Dipeptidyl aminopeptidase yspI mutants of Schizosaccharomyces pombe: Genetic mapping of dpa1+ on chromosome III

Abstract A mutant strain of Schizosaccharomyces pombe lacking dipeptidyl aminopeptidase yspI was isolated from a strain already defective in aminopeptidase activity by means of a staining technique with the chromogenic substrate ala-pro-4-methoxy-β-naphthylamide to screen colonies for the absence of the enzyme. The defect segregated 2⁺ :2⁻ in meiotic tetrads, indicating a single chromosomal gene mutation, which was shown to be recessive. Gene dosage experiments indicated that the mutation resides in the structural gene of dipeptidyl aminopeptidase yspI, dpa 1⁺. The dpa 1⁺ gene was located on chromosome III by using l m- fluorophen-ylalanine-induced haploidization and mitotic analysis. dpa1 mutants did not show any obvious phenotype under a variety of conditions tested.     

Using FTA® cards to store avian blood samples for genetic studies. Their application in sex determination

FTA® cards were used for long‐term storage of avian blood samples. Blood DNA was extracted by a simple method and used in PCR for sex identification of adult and nestling Great Grey Shrikes Lanius excubitor.     

Can silicon partially alleviate micronutrient deficiency in plants? a review

Silicon protects plants against various biotic and abiotic stresses, including metal toxicity. Under a high metal concentration, Si can externally decrease metal availability to the plant by its precipitation in the growth media, and Si also affects the metal distribution inside the plant, diminishing the damage. Could Si also protect plants against metal deficiency stress? Recently, the physiological role of Si in relation to micronutrients deficiency symptoms has been assessed in several plant species in hydroponics. In cucumber, Si supply mitigated the symptoms of Fe deficiency, but this effect was not clear under Zn- or Mn-deficiency conditions. The main factor controlling this beneficial effect seems to be the Si contribution to the formation of metal deposits in the root and/or leaves apoplast and its role in their following remobilization when required. The enhancement of the content of long-distance transport molecules (such as citrate) due to Si addition should also contribute to the metal transport from root to shoot, which will diminish deficiency symptoms.     

Ammonia Assimilation in Canavalia ensiformis Plants under Water and Salt Stress

Nitrogen fixation and ammonia assimilation in nodules have beenthoroughly studied under stress conditions, but the behaviorof enzymes involved in ammonia assimilation to organic compoundsin plants of the Leguminosae family subjected to stress stillremains to be conclusively established. We found that understress conditions, C. ensiformis plants can switch from theirusual pathway of assimilation to an alternative one dependingon the nature of the stress and the tissue in which the processtakes place. In roots, it switches from the glutamate dehydrogenase(GDH) pathway to the glutamine synthetase (GS)/glutamate synthase(GOGAT) cycle under water stress but not under salt stress.However, in leaves under salt stress, GDH activity is maintainedbut GS activity markedly decreases (Received March 24, 1987; Accepted March 4, 1988)     

Mutation analysis of phenylketonuria in Spain: prevalence of two Mediterranean mutations

Summary We have screened seven Spanish phenylketonuric (PKU) families for the most prevalent Mediterranean and Caucasian mutations, and have subsequently found mutations P281L and IVS10. We have analyzed these two mutations in 23 of our patients. The frequencies found correspond to those of Mediterranean countries, such as Italy. This is the first report of a mutation analysis in the Spanish PKU population.     

Cytosolic free calcium concentrations in synaptosomes during histotoxic hypoxia

Altered cytosolic free calcium concentrations ([Ca²⁺]_i) accompany impaired brain metabolism and may mediate subsequent effects on brain function and cell death. The current experiments examined whether hypoxia-induced elevations in [Ca²⁺]_i are from external or internal sources. In the absence of external calcium, neither KCl depolarization, histotoxic hypoxia (KCN), nor the combination changed [Ca²⁺]_i. However, with external CaCl₂ concentrations as small as 13 M, KCl depolarization increased [Ca²⁺]_i instantaneously while hypoxia gradually raised [Ca²⁺]_i. The combination of KCN and KCl was additive. Increasing external calcium concentrations up to 2.6 mM exaggerated the effects of K⁺ and KCN on [Ca²⁺]_i, but raising medium calcium to 5.2 mM did not further augment the rise. Diminishing the sodium in the media, which alters the activity and perhaps the direction of the Na/Ca exchanger, reduced the increase in [Ca²⁺]_i due to hypoxia, but enhanced the KCl response. The changes in ATP following K⁺ depolarization, KCN or their combination in the presence of physiological calcium concentrations did not parallel alterations in [Ca²⁺]_i, which suggests that diminished activity of the calcium dependent ATPase does not underlie the elevation in [Ca²⁺]_i. Valinomycin, an ionophore which reduces the mitochondrial membrane potential, elevated [Ca²⁺]_i and the effects were additive with K⁺ depolariration in a calcium dependent manner that paralleled the effects of hypoxia. Together these results suggest that hypoxia-induced elevations of synaptosomal [Ca²]_i are due to an inability of the synaptosome to buffer entering calcium.     

Selective Changes in Cell Bodies and Growth Cones of Nerve Growth Factor-Differentiated PC12 Cells Induced by Chemical Hypoxia

Abstract: Cytosolic free Ca²⁺ concentration ([Ca²⁺]_i) was measured in differentiated PC12 cells to test whether chemical hypoxia selectively alters intracellular Ca²⁺ in growth cones and cell bodies. Hypoxia increased [Ca²⁺]_i and exaggerated its response to K⁺ depolarization in both parts of the cells. [Ca²⁺]_i in the cell bodies was greater than that in the growth cones under resting conditions and in response to K⁺ or hypoxia. Ca²⁺-channel blockers selectively altered these responses. The L-channel blocker nifedipine reduced [Ca²⁺]_i following K⁺ depolarization by 67% in the cell bodies but only 25% in the growth cones. In contrast, the N-channel blocker ω-conotoxin GVIA (ω-CgTX) diminished K⁺-induced changes in [Ca²⁺]_i only in the growth cones. During hypoxia, nifedipine was more effective in the cell bodies than in the growth cones. During hypoxia, ω-CgTX diminished K⁺-induced changes by 50–75% in both parts of the cell, but only immediately after depolarization. The combination of nifedipine and ω-CgTX diminished the [Ca²⁺]_i response to K⁺ with or without hypoxia by >90% in the cell body and 70% in the growth cones. Thus, the increased Ca²⁺ entry with K⁺ during hypoxia is primarily through L channels in the cell bodies, whereas in growth cones influx through L and N channels is about equal. The results show that chemical hypoxia selectively alters Ca²⁺ regulation in the growth cone and cell body of the same cell.     

Cytosolic Free Calcium and Gene Expression During Chemical Hypoxia

Understanding the cellular response to hypoxia may help elucidate the role of altered oxidation in neuronal death or abnormal cell function. In PC12 cells, 30 min of chemical hypoxia (i.e., KCN) reduced ATP concentrations by 92%, but diminished viability by only 10%. Ten minutes of hypoxia increased cytosolic free calcium ([Ca2+]i) 2.5-fold above control, but after 30 min of hypoxia, [Ca2+]i was slightly below that of nonhypoxic cells. Short periods of hypoxia also exaggerated the K(+)-induced elevation of [Ca2+]i, but by 30 min these ATP-depleted cells reestablished a calcium gradient that was equal to nonhypoxic, K(+)-depolarized cells. Thus, 30 min of severe ATP depletion left [Ca2+]i and viability relatively unaffected. Nerve growth factor caused slight, but significant, improvements in ATP and viability of hypoxic cells, but had no effect on [Ca2+]i. Although [Ca2+]i was equivalent in control and hypoxic cells after 30 or 60 min, hypoxia abolished the K(+)-stimulated elevation of [Ca2+]i. The nerve growth factor induction of c-fos, an indicator of the genomic response, was diminished by approximately 80%. Thus, hypoxic PC12 cells with greatly reduced ATP stores maintained normal [Ca2+]i, but their ability to respond to external stimulation was impaired. Further, the reduced oxidation that occurs in the brain in a variety of pathological conditions may interfere with the cellular response to stimulation and growth factors.     

C-methyl phenolics from Qualea species

The trunk wood of Qualea labouriauana contains, besides (2R)-5,7,4′-trihydroxy-3′-methoxy-6,8-dimethylflavanone, (2R)-5,7,4′-trihydroxy-8-methylflavanone, the biosynthetically interesting 2,2′-dihydroxy-4,6,4′,6′-tetramethoxy-3,3′-dimethylbenzophenone. From the trunk wood extract of Q. paraensis the first named flavanone crystallized out directly.