A standard form for the Kermack-McKendrick epidemic equations

The classical epidemic equations of Kermack and McKendrick are cast into dimensionless form. This allows discussion of the assumptions underlying the standard approximate solutions.     

C2 deficiency in man. genetic relationship to a mixed lymphocyte reaction determinant (7a*)

Three unrelated individuals with, respectively, lupus erythematosus, polyarteritis, and membranoproliferative glomerulonephritis and totally deficient in the second component of complement are demonstrated to be mutually poorly reactive in mixed lymphocyte culture and homozygous for the mixed lymphocyte reaction determinant (MLR-S or LD) short 7a (7a^*). The gene controlling the elaboration of C2 in man is shown to be separate from, and probably to map outside of, the second locus ofHL-A and theMLR-S locus. Genetic linkage disequilibrium is strongly suggested between HL-A 10, W18, 7a^*, and C2 deficiency.     

Influence of clay minerals on sorption of bacteriolytic enzymes

Myxobacteria presumably produce extracellular bacteriolytic enzymes when they are growing in soil. In order to study their ecological significance, adsorption experiments were performed with lytic enzymes produced byMyxococcus virescens in casitone media. Different soils as well as montmorillonite and kaolinite can rapidly adsorb the bacteriolytic but not the proteolytic enzymes. About 1 gm of montmorillonite per liter of cell-free culture solution is enough for the adsorption of 97% of the bacteriolytic enzymes. The adsorption per unit weight is about 100 times greater on montmorillonite than on kaolinite. About 40% of the adsorbed enzymes can be eluted with solutions of high pH or high ionic strength. The only desorbed bacteriolytic enzyme is the alanyl-∈-N-lysine endopeptidase.     

Differential fluorescence labelling with 5-dimethyl-aminonaphthalene-1-sulfonyl chloride of intact cells and isolated membranes in Salmonella typhimurium and Acholeplasma laidlawii

For fluorescence labelling intact cells and isolated cell envelopes (membranes) from Salmonella typhimurium and Acholeplasma laidlawii were treated with mixed dansylchloride-lecithin-cholesterol vesicles. This kind of dansylation, which has been supposed to be specific for cell surface proteins, produced fluorescent protein pattern after SDS-polyacrylamide gel electrophoresis only when isolated envelopes were dansylated. Acid hydrolysis of fluorescent cell envelopes of Salmonella typhimurium yielded O-dansyltryosine and epsilon-N-dansyl-lysine besides the free sulfonic acid and unidentified compounds. However, no fluorescent proteins were detectable in cell envelopes isolated from dansylated intact bacteria from Salmonella typhimurium. In accord Acholeplasma laidlawii showed only fluorescence from proteins with a molecular weight higher than 100000.     

Extensor motor neurons of the crayfish abdomen

Summary The somata of five deep extensor motoneurons of the third abdominal ganglion of the crayfish(Procambarus clarkii) were located and identified. The positions of these somata within the ganglion and their distal distribution to muscles have been mapped and were constant. The soma of the extensor inhibitor was noted to touch the soma of the flexor inhibitor. Three of the excitatory neurons were clustered near their exit route.Sensory and cord routes of activation of the extensor motoneurons were also found and were constant from preparation to preparation. Sub-threshold recording showed that these motoneurons exhibited radically different types of post-synaptic response to stimuli at different sites in the nervous system. No interaction between extensor motoneurons or between the extensor and flexor motoneurons was observed.     

Fat metabolism in higher plants. The determination of acyl-acyl carrier protein and acyl coenzyme A in a complex lipid mixture 1,2.

A method has been developed that permits the quantitative analysis of [¹⁴C]acyl-acyl carrier proteins and [¹⁴C]acyl CoAs from a typical reaction mixture. The method is based on (a) the initial extraction of free fatty acids and the less polar lipids into petroleum ether from aqueous isopropanol; (b) the precipitation of [¹⁴C]acyl-acyl carrier proteins in the presence of ammonium sulfate and chloroform-methanol; and (c) the final separation of acyl CoAs from the more polar lipids by selective adsorption on neutral alumina gel. All fractions can then be analyzed for the composition of complex lipids and ¹⁴C-labeled fatty acids by the usual methods.