Ecophysiology and distribution of the endemic leafless spurgeEuphorbia aphylla and the introducedE. tirucalli (Euphorbiaceae,Euphorbia sect.Tirucalli) in the Canary Islands

The leafless spurgeEuphorbia aphylla (Euphorbiaceae), an endemic species restricted to several of the Canary Islands where it inhabits coastal and arid localities, expresses Crassulacean Acid Metabolism (CAM) when it is subjected to summer drought. A flexible CAM is consistent with the general ecology of the species. It is the only member of sect.Tirucalli native to the Canary Islands and is at the north-western edge of the section's biogeographical range. The other members of the section have a paleotropic distribution and are found throughout Africa. Many of them are regarded as obligate CAM plants, includingE. tirucalli which was used as a comparison in ecophysiological experiments examining the response ofE. aphylla to drought and temperature.     

Artificial hybridization within Saxifraga pentadactylis (Saxifragaceae)

Saxifraga pentadactylis subsp. almanzorii , an endemic to the subalpine nucleus of Sierra de Gredos (central Spain), differs from its closest relative, subsp. willkommiana , by its less showy petals. An artificial crossing program was carried out in order to assess the degree of reproductive isolation between the subspecies. To facilitate interpretation of the results, the program was extended to 10 other interspecific hybrid combinations within sect. Saxifraga . All the data gathered are congruent with the occurrence of two evolutionary scenarios. Interspecific crossings, rendering moderate to high seed-set (in obtaining the F₁), and vigorous but relatively sterile F₁ offspring, reveal reproductive barriers at the level of the F₁ fertility, probably originated as a byproduct of divergent evolution. In contrast, intraspecific crossings within S. pentadactylis resulted in seed-set values lower than expected (in obtaining the F₁), in a majority of weak non-viable F₁ offspring but also in a few fertile F₁ hybrid specimens which were able to originate F₂ offspring. This second pattern reveals reproductive barriers at the level of the F₁ vitality, probably arisen in a quite abrupt fashion. The lower P/O for subsp. almanzorii as compared to subsp. willkommiana , together with the rest of the evidence suggest that the reproductive barriers between them might be the product of active selection against hybridization achieved by incrementing the levels of autogamy in the former.     

Candida biotypes in patients with oral leukoplakia and lichen planus

Prevalence of yeasts in 35 leukoplakia and 34 oral lichen planus patients was compared with that observed in persons without oral diseases. Serotype and morphotype were determined on Candida albicans isolates. Yeasts were isolated from the oral cavity specimens of 43.7% of the patients. C. albicans (serotype A) was the predominant species (76% in leukoplakia, 88.2% in lichen planus and 60.8% in healthy persons). Sixteen morphotypes were encountered on malt extract agar, being 732, 733, 734, 753 and 754 the most frequently found. Morphotypes SP1N and SP1Y were the most common on Sabouraud-trypheniltetrazolium agar (68.4% of the isolates from leukoplakia and 73.3% from lichen planus, but only 46.6% of the isolates from healthy oral mucosa showed SP1N morphotype). Presence of oral lesions was associated with a marked reduction in the yeast species and C. albicans biotypes, suggesting that C. albicans and particularly some of its biotypes, show a high potential of adaptation to the changes associated with the development of oral leukoplakia and lichen planus.     

Whisker-mediated plant transformation: An alternative technology

A number of different methods, involving direct DNA delivery are now available for plant transformation. Here we review the most recently developed technique which involves the mixing of silicon carbide whiskers with plant cells and plasmid DNA. Fertile transgenic plants have now been produced using whisker-mediated transformation, and this method can now be considered as a simple, inexpensive alternative for plant transformation. A brief review on transformation of animal cells andChlamydomonas using whiskers technology is also included.     

Advance directives, autonomy and unintended death

This Paper argues that Living wills are typically nebulous and confused documents that do not effectively enable you to determine your future treatment. Worse, signing a living will can end your life in ways you never intended, long before you are either incompetent or terminally ill. This danger is compounded by the fact that those who implement living wills are often themselves dangerously confused, so that, for example, they cannot be relied upon to distinguish living wills from DNR orders. In addition, the Paper argues that advance directives concerning resuscitation are often so confused that they end the lives of healthy, alert people who have not suffered cardiac or pulmonary arrest. Finally, the paper argues that advance directives establishing durable power of attorney for health care often preserve the chief dangers of living wills. Suggestions are offered as to how you can most effectively direct your future treatment without endangering your life.     

Elemental microanalysis of fibroblasts by a scanning proton microprobe and application to Menkes’ disease

A scanning proton microprobe has been used for the elemental microanalysis of individual fibroblast cells. Both normal fibroblasts and fibroblasts cultured from patients with Menkes' disease, an X-linked genetic disorder known to be associated with defective copper metabolism, were examined by the probe. The cells were cultured on a thin ultra-clean nylon foil and retained on that surface for analysis. The focused high-energy proton beam was used to irradiate selected individual cells and elemental information was derived from X-ray and backscattered proton data. The sensitivity of the scanning proton microprobe to trace concentrations of heavy elements has allowed this elemental information to be used to identify individual cells as being either normal or a Menkes' mutant. The cell identification was based on the application of discriminate analysis to a data set formed from the ratios of copper to each of the macroelements present in the cell. This method of cell identification offers the promise of rapid diagnosis of Menkes' disease.     

Mother-cub relationships in giant pandas in the Qinling Mountains,China, with comment on rescuing abandoned cubs

Six cases of mother-cub relationships in wild giant pandas (Ailuropoda melanoleuca) were observed in the Qinling Mountains, China. It was found that panda cubs are normally left alone in the den for 4–8 h while mothers forage. The mother's absence during bouts of foraging should be considered when rescuing abandoned cubs in order to avoid adding to the decline of the wild population. © 1994 Wiley-Liss, Inc.     

Synaptic patterns of rye B chromosomes. II. The effect of the standard B chromosomes on the pairing of the A set

In order to elucidate the possible effects of rye B chromosomes (Bs) on synapsis and metaphase-I associations of the A set, a comparative study between pachytene and metaphase-I-cells of rye plants carrying different numbers of Bs (0–8) has been carried out. The number of Bs was found to be positively correlated with the frequency of synaptic irregularities of the A set, i.e. multivalents and foldback pairing, and with the frequency of pachytene interlockings. It is proposed that interlockings are the origin of these irregularities because both appeared in close proximity in many nuclei. Examples of A-B pairing are described. The frequency of synaptic abnormalities seems to be unrelated to the mean of A chromosome-bound arms at metaphase I.     

Transport and transformation of hexavalent chromium through soils and into ground water

A detailed characterization of the underlying and adjacent soils of a chrome‐plating shop was performed to provide information on the extent of soil and aquifer contamination at the site and on the potential for off‐site migration and environmental impact. Intact, moist cores were obtained from more than 40 different locations, resulting in more than 200 discrete samples for total metal analysis, selective extraction tests, and adsorption‐reduction experiments, to assess the chemical speciation and distribution of chromium on the contaminated soils and its leaching potential. Surface analytical techniques were also used to determine chemical speciation and to further elucidate mineral fractions responsible for retention of the chromium on the soils and sediments. Adsorption and reduction capacities of the saturated aquifer sediments were variable and low, while the unsaturated soils’ reduction capacities were much greater and were correlated with depth (decreasing capacity with increasing depth). The soils’ adsorption and reduction capacities were eventually overwhelmed, however, and permitted the passage of Cr(VI) into the underlying ground water. Adsorption capacity differences were primarily related to clay content and pH, and less so to the presence of amorphous iron oxide coatings on matrix minerals as operationally defined by the selective extraction methods used in the study. Reduction of Cr(VI) to Cr(III) and subsequent precipitation as (Fe, Cr)(OH)₃ is proposed as the primary attenuation mechanism in the unsaturated soils immediately beneath the shop, based on extraction and surface analyses results.     

Kinetic study of the cytotoxic effect of α-sarcin,a ribosome inactivating protein fromAspergillus giganteus,on tumour cell lines: protein biosynthesis inhibition and cell binding

-Sarcin is a ribosome inactivating protein produced by the mouldAspergillus giganteus. The effect of this protein on eight different tumour cell lines has been studied in the absence of any agent affecting membrane permeability. The protein is cytotoxic for all the tumour cell lines considered. -Sarcin modifies the cell proliferation pattern by inhibiting the protein biosynthesis of the cultured cells. No membrane damage produced by -sarcin has been observed by measuring lactic dehydrogenase leakage. Alteration on the cell mitochondrial activity has not been detected upon treatment with -sarcin. Differences on the extent of the protein binding to the cells have been observed by flow cytometric measurements. The kinetic analysis of the protein biosynthesis inhibition produced by -sarcin reveals an -sarcin concentration-dependent lag phase followed by a first order decrease of the protein synthesis rate. This parameter is dependent on the external -sarcin concentration. A saturable component for the action of -sarcin is also deduced from these experiments. Results are discussed in terms of the protein passage across the cell membrane as the potential rate-limiting step for the action of -sarcin.