Lethal and Mutagenic Action of Black Light (325 to 400 nm) on Haemophilus influenzae in the Presence of Air

Near-ultraviolet (UV) light (325 to 400 nm), in the presence of air and the absence of exogenous photosensitizing compounds, is lethal and mutagenic for Haemophilus influenzae. The lethal effect is the same for both wild type and streptomycin-resistant mutants, indicating that the mutants are not selected by the irradiation. The inactivation and mutagenicity show a large shoulder, suggesting the existence of repair systems. Filters were used to eliminate the possibility of short-UV irradiation. The effective radiation is between 325 to 400 nm. The lethal and mutagenic effects are higher during mid and late log phase than during early log or stationary phase.     

A strain of Holmes' ribgrass virus occurring in Yugoslavia

A virus having 300 nm long rod-shaped particles was isolated fromPlantago media L. in Yugoslavia. The virus was transmitted to 15 species of host plants the symptoms of which are described in detail. The symptoms corresponded to those that appeared after infection by the original Holmes' ribgrass virus (HRV). The investigated virus was compared both with the common strain of tobacco mosaic and the original Holmes' ribgrass viruses by means of serological tests. The agar double-diffusion tests showed that it is closely related to HRV and remotely related to the common strain of TMV. On the basis of these results we concluded that this virus represented a strain of the HRV. The investigations of the cell inclusions showed that our virus produced rounded plates instead of hexagonal prisms. Electron micrographs of ultrathin sectioned material demonstrated that these plates were formed by virus particles lying perpendicularly to the layers of the plates. The presence of plates also points to the fact that the investigated virus belongs to the HRV.     

A model for dynamics of cell division cycle in onion roots

Summary The study of the cell division cycle by means of caffeine labelling inAllium roots, at 15° C, employing intact root and decapitated roots at several levels (0.5, 1.0, 1.5, 2.0, and 2.5 mm) has shown that the number of cycles developed by the cells is constant at each meristem level. This number and the durations of the cycles are not affected by the decapitation. It is suggested that the cell cycle is controlled in the meristematic cells by an intracellular programme which would be developed throughout the meristem.However, the larger the region decapitated is, the more decreases the growth rate of the roots. The removal of the root cap (about 0.5 mm) did not modify the rate of root growth, although it blocked the geotropic response. The quiescent center is proposed as a source of auxin controlling cell elongation.     

Micromorphology of Cryptococcus neoformans

Fine details of the internal and external morphology of Cryptococcus neoformans as seen in ultrathin sections are described and illustrated with electron micrographs. The capsule characteristic of this species contained microfibrils (30 to 40 A in diameter) that appeared to radiate from the cell wall and to coil and intertwine in various directions. These thin, uniformly structured, electron-dense filaments are believed to represent complex polysaccharide molecules. The internal morphology of C. neoformans was in many ways similar to that of yeasts studied by other authors. The cell was uninucleate with a single nucleolus. The nuclear envelope, a pair of unit membranes interrupted by pores, was typical of that found in eucaryotic organisms. Smooth endoplasmic reticulum, mitochondria, vacuoles, storage granules, and ribosomes were consistent features of the cytoplasm. In addition, C. neoformans presented membranous organelles derived from the plasma membrane and comparable to bacterial mesosomes and mitochondria of an annulate type.     

Histochemical demonstration of purine nucleoside phosphorylase (PNPase) in microglial and astroglial cells of adult rat brain

The histochemical localization of enzymes associated with purine nucleoside metabolism indicates that glial cells might participate in the regulation of these compounds in the central nervous system. In the present study we examined the histochemical localization of purine nucleoside phosphorylase (PNPase) in sections from adult rat brain. Some sections were also sequentially stained immunocytochemically for astroglial or microglial cells utilizing glial fibrillary acidic protein (GFAP) or OX-42 antibodies, respectively. Our observations showed that PNPase was restricted to glial cells, whereas neurons always remained negative. Brain sections stained for both PNPase and GFAP showed that the GFAP-positive astroglial cells were always PNPase positive. Other PNPase-positive but GFAP-negative cells were also observed. These cells resembled microglial cells, and brain sections reacted for both PNPase and OX-42 confirmed this by showing that the major part of OX-42-positive microglial cells were PNPase positive. In these sections, the PNPase-positive but OX-42-negative cells present resembled astroglial cells. From our double staining experiments, we conclude that PNPase is present in both astroglial and microglial cells in normal adult brain.     

Surface and virulence properties of environmental Vibrio cholerae non-O1 from Albufera Lake (Valencia, Spain).

A total of 140 environmental Vibrio cholerae non-O1 isolates, together with several culture collection strains from both environmental and clinical sources, were studied in relation to hemagglutination, surface hydrophobicity, and the enzymatic, hemolytic, cytotoxic, and enterotoxic activities of their extracellular products. A total of 78 and 62% of the strains produced hemagglutinins and exohemagglutinins, respectively. Four different hemagglutinating and two exohemagglutinating activities were found by using eight sugars in the inhibition assays. Cell-bound mannose-sensitive hemagglutination was detected mainly in chicken blood, whereas fucose-sensitive hemagglutination was recorded only in human blood. Cell-bound hemagglutinin resistant to all sugars tested was the only one related to surface hydrophobicity. The surface properties varied along the growth curves. The non-O1 strains displayed strong enzymatic and hemolytic activities, except for esculin hydrolysis. Of 26 non-O1 isolates selected for cytotoxin and enterotoxin production, 23 showed a wide spectrum of cytotoxic effects on cell lines of poikilothermic and homoiothermic species, but they were weakly enterotoxigenic in the infant mouse test. All extracellular products of cytotoxic strains were proteolytic, lipolytic, and hemolytic, and a high percentage produced hemagglutination of chicken blood. The cytotoxic factors in the non-O1 strains analyzed were not R plasmid mediated.     

Fine needle aspiration cytology of primary soft tissue tumors. Morphologic analysis of the most frequent types.

We reviewed 98 cases of fine needle aspiration of soft tissue tumors with histologic confirmation performed during an eight-year period and propose a working morphologic classification based on the most prominent cytologic features. Six main tumor groups are recognized: myxoid, round cells, spindle cells, pleomorphic cells, polygonal cells and well differentiated. We believe that this classification allows recognition of the most common soft tissue tumors while helping with the differential diagnosis of other neoplasia, primary or secondary, with similar morphology and a similar presentation.     

Fine needle aspiration of peripheral neuroepithelioma of soft tissues.

Peripheral neuroepithelioma of soft tissue is a malignant primitive neuroectodermal tumor that appears both in children and adults and usually has a poor outcome. Fine needle aspiration on two patients with tumors in the lower limbs showed small round cells with unipolar processes and a tendency to form Homer-Wright rosettes. The cells had a round to oval nucleus with fine chromatin, up to four small, conspicuous nucleoli and vacuolated, periodic acid-Schiff-positive cytoplasm. The diagnosis was supported by electron microscopic study of the aspirate, which showed features of neuroblastic differentiation (i.e., neurosecretory granules), and by histologic, immunohistochemical and cytogenetic study of the resected tumors.