An assay for intercellular adhesive specificity

A modification of an assay for intercellular adhesive specificity is described. The method involves the collection of radioactively labeled cells by aggregates of the same (isotypic aggregates) or different (heterotypic aggregates) types of tissue and determination of the number of cells collected by liquid scintillation counting. The use of (32)P to label the tissues permitted a much more rapid estimation of cell collection than was obtained previously. With the use of chick embryo neural retina, liver, forebrain, pectoral muscle, and heart ventricle tissue, it was shown that isotypic was always greater than heterotypic collection. Labeled neural retina cell collection by neural retina aggregates was studied as a function of time, cell suspension density, aggregate diameter, temperature, and aggregate number. Neural retina aggregates were treated with certain enzymes in an attempt to determine whether specific changes on the surface of the aggregates would interfere with labeled neural retina cell collection. Of the various proteases and glycosidases tested, only beta-galactosidase rendered the surface more nonspecific.

Abnormal autolytic enzyme in a pneumococus with altered teichoic acid composition

Pneumococci in which the choline component of the cell wall teichoic acid was replaced by ethanolamine contain an abnormal autolytic enzyme that has a low molecular weight and low activity in contrast to the enzyme typical of choline-containing bacteria that has a high molecular weight and high activity. The abnormal autolysin can be converted to the normal (cholinetype) enzyme by incubation in vitro with choline-containing cell walls.

Neuraminidase activity in bacterial meningitis

The relation of neuraminidase to morbidity and mortality was examined in patients with Haemophilus influenzae, meningococcal, and pneumococcal meningitis. Ten strains of H. influenzae and eight strains of meningococci from infected cerebrospinal fluid (CSF) did not elaborate neuraminidase. Each of 27 strains of pneumococci from infected CSF elaborated both neuraminidase and N-acetylneuraminic acid (NANA) aldolase. There was no correlation between amount of neuraminidase secreted in vitro and survival of patients. Values for free and total NANA concentrations were derived from admission CSF samples of 63 patients with meningitis; 18 patients infected with Neisseria meningitidis, 10 with H. influenzae and 35 with Diplococcus pneumoniae. Mean values for total NANA were elevated in each type of bacterial meningitis; however, abnormal concentrations of free CSF NANA were detected only in 17 patients with pneumococcal meningitis. 11 of 18 patients with pneumococcal meningitis showing normal free CSF NANA concentrations were cured, whereas only 4 patients with abnormal free NANA levels survived without residua. Both coma and bacteremia occurred significantly more often among patients with elevated concentrations of free CSF NANA. The association of elevated concentrations of free CSF NANA with coma and with an adverse prognosis suggested that neuraminidase may be a factor in the pathogenesis of penumococcal meningitis.

Inhibitory effects and metabolism of 5-fluoropyrimidine derivatives in pneumococcus

5-Fluorouracil (FU), 5-fluorocytosine, and the riboside and deoxyriboside derivatives of these fluoropyrimidines each exhibit a different spectrum of inhibitory effects in pneumococci. The biochemical basis of this finding seems to be the extremely low level of nucleoside phosphorylase (hydrolase) and N-trans-deoxyribosylase activity in pneumococcus and the consequent, relatively limited metabolic interconversion of the different fluoropyrimidines, which can therefore selectively affect one or the other of the several drug-sensitive biochemical reactions in this bacterium. Special attention was paid to the effect of fluoropyrimidines on the metabolism of cytosine and thymidine. In spite of the fact that FU is converted to both fluorouridine triphosphate and fluorocytidine triphosphate, only fluorouridylate but no fluorocytidylate can be detected in the ribonucleic acid Exogenous FU and fluorouridine also inhibit the synthesis of cytosine nucleotides from supplied uridine in a pyrimidine auxotroph. Thymidine was found to be a poor reversing agent for any of the fluoropyrimidine inhibitions. In both the wild type and in a thymidine-requiring (thymidylate-synthetase deficient) mutant, growing with supplied thymidine in the medium, fluorodeoxyuridine (FUdR) treatment caused cell death and inhibition of the incorporation of radioactive thymidine, adenosine, or uracil into deoxyribonucleic acid. It is suggested that FUdR (or a metabolic derivative) inhibits the transport of phosphorylation of thymidine in this microorganism.

High dihydrofolate reductase levels in Diplococcus pneumoniae after mutation in the structural gene: biochemical and immunological evidence for increased synthesis

A unique class of missense mutations in the dihydrofolate reductase structural gene of Diplococcus pneumoniae determines marked increases in the corresponding enzyme activity. Immunological evidence, based on precipitating and neutralizing antibody reactions, is presented in support of previously derived findings which attribute this increase in activity to an increase in the amount of enzyme protein. Biochemical evidence was obtained which shows that the increased amounts of dihydrofolate reductase protein in the mutants not owing to a decrease in degradation, reducing turnover, or to an increase in stability, and, therefore, probably related to an increase in the rate of synthesis of new protein. The manner in which a missense alteration of a structural gene might quantitatively alter the expression of that gene is discussed.

DNA-membrane complex: macromolecular content and stimulation of enzymatic activity by polyadenylic acid

A DNA-cell membrane complex has been isolated from cell suspensions of virulent pneumococci by sarcosyl lysis followed by centrifugation on a sucrose gradient. When polyadenylic acid plus the eight naturally occurring deoxyribonucleosides and deoxyribonucleotides are added to cell suspensions, the percentage of total DNA in the complex increases with incubation time. This increase is not observed in unsupplemented cell suspensions. However, the percentages of RNA, protein, and phospholipid do not increase with incubation time in either supplemented or control complexes. A variety of deoxyribonucleotide kinases and the DNA polymerase are also detected in the DNA-membrane complex, and their specific activities are greater in complexes extracted from supplemented cell suspensions than in those extracted from controls.

Mutants of Diplococcus pneumoniae that lack deoxyribonucleases and other activities possibly pertinent to genetic transformation

Mutants of Diplococcus pneumoniae that lacked the two major deoxyribonucleases of the cell-one an endonuclease, the other an exonuclease preferentially active on native deoxyribonucleic acid (DNA)-were obtained. The development of a method for detecting mutant colonies, based on the binding of methyl green to DNA, facilitated isolation of the mutants. Neither enzyme was essential for growth of the cells, for repair of ultraviolet damage, or for any phase of DNA-mediated transformation. Residual deoxyribonuclease activity in the double mutant corresponded to an exonuclease, approximately one-fifth as active as the major exonuclease, that attacked native and denatured DNA equally well. This activity appeared to be associated with the DNA-polymerase enzyme. A mutant that apparently lacked a cell wall lytic enzyme was also fully transformable. A mutant strain that was four times more sensitive to ultraviolet light than the wild type also transformed normally. Recipient cells of this strain were deficient in the repair of ultraviolet-irradiated transforming DNA. Mutants were found which, unlike the wild type, integrated donor markers only with high efficiency, thereby indicating that a particular cellular component that is susceptible to loss by mutation, such as an enzyme, is responsible for low integration efficiency.

Competent Diplococcus pneumoniae accept both single- and double-stranded deoxyribonucleic acid

The transforming activity of fractionated complementary strands of Diplococcus pneumoniae deoxyribonucleic acid (DNA) bands at the position of fully denatured DNA in CsCl at pH 11.0, and is completely (> 99.8%) destroyed by digestion with exonuclease-I. These results prove that pure single strands transform the normally prepared competent cells of this species. Their efficiency is about 0.5% that of native DNA of comparable size.