Number and pattern of association of chromonemata in the chromosomes of Tradescantia

Summary Analysis of reconstructions, prepared from electron micrographs of successive longitudinal serial sections, has led to the conclusion that the somatic telophase chromosome of Tradescantia paludosa contains four cytologically separable chromonemata. The four represent a pair of pairs, that is, two diplospiremes — one with its two chromonemata arranged helically in dextrorse relationship, and the other with its two in sinistrorse relationship — which are associated to form a tetraspireme. During anaphase and telophase the tetraspireme constitutes the chromosome; during prophase and metaphase the tetraspireme represents one of the two chromatids of the chromosome, which is accordingly an octospireme in terms of the number of cytologically identifiable chromonemata. Loose intertwining of the two tetraspiremes during late prophase accounts for the so-called relational coiling.This paper is dedicated to Professor Hans Bauer on his sixtieth birthday anniversary in appreciation of his contributions to the development of modern cytology.The work reported here was supported in part by Research Grants GM-10499 from the National Institutes of Health, U.S. Public Health Service, and GB-290 from the National Science Foundation, and in part by a NATO fellowship awarded to E. Sparvoli by the Italian National Council of Research.     

Myotonia congenita (Thomsen's disease) excluded from the region of the myotonic dystrophy locus on chromosome 19

Summary Linkage analysis has been carried out in six German families with autosomal dominantly inherited myotonia congenita (Thomsen's disease) using five chromosome 19 markers known to be linked to the gene for myotonic dystrophy (DM). Two of the markers, APOC1 and APOC2, are tightly linked to DM. Close linkage between these markers and myotonia congenita (MC) has been excluded to a distance of 9cM (z=-2.158). These data support the clinical suggestion that MC and DM are non-allelic disorders.     

Presence of haemocyte-like cells in coccinellid reflex blood

Abstract.  Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction.     

Optimization of bovine satellite cell-derived myotube formation in vitro

Post-natal myogenic satellite cells, isolated from the sternomandibularis muscles of bovine at slaughter were used for primary culture studies. Isolated satellite cells tended to differentiate into multinucleated myotubes more efficiently if initially plated on to a fibronectin substratum. Bovine-derived satellite cells displayed greater fused cell numbers when exposed to Dulbecco's Modified Eagle's Medium (DMEM) supplemented with horse serum than similar supplementation with fetal calf serum (P less than 0.05) or sheep serum (P less than 0.05). In addition, differentiation appeared nearly complete after 4 days exposure to DMEM-1% horse serum as verified by beta-D-arabinofuranosyl-cytosine addition to cultures. Collectively, these data provide the first evidence that satellite cells can be isolated from a bovine skeletal muscle. Furthermore, these data indicate that bovine-derived satellite cells can be induced to undergo substantial morphological differentiation in vitro.     

Linkage studies with chromosome 17 DNA markers in 45 neurofibromatosis 1 families

A locus for von Recklinghausen neurofibromatosis (NF1) has recently been mapped near the chromosome 17 centromere. We have extended these linkage studies by genotyping 45 NF1 families with three DNA probes known to be linked to the chromosome 17 centromeric region. Of 34 families informative for NF1 and at least one of the three probes, 28 families show no recombinants with the disease gene. These data provide additional support for genetic homogeneity of NF1 and for a primary NF1 locus linked to the chromosome 17 centromere. Among the informative families were 7 families with apparent new NF1 mutations. Our data suggest that these mutations are probably at the chromosome 17 NF1 locus.     

Functional Changes Associated with Structural Alterations Induced by Mobilization of a P Element Inserted in the Sex-lethal Gene of Drosophila

Genetic analysis of rearrangements within the multifunctional sex determining gene Sex-lethal has allowed correlation of changes in specific functions with DNA alterations. Rearrangements were isolated by mobilization of a P element which is on the 5' side of the gene, at coordinate 0. Previous work has shown that rearrangements associated with alterations in Sxl gene function are found within an 11-kb region between coordinates-11 and 0. Here it is shown that insertion of foreign DNA, per se, at coordinate 0 is compatible with wild-type gene function. However, deletion of sequences on either side of this point generates a mutant phenotype. Deletions extending distally beyond coordinate -6.5 kb result in a null phenotype, whereas smaller distal deletions or proximal deletions eliminate only some Sxl functions.