary site of molecular exchange during peritoneal dialysis, a life support system for over 50,000 patients worldwide. In this study, techniques are described for the isolation and propagation in culture of peritoneal mesothelial cells from rats and rabbits. For comparison, mesothelial cells were also obtained from the serosal surface of human colonic tissue. By electron microscopy the cultured cells were found to exhibit microvilli, a well-developed endoplasmic reticulum and golgi apparatus, micropinocytotic vesicles, and lipid-filled intracellular vesicles. Immunochemical probes revealed the expression by these cells in vitro of cytokeratin, fibronectin, vimentin, and keratin, but not von Willebrand factor. Mesothelial cells from rat, rabbit, and human exhibited contact inhibition, but differences in growth rates and dependence on supplements to the growth media. This work provides a multispecies comparison of the behavior of mesothelial cells in vitro for the purpose of developing an experimental system for the study of mesothelial cell biology and the role of these cells in peritoneal dialysis.