Cholesterol requirement of mycoplasmas

Cholesterol requirement for growth of mycoplasmas was tested in a serum-free medium supplemented with albumin, l-arginine, palmitic acid, and various concentrations of cholesterol dissolved in Tween 80. In cases in which Tween 80 was shown to inhibit growth, the test medium was supplemented with cholesterol dissolved in ethanol. Of the 31 species examined, all but Mycoplasma laidlawii, M. granularum, and Mycoplasma species strain S-743 exhibited a growth response to cholesterol. No requirement for cholesterol could be shown with the stable L-phase variants of Streptobacillus moniliformis and Proteus species. The results provide experimental support for the view that the large majority of the established Mycoplasma species require cholesterol for growth.     

Internal Rhythmic Pattern of ECG Signal and the Efficiency of Adaptation to Cyclic Muscular Work

Spectral, coherent, and phase analysis within the low-frequency range of ECG records of athletic runners revealed that oscillations of ECG intervals (PQ-, RT-, P–T-, TP, and PP-intervals) were observed during orthostasis. These data were compared with the results of athletic exercise tests performed after the ECG examination. It was shown that the most effective type of adaptive reaction in these tests corresponds to a phase advance of the PQ-interval oscillations relative to the RT-interval oscillations. In the low-frequency range, the phases of the PQ-, RT-, and (P–T)-interval oscillations were ahead of the TP-interval oscillations, whereas the spectral density of the TP interval oscillations was significantly higher than the spectral density of the oscillations of the PC-, RT-, and (P–T)-intervals measured at the same frequency. The least effective type of adaptive reaction was shown to correlate with the phase advance of the TP-interval oscillations relative to the PQ-, RT-, and (P–T)-interval oscillations within the low-frequency range as well as with the lack of low-frequency modulation of the autospectra of the cardiac intervals of interest.     

Endophytic fungi in wild and cultivated grasses in Finland

We examined the occurrence of vertically via host seeds transmitted endophyte infections of 14 grass species in natural populations in Finland and totally 97 agricultural cultivars of 13 grass species. Although endophyte infections were widespread in native grass species, overall endophyte occurrence and frequencies were lower than published reports have suggested. In natural populations, 10 out of 14 grass species examined harbor fungal endophytes in their seeds. The highest species-specific mean incidences of endophyte infected plants in infected populations were found in Agrostis capillaris. Festuca arundinacea. F. ovina. F. Pratensis. F. rubra and Phleum pratense (67%, 98%, 29%., 42%. 32% and 33%, respectively). Mean incidences were < 20% in Dactylis glomerata. Deschampsia flexuosa. D. cespitosa and Elymus repens. and no infections were detected in Calamagrostis lapponica. C. epigejos. Alopecurus pratensis and Phalaris arundinacea. However, we detected a very high variation in infection incidences among natural populations and a large proportion of populations was, indeed, endophyte-free. This supports the ideas that 1) endophytic fungi provide selective advantage of infected grasses to their uninfected eonspecifics in some habitats, and/or 2) fungi are occasionally transmitted horizontally by spores. In grass cultivars, endophyte infected seeds were detected only in F. Pratensis and Lolium perenne. and endophyte frequencies were either very high or very low. Cultivars of 11 other grass species were endophyte-free.     

Role of superoxide in radiation-killing of Escherichia coli and in thymine release from thymidine

The role of superoxide and hydroxyl radicals in gamma-radiation-killing of Escherichia coli K12 was studied in aerated suspensions supplemented with formate, phosphate, superoxide dismutase, catalase and saturated with nitrous oxide. Nitrous oxide, which converts e-aq to .OH, caused decreased radiosensitivity. On the other hand, formate, which results in conversion of .OH to .O2-, resulted in an increased radiosensitivity. The results implicated .O2- as a major cause of radiation-mediated cell-killing. The addition of the enzymes, superoxide dismutase or catalase to the E. coli suspensions prior to and during irradiation had no effect on cell survival, indicating that the biologically significant site of generation and action of .O2- is an intracellular one. Further studies were undertaken to examine the role of superoxide in DNA damage. The release of thymine from the DNA base, thymidine was studied as a result of gamma-irradiation and of chemically generated superoxide (using KO2 in dimethyl sulfoxide). Thymine was identified by HPLC and mass spectrometry. C-13 NMR analysis of the reaction mixture of thymidine with KO2 in dimethyl sulfoxide provided evidence for attack of .O2 at the ribosyl Cl' atom.     

Segregation of infectious pancreatic necrosis resistance QTL in the early life cycle of Atlantic Salmon (Salmo salar)

In a previous study, three significant quantitative trait loci (QTL) associated with resistance to Infectious Pancreatic Necrosis (IPN) disease were identified by analysing challenge data from one sub-population of Landcatch Atlantic salmon (Salmo salar) smolt. While these QTL were shown to affect the resistance in seawater, their effect in freshwater was unknown. This study investigates the effect of these QTL on IPN resistance in salmon fry in freshwater. Twenty families with intermediate levels of IPN mortality were analysed from a freshwater challenge trial undertaken on a different sup-population of LNS salmon to that studied previously. Only the QTL from linkage group 21 (LG21) appeared to have a significant and large effect on resistance in freshwater; the same QTL was found to have the largest effect in seawater in the previous study. Variance component analysis showed a high heritability for the QTL: 0.45 ± 0.07 on the liability scale and 0.25 ± 0.05 on the observed scale. In a family where both parents were segregating for the QTL, there was a 0% vs. 100% mortality in homozygous offspring for resistant and susceptible QTL alleles. The finding that the same QTL has major effect in both freshwater and seawater has important practical implications, as this will allow the improvement of resistance in both phases through marker assisted selection by targeting this QTL. Moreover, the segregation of the LG21 QTL in a different sub-population gives further evidence of its association with IPN-resistance.     

Synthesis of cytochrome c oxidase in the liver of Rana catesbeiana tadpole treated with griseofulvin

The effect of griseofulvin treatment on the synthesis of cytochrome c oxidase was studied with the liver of the tadpole, Rana catesbeiana. (1) In the liver of tadpole treated with griseofulvin, a ferrochelatase inhibitor, the synthesis of heme a, but not cytochrome c oxidase protein, is inhibited. (2) The apocytochrome c oxidase which is formed in the liver of tadpole treated with griseofulvin is converted to the active holoenzyme by exogenously added heme a.     

Effects of the thyroid status on the sarcoplasmic reticulum in slow skeletal muscle of the rat

The effects of the thyroid status on the Ca++-transporting capabilities of rat slow skeletal muscle (m.soleus) were studied. The oxalate supported Ca++-uptake activity and Ca++-loading capacity of muscle homogenates from hyperthyroid rats showed an approximate 4.2 and 2.5 fold increase, respectively, as compared to values found in the hypothyroid group. Muscle homogenates of euthyroid rats gave intermediate values. The specific activity of oxalate supported Ca++ uptake, but not the Ca++-loading capacity, of membrane preparations enriched with respect to sarcoplasmic reticulum (SR) increased in proportion to the thyroid status. This was paralleled by a 3.5 fold increase in the amount of active Ca++ pumps in the SR preparations in the transition from hypothyroidism to hyperthyroidism as determined by measurement of Ca++-dependent 32P incorporation. These observations are not explained by differences in degree of purification of the examined SR preparations. Protein profiles of the membrane preparations obtained by gel electrophoresis indicated a thyroid-hormone dependent increase in Ca++-pump content relative to other SR proteins. The results suggest that thyroid hormone stimulates the proliferation of the SR and possibly also increases the Ca++-pump density in the SR membrane.     

Degranulation and histamine release from murine mast cells sensitized with dengue virus-immune sera

Mice were immunized with dengue type 2 virus (DEN 2) under a schedule favoring the production of IgE antibody. The antibody obtained could sensitize peritoneal resident mast cells both in vitro and in vivo so that the sensitized cells were degranulated and released histamine on challenge with the DEN 2 antigen. It was also demonstrated that the antibody was cytophilic and heat-labile. The above observations suggest that the present experimental system can be used to detect anti-DEN 2 IgE antibody in mice.     

Analysis of Hill slopes predicted by the four-ligand exponential model for a regulatory enzyme.

The four-ligand exponential model for a regulatory enzyme is described as it is applied to kinetic studies of yeast pyruvate kinase in which the concentrations of four ligands are systematically varied. The Hill slopes predicted by this model are calculated for the two situations in which the fourth ligand is either a substrate or an effector. It is shown that the individual terms that make up the expression for the Hill slope assist the interpretation of the observed behaviour in terms of the constants employed by the model.