BACKGROUND： Thyroid hormones modulate proliferation of astrocytes and microglia depending on maturation stage and localization. Studies have demonstrated that triiodothyronine treatment or thyroidectomy during develo...BACKGROUND： Thyroid hormones modulate proliferation of astrocytes and microglia depending on maturation stage and localization. Studies have demonstrated that triiodothyronine treatment or thyroidectomy during developmental stages results in morphological alterations and changes in the number of astrocytes and microglia. Little is known about the effects of hypothyroidism on astrocytes and microglia in adults. OBJECTIVE： To investigate the effects of hypothyroidism on morphology and number of astrocytes and microglia in the adult rat hippocampus. DESIGN, TIME AND SETTING： A randomized, controlled, neuroendocrinological, animal study was performed at the College of Medicine, Hallym University, South Korea between May 2008 and April 2009. MATERIALS： Methimazole, rabbit anti-glial fibrillary acidic protein （GFAP） antiserum, and rabbit anti-lba-1 antiserum were purchased from Sigma, USA. Rabbit anti-GFAP polyclonal antibody was provided by Chemicon, USA. Rabbit anti-lba-1 polyclonal antibody was purchased from Wako, Japan. Terminal deoxynucleotidyl transferase dUTP-biotin nick-end-labeling （TUNEL） kit was provided by Roche Molecular Biochemicals, Mannheim, Germany. METHODS： Hypothyroidism was induced in Wistar rats via methimazole administration （0.025%） in drinking water for 5 weeks, starting at 6 months of age. MAIN OUTCOME MEASURES： Following methimazole treatment, hippocampai neuronal death was determined using TUNEL staining. The morphology and number of GFAP and lba-1 immunoreactive cells were detected by immunohistochemistry. Hippocampal GFAP and lba-1 protein levels were detected by Western blot analysis. Serum-free triiodothyronine and thyroxine levels were quantified. RESULTS： TUNEL-positive neurons were not observed in the hippocampus of euthyroid and hypothyroid rats. Compared with the euthyroid rats, the number of GFAP immunoreactive astrocytes was decreased, and serum triiodothyronine and thyroxine levels were significantly decreased. In contrast, the number of lba-1 immunoreactive microglia was significantly increased in the hypothyroid rats （P 〈 0.05）. In addition, GFAP immunoreactive astrocytes were morphologically at a resting state, and lba-1 immunoreactive microglia were morphologically hypertrophic. GFAP and IBa-1 protein changes in the hippocampus of euthyroid and hypothyroid rats were in accordance with immunohistochemical data. CONCLUSION： Although methimazole-induced hypothyroidism did not induce neuronal injury in the adult rat hippocampus, it did result in decreased astrocyte numbers and increased microglial hypertrophy.展开更多
The neurotrophin receptor （p75） activates the c-Jun N-terminal kinase （JNK） pathway. Activation of JNK and its substrate c-Jun can cause apoptosis. Here we evaluate the role of p75 in spinal motoneurons by compari...The neurotrophin receptor （p75） activates the c-Jun N-terminal kinase （JNK） pathway. Activation of JNK and its substrate c-Jun can cause apoptosis. Here we evaluate the role of p75 in spinal motoneurons by comparing immunoreactivity for p75 and phosphorylated c-Jun （p-c-Jun）, the production of JNK activation in axotomized motoneurons in postnatal day （PN）I, PN7, PN14 and adult rats. Intensive p-c-Jun was induced in axotomized motoneurons in PN1 and PN7. In PN14, p-c-Jun expression was sharply reduced after the same injury. The decreased expression of p-c-Jun at this age coincided with a developmental switch of re-expression of p75 in axotomized cells. In adult animals, no p-c-Jun but intensive p75 was detected in axotomized motoneurons. These results indicate differential expression or turnover of phosphorylation of c-Jun and p75 in immature versus mature spinal motoneurons in response to axonal injury. The non-co-occurrence of p75 and p-c-Jun in injured motoneurons indicated that p75 may not activate JNK pathway, suggesting that the p75 may not be involved in cell death in axotomized motoneurons.展开更多
Spontaneous Ca2+ oscillations in vascular smooth muscle cells have been modeled using a single Ca2+ pool. This report describes spontaneous Ca2+ oscillations dependent on two separate Ca2+ sources for the nuclear vers...Spontaneous Ca2+ oscillations in vascular smooth muscle cells have been modeled using a single Ca2+ pool. This report describes spontaneous Ca2+ oscillations dependent on two separate Ca2+ sources for the nuclear versus cytoplas- mic compartments. Changes in free intracellular Ca2+ were monitored with ratiometric Ca2+- fluorophores using confo- cal microscopy. On average, spontaneous oscillations developed in 79% of rat aortic smooth muscle cells that were synchronous between the cytoplasm and nucleus. Reduction of extracellular Ca2+ (< 1 μM) decreased the frequency and amplitude of the cytoplasmic oscillations with 48% of the oscillations asynchronous between the nuclear and cytoplasmic compartments. Similar results were obtained with the Ca2+ channel blockers, nimodipine and diltiazem. Arg-vasopressin (AVP) induced a rapid release of intracellular Ca2+ stores that was greater in the nuclear compartment (4.20 ± 0.23 ratio units, n = 56) than cytoplasm (2.54 ± 0.28) in cells that had spontaneously developed prior oscillations. Conversely, cells in the same conditions lacking oscillations had a greater AVP-induced Ca2+ transient in the cytoplasm (4.99 ± 0.66, n = 17) than in the nucleus (2.67 ± 0.29). Pre-treatment with Ca2+ channel blockers depressed the AVP responses in both compartments with the cytoplasmic Ca2+ most diminished. Depletion of internal Ca2+ stores prior to AVP exposure blunted the nuclear response, mimicking the response of cells that lacked prior oscillations. Spontaneous oscillating cells had a greater sarcoplasmic reticulum network than cells that did not oscillate. We propose that sponta- neous nuclear oscillations rely on perinuclear sarcoplasmic reticulum stores, while the cytoplasmic oscillations rely on Ca2+ influx.展开更多
基金Supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD,Basic Research Promotion Fund), No. KRF-2007-412-J00502
文摘BACKGROUND： Thyroid hormones modulate proliferation of astrocytes and microglia depending on maturation stage and localization. Studies have demonstrated that triiodothyronine treatment or thyroidectomy during developmental stages results in morphological alterations and changes in the number of astrocytes and microglia. Little is known about the effects of hypothyroidism on astrocytes and microglia in adults. OBJECTIVE： To investigate the effects of hypothyroidism on morphology and number of astrocytes and microglia in the adult rat hippocampus. DESIGN, TIME AND SETTING： A randomized, controlled, neuroendocrinological, animal study was performed at the College of Medicine, Hallym University, South Korea between May 2008 and April 2009. MATERIALS： Methimazole, rabbit anti-glial fibrillary acidic protein （GFAP） antiserum, and rabbit anti-lba-1 antiserum were purchased from Sigma, USA. Rabbit anti-GFAP polyclonal antibody was provided by Chemicon, USA. Rabbit anti-lba-1 polyclonal antibody was purchased from Wako, Japan. Terminal deoxynucleotidyl transferase dUTP-biotin nick-end-labeling （TUNEL） kit was provided by Roche Molecular Biochemicals, Mannheim, Germany. METHODS： Hypothyroidism was induced in Wistar rats via methimazole administration （0.025%） in drinking water for 5 weeks, starting at 6 months of age. MAIN OUTCOME MEASURES： Following methimazole treatment, hippocampai neuronal death was determined using TUNEL staining. The morphology and number of GFAP and lba-1 immunoreactive cells were detected by immunohistochemistry. Hippocampal GFAP and lba-1 protein levels were detected by Western blot analysis. Serum-free triiodothyronine and thyroxine levels were quantified. RESULTS： TUNEL-positive neurons were not observed in the hippocampus of euthyroid and hypothyroid rats. Compared with the euthyroid rats, the number of GFAP immunoreactive astrocytes was decreased, and serum triiodothyronine and thyroxine levels were significantly decreased. In contrast, the number of lba-1 immunoreactive microglia was significantly increased in the hypothyroid rats （P 〈 0.05）. In addition, GFAP immunoreactive astrocytes were morphologically at a resting state, and lba-1 immunoreactive microglia were morphologically hypertrophic. GFAP and IBa-1 protein changes in the hippocampus of euthyroid and hypothyroid rats were in accordance with immunohistochemical data. CONCLUSION： Although methimazole-induced hypothyroidism did not induce neuronal injury in the adult rat hippocampus, it did result in decreased astrocyte numbers and increased microglial hypertrophy.
基金supported by Direct Grant (Project No.2030392) of the Chinese University of Hong KongHK Spinal Cord Injury FoundationNational Key Basic Research Support Foundation (973 Project: 2011CB504402)
文摘The neurotrophin receptor （p75） activates the c-Jun N-terminal kinase （JNK） pathway. Activation of JNK and its substrate c-Jun can cause apoptosis. Here we evaluate the role of p75 in spinal motoneurons by comparing immunoreactivity for p75 and phosphorylated c-Jun （p-c-Jun）, the production of JNK activation in axotomized motoneurons in postnatal day （PN）I, PN7, PN14 and adult rats. Intensive p-c-Jun was induced in axotomized motoneurons in PN1 and PN7. In PN14, p-c-Jun expression was sharply reduced after the same injury. The decreased expression of p-c-Jun at this age coincided with a developmental switch of re-expression of p75 in axotomized cells. In adult animals, no p-c-Jun but intensive p75 was detected in axotomized motoneurons. These results indicate differential expression or turnover of phosphorylation of c-Jun and p75 in immature versus mature spinal motoneurons in response to axonal injury. The non-co-occurrence of p75 and p-c-Jun in injured motoneurons indicated that p75 may not activate JNK pathway, suggesting that the p75 may not be involved in cell death in axotomized motoneurons.
文摘Spontaneous Ca2+ oscillations in vascular smooth muscle cells have been modeled using a single Ca2+ pool. This report describes spontaneous Ca2+ oscillations dependent on two separate Ca2+ sources for the nuclear versus cytoplas- mic compartments. Changes in free intracellular Ca2+ were monitored with ratiometric Ca2+- fluorophores using confo- cal microscopy. On average, spontaneous oscillations developed in 79% of rat aortic smooth muscle cells that were synchronous between the cytoplasm and nucleus. Reduction of extracellular Ca2+ (< 1 μM) decreased the frequency and amplitude of the cytoplasmic oscillations with 48% of the oscillations asynchronous between the nuclear and cytoplasmic compartments. Similar results were obtained with the Ca2+ channel blockers, nimodipine and diltiazem. Arg-vasopressin (AVP) induced a rapid release of intracellular Ca2+ stores that was greater in the nuclear compartment (4.20 ± 0.23 ratio units, n = 56) than cytoplasm (2.54 ± 0.28) in cells that had spontaneously developed prior oscillations. Conversely, cells in the same conditions lacking oscillations had a greater AVP-induced Ca2+ transient in the cytoplasm (4.99 ± 0.66, n = 17) than in the nucleus (2.67 ± 0.29). Pre-treatment with Ca2+ channel blockers depressed the AVP responses in both compartments with the cytoplasmic Ca2+ most diminished. Depletion of internal Ca2+ stores prior to AVP exposure blunted the nuclear response, mimicking the response of cells that lacked prior oscillations. Spontaneous oscillating cells had a greater sarcoplasmic reticulum network than cells that did not oscillate. We propose that sponta- neous nuclear oscillations rely on perinuclear sarcoplasmic reticulum stores, while the cytoplasmic oscillations rely on Ca2+ influx.
