Polar lobe formation and cytokinesis in fertilized eggs of Ilyanassa obsoleta: III. Large bleb formation caused by Sr2+, ionophores X537A and A23187, and compound 4880

Fertilized eggs of Ilyanassa obsoleta form a protuberance which resembles a normal polar lobe when injected with Sr²⁺ or Ca²⁺ by microiontophoresis. Eggs also form a lobe-like protuberance when exposed to any of three drugs: compound $\text{48}\text{80}$, ionophore X537A, and ionophore A23187. Protuberances form more quickly and at lower drug concentrations if additional exogenous Ca²⁺ is added, whereas higher concentrations of Mg²⁺ do not have such an effect. When eggs are exposed to these drugs in Ca²⁺-, Mg²⁺-“free” seawater, with or without 10 mM EDTA, the eggs are still able to undergo extensive shape changes and form protuberances. Drug-induced shape changes are prevented by cytochalasin B, but will still occur in the presence of colchicine. Approximately 75% of Ilyanassa eggs are capable of forming and resorbing their third polar lobe and undergoing cytokinesis in Ca²⁺-, Mg²⁺-“free” artificial seawater (even containing 10 mM EDTA), solutions which by atomic absorption spectroscopy are shown to contain low concentrations of Ca²⁺ (3–5 μM) and Mg²⁺ (1.0–3.5 μM). The data suggest that if Ca²⁺ is required for normal polar lobe formation and cytokinesis, it is derived from intracellular sources or is required in only very low exogenous concentrations (i.e., less than 10^?2 μM free Ca²⁺, in the presence of 10 mM EDTA).     

A Study of the Mechanism of the Reactions Catalyzed by the Amidase Brevibacterium sp. R312

Besides its amide hydrolase activity, the amidase from Brevibacterium sp. R312 also exhibits an acyl-transferase activity.

The mechanism of the transfer reaction of the acyl from acetamide to hydroxylamine was studied. This is a “Bi Bi Ping Pong” type reaction. The kinetic parameters of the reaction were determined:

– Apparent V_m = 135 μmol · min ^–1 · mg^–1

– Acetamide K_m = 18.2 mM

– Hydroxylamine K_m = 131 mM     

PHYSIOLOGICAL ECOTYPES IN THE MARINE ALGA BOSTRYCHIA RADICANS (CERAMIALES,RHODOPHYTA) FROM THE EAST COAST OF THE U.S.A1

The comparative ecophysiology of nine culture isolates of the eulittoral red alga Bostrychia radicans (Montagne) Montague collected at sites from seven states along the east coast of the U.S.A. was investigated. The growth response in relation to different salinity and light conditions as well as photosynthesis-irradiance curves were studied. In addition, the effect of salt treatment on the content of the isomeric polyols d -sorbitol and d -dulcitol was also studied. All isolates grew between salinities of 5.3 and 70 ppt but with quite different optima and maxima. The isolates were all adapted to low light levels, i.e. growth was already recorded at 2.5 μmol photons·m^?2·s^?1, and growth rates peaked between 40 and 60 μmol photons·m^?2·s_-1. These low-light requirements were also reflected by the photosynthesis-irradiance curves: all plants had low light compensation points (2.5–9.7 μmol photons ·m^?2·^?1) and low photon fluence rates for initial saturation of photosynthesis (38.1–84.7 μmol photons·m^?2·s^?1, indicating that these isolates are “shade-adapted.” Isolates from Florida and Georgia synthesized and accumulated both the osmolytes d -sorbitol and d -dulcitol in increasing salinities, whereas only d -sorbitol was present in plants from North Carolina north to Connecticut. d -sorbitol was always strongly involved in osmotic acclimation. In various isolates from the same location in South Carolina, both polyol patterns were found, i.e. d -sorbitol plus d -dulcitol and d -sorbitol only. All data indicate that B. radicans exhibits a broad salinity tolerance and a low-light preference, which explain the successful colonization of this alga on various intertidal and shaded substrates. The data also clearly indicate intraspecific differences among the nine isolates, which is interpreted as development of different physiological ecotypes.     

Taurine uptake by cultured human lymphoblastoid cells

Cultured human lymphoblastoid cells take up taurine from the medium by two processes: 1) a temperature-dependent, Na⁺-dependent, saturable “active”-transport system and 2) diffusion. The active transport has properties similar to those reported for taurine transport by other tissues. Apparent K_m is about 25 μM and V_max about 7.2 pmol/min/10⁶ cells; saturation occurs at 100 μM taurine. Uptake is competitively inhibited by the β-amino acids hypotaurine (50% inhibition at 44 μM) and β-alanine (50% at 152 μM), as measured at 50 μM taurine. Taurocyamine inhibits 50% at 260 μM. Chlorpromazine and imipramine are strong uncompetitive inhibitors, giving 50% inhibition at 26 μM and 115 μM, respectively; at these concentrations cellular viability per se is not affected. Ouabain inhibits 40–50% over a concentration range of 4–500 μM. Diffusion of taurine into the cells is proportional to concentration up to 20 mM. However, at the concentration of taurine in human plasma, 40–100 μM, active transport would provide 90% of the taurine taken up.     

Enzyme loading of electrically homogeneous human red blood cell ghosts prepared by dielectric breakdown

Human red blood cell ghosts were prepared by electrical haemolysis at 0 °C in isotonic solutions using a discharge chamber which was part of a high voltage circuit. The size distribution of the ghosts was normally distributed, the modal ($\text{=}\text{mean}$) volume was approx. 115 μm³, performing the electrical haemolysis in the following solution: 105 mM KCl, 20 mM NaCl, 4 mM MgCl₂, 7.6 mM Na₂H₂PO₄, 2.4 mM Na₂HPO₄, 10 mM glucose, pH 7.2.Resealing was carried out at 0 °C for 10 min (after the haemolytic step) and then for futher 20 min at 37 °C.The mean volume of the ghost preparation could be changed by variation of the phosphate concentration in the above solution replacing a part of NaCl by phosphate (5 mM phosphate: 94 μm³, 15 mM phosphate: 134 μm³).The breakdown voltage of the ghost cell membranes measured with a hydrodynamic focusing Coulter Counter depends on the mean volume ($\text{94 μ}\text{m}{}^3\text{= 1.04 V, 134 μ}\text{m}{}^3\text{= 1.36}\text{V}$). On the other hand, the breakdown voltage is constant throughout each size distribution pointing to an “electrically homogeneous” ghost preparation. The sensitivity of the Coulter Counter to detect electrical inhomogeneities in the membranes of a ghost population is demonstrated by dielectric breakdown measurements of an apparently normally distributed ghost preparation containing two different “electrically homogeneous” ghost populations i.e. with two different breakdown voltages. The ghost cells obtained by electrical haemolysis in the above solution containing 10 mM phosphate were fairly impermeable to sucrose and behave like an ideal osmometer.It is further demonstrated that ghost cells can be loaded with enzymes (e.g. urease) and drugs using this technique and that these loaded ghost cells can be used as bioactive capsules for clinical application.     

Insulin Resistance,Hyperleptinemia, and Obstructive Sleep Apnea in Launois‐Bensaude Syndrome

Objective: Launois‐Bensaude Syndrome (LBS) is a very rare cause of obesity, characterized by a symmetrical accumulation of a very large number of lipomata in different regions of the body, excluding the face, the forearms, and the shanks. Obesity is known to be closely associated with insulin resistance, hyperleptinemia, and obstructive sleep apnea (OSA). We were interested in studying whether these conditions are also present in patients with obesity due to LBS with a similar frequency as in patients with “simple” truncal obesity. Research Methods and Procedures: We performed polysomnography and hyperinsulinemic euglycemic clamp studies and measured serum leptin in three patients with LBS and in six patients with “simple” truncal obesity, matched for sex and body mass index (LBS group, 36.39 kg/m²; controls, 35.82 kg/m²). Results: Polysomnography revealed severe OSA in one LBS patient with marked “horsecollar lipomata.” In the other LBS patients, no OSA could be demonstrated. The leptin levels of the two groups were comparable (LBS group, 36.39 μg/liter; controls, 37.18 μg/liter) and the insulin responsiveness index was also comparable in the two groups (LBS group, 3.47 μmol/kg · minute; controls, 3.79 μmol/kg · minute). Discussion: Patients with LBS demonstrated similar metabolic features in terms of insulin sensitivity and hyperleptinemia as patients with “simple” truncal obesity. LBS is not strictly associated with OSA.     

PHOTOSYNTHESIS AND RESPIRATION OF THE CONCHOCELIS STAGE OF ALASKAN PORPHYRA (BANGIALES,RHODOPHYTA) SPECIES IN RESPONSE TO ENVIRONMENTAL VARIABLES1

Photosynthesis and respiration of three Alaskan Porphyra species, P. abbottiae V. Krishnam., P. pseudolinearis Ueda species complex (identified as P. “pseudolinearis” below), and P. torta V. Krishnam., were investigated under a range of environmental parameters. Photosynthesis versus irradiance (P–I) curves revealed that maximal photosynthesis (P_max), irradiance at maximal photosynthesis (I_max), and compensation irradiance (I_c) varied with salinity, temperature, and species. The P_max of Porphyra abbottiae conchocelis varied between 83 and 240 μmol O₂ · g dwt^?1 · h^?1 (where dwt indicates dry weight) at 30–140 μmol photons · m^?2 · s^?1 (I_max) depending on temperature. Higher irradiances resulted in photoinhibition. Maximal photosynthesis of the conchocelis of P. abbottiae occurred at 11°C, 60 μmol photons · m^?2·s^?1, and 30 psu (practical salinity units). The conchocelis of P. “pseudolinearis” and P. torta had similar P_max values but higher I_max values than those of P. abbottiae. The P_max of P. “pseudolinearis” conchocelis was 200–240 μmol O₂ · g dwt^?1 · h^?1 and for P. torta was 90–240 μmol O₂ · g dwt^?1 · h^?1. Maximal photosynthesis for P. “pseudolinearis” occurred at 7°C and 250 μmol photons · m^?2 · s^?1 at 30 psu, but P_max did not change much with temperature. Maximal photosynthesis for P. torta occurred at 15°C, 200 μmol photons · m^?2 · s^?1, and 30 psu. Photosynthesis rates for all species declined at salinities <25 or >35 psu. Estimated compensation irradiances (I_c) were relatively low (3–5 μmol · photons · m^?2 · s^?1) for intertidal macrophytes. Porphyra conchocelis had lower respiration rates at 7°C than at 11°C or 15°C. All three species exhibited minimal respiration rates at salinities between 25 and 35 psu.     

A LIMNOLOGICAL PROFILE OF THE UPPER OKAVANGO DELTA AT LOW WATER LEVEL

Summary

Selected limnological attributes of the Okavango Delta panhandle were measured during a brief summer survey of “open-water” habitats extending from the permanent mainstream channel, through contiguous off-channel lagoons and still backwaters, to seasonally isolated floodplain lagoon and temporary pool biotopes on the left-bank of the Okavango River at Seronga.

Wide ranges in most determinants were evident along this profile:- temperature (27–34°C); conductivity(4–12.7mS m^?1); pH(5.7–9.2); transparency(0.2–>2.5 m Secchi depth); dissolved oxygen (20–220% saturation); PO₄-P (61–110 μg ?^?1): SiO₂—Si (6.9–14.0 mg ?^?1): NH₄-N (30–44 μg ?^?1): chlorophyll (1.3–183 μ.g ?^?1). Zooplankton was variably diverse (species richness from ≥ 3 to 20), comprising both euplanktonic (Bosmina, Ceriodaphnia, Daphnia, Diaphanosoma, Moina, Mesocyclops, Thermocyclops, Tropodiaptomus) and more typical epiphytic crustacean taxa (Alona, Macrothrix, Pleuroxus), along with various rotifers (Brachionus, Hexarthra, Keratella, Trichocera) and other taxa (Arcella, Ostracoda. Chaoborus). Abundance varied widely between habitats. The littoral macrozoobenthos showed surprisingly low diversity, and was dominated by freshwater shrimps (Caridina).

Substantial allochthonous inputs to the Okavango swamps were evident from the significant concentrations of total suspended solids (7.6–12.6 mg ?^?1 , organic content of 33–41%) carried by the mainstream Okavango River during the survey.     

Stable carbon and oxygen isotopes in human tooth enamel: Identifying breastfeeding and weaning in prehistory. Am. J. Phys. Anthropol. 106: 1–18.

ERRATUM: Wright LE and Schwarcz HP (1998) Stable Carbon and Oxygen Isotopes in Human Tooth Enamel: Identifying Breastfeeding and Weaning in Prehistory. Am. J. Phys. Anthropol. 106: 1–18. Isotopic ratios were incorrectly printed as percentages (%) rather than units permil (‰). Wherever “breast feeding” and “breast fed” occur, the words should be combined into “breastfeeding” and “breastfed” respectively. The correct information on isotopic ratios is the following: p. 1, Abstract: all % signs should be “‰”; p. 2, column two, last line: “… δ¹³C values¹, have been …”; p. 2, Footnote 1 should read: “Isotope ratios of carbon and oxygen are expressed in δ notation as follows, δ = [(R_sample/R_standard) − 1] × 1000, where R = ¹³C/¹²C for δ¹³C, and R = ¹⁸O/¹⁶O for δ¹⁸O, and are in units permil, ‰.”; p. 3, column two: all % signs should be “‰”, except for the 23rd line from the bottom, which reads: “… provided 95% of water intake by all infants …”; p. 5: all % signs should be “‰”; p. 6, column one: 8th and 9th line from bottom should be “… mean deviations were 0.029‰ for δ¹³C and 0.024‰ for δ¹⁸O …”; p. 6, column one: 2nd line from bottom should be “… only 0.208‰ for δ¹³C and only 0.091‰ for δ¹⁸O …”; p. 6, column two: top line: “… of 0.5‰ in δ¹³C and 0.2‰ in δ¹⁸O …”; p. 8, 9 and 10: all % signs should be “‰”; p. 11, column two: 7th line from top: “… the lipids are 4-6‰ lighter …”; p. 12, 13 and 14: all % signs should be “‰.”     

A new bioreactor with a semi-fixed packing: investigation of degradation of phenol

A new bioreactor using a semi-fixed packing of frames with “sacks” made of a fabric of “Raschell” type stretched on them is proposed. The construction provides not only a large surface area of the biofilm carrier per unit volume of the apparatus, but also the possibility for an easy removal of the biomass after reaching a certain thickness of the biofilm increasing the gas velocity. Aerobic degradation of phenol in the new bioreactor, using microorganisms of the strain Pseudomonas putida, was studied. The experiments are carried out using water containing 0.7?g/l of phenol at a temperature of 27–30?°C. Different specific surface area of the packing (within 176 and 387?m²/m³) are studied. Degradation rates from 60 to 140?mg/(1?h) are attained. A retardation of the process at the end is observed, probably due to inhibition effect. This rate is 5–6 times higher than the rate observed when using free cells. At air velocity of 0.03–0.035?m/s (related to the total cross section of the bioreactor) the vibrations of the packing material lead to destruction and removal of the old biomass.     

Method of simplified kinetic equation for simulating the electron kinetics in dense gases in strong electric fields

A method for calculating the electron kinetics in dense gases in strong electric fields is developed. The method differs from the forward-backward approximation proposed by Ra?zer and Shne?der for “high-energy” electrons in that it introduces the effective cosines of the scattering angles with respect to the electric force, μ⁺(?, E) and μ^?(?, E), which are different from +1 and ?1, as in the forward-backward approximation. The method was implemented numerically for atmospheric-pressure helium and molecular nitrogen for fields in the ranges 10–200 and 50–800 kV/cm, respectively. The cosines μ⁺(?, E) and μ^?(?, E), the frequency of “fatal” collisions making high-energy electrons to pass from an acceleration regime to a deceleration one, and the rate at which the electrons leave the low-energy reservoir with energies of ≤15 eV for nitrogen and of ≤20 eV for helium are calculated.     

TIP CELL GROWTH AND THE FREQUENCY AND DISTRIBUTION OF CELLULOSE MICROFIBRIL-SYNTHESIZING COMPLEXES IN THE PLASMA MEMBRANE OF APICAL SHOOT CELLS OF THE RED ALGA PORPHYRA YEZOENSIS1

The supramolecular organization of the plasma membrane of apical cells in shoot filaments of the marine red alga Porphyra yezoensis Ueda (conchocelis stage) was studied in replicas of rapidly frozen and fractured cells. The protoplasmic fracture (PF) face of the plasma membrane exhibited both randomly distributed single particles (with a mean diameter of 9.2 ± 0.2 nm) and distinct linear cellulose microfibril-synthesizing terminal complexes (TCs) consisting of two or three rows of linearly arranged particles (average diameter of TC particles 9.4 plusmn; 0.3 nm). The density of the single particles of the PF face of the plasma membrane was 3000 μm^?2, whereas that of the exoplasmic fracture face was 325 μm^?2. TCs were observed only on the PF face. The highest density of TCs was at the apex of the cell (mean density 23.0 plusmn; 7.4 TCs μm^?2 within 5 μm from the tip) and decreased rapidly from the apex to the more basal regions of the cell, dropping to near zero at 20 μm. The number of particle subunits of TCs per μm² of the plasma membrane also decreased from the tip to the basal regions following the same gradient as that of the TC density. The length of TCs increased gradually from the tip (mean length 46.0 plusmn; 1.4 nm in the area at 0–5 μm from the tip) to the cell base (mean length 60.0 plusmn; 7.0 μm in the area at 15–20 μm). In the very tip region (0–4 μm from the apex), randomly distributed TCs but no microfibril imprints were observed, while in the region 4–9 μm from the tip microfibril imprints and TCs, both randomly distributed, occurred. Many TCs involved in the synthesis of cellulose microfibrils were associated with the ends of microfibril imprints. Our results indicate that TCs are involved in the biosynthesis, assembly, and orientation of cellulose microfibrils and that the frequency and distribution of TCs reflect tip growth (polar growth) in the apical shoot cell of Porphyra yezoensis. Polar distribution of linear TCs as “cellulose synthase” complexes within the plasma membrane of a tip cell was recorded for the first time in plants.     

THF INFLUENCE OF IRRADIANCE ON THF BIOCHEMICAL COMPOSITION OF THE PRYMNESIOPHYTE ISOCHRYSIS SP. (CLONE T-ISO)1

The effects of irradiance on the biochemical composition of the prymnesiophyte microalga, Isochrysis sp. (Parke; clone T-ISO), a popular species for mariculture, were examined. Cultures were grown under a 12:12 h light: dark (L:D) regime at five irradiances ranging from 50 to 1000 μE·m ²·s^?1 and harvested at late-logarithmic phase for analysis of biochemical composition. Gross composition varied aver the range of irradiances. The highest levels of protein were present in cells from cultures grown at 100 and 250 μE·m ³·s¹, and minimum levels of carbohydrate and lipid occurred at 50 μE·m^?2·s^?1. Because the cell dry weight was reduced at lower irradiances, different trends were evident when results were expressed as percentage of dry weights. Protein percentages were highest at Wand 100 μE·m^?2·s^?1 and carbohydrate at 100 μE·m^?2·s^?1. The composition of amino acids did not differ over the range of irradiances. Glutamate and aspartate were always present in high proportions (9.0–13.5%); histidine. methionine, tryptophan, cystine, and hydroxy-proline were minor constituents (0.0–2.6%). Glucose was the predominant sugar in all cultures, ranging from 23.0% (50 μE·m^?2·s^?1) to 45.0% (100 μE·m^?2·s^?1) of total polysaccharide. No correlation was found between the proportion of any of the sugars and irradiance. The proportions of the lipid class components and fatty acids showed little change with irradiance. The main fatty acids were 14:0, 16:0, 16:1(n-7), 18:1(n-9), 18:3(n-3). 18:4(n-3), 18:5(n-3), and 22:6(n-3). Proportions of 22: 6(n-3) increased, whereas l8:3(n-3). 18:3(n-6). and 18:4(n-3) decreased, with increasing irradiance. Pigment concentrations were highest in cultures grown at 50 μE·m^?2·s^?1, except for fucoxanthin and diadinoxanthin (100 μE·m^?2·s^?1). The concentrations of accessory pigments correlated with chlorophyll a, which decreased in concentration with increasing irradiance. On the basts of biochemical composition, an irradiance of 100 μE·m^?1·s^?1 (12:12 h L:D cycle)for the culture of Isochrysis sp. (clone T-ISO) may provide optimal nutritional value for maricultured animals, although feeding trials are now necessary to substantiate this.     

Electric field-induced changes in agonist-stimulated calcium fluxes of human HL-60 leukemia cells

The mechanism of biological effects of extremely-low-frequency electric and magnetic fields may involve induced changes of Ca²⁺ transport through plasma membrane ion channels. In this study we investigated the effects of externally applied, low-intensity 60 Hz electric (E) fields (0.5 V/m, current density 0.8 A/m²⁺) on the agonist-induced Ca²⁺ fluxes of HL-60 leukemia cells. The suspensions of HL-60 cells received E-field or sham exposure for 60 min and were simultaneously stimulated either by 1 μM ATP or by 100 μM histamine or were not stimulated at all. After E-field or sham exposure, the responses of the intracellular calcium levels of the cells to different concentrations of ATP (0.2–100 μM) were assessed. Compared with control cells, exposure of ATP-activated cells to an E-field resulted in a 20–30% decrease in the magnitude of [Ca²⁺]_i elevation induced by a low concentration of ATP (<1 μM). In contrast, exposure of histamine-activated HL-60 cells resulted in a 20–40% increase of ATP-induced elevation of [Ca²⁺]_i. E-field exposure had no effect on non-activated cells. Kinetic analysis of concentration-response plots also showed that compared with control cells, exposure to the E-field resulted in increases of the Michaelis constant, K_m, value in ATP-treated cells and of the maximal [Ca²⁺]_i peak rise in histamine-treated HL-60 cells. The observed effects were reversible, indicating the absence of permanent structural damages induced by acute 60 min exposure to electric fields. These results demonstrate that low-intensity electric fields can alter calcium distribution in cells, most probably due to the effect on receptor-operated Ca²⁺ and/or ion channels. Bioelectromagnetics 19:366–376, 1998. © 1998 Wiley-Liss, Inc.     

Growth in high-K+ medium induces Friend cell differentiation.

Friend erythroleukemic cells can be induced to differentiate by growth in high-K⁺ medium. Growth of Friend cells in medium containing 60–90 mM K⁺ and 90-60 mM Na⁺ (keeping the osmotic pressure constant) induced differentiation as measured by iron-59 incorporation into heme, accumulation of globin mRNA, the appearance of benzidine-positive cells, and the expression of erythrocyte membrane antigens. In addition, these “high-K⁺, low-Na⁺” conditions were synergistic with low doses of dimethylsulfoxide (DMSO) for the induction of erythroid differentiation. Not all Friend cell clones examined could be induced to differentiate in high-K⁺, low-Na⁺ medium alone, but the synergism between DMSO and high-K⁺, low-Na⁺ was observed in all cases.     

Virus particle packaging in baculovirus and cytoplasmic polyhedrosis virus inclusion bodies

The structure of the inclusion bodies (IBs) of three multiply enveloped nuclear polyhedrosis viruses (MNPVs), one singly enveloped NPV (SNPV), two granulosis viruses (GVs) and one cytoplasmic polyhedrosis virus (CPV) were compared. A method was devised to calculate the numbers of virus particles and nucleocapsids in IBs using data from light microscopy and thin sections. The three MNPVs, from Agrotis segetum (English and Polish virus isolates) and Mamestra brassicae had similar concentrations of virus particles ranging from 17.3 to 19.6 per μm³ of IB. Plusia gamma SNPV had a higher density of 59.6 virus particles per μm³ of IB, which partly compensated for its having smaller IBs (mean volume 0.65 μm³) than the MNPVs (2.60–9.71 μm³). The English A. segetum MNPV isolate had the most nucleocapsids in each virus particle (mean, 4.04) and the largest IBs (mean volume, 9.71 μm³), giving 674 nucleocapsids per IB on average. The GVs, from A. segetum and Pieris brassicae, mainly contained one nucleocapsid per IB. P. gamma CPV IBs had a much higher density of virus particles than the baculoviruses (260 per μm³ compared with 17–60 per μm³). These data are discussed in relation to the biological properties of these viruses, and possible adaptational advantages of alternative IB designs are considered.     

Dose- and time-dependent synthesis of 20-hydroxyecdysone modulated polypeptides in the epidermis of Tenebrio molitor

Cellular (non-cuticular) polypeptides were isolated from mid-instar larval epidermis incubated in the presence or absence of 20-hydroxyecdysone (20HE) for 14–16 h in vitro. Polypeptides synthesized during the last few hours of incubation were labelled with [³⁵S]methionine, separated in cell lysates by two-dimensional polyacrylamide gel electrophoresis and detected fluorographically. Cells incubated with hormone incorporated 28% more label into polypeptide. The synthesis of over 250 polypeptides was detected in total cell lysates. Of these, 54 showed an altered level of synthesis in response to 20HE treatment. The synthesis of most (33) was depressed. The relative synthetic rate of most “down-regulated” 20HE-sensitive polypeptides began to drop at 10⁻³ μg/ml whereas that of most “up-regulated” polypeptides increased only at concentrations above 10⁻¹ μg/ml. An early response to 20HE, involving the de novo synthesis of a 43 kDa polypeptide, was first detectable after 2 h of exposure to hormone, and peaked after 4 h. The synthesis of this 43 kDa polypeptide was selectively enhanced by the addition of 10⁻² μg/ml cycloheximide to medium containing 20HE. The long-term effect (12–16 h) of 20HE on polypeptide synthesis in subcellular fractions of the epidermis was also examined. Polypeptide synthesis found in the nuclear, mitochondrial-lysosomal, microsomal and soluble fractions changed in response to 20HE. It appears that 20HE influences epidermal behaviour predominantly through its ability to modulate the synthetic rate of many cellular polypeptides, rather than by turning off the synthesis of a few pre-existing ones and switching on that of a few new ones.     

Biological treatment of n-hexane and methanol in trickle bed air biofilters under acidic conditions

This study focuses on evaluating the degradation of n-hexane/methanol mixture in trickle-bed-air-biofilters (TBABs). Two different concentration ratios of methanol:n-hexane were evaluated (3:1) for TBAB “A” and (5:1) for TBAB “B”. Both TBABs were run and fed with nutrients buffered at pH 4 for encouraging the growth of fungi. The TBABs were loaded with pelletized diatomaceous earth support media and were run at an empty bed residence time of 120 s. n-Hexane loading rates (LRs) ranged from 0.9 to 13.2 g/m³ h for both TBABs. The corresponding methanol LRs varied from 2.3 to 37.7 g/m³ h and from 4.6 to 64.5 g/m³ h for TBABs “A” and “B”, respectively. Experimental results have shown that the degradation of n-hexane in presence of methanol is enhanced for n-hexane LRs less than 10.6 g/m³ h as compared to previous study for sole-fed n-hexane, but for n-hexane LRs of 13.2 g/m³ h, the performance of TBABs in eliminating n-hexane depended on the methanol to n-hexane ratios. The impact was less severe for TBAB “A” (RE 85%) as compared to TBAB “B” (RE 72%). This is attributed to the high LRs of methanol in TBAB “B”. n-Hexane performance stability was another advantage attained.     

The Mechanism Controlling Plant Nutrient Concentrations in the Northern Adriatic Sea

A 20 year data set for the northern Adriatic was analyzed and the factors establishing the nutrient environment identified. Concentrations ranged widely (TIN 0.0–78, PO₂ 0.01–1.1, and SiO₄ 0.0–59 mmol m⁻³). In early winter remineralization increased concentrations. Characteristic winter, late spring and fall phytoplankton blooms alternately decreased and increased concentrations, as modified by river input. In summer nutrients were minimal under a semi-closed circulation pattern and high vertical stability, due to closely coupled nitrogen and phosphorus assimilation-regeneration processes and biogenic silica sedimentation. “New” primary production supported mainly by river input of “new” nutrients approximated “regenerated” primary production supported by regenerated nutrients, making the ecosystem especially sensitive to eutrophication pressure from anthropogenic increases in the Po River nutrient load.     

The functional roles of m6A modification in T lymphocyte responses and autoimmune diseases

RNA N6-methyladenosine (m⁶A) modification is abundant in eukaryotes, bacteria and archaea. It is an RNA modification mainly existing in messenger RNA (mRNAs) and has a significant effect on the metabolism and function of mRNAs. m⁶A modification is controlled by three types of proteins, namely methyltransferase as the “writers”, demethylase as the “erasers”, and specific m⁶A recognized protein (YTHDF1–3) as the “readers”. Recent studies have shown that m⁶A modification plays an important role in cancer, viral infection and autoimmune diseases. In this review, we will elaborate on the m⁶A modifications in the homeostasis and differentiation of T cells. Then we will further summarize the effects of m⁶A modification on the T cell responses and T cell-mediated autoimmune diseases. This will advance T cell epigenetics research and provide potential biomarkers and therapeutic targets for autoimmune diseases.