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Biomedical subjects

P Seifert

Publications and source records attributed to P Seifert.

At least 37 records · Page 2Linked to original sources
PubMed1998

Capillaries in the epithelium of pterygium.

AIM: To present new morphological observations of intraepithelial capillaries in pterygium and to provide some explanations for this phenomenon. METHODS: The ultrastructural features of pterygia from 26 patients were examined. Surgically excised tissue was processed for conventional light and transmission electron microscopy. RESULTS: Individual capillaries within the epithelium of the anterior half towards the head of pterygia were identified in 11 specimens out of 26 pterygia examined (42.3%). The perivascular connective tissue of the intraepithelial capillaries contained fibroblasts, collagen fibrils, and elastin-like material. Epithelial cells surrounding these capillaries showed defects in the basal lamina in contrast with the continuous basal lamina of the endothelium. In the intercellular space of the epithelium an amorphous substance, occasional fibroblast processes, and collagen fibrils were frequently observed. CONCLUSION: Capillaries in the epithelium of pterygia are rare, but not exceptional. The ingrowth of these vessels from the stroma into the epithelium can be interpreted as a reaction to hypoxia or deficiency of any other substance transported via the bloodstream. Apparently, the perivascular connective tissue can be used by ingrowing fibroblasts as a migration pathway. The migrating fibroblasts appear to use the defects of the epithelial basal lamina (whether partially or complete) in order to reach the intercellular space. It is possible that collagen fibrils in the epithelial intercellular space have been laid down by fibroblasts which contribute to the pathological dedifferentiation of the conjunctival epithelium.

Adult↗
PubMed1998

Design-Dependent Variations in Coronary Stent Stenosis Measured as Precisely by Angiography as by Histology.

BACKGROUND: Coronary stent restenosis is a growing clinical concern which, because restenosis may vary with stent design, requires a validated, accurate, and sensitive method of evaluation as new stents are developed. Histologic analysis of arterial cross sections, a highly accurate tool in animal models, has limited applicability in humans. Quantitative coronary angiography, while commonly used in the clinical evaluation of coronary interventions, has a controversial role as an adequate measure of restenosis, and few studies have validated quantitative angiography in diseased arteries. We tested the hypothesis that in-stent stenosis could be assessed as accurately by pre-mortem angiography as by post-mortem histology, allowing angiographic discrimination of variable late luminal loss provoked by stents of different designs. METHODS AND RESULTS: Stent stenosis in porcine coronary arteries was assessed by quantitative coronary angiography and histology at 3, 28 and 56 days. Four stainless steel stent designs were studied: a slotted tube configuration with or without a polymer wrap and a corrugated ring configuration with or without a polymer coating. Although acute luminal gain (mean stent:artery ratio 1.07 +/- 0.01) and stent recoil (mean stent diameter at follow-up 2.65 +/- 0.02 mm) were similar for all designs and time points, significant differences in late luminal loss were observed and were detected as accurately by angiography as by histology. At 28 days, the polymer wrapped slotted tube design resulted in a nearly two-fold greater late loss than its bare metal counterpart (1.40 +/- 0.09 mm vs. 0.80 +/- 0.12 mm, p <.001 by angiography; 1.33 +/- 0.10 mm vs. 0.67 +/- 0.06 mm, p <.0001 by histology), while there was no significant difference in 28 day late loss between the polymer coated and bare metal corrugated ring designs (p = NS by angiography or histology). Time point differences were also observed both angiographically and histologically, with marked progression of lumen loss between 3 and 28 days and slower but persistent progression between 28 and 56 days. Overall comparison of individual lumen diameter measurements for all stented arteries independent of design or duration of follow-up demonstrated a precise correlation between angiography and histology (y = 0.96x +0.25, p <.0001, r2 = 0.82). CONCLUSIONS: Coronary stents of varied designs provoke markedly different degrees of late luminal loss, and these differences can be measured as accurately by quantitative angiography as by histologic analysis of arterial cross sections. This may be due to optimization of angiographic measurements by the concentric nature of intimal thickening in stented arteries, and to structural rigidity imparted by the stent, preserving arterial lumen size for histologic analysis. Quantitative angiography, therefore, may represent an adequate endpoint in clinical trials comparing stent designs.

Journal Article↗
PubMed1998

Design-Dependent Variations in Coronary Stent Stenosis Measured as Precisely by Angiography as by Histology.

BACKGROUND: Coronary stent restenosis is a growing clinical concern which, because restenosis may vary with stent design, requires a validated, accurate and sensitive method of evaluation as new stents are developed. Histologic analysis of arterial cross sections, a highly accurate tool in animal models, has limited applicability in humans. Quantitative coronary angiography, while commonly used in the clinical evaluation of coronary interventions, has a controversial role as an adequate measure of restenosis, and few studies have validated quantitative angiography in diseased arteries. We tested the hypothesis that in-stent restenosis could be assessed as accurately by pre-mortem angiography as by post-mortem histology, allowing angiographic discrimination of variable late luminal loss provoked by stents of different designs. METHODS AND RESULTS: Stent stenosis in porcine coronary arteries was assessed by quantitative coronary angiography and histology at 3, 28 and 56 days. Four stainless steel stent designs were studied: a slotted tube configuration with or without a polymer wrap and a corrugated ring configuration with or without a polymer coating. Although acute luminal gain (mean stent:artery ratio of 1.07 +/- 0.01) and stent recoil (mean stent diameter at follow-up 2.65 +/- 0.02 mm) were similar for all designs and time points, significant differences in late luminal loss were observed and were detected as accurately by angiography as by histology. At 28 days, the polymer wrapped slotted tube design resulted in a nearly two-fold greater late loss than its bare metal counterpart (1.40 +/- 0.09 mm vs. 0.80 +/- 0.12 mm, p <.001 by angiography; 1.33 +/- 0.10 mm vs. 0.67 +/- 0.06 mm, p <.0001 by histology), while there was no significant difference in 28 day late loss between the polymer coated and bare metal corrugated ring designs (p = NS by angiography or histology). Time point differences were also observed both angiographically and histologically, with marked progression of lumen loss between 3 and 28 days and slower but persistent progression between 28 and 56 days. Overall comparison of individual lumen diameter measurements for all stented arteries independent of design or duration of follow-up demonstrated a precise correlation between angiography and histology (y = 0.96x +0.25, p <.0001, r2 = 0.82). CONCLUSIONS: Coronary stents of varied designs provoke markedly different degrees of late luminal loss, and these differences can be measured as accurately by quantitative angiography as by histologic analysis of arterial cross sections. This may be due to optimization of angiographic measurements by the concentric nature of intimal thickening in stented arteries, and to structural rigidity imparted by the stent, preserving arterial lumen size for histologic analysis. Quantitative angiography, therefore, may represent an adequate endpoint in clinical trials comparing stent designs.

Journal Article↗
PubMed1998

Comparison of models used for UV index calculations.

Eighteen radiative transfer models in use for calculation of UV index are compared with respect to their results for more that 100 cloud-free atmospheres, which describe present, possible future and extreme conditions. The comparison includes six multiple-scattering spectral models, eight fast spectral models and four empirical models. Averages of the results of the six participating multiple-scattering spectral models are taken as a basis for assessment. The agreement among the multiple-scattering models is within +/- 0.5 UV index values for more than 80% of chosen atmospheric parameters. The fast spectral models have very different agreement, between +/- 1 and up to 12 UV index values. The results of the empirical models agree reasonably well with the reference models but only for the atmospheres for which they have been developed. The data to describe the atmospheric conditions, which are used for the comparison, together with the individual results of all participating models and model descriptions are available on the Internet: http://www.meteo.physik.uni-muenchen.de/++ +strahlung/cost/.

Computer Simulation↗
PubMed1997

Distribution pattern of nervous tissue and peptidergic nerve fibers in accessory lacrimal glands.

PURPOSE: Demonstration of the distribution pattern of nervous tissue and the occurrence of neuropept human accessory lacrimal glands by means of immunohistochemical methods. METHODS: Paraffin sections of tissue samples were incubated with antisera against protein gene product (PGP), S-100 protein (S-100), calcitonin gene-related peptide (CGRP) and substance P (SP). The immunoreactions were visualized using both species-specific secondary antibodies and a streptavidin-biotin-peroxidase complex (ABC method). RESULTS: PGP- and S-100-immunoreactive nerve fibers were distributed in the entire intertubular stroma. In addition, myoepithelial cells, a few clusters of tubulus cells, groups of wandering cells, and scattered cells of the excretory duct system were S-100-immunoreactive. CGRP- and SP-immunoreactivity was found in a few nerve fibers in the intertubular glandular stroma with an association to secretory tubules, blood vessels, intralobular ducts and excretory duct. CONCLUSIONS: These observations are in agreement with findings in the main lacrimal gland.

Adult↗
PubMed1997

Tsukamurella tyrosinosolvens sp. nov.

Chemotaxonomic and 16S ribosomal DNA sequence analyses of four bacterial isolates from blood cultures from patients with cardiac pacemaker implants and sputa of patients with chronic lung infections clearly demonstrated that these bacteria belong to the genus Tsukamurella. DNA-DNA hybridization data, as well as the physiological characteristics of the isolates, indicate that they are closely related and belong to a single species that differs from previously described members of the genus Tsukamurella. The name Tsukamurella tyrosinosolvens sp. nov. is proposed for these isolates, and the new species is represented by strain IMMIB D-1397T (= DSM 44234T). Strain IMMIB D-1397T exhibits 53.4, 53.5, and 54.7% DNA-DNA relatedness to Tsukamurella paurometabola DSM 20162T, Tsukamurella inchonensis DSM 44067T, and Tsukamurella pulmonis DSM 44142T, respectively.

Actinomycetales↗
PubMed1997

Description of Nocardiopsis synnemataformans sp. nov., elevation of Nocardiopsis alba subsp. prasina to Nocardiopsis prasina comb. nov., and designation of Nocardiopsis antarctica and Nocardiopsis alborubida as later subjective synonyms of Nocardiopsis dassonvillei.

Data from chemotaxonomic and 16S ribosomal DNA sequence analyses of an isolate obtained from the sputum of a kidney transplant patient identified the isolate as a member of the genus Nocardiopsis. DNA-DNA hybridization data, as well as physiological characteristics, indicated that the isolate represents a new species of the genus Nocardiopsis, designated Nocardiopsis synnemataformans; the type strain is strain IMMIB D-1215 (= DSM 44143). In addition, DNA-DNA hybridization data, as well as the results of biochemical tests, indicated that Nocardiopsis alborubida DSM 40465T, Nocardiopsis antarctica DSM 43884T, and Nocardiopsis dassonvillei DSM 43111T represent a single species designated N. dassonvillei. We also found that Nocardiopsis alba subsp. alba DSM 43377T and N. alba subsp. prasina DSM 43845T are genetically different and therefore propose that N. alba subsp. prasina be elevated to species status as Nocardiopsis prasina comb. nov., whose type strain is strain DSM 43845.

Base Composition↗
PubMed1996

Regulation by adrenocorticotropic hormone of the in vivo expression of scavenger receptor class B type I (SR-BI), a high density lipoprotein receptor, in steroidogenic cells of the murine adrenal gland.

The class B, type I scavenger receptor, SR-BI, binds high density lipoprotein (HDL) and can mediate selective uptake of HDL cholesteryl esters by cultured cells. The high levels of expression of SR-BI in steroidogenic tissues and the importance of selective uptake from HDL as a source of cholesterol for steroidogenesis raised the possibility that SR-BI may participate in cholesterol delivery to steroidogenic tissues in vivo. We have used immunoblotting and immunohistochemical methods to show that SR-BI is specifically expressed in a distinctive pattern on the surfaces of steroid-producing cells in the murine adrenal gland's cortex and that its expression in vivo is induced by adrenocorticotropic hormone and suppressed by glucocorticoids. Thus, expression of SR-BI protein is coordinately regulated with adrenal steroidogenesis. These data provide strong support for the hypothesis that SR-BI is a physiologically relevant HDL receptor that provides substrate cholesterol for steroid hormone synthesis.

Adrenal Glands↗
PubMed1996

Endogenous cell seeding. Remnant endothelium after stenting enhances vascular repair.

BACKGROUND: Endothelial integrity is essential for maintaining vascular homeostasis, and endothelial denudation results in neointimal thickening. Balloon-expandable endovascular stents provide a luminal scaffolding within atherosclerotic arteries with minimal direct contact between balloon and endothelium. We wondered whether stents cause diminished endothelial ablation, and if so, whether the degree of endothelial damage might determine later proliferative sequelae. METHODS AND RESULTS: Stainless steel stents were expanded in normal or previously denuded iliac arteries of New Zealand White rabbits. Stented arteries were harvested 15 minutes, 1 hour, 3 days, or 14 days later. En face staining of the luminal surfaces of stented arteries demonstrated that endothelial cell loss began immediately after stent expansion and was restricted to interstices between stent struts. Remnant endothelium adjacent to struts provided the foundation for complete endothelial regeneration of the stented segment within 3 days. Both early monocyte adhesion and later intimal macrophage accumulation were reduced > 80% in nonballooned but stented arteries, in concert with a twofold reduction in intimal thickening after 14 days, compared with arteries completely denuded with a balloon before stent expansion. CONCLUSIONS: It is accepted that deep injury caused by balloon-expanded endovascular stents is a critical contributor to experimental stent-induced neointimal hyperplasia. Our data indicate that the degree of endothelial injury may also be an important component of vascular repair after stenting and an important consideration in stent and balloon design and use. The use of stents for primary endovascular intervention may allow partial retention of endothelium within treated arteries, thereby modulating vascular repair with less need for adjunctive pharmacological therapy.

Angioplasty, Balloon↗
PubMed1996

Organ culture of human main and accessory lacrimal glands and their secretory behaviour.

The purpose of this study was to investigate the in vitro viability and secretory behaviour of human main and accessory lacrimal glands using an organ culture technique. We evaluated the influence of the second messengers cAMP and cGMP on secretion. Fragments less than 1 mm3 of main and accessory lacrimal glands as well as conjunctiva were cultured for 2-72 hr at 37 degrees C in an atmosphere consisting of 50% O2, 45% N2 and 5% CO2, using a specially devised culture medium (+/- cAMP or cGMP). The conjunctival tissue served as negative control. Supernatants were assayed for secretory-component-bound IgA, lactoferrin and lysozyme using ELISA. Cultured tissue pieces were embedded in paraffin, serially sectioned, stained and their volumes calculated using an image-analysis system. This enabled us to differentiate between secretory, connective and fatty tissue. Secreted exudate was correlated to the volume of secretory tissue. Viability of cultured organ pieces was determined by electron microscopic examination. Suitable organ culture conditions for human lacrimal glands were successfully established. Electron microscopic examinations proved that the structural characteristics of the organ and the polarity of the individual cells were well preserved up to 22 days of culture. Culture supernatants were assayed for secretory-component-bound IgA, lactoferrin, and lysozyme and showed that the amount of protein secreted increased with time. Upon addition of cAMP (1 x 10(-3) M) and cGMP (4 x 10(-3) M), secretion was elevated in both main and accessory lacrimal glands. An organ culture system for lacrimal glands was developed that maintains their structural and cellular characteristics as well as their secretory function for up to 22 days. We believe that this system mimics the in vitro state of the organ better than monolayer cultures and thus proves to be a valuable tool when examining lacrimal function in vitro. The fact that both cAMP and cGMP enhance secretion may help to shed some light on the cellular pathways human main and accessory lacrimal glands use for signal transduction.

Animals↗
PubMed1996

Immunocytochemical and ultrastructural evaluation of the distribution of nervous tissue and neuropeptides in the meibomian gland.

BACKGROUND: The ultrastructure of the meibomian gland, of its innervation and the localization of neuropeptides in the glandular tissue of the guinea pig and humans are incompletely known. Therefore they have been investigated in the present study. METHODS: The ultrastructure of the tissue was examined using standard transmission electron microscopic techniques. Additional scanning electron microscopy was carried out on rabbit tissue. Antisera against the neuronal marker protein gene product were used to demonstrate the distribution pattern of the nerve fibers. The neuropeptides substance P (SP) and neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP) and the neuronal enzyme tyrosine hydroxylase (TH) were identified by their specific antisera. RESULTS: The glands were found to be composed of arrays of alveoli. The outer cells of the alveoli form a germinal layer. Toward the inside of the alveolus the cells are laden with a secretory substance. The cells disintegrate as they approach the excretory duct. Nerve fibers form a plexus around the alveoli. These nerve fibers form synapses à distance to the basal alveolar cells and enter the basal lamina of the capillaries. In guinea pigs many nerve fibers were positive for the neuropeptides SP and NPY and for VIP, and fewer for CGRP and TH; in humans only SP and CGRP were demonstrated. CONCLUSION: Both the density of nerve fibers and the presence of various neuropeptides suggest that the stimulation of the meibomian gland is subject to nervous control.

Animals↗
PubMed1996

Differential distribution of neuronal markers and neuropeptides in the human lacrimal gland.

BACKGROUND: The present study was undertaken in an attempt to broaden the spectrum of known neuronal markers and neuropeptides in the main lacrimal gland of the human by light-microscopic immunohistochemistry. METHODS: Using antisera against the neuronal markers protein gene product (PGP) and S-100 protein (S-100), the distribution of nerve fibers in the human main lacrimal gland was studied. Vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were identified by their specific antisera. RESULTS: The nerve fibers are distributed throughout the interstice between the glandular tubules. Associations were also found between nerve fibers and both the interlobular ductal system and blood vessels (mainly arterioles). Within the glandular lobules isolated groups of secretory cells stained positive for S-100 protein. Nerve fibers situated in the glandular interstice between the tubules showed predominantly positive immunoreactions for the neuropeptide VIP, while only very few fibers stained positive for CGRP, NPY and the catecholamine marker TH. Nerve fibers associated with interlobular blood vessels were mainly CGRP and NPY positive and stained only very rarely for VIP. The epithelia of interlobular ducts and excretory ducts were associated with CGRP-immunoreactive nerve fibers. CONCLUSION: The neuropeptides identified in the lacrimal gland indicate the complexity with which a variety of biologic signals regulate and modulate the lacrimal gland.

Animals↗
PubMed1996

Tsukamurella pulmonis sp. nov.

Chemotaxonomic and 16S ribosomal DNA sequence analyses of an isolate from the sputum of a patient with a mycobacterial lung infection clearly delineated a new species of the genus Tsukamurella. This new species can be defined on the basis of genotypic and phenotypic data. The name Tsukamurella pulmonis sp. nov. is proposed for this organism; the type strain is IMMIB D-1321T (= DSM 44142T). This isolate shows 44.2 and 36.2% DNA relatedness to Tsukamurella paurometabola DSM 20162T (T = type strain) and Tsukamurella inchonensis DSM 44067T, respectively.

Aged↗
PubMed1996

Monoclonal corneal gammopathy: topographic considerations.

Desposition of immunoglobulins in the cornea occasionally occurs in benign and malignant lymphoproliferative conditions. A 52-year-old woman with recently discovered monoclonal gammopathy of undetermined significance (MGUS) was referred to our hospital. Slit-lamp and ultrasound biomicroscopy revealed bilateral deposits within all corneal layers. The precipitates were organized in a circle, leaving a perilimbal zone and the axial cornea clear. Light microscopy of a biopsy disclosed confluent subepithelial deposits and defects in Bowman's layer. Immunoperoxidase reaction was positive only for IgG and IgG-kappa. Transmission electron microscopy confirmed the presence of extracellular rectangular and arcuate immunoglobulin crystalloids with a 10-nm periodicity but a non-crystalline defraction pattern. A review of the literature showed that the circumferential pattern of immunoglobulin deposition is associated with short-term visual symptoms and good visual acuity. The present report supports a hypothesis of immunoglobulin deposition via the limbal arcade and contradicts the "tear theory."

Biopsy↗
PubMed1994

Demonstration of nerve fibers in human accessory lacrimal glands.

To provide morphologic evidence for the innervation of accessory lacrimal glands, glands were biopsied and examined using standard transmission electron microscopic techniques. Non-myelinated nerve fibers were found in the connective tissue between the glandular epithelia where they made contact with glandular epithelial cells, myoepithelial cells, vascular endothelial cells, plasma cells and fibroblasts. The distances measured between axons and target cells ranged from 30 to 130 nm. Where nerve fibers approached cells sustaining a basement membrane, their basement membranes fused to form a discrete unit resembling so-called 'synapses à distance'. Cells with no basement membrane were situated in direct contact with the basement membrane of a nerve fiber. Single axons were identified between glandular epithelial cells and cells of intralobular ducts. Most of these axons contained many small clear vesicles and a few large, dense core vesicles, a finding considered typical of cholinergic parasympathetic nerve fibers. In addition, one of the axons identified contained small dense core vesicles typical of sympathetic nerve fibers. Human accessory lacrimal glands are therefore definitely innervated, with parasympathetic structures morphologically prevailing over sympathetic structures.

Axons↗
PubMed1993

Enameloid formation in two tetraodontiform fish species with high and low fluoride contents in enameloid.

Forming teeth of parrotfish and pufferfish were viewed by transmission electron microscopy to correlate cytological features of the enameloid organ with the species' fluoride (F) content in mature enameloid. Secretory-stage inner dental epithelial cells (IDE) of parrotfish (high F) and pufferfish (low F) secreted procollagen granules into the enameloid collagen matrix. The odontoblasts of both species, less numerous than IDE cells, also contained procollagen granules at the enameloid matrix formation stage. After the full thickness of enameloid matrix collagen had been deposited, enameloid crystallites formed parallel to the long axis of the enameloid collagen fibres. Concurrently, the plasma membranes of the outer dental epithelial cells (ODE) became invaginated in both species, but to a much greater extent in parrotfish. Highly undulating parrotfish ODE cells surrounded numerous fenestrated capillaries. In contrast, pufferfish ODE cells remained straight with few adjacent capillaries. Extensive tight junctions formed between ODE and IDE cells of both species, sealing the extracellular space. With increased mineralization, enameloid collagen fibres were no longer discernible. A thin layer of amorphous material, which subsequently mineralized, was secreted on to the enameloid surface by IDE cells in both species. Pufferfish odontoblasts secreted a mineralizing amorphous layer on the pulpal aspect of the enameloid. The results suggest that at the mineralization stage, a triad of cytostructural features, highly invaginated ODE cells, highly vascularized ODE cells, and extensive tight junctions are strongly correlated with high fluoride content of mature enameloid mineral. Species without any one of these features have lower fluoride in the enameloid.

Animals↗
PubMed1993

The architecture of human accessory lacrimal glands.

Human accessory lacrimal glands were examined both light and electron microscopically and their gross architecture was reconstructed from serial sections. Every accessory lacrimal gland nodule is an individual organ with its own connective tissue coat and excretory duct. Within the gland proper, the excretory duct ramifies to form intralobular ducts, which are connected to the secretory glandular epithelia. The secretory epithelia are composed of elongated tubules terminating in short end pieces with lumina of variable width. True acini are absent. Thus, the accessory lacrimal glands are tubular glands. The cells of tubules and end pieces contain large secretory granules suggestive of a regulated mechanism of secretion. The content of organelles and the amount of secretory material present in neighboring cells can show pronounced differences. Both end pieces and tubules and, to a lesser extent, the intralobular ducts are surrounded by myoepithelial cells. The interstitial connective tissue contains blood vessels, free cells, and fibroblasts. Axons of nonmyelinated nerve fibers are in close spatial contact to vascular endothelial cells, connective tissue cells, free cells, and glandular epithelial cells. A few axons with parasympathetic characteristics and, less frequently, with sympathetic characteristics were identified between the epithelial cells of both secretory epithelium and intralobular ducts.

Blepharoptosis↗