Fine structure of a murine mammary carcinoma cell line

Summary A fine structural study was made of cells from the epithelioid MCF-8/5-2A cell line derived from a MuMTV-free, D2 transplantable hyperplastic outgrowth. Electron microscopy shows the cells to be truly epithelial with many cell-to-cell junctions and microvilli. The cells are similar in many respects to normal mouse mammary gland and some of the conventional mammary tumor derived cell lines. This study supports previous observations of the absence of MuMTV in MCF-8 within the limits of morphological detection, and demonstrates the presence of numerous virus particles within, or budding into, cisternae of the endoplasmic reticulum and nuclear envelope. These intracisternal A particles have not been previously described in such abundance in mammary tumor tissue culture cells. This study was supported by Contract NIH-NCI-E-71-2421, with the NIH and by an institutional grant to the Michigan Cancer Foundation from the United Foundation of Detroit, Michigan.     

Active, inactive and in vitro synthesized forms of polyphenoloxidase during leaf development

Polyphenoloxidase (PPO; EC 1.14.18.1) activity decreased 8-fold from young to mature Vicia faba L. Moensch (cv. Long pod) leaves. The K_m for catechol remained relatively constant from young to mature leaves. Electrophoretic separation and analysis showed that only one active form was present in extracts from various leaf sizes. The amount of this form appeared to decrease with leaf size/age. In extracts which had not tanned, electroblotting and immunostaining indicated that one enzyme form was present with a molecular mass of 45 kDa. Two leaf categories contained greater amounts of this immunological cross-reacting PPO than other leaf categories. When extracts were allowed to darken, immunoblotting detected three enzyme forms with molecular masses of 45, 59 and 63 kDa. The latter two immunological crossracting species had no detectable enzyme activity. Poly-A⁺ mRNA was isolated from six leaf sizes and translated in vitro. A product corresponding to PPO was present in all leaf categories. Greater amounts of this translation product were observed in medium-sized leaves than in very young or mature leaves. These results suggest that: (1) enzymatic assays for PPO are not reliable indicators of the total amount of PPO protein present in developing leaves, (2) immunoblotting can detect inactive enzyme forms, (3) only one active form of the enzyme is present at all developmental stages, and (4) mRNA corresponding to PPO is present at all developmental stages but appears to be more abundant in certain leaf sizes/ages.     

A new variety of Draba oreibata (Brassicaceae) from Nevada,U.S.A.

A new variety ofDraba oreibata, var.serpentina, is described, illustrated, and discussed.     

Exclusion of ZFM1 as a candidate gene for multiple endocrine neoplasia type 1 (MEN1)

The multiple endocrine neoplasia type 1 (MEN1) locus has been previously localised to 11q13 by combined tumour deletion mapping and linkage studies and a 3.8-cM region flanked by PYGM and D11S97 has been defined. The zinc finger in the MEN1 locus (ZFM1) gene, which has also been mapped to this region, represents a candidate gene for MEN1. The ZFM1 gene, which consists of 14 exons, encodes a 623-amino acid protein and exons 2, 8 and 12 encode the putative nuclear localisation signal, a zinc finger motif, and a proline-rich region, respectively. We have investigated these potentially functional regions for germ-line mutations by single-stranded conformational polymorphism (SSCP) analysis in 64 unrelated MEN1 patients. In addition, we performed DNA sequence analysis of all the 14 exons and 13 of the 26 exon-intron boundaries in four unrelated MEN1 patients. A 6-bp deletion that resulted in the loss of two proline residues at codons 479 and 480 in exon 12 was found in one MEN1 patient. However, this did not co-segregate with MEN1 in the family and represented a rare polymorphism. Analysis by SSCP, DNA sequencing, northern blotting, Southern blotting and pulsed field gel electrophoresis revealed no additional genetic abnormalities of ZFM1 in the other MEN1 patients. Thus, our results indicate that ZFM1 is excluded as a candidate gene for MEN1. Received: 29 October 1996 / Revised: 16 December 1996     

Probabilism and Phylogenetic Inference

The maximum likelihood approach to phylogenetics rests on frequency probability theory. This stands in stark contrast to the logical probability of corroboration-based cladistic parsimony. History is particular and cannot be described in terms of universal statements about abstract generalities, the task of the historical sciences being one of explanation, not prediction. Thus, frequency probability methods of estimation are inappropriate for making historical inferences. Maximum likelihood estimation procedures are deconstructed from numerous perspectives in spite of their supposed impressive technicalities. Charges of parsimony's inconsistency are rendered mute, because its justification lies elsewhere, yet maximum likelihood is still subject to Wald's dilemma if realism is of any interest. Although all epistemologies make assumptions, the models employed by maximum likelihood are problematic and deterministic, as opposed to the unproblematic background knowledge characteristic of cladistics. Apart from issues of logical and sampling dependencies, the requirements of frequency probability theory are non-trivial and the maximum likelihood estimation of phylogeny can neither escape, nor satisfy the tenets of calculus independence (e.g. i.i.d.) inherent in the multiplicative relations of the method. If phylogeneticists are to maintain a rational foundation for their epistemology, neo-justificationist appeals to some metaphysical truth must be abandoned in favour of the realism of sophisticated falsification.     

Caesium fluoride-induced changes in the c.d. spectra of synthetic DNA fragments

Ten DNA fragments containing self-complementary alternating sequences of adenine and thymine differing in length and the starting nucleotide were studied by c.d. spectroscopy. It was found that d(TATATATA) but not d(ATATATAT), d(TATATA), d(CTATATAG) or (dT-dA)20 isomerized into the unusual X-DNA double helix at molar concentrations of CsF in solution. But in contrast to poly(dA-dT), the octamer (dT-dA)4, isomerized very slowly, at relatively low CsF concentrations and the isomerization was strongly dependent on the octamer concentration. A model is proposed to account for the observed properties of the B-to-X isomerization on the oligomer level.