Characterization and molecular cloning of Bifidobacterium longum cryptic plasmid pMB1

The small cryptic plasmid pMB1 (1.9 kb), previously isolated from Bifidobacterium longum, has been characterized by physical mapping. Two cloning vectors, pMR3 and pDG7, carrying chloramphenicol and ampicillin resistances derived from pJH101, have been electroporated in Escherichia coli.     

Polyamine oxidase activity and polyamine content in maize during seed germination

Polyamine oxidase (PAO, EC 1.5.3.3) activity and polyamine content in the cell wall and soluble fractions obtained from embryos, endosperms and shoots and roots of etiolated or green seedlings of maize ( Zea mays L. cv. WF9) during the first 7 days of germination were investigated. Polyamine content was also determined in the trichloroacetic acid-soluble (free polyamines) and trichloroacetic acid insoluble (bound polyamines) fraction obtained from the same tissues. PAO activity, determined by the radiometric method based on the recovery of the labelled reaction product 1-pyrroline, was mostly localized in the cell wall fraction. The activity was very low in embryos and endosperms and present in traces in roots. In etiolated shoots PAO activity increased sharply, while in green shoots it was low and increased slowly. No polyamines were found in the cell wall fraction and only putrescine was detected in the soluble fraction, with the exception of the embryo, where spermidine and spermine were also present. In the TCA-soluble fraction of embryos, putrescine increased during imbibition, while spermidine and spermine decreased; in the endosperm no relevant changes in polyamines occurred. In the same fraction of green and etiolated seedlings, putrescine increased, giving a peak at days 3–5, while spermidine decreased to very low levels. The amount of bound polyamines was 1–4% of the free ones. The pattern of PAO activity seems to be unrelated to endogenous free polyamine content, which is the same in shoots and roots of etiolated and green seedlings. Enzyme activity, very low in ungerminated seeds, increased continuously during the progression of germination, especially in etiolated shoots, indicating a possible involvement in cell wall formation.     

Development of tool use in a macaque and a gorilla

The development of the capacity to use a stick as a tool was tested in a macaque (Macaca fuscata) and a gorilla (Gorilla gorilla gorilla) infants that had previously shown to be able to use strings and supports as dragging tools. Subjects were tested between 15 and 38 months of age. Different levels of competence between the subjects emerged over testing. The macaque developed a stereotyped strategy to cope with the problem, only getting random successes, whilst the gorilla developed a flexible strategy and revealed to be able to mentally represent the solution of the problem. In fact, when not successful using the stick, the gorilla thought out an alternative strategy, choosing and adapting a new object to use it as a tool.     

Population cytogenetics of aphidicolin-induced fragile sites

Summary Chromosome fragile sites are inducible by aphidicolin in cultured human lymphocytes. To assess the frequency and distribution of these common fragile sites in the general population, a cytogenetic survey was performed on 126 subjects, 59 males and 67 females, whose age ranged from 1 day to 72 years. Common fragile sites, induced by aphidicolin, were widespread and showed a remarkably different sensitivity among individuals; age influenced the overall frequency of fragile sites. Moreover, both age and sex seemed to modulate the expression of specific fragile sites. In our population, the most common fragile sites were: 3p14, 16q23, Xp22, 6q26, 1p31, 4q31, 1p22, 7q22, 2q33, 3q27, 2q31, 7q32, 14q24, 10q22, 5q31, 2q37, 6p21.     

The localization and rate of disappearance of a synaptic vesicle antigen following denervation

Summary A proteoglycan-specific antiserum has been used to monitor the effects of denervation in the electric organ of Torpedo marmorata. The antiserum was produced by injecting a highly purified synaptic vesicle fraction prepared from the electric organs of Torpedo marmorata. Following absorption the serum appears to be specific towards synaptic vesicles. The ultrastructural localization of the antigen determined by immuno-electron microscopy confirmed the specificity of the antiserum and showed that it did not crossreact with the proteoglycans of the basal lamina. The rate of disappearance of the vesicle proteoglycans following denervation was evaluated by means of the antiserum and was compared to the rate of disappearance of other vesicular and nerve terminal-associated markers. The results suggest that degeneration affects the vesicular constituents at varying rates resulting in a progressive disappearance of the entire functional capacity of the synaptic vesicles.     

Sensitivity of Saccharomyces cerevisiae vegetative cells and spores to antimicrobial compounds

The sensitivity of Saccharomyces cerevisiae spores and vegetative cells to various antimicrobial compounds was compared. Sulphur dioxide, benzoic acid, potassium sorbate, salicylic acid, nystatin, actidione and pimaricin were tested. Generally, the Saccharomyces spores were more resistant than the corresponding vegetative cells. It was also observed that this greater resistance shown by the spores varied with the antimicrobial compound used. Only potassium sorbate was not selective and killed both vegetative cells and spores at about the same rate.     

NADPH-generating system: Influence on microsomal mono-oxygenase stability during incubation for the liver-microsomal assay with rat and mouse S9 fractions

Activity levels of 7-ethoxycoumarin O-deethylase (ED), aminopyrine N-demethylase (APD), p-nitroanisoleO-demethylase (p-NAD) and glucose-6-phosphate dehydrogenase (G-6-PDH) were determined in incubation mixtures for the liver-microsomal assay (LMA) at time 0 and after 1 and 2 h incubation under conditions for mutagenic assay. The experiments were performed with S9 liver fractions from mice (induced with Na-phenobarbital and β-naphthoflavone) and rats (induced with Aroclor 1254) with and without G-6-PDH in the incubation mixtures.

In the absence of G-6-PDH the activities were significantly lower at time 0 in the mouse. The pattern of stability, however, was similar for the activities, with an increase of stability after 1 and 2 h of pre-incubation (an exception for p-NAD).

Only ED activity showed a similar behaviour in the rat. No differences were present for APD and p-NAD activities at time 0 in the rat, but the enzyme stabilities were significantly decreased after 2 h of incubation (about 15% and 10% for APD and p-NAD respectively) in the absence of G-6-PDH.

At time 0, the amounts of G-6-PDH differed between mouse and rat fractions; however, during the incubations for LMA they decreased by about 57% and 53% for the two species, respectively. In addition to the above biochemical results, the presence of exogenous G-6-PDH in the incubations for the mutagenic assay, significantly increased the mitotic gene conversion and mitotic crossing-over of dimethylnitrosamine (DMN) and AR2MNFN (a nitroimidazo[2,1-b]thiazole) in the D₇ strain of Saccharomyces cerevisiae.     

Activation of human ribosomal genes by 5-azacytidine

Cultured human fibroblasts were exposed to 5-azacytidine which inhibits methylation of newly synthesized DNA. A significant increase in the mean number of Ag-stained active nucleolus organizers has been observed in treated cells. This suggests that DNA methylation is involved in modulation of human rRNA synthesis.     

Distribution of diamine oxidase activity and polyamine pattern in bean and soybean seedlings at different stages of germination

Diamine oxidase (DAO, EC 1.4.3.6.) activity and polyamine content were measured in the shoot apex, leaves, epicotyl, cotyledons, hypocotyl and roots of light-grown bean ( Phaseolus vulgaris L. cv. Lingot) and soybean ( Glycine max L. cv. Sakai) seedlings at 3 different stages of germination (5, 8 and 14 days) as well as in embryos and cotyledons from soaked seeds. No DAO activity was detected in embryos and cotyledons of either plants. In bean seedlings DAO activity was only detectable in the shoot apex, primary leaves and cotyledons, while in soybean the activity was only detectable in the hypocotyl and roots. During seedling growth, in both plants, a different pattern of DAO activity was observed. In both species spermidine and spermine were the most abundant polyamines in embryos and cotyledons. Cadaverine, absent in bean, was only detected in soybean embryos. In the seedlings of both plants, increasing gradients of putrescine, spermidine and spermine from base to shoot apex were found. A high concentration of cadaverine was present in soybean hypocotyls and roots. A possible correlation between DAO activity and the endogenous content of the preferential substrate is discussed in relation to the possible involvement of the enzyme in regulating the cellular level of polyamines.