| dc.description.abstract | In Kenya the most important and prevalent pests that
attack maize and sorghum are the stalk-borers. There are
three species of the stalk borer in Kenya namely, GhilQ
which thrives in high altitude areas with cool climate,
poses the greatest threat to the crops.
Lipophorin acts as a reusable shuttle in the
transportation of a variety of lipid classes from sites of
storage, absorption and synthesis to sites of utilization
(Chino, 1985). Lipids playa vital role in insect
development as components of cell membranes and cuticle,
source of metabolic energy and as hormones and pheromones.
Interference with lipid transport would therefore be fatal
to the insects. Studies of lipophorins thus hold potential
for selective control of destructive insect pests. In this
study, lipophorin, the principal haemolymph lipoprotein in
most insects, was isolated and characterized from B. Lipophorin was isolated from larvae by density gradient ultracentrifugation. The apoproteins were
isolated by electroellution following SDS-PAGE. The
isolated lipophorin (Mr-700,000) was a high density
lipoprotein (density = 1.13 g/ml), composed of 46% lipid,
50% protein and 4% carbohydrate. Analysis by SDS-PAGE
revealed that it consisted of two apoproteins, apoLp-I
(Mr-210,OOO) and apoLp-II (Mr-78,OOO), which were present in
a molar ratio of 1:2 (apoLp-I: apoLp-II) in the intact
lipophorin molecule. Both apoproteins were glycosylated and
lipidated as shown by PAS and Sudan Black staining,
respectively. The presence of high mannose containing
oligosaccharide chains was demonstrated by the binding of
lipophorin to concanavalin A-Sepharose column. Studies on
the lipid lipophorin indicated
predominance of phospholipids and diacylglycerol.
Amino acid composition analysis of lipophorin showed
predominance of glutamate (9%), aspartate (13%) and glycine
(9%). Methionine was only present in trace amounts.
Structural organization of the apoproteins was
investigated by limited trypsin digestion and immunological
studies. Limited trypsin digestion of the isolated
lipophorin showed that apoLp-I was more susceptible to
cleavage than apoLp-II, suggesting an interior location of
apoLp-II .By immunoblotting,both apoproteins were shown to
be immunoreactive towards antibodies to the isolated
lipophorin .However,double radial immunodiffusion of the
apoprotein against the antisera only showed precipitin line
with apoLp-I. Thus in the intact lipophorin,apoLp-I is more
exposed to the aqueos haemolymph enviroment than apoLp~II.
An investigation was carried out to determine whether
there was immunological cross-reactivity between lipophorins
showed the same cross-reactivity. The
results suggested that lipophorins from insects of the same
order share antigenic determinants predominantly on apoLp-I. | en |
