Isolation and partial characterization of phages infectingCitrobacter intermedius C3

Several new bacteriophages infecting strain C3 ofCitrobacter intermedius have been isolated from fresh waters. The physicochemical properties, plaque morphology, growth characteristics, virion structure, and immunology of eight bacteriophage isolates are reported. The phages are classified into three groups according to their characteristics.     

Banding patterns of the chromosomes ofCercopithecus neglectus: Comparison withMiopithecus talapoin andErythrocebus patas

The G, Q, and C bands and the location of the nucleolar organizing regions (NORs) of the chromosomes of two male Cercopithecus neglectusare described. The diploid number of the species is 2n =62. Comparison with the karyotypes of Miopithecus talapoin (2n =54), and Erythrocebus patas (2n =54)showed the presence of total banding homeology for only 10 chromosome pairs.     

Could life have evolved in cometary nuclei?

Hoyle and Wickramasinghe have recently suggested that life may have originated in cometary nuclei rather than directly on Earth. Even though comets are known to contain substantial amounts of organic compounds which may have contributed to the formation of biochemical molecules on the primitive Earth, it is doubtful that the process of chemical evolution has proceeded in comets beyond the stage that has occurred in carbonaceous chondrites. Some of the arguments which do not favor the occurrence of biopoesis in comets are:

1. A large layer of cometary ices is ablated from the nucleus' surface each time the comet passes through perihelion, so that essentially most of the organic products on the surface would be sublimed, blown off or polymerized.
2. Because of the low temperatures of the cometary ices, polymers formed on one perihelion passage would not migrate deep enough into the nucleus to be preserved before they would be ablated away by the next perihelion passage.
3. In the absence of atmosphere, and discrete liquid and solid surfaces, it is difficult to visualize the synthesis of key life molecules, such as oligopeptides, oligonucleotides and phospholipids by condensation and dehydration reactions as is presumed to have occurred in the evaporating ponds of the primitive Earth.
4. Observations suggest that cometary nuclei have a rather weak structure. Hence, the low central pressures in comets combined with the high vapor pressures of cometary ices at the melting point of water ice, suggest that a liquid core is not a tenable structure. Yet, even if a cometary nucleus is compact enough to hold a liquid core and a transient liquid water environment was provided by the decay of²⁶Al, the continuous irradiation in water of most of the biologically relevant polymers would have hydrolyzed and degraded them.
5. Needless to say that the effects of radiation on self-replicating systems would also have caused the demise of any life forms which may have appeared under any circumstances.
6. Concerning viruses, the high specificity of host-parasite relationships and their coevolutionary lines of descent, rule out a cometary origin for them.

In summary, the view that life originated in comets is untenable in the light of all the available evidence.     

Glycine transport into plasma-membrane vesicles derived from rat brain synaptosomes.

1. Transport of glycine has been demonstrated in membrane vesicles isolated from rat brain, using artificially imposed ion gradients as the sole energy source. 2. The uptake of glycine is strictly dependent on the presence of Na+ and Cl- in the medium, and the process can be driven either by an Na+ gradient (out greater than in) or by a C1- gradient (out greater than in) when the other essential ion is present. 3. The uptake of glycine is stimulated by a membrane potential (interior negative), as demonstrated by the effects of the ionophores valinomycin and carbonyl cyanide m-chlorophenylhydrazone and anions of different permeabilities. 4. The kinetic analysis shows that glycine is accumulated by two systems with different affinities. 5. The presence of ouabain, an inhibitor (Na+ + K+)-activated ATPase, does not affect glycine transport. 6. The existence of a high-affinity, Na+-dependent glycine-uptake system in membrane vesicles derived from rat brain suggests that this amino acid may have a transmitter role in some areas of the rat brain.     

The effect of glucagon on the kinetics of hepatic mitochondrial calcium uptake

Summary Previous work by this and other laboratories has shown that glucagon administration stimulates calcium uptake by subsequently isolated hepatic mitochondria. This stimulation of hepatic mitochondrial Ca²⁺ uptake byin vivo administration of glucagon was further characterized in the present report. Maximal stimulation of mitochondrial Ca²⁺ accumulation was achieved between 6–10 min after the intravenous injection of glucagon into intact rats. Under control conditions, Ca²⁺ uptake was inhibited by the presence of Mg²⁺ in the incubation medium. Glucagon treatment, however, appeared to obliterate the observed inhibition by Mg²⁺ of mitochondrial Ca²⁺ uptake. Kinetic experiments revealed the usual sigmoidicity associated with initial velocity curves for mitochondrial calcium uptake. Glucagon treatment did not alter this sigmoidal relationship. Glucagon treatment significantly increased the V_max for Ca²⁺ uptake from 292±22 to 377±34 nmoles Ca²⁺ /min per mg protein (n=8) but did not affect the K_0.5, (6.5–8.6 μM). Since the major kinetic change in mitochondrial Ca²⁺ uptake evoked by glucagon is an increase in V_max, the enhancement mechanism is likely to be an increase either in the number of active transport sites available to Ca²⁺ or in the rate of Ca²⁺ carrier movement across the mitochondrial membranes.     

Reactivity of sulphydryl groups of cytosolic and mitochondrial bovine aspartate aminotransferases

Summary Reactivity of sulphydryl groups of cytosolic and mitochondrial aspartate aminotransferases from ox heart has been studied. A total of 5 and 7 cysteine residues per monomer are present in cAATo and mAATo, respectively. In native conditions only a single sulphydryl group can be titrated by Nbs₂ while the catalytic activity remains unchanged, however in the mitochondrial isozyme the reactivity depends on the functional state of the enzyme. Reactivity toward NEM reveals the existence of a syncatalytic sulphydryl group in the cytosolic isozyme. Titration of cAATo with pMB at pH 8 and pH 5 confirms the existence of two exposed sulphydryl groups with a different reactivity. The results compared with those reported on the corresponding isozymes from pig and chicken heart show that syncatalytic sulphydryl groups are of general occurrence in these enzymes.     

Distribution of intermediate filaments in amphibian oxyntic cells

Summary Intermediate filaments of toad oxyntic cells were isolated and analysed by SDS-PAGE. The major proteins of the residue were identified as actin and a 51,000 dalton polypeptide. Immunological crossreactivity between toad oxyntic cell intermediate filament components and anti-prekeratin, was shown by double immunodiffusion tests and indirect immunofluorescence. The immunofluorescent decoration of oxyntic cells and the electron microscope images are coincident in locating the intermediate filaments mainly at the cortical and perinuclear basal zones. Furthermore, the cortical zone appears especially rich in prekeratin-like material at its adluminal third. This results in a cup-like structure that encloses the cell portion occupied by the tubulovesicular system, which does not contain intermediate filaments. The translocation of membranes occurring during the secretory cycle of the oxyntic cell, has been attributed to a system of contractile proteins. The disposition of the prekeratin-like material suggests a role for intermediate filaments in the generation of movement, produced by actin and myosin interaction, by providing a fixed plane for the anchoring of actin microfilaments.     

Effect of the level of the carbon source on the activity of some lytic enzymes released during autolysis of Aspergillus niger

Changes in the activity of -N-acetylglucosaminidase, chitinase, invertase, esterases, glucanases and phosphatases liberated into the culture fluid were followed during the autolytic phase of growth of Aspergillus niger on media with various initial levels of the carbon source. The general pattern was of an accumulation of these lytic enzymes in the culture fluid during autolysis, but some enzymes reached maximum activity and then declined. The initial level of the carbon source affected the enzyme pattern during autolysis. Maximum activity for the various enzymes was always observed either for the lowest initial level of carbon or the highest (3.5 mM glucose, 111 mM glucose). The highest specific activities were those for exopolygalacturonidase (500 mU/mg at 3.45 mM glucose), and for -amylase (about 500 mU/mg at 3.45 mM glucose). Cellulase, chitinase and esterase showed the weakest activity. Acid phosphatase was most active (about 200 mU/mg) at 3.45 mM initial glucose, whereas alkaline phosphatase was most active (45 mU/mg) at 111 mM glucose, both during the autolytic phase of growth.