Pharmacokinetics of a porcine insulin zinc suspension in diabetic dogs

Ten dogs with naturally occurring diabetes mellitus were injected with a highly purified porcine insulin zinc suspension at a dose according to their expected requirement. Plasma insulin and glucose concentrations were measured at two-hourly intervals over 24 hours following injection. There were either one or two peaks in plasma insulin concentration: one at about four hours (mean 4.3 21.3 [SD]) and another at about 11 hours (mean 11 pM1-85) after the injection. The second insulin peak was seen in only eight dogs. Persistence of elevated plasma insulin concentrations ranged from 14 to 24 hours (mean 17.4 pM 3.65). These results compare favourably with those published for other intermediate-acting insulin preparations used to treat canine diabetes mellitus and suggest that this preparation has useful properties for the successful management of many canine diabetics.     

Performance of Solanum habrochaites LA1777 introgression line hybrids for marketable tomato fruit yield in Asia

Wild relatives of the cultivated tomato (Solanum lycopersicum L.) are major sources of new genetic diversity for tomato improvement. Introgression lines (IL) are near-isogenic lines homozygous for one or several mapped wild DNA fragments in a common recurrent parent. A set of ILs developed by Cornell University from Solanum habrochaites accession LA1777 and recurrent parent E6203 has been made publicly available through the Tomato Genetics Resource Center of the University of California-Davis. Our objective was to identify LA1777 introgressions with potential to increase the marketable fruit yield of tomato grown in the tropics. A subset of ILs were each crossed to CLN2498E (resistant to bacterial wilt and some begomoviruses) to create IL hybrids (ILH). ILH, IL recurrent parent E6203, CLN2498E, and CLN2498E × E6203 (Hchk) were evaluated in replicated trials in Thailand, India, and Taiwan during two dry seasons. Highly significant effects for marketable fruit yield were detected in Thailand and Taiwan. ILH heterozygous for S. habrochaites segments at the bottom of chromosome 1 yielded about 20% than the Hchk at Thailand and Taiwan. Our results agree with previous results from Cornell University researchers who found a segment of S. habrochaites DNA located between TG158 and TG27 associated with increased total fruit yield in previous trials conducted in upper state New York. Yield improvement due to this S. habrochaites introgression can occur over a wide range of environments.     

Quantitative trait loci for phytate in rice grain and their relationship with grain micronutrient content

Phytate (inositol-hexa-phosphate) has an important role in plants but it also may have anti-nutritional properties in animals and humans. While there is debate within the plant breeding and nutrition communities regarding an optimum level in grain, there appears to be little information at the molecular level for the genetics of this trait, and its association with important trace elements, in particular, Fe and Zn. In this preliminary study, quantitative trait loci (QTL) for grain phytates, Zn and Fe in glasshouse-grown rice lines from an IR64 × Azucena doubled haploid population were identified. Correlations between phytate and essential nutrients were also studied. Transgressive segregation was found for most traits. Phytate and total P concentrations had one QTL in common located on chromosome five with the (high concentration) allele contributed from Azucena. There were significant positive correlations between phytate and inorganic phosphorus (P), total P, Fe, Zn, Cu and Mn concentrations for both grain concentration and content. However, the QTLs of phytate were not located on the same chromosomal regions as those found for Fe, Zn and Mn, suggesting that they were genetically different and thus using molecular markers in breeding and selection would modify the phytate level without affecting grain micronutrient density.     

Conservation of marker synteny during evolution

Summary An aspect of cereal science that is becoming increasingly important is comparative genetics. Establishment of the relationship between genomes within polyploids, between species within tribes and between species within families will allow not only the integration of genetic maps but also the knowledge acquired of each of the species. Using a set of homoeologous probes, workers found the relationship between the three wheat genomes to be precisely collinear, after taking a few major translocation events into account. Transfer of the wheat map to rye led to the elucidation of similar relationships between the three wheat genomes and that of rye. Genome collinearity, however, extends even beyond tribes. In a comparison of the genomes of wheat, rice and maize, it was shown that despite the separation of these genomes for possibly 50 million years, gene order was still highly conserved. This collinearity between genomes can be exploited in a number of ways.     

A gene for hybrid necrosis in an inbred line of rye (Secale cereale L.)

Summary An inbred line of rye (Secale cereale L.) has been found to carry a gene for hybrid necrosis. This gene was detected in crosses with a highly crossable wheat (Triticum aestivum L.) genotype which carries the gene Ne₂. This appears to be the first report of a gene for hybrid necrosis being present in the rye genome.     

Progress in mapping agronomic genes in apple (The European Apple Genome Mapping Project)

Summary The progress of the European Apple Genome Mapping Project is described. Populations segregating for a range of agronomic genes have been established in six European countries. The need for robust methods of analysis has been identified, especially with regard to the development of molecular markers. Isozyme systems, RAPDs, RFLPs and amplified genes are being used to construct a reference genetic linkage map. Standardisation and precise definition of both genotypic and phenotypic measurements has been recognised as being essential for future exploitation of genetic markers in apple breeding. Phenotypic measurements are being replicated in different geographical locations over several years. Statistical and genetic analyses are aimed at defining components of genetic variation which account for ‘genes’, as defined by apple breeders. A relational database is being constructed which will combine disparate sources of data relating to the genetics of apple. Comparative mapping has been identified as an efficient means of expanding genetic knowledge within and between Rosaceae genomes.     

Leaf litter decomposition in a chaparral ecosystem, Southern California

Decomposition losses from leaves of three evergreen chaparral species, scrub oak (Quercus dumosa), ceanothus (Ceanothus crassifolius), and manzanita (Arctostaphylos glauca), were quantified over a 2-y field exposure using litterbags. Changes in ash-free dry mass, C, and N were monitored at 2- to 6-month intervals at four replicate sites composed of patches of these three chaparral species. Three proximate C fractions were extracted from fresh and decomposing litter samples: polar and non-polar extractives (EXT), acid-solubles (ACID), and acid-insolubles (KLIG). The chemical structure of fresh and decomposed litter was additionally characterized using high-resolution solid-state ¹³C NMR spectroscopy, while morphological properties were examined by scanning electron microscopy (SEM). After 2 y, the litters had lost between 20.7%±1.2 (Ceanothus) and 35.2%±6.8 (Quercus) of their original ash-free dry mass. The manzanita decomposed at a significantly faster rate than the other two litter types during the first few months of field exposure. Yet, after 2 y, mass loss was greater for the oak. Differences in decomposition rates could not be accounted for based on a single litter quality index. Fresh manzanita exhibited a significantly higher N content, which could explain its initially faster decay rate. Fresh oak litter, on the other hand, had a relatively high ACID and O-alkyl C (O-ALK) content, which may have been responsible for its decay pattern. Fresh ceanothus contained a relatively low KLIG content, yet it decomposed more slowly than the two other species. The solid-state ¹³C NMR spectra of the ceanothus litter had two peaks characteristic of proanthocyanidins, which likely contributed to the recalcitrance of this litter type. SEM revealed that ceanothus leaf surfaces were left nearly unchanged after field exposure. In comparison, the oak and manzanita leaf surfaces were pitted and covered by microbial growth to the point of being unrecognizable. Taken together, our results indicate that a combination of biological, physical and chemical factors need to be examined to clarify the different decomposition rates and patterns of these three chaparral species.     

Organic matter status and the size,activity and metabolic diversity of the soil microflora as indicators of the success of rehabilitation of mined sand dunes

The effectiveness of the rehabilitation of mined sand dunes on the northern coast of KwaZulu–Natal, South Africa, was assessed based on measurements of the total and labile organic matter content and the size, activity and metabolic diversity of the soil microflora. Soil was sampled (0–10 cm) after 0, 5, 10, 20 and 25 years of rehabilitation and compared with soil under undisturbed native forest and under long-term commercial pine forest. Following topsoil removal, stockpiling and respreading on reformed dunes, there was a massive loss of organic C such that, at time zero, organic C content was only 24% of that present under native forest. Soil organic C content increased progressively during rehabilitation until, after 25 years, it represented 93% of that present under native forest. The pattern of change in light-fraction C, KMnO₄-extractable C, water-soluble C, microbial biomass C, basal respiration and arginine ammonification rate was broadly similar to that for organic C, but the extent of the initial loss and the magnitude of the subsequent increase differed. Microbial biomass C, water-soluble C and KMnO₄-extractable C, expressed as a percentage of organic C, declined during rehabilitation as humic substances progressively accumulated. Principal component (PC) analysis of catabolic response profiles to 36 substrates revealed that the catabolic diversity of microbial communities differed greatly between native forest, commercial pine forest, 0 years and 10 years of rehabilitation. On the PC1 axis, values for soils under native forest and after 25 years rehabilitation were similar, but there was still separation on the PC2 axis. The main factor explaining variation in response profiles on the PC1 axis was organic C content; and the greatest catabolic diversity occurred in soils under native forest and after 25 years of rehabilitation.     

Spatiotemporally interactive growth dynamics in selected South African forests: Edaphoclimatic environment, crowding and climate effects

Stand-level tree diameter growth patterns were explored for evergreen moist forests in the southern Cape, South Africa. Results of standard multiple regression analyses, involving 934 permanent sample plots with data spanning a 10-year interval, revealed that stand-level increment of canopy species in the canopy layer (>30 cm dbh) was significantly determined by inherent species-specific growth capacities (species composition of the stand), water availability, forest matrix crowding and tree condition impairment (age-related manifestations of reduced vitality indicated by signs of crown die-back, damage and stem rot). In contrast, stand-level increment of trees of canopy species in the subcanopy layer (10-20 cm dbh) was prominently shaped by light availability, as mainly determined by the degree of canopy-level disturbance (mortality rate of trees >30 cm dbh), crowding (canopy-level overhead and forest matrix crowding) and proximity to conspecific adults (within 6-8 m). In addition to species-inherent and resource factors, considerable variation in stand-level growth resulted from site-climate interactions. For 507 of the permanent sample plots, increment data was available for two consecutive 10-year intervals; permitting the analysis of spatiotemporal interactions of growth patterns (repeated measures ANOVA). In the Knysna forests higher canopy-level increment rates were associated with the moister southerly facing slope sites in comparison with the drier northerly facing and ridge sites during the first increment period. During the second increment period, increment rates on the drier, but better illuminated sites had increased disproportionately. In contrast, in the Tsitsikamma forests, higher increment rates during the second increment period were encountered on moister flat bottomland sites (with extended periods of subsoil wetness) than on the comparatively drier southerly facing slope sites (increment period × site-based water availability × forests interaction). In both forests relatively higher growth performance of subcanopy-level trees during the second increment period was associated with stands experiencing conditions of enhanced light availability. Atmospheric temperatures were higher during the second increment period (mean periodic T_max: + 0.64 °C). The detected spatiotemporal interactions were interpreted as site × climate interactions where site-related conditions of favourable light or water availability resulted in enhanced temperature-linked growth responses during the second increment period. A metabolic performance trade-off model provided a framework for the interpretation of these complex site-climate interactions by placing the patterns of forest growth into an ecophysiological explanatory context.