An immunohistochemical study of the germinal layer in the late gestation human fetal brain

Postnatal phenobarbital for the prevention of intraventricular haemorrhage in preterm infants

BACKGROUND

Intraventricular haemorrhage (IVH) is a major complication of preterm birth. Large haemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood in the newborn flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. It has been suggested that phenobarbital stabilises blood pressure and may protect against free radicals. This is an update of a review first published in 2001 and updated in 2007 and 2013.

OBJECTIVES

To assess the benefits and harms of the postnatal administration of phenobarbital in preterm infants at risk of developing IVH compared to control (i.e. no intervention or placebo).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, CINAHL and clinical trial registries in January 2022. A new, more sensitive search strategy was developed, and searches were conducted without date limits.  SELECTION CRITERIA: We included randomised controlled trials (RCTs) or quasi-RCTs in which phenobarbital was given within the first 24 hours of life to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birth weight below 1500 g or respiratory failure. Phenobarbital was compared to no intervention or placebo. We excluded infants with serious congenital malformations.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were all grades of IVH and severe IVH (i.e. grade III and IV); secondary outcomes were ventricular dilation or hydrocephalus, hypotension, pneumothorax, hypercapnia, acidosis, mechanical ventilation, neurodevelopmental impairment and death. We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included 10 RCTs (792 infants). The evidence suggests that phenobarbital results in little to no difference in the incidence of IVH of any grade compared with control (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.84 to 1.19; risk difference (RD) 0.00, 95% CI -0.06 to 0.07; I² for RD = 65%; 10 RCTs, 792 participants; low certainty evidence) and in severe IVH (RR 0.88, 95% CI 0.64 to 1.21; 10 RCTs, 792 participants; low certainty evidence). The evidence is very uncertain about the effect of phenobarbital on posthaemorrhagic ventricular dilation or hydrocephalus (RR 0.62, 95% CI 0.31 to 1.26; 4 RCTs, 271 participants; very low certainty evidence), mild neurodevelopmental impairment (RR 0.57, 95% CI 0.15 to 2.17; 1RCT, 101 participants; very low certainty evidence), and severe neurodevelopmental impairment (RR 1.12, 95% CI 0.44 to 2.82; 2 RCTs, 153 participants; very low certainty evidence). Phenobarbital may result in little to no difference in death before discharge (RR 0.88, 95% CI 0.64 to 1.21; 9 RCTs, 740 participants; low certainty evidence) and mortality during study period (RR 0.98, 95% CI 0.72 to 1.33; 10 RCTs, 792 participants; low certainty evidence) compared with control. We identified no ongoing trials.

AUTHORS' CONCLUSIONS

The evidence suggests that phenobarbital results in little to no difference in the incidence of IVH (any grade or severe) compared with control (i.e. no intervention or placebo). The evidence is very uncertain about the effects of phenobarbital on ventricular dilation or hydrocephalus and on neurodevelopmental impairment. The evidence suggests that phenobarbital results in little to no difference in death before discharge and all deaths during the study period compared with control. Since 1993, no randomised studies have been published on phenobarbital for the prevention of IVH in preterm infants, and no trials are ongoing. The effects of postnatal phenobarbital might be assessed in infants with both neonatal seizures and IVH, in both randomised and observational studies. The assessment of benefits and harms should include long-term outcomes.

Predictors of severe intraventricular hemorrhage in preterm infants under 29-weeks gestation

Purpose: Preterm infants <29 weeks of gestation are at risk for severe intraventricular hemorrhage (IVH). Lower gestational age, birth weight, severe illness, as indexed by higher Score for Neonatal Acute Physiology - Perinatal Extension II (SNAPPE-II) are associated with severe IVH. The role of coagulation abnormalities on the first day after birth in severe IVH remains controversial. The present study investigated factors that predict the risk of severe IVH, including SNAPPE-II at 12 h and coagulation parameters on the first day after birth.Materials and methods: A retrospective chart review of infants < 29 weeks of gestation from January 2008 to December 2013 was performed. Prenatal and postnatal characteristics, SNAPPE-II at 12 h, coagulation parameters [prothrombin time (PT), INR, partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen] on the first day and cranial ultrasound examination records were collected. The association between clinical and laboratory variables and severe IVH was determined. A joint predictive model for the risk of severe IVH (grades 3 and 4) versus no-mild IVH (grades 0, 1, and 2) was developed using multiple regression analysis.Results: Preterm infants of gestational age < 29 weeks were included (n = 101). Fifteen (15%) infants had severe IVH. Lower gestational age (p = .006), birth weight (p = .008), African American race (p = .031) and higher SNAPPE-II at 12 h (p = .001) were associated with severe IVH. Infants with severe IVH had longer PT (p = .004), higher INR (p = .004) and lower platelet count (p = .034) than those with no-mild IVH. Stepwise logistic regression showed that only SNAPPE-II at 12 h was an independent predictor of severe IVH. For each unit increase in SNAPPE-II, the log odds of severe IVH increased by 0.045 (95% CI: [0.017, 0.073]; p = .002). A threshold of 55 on the SNAPPE-II yielded a sensitivity of 60% (9/15), a specificity of 91% (78/86), a positive predictive value (PPV) of 53% (9/17) and a negative predictive value (NPV) of 93% (78/84). All other demographic and clinical variables and coagulation abnormalities had an insignificant coefficient (p > .05) when included in a bivariate logistic model with SNAPPE-II.Conclusion: SNAPPE-II at 12 h after birth is an independent predictor of severe IVH in preterm infants with gestational age < 29 weeks.

Coagulation indices in very preterm infants from cord blood and postnatal samples

BACKGROUND

Very premature infants are at high risk of bleeding complications; however, few data exist on ranges for standard coagulation tests.

OBJECTIVES

The primary objective of this study was to measure standard plasma coagulation tests and thrombin generation in very premature infants compared with term infants. The secondary objective was to evaluate whether an association existed between coagulation indices and intraventricular hemorrhage (IVH).

PATIENTS/METHODS

Cord and peripheral blood of neonates < 30 weeks gestational age (GA) was drawn at birth, on days 1 and 3 and fortnightly until 30 weeks corrected gestational age. Prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen and coagulation factor levels were measured and tissue factor-stimulated thrombin generation was characterized. Control plasma was obtained from cord blood of term neonates.

RESULTS

One hundred and sixteen infants were recruited. Median (range) GA was 27.7 (23.7-29.9) weeks and mean (SD) birth weight was 1020 (255) g. Median (5th-95th percentile) day 1 PT, APTT and fibrinogen were 17.5 (12.7-26.6) s, 78.7 (48.7-134.3) s and 1.4 (0.72-3.8) g L(-1) , respectively. No difference in endogenous thrombin potential between preterm and term plasma was observed, where samples were available. Levels of coagulation factors II, VII, IX and X, protein C, protein S and antithrombin were reduced in preterm compared with term plasma. Day 1 APTT and PT were not associated with IVH.

CONCLUSION

In the largest cross-sectional study to date of very preterm infants, typical ranges for standard coagulation tests were determined. Despite long clotting times, thrombin generation was observed to be similar in very preterm and term infants.

Platelets in neonates: central mediators in haemostasis, antimicrobial defence and inflammation

Platelets are not only centrally involved in haemostasis, but also in antimicrobial defence and inflammation. Since evaluation of platelet physiology in the particular patient group of preterm and term neonatal infants is highly restricted for ethical reasons, there are hardly any data available in healthy and much less in extremely immature or ill neonates. By summarising current knowledge and addressing both platelet researchers and neonatologists, we describe neonatal platelet count and morphology, report on previous analyses of neonatal platelet function in primary haemostasis and provide insights into recent advances in platelet immunology that considerably impacts our clinical view on the critically ill neonatal infant. We conclude that neonatal platelets, originating from liver megakaryocytes, substantially differ from adult platelets and may play a pivotal role in the pathophysiology of neonatal sepsis or intraventricular haemorrhage, both complications which seriously augment perinatal morbidity and mortality.

Postnatal phenobarbital for the prevention of intraventricular haemorrhage in preterm infants

BACKGROUND

Intraventricular haemorrhage (IVH) is a major complication of preterm birth. Large haemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. Phenobarbital has been suggested as a safe treatment that stabilises blood pressure and may protect against free radicals.

OBJECTIVES

To determine the effect of postnatal administration of phenobarbital on the risk of IVH, neurodevelopmental impairment or death in preterm infants.

SEARCH METHODS

We used the search strategy of the Neonatal Collaborative Review Group. The original review author (A Whitelaw) was an active trialist in this area and had personal contact with many groups in this field. He handsearched journals from 1976 (when cranial computed tomography (CT) scanning started) to October 2000; these included: Pediatrics, Journal of Pediatrics, Archives of Disease in Childhood, Pediatric Research, Developmental Medicine and Child Neurology, Acta Paediatrica, European Journal of Pediatrics, Neuropediatrics, New England Journal of Medicine, Lancet and British Medical Journal. We searched the National Library of Medicine (USA) database (via PubMed) and the Cochrane Central Register of Controlled Trials (CENTRAL, 2012, Issue 10) through to 31 October 2012. We did not limit the searches to the English language, as long as the article included an English abstract. We read identified articles in the original language or translated.

SELECTION CRITERIA

We included randomised or quasi-randomised controlled trials in which phenobarbital was given to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birthweight below 1500 g or respiratory failure. Adequate determination of IVH by ultrasound or CT was also required.

DATA COLLECTION AND ANALYSIS

In addition to details of patient selection and control of bias, we extracted the details of the administration of phenobarbital. We searched for the following endpoints: IVH (with grading), posthaemorrhagic ventricular dilation or hydrocephalus, neurodevelopmental impairment and death. In addition, we searched for possible adverse effects of phenobarbitone, for example hypotension, mechanical ventilation, pneumothorax, hypercapnia and acidosis.

MAIN RESULTS

We included 12 controlled trials that recruited 982 infants. There was heterogeneity between trials for the outcome IVH, with three trials finding a significant decrease in IVH and one trial finding an increase in IVH in the group receiving phenobarbital. Meta-analysis showed no difference between the phenobarbital-treated group and the control group in either all IVH (typical risk ratio (RR) 0.91; 95% CI 0.77 to 1.08), severe IVH (typical RR 0.77; 95% CI 0.58 to 1.04), posthaemorrhagic ventricular dilation (typical RR 0.89; 95% CI 0.38 to 2.08), severe neurodevelopmental impairment (typical RR 1.44; 95% CI 0.41 to 5.04) or death before hospital discharge (typical RR 0.88; 95% CI 0.64 to 1.21). There was a consistent trend in the trials towards increased use of mechanical ventilation in the phenobarbital-treated group, which was supported by the meta-analysis (typical RR 1.18; 95% CI 1.06 to 1.32; typical risk difference 0.129; 95% CI 0.04 to 0.21), but there was no significant difference in pneumothorax, acidosis or hypercapnia.

AUTHORS' CONCLUSIONS

Postnatal administration of phenobarbital cannot be recommended as prophylaxis to prevent IVH in preterm infants and is associated with an increased need for mechanical ventilation.

Neonatal IVH--mechanisms and management

Intra-ventricular hemorrhage (IVH) occurs predominantly in very low birth weight premature infants. Survivors of severe IVH frequently experience long-term consequences including major neurological deficits. Advances in neonatal and obstetric care in the last decades, have led to a steady decline in mortality and in the incidence of IVH. However, significant improvements in the survival rates small premature infants have led to an increase in the population of newborns prone to IVH. The pathogenesis of IVH is multifactorial. Prematurity of the germinal matrix, fluctuations in cerebral blood flow, hypoxic ischemic cerebral injury and developmental hemostatic abnormalities of newborns are important risk factors. The following manuscript will address the epidemiology and pathogenesis of IVH and review studies regarding potential pro-coagulant therapy.

Cell proliferation in human ganglionic eminence and suppression after prematurity-associated haemorrhage

In premature infants, germinal matrix haemorrhage in the brain is a common occurrence. However, cell proliferation and fate determination in the normal human germinal matrix is poorly understood. Human ganglionic eminence samples were collected prospectively from autopsies of premature and term infants with no evidence of pathological process (n=78; dying at post-menstrual age 14-88 weeks). The ganglionic eminence was thickest at 20-26 weeks and involuted by 34-36 weeks. Proliferating cells, detected by Ki67 immunoreactivity, were abundant throughout the ganglionic eminence prior to 18 weeks, after which a sharp boundary between the dorsal and ventral ganglionic eminence appeared with reduced cell proliferation in the dorsal region. Ki67 immunoreactivity persisted in the majority of ventral cells until ∼28 weeks, after which time the proportion of proliferating cells dropped quickly. The expression of cell lineage markers (such as Olig2, SOX2, platelet-derived growth factor receptor alpha) showed partitioning at the microscopic level. The hypothesis that germinal matrix haemorrhage suppresses cell proliferation was then addressed. In comparison to controls, germinal matrix haemorrhage (n=47; born at post-menstrual age 18-34 weeks followed by survival of 0 h to 98 days) was associated with significantly decreased cell proliferation if survival was >12 h. The cell cycle arrest transcription factor p53 was transiently increased and the oligodendroglial lineage markers Olig2 and platelet-derived growth factor receptor alpha were decreased. Cell death was negligible. A low level of microglial activation was detected. Haemorrhage-associated suppression of cell proliferation in premature human infants could partially explain the reduced brain size and clinical effects in children who suffer germinal matrix haemorrhage after premature birth.

Intraventricular hemorrhage in premature infants: mechanism of disease

Intraventricular hemorrhage (IVH) is a major complication of prematurity. IVH typically initiates in the germinal matrix, which is a richly vascularized collection of neuronal-glial precursor cells in the developing brain. The etiology of IVH is multifactorial and is primarily attributed to the intrinsic fragility of the germinal matrix vasculature and the disturbance in the cerebral blood flow (CBF). Although this review broadly describes the pathogenesis of IVH, the main focus is on the recent development in molecular mechanisms that elucidates the fragility of the germinal matrix vasculature. The microvasculature of the germinal matrix is frail because of an abundance of angiogenic blood vessels that exhibit paucity of pericytes, immaturity of basal lamina, and deficiency of glial fibrillary acidic protein (GFAP) in the ensheathing astrocytes endfeet. High VEGF and angiopoietin-2 levels activate a rapid angiogenesis in the germinal matrix. The elevation of these growth factors may be ascribed to a relative hypoxia of the germinal matrix perhaps resulting from high metabolic activity and oxygen consumption of the neural progenitor cells. Hence, the rapid stabilization of the angiogenic vessels and the restoration of normal CBF on the first day of life are potential strategies to prevent IVH in premature infants.

Postnatal phenobarbital for the prevention of intraventricular hemorrhage in preterm infants

BACKGROUND

Intraventricular hemorrhage (IVH) is a major complication of preterm birth. Large hemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. Phenobarbital has been suggested as a safe treatment that stabilises blood pressure and may protect against free radicals.

OBJECTIVES

To determine the effect of postnatal administration of phenobarbital on the risk of intraventricular hemorrhage (IVH), neurodevelopmental impairment or death in preterm infants.

SEARCH STRATEGY

See the Search Strategy of the Neonatal Collaborative Review Group. The reviewer has been a active trialist in this area and has personal contact with many groups in this field. Journals handsearched from 1976 (when cranial CT scanning started) to October 2000 include: Pediatrics, J Pediatrics, Archives of Disease in Childhood, Pediatric Research, Developmental Medicine and Child Neurology, Acta Paediatrica, European J of Pediatrics, Neuropediatrics, New England J of Medicine, Lancet and British Medical J. The National Library of Medicine (USA) database (via PubMed) and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) were searched through to April 2007 using the MeSH terms intraventricular hemorrhage, newborn infants, premature infant, intracranial hemorrhage, phenobarbitone, phenobarbital. The searches were not limited to the English language, as long as the article included an English abstract. Promising articles were read in the original language or translated.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials in which phenobarbital was given to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birthweight below 1500 g, or respiratory failure were included. Adequate determination of IVH by ultrasound or CT was also required.

DATA COLLECTION AND ANALYSIS

In addition to details of patient selection and control of bias, the details of the administration of phenobarbital were extracted. The end-points searched for included: IVH ( with grading), posthemorrhagic ventricular dilatation or hydrocephalus, neurodevelopmental impairment and death. In addition, possible adverse effects of phenobarbitone such as hypotension, mechanical ventilation, pneumothorax, hypercapnia, and acidosis were searched for.

MAIN RESULTS

Ten controlled trials were included with 740 infants recruited. There was heterogeneity between trials for the outcome IVH, with one trial finding a significant decrease in IVH and another trial finding an increase in IVH in the group receiving phenobarbital. Meta-analysis showed no difference between the phenobarbital treated group and the control group in either IVH (typical relative risk 1.04, 95% CI 0.87, 1.25), severe IVH (typical relative risk 0.91, 95% CI 0.66, 1.24), posthemorrhagic ventricular dilatation (typical relative risk 0.89, 95% CI 0.38, 2.08), severe neurodevelopmental impairment (typical relative risk 1.44, 95% CI 0.41, 5.04) or death before hospital discharge (typical relative risk 0.88, 95% CI 0.64, 1.21) There was a consistent trend in the trials towards increased use of mechanical ventilation in the phenobarbital treated group, which was supported by the meta-analysis (typical relative risk 1.18, 95% CI 1.06, 1.32; typical risk difference 0.129, 95% CI 0.045, 0.213), but there was no significant difference in pneumothorax, acidosis or hypercapnia.

AUTHORS' CONCLUSIONS

Postnatal administration of phenobarbital cannot be recommended as prophylaxis to prevent IVH in preterm infants and is associated with an increased need for mechanical ventilation.

The Human Brain Subventricular Zone: Stem Cells in This Niche and Its Organization

The human brain harbors stem cells in the subventricular zone (SVZ). The authors have collected postmortem and intraoperative tissue from adult human patients and found that it contains a unique ribbon of astrocytes that proliferate in vivo and can function as neural stem cells in vitro. Furthermore, they have conducted an anatomic, cytoarchitectural, and ultrastructural study in complete postmortem brains to define the precise organization of the lateral walls of the human lateral ventricles. With immunohistochemistry, the authors mapped a proliferative glial fibrillary acidic protein (GFAP)--positive ribbon of astrocytic cells in the human SVZ. In this article, the authors report on four main types of SVZ walls in the human brain. Types A through C line the striatum from dorsal (type A), to middle (type B), to ventral (type C) regions along the lateral wall of the lateral ventricle. Type D wall lines the floor of the temporal horn over the hippocampus. Understanding the organization of the adult human SVZ represents a necessary first step in understanding cellular proliferation, precursor migration, and the neurogenic niche of the largest known germinal region in the adult human brain.

Development of microglia in the cerebral white matter of the human fetus and infant

Although microglial activation may be an initial beneficial response to a variety of insults, prolonged activation can release toxic substances and lead to cell death. Microglial activation secondary to hypoxia-ischemia and/or infection in immature cerebral white matter is important in the pathogenesis of periventricular leukomalacia (PVL), the major pathological substrate of cerebral palsy in the premature infant. We hypothesize that a transient overexpression in activated microglial density occurs normally in the cerebral white matter of the human fetus during the peak window of vulnerability for PVL. Such an increase could render this region susceptible to insults that cause prolonged microglial activation, as conceptualized in PVL. To examine the developmental profile of microglia in the human fetus and infant brain, immunocytochemistry with microglial specific markers were used in 23 control (non-PVL) cases ranging from 20 to 183 postconceptional (PC) weeks. Tomato lectin, used to identify microglial morphology, revealed that the cerebral white matter of the human fetus and infant is densely populated with intermediate and amoeboid microglia; the latter is indicative of an activated state. Quantitative analysis with CD68 showed increased density of activated microglia in the cerebral white matter of the fetus (<37 PC weeks) relative to the neonate/infant (> or =37 PC weeks) and to the overlying cortex of either age group (P = 0.01). The primary finding of a transient, developmental-dependent overabundance of CD68-activated microglia in the cerebral white matter of the fetus suggests a potential "priming" of this area for diverse brain insults characterized by activation of microglia, particularly PVL. J.

Astrocyte end-feet in germinal matrix, cerebral cortex, and white matter in developing infants

Astrocyte end-feet ensheathe blood vessels in the brain and are believed to provide structural integrity to the cerebral vasculature. We sought to determine in developing infants whether the coverage of blood vessels by astrocyte end-feet is decreased in germinal matrix (GM) compared with cerebral cortex and white matter (WM), which may cause fragility of the GM vasculature. Therefore, we evaluated the perivascular coverage by astrocyte end-feet in these areas. We double-labeled the brain sections with astroglial markers [glial fibrillary acidic protein (GFAP), aquaporin-4 (AQP4), and S-100beta] and a vascular marker, laminin. Perivascular coverage by GFAP+ astrocyte end-feet increased consistently as a function of gestational age (GA) in cortex and WM from 19 to 40 wk. Compared with GFAP, AQP4+ astrocyte end-feet developed at an earlier GA, ensheathing about 63% of blood vessels for 23-40 wk in cortex, WM, and GM. Coverage by GFAP+ perivascular end-feet was decreased in GM compared with cortex and WM from 23 to 34 wk. There was no difference in the coverage by AQP4+ end-feet among the three areas in these infants. The expression of AQP4, a water channel molecule, in the astrocyte end-feet was not significantly different between premature and mature infants, suggesting similar risk of brain edema in preterm and term infants in pathologic conditions. More importantly, the lesser degree of GFAP expression in astrocyte end-feet of GM compared with cortex and WM may reflect a cytoskeletal structural difference that contributes to the fragility of GM vasculature and propensity to hemorrhage.

Cellular composition and cytoarchitecture of the adult human subventricular zone: a niche of neural stem cells

The lateral wall of the lateral ventricle in the human brain contains neural stem cells throughout adult life. We conducted a cytoarchitectural and ultrastructural study in complete postmortem brains (n = 7) and in postmortem (n = 42) and intraoperative tissue (n = 43) samples of the lateral walls of the human lateral ventricles. With varying thickness and cell densities, four layers were observed throughout the lateral ventricular wall: a monolayer of ependymal cells (Layer I), a hypocellular gap (Layer II), a ribbon of cells (Layer III) composed of astrocytes, and a transitional zone (Layer IV) into the brain parenchyma. Unlike rodents and nonhuman primates, adult human glial fibrillary acidic protein (GFAP)+ subventricular zone (SVZ) astrocytes are separated from the ependyma by the hypocellular gap. Some astrocytes as well as a few GFAP-cells in Layer II in the SVZ of the anterior horn and the body of the lateral ventricle appear to proliferate based on proliferating cell nuclear antigen (PCNA) and Ki67 staining. However, compared to rodents, the adult human SVZ appears to be devoid of chain migration or large numbers of newly formed young neurons. It was only in the anterior SVZ that we found examples of elongated Tuj1+ cells with migratory morphology. We provide ultrastructural criteria to identify the different cells types in the human SVZ including three distinct types of astrocytes and a group of displaced ependymal cells between Layers II and III. Ultrastructural analysis of this layer revealed a remarkable network of astrocytic and ependymal processes. This work provides a basic description of the organization of the adult human SVZ.

Germinal matrix cells associate with veins and a glial scaffold in the human fetal brain

Germinal matrix (GM) in the subventricular zone (SVZ) includes progenitor cells of neurons and glia, which migrate from the SVZ to regions where they become integrated into the developing brain. In the human fetal brain, GM cells pack into high density clusters that encircle GM veins producing a profile we describe as a venous cuff. Venous cuffs are, in turn, encircled by GFAP-positive astrocytes that project processes through the cuff to the venous wall. The high cell density exhibited by cuffs, as well as their association with astrocytes, are reminiscent of features associated with chain migration. However, chain migration has not been associated previously with veins. We suggest that the GM cuff cells may represent a distinct subset of GM cells that migrate away from the GM on a pathway consisting of a vein and its associated astrocytic scaffold.

Morphometric assessment of collagen accumulation in germinal matrix vessels of premature human neonates

Germinal matrix haemorrhage in premature neonates is commonly attributed to vascular immaturity, possibly related to an abbreviated process of angiogenesis. Terminal steps in the progression of angiogenesis are the formation of a subendothelial basal lamina containing collagen IV and an extracellular matrix containing collagens I and III. Immature vessels would predictably be deficient in these collagen subtypes. We analysed germinal matrix (GM), cortical, and white matter (WM) vessels with antibodies specific for collagens I, III and IV to test the hypothesis that GM vessels are immature. Brains were collected during post-mortem from prematurely born human neonates ranging in age from 17 weeks to 36 weeks postconception. All GM vessels were immunoreactive for collagen subtypes I, III and IV. Using digital image analysis, collagen IV immunoperoxidase-labelling was measured in vessels in GM, cortex and WM. Intensity values in GM and WM were normalized relative to cortical intensity within the same subject. At week 17 of gestation, GM vessels exhibited a higher concentration of collagen IV than did WM or cortical vessels. Regression analysis demonstrated that collagen intensity in GM was greater than that in cortex and WM at all stages. We conclude that GM vessels in even the youngest, prematurely born, viable neonates do not exhibit evidence of structural immaturity. The high incidence of GM haemorrhage in premature neonates may be related to factors other than a deficiency in accumulated collagen.

The blood-brain barrier: an overview: structure, regulation, and clinical implications

The blood-brain barrier (BBB) is a diffusion barrier, which impedes influx of most compounds from blood to brain. Three cellular elements of the brain microvasculature compose the BBB-endothelial cells, astrocyte end-feet, and pericytes (PCs). Tight junctions (TJs), present between the cerebral endothelial cells, form a diffusion barrier, which selectively excludes most blood-borne substances from entering the brain. Astrocytic end-feet tightly ensheath the vessel wall and appear to be critical for the induction and maintenance of the TJ barrier, but astrocytes are not believed to have a barrier function in the mammalian brain. Dysfunction of the BBB, for example, impairment of the TJ seal, complicates a number of neurologic diseases including stroke and neuroinflammatory disorders. We review here the recent developments in our understanding of the BBB and the role of the BBB dysfunction in CNS disease. We have focused on intraventricular hemorrhage (IVH) in premature infants, which may involve dysfunction of the TJ seal as well as immaturity of the BBB in the germinal matrix (GM). A paucity of TJs or PCs, coupled with incomplete coverage of blood vessels by astrocyte end-feet, may account for the fragility of blood vessels in the GM of premature infants. Finally, this review describes the pathogenesis of increased BBB permeability in hypoxia-ischemia and inflammatory mechanisms involving the BBB in septic encephalopathy, HIV-induced dementia, multiple sclerosis, and Alzheimer disease.

NOVOcan: a molecular link among selected glial cells

The nervous system is generated from cells lining the ventricular system. Our understanding of the fate potentials and lineage relationships of these cells is being re-evaluated, both because of recent demonstrations that radial glia can generate neurons and because of the identification of fate-determining genes. A variety of intrinsic and extrinsic molecules, including proteoglycans, regulate embryonic and postnatal brain development. Using probes modeled after species conserved domains of heparan sulfate proteoglycans, we cloned a novel gene called novocan, raised monoclonal antibodies against a segment of the predicted amino acid sequence of the expressed protein (NOVOcan) and used the antibodies to establish the cell and tissue localization of NOVOcan in postnatal rat brains by immunohistochemistry. NOVOcan was expressed in cells lining the ventricles, including a variety of radial glia during early postnatal development. Later, as radial glia disappeared and ependymal cells appeared, NOVOcan was detected in ependymal cells and in tanycytes, a specialized form of ependymal cell resembling radial glia. NOVOcan was absent in two known progeny of radial glia, mature astrocytes and neurons. Whereas NOVOcan was also absent in mature oligodendrocytes (OLGs), it was present in OLG precursors in developing white matter. These studies set the stage for determining the roles of NOVOcan in brain cell lineage patterns as well as in other aspects of development.

Neonatal venous cerebral hemorrhage

Intracranial pathological changes can occur as a result of impaired craniocervical venous return. Thrombosis of central venous access catheters was demonstrated in two neonates born at 38 and 27 weeks' gestation. Neither infant developed hemorrhage of prematurity as confirmed on cranial ultrasonography. Clinical evidence of vena cava thrombosis and associated spontaneous intraventricular hemorrhage developed on Day 24 and 36, respectively, and these findings were confirmed on imaging studies. In one infant the hemorrhage was accompanied by communicating hydrocephalus.

The cause of the intracranial disease was attributable to the retrograde cerebral venous congestion. This, together with the primitive venous bed developing in the periventricular region, was associated with the spontaneous hemorrhage in the region of the foramen of Monro.

To the authors' knowledge, this is the first report in the English-language literature of spontaneous neonatal intra-cerebral hemorrhage, due to thrombosis of the superior or inferior vena cava.

The natural history of this condition is resolution without sequelae after appropriate therapeutic intervention for the vena cava thrombosis.

Intraventricular haemorrhage and posthaemorrhagic hydrocephalus: pathogenesis, prevention and future interventions

Intraventricular haemorrhage (IVH) is still a major complication of preterm birth with serious disability resulting. The fragile blood vessels in the germinal matrix below the ventricular lining and the instability of blood flow to this highly vascular area are the main mechanisms behind IVH. There is good evidence that corticosteroid therapy before preterm delivery reduces mortality and IVH substantially with a trend towards a reduction in disability. There is good evidence that postnatal indomethacin reduces IVH but no evidence that mortality or disability is reduced. There is evidence that stabilizing cerebral blood flow with pancuronium in infants with respiratory distress reduces IVH in the minority of infants with marked fluctuations. There is limited evidence that postnatal vitamin E and ethamsylate reduce IVH but insufficient evidence of reduced mortality or disability. Hydrocephalus following IVH results initially from multiple small blood clots throughout the CSF channels impeding circulation and re-absorption. Transforming growth factor beta is released into the CSF and there is mounting evidence that this cytokine stimulates the laying down of extracellular matrix proteins such as laminin and fibronectin which produce permanent obstruction to the CSF pathways. Interventions such as early lumbar punctures, diuretic drugs to reduce CSF production and intraventricular fibrinolytic therapy have been tested and, not only fail to prevent shunt dependence, death or disability, but have significant adverse effects. Surgical interventions such as subcutaneous reservoir and external drain have not been subject to controlled trial. Ventriculoperitoneal shunt is not feasible in the early phase after IVH but, despite the problems with blockages and infections, remains the only option for infants with excessive head expansion over periods of weeks. New treatment approaches aimed at preventing hydrocephalus are needed.

Biosynthesis and molecular biology of the secretory proteins of the subcommissural organ

Ependymal cells are specialized in the synthesis and release of different factors into the cerebrospinal fluid (CSF). The subcommissural organ (SCO) is one of the most active areas of the ventricular walls secreting into the CSF. This gland is localized in the roof of the third ventricle covering the posterior commissure. Glycoproteins synthesized in SCO cells are released into the ventricular CSF where they aggregate, in a highly ordered fashion, forming an elongated supramacromolecular structure known as the Reissner's fiber (RF). RF grows caudally and extends along the brain aqueduct, the fourth ventricle, and the whole length of the central canal of the spinal cord. The SCO cells synthesize glycoproteins of high molecular weight. A precursor form of 540 kDa is synthesized in bovine and chick SCO cells, and a transcript of 10--14 kb is expressed selectively in the bovine SCO cells. The processing of this molecule generates at least one protein of about 450 kDa (RF-Gly-I), which, after being released, is involved in the formation of RF. Additionally, biochemical data indicate that bovine SCO cells synthesize a second precursor compound of 320 kDa, which is also detected in rat, rabbit, and dog. We postulate that RF is formed by two different complexes, one of which has a very high molecular mass (700 kDa or more) and is made up of at least six polypeptides, with the polypeptide of 450 kDa being its main component. The molecules that form RF in different species have different primary structures but they express common epitopes associated to the existence of cysteine bridges, which are probably crucial for polymerization of RF. Molecular procedures involving the use of anti-RF antibodies have led to the isolation of cDNA clones encoding two proteins known as RF-GLY-I and SCO-spondin. In the last 3 years, five partial cDNA sequences encoding SCO-spondin-like proteins have been obtained (Y08560, Y08561, AJ132107, AJ132106, AJ133488). These clones along with RF-GLY-I and SCO-spondin were computer-assembled generating a cDNA consensus sequence of 14.4 kb. Analyses of the long consensus sequence revealed an extended open reading frame (ORF-1) spanning from base 1,634 to 14,400 that encodes for a putative protein of 4,256 amino acids (approximately 450 kDa). The Mr of the predicted protein is consistent with the observed Mr of the largest protein recognized with anti-RF antibodies in SCO and RF extracts. However, the absence of consensus sequences typically present near the 5J'-end of the translation initiation site suggests the existence of a second open reading frame (ORF-2) extending from base 1 to base 14,400 in frame with the ORF-1 and probably encoding for the largest protein precursor (540 kDa). An antibody raised against a peptide sequence, deduced from the open reading frame encoded by a SCO cDNA, reacted specifically with the bovine and rat SCO-RF complex, thus indicating that the protein encoded by the cloned cDNA is part of RF. Immunoblots of bovine SCO extracts using the anti-peptide serum revealed bands of 540 kDa and 450 kDa, but it did not react with the proteins of 320 and 190 kDa. These data support the existence of two precursors for the bovine RF-glycoproteins (540 and 320 kDa) with the 450-kDa protein being a processed form of the 540-kDa precursor. We postulate that the cloned cDNAs encode for a protein that corresponds to the 540-kDa precursor and that at least part of this sequence is present in the processed form of 450 kDa that is secreted to form the RF.

Postnatal phenobarbitone for the prevention of intraventricular hemorrhage in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To determine whether postnatal administration of phenobarbitone to preterm infants reduces the risk of intraventricular hemorrhage (IVH), neurodevelopmental impairment or death.

SEARCH STRATEGY

See the Search Strategy of the Neonatal Collaborative Review Group. The reviewer has been a active trialist in this area and has personal contact with many groups in this field. Journals handsearched from 1976 (when cranial CT scanning started) to November 1998 include: Pediatrics, J Pediatrics, Archives of Disease in Childhood, Pediatric Research, Developmental Medicine and Child Neurology, Acta Paediatrica, European J of Pediatrics, Neuropediatrics, New England J of Medicine, Lancet and British Medical J. The National Library of Medicine (USA) database (via PubMed) and the Cochrane Controlled Trials Register were searched through to November 1998 using the MeSH terms intraventricular hemorrhage, newborn infants, premature infant, intracranial hemorrhage, phenobarbitone, phenobarbital. The searches were not limited to the English language, as long as the article included an English abstract. Promising articles were read in the original language or translated.

SELECTION CRITERIA

Included were randomized or quasi-randomized controlled trials in which phenobarbitone was given to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birthweight below 1500 g, or respiratory failure. Adequate determination of IVH by ultrasound or CT was also required.

DATA COLLECTION AND ANALYSIS

In addition to details of patient selection and control of bias, the details of the administration of phenobarbitone were extracted. The end-points searched for included: IVH ( with grading), posthemorrhagic ventricular dilatation or hydrocephalus, neurodevelopmental impairment and death. In addition, possible adverse effects of phenobarbitone such as hypotension, mechanical ventilation, pneumothorax, hypercapnia, and acidosis were searched for.

MAIN RESULTS

Nine controlled trials were included with 740 infants recruited. There was heterogeneity between trials for the outcome IVH, with one trial finding a significant decrease in IVH and another trial finding an increase in IVH in the group receiving phenobarbitone. Meta-analysis showed no difference between the phenobarbitone treated group and the control group in either IVH (typical relative risk 1.04, CI 0.87, 1.25), severe IVH (typical relative risk 0.91, CI 0.66, 1.27), posthemorrhagic ventricular dilatation (typical relative risk 0.89, CI 0.38, 2.08), severe neurodevelopmental impairment (typical relative risk 1.44, CI 0.41, 5.04) or death before hospital discharge (typical relative risk 0.88, CI 0.64, 1.21) There was a consistent trend in the trials towards increased use of mechanical ventilation in the phenobarbitone treated group, which was supported by the meta-analysis (typical relative risk 1.18, CI 1.06, 1.32; typical risk difference 0.129, CI 0.045, 0.213), but there was no significant difference in pneumothorax, acidosis or hypercapnia.

REVIEWER'S CONCLUSIONS

Postnatal administration of phenobarbitone cannot be recommended as prophylaxis to prevent IVH in preterm infants and is associated with an increased need for mechanical ventilation.

Colonisation of the developing human brain and spinal cord by microglia: a review

Microglia are the immune effector cells of the nervous system. The prevailing view is that microglia are derived from circulating precursors in the blood, which originate from the bone-marrow. Colonisation of the central nervous system (CNS) by microglia is an orchestrated response during human fetal development related to the maturation of the nervous system. It coincides with vascularisation, formation of radial glia, neuronal migration and myelination primarily in the 4th-5th months and beyond. Microglial influx generally conforms to a route following white matter tracts to gray areas. We have observed that colonisation of the spinal cord begins around 9 weeks, with the major influx and distribution of microglia commencing around 16 weeks. In the cerebrum, colonisation is in progress during the second trimester, and ramified microglial forms are widely distributed within the intermediate zone by the first half of intra-uterine life (20-22 weeks). A distinct pattern of migration occurs along radial glia, white matter tracts and vasculature. The distribution of these cells is likely to be co-ordinated by spatially and temporally regulated, anatomical expression of chemokines including RANTES and MCP-1 in the cortex; by ICAM-2 and PECAM on radiating cerebral vessels and on capillaries within the germinal layer, and apoptotic cell death overlying this region. The phenotype and functional characteristics of fetal microglia are also outlined in this review. The need for specific cellular interactions and targeting is greater within the central nervous system than in other tissues. In this respect, microglia may additionally contribute towards CNS histogenesis.

Antenatal glucocorticoid, magnesium exposure, and the prevention of brain injury of prematurity

Prevention of perinatal white matter injury with or without severe intraventricular hemorrhage (IVH) is critical to reduce cerebral palsy (CP) in premature infants. Antenatal therapies that may afford neuroprotection include glucocorticoids, which are associated with a significant reduction in severe IVH, and magnesium, which is associated with reduced CP. Potential protective mechanisms of glucocorticoids include a direct effect on brain, improved respiratory function, and more stable blood pressure hemodynamics. Because magnesium is often administered to mothers with pregnancy-induced hypertension, a condition associated with reduction in severe IVH, the independent neuroprotective role of magnesium remains unclear and warrants additional studies.

Lectin staining in the basal nucleus (Meynert) and the hypothalamic tuberomamillary nucleus of the developing human prosencephalon

Previous studies have demonstrated that extracellular matrix glycoconjugates, shown by lectin-histochemistry with Vicia villosa agglutinin (VVA) and peanut agglutinin (PNA) as so-called perineuronal nets, play an important role in brain maturation. Concanavalin A (ConA) binding to neuronal surface glycoconjugates may be a marker of synaptic junctions. The present study was done to demonstrate the binding sites of these lectins in two functionally related nuclei of the prosencephalon, the basal nucleus (Meynert) and the hypothalamic tuberomamillary nucleus. Fetal brains of 16-36 weeks of gestation were examined by using VVA, PNA, and ConA to determine appearance and distribution patterns of specific lectin-binding sites on glycoconjugates during fetal brain development. The basal nucleus and the tuberomamillary nucleus showed a characteristic "cellular staining" that may have been due to cytoplasmatic labeling, surface labeling, or both. Lectin-staining occurred much earlier in the basal nucleus than in the tuberomamillary nucleus. Although all three lectins were bound to neurons of the basal nucleus, only ConA-positive neurons were observed in the tuberomamillary nucleus. In conclusion, lectin-labeled cells most probably represent projection neurons that are GABAergic (tuberomamillary nucleus) or cholinergic (basal nucleus). Labeling with the three lectins demonstrated nuclear-specific staining patterns that occur early in fetal development and gradually increase. Binding sites for lectins characterizing perineuronal nets (VVA, PNA) occurred only in the basal nucleus, whereas binding sites for ConA on neuronal-surface glycoconjugates, which seem to play a role in early synaptogenesis, were present in the basal and the tuberomamillary nucleus. The basal nucleus, however, expressed ConA binding sites distinctly earlier, probably indicating early arriving afferents.

Ependymal development, proliferation, and functions: a review

A survey of the literature shows that proliferation of ependyma occurs largely during the embryonic and early postnatal periods of development in most species. Differentiation of these cells proceeds along particular regional and temporal gradients as does the expression of various cytoskeletal (vimentin, cytokeratins, glial fibrillary acidic protein) and secretory proteins (S-100). Turnover declines significantly postnatally, and only low levels of residual activity persist into adulthood under normal conditions. Although the reported response of ependyma to injury is somewhat equivocal, only limited regenerative capacity appears to exist and to varying degrees in different regions of the neuraxis. Proliferation has been most often observed in response to spinal cord injury. Indeed, the ependyma plays a significant role in the initiation and maintenance of the regenerative processes in the spinal cord of inframammalian vertebrates. In the human, however, ependyma appears never to regenerate at any age nor re-express cytoskeletal proteins characteristic of immature cells. The functions of ependyma including tanycytes, a specialized form of ependymal cell that persists into adulthood within circumscribed regions of the nervous system, are still largely speculative. Fetal unlike mature ependyma is believed to be secretory and is believed to play a role in neurogenesis, neuronal differentiation/axonal guidance, transport, and support. In the adult brain, mature ependyma is not merely an inert lining but may regulate the transport of ions, small molecules, and water between the cerebrospinal fluid and neuropil and serve an important barrier function that protects neural tissue from potentially harmful substances by mechanisms that are still incompletely understood.

Glial fibrillary acidic protein is increased in the cerebrospinal fluid of preterm infants with abnormal neurological findings

Glial fibrillary acidic protein (GFAP) is the structural protein of the intermediate filament of astroglia. The aims of the present study were to examine GFAP in the cerebrospinal fluid (CSF) of preterm infants at different postmenstrual ages and to evaluate the potential of GFAP to predict abnormal neurodevelopmental outcome. GFAP increased in correlation with postmenstrual age in preterm infants (n = 17) and full-term infants (n = 9). The levels were five times higher in preterm infants (n = 10) with an abnormal neonatal course and/or an abnormal neurological outcome than in healthy preterm infants. The positive predictive value of a GFAP higher than the 98th percentile of normal infants was 69%, while a GFAP level below this limit invariable predicted a good outcome. Simultaneously analysed noradrenaline, hypoxanthine and glutamate did not differ between the groups. We conclude that CSF GFAP increases with maturity and that CSF GFAP appears to be a promising marker for perinatal brain damage.

Analysis of glial fibrillary acidic protein, neurofilament protein, actin and heat shock proteins in human fetal brain during the second trimester

Glial fibrillary acidic protein (GFAP), the 66 kDa neurofilament protein (NF-66), actin, the 27 kDa heat shock protein (HSP27) and the 70 kDa constitutive heat shock protein (HSC70) were analyzed in human fetal brain during the second trimester, from 10 to 24 gestational weeks (GW). By immunohistochemistry, cell-type specific localization of GFAP and NF-66 in astrocytes and neurons, respectively, was confirmed. HSP27 was expressed mostly in the nuclear region of neurons and non-neuronal cells, and HSC70 was widely distributed throughout the tissue. By quantitative immunoblotting, GFAP was not detectable in gray matter of prefrontal cortex prior to 16 GW. Between 16 and 21 GW, the content of GFAP rose slowly. Thereafter, GFAP accumulated rapidly. The content of GFAP in different brain regions (prefrontal, parietal, and occipital cortices) differed significantly at 22 GW. In contrast, NF-66 was already highly expressed at 10 GW, slowly rose to maximal values by 18 GW, and thereafter remained stationary. In contrast to GFAP, the content of NF-66 was similar in different brain regions at 22 GW. Although actin was abundant throughout the second trimester, a sharp drop in its content in the prefrontal cortex was detected at 17 GW. To explain such a decrease, two heat shock proteins were analyzed. HSP27, known to modulate actin polymerization, was found to increase sharply at 16-17 GW. In contrast, HSC70 remained constant during the second trimester and was highly expressed in the fetal brain, at a level comparable to that in the adult brain.

A lectin and synaptophysin study of developing brain

Lectins which bind to carbohydrate residues of glycoconjugates can be used as histochemical markers of these substances. A battery of lectins including peanut agglutinin, ricinus communis, wheat germ agglutinin, soybean agglutinin, concanavalin ensiformis, Ulex europaeus, and Dolichos biflorus as well as synaptophysin was used on paraffin-embedded human fetal and infant brains of varying gestation (20 weeks to term) to determine whether there were changes in the pattern of glycoconjugate staining. The findings indicate that lectin binding of several of these markers changes with gestation as does synaptophysin.

The ependyma: a protective barrier between brain and cerebrospinal fluid

This review summarizes the current scientific literature concerning the ependymal lining of the cerebral ventricles of the brain with an emphasis on selective barrier function and protective roles for the common ependymal cell. Topics covered include the development, morphology, protein and enzyme expression including reactive changes, and pathology. Some cells lining the neural tube are committed at an early stage to becoming ependymal cells. They serve a secretory function and perhaps act as a cellular/axonal guidance system, particularly during fetal development. In the mature mammalian brain ependymal cells possess the structural and enzymatic characteristics necessary for scavenging and detoxifying a wide variety of substances in the CSF, thus forming a metabolic barrier at the brain-CSF interface.

IT15 gene expression in fetal human brain

To examine the expression of the gene which causes Huntington's disease (HD), IT15, during development, in situ hybridization of radiolabeled riboprobes was performed in human fetal (gestational ages 20-23 weeks) and adult brain. Optical densities of autoradiographs were determined in various brain regions and compared to cell density in those regions. IT15 expression was found in all regions of the fetal and adult brain, and there was a high degree of correlation of autoradiographic signal with cell number in all regions but germinal matrix in fetal brain and white matter in adult brain. These two regions are notable for their significant proportion of glial cells, and suggest that IT15 expression is predominantly neuronal. There was no preponderance of IT15 expression in striatal compartments in fetal brain as demonstrated by acetylcholinesterase activity, nor was there differential expression of IT15 in brain regions known to be particularly affected in HD. IT15 gene expression is present by 20 weeks gestation in human brain, and at that stage of development exhibits a pattern of distribution which is similar to adult brain. If a developmentally-regulated role for IT15 exists in the pathogenesis of HD, it must occur prior to 20 weeks gestation.

The development of ependyma in the human fetal brain: an immunohistological and electron microscopic study

The stratified inner layer of the embryonic fetal brain, the ventricular zone (VZ), contains glial fibrillary acidic protein (GFAP)-positive cell bodies of radial glia. The adult cerebral ventricle is lined by a single layer of cuboidal, ciliated common ependymal cells which are, immunohistologically, GFAP negative. In late gestation, the ventricular lining is formed by tanycytes, ependymal cells with short, intensely GFAP-positive basal fibres. The development of ependyma was examined, morphologically and immunohistologically, in human fetal brain from between 11 weeks gestation to 6 months post-term to determine the relationship between the radial glia cell, tanycyte and common ependymal cell. This study was not able to show whether tanycytes were formed from radial glia or were formed from a previously uncommitted population of VZ cells. The study did show, however, that tanycytes probably mature into common ependymal cells following acquisition of cilia and loss of basal fibres. Electron microscopic data indicate that tanycytes have features suggestive of a secretory and/or transport function.

Glial and neuronal differentiation in the human fetal brain 9-23 weeks of gestation

Nineteen human fetal brains ranging from 9-23 weeks of gestation were examined immunocytochemically for evidence of glial and neuronal differentiation. Radial glia were positive for vimentin and glial fibrillary acidic protein (GFAP) throughout the age range. S100-positive cells which were presumed to be astrocytes were present from 9 weeks; they were always more widespread in the cerebrum and the brainstem than GFAP-positive mature astrocytes, which could be detected with certainty only at 14 weeks. Carbonic anhydrase II (CA II)-positive oligodendrocytes were present in the brainstem in small numbers from 17 weeks. Neuronal fibre tracts in the cerebrum were positive for 160 kD phosphorylated neurofilament protein (BF10) from 9 weeks, but negative for 200 kD phosphorylated neurofilament protein (RT97) and for 70 and 200 kD non-phosphorylated neurofilament protein (NFP) whereas most tracts in the brainstem were positive for BF10 from 9 weeks and positive for the other neurofilament proteins from 14 weeks. Corticospinal tracts differed in remaining negative for neurofilament proteins other than BF10, which showed positive reaction throughout. Perikarya of differentiated neurons in all areas of the brain were neurofilament-negative but neuron specific enolase (NSE)-positive. Germinal eminence cells were focally vimentin-positive from 15 weeks, focally GFAP-positive from 17 weeks, and negative for all NFP and for NSE. The value of a short fixation time and pretreatment with trypsin in the immunocytochemical demonstration of GFAP is stressed.

The astroblastoma and its possible cytogenic relationship to the tanycyte. An electron microscopic, immunohistochemical, tissue- and organ-culture study

Two examples of cerebral astroblastoma have been studied by electron microscopy and immunohistochemistry, one of them having been maintained in vitro in an organ-culture matrix system for 8 months and the explants studied by light and electron microscopy at different time intervals. The fine structural characteristics were those of a glial cell type with features intermediary between those of astrocytes and ependymocytes. They recapitulated the structure of the tanycyte, a glial precursor cell which is normally found scattered along the ependymal lining of the embryonal and neonatal mammalian brain, but is distinct from epithelial ependymocytes. The possible origin of some astroblastomas from such a cell would account for a number of characteristics in this enigmatic type of glioma.

An immunocytochemical study of the germinal layer vasculature in the developing fetal brain using Ulex europaeus 1 lectin

The characteristics of the germinal matrix vasculature were studied in the developing fetal brain using immunocytochemical methods. A preliminary comparative immunocytochemical study was made on six fetal brains to compare endothelial staining by Ulex europaeus I lectin with that of antibody to Factor VIII related antigen. Ulex was found to stain germinal layer vessels better than Factor VIII related antigen. Subsequently, the germinal layers of a further 15 fetal and preterm infant brains ranging from 13 to 35 weeks' gestation were stained with Ulex europaeus I to demonstrate the vasculature. With increasing gestation, there was a gradual increase in vessel density, particularly of capillaries. This was not a uniform process. A plexus of capillaries was prominent immediately beneath the ependyma while the more central parts of the germinal matrix contained fewer, but often larger diameter, vessels. The variation in vessel density which was a feature of the later gestation brains may have implications for local blood flow and may be a factor in haemorrhage at this site.

Glial differentiation in the germinal layer of fetal and preterm infant brain: an immunocytochemical study

The germinal layer in preterm infants is a common site of intracerebral hemorrhage that is associated with increased mortality and morbidity in survivors. This matrix is composed of a mass of immature cells containing many thin-walled blood vessels. A major factor in the occurrence of hemorrhage at this site is the absence of a network of fibers to support these vessels. This immunocytochemical study has examined glial differentiation within the germinal layer of brains from fetuses and preterm infants of gestational ages 18 to 35 weeks. Progressive glial differentiation with gestation is described. This process is not uniform and the more posterior germinal layer, lying over the body of the caudate nucleus, demonstrates more rapid maturation than that lying anteriorly near the head of the caudate nucleus. Anteriorly, even at 35 weeks of gestation, a central core of germinal layer cells remains immature with little evidence of glial differentiation. These changes may be related to the occurrence and distribution of germinal layer hemorrhages in preterm infants of varying gestations.