Decreased neointimal formation in Mac-1(-/-) mice reveals a role for inflammation in vascular repair after angioplasty

Inflammation plays an essential role in the initiation and progression of atherosclerosis, but its role in vascular repair after mechanical arterial injury (i.e., percutaneous transluminal coronary angioplasty, PTCA) is unknown. In animal models of vascular injury, leukocytes are recruited as a precursor to intimal thickening. Furthermore, markers of leukocyte activation - in particular, increased expression of the beta2-integrin Mac-1 (alphaMbeta2, or CD11b/CD18), which is responsible for firm leukocyte adhesion to platelets and fibrinogen on denuded vessels - predict restenosis after PTCA. To determine whether Mac-1-mediated leukocyte recruitment is causally related to neointimal formation, we subjected mice lacking Mac-1 to a novel form of mechanical carotid artery dilation and complete endothelial denudation. We now report that the selective absence of Mac-1 impairs transplatelet leukocyte migration into the vessel wall, reducing leukocyte accumulation over time. Diminished medial leukocyte accumulation was accompanied by markedly reduced neointimal thickening after vascular injury. These data establish a role for inflammation in neointimal thickening and suggest that leukocyte recruitment to mechanically injured arteries may prevent restenosis.

Vasoactive intestinal polypeptide (VIP) innervation of the human eyelid glands

This study was conducted to obtain morphological proof of innervating nerve fibres in the glands of the human eyelid (accessory lacrimal glands of Wolfring, meibomian glands, goblet cells, glands of Zeis, glands of Moll, sweat glands, glands of lanugo hair follicles) and identification of the secretomotorically active neuropeptide vasoactive intestinal polypeptide (VIP) as a common transmitter. Epoxy-embedded ultrathin sections of tissue samples from human eyelids were studied using electron microscopy. Paraffin sections fixed in Bouin-Hollande solution were immunostained with rabbit antiserum against VIP. With the electron microscope we were able to identify nerves in the glandular stroma of all the glands examined with the exception of goblet cells. Intraepithelial single axons were only seen in the parenchyma of Wolfring glands. The morphological findings corresponded with the immunological finding of VIP-positive, nerve-like structures in the same locations, with the exception of lanugo hair follicle glands, and goblet cells. Our findings indicate that the glands of the eyelids and main lacrimal gland represent a functional unit with VIP as a possible common stimulating factor.

Acute corneal necrosis after excimer laser keratectomy for hyperopia

OBJECTIVE

To describe a new, rare clinical complication after routine excimer laser photorefractive keratectomy to correct hyperopia.

DESIGN

Case report with clinicopathologic correlation.

MAIN OUTCOME MEASURES

Four weeks after treatment with excimer laser, a perforating keratoplasty was performed for persistent corneal opacities. The corneal button was examined using light and electron microscopy. Special immunohistochemical stains were used to detect apoptosis.

RESULTS

The patient developed corneal opacities, endothelial precipitates, and a fibrinous exudate in the anterior chamber after the laser treatment. The changes did not respond to therapy directed against bacteria, fungi, and Acanthamoeba. All examinations and special stains were negative for micro-organisms. By light microscopy, an anterior zone of corneal necrosis was present with a moderate amount of acute inflammatory cells. At the interface between necrotic and viable corneal stroma, keratocytes with typical features of apoptosis were detected by immunohistochemistry and electron microscopy.

CONCLUSION

This is the first full histopathologic report of a case of acute corneal necrosis with signs of apoptosis after excimer laser therapy of the cornea. Surgeons should be aware of this rare but potentially severe complication.

Long-term ultrastructural changes in human corneas after tattooing with non-metallic substances

AIM

To investigate the ultrastructural appearance and the deposition pattern of dye particles in long term non-metallic corneal tattooing.

METHODS

Two tattooed human corneas were obtained by keratoplasty. One corneal button was fixed in Karnovsky's solution and the other in Trumps' solution. Both corneas were divided and processed for conventional light (LM) and transmission electron microscopy (TEM). Five additional formalin fixed corneas with tattoos were retrieved from paraffin for TEM. The time between tattoo and removal of the corneal button/enucleation ranged from 7 to 61 years. All seven corneas were examined using a Jeol JCXA733 microprobe for wave length dispersive analysis in order to exclude any presence of metallic salts in the tattooed area.

RESULTS

Histologically, clumps of brown-blackish granules were present mainly in the mid stroma, but also in anterior and partially in the posterior half of the stroma. On TEM, numerous round and oval electron dense particles were seen in the cytoplasm of keratocytes arranged as clusters or large islands. The larger particles appeared black, while the smaller particles were grey. In well fixed tissue a unit membrane was observed around these clusters. No granules were detected in the extracellular matrix.

CONCLUSIONS

Keratocytes can actively ingest and retain tattooing particles of non-metallic dyes within their cell membrane for very long periods of time.

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/.

Hydroxyapatite orbital implant. A light- and electron-microscopic and immunohistochemical study

OBJECTIVE

This study aimed to characterize the constituents of the ingrown host tissue in explanted orbital coral spheres by means of light electron microscopy and immunohistochemistry and to compare findings at different intervals after implantation.

DESIGN AND METHODS

A microscopic retrospective laboratory study of three explanted coral spheres from three different patients was undertaken. The first specimen was an infected hydroxyapatite orbital implant, which was removed after 18.5 months and processed for standard light microscopy and transmission electron microscopy. Immunohistochemistry was performed using vimentin, actin, CD-68, and CD-34 marker. Two other explanted spheres (after 3 weeks and 2.5 months) were examined by light microscopy only, because no fibrovascular ingrowth could be detected.

RESULTS

On light microscopy, the pores of the first coral were filled entirely with the fibrovascular tissue. A basophilic line reminiscent of calcium deposition was seen along hydroxyapatite spicules, where it often was associated with newly formed bony lamellae. Similar lines were seen partially in the 2.5-month specimen but not in the 3-week specimen. Immunohistochemistry of the first specimen enhanced visualization of the capillary network when the CD-34 marker was used. The fibrovascular tissue was uniformly vimentin-positive and partially actin-positive. On transmission electron microscopy, typical fibroblasts and myofibroblasts were observed. The latter were separated by thin sheets of banded collagen and formed pseudoepithelial structures. Proliferating vessels often showed high endothelial cells.

CONCLUSIONS

The fibrovascular ingrowth contains not only vimentin-positive regular fibroblasts but also actin-positive myofibroblasts. Interaction between the invading tissue and hydroxyapatite structures leads to long-term ossification.

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.

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.

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.

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.

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.

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.

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.

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."

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.

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.

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.

Ultrastructure of the anterior lens capsule after vitrectomy with silicone oil injection. Correlation of clinical and morphological features

To clarify the mechanical difficulties experienced when performing anterior capsulorhexis in vitrectomized eyes filled with silicone oil. Five anterior lens capsules removed from eyes with a silicone oil history were submitted to light and electron microscopic analysis and then compared to two capsules from eyes with trauma history and seven capsules from eyes without silicone oil or trauma history. Comparable abnormalities of the inner and outer surface of the anterior lens capsule were consistently observed after silicone oil fill of the vitreous cavity or after traumatic impact to the lens: patches of multilayer epithelial cells with interspersed capsule material and connective tissue were observed on the posterior surface of the anterior lens capsule. The development of this anterior subcapsular tissue plaque is obviously influenced not only by the PVR process or by side effects of the surgical procedure but also by the silicone oil tamponade or a trauma history. The plaque can be considered primarily responsible for the increased mechanical resistance of the lens capsule in all eyes with silicone oil / trauma history examined in this study.

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.

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.

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.

Serum fluoride level and fluoride content of enameloid

We investigated diverse groups of fish species to determine whether the fluorine (F) contents of the dental hard tissues were related to baseline serum F levels. Serum samples, enameloid, dentin, ganoid/enamel, and bone were analyzed for F by either electron microprobe or wet chemistry. Species were categorized into two groups based on the F content of the enameloid. One group contained greater than 2.6 wt% F in enameloid, whereas the other group had less than 0.45 wt% F in enameloid. The dentin and bone from all species (or, in skates, the cartilage), as well as the ganoid/enamel layer of a Holostean fish (alligator gar), showed consistently low F content. In those species whose teeth developed in sequential rows, the F content of enameloid increased with progressive tooth development. The serum F levels of all fish were below 0.05 microgram F/mL (2.63 mumol/L) and were not significantly related to the F content of the enameloid. The results substantiate the idea that F incorporation into enameloid is related to fish phylogeny, not food or habitat. It is suggested that specialized outer dental epithelial cell configurations may facilitate the incorporation of F into enameloid.