Human Medulla Research Articles

A morphometric analysis of the circumolivary fiber bundle of the human brainstem.

The circumolivary fiber bundle (CFB) is considered to be an anatomical variation, which can be found on the surface of the human medulla oblongata. The macroscopical fiber bundle runs downwards from either the anterior median fissure, the pyramid, or both, around the inferior pole of the olive and turns upwards to reach the restiform body of the inferior cerebellar peduncle. Multiple fiber systems feed the constitution of the CFB (collateral corticospinal fibers, fibers connecting to the reticular formation, anterior external arcuate fibers). With this examination we provide a systematic analysis of the frequency of occurrence (6.14%), size, and laterality of the CFB. Including all three fiber bundle parts (descending part, genu, and ascending part), the left-sided sizes were increased. Likewise, the appearance of an unilateral left-sided CFB could be detected in more than 60% of our cases. Our morphometrical analysis currently covers the largest sample of investigated brainstem sides (n = 489) so far. This investigation should widen the perspective on how anatomists, neuroradiologists, and neurosurgeons expect the anterolateral surface of the human medulla oblongata.

Severe tauopathy and axonopathy in the medulla oblongata in Alzheimer’s disease implicate the changes in autonomic nervous function

The autonomic dysfunctions in Alzheimer’s disease (AD) have been identified from many clinical studies, however, there is still a lack of evidence directly verifying the structural abnormalities of the autonomic nervous system in AD. Human medulla oblongatas from four AD patients or five non-AD subjects were obtained and observed by using immunohistochemical staining of hyperphosphorylated tau and Aβ amyloid, and post-mortem tracing techniques. We found distinct axonal and somatic immunoreactivities for the tau markers AT8 and Tau-5 in the different areas of the medulla oblongata in AD patients, which was particularly obvious in the dorsal nucleus of the vagus nerve, the nucleus of the solitary tract and the reticular nucleus. The swollen axons, which are a typical feature of axonopathy, were not only identified in the axons with immunohistochemical labeling of AT8 and Tau-5 in the different nuclei of the medulla oblongata, but also in the tracer-labeled afferent and efferent fibres of the vagus nerve in AD patients. Such changes in tauopathy and axonopathy were only occasionally found in the non-AD aged subjects. Interestingly, we did not observe any intra- or extracellular Aβ deposits in the medulla oblongatas of the AD patients or of the non-AD subjects. These results in small samples suggest that occurrence of tauopathy and axonopathy in the parasympathetic nuclei of the medulla oblongata in AD patients may implicate the change of autonomic nervous function.

O-081 High variability of molecular isoforms of AMH in follicular fluid and granulosa cells from human small antral follicles

Abstract Study question Is the composition of AMH isoforms different in follicular fluids (FF) and granulosa cells (GCs) from human small antral follicles? Summary answer There is a high viability of AMH isoforms in FFs and GCs. Even between same size follicles from the same women, the isoform composition differs. What is known already Anti Müllerian Hormone (AMH) is a member of the TGF-β superfamily produced by follicular granulosa cells (GCs) in women from late gestation to the end of reproductive live. AMH is suggested to inhibit aromatase (i.e. CYP19) expression and thereby decreasing the conversion of androgens to oestrogens in humans, especially in small antral follicles before dominance is achieved and thereby act as a gatekeeper of ovarian steroidogenesis. However, the exact function and processing of AMH in human follicles is still not clarified. Study design, size, duration This retrospective study measured AMH isoforms in human FF and GCs from small antral follicles using ELISA, Western blot, and immunofluorescence analysis. A total of 41 female adolescents and women aged 15 to 38 years (mean age: 29.7 years), who underwent ovarian tissue cryopreservation (OTC) at the University Hospital of Copenhagen, Rigshospitalet were included between year 2006 and 2020 included. Participants/materials, setting, methods Donated human ovarian medulla tissue were FFs and GCs were obtained in connection with OTC. The following isoforms were evaluated in FFs using ELISA analysis: full-length AMH precursor (proAMH), cleaved associated AMH (AMHN,C), N-terminal pro-region (AMHN), and active C-terminal (AMHC) AMH. Antibodies specific for the N-terminal and the C-terminal AMH were used in both Western blot and immunofluorescence analysis of FFs and GCs. Main results and the role of chance A negative correlation between follicle diameter and the mentioned AMH forms were detected. Moreover, Western blot analysis detected various AMH forms in both FFs and GCs, which did not match the above-mentioned consensus forms suggesting an unknown proteolytic processing of AMH. The presence of these new molecular weight isoforms of AMH differs between individual follicles of identical size from the same woman. Limitations, reasons for caution The study group is limited and the significance of the variable AMH isoforms compositions between follicles cannot not be clarified from this data. Wider implications of the findings Collectively, these data suggest that intrafollicular processing of AMH is complex and variable, and thus, it may be difficult to develop an antibody based AMH assay that detect all AMH isoforms. Furthermore, the variability between follicles suggests that designing a proper standard will be difficult. Trial registration number not applicable

Visualizing the trigeminovagal complex in the human medulla by combining ex-vivo ultra-high resolution structural MRI and polarized light imaging microscopy

A trigeminovagal complex, as described in some animals, could help to explain the effect of vagus nerve stimulation as a treatment for headache disorders. However, the existence of a trigeminovagal complex in humans remains unclear. This study, therefore investigated the existence of the trigeminovagal complex in humans. One post-mortem human brainstem was scanned at 11.7T to obtain structural (T1-weighted) and diffusion magnetic resonance images ((d)MR images). Post-processing of dMRI data provided track density imaging (TDI) maps to investigate white matter at a smaller resolution than the imaging resolution. To evaluate the reconstructed tracts, the MR-scanned brainstem and three additional brainstems were sectioned for polarized light imaging (PLI) microscopy. T1-weighted images showed hyperintense vagus medullar striae, coursing towards the dorsomedial aspect of the medulla. dMRI-, TDI- and PLI-images showed these striae to intersect the trigeminal spinal tract (sp5) in the lateral medulla. In addition, PLI images showed that a minority of vagus fibers separated from the vagus trajectory and joined the trigeminal spinal nucleus (Sp5) and the sp5. The course of the vagus tract in the rostral medulla was demonstrated in this study. This study shows that the trigeminal- and vagus systems interconnect anatomically at the level of the rostral medulla where the vagus fibers intersect with the Sp5 and sp5. Physiological and clinical utility of this newly identified interconnection is a topic for further research.

Cultured Human Thymic-Derived Cells Display Medullary Thymic Epithelial Cell Phenotype and Functionality.

Thymic epithelial cells are one of the main components of the thymic microenvironment required for T-cell development. In this work, we describe an efficient method free of enzymatic and Facs-sorted methods to culture human medullary thymic epithelial cells without affecting the cell phenotypic, physiologic and functional features. Human medulla thymic epithelial cells (mTECs) are obtained by culturing thymic biopsies explants. After 7 days of primo-culture, mTECs keep their ability to express key molecules involved in immune tolerance processes such as autoimmune regulator, tissue-specific antigens, chemokines, and cytokines. In addition, the cells sensor their cultured environment and consequently adjust their gene expression network. Therefore, we describe and provide a human mTEC model that may be used to test the effect of various molecules on thymic epithelial cell homeostasis and physiology. This method should allow the investigations of the specificities and the knowledge of human mTECs in normal or pathological conditions and therefore discontinue the extrapolations done on the murine models.

Renal Medullary and Cortical Correlates in Fibrosis, Epithelial Mass, Microvascularity, and Microanatomy Using Whole Slide Image Analysis Morphometry.

Renal tubulointerstitial injury often leads to interstitial fibrosis and tubular atrophy (IF/TA). IF/TA is typically assessed in the renal cortex and can be objectively quantitated with computerized image analysis (IA). However, the human medulla accounts for a substantial proportion of the nephron; therefore, medullary scarring will have important cortical consequences and may parallel overall chronic renal injury. Trichrome, periodic acid–Schiff (PAS), and collagen III immunohistochemistry (IHC) were visually examined and quantitated on scanned whole slide images (WSIs) (N = 67 cases). When tuned to measure fibrosis, IA of trichrome and Trichrome-PAS (T-P) WSIs correlated for all anatomic compartments (among cortex, medulla, and entire tissue, r = 0.84 to 0.89, P all <0.0001); and collagen III deposition correlated between compartments (r = 0.69 to 0.89, P <0.0001 to 0.0002); however, trichrome and T-P measures did not correlate with collagen deposition, suggesting heterogeneous contributions to extracellular matrix deposition. Epithelial cell mass (EPCM) correlated between cortex and medulla when measured with cytokeratin IHC and with the trichrome red portion (r = 0.85 and 0.66, respectively, all P < 0.0001). Visual assessment also correlated between compartments for fibrosis and EPCM. Correlations were found between increasing medullary inner stripe (IS) width and fibrosis in all of the tissue and the medulla by trichrome morphometry (r = 0.56, P < 0.0001, and r = 0.48, P = 0.00008, respectively). Weak correlations were found between increasing IS width and decreasing visual assessment of all tissue EPCM. Microvessel density (MVD) and microvessel area (MVA) measured using a MVD algorithm applied to CD34 IHC correlated significantly between all compartments (r = 0.76 to 0.87 for MVD and 0.71 to 0.87 for MVA, P all < 0.0001). Overall, these findings demonstrate the interrelatedness of the cortex and medulla and the importance of considering the renal parenchyma as a whole.

Cross-validation of serial optical coherence scanning and diffusion tensor imaging: A study on neural fiber maps in human medulla oblongata

We established a strategy to perform cross-validation of serial optical coherence scanner imaging (SOCS) and diffusion tensor imaging (DTI) on a postmortem human medulla. Following DTI, the sample was serially scanned by SOCS, which integrates a vibratome slicer and a multi-contrast optical coherence tomography rig for large-scale three-dimensional imaging at microscopic resolution. The DTI dataset was registered to the SOCS space. An average correlation coefficient of 0.9 was found between the co-registered fiber maps constructed by fractional anisotropy and retardance contrasts. Pixelwise comparison of fiber orientations demonstrated good agreement between the DTI and SOCS measures. Details of the comparison were studied in regions exhibiting a variety of fiber organizations. DTI estimated the preferential orientation of small fiber tracts; however, it didn't capture their complex patterns as SOCS did. In terms of resolution and imaging depth, SOCS and DTI complement each other, and open new avenues for cross-modality investigations of the brain.

Unique Features of the Human Brainstem and Cerebellum

The cerebral cortex is greatly expanded in the human brain. There is a parallel expansion of the cerebellum, which is interconnected with the cerebral cortex. We have asked if there are accompanying changes in the organization of pre-cerebellar brainstem structures. We have examined the cytoarchitectonic and neurochemical organization of the human medulla and pons. We studied human cases from the Witelson Normal Brain Collection, analyzing Nissl sections and sections processed for immunohistochemistry for multiple markers including the calcium-binding proteins calbindin, calretinin, and parvalbumin, non-phosphorylated neurofilament protein, and the synthetic enzyme for nitric oxide, nitric oxide synthase. We have also compared the neurochemical organization of the human brainstem to that of several other species including the chimpanzee, macaque and squirrel monkey, cat, and rodent, again using Nissl staining and immunohistochemistry. We found that there are major differences in the human brainstem, ranging from relatively subtle differences in the neurochemical organization of structures found in each of the species studied to the emergence of altogether new structures in the human brainstem. Two aspects of human cortical organization, individual differences and left–right asymmetry, are also seen in the brainstem (principal nucleus of the inferior olive) and the cerebellum (the dentate nucleus). We suggest that uniquely human motor and cognitive abilities derive from changes at all levels of the central nervous system, including the cerebellum and brainstem, and not just the cerebral cortex.

Locus K: cuneate subnuclear regions in human dorsal column nuclei with neurochemical, cyto- and myeloarchitectural features of protopathic sensory nuclei

This study is aimed to further characterize on a neurochemical, histological and morphometric ground the human Locus K, a newly identified region in the human nucleus cuneatus that shares neurochemical features with protopathic second order sensory nuclei (Del Fiacco et al., 2013; Serra et al., 2013). Human brainstem sections were observed by means of ABC immunohistochemistry for calcitonin gene-related peptide (CGRP), substance P (SP) and transient receptor potential vanilloid type-1 receptor (TRPV1), Kluver-Barrera, Black Gold kit II and Nissl staining followed by computerized analysis of cell size and density. As for CGRP and SP, at both pre- and postnatal age, immunoreactivity to TRPV1 occurs in Locus K with a distribution alike that present in the spinal trigeminal nucleus, caudal part. Morphometric analysis shows that, in adult tissue, the mean diameter and density of Nissl stained neurons in the Locus K are consistent with those of the caudal spinal trigeminal and solitary nuclei, and different from those in the gracile, cuneate and external cuneate nuclei. Kluver-Barrera and Black Gold kit II staining shows that myelinated fibres, abundant in the main cuneate, gracile and trigeminal magnocellular nuclei, are scarce in both the Locus K and trigeminal substantia gelatinosa. Immunohistochemical and cyto- and myeloarchitectural analysis uphold the parallel neurochemical and structural arrangement for Locus K and protopathic nuclei in the human medulla oblongata, and support the concept that Locus K represents a special component of the human dorsal column nuclei. Work funded by Fondazione Banco di Sardegna.

Astrocitary niches in human adult medulla oblongata

Astrocytes are considered as neuromodulators of the CNS. Whereas experimental studies on astrocitary functions are gaining importance, the anatomy of the astrocitary niches in the human CNS has been overlooked. The study was performed on the brainstem of 10 adult cadavers. We aimed to determine astrocitary niches in the human medulla oblongata using immunohistochemical labeling with vimentin and also CD34 immunostaining to accurately diagnose associated microvessels. Niches rich in astrocytes were identified as follows: (a) the superficial layer of astrocytes, ventral and ventrolateral, in the rostral medulla oblongata; (b) the median raphe; (c) medullary nuclei: arcuate nucleus, area postrema, nucleus of the solitary tract; (d) the subependymal zone (SEZ, caudal medulla) and subventricular zone (SVZ, rostral medulla). Astrocytes were scarce in the ventrolateral medulla, and mostly present within the pyramidal tract and the olivary nucleus. Apart from the SEZ and SVZ, the brainstem niches of astrocytes mostly overlap those regions known to perform roles as central respiratory chemoreceptors. The astrocytes of the SEZ and SVZ, which are known as stem cell niches, are related to an increased microvascular density.

Preliminary observations on the vasomotor responses to electrical stimulation of the ventrolateral surface of the human medulla

Pulsatile arterial compression (AC) of the ventrolateral medulla (VLM) is hypothesized to produce the hypertension in a subset of patients with essential hypertension. In animals, a network of subpial neuronal aggregates in the VLM has been shown to control cardiovascular functions. Although histochemically similar, neurons have been identified in the retro-olivary sulcus (ROS) of the human VLM, but their function is unclear. The authors recorded cardiovascular responses to electrical stimulation at various locations along the VLM surface, including the ROS, in patients who were undergoing posterior fossa surgery for trigeminal neuralgia. This vasomotor mapping of the medullary surface was performed using a bipolar electrode, with stimulation parameters ranging from 5- to 30-second trains (20-100 Hz), constant current (1.5-5 mA), and 0.1-msec pulse durations. Heart rate (HR) and blood pressure (BP) were recorded continuously from baseline (10 seconds before the stimulus) up to 1 minute poststimulus. In 6 patients, 17 stimulation responses in BP and HR were recorded. The frequency threshold for any cardiovascular response was 20 Hz; the stimulation intensity threshold ranged from 1.5 to 3 mA. In the first patient, all stimulation responses were significantly different from sham recordings (which consisted of electrodes placed without stimulations). Repeated stimulations in the lower ROS produced similar responses in 3 other patients. Two additional patients had similar responses to single stimulations in the lower ROS. Olive stimulation produced no response (control). Hypotensive and/or bradycardic responses were consistently followed by a reflex hypertensive response. Slight right/left differences were noted. No patient suffered short- or long-term effects from this stimulation. This stimulation technique for vasomotor mapping of the human VLM was safe and reproducible. Neuronal aggregates near the surface of the human ROS may be important in cardiovascular regulation. This method of vasomotor mapping with measures of responses in sympathetic tone (microneurography) should yield additional data for understanding the neuronal network that controls cardiovascular functions in the human VLM. Further studies in which a concentric bipolar electrode is used to generate this type of vasomotor map should also increase understanding of the pathophysiological mechanisms of neurogenically mediated hypertension, and assist in the design of studies to prove the hypothesis that it is caused by pulsatile AC of the VLM.

Acceleration of gene transfection efficiency in neuroblastoma cells through polyethyleneimine/poly(methyl methacrylate) core-shell magnetic nanoparticles

BackgroundThe purpose of this study was to demonstrate the potential of magnetic poly(methyl methacrylate) (PMMA) core/polyethyleneimine (PEI) shell (mag-PEI) nanoparticles, which possess high saturation magnetization for gene delivery. By using mag-PEI nanoparticles as a gene carrier, this study focused on evaluation of transfection efficiency under magnetic induction. The potential role of this newly synthesized nanosphere for therapeutic delivery of the tryptophan hydroxylase-2 (TPH-2) gene was also investigated in cultured neuronal LAN-5 cells.MethodsThe mag-PEI nanoparticles were prepared by one-step emulsifier-free emulsion polymerization, generating highly loaded and monodispersed magnetic polymeric nanoparticles bearing an amine group. The physicochemical properties of the mag-PEI nanoparticles and DNA-bound mag-PEI nanoparticles were investigated using the gel retardation assay, atomic force microscopy, and zeta size measurements. The gene transfection efficiencies of mag-PEI nanoparticles were evaluated at different transfection times. Confocal laser scanning microscopy confirmed intracellular uptake of the magnetoplex. The optimal conditions for transfection of TPH-2 were selected for therapeutic gene transfection. We isolated the TPH-2 gene from the total RNA of the human medulla oblongata and cloned it into an expression vector. The plasmid containing TPH-2 was subsequently bound onto the surfaces of the mag-PEI nanoparticles via electrostatic interaction. Finally, the mag-PEI nanoparticle magnetoplex was delivered into LAN-5 cells. Reverse-transcriptase polymerase chain reaction was performed to evaluate TPH-2 expression in a quantitative manner.ResultsThe study demonstrated the role of newly synthesized high-magnetization mag-PEI nanoparticles for gene transfection in vitro. The expression signals of a model gene, luciferase, and a therapeutic gene, TPH-2, were enhanced under magnetic-assisted transfection. An in vitro study in neuronal cells confirmed that using mag-PEI nanoparticles as a DNA carrier for gene delivery provided high transfection efficiency with low cytotoxicity.ConclusionThe mag-PEI nanoparticle is a promising alternative gene transfection reagent due to its ease of use, effectiveness, and low cellular toxicity. The mag-PEI nanoparticle is not only practical for gene transfection in cultured neuronal cells but may also be suitable for transfection in other cells as well.

Culture of Isolated Preantral Follicles from Human Ovarian Medulla.

Culture of Isolated Preantral Follicles from Human Ovarian Medulla.

Pulsatile arterial compression of cranial nerves

The authors are to be commended for their observations on patients undergoing retromastoid craniectomy with microvascular decompression of the right ventrolateral medulla (VLM) and vagus nerve for type 2 diabetes mellitus. Seven of the 10 patients observed demonstrated overall glycemic control that either improved or did not worsen at the 12-month postoperative follow-up visit. These observations point the way to further questions that need to be answered to conclude definitively that pulsatile arterial compression of the right VLM is an independent risk factor for type 2 diabetes mellitus. As stated by the authors, a neurogenic basis for various cranial nerve hyperactive syndromes has long been postulated in the literature, with the first on essential hypertension made by Dr. Jannetta in the 1970s. Animal studies confirmed the presence of a subpial catecholamine-synthesizing neuronal group (C1) in the rostral ventrolateral medulla, which produces a transient pressor response when stimulated electrically, chemically or mechanically.[3,4,7,10] Histochemical studies of human medullae obtained at autopsy showed a similar group of catecholamine neurons in the subpial regions of the retro-olivary sulcus (ROS) near the root-entry zone of the ninth and tenth cranial nerves.[1,6] Conflicting results from early studies of the association between arterial compression and essential hypertension may have been due in part to inconsistencies in the exact location of compression or the failure to identify the subgroup of hypertensive patients most likely to benefit from microvascular decompression. Later studies began to address these questions. It was hypothesized that arterial pulsatile compression may either directly stimulate the C1 neurons or disinhibit them via an effect on the caudal ventrolateral medulla resulting in elevation of central sympathetic outflow or tone.[5] In support of this hypothesis, it was found that in a group of 18 subjects, those with vascular contact along the left ROS (presumed location of the C1 neurons) had higher baseline plasma norepinephrine concentrations and greater clonidine depressor response (sympathetic dependence of blood pressure) than those without vascular contact along the left ROS.[5] To better address the question of location, electrical stimulation studies were undertaken to precisely define the location of the sympatho-excitatory and inhibitory neuronal aggregates in humans.[9,11] A defined area of hypertensive responses was found at the mid ROS, centered 6 mm rostral to the lowest nerve root. Microneurography data suggested that the observed elevation of arterial blood pressure associated with electrical stimulation of this area was due to an activation of the sympathetic system, with no conclusive evidence of lateralization.[9,11] The question of whether arterial compression acted as an independent predictor of essential hypertension (apart from other known risk factors) was addressed in larger multivariable retrospective designs.[2,8] In a case-control study of 147 patients, it was found that the odds of arterial compression among hypertensive subjects were 2.99 times the odds among normotensive subjects (P= .04), controlling for hypertension risk factors such as age, body mass index, race, diabetes and family history of hypertension. Of compressed hypertensive subjects, 56% were compressed on the left and 44% on the right.[8] Collectively, these studies are building a body of evidence to aid the selection of patients eligible for microvascular decompression, i.e., those with intractable hypertension, elevated sympathetic tone, and arterial compression in accordance with a refined map of the human ventrolateral medullary surface and its relationship to cardiovascular control. Like Dr. Jannetta’s earlier observations on essential hypertension, the observations presented in the manuscript “Type 2 Diabetes Mellitus: A Central Nervous System Etiology” are valuable starting points for questions related to the exact location of arterial compression relevant to type 2 diabetes mellitus, the best experimental measure of response, and the subset of patients most likely to benefit from microvascular decompressive surgery. The authors have made a start in this direction by observing that non-obese patients with type 2 diabetes mellitus appear to respond better to decompression than obese patients. We encourage their continued efforts and those of other researchers in addressing those questions raised by this valuable contribution to our understanding of type 2 diabetes mellitus and its treatment.

Neuroanatomic relationships between the GABAergic and serotonergic systems in the developing human medulla

γ-Amino butyric (GABA) critically influences serotonergic (5-HT) neurons in the raphé and extra-raphé of the medulla oblongata. In this study we hypothesize that there are marked changes in the developmental profile of markers of the human medullary GABAergic system relative to the 5-HT system in early life. We used single- and double-label immunocytochemistry and tissue receptor autoradiography in 15 human medullae from fetal and infant cases ranging from 15 gestational weeks to 10 postnatal months, and compared our findings with an extensive 5-HT-related database in our laboratory. In the raphé obscurus, we identified two subsets of GABAergic neurons using glutamic acid decarboxylase (GAD65/67) immunostaining: one comprised of small, round neurons; the other, medium, spindle-shaped neurons. In three term medullae cases, positive immunofluorescent neurons for both tryptophan hydroxylase and GAD65/67 were counted within the raphé obscurus. This revealed that approximately 6% of the total neurons counted in this nucleus expressed both GAD65/67 and TPOH suggesting co-production of GABA by a subset of 5-HT neurons. The distribution of GABA A binding was ubiquitous across medullary nuclei, with highest binding in the raphé obscurus. GABA A receptor subtypes α1 and α3 were expressed by 5-HT neurons, indicating the site of interaction of GABA with 5-HT neurons. These receptor subtypes and KCC2, a major chloride transporter, were differentially expressed across early development, from midgestation (20 weeks) and thereafter. The developmental profile of GABAergic markers changed dramatically relative to the 5-HT markers. These data provide baseline information for medullary studies of human pediatric disorders, such as sudden infant death syndrome.

Nitroxidergic neurons in nuclei of rat and human medulla oblongata

Four types of neurons distinguished by NADPH-diaphorase reaction have been identified in seven nuclei of human and rat medulla oblongata. It was found that nitrogen oxide (NO)-positive neurons had similar distributions; neurons with high NO-synthase activity predominated in vasomotor nuclei and, in sensitive nuclei, most neurons had low NO-syntase activity.

5-HT 2A receptors are concentrated in regions of the human infant medulla involved in respiratory and autonomic control

The serotonergic (5-HT) system in the human medulla oblongata is well-recognized to play an important role in the regulation of respiratory and autonomic function. In this study, using both immunocytochemistry ( n = 5) and tissue section autoradiography with the radioligand 125I-1-(2,5-dimethoxy-4-iodo-phenyl)2-aminopropane ( n = 7), we examine the normative development and distribution of the 5-HT 2A receptor in the human medulla during the last part of gestation and first postnatal year when dramatic changes are known to occur in respiratory and autonomic control, in part mediated by the 5-HT 2A receptor. High 5-HT 2A receptor binding was observed in the dorsal motor nucleus of the vagus (preganglionic parasympathetic output) and hypoglossal nucleus (airway patency); intermediate binding was present in the nucleus of the solitary tract (visceral sensory input), gigantocellularis, intermediate reticular zone, and paragigantocellularis lateralis. Negligible binding was present in the raphé obscurus and arcuate nucleus. The pattern of 5-HT 2A immunoreactivity paralleled that of binding density. By 15 gestational weeks, the relative distribution of the 5-HT 2A receptor was similar to that in infancy. In all nuclei sampled, 5-HT 2A receptor binding increased with age, with significant increases in the hypoglossal nucleus ( p = 0.027), principal inferior olive ( p = 0.044), and medial accessory olive (0.038). Thus, 5-HT 2A receptors are concentrated in regions involved in autonomic and respiratory control in the human infant medulla, and their developmental profile changes over the first year of life in the hypoglossal nucleus critical to airway patency and the inferior olivary complex essential to cerebellar function.

The development of nicotinic receptors in the human medulla oblongata: Inter-relationship with the serotonergic system

Maternal cigarette smoking during pregnancy adversely affects fetal development and increases the risk for the sudden infant death syndrome (SIDS). In SIDS we have reported abnormalities in the medullary serotonergic (5-HT) system, which is vital for homeostatic control. In this study we analyzed the inter-relationship between nicotinic receptors (nAChRs), to which nicotine in cigarette smoke bind, and the medullary 5-HT system in the human fetus and infant as a step towards determining the mechanisms whereby smoking increases SIDS risk in infants with 5-HT defects. Immunohistochemistry for the α4 nAChR subunit and 5-HT neurons was applied in fetal and infant medullae (15–92 postconceptional weeks, n = 9). The distribution of different nAChRs was determined from 39–82 postconceptional weeks ( n = 5) using tissue autoradiography for 3H-nicotine, 3H-epibatidine, 3H-cytisine, and 125I-bungarotoxin; the findings were compared to laboratory 5-HT 1A and 5-HT transporter binding data, and 5-HT neuronal density. Alpha4 immunoreactivity was ubiquitously expressed in medullary nuclei related to homeostatic functions from 15 weeks on, including rhombic lip germinal cells. At all ages, α4 co-localized with 5-HT neurons, indicating a potential site of interaction whereby exogenous nicotine may adversely affect 5-HT neuronal development and function. Binding for heteromeric nAChRs was highest in the inferior olive, and for homomeric nAChRs, in the vagal complex. In the paragigantocellularis lateralis, 5-HT 1A receptor binding simultaneously increased as α7 binding decreased across infancy. This study indicates parallel dynamic and complex changes in the medullary nicotinic and 5-HT systems throughout early life, i.e., the period of risk for SIDS.

Temporal sequencing of brain activations in menopausal hot flashes

The insula, associated with interoception and representation of internal physiological states is a terminus in the thermoreceptive spinothalamocortical pathway within which the dorsal raphe (DR), is an early signaling region. Menopausal hot flashes (HF) are internal thermal events that activate the insula but the precedents of this activity are unknown. We assessed the time course of activity in the DR and insula in the context of HFs using fMRI conducted on 20 postmenopausal women with HFs (mean age 52 yrs). Subjects were heated with ventral and dorsal heating pads (42°C) throughout. HF onset was signaled with an increase of 2μmho/30 s in sternally recorded SCL's acquired synchronously with fMRI. Data were analyzed using SPM2 in a 30 image (1 minute) tri‐partitioned (Baseline, Pre‐Flash, post‐Flash: 10 images/partition) window around HF onset. Extracted time series from the raphe and insula were normalized to the mean activation value in Baseline. A significant interaction between partition and region, F(2,2388)=3.39, p&lt;.034, indicated a rise in DR but not insula activity in the pre‐Flash partition. These results document a temporally ordered pattern of detectable physiological events associated with endogenously generated thermal events, and suggest that activity in the human medulla, central to homeostatis, precedes the detectable onset of menopausal flashes and the response of regions such as the insula.

Comparison of Preparation Methods for the Evaluation of Nerve Axons

We have conducted a study to compare various preparation methods, including a certain number of new methods, to find which ones are best suited to the morphological evaluation of nerve fibers in the pyramidal tract of the human medulla oblongata. Our main concern was to find fixation and staining methods that would minimize errors, especially regarding the tissue shrinkage ratio and the ease of staining. From the two fixation methods we examined, the most satisfactory was the secondary chromic acid fixation (which gave the best overall results when followed by nitrocellulose embedding), as it gives the lowest shrinkage ratio with the narrowest range (10 +/- 0%). Among the ten staining methods we tested, we found that the most suitable for morphological evaluation were the discriminative staining methods (Luxol fast blue-Periodic acid-Schiff-Hematoxylin stain, Masson-Goldner-Goto method and modified Hematoxylin-Eosin stain) and the silver impregnation methods (Luxol fast blue-Silver impregnation and Luxol fast blue-Silver impregnation-Periodic acid-Schiff-Hematoxylin).