Assessing the quality and value of metabolic chart data for capturing core outcomes for pediatric medium-chain acyl-CoA dehydrogenase (MCAD) deficiency

BACKGROUND

Generating rigorous evidence to inform care for rare diseases requires reliable, sustainable, and longitudinal measurement of priority outcomes. Having developed a core outcome set for pediatric medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, we aimed to assess the feasibility of prospective measurement of these core outcomes during routine metabolic clinic visits.

METHODS

We used existing cohort data abstracted from charts of 124 children diagnosed with MCAD deficiency who participated in a Canadian study which collected data from birth to a maximum of 11 years of age to investigate the frequency of clinic visits and quality of metabolic chart data for selected outcomes. We recorded all opportunities to collect outcomes from the medical chart as a function of visit rate to the metabolic clinic, by treatment centre and by child age. We applied a data quality framework to evaluate data based on completeness, conformance, and plausibility for four core MCAD outcomes: emergency department use, fasting time, metabolic decompensation, and death.

RESULTS

The frequency of metabolic clinic visits decreased with increasing age, from a rate of 2.8 visits per child per year (95% confidence interval, 2.3-3.3) among infants 2 to 6 months, to 1.0 visit per child per year (95% confidence interval, 0.9-1.2) among those ≥ 5 years of age. Rates of emergency department visits followed anticipated trends by child age. Supplemental findings suggested that some emergency visits occur outside of the metabolic care treatment centre but are not captured. Recommended fasting times were updated relatively infrequently in patients' metabolic charts. Episodes of metabolic decompensation were identifiable but required an operational definition based on acute manifestations most commonly recorded in the metabolic chart. Deaths occurred rarely in these patients and quality of mortality data was not evaluated.

CONCLUSIONS

Opportunities to record core outcomes at the metabolic clinic occur at least annually for children with MCAD deficiency. Methods to comprehensively capture emergency care received at outside institutions are needed. To reduce substantial heterogeneous recording of core outcome across treatment centres, improved documentation standards are required for recording of recommended fasting times and a consensus definition for metabolic decompensations needs to be developed and implemented.

A novel pathway of levodopa metabolism by commensal Bifidobacteria

The gold-standard treatment for Parkinson's disease is levodopa (L-DOPA), which is taken orally and absorbed intestinally. L-DOPA must reach the brain intact to exert its clinical effect; peripheral metabolism by host and microbial enzymes is a clinical management issue. The gut microbiota is altered in PD, with one consistent and unexplained observation being an increase in Bifidobacterium abundance among patients. Recently, certain Bifidobacterium species were shown to have the ability to metabolize L-tyrosine, an L-DOPA structural analog. Using both clinical cohort data and in vitro experimentation, we investigated the potential for commensal Bifidobacteria to metabolize this drug. In PD patients, Bifidobacterium abundance was positively correlated with L-DOPA dose and negatively with serum tyrosine concentration. In vitro experiments revealed that certain species, including B. bifidum, B. breve, and B. longum, were able to metabolize this drug via deamination followed by reduction to the compound 3,4-dihydroxyphenyl lactic acid (DHPLA) using existing tyrosine-metabolising genes. DHPLA appears to be a waste product generated during regeneration of NAD +. This metabolism occurs at low levels in rich medium, but is significantly upregulated in nutrient-limited minimal medium. Discovery of this novel metabolism of L-DOPA to DHPLA by a common commensal may help inform medication management in PD.

A Novel Homozygous Mutation Causing Complete TYK2 Deficiency, with Severe Respiratory Viral Infections, EBV-Driven Lymphoma, and Jamestown Canyon Viral Encephalitis

Autosomal recessive tyrosine kinase 2 (TYK2) deficiency is characterized by susceptibility to mycobacterial and viral infections. Here, we report a 4-year-old female with severe respiratory viral infections, EBV-driven Burkitt-like lymphoma, and infection with the neurotropic Jamestown Canyon virus. A novel, homozygous c.745C > T (p.R249*) variant was found in TYK2. The deleterious effects of the TYK2 lesion were confirmed by immunoblotting; by evaluating functional responses to IFN-α/β, IL-10, and IL-23; and by assessing its scaffolding effect on the cell surface expression of cytokine receptor subunits. The effects of the mutation could not be pharmacologically circumvented in vitro, suggesting that alternative modalities, such as hematopoietic stem cell transplantation or gene therapy, may be needed. We characterize the first patient from Canada with a novel homozygous mutation in TYK2.

Expanding the phenotypic and molecular spectrum of NFS1-related disorders that cause functional deficiencies in mitochondrial and cytosolic iron-sulfur cluster containing enzymes

Iron-sulfur cluster proteins are involved in critical functions for gene expression regulation and mitochondrial bioenergetics including the oxidative phosphorylation system. The c.215G>A p.(Arg72Gln) variant in NFS1 has been previously reported to cause infantile mitochondrial complex II and III deficiency. We describe three additional unrelated patients with the same missense variant. Two infants with the same homozygous variant presented with hypotonia, weakness and lactic acidosis, and one patient with compound heterozygous p.(Arg72Gln) and p.(Arg412His) variants presented as a young adult with gastrointestinal symptoms and fatigue. Skeletal muscle biopsy from patients 1 and 3 showed abnormal mitochondrial morphology, and functional analyses demonstrated decreased activity in respiratory chain complex II and variably in complexes I and III. We found decreased mitochondrial and cytosolic aconitase activities but only mildly affected lipoylation of pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase enzymes. Our studies expand the phenotypic spectrum and provide further evidence for the pathogenicity and functional sequelae of NFS1-related disorders with disturbances in both mitochondrial and cytosolic iron-sulfur cluster containing enzymes.

Evaluation of the quality of clinical data collection for a pan-Canadian cohort of children affected by inherited metabolic diseases: lessons learned from the Canadian Inherited Metabolic Diseases Research Network

BACKGROUND

The Canadian Inherited Metabolic Diseases Research Network (CIMDRN) is a pan-Canadian practice-based research network of 14 Hereditary Metabolic Disease Treatment Centres and over 50 investigators. CIMDRN aims to develop evidence to improve health outcomes for children with inherited metabolic diseases (IMD). We describe the development of our clinical data collection platform, discuss our data quality management plan, and present the findings to date from our data quality assessment, highlighting key lessons that can serve as a resource for future clinical research initiatives relating to rare diseases.

METHODS

At participating centres, children born from 2006 to 2015 who were diagnosed with one of 31 targeted IMD were eligible to participate in CIMDRN's clinical research stream. For all participants, we collected a minimum data set that includes information about demographics and diagnosis. For children with five prioritized IMD, we collected longitudinal data including interventions, clinical outcomes, and indicators of disease management. The data quality management plan included: design of user-friendly and intuitive clinical data collection forms; validation measures at point of data entry, designed to minimize data entry errors; regular communications with each CIMDRN site; and routine review of aggregate data.

RESULTS

As of June 2019, CIMDRN has enrolled 798 participants of whom 764 (96%) have complete minimum data set information. Results from our data quality assessment revealed that potential data quality issues were related to interpretation of definitions of some variables, participants who transferred care across institutions, and the organization of information within the patient charts (e.g., neuropsychological test results). Little information was missing regarding disease ascertainment and diagnosis (e.g., ascertainment method - 0% missing).

DISCUSSION

Using several data quality management strategies, we have established a comprehensive clinical database that provides information about care and outcomes for Canadian children affected by IMD. We describe quality issues and lessons for consideration in future clinical research initiatives for rare diseases, including accurately accommodating different clinic workflows and balancing comprehensiveness of data collection with available resources. Integrating data collection within clinical care, leveraging electronic medical records, and implementing core outcome sets will be essential for achieving sustainability.

Variable developmental delays and characteristic facial features-A novel 7p22.3p22.2 microdeletion syndrome?

Isolated 7p22.3p22.2 deletions are rarely described with only two reports in the literature. Most other reported cases either involve a much larger region of the 7p arm or have an additional copy number variation. Here, we report five patients with overlapping microdeletions at 7p22.3p22.2. The patients presented with variable developmental delays, exhibiting relative weaknesses in expressive language skills and relative strengths in gross, and fine motor skills. The most consistent facial features seen in these patients included a broad nasal root, a prominent forehead a prominent glabella and arched eyebrows. Additional variable features amongst the patients included microcephaly, metopic ridging or craniosynostosis, cleft palate, cardiac defects, and mild hypotonia. Although the patients' deletions varied in size, there was a 0.47 Mb region of overlap which contained 7 OMIM genes: EIP3B, CHST12, LFNG, BRAT1, TTYH3, AMZ1, and GNA12. We propose that monosomy of this region represents a novel microdeletion syndrome. We recommend that individuals with 7p22.3p22.2 deletions should receive a developmental assessment and a thorough cardiac exam, with consideration of an echocardiogram, as part of their initial evaluation.

Cloning and identification of differentially expressed transcripts in primary culture of GABAergic neurons

A RNA based arbitrarily primed polymerase chain reaction (RAP-PCR) was used to identify differentially expressed transcripts in primary cultures of cerebral cortical neurons prepared from E16 mouse cerebral cortex. The majority of neurons found in this culture preparation are known to be GABAergic. Different primer combinations were used, and the PCR products were separated on PAGE. Visualization by silver staining revealed a high resolution RNA fingerprint pattern with a total of about 200 transcripts. Six differentially expressed cDNA fragments were recovered, cloned and sequenced. The results of a NCBI database search showed that 6 clones were highly homologous to known genes and expressed sequence tags (ESTs), and that they were either up-regulated or down-regulated during development. Among these clones, Clone 3.1.7 shared 99% sequence homology to mouse Reelin, a neuronal migration and positioning related protein. Clone 4.6.2 shared 91% homology to Rat prepro bone morphogenetic protein-3 mRNA. Clone 6.10.2 had 90% homology to a novel orphan gene of calcium-independent alpha-latrotoxin receptor, which stimulates presynaptic neurotransmitter release. Northern blot analysis confirmed the up-regulated expression profile of Clone 6.10.2 in neuron from Day 2 to 7 during stages of differentiation and development.

Bcl-2, Bcl-x, and Bax expression by immunohistochemistry in inclusion body myositis: a study of 27 cases

CONTEXT

Bcl-2, Bcl-x, and Bax are among the variety of proteins that have been described as being involved in the regulation of apoptotic cell death. Bcl-2 and Bcl-x(L) inhibit apoptosis, and Bax is proapoptotic.

OBJECTIVE

To evaluate the expression of Bcl-2, Bcl-x, and Bax in inclusion body myositis (IBM).Design.-We examined muscle specimens from 27 patients (17 men, 10 women) with IBM to evaluate Bcl-2, Bcl-x, and Bax expression by immunohistochemistry.

RESULTS

Patient ages ranged from 29 to 80 years (mean 62.2 years). All biopsies were marked by endomysial chronic inflammation, muscle fiber necrosis, and regeneration. Rimmed (autophagic) vacuoles were present in all cases. Ragged red fibers were noted in 4 biopsies (15%), and cytochrome oxidase-deficient fibers were found in 10 biopsies (37%). Ultrastructural evidence of intranuclear or cytoplasmic tubulofilamentous inclusions, confirming the diagnosis of IBM, were noted in all cases. Paracrystalline mitochondrial inclusions were seen in 5 biopsies (18.5%). Inflammatory cells stained positively with Bcl-2 in all biopsies, Bax in 26 biopsies (96%), and Bcl-x in 8 biopsies (30%). Degenerating muscle fibers were highlighted with Bax in 24 biopsies (89%), Bcl-2 in 2 biopsies (7%), and Bcl-x in 3 biopsies (11%). Regenerative muscle fibers were noted to stain with Bax in 24 muscles (89%), Bcl-2 in 21 muscles (78%), and Bcl-x in 4 muscles (15%). Rimmed vacuoles were highlighted by Bax in 24 biopsies (89%) and only rarely by Bcl-2 (n = 2, 7%) and Bcl-x (n = 3, 11%). A subsarcolemmal staining pattern was observed in 21 biopsies (78%) with Bax, 6 biopsies (22%) with Bcl-2, and only 1 biopsy (4%) with Bcl-x.

CONCLUSIONS

(1) Bax (proapoptotic) immunostaining highlighted most autophagic vacuoles; (2) subsarcolemmal Bax and Bcl-2 immunoreactivity may be associated with mitochondrial defects that are commonly noted in IBM; (3) Bcl-2 and Bax immunoreactivity were not confined to degenerating muscle fibers and in fact appeared to be expressed more commonly in regenerating fibers, suggesting that their expression may be independent of apoptosis in the setting of IBM.

Ischemia-induced apoptosis in primary cultures of astrocytes

Astrocytes participate in a wide variety of important physiological processes and pathological insults, including ischemia. Information on the mechanism of astroglial injury and death during ischemic insult, however, is scarce. In this study, we investigated the mode of astrocytic cell death using an in vitro ischemic model. Cultured astrocytes exhibited several distinct morphological and biochemical features of apoptosis under ischemia. At 4 h of ischemia, Annexin V staining demonstrated an early commitment of some astrocytes to apoptosis. Condensed nuclei became visible from 4 h and the number increased with ischemic incubation time. Electron microscopy showed compacted and segregated chromatin along the edges of nuclear membranes. The number of TUNEL-positive nuclei and the degree of DNA laddering increased with ischemic incubation. Caspase-3, but not caspase-1, activity was increased in ischemia-injured astrocytes. Swollen mitochondria and vacuoles found in some cells with chromatin condensation indicated that these apoptotic-like cells might die of necrosis. The results imply that astrocytes are capable of undergoing apoptosis without the presence of other cell types, such as neurons. Ischemia can induce apoptosis in astrocytes contributing to the pathogenesis of ischemic injury in the CNS.

Astrocytes produce and release interleukin-1, interleukin-6, tumor necrosis factor alpha and interferon-gamma following traumatic and metabolic injury

The brain is no longer considered immune-privileged due to its capability of producing cytokines in response to neurotrauma; however, the cellular sources of cytokines have not been defined. This study focused on the production of four inflammatory cytokines, interleukin-1 (IL-1alpha), interleukin-6 (IL-6), tumor necrosis factor alpha (TNFalpha), and interferon gamma (IFN-gamma) in primary culture of astrocytes under two different injury models which simulated in vivo mechanical trauma (scratch injury) and ischemia. Results demonstrated that astrocytes after scratch injury were positively immunostained with IL-1alpha, IL-6, and TNFalpha. A slot-blot study of culture media showed that the release of IL-1alpha, IL-6, TNFalpha, and IFN-gamma by astrocytes subsequent to scratch and ischemic injury reached approximately twice the control values. The temporal expression of these cytokines was different for the two models. All four cytokines began to increase 1 h postscratch and remained at high levels throughout the experiment. In the ischemic model, however, the increase of cytokine expression was delayed until 4-8 h of ischemia, when sharp increases were seen in all four cytokines. In this culture system, the exogenous influence of blood-borne factors and leukocytes, which occur with in vivo trauma and ischemia, was eliminated. Accordingly, the cytokines detected in the culture media were derived from astrocytes. This study provides the first evidence that astrocytes, without the influence from other cell types, can produce and release cytokines following mechanical and ischemic injury.

Endothelin-1 protects astrocytes from hypoxic/ischemic injury

Under pathological conditions such as ischemia (I), subarachnoid hemorrhage, and Alzheimer's disease, astrocytes show a large increase in endothelin (ET) -like immunoreactivity. However, it is not clear whether ET is protective or destructive to these cells during brain injury. Using astrocytes from ET-1-deficient mice, we determined the effect of ET-1 on these cells under normal, hypoxic (H), and hypoxic/ischemic (H/I) conditions. Under normal culture conditions, astrocytes from wild-type and ET-1-deficient mice showed no difference in their morphology and cell proliferation rates. ET-3 and ETA receptor mRNAs were up-regulated whereas ETB receptor mRNA was down-regulated in ET-1-deficient astrocytes, suggesting that ET-1 and ET-3 may complement each other's functions and that the expressions of these endothelins and their receptors are regulated by a complex feedback mechanism. Under H and H/I conditions, ET-1 peptide and mRNA were up-regulated in wild-type astrocytes, and the astrocytes without ET-1 died faster than the wild-type astrocytes, as indicated by greater efflux of lactate dehydrogenase. The present study suggests that astrocytes without ET-1 are more vulnerable to H and H/I injuries and that the up-regulation of astrocytic ET-1 is essential for the survival of astrocytes.

Quercetin inhibits c-fos, heat shock protein, and glial fibrillary acidic protein expression in injured astrocytes

Quercetin, a bioflavonoid, is found widely in many kinds of fruits and vegetables. It is known to engage in many bioactivities, such as interfering with of the progress of stress responses to injury. In the present study, we investigated the effects of quercetin on some injury responses in primary cultures of astrocytes. These injury responses included the elevation of c-fos protein, heat shock protein (HSP70), and glial fibrillary acidic protein (GFAP). After heat shock insult, the levels of c-fos protein and HSP70 in astrocytes increased. With quercetin treatment, these proteins were significantly reduced. The inhibition of these injury responses by quercetin in astrocytes indicated a dose dependency, with the highest effect at 100 microM. We have previously established a scratch injury model in a primary culture of astrocytes. In that model, astrocytes responded to the scratch injury by an elevation in their GFAP level and formation of hypertrophic cell processes, which extend into the scratch areas. Quercetin treatment reduced the number of hypertrophic cell processes being extended into the scratch areas. With 100 microM of quercetin, there was a complete inhibition of the formation of the hypertrophic cell process. Western blot analysis for GFAP indicated that quercetin significantly reduced the induction of GFAP in the scratch model. At 100 microM, the total GFAP content in the injured cultures was reduced to a level lower than that of the control. This implied that quercetin might possess an antigliotic property.

Multi-lipofection efficiently transfected genes into astrocytes in primary culture

This study demonstrated that liposome-mediated transfection - lipofection - is suitable for delivering genes into astrocytes. By repeatedly lipofecting the same astrocyte cultures, a process we call multi-lipofection, the transfection efficiency of the beta-galactosidase (beta-gal) gene was improved from 2.6+/-0.6 to 17. 4+/-1.1%. This is the highest efficiency ever reported in gene-transfer with Lipofectin(R) in a primary culture of mouse cerebral cortical astrocytes. Furthermore, multi-lipofection did not cause observable disturbance to astrocytes as indicated by insignificant changes in the glial fibrillary acidic protein content in the cultures. In order to demonstrate that the transfected gene achieved a physiologically relevant expression level, a plasmid containing the pEF-hsp70 protein gene was lipofected into astrocytes. This produced colonies of astrocytes showing an increased resistance to heat-induced cell death. A similar experiment was performed with the glial-derived neurotrophic factor (GDNF) gene. Control astrocytes had no detectable GDNF. In the transfected astrocytes, the GDNF protein could be identified intracellularly by immunocytochemistry. Western blot analysis revealed, as compared to astrocytes with one lipofection, a 2.9-fold increase of GDNF with four lipofections. GDNF remained detectable in astrocytes 2 weeks after four lipofections. Thus, multi-lipofection provides a mild and efficient means of delivering foreign genes into astrocytes in a primary culture, making astrocytes good candidate vehicle cells for gene/cell therapy in the CNS.

Neuronal-astrocytic and cytosolic-mitochondrial metabolite trafficking during brain activation, hyperammonemia and energy deprivation

A novel concept is described, according to which both neurons and astrocytes are capable of metabolizing glucose all the way to CO(2) and water, but in addition interact metabolically in a process generating glutamate from glucose, and subsequently, metabolizing excess glutamate to CO(2) and water Hertz, L., Dringen, R., Schousboe, A., Robinson, S.R., 1999. Astrocytes: Glutamate producers for neurons (Journal of Neuroscience Research 57, 417-428). The proposed metabolic degradation of glucose via glutamate serves the purpose of adjusting transmitter pools of glutamate to the demands for glutamatergic transmission, and it must account for a major fraction of glucose utilization. Evidence in favor of this concept is presented and a multitude of in vivo data are interpreted in the context of metabolic trafficking between neurons and astrocytes. In addition, intracellular trafficking occurs between cytosol and mitochondria during synthesis of transmitter glutamate, partly explaining a robust quantitative correlation between glutamine synthesis, as a measure of release of transmitter glutamate, and glucose utilization, reported by several authors. Both intracellular and intercellular metabolic trafficking may be affected during pathological conditions, as evidenced by effects of hyperammonemia (mimicking hepatic encephalopathy) and energy deprivation (mimicking stroke). It is suggested that neuronal-astrocytic interactions may also be impaired during degenerative dementing diseases.

Protection against ischemic injury in primary cultured mouse astrocytes by bis(7)-tacrine, a novel acetylcholinesterase inhibitor [corrected]

The effects of bis(7)-tacrine, a novel acetylcholinesterase inhibitor, on ischemia-induced cell death and apoptosis were investigated in primary cerebral cortical astrocytes of mice. Following a 6 h in vitro ischemic incubation of the cultures, a marked decrease in the percentage of viable cells was observed by lactate dehydrogenase (LDH) release assay. Furthermore, using bisbenzimide staining, we determined that approximately 65% of the cells underwent apoptosis. Treatment with bis(7)-tacrine (1-10 nM) during ischemic incubation effectively inhibited the ischemia-induced apoptosis, as demonstrated by morphological and biochemical tests. Our results demonstrated that bis(7)-tacrine could protect astrocytes against ischemia-induced cell injury, indicating that the drug might be beneficial for the treatment of vascular dementia, in addition to Alzheimer's disease.

The expression of Cdk5, p35, p39, and Cdk5 kinase activity in developing, adult, and aged rat brains

The expression of cyclin-dependent kinase 5 (Cdk5) and its regulatory subunits, p35 and p39, was investigated in rat brain from embryonic day 12 (E12) to postnatal 18 months (18M). The Cdk5 protein levels increased from E12 to postnatal day 7 (P7) and remained at this level until 18M. The Cdk5 kinase activity and the levels of both p35 mRNA and protein were low at E12, became prominent at E18-P14 but then decreased in the adult and aged rat brains of 3M to 18M. In comparison, the expression pattern of p39 appeared to have an inverse relationship to that of Cdk5 and p35. In regional distribution studies, p35 protein levels and Cdk5 kinase activity were significantly higher in the cerebral cortex and hippocampus, but lower in the cerebellum and striatum. These results suggested that Cdk5, p35 and p39 might have region-specific and developmental stage-specific functions in rat brain.

Dexmedetomidine-induced stimulation of glutamine oxidation in astrocytes: a possible mechanism for its neuroprotective activity

Dexmedetomidine is a highly specific alpha2-adrenergic agonist, which is used clinically as an anesthetic adjuvant and in animal experiments has a neuroprotective effect during ischemia. The current study showed that dexmedetomidine enhances glutamine disposal by oxidative metabolism in astrocytes. This effect occurs at pharmacologically relevant concentrations. It is exerted on alpha2-adrenergic receptors and not on imidazoline-preferring sites, and it is large enough to reduce the availability of glutamine as a precursor of neurotoxic glutamate.

Expression of interleukin-1 alpha, tumor necrosis factor alpha and interleukin-6 genes in astrocytes under ischemic injury

Astrocytes form an integral part of the blood brain barrier and are the first cell type in the central nervous system to encounter insult if there is an ischemic attack. The immunologic reaction of astrocytes to an ischemic insult would be affective to the subsequent responses of other nerve cells. We previously showed that ischemia caused an increase in the levels of interleukin 1alpha (IL-1alpha), tumor necrosis factor alpha (TNF alpha), and interleukin 6 (IL-6) in the culture medium of mouse cerebral cortical astrocyte. We did not have evidence on the source of these cytokines. This study aimed to investigate the expressions of these cytokine mRNAs in the astrocytes under ischemia. Results demonstrated that ischemia could induce necrosis and apoptosis in astrocytes. By using the RT-PCR method, we demonstrated for the first time that the mRNA levels of IL-1alpha, TNF alpha and IL-6 in normal astrocyte was very low, but their expressions could be induced quickly under ischemia. These cytokines might be interactive as indicated by the difference in time course of their expressions, with IL-1alpha being the earliest and IL-6 being the latest. The result provided some understanding of the induction and progression of these immunologic responses in astrocytes under ischemia. It also supported our previous findings that astrocytes contributed to the cytokines released under ischemia.

Epidemiology of diabetes mellitus in children in Hong Kong: the Hong Kong childhood diabetes register

OBJECTIVES

To establish a registry for Chinese children with onset of type 1 (insulin dependent) diabetes mellitus before 15 years of age and to determine the incidence of childhood onset type 1 diabetes mellitus in Chinese children in Hong Kong.

RESEARCH DESIGN AND METHODS

A registry was established in 1997 to collect childhood diabetes cases retrospectively from all districts in Hong Kong. The study included all newly diagnosed cases of diabetes with onset < 15 yr of age from 1st January 1984 to 31 December 1996. Primary ascertainment was based on review of medical records at all regional public hospitals in Hong Kong and survey of all the registered practitioners in Hong Kong. The secondary source of validation was made impractical, if not impossible, because of the recent implementation of the Personal Data Privacy Ordinance in Hong Kong.

RESULTS

A total of 255 diabetic cases were identified, 227 type 1 diabetes mellitus (218 were Chinese), 18 type 2 diabetes mellitus and 11 secondary diabetes. 246 patients were Chinese and 9 non-Chinese. The age-standardized incidence of type 1 and type 2 diabetes mellitus in southern Chinese children in Hong Kong was 1.4/100,000/yr and 0.1/100,000/yr respectively for children < 15 yr of age during the study period. The incidence rates for type 1 diabetes were 0.9, 1.5 and 1.7 per 100,000/yr for 0-4 years, 5 to 9 years and 10 to 14 years age-groups respectively. The incidence for males was 1.2/100,000/yr and for females 1.7/100,000/yr. A significant increase in the incidence was demonstrated during the study period by simple linear regression (slope 0.14/100,000/year, r2 = 0.73, p = 0.0002)

CONCLUSIONS

A diabetic registry is established in Hong Kong. This study documents a very low incidence rate of childhood type 1 diabetes mellitus in southern Chinese children in Hong Kong and we have seen an increasing incidence of the disease in the past 13 years.

[A brief introduction to the methods for novel gene cloning]

There are a lot of methods for novel gene cloning, but how to clone candidate gene(s) quickly and correctly? This is a brief introduction to methods of novel gene cloning, these methods includes: differential display reverse transcriptase polymerase chain reaction(DD RT-PCR), suppression subtractive hybridization(SSH), RNA arbitrarily primed PCR(RAP-PCR), representational difference analysis(RDA), yeast two-hybrid system, cDNA capturation, et al. We not only introduced these methods, but also discussed the advantages and disadvantages of them. However, no single method is omnipotent, one should pick up the method most suitable for a special purpose.

Bilirubin toxicity and differentiation of cultured astrocytes

OBJECTIVE

To study the toxicity of bilirubin in primary cultures of newborn rat cerebral cortical astrocytes.

STUDY DESIGN

Primary cultures of newborn rat astrocytes were incubated at bilirubin concentrations of 0, 1, 5, 10, 25, 50, 100, 200, and 2000 microM, at a bilirubin:albumin molar ratio of 1.7. Bilirubin toxicity was determined by changes in cellular morphology, trypan blue staining, and lactate dehydrogenase (LDH) release into the culture medium at various times of incubation. To determine if differentiation of astrocytes affects bilirubin toxicity, cultures were treated with dibutyryl cyclic adenosine monophosphate.

RESULTS

All three indices of toxicity showed a bilirubin concentration dependence. LDH release in experimental cultures was significantly elevated (p < 0.05) above that of control cultures by 24 hours at bilirubin concentrations of > or = 100 microM. The absolute amount of LDH release differed significantly between the 200 and 2000 microM cultures from 1.5 to 24 hours, after which duration of exposure appeared to take over and all cultures approached maximum. LDH release for the lower concentrations all reached maximum by 120 hours, except for the 1 microM cultures, which showed no significant elevation above control throughout the study period. At 100 and 200 microM bilirubin, LDH release by untreated cells was significantly higher (p < 0.05) than release by treated cells by 36 hours.

CONCLUSION

Undifferentiated astrocytes appeared to be more sensitive to bilirubin toxicity, which may correlate with the greater susceptibility of newborns to kernicteric injury. Studies with primary astrocyte culture may provide insight into how bilirubin sensitivity changes with brain development as well as the cellular and biochemical mechanisms of bilirubin encephalopathy.

Behavioral state modulation of auditory activity in a vocal motor system

Neurons of the song motor control nucleus robustus archistriatalis (RA) exhibited far weaker auditory responses in awake than in anesthetized zebra finches. Remarkably, sleep induced complex patterns of bursts in ongoing activity and uncovered vigorous auditory responses of RA neurons. Local injections of norepinephrine suggested that the changes in response strength occur through neuromodulatory control of the sensorimotor nucleus HVc, which projects to RA. Thus, motor access to auditory feedback, which zebra finches require for song learning and maintenance, may be regulated through neuromodulation. During sleep, the descending motor system may gain access to sensorimotor song memories represented as bursting patterns of activity.

Temporal hierarchical control of singing in birds

Songs of birds comprise hierarchical sets of vocal gestures. In zebra finches, songs include notes and syllables (groups of notes) delivered in fixed sequences. During singing, premotor neurons in the forebrain nucleus HVc exhibited reliable changes in activity rates whose patterns were uniquely associated with syllable identity. Neurons in the forebrain nucleus robustus archistriatalis, which receives input from the HVc, exhibited precisely timed and structured bursts of activity that were uniquely associated with note identity. Hence, units of vocal behavior are represented hierarchically in the avian forebrain. The representation of temporal sequences at each level of the hierarchy may be established by means of a decoding process involving interactions of higher level input with intrinsic local circuitry. Behavior is apparently represented by precise temporal patterning of spike trains at lower levels of the hierarchy.

Tumor necrosis factor-alpha and basic fibroblast growth factor decrease glial fibrillary acidic protein and its encoding mRNA in astrocyte cultures and glioblastoma cells

Tumor necrosis factor-alpha is a pluripotent cytokine that is reportedly mitogenic to astrocytes. We examined expression of the astrocyte intermediate filament component glial fibrillary acidic protein in astrocyte cultures and the U373 glioblastoma cell line after treatment with tumor necrosis factor-alpha. Treatment with tumor necrosis factor-alpha for 72 h resulted in a decrease in content of glial fibrillary acidic protein and its encoding mRNA. At the same time, tumor necrosis factor-alpha treatment increased the expression of the cytokine interleukin-6 by astrocytes. The decrease in glial fibrillary acidic protein expression was greater when cells were subconfluent than when they were confluent. Thymidine uptake studies demonstrated that U373 cells proliferated in response to tumor necrosis factor-alpha, but primary neonatal astrocytes did not. However, in both U373 cells and primary astrocytes tumor necrosis factor-alpha induced an increase in total cellular protein content. Treatment of astrocytes and U373 cells for 72 h with the mitogenic cytokine basic fibroblast growth factor also induced a decrease in glial fibrillary acidic protein content and an increase in total protein level, demonstrating that this effect is not specific for tumor necrosis factor-alpha. The decrease in content of glial fibrillary acidic protein detected after tumor necrosis factor-alpha treatment is most likely due to dilution by other proteins that are synthesized rapidly in response to cytokine stimulation.

Adult height in women with early-treated congenital adrenal hyperplasia (21-hydroxylase type): relation to body mass index in earlier childhood

To investigate if obesity, as judged by increased body mass index (BMI), during childhood is associated with impaired adult stature in patients with 21-hydroxylase-type congenital adrenal hyperplasia (CAH), a retrospective analysis was carried out on outpatient records of 30 girls with CAH who had reached adult height. Height SD score for age (HtSDS(ca)), HtSDS for bone age (HtSDS(ba)), BMI and steroid dosage in early childhood (3.2-4.6 years) and later childhood (7.2-9.1 years), were compared with adult HtSDS (HtSDS(adlt)), adult HtSDS less mid-parental HtSDS (HtSDS(adlt)-HtSDS(mp)), predicted adult height SDS (HtSDS(pdct)), adult height SDS less predicted adult HtSDS (HtSDS(adlt)-HtSDS(pdct)) and age at menarche. Mean (SD) for HtSDS(adlt) was -1.13 (1.05), mean HtSDS(pdct) -0.12 (0.9) and mean age at menarche 13.5 (1.9) years. BMI in childhood was not correlated with HtSDS(adlt) but showed negative correlations with HtSDS(adlt)-HtSDS(mp) (r = -0.43; p < 0.02) and HtSDS(adlt)-HtSDS(pdct) (r-0.45; p < 0.02). BMI in later childhood showed negative correlations with HtSDS(adlt)-HtSDS(pdct) (r = -0.61; p < 0.001) and age at menarche (r = -0.63; p < 0.001). We conclude that in girls with early-treated CAH, a high BMI during early childhood is associated with loss of genetic height potential, and in later childhood with over-prediction of adult height and early menarche.

Astrogliosis in culture. IV. Effects of basic fibroblast growth factor

Previous studies have shown that the mechanical wounding of 3-week-old cultured rat astrocytes results in cell proliferation and hypertrophy resembling astrocyte responses to a brain injury in vivo. We now report the effects of basic fibroblast growth factor (bFGF) and an anti-bFGF antibody on astrocyte morphology, proliferation, and migration following in vitro wounding of confluent secondary cultures. Addition of bFGF (20 ng/ml) to wounded cultures induced morphological changes characteristic of differentiation in wounded and nonwounded areas of the culture. Combined treatment with bFGF and an anti-bFGF antibody (100 micrograms/ml) prevented this effect. Astrocyte proliferation along the edges of a scratch wound was at maximum 24 hr after wounding in cells growing in Eagle's minimum essential medium (EMEM) containing 10% serum. Low serum concentration and treatment with dibutyryl cyclic adenosine monophosphate (dbc-AMP) reduced injury-associated astrocyte proliferation. Addition of bFGF to cultures in EMEM with serum increased astrocyte proliferation at 18 and 24 hr after wounding. This effect was reduced considerably by treatment of cultures with bFGF in combination with an anti-bFGF antibody. The combined treatment and the antibody alone reduced cell division to a level lower than in control cultures. Twenty-four hr following wounding, astrocytes along the edges of the wound exhibited extension of thick, flat processes into the wound area. At 3 and 5 days after wounding, a bodily migration of astrocytes into the wounded area was observed. Addition of bFGF significantly increased astrocyte migration 1 day after wounding, with maximum effect on day 3 and no subsequent increase on day 5. A combination of bFGF and anti-bFGF antibody as well as the antibody alone reduced astrocyte migration to a level lower than in controls. Immunohistochemical localization and isoform pattern of bFGF in astrocytes did not change with dbc-AMP treatment or wounding. We conclude that mechanically wounded confluent astrocytes respond to bFGF added to the culture medium by enhancing cell division, differentiation, and migration. In addition, the results of the antibody treatment also suggest a role for endogenous bFGF in astrocyte proliferation and migration elicited by wounding in vitro. These results support the notion that in vivo, both bFGF released by injury and endogenous bFGF synthesized by astrocytes, contribute to the cellular responses that lead to astrogliosis.

Gene expression in astrocytes during and after ischemia

Involvement of the IEGs in brain injury and ischemia is under intensive investigation (Gubits et al., 1993). There are several families of the IEGs. They include the fos, jun, and zinc finger genes that encode transcription factors. Products of the fos family (c-fos, fra-1, fra-2, and fos B) bind to members of the jun family (c-jun, jun B, jun D) via leucine zippers, and this dimer then binds to the AP-1 site (consensus sequence -TGACTCA-) in the promoter of target genes, which in turn regulate the expression of late response genes that produce long-term changes in cells. For example, c-fos may regulate the long-term expression of preproenkephalin, nerve growth factor, dynorphin, vasoactive intestinal polypeptide, tyrosine hydroxylase and other genes with AP-1 sites in their promoters (Curran and Morgan, 1987; Sheng and Greenberg, 1990). It is likely that the c-fos gene up-regulation observed in ischemic astrocytes leads to the changes observed in the expressions of hsp and cytoskeleton protein genes in this experimental model. This is supported by the findings of Sarid (1991) and Pennypacker et al. (1994) who have shown that AP-1 DNA binding activity in hippocampus recognized an AP-1 sequence from the promoter region of the GFAP which is a potential target gene. van de Klundert et al. (1992) also suggested the involvement of AP-1 in transcriptional regulation of vimentin. IEGs can be induced within minutes by extracellular stimuli including transmitters, peptides, and growth factors. In this study, we have shown that c-fos induction by ischemia was rapid and transient.(ABSTRACT TRUNCATED AT 250 WORDS)

Astrogliosis in culture: III. Effect of recombinant retrovirus expressing antisense glial fibrillary acidic protein RNA

Injury to the central nervous system (CNS) either from trauma or due to demyelinating/degenerating diseases results in a typical response of astrocytes, termed astrogliosis. This reaction is characterized by astrocyte proliferation, extensive hypertrophy of nuclei, cell body, and cytoplasmic processes and an increase in immunodetectable glial fibrillary acidic protein (GFAP). GFAP accumulation may cause a physical barrier preventing the reestablishment of a functional environment. Our studies have aimed at modulating astrogliosis by inhibiting or delaying GFAP synthesis in damaged and reactive astrocytes. The present study investigates the use of a recombinant retrovirus expressing antisense GFAP RNA in controlling the response of mechanically injured astrocytes. A 650 bp fragment from the coding region of mouse GFAP cDNA was cloned in the antisense orientation under the control of long terminal repeat (LTR) promoter of Moloney murine leukemia virus. Increase in GFAP as detected by immunocytochemical staining in injured astrocytes was inhibited by treatment with retrovirus expressing antisense GFAP RNA. Also, astrocytes at the site of injury in these scratched cultures did not show cell body hypertrophy compared to control cultures. These observations demonstrate that the increase in GFAP at the site of injury can be inhibited using retroviral treatment and indicate the potential of retrovirus-mediated gene transfer in modulating scar formation in the CNS in vivo. These studies also shed light on the role of GFAP in maintaining the morphology of astrocytes.

Distributed representation in the song system of oscines: evolutionary implications and functional consequences

This paper reviews the organizational principles and implications that have emerged from the analysis of HVc, a forebrain nucleus that is a major site of sensory, motor, and sensorimotor integration in the song control system of oscine passerine birds (songbirds). Anatomical, physiological, and behavioral data support the conclusion that HVc exists within a hierarchically organized system with parallel pathways that converge onto HVc. The organization of HVc is distributed and redundant, and its outputs exhibit broad divergence. A similar pattern of connectivity exists for neostriatum adjacent to HVc. This and other data support the hypothesis that the song system arose from an elaboration or duplication of pathways generally present in all birds. Spontaneous and auditory response activity is strongly correlated throughout HVc, with auditory responses exhibiting strong temporal modulation in a synchronized fashion throughout the nucleus. This suggests that the auditory representation of song is encoded in the synchronized temporal patterns of activation, and that the predominant selectivity for the individual's own song that is observed for HVc neurons results from interactions of auditory input with central pattern generators for song. Most, or all HVc neurons are recruited during singing. The auditory response and motor recruitment properties of individual HVc neurons have no simple relationship, and the spontaneous activity in HVc may build up in the seconds preceding a song. To the extent HVc participates in perceptual phenomena associated with song, production and perception are not tightly linked in adults but may be linked by shared developmental processes during periods of sensorimotor learning.

Reverse transcription and polymerase chain reaction technique for quantification of mRNA in primary astrocyte cultures

The reverse transcription and polymerase chain reaction technique (RT-PCR) was assessed for the quantification of changes in mRNA levels from primary astrocyte cultures. The effects of dibutyryl cyclic AMP (dBcAMP) on glial fibrillary acidic protein (GFAP) mRNA and the effects of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and lipopolysaccharide (LPS) on interleukin-6 (IL-6) mRNA were examined. Two quantitative PCR methods were used: one involved carrying out the reaction in the exponential phase and the other involved the coamplification of a competitive target sequence. Increased GFAP mRNA in response to chronic dBcAMP treatment and increased IL-6 mRNA in response to TNF-alpha/IL-1 beta were readily detected. Both RT-PCR techniques were found to be suitable for the detection of large as well as smaller (twofold) changes in mRNA levels. The advantages and limitations of RT-PCR for mRNA quantification are discussed.

Astrogliosis in culture: I. The model and the effect of antisense oligonucleotides on glial fibrillary acidic protein synthesis

Astrogliosis is a predictable response of astrocytes to various types of injury caused by physical, chemical, and pathological trauma. It is characterized by hyperplasia, hypertrophy, and an increase in immunodetectable glial fibrillary acidic protein (GFAP). As GFAP accumulation is one of the prominent features of astrogliosis, inhibition or delay in GFAP synthesis in damaged and reactive astrocytes might affect astrogliosis and delay scar formation. The aim of this study is to investigate the possibility of utilizing antisense oligonucleotides in controlling the response of astrocytes after mechanically induced injury. We scratched primary astrocyte cultures prepared from newborn rat cerebral cortex with a plastic pipette tip as an injury model and studied the astrogliotic responses in culture. Injured astrocytes became hyperplastic, hypertrophic, and had an increased GFAP content. These observations demonstrate that injured astrocytes in culture are capable of becoming reactive and exhibit gliotic behaviors in culture without neurons. The increase in GFAP content in injured astrocytes could be inhibited by incubating the scratched culture with commercially available liposome complexed with 3' or 5' antisense oligonucleotides (20 nt) in the coding region of mouse GFAP. The scratch model provides a simple system to examine in more detail the mechanisms involved in triggering glial reactivity and many of the cellular dynamics associated with scar formation. Antisense oligonucleotide treatment could inhibit the GFAP synthesis in injured astrocytes, hence it may be applicable in modifying scar formation in CNS injury in vivo.

Selective brain cooling during and after prolonged global ischemia reduces cortical damage in rats

BACKGROUND AND PURPOSE

Studies of the cerebroprotective effects of selective brain cooling have failed to show amelioration of ischemic injury in the cerebral cortex. This study was designed to test the hypothesis that mild-to-moderate selective brain cooling initiated after the onset of global brain ischemia in rats protects the cerebral cortex and improves neurological outcome.

METHODS

Global forebrain ischemia for 30 minutes in 27 fasted adult male Wistar rats was achieved by bilateral carotid occlusion and hypotension. In group 1, brain temperature, measured in the temporalis muscle, was maintained at 37-38 degrees C throughout the experiment. In group 2, brain temperature fell spontaneously during ischemia to 34.7 +/- 0.1 degrees C and rose spontaneously to 36-37 degrees C after 10 minutes of recirculation. In group 3, brain temperature was lowered with ice packs placed around the head after 15 minutes of ischemia to 24.1 +/- 0.9 degrees C by the end of ischemia, maintained at 30.0 +/- 1.0 degrees C for the first hour of recirculation, then allowed to rise to 36-37 degrees C.

RESULTS

Seven-day survival was 0% (0 of 6) in group 1, 73% (8 of 11) in group 2, and 100% (6 of 6) in group 3. Severity of neuronal damage was less in group 2 than in group 1 in the cortex (p < 0.05) and hippocampal CA1 (p < 0.05) and CA3 regions (p < 0.05). Group 3 had less neuronal damage than group 2 in both cortex (p < 0.02) and striatum (p < 0.02). Furthermore, postischemic weight loss was less and neurobehavioral scores were significantly higher in group 3.

CONCLUSIONS

This study shows that selective brain cooling increases survival from prolonged global ischemia and reduces neuronal injury in the cerebral cortex as well as the striatum and hippocampus.

Uptake and metabolism of malate in neurons and astrocytes in primary cultures

Uptake and oxidative metabolism of [14C]malate as well as its incorporation into aspartate, glutamate, glutamine, and GABA were studied in cultured cerebral cortical neurons (GABAergic), cerebellar granule neurons (glutamatergic), and cerebral cortical astrocytes. All cell types exhibited high affinity uptake of malate (Km 10-85 microM) with slightly higher Vmax values in neurons (0.1-0.2 nmol x min-1 x mg-1) than in astrocytes (0.06 nmol x min-1 x mg-1). Malate was oxidatively metabolized in all three cell types with nominal rates of 14CO2 production of 2-15 pmol x min-1 x mg-1. The oxidation of malate was only slightly inhibited by 5 mM aminooxyacetic acid (AOAA). In granule cell preparations [14C]malate was incorporated into aspartate and glutamate and, to a much less extent, into glutamine. This incorporation was blocked by 5 mM AOAA. Astrocytes exhibited slightly higher incorporation rates into aspartate and glutamate, but in these cells glutamine was labelled to a considerable extent. AOAA (5 mM) inhibited the incorporation by 60-70%. In cultures of cerebral cortical neurons, very low levels of radioactivity derived from [14C]malate were found in aspartate and glutamate, and GABA was not labelled at all. Glutamine had the same specific activity as glutamate, indicating that the low rates of incorporation of radioactivity into amino acids in this preparation is likely to exclusively represent metabolism of malate in the small population of astrocytes (5% of total cell number), contaminating the neuronal cultures. The findings suggest that exogenous malate to a quantitatively limited extent may serve as a precursor for transmitter glutamate in glutamatergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of GFAP synthesis by antisense RNA in astrocytes

Glial fibrillary acidic protein (GFAP) accumulation is a prominent feature of astrocytic gliosis. The inhibition or delay in GFAP synthesis might delay scar formation resulting from an insult such as spinal cord injury or central nervous system (CNS) demyelination. The delay in the formation of a physical barrier might allow the neurons and oligodendrocytes to reestablish a functional environment. We delivered antisense GFAP RNA complexed with Lipofectin (LF), a cationic liposome, into cerebral astrocytes in culture and tested the feasibility of inhibiting GFAP synthesis. Our results demonstrate that LF facilitated antisense RNA uptake into astrocytes. Astrocytes took up 3H-antisense GFAP RNA alone and reached an equilibrium of 7-8.8 eta g per mg protein after 2.5 hr. When complexed with LF, astrocytes could increase the uptake to 14 eta g per mg protein and the time for reaching this quantity was shortened to 10 min. This uptake level was further enhanced if experiments were carried out in HEPES buffered saline (HBS). All uptake studies were dose- and time-dependent. Dibutyryl cyclic AMP (dBcAMP) is known to induce an increase of GFAP content in cultured astrocytes. We studied the effect of LF/antisense GFAP RNA on the GFAP content in dBcAMP (0.25 mM)-treated astrocytes. Cultures of astrocytes treated with dBcAMP contained almost twice as much GFAP as untreated cultures after 2 days. Similar cultures treated with LF/antisense RNA in HBS did not show an increase but a 30-40% decrease in GFAP content 2 days after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Phagocytosis of peripheral nerve myelin in vitro: effect of antibody

We have previously shown that antisera to whole CNS myelin, whole PNS myelin, galactocerebroside (GC), and myelin basic protein (MBP) promote the uptake of CNS myelin by cultured macrophages, and stimulate the conversion of myelin lipids to cholesterol ester and triglycerides. Here we report the results of similar studies using PNS myelin purified from the rat sciatic nerve. Antisera to whole CNS myelin, whole PNS myelin, GC, and MBP preincubated with 14C-labeled PNS myelin increased the production of radioactive cholesterol ester by macrophages in culture to a level about twice that with preimmune serum, and five to six times that of untreated myelin. The amounts of [14C]triglyceride were similarly increased with these antisera, whole P0 and P2 antisera had little or no effect. IgG prepared from the antisera stimulated lipid metabolism to almost the same extent, while heating the antisera did not decrease the stimulatory effect, indicating that myelin was opsonized by IgG, but not likely by complement. With a few exceptions, the four active sera and their IgGs promoted the macrophage metabolism of CNS and PNS myelin almost equally. The cultured macrophages converted about 3% of untreated CNS myelin and about 6% PNS myelin cholesterol to cholesterol ester. Under phase contrast microscopy it was noted that vesicles of CNS myelin appeared to bind individually to macrophages, whereas PNS myelin vesicles tended to self-associate to form large clumps which were found to macrophages. Binding studies showed PNS myelin to be bound more firmly to macrophages than CNS myelin.(ABSTRACT TRUNCATED AT 250 WORDS)

Fructose-1,6-bisphosphate reduces ATP loss from hypoxic astrocytes

Hypoxia caused injury and metabolic dysfunction of astrocytes, as indicated by a time-dependent loss of lactate dehydrogenase (LDH) activity and ATP content. The combination of 3.5 mM fructose-1,6-bisphosphate (FBP) and 7.5 mM glucose (GLC) reduced the decrease of ATP and prevented the loss of LDH. These data indicate that the combination of GLC + FBP protects astrocytes from hypoxia. The results also suggest that the maintainance of ATP concentration is the mechanism by which FBP prevents hypoxic injury.

Glutamate increases glycogen content and reduces glucose utilization in primary astrocyte culture

The glycogen content of primary cultured astrocytes was approximately doubled by incubation with 1 mM L-glutamate or L-aspartate. Other amino acids and excitatory neurotransmitters were without effect. The increase in glycogen level was not blocked by the glutamate receptor antagonist kynurenic acid but was completely blocked by the glutamate uptake inhibitor threo-3-hydroxy-D,L-aspartate and by removal of Na+ from the medium. Incubation with radiolabeled glucose and glutamate revealed that the increased glycogen content was derived almost entirely from glucose. Glutamate at 1 mM was also found to cause a 53 +/- 12% decrease in glucose utilization and a 112 +/- 69% increase in glucose-6-phosphate levels. These results suggest that the glycogen content of astrocytes is linked to the rate of glucose utilization and that glucose utilization can, in turn, be affected by the availability of alternative metabolic substrates. These relationships suggest a mechanism by which brain glycogen accumulation occurs during decreased neuronal activity.

Regulation of glycogen content in primary astrocyte culture: effects of glucose analogues, phenobarbital, and methionine sulfoximine

Compounds known to affect glycogen metabolism in vivo or in cell-free preparations were used to investigate the regulation of glycogen content in intact astrocytes cultured from newborn rat cortex. Compounds were added with fresh medium to culture dishes, and astrocyte glucose and glycogen content determined 24 h later. Increasing the medium glucose concentration from 7.5 mM to 30 mM increased cell glycogen content 80%. Addition of 2-deoxyglucose or 3-O-methyl glucose (2.5-10 mM) also increased cell glycogen content, 50-100%, suggesting a regulatory rather than mass action effect of glucose on astrocyte glycogen content. The phosphorylase b inhibitors 2,2',4,4',5,5'-hexabromobiphenyl and riboflavin had no effect on astrocyte glycogen content, consistent with negligible phosphorylase b activity in normal astrocytes. Phenobarbital and L-methionine-DL-sulfoximine (MSO) are both known to induce astrocyte glycogen accumulation in vivo. The addition of phenobarbital (2 mM) had no effect on the glycogen content of cultured astrocytes, suggesting an indirect mechanism for the in vivo effect. MSO at 1 mM, however, induced a 300% increase in glycogen content. The time course of glucose and glycogen content after MSO administration suggests this increase to be the result of slowed glycogenolysis rather than accelerated glycogen synthesis.

Hypoxia-induced dysfunctions and injury of astrocytes in primary cell cultures

The effects of severe hypoxia were studied in a primary culture of astrocytes prepared from newborn rat cerebral cortex. Hypoxia was created by placing cultures in an airtight chamber that was flushed with 95% N2/5% CO2 for 15 min before being sealed. The hypoxic environment was maintained constant for up to 24 h. During the first 12 h of hypoxia, astrocytes showed no morphological changes by phase-contrast microscopy. After 18 h of hypoxia, some astrocytes in culture became swollen and started to detach from the culture dish. All cells in the culture were destroyed after 24 h of hypoxia. The lactate dehydrogenase level in the culture medium increased more than tenfold between 12 and 24 h of hypoxia. Glutamate uptake was inhibited 80% by similar hypoxic conditions. The cell volume of astrocytes, as measured by 3-O-methyl-[14C]-D-glucose uptake, was increased. These observations suggested cell membrane dysfunction. The malondialdehyde level of hypoxic cultures increased two-fold after 24 h of hypoxia. Verapamil (0.5 mM), furosemide (1 mM), indomethacin (1 mM), MgCl2 (10 mM), and mannitol (10 mM) reduced but never completely abolished the release of lactate dehydrogenase from hypoxic astrocytes. These data suggest multifactorial causes for severe injury in hypoxic astrocytes.

Fructose-1,6-bisphosphate protects astrocytes from hypoxic damage

To determine the effects of glucose and fructose-1,6-bisphosphate (FDP) on hypoxic cell damage, primary cultures of astrocytes were incubated for 18 h in an air-tight chamber that had been flushed with 95% N2/5% CO2 for 15 min before it was sealed. Cultures containing 7.5 mM glucose without FDP or FDP without glucose showed evidence of significant cell injury after 18 h of hypoxia (increased lactate dehydrogenase content in the culture medium; cell edema and disruption by phase-contrast microscopy). Cultures exposed to glucose + FDP had normal lactate dehydrogenase concentrations and appeared normal microscopically. Maximal protection of hypoxic cells occurred at 6.0 mM FDP. Lactate concentrations of the culture medium of hypoxic cells increased 2.5 times above normoxic control values when glucose was present, but neither FDP alone nor glucose + FDP caused the lactate concentrations to increase further. This implies that anaerobic glycolysis was not increased by adding FDP to the medium. Cell volumes (water space) measured with [14C]-3-0-methyl-D-glucose were normal with glucose + FDP in the culture medium of hypoxic cells but were significantly larger than normal when glucose alone was present. Increases in cell volume paralleled changes in lactate dehydrogenase in the culture medium. Uptake of [14C]FDP occurred rapidly in normoxic cells and was maximal after 5 min of incubation. The data indicate that the presence of glucose + FDP in the culture medium protects primary cultures of hypoxic astrocytes from cell damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of intracellular superoxide radical formation by arachidonic acid and by polyunsaturated fatty acids in primary astrocytic cultures

The effects of arachidonic acid and other polyunsaturated fatty acids (PUFAs) on both oxidative and metabolic perturbation were studied in primary cultures of rat cerebral cortical astrocytes. In the presence of 0.1 mM arachidonic acid, the rate of the reduction of nitroblue tetrazolium (NBT) to nitroblue formazan (NBF) was stimulated from 0.65 +/- 0.10 to 1.43 +/- 0.15 and from 0.092 +/- 0.006 to 0.162 +/- 0.009 nmol/min/mg protein in intact and broken cell preparations, respectively. The rate of superoxide radical formation, as measured by the superoxide dismutase (SOD)-inhibitable NBT reduction was 0.042 nmol/mg protein in broken cells and was negligible in intact cells. The latter is due to the impermeability of SOD into the intact cell preparation. NBF formation in intact astrocytes stimulated by arachidonic acid was both time- and dose-dependent. Other PUFAs, including linoleic acid, linolenic acid, and docosahexaenoic acid, were also effective in stimulating NBF formation in astrocytes, whereas saturated palmitic acid and monounsaturated oleic acid were ineffective. Similar effects of these PUFAs were observed in malondialdehyde formation in cells and lactic acid accumulation in incubation medium. These data indicate that both membrane integrity and cellular metabolism were perturbed by arachidonic acid and by other PUFAs. The sites of superoxide radical formation appeared to be intracellular and may be associated with membrane phospholipid domains, because liposome-entrapped SOD, which was taken up by intact astrocytes, reduced the level of superoxide radicals and lactic acid content, whereas free SOD was not effective.