Hallie M. Krider

The avian low score normal muscle weakness alters decorin expression and collagen crosslinking.

Extracellular matrix development of chicken pectoral muscle was examined in the Low Score Normal (LSN) genetic muscle weakness and compared to both normal and avian muscular dystrophy (MD). At 20 days of embryonic development significant elevations were noted in LSN total glycosaminoglycan concentration and decorin, while at 14 days, LSN glycosaminoglycan and decorin levels were indistinguishable from the controls. Levels of a large skeletal muscle chondroitin sulfate proteoglycan (M-CSPG) appear to be unaffected. Morphologically, at 20 days, the extracellular matrix space between muscle fibers increased to a level characteristic to that observed in avian muscular dystrophy. At six weeks posthatch a marked increase in LSN collagen crosslinking relative to MD or control tissues was observed, while collagen concentration was not altered. By one year posthatch LSN collagen crosslink levels did not significantly differ from normal tissue. These data support the concept that the LSN muscle weakness is associated with changes in both proteoglycan and collagen characteristics.

Ultrastructure and Morphogenesis of the Apyrene and Eupyrene Spermatozoa in the Gypsy Moth (Lepidoptera: Lymantriidae)

Abstract The ultrastructure and morphogenesis of apyrene and eupyrene spermatozoa of Lymantria dispar (L.) is examined. Apyrene prophase I spermatocytes are characterized by sparse perinuclear membrane, smaller nuclei, bivalents lacking synaptonemal complexes, and few mitochondria. Eupyrene prophase I spermatocytes are characterized by dense perinuclear sheathing, large nuclei, diffuse chromatin, synaptonemal complexes, and numerous mitochondria. Apyrene metaphase I is atypical involving chromatin clumping and mis-segregation. Eupyrene metaphase I spermatocytes show localized meiotic centromeres and sheathed nuclear division. However, kinetochores are amorphous and difficult to discern. Apyrene spermiogenesis involves the morphogenesis of the axoneme and mitochondrial derivatives in the absence of differentiating nuclei and acrosomes. Eupyrene spermiogenesis involves the differentiation of nuclei, axonemes, acrosome tubes, mitochondrial derivatives, lacinate appendages, and reticular appendages. Both eupyrene spermatozoa and apyrene spermatozoa undergo additional morphogenesis upon leaving the testis. The most apparent of these are the loss of lacinate appendages in eupyrene sperm and the gain of an extracellular sheathing in both eupyrene sperm and apyrene sperm.

Analysis of disproportionate replication of ribosomal DNA in Drosophila melanogaster by a microhybridization method.

A microhybridization technique is described which requires only 1% of the starting material normally needed for filter-bound methods. Employing this technique, we have investigated the disproportionate replication (compensation) of ribosomal DNA in larval and adult stages of two strains of Drosophila melanogaster. Both stages of the Oregon R strain demonstrate XO compensation while neither stage of Canton S shows a significant elevation of ribosomal DNA content in XOs. It is demonstrated that the lack of disproportionate replication in the latter strain does not result from the absence of the genetic site cr+ which normally controls this process.

Meiotic chromosome missegregation during apyrene meiosis in the gypsy moth, Lymantria dispar, is preceded by an aberrant prophase I.

Abstract. The gypsy moth, Lymantria dispar, produces two structurally and genetically distinct types of spermatozoa. The eupyrene spermatozoa are genetically haploid and structurally typical. The apyrene spermatozoa are anucleate and structurally different from eupyrene spermatozoa. To understand further the events contributing to meiotic chromosome missegregation in apyrene spermatocytes, we examined the progression of meiosis in these cells with respect to their eupyrene counterparts. Chromosomal bouquet formation and fusion of nucleolar organizing regions are disrupted in apyrene nuclei. In addition, the chromatin of apyrene nuclei is prematurely and extremely condensed compared with that of eupyrene nuclei. An antibody to the conserved synaptonemal complex protein 3 (SCP3) labeled eupyrene pachytene chromosomes, but not apyrene pachytene chromosomes. In addition, apyrene meiotic spindles are missing a subset of microtubules, which likely include kinetochore microtubules. Because the condensation behavior of meiotic chromatin in apyrene spermatocytes deviates from that of eupyrene spermatocytes, we examined the appearance and distribution of the phosphorylated form of histone H3, but no significant differences in histone H3 phosphorylation were found between apyrene and eupyrene spermatocytes. We argue that because a pachytene checkpoint is not initiated in apyrene spermatocytes, this system may provide a way to understand better the underlying biochemical connections between pairing, recombination, synapsis, kinetochore assembly and segregation of chromosomes during meiosis in a higher eukaryote.

Expression and amplification of the genes for ribosomal RNA in bobbed mutants of Drosophila melanogaster.

We have employed stocks bearing clonally derived X chromosomes to investigate several features of the bobbed mutant syndrome, and the amplification of rDNA genes in D. melanogaster. We report that posterior macroscutellar bristle length correlates well with the rDNA content (i.e. dose of ivs—, or uninterrupted genes) in cloned X derivative strains. X/0 males and X/X females with statistically indistinguishable rDNA contents have virtually identical bristle lengths. This indicates that (with respect to this phenotypic character) the rDNAs in these two genotypes are expressed equally, without apparent sexual dimorphism or dosage compensation. However, the severity of bobbed phenotype in terms of bristle morphology, turgite etching, and delayed eclosion is greater in the X/X°female than in the X/0 male genotype for the alleles examined. We estimate the minimum dose of functioning rRNA genes required for viability at 26 °C to be 70 genes per diploid genome. We have examined the capacity of several X chromosomes which bear bobbed mutant alleles to compensate in X/0 males, and find that disproportionate replication of these rDNAs does not take place. In contrast, at least one of the non-compensating bobbed alleles does appear to undergo rDNA magnification.

The organization and composition of the ribosomal RNA gene non-transcribed spacer of D. busckii is unique among the drosophilids.

Several ribosomal RNA (rRNA) genes from D. busckii were cloned and characterized. The prominent repeat classes have lengths of 12·8 and 13·6 kb and lack 28S introns. rRNA genes were cloned containing 28S insertions which exhibit heterogeneity in size and sequence. The non-transcribed spacer (NTS) contains two regions composed of different repeated sequences that exhibit pronounced instability in HB 101. NTS region II, centrally located within the NTS, contains predominately 11 or 16 Hin cII generated 160 bp repeats. NTS region III, next to the 18S gene, contains repeats that are variable in number, and are either heterogeneous in length or are dispersed within unique sequences. The organization and composition of the rRNA gene NTS of D. busckii is different in comparison to the NTSs of other drosophilids. In addition, the pronounced instability of two different NTS regions is unique in comparison to all other cloned rRNA genes.

Direct detection of Lyme disease by digital microscopy

Studies were performed to test the hypothesis that an early direct diagnostic test for Lyme disease can be developed. This test involves automatic microscopic scanning of a relatively large volume of body fluids for the sparsely occurring Lyme disease causing agent, the spirochete bacterium Borrelia burgdorferi. Preliminary results indicate that segmentation, measurement, and classification techniques can be used to differentiate spirochetes from other materials in microscope images of blood smears stained with a fluorescent dye.<<ETX>>