Determination of C distribution in photosynthetic serine and phosphoglycerate from grape leaves

Serine and phosphoglyceric acid are the classical marker intermediates of photorespiration and reductive carbon assimilation in C₃ plants. The present paper introduces a new and fast method for the determination of ¹⁴C distribution in these compounds by selective elimination of C-3 (NaIO₄) or C-1 (ninhydrin/ceric sulfate). Reproducibility of the procedure was found to be better than ±1% upon degradation of [U-¹⁴C]serine and [U-¹⁴C]glycerate standards.     

Low doses of X-rays decrease the risk of diploidy in mouse oocytes

Females from the NMRI/Han mouse strain ovulate a high number of diploid oocytes (about 12%) after gonadotrophin-stimulated ovulation. These oocytes can be fertilized and develop into triploid embryos subsequently. The exposure of such gonadotrophin-primed females to X-ray doses of 0.05, 0.10, 0.20 or 0.40 Gy during the preovulatory period (2 h after the HCG dose) significantly decreased the percentage of diploid oocytes. After the highest dose used, i.e. 0.80 Gy, however, the incidence was on the level from unirradiated females, again. We suggest that the observed negative hump-shaped dose response of diploidy is not caused by secondary modifications induced by irradiation, such as a selective killing of diploid oocytes before ovulation, or a (compensatory) super-ovulation of only normal oocytes, but rather is caused by a direct radiobiological interference of low doses in protecting from gonadotrophin-induced aneuploidy.     

The effect of soil water status on critical phosphorus concentrations inStylosanthes hamata cv. Verano

Summary The effect of soil water status on the critical phosphorus concentration (CPC) determined in apices and whole tops ofStylosanthes hamata cv. Verano was investigated in a glasshouse trial. The species was grown with six rates of P and three ranges of soil water potential and was harvested at 10 and 14 weeks after germination. The CPC of both whole tops and apices decliced between the two harvests. At the first harvest the CPC of both whole tops and apices increased as the soil water potential decreased but at the second harvest there was no effect of soil water potential on CPC. It is suggested that at the earlier harvest water stress was delaying physiological development, resulting in a CPC characteristic of chronologically younger tissue, but that by the second harvest the decline in CPC with age had ceased for all water treatments.     

World Health Organization's programme on the prevention of blindness

The WHO Programme for the Prevention of Blindness was established in 1978, reflecting the need for action against the burden of avoidable blindness, which constitutes an increasingly serious socioeconomic problem in many countries. A vast majority of the world's blind live in developing countries, where unoperated cataract, trachoma, xerophthalmia and onchocerciasis are the main causes of visual loss. Thus, more than two-thirds of blindness encountered in such areas is either preventable or curable. The objectives of the WHO Programme for the Prevention of Blindness are to reduce the amount of avoidable blindness in developing countries, and to make essential eye care available to all. In order to achieve this, blindness prevention must form part of primary health care, which is the basic strategy of the World Health Organization to attain the overall goal of "Health for All by the Year 2000". Emphasis is placed on the establishment of national programmes for the prevention of blindness, geared to local needs and resources. This implies a need for a careful programming process, in relation to the general provision of health services.     

In vitro and in vivo studies of Trypanosoma cruzi DNA polymerase

One major DNA polymerase has been purified and characterized from Trypanosoma cruzi. The enzyme has a sedimentation coefficient of 6.8 S corresponding to an approximate molecular weight of 180,000 assuming a globular shape. The enzyme recognizes activated DNA very efficiently, as well as synthetic polydeoxynucleotides, whereas poly rA-dT12 is very poorly utilized. Trypanosoma cruzi DNA polymerase is not inhibited at all by aphidicolin, while araCTP inhibits the enzyme very slightly. The purified enzyme is strongly inhibited by N-ethyl maleimide, dideoxyTTP, ethidium bromide and berenil. All our attempts to find a DNA polymerase sensitive to aphidicolin in vitro have failed, nor have we been able to find a low molecular weight DNA polymerase in this organism. However, when DNA synthesis was studied in whole trypanosomes, aphidicolin was shown to inhibit DNA synthesis more efficiently than ethidium bromide and berenil.     

Amiloride-inhibited Na+ uptake into toad bladder microsomes is Na+-H+ exchange

Amiloride-inhibited Na+ transport into toad urinary bladder microsomes is sensitive to a pH gradient across the vesicular membrane. The magnitude of the gradient was measured directly with acridine orange. Also Na+ could stimulate amiloride-sensitive proton efflux from the microsomes. These results indicated that the transport process was Na+-H+ exchange.     

Morphogenetic Potential of Embryo- and Seedling-Derived Callus of Elaeis guineensis Jacq. var. pisifera Becc.

The oil palm of commerce, Elaeis guineensis (tenera), derivesfrom hybridization of variety dura x pisifera. Germ plasm ofpisifera is limited, however, because of varying degrees offemale sterility. Efforts to increase the range of availablepisifera male germ plasm have thus far been limited to fertilepisiferas but it is anticipated that clonal multiplication ofembryos and explanted organs from less female-fertile, but nonethelessfertile, male, plants could play a significant role in breedingprogrammes. Callus has been produced from mature pisifera embryosand leaf explants from young plantlets using a half-strengthMurashige and Skoog medium supplemented with inositol, caseinhydrolysate, activated charcoal and varying concentrations ofauxins. After sub-culture on media of similar composition, organizedstructures can develop. Those which form in stale nutrient media(e.g. left in the same medium for up to 3 months) give riseto embryonal structures which do not readily develop furtherand can be regarded as neomorphs. If callus once formed is transferredto media with lower auxin concentrations (40–0 mg l^–1)embryonal buds and well-formed shoots are produced; additionof gibberellic acid (GA₃) fosters the production of well-organizedshoots accompanied by roots. Elaeis guineensis var pisifera, oil palm, tissue culture, micropropagation, embryo development, morphogenetic potential, callus     

Circular dichroism of biological membranes: I. Mitochondria and red blood cell ghosts

Improved circular dichroism curves are reported for mitochondria and red blood cell ghosts. The red shift and low amplitudes of the suspension spectra are shown to be due to distortions arising from the particulate nature of the samples. Previously proposed details of membrane structure based on the “red shift” are not supported by the corrected spectra.