Depsidone constituents from the quintaria group of Nephroma species

A new lichen depsidone was isolated, in the form of its triacetate derivative from the acetylated extracts of Nephroma antarcticum and has been demonstrated to be hypoconstictic acid-triacetate. Two related depsidones, hypostictic acid hyposalazinic acid, were isolated from N. australe.     

A variation of the smooth septate junction in sea spiders (Pycnogonida)

A new type of septate junction considered to be a variation of the arthropod smooth septate junction is described in pycnogonid (sea spider) endothermal tissue based on the use of conventional thin-section, lanthanum tracer and freeze-fracture techniques. This new type of septate junction is apparently unique to the Pycnogonida but closely resembles septate junctions previously described in the Merostomata and Collembola. This work in conjunction with previous work suggests that the septa of smooth septate junctions may not be as ‘smooth’ as generally thought and probably have a complex substructure.     

Peptide accumulation during growth of peptidase deficient mutants

Mutant strains of Salmonella typhimurium simultaneously lacking peptidases N, A, B and D accumulate a heterogeneous mixture of small, trichloroacetic acid-soluble peptides during growth in minimal medium. Approximately 20% of the labelled leucine supplied to a growing culture of the mutant strain is converted to peptides. These peptides accumulate inside the cells before being released into the growth medium. Although the origin of these peptides has not been established, there are several processes that might contribute peptides to this pool. These include (1) turnover of signal sequences, (2) turnover of attenuator peptides, and (3) degradation of prematurely terminated proteins. These results indicate that the same family of peptidases that catabolizes exogenously supplied peptides and functions in carbon-starvation-induced protein turnover also hydrolyzes peptides generated during normal exponential growth.     

Arrangement of Integrated Avian Sarcoma Virus DNA Sequences Within the Cellular Genomes of Transformed and Revertant Mammalian Cells

We have examined the arrangement of integrated avian sarcoma virus (ASV) DNA sequences in several different avian sarcoma virus transformed mammalian cell lines, in independently isolated clones of avian sarcoma virus transformed rat liver cells, and in morphologically normal revertants of avian sarcoma virus transformed rat embryo cells. By using restriction endonuclease digestion, agarose gel electrophoresis, Southern blotting, and hybridization with labeled avian sarcoma virus complementary DNA probes, we have compared the restriction enzyme cleavage maps of integrated viral DNA and adjacent cellular DNA sequences in four different mouse and rat cell lines transformed with either Bratislava 77 or Schmidt-Ruppin strains of avian sarcoma virus. The results of these experiments indicated that the integrated viral DNA resided at a different site within the host cell genome in each transformed cell line. A similar analysis of several independently derived clones of Schmidt-Ruppin transformed rat liver cells also revealed that each clone contained a unique cellular site for the integration of proviral DNA. Examination of several morphologically normal revertants and spontaneous retransformants of Schmidt-Ruppin transformed rat embryo cells revealed that the internal arrangement and cellular integration site of viral DNA sequences was identical with that of the transformed parent cell line. The loss of the transformed phenotype in these revertant cell lines, therefore, does not appear to be the result of rearrangement or deletions either within the viral genome or in adjacent cellular DNA sequences. The data presented support a model for ASV proviral DNA integration in which recombination can occur at multiple sites within the mammalian cell genome. The integration and maintenance of at least one complete copy of the viral genome appear to be required for continuous expression of the transformed phenotype in mammalian cells.     

mus(3)312D1, a mutagen sensitive mutant with profound effects on female meiosis in Drosophila melanogaster

The third chromosome, mutagen sensitive mutant mus(3)312^D1 impairs the meiotic process in females by increasing the frequency of first division nondisjunction and decreasing the frequency of meiotic crossing over. These genetic properties connote 312 to be defective in DNA replication and/or repair intimately associated with the crossing over exchange process. The mutant maps to the left arm of chromosome III between ru and h, and represents a new genetic site for a meiotic mutant. It is a pleasure and honor to dedicate this paper to my longtime younger friend and collaborator Wolfgang Beermann, cytologist par excellence, on the occasion of his 60th birthday     

Isolation and properties of chloroplast coupling factor from wheat

1. Wheat chloroplast coupling factor (CF1) was extracted with a modification of the chloroform extraction method of Younis et al. (J. Biol. Chem. 252, 1814--1818, 1977). A one-step purification on an 8--25% sucrose gradient yielded a CF1 which was at least 98% pure as judged by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. 2. Inclusion of proteolysis inhibitors during extraction and purification consistently gave a CF1 containing all five subunits. Selective loss of the sigma and epsilon subunits was observed when proteolysis inhibitors were omitted. 3. Proteolysis inhibitors prevented the release of wheat CF1 from the thylakoid by the low-ionic-strength wash method of Strotmann et al. (Biochim. Biophys. Acta, 314, 202--210, 1973). The enzyme extracted with chloroform and low ionic strength were compared by electrophoresis and no evidence of a difference in molecular weight of any subunit was observed. This suggests that a proteolytic event is not required for release of wheat CF1 by the low-ionic-strength method, even though release is inhibited by proteolysis inhibitors. 4. The gamma subunit of wheat CF1 probably contains at least one internal disulfide bridge, as the electrophoretic mobility of this subunit is lower in the presence of reducing agent than in its absence. 5. Wheat CF1 was viewed by the electron microscope after negative staining. Discrete particles, many appearing hexagonal, were observed at high magnifications. Markham rotational analysis confirmed that the enzyme has sixfold symmetry in at least one of its orientations.     

Linkage of the gene controlling the synthesis of the fourth component of complement to the major histocompatibility complex of the guinea pig

C4-deficient (C4D) guinea pigs are lacking in C4 synthesis, a condition that appears to be caused by a structural gene defect. This defect is inherited as a simple autosomal recessive trait. We have demonstrated linkage between C4D and the major histocompatibility complex of the guinea pig (GPLA). Inbred C4D and inbred strain 13 guinea pigs appear to have the same GPLA haplotype. The use of these two strains should provide an animal model for reconstitution studies of C4 synthesis and for studied exploring the possible role of C4 in cellular and humoral immune responses.Abbreviations used in this paper are C4D deficiency of the fourth component of complement - MHC major histocompatibility complex - GPLA major histocompatibility complex of the guinea pig - MLC mixed lymphocyte culture