The process of selective nuclear protein transport is divided into at least two steps: 1) ATP-independent, nuclear localization signal (NLS)-dependent binding to the cytoplasmic face of nuclear pores and 2) ATP-dependent translocation through the nuclear pores. Using a digitonin-permeabilized cell-free transport assay, it was found that a karyophile forms a stable complex with a cytoplasmic fraction to target the nuclear pores. Since this complex shows nuclear porebinding activity, we have referred to it as the nuclear pore-targeting complex (PTAC). The complex contains two essential proteins. The 58 kDa component of PTAC (PTAC 58; importin α; karyopherin α) was found to bind directly to NLS. The 97 kDa component of PTAC (PTAC 97; importin β; karyopherin β) associates with PTAC 58, but not karyophile. A complex of PTAC 58 and PTAC 97 targets nuclear pores, depending on the presence of a karyophile. The data suggest that the initial step in nuclear protein transport occurs as a result of complex formation of a karyophile with PTAC 58 which is, in turn, bound to PTAC 97.

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Myofibroblasts of the lamina propria of human seminiferous tubules were studied in testes having normal or slightly reduced spermatogenesis by means of electron microscopy, confocal laser microscopy and immunocytochemistry. Myofibroblasts are large, flat individual cells braced in a network of microfibrils and collagen fibrils in the tubular wall. They are arranged in discontinuous cell layers with interposed layers of an extracellular matrix.
Myofibroblasts of the lamina propria exhibit an unique cell shape with the peripheral cytoplasm split up in two or more layers. After FITC-phalloidin staining and by means of confocal laser microscopy, actin filaments of variable orientation are visible in their cytoplasm. The thickness and preferential direction of actin filaments differ in the outer and innermost cell layers. The myofibroblasts express both antigens of smooth muscle cells (α-smooth muscle actin, pan-actin, desmin, GB 42, smooth muscle myosin), and of connective tissue cells (vimentin, fibroblast surface protein). The variable expression of these antigens evidenced the existence of different phenotypes of myofibroblasts.
Immunoreactivity for basic fibroblast growth factor and transforming growth factor β as well as for com-ponents of the extracellular matrix indicate that these agents may be important for the phenotypic differentiation of the lamina propria cells. The detection of CNPase- and galactocerebroside-immunoreactivity in a number of lamina propria cells and some cells of the intertubular tissue gives rise to the hypothesis that components of the testicular tissue share some structural similarities with glia cells of the nervous system.
Finally, immunoreactivities for the neuronal and endothelial nitric oxide synthase, soluble guanylyl cyclase, cyclic GMP, calmodulin, calcium-dependent protein kinase II and glutamate indicate that thecontractility of myofibroblasts in the lamina propria of human seminiferous tubules may be in part modulated by the NO/cGMP-system.

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This paper describes the spatial organization of the collagen fibrillar skeleton in pregnant rabbit endometrium at term, employing an alkali/low temperature/maceration technique followed by scanning electron microscopic (SEM) observations. Parallel light microscopic (LM) and transmission electron microscopic (TEM) investigations were made to identify the location and possible changes in the endometrial collagen network. Two different types of NaOH maceration were applied, demonstrating separately: 1) the collagen structures (2N-NaOH maceration removes the cells and basal laminae); and 2) the cellular elements (6N-NaOH maceration removes the collagen fibrils).
After 2N-NaOH maceration, the collagen network of the endometrium is seen in a superficial compartment around the glands and a deep compartment situated near the endometrial-myometrial junction. Significant changes are observed only in the superficial compartment. The luminal mucosal surface is characterized by numerous thin projections reducing the uterine cavity which, as a consequence, further appears very irregular and highly convoluted. The subepithelial collagen network is composed of densely packed fibrils with a woven course. It contains many tubular or channel-like invaginations (100-150μm in width and 200-300μm in length) where endometrial glands are located. These invaginations, corresponding to the glandular impressions, are extremely dilated, enlarged and variable in shape. The collagen fibrils are arranged concentrically around the glandular orifices without forming bundles. At the bottom of the spaces between the mucosal projections, small fenestrations (4-8μm in diameter each) are present. They form small groups of about 10-20 in number and are due to the endometrial blood capillaries. The deep compartment of the endometrial collagen network is little altered, preserving its general lamellar arrangement.
The changes in the endometrial collagen skeleton are due to a variety of complex mechanical and hormonal stimuli affecting the uterus during pregnancy. These may be significant for correct implantation, placentation and delivery.

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This paper reports on the distribution, relationship and seasonal variations of neuropeptide Y (NPY)-like and gonadotropin-releasing hormone (GnRH)-like immunoreactants in the brain and hypophysis of the bony fish, the ayu Plecoglossus altivelis. NPY-like immunoreactivity was widely distributed in the brain: labeled cells were found in the nervus terminalis, the nucleus entopeduncularis, the habenula, the nucleus preopticus periventricularis, the nucleus tuberis lateralis, the mediodorsal hypothalamus, the dorsal tegmentum, and other sites. NPY fibers were considerably dense in the telencephalon and hypothalamus, and innervated the hypophysis. GnRH-positive cells occurred in the nervus terminalis and were sparsely distributed in the preoptic and tuberal areas of the hypothalamus. GnRH fibers were found in various regions of the brain. They were relatively dense in the hypothalamus, showing a local concentration in the middle region of the neurohypophysis. The GnRH-positive cells and fibers in the hypothalamo-hypophyseal complex increased in density around the spawning season. In tandem with gonadal maturation, NPY labeling in the cells of the nucleus tuberis lateralis became intense concomitantly with an increase in the labeled varicosities in the middle region of the neurohypophysis. Double immunostaining showed that NPY fibers were closely apposed to GnRH cells in the preoptic area. These results suggest a correlative involvement of NPY and GnRH in the control of the hypophyseal gonadotropic function of the ayu.

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We investigated the existence of functional subpopulations of thyrotropes in pituitary glands of male rats, also seeking to establish any correlation of thyrotropin secretion with morphometric data of secretory granules. Pituitary cells secreting thyrotropin were detected using a reverse hemolytic plaque assay. Population analysis of the plaque sizes (TSH secreted) of individual thyrotropes in control cultures from male rats revealed a unimodal frequency distribution. TRH added to the medium resulted in a shift to a bimodal distribution of sizes, consisting of small and large modes, but did not alter the fraction of plaque-forming thyrotropes. The plaque size of control cultures was the same as that of the fraction of TRH-stimulated thyrotropes forming small plaques. Because the extent of hemolysis is related to the amount of thyrotropin secreted by each individual thyrotrope, these results suggest that: a) all thyrotropes secrete thyrotropin even in the absence of a stimulatory dose of TRH; b) the thyrotrope subpopulation secreting small amounts of thyrotropin when incubated with TRH may be unresponsive to this stimulatory factor. After performing reverse hemolytic plaque assay, plaque-forming cells were subsequently processed for electron microscopy. Morphometric analysis of the secretory granules correlated well with plaque size (TSH secreted). It is thus concluded that the functional subtypes of thyrotropes can be recognized on the basis of their ultrastructural images.

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At the boundary between the proximal and distal divisions of the colon in the guinea-pig is a ring-like section which rhythmically contracts. HUKUHARA and his co-researchers demonstrated that antiperistaltic movements in the proximal colon start from this ring-like section, the so-called pacemaker area. Tissue specimens, 0.1-0.3mm in width/height×4-7mm in length, were prepared from various parts of this area. Significantly, in the circular muscle at the mesenteric border, a nodular structure spontaneously producing 10-12 cycle/min regular mechanical contractions was found. Moreover, histological investigations after physiological recording revealed that the presence of the innermost and/or outermost portions of the circular muscle coat was not necessary for these spontaneous activities. Champy-Maillet (ZIO) staining showed that smooth muscle cells in this spontaneously contracting nodule were heavily innervated. Transmission electron microscopy showed that the smooth muscle tissue of this particular area was characterized by scanty interstitial elements such as fibroblasts. Plasma membranes of adjacent smooth muscle cells were frequently in direct contact with each other, forming many gap junctions. Scanning electron microscopy in the specimen prepared using a NaOH-maceration method revealed fine three-dimensional relationships between nerve terminals and smooth muscle cells. The nodular structure described in this paper may provide a useful experimental model for the investigation of colonic motility and its neural control.

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Large aggregations of endocrine cells at the top of villi in the upper small intestine, discovered by SEGI (1935) in human fetuses and hence called SEGI's caps, have been known to occur also in bovine and porcine fetuses. Using bovine fetuses and newborns, this study aimed to clarify the fate of and changes in the SEGI's cap during the perinatal period. Immunocytochemistry was performed for CgA and PGP 9.5 as markers of the endocrine and nervous elements concerned.
In the second trimester in bovine fetuses, numerous endocrine cells were confirmed, by CgA immunocytochemistry, to gather in the epithelium on the top of almost every duodenal villus, either in a single layer or accumulating in a rounded cell mass. They persisted until birth, though decreasing in number during the third trimester. In these fetal periods the endocrine cells came to be invaginated into the lamina propria, and to be separated from the epithelium. They were attached by nerve fibers and shifted to the base of the villi and to the intercryptal tissue. The endocrine cell aggregations at the villous tips rapidly disappeared within three days after birth.
The intraepithelial endocrine cells (paraneurons) decreased in their immunoreactivity for CgA after they shifted into the lamina propria, whereas they increased in their immunoreactivity for PGP 9.5 while descending the villous interstitium. Using immunocytochemistry for PGP 9.5, we were able to trace the descent of the endocrine cells in association with nerve fibers. Microscopic images were obtained supporting the possibility that the endocrine-type cells eventually might be taken up by the intramural plexuses of Meissner and Auerbach. Furthermore, the fetal and perinatal intestine revealed enlarged solitary endocrine cells and authentic neurons, as well as their intermediate types, in the villous and intercryptal interstitium.
The present results indicate that the SEGI's caps in cattle are best developed in the second trimester of the fetal life, and do not support a hypothesis that the endocrine sensor cells in the caps principally function at the time of birth, especially for responding to the advent of colostrum. The endocrine or paraneuronal elements of the SEGI's cap appear to migrate into the interstitium to obtain more neuron-like features. A possibility that they may be incorporated in the intramural ganglia and further be transformed into neurons awaits further investigation.

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Lipid secreting Harderian glands in the ocular region of rodents contain a large amount of metal-free porphyrins. The localization of these porphyries and the areas of formation of the lipidporphyrin complexes in the glandular lumina have not been clearly defined. We therefore examined the intracellular localization of porphyrin fluorescence both in tissue sections and in cultured cells of Harderian glands of 5 week old female ICR mice, using confocal UV-laser scanning microscopes. The fluorescence appeared in glandular cells containing lipid droplets, but not in non-glandular cells (e. g. myoepithelial or interstitial) without these droplets. Fluorescence in the cells was recognized in the cytoplasm, but there was no evidence indicating that porphyrins were restrictively stored in mitochondria. Nuclei and lipid droplets lacked fluorescence. It is thus reasonable to conclude that porphyrins accumulate in the cytoplasm, and that porphyrins and lipids are secreted separately from glandular cells. The lipid-porphyrin complex is therefore probably formed in the glandular lumina and not within the glandular cells.

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Distribution of neurotensin-containing cells and neurotensin receptor-expressing cells was examined in the chicken thymus using a combination of in situ hybridization histochemistry for neurotensin receptor mRNA and immunohistochemistry for neurotensin. Neurotensin receptor mRNA-expressing cells and neurotensin-immunoreactive cells were localized in the medulla. Neurotensin receptor mRNA-expressing cells showed a round or elongated shape, while neurotensin-immunoreactive cells revealed round, ovoid, spindle or reticular shapes. Neurotensin-immunoreactive cells were much more numerous than those displaying labeling for the neurotensin receptor mRNA in males and females. Furthermore, electron microscopic immunohistochemistry for neurotensin showed that immunoreactive cells contained a large number of round or spherical granules which were 250-350nm in diameter. This evidence indicates that neurotensin is localized in endocrine cells, and that neurotensin receptor mRNA is expressed in epithelial cells. It further suggests the possibility of microenvironmental interaction of neurotensin between endocrine cells and epithelial cells within the chicken thymus.

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