Functional and molecular outcomes of the human masticatory muscles

The masticatory muscles achieve a broad range of different activities such as chewing, sucking, swallowing, and speech. In order to accomplish these duties, masticatory muscles have a unique and heterogeneous structure and fiber composition, enabling them to produce their strength and contraction speed largely dependent on their motor units and myosin proteins that can change in response to genetic and environmental factors. Human masticatory muscles express unique myosin isoforms, including a combination of thick fibers, expressing myosin light chains (MyLC) and myosin class I and II heavy chains (MyHC) -IIA, -IIX, α-cardiac, embryonic and neonatal and thin fibers, respectively. In this review, we discuss the current knowledge regarding the importance of fiber-type diversity in masticatory muscles versus supra- and infrahyoid muscles, and versus limb and trunk muscles. We also highlight new information regarding the adaptive response and specific genetic variations of muscle fibers on the functional significance of the masticatory muscles, which influences craniofacial characteristics, malocclusions, or asymmetry. These findings may offer future possibilities for the prevention of craniofacial growth disturbances.

Histochemical and morphological aspects of fresh frozen bone: a preliminary study

Bone graft are used in dentistry for the reconstruction of severely atrophic jaws. Fresh frozen bone has no osteogenic property but it has osteoconductive and osteoinductive properties because its matrix contains growth factors such as vascular endothelial growth factor. The purpose of the present study was to evaluate morphological and protein expression characteristics of fresh frozen bone before graft and after six months of graft in patients who needed maxillary reconstruction. After 6 month of graft we observed the presence of viable bone as evidenced by full osteocyte lacunae and by the presence of RANKR, osteocalcin positive cells and vascular endothelial growth factor. In conclusion, our findings show that the fresh frozen bone after six month of graft is for the most part viable bone, encouraging its use as an alternative to autogenous bone for reconstructing maxillary bone defects prior to implant.

Morphofunctional compensation of masseter muscles in unilateral posterior crossbite patients

Unilateral posterior crossbite is a widespread, asymmetric malocclusion characterized by an inverse relationship of the upper and lower buccal dental cusps, in the molar and premolar regions, on one side only of the dental arch. Patients with unilateral posterior crossbite exhibit an altered chewing cycles and the crossbite side masseter results to be less active with respect to the contralateral one. Few studies about morphological features of masticatory muscle in malocclusion disorders exist and most of these have been performed on animal models. The aim of the present study was to evaluate morphological and protein expression characteristics of masseter muscles in patients affected by unilateral posterior crossbite, by histological and immunofluorescence techniques. We have used antibody against PAX-7, marker of satellite cells, and against α-, β-, γ-, δ-, ε- and ζ-sarcoglycans which are transmembrane glycoproteins involved in sarcolemma stabilization. By statistical analysis we have evaluated differences in amount of myonucley between contralateral and ipsilateral side. Results have shown: i) altered fibers morphology and atrophy of ipsilateral muscle if compared to the contralateral one; ii) higher number of myonuclei and PAX-7 positive cells in contralateral side than ipsilateral one; iii) higher pattern of fluorescence for all tested sarcoglycans in contralateral side than ipsilateral one. Results show that in unilateral posterior crossbite hypertrophic response of contralateral masseter and atrophic events in ipsilateral masseter take place; by that, in unilateral posterior crossbite malocclusion masticatory muscles modify their morphology depending on the function. That could be relevant in understanding and healing of malocclusion disorders; in fact, the altered balance about structure and function between ipsilateral and contralateral muscles could, long-term, lead and/ or worsen skeletal asymmetries.

Sarcoglycan complex in masseter and sternocleidomastoid muscles of baboons: an immunohistochemical study

The sarcoglycan complex consists of a group of single-pass transmembrane glycoproteins that are essential to maintain the integrity of muscle membranes. Any mutation in each sarcoglycan gene causes a series of recessive autosomal dystrophin-positive muscular dystrophies. Negative fibres for sarcoglycans have never been found in healthy humans and animals. In this study, we have investigated whether the social ranking has an influence on the expression of sarcoglycans in the skeletal muscles of healthy baboons. Biopsies of masseter and sternocleidomastoid muscles were processed for confocal immunohistochemical detection of sarcoglycans. Our findings showed that baboons from different social rankings exhibited different sarcoglycan expression profiles. While in dominant baboons almost all muscles were stained for sarcoglycans, only 55% of muscle fibres showed a significant staining. This different expression pattern is likely to be due to the living conditions of these primates. Sarcoglycans which play a key role in muscle activity by controlling contractile forces may influence the phenotype of muscle fibres, thus determining an adaptation to functional conditions. We hypothesize that this intraspecies variation reflects an epigenetic modification of the muscular protein network that allows baboons to adapt progressively to a different social status.

Sarcoglycan immunoreactivity is lacking in infantile hypertrophic pyloric stenosis. A confocal laser scanning microscopic study

OBJECTIVES

The Dystrophin-Glycoprotein Complex (DGC) is a large multisubunit complex that plays a crucial role in maintaining the structural integrity and physiology of muscle fibers. Dystrophin has been reported to be absent in the pyloric muscle of infantile hypertrophic pyloric stenosis (IHPS) patients. The present study was designed to investigate the other two patterns of DGC (dystroglycan and sarcoglycan complexes) in normal pyloric muscle and their possible modifications in IHPS patients.

METHODS

Ten pyloric muscle biopsies were obtained from babies operated for IHPS and five control pylorus biopsy taken at autopsy from cases without gastrointestinal disease. The DGC sub-complexes (beta-dystroglican and beta, delta- sarcoglycans) were localized immunohistochemically using specific monoclonal antibodies. The results were evaluated using a confocal laser scanning microscope.

RESULTS

Positive immunolocalization of the two DGC sub complexes was demonstrated in the smooth muscle cells (SMCs) of the pyloric region of control patients. Similarly, a positive immune expression of beta-dystroglican was observed in the pyloric SMCs of IHPS patients. On the other hand a negative immunoreaction for sarcoglycans was recorded within the full thickness of the pyloric SMCs of these patients.

CONCLUSIONS

The absence of sarcoglycans within the hypertrophied pyloric muscle may be a predisposing factor in the pathogenesis of IHPS since it could alter the normal physiology of SMCs through the modifications of structural integrity of sarcolemma and signaling between the extracellular and intracellular compartment.

Sarcoglycan subcomplex in normal and pathological human muscle fibers

Sarcoglycans are a sub-complex of transmembrane proteins which are part of the dystrophin-glycoprotein complex (DGC). They are expressed above all in the skeletal, cardiac and smooth muscle. Although numerous studies have been conducted on the sarcoglycan sub-complex in skeletal and cardiac muscle, the manner of distribution and localization of these proteins along the non-junctional sarcolemma is still not clear. Furthermore, there are unclear data about the actual role of sarcoglycans in human skeletal muscle affected by sarcoglycanopathies. In our studies on human skeletal muscle, normal and pathological, we determined the localization, distribution and interaction of these glycoproteins. Our results, on normal human skeletal muscle, showed that the sarcoglycans can be localized both in the region of the sarcolemma over the I band and over the A band, hypothesizing a correlation between regions of the sarcolemma occupied by costameres and the metabolic type of the fibers (slow and fast). Our data on skeletal muscle affected by sarcoglycanopathy confirmed the hypothesis of a bidirectional signaling between sarcoglycans and integrins and the interaction of filamin2 with both sarcoglycans and integrins. In addition, we have recently demonstrated, in smooth muscle, the presence of alpha-SG, in contrast with data of other Authors. Finally, we analyzed the association between contractile activity and quantitative correlation between alpha- and epsilon-SG, in order to better define the arrangement of sarcoglycan subcomplex.

Integrins, muscle agrin and sarcoglycans during muscular inactivity conditions: an immunohistochemical study

Sarcoglycans are transmembrane proteins that seem to be functionally and pathologically as important as dystrophin. Sarcoglycans cluster together to form a complex, which is localized in the cell membrane of skeletal, cardiac, and smooth muscle. It has been proposed that the dystrophin-glycoprotein complex (DGC) links the actin cytoskeleton with the extracellular matrix and the proper maintenance of this connection is thought to be crucial to the mechanical stability of the sarcolemma. The integrins are a family of heterodimeric cell surface receptors which play a crucial role in cell adhesion including cell-matrix and intracellular interactions and therefore are involved in various biological phenomena, including cell migration, and differentiation tissue repair. Sarcoglycans and integrins play a mechanical and signaling role stabilizing the systems during cycles of contraction and relaxation. Several studies suggested the possibility that integrins might play a role in muscle agrin signalling. On these basis, we performed an immunohistochemical analyzing sarcoglycans, integrins and agrin, on human skeletal muscle affected by sensitive-motor polyneuropathy, in order to better define the correlation between these proteins and neurogenic atrophy due to peripheral neuropathy. Our results showed the existence of a cascade mechanism which provoke a loss of regulatory effects of muscle activity on costameres, due to loss of muscle and neural agrin. This cascade mechanism could determine a quantitative modification of transmembrane receptors and loss of alpha7B could be replaced and reinforced by enhanced expression of the alpha7A integrin to restore muscle fiber viability. Second, it is possible that the reduced cycles of contraction and relaxation of muscle fibers, during muscular atrophy, provoke a loss of mechanical stresses transmitted over cell surface receptors that physically couple the cytoskeleton to extracellular matrix. Consequently, these mechanical changes could determine modifications of chemical signals through variations of pathway structural integrins, and alpha7A could replace alpha7B.

Sarcoglycan and integrin localization in normal human skeletal muscle: a confocal laser scanning microscope study

Many studies have been performed on the sarcoglycan sub-complex and a7B and b1D integrins, but their distribution and localization patterns along the non-junctional sarcolemma are still not clear. We have carried out an indirect immunofluorescence study on surgical biopsies of normal human skeletal muscle, performing double localization reactions with antibodies to sarcoglycans, integrins and sarcomeric actin. Our results indicate that the tested proteins colocalize with each other. In a few cases, a-sarcoglycan does not colocalize with the other sarcoglycans and integrins. We also demonstrated, by employing antibodies to all the tested proteins, that these proteins can be localized to regions of the sarcolemma corresponding either to the I-band or A-band. Our results seem to confirm the hypothesis of a correlation between the region of the sarcolemma occupied by costameric proteins and the metabolic type (fast or slow) of muscle fibers. On this basis, we suggest that slow fibers are characterized by localization of costameric proteins to I-bands, while fast fibers are characterized by localization of costameric proteins to A-bands. The results open a new line of research in understanding interactions between the components of the DGC and vinculin-talin-integrin complexes in the context of different fiber types. Moreover, the same results may be extended to skeletal muscle fibers affected by neuromuscular diseases to detect possible structural alterations.

Distribution and Localization of Vinculin-Talin-Integrin System and Dystrophin-Glycoprotein Complex in Human Skeletal Muscle

The vinculin-talin-integrin system and the dystrophin-glycoprotein complex (DGC) are two protein systems with structural and signaling functions, allowing interaction between muscle fibers and extracellular matrix. Although numerous studies have been conducted on these systems, their localization and distribution patterns along the nonjunctional sarcolemma are not clear. On this basis, we carried out an indirect immunofluorescence study on the vastus lateralis muscle of human adults not affected by neuromuscular diseases to better define these patterns. Our results showed that all tested proteins of the two systems have a costameric distribution; all tested proteins of the two systems colocalize with each other (about 90-95% of the cases); only alpha-sarcoglycan in a few cases (about 6%) does not colocalize with other proteins; in about 9-10% of the cases, dystrophin and beta-dystroglycan colocalize partially with other proteins; all tested proteins can be localized in different fibers, both in the region of the sarcolemma over I or A bands. The colocalization between the vinculin-talin-integrin and DGC systems may imply their functional interaction involving the structural aspect, by providing a stronger adhesion between sarcolemma and extracellular matrix in well-defined regions of the muscle fiber. Besides, their colocalization may suggest the existence of a mechanism of mutual modulation of the transmitted signals. This reciprocal control may determine, in different conditions, the prevalence of one system over another with a consequent transmission of different messages to the sarcolemma-associated cytoskeleton.

Sarcoglycans in human skeletal muscle and human cardiac muscle: a confocal laser scanning microscope study

Sarcoglycans are a subcomplex of transmembrane proteins which are part of the dystrophin-glycoprotein complex. They are expressed in the skeletal, cardiac and smooth muscle. Although numerous studies have been conducted on the sarcoglycan subcomplex in skeletal and cardiac muscle, the manner of the distribution and localization of these proteins along the nonjunctional sarcolemma is not clear. We therefore carried out an indirect immunofluorescence study on surgical biopsies of normal human skeletal muscle and of healthy human atrial myocardium biopsies of patients affected by valvulopathy. Our results indicate that, in skeletal muscle, sarcoglycans have a costameric distribution and all colocalize with each other. Only in a few cases did the alpha-sarcoglycan not colocalize with other sarcoglycans. In addition, these glycoproteins can be localized in different fibers either in the regions of the sarcolemma over band I or band A. In cardiac muscle, our results show a costameric distribution of all proteins examined and, unlike in skeletal muscle, they show a constant colocalization of all sarcoglycans with each other, along with a consistent localization of these proteins in the region of the sarcolemma over band I. In our opinion, this situation seems to confirm the hypothesis of a correlation between the region of the sarcolemma occupied by costameric proteins and the metabolic type, fast or slow, of the muscular fibers. These data, besides opening a new line of research in understanding interactions between the sarcoglycans and other transmembrane proteins, could also be extended to skeletal and cardiac muscles affected by neuromuscular and cardiovascular pathologies to understand possible structural alterations.

Actin-associated proteins in ameloblast differentiation

Focal contacts are systems of adherens junctions of the cell-extracellular matrix type, which allow the transfer of fundamental signals from the extracellular matrix to nuclear compartments, capable of regulating adhesion, proliferation, migration and differentiation of cells. Recently, many authors have concentrated their attention on epitheliomesenchymal interactions which guide organogenesis of dental germ, identifying numerous growth and differentiation factors and having the inner enamel epithelial cells of the enamel organ as a target. Given that the two cellular compartments in their tooth germ are separated by a basal membrane and by an extracellular matrix, which touches it, we wanted to evaluate the presence of focal contacts through the identification of talin and vinculin, proteins of the actin-associated protein complex. In this study we utilized the hemimandibles of young Wistar rats and we extracted the related odontogenic tooth organs present at their apical end. Specimens are processed with antibody against vinculin and talin. Results show that these junctional system proteins are present at the apical poles of both cellular compartments suggesting that putative epithelial-mesenchymal interactions, other than marker molecules, may use focal contacts as a system for transmission of signals.

AQP1 in red blood cells of uremic patients during hemodialytic treatment

Hemodialysis influences the transport of water through the erythrocytic membrane, and induces morphologic and functional modifications. Recently water channels, called aquaporins (AQP), have been identified on the membrane of red blood cells. The aim of the present study was, therefore, to evaluate any relationships between volumetric changes in erythrocytes (MCV), plasma osmolarity and membrane expression of AQP1 in 22 uremic patients during a hemodialysis session, and compare value with those in a control group of 22 healthy volunteers. Membranal AQP1 expression was evaluated using three methods: indirect immunofluorescence under confocal microscopy, immunoenzymatic method after membrane extraction, and immunoblotting. In uremic subjects, at baseline membrane AQP1 expression was significantly lower, whereas plasma osmolality was higher than in controls. At 1 and 2 h of replacement therapy, a progressive increase was observed in erythrocytic AQP1, values similar to those in controls being attained after 3.5 h. During the session osmolality values reduced progressively, becoming significantly lower than basal values. The mean erythrocytic corpuscular volume in patients with ESRD was significantly lower than in cntrols at baseline. This value increased during hemodialysis, attaining statistical significance with respect to the basal value at 3.5 h of dialysis. Close correlations were found between plasma osmolality and AQP1 values (r = -0.930; p < 0.05), and also between MCV and plasma osmolality trend (r = -0.909; p < 0.05). There was a linear correlation (r = 0.63, p < 0.05) between plasma AVP concentrations and plasma osmolality. The variations found in plasma osmolarity during hemodialysis, may induce AQP1 expression on the membrane of intact red blood cells.

Early events of experimental exposure to amorphous and crystalline silica in the rat: time course of surfactant protein D

Pneumoconioses determined by chronic inhalation of different kinds of silica present with peculiar clinical and histopathological features. Silicosis, caused by crystalline silica, is characterized by typical fibrous parenchymal nodules. Less defined are pneumoconioses due to amorphous silica. Aim of current experimental research on silicosis is to investigate the early events that lead to nodular fibrosis of the lung. A secretory component of the pulmonary environment, surfactant, seems to be involved in silica toxicity; surfactant protein D is a protein constituent, apparently involved in the homeostasis of the phospholipid component. We studied the behaviour of SP-D 2, 12 and 24 hours after treatment with 200 mg/kg crystalline silica or pumice powder suspended in 400 microl/kg saline solution and instiled intratracheally to rats. Both immunohistochemical localization and immunoblotting quantification demonstrated a sensible increase in intracellular SP-D, localized in alveolar type II cells and some bronchiolar epithelial cells, 2 hours after treatment. Increment appears less marked 12 hours after administration, reaching again levels comparable to control at 24 hours. The behaviour of SP-D after pumice instilation is similar, but with a significantly minor increment at 2 hours. These results indicate crystalline silica as responsible for a stronger acute injury of pulmonary tissue.

Changes in the distribution of laminin alpha1 chain in psoriatic skin: immunohistochemical study using confocal laser scanning microscopy

BACKGROUND

Recent studies have demonstrated the presence in psoriatic skin of ultrastructural and molecular alterations in the basement membrane and an altered polarized distribution of the integrins. Previous studies have demonstrated the existence of some epithelial cell lines synthesizing only laminin beta and gamma chains that, in the absence of the laminin alpha chain, do not form a distinct basal lamina.

OBJECTIVES

To investigate a possible reduction/absence of the laminin alpha 1 chain in keratinocytes in psoriatic skin and to correlate this with fibronectin distribution.

METHODS

Using monoclonal antibodies against the laminin alpha1 chain or human plasma fibronectin and using confocal laser scanning microscopy, we evaluated the immunohistochemical expression of these two proteins in cutaneous biopsies from involved and uninvolved skin of the sacral region of 12 men with extensive chronic plaque psoriasis. Site-matched biopsies of normal skin from four men without psoriasis were used as controls.

RESULTS

In normal skin antilaminin alpha 1 chain antibodies stained the dermal-epidermal junction in a regular and continuous manner. In involved and uninvolved psoriatic skin large regions of discontinuous immunostaining were observed, mainly at the apex of the dermal papillae; in the same regions, clusters of keratinocytes appeared markedly reactive and fibronectin was overexpressed in the papillary dermis under the interruptions of the basement membrane.

CONCLUSIONS

The present study defines the location of the laminin alpha1 chain in involved and uninvolved psoriatic skin and suggests a possible role of the alteration of this chain, together with T-cell lymphokines and fibronectin, in the dysregulation of cell morphological processes.

Nitric oxide synthase patterns in normal and varicocele testis in adolescents

OBJECTIVE

To determine if the testes of normal adolescents can produce nitric oxide (NO), by assessing NO synthase (NOS) activity, and whether this activity changes in adolescents with left idiopathic varicocele.

PATIENTS AND METHODS

After obtaining informed consent, testicular biopsies were obtained from eight adolescents (mean age 16.4 years; controls) who underwent surgery for inguinal hernia or hydrocele, and from 20 adolescents (mean age 16.2 years) operated for left idiopathic varicocele. Inducible and endothelial NOS (iNOS and eNOS) isoforms were investigated in the biopsy specimens by immunohistochemical localization and Western blot analysis using specific fluorescein-conjugated antibodies.

RESULTS

Both normal and pathological samples expressed eNOS at the level of vessels and Leydig cells. The iNOS was expressed in Leydig cells of normal testes and over-expressed in Leydig cells of varicocele testes.

CONCLUSION

Leydig cells of adolescent testes constitutively express iNOS. Under pathological conditions, e.g. varicocele, iNOS is up-regulated and is a possible source of NO overproduction. These results could be useful in explaining the pathogenesis of both testis and sperm dysfunction in varicocele.

Supravital exposure to propidium iodide identifies apoptosis on adherent cells

BACKGROUND

Several studies indicate that plasma membrane changes during apoptosis are a general phenomenon. Among the flow cytometric methods to measure apoptosis, the Annexin V assay that detects the membrane exposure of phosphatidylserine (PS) is one of the most commonly used. However, the various treatments used for the detachment of adherent cells generally interfere with the binding of Annexin V to membrane PS, making apoptosis measurement a technical problem. Materials and Methods Apoptosis of different cell lines was investigated by fluorescence microscopy and multiple flow assays designed to assess loss of membrane integrity, translocation of PS, DNA fragmentation, and light scatter changes. Results and Conclusions We show that supravital propidium iodide (PI) assay stains adherent apoptotic cells, allowing flow cytometric quantification. Moreover, supravital exposure to PI without prior permeabilization identifies apoptotic cells as well as Annexin V and permits the simultaneous surface staining by FITC- and PE-conjugated monoclonal antibodies. As in the case of necrotic or permeabilized cells, fluorescence microscopy has revealed that PI staining of apoptotic cells is localized in the nucleus. This suggests that the binding of PI to the DNA/RNA structures is stable enough to withstand the trypsinization and/or washing procedures necessary to detach adherent cells.

Histochemical and biochemical analysis of phospholipase C isoforms in normal human gastric mucosa cells

The expression and activity of PIP2-specific phospholipase C (PLC) in healthy human gastric mucosa cells were investigated by means of Western blotting, immunohistochemistry and in vitro activity assays. The results provide direct evidence for an almost exclusive expression of the PLC beta family and at the same time supply a cellular cartography of each represented isoform of this family. In this context, the putative roles of each isoform in the signaling events regulating the gastric mucosa metabolic machinery are discussed. These data provide a unique map of the specific expression and cellular distribution of the most represented PLC isoforms in healthy human gastric mucosa cells, which may constitute a reference point in future studies aimed at highlighting possible cytochemical and biochemical hallmarks of metaplastic or malignant transformation.

Nitric oxide production is increased in the spermatic veins of adolescents with left idiophatic varicocele

BACKGROUND/PURPOSE

The existence of an excessive release of nitric oxide (NO) within dilated spermatic veins has been recorded in adults with varicocele suggesting a high oxidative stress. The authors investigated whether NO overproduction is already present in the dilated veins of adolescent varicocele and which enzymatic isoforms in the spermatic vein could be expressed.

METHODS

The study group consisted of 10 adolescent patients affected by left idiophatic varicocele of grade II and III. The increase in NO production was established by determination of serum concentration of L-hydroxyarginine (L-NHA) and Nitrite/nitrate (NOx). Both endothelial and inducible NOsynthase (NOS) were investigated by Western blot analysis and by immunohistochemical localization using specific monoclonal fluorescein conjugated antibodies.

RESULTS

Serum L-NHA levels were significantly greater in the spermatic veins when compared with the peripheral veins 176.8 +/- 32.3 micromol/L versus 3.38 +/- 0.64 micromol/L (P =.0004 Similarly, NOx levels were increased, respectively, 68.2 +/- 16.7 nmol/mL versus 12.9 +/- 2.65 nmol/mL (P =.029). Endothelial NOS was localized in the spermatic vein of varicocele patients, but not overexpressed; the inducible isoform was not detected.

CONCLUSIONS

Adolescents with varicocele already present an increase in NO within dilated veins. The dilated spermatic vein is not the major source for the increase in NO level. These results could have an implication in the natural history of adolescent varicocele and in programming the ideal time for surgical treatment.

Differential effects of stromal derived factor-1 alpha (SDF-1 alpha) on early and late stages of human megakaryocytic development

Stromal derived factor-1 alpha (SDF-1 alpha), the high-affinity ligand of CXC-chemokine receptor 4 (CXCR4), was added to human CD34(+) hematopoietic progenitor cells that can be induced to differentiate along the monocytic or megakaryocytic lineages. In control liquid cell cultures supplemented with two different cytokine cocktails: stem cell factor (SCF), interleukin-3 (IL-3), macrophage-colony stimulating factor (M-CSF), and 10% fetal calf serum (FCS), or, SCF and thrombopoietin (TPO), the expression of surface CXCR4 progressively increased in both the CD14(+) monocytic and CD41(+) megakaryocytic lineages. While SDF-1 alpha caused only modest effects on cells of the monocytic lineage, it induced profound down-regulation of CXCR4 in megakaryocytic cells at all stages of differentiation. Moreover, while SDF-1 alpha initially up-regulated the early megakaryocytic antigen CD41, at later time points (days 12-16) it induced down-regulation of the late megakaryocytic antigen CD42b. Consistently, at day 16, the number of mature megakaryocytes was significantly decreased in cultures supplemented with SDF-1 alpha. These findings indicate that, besides its primary role in regulating the retention of precursor cells in hematopoietic tissues, the SDF-1 alpha/CXCR4 system participates in the regulation of megakaryocytic development by stimulating the formation of immature megakaryoblasts and inhibiting the formation of mature megakaryocytes.

Phosphatidylinositol-3-kinase activation and atypical protein kinase C zeta phosphorylation characterize the DMSO signalling in erythroleukemia cells

Here we provide evidence for a role of phosphatidylinositol-3-kinase (PI-3-kinase) and for its product phosphatidylinositol-3,4, 5-triphosphate (PI3,4,5P3) in the occurrence of the metabolic differentiation state induced by DMSO in murine Friend erythroleukemia cells. Of note, the activation of PI-3-kinase correlated with the modulation of the activation of another enzyme, the atypical protein kinase C zeta (aPKC zeta). In particular, the expression of PI-3-kinase was substantially unaffected by DMSO treatment while its phosphorylation and the production of PI3,4,5P3 was strongly increased within 24 h of DMSO. Such a result was paralleled by an evident phosphorylation of a PKC zeta. Treatment of the cells with the two unrelated PI-3-kinase inhibitors wortmannin and LY 294002 impaired the recovery of the number of differentiated cells, therefore indicating that PI-3-kinase might be involved in the induction of erythroid differentiation, possibly engaging a protein kinase C zeta as downstream effector.

The ameloblast movement in rat incisor. L.M., S.E.M. and C.L.S.M. study

The internal epithelium of enamel organ and the below enamel surface during growth of the lower incisor, were examinated in ten Wistar rat 12-27 weeks old and weighing between 150/200 gr, by means of immuno histochemical, light and scanning electron microscopy techniques. Our specimens indicate that during the outer enamel secretion the anti-actin positivity goes from distal terminal web to infra nuclear region of cell body. The results of the present study do not support the active movement hypothesis, conversely they support the Warshawsky (1992) hypothesis, i.e. the distal terminal web permits the maintenance and the assembling of ameloblasts during enamel growth. Hence we do agree with Osborn (1970) who reported that, during secretion, ameloblasts move passively in response to secretory forces.

Immunofluorescence distribution of actin-associated proteins in human seminiferous tubules of adolescent testes, normal and pathologic

The aim of our study on human seminiferous tubules of adolescent testes was to study the localization of two actin-associated proteins of the adherens junctions, such as vinculin and talin, and to verify if there were modifications in their pattern in varicocele, a frequent disease of the testis in adolescent age. The study group consisted of 8 biopsies from normal testes (i.e., adolescents operated on for hydrocele or inguinal hernia) and 20 biopsies from pathological testes (i.e., adolescents operated on for idiophatic left varicocele). Biopsies were evaluated by indirect immunofluorescence using anti-human vinculin and anti-human talin antibodies. Observation was recorded with a Leica TCS 4D upright confocal microscope. In the normal testes, there was a strong positive immunoreactivity for vinculin, which was localized in the interstitial cells of Leydig, and both basal pole and lateral cell surface of Sertoli cells; the pattern of talin immunoreactivity was the same except that the lateral cell surface of Sertoli cells was not stained. In the varicocele group the pattern was different. Vinculin immunoreactivity showed small patches of fluorescence only in the cytoplasm of Sertoli cells while talin immunoreactivity showed a scanty distribution at the basal surface of Sertoli cells. These results confirm that, similarly to other tissues, vinculin is expressed at cell-cell and cell-matrix adherens junctions, while talin is present at cell-matrix adherens junctions in human seminiferous tubules of normal adolescents. Varicocele alters the patterns of these two proteins both quantitatively and qualitatively.

Ameloblast morphogenesis during amelogenesis. S.E.M. study

A study has been carried out on the S.E.M. on the enamel of an albino rat's inferior incisor. The observations concern almost the entire ameloblastic cycle, specifically, from the end of the cellular differentiation phase (pre-ameloblasts III) to the end of the modulation phase. The authors have pointed out some morphogenetical variations which during the depositing phase, are manifested on the distal extremity of the cells and are concentrated at this level in the differentiation of the Tomes' processes. Successively, during the transitional post-secretory and cellular modulation phases, the morphogenetical differences at the distal extremities also involve the lateral walls of the ameloblasts and their spatial relationships. Some morphological differences are correlated with different functional moments and revealed by an examination of the corresponding superficial areas of the enamel in the course of its formation. In this study, the constant orientation of the perpendicular is evident at the secretion plane in opposition with other studies that propose a 'pendulum movement' theory of these cells during the depositing phase of the prismatic layers. In addition, a morphological classification is proposed consisting of four types of modulative ameloblasts.

The non-junctional sarcolemmal cytoskeleton: the costameres

In skeletal muscle fibers the costameres have been defined by Pardo et al. (1983) as transverse circumferential elements of the cytoskeleton associated to the sarcolemma. Since the first immunolocalization, carried out with purified antivinculin antibodies to the present day, about 10 proteins have been located in costameres, as well as some transmembrane proteins of the integrin superfamily. In particular the colocalization of vinculin and talin and the presence of the integrins confers to this system the description of the adherens junctions type cell-ECM, while the presence of dystrophin in correspondence to both A and I bands with Z line negative is important for the stabilization of the membrane of the skeletal muscle fiber. We are therefore of the opinion that costameres can be defined as a real proteic "machinery".

Immunolocalization of the costameres in human skeletal muscle fibers: confocal scanning laser microscope investigations

BACKGROUND

The costameres in skeletal muscle fibers were first described by Pardo et al. (1983a) and have been defined as transverse circumferential elements of the cytoskeleton associated to the sarcolemma. Specific immunostaining for vinculin shows that the costameres overlie I bands. However, an exact correlation between the costameres and the Z line is uncertain, although approximately 10 proteins so far have been localized in the costameres. To define the exact localization of costameres in human skeletal muscle fibers, we carried out an immunofluorescence study using confocal scanning laser microscopy on the fascia lata muscle of adult males.

METHODS

Samples were fixed in 3% paraformaldehyde; frozen sections were treated with antivinculin, antitalin, antidesmin, and anti-alpha-actinin, then immunostained with TRITC. For double localization, the TRITC-streptavidin, as a marker for vinculin and FITC-streptavidin a marker for desmin, were used.

RESULTS

The distance between two subsequent transverse lines of actininf indicated that muscle fibers were well stretched. Processing, with different software functions of the images obtained using CLSM, shows that vinculin and talin are only present in the sarcolemmal lattice. Immunostaining for vinculin and double immunostaining for vinculin and desmin demonstrate that costameres superimpose underlying I bands without interruption at the Z line. Immunostaining for talin showed that the protein is located in correspondence with the I band and M line.

CONCLUSIONS

We believe that costameres are "proteic machinery." The findings of the present study suggest that it is possible to determine the width and the period of each proteic component. In addition, we indicate that costameres are present in correspondence with M line.

[Use of synthetic resin cases for the scanning electron microscopic study of the kidney tubule system]

Aim of our present work was to investigate a new method to study the three-dimensional arrangement, the length and the diameter of the different parts of the renal tubules. The ureter was cannulated after blocking the urinary flow with a binding of the ureter itself at its intermediate third, and injected in it against flow a synthetic resin (Mercox) normally used for vascular corrosion casts. It was demonstrated that the binding maintained only for 24 hours is adequate for morphological studies of the urinary tracts from papillar ducts until the Henle's loop. On the contrary the binding maintained for 7 days induced marked changes in the tubular architecture similar to the first anatomo-pathological changes of the nephrosclerosis following a chronic obstructive nephropathy.

[Computerized reconstruction of the spatial organization of enamel rods]

Morphometric reliefs on the enamel of the lower incisor of albino rats in correspondence with the prism compaction area during the first third of the ameloblastic modulation phase have been carried out. The reliefs were done on the longitudinal and median fracture plane and on the transversal fracture plane 8 mm from the cervical ansa. Measurements of the diameters of the honeycomb pits were carried out during the deposition phase, following removal of the ameloblastic coat. The data obtained were fed into an Apple Macintosh 512K/800 computer to obtain the geometric reconstruction of an isolated prism, the relations between each portion of the prism and the respective pits and a graphic example of the architectural organization of the enamel. It was shown that each prism consists of three distinct portion, just as there are three types of honeycomb pit. The external orifice of each pit is complementary to the interdigitant portion of the Tomes process, so the study of the pits may be used to evaluate the spatial orientation of the rods and not the morphology of their section. Cross-over between rows of contiguous rods occurs throughout the thickness of the internal enamel layer. The enamel possesses a particularly suitable structure for the transformation of surface type tangential forces into stresses or prevalently compression type.