Potato Lectin: A Cell-Wall Glycoprotein

The activity and the amount of potato lectin were measured inpotato tuber slices (Solanum tuberosum cv. Huinkul) aeratedfor 48 h. Lectin was found in a soluble form, liberated to themedium and associated with insoluble structures. Polyacrylamidegel electrophoresis in denaturating conditions and immunologicaltechniques indicated that the lectins associated to cell wall,soluble or liberated to the medium, were identical. The cell-wallfraction was found to contain 65% of total lectin in the tuber.The possible role of potato lectin in tubers was discussed. (Received June 5, 1985; Accepted September 3, 1985)     

Inhibition of beta-1,4-Glucan Biosynthesis by Deoxyglucose : The Effect on the Glucosylation of Lipid Intermediates

GDP- and UDP-deoxyglucose inhibit the incorporation of glucose from UDP-glucose into dolichyl phosphate glucose and dolichyl pyrophosphate oligosaccharides. GDP-deoxyglucose inhibits by competing with the physiological nucleotide sugars for dolichyl phosphate, and dolichyl phosphate deoxyglucose is formed. This inhibition is reversed by excess of dolichyl phosphate. UDP-deoxyglucose does not give rise to a lipid-linked derivative, and inhibition by this analog is not reversed by dolichyl phosphate. The UDP- and GDP-derivatives of deoxyglucose inhibit the incorporation of glucose into glucose-containing glycoproteins. This effect seems to be the result of the inhibition of lipid intermediates glucosylation and is comparable to the effect produced by coumarin. Cellulose synthetase activity is not affected by UDP- or GDP-deoxyglucose. On the other hand, deoxyglucose inhibits the formation of β-1,4-glucans in vivo.     

Dissociation of intracellular lysosomal rupture from the cell death caused by silica

The relationship between intracellular lysosomal rupture and cell death caused by silica was studied in P388d(1) macrophages. After 3 h of exposure to 150 μg silica in medium containing 1.8 mM Ca(2+), 60 percent of the cells were unable to exclude trypan blue. In the absence of extracellular Ca(2+), however, all of the cells remained viable. Phagocytosis of silica particles occurred to the same extent in the presence or absence of Ca(2+). The percentage of P388D(1) cells killed by silica depended on the dose and the concentration of Ca(2+) in the medium. Intracellular lyosomal rupture after exposure to silica was measured by acridine orange fluorescence or histochemical assay of horseradish peroxidase. With either assay, 60 percent of the cells exposed to 150 μg silica for 3 h in the presence of Ca(2+) showed intracellular lysosomal rupture, was not associated with measureable degradation of total DNA, RNA, protein, or phospholipids or accelerated turnover of exogenous horseradish peroxidase. Pretreatment with promethazine (20 μg/ml) protected 80 percent of P388D(1) macrophages against silica toxicity although lysosomal rupture occurred in 60-70 percent of the cells. Intracellular lysosomal rupture was prevented in 80 percent of the cells by pretreatment with indomethacin (5 x 10(-5)M), yet 40-50 percent of the cells died after 3 h of exposure to 150 μg silica in 1.8 mM extracellular Ca(2+). The calcium ionophore A23187 also caused intracellular lysosomal rupture in 90-98 percent of the cells treated for 1 h in either the presence or absence of extracellular Ca(2+). With the addition of 1.8 mM Ca(2+), 80 percent of the cells was killed after 3 h, whereas all of the cells remained viable in the absence of Ca(2+). These experiments suggest that intracellular lysosomal rupture is not causally related to the cell death cause by silica or {"type":"entrez-nucleotide","attrs":{"text":"A23187","term_id":"833253","term_text":"A23187"}}A23187. Cell death is dependent on extracellular Ca(2+) and may be mediated by an influx of these ions across the plasma membrane permeability barrier damaged directly by exposure to these toxins.     

Paracrine effects of oocyte secreted factors and stem cell factor on porcine granulosa and theca cells <Emphasis Type="Italic">in vitro</Emphasis>

Oocyte control of granulosa and theca cell function may be mediated by several growth factors via a local feedback loop(s) between these cell types. This study examined both the role of oocyte-secreted factors on granulosa and thecal cells, cultured independently and in co-culture, and the effect of stem cell factor (SCF); a granulosa cell derived peptide that appears to have multiple roles in follicle development. Granulosa and theca cells were isolated from 2–6 mm healthy follicles of mature porcine ovaries and cultured under serum-free conditions, supplemented with: 100 ng/ml LR3 IGF-1, 10 ng/ml insulin, 100 ng/ml testosterone, 0–10 ng/ml SCF, 1 ng/ml FSH (granulosa), 0.01 ng/ml LH (theca) or 1 ng/ml FSH and 0.01 ng/ml LH (co-culture) and with/without oocyte conditioned medium (OCM) or 5 oocytes. Cells were cultured in 96 well plates for 144 h, after which viable cell numbers were determined. Medium was replaced every 48 h and spent medium analysed for steroids.     

Phylogenetic analysis of the tenascin gene family: evidence of origin early in the chordate lineage

Background  

Tenascins are a family of glycoproteins found primarily in the extracellular matrix of embryos where they help to regulate cell proliferation, adhesion and migration. In order to learn more about their origins and relationships to each other, as well as to clarify the nomenclature used to describe them, the tenascin genes of the urochordate Ciona intestinalis, the pufferfish Tetraodon nigroviridis and Takifugu rubripes and the frog Xenopus tropicalis were identified and their gene organization and predicted protein products compared with the previously characterized tenascins of amniotes.     

Prevalence of ergot derivatives in natural ryegrass pastures: detection and pathogenicity in the horse

In the present study, we determined the incidence and effects of season and weather on clinical manifestations of endophyte-infected ryegrass toxicity, performed chemical detection and pharmacological bioassays on ryegrass extracts, and conducted trials on: (i) effects of domperidone or metochlopramide on ovarian inactivity induced by endophyte-infected ryegrass; (ii) efficacy of buspirone or dihydrochloro phenyl piperazine (m-CPP) for preventing suppressed milk production induced by endophyte-infected ryegrass; and (iii) efficacy of domperidone to induce ovulation during winter anestrus. Mares with toxicosis had prolonged gestation, embryonic losses, dystocia, poor mammary gland development, low milk production, prolonged uterine involution, and suppressed ovarian activity. Foals had respiratory failure, abnormalities of the skin, umbilicus, bone, and muscle, failure to thrive, blindness, testicular atrophy, and decreased serum total immunoglobulin concentrations. Endophyte-infected ryegrass and the incidence of toxicosis were correlated (r=0.861, P=0.03). Ergot alkaloids were not detected in extracts of endophyte-infected ryegrass by either thin-layer chromatography or spectrophotometry, but their presence was inferred in bioassays of extracts (dose-related increases in the contractile response of rat uterus). Mares given metoclopropamide (0.6 mg/kg/d), given orally every 8h for up to 7d) ovulated earlier (4-7d vs. 15-18d, P<0.001) than those given domperidone (1.1mg/kg/d) orally for up to 18d). Although both metoclopropamide and domperidone induced milk production, the latter did not induce ovarian cyclicity in healthy mares during seasonal anestrus. Based on these findings, we inferred that endophyte-infected ryegrass is associated with ergot alkaloid intoxication in horse.     

Synthesis of beta-glucans in Prototheca zopfii. Evidence for the existence of a glycoprotein primer

Membrane preparations from the non-photosynthetic alga Prototheca zopfii incorporate glucose from UDP-[3H]glucose into the trichloroacetic-acid-insoluble fraction and the polysaccharides insoluble in hot alkali. Time course and pulse-chase experiments indicate that the acid-insoluble fraction was a precursor of the alkali-insoluble fraction. Isolation of 3H-labeled membrane or soluble fraction showed that only membrane fractions were able to transfer radioactivity into polysaccharides. Treatment of glucosylated membranes with trypsin or cellulase only partially affect their transfer ability, indicating that the precursor was internalized in vesicles. Analysis of the in vitro synthesized polysaccharides by enzymatic and acid hydrolysis showed that glucose and cellobiose were present as radioactive sugars. Permethylation of the polysaccharide indicates that 80% of the glucose was beta-1,4-bonded with 20% in beta-1,3-linkages. This polysaccharide was found to be identical with the cell-wall beta-glucan obtained in vivo [Rivas, L.A. & Pont Lezica, R. (1978) Planta (Berl.) 165, 348-353].     

Estimation of rRNA synthesis and degradation rates in senescing wheat leaves

Changes in cytoplasmic and chloroplast rRNA content and rates of rRNA synthesis and degradation of detached wheat leaves were determined. It was found that rRNA loss is proportionally higher in chloroplasts than in cytoplasm. Rates of synthesis were measured by incorporation of large amounts of [3H]orotic acid into rRNA. This approach overcame size differences between pyrimidine pools of cells under different physiological status. Furthermore, these pools reached nearly the same specific radioactivity as that of the administered solution. Rates of degradation were estimated either as the difference between synthesis and net variation of rRNA or by disappearance of radioactivity from 32P-labeled rRNA. Results indicated a decrease in the net rRNA synthesis capacity of leaves after 48 h of detachment. However, the fractional rates of rRNA synthesis were maintained in both cytoplasm and chloroplasts. Ribosomal RNA degradation rates were 2.5-fold higher in chloroplast than in cytoplasm. The observed chloroplast rRNA loss is due to an increased degradation rate which is 15-fold higher than the synthesis rate 48 h after detachment.     

Quantification of the kinetin effect on protein synthesis and degradation in senescing wheat leaves

Wheat leaves (Triticum aestivum L. cv San Agustin INTA) were detached when they reached maximum expansion, put individually in tubes containing water and left in darkness. After 3 days the protein content had decreased to 46% of the initial value. When the leaves were placed in 1 micromolar kinetin, they retained 60% of the initial protein content for the same period. This effect was observed only when leaves were treated with kinetin within the first 24 hours after detachment. The action of kinetin on both protein synthesis and degradation was quantitatively measured. Synthesis was estimated by the incorporation of l-[³H]leucine into proteins. It was higher in kinetin treated than in non treated leaves. It contributed to about 14 micrograms of protein retention per leaf in 3 days. Measurement of protein degradation, evaluated by the decay of radioactivity in leaf proteins previously labeled with l-[³H] leucine or as the difference between rates of protein synthesis and protein content, showed that kinetin decreased protein breakdown rates. It accounted for about 186 micrograms of protein retention per leaf in 3 days. Hence, kinetin action on protein breakdown was 13-fold average higher than its action on synthesis for the conservation of leaf protein. This difference is higher in early stages of the process.