2 research outputs found
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Cytophotometric determinations of nuclear DNA content in tissues of the wax moth larva, Galleria mellonella Linnaeus
The present study was undertaken to determine, by measurement
of nuclear DNA, the degrees and frequencies of ploidy in the
last larval instar of the moth Galleria mellonella Linnaeus. While
such data have been amassed for a wide variety of vertebrate tissues,
few studies have been concerned with invertebrates and especially
insects where somatic polyploidy is developed to an unusually high
degree.
Relative amounts of DNA were determined cytophotometrically
on individual Feulgen-stained nuclei of hypodermis, ventriculus, fat
cells, blood cells, anterior silk gland, and proventriculus. Graphs
of the determined DNA values indicated the presence of nuclear
classes falling into polyploid ratios,
The majority of blood cell and fat cell nuclei had class I
values (= diploid), while class II and III (= tetraploid and octoploid) DNA values represented about 17 to 20 percent of the total nuclear
population. The majority of DNA values of the ventriculus nuclei fell
into the second class while 6.8 percent were considered as class I.
The hypodermal nuclei were mostly of class I, while class II values
represented 5.5 percent of the total number of determinations.
Nuclei of the proventriculus and the anterior silk gland showed
a broad spectrum of DNA values ranging from classes IV to VIII
including many intermediate values.
The method of measurement was analyzed for sources of
error. Various interpretations were offered for the variations in DNA
values including the role of endomitosis, definitive polyploidy, aneuploidy,
differential gene replication, etc. In the case of the anterior
silk gland and the proventriculus a possible relationship between DNA
amounts and ceIl activity is indicated
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The fine structure of spermatid differentiation in the mussel, Mytilus edulis, Linn
The spermiogenesis of Mytilus edulis (a marine mussel) has
been studied, employing techniques of light and electron microscopy
and cytochemical preparations. The observations trace the development
of the acrosomal complex, the nucleus, the mitochondrial
middle-piece, and the flagellum.
In early spermatids numerous membrane-bounded proacrosomal
vesicles arise from several Golgi complexes and coalesce to
form a single large acrosomal vesicle. This comes to rest on the
anterior surface of the nucleus and invaginates to become an elongated
cone-shaped structure.
An electron dense, spherical mass of membranoid sleeve
material, also arising from the Golgi complex, adjoins the acrosomal
vesicle and later occupies its indentation. In mature spermatozoa
the membranoid sleeve lines the cavity of the cone-shaped acrosomal vesicle and surrounds the axial rod.
Precursor material of the axial rod is first observed between
the nucleus and the acrosomal vesicle as an aggregation of fibers.
This later extends posteriorly into the nucleus and anteriorly into
the cavity of the acrosomal vesicle. In the mature spermatozoon
the fibrous axial rod ends posteriorly in the centriolar region of the
middle-piece.
The endoplasmic reticulum of early spermatids is a rudimentary
system of membrane-bounded canaliculi and flattened
vesicles which is predominantly free of ribosomes. Independent
or clustered ribosome-like particles are present in the ground cytoplasm.
By late spermiogenesis the reticulum has largely disappeared
and the ground cytoplasm containing a dense particulate
aggregate is sloughed off.
In the early spermatid a dense filamentous network of chromatin
in the interior and along the periphery of the nucleus increases
in size by accretion of the finer karyoplasm. Eventually the interaggregate spaces are obliterated as the large, coarsely granular
masses coalesce to form the compact, barrel-shaped nucleus of
the sperm.
By mid-spermiogenesis the randomly distributed elipsoid
mitochondria become localized around the nucleus. The association
with the nucleus is intimate and in many cases the mitochondria may be found in shallow recesses with the nuclear envelope reflected
over their surface. Subsequently the mitochondria became spheroid,
reduced to five in number, and restricted to the sperm middle-piece.
Two cylindrical centrioles are situated near the base of the
nucleus and are surrounded by the mitochondria of the middle-piece.
The distal centriole elongates and from it the longitudinal fibrils of
the sperm flagellum originate. The proximal centriole, oriented
obliquely to the distal centriole, retains its initial structure.
Tests with Sudan black B showed the presence of phospholipids
in the mitochondria of late spermatids and mature sperm.
Cytochemical techniques for carbohydrates indicated a neutral
mucoprotein for the proacrosomal vesicles and allowed these to be
identified in early spermatogenesis.
The development of the Mytilus spermatid was compared with
that of other vertebrate and invertebrate species