Histochemical studies on the lipids in the epithelium of the fetal colon

Summary Large intestines from 30 fetuses with crown-rump lengths ranging from 26 to 180 mm have been studied histochemically as to their epithelial content of lipids. These lipids have been localized intracellularly and basally in the cells, and comparative studies of the colon and the small intestine have demonstrated that there are considerable amounts of lipids in the colon as compared with the small intestine.It is concluded that the main part of the lipids consist of saturated and unsaturated constituents.The possible explanations of the lipids as absorbed material, biological active material synthetized de novo or as material involved in the metabolism of fetal surface cells are discussed.This work was supported by a grant from the Aid of the Crippled Children, New York.     

Lectin binding in skeletal muscle. Evaluation of alkaline phosphatase conjugated avidin staining procedures

Summary Cryostat sections from rat gracilis muscles were incubated with different biotinylated lectins: Con A (Concanavilin A), WGA (Wheat germ agglutinin), SBA (soybean agglutinin), GS I and GS II (Griffonia simplicifolia agglutinin), LCA (Lens culinaris agglutinin), PNA (peanut agglutinin) and PSA (Pisum sativum agglutinin). The sections were subsequently treated with alkaline phosphatase conjugated avidin. The lectin binding sites were visualized after incubation in substrate media containing: (1) 5-bromo-4-chloro indoxyl phosphate and Nitro Blue tetrazolium or copper sulphate; (2) naphthol AS-MX phosphate or naphthol AS-BI phosphate and various types of diazonium salts; (3) -naphthylphosphate and Fast Blue BB; (4) -glycerophosphate according to the method of Gomori. The results obtained with the alkaline phosphatase methods were compared with those seen with a streptavidin-horseradish peroxidase procedure. Several chromogen protocols for visualizing alkaline phosphatase activity showed differences in the ability to detect lectin binding sites. A sarcoplasmic reaction was evident for Con A, GS II, WGA, LCA, and PSA after incubation in the indoxyl phosphate medium. Sarcoplasmic reaction for GS II was also noticed after incubation with naphthol AS-MX Fast Blue BB and -glycerophosphate. The latter substrate also gave rise to a sarcoplasmic Con A reaction. With the indoxylphosphate tetrazolium salt method some muscle fibres showed a very strong intracellular reaction after incubation with Con A and GS II while the staining intensity was weak in other fibres. The same muscle fibres were stained with PAS. No sarcoplasmic reactions were observed with either naphthol phosphate media or with the diaminobenzidine peroxidase methods. Further, the staining of the muscle fibre periphery, connective tissue, and capillaries was intensified using the indoxyl method. The indoxylphosphate-tetrazolium salt method seems to be suitable for future investigations of lectin binding sites in muscle sections.     

Genetic diversity and phylogenetic analysis of native mountain ponies of Britain and Ireland reveals a novel rare population

The conservation of unique populations of animals is critical in order to preserve valuable genetic diversity and, where populations are free‐living, maintain their irreplaceable influence upon habitat ecology. An accurate assessment of genetic diversity and structure within and between populations is crucial in order to design and implement conservation strategies in natural and domesticated species. Moreover, where it is possible to identify relic populations that are related to a structured breed an ideal opportunity presents itself to model processes that reveal historical factors that have shaped genetic diversity. The origins of native UK mountain and moorland ponies are uncertain, but they may have directly descended from prehistoric populations and potentially harbour specific adaptations to the uplands of Britain and Ireland. To date, there have been no studies of population structure and genetic diversity present within a free‐living group of ponies in the Carneddau mountain range of North Wales. Herein, we describe the use of microsatellites and SNPs together with analysis of the mitochondrial control region to quantify the extent and magnitude of genetic diversity present in the feral Carneddau pony and relate this to several recognised British and Irish pony breeds. Our results establish that the feral Carneddau ponies represent a unique and distinctive population that merits recognition as a defined population and conservation priority. We discuss the implications for conservation of this population as a unique pool of genetic diversity adapted to the British uplands and potentially of particular value in maintaining the biodiversity of these habitats.     

Evidence of glutathione transferase complexing and signaling in the model nematode Caenorhabditis elegans using a pull-down proteomic assay

Phage display techniques using random peptide interactions have supported the role of mammalian glutathione transferase (GST) as part of a signalling pathway for both oxidative stress and an apoptosis pathway. Little is known about the interaction of nonmammalian GST with other proteins. GSTs have been implicated in the development of chronic nematode infections by neutralising cytotoxic products arising from host immune initiated reactive oxygen species (ROS) assault. In this study we attached one of the key GSTs expressed in the model nematode Caenorhabditis elegans to an affinity support matrix and directly identified major interacting proteins by two-dimensional electrophoresis and peptide mass fingerprinting before and following oxidative stress. Nematode GST does not appear to be a stand-alone enzyme and interacts with many types of proteins in both normal and ROS stress conditions. Pull-down proteomic presents a flexible, label free, rapid and economical assay without specialised ligand fishing equipment to identify protein binding partners.     

Pollen and non-pollen palynomorph evidence of medieval farming activities in southwestern Greenland

Radiocarbon dating, pollen and non-pollen palynomorph analyses from a lake core were used to establish the timing and effects of farming activities around Lake Igaliku, Eastern Settlement, Greenland. The absence of agro-pastoral impact before the medieval colonization by Europeans provides an opportunity to understand the development of farming activity in a pristine landscape. The results show that the first phase of clearance and grazing pressure, without the expansion of the Norse apophyte (native plant, in habitats created by humans) Rumex acetosa type, could have occurred in the 9–10th century a.d. The presence of Norse settlers and livestock is clearly recorded from the 11–12th century a.d. with increasing frequencies of the Norse apophytes Rumex acetosa type and Ranunculus acris type, and coprophilous fungi. This colonization phase is followed by a period of decreasing human impact at the beginning of the 14th century, with a decrease in weeds, apophytes and coprophilous fungi suggesting a reduced grazing pressure. The regrowth of Salix and Betula and the disappearance of anthropogenic indicators except Rumex acetosa type between the 15th and 18th century demonstrate the abandonment of the settlement, until the development of contemporary agriculture in the 20th century.     

Microclimate variability in alpine ecosystems as stepping stones for non‐native plant establishment above their current elevational limit

Alpine environments are currently relatively free from non‐native plant species, although their presence and abundance have recently been on the rise. It is however still unclear whether the observed low invasion levels in these areas are due to an inherent resistance of the alpine zone to invasions or whether an exponential increase in invasion is just a matter of time. Using a seed‐addition experiment on north‐ and south‐facing slopes (cf. microclimatic gradient) on two mountains in subarctic Sweden, we tested the establishment of six non‐native species at an elevation above their current distribution limits and under experimentally enhanced anthropogenic pressures (disturbance, added nutrients and increased propagule pressure). We found a large microclimatic variability in cumulative growing degree days (GDD) (range = 500.77°C, SD = 120.70°C) due to both physiographic (e.g. aspect) and biophysical (e.g. vegetation cover) features, the latter being altered by the experimental disturbance. Non‐native species establishment and biomass production were positively correlated with GDD along the studied microclimatic gradient. However, even though establishment on the north‐facing slopes caught up with that on the south‐facing slopes throughout the growing season, biomass production was limited on the north‐facing slopes due to a shorter growing season. On top of this microclimatic effect, all experimentally imposed anthropogenic factors enhanced non‐native species success. The observed microclimatic effect indicates a potential for non‐native species to use warm microsites as stepping stones for their establishment towards the cold end of the gradient. Combined with anthropogenic pressures this result suggests an increasing risk for plant invasion in cold ecosystems, as such stepping stones in alpine ecosystems are likely to be more common in a future that will combine a warming climate with persistent anthropogenic pressures.     

Histochemical and electron microscopical studies on the epithelium of the fetal colon with special reference to the occurrence of lipids

Summary Absorbing cells of the colon of 28 human fetuses were studied histochemically while 4 were studied ultrastructurally. Cellular ultrastructure included: microvilli with a fuzz, typically lateral specializations, small mitochondria placed at the peripheral part of the cells, apically placed lysosomes, basally placed lipid droplets and disperse accumulations of glycogen. Only a slight pinocytosis was observed and the endoplasmic reticulum and Golgi apparatus were only poorly developed. Comparing the enzymatic findings with the ultrastructural findings, it is suggested that some absorption may take place in the fetal large intestine. It is further considered whether an intracellular synthesis of lipids may occur.This study has been supported by a grant from the Association of the Aid of the Crippled Children, New York.     

Eme1 is involved in DNA damage processing and maintenance of genomic stability in mammalian cells

Yeast and human Eme1 protein, in complex with Mus81, constitute an endonuclease that cleaves branched DNA structures, especially those arising during stalled DNA replication. We identified mouse Eme1, and show that it interacts with Mus81 to form a complex that preferentially cleaves 3'-flap structures and replication forks rather than Holliday junctions in vitro. We demonstrate that Eme1-/- embryonic stem (ES) cells are hypersensitive to the DNA cross-linking agents mitomycin C and cisplatin, but only mildly sensitive to ionizing radiation, UV radiation and hydroxyurea treatment. Mammalian Eme1 is not required for the resolution of DNA intermediates that arise during homologous recombination processes such as gene targeting, gene conversion and sister chromatid exchange (SCE). Unlike Blm-deficient ES cells, increased SCE was seen only following induced DNA damage in Eme1-deficient cells. Most importantly, Eme1 deficiency led to spontaneous genomic instability. These results reveal that mammalian Eme1 plays a key role in DNA repair and the maintenance of genome integrity.