MICROSPECTROPHOTOMETRIC ANALYSIS OF NUCLEAR DNA IN CHARA ZEYLANICA

Microspectrophotometric analysis of the DNA content of nuclei in various parts of Chara zeylanica Willd. revealed that the amount of DNA in the nucleus of an internodal cell equals twice the amount of DNA in the nucleus of a sperm, while the half-anaphase stage of the same nodal cells contains the same amount of DNA as the nuclei of the male gametes. The DNA content of the nuclei of internodal cells may rise as much as 50 times higher than that of the gametes. However, in the oldest (most basal) internodal cells, the DNA content of the minute nuclei falls again to the basic (1 C) amount. Measurements of sister nuclei derived by amitosis indicated that both nuclei have equal amounts of DNA; this was interpreted as further evidence that amitosis is not a disorganized process or manifestation of degeneration. The bearing of these analyses on the question of the site of meiosis in these plants is discussed.     

Behaviour of photosynthetic products associated with growth and grain production in the rice plant

Summary A study of the behaviour of the photosynthetic products assimilated at different growth stages was conducted in the field and in the greenhouse using C¹⁴ tracer.In general, the assimilated carbon is translocated to and accumulates in the growing organs. The carbon assimilated at the maximum tiller number stage is distributed mostly to the lower leaves. The carbon assimilated at the booting stage is distributed mostly to the spikelet, certain leaf sheaths and culms. The carbon accumulated in the form of carbohydrates in the leaf sheaths and the culm before flowering is retranslocated to the panicle after flowering. However, because of the consumption by respiration, the efficiency of this type of carbohydrate in grain production is not very high. The carbon assimilated after flowering accumulated mostly and efficiently in the brown rice.The release of the assimilated carbon as CO₂ is most intense immediately after assimilation. Thirty-five to 60 per cent of the assimilated carbon is consumed through respiration under the conditions of this experiment. As the carbon, which is in the form of sugars, rapidly changes to other forms, and also is consumed by respiration, the consumption declines rapidly. The retention percentage of assimilated carbon decreases as mutual shading increases.The large proportion of carbon released through respiration indicates the importance of studies on the significance of respiration in relation to growth.A portion of the thesis for the Master of Science degree submitted by Mr. Shen Lian to the Graduate School, University of the Philippines, College of Agriculture.     

Stereoselective high-performance liquid chromatographic assay for propranolol enantiomers in serum

A simple and sensitive stereoselective high-performance liquid chromatographic assay for the quantitation of propranolol enantiomers in serum is described. The method involves conversion of the propranolol enantiomers to diastereomeric urea derivatives by reaction with the chiral reagent (+)-phenylethylisocyanate, followed by chromatographic separation of the diastereomeric products. Conditions of the derivatization reaction were optimized to achieve rapid and quantitative yield with either of the enantiomers. Baseline resolution of the diastereomers was achieved on a reversed phase C₈ column with an isocratic mobile phase. Fluorescence detection afforded an absolute on-column detection limit of 100 pg. The assay has been applied to pharmacokinetic studies in humans and small laboratory animals.     

Pulmonary surfactant will secure free airflow through a narrow tube

Well functioning pulmonary surfactant is necessary to ensure alveolar stability. It is proposed that surfactant is also required to keep the finest cylindrical airways open, thereby securing an unrestricted flow of air to and from the alveoli. If the surfactant is inadequate in quality or quality there is a risk that liquid will accumulate in the most marrow section of the airway and form a blocking column. To study that possibility special glass capillaries were used. The glass capillaries were heated and extended to make a short section very narrow. In the lumen of that section a minute volume (1 microliter) of liquid was deposited, which formed a blocking column. When pressure was raised on one side of the column, it forced the liquid to move away from the narrow section. Pressure dropped to zero as air could pass, and if the liquid column consisted of calf lung surfactant extract (CLSE), pressure remained at zero because a new liquid column did not form. If, on the other hand, the liquid column consisted of saline solution it would repeatedly reform as soon as it had been pressed out of the capillary's narrow section. The same occurred if the CLSE suspension forming the liquid column was very dilute or contained inhibiting proteins. These observations did not require that the capillary consisted of the material glass; they were also noted when the narrow tube was outlined by epithelium.