Genetic diversity of the rice bean (Vigna umbellata) genepool as assessed by SSR markers

The genetic diversity of 472 rice bean accessions (388 cultivated and 84 wild) from 16 Asian countries was evaluated by 13 simple sequence repeat (SSR) markers. In total, 168 alleles were detected, and the numbers of alleles in cultivated and wild accessions were 129 and 132, respectively. The gene diversity in cultivated populations (0.565) was about 83% of that for wild (0.678) populations. Cultivated populations from Vietnam, Myanmar, Nepal, and India had the highest gene diversity (>0.5). East Asian accessions formed a distinct genepool. Indonesian cultivated accessions showed high genetic divergence from other cultivated populations and had the most similar genetic structure to wild accessions. In Nepalese cultivated accessions, many accessions from western regions were quite distinct from others and formed a specific group. These Nepalese accessions could be considered a unique gene source for rice bean breeding. In contrast, eastern Nepalese accessions showed an SSR profile similar to that of Southeast Asian rice beans. The present study represents the first comprehensive SSR analysis in cultivated and wild rice bean germplasm and clarifies geographical distribution of genetic profile that might be used to broaden the genetic base of currently grown rice bean cultivars.

A model to predict the frequency of integration of fitness-related QTLs from cultivated to wild soybean

With the proliferation of genetically modified (GM) products and the almost exponential growth of land use for GM crops, there is a growing need to develop quantitative approaches to estimating the risk of escape of transgenes into wild populations of crop relatives by natural hybridization. We assessed the risk of transgene escape by constructing a population genetic model based on information on fitness-related QTLs obtained from an F (2) population of wild soybean G. soja × cultivated soybean Glycine max. Simulation started with ten F (1) and 990 wild soybeans reproducing by selfing or outcrossing. Seed production was determined from the genetic effects of two QTLs for number of seeds (SN). Each seed survived winter according to the maternal genotype at three QTLs for winter survival (WS). We assumed that one neutral transgene was inserted at various sites and calculated its extinction rate. The presence of G. max alleles at SN and WS QTLs significantly decreased the probability of introgression of the neutral transgene at all insertion sites equally. The presence of G. max alleles at WS QTLs lowered the risk more than their presence at SN QTLs. Although most model studies have concentrated only on genotypic effects of transgenes, we show that the presence of fitness-related domestication genes has a large effect on the risk of transgene escape. Our model offers the advantage of considering the effects of both domestication genes and a transgene, and they can be widely applied to other wild × crop relative complexes.

The origin and fate of morphological intermediates between wild and cultivated soybeans in their natural habitats in Japan

The spread of transgenes into the genome of wild soybean is a concern when transgenic and wild soybeans are planted sympatrically. The objectives of this study were to investigate the origin and fate of morphological intermediates between wild and cultivated soybeans in their natural habitats in Japan. Twenty nuclear microsatellite and two chloroplast dCAPS markers were used to evaluate genetic variation of 468 wild, 17 intermediate, and 12 cultivated soybean samples collected from six sites between 2003 and 2006. Allelic differentiation of microsatellite markers between wild and cultivated soybeans was sufficient to detect their hybrids. Based on levels of observed heterozygosity, intermediate soybean plants were from two generations: either F(1) or an early segregating generation. Genetic admixture analysis and parentage assignment analysis revealed that the parents of all intermediate soybean plants could be assigned to a particular wild soybean plant and late-maturing cultivar. The chloroplast DNA haplotypes revealed that all intermediate soybean plants originated from gene flow from cultivated to wild soybeans at all sites. Based on monitoring at both the phenotypic and molecular levels, hybrids quickly disappeared from natural habitats, and secondary gene flow from these plants to wild soybean was not detected. Thus, while gene flow from transgenic soybean into wild soybean can occur, gene introgression appears to be rare in natural habitats in Japan. This is the first report on the detection of gene flow from cultivated to wild soybean at the molecular level.

Genetic diversity of the azuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) gene pool as assessed by SSR markers

To facilitate the wider use of genetic resources including newly collected cultivated and wild azuki bean germplasm, the genetic diversity of the azuki bean complex, based on 13 simple sequence repeat (SSR) primers, was evaluated and a core collection was developed using 616 accessions originating from 8 Asian countries. Wild germplasm from Japan was highly diverse and represented much of the allelic variation found in cultivated germplasm. The SSR results together with recent archaeobotanical evidence support the view that Japan is one center of domestication of azuki bean, at least for the northeast Asian azuki bean. Cultivated azuki beans from China, Korea, and Japan were the most diverse and were genetically distinct from each other, suggesting a long and relatively isolated history of cultivation in each country. Cultivated azuki beans from eastern Nepal and Bhutan were similar to each other and quite distinct from others. For two primers, most eastern Nepalese and Bhutanese cultivated accessions had null alleles. In addition, wild accessions from the Yangtze River region of China and the Himalayan region had a null allele for one or the other of these primers. Whether the distinct diversity of azuki bean in the Himalayan region is due to introgression or separate domestication events requires further study. In contrast, western Nepalese azuki beans showed an SSR profile similar to that of Chinese azuki beans. The genetic distinctness of cultivated azuki beans from Vietnam has been revealed for the first time. The specific alleles indicate that Vietnamese azuki beans have been cultivated in isolation from Chinese azuki beans for a long time. Wild germplasm from the Himalayan region showed the highest level of variation. Based on the results, Himalayan germplasm could be considered a novel gene source for azuki bean breeding. A comparison with mungbean SSR analysis revealed that the mean gene diversity of cultivated azuki bean (0.74) was much higher than that of cultivated mungbean (0.41). The reduction in gene diversity due to domestication, the domestication bottleneck, in azuki bean is not strong compared with that in mungbean.

Development of a black gram [Vigna mungo (L.) Hepper] linkage map and its comparison with an azuki bean [Vigna angularis (Willd.) Ohwi and Ohashi] linkage map

The Asian Vigna group of grain legumes consists of six domesticated species, among them black gram is widely grown in South Asia and to a lesser extent in Southeast Asia. We report the first genetic linkage map of black gram [Vigna mungo (L.) Hepper], constructed using a BC(1)F(1) population consisting of 180 individuals. The BC(1)F(1) population was analyzed in 61 SSR primer pairs, 56 RFLP probes, 27 AFLP loci and 1 morphological marker. About 148 marker loci could be assigned to the 11 linkage groups, which correspond to the haploid chromosome number of black gram. The linkage groups cover a total of 783 cM of the black gram genome. The number of markers per linkage group ranges from 6 to 23. The average distance between adjacent markers varied from 3.5 to 9.3 cM. The results of comparative genome mapping between black gram and azuki bean show that the linkage order of markers is highly conserved. However, inversions, insertions, deletions/duplications and a translocation were detected between the black gram and azuki bean linkage maps. The marker order on parts of linkage groups 1, 2 and 5 is reversed between the two species. One region on black gram linkage group 10 appears to correspond to part of azuki bean linkage group 1. The present study suggests that the azuki bean SSR markers can be widely used for Asian Vigna species and the black gram genetic linkage map will assist in improvement of this crop.

Population genetic structure of Japanese wild soybean (Glycine soja) based on microsatellite variation

The research objectives were to determine aspects of the population dynamics relevant to effective monitoring of gene flow in the soybean crop complex in Japan. Using 20 microsatellite primers, 616 individuals from 77 wild soybean (Glycine soja) populations were analysed. All samples were of small seed size (< 0.03 g), were directly collected in the field and came from all parts of Japan where wild soybeans grow, except Hokkaido. Japanese wild soybean showed significant reduction in observed heterozygosity, low outcrossing rate (mean 3.4%) and strong genetic differentiation among populations. However, the individual assignment test revealed evidence of rare long-distance seed dispersal (> 10 km) events among populations, and spatial autocorrelation analysis revealed that populations within a radius of 100 km showed a close genetic relationship to one another. When analysis of graphical ordination was applied to compare the microsatellite variation of wild soybean with that of 53 widely grown Japanese varieties of cultivated soybean (Glycine max), the primary factor of genetic differentiation was based on differences between wild and cultivated soybeans and the secondary factor was geographical differentiation of wild soybean populations. Admixture analysis revealed that 6.8% of individuals appear to show introgression from cultivated soybeans. These results indicated that population genetic structure of Japanese wild soybean is (i) strongly affected by the founder effect due to seed dispersal and inbreeding strategy, (ii) generally well differentiated from cultivated soybean, but (iii) introgression from cultivated soybean occurs. The implications of the results for the release of transgenic soybeans where wild soybeans grow are discussed.

A genetic linkage map for azuki bean [Vigna angularis (Willd.) Ohwi & Ohashi]

To make progress in genome analysis of azuki bean (Vigna angularis) a genetic linkage map was constructed from a backcross population of (V. nepalensis x V. angularis) x V.angularis consisting of 187 individuals. A total of 486 markers-205 simple sequence repeats (SSRs), 187 amplified fragment length polymorphisms (AFLPs) and 94 restriction fragment length polymorphisms (RFLPs) -were mapped onto 11 linkage groups corresponding to the haploid chromosome number of azuki bean. This map spans a total length of 832.1 cM with an average marker distance of 1.85 cM and is the most saturated map for a Vigna species to date. In addition, RFLP markers from other legumes facilitated finding several orthologous linkage groups based on previously published RFLP linkage maps. Most SSR primers that have been developed from SSR-enriched libraries detected a single locus. The SSR loci identified are distributed throughout the azuki bean genome. This moderately dense linkage map equipped with many SSR markers will be useful for mapping a range of useful traits such as those related to domestication and stress resistance. The mapping population will be used to develop advanced backcross lines for high resolution QTL mapping of these traits.

The development of SSR markers by a new method in plants and their application to gene flow studies in azuki bean [Vigna angularis (Willd.) Ohwi & Ohashi]

To gain a better understanding of wild and weedy azuki population structures in relation to the cultigens we have developed simple sequence repeat (SSR) markers based on a new methodology for plant material. In the azuki bean genome, the number of (AG)(n) and (AC)(n) motif loci per haploid genome has been estimated to be 3,500 and 2,100, respectively, indicating that (AG)(n) motifs are a rich source of markers. We constructed a (AG)(n)-SSR-enriched library in azuki bean in order to obtain a comprehensive range of SSR markers efficiently. The method applied in this study resulted in a 116-fold enrichment over the non-enriched genomic library, with a high percentage (98%) of successful single-locus amplification by the primer pairs designed. Consequently, this method can be applied to construct SSR-enriched libraries suitable for large-scale sequencing. We obtained 255 unique sequences from an (AG)(n)-enriched library for azuki bean. Fifty primer pairs were designed and screened against five populations of wild azuki bean. Among these five populations, one population from Bato town, Tochigi prefecture, Japan, showed greater polymorphism using these primers than the others and was therefore chosen for the in-depth study. The genotypes of 20 individuals were investigated using eight of the SSR primers developed. The genetic relationships among individuals revealed a complex spatial pattern of population structure. Although azuki bean is considered to be a predominantly self-pollinating species, 3 of the 20 individuals tested in the population showed heterozygous genotypes, indicating outcrossing. Allele size and DNA sequence in each of the 20 individuals were compared with those of landraces and released cultivars of azuki bean. Plants in part of the population had many alleles of the same size and with the same sequence as those in cultivated azuki bean, suggesting that gene flow from the cultigen to wild plants has occurred in this population. Unintentional transgene escape from azuki could therefore occur when transgenic azuki is grown in areas where its wild and weedy relatives occur. The approach used here could be applied to biosafety monitoring of transgenic azuki bean.

Motor evoked potentials following transcranial magnetic stimulation after middle cerebral artery and/or basilar artery occlusions in rats

To clarify the significance of motor evoked potentials following transcranial magnetic stimulation (MMEPs) in acute stage of cerebral ischemia, MMEPs were recorded in rats with the right middle cerebral artery (MCA) and/or the basilar (BA) artery occlusions. MMEPs from bilateral forelimb muscle and regional cerebral blood flow (rCBF) of the pons were recorded simultaneously. After MCA occlusion, the amplitudes of MMEPs from left forelimb were increased up to approximately 184-221% of the pre-ischemic value for 60 min, though the latencies were unchanged. On the other hand, in the rats of BA occlusion and both BA and MCA occlusion groups, MMEPs amplitudes were decreased to 8-25% of the pre-ischemic value for 60 min. Pontine rCBF was decreased to 28-44% in both groups. As a mechanism of the facilitation of MMEPs after MCA occlusion, the affection of the inhibitory mechanism between the cerebral cortex and the generator of MMEPs by MCA occlusion is speculated.

Characterization of resistance to three bruchid species (Callosobruchus spp., Coleoptera, Bruchidae) in cultivated rice bean (Vigna umbellata)

Resistance of wild and cultivated rice bean (Vigna umbellata [Thunberg] Ohwi and Ohashi) to three bruchid species, Callosobruchus chinensis L., Callosobruchus maculatus F., and Callosobruchus analis F., was evaluated. All but three accessions of cultivated, and all wild rice bean accessions tested, exhibited complete resistance to all three bruchid species. Rice bean seeds with seed coat removed also showed complete resistance to the three bruchid species. Results indicate that physical attributes and/or chemical(s) present in the seed coat of rice bean are not the main factors responsible for resistance. Feeding tests were performed by using artificial beans prepared with varying proportions of rice bean (resistant) and azuki bean (susceptible) flour. Number of bruchid adults that emerged decreased, and larval developmental period (days) was extended, when artificial beans with an increasing proportion of rice bean flour were used. These tests revealed that a chemical compound(s) contained in the cotyledon of rice bean has an inhibitory effect on the growth of these bruchid species. The results also indicate that the chemical(s) in rice bean cotyledon is most effective against C. maculatus.

Molecular phylogeny of genus Vigna subgenus Ceratotropis based on rDNA ITS and atpB-rbcL intergenic spacer of cpDNA sequences

The genetic diversity and phylogenetic relationships among species in the genus Vigna subgenus Ceratotropis were investigated using sequence data from the ribosomal DNA ITS and atpB-rbcL intergenic spacer of chloroplast DNA regions. While both sets of sequences were of similar lengths about 700 bp the rDNA-ITS was more informative than atpB-rbcL having 170% more polymorphic sites and five times as many parsimony-informative sites. The atpB-rbcL spacer may be appropriate for analysis of taxa above the species level in the genus Vigna. Results of analyzing rDNA-ITS revealed, with low level of statistical bias, separation of the subgenus into three groups that correspond to the three sections Aconitifoliae, Angulares, and Ceratotropis. The ancestral section is Aconitifoliae based on comparison with the outgroup species cowpea, Vigna unguiculata. The V minima complex, V minima, V riukiuensis, and V nakashimae, has a distinct evolutionary path within section Angulares. Other species in section Angulares are very closely related except V trinervia. Vigna trinervia has an intermediate position between sections. Sequence data suggests one genome donor to V reflexo-pilosa came from a lineage within section Angulares close to V exilis, V hirtella, and V umbellata. Data presented supports the view that section Angulares is the most recently diversified section in the subgenus, as inferred by short terminal branch lengths among the species of this section.

Diversity in the integrase coding domain of a gypsy-like retrotransposon among wild relatives of rice in the Oryza officinalis complex

The Oryza officinalis complex is a genetically diverse, tertiary genepool of rice. We analyzed part of the primary structure of the integrase coding domain (ICD) of a gypsy-like retrotransposon from species of the O. officinalis species complex. PCR was performed with degenerate primers that hybridized to conserved sequences in the integrase genes of gypsy-type retrotransposons, using total DNA from different species of the O. officinalis complex as templates. Cloning and sequencing of the PCR products showed that the amplified fragments are highly homologous to each other (75-90%) and belong to one family of retrotransposons that is related to the previously studied RIRE-2 element from rice. Two main subfamilies of 292 and 351 bp were distinguished. Analysis of primary sequence data supports previous reports that sequence divergence during vertical transmission has been the major influence on the evolution of gypsy-type retrotransposons in Oryza species. Based on sequence data phylogenetic relationships among species of the O. officinalis complex were estimated. The data suggests that O. eichingeri is more closely related to the ancestral species of the complex.

Insecticidal activity of an alpha-amylase inhibitor-like protein resembling a putative precursor of alpha-amylase inhibitor in the common bean, Phaseolus vulgaris L

alpha-Amylase inhibitor (alphaAI) in the common bean, Phaseolus vulgaris L., protects seeds from insect pests such as the cowpea weevil (Callosobruchus maculatus) and the azuki bean weevil (C. chinensis). Cultivars which lack alphaAI still show resistance to both bruchids. These cultivars have a glycoprotein that reacts with anti-alphaAI-1 antibodies. The glycoprotein with a molecular mass of 29 kDa (Gp29) was purified and the encoding gene was isolated. The primary structure of Gp29 is the same as alpha-amylase inhibitor-like protein (AIL) from which the encoding gene has already been isolated. AIL resembles a putative precursor of alphaAI, even though it does not form the active inhibitor. However, AIL has some inhibitory effect on the growth of C. maculatus but not C. chinensis. The presence of AIL alone is insufficient to explain the bruchid resistance of common bean cultivars lacking alpha-AI. Common bean seeds appear to contain several factors responsible for the bruchid resistance.

Genetic localization of a bruchid resistance gene and its relationship to insecticidal cyclopeptide alkaloids, the vignatic acids, in mungbean (Vigna radiata L. Wilczek)

Bruchid resistance, controlled by a single dominant gene (Br) in a wild mungbean accession (TC1966), has been incorporated into cultivated mungbean (Vigna radiata). The resistance gene simultaneously confers inhibitory activity against the bean bug, Riptortus clavatus Thunberg (Hemiptera: Alydidae). The resultant isogenic line (BC20 generation) was characterized by the presence of a group of novel cyclopeptide alkaloids, called vignatic acids. A linkage map was constructed for Br and the vignatic acid gene (Va) using restriction fragment length polymorphism (RFLP) markers and a segregating BC20F2 population. By screening resistant and susceptible parental lines with 479 primers, eight randomly amplified polymorphic DNA (RAPD) markers linked to Br were identified and cloned for use as RFLP probes. All eight RAPD-based markers, one mungbean, and four common bean genomic clones were effectively integrated around Br within a 3.7-cM interval. Br was mapped to a 0.7-cM segment between a cluster consisting of six markers and a common bean RFLP marker, Bng110. The six markers are closest to the bruchid resistance gene, approximately 0.2 cM away. The vignatic acid gene, Va, cosegregated with bruchid resistance. However, one individual was identified in the BC20F2 population that retained vignatic acids in spite of its bruchid susceptibility. Consequently, Va was mapped to a single locus at the same position as the cluster of markers and 0.2 cM away from Br. These results suggest that the vignatic acids are not the principal factors responsible for bruchid resistance in V. radiata but will facilitate the use of map-based cloning strategies to isolate the Br gene.

[Neovascularization after encephalo-duro-arterio-synangiosis in elderly quasi-moyamoya disease: a case report]

A 65-year-old man who had a history of diabetes mellitus visited a hospital for recent memory disturbance. MR angiography showed stenoses of the main trunks of the intracranial arteries. He was admitted to our hospital, and angiography revealed occlusion of the left cervical internal carotid and right middle cerebral arteries, and stenoses of the right internal carotid, right anterior cerebral, left vertebral, and right posterior cerebral arteries. There was collateral circulation formed from the left external carotid and left posterior cerebral arteries. Basal moyamoya vessels were also observed. 123I-IMP SPECT showed low perfusion of the right cerebral hemisphere, and response to acetazolamide was poor. Based on the angiographical findings and the presence of diabetes mellitus, the patient was diagnosed as having quasi-moyamoya disease. Vascular reconstructive surgery was indicated. Since there was no recipient artery adequate for STA-MCA anastomosis, encephalo-duro-arterio-synangiosis was performed on the right side. Postoperatively, the patient's recent memory improved gradually, and angiography performed 7 months after the operation revealed neovascularization from the superficial and deep temporal arteries. Although indirect bypass surgery has been applied mainly to child moyamoya disease, its effectiveness for cerebral ischemia in adult patients has also been reported, particularly in cases with misery perfusion. Neovascularization with indirect bypass surgery can be expected if the patient is under misery perfusion, even in elderly patients.

A genetic linkage map of azuki bean constructed with molecular and morphological markers using an interspecific population (Vigna angularis x V. nakashimae)

A genetic linkage map of azuki bean (Vigna angularis) was constructed with molecular and morphological markers using an F2 population of an interspecific cross between azuki bean and its wild relative, V. nakashimae. In total, 132 markers (108 RAPD, 19 RFLP and five morphological markers) were mapped in 14 linkage groups covering 1250 cM; ten remained unlinked. The clusters of markers showing distorted segregation were found in linkage groups 2, 8 and 12. By comparing the azuki linkage map with those of mungbean and cowpea, using 20 RFLP common markers, some sets of the markers were found to belong to the same linkage groups of the respective maps, indicating that these linkage blocks are conserved among the three Vigna species. This map provides a tool for markerassisted selection and for studies of genome organization in Vigna species.

Effect of spinal cord stimulation on cerebral blood flow in cats

Effects of electric spinal cord stimulation (SCS) on cerebral blood flow (CBF) were investigated in anesthetized adult cats. SCS was performed under various stimulus conditions for 1 h via a wire electrode inserted into the dorsal epidural space at various levels in the spinal cord. CBF was measured in the subcortex of the parietal lobe by hydrogen clearance method before, during, and after SCS. After the start of SCS in the high cervical cord with a frequency of 20 Hz, CBF gradually increased up to 140% of the pre-SCS value, and remained high for 15 min after the end of SCS. SCS of the low cervical or midthoracic cord under the same condition caused no significant increase in CBF. Nor did SCS of the high cervical cord with frequencies of 200 and 2,000 Hz increase CBF. No CBF increase was observed after SCS of the high cervical cord with 20 Hz when the dorsal column was sectioned at the medullo-cervical junction. These results suggest that the ability of SCS to increase CBF is peculiar to high cervical cord stimulation with moderately low frequencies.

[Cavernous angioma of falx cerebri; case report]

A first case of cavernous angioma of falx cerebri is reported. A 62-year-old woman who had a history of intermittent headache and dizziness was admitted to our hospital. On admission she had no neurological deficit, but CT scan showed a slightly high density tumor located beneath the falx cerebri. This was markedly and homogeneously enhanced by contrast medium. MRI showed a tumor with low intensity in T1-weighted image and high intensity speckled with low intensity in T2-weighted image. Angiogram revealed a faint tumor-stain fed by the bilateral pericallosal arteries at middle arterial to late venous phases. With the tumor attached to the lower edge, the falx was totally removed through a left front-parietal craniotomy. Histologically the tumor was diagnosed as cavernous angioma and thought to have originated from the dura mater of the falx. A search in the literature revealed that only 7 cases of extracerebral cavernous angiomas excluding ones in the middle cranial fossa have been previously reported. Five of them were located at the tentorium cerebelli and two at the convexity. The MRI finding such as speckled mixed intensity may reflect the vascular lumens or their thromboses in the tumor. Angiographic finding such as faint tumor stain at middle arterial to late venous phases due to slow blood flow in the tumor are thought to be specific to intracranial cavernous angiomas. These findings are of particular importance in differentiating cavernous angiomas from meningiomas.

[Formation of experimental obesity by Crisco]

Randomized male litter S.D. rats (weight: about 60 g, 1 group: 10 rats) were used. By using Crisco (hydrogenated cotton seed oil) within the limits of 10 approximately 60%, the intake of the 30% group was high and a good incidence rate of obesity (about 100%) was obtained in the 6 month experiment. In the 30% group, increases of wet weight in perirenal retroperitoneal and subcutaneous fat depots, increases of the number and diameter of fat cells (perirenal retroperitoneal fat depot), elevations of liver fat % and serum insulin level, and a fall of liver phosphoenolpyruvate carboxykinase activity were observed in the 3 month experiment.

[Biochemical and histological studies on the exposure with concentrated oxygen. Special attention to the generation of peroxidized lipids (author's transl)]

In the present studies, rats are fed with four different kinds of diet; (i) normal diet, (ii) B2-deficient diet, (iii) B2-tetrabutyrate added normal diet, and (iv) B2-tetrabutyrate added B2-deficient diet. The number or rats in each group is 10 and the term of raising is 18 to 46 days. In the normal diet group, when exposed to 90% oxygen, cholesterol, triglycerides, and the TBA value are increased in blood serum. The addition of B2-tetrabutyrate in diets reduces these elevation. Through electron microscope observation, oxygen exposure leads to puffing of mitochondria and increasing lipofuscin granules in livers and lungs. The destruction of mitochondria is also observed in brain. The addition of B2-teterabutyrate reduces the destruction of mitochondria and suppresses formation of lipofuscin.

[Influence of food browning on nutrition. IV. Effect on trypsin action on a synthetic substrate (author's transl)]

The action of brown substances on trypsin inhibition was studied using casein and a synthetic substrate, alpha-N-benzoyl-DL-arginine-p-nitroaniline. It was found that brown substances inhibit trypsin action similarly on both substrates. Lineweaver-Burk plots revealed that the inhibition was of irreversible, noncompetitive type in either case. Inhibitory action of each fraction after Sephadex G-25 passage was found to be proportional to the degree of food browning or oxidation.

[Influence of food browning on nutrition. III. Effect of brown substances on digestive enzyme activity (author's transl)]

In the present study, we separated and partially purified brown substances from eggplants and examined their inhibitory action on trypsin activity. The following results were obtained: 1. The first half of the elute after passing ethanol-extractable brown substances through DEAE-cellulose column showed no inhibitory action on trypsin, whereas the middle portion of the elute contained a trypsin inhibitor(s). Similar results were obtained after fractionation with Sephadex G-25. The degree of inhibition was increased after purification. 2. Both crude ethanol extracts of eggplant brown substances and acetate buffer extracts from eggplant exocarps showed similarly an enzyme inhibition of competitive type. 3. Both nondialyzable portion of ethanol extracts and purified fraction after Sephadex G-25 passage showed a noncompetitive type of inhibition. DOPA-melanin and chlorogenic acid-melanin as model substances exhibited a similar noncompetitive inhibition. Purified ethanol extracts of eggplant brown substances showed an ultraviolet absorption spectrum similar to that of chlorogenic acid. From these findings it is concluded that both eggplant brown substances and polyphenol substances play an essential role in the inhibition of digestive enzymes.