Regulation of Lipid Droplet Size in Mammary Epithelial Cells by Remodeling of Membrane Lipid Composition—A Potential Mechanism

Milk fat globule size is determined by the size of its precursors—intracellular lipid droplets—and is tightly associated with its composition. We examined the relationship between phospholipid composition of mammary epithelial cells and the size of both intracellular and secreted milk fat globules. Primary culture of mammary epithelial cells was cultured in medium without free fatty acids (control) or with 0.1 mM free capric, palmitic or oleic acid for 24 h. The amount and composition of the cellular lipids and the size of the lipid droplets were determined in the cells and medium. Mitochondrial quantity and expression levels of genes associated with mitochondrial biogenesis and polar lipid composition were determined. Cells cultured with oleic and palmitic acids contained similar quantities of triglycerides, 3.1- and 3.8-fold higher than in controls, respectively (P < 0.0001). When cultured with oleic acid, 22% of the cells contained large lipid droplets (>3 μm) and phosphatidylethanolamine concentration was higher by 23 and 63% compared with that in the control and palmitic acid treatments, respectively (P < 0.0001). In the presence of palmitic acid, only 4% of the cells contained large lipid droplets and the membrane phosphatidylcholine concentration was 22% and 16% higher than that in the control and oleic acid treatments, respectively (P < 0.0001). In the oleic acid treatment, approximately 40% of the lipid droplets were larger than 5 μm whereas in that of the palmitic acid treatment, only 16% of the droplets were in this size range. Triglyceride secretion in the oleic acid treatment was 2- and 12-fold higher compared with that in the palmitic acid and control treatments, respectively. Results imply that membrane composition of bovine mammary epithelial cells plays a role in controlling intracellular and secreted lipid droplets size, and that this process is not associated with cellular triglyceride content.     

Intrinsic potential for high fetal hemoglobin production in a Druze family with β-thalassemia is due to an unlinked genetic determinant

Summary The mechanism for elevated production of fetal hemoglobin (Hb F) in a Druze patient with °-thalassemia intermedia was investigated. Heterozygous family members exhibited normal Hb F levels, suggesting that the increase in -gene expression in the propositus may be partly due to anemic stress. Erythroid progenitors of these family members cultured in vitro [burst forming units (erythroid); (BFUe)] showed elevated synthesis of Hb F, indicating the existence of a genetically determined intrinsic capacity for high Hb F production in this family. The propositus was found to be homozygous for a IVS2-position 1 mutation, on the background of Mediterranean haplotype I, which is not known to be linked to high Hb F production. Moreover, extensive molecular studies of the -globin gene cluster, including sequence analysis of the promoter regions of the -globin genes, did not reveal any cisacting mechanism that could account for the high Hb F production in the propositus. A young niece of the propositus with °-thalassemia major was recently discovered, who was homozygous for the same -globin allele and haplotype as the propositus. However, unlike her uncle, she does not have a high Hb F level and presents with a severe clinical course. Her inability to produce high Hb F suggests that the genetic determinant for increased -gene expression in the propositus is unlinked to the -globin gene cluster.     

Effect of Nitrogen on Polysaccharide Production in a Porphyridium sp

Porphyridium cultures grown on either nitrate or ammonium as the nitrogen source showed similar patterns of growth and cell wall polysaccharide production. The effect of nitrogen on growth and cell wall polysaccharide production was studied by applying three regimens of supply: batch mode, in which nitrate was supplied at the beginning of the experiment and became depleted at day 6; continual mode, in which nitrate was added daily; and deficient mode, in which the cells were cultured in a nitrate-free medium. Growth was similar in the batch- and continual-mode cultures, whereas it was totally inhibited in the deficient-mode culture. Polysaccharide content (per volume) was highest in the batch-mode culture and lowest in the deficient-mode culture. However, polysaccharide production per cell was similar in the continual- and deficient-mode cultures, the highest value being found in the batch-mode culture. In addition to its effect on polysaccharide content, nitrogen affected the polysaccharide distribution between soluble and bound polysaccharides. In the deficientmode culture, most of the cell wall polysaccharide was dissolved in the medium.     

Environmental Factors and Admission Rates in Patients with Major Psychiatric Disorders

The aim of this study was to identify environmental factors that might correlate with the admission rate of patients with major psychiatric disorders. During the years 1988-90, 393 consecutive admissions (119 unipolar depressed patients, 211 schizophrenic patients, and 63 bipolar depressed patients) were monitored. Correlations were calculated between the mean daily admission rate for each month and monthly photoperiod, rate of change in photoperiod, mean temperature, mean relative humidity, and mean barometric pressure. It was found that the admission rate of bipolar depressed patients negatively correlated with monthly photoperiod, which means that during winter the admission rate of these patients increased.     

Synthesis and secretion of the mouse whey acidic protein in transgenic sheep

The synthesis of foreign proteins can be targeted to the mammary gland of transgenic animals, thus permitting commercial purification of otherwise unavailable proteins from milk. Genetic regulatory elements from the mouse whey acidic protein (WAP) gene have been used successfully to direct expression of transgenes to the mammary gland of mice, goats and pigs. To extend the practical usefulness of WAP promoter-driven fusion genes and further characterize WAP expression in heterologous species, we introduced a 6.8 kb DNA fragment containing the genomic form of the mouse WAP gene into sheep zygotes. Two lines of transgenic sheep were produced. The transgene was expressed in mammary tissue of both lines and intact WAP was secreted into milk at concentrations estimated to range from 100 to 500 mg/litre. Ectopic WAP gene expression was found in salivary gland, spleen, liver, lung, heart muscle, kidney and bone marrow of one founder ewe. WAP RNA was not detected in skeletal muscle and intestine. These data suggest that unlike pigs, sheep may possess nuclear factors in a variety of tissues that interact with WAP regulatory sequences. Though the data presented are based on only two lines, these findings suggest WAP regulatory sequences may not be suitable as control elements for transgenes in sheep bioreactors.     

Phosphorylation of p90 and p52 in response to phorbol-esters in Swiss/3T3 cells overexpressing protein kinase C-alpha.

Cell lines stably overexpressing protein kinase C (PKC)-alpha were previously described by us. These cell lines were generated by the introduction of the full length cDNA coding for PKC-alpha into Swiss/3T3 cells. Here we show that activation of PKC-alpha by phorbol-esters induced in these cells specific phosphorylation of two cellular proteins p90 and p52. Phosphorylation of p80 (MARCKS protein), previously identified as a substrate for PKC, was also enhanced. Phosphorylated p90 and p52 proteins were associated with particulate membrane-enriched fractions and were extractable with the use of nonionic detergents. Time course analysis of phorbol-ester induced phosphorylation of p90 and p52 revealed maximal stimulation of phosphorylation after 15-30 min. Phosphamino acid analysis showed that phosphorylation of p90 and p52 occurred mainly on serine residues. Phosphorylation of p52 was also on threonine residues. Whereas, phorbol ester activation induced phosphorylation of both p90 and p52, the mitogens platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) enhanced phosphorylation of p90, but not p52. Thus, our studies showed the involvement of PKC-alpha in the regulation of p90 and p52 phosphorylation and provided direct evidence for the role of PKC-alpha in cellular signaling by PDGF and FGF. Moreover, the fact that phosphorylation of p52 was specific to phorbol ester activation may suggest its involvement in tumor promotion. Characterization of p90 and p52 will enable us to reveal the phosphorylation cascade activated downstream to PKC-alpha and to determine their role in mitogenic signaling and tumor promotion.     

Why are adaptations for long-range seed dispersal rare in desert plants?

Summary The rarity of long-range seed dispersal (telechory) and commonness of antitelechory in desert plants are examined in light of contemporary mathematical theories of the evolution of dispersal and germination behaviors. Analysis of dispersal 3-habitat relationships in the flora of Israel supports the general trend towards atelechory in deserts; in particular epizoochory and tumbleweeds are practically absent from the desert and heterocarpy is centered in the Mediterranean region. In contradiction to the accepted mother-site theory, we find that (a) there is a high turnover in microscale spatial pattern among antitelechoric species; (b) antitelechoric (especially basicarpic) species are widespread and dominant in the desert vegetation of Israel; (c) amphicary and geocary are rare in the desert flora of Israel.We argue that the openness of desert vegetation and the patterns of climatic variation favor atelechory while antitelechory is generally a side-effect of mechanisms whose adaptive value is not directly related to dispersal. Thus for example the desert plants of Israel have evolved a variety of dispersal-restricting seed-containers that protect the seed from predation and flooding, regulate the within-season timing of germination, and spread dispersal and germination over several years.Dedicated to Professor Dr. Michael Evenari     

Phytomelatonin in the leaves and fruits of wild perennial plants

Phytomelatonin has been documented in numerous flowering plants, mostly in cultivated species consumed by humans. Although frugivorous animals feed on fruits, the phytomelatonin content of these organs has hardly ever been tested in wild plants. The aim of this study was to determine the levels of phytomelatonin in the leaves and fleshy fruits of 31 wild perennial species known to be eaten by herbivorous and frugivorous mammals and birds. Considerable levels of phytomelatonin were found in the leaves of all the tested species, and some contained melatonin in their fruits as well. The melatonin content was found to vary significantly in different life forms (trees, shrubs, and climbers), with trees possessing the highest levels. The analysis revealed a significant positive correlation between the phytomelatonin levels in the leaves and the fruits of various species. However, the concentration found in the fruits was generally lower than that found in the leaves of the same species. Despite the presence of phytomelatonin in the fleshy fruits of different families, there was no noticeable common attribute among them. Phytomelatonin was exhibited in both the seeds and the pulp, with no obvious preference for either one. Although it was determined that ingested melatonin enters the bloodstream of birds and mammals, its specific role is still not certain. The potential impact of edible phytomelatonin on the circadian rhythm of herbivores and frugivores is discussed on the basis of these findings.