Abnormal development of pacinian corpuscles in double trkB;trkC knockout mice

Pacinian corpuscles depend on either Aalpha or Abeta nerve fibers of the large- and intermediate-sized sensory neurons for the development and maintenance of the structural integrity. These neurons express TrkB and TrkC, two members of the family of signal transducing neurotrophin receptors, and mice lacking TrkB and TrkC lost specific neurons and the sensory corpuscles connected to them. The impact of single or double targeted mutations in trkB and trkC genes in the development of Pacinian corpuscles was investigated in 25-day-old mice using immunohistochemistry and ultrastructural techniques. Single mutations on trkB or trkC genes were without effect on the structure and S100 protein expression, and caused a slight reduction in the number of corpuscles. In mice carrying a double mutation on trkB;trkC genes most of the corpuscles were normal with a reduction of 17% in trkB-/-;trkC+/- mice, and 8% in trkB +/-;trkC -/- mice. Furthermore, a subset of the remaining Pacinian corpuscles (23% in trkB-/-;trkC+/- mice; 3% in trkB+/-;trkC-/- mice) were hypoplasic or atrophic. Present results strongly suggest that the development of a subset of murine Pacinian corpuscles is regulated by the Trk-neurotrophin system, especially TrkB, acting both at neuronal and/or peripheral level. The precise function of each member of this complex in the corpuscular morphogenesis remains to be elucidated, though.

Effects of increased nerve growth factor plasma levels on the expression of TrkA and p75 in rat testicles

In addition to their well-known roles within the nervous system, the neurotrophins and their receptors regulate some functions in the reproductive system. In this study we used combined morphological and immunohistochemical techniques to investigate the presence and cellular localization in the rat testicle of the two receptors of nerve growth factor (NGF), i.e. TrkA and p75(NTR). Furthermore, to evaluate whether increased plasma levels of NGF affect the ageing process, 4-methylcathechol (4-MC), an inductor of NGF synthesis, was administered. Both TrkA and p75(NTR) were expressed in rat testicles, but the pattern and intensity of immunoreaction were marginally different between them. In adult rats TrkA was expressed in spermatozoa and spermatids, and p75 was expressed in spermatogonia. In newborn rats TrkA immunoreactivity was found in the Leydig cells, whereas p75 was detected in a cellular layer that surrounds the seminiferous tubules. In adult treated animals the immunoreaction for TrkA and p75(NTR) was also localized in the spermatocytes, whereas in newborn treated rats no changes in the pattern of immunoreaction was observed. The present findings suggest a role of the NGF/TrkA/p75 system in the physiology of reproduction, but the practical relevance of this remains to be established.

Bcl-2 immunoreactivity in human cutaneous Meissner and Pacinian corpuscles

The occurrence and distribution of Bcl-2, a protein involved in the death-life cell pathways, was investigated in the peripheral sensory nervous system of healthy adult humans, including lumbar dorsal root ganglia, nerve trunks and glabrous skin (to analyze sensory corpuscles) using Western blot and immunohistochemistry. The antibody used labelled a protein of 26 kDa of estimated molecular weight corresponding with Bcl-2. Immunohistochemistry showed that only a neuronal population in dorsal root ganglia, some axons in peripheral nerves and the axon supplying Meissner and Pacinian corpuscles contained Bcl-2, whereas peripheral glial cells (i.e. satellite glial cells, Schwann cell, and lamellar cells of sensory corpuscles) did not. These results suggest that in normal conditions, Bcl-2 is only present in some neuronal, but not glial, elements of the sensory peripheral nervous system. The functional significance, if any, of these results remains to be determined.

TrkA and p75NTR in the ovary of adult cow and pig

Neurotrophins play a critical role in the development of the mammalian ovary, oogenesis and folliculogenesis. In this study we investigated the cell localization of the two main receptors for nerve growth factor (NGF), TrkA and p75NTR, in the cow and pig ovary, using immunohistochemistry. Specific immunoreactivity for TrkA and p75NTR was detected in the ovary of both species, but the pattern and intensity of immunostaining were marginally different between them. The follicular cells regularly expressed immunoreactivity for both receptors. Immunoreactivity was also detected in the oocytes, independently of the maturational stage of the follicles, with the exception of primordial and primary follicles of the pig which did not display p75NTR. Taken together, these results suggest a possible direct role of NGF on oocytes expressing TrkA and p75NTR, in addition to the well-known roles in other ovary functions. The practical relevance of these data remains to be clarified.

Effects of neurotrophin-3 gene mutation in the expression of neurocalcin

Neurocalcin (NC) is a neuron-specific "EF-hand" calcium-binding protein present in a non-fully characterized subpopulation of dorsal root ganglion (DRG) neurons, some kinds of mechanoreceptors and proprioceptors, and in motor end-plates. In the present study we have characterized NC expression in spinal sensory and motor neurons, and their endings in newborn mouse. Because the neurotrophic factor neurotrophin-3 (NT-3) appears to plays a major role in the development and maturation of sensory and motor neuronal populations, we have studied NC immunoreactivity in newborn NT-3 null mutant. In NT-3 deficient animals the overall number of NC-immunoreactive DRG neurons was reduced by as much as 70% including all large neurons, but subpopulations of NC expressing small and intermediate-sized neurons survived. As expected no muscle spindles were found in NT-3 mutant mice while they were present and normally innervated by NC-positive nerve fibers in wild-type animals. On the other hand, NC immunoreactivity was dramatically decreased in motoneurons of the spinal cord, ventral root nerves and motor end-plates in the absence of NT-3. The present results demonstrate that NC-containing DRG neurons include all proprioceptive, and a subset of mechanoreceptive and proprioceptive. Furthermore, they strongly suggest that NT-3 is involved in the maturation of motor end-plates.

Immunohistochemical detection of [corrected] TrkB in the enteric nervous system of the small intestine in pigeon (Columba livia)

The presence and cell localization of TrkB, the main receptor for the neurotrophins (NTs), was investigated immunohistochemically in the small intestine of adult pigeons, with special reference to the enteric nervous system (ENS). Several neuronal (neurofilament proteins and PGP 9.5) and glial cell (S100 protein) markers were studied in parallel. TrkB immunoreactivity (TrkB-IR) was found to be restricted to immunohistochemically-identified glial cells present in the enteric plexuses, and to Schwann cells forming the perivascular plexus. Also, TrkB-IR was detected in enterochromaffin cells and in unidentified dendritic cells within the gut-associated lymphoid tissue. The present results demonstrate that as for mammals, TrkB in the ENS is restricted to the glial cells. The possible function of the TrkB ligands, however, remains to be established.

S100 protein is a useful and specific marker for hair cells of the lateral line system in postembryonic zebrafish

The neuromast of the lateral line system of zebrafish has become an ideal model for the study of both developmental genetics and the vertebrate auditory system. Interestingly, the hair cells of this system have been found to selectively display immunoreactivity for S100 protein in some teleosts. In order to provide a selective marker for the sensory cells of the lateral line system, we have analyzed immunohistochemically the expression of S100 protein in zebrafish from the larval to the adult stage. In larval and adult animals S100 protein immunoreactivity was detected restricted to the hair cells of both superficial and canal neuromasts. Apparently the expression of S100 protein by hair cells was independent of the age, but it was expressed heterogeneously in the hair cells of canal neuromasts. The results of this work provide a feasible method to easily identify sensory cells in the neuromasts, and may be of interest in studies regarding development, differentiation or turnover of hair cells.

Structural and ultrastructural aspects of the pericardial sac in some sea water teleosts

Generally, in fishes the parietal pericardium is considered to be a semi-rigid structure. It is widely known that the entire parietal pericardium in fish, in contrast to that of higher vertebrates, is fixed to the body wall which consists mainly of skeletal muscle. This structural arrangement could explain the low end-systolic intrapericardial pressure in fishes. The morphology of the parietal pericardium of 11 sea-water teleosts, either free or breeding, coming from various areas of the southern Italy was studied. Macroscopical evaluation, but even more, histological and ultrastructural studies, showed some differences among the hearts of the examined subjects, more pronounced in the European hake (Merluccius merluccius, L.), in which a true pericardial sac was demonstrated, well differentiated and distinguishable from the other structures, in contrast to the observations in other subjects. The pericardial connective tissue showed no continuity with that of the surrounding structures, mainly skeletal muscle. This difference could be retraced to the well-known pattern of life and, therefore, to other individual as well as evolutionary factors in comparison with other teleosteans examined.

Diprosopiasis in a lamb. A case report

Conjoined twinning has been reported in most of the domestic animal species. Among them, sheep have the highest incidence of craniofacial defects. A live male crossbreed dystocic two-headed lamb was delivered from a 2-year-old Pinzerita sheep after first mating. After 40 h of life, the lamb spontaneously died. The most important gross findings involved the head, whereas the examination of different organ and tissue sections did not reveal remarkable histomorphological changes. The lamb was classified as a conjoined twinning and, on the basis of the facial duplication, as a diprosopus tetraophtalmus.

S-100 protein is a selective marker for sensory hair cells of the lateral line system in teleosts

The distribution of S100 protein in the neuromast of the lateral line system (LLS) was investigated immunohistochemically in alevins of three species of teleosts (Salmo trutta, Salmo salar and Dicentrarchus labrax), using a polyclonal antibody. In both the neuromasts of the canals, as well as in the pit organs, the hair cells, regarded as the specific sensory cells, displayed cytoplasmic immunoreactivity for S100 protein. Conversely, the supporting cells, mantle cells and basal cells were devoid of immunoreaction. These results demonstrate for the first time the occurrence of S100 in the LLS of teleosts. Due to the cell specific localization, this protein might serve as a marker for sensory hair cells in neuromasts.

Involvement of the NGF receptors (Trka and p75lngfr) in the development and maintenance of the thymus

Nerve growth factor (NGF) and its main low- (p75LNGFR) and high-affinity (TrkA) receptors have been found in the vertebrate thymus, thus suggesting they are involved in the control of thymic function. However, its role in this organ is poorly known. In the present study we used combined morphological and immunohistochemical techniques to analyze the distribution of TrkA and p75LNGFR in the rat thymus, as well as the structural changes in the thymus of p75 LNGFR or TrkA deficient mice. In adult rats both TrkA and p75LNGFR were localized in a subset of thymic epithelial cells found primarily in the subcapsular and medullary thymic regions, regarded to be endodermal-derived cells. Consistently, animals with a non-functional TrkA, but not those lacking p75LNGFR, showed structural changes consisting of a decrease in the density of thymocytes, absence of cortico-medullary border, and large cysts lined of endodermal epithelium. These results strongly suggest a function of the TrkA-NGF system in thymic functions mediated by epithelial cells, as well as a role of TrkA in the development of the murine thymus. The function of p75LNGFR remains to be established.

Immunohistochemical localization of neurotrophin receptor proteins in human skin

The target organs of neurotrophin-dependent sympathetic and sensory neurons, including the skin, synthesize and release neurotrophins, primarily NGF. Neurotrophins undergo retrograde axonal transport, and exert specific function in the perikarya of the responsive neurons. Moreover, evidence exists for an autocrine and/or paracrine function of neurotrophins in the skin. This study analyses the immunohistochemical localization of low (gp75) and high-affinity (gp140 trkA, gp145trkB and gp145trkC) neurotrophin receptor proteins in the human glabrous skin. We consider that the expression of neurotrophin receptors may be indicative of neurotrophin activity. Specific gp75 and gp140trkA-like immunoreactivity (IR) were observed highly co-localized in (1) epidermis, primarily in the basal keratinocytes; 2) sweat glands; (3) blood vessel walls, mainly in the muscular layer; (4) Schwann and perineurial cells of nerve trunks; (5) periaxonic cells forming sensory nerve formations (Meissner's and Pacini's corpuscles); (6) large axons of nerve bundles and of sensory corpuscles; gp145trkB-like and gp145trkC-like were found labelling nerve fibers and sensory nerve formations, as well as blood vessels and sweat glands, but not epidermic cells. The results suggest that, in addition to the well known neurotrophic functions, neurotrophins may also regulate unknown functions in non-nervous cutaneous cells, which are targets for neurotrophin-dependent sympathetic and sensory neurons.

Immunohistochemical localization of S100 proteins in dorsal root, sympathetic and enteric ganglia of several mammalian species, including man

The occurrence of S100 proteins in neurons of the mammalian peripheral nervous system is still controversial. This study was designed to investigate this topic in dorsal root ganglia (DRG) and the enteric nervous system (ENS) of several mammalian species (horse, buffalo, cow, sheep, pig, dog, rabbit and rat), as well as in DRG, paravertebral sympathetic ganglia (SG) and ENS of the adult man. Rat embryos of E17 and E19 were also examined. The material was fixed in Bouin's fixative, paraffin-embedded and processed for immunohistochemistry, combined with image analysis, using a panel of mono and polyclonal antibodies against S100alpha, S100beta or S100alpha + beta (referred to here as S100) proteins. In all species examined, strong S100 protein immunoreactivity (IR) was found in satellite glial cells and Schwann cells, which also showed S100alpha and S100beta IR in humans. Furthermore, faint S100 protein IR was observed in a subpopulation of DRG intermediate- and large-sized sensory neurons in humans, buffalo, sheep, and pig. The rat was the only species showing clear S100 and S100beta in neurons, labelling in about 30-35% in adults (small, intermediate and large in size), and about 88% at E17 and 42% at E19, respectively. Weak S100alpha protein IR was observed in most of human SG neurons. In ENS, S100 protein IR was restricted to enteric glial and Schwann cells, with the exception of cow and goat in which a subset of neurons in both the myenteric and submucous plexuses displayed strong S100 protein IR. Neuronal S100alpha IR and glial S100beta IR was found in the human ENS. The present results demonstrate intra- and inter-specific differences in the expression of S100 proteins by neurons of the peripheral nervous system among mammalian species. Furthermore, they also suggest that neuronal S100 protein, at least in humans, consists of both S100alpha and S100beta.

Neurocalcin-immunoreactive neurons in the mammalian dorsal root ganglia, including humans

Neurocalcin (NC) is a recently characterized EF-hand calcium-binding protein present in a discrete population of sensory neurons and their peripheral mechanoreceptors, but its presence in peripheral nervous system neurons other than in the rat is still unknown. The present study was designed to investigate the occurrence of NC in the dorsal root ganglia (DRG) of several mammalian species (horse, buffalo, cow, sheep, pig, dog, and rat), including humans. DRG were fixed, embedded in paraffin, and processed for immunohistochemistry using a polyclonal antibody against NC. The size of the immunoreactive neurons was measured. In all species examined, NC immunoreactivity (IR) was restricted to neurons but the percentage, as well as the size of the immunoreactive neurons, varied among different species. As a rule, small neurons (diameter <20 microm) lack NC IR. In some species (pig, dog, buffalo, cow), only the largest neurons showed IR, whereas in others (sheep, horse, rat, and humans) they covered the entire range of neuron sizes. The pattern of immunostaining was cytoplasmic, although in some species (cow and buffalo), it formed a peripheral "ring." The present results demonstrate that mammalian DRG contain a subpopulation of NC-positive neurons, which varies from one species to another. Based on the neuron size, the possible function of the NC-containing neurons is discussed.

Immunohistochemical localization of neurocalcin in human sensory neurons and mechanoreceptors

The localization of neurocalcin in the developing and adult human peripheral nervous system (dorsal root and sympathetic ganglia (DRG, SG), and enteric nervous system (ENS)) was investigated using immunohistochemistry. A subpopulation of large-sized neurons in DRG of 9 and 12 weeks old embryos showed immunoreactivity (IR), whereas the sympathetic ganglia or enteric neurons did not. In adults, neurocalcin IR was restricted to a subpopulation of large (13%) and intermediate (15%) sized neurons in DRG. The protein was also found in muscular (67%) and cutaneous (12%) nerve fibers, as well as in the axons supplying muscular (muscle spindles, Golgi's tendon organs, and perimysial Pacinian corpuscles) and cutaneous (Meissner's but not Pacinian corpuscles) mechanoreceptors, as well as motor end-plates. Present results demonstrate that neurocalcin in both developing and adult humans can be used as a specific marker for a subpopulation of sensory neurons coupled to proprioception and touch, and for axons of motoneurons forming motor end-plates.

A neuronal subpopulation in the mammalian enteric nervous system expresses TrkA and TrkC neurotrophin receptor-like proteins

Increasing evidence suggests that, in addition to peripheral sensory and sympathetic neurons, the enteric neurons are also under the control of neurotrophins. Recently, neurotrophin receptors have been detected in the developing and adult mammalian enteric nervous system (ENS). Nevertheless, it remains to be established whether neurotrophin receptors are expressed in all enteric neurons and/or in glial cells and whether expression is a common feature in the enteric nervous system of all mammals or if interspecific differences exist. Rabbit polyclonal antibodies against Trk proteins (regarded as essential constituents of the high-affinity signal-transducing neurotrophin receptors) and p75 protein (considered as a low-affinity pan-neurotrophin receptor) were used to investigate the cell localization of these proteins in the ENS of adult man, horse, cow, sheep, pig, rabbit, and rat. Moreover, the percentage of neurons displaying immunoreactivity (IR) for each neurotrophin receptor protein was determined. TrkA-like IR and TrkC-like IR were observed in a neuronal subpopulation in both the myenteric and submucous plexuses, from esophagus to rectum in humans, and in the jejunum-ileum of the other species. Many neurons, and apparently all glial cells, in the human and rat enteric nervous system also displayed p75 IR. TrkB-like IR was found restricted to the glial cells of all species studied, with the exception of humans, in whom IR was mainly in glial cells and a small percentage of enteric neurons (about 5%). These findings indicate that the ENS of adult mammals express neuronal TrkA and TrkC, glial TrkB, and neuronal-glial p75, this pattern of distribution being similar in all examined species. Thus, influence of specific neurotrophins on their cognate receptors may be considered in the physiology and/or pathology of the adult ENS.

Morphological and immunohistochemical considerations on the basal ganglia in pigeon (Columba livia)

Morphological and immunohistochemical studies carried out particularly around the level of the basal ganglia (BG) in birds, are reported and commented on. Our results showed, on paraffin embedded avian BG, both the histological features and the immunohistochemical findings on immunofluorescence distribution of some neuropeptides (especially Metenkephalin) in the striatal complex. By comparing our results of Metenkephalin immunoreactivity (Menkir) with the referred analogous ones of Substance P (SP) quoted in literature, we confirmed the strikingly similar labelling at the levels of the Lobus paraolfactorius (LPO) and Paleostriatum augmentatum (PA), in contrast with the very low immunoreactivity at the Paleostriatum primitivum (PP) levels. We were able also to demonstrate the strong MEnk-ir of the neurons of the Nucleus accumbens, Nucleus septalis and paraventricularis. All these findings are also in accord to the interpretation by many AA (Wynne and Gunturkun, 1995; Reinez et al., 1983), about the anatomical correspondence between the LPO-PA complex of birds and the caudate-putamen in mammals. Some MEnk + 'wooly like fibres' described in our specimens in the PA (on the contrary reported in the Gpe segment of mammals) apparently escape these correspondence.

Neurotrophin receptor-like proteins in Peyer's patches

BACKGROUND

The neurotrophins are a family of growth factors that act on responsive cells through specific high-affinity signal-transducing receptors called Trk (A, B, and C) proteins. The neurotrophin receptor proteins are widely distributed in both nervous and nonnervous tissues, including the lymphoid organs. The expression of these receptor proteins by a cell population is an indication of responsiveness to the respective binding neurotrophin. The present study investigated the presence and cellular localization of high-affinity neurotrophin receptor proteins in equine and bovine Peyer's patches.

METHODS

Peyer's patches from horse and cow intestine were fixed in Bouin's fixative, embedded in paraffin cut 10 microns thick, and studied immunohistochemically using rabbit polyclonal antibodies against specific epitopes of the intracellular domain of the Trk receptor proteins.

RESULTS

Immunoreactivity (IR) for Trk-like proteins was found in specific cell populations in Peyer's patches. TrkA-IR in the horse was localized in dendritic cells of the interfollicular T-cell zones and in follicular dendritic cells of the lymphoid follicles; in the cow, TrkA-ir was present in reticulum cells. TrkB-like IR was present in cells found inside lymphoid follicles of the horse, probably reticulum cells. Furthermore, in both species, TrkB-IR was found in interstitial dendritic cells and/or macrophages of the intestinal lamina propria. No specific TrkC-like immunostaining was found in immunocompetent cells of Peyer's patches.

CONCLUSIONS

Present findings demonstrate that, as in other lymphoid organs, the accessory nonlymphoid cells express immunoreactivity for high-affinity neurotrophin receptor proteins. These results seem to favor the notion that neurotrophins, especially nerve growth factor, could have a physiological role in secondary lymphoid organs, possibly acting on accessory cells and not directly on lymphocytes.

The architecture of the myosalpinx in the sow as revealed by scanning electron microscopy

OBJECTIVE

To provide a definitive settlement of data on the architecture of myosalpinx in the sow in consideration of controversial data existing in literature.

STUDY-DESIGN

To allow direct visualization of muscular architecture, segments of tube from fifteen sows were investigated by means of scanning electron microscopy after the removal of interstitial connective tissue with NAOH digestion.

RESULTS

In the extramural portion of the tubo-uterine junction, in the isthmus and ampulla, the myosalpinx is mainly constituted by oblique bundles of variable length, which run around the tube and merge into the surrounding musculature, giving origin to a plexiform arrangement. In the ampulla the fibers join in short bundles variously oriented.

CONCLUSION

The three-dimensional architecture of the sow myosalpinx consists of muscular bundles independent of one another which follow multiple spatial arrangements and form a complex network. Such a muscular structure is likely more suitable for stirring rather than pushing the embryo and gametes.

The three-dimensional architecture of the myosalpinx in the cow as revealed by scanning electron microscopy

The three-dimensional architecture of the myosalpinx in the cow has been investigated by means of scanning electron microscopy after removal of interstitial connective tissue with NaOH digestion. In the extramural portion of the tubo-uterine junction, in the isthmus and ampulla, the myosalpinx is made up of oblique bundles of variable orientation and length, which are loosely distributed in the tubo-uterine junction and densely packed in both isthmus and ampulla. These bundles intersect and merge into the surrounding musculature. Our observations demonstrate how myosalpinx consists mainly of bundles of muscular fibers independent one of another, which show a multiple spatial arrangement and form a complex network. Such a muscular architecture is likely more suitable for stirring rather than pushing the embryos and gametes through the tube.

Sensory epithelium of the vomeronasal organ express TrkA-like and epidermal growth factor receptor in adulthood. An immunohistochemical study in the horse

BACKGROUND

The medial wall of the vomeronasal organ (VNO) is lined with a sensory epithelium that is closely related to the olfactory epithelium, which is developed from the olfactory placode. It undergoes continuous replacement during its life span. In other sensory epithelia, cell proliferation is under the control of some trophic factors. Whether these proteins are involved in the continuous turnover of the VNO epithelium is unknown. This study approaches this topic by analyzing the occurrence of signal-transducing receptor proteins for neurotrophins (Trk proteins) and epidermal growth factor (EGFr).

METHODS

VNO samples were obtained from adult horses (n = 9) and processed for Western blot or immunohistochemical detection of TrkA, TrkB, TrkC, and EGFr. For immunohistochemistry, both frozen and formalin-fixed, paraffin-embedded sections were used. Antibodies against Trk proteins were polyclonal antibodies that map within the intracytoplasmic domain. Antibodies against EGFr were monoclonal antibodies that map within the external (clone EGFR1) or the cytoplasmic (clone F4) domains.

RESULTS

TrkA-like, but not TrkB- or TrkC-like, protein was detected in the VNO. By using immunoblotting, protein bands of TrkA-like protein with estimated molecular weights of 43-45, 55, and 60 kDa were found. In agreement with these findings, the sensory epithelium lining the VNO displayed strong TrkA-like immunoreactivity. On the other hand, regular protein bands with estimated molecular weights of 100 and 170 kDa, corresponding with immature and full-length EGFr, respectively, were found with the clone F4, whereas the clone EGFR1 was ineffective in detecting EGFr with Western blot analysis. Positive EGFr immunolabelling was observed regularly in the supranuclear pole of the sensory epithelial cells, and the pattern was identical with both antibodies used.

CONCLUSIONS

The present results provide evidence for the occurrence of EGFr in the VNO of the adult horse, suggesting a role for their ligands (EGF and transforming growth factor-alpha) in this organ, probably in continuous cell replacement, during the adult life span. However, although immunoreactivity for TrkA-like protein was regularly observed, because the full-length protein was not found, whether or not its putative ligands (nerve growth factor and neurotrophin-3) act on these cells remains to be demonstrated.

Age-related changes in the medullary reticular epithelial cells of the pigeon bursa of Fabricius

BACKGROUND

The medulla of the avian bursal lymphoid follicles contains heterogeneous cell populations, including the so-called medullary reticular epithelial cells (REC). These cells may contribute to the bursal microenvironment for B-lymphocyte differentiation and maturation. The bursa of Fabricius undergoes well-characterized posthatching developmental changes, but the age-related changes of the medullary REC have not been studied. The present study approaches this topic by analyzing hallmarks of epithelial cells: the occurrence of cytokeratin-type intermediate filaments and of desmosomes and desmoplakins in pigeon medullary REC.

METHODS

The bursae of Fabricius of male king pigeons (Columba livia L.) Morini's strain were examined at different ages (from hatching to 120 days after hatching) by light microscopic immunohistochemistry for pan-cytokeratins and desmoplakins and by transmission electron microscopy. The area occupied by medullary cytokeratin-immunoreactive cells was evaluated with quantitative image analysis.

RESULTS

At hatching, cytokeratin immunoreactivity was not detected in the bursal lymphoid follicles. During the posthatching growth period of the organ (7-75 days), there was a progressive and significant increase in the area occupied by cytokeratin-immunoreactive medullary REC, in the intermediate filaments filling the cytoplasm of REC, and in the number of desmosomes. Conversely, during the regressive period analyzed (90-120 days), the density of cytokeratin-positive cells progressively decreased, although they retained their ultrastructural characteristics. The evaluation of desmoplakin immunoreactivity paralleled that of cytokeratin.

CONCLUSION

The present results demonstrate that the medullary REC of the pigeon bursa of Fabricius undergoes age-dependent changes parallel with that involving the whole organ. The possible contribution of medullary REC to the bursal microenvironment is discussed.

The three-dimensional architecture of the myosalpinx in the rat (Rattus norvegicus) as revealed by scanning electron microscopy

The three-dimensional (3-D) architecture of myosalpinx in the rat has been investigated by means of scanning electron microscopy after microdissection and removing interstitial connective tissue with 6N NaOH digestion. In the extramural portion of tube-uterine junction the myosalpinx shows circularly arranged fibers originating from the uterus, together with oblique fibers typical for the salpinx, which occur more frequently in the deeper layers. As fibers approach the mucous folds they assume a plexiform arrangement, which is maintained through all tubal segments. In the isthmus surface fibers form wide muscle rings around the elbow of loops, peculiar to the rat tubal morphology. Surface fibers in the ampulla and pre-ampulla have an even circular course. Our 3-D results reveal that the muscular architecture of rat tube is mainly organized in concentric, monolayered shells with a plexiform arrangement tightly fastened together. Functionally, this muscular arrangement seems to be capable of stirring rather than pushing the embryo and gametes. Finally, such a plexiform network might work as a mechanism of "tube locking" in proximity of isthmic loops as well as at the level of the ampullary-isthmic junction.

The three-dimensional architecture of the myosalpinx in the sheep as revealed by scanning electron microscopy

The three-dimensional (3-D) architecture of the myosalpinx in the sheep was studied by scanning electron microscopy after the removal of interstitial connective tissue with NaOH digestion. In the extramural portion of the tubo-uterine junction, the myosalpinx is made up of densely packed, circularly arranged superficial fibers and of innermost loose fiber bundles following an almost longitudinal course. In the isthmus and ampulla, the myosalpinx is constituted by oblique bundles of variable length, which run around the tube and merge into the surrounding musculature, giving rise to a plexiform arrangement. The present 3-D observations demonstrate that the sheep myosalpinx consists mainly of single muscular fibers and more complex bundles which show a multiple spatial arrangement and a plexiform distribution. Such a muscular architecture is more likely suited for stirring rather than pushing the embryos and gametes through the tube.

Localization of Trk neurotrophin receptor-like proteins in avian primary lymphoid organs (thymus and bursa of Fabricius)

The avian thymus and bursa of Fabricius are the specific organs where the maturation and differentiation of T- and B-lymphocytes, respectively, take place. In the mammalian lymphoid organs mRNAs of the neurotrophins and their receptors have been identified but their localization at the protein level remains still unknown. This study was undertaken to analyze the localization of the Trk family of tyrosine kinase receptors in the avian primary lymphoid organs (thymus and bursa of Fabricius) during the posthatching development using immunohistochemistry. These proteins serve as essential constituents of the high affinity receptors for neurotrophins. In the thymus of all groups of age specific immunoreactivity (IR) was observed for all three Trks: TrkA-like IR was found labelling medullary epithelial cells and a subpopulation of cortical epithelial cells; TrkB-like IR was found in the medullar dendritic cells and cortical macrophages; TrkC-like IR labelled the cortical epithelial cells and scattered medullar clusters of epithelial cells (including Hassal's corpuscles). Quantitative analysis revealed age-dependent decrease in the area occupied by TrkA-like IR in the cortex, and age-dependent increase in the medulla; no changes were detected in the area occupied by TrkB-like IR; the TrkC-like immunoreactive cells increase from 7 to 30 days and then decrease. Regarding to the bursa of Fabricius, TrkA-and TrkC-like IR were exclusively found in the epithelial cells of the follicle associated and the interfollicular epithelia, as well as TrkC-like IR in some medullary reticular epithelial cells of adult animals. Nevertheless, TrkB-like IR labelled extrafollicular unidentified cells in 7 days old animals, and the follicular secretory dendritic cells at 30 and 60 post-hatching. The area occupied by the medullary TrkB-like IR cells increased between 30 and 60 days. No immunostaining of lymphocytes was observed for any of the assessed antigens. The blood vessels of both the thymus and the bursa of Fabricius were immunoreactive for TrkA- and TrkC-like proteins. The present results provide evidence for the localization of Trks in the non-lymphoid cells (epithelial and dendritic) of the avian primary lymphoid organs, suggesting a role for neurotrophins in these cells. Moreover, the selective cell localization of each Trk protein, and the absence of apparent overlapping, claims for a differential role of the specific Trk ligands. Whether or not these findings have functional relevance for T- and B-lymphocytes processing in avian primary lymphoid organs is discussed.

Muscarinic cholinergic receptor subtypes in the pigeon bursa of Fabricius: a radioligand binding and autoradiographic study

The pharmacological profile and the anatomical localisation of muscarinic cholinergic receptor subtypes were studied in the pigeon bursa of Fabricius, using radioligand binding and autoradiographic techniques with [3H]quinuclidinyl benzilate (QNB) as a ligand. [3H]QNB was specifically bound to sections of bursa of Fabricius. The binding was time-, temperature- and concentration-dependent. The dissociation constant was 0.31 +/- 0.02 nM, and the maximum density of binding sites averaged 38 +/- 2.5 fmol/mg protein. The pharmacological profile of [3H]QNB binding to sections of pigeon bursa of Fabricius was consistent with the labelling of M2, M3 and M4 muscarinic receptor subtypes. Light microscope autoradiography showed the localisation of [3H]QNB binding sites in the medulla, in follicular septa, in the cortico-medullary border and in lesser amounts in the cortical layer. The functional significance of these receptors should be clarified in future studies.

Age-related changes of the noradrenergic and acetylcholinesterase reactive nerve fibres innervating the pigeon bursa of Fabricius

Age-dependent changes in the innervation of the pigeon (Columba livia, L.) bursa of Fabricius, from hatching to 120 days of age, were studied by fluorescence-histochemical and neurochemical methods for demonstrating noradrenergic and acetylcholinesterase (AChE)-reactive nerve fibres respectively. The distribution of both nerve fibre types was largely perivascular. Furthermore, a few isolated nerve fiber profiles were observed beneath the bursal epithelium, in the interfollicular septa and in the follicular cortex. No nerve fibre profiles reaching the medulla of the lymphoid follicles were observed. In addition to nerve fibres, AChE reactive neuron-like cells were encountered within the capsule and interfollicular septa. AChE reactivity was also found in dendritic-like cells localized in the cortical and cortico-medullary border. No changes in the density of perivascular noradrenergic innervation were noticeable during the ages studied, whereas the density of AChE-reactive fibres supplying vessels reached the adult pattern at 30 days, and then remained unvaried. The density of non-perivascular nerve fiber profiles, specially the AChE reactive type, increased until 30 days, remained unchanged until 75 days and then increased with aging (90-120 days). The interrelationship between the autonomic nervous system and the immune system is discussed.

Experimental incomplete spinal cord injury: treatment with a combination of nimodipine and adrenaline

The effect of combination of nimodopine and adrenaline treatment on the motility deficits following secondary spinal cord damage was studied. Morphometric axonal analyses were also done. Incomplete spinal compression was induced in albino New Zealand rabbits anesthetized with ketamine. Neurological deficit was assessed by Tarlov's scale. The animals were divided into different groups. In one group the animals were anesthetized and subjected to all procedures except spinal cord injury and pharmacological treatment. Each of the other groups were divided into 2 subgroups; the spinal cord compression was induced for 2 min in one subgroup and 5 min in other subgroup. The pharmacological treatment in different groups consisted of slow intravenous infusions of saline alone, combination of adrenaline and nimodipine, nimodipine alone and adrenaline alone. The evolution of the motor damage was evaluated by comparing scores obtained with Tarlov's scale 1, 24 and 48 hrs after the end of spinal cord compression. In all animals, spinal cord compression for 2 and 5 min induced a 5th degree motor deficit. Treatment with saline improved slightly the motor deficit. The improvement of motor deficit was much better when a combination of nimodipine and adrenaline was used. The animals treated with nimodipine alone showed a better recovery in comparison with the animals treated with saline alone.

Age-related changes in the secretory-dendritic cells of the pigeon bursa of Fabricius: an immunohistochemical and ultrastructural study

The present study was undertaken to determine, by means of immunohistochemical techniques, image analysis and ultrastructural methods, whether the secretory-dendritic cells (SDC) of the pigeon bursa of Fabricius undergo changes from hatching to the involutive stage (120 days) of the organ. A monoclonal antibody against vimentin (VIM) was used to label SDC. VIM-like immunoreactivity (VIM-L IR) was observed labelling dendritic cell profiles in all age groups. These cells are primarily localized within the medulla and at the cortico-medullary border of the lymphoid follicles. At hatching VIM-L IR was present mainly in the cell bodies, whereas during post-hatching bursal growth (7 to 75 days) it was also present in the cell processes. Conversely, the involutive period examined (90-120 days) was characterized by a progressive decrease of VIM-L IR in the SDC processes. Quantitative studies confirmed the immunohistochemical findings. At the ultrastructural level, there was a progressive increase from 0 to 90 days of age in both the number and size of secretory granules and break-down bodies, as well as in the length of the SDC processes. The involutive stage showed the reverse phenomena. The present results demonstrate that the SDC of the pigeon bursa of Fabricius undergo age-related changes parallel with that of the organ. The possible involvement of SDC in the maintenance of the bursal microenvironment and their role in the maturation of lymphoid line cells is discussed.

Stimulatory effects on lactotrophs and crop-sac of interleukin-1 and interleukin-2 in pigeons (Columba livia)

The ultrastructural effects of human-recombinant interleukin-1 beta (IL-1 beta) and human-recombinant interleukin-2 (IL-2) on the crop-sac (the target organ for prolactin secretion in birds) and the anterior pituitary lactotrophs, were studied in pigeons (Columba livia). The intraventricular microinfusion of the two interleukins produced maximal crop-sac stimulation with milk-like secretion, as demonstrated by the observation of ultrastructural changes in the lactiferous areas through scanning and transmission electron microscopy of crop-sac mucosa. A marked activation of the anterior pituitary lactotrophs was also observed. Crop-sac and pituitary lactotrophs stimulatory effects were prevented by a previous intraventricular treatment with monoclonal antibodies for IL-1 beta and IL-2 receptors, but not by an intraperitoneal administration of naloxone. The present results show that interleukins possess in pigeons marked stimulatory effects on prolactin secretion and that these are mediated by specific receptors.

[Comparative anatomo-microscopic observations on the esophagus of teleosts with different feeding habits]

The authors describe the micro-anatomy of the oesophagus of different diet fish: herbivorous (Boops salpa), omnivorous (Liza aurata) and carnivorous fish (Blennius gattorugine and Gaidropsarus mediterraneus). In all the observed species the oesophagus is formed by a tunica mucosa, tunica muscularis and tunica serosa. The tunica mucosa of the herbivorous fish arises to form thin plicae which protrude into the lumen and are covered with squamous stratified epithelium. The goblet cells do not arrange among the covering cells but take place laterally and on the basis of the plicae. The tunica muscularis is constituted by an external circular layer and an inner longitudinal layer of striated muscle. The oesophagus of omnivorous fish shows thick plicae covered with a higher epithelium than that of the herbivorous fish. Among the epithelial cells a lot of taste buds have been found. The tunica muscularis is like that of the herbivorous fish. In the carnivorous fish Blennius the tunica mucosa presents thin plicae like those of the herbivorous fish but they are covered with a thicker epithelium. The tunica muscularis is formed by an external circular layer and by an inner longitudinal layer which constitutes two diametrically opposed bundles placed dorsally and ventrally. In the other carnivorous fish Gaidropsarus, the tunica mucosa shows very thick plicae covered with a quite high squamous epithelium among which there are many goblet cells. In this fish too numerous taste buds have been found. The tunica muscularis is arranged in the same manner observed in the other carnivorous fish.

Circadian rhythm of glucose utilization in the pineal body of rats of different ages

Employing quantitative autoradiography, pineal body glucose utilization (GU) was measured in daytime or at night in prepubertal (aged 1 month), adult (aged 3 months), and mature (over 12 months old) rats. In prepubertal and adult rats, in daytime, GU values within the pineal tissue were homogeneously distributed around 65 mumol glucose/100 g per min. In prepubertal animals no significant variations in GU were observed between daytime and nocturnal measurements. A circadian metabolic rhythmicity was evident in adult rats, with a GU peak measured at 2 a.m. In mature animals, GU also varied between day and night, with an increment in the relative difference between the two values. The present investigation is the first to demonstrate that circadian metabolic rhythmicity is absent before sexual maturation while it is enhanced in 12-month-old rats. These changes in pineal energy metabolism with advancing age are intriguing in view of the concept that the pineal gland may be involved in functional changes occurring during the process of aging.

[Morphometric analysis of the sciatic nerve and its principal branches in the pigeon (Columba livia)]

The methodological approach used in this study is to characterize the number, the density and the diameter distribution of myelinated fibers (MFs) and unmyelinated fibers (UMFs) in sciatic nerve and its main branches of pigeon. The results have shown that the fiber composition is quite variable because in pigeon there are relatively MF with thin myelin sheaths and MF with thicker sheaths. Our data suggest that morphometric analysis could represent a helpful methodological approach to better characterize these systems.

The three-dimensional architecture of the myosalpinx in the rabbit as revealed by scanning electron microscopy

The three-dimensional (3-D) architecture of the myosalpinx in the rabbit has been investigated by means of scanning electron microscopy after microdissection and the removal of interstitial connective tissue with KOH digestion. In the extramural portion of the tubo-uterine junction, the myosalpinx presents outer longitudinal bundles which form a well-defined continuous muscular layer extending towards the ampulla. Underlying this layer there are single muscular bundles which follow an uneven circular arrangement. At a deeper level the same bundles present a plexiform arrangement. Several bundles reach the base of the mucous folds and follow a discontinuous, approximately longitudinal arrangement. In the isthmus, the myosalpinx shows superficial longitudinal strips that abruptly bend sideways as they approach the ampulla, thereby enveloping the underlying muscular structure. The latter is arranged in the same way as at the extramural portion of the tubo-uterine junction, except for the lack of the outer longitudinal layer originating from the uterus. Our 3-D results revealed that the architecture of the rabbit myosalpinx consists of muscular bundles independent of one another that follow multiple spatial arrangements and form a complex network. Such a type of structure seems to be capable of stirring rather than pushing the embryo and gametes.

Clinical, morphometric and ultrastructural aspects in a new model of spinal cord compression

A new model of spinal cord compression is presented. Forty-two New Zealand albino rabbits weighing between 1.2 and 1.5 kg were submitted to spinal cord compression to about half of its normal diameter by vascular Sugita's clip to different compression time (sham, 5-10-20 minutes e 1-6-12 hours) and sacrified after 72 hours. The consequent neurological dysfunction size of lesion was graded by Tarlov's scale for voluntar motility. Ultrastructural and morphometrical studies were carried out to evaluate changes in shape, perimeters, axonal and myelin areas of the lateral and the posterior tract of spinal cord. A 10 minute decrease of 50% of the transverse diameter of the spinal cord causes a defined damage. The swelling of myelin is a useful index of the importance of the damage.

Architecture of the myosalpinx of the isthmus in the guinea pig by means of scanning electron microscopy

The three-dimensional architecture of the isthmic myosalpinx in the guinea pig was investigated by means of a technique that involves stretching the myosalpinx under a dissecting microscope, followed by selective digestion of the interstitial connective tissue with KOH and, finally, observation under a scanning electron microscope. The images obtained in this way prove that the myosalpinx is arranged in single bundles of smooth muscle cells which essentially do not show any specific geometrical course. Furthermore, smooth muscle cell bundles following an oblique course, not referred in the literature prior to this report, were demonstrated. These new three-dimensional microanatomical results call for a reevaluation of the functional role of oviduct motility.

Experimental investigations on a model of cryogenic edema

The role of mechanisms underlying formation and progression of vasogenic brain edema is investigated. On this purpose, cerebral edema was produced by cortical freezing in two different brain situations in rabbits (with or without replacement of bone flap). BBB (Blood-Brain Barrier) breakdown was evaluated by observation of Evans blue extravation, while a histopathological evaluation was carried out by light and transmission electron microscopy. Water content of brain tissue was determined by the wet/dry weight ratio method. Comparison of extension and intensity of cerebral edema between these two groups of animals shows a statistically significant difference: there was evidence of higher water content in the animals undergone replacement of bone flap. The Authors emphasize the importance of tissue pressure gradients in determining diffusion of cerebral edema.

Stimulation of crop sac and pituitary lactotrophs after intraventricular administration of dermorphin in pigeons

The effects of dermorphin, a new potent opioid peptide, on structural and ultrastructural changes in the crop sac and in pituitary lactotrophs were assessed in pigeons (Columba livia). A single administration of dermorphin into the third cerebral ventricle (1 microgram) and the same dose repeated for 3 consecutive days both produced maximal crop sac stimulation, as documented by the presence of milk-like material as well as by scanning and transmission electron microscopy of crop sac mucosa. In addition, marked stimulatory effects were also observed in pituitary lactotrophs, as shown by stimulation of Golgi apparatus, enlargement of rough endoplasmic reticulum, increase in mitochondria size, and the presence of lysosomes and electron-opaque granules. The stimulatory effects of dermorphin on the crop sac and lactotrophs were completely prevented by naloxone, an antagonist at opiate receptors. Since dermorphin is a natural constituent of the avian brain, it has been suggested that this peptide may represent the still-obscure hypothalamic prolactin stimulatory factor.

Histochemical characteristics of rabbit stapedius muscle

A histochemical analysis of rabbit stapedius muscle fibers was conducted using the myofibrillar ATPase and NADH-tetrazolium reductase techniques. Two different fiber types, type 1 and type 2b, were identified. The functional significance of the results is discussed.

Crop-sac response after systemic and intraventricular administration of neuroleptic drugs

Present experiments were aimed at studying in pigeons the effects of some neuroleptic agents given systemically or into the 3rd cerebral ventricle on PRL secretion and following morphological changes of the crop-sac mucosa both by classical histological methods and scanning electron microscopy. In addition, such changes were also evaluated on the basis of a semiquantitative method using a 1-4 rating scale. 3- or 5-day systemic treatment with reserpine, haloperidol and (ł/-)-sulpiride produced an intense crop-sac response consisting of a marked epithelial hyperplasia and presence of milk-like material. Similarly, a much lower dose of haloperidol, clozapine, and the two enantiomers of sulpiride given into the 3rd cerebral ventricle for 3 consecutive days produced a marked crop-sac response. The l-sulpiride was more active in comparison to the d-enantiomer. In conclusion, present experiments show that, similarly to mammals, in pigeons neuroleptic drugs are able to stimulate prolactin secretion and suggest that these effects are mediated through an action at the hypothalamic and/or pituitary level by removing a tonic dopaminergic inhibition.