Identification of quantitative trait loci for wood and fibre properties in two full-sib pedigrees of Eucalyptus globulus

Regions of the genome influencing wood and fibre traits in Eucalyptus globulus Labill. have been identified in two full-sib pedigrees that share a common male parent. The first pedigree, cross A, contains 148 progeny, and the second pedigree, cross B, contains 135 progeny. Subsets of progeny of these two controlled crosses were planted at seven sites throughout Australia in 1990. Wood cores were taken at 0.9 m above ground in 1997, and wood and fibre traits were analysed for each individual. Three quantitative trait loci (QTL) affecting wood density, one QTL affecting pulp yield and one QTL affecting microfibril angle have been located in both pedigrees, using single-factor analysis of variance. Other QTLs affecting these traits, as well as fibre length and cellulose content were located in cross A only.     

Adult reserve stem cells and their potential for tissue engineering

Tissue restoration is the process whereby multiple damaged cell types are replaced to restore the histoarchitecture and function to the tissue. Several theories, have been proposed to explain the phenomenon of tissue restoration in amphibians and in animals belonging to higher order. These theories include dedifferentiation of damaged tissues, transdifferentiation of lineage-committed progenitor cells, and activation of reserve, precursor cells. Studies by Young et al. and others demonstrated that connective tissue compartments throughout postnatal individuals contain reserve precursor cells. Subsequent repetitive single cell-cloning and cell-sorting studies revealed that these reserve precursor cells consisted of multiple populations of cells, including, tissue-specific progenitor cells, germ-layer lineage stem cells, and pluripotent stem cells. Tissue-specific progenitor cells display various capacities for differentiation, ranging from unipotency (forming a single cell type) to multipotency (forming multiple cell types). However, all progenitor cells demonstrate a finite life span of 50 to 70 population doublings before programmed cell senescence and cell death occurs. Germ-layer lineage stem cells can form a wider range of cell types than a progenitor cell. An individual germ-layer lineage stem cell can form all cells types within its respective germ-layer lineage (i.e., ectoderm, mesoderm, or endoderm). Pluripotent stem cells can form a wider range of cell types than a single germ-layer lineage stem cell. A single pluripotent stem cell can form cells belonging to all three germ layer lineages. Both germ-layer lineage stem cells and pluripotent stem cells exhibit extended capabilities for self-renewal, far surpassing the limited life span of progenitor cells (50–70 population doublings). The authors propose that the activation of quiescent tissue-specific progenitor cells, germ-layer lineage stem cells, and/or pluripotent stem cells may be a potential explanation, along with dedifferentiation and transdifferentiation, for the process of tissue restoration. Several model systems are currently being investigated to determine the possibilities of using these adult quiescent reserve precursor cells for tissue engineering.     

Peptide inhibitors of alpha-amylase based on tendamistat: development of analogues with omega-amino acids linking critical binding segments

Peptide analogues of Tendamistat which include the most essential residues linked by novel omega-amino acids (X,Y,Z: H2N-(CH2)n-CO(2)H, where n=2-10) were designed, synthesized (Ac-Tyr(15)-X-Trp(18)-Arg(19)-Tyr(20)-Y-Thr(55)-Z-Asp(58)-Gly(59)-Tyr(60)-Ile(61)-Gly(62)-NH2), and analyzed for alpha-amylase inhibitory activity. Native dipeptide spacers sometimes were left intact at X and Z. Analogues demonstrated competitive inhibition with K(i) values ranging from 23 to 767 microM. 8-Aminooctanoic acid was the optimal linker at Y, while longer linkers were favored at the other positions.     

How do frugivores track resources? Insights from spatial analyses of bird foraging in a tropical forest

Frugivores often track ripe fruit abundance closely across local areas despite the ephemeral and typically patchy distributions of this resource. We use spatial auto- and cross-correlation analyses to quantify spatial patterns of fruit abundance and avian frugivory across a 4-month period within a forested 4.05-ha study grid in Puerto Rico. Analyses focused on two tanager species, Spindalis portoricensis and Nesospingus speculiferus, and their principal food plants. Three broad questions are addressed: (1) at what spatial scales is fruit abundance and frugivory patchy; (2) at what spatial scales do frugivores respond to fruit abundance; and (3) to what extent do spatial patterns of frugivory overlap between bird species? Fruit patch size, species composition, and heterogeneity was variable among months, despite fruit patch locations remaining relatively consistent between months. Positive correlations between frugivory and fruit abundance suggested tanagers successfully tracked fruit abundance. Frugivory was, however, more localized than fruit abundance. Scales of spatial overlap in frugivory and monthly variation in the foraging locations of the two tanager species suggested that interspecific facilitation may have been important in determining bird foraging locations. In particular, S. portoricensis, a specialist frugivore, may have relied on the loud calls of the gregarious generalist, N. speculiferus, to find new foraging areas. Such a mechanism could help explain the formation of mixed species feeding flocks and highlights the potential importance of facilitation between species that share resources.     

The development of an amperometric microbial biosensor using Acetobacter pasteurianus for lactic acid

A microbial biosensor, using Acetobacter pasteurianus cells and an oxygen electrode, was developed for the determination of lactic acid. The bacterial cells were retained on a nylon membrane and attached to the surface of the oxygen electrode. In view of response time, stability and sensitivity, the biosensor performed best at 26°C and in pH 6 phthalate buffer containing magnesium sulfate. The activity of the retained cells was stable for approximately 170 h and was regenerable. The biosensor exhibited a hyperbolic response to both D- and L-lactic acid in the range of 10⁻⁴ M to 25 × 10⁻³ M. However, in the range 10⁻⁴ M to 15 × 10⁻⁴ M the response was linear. The microbial biosensor was applicable for detecting lactate concentration in yogurt and milk, since it was not sensitive to lactose, sucrose and glucose — three major components of such dairy products.     

Continuous alpha-amylase production using Bacillus amyloliquefaciens adsorbed on an ion exchange resin

Summary A method for the continuous production of extracellular alpha amylase by surface immobilized cells of Bacillus amyloliquefaciens NRC 2147 has been developed. A large-pore, macroreticular anionic exchange resin was capable of initially immobilizing an effective cell concentration of 17.5 g DW/1 (based on a total reactor volume of 160 ml). The reactor was operated continuously with a nutrient medium containing 15 g/l soluble starch, as well as yeast extract and salts. Aeration was achieved by sparging oxygen enriched air into the column inlet. Fermentor plugging by cells was avoided by periodically substituting the nutrient medium with medium lacking in both soluble starch and yeast extract. This fermentor was operated for over 200 h and obtained a steady state enzyme concentration of 18700 amylase activity units per litre (18.7 kU/l), and an enzyme volumetric productivity of 9700 amylase activity units per litre per hour (9.7 kU/l-h). Parallel fermentations were performed using a 2 l stirred vessel fermentor capable of operation in batch and continuous mode. All fermentation conditions employed were identical to those of the immobilized cell experiments in order to assess the performance of the immobilized cell reactor. Batch stirred tank operation yielded a maximum amylase activity of 150 kU/l and a volumetric productivity of 2.45 kU/l-h. The maximum cell concentration obtained was 5.85 g DW/l. Continuous stirred tank fermentation obtained a maximum effluent amylase activity of 6.9 kU/l and a maximum enzyme volumetric productivity of 2.73 kU/l-h. Both of these maximum values were observed at a dilution rate of 0.345 l/h. The immobilized cell reactor was observed to achieve larger volumetric productivities than either mode of stirred tank fermentation, but achieved an enzyme activity concentration lower than that of the batch stirred tank fermentor.     

The diet of Herring Gulls (Larus argentatus) during winter and early spring on the lower Great Lakes

In the Great Lakes, the Herring Gull (Larus argentatus) is a prominent member of the aquatic bird community, and has been used to monitor spatial and temporal trends in contaminant levels. To understand more fully contaminant loading outside the breeding season, we analysed the contents of 1298 freshly regurgitated pellets and 179 fresh faeces, collected in March and early April 1978–83, and between late December and late February 1990–91, from the vicinity of breeding colonies in Lakes Ontario and Erie, the Niagara River, Detroit River, and south-eastern parts of Lake Huron. Most adult Herring Gulls from the Great Lakes population winter in these areas, but there is no published account of their food habits other than during the breeding season. Most pellets from colonies close to large urban centres contained remains of garbage, as well as various fish species. Small mammals, notably Deer Mice (Peromyscus maniculatus) dominated the early spring diet at Lake Huron colonies near agricultural areas. At all other sites fish predominated in pellets and faeces, but garbage items were also recorded regularly. The species of fish consumed varied regionally, probably reflecting local availability. In Lake Ontario, Rainbow Smelt (Osmerus mordax) and Alewife (Alosa pseudoharengus) occurred most frequently in samples, whereas Freshwater Drum (Aplodinotus grunniens) was the main fish prey in Lake Erie and the Detroit River. Dietary differences were apparent between years, within seasons, and amongst areas. While these may have reflected some real differences in food availability, interpretation of these results was confounded by various biases inherent in the sampling of pellets and faeces to determine diet in such an opportunistic species. Therefore, it would be unwise to draw rigid conclusions as to regional or seasonal differences in the diets of piscivorous birds, based upon analyses of diet from only a small sample of sites or years. Herring Gulls appear to feed mainly on fish and garbage in winter and early spring on the lower Great Lakes (much as during the breeding season), but any locally abundant food source is probably exploited opportunistically.     

Health checks on patients 75 years and over in Nottinghamshire after the new GP contract.

OBJECTIVE--To investigate annual health checks for patients of 75 years and over required by the 1990 contract for general practitioners. DESIGN--Visits to practices to collect information on how assessments were organised and carried out; completion of questionnaires for every patient who had been assessed in a sample month, using information provided by the practice records. SETTING--20 general practices in one family health services authority. SUBJECTS--Patients of 75 years and over in 20 general practices. RESULTS--Three practices (15%) had not performed checks. Thirteen practices sent a letter to invite patients to undergo a check. Of these practices, seven followed up non-responders. Two practices visited patients'' homes unannounced, and two did checks on an opportunistic basis only. Sixteen practices used a checklist. Sixteen practices involved their practice nurses; at eight of these, doctors also performed checks; in six practices the nurses undertaking the checks had no training in assessing old people. Ten practices assessed more than 75% of their old people in the first year of the new contract. Practices that did not follow up patients who had not responded to the invitation for assessment completed significantly fewer checks. During the sample month, 331 patients were assessed in the 17 practices. 204 new problems were discovered in 143 patients. Significantly more problems per patient were found in inner city areas. CONCLUSIONS--The way health checks were performed varied greatly, both in their organisation and the practices'' attitudes. Many old people did not respond to letters asking if they wanted an assessment but very few refused one if followed up. Forty three per cent of those assessed had some unmet need. The number of new problems found per patient may reduce over the next few years if the assessments are successful. The need for annual assessment should be kept under review and adequate resources made available for the needs uncovered. Improved training for practice nurses in assessment is needed. Effectiveness of the checks must be monitored. If most unmet need falls in particular high risk groups it would seem sensible to modify the annual check to target these groups.     

Direct arteriovenous connections and the intermediate circulation in dog spleen,studied by scanning electron microscopy of microcorrosion casts

Summary The exact nature of the circulatory pathways in dog spleen, particularly with reference to the intermediate circulation and the possible existence of direct arteriovenous connections, has been studied by scanning electron microscopy (SEM) of microcorrosion casts. A new casting procedure was developed in which minimal amounts of material were injected into contracted spleens, thus filling preferentially the faster channels for flow. Extensive filling of the red pulp was thereby avoided, leaving an open view of blood vessels and their connections. The depth of focus of the SEM, incomparably greater than those of transmission electron or light microscopes, enabled vascular pathways to be traced over considerable distances.Using this approach, we have obtained clear evidence for abundant connections between arterial capillaries and venous sinuses (i.e., closed circulation). Typically, the terminal arteriole bifurcates repeatedly, in quick succession, giving rise to as many as twelve short capillaries, each leading directly to at least one sinus. However, an open circulation also exists, inasmuch as the majority of all capillaries end in the marginal zone around lymphatic nodules. In the dilated spleen, direct connections to sinuses are rarely visible but endings in the red pulp are found, in addition to those going to the marginal zone.