Biomedical subjects
Publications and source records attributed to J A Lippincott.
Using the Index of Attitudes Toward Homosexuals to study the attitudes of 34 Asian students and 32 American students toward lesbians and gay men showed these Asian students were more likely to harbor homophobic attitudes than these American students. There were no significant sex differences between groups.
This study compared attitudes toward eating among 226 women undergraduates at universities in Pennsylvania and South Korea. Analysis indicated that both groups (ns = 111 and 115, respectively) had similar percentages (21% and 18%, respectively) of respondents with scores suggesting symptomatology of eating disorders. Mean differences between groups on the Eating Attitudes Test-26 were not significant. Implications for research are discussed.
The authors used the somaticization scale of the Brief Symptom Inventory to study Asian and American college students' propensity for seeking counseling at an American university. They found that the Asian students were more likely than the American students were to report that they would seek counseling services when they experience somatic discomfort. The Asian students scored significantly higher on inclination for seeking counseling than did the American students.
We have identified a previously reported open reading frame (ORF13) that maps between pepA and valS at 96.6 centisomes of the Escherichia coli genome as the structural gene for the chi subunit of DNA polymerase III holoenzyme. This conclusion is supported by a perfect match of the amino-terminal 24 residues of chi with the DNA sequence of ORF13 and a demonstration that ORF13 directs expression of a protein that co-migrates with authentic chi on SDS-polyacrylamide gels. ORF13, designated holC, was isolated from the E. coli chromosome and inserted into a tac promoter-based expression plasmid to direct production of the chi subunit to 5-7% of the total soluble protein. The 3' end of holC was sequenced to resolve discrepancies between two published versions.
Cell wall preparations from primary bean leaves were found to inhibit tumor initiation by Agrobacterium tumefaciens strain B6 when inoculated with the bacteria on bean leaves. Membrane fractions from these same leaves were noninhibitory. The cell walls were effective when applied prior to or with bacteria, but application of cell walls about 15 minutes after bacteria did not affect the number of tumors initiated. Much of the inhibitory activity of the plant cell walls was eliminated by pretreatment with dead site-attaching bacteria or with lipopolysaccharide from these bacteria. Cells and lipopolysaccharide from non-site-attaching agrobacteria had no effect on the activity of the plant cell walls. About 30% inhibition of tumor initiation was obtained with plant cell walls at 50 mug/ml dry weight, and at 10 mg/ml dry weight about 70% inhibition was typical. Both early and late appearing tumors were affected by the cell walls, indicating that they do not exclusively affect tumors arising from either small or large wounds. These data show that plant cell walls but not membranes contain surfaces to which A. tumefaciens adheres and these exhibit the specificity typical of the host site to which virulent agrobacteria must attach to induce tumors. It is concluded that some portion of wound-exposed plant cell wall constitutes the host adherence site in Agrobacterium infections.
Avirulent strains IIBNV6 and NT1, derived from virulent strains of Agrobacterium tumefaciens, were tested for their ability to enhance tumor initiation (complement) on coinoculation with tumorigenic strains. Strain NT1, cured of the Agrobacterium virulence plasmid, failed to complement when inoculated with its virulent parental strain or with other virulent strains. Strain IIBNV6, however, complemented with all virulent strains tested. Attachment to host wound sites by both strain IIBNV6 and the virulent strain was essential for this effect. Inoculation of the tumorigenic strain at different times on leaves previously inoculated with IIBNV6 showed that the capacity to complement is lost during the period between 4 and 8 h after IIBNV6 inoculation. The rate of tumor appearance obtained with an inoculum containing IIBNV6 and a virulent auxotrophic strain was characteristic of the appearance rate obtained with prototrophic bacteria. Evidence is summarized which suggests that strain IIBNV6 can induce tumors when supplied with a substance produced or induced by a virulent bacterium at a separate site. A deoxyribonucleic acid plasmid about 40% the size of the Agrobacterium virulence plasmid was obtained from strain IIBNV6. We propose that this plasmid accounts for the ability of strain IIBNV6 to complement and that it contains part of the genetic information necessary for tumor initiation.
Lipopolysaccharide (LPS) isolated from Agrobacterium tumefaciens inhibited tumor induction by virulent bacteria. LPS from site-binding strains was not effective if added to the plant wound shortly after the bacteria, and LPS from avirulent, non-site-binding strains of Agrobacterium was not inhibitory regardless of the order of addition. However, LPS and whole cells of avirulent strains NT1 and IIBNV6, which lack of Agrobacterim virulence plasmid, were inhibitory. Chromosomal deoxyribonucleic acid thus determines specificity of this essential component of the Agrobacterium infection process.
Bean leaf tumors induced by Agrobacterium tumefaciens strain 181 show enhanced growth in response to octopine or lysopine only if one of these compounds is present during the period of tumor induction. Either compound applied during this period results in tumors which subsequently respond to both. The combined action of the bacterium plus octopine or lysopine at induction is proposed to induce transcription of plant genes coding for enzymes involved in the degradation and/or biosynthesis of octopine and lysopine.
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Tests for utilization of d-octopine and nopaline in defined media containing a carbon and nitrogen source were made on 60 strains of Agrobacterium representing four species and on a representative of each of five species of Rhizobium. Among 46 virulent strains of Agrobacterium, only two strains were found which utilized neither compound, while three strains were found which could utilize both. Of the remaining virulent strains, 27 utilized octopine and 14 utilized nopaline. Each of six strains of A. rhizogenes tested utilized only octopine but at a slower rate relative to growth than most A. tumefaciens. All eight of the A. radiobacter strains failed to utilize either compound, as did four of six nonvirulent strains of A. tumefaciens. The rhizobia did not utilize octopine or, with the possible exception of R. japonicum, nopaline. Virulence in the genus Agrobacterium is concluded to be highly correlated with the ability to utilize one or both of these compounds.
DNA of Agrobacterium tumefaciens bacteriophage PS8 was isolated by using several procedures. Whole phage and phage DNA were tested for tumor-inducing ability on 10 species of plants with various additions to assist such activity. The reported tumorigenicity of phage PS8 DNA could not be confirmed, and no evidence to implicate phage PS8 involvement in tumor initiation was obtained.
The growth of crown-gall tumors on primary bean leaves (Phaseolus vulgaris L. cv. "Pinto") was promoted by the addition of d-lysopine, d-octopine, l-carnosine, or nopaline. Assayed on tumors induced by Agrobacterium tumefaciens strain B6, the relative activity was octopine = carnosine > lysopine >> nopaline; assayed on tumors induced by A. tumefaciens strain T-37, which induces tumors which form nopaline, the relative activity was nopaline = octopine = carnosine > lysopine. From one to three applications of carnosine or octopine gave equal additive increments in tumor growth, showing that a continual supply of these substances is required to maintain an increased rate of growth. At concentrations above 0.1 mm, pairs of these growth-promoting substances were less active than when applied singly. Inhibition of octopine-induced growth was obtained by applying 0.01 mm carnosine with 1 mm octopine and partial inhibition was obtained when carnosine was added 10 hr after octopine. Equimolar mixtures of lysopine, octopine, and carnosine, however, were at least as active in promoting tumor growth as any of the compounds added singly at equivalent concentrations. The activity of 0.1 to 0.5 mm lysopine, octopine, and carnosine was inhibited, respectively, by 1 mml-lysine, l-arginine, and l-histidine and this inhibition was limited in each case to the basic amino acid corresponding to that of the growth factor. Arginine fully inhibited octopine-induced tumor growth when applied as much as 6 hr after octopine, indicating that this inhibition was not due to prevention of octopine uptake. Although four separate substances were found which promoted tumor growth, the molecular specificity required for activity of each compound was high. Evidence is presented which suggests that a tumor growth-promoting substance extracted from tumorous leaves is a carnosine-like derivative of l-histidine.
Incubation of embryoless barley (Hordeum vulgare) half-seeds for 24 hours with 0.1 m glutamate or aspartate resulted in the release of 17 to 48% as much alpha-amylase as did incubation with 260 mmum gibberellin. With incubation periods of 48 to 51 hours these amino acids were on the average about half as active as response-saturating concentrations of gibberellin, and in some experiments they were essentially as active. Citric acid cycle intermediates, glycolytic pathway intermediates, and cofactors of these pathways failed to induce alpha-amylase synthesis, while the following compounds were active: asparagine, homoserine, diaminopimelate, isoleucine, methionine, glutamine, ornithine, citrulline, argininosuccinate, and delta-aminolevulinate. However, threonine, lysine, beta-alanine, alanine, gamma-aminobutyrate, alpha-ketobutyrate, proline, arginine, glycine, leucine, and putrescine were inactive. Two patterns were noted in the list of active and inactive compounds: (a) all of the active compounds contain an amino group and are biosynthetically derived from citric acid cycle intermediates; and (b) biosynthetic precursors of the amino acids arginine, proline, threonine, and lysine were active whereas these amino acids were not.
An improved bioassay is described for a factor that promotes tumor growth which was first obtained from extracts of pinto bean leaves with crown gall tumors. Sixteen primary pinto bean leaves per sample are inoculated with sufficient Agrobacterium tumefaciens to initiate about 5 to 10 tumors per leaf and treated with tumor growth factor at day 3 after inoculation. The diameters of 30 to 48 round tumors (no more than 3 randomly selected per leaf) are measured per test sample at day 6. Mean tumor diameter increased linearly with the logarithm of the concentration of tumor growth factor applied. The tumor growth factor was separated by column chromatography from an ultraviolet light-absorbing compound previously reported to be associated with fractions having maximal tumor growth factor activity. Partly purified tumor growth factor showed no activity in a cytokinin bioassay or an auxin bioassay, and negligible activity in gibberellin bioassays. Representatives of these three classes of growth factors did not promote tumor growth. Extracts from crown gall tumors on primary pinto bean leaves, primary castor bean leaves, Bryophyllum leaves, carrot root slices, and tobacco stems showed tumor growth factor activity, whereas extracts from healthy control tissues did not. Extracts from actively growing parts of healthy pinto beans, Bryophyllum, and tobacco, however, showed tumor growth factor activity. Tumor growth factor is proposed to be a normal plant growth factor associated with rapidly growing tissues. Its synthesis may be activated in nongrowing tissues by infection with Agrobacterium sp.
Mixtures of two strains of Agrobacterium from the species A. tumefaciens (11 strains), A. rhizogenes (6 strains), and A. radiobacter (7 strains) were tested for their ability to initiate tumors on primary pinto bean leaves. Intra- and interspecific mixtures of A. tumefaciens and A. rhizogenes strains induced 10- to 20-fold increases in the number of tumors initiated. This complementation was observed only in mixtures in which at least one of the strains was tumorigenic when inoculated separately. Tests of various combinations of strains that formed complementary pairs showed two groups described as tumorigenic "helper" strains (donors) and conditionally tumorigenic strains (receptors). Donor, receptor, and noncomplementing strains were found among the strains of A. rhizogenes and A. tumefaciens. Donor or receptor A. tumefaciens strains substituted respectively for A. rhizogenes donor or receptor strains to form complementary pairs. A. radiobacter strains mixed with strains of the same or other Agrobacterium species did not initiate tumors and failed to promote tumor initiation in combination with a tumorigenic strain. Washing the complementing strains prior to mixing had no effect on the response, and the centrifuge supernatants from either donor or receptor strains when inoculated with cells of the opposite type did not increase tumor initiation. Neither indole acetic acid, kinetin, nor gibberellic acid could substitute for either the donor or receptor strain when tested separately on each member of a representative pair of complementing organisms. It is proposed that a substance is either produced or induced in the host by the donor strain after its inoculation on the leaf which permits tumor initiation by a receptor strain at a separate site.
The number of tumors initiated by Agrobacterium tumefaciens strain B6 on primary pinto bean leaves was decreased when cells of an avirulent strain (IIBNV6) were included in the inoculum. With sufficient B6 cells to initiate ca. 50% of the maximal number of tumors per leaf, inhibition was detected at a 1:1 ratio of B6 to IIBNV6 cells and increased linearly with the logarithm of the number of IIBNV6. Varying the number of B6 in the presence of a constant number of IIBNV6 or varying the number of both, while maintaining a constant ratio of B6 to IIBNV6, showed that the inhibition was a function of the absolute concentration of each cell type. The data fit a one-particle dose response curve, which indicates that a single IIBNV6 cell can prevent tumor initiation by a single B6 cell. Inhibition was obtained with mixed inocula and when the addition of IIBNV6 preceded B6, but not when B6 preceded IIBNV6. Heat-inactivated IIBNV6 inhibited, as did ultraviolet or heat-inactivated B6. Several unrelated bacteria and certain strains of Agrobacterium failed to inhibit, whereas other related strains gave inhibition. Attachment of IIBNV6 to a specific would site, thus excluding B6 from the site, is proposed to account for these data. A specific complementary binding of a virulent bacterium to a host wound site exposed by the inoculation procedure is suggested as an essential early event in the crown-gall tumor initiation process.
The ability of 31 strains of Agrobacterium to initiate the production of a tumor growth factor (TGF) which is associated with crown-gall tumors on primary pinto bean leaves was determined. Extracts from bean leaves inoculated with these bacteria were tested and they showed that 16 of the 19 strains that induced tumors on the leaves also initiated TGF production. The three strains for which no TGF was detected were of low infectivity and included two strains of A. tumefaciens and a strain of A. rhizogenes. Five of the 12 strains that did not induce pinto bean leaf tumors were found to initiate TGF production. Representatives of A. tumefaciens, A. rhizogenes, and A. radiobacter among these 12 strains were present in both categories. Mixed inocula composed of one of the three infectious TGF-negative strains and one of the five nontumorigenic TGF-positive strains resulted in increased growth of tumors induced by the former. These growth changes were not correlated with changes in tumor number. The ability of different strains to show these tumor growth complementation effects corresponded fully with their ability to initiate TGF, as determined by the assay of leaf extracts. The nontumorigenic TGF-positive strains also promoted the growth of tumors initiated by low concentrations of strain B6. These complementation effects were due, therefore, to the same TGF found in extracts of B6 inoculated leaves and of leaves inoculated with most tumorigenic as well as many nontumorigenic strains of Agrobacterium. Heat-inactivated cells of strain B6 failed to initiate sufficient TGF to be detected in extracts, and heat-inactivated cells of several strains failed to show tumor growth complementation, indicating bacterial viability to be one prerequisite for TGF initiation. Heat inactivated cells also inhibited TGF production by viable cells, similar to their ability to inhibit tumor initiation. Consequently, bacteria capable of attaching to the A. tumefaciens infection site may initiate one of four patterns of events: (i) TGF production only, (ii) tumor induction only, (iii) both, or (iv) neither. Suggestive evidence for a second tumor-associated growth factor is presented.
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