SEARCH · PubMed Health

Results for “Morphological Characterization”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources

PubMed1977

An electron microscope observation of the right and the two left portions of the habenular nuclei of the frog.

The right dorsal habenula (RDH), the left dorsal habenula, lateral portion (LDH-LP) and the left dorsal habenula, medial portion (LDH-MP) of the adult frog Rana esculenta have been studied by the electron microscope with the use of three types of fixatives: osmium tetroxide, aldehydes and potassium permangarate. The study has demonstrated in the habenulae of both sides a variety of syraptic vesicles, special synaptic patterns (en passant, serial, axo-somatic) containing small spherical transparent vesicles, never mixed with other types of vesicles, and large pale processes containing big granules. However, a particular type of synaptic vesicles characterized by small clear spherical vesicles with a tiny dark granule revealed by potassium permanganate fixition has been demonstrated only in the neuropil of the LDH and not in the RDH. Further, a peculiar type of intracytoplasmic inclusion appears in the form of myelin-like and crystal-like formations only in the LDH-MP. On the basis of these consistent ultrastructural differences, the dorsal habenular nuclei of the frog can be considered as composed of three individual nuclei, each with its own morphological characterization, dislocated, for some unknown reason, one on the right and two on the left side of the epithalamus. The results suggest that the LDH-MP is a nucleus metabolically different from the others and that the projections to the dorsal habenular nuclei are different on the right and left sides of the brain.

Animals↗

PubMed1990

Response of rat tracheal epithelium to ozone and oxygen exposure in vitro.

Although ozone-induced epithelial injury in vivo has been morphologically characterized, effects of gaseous oxidants on respiratory epithelium in organ culture, where tissue organization is maintained but systemic influences are eliminated, have not been thoroughly investigated. In this study, we exposed tracheal organ cultures from rats to 95% oxygen and 1 ppm ozone, alone and in combination, to determine (1) whether epithelial responses to ozone similar to those observed in vivo occur in airways separated from systemic physiologic, secretory, and inflammatory reactions; (2) whether concentrations of oxygen sufficient to potentially cause oxidant injury result in morphologic epithelial alterations similar to those that occur in ozone toxicity; and (3) if the combined oxidant insult of oxygen and ozone results in more severe damage to the tracheal epithelium than occurs with ozone in air. Tracheal organ cultures were exposed to filtered air and 5% carbon dioxide; filtered air, 5% carbon dioxide, and 1 ppm ozone; 95% oxygen and 5% carbon dioxide; or 95% oxygen, 5% carbon dioxide, and 1 ppm ozone for 96 hr. Light- and quantitative electron-microscopic evaluation showed that epithelia exposed to 1 ppm ozone in air exhibited loss of ciliated cells and ciliated cell damage. The epithelia exposed to 95% oxygen and 5% carbon dioxide were pseudostratified, columnar, ciliated, and hyperplastic. Epithelia exposed to 95% oxygen plus 1 ppm ozone were stratified and nonciliated or very sparsely ciliated. The predominant cell types in epithelia exposed to oxygen plus ozone were serous cells and metaplastic cells, and focal aggregates of adherent necrotic cells were present. We conclude that there was a synergism between oxygen and ozone exposure leading to enhanced epithelial injury and metaplasia.

Animals↗

PubMed2005

Scanning probe microscopy characterization of single chains based on a one-dimensional oxalato-bridged manganese(II) complex with 4-aminotriazole.

The compound [Mn(mu-ox)(4atr)2]n (1) (ox = oxalato and 4atr = 4-amine-1,2,4-triazole) has been synthesized and characterized by FT-IR spectroscopy, thermal analysis, variable-temperature magnetic measurements, and X-ray single-crystal diffraction methods. The crystal structure of compound 1 consists of one-dimensional linear chains in which trans-[Mn(4atr)2]2+ units are sequentially bridged by centrosymmetric bis-bidentate oxalato ligands. Cryomagnetic measurements show an overall antiferromagnetic behavior of the compound. Isolated chains of this polymer have been obtained by sonication of 1 in ethanol or treatment of the polymer with NaOH and morphologically characterized on highly oriented pyrolitic graphite and mica surfaces by atomic force microscopy and scanning tunneling microscopy. The procedures employed to obtain single chains of this coordination polymer open a route for future nanotechnological applications of these types of materials.

Journal Article↗

PubMed1998

MLL and CALM are fused to AF10 in morphologically distinct subsets of acute leukemia with translocation t(10;11): both rearrangements are associated with a poor prognosis.

The translocation t(10;11)(p13;q14) has been observed in acute lymphoblastic leukemia (ALL) as well as acute myeloid leukemia (AML). A recent study showed a MLL/AF10 fusion in all cases of AML with t(10;11) and various breakpoints on chromosome 11 ranging from q13 to q23. We recently cloned CALM (Clathrin Assembly Lymphoid Myeloid leukemia gene), the fusion partner of AF10 at 11q14 in the monocytic cell line U937. To further define the role of these genes in acute leukemias, 10 cases (9 AML and 1 ALL) with cytogenetically proven t(10;11)(p12-14;q13-21) and well-characterized morphology, immunophenotype, and clinical course were analyzed. Interphase fluorescence in situ hybridization (FISH) was performed with 2 YACs flanking the CALM region, a YAC contig of the MLL region, and a YAC spanning the AF10 breakpoint. Rearrangement of at least one of these genes was detected in all cases with balanced t(10;11). In 4 cases, including 3 AML with immature morphology (1 AML-M0 and 2 AML-M1) and 1 ALL, the signals of the CALM YACS were separated in interphase cells, indicating a translocation breakpoint within the CALM region. MLL was rearranged in 3 AML with myelomonocytic differentiation (2 AML-M2 and 1 AML-M5), including 1 secondary AML. In all 3 cases, a characteristic immunophenotype was identified (CD4+, CD13-, CD33+, CD65s+). AF-10 was involved in 5 of 6 evaluable cases, including 1 case without detectable CALM or MLL rearrangement. In 2 complex translocations, none of the three genes was rearranged. All cases had a remarkably poor prognosis, with a mean survival of 9.6 +/- 6.6 months. For the 7 AML cases that were uniformly treated according to the AMLCG86/92 protocols, disease-free and overall survival was significantly worse than for the overall study group (P = .03 and P = .01, respectively). We conclude that the t(10;11)(p13;q14) indicates CALM and MLL rearrangements in morphologically distinct subsets of acute leukemia and may be associated with a poor prognosis.

Acute Disease↗

PubMed2004

Overestimating hybrid layer quality in polished adhesive/dentin interfaces.

The most popular techniques for determining the quality of the hybrid layer (HL) have relied on morphologic characterization of the polished adhesive/dentin (a/d) interfaces before and after acid-bleach chemical treatment. Using these techniques, the existence of smooth, acid-resistant layers has been consistently reported for most adhesive systems. The purpose of this study was to determine whether popular specimen preparation techniques that include polishing and acid-bleach treatment modify the a/d interface, mask the complexity of the HL, and lead to inaccurate assessment of the quality of the HL. To understand the impact of specimen preparation techniques on the morphology of the resin-dentin interface, polished and unpolished specimens from the same tooth were closely compared after different acid-bleach chemical treatment procedures. Two one-bottle adhesives, that is, 3M Single Bond and Pulpdent UNO, exhibiting distinct differences in hydrophilic/hydrophobic composition, were used in this investigation. Using specimens from the same tooth, the effect of chemical treatments on the morphology of the resin-dentin interdiffusion zone and the differences in the morphology of polished and unpolished specimens after these same treatments were studied with scanning electron microscopy. It was shown that conventional specimen preparation techniques that include polishing and acid-bleach treatment can adversely affect and even obscure the structural detail of the a/d interface in specimens that possess a porous HL. The results indicated that the Pulpdent UNO/dentin interface had better quality than the 3M Single Bond/dentin interface. The difference in the quality of HL can be attributed to factors such as compositional differences that impact the adhesive interaction with water, that is present within the substrate during wet bonding. The inability of the conventional acid-bleach procedure to reveal the differences in the scanning electron microscopy interfacial morphology was overcome in this investigation by using a multistep technique.

Acid Etching, Dental↗

PubMed2005

Endogenous neuregulin restores radial glia in a (ferret) model of cortical dysplasia.

Radial glia are integral components of the developing neocortex. During corticogenesis, they form an important scaffold for neurons migrating into the cortical plate. Recent attention has focused on neuregulin (NRG1), acting through erbB receptors, in maintaining their morphology. We developed a model of developmental radial glial disruption by delivering an antimitotic [methylazoxy methanol (MAM)] to pregnant ferrets on embryonic day 24 (E24). We previously found that normal ferret cortex contains a soluble factor capable of realigning the disorganized radial glia back toward their normal morphology. Characterization of the reorganizing activity in normal cortex demonstrated that the probable factor mediating these responses was a 30-50 kDa protein. To test whether this endogenous soluble factor was NRG1, we used organotypic cultures of E24 MAM-treated ferret neocortex supplemented with the endogenous factor obtained from normal cortical implants, exogenous NRG1beta, antibodies that either blocked or stimulated erbB receptors, or a soluble erbB subtype that binds to available NRG1. We report that exogenous NRG1 or antibodies that stimulate erbB receptors dramatically improve the morphology of disrupted radial glia, whereas blockade of NRG1-erbB signaling prevents the radial glial repair. Our results suggest that NRG1 is an endogenous factor in ferret neocortex capable of repairing damaged radial glia and that it acts via one or more erbB receptors.

Animals↗

PubMed2002

[Argyrophilic grain disease (AgD), a frequent and largely underestimated cause of dementia in old patients].

Argyrophilic grain disease (AgD) is a late-onset dementia morphologically characterized by abundant neuropil grains (ArGs). ArGs are mainly found in the CA1 subfield of the cornu ammonis, entorhinal and transentorhinal cortices, the amygdala and the hypothalamic lateral tuberal nuclei. We have recently shown that abnormally phosphosphorylated tau protein is the main protein constituent of ArGs and that tau is hyperphosphorylated in up to 80p.100 of nerve cels in areas rich in ArGs. We could demonstrate that at least a subset of grains are formed within dendrites and dendritic side-branches of neurons containing hyperphosphylated tau. Morphology of dendrites containing grains suggests that a process of progressive dendritic shrinkage is taking place in neurons bearing ArGs. Furthermore it became apparent that the presence of ArGs is not necessarily associated with a cognitive decline. Our studies on AgD cases with and without dementia suggest that AgD is a progressive neurodegenerative disorder with early subclinical lesions in anterior part of the hippocampal formation. At later stages involvement of more caudal parts of the hippocampal formation generally results in a cognitive decline. Thus, one possible explanation for the dementia observed in some subjects with AgD is that there is a more widepread loss of postsynaptic structures, including synaptic contacts, throughout the hippocampus-entorhinal/parahippocampal complex and the amygdaloid nuclei. Most of the reported AgD cases are associated with neurofibrillary lesions (e.g. neurofibrillary tangles) which are also typical of Alzheimer's disease (AD). However, neurofibrillary changes do not exceed early (entorhinal and limbic) Braak stages which generally are not associated with a cognitive decline. Additional neuropathological features of AgD include oligodendroglial tau filamentous inclusions ( coiled bodies ), ballooned neurons and astrocytic tau pathology. The clinical features of AgD are poorly understood. However, preliminary data from retrospective studies suggest that in AgD behavioural disturbances will precede memory failure and memory decline. Furthermore, it has been shown that the ApoEe4 allele does not constitute a risk factor for the development of AgD. In conclusion it seems very likely that AgD is a distinct dementing disorder of old age that has to be distinguished from other tauopathies, e.g. AD, by both morphological and genetic criteria.

Age Factors↗

PubMed2001

[Alcoholic and nonalcoholic steatohepatitis. Histopathologic and pathogenetic considerations].

Alcoholic (ASH) and nonalcoholic (NASH) steatohepatitis show an almost identical morphology. Since the clinical picture is not characteristic, liver biopsy is still the diagnostic gold standard. ASH and NASH are morphologically characterized by a combination of steatosis, hepatocellular injury (ballooning degeneration, apoptosis, necrosis), perivenular and pericellular fibrosis, and inflammation (mostly neutrophils). A definitive differentiation of ASH and NASH is only possible by exclusion of alcohol abuse. Although NASH comprises a syndrome with a multifactorial etiology, adipositas seems to be the most constant associated causal factor. The pathogenesis of both diseases is still unclear. Clinical evidence and experimental studies suggest an important toxic role of reactive oxygen species (oxidative stress). According to our experience, ballooning of hepatocytes is a constant morphologic feature of ASH and NASH and already present in the early stages of disease. Ballooned cells often (but not always) contain Mallory bodies (alcoholic hyalin), which are irregular cytoplasmic inclusions consisting of keratins and nonkeratin components, including ubiquitin. Ballooning is associated with a disturbance and finally almost disappearance of the keratin-intermediate filament cytoskeleton. In our studies on the pathogenesis of ASH and NASH, we concentrated on these cytoskeletal alterations and Mallory body formation. It could be shown that in the early stages overexpression and hyperphosphorylation of keratins take place. Moreover, the 1:1 ratio of keratin type I (keratin 18) and type II (keratin 8) necessary for the assembly of intermediate filaments is disturbed and the equilibrium shifted toward keratin 8. Thus, the pool of soluble keratin 8 increases. The resulting keratin monomers are sensitive to misfolding and either degraded or aggregated as inclusion bodies. If the proteolytic capacity is impaired (e.g., by inhibition of the proteasomal system) in the chronically stressed cell aggregation prevails,finally leading to Mallory body formation. Convincing evidence exists on the basis of clinical and experimental studies that keratins exert a nonskeletal protective function in simple epithelia (e.g., liver cells). Disturbance of the keratin system may thus significantly contribute to cell damage.

Biopsy↗

PubMed1985

Functional and morphological features of neurons in the midline region of the caudal spinal cord of the cat.

Neurons surrounding and dorsal to the central canal in caudal segments of the cat spinal cord were functionally and morphologically characterized. From electrophysiologically obtained responses these neurons were categorized into 3 functional groups based on excitation by somatic afferent stimulation. Eighteen of 36 units were activated by both low threshold and high threshold primary afferent inputs. Of the remaining 18 units, 9 responded only to innocuous intensities of stimulation and the other 9 were excited selectively by noxious peripheral stimulation. Neurons intracellularly marked with horseradish peroxidase formed a heterogeneous population with respect to perikaryal size, dendritic orientation and dendritic extent, and no evident correlations between functional categories and morphological features were observed in light microscopic analyses. Neurons immediately surrounding the central canal were functionally similar to neurons located in the dorsally adjacent gray matter.

Animals↗

PubMed1994

Electron microscopic observation of the transitional portion in the human eccrine sweat gland.

The transitional portion in human eccrine sweat glands was observed by transmission electron microscope (TEM). The transitional portion, consisting of columnar epithelial cells (columnar cells) and basal cells, formed a very short segment about 25 to 50 microns in length. The portion was abruptly connected to the secretory segment, and shifted to the excretory duct without marked ultrastructural changes. The columnar cells were morphologically characterized by small apical vesicles as reported in previous reports. Considering the frequency of the mitosis of the columnar cells, the transitional portion seemed to be one of the areas of cell proliferation in the gland. Basal cells were sparse in the region connecting the secretory segment, but dense near the duct. Basal cells in the secretory segment side of the transitional portion, containing thin microfilament-bundles in the infranuclear cytoplasm, were considered to be immature myoepithelial cells. On its ductal side, however, the basal cells showed morphological profiles similar to ductal peripheral cells. These findings suggest that the differentiation of myoepithelial cells occurs in the transitional portion of eccrine sweat glands.

Adult↗

PubMed1995

[Preoperative diagnosis of xanthogranulomatous cholecystitis].

Xanthogranulomatous cholecystitis (XGC) is a benign chronic inflammation of the gallbladder, rarely described in the radiologic literature. Like xanthogranulomatous pyelonephritis, it can clinically and radiologically mimic carcinoma. This unusual entity is characterized morphologically by a broad spectrum of xanthogranulomatous changes seen from a small limited focus within yellow nodule in the gallbladder wall, to diffuse involvement of the entire gallbladder with extension of the fibrosis into surrounding tissues. It is clear that recurrent inflammation and calculi are important for the pathogenesis, which is not well understood. The clinical presentation and radiologic findings of XGC are non specific. Irregular thickening of the gallbladder wall and local extension of the process can mimic carcinoma. Diagnosis of XGC is always established by histological examination, characterized by the infiltration of round cells, lipid laden histocytes and multinucleated giant cells in the muscle layer. We report a case of 76-year-old woman who had an episode of epigastric and right upper quadrant pain, 4 months before admission. Physical examination demonstrated a palpable mass in gallbladder region. Echography and computed tomography showed a large gallbladder, a thickened wall and an infiltration of the adjacent liver. The relatively well defined gallbladder internal border and the absence of biliary tract's dilatation allowed us to suggest the diagnosis of XGC, which was confirmed intraoperatively by frozen section histology. Once the diagnosis was established, cholecystectomy was performed. Occasionally, the inflammatory reaction is so severe that a subtotal cholecystectomy is required. Postoperative recovery was, as usually, uneventful. Although a rare entity, XGC should be considered in the differential diagnosis of complex right upper quadrant masses, as well as neoplastic gallbladder disease.

Aged↗

PubMed1991

Fractionated irradiation and early changes in salivary glands. Different effects on potassium efflux, exocytotic amylase release and gland morphology.

Irradiation is a potent treatment modality of head and neck cancer. However, the irradiation is usually associated with an influence on salivary glands with ensuing dryness and discomfort for the patients. In the present study we used different in vitro secretory models and morphologic characterization of rat parotid gland. Radiation was given to one gland on a 5-day schedule with 6 MV photons (total dose 20, 30, 35, 40, 45 Gy). The contralateral gland served as control, and the analysis of glands were performed 10 days after the last irradiation treatment. The noradrenaline stimulated electrolyte secretion (86rubidium tracer for potassium) was decreased in relation to the irradiation dose and in comparison to contralateral control glands. Noradrenaline stimulated exocytotic amylase release was not affected by irradiation and, there were no signs of obvious quantitative morphologic alterations after irradiation compared with controls. The results suggest that there are differences in the sensitivity to radiation for the two different secretory processes in salivary glands, and, thus, the structures regulating electrolyte and fluid secretion seem to be more vulnerable to irradiation than the process of exocytosis. The results, however, do not allow discrimination between temporary cellular impairment and irreversible damage leading to cell death.

Amylases↗

PubMed1991

Characterization of luminal and basal cells flow-sorted from the adult rat mammary parenchyma.

Differentially expressed membrane antigens have been used to flow-sort viable luminal epithelial and myoepithelial cells from freshly disaggregated adult virgin rat mammary parenchyma. Resulting cultures and clones have been characterized morphologically and by a panel of antibodies that recognise cell-type-specific cytoskeletal antigens in the intact mammary gland. Five clonal phenotypes were recognisable by morphological criteria, three (types 1-3) exclusively associated with sorted luminal epithelial (25.5-positive) cells, and two (types 4 and 5) generated from the sorted myoepithelial (CALLA/neutral endopeptidase 24.11-positive) cells. All clones derived from myoepithelial cells continued to express a basal parenchymal marker in the form of the rat equivalent of human cytokeratin 14, while smooth muscle alpha-actin was expressed by the small slowly growing type 4 clones but was found in fewer cells in rapidly proliferating type 5 myoepithelially derived clones. Two of the luminal clone types, characterized by an attenuated appearance and slow growth (types 1/2), expressed only luminal-specific markers, including the equivalent of human cytokeratins 7/18/19. Type 3 clones, by contrast, consisted of rapidly proliferating cells, many of which either co-expressed CK14 and CK18 antigens (type 3a) or were composed of a mosaic of CK14+/CK18-, CK14+/CK18+ and CK14-/CK18+ cells (type 3b). The sorted myoepithelially derived clones grew faster than clones from sorted luminal cells as evidenced by the larger fraction of cells synthesizing DNA. All types of clone could be obtained from both isolated ducts and alveoli, when these were cloned separately, although there were some differences in their relative frequency.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Neuronal death in brain infarcts in man.

The mechanism of neuronal death in brain ischaemia remains unclear. Morphology, terminal transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) and immunohistochemistry for the pro-apoptotic enzyme caspase-3 (CASP3), for its substrates poly(ADP-ribose) polymerase (PARP) and the DNA-dependent protein kinase catalytic subunit (DNA-PKCS) and for poly(ADP-ribose) (PAR), an end-product of PARP activity, were used to investigate neuronal death in brain infarcts from 15 men and 20 women, aged 46-95 years. The infarcts varied in age from 18 h to several months. Neuronal death was characterized morphologically by cell shrinkage, cytoplasmic hypereosinophilia and moderate nuclear pyknosis with later chromatin dispersal and disintegration, but not features of apoptosis. Occasional apoptotic bodies were seen but these appeared to be related to inflammatory cells, endothelial cells and occasional glia, including satellite cells. Neurones within infarcts showed strong nuclear and cytoplasmic labelling for CASP3 during the first 2 days after infarction. Neuronal DNA-PKCS, PARP and poly(ADP-ribose) immunoreactivity was demonstrable in scattered neurones in and adjacent to infarcts for 18-24 h but thereafter declined to below detectable levels in most cases. TUNEL labelled cells towards the edge of the infarcts, particularly at 2-4 days, but most of the labelling could be prevented by preincubation of the sections in diethyl pyrocarbonate to inactivate endogenous nucleases. Between 3 days and 3 weeks, CASP3 and DNA-PKCS were detected in proliferating capillaries and CASP3, PARP and poly(ADP-ribose) in infiltrating macrophages. Our findings indicate that neuronal death in human brain infarcts has some of the early biochemical features of programmed cell death, with upregulation of CASP3 and rapid disappearance of DNA-PKCS and PARP. However, the morphological changes are not those of apoptosis, the DNA cleavage occurs relatively late, and some of the TUNEL is probably mediated by the release of endogenous endonucleases during protease or microwave pretreatment of the damaged tissue.

Adult↗

PubMed2006

The influence of sulcal variability on morphometry of the human anterior cingulate and paracingulate cortex.

Human anterior cingulate (ACC) and paracingulate (PaC) cortices play an important role in cognitive and affective regulation and have been implicated in numerous psychiatric and neurological conditions. The region they comprise displays marked inter-individual variability in sulcal and gyral architecture, and although recent evidence suggests that this variability has functional significance, it is often ignored in automated and region-of-interest (ROI) morphometric investigations. This has lead to confounded interpretation of results and inconsistent findings across a number of studies and in a variety of clinical populations. In this paper, we present a reliable method for parcellating the dorsal, ventral, and subcallosal ACC and PaC that accounts for individual variation in the local cortical folding pattern. We also investigated the effect of one well characterized morphological variation, the incidence of the paracingulate sulcus (PCS), on regional volumes in 24 (12 male, 12 female) healthy participants. The presence of a PCS was shown to affect both ACC and PaC volumes, such that it was associated with an 88% increase in paracingulate cortex and a concomitant 39% decrease in cingulate cortex. These findings illustrate the potential confounds inherent in morphometric approaches that ignore or attempt to minimize inter-individual variations in sulcal and gyral anatomy and underscore the need to consider this variability when attempting to understand disease processes or characterize brain structure-function relationships.

Adult↗

PubMedDate not supplied

Isolation and characterization of metastatic sublines from a murine transitional cell bladder carcinoma.

Four sublines of a murine N-[4-(5-nitro-2-furyl)-2-thiazolyl]-foramide (FANFT)-induced transitional cell carcinoma (MBT-2) possessing spontaneous metastatic ability were isolated via in vivo/in vitro serial selection of metastatic lung lesions. Subcutaneous inoculation of the parent cell line (MBT-2) produced primary tumors when injected into C3H mice. These primary tumors rarely metastasize. A subline designated L3F1 was established from 1 MBT-2 pulmonary metastatic tumor. Further in vivo/in vitro selections established three additional sublines designated L3F2, L3F3 and L3F4. Serial selection resulted in MBT-2 sublines of greater metastatic potential in terms of both incidence of metastasis and the number of metastatic tumors per lung. The parent line differed from the four sublines in metastatic potential, in vitro cell morphology, and in vitro growth parameters. The L3F2 subline was examined for the time of onset of metastasis by removal of the primary tumor. Metastasis of the subcutaneously transplanted tumor occurred between 14 and 21 days after injection of the L3F2 subline. The L3F2 primary tumors and lung metastases were morphologically characterized by light and electron microscopy.

Animals↗

PubMed1999

Developmental analysis of the evolutionary origin of vegetative propagules in Mimulus gemmiparus (Scrophulariaceae).

Mimulus gemmiparus (Scrophulariaceae), a rare endemic of Colorado, has a novel life history that depends on an unusual method of vegetative reproduction. The plants are functionally annuals; however, reproduction is asexual via propagules that have been termed gemmae. The morphological identity and the evolutionary antecedent of these propagules are unclear. We approached this problem through comparative developmental analyses of M. gemmiparus and the presumed progenitor species, Mimulus guttatus. In M. gemmiparus there are two meristems initiated in the axil of each leaf primordium. The distal meristem has the potential to produce either a lateral branch or a flower, and the proximal meristem becomes a vegetative propagule (the gemma) that is ultimately surrounded by an expanded, ensheathing petiole. The first leaves of the propagules are thickened and are the site of nutrient storage. Consequently, these propagules can be characterized morphologically as brood bulbils. Mimulus guttatus also has two meristems in each leaf axil; however, the proximal meristem typically remains dormant and serves no function in the life history of this species. Based on architectural and developmental correspondence, we hypothesize that the propagule of M. gemmiparus is homologous to the proximal meristem of M. guttatus. Comparative analysis shows that evolution of the bulbil has involved both the incorporation of features present in shoots of M. guttatus and the acquisition of novel features.

Journal Article↗

PubMed1984

Ultrastructure of trypan blue-induced ocular defects II. Cornea and mesenchyme.

Using scanning and transmission electron microscopy, the histological and cytological alterations induced in the developing eye by trypan blue were examined. Microphthalmic and anophthalmic eyes were analyzed from 16-day rat fetuses whose dams had received a teratogenic dose of trypan blue. Cell and tissue damage within cornea and mesenchyme were assessed. Corneas from the treated groups were undulating and uneven owing to abnormal lens placement and corneal cell injury. Extensive extracellular spacing, few cell-to-cell contacts, patchy glycocalyces, and abnormal surface morphology characterized the corneal cells of treated tissues. Mesenchyme of severely malformed eyes typically filled the eye field in regions normally occupied by retina and lens. As a tissue, mesenchyme lacked organization and those surface features normally present in component cells were altered. Mesenchymal cells were packed so closely that extracellular spaces were nearly obliterated. Microvilli, filopodia, and lamellipodia, cell processes observed in normal mesenchyme, were altered in both number and structure. The cytoplasm of mesenchymal cells was condensed and decreased in volume. These data suggested that 1) in this trypan blue ocular model, virtually all major tissue types were morphologically altered; 2) because healthy mesenchyme and cornea are required for normal development of lens, optic vesicle and ocular adnexa it follows that abnormal cornea and mesenchyme also will compromise these tissues; and 3) since necrotic reminants were not present, this trypan blue model probably causes developmental arrest. The most likely teratogenic pathway is presented with emphasis on the cell surface as a probable site of dye action.

Abnormalities, Drug-Induced↗