Development of tannin vacuoles in chalaza and seed coat of barley in relation to early chalazal necrosis in the seg1 mutant

Structural development of grain tissues of maternal origin in normal and seg1 barley (Hordeum vulgare L. cv. Betzes) was examined using light and electron microscopy. Chalaza and seedcoat cells of normal grains developed prominent tannin vacuoles which persisted throughout the grain-filling period. Tannins were present in the same tissues of seg1, but no large central vacuoles developed. Instead, the chalaza and nucellar projection degenerated and were crushed, presumably terminating sugar flow and causing formation of shrunken grains (35–55% normal dry weight). Tannins were localized using various histochemical stains. Extracts of chalaza and adjacent tissues contained proanthocyanidins which yielded delphinidin and cyanidin upon hydrolysis in boiling HCl. We suggest that the basis of the seg1 phenotype may be abnormal compartmentation of tannins causing precipitation of cytoplasmic proteins and early death of chalazal cells.Abbreviations FAA Formalin-acetic acid-ethanol - PAS periodic acid Schiffs reagent     

Glycosyl transferases in mouse and human milk fat globule membranes

Summary Membranes isolated from mouse and human milk fat globules were found to contain the enzymes responsible for the synthesis of dolichol monophosphate mannose and dolichol monophosphate glucose as well as those involved in the transference of the glycosyl residues from the two dolichol derivatives to dolichol diphosphate oligosaccharides. The levels of most of the enzymes were comparable to those found in mouse mammary gland microsomes. The presence of enzymes involved in protein glycosylation via dolichol derivatives in the milk fat globule membrane provides evidence in favor of an outward flow of membrane components from the rough endoplasmic reticulum, where these enzymes are active in vivo, towards the cell surface.     

Suppression of lymphocyte proliferation by a nonspecific factor produced by the burkitt lymphoma-derived lymphoblast cell line

Summary The DAUDI lymphoblast cell line derived from a patient with Burkitt lymphoma was obtained from two different sources. One of these (DAUDI-I) produced a factor that inhibited lymphocyte proliferation in both human and mouse regardless of the stimulator, i.e. allogeneic lymphocytes or mitogens. Glutaraldehyde treatment eliminated production of the factor and demonstrated that DAUDI-I was capable of stimulating normal lymphocytes in MLR. A second DAUDI cell line (DAUDI-S) did not produce the inhibitory factor and was capable of MLR stimulation. Supported by the Children's Leukemia Foundation of Michigan, NIH Grants AI 11013 and AI 11335, and the Kidney Foundation of Michigan.     

The formation of an azo anion free radical metabolite during the microsomal azo reduction of sulfonazo III.

An ESR spectrum is observed during the anaerobic incubation of the diazonaphthol dye sulfonazo III, with rat hepatic microsomes and NADPH. This spectrum is characterized by a partially resolved 17-line hyperfine pattern and g = 2.0043, as is consistent with the spectrum of an azo anion free radical, [R-N-N-R′]^$\text{?}$. Oxygen, which strongly inhibits microsomal azoreductase, destroys the ESR signal. The oxidation of the azo anion radical metabolite by oxygen to the parent azo dye may account for the oxygen inhibition of microsomal azoreductase.     

Soluble aldehyde dehydrogenase and metabolism of aldehydes by soybean bacteroids.

A soluble aldehyde dehydrogenase (EC 1.2.1.3) was partially purified from Rhizobium japonicum bacteroids and from free-living R. japonicum 61A76. The enzyme was activated by NAD+, NADH, and dithiothreitol, and it reduced NAD(P)+. Acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, and succinic semialdehyde were substrates. The Km for straight-chain aldehydes decreased with increasing carbon chain length. The aldehyde dehydrogenase was inhibited by 6-cyanopurine, but not by metronidazole. These compounds inhibited acetylene reduction, but not respiration, by isolated bacteroids.     

Purification and characterization of the m7G(5')pppN-pyrophosphatase from human placenta

A purification scheme has been developed for the m7G(5')pppN-pyrophosphatase from human placenta. The 1400-fold purified placental enzyme exhibited physical and enzymatic properties similar to those previously reported for a crude preparation of the human m7G(5')pppN-pyrophosphatase obtained from HeLa cells. Polyacrylamide gel analysis of enzyme fractions at different stages of purification revealed a Mr = 40,000 polypeptide that increased in relative concentration as the specific activity of the enzyme fractions increased. Copurification of this polypeptide with m7G(5')pppN-pyrophosphatase activity suggests the possibility that the 81,000-dalton native enzyme is a dimer composed of subunits of identical molecular weight. The highly purified placental enzyme, like the crude HeLa enzyme, failed to hydrolyze the cap moiety of intact mRNA even under conditions known to reduce mRNA secondary structure. Moreover, when a series of capped oligonucleotides that differed progressively in chain length by a factor of one nucleotide was tested as substrate, the rate of enzyme-catalyzed cap hydrolysis decreased as the chain length increased. The purified placental enzyme failed to release m7pG from oligonucleotides containing the cap and 3 or more additional nucleotides. These results are discussed in terms of the probable biological function of the m7G(5')pppN-pyrophosphatase.     

Development of a system useful for studying the formation of unstable alleles of IS2

Summary IS2-induced deletions of the gal control region were isolated in a plasmid carrying gal OP-308 :: IS2-7. This contains a 54 basepair long, unstable mini insertion within IS2, thus allowing constitutive expression of the gal structural genes. Deletion PPI is 11.9 kilobasepairs (kb) long and is Gal⁺ because it has retained the mini insertion. In PP4 7.2 kb DNA material including markers gal OP, chlD and pgl are deleted. PP4 has lost the mini insertion and is therefore Gal negative. DNA sequencing of the newly formed junction in PP4 reveals that the deletion terminates precisely at nucleotide 1 of IS2 and that no DNA sequence homology is involved in this IS2-mediated deletion formation. PPI segregates Gal^- clones due to the loss of the mini insertion. One such segregant PPIS and PP4 both give only constitutive Gal⁺ revertants, which consist of the previously known mini insertions and also a new class of supermini inserts within IS2 of about 10 to 20 basepairs long. Therefore, PPIS and PP4 can be used to study various parameters involved in the formation of mini insertions.     

Selective vital staining of companion cells of potato tuber and parsnip root with neutral red.

When staining the internal phloem region of a potato tuber with the vital stain neutral red, it was observed that files of elongated cells of narrow diameter were heavily stained and were easily distinguishable from the more isodiametric parenchyma cells, many of which did not stain with neutral red. The elongated cells were identified as companion cells by locating the adjacent sieve-tube members through counterstaining with aniline blue and reviewing under violet light. Of a number of other plants surveyed, only parsnip roots possessed companion cells exhibiting a similar slective staining. In other plants both the companion cells and the surrounding parenchyma cells usually stained. Sieve-tube members never accumulated neutral red. It was concluded that the vacuoles of the companion cells of the potato tuber were stained by the ion trap mechanism because of the color of the accumulated stain, the lack of staining when neutral red was applied in an acidic solution, and the complete destaining after soaking in dilute ammonium hydroxide.