A Novel Understanding of Phocidae Hearing Adaptations Through a Study of Northern Elephant Seal (Mirounga angustirostris) Ear Anatomy and Histology.

The most conspicuous aural adaptation in northern elephant seals (NES) is complete absence of an auricle and a tortuous collapsed external acoustic meatus. The NES epitympanic recess contains massive ossicles immersed in the middle ear cavernous sinuses. Engorgement of the cavernous sinuses would make ossicles fully buoyant during deep diving. NES have a comparatively larger cochlear nerve, which carries a significantly larger number of axons than in terrestrial mammals, which would give them auditory ability similar to the obligate marine mammals such as cetaceans. Our calculations show that the traditional "air-dependent" impedance matching mechanism in NES functions to just half of the capacity compared with the one described in terrestrial mammals. Impedance matching would be further hindered in NES while diving due to fully collapsed external acoustic meatus. Thanks to similarities of acoustic impedance between the sea water, soft tissues, and blood sinuses, very little sound energy would be reflected and lost. When sound is generated underwater, the large ossicles, buoyant in the cavernous sinus, would not move due to oscillation of tympanic membrane. Rather, they would be oscillating due to their inertia and process of acoustic streaming. Our mathematical simulation shows that an increase in sound frequency would cause increased displacement of the stapedial footplate and thus transmit the sound energy to the inner ear. We contend that during diving, impedance matching and sound signal amplification in the middle ear courses through the cavernous sinuses and oscillates the enlarged ossicles, thus enabling a high-frequency ultrasonic hearing range in Phocidae. Anat Rec, 302:1605-1614, 2019. © 2018 American Association for Anatomy.

Ultrastructure of Developing Feline Nonciliated Bronchiolar Epithelial Cells.

The ultrastructure of the developing bronchiolar cell was studied in six age groups: prenatal (60 d post-conception); postnatal (1-, 7-, 14- and 21-day-old); and adult. Following intratracheal fixation, the lung tissue was processed for scanning and transmission electron microscopy. The lining of terminal bronchioles consists of cuboidal to columnar nonciliated bronchiolar cells (NBCs) and ciliated with or without microvilli. NBCs were recognized by indented centrally located nucleus. The apical surface extended beyond the surface of neighboring cells and was covered by minute microvilli, except in prenatal kittens. The NBCs of the adult were characterized by abundant mitochondria and glycogen inclusions. In prenatal kittens, the cytoplasm was filled with patches of alpha and beta form of glycogen. Postnatally, glycogen was reduced in quantity, became scattered throughout the cytoplasm and was predominantly of the beta form. Islands of cytoplasm, separated from the apical cytoplasm were observed in the lumen of adult bronchioles. This suggests an apocrine mode of secretion. The NBCs attain maturity by three weeks of age.

Histomorphology and immunohistochemistry of the lower esophageal sphincter of the least shrew (Cryptotis parva).

The biochemical and histopathological changes in the lower esophageal sphincter (LES) in the pathogenesis of gastroesophageal reflux disease have gained interest. The least shrew is able to vomit in response to emetogens and provides a good model to study the histology of this phenomenon relative to the published reports in the commonly used but vomit-incompetent laboratory species. The LES is located at the junction of the esophagus and stomach. It typically closes at rest and opens in response to swallowing. Our findings demonstrate that the least shrew does not have a well-defined LES, lacks esophageal glands and has a mucosal valve-like projection from the terminal end of the esophagus before joining the gastric epithelium at the lesser curvature. In addition, the least shrew has thoracic and abdominal components prior to joining the gastric epithelium. The mucosal lining of the esophagus is folded, becoming clearly convoluted and forming a bucket-like structure at the level of the esophageocardiac junction (ECJ). No significant differences are to be found between the structure and thickness of the wall before and after the ECJ. Thus, the ECJ forming the LES is relatively less complex than those of other mammals including man. The distribution of enterochromaffin (EC) cells is confined to the lamina propria of the junction and is not associated with the cardiac glands, suggesting its functional involvement with the smooth muscle in and around the ECJ. In conclusion, the least shrew's anatomical sphincter appears ill-defined and is replaced by a less sturdy valve-like mucosal flap.

Distribution of serotonin-immunoreactive enterochromaffin cells in the gastrointestinal tract of the least shrew (Cryptotis parva) / Distribución de las células enterocromafines serotonina-inmunorreactiva del tracto gastrointestinal de la musaraña enana (Cryptotis parva)

Serotonin is an important neurotransmitter in the central (CNS) and peripheral (PNS) nervous systems. It is involved in a variety of physiological processes both in the gut and in the CNS. The present study examined the distribution of serotonin containing enterochromaffin cells in the gastrointestinal tract (GIT) of a vomit competent species, the least shrew. These cells were easily recognized by their globular granules stained with the H&E and serotonin immune-positive stain. The immunoreactive enterochromaffin cells (IERCs) were mainly confined to the basal portion of the glandular epithelium and were distributed throughout the shrew stomach, small and large intestine. None was found to be associated with the mucosal epithelial lining. Moreover, their distribution and count varied in different regions of the GIT suggesting specific functions for these regions. The highest concentration of IERCs was found in the colon followed by the Jejunum. Appreciable numbers of IERCs were found in the stomach especially at the esophageo-gastric junction. The gastric location of the IERCs was mainly in the basal portion of the gland. However, some IERCs were associated with the parietal cells of the stomach. Two types of IERCs were observed: One with globular secretory granules in their apical portion of the cytoplasm which were located within the glandular epithelial cells facing the glandular lumen which release their secretions into the lumen; and the second were basally located, facing the lamina propria of the mucosa. Their secretory granules were not distinct in shape, and are most probably paracrine in their mode of secretions...

La serotonina es un importante neurotransmisor del sistema nervioso central (SNC) y periférico (SNP). Está implicado en una variedad de procesos fisiológicos, tanto en el intestino y el SNC. El presente estudio examinó la distribución de la serotonina contenida en las células enterocromafines del tracto gastrointestinal (TGI) de una especie competente al vómito, la musaraña enana. Estas células se reconocen fácilmente por sus gránulos globulares teñidas con H-E y la inmuno-tinción positiva para serotonina. Las células enterocromafines inmunorreactivas (CEI) se limitan principalmente a la parte basal del epitelio glandular y se distribuyeron por todo el estómago, intestino delgado e intestino grueso de la musaraña. Ninguna célula se encontró asociada al revestimiento epitelial mucoso. Además, su distribución y el recuento varió en diferentes regiones del TGI sugiriendo funciones específicas de estas regiones. La mayor concentración de CEI se encuentran en el colon seguido por el yeyuno. Números apreciables de CEI se encontraron en el estómago, especialmente en la unión esofago-gástrica. La ubicación de las CEI gástricas fue principalmente en la porción basal de la glándula. Sin embargo, algunas CEI se asociaron con las células parietales del estómago. Dos tipos de CEI se observaron, una con gránulos secretores globulares en su porción apical del citoplasma que se encuentra dentro de las células epiteliales glandulares que enfrenta el lumen glandular que liberan sus secreciones en el lumen, y el segundo se encuentra basalmente, frente a la lámina propia de la mucosa. Sus gránulos secretores no fueron diferentes en forma, y probablemente son más paracrinas en su modo de secreción...

SPECT imaging with the serotonin transporter radiotracer [123I]p ZIENT in nonhuman primate brain.

INTRODUCTION: Serotonin dysfunction has been linked to a variety of psychiatric diseases; however, an adequate SPECT radioligand to probe the serotonin transporter system has not been successfully developed. The purpose of this study was to characterize and determine the in vivo selectivity of iodine-123-labeled 2beta-carbomethoxy-3beta-(4'-((Z)-2-iodoethenyl)phenyl)nortropane, [(123)I]p ZIENT, in nonhuman primate brain. METHODS: Two ovariohysterectomized female baboons participated in nine studies (one bolus and eight bolus to constant infusion at a ratio of 9.0 h) to evaluate [(123)I]p ZIENT. To evaluate the selectivity of [(123)I]p ZIENT, the serotonin transporter blockers fenfluramine (1.5, 2.5 mg/kg) and citalopram (5 mg/kg), the dopamine transporter blocker methylphenidate (0.5 mg/kg) and the norepinephrine transporter blocker nisoxetine (1 mg/kg) were given at 8 h post-radiotracer injection. RESULTS: In the bolus to constant infusion studies, equilibrium was established by 4-8 h. [(123)I]p ZIENT was 93% and 90% protein bound in the two baboons and there was no detection of lipophilic radiolabeled metabolites entering the brain. In the high-density serotonin transporter regions (diencephalon and brainstem), fenfluramine and citalopram resulted in 35-71% and 129-151% displacement, respectively, whereas methylphenidate and nisoxetine did not produce significant changes (<10%). CONCLUSION: These findings suggest that [(123)I]p ZIENT is a favorable compound for in vivo SPECT imaging of serotonin transporters with negligible binding to norepinephrine and dopamine transporters.

Synthesis, radiolabeling and baboon SPECT imaging of 2beta-carbomethoxy-3beta-(3'-[(123)I]iodophenyl)tropane ([(123)I]YP256) as a serotonin transporter radiotracer.

To develop a potential SPECT probe to evaluate the integrity of the serotoninergic system (5-HTT) whose dysfunction is linked to several disease conditions such as Parkinson's disease, Alzheimer's disease and depression, we report the synthesis, radiolabeling and in vivo baboon imaging of 2beta-carbomethoxy-3beta-(3'-[(123)I]iodophenyl) tropane (YP256, 6). The radiolabeling was performed by iododestannylation using sodium [(123)I]iodide and peracetic acid. Although the ligand displayed high selectivity for 5-HTT over dopamine transporter in vitro, SPECT imaging in baboons did not reveal selective 5-HTT accumulation in brain in vivo.

Chemical fate of the nicotinic acetylcholinergic radiotracer [123I]5-IA-85380 in baboon brain and plasma.

The fate of the nicotinic acetylcholinergic receptor radiotracer [123I]5-IA-85380 ([123I]5-IA) was studied in baboon by analyzing the chemical composition of brain tissue and plasma after intravenous administration of the tracer. Acetonitrile denaturation and high-performance liquid chromatography (HPLC) analysis showed predominantly unchanged (91-98%) parent tracer in all brain tissues examined, compared to significant metabolism (23% parent) in the plasma at 90 min postinjection, and control tissue recovery of 95-98%. [123I]5-IA was distributed to the thalamus with a standardized uptake value of 9.2 (0.04% dose/g) or a concentration 5.8 times higher than that of the cerebellum. The HPLC behavior of a synthesized sample of one hypothesized metabolite, 5-iodo-3-pyridinol (5-IP), was consistent with plasma radiometabolite fraction. Since only parent radiotracer compound was found in brain tissue, these results add confidence that information derived from single photon emission computed tomography images of 123I activity in the brain after [123I]5-IA administration can be interpreted as distribution of an intact radiotracer.

Radiosynthesis of [18F] N-(3-Fluoropropyl)-2-beta-Carbomethoxy-3-beta-(4-Bromophenyl) Nortropane and the regional brain uptake in non human primate using PET.

A synthetic procedure for the preparation of [18F]FPCBT, an imaging agent for the dopamine transporter (DAT), has been developed. The radiosynthesis was carried out in a two step procedure. Even though the yield was low, we were able to prepare 20 to 30 mCi of the product, which was enough for two or three studies. The radiochemical purity was greater than 96%. The in vivo properties of this radiotracer were evaluated using baboon and it showed highest uptake in the striatum. The studies also revealed that the maximum uptake was reached within 7 to 10 minutes post injection. Plasma metabolite analysis indicated that there is only one metabolite and it is less lipophilic than the parent compound. [18F]FPCBT displayed good brain uptake and its high target to non target ratio indicate that it is a potential candidate for DAT imaging.

Influence of acetylcholine levels on the binding of a SPECT nicotinic acetylcholine receptor ligand [123I]5-I-A-85380.

Although in vitro theory indicates that ligand binding is sensitive to competition with neurotransmitters, only some imaging ligands have shown such competition in vivo. The purpose of this study was to determine whether increases in acetylcholine (ACh) levels induced by an acetylcholinesterase inhibitor, physostigmine, inhibit in vivo binding of [(123)I]5-iodo-3-(2(S)-2-azetidinyl-methoxy) pyridine (5-I-A-85380), a single photon emission computed tomography ligand for the high-affinity type nicotinic ACh receptor (nAChR). Baboons were used for seven studies with a bolus plus constant infusion equilibrium paradigm. After achieving equilibrium at 5 h, physostigmine (0.02 (n = 1), 0.067 (n = 3), and 0.2 (n = 3) mg/kg) was administered intravenously and data were acquired for up to 8 h. To confirm equilibrium conditions, [(123)I]5-I-A-85380 plasma levels were measured in four studies, including all studies with 0.2 mg/kg physostigmine. Prior to physostigmine administration, thalamic activities were stable, with changes of 1.1%/h or less, except in one study with a gradual increase of 4.2%/h. Thalamic activities were decreased by 15% in one study with 0.067 mg/kg and 14-17% in all studies with 0.2 mg/kg physostigmine administration (P = 0.009). In these studies with 0.2 mg/kg physostigmine administration, [(123)I]5-I-A-85380 plasma levels showed a transient or a sustained increase after physostigmine administration that would have increased thalamic activities. These results suggest that elevated ACh levels induced by physostigmine can effectively compete in vivo with [(123)I]5-I-A-85380 binding at nAChRs. However, decreased thalamic activities could have been caused by other mechanisms, including internalization of the receptor with an associated decreased affinity for radioligand.

Measurement of plasma metabolites of (S)-5-[123I]iodo-3-(2-azetidinylmethoxy)pyridine (5-IA-85380), a nicotinic acetylcholine receptor imaging agent, in nonhuman primates.

The iodinated analog (S)-5-[123I]iodo-3-(2-azetidinylmethoxy)pyridine of A-85380 is a new potential SPECT tracer specific for the alpha4beta2 subtype nicotinic acetylcholine receptors, which play an important role in neurodegenerative diseases and in tobacco dependence. To evaluate the possibility of using this tracer for the in vivo quantification of these receptors, an accurate measurement of the plasma concentration of the parent compound is necessary. In human or nonhuman primate whole blood as well as in plasma, the parent compound is only stable for approximately 5 min, after which it decomposes. The radioligand is stable in the injection solution and in protein-free ( >30 K M.W.) plasma ultrafiltrate for at least 18 h. To preserve the parent compound in plasma the radioactive plasma must be mixed with equal volumes of acetonitrile within 5 min after its collection or, alternatively, radioactive blood should be collected and mixed with sodium azide (3 mg/ml blood). The in vivo metabolism of [123I]5-IA resulted in two components: a radiometabolite that is less lipophilic than the parent compound and a polar radiometabolite that is not free radioiodide because of the absence of radioactivity accumulation in the thyroid.