Inhibition of ATPase Activity in Pea Plasma Membranes In Situ by a Suppressor from a Pea Pathogen, Mycosphaerella pinodes

A pathogenic fungus of pea, Mycosphaerella pinodes, secretesa so-called "suppressor" in its pycnospore germination fluid.The suppressor blocks the defense responses and induces localsusceptibility (accessibility) in pea plants to agents thatare not pathogenic in pea. The suppressor nonspecifically inhibitsthe ATPase activity in plasma membranes prepared from pea, soybean,kidney bean, cowpea and barley plants. However, cytochemicalstudies by electron microscopy indicate that the suppressorspecifically inhibits the ATPase in pea cell membranes, butnot in those of four other plant species tested. That is, thespecificity of the suppressor appears at the cell and/or tissuelevel, but is not evident in vitro. Furthermore, the inhibitoryeffect of the suppressor is temporary because the ATPase activityrecovers 9 h after the treatment. A similar effect was observedafter inoculation with M. pinodes but not with a nonpathogenof pea, M. ligulicola. The role of the suppressor in host-parasitespecificity is discussed. (Received April 9, 1991; Accepted August 6, 1991)     

Biotransformation of germacrane-type sesquiterpenoids by Aspergillus niger

Three germacrane-type sesquiterpenoids, (+)-germacrone-4,5-epoxide, germacrone and (+)-curdione were biotransformed by Aspergillus niger to give hydroxylated guaiane-type sesquiterpenoids together with allylic alcohols and spirolactone.     

Preparation of subfragment-1 from abalone smooth muscle myosin

Myosin subfragment-1 (S1), which has one heavy chain (HC) (93 kDa) and two light chains (LC1 and LC2), was prepared by papain digestion of myosin from abalone-smooth muscle in the presence of Ca2+. The Ca-sensitivity of abalone S1 itself was not lost completely (about 30%). The tryptic digestion of S1 showed that in the presence of EDTA, S1 HC was split into 68, 55, and 23 kDa fragments, as in the presence of Ca2+, but 23 kDa was further degraded into 19 kDa. In contrast to the result in the presence of Ca2+, LCs disappeared in the early stage of reaction and Ca-ATPase activity decreased rapidly to about 70% of that of intact S1. This rapid decrease of Ca-ATPase activity seemed to be accompanied with the digestion of LCs. Therefore, LCs contribute to the protection of 23 kDa fragment from further digestion, to the maintenance of Ca-ATPase activity by stabilizing the structure of S1 to some extent in the presence of Ca2+. Since F-actin suppressed the cleavage of S1 HC to 68 and 23 kDa during tryptic digestion, it might be that 23 and 68 kDa corresponded to 20 kDa (C-terminal fragment) and to 50 + 25 kDa (N-terminal fragment) of skeletal myosin S1, respectively.     

Two-dimensional gel studies of genetic variation in the plasma proteins of Amerindians and Japanese

Summary Genetic variation has been studied in plasma samples from 107 Amerindian children and their parents, and 110 Japanese children and their parents by means of two-dimensional polyacrylamide gel electrophoresis. Twenty-three polypeptides were scored; the identity of nine of these is at present still unknown. Genetic variation was encountered in 11 of these polypeptides. We have previously reported that the index of heterozygosity was 6.2±0.7% for 20 randomly selected, silver stained polypeptides scored for genetic variation in Caucasoids (Rosenblum et al. 1983b). For technical reasons only 11 of these 20 polypeptides could be routinely scored in preparations from the Amerindian samples. For these 11 polypeptides, the indices of heterozygosity in the three populations were: Amerindians, 4.5±0.6%; Japanese, 5.7±0.7%; Caucasoids, 8.0±1.1%. Even with these relatively small numbers some striking ethnic differences as regards individual polypeptides are apparent.     

Effects of somatomedin and other factors on glycosaminoglycan synthesis in cultured rat chondrocytes

We have investigated the effects of hormones and serum on glycosaminoglycan (GAG) synthesis, using cultured rat chondrocytes isolated from growing cartilage. Somatomedin A stimulated GAG synthesis at a physiological concentration, however in the case of insulin the dose required to stimulate GAG synthesis was 500 times as great as the physiological concentration. Parathyroid hormone also increased GAG synthesis. In contrast, hydrocortisone inhibited GAG synthesis at a pharmacological dosage. None of the following had any effect on GAG synthesis: epidermal growth factor, fibroblast growth factor, triiodothyronine, growth hormone, sex steroid or vitamin D3. Human serum up to a concentration of 1% stimulated GAG synthesis. Serum from patients with acromegaly stimulated GAG synthesis more than that from those with hypopituitarism.     

Interaction of Benzoquinones with QA- and QB- in Oxygen-Evolving Photosystem II Particles from the Thermophilic Cyanobacterium Synechococcus elongatus

The interactions of benzoquinones with the reduced forms ofthe bound plastoquinone acceptors, Q_A and Q_B, were studied withoxygen-evolving photosystem II (PS II) particles from the thermophiliccyanobacterium Synechococcus elongatus, which largely lack poolplastoquinone molecules [Takahashi and Katoh (1986) Biochim.Biophys. Acta 845: 183]. Oxygen evolution in the presence ofvarious electron acceptors was determined and flash-inducedchanges in absorbance in the blue region were analyzed in termsof difference spectra, dependence on the concentration of benzoquinoneand on temperature, and sensitivity to 3-(3,4-dichlorophenyl)-1,1-dimethylurea(DCMU). The more hydrophobic the quinone molecule, the higherwas the rate of oxygen evolution, and the maximum rate of 3,000µmoles O₂.(mg chlorophyll)^–1.h^–1 was recordedin the presence of phenyl- and dichloro-p-benzoquinones. DCMUinhibited oxygen evolution by more than 95%. However, spectrophotometricstudies revealed that, even though electrons were transferredto benzoquinones predominantly via the direct oxidation of by added benzoquinones occurred in such a way as to indicate thatabout 40% of PS II reaction centers were not associated withfunctional Q_B sites. was very stable in the presence of ferricyanide. However, benzoquinonesinduced the slow oxidation of . The characteristics of the benzoquinone reductioin in thePS II preparation is discussed. ¹Present address: Department of Life Sciences, Faculty of Science,Himeji Institute of Technology, Shosha 2167, Himejishi, Hyogo-ken,671-22 Japan (Received May 8, 1990; Accepted August 14, 1990)     

Studies of the Inheritance of Human Ribosomal DNA Variants Detected in Two-Dimensional Separations of Genomic Restriction Fragments

We have investigated the variation in human ribosomal DNA repeat units as revealed in two-dimensional electrophoretic separations of genomic restriction fragments that were end-labeled at NotI cleavage sites. The transcribed portion of the ribosomal DNA results in ~20 labeled fragments visible on each gel as multicopy spots. We have mapped these spots to the sequences responsible for their appearance on the gels, based on their migration positions and direct sequencing of spots, and describe several previously unreported sources of variation. By studying mother/father/child families we gained information on how much of the between-repeats variation is due to differences between and within repeat arrays on homologous chromosomes. Two instances in which a child exhibited more copies of a particular fragment than were present in the parents are described and hypothesized to be due to events such as multiple unequal sister-chromatid exchanges or gene conversions.     

Two genes controlling acute phase responses by the antitumor polysaccharide,lentinan

Lentinan, a -1,6;1,3-glucan, is tumor-specific for transplantable mouse solid-type tumors and it also stimulates the production of acute phase proteins (APPs). The APP response to lentinan is of the delayed type (DT-APR) and differs from that to lipopolysaccharide, which is acute. We found that the responses were genetically controlled in mice and that low responsiveness is dominant (Maeda et al. 1991). Using 123 segregants of crosses between SWR/J (a high responder) andMus spretus (a low responder), we analyzed the linkage between DT-APR responsiveness and the DNA polymerase chain reaction-simple sequence lenght polymorphism (PCR-SSLP) phenotype using 80 chromosome-specific microsatellite markers. We identified two loci (ltn1.1 andltn1.2) responsible for DT-APR.ltn1.1 is closely linked toD3Mit11 on chromosome 3 andltn1.2 toD11Nds9 on chromosome 11 (P<0.001). The linkage analysis also suggested thatltn1.2 is the major determinant for DT-APR. Correlation between lentinan-specific IL-6 mRNA expression (the late expression) controlled recessively and DT-APR induction suggests that theltn1 loci control some process(es) of IL-6 expression in the regulation step before NF-IL6.