Search

The development and growth of rye (Secale cereale L. cv. Rheidol) was studied in seedlings grown hydroponically in complete nutrient solutions containing between 10 and 600 μM K+. The phyllochron (defined as the interval between the appearance of successive leaves) was used as a developmental timescale to compare plants. The pattern of both shoot and root development was strictly ordered on a phyllochron basis and was unaffected by solution K+ concentration, with the exception that tillers in plants grown at the lowest K+ concentrations were occasionally either not initiated or aborted at an early stage of development. However, both the rate of leaf appearance on the main stem and successive tillers and the rate of tiller appearance were slower in plants grown at lower K+ concentrations. The rate of leaf appearance on the main stem was reduced to below 90% of its maximal value at solution concentrations below about 50 μM K+. Plant relative growth rate (RGR) was also reduced by lowering the K+ concentration of the nutrient solution and fell to below 90% of its maximal value at solution concentrations below about 200 μM K+. There was a complex relationship between tissue K+ concentration and the K+ concentration of the nutrient solution, which differed between leaves and root. Leaf K+ concentration increased steadily from about 50 μmol g-1 f. wt to about 200 μmol g-1 f. wt as solution K+ concentration was increased from 10 to 400 μM. In contrast, root K+ concentration exhibited a sigmoidal dependence on solution K+ concentration, maintaining a minimal value of approximately 20 μmol g-1 f. wt at concentration below 100 μM K+, then increasing progressively to about 120 μmol g-1 f. wt at a solution concentration of 600 μM K+. The 'critical' leaf K+ concentration, i.e. the concentration at which either plant RGR or plant development was reduced 90% of its maximal value, was 86 μmol g-1 f. wt for plant RGR and 150 μmol g-1 f. wt for plant development. The 'critical' root K+ concentration was 24 μmol g-1 f. wt K+ for both RGR and development. A decline in tissue K+ concentration below these thresholds reduced plant growth considerably. Root K+ concentration was a sensitive indicator of the K+ status of the plant with respect to potential growth since plant growth declined abruptly as root K+ concentration approached its 'critical' value, whereas plant growth showed a less defined relationship with shoot K+ concentration.

Slime isolated after growth of four strains of coagulase-negative staphylococci on chemically defined medium plus agar was rich in galactose. However, when sterile agar plates were extracted with saline, high-molecular-weight material with similar properties was obtained that also was galactose-rich. Most of the dry weight attributed to slime, and probably all the galactose, originated from agar. Slime isolated by gel and ion-exchange chromatography from liquid culture in the same medium contained glycerol phosphate, glucose (no galactose), glucosamine, alanine, uronate, an unidentified component, and protein. Separation of protein from carbohydrate was achieved by affinity chromatography. [14C]glucose in the medium labeled the carbohydrate polymer; [14C]amino acids chiefly labeled extracellular proteins. Slime from bacteria grown on medium solidified with silica gel or on dialysis membrane above an agar surface showed essentially the same composition and behavior after purification as the material isolated from liquid culture.

Theme The conservation of bison (Bison bison) in Yellowstone National Park from near extinction to a high of 5000 animals has led to societal conflict regarding overabundance and potential transmission of brucellosis to cattle with widespread economic consequences. As abundance increased during 1971–1996, more bison migrated from the Hayden and Pelican valleys to the lower-elevation Madison headwaters area and, eventually, outside the park (Meagher 1998, Fuller et al. 2007). Meagher (1998) and others (Taper et al. 2000, Gates et al. 2005) concluded these migratory movements were stress-related responses to decreased food availability as bison fully occupied habitat in the Pelican and Hayden valleys and, subsequently, the Firehole and Madison river drainages. This hypothesis implies that these areas have a relatively fixed capacity for wintering bison and, as a result, a larger proportion of bison migrate to the Madison headwaters and elsewhere as bison numbers increase beyond this capacity. However, density-independent factors such as genetic predisposition, individual asymmetries (e.g., age, sex), and stochastic variations in climate that influence food availability may also affect migration (Lundberg 1987). We used data collected during 1970–1971 through 2005–2006 to quantify annual variations in the magnitude and timing of migration by central herd bison, identify potential factors driving this variation, and evaluate if the proportion of migrants increased with abundance.

Richmond Harbor is on the eastern shoreline of central San Francisco Bay and its access channels and several of the shipping berths are no longer wide or deep enough to accommodate modem deeper-draft vessels. The Water Resources Development Act of 1986 (PL99-662) authorized the US Army Corps of Engineers (USACE), San Francisco District to deepen and widen the navigation channels in Richmond Harbor. Several options for disposal of the material from this dredging project are under consideration by USACE: disposal within San Francisco Bay, at open-ocean disposal sites, or at uplands disposal sites. Purpose of this study was to conduct comprehensive evaluations, including chemical, biological, and bioaccumulation testing of sediments in selected areas of Richmond Harbor. This information was required by the Environmental Protection Agency (EPA) and USACE. Battelle/Marine Sciences Laboratory collected 20 core samples, both 4-in. and 12-in., to a project depth of -40 ft mean lower low water (MLLW) (-38 ft MLLW plus 2 ft of overdepth) using a vibratory-hammer core. These 20 field samples were combined to form five test composites plus an older bay mud (OBM) composite that were analyzed for physical/chemical parameters, biological toxicity, and tissue chemistry. Solid-phase tests were conducted with the amphipod, Rhepoxynius abronius; the clam, Macoma nasuta; and the polychaete worm, Nephtys caecoides. Suspended-particulate-phase (SPP) tests were conducted with the sanddab, Citharichthys stigmaeus; the mysid, Holmesimysis costata; and the bivalve, Mytilus galloprovincialis. Bioaccumulation of contaminants was measured in tissues of Macoma nasuta and Nereis virens. Sediments from one ocean reference sediment, and two in-bay reference sediments, were tested concurrently. Results from analysis of the five test treatments were statistically compared with the reference sediment R-OS in the first five sections of this report.

In recent years, infections of implanted plastic devices by coagulase-negative staphylococci have become a major cause of septicaemia in human patients. The causal bacterial species is usually Staphylococcus epidermidis and these organisms grow as a biofilm adherent to a solid surface. Several methods have been introduced to assess the mass of adherent bacteria and the slimy matrix in which they are embedded. Some methods measure total biofilm, others measure the organisms or the slime alone. In vitro, the type of medium, the atmosphere during incubation, and the nature of the solid surface, affect the quantity of biofilm that is formed. In most studies on the chemistry of the slime, the material used was formed on complex media solidified with agar. Contamination by ingredients of the media or by agar may not always have been recognised. Recent work with chemically defined medium (liquid or solidified with silica gel) shows that the slime is a mixture of about 80% (w/w) teichoic acid and 20% protein. Growth as a biofilm may protect the staphylococci from antibiotics. At present, the greatest success in preventing infection has come from improved surgical techniques during the insertion of implants.

Marked differences in both the production of slime and adherence by Staphylococcus epidermidis were observed when comparing four culture media. Slime isolated from a strain cultured in a chemically defined medium (HHW) in air was chemically indistinguishable from that formed in both HHW and synthetic dialysis fluid (SDF) in air with 5% CO2. The presence of a physiological level of CO2 during culture in tryptone soya broth (TSB) prevented production of slime. It was not possible to separate the constituents of slime from those of the culture medium in bacteria grown in TSB in air using DEAE cellulose. Slime production was notably poor in used peritoneal dialysis fluid (PUD). Adherent growth was marked in HHW and SDF but was poor in TSB and PUD when air with 5% CO2 was used. These findings emphasize the advantages in using chemically defined and biological fluids when studying slime production and adherence by S. epidermidis.

Burnet's theory that Graves' and other autoimmune diseases are caused by forbidden clones of immunocytes, reactive against host antigens and emerging in post-natal life due to somatic events (somatic mutations of V genes and inter-clonal deletions), remains the most comprehensive and likely concept of the pathogenesis. The MHC antigens, B8 and D/DR3, have a predisposing influence of X 2.5 and X 3.7 respectively, whilst male sex has a protective influence, divided by 6. Family studies testing for associated inheritance of Graves' disease and immunoglobulin allotypes (Gm and Km), by observation of the segregation of known heterozygous allotypes and also by Penrose's sibling pair method, have failed to show involvement of immunoglobulin genes. The H gene theory, prompted by studies on the inheritance of autoimmune diseases in the New Zealand mice, postulates that germline genes influencing the prevalence of Graves' and other autoimmune diseases code for major and minor histocompatibility or other alloantigens. By deleting complementary clones, alloantigens alter the immune response repertoire of each individual and this could alter the chance of emergence of a forbidden clone by the somatic mutations and the inter-clonal deletions envisaged by Burnet and Jerne. The H gene theory is superior to the linkage disequilibrium theory in that it accounts for all the known genetic features of Graves' disease, including the female sex preponderance, which is ascribed to the effect of clonal deletions imposed by the H-Y antigen.

Studies of the segregation of heterozygous immunoglobulin allotypes in families with several cases of insulin-dependent diabetes mellitus (IDDM) show that germline heavy-chain V (variable region) genes are not major genetic determinants for IDDM, but data for IDDM and Graves' disease together suggest involvement of x light-chain V genes. Absence of IDDM at birth, the semi-random age of onset, and the 50% discordance of identical twins suggest that somatic mutation of germline V genes is involved in the development of the pathogenetic anti-beta-cell clones. The effect of histocompatibility and other alloantigens on the prevalence of IDDM is readily accounted for by the effect of the "holes" they induce, by natural tolerance, in the immune response repertoire; these alterations apparently affect the chance of emergence of anti-beta-cell clones by the somatic mutations and network of interclonal deletions that constantly change the fringes of the repertoire. Histocompatibility antigens can also influence repertoire development by changing the specificity of conjoint presentation of foreign antigens by macrophages. Antigenic stimulation by particular environmental microorganisms is probably essential to the repertoire development necessary for the occurrence of IDDM. Additionally, beta-cell damage by local infection may play a part by facilitating autoantigen presentation to the immune system.