Preparation of carotenoid extracts and nanoemulsions from Lycium barbarum L. and their effects on growth of HT-29 colon cancer cells

Lycium barbarum L., a traditional Chinese herb widely used in Asian countries, has been demonstrated to be protective against chronic diseases such as age-related macular degeneration. The objectives of this study were to determine the carotenoid content in L. barbarum by high-performance liquid chromatography-mass spectrometry, followed by preparation of a carotenoid nanoemulsion to evaluate the mechanism of inhibition on HT-29 colon cancer cells. The highest extraction yield of carotenoids was attained by employing a solvent system of hexane-ethanol-acetone (1:1:1, v/v/v). Nine carotenoids, including neoxanthin (4.47 μg g-1), all-trans-zeaxanthin and its cis-isomers (1666.3 μg g-1), all-trans-β-cryptoxanthin (51.69 μg g-1), all-trans-β-carotene and its cis-isomers (20.11 μg g-1), were separated within 45 min and quantified using a YMC C30 column and a gradient mobile phase of methanol-water (9:1, v/v) (A) and methylene chloride (B). A highly stable carotenoid nanoemulsion composed of CapryolTM 90, Transcutol®HP, Tween 80 and deionized water was prepared with a mean particle size of 15.1 nm. Characterization of zeaxanthin standard, blank nanoemulsion, carotenoid extract and carotenoid nanoemulsion by differential scanning calorimetry curves and Fourier transform infrared spectra revealed a good dispersion of zeaxanthin-dominated carotenoid extract with no significant chemical change after incorporation into nanoemulsion. The in vitro release kinetic study showed a higher release profile at pH 5.2 than at physiological pH 7.4, suggesting a rapid release of carotenoids in the acidic environment (pH 4.5-6.5) characteristic of tumors. Both the carotenoid nanoemulsion and the extract were effective at inhibiting growth of HT-29 colon cancer cells, with an IC50 of 4.5 and 4.9 μg ml-1, respectively. Also, both treatments could up-regulate p53 and p21 expression and down-regulate CDK2, CDK1, cyclin A and cyclin B expression and arrest the cell cycle at G2/M. The study may form a basis for further exploration of L. barbarum nanoemulsion in cancer treatment.

Cytotoxicity and antibacterial activity of gold-supported cerium oxide nanoparticles

Background

Cerium oxide nanoparticles (CeO₂) have been shown to be a novel therapeutic in many biomedical applications. Gold (Au) nanoparticles have also attracted widespread interest due to their chemical stability and unique optical properties. Thus, decorating Au on CeO₂ nanoparticles would have potential for exploitation in the biomedical field.

Methods

In the present work, CeO₂ nanoparticles synthesized by a chemical combustion method were supported with 3.5% Au (Au/CeO₂) by a deposition-precipitation method. The as-synthesized Au, CeO₂, and Au/CeO₂ nanoparticles were evaluated for antibacterial activity and cytotoxicity in RAW 264.7 normal cells and A549 lung cancer cells.

Results

The as-synthesized nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, and ultraviolet-visible measurements. The X-ray diffraction study confirmed the formation of cubic fluorite-structured CeO₂ nanoparticles with a size of 10 nm. All synthesized nanoparticles were nontoxic towards RAW 264.7 cells at doses of 0–1,000 μM except for Au at >100 μM. For A549 cancer cells, Au/CeO₂ had the highest inhibitory effect, followed by both Au and CeO₂ which showed a similar effect at 500 and 1,000 μM. Initial binding of nanoparticles occurred through localized positively charged sites in A549 cells as shown by a shift in zeta potential from positive to negative after 24 hours of incubation. A dose-dependent elevation in reactive oxygen species indicated that the pro-oxidant activity of the nanoparticles was responsible for their cytotoxicity towards A549 cells. In addition, cellular uptake seen on transmission electron microscopic images indicated predominant localization of nanoparticles in the cytoplasmic matrix and mitochondrial damage due to oxidative stress. With regard to antibacterial activity, both types of nanoparticles had the strongest inhibitory effect on Bacillus subtilis in monoculture systems, followed by Salmonella enteritidis, Escherichia coli, and Staphylococcus aureus, while, in coculture tests with Lactobacillus plantarum, S. aureus was inhibited to a greater extent than the other bacteria.

Conclusion

Gold-supported CeO₂ nanoparticles may be a potential nanomaterial for in vivo application owing to their biocompatible and antibacterial properties.

The synthesis and characterization of poly(γ-glutamic acid)-coated magnetite nanoparticles and their effects on antibacterial activity and cytotoxicity

Magnetite nanoparticles (MNPs) modified with sodium and calcium salts of poly(γ-glutamic acid) (NaPGA and CaPGA) were synthesized by the coprecipitation method, followed by characterization and evaluation of their antibacterial and cytotoxic effects. Superparamagnetic MNPs are particularly attractive for magnetic driving as well as bacterial biofilm and cell targeting in in vivo applications. Characterization of synthesized MNPs by the Fourier transform infrared spectra and magnetization curves confirmed the PGA coating on MNPs. The mean diameter of NaPGA- and CaPGA-coated MNPs as determined by transmission electron microscopy was 11.8 and 14 nm, respectively, while the x-ray diffraction pattern revealed the as-synthesized MNPs to be pure magnetite. Based on agar dilution assay, both NaPGA- and CaPGA-coated MNPs showed a lower minimum inhibitory concentration in Salmonella enteritidis SE 01 than the commercial antibiotics linezolid and cefaclor, but the former was effective against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 10832, whereas the latter was effective against Escherichia coli O157:H7 TWC 01. An in vitro cytotoxicity study in human skin fibroblast cells as measured by MTT assay implied the as-synthesized MNPs to be nontoxic. This outcome demonstrated that both γ-PGA-modified MNPs are cytocompatible and possess antibacterial activity in vitro, and thereby should be useful in in vivo studies for biomedical applications.

Inhibition effect of poly(γ-glutamic acid) on lead-induced toxicity in mice

The objectives of this study were to evaluate the efficiency in treatment of lead-induced intoxication in mice with γ-PGA as chelating agent and compare with the drug (meso-2,3-dimercaptosuccinic acid). The results showed the incorporation of γ-PGA at 200 and 400 mg/kg could reduce the accumulation of lead in the liver, heart, and testis; however, the latter was more effective in decreasing the lead content in the kidney and spleen. Nevertheless, both doses failed to inhibit the lead accumulation in the lung and brain. Additionally, both doses of γ-PGA could reduce TBARs in the kidney and brain, as well as elevate δ-aminolevulinic acid dehydrase (δ-ALAD) activity in blood and decrease glutamic pyruvic transaminase (GPT) and lactic dehydrogenase (LDH) activities in the serum. For hematological parameters, both white blood cells (WBCs) and hematocrite (HCT) were raised by 400 mg/kg of γ-PGA, while for both doses of γ-PGA, a slight decline in hemoglobin (HGB), mean cell volume (MCV), mean cell hemoglobin (MCH), and mean cell hemoglobin concentration (MCHC) was observed, with the red blood cells (RBCs) being unaffected.

Anti-inflammatory effects of isoflavone powder produced from soybean cake

Soybean cake, a byproduct obtained during the processing of soybean oil, has been shown to be a rich source of isoflavones. The objectives of this study were to use soybean cake as raw material for processing into powder and to evaluate the anti-inflammatory activity. Eleven treatments, including powders of malonylglucoside, glucoside, acetylglucoside, aglycone, ISO-1, and ISO-2, as well as genistein standard, gamma-PGA, control, normal, and PDTC, were used for evaluation. A total of 77 mice were each provided daily with tube feeding for 4 weeks at a dose of 0.3 mL of aqueous solution from each treatment, and inflammation was induced with intraperitoneal injection of 1 mg/kg of body weight lipopolysaccharide (LPS). Results showed that all of the isoflavone powders and genistein standard were effective in inhibiting LPS-induced inflammation, lowering leukocyte number in mice blood and reducing production of IL-1beta, IL-6, NO, and PGE2 in both peritoneal exudate cell supernatant and peritoneal exudate fluid. All of the isoflavone treatments failed to retard T cell proliferation; however, both ISO-1 and ISO-2 could inhibit B cell proliferation. The difference in anti-inflammatory activity was minor between any of the isoflavone treatments.

Effects of heating time and antioxidants on the formation of heterocyclic amines in marinated foods

The effect of heating time and antioxidants on the heterocyclic amine (HAs) formation in marinated foods were studied. Food samples were cooked at 98 +/- 2 degrees C for 1, 2, 4, 8, 16 and 32 h in a closed pan in the presence of water, soy sauce and rock candy with or without antioxidants. The various HAs in marinated food samples and juice were analyzed by HPLC with photodiode-array detection. Results showed that the amount of HAs formed during heating followed an increased order for each increasing heating time. A larger variety and higher amount of HAs were generated in marinated pork when compared to marinated eggs and bean cake. In marinated juice, the levels of HAs were present in greater amount than in marinated foods. The incorporation of antioxidants Vitamin C, Vitamin E and BHT were found to be effective towards HAs inhibition, however, the effect was minor.

Extraction of Cu and Pb from printed circuit board sludge using ammonia solutions

Sludge from a printed circuit board factory containing high concentrations of Cu and Pb was characterized. Aqueous ammonia solutions were used to extract metals from the sludge. The extraction reactions were completed within 6 hrs. The best extraction efficiency was found at pH of 10.0. Higher solid-liquid ratio and higher ammonia concentration resulted in better extraction efficiency. Fractionation experiments showed that Cu and Pb were mainly extracted from the Fe-Mn oxide-bound and carbonate-bound fractions. Extracted sludge could meet the TCLP regulation limit and be categorized as a non-hazardous waste. Results show that ammonia extraction is of potential in resource recovery and in detoxification of hazardous waste.

Changes in root cap pH are required for the gravity response of the Arabidopsis root

Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall pH sensor (a cellulose binding domain peptide-Oregon green conjugate) and a cytoplasmic pH sensor (plants expressing pH-sensitive green fluorescent protein) to monitor pH dynamics throughout the graviresponding Arabidopsis root. The root cap apoplast acidified from pH 5.5 to 4.5 within 2 min of gravistimulation. Concomitantly, cytoplasmic pH increased in columella cells from 7.2 to 7.6 but was unchanged elsewhere in the root. These changes in cap pH preceded detectable tropic growth or growth-related pH changes in the elongation zone cell wall by 10 min. Altering the gravity-related columella cytoplasmic pH shift with caged protons delayed the gravitropic response. Together, these results suggest that alterations in root cap pH likely are involved in the initial events that mediate root gravity perception or signal transduction.

Interaction of PRK1 receptor-like kinase with a putative elF2B beta-subunit in tobacco

PRK1, a receptor-like kinase that is expressed in pollen, pollen tubes, and ovaries, has been shown to play important roles in pollen development and embryo sac development in Petunia inflata. We have used the kinase domain of PRK1 as a bait in the yeast two-hybrid system to identify PRK1-interacting proteins. The screening resulted in isolation of a cDNA encoding a protein highly homologous to the human and yeast beta-subunit of translation initiation factor 2B (eIF2B-beta), which was designated NeIF2Bbeta. eIF2B is a guanine nucleotide exchange protein that functions in the regulation of translation in eukaryotic cells. Deletion mutants of NeIF2Bbeta were analyzed for their interaction with PRK1, and the results suggested that the N-terminal half of NeIF2Bbeta, especially the region between residue 103 and 235, is important for the interaction. This protein association was confirmed by in vitro binding assay of the recombinant NeIF2Bbeta and PRK1 proteins. Despite high sequence homology between NeIF2Bbeta and its yeast counterpart, the NeIF2Bbeta cDNA could not rescue the phenotype of the yeast mutant strain lacking the GCD7 gene encoding eIF2B-beta, when transferred into the mutant strain.

Plant Signaling 2000. Cross talk among geneticists, physiologists, and ecologists

Plants respond in complex ways to their environment, to their internal physiological status, and to the activity of other plants, pathogens, herbivores, and organisms. Plant Signaling 2000, a symposium sponsored by the Penn State Intercollege Graduate Program in Plant Physiology (May 18-20, 2000), explored the machinery underlying these responses and their potential for cross talk. We recount here some of the major themes emerging from this interdisciplinary symposium, which ranged from genetic and biochemical analyses of signaling pathways in Arabidopsis and other model plants to field studies of plants responding to insect damage.

Identification of self-incompatibility (S-) locus linked pollen cDNA markers in Petunia inflata

Solanaceous type self-incompatibility (SI) is controlled by a single polymorphic locus, termed the S-locus. The only gene at the S-locus that has been characterized thus far is the S-RNase gene, which controls pistil function, but not pollen function, in SI interactions between pistil and pollen. One approach to identifying additional genes (including the pollen S-gene, which controls pollen function in SI) at the S-locus and to study the structural organization of the S-locus is chromosome walking from the S-RNase gene. However, the presence of highly repetitive sequences in its flanking regions has made this approach difficult so far. Here, we used RNA differential display to identify pollen cDNAs of Petunia inflata, a self-incompatible solanaceous species, which exhibited restriction fragment length polymorphism (RFLP) for at least one of the three S-haplotypes (S1, S2, and S3) examined. We found that the genes corresponding to 10 groups of pollen cDNAs are genetically tightly linked to the S-RNase gene. These cDNA markers will expedite the mapping and cloning of the chromosomal region of the Solanaceae S-locus by providing multiple starting points.

How flowering plants discriminate between self and non-self pollen to prevent inbreeding

Flowering plants have evolved various genetic mechanisms to circumvent the tendency for self-fertilization created by the close proximity of male and female reproductive organs in a bisexual flower. One such mechanism is gametophytic self-incompatibility, which allows the female reproductive organ, the pistil, to distinguish between self pollen and non-self pollen; self pollen is rejected, whereas non-self pollen is accepted for fertilization. The Solanaceae family has been used as a model to study the molecular and biochemical basis of self/non-self-recognition and self-rejection. Discrimination of self and non-self pollen by the pistil is controlled by a single polymorphic locus, the S locus. The protein products of S alleles in the pistil, S proteins, were initially identified based on their cosegregation with S alleles. S proteins have recently been shown to indeed control the ability of the pistil to recognize and reject self pollen. S proteins are also RNases, and the RNase activity has been shown to be essential for rejection of self pollen, suggesting that the biochemical mechanism of self-rejection involves the cytotoxic action of the RNase activity. S proteins contain various numbers of N-linked glycans, but the carbohydrate moiety has been shown not to be required for the function of S proteins, suggesting that the S allele specificity determinant of S proteins lies in the amino acid sequence. The male component in self-incompatibility interactions, the pollen S gene, has not yet been identified. The possible nature of the pollen S gene product and the possible mechanism by which allele-specific rejection of pollen is accomplished are discussed.

S-allele sequence diversity in natural populations of Solanum carolinense (Horsenettle)

S-allele diversity in Solanum carolinense was surveyed in two natural populations, located in Tennessee and North Carolina, with a molecular assay to determine the genotype of individual plants. A total of 13 different S-alleles were identified and sequenced. There is high overlap between the two populations sampled, with 10 alleles shared in common, one allele found only in Tennessee, and two found only in North Carolina. The number of alleles in this species appears to be extremely low compared with other species with gametophytic self-incompatibility. Sequence comparisons show that most alleles are extremely different one from another in their primary sequence and a phylogenetic analysis indicates extensive trans-specific evolution of S-lineages. In addition, some alleles appear to be derived much more recently. The implications of these observations are discussed in the light of recent theoretical results on S-allele population diversity and persistence.

Eosinophil differentiation and hypodensity alteration activities in Dermatophagoides pteronyssinus-stimulated mononuclear cell culture supernatants derived from asthmatics

We investigated the contributing effect of Dermatophagoides pteronyssinus-stimulated mononuclear cell (MNC) cultured supernatants on the differentiation and density alteration of eosinophils. MNC, obtained from either normal subjects or asthmatics, were cultured with or without D. pteronyssinus. The supernatants were tested for the activity of eosinophil differentiation and density alteration. The results showed a significant increase in eosinophil differentiation activity in D. pteronyssinus-stimulated MNC supernatants of asthmatics when compared with normal subjects. This activity can be blocked by anti-IL-5 antibodies. Eosinophil hypodensity change was also noted after treatment with D. pteronyssinus-stimulated MNC supernatants or IL-5, but not after D. pteronyssinus treatment. In conclusion, MNCs, activated by D. pteronyssinus, might contribute to the eosinophil differentiation and hypodensity change in asthmatics.

Characterization of a predominantly pistil-expressed gene encoding a gamma-thionin-like protein of Petunia inflata

We isolated a cDNA clone from a pistil cDNA library of Petunia inflata which encodes a protein, PPT, with sequence similarity to gamma-thionins. Characterization of a genomic clone containing a PPT gene revealed the presence of a single intron. Northern analysis revealed that the PPT gene was predominantly expressed in the pistil during all stages of flower development. Since thionins have been implicated in plant defense against pathogens, PPT may play a role similar to that of other defense-related proteins found in the pistil, defending the pistil against pathogen infection.

Ribonuclease activity of Petunia inflata S proteins is essential for rejection of self-pollen

S proteins, pistil-specific ribonucleases that cosegregate with S alleles, have previously been shown to control rejection of self-pollen in Petunia inflata and Nicotiana alata, two solanaceous species that display gametophytic self-incompatibility. The ribonuclease activity of S proteins was thought to degrade RNA of self-pollen tubes, resulting in the arrest of their growth in the style. However, to date no direct evidence has been obtained. Here, the ribonuclease activity of S3 protein of P. inflata was abolished, and the effect on the pistil's ability to reject S3 pollen was examined. The S3 gene was mutagenized by replacing the codon for His-93, which has been implicated in ribonuclease activity, with a codon for asparagine, and the mutant S3 gene was introduced into P. inflata plants of S1S2 genotype. Two transgenic plants produced a level of mutant S3 protein comparable to that of the S3 protein produced in self-incompatible S1S3 and S2S3 plants, yet they failed to reject S3 pollen. The mutant S3 protein produced in these two transgenic plants did not exhibit any detectable ribonuclease activity. We have previously shown that transgenic plants (S1S2 plants transformed with the wild-type S3 gene) producing a normal level of wild-type S3 protein acquired the ability to reject S3 pollen completely. Thus, the results reported here provide direct evidence that the biochemical mechanism of gametophytic self-incompatibility in P. inflata involves the ribonuclease activity of S proteins.

Characterization of a pollen-expressed receptor-like kinase gene of Petunia inflata and the activity of its encoded kinase

From a pollen tube cDNA library of Petunia inflata, we isolated clones encoding a protein with structural features and biochemical properties characteristic of receptor-like kinases. It was designated PRK1 for pollen receptor-like kinase 1. The cytoplasmic domain of PRK1 is highly similar to the kinase domains of other plant receptor-like kinases and contains nearly all of the conserved amino acids for serine/threonine kinases. The extracellular domain of PRK1 contains leucine-rich repeats as found in some other plant receptor-like kinases, but overall its sequence in this region does not share significant similarity. Characterization of a gene encoding PRK1 revealed the presence of two introns. During pollen development, PRK1 mRNA was first detected in anthers containing mostly binucleate microspores; it reached the highest level of mature pollen and remained at a high level in in vitro-germinated pollen tubes. The recombinant cytoplasmic domain of PRK1 autophosphorylated on serine and tyrosine, suggesting that PRK1 may be a dual-specificity kinase. Monospecific immune serum to the recombinant extracellular domain of PRK1 detected a 69-kD protein in microsomal membranes of pollen and pollen tubes. The characteristics of PRK1 suggest that it may play a role in signal transduction events during pollen development and/or pollination.

Expression of two S-ribonucleases of Petunia inflata using baculovirus expression system

We have previously shown that three Petunia inflata S-proteins, products of the multiallelic S-gene of the self-incompatibility system, are ribonucleases. Here we report the expression of cDNAs for two of these S-proteins using the baculovirus expression system. S2- and S3-proteins were found in both supernatants and lysates of Spodoptera frugiperda cells infected with recombinant baculoviruses. Both recombinant S-proteins contained glycosylated (25 kD) and nonglycosylated (23 kD) forms. Recombinant S2- and S3-proteins were purified from insect cell cultures, and the amino-terminal sequences determined from glycosylated S2- and S3-proteins indicated that the leader peptide encoded by each cDNA was correctly removed. Both glycosylated and nonglycosylated forms of S2- and S3-proteins exhibited ribonuclease activity.

Ethylene Synthesis and Floral Senescence following Compatible and Incompatible Pollinations in Petunia inflata

Ethylene production and floral senescence following compatible and incompatible pollinations were studied in a self-incompatible species, Petunia inflata. Both compatible and incompatible pollinations resulted in a burst of ethylene synthesis that peaked 3 hours after pollination. P. inflata pollen was found to carry large amounts of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). The amount of pollen-held ACC varied in different genetic backgrounds, and the magnitude of the peak correlated with the amount of ACC borne by the pollen. Aminooxyacetic acid (AOA), an inhibitor of ACC synthesis, had no inhibitory effect on this ethylene response, indicating that pollen-borne ACC was largely responsible for the early synthesis of ethylene. After compatible pollination, a second increase in ethylene synthesis began at 18 hours, and the first sign of senescence appeared at 36 hours. Upon treatment with AOA, the second phase of ethylene production was reduced by 95%, indicating that endogenous ACC synthesis was required for this phase of ethylene synthesis. AOA treatment also delayed senescence to 6 days after anthesis. After incompatible pollination, a second increase in ethylene production did not occur until 3 days, and the first sign of senescence occurred 12 hours later. Unpollinated flowers showed an increase in ethylene production 3 to 4 days after anthesis and displayed signs of senescence 1 day later. The significance of the early and late phases of pollination-induced ethylene synthesis is discussed.

S-alleles are retained and expressed in a self-compatible cultivar of Petunia hybrida

We identified two S-allele-associated proteins (S-proteins) in a self-compatible cultivar of Petunia hybrida based on their segregation in F1 hybrids between P. hybrida and its self-incompatible relative, Petunia inflata (with S2S2 genotype), and in selfed progeny of P. hybrida. These two S-proteins, designated Sx-protein (24 kDa) and So-protein (31 kDa), are pistil specific, and their expression follows a temporal and spatial pattern similar to that of S-proteins characterized in self-incompatible solanaceous species. Their amino-terminal sequences also share a high degree of similarity with those of solanaceous S-proteins. Selfing of P. hybrida yielded plants with SoSo,SxSo, and SxSx genotypes in an approximately 1:2:1 ratio, indicating that the Sx-and So-alleles, though expressed in the pistil, failed to elicit a self-incompatibility response. The S2-allele of P. inflata is expressed in all the F1 hybrids, rendering them capable of rejecting pollen bearing the S2-allele. The So-allele is not functional in the F1 hybrids, because all the F1 progeny with S2So genotype are self-compatible. However, in F1 hybrids with S2Sx genotype, approximately half are self-incompatible and half are self-compatible, indicating that the function of the Sx-allele depends on the genetic background. These results strongly suggest that the presence of functional S-alleles alone is not sufficient for expression of a self-incompatibility phenotype, and reaffirm the multigenic nature of gametophytic self-incompatibility suggested by earlier genetic studies.

Excess nonsynonymous substitution of shared polymorphic sites among self-incompatibility alleles of Solanaceae

The function of the self-incompatibility locus (S locus) of many plant species dictates that natural selection will favor high levels of protein diversity. Pairwise sequence comparisons between S alleles from four species of Solanaceae reveal remarkably high sequence diversity and evidence for shared polymorphism. The level of amino acid constraint was found to be significantly heterogeneous among different regions of the gene, with some regions being highly constrained and others appearing to be virtually unconstrained. In some regions of the protein, there was an excess of nonsynonymous over synonymous substitution, consistent with the strong diversifying selection that must operate on this locus. These hypervariable regions are candidates for the sites that determine functional allelic identity. Simple contingency table tests show that sites that have polymorphism shared between species have more nonsynonymous substitution than polymorphic sites that do not exhibit shared polymorphism. This is consistent with the idea that adaptive evolution favoring amino acid replacement is occurring at sites with shared polymorphism. Tests of clustered polymorphism reveal that an unusually low rate of recombination must be occurring in this locus, allowing very ancient alleles to preserve their identity.

Characterization of Ribonuclease Activity of Three S-Allele-Associated Proteins of Petunia inflata

Three S-allele-associated proteins (S-proteins) of Petunia inflata, a species with gametophytic self-incompatibility, were previously found to share sequence similarity with two fungal ribonucleases, RNase T(2) and RNase Rh. In this study, the S-proteins from P. inflata plants of S(1)S(2) and S(2)S(3) genotypes were purified to homogeneity by gel filtration and cation-exchange chromatography, and their enzymatic properties were characterized. The three S-proteins (S(1), S(2), and S(3)), with pairwise sequence identity ranging from 73.1 to 80.5%, were similar in most of the enzymatic properties characterized. The ribonuclease activity had a pH optimum of 7.0 and a temperature optimum of 50 degrees C. Diethylpyrocarbonate at 1 millimolar almost completely abolished the ribonuclease activity; cupric sulfate and zinc sulfate at 1 millimolar reduced the ribonuclease activity of the three S-proteins by 50 to 75%. EDTA and RNasin had no inhibitory effect. All three S-proteins hydrolyzed polycytidylic acid preferentially, but varied in their nucleolytic activity toward polyadenylic acid and polyuridylic acid.

Polymorphism at the self-incompatibility locus in Solanaceae predates speciation

Sequences of 11 alleles of the gametophytic self-incompatibility locus (S locus) from three species of the Solanaceae family have recently been determined. Pairwise comparisons of these alleles reveal two unexpected observations: (i) amino acid sequence similarity can be as low as 40% within species and (ii) some interspecific similarities are higher than intraspecific similarities. The gene genealogy clearly illustrates this unusual pattern of relationships. The data suggest that some of the polymorphism at the S locus existed prior to the divergence of these species and has been maintained to the present. In support of this hypothesis, the number of shared polymorphic sites was found to exceed the number found in simulations with independent accumulation of mutations. Strictly neutral evolution is exceedingly unlikely to maintain the polymorphism for such a long time. The allele multiplicity and extreme age of the alleles is consistent with Wright's classic one-locus population genetic model of gametophytic self-incompatibility. Similarities between the plant S locus and the mammalian major histocompatibility complex are discussed.

Cloning and sequencing of cDNAs encoding two self-incompatibility associated proteins in Solanum chacoense

We have isolated and sequenced cDNAs for S2- and S3-alleles of the self-incompatibility locus (S-locus) in Solanum chacoense Bitt., a wild potato species displaying gametophytic self-incompatibility. The S2- and S3-alleles encode pistil-specific proteins of 30 kDa and 31 kDa, respectively, which were previously identified based on cosegregation with their respective alleles in genetic crosses. The amino acid sequence homology between the S2- and S3-proteins is 41.5%. This high degree of sequence variability between alleles is a distinctive feature of the S-gene system. Of the 31 amino acid residues which were previously found to be conserved among three Nicotiana alata S-proteins (S2, S3, and S6) and two fungal ribonucleases (RNase T2 and RNase Rh), 27 are also conserved in the S2- and S3-proteins of S. chacoense. These residues include two histidines implicated in the active site of the RNase T2, six cysteines, four of which form disulfide bonds in RNase T2, and hydrophobic residues which might form the core structure of the protein. The finding that these residues are conserved among S-proteins with very divergent sequences suggests a functional role for the ribonuclease activity of the S-protein in gametophytic self-incompatibility.

[Sensory nerve endings of the medium and posterior parts of Cebus apella monkey's tongue mucosa]

Sensory nerve endings of tongue mucosa of Cebus apella monkey were studied using the silver impregnation technique (WINKELMANN & SCHIMITT). Subepithelial sensory nerve endings of different forms are present in the medium and posterior parts of tongue mucosa. The nerve fibers have their origin in the deep layers of the tongue and form single and complex sensory nerve endings. The fungiform papillae contain numerous ramified nerve fibers, which constitute a subepithelia network, but the filiform papillae usually possess single free nerve endings disposed longitudinally into the connective tissue.

Peculiar characteristics of the insertion area of the masseter muscle in rats. Scanning electron microscopic study

The structure of the bone surface of the insertion area of the masseter muscle was studied in 20 albinus Wistar rats. Specimens were fixed in a modified Karnovsky solution and treated according to the technique described by LESTER et alii and examined in a JEOL scanning electron microscope, JSM-P15. The results showed that the insertion area of the masseter muscle of rats presents a smooth surface covered by thick layers of calcified collagen fibers. In adjacent areas of the lower edge of the mandibular angle an irregular surface with bone reabsorption and foraminae was observed. The vascular foraminae measure from 30 to 50 microns in diameter and the distance between them ranges from 200 to 460 microns. Osteocyte lacunae were seen at the surface and their measures range from 18 to 25 microns in diameter, which were surrounded by collagen fiber bundles of longitudinal disposition.

Rice mitochondrial genome contains a rearranged chloroplast gene cluster

We have previously reported the isolation and partial sequence analysis of a rice mitochondrial DNA fragment (6.9 kb) which contains a transferred copy of a chloroplast gene cluster coding for the large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL), beta and epsilon subunits of ATPase (atpB and atpE), methionine tRNA (trnM) and valine tRNA (trnV). We have now completely sequenced this 6.9 kb fragment and found it to also contain a sequence homologous to the chloroplast gene coding for the ribosomal protein L2 (rpl2), beginning at a site 430 bp downstream from the termination codon of rbcL. In the chloroplast genome, two copies of rpl2 are located at distances of 20 kb and 40 kb, respectively, from rbcL. We have sequenced these two copies of rice chloroplast rpl2 and found their sequences to be identical. In addition, a 151 bp sequence located upstream of the chloroplast rpl2 coding region is also found in the 3' noncoding region of chloroplast rbcL and other as yet undefined locations in the rice chloroplast genome. Hybridization analysis revealed that this 151 bp repeat sequence identified in rice is also present in several copies in 11 other plant species we have examined. Findings from these studies suggest that the translocation of rpl2 to the rbcL gene cluster found in the rice mitochondrial genome might have occurred through homologous recombination between the 151 bp repeat sequence present in both rpl2 and rbcL.

Rice chloroplast DNA molecules are heterogeneous as revealed by DNA sequences of a cluster of genes

We describe the isolation of two rice chloroplast HindIII fragments (9.5 kb and 5.3 kb) each containing a gene cluster coding for the large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL), beta and epsilon subunits of ATPase (atpB and atpE), tRNAmet (trnM) and tRNAval (trnV). All five genes contained in the 9.5 kb fragment are potentially functional, whereas in the 5.3 kb fragment, rbcL is truncated and atpB is frame-shift mutated. The copy number of the 9.5 kb fragment is 10 times that of the 5.3 kb fragment, indicating that the two fragments are probably located on different chloroplast genomes and represent two different (major and minor) genomic populations. Thus, the rice chloroplast genome appears to be heterogeneous, contrary to general belief. We also describe the isolation of a rice mitochondrial HindIII fragment (6.9 kb) which contains an almost complete transferred copy of this chloroplast gene cluster. In this transferred copy, the coding sequences of rbcL, atpE and trnM contain perfectly normal reading frames, whereas atpB has become grossly defective and trnV is truncated.

Pea cytochrome oxidase subunit II gene has no intron and generates two mRNA transcripts with different 5'-termini

We have isolated and sequenced the cytochrome oxidase subunit II (COII) gene from pea mitochondria. The coding sequence (777 bp) shows over 90% homology to the COII genes from three monocotyledonous plants (rice, maize and wheat) and one dicotyledonous plant (Oenothera berteriana). Several codons are deleted, however, in the pea COII gene. Of interest is the deletion in pea of the last three codons, including the stop codon, found at the 3' end of the other four COII genes. Instead, a new stop codon has been created due to a single-base substitution at the 13th bp downstream from the position of the original stop codon. This pea gene does not contain an intron which is found in all three monocots. Two distinct 5' termini of the pea COII transcripts have been identified by S1 nuclease mapping, one at 285 bp (site I) and the other at 302 bp (site II) upstream from the ATG codon. They are located at two identical sites within nearly perfect direct repeats. Transcripts with the 5' end corresponding to site I occur five time more frequently than those with the 5' end corresponding to site II. Both transcripts have the same 3' terminus which has been mapped to be at 193 to 195 bp downstream from the stop codon.

Isolation and characterization of rat and human glyceraldehyde-3-phosphate dehydrogenase cDNAs: genomic complexity and molecular evolution of the gene

Full length cDNAs encoding the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from rat and man have been isolated and sequenced. Many GAPDH gene-related sequences have been found in both genomes based on genomic blot hybridization analysis. Only one functional gene product is known. Results from genomic library screenings suggest that there are 300-400 copies of these sequences in the rat genome and approximately 100 in the human genome. Some of these related sequences have been shown to be processed pseudogenes. We have isolated several rat cDNA clones corresponding to these pseudogenes indicating that some pseudogenes are transcribed. Rat and human cDNAs are 89% homologous in the coding region, and 76% homologous in the first 100 base pairs of the 3'-noncoding region. Comparison of these two cDNA sequences with those of the chicken, Drosophila and yeast genes allows the analysis of the evolution of the GAPDH genes in detail.

A proton-coupled conformational switch of Escherichia coli 5S ribosomal RNA

We report temperature-jump kinetic studies of the early melting transition of Escherichia coli 5S rRNA. A single measurable relaxation time tau, independent of concentration, was found at 266 nm. We monitored the transition temperature tm for this process (in the range from 0 to 40 degrees C) as a function of Mg2+, Na+, K+, spermidine, and H+ concentrations. Contrary to the usual effect of salts on nucleic acid stability, addition of mono- and multivalent counterions decreases tm for the early melting transition. Also unexpectedly, we found a strong dependence of tm on pH in the physiological range of 7--8. Quantitative analysis of the data indicates that about 0.7 protons are release when the ordered (low-temperature) form melts, whereas about 2 NA+ (or K+) and 0.5 Mg2+ are taken up by the melted (high-temperature) form. We estimate the enthalpy of the transition to be 15--20 kcal/mol (63--84 kJ/mol) and also report the forward and reverse rate constants and activation energies for the transition, along with the influence of ions on the transition dynamics. Diffusion constant measurements reveal that the low-temperature form has a frictional coefficient about 10% larger than that of the high-temperature form. The data imply a low-temperature tertiary structure capable of binding a proton. Increase of pH, temperature, or counterion concentration (all at near-physiological values) causes a tertiary conformational switch to a more compact form that has greater counterion binding but less proton binding. We discuss possible physiological roles for the transition.