The ultrastructural picture of cerebral cortex of rat after hypoxia. I. Findings after inhalation of 5% O2 and 95% N2

The ultrastructure of some elements in the motor region of the cerebral cortex of the rat were studied after hypoxia. The experimental animals, after receiving intraperitoneal chloral hydrate anaesthesia, were placed in a chamber with a controlled supply of a mixture of 95% N2 and 5% O2. After 2- and 3-hour exposure to hypoxic conditions the animals were processed for electron optic study. Edematous mitochondria pith partial or total destruction of the mitochondrial matrix were observed. Some mitochondria were changed into large vacuolar formations. The granular endoplasmic reticulum of neurocytes was dilated and in the broad dilatation structures of lamellar shape were sporadically found. The Golgi complex contained vacuoles of different sizes and long cisterns. Hydrated astrocytes were visualized in the neuropil and perivascular astrocyte processes displayed edematous changes. In the group of animals exposed to hypoxia for 3 hours but processed only 24 hours after termination of hypoxia the same changes were observed yet their extent was considerably diminished. This finding indicates that changes induced by hypoxia tend to return to normal conditions.     

Purinergic receptor stimulation reduces cytotoxic edema and brain infarcts in mouse induced by photothrombosis by energizing glial mitochondria

Treatments to improve the neurological outcome of edema and cerebral ischemic stroke are severely limited. Here, we present the first in vivo single cell images of cortical mouse astrocytes documenting the impact of single vessel photothrombosis on cytotoxic edema and cerebral infarcts. The volume of astrocytes expressing green fluorescent protein (GFP) increased by over 600% within 3 hours of ischemia. The subsequent growth of cerebral infarcts was easily followed as the loss of GFP fluorescence as astrocytes lysed. Cytotoxic edema and the magnitude of ischemic lesions were significantly reduced by treatment with the purinergic ligand 2-methylthioladenosine 5' diphosphate (2-MeSADP), an agonist with high specificity for the purinergic receptor type 1 isoform (P2Y(1)R). At 24 hours, cytotoxic edema in astrocytes was still apparent at the penumbra and preceded the cell lysis that defined the infarct. Delayed 2MeSADP treatment, 24 hours after the initial thrombosis, also significantly reduced cytotoxic edema and the continued growth of the brain infarction. Pharmacological and genetic evidence are presented indicating that 2MeSADP protection is mediated by enhanced astrocyte mitochondrial metabolism via increased inositol trisphosphate (IP(3))-dependent Ca(2+) release. We suggest that mitochondria play a critical role in astrocyte energy metabolism in the penumbra of ischemic lesions, where low ATP levels are widely accepted to be responsible for cytotoxic edema. Enhancement of this energy source could have similar protective benefits for a wide range of brain injuries.     

The morphological picture of implanted foetal rat brain tissue

The authors studied the morphological picture of implanted foetal brain tissue. Macroscopically, they found that the grafts used for morphological study had taken in every case and that the size of the graft had doubled or trebled. The surface of the implant grew above the level of the recipient's cortex and numerous branching blood vessels were observed in the graft-cortex contact area. In the light microscope, organization of the cells in circular clusters or strips was found in the implant. Large numbers of blood vessels of varying calibre were present in the vicinity of large cell concentrations. Distinct differences between the cytoarchitectonics of the normal tissue of the recipient and the graft tissue were seen. Cells with a normal appearance or an apolar form, whose nucleus contained irregularly scattered chromatin and mosaic-like nucleoli, were observed at ultrastructural level. The nuclear membrane was thrown into multiple folds which invaginated deep into the nuclear matter. The Golgi complex covered a large area. Axodendritic synapses indistinguishable from the control were found in the neuropil. No changes were observed in the walls of the capillaries. The pericapillary zone was characterized by the presence of light astrocyte processes.     

Extreme endurance training: evidence of capillary and mitochondria compartmentalization in human skeletal muscle.

Biopsies from the medial gastrocnemius muscle of three experienced endurance runners who had completed an ultramarathon run (160 km) the previous day were assessed for their oxidative characteristics (fibre types, capillarization and mitochondria content). Also, a regional comparison was made for fibres located centrally (completely surrounded by other fibres) versus fibres located peripherally (next to the interfascicular space) and the capillarization of these peripheral fibres was determined. Subsarcolemmal mitochondria were abundant and 'compartmentalized' close to the capillaries. The number of capillaries around fibres ranged from 5.8 to 8.5 and 5.7 to 8.5, and the number of capillaries.mm-2 ranged from 665 to 810 and 727 to 762, for type I (slow twitch) and type II (fast twitch) fibres, respectively. Central fibres contained a greater number of capillaries and more capillaries.mm-2 than their peripheral counterparts. Peripheral fibres contained more capillaries.micron-1 between fibres than at the interfascicular space. Type I fibres were more distributed (63%-78%) and larger than type II fibres. An abundance of subsarcolemmal mitochondria located close to the capillaries, efficient capillary proliferation between fibres where sharing can occur and greater relative distribution and size of type I fibres are, collectively, efficient characteristics of extreme endurance training.     

The Calcium Content of Mitochondria from Brain Subregions Following Short-Term Forebrain Ischemia and Recirculation in the Rat

Abstract: A procedure was established for determining the calcium content of mitochondria isolated from rat brain subregions based on changes in fura-2 fluorescence after disruption of the organelles with Triton X-100 and sodium dodecyl sulfate. Mitochondria isolated from the forebrain of normal rats contained 2.5 ± 0.9 nmol of calcium/mg of protein. A 30-min ischemic period produced an approximately twofold increase in the calcium content of mitochondria isolated from the dorsolateral striatum, a region in which most neurons die within 24 h after this period of ischemia. The calcium content of mitochondria from the paramedian cortex, a region in which there are few ischemia-susceptible neurons, tended to be similarly increased, although this difference was not statistically significant. Larger increases (to approximately five times control values) were seen in mitochondria isolated from both regions after 10 min of recirculation. By 1 h of recirculation, mitochondrial calcium had returned close to preischemic control values in both regions. Longer recirculation periods produced no further changes in the calcium content of mitochondria from the paramedian cortex. However, mitochondrial calcium was again increased in the dorsolateral striatum after 6 h (6.5 nmol of calcium/mg of protein) and 24 h (8.7 nmol of calcium/mg of protein) of recirculation. This regionally selective increase in calcium in the dorsolateral striatum preceded the period during which the majority of neurons in this region exhibit advanced degenerative changes. Thus, this increase may be an essential step, albeit a late one, in the development of neuronal loss.     

Electron microscopy study of microcirculation in the rat cerebral cortex after total neutron irradiation

It was established that the ultrastructure of blood capillaries of the brain changes during the first six hours following whole-body neutron irradiation of rats (10 Gy) which was indicative of the capillary wall swelling, the increase in the microcirculatory bed permeability, and pericapillary edema development. Those processes seemed to be reversible since during this period no severe destructive changes were detected in the microvessel wall.     

Functional Coupling of Endogenous Serotonin (5-HT1B) and Calcitonin (C1a) Receptors in CHO Cells to a Cyclic AMP-Responsive Luciferase Reporter Gene

Abstract: The hypothesis that P-glycoprotein plays a functional role at the brain capillary endothelium, which makes up the blood-brain barrier in vivo, is based largely on immunocytochemical studies showing immunoreactive P-glycoprotein localized to either isolated brain microvessels or microvessels within tissue sections. The present studies use the MRK16 monoclonal antibody to human P-glycoprotein to demonstrate that the pattern of immunolocalization of P-glycoprotein in microvessels of human or primate brain is similar to the pattern of immunolocalization of an astrocyte protein, glial fibrillary acidic protein. In contrast, the discontinuous staining pattern of MRK16 is not colocalized with the continuous immunostaining of the brain endothelial GLUT1 glucose transporter. The MRK16 antibody was radiolabeled with [¹²⁵I]-iodine, and ¹²⁵I-MRK16 avidly bound isolated human brain capillaries via a saturable mechanism. However, the ¹²⁵I-MRK16 antibody was not taken up by primate brain capillaries in vivo following intravenous injection. In conclusion, these studies provide evidence that P-glycoprotein does not play a functional role at the luminal membrane of the brain capillary endothelium in vivo, and that a principal site of immunoreactive P-glycoprotein in brain microvasculature is localized to astrocyte foot processes.     

Changes of Adenine Nucleotide in the Course of Mitochondrial Development of Mung Bean Cotyledon and Their Effect on Cellular Energy Status

The changes of adenine nucleotide and adenylate energy charge (AEC) during the development of mitochondria in imbibed mung bean cotyledons and the relationship between these changes and cellular energy status are studied. After cotyledons were imbibed in water for two hours, mitochondrial cristae were not observed, but for 12 hours, they appeared obviously on the inner membrane. With the structural integrity of the mitochondria, the functional mitochondria were graduately shown. For instance, the activity of H+-ATPase of cotyledons imbibed for 24 hours was about twice higher than that of 2 hours. The ATP content and the AEC value in the cotyledons imbibed for 24 hours increased sharply and the AMP decreased, but these were not observed in the mitochondria of the cotyledons imbibed either for 24 hours or 2 hours. When the cotyledons were imbibed in 1 × 10-4 mol/l or 5 × 10-4 mol/l DNP solution for 24 hours, the ATP and the AEC in the Cells exhibited a rapid decrease, but in the mitochondria they remained canstant. In the same DNP solution with cotyledons for 24 hours, the activity of mitochondrial adenylate kinase (AK) not only was not decreased but also increased by about 50% over the control. This result shows that the energy equilibration in the mitochondria seems likely to be regulated by adenylate kinase locating between inner and out membranes of the mitochondria.     

低氧脑水肿大鼠脑组织VEGF和AQPs基因及蛋白表达的变化

目的：探讨低氧脑水肿时血管内皮细胞生长因子（VEGF）、水通道蛋白（AQP1和AQP4）基因和蛋白表达变化,为阐明急性低氧对脑组织的损伤及低氧脑水肿的发病机制提供实验依据。方法：Wistar大鼠随机分为4个组：常氧对照组（Control）、低氧暴露4 000 m组（4 000 m）、低氧暴露6 000 m组（6 000 m）和低氧暴露8 000 m组（8 000 m）,低氧组于低压舱中模拟相应海拔高度持续暴露8 h建立低氧脑水肿模型。用干-湿重法测定脑组织水含量,常规光镜观察脑组织形态学的改变;用RT-PCR法和免疫组化法检测低氧脑水肿时大鼠脑组织VEGF、AQP1和AQP4mRNA和蛋白表达的变化。结果：①干-湿重法测定表明,低氧（≥6 000 m）暴露后,大鼠脑组织水含量明显增加（P〈0.01）。②常规光镜检测结果表明,低氧暴露4 000 m时大鼠脑神经细胞、血管内皮细胞和星形胶质细胞足突轻度肿胀,组织中出现漏出液;低氧暴露6 000 m时脑血管内皮细胞和星形胶质细胞足突肿胀加重,血管与组织间隙扩大,组织中漏出液增多;低氧暴露8 000m时脑血管内皮细胞和星形胶质细胞足突重度肿胀,血管与组织间隙进一步扩大,组织中漏出液明显增多。③低氧脑水肿时,VEGF、AQP1、AQP4mRNA表达水平增高,AQP1在内皮细胞异常表达,内皮细胞VEGF和AQP1、星形胶质细胞足突AQP4蛋白质表达水平增高。结论：低氧脑水肿时,VEGF、AQP1和AQP4表达和分布的变化可能是引起血脑屏障损伤、导致低氧脑水肿的发病机制之一。     

胆红素脑病SD乳鼠模型中脑水通道蛋白-4表达发生变化

神经细胞水肿是胆红素脑病（bilirubin encephalopathy,BE）发生发展过程中的重要病理变化。水通道蛋白-4（aquaporin-4,AQP4）的表达及分布异常与多种疾病所致细胞毒性脑水肿的发生发展具有密切联系。但胆红素脑病中AQP4的表达变化规律及其在病理进展中的作用尚不清楚。采用7日龄SD大鼠小脑延髓池注射胆红素溶液的方法,建立新生大鼠胆红素脑病模型。胆红素脑病模型根据胆红素作用时间的不同,分为12 h、24 h、48 h、72 h和7 d组。采用HE及尼氏染色,检测各新生大鼠脑组织的病理改变;应用透射电镜(TEM),检测胆红素作用24 h后,鼠脑组织超微结构的变化;应用免疫荧光及Western 印迹,检测 AQP4在脑组织中的表达变化。通过上述实验,以探讨AQP4的表达变化与胆红素所致脑损伤的关系。HE及尼氏染色结果显示,随着胆红素沉积时间的延长,神经细胞逐渐肿胀,细胞间隙增大,尼氏小体数量逐渐减少;电镜结果显示,胆红素脑病24 h后神经细胞线粒体出现肿胀;免疫荧光染色显示,24 h组AQP4的表达范围明显增加,其后表达范围逐渐减少,表达强度也随之减弱;Western 印迹结果显示,AQP4表达在不同时间点呈现先增高后降低的趋势,在24 h达到峰值（24 h组1.38 ± 0.11 vs 对照组0.87 ± 0.21, P＜0.05）,在之后的各时间点上,AQP4的表达呈现下降趋势,而72 h组与7 d组AQP4表达均低于48 h组（P＜0.05）,基本恢复到对照组的表达水平（P＞0.05）。上述结果提示,胆红素脑病中胆红素的毒性作用将引起AQP4表达量的改变,AQP4的表达变化与胆红素脑病中细胞毒性脑水肿的发生相关,并且可能在胆红素脑病脑损伤的进展中发挥作用。     

胆红素脑病SD乳鼠模型中脑水通道蛋白-4表达发生变化

神经细胞水肿是胆红素脑病（bilirubin encephalopathy,BE）发生发展过程中的重要病理变化。水通道蛋白-4（aquaporin-4,AQP4）的表达及分布异常与多种疾病所致细胞毒性脑水肿的发生发展具有密切联系。但胆红素脑病中AQP4的表达变化规律及其在病理进展中的作用尚不清楚。采用7日龄SD大鼠小脑延髓池注射胆红素溶液的方法,建立新生大鼠胆红素脑病模型。胆红素脑病模型根据胆红素作用时间的不同,分为12 h、24 h、48 h、72 h和7 d组。采用HE及尼氏染色,检测各新生大鼠脑组织的病理改变;应用透射电镜(TEM),检测胆红素作用24 h后,鼠脑组织超微结构的变化;应用免疫荧光及Western 印迹,检测 AQP4在脑组织中的表达变化。通过上述实验,以探讨AQP4的表达变化与胆红素所致脑损伤的关系。HE及尼氏染色结果显示,随着胆红素沉积时间的延长,神经细胞逐渐肿胀,细胞间隙增大,尼氏小体数量逐渐减少;电镜结果显示,胆红素脑病24 h后神经细胞线粒体出现肿胀;免疫荧光染色显示,24 h组AQP4的表达范围明显增加,其后表达范围逐渐减少,表达强度也随之减弱;Western 印迹结果显示,AQP4表达在不同时间点呈现先增高后降低的趋势,在24 h达到峰值（24 h组1.38 ± 0.11 vs 对照组0.87 ± 0.21, P＜0.05）,在之后的各时间点上,AQP4的表达呈现下降趋势,而72 h组与7 d组AQP4表达均低于48 h组（P＜0.05）,基本恢复到对照组的表达水平（P＞0.05）。上述结果提示,胆红素脑病中胆红素的毒性作用将引起AQP4表达量的改变,AQP4的表达变化与胆红素脑病中细胞毒性脑水肿的发生相关,并且可能在胆红素脑病脑损伤的进展中发挥作用。     

Coconut oil induces short-term changes in lipid composition and enzyme activity of chick hepatic mitochondria

We studied the short-term effects of a 20% coconut oil supplementation to the chick diet on lipid composition of liver and hepatic mitochondria, and changes that occurred in mitochondrial-associated enzymes as a result of this diet. No significant differences were observed in the lipid contents of liver when young chicks were fed the experimental diet, whereas hepatic mitochondria rapidly changed in response to this diet. Total cholesterol significantly increased in mitochondria at 24 hours of coconut oil diet feeding and decreased when dietary treatment was prolonged for 5 to 14 days. Changes in total mitochondrial phospholipids showed an inverse profile. A significant decrease in phosphatidylethanolamine and an increase in sphingomyelin were found at 24 hours. The cholesterol/phospholipid molar ratio significantly and rapidly (24 hours) increased in mitochondria from treated animals. Cytochrome oxidase activity drastically increased after 24 hours of experimental diet feeding and lowered to the control values when dietary manipulation was prolonged for 5 to 14 days. ATPase activity showed an inverse profile. Changes in cytochrome oxidase activity were parallel to changes in the cholesterol/phospholipid molar ratio, whereas changes in ATPase activity showed an inverse correlation with changes in this molar ratio. To our knowledge, this is one of the first reports on the very rapid response (24 hours) of mitochondrial lipid composition and function to saturated fat feeding.     

Effect of the inhibitory neurotransmitter glycine on slow destructive processes in brain cortex slices under anoxic conditions

Slow destructive processes in brain cortex were studied under deep hypoxia (anoxia). Study of the character and dynamics of DNA destruction showed that apoptosis and necrosis run in parallel under the experimental conditions. These processes typically develop in tens of hours. A similar conclusion was reached from electron microscopic study of the tissue ultrastructure. More detailed study revealed that a relatively rare type of apoptosis not involving cytochrome c release from the intermembrane space of mitochondria and not associated with opening of the mitochondrial nonspecific pore occurs under the experimental conditions. As this is occurring, the process can be slowed by high concentrations of glycine, an inhibitory neurotransmitter. The study of DNA destruction demonstrated that high concentrations of glycine selectively slow apoptosis but have almost no effect on necrosis. Glycine also drastically decreases changes in the tissue ultrastructure, particularly of mitochondria, arising under anoxia. Glycine does not notably influence the mitochondrial oxidative phosphorylation system. Study of impairment of mitochondrial function demonstrated that the oxidative phosphorylation system is not disturbed for 1 h, which is several times longer than the inhibition time of brain function under deep hypoxia. The mitochondrial respiratory system is preserved for a relatively long time (24 h). Malate oxidase activity is deactivated after 48 h. The succinate oxidase fragment of the mitochondrial respiratory chain proved especially resistant; it retains activity under anoxia for more than 72 h. A possible mechanism of the effect of high glycine concentrations is discussed.     

In vivo angiogenesis in adult rat skeletal muscle: early changes in capillary network architecture and ultrastructure

The individual structural stages in capillary growth have been identified during development and under pathological circumstances in adults (wound healing, tumors), but there are no data to indicate whether these steps are similar when angiogenesis is induced in a fully differentiated microvascular bed in normal, uninjured adult skeletal muscle. In this study changes in capillary ultrastructure were correlated with capillary density and network morphology to elucidate the sequelae of angiogenesis in adult rat extensor digitorum longus (EDL) muscle whose activity was increased by stimulation at 10rHz (8rh/day). This resulted in an increased capillary/fiber (C/F) ratio (based on staining for alkaline phosphatase) after 4rdays; by 7rdays C/F ratio was increased further, by approximately 50%. The ultrastructure of capillary endothelium in both the EDL and extensor hallucis proprius (EHP) was similar to control muscles after 2rdays of stimulation, whereas endothelial cells in some capillaries in muscle stimulated for 4rdays revealed signs of metabolic activation such as proliferation of organelles (Golgi apparatus, endoplasmic reticulum, ribosomes and mitochondria) and fewer pinocytic vesicles. Luminal surfaces were often irregular with numerous pseudopodial processes. Basement membranes were always present but amorphous regions were observed, particularly near pericyte processes. Unusually small capillary profiles, with either a slit-like lumen or with cisternae but no lumen, probably represented capillary sprouts. The interstitium contained increased collagenous and granular extracellular matrix surrounding capillaries, and numerous activated fibroblasts which were closely apposed to many capillaries. Capillary growth in EHP was also evaluated by confocal microscopy using whole mounts. The complex pattern of vessels underwent remodelling between 2 and 7rdays of stimulation, resulting in more tortuous capillaries with numerous sprouts and loops. These combined observations suggest that angiogenesis may occur by a combination of sprouting, intussusceptive growth and elongation; also, that activation of endothelial cells occurs at the same time as disturbance of basement membranes during the earliest phase of growth and remodelling of the capillary bed. These changes are postulated to occur in connection with increased shear stress and/or capillary wall tension, which have been demonstrated previously.     

Exercise-induced focal skeletal muscle fiber degeneration and capillary morphology

The relationship between exercise-induced focal muscle fiber degeneration and changes in capillary morphology was investigated in male Wistar rats. Untrained animals ran on a treadmill for 1 h at submaximal intensity and were killed 0, 6, or 24 h after running. Nonexercised rats served as controls. In situ perfused soleus muscles were prepared for electron microscopy. Micrographed cross sections were quantitatively analyzed for parameters indicative of capillary blood flow or transcapillary exchange. Capillary lumina were ovally rather than circularly shaped, and no indications for obstruction of blood flow at the capillary level were found. Endothelial cells and their organelles had a normal appearance in all groups. However, immediately after exercise, capillaries showed a decreased thickness of their endothelium and basal membrane, probably caused by dehydration. Six hours after exercise, muscle fibers were swollen (28% increase in cross-sectional area), resulting in a slightly increased diffusion distance. This fiber swelling was not associated with an increase in muscle water content, a finding for which no explanation could be found. Twenty-four hours after the animals ran, capillaries located near degenerated muscle fibers had an increased cross-sectional luminal area and an increased luminal circumference. This effect decreased gradually with increasing distance from the degenerated fiber area. The present morphometric results do not support the hypothesis that changes in capillary morphology primarily contribute to exercise-induced focal muscle fiber degeneration.     

Human astrocytes can be induced to differentiate into cells with neuronal phenotype

Several recent studies have proposed that astrocytes may contribute to neurogenesis, not only as a source of trophic substances regulating it, but also as stem cells themselves. In order to better understand these mechanisms, primary astrocyte cultures were established from human fetal brain. After 3-4 weeks in culture, astrocytes (about 95% GFAP+; neurofilament, NF-; neuro-specific enolase, NSE-) were treated with a cocktail of protein kinase activators and FGF-1. After 5 h of treatment, most cells showed morphological changes that increased progressively up to 24-48 h, exhibiting a round cell body with long processes. Immunocytochemistry showed that treatment-induced NF and NSE expression in about 40% of cells. Nestin expression increased after treatment, whereas GFAP immunostaining was not significantly modified. Western blot and RT-PCR confirmed the results. No neuronal electrophysiological properties were observed after treatment, suggesting an incomplete maturation under these experimental conditions. Understanding the regenerative capability and neurogenic potential of astrocytes might be useful in devising therapeutic approaches for a variety of neurological disorders.     

Rapid depletion of serum tryptophan, brain tryptophan, serotonin and 5-hydroxyindoleacetic acid by a tryptophan-free diet

Rats were trained for 20 days to eat their normal daily meal in a period of 2 hours. On the twentyfirst day they received a diet in which tryptophan was omitted instead of the usual balanced diet. The ingestion of the tryptophan-free diet produced a marked depletion of free serum tryptophan (90%), brain tryptophan (85%), brain 5-HT (58%) and brain 5-HIAA (76%). These changes were almost maximal within 2 hours after food presentation and persisted for more than 24 hours. The mechanism of these changes is discussed.     

Brain microvascular P-glycoprotein and a revised model of multidrug resistance in brain

1. P-Glycoprotein is a 170-kDa transmembrane glycoprotein active efflux system that confers multidrug resistance in tumors, as well as normal tissues including brain.2. The classical model of multidrug resistance in brain places the expression of P-glycoprotein at the luminal membrane of the brain microvascular endothelial cell. However, recent studies have been performed with human brain microvessels and double-labeling confocal microscopy using (a) the MRK16 antibody to human P-glycoprotein, (b) an antiserum to glial fibrillary acidic protein (GFAP), an astrocyte foot process marker, or (c) an antiserum to the GLUT1 glucose transporter, a brain endothelial plasma membrane marker. These results provide evidence for a revised model of P-glycoprotein function at the brain microvasculature. In human brain capillaries, there is colocalization of immunoreactive P-glycoprotein with astrocytic GFAP but not with endothelial GLUT1 glucose transporter.3. In the revised model of multidrug resistance in brain, P-glycoprotein is hypothesized to function at the plasma membrane of astrocyte foot processes. These astrocyte foot processes invest the brain microvascular endothelium but are located behind the blood–brain barrier in vivo, which is formed by the brain capillary endothelial plasma membrane.4. In the classical model, an inhibition of endothelial P-glycoprotein would result in both an increase in the blood–brain barrier permeability to a given drug substrate of P-glycoprotein and an increase in the brain volume of distribution (V _D) of the drug. However, in the revised model of P-glycoprotein function in brain, which positions this protein transporter at the astrocyte foot process, an inhibition of P-glycoprotein would result in no increase in blood–brain barrier permeability, per se, but only an increase in the V _D in brain of P-glycoprotein substrates.     

Effects of PACAP and VIP on cyclic AMP formation in rat neuronal and astrocyte cultures under normoxic and hypoxic condition

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) concentration (0.001-1000 nM)-dependently stimulated cyclic AMP production in rat primary neuronal and glial cell (astrocyte) cultures. The actions of both peptides were much more pronounced in astrocytes than in neuronal cultures. Stimulatory effects of PACAP and VIP on cyclic AMP formation were significantly smaller in cell cultures subjected to 24h lasting hypoxic conditions, induced either chemically (100 microM cobalt chloride) or by low 3% oxygen hypoxia, compared to the normoxic condition (95% air and 5% CO(2)). This picture contrasted with the effects of forskolin that were similar under normoxic and hypoxic conditions. It is suggested that hypoxia leads to changes in PACAP- and VIP-driven cyclic AMP-dependent signaling in the rat brain by influencing molecular processes likely occurring at the level of receptor protein or receptor-Gs protein coupling.     

Ultrastructural study of the mycelium-yeast transition in Histoplasma capsulatum. I. Changes at 37 degrees C

Ultrastructural changes observed during the first 24 hours of mycelium to yeast transition in the dimorphic fungus Histoplasma capsulatum are reported. During this period the plasma membrane becomes undulated and the cell wall loses its characteristic fibrous outer layer. At 8 h the ordered lamellar structure of the mitochondria is no longer apparent. 24 h after the temperature shift 70% of the cells are lysed. The remaining cells contain many cytoplasmic membrane structures; mitochondria are rarely observed. These morphological changes are probably correlated with the physiological events characteristic of mycelial to yeast transition.