Comparison of Undefined Medium and Its Dialyzable Fraction for Growth of Mycoplasma

In examining the medium used in cultivation of Mycoplasma for deoxyribonucleic acid isolation, it was found that an aggregate was present which sedimented with the organisms and which was ethyl alcohol-precipitated during deoxyribonucleic acid purification. To eliminate the contaminating material, a method was devised to obtain only the dialyzable constituents of the medium. This report describes the preparation of a dialysate of soy peptone-yeast extract. The medium, obtained by immersion of the encased dehydrated ingredients in sodium chloride solution for 5.5 hr at approximately 80 C, has been employed as the basal medium for cultivation of a number of Mycoplasma species. Comparative growth curves of two saprophytic strains and two parasitic species indicated that multiplication in dialysate, with suitable supplement, followed the pattern typical of the common eubacteria. Thus, by elimination of the sediment which occurred in nondialyzed medium, Mycoplasma could be concentrated without concomitant accumulation of contaminating macromolecules.     

Deoxyribonucleic Acid Homology and Relative Genome Size in Mycoplasma

The deoxyribonucleic acid homologies of Mycoplasma laidlawii type A and type B, M. pulmonis (#47 and #63), and M. hominis were determined by membrane methodology. The homology data revealed a difference in genome size between M. laidlawii type A and type B. This difference also held with stringent conditions of annealing (high temperature). Little or negligible homology was shown to exist between the M. laidlawii strains type A and type B and M. pulmonis strains 47 and 63 and M. hominis. M. hominis showed less than 10% homology to the M. pulmonis and M. laidlawii strains. Neither of the M. laidlawii strains showed more than 2% annealing to the M. pulmonis strains. Reaction rate studies are suggested as a means of demonstrating the phylogenetic relationship between the Mycoplasma and other microorganisms.     

Systemic lupus erythematosus.

Systemic lupus erythematosus is a polysystemic disease with a high incidence of associated glomerulonephritis. Patients with sle rarely have the destructive arthritis so characteristic of rheumatoid arthritis. An unusual case is presented in which both glomerulonephritis and destructive arthritis occurred simultaneously, justifying the diagnosis of both systemic lupus erythematosus and rheumatoid arthritis.Immunohistochemical studies in lupus glomerulonephritis suggest that the pathogenetic mechanisms involve the deposition of immune complexes containing “nuclear” antigens and antinuclear antibodies in the lesions. The detection of mixed cryoglobulins in the sera of patients with sle suggests that a portion of the circulating immune complexes may precipitate at reduced temperatures and be detected as mixed cryoglobulins. The therapy of lupus glomerulonephritis with combinations of corticosteroids and azathioprine, though still in an investigative state, holds great promise. Similar abnormalities in diseases of minks and mice and in sle suggest similar pathogenetic mechanisms in the three species involved. Since the diseases in the lower animals have been associated with persistent viral infection, the investigation of the role of persistent infection in sle seems warranted.     

Acetamide Agar Medium Selective for Pseudomonas aeruginosa

A synthetic base of acetamide and salts in agar permitted isolation of small numbers of Pseudomonas aeruginosa from swarming Proteus and other gram-negative species.     

Methacarn (methanol-Carnoy) fixation

Summary According to chemical data, methanol raises the shrinkage temperature of collagen significantly more than ethanol (86° C versus 70° C). Since increase of shrinkage temperature appears desirable in tissues to be embedded in paraffin, methanol was substituted for ethanol in Carnoy's fluid. This methanol-Carnoy mixture is referred to as methacarn solution. The fixation-embedding procedure was similar to that described in the study of Carnoy fixation. Methacarn-fixed sections showed little or no shrinkage and compared well with material fixed in Carnoy's or Zenker's fluid. Myofibrils, especially in endothelial and epithelial cells, were more prominent in methacarn- than in Carnoy-fixed tissues.A review of the chemical literature showed that methanol, ethanol and chloroform stabilize or even enhance helical conformations of proteins, presumably by strengthening of hydrogen bonds. Interference with hydrophobic bonds causes unfolding and/or structural rearrangements in globular proteins. The twin-helical structure of DNA collapses in alcoholic solutions. Hence, methacarn fixation can be expected to preserve the helical proteins in myofibrils and collagen, but the conformations of globular proteins and DNA will be significantly altered. Literature on conformational effects produced by fixatives used in electron microscopy was also reviewed. Glutaraldehyde and OsO₄ cause considerable loss of helix (22–29% and 39–66% respectively). KMnO₄ and glutaraldehyde followed by OsO₄ produce extensive transitions from helical to random-coil conformations similar to those seen in powerful denaturants such as 8 M urea. Evidently these fixatives are unsuitable for studies of helical proteins. In contrast ethylene glycol preserves helical conformations.     

Photosynthetic Membrane System in Anacystis nidulans

Cultures of Anacystis nidulans were grown under conditions of varying light intensity and temperature. Changes in pigment content were compared with changes in the fine structure of these cells. Pigment concentration and lamellar content varied inversely with the light intensity in cells grown with 100 and 1,000 foot candles of fluorescent light. Estimations of the relative area and volume of lamellae in cells showed that the amount of double membrane was directly proportional to the chlorophyll content of whole cells. Continuity of double membranes with cytoplasmic membrane was observed.