Acetyl-l-carnitine as a precursor of acetylcholine

Synthesis of [³H]acetylcholine from [³H]acetyl-l-carnitine was demonstrated in vitro by coupling the enzyme systems choline acetyltransferase and carnitine acetyltransferase. Likewise, both [³H] and [¹⁴C] labeled acetylcholine were produced when [³H]acetyl-l-carnitine andd-[U-¹⁴C] glucose were incubated with synaptosomal membrane preparations from rat brain. Transfer of the acetyl moiety from acetyl-l-carnitine to acetylcholine was dependent on concentration of acetyl-l-carnitine and required the presence of coenzyme A, which is normally produced as an inhibitory product of choline acetyltransferase. These results provide further evidence for a role of mitochondrial carnitine acetyltransferase in facilitating transfer of acetyl groups across mitochondrial membranes, thus regulating the availability in the cytoplasm of acetyl-CoA, a substrate of choline acetyltransferase. They are also consistent with a possible utility of acetyl-l-carnitine in the treatment of age-related cholinergic deficits.     

Seed size variation: magnitude,distribution, and ecological correlates

Summary We examined seed-mass variation in 39 species (46 populations) of plants in eastern-central Illinois, USA. The coefficient of variation of seed mass commonly exceeded 20%. Significant variation in mean seed mass occurred among conspecific plants in most species sampled (by hierarchical ANOVA), averaging 38% of total variance. For most species, within-plant variation was the larger component of total variance, averaging 62% of total variance. Variation in seed mass among fruits within crops was significant in most species tested.We conclude that variation in seed mass among and within plants is widespread and common. There was little evidence of trade-offs between number of seeds and mean or variance of seed mass, and little correlational evidence of local competition for maternal resources. No consistent ecological (dispersal mode and growth form) correlates of variance of seed mass were evident.     

The nature and role of learning in the orientation and migratory behavior of fishes

Synopsis Fish migration may be viewed as the product of two processes; the selection and tracking of optimal environmental conditions through time and space, and the use of predictive information about environmental structure to bias movements towards a goal. The establishment and maintenance of directional bias is based on the interaction of experience and instinct. The preoccupation of much fish orientation research with innate fixed patterns of behavior on one hand and hydrodynamics on the other has led us to underestimate the possibility that orientation is a flexible process relying on developmental sequences, calibration of the motor-sensory interaction based on experience and the learning of environmental pattern. Evidence illustrating how experience and learning may influence the direction of movement and how the goal is recognized is presented according to two general categories: (a) imprinting and early experience and (b), spatial learning, including the social transmission of migratory routes and directions. In the first category, the olfactory hypothesis of salmon homing is briefly reviewed and new data presented describing olfactory imprinting in Atlantic salmon,Salmo salar. In the second category, evidence is presented demonstrating the modifiability of sun-compass orientation and the ability of some fish species to learn the spatial distribution of landmarks. The role of social transmission in the migration of coral reef fishes is reviewed. The possible role of these learning phenomena in the formation of familiar area maps, route-based and location-based navigation and the critical distance factor is considered. The relationship between life history and the nature of learning in migratory orientation is discussed     

Agroinfection and nucleotide sequence of cloned wheat dwarf virus DNA

Cloned DNA of the geminivirus wheat dwarf virus (WDV) was successfully used to infect seedling wheat plants. The clone was derived from circular double-stranded viral DNA isolated from naturally infected tissue. The initiation of infection was mediated by Agrobacterium tumefaciens using cloned dimeric WDV genomes in a binary Agrobacterium vector. The WDV DNA which comprised the infectious clone was sequenced and is compared with the published sequence of a Swedish isolate of the same virus. The results confirm that the single WDV genome component of 2.75 kb carries all the information necessary for production of viral symptoms, virus particles and viral double- and single-stranded DNA forms.     

Comparison of bioassay and radioimmunoassay data for study of changes in the pattern of LH secretion from birth to puberty in the heifer

To define gonadotrophin secretion rates in the prepubertal heifer, 12 Hereford x Friesian heifers were blood-sampled at 15-min intervals for periods of 24 h every 4 weeks from 3 weeks of age until puberty. Radioimmunoassay of plasma LH concentrations showed that, although LH episode frequency increased with age, overall mean LH concentrations and basal LH concentrations decreased between 3 and 15 weeks of age and then increased to 35 weeks of age. The validity of these trends in relation to biological activity of plasma LH was investigated using an in-vitro Leydig cell bioassay. Samples were selected from 24-h profile bleeds of 4 heifers at 3, 7, 11, 15, 19, 27 and 39 weeks of age. No significant differences were found in the patterns of change in overall mean LH concentrations, basal LH concentrations or LH episode amplitude when comparing the estimates obtained by radioimmunoassay with those by bioassay from birth over the prepubertal period. These results indicate that the changes with age observed by radioimmunoassay are representative of changes in biologically active hormone.     

Determination of the age of young American eels, Anguilla rostrata, in fresh water, based on otolith surface area and microstructure

The time elvers of the American eel, Anguilla rostrata , spend in an estuary prior to their migration into fresh water was assessed. A distinct mark was formed on elvers' otoliths during their first 2 to 3 weeks in the river estuary. This mark was used to distinguish between growth in fresh water and in salt water. Migrating eels collected at a falls 4 km from the estuary exhibited bimodal length and weight distributions. Frequency distributions showed that eels collected in the estuary were smaller and had smaller otoliths than eels collected at the falls, indicating that elvers do not reach the falls in the same year as they enter the estuary. The three modal groups most probably represent three age–classes. However, the otoliths of elvers collected in the estuary had only the mark of transition whereas eels in the first and second mode at the falls usually had two rings (1–4) and four rings (3–6) per otolith, respectively, in addition to the mark of transition, as viewed under SEM. The possibility that ring formation is not annual means that the use of otoliths for the age determination of eels in this study has not been validated.     

Improved media for normal human muscle satellite cells: Serum-free clonal growth and enhanced growth with low serum

Summary We have developed a serum-free medium for clonal growth of normal human muscle satellite cells (HMSC). It consists of an optimized nutrient medium MCDB 120, plus a serum-free supplement, designated SF, that contains epidermal growth factor (EGF), insulin, dexamethasone, bovine serum albumin, and fetuin. Fibroblast growth factor was needed with dialyzed fetal bovine serum (dFBS) as the only other supplement, but in media containing SF, it was only slightly beneficial, and was omitted from the final medium without significant loss. Clonal growth of HMSC in MCDB 120 plus SF is as good as with 15% serum and 0.5% chicken embryo or bovine pituitary extract. However, growth is further improved by use of a doubly-supplemented (DS) medium containing both SF and 5% dFBS. Clonal growth of HMSC in the DS medium far exceeds that in previous media with any amount of serum, and monolayer growth is at least equal to that in conventional media with higher levels of serum. Cells grown in these media exhibit little differentiation, even when grown to high densities. However, they retain the capacity for extensive fusion and synthesis of increased creatine kinase when transferred to a serum-free differentiation-promoting medium, such as Dulbecco's modified Eagle's medium plus insulin. All experiments were done with clonal cultures of HMSC to insure that observed growth responses were always those of muscle cells. This research was supported by a grant from the Muscular, Dystrophy Association. Editor's statement This article describes the optimization of both the basal nutrient medium and growth factor requirements for human muscle cells in vitro. This system is critical for studies of normal muscle cell and molecular biology, as well as for understanding diseases of muscle such as Duchenne, Muscular Dystrophy.     

Mapping of FMR1, the gene implicated in fragile X-linked mental retardation, on the mouse X chromosome

A genetic map of the Cf-9 to Dmd region of the mouse X chromosome has been established by typing 100 offspring from a Mus musculus x Mus spretus interspecific backcross for the four loci Cf-9, Cdr, Gabra3, and Dmd. The following order and genetic distances in centimorgans were determined: (Cf-9)-2.4 +/- 1.7-(Cdr)-2.0 +/- 1.4-(Gabra3)-4.1 +/- 2.0-(Dmd). Six backcross offspring carrying X chromosomes with recombination events in the Cdr-Dmd region were identified. These recombination events were used to define the position of Fmr-1, the murine homologue of FMR1, which is the gene implicated in the fragile X syndrome in man, and that of DXS296h, the murine homologue of DXS296. Both Fmr-1 and DXS296h were mapped into the same recombination interval as Gabra3 on the mouse X chromosome. These findings provide strong support for the concept that the order of loci lying in the Cf-9 to Gabra3 segment of the X chromosome is highly conserved between human and mouse.     

Fingerprinting human chromosomes by polymerase chain reaction-mediated DNA amplification.

We describe here a method for DNA fingerprinting of human chromosomes by Alu-polymerase chain reaction (PCR) amplification of DNA from monochromosomal hybrids, following digestion with restriction endonucleases. DNA digestion with restriction enzymes prior to PCR amplification reduces the total number of amplified fragments. The number and pattern of bands of PCR products observed in an electrophoretic medium are chromosome specific and provide a "fingerprint signature" for individual human chromosomes. Using this approach, we have produced fingerprints for human chromosomes 2, 5, 7, 9, and 12. The applicability of this approach to chromosome identification was assessed by comparing the fingerprints obtained for two different hybrids containing chromosome 7. DNA fragments specific for the long and the short arms of human chromosome 12 have also been identified. In addition, Alu-PCR-generated DNA fragments, specific for different chromosomes, were used to probe Southern blots of a hybrid cell panel to identify human chromosomes present in hybrid cell lines. The chromosomal specificity of these probes permits the identification of intact as well as rearranged chromosomes composed of segments arising from more than one chromosome.     

Genotoxic evaluation of Ara-C by multiple parameters

The cytogenetic effects of the antimetabolite, cytosine arabinoside (Ara-C) are evaluated using in vivo and in vitro test systems and applying multiple parameters. The in vivo assay was carried out on 8-10-week-old inbred Swiss albino male mice using bone marrow as the somatic test system and the cells of testis as the meiotic test system. In vitro human leukocyte cultures were also employed. In vivo experimental doses were computed on surface area basis within the therapeutic dose range and injected intraperitoneally and for in vitro they were calculated on blood volume basis. Evaluation of somatic chromosome mutations included conventional screening for chromosome aberrations, variations in mitotic index and sister-chromatid exchanges (SCEs) by in vivo and in vitro methods besides studies on meiotic test systems using conventional screening for chromosome and sperm-head abnormalities. The quantitative data were subjected to statistical analysis by applying appropriate tests to evaluate their significance. The results of in vivo and in vitro experiments reveal the chromosome mutational activity of the compound. This is further supported by data on SCEs from both systems. However, a comparison of both demonstrated a differential mutagenic response of the drug, more in vivo than in vitro. This is also true for SCEs. Even though the mechanisms involved in causing chromosome aberrations and SCEs are different, the data on both corroborate each other on induction of chromosome mutations.