Current hematological findings in cobalamin deficiency. A study of 201 consecutive patients with documented cobalamin deficiency

With the introduction of automated assays for measuring serum cobalamin levels over the last decades, the hematological manifestations related to cobalamin deficiency have been changed from the description reported in 'old' studies or textbooks. We studied the hematological manifestations or abnormalities in 201 patients (median age: 67 +/- 6 years) with well-documented cobalamin deficiency (mean serum vitamin B12 levels 125 +/- 47 pg/ml) extracted from an observational cohort study (1995-2003). Assessment included clinical features, blood count and morphological review. Hematological abnormalities were reported in at least two-third of the patients: anemia (37%), leukopenia (13.9%), thrombopenia (9.9%), macrocytosis (54%) and hypegmented neutrophils (32%). The mean hemoglobin level was 10.3 +/- 0.4 g/dl and the mean erythrocyte cell volume 98.9 +/- 25.6 fl. Approximately 10% of the patients have life-threatening hematological manifestations with documented symptomatic pancytopenia (5%), 'pseudo' thrombotic microangiopathy (Moschkowitz; 2.5%), severe anemia (defined as Hb levels <6 g/dl; 2.5%) and hemolytic anemia (1.5%). Correction of the hematological abnormalities was achieved in at least two-thirds of the patients, equally well in patients treated with either intramuscular or oral crystalline cyanocobalamin. This study, based on real data from a single institution with a large number of consecutive patients with well-documented cobalamin deficiency, confirms several 'older' findings that were previously reported before the 1990s in several studies and in textbooks.

[Update of clinical findings in cobalamin deficiency: personal data and review of the literature]

PURPOSE

During last decades, several progresses have been made in the diagnosis of cobalamin (vitamin B12) deficiency. Routine used of cobalamin standardized assays have potentially modified the frequency and the type of hematologic abnormalities.

CURRENT KNOWLEDGE AND KEY POINTS

Current studies on cobalamin deficiency, including more precise definitions and the description of new etiologies of cobalamin deficiency in adults, as the food-cobalamin malabsorption syndrome, show that hematological abnormalities are generally incomplete compared to historical descriptions of megaloblastic anemia. Nevertheless, they include severe manifestations in 10% of the patients: pancytopenia, severe anemia (hemoglobin < 6 g/dl) or hemolytic anemia and pseudo thrombotic microangiopathy related to cobalamin deficiency. These studies also show the efficacy of new treatment modalities including oral cobalamin administration.

PROSPECTS AND PROJECTS

Future studies will confirm these data with the routine use of the new cobalamin assay: holotranscobalamin and validate the usefulness of oral cobalamin therapy.

Ionotropic glutamate receptors and glutamate transporters are involved in necrotic neuronal cell death induced by oxygen-glucose deprivation of hippocampal slice cultures

Organotypic hippocampal slice cultures represent a feasible model for studies of cerebral ischemia and the role of ionotropic glutamate receptors in oxygen-glucose deprivation-induced neurodegeneration. New results and a review of existing data are presented in the first part of this paper. The role of glutamate transporters, with special reference to recent results on inhibition of glutamate transporters under normal and energy-failure (ischemia-like) conditions is reviewed in the last part of the paper. The experimental work is based on hippocampal slice cultures derived from 7 day old rats and grown for about 3 weeks. In such cultures we investigated the subfield neuronal susceptibility to oxygen-glucose deprivation, the type of induced cell death and the involvement of ionotropic glutamate receptors. Hippocampal slice cultures were also used in our studies on glutamate transporters reviewed in the last part of this paper. Neurodegeneration was monitored and/or shown by cellular uptake of propidium iodide, loss of immunocytochemical staining for microtubule-associated protein 2 and staining with Fluoro-Jade B. To distinguish between necrotic vs. apoptotic neuronal cell death we used immunocytochemical staining for active caspase-3 (apoptosis indicator) and Hoechst 33342 staining of nuclear chromatin. Our experimental studies on oxygen-glucose deprivation confirmed that CA1 pyramidal cells were the most susceptible to this ischemia-like condition. Judged by propidium iodide uptake, a selective CA1 lesion, with only minor affection on CA3, occurred in cultures exposed to oxygen-glucose deprivation for 30 min. Nuclear chromatin staining by Hoechst 33342 and staining for active caspase-3 showed that oxygen-glucose deprivation induced necrotic cell death only. Addition of 10 microM of the N-methyl-D-aspartate glutamate receptor antagonist MK-801, and 20 microM of the non-N-methyl-D-aspartate glutamate receptor antagonist 2,3-dihyroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline to the culture medium confirmed that both N-methyl-D-aspartate and non-N-methyl-D-aspartate ionotropic glutamate receptors were involved in the oxygen-glucose deprivation-induced cell death. Glutamate is normally quickly removed, from the extracellular space by sodium-dependent glutamate transporters. Effects of blocking the transporters by addition of the DL-threo-beta-benzyloxyaspartate are reviewed in the last part of the paper. Under normal conditions addition of DL-threo-beta-benzyloxyaspartate in concentrations of 25 microM or more to otherwise untreated hippocampal slice cultures induced neuronal cell death, which was prevented by addition of 2,3-dihyroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline and MK-801. In energy failure situations, like cerebral ischemia and oxygen-glucose deprivation, the transporters are believed to reverse and release glutamate to the extracellular space. Blockade of the transporters by a subtoxic (10 microM) dose of DL-threo-beta-benzyloxyaspartate during oxygen-glucose deprivation (but not during the next 48 h after oxygen-glucose deprivation) significantly reduced the oxygen-glucose deprivation-induced propidium iodide uptake, suggesting a neuroprotective inhibition of reverse transporter activity by DL-threo-beta-benzyloxyaspartate during oxygen-glucose deprivation under these conditions. Adding to this, other results from our laboratory have demonstrated that pre-treatment of the slice cultures with glial cell-line derived neurotrophic factor upregulates glutamate transporters. As a logical, but in some glial cell-line derived neurotrophic factor therapy-related conditions clearly unwanted consequence the susceptibility for oxygen-glucose deprivation-induced glutamate receptor-mediated cell death is increased after glial cell-line derived neurotrophic factor treatment. In summary, we conclude that both ionotropic glutamate receptors and glutamate transporters are involved in oxygen-glucose deprivation-induced necrotic cell death in hippocampal slice cultures, which have proven to be a feasible tool in experimental studies on this topic.

Clinical and immunological aspects of HLA class I deficiency

Human leukocyte antigen (HLA) class I deficiency is a rare disease with remarkable clinical and biological heterogeneity. The spectrum of possible manifestations extends from the complete absence of symptoms to life-threatening disease conditions. It is usually diagnosed when HLA class I serological typing is unsuccessful; flow cytometric studies then reveal a severe reduction in the cell surface expression of HLA class I molecules (90-99% reduction compared to normal cells). In most cases to date, this low expression is due to a homozygous inactivating mutation in one of the two subunits of the transporter associated with antigen processing (TAP), critically involved in the peptide loading of HLA class I molecules. Although asymptomatic cases have been described, TAP deficiencies are usually characterized by chronic bacterial infections of the upper and lower airways, evolving to bronchiectasis, and in half of the cases, also skin ulcers with features of a chronic granulomatous inflammation. Despite the defect in HLA class-I-mediated presentation of viral antigens to cytotoxic T cells, the patients do not suffer from severe viral infections, presumably because of other efficient antiviral defence mechanisms such as antibodies, non-HLA-class-I-restricted cytotoxic effector cells and CD8+ T-cell responses to TAP-independent antigens. Treatment is at present exclusively symptomatic, and should particularly focus on the prevention of bronchiectasis, which requires early detection.

Characterization of organotypic ventral mesencephalic cultures from embryonic mice and protection against MPP toxicity by GDNF

We characterized organotypic ventral mesencephalic (VM) cultures derived from embryonic day 12 (E12) mice (CBL57/bL6) in terms of number of dopaminergic neurons, cell soma size and dopamine production in relation to time in vitro and tested the effects of 1-methyl-4-phenylpyridinium (MPP(+)) and glial derived neurotrophic factor (GDNF) to validate this novel culture model. Dopamine production and dopaminergic neuron soma size increased dramatically with time in vitro, whereas the number of dopamine neurons declined by approximately 30% between week 1 and week 2, which was further reduced after week 4. GDNF treatment (100 ng/mL) increased dopaminergic neuron soma size (up to 43%) and DOPAC production (approximately three-fold), but not the number of dopamine neurons in control cultures. One-week-old cultures were more vulnerable to MPP(+), than three-week-old cultures. The EC(50) for dopamine depletion after 2 days exposure and 15 days of recovery were 0.6 and 7 microm, respectively. Both pre-treatment and post-treatment with GDNF are important to obtain maximal protection against MPP(+) toxicity. In one-week-old cultures (5 microm MPP(+), 2 days) GDNF provided potent neuroprotection with dopamine contents reaching control levels and number of tyrosine hydroxylase (TH)(+) cells up to 80% of control, but in three-week-old cultures (10 microm MPP(+), 2 days) the protective potential of GDNF was markedly reduced. Long recovery periods after MPP(+) exposure are required to distinguish between reversible or irreversible toxic and/or trophic effects.

Current management of adult idiopathic thrombocytopenic purpura in practice: a cohort study of 201 patients from a single center

To define usefulness and response to therapy and outcome in adults with idiopathic thrombocytopenic purpura (ITP) in clinical practice. We retrospectively reviewed a cohort of 201 consecutive patients with ITP, diagnosed between 1985 and 1994. In particular, we analyzed the therapies used, their response rates, prognostic indicators of response and outcome. In 62 patients, with minor bleeding episodes and a mean (+/- SD) platelet count of 88 +/- 23 x 10(9)/l, no treatment was used and chronic ITP was diagnosed in 59%. A total of 139 patients, with bleeding episodes in 71.2% cases and a mean platelet count of 20 +/- 13 x 10(9)/l, received at least one treatment. Three patients died (1.5% of the series). Corticosteroids were used in 118 patients, with an initial response rate of 82.2% and a long-term complete response (CR) of only 22.9%. Intravenous immunoglobulin was used in 26 patients, with an initial transient response in more than 60%. A splenectomy was performed in 55 patients, with an initial response rate of 92.5% and a long-term CR in 60%. Young age and prior response to corticosteroids were significant predictors of a durable response to splenectomy. Danazol was given in 37 patients, with a favorable response in 73% of cases. Our results illustrate the guidelines of the American Society of Hematology. Patients with moderate thrombocytopenia do not require treatment. In severe cases, splenectomy is the only treatment giving durable cures in a significant proportion of patients. Despite frequent chronicity, ITP is life-threatening only in a minor subset of patients.

Tyrosine hydroxylase and acetylcholinesterase in the domestic pig mesencephalon: An immunocytochemical and histochemical study

The mesencephalon of the young domestic pig was studied by tyrosine hydroxylase (TH) immunocytochemistry and acetylcholinesterase (AChE) histochemistry with focus on the substantia nigra (SN), the ventral tegmental area (VTA), and related areas. The purpose was to obtain information on the organization of the mesencephalic, TH immunoreactive (TH-i), and dopaminergic areas of the pig, in order to provide the necessary background for the possible use of the pig as an alternative large animal experimental model for research on Parkinson's disease, including the use of encapsulated pig dopaminergic neurons for intracerebral xenotransplantation. Significant findings in the pig, compared to observations in other species, included the presence of prominent bundles of TH-i dendrites passing in a dorsoventral direction from pars compacta into pars reticulata at middle and caudal levels of the SN, and the presence of a distinct TH-i substantia nigra pars lateralis (SNL). Caudally in the pig mesencephalon, the retrorubral field (RRF) was found to be very extensive. The view of the RRF, SN, and VTA as parts of the same integrated system was indicated by the crisscrossing of TH-i dendrites at the transitions between these areas. Estimation of the number of TH-i neurons in the SN and the VTA showed that these nuclei were of equal size in the pig. Further, it was found that TH-i nerve cells were present in the midline between the VTA in the interfascicular and rostral linear groups. TH-i nerve cells were also present in the otherwise serotoninergic dorsal raphe nuclei, just as other TH-i cells formed a perirubral cell group. AChE-positive neurons were present in both SN and VTA, and appeared to have the same size and morphology as the TH-i neurons in these areas. Within both nuclei, there were local differences in the AChE staining density, but perhaps more significantly were some marked differences in the structure of the AChE-positive neuropil of the two areas. We anticipate that the present description of the cellular organization of the TH-i dopaminergic areas in the domestic pig ventral mesencephalon will be useful for the development of a nonprimate, large animal, experimental model of Parkinson's disease.

Grundumsatz und Energieverbrauch im h�heren Lebensalter

The purpose of this study was to investigate energy requirements in healthy elderly subjects. Total daily energy expenditure (TEE) and resting metabolic rate (RMR) were measured by the doubly labeled water technique and indirect calorimetry in 36 healthy free living elderly men and women. Over a 15 day period additional measurements were made of dietary intake, physical activity and body composition. TEE did not differ between women and men (2941+/-439 vs 2965+/-543 kcal/d; p=ns), ranging from 2124 to 3968 kcal/d. Resting metabolic rate was significantly lower in women compared to men (1345+/-194 vs 1543+/-303 kcal/d; p=0.016). The TEE data were compared to the food diaries. Women and men underestimated their food intake significantly. TEE varies greatly within elderly subjects due to the variation in body weight and physical activity.

The AZFa gene DBY (DDX3Y) is widely transcribed but the protein is limited to the male germ cells by translation control

We explored the function of the human DEAD-box Y RNA helicase DBY (DDX3Y) gene located in the (AZFa) region on the human Y chromosome (Yq11.21). Deletion of this Y interval is known to be a major cause for the occurrence of a severe testicular pathology, the Sertoli-cell-only (SCO) syndrome. DBY has a structural homologue on the short arm of the X chromosome DBX (DDX3X) (Xp11.4). We found widespread transcription of both genes in each tissue analyzed, although predominantly in testis tissue. However, translation of DBY was detected only in the male germ line, whereas DBX protein was expressed in all tissues analyzed. In testis tissue sections, DBY protein was found predominantly in spermatogonia, whereas DBX protein was expressed after meiosis in spermatids. We conclude that although both RNA helicases are structurally very similar, they have diverged functionally to fulfill different roles in the RNA metabolism of human spermatogenesis, and that deletion of the DBY gene is the most likely cause of the severe testicular pathology observed in men with AZFa deletions.

Domoic acid neurotoxicity in hippocampal slice cultures

The neurotoxicity of domoic acid was studied in 2-3 week old rat hippocampal slice cultures, derived from 7 day old rat pups. Domoic acid 0.1-100 microM was added to the culture medium for 48 hrs, alone or together with the glutamate receptor antagonists NS-102 (5-Nitro-6,7,8,9-tetrahydrobenzo[G]indole-2,3-dione-3-oxime), NBQX (2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(F)quinoxaline) or MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine hydrogen maleate), followed by transfer of the cultures to normal medium for additional 48 hrs. Neuronal degeneration in the fascia dentata (FD), CA3 and CA1 hippocampal subfields was monitored and EC(50) values estimated by densitometric measurements of the cellular uptake of propidium iodide (PI). The CA1 region was most sensitive to domoic acid, with an EC(50) value of 6 microM domoic acid, estimated from the PI-uptake at 72 hrs. Protective effects of 10 microM NBQX against 3 and 10 microM domoic acid were observed for both dentate granule cells and CA1 and CA3c pyramidal cells. NS102 and MK 801 only displayed protective effects when combined with NBQX. MK801 significantly increased the combined neuroprotective effect of NBQX and NS102 against 10 microM domoic acid in both CA1 and FD, but not in CA3. We conclude, that domoic acid neurotoxicity in CA3 and in hippocampal slice cultures in general primarily involves AMPA/kainate receptors. At high concentrations (10 microM domic acid) NMDA receptors are, however, also involved in the toxicity in CA1 and FD.

Differential expression of brain-derived neurotrophic factor transcripts after pilocarpine-induced seizure-like activity is related to mode of Ca2+ entry

Activity-dependent brain-derived neurotrophic factor (BDNF) expression is Ca2+-dependent, yet little is known about the Ca2+ channel contributions that might direct selective expression of the multiple BDNF transcripts. Here, effects of pilocarpine-induced seizure activity on total BDNF expression and on the individual sensitivity of BDNF transcripts to glutamate receptor and Ca2+ channel blockers were evaluated using hippocampal slice cultures and in situ hybridization of transcript-specific cRNA probes directed against mRNAs for the four 5' exons (I-IV) of the BDNF gene. mRNAs for nerve growth factor (NGF) and tyrosine kinase B (trkB) also were studied. Pilocarpine (5 mM) induced a dose- and time-dependent increase in total BDNF (exon V) mRNA expression in the dentate granule cells and CA3-CA1 pyramidal cells with maximal effects at 6 and 24 h, respectively. Increases were blocked by co-treatment with the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/kainate 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX: 25 microM) and the N-methyl-d-aspartic acid receptor antagonist 2-amino-5-phosphonovaleric acid (APV; 25 microM), whereas the L-type voltage sensitive Ca2+ channel blocker nifedipine (20 microM) was without detectable effect. Maximal NGF and trkB mRNA expression was induced by pilocarpine at 4 and 12 h, respectively. For the individual BDNF transcripts, APV blocked pilocarpine-induced increases in transcript II, whereas nifedipine blocked increases in transcripts I and III. Transcript IV levels were not altered by treatment. These results indicate that transcript II makes the greatest contribution to pilocarpine effects on total BDNF mRNA content in this model and provides evidence for regional and Ca2+ channel-specific differences in activity-dependent regulation of the different BDNF transcripts in hippocampus.

Neurotoxic and neuroprotective effects of the glutamate transporter inhibitor DL-threo-beta-benzyloxyaspartate (DL-TBOA) during physiological and ischemia-like conditions

Maintenance of low extracellular glutamate ([Glu](O)) preventing excitotoxic cell death requires fast removal of glutamate from the synaptic cleft. This clearance is mainly provided by high affinity sodium-dependent glutamate transporters. These transporters can, however, also be reversed and release glutamate to the extracellular space in situations with energy failure. In this study the cellular localisation of the glutamate transporters GLAST and GLT-1 in organotypic hippocampal slice cultures was studied by immunofluorescence confocal microscopy, under normal culture conditions, and after a simulated ischemic insult, achieved by oxygen and glucose deprivation (OGD). In accordance with in vivo findings, GLAST and GLT-1 were primarily expressed by astrocytes under normal culture conditions, but after OGD some damaged neurons also expressed GLAST and GLT-1. The potential damaging effect of inhibition of the glutamate transporters by DL-threo-beta-benzyloxyaspartate (DL-TBOA) was studied using cellular uptake of propidium iodide (PI) as a quantitative marker for the cell death. Addition of DL-TBOA for 48 h was found to induce significant cell death in all hippocampal regions, with EC(50) values ranging from 38 to 48 microM for the different hippocampal subregions. The cell death was prevented by addition of the glutamate receptor antagonists NBQX and MK-801, together with an otherwise saturating concentration of DL-TBOA (100 microM). Finally, the effect of inhibition of glutamate release, via reverse operating transporters during OGD, was investigated. Addition of a sub-toxic (10 microM) dose of DL-TBOA during OGD, but not during the subsequent 48 h recovery period, significantly reduced the OGD-induced PI uptake. It is concluded: (1) that the cellular expression of the glutamate transporters GLAST and GLT-1 in hippocampal slice cultures in general corresponds to the expression in vivo, (2) that inhibition of the glutamate transporters induces cell death in the slice cultures, and (3) that partial inhibition during simulation of ischemia by OGD protects against the induced PI uptake, most likely by blocking the reverse operating transporters otherwise triggered by the energy failure.

GDNF pre-treatment aggravates neuronal cell loss in oxygen-glucose deprived hippocampal slice cultures: a possible effect of glutamate transporter up-regulation

Besides its neurotrophic and neuroprotective effects on dopaminergic neurons and spinal motoneurons, glial cell line-derived neurotrophic factor (GDNF) has potent neuroprotective effects in cerebral ischemia. The protective effect has so far been related to reduced activation of N-methyl-D-aspartate receptors (NMDAr). This study tested the effects of GDNF on glutamate transporter expression, with the hypothesis that modulation of glutamate transporter activity would affect the outcome of cerebral ischemia. Organotypic hippocampal slice cultures, derived from 1-week-old rats, were treated with 100 ng/ml GDNF for either 2 or 5 days, followed by Western blot analysis of NMDAr subunit 1 (NR1) and two glutamate transporter subtypes, GLAST and GLT-1. After 5-day exposure to GDNF, expression of GLAST and GLT-1 was up-regulated to 169 and 181% of control values, respectively, whereas NR1 was down-regulated to 64% of control. However, despite these changes that potentially would support neuronal resistance to excitotoxicity, the long-term treatment with GDNF was found to aggravate the neuronal damage induced by oxygen-glucose deprivation (OGD). The increased cell death, assessed by propidium iodide (PI) uptake, occurred not only among the most susceptible CA1 pyramidal cells, but also in CA3 and fascia dentata. Given that glutamate transporters are able to release glutamate by reversed action during energy failure, it is suggested that the observed increase in OGD-induced cell death in the GDNF-pretreated cultures was caused by the build-up of excitotoxic concentrations of extracellular glutamate released through the glutamate transporters, which were up-regulated by GDNF. Although the extent and consequences of glutamate release via reversal of GLAST and GLT-1 transporters seem to vary in different energy failure models, the present findings should be taken into account in clinical trials of GDNF.

Impaired learning correlates with size of excitotoxic hippocampal CA3 lesions in adult rats, but shows no amelioration by CA3 transplants

Hippocampal CA3 pyramidal cells grafted as cell suspensions to excitotoxic hippocampal lesions in adult rats can exchange several types of short and long range nerve connections with the host brain. We now examined whether such grafts also had functional effects in terms of ameliorating lesion-induced learning and memory deficits. Adult, male rats with bilateral, one week old, ibotenic acid-lesions of the hippocampal CA3 region, were grafted with suspensions of fetal (E18-19) CA3 cells. Seven weeks later the animals were tested for spatial navigation in the Morris Watermaze, together with groups of lesion-only and sham-operated, control rats. The tests were performed over 5 days, with 4 trials per day. At the end of the trials, the size of the lesions and the size and structural incorporation of the transplants in the host brains were evaluated morphometrically for correlations with the behavioural data. We found significant differences in swim pathlength and latency to find the platform in the Morris Watermaze between the lesion-only group and the grafted group versus the sham operated group, but no significant difference between the lesion-only and the grafted group. There was a significant positive correlation between the size of the CA3 lesions and the paucity of performance of the rat in the Watermaze, just as spontaneous recovery accordingly had not occurred over the 8 weeks postlesion. We conclude that the behavioural improvement exerted by the CA3 cell suspension grafts, at a time point when graft-host connections have had time to establish, is at most incomplete by these transplants, pointing to the difficulties there may be in obtaining full functional integration.

Asymptomatic deficiency in the peptide transporter associated to antigen processing (TAP)

Human HLA class I deficiency is a rare disease which, in most of the patients described to date, results from a defect in subunit 1 or 2 of the peptide transporter associated with antigen processing (TAP). The clinical features of TAP deficiency include a chronic inflammation of the respiratory tract and/or granulomatous skin lesions. In this report, we describe two adult siblings with an HLA class I deficiency. One individual had only spontaneously-healing skin granulomatous lesions, while the second did not display any of the symptoms associated with HLA class I deficiency and could be considered to be healthy. We show that the patients display a homozygous TAP2 mutation which blocks the maturation of HLA class I molecules. Cell surface expression of these molecules is strongly reduced, but three times higher than on cells from other previously described TAP-deficient individuals. This higher expression results, at least in part, from the presence of HLA-B7 molecules which are probably empty of peptide. The numbers of CD8+ alphabeta T cells are almost normal in these patients. The anti-EBV T-cell response of one patient is mediated by HLA-B7 restricted CD8+ alphabeta T lymphocytes recognizing the BMRF1 nuclear EBV antigen, demonstrating that CD8+ alphabeta T cells can participate in anti-viral responses. This study shows that TAP deficiency can remain totally asymptomatic for several decades, and suggests that in some cases, TAP-independent immune responses provide efficient protection from most of the common intracellular pathogens.

Additive effect of glial cell line-derived neurotrophic factor and neurotrophin-4/5 on rat fetal nigral explant cultures

Transplantation of embryonic dopaminergic neurons is an experimental therapy for Parkinson's disease, but limited tissue availability and suboptimal survival of grafted dopaminergic neurons impede more widespread clinical application. Glial cell line-derived neurotrophic factor (GDNF) and neurotrophin-4/5 (NT-4/5) exert neurotrophic effects on dopaminergic neurons via different receptor systems. In this study, we investigated possible additive or synergistic effects of combined GDNF and NT-4/5 treatment on rat embryonic (embryonic day 14) nigral explant cultures grown for 8 days. Contrary to cultures treated with GDNF alone, cultures exposed to NT-4/5 and GDNF+NT-4/5 were significantly larger than controls (1.6- and 2.0-fold, respectively) and contained significantly more protein (1.6-fold). Treatment with GDNF, NT-4/5 and GDNF+NT-4/5 significantly increased dopamine levels in the culture medium by 1.5-, 2.5- and 4.7-fold, respectively, compared to control levels, and the numbers of surviving tyrosine hydroxylase-immunoreactive neurons increased by 1.7-, 2.1-, and 3.4-fold, respectively. Tyrosine hydroxylase enzyme activity was moderately increased in all treatment groups compared to controls. Counts of nigral neurons containing the calcium-binding protein, calbindin-D28k, revealed a marked increase in these cells by combined GDNF and NT-4/5 treatment. Western blots for neuron-specific enolase suggested an enhanced neuronal content in cultures after combination treatment, whereas the expression of glial markers was unaffected. The release of lactate dehydrogenase into the culture medium was significantly reduced for GDNF+NT-4/5-treated cultures only. These results indicate that combined treatment with GDNF and NT4/5 may be beneficial for embryonic nigral donor tissue either prior to, or in conjunction with, intrastriatal transplantation in Parkinson's disease.

Neurons in the monoaminergic nuclei of the rat and human central nervous system express FA1/dlk

The gene DLK1 encodes a member of the epidermal growth factor (EGF) superfamily, delta-like (dlk). When exposed in vivo to the action of an unknown protease, this type 1 membrane protein generates a soluble peptide referred to as Fetal antigen 1 (FA1). By acting in juxtacrine as well as paracrine/autocrine manners, both forms have been shown to be active in the differentiation/proliferation process of various cell types. In adults, FA1/dlk has been demonstrated mainly within (neuro) endocrine tissues. In this study we investigated the presence of FA1/dlk in other parts of the developing and adult rat and human CNS. Using immunocytochemistry and in situ hybridization we found that in both species FA1/dlk was expressed in neurons of the Edinger-Westphal's nucleus as well as in substantia nigra, ventral tegmental area (VTA), locus coeruleus and in certain parts of the raphe nuclei.

Cre recombinase-mediated inactivation of H-2Dd transgene expression: evidence for partial missing self-recognition by Ly49A NK cells

We have established H-2D(d)-transgenic (Tg) mice, in which H-2D(d) expression can be extinguished by Cre recombinase-mediated deletion of an essential portion of the transgene (Tg). NK cells adapted to the expression of the H-2D(d) Tg in H-2(b) mice and acquired reactivity to cells lacking H-2D(d), both in vivo and in vitro. H-2D(d)-Tg mice crossed to mice harboring an Mx-Cre Tg resulted in mosaic H-2D(d) expression. That abrogated NK cell reactivity to cells lacking D(d). In D(d) single Tg mice it is the Ly49A+ NK cell subset that reacts to cells lacking D(d), because the inhibitory Ly49A receptor is no longer engaged by its D(d) ligand. In contrast, Ly49A+ NK cells from D(d) x MxCre double Tg mice were unable to react to D(d)-negative cells. These Ly49A+ NK cells retained reactivity to target cells that were completely devoid of MHC class I molecules, suggesting that they were not anergic. Variegated D(d) expression thus impacts specifically missing D(d) but not globally missing class I reactivity by Ly49A+ NK cells. We propose that the absence of D(d) from some host cells results in the acquisition of only partial missing self-reactivity.

H-2D ligand expression by Ly49A+ natural killer (NK) cells precludes ligand uptake from environmental cells: implications for NK cell function

To study the adaptation of natural killer (NK) cells to their major histocompatibility complex (MHC) class I environment we have established a novel mouse model with mosaic expression of H-2D(d) using a Cre/loxP system. In these mice, we noticed that NK cells expressing the inhibitory receptor for D(d), Ly49A, were specifically underrepresented among cells with low D(d) levels. That was due to the acquisition of D(d) molecules by the Ly49A+ NK cells that have lost their D(d) transgene. The uptake of H-2D molecules via the Ly49A receptor was restricted to strong ligands of Ly49A. Surprisingly, when Ly49A+ NK cells were D(d+), uptake of the alternative ligand D(k) was not detectable. Similarly, one anti-Ly49A mAb (A1) bound inefficiently when Ly49A was expressed on D(d+) NK cells. Concomitantly, functional assays demonstrated a reduced capacity of Ly49A to inhibit H-2(b)D(d) as compared with H-2(b) NK cells, rendering Ly49A+ NK cells in D(d+) mice particularly reactive. Minor reductions of D(d) levels and/or increases of activating ligands on environmental cells may thus suffice to abrogate Ly49A-mediated NK cell inhibition. The mechanistic explanation for all these phenomena is likely the partial masking of Ly49A by D(d) on the same cell via a lateral binding site in the H-2D(d) molecule.

Chronic exposure of kainate and NBQX changes AMPA toxicity in hippocampal slice cultures

Receptor agonist/antagonist mediated modulation of the excitotoxic effect of AMPA was studied in organotypic hippocampal slice cultures. Treatment of developing cultures for 2 weeks with a subtoxic dose of 2 microM kainate reduced the toxicity of 3 microM AMPA, applied for 48 h with 24 h of recovery, as measured by cellular uptake of the fluorescent dye propidium iodide. In contrast long-term treatment with 0.3 microM of the AMPA/KA antagonist NBQX increased the susceptibility of the cultures to an even lower dose of 2 microM AMPA. The modulatory effects of long-term application of low doses of kainate and NBQX, have implications for the development and use of related drugs that aim to protect against glutamate receptor-mediated disturbances.

Comparison of excitotoxic profiles of ATPA, AMPA, KA and NMDA in organotypic hippocampal slice cultures

The excitotoxic profiles of (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl)propionic acid (ATPA), (RS)-2-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), kainic acid (KA) and N-methyl-D-aspartate (NMDA) were evaluated using cellular uptake of propidium iodide (PI) as a measure for induced, concentration-dependent neuronal damage in hippocampal slice cultures. ATPA is in low concentrations a new selective agonist of the glutamate receptor subunit GluR5 confined to KA receptors and also in high concentrations an AMPA receptor agonist. The following rank order of estimated EC(50) values was found after 2 days of exposure: AMPA (3.7 mM)>NMDA (11 mM)=KA (13 mM)>ATPA (33 mM). Exposed to 30 microM ATPA, 3 microM AMPA and 10 microM NMDA, CA1 was the most susceptible subfield followed by fascia dentata and CA3. Using 8 microM KA, CA3 was the most susceptible subfield, followed by fascia dentata and CA1. In 100 microM concentrations, all four agonists induced the same, maximal PI uptake in all hippocampal subfields, corresponding to total neuronal degeneration. Using glutamate receptor antagonists, like GYKI 52466, NBQX and MK-801, inhibition data revealed that AMPA excitotoxicity was mediated primarily via AMPA receptors. Similar results were found for a high concentration of ATPA (30 microM). In low GluR5 selective concentrations (0.3-3 microM), ATPA did not induce an increase in PI uptake or a reduction in glutamic acid decarboxylase (GAD) activity of hippocampal interneurons. For KA, the excitotoxicity appeared to be mediated via both KA and AMPA receptors. NMDA receptors were not involved in AMPA-, ATPA- and KA-induced excitotoxicity, nor did NMDA-induced excitotoxicity require activation of AMPA and KA receptors. We conclude that hippocampal slice cultures constitute a feasible test system for evaluation of excitotoxic effects and mechanisms of new (ATPA) and classic (AMPA, KA and NMDA) glutamate receptor agonists. Comparison of concentration-response curves with calculation of EC(50) values for glutamate receptor agonists are possible, as well as comparison of inhibition data for glutamate receptor antagonists. The observation that the slice cultures respond with more in vivo-like patterns of excitotoxicity than primary neuronal cultures, suggests that slice cultures are the best model of choice for a number of glutamate agonist and antagonist studies.

Radiobiological hypoxia, oxygen tension, interstitial fluid pressure and relative viable tumour area in two human squamous cell carcinomas in nude mice during fractionated radiotherapy

Very little is known about the correlation between the radiobiological hypoxic fraction (rHF) and other measures of tumour oxygenation during fractionated irradiation. In the present study the rHF is determined in untreated human FaDu and GL squamous cell carcinoma in nude mice and in tumours irradiated with 10 fractions in 2 weeks and 20 fractions in 4 weeks, using tumour control as the experimental endpoint. The results were compared with measurements of the pO2, the interstitial fluid pressure (IFP) and the relative viable tumour area. In FaDu tumours the radiobiological hypoxic fractions (rHFs) before and during irradiation were not statistically different from 100%. Depending on the assumptions made for D0, the rHFs of GL tumours were between 0.2 and 4% or 30 and 53%. The median pO2 values were 2.8 mmHg for untreated FaDu tumours and 0.2 mmHg for GL tumours (p < 0.001). The median IFP values were 2.6 mmHg in FaDu and 5.3 mmHg in GL tumours (p = 0.01). No important changes in the pO2 and IFP values were observed during fractionated irradiation. The relative viable tumour area during irradiation decreased by 83% in FaDu tumours (p = 0.002) and by 54% in GL tumours (p = 0.003). It is concluded that differences in rHF exist between FaDu and GL tumours before and during fractionated irradiation and that these differences are not reflected by pO2 and IFP values and the relative viable tumour area.