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The entorhinal cortex has been shown to be involved in high-level cognitive functions in terrestrial mammals. It can be divided into two main areas: the lateral entorhinal area (LEA) and the medial entorhinal area (MEA). Understanding of its structural organization in cetaceans is particularly important given the extensive evidence for their cognitive abilities. The present study describes the cytoarchitectural and immunohistochemical properties of the entorhinal cortex of the bottlenose dolphin ( , Montagu, 1821), perhaps the most studied cetacean species and a paradigm for dolphins and other small cetaceans. Four bottlenose dolphins' entorhinal cortices were processed. To obtain a precise overview of the organization of the entorhinal cortex we used thionin staining to study its laminar and regional organization, and immunoperoxidase technique to investigate the immunohistochemical distribution of three most commonly used calcium-binding proteins (CBPs), calbindin D-28k (CB), calretinin (CR) and parvalbumin (PV). Entorhinal cortex layers thickness were measured, morphological and morphometric analysis for each layer were conducted and statistically compared. Six layers in both the LEA and MEA were identified. The main difference between the LEA and the MEA is observed in layers II and III: the neurons in layer II of the LEA were denser and larger than the neurons in layer II of MEA. In addition, a relatively cell-free zone between layers II and III in LEA, but not in MEA, was observed. The immunohistochemical distribution of the three CBPs, CB, CR and PV were distinct in each layer. The immunostaining pattern of CR, on one side, and CB/PV, on the other side, appeared to be distributed in a complementary manner. PV and CB immunostaining was particularly evident in layers II and III, whereas CR immunoreactive neurons were distributed throughout all layers, especially in layers V and VI. Immunoreactivity was expressed by neurons belonging to different morphological classes: All CBPs were expressed in non-pyramidal neurons, but CB and CR were also found in pyramidal neurons. The morphological characteristics of pyramidal and non-pyramidal neurons in the dolphin entorhinal cortex are similar to those described in the entorhinal cortex of other species, including primates and rodents. Interestingly, in primates, rodents, and dolphins, most of the CBP-containing neurons are found in the superficial layers, but the large CR-ir neurons are also abundant in the deep layers. Layers II and III of the entorhinal cortex contain neurons that give rise to the perforant pathway, which conveys most of the cortical information to the hippocampal formation. From the hippocampal formation, reciprocal projections are directed back to the deep layer of the entorhinal cortex, which distributes the information to the neocortex and subcortical area. Our data reveal that in the dolphin entorhinal cortex, the three major CBPs label morphologically heterogeneous groups of neurons that may be involved in the information flow between entorhinal input and output pathways.

Abstract Introduction/Objective Hirschsprung disease (HD), a congenital absence of enteric ganglion cells, affects 2-10% of patients with Down syndrome (DS). Submucosal nerve hypertrophy (SNH) and abnormal calretinin immunohistochemistry (IHC) support a diagnosis of HD, but the concordance of these findings can be variable in DS. Recognizing differences in HD occuring in DS can provide insight into the disease and help to improve outcomes and reduce delays in diagnosis for these patients. We sought to describe the histologic and calretinin staining patterns in HD occurring in patients with DS. Methods/Case Report From 2017-2023, 22 rectal biopsies from 20 patients with DS were retrospectively collected and reviewed. Subsequent pull-through (PT) resections were evaluated from 8 patients. Biopsies were evaluated for ganglion cells and SNH. Calretinin IHC was qualitatively evaluated for intensity (strong, weak) and density (many, partial, rare). Quantitative analysis used a calculation of the percent area above threshold (%AAT) function of the NIH ImageJ software version 2.1.0. Representative areas of the PT resections were also evaluated by ImageJ %AAT analysis. Results (if a Case Study enter NA) HD biopsies (12/22, 54.5%) were from male patients (age 3 days-6 weeks) and showed SNH in 11/12 (91.7%) with a mean nerve diameter of 57.3 microns (range 25-89 microns). Ganglionated biopsies (10/22, 45.5%) were collected from patients 3 days to 12 years old (M:F ratio 1:1.5) and showed SNH in 6/10 (60%) with a mean nerve diameter of 44.4 microns (range 10-70 microns). Strong normal calretinin staining was only seen in ganglionated biopsies (7/10 non-HD versus 0/12 HD). Negative calretinin staining was only seen in HD (0/10 non-HD vs 7/12 HD). Abnormal staining was seen in both non-HD (3/10, 30%) and HD (5/12, 41.7%) as partial strong positivity and rare weak positivity, respectively. ImageJ %AAT quantitative analysis revealed an average of 1.71 in biopsies with strong calretinin expression, 0.130 with weak staining, and 0.033 with negative staining. Evaluation of 8 PT resections (mean length of aganglionosis 7.1 cm) showed a mean nerve diameter in the aganglionic segment of 88.3 microns, 49.6 microns in the TZ, and 32.7 microns in the ganglionated segment. ImageJ %AAT quantitative analysis of calretinin revealed a mean of 0.044 in the aganglionic area, 0.66 in the TZ, and 1.56 in the ganglionated segment. Conclusion Recognition of the variable calretinin patterns seen in rectal biopsies from patients with DS can assist in accurate and timely diagnosis of HD.

The hexa-EF-hand Ca(2+)-binding protein calretinin (CR) is predominantly expressed in specific neurons of the central and peripheral nervous system. However, CR expression is also observed in non-neuronal cells, e.g., during embryonic development and in mesothelioma cells. Of the 6 EF-hand domains, 5 are functional; the first 4 domains form 2 pairs showing high cooperativity within a pair that results in non-linear modulation of intracellular Ca(2+) signals by CR. EF-hand domain 5 has a low affinity and represents the identified interaction site with CR-binding partners present in mouse cerebellar granule cells. CR binding to other targets including the pore-forming α1 subunit of the Ca(2+) channel Ca V 2.1, as well as to huntingtin indicates additional Ca(2+) sensor functions besides the well-known Ca(2+)-buffering functions. The absence of CR in cerebellar granule cells of CR(-/-) mice results in increased excitability and altered firing of Purkinje cells and promotes cerebellar 160-Hz oscillations impairing motor coordination. The putative role of CR in neuroprotection is still highly discussed. Altogether, CR emerges as a multi-functional protein also associated with development, i.e., cell proliferation, differentiation, and cell death.

The perception and discriminating of odors are sensory activities that are an integral part of our daily life. The first brain region where odors are processed is the olfactory bulb (OB). Among the different cell populations that make up this brain area, interneurons play an essential role in this sensory activity. Moreover, probably because of their activity, they represent an exception compared to other parts of the brain, since OB interneurons are continuously generated in the postnatal and adult period. In this review, we will focus on periglomerular (PG) cells which are a class of interneurons found in the glomerular layer of the OB. These interneurons can be classified into distinct subtypes based on their neurochemical nature, based on the neurotransmitter and calcium-binding proteins expressed by these cells. Dopaminergic (DA) periglomerular cells and calretinin (CR) cells are among the newly generated interneurons and play an important role in the physiology of OB. In the OB, DA cells are involved in the processing of odors and the adaptation of the bulbar network to external conditions. The main role of DA cells in OB appears to be the inhibition of glutamate release from olfactory sensory fibers. Calretinin cells are probably the best morphologically characterized interneurons among PG cells in OB, but little is known about their function except for their inhibitory effect on noisy random excitatory signals arriving at the main neurons. In this review, we will mainly describe the electrophysiological properties related to the excitability profiles of DA and CR cells, with a particular view on the differences that characterize DA mature interneurons from cells in different stages of adult neurogenesis.

Neuronal subpopulations display differential vulnerabilities to disease, but the factors that determine their susceptibility are poorly understood. Toxic increases in intracellular calcium are a key factor in several neurodegenerative processes, with calcium-binding proteins providing an important first line of defense through their ability to buffer incoming calcium, allowing the neuron to quickly achieve homeostasis. Since neurons expressing different calcium-binding proteins have been reported to be differentially susceptible to degeneration, it can be hypothesized that rather than just serving as markers of different neuronal subpopulations, they might actually be a key determinant of survival. In this review, we will summarize some of the evidence that expression of the EF-hand calcium-binding proteins, calbindin, calretinin and parvalbumin, may influence the susceptibility of distinct neuronal subpopulations to disease processes.

Our original review, \"Heterogeneity and Diversity of Striatal GABAergic Interneurons,\" to which this is an invited update, was published in December, 2010 in Frontiers is Neuroanatomy. In that article, we reviewed several decades' worth of anatomical and electrophysiological data on striatal parvalbumin (PV)-, neuropeptide Y (NPY)- and calretinin(CR)-expressing GABAergic interneurons from many laboratories including our own. In addition, we reported on a recently discovered novel tyrosine hydroxylase (TH) expressing GABAergic interneuron class first revealed in transgenic TH EGFP reporter mouse line. In this review, we report on further advances in the understanding of the functional properties of previously reported striatal GABAergic interneurons and their synaptic connections. With the application of new transgenic fluorescent reporter and Cre-driver/reporter lines, plus optogenetic, chemogenetic and viral transduction methods, several additional subtypes of novel striatal GABAergic interneurons have been discovered, as well as the synaptic networks in which they are embedded. These findings make it clear that previous hypotheses in which striatal GABAergic interneurons modulate and/or control the firing of spiny neurons principally by simple feedforward and/or feedback inhibition are at best incomplete. A more accurate picture is one in which there are highly selective and specific afferent inputs, synaptic connections between different interneuron subtypes and spiny neurons and among different GABAergic interneurons that result in the formation of functional networks and ensembles of spiny neurons.

Abstract Introduction/Objective Perivascular epithelioid cell neoplasms (PEComas) are a rare group of neoplasms that characteristically show both smooth muscle and melanocytic differentiation. The most common tumor in this family is renal angiomyolipoma but may occur in various sites. Sclerosing PEComa (S-PEComa) is an extremely rare variant. its only reported in females and it is usually an incidental finding in the retroperitoneum, in close proximity to the kidney. Methods/Case Report . We present a 52-year-old female, who had a chest CT scan for worsening cough. An - 4 cm exophytic renal mass in the left renal upper pole was found. Patient underwent left partial nephrectomy. Grossly the specimen consisted of 2.5 cm well-circumscribed, white tan mass, abutting the renal capsule, and extending into perinephric adipose tissue. Histology revealed uniform bland epithelioid cells with palely eosinophilic cytoplasm and round nuclei embedded in abundant densely sclerotic stroma. No fat was identified. Immunohistochemistry showed the tumor to be positive for desmin, HMB-45 and SMA with focal staining for AE1/AE3 and negative staining for EMA, cam 5.2, CD 117, calretinin, CD 34, S-100, PAX 8, and Melan A, which confirming the diagnosis of S-PEComa. Results (if a Case Study enter NA) NA Conclusion PEComas, excluding the epithelioid variant, usually has a benign course. In the 13 cases previously reported S-PEComa, 2 patients had metastasis. Our patient, 3-month post-op, has no evidence of disease, but close follow up still warranted.

Abstract Introduction/Objective Adenomatoid tumors are slow-growing benign tumors of mesothelial origin. They comprise 30% of all tumors of the paratesticular area. In this location, they commonly involve the epididymis, spermatic cord, ejaculatory duct and rarely testicular parenchyma. Histologically, a spectrum of growth patterns can be seen, such as adenoid, tubular, glandular, solid, or cystic. In some cases, a smooth muscle component can also be present. The purpose of this report is to describe a case of adenomatoid tumor with exuberant smooth muscle component, mimicking leiomyoma. Methods/Case Report A 28-year-old male presented with painless left inguinal bulge. He noticed it five years prior, and it had been slowly growing since then. Examination revealed a paratesticular mass which was subsequently excised. Grossly, the tumor was firm with smooth, white-tan cut surfaces. Microscopically, the tumor was well- circumscribed, showing predominance of smooth muscle bundles and rare cuboidal to ovoid cells in tubular growth pattern. In the background there was little intervening stroma. Immunohistochemical stains showed the cuboidal cells to be positive for WT1 and calretinin, confirming the mesothelial origin. Diagnosis of adenomatoid tumor was rendered. In contrast to adenomatoid tumors, leiomyomas are whiter and firmer on gross examination and lack the characteristic tubules or cystic spaces lined by mesothelial cells. Results (if a Case Study enter NA) N/A Conclusion Exuberant smooth muscle differentiation in adenomatoid tumor can mislead to diagnosis of leiomyoma. Careful inspection for tubules of mesothelial origin and appropriate immunohistochemical stains are key to accurate diagnosis. Pathologists need to be aware of this potential pitfall.

Abstract Introduction/Objective Primary peritoneal mucinous adenocarcinoma is an extremely rare entity with no well- established treatment protocol. It occurs more commonly in females as compared to males which supports its less understood pathogenesis of arising from heterotopic ovarian tissue or mucinous metaplasia of mesothelial cells. Methods/Case Report We present a case of a 31-year-old female who presented with right flank pain after a fall. On imaging studies, a cyst measuring 11.4 x 9.6 x 8.8 cm with an enhancing mural nodule was identified in abdomen (Figure 1). Patient underwent exploratory laparotomy. We received 402.1 grams, 12.5 x 10.0 x 8.0 cm cystic mass. Cut surface showed an unilocular cyst filled with seromucinous fluid and 4.0 x 2.5 x 1.7 cm friable excrescences. Histologic examination showed an adenocarcinoma arising from background mucinous cystadenoma. The tumor cells were positive for AE1/AE3, CK7, CK20, villin (focal), PAX8 (focal), p53 (wild-type) and negative for WT-1, AMACR, CDX-2, TTF-1, GATA-3, inhibin and calretinin. ER and PR immunostains were positive in the ovarian-type stroma in the background mucinous cystadenoma. As the radiology work-up was negative for any other tumor in the pelvis or other sites, the diagnosis of primary peritoneal cystadenocarcinoma was rendered. Molecular analysis showed presence of KRAS and TP53 mutations. Patient is doing well at 6 months follow-up without any recurrence. Results (if a Case Study enter NA) NA Conclusion This case is an extremely rare case of primary peritoneal mucinous cystadenocarcinoma and thus requires consideration that it should be included in the differential diagnosis of peritoneal tumors.