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Biomedical subjects

G Bertoloni

Publications and source records attributed to G Bertoloni.

At least 37 records · Page 2Linked to original sources
PubMed1986

Comparison of effects of penicillin minimal inhibitory and sub-inhibitory concentration on Staphylococcus aureus and Streptococcus faecium does not support the view that antibiotic sub-inhibitory concentrations can specifically interfere with bacterial virulence.

The effect of minimal (MIC) and sub-minimal (sub-MIC) inhibitory concentrations of penicillin on Staphylococcus aureus and Streptococcus faecium were compared. It was found that similar alterations in both cell shape and ultrastructure were found in the presence of penicillin MIC and sub-MICs, the only difference being that while in the presence of penicillin MIC all individual cells were altered, in the presence of sub-MICs the damaged portion was smaller the lower the penicillin concentration and the longer the incubation time. By testing the effect of inoculum size on the penicillin MIC, it was found that penicillin concentrations, which were sub-MICs for rather dense population, turned out to be the MICs for lower density populations. These findings do not support the view that sub-MICs of antibiotics can cause specific damage to bacterial cells which, although not leading to growth inhibition, lowers their virulence. On the contrary, it is suggested that penicillin sub-MICs have no specific effect on Staphylococcus aureus and Streptococcus faecium cells, but simply differ from MIC in that they do not inhibit all cells.

Microbial Sensitivity Tests↗
PubMed1985

The photosensitizing activity of haematoporphyrin on mollicutes.

The photosensitizing activity of haematoporphyrin (HP) on Mycoplasma hominis and Acholeplasma laidlawii was studied as a function of the phase of growth and the amount of sterols in the cell membrane. Less HP was bound to cells when the membrane had a high sterol content. Both strains in the exponential but not in the stationary phase of growth were sensitive to HP treatment (above 1 microgram ml-1) in the dark. Visible light irradiation of HP-loaded cells caused in all cases a decrease of cell survival, with concomitant changes in the pattern of membrane proteins that suggested protein-protein cross-linking, and the appearance of ultrastructural alterations (rounded and lysed cells); the photosensitivity was indirectly related to the sterol content of the cell membrane. On the whole, our findings suggest that the cell membrane is a major target for HP photosensitization of mycoplasma cells.

Acholeplasma laidlawii↗
PubMed1984

Mycoplasmic localization patterns on spermatozoa from infertile men.

Two mycoplasmas have been observed with increasing frequency in patients with genitourinary disorders: Mycoplasma hominis and Ureaplasma urealyticum. Mycoplasma cells of both these species have been demonstrated to be capable of attaching to human spermatozoa of infertile patients. The mechanisms for the association of infertility and mycoplasma infection have not been established. The main objective of this article was to explain the significance of some morphologic features of spermatozoa of patients with unexplained infertility using light and electron microscopy. These studies and quantitative analysis of ureaplasmas in the semen indicate that at least two patterns can be seen. Frequently, sphere-shaped particles adhering mainly to the midpiece of spermatozoa were detected. In a second, more complex pattern ureaplasmas were seen inside a swollen zone on the midpiece, which suggests that the infection does not occur in the urethra, but at another unknown site. Furthermore, the sphere-shaped particles cannot be associated with ureaplasmas because their titers in the semen of infertile patients were much lower than those expected.

Adult↗
PubMed1982

Interference of concomitant tasks on simple reaction time: attentional and motor factors.

Simple reaction times to lateralized unstructured visual stimuli were measured in normal subjects while they were carrying out concomitant left hemisphere tasks. Three tasks were used. In the first task the subjects had to pay attention to strings of digits, acoustically presented, and detect letters randomly interspersed among the digits; in the second task the subjects had to memorize strings of acoustically presented digits; in the third task they had to repeat each digit of a string as soon as they heard it. In spite of the greater difficulty of the first two tasks with respect to the third one, only this last task, the only one requiring a verbo-motor response, produced a significant disadvantage for the left hemisphere responses to light. It is argued that in RT experiments a specific left hemisphere interference takes place when the secondary task requires the organization of a motor response

Attention↗
PubMed1981

Survival of genital mycoplasma on various bacteriological swabs and transport media.

An approach to diagnostic microbiology necessitates measures which maintain the flora unchanged during the transportation of the specimens to the laboratory, preserving the viability of labile and fastidious organisms such as mycoplasma. Some of these problems have been studied in the present investigation. Five different swabs (untreated, albu, charcoal, alginate and phosphate-buffered albumin) and three transport media (Stuart, Amies and MTB) were examined using genital mycoplasma. Absorbent effect of swabs treated with albumin is lower than all the others while the antimycoplasma activity, due to the toxic substances present in the fiber of tip swab, is always lower for the charcoal swab. Concerning transport media, the most favourable results were obtained with the MTB medium. In this medium M. hominis and U. urealyticum counts decreased about 0.5 log and M. fermentans decreased 1.25 log after seven days at 4 degrees C. Furthermore, after inoculation of mycoplasma, MTB can be frozen at -20 degrees C without greatly modifying the titer. The reasons of the different performance of transport media on mycoplasma survival were discussed.

Absorption↗
PubMed1980

[Cognitive tasks and simple reaction times: new observations].

Simple reaction times to lateralized unstructured visual stimuli were studied in normal subjects while they were carrying out a concomitant task. In one task strings of four digits, randomly chosen from 1 to 9, were acoustically presented to the subjects who had to repeat them at the end of each presentation, in a second task again strings of four digits were presented and the subjects were asked to pay attention to the stimuli without memorizing them. In order to compel the subjects to listen carefully to the stimuli, in the second experiment, intermixed with the digits, a letter was occasionally presented and the subjects had to repeat it. It was found that the memory task facilitates reaction times mediated by the left hemisphere, whereas no hemispheric differences were found in the purely attentional task.

Acoustic Stimulation↗
PubMed1980

Colony morphology, ultrastructure and morphogenesis in Mycoplasma hominis, Acholeplasma laidlawii and Ureaplasma urealyticum.

Colonies of Mycoplasma hominis, Acholeplasma laidlawii (three strains) and Ureaplasma urealyticum were examined by light and electron microscopy and their characteristic morphology, ultrastructure and morphogenesis are described. Mycoplasma hominis and A. laidlawii, PG8 and oral strains, developed typical 'fried-egg' colonies which were remarkably heterogeneous in size. The colonies of A. laidlawii strain NCTC 10116 were more homogeneous and grew mainly on the surface of the agar showing a fine granular appearance. Ureaplasma urealyticum produced smaller, granular colonies which grew deeply embedded in the agar and generally without much surface growth. The cellular ultrastructure in these colonies was also examined. The results indicate that several aspects of colony morphogenesis and ultrastructure varied for each of the three species examined.

Acholeplasma laidlawii↗
PubMed1975

[Induction of prophage gamma by means of bleomycin treatment].

The kinetics of induction of lambda prophage with bleomycin A2-CP3, mitomycin C and a combination of these two antibiotics have been studied. Bleomycin has been found to cause a rapid induction of prophage in exponentially growing cultures of E. coli K12 (lambda), and the maximal values of including activity are obtained after treatment for 16 minutes with a concentration of 10 mug/ml. The per cent of induction, calculated from the total number of surviving cells, including the phage producing cells, better expresses the dynamics of the phenomenon. The number of inducing events in the population of exposed cells is proportional to the length of bleomycin treatment. These values are greater than those observed after treatment with mitomycin, at the same concentration. Inducing activity is enhanced by combination of the two antibiotics and this effect is not additive, but synergic. After the 16 minutes of treatment with bleomycin the burst sizes are lower than those which are obtained with mitomycin or with the combination of the two antibiotics. The results are interpreted as a consequence and a confirmation of the different mechanisms of action that distinguishes bleomycin from mitomycin.

Bleomycin↗
PubMedDate not supplied

Efficient photosensitization of malignant human cells in vitro by liposome-bound porphyrins.

Comparative kinetics of porphyrin uptake and release by HeLa cells, incubated with equivalent concentrations of either hematoporphyrin (Hp) in aqueous solution or Hp and its dimethylester (HpDME) bound to unilamellar liposomes, show that liposomal porphyrins are bound at a higher rate and in considerably larger amounts. Moreover, the release of cell-bound porphyrins into the medium is remarkably reduced and slowered after cell loading with liposome-bound porphyrins. The presence of 1% bovine or human serum albumin (but not serum globulins) in the medium has no effect on uptake and release of liposome-bound porphyrins by HeLa cells, whereas it remarkably decreases the uptake of aqueous Hp. Parallel studies of cell photodamages under known concentrations of cell-bound porphyrin unequivocally demonstrate that the photodynamic effect is strictly related to the porphyrin load. As a consequence a dramatic increase of cell-photosensitizing efficiency is obtained by binding Hp (and even more HpDME) with liposomes. Electron microscopy investigations on cell damages caused by loading with liposome-bound porphyrins and subsequent illumination show that the plasmatic membrane is one important cell site of porphyrin interaction and photodynamic effect.

Cell Membrane↗
PubMedDate not supplied

Photobiological studies of new cyclopentene-psoralens.

Psoralen analogues bearing a cyclopentane ring fused to either the 4',5' double bond (compound 4) or the 3,4 double bond (compound 7) of the tricyclic furocoumarin structure were prepared. AM1 theoretical calculations performed for these compounds indicated that the electronic properties of their reactive double bonds were very similar to those of psoralen and its derivative 8-methoxypsoralen (8-MOP), though the overall molecular geometries were clearly different, particularly as regards the change in molecular curvature produced by the introduction of the cyclopentane ring. Compound 4 showed a capacity similar to that of 8-MOP to inhibit the growth of human cervix adenocarcinoma cells (HeLa) and to induce mutagenic effects, but it was definitely less phototoxic to skin than 8-MOP. Its ability to photoadd to DNA and to cross-link DNA strands was also demonstrated. Instead, compound 7 was practically devoid of biological activity and no interaction with the macromolecule could be detected. These differences in behaviour between 4 and 7 are probably due to the molecular curvature resulting from the introduction of the cyclopentane ring.

Adenocarcinoma↗