Effect on breathing of ventral medullary surface cooling in neonatal goats.

The present study was designed to determine whether neurons near the ventral medullary surface (VMS) that are important to control of breathing in adult mammals are also important to control of breathing in neonates. In 7-day-old goats (n = 22), the VMS was surgically exposed under halothane anesthesia. Stainless steel thermodes (2 x 2 mm) were used to cool (20 degrees C) and thereby create neuronal dysfunction of discrete VMS sites. Bilateral cooling under anesthesia 0-2 or 2-4 mm lateral to the midline between the exit of cranial nerves VI and XII resulted in a reduction (P < 0.05) of breathing and most often in apnea. Cooling caudal or rostral to this area did not have a consistent effect on breathing. In 7-day-old goats (n = 8), 3 x 3-mm thermodes were chronically implanted bilaterally on the VMS surface between the exit of cranial nerves VI and XII. The goats recovered and were studied over several days thereafter. VMS cooling while the goats were awake caused breathing to decrease (P < 0.05), but apnea was never observed. The decrease was less (P < 0.05) than while the goats were anesthetized. After 10 s of cooling, the hypopnea while the goats were awake was uniform during eupnea, hypercapnia, hyperoxia, and hypoxia, but after 10 s of cooling, the decrease was relatively greater (P < 0.05) during hyperoxia and hypercapnia. These effects of VMS cooling are qualitatively the same as in adult goats; thus the data are consistent with mature VMS contribution to the control of breathing in neonatal goats.

Patterns of glial development in the human foetal spinal cord during the late first and second trimester.

Although the presence of radial glia, astrocytes, oligodendrocytes and microglia has been reported in the human foetal spinal cord by ten gestational weeks, neuroanatomic studies employing molecular probes that describe the interrelated development of these cells from the late first trimester through the late second trimester are few. In this study, immunocytochemical methods using antibodies to vimentin and glial fibrillary acidic protein were used to identify radial glial and/or astrocytes. An antibody to myelin basic protein was used for oligodendrocytes and myelin; and, an antibody to phosphorylated high and medium molecular weight neurofilaments identified axons. Lectin histochemistry using Ricinus communis agglutinin-I was employed to identify microglia. Vibratome sections from 35 human foetal spinal cord ranging in age from 9-20 gestation weeks were studied. By 12 gestational weeks, vimentin-positive radial glia were present at all three levels of the spinal cord. Their processes were easily identified in the dorsal two-thirds of cord sections, and reaction product for vimentin was more intense at cervical and thoracic levels than lumbosacral sections. By 15 gestational weeks, vimentin-positive processes were radially arranged in the white matter. At this time, glial fibrillary acidic protein-positive astrocytes were more obvious in both the anterior and anterolateral funiculi than in the dorsal funiculus, and the same rostral to caudal gradient was seen for glial fibrillary acidic protein as it was for vimentin. Myelin basic protein expression followed similar temporal and spatial patterns. Ricinus communis agglutinin-I labelling revealed more microglia in the white matter than in grey matter throughout the spinal cord from 10-20 gestational weeks. By 20 gestational weeks, the gradients of glial fibrillary acidic protein and vimentin expression were more difficult to discern. White matter contained more microglia than grey matter. These results suggest that astrocytes as well as oligodendrocytes follow anterior-to-posterior and rostral-to-caudal developmental patterns in the human foetus during middle trimester development.

Neuroanatomical localization of myelin basic protein in the late first and early second trimester human foetal spinal cord and brainstem.

The temporal and spatial expression of myelin basic protein in the first and second trimester human foetal spinal cord and brainstem from 9 to 20 gestational weeks was determined by immunocytochemistry in sections of cervical, thoracic and lumbosacral levels from 41 human foetal spinal cords and ten brainstems. Myelin basic protein-positive oligodendrocytes were observed peripheral to the ependyma at 9-10 gestational weeks. Oligodendrocytes expressing myelin basic protein were seen at 10-12 gestational weeks in the anterior and lateral funiculi. Myelin basic protein was detected later in the posterior funiculi than in the anterolateral white matter and most spinal cord tracts could not be identified by means of variation in myelin basic protein expression. Myelin basic protein was found in the midline of the brainstem at ten gestational weeks and spread laterally during the second trimester. We conclude that in the human foetal spinal cord, myelin basic protein is present by 10 gestational weeks in the anterolateral cervical spinal cord and midline of the brainstem. It is expressed in a rostral-to-caudal and anterolateral-to-posterior manner in most tracts of the spinal cord. However, an exception to these findings is that the fasciculus gracilis, upon developing into a defined region, had more myelin basic protein-positive cells at the lumbar level than in more rostral regions. Definition of the kinetics of myelin basic protein expression in the normal human foetal spinal cord provides a baseline for study of aberrant myelination and demyelination.

Immunocytochemical identification of T-cells in HIV-1 encephalitis: implications for pathogenesis of CNS disease.

T-lymphocytes enter the brain in viral encephalitides. The monoclonal antibodies UCHL1 and Leu22 are widely used to identify these cells; however, both antibodies cross-react with peripheral blood monocytes, cells ontologically related to brain macrophages and microglia. This study examines the nature of UCHL1- and Leu22-positive cells in HIV-1 encephalitis, and investigates whether they carry the gp41 epitope of HIV-1. Formalin-fixed sections of brain from eight AIDS patients were double-stained using combinations of UCHL1 and Leu22 antibodies with the lectin Ricinus communis agglutinin (RCA), a lectin that binds to microglia, macrophages, and multinucleated giant cells (MNGC), or antibody to the gp41 transmembrane protein of HIV-1 and UCHL1. Some sections were also stained with the OPD4 antibody to helper/inducer T-cells. Small round cells were single-stained for UCHL1 and Leu22 in all cases. A few cells having morphologic characteristics of microglia, macrophages, and MNGC were observed using double stains employing UCHL1 or Leu22 and RCA, or UCHL1 or Leu22 and anti-gp41. Small round cells positive for both UCHL1 or Leu22 and gp41 could represent either macrophages or lymphocytes. The presence of small round cells positive only for UCHL1 or Leu22 in double-stained sections strongly suggests that T-cells are present in the brain in HIV encephalitis. Only a few of these cells were positive with OPD4 antibody for T-helper cells. Inability to demonstrate unequivocally HIV-1-infected T-cells suggests that microglia and macrophages, not T-cells, are the more important reservoirs of retrovirus in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Early myelination in the human fetal lumbosacral spinal cord: characterization by light and electron microscopy.

Myelination in the human central nervous system is well documented after 20 weeks of gestation (WOG). However, earlier stages of this process have not been described in detail, although it is assumed that human myelinogenesis is similar to that observed in other animals. We used light and electron microscopy to study myelination in the human lumbosacral spinal cord during the second trimester of gestation. The kinetics of myelin-associated gene expression were analyzed by immunocytochemistry using antibodies to the myelin markers myelin basic protein (MBP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase). These studies show that in 12-13 WOG specimens, occasional MBP-positive processes are found in developing white matter in areas distinct from the root entry zones. At this time, ultrastructural study revealed early investment of axons by glial processes and rare compacted myelin. CNPase staining was qualitatively and quantitatively less than that of MBP. The numbers of MBP- and CNPase-positive myelin sheaths increased with time, and by 24 WOG many were evident in all areas of the spinal cord except in the corticospinal tracts. Ultrastructural study of corresponding areas revealed many thin lamellae of compact myelin. This study provides initial normative data for early human myelination in the lumbosacral spinal cord and may serve as a baseline for future developmental and pathological studies.