Scanning electron microscopy of the mammalian adrenal medulla.
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Adrenal Medulla↗
Biomedical subjects
R G Ulrich
Publications and source records attributed to R G Ulrich.
Microbiota Associated with the Gastrointestinal Tract of the Common House Cricket, Acheta domestica.
The location and morphology of the bacteria associated with the gastrointestinal tract of Acheta domestica were studied, and these bacteria were partially characterized. Bacteria were associated with the peritrophic membrane in the midgut and with the gut wall and cuticular structures of the hindgut. No bacteria were associated with the fat bodies. Colony-forming unit determinations indicated that there were three times more cultivatable bacteria in the hindgut than in the midgut. Of these bacteria, 40 to 85% cleared uric acid anaerobically, and 90 to 100% cleared uric acid aerobically. Of the 25 isolates obtained, 21 belonged to the genera Citrobacter, Klebsiella, Yersinia, Bacteroides, and Fusobacterium.
Journal Article↗
Morphology of temperature-sensitive strains of viral-transformed 3T3 mouse fibroblasts in vitro as determined by SEM and STEM.
The morphological characteristics of BALB/c 3T3 mouse fibroblasts transformed with two temperature-sensitive strains of simian virus 40 (SV-40) were studied. When grown at the permissive temperature (32 degrees C, transformed phenotype) strains A7B4b and A209B4a both closely resemble the morphology described for wild-type SV-40 cells. Scanning electron images show numerous knobs and filopodia as characteristic surface features in both subconfluent and confluent cultures. Scanning-transmission electron images reveal that the two strains are also similar in intracellular structure. When grown at the restrictive temperature (39 degrees C, untransformed phenotype) the two strains differ from each other. The A209B4a strain is more elongated in subconfluent cultures, and shows interactions of filopodia at cell-cell interfaces when confluent similar to those described for wild-type 3T3 cells. This strain also shows intracellular accumulation of polymorphic material thought to be secondary lysosomes. The A7B4b cells are flattened but generally not elongated when subconfluent, and do not show any obvious interactions at confluency. Intracellularly, this strain also differs from A209B4a.
Animals↗
Surface morphology of the ciliary apparatus in the eye of Galago senegalensis.
The folded portion of the ciliary body (pars plicata) in Galago senegalensis consists of a series of processes extending from the flat region (pars plana) over the posterior half of the ciliary muscle to the posterior surface of the iris near the limbus. Each process has an anterior portion (iridial process) that is distinguished by its surface morphology from a posterior portion (ciliary process). Iridial processes attach to the iris and are devoid of zonular fibers, while ciliary processes, although continuous with iridial processes, are covered completely with fibers. The transition from one to the other occurs at a point nearest the lens where zonular fibers leave the ciliary body to transverse the posterior chamber. The innermost margin of both processes is an expanded crest (ciliary crest) running along each shelflike ridge (ciliary ridge). The ridges represent inward projections of the ciliary body forming the mesentery-like membrane of the pars plicata. Zonular fibers take origin from a complex multilayered basal lamina of the ciliary epithelium found in all regions except on iridial processes. The pars plana is covered by longitudinally-oriented fibers, many of which are attached at the retinociliary junction. These zonular fibers converge on the base of ciliary processes, some entering each ciliary cleft to insert on ridges and many others continuing anteriorly over the surface of ciliary crests. The fibers on crests lift away from the ciliary process at its transition with the iridial process and extend to the lens. Other fibers that project to the lens originate on ciliary ridges and make their way onto each crest near this transition and appear to be projecting from ciliary clefts.
Animals↗
Morphology of differentiating epithelial cells in the respiratory tract of the postnatal opossum (Didelphis virginiana).
Correlative microscopy of the developing respiratory epithelium during mucous cell differentiation reveals a decrease in the concentration of ciliated cells concomitant with proliferation of mucous cells and formation of an inner layer of the mucous blanket. Nonciliated cells increase in concentration between 40 and 80 days postnatal and provide the major surface area of the tracheal epithelium. Nonciliated cells change from isolated small patches with flat, finely-corrugated surfaces to larger, rounded aggregates with bulging cytoplasmic contents. Individual, nonadjacent ciliated cells are distributed around the borders of aggregates. By 120 days the precise boundary of each aggregate is lost as the epithelium develops more smooth contour. In the major bronchi, ciliated cells occur primarily in the clefts between bronchial folds. Cells in these clefts also provide for the origin of goblet cells, observed by 80 days and heavily concentrated here at 120 days. Nonciliated cells with smooth surfaces (dome cells) occupy the ridges of bronchial folds and their morphology varies little up to 120 days. A tannic acid technique was used to demonstrate the development of the inner layer of the mucous blanket. The layer begins as a thin fibrillar coat on the surface of the tracheal and bronchial epithelium at 40 days. It becomes progressively thicker in the trachea but changes little in the bronchi.
Age Factors↗
Preparation and observation by SEM of hemopoietic cells cloned in soft agar.
A method is described to prepare clones of hemopoietic cells grown in soft agar for scanning electron microscopy (SEM). A critical modification of the otherwise quite standard SEM processing procedure for biological samples involved the use of silver micropore disks as an adherent substrate to support the highly labile, deformable agar slabs. This support allows maintenance of the normal flat pancake shape of the specimen through the thiocarbohydrazide osmium ligand binding steps, dehydration, and critical point drying. With this support and careful dissection of the surface agar with a fine steel needle using a stereomicroscope, selected areas and depths within the colony can be exposed and examined by SEM. Surface topography of cloned cells can be correlated with intracellular cytological features by excising areas of interest and directly embedding them in plastic for thin-section preparation and viewing by transmission electron microscopy (TEM). The dried-specimen-teasing method appears useful, because of the ease of preparation of the specimens, its reproducibility, and the degree of visibility and preservation of cell surface structures and intraclonal relationships. Our initial observations, using combined EM techniques, indicate that clonal cell topography is highly variable and that this variability appears to be related both to the relative age and proliferative status of the colony. Based on work to date, we suggest that topographical and spatial analysis, in vitro of cloned, agar-embedded hemopoietic stem cells is possible with simple modifications of conventional SEM preparative techniques.
Agar↗
DR beta peptides block the antigen-specific response but not the alloresponse of a dual-reactive T-cell clone.
It is generally assumed that alloreactivity and the response to foreign antigens are equivalent T-cell recognition events. We have addressed this issue by examining the antigen presentation of beef insulin by two DR1-restricted human T-clones. One of the clones was dual-reactive and exhibited alloreactivity. By employing 20 synthetic consecutive overlapping peptides representing the entire extracellular (residues 1-198) and intracellular (residues 222-273) parts of the DR2 beta molecule, the effects of each of these peptides on antigen presentation and alloreactivity were examined. The DR1-restricted response to beef insulin by both clones was inhibited by peptides from DR2 beta region 1-25. Other DR2 beta (residues 21-198 en 222-237) or control peptides had no effect. The DR3-associated alloresponse of the dual-reactive clone was not inhibited by any peptide. These observations suggest that recognition of antigen is fundamentally different from allorecognition.
Amino Acid Sequence↗
Are DNA-based vaccines useful for protection against secreted bacterial toxins? Tetanus toxin test case.
Polypeptide and DNA vaccine alternatives to the conventional tetanus toxoid were compared. Mouse immunizations with plasmid DNA that encoded the tetanus toxin C fragment polypeptide induced consistently lower antibody responses than direct immunization with the C fragment polypeptide or toxoid, yet provided some degree of protection from a lethal toxin challenge. Cytotoxic T-cell responses dominated DNA immunizations, while specific T-cell proliferation resulted from all vaccines tested. Immune responses to the DNA vaccine exhibited a T-helper type-1 propensity, while polypeptides elicited T-helper type-2 responses. The lower antibody response to the plasmid vaccine was not due to insufficient quantity of C fragment in vivo but was likely the result of a mode of antigen presentation that was less efficient for supporting antibody production. Collectively, these results suggest that polypeptide or toxoid vaccines are preferable to plasmid-based vaccination for control of diseases caused by tetanus toxin.
Amino Acid Sequence↗
Microarray-based compendium of hepatic gene expression profiles for prototypical ADME gene-inducing compounds in rats and mice in vivo.
To examine species-specific aspects of the induction of absorption, distribution, metabolism and excretion (ADME)-related genes, we used 25 000 gene oligonucleotide microarrays to construct a rodent gene-response compendium that compared hepatic gene expression profiles and developed consensus aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR) and pregnane X-receptor (PXR) ligand signatures relevant to drug clearance. Twenty-six inducer compounds were chosen from the literature. Rats and mice received one of six dose levels (log2 dose escalation, 32-fold dose range) of each compound daily for 3 days. Animals were necropsied 6-9 h after the last dose, and tissues were collected for RNA analysis. Hepatic gene expression profiles were obtained using Rosetta Resolver expression analysis system, and ADME-related genes were extracted. Cross-talk among nuclear receptors or hepatoxicity at high dose levels resulted in large signatures (usually >1000 genes at p < 0.01) for most compounds. After ADME gene transcript enrichment, agglomerative clustering separated AhR ligands from CAR/PXR ligands, but it was difficult to distinguish CAR from PXR ligands. Consensus signatures were derived from groups of AhR, CAR and PXR ligands; and cross-talk among responding genes was determined. Many compounds had distinct log dose-response profiles, and relative potencies for ligands were established. Robust responses by CYP1A1, CYP2B10 (CAR responsive in mice) and CYP2B15 (CAR responsive in rats) and CYP3A1 (PXR responsive in rats) were used to benchmark the relative potency of different ligands and to determine the relative selectivity for AhR, CAR or PXR. By using a compendium of gene expression profiles, we defined species-specific induction patterns across the ADME transcriptome.
Animals↗
Compendium of gene expression profiles comprising a baseline model of the human liver drug metabolism transcriptome.
Oligonucleotide microarrays were used to study the variability of pharmacokinetics and drug metabolism (PKDM)-related gene expression in 75 normal human livers. The objective was to define and use absorption, distribution, metabolism and excretion (ADME) gene expression variability to discern co-regulated genes and potential surrogate biomarkers of inducible gene expression. RNA was prepared from donor tissue and hybridized on Agilent microarrays against an RNA mass balanced pool from all donors. Clustering of PKDM gene sets revealed donors with distinct patterns of gene expression that grouped genes known to be regulated by the nuclear receptor, pregnane X-receptor (PXR). Fold range metrics and frequency distributions from the heterogeneous human population were used to define the variability of individual PKDM genes in the 75 human livers and were placed in context by comparing expression data with basal ADME gene expression variability in an inbred and diet/environment controlled population of 27 Rhesus livers. The most variable genes in the hepatic transcriptome were mainly related to drug metabolism, intermediary metabolism, inflammation and cell cycle control. Unique patterns of expression across 75 individuals of inducible ADME gene expression allowed their expression to be correlated with the expression of many other genes. Correlated genes for AhR, CAR and PXR responsive genes (CYP1A2, CYP2B6 and CYP3A4) were identified that may be co-regulated and, therefore, provide clues to the identity of surrogate gene or protein markers for CYP induction. In conclusion, microarrays were used to define the variable expression of hepatic ADME genes in a diverse human population, the expression variability of ADME genes was compared with the expression variability in an inbred population of Rhesus monkeys, and genes were defined that may be co-regulated with important inducible CYP genes.
Animals↗
Expression profiles of 50 xenobiotic transporter genes in humans and pre-clinical species: a resource for investigations into drug disposition.
Carrier-mediated transporters play a critical role in xenobiotic disposition and transporter research is complicated by species differences and their selective tissue expression. The purpose of this study was to generate a comprehensive data set of xenobiotic transporter gene expression profiles in humans and the pre-clinical species mouse, rat, beagle dog and cynomolgus monkey. mRNA expression profiles of 50 genes from the ABC, SLC and SLCO transporter superfamilies were examined in 40 human tissues by microarray analyses. Transporter genes that were identified as enriched in the liver or kidney, or that were selected for their known roles in xenobiotic disposition, were then compared in 22 tissues across the five species. Finally, as clinical variability in drug response and adverse reactions may be the result of variability in transporter gene expression, variability in the expression of selected transporter genes in 75 human liver donors were examined and compared with the highly variable drug metabolizing enzyme CYP3A4.
Animals↗
Distribution and disposition of trospectomycin sulfate in the in vivo rat, perfused rat liver, and cultured rat hepatocytes.
Trospectomycin sulfate is an experimental, aminocyclitol antibiotic. It has been shown in preclinical, chronic safety studies in the dog and rat to elicit a reversible, lysosomal phospholipidosis in liver. The present experiments were conducted to characterize the tissue distribution and disposition of 3H]trospectomycin sulfate in the male rat, perfused rat, perfused rat liver, and cultured rat hepatocytes. Following a 5 mg/kg iv dose to four rats, approximately 70% of the dose was recovered within 24 hr primarily in urine as unchanged drug, and the remainder was eliminated with a terminal phase half-life in blood and tissues of 3 days. Fecal excretion was relatively minor (16% of the dose recovered in feces in 7 days) until later timepoints, when it was the principal pathway of terminal phase elimination. The liver sequestered approximately 10% of the dose and had the highest tissue levels of drug at all times measured. Liver perfusion experiments indicated that trospectomycin accumulated in a hepatic depot compartment as parent drug by a first-order process which was nonsaturable up to a 1 mM concentration of drug. Biliary excretion of unchanged trospectomycin by the perfused liver was slow (approximately 3% of the dose in 2 hr) and occurred by both paracellular and transcellular mechanisms. The hepatic depot compartment appeared to be responsible for transcellular biliary excretion, and thus for the sustained fecal excretion observed in vivo. Subcellular distribution experiments indicated that at least 50% of the drug in the hepatic depot was sequestered in organelles having a broad density range. The existence of a trospectomycin depot compartment was also demonstrated in cultured hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗