William N. Norton

Correlating the initiation of virus replication with a specific pupal developmental phase of an ichneumonid parasitoid

SummaryThe morphogenesis of virus particles associated with the calyx region of the lateral oviduct of the ichneumonid parasitoid Campoletis sonorensis is initiated during a specific phase of pupal development. The extent of body pigmentation proved to be the most reliable visual marker for correlation of induction of virus replication with particular phases of pupal development. Parasitoids removed from their pupal cases at 15 and 16 days after egg deposition were categorized into one of four developmental groups based on the degree of pigmentation. Viruses were not evident in the calyx cells of pupae representing the intial developmental stage, however, in all subsequent stages the concentration of particles gradually increased as development progressed. Observations of freeze-fractured tissue support previous suppositions that the viruses bud through the nuclear envelope following synthesis de novo within the nucleus.

Nuclear secretory particles associated with the calyx cells of the ichneumonid parasitoid Campoletis sonorensis (Cameron)

SummaryThe present study is an ultrastructural investigation of the calyx region of the ichneumonid endoparasitoid Campoletis sonorensis. It appears that synthesis of electrondense secretory particles occurs within nuclei of calyx cells. The particles consist of an ovocylindrical electron-dense inner core and a surrounding unit membrane. After their formation the particles pass from the nucleus by budding through both membranes of the nuclear envelope. The particles, along with fully developed parasitoid eggs concentrate within the lateral oviduct lumen. Feulgen histochemical studies suggest the presence of DNA within the calyx fluid. The possible function of the particles is discussed.

Adherence and growth of a Bacillus species on an insoluble polyester polyurethane

Abstract Laser Doppler velocimetry, electrical impedance, and static light scattering measurements were employed to quantify the growth of a Bacillus species at the expense of a heterogeneous, insoluble polyester polyurethane. Progress of the culture was arbitrarily divided into 3 phases: adherence of polyurethane to the bacteria, bacterial multiplication, and aggregation of the bacteria with the remaining, undegraded polymer. Observations with all 3 instruments indicated that multiple binding of the small colloidal polyurethane to the bacterium occurred over the course of 4 to 5 hours. During this extended lag period, the average volume of the bacterium–polyurethane complex increased to nearly three times that of the bacterium alone. The Bacillus cells then entered an exponential phase of growth with a doubling time of 55 minutes. Beyond 8 hours, the number of free bacteria in the culture declined concomitant with the appearance of large aggregrates composed of hundreds of cells and residual polyurethane. Further culture development ceased beyond 24 hours, leaving portions of the heterogeneous substrate unmetabolized. Phase contrast, scanning electron, and transmission electron microscopic observations provided qualitative corroboration of the significant events in the culture deduced from the instrumental analyses. These data demonstrate that physical measurements of colloidal suspensions may be used to study and quantify the complex interactions of bacteria with heterogeneous insoluble substrates.

Simulated Microgravity and Hypergravity Attenuate Heart Tissue Development in Explant Culture

Exposure to altered gravity may disturb the cytoskeleton-cell surface-extracellular matrix (ECM) interface of embryonic cells. Development of organs such as the heart depends on dynamic interactions across cell surfaces. Fibronectin (FN), for example, a glycoprotein that links the ECM to the cytoskeleton through integrin surface receptors, is required for normal heart development. Thus, altered gravity may perturb organogenesis. We cultured precardiac explants from chick embryos in a rotating bioreactor vessel to simulate microgravity (μG), or in a tissue culture centrifuge, for 18 h during heart development. Bioreactor μG did not alter external morphology of explants, but did significantly reduce the proportion that developed contractions. Immunostaining for FN of explant sections showed that it also significantly reduced the linear extent of staining present in basement membrane regions. Analysis of ultrastructure revealed a significant reduction in the number of desmosomes per unit area and other differences. Hypergravity dramatically abolished development of contractions and altered morphogenesis. The results indicate a probable sensitivity of cardiomyogenic development involving FN to altered gravity.

Synthesis of the vitelline and chorionic membranes of an ichneumonid parasitoid

A reduction in free ribosomes and increases in rough endoplasmic reticulum and Golgi complexes in follicle cells during oogenesis suggest their involvement in supplying precursor material for synthesis of the vitelline and chorionic membranes of the ichneumonid parasitoid Campoletis sonorensis. The inner region of the vitelline membrane is composed of a narrow band of electron‐opaque material; an outer region adjacent to the chorion consists of overlapping, irregularly shaped laminae. The fully developed chorion can be divided morphologically into three distinct regions. Its inner region adjacent to the lamellar plates of the vitelline membrane is composed of a lamellar membrane exhibiting a regular periodicity of crossbands. The middle section is composed of longitudinal chambers, some of which contain particulate matter. The outer region consists of slender projections which extend perpendicularly from the chorion surface. A fine layer of fibrous material adheres to the projections. The possibility of a relationship between the presence of fibrous material on the surface of parasitoid eggs and the inactivation or inhibition of host immune systems is mentioned.

Effects of galactoflavin-induced riboflavin deficiency upon rat hepatic cell ultrastructure.

SummaryThe primary cytoplasmic effect of galactoflavin-induced riboflavin deficiency upon rat liver cells involved focal sites of degradation which were manifested by the formation of membranous whorls. The nuclear effect of riboflavin deficiency concerned fluctuations in the total number of perichromatin granules per nucleus. These granules increased in number during the deficiency reaching a peak at three weeks. Nucleoli appeared compact with no evidence for segregation of nucleolar components. The possible correlation between increased synthesis of perichromatin granules and altered protein synthesis is discussed.

Asynchrony of erythroblast maturation induced by riboflavin deficiency

SummaryUltrastructural studies indicate that galactoflavin-induced riboflavin deficiency induces asynchrony of rat erythroblast maturation. During the latter stages of maturation erythroblasts retain significantly larger numbers of ribosomes as compared to control cells. Nucleoli are not evident in erythroblasts whose nuclei indicate cells in the latter stages of development. Membrane whorls develop within the mitochondria of plasma cells, eosinophils and neutrophils during the fifth week of riboflavin deficiency. No further evidence of degeneration was noted among aditional cell organelles.

Association of the Genus Acinetobacter with the Decomposition of a Swine Carcass and the Isolation and Characterization of a Novel Strain of Acinetobacter sp. P4

Using fluorescence in situ hybridization (FISH) and a selective and differential medium, Acinetobacter numbers were enumerated over the time course of decomposition, from fresh to putrid/dry, of a swine carcass. In addition, Acinetobacter diversity and succession were also characterized. Acinetobacter bacterial counts were observed to be the lowest before exposure (undetectable) and increased to their highest during active decay then decreased and leveled during advanced decay through putrid/dry. FISH analysis revealed Acinetobacter cells were mostly clustered together, which is consistent with growth in a non-mixed environment, such as soil. The abundance of Acinetobacter cells decreased from active decomposition to putrid/dry. BLAST analysis using the 16S rRNA-gene sequence identified the isolates as one of the following Acinetobacter spp: A. baumannii, A. haemolyticus, A. junii, A. johnsonii, and A. gerneri. Phenotypic description of the identified isolates closely matched those of known genomic species. One isolate, P4, was observed to be unique in its phenotypic and phylogenetic characteristics and was more closely related to A. sp E10. The isolates from this study displayed multi-antibiotic resistance. The results from the study revealed the association of Acinetobacter spp. with that of carrion which adds to our knowledge of the ecology of this genus along with the potential implications of infection for this opportunistic pathogen.

SEM Analysis of Insect Structures which Instigate Human Allergic Reactions

(1976). SEM Analysis of Insect Structures which Instigate Human Allergic Reactions. Journal of Asthma Research: Vol. 13, No. 4, pp. 187-192.