Anastomosis formation and nuclear and protoplasmic exchange in arbuscular mycorrhizal fungi.

We observed anastomosis between hyphae originating from the same spore and from different spores of the same isolate of the arbuscular mycorrhizal fungi Glomus mosseae, Glomus caledonium, and Glomus intraradices. The percentage of contacts leading to anastomosis ranged from 35 to 69% in hyphae from the same germling and from 34 to 90% in hyphae from different germlings. The number of anastomoses ranged from 0.6 to 1.3 per cm (length) of hyphae in mycelia originating from the same spore. No anastomoses were observed between hyphae from the same or different germlings of Gigaspora rosea and Scutellospora castanea; no interspecific or intergeneric hyphal fusions were observed. We monitored anastomosis formation with time-lapse and video-enhanced light microscopy. We observed complete fusion of hyphal walls and the migration of a mass of particles in both directions within the hyphal bridges. In hyphal bridges of G. caledonium, light-opaque particles moved at the speed of 1.8 +/- 0.06 microm/s. We observed nuclear migration between hyphae of the same germling and between hyphae belonging to different germlings of the same isolate of three Glomus species. Our work suggests that genetic exchange may occur through intermingling of nuclei during anastomosis formation and opens the way to studies of vegetative compatibility in natural populations of arbuscular mycorrhizal fungi.

Influence of arbuscular mycorrhizae and phosphate fertilization on shoot apical growth of micropropagated apple and plum rootstocks.

We studied the effects of phosphate fertilization and inoculation with the arbuscular mycorrhizal fungi Glomus mosseae (Nicol. and Gerd.) Gerdmann and Trappe, Glomus intraradices Schenck and Smith or Glomus viscosum Nicolson on shoot apical growth of plantlets that had been micropropagated from MM 106 apple (Malus pumila L.) and Mr.S. 2/5 plum (Prunus cerasifera Ehrh.) rootstocks. Unfertilized and non-mycorrhizal plantlets showed no apical growth during the post in vitro acclimation phase, whereas P fertilization induced early resumption of shoot apical growth. Growth enhancement and percentage of actively growing apices of mycorrhizal-inoculated plantlets were comparable to those obtained in plantlets fertilized with P. Furthermore, tissue P concentrations of mycorrhizal plantlets were similar to those of plantlets fertilized with P. We conclude that mycorrhizal inoculation can be used as a biotechnological tool to overcome blocked apical growth and to reduce chemical inputs, especially P inputs, to micropropagated fruit trees.

[Vaginal colonization of Streptococcus B in pregnancy]. / Colonizzazione vaginale da streptococco B in gravidanza.

In the last few years the importance of GBS as the cause of serious neonatal sepsis has become more evident. The number of cases of this infection clearly exceeds the number of other congenital infections, for which antenatal screening is performed. Asymptomatic colonization of the genital tract of the pregnant woman has the most important role in transmission of GBS and several risk factors are connected to neonatal infection. In order to assess the epidemiological situation in Tuscany, 5079 pregnant women have been recruited by the Obstetrical Department of 16 Hospitals and evaluated for the vaginal colonization by GBS. 3654 couples mother-neonate have also been studied to ascertain the transmission of this germ to the neonate. A vaginal swab was collected at the admission to the Hospital at delivery-time and swabs from several sites of the neonate were obtained just after birth. A blood-agar culture and a latex agglutination test were employed to detect the GBS. GBS was present in 6.6% of the vaginal cultures, with a wide variation in colonization rates. 2.2% of the neonates were positive. The transmission of GBS from the positive mother to the neonate occurred in 20% of the cases. Furthermore one positive neonate out of three was born from a negative mother. No correlation between GBS positivity and preterm delivery was found. The rates of prevalence of GBS in our population, both mother and neonates, suggest a situation that can no longer be neglected. Our data are probably underestimated because of the low sensibility of the culture method. A preventive strategy has to be employed to avoid serious neonatal sepsis. An antenatal screening that provides a vaginal culture at the 36th week of gestation and a chemoprophylaxis intra-partum in the positive cases appears to be the most effective approach.

[Screening for Salmonella in pregnancy]. / Screening per Salmonella in gravidanza.

National and Regional Health Authorities advise a stool culture in pregnant women before term in order to detect Salmonella carriers, prevent the spread of this microorganism to the newborn and avoid outbreaks of this infection in the nurseries. The Tuscany section of the Italian Association of Obstetricians and Gynecologists decided to test the usefulness of this Salmonella screening. In 7431 pregnant women at the 36th week a stool sample was examined for the presence of Salmonella. The occurrence of diarrhoea in these women was also investigated. The prevalence of Salmonella excretors in our obstetric population was 0.27%. Thirty per cent of the positive women complained of diarrhoea; that means that the risk of being positive in the presence of this symptom is 11.8 times larger. The positive cases were detected essentially in late summer and fall. No nursery outbreak occurred during the period studied. The Salmonella-carrying mother can not take advantage of an effective antimicrobic therapy and a single stool sample allows the detection of only part of the carriers. Therefore screening can not prevent the possibility of transmission during birth. The unfavorable ratio between costs and benefits suggests that stool culture for Salmonella may be useful only in late summer and fall and in symptomatic women. In order to obtain better results in the prevention of infections among newborns the observance of careful hygienic rules in the delivery rooms and in the nurseries is mandatory.

Effects of the antimycotic molecule Iturin A2, secreted by Bacillus subtilis strain M51, on arbuscular mycorrhizal fungi.

A new system, devised for the study of early stages of arbuscular mycorrhizal infection, was used to test the effect of the biological control agent Iturin A2, secreted by the strain M51 of Bacillus subtilis, on the development of arbuscular mycorrhizal fungi. The saprophytic growth of the fungus Glomus mosseae was inhibited by Iturin A2 concentrations higher than 100 micrograms/g of sand; whereas, in the presence of the tomato host plant, both, pre-infection events and intraradical growth were not negatively influenced by the antifungal compound; furthermore, the development of arbuscular mycorrhizal symbiosis was not impeded by the biocontrol agent in field conditions, while Fusarium oxysporum f. sp. lycopersici infection was hindered.

Differential hyphal morphogenesis in arbuscular mycorrhizal fungi during pre-infection stages.

Roots of host plants elicit a local change in morphology in the hyphae of arbuscular mycorrhizal fungi, prior to the formation of appressoria. The elicited hyphae switch from their original branching pattern and apical dominance to differentiate in a new irregular, septate branching pattern with reduced inter-hyphal spacing. The extensive hyphal development associated with roots of host plants was shown to be due to the differential growth pattern described, and to precede the further cascade of events leading to appressorium formation and the development of a functional symbiosis.

Endometrial carcinoma in tamoxifen-treated breast cancer patients.

Tamoxifen is an important agent for the treatment of breast cancer. Occasionally the drug, which is an antiestrogen, has agonistic estrogenic activity. The authors describe three new cases of endometrial carcinoma developing in breast cancer patients taking tamoxifen and stress the necessity of carefully monitoring the uterine cavity under tamoxifen treatment.

Pre-neoplastic lesions of vulvar cancer.

The monitoring of potentially neoplastic lesions is based on the determination of the histopathologic characteristics of the lesion, which is done either by large surgical resection of the lesions "in toto" or by biopsy of the lesion. Chronic vulvar dystrophy may develop into carcinoma, the supposed likelihood varying according to the various Authors. The lesion which is histologically defined as atypical keratoacanthoma is the most frequent precursor of carcinoma. Most Authors agree in believing that lichen scleroatrophic does not often develop into carcinoma. It is, nevertheless, the most frequent precursor of leukoplakia which is, on the other hand, a risk lesion. However, any chronic vulvar irritation may increase the risk of cancer and must therefore be carefully monitored by multiple biopsies to be examined at regular intervals.