Earl A. Zimmerman

Fibrillary astrocytes proliferate in response to brain injury: A study combining immunoperoxidase technique for glial fibrillary acidic protein and radioautography of tritiated thymidine☆

Abstract To determine whether fibrillary astrocytes proliferate in response to brain injury, cells identified as fibrillary astrocytes using immunoperoxidase technique for glial fibrillary acidic protein (GFAP) were examined for uptake of radiolabeled thymidine by autoradiography. In injured mouse brain, autoradiographic label was present over nuclei of immunoreactive fibrillary astrocytes in the lesion site 1 hr following injection of radiolabeled thymidine. The data suggest that fibrillary astrocytes which are sufficiently differentiated to accumulate GFAP retain the capacity to proliferate in response to injury.

Vasoactive intestinal polypeptide (VIP) in mouse and rat brain: An immunocytochemical study

Immunoperoxidase technique and light microscopy were used to investigate the distribution of vasoactive intestinal polypeptide (VIP) in mouse and rat brain. Both 50 micrometers unmounted cryostat and 6 micrometers deparaffinized sections were studied in coronal or sagittal plane. At least 4 different major VIP systems were found: (1) an intracerebral cortical system; (2) one innervating the central amygdala and nucleus of the stria terminalis; (3) a pathway originating in the suprachiasmatic nucleus of the hypo thalamus; and (4) another originating in the central grey of the midbrain. Specific cell body staining was seen in the limbic and neocortex, in the basal-caudal portion of the suprachiasmatic nucleus of the hypothalamus, and in the central grey of the midbrain. Heavy terminal field patterns were noted in the suprachiasmatic nucleus, central amygdaloid nucleus, bed nucleus of the stria terminalis and nucleus accumbens. Fiber density was moderate in the tuberculum olfactoriu, anterior hypothalamus including the medial preoptic area, mediobasal hypothalamus (especially dorsomedial region), periventricular thalamus, lateral lemniscal system, parabrachial nucleus, nucleus solitarius, and area postrema. Fibers could be traced dorsally from the suprachiasmatic nucleus to the dorsomedial and paraventricular nuclei of the hypothalamus and the periventricular nucleus of the thalamus. Scattered cell bodies and fibers were found in a number of other forebrain and brain stem areas with only a rare fiber seen in median eminence.

The descending afferent connections of the paraventricular nucleus of the hypothalamus (PVN)

The distribution of afferents to the paraventricular nucleus of the hypothalamus (PVN) was studied following iontophoresis of horseradish peroxidase (HRP) into the nucleus. This report describes the descending connections to this structure. The PVN receives a substantial input from limbic system structures, especially from the lateral septal nucleus and the ventral portion of the subicular cortex. A small number of labeled cells were found in the amygdala, primarily the medial nucleus. Of the circumventricular organs, the subfornical organ and OVLT both project to the PVN, the former very strongly. In both the preoptic area and hypothalamus, medial cell groups have more input than do the lateral areas. Labeled cells were found in the medial and hypothalamus, medial cell groups have more input than do the lateral areas. Labeled cells were found in the medial and lateral preoptic areas, suprachiasmatic nucleus, ventromedial nucleus, arcuate nucleus, retrochiasmatic and lateral hypothalamic areas. Of particular interest is the finding that the PVN receives input from the contralateral PVN and ipsilateral SON. Of the other diencephalic structures only the zone incerta showed a consistent number of labeled cells. The results are discussed in relationship to the possible neural structures that might mediate the response of the PVN neurons to adrenalectomy.

Magnocellular Hypothalamic Projections to the Lower Brain Stem and Spinal Cord of the Rat

The paraventricular nucleus of the rat hypothalamus has been shown to project to the medulla and spinal cord. The proportion of oxytocin-neurophysin (OTNP) axons to vasopressin-neurophysin (VPNP) axons in these structures is unknown. A major difficulty in resolving this problem in previous immunocytochemical studies was the lack of a specific antiserum to each rat neurophysin. In this study two approaches have been used: (1) comparison of immunostaining for neurophysin in normal versus homozygous Brattleboro rats with diabetes insipidus (HODI) which lack VPNP, and (2) application of an antiserum to both rat neurophysins absorbed with HODI rat hypothalamic-pituitary extracts which contain only OTNP. The latter would result in an antiserum specific for VPNP. Our results indicate that the axons which constitute the caudal projections from the paraventricular nucleus are predominately oxytocinergic, the vasopressinergic innervation being limited to the nucleus tractus solitarius, the dorsal motor nucleus of vagus, and the substantia gelatinosa. A similar number of reactive fibers were seen in the medulla and spinal cord of normal and HODI rats. No positive perikarya were observed caudal to the hypothalamus. Fibers in the medulla appeared to terminate in the nucleus of the solitary tract and in the dorsal motor nucleus of the vagus nerve. Positive fibers throughout the cord were present in the substantia gelatinosa and in the intermediolateral grey. The possible role(s) of these projections in integrating autonomic functions and afferent information with neuroendocrine regulation is discussed.

Transthyretin: A choroid plexus‐specific transport protein in human brain: The 1986 S. Weir Mitchell Award

Plasma transthyretin (TTR, formerly called prealbumin) is a 55-kd protein that participates in the plasma transport of both thyroxine and retinol (vitamin A). TTR concentrations are disproportionately high in human ventricular CSF, suggesting that TTR is either selectively transported across or synthesized de novo within the blood-CSF barrier. To address this question, we adopted a molecular genetic approach; after isolating a cDNA clone encoding human TTR, we previously demonstrated specific TTR messenger RNA (mRNA) synthesis in rat choroid plexus. We have now extended these investigations to the human brain. Northern analysis of postmortem brain homogenates revealed abundant TTR mRNA in choroid plexus, but not in cerebellum or cerebral cortex. Choroid plexus mRNA was readily translated into TTR preprotein in an in vitro translation system. An immunocytochemical survey of human postmortem brain sections revealed the presence of TTR protein specifically and uniquely in the cytoplasm of choroid plexus epithelial cells; these results were corroborated at the mRNA level by an extensive survey of whole rat-brain sections by in situ hybridization. Therefore, within the mammalian CNS, TTR is the first known protein synthesized solely by the choroid plexus, suggesting a special role for TTR in the brain or CSF. Whether this function differs from its established plasma transport functions is presently unknown.

T2* and FSE MRI distinguishes four subtypes of neurodegeneration with brain iron accumulation

Background: Neurodegeneration with brain iron accumulation (NBIA) defines a group of genetic disorders characterized by brain iron deposition and associated with neuronal death. The known causes of NBIA include pantothenate kinase-associated neurodegeneration (PKAN), neuroferritinopathy, infantile neuroaxonal dystrophy (INAD), and aceruloplasminemia. Objective: To define the radiologic features of each NBIA subtype. Methods: Brain MRIs from patients with molecularly confirmed PKAN (26 cases), neuroferritinopathy (21 cases), INAD (four cases), and aceruloplasminemia (10 cases) were analyzed blindly to delineate patterns of iron deposition and neurodegeneration. Results: In most cases of PKAN, abnormalities were restricted to globus pallidus and substantia nigra, with 100% having an eye of the tiger sign. In a minority of PKAN cases there was hypointensity of the dentate nuclei (1/5 on T2* sequences, 2/26 on fast spin echo [FSE]). In INAD, globus pallidus and substantia nigra were involved on T2* and FSE scans, with dentate involvement only seen on T2*. By contrast, neuroferritinopathy had consistent involvement of the dentate nuclei, globus pallidus, and putamen, with confluent areas of hyperintensity due to probable cavitation, involving the pallida and putamen in 52%, and a subset having lesions in caudate nuclei and thalami. More uniform involvement of all basal ganglia and the thalami was typical in aceruloplasminemia, but without cavitation. Conclusions: In the majority of cases, different subtypes of neurodegeneration associated with brain iron accumulation can be reliably distinguished with T2* and T2 fast spin echo brain MRI, leading to accurate clinical and subsequent molecular diagnosis.

Clinical and Pathological Continuum of Multisystem TDP-43 Proteinopathies

OBJECTIVE To determine the extent of transactivation response DNA-binding protein with a molecular weight of 43 kDa (TDP-43) pathology in the central nervous system of patients with clinically and autopsy-confirmed diagnoses of frontotemporal lobar degeneration with and without motor neuron disease and amyotrophic lateral sclerosis with and without cognitive impairment. DESIGN Performance of immunohistochemical whole-central nervous system scans for evidence of pathological TDP-43 and retrospective clinical medical record review. SETTING An academic medical center. PARTICIPANTS We included 64 patients with clinically and pathologically confirmed frontotemporal lobar degeneration with ubiquitinated inclusions with or without motor neuron disease and amyotrophic lateral sclerosis with or without cognitive impairment. MAIN OUTCOME MEASURE Neuronal and glial TDP-43 pathology. RESULTS We found evidence of neuronal and glial TDP-43 pathology in all disease groups throughout the neuraxis, albeit with variations in the frequency, morphology, and distribution of TDP-43 lesions. Moreover, the major clinical manifestations (eg, cognitive impairments, motor neuron signs, extrapyramidal symptoms, neuropsychiatric features) were reflected by the predominant distribution and burden of TDP-43 pathology. CONCLUSION These findings strongly suggest that amyotrophic lateral sclerosis, frontotemporal lobar degeneration with amyotrophic lateral sclerosis or motor neuron disease, and frontotemporal lobar degeneration with ubiquitinated inclusions are different manifestations of a multiple-system TDP-43 proteinopathy linked to similar mechanisms of neurodegeneration.

Vasopressin and Neurophysin: High Concentrations in Monkey Hypophyseal Portal Blood

Vasopressin and its binding protein, neurophysin, were measured by radioimmunoassay in the hypophyseal portal blood of monkeys after cannulation of individual long portal veins. Mean vasopressin concentrations (13,800 picograms per milliliter) in portal blood were more than 300 times as high as those in the systemic circulation (42 picograms per milliliter). Neurophysin concentration was approximately 25 times as high in portal as in systemic blood. By immunoperoxidase techniques, high concentrations of neurophysin were demonstrated around portal capillaries of the median eminence. These studies indicate direct secretion of vasopressin and neurophysin into the portal circulation; the quantities secreted during stress may be sufficient to exert significant effects on secretion of anterior pituitary hormone.

Immunohistochemical localization of neurotensin in endocrine cells of the gut

SummaryEndocrine cells displaying neurotensin immunoreactivity are found scattered in the jejuno-ileum of all mammals studied, including man. They are rather scarce in rat, guinea pig, rabbit and pig and fairly numerous in cat, dog and man. In most mammals the neurotensin cells predominate on the villi. Only in the dog are they more numerous in the crypts. In the chicken, neurotensin cells occur all along the intestinal tract. They are particularly numerous in the zone that joins the gizzard with the duodenum. The ontogeny of the neurotensin cells in the gut was studied in rats and chickens. In the rat, the cells are first observed in the jejuno-ileum immediately before birth. The adult frequency is reached 4–5 days later. In the chicken, neurotensin cells first appear in the colon in the 18 day old embryo and in the small intestine two days later (i.e. one or two days before hatching). A few days after hatching, the gut has achieved the adult number of neurotensin cells per unit area.

Comparative Distribution of Vasopressin and Oxytocin Neurons in the Rat Brain Using a Double-Label Procedure

The distribution of vasopressin (VP) and oxytocin (OT) neurons in the rat supraoptic (SON), paraventricular (PVN), and accessory magnocellular (AMN) nuclei was studied by localizing both peptides on the same section with a double immunocytochemical staining procedure employing specific monoclonal antibodies (MAB). This procedure allows us to visualize the distribution of one cell type relative to the other. In the rostral SON, VP cells lie dorsal and medial to the OT cells. Near the mid-point of the nucleus along its rostral-caudal length, there is a transition zone in which the two cell types are mixed. Proceeding caudalward, the relative locations of OT and VP cells are exchanged so that most of VP cells are located in the ventral and medial sector of the nucleus, whereas the OT cells are situated dorsal and lateral. However, there is no absolute segregation of the two types of cells anywhere in the nucleus. In the anterior part of the PVN a rostral group (rPVN) of cells composed of a medial portion and a lateral wing can be recognized. Nearly all of the cells in the rPVN are oxytocin-containing. The rPVN is separated from the next group, the middle PVN (mPVN), by a cell poor zone of about 100-150 micron. The mPVN contains both OT and VP neurons. As one proceeds caudally, the OT cells extend in the rostrocaudal direction from an anterior and ventromedial location, forming a shell around a core of VP neurons. In the most caudal PVN (cPVN), a triangular cell group characterized by fusiform cells with long-beaded processes can be distinguished from the more rounded cells of the remaining PVN. Many fusiform cells in the cPVN appear to send their axons to the posterior perifornical nucleus and the nucleus of the medial forebrain bundle. Other fusiform cells of the cPVN are oriented in a rostral-caudal plane and are situated more medially in this subdivision. The dendrites of these cells project into the mPVN while their posterior processes, most of which also appear to be dendrites, project caudally along a medial route.