Infection of Macrophages in Culture by Leptomonads of Leishmania donovani

SYNOPSIS. Peritoneal macrophages from hamsters were monolayered on coverslips in Leighton tubes. Twenty-four hours later these were transferred to a perfusion chamber. Leptomonads were added with fresh medium and the infection process observed with the aid of phase contrast. In the perfusion chamber free-swimming leptomonads attached to the macrophage by the tip of their flagella. Shortly after this initial attachment the macrophage extended a narrow pseudopodium around the flagellum which eventually reached and enveloped the body of the parasite. Upon complete envelopment the pseudopod containing the leptomonad was retracted into the central body of the macrophage. When first seen in the granular endoplasm of the macrophage, most of the leptomonads appeared to be surrounded by vacuoles. In most cases these vacuoles disappeared in a few minutes making it difficult to distinguish the parasite from the host cell cytoplasm.
Leptomonads also were added directly to Leighton tube cultures, and the coverslips with the adherent macrophages and parasites were removed, fixed and stained periodically during the infection process. In these preparations most of the parasites were in clumps in the vicinity of macrophages. Details of the ingestion of the clumps could not be seen, but occasionally a single organism was seen with its flagellum and part of its body enclosed by an extended pseudopod. Most of the intracellular leptomonads were in large vacuoles. Forms intermediate between elongate leptomonads and LD bodies were surrounded by smaller vacuole-like spaces. The halo-like vacuoles most frequently seen around LD bodies may have been fixation artifacts. Under favorable conditions the leptomonads transformed to LD bodies in 1–4 hours, but it was 48 hours before a population increase could be found.     

Use of a nematode, Heterorhabditis heliothidis, to control black vine weevil, Otiorhynchus sulcatus, in potted plants

Application of aqueous suspensions of infective juvenile Heterorhabditis heliothidis, isolate T327, to the soil resulted in up to 100% parasitisation of larvae of the black vine weevil, Otiorhynchus sulcatus, in potted yew, raspberries and grapes in nurseries, and over 87% parasitisation on potted cyclamens and strawberries. Pupae and newly emerged adults on grapevines were also parasitised. Another isolate, T310, produced 92.5 to 98.5% parasitism of O. sulcatus larvae on potted cyclamens in glasshouse, but was less effective on strawberries. Neoaplectana bibionis was found to be less effective than H. heliothidis T327 strain. The use of these nematodes provides an economical and effective method for controlling O. sulcatus on potted plants in glasshouses and nurseries.     

A Rapid Bioassay Method for Gramicidin by Measuring Rubidium Ion Leakage from Streptococcus faecalis

Gramicidin was seen to promote rapid release of Rb⁺ from cells of Streptococcus faecalis ATCC 10541 which had been previously enriched with this cation. This response was logarithmic between gramicidin concentrations of 0.25 μg/ml and 2.5 μg/ml. This efflux was measured by flame emission spectroscopy. The results presented here form the basis for a potential rapid bioassay for gramicidin.     

Incidence of poliomyelitis; the effect of tonsillectomy and other operations on the nose and throat

A statistical survey was made of all the cases of poliomyelitis occurring in all of Los Angeles County during the three years of 1949, 1950 and 1951 in an attempt to determine the effect of operations on the nose and throat on the incidence of poliomyelitis. Tonsillectomy and adenoidectomy were the only operations noted with any degree of frequency. Yet, in the total of 3,601 cases of poliomyelitis that occurred in this three-year period there were only 20 (0.55 per cent) in which the patient had had recent tonsillectomy and adenoidectomy. The incidence of this disease in patients who had had tonsillectomy and adenoidectomy was compared with the "expected" incidence as determined from the incidence in other patients, in the same age group. There was no significant difference between actual and expected incidence even during the summer months when most cases of poliomyelitis occurred. The same was true with regard to recently tonsillectomized patients in the epidemic months of July through October. In a separate survey of 675 patients with poliomyelitis, it was noted that only 30 per cent ever had had tonsillectomy or adenoidectomy. Inasmuch as it is estimated that one of every three persons in the general young population nowadays has had tonsillectomy and adenoidectomy, this figure is no more or less than could be expected.