BIOCHEMICAL COMPOSITION AND PHOTOSYNTHETIC CARBON METABOLISM OF NUTRIENT LIMITED CULTURES OF MERISMOPEDIA TENUISSIMA (CYANOPHYCEAE)1

Continuous cultures of Merismopedia tenuissima Lemmerman, limited by phosphorus, nitrogen, sulfur, or carbon, were compared to non limited batch cultures by two methods. The cellular content of photosynthetic pigments (chlorophyll and phycocyanin) was found to decrease in all nutrient limited cultures, except for the carbon limited culture. The ratio of carbohydrate to protein was 4- to 7-fold higher in P, N or S limited cultures than in non-limited or C limited cultures. The macromolecular products of photosynthesis were determined in samples to which NaH¹⁴CO₃ was added. Relative incorporation into protein decreased in P or N limited cultures, increased accumulation of low molecular weight compounds was found in S and P limited cultures, and little change was noted in C limited cultures as compared to non-limited cultures. Although relative incorporation into protein was significantly greater at 20μEin·m^?2·s^?1 light intensity than at 180 μEin·m^?2.s^?1 in non-limited cultures, this effect was abolished in all nutrient limited cultures. These results suggest that measurement of the cellular carbohydrate to protein ratio and the products of photosynthesis would be useful in the analysis of algal population dynamics in nature.     

Depsidone constituents from the quintaria group of Nephroma species

A new lichen depsidone was isolated, in the form of its triacetate derivative from the acetylated extracts of Nephroma antarcticum and has been demonstrated to be hypoconstictic acid-triacetate. Two related depsidones, hypostictic acid hyposalazinic acid, were isolated from N. australe.     

Gas chromatographic method for the simultaneous determination of hydralazine and its acetylated metabolite in serum using a nitrogen-selective detector

A relatively simple gas chromatographic method has been developed for the quantitative determination of hydralazine simultaneously with its acetylated metabolite, 3-methyl-s-triazolo[3,4-α]phthalazine (MTP). The proteins were removed by means of sulfosalicylic acid and Sure-Sep®. On treatment with formic acid, hydralazine and its internal standard were converted into their formylated derivatives. These derivatives, MTP and its internal standard were extracted with toluene and determined by gas chromatography with a nitrogen-selective detector. The lower limits of detection for hydralazine and MTP were 0.13 and 0.27 μmol/l, respectively.     

Rational men and the explanatory model approach

The previous issue of Culture, Medicine and Psychiatry (Vol. 5, N. 4) included my article When Rational Men Fall Sick: An Inquiry into Some Assumptions Made by Medical Anthropologists together with a series of comments. This paper consists of my replies to some of the commentators and a case study illustrating my points.My collaborators in this research were two physicians, Dr. Robert Like, of the Department of Family Practice of Case Western Reserve University and Dr. Rivka Plotkin of the Ben-Gurion University of the Negev (Israel). Also, I want to thank Avraham Blidstein for his invaluable assistance.     

Individual variation of nucleoside triphosphate pyrophosphohydrolase activity in human erythrocytes,granulocytes, lymphocytes,and platelets

Analysis of the nucleoside triphosphate pyrophosphohydrolase specific activity of red cells obtained from a random Caucasian population indicated at least two subclasses. The specific activity of 18% of the population ranged from undetectable activity to 27.5 nmol ITP cleaved/20 min/mg hemoglobin. The remainder of the population had higher activity, 27.5–125 nmoles ITP cleaved/20 min/mg hemoglobin. The variation of NTPH activity evident in the red cells of an individual is reflected in granulocytes, lymphocytes, and platelets of that individual. Erythrocyte activity ranges from 0.7 to 21 units (nmol of ITP cleaved in 20 min)/10⁷ cells, granulocytes have 17–201 units/10⁷ cells, lymphocytes have 91–462 units/10⁷ cells, and platelets have 1.1–7.1 units/10⁷ platelets. These cell differences are discussed with respect to the hypothesis that NTPH prevents incorporation of ITP or dITP into nucleic acids.This work was supported by funds allocated by the Agricultural Experiment Station, Michigan State University. Michigan Agricultural Experiment Station Journal No. 8727.     

Effect of concanavalin a on ganglioside metabolism of human lymphocytes

The effect of Con-A on the incorporation of radioactivity from [¹⁴C]-glucosamine into gangliosides of human lymphocytes was investigated. Compared with non-stimulated lymphocytes there was increased incorporation into gangliosides and total lipids within the first 24 hours of exposure to Con-A. Ganglioside synthesis also occurred in later time intervals within the 96 hour incubation period. GM3 accounted for 80% of the labeled ganglioside in Con-A stimulated cells at all times studied. Thus ganglioside synthesis is not only associated with cellular division, but also occurs within a few hours of lymphocyte activation representing an extremely early prereplicative event.     

Identification of a distinct phase during melanogenesis that is sensitive to extracellular pH and ionic strength

The cell line B16/C3 will undergo melanogenesis at a specific time after plating. We have found that this time can be modulated by varying the pH of the culture medium. At high pH levels (8.2–8.6) the onset of melanogenesis occurs in 3 or 4 days, while at lower pH (6.7–7.2) it occurs in 7 or 8 days. Furthermore, the time of onset is also sensitive to the extracellular ionic strength. The addition of sodium lactate, sodium chloride, or any other salt tested delays or blocks completely the onset of melanogenesis. These effects are not simply consequence of growth inhibition, nor can they be correlated with patterns of lactate accumulation. These cells are sensitive to pH or ionic strength after entering the stationary phase just prior to the time of onset of melanogenesis. The existence of a specific pH-and ionic-strength-sensitive phase may provide an important clue to the events responsbile for differentiation in this system.     

Effects of tetracyclines on aldosterone- and insulin-mediated Na+ transport in the toad urinary bladder

The effect of oxytetracycline and demethylchlortetracycline on aldosterone- and insulin-mediated Na⁺ transport (short-circuit current) were examined in toad urinary bladders mounted in modified Ussing chambers. Oxytetracycline had little or no effect on either basal or aldosterone-mediated Na⁺ transport. In contrast, demethylchlortetracycline markedly inhibited both basal and aldosterone-mediated Na⁺ transport. Furthermore, demethylchlortetracycline inhibited the aldosterone response significantly out of proportion to its effects on basal Na⁺ transport. Neither of the drugs had an effect on insulin-mediated Na⁺ transport. Consequently, the natriuresis observed in certain patients treated with demethylchlortetracyline may be related to drug-induced renal resistance to the effects of aldosterone.     

Liver as a source of transformed cell growth factor

Isolated rat hepatocytes release an acidic glycoprotein(s) that can selectively promote the growth of transformed cells. This factor has a molecular weight of 60 000–70 000 D. Liver microsomal and cytosol fractions contain two species of stimulatory activity—44 000 and 3 500 D. Mitochondrial and nuclear fractions contain only the lower molecular weight factor.