The effect of light on the growth rate of intertidal Acropora pulchra (Brook) from Phuket,Thailand, lat. 8°N

Series of apices of Acropora pulchra from an intertidal reef at Phuket, Thailand, were grown at different depths in the sea, and the length growth was monitored at 12–24 h intervals with laser diffraction. The growth rates of actively growing apices were normally distributed and showed a high variability, with an average coefficient of variation of 58%. There was a highly significant difference in average growth rate between adjacent colonies. A significant linear relationship was found between irradiance and length growth, with a saturating level at 300–400 Wm^-2. At 1000 Wm^-2 length growth was significantly reduced. Under normal daylight conditions, day and night growth rates were equal.     

Dose-response function for Painter's SCE-model

Summary The replication model for sister chromatid exchange (SCE), when introduced in 1980 by Painter, was claimed to be consistent with the one hit property of SCE. However, the argument offered in favour of the one hit property was based on a defective dose-response function, as shown in this paper, since dose as the independent parameter of any dose-response function was not included in the considerations. This missing part of the model's dose-response function is added and, by using Bessel functions, a formula for the complete dose-response function is presented. A re-examination of the newly derived function shows that, in the model, linearity holds only under certain restricted circumstances.     

Regulation of thyroid hormone metabolism in rat liver fractions

The nature of the conversion of thyroxine (T₄) to triiodothyronine (T₃) and reverse triiodothyronine (rT₃) was investigated in rat liver homogenate and microsomes. A 6-fold rise of T₃ and 2.5-fold rise of rT₃ levels determined by specific radioimmunoassays was observed over 6 h after the addition of T₄. An enzymic process is suggested that converts T₄ to T₃ and rT₃. For T₃ the optimal pH is 6 and for rT₃, 9.5. The converting activity for both T₃ and rT₃ is temperature dependent and can be suppressed by heat, H₂O₂, merthiolate and by 5-propyl-2-thiouracil. rT₃ and to a lesser degree iodide, were able to inhibit the production of T₃ in a dose related fashion. Therefore the pH dependendy, rT₃ and iodide may regulate the availability of T₃ or rT₃ depending on the metabolic requirements of thyroid hormones.     

Inhibitory effect of cortisone acetate on the stimulation of rat liver cytosol l-serine Pyruvate aminotransferase by dibutyryl adenosine 3′,5′-monophosphate

An injection of cortisone acetate at a dose of 5 mg/100 g body weight concomitant with dibutryl cyclic AMP prevents the increase in the activity of rat liver cytosol serine aminotransferase (L-serine: pyruvate aminotransferase, EC 2.6.1.51) elicited by the nucleotide with a lag of about 2 h. If the glucocorticoid is given 2 h prior to the nucleotide inducer, the lag disappears. The inhibitory effect of cortisone acetate gradually decays and is no longer detectable 12 h following its administration. Theophylline, insulin and glucose at doses which affect significantly the level of tyrosine aminotransferase, have no effect on the level of serine aminotransferase and on the cortisone inhibition. The inhibitory effect of the glucocorticoid on the dibutyryl cyclic AMP-mediated increase in serine aminotransferase diminishes with the age of animals. Increase in the enzyme activity by a single dose of glucagon can also be inhibited by cortisone acetate and actinomycin D as in the case with dibutyrl cyclic AMP as an inducer. The possibility of the existence of a specific inhibitory factor which is formed in response to cortisone acetate is discussed.     

Phase memory relaxation times of spin labels in human carbonic anhydrase II: pulsed EPR to determine spin label location.

Phase memory relaxation times (T(M) or T(2)) of spin labels in human carbonic anhydrase II (HCA II) are reported. Spin labels (N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)iodoacetamide, IPSL) were introduced at cysteines, by site-directed mutagenesis at seven different positions in the protein. By two pulse electron paramagnetic resonance (EPR), electron spin echo decays at 45 K are measured and fitted by stretched exponentials, resulting in relaxation parameters T(M) and x. T(M) values of seven positions are between 1.6 micros for the most buried residue (L79C) and 4.7 micros for a residue at the protein surface (W245C). In deuteriated buffer, longer T(M) are found for all but the most buried residues (L79C and W97C), and electron spin echo envelop modulation (ESEEM) of deuterium nuclei is observed. Different deuterium ESEEM patterns for W95C and W16C (surface residue) indicate differences in the local water concentration, or accessibility, of the spin label by deuterium. We propose T(M) as a parameter to determine the spin label location in proteins. Furthermore, these systems are interesting for studying the pertaining relaxation mechanism.     

Exopolysaccharide-producing strains of thermophilic lactic acid bacteria cluster into groups according to their EPS structure

AIMS: To compare galactose-negative strains of Streptococcus thermophilus and Lactobacillus delbrueckii subspecies bulgaricus isolated from fermented milk products and known to produce exopolysaccharides (EPSs). METHODS AND RESULTS: The structures of the EPSs were determined using nuclear magnetic resonance (NMR) and their genetic relationships determined using restriction endonuclease analysis (REA) and random amplification of polymorphic DNA (RAPD). Similar groupings were apparent by REA and RAPD, and each group produced an EPS with a particular subunit structure. CONCLUSION: Although none of the strains assimilated galactose, all inserted a high proportion of galactose into their EPS when grown in skimmed milk, and fell into three distinct groups. Significance and Impact of the Study: This information should help in an understanding of genetic exchanges in lactic acid bacteria.     

Effects of cultivation techniques and media on yields and morphology of the basidiomycete Armillaria mellea

Summary The yield of cell mass and the morphology of Armillaria mellea, strain ATCC 11114, was studied using a variety of cultivation methods: solid media, standing liquid culture, shake flasks, tower reactors and impeller-stirred reactors. Two different media, malt extract broth and a glucose/asparagine/peptone-medium, and the corresponding agar media, were used. Yields were higher in the malt extract media than in the glucose media. Generally the highest yields were obtained on solid media while agitated cultures gave the lowest yields. Morphological characteristics such as pellet formation, adhesion to surfaces and pigment production were significantly affected by culture conditions.     

Large Alterations in Ganglioside and Neutral Glycosphingolipid Patterns in Brains from Cases with Infantile Neuronal Ceroid Lipofuscinosis/Polyunsaturated Fatty Acid Lipidosis

Lipid composition was studied on cerebral tissue from nine children who had died of a progressive encephalopathy called the infantile form of neuronal ceroid lipofuscinosis (INCL) or polyunsaturated fatty acid lipidosis (PFAL). In the terminal stage of the disease, the concentrations of all lipid classes were found to be significantly reduced in the cerebral and cerebellar cortex and white matter. The concentration of gangliosides of the cerebral cortex was 15% and that of cerebrosides (galactosylceramide) in white matter 0.2-5% of the normal values for the children's ages. The reduction of gangliosides mainly affected those of the gangliotetraose series, particularly GD1a. The fatty acids of the linolenic acid series were strongly reduced in ethanolamine and serine phosphoglycerides. A very large increase up to 100-fold of oligoglycosphingolipids of the globo series and two fucose-containing lipids of the neolacto series was found in the forebrain of the three advanced cases examined. The brain tissue also contained very high concentrations of mono-, di-, and trisialogangliosides of the lacto and neolacto series, gangliosides with type 1 chain dominating. The structures of the gangliosides were tentatively identified by gas chromatography-mass spectrometry and monoclonal antibodies with carefully determined epitope specificity. The gangliosides and neutral glycosphingolipids had very similar fatty acid composition, consisting of about 40% stearic acid and 40% C24-acids.     

The population dynamics of Cheilosia fasciata (Diptera,Syrphidae): significance of environmental factors and behavioural adaptations in a phytophagous insect

Summary A population of Cheilosia fasciata Schin. & Egg., 1853 was studied in a beech forest (Melico-Fagetum allietosum) near Göttingen (FRG). This syrphid species is closely associated with ramson (Allium ursinum L.), as the larvae mine the plant's leaves. Adult abundance was determined using emergence traps (1981–1986); egg and larval abundance was determined by examining ramson leaves: puparia were extracted from soil samples (1984 and 1986). Cheilosia fasciata is a univoltine species; the imagines emerge in late April/early May. Larval development took five (1986) to six (1984) weeks. In late June/early July the larvae enter the soil for pupariation. A linear relationship was found between the area of the mines and larval biomass (dry wt.). It was concluded that one larva had to mine 51.90 cm² of leaf area in order to gain the mean maximum dry weight (11.15 mg). Furthermore, it was shown that ovipositing females, laying just one egg per leaf, tended to select large leaves providing this minimum amount of food. It is hypothesized that females probably follow straight-lined routes on their oviposition flights, rather than ovipositing on leaves chosen at random. By applying such a strategy, females can almost completely avoid competition for food among their own offspring. Furthermore, competition among the progeny of the whole population is also reduced, particularly in years when adult abundance is very low. The significance of certain factors influencing the population dynamics of Cheilosia fasciata was evaluated by applying a rank correlation analysis. It was shown that high precipitation rates in April reduced the time available for mating and oviposition resulting in low emergence abundance in the next spring. Larval survivorship was enhanced by high precipitation rates in May and June, indicating that drought may be unfavourable to larvae and reduce food availability. Predation by a parasitoid Phygadeuon ursini Horstmann, 1986 (Hymenoptera, Ichneumonidae), appears to be just an imperfect (Milne 1984) density-dependent control mechanism; in fact, it was shown that food limitation is the only significant mechanism of density-dependent population control.