20
NUCLEIC ACIDS OF EIMERIA TENELLA
[Vol. XXV, Part I,
the protein synthesis, leads us to a realm of speculation. They are said to 'funnel
energy into protein synthesising mechanism' [Spiegelman and Kamen, 1946; Muller,
1947]. Some believe that they invoke some sort of templet action (chiefly based
on an analogy of Astbury and Bell's X-ray crystallographic experiment [1948].
Danielli's hypothesis that nucleic acids act as 'folding' and 'trapping' agents is
quite plausible, but proof of incontrovertible nature has yet to be furnished in its
support.
The euchromatin (DNA) of E. tenella appeared most active in the nuclei of
macrogametocytes, sporozoites and trophozoites, a little less so in the schizonts while
the nuclei of merozoites were of the least order in this respect. These differences in
the metabolism of DNA is in keeping with the differential demands on the nuclei
for repeated division.
A microgametocyte gives rise to innumerable microgametes the whole comma-
shaped body of which now appears to be full of DNA. The total absence of detec-
table DNA in a macrogamete is surprising, for, it can be expected to contribute
its quota of hereditary characters which are known to be transmitted only through
genes of which the DNA is the single largest constituent.
Sporozoites and trophozoites are marked by rapid nuclear division to form
schizonts. When a destined number of nuclei is produced protein metabolism of
their cytoplasm is geared up which is now showing a high RNA content for it has
now to apportion around each nucleus to form merozoites.
Though RNA is present only in the form of a stretch across the body of the
microgametes yet the concentration of the acid is very high in them as indicated
by its brilliant red colour with pyronin. The karyosome and the cytoplasm of
microgametocyte give fairly strong reactions for RNA but judging from the dimi-
nishing colour reactions with age it can be safely presumed that as the parasite
reaches maturity a physiological depression, (at least as far as protein metabolism
is concerned) sets in. From the evidence presented it can be deduced that there
exists certain correlations between the chemical findings on one hand and tempo
of the biological activities on the other in Eimeria tenella.
Observations on E. tenella add to the view that most rapidly growing parasites
undoubtedly synthesise rather large amounts of nucleic acid. Deane [1945] and
Ball, et al., [1948] have established that Plasmodium knowlesi possesses a very high
rate of nucleic acid synthesis. Such as acitivity has also been reported from the
blood stream form of African pathogenic trypanosomes [Moraczewski and Kelsey
1948]. The work of Painter [1945] Moses [1950] and Seshachar [1950] shows that
ciliate cytoplasm has abundant quantities of RNA, which is in keeping with
the rapid multiplication of the protozoa. Majority (nearly 90 per cent) of
oocysts have failed to show the presence of DNA in them whereas a small
proportion definitely contained highly polymerised DNA (Feulgen and methyl-
green-positive) both in the nucleus and in the cytoplasm (Plate II, Fig. 10).
Extra nuclear distribution of DNA is known only in a few instances, such as
the Purkinje cells which contain only DNA in their cytoplasm [cited by
Seshachar, 1952], whereas in a small minority (approx. 10 per cent) of oocysts
of E. tenella it is present along with RNA. Preer [1950] demonstrated
microscopic Feulgen positive particles, which are known to be the
Kappa factor in the cytoplasm of the killer race of Paramaecium. It is of the