Correlation of tumor metastasis with sterol carrier protein and plasma membrane sterol levels

Squalene and sterol carrier protein (SCP) levels and sterol/phospholipid molar ratios of whole cells and plasma membranes were measured in cultured primary tumor and metastatic cell lines. SCP is abundant in all cell lines. However, metastatic lines have significantly lower SCP levels and plasma membrane sterol/phospholipid ratios than do primary lines. The results indicate that extremely malignant, metastatic cells are unable to produce or maintain adequate levels of both SCP and plasma membrane sterols when grown in lipoprotein deficient media. This defect, in vivo, probably causes excess uptake of SCP and lipid.     

Comparison of gravimetry and planimetry in determining dry matter budgets for three species of phytophagous lepidopteran larvae

Gravimetric and a combination areal-gravimetric methods for determining dry matter budgets for leaf eating Lepidoptera were compared. The gravimetric method is based on dry weight/live weight ratios of the leaves fed to the larvae. In the areal-gravimetric method, the quantity of food offered to the larvae is determined from the area of leaf tracings and the dry matter content per unit area of the leaves. The areal-gravimetric method permits the use of larger leaf sprays and an open, gauze enclosed rearing chamber. There were no consistent differences in budget factors (growth, ingestion or egestion), nor were there any differences in the observed variability of the data attributable to the method used. However, the expected variability based on instrument precision for the gravimetric method is less than for the areal-gravimetric method. Experimental factors inherent in the gravimetric method introduce variability to the measurements that are not present in the areal method. Thirty to 60% of the variability in budget factors was attributed to intrinsic properties of the larvae, even though the larvae were taken from the same egg masses.

---

Résumé Les budgets en matière sèche consommée par des lépidoptères ont été comparés par les méthodes gravimétrique et planimétrique. La méthode gravimétrique est basée sur le rapport poids sec/poids frais de feuilles consommées par les chenilles. Avec la méthode planimétrique, la quantité d'aliment proposée aux chenilles est déterminée par les tracés de la surface des feuilles et le contenu de matière sèche par unité de surface des feuilles. La méthode de planimétrie permet l'utilisation de plus grands rameaux de feuilles et de cages d'élevage extérieures en gaze. Il n'y avait pas de différence appréciable dans les éléments du budget (croissance, ingestion et déjection), ni aucune différence dans la variabilité observée des données attribuable à la méthode utilisée. Cependant, la variabilité attendue d'après la précision des mesures avec la méthode gravimétrique est inférieure à celle de la méthode planimétrique. est inférieure à celle de la méthode planimétrique. Des éléments expérimentaux, inhérents à la méthode gravimétrique, introduisent une variabilité dans les mesures que l'on n'a pas avec la méthode planimétrique. 30–60% de la variabilité dans la consommation ont été attribués à des paramètres internes à la chenille, même quand elles provenaient toutes de la même ooplaque.

     

Microtubule arrays in the cortex and near the germinal vesicle of immature starfish oocytes

An extensive array of long, crisscrossing microtubules has been discovered in the cortex of oocytes of the starfish Pisaster ochraceus. The microtubules were visualized in cortex preparations by indirect immunofluorescence microscopy using antibodies to tubulin. The cortical array of microtubules is present in all oocytes before and for about 30 min after the application of 1-methyladenine, the hormone that induces oocyte maturation. The presence of microtubules was confirmed by electron microscopy. The microtubules in this array are depolymerized when oocytes are treated with colchicine or nocodozole and are augmented when oocytes are treated with taxol. Dihydrocytochalasin B treatment of the oocytes causes the microtubules to aggregate, presumably by altering a microfilament network also found in the cortex. The distribution of microtubules was also explored in whole oocytes stained with antitubulin. One or two aster-like structures were observed adjacent to the germinal vesicle of each oocyte.     

Organization of microtubules in stabilized meristematic plant cells revealed by a rat monoclonal antibody reacting only with the tyrosinated form of alpha-tubulin

A rat monoclonal antibody against yeast tubulin (clone YL 1/2; Kilmartin et al., 1982) that reacts specifically with mammalian alpha-tubulin carrying a carboxyterminal tyrosine residue (Wehland et al., 1983) was used to localize microtubules in plant cells derived from onion root apices (Allium cepa L.). YL 1/2 reacted with all types of microtubular arrays known to occur in higher plant meristematic cells such as interphase cortical microtubules, pre-prophase bands, the mitotic spindle and phragmoplast microtubules. The specific labeling of microtubules in isolated cells from onion root tips by YL 1/2 indicates that plant cells like animal cells contain tubulin tyrosine ligase, the enzyme which posttranslationally modifies alpha-tubulin. This enzyme could be involved in the dynamic regulation of microtubular arrays in all eukaryotic cells.     

Influence of phage T3 and T7 gene functions on a type III(EcoP1) DNA restriction-modification system in vivo

Summary The ocr ⁺ gene function (gp 0.3) of bacteriophages T3 and T7 not only counteracts type I (EcoB, EcoK) but also type III restriction endonucleases (EcoP1). Despite the presence of recognition sites, phage DNA as well as simultaneously introduced plasmid DNA are protected by ocr ⁺ expression against both the endonucleolytic and the methylating activities of the EcoP1 enzyme. Nevertheless, the EcoP1 protein causes the exclusion of T3 and T7 in P1-lysogenic cells, apparently by exerting a repressor-like effect on phage gene expression. T3 which induces an S-adenosylmethionine hydrolase is less susceptible to the repressor effect of the SAM-stimulated EcoP1 enzyme. The abundance of EcoP1 recognition sites in the T7 genome is explained by their near identity with the T7 DNA primase recognition site.Abbreviations d.p.m. decompositions per min - EcoB, EcoK, EcoP1, EcoP15, EcoRII, EcoR124, HinfIII restriction endonucleases coded by Escherichia coli strains B or K, E. coli plasmids P1, P15, RII or R124, and Haemophilus influenzae Rf 232, resp. - e.o.p. efficiency of plating - gp gene product (in the sense of protein) - m.o.i. multiplicity of infection (phage/cell) - ocr ⁺ gene function which overcomes classical restriction - p.f.u. plaque-forming units - SAM S-adenosylmethionine - sam ⁺ gene function with S-adenosylmethionine-cleaving enzyme (SAMase) activity - UV ultraviolet light Dedicated to Professor Konstantin Spies on the occasion of his sixtieth birthday     

Postreplication repair in Neurospora crassa

Summary Changes in the molecular weight of nascent DNA made after ultraviolet (UV) irradiation have been studied in the excision-defective Neurospora mutant uvs-2 using isotopic pulse labeling, alkaline gradient centrifugation and alkaline filter elution. Both the size of nascent DNA and the rate of incorporation of label into DNA was reduced by UV light in a dose dependent manner. However, this DNA repair mutant did recover the ability to synthesize control-like high molecular weight DNA 3 hours after UV treatment, although the rate of DNA synthesis remained depressed after the temporary block to elongation (or ligation) had been overcome. Photoreactivation partially eliminated the depression of DNA synthesis rate and UV light killing of cells, providing strong evidence that the effects on DNA synthesis and killing were caused by pyrimidine cyclobutane dimers. The caffeine inhibition repair studies performed were difficult to quantitate but did suggest either partial inhibition of a single repair pathway or alternate postreplication DNA repair pathways in Neurospora. No enhancement in killing was detected after UV irradiation when cells were grown on caffeine containing plates.     

Expressions of the prefertilization polar axis in sea urchin eggs

The distribution of pigment granules in eggs of three species of sea urchins is described with reference to developmental stage and an egg's animal-vegetal axis of organization. Polarity in unfertilized sea urchin eggs has been a debated subject; present evidence demonstrates that the animal-vegetal axis is established before fertilization. The pigment pattern in some batches of Paracentrotus eggs exhibiting the celebrated “pigment band,” originally described by Theodor Boveri, is revised and is interpreted as a comparatively precocious expression of the underlying egg polarity. “Unbanded” Paracentrotus eggs and eggs of Arbacia lixula and Arbacia punctulata can be induced to exhibit the same pigment pattern by artificial activation. The induced pigment pattern aligns with an axis defined by polar bodies and the jelly canal, which are two external markers of the animal pole which are only rarely seen. It is therefore concluded that all of these eggs possess an animal-vegetal axis before fertilization even though it usually remains unexpressed until later developmental stages. Polarized changes in pigmentation are consistent with the following general mechanism: A change is triggered in the cortex of the vegetal pole; the change is programmed for a time which corresponds to the fourth mitotic division, even though mitosis itself is not involved; activation at fertilization initiates the “clock” in most cases, although in “banded” Paracentrotus eggs the “clock” is apparently started before ovulation; only the vegetal hemisphere's pigment is affected by the change. The nature of the underlying axis which defines animal and vegetal poles is discussed. Aspects of the axis have been tentatively traced back to the primary oocyte stage, but its fundamental nature remains unknown.     

Neuronal membrane lipid asymmetry.

The outer surface of intact synaptosomes was covalently labelled with trinitrobenzenesulfonic acid prior to isolation of the synaptic plasma membrane. Analysis of the membrane lipid demonstrated an asymmetric distribution of phospholipids across the synaptosomal plasma membrane. In addition, the fatty acyl composition of phosphatidylethanolamine from this neuronal membrane fraction was also distributed asymmetrically. The data are consistent with a $\text{de novo}$ generation of phospholipid asymmetry independent of serum lipid exchange processes. This structural asymmetry may have important consequences for neurotransmission.     

Quantitative and qualitative assay of amniotic-fluid acetylcholinesterase in the prenatal diagnosis of neural tube defects

Summary In 110 amniotic fluids the specific acetylcholinesterase was determined quantitatively and qualitatively. In the quantitative assay there were a considerable number of false positives and false negatives, although the mean value of the normal controls differed significantly from that of neural tube defect pregnancies. By the electrophoretic separation of acetylcholinesterase, however, all fluid samples with borderline alpha-fetoprotein levels or fetal blood contamination could be correctly classified. With the exception of one skin-covered spina bifida all neural tube defects in the second trimester could be identified by this method. The second fast-moving band characteristic of the specific acetylcholinesterase was also present in abdominal wall defects and intrauterine death.