CD44 Expression in Microglia of the Retina and Cerebellum of Developing and Adult Chicken / 체질인류학회지

CD44 is a transmembrane protein that acts as a receptor for an adhesion molecule, hyaluronic acid. The type of cells expressing CD44 and roles of CD44 are still controversial and need to be elucidated. The aim of the present study was to examine the type of cells expressing CD44 and the changes in their distribution in the retina and the cerebellum of the developing and adult chicken. Embryonic day 14 (E14) and post-hatch day 90 (P90) chickens were used in this study. CD44-immunoreactive (ir) cells were observed both in the retina and the cerebellum of the two developmental stages examined. In the retina of E14, CD44-ir cells were mainly located in the nerve fiber layer. In adults, most of the CD44-ir cells were in the nerve fiber layer and some were dispersed in other layers of the retina. In the cerebellum of E14, CD44-ir cells were distributed throughout the cerebellar cortex, including the external and internal granular layers. CD44-ir cells were more frequently found in the cerebellum of P90 adult chickens than in that of E14 embryos. At higher magnification, CD44-ir cells showed ramified cytoplasmic processes irradiating from their cell bodies. In the retina and in the cerebellum of all ages examined, double staining showed that most of the CD44-ir cells also expressed RCA-1, a marker of microglia. In contrast to that, at the same locations, GFAP and CD44 were not co-expressed in cells. When the adult retina was stimulated by LPS, CD44 immunoreactivity increased, and CD44-ir cells were also RCA-1-positive. The present results indicated that CD44 was expressed in microglia of the retina and the cerebellum of the developing and adult chicken even in normal conditions, and microglial CD44 expression was increased upon LPS stimulation.

Assessment of Formaldehyde Concentrations in an Anatomy Laboratory Equipped Dissecting Tables with Inbuilt Exhaust and an Air Diffuser/Return System / 체질인류학회지

Formaldehyde (FA) used for preserving the body for anatomy dissection is harmful to the human body. In many countries, for the purpose of protecting the health of workers in the industrial field, the maximal allowable air concentration of FA has been set. The threshold limit values of time weighted average (TLV-TWA) and short-term exposure limit (TLV-STEL) of FA recommended by Ministry of Employment and Labor (MOEL) of Korea are less than 0.5 and 1 ppm, respectively. In the United States and Europe, TLV-TWAs of FA are recommended at between 0.3 and 2 ppm. In this study, we compared the air concentration of FA to domestic and foreign standards of FA in an anatomy laboratory equipped dissecting tables with inbuilt exhaust and an air diffuser/return system. We installed ten elevated dissection tables, 18 air diffusers on the ceiling, and 10 air returns at the bottom of both side walls. The concentration of FA was measured at five sites in the anatomy laboratory and above the cadavers on the dissecting tables at a height of 1.5 m from the floor using a Formaldemeter. The average concentration of FA in the anatomy laboratory (five sites) was 0.31 ppm (0.45 mg/m³), range 0.21 to 0.41 ppm (0.26~0.51 mg/m³). The average concentration of FA above the cadavers was 0.45 ppm (0.56 mg/m³), range 0.31 to 0.64 ppm (0.39~0.80 mg/m³). The average TWA of FA in the anatomy laboratory was 0.19 ppm (0.24 mg/m³), range 0.13 to 0.26 ppm. The average TWA of FA above the cadavers was 0.28 ppm (0.35 mg/m³), range 0.19 to 0.40 ppm. The anatomy laboratory dissecting tables equipped with inbuilt exhaust and air diffuser/return system met the criteria of the FA concentration recommended by MOEL of Korea and most foreign countries. This study was the first evaluation of the air concentration of FA in an anatomy laboratory equipped dissecting tables with inbuilt exhaust and an air diffuser/return system in Korea. We expect it will be not only used as a standard of comparison for anatomy laboratories, but as a reference for design and construction to improve air quality in Korean Medical Colleges.

Expression of Heat Shock Protein 27 and Alpha B Crystallin in the Retina and Optic Nerve of the Chick Embryo / 체질인류학회지

Heat shock protein 27 (HSP27) and alpha B crystallin (aBC) belong to the small heat shock protein (sHSP) family and have similar amino acid sequences. However, no study has compared the distributional patterns of these two sHSPs in the retina and optic nerve. In this study, we compared the spatiotemporal distributions of the expressions of HSP27 and aBC in the developing chick retina and optic nerve. Both HSP27 and aBC were first expressed in the retina and optic nerve at embryonic day 16 (E16). At E20 the expressions of the two proteins were increased in the retina and optic nerve. Double immunofluorescence demonstrated that HSP27 and aBC were expressed in oligodendrocytes of the retina and optic nerve. In addition, HSP27 was also found to be expressed in ganglion cells in the retina. The findings of this study suggest that HSP27 and aBC act to protect ganglion cells and oligodendrocytes during late development of the chick retina and optic nerve.

Caffeine-induced endothelial cell death and the inhibition of angiogenesis / 대한해부학회지

Numerous studies have shown that adenosine or adenosine agonists can stimulate angiogenesis. However, the effect of caffeine (a known adenosine receptor antagonist) on angiogenesis has not been previously studied. Accordingly, this study was undertaken to examine the effect of caffeine on angiogenesis and to clarify the mechanism involved. Chick chorioallantoic membrane assays were used to investigate the effect of caffeine on angiogenesis and proliferation assays using human umbilical vein endothelial cells (HUVECs), were used to study its effects on specific aspects of angiogenesis. The expressions of caspase-3 and Bcl-2 were examined by western blotting, immunofluorescence staining was used to identify HUVEC morphological changes, and fluorescence activated cell sorting (FACS) and DAPI staining were used to detect HUVEC apoptosis. Caffeine was found to inhibit blood vessel formation dose-dependently and to inhibit the proliferation of HUVECs time- and dose-dependently. FACS analysis and DAPI staining showed that inhibitory effect of caffeine on HUVEC proliferation was the result of apoptosis and the up-regulation of thrombospondin-1 (TSP-1). Furthermore, TSP-1 levels were down-regulated by NECA but were unaffected by CGS21680, indicating that caffeine regulated TSP-1 expression via adenosine A2B receptor. In addition, caffeine up-regulated caspase-3 and down-regulated Bcl-2 at the protein level. These results suggest that the inhibitory effect of caffeine on angiogenesis is associated, at least in part, with its induction of endothelial cell apoptosis, probably mediated by a caspase-3 dependent mechanism.

Electrophysiological and Histologic Evaluation of the Time Course of Retinal Degeneration in the rd10 Mouse Model of Retinitis Pigmentosa

Among several animal models of retinitis pigmentosa (RP), the more recently developed rd10 mouse with later onset and slower rate of retinal degeneration than rd1 mouse is a more suitable model for testing therapeutic modalities. We therefore investigated the time course of retinal degeneration in rd10 mice before adopting this model in our interventional studies. Electroretinogram (ERG) recordings were carried out in postnatal weeks (PW) 3~5 rd10 (n=23) and wild-type (wt) mice (n=26). We compared the amplitude and implicit time of the b-wave of ERG records from wt and rd10 mice. Our results showed that b-wave amplitudes in rd10 mice were significantly lower and the implicit time of b-waves in rd10 mice were also significantly slower than that in wt mice (20~160 microV vs. 350~480 microV; 55~75 ms vs. 100~150 ms: p<0.001) through PW3 to PW5. The most drastic changes in ERG amplitudes and latencies were observed during PW3 to PW4. In multichannel recording of rd10 retina in PW2 to PW4.5, we found no significant difference in mean spike frequency, but the frequency of power spectral peak of local field potential at PW3 and PW3.5 is significantly different among other age groups (p<0.05). Histologic examination of rd10 retinae showed significant decrease in thickness of the outer nuclear layer at PW3. TUNEL positive cells were most frequently observed at PW3. From these data, we confirm that in the rd10 mouse, the most precipitous retinal degeneration occurs between PW3~PW4 and that photoreceptor degeneration is complete by PW5.

Variant Origin of Obturator Artery: A Branch of Inferior Epigastric Artery from External Iliac Artery / 체질인류학회지

The obturator artery normally originates from the internal iliac artery. However, variation in the origin of obturator artery has been reported in many countries. Since no such case has been reported in Korea, we examined variations in the origin of obturator artery in cadavers donated to the medical school at the Chungbuk National University. Thirty-six pelvic halves from 18 cadaveric subjects (13 males and 5 females) were studied in this study. Normal origin of the obturator artery from the internal iliac artery was observed in 88.9% (16/18) of cadavers or in 91.7% (33/36) of pelvic halves. A variation in the origin of obturator artery was observed in 11.1% (2/18) of cadavers or in 8.3% (3/36) of pelvic halves. All of the variant obturator arteries originated from external iliac arteries as branches of inferior epigastric arteries. Bilateral presence of variant obturator arteries was observed in 5.6%(1/18) of cadavers. The obturator artery arose from inferior epigastric artery at a distance of 1 to 2.4 cm from origin point of inferior epigastric artery, and then the obturator artery ran inferiorly and medially with the inferior epigastric artery running superiorly and laterally. Presence of variant obturator artery would be important to clinical fields with interest to pelvic anatomy, such as radiology and surgery.

Characterization of the antigenic phenotype of alphaB-crystallin-expressing peripapillary glial cells in the developing chick retina / 대한해부학회지

Radial glia are transdifferentiated into astrocytes within the developing brain and spinal cord. The neural retina contains Muller cells, which are retinal radial glia. Some of the cells that surround the optic nerve head among Muller cells in the chicken retina are called peripapillary glial cells (PPGCs). PPGCs express different molecules compared to typical Muller cells. However, an antigenic PPGC phenotype has not yet been clearly established. In this study, we classified the antigenic PPGC phenotypes and identified the differentiation stages of these cells. At embryonic day (E)8, alphaB-crystallin-positive PPGCs had a bipolar shape with long processes that traversed entire layers of the retina. Pax2 and vimentin were expressed in alphaB-crystallin-positive PPGCs. Glial fibrillary acidic protein (GFAP) immunoreactivity was not observed in PPGCs. At E18, alphaB-crystallin immunoreactivity disappeared from the vitread processes of PPGCs. However, the PPGC cell bodies and ventricular processes contained alphaB-crystallin protein, and the PPGCs retained the same Pax2-positive/vimentin-positive/GFAP-negative profile as that seen at E8. At post-hatch day 120, alphaB-crystallin and Pax2 immunoreactivity was not observed, but vimentin and GFAP expression was clearly observed in the presumptive location of the PPGCs. Furthermore, these two proteins overlapped within that location. Considering that vimentin expression is prolonged until the post-hatching period in chicken brain, these findings suggest that Pax2-negative/vimentin-positive/GFAP-positive PPGCs are phenotypically identical to mature astrocytes in this avian species.

Detection of alphaB-crystallin mRNA using Single-stranded DNA Probe in Oligodendrocytes of the Developing Chick Retina / 체질인류학회지

In situ hybridization (ISH) using single-stranded DNA probe (ssDNA probe) is a useful method for observing the specific transcripts in cells, since it is convenient to prepare probe which is specific and sensitive. In this study, ssDNA probe for detection of alphaB-crystallin (aBC) mRNA, transcript of a heat shock protein, was prepared and aBC mRNA-expressed cells were spatiotemporally observed in the retina of the developing chick embryos. Single-stranded antisense probe produced by reverse transcription and polymerase chain reaction was identified as a specific probe for aBC mRNA in comparison to negative control using sense probe and immunohistochemistry for aBC protein. In the ISH experiment, aBC mRNA was expressed only in the peripapillary glial cells which are a specific cell type located in the avian retina adjacent to the optic nerve at E12 and E14 retinas. At E16, a small number of aBC mRNA-expressed cells were identified in the nerve fiber layer (NFL) of the retina. At E18, aBC mRNA-expressed cells were observed in the ganglion cell layer (GCL) as well as the NFL. At E20, the number of aBC mRNA-expressed cells was increased in the GCL and the NFL. Based on the same localization of nkx2.2 immunoreactive cells and aBC mRNA-expressed cells, aBC mRNA-expressed cells were identified as oligodendrocytes. These results indicate that ssDNA probe for aBC mRNA detection is very useful tool for oligodendrocyte research such as distribution, migration and differentiation of the cells.

Comparison of Retinal Waveform between Normal and rd/rd Mouse / 의학물리

Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa or age-related macular degeneration. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we investigated differences of the retinal waveforms in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). 8x8 grid layout MEA (electrode diameter: 30micrometer, electrode spacing: 200micrometer, and impedance: 50 k omega at 1 kHz) was used to record in-vitro retinal ganglion cell activity. In normal mice (C57BL/6J strain) of postnatal day 28, only short duration (<2 ms) retinal spikes were recorded. In rd/rd mice (C3H/HeJ strain), besides normal spikes, waveform with longer duration (~100 ms), the slow wave component was recorded. We attempted to understand the mechanism of this slow wave component in degenerate retina using various synaptic blockers. We suggest that stronger glutamatergic input from bipolar cell to the ganglion cell in rd/rd mouse than normal mouse contributes the most to this slow wave component. Out of many degenerative changes, we favor elimination of the inhibitory horizontal input to bipolar cells as a main contributor for a relatively stronger input from bipolar cell to ganglion cell in rd/rd mouse.

Two-phalanged Fifth Toe in Korean Children / 체질인류학회지

Radiographic research was performed to know the frequency of two-phalanged fifth toe and its relation to presence of the ossification centers in normal Korean children. Previous study showed more than 74% of the incidence in adulthood and less than 30% in childhood. Fifty children (33 male and 17 female, aged 2 to 15; mean age 9.6) were studied by plain foot radiographs focused on the fifth toe. In the 3~8 yr old 20 subjects, secondary ossification center of distal phalangeal bone was seen as a ossicle (small bone) placed at proximal to the distal phalanx. Secondary ossification center of middle phalangeal bone and the bony shaft of the phalanx was hard to distinguish. So keeping up the objectivity, regardless of distinguishable ossification center or the bony shaft of phalanges, ossicles seen on the 5th toe was counted to classify the presumptive type of the toe. Epiphyseal ossification center of proximal phalanx was excluded from the count. There were three types of the fifth toe which has 2 ossicles to 4 ossicles. Overall incidence of the type of 2 ossicles was 24% (12/50). Above 12 yr old group the incidence was 61% (11/18), and above 13 yr old group the incidence was 75% (9/12). The incidence of biphalangism came closer to the adult's after late childhood. This finding represent that progress of biphalangealization completed after late childhood. It seems that the progress starts earlier than 3 yr old. We made the hypothesis by the incidence of 30% (6/20) of the type which has 4 ossicles on the fifth toe at 3~8 yr old group. Four ossicles might be a secondary ossification center of distal phalanx and the bony shaft of distal, middle and proximal phalanx. They might form a distal interphalageal joint and the triphalangeal toe. To know more about the morphogenesis of biphalalngeal 5th toe, further progressive study in childhood is needed.

Expression of HSP27 and alphaB-crystallin in Avian Cerebellum during Development / 대한해부학회지

It is well known that small heat shock proteins play a role as molecular chaperone. However, during normal development of the cerebellum, expression and distribution of HSP27 and alphaB-crystallin (alphaBC) which are small heat shock proteins have not been reported. To verify the protective role of HSP27 and alphaBC in neurons and glial cells, we examined the expression and distribution of HSP27 and alphaBC in the developing chick cerebellum using immunoblot, immunohistochemical and double immunofluorescence staining. Expression of both HSP27 and alphaBC was first identified in the cerebellum of the embryonic day 14 (E14) embryo, and was increased at E18. Double immunofluorescence analysis with myelin-basic protein (MBP) demonstrated that alphaBC positive (+) cells were mature myelinating oligodendrocytes. alphaBC+ cells were observed in the white matter of the E14 cerebellum. At E18, there were a number of alphaBC+ cells in the white matter and a few cells in the granular layer of the gray matter. On the other hand, HSP27+ cells were observed in the white matter and the Purkinje cell layer at E14. At E18, HSP27+ signals were observed in Purkinje cells and neurons of cerebellar nucleus as well as oligodendrocytes in the white matter and the granular layer. The results that HSP27 and alphaBC were expressed in specific neurons and glial cells in the developing cerebellum suggest that HSP27 and alphaBC may be involved in the protective mechanism for the apoptosis of neurons and the physiological stress occurred in oligodendrocyts during cell maturation.

Origin of the Retinal Oligodendrocyte in the Chicken Embryo / 대한해부학회지

Unlike other retinal cells, oligodendrocytes originate from the ventral midline of the third ventricle, and migrate to the retina at embryonic day 10 (E10) through the optic chiasm and the optic nerve in the bird. Recent studies have demonstrated that sonic hedgehog (shh), a differentiation factor for oligodendrocytes, was secreted by ganglion cells in the developing retina, indicating that microenvironment of the retina is sufficient for the generation of oligo-dendrocytes. Furthermore, it was revealed that uncommitted progenitors could differentiate into all cell types in the murine retina. On the basis of these reports, we proposed that a subpopulation of oligodendrocytes might generate in the retina in situ of the chick embryo. In order to verify our hypothesis, we injected the intraretinal space of chick embryos with a replication-defective retroviral vector (LZ12), and identified oligodendrocytes among LZ12-incorporated cells. Plp/dm-20 and pdgfr-alpha, oligodendrocyte specific transcripts were already expressed in the E5 retina. The expression of shh transcripts was also detected in the same stage. Analysis of the retina with intraretinal space injection demonstrated many clones consisting of various cell types arranged vertically through the retina. In addition, we found a few clones that had O4 +/-oligodendrocytes. In case of third ventricle injection, we found that LZ12-incorporated cells occurred in rows, the typical shape of interfascicular oligodendrocytes in the optic nerve, and were located in the nerve fiber layer adjacent to the ganglion cells in the retina. These cells were also labeled with TfBP antibody. These results indicate that retinal oligodendrocytes of birds are differentiated from retinal precursor cells, together with undifferentiated cells adjacent to the third ventricle.

Immunohistochemical Study on the TfBP Expression in the Embryonic Chick Cerebellum / 대한해부학회지

We have previously demonstrated that transferrin binding protein (TfBP) is a reliable marker for mature oligoden-drocytes (OLGs) in the avian central nervous system (CNS). Unlike mammalian CNS in which OLGs are generated largely postnatally, avian OLGs are differentiated during embryonic development of CNS. In this study, several aspects of TfBP(+/-) OLG development were immunohistochemically examined in the embryonic chick cerebellum : (1) change in shapes of immature cells with respect to time and to location within the cerebellum, (2) possible sites of origin, and (3) pathways of precursor cell migration. Our results indicate that TfBP expression gradually increases and extends from the deep portion of the white matter to gray matter with proportion to progress of cerebellar development. A few TfBP? cells were first observed in the deep portion of the cerebellum at E9. At E13, TfBP(+/-) cells were distributed evenly within the white matter. At E17, many TfBP(+/-) OLGs were located at granular layer and at the near place of Purkinje cell layer. At E20, a large number of TfBP cells appeared at the granular layer with a few in the molecular layer. Our data demonstrated distinct patterns of morphology and location of TfBP(+/-) OLGs in the cerebellum during development and suggest a role of TfBP in OLG development.

The Alteration of Avian Retinal Microglia Induced by Optic Nerve Transection / 대한해부학회지

Retina, a part of CNS, has served valuable and accessible tissue for elucidating the cellular properties of neurons and glia due to its similarity to brain. Unlike mammalian counterpart, avian retina is devoid of vessels and astrocytes. However little is known about glial reaction to neuronal injuries in this species. Therefore, this study was performed to investigate the microglial responses in the quail retina following neuronal injuries. The retinae from normal and optic nerve transected adult quails were studied immunohistochemically with anti-QH1, a marker known to be specific for microglia. In the normal retina, QH1-labeled microglial cells displayed typical feature of ramified (resting) form and were localized mainly in the inner plexiform layer. After optic nerve transection (ONT) morphology of microglial cells changed from the ramified to the amoeboid form. This feature of microglial cells maintained throughout the post operational periods until 28 days after ONT. Particularly, at 14 and 21 days after ONT amoeboid microglia displayed cell bodies with stout and bushy processes, suggesting active phagocytosis. The distribution pattern of microglia also changed in accord to ganglion cell degeneration: they gradually moved to layers of ganglion cells and optic nerve fibers where ganglion cell bodies and axons were under degeneration. This change of microglial distribution was most prominent at 14 days of ONT. The result of this study is generally consistent with that reported in mammalian counterpart and this similarity between the avascular avian retina and the vascularized mammalian counterpart suggests that processes of microglial activation, such as migration and phagocytosis, can occur in the vessel-free CNS tissue.

Carbonic anhydrase II immunostaining in the cerebellum of postnatal mice / 대한해부학회지

The carbonic anhydrase II (CA-II) is specifically expressed in oligodendrocytes, the cells responsible for myelination in the central nervous system. However no direct evidence on relationship between myelin formation and CA-II immunoreactivity has been described. The aims of these studies are to investigate the relationship between CA-II and myelination during cerebellar development of mouse. Myelin staining was found on postnatal (P) 14, and its intensity increased in proportion to developmental age. CA-II positive oligodendrocytes were observed in the white matter of cerebellum on P 14 day. CA-II positive oligoden-drocytes also occured in the granular layer and Purkinje cell layers in the later stage of dvelopment. The parallel development in the CA-II expression and myelination during development suggests that CA-II in oligoendrocyte play a role to myelination.

The Studies on Central Neural Axis to Innervate Rat Digastric Muscle / 대한해부학회지

The present study has been performed to investigate the neural axis of rat digastric muscle using viral tracer, pseudorabies virus. The upper nuclei to innervate digastric muscle were in accumbens nucleus, agran-ular insular cortex, central nucleus of amygaloid, lateral septal nucleus, frontal cortex, and subfornical organ etc, in telencephalon ; arcuate hypothalamic nucleus, lateral hypot-halamic area, medial preoptic nucleus, bed nucleus of stria terminalis, dorsomedial hypot-halamic nucleus, suprachiasmatic nucleus, paraventricular nucleus, and retrochiasmatic area etc, in diencephalon ; nucleus Darkschewitsch, interstitial nucleus of the medial logitudinal fasciculus, parabrachial nucleus, locus ceruleus, Kolliker-Fuse nucleus, trigeminal mesencephalic nucleus, red nucleus, substantia nigra, nucleus of posterior commissure, Edinger-Westphal nucleus, and dorsal raphe nucleus etc, in mesencephalon ; giganto-cellular reticular nucleus, raphe magnus nucleus, raphe pallidus nucleus, raphe obscuous nucleus, nucleus of solitary tracts, lateral reticular nucleus, parvocellular reticular nucleus, area postrema, facial nucleus, pontine reticular nucleus, pontine nucleus of trigeminal nerve and spinal nucleus of trigeminal nerve etc, in rhombencephalon. There are significant difference of numbers of PRV-Ba immunoreactive cells between right and left sides of brain in almost nuclei[P< 0.05]. But PRV-Ba immunoreactive cells were observed only ipsilaterally in accessory trigeminal motor nucleus, accessory facial nucleus and agranular insular cortex. Frontal cortex was the only area which were shown contralateral immunoreactivity. The results of this study provide anatomical support that both the cranial and caudal bellies are innervated by the same upper nuclei. The results also support the suggestion that the lower nuclei of digastric muscle, accessory trigeminal motor nucleus and accessory facial nucleus consist of somatotopic motor complex.

Immunohistochemical Localization of Adenohypophyseal Gonadotropes in Korean Native Goat , Capra hircus / 대한해부학회지

The localizations and morphological characteristics of gonadotropes in the adenohypophy-sis of Korean native goat were investigated with double immunohistochemistry. The gonadotropes were present in the pars distalis and pars tuberalis, but not in the pars intermedta. Gonadotropes occupied about 49.0% of the cells in the pars distalis in females, and about 40.8% in males. Three types of gonadotropes ; FSH immunoreactive cells[FSH cells], LH immunoreac-tive cells[LH cells], and FSH and LH immunoreactive cells[FSH/LH cell], were identified according to their immunoreactivities for FSH and LH antisera. The possessional perce-ntages of FSH cells, LH cells and FSH/LH cells were 1.1%, 40.6%, 58.3% in females and 1.8%, 30.0%, 68.8% in males, respectively. FSH/LH cells were large and oval or round in shape. These cells were distributed throughout the pars distalis, but were more abundant on the dorsal part adjacent to the hypophyseal cavity and along the lateral and ventral peripheral regions. LH cells were smaller than other gonadotropes and were observed throughout the pars distalis, but predominant in the central region. FSH cells were large and oval in shape. These cells were intercalated between FSH/LH cells.