Cell suspension cultures ofOnonis natrix L. subspeciesramosissima: Establishment and culture conditions

Summary Explants from petioles, folioles or hypocotyls ofOnonis natrix have been used for calli initiation. Hypocotyls inoculated on MS medium supplemented with 2% sucrose and 0.5 mg.1^–1 2,4-D / 1 mg.1^–1 Kin showed to be the best primary explant. Cell suspension cultures were established in MS basal medium supplemented with 2% sucrose, 0.5 mg.1^–1 NAA or 2,4-D and 1 mg.1^–1 Kin. Different subculturing periods, inoculum density, hormonal supplementation and sucrose concentration were assayed in order to obtain the best culture growth conditions. The optimal conditions were achieved with cultures initiated with 40 g.1^–1 of initial inoculum, growing in MS basal medium supplemented with 4% sucrose, 0.5 mg.1^–1 NAA and 1 mg.1^–1 Kin subcultured every twelve days. Under these experimental conditions, the cultures showed a doubling time of 36.3 hours.     

Urinary zinc and its relationships with microalbuminuria in type I diabetics

We investigated whether zincuria is associated with microalbuminuria in type I (insulin-dependent) diabetics (IDDM). In 169 IDDM, 215 overnight urine samples were collected for simultaneous assay of zinc and albumin. In 76 samples with excessive microalbuminuria (>15 mg/L), zincuria was higher than in the 139 other samples (0.83±0.06 vs 0.58±0.03 mg/Lp<0.001), though zincuria and microalbuminuria were not significantly correlated. An exercise provocation test was performed in 78 IDDM. Although microalbuminuria increased, zincuria did not change during the test. Another group of 83 IDDM underwent urinary zinc determination over a period of 1 h of recumbency. The 48 patients who had a zincuria higher than the mean+2 SD of control values had higher microalbuminuria at rest (48±16 μg/min vs 12±2p<0.01) and after exercise (111±33 vs 42±14p<0.02) than the remaining 35 subjects. Both subgroups did not differ for zinc intake and zincemia. Thus, incipient nephropathy as detected by the measurement of microalbuminuria is associated with a highly significant increase in zinc excretion, which is not proportional to albumin leakage, nor is it amplified during exercise. Hyperzincuria is not explained by an increase in zinc intake and does not result in hypozincemia.     

Chromium content in human milk,Cow's milk,and infant formulas

Chromium was measured by Electrothermal Atomic Absorption Spectrometry in human milk, cow's milk, and infant formulas. The mean levels found were 1.56, 0.83, and 4.84 (13%) μg/L, respectively. According to our data, the daily intake for the Spanish neonates is lower than the Recommended Dietary Allowances (RDAs) (10–40 μg/d) for this element.     

Description of the oöcysts of three new species of coccidia (Apicomplexa: Eimeriidae) from lizards in Namibia

Three new species of coccidian were recovered from the intestinal contents and faeces of lizards in Namibia, southwest Africa. Oöcysts of Eimeria barnardi n. sp. are described from Rhoptropus barnardi (Gekkonidae) and are ellipsoidal, 24.3 × 19.9 (21–26.5 × 16–22) m; shape index (length/width) 1.22 (1.12–1.30). A micropyle and oöcyst residuum are absent but a fragmented polar granule is present. Sporocysts are subspherical, 9.2 × 8.3 (8–11 × 7.5–9) m; shape index 1.11 (1.02–1.27). Oöcysts of Eimeria pachybibroni n. sp. were found in Pachydactylus bibroni (Gekkonidae) and are ellipsoidal, 26.2 × 18.2 (21.5–28 × 16–19) m; shape index 1.44 (1.30–1.52). A micropyle and oöcyst residuum are absent but a polar granule is present. Sporocysts are subspherical, 8.9 × 8.0 (8–9.5 × 7–8.5) m; shape index 1.12 (1.03–1.20). Oöcysts of Isospora spilogaster n. sp. are reported from Mabuya spilogaster (Scincidae) and are subspherical, 27.4 × 26.0 (21.5–35 × 21–35) m; shape index 1.05 (1.00–1.13). Micropyle, oöcyst residuum and polar granules are absent. Sporocysts are ellipsoidal, 13.2 × 9.7 (10.5–15 × 9–11) m; shape index 1.36 (1.08–1.50).     

Direct screening for high-level expression of an introduced α-amylase gene in plants

A method is described for obtaining transgenic plants with a high level of expression of the introduced gene. Tobacco protoplasts were transformed with an expression construct containing a translational fusion between mature -amylase from Bacillus licheniformis and the signal peptide of the tobacco PR-S protein. A total number of 5200 transformed protoplasts was cultured to microcalli and screened for -amylase expression by incubation on media containing starch followed by staining with iodine. The calli were divided into four classes, based on the resulting halo sizes on the plates. The halo sizes were found to correlated with the expression levels in transgenic plants regenerated from the calli. The expression levels varied between 0 and 0.5% of soluble leaf protein in the regenerated transgenic plants. Wider implications of this method are discussed.     

Effect of imazaquin on absorption,translocation, and pattern of distribution of chlormequat chloride in winter wheat

The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL^* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)¹⁴C-chlormequat chloride, (2) CYCOCEL^* CL containing¹⁴C-chlormequat chloride, and (3) CYCOCEL^* CL containing¹⁴C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the¹⁴C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant.     

3D structure of bovine pancreatic ribonuclease A in aqueous solution: An approach to tertiary structure determination from a small basis of1H NMR NOE correlations

Summary A method is proposed to generate initial structures in cases where the distance geometry method may fail, such as when the set of¹H NMR NOE-based distance constraints is small in relation to the size of the protein. The method introduces an initial correlation between the and backbone angles (based on empirical observations) which is relaxed in later stages of the calculation. The obtained initial structures are refined by well-established methods of energy minimization and restrained molecular dynamics. The method is applied to determine the solution structure of Ribonuclease A (124 residues) from a NOE basis consisting of 467 NOE cross-correlations (97 intra-residue, 206 sequential, 23 medium-range and 141 long-range) obtained at 360 MHz. The global shape and backbone overall fold of the eight final refined structures are close to those shown by the crystal structure. A meaningful difference in the positioning of the catalytically important His¹¹⁹ side chain in the solution and crystal structures has been detected.     

Genetic and developmental analyses of chaetae pattern formation in Drosophila tergites

Summary The role of the achaete-scute complex and extramacrochaetae, Notch, Delta, Enhancer of split and Hairless genes in chaeta patterning in Drosophila tergites was studied in genetic mosaics and in mutant combinations. The mutant phenotypes of different alleles of each gene can be ordered in characteristic topographical seriations. These seriations are related to the pattern of proliferation of histoblasts and the time of singularization of sensory organ mother cells from surrounding epidermal cells. Genetic mosaics of lethal alleles show that these genes are fundamentally involved in this singularization and subsequent differentiation. The study of mutant combinations of alleles of these genes reveals specific relationships of epistasis and synergism between them. The results suggest that spatial and temporal variations in achaete-scute complex functional products in cells, modulated by the activity of other genes involved in signal transduction, define the patterned differentiation of sensory organs in tergites. Offprint requests to: A. García-Bellido     

Haematological and rheological characteristics of blood in seven marine mammal species: physiological implications for diving behaviour

The haeniatological and rheological characteristics of blood from seven marine mammal species have been examined to determine the relationship between increased haematocrit. which is correlated with the ability to increase aerobic dive limits. and blood viscosity. The species examined reflect adaptations to a variety of marine niches ranging from coastal to pelagic to iceedge environments. and exhibit a wide range of diving behaviours. Average haematocrits ranged from43–45% in bottlenose dolphins. killer whales and California sea lions to more than 60% in the deeper diving species (beluga whales and northern elephant seals). Whole blood viscosity () increased exponentially with haematocrit (= 0.96*e^0-0335*Hct). representin a two-fold increase from 4.1 cP for killer whale blood to 8.9 cP for northern elephant seal. There was no apparent compensatory mechanism to reduce viscosity at any shear rate. The optimal haematocrit for oxygen transport was calculated to be40–50% for all species tested. The species with lower haematocrits were within optimal values for oxygen transport. while the two species with the highest haematocrits (beluga whales and northern elephant seals) were above predicted optimal oxygen transport values. On the basis of comparisons of the diving behaviour of these seven species, we suggest that marine mammal species with the greatest adaptation for increased oxygen stores via increased haematocrit have the capacity for deep, long-duration dives, but a limited oxygen transport capacity. We predict that this compromise precludes fast sustainable swimming behaviour in these species.