Cell-specific expression of the parathyroid hormone (PTH)/PTH-related peptide receptor gene in kidney from kidney-specific and ubiquitous promoters

The kidney is the major site of expression of the PTH/PTH-related peptide receptor (PTHR) gene. Previously we have shown that the PTHR gene is expressed from two promoters in kidney, an upstream kidney-specific promoter (P1) and a downstream promoter (P2) that is active in a wide variety of tissues. Here, we have used immunohistochemical and transcript-specific in situ hybridization techniques to map the expression of the PTHR gene and protein and to determine the distribution of P1- and P2-driven messenger RNAs in renal tissue. Immunohistochemical and immunoelectron microscopic analysis showed that PTHR protein is expressed on both basolateral and luminal membranes of proximal tubular epithelial cells, strongly suggesting a bipolar mode of action of PTH. Receptor protein also was detected on the surface of glomerular podocytes. Strikingly, immunoelectron microscopic analysis showed that endothelial cells of the peritubular vasculature, but not the glomerular vasculature, contain high levels of PTHR protein. We found that both P1 and P2 are expressed at moderate levels in both cortical and medullary epithelial cells of nephrons, correlating well with the immunohistochemical localization of PTHR protein. However, although abundant transcripts were detected in peritubular endothelial cells with P1-specific and coding sequence probes, P2-specific expression was not observed in these cells. These results provide evidence that the physiological effects of PTH- and/or PTH-related peptide on renal tubular function may be mediated not only through direct effects on epithelial cells but also indirectly through endothelial cell-based signaling. In addition to expression in vascular endothelial cells, high levels of P1-specific, but not P2-specific, PTHR messenger RNA were detected in vascular smooth muscle. Taken together, these experiments provide evidence for strong PTHR gene expression in renal vascular tissues. Moreover, given that previous studies have shown that P2, but not P1, is active in other tissues with an abundant vasculature, our results suggest that regulation of PTHR gene expression in renal vascular tissue is distinct from that of other organs.

Alteration of glutamyltranspeptidase binding proteins in postmortem brains of heroin addicts

Glutamyltranspeptidase binding (G) proteins play an important role in intracellular signal transduction downstream from many receptors, including opioid receptors. Moreover, it was recently reported that the beta-subunits of G proteins, in addition to the alpha-subunits, regulate effector pathways. In this study, membrane G protein immunoreactivity was estimated by Western blotting with polyclonal antibodies (RM/1, AS/7, GC/2, QL, and SW/1) against specific G proteins (G alpha S, G alpha i-1,2, G alpha o, G alpha q, and G beta, respectively) in postmortem temporal cortex obtained from 6 heroin addicts and 6 control subjects without a history of drug abuse. Immunoreactivities of the G beta-subunit increased significantly (p < 0.05) in heroin addicts, compared with controls, and that of G alpha i-1,2 tended to increase in heroin addicts. Present findings suggest that the alterations in G protein-mediated signal transduction may be involved in the mechanism of opiate addiction.

A case of moderate hypertriglyceridemia with apolipoprotein E phenotype E4/3

Hyperlipoproteinemic subjects with apo(lipoprotein)E4 are usually hypercholesterolemic and those with apoE2 are hypertriglyceridemic. We report a case of moderate hypertriglyceridemia with apoE phenotype E4/3. Plasma levels of total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL)-C, apoAI, apoB, apoCII, apoCIII, and apoE were 200mg/dL, 451 mg/dL, 31 mg/dL, 115 mg/dL, 99 mg/dL, 10.0 mg/dL, 22.2 mg/dL, and 12.0 mg/dL, respectively. Plasma levels of very low density lipoprotein (VLDL)-C and intermediate density lipoprotein (IDL)-C were high, and those of low density lipoprotein (LDL)-C and HDL2-C were low. All lipoprotein subfractions except VLDL were TG-rich. These findings are common in moderate hypertriglyceridemia. The plasma level of remnant-like particle (RLP, equivalent to chylomicron remnant)-C, was high. The lipoprotein lipase which removes TG from chylomicron and VLDL was normal. The activity of LDL receptor which removes remnants of chylomicron and VLDL as well as LDL was high. ApoE4 actively binds to receptors of remnant and LDL. Thus, the removal of TG-rich lipoproteins should not be impaired in this patient. Plasma levels of insulin during oral glucose tolerance test were high. Hyperinsulinism stimulates VLDL synthesis in the liver. Subjects with apoE4 show active synthesis of chyromicron. Thus, we concluded that the moderate hypertriglyceridemia in this E4/3 patient was due to the overproduction of chylomicron and VLDL.

Reduced immunoreactivity of adenylyl cyclase in dementia of the Alzheimer type

The amounts of three adenylyl cyclase (AC) subtypes in membranes from brain obtained post-mortem from patients with dementia of Alzheimer type (DAT) and controls were studied by Western blotting using polyclonal antibodies. AC subtypes were characterized by preabsorption by complementary peptides, species difference, tissue distribution and by using AC-VI-transfected cells. Immunoreactivities of AC-I and AC-II subtypes, which are predominant in brain tissue were decreased 40.5% (p < 0.02) and 52.0% (p < 0.02), respectively in DAT compared with controls. No significant difference in immunoreactivity of AC-V/VI subtypes distributed in various other tissues was observed. Our results are the first to indicate that reduced levels of brain-specific AC subtypes occur in DAT.

Programmed cell death of chondrocytes and aberrant chondrogenesis in mice homozygous for parathyroid hormone-related peptide gene deletion

In previous work we showed that the chondrodysplastic phenotype of mice homozygous for a null mutation of the PTH-related peptide (PTHrP) gene was due in part to reduced proliferation and aberrant differentiation of growth plate chondrocytes. In the present study we have extended those observations by examining chondrocytes for evidence of PTH/PTHrP receptor expression, proliferation, and programmed cell death. Receptor messenger RNA and protein were expressed in chondrocytes in the resting and proliferative zones of both wild-type and mutant mice. In normal animals, expression was abundant in the area of transition between proliferative and hypertrophic chondrocytes and absent from cells in the lower hypertrophic region. On the other hand, the hypertrophic zone in mutant mice contained nonhypertrophic chondrocytes, which exhibited characteristics of proliferating cells, including PTH/PTHrP receptor expression, [3H]thymidine incorporation, and expression of proliferating cell nuclear antigen. In contrast to the situation in normal animals, some cells adjacent to the zone of vascular invasion in mutant growth plates showed biochemical and morphological evidence of programmed cell death. In addition to these alterations in the maturation of growth plate chondrocytes, homozygous mutants demonstrated signs of aberrant differentiation of periosteal precursor cells. In some specimens, clusters of chondrocytes embedded in a cartilaginous matrix were observed between the layers of periosteal osteoblasts and the bony collar in the sterna and tibiae of mice homozygous for a null mutation of the PTHrP gene. Taken together, these observations indicate that PTHrP plays a pivotal role in the orderly progression of chondrocytes through stages of proliferation, differentiation, and programmed cell death in the epiphyseal growth plate and may also facilitate the commitment of precursors to cells of the chondrocytic or osteoblastic lineages.

[Atherosclerosis and clinical examination: epidemiology of stroke and ischemic heart disease]

We discussed the risk factors for stroke and ischemic heart disease (IHD) as a main atherosclerotic disease. We showed that hypertension was the most principal risk factor for both cerebral hemorrhage and cerebral infarction, and the increase of total cholesterol (TCH) was inversely related with the incidence of cerebral hemorrhage. Many of the cerebral infarctions occurred where a large number of the cerebral hemorrhages did. We indicated that the mechanism of occurrence was different between stroke and IHD. In Japan, TCH has been recognized as a risk factor for IHD as same as western countries, but there are not many IHD. The mean of TCH was lower before one or two decade. But, it has increased in the last decade, and recently is nearing the level of American people in the thirties and forties. Death statistics of IHD became more accurate in Japan by reason for revision of the death certificate form from ICD-9 to ICD-10. The recognition of IHD death statistics will be changed. Incidence of stroke has been decreasing because of the decrease of hypertension. However, we will have to reconsider a preventive measure of IHD.

Immunolocalization of CD44 and the ERM family in bone cells of mouse tibiae

We studied the immunohistochemical localization of CD44, hyaluronate receptor, and the ezrin-radixin-moesin (ERM) family, actin binding proteins, in bone cells using confocal laser scanning microscopy and transmission electron microscopy to clarify the mechanism of the organization of their cytoskeletons. In osteoclasts, intense immunoreactivity to CD44 could be detected on their basolateral plasma membranes. There was less reactivity observed in the area of the plasma membrane in direct contact with the bone surface. The immunogold electron-microscopical method revealed that CD44 was mainly localized on the microvilli of the basolateral plasma membrane. The plasma membrane of the clear zone and the ruffled border were not immunolabeled with CD44. As for the ERM family, the basolateral plasma membrane of osteoclasts was stained with antimoesin monoclonal antibody, but not with ezrin or radixin. In osteoblasts attached to the bone surface, immunoreactivity to CD44 was restricted to their cytoplasmic processes. They showed immunoreactivities to radixin and moesin on the cytoplasmic side of their plasma membrane when in contact with each other. However, although osteocytes in the bone matrix demonstrate an intense immunolabeling with CD44 on their plasma membrane, they scarcely show immunoreactivity to the ERM family. These findings suggest that: (1) the CD44-moesin-actin filament system is involved in the organization of cytoskeletons in the basolateral plasma membrane of osteoclasts; and (2) other mechanisms, rather than the CD44 and the ERM family, may be involved in the cells of osteoblast lineage.

Effects of bisphosphonate (pamidronate) on bone resorption resulting from metastasis of a squamous cell carcinoma: report of an autopsy case and evaluation of bone resorbing activity in an experimental animal model

PURPOSE

This study evaluated the ability of bisphosphonate to prevent bone resorption induced by metastatic tumor cells.

MATERIALS AND METHODS

Autopsy specimens of a bone metastasis from a woman with a primary squamous cell carcinoma of the tongue who developed multiple osteolytic lesions and hypercalcemia and was treated with pamidronate were studied histologically, histochemically, and ultrastructurally. In an animal experiment, cultured tumor cells (1 x 10(5)) obtained from a metastatic submandibular lymph node in the same patient were injected in the left ventricle of nude mice, and a resulting metastatic bone lesion was studied histologically and histochemically.

RESULTS

In the autopsy specimens, despite the presence of many resorption lacunae on bone surface, only a few small tartrate-resistant acid phosphatase (TRAPase)-positive cells were observed, and most of them were stained weakly and detached from the bone surface. In the animal experiment, 1 of 10 animals (10%) formed osteolytic bone metastasis, and many TRAPase-positive cells were observed histochemically.

CONCLUSIONS

Biphosphonate inhibits bone resorption induced by tumor, possibly by decreasing the number of osteoclasts and inhibiting their function.

Distribution of glucocorticoid receptor immunoreactivity and mRNA in the rat brain: an immunohistochemical and in situ hybridization study

The localization of glucocorticoid receptor (GR) immunoreactivity and mRNA in the adult rat brain was examined by light microscopic and electron microscopic immunohistochemistries, and in situ hybridization. For the purpose of detailed investigation of the distribution and comparison of GR immunoreactivities and mRNAs, specific polyclonal antibodies against a part of the transcription modulation (TR) domain of rat GR were used in the immunohistochemistry, whereas fluorescein-labeled RNA probes, complementary to the TR domain in the GR cDNA were used in the in situ hybridization. In the rat brain, GR immunoreactivity was predominantly localized in the cell nucleus, and the expression of GR mRNA was detected in the cytoplasm. GR-immunoreactive and GR mRNA-containing cells were widely distributed from the olfactory bulb of the forebrain to the gracile-cuneate nuclei of the medulla oblongata. The highest densities of GR-immunoreactive and mRNA-containing cells were observed in the subfields of cerebral cortex, olfactory cortex, hippocampal formation, amygdala, septal region, dorsal thalamus, hypothalamus, trapezoid body, cerebellar cortex, locus coeruleus and dorsal nucleus raphe. The distributional pattern of GR immunoreactivity in many regions was well-correlated with that of GR mRNA, but in the CA3 and CA4 pyramidal layers of the hippocampus, different localization was noted. The present study provides the groundwork for elucidating the role of GRs in brain function.

Dimeric tubulin-stimulated adenylyl cyclase activity is augmented after long-term amitriptyline treatment

We have investigated altered association of tubulin dimers interacting with G proteins and modulating adenylyl cyclase (AC) as a result of long-term amitriptyline (AMT) treatment. Gpp(NH)p-stimulated, but not basal or manganese-stimulated, AC activity was significantly augmented in cortex membranes prepared from rats chronically treated with AMT. The enhancement of AC activity by Gpp(NH)p-liganded tubulin (tubulin-Gpp(NH)p) was significantly higher in chronically AMT-treated rats than in control rats. Moreover, in cortex membranes from controls, tubulin-Gpp(NH)p prepared from chronically AMT-treated rats was more effective to activate AC activity than tubulin-Gpp(NH)p from controls. Immunoblotting and photoaffinity guanine nucleotide binding procedures showed no significant differences in the amount and the function of G proteins between controls and AMT-treated groups. It is suggested that long-term AMT treatment causes alteration in the functional interaction between tubulin and G protein, and this modification may participate in enhanced coupling of Gs to the catalytic subunit of AC induced by the chronic antidepressant treatment.

[A case of amotivational syndrome as a residual symptom after methamphetamine abuse]

We had a case of psychiatric evidence who was homeless and exhibited severe abulia and autism on detention for assault and battery. It was thought that his past history of chronic methamphetamine abuse and his familial history played some part in his showing such symptoms. His mother was alcohol dependent. He was an ACOA (adult child of alcoholics), which might have led to his chronic abuse of methamphetamine. On the other hand, it is well-known fact that the amotivational syndrome induced by marijuana abuse is typified by a diminution of ambition, productivity, and motivation. However, it has been contended that amotivational syndrome is induced not only by marijuana but also by amphetamine and its analogs, cocaine and volatile solvents. Since we positively support this view, we diagnosed the case as amotivational syndrome after long-term methamphetamine abuse. This was also a rare criminal case of amotivational state without hallucinations and delusions after methamphetamine abuse. We suggested that the crime committed in this case was closely related to crime induced by economic problems in residual states of schizophrenic offenders. This could be a case of both ACOA and methamphetamine dependence. There were unresolved alcohol- and drug-related problems in this case. Therefore, careful early intervention in a crisis, cooperation with the authorities and the institutions concerned, and comprehensive rehabilitation should be employed to resolve such alcohol- and drug-related problems.

Long-term evaluation of recombinant human bone morphogenetic protein-2 induced bone formation with a biologic and synthetic delivery system

The efficacy of microspheres made of polylactic acid polyglycolic acid copolymer mixed with blood clot as a delivery system for recombinant human bone morphogenetic protein-2 (rhBMP-2) was evaluated and the long term behaviour of rhBMP-2 in rats was studied. Twenty micro grams of rhBMP-2 in 200 microliter carrier (blood coagulum and polylactic acid polyglycolic acid porous microspheres) were implanted subcutaneously over both sides of the chest muscles in 40 5-week-old male Long Evans rats. The control group were implanted with carrier alone. Specimens were retrieved after 3 days and weekly for 9 weeks. Outcome was measured by signs of bone formation on low power radiographs, and signs of bony growth on histological examination. There were no signs of foreign body or inflammatory reactions to the carrier in either group. In the experimental group signs of bone formation had started to appear by the end of the first week, and there was a gradual increase in both radio-opacity and size during the observation period. Histologically the bony growth was beginning to mature by 4 weeks and was fully mature by 7-9 weeks. In contrast there was no sign of cartilage or bone formation in the control group and the carrier had resorbed by 4-6 weeks. It is concluded that rhBMP-2 implanted in a carrier consisting of blood clot and porous microspheres made of polylactic acid polyglycolic acid induces rapid proliferation of mesenchymal cells that lead to formation of cartilage and bone by 7 days which had matured by 9 weeks. rhBMP-2 in this carrier may be useful clinically because of its capacity to induce early formation of bone.

17 beta-estradiol increases calcium content in fetal mouse parietal bones cultured in serum-free medium only at physiological concentrations

Using a bone organ culture system that shows mineralization in vitro, we investigated whether 17 beta-estradiol dose-dependently increases calcium content in cultured calvarial bones in serum-free medium. Fetal mouse parietal bones (3 x 3 mm) were cultured in phenol red-free BGJ medium containing phosphate (3-4 mmol/L), calcium (1-1.25 mmol/L), insulin (6 micrograms/ML), and transferrin (6 micrograms/mL) for 4-5 days. Under these culture conditions, the calcium content of the cultured bones (at dissection 34.0 +/- 4.6 micrograms/bone [mean +/- SD], n = 50) increased by 15-20 micrograms during 4-5 days of culture. 17 beta-Estradiol increased the calcium content significantly at 10(-12) to 10(-11) mol/L, but not at lower (10(113) mol/L) or higher (10(-10) to 10(-9) mol/L) concentrations. 17 alpha-Estradiol had no effect. The stimulatory effect of 17 beta-estradiol was completely inhibited by the antiestrogen agent ICI-182,780. The anabolic effect of 17 beta-estradiol was elicited not only in bones from females but also in those from males. 17 beta-Estradiol had no significant effect on 45Ca release from prelabeled parietal bones. Furthermore, light- and electron-microscopic examinations revealed that bone mineralization proceeded through formation of matrix vesicles, without any metastatic or dystrophic calcification. These in vitro findings suggest that 17 beta-estradiol elicits small, but reproducible, direct effects on calcium content in the parietal bones not only in female but also in male fetal mice at physiological-free E2 concentrations (10(-12)-10(-11) mol/L), which is attainable in serum of normal human subjects. In contrast to in vivo studies, pharmacological doses of 17 beta-estradiol had no anabolic effect on parietal bones. The mechanism of such a biphasic effect of estrogens remains to be elucidated.

An experimental model of bone metastasis by human lung cancer cells: the role of parathyroid hormone-related protein in bone metastasis

In the formation of bone metastasis, osteoclastic bone resorption is necessary before the expansion of tumor cells from bone marrow to bone, and several cytokines, which possess osteoclast-stimulating activity, could be involved in this step. In this paper, we describe a bone metastasis model in nude mice using human lung squamous cell carcinoma-derived cells (HARA), in which the parathyroid hormone-related protein (PTHrP) gene, one of the most potent osteoclast-activating factors, is strongly expressed. The injection of HARA cells (1 x 10(5)) into the left cardiac ventricle resulted in tumor colonies exclusively in the skeletal system at 4 and/or 8 weeks after inoculation. An anti-PTHrP antibody injected via a tail vein reduced the incidence of bone metastases, number of tumor colonies, and tumor volume after the inoculation of HARA cells. The injection of another line of human lung squamous cell carcinoma-derived cells (QG-56), in which the PTHrP gene is not expressed, resulted in no bone metastasis. These findings suggest that PTHrP plays an important role in the formation of bone metastasis.

Immunolocalization of fibronectin during reparative dentinogenesis in human teeth after pulp capping with calcium hydroxide

Exposed dental pulp is known to possess the ability to form a hard-tissue barrier (dentin bridge). The exact mechanisms by which pulp cells differentiate into odontoblasts in this process are unknown. Fibronectin has been demonstrated to play a crucial role in odontoblast differentiation during tooth development. This study tested the hypothesis that fibronectin is involved in the initial stages of replacement odontoblast differentiation and reparative dentin formation. We observed its immunohistochemical localization during dentin bridge formation in human teeth, after pulp was capped with calcium hydroxide [Ca(OH)2]. One day after the capping, precipitation of crystalline structures was observed at the TEM level in association with cell debris at the interface between the superficial necrotic zone and underlying pulp tissue. This layer of dystrophic calcification showed positive reaction for fibronectin, and pulp cells appeared to be closely associated with this layer, seven to ten days post-operatively. At 14 days, an alignment of cells, some of which were elongated and odontoblast-like, was observed adjacent to the fibronectin-positive irregular matrix. Between the cells, corkscrew fiber-like fluorescence was visible. At 28 days, the irregular fibrous matrix was followed by the formation of tubular dentin-like matrix lined with odontoblast-like cells. Therefore, it would seem that fibronectin associated with the initially formed calcified layer might play a mediating role in the differentiation of pulp cells into odontoblasts during reparative dentinogenesis, after pulp was capped with Ca(OH)2.

Ultrastructural, enzyme-, lectin, and immunohistochemical studies of the erosion zone in rat tibiae

To clarify the process of endochondral ossification, we used ultrastructural, enzyme-, lectin-, and immunohistochemical techniques to study perivascular cells located in the erosion zones of rat tibiae. In growth plate erosion zones, perivascular cells directly connected to blood capillaries were seen invading cartilage. These cells contained a well-developed rough endoplasmic reticulum and Golgi apparatus in their cytoplasm and formed finger-like cytoplasmic processes toward uncalcified transverse cartilage walls. These processes were seen to stretch as far as the degenerated chondrocytes located in the calcified layer of the growth plate. Interestingly, these perivascular cells showed neither alkaline phosphatase activity nor tartrate-resistant acid phosphatase activity. Lectin histochemistry revealed specific staining by Dolichos Biflorus agglutinin (DBA) on the perivascular cells. No reactivity for DBA was detected on either endothelial cells, osteoblasts, chondroclasts, or osteoclasts. In addition, immuno-histochemical studies showed that the perivascular cells neither expressed CD44, which was localized on the plasma membrane of chondroclasts, osteoclasts, and osteocytes, nor were surrounded by laminin. These results suggest that the perivascular cells in the erosion zone are distinct from endothelial cells, osteoblasts, chondroclasts, and osteoclasts; that they may resorb uncalcified cartilage matrix and degenerated chondrocytes; and that perivascular cells may play an important role in the capillary invasion during the process of endochondral ossification.

Immunohistochemical localization of HLA-DR-positive cells in unerupted and erupted normal and carious human teeth

Class II major histocompatibility complex (MHC) antigen-expressing cells are generally associated with the early phase of the immune response. We have studied the distribution of class II-expressing cells in developing, normal, and carious human teeth to clarify when human pulp acquires an immunologic defense potential and how this reacts to dental caries. Antigen-expressing cells were identified immunohistochemically by means of HLA-DR monoclonal antibody. In the pulp of unerupted developing teeth, numerous HLA-DR-positive cells were distributed mainly in and around the odontoblast layer. In erupted teeth, HLA-DR-positive cells were located, for the most part, just beneath the odontoblast layer, with slender cytoplasmic processes extending into the layer. Superficial caries lesions caused an aggregation of HLA-DR-positive cells in dental pulp corresponding to the lesion. In teeth with deeper caries lesions, this aggregation of cells expanded to include the odontoblast layer. Also noted were HLA-DR-positive cells lying along the pulp-dentin border, with cytoplasmic processes projecting deep into the dentinal tubules, where they co-localized with odontoblast processes. These findings suggest that: (1) human dental pulp is equipped with immunologic defense potential prior to eruption; (2) in the initial stage of caries infection, an immunoresponse mediated by class-II-expressing cells is initiated in human dental pulp; and (3) HLA-DR-positive cells trespass deep into dentinal tubules as the caries lesion advances.

Generation and characterization of anti-sulfoglucuronosyl paragloboside monoclonal antibody NGR50 and its immunoreactivity with peripheral nerve

Sulfoglucuronosyl paragloboside (SGPG) is a member of the sulfated glucuronic acid-containing glycolipid (SGGL) family found primarily in peripheral nerves. These glycolipids contain the HNK-1 carbohydrate epitope and are recognized by monoclonal IgM from patients with chronic demyelinating neuropathy and paraproteinemia. Recent studies indicate that SGGLs may serve as ligands for selectins, amphoterin, and laminin, suggesting that these glycolipids may play an important role in cellular adhesion. To elucidate the biological function of these glycolipids, we produced a murine monoclonal antibody (mAb) and studied its antigenic specificity. Using an enzyme-linked immunosorbent assay (ELISA), we found that the mAb designated as NGR50 belonged to the IgG2a subclass, and that the minimal titer (2 SD above the mean optical density value of control) of this mAb was 1:640, with 20 ng of purified SGPG as the antigen. Thin-layer chromatography (TLC) immunoblotting revealed that this mAb reacted specifically with SGPG and sulfoglucuronosyl lactosaminyl paragloboside (SGLPG), which is a structural analogue of the former, but not with other glycolipids. Desulfated derivates of SGPG and SGLPG did not react with mAb NGR50. Western blot analysis showed crossreactivity with human myelin-associated glycoprotein (MAG), but not with rat MAG or rat glycoprotein P0. Unlike anti-HNK-1 monoclonal antibody, however, NGR50 reacted only weakly with several proteins in the 20-30-kD regions, including human P0, suggesting that mAb50 has a different fine specificity as an anti-HNK-1 antibody. Immunocytochemical study of rat sciatic nerve using mAb NGR50 revealed positive staining at the outer surface of the myelin sheath and Schwann cells, as well as in the intervening connective tissues. Faint staining was also visible at the axolemmal-myelin interface; however, compact myelin was not stained.

Production of amelogenin by enamel epithelium of Hertwig's root sheath

OBJECTIVE

To study the multiple potentials of differentiating odontogenic epithelial cells.

STUDY DESIGN

Bilateral first and second maxillary molars of 30 immature rats were perforated into the pulp chambers with a round bur. The pulps were observed histologically and immunohistochemically for amelogenin 3, 7, and 14 days after the perforation.

RESULTS

On day 7, the enamel epithelium of Hertwig's root sheath migrated and formed oval-shaped epithelial islands that resembled epithelial rests of Malassez. On day 14, the islands consisted of epithelial cells with large nuclei and cytoplasm partially surrounded by a subsequently formed osteodentin and cementum. Immunoreactivity for amelogenin was observed in the large epithelial cells and in the area between the cells as well as the calcified tissues. Some of the enamel epithelium resembling columnar ameloblasts of the enamel organ were also positive for amelogenin.

CONCLUSIONS

The enamel epithelium of Hertwig's root sheath appeared to differentiate into ameloblasts and produce amelogenin.

Haploinsufficiency of parathyroid hormone-related peptide (PTHrP) results in abnormal postnatal bone development

Although apparently phenotypically normal at birth, mice heterozygous for inactivation of the gene encoding parathyroid hormone-related peptide (PTHrP) develop haplotype insufficiency by 3 months of age. In addition to histologic and morphologic abnormalities similar to those seen in homozygous mutants, heterozygous animals demonstrated alterations in trabecular bone and bone marrow. These included metaphyseal bone spicules which were diminished in volume, irregularly distributed, and less well developed than those seen in age-matched controls as well as bone marrow, which contained an inordinate number of adipocytes. A substantial reduction in PTHrP mRNA was detected in heterozygous tissue, while circulating parathyroid hormone (PTH) and calcium concentrations were normal. Thus, while a physiologic concentration of PTH was capable of maintaining calcium homeostasis, it was incapable of compensating for PTHrP haploinsufficiency in developing bone. In normal animals, both PTHrP and the PTH/PTHrP receptor were expressed predominantly in chondrocytes situated throughout the proliferative zone of the tibial growth plate. In the metaphysis, the PTH/PTHrP receptor was identified on osteoblasts and preosteoblastic cells situated in the bone marrow, while PTHrP was expressed only by osteoblasts. These observations indicate that postnatal bone development involves susceptible pathways that display exquisite sensitivity to critical levels of PTHrP and imply that the skeletal effects of PTH are influenced by locally produced PTHrP. Moreover, identification of both the ligand and its N-terminal receptor in metaphyseal osteoblasts and their progenitors suggests an autocrine/paracrine role for the protein in osteoblast differentiation and/or function. Impairment in this function as a consequence of PTHrP haploinsufficiency may critically influence the course of bone formation, resulting in altered trabecular architecture and perhaps low bone mass and increased bone fragility.

Immunolocalization of the small proteoglycan decorin in human teeth

The immunolocalization of decorin was studied by confocal laser scanning microscopy and transmission electron microscopy. In the apical area of developing teeth, labelling for decorin was found in the dental papilla cells, prodontoblasts and also in the Hertwig's epithelial cells. Mantle dentine and the initial predentine were negative. In circumpulpal dentine, intense reactivity extended along the calcification front and dentinal tubules. Fluorescence was also evident in odontoblast cell bodies and their processes in predentine. None was perceived, however, in the predentinal matrix. Faint staining was observed on the calcified dentinal matrix. Immunoelectron microscopy revealed staining for decorin in collagen fibrils lining the predentine-dentine junction, and where arrays of labelled filaments were noted orthogonal to the collagen fibrils. Staining extending from the calcification front was observed in the matrix adjacent to the dentinal tubule. The decorin observed at the calcification front might regulate the mineralization of dentinal matrix.

[Cerebellopontine angle epithelial cyst presenting as hemifacial spasm]

A rare case of cerebellopontine angle epithelial cyst presenting as hemifacial spasm is reported. The patient was a 35-year-old man with right hemifacial spasm of 2 months duration. A preoperative CT scan showed a well-demarcated low density area in the right cerebellopontine angle. The cyst was totally excised under an operating microscope. The postoperative course was uneventful, and the right hemifacial spasm resolved immediately. Histologically, the cyst wall was composed of a stratified epithelial lining composed of non-ciliated cuboidal or squamous cells. Ultrastructurally, the epithelial layer consisted of two types of cells: non-ciliated cells with microvilli coated with electron-dense material, and basally located cells with tonofilaments and well-developed desmosomes. The latter type of cells appear identical to the basal cells characteristically seen in the upper respiratory tract and the gastrointestinal tract. This findings suggest that the cyst was of endodermal origin rather than neuroectodermal origin.

Interleukin-1 beta and granulocyte-macrophage colony-stimulating factor mediate Langerhans cell maturation differently

It has been reported that the in vivo maturation of Langerhans cells after hapten painting is mediated by IL-1 beta while Langerhans cell maturation after in vitro culture is mediated by granulocyte-macrophage colony-stimulating factor (GM-CSF). To clarify the reason for this discrepancy, we examine the expression of Ia antigen and several co-stimulatory molecules on Langerhans cells that were activated by in vitro culture, by hapten painting, or by an intradermal injection of several cytokines. Both cultured Langerhans cells and those activated by hapten painting increased the expression of Ia antigen and all the co-stimulatory molecules (i.e., intercellular adhesion molecule-1 [ICAM-1], B7-1, B7-2, and CD40). In contrast, an intradermal injection of interleukin-1 beta (IL-1 beta) or tumor necrosis factor-alpha (TNF-alpha) increased the expression of Ia antigen, ICAM-1, B7-2, and CD40, but not that of B7-1. These data indicate that IL-1 beta or TNF-alpha is not sufficient to induce B7-1 expression on Langerhans cells in vivo. Subsequently we examined the effect of anti-cytokine antibodies (Abs) on the expression of those molecules on cultured Langerhans cells. While none of the Abs to IL-1 beta, TNF-alpha, or GM-CSF changed the upregulation of Ia antigen, ICAM-1, or CD40 on cultured Langerhans cells, anti-GM-CSF Ab suppressed that of B7-1 and B7-2. Taken together, our present results suggest that IL-1 beta is required for the upregulation of Ia, ICAM-1, B7-2, and CD40, while GM-CSF is required for the upregulation of B7-1 and B7-2, although it still remains unclear why the injected GM-CSF could not augment B7-1 expression on Langerhans cells in vivo and why anti-IL-1 beta Ab did not suppress the upregulation of Ia, ICAM-1, or CD40 on cultured Langerhans cells.