Combination effect of systemic hypothermia and caspase inhibitor administration against hypoxic-ischemic brain damage in neonatal rats

Caspases are believed to play a key role in the delayed neuronal cell death observed in the rat brain after hypoxic-ischemic (HI) insult. Caspase inhibitors have been developed as antiapoptotic agents. Hippocampal damage after HI insult is strongly related to tissue temperature, and systemic hypothermia has been introduced clinically for brain protection. In this study, we examined the effects of a caspase inhibitor and systemic hypothermia on neuronal protection in the developing rat brain. Postnatal d 7 rat pups were subjected to the Rice model of hypoxia for 1 h. Systemic hypothermia was induced with a water bath at 29 degrees C. Before HI insult, a pan-caspase inhibitor, boc-aspartyl-(OMe)-fluoromethyl-ketone (BAF), was injected into the cerebral ventricle. The ipsilateral hippocampus was subjected to caspase assays and histologic assessment. The HI group at 37 degrees C (HI-37 degrees C) showed a peak of caspase-3 activity 16 h after insult. This activity was significantly reduced in the presence of BAF or hypothermia (HI-29 degrees C group, p < 0.05) or by the combination of HI-29 degrees C + BAF (p < 0.01 versus HI-37 degrees C). The number of neuronal cells in the ipsilateral hippocampal CA1 region in the HI-37 degrees C group was significantly decreased (62.9% versus control). The number of neuronal cells was maintained in the HI-37 degrees C + BAF group (82.7%), the HI-29 degrees C group (78.7%), and the combination group (95.2%) (p < 0.05 versus HI-37 degrees C). A combination of systemic hypothermia and BAF produced a strong protective effect against neuronal damage in the developing rat brain, along with a reduction in caspase-3 activity.

Induction of heat shock proteins and its effects on glial differentiation in rat C6 glioblastoma cells

Heat shock proteins (HSPs) are immediately expressed in neuronal and glial cells under various stressful conditions and play a protective role through molecular chaperones. We investigated the characteristics of the induction manner of heme oxygenase-1 (HO-1) and HSP70 in rat C6 glioblastoma cells. In heat treatment (42 degrees C for 30 min), C6 cells expressed high level of HO-1 and HSP70 mRNAs within 30-60 min, and their proteins at 3 hrs. Heat-induced expressions of HSPs mRNAs were completely inhibited with actinomycin D, suggesting the transcriptional regulation. Oxygen-glucose deprivation (OGD), cystine-free (inhibition of synthesis of glutathione), cyto-toxic (ethanol, sodium butyrate) treatments resulted in different expression manners between HO-1 and HSP70, which suggested that HO-1 and HSP70 play different protective roles against a variety kind of stressful conditions in glial cells. C6 cells can differentiate toward both astrocyte and oligodendrocyte directions. Treatment with dibutyryl cyclic AMP (cAMP) induces expression of glial fibrillary acidic protein (GFAP), a marker of astrocytes, and treatment with retinoic acid (RA) induces expression of myelin proteolipid protein (PLP), a marker of oligodendrocytes, respectively. Heat treatment before the initiation of differentiation by RA reduced the RA-induced expression of PLP mRNA profoundly, but not in GFAP mRNA level induced by cAMP. Heat treatment after the initiation of differentiation by cAMP or RA accelerated the expression of GFAP or PLP mRNAs. Astroglial differentiation by cAMP reduced the heat-induced expressions of HSPs mRNAs, but no change with RA pre-treatment. These results suggested that HSPs may modulate the glial differentiation in the developing brain. On the contrary, glial differentiation may give influence on the stress-induced HSPs expression. The timing of stressful damages, resulting in the expression of HSPs, on the developing brain is critically important for the pathogenesis of glial lesion. In the heat-treated C6 cells, the expression of platelet-derived growth factor (PDGF) receptor-alpha mRNA was significantly decreased. HSPs may have ability to induce the glial differentiation in part through down-regulation of the PDGF pathway.

Effects of preterm extrauterine visual experience on the development of the human visual system: a flash VEP study

To compare the functional maturation of the human visual system between intra- and extrauterine course flash visual evoked potentials (VEPs) in preterm infants (gestational age 24 to 36 weeks). Previously established normal values, with special reference to the two components of the N1 wave, were employed (Tsuneishi 1995). A cross-sectional analysis of 124 infants at 36 weeks postmenstrual age (PMA), showed that there are no differences in the absolute values of VEP peak latencies depending on the postnatal age (PNA). Conversely, the N1 wave form changes with increasing PNA from a wave in which the early peak (N1a) has a higher amplitude than the late peak (N1b) into the reverse situation with a higher amplitude of the N1b as compared to N1a. This observation may correlate with the maturation of the neuronal networks in the visual cortex. In a longitudinal analysis of 50 infants followed for more than 5 sessions of weekly recordings, we found that the individual rapid decrease in the N1a latency, which may reflect the initiation of myelination in the optic radiation, most frequently occurs at around 37 weeks PMA, regardless of PNA. Preterm extrauterine visual experience has little effect on the myelination process in the visual pathway, but has a marked effect on the developmental changes in VEP wave form which reflect the developmental changes of the neuronal networks in the visual cortex.

Stepwise decrease in VEP latencies and the process of myelination in the human visual pathway

To assess the progress in myelination in the developing human brain, a prospective longitudinal study of flash visual evoked potentials (VEPs) was performed in 22 healthy preterm infants with the same gestational age at birth (between 30 weeks 0 day and 31 weeks 0 day). The individual curves of the changes in the N1a peak latency (the early peak of the N1 wave) decrease not linearly but in a stepwise pattern in the preterm period. Twenty-one infants out of the 22 have one or more 'acceleration week(s)' in which the latency decreases at a rate of more than 6 ms per week. These stepwise decreases in the latency may reflect a synchronized progress in myelination in several parts of the visual pathway. A detailed analysis of the 'acceleration weeks' in relation to postmenstrual age (PMA) indicates that they most prominently occur at 37 weeks PMA. At 37 weeks an initiation of myelination in the optic radiation has been demonstrated in post-mortem studies. We propose that a longitudinal follow-up study of VEPs can be accepted as a functional in vivo evaluation of myelination in the developing human brain.

Neonatal renal artery blood flow velocities using color Doppler ultrasonography

BACKGROUND

It is essential to evaluate the renal function for the management of high risk neonates. Color Doppler ultrasound technique can provide a useful information to evaluate the neonatal renal artery blood flow velocities. This study was performed to obtain the normative data of renal blood flow velocities in preterm and fullterm neonates and to compare the renal blood flow velocities with the aortic blood flow velocities. The normal volumetric state of fluid balance and renal function are essential in the management of the sick neonates.

METHODS

The renal peak systolic blood flow velocity (renal PSFV), the renal mean blood flow velocity (renal MFV), the renal end diastolic blood flow velocity (renal EDFV) and the renal resistance index (renal RI) and also the cardiac output, the aortic peak systolic blood flow velocity (aortic PSFV) and the aortic mean blood flow velocity (aortic MFV) were serially recorded from one to 7 days after birth in 16 preterm and one to 5 days in 23 normal fullterm neonates.

RESULTS

The renal PSFV was significantly increased with the postnatal age, and the renal MFV was significantly increased between three and five days of age in the preterm neonates. In the fullterm neonates there was no significant change of the renal PSFV between one and five days of age, but the renal MFV was significantly increased between three and five days of age. There were no statistically significant differences of the renal PSFV, the renal MFV, the renal EDFV and the renal RI between the preterm and the fullterm neonates in the first five days after birth. The cardiac output in the preterm neonates was higher than that in the fullterm neonates: on day 3; 313 +/- 59 vs. 254 +/- 40 ml/kg/min. (p < 0.001) and on day 5; 357 +/- 95 vs. 280 +/- 35 ml/kg/min. (p < 0.01). The renal blood flow velocities were not significantly correlated with the aortic blood flow velocities in the normal fullterm neonates, whereas, in the preterm neonates the renal PSFV correlated with the cardiac output (r = 0.35, p < 0.01), the aortic PSFV (r = 0.45, p < 0.001) and the aortic MFV (r = 0.39, p < 0.01), and the renal MFV also correlated with the aortic PSFV (r = 0.30, p < 0.05) and the aortic MFV (r = 0.32, p < 0.05).

CONCLUSIONS

The increased renal flow velocities with the postnatal age in the preterm infants might depend on the increased cardiac output.

Struggles of neonatology staff and the network system in the Hanshin-Awaji earthquake disaster

More than 5500 people were killed in the Hanshin-Awaji earthquake disaster. Most of the neonatal intensive care units (NICU) could not offer proper services as a result of the earthquake and the Hyogo Emergency System for Neonates could not function. No one imagined that such a great disaster would occur in their home town, Kobe; however, the devastation of the quake has raised the opportunity to examine the operation of neonatal medicine in an emergency. We sent out questionnaires to perinatologists in the damaged area 2-3 months after the quake. Some hospitals in the demolished area suffered such serious damage that they could not continue work as NICU, and some in the surrounding area had problems in a number of areas, including staff, room capacity and transport methods. Under these difficult circumstances the greatest problem encountered by staff was maintaining fundamental care in NICU, that is to say keeping temperature, formula (nutrition) and prevention of infection techniques operating. In this report we discuss the effects on neonatal medicine of the earthquake in Kobe. Medical staff struggled patiently and made great efforts to recover and maintain the functioning of NICU. We believe this information will be useful for neonatology staff in other areas which may experience an earthquake in the future.

Difficulties of families with handicapped children after the Hanshin-Awaji earthquake

In order to clarify the difficulties which handicapped people experienced in the Hanshin-Awaji earthquake disaster, 678 families with handicapped children were studied 1.5 months after the earthquake. All the students who were enrolled in this study were going to some type of school or training classes for handicapped children in January 1995. The study was completed between 1 and 10 March. The questionnaires which were designed for this study consisted of three parts: the difficulties which the families were faced with, their requirements for social and medical services and the symptoms and reactions of their children after the earthquake. A total of 466 answers were obtained from their parents. The kinds of difficulties differed between the families of mentally retarded children and those of the physically handicapped. While many parents with physically handicapped children desired better medical information or materials, many parents with mentally retarded children wanted better care services for their children. Physical and psychological effects of the earthquake were only temporary in most cases. However, some of the handicapped children were still suffering from such reactions as of 10 March. From the results of our study it became evident that a systematic relief program for these handicapped people should be established. The relief program should include the distribution of information regarding medical and social services. Psychological reactions such as panic, excitement and suppression of mental activity were still observed in some handicapped children on 10 March. Further observation will therefore be necessary.

Establishment of normal values for flash visual evoked potentials (VEPs) in preterm infants: a longitudinal study with special reference to two components of the N1 wave

To establish normal values for flash visual evoked potentials (VEPs) in the preterm period, we analyzed 356 records from 63 neurologically normal infants (26-35 weeks gestation) followed longitudinally. Using both sleep and drowsy state recording within the same session and a mean of 5.7 weekly recording sessions per infant, we hypothesized that the prominent negative wave (N1) consisted of 2 negative components, N1a (early) and N1b (late). This hypothesis could explain the previously reported variability in VEP indices. With a precise definition of the N1a peak, we were able to establish reference ranges for N1a peak latencies at various postmenstrual ages (PMA) which, unlike those previously reported, are narrow enough to be clinically useful. From a cross-sectional analysis we found that the N1a peak latency decreased with maturation at about 4.6 msec/week between 30 and 40 weeks PMA (P < 0.001). We also analyzed the N1 wave form and demonstrated its developmental maturation during this period. There were significant decreases in the amplitudes of both the N1a and N1b peaks with maturation (P < 0.001), but the decrease of the N1a amplitude was steeper than that of N1b. The N1 wave form changed from a wave in which the early peak (N1a) was higher than the late peak (N1b) into the reverse with N1b higher than N1a. This wave change may be related to developmental processes in the visual system. Longitudinal follow-up revealed that extra-uterine life may accelerate the maturation of the N1 wave form but has no effect on the decrease of the absolute values of peak latencies.

[A case of perinatal cytomegalovirus infection with severe progressive brain atrophy]

A 2-month-old girl had focal tonic convulsions. Brain CT showed no abnormalities on admission. Three weeks later she got a severe epileptic status. T 1-weighted MRI demonstrated low intensity areas in the right occipital and left frontal regions, and enhanced CT demonstrated low density areas in the same region. An increase of CMV antibody titer in serum suspected CMV infection associated with brain infarction. Then gamma-globulin was given in addition to PB, CBZ, and VPA, resulting in suppression of seizures. At 9 months of age, she had right tonic hemiconvulsions. An increase of CMV IgM antibody titer showed reactivation of CMV infection. Acyclovir and gamma-globulin were given, and her seizures were controlled. However, she showed progressive motor disability with spastic muscle tonus. CT and MRI showed a severe progressive atrophy of the cerebrum and brain stem.

Serum depletion increases the neurofilament protein mRNA levels in a neuroblastoma cell line, GOTO

A human neuroblastoma cell line, GOTO, extends neurite-like processes upon withdrawal of serum from culture medium. This morphological change was accompanied by a 5-fold increase in the neurofilament (NF)-L and a 10-fold increase in the NF-M mRNA levels after 24 h. The addition of a protein kinase inhibitor, H-7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride) also induced the extension of neurite-like processes; however, it did not increase the NF mRNA levels. Thrombin inhibited the extension of neurite-like processes in serum-free culture without affecting the increase in the NF mRNA levels. There was no difference in the number of cells progressing through the S phase between serum-containing and -free cultures at 24 h. This indicates that the increase in the NF mRNA levels upon withdrawal of serum was not preceded by the growth arrest. Treatment with actinomycin D and cycloheximide inhibited the increase in the NF mRNA levels. The half life of the NF gene transcripts was prolonged in the serum-free condition. These results indicate that the serum depletion-induced increase in the NF-L and -M mRNA levels was regulated by both transcriptional and post-transcriptional mechanisms, and the increase in the expression of the NF genes was not simply mediated by growth arrest but controlled by unknown regulator proteins.

Regulation of neurite outgrowth through protein kinase C and protease nexin-1 in neuroblastoma cell

Accumulating evidence has demonstrated that protein kinase C (PKC) and protease nexin-1 (PN-1) may be involved in neuronal differentiation including migration, neurite outgrowth, target recognition, and synaptogenesis. We investigated the potential roles of PKC and PN-1 in neurite outgrowth of human neuroblastoma cell line, GOTO. Upon withdrawal of serum GOTO cells extended neurite processes within 3 h and formed fine network of neurites after 24 h. This morphological change was completely inhibited by thrombin and phorbol-12-myristate-13-acetate (PMA). Withdrawal of serum increased the neurofilament (NF)-L and -M mRNA levels and thrombin did not inhibit the effect of withdrawal of serum. A potent PKC inhibitor, H-7 induced neurite outgrowth in the presence of serum, however, it did not increase the NF mRNA levels. Actinomycin D and cycloheximide did not inhibit the initial neurite outgrowth induced by withdrawal of serum, while these inhibited the increase in the NF mRNA levels. Thrombin retracted the serum depletion-induced neurites but did not retract the neurites induced by H-7. The specific activity and subcellular localization of PKC did not differ between GOTO cells cultured in serum-containing and -free media for 12 h. The serine protease inhibitory activity was undetectable in the serum-free conditioned medium of GOTO cells but the PN-1 mRNA was clearly detected by Northern blot analysis to a less extent than glial cells. Withdrawal of serum or treatment with H-7 did not increase the PN-1 mRNA level in GOTO cells, but thrombin increased its level about 7 folds in serum-free condition. These results indicate that the initial neurite outgrowth requires neither new RNA nor protein synthesis, and that PKC negatively regulates neurite outgrowth and thrombin blocks neurite outgrowth through PKC-dependent pathways.

Expression and localization of smg p25A (= rab3A) in cultured rat hippocampal cells

We have studied the expression of smg p25A and synaptophysin in cultured hippocampal neurons isolated from 5-day-old rat brain by an immunocytochemical technique. In a dispersed cell culture seeded on astrocyte monolayers, well-branching neurite proliferation was observed along with age in culture. The synaptophysin immunoreactivity was present in the neuronal cell bodies and neurites at 1 and 5 days in vitro (DIV) and was eventually localized to discrete areas along neurites at 15 DIV while the immunoreactivity in cell bodies became less prominent. On the other hand, the smg p25A immunoreactivity was observed in the neuronal cell bodies and neurites at 1 through 15 DIV. The immunoreactivity for smg p25A or synaptophysin was not observed in astrocytes and this finding was confirmed by an immunoblot analysis. These results indicate that smg p25A as well as synaptophysin is present exclusively in neurons and suggest that these two synapse-associated proteins have different sites of function and different kinetics of synthesis, transport, and/or turnover in cultured hippocampal neurons.

Effects of dexamethasone on the expression of myelin basic protein, proteolipid protein, and glial fibrillary acidic protein genes in developing rat brain

Effects of dexamethasone (DEX) on the relative abundance of myelin basic protein (MBP), proteolipid protein (PLP) and glial fibrillary acidic protein (GFAP) mRNAs in the developing rat brain were examined. After DEX (1.0 mg/kg body weight) or saline was administered intraperitoneally to 3-day-old rats for 7 consecutive days, wet weight, DNA content and the relative abundance of the glia-specific mRNAs in cerebrum and cerebellum were analyzed at postnatal days (P) 10, 20 and 30. DEX decreased both wet weight and DNA content in cerebellum more profoundly than in cerebrum. The appearance of MBP, PLP and GFAP mRNAs in cerebellum preceded that in cerebrum in the control group. In cerebrum, the relative abundance of MBP and PLP mRNAs was significantly less in the DEX group than that in the control group at P20 and P30. The relative abundance of the GFAP mRNA was significantly less in the DEX group than in the control group at P10 and P20, but there was no significant difference at P30. In cerebellum, a significant decrease in the abundance of MBP, PLP and GFAP mRNAs in the DEX group was observed only at P10 but not at P20 and P30. Our findings indicate that DEX suppresses expression of genes related to glial functions, especially myelination when administered in the early postnatal period.

Effect of dexamethasone on pulmonary surfactant metabolism in hyperoxia-treated rat lungs

We have examined the effect of dexamethasone on the metabolism of pulmonary surfactant in normal and hyperoxia-treated rats. The relative abundance of the surfactant-specific apoprotein A (SP-A) mRNA in lung tissues and the contents of disaturated phosphatidylcholine (DSPC) and SP-A were measured in bronchoalveolar lavage fluids and in lung tissues in 4-wk-old rats exposed to room air or greater than 90% oxygen for 7 d with or without simultaneous treatment with dexamethasone (0.5 mg/kg body wt for 7 d). The relative abundance of the SP-A mRNA was marginally increased by hyperoxia (1.3-fold over controls). Dexamethasone increased the relative abundance of the SP-A mRNA to a level comparable to that with hyperoxia treatment (1.5-fold over controls). In lavage fluids, the contents of DSPC and SP-A were increased by 4- and 6-fold over controls by hyperoxia, respectively, but they were increased only by 2-fold by dexamethasone. In lung tissues, the contents of DSPC and SP-A were increased by 3- and 2-fold over controls by hyperoxia, respectively. These values in lung tissues in the air-exposed rats were not significantly increased by dexamethasone. In hyperoxia-treated rats, dexamethasone did not significantly affect the relative abundance of the SP-A mRNA level and the contents of DSPC and SP-A in lavage fluids and lung tissues. These results indicate that mechanisms other than increased synthesis of SP-A are involved in hyperoxia-induced SP-A accumulation and that dexamethasone does not affect the abnormal accumulation of pulmonary surfactant induced by hyperoxia.

Expression of smg p25A, a ras p21-like small GTP-binding protein, during postnatal development of rat cerebellum

Changes in expression and localization of smg p25A, a ras p21-like small GTP-binding protein, in developing rat brain were analyzed in comparison with those of synaptophysin, a well-known synaptic vesicle-specific protein. The smg 25A mRNA was detected in whole brain of rat fetus at 14 days of gestation and its level was increased along with the age and reached the maximum level at postnatal day (P) 20. In postnatal cerebellum, the smg25A mRNA level was also increased age-dependently and the maximum level was observed at P30. Immunoblot analysis with an anti-smg p25A monoclonal antibody (MAb SG-11-7) and an anti-synaptophysin monoclonal antibody (SY 38) showed that expression of both smg p25A and synaptophysin was increased age-dependently in postnatal rat cerebellum. By immunofluorescent cytochemical study with the anti-smg p25A antibody, bright fluorescence was observed in the molecular layer of cerebellum and it was increased in accordance with the cerebellar development. In early postnatal cerebellum, the perikarya of Purkinje cells and the white matter were brightly stained with the antibody, but the fluorescence of these portions was faint in adult cerebellum. The anti-synaptophysin monoclonal antibody also stained the molecular layer of cerebellum but the perikarya of Purkinje cells and the white matter had only a weak immunoreactivity with the antibody irrespective of the age. These results indicate that smg p25A is predominantly present in the nerve terminals and that its amount is increased along with the development of postnatal rat cerebellum. Our results also suggest that smg p25A and synaptophysin have the different kinetics of synthesis, transport, and/or turnover in developing rat cerebellum.