Isolation and characterization of a chitinase-secreting mutant of mortierella pusilla with altered interaction with the mycoparasite piptocephalis virginiana

Mortierella pusilla is a susceptible host and supports good growth of the mycoparasite, Piptocephalis virginiana. Uninucleate spores of M. pusilla were sUbjected to N-methyl-N'-nitro-nitrosoguanidine (MNNG). To attain a high mutation frequency , a 1o-minute exposure to 10 mg/ml MNNG was used and lead to the survival of about 10 % of the spores. The exposed spores then were plated on chitin or milk plates. Approximately 30,000 colonies were examined after mutagenesis on the screening media. A strain, MUT23 , with abnormal slow growth morphology was found to delay parasitism by £. virginiana. The particular morphology was not due to auxotrophy, because this strain displayed normal hyphae when glucose was used as the sole carbon source. One interesting phenomenon was that MUT23 showed an extensive clearing zone around the colony on colloidal chitin agar after 20-25 d. On the same conditions, wild type strain did not show this phenotype. In addition, the MUT23 strain produced the same normal hypha as the wild type strain when it was grown on colloidal chitin agar. The MUT23 was also able to produce more spores on colloidal chitin agar than on malt-yeast extract and minimal media. The parasite germ tubes formed appressoria at the point of contact on the cell surface of wild type and MUT23 grown for 6 days cell surface but not on the cel surface of MUT23 grown for 2 days. Thus, interaction between MUT23 strain and the mycoparasite was dependent on MUT23 age. The effect of MUT23 filtrate on germination of the parasite was tested. Lysis of germinated spores of the parasite were observed in concentrated MUT23 filtered solution. MUT23 was compared to the wild type strain for their chitinase production in sUbmerged culture. The chitinase isozymes of both wild type and MUT23 were shown by immunoblotting. Eight distinct chitinase molecules were detected. MUT23 showed markedly higher chitinase activity than the wild type cultured in chitin-containing medium. Maximum chitinase activities of MUT23 were 13.5 fold higher at 20 day of the culture then that of wild type.

Isolation and partial characterization of host cell wall surface glycoproteins: their involvement in agglutination, attachment and appressorium formation by piptocephalis virginiana

Cell surface proteins obtained by alkaline extraction from isolated cell walls of Mortierella pusilla and M. candelabrum, host and nonhost, respectively, to the mycoparasite, Piptocephalis virginiana, were tested for their ability to agglutinate mycoparasite spores. The host cell wall protein extract had a high agglutinating activity (788 a.u. mg- t ) as compared with the nonhost extract (21 a.li. mg- t ). SDS-polyacrylamide gel electrophoresis of the cell wall proteins revealed four protein bands, a, b, c, and d (Mr 117, 100, 85 and 64 kd, respectively) at the host surface, but not at the nonhost surface, except for the faint band c. Deletion of proteins b or c from the host cell wall protein extract significantly reduced its agglutinating activity. Proteins band c, obtained as purified preparations by a series of procedures, were shown to be two glycoproteins. Carbohydrate analysis by gas chromatography demonstrated that glucose and Nacetylglucosamine were the major carbohydrate components of the glycoproteins. It was further shown that the agglutinating activity of the pure preparation containing both band c was 500-850 times that of the single glycoproteins, suggesting the involvement of both glycoproteins in agglutination. The results suggest that the glycoproteins band c are the two subunits of agglutinin present at the host cell surface. The two glycoproteins band c purified from the host cell wall protein extract were further examined after various treatments for their possible role in agglutination, attachment and appressorium formation by the mycoparasite. Results obtained by agglutination and attachment tests showed: (1) the two glycoprotein-s are not only an agglutinin responsible for the mycoparasite spore agglutination, but may also serve as a receptor for the specific recognition, attachment and appressorium formation by the mycoparasite; (2) treatment of the rnycoparasite spores with various sugars revealed that arabinose, glucose and N-acetylglucosamine inhibited the agglutination and attachment activity of the glycoproteins, however, the relative percentage of appressorium formation was not affected by the above sugars; (3) the two glycoproteins are relatively stable with respect to their agglutinin and receptor functions. The present results suggest that the agglutination and attachment may be mediated directly by certain sugars present at the host and mycoparasite cell surfaces while the appressorlum formation may be the response of complementary combinations of both sugar and protein, the two parts of the glycoproteins at the interacting surfaces of two fungi.

Isolation and partial characterization of a complementary protein from the mycoparasite, Piptocephalis virginiana, which specifically binds to two glycoproteins b and c of the host cell surface

Presence of surface glycoprotein in Piptocephalis virginiana that recognizes the host glycoproteins band c, reported earlier from our laboratory, was detected by immunofluorescence microscopy. Germinated spores of P. virginiana treated with Mortierella pusilla cell wall protein extract, primary antibodies prepared against glycoproteins band c and FITC-goat anti-rabbit IgG conjugate showed fluorescence. This indicated that on the surfaces of the biotrophic mycoparasite P. virginiana , there might be a complementary molecule which recognizes the glycoproteins band c from M. pusilla. Immunobinding analysis identified a glycoprotein of Mr 100 kDa from the mycoparasite which binds with the host glycoproteins band c, separately as well as collectively. Purification of this glycoprotein was achieved by (i) 60% ammonium sulfate precipitation, (ii) followed by heat treatment, and (iii) Sephadex G-IOO gel filtration. The glycoprotein was isolated by preparative polyacrylamide gel electrophoresis by cutting and elution. The purity of the protein ·was ascertained by SDS-PAGE and Western blot analysis. Positive reaction to periodic acid-Schiff reagent revealed the glycoprotein nature of this 100 kDa protein. Mannose was identified as a major sugar component of this glycoprotein by using a BoehringerMannheim Glycan Differentiation Kit. Electrophoretically purified glycoprotein was used to raIse polyclonal antibody in rabbit. The specificity of the antibody was determined by dot-immunobinding test and western-blot analysis. Immunofluorescence mIcroscopy revealed surface localization of the protein on the germ tube of Piptocephalis virginiana. Fluorescence was also observed at the surfaceJ of the germinated spores and hyphae of the host, M. pusilla after treatment with complementary protein from P. virginiana, primary antibody prepared against the complementary protein and FITC-goat anti-rabbit IgG conjugate.

Isolation of DNA sequences with homology to a degenerate FaRP oligonucleotide from the crayfish Procambarus clarkii

The neuropeptide Th1RFamide with the sequence Phe-Met-Arg-Phe-amide was originally isolated in the clam Macrocallista nimbosa (price and Greenberg, 1977). Since its discovery, a large family ofFl\1RFamide-related peptides termed FaRPs have been found to be present in all major animal phyla with functions ranging from modulation of neuronal activity to alteration of muscular contractions. However, little is known about the genetics encoding these peptides, especially in invertebrates. As FaRP-encoding genes have yet to be investigated in the invertebrate Malacostracean subphylum, the isolation and characterization ofFaRP-encoding DNA and mRNA was pursued in this project. The immediate aims of this thesis were: (1) to amplify mRNA sequences of Procambarus clarkii using a degenerate oligonucleotide primer deduced from the common amino acid sequence ofisolated Procambarus FaRPS, (2) to determine if these amplification products encode FaRP gene sequences, and (3) to create a selective cDNA library of sequences recognized by the degenerate oligonucleotide primer. The polymerase chain reaction - rapid amplification of cDNA ends (PCR-RACE) is a procedure in which a single gene-specific primer is used in conjunction with a generalized 3' or 5' primer to amplify copies ofthe region between a single point in the transcript and the 3' or 5' end of cDNA of interest (Frohman et aI., 1988). PCRRACE reactions were optimized with respect to primers used, buffer composition, cycle number, nature ofgenetic substrate to be amplified, annealing, extension and denaturation temperatures and times, and use of reamplification procedures. Amplification products were cloned into plasmid vectors and recombinant products were isolated, as were the recombinant plaques formed in the selective cDNA library. Labeled amplification products were hybridized to recombinant bacteriophage to determine ligated amplification product presence. When sequenced, the five isolated PCR-RACE amplification products were determined not to possess FaRP-encoding sequences. The 200bp, 450bp, and 1500bp sequences showed homology to the Caenorhabditis elegans cosmid K09A11, which encodes for cytochrome P450; transfer-RNA; transposase; and tRNA-Tyr, while the 500bp and 750bp sequences showed homology with the complete genome of the Vaccinia virus. Under the employed amplification conditions the degenerate oligonucleotide primer was observed to bind to and to amplify sequences with either 9 or 10bp of 17bp identity. The selective cDNA library was obselVed to be of extremely low titre. When library titre was increased, white. plaques were isolated. Amplification analysis of eight isolated Agt11 sequences from these plaques indicated an absence of an insertion sequence. The degenerate 17 base oligonucleotide primer synthesized from the common amino acid sequence ofisolated Procambarus FaRPs was thus determined to be non-specific in its binding under the conditions required for its use, and to be insufficient for the isolation and identification ofFaRP-encoding sequences. A more specific primer oflonger sequence, lower degeneracy, and higher melting temperature (TJ is recommended for further investigation into the FaRP-encoding genes of Procambarlls clarkii.

Personality type and self-directed learning

This correlational study was designed to investigate the relationship between self-directed learning and personality type. A sample of 133 graduate and undergraduate education students completed the MBTI and the SDLRS. Two hypotheses were examined: (a) scores on the intuitive scale will account for a significant amount of the variance in the prediction of selfdirected learning readiness and, (b) scores on the introverted scale will account for a significant amount of the variance in self-directed learning readiness. Stepwise multiple regression analyses indicated that psychological type accounts for 28% of the variance in self-directed learning. Support for the first hypothesis was found with 15% of the variance in selfdirected learning accounted for by intuition. The second hypothesis was not supported. Introversion accounted for 13% of the variance but in a negative manner. Results of this study indicate that personality type does influence the ability of the learner to be self-directed in studies. These findings add another dimension for the adult educator to consider when attempting to develop self-directedness in learners.

Shop-floor narratives : how six workers and a researcher describe learning activities

I am a part-time graduate student who works in industry. This study is my narrative about how six workers and I describe shop-floor learning activities, that is learning activities that occur where work is done, outside a classroom. Because this study is narrative inquiry, you wilileam about me, the narrator, more than you would in a more conventional study. This is a common approach in narrative inquiry and it is important because my intentions shape the way that I tell these six workers' stories. I developed a typology of learning activities by synthesizing various theoretical frameworks. This typology categorizes shop-floor learning activities into five types: onthe- job training, participative learning, educational advertising, incidental learning, and self-directed learning. Although learning can occur in each of these activities in isolation, it is often comprised of a mixture of these activities. The literature review contains a number of cases that have been developed from situations described in the literature. These cases are here to make the similarities and differences between the types of learning activities that they represent more understandable to the reader and to ground the typology in practice as well as in theory. The findings are presented as reader's theatre, a dramatic presentation of these workers' narratives. The workers tell us that learning involves "being shown," and if this is not done properly they "learn the hard way." I found that many of their best case lean1ing activities involved on-the-job training, participative learning, incidentalleaming, and self-directed learning. Worst case examples were typically lacking in properly designed and delivered participative learning activities and to a lesser degree lacking carefully planned and delivered on-the-job training activities. Included are two reflective chapters that describe two cases: Learning "Engels" (English), and Learning to Write. In these chapters you will read about how I came to see that my own shop-floor learning-learning to write this thesis-could be enhanced through participative learning activities. I came to see my thesis supervisor as not only my instructor who directed and judged my learning activities, but also as a more experienced researcher who was there to participate in this process with me and to help me begin to enter the research community. Shop-floor learning involves learners and educators participating in multistranded learning activities, which require an organizational factor of careful planning and delivery. As with learning activities, which can be multi-stranded, so too, there can be multiple orientations to learning on the shop floor. In our stories, you will see that these six workers and I didn't exhibit just one orientation to learning in our stories. Our stories demonstrate that we could be behaviorist and cognitivist and humanist and social learners and constructivist in our orientation to learning. Our stories show that learning is complex and involves multiple strands, orientations, and factors. Our stories show that learning narratives capture the essence of learning-the learners, the educators, the learning activities, the organizational factors, and the learning orientations. Learning narratives can help learners and educators make sense of shop-floor learning.

The assessment of self-directed learning among pre-service students in an Ontario faculty of education

The study determined students' perceptions of self-directed learning in their courses. Tests to assess perceptions are not being used in many programs. Assessments such as the Self-Directed Readiness Scale (SDLRS) and the Oddi continuing Learning Inventory (OCLI) have weaknesses that may have affected the use of tests. In this study, the creation of the Self-Directed Learning Test (SDLT) monitored students' perceptions by addressing what students were told before registration, how much input students had in developing the structure of the course, how much input students have in determining the evaluation for the course, what style of learning is taking place, and the characteristics of learning found among students. Fifty-one students in the pre-service program at Brock University completed the SDLT. Results showed that 47.1% of the sample liked self-directed learning. Several students who stated that they did not like selfdirected learning did not know what self-directed learning was. Results supported Brookfield's (1986) claim for more education on what self-directed learning is. The study did not support Knowles' (1980) assumption that adult students know and want to follow self-directed approaches to learning. The SDLT is a good method for monitoring self-directed learning and how students perceive their courses.

The isolation, partial purification and preliminary characterization of a growth factor from chick embryo brains

Chicl( brain growth factor (CBGF) is a mitogen isolated from embryonic chick brains thought to have a potential role as a trophic factor involved in nerve dependent amphibian limb regeneration. In addition, CBGF stimulates 3H-thymidine incorporation in chick embryo brain astrocytes in vitro. In this study, cultured chick embryo brain non-neuronal cells were employed in a bioassay to monitor CBGF activity throughout various stages of its pllrification. Cell culture and assay conditions were optimized. Nonneuronal cells grew best on collagen-coated culture dishes in complete medium, were most responsive to a growth stimulus [10% fetal bovine serum (FBS)] at the second and third subcultures, and were healthiest when rendered "quiescent" in medium supplemented with 1% FBS. The most effective bioassay conditions consisted of a minimum 14.5 hour "quiescence" time (24 hours was used), a 6 hour "prestimulation" time, and a 24 hour 3H-thymidine labeling time. Four-day subconfluent primary non-neuronal cells consisted of 6.63% GFAP positive cells; as a result cultures were thought to be mainly composed of astroblasts. CBGF was purified from 18-day chick embryo brains by ultrafiltration through Amicon PM-30 and YM-2 membranes, size exclusion chromatography through a Biogel P6 column, and analytical reverse-phase high-performance liquid chromatography (rp-HPLC). The greatest activity resided in rp-HPLC fraction #7 (10 ng/ml) which was as effective as 10% FBS at stimulating 3H-thymidine incorporation in chick embryo brain nonneuronal cells. Although other researchers report the isolation of a mitogenic fraction consisting of 5'-GMP from the embryonic chick brain, UV absorbance spectra, rp-HPLC elution profiles, and fast atom bombardment (FAB) mass spectra indicated that CBGF is neither 5'-GMP nor 51-AMP. 2 Moreover, commercially available 5t-GMP was inhibitory to 3H-thymidine incorporation in the chick non-neuronal cells, while Sf-AMP had no effect. Upon treatment with pronase, the biological activity of fraction P6-3 increased; this increase was nearly 30% greater than what would be expected from a simple additive effect of any mitogenic activity of pronase alone together with P6-3 alone. This may suggest the presence of an inhibitor protein. The bioactive component may be a protein protected by a nucleoside/nucleotide or simply a nucleoside/nucleotide acting alone. While the FAB mass spectrum of rp-HPLC fraction #7 did not reveal molecular weight or sequence information, the ion of highest molecular weight was observed at m/z 1610; this is consistent with previous estimations of CBGF's size. 3

Isolation and characterization of genomic DNA sequences that enhance the stability of plasmid DNA in mammalian cells /

The ease of production and manipulation has made plasmid DNA a prime target for its use in gene transfer technologies such as gene therapy and DNA vaccines. The major drawback of plasmid however is its stability within mammalian cells. Plasmid DNA is usually lost by cellular mechanisms or as a result of mitosis by simple dilution. This study set out to search for mammalian genomic DNA sequences that would enhance the stability of plasmid DNA in mammalian cells.Creating a plasmid based genomic DNA library, we were able to screen the human genome by transfecting the library into Human Embryonic Kidney (HEK 293) Cells. Cells that contained plasmid DNA were selected, using G418 for 14 days. The resulting population was then screened for the presence of biologically active plasmid DNA using the process of transformation as a detector.A commercially available plasmid DNA isolation kit was modified to extract plasmid DNA from mammalian cells. The standardized protocol had a detection limit of -0.6 plasmids per cell in one million cells. This allowed for the detection of 45 plasmids that were maintained for 32 days in the HEK 293 cells. Sequencing of selected inserts revealed a significantly higher thymine content in comparison to the human genome. Sequences with high A/T content have been associated with Scaffold/Matrix Attachment Region (S/MAR) sequences in mammalian cells. Therefore, association with the nuclear matrix might be required for the stability of plasmids in mammalian cells.

Isolation and analysis of a corprinus cinereus DNA fragment showing homology to a fimbrial cDNA from ustilago violacea

Surface proteinaceous fibrils, termed fimbriae, were first identified on gram negative bacteria in the 1940s. Fungal fimbriae, discovered some 25 years later, are found on members of all fungal classes. In the present study, polyclonal antiserum raised against the fimbrial proteins of U. vio/acea were used in order to identify antigenically related proteins from Coprinus cinereus and Schizophy//um commune. Two polypeptides with molecular masses of 37 and 39 kDa from C. cinereus were observed and confirm earlier results. A single previously unidentified 50 kDa polypeptide in S. commune crossreacted with the antiserum. The 50 kDa protein was found to consist of 3 isoforms with isoelectric points ranging from 5.6 to 5.8. A fimbrial cDNA derived from U. vio/acea was used to identify DNA restriction fragments from C. cinereus and S. commune showing homology to the fimbrial transcript of U. vio/acea. Heterologous hybridization with this cDNA was used in order to screen a C. cinereus genomic DNA library. A single clone, A2-3A, with a 14 kbp insert showed strong homology to the pfim3-1 cDNA. The region of homology, a 700 bp Xba I fragment, was subcloned into pUG19. This plasmid was refered to as pXX8. DNA sequence determinations of pXX8 and adjacent fragments from A2-3A suggested that the cloned DNA was a portion of the rONA repeat encoding the small subunit rRNA. DNA sequence analysis of pfim3-1 yielded an incomplete open reading frame. The predicted amino acid sequence codes for a 206 amino acid, 22 kDa polypeptide which contains a domain similar to a transmembrane domain from rat leukocyte antigen, GDS3. As well, an untranslated 576 nucleotide domain showed 81 % homology to pXX8 and 830/0 homology to the 188 rRNA sequence of Ustilago maydis. This sequence was found adjacent to a region of adenine-thymine base pairs presumed to represent the polyadenylation sequence of the fimbrial transcript. The size and extent of homology is sufficient to account for the hybridization of pfim3-1 to rDNA. It is suggested that this domain represents a completely novel regulatory domain within eukaryotes that may enable the observed rapid regeneration of fimbriae in U. violacea.

Self-directed learning, lifelong learning and transformative learning in the Society for Creative Anachronism

This study examines the connection between leisure group participation and learning activities undertaken by participants in the Society for Creative Anachronism (SCA), a medieval recreationist group. The thesis of this connection was developed through the researcher's observations during SCA participation. The intent of this study is to understand adult learning from the self-directed learning, lifelong learning, and -transformative learning components derived from participant's SCA experiences. This qualitative study was conducted by interviewing eight active SCA participants, two in each participation theme of historical research, artistic representation, performance, and martial skills. Informants' responses demonstrated an integration of their leisure activity with learning. The contextualization of learning a s both a primary activity and a necessary support to participation, places learning a t the heart of participants' SCA related activities. The positive descriptions of learning activities, descriptive terms of ownership, and situating learning as an enjoyable activity engaged for the pleasure of the experience, provides adult educators with a fascinating glimpse of willing and engaged adult learners pursuing lifelong learning outside of the traditional educational structure. Two themes emerged during the interviews. First, bonding with others provided the motivation to continue their activities. Secondly, a feeling of commitment and helonging defined their enjoyment and satisfaction with SCA participation. The clear implications are that adult educators can create effective learning communities by developing educational structures that engage adult learners wi th meaningful social interaction.

Synthesis and utilization of guanidine catalysts for applications directed towards the preparation of butenolide and modified amino acid derivatives

Development of guanidine catalysts is explored through direct iminium chloride and amine coupling, alongside a 2-chloro-l,3-dimethyl-IH-imidazol-:-3-ium chloride (DMC) induced thiourea cyclization. Synthesized achiral catalyst N-(5Hdibenzo[ d,t][1,3]diazepin-6(7H)-ylidene)-3,5-bis(trifluoromethyl) aniline proved unsuccessful towards O-acyl migrations, however successfully catalyzed the vinylogous aldol reaction between dicbloro furanone and benzaldehyde. Incorporating chirality into the guanidine catalyst utilizing a (R)-phenylalaninol auxiliary, generating (R)-2-((5Hdibenzo[ d,t] [1,3 ]diazepin-6(7H)-ylidene ) amino )-3 -phenylpropan-l-ol, demonstrated enantioselectivity for a variety of adducts. Highest enantiomeric excess (ee) was afforded between dibromofuranone and p-chlorobenzaldehyde, affording the syn conformation in 96% ee and the anti in 54% ee, with an overall yield of30%. Attempts to increase asymmetric induction were focused on incorporation of axial chirality to the (R)phenylalaninol catalyst using binaphthyl diamine. Incorporation of (S)-binaphthyl exhibited destructive selectivity, whereas incorporation of (R)-binaphthyl demonstrated no effects on enantioselectivity. Current studies are being directed towards identifying the catalytic properties of asymmetric induction with further studies are being aimed towards increasing enantioselectivity by increasing backbone steric bulk.

DNA-Directed DNA Polymerases Evolve From Reverse Transcriptase

Scientists have been debating for decades the origin of life on earth. A number of hypotheses were proposed as to what emerged first RNA or DNA; with most scientists are in favour of the "RNA World" hypothesis. Assuming RNA emerged first, it fellow that the RNA polymerases would've appeared before DNA polymerases. Using recombinant DNA technology and bioinformatics we undertook this study to explore the relationship between RNA polymerases, reverse transcriptase and DNA polymerases. The working hypothesis is that DNA polymerases evolved from reverse transcriptase and the latter evolved from RNA polymerases. If this hypothesis is correct then one would expect to find various ancient DNA polymerases with varying level of reverse transcriptase activity. In the first phase of this research project multiple sequence alignments were made on the protein sequence of 32 prokaryotic DNA-directed DNA polymerases originating from 11 prokaryotic families against 3 viral reverse transcriptase. The data from such alignments was not very conclusive. DNA polymerases with higher level of reverse transcriptase activity were non-confined to ancient organisms, as one would've expected. The second phase of this project was focused on conditions that may alter the DNA polymerase activity. Various reaction conditions, such as temperature, using various ions (Ni2+, Mn2+, Mg2+) were tested. Interestingly, it was found that the DNA polymerase from the Thermos aquatics family can be made to copy RNA into DNA (i.e. reverse transcriptase activity). Thus it was shown that under appropriate conditions (ions and reactions temperatures) reverse transcriptase activity can be induced in DNA polymerase. In the third phase of this study recombinant DNA technology was used to generate a chimeric DNA polymerase; in attempts to identify the region(s) of the polymerase responsible for RNA-directed DNA polymerase activity. The two DNA polymerases employed were the Thermus aquatic us and Thermus thermophiles. As in the second phase various reaction conditions were investigated. Data indicated that the newly engineered chimeric DNA polymerase can be induced to copy RNA into DNA. Thus the intrinsic reverse transcriptase activity found in ancient DNA polymerases was localized into a domain and can be induced via appropriate reaction conditions.

The Impact of Directed Mirror Focus and Technique Cues on Psychological, Cognitive and Emotional Exercise Correlates in an Introductory Weight Training Orientation

The purpose of the study was to investigate whether teaching inactive and low active women to use mirrors for form and technique purposes could lessen the negative impact of mirrors on self-presentational concerns, affect, and self-efficacy. Eligible women (N = 82) underwent a one-on-one weight training orientation with a personal trainer. Participants were randomized into one of four experimental groups, each unique in the type of feedback (general or technique-specific) and the degree of focus on the mirror for technique reinforcement. Questionnaires assessed study outcomes pre- and post-orientation. Results indicated groups did not significantly differ on any post-condition variables, when controlling for pre-condition values (all p’s >.05). All groups showed outcome improvements following the orientation. This suggests that during a complex task, a personal trainer who emphasizes form and technique can facilitate improvements to psychological outcomes in novice exercisers, independent of the presence of mirrors or directional cues provided.

Directed Technical Change and International Trade

Recent changes in comparative advantage in the largest OECD economies differ significantly from the predictions of Heckscher-Ohlin-Vanek theory. Japan's rising share of OECD machinery exports and the improvement in the comparative advantage of the USA and Germany in heavy industry were accompanied by growing scarcities of the factors used intensively in the favored sector of each country. Here we examine Acemoglu's (1998, 2002) hypothesis that technical change may be directed toward raising the marginal productivity of abundant factors. Testing this hypothesis with 1970-1992 export data from 14 OECD countries, we find evidence that international comparative advantage was reshaped by innovation biased toward the abundant factors in the largest economies.