Polysomes from winter rye seedlings grown at low temperature : I. Size class distribution, composition, and stability

We have studied the influence of growth at low temperature on size class distribution, stability and composition of leaf cytoplasmic polysomes from rye seedlings (Secale cereale, cv Puma) grown at 5°C and at 20°C. Leaves of seedlings grown at 5°C contain 2.7 times more cytoplasmic polysomes (expressed on a DNA basis) and the polysome size class distribution is skewed toward larger polysomes. These changes were more pronounced in the free polysome fraction than in the membrane-bound fraction. The melting point of the total ribosome fraction from cold-grown leaves was decreased by 3.7°C. Electrophoresis did not reveal any difference in the rRNA or in core-ribosomal proteins (KCl nondissociable) following growth at low temperature. Some differences were noted in peripheral ribosomal proteins. This study is the first to examine the effect of growth at low and high temperatures on polysome metabolism using plants of similar developmental stage. Polysome quantity, polymerization, melting point and peripheral ribosomal proteins in rye seedlings are modified during growth at low temperature.     

Isolation and in vitro translation of polysomes from mature rye leaves

Cytoplasmic polysomes have been prepared from mature leaves of winter rye (Secale cereale L. cv Puma). This is the first time a method has been developed for isolation of highly polymerized polysomes from mature leaves. The degree of intactness of isolated plant polysomes has been determined by two independent but complementary methods: size class distribution by sucrose gradient centrifugation and in vitro translation. The polymerization of isolated polysomes was estimated by the ratio of the proportion of large polysomes to the proportion of small polysomes obtained from the profiles. Our results show that the composition of the optimal polysome isolation buffer for mature rye leaves is different from that reported for young tobacco and pea leaves. Polysomes were translated in vitro with the S-105 wheat germ fraction. The degree of polysome polymerization has a significant effect on their in vitro translation since both the incorporation of amino acid and the presence of high molecular weight polypeptides are proportional to the large polysomes/small polysomes ratio. This study emphasizes the need to evaluate isolation conditions carefully before proceeding with polysome studies in any particular tissue or in tissues under different physiological status.     

Enthalpy and entropy changes for the intercalation of small molecules to DNA. II. Ethidium and propidium fluoride

Enthalpy changes (ΔH_B) for the binding of ethidium (a monocation) and propidium (a dication) to calf thymus DNA have been determined calorimetrically in piperazine-N, N′-bis(2-ethanesulfonic acid) buffer with the fluoride ion as the counterion. Heats of dilution for the fluoride salts of ethidium and propidium were substantially less than the corresponding values found for other halide salts of these cations. At a Na⁺ ion concentrations of 0.019, ΔH_B = ?8.3 and ?7.9 ± 0.3 kcal mol^?1 for ethidium and propidium, respectively. For these two cations, just as was observed for the naphthalene monoimide (monocation) and diimide (dication) [H. P. Hopkins, K. A. Stevenson, and W. D. Wilson, (1986) J. Sol. Chem. 15 , 563–579], ΔH_B is within the same experimental error for both cations. Apparently, charge–charge interactions in DNA–cation complexes produce only small changes in the enthalpy for the system. In the concentration range 0.019–0.207, the ΔH_B values for propidium did not depend appreciably on the Na⁺ ion concentration, and a similar pattern was shown to exist for ethidium. When these results were combined with ΔG_B values for the binding of these cations to DNA, we found the variation of ΔS_B with Na⁺ ion concentration to be remarkably close to the predictions of modern polyelectrolyte theory, i.e., propidium binding to DNA causes approximately twice as many Na⁺ ions to be released into the bulk solution as does the binding of ethidium. The much stronger binding of propidium, relative to ethidium, at low ionic strengths is thus seen to be primarily due to entropic effects.     

Farrowing induction with cloprostenol-xylazine combination

Eighty crossbred, multiparous sows, weighing between 190 and 320 kg, were randomly assigned to the following four treatment groups of 20 sows each: 1) saline-saline, 2) cloprostenol-saline, 3) saline-xylazine and 4) cloprostenol-xylazine. The mean gestation length of each multiparous sow was calculated. Cloprostenol (250 ug/sow, i.m.) or saline was given 3 d prior to the calculated due date at 11:30 a.m. Xylazine (2 mg/kg, i.m.) or saline was given 20 h after either the cloprostenol or previous saline treatment. Cloprostenol-xylazine treated sows had the shortest mean farrowing interval (1.5 +/- 0.3 h) when compared with the rest of the treatment groups (saline-saline:66.0 +/- 8.1, cloprostenol-saline:10.5 +/- 1.9, saline-xylazine:60.6 +/- 5.6 h). Farrowing time, percentage of stillbirths, average birth weight, d-5 and d-21 postbirth weights, number of pigs born, number of pigs born alive, and number of pigs surviving at 5 and 21 d afterbirth were not significantly different among the four groups. This study demonstrated that cloprostenol-xylazine treatment decreases the time to onset of farrowing with less variation than cloprostenol or xylazine alone. Therefore, the use of a cloprostenol-xylazine combination is suggested as an alternative method for inducing farrowing.     

Morphometric analysis of collagen in gestational and retained bovine placentomes

Bovine placentome collagen was quantified (P<0.01) at four gestational stages (90, 150, 210 and 270 d, n = 8 d ), at 2 h post partum without (n = 4) and at 2 and 12 h post partum with (n = 8) experimentally-induced placental retention. Placentome sections were fixed and stained for collagen. Fetal cotyledonary (FC) collagen volume fraction (V(V)) increased over days of gestation studied (V(V)=0.03+/-0.01, 0.06+/-0.01, 0.13+/-0.01 and 0.19+/-0.01). Fetal cotyledonary hydroxyproline (3.15+/-0.41, 4.55+/-0.41 and 7.04+/-0.41 mg/g) and FC protein (432.0+/-17.1, 479.9+/-17.1, 585.4+/-17.1 mg/g) increased over Days 90, 150 and 210 and were similar on Days 210 and 270. Fetal cotyledonary collagen V(V) and hydroxyproline did not differ between Day 270, retained and nonretained cotyledons. Protein concentration was higher in 2 h (578.1+/-18.5 mg/g) and 12 h (526.0+/-18.5 mg/g) retained versus nonretained (400.4+/-36.2 mg/g) cotyledons. Maternal caruncular (MC) collagen V(V) and protein concentration were higher on Days 90 and 150 than on Days 210 and 270. Maternal caruncular hydroxyproline was similar from Day 90 to 210 and increased from Day 210 to 270. Maternal caruncular collagen V(V), hydroxyproline and protein concentrations were similar on Day 270 and in 2 h and 12 h retained membrane caruncles. Gestational increases in placentome collagen occurred from FC sources. No difference in FC or MC collagen V(V) existed between Day 270, retained and nonretained placentomes.     

Arachidonic acid and linoleic acid supplementation increase prostanoid production in rats fed a butter-enriched diet

Male Sprague Dawley rats were fed a butter-enriched diet (50% fat) for 2 weeks and then supplemented orally with either 90 mg of ethyl arachidonate or ethyl linoleate daily for 2 weeks. For comparative reasons, one group of animals was fed standard laboratory rat chow for 4 weeks. Aortic prostacyclin (PGI2) production, platelet aggregation and thromboxane A2 (TXA2) production and plasma and aortic phospholipid (PL) fatty acids were measured. When compared to butter-fed rats, aortic PGI2 production, collagen-induced platelet aggregation and TXA2 production were significantly increased in rats supplemented with ethyl arachidonate to levels similar to those seen in chow-fed rats. Ethyl linoleate supplementation also tended to increase aortic PGI2 production, collagen-induced platelet aggregation and TXA2, but not to the same extent. These changes were accompanied by increases in the level of arachidonic acid and linoleic acid in aortic and plasma PL and a decrease in the level of eicosapentaenoic acid (EPA) and docsahexaenoic acid (DHA). These data indicate that supplementation with small doses of preformed arachidonic acid was more effective than supplementation with its precursor, linoleic acid, in reversing the effects on prostanoid production and phospholipid fatty acid composition in rats fed diets enriched with butter.     

Absence of uterokinetic effects of prostaglandin F 2 alpha on oxytocin-reactive uterus in the mare

In most cyclic females, prostaglandin F(2alpha) (PGF(2alpha)) triggers a uterine motility response resembling that of oxytocin (OT). To determine if PGF(2alpha) is a uterokinetic substance in the cycling mare, uterine motility was measured by intrauterine balloon technique in 12 conscious, normally cyclic mares. After 60 min of saline infusion, continuous intravenous (i.v.) infusion with OT (1 i.u./min) was followed by PGF(2alpha) (200 mug/min) for 60 min each. The experiment was repeated 3 wk later except with PGF(2alpha) preceeding OT. A second group of mares was administered OT (60 i.u.) either i.v., intramuscularly (i.m.), or intrauterinely (i.u.). Plasma samples were studied for progesterone concentration. Control uterine motility for the first group of mares was (mean +/- SEM) 545.83 +/- 45.10 mm(2). Significant (P<0.05) elevation in uterine motility was recorded for OT (1118.60 +/- 70.56 mm(2)) regardless if PGF(2alpha) preceded OT infusion or vice-versa. No significant difference (P>0.05) was seen in motility after PGF(2alpha) (423.33 +/- 31.12 mm(2)) infusion. The uterokinetic effect of OT was greatest when OT was administered i.v. (1696.50 +/- 195.46 mm(2)) followed by i.m. (819.82 +/- 39.96 mm(2)), and it was least effective when administered i.u. (607.83 +/- 21.56 mm(2)) as compared to control uterine motility (279.78 +/- 22.33 mm(2)). Skin electrical resistance values rose from 0 to 2000 ohms with PGF(2alpha) infusion (but not with OT), indicating that PGF(2alpha) was bioactive. It was concluded that PGF(2alpha) was not a uterokinetic substance in the cyclic mare.     

The zooplankton community in the vicinity of the ice edge,western Weddell Sea,March 1986

Summary The zooplankton community in the vicinity of the ice edge in the west central Weddell Sea was investigated in the late austral summer (March 1986). Sampling was done with two ships operating concurrently, one in the pack ice and the other in the adjcent open sea. Metazoan microzooplankton (<1 mm) was most abundant in the epipelagic zone. It consisted mostly of copepod nauplii and copepods of the genera Oithona, Oncaea, Ctenocalanus and Microcalanus. While species composition was similar in both areas, vertical patterns differed in that the microzooplankton had sparse populations in the upper 50 m under the ice. This may have been related to water temperature which in the upper 50 m under the ice was more than 1°C cooler than in the open sea. Zooplankton in the 1–20 mm size range was dominated by the calanoid copepods Metridia gerlachei, Calanus propinquus and Calanoides acutus which constituted half the biomass in the upper 1000 m. Their populations had highest densities in the upper 150 m, though much of the C. acutus population resided below 300 m. Metridia gerlachei and C. propinquus underwent diel vertical migrations in both areas whereas C. acutus did not migrate. Species diversity in the epipelagic zone was moderate and the fauna was characterized by species typical of the oceanic east wind drift. Diversity increased with depth and was due primarily to the appearance of circumpolar mesopelagic copepods in Weddell Warm Deep Water. Biomass of 1–20 mm zooplankton in the 0–1000 m zone was low (1.1–1.3 gDWm^-2) compared to other Southern Ocean areas investigated with comparable methods. It is suggested that this is related to Weddell circulation patterns and the resulting low annual primary production in the central Weddell Sea.     

Rhinovirus 3C protease catalyzes efficient cleavage of a fluorescein-labeled peptide affording a rapid and robust assay.

The 3C protease encoded by human rhinovirus type 2 catalyzes with equal efficiency cleavage of a peptide substrate with or without a fluorescein label attached to the amino acid at the P7' position. Substrates Ac-MEALFQGPLQYKDL-NH2 and MEALFQGPLQYKE(fluorescein)L are hydrolyzed with values of Vmax/KM of 970 M-1 s-1 and 1100 M-1 s-1, respectively. With the labeled substrate, HPLC achieves separation of substrate and product in 2.5 min. Separation in as little as 12 s is feasible. Fluorescein was derivatized so that it could be incorporated into peptides using automated solid-phase peptide synthesis.