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PubMed2002

Cone neurite sprouting: an early onset abnormality of the cone photoreceptors in the retinal degeneration mouse.

PURPOSE: Mutations in many rod genes can cause inherited blinding neurodegeneration in the retina characterized by sequential death of rod and cone photoreceptors. This study was to examine the morphological changes of the cone photoreceptors in retinal degeneration (rd1) mice caused by rod-specific cGMP phosphodiesterase beta-subunit gene mutation and to gain insights into the early cellular events underlying the secondary cone death. METHODS: Transgenic mice that have their living cones labeled by the green fluorescent protein (GFP) transgene and carry the homozygous rd1 mutation were generated, and identified by PCR analysis of the mouse tail DNA and PCR coupled Dde I digestion. The morphology of cone cells in live and fixed retinas from developing and adult mice was examined with fluorescence and scanning laser confocal microscopy. Some fixed mouse retinas were also examined by immunocytochemical staining. Volume images from the confocal three-dimensional (3D) data sets were processed with IMARIS software for 3D view of the detailed cone cell morphology. RESULTS: The cone photoreceptors in the rd1 retinas exhibited a novel process of neurite sprouting, in addition to the general pathological changes of cone degeneration such as shortening and loss of cone outer and inner segments, and loss and death of the cones. The cones gave rise to prominent neurite outgrowth from their axons and synaptic pedicles as well. Most neurites had beaded varicosities along their length and some terminated as bulbous structures. Some cone pedicles showed abnormally elongating and branching processes. The degenerating cones were disorganized, and migrated into the inner nuclear layer. Some cone neurites extended horizontally and appeared to contact the rod bipolar cells, while others projected into the inner plexiform layer. The aberrant cone sprouting started from P8 when rod degeneration generally began, and became evident by P10. In contrast, this abnormal cone neurite sprouting was not observed in the examined control mice that did not carry the rd1 mutation. Double-labeling with cone cell-specific peanut agglutinin confirmed that the fluorescent cells expressing the GFP in the rd1 retinas were indeed the cone photoreceptors. CONCLUSIONS: Cone photoreceptors in the rd1 mice underwent a remarkable process of neurite sprouting that appeared to start before the onset of cone cell death and persisted throughout the course of cone degeneration. This novel process of cone neurite sprouting may be a part of the early cellular events leading to the cone photoreceptor death in retinal degeneration of the rd1 mice.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed1998

Beta-adrenergic and fibroblast growth factor receptors induce neuronal process outgrowth through different mechanisms.

The mechanisms that initiate and direct neuronal process formation remain poorly understood. We have recently described a neuronal progenitor cell line, AS583-8.E4.22 (AS583-8) which undergoes neurite formation in response to beta2-adrenergic and basic fibroblast growth factor (bFGF) receptor activation [Kwon, J.H. et al., (1996) Eur. J. Neurosci., 8, 2042-2055]. In the present study, a comparison of these responses revealed that isoproterenol (ISO), a beta-adrenergic receptor agonist, induces multiple, highly branched processes within 30 min while bFGF induces fewer, unbranched processes within 24 h. In contrast to the ISO response, bFGF induces mitogen-activated protein kinase activation and c-fos expression in the cell line and results in neurite outgrowth that is dependent on new mRNA and protein synthesis. Two-dimensional isoelectric focusing-sodium dodecyl sulphate-polyacrylamide gel electrophoresis of cytoskeletal preparations revealed different patterns following ISO vs. bFGF exposure suggesting selective changes in protein expression and/or post-translational modifications. Immunoblot analysis of these preparations for beta-tubulin, tyrosinated alpha-tubulin and acetylated alpha-tubulin also revealed different patterns following each type of treatment. Follow-up confocal microscopy revealed that following ISO, the distribution of tyrosinated tubulin extends to the distal ends of processes whereas acetylated alpha-tubulin is diminished within distal ends. This pattern has been reported to be associated with enhanced microtubule dynamics, a state in which process outgrowth is facilitated. In contrast, following bFGF treatment the distributions of tyrosinated and acetylated alpha-tubulin were identical, a state associated with a diminution of microtubule dynamics. These results, a different time course of neurite formation, dependency on new gene expression and differential expression and cellular distribution of major cytoskeleton proteins suggest that neurite outgrowth induced by ISO vs. bFGF is mediated by two distinct intracellular effector mechanisms in AS583-8 cells. In addition, studies, using the differential distribution of post-translational modified alpha-tubulins in neurites of primary neuronal cultures as marker for the two distinct processes of neurite formation suggest, that similar mechanisms are present in vivo. Therefore, the AS583-8 cell line provides a useful model to study these signalling mechanisms that couple neurotransmitter and growth factor receptor activation to the cytoskeletal changes that mediate neurite formation.

Animals↗

PubMed2001

Analysis of fractal dimension of O2A glial cells differentiating in vitro.

Fractal dimension is a quantitative measure of morphological complexity. Glial cells of the oligodendrocyte-type 2 astrocyte (O2A) lineage exhibit increasing morphological complexity as they differentiate in vitro. Enriched populations of O2A progenitor cells isolated from neonatal rat cerebral hemispheres or optic nerves were allowed to differentiate in vitro, and their fractal dimensions were measured over time. The fractal dimensions of the maturing cells correlated with perceived complexity; cells with elaborate process branching had larger fractal dimensions than cells with a simpler morphology. An analysis of changes in fractal dimension revealed distinct rates of growth for both oligodendrocytes and type 2 astrocytes. The fractal dimension remained constant over a 10-fold range in optical magnification, demonstrating that cultured O2A glial cells exhibit self-similarity, a defining characteristic of fractal objects. These results illustrate that fractal dimension analysis of maturing cell populations is a useful method for quantitatively describing the process of cell differentiation.

Animals↗

PubMed2005

Absorbing-state phase transitions with extremal dynamics.

Extremal dynamics represents a path to self-organized criticality in which the order parameter is tuned to a value of zero. The order parameter is associated with a phase transition to an absorbing state. Given a process that exhibits a phase transition to an absorbing state, we define an "extremal absorbing" process, providing the link to the associated extremal (nonabsorbing) process. Stationary properties of the latter correspond to those at the absorbing-state phase transition in the former. Studying the absorbing version of an extremal dynamics model allows to determine certain critical exponents that are not otherwise accessible. In the case of the Bak-Sneppen (BS) model, the absorbing version is closely related to the "f -avalanche" introduced by Paczuski, Maslov, and Bak [Phys. Rev. E 53, 414 (1996)], or, in spreading simulations to the "BS branching process" also studied by these authors. The corresponding nonextremal process belongs to the directed percolation universality class. We revisit the absorbing BS model, obtaining refined estimates for the threshold and critical exponents in one dimension. We also study an extremal version of the usual contact process, using mean-field theory and simulation. The extremal condition slows the spread of activity and modifies the critical behavior radically, defining an "extremal directed percolation" universality class of absorbing-state phase transitions. Asymmetric updating is a relevant perturbation for this class, even though it is irrelevant for the corresponding nonextremal class.

Journal Article↗

PubMed1980

Multinucleate neurons with neurohaemal and synapsing axons at the heart and alary muscles of the butterfly Caligo beltrao Illiger (Lepidoptera).

The segmental heart nerves of Caligo beltrao Illiger (Brassolidae) were examined by transmission and scanning electron microscopy. Heart and alary muscles are innervated by branching processes of single multinucleate neurons (MNNs). There is one MNN situated at each segmental fan-shaped group of alary muscles. The main nerve of the MNN consists of a bundle of processes. This nerve extends centripetally toward the CNS and corresponds to the dorsal portion of the transverse nerve. However, neither axo-somatic nor axo-axonic synapses were found, the presence of which might suggest that this nerve contains axons of different neuronal origin. The synaptic contacts of the MNN with axons originating from the CNS are therefore assumed to be established beyond the spiracular region. In addition to the neuro-muscular junctions of the smaller centrifugal axon branches there are neurohaemal release sites along the entire length of all MNN axon bundles. Axon terminals are packed with either dense-cored or multigranular vesicles. Both morphological types of vesicles are, however, found side by side in the large axons and in the perikaryon, often at the same golgi element. These morphological findings may support the concept that more than one transmitter is produced in a single neuron. Questions that arise in reference to dual or polyfunctional neurons and to the control of cardiac activity are discussed.

Animals↗

PubMed1980

Peptidergic pathways in the central nervous system.

Before detailed studies of the physiology and pharmacology of central peptidergic neurons can be undertaken, the location of these neurons must be determined and the mechanism(s) by which they synthesize their peptide products must be explored. In the previous paper, Dr Hökfelt described his elegant immunohistochemical studies, which are designed to answer the questions: Where are peptidergic perikarya?; Where do these perikarya send their processes?; Do these processes branch extensively and innervate several structures?; and Do peptidergic cells contain more than one active product? By studying the effects of lesions on peptide levels in microdissected tissue samples, immunocytochemical data can be confirmed and extended. The microanalytical approach also allows one to determine the nature of the immunologically active substances in a tissue extract, and in vivo or in vitro pulse--chase studies provide the ultimate validation of immunohistological localization of peptidergic perikarya and new information about the biosynthesis of peptides and regulation of this biosynthetic process. Our recent studies of central proopiocortin- and neurophysin/vasopressin-producing neurons will illustrate the above points.

Adrenocorticotropic Hormone↗

PubMed1999

Innervation and myoepithelial arrangements in the submandibular salivary gland of ferret investigated by enzyme, catecholamine and filament histochemistry.

Although the submandibular gland of ferret is useful for studying salivary secretory processes which are regulated by nerves and involve myoepithelial activity, little attention has been paid to its parenchymal innervation and myoepithelial arrangements. Therefore, glands obtained postmortem from mature ferrets of both sexes were here examined with the use of light-microscopic histochemical techniques for cholinesterases, phosphatases and phosphorylase, histofluorescence for catecholamines, and milling dyes. Acetylcholinesterase staining was associated with nerve trunks in the interlobular stroma and an extensive intralobular network of nerve fibres, presumably of a cholinergic type, embracing acini and ducts. There were fewer fibres containing fluorescing catecholamines, presumably adrenergic. They were largely associated with acini. Numerous stellate cells with fine branching processes embracing acini, presumably myoepithelial cells, and a few spindle-shaped basal cells, investing striated ducts, were demonstrated on frozen tissue by alkaline phosphatase, but not by adenosine triphosphatase, inosine diphosphatase and phosphorylase. Cells of similar shape and distribution were also demonstrated by staining with milling dyes on fixed tissues, indicating possibly a filamentous constituent conferring mechanical stability and/or contractile ability. Together, these results suggest, firstly, that a cholinergic-type parenchymal innervation is prominent in the submandibular gland of ferret, although many adrenergic nerves are also present, and, secondly that the gland has a very extensive myoepithelial network which is possibly involved in membrane transport, and the support and or contraction of the secretory parenchyma.

Actin Cytoskeleton↗

PubMed1978

Development of distinct cell types in the feline red nucleus: a Golgi-Cox and electron microscopic study.

The feline RN contains neurons which fall into three size categories: giant (40--80 micrometer), medium (25--35 micrometer) and small (6--20 micrometer). These three populations of rubral neurons are distinguishable on the basis of a number of ultrastructural criteria and form classes not dissimilar from the traditional three divisions of cell types. Each of the three populations of rubral neurons can be further divided into three subgroups on the basis of a large number of configurational criteria discernible by the Golgi-Cox method. Each of these nine cell types are clearly separate, distinguishable by at least three criteria, and are found in different regions of the RN. It is shown that in the 5-day prenatal kitten, rubral neurons are already organized into the aforementioned three size categories. At this age most of the subpopulations are also distinguishable by the Golgi-Cox method. However, the giant rubral neurons (about 30 micrometer) and the medium sized cells (about 20 micrometer) are much smaller than in the adult cat. The dendrites elaborate many fine processes which emerge from multiple varicosities. The neuropil differs strikingly from that of the adult in that the vast majority of axons are small and unmyelinated. A number of changes in the RN are apparent as the kitten matures. The larger rubral cells undergo configurational changes before the smaller neurons, yet the giant cells continue to grow for a longer period of time. In the perinatal period, the extent of arborization of the dendritic trees diminishes, the number of spines decreases, and the long dendritic spines shorten. Somatic spines first appear in the giant cells at about one week after birth. In prenatal kittens, large cells frequently elaborate a tuft of fine branching processes in one region of the soma. These tufts later diminish in size and disappear by one week postnatal. Recent investigations (Pompeiano, '59; Condé, '66; King et al., '73' Sadun, '75) indicate that the RN of the cat is highly organized and very heterogenous. Afferent terminals are restricted to certain regions of certain cell types which are themselves specifically located within the RN. This specificity is apparent in perinatal kittens, despite the manifest immature appearance of the RN.

Animals↗

PubMed2005

Analysis of the plant architecture via tree-structured statistical models: the hidden Markov tree models.

Plant architecture is the result of repetitions that occur through growth and branching processes. During plant ontogeny, changes in the morphological characteristics of plant entities are interpreted as the indirect translation of different physiological states of the meristems. Thus connected entities can exhibit either similar or very contrasted characteristics. We propose a statistical model to reveal and characterize homogeneous zones and transitions between zones within tree-structured data: the hidden Markov tree (HMT) model. This model leads to a clustering of the entities into classes sharing the same 'hidden state'. The application of the HMT model to two plant sets (apple trees and bush willows), measured at annual shoot scale, highlights ordered states defined by different morphological characteristics. The model provides a synthetic overview of state locations, pointing out homogeneous zones or ruptures. It also illustrates where within branching structures, and when during plant ontogeny, morphological changes occur. However, the labelling exhibits some patterns that cannot be described by the model parameters. Some of these limitations are addressed by two alternative HMT families.

Combretaceae↗

PubMed1978

[Effect of electrostimulation of the medial portion of the hypothalamus of cats on features of sciatic nerve fiber restructuring in experimental neuritis].

In order to study the processes of rearrangement in nerve fibers of the ischiatic nerve and its nervi nervorum at experimentally induced neuritis, the middle part of the hypothalamus was electrically stimulated in 74 mature cats. Twenty three cats were electrically stimulated with alternating current of a rectangular form, 50 Hz 1 m/sec, 1.5 V, for 30 min on each side of the hypothalamic subtubercle. Seven days after electrode implantation, the experimental neuritis was produced by inserting aseptic mica plates subepineurally into the ischiatic nerve. Samples of the nerve stem were taken from the traumatized area and histological sections and film preparations were made. The material was treated after Foot, Ramon y Cajal, Rasskazova, Bielschowsky-Gross-Kampos, Sokoliansky, McManus. As demonstrated the analysis of the preparations, at early stages of the experiments the nerve fibers were preserved better under the electrostimulation than in the intact hypothalamus. However, by the 60th day, resulting from the pathology of the diencephalon, some distrophic changes developed in the peripheral nerve. Lateral branching processes were forming on the axonal cylinders. Nervi nervorum were spreading and forming long and dense wrappings around the endoneural sheaths where they terminated with loops simulating Perroncito's spirals.

Animals↗

PubMed1999

Development of catecholaminergic neurons in the pond snail, Lymnaea stagnalis: I. Embryonic development of dopamine-containing neurons and dopamine-dependent behaviors.

The embryonic development of the catecholaminergic system of the pond snail, Lymnaea stagnalis, was investigated by using chromatographic and histochemical methods. High performance liquid chromatography suggested that dopamine was the only catecholamine present in significant concentrations throughout the embryonic development of Lymnaea. Dopamine first became detectable at about embryonic stage (E) 15 (15% of embryonic development) and then increased in amount during early development to reach about 120-140 fmol per animal by around E40. Dopamine content remained stable during mid-embryogenesis (E40-65), increased slowing for the next couple of days, and then increased rapidly to culminate at about 400 fmol per animal by hatching. The detection of aldehyde- and glyoxylate-induced fluorescence and of tyrosine hydroxylaselike immunoreactivity indicated that the first catecholaminergic cells appeared in the late trochophore or early veliger stage of embryonic development (E32-35). The paired perikarya of these transient apical catecholaminergic (TAC) neurons were located beneath the apical plate, remained outside of the central ganglia during embryogenesis, and no longer contained detectable catecholamines close to hatching. TAC neurons bore cilia on the ends of short processes that penetrated the overlying epithelium; their long processes branched repeatedly under the ciliated apical plate. Several smaller catecholaminergic cells first appeared in the anterior margin of the foot at a stage when the embryos began to metamorphose from the veliger form (E55). Similar bipolar cells later appeared in the tentacle and lips. The axons of all of these small peripheral cells projected centrally and terminated within the neuropil of different central ganglia. Central catecholaminergic neurons, including RPeD1, differentiated only after metamorphosis was complete (E75). Development of locomotor, respiratory, and feeding behaviors correlated with maturation of catecholaminergic neurons, as indicated by histology and chromatography.

Animals↗

PubMed1999

Fas ligand expression in the germinal centre.

Whereas the importance of the Fas/FasL system in the regulation of T-cell homeostasis is well established, it is not yet clear if FasL is involved in B-cell regulation, especially in the clonal selection of B lymphocytes in the germinal centre (GC). This study therefore investigated the expression of FasL protein in tonsils and lymph nodes with lymphofollicular hyperplasia by western blotting and immunohistochemistry. In all the samples examined, western blot analysis showed FasL proteins of 33 and 52 kD, which presumably correspond to membrane-bound and soluble forms of the FasL protein. Immunohistochemically, FasL was found in a limited number of cells confined to a cluster in the light zone of the GC. The signal showed a delicate meshwork-like pattern of branching processes enmeshing the centrocytes and the few centroblasts of the light zone. In serial sections, the immunostaining pattern for FasL was found largely to coincide with the CD23 staining of follicular dendritic cells (FDCs), which are typically located in the light zone. In contrast, the FasL signal did not correspond to the distribution of the CD4-positive GC T-cells. In conclusion, expression of FasL in lymphofollicular hyperplasia seems to be largely confined to the light zone of the GCs, where selection of FDC-associated centrocytes is known to occur. These observations thus suggest that FasL is involved in selection processes of the B-cell system.

Adolescent↗

PubMed1997

The cAMP analog 8-Cl-cAMP inhibits growth and induces differentiation and apoptosis in retinoblastoma cells.

Retinoblastomas appear to be derived from a multipotential stem cell of the retina, due to alterations of the Rb1 gene. These tumors arise only within a discrete time frame during childhood, prior to terminal differentiation of the retinal precursor cells. Treatment of retinoblastoma cells with certain agents can induce a partial differentiation of cell types resembling those of the mature retina, such as rod and cone photoreceptors, glia, conventional neurons and pigment epithelia. We have tested the effects of 8-Cl-cAMP, a synthetic analog of cAMP which preferentially binds to and activates the RII subunit of protein kinase A on the Y-79 retinoblastoma cell line in vitro. Y-79 cells treated with 8-Cl-cAMP produced short, branching processes and showed a substantial increase in staining for neuron-specific enolase, a marker for conventional neuronal differentiation. In contrast, dibutyryl-cAMP gives a strong increase in the glial marker glial acidic fibrillary protein. Y-79 cell proliferation was strongly inhibited by 8-Cl-cAMP at concentrations as low as 5-25 microM. 8-Cl-cAMP significantly increased the rate of apoptosis of Y-79 cells in a dose-dependent manner. It also modulated expression of the RI regulatory subunit of intracellular cAMP-dependent protein kinase A, which is produced in abnormal quantities by Y-79 cells. A decrease in protein production was observed, with no clear effect on the RI subunit mRNA expression, suggesting that RI regulation occurs post-transcriptionally.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2000

Tracing human oligodendroglial development in vitro.

Human neural precursor cell cultures (neurospheres) were established from fetal brain tissues of 15-20 gestation weeks and propagated for over a year in the presence of epidermal growth factor, basic fibroblast growth factor and leukemia inhibitory factor. Neurospheres were differentiated without the presence of above growth factors to follow the development of oligodendroglia. Oligodendroglial progenitors, identified by their bipolar morphology and expression of platelet-derived growth factor receptor-alpha (PDGFRalpha), emerged from spheres as early as 1 DIV; O4+ cells with bipolar to multipolar processes were observed at 3 DIV whereas O1+ multiprocess-bearing oligodendroglia did not appear until 5-7 DIV. They further differentiated to myelin basic protein-expressing oligodendrocytes after 2-3 weeks in culture. Thus, human oligodendroglial maturation in vitro follows the same pathway as rat cells but takes twice as long as their rodent counterparts. Bromodeoxyuridine incorporation indicated that PDGFRalpha-expressing cells but not O4+ oligodendroglia proliferated. More oligodendroglial progenitors incorporated BrdU and more O4+ cells survived when they were in contact with neurons and astrocytes than when they developed beyond the astrocyte layer. In addition, oligodendroglia on astrocytes had a complex process branching whereas those growing beyond astrocyte layer often formed membrane sheaths. Thus the survival, proliferation and maturation of oligodendroglia are influenced by other cell types.

Brain↗

PubMed1999

Impact of demographic distribution and population growth rate on haplotypic diversity linked to a disease gene and their consequences for the estimation of recombination rate: example of a French Canadian population.

A disease gene introduced into a rapidly growing population by a single individual remains in strong linkage disequilibrium with the surrounding molecular markers. Mapping strategies taking advantage of this phenomenon allow increased mapping resolution as compared to pedigree analysis. Demographic models underlying these strategies usually assume the population exponential growth approximated by Poisson distribution of the number of children per individual. Knowing the real demographic distribution in the studied French-Canadian population, we analyzed the validity of the Poisson approximation. We adapted the existing model of the Poisson branching process to the case of a rapidly growing population and to non-Poisson distributions. In consequence, we were able to apply maximum-likelihood methods to estimate the recombination rate under various demographic scenarios. Our analysis shows that the growth rate has a higher impact on the estimation of recombination rate than the shape of the demographic distribution. The choice of the demographic model (Poisson vs. non-Poisson) has little effect on the estimation of the recombination rate but affects the expected distribution of haplotype frequencies. This distribution, however, depends much more on the population growth rate. Finally, we also demonstrate the usefulness of the Luria-Delbrück method, which gives a correct estimation of the recombination rate in a growing population, provided the sampling error is taken into account in the confidence intervals.

Confidence Intervals↗

PubMed1975

Fine structure of a radiation-induced osteogenic sarcoma.

An osteogenic sarcoma arose in the right orbit of a 7-year-old boy some 5 years after the right orbit had been treated by four courses of radiotherapy (total dose approximately 13,000 rads) for a multicentric retinoblastoma. Death occurred 6 months after the orbital tumor was first detected. Study of the orbital tumor by electron microscopy revealed a cell population of varied morphology in which two main types were identified. In one group, the cells were large with radiolucent cytoplasm, which contained long branching segments of rough endoplasmic reticulum. In the second group, the cells were smaller with irregular nuclei and an electron-dense cytoplasm, which contained short segments of dilated rough endoplasmic reticulum and numerous mitochondria. The first group of cells closely resembled osteoblasts, while the second group had some features of osteoclasts or their percursors. The branching processes of the tumor cells were separated by an amorphous ground substance, which contained collagen-like fibrils and hydroxyapatite crystals. Crystal deposition was in some instances in close relation to extracellular membrane-bound vesicles.

Cell Nucleus↗

PubMed1991

Regulation of neurogenesis and neuronal differentiation in primary and immortalized cells from mouse olfactory epithelium.

We have developed an in vitro system for studying molecular events regulating neurogenesis in the mouse olfactory epithelium (OE). Our observations suggest that two types of neuronal precursor may be involved: (1) a transiently existing, immediate neuronal precursor (INP), which generates two postmitotic daughter neurons; and (2) a neuroepithelial stem cell, which may be the basal cell (or some subclass of basal cell) of the OE, and is presumed to be the progenitor of the INP. Using antibody markers that distinguish basal cells and postmitotic receptor neurons in vitro and in vivo, we have shown that neurogenesis occurs early on in OE cultures, but then ceases because INPs divide only once to generate postmitotic neurons and no new INPs are produced by basal cells. To determine whether the basal cell-to-INP transition, or proliferation and neuronal differentiation of the INP, are regulated by crucial growth factors or cellular interactions, we are testing various polypeptide growth factors and extracellular matrix proteins for their effects on OE neurogenesis in vitro. We have also generated immortalized OE cell lines by using retroviruses to transduce oncogenes into cultured OE cells. One such cell line (derived from a primary OE basal cell culture) develops branching processes when transplanted into neonatal mouse brain--a condition in which cells from freshly isolated OE can undergo apparent morphological differentiation into neurons.

Animals↗

PubMed1985

Dynamic histology of the antral epithelium in the mouse stomach: I. Architecture of antral units.

The architecture of the pure mucous units of the pyloric antrum was investigated in 3- to 4-month-old CD1 mice. Units were serially cut in cross section and stained by a method combining the periodic acid-Schiff sequence, a modified Grimelius's silver nitrate procedure, and Regaud's hematoxylin. A total of 195 units were then reconstructed. Of these, six were cast in polyester resin and 189 were two-dimensionally reproduced on graph paper. The reconstructions showed antral units to be divided among three main classes. The first class, which contained 32% of the units, consisted of fingerlike tubules referred to as "singlets." Three types of singlets were observed. The first or type A, which represented 76% of the singlets, was divisible into three successive portions: a pit (foveola) opening onto the mucosal surface and lined by mucous cells referred to as pit cells, an isthmus continuous with the pit and containing immature proliferative mucous cells, and a gland forming the blind end of the tubule and lined by mucous cells referred to as gland cells. Type B (14% of singlets) was similar to type A except that its gland was forked. Type C (10% of singlets) differed by the absence of a gland. The units of the second class, which contained 53% of the total number, were joined together along part of their length and were named "multiplets." Most of them (90%) were organized into clusters of two, and 10% into clusters of three. In the joined portion, the epithelial cells of the adjacent units were in contact through junctional complexes and, therefore, were not separated by basement membranes. Otherwise the units showed the same component parts as in singlets. Also, as in singlets, the majority of the units were type A and a few were type B or C. The units of the third class, or "intermediates," consisted of tubules which exhibited a branching process. This process was of variable length but could include gland, isthmus, and sometimes pit. Thus, the process duplicated a varying proportion of the unit. In conclusion, the pure mucous units of the antrum exhibit various patterns which have been designated singlet, multiplet, or intermediate. It is proposed that these three patterns are related and represent temporal differences in the duplication and production of new units. Based on this assumption, a model has been elaborated to depict the likely sequence in the proliferation of pure mucous units. It is proposed that this proliferation takes place in the antrum of young adult mice.

Animals↗