Streptozotocin treatment of streptozotocin-induced islet cell adenomas in rats.

Hypoglycemic rats bearing insulin-secreting islet-cell adenomas produced by the combined action of streptozotocin and nicotinamide were treated with streptozotocin. Antitumor response was demonstrated by elevation of blood glucose, reduction in plasma and tumor IRI, and histopathologic changes in the beta-cell neoplasm. The rodent tumor model may serve as a predictive system for selection and investigation of mechanisms of action of future antitumor agents to be used in the treatment of malignant insulinoma in man.     

Treatment of asthma by a controlled-release theophylline tablet formulation: a review of the North American experience with nocturnal dosing

As many as 80 percent of asthmatics experience nighttime or early-morning episodes, which are difficult to treat and potentially fatal. The greater-than-normal amplitude of circadian airflow variation in many asthmatics contributes heavily to the genesis of the early 'morning dip'. Beta-agonists and corticosteroids are of limited usefulness in nocturnal asthma, and slow-release theophylline drugs, while potentially effective, vary in 24-hr blood profile and hence their influence on nocturnal episodes. Traditional 12-hr 'symmetric' theophylline regimens, instead of meeting increased nocturnal demands, may actually produce lower night- than daytime blood levels. On the other hand, appropriately timed administration of a once-daily theophylline drug might provide maximum blood levels when needed and help stabilize 24-hr airflow. Accumulated data, summarized in this review, demonstrate the chronotherapeutic potential of single-daily evening doses of a controlled-release theophylline preparation (Uniphyl 400-mg tablets) in nocturnal and early morning asthma. Nighttime blood concentrations with this regimen were higher than were those with Theo-Dur tablets, B.I.D., in the same total daily doses, or with once-daily morning Uniphyl administration. In fed and fasted subjects, evening administration of Uniphyl 400-mg tablets was well tolerated and did not lead to 'dose dumping.' Clinically, this treatment demonstrated advantages over B.I.D. theophylline, over single-daily morning regimens, and over prior theophylline therapy. Advantages of the evening regimen included better early-morning airflow (without significant decline later in the day), more effective symptom control, better patient acceptance, fewer night awakenings, and the obvious convenience of once-daily dosing. In addition, lung function showed greater stability, throughout the day, with once-daily evening therapy than with traditional 12 hr dosing. Uniphyl 400-mg tablets may be administered once daily to provide maximum blood levels at the time of peak bronchoconstriction, whether at night or during the day.     

Allocation of Photosynthate to Individual Tubers of Solanum tuberosum L.: I. RELATIONSHIP BETWEEN TUBER GROWTH RATE AND ENZYME ACTIVITIES OF THE STARCH METABOLISM

Potato plants (Solanum tuberosum L.) were grown in water culturein a controlled environment. Cooling (+8°C) of individualtubers decreased their growth rates and increased the growthrates of non-cooled tubers of the same plant. The carbohydrateconcentration in non-cooled and cooled tubers did not differsignificantly, but ¹⁴C-import from labelled photosynthate waslower in cooled than in non-cooled tubers. The markedly lowerconversion rate of ethanol-soluble ¹⁴C to starch in cooled,in comparison to non-cooled tubers, was not associated withsignificant differences in the in vitro activities of starchsynthase, ADPG-pyrophosphorylase and starch phosphorylase understandard assay conditions (+30°C). However, the Q₁₀-valuesof the enzymes differed in vitro in the temperature range between30°C and 8°C, leading to a marked decrease in the activityratio of ADPG-pyrophosphorylase/starch phosphorylase in cooledtubers. In tubers differing in growth rates without manipulation, 14d after tuber initiation significant positive correlations werefound between ¹⁴C-concentration of tuber tissue and the in vitroactivities of starch synthase and ADPG-pyrophosphorylase anda significant negative correlation between ¹⁴C-concentrationand starch phosphorylase. In contrast, in tubers which wereanalysed 5 d after initiation, there were only small differencesbetween tubers in growth rate, ¹⁴C import and the activity ratioADPG-pyrophosphorylase/starch phosphorylase. From various directand indirect evidence it is concluded that the growth rate ofindividual tubers, and thus the sink strength, is at least inpart controlled by the activity of starch synthesizing enzymes. Key words: Potato tuber, cooling, starch synthesizing enzymes     

Uracil in formic acid hydrolysates of deoxyribonucleic acid

1. When DNA is hydrolysed with formic acid for 30min. at 175 degrees and the hydrolysate is chromatographed on paper with propan-2-ol-2n-hydrochloric acid, in addition to expected ultraviolet-absorbing spots corresponding to guanine, adenine, cytosine and thymine, an ultraviolet-absorbing region with R(F) similar to that of uracil can be detected. Uracil was separated from this region and identified by its spectra in acid and alkali, and by its R(F) in several solvent systems. 2. Cytosine, deoxyribocytidine and deoxyribocytidylic acid similarly treated with formic acid all yielded uracil, as did a mixture of deoxyribonucleotides. 3. Approx. 4% of deoxyribonucleotide cytosine was converted into uracil by the formic acid treatment.     

Active and passive cation transport and L antigen hertogeneity in low potassium sheep red cells

Several lines of experimental evidence are presented suggesting that the L antigens in low potassium (LK) sheep red cells are associated with separate Na(+)K(+) pump flux is distinct from the action of anti-L(l) on K(+) leak flux, implying that K(+) leak transport sites may not be converted into active pumps by the L antiserum. Treatment of LK red cells with trypsin completely abolished both the stimulation of K(+) pump flux and the enhancement of the rate of ouabain binding brought about by anti- L. That this effect is due to a total destruction of the L(p) determinant associated with the LK pump was evident from the complete failure of anti-L(p) to bind to trypsinized LK red cells. The L(p) antigen can be effectively protected against the trypsin attack by prior incubation with anti-L, indicating that the sites for antibody binding and trypsin action may be closely adjacent at the structural level. Trypsin treatment, however, did not interfere with anti-L(l) reducing ouabain insensitive K(+) leak influx, nor did it prevent binding of anti-L(ly), the hemolytically active L antibody which is probably identical with anti-L(l). The functional independence of the L(p) and L(l) sites was documented by the observation that anti-L(l) still reduced K(+) leak influx in LK cells with experimentally induced high potassium concentrations, at which K(+) pump flux is fully suppressed, whether or not anti-L(p) was binding to the L(p) antigen associated with the LK pump.     

Electron microscopic studies of the development of kinetes in Theileria annulata Dschunkowsky & Luhs, 1904 (Sporozoa, Piroplasmea).

Gamogony of Theileria annulata Dschunkowsky & Luhs occurs within the intestine of nymphs of the tick Hyalomma anatolicum excavatum Koch. After the 5th day post repletionem (p.r.) of the ticks spherical and ovoid parasites were found within the intestinal cells. These stages were thought to represent fertilized macrogametes. These underwent a transformation process leading ultimately to the differentiation of a motile stage, the kinete, which leaves the intestinal cells on the 14th-17th day p.r. and penetrates the alveoles of the salivary glands. The transformation of the stationary into a motile stage takes place by formation of a growing protrusion (= anlage) into an inner, enlarging vacuole. During this process the limiting membrane of the vacuole serves as the outer membrane of the developing motile stage, whereas the 2 inner membranes of its pellicle are newly formed. The steps of this differentiation in T. annulata are compared to the process of ookinete formation in haemosporina.