First-line surgery in prolactinomas: lessons from a long-term follow-up study in a tertiary referral center

CONTEXT

Although consensus guidelines recommend dopamine agonists (DAs) as the first-line approach in prolactinomas, some patients may opt instead for upfront surgery, with the goal of minimizing the need for continuation of DAs over the long term. While this approach can be recommended in selected patients with a microprolactinoma, the indication for upfront surgery in macroprolactinomas remains controversial, with limited long-term data in large cohorts. We aimed at elucidating whether first-line surgery is equally safe and effective for patients with micro- or macroprolactinomas not extending beyond the median carotid line (i.e., Knosp grade ≤ 1).

METHODOLOGY

Retrospective study of patients with prolactinomas Knosp grade ≤ 1 treated with upfront surgery. The primary endpoint was patients' dependence on DAs at last follow-up. The secondary endpoint was postoperative complications. Independent risk factors for long-term dependence on DAs were analyzed.

RESULTS

A microadenoma was noted in 45 patients (52%) and a macroadenoma in 41 (48%), with 17 (20%) harboring a Knosp grade 1 prolactinoma. Median follow-up was 80 months. First-line surgery resulted in long-term remission in 31 patients (72%) with a microprolactinoma and in 18 patients (45%) with a macroprolactinoma (p = 0.02). DA therapy was ultimately required in 11 patients (24%) with microadenomas vs. 20 (49%) with macroadenomas (p = 0.03). As for the latter, DA was required in 13 patients (76%) with Knosp grade 1 macroadenomas vs. 7 patients (29%) with Knosp grade 0 macroadenomas (p = 0.004). There was no mortality, and morbidity was minimal. Knosp grade 1 prolactinomas (OR 7.3, 95% CI 1.4-37.7, p = 0.02) but not adenoma size (i.e., macroprolactinomas) were an independent predictor of long-term dependence on DAs.

CONCLUSIONS

First-line surgery in patients with microprolactinomas or macroprolactinomas Knosp grade 0 resulted in a good chance of non-dependency on DA therapy. However, in patients with prolactinomas Knosp grade 1, first-line surgery cannot be recommended, as adjuvant DA therapy after surgery is required in the majority of them over the long term.

Primary Postnatal Dorsal Root Ganglion Culture from Conventionally Slaughtered Calves

Neurological disorders in ruminants have an important impact on veterinary health, but very few host-specific in vitro models have been established to study diseases affecting the nervous system. Here we describe a primary neuronal dorsal root ganglia (DRG) culture derived from calves after being conventionally slaughtered for food consumption. The study focuses on the in vitro characterization of bovine DRG cell populations by immunofluorescence analysis. The effects of various growth factors on neuron viability, neurite outgrowth and arborisation were evaluated by morphological analysis. Bovine DRG neurons are able to survive for more than 4 weeks in culture. GF supplementation is not required for neuronal survival and neurite outgrowth. However, exogenously added growth factors promote neurite outgrowth. DRG cultures from regularly slaughtered calves represent a promising and sustainable host specific model for the investigation of pain and neurological diseases in bovines.

Effects of Forskolin on Trefoil factor 1 expression in cultured ventral mesencephalic dopaminergic neurons

Trefoil factor 1 (TFF1) belongs to a family of secreted peptides that are mainly expressed in the gastrointestinal tract. Notably, TFF1 has been suggested to operate as a neuropeptide, however, its specific cellular expression, regulation and function remain largely unknown. We have previously shown that TFF1 is expressed in developing and adult rat ventral mesencephalic tyrosine hydroxylase-immunoreactive (TH-ir) dopaminergic neurons. Here, we investigated the expression of TFF1 in rat ventral mesencephalic dopaminergic neurons (embryonic day 14) grown in culture for 5, 7 or 10 days in the absence (controls) or presence of either glial cell line-derived neurotrophic factor (GDNF), Forskolin or the combination. No TFF1-ir cells were identified at day 5 and only a few at day 7, whereas TH was markedly expressed at both time points. At day 10, several TFF1-ir cells were detected, and their numbers were significantly increased after the addition of GDNF (2.2-fold) or Forskolin (4.1-fold) compared to controls. Furthermore, the combination of GDNF and Forskolin had an additive effect and increased the number of TFF1-ir cells by 5.6-fold compared to controls. TFF1 expression was restricted to neuronal cells, and the percentage of TH/TFF1 co-expressing cells was increased to the same extent in GDNF and Forskolin-treated cultures (4-fold) as compared to controls. Interestingly, the combination of GDNF and Forskolin resulted in a significantly increased co-expression (8-fold) of TH/TFF1, which could indicate that GDNF and Forskolin targeted different subpopulations of TH/TFF1 neurons. Short-term treatment with Forskolin resulted in an increased number of TFF1-ir cells, and this effect was significantly reduced by the MEK1 inhibitor PD98059 or the protein kinase A (PKA) inhibitor H89, suggesting that Forskolin induced TFF1 expression through diverse signaling pathways. In conclusion, distinct populations of cultured dopaminergic neurons express TFF1, and their numbers can be increased by factors known to influence survival and differentiation of dopaminergic cells.

Loss of Nogo-A-expressing neurons in a rat model of Parkinson's disease

The myelin-associated protein Nogo-A is among the most potent neurite growth inhibitors in the adult CNS. Recently, Nogo-A expression was demonstrated in a number of neuronal subpopulations of the adult and developing CNS but at present, little is known about the expression of Nogo-A in the nigrostriatal system, a brain structure severely affected in Parkinson's disease (PD). The present study sought to characterize the expression pattern of Nogo-A immunoreactive (ir) cells in the adult ventral mesencephalon of control rats and in the 6-hydroxydopamine (6-OHDA) rat model of PD. Immunohistochemical analyses of normal adult rat brain showed a distinct expression of Nogo-A in the ventral mesencephalon, with the highest level in the substantia nigra pars compacta (SNc) where it co-localized with dopaminergic neurons. Analyses conducted 1week and 1 month after unilateral striatal injections of 6-OHDA disclosed a severe loss of the number of Nogo-A-ir cells in the SNc. Notably, at 1week after treatment, more dopaminergic neurons expressing Nogo-A were affected by the 6-OHDA toxicity than Nogo-A-negative dopaminergic neurons. However, at later time points more of the surviving dopaminergic neurons expressed Nogo-A. In the striatum, both small and large Nogo-A-positive cells were detected. The large cells were identified as cholinergic interneurons. Our results suggest yet unidentified functions of Nogo-A in the CNS beyond the inhibition of axonal regeneration and plasticity, and may indicate a role for Nogo-A in PD.

Effects of creatine treatment on survival and differentiation of GABA-ergic neurons in cultured striatal tissue

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder, characterized by a prominent loss of GABA-ergic medium-sized spiny neurons in the caudate putamen. There is evidence that impaired energy metabolism contributes to neuronal death in HD. Creatine is an endogenous substrate for creatine kinases and thereby supports cellular ATP levels. This study investigated the effects of creatine supplementation (5 mm) on cell survival and neuronal differentiation in striatal cultures. Chronic creatine treatment resulted in significant increased densities of GABA-immunoreactive (-ir) neurons, although total neuronal cell number and general viability were not affected. Similar effects were seen after short-term treatment, suggesting that creatine acted as a differentiation factor. Inhibitors of transcription or translation did not abolish the creatine-mediated effects, nor did omission of extracellular calcium, whereas inhibition of mitogen-activated protein kinase and phosphatidylinositol-3-kinase significantly attenuated the creatine induced increase in GABA-ir cell densities. Creatine exhibited significant neuroprotection against toxicity instigated either by glucose- and serum deprivation or addition of 3-nitropropionic acid. In sum, the neuroprotective properties in combination with promotion of neuronal differentiation suggest that creatine has potential as a therapeutic drug in the treatment of neurodegenerative diseases, like HD.

Effects of creatine treatment on the survival of dopaminergic neurons in cultured fetal ventral mesencephalic tissue

Parkinson's disease is a disabling neurodegenerative disorder of unknown etiology characterized by a predominant and progressive loss of dopaminergic neurons in the substantia nigra. Recent findings suggest that impaired energy metabolism plays an important role in the pathogenesis of this disorder. The endogenously occurring guanidino compound creatine is a substrate for mitochondrial and cytosolic creatine kinases. Creatine supplementation improves the function of the creatine kinase/phosphocreatine system by increasing cellular creatine and phosphocreatine levels and the rate of ATP resynthesis. In addition, mitochondrial creatine kinase together with high cytoplasmic creatine levels inhibit mitochondrial permeability transition, a major step in early apoptosis. In the present study, we analyzed the effects of externally added creatine on the survival and morphology of dopaminergic neurons and also addressed its neuroprotective properties in primary cultures of E14 rat ventral mesencephalon. Chronic administration of creatine [5 mM] for 7 days significantly increased survival (by 1.32-fold) and soma size (by 1.12-fold) of dopaminergic neurons, while having no effect on other investigated morphological parameters. Most importantly, concurrent creatine exerted significant neuroprotection for dopaminergic neurons against neurotoxic insults induced by serum and glucose deprivation (P < 0.01), 1-methyl-4-phenyl pyridinium ion (MPP+) [15 microM] and 6-hydroxydopamine (6-OHDA) [90 microM] exposure (P < 0.01). In addition, creatine treatment significantly protected dopaminergic cells facing MPP+-induced deterioration of neuronal morphology including overall process length/neuron (by 60%), number of branching points/neuron (by 80%) and area of influence per individual neuron (by 60%). Less pronounced effects on overall process length/neuron and number of branching points/neuron were also found after 6-OHDA exposure (P < 0.05) and serum/glucose deprivation (P < 0.05). In conclusion, our findings identify creatine as a rather potent natural survival- and neuroprotective factor for developing nigral dopaminergic neurons, which is of relevance for therapeutic approaches in Parkinson's disease and for the improvement of cell replacement strategies.

Glial cell line-derived neurotrophic factor up-regulates GTP-cyclohydrolase I activity and tetrahydrobiopterin levels in primary dopaminergic neurones

Glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic neurones against toxic and physical damage. In addition, GDNF promotes differentiation and structural integrity of dopaminergic neurones. Here we show that GDNF can support the function of primary dopaminergic neurones by triggering activation of GTP-cyclohydrolase I (GTPCH I), a key enzyme in catecholamine biosynthesis. GDNF stimulation of primary dopaminergic neurones expressing both tyrosine 3-monooxygenase and GTPCH I resulted in a dose-dependent doubling of GTPCH I activity, and a concomitant increase in tetrahydrobiopterin levels whereas tyrosine 3-monooxygenase activity was not altered. Actinomycin D, asan inhibitor of de novo biosynthesis, abolished any GDNF-mediated up-regulation of GTPCH I activity. However, GTPCH I mRNA levels in primary dopaminergic neurones were not altered by GDNF treatment, suggesting that the mode of action for that up-regulation is not directly connected to the regulation of GTPCH I transcription. We conclude that GDNF, in addition to its action in structural differentiation, also promotes differentiation regarding expression and enzymatic activity of a crucial component in the dopaminergic biosynthetic pathway.

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.

GDNF and NGF family members and receptors in human fetal and adult spinal cord and dorsal root ganglia

We describe the expression of mRNA encoding ligands and receptors of members of the GDNF family and members of the neurotrophin family in the adult human spinal cord and dorsal root ganglia (DRG). Fetal human spinal cord and ganglia were investigated for the presence of ligands and receptors of the neurotrophin family. Tissues were collected from human organ donors and after routine elective abortions. Messenger RNA was found encoding RET, GFR alpha-1, BDNF, trkB, and trkC in the adult human spinal cord and BDNF, NT-3, p75, trkB, and trkC in the fetal human spinal cord. The percentage of adult human DRG cells expressing p75, trkA, trkB, or trkC was 57, 46, 29, and 24%, respectively, and that of DRG cells expressing RET, GFR alpha-1, GFR alpha-2, or GFR alpha-3 was 79, 20, 51, and 32%, respectively. GFR alpha-2 was expressed selectively in small, GFR alpha-3 principally in small and GFR alpha-1 and RET in both large and small adult human DRG neurons. p75 and trkB were expressed by a wide range of DRG neurons while trkA was expressed in most small diameter and trkC primarily in large DRG neurons. Fetal DRG cells were positive for the same probes as adult DRG cells except for NT-3, which was only found in fetal DRG cells. Messenger RNA species only expressed at detectable levels in fetal but not adult spinal cord tissues included GDNF, GFR alpha-2, NT-3, and p75. Notably, GFR alpha-2, which is expressed in the adult rat spinal cord, was not found in the adult human spinal cord.

Sustained delivery of GDNF: towards a treatment for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by the progressive loss of nigral dopaminergic neurons. Although symptomatic therapies to substitute for the missing neurotransmitter dopamine are efficient at the early stages of the disease, the goal is to find alternative therapies which could protect dopaminergic neurons from the degenerative process. We have used two distinct gene therapy approaches to deliver the neuroprotective molecule glial cell line-derived neurotrophic factor (GDNF) in animal models of the disease: (i) an encapsulated genetically engineered cell line releasing GDNF (ex vivo gene therapy); and (ii) a lentiviral vector encoding the GDNF gene (in vivo gene therapy). Both approaches allowed protection of nigral dopaminergic neurons against lesion-induced cell death in rodent as well as monkey models of PD. Behavioral symptoms were also ameliorated in these animals. In addition, co-transplantation of embryonic dopaminergic neuronal grafts and a GDNF-releasing capsule allowed improvement of graft survival and differentiation, thereby accelerating behavioral recovery. These results should lead to clinical application in the near future.

Liposome-mediated gene transfer to fetal human ventral mesencephalic explant cultures

The feasibility of non-viral gene transfer using liposomes is described for human fetal nigral tissue. Ventral mesencephalic explants from 6 to 12 week old fetuses were grown as free-floating roller tube cultures. For the transfection, a vector coding for beta-galactosidase driven by the Rous Sarcoma Virus promoter was used. The developmental stage of the human tissue, time in vitro and the amount of vector DNA used significantly influenced the transfection efficiency. Optimal transfection results were obtained with tissue from a 10 week old fetus, cultured for 4 days and transfected with mixtures containing 4 microg vector DNA. Histological analysis suggested that a specific population of ventral mesencephalic precursor cells were the target for the gene transfer. This finding might have implications for gene delivery and cell replacement strategies in Parkinson's disease.

Influence of time in culture and BDNF pretreatment on survival and function of grafted embryonic rat ventral mesencephalon in the 6-OHDA rat model of Parkinson's disease

Embryonic midbrain can be maintained as free-floating roller tube cultures prior to grafting in experimental Parkinson's disease. We examined the influence of pregrafting culture time and pretreatment with brain-derived neurotrophic factor on graft survival and function. Cultures were prepared from solid pieces of embryonic (E14) rat ventral mesencephalon and maintained 4, 8, or 12 days in vitro with or without brain-derived neurotrophic factor (100 ng/ml) and grafted into the striatum of 6-hydroxydopamine-lesioned rats. Graft survival and function were evaluated by amphetamine-induced rotation behavior, number of tyrosine hydroxylase-immunoreactive neurons, striatal reinnervation, and graft volume. Rats receiving untreated tissue cultured for 4 or 8 days displayed no differences in graft quality, while grafts from 12-day-old cultures contained significantly fewer (P < 0.05) tyrosine hydroxylase-immunoreactive neurons (340 +/- 97, 267 +/- 92, and 62 +/- 19) and displayed a lower survival rate (9.6 +/- 2.7, 7.9 +/- 2.7, and 2.6 +/- 0.8% for 4, 8, and 12 days in vitro, respectively). Only rats grafted with 4- and 8-day-old cultures recovered significantly (P < 0.05) from lesion-induced rotations (69.4 +/- 18.6, 70.3 +/- 13.9, and 23.2 +/- 12.1% for 4, 8, and 12 days in vitro, respectively). Striatal reinnervation decreased with increasing culture time (P < 0.05). Pretreatment of the cultures with brain-derived neurotrophic factor affected only graft-induced fiber reinnervation, which was reduced even after short culture times. We therefore suggest that a storage period of 8 days is well suited to maintain embryonic rat ventral mesencephalon with the free-floating roller tube culture technique prior to transplantation. BDNF pretreatment as a new strategy to improve graft survival and function, however, was not effective.

Nonviral glial cell-derived neurotrophic factor gene transfer enhances survival of cultured dopaminergic neurons and improves their function after transplantation in a rat model of Parkinson's disease

Transplantation of dopaminergic fetal mesencephalic tissue into the striatum is currently being developed for treatment of patients with advanced Parkinson's disease. Ethical concerns regarding the use of human fetal tissue, and the limited availability as well as poor survival and differentiation of dopaminergic neurons after transplantation have reduced the extent and outcome of this approach so far. With the purpose of finding means to increase the yield of dopaminergic neurons in transplants, and to reduce the amount of fetal tissue needed for each transplanted patient, we transfected rat fetal ventral mesencephalic (VM) tissue grown as organotypic free-floating roller tube (FFRT) cultures with a vector encoding human glial cell-derived neurotrophic factor (hGDNF). For transfer of an episomal expression vector (pRep7-GDNF8) a nonviral, nonliposomal cationic transfection technique was applied and optimized. Recombinant hGDNF expression resulted in a higher number of TH-positive neurons in the cultures as measured 6 days after transfection. Ventral mesencephalic cultures expressing hGDNF were then grafted into the striatum of unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats. Grafting of genetically modified VM cultures resulted in earlier functional recovery compared with grafting nontransfected cultures. We conclude that organotypic free-floating roller tube cultures can be successfully transfected to produce hGDNF with effects on TH-expressing neurons in vitro and functional effects after grafting in a rat Parkinson's disease model.

Glial cell line-derived neurotrophic factor stimulates the morphological differentiation of cultured ventral mesencephalic calbindin- and calretinin-expressing neurons

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for mesencephalic dopaminergic neurons. Subpopulations of these neurons express the calcium-binding proteins calbindin (CB) and calretinin (CR). Understanding the specific effects of GDNF on these neurons is important for the development of an optimal cell replacement therapy for Parkinson's disease. To investigate the effects of GDNF on the morphological complexity of mesencephalic tyrosine hydroxylase (TH)-immunoreactive (-ir), CB-ir, and CR-ir neurons, dissociated cultures of embryonic (E14) rat ventral mesencephalon were prepared. Chronic administration of GDNF (10 ng/ml) for 7 days promoted the survival of TH-ir and CB-ir neurons but did not alter the density of CR-ir neurons. Total fiber length/neuron and number of branching points/neuron of CB-ir and CR-ir cells were significantly increased after GDNF treatment (2x for CB-ir cells and 1.4x and 1.7x, respectively, for CR-ir cells), which resulted in a significantly larger size of neurite field/neuron (2.9x and 1.5x for CB-ir and CR-ir neurons, respectively). The number of primary neurites/neuron of CB-ir neurons was found to be 1.5x larger, while no difference could be detected for CR-ir cells. Assessment of the effects of GDNF on TH-ir neurons unveiled a similar outcome with an increased total fiber length/neuron (1.5x), an increased number of primary neurites/neuron (1.6x), and a twofold larger size of neurite field/neuron. In conclusion, our findings recognize GDNF as a neurotrophic factor that stimulates the morphological differentiation of ventral mesencephalic CB-ir and CR-ir neurons.

Imaging the rat brain on a 1.5 T clinical MR-scanner

Magnetic resonance imaging (MRI) offers a noninvasive technique for studying neurodegenerative events in the rat brain, however, most of the studies are performed on small bore purpose dedicated MR scanners of limited availability and at high cost. The present study explored the feasibility of using a clinical whole body MR-scanner to perform imaging in rat brain and specifically in models of Parkinson's (PD) and Huntington's disease (HD). For that purpose rats were placed into a specially designed PVC device equipped with a flexible surface coil-and T2-weighted spin echo sequences were acquired on a Siemens Magnetom Vision at 1.5 T. In the experimental protocols of PD and HD, animals underwent 6-hydroxydopamine (6-OHDA) and quinolinic acid (QA) injections, respectively and were subsequently grafted with fetal tissue. T2-weighted images showed a small hyperintense area at the 6-OHDA lesion site and a diffuse hyperintensity in the striata with QA lesions. Transplants were seen as a hypointense area surrounded by a hyperintense rim on T1-weighted images. Moreover, disturbances of the blood-brain-barrier and its time of restoration could be monitored. In conclusion, high-resolution in vivo imaging of small animals is feasible with clinical MR-scanners and hence allows the study of various experimental protocols.

GDNF, RET and GFRalpha-1-3 mRNA expression in the developing human spinal cord and ganglia

The identification of endogenous neurotrophic factors and their receptors in human spinal cord is important not only to understand development, but also in the consideration of possible future therapies for neurodegenerative disorders and trauma. Using in situ hybridization, the expression of glial cell line-derived neurotrophic factor (GDNF), neurturin (NTN), persephin (PSP), GFRalpha-1, GFRalpha-2, GFRalpha-3 and RET mRNA in human fetal spinal cord was studied. Strong GDNF mRNA hybridization signal, presumably restricted to Clarke's nucleus, was detected in the thoracic spinal cord. mRNA encoding GFRalpha-1 was expressed in the entire spinal cord gray matter with particularly high expression in the ventral horn. GFRbeta-1 was also expressed more weakly in dorsal root ganglia. NTN and persephin mRNA were not detected in either the fetal spinal cord or the dorsal root ganglia. mRNA coding for GFRalpha-2, however, was found in most cells of the spinal cord gray matter. A strong expression of GFRalpha-3 mRNA was detected in dorsal root ganglia cells and Schwann cells. The transducing receptor RET was expressed strongly in motorneurons and dorsal root ganglion neurons. We conclude that basic features concerning the role of the GDNF family of ligands and their receptors revealed in rodents applies to humans.

Striatal grafts in a rat model of Huntington's disease: time course comparison of MRI and histology

Survival and integration into the host brain of grafted tissue are crucial factors in neurotransplantation approaches. The present study explored the feasibility of using a clinical MR scanner to study striatal graft development in a rat model of Huntington's disease. Rat fetal lateral ganglionic eminences grown as free-floating roller-tube cultures were grafted into the quinolinic acid-lesioned striatum, and T1- and T2-weighted sequences were acquired at 2, 7, 21, and 99 days posttransplantation. MR images were then compared with images of corresponding histological sections. The lesion-induced striatal degeneration caused a progressive ventricle enlargement, which was significantly different from controls at 21 days posttransplantation. Seven days posttransplantation, T1-weighted images revealed a defined liquid-isointense signal surrounded by a hyperintense rim at the site of graft placement, which was found unaltered for the first 21 days posttransplantation, whereas a hypointense graft signal was detected at 99 days posttransplantation. At 2 days posttransplantation, T2-weighted images showed the graft region as a hyperintense area surrounded by a rim of low signal intensity but at later time-points graft location could not be further verified. Measures for graft size and ventricle size obtained from MR images highly correlated with measures obtained from histologically processed sections (R = 0.8, P < 0.001). In conclusion, the present study shows that fetal rat lateral ganglionic eminences grown as free-floating roller-tube cultures can be successfully grafted in a rat Huntington model and that a clinical MR scanner offers a useful noninvasive tool for studying striatal graft development.

GDNF increases the density of cells containing calbindin but not of cells containing calretinin in cultured rat and human fetal nigral tissue

Among the dopaminergic neurons in substantia nigra pars compacta and in the ventral tegmental area, subpopulations express the calcium-binding proteins calbindin (CB) and calretinin (CR), and the CB-containing neurons are supposed to be less prone to degeneration in Parkinson's disease. Glial cell line-derived neurotrophic factor (GDNF) is a potent survival factor for nigrostriatal dopaminergic neurons. Using free-floating roller-tube (FFRT) cultures derived from fetal rat (E14) ventral mesencephalon we found that GDNF (10 ng/ml) significantly increased the number of surviving tyrosine hydroxylase (TH)-immunoreactive neurons. The possible effects of GDNF treatment on CB-immunoreactive (CB-ir) and CR-ir neurons in such cultures were examined in the present study. The neuronal cell densities were measured by quantifying the numbers of CB-ir and CR-ir neurons in areas of sections through the most extensive parts of the spherical cultures. In 4-day-old and 8-day-old cultures GDNF treatment increased the density of CB-ir neurons by 50% and 59%, respectively. Partial co-existence of TH and CB was shown using the method of double immunolabeling. The density of CR-containing neurons was unaffected by GDNF treatment as confirmed by Western blotting for CR. Parallel effects of GDNF treatment were obtained for cultures of human fetal ventral mesencephalon (8 weeks postconception). In conclusion, our findings identify GDNF as a potent factor for fetal rat and human nigral CB-ir neurons able to promote their survival in culture. Referring to a suggested neuroprotective role of CB, the results may be of relevance in the context of neuronal transplantation of patients suffering from severe Parkinson's disease.

Rat fetal ventral mesencephalon grown as solid tissue cultures: influence of culture time and BDNF treatment on dopamine neuron survival and function

Free-floating roller tube (FFRT) cultures of fetal rat and human nigral tissue are a means for tissue storage prior to grafting in experimental Parkinson's disease. In the present study, FFRT cultures prepared from embryonic-day-14 rat ventral mesencephalon were maintained for 4, 8, 12, or 16 days in vitro (DIV) in the presence or absence (controls) of BDNF [100 ng/ml]. The dopamine content in the culture medium, analyzed by HPLC, was significantly higher (4-5 fold) in the BDNF group at DIV 8 and DIV 12 compared to the corresponding control levels (40 pg/ml). The number of tyrosine hydroxylase immunoreactive neurons was significantly higher for BDNF treated cultures (2729+/-300) at DIV 8, as compared to controls (1679+/-217). At DIV 12, the culture volume was significantly increased by BDNF (1.05+/-0.12 vs. 0.71+/-0.04 mm3). Similar results were obtained for total protein. Western blot analysis demonstrated increasing signals for GFAP with increasing time in culture, but levels for control and BDNF treated cultures did not differ at any time-point investigated. In conclusion, it is suggested that the time window for effective storage of dopaminergic tissue prior to grafting can be extended by using the FFRT culture technique and that the in vitro storage may be further prolonged by treatment with BDNF.

Effects of combined BDNF and GDNF treatment on cultured dopaminergic midbrain neurons

Neural transplantation is an experimental therapy for Parkinson's disease. Pretreatment of fetal donor tissue with neurotrophic factors may improve survival of grafted dopaminergic neurons. Free-floating roller tube cultures of fetal rat ventral mesencephalon were treated with brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), or a combination of both. Dopamine content of the culture medium, the number of tyrosine hydroxylase-immunoreactive neurons, and culture volumes were moderately increased in the BDNF- and GDNF-treated cultures but significantly increased by 6.8-, 3.2- and 2.4-fold, respectively after treatment with the combination of both factors. We conclude that pretreatment of dopaminergic tissue in culture with a combination of BDNF and GDNF may be an effective means to improve the quality of tissue prior to grafting.

Comparison of mesencephalic free-floating tissue culture grafts and cell suspension grafts in the 6-hydroxydopamine-lesioned rat

Ventral mesencephalon (VM) of fetal rat and human origin grown as free-floating roller-tube (FFRT) cultures can survive subsequent grafting to the adult rat striatum. To further explore the functional efficacy of such grafts, embryonic day 13 ventral mesencephalic tissue was grafted either after 7 days in culture or directly as dissociated cell suspensions, and compared with regard to neuronal survival and ability to normalize rotational behavior in adult rats with unilateral 6-hydroxydopamine (6-OHDA) lesions. Other lesioned rats received injections of cell-free medium and served as controls. The amphetamine-induced rotational behavior of all 6-OHDA-lesioned animals was monitored at various time points from 18 days before transplantation and up to 80 days after transplantation. Tyrosine hydroxylase (TH) immunostaining of the histologically processed brains served to assess the long-term survival of grafted dopaminergic neurons and to correlate that with the behavioral effects. Additional cultures and acutely prepared explants were also fixed and stored for histological investigation in order to estimate the loss of dopaminergic neurons in culture and after transplantation. Similar behavioral improvements in terms of significant reductions in amphetamine-induced rotations were observed in rats grafted with FFRT cultures (127%) and rats grafted with cell suspensions (122%), while control animals showed no normalization of rotational behavior. At 84 days after transplantation, there were similar numbers of TH-immunoreactive (TH-ir) neurons in grafts of cultured tissue (775 +/- 98, mean +/- SEM) and grafts of fresh, dissociated cell suspension (806 +/- 105, mean +/- SEM). Cell counts in fresh explants, 7-day-old cultures, and grafted cultures revealed a 68.2% loss of TH-ir cells 7 days after explantation, with an additional 23.1% loss after grafting, leaving 8.7% of the original number of TH-ir cells in the intracerebral grafts. This is to be compared with a survival rate of 9.1% for the TH-ir cells in the cell-suspension grafts. Immunostaining for the calcium-binding proteins calretinin, calbindin, and parvalbumin showed no differences in the neuronal expression of these proteins between the two graft types. In conclusion, we found comparable dopaminergic cell survival and functional effects of tissue-culture grafts and cell-suspension grafts, which currently is the type of graft most commonly used for experimental and clinical grafting. In this sense the result is promising for the development of an effective in vitro storage of fetal nigral tissue, which at the same time would allow neuroprotective and neurotrophic treatment prior to intracerebral transplantation.

Expression of fos and jun genes in human skeletal muscle after exercise

It is believed that the induction of the fos and jun gene family of transcription factors might be at the origin of genetic events leading to the differential regulation of muscle-specific genes. We have investigated the effect of a 30-min running bout in untrained subjects on the expression of the mRNAs of all members of the fos and jun gene families, including c-fos, fosB, fosBdel, fra-1, and fra-2 as well as c-jun, junB, and junD. While the fos family members were transiently upregulated 10- to 20-fold (an exception being fra-2) the induction of the jun family members was up to 3-fold only. The induction of c-fos could also be demonstrated at the protein level. Both c-fos and c-jun mRNAs were coinduced in muscle fiber nuclei. The induction was not restricted to a particular fiber type, as expected from established muscle fiber recruitment schemes, but followed a "patchy" pattern confined to certain regions of the muscle. The signals leading to the expression of these immediate early genes are therefore unclear.

Implants of polymer-encapsulated genetically modified cells releasing glial cell line-derived neurotrophic factor improve survival, growth, and function of fetal dopaminergic grafts

Neural transplantation as an experimental therapy for Parkinsonian patients has been shown to be effective in several clinical trials. Further benefit, however, may be expected if the grafting is combined with a treatment of neurotrophic factors thus improving the survival and growth of grafted embryonic dopaminergic neurons. Continuous trophic support may be needed and therefore requires the long-term delivery of neurotrophic factors to the brain. We demonstrate here that the implantation of polymer-encapsulated cells genetically engineered to continuously secrete glial cell line-derived neurotrophic factor to the adult rat striatum improves dopaminergic graft survival and function. Near complete compensation of 6-hydroxydopamine-induced rotation was already achieved within 3 weeks postgrafting in rats that received glial cell line-derived neurotrophic factor-releasing capsules in addition to dopaminergic cell grafts of cultured tissue. Rats without trophic factor supply showed only little recovery at the same time point and sham grafted rats showed no recovery. The number of tyrosine hydroxylase-immunoreactive cells per graft was increased 2.6-fold in the presence of glial cell line-derived neurotrophic factor 6 weeks postgrafting. Similarly, tyrosine hydroxylase-immunoreactive fibers around the graft were increased by 53%. Moreover, these fibers showed a preferential growth towards the trophic factor-releasing capsule. Taken together, these results provide evidence that encapsulated genetically engineered cells are an effective means of long-term trophic factor supply into the adult rat brain and that the delivery of glial cell line-derived neurotrophic factor can sustain dopaminergic graft function and survival.

Nondevelopment of resistance by bacteria during hospital use of povidone-iodine

Since the bacterial ability to develop resistance against various factors of their surroundings is a well-known phenomenon, resistance against iodine and specifically against povidone-iodine (PVP-I) has been widely investigated. Yet there is little known about bacterial resistance in long-term daily use of disinfectants in continuous ambulatory peritoneal dialysis (CAPD) patients. The aim of our study was to investigate whether on daily use of PVP-I over a period of at least 6 months coagulase-negative staphylococci (CNS)--the predominant infective organisms of peritonitis--developed resistance against PVP-I. At the catheter exit site of 40 CAPD patients we isolated 36 CNS. 23 CNS (CNS + PVP) orginate from patients using PVP-I, 13 CNS (CNS + CI) from patients using sodium hypochlorite (NaOCl) as disinfectant. The strains were biotyped, antibiotic resistance patterns were determined and resistance against PVP-I or NaOCl was calculated as reduction factor using the quantitative suspension test combined with a turbidimetric standardization. Resistance against PVP-I 0.01% and against NaOCl 0.005% was determined at two contact times (30 and 300 s) for each patient group. In addition, we investigated the effects of plasmid loss on sensitivity to PVP-I. Out of 5 multiple-antibiotic-resistant CNS, 3 strains showed no difference in reduction factor against PVP-I before and after curing. There was no significant difference in reduction factor against NaOCl. CNS + PVP were even significantly more sensitive to PVP-I than CNS + Cl. Taken together, our results demonstrate that long-term use of PVP-I does not cause any bacterial resistance in CNS of CAPD patients.

Nuclear transport of insulin-like growth factor-I and insulin-like growth factor binding protein-3 in opossum kidney cells

When added to cultured opossum kidney cells, IGF-I is internalized and transported to distinct intracellular compartments that depend on the cell location within the monolayer. In resting cells away from the periphery of the monolayer, IGF-I is internalized by a clathrin coated pit pathway and delivered to the endosomal compartment. In contrast, cells growing at the edges of a monolayer or an experimental wound internalize IGF-I by an alternative route which rapidly delivers IGF-I to the nucleus. Similarly to IGF-I, IGFBP-3 is also internalized and accumulates in the endosomal compartment in resting cells whereas it is targeted to the nucleus in proliferating cells. IGFBP-3, which contains a putative nuclear targeting signal, may act as a carrier for IGF-I nuclear transport. The transport of IGF-I and IGFBP-3 to two different compartments may influence their biological activity.

Working underground: respiratory adaptations in the blind mole rat

Mole rats (Spalax ehrenbergi superspecies) perform the heavy work of digging their subterranean burrows in Israel under highly hypoxic/hypercapnic conditions. Unlike most other mammals, they can achieve high levels of metabolic rate under these conditions, while their metabolic rate at low work rates is depressed. We explored, by comparing mole rats with white rats, whether and how this is related to adaptations in the design of the respiratory system, which determines the transfer of O2 from the lung to muscle mitochondria. At the same body mass, mole rats were found to have a significantly smaller total skeletal muscle mass than ordinary white rats (-22%). In contrast, the fractional volume of muscle mitochondria was larger by 46%. As a consequence, both species had the same total amount of mitochondria and achieved, under normoxia, the same V(O2max). Whereas the O2 transport capacity of the blood was not different, we found a larger capillary density (+31%) in the mole rat muscle, resulting in a reduced diffusion distance to mitochondria. The structural pulmonary diffusing capacity for O2 was greater in the mole rat (+44%), thus facilitating O2 uptake in hypoxia. We conclude that structural adaptations in lung and muscle tissue improve O2 diffusion conditions and serve to maintain high metabolic rates in hypoxia but have no consequences for achieving V(O2max) under normoxic conditions.

Hsp70 expression in human skeletal muscle after exercise

Prolonged exercise of a sufficiently high intensity is thought to create physiological stress and to disturb cellular homeostasis, ultimately inducing cellular adaptations which enable the organism to better deal with any future exercise challenge. Heat shock proteins (hsp) are expressed when cells are exposed to different types of stress. In this study, we have investigated whether the expression of the heat inducible form of hsp70 is increased in human skeletal muscle cells after a single bout of exercise. Five untrained subjects performed an exercise bout at their individual anaerobic threshold for 30 min on a treadmill. Hsp70 mRNA concentration was significantly increased by a factor of four at 4 min post-exercise. Similarly high levels were also observed 30 min and 3 h after the end of exercise. Hsp70 protein concentration, on the contrary, did not change within 3 h after cessation of exercise. Thus, a single exercise bout in humans is able to increase the steady state concentration of hsp70 mRNA, but is probably not sufficient to have an effect on the already high basal level of its protein. The analysis of hsp70 mRNA is potentially useful as a method to detect stress in tissues with a high basal level of heat shock proteins.

Neurotrophin-4/5 treatment reduces infarct size in rats with middle cerebral artery occlusion

The aim of this study was to determine whether neurotrophin-4/5 (NT-4/5) treatment alters infarction volume following permanent focal cerebral ischemia in the rat. Permanent focal cerebral ischemia was produced in adult male rats by intraluminal occlusion of the right middle cerebral artery. NT-4/5 was administered intraventricularly one day before and immediately following occlusion. Rats were sacrificed at 1, 4 and 7 days after occlusion. NT-4/5 treatment reduced infarction volume by 34% when compared to control rats 1 day after occlusion. Infarction volume was unaltered by treatment 4 to 7 days after occlusion. Middle cerebral artery occlusion led to a significant reduction in levels of mRNAs coding for catalytic and truncated TrkB receptors. This expression was unaffected by NT-4/5 treatment.

Immunohistochemical visualization of brain-derived neurotrophic factor in the rat brain

A purified polyclonal antibody preparation was made against recombinant brain-derived neurotrophic factor (BDNF) in guinea pig and characterized for use in immunoassays and immunohistochemistry. The anti-BDNF antibodies specifically recognized BDNF in Western blots and immunoprecipitation. There was no cross-reactivity with the other known mammalian members of the neurotrophin family, nerve growth factor, neurotrophin-3 and neurotrophin-4/5. In immunohistochemical analysis, the anti-BDNF recognized exogenous BDNF injected into the brain of rats, whereas no signal was obtained with the other neurotrophins. Preabsorption with native BDNF abolished the immunoreactivity in brain sections. These studies identify the anti-BDNF as a tool for immunocytochemistry and the development of an immunoassay. Immunohistochemical analysis revealed widespread neuronal localization of BDNF in many brain areas. BDNF was localized in all subpopulations of hippocampal neurons. The distribution in the hippocampus suggests localization in the cytoplasm of cell bodies and dendrites.

Igf1 gene disruption results in reduced brain size, CNS hypomyelination, and loss of hippocampal granule and striatal parvalbumin-containing neurons

Homozygous Igf1-/- mice at 2 months of age had reduced brain weights, with reductions evenly affecting all major brain areas. The gross morphology of the CNS was normal, but the size of white matter structures in brain and spinal cord was strongly reduced, owing to decreased numbers of axons and oligodendrocytes. Myelinated axons were more strongly reduced in number than unmyelinated axons. The volume of the dentate gyrus granule cell layer was reduced in excess of the decrease in brain weight. Among populations of calcium-binding protein-containing neurons, there was a selective reduction in the number of striatal parvalbumin-containing cells. Numbers of mesencephalic dopaminergic neurons, striatal and basal forebrain cholinergic neurons, and spinal cord motoneurons were unaffected. Cerebellar morphology was unaltered. Our findings suggest cell type- and region-specific functions for IGF-I and emphasize prominent roles in axon growth and maturation in CNS myelination.

Okadaic acid potentiates heat-induced activation of erk2

Subjecting exponentially growing HeLa cells to heat shock at 45 degrees C for 30 min leads to retarded migration of erk1 and erk2, as revealed on immunoblots indicating their activation. Renaturation gels confirmed activation of erk2 but not erk1. Treatment of cells with okadaic acid (OA) alone marginally upregulated erk1 and erk2, whereas simultaneous exposure to heat shock and OA led to a considerably augmented response for erk2 which was approximately 3-fold higher than the sum of heat- and OA-induced activation. Chronic treatment of cells with 12-O-tetradecanoyl-phorbol 13-acetate marginally diminished the extent of erk2 stimulation, but had no influence on the OA-induced potentiation of heat-induced erk2 activity.

In vitro megakaryocytopoietic and thrombopoietic activity of c-mpl ligand (TPO) on purified murine hematopoietic stem cells

Recently, the ligand for c-mpl has been identified and cloned. Initial studies of this molecule indicate that it is the platelet regulatory factor, thrombopoietin (TPO). Previous work has indicated that c-mpl is expressed in very immature hematopoietic precursors and thus raised the possibility that TPO may act directly on the hematopoietic stem cell. Therefore, in these studies, we investigate the effects of TPO on hematopoietic stem cell populations isolated from the murine fetal liver and bone marrow. Cocultivation of stem cells with fetal liver stroma give rise to multilineage expansion of the stem cells but with little or no megakaryocytopoiesis. Addition of TPO to these cocultures gives significant megakaryocyte production. This production is enhanced in combination with Kit ligand or interleukin-3. The addition of TPO to stem cell suspension cultures produces a dynamic thrombopoietic system in which stem cells undergo differentiation to produce megakaryocytes and proplatelets. These experiments show that the megakaryocytopoietic and thrombopoietic activities of TPO are initiated at the level of an early progenitor cell or upon the hematopoietic stem cell.

Neurotrophin-4/5 promotes survival and differentiation of rat striatal neurons developing in culture

Cultures of dissociated striatal neurons from fetal rats were prepared, and were grown in the presence of neurotrophin-4/5 (NT-4/5) as well as the other known neurotrophins, nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3). We found that acute administration of NT-4/5 to 7-day-old cultures stimulates the hydrolysis of phosphatidylinositol, an event involved in neurotrophin signal transduction. Growth of striatal cultures in the presence of NT-4/5 resulted in increased cell survival, as indicated by elevations in cell number, protein content, and a measure of mitochondrial enzyme activity (MTT assay). NT-4/5 increased GABA uptake and staining intensity in these cultures, as indicated by GABA immunocytochemistry, indicating a trophic action on GABAergic neurons, the predominant neuron type in the striatum. To further identify responsive cell populations we analysed for calretinin, a calcium-binding protein known to colocalize with GABA in a number of neuronal cells. In cultures prepared from rats of embryonic day 15, NT-4/5 strongly increased the number of calretinin-positive cells as well as calretinin levels, as determined by Western blot analysis. When the cultures were prepared from embryonic day 18 rats, NT-4/5 very strongly increased the morphological differentiation of calretinin-positive cells, whereas the increase in cell number was less prominent. All effects produced by NT-4/5 were mimicked by BDNF with similar potency. NT-3 was less effective than NT-4/5 and BDNF, and its effects were limited to cultures prepared from embryonic day 15 rats, suggesting a role in the regulation of cell survival at early developmental stages. NGF did not affect any of the measured parameters. Our findings identify NT-4/5 as potent neurotrophic factor for striatal neurons, able to promote their survival and differentiation.

Deafferentation removes calretinin immunopositive terminals, but does not induce degeneration of calbindin D-28k and parvalbumin expressing neurons in the hippocampus of adult rats

Unilateral combined transections of the fimbriafornix and angular bundle in adult Fischer 344 rats were used to study the effects of deafferentation on hippocampal expression of calretinin, calbindin D-28k, and parvalbumin. Reflecting the widespread degeneration of synaptic contacts, immunostaining for glial fibrillary acidic protein 6 days after the lesions was increased in lacunosum-molecular and oriens layers of CA1, 2, and 3 in ipsi- and contralateral hippocampus and in the ipsilateral dentate gyrus outer molecular layer. At 21 days the immunoreactivity had decreased to control levels except for a still slightly increased signal in the oriens layer of CA1-3. At 6 and 21 days after the combined lesions the numbers of hippocampal neurons containing calretinin, parvalbumin, and calbindin D-28k was unaltered. The combined lesions abolished calretinin containing terminals in the dentate gyrus inner molecular layer on the deafferentated side. This could be reproduced by single unilateral fimbria-fornix transections, suggesting that the axons of these calretinin positive terminals project to the hippocampus through the fimbria-fornix. The most likely origin of the calretinin positive terminals are neurons in the supramammillary hypothalamic nucleus. Our findings demonstrate that the extensive lesion-induced synaptic rearrangements in the adult hippocampus do not induce degeneration of hippocampal neurons expressing calretinin, calbindin D-28k, and parvalbumin, but do remove calretinin containing terminals which reach their targets in the hippocampus through the fimbria-fornix.

Epidermal growth factor induces PC12 cell differentiation in the presence of the protein kinase inhibitor K-252a

The protein kinase inhibitors K-252a and K-252b have been shown earlier to block the actions of nerve growth factor and other neurotrophins and, at lower concentrations, to selectively potentiate neurotrophin-3 actions. In the present study we show that K-252a, but not K-252b, enhances epidermal growth factor (EGF)-and basic fibroblast growth factor (BFGF)-induced neurite outgrowth of PC12 cells at higher concentrations than required for neurotrophin inhibition. In parallel, tyrosine phosphorylation of extracellular signal-regulated kinases (Erks) elicited by EGF of bFGF was also increased in the presence of K-252a, and this signal was prolonged for 6 h. EGF- and bFGF-induced phosphorylation of phospholipase C-gamma 1 were not changed. The effect of K-252a on Erks was resistant to chronic treatment with phorbol ester, indicating that protein kinase C is not involved in this potentiation. In partial contrast to the actions of K-252a, the neurotrophin-3-potentiating effect of K-252b was accompanied by an increase in tyrosine phosphorylation of the Erks and of phospholipase C-gamma 1. Finally, although K-252a alone did not induce neurite outgrowth or tyrosine phosphorylation of Erks or phospholipase C-gamma 1, this compound alone stimulated phosphatidylinositol hydrolysis. Our findings identify activities of K-252a besides the direct interaction with neurotrophin receptors and suggest that a K-252a-sensitive protein kinase or phosphatase might be involved in signal transduction of EGF and bFGF. Our results are further compatible with the hypothesis that sustained activation of Erks may be important in PC12 differentiation.

Induction of apoptosis in the murine liver with recombinant human activin A

Recombinant human activin A, a member of the transforming growth factor-beta superfamily, induced significant cell loss in rodent livers and in primary hepatocyte cultures. Histologically and biochemically the hepatocyte death was mediated by apoptosis, a form of programmed cell death. Male mice were treated with 200 or 500 micrograms recombinant human activin A/kg body wt/day for up to 3 days by means of a subcutaneously implanted minipump. Livers were taken for light and electron microscopy, DNA isolation and in situ nick end-labeling. Primary cultures of rat hepatocytes were treated with 10 ng/ml recombinant human activin A for 24 hr before being harvested for electron microscopy and DNA isolation. Infusion of activin A evoked dose-dependent loss of liver mass due to the atrophy and death of hepatocytes around the central vein. Morphologically, the dying cells demonstrated all the characteristic nuclear and cytoplasmic features of apoptosis. Low molecular weight DNA isolated activin A-treated intact livers and primary cultures exhibited the typical oligosomal ladder. Nick end-labeling of DNA in situ confirmed that virtually all topographical apoptotic hepatocytes had fragmented DNA. The currently accepted criteria for apoptosis (i.e., specific morphological alterations and internucleosomal clipping of DNA) were evident in activin A-treated hepatocytes both in vitro and in vivo, leading to the conclusion that cell loss occurs mainly through apoptosis. These observations suggest that activin A may be important in hepatic homeostasis.

Stimulation of GABAergic neuron differentiation by NT-4/5 in cultures of rat cerebral cortex

Primary cultures of fetal rat cortical cells were used to investigate trophic effects of neurotrophin-4/5 (NT-4/5) on GABAergic neurons. Chronic administration of NT-4/5 resulted in a significant increase in high-affinity GABA uptake and in a stronger immunohistochemical staining pattern and bigger cells size of neurons visualized by GABA immunohistochemistry. Brain-derived neurotrophic factor (BDNF) exerted similar actions. These effects were observed in cultures prepared from rat fetuses from embryonic day (ED) 15 and ED18. The total number of cells was marginally increased in ED15 but not ED18 cultures. NT-4/5 did not elevate uptake of excitatory amino acids. Administration of NT-4/5 and BDNF resulted in higher levels of the calcium binding protein, calbindin, in these cultures. Our findings suggest that subpopulations of cortical GABAergic and calbindin-expressing neurons respond to NT-4/5 during development.

Response of embryonic rat hippocampal neurons in culture to neurotrophin-3, brain-derived neurotrophic factor and basic fibroblast growth factor

Primary cultures of rat hippocampal cells have been used to evaluate trophic effects of neurotrophin-3, brain-derived neurotrophic factor, nerve growth factor, and basic fibroblast growth factor. There was little survival in cultures prepared from embryonic day 17 embryos and grown in defined medium without growth factors. Addition of basic fibroblast growth factor produced a massive increase in the number of neurons present in the cultures seven days after plating. This action reflected proliferation of neuronal precursor cells rather than increased survival of initially plated neurons. Brain-derived neurotrophic factor was ineffective under these conditions, whereas neurotrophin-3 produced a very small, but statistically significant increase in neuronal survival in the range of 20%. However, hippocampal neurons were responsive to brain-derived neurotrophic factor and neurotrophin-3 as demonstrated under culture conditions, resulting in survival in absence of the neurotrophins. Acute administration of brain-derived neurotrophic factor and neurotrophin-3 to hippocampal cultures grown at high density stimulated the hydrolysis of phosphatidylinositol, a response earlier shown to be mediated by tyrosine receptor kinase neurotrophin receptors. Furthermore, when such cultures were grown in presence of neurotrophin-3 rates of glutamate and GABA uptake were increased. In contrast to the findings obtained in cultures of embryonic day 17, cultures prepared from embryonic day 14 or 15 animals were viable in absence of exogenous growth factors. The specific neurotrophin receptor inhibitor, K-252b reduced survival in these cultures and this effect was partly overcome by exogenous neurotrophin-3. Our findings suggest that hippocampal neuron survival at early embryonic stages may involve paracrine neurotrophin mechanisms, whereas the survival of hippocampal neurons of embryonic day 17 is not markedly enhanced by brain-derived neurotrophic factor or neurotrophin-3. However, at this embryonic stage there is a functional response to both neurotrophins as made evident by the activation of tyrosine kinase receptor-linked signal transduction mechanisms and by the stimulation of transmitter-specific differentiation.

Down-regulation of phosphatidylinositol response to BDNF and NT-3 in cultures of cortical neurons

The hydrolysis of phosphatidyl 4,5-bisphosphate (PI), which is involved in the transduction mechanism of neurotransmitters and growth factors, is stimulated by brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in primary cultures of fetal brain neurons. In the present study we sought to examine the effect of pretreatment with these factors on their acute stimulation capabilities and, furthermore, to substantiate that the effects of BDNF and NT-3 reflect actions on neurons rather than glial cells. Pretreatment with BNDF and NT-3 for 4 days followed by 1 day without growth factor abolished the effect of an acute stimulation with these factors. The growth factors were mutually effective so that BDNF pretreatment abolished the acute response to NT-3 and vice versa. In contrast, the effects of bFGF (basic fibroblast growth factor, a non-neurotrophin growth factor) also stimulating PI hydrolysis in these culture systems, were not reduced by neurotrophin pretreatment. Pretreatment with K-252b, at concentrations known to inhibit trk receptors, did not alter the acute stimulation of PI hydrolysis induced by the neutrophins. PI hydrolysis stimulated by BDNF and NT-3 in cultures grown in presence of cytosine arabinoside C, containing > 95% neurons, was higher than in cultures containing non-neuronal cells, indicating that the neurotrophin stimulation occurs in neuronal cells. No stimulatory effect was detected in bFGF treated pure neuronal cultures. The findings suggest that prolonged exposure of responsive neurons to BDNF and NT-3 down-regulates their stimulatory effects on PI hydrolysis.

Rapid phosphorylation of phospholipase C gamma 1 by brain-derived neurotrophic factor and neurotrophin-3 in cultures of embryonic rat cortical neurons

Phospholipase C gamma 1 (PLC-gamma 1) is involved at an early step in signal transduction of many hormones and growth factors and catalyzes the hydrolysis of phosphatidylinositol (PI) 4,5-bisphosphate to diacylglycerol and inositol trisphosphate, two potent intracellular second messenger molecules. The transformation of PC12 cells into neuron-like cells induced by nerve growth factor is preceded by a rapid stimulation of PLC-gamma 1 phosphorylation and PI hydrolysis. The present study analyzed the effects of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) on phosphorylation of PLC-gamma 1 in primary cultures of embryonic rat brain cells. BDNF and NT-3 stimulated the phosphorylation of PLC-gamma 1, followed by hydrolysis of PI. The stimulation of PLC-gamma 1 phosphorylation occurred within 20 s after addition of BDNF or NT-3 and lasted up to 30 min, with a peak after 4 min. ED50 values were similar for BDNF and NT-3, with approximately 25 ng/ml. Phosphorylation of PLC-gamma 1 by BDNF and NT-3 was found in cultures from all major brain areas. K-252b, a compound known to inhibit selectively neutrophin actions by interfering with the phosphorylation of trk-type neutrophin receptors, prevented the BDNF- and NT-3-stimulated phosphorylation of PLC-gamma 1. Receptors of the trk type were coprecipitated with anti-PLC-gamma 1 antibodies. The presence of trkB mRNA in the cultures was substantiated by northern blot analysis. The action of BDNF and NT-3 seems to be neuron specific because no phosphorylation of PLC-gamma 1 was observed in cultures of nonneuronal brain cells. The results provide evidence that developing neurons of the cerebral cortex and other brain areas are responsive to BDNF and NT-3, and they indicate that the transduction mechanism of BDNF and NT-3 in the brain involves rapid phosphorylation of PLC-gamma 1 followed by PI hydrolysis.

BDNF protection of basal forebrain cholinergic neurons after axotomy: complete protection of p75NGFR-positive cells

To elucidate the role of brain derived neurotrophic factor (BDNF) in the protection of cholinergic neurons in the basal forebrain, recombinant human BDNF and as a positive control, human recombinant nerve growth factor (NGF), were infused for 20 days into the lateral ventricle of adult rats with fimbrial transections. BDNF and NGF administration protected cholinergic basal forebrain cells from degenerative changes after axotomy, as assessed with immunohistochemical analysis of the two cholinergic marker proteins ChAT and p75NGFR. Both BDNF and NGF treatment completely prevent the lesion induced loss of p75NGFR-positive cells in the septal area of animals with fimbrial transections. This finding contrasts with the result obtained with ChAT immunohistochemistry, where BDNF treatment protects only part of the population of neurons which disappear following the transections. These findings are compatible with the view that there is a cascade of events induced in cholinergic neurons by the transections, so that ChAT expression is lost before p75NGFR expression, and that BDNF reduces degenerative events in the entire population of cholinergic neurons, maintaining some of them as p75NGFR-positive but ChAT-negative cells.

TGF alpha stimulation of phosphatidylinositol hydrolysis in mesencephalic cultures requires neuron-glia interactions

To elucidate the role of TGF alpha as a growth factor in the developing brain and to obtain information on signal transduction mechanisms mediating these effects, we measured the hydrolysis of phosphatidylinositol (PI) in cultures from fetal rat brain cells. Stimulation of PI breakdown induced by TGF alpha was observed in cultures of mesencephalic cells containing both neuronal and non-neuronal cells, whereas TGF alpha was ineffective in both pure neuronal and pure glial cultures. These findings are compatible with the view that TGF alpha plays a role during brain development and that its actions on PI hydrolysis, requires the presence of neuronal and glial cells.

Stimulation of phosphatidylinositol hydrolysis by brain-derived neurotrophic factor and neurotrophin-3 in rat cerebral cortical neurons developing in culture

Phosphatidylinositol (PI) breakdown represents a powerful system participating in the transduction mechanism of some neurotransmitters and growth factors and producing two second messengers, diacylglycerol and inositol trisphosphate. The transformation of PC12 neuroblastoma cells into neuron-like cells induced by nerve growth factor (NGF) is preceded by a rapid stimulation of PI breakdown; however, it was not known whether PI breakdown mediates actions of other members of the neurotrophin family. The present study analyzed the effects of NGF, brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) on PI breakdown in primary cultures of embryonic rat brain cells. Cultures were grown for 7 days; PI was then labeled by incubating cultures with myo-[3H]inositol, which then were exposed acutely to growth factors. BDNF and NT-3, but not NGF, elevated the levels of labeled inositol phosphates within 10-15 min after addition to the cultures in a dose-dependent manner. ED50 values for BDNF and NT-3 were 12.4 and 64.5 ng/ml, respectively. Comparable effects were found in cultures of cortical, striatal, and septal cells. The actions of BDNF and NT-3 probably reflect actions on neurons, because no effects were seen in cultures of nonneuronal cells. In contrast, basic fibroblast growth factor induced a marked stimulation of PI breakdown in cultures of nonneuronal cells. K252b, which selectively blocks neurotrophin actions by inhibiting trk-type receptor proteins, prevented the PI breakdown mediated by BDNF and NT-3. The findings suggest that rapid and specific induction of PI breakdown is involved in the signal transduction of BDNF and NT-3, and they provide evidence that cortical neurons are functionally responsive to BDNF and NT-3 during development.

Brain-derived neurotrophic factor administration protects basal forebrain cholinergic but not nigral dopaminergic neurons from degenerative changes after axotomy in the adult rat brain

Cell culture studies with dissociated primary cultures from embryonic rat brain revealed that brain-derived neurotrophic factor (BDNF) promotes the developmental differentiation of both basal forebrain cholinergic and mesencephalic dopaminergic neurons. These studies suggested that, in the adult brain, BDNF may be able to protect cholinergic and dopaminergic neurons from degenerative changes induced by axotomy, similar to the known protective action of NGF in cholinergic neurons. Testing this hypothesis, we found that intraventricular administration of recombinant human BDNF (rhBDNF) to adult rats with transections of the fimbria significantly reduces axotomy-induced degenerative changes of the cholinergic cells in the basal forebrain. No such effect was seen on the dopaminergic neurons of the ventral mesencephalon after transection of their axons ascending in the medial forebrain bundle. Injected in equal amounts, rhBDNF and recombinant human NGF had quantitatively different effects on the cholinergic neurons. BDNF sustained only part of the population of cholinergic neurons affected by the lesion, whereas the entire population was protected by NGF treatment.

Neurotrophin-induced trk receptor phosphorylation and cholinergic neuron response in primary cultures of embryonic rat brain neurons

Tyrosine phosphorylation of trk type neurotrophin receptors in primary cultures of embryonic rat brain cells was studied by immunoprecipitation and immunoblotting. In cultures containing basal forebrain cholinergic neurons, but not in cultures of cerebral cortex, nerve growth factor (NGF) treatment for 4 min induced tyrosine phosphorylation of trk family proteins. Stimulation with brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3), resulted in a very robust phosphorylation signal in basal forebrain and cortical cultures, suggesting actions of these neurotrophins not only on cholinergic cells but probably on most embryonic brain neurons. Trk tyrosine phosphorylation was completely abolished by 5 microM K-252b. Inhibition was rapid, being evident by 30 s following addition of the drug. Corresponding stimulatory and inhibitory effects were seen for phospholipase-C gamma 1 (PLC gamma 1) and extracellular signal-regulated kinase 1 (Erk1), two enzymes involved in second messenger mechanisms. Our findings indicate involvement of trk receptor activation in the NGF response of basal forebrain cholinergic cells and provide evidence for widespread presence of BDNF and NT-3 responsive neurons in the embryonic brain.

Pre- and postnatal lead exposure affects the serotonergic system in the immature rat brain

The effect of pre- and postnatal lead exposure on the development of the serotonergic system in striatum and brain stem was investigated. Serotonin and its metabolite 5-HIAA where determined by HPLC-EC. A significant decrease of 5-HT was detected in the brain stem at postnatal day 28. At both days 6 and 28 postnatal, 5-HIAA was reduced in striatum and brain stem. The results provide support to the hypothesis that developing 5-HT neurons are sensitive to relatively low levels of lead exposure.

[Public health and isolation measures with regard to infectious patients]

Patient isolation aims at reducing the risk of infection transmission to other patients and the hospital personnel. Three types of disease-specific isolation procedures and their indications are described: strict isolation, respiratory isolation and enteral isolation. The type of patient isolation to be applied depends on the mode of pathogen transmission and on the severity of the disease it produces.

[Hygienic rituals and proposals for practical action]

For years hygiene rituals have been performed in hospitals without awareness of their sense or usefulness. The present study sets out to show that entrance mats with tacky or disinfectant surfaces, complete disinfection of the hospital and routine general disinfections can be dispensed with. Shortcomings in surgical hand disinfection, placing and care of drains, and rinsing of stomach probes are also pointed out. Modern proposals should be aimed at raising the standard of hygiene in our hospitals, with special emphasis on the time-honoured rule of Semmelweis regarding strict and permanently available hygienic disinfection for the hands.