Isolation of the glucose oxidase gene from Talaromyces flavus and characterisation of its role in the biocontrol of Verticillium dahliae

The glucose oxidase gene from the biocontrol fungus Talaromyces flavus has been isolated and shown to be only 64% identical at the amino-acid sequence level to the similar enzyme from Aspergillus niger. A transformation system has been developed for both T. flavus and the related T. macrosporus and has been used to create Talaromyces spp. which either over-express or are deficient in glucose oxidase. In vitro inhibition experiments on Verticillium dahliae using culture filtrates from these transformants indicates that secreted glucose oxidase is responsible for a large part of the growth inhibition of V. dahliae microsclerotia and hyphae by T. flavus, although other inhibitory compounds may also play a role. In pot trials with cotton plants, both Talaromyces species had some biocontrol activity, but there was no significant difference in the incidence of Verticillium wilt with either the presence or absence of glucose oxidase activity in the biocontrol fungus. Under the experimental conditions used, insufficient glucose is presumably present in the soil around cotton roots to generate sufficient hydrogen peroxide to inhibit V. dahliae and the observed biocontrol activity must be attributed to other factors.

Bilateral neuropathologic changes in a child with hemimegalencephaly

Evaluation of a 7-month-old girl with developmental delay and intractable seizures revealed hemispheric asymmetry and an enlarged right cerebral hemisphere. Because of a history of seizures refractory to medical therapy, she was admitted for right hemispherectomy, but died of complications of surgery. Postmortem brain examination revealed asymmetric enlargement of the right cerebral hemisphere but no gross abnormalities in the left hemisphere. Microscopic examination demonstrated bilateral neuropathologic changes consistent with severe cortical dysplasia in the right cerebral hemisphere and mild cortical dysplasia in the left. Although white matter abnormalities in the unaffected hemisphere have been reported in hemimegalencephaly, bilateral cortical abnormalities, not reported previously in patients with hemimegalencephaly, may account for the varied clinical outcome with medical therapy or after hemispherectomy.

Eucalyptus has functional equivalents of the Arabidopsis AP1 gene

Two Eucalyptus homologues of the Arabidopsis floral homeotic gene AP1 (EAP1 and EAP2) show 60-65% homology to AP1. EAP1 and EAP2 are expressed predominantly in flower buds. EAP2 produces two different polypeptides arising from differential splicing at an intron, the shorter EAP2 protein diverging from the longer sequence after amino acid 197 and having a translation stop after residue 206. This truncated protein includes both MADS- and K-box amino acid sequences. Ectopic expression of the EAP1 or either of the two EAP2 polypeptides in Arabidopsis driven by the 35S promoter produces effects similar to the corresponding AP1 construct, causing plants to flower earlier, have shorter bolts and resemble the terminal flower mutant (tfl).

Two hemoglobin genes in Arabidopsis thaliana: the evolutionary origins of leghemoglobins

We cloned two hemoglobin genes from Arabidopsis thaliana. One gene, AHB1, is related in sequence to the family of nonsymbiotic hemoglobin genes previously identified in a number of plant species (class 1). The second hemoglobin gene, AHB2, represents a class of nonsymbiotic hemoglobin (class 2) related in sequence to the symbiotic hemoglobin genes of legumes and Casuarina. The properties of these two hemoglobins suggest that the two families of nonsymbiotic hemoglobins may differ in function from each other and from the symbiotic hemoglobins. AHB1 is induced, in both roots and rosette leaves, by low oxygen levels. Recombinant AHB1 has an oxygen affinity so high as to make it unlikely to function as an oxygen transporter. AHB2 is expressed at a low level in rosette leaves and is low temperature-inducible. AHB2 protein has a lower affinity for oxygen than AHB1 but is similar to AHB1 in having an unusually low, pH-sensitive oxygen off-rate.

Developmental outcomes in children receiving resection surgery for medically intractable infantile spasms

Two-year postsurgical developmental outcomes were assessed in 24 children with infantile spasms who underwent resective surgery. The mean age of onset of infantile spasms was 12.0 weeks and the mean age at surgery was 20.8 months. Developmental outcomes were assessed using the Vineland Adaptive Behavior Scales (VABS). There was a significant increase in developmental level at 2 years postsurgery compared with presurgical levels. At 2 years postsurgery only one of the children in this series was severely retarded. The developmental outcomes of patients in the series were better than those in prior studies of symptomatic patients receiving medical treatment for infantile spasms. It is surprising that the children in the UCLA series frequently had developmental outcomes equal to and sometimes superior to other groups of children with infantile spasms, since all the UCLA patients were symptomatic, had neurologic deficits and had failed to respond to adrenocorticotrophic hormone (ACTH) and antiepileptic drugs. The 2-year postsurgery developmental outcomes were best for the children who received surgery when they were relatively young and who had the highest level of developmental attainments presurgically.

Cloning of the Arabidopsis and rice formaldehyde dehydrogenase genes: implications for the origin of plant ADH enzymes

This article reports the cloning of the genes encoding the Arabidopsis and rice class III ADH enzymes, members of the alcohol dehydrogenase or medium chain reductase/dehydrogenase superfamily of proteins with glutathione-dependent formaldehyde dehydrogenase activity (GSH-FDH). Both genes contain eight introns in exactly the same positions, and these positions are conserved in plant ethanol-active Adh genes (class P). These data provide further evidence that plant class P genes have evolved from class III genes by gene duplication and acquisition of new substrate specificities. The position of introns and similarities in the nucleic acid and amino acid sequences of the different classes of ADH enzymes in plants and humans suggest that plant and animal class III enzymes diverged before they duplicated to give rise to plant and animal ethanol-active ADH enzymes. Plant class P ADH enzymes have gained substrate specificities and evolved promoters with different expression properties, in keeping with their metabolic function as part of the alcohol fermentation pathway.

An enzyme immunoassay for neuron-specific enolase in cerebrospinal fluid

A direct (as opposed to competitive) enzyme immunoassay (EIA) was developed to detect neuron-specific enolase (NSE) in cerebrospinal fluid (CSF). Most common methods of evaluating NSE levels have utilized radioimmunoassay. These are highly sensitive, but cannot be employed in laboratories not equipped or licensed for the use of radioisotopes. The EIA developed here shows sensitivity within the physiological range of values for CSF-NSE (> I ng/ml) and can be used in laboratories with appropriate densitometric scanning capabilities. The assay was applied to CSF samples obtained from patients with a variety of diagnoses at the time of surgical intervention for their respective disorders. While there were no diagnostically significant differences between the level of NSE in CSF from patients with different neurological disorders utilized in the development of this procedure, we were able to differentiate between marginally different levels of NSE. We conclude that we have developed a safe, fast, reliable, and sensitive assay for NSE in the CSF that can be used to study NSE levels in a variety of neurological cases.

Fertilization-independent seed development in Arabidopsis thaliana

We report mutants in Arabidopsis thaliana (fertilization-independent seed:fis) in which certain processes of seed development are uncoupled from the double fertilization event that occurs after pollination. These mutants were isolated as ethyl methanesulfonate-induced pseudo-revertants of the pistillata phenotype. Although the pistillata (pi) mutant has short siliques devoid of seed, the fis mutants in the pi background have long siliques containing developing seeds, even though the flowers remain free of pollen. The three fis mutations map to loci on three different chromosomes. In fis1 and fis2 seeds, the autonomous endosperm nuclei are diploid and the endosperm develops to the point of cellularization; the partially developed seeds then atrophy. In these two mutants, proembryos are formed in a low proportion of seeds and do not develop beyond the globular stage. When FIS/fis plants are pollinated by pollen from FIS/FIS plants, approximately 50% of the resulting seeds contain fully developed embryos; these seeds germinate and form viable seedlings (FIS/FIS). The other 50% of seeds shrivel and do not germinate; they contain embryos arrested at the torpedo stage (FIS/fis). In normal sexual reproduction, the products of the FIS genes are likely to play important regulatory roles in the development of seed after fertilization.

Cell-specific expression of the promoters of two nonlegume hemoglobin genes in a transgenic legume, Lotus corniculatus

The promoters of the hemoglobin genes from the nitrogen-fixing tree Parasponia andersonii and the related nonnitrogen-fixing Trema tomentosa both confer beta-glucuronidase reporter gene expression to the central zone of the nodules of a transgenic legume, Lotus corniculatus. beta-Glucuronidase expression was high in the uninfected interstitial cells and parenchyma of the surrounding boundary layer and was low in the Rhizobium-infected cells. This contrasts with the expression of both the P. andersonii hemoglobin protein in P. andersonii nodules and the endogenous Lotus leghemoglobins that are expressed in the infected cells at very high levels. The expression pattern of the P. andersonii and T. tomentosa hemoglobin promoters in L. corniculatus resembles that of a nonsymbiotic hemoglobin gene from Casuarina glauca, which was introduced into this legume, and suggests that only the nonsymbiotic functions of the P. andersonii promoter are being recognized. Deletion of the distal segments of both the P. andersonii and T. tomentosa promoters identified regions important for the control of their tissue-specific and temporal activity in Lotus. Potential regulatory elements, which enhance nodule expression and suppress nonnodule expression, were also identified and localized to a distal promoter segment. A proximal AAGAG motif is present in the P. andersonii, T. tomentosa, and nonsymbiotic Casuarina hemoglobin genes. Mutation of this motif in the P. andersonii promoter resulted in a significant reduction in both the nodule and root expression levels in L. corniculatus. Some of the regulatory motifs characterized are similar to, but different from, the nodulin motifs of the leghemoglobins.

Reduced DNA methylation in Arabidopsis thaliana results in abnormal plant development

Arabidopsis plants transformed with an antisense construct of an Arabidopsis methyltransferase cDNA (METI) have reduced cytosine methylation in CG dinucleotides. Methylation levels in progeny of five independent transformants ranged from 10% to 100% of the wild type. Removal of the antisense construct by segregation in sexual crosses did not fully restore methylation patterns in the progeny, indicating that methylation patterns are subject to meiotic inheritance in Arabidopsis. Plants with decreased methylation displayed a number of phenotypic and developmental abnormalities, including reduced apical dominance, smaller plant size, altered leaf size and shape, decreased fertility, and altered flowering time. Floral organs showed homeotic transformations that were associated with ectopic expression of the floral homeotic genes AGAMOUS and APETALA3 in leaf tissue. These observations suggest that DNA methylation plays an important role in regulating many developmental pathways in plants and that the developmental abnormalities seen in the methyltransferase antisense plants may be due to dysregulation of gene expression.

Characterization of pyruvate decarboxylase genes from rice

The pdc1 gene encoding pyruvate decarboxylase has been isolated and sequenced from an IR54 rice genomic library. In contrast to a previously isolated intron-less rice genomic pdc, pRgpdc3, this gene contains five intervening introns in the coding region and corresponds to a cDNA clone, pRcpdc1, isolated from an IR54-cDNA library constructed from anaerobically-induced mRNAs. Comparison of the deduced amino acid sequence of this gene with that of the rice pdc2 and pdc3 showed 88% and 89% similarity, and 78% and 79% identity, respectively. Southern blots indicated that more than three genes constitute the pdc gene family in rice. pdc1 is highly inducible under anaerobic conditions. Rice pdc2 is also inducible by anoxia but to a much lesser extent than pdc1.

Hemispherectomy for intractable seizures in children: a report of 58 cases

Fifty-eight children who underwent anatomical, functional, or modified anatomical hemispherectomy for intractable seizures from 1986 to 1995 were evaluated for seizure control, motor function, and complications. Age at surgery ranged from 0.3 to 17.3 years (median 2.8 years). Twenty-seven anatomical, 27 functional, and 4 modified anatomical hemispherectomies were performed. Seizure control and motor function in the 50 patients with more than 1 year follow-up revealed a 90% or better reduction in seizure frequency in 44/50 (88%) overall: 19/22 (86%) anatomical, 23/26 (89%) functional, and 2/2 modified anatomical. Motor function of the preoperatively hemiparetic extremities was improved or unchanged postoperatively in 38/50 (76%) of the patients. Complications included one intraoperative death, one late death from shunt obstruction managed elsewhere, late postoperative seizure breakthrough requiring reoperation and further disconnection in 5/27 functional hemispherectomy patients, mild cerebrospinal fluid infections in 3/27 anatomical hemispherectomy patients, and hydrocephalus requiring shunting in 3/27 functional hemispherectomy patients. A review of the literature and comparison of techniques is presented.

A new hemoglobin gene from soybean: a role for hemoglobin in all plants

We have isolated a new hemoglobin gene from soybean. It is expressed in cotyledons, stems of seedlings, roots, young leaves, and in some cells in the nodules that are associated with the nitrogen-fixing Bradyrhizobium symbiont. This contrasts with the expression of the leghemoglobins, which are active only in the infected cells of the nodules. The deduced protein sequence of the new gene shows only 58% similarity to one of the soybean leghemoglobins, but 85-87% similarity to hemoglobins from the nonlegumes Parasponia, Casuarina, and barley. The pattern of expression and the gene sequence indicate that this new gene is a nonsymbiotic legume hemoglobin. The finding of this gene in legumes and similar genes in other species strengthens our previous suggestion that genomes of all plants contain hemoglobin genes. The specialized leghemoglobin gene family may have arisen from a preexisting nonsymbiotic hemoglobin by gene duplication.

Abscisic acid induces the alcohol dehydrogenase gene in Arabidopsis

Exogenous abscisic acid (ABA) induced the alcohol dehydrogenase gene (Adh) in Arabidopsis roots. Both the G-box-1 element and the GT/GC motifs (anaerobic response element) were required for Adh inducibility. Measurement of endogenous ABA levels during stress treatment showed that ABA levels increased during dehydration treatment but not following exposure to either hypoxia or low temperature. Arabidopsis ABA mutants (aba1 and abi2) displayed reduced Adh mRNA induction levels following either dehydration treatment or exogenous application of ABA. Low-oxygen response was slightly increased in the aba1 mutant but was unchanged in abi2. Low-temperature response was unaffected in both aba1 and abi2 mutants. Our results indicate that, although induction of the Adh gene by ABA, dehydration, and low temperature required the same cis-acting promoter elements, their regulatory pathways were at least partially separated in a combined dehydration/ABA pathway and an ABA-independent low-temperature pathway. These pathways were in turn independent of a third signal transduction pathway leading to low-oxygen response, which did not involve either ABA or the G-box-1 promoter element.

Childhood generalized and mesial temporal epilepsies demonstrate different amounts and patterns of hippocampal neuron loss and mossy fibre synaptic reorganization

In this study, we determined whether childhood seizures were associated with hippocampal neuron loss and mossy fibre synaptic reorganization and if hippocampal sclerosis evolved from longer seizure histories. Children undergoing surgical treatment for catastrophic epilepsy were grouped into the following pathology categories: (i) those with generalized seizures and extra-hippocampal congenital pathologies (i.e. prenatal cortical dysplasia; n = 17); (ii) cases of generalized seizures and extra-hippocampal acquired lesions. (i.e. postnatal ischaemic injuries and encephalitis; n = 7); (iii) children with complex partial hippocampal epilepsy (n = 4). Further, to determine whether the epileptogenic location influenced hippocampal pathology, the seizure focus was classified as (i) hippocampal, (ii) temporal (n = 13) or (iii) extra-temporal (n = 11). Surgical and autopsy (n = 23) hippocampi were studied for (i) fascia-dentata (FD) and Ammon's horn (AH) neuron densities; (ii) thickness; height or length of the FD molecular layer, stratum granulosum (SG) and stratum pyramidale; and (iii) grey value (GV) densities of supragranular neo-Timm's staining. Statistically significant results (P < 0.05) showed the following. (i) Autopsy hippocampal neuron densities for the hilus (H), AH and prosubiculum (Pro) decreased logarithmically at the same time as the thickness of the stratum pyramidale and Pro increased. By contrast, autopsy granule cell densities and thickness did not significantly change with age; however, the SG lengthened-expanding around the enlarging H. Further, the supragranular molecular layer height increased logarithmically, and took longer than the increase in stratum pyramidale thickness. (ii) Compared with age-matched autopsies, young children with a history of hippocampal seizures showed decreased granule cell, hilar and regio superior neuron densities similar to adults with hippocampal sclerosis (average loss 70%). By contrast, children with extra-hippocampal congenital or acquired pathologies showed only decreased granule cell densities, along with a thinner and shorter SG. Compared with extra-temporal locations, those with temporal lobe lesions showed decreased hilar and AH neuron densities, but averaged 20-30% less than autopsies and not in the pattern typical of hippocampal sclerosis. (iii) The neo-Timm's GV densities, when compared with autopsies, showed supragranular mossy fibre sprouting in children with congenital pathologies and temporal lobe lesions; however, the greatest GVs were in children with hippocampal seizures. (iv) Of the children with extra-hippocampal congenital or acquired pathologies there were no statistical correlations between longer duration of seizures with changes in neuron densities, hippocampal heights, or mossy fibre sprouting. These results indicate the following. (i) In the human there is anatomical evidence for postnatal maturation of the hippocampus and our results are consistent with the notion that AH pyramids are a stable population; however, there are probably increases in granule cell numbers. Further, compared with the AH, dendritic maturation of the FD granule cells appears to take longer. (ii) Extra-hippocampal childhood seizures whether from prenatal or postnatal aetiologies are associated with moderate FD and minimal AH neuron losses and signs of aberrant mossy fibre sprouting. (iii) By contrast, young children with the syndrome of mesial temporal epilepsy show patterns of neuron loss and mossy fibre sprouting, typical of hippocampal sclerosis. (iv) Repeated extra-hippocampal childhood seizures are not associated with progressive evolution of hippocampal damage or mossy fibre sprouting. These findings support the hypothesis that childhood seizures can damage or alter the postnatally developing granule cells of the human hippocampus, and that early neuron loss and aberrant axon circuits may contribute to chronic hippocampal seizures. However, repeated childhood generalized seiz

Aberrant hippocampal mossy fiber sprouting correlates with greater NMDAR2 receptor staining

This study determined in temporal lobe epilepsy patients and rats injected with intrahippocampal kainate (KA) whether fascia dentata molecular layer mossy fiber sprouting was associated with increases in NMDAR2 immunoreactivity (IR). Patients with hippocampal sclerosis (n = 11) were compared with those with temporal mass lesions (n = 7) and material obtained at autopsies (n = 4); and unilateral KA-injected rat hippocampi (n = 7) were compared with the contralateral saline-injected side and non-lesioned animals (n = 7; control). Hippocampi were studied for neo-Timm's stained mossy fiber sprouting and NMDAR2 IR. The staining was quantified as gray values (GV) using computer image analysis. Hippocampal sclerosis patients and KA-injected rats showed the greatest inner molecular layer (IML) mossy fiber sprouting and NMDAR2 staining. Compared with autopsies and patients with mass lesions, hippocampal sclerosis patients had greater IML neo-Timm's (p = 0.0018) and NMDAR2 staining (p = 0.0063). Similarly, compared with controls and saline-injected rats, KA-injected hippocampi showed greater IML mossy fiber sprouting and NMDAR2 IR (p = 0.0001). Furthermore, IML mossy fiber sprouting positively correlated with greater IML NMDAR2 staining in both human and experimental rat groups (p < 0.0099). These results support the hypothesis that in severely damaged hippocampi abnormal mossy fiber sprouting and concordant increases in IML NMDAR2 receptor staining may contribute or partially explain granule cell hyperexcitability and the pathophysiology of hippocampal epilepsy.

Electrical properties of neocortical neurons in slices from children with intractable epilepsy

1. The intrinsic electrical properties of human neocortical neurons were studied with current-clamp and single-electrode voltage-clamp techniques in slices obtained from children, aged 3 mo to 15 yr, undergoing surgical treatment of intractable epilepsy. Neocortical samples were classified as most or least abnormal based on clinical data. Recorded neurons were labeled with biocytin for correlation of electrical properties with morphological characteristics and laminar position. All recorded neurons were divided into three cell types--fast-spiking, low-threshold spiking (LTS) and non-LTS cells--on the basis of their electrical characteristics. 2. Fast-spiking cells generated brief, rapidly repolarizing action potentials. Most of these cells showed only weak spike-frequency adaptation. Fast-spiking cells labeled with biocytin were aspiny or sparsely spiny nonpyramidal neurons located in cortical layers 2-4. 3. LTS cells generated Ca(2+)-dependent low-threshold potentials and were the most numerous of the three cell types. Their Na(+)-dependent action potentials were broader than those of fast-spiking cells and showed marked spike-frequency adaptation. The size of low-threshold Ca2+ potentials and currents varied across cells, but they never supported more than two or, occasionally, three fast action potentials. LTS cells were pyramidal neurons located throughout cortical layers 2-6. Unlike the bursting neocortical cells described in lower mammals, LTS neurons in neocortex from children failed to generate bursts of inactivating Na+ action potentials. 4. Non-LTS cells also had relatively broad Na(+)-dependent action potentials and showed spike-frequency adaptation, but they did not generate detectable low-threshold potentials or currents. Non-LTS cells were also pyramidal neurons located throughout layers 2-6. 5. The electrical properties of cells from different age groups (< or = 1, 2-8, and 9-15 yr) and from most-abnormal and least-abnormal tissue samples were compared. A statistically significant trend toward a lower input resistance, a faster membrane time constant, and a decreased spike duration was observed with increasing age. There were no significant differences between the electrical properties of cells from the most-abnormal tissue and cells from the least-abnormal tissue. 6. These data indicate that the intrinsic electrical properties of neocortical neurons from children vary according to cell morphology and change with increasing age, as has been observed in rodent and feline neocortical neurons. No obvious evidence of epileptogenicity was detected in the intrinsic electrical properties of any of the neurons studied.

Perioperative complications in children undergoing selective posterior rhizotomy: a review of 105 cases

Medical histories for 105 consecutive children who underwent selective posterior rhizotomy (SPR) were reviewed to determine the incidence and clinical significance of adverse events related to anaesthesia and surgery. No intraoperative or postoperative events with potential for lasting morbidity, nor life threatening events, were identified. Intraoperatively, the most common adverse events were moderate elevation of body temperature (13/105) and transient dysrhythmias (8/105). The most frequent postoperative complications were fever, marginal oxygen saturation in the absence of supplemental oxygen, and postcatheterization cystitis. Early surgical complications, such as wound infection, cerebrospinal fluid leak, haemorrhage, and bowel or bladder disturbance were absent in this series. Surgical technique and anaesthetic management are described.

Metabolic responses of the neonatal rabbit brain to hydrocephalus and shunting

The metabolic changes that occur in the neonatal brain as a result of hydrocephalus, and the response to ventriculoperitoneal shunting, vary with the maturational stage of the brain. In this study, local glucose utilization (LCMRglu) and oxidative metabolic capacity were estimated using 2-deoxyglucose autoradiography and cytochrome oxidase histochemistry, respectively. Hydrocephalus was induced in rabbit pups via intracisternal kaolin injections at 4-6 days of age. Shunting occurred at 19-26 days of age and the animals were sacrificed at ages ranging from 33 to 331 days. In normal animals there was a high glucose demand early in life which showed a decrease at about 60 days of age. In rabbits sacrificed prior to 60 days of age the controls showed the highest LCMRglu with significant decreases in both the hydrocephalic and shunted animals. After 60 days of age the shunted animals had higher LCMRglu than both the hydrocephalic and control subjects. Oxidative metabolic capacity peaked before 50 days of age in normal animals. At the youngest age, both the hydrocephalic and shunted animals showed higher cytochrome oxidase density rates than the control rabbits. In the older group, the hydrocephalic animals remained high while the shunted animals approximated the control densities. Neither the changes seen in the LCMRglu nor the oxidative metabolic capacity were correlated with changes in cell packing density or increased intracranial pressure. These data suggest that when the brain is compromised by hydrocephalus, there is an initial compensatory increase in oxidative metabolic capacity. The development of the glycolytic pathway appears to be retarded by hydrocephalus, but with shunting and the passage of time, the LCMRglu rebounds to levels above that of controls.

Intraoperative monitoring during selective posterior rhizotomy: technique and patient outcome

We evaluated intraoperative electromyographic (EMG) results among 110 pediatric patients with spastic cerebral palsy who underwent selective posterior rhizotomy. We analyzed surgical outcomes for 60 of these patients who returned for follow-up assessment between 4 and 17 months postoperatively. Reduction in muscle tone (resistance to passive movement), increased range of motion and improvements in functional skills were seen at follow-up. To control for possible changes due to development, participation in therapy, or instability of measurements, 30 rhizotomy patients were evaluated twice during a baseline period of several months prior to surgery. No significant changes were found between these two measurement sessions during the baseline control period suggesting that the rhizotomy surgery itself caused the postoperative improvements. These intraoperative EMG monitoring techniques have been adopted at many other centers but variations in specific methods and EMG criteria have developed subsequently among major hospitals where selective posterior rhizotomy is performed. These variations in neurophysiologic methods and recent controversy about the usefulness of such intraoperative EMG monitoring created a need for us to publish our standard EMG selection technique. We describe here, in detail, methods for nerve rootlet testing and selection.

Neuroamine related compounds in the CSF of hydrocephalic rabbits

The effects of neonatal hydrocephalus on the levels of tyrosine, tryptophan, 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) in CSF were determined by high-performance liquid chromatography (HPLC) with fluorometric detection in normal and chronically hydrocephalic rabbits. The hydrocephalic rabbits showed a highly significant increase in both the serotonin metabolite 5-HIAA and the dopamine metabolite HVA. There were no significant effects of the hydrocephalus on either tyrosine or tryptophan levels. There was a significant positive correlation between the intracranial pressure (ICP) and the increase in 5-HIAA and HVA, but not with the two precursor amino acids. There was a significant decrease in these amino acid precursors with age in both groups. A trend towards higher levels of 5-HIAA and HVA in older rabbits was also evident, however this change was not to the degree found in the hydrocephalics. These data indicate that increased ICP affects the mechanism of removal of 5-HIAA and HVA from the cerebrospinal fluid.

Hemispherectomy for the treatment of intractable seizures in childhood

This article discusses the role of hemispherectomy in the treatment of children with intractable seizures associated with hemiplegia. The postnatal development and plasticity of the brain are discussed, leading to a justification for early surgery in appropriate candidates. Methods of investigation, the process of selection, and the various surgical techniques are outlined.

Effective ribozyme delivery in plant cells

Hammerhead ribozyme sequences were incorporated into a tyrosine tRNA (tRNA(Tyr)) and compared with nonembedded molecules. To increase the levels of ribozyme and control antisense in vivo, sequences were expressed from an autonomously replicating vector derived from African cassava mosaic geminivirus. In vitro, the nonembedded ribozyme cleaved more target RNA, encoding chloramphenicol acetyltransferase (CAT), than the tRNA(Tyr) ribozyme. In contrast, the tRNA(Tyr) ribozyme was considerably more effective in vivo than either the nonembedded ribozyme or antisense sequences, reducing CAT activity to < 20% of the control level. A target sequence (CM2), mutated to be noncleavable, showed no reduction in CAT activity in the presence of the tRNA(Tyr) ribozyme beyond that for the antisense construct. The reduction in full-length CAT mRNA and the presence of specific cleavage products demonstrated in vivo cleavage of the target mRNA by the tRNA(Tyr) ribozyme. The high titer of tRNA(Tyr) ribozyme was a result of transcription from the RNA polymerase III promoter and led to the high ribozyme/substrate ratio essential for ribozyme efficiency.

Neurophysiology of neocortical slices resected from children undergoing surgical treatment for epilepsy

The recent emergence of surgical treatment of childhood epilepsy has led to the accessibility of young human cerebral tissue for electrophysiological studies of the mechanisms involved in epileptogenesis. Intracellular recordings were obtained from neurons in slices prepared from neocortical tissue resected from children (3 months to 15 years) with catastrophic epilepsy. Data from 'least abnormal' versus 'most abnormal' tissue were compared; the evaluation of the degree of abnormality was based on several clinical criteria. Hypotheses concerning NMDA receptors, local synaptic circuits, and epileptiform bursts were tested. The NMDA receptor-mediated component of synaptic responses, which was isolated pharmacologically, had a voltage dependence that was functionally mature by 8-10 months of age and did not appear to be altered even in the most abnormal tissue. Local inhibitory and excitatory synaptic circuits were present as early as 11 months and 8 months, respectively. Local excitatory circuits were sufficiently extensive in young children to initiate and sustain epileptiform activity when synaptic inhibition was suppressed. Bicuculline-induced epileptiform bursts were similar to those in adult human or animal neocortical slices. Burst duration and the presence of after-discharges were unrelated to patient age or tissue abnormality. These data demonstrate that (1) the electrophysiological properties of human neocortical neurons are very similar to those observed in animal experiments, (2) the mechanisms of neuronal communication are qualitatively mature within the first year of life, and (3) synaptic transmission and local neuronal circuits appear qualitatively normal, even in the most abnormal tissue from children with catastrophic epilepsy.