Further investigations on the structure and function of the saccus vasculosus of the rainbow trout,Salmo gairdneri Richardson

Alkaline phosphatase activity in coronet cells of the saccus vasculosus of the rainbow trout was localized ultracytochemically. Deposits of reaction product were found in varying amounts on the membranes of primary vesicles in the globules. This observation is discussed in relation to other morphological data and the possible resorptive function of the coronet cells in the homeostasis of the CSF.     

Pregnancy-induced long-term uterine vascular remodeling in the rat

Despite the available research investigating uterine physiology during and immediately following pregnancy, including at the vascular and muscular levels, knowledge of the potential long-term timeline of such changes is limited. Thus, our study sought to investigate the potential long-term changes in uterine vasculature and horn length in the postpartum rat, following delivery and weaning. Female Long-Evans rats (n = 9–11 rats/group/timepoint) were divided into two groups: a pregnant group and an age-matched virgin control group. Rat weight, food consumption and vaginal impedance measurements were recorded throughout the experiment. Rats in the pregnant group were bred and pregnancy was confirmed using ultrasound imaging. The uterus and its vasculature were collected at various timepoints following weaning: 3 (week of weaning), 8–9 and 13 weeks postpartum, and at age-equivalent timepoints in the virgin group, and the diameters of the main uterine artery and vein, and lengths of the mesometrial segmental vessels (MSV) and uterine horns were recorded. The results indicated a significant difference between the previously-pregnant and virgin rats in both internal and external arterial diameters (but not arterial wall thickness), as well as the uterine horn length, 3 weeks postpartum, but not 8–9 and 13 weeks postpartum. Significant differences were observed in both venous diameter and MSV length at all timepoints measured. Placental scars were also observed in previously-pregnant rats at all timepoints measured. Our study highlights the long-term impact of pregnancy on the uterine vasculature and the necessity for consideration of such changes on subsequent pregnancies, as well as pregnancy-related vascular pathologies.     

Bacterial induction and inhibition of a fast mecrotic response in Gracilaria conferta (Rhodophyta)

Of 45 bacterial isolates from healthy tips of Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann, 29% were identified as ‘conditional inducers’ of an apical necrosis. That is, the isolates induced necrotic tips in G. conferta within 16 h after elimination of most of the resident microflora from the alga. Several disinfectants and antibiotics were screened for their ability to induce algal susceptibility to the bacteria and to suppress uncontrolled appearance of tip necrosis. Treatment with 100 mg L^-1 Cefotaxim + 100 mg L^-1Vancomycin over three days was the least damaging and most efficient. Tip necrosis was related to isolates of the Corynebacterium-Arthrobacter-group and to the Flavobacterium-Cytophaga-group. The damaging effect occurred due to the bacterial excretion of active agents and was not correlated with acapability to degrade agar. The damaging influence of four Cytophaga-likestrains was inhibited by 20 of 40 isolates. This protective effect was caused by very different organisms. In five of six cases examined further, the effect was not cellbound, but due to the excretion of agents. These were not antimicrobially active, but inactivated necrosis-inducing excretions. These results indicate that epiphytic bacterial degradation or inactivation of damaging agents is a protecting factor in Gracilaria, which prevents the alga from being harmed by epiphytes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Vitiligo in Two Water Buffaloes: Histological,Histochemical, and Ultrastructural Investigations

Vitiligo, a skin disease, characterized by the spontaneous loss of melanin, has been described in several animals as well as in humans. Most of the reports of large domestic animals have dealt with clinical investigations without morphological data. In this report, the histological and ultrastructural characteristics of two cases of vitiligo in water buffaloes (Bubalus bubalis) are presented. Interestingly, many of the ultrastructural observations for vitiliginous buffaloes resemble those previously described for other species, e.g., humans, mouse, and chicken. These data suggest that one or more forms of human vitiligo may have a similar etiopathogenesis to that of the buffalo. Therefore, it is proposed that vitiliginous buffalo may prove to be a useful animal model for the human disease.     

Cell surface control of differentiation in acanthamoeba

Acanthamoeba castellanii (Neff) is a free-living soil amoeba with close relatives that are opportunistic pathogens. Trophozoites differentiatite into cysts when deprived of nutrients; cysts convert into trophozoites, leaving the well behind, in the presence of nutrients. The data presented here, which includes immunoaffinity purification of the receptor, indicate that cell surface molecular signals also control Acanthamoeba differentiation in both directions. Monoclonal antibodies that bind specifically to a 40 kD trophozoite protein initiate the encystment of trophozoites. When bound to cysts the same monoclonal antibodies prevent excystment. Washing away the antibody allows both trophozoites and cysts to resume normal activity. One of these monoclonal antibodies inhibits pinocytosis, while another has effect on pinocytosis.     

Longevity of Toxocara cati Larvae and Pathology in Tissues of Experimentally Infected Chickens

This study was conducted to determine the distribution patterns and duration of stay of Toxocara cati larvae in organs of chickens and to investigate chronic phase and potential zoonotic risk of toxocariasis in chickens. Chickens were orally infected with 1,000 embryonated T. cati eggs and necropsied 240 days post-infection. Organs of the chickens were examined at gross and microscopic levels; tissues were digested to recover larvae. Peribronchiolitis with infiltration of lymphocytes, and hyperplasia of bronchiolar associated lymphatic tissues (BALT) and goblet cells, were evident in the lungs of infected chickens. There were mild hemorrhages and infiltration of lymphocytes and a few eosinophils in the meninges. Larvae were recovered from 30% of the exposed chickens. Larvae recovery indicated that T. cati larvae stay alive for at least 240 days in the chicken brain. Therefore, chickens may potentially act as a paratenic host in nature and transfer T. cati larvae to other hosts.     

Purification and immuno-electron microscopical characterization of crystalline inclusions from plant peroxisomes

Summary This paper describes the first purification method for crystalline inclusions (cores) from plant peroxisomes and an ultrastructural characterization of these isolated cores. 5-day-old sunflower (Helianthus annuus L.) cotyledon fractions which were highly enriched in cores showed negligible activity of the matrix enzyme glycolate oxidase but high catalase activity. As proven by electron microscopy, crystalline particles were surrounded neither by matrix material nor by membranes. Their geometrical outlines and ultrastructure were identical to those of cores in tissue sections, as was their reactivity with three different polyclonal catalase antibodies in the immunogold technique. Three-dimensional reconstruction, based on the geometrical outlines and ultrastructure of sectioned isolated cores from sunflower, suggested that they were quadrangular blocks. Ultrastructural analysis revealed an even periodic arrangement of repeating units which are probably cubes with 20 nm long edges. Isolated peroxisomal cores from potato (Solanum tuberosum L.) tubers had outlines which suggested that they were even rhomboidal prisms. They showed a granular ultrastructure without any repeating units and contained catalase, demonstrated by immunogold labelling and enzyme activity measurement. The results presented here suggested the hypothesis that the structural elements in plant peroxisomal cores are made of enzymatically active catalase, although the substructure may vary from species to species.Abbreviations ACOx acyl-CoA oxidase - BSA bovine serum albumin - EDTA ethylenediamine-tetraacetate - GDH glutamate dehydrogenase - GOx glycolate oxidase - KPB potassium phosphate buffer     

Detection of polysaccharides and ultrastructural modification of the photobiont cell wall produced by two arginase isolectins fromXanthoria parietina

Morphological and structural studies carried out inXanthoria parietina reveal some fungal mechanisms to regulate both growth and development of the phycobiont as well as the number of photobiont cells present in the holobiont. This regulation is performed by phenolic acids and glycosyl-enzymes. An ultrastructural analysis using the polysaccharide detection technique PATAg shows that plasmolysis of cells occur when freshly isolated phycobionts are incubated with two arginase lectins (ABP, algal binding protein and SA, secreted arginase), with development of large cytoplasmic vesicles filled with amorphous polysaccharides that are exocyted to the periplasmic space. Finally, membranes of organelles and plasma membrane are altered and the cell wall is broken. The results presented here provide evidence of a possible fungus-to-algal action as deduced from the hemiparasitic symbiosis theory.     

Embryology of barley. IV. Ultrastructure of the antipodal cells of Hordeum vulgare L. cv. Bomi before and after fertilization of the egg cell

The antipodal cells have been the stepchildren in most investigations of the female gametophyte. In Hordeum vulgare cv. Bomi, three antipodal cells are originally developed chalazally but because of differential growth of the embryo sac they soon become laterally situated and their number increases to 35–50 cells and the shape, size and structure of the cells change in the time before as well as after fertilization. The cells persist until about 60–70 h after pollination. At that time, the embryo consists of about 12–15 cells and a cellularization of the nuclear endosperm has started peripherally. The size of nuclei, and especially nucleoli, in the antipodal cells increases tremendously in the investigated period and the amounts of organelles also change. The walls of antipodals are diversified depending on which cells they are separating, and wall invaginations are developed especially between antipodal cells and surrounding nucellar cells in the placental region. The mitochondria appear in various shapes in section view, very often as cups or dumbbells with a rim in the ends containing cristae and a thin cristae-free base. These bases are sometimes stretched out as thin parts and at last a simple parting occurs. Binary fissions of the plastids happen especially in the hours before and just after egg fertilization. ER is extraordinarily well developed in the whole period of investigation and many ribosomes are attached to the membranes. Dictyosomes form numerous vesicles, especially in the antipodals near the nucellar cells in the placental region. These ultrastructural details support the opinion that antipodal cells may play an important role in the embryo sac and are able to be responsible for the supply of nutrition for the whole gametophyte and take part in the supply of nutrition during embryo formation.