Population Differentiation under the Charge State Model

The extent of divergence between partially isolated sub-populations for electrophoretically detectable alleles was formulated assuming the island model of migration and the charge state model of mutation. At equilibrium the ratio of the variance of charge between the means of k different islands to the average within-island variance of charge was shown to be approximately 4Nemk2/(k-1)2 where Ne is the effective size of each island population and m is the migration rate. This ratio was calculated from published data for eight polymorphic loci in six island populations of Drosophila willistoni. Under the assumption that all variants are selectively neutral, migration rates of greater than 10 adults per generation per island are required to explain the observed similarity of the allelic profiles in D. willistoni. Since the islands studied appear to be virtually completely isolated it was concluded either that the observed protein variants are adaptive and maintained in populations by some form of balancing selection or that the observed variants themselves are neutral but natural selection acts to restrict the appearance of more extreme variants in the charge carried.     

Purification from human plasma of a heparin-released lipase with activity against triglyceride and phospholipids.

A triglyceride lipase different from lipoprotein lipase, but measurable only after intravenous heparin injection, has been isolated from human plasma by sequential use of heparin-Sepharose and concanavalin A-Sepharose affinity chromatography. Using these procedures, phospholipase A1 activity was found to chromatograph identically with the triglyceride lipase. The constancy of the ratio of activities after isoelectric focusing (pI 4.1) and during thermal deactivation indicates that this enzyme has hydrolase activity against both triglycerides and phospholipids. This conclusion was supported further by the homogeneity of the protein as indicated by sodium dodecyl sulfate polyacrylamide gel electrophoresis.     

Effects of lysolecithin on the surface properties of human erythrocytes

Human red blood cells (RBCs), transformed by incubation with the amphiphatic compound lysolecithin from their normal discocyte shape into echinocytes, have increased rates of agglutination in the presence of either poly- -lysine (PLL) or soybean agglutinin (SBA). Removal of lysolecithin by washing caused a reversal of shape back to the discocyte configuration and a lowering of agglutination rates. Methochlorpromazine, another amphiphatic echinocytogenic substance produced a similar increase in agglutination rates, suggesting that increased agglutinability may be a general property of echinocytes. Lysolecithin treatment of RBCs caused a decrease in the binding of cationized ferritin (CF) particles/μm² of RBC surface. The decrease in CF binding is due to a rearrangement of negative charge bearing molecules on the RBC surface rather than shedding of charged groups. These observations support the hypothesis that integral membrane proteins which bear negative charges and receptors are associated with a cytoskeleton within the red cell. Alterations in cell shape which result in distortion of the cytoskeleton may cause a redistribution of integral membrane proteins which bear charged groups at the RBC surface.     

Analysis of autolysins in temperature-sensitive morphological mutants of Bacillus subtilis.

The content and distribution of autolysin were measured in temperature-sensitive morphological mutants of Bacillus subtilis. Strains RUB1000 and RUB1012 grew as rods at 30 C. At 45 C the mutants contained disproportionately less teichoic acid than peptidoglycan and grew as irregular spheres. The amount of enzyme that could be extracted from rods was at least 31 times the amount extracted from spheres. The rate of autolysis of cell walls was 7- to 28-fold greater in rods than in spheres. The low activity found associated with the cell walls of spheres was not compensated for by larger amounts of autolytic activity in the cytoplasm. No activity was found in the growth medium at either temperature. The failure of the mutant cells to autolyze was due to low amidase activity and relatively resistant cell walls. Revertants of RUB1012 were isolated that had 13, 23, and 55% of the normal proportions of teichoic acid when grown at the nonpermissive temperature. Cell walls from the revertants were as sensitive to added amidase as the wild-type strain. None of the revertant strains regained the wild-type ability to produce more amidase at 45 C. However, the deficiency in autolysin observed with RUB1012 was partially restored in revertants containing higher proportions of teichoic acid.     

Morphogenesis of Sindbis virus in cultured Aedes albopictus cells.

Cultured mosquito cells were found to produce Sindbis virus nearly as efficiently as BHK-21 cells at 28 C. In virtually all of the cells observed in the electron microscope, virus morphogenesis was found to occur within complex vesicular structures which developed after viral infection. Viral nucleocapsids were first seen in these vesicles and appeared to be enveloped within these structures. The process of envelopment within these inclusions differed in some respects from the process previously described for the envelopment of nucleocapsids at the plasma membrane of vertebrae cells. Free nucleocapsids were only rarely seen in the cytoplasm of infected mosquito cells, and budding of virus from the cell surface was detected so infrequently that this process of virus production could not account for the amount of virus produced by the infected cells. The vast majority of extracellular virus was produced by the fusion of the virus-containing vesicles with the plasma membrane releasing mature virions and membrane nucleocapsid complexes in various stages of development.     

Comparison of membrane organization in mitochondria from yeast and rat liver by nuclear magnetic resonance spectroscopy

Summary Proton magnetic resonance (PMR) and carbon-13 magnetic resonance (CMR) spectra of intact, unsonicated yeast and rat liver motochondria show differences which may be correlated with the composition of the membranes. High resolution PMR and CMR signals in intact yeast mitochondria have been assigned to regions of fluid lipid-lipid interaction on the basis of spectra of extracted lipid and protein, and the temperature dependence of NMR signals from the intact membrane. PMR spectra suggest that about 20% of total yeast phospholipid is in regions where both intramolecular fatty acid chain mobility and lateral diffusion of entire phospholipid molecules are possible. No such regions appear to exist in rat liver mitochondria. For both yeast and rat liver mitochondria, comparison of PMR and CMR spectra suggests that about 50% of phospholipid appears to be in regions where intramolecular fatty acid chain motion is considerable, but lateral diffusion is restricted. The remaining phospholipid appears to have little inter- or intramolecular mobility. Since NMR observation of lipid extracts from membranes indicates that phospholipid-sterol interactions do not account for the spectra of intact mitochondria, these effects are interpreted in terms of extensive lipid-protein interactions.     

Stability of rapidly labelled messenger ribonucleic acid in Bacillus amyloliquefaciens during the phases of minimum and maximum extracellular enzyme formation.

The stability of rapidly labelled hybridizable messenger RNA in both exponential and post-exponential phase cells of Bacillus amyloliquefaciens was measured in terms of the rate of loss of its radioactivity. In the exponential phase, where 96% of the mRNA was specific for cell proteins and only 4% was exoprotein mRNA, the label was lost exponentially from the rapidly labelled hybridizable mRNA fraction with a half-life of six minutes at 30 °C. The antibiotic rifampicin, at a concentration of 10 μg/ml, had no effect on the characteristics of decay of this exponential-phase mRNA. In the post-exponential phase, where there were equal amounts of cell protein and exoprotein-specific mRNA, rapidly labelled hybridizable mRNA decayed exponentially in the presence of rifampicin (10 μg/ml), with a half-life of six minutes at 30 °C. In the absence of rifampicin the characteristics of decay were more complex. The evidence available suggested that this was due to the superimposition of a component attributable to reincorporation of degradation products of radioactive RNA on the characteristic exponential decay pattern of the post-exponential mRNA.Measurement of the stability of active mRNA, by studying the loss of ability to incorporate l-[¹⁴C]leucine into protein in the presence of rifampicin (10 μg/ml), gave half-lives of 4.5 minutes and six minutes, respectively, for exponential and post-exponential material.     

Factors affecting the yield of virus in a cloned cell line of Trichoplusia ni infected with a nuclear polyhedrosis virus

The TN-368 tissue culture line of the cabbage looper, Trichoplusia ni, has been cloned. The doubling times of three clones at 27°C were 27.6 ± 3.4 hr, 21.9 ± 1.7 hr, and 27.4 ± 5.9 hr and that of the uncloned culture was 15.8 ± 1.5 hr. Growth of cells in all cultures was arrested after infection with a nuclear polyhedrosis virus of T. ni. There was little difference in the yield of polyhedra from cultures of uncloned or cloned cells infected at a multiplicity of infection (m.o.i) = 4. Yields of polyhedra were about the same when a m.o.i. was in the range of 0.01–4.0, but the yield tripled in the range m.o.i. = 20–30. At higher multiplicities, up to m.o.i. = 500 the yield of polyhedra progressively fell. It is concluded that the observed variation in numbers of polyhedra borne by individual cells in culture is not due to genetic variability among cells, nor can it be accounted for as a consequence of differing m.o.i. by virus. It is postulated that variation in polyhedra yield among cells in culture may be due to such factors as (1) strain differences in the virus, (2) the stage in the cell cycle at which a particular cell is present when infected.     

Effects of the egg cycle and route of administration of prostaglandin-induced oviposition of hens and Japanese quail.

Lactoferrin isolated from sow milk (about 0-6 mg/ml) was shown to be chromatographically homogeneous, an observation supported by electrophoresis and by reaction against monospecific anti-lactoferrin antiserum. Isoelectric focusing showed multiple forms of the protein (i.e.p., 9-3 to 10-0) converted by neuraminidase to one form (i.e.p., 9-65). Boar seminal plasma contains immunologically identical lactoferrin (0-1 to 0-5 mg/ml) which binds strongly to boar spermatozoa.     

Structure and composition of the adenovirus type 2 core.

The structure and composition of the core of adenovirus type 2 were analyzed by electron microscopy and biochemical techniques after differential degradation of the virion by heat, by pyridine, or by sarcosyl treatment. In negatively stained preparations purified sarcosyl cores reveal spherical subunits of 21.6-nm diameter in the electron microscope. It is suggested that these subunits are organized as an icosahedron which has its axes of symmetry coincident with those of the viral capsid. The subunits are connected by the viral DNA molecule. The sarcosyl cores contain the viral DNA and predominantly the arginine/alanine-rich core polypeptide VII. When sarcosyl cores are spread on a protein film, tightly coiled particles are observed which gradually unfold giving rise to a rosette-like pattern due to the uncoiling DNA molecule. Completely unfolded DNA molecules are circular. Pyridine cores consist of the viral DNA and polypeptides V and VII. In negatively stained preparations of pyridine cores the subunit arrangement apparent in the sarcosyl cores is masked by an additional shell which is probably formed by polypeptide V. In freeze-cleaved preparations of the adenovirion two fracture planes can be recognized. One fracture plane probably passes between the outer capsid of the virion and polypeptide V exposing a subviral particle which corresponds to the pyridine core. The second fracture plane observed could be located between polypeptide V and the polypeptide VII-DNA complex, thus uncovering a subviral structure which corresponds to the sarcosyl core. In the sarcosyl core polypeptide VII is tightly bound to the viral DNA which is susceptible to digestion with DNase. The restriction endonuclease EcoRI cleaves the viral DNA in the sarcosyl cores into the six specific fragments. These fragments can be resolved on polyacrylamide-agarose gels provided the sarcosyl cores are treated with pronase after incubation with the restriction endonuclease. When pronase digestion is omitted, a complex of the terminal EcoRI fragments adenovirus DNA and protein can be isolated. From this complex the terminal DNA fragments can be liberated after pronase treatment. The complex described is presumably responsible for the circularization of the viral DNA inside the virion. The nature of the protein(s) involved in circle formation has not yet been elucidated.