Two color light scattering identifies physical differences between lymphocyte subpopulations

Forward angle light scattering of two different wavelengths by cells in a flow cytometer was used to investigate physical differences between lymphocytes of different lineage, functional subclass and developmental stage. Correlation of the ultraviolet (UV: 351 nm and 364 nm) and 488 nm light scattering signals produced by lymphoid cells demonstrated that the two signals were not equivalent and that they placed different emphasis on the physical parameters characterizing lymphocytes. Both small T and B lymphocytes from peripheral lymphoid tissues and mitogenically activated large T and B lymphocyte blasts were discriminated by both wavelengths. Differences between the Lyt-2 negative and Lyt-2 positive T lymphocyte subsets were also apparent. Two color light scattering could also discriminate between immature thymocytes and mature peripheral T cells and between small bone marrow cells and mature peripheral B cells. In bone marrow an increase in UV light scattering coincided with the appearance of cell surface immunoglobulin on small cells. These data establish that two color light scattering is a sensitive probe for distinguishing cells of apparently similar morphology and that it can be used to study the physical changes that occur during lymphoid cell differentiation.     

Energy and biological evolution—I. The equilibrium states of biochemical processes

The Thom gradient model of morphogenesis poses the followinga posteriori problem: “From the observed morphology of a given natural process (effect) determine the dynamics of the process (cause)”. In this paper we consider the classicala priori problem: “Given the cause (dynamics) determine the effect (resultant morphology)”. We find that in biochemical processes the mechanisms for energy activation, energy-matter interaction and energy dissipation determine the dynamics. Furthermore there exists basic energy mechanisms which drive the equilibrium states through the elementary catastrophes of Thom. A comparison with current theories shows that our models describe open ecological food chains and their dynamical systems generalize the equations of organisation posed by M. Eigen. Work supported by a Research Associateship of the International Centre for Theoretical Physics, P.O.B. 586, Miramare, 34100 Trieste, Italy.     

Purification and characterization of a membrane-bound protein kinase from spinach thylakoids

A protein kinase was isolated from spinach thylakoid membranes by solubilization with octyl glucoside and cholate. The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, and sucrose density centrifugation, followed by affinity chromatography on either Affi-Gel blue (yielding denatured enzyme) or on histone cross-linked to Sepharose (yielding active enzyme). Electrophoresis on denaturing polyacrylamide gels, followed by staining with silver, revealed the kinase as a single band corresponding to an apparent molecular mass of 64 kDa. The active enzyme underwent autophosphorylation and could be detected by autoradiography following incubation with [gamma-32P]ATP and Mg2+ ion. The specific phosphotransferase activity of purified kinase was approximately 30 nmol of phosphate min-1 (mg protein)-1 with lysine-rich histone (III-S or V-S) as substrate; casein was phosphorylated at approximately 30% of this rate. The physiological substrate for the kinase is presumed to be light-harvesting chlorophyll a/b protein complex. In solubilized form, this was phosphorylated at approximately 10% of the rate observed with histone III-S as substrate, or 10-100 times slower than the estimated rate of phosphorylation of the light-harvesting complex in situ. Possible reasons for this shortfall are considered. The kinase is proposed as the principal effector of thylakoid protein phosphorylation and associated State transition phenomena.     

The influence of hormones and other substances on lens regeneration in vitro

Culturing the dorsal iris epithelium of a newt with a pituitary gland in organ culture greatly enhances the ability of the iris epithelium to produce advanced lens regenerates in vitro. In an attempt to elucidate the mechanism by which the pituitary enhances lens regeneration irido-corneal complexes from adult newts were cultured in medium to which various substances had been added either singly or in numerous combinations. Prolactin, insulin, hydrocortisone, and thyroxine failed to enhance the production of advanced lens regenerates in any of the doses or combinations tested. Similarly, addition of 50 microgram/ml of sodium or calcium ascorbate had no effect on the progress of lens regeneration in vitro. Addition of dibutyryl cyclic-AMP caused an inhibition of depigmentation and regeneration at high doses. The results of these experiments show that the effects of the pituitary cannot be duplicated by hormones which other authors have asserted to be beneficial to limb or tail regenerates in vitro. The results with cyclic AMP suggest that prolonged exposure to high doses of cyclic AMP inhibit regeneration and indicate that further studies on the fluctations in cyclic AMP levels throughout the process of lens regeneration must be done.     

Cat satellite DNA. Isolation using netropsin with CsCl gradients

The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments.     

Structure—activity relationships in the mutagenicity of quinone methides of 7-hydroxyflavylium salts for Salmonella typhimurium

Several synthetic 7-hydroxyflavylium salts related to apigeninidin, a natural 3-deoxyanthocyanidin, have been studied in the Ames mutagenicity test using strain TA1537 of Salmonella typhimurium. Under the neutral pH conditions of the test, these flavylium salts are deprotonated through ionization of the C7-OH (pK_a′ = 4.2–4.4) to form quinone methides. Only the quinone methides of 4-methyl-7-hydroxyflavylium chloride and 4′-methoxy-4-methyl-7-hydroxy-flavylium chloride showed mutagenicity. Responses of 4–8 times the background were observed at the higher doses (1000 μg/plate), both with and without metabolic activation. It was concluded that the induction of frameshift mutagenicity by this group of compounds is caused by those quinone methides that have non-ionic, stable polycyclic structures at neutral pH.     

Aggregation of tobacco mosaic virus by sodium chondroitin sulfate

The precipitation of tobacco mosaic virus by sodium chondroitin sulfate in an aqueous solution was investigated kinetically by means of turbidimetry. The virus solution became turbid after the addition of chondroitin sulfate. A threshold concentration of chondroitin, 1.33 mg/ml, was required for virus precipitation, irrespective of the virus concentration. The precipitation resulted from a mutual spatial exclusion phenomenon, leading to the separation of the virus as a crystalline phase. The dimension of chondroitin sulfate calculated at the threshold concentration agreed well with that obtained by other methods. The initial slopes and the aggregation half-times of the virus aggregates depended on both chondroitin and virus concentrations and the former increased with the increase in concentration of each. Above the threshold concentration of chondroitin sulfate, tobacco mosaic virus aggregation was a rapid-aggregation process and ended within 100 sec.