Cytological relationships of selected species ofPanicum L.

The cytological investigation of 12 taxa ofPanicum L. revealed that the vast majority of them have the basic number x=9 at different ploidy levels. The basic number x=8 was recorded only in the tetraploid speciesP. maximum with 2n=32. The diploid number 2n=18 was encountered inP. capillare, P. laevifolium, P. antidotale andP. coloratum (2) with 3B-chromosomes recorded in the latter species. The tetraploid chromosome number 2n=36 was found to exist inP. miliaceum, P. miliare, P. coloratum (1) andP. virgatum. The hexaploid number 2n=54 was recorded inP. bulbosum, P. dichotomiflorum andP. esculentum. The karyotypes of all accessions were mostly symmetrical and mainly comprised of meta- and submetacentric chromosomes with little variation in length among them within each karyotype. Investigation of chromosome association during metaphase I of meiosis revealed that the frequency of bivalents/cell was the highest among all investigated diploid, tetraploid and hexaploid accessions. Univalents were also frequently encountered in various accessions. These results may indicate that segmental alloploidy has been the major process by which polyploid species have originated.     

Seed germination of the Australian desert shrubEremophila (Myoporaceae)

Eremophila is an Australian genus of 212 species ranging from prostrate shrubs to small trees, the great majority of which occur in Western Australia. Recent interest in the genus’s germination strategies developed out of a need to seek rehabilitation techniques for mine-site and rangeland areas. The genus is of special interest because of its broad geographic range and prominence in vegetation associations of the arid zone, especially in Western Australia, where it often dominates or codominates over wide areas. ManyEremophila species are known to be tolerant of drought, fire, frost, grazing, and salinity, and would be very suitable for revegetation programmes; however, the genus germinates poorly, for reasons that are not fully understood. During the early 1980s attempts were made, with limited success, to rehabilitate open-cut mine-site waste dumps at Mt. Newman using broadcast seed and rooted cuttings and transplanted seedlings at the Pilbara mine venture at Paraburdoo. Tissue culture and grafting have also been attempted, but environmental management acknowledges that the broadcast seed method is the only cost-effective means of mine-site rehabilitation. Under field conditions the germination ofEremophila occurs in response to heavy rain in autumn and winter, especially with milder temperatures; however, up until now the use ofEremophila in rehabilitation practices has been limited because of the high percentage of seeds that fail to germinate. Two causes for this have been postulated. First, the environmental conditions may not be appropriate for germination. Physical dormancy resulting from the hard woody fruits may be overcome by using a scarification pre-treatment. Second, seed may still fail to germinate even though favourable conditions exist; a secondary chemical mechanism in the form of inhibitors associated with the fruit wall is hypothesised. Chemical properties of the seed, seed coat, or fruit may regulate germination until the fruit wall has been effectively worn away and the chemicals leached out. Few experimental procedures have been carried out to verify these hypotheses, and few studies have examined either fruit productivity (seeds per fruit) or seed viability. Eremophila fruit are dry with a papery exocarp or drupaceous with a fleshy or succulent mesocarp and a woody or crustaceous endocarp and contain between 2 and 12 seeds. Seed viability inE. maculata ranges from 74% to 92% in the first 3 years after fruit maturity, decreasing markedly to 8% after 13 years. Similar patterns have been recorded forE. goodwinii. Effective environmental management utilisingEremophila may be approached in three ways. First, scarify fruit to promote the uptake of water and oxygen; second, use fruit between 1 and 5 years to ensure the highest viability rating; and third, collect fruit from healthy shrubs showing no evidence of insect or fungal attack to ensure quality of fruit. Further research on the genus should include ecological studies, currently poorly understood, and edaphic and soil amelioration projects (e.g., on post mine-site tailings) in an attempt to optimise the vegetation potential ofEremophila.     

Flow cytometric estimation of nuclear DNA amount in diploid bananas (Musa acuminata andM. balbisiana)

Cell nuclei were isolated from leaf tissues of wild banana (Musa balbisiana, M. acuminata ssp.banksii andM. acuminata ssp.errans) and of the two vegetative clones of diploid cultivar “Pisang Mas”. Relative fluorescence intensity was measured on propidium iodide-stained nuclei by flow cytometry. Nuclei isolated fromGlycine max with known nuclear genome size were used as internal standard to determine nuclear DNA content ofMusa in absolute units. The results of the study showed that the size of nuclear genome ofMusa is smaller than previously estimated. In general, it is smaller in comparison with many other angiosperms. Furthermore, it was found that nuclear DNA content ofM. balbisiana (genome BB) is significantly lower than that ofM. acuminata subspecies and cultivars (genome AA). This finding should permit estimation of genome composition in triploidMusa clones with expected hybrid composition. Flow cytometry is proposed as a useful technique with potential applications in taxonomy, breeding and biotechnology ofMusa.     

Le syndrome de Klinefelter chez l'enfant

Klinfelter syndrome was first described in adult males with gynecomastia, azoospermia and hypergonadotropic hypogonadism. Children with the 47, XXY karyotype demonstrate few clinical findings so Klinefelter syndrome is rarely diagnosed until adult life. Besides children who have been diagnosed during prenatal genetic testing, in infancy a male with 47, XXY (or variants: 46, XY-47, XXY; 48, XXXY; 48, XXYY, 49, XXXXY) may be found while undergoing evaluation of micropenis, hypospadias, cryptorchidism or facial anomalies. The older child may present with learning disabilities, behavior disorders or tall stature. At the time of puberty, the clinical picture includes small testes, gynecomastia and an eunuchoid habitus. Early diagnosis of Klinefelter syndrome must be performed since it has been demonstrated that early treatment with androgens may ameliorate many aspects of the clinical symptoms and attenuate or prevent behavioral and psychiatric disorders associated with 47, XXY males.     

Hormone-like product of vascular tissue stimulating starch accumulation in pith explants of kale and endogenous cytokinins

When stem explants of kale (Brassica oleracea L. var.medullosa), containing pith parenchyma and a strip of vascular tissue, were cultured on simple sucrose medium, a hormone-like factor was transported from the vascular tissue to the adjacent pith, where it stimulated accumulation of starch. Similarly, up to a sevenfold increase of starch content in explants could be induced by cytokinins added to the culture medium. The relative stimulatory effect of several cytokinins (5×10^?6 M) and hormone-like product of vascular tissue (HPVT) in a typical experiment were: control (1.0), trans-zeatin (6.7), HPVT (6.2), N⁶-[2-isopentenyl]adenine (5.4), transzeatin riboside (5.2), N⁶-[2-isopentenyl]adenosine (5.4), kinetin (3.6), 6-benzylaminopurine (3.5), and adenine (2.1). Concentration of endogenous cytokinins was determined using ELISA (trans-zeatin, N⁶-[2-isopentenyl]adenine and their ribosides) andAmaranthus bioassay (total cytokinins). No effect of vascular tissue on the level of endogenous cytokinins in explants was found. The results support the conclusions of previous experiments that the HPVT stimulating starch accumulation is not a cytokinin.     

Detection of plum pox virus in leaves and aphids by SIBA and DAS-ELISA assays

The slot-immunobinding assay (SIBA) was adapted for detection of plum pox virus (PPV) and compared with DAS-ELISA. SIBA was easy to perform and as sensitive as DAS-ELISA in detection of various PPV isolates in herbaceous and woody plants, but not in aphids (Myzus persicae).     

Procréation médicalement assistée et paraplégie masculine — Expérience Montpellieraine

Between 1980 and 1993, seventy one tetra or paraplegic patients consulted in order to know more about their “procreative status”. After being taken into care in an appropriate enviroinment, specialized in the treatment of ejaculation disorders and following a semen analysis, twenty two patients decided to procreate. Their vertebral lesions were located in the cervical region (5 cases), drom D1 to D10 (10 cases), from D11 to L1 (6 cases) and from L2 to L5 (1 case). Eighteen patients suffered from complete lesions. Nineteen patients achieved an ejaculation: fifteen cases of antegrade ejaculations, three cases of retrograde ejaculations and one mixed one. Out of eighteen pregnancies — for fourteen couples — nine were obtained in Assisted Reproductive Technology: three of them after an intravaginal artificial insemination, one following an intracervical artificial insemination, two after an intrauterine artificial insemination, two through an in vitro fertilization (IVF), one following a transfer of frozen embryos obtained through IVF with some epididymal spermatozoon. An Assisted Reproductive Technology strategy is being proposed, which takes into account the number of available progressive moving spermatozoon.     

Indications d’une étude méiotique dans l’infertilité masculine

Meiotic investigation is rare in male infertility. Now, some mutations affecting spermatogenesis exhibit characteristic cytogenetic figures, whereas testicular histology does not show specific aspects of this pathology. In male infertility with abnormal somatic caryotype, the aim of meiotic survey is to find the mechanisms inducing spermatogenic failure, and thus to lead to a better understanding of normal spermatogenesis. In addition to cytogenetic techniques, meiosis is also investigated by electron microscopy and molecular biology. Also, we think that a larger place must be grant to meiotic study in male infertility evaluation when the indication of testicular histopathology was settled.     

RAPD reactions from crude plant DNA

As opposed to standard polymerase chain reaction (PCR) using specific primers, genome analysis involving short random primers, for example RAPD, may yield inconsistent results if crude plant DNA preparations are used as the template. When RNase A, a thermostable enzyme, was added to such reactions, highly repeatable banding patterns were obtained from crude plant DNA, thus speeding up analyses substantially.     

Anomalies des autosomes et infertilité masculine

Spermatogenesis impairment is frequently associated with autosomal rearrangements. A meiotic study was performed on testicular biopsies of men ascertained through primary fertility and found to be heterozygous for reciprocal translocation, Robertsonian translocations, inversions and extra chromosomes. Pairing failure at meiosis as well as intimate associations between rearranged autosomes and the XY bivalent have been discussed as a cause of gametogenic arrest.     

Altered GABAergic and glutamatergic transmission in audiogenic seizure-susceptible mice

The C57BL/10 SPS/sps mouse mutant are audiogenic seizure-susceptible. The enzymatic activities of glutamate decarboxylase (GAD), GABA aminotransferase (GABA-T), alanine aminotransferase (ALA-T), aspartate aminotransferase (ASP-T), and glutamate dehydrogenase (GDH) of whole brain supernatant are significantly reduced in these epileptic mice. GABA uptake is decreased in cortex, midbrain, and pons medulla. Previous studies showed the presence of two sodium-dependent GLU uptake systems in normal (SPS/SPS) mice. Glutamate U_max by System 1 is significantly decreased in these mice, whereas the U_max value for System 2 is significantly increased in the epileptic mice.     

Variation in species richness: Towards a unification of hypotheses

The question, “why do areas vary in species richness?” has been important throughout the history of ecology. It is difficult to answer definitively because we have so many (at least 120) plausible hypotheses. This abundance of hypotheses has led to a number of attempts to classify them. Unfortunately, richness hypotheses often defy such categorization. Instead of placing species richness hypotheses into categories, I suggest an alternative approach: to treat species richness hypotheses as violations of the assumptions of Gause’s Competitive Exclusion Principle. This is a very similar approach to the pedagogy of population genetics: evolution occurs if and only if at least one assumption of the Hardy-Weinberg principle is violated. The classification of hypotheses advocated here treats interspecific competition as a central organizing concept in community theory. However, it does not treat competition as an organizing concept in communities: indeed, the relaxation or disruption of competition is considered to be the status quo in the majority of communities.     

Direct sequencing of PCR-amplified DNA

This article describes the direct sequencing of PCR-amplified DNA, a technique that bypasses the problem of replication errors sometimes associated with other PCR procedures. The direct sequencing procedure produces an “average sequence” of all the copies of the target. Any miscopied molecule usually represents only a small proportion of the total. The technique described here is based on the “traditional” ddNTP sequencing method of Sanger et al.     

Cleavage polyembryonyin vivo andin vitro

The development of cleavage polyembryos of wheat, maize and radishin vivo andin vitro was compared. Some frequent features (such as common suspensors or suspensor-like structures, “concrescences”, enlarged radicular meristems) suggest a similar origin of cleavage polyembryos inducedin vivo and those inducedin vitro from the proembryo. Cleavage of the original zygotic or somatic proembryo may occur either at a few-celled stage or later in the phase of radicular meristem establishment.     

l-phenylalanine production by double auxotrophic multianalogue-resistant mutant ofArthrobacter globiformis

Tryptophan-plus-tyrosine double auxotrophic mutants resistant to fluorophenylalanine (PFP) and β-2-thienylalanine (TA) were isolated from a biotin-requiring glutamate-producingArthrobacter globiformis. The mutants were found to producel-phenylalanine in mineral salts medium. Further improvement ofl-phenylalanine production was achieved by isolation of mutants resistant to 5-methyltryptophan (MT) and 3-nitrotyrosine (NT) from a double auxotrophic PFP^r and TA^r mutant. Under optimal cultural condition one mutant yielded 9.6g phenylalanine per L medium in flask culture. Enzymic activity of regulatory enzymes (deoxy-d-arabino-heptulosonate-7-phosphate synthase, chorismate mutase and prephenate dehydratase) were observed in the wild type, double auxotroph and double-auxotrophic multianalogue-resistant mutant.     

Purification,characterization and accumulation of three virus-induced cucumber peroxidases

Three anionic peroxidases (EC 1.11.1.7), named Prx1, 2, and 3, which are rapidly accumulated in cucumber (Cucumis sativus L., cv. Laura) reacting hypersensitively to tobacco necrosis virus, were purified to homogeneity. The three enzymes had an isoelectric point about 4.3, and the relative molecular masses of Prx1, 2, and 3 estimated by SDS-PAGE were 40 700, 38 000, and 37 100, respectively. These peroxidases had a similar pH stability, but differed in their specific activity, pH optimum, and thermal stability By Ouchterlony double diffusion tests with antisera raised against the three purified enzymes, close serological relationships have been demonstrated between the three peroxidases.     

Superoxide dismutase level in response to paraquat and high temperature in the cyanobacteriumGloeocapsa sp

Paraquat (methylviologen) at concentrations above 0.05 mM inhibited the growth of photoautotrophic cyanobacteriumGleeocapsa sp. in axenic cultures. The growth rate was not affected by concentrations of 0.01 mM or less. This concentration resulted after a lag period in a moderate increase in superoxide dismutase level. After removal of paraquat, the cyanobacterium continued to generate higher levels of superoxide dismutase. There was a lag period of one hour before resumption of normal enzyme activity. Addition of puromycin at concentration of 0.5 mg cm^?3 had no effect on cell survival, but greatly enhanced the sensitivity of the culture to the toxicity of paraquat. The data showed an increase of SOD activity by temperatures above the normal growth temperature level. However, this increase was suppressed by chloramphenicol which revealed that the induction of superoxide dismutase by high temperatures was associated withde novo protein synthesis.     

Aspartate aminotransferase isozymes in plants: Comparison of two staining methods in polyacrylamide gels

Two staining methods for aspartate aminotransferase were compared after electrophoretic resolution of its isozymes in polyacrylamide gels. The first one uses L-aspartic acid and Fast Blue BB salt (classical method), the second uses L-cysteine sulfinic acid and a redox system with phenazine methosulfate and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide. The seeds of pea, horse bean and soybean were used as a model plant source of the enzyme. The staining method with L-cysteine sulfinic acid is very reliable and more sensitive than the Fast Blue BB method and allows detection at very low isozyme activities in the gel.     

Crop/Weed gene flow:Cucurbita argyrosperma Huber andC. fraterna L. H. Bailey (Cucurbitaceae)

A mixed population of Cucurbita at Vado El Mow in northern Tamaulipas, Mexico showed an anomalous pattern of fruit bitterness. Some domesticated plants (C. argyrosperma andC. moschata) expressed cucurbitacin bitterness whereas some sympatric free-living plants produced non-bitter fruits. This reversal of typical cucurbitacin expression suggested gene flow between crop and weed at the site. Isozyme analysis provided little insight as to taxa involved in gene exchange, although progeny from a single free-living plant carried IDH allozymes that are associated with Mexican landraces ofC. pepo. Synthetic hybridization revealed that fertile F, hybrids are produced from crosses involvingC. fraterna as the pistillate parent andC. argyrosperma as the staminate parent. Interspecific crop/weed hybrids can produce viable progeny upon self-pollination or backcrossingto either parent, andF₂ families display normal allozyme segregation. Hybrid fertility, as indicated by pollen stainability, increases in progeny produced by backcrossingfrom theC. argyrosperma parent. Interspecific hybridfertility represents a potential for crop/weed gene flow that would be realized under natural conditions if pollen flow occurs betweenC. fraterna andC. argyrosperma in the fields of Tamaulipas. Oligolectic “squash bees” (Teponapis), efficientCucurbita pollen vectors, are present at the site. Thus, it is likely that natural interspecific crop/weed hybridization has occurred at Vado El Moro and this might at least partially explain the anomalous distribution of fruit bitterness among extant populations at the site.