Cytokinins in the soluble RNA of plant tissues.

The cytokinin, N(6)-(Delta(2)-isopentenyl) adenosine occurs in the soluble RNA of yeast and mammalian tissue and has now been detected in plant soluble RNA. A hydroxylated derivative of this cytokinin 6-(cis-4-hydroxy-3-methylbut-2-enylamino)-9-,beta-D-ribofuranosylpurine has also been identified as a constituent of plant soluble RNA.

Raphides with barbs and grooves in Xanthosoma sagittifolium (Araceae).

Raphides in petioles of Xanthosoma sagittifolium are needlelike crystals about 50 micrometers long. The rectangular cross sections have maximum dimensions of approximately 850 by 250 nanometers. The raphides have two distinct end structures. One end is narrow, acute, and tapered to a point; the other is broad, acute, and abruptly pointed. Barbs, about 750 angstroms long with tips oriented away from the narrow end, occur along the length of the raphide on ridges on either side of two longitudinal grooves. These grooves, located opposite each other, give the raphide cross section an H-shape.

Taste-modifying protein from miracle fruit.

The active principle of miracle fruit (Synsepalum dulcificum) is a basic glycoprotein with a probable molecular weight of 44,000. Application of the protein to the tongue modifies the taste so that one tastes sour substances as sweet.

Trans unsaturated fatty acids in natural products and processed foods.

Various representatives of trans unsaturated fatty acids have been detected in plants. The main trans monoenoic acids in ruminants, elaidic acid and vaccenic acid are not found in plants. Most oil seeds used for production of edible fats do not contain any trans fatty acids. Trans fatty acids in non-ruminant animals are derived from food. In adult ruminants, however, trans fatty acids are produced by microbial hydrogenation of linoleic acid and linolenic acid in the rumen; in consequence, a variety of positional and stereoisomers of both cis and trans fatty acids appear in both meat and milk. The total trans content of 5-10% in beef fat is largely trans monoene, mainly 9-trans (elaidic acid), 10-trans and 11-trans (vaccenic acid). The trans fatty acid content of human fat is dependent on the uptake of trans fatty acid from food. The usual content is about 2%, though up to 15% has been recorded. The isomer distribution is similar to that of the trans isomers of butter and margarine. The trans fatty acid content in ruminant products such as milk, butter, cheese, curds and tallow is 5-10%. These products contain nearly all possible stereo- and positional isomers of oleic and linoleic acid. The trans fatty acid content of margarines fluctuates widely according to raw material and process conditions. According to one investigation, an average of 16% of all unsaturated fatty acids in margarines consists of geometrical and positional isomers of the "natural" acids, a similar percentage to that in butter. Diet and health margarines have much lower contents of trans fatty acids. The total trans content of margarines is largely due to trans-18:1 monoenes. The positional isomers of the trans-monoenes are more evenly distributed in margarine than in butter. Hardened oils do not contain trans fatty acid isomers other than those produced by the microflora of ruminants. Therefore, claims that trans fatty acid isomers are "synthetic", "nonphysiological" or "unnatural" are unjustified if these words are used to imply "not produced by the living organism".

Stability of polyadenylic and polyadenylated ribonucleic acids in radish (Raphanus sativus) seedlings.

The stability of polyadenylic acid and polyadenylated RNA was investigated in young radish (Raphanus sativus) seedlings. We first studied the decay of poly(A) content, using a [3H]poly(U) assay, following a complete block of transcription by cordycepin (200 microgram/ml). Two lifetime classes of polyadenylic acid have been determined in these seedlings: a short-lived component with a half-life of 30 min which represents 60% of poly(A) and a more stable component with varying half-lives of which the majority range from 4-10 h and a few are considerably longer. During this period rRNA was shown to decay linearly, taking about 41 h for half of this RNA to disappear. The life-time of the other moiety of polyadenylated-RNA was analysed by continuous labelling with [3H]uridine. We have been able to demonstrate that a significant part of the mRNA molecules turns over with a half-life similar to that of the more slowly turning-over poly(A). No evidence could be obtained for rapidly turning-over messenger RNA. Thus the rapidly turning over poly(A) could correspond to a poly(A) turn-over independent of the remainder of the sequence. When labelling was very long, an apparent steady-state was reached and we determined the polyadenylated RNA content of seedlings to be 2.2% of whole cell RNA. Finally, these results were compared with those previously obtained in studying early germination of radish embryo axes. In contrast with stored mRNA which is rapidly degraded following imbibition, part of the mRNA present in 22 h old seedlings is stable for several hours.

Naturally occurring toxic substances in foods.

Numerous chemical toxins, including normal components of natural foods, e.g., mycotoxins, and toxic chemicals as contaminants such as pesticides, fertilizers, food additives, and preservatives, which are potentially toxic to humans, are discussed. Potential toxicity, the hazard to man represented by most of these chemicals, may be low because the concentration in food may be low. The gap in our knowledge of long-term effects makes rational decisions as to allowable levels of these substances a major problem. On the other hand, nitrosamines and aflatoxins are toxins for which there exists a voluminous literature documentaing extreme biologic activity in experimental animals and indirect evidence for activity in man. Epidemiologic evidence has linked them to human cancers, and because of increasing evidence of long-term human exposure to these toxins either as inadvertent contaminants during food preparation or as the metabolites of mycotic infestation this possible hazard demands intensive investigation. An exhaustive review of data from epidemiologic surveys in various parts of the world, as well as from long-term laboratory studies, represents an impressive start in this direction.

Correlation of some published amino acid sequences for photosystem I polypeptides to a 17 kDa LHCI pigment-protein and to subunits III and IV of the core complex.

Photosystem I (PSI) in barley consists of at least 11 polypeptides of which three have apparent sizes of 15-19 kDa. Two of these polypeptides (subunits III and IV) are constituents of the core complex (CCI), the third is a component of the light-harvesting complex (LHCI). After fractionation of PSI into its CCI and LHCI components, each of the polypeptides has been isolated and its N-terminal region sequenced. We conclude that the gene sequence published for subunit IV of spinach [(1988) FEBS Lett. 237, 108-112] is not that of subunit IV but rather that of the 17 kDA LHCIc pigment protein. We confirm that the published sequence for subunit III [(1988) Curr. Genet. 14, 511-518] is indeed that of subunit III; seemingly conflicting identifications, based on apparent sizes on SDS-PAGE, of which polypeptides are subunits III and IV are probably explained by subunit III's electrophoretic migration rate being dependent on the solvent.

Endemic selenium intoxication of humans in China.

An endemic disease was discovered in 1961 in parts of the population of Enshi County, Hubei Province of the People's Republic of China. During the years of the highest prevalence, from 1961 to 1964, the morbidity was almost 50% in the 248 inhabitants of the five most heavily affected villages; its cause was determined to be selenium intoxication. The most common sign of the poisoning was loss of hair and nails. In areas of high incidence, lesions of the skin, nervous system, and possibly teeth may have been involved. A case is reported of a middle-aged, female hemiplegic, whose illness and death apparently were related to selenosis. Daily dietary intakes of selenium, estimated after the peak prevalence had subsided, averaged 4.99 (range 3.20 to 6.69) mg and hair and blood selenium levels averaged 32.2 and 3.2 micrograms/ml, respectively. Up to 1000x differences occurred when selenium contents of vegetables, cereals, scalp hair, blood, and urine from the selenosis areas were compared with those from Keshan disease (selenium deficiency) areas. The ultimate environmental source of selenium was a stony coal of very high selenium content (average more than 300 micrograms/g; one sample exceeded 80,000 micrograms/g). Selenium from the coal entered the soil by weathering and was available for uptake by crops because of the traditional use of lime as fertilizer in that region. This particular outbreak of human selenosis was due to a drought that caused failure of the rice crop, forcing the villagers to eat more high-selenium vegetables and maize and fewer protein foods.

Plant cell wall fractionation and structural analysis.

The structure of the major plant polysaccharides contributing to dietary fiber, their organization within the plant cell wall, and the problems associated with their analysis are briefly reviewed. Alkaline, acidic, and detergent fractionation methods are described and considered in relation to their specificity. The analysis of pectin, often ignored as a component of dietary fiber, is examined in detail. The solubility of pectins from a number of common plant foods was determined, indicating that a considerable portion of pectin polyuronide is lost to many of the commonly used analytical procedures.

The lignin fraction of plant cell walls.

Methods are discussed for determining lignin in plant cell walls. The increase in apparent lignin content that may occur as a result of artifacts produced during food preparation is also discussed. The phenolic components, including lignin, of cell walls separated from 12 vegetable, fruit, and cereal foods are determined. Wheat bran, on a fresh weight basis, had a high cell wall content (48.6%) compared with the vegetables and fruit whose contents ranged from 1.0 to 6.0%. Wheat bran and spinach cell walls had the highest lignin contents (11.4 and 4.4%, respectively) and the lowest degradabilities (35.8 and 39.6%, respectively) as determined by a cellulase technique. Cell walls of spinach, beetroot, sweet corn, pineapple, and wheat bran contained the phenolic acids (ferulic, p-coumaric, and diferulic) bound to polysaccharide components. Cell walls of cabbage, Brussels sprout, celery, cauliflower, green bean, carrot, and pea contained only traces of these acids.

Mineral components of plant cell walls.

Plant cell walls that are secondarily thickened contain silicon and metal cations. The silicon occurs predominantly as silica (SiO2.nH2O) deposited in intimate association with the organic components of the walls and, according to recent evidence, as an integral constituent of polyuronides. Relatively large amounts of deposited (i.e., solid) silica are found in rice and other cereals and in grasses. When ingested by ruminant animals, practically all the solid silica may be recovered in the feces. However, microscopic particles of silica from plants are, to a small extent, absorbed as such through the gastrointestinal wall in both man and ruminant animals. It has now been shown that silicon is essential for animals, and that it is a constituent of certain mucopolysaccharides, thereby contribution to the architecture of connective tissues. The acidic silanol group of solid silica in plant cell walls may be involved in binding metal cations, but carboxyl and phenolic hydroxyl groups of the organic components of the walls are probably mainly responsible. Binding of metal cations by these components of plant cell walls, and possibly by silica, is likely to reduce availability of the cations for intestinal absorption.

Beyond dietary fiber.

The complexity of plant foods high in dietary fiber poses new challenges to clinical investigators and leads to many study-design dilemmas. There are basic differences in studying purified polymers, highly concentrated but not purified fibers, and diets high in high-fiber whole foods. The fibrils of the plant cell wall are most likely altered when prepared as a pure chemical entity, and when fiber concentrates (eg, wheat bran) are used, the method of preparation may alter the composition of the final product. Whole-plant, high-fiber foods are complex storehouses of a diversity of polymers, including resistant starch, and of bioactive compounds. Furthermore, the addition of a reasonable amount of high-fiber food to the diet not only adds dietary fiber but many digestible, caloric macronutrients that alter the entire diet composition. These problems and dilemmas are reviewed.

2-Amino-3-(methylamino)-propanoic acid (BMAA) in cycad flour: an unlikely cause of amyotrophic lateral sclerosis and parkinsonism-dementia of Guam.

We conducted an investigation of the levels of the neurotoxin 2-amino-3-(methylamino)-propanoic acid (BMAA) in cycad flour. Analysis of 30 flour samples processed from the endosperm of Cycas circinalis seeds collected on Guam indicated that more than 87% of the total BMAA content was removed during processing. Furthermore, in 1/2 the samples almost all (greater than 99%) of the total BMAA was removed. We found no significant regional differences in the BMAA content of flour prepared from cycad seeds collected from several villages on Guam. Testing of different samples prepared by the same Chamorro woman over 2 years suggests that the washing procedure probably varies in thoroughness from preparation to preparation but is routinely efficient in removing at least 85% of the total BMAA from all batches. Analysis of a flour sample that had undergone only 24 hours of soaking indicated that this single wash removed 90% of the total BMAA. We conclude that processed cycad flour as prepared by the Chamorros of Guam and Rota contains extremely low levels of BMAA, which are in the order of only 0.005% by weight (mean values for all samples). Thus, even when cycad flour is a dietary staple and eaten regularly, it seems unlikely that these low levels could cause the delayed and widespread neurofibrillary degeneration of nerve cells observed in amyotrophic lateral sclerosis and the parkinsonism-dementia complex of Guam (ALS-PD).

[Biological applications of Raman resonance spectroscopy and micro-Raman resonance spectroscopy]. / Applications biologiques de la spectroscopie Raman de résonance et de la spectroscopie micro-Raman de résonance.

Advantages are given to illustrate the possibilities of resonance Raman spectroscopy in the studies of biological systems. A relation giving the size of porphinato-core of metalloporphyrins from resonance Raman frequency is proposed. It can be applied to heme, even in lived state. By illuminating the sample through a microscope, resonance Raman effect can be collected from 1 (micrometer)2 of sample. Spectra of a vegetal-cell wall (pimento) and of a red corpuscle (hemoglobin) are shown as examples.

Effect of storage on carcinogenic activity of bracken fern.

Effect of storage on carcinogenic activity of bracken fern was examined with inbred strain ACI rats of both sexes. The experiment was broken down into 3 groupings: Group I received a diet containing fresh dry bracken powder: Group II received a diet which contained the same dry bracken powder used in Group I but preserved for 1 year at 4 degrees C (Group II-C) or room temperature (Group II-R); Group III received the diet containing bracken powder preserved for 2 years at 4 degrees C (Group III-C) or room temperature (Group III-R). Three control groups corresponding to Groups I, II and III were fed a normal basal diet. Significant differences in incidence of ileal tumors were observed between Group I and both groups of Group III and latent period of intestinal tumors in Group II or III was longer than that of Group I. The results indicate a decreased carcinogenic activity of bracken fern by preservation.

Screening of edible plants against possible anti-tumor promoting activity.

One hundred twenty-one species of edible plants (133 test-parts) were screened against possible anti-tumor promoting activity by an in vitro short-term assay system of inhibition of Epstein-Barr virus (EBV) activation induced by a phorbol-ester promoter, 12-O-hexadecanoylphorbol-13-acetate (HPA). The methanol-extracts (ME) of 14 species of the edible plants strongly inhibited the activation, 7 moderately and 12 weakly inhibited it. On partition of the randomly selected inactive ME (26 species) with ethyl acetate and water, 13 and 2 species were active, more or less, in the ethyl acetate and water soluble part, respectively. Thus, this result suggested that anti-tumor promoters occur in a wide variety of edible plants. The anti-tumor promoting activity in the crude extracts may be enhanced or reduced with co-occurring factors acting additively, synergistically or antagonistically.

Occurrence and distribution of arsenic in soils and plants.

Inorganic arsenicals have been used in agriculture as pesticides or defoliants for many years and, in localized areas, oxides of arsenic have contaminated soils as a result of fallout from ore-smelting operations and coal-fired power plants. Use of inorganic arsenicals is no longer permitted in most agricultural operations, and recent air pollution controls have markedly reduced contamination from smelters. Thus, this paper will concentrate on the effect of past applications on arsenic accumulation in soil, phytotoxicity to and uptake by plants as influenced by soil properties, and alleviation of the deleterious effects of arsenic. Once incorporated into the soil, inorganic arsenical pesticides and arsenic oxides revert to arsenates, except where the soil is under reducing conditions. The arsenate ion has properties similar to that of orthophosphate, and is readily sorbed by iron and aluminum components. This reaction greatly restricts the downward movement (leaching) of arsenic in soils and the availability of arsenic to plants. Several methods of estimating plant available arsenic in soils have been developed. They involve extraction of the soil with reagents used to estimate phosphorus availability. This extractable arsenic is reasonably well correlated with reduced plant growth by, and plant uptake of arsenic. For most plants, levels of arsenic in the edible portion of the plant are well below the critical concentration for animal or human consumption, even when severe phytotoxicity occurs. Alleviation of arsenic phytotoxicity has been attempted by increasing the soil pH, by use of iron or aluminum sulfate, by desorbing arsenate with phosphate and subsequent leaching, and by cultural practices such as deep plowing. Only limited benefits have accrued from these procedures the cost of which is often prohibitively high. Since attempts to reduce arsenic toxicity have not been very successful, its excessive accumulation in soils should be avoided.

Sterol content of foods of plant origin.

Available data on phytosterols from the world's literature have been compiled and summarized. There still exists a paucity of data on the quantities of plant sterols in many foods. More extensive data are available on the relative sterol composition. Our compilation shows that plant oils are excellent sources of phytosterols. Nuts and seeds contain moderate levels, and fruits and vegetables generally contain the lowest concentrations of plant sterols. Analyses of the minor sterols, namely, the delta5- and delta7-phytosterols, have become available only recently.

Predicting pesticide residues to reduce crop contamination.

The system of dynamics between pesticides and plants is reviewed, and a conceptual model capable of reflecting the necessary qualitative and structural peculiarities is proposed as a means of predicting residue levels. The degradation processes of various chemical classes of pesticides in plants under different conditions of use are analyzed. Formulas are developed that enable recognition and estimation of residue levels and duration of retention for "new" pesticides and "old" substances under varying treatment conditions. Estimated data are verified to provide positive assessments of the accuracy of the predictions. Mathematical modeling as a means of perception is stressed. With this method, the outlet value can be controlled by changing such inlet parameters as application rate, frequency of treatments, types of plants, and so on. Residue levels are predicted for different combinations of use conditions in various climatic-geographical regions. The method of estimation also enables the development of important standards such as post-treatment waiting intervals. A more flexible technique can be employed, in which specific periods are established for different plants under various treatment conditions. Thus, both unjustified shortened waiting intervals or unnecessarily elongated intervals periods can be avoided. The greatest value of the modeling approach is that information can be obtained on the degree of potential food contamination and major standards can be developed without the need for extensive experimental use of pesticides under actual conditions. This technique fully considers optimal use conditions for agrochemicals in terms of human requirements and protection of plants. Mathematical modeling protects the environment while enabling the speedy selection of safe parameters for pesticide use conditions nd realization of significant savings in manpower and time. Overall, this estimation method appears to be an efficient link in the broad system of preventing environmental pesticide contamination and protecting human health.

Natural pesticides and bioactive components in foods.

In this review, some common food plants and their toxic or otherwise bioactive components and mycotoxin contaminants have been considered. Crucifers contain naturally occurring components that are goitrogenic, resulting from the combined action of allyl isothiocyanate, goitrin, and thiocyanate. Although crucifers may provide some protection from cancer when taken prior to a carcinogen, when taken after a carcinogen they act as promoters of carcinogenesis. The acid-condensed mixture of indole-3-carbinol (a component of crucifers) binds to the TCDD receptor and causes responses similar to those of TCDD. Herbs contain many biologically active components, with more than 20% of the commercially prepared human drugs coming from these plants. Onion and garlic juices can help to prevent the rise of serum cholesterol. Most herbs used in treatments may have many natural constituents that act oppositely from their intended use. Some herbs like Bishop's week seed contain carcinogens, and many contain pyrrolizidine alkaloids that can cause cirrhosis of the liver. The general phytoalexin response in plants (including potatoes, tomatoes, peppers, eggplant, celery, and sweet potatoes) induced by external stimuli can increase the concentrations of toxic chemical constituents in those plants. In potatoes, two major indigenous compounds are alpha-solanine and alpha-chaconine, which are human plasma cholinesterase inhibitors and teratogens in animals. Because of its toxicity, the potato variety Lenape was withdrawn from the market. Celery, parsley, and parsnips contain the linear furanocoumarin phytoalexins psoralen, bergapten, and xanthotoxin that can cause photosensitization and also are photomutagenic and photocarcinogenic. Celery field workers and handlers continually have photosensitization problems as a result of these indigenous celery furanocoumarins. A new celery cultivar (a result of plant breeding to produce a more pest-resistant variety) was responsible for significant incidences of phytophotodermatitis of grocery employees. Since there is no regulatory agency or body designated to oversee potential toxicological issues associated with naturally occurring toxicants, photodermatitis continues to occur from celery exposure. Sweet potatoes contain phytoalexins that can cause lung edema and are hepatotoxic to mice. At least one of these, 4-ipomeanol, can cause extensive lung clara cell necrosis and can increase the severity of pneumonia in mice. Some phytoalexins in sweet potatoes are hepatotoxic and nephrotoxic to mice. The common mushroom Agaricus bisporus contains benzyl alcohol as its most abundant volatile, and A. bisporus and Gyromitra esculenta both contain hydrazine analogues. Mycotoxins are found in corn, cottonseed, fruits, grains, grain sorghums, and nuts (especially peanuts); therefore, they also occur in apple juice, bread, peanut butter, and other products made from contaminated starting materials.(ABSTRACT TRUNCATED AT 400 WORDS)