Sialidase of swine influenza A viruses: variation of the recognition specificities for sialyl linkages and for the molecular species of sialic acid with the year of isolation

The sialidase of swine influenza A viruses of N1 and N2 subtypes, isolated from 1930 to 1992, was studied for substrate specificity with ganglio-series, lacto-series type II and GM3 gangliosides containing Neu5Ac2-3Gal, Neu5Gc2-3Gal and Neu5Ac2-6Gal linkages. All viral sialidases tested showed that the activity for hydrolysing substrates with Neu5Ac2-3Gal was higher than the activities with Neu5Gc2-3Gal and Neu5Ac2-6Gal linkages. When GM1b, GM3 and sialylparagloboside were used as substrates, the earliest strain (A/Wisconsin/15/30 H1N1, isolated in 1930) showed the activity ratio of Neu5Ac2-6Gal to Neu5Ac2-3Gal to be 0.13:0.2, and the ratio Neu5Gc2-3Gal/Neu5Ac2-3Gal to be 0.19:0.37, while those strains isolated from 1978 to 1992 exhibited ratios of 0.29:0.58 for Neu5Ac2-6Gal/Neu5Ac2-3Gal and 0.51:0.76 for Neu5Gc2-3Gal/Neu5Ac2-3Gal. The above results indicate that the substrate specificities of sialidases from swine influenza A viruses towards sialyl linkages and the molecular species of sialic acid are related to the year of isolation, i.e. strains isolated after 1978 exhibited higher activity towards Neu5Ac2-6Gal and Neu5Gc2-3Gal linkages when compared with strains isolated in an earlier year, 1930.Abbreviation Neu5Ac 5-N-acetylneuraminic acid - Neu5Gc 5-N-glycolyneuraminic acid - Gal d-galactose - Glc d-glucose - Cer Ceramide - II³(Neu5Ac)Lac Neu5Ac2-3Gal1-4Glc - GM3(Neu5Ac2-3Gal) Neu5Ac2-3Gal1-4Glc1-Cer - GM3(Neu5Gc2-3Gal) Neu5Gc2-3Gal1-4Glc1-Cer - GM1b(Neu5Ac2-3Gal) Neu5Ac2-3Gal1-3GalNac1-4Gal1-4Glc1-Cer - GMlb(Neu5Gc2-3Gal) Neu5Gc2-3Gal1-3GalNAc1-4Gal1-4Glc1-Cer - IV³(Neu5Ac)nLc4Cer Neu5Ac2-3Gal1-3GlcNAc1-4Gal1-4Glc1-Cer - IV³(Neu5Gc)nLc4Cer Neu5Gc2-3Gal1-3GlcNAc1-4Gal1-4Glc1-Cer - IV⁶(Neu5Ac)nLc4Cer Neu5Ac2-6Gal1-3GlcNAc1-4Gal1-4Glc1-Cer - TDC taurodeoxycholate.     

Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves ofClusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela

Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (), hydrogen isotope ratio (D) and N-levels, and with altitude were assessed. In the samples, where values of above 15 indicate predominant performance of C₃ photosynthesis, there were slight tendencies of increasing , D and N-levels with increasing altitude and of increasing with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of with altitude in the samples, where values of below 10 indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C₃-CAM transitions in C₃/CAM intermediate species, low availability of water is the most important.     

Bi-antennary oligo-(N-acetyllactosamino)glycans of I-type are galactosylated preferentially at the GlcNAcβ1-6Gal linked arms by α1,3-galactosyltransferase of bovine thymus

1,3-Galactosylation of radiolabelled bi-antennary acceptors Gal1-4GlcNAc1-3(Gal1-4GlcNAc1-6)Gal-R (R=1-OH, 1-4GlcNAc or 1-4Glc) with bovine thymus 1,3-galactosyltransferase was studied. At all stages of the reactions the three acceptors reacted faster at the 1 6 linked arm than at the 1 3 linked branch. Hence, in addition to the doubly 1,3-galactosylated products, practically pure Gal1-4GlcNAc1-3(Gal1-3Gal1-4GlcNAc1-6)Gal-R could be obtained from the three acceptors in reactions that had proceeded to near completion. The isomeric mono-1,3-galactosylated products were identified by using exoglycosidases to remove the branches unprotected by 1,3-galactoses and by subsequently identifying the resulting linear glycans chromatographically.Abbreviations Gal d-galactose - GlcNAc N-acetyl-d-glucosamine - Lac lactose - LacNAc Gal1-4GlcNAc - MH maltoheptaose - MP maltopentaose - MT maltotriose - MTet maltotetraose - WGA wheat germ agglutinin - 3 position 3 of the galactose unit of LacNAc or Lac - 6 position 6 of the galactose unit of LacNAc or Lac     

MHC class II sequences of an HLA-DR2 narcoleptic

Narcolepsy has a 98% association with the DR2-Dw2/DQw1 haplotype. To establish if a disease-specific allele is present in narcolepsy, a cDNA library was made from a B-cell line from a DR2,4/DQw1,3 narcoleptic. Clones encoding the two expressed DR2 chains, along with DQw1 and chains, were isolated and completely sequenced. The coding regions of these four genes were similar to published nucleotide and protein sequences from corresponding healthy controls, with some minor exceptions. The 3 untranslated region of one of the DR2 genes in the narcoleptic was extended by 42 bp. Complete sequences were not available for DQw1.2 or from healthy individuals, but first domain nucleotide sequences showed only a single nonproductive difference in DQ. Partial protein sequences of both DQ and from published data were identical. Although the effects of minor differences cannot be ruled out completely, it is concluded that there are probably no narcolepsy-specific DR or DQ / sequences, and that the alleles found in narcolepsy are representative of those found in the healthy population.     

Unique sequences for two HLA-DRB1 genes expressed on distinct DRw6 haplotypes

We have used restriction fragment length polymorphism (RFLP) analysis and DNA sequencing to characterize two distinct DRB1 alleles expressed on DRw52 and DQw7-associated haplotypes but not readily defined by conventional DR serology. These two haplotypes, designated HLA-D HAG and PEV, react variably with DRw13(w6), DRw14(w6), and the more broad DR 3+6 antisera. Analysis of RFLP revealed that HLA-D HAG and PEV are associated with different DRw52 variants, and that HAG is indistinguishable from DRw18(3) haplotypes. Sequencing of the HAG and PEV DRB1 genes showed each to represent novel alleles. Nevertheless, these sequences show similarities with the other alleles of the DR5, w6, and w8 family. HAG (DRB1*1303) appears to have arisen either from two recombinational events involving at least three DRB1 sequences (DRB1*1101, DRB1*0803, DRB1*0401) or from a single recombinational event together with multiple point mutational events. PEV appears to represent a DRB1*1301-1302/DRB1*1101 recombinant allele, with recombination having occured in the region of bases 175 – 198. The results of this study suggest that the DRw52 family haplotypes is derived from a relatively restricted number of ancestral sequences, with diversity among DRB1 alleles within this family arising through gene conversion or recombination events.     

Why the aristocrats were ‘heavy’ or how ethnopsychology legitimized inequality among the Tlingit

Conclusion Even a cursory look at the ethnographic literature on other Northwest Coast societies reveals some striking similarities with the Tlingit way of conceptualizing aristocrats as special persons. Thus the Kwakiutl referred to their chiefs as real or complete people, who were heavier than commoners. The Coast Tsimshian called their highest aristocrats real or ripe persons, in contrast to the low-ranking ones, who were described as unhealed or green. The Coast Tshimshian also referred to their chiefs as strong, heavy, and solid like a rock. The neighboring Gitksan contrasted the chiefs, described as people who were good and clean and stayed put, with the commoners, who were said to be dirty, ignorant, and always moving around. Because spirits of the dead liked to return to persons who were clean and showed respect by giving away wealth and feasts, there was considerable moral and practical pressure on the aristocrats to remain pure, train knowledgeable and clean heirs, and continue potlatching. Finally, among the Haida, rank was tied to a wider system of symbolic classification, associating aspects of food, space, clothing, ritual pollution and the ethic of industry with attributes of seniority.While some of the symbolic associations of aristocratic status are culture specific, others are present in several, if not all, of the NWC cultures. What we need is a comparative symbology of aristocratic status, which would combine the reanalysis of the existing ethnographic data with the introduction of some new materials that can still be obtained in the field. Such work would be the best tribute to Irving Goldman himself and to our common illustrious ancestors—Franz Boas and Marcel Mauss.Sergei Kan is Professor of Anthropology at Dartmouth College.     

High D-glucose does not affect binding of α-tocopherol to human erythrocytes

The role of -tocopherol uptake system in human erythrocyte in the uptake of plasma -tocopherol has been suggested. However no information is available on -tocopherol uptake activity of human erythrocytes in the presence of high levels of D-glucose which is known to lead to pathological alterations in different cells including human erythrocytes. Therefore, in order to examine the effect of D-glucose on the binding of -tocopherol to human erythrocytes, the binding characteristics of -tocopherol to these cells were established first. Binding of [3H]-tocopherol to human erythrocytes was both saturable and specific. Scatchard analysis of -tocopherol binding to these cells showed the presence of two independent classes of binding sites with widely different affinities. The high affinity binding sites had a dissociation constant (Kd1) of 90 nM with a binding capacity (n1) of 900 sites per cell, whereas the low affinity binding sites had a dissociation constant (Kd2) of 5.2 M and a binding capacity (n2) of 105,400 sites per cell. Trypsin treatment abolished all the -tocopherol binding activity. Competition for the binding of -tocopherol to human erythrocytes was effective with other homologues of -tocopherol (-tocopherol, -tocopherol and -tocopherol) and their potency was almost equal to -tocopherol itself. The order of preference was -tocopherol > -tocopherol -tocopherol -tocopherol. Incubation of human erythrocytes with various concentrations of D-glucose did not affect -tocopherol uptake activity. Our data demonstrate the presence of an -tocopherol uptake system in human erythrocytes and that the -tocopherol uptake activity is not modulated by the presence of D-glucose.     

An elongated segment of DNA observed between two human α globin genes

Summary Detailed restriction enzyme analysis of the DNA from a Chinese female showed that one of her chromosomes had a >17.5 kb deletion of DNA, including the , 2, and 1 globin genes, which is present in many Southeast Asians with an -thalassemia-1 chromosome. Her normal chromosome had the expected cluster of -like globin genes (5----2-1-3), but the segment of DNA between the two globin genes was elongated by some 0.5–0.7 kb. Analyses of various restriction sites suggested that this normal variant of the human globin gene complex is due to a crossover between a normal chromosome with () and a chromosome with an -thalassemia-2 (–^3.7) and an -21-hybrid gene.     

Transformation of Atriplex gmelini plants from callus lines using Agrobacterium tumefaciens

Atriplex gmelini plants were regenerated via organogensis from hypocotyl explants. Callus lines were induced from the hypocotyl explants on Linsmaier and Skoog (LS) medium supplemented with 1 M benzyladenine and 5 M -naphthaleneacetic acid in the dark. Shoots were regenerated from the callus lines on LS medium supplemented with 20 M thidiazuron and 0.1 M -naphthaleneacetic acid under a high-intensity light condition (450 mol m^–2 s^–1). The regenerated shoots were rooted on LS medium without growth regulators to obtain fully developed plants. We succeeded in transforming Atriplex gmelini from callus lines using Agrobacterium tumefaciens.     

Involvement of Erks activation in cadmium‐induced AP‐1 transactivation in vitro and in vivo

Cadmium is a potent and effective carcinogen in rodents and has recently been accepted by IARC (International Agency for Research on Cancer) as a category 1 carcinogen. Cadmium-induced upregulation of intracellular signaling pathways leading to increased mitogenesis is thought to be a major mechanism for the carcinogenic activity following chronic cadmium exposure. In the present study, we found that exposure of cells to cadmium induced significant activation of AP1 and all three members of the MAP kinase family in mouse epidermal JB6 cells. The induction of AP1 activity by cadmium appears to involve activation of Erks, since the induction of AP1 activity by cadmium was blocked by pretreatment of cells with PD98058. Interestingly, the induction of AP1 by cadmium was greatly enhanced by the chemical tumor promoter, TPA and the growth factor EGF, but not by ultraviolet C radiation. In vivo studies demonstrated that cadmium could also induce transactivation of AP1 in AP1luciferase report transgenic mice. Considering the role of AP1 activation in tumor promotion, the results presented in this study provide a possible molecular mechanism for cadmiuminduced carcinogenesis.     

Binding of the galactose-specificPseudomonas aeruginosa lectin,PA-I,to glycosphingolipids and other glycoconjugates

The carbohydrate-binding specificity ofPseudomonas aeruginosa lectin I (PA-I) in iodinated or biotinylated form was studied. A large number of glycosphingolipids, as well as some glycoproteins and neoglycoproteins were used as ligands. Also, inhibition by free saccharides of PA-I binding to glycosphingolipids was tested. It was found that the lectin binds most strongly to terminal and nonsubstituted Gal3Gal- or Gal4Gal-structures.Abbreviations PA-I Pseudomonas aeruginosa lectin I - Cer ceramide - lactosylceramide Gal4GlcCer - iso globotriaosylcerami Gal3Gal4GlcCer - globotriaosylceramide Gal4Gal4GlcCer - globoside or globotetraosylceramide GalNAc3Gal4Gal4GlcCer - Forssman glycolipid GalNAc3GalNAc3Gal4Gal4GlcCer - P1 glycolipid Gal4Gal4GlcNAc3Gal4GlcCer - lactoneotetraosylceramide Gal4GlcNAc3Gal4GlcCer - B5 glycolipid Gal3Gal4GlcNAc3Gal4GlcCer - gangliotetraosylceramide Gal3GalNAc4Gal4GlcCer - GM1 Gal3GalNAc4(NeuAc3)Gal4GlcCer - RBC red blood cells - BSA bovine serum albumin - PBS phosphate-buffered saline - SDS sodium dodecyl sulfate - TLC thin-layer chromatography - HPLC high pressure liquid chromatography - MS mass spectrometry - FAB fast-atom bombardment - EI electron impact     

Regio- and stereo-selective synthesis of vinyl glucose ester catalyzed by an alkaline protease of Bacillus subtilis

The transesterification of -d-glucose with divinylsuccinate, divinyladipate and divinylsebacate in pyridine at 55 °C for 3 days was catalyzed by an alkaline protease from Bacillus subtilis to give corresponding 6-O-vinyl glucose esters at 30%, 53% and 35% yield, respectively. The stereo-selectivity of the alkaline protease toward the -anomer was affected by the acyl donor chain length. 6-O-Vinylsuccinyl-d-glucose was mixture of - and -anomers (/=44/56), the other two products were the pure -d-glucose derivatives.     

Non-reciprocal gonadal dysgenesis in hybrids of the chironomid midge Chironomus thummi

In male hybrids of the cross Chironomus thummi thummi (stock Hl) x Ch. th. piger (stock E) , but not the reciprocal cross, rudimentary testes develop at a growth temperature of 21 ° C. Within the dysgenic testes of these hybrids a number of abnormalities are observed which are restricted to the germ line. Approximately 60% of the hybrid males show allocyclic chromosome behaviour in spermatogonia and spermatocyte I nuclei. Within these nuclei two groups of four chromosomes are formed which differ from one another in their state of condensation. Each chromosome group consists of three long and one short chromosome. In cases where allocycly is very pronounced, the chromosomes of both groups disintegrate into numerous unequally sized fragments at meiotic prometaphase I, and gametes are not produced. In individuals, in which the allocycly is less pronounced or absent the nuclear divisions appear to be normal but chromosome and chromatid aberrations are frequent, and the number of viable sperm is reduced. In these males, the chiasma frequency is also decreased more than 12-fold in comparison with the reciprocal, unaffected piger x thummi hybrids.     

On genetic components in autoimmunity: a critical review based on evolutionarily oriented rationality

The immune system furnishes the organism with the utmost effective defence mechanisms against foreign and changes in self without doing self-harm. However, optimized efficacy in the defence against the immense variety of foreign antigens generates a higher risk for inadvertent self challenge. Such inherent short-comings are the inevitable burden traded for the benefits of an optimally organized defence system. The central molecules involved in specific immune reactions include antigen receptors of B and T lymphocytes, and antigen-presenting proteins encoded by the major histocompatibility complex (MHC; in man HLA). The genetics and evolution of these multigene families is discussed here with respect to their potential contributions to disturbances of self recognition. Simple molecular biological tools and procedures for efficiently screening the immunologically relevant genes are described.Dedicated to Professor Dr. U. Wolf on the occasion of his 60th birthday     

Extracellular matrix proteins,integrin receptors (VLA-β1, VLA-α2 and VLA-α5) and growth fraction in atypical macroregenerative nodules of the liver: an immunocytochemical case study

A case of cirrhotic liver harbouring three atypical macroregenerative nodules and an hepatocellular carcinoma was immunocytochemically investigated for the expression of VLA- 1, VLA-2 and VLA-5 integrins and for different extracellular matrix (ECM) components (collagen I, collagen IV, laminin, fibronectin and tenascin). In addition, the proliferative activity within the nodules was evaluated, using the MIB 1 monoclonal antibody (MAb). The cirrhotic liver disclosed a continuous staining pattern of the ECM proteins investigated, as well as a sinusoidal immunostaining of VLA-1, VLA-2 and VLA-5. The macroregenerative nodules showed a discontinued immunoreactivity for ECM proteins while maintaining a VLA-1 sinusoidal immunostaining, coupled with intercellular immunostaining. VLA-2 and VLA-5 expression was lacking. The growth fraction was low in both the above pathological conditions. The hepatocellular carcinoma was devoid of any ECM immunostaining. VLA-1 immunoreactivity exhibited a honeycomb pattern of staining, whereas VLA subunits were absent. MIB1 expression was high, being present in 30% of neoplastic nuclei. A possible relationship between atypical macroregenerative nodules and hepatocellular carcinoma is discussed.This paper was partly presented at the 35th Symposium of the Society for Histochemistry, Gargellen, Austria, Sept. 29–Oct. 3, 1993     

Nuclear and cytoplasmic gene control of resistance to loose smut (Ustilago tritici (Pers.) Rostr.) in wheat (Triticum aestivum L.)

Summary Using disomic chromosome substitution lines based on the susceptible wheat cultivar Chinese Spring, loose smut resistance of wheat cultivars Hope and Thatcher was shown to be conferred in each case by a single dominant major gene carried on chromosome 7 A (Hope) or 7 B (Thatcher). Partial resistance was determined by genes on an additional eight Hope or seven Thatcher chromosomes, and similarities were evident between the partial resistance genotypes ofHope and Thatcher. Chinese Spring exhibited a mean infection value of approximately 50%, indicating a significant level of partial resistance, which was found to be due, in part, to genes on the homoeologous chromosome arms 1 As, 1 Es and 1 Ds, and to cytoplasmic genes. Substitution of the Chinese Spring nucleus into the cytoplasm of Aegilops squarrosa, Ae. variabilis or Ae. mutica resulted in increased susceptibility to Ustilago tritici. Several alloplasmic lines of the resistant wheat cultivars Selkirk and Chris exhibited race-specific susceptibility to U. tritici.     

?kologische untersuchungen an aphiden

Zusammenfassung In Temperaturkabinen wird die Fortpflanzungspotenz von Myzus persicae (Sulzer) (Herkunft Groß-Lüsewitz) bei Dauertemperaturen von 15 bis 30° auf Kohlrüben (Brassica napus subspec. rapifera) untersucht.Eine Populationsanalyse nach Birch (1948) (intrinsic rate of increase) ergab den höchsten Wachstumsfaktor bei Dauertemperaturen zwischen 20 und 23°.Dauertemperaturen >25° führten zu einer starken Minderung der. Fortpflanzungspotenz. 30° ist die obere Grenze der Fortpflanzung der untersuchten Myzus persicae-Population.

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The reproductive potential of the peach-potato aphid (origin Gross-Lüsewitz) was studied at temperatures between 15° and 30° in constant temperature chambers. They were cultivated on Swede (Brassica napus spp. rapifera) which stood in Knop's nutrient under gauze cloches in petri dishes. The production of juvenile larvae and the mortality of the mothers was measured daily. The total of all larvae (including those which were dropped) and the total of larvae on the leaf were separately enumerated. The larvae on the leaf were designated as viable larvae. A population analysis using Birch's method showed a maximum value for the growth factor k (difference between birth and mortality rates) of 23° for the total of all larvae, and of 20° for the viable larvae (Fig. 6). The daily relative growth-ratio was at the same temperatures respectively 1.36 and 1.34 (Table IV). Optimum development of M. persicae on swedes occurs thus between 20° and 23°. The percentages of viable larvae which add to the net production of total larvae are 53, 61, 30, and 24 (Table III) at temperatures of 15, 20, 25, and 30° respectively. The average length of a generation was 18.5 days at 15° and less than 13 days at 28 to 30° (Fig. 5). The multiplication rate per generation was 38 at 15°, 48 at 20°, but only 5.5 at 30° (Fig. 4). The time of development from first-stage larva to adult was 12.5 days at 15°, 5 days at 28° and 6 days at 30° (Table VII). The upper limit, where a weak multiplication was still possible, was at 30°. It is concluded that in regions where such limiting temperatures occur during some part of the day, the temperature can be the major regulating factor of the insect populations.

     

Cytogenetic analysis of structural rearrangements in three varieties of common wheat,Triticum aestivum

Summary The winter wheat varieties Starke and Cappelle Desprez and the spring wheat Chinese Spring were analysed for structural chromosome rearrangements that resulted in the formation of multivalents in F₁ hybrids. The analyses were carried out using hybrids involving euploids, monosomic and ditelosomic stocks, and double-monotelodisomic constructs. The study confirmed that Cappelle Desprez differs from Chinese Spring in a reciprocal translocation between chromosomes 5B and 7B (Riley et al. 1967); a translocation involving chromosomes 3B and 3D could not be verified. Furthermore, the analysis showed that Starke differs from Chinese Spring in a reciprocal translocation between chromosomes 7A and 7D. Both translocations have a coefficient of multivalent realisation of about 0.84. Further multivalents in euploid Starke, in euploid and some aneuploid stocks of Cappelle Desprez, and in euploid as well as various types of aneuploid hybrids between all three varieties could nearly all be explained hypothesizing that chromosome 2B of both Starke and Cappelle Desprez is a duplication-deficiency chromosome. In the hypothesis a part of the long arm of 2B is missing and replaced by a duplicated part of the long arm of chromosome 2D. The multivalents of this rearrangement showed an average coefficient of realisation of about 0.09.Sven Ellerström died in December 1985     

The effects of collembola grazing on microbial activity in decomposing leaf litter

Summary Ground leaf litter was inoculated with the fungus Coriolus versicolor and incubated in respirometers for 6 days (fresh cultures) or 33 days (senescent cultures) before different number of Folsomia candida were added. Grazing by 5 animals stimulated O₂ consumption in both series of cultures but 10, 15 or 20 animals inhibited microbial respiration. The stimulatory effect was less marked in the senescent cultures. Bacterial and fungal standing crops increased in fresh cultures during the course of the experiment but grazing by collembola increased bacterial and reduced fungal standing, crops in proportion to the grazing intensity. Microbial standing crops were not determined for senescent cultures. Microarthropod feeding activities can therefore exert a strong differential effect on fungal and bacterial populations which has not been previously recognised.     

Phenylacetic acid-induced somatic embryogenesis in cultured hypocotyl explants of geranium (Pelargonium x hortorum Bailey)

Summary The effect of a non-indole compound, phenylacetic acid (PAA), on the induction of somatic embryogenesis in tissue cultures of geranium (Pelargonium x hortorum Bailey cv. Scarlet Orbit Improved) was investigated. Hypocotyl explants derived from young, dark-grown seedlings were cultured on Murashige and Skoog (1962) medium (MS) supplemented with PAA or IAA (0.01–120 M) alone or in combination with BAP (8 M). Somatic embryogenesis was induced by both PAA and IAA at 0.01–20 M with 8 M BAP, however, the optima differed considerably for the two compounds. Maximal activity of IAA for somatic embryogenesis was found at 0.1–2.5 M, whereas PAA gave best results at 10 and 20 M under identical culture conditions. Higher concentrations (30–120 M) of IAA or PAA in the medium induced callusing in the explants, but the callus was neither embryogenic nor morphogenic.Abbreviations BAP N⁶-benzylaminopurine - IAA indole-3-acetic acid - MS Murashige and Skoog (1962) - PAA phenylacetic acid