BioEssays 10/2020

Frequent independent origins of environmental sex determination (ESD) are assumed within amniotes. However, the phylogenetic distribution of sex-determining modes suggests that ESD is likely very ancient and may be homologous across ESD groups. Sex chromosomes are demonstrated to be old and stable in endothermic (mammals and birds) and many ectothermic (non-avian reptiles) lineages, but they are mostly non-homologous between individual amniote lineages. The phylogenetic pattern may be explained by ancestral ESD with multiple transitions to later evolutionary stable genotypic sex determination. It is pointed out here that amniote ESD shares several key aspects with sequential hermaphroditism of fishes such as a lack of sex differences in genomes, biased population sex ratios, and potentially also molecular mechanism related to general stress responses. Here, it is speculated that ESD evolves via a heterochronic shift of the sensitive period of sex change from the adult to the embryonic stage in a hermaphroditic amniote ancestor. Also see the video abstract here https://youtu.be/q2mjtlCefu4 .     

Dual compartment (bicameral) culture: role of basement membrane in epithelial differentiation

A number of years ago we reported that tight junctions between adjacent Sertoli cells subdivide the seminiferous epithelium into two compartments, basal and adluminal, thus forming the morphological basis of the blood-testis barrier. It is now generally believed that the special milieu created by the Sertoli cells in the adluminal compartment is essential for germ cell differentiation. In order to duplicate the compartmentalization that occurs in vivo, Sertoli cells were cultured in bicameral chambers on Millipore filters impregnated with a reconstituted basement membrane. Confluent monolayers of these cells were tall columnar (40–60 µ in height) and highly polarized. These Sertoli cell monolayers established electrical resistance that peaked when the Sertoli-Sertoli tight junctions developed in culture. In addition, the monolayers formed a permeability barrier to ³H-inulin and lanthanum nitrate. The bicameral chambers were utilized in a number of studies on protein secretion, and it was revealed that numerous proteens are secreted in a polarized manner. In another study, hormone- stimulated aromatase activity was measured in Sertoli cells grown on plastic culture dishes, plastic dishes coated with laminin or Matrigel, and in the bicameral chambers. Cell culture on basement membrane substrate decreased the FSH-dependent estrogen production. No estrogen production was observed when the Sertoli cells were cultured in the bicameral chambers. These results are in accord with the hypothesis that differentiated Sertoli cells lose their ability to metabolize androgen to estrogen in an hormone-dependent manner, whereas undifferentiated cells in culture, or in vivo, have a very active FSH-dependent aromatase activity. This bicameral culture system could serve as an important model system to examine various functions of Sertoli cells including interactions of Sertoli cells with germ, Leydig, and myoid cells.     

Albumin evolution in polyploid species of the genusXenopus

Electrophoresis of serum from 21 Xenopus species and subspecies reveals variable numbers of albumin bands. The diploid X. tropicalis has one albumin, while the tetraploid species (laevis, borealis, muelleri, clivii, fraseri, epitropicalis) have two. The octoploid species (amieti, boumbaensis, wittei, vestitus, andrei) have two to three bands, and the dodecaploid X. ruwenzoriensis has three. The molecular weight of the Xenopus albumins varies from 68 kd (in the tropicalis group) to 74 kd. The subspecies of X. laevis possess two albumins of different molecular weights (70 and 74 kd), whereas most species have only 70-kd albumins. Peptide maps have been obtained from albumin electromorphs by limited proteolysis in sodium dodecyl sulfate (SDS) gels, using S. aureus V8 protease. The peptide patterns produced by electromorphs from the same tetraploid Xenopus species generally differ from each other, suggesting that the two albumin genes contain a substantial amount of structural differences. In addition, the peptide maps are diagnostic for most tetraploid species and for some subspecies of X. laevis as well. Proteolysis of albumins from most octoploid and dodecaploid species results in patterns which are very similar to the ones produced by the electromorphs from X. fraseri. The albumins of X. vestitus differ from those of the other octoploid species. X. andrei possesses two fraseri-type and one vestitus-type albumin, which indicates that it probably originated by allopolyploidy.     

Lipids of Pinus halepensis pollen

The total lipids of Pinus halepensis pollen were separated into individual classes of neutral and polar lipids and the components of each class were identified and determined quantitatively. Free fatty acids, waxes and triacylglycerols were found as the main constituents of neutral lipids and phosphatidylcholine and phosphatidylethanolamine of polar lipids. Glycerylether derivatives were detected in neutral and polar lipid fractions. Free and esterified volatile fatty acids were also found in pollen and its neutral lipid fraction.     

Ion transport and regulation ofTetrahymena pyriformis in isotonic and hypotonic media

Summary The ion and volume regulatory mechanisms ofTetrahymena pyriformis were studied in normal or hypotonic nutrient media and in isotonic inorganic media with different Na/K ratios, in conjunction with the effects of a general metabolic inhibitor (low temperature) and a specific inhibitor (iodoacetate). For K two mechanisms of active influx were found: The first is sensitive to IAc and seems to be the basic mechanism for the maintenance of the K_i/K_o gradient. The second is sensitive to cooling and related to the function of the contractile vacuole; it is also responsible for the high intracellular levels of K. The passive K efflux seems to be a basic factor for volume regulation, together with the contractile vacuole. It increases in hypotonic media and this seems to be related to structural changes of the membranes occurring in hypotonic media. For Na two mechanisms of active transport were also found: One for active Na efflux with highK _m, which is associated with the contractile vacuole and another, for active Na influx with lowK _m, which is inhibited by high levels of intracellular K.The electrochemical potentials of Na and K and the membrane potential (Cl Nernst potential) were also studied in isotonic inorganic media. The membrane is negatively polarized, except if Na_o<5 mM when it becomes positive. In normal conditions, Na is transported outwards actively and leaks passively, while K is transported inwards actively and leaks 56 times more rapidly than Na ions.A model for the overall transport and regulation of ions inTetrahymena is proposed.Abbreviations IAc iodoacetate - PCV packed cell volume - Na _i,K _i,Cl intracellular concentrations ofNa ⁺,K ⁺,Cl ^–, respectively - Na _o,K _o, Cl_o extracellular concentrations of Na⁺, K⁺, Cl^–, respectively - DR distribution ratio - HyN hypotonic nutrient medium - IsN isotonic nutrient medium - HyS IsS hypotonic, and isotonic salt medium, respectively     

Polymeric derivatives of plant growth regulators: synthesis and properties

The polymeric formulations of plant growth regulators (PGRs) are high molecular weight systems in which the PGR unit is attached to the polymeric chain by a hydrolysable chemical bond. These polymeric derivatives (esters, ethers, or else) of PGRs are characterised by the ability to release the active compound (PGR) from their solutions (mainly aqueous) in certain conditions. The release of the PGR can be controlled by external factors (pH, temperature, enzymes, solution concentration), and inherent properties of the whole macrosystem chemical structure, such as the type of the hydrolysable bond between PGR unit and the main polymeric chain, the structure of the polymer chain (e.g. molecular weight, level of hydrophilicity, and the content of hydrophobic groups, macromolecular conformation in solution etc.). These controlled (slow) release PGRs display certain advantages over conventional PGR formulations due to their prolonged action, improved efficiency (e.g. wide range of effective concentrations) greater safety to non-target organisms and the applicators. In addition the ability of altering the solubility level and modifying the aplication form is of considerable interest. The biological activity efficiency of polymeric PGRs has been documented and the relation of this efficiency to the PGR unit hydrolytic release ability has been mentioned. Slow release polymeric PGRs are considered to solve certain problems in agriculture.Abbreviations PGR plant growth regulator - C(S)RF controlled (slow) release form - PD polymeric derivative - ACC 1-amino-cyclopropane-1-carboxylic acid - NAA 1-naphthylacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - BAP N⁶-benzylaminopurine - ABA abscisic acid - GA gibberellin - LMW low molecular weight - HMW high molecular weight     

Biochemical and genetic studies on alkaline phosphatase ofCeratitis capitata

Two forms of alkaline phosphatase exist in the integument of the “white pupae” (wp) and dark pupae (dp) mutant strains ofCeratitis capitata, during transition from larvae to pupae. They were separated by DEAE-cellulose chromatography. Both isoenzymes have a molecular weight of approximately 180,000 and two pH optima, at 9.4 and at 11.0. The isoenzymes of the “dark pupae” mutant catalyze the hydrolysis of phosphotyrosine and β-glycerophosphate but not phosphoserine, phosphothreonine, ATP, and AMP. In contrast, the isoenzymes of the white pupae mutant hydrolyze all the substrates tested. The ALPase 1 of the dark pupae mutant was inhibited byL-tyrosine, butL-phenylalanine had no effect on either isoenzyme. The effects of divalent cations, EDTA, temperature, urea, and 2-mercaptoethanol were also investigated. Electrophoretic analysis did not reveal any variants of the larval and pupal isoenzymes, but ALPase A, an adult stage-specific isoenzyme, was found to be polymorphic. The electrophoretic variants were shown to be controlled by three codominant alleles located on the third chromosome ofCeratitis capitata. Since we found no hybrid enzyme, we conclude that ALPase A is monomeric.     

The anti-platelet approach targeting the fibrinogen ligand of the GPIIB/IIIa receptor.

Activation of the platelet surface receptor GPIIb/IIIa is the final pathway of platelet aggregation, regardless of the initiating stimulus. RGD analogues, peptidomimetics and monoclonal antibodies to GPIIb/IIIa have been developed targeting the blockage of the receptor and inhibition of the fibrinogen binding. However, the intrinsic activating effect of GPIIb/IIIa blockers is widely discussed as one potential contributing factor for the disappointing outcome of trials with GPIIb/IIIa inhibitors. An alternative method for thrombus prevention could be the use of specific fibrinogen blockers since they will act at the final step of the platelet aggregation and are expected to leave the receptor unaffected. To achieve this target the design of the fibrinogen ligands could be based on (i) sequences derived from GPIIb/IIIa ligand binding sites, and (ii) sequences complementary to RGD and/or to fibrinogen gamma-chain. The available information, which could be used as a starting point for developing potent fibrinogen ligands, is reviewed.