Retroviral-mediated gene transfer into mammalian cells

Retroviruses may be used as genetic vectors to transfer genes into mammalian cells with high efficiency. We have shown that the N2 vector will transfer a functional bacterial gene for neomycin resistance (NeoR) into more than 80% of mouse spleen foci. A derivative of the N2 vector was constructed to study transfer and expression of the human gene for adenosine deaminase (ADA) in mammalian lymphoid and hematopoietic stem cells. This vector, termed SAX, contains the human ADA cDNA with an SV40 promoter in addition to the NeoR gene. The SAX vector was found to efficiently transfer and express the ADA gene in an ADA-deficient human T-cell line. Gene transfer by SAX using an autologous nonhuman primate bone marrow transplant model resulted in expression of the human ADA gene in peripheral blood cells of treated animals. Human bone marrow treated with SAX produced 1%-2% of colonies in vitro that were expressing the vector genes. Transfer of genes into circulating hematopoietic stem cells of fetal sheep in utero was most efficient; vector gene expression was evident in 20%-40% of hematopoietic colonies. Therefore, retroviral vectors are capable of transferring functional genes into a wide variety of mammalian lymphoid and hematopoietic cells. Such vectors may be useful for clinical trials of gene therapy, that is, the correction of genetic diseases by insertion of a normal gene into a patient's defective cells.     

A new moderately repetitive DNA sequence family of novel organization.

In cloning adenovirus homologous sequences, from a human cosmid library, we identified a moderately repetitive DNA sequence family consisting of tandem arrays of 2.5 kb members. A member was sequenced and several non-adjacent, 15-20 bp G-C rich segments with homology to the left side of adenovirus were discovered. The copy number of 400 members is highly conserved among humans. Southern blots of partial digests of human DNA have verified the tandem array of the sequence family. The chromosomal location was defined by somatic cell genetics and in situ hybridization. Tandem arrays are found only on chromosomes 4 (4q31) and 19 (q13.1-q13.5). Homologous repetitive sequences are found in DNA of other primates but not in cat or mouse. Thus we have identified a new family of moderately repetitive DNA sequences, unique because of its organization in clustered tandem arrays, its length, its chromosomal location, and its lack of homology to other moderately repetitive sequence families.     

Presence and development of populations of the introduced brown alga Sargassum muticum in the southwest Netherlands

Of the three Brachionus species used in aquaculture, Brachionus rubens, B. calycilorus and B. plicatilis, the latter is most widely used in raising marine fish and shrimp larvae due to its tolerance to the marine environment. In freshwater aquaculture the use of B. rubens and B. calycilorus is limited, probably because inert food products are readily available as feed for freshwater larvae.The rotifer Brachionus plicatilis is used in large numbers as the first food organism in intensive cultures of marine fish and shrimp larvae. An adequate supply of these rotifers relies on mass cultures. The reproductive rate of rotifers in these cultures depends on food quality and quantity, salinity, temperature and pH of the medium. Removal of waste products from culture tanks leads to higher and more efficient production of rotifers over extended periods of time. Rotifers have to be enriched with polyunsaturated fatty acids, which are essential for proper development and survival of marine fish and shrimp larvae.The future use of preserved rotifers and their resting eggs may help to overcome unforeseen failures of live cultures and may lead to more efficient use of these organisms in raising freshwater and marine fish and shrimp larvae.     

A quantitative analysis of the annual phytoplankton cycle of the Magdalena lagoon complex (Mexico)

An annual cycle of the micro- and nanophytoplankton cell densitiesof whole water samples in combination with the species composition,distribution and diversity of the microphytoplankton fractionin the Magdalena lagoon system, Mexico, has been studied ona bi-monthly basis. Two major patterns were detected: from Novemberto May, high microphytoplankton densities (0.5–1.5 10⁶cells l^–1 prevail throughout a large part of the investigatedarea; from late spring to late autumn cell densities are muchlower (5–250 10³ cells l^–1). During each perioda number of microplankton assemblages occur, each with its characteristicdiversity and stability. The distribution and density of themicrophytoplankton is clearly related to the presence of nutrient-richwater pockets and the prevailing winds for part of the year,as documented in earlier hydrological studies. The nanophytoplanktonplayed a minor role during most of the year; this fraction dominatedquantitatively in only a few cases. Based on these data, theMagdalena lagoon complex can be considered a very productivearea. This is further substantiated by the presence of largequantities of several sardine and mackerel species, feedingalmost exclusively on microphytoplankton. This reveals the existenceof an important short chain pathway in the food web of thiscoastal lagoon system     

The functioning of the ecosystem of the Banc d'Arguin,Mauritania: a review

The Banc d'Arguin, Mauritania, is an area of over 10 000 km² of shallow water and tidal flats between the Sahara and the upwelling system off the Mauritanian coast. The results of the Dutch-Mauritanian project Banc d'Arguin 1988 as well as the relevant literature are reviewed in order to develop a preliminary conceptual model of the functioning of this ecosystem. Hydrographically the Banc d'Arguin can be characterized as a large-scale negative estuary with higher salinities near the shore. It is concluded that ultimately the Banc d'Arguin ecosystem is fueled by nutrients and organic matter derived from the upwelling area. The inner part of the Banc d'Arguin system is dominated by a detritus-based benthic foodweb in which seagrasses are the principal primary producers. Little of the seagrass production seems to be exported to other parts of the system or other areas. Zooplankton and zoobenthos biomasses are relatively low, but nevertheless support high densities of consumers. Aquatic birds are especially numerous. The study identifies many research topics for the future.     

Can martial arts techniques reduce fall severity? An in vivo study of femoral loading configurations in sideways falls

Sideways falls onto the hip are a major cause of femoral fractures in the elderly. Martial arts (MA) fall techniques decrease hip impact forces in sideways falls. The femoral fracture risk, however, also depends on the femoral loading configuration (direction and point of application of the force). The purpose of this study was to determine the effect of fall techniques, landing surface and fall height on the impact force and the loading configuration in sideways falls. Twelve experienced judokas performed sideways MA and Block ('natural') falls on a force plate, both with and without a judo mat on top. Kinematic and force data were analysed to determine the hip impact force and the loading configuration. In falls from a kneeling position, the MA technique reduced the impact force by 27%, but did not change the loading configuration. The use of the mat did not change the loading configuration. Falling from a standing changed the force direction. In all conditions, the point of application was distal and posterior to the greater trochanter, but it was less distal and more posterior in falls from standing than from kneeling position. The present decrease in hip impact force with an unchanged loading configuration indicates the potential protective effect of the MA technique on the femoral fracture risk. The change in loading configuration with an increased fall height warrant further studies to examine the effect of MA techniques on fall severity under more natural fall circumstances.