Rat model of Parkinson's disease: chronic central delivery of 1-methyl-4-phenylpyridinium (MPP+).

Mitochondrial dysfunction is observed in sporadic Parkinson's disease (PD) and may contribute to progressive neurodegeneration. While acute models of mitochondrial dysfunction have been used for many years to investigate PD, chronic models may better replicate the cellular disturbances caused by long-standing mitochondrial derangements and may represent a better model for neurotherapeutic testing. This study sought to develop a chronic model of PD that has the advantages of continuous low level toxin delivery, low mortality, unilateral damage to minimize aphagia and adipsia as well as minimal animal handling to reduce stress-related confounds. Infusion by osmotic minipump of the complex I toxin, 1-methyl-4-phenylpyridinium (MPP+), for 28 days into the left cerebral ventricle in rats caused a selective ipsilateral loss of nigral tyrosine hydroxylase immunoreactive somata (35% loss). In animals that were sacrificed 14 days after the chronic MPP+ administration, there was an even greater loss of nigral tyrosine hydroxylase cells (65% loss). Lewy-body-like structures that stained positive for ubiquitin and alpha-synuclein were found in striatal neurons near the infusion site but were not observed in nigral neurons. At the electron microscope level, however, swollen and abnormal mitochondria were observed in the nigral dopamine neurons, which may represent the early formation of an inclusion body. There were no animal deaths with the chronic treatment regimen that was utilized, and the magnitude of nigrostriatal neuronal loss was relatively consistent among the animals. This model of progressive neurodegeneration of nigrostriatal dopamine neurons may be useful for studying neuroprotective therapeutic agents for PD.

Neurodegeneration in the Niemann-Pick C mouse: glial involvement.

A mouse model of Niemann-Pick type C disease has been found that exhibits neuropathology similar to the human condition. There is an age-related neurodegeneration in several brain regions and a lack of myelin in the corpus callosum in these mice. The purpose of the present study was to examine the Niemann-Pick mouse and determine whether: (1) microglia and astrocytes exhibit ultrastructural pathology similar to that found in neurons; (2) nerve fiber number is reduced when the myelin sheath is absent; and (3) the lysosomal hydrolase, cathepsin-D, is involved in the neurodegenerative process. Using light and electron microscopic methods, and immunocytochemistry, Niemann-Pick and control animals were examined at several ages. Cathepsin-D content was semi-quantitatively measured in neurons and glial cells in brain regions known to exhibit neurodegeneration, as was the density of glial fibrillary acidic protein-labeled astrocytes. The Niemann-Pick mouse exhibited: (1) an age-related increase in inclusion bodies in microglia and astrocytes, similar to that observed within neurons; (2) an almost complete absence of myelin in the corpus callosum by 7-8 weeks of age, along with a 30% reduction in the number of corpus callosum axons; (3) a mild age-related increase in cathepsin-D content within nerve cells in many brain regions. However, the cathepsin-D elevation was greatest in microglial cells; (4) an age-related increase in the number of microglial cells containing intense cathepsin-D immunoreactivity in both the thalamus and cerebellum. Both of these brain regions have been shown previously to exhibit an age-related loss of neurons; and (5) an increase in the number of reactive astrocytes immunostained for glial fibrillary acidic protein, especially in the thalamus and cerebellum. These data indicate that glial cells are a major target for pathology in the Niemann-Pick mouse. The lack of myelin within the corpus callosum may be related to the loss of nerve fibers in this structure. The increase in cathepsin-D-laden microglial cells, in brain regions previously shown to undergo neurodegeneration, is consistent with a role for microglia in the phagocytosis of dead neurons and in actively contributing to the neurodegenerative process. The activation of astrocytes in regions that undergo neurodegeneration is also consistent with a role for these glial cells in the neurodegenerative process.

Degeneration of neurons and glia in the Niemann-Pick C mouse is unrelated to the low-density lipoprotein receptor.

The BALB/c mouse model of Niemann-Pick type C disease exhibits similar neuropathological features to the human condition, including cerebral atrophy, demyelination of the corpus callosum, and degeneration of cerebellar Purkinje cells. The gene defect in Niemann-Pick C disease causes cholesterol to accumulate within the lysosomal compartment of neurons and glial cells. In order to determine whether cholesterol accumulation through the low-density lipoprotein receptor pathway plays an important role in the degenerative process, Niemann-Pick C mice were crossed with low-density lipoprotein receptor knockout mice. The purpose of the present study was to determine whether degeneration of neurons and glial cells is reduced in Niemann-Pick C animals lacking the low-density lipoprotein receptor. Using stereological counting methods, Purkinje cells were counted in the cerebellum and glial cell bodies were counted in the corpus callosum in mice at 3, 7.5 and 11 weeks of age. In the Niemann-Pick C animals, compared to wild-type control mice, there were 48% fewer glial cells at 3 weeks of age, and by 11 weeks of age there were 63% fewer glial cells. Purkinje cells were decreased in number by 13% at 3 weeks of age, and by 11 weeks of age there was a 96% loss. In the Niemann-Pick C animals lacking low-density lipoprotein receptors, there was no difference in the magnitude of glial cell or Purkinje cell loss compared to the Niemann-Pick C animals. These data indicate that both neurons and glia are vulnerable to degeneration in the Niemann-Pick C mouse, but that blocking the accumulation of cholesterol through the low-density lipoprotein receptor pathway does not alter the degenerative phenotype of Niemann-Pick C disease.

Selective neurodegeneration, without neurofibrillary tangles, in a mouse model of Niemann-Pick C disease.

The BALB/c mouse model of Niemann-Pick type C (NPC) disease exhibits neuropathological similarities to the human condition. There is an age-related cerebral atrophy, demyelination of the corpus callosum, and degeneration of cerebellar Purkinje cells in the NPC mouse. In human NPC, many cortical and subcortical neurons contain neurofibrillary tangles, which are thought by some investigators to play an important role in the neurodegenerative process. The purpose of the present study was to determine whether neurodegeneration occurs in the NPC mouse, in brain regions other than the cerebellum and whether the degeneration is related to the presence of neurofibrillary tangles. Using light microscopic methods with immunohistochemistry, electron microscopy, and cell counting methods, 11-week-old NPC(+/+) and NPC(-/-) animals were examined. In the NPC(-/-) mice, there were 96% fewer Purkinje cells, 28% fewer neurons in the prefrontal cortex, 20% fewer neurons in the thalamus, and 63% fewer glial cells in the corpus callosum. On the other hand, previous studies indicate normal numbers of neurons and glial cells in these same neuroanatomical regions in young NPC(-/-) mice. There were normal numbers of cholinergic neurons in sections assessed in the striatum and basal forebrain in the 11-week-old animals and no evidence of neurofibrillary tangles within cells. The present data indicate that both neurons and glial cells die in the NPC mouse but that all cells are not equally vulnerable. There was no evidence for neurofibrillary tangles in the NPC mouse, and therefore the degenerative process in the mouse is unrelated to the neurofibrillary tangle.

Pharmacological inactivation of the vesicular monoamine transporter can enhance 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurodegeneration of midbrain dopaminergic neurons, but not locus coeruleus noradrenergic neurons.

The vesicular monoamine transporter in the brain can sequester the neurotoxin 1-methyl-4-phenylpyridinium into synaptic vesicles and protect catecholamine-containing neurons from degeneration. Mouse nigrostriatal dopaminergic neurons, and to a lesser extent locus coeruleus noradrenergic neurons, are vulnerable to toxicity produced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. The present study sought to determine whether pharmacological inactivation of the vesicular monoamine transporter in the brain would enhance the degeneration of substantia nigra dopaminergic neurons and locus coeruleus noradrenergic neurons in 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine-treated animals. Mice were treated subacutely with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine alone, or in combination with vesicular monoamine transporter inhibitors (tetrabenazine or Ro4-1284), and 10-24 days later striatal dopamine and cortical norepinephrine levels were measured using chromatographic methods. In the same animals, substantia nigra and locus coeruleus catecholaminergic neurons were counted using tyrosine hydroxylase immunohistochemical staining with computer imaging techniques. Mice in which pharmacological blockage of the vesicular monoamine transporter enhanced the effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity in the depletion of striatal dopamine concentrations also exhibited enhanced degeneration of substantia nigra dopaminergic neurons. In the same animals, however, vesicular monoamine transporter blockade did not enhance the effects of 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine in the locus coeruleus noradrenergic system. These data are consistent with the hypothesis that the vesicular monoamine transporter can protect catecholamine-containing neurons from 1-methyl-4-phenylpyridinium-induced degeneration by sequestration of the toxin within brain vesicular monoamine transporter-containing synaptic vesicles. Since the amount of vesicular monoamine transporter in locus coeruleus neurons is more than in substantia nigra neurons, and because 1-methyl-4-phenylpyridinium is sequestered within locus coeruleus neurons to a far greater extent than within substantia nigra neurons, it may be that a greater amount of vesicular monoamine transporter inhibition is required for 1-methyl-4-phenylpyridinium to be toxic to locus coeruleus neurons than to substantia nigra dopaminergic neurons.

Upregulation of estrogen receptors in the forebrain of aromatase knockout (ArKO) mice.

Estrogens have numerous reproductive and nonreproductive functions in brain. The actions of estrogens are mediated by estrogen receptors (ERs), and estrogens are believed to down-regulate their own receptors in many tissues. Assuming this to be true, if estrogens are removed there should be an upregulation of ERs. We have developed a mouse model in which estrogen synthesis is completely eliminated by homologous recombination to delete the gene encoding aromatase cytochrome P450 (P450(arom)). The P450(arom) enzyme catalyzes the synthesis of estrogens from androgens in the brain. The localization and density of ERs was studied in the brains of aromatase knockout (ArKO) and wild type male mice by using immunohistochemistry with a peptide antibody to ERalpha (ER-21) and computer imaging. In the wild-type animals a high density of ERalpha was found in a small number of hypothalamic cells; in the medial preoptic area, periventricular, arcuate, and ventromedial nuclei. A low and medium density of ERalpha was observed in cells of the lateral preoptic area, supraoptic, bed nucleus of the stria terminalis, and in central, medial and anterior cortical amygdaloid nuclei. The number of cells containing ERalpha-immunoreactivity was significantly increased (244%) in the medial preoptic area of the ArKO mice. In neither wild type nor ArKO animals was immunoreactivity observed in the cerebral cortex or striatum. There was intense ER-immunostaining in the nucleus of neurons in both wild type and ArKO mice. These data indicate that in the absence of estrogens there is as much as a 2-fold increase in the number of cells with ERalpha-immunoreactivity in certain hypothalamic and limbic regions. Thus, estrogens can down-regulate ERalpha in brain.

Reduced number of mediodorsal and anterior thalamic neurons in schizophrenia.

BACKGROUND: The thalamus is a brain region of interest in the study of schizophrenia because it provides critical input to brain regions such as the prefrontal, cingulate, and temporal cortices, where abnormalities have been repeatedly observed in patients with schizophrenia. Postmortem anatomic studies have rarely investigated the thalamus in this population. METHODS: Postmortem tissue was obtained from the left hemisphere of eight male schizophrenic patients and eight male age-matched control subjects. The optical dissector stereologic procedure was used to count neurons in the mediodorsal (MD) and anteroventral/anteromedial (AV/AM) nuclei of the thalamus. RESULTS: The number of neurons and volume of the MD were significantly reduced by 35% and 24%, respectively. The MD cell number reduction was a consistent finding; every control subject had more and every schizophrenic subject had fewer than 3.5 million neurons. Neuron number was also significantly reduced (16%) in the AV/AM nuclei. CONCLUSIONS: The present data indicate that schizophrenia is associated with robust reductions in nerve cell numbers in nuclei that communicate with the prefrontal cortex and limbic system. These thalamic anatomic deficits may be responsible, in part, for previous reports of such prefrontal cortical abnormalities as reduced synaptic density, reduced volume, and metabolic hypofunction.

In vitro studies of striatal vesicles containing the vesicular monoamine transporter (VMAT2): rat versus mouse differences in sequestration of 1-methyl-4-phenylpyridinium.

Significant differences exist in the sensitivity of mice and rats to the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) that cannot be explained by differences in exposure to or uptake of 1-methyl-4-phenylpyridinium (MPP(+)) into dopamine (DA) neurons. MPP(+) is also a substrate for the brain vesicular monoamine transporter (VMAT2), and sequestration into synaptic vesicles may be one mechanism of protection against MPP(+) toxicity. A greater sequestration of MPP(+) into vesicles of DA neurons in rats versus mice could explain the lower vulnerability of DA neurons in the rat to MPP(+) toxicity. To test this hypothesis, the kinetics of uptake for [(3)H]MPP(+) and [(3)H]DA as well as [(3)H]dihydrotetrabenazine binding to VMAT2 were compared in vesicles isolated from the striata of rats and mice. The K(m) value of [(3)H]MPP(+) transport was similar in the two species. In contrast, the maximal transport rate (V(max)) was 2-fold greater in vesicles from rats than in those from mice. Likewise, the K(m) value for [(3)H]DA transport was similar in both preparations, but the V(max) value was 2-fold greater in rat than in mouse vesicles. The B(max) value for [(3)H]dihydrotetrabenazine binding was also 2-fold greater in striatal vesicles from rats than in those from mice. Electron micrographs demonstrated that vesicles isolated from rats and mice were approximately the same size. Based on these observations, we propose that striatal vesicles from rats have more VMAT2 than vesicles from mice and that this species difference in VMAT2 density may help explain the reduced vulnerability of rat DA neurons to MPP(+) neurotoxicity.

Factors affecting access to menopause information.

OBJECTIVE: As female life expectancy increases, women spend a greater proportion of their life in menopause. Menopausal women may benefit from preventive treatments, such as hormone replacement therapy, and are more likely to use medical treatments if they have access to information about menopause. The purpose of this study was to identify women's needs with respect to learning about menopause. DESIGN: A 20-question survey was administered anonymously to 116 women during outreach programs. Data were separated and evaluated by race and level of education. RESULTS: A significant association was found between access to information about menopause and both race and education level. Being African American or having less than a college education was associated with a twofold risk (p < 0.01) for not having a source of menopause information. A significant relationship was found between a woman's rating of her current knowledge of menopause and access to source of information (p = 0.03); women who did not have an information source felt the least knowledgeable about the subject. Women varied in the ways in which they are comfortable with learning about menopause. Different groups of women seemed to prefer different methods of learning about menopause. CONCLUSIONS: Both level of education and race are associated with a woman's ability to obtain information about menopause. To enhance women's understanding of health during menopause, information must be readily available. This information should be presented to women through educational programs that are designed to meet the needs of varied groups of adult women.

Evidence for a deficit in cholinergic interneurons in the striatum in schizophrenia.

Neurochemical and functional abnormalities of the striatum have been reported in schizophrenic brains, but the cellular substrates of these changes are not known. We hypothesized that schizophrenia may involve an abnormality in one of the key modulators of striatal output, the cholinergic interneuron. We measured the densities of cholinergic neurons in the striatum in schizophrenic and control brains in a blind analysis, using as a marker of this cell population immunoreactivity for choline acetyltransferase, the synthetic enzyme of acetylcholine. As an independent marker, we used immunoreactivity for calretinin, a protein which is co-localized with choline acetyltransferase in virtually all of the cholinergic interneurons of the striatum. A significant decrease in choline acetyltransferase-positive and calretinin-positive cell densities was found in the schizophrenic cases compared with controls in the striatum as a whole [for the choline acetyltransferase-positive cells: controls: 3.21 +/- 0.48 cells/mm2 (mean +/- S.D.), schizophrenics: 2.43 +/- 0.68 cells(mm2; P < 0.02]. The decrease was patchy in nature and most prominent in the ventral striatum (for the choline acetyltransferase-positive cells: controls: 3.47 +/- 0.59 cells/mm2, schizophrenics: 2.52 +/- 0.64 cells/ mm2; P < 0.005) which included the ventral caudate nucleus and nucleus accumbens region. Three of the schizophrenic cases with the lowest densities of cholinergic neurons had not been treated with neuroleptics for periods from more than a month to more than 20 years. A decrease in the number or function of the cholinergic interneurons of the striatum may disrupt activity in the ventral striatal-pallidal-thalamic-prefrontal cortex pathway and thereby contribute to abnormalities in function of the prefrontal cortex in schizophrenia.

Mesopontine cholinergic and non-cholinergic neurons in schizophrenia.

Mesopontine cholinergic neurons influence midbrain dopaminergic neurons, and thalamic and cerebellar structures which have been implicated in the neuroanatomy of schizophrenia. It has been reported that there are approximately twice as many mesopontine cholinergic neurons in schizophrenics than in normals, using nicotinomide adenosine dinucleotide phosphatediaphorase histochemistry to identify the cholinergic neurons. The present study sought to replicate this finding by analysing mesopontine cholinergic neurons using an antibody against choline acetyltransferase. The mesopontine cholinergic neurons are located in the pars compacta and pars dissipata of the pedunculopontine nucleus, and in the laterodorsal tegmental nucleus. Quantitative computer imaging techniques were used to map the distribution of mesopontine cholinergic neurons. In addition, all medium-sized and large neurons in a region of interest containing the middle portion of the pedunculopontine nucleus pars compacta were counted in Nissl-stained sections. There was no difference between schizophrenic and normal brains in terms of: (i) the rostral-caudal length of the cholinergic cell complex, approximately 10 mm; (ii) the estimated total number of cholinergic neurons in the combined pedunculopontine nucleus and laterodorsal tegmental nucleus, approximately 20,000 cells unilaterally; and (iii) the combined number of cholinergic and non-cholinergic Nissl-stained neurons in the middle portion of the pedunculopontine nucleus. The present data do not support the previous observation of increased numbers of mesopontine cholinergic neurons in schizophrenia.

Quantification of cholinergic and select non-cholinergic mesopontine neuronal populations in the human brain.

The pars compacta and pars dissipata of the pedunculopontine nucleus contain cholinergic cell group Ch5, and the laterodorsal tegmental nucleus contains cholinergic cell group Ch6. The pedunculopontine nucleus has been implicated in a variety of functions, including mediation of rapid eye movement sleep and in extrapyramidal motor function, although the role of cholinergic and non-cholinergic neurons is unclear. Quantitative neuroanatomical techniques were used to map the distribution of cholinergic neurons in the mesopontine nuclei of the adult human brain. In addition, the number and distribution of comparably sized non-cholinergic neurons at selected anatomical levels were compared. An antibody raised against human choline acetyltransferase was used to stain immunohistochemically the mesopontine neurons in six brains, ranging in age from 28 to 60 years. The rostrocaudal length of the Cb5/Ch6 cell complex was approximately 10 mm. The estimated total number of cells was similar for all brains, and varied by less than 7%. The estimated average number of cholinergic cells in the combined pedunculopontine and laterodorsal tegmental nuclei was approximately 20,000, with 30% of the cells in the pedunculopontine nucleus pars compacta, 57% in the pedunculopontine nucleus pars dissipata and 13% in the laterodorsal tegmental nucleus. There was no correlation between cell number and age. Within areas of mesopontine tegmentum occupied by the Ch5 cholinergic neurons, there were often more noncholinergic neurons than comparably sized cholinergic neurons. The present study provides detailed maps of the distribution and number of mesopontine cholinergic neurons in the normal human brain. Many non-cholinergic neurons are intermixed with the cholinergic pedunculopontine neurons. One region of the pedunculopontine nucleus pars dissipata containing few cholinergic neurons, located adjacent to the ventral border of the pedunculopontine nucleus pars compacta, may correspond to the midbrain-extrapyramidal area as defined previously in rodent and in non-human primate. These data will be useful for quantitative neuropathological studies concerning the role of both cholinergic and non-cholinergic mesopontine neurons in diseases proposed to affect these neurons, including Parkinson's disease, schizophrenia and progressive supranuclear palsy.

The neurotoxin 1-methyl-4-phenylpyridinium is sequestered within neurons that contain the vesicular monoamine transporter.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine produces a parkinsonian syndrome in man and experimental animals. The toxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, 1-methyl-4-phenylpyridinium, exhibits high-affinity uptake by plasma membrane monoamine transporters and also by the vesicular monoamine transporter. Using autoradiographic and immunohistochemical methods in mice, we demonstrate the accumulation of [3H]1-methyl-4-phenylpyridinium within neurons that contain the vesicular monoamine transporter, following systemic administration of [3H]1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Within 1-24 h following the intraperitoneal administration of 10 microg/kg of [3H]1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, [3H]1-methyl-4-phenylpyridine labelling was found within such regions as the locus coeruleus, dorsal, medial, and pallidal raphe nuclei, substantia nigra pars compacta, ventral tegmental area, and paraventricular nucleus of the hypothalamus. These regions all contain monoaminergic somata as defined by immunohistochemical staining with an antibody against the vesicular monoamine transporter. There was a positive relationship between the density of [3H]1-methyl-4-phenylpyridinium label and the density of vesicular monoamine transporter immunoreactivity: the highest densities of both were found in the locus coeruleus and lowest densities in the midbrain dopaminergic neurons. In addition, [3H]1-methyl-4-phenylpyridinium labelling was detected in the bed nucleus of the stria terminalis and paraventricular nucleus of the thalamus, which also contained vesicular monoamine transporter immunoreactive nerve terminals. The present data indicate that low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine cause a significant accumulation of 1-methyl-4-phenylpyridinium within monoaminergic somata in parallel with the amount of vesicular monoamine transporter in the neuron. Since nuclei with intense labelling are not damaged by doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine that are toxic to midbrain dopaminergic neurons, these data are consistent with the hypothesis that sequestration of 1-methyl-4-phenylpyridinium within monoaminergic synaptic vesicles can protect the neurons from degeneration caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

Calbindin-D28k buffers intracellular calcium and promotes resistance to degeneration in PC12 cells.

The calcium-binding protein calbindin-D28k (CB) has been hypothesized to function, in part, as a neuroprotective protein. CB is localized within nerve cells that are often less vulnerable to degeneration in patients with Alzheimer's disease and Parkinson's disease, and cells containing CB can buffer intracellular calcium concentrations ([Ca2+]i). The present study was designed to directly test the hypothesis that CB can protect cells from degeneration by reducing [Ca2+]i. PC12 cells, transfected to express different levels of CB, were found to be significantly less vulnerable to degeneration caused by serum withdrawal, glutamate, and the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). However, CB did not protect cells from degeneration caused by the calcium ionophore A23187. CB-transfected cells exhibited reduced elevations in [Ca2+]i following treatment with bradykinin, or ATP compared to non-CB-containing cells. These data indicate that CB can protect cells from degeneration caused by certain conditions, and it reduces elevations in [Ca2+]i caused by influx from extracellular sources.

Inhibition of striatal energy metabolism produces cell loss in the ipsilateral substantia nigra.

This study examined whether damage to dopamine (DA) nerve terminals via inhibition of energy metabolism in the striatum would result in the retrograde loss of cell bodies in the substantia nigra. Infusion of 2 micromol malonate into the left striatum of rats resulted in a 67% loss of striatal DA and a 40% loss of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. No change in the number of Nissl-positive-TH-negative neurons was observed. These findings demonstrate the retrograde destruction of DA cell bodies in the substantia nigra resulting from energy impairment at their terminal projection site.

Dopamine transporter mRNA levels are high in midbrain neurons vulnerable to MPTP.

The neurotoxin MPTP kills only certain midbrain dopaminergic (DA) neurons to produce a model of Parkinson's disease. The dopamine transporter (DAT) is important to MPTP toxicity because to be neurotoxic, an MPTP metabolite must first gain access to the DA neuron via the DAT. Also, MPTP is less toxic to DA neurons that contain the putative neuroprotective calcium-binding protein calbindin-D28k (CB). The present study examined the relative importance of DAT activity and CB for cellular vulnerability to MPTP-induced degeneration in the C57BL/6 mouse. Cells that were vulnerable to MPTP were found to contain high levels of DAT mRNA, whereas cells that were not vulnerable contained low levels. Also, the few substantia nigra cells remaining after a toxic dose of MPTP contained only low levels of DAT mRNA. However, there was not a strong relationship between cellular resistance to MPTP toxicity and cells containing CB. These data provide in vivo evidence for a direct correlation between midbrain cellular vulnerability to MPTP toxicity and the activity of the DAT.

Calbindin-D28k in nerve cell nuclei.

Calbindin-D28k is a member of the large EF-hand family of calcium-binding proteins, that is believed to function, in part as a cytosolic calcium buffer. Recent studies have demonstrated that cells containing Calbindin-D28k are protected from degeneration caused by conditions that elevate intracellular calcium concentrations. Since its initial discovery in 1966, Calbindin-D28k has been localized in the cytoplasm of many neuronal populations, but its nuclear localization has been uncertain. Using light and electron microscopic immunohistochemistry, and nuclear fractionation methods, we demonstrate localization of Calbindin-D28k not only in the cytoplasm, but also in the nucleus of rodent midbrain dopaminergic neurons and cerebellar Purkinje cells. The Calbindin-D28k immunoreactive staining intensity in the nucleus was routinely equal or greater than that in the cytoplasm. Since calcium signals are propagated to the nucleus, where they can regulate gene expression, the existence of nuclear Calbindin-D28k has important implications for cellular function.

Practice tips: a simple measurement to monitor the size of gouty tophi and rheumatoid nodules.

An easy office technique is described for measuring tophi or rheumatoid nodules. Quantitative measurements obtained can provide objective evidence for early reduction in size of tophi under therapy and can document increases or decreases in rheumatoid nodules.

Prodromal urticaria with seronegative rheumatoid arthritis.

This case report describes an association of chronic diurnal urticaria with the onset of seronegative arthritis in a 38-year-old woman after her first pregnancy. Remission of the urticaria and rheumatoid arthritis occurred with methotrexate therapy. The variety of urticarial lesions that can be seen with arthritis are noted.