Cleavage maps of a tetracycline plasmid from Staphylococcus aureus

The cleavage maps of a Staphylococcus aureus plasmid, pSN1 (2.75 megadaltons), conferring tetracycline resistance, were determined. Cleavage maps are given for HpaI and HindIII restriction endonucleases by using the single HpaII site as a reference point. Nucleases EcoRI, BamHI, SalI, and HaeIII have no sites on this plasmid.     

Specific binding of T lymphocytes to macrophages. III. Spontaneous dissociation of T cells from antigen-pulsed macrophages.

Peritoneal exudate lymphocytes (PEL) from immune guinea pigs that adhere to antigen-pulsed macrophages (MO) were cultured for 1 week to yield a population enriched in antigen-specific (selected) T cells. These cells bind specifically within hours to fresh autologous antigen-pulsed MO. Thd dissociation of these selected PEL from antigen-pulsed MO was studied. No evidence was obtained that factors in the culture medium play a role in dissociation. Lymphocytes that have dissociated from antigen-pulsed MO are usually fully capable of rebinding to MO freshly pulsed with antigen, suggesting that there is no deficiency in the lymphocytes ability to bind. In contrast, readding antigen to cultures during incubation prevents the predicted dissociation. Moreover, repulsing MO cultured without selected PEL restores their capacity to bind fresh selected PEL. These findings indicate that decay of antigen associated with with MO is the major mechanism underlying the observed dissociation.     

Thermosensitive H1 plasmids determining citrate utilization.

Twelve thermosensitive H1 plasmids from strains of Salmonella typhi that had caused outbreaks of chloramphenicol-resistant typhoid fever in Vietnam, Thailand and India mediated citrate utilization (Cit+) in a prototrophic Escherichia coli K12 strain but not in the S. typhi strains from which they were derived. Four H1 plasmids from a similar outbreak in Mexico differed from the Far Eastern plasmids in not mediating citrate utlization but in mediating mercury resistance. H1 plasmids resembling the Far Eastern and the Mexican plasmids in regard to citrate utilization and mercury resistance were found in sewage in Britain. Citrate utilization was transferred to eight pathogenic strains of E. coli and to one strain each of Shigella flexneri and Shigella sonnei. Cultures of Cit+ bacteria grew more rapidly in citrate media at 28 degrees C than at 37 degrees C. Plasmid mutants that were more efficient at utilizing citrate were present in all such cultures--they grew equally well or better at 37 degrees C than at 28 degrees C. None of 222 strains of E. coli or Shigella that contained a variety of different plasmids were able to utilize citrate. This property was not transferred to the prototrophic E. coli K12 strain from Citrobacter (3 strains), Salmonella (39 strains), Proteus (44 strains), Klebsiella pneumoniae (33 strains) or Pseudomonas aeruginosa (44 strains).     

Tissue tropism of different Trypanosoma cruzi strains.

A systematic study of the distribution of intracellular parasites in the organs and tissues was performed in groups of mice inoculated with 4 different Trypanosoma cruzi strains. An extremely high parasitism of spleen, liver, and bone marrow was observed in mice inoculated with Y and Berenice strains; with CL strain, however, parasites were almost absent in those organs. Bloodstream forms apparently present differences which facilitate or prevent their uptake by macrophages from the mononuclear phagocytic system. Parasitism of the smooth muscle from hollow organs was significantly higher with ABC and Berenice strains than with Y and CL. The importance of the distribution of intracellular stages in the pathogenesis of the disease is discussed.     

Stereotyped behaviour after cholinergic, but not dopaminergic, stimulation of the substantia nigra in rats

Stereotyped behaviour of the rat was measured after intracerebral drug application in an objective and quantitative way by means of a new method developed in this laboratory. Bilateral intranigral injection of apomorphine /APO/, a specific dopaminergic agonist, did not evoke any signs of stereotyped behaviour. Also ineffective was the application of APO in the amygdaloid nucleus. Dopaminergic blockade of the substantia nigra by topical application of triperidol, a potent dopaminergic antagonist, failed to influence the stereotypy elicited by systematic APO administrationDirect cholinergic stimulation of the substantia nigra with carbachol resulted in a dose-related stereotyped behaviour not distinguishable by sight from that evoked by systematic APO administration. The effect of intranigral carbachol was antagonized by a previous intraperitoneal injection of 10 mg/kg of atropine. Stereotypy could easily be produced also by intracaudate application of APO. Topical triperidol blockade of the caudate nucleaus prevented the stereotypy caused by intraperitoneal application of APO.It is concluded that at least a part of nigral neurons cannot be directly excited by apomorphine. However, they can be excited by carbacol and seem thus, to contain muscarinic receptors. The stimulation of these receptors results in an excitation of the neurons involved and produces marked stereotyped behaviour.     

Burn syndactyly.

When the entire digital web space has been destroyed by burn scarring and there is a contracture of the volar aspect of the web as well as the dorsum, Z-plasties and skin grafts alone seldom produce a satisfactory web space. During the past 3 years, for the release of 46 contracted web spaces in 20 burned patients, we have turned a rectangular flap from the dorsal surface of the web through into an inverted-T incision in the palm. The adjacent sides of the defects have been skin grafted. In all these patients, we obtained satisfactory release of the contracture and restoration of the web space.