Protein synthesis in the cotyledons of Pisum sativum L. Protein factors involved in the binding of phenylalanyl-transfer ribonucleic acid to ribosomes

1. Proteinaceous factors contained in a 0.5m-KCl extract of ribosomes from pea cotyledons form a ternary complex at 0 degrees C with [(14)C]phenylalanyl-tRNA and poly(U). The complex is measured by its quantitative retention on Millipore filters. 2. Complex-assembly is optimal at 5mm-Mg(2+) and is independent of GTP and ribosomes. 3. The addition of ribosomes is required to stabilize the complex at 34 degrees C. The complex binds to a puromycin-sensitive site on the ribosome. 4. Soluble factors from the 250000g supernatant of pea cotyledon form a Millipore-retainable complex dependent on GTP and ribosomes. 5. Complex-formation by soluble factors has a Mg(2+) optimum of 10-12mm and forms a puromycin-insensitive complex with ribosomes. 6. The function of the ribosomal protein factors and the supernatant fraction in initiation of protein synthesis is discussed.     

The fossil evidence of anthropoid brain evolution

The endocast of Aegyptopithecus, a 27 million year old ape, reveals that its brain was advanced over that of prosimians and comparable to that of modern anthropoids in relative size and in having expanded visual cortex, reduced olfactory bulbs, and a central sulcus separating primary somatic sensory and motor cortex. The early appearance of those features suggests that they may have been among the adaptations responsible for the evolution of anthropoids from prosimian ancestors. The frontal lobe was relatively smaller in Aegyptopithecus than in modern anthropoids. An endocast of Dolichocebus, one of the oldest known New World monkeys (25–30 million years old), reveals visual cortex expanded as in modern anthropoids. The 19 million year old Napak frontal bone displays a hominoid rather than cercopithecoid sulcal pattern. An 18 million year old endocast of the ape Dryopithecus (Proconsul) was neither monkey-like nor primitive, as originally described, but rather apelike and essentially modern in all observable features. The oldest undoubted Old World monkey endocast, from nine million year old Mesopithecus, reveals that the brain was modern in sulcal pattern and proportions. The sulcal pattern was like that of modern colobines, but that appears to be the more primitive condition, from which features characteristic of modern cercopithecine brains have evolved. The brain of six million year old Libypithecus was similar to that of Mesopithecus. A two million year old endocast of “Dolichopithecus” arvernensis displays a modern cercopithecine sulcal pattern.     

Yields of Hydrogenomonas eutropha from Growth on Succinate and Fumarate

Molar growth yields were determined from chemostat cultures of Hydrogenomonas eutropha on succinate and on fumarate. The yields from culture on succinate were about 12 g higher than on fumarate. Assuming this difference to be equivalent to 1 molecule of adenosine triphosphate, it is concluded that the oxidation by oxygen of the Hydrogenomonas cytochrome b yields 1 molecule of adenosine triphosphate.     

PREPARATION AND CHARACTERIZATION OF A PLASMA MEMBRANE FRACTION FROM ISOLATED FAT CELLS

A rapid method of preparing plasma membranes from isolated fat cells is described. After homogenization of the cells, various fractions were isolated by differential centrifugation and linear gradients. Ficoll gradients were preferred because total preparation time was under 3 hr. The density of the plasma membranes was 1.14 in sucrose. The plasma membrane fraction was virtually uncontaminated by nuclei but contained 10% of the mitochondrial succinic dehydrogenase activity and 25–30% of the RNA and reduced nicotinamide adenine dinucleotide cytochrome c reductase activity of the microsomal fraction. Part of the RNA and NADH-cytochrome c reductase activity was believed to be native to the plasma membrane or to the attached endoplasmic reticulum membranes demonstrated by electron microscopy. The adenyl cyclase activity of the plasma membrane fraction was five times that of Rodbell's "ghost" preparation and retained sensitivity to epinephrine. The plasma membrane ATPase activity was five times that of the homogenate and microsomal fractions. Electron microscopic evidence suggested contamination of the plasma membrane fraction by other subcellular components to be less than the biochemical data indicated.     

Early Events in Development of Streptococcal Competence

Appropriately timed use of trypsin, which inactivates competence factor (CF), and chloramphenicol made feasible a separation and characterization of early events in the development of competence in group H streptococci. Step 1 is production of CF, which is inseparable in time from the concomitant release of free CF into the medium. The producing cells, which are noncompetent at the time, also accumulate cell-bound CF (CB-CF) from the onset of CF synthesis. In step 2, the released CF is adsorbed or taken up in a trypsin-insensitive state by the producing cells and is not destroyed as previously suggested. This occurs rapidly in a transformation-supporting (complete) medium. The rapid decline in free CF is concomitant with the rise in CB-CF, and a maximal increase in the latter does not occur in cultures exposed to trypsin, which inactivates any trypsin-accessible CF. The rapid increase in CB-CF (above trypsin-treated levels) leads to step 3, the induction of competence. All of these steps probably require protein synthesis, because each is inhibited by chloramphenicol. The data also indicate that only free CF that is subsequently adsorbed, and which thus leads to maximal levels of trypsin-insensitive CB-CF, is the effective inducer of competence in either CF-producing (Challis) or CF-nonproducing (Wicky) cultures. The processes induced by the newly bound CF are not fully understood, but certain new properties, previously described by others as indicating competence, were measured during the several steps of competence development. Cell aggregation at pH 2 appears to be related to CB-CF and can be shown before this bound CF has induced competence. The ability of cultures to autolyze maximally can be diminished by trypsin treatment of precompetent cells without affecting subsequent competence development as measured by transformation.     

Ecology of Staphylococci in a General Medical Service

Investigation of the ecology of Staphylococcus aureus on the medical service of the Cincinnati General Hospital was carried out from 1964 to 1970. S. aureus was cultured from 1,442 patients. Overall, there was a progressive increase in the susceptibility of S. aureus to commonly used antibiotics, but not to penicillin. Hospital-acquired S. aureus remained highly resistant to all antibiotics except penicillinase-resistant penicillins. There was a progressive decline in the percentage of hospital-acquired infections from January 1964 to September 1969, followed by a rise during September 1969 to September 1970. No single bacteriophage group predominated among nosocomially acquired S. aureus. Major changes in the hospital environment did not appear to influence the prevalence of nasal carriage or hospital acquisition of S. aureus. This study identified the continuing problem of acquisition of S. aureus in the hospital, but no specific "epidemic strain."     

Thymus cell maturation: II. Differentiation of three “mature” subclasses in Vivo

Several thymus cell subclasses may be defined on the basis of their sedimentation velocity, their light-scattering properties (a measure of cell volume), or binding of a fluoresceinated anti-Thy 1.2 antiserum. Using a multiparameter fluorescence-activated cell sorter (FACS), cells with distinguishable light-scattering or fluorescence intensity (after staining with fluorescein anti-Thy 1.2) were separable for analysis of intrathymic maturation pathways. Outer thymic cortical large and medium lymphocytes were the only cells labeled within 1 hr after transcapsular diffusion of administered [³H]thymidine. These labeled cells were also entirely contained in the brightest fluorescence intensity (with fluorescein anti-Thy 1.2) subclass. Under conditions of [¹H] thymidine “chase” in vivo, label shifted proportionately and apparently in parallel to three “mature” subclasses: (1) small thymocytes with high surface concentrations of Thy 1.2, representing ~ 80% of all thymus cells; (2) slightly larger cells, with very low surface Thy 1.2, which are indistinguishable from cortisone-resistant thymocytes, and which make up less than 10% of all thymus cells; (3) dead or fragile cells.     

Characterization of subpopulations of T lymphocytes: I. Separation and functional studies of peripheral T-cells binding different amounts of fluorescent anti-Thy 1.2 (theta) antibody using a fluorescence-activated cell sorter (FACS)

Peripheral T lymphocytes in mice can be distinguished by the presence of the Thy 1.2 (theta) cell surface antigen. The fluorescence-activated cell sorter (FACS) was used to analyze and separate T-cells from peripheral lymphoid cell suspensions after incubation with fluorescein-labeled anti-Thy 1.2 (F anti-Thy 1.2). Stained cells were markedly reduced in nu/nu mice, in mice carrying the Thy 1.1 allele (theta-AKR), and were not seen after incubation with anti-Thy 1.2 that had been absorbed with CBA brain. According to these criteria, the stained cells were termed “T lymphocytes.”Among the T lymphocytes, there was considerable heterogeneity of fluorescent staining. The FACS was used to separate T-cells from other cells and further to separate T-cells with high intensity F anti-Thy 1.2 fluorescence (bright T-cells) from those with less F anti-Thy 1.2 fluorescence (dull T-cells). Separated bright T and dull T lymphocytes were shown to have several different functional properties. Dull T-cells appeared more sensitive to small doses of ALS in vivo, homed to lymph node in higher proportions than did bright T-cells, and were not affected by the short-term effects of thymectomy in adult life. Bright T lymphocytes, by contrast, were resistant to the in vivo effects of ALS, homed preferentially to spleen rather than lymph node in irradiated hosts, and were reduced shortly after adult thymectomy. Separated populations of bright and dull T-cells showed reduced ability to produce cytotoxic activity after in vitro sensitization, while mixtures of these two subpopulations of T-cells produced synergistic cytototoxic responses. The ontogenic and functional implications of these findings are discussed.