A method for intercultivar comparison of potato tuber nutrient content using specific tissue weight proportions.

Potato tubers are a staple food item in the North American diet. Each potato cultivar has unique tuber appearance and nutritional composition. A method was developed to facilitate better cultivar selection for dietary purposes and obtain a better understanding of the nutrient distribution within specific tissues of potato tubers. This involved a procedure for estimating the percent weight contribution of the 3 major tissue components, including periderm or "skin," cortex, and pith for 20 potato cultivars. Weight determination was based on the volume (calculated through an ellipsoid formula) and density of each component tissue. Calculated percent weight and dry matter data for each tuber tissue provided conversion factor values that were tabulated for all cultivars. An example is provided to illustrate the application of this procedure in facilitating identification of cultivars with significantly greater or lesser protein content.

mRNAs and a cloned histone gene are differentially expressed during anther and pollen development in rice (Oryza sativa L.).

Spatial and temporal changes in the distribution of mRNA sequences during anther and pollen development in rice (Oryza sativa) were investigated by in situ hybridization with [3H]polyuridylic acid ([3H]poly(U)) and a cloned rice histone gene probe. Annealing of sections with [3H]poly(U) showed that poly(A)-containing RNA (poly(A)+RNA) was uniformly distributed in the cells of the anther primordium. During the formation of the archesporial initial, the primary parietal cell, the primary sporogenous cell and tapetum, there was no differential accumulation of poly(A)+RNA in their progenitor cells. Preparatory to meiosis, there was a sharp decrease in poly(A)+RNA concentration in the epidermis and middle layer of the anther wall, although the label persisted in the endothecium, tapetum and microsporocytes. Poly(A)+RNA concentration decreased in these cell types during meiosis and attained very low levels in the disintegrating tapetum and the persistent endothecium of the post-meiotic anther. Pollen development was characterized by the absence of [3H]poly(U) binding sites in the uninucleate microspores and by their presence in the vegetative and generative cells of the bicellular pollen grain. In anther sections hybridized with [3H]histone probe, gene expression was only detected in the endothecium of the premeiotic anther and in the bicellular pollen grains.

Nifedipine prevents the pressor response to laryngoscopy and tracheal intubation in patients with coronary artery disease.

The efficacy of sublingual nifedipine, administered one minute before anaesthetic induction, in order to minimise the pressor response to laryngoscopy and tracheal intubation was studied in a group of 15 patients who underwent coronary artery bypass surgery. Another group of 15 similar patients served as control. Premedication consisted of oral diazepam 5-10 mg, intramuscular morphine 0.2 mg/kg and promethazine 0.4 mg/kg. Anaesthesia was induced with morphine 0.1-0.15 mg/kg and thiopentone 3-5 mg/kg. Laryngoscopy and tracheal intubation were facilitated with suxamethonium 1.5 mg/kg. A significant increase in blood pressure occurred during and after laryngoscopy and tracheal intubation in the control group. This increase was absent in the patients pretreated with nifedipine. The nifedipine group also maintained a lower rate-pressure-product than the control group during the period of study. It is concluded that nifedipine 10 mg is a useful pretreatment to prevent the pressor response to laryngoscopy and tracheal intubation in patients with coronary artery disease.

Developmental strategies of the angiosperm pollen: a biochemical perspective.

The current state of our knowledge of the biochemistry and biochemical cytology of normal pollen development and embryogenic transformation of pollen grains of cultured anthers of angiosperms is reviewed. Recent research shows that normal pollen development is characterized by gene activity for the synthesis of specific mRNAs associated with the gametophytic program. As a result of the trauma of excision and culture of anthers in a mineral salt medium, a small number of the enclosed pollen grains probably synthesize new mRNAs which code for the proteins involved in embryogenic divisions. Since these conclusions are based on the study of a small number of species, the need for sustained investigations on the molecular biology of pollen developmental transformations is emphasized.

Distribution of poly(A)-containing RNA during normal pollen development and during induced pollen embryogenesis in Hyoscyamus niger.

The distribution of poly(A)-containing RNA [poly(A)+RNA] in pollen grains of Hyoscyamus niger during normal gametophytic development and embryogenic development induced by culture of anther segments was followed by in situ hybridization with [3H]-polyuridylic acid as a probe. No binding of the isotope occurred in pollen grains during the uninucleate phase of their development. Although [3H]polyuridylic acid binding sites were present in the generative and vegetative cells of maturing pollen grains, they almost completely disappeared from mature grains ready to germinate. During pollen germination, poly(A)+RNA formation was transient and was due to the activity of the generative nucleus, whereas the vegetative nucleus and the sperm cells failed to interact with the applied probe. In cultured anther segments, moderate amounts of poly(A)+RNA were detected in the uninucleate, nonvacuolate, embryogenically determined pollen grains. Poly(A)+RNA accumulation in these grains was sensitive to actinomycin D, suggesting that it represents newly transcribed mRNA. After the first haploid mitosis in the embryogenically determined pollen grains, only those grains in which the generative nucleus alone or along with the vegetative nucleus accumulated poly(A)+RNA in the surrounding cytoplasm were found to divide in the embryogenic pathway. Overall, the results suggest that, in contrast to normal gametophytic development, embryogenic development in the uninucleate pollen grains of cultured anther segments of H. niger is due to the transcriptional activation of an informational type of RNA. Subsequent divisions in the potentially embryogenic binucleate pollen grains appeared to be mediated by the continued synthesis of mRNA either in the generative nucleus or in both the generative and vegetative nuclei.

Patterns of DNA synthesis during pollen embryogenesis in henbane.

Continued DNA synthesis in the generative cell nucleus, followed by mitosis and cytokinesis, results in the formation of pollen embryoids in cultured anthers of H. niger. In contrast, the nucleus of the vegetative cell undergoes no DNA synthesis after it is cut off, or synthesizes DNA only during a limited number of cell cycles. DNA synthetic patterns in the generative and vegetative cell nuclei confirm the ontogeny of embryoids described in this plant.