Locating the initial in the vascular cambium of Pinus strobus L. by electron microscopy

Summary The results of this investigation by electron microscopy on the vascular cambium in Pinus strobus L. confirm the results of earlier investigations by light microscopy. First, they showed that differences in the thickness of tangential walls of cambial cells exist and that these differences permit grouping of cells according to the sequence of the previous divisions of the initial. This, in turn, permits the site of the initial cell in the cambial zone to be deducted. The thicker distal tangential wall of the initial in the successive series of tissue production allows for precluding the direction in which the initial function proceeds, toward the xylem or toward the phloem. Second, it was demonstrated that immature xylem cells exist in groups of four, that immature phloem cells exist in pairs, and that at all times more cells are produced toward the xylem than toward the phloem. Third, it was shown that the extra-thick tangential wall in immature xylem serves as a landmark to signal the changeover in the initial function from phloem to xylem production.     

Seasonal development of secondary xylem in Pinus Strobus L.

Secondary xylem, or wood, is the tissue that conducts water and minerals in the tree; thus it performs physiologically one of the most important functions for the tree. In addition secondary xylem is the tissue that primarily determines the suitability of a tree for various economic uses.Investigation of the development of secondary xylem shows that it was gradual. Xylem mother cells, the immediate derivatives of cambial initals, were, at first, small cells with thin cell walls. Then the xylem mother cells enlarged radially, but still retained thin cell walls. When these cells reached the radial diameter of mature tracheids, the secondary wall deposition began. This continued until thick, rigid cell walls were attained. These thick, rigid walls determine the physical properties of a certain species of wood. This investigation shows that physical properties of tracheids can differ with stages of development.

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Zusammenfassung Das Sekundärxylem, oder das Holz, ist dasjenige Gewebe, welches Wasser und Mineralstoffe im Baum führt. Damit erfüllt es eine der wichtigsten physiologischen Funktionen für den Baum. Außerdem bestimmt das Gewebe des Sekundärxylems in erster Linie die Verwendbarkeit des Baumes bzw. des Holzes zu wirtschaftlichen Zwecken. Die Untersuchung der Entwicklung des Sekundärxylems zeigte, daß diese Entwicklung abgestuft vor sich geht. Die Xylem-Mutterzellen, unmittelbare Abkömmlinge der Kambium Initialen, zeigten sich zuerst als kleine Zellen mit dünnen Zellwänden. Dann erweiterten sie sich in radialer Richtung, blieben aber immer noch dünn in ihren Zellwänden. Als diese Zellen etwa den Durchmesser von reifen Tracheiden erreicht hatten, begann die Auflagerung der Sekundärschicht. Dieser Vorgang setzte sich fort bis sich dicke, feste Zellwände gebildet hatten. Diese dicken, steifen Zellwände bestimmen weitgehend die physikalisch-mechanischen Eigenschaften der betreffenden Holzart. Die vorliegenden Untersuchungen zeigen, daß die physikalischen Eigenschaften der Tracheiden je nach der Entwicklungsstufe schwanken können.

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This report is based on portions of work in fulfillment of the requirements for the Ph.D. degree in Botany at the University of Wisconsin.

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Maintained at Madison, Wisconsin, 53705, U. S. A., in cooperation with the University of Wisconsin.     

Formation of tyloses in felled Quercus rubra L.

Summary Tyloses form in red oak (Quercus rubra L.) sapwood in a period of hours if the wood is cut during the active growth season and stored in green condition in the laboratory. If the wood is cut during dormancy and stored in green condition, tyloses form in a period of months. Electron microscopic examination reveals that the wall of a tylosis forms from a promonths. Electron microscopic examination reveals that the wall of a tylosis forms from a protective layer that develops inside the secondary wall of the ray cell in the vessel-ray pit-pair. Protective layers are also present in fiber-parenchyma pit-pairs. Protective layers may exhibit variable thicknesses, with light and dark layers alternating. A young tylosis wall consists of two layers: An electron-dense outer layer and an electron-transparent inner layer. Tyloses walls may attach to each other and form multilamellate tyloses. Sometimes the individual layers of tyloses walls appear lamellated. Because of the type of formation and structure, the tylosis wall in red oak apparently is a primary wall rather than a secondary. Tyloses walls have simple pits. The findings of this study enable felled hardwoods with potential for forming tyloses to be used without the destructive influence of tyloses.     

Cell wall formation in secondary xylem of Pinus strobus L.

Summary Vesicular membrane-bound bodies that participate in forming the cell wall of differentiating xylem cells in white pine appeared on electron microscopical examination to originate from the Golgi apparatus. Golgi bodies released vesicles that contained dark material, fibrillar material, or no contents. The vesicles were seen at different stages on their path to the cell wall; their contents came in contact with the wall by fusion of vesicular membranes with the plasmalemma. Individual filaments of fibrillar material within the vesicles were 60 to 80 Å in diameter; structurally they resembled the fibrillar component of the existing wall and became intertwined with the wall. The authors assume the dark material in the Golgi-derived vesicles represents the hemicellulosic and the pectic components of the wall, and the fibrillar material, the cellulosic.Maintained in cooperation with the University of Wisconsin.     

Comparison of mouse and rabbit model for the assessment of strong PGM-containing oil-based adjuvants

Peptidoglycan monomer (PGM) is an adjuvant active molecule with potential for use in human and veterinary vaccine. PGM's action is short-lived in mammals hence its effects might be limited. Novel PGM-containing oil-based formulations have been developed recently by incorporation of PGM into Montanide ISA720 and ISA206 adjuvants with the aim to prolong and improve immunostimulating activities of PGM. In the present work we studied the efficacy of such novel adjuvant formulations using two different antigens, ovalbumin and snake venom, respectively. Novel formulations were also tested in two experimental models, mice and rabbits. In rabbits the incorporation of PGM into oil-based adjuvants led to overall improvement of antigen-specific IgG response. However, in the mouse model, under experimental conditions used, it was not possible to distinguish differences in antigen-specific IgG response among several strong oil-based adjuvant formulations.     

Alkaline Comet Assay as a Potential Tool in the Assessment of DNA Integrity in Freshwater Zooplankton Affected by Pollutants from Water Treatment Facility

Water, Air, & Soil Pollution - In this pilot study, we evaluated the usefulness of the alkaline comet assay as a biomonitoring tool at the level of plankton communities affected by varying...     

Description of the Infection Status in a Norwegian Cattle Herd Naturally Infected by Mycobacterium avium subsp. paratuberculosis

The Norwegian surveillance and control programme for paratuberculosis revealed 8 seroreactors in a single dairy cattle herd that had no clinical signs of Mycobacterium avium subsp. paratuberculosis (M. a. paratuberculosis) infection. Paratuberculosis had been a clinical problem in goats several years previously in this herd. All 45 cattle were culled and a thorough investigation of the infection status was conducted by the use of interferon-γ (IFN-γ) immunoassay, measurement of antibodies, and pathological and bacteriological examination.In the IFN-γ immunoassay, 9 animals gave positive results, and 13 were weakly positive, while 19 animals were negative. In the serological test,10 animals showed positive reactions, and 5 were doubtful, while 30 animals gave negative reactions. There appeared to be a weak trend toward younger animals having raised IFN-γ and older animals having raised serological tests. Histopathological lesions compatible with paratuberculosis were diagnosed in 4 animals aged between 4 and 9 years. Three of these animals had positive serological reaction and one animal gave also positive results in the IFN-γ immunoassay. Infection was confirmed by isolation of M. a. paratuberculosis from 2 of these 4 animals. One single bacterial isolate examined by restriction fragment length polymorphism (RFLP) had the same profile, B-C1, as a strain that had been isolated from a goat at the same farm several years previously.Despite many animals being positive in one or both of the immunological tests, indicative of a heavily infected herd, none of the animals showed clinical signs and only one cow was shown to be shedding bacteria. A cross-reaction with other mycobacteria might have caused some of the immunoreactions in these animals. It is also possible that the Norwegian red cattle breed is resistant to clinical infection with M. a. paratuberculosis.     

Growth of rainbow trout fed a diet supplemented with earthworms,after chemical treatment

Whole frozen earthworms (Eisenia foetida) were evaluated as a partial replacement for commercial pellets for rainbow trout, Oncorhynchus mykiss. Earthworms were blanched and treated with concentrated sodium chloride (10%). Fish were submitted to four treatments: control fish were fed with a commercial diet and three groups of fish were fed with diets partially supplemented with earthworms. All fish showed the same appetite for the earthworm-supplemented diets as for the control diet during the course of the experiment (8 weeks). No significant differences (p > 0.05) were detected in the mean final body weights of all groups of fish. A significant decrease was found in the whole-carcass lipid content of fish fed diets containing 25%, 50% and 75% frozen earthworms. The results on growth rate and feed utilization efficiency of fish fed diets containing high levels of whole frozen worms suggested an adverse effect of worm incorporation, probably due to dietary energy/protein imbalance.     

Immune development in jejunal mucosa after colonization with selected commensal gut bacteria: a study in germ-free pigs

The immunological structure of the porcine jejunal lamina propria in germ-free piglets was compared with that of their counterparts associated with two strains of commensal Escherichia coli, A0 34/86 serotype O83:K24:H31 and the O86 E. coli strain, up to 20 days post-colonization. In the antigen-presenting compartment, both dendritic cells (DC) and cells expressing CD163, probably macrophages were investigated. In addition we also assessed the number of CD2+/CD3+ (T) cells. In contrast to some previous reports, we show a total lack of both DC and T cells for germ-free animals in the diffuse lymphoid tissue of villi and crypts of the jejunum. Association with either strain of commensal E. coli had a profound effect on the immune structure and resulted in extensive recruitment of DC to the lamina propria and of T cells to epithelium and lamina propria. The data suggest that the earliest immigrant cells were monocytes, which soon acquired the phenotype of mucosal DC. T cells migrated in at a slightly slower rate. Nevertheless, the response could be extremely rapid: within 3 days of colonization with O83, the magnitude of this response was comparable to that observed 20 days post-colonization.     

Fatty acid and proximate composition of bluefin tuna (Thunnus thynnus) muscle with regard to plasma lipids

The composition of tail muscle fatty acids from wild and cultured bluefin tuna reared on a diet based on herring and sardine, along with the plasma lipid profile of the farmed individuals, was determined. The total lipid content of farmed bluefin in this study was 0.922 g/100 g or 3.49 g of saturated fatty acids (SAFA), 4.48 g of monounsaturated fatty acids (MUFA), 2.58 g polyunsaturated fatty acids (PUFA) n‐3 and 0.37 g of PUFA n‐6 fatty acids; for wild specimens, it was 0.920 g/100 g, or 2.85 g of SAFA, 4.82 g of MUFA, 2.78 g PUFA n‐3 and 0.27 g of PUFA n‐6 fatty acids. The major fatty acids in this study were 16:0; 16:1, n‐7; 18:1, n‐9 and DHA 22:6, n‐3 acids. The sum of these major components accounted for more than 57% and 80% of the total fatty acids in all the samples of farmed and wild tuna respectively. No significant differences in the proximate composition were demonstrated between farmed and wild samples, except for the energy value, in favour of the farmed tuna. Statistically, glucose tends to increase together with cholesterol (CHOL) and plasma triglyceride, as for these pairs, it showed positive correlation coefficients and P>0.05. Some measured tuna metabolites demonstrated strong mutual correlations, especially GLU, CHOL and TRIG, which are crucial factors in the lipid profile of animals.