Implications of the placental structure compatibility for interspecies embryo transfer

Comparative histological features of the chorionic villi in placental cotyledons of the common eland (Taurotragus oryx ) and bongo (Boocercus euryceros ) antelopes and okapi (Okapia johnstoni ) and giraffe (Giraffa camelopardalis ) were examined. The chorionic villi in both antelope species showed only moderate branching and/or surface corrugation and their cross-sections were polygonal to oval. The close similarity in the structure of cotyledons has been apparently a contributing factor for success in mutual interspecies embryo transfer. The chorionic villi in okapi and giraffe had very different structures. In okapi the villi on cross-section were round and filled with thin connective tissue. They showed minimal branching and surface corrugation. In giraffe the villi showed extensive surface corrugation, had multiple fine branches, and were filled with a more dense connective tissue. Prospect for materno-fetal compatibility in mutual embryo transfer between these species is guarded.     

Some Properties of Extracellular Acetylxylan Esterase Produced by the Yeast Rhodotorula mucilaginosa

The red yeast Rhodotorula mucilaginosa produced an esterase that accumulated in the culture supernatant on induction with triacetin. The enzyme was specific for substrates bearing an O-acetyl group, but was relatively nonspecific for the rest of the molecule, which could consist of a phenol, a monosaccharide, a polysaccharide, or an aliphatic alcohol. The esterase was more active against acetylxylan and glucose beta-d-pentaacetate than were a number of esterases from plant and animal sources, when activities on 4-nitrophenyl acetate were compared. The enzyme exhibited Michaelis-Menten kinetics and was active over a broad pH range (5.5 to 9.2), with an optimum between pH 8 and 10. In addition, the enzyme retained its activity for 2 h at 55 degrees C. The yeast that produced the enzyme did not produce xylanase and, hence, is of interest for the production of acetylxylan esterase that is free of xylanolytic activity.     

Determining [H]Thymidine Incorporation into Bacterioplankton DNA: Improvement of the Method by DNase Treatment

Determination of [H] thymidine incorporation into bacterial DNA versus other macromolecules is usually achieved by NaOH and hot trichloroacetic acid hydrolysis. This procedure was found not to be specific enough. An alternative method founded on DNase treatment is proposed. Under the new method, the fraction of thymidine incorporated into DNA ranged from 10 to 83%.     

Immunity in human schistosomiasis

Field studies on immunity in human schistosomiasis are expensive, labour-intensive and extremely time-consuming, requiring many years to yield even provisional results. In this review, Anthony Butterworth and Paul Hagan summarize the need for such studies, the evidence for immunity in man, the immunological factors that may govern the expression of immunity, and the implications of such work for the development of new methods of control through vaccination.     

Professional ecologists and the education of young children

Efforts to conserve natural habitats and their non-human occupants, a concern of most ecologists and evolutionary biologists, are ultimately futile unless there is a change in concepts and attitudes among decision-makers throughout the general public, from subsistence farmers to presidents of multinational corporations. One way to encourage this change is to upgrade the biological and environmental education that children receive.     

Malaria invasion of human erythrocytes

The invasion of human red blood cells (RBC) by plosmodiol merozoites is a key event during malaria infection, and the inhibition o f invasion is regarded as a crucial goal of malaria vaccine development. For Plasmodium falciparum it has been suggested that the red cell sialoglycoproteins, glycophorins A, B and C, are receptors for invasion and that O-linked or N-linked carbohydrate structures may be involved as receptor sites(1-3). However, recent evidence suggests that the role o f these sialoglycoproteins and carbohydrates may have been overestimated. In this article, Peter Hermentin discusses the contradictory findings and presents a revised model for the invasion process.     

Agrobacterium rhizogenes T-DNA genes capable of inducing hairy root phenotype

Summary Segments of the TL-DNA of the agropine type Ri plasmid pRi 1855 encompassing single and groups of open-reading frames were cloned in the Ti plasmid-derived binary vector system Bin 19. Leaf disc infections on Nicotiana tabacum led to transformed plants, some of which showed typical hairy root phenotypes, such as the wrinkled leaf morphology, excessive and partially non geotropic root systems and the ability of leaf explants to differentiate roots in a hormone-free culture medium. Particularly interestingly, most of these traits were shown by plants transformed with a TL-DNA segment encompassing the single ORF 11, corresponding to the rolB locus. Hairy root can be induced by this latter T-DNA segment on wounded stems of tobacco plants; hairy root induction on carrot discs requires, on the contrary, a more complex complement of TL-DNA genes.Abbreviations YMB yeast mannitol broth - MS Murashige and Skoog medium - 6-BAP 6-benzylaminopurine - NAA naphthalene acetic acid - Km kanamycin - Cb carbenicillin     

Solubilization and Purification of NAD(P)H Dehydrogenase of Cucurbita Microsomes

An NAD(P)H dehydrogenase stimulated by quinone (P Pupillo, V Valenti, L de Luca, R Hertel 1986 Plant Physiol 80: 384-389) was solubilized from washed microsomes of zucchini squash hypocotyls (Cucurbita pepo L.) by use of 1% Triton X-100. The solubilized enzyme remained in solution in aqueous buffer and could be purified by a combination of Sepharose 6B chromatography and Blue Ultrogel chromatography. Of the three peaks of activity eluted from the latter column with a salt gradient, peak 3 had 50% or more of the activity and was almost pure enzyme. The preparation examined in SDS-gel electrophoresis consisted of two types of subunits, a (molecular weight 39,500) and b (37,000) in equal amounts. Peak 2 was less pure but had a similar polypeptide pattern. The active protein is proposed to be a heterotetramer (a₂b₂) having a molecular weight of about 150,000, as found by gel exclusion chromatography. The purified enzyme can reduce several quinones, DCPIP, cytochrome c, and with best efficiency ferricyanide, and is therefore a diaphorase. The kinetics for the substrates are negatively cooperative with Hill coefficients n_H = 0.55 ± 0.05 for NADPH and 0.22 ± 0.04 for duroquinone. A weak inhibition by p-hydroxymercuric benzoate and mersalyl (stronger with microsomal preparations) suggests the presence of essential sulfhydryl group(s). The possibility is discussed that the dehydrogenase is an NAD(P)H-P450 reductase or similar flavoprotein, and that it is responsible for the NADPH-cytochrome c reductase activity of plant microsomes.     

Transport Properties of the Tomato Fruit Tonoplast : I. Identification and Characterization of an Anion-Sensitive H-ATPase

An anion-sensitive H⁺-translocating ATPase was identified in membrane vesicles isolated from mature green tomato (Lycopersicon esculentum) fruit. The H⁺-ATPase was associated with a low density membrane population having a peak density of 1.11 grams per cubic centimeter, and its activity was inhibited by NO₃⁻, N,N′-dicyclohexylcarbodiimide and diethylstilbestrol but not by vanadate, azide, molybdate, or oligomycin. This H⁺-ATPase has an unusual pH dependence indicating both a slightly acidic and a near neutral peak of activity. Chloride was found to be a potent stimulator of ATPase activity. The K_m for the H⁺-ATPase was approximately 0.8 millimolar ATP. The characteristics of this H⁺-ATPase are very similar to those described for a number of plant cell tonoplast H⁺-ATPases suggesting that the activity identified in tomato fruit membranes is tonoplast-associated. This report demonstrates the feasibility of isolating tonoplast vesicles from acidic fruit tissues for studies of transport activities associated with fruit development and maturation.     

Amino Acid Metabolism of Lemna minor L. : II. Responses to Chlorsulfuron

Chlorsulfuron, an inhibitor of acetolactate synthase (EC 4.1.3.18) (TB Ray 1984 Plant Physiol 75: 827-831), markedly inhibited the growth of Lemna minor at concentrations of 10⁻⁸ molar and above, but had no inhibitory effects on growth at 10⁻⁹ molar. At growth inhibitory concentrations, chlorsulfuron caused a pronounced increase in total free amino acid levels within 24 hours. Valine, leucine, and isoleucine, however, became smaller percentages of the total free amino acid pool as the concentration of chlorsulfuron was increased. At concentrations of chlorsulfuron of 10⁻⁸ molar and above, a new amino acid was accumulated in the free pool. This amino acid was identified as α-amino-n-butyrate by chemical ionization and electron impact gas chromatography-mass spectrometry. The amount of α-amino-n-butyrate increased from undetectable levels in untreated plants, to as high as 840 nanomoles per gram fresh weight (2.44% of the total free pool) in plants treated with 10⁻⁴ molar chlorsulfuron for 24 hours. The accumulation of this amino acid was completely inhibited by methionine sulfoximine. Chlorsulfuron did not inhibit the methionine sulfoximine induced accumulations of valine, leucine, and isoleucine, supporting the idea that the accumulation of the branched-chain amino acids in methionine sulfoximine treated plants is the result of protein turnover rather than enhanced synthesis. Protein turnover may be primarily responsible for the failure to achieve complete depletion of valine, leucine, and isoleucine even at concentrations of chlorsulfuron some 10⁴ times greater than that required to inhibit growth. Tracer studies with ¹⁵N demonstrate that chlorsulfuron inhibits the incorporation of ¹⁵N into valine, leucine, and isoleucine. The α-amino-n-butyrate accumulated in the presence of chlorsulfuron and [¹⁵N]H₄⁺ was heavily labeled with ¹⁵N at early time points and appeared to be derived by transamination from a rapidly labeled amino acid such as glutamate or alanine. We propose that chlorsulfuron inhibition of acetolactate synthase may lead to accumulation of 2-oxobutyrate in the isoleucine branch of the pathway, and transamination of 2-oxobutyrate to α-amino-n-butyrate by a constitutive transaminase utilizing either glutamate or alanine as α-amino-N donors.