Influence of urethane and of hydrostatic pressure on the growth of bacteriophages T2, T5, T6, and T7

In 0.5 per cent NaCl, nutrient broth at 35 degrees C., urethane in a concentration of 0.4 M stops the reproduction of Escherichia coli, strain B. On dilution with 20 volumes of sterile medium, growth is resumed at its former rate after a short lag. In the one-step growth of T2, 15, T6, or T7, in the same medium at the same temperature, 0.4 M urethane, when added at the time of infection, had no apparent effect on adsorption and caused no decrease in titer throughout the latent period of the control, but completely prevented a rise in titer. If diluted 1:20 with sterile medium prior to a certain critical time in the latent period, however, bacteriophage was liberated at the same time, and in the same amount as in the control. The initial stage of apparent insensitivity to the drug lasts from the time of infection until the approximate critical times of 7 minutes with T7, T2, or T6, or 13 minutes with T5. Under the conditions described, the normal latent periods were 14, 23, 30, and 44 minutes for T7, T2, T6, and T5, respectively. At the critical times referred to above, there begins a stage characterized by complete sensitivity, rather than complete insensitivity, to 0.4 M urethane, in the sense that no active phage is subsequently liberated in continued presence of the drug. The length of this completely sensitive stage, as judged by addition of the drug at successive intervals during the latent period, extends from approximately 7 until 9 minutes after infection with T7, 7 until 15 minutes with T2 or T6, or 13 until 25 minutes with T5. When the urethane is added late in this stage of T2, a decrease in initial titer takes place as judged by assays made 40 minutes after infection, the maximum effect occurring when the drug is added between 14 and 15 minutes after infection. When added subsequently to the completely sensitive stage of each type, i.e. subsequently to 9 minutes after infection with T7, 15 minutes with T2 or T6, or 25 minutes with T5, liberation of the bacteriophage takes place in presence of the drug, but the yield is reduced, the amount of reduction being greater the sooner it is added. The yield increases as addition of the drug is delayed, but it is measurably reduced when added late in the rise period. Macroscopic lysis with T7 is delayed by 0.4 M urethane, when present from the time of infection. The delay is less with increased multiplicities of infection. A similar delay occurs with T6r at a multiplicity of 4. The application of hydrostatic pressures of 7,000 to 9,000 p.s.i. early in the latent period, within 5 to 8 minutes after infection, prevents a yield in each of the four phage types, and if maintained for lengthy periods of time a reduction in initial titer occurs. If released at various times shortly after the latent period, a rise in the titer occurred after a certain interval whose length was characteristic of the phage type. The yield was less the longer the release of pressure was delayed. When the pressure was first applied late in the latent period, large amounts of phage were liberated either under pressure or explosively when pressure was released to make the assays. Hydrostatic pressure at 6,000 p.s.i. had little effect on the rate or amount of macroscopic clearing with T7 in relatively high multiplicity of infection, when applied at the start of lysis, but slowed the rate and reduced the amount of clearing when applied shortly after infection.     

Cultivation in a semi-defined medium of animal infective forms of Trypanosoma brucei, T. equiperdum, T. evansi, T. rhodesiense and T. gambiense.

A semi-defined medium for the cultivation of bloodstream forms of the African trypanosome brucei subgroup was developed. Out of 14 different strains tested, 10 could be cultured including Trypanosoma brucei, T. equiperdum, T. evansi, T. rhodesiense and T. gambiense. The presence of a reducing agent (2-mercaptoethanol or thioglycerol) was found to be essential for growth. The standard medium consisted of Hepes buffered minimum essential medium with Earle's salts supplemented with 0.2 mM 2-mercaptoethanol, 2 mM pyruvate and 10% inactivated serum either from rabbit (T. brucei, T. equiperdum, T. evansi and T. rhodesiense) or human (T. gambiense). Although a general medium could be defined for the long-term maintenance of trypanosome cultures, the initiation to culture nevertheless required particular conditions for the different strains. The cultured trypanosomes had all the characteristics of the in vivo bloodstream forms including: morphology, infectivity, antigenic variation and glucose metabolism.     

Differences in sensitivity of T3, T7, T4 and lambda phages to bleomycin and phleomycin]

In contrast to phage lambda the phages T3, T7 and T4 are not inhibited by as much as 150 microgram bleomycin/ml, while the chemically related antibiotic phleomycin increasingly inhibits the propagation of the phages in the order T4-T3-lambda. 20 microgram phleomycin/ml inhibit T3 by 95%. The resistance against bleomycin is surprising, because 10 microgram BM/ml block completely the colony-forming capacity of the host bacterium. The drug resistance of the phage growth correlates with the weak decrease of phage DNA synthesis, while the host cell DNA synthesis ceases rapidly. In accordance with these data is the in vivo inhibition of Escherichia coli cells and the in vitro degradation of their DNA. However, a contradiction exists between the in vivo resistance of T3 and T4 and the in vitro susceptibility of their DNA against nucleolytical fragmentation by bleomycin. The mechanism of the insensitivity of T3, T7 and T4 against bleomycin is unknown.     

Acanthamoeba belonging to T3, T4, and T11: genotypes isolated from air-conditioning units in Santiago, Chile

Free-living amoebae (FLA) of the genus Acanthamoeba are widely distributed in the environment, in the air, soil, and water, and have also been isolated from air-conditioning units. The objective of this work was to investigate the presence of this genus of FLA in the air-conditioning equipment at the Institute of Public Health of Chile in Santiago, Chile. Water and air samples were collected from air-conditioning systems and were checked for the presence of Acanthamoeba spp. Positive samples were further classified at the genotype level after sequencing the highly variable diagnostic fragment 3 (DF3) region of the 18S rRNA gene. This is the first report of the T3, T4, and T11 genotypes of Acanthamoeba in air-conditioning units from Chile. Overall, the widespread distribution of potentially pathogenic Acanthamoeba strains in the studied source demands more awareness within the public and health professionals in Chile as this pathogen is emerging as a risk for human health worldwide.     

Serum T4, T3 and reverse T3 in ethanol fed rats.

To investigate the influence of chronic ethanol consumption on circulating thyroid hormone levels, male and female rats were given 20% ethanol as the only drinking solution daily for 8 weeks. Blood ethanol levels ranged 30–45 mg/L. In male rats serum T₄ decreased from the initial mean ± SD value of 5.2±1.4 to3.0 ±0.7 μg/dl; T₃ decreased from initial value of 97±14 to 66±11 ng/dl and rT₃ decreased from initial value of 19±9 to 10±1 ng/dl after 8 weeks of ethanol ingestion. Under similar experimental conditions, female rats showed a significant decrease in serum T₄ and rT₃ levels; however, T₃ levels decreased slightly but not significantly as compared to initial values. The results indicate adverse effect of chronic ethanol intake on serum thyroid hormone levels in rats.     

Distribution of tryptophan groups in molecules of troponin T, troponin I-troponin T complex, and alpha-actinin

The method of fluorescence quenching was used to experimentally determine the distribution of tryptophan residues in molecules of troponin T, troponin T-troponin I complexes, and alpha-actinin. Iodide and cesium ions, and acrylamide were used as quenchers. It was shown that cesium ions decrease the fluorescence intensity of troponin T and its complex with troponin I by the mode of dynamic quenching. For alpha-actinin such a dynamic quencher is anionic iodide. By using the modified Stern-Volmer equation, the quenching was found to be about 90% of total fluorescence intensity for troponin T, approximately 70% for the troponin T-troponin I complexes, and 20% for alpha-actinin. The penetration of cesium ions to tryptophan 206 (tryptophan 204) in the troponin T-troponin I complex is hindered, probably due to the participation of this tryptophan in the formation of bonds between troponin subunits.     

Circadian and circannual rhythms of LH, FSH, testosterone (T), prolactin, cortisol, T3 and T4 in plasma of mature, male white-tailed deer

Circadian and circannual rhythm of plasma LH, FSH, testosterone (T), prolactin, cortisol, triiodothyronine (T3) and thyroxine (T4) were investigated in two mature male white-tailed deer. No circadian rhythms were detected. Seasonal levels of LH and FSH were reached in September and October; troughs occur in May and June. Maximal T values were detected in November and December (the time of the rut); minimal levels occur between February and July. Prolactin peaked in May and June; minimal levels were detected between October and February. T3 exhibited two maxima; the first in the May-June period, the second in the September-October period. T4 showed no recognizable circannual rhythm. Cortisol levels were found to be much higher during cold months (December-April) than during the rest of the year. The least variable circadian levels were that of FSH and prolactin, with LH, T4, T3, cortisol and testosterone following in descending order. Cannulation stress might have some effect on the levels of testosterone, LH and cortisol. Correlation between LH and testosterone levels were detected mainly during sexually active periods.     

Serum T3, T4, FT3, TSH and TBG in Turner's syndrome]

Turner's syndrome was originally reported as sexual infantilism, short stature, webbed neck and cubitus valgus. Subsequent investigations, however, have disclosed many other abnormalities both in chromosomal and physical features occurring in this syndrome. An increased prevalence of Hashimoto's thyroiditis in patients with Turner's syndrome has been well documented and molecular defects of the TBG have been described. In our study we examined serum T3, T4, FT3, FT4, TSH and TBG levels in 18 girls with Turner's syndrome, in 18 healthy control girls and in the parents of both groups. We reported significant elevated levels of T3 and FT3 in the Turner's group (P 0.01). We did not find any quantitative abnormalities of immunoreactive TBG in the same patients.     

Study of the transfer RNAs coded by T2, T4, and T6 bacteriophages.

T2, T4, and T6 bacteriophage tRNAs coding for arginine, leucine, proline, isoleucine, and glycine were isolated under conditions of short term and long term infection of Escherichia coli B cells. The corresponding phage tRNA species were examined for sequence homology by RNA-DNA hybridization analysis and by their relative behavior on reversed phase chromatography. The results indicate that all three T-even phages code for similar tRNA species; however, some tRNA species are homologous, others are not, and not all of the same tRNA species are coded by each bacteriophage. Reversed phase chromatography showed the presence of isoacceptor tRNAs for each phage aminoacyl-tRNA species. Pulse-chase experiments for [32P]tRNAGly suggest that the multiple isoacceptor species observed derive from the intracellular modification of a single tRNAGly gene product.     

Leaf volatiles from Thymus vulgaris, T. serpyllum, T. praecox, T. pulegioides and T. x citriodorus (Labiatae)

Wound–emitted leaf volatiles in soe species of Thymus were analysed. Fresh shoots without flowers were used. The volatiles were isolated by adsorption on a porous polymer (Tenax GC). The emitted components were separated by a capillary gas chromatograph modified to give reproducible retention time values. The identifications are based on mass spectra and retention time values of reference compounds. The results indicate the mildness of the method used. This is one part of the methodological work of an investigation concerning the biochemical background of pest and disease resistance in plants. Attention is drawn to the urgent need in resistance breeding for a taxonomic survey of the intraspecific allelochemic multitude.