Asexual reproduction,regeneration, and somatic embryogenesis in the planarian Dugesia tigrina (Turbellaria)

In reviewing recent research published in Russian on regeneration and asexual reproduction, the following morphogenetic processes in the planarian Dugesia tigrina are considered: 1) regeneration of lost parts of the body; 2) regeneration of the whole worm from fragments of the body, either by normal regeneration when the inital polarity of the fragment is retained or by somatic embryogenesis when one or more new axes of polarity arise; 3) somatic embryogenesis, or development of individuals from somatic cells; 4) hypermorphosis, or the presence of more than the usual number of organs or body parts, a process that can be interpreted in terms of somatic embryogenesis; and 5) asexual reproduction. Some morphological, biochemical, and physiological studies of the division zone in D. tigrina demonstrate peculiarities of a local breakdown of integrative functions, a breakdown which in turn causes division of the individual to take place at this zone; timing of division is controlled by the organism as an integrated whole.     

Glycerated hemoglobin, alpha 2A beta 2(82) (EF6) N epsilon-glyceryllysine. A new post-translational modification occurring in erythrocyte bisphosphoglyceromutase deficiency

A new minor Hb fraction initially designated Hbx, has been found in the hemolysate of an erythremic patient that we have previously described with a complete erythrocyte bisphosphoglycerate mutase (EC 5.4.2.4) deficiency. Hbx (3.5% of the total) was detected by isoelectric focusing and exhibited electrophoretic and chromatographic properties similar to those of several variants of the Hb central cavity. By density fractionation of red cells, it was demonstrated that Hbx was an aging hemoglobin as in the case of glycated Hb A1c. Functional studies revealed a low oxygen affinity and almost complete inhibition of the allosteric effect of the organic phosphate effectors. Structural studies demonstrated an absence of tryptic cleavage between the peptides beta T9 and beta T10 suggesting the presence of an adduct on Lys beta 82 or on a neighboring residue. Fast atom bombardment mass spectrometry and a specific enzymatic assay with glyoxylate reductase demonstrated that the beta 82 adduct was a glycerate moiety. It was concluded that Hbx was a glycerylated Hb, alpha 2A beta 2(82) (EF6) N epsilon-glyceryllysine, to our knowledge the first example of glycerylated protein. The mechanism of formation of glyceryl Hb, which was found in the four studied subjects with a bisphosphoglyceromutase deficiency, remains to be determined.     

Seasonal changes in the photosynthetic response ofMercurialis perennis plants from different light regime conditions

Curves relating net photosynthetic rate to irradiance [P(I) curve relation] were estimated and analysed inMercurialis perennis L. plants stemming from three forest (spruce, beech and ash) stands with different tree leaf canopy development and different light regime. The saturating irradiance (I_s) reached the highest values in plants of all three stands in spring (spruce forest: 438 W m⁻², beech forest: 440 W m⁻² and ash forest: 367 W m⁻²), it declined sharply in the middle of the growing season (283, 285 and 297 W m^-2, respectively) and this I_s level persisted until autumn. A pronounced dynamics in plants from spruce and beech forests made itself manifest also in the adaptation (I_a) and compensating (I_c) irradiances, respectively. After a sudden decline in summer, values in autumn were close to those of the vernal season. The most pronounced parameter, which optimally expressed the adaptation ofMercurialis perennis to various light conditions, was the photosynthetic efficiency (α) calculated as the slope of the linear part of the curve relating net photosynthetic rate to irradiance. At the time of the highest P_{N sat.} value in course of the growing season (August) (spruce forest: 100, beech forest: 98.7 and ash forest: 85.8 μg CO₂ m⁻² s⁻¹), R_D was in its minimum; in autumn P_{N sat.} reached the lowest values which corresponded to the most intensive R_D. It was found thatMercurialis perennis plants stemming from forest stands with different light conditions did not make use equally of the altering light conditions in the course of the growing season. By the underlying analysis of P(I) curves this rhizomatous perennial herb (geophyte) may be characterized as a shade tolerant species.     

Studies on enzyme-substrate interactions of cholinephosphotransferase from rat liver

In order to elucidate the reaction mechanism and the substrate-binding sites, CDPcholine:1,2-diacylglycerol cholinephosphotransferase (EC 2.7.8.2), prepared from rat liver microsomal fraction, has been subjected to kinetic analysis and substrate specificity studies. Kinetic evidence supports the hypothesis of a Bi-Bi sequential mechanism, involving a direct nucleophilic attack of diacylglycerol on CDPcholine during the reaction. To investigate the substrate requirements for recognition and catalysis, several CDPcholine analogs, modified in the nitrogen base or in the sugar or in the pyrophosphate bridge, have been synthesized, characterized and assayed as substrates and/or inhibitors of the reaction. The amino group on the pyrimidine ring, the 2'-alcoholic function of the ribose moiety as well as the pyrophosphate bridge have been identified as critical sites for enzyme-substrates interactions.     

Structure and polymorphism of bipolar isopranyl ether lipids from archaebacteria

We describe in this work the structure and polymorphism of a variety of lipids extracted from Sulfolobus solfataricus, an extreme thermoacidophilic archaebacterium growing at about 85 °C and pH 2. These lipids are quite different from the usual fatty acid lipids of eukaryotes and prokaryotes: each molecule consists of two C₄₀ ω-ω′ biphytanyl residues (with 0 to 4 cyclopentane groups per residue), ether linked at both ends to two (variably substituted) glycerol or nonitol groups. Four lipid preparations were studied; the total and the polar lipid extracts, and two hydrolytic fractions, the symmetric glycerol dialkyl glycerol tetraether and the asymmetric glycerol dialkyl nonitol tetraether, as a function of water content and temperature, using X-ray scattering techniques. The main conclusions from the study of the four lipid preparations can be summarized as follows. (1) As with other lipids, a remarkable number and variety of phases are observed over a temperature-concentration range close to “physiological” conditions. The possibility is discussed that this polymorphism reflects a fundamental property of lipids, closely related to their physiological rôle. (2) As in other lipids, two types of chain conformations are observed: a disordered one (type α) at high temperature; at lower temperature, a more ordered packing of stiff chains, all parallel to each other (type β′). At temperatures and degrees of hydration approaching the conditions prevailing in the living cell, the conformation is of type α. (3) In all the phases with chains in the α conformation, the unsubstituted glycerol headgroups, whose concentration is high in these lipids, segregate in the hydrocarbon matrix, away from the other polar groups. This property may have interesting biological consequences: for example, the chains of a fraction of the bipolar lipid molecules can span hydrocarbon gaps as wide as 75 Å. (4) Two cubic phases are observed in the total and the polar lipid extracts, which display a remarkable degree of metastability, most unusual in lipid phase transitions involving structures with chains in the α conformation. This phenomenon can be explained by the interplay of the physical structure of the cubic phases (the two contain two intertwined and unconnected three-dimensional networks of rods) and the chemical structure of the lipid molecules: the two headgroups of most molecules being anchored on each of the two networks of rods, the migration of the lipid molecules is hindered by the two independent diffusion processes and by the entanglement of the chains. The possibility is discussed that this phenomenon may reflect an evolutionary response to a challenge of the natural habitat of these archaebacteria.     

A comparison of the translational diffusion of a normal and a membrane-spanning lipid in Lα phase 1-palmitoyl-2-oleoylphosphatidylcholine bilayers

We have used the fluorescence recovery after photobleaching technique to study the translational diffusion, in L phase multibilayers of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), of fluorescent derivatives of 1-palmitoyl-2-oleoylphosphatidylethanolamine (NBD-POPE) and a membrane-spanning phosphatidylethanolamine (NBD-MSPE). The latter derivative was prepared from a membrane-spanning glycerol-dialkyl-glycerol tetraether lipid isolated from the thermophilic and acidophilic archaebacterium Sulfolobus solfataricus. The translational diffusion was examined between about 15° and 45°C. It is shown that over this temperature range the translational diffusion coefficient for NBD-MSPE is 2/3 that for NBD-POPE which spans only one monolayer of the bilayer. The result is interpreted in terms of existing models for translational diffusion in lipid membranes.Abbreviations D _t translational diffusion coefficient - FRAP fluorescence recovery after photobleaching - MSPE a membrane-spanning phosphatidylethanolamine derived from a glycerol-dialkyl-glycerol tetraether lipid isolated from Sulfolobus solfataricus - NBD 4-nitrobenz-2-oxa-1,3-diazolyl - PE phosphatidylethanolamine - POPC 1-palmitoyl-2-oleoylphosphatidylcholine - POPE 1-palmitoyl-2-oleoylphosphatidylethanolamine     

A spin label ESR and saturation transfer-ESR study of archaebacteria bipolar lipids

A spin label study has been carried out on bipolar lipids extracted from Sulfolobus solfataricus, an extreme thermophilic archaebacterium growing at about 85°C and pH 3. These lipids are cyclic diisopranyl tetraether molecules, quite different from the usual fatty acid lipids. Two hydrolytic fractions of the membrane complex lipids have been studied: the symmetric lipid glycerol-dialkyl-glycerol-tetraether (GDGT) and the asymmetric lipid glyceroldialkyl-nonitol-tetraether (GDNT). The ESR spectra confirm the results previously obtained from calorimetric and X-ray diffraction experiments showing a polymorphic behaviour of these lipids and indicating the critical temperature ranges at which structural transitions occur. Moreover, the present study adds information on the dynamics of the different portions of the hydrophobic chain. ST-ESR measurements show correlation times ranging from 10^-8 s up to 10^-5 s, depending upon the lipid sample, the label position and the degree of hydration. At very high temperatures, i.e. the physiological temperatures of Sulfolobus solfataricus, the nonitol head groups of the asymmetric lipids form a strongly immobilized structure. Indeed, the molecular correlation times of the outermost hydrophobic portion of GDNT are higher, by a factor up to 10³, than those of usual monopolar lipids. Anisotropic motional behaviour is observed even at such very high temperatures. Possible biological implications are discussed.Abbreviations used are ESR electron spin resonance - St-ESR saturation transfer electron spin resonance - GDGT glyceroldialkyl-glycerol-tetracther - GDNT glycerol-dialkyl-nonitoltetraether - 5 SASL 12SASL and 16SASL, stearic acid spin labels, N-oxyl-4,4-dimethyloxazolidine derivatives of 5-ketostearic acid, 12-ketostearic acid and 16-ketostearic acid, respectively - DSC differential scanning calorimetry     

Evidence for a rate-limiting role of cysteinesulfinate decarboxylase activity in taurine biosynthesis in vivo

The relationship between activities of enzymes involved in cysteine oxidation and the apparent conversion of cysteine to taurine in vivo were investigated in the rat and cat. Both hepatic cysteinesulfinate decarboxylase activity and the oxidation in vivo of cysteine to taurine were lower in the kitten than in the adult female rat and lower in the latter than in the young male rat. Our data support the hypothesis that cysteinesulfinate decarboxylase plays a rate-limiting role in taurine biosynthesis.     

Microbiological dehydrogenation of polyfunctional Δ5-3β-acetoxy steroids by Corynebacterium mediolanum strain B-964

Summary A high-yield microbiological transformation of polyfunctional ⁵-3-acetoxy steroids, containing an additional ring E, by Corynebacterium mediolanum strain B-964 was carried out, resulting in the corresponding ⁴-3-ketones. It was shown that the type of transformation and the yield of the reaction depend on the degree of saturation of the ring E and on the position of the oxygen-containing substituents in it.     

Value of serum arabinitol for the management of Candida infections in clinical practice

To determine the value of serum arabinitol concentrations in clinical practice, we identified all patients at the University of Utah Medical Center for whom a serum arabinitol determination had been requested by the attending physician or housestaff to assist in the management of candidiasis. The patient populaton was divided into three categories on the basis of clinical and pathological findings: (1) superficial candidiasis, (2) possible deep, invasive candidiasis, and (3) definite, deep invasive candidiasis. Abnormal renal function was associated with elevated concentrations of serum arabinitol in proportion to the degree of renal dysfunction. Both the serum arabinitol concentration and the arabinitol/creatinine ratio were increased in the combined patient population with candidiasis relative to normal uninfected controls (p=0.06 and 0.001, respectively). However, neither of these tests reliably distinguished patients with invasive candidiasis from those with only superficial candidal disease.