Viral meningoencephalitis: a review of diagnostic methods and guidelines for management

BACKGROUND

Viral encephalitis is a medical emergency. The prognosis depends mainly on the pathogen and host immunologic state. Correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury.

METHODS

We searched the literature from 1966 to 2009. Recommendations were reached by consensus. Where there was lack of evidence but consensus was clear, we have stated our opinion as good practice points.

RECOMMENDATIONS

Diagnosis should be based on medical history and examination followed by CSF analysis for protein and glucose levels, cellular analysis, and identification of the pathogen by polymerase chain reaction amplification (recommendation level A) and serology (level B). Neuroimaging, preferably by MRI, is essential (level B). Lumbar puncture can follow neuroimaging when immediately available, but if this cannot be performed immediately, LP should be delayed only under unusual circumstances. Brain biopsy should be reserved only for unusual and diagnostically difficult cases. Patients must be hospitalized with easy access to intensive care units. Specific, evidence-based, antiviral therapy, acyclovir, is available for herpes encephalitis (level A) and may also be effective for varicella-zoster virus encephalitis. Ganciclovir and foscarnet can be given to treat cytomegalovirus encephalitis, and pleconaril for enterovirus encephalitis (IV class evidence). Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered to be effective, and their use is controversial, but this important issue is currently being evaluated in a large clinical trial. Surgical decompression is indicated for impending uncal herniation or increased intracranial pressure refractory to medical management.

Viral encephalitis: a review of diagnostic methods and guidelines for management

Viral encephalitis is a medical emergency. The spectrum of brain involvement and the prognosis are dependent mainly on the specific pathogen and the immunological state of the host. Although specific therapy is limited to only several viral agents, correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury in survivors. We searched MEDLINE (National Library of Medicine) for relevant literature from 1966 to May 2004. Review articles and book chapters were also included. Recommendations are based on this literature based on our judgment of the relevance of the references to the subject. Recommendations were reached by consensus. Where there was lack of evidence but consensus was clear we have stated our opinion as good practice points. Diagnosis should be based on medical history, examination followed by analysis of cerebrospinal fluid for protein and glucose contents, cellular analysis and identification of the pathogen by polymerase chain reaction (PCR) amplification (recommendation level A) and serology (recommendation level B). Neuroimaging, preferably by magnetic resonance imaging, is an essential aspect of evaluation (recommendation level B). Lumbar puncture can follow neuroimaging when immediately available, but if this cannot be obtained at the shortest span of time it should be delayed only in the presence of strict contraindications. Brain biopsy should be reserved only for unusual and diagnostically difficult cases. All encephalitis cases must be hospitalized with an access to intensive care units. Supportive therapy is an important basis of management. Specific, evidence-based, anti-viral therapy, acyclovir, is available for herpes encephalitis (recommendation level A). Acyclovir might also be effective for varicella-zoster virus encephalitis, gancyclovir and foscarnet for cytomegalovirus encephalitis and pleconaril for enterovirus encephalitis (IV class of evidence). Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered to be effective and their use is controversial. Surgical decompression is indicated for impending uncal herniation or increased intracranial pressure refractory to medical management.

Five new cases of a recently described leukoencephalopathy with high brain lactate

BACKGROUND

A new leukoencephalopathy with brainstem and spinal cord involvement and high brain lactate was recently defined. The authors describe five new patients with this entity.

METHODS

Brain MRI was performed in all patients and spinal MRI and proton magnetic resonance spectroscopy (1H-MRS) in four patients. Laboratory examinations ruled out classic leukodystrophies.

RESULTS

MRI showed signal abnormalities in the periventricular and deep white matter, in the pyramidal tracts, mesencephalic trigeminal tracts, in the cerebellar connections, and in dorsal columns of the spinal cord. MRS showed decreased N-acetylaspartate and increased lactate in the white matter of all patients. In one patient choline-containing compounds were elevated. A slowly progressive sensory ataxia and tremor manifested at the age of 3 to 16 years and distal spasticity in adolescence. One 13-year-old patient was asymptomatic.

CONCLUSIONS

A slowly progressive sensory ataxia is a typical feature in this new leukodystrophy. MRS favors a primary axonal degeneration.

Follow-up of children with cerebral palsy after selective posterior rhizotomy with intensive physiotherapy or physiotherapy alone

In all 21 children with spastic cerebral palsy (CP) underwent surgery involving selective posterior rhizotomy (SPR), followed by six months intensive physiotherapy (PT). Neurological and physiotherapeutic assessments were made one, three and five years after the operation. The children undergoing surgery were compared to 21 comparison children who took part in a regular physiotherapy programme during the same time period. At the preoperative assessment, the children undergoing surgery were similar to the comparative children in terms of age, sex, type of CP, spasticity of the legs and mean functional scores. The children were selected for SPR on the basis of more than half a year's arrest of motor development, which was the only significant difference to the comparative group. Motor function was measured using two different methods, the Illinois-St Louis Scale and the Gross Motor Functional Classification System (GMFC). Both groups experienced steady development during the five-year follow-up period and no significant differences were observed in the mean functional scores between the groups. We conclude that this comparative study, like most controlled studies, failed to demonstrate any additional effect of SPR on motor development of children with spastic CP. Nevertheless, SPR may contribute to a resumption of motor development in children with arrested motor development despite vigorous conservative therapy. SPR is therefore justified as treatment in selected cases.

DC-EEG discloses prominent, very slow activity patterns during sleep in preterm infants

OBJECTIVES

The objective of this study is to test the hypothesis that the immature human brain exhibits slow electrical activity that is not detected by conventional (i.e. high-pass filtered) electroencephalography (EEG).

METHODS

Six healthy preterm infants (conceptional age 33-37 weeks) were recorded bedside with direct current (DC) EEG during sleep. Epochs with quiet sleep were selected to study the delta frequency bursts during discontinuous EEG patterns (trace discontinu or trace alternant), and we compared the waveforms obtained without filtering (i.e. genuine DC-EEG) to those seen after high pass filtering of the same traces.

RESULTS

In all infants, DC-EEG demonstrated that the typical delta frequency bursts are consistently embedded in very large amplitude (200-700 microV) and long lasting (1-5s) occipitally negative transients, which are not seen in conventional EEG.

CONCLUSIONS AND SIGNIFICANCE

Our study demonstrates that (i) the most prominent spontaneous EEG activity of a sleeping preterm infant consists of very slow, large amplitude transients, and (ii) the most salient features of these transients are not seen in conventional EEG. Proper recording of this type of brain activity by DC-EEG provides a novel way for non-invasive assessment of neonatal brain function.

Enlarged SI and SII somatosensory evoked responses in the CLN5 form of neuronal ceroid lipofuscinosis

OBJECTIVES

To examine in detail the activation of the primary (SI) and secondary (SII) somatosensory cortex in CLN5, the Finnish variant of late infantile neuronal ceroid lipofuscinoses (NCL).

METHODS

Somatory evoked magnetic fields were recorded with a 122-channel planar gradiometer in response to median nerve stimulation in 5 CLN5 patients (aged 8.8-16.7 years) and in 10 healthy age-matched controls.

RESULTS

The first two responses from contralateral SI, N20m and P35m, were 6-20 times stronger in the patients than in the controls. The morphology of the subsequent deflections from SI was abnormal in the patients: a prominent N45m was detected, while the normally present P60m deflection was missing. In 4 patients the contra- and in two patients the ipsilateral SII responses were also enlarged. Furthermore, the SII activation was detected at shorter latency in patients than in controls.

CONCLUSIONS

At SI, CLN5 is associated with a selective enhancement of the early cortical responses. We propose that the enlargement of N20m most likely reflects increased synchronous input from thalamus, whereas the altered morphology of the following responses may reflect defective interneuronal inhibition at the cortex. The enlargement of SII responses shows that the imbalance between excitation and inhibition in CLN5 extends outside the primary somatosensory areas.

Central auditory processing of durational changes in complex speech patterns by newborns: an event-related brain potential study

In this study, newborns' ability to discriminate durational changes in the fricative /s/ within a nonsense word was investigated. The results showed that infrequent increments and decrements of a speech sound duration elicit a mismatch negativity kind of response in sleeping human newborns. In the auditory event-related potential to these deviant stimuli two negative waves of this response were revealed. The first negative wave peaked at about 150 msec and the second at about 350 msec after the change onset. At least one negative deflection, which was interpreted as evidence for stimulus change-detection, was observed in every infant.

Neuronal ceroid lipofuscinoses in childhood

NCL disorders are progressive brain diseases with an autosomal recessive inheritance in all eleven childhood types. These occur world-wide but may be enriched in some countries. In Finland altogether about 400 patients have been diagnosed during the last forty years. The most common types are the infantile and classic juvenile forms with an incidence of 1: 20,000 and 1: 21,000, respectively Personally followed-up are patients with infantile, classic and Finnish variant late infantile and classic juvenile types. Clinical, neurophysiological and neuroimaging findings in these four NCL forms are reviewed including also management and diagnostic aspects.

Electroencephalography in juvenile neuronal ceroid lipofuscinosis: visual and quantitative analysis

Fourteen patients with a confirmed diagnosis of juvenile neuronal ceroid lipofuscinosis (JNCL) (aged 6-12.5 years at the beginning of the study) were prospectively followed for 5 years. An electroencephalogram (EEG) was recorded and analysed both visually and quantitatively and a neuropsychological examination was performed once a year. In addition, a cross-sectional EEG study of 32 patients aged 5-27 years was performed. The EEG was often normal before the age of 9 years, and thereafter a progressive background abnormality and increase in paroxysmal activity took place. The EEGs were significantly slower than those of the controls, and the speed of slowing of EEG correlated to the decrease in intelligence quotients (IQ). Quantitative analysis was superior to visual analysis in detecting the deterioration of the background activity. The best parameter describing this was the fast/slow ratio. Peak frequency, percentage of theta and the fast/slow ratio correlated with IQ.

Initial differentiation of the metanephric mesenchyme is independent of WT1 and the ureteric bud

The early development of the metanephric kidney is characterized by the induced differentiation of mesenchymal cells into a stem cell population that undergoes a mesenchymal to epithelial transformation in response to stimuli from the ureteric bud. The Wilms' tumor suppressor gene, Wt1, is required for mesenchymal cells to complete this developmental program. In the absence of WT1, a prospective metanephric mesenchyme appears, but becomes apoptotic, and outgrowth of the ureteric bud from the Wolffian duct does not occur. Therefore, the examination of Wt1 -/- embryos allows the determination of those markers of early metanephric differentiation that do not require the ureteric bud or WT1 for their expression. Here, we demonstrate that several markers, including Pax-2, Six-2, and GDNF, were present as RNAs in the metanephric mesenchyme of Wt1 -/- embryos. These findings demonstrate that the metanephric mesenchyme in mutant embryos has begun to differentiate towards the nephrogenic lineage, and that this early differentiation does not require either WT1 or the presence of the ureteric bud. To determine whether WT1 functions other than to induce expression of factors that stimulate ureteric bud outgrowth, Wt1 -/- metanephric mesenchymes were recombined with wild-type ureteric buds in organ culture, but this failed to rescue tubulogenesis. However, the Wolffian duct from Wt1 -/- embryos was a competent inducer of wild-type metanephric mesenchyme.

Sleep alterations in juvenile neuronal ceroid-lipofuscinosis

In juvenile neuronal ceroid-lipofuscinosis (JNCL), sleep disorders are common. The purpose of this study was to investigate the sleep structure of 28 patients with JNCL compared with healthy controls subjects and to clarify the pathophysiology underlying the sleep disturbances in these patients. Each of 28 patients with JNCL (age range = 6-27 years), with or without sleep complaints, underwent one night of polysomnography. Electroencephalographic, electro-oculographic, electromyographic, and electrocardiographic findings were recorded. Sleep was scored and analyzed visually. The sleep parameters of the patients were compared with those of healthy control subjects. In most of the patients, the total sleep time, sleep efficiency, and percentages of rapid eye movement (REM) and non-REM (NREM) stage 2 sleep were significantly decreased, and the percentages of NREM stage 1 and slow-wave sleep and the number of nocturnal awakenings significantly increased. The percentage of NREM stage 1 and the number of awakenings increased with age and clinical stage. Paroxysmal epileptiform activity during light sleep (NREM stages 1-2) and high-amplitude delta-wave activity with intermingled sharp waves during slow-wave sleep were characteristic of the recordings. The present study revealed that in patients with JNCL, sleep is consistently altered.

Regulation of cell fate decision of undifferentiated spermatogonia by GDNF

The molecular control of self-renewal and differentiation of stem cells has remained enigmatic. Transgenic loss-of-function and overexpression models now show that the dosage of glial cell line-derived neurotrophic factor (GDNF), produced by Sertoli cells, regulates cell fate decisions of undifferentiated spermatogonial cells that include the stem cells for spermatogenesis. Gene-targeted mice with one GDNF-null allele show depletion of stem cell reserves, whereas mice overexpressing GDNF show accumulation of undifferentiated spermatogonia. They are unable to respond properly to differentiation signals and undergo apoptosis upon retinoic acid treatment. Nonmetastatic testicular tumors are regularly formed in older GDNF-overexpressing mice. Thus, GDNF contributes to paracrine regulation of spermatogonial self-renewal and differentiation.

BMP-4 affects the differentiation of metanephric mesenchyme and reveals an early anterior-posterior axis of the embryonic kidney

Bone morphogenetic protein-4 (BMP4), a member of the transforming growth factor-beta (TGF-beta) family, regulates several developmental processes during animal development. We have now studied the effects of BMP-4 in the metanephric kidney differentiation by using organ culture technique. Human recombinant BMP-4 diminishes the number of ureteric branches and changes the branching pattern. Our data suggest that BMP-4 affects the ureteric branching indirectly via interfering with the differentiation of the nephrogenic mesenchyme. The clear positional preference of the defects to posterior mesenchyme might reflect an early anterior-posterior patterning of the metanephric mesenchyme. The smooth muscle alpha-actin expressing cell population around the ureteric stalk, highly expressing Bmp-4 mRNA, is also expanded in kidneys treated with BMP-4. Thus, BMP-4 may be a physiological regulator of the development of the periureteric smooth muscle layer and ureteric elongation.

Mesonephric kidney--a stem cell factory?

Mesonephros is a vestige, transient renal organ that functions only during embryonic development. The anatomy, position and even cellular fate of the mesonephric kidney varies drastically among mammalian species. The origin of mesonephros from intermediate mesoderm and the dependence of its differentiation on the nephric or Wolffian duct have been well established. Commonly accepted is also the mesonephric origin of epididymal ducts of the male reproductive tract. Recently, upon the more profound understanding of the molecular mechanisms involved in the development of the permanent mammalian kidney, some light has been shed over the molecular events taking place during the mesonephric development as well. Because of the functional and structural similarities between the mesonephric and metanephric kidneys, it is not surprising that many molecules regulating metanephric development are also activated during mesonephric development. However, the multifunctional nature of mesonephros has been unexpected. First, it serves as an embryonic secretory organ, in some mammalian species more so than in others. It is thereafter removed by programmed cell death. Second, it is a source of multiple stem cells including somatic cells in the male gonad, vascular endothelial cells, and hematopoietic stem cells. Thus, mesonephros is a challenging model for studies on epithelial differentiation and organogenesis, regulation of apoptosis, sex determination and stem cell differentiation. In this review, we focus in the molecular and stem cell aspects in the differentiation of the mammalian mesonephros.

Cell lineages in the embryonic kidney: their inductive interactions and signalling molecules

The first signalling genes acting in the inductive interactions in the kidney have now been identified. Differentiation of the permanent kidney or the metanephros is critically dependent on inductive signalling between the nephrogenic mesenchyme and ureteric bud epithelium. Further inductive interactions occur between developing nephrons, interstitial stroma, endothelial cells and neurones. Glial-cell-line-derived neurotrophic factor is a signal for the ureteric bud initiation and branching, and Wnt4 is an autocrine epithelializing signal at the pretubular stage of nephron formation. The signals for renal angiogenesis and innervation are less well defined, but seem to include vascular endothelial growth factor and neurotrophins, at least. The ureteric-bud-derived signal for induction of the nephrogenic mesenchyme (to bring the cells to the condensate stage) is not yet known, but fibroblast growth factor 2 is a good candidate. None of the signalling genes identified from the embryonic kidney is specific to the organ, which raises some general questions. How do the organs develop from similar rudiments to various patterns with different cell types and functions? Does the information for organ-specific differentiation pathways retain in the epithelial or mesenchymal compartment? The present, rather fragmentary molecular data would favour the view that similar molecules acting in different combinations and developmental sequences, rather than few organ-specific master genes, could be responsible for the divergence of patterning.

Melatonin ineffective in neuronal ceroid lipofuscinosis patients with fragmented or normal motor activity rhythms recorded by wrist actigraphy

Melatonin was tested as a sleeping pill in five patients with neuronal ceroid lipofuscinoses. The single-blind, placebo-controlled study consisted of motor activity recordings, sleep logs, and administration of placebo or melatonin (2.5 or 5 mg). Daily motor activity rhythms were measured by wrist actigraphy during four 7-day periods (baseline, placebo, melatonin 2.5 mg, and melatonin 5 mg). The placebo or melatonin was administered in the evenings for 3 weeks, and the recordings were made during the last week of the 3-week treatment. Sleep logs were kept by the caregivers during the recordings. Based on period analyses, the activity recordings were evaluated to display a normal (24-h) or fragmented rhythm. Three patients had normal motor activity patterns during the baseline recordings, and administration of placebo or melatonin did not affect their rest/activity rhythms. Two patients had abnormally fragmented activity rhythms during the baseline periods, and administration of placebo or melatonin did not induce synchronization. According to the actigraphic data, there were no changes in activity rhythms resulting from administration of melatonin. However, based on the observations, three families reported that melatonin slightly improved the sleep quality of the patients. These controversial findings show the difficulties involved in specifying the role of melatonin in modulating sleep. Thus, we conclude that more evidence is required before the significance of melatonin as a sleeping pill is defined.

Distribution of glial cell line-derived neurotrophic factor mRNA in human colon suggests roles for muscularis mucosae in innervation

BACKGROUND/PURPOSE

Glial cell line-derived neurotrophic factor (GDNF) is a ligand for the receptor complex of GDNF family receptor alphas (GFRalphas) and Ret receptor tyrosine kinase, the product of a known Hirschsprung's disease gene. The aim of this study was to analyze the mRNA distribution of these genes in the developing human intestine to understand their roles in enteric innervation.

METHODS

Cryosections of fetal and newborn stomach, ileum, and colon were hybridized in situ with S35-labeled cRNA probes to GDNF, Ret, GFRalpha-1 or GFRalpha-2. GDNF mRNA levels in fetal ileum and colon were compared by reverse transcription-polymerase chain reaction (PCR).

RESULTS

GDNF mRNA expression was abundant in the muscularis mucosae of both fetal and newborn colon but was found neither in the neural plexuses nor in other regions of the intestine. Accordingly, by reverse transcription-PCR, GDNF mRNA level was many times higher in colon than ileum. Ret, GFRalpha-1 and GFRalpha-2 mRNA were expressed in the ganglionic cells of both myenteric and submucosal plexuses throughout the intestine.

CONCLUSIONS

The highly restricted distribution of GNDF mRNA suggests an important role for muscularis mucosae in the development of human enteric nervous system. Ret, GFRalpha-1, and GFRalpha-2 most likely act as GDNF receptors in colon but may have alternative ligands in other enteric segments.

Maturation of mismatch negativity in infants

The mismatch negativity (MMN) is a pre-attentive change-specific component of the event-related brain potentials (ERPs). During the last decade this response has been intensively studied in adults, but investigations in children and especially in infants are still rare. Recent studies, however, have shown that MMN is also elicited in infants in response to changes in pure tones as well as in phonemes. The present study compared MMN in pre-term infants (conceptional age at the time of recording, 30-35 weeks), full-term newborns and full-term 3-month-old infants. Stimuli were Klatt-synthesized Finnish vowels /y/ and /i/. Previous studies have reported larger MMN amplitudes in school-age children compared with those obtained in adults. According to the results, however, the infant MMN amplitude seems to resemble that of adults. No significant differences in MMN amplitudes were found between the three age groups either. The mean MMN latency, however, decreased significantly with age, although in 3-month-old infants it was not much longer than in a previous study conducted in adults with the same stimuli.

Bright light suppresses melatonin in blind patients with neuronal ceroid-lipofuscinoses

We studied whether light information can reach the pineal glands of clinically blind patients with neuronal ceroid-lipofuscinoses. The suppression of melatonin by light was used as an indicator. Seven patients and seven control subjects were exposed to 3,000-lux light for 60 minutes at the rising phase of the melatonin synthesis. Most patients were not cooperative, and their eyelids were opened by a researcher every 2 minutes for 2 seconds. The control subjects opened and closed their eyes similarly by themselves. Light suppressed melatonin in three of seven control subjects and in all patients. The average postlight levels were 80% (control subjects) and 51% (patients) of the corresponding levels during the dim-light session. Despite degenerated retinas of the blind patients, light can penetrate their visual system to the hypothalamic and pineal levels and regulate neuroendocrine function.

Muscle-eye-brain disease: clinical features, visual evoked potentials and brain imaging in 20 patients

Clinical features, magnetic resonance imaging and visual evoked potentials were analysed and correlated in 20 Finnish patients with muscle-eye-brain disease. Significantly enhanced visual evoked potentials were found in 15 patients (giant in 14 of them). Magnetic resonance images were available in 17 cases. The images of 12 patients with giant visual evoked potentials showed typical brain malformation pachygyria with a nodular cortical surface i.e. cobblestone cortex, midline defect and hypoplastic pons but no significant abnormalities in the grey-white matter. One male had typical structural changes but flat visual evoked potentials. His extreme hydrocephalus with optic nerve compression may explain the findings. No structural changes on magnetic resonance images were found in the remaining four patients; however, in two of them marked alterations in the white matter were found. Three of these patients showed normal and one flat visual evoked potentials. Only one patient with giant visual evoked potentials and typical structural findings on magnetic resonance imaging had changes in a large area in the white matter (several attacks of status epilepticus might have caused the alterations in the white matter). Thus, the combination of giant visual evoked potentials and typical structural changes on magnetic resonance imaging with normal intensities of white matter and deep grey matter seems to be a good marker for patients with muscle-eye-brain disease.

The tip-top branching ureter

Organ rudiments with their epithelial bud and adjacent mesenchyme look much the same at their initial stage of differentiation. The subsequent branching of the epithelial anlagen determines the final pattern of the organs, but the mesenchyme provides essential signals for epithelial differentiation. Glial cell line derived neurotrophic factor (GDNF) has recently been shown to regulate ureteric branching morphogenesis and is thereby the first defined signalling molecule in the embryonic metanephric kidney. GDNF is expressed by the mesenchyme, binds to the tip of the ureteric bud and functions in both bud induction and bud orientation. The active receptor complex for GDNF includes the receptor tyrosine kinase Ret and a novel class of glycosylphosphatidylinositol-linked receptors, called GDNF family receptor alpha s.

Are non-heart-beating donors really dead?

Brain dead patients are ideal donors for organ transplantation. The lack of organs has aroused new interest in other kinds of patients who are called non-heart-beating donors. In these donors the warm ischaemia time should be as short as possible. This problem has led to a discrepancy between a proper diagnosis of death and a fast organ procurement. In non-heart-beating donor protocols the death should be determined in an unambiguous manner that can also be accepted in other situations. The best solution would be to create one set of criteria of death that can be applied to all situations. Brain death as the criterion of death also in patients with asystole would serve this purpose.

Glial-cell-line-derived neurotrophic factor is required for bud initiation from ureteric epithelium

The shapes of different organs can be explained largely by two fundamental characteristics of their epithelial rudiments - the pattern of branching and the rate of proliferation. Glial-cell-line-derived neurotrophic factor (GDNF) has recently been implicated in the development of metanephric ureteric epithelium (Pichel, J. G., Shen, L., Sheng, H. Z., Granholm, A.-C., Drago, J., Grinberg, A., Lee, E. J., Huang, S. P., Saarma, M., Hoffer, B.J., Sariola, H. and Westphal, H. (1996). Nature 382, 73–76; Sanchez, M.P., Silos-Santiago, I., Frisen, J., He, B., Lira, S.A. and Barbacid, M. (1996). Nature 382, 70–73; Vega, Q.C., Worby, C.A., Lechner, M.S., Dixon, J.E. and Dressler, G.R. (1996). Proc. Nat. Acad. Sci. USA 93, 10657–10661). We have analysed the target cells of GDNF and the manner in which it controls ureteric development, and have compared it with other growth factors that have been associated with the regulation of branching morphogenesis, namely hepatocyte growth factor (HGF) and transforming growth factor-beta1 (TGFbeta1). We show that GDNF binds directly to the tips of ureteric bud branches, and that it has the ability to promote primary ureteric buds from various segments of Wolffian duct and to attract ureteric branches towards the source of GDNF. It increases cell adhesion, but is not obviously mitogenic for ureteric cells. The data indicate that GDNF is required primarily for bud initiation. Comparison of GDNF, HGF and TGFbeta1 suggests that the latter act later than GDNF, and may represent a partially redundant set of mesenchyme-derived growth factors that control ureteric development. Thus, GDNF is the first defined inducer in the embryonic metanephric kidney.

Neurotrophin mRNA expression in the developing tooth suggests multiple roles in innervation and organogenesis

To analyze the roles of neurotrophins during early development of rat teeth, we studied the expression of neurotrophin mRNAs from the initiation of first molar formation to the completion of crown morphogenesis. With RNAase protection assay all neurotrophin mRNAs were detected in embryonic teeth. In situ hybridization analysis revealed developmentally changing, distinct expression patterns for nerve growth factor (NGF) and neurotrophin-3 (NT-3), which were shown not to be regulated by or dependent on peripheral innervation. NGF mRNAs appeared in the mesenchymal target field of the tooth at the time of the trigeminal axon ingrowth (embryonic days 14-15: E14-E15), and they were also present along the pathway taken by growing trigeminal axons. NT-4/5 mRNAs were uniformly expressed in all epithelial cells, but brain-derived neurotrophic factor (BDNF) transcripts were not detected. All neurotrophins induced neurite outgrowth from E13-E16 trigeminal ganglion explants. These results suggest that NGF is involved in the guidance of trigeminal axons to embryonic teeth. In postnatal teeth, expression of NGF mRNAs, but not other neurotrophins, correlated with trigeminal axon ingrowth, proposing that NGF is involved in local sprouting and establishment of the final innervation pattern of the dental papilla and dentin. These results suggest that NGF is required for tooth innervation and that other neurotrophins may also have regulatory roles. In addition, the expression patterns of NGF, NT-3, and NT-4/5 as well as of neurotrophin receptors suggest that the neurotrophin system may also serve non-neuronal functions during tooth development.

Somatosensory evoked magnetic fields from primary sensorimotor cortex in juvenile neuronal ceroid lipofuscinosis

The present study evaluated neurophysiologic function of the primary sensorimotor cortex in juvenile neuronal ceroid lipofuscinosis. A 122-channel magnetometer, which allowed studies of the somatosensory system in millimeter and millisecond precision, was used to record somatosensory evoked magnetic fields to median nerve stimulation from 10 patients and their matched control subjects. In both patients and controls, the somatosensory evoked magnetic fields from primary sensorimotor area typically consisted of N20m, P35m, and P60m deflections. In the patients, N20m was significantly delayed, whereas P35m peaked earlier than in the control subjects. The source strengths for N20m and P35m were greater in the patients than in the controls. Both deflections showed a significant positive correlation with the disease duration: the sources were stronger in the older patients than in the younger ones. P60m deflections were normal or reduced in the patients. The results indicated increased thalamocortical excitability in the sensorimotor cortex in juvenile neuronal ceroid lipofuscinosis.

EEG and evoked potentials in infantile neuronal ceroid-lipofuscinosis

Sixteen children with infantile neuronal ceroid-lipofuscinosis (INCL), age range 0.5 to 5.4 years, were studied using EEG, electroretinograms (ERG), visual evoked potentials (VEP) and somatosensory evoked potentials (SEP). Electroencephalography was the first of these examinations to reveal abnormalities, however the EEG may be normal at the preclinical stage. The first abnormality to appear was an attenuated reaction to passive eye opening and closing which was followed by disturbances in background activity and diminution in amplitude, and by disappearance of sleep spindles. The gradual disappearance of posterior rhythm reactivity and of sleep spindles suggests that thalamic dysfunction progresses with time. EEG inactivity appeared by the age of 3 years. Evoked potentials were normal in the early stages of the disease. SEP showed abnormalities at Stage 2 (1.7 years), while ERG and VEP abnormalities appeared at Stage 3 (by the age of 2.5 years). All neurophysiological reactions examined were abolished by the age of 4 years. Follow-up EEG gives important hints as to the early diagnosis of INCL. Progression of the disease can be followed by evoked potentials which may also be helpful in the differential diagnostics.

Arthrogryposis multiplex congenita: perinatal and electromyographic findings, disability, and psychosocial outcome

Fifty-two patients with arthrogryposis multiplex congenita were followed up for 1 to 36 years. There were six twin pregnancies, and delivery was complicated by breech position in 16 cases. In 19 cases the cause was atrophy of the alpha motoneurons of the spinal cord, detected by electromyography. Six patients did not achieve walking ability. Severe disability for other reasons was noted in two patients who had bilateral rigid extension contractures of the elbows and in six patients whose spinal deformities interfered with the balance of the trunk. Treatment of flexion contractures of the hips and knees seemed to be important in case it promotes the walking ability. Spinal deformities interfering with the balance of the trunk should be treated operatively. Restoration of elbow flexion was the main goal in operative treatment of the upper extremities. The intelligence of the patients was slightly above normal. The psychological analysis revealed significant diverging features compared with average population in testing situation. Socially the patients seemed to cope well.

Localization of nerve cells in the developing rat tooth

Earlier studies have shown that mammalian tooth formation can take place in the absence of peripheral nerve fibers. This has been taken to indicate that neurons are not needed for mammalian tooth development. However, our recent localization of peripherin, which is a neuronal cell marker, has suggested that neuronal cell bodies may be associated with developing teeth. In this study, we have analyzed in vivo and in vitro the presence of neuronal cells in developing rat tooth germs. When E14 and E16 rat first molars (thickening of presumptive dental epithelium and bud-stage tooth germ, respectively) were cultured in vitro, peripheral trigeminal axons degenerated. However, with antibodies against peripherin and L1 neural cell adhesion protein, we detected neuronal cell bodies and their axons in the explants. Next, the expression of neurofilament light-chain (NF-L) mRNAs was studied by in situ hybridization of embryonic E12 first branchial arches and tooth germs from initiation to completion of crown morphogenesis (E13, five-day post-natal teeth). NF-L transcripts were first seen at the bud stage (E15) next to the dental epithelium at the buccal side of the tooth germ. At the cap stage (E18), NF-L mRNAs were located under the oral epithelium at some distance from dental epithelium. These expression patterns correlate to the previous localization of peripherin-positive cells and suggest that NF-L expression also revealed neuronal cells. Taken together, these results demonstrate that, in addition to projections of peripheral neurons, neuronal cells are associated with the developing teeth. Hence, it is possible that neuronal cells may participate in the regulation of mammalian tooth formation.

Differential regulation of two sets of mesonephric tubules by WT-1

Mammalian renal development undergoes two transient stages, the pronephros and the mesonephros. While the regulation of metanephric differentiation has received considerable attention, very little is known about the mode of differentiation of the mesonephros and its regulation. We have followed mesonephric differentiation to unravel the developmental mechanisms and fates of mesonephric tubules by whole-mount immunohistology using antibodies to laminin, brush border epitopes, cytokeratin-8/18, p75 neurotrophin receptor and some other renal antigens as markers. In rat and mouse embryos, two distinct sets of tubules were observed throughout mesonephric development. Four to six pairs of cranial mesonephric tubules developed as outgrowths from the Wolffian duct. The majority of tubules were caudal tubules which never fused with the Wolffian and differentiated similarly to metanephric nephrons. The murine mesonephric tubules degenerate by apoptosis, except in males where the cranial tubules become the epididymal ducts. These developmental differences between the cranial and caudal sets of tubules suggested different regulatory systems for each. Targeted disruption of the Wilms' tumour gene product, WT-1, results in renal aplasia, and a reduction in the number of mesonephric tubules (Kreidberg, J. A., Sariola, H., Loring, J., Maeda, M., Pelletier, J., Housman, D. and Jaenisch, R. (1993). Cell 74, 679–691). We therefore analysed more closely mesonephric differentiation in WT-1-deficient mice, and showed that they only develop the cranial mesonephric tubules but not the caudal ones. Thus, WT-1 appears to regulate only the development of the caudal mesonephric tubules that conceivably are formed from mesenchymal cells like the metanephric tubules. WT-1 therefore seems to be necessary for the mesenchyme to epithelium transitions at different stages of nephrogenesis.

Brain perfusion SPECT and EEG findings in Rett syndrome

Thirteen patients (mean age 8.4 + 5.3 years) with Rett syndrome (RS) were studied with EEG and 99mTc-HMPAO SPECT. Eleven patients had background abnormalities and 10 patients paroxysmal activity in EEG. Hypoperfusion of varying severity was detected in 11 patients, 7 patients having multiple lesions. Bifrontal hypoperfusion, observed in 6 patients, was the most distinctive finding. Hypoperfusion was observed also in other cortical regions, except for the occipital lobes. There was no correlation between severity of the background abnormality or presence of paroxysmal activity in EEG and grade of hypoperfusion. There was, however, an association between the severity of hypoperfusion and early manifestation of symptoms in patients with RS. Whether this early-onset group of patients represents a different disease entity or only reflects disease variability the basic pathology being the same, is a possibility that deserves further clarification.

The ontogenetically earliest discriminative response of the human brain

Speech sounds elicited electric brain responses in healthy premature infants born 30-35 weeks after conception, demonstrating that the human brain is able to discriminate speech sounds even at this early age, well before term, and supporting previous results suggesting that the human fetus may learn to discriminate sounds while still in the womb. We presented preterm infants with stimulus sequences consisting of a repetitive vowel that was occasionally replaced by a different vowel. This infrequent vowel elicited a response resembling the adult mismatch negativity, which is known to reflect the brain's automatic detection of stimulus change. The present results constitute the ontogenetically earliest discriminative response of the human brain ever recorded.

Expression of neurotrophin receptors during rat tooth development is developmentally regulated, independent of innervation, and suggests functions in the regulation of morphogenesis and innervation

Low-affinity neurotrophin receptor (LANR) and trk receptor tyrosine kinases (trks) serve as low- and high-affinity receptors for neurotrophins. Besides promoting the development and maintenance of the mammalian nervous system, it has been suggested that neurotrophins may have broader functions in the development of non-neuronal tissues. To evaluate the possible roles of neurotrophic factors in tooth development, we performed a detailed examination of the expression patterns of neurotrophin receptors during development of the rat tooth from initiation to completion of crown morphogenesis. mRNA expression was studied by in situ hybridisation and LANR protein was localised by immunohistochemistry. Furthermore, dissected tooth germs were cultured in vitro to examined the role of trigeminal innervation in the expression of neurotrophin receptors. mRNAs for LANR, trkB, and trkC, but not trkA, were detected in developing teeth. LANR and the truncated form of trkB, which lacks the intracellular tyrosine kinase domain, were expressed throughout tooth morphogenesis and their expression patterns were largely non-overlapping and changed spatio-temporally. trkC was expressed after birth, and it was restricted to dental papilla mesenchyme. The expression of all receptors correlated with the development of innervation, but, in addition, the expression of LANR and trkB appeared to be associated with cell differentiation and epithelial-mesenchymal interactions. The patterns of LANR, trkB, and trkC in teeth which underwent morphogenesis in organ culture were similar to those in vivo, which indicates that the expression of these neurotrophin receptors is not regulated by and does not depend on trigeminal innervation. The data suggest that neurotrophin receptors have roles in the development of tooth innervation, but that they also have non-neuronal, organogenetic functions.

Brain perfusion SPECT in infantile neuronal ceroid-lipofuscinosis (INCL). Comparison with clinical manifestations and MRI findings

We studied brain perfusion in 19 patients with infantile neuronal ceroid-lipofuscinosis (INCL), aged 13 months to 11 years, using 99mTc-HMPAO single photon emission computed tomography (SPECT). SPECT findings were compared with clinical manifestations and MRI findings. The typical SPECT findings at an early stage of INCL were bilateral anterior frontal, posterior temporoparietal and occipital hypoperfusion. Initially cerebral hypoperfusion was localized and symmetrical, whereas atrophic findings were more generalized. Reduction in cerebellar perfusion appeared later, as did cerebellar atrophy. Progression from mild to severe cerebral and cerebellar hypoperfusion was rapid, corresponding to the clinical progression. However, the perfusion of deep grey matter structures (basal ganglia and thalami), although atrophic on MRI, was often well preserved up to the terminal stage. Severe perfusion defects in INCL, which appeared approximately at the age of four, were associated with grave clinical manifestations and neuropathologic findings. Particularly, the early SPECT perfusion abnormalities may assist in the differential diagnosis between INCL and other neurode-generative diseases.

Localization of glial cell line-derived neurotrophic factor (GDNF) mRNA in embryonic rat by in situ hybridization

The localization of glial cell line-derived neurotrophic factor (GDNF) mRNA was studied by in situ hybridization in rat from embryonic (E) day E10 to E15. At E10, GDNF mRNA is found in the urogenital field and the cranial part of the gut. At E11, the most abundant expression of GDNF mRNA is seen in the epithelial cells of the second, third and fourth pharyngeal pouches, the third and fourth pharyngeal arches and pharynx. Also mesenchymal cells of the gut and mesonephric tubules contain GDNF mRNA. At E13, expression is observed in the mesenchymal cell layers of the oesophagus, intestine and stomach, the mesenchymal cells around the condensing cartilages and metanephric kidney mesenchyme. Also, the epithelia of Rathke's pouch and pharynx are intensely labelled. High expression of GDNF mRNA continues at E15 in kidney, gastrointestinal tract and cartilage. At that stage, GDNF mRNA is seen also in whisker pad and skeletal muscles. The distribution of GDNF mRNA in embryonic rat suggests important roles for GDNF in the early differentiation of the kidney tubules, the innervation of the gastrointestinal tract and the differentiation process of the cartilage and muscle. Our results indicate novel functions for GDNF outside the nervous system.

Structure of the human laminin gamma 2 chain gene (LAMC2): alternative splicing with different tissue distribution of two transcripts

We have determined the structure of the human laminin gamma 2 chain gene (LAMC2), which is mutated in some patients with junctional epidermolysis bullosa. Eight lambda phage clones isolated from a genomic library and three subgenomic lambda phage clones made from a plasmid artificial chromosome clone spanned 75 kb, including the 55-kb gene. The LAMC2 gene contains 23 exons and is structurally highly homologous with the 28-exon LAMC1 gene (Kallunki et al., 1991, J. Biol. Chem. 266: 221-228), with 16 exons having identical sizes in the two genes. The gene analysis demonstrated that two previously described different size gamma 2 chain cDNAs (Kallunki et al., 1992, J. Cell Biol. 119: 679-693) are the result of alternative splicing. The longer gamma 2 chain is formed by using the coding sequence of the last exon 23, while the shorter gamma 2* chain is formed by using only 22 exons, together with part of the 5' end of intron 22. The two mRNAs were shown to have different expression patterns in 17-week-old human embryonic tissues, with the longer gamma 2 chain transcript strongly expressed in epithelia of all tissues studied, while distinct expression of the shorter gamma 2* chain mRNA was observed only in the cerebral cortex, in lung, and in distal tubules of the kidney.

Neurotrophin 3 rescues neuronal precursors from apoptosis and promotes neuronal differentiation in the embryonic metanephric kidney

We analyzed the developmental regulation and role of the neurotrophins during metanephric kidney morphogenesis. RNase protection assay revealed the presence of nerve growth factor, neurotrophin 3 (NT-3), and brain-derived neurotrophic factor mRNAs and the regulation of their expression during embryonic development of rat metanephros. NT-3 induced differentiation (neurite outgrowth) and survival (inhibition of apoptosis) of the neuronal precursors in cultured nephrogenic mesenchymes and neuronal differentiation in cultured whole kidneys, whereas NT-4/5, brain-derived neurotrophic factor, and nerve growth factor were without effect. The neurotrophins did not trigger tubular differentiation of isolated nephrogenic cells, which underwent apoptosis when cultured with or without the neurotrophins. NT-3 is thus an inducer of differentiation and a survival factor for renal neuronal cells, but none of the neurotrophins is a morphogen in kidney tubule induction.

Primary structure and expression of a novel human laminin alpha 4 chain

The complete primary structure of a novel human laminin alpha 4 chain was derived from cDNA clones. The translation product contains a 24-residue signal peptide preceding the mature alpha 4 chain of 1792 residues. The domain structure is similar to that of the recently described alpha 3 chain [Ryan, Tizard, Van Devanter and Carter (1994) J. Biol. Chem. 269, 22779-22787]. Northern analysis of RNA from human fetal and adult tissues revealed developmental regulation of expression. In adult, strong expression was observed in heart as well as lung, ovary, small and large intestines, placenta and liver, whereas weak or no expression was detected in skeletal muscle, kidney, pancreas, testis, prostate or brain. In contrast, fetal lung and kidney revealed high expression. In situ hybridization analysis of human fetal and newborn tissues showed expression of the laminin in alpha 4 chain in certain mesenchymal cells in tissues such as smooth muscle and dermis.

The glomerular mesangium: studies of its developmental origin and markers in vivo and in vitro

Cultured mesangial cells are widely used to explore their role in kidney glomerular functions, but methods to reliably identify these cells in vivo and in vitro are lacking. Furthermore, the proposed relationship of mesangial cells to e.g. fibroblasts and smooth muscle cells has not been systematically studied. Here we wanted to search for markers of practical use also in identifying cultured mesangial cells, and to apply these markers in a study of the origin of glomerular mesangium. No epitopes specific for only mesangial cells could be identified, and no evidence of their true relationship with neural or lymphocytic lineages could be found. Findings with the variety of markers used suggest that mesangial cells may be indistinguishable from smooth muscle cells and fibroblasts. A panel of antibodies, including those against Thy1.1, smooth muscle actin, desmin, cellular fibronectin and beta 1 integrin alpha 1 and alpha 5 chains, and Wistaria floribunda (WFA) and Ricinus communis (RCA I) lectins, were found useful for mesangial cell detection in vivo and in vitro. The origin of glomerular mesangial cells could not be conclusively determined, although the results indirectly suggest that mesangial cells together with endothelial cells migrate to the glomerulus from the outside.

Activin disrupts epithelial branching morphogenesis in developing glandular organs of the mouse

We report that activin profoundly alters epithelial branching morphogenesis of embryonic mouse salivary gland, pancreas and kidney rudiments in culture, indicating that it may play a role as a morphogen during mammalian organogenesis. In developing pancreas and salivary gland rudiments, activin causes severe disruption of normal lobulation patterns of the epithelium whereas follistatin, an activin-binding protein, counteracts the effect of activin. In the kidney, activin delays branching of the ureter bud and reduces the number of secondary branches. TGF-beta induces a pattern of aberrant branching in the ureter bud derived epithelium distinct from that seen for activin. Reverse-transcriptase polymerase chain reaction, Northern hybridization and in situ hybridization analyses indicate that these developing tissues express the mRNA transcripts for activin subunits, follistatin or activin receptors. Our results are suggestive of a potential role for the activin-follistatin system as an intrinsic regulator of epithelial branching morphogenesis during mammalian organogenesis.

The human laminin beta 2 chain (S-laminin): structure, expression in fetal tissues and chromosomal assignment of the LAMB2 gene

The sequence of the human laminin beta 2 chain (previously s-laminin) was derived from cloned cDNAs. The complete translation product has 1798 amino acid residues, including a 32-residue signal peptide. The human chain lacks the tripeptide sequence LRE in domain I which is present in the rat polypeptide chain and has been shown to promote motor neuronal cell adhesion. The human gene (LAMB2) was localized to chromosome 3p21 using somatic cell hybrids and fluorescent in situ hybridization analysis. Northern and in situ hybridization analyses from numerous fetal tissues revealed that the beta 2 chain is generally widely expressed. beta 2, but not beta 1, was shown by in situ hybridization to be expressed in fetal brain and renal glomeruli. In fetal skin, beta 2 was expressed both in epidermal and dermal cells, while beta 1 was expressed only in the dermis. Expression of beta 2 in fetal liver was seen in hepatocytes, while no signals were observed for beta 1. In lung, both beta 1 and beta 2 were expressed in alveoli and bronchial smooth muscle cells, whereas only the beta 2 chain was expressed in bronchial epithelial cells. In striated muscle, however, the beta 1 chain, but not beta 2, was expressed. These results indicate different biological roles for the laminin beta 1 and beta 2 chains.

Mismatch negativity indicates vowel discrimination in newborns

The present study shows that an infrequent vowel ('deviant') presented among frequent vowels ('standard') elicits in sleeping human newborns a negativity in the auditory event-related potential (ERP) resembling the mismatch negativity (MMN) recorded in adults. Thus, the MMN appears to provide means to investigate brain mechanisms of vowel perception in infants.

Ocular findings in muscle-eye-brain (MEB) disease: a follow-up study

We present ocular findings of 20 patients with the recessively inherited muscle-eye-brain (MEB) disease, characterised by severe visual failure, mental retardation, a pachygyria-polymicrogyria type neuronal migration disorder and congenital muscular dystrophy. The ocular findings consisted of myopia ranging from -6 to -27 D, retinal degeneration and optic atrophy. Five infants had congenital glaucoma, and juvenile cataracts developed in 9 children. The visual evoked potentials were abnormally high (> 50 microV) and delayed in 70% of patients. The electroretinogram was abolished in 12 patients. The changes were progressive during the follow-up time, which was up to 20 years.

Antisense inhibition of low-affinity nerve growth factor receptor in kidney cultures: power and pitfalls

1. Antisense inhibition of gene expression implies that the expression of the target protein is selectively inhibited at either the translational or the transcriptional level by complementary DNA or RNA constructs that are antiparallel to the target sequence. The antisense inhibition strategy provides means to study the roles of individual proteins and has, in spite of its limitations, gained a wide range of both therapeutic and experimental applications. 2. In developmental biology, protein expression has been selectively inhibited by the use of antisense gene transfection and by antisense deoxyoligonucleotides. The transfectability of embryonic tissues is variable, but in general fetal and embryonic cells take up foreign DNA relatively efficiently, in particular, short deoxyoligonucleotides that penetrate mesenchymal cells within a few hours without any manipulation. 3. We have now evaluated the advantages and pitfalls of antisense inhibition by deoxyoligonucleotides in organ culture and describe our experience from the inhibition of low-affinity nerve growth factor receptor expression in embryonic mouse and rat kidneys. 4. The expression of nerve growth factor receptor can be specifically inhibited by deoxyoligonucleotides, but the target sequence-dependent window of, in particular, phosphorothioate-modified oligonucleotides is quite narrow. The culture conditions affect the response to the oligonucleotides and their cellular incorporation is variable with respect to the cell type and stage of differentiation.

Neurotrophins and ciliary neurotrophic factor: their biology and pathology

Neurotrophins (NTFs) and ciliary neurotrophic factor (CNTF) induce the differentiation of neuronal cells, rescue them from naturally occurring death, and trigger neuronal regeneration. The NTFs bind to two classes of cell surface receptors, whereas CNTF receptor is composed of three subunits. The functions of these polypeptide survival factors with trophic action on nerve cells have recently been approached by the targeted disruption of the CNTF, NTF and their receptor genes by the homologous recombination technique. The embryonic growth and morphogenesis of these gene 'knock-out' mice is normal, but they develop with defects in various subsets of the peripheral nervous system, and the homozygous mutant mice often die during the early postnatal period. Disturbances in the biology of NTFs and CNTF have recently been implicated in the pathogenesis of certain common neurodegenerative disorders, such as Parkinson's disease, motor neurone diseases, and Alzheimer's disease. Intensive research on their pharmaceutical perspective has, therefore, been provoked. All neurotrophins and CNTF can now be synthesized on a large scale as biologically active recombinant proteins, and several alternatives for their local applications to the target tissue have been presented. Their therapeutic potential is discussed.

Sensory neuropathy in infantile onset spinocerebellar ataxia (IOSCA)

Infantile onset spinocerebellar ataxia with sensory neuropathy is a new, inherited multisystem disorder discovered in 19 Finnish patients. In order to define the neuropathy of the disease, we measured sensory nerve action potentials and nerve conduction velocities in 18 patients, and recorded somatosensory evoked potentials (SEP) in 10 patients and performed a sural nerve biopsy in 13 patients. The fixed and teased nerve fascicles were examined by light and electron microscopy, and the whole transverse section of a nerve fascicle was photographed and enlarged for morphometric measurements. Our investigation revealed an early onset, rapidly progressive axonal neuropathy: the sensory action potentials were decreased after the age of 2 and a severe loss of mainly large myelinated fibers was found.