Expanded polyglutamine stretches interact with TAFII130, interfering with CREB-dependent transcription

At least eight inherited neurodegenerative diseases are caused by expanded CAG repeats encoding polyglutamine (polyQ) stretches. Although cytotoxicities of expanded polyQ stretches are implicated, the molecular mechanisms of neurodegeneration remain unclear. We found that expanded polyQ stretches preferentially bind to TAFII130, a coactivator involved in cAMP-responsive element binding protein (CREB)-dependent transcriptional activation, and strongly suppress CREB-dependent transcriptional activation. The suppression of CREB-dependent transcription and the cell death induced by polyQ stretches were restored by the co-expression of TAFII130. Our results indicate that interference of transcription by the binding of TAFII130 with expanded polyQ stretches is involved in the pathogenetic mechanisms underlying neurodegeneration.

Effects of PS1 deficiency on membrane protein trafficking in neurons

We have examined the trafficking and metabolism of the beta-amyloid precursor protein (APP), an APP homolog (APLP1), and TrkB in neurons that lack PS1. We report that PS1-deficient neurons fail to secrete Abeta, and that the rate of appearance of soluble APP derivatives in the conditioned medium is increased. Remarkably, carboxyl-terminal fragments (CTFs) derived from APP and APLP1 accumulate in PS1-deficient neurons. Hence, PS1 plays a role in promoting intramembrane cleavage and/or degradation of membrane-bound CTFs. Moreover, the maturation of TrkB and BDNF-inducible TrkB autophosphorylation is severely compromised in neurons lacking PS1. We conclude that PS1 plays an essential role in modulating trafficking and metabolism of a selected set of membrane and secretory proteins in neurons.

Discrimination of brain abscess from necrotic or cystic tumors by diffusion-weighted echo planar imaging

Diagnostic difficulties in discriminating brain abscess from necrotic or cystic tumors using conventional CT and MRI have been reported. In this article, we examine the diagnostic ability of diffusion-weighted imaging to discriminate brain abscess from necrotic or cystic tumors. In previous reports, necrotic or cystic tumors show low signal intensity in diffusion-weighted imaging, indicating a high apparent diffusion coefficient (ADC). In contrast, in our study, high signal intensity was observed in the abscess fluid, associated with low ADC.

Initial MRI findings of non-traumatic osteonecrosis of the femoral head in renal allograft recipients

Fifty-one renal allograft recipients (15-62 years old, mean: 37 years) were monitored for 2.5-6.5 years (average: 4.3 years) after surgery by using magnetic resonance imaging (MRI) to find (i) initial signs of osteonecrosis of the femoral head (ONF), (ii) the presence of bone marrow edema as an initial sign of ONF, (iii) any changes of MRI patterns, and (iv) the relationship between these MRI findings and prognosis. MRI was performed preoperatively (baseline), and whenever possible during the 6-9th week, 12-16th week, 12th month, and yearly thereafter. T1- and T2-weighted images were obtained by using a spin echo technique. Abnormalities were first detected on MRI of 23 femoral heads in 13 patients between 6 weeks and 12 months. All lesions first showed a low intensity band on T1-weighted images and a high intensity band on T2-weighted images. No symptoms or diffuse patterns, such as bone marrow edema, preceded the appearance of the band pattern. After the 12th month, no new abnormal findings on MRI were detected. The lesions were classified into Type A, B, or C, according to the location. 12 of the 16 Type C femoral head lesions, which extend beyond the medial two thirds of the weight-bearing portion of the acetabulum, became symptomatic 7-14 months after transplantation and then progressed to collapse. Bone marrow edema appeared with radiological collapse and symptoms. With the exception of five lesions in three patients who failed to be MR imaged until 12 months postoperatively, all lesions were first detected on MRI within 16 weeks after transplantation. We therefore postulate that the ischemic event that causes ONF will have occurred within 12 weeks after transplantation, considering the time lag of reparative reaction to the dead bone.

Discrimination between different types of white matter edema with diffusion-weighted MR imaging

Brain edema can be classified into three categories: vasogenic, cytotoxic, and interstitial. The mechanism of edema is thought to be different in each type. The authors studied the movement of water molecules in each type of white matter edema in a rat model by using diffusion-weighted magnetic resonance imaging. Conventional T2-weighted imaging did not allow distinction between the three types of white matter edema; the three types of edema were, however, distinguished by using diffusion-weighted imaging. The apparent diffusion coefficient (ADC) of water was different in each type of edema. Water molecules in cytotoxic edema induced by triethyl-tin intoxication showed a smaller and less anisotropic ADC than in normal white matter. In contrast, water in vasogenic edema induced by cold injury had a larger and more anisotropic ADC than in normal white matter. Water in interstitial edema due to kaolin-induced hydrocephalus had an anisotropic and very large ADC.

An Alzheimer's disease-linked PS1 variant rescues the developmental abnormalities of PS1-deficient embryos

Mutations in presenilin 1 (PS1) cosegregate with approximately 25% of early onset familial Alzheimer's disease (FAD) pedigrees. A variety of in vitro and in vivo paradigms have established that one mechanism by which PS1 variants cause AD is by elevating the production of highly amyloidogenic Abeta1-42/43 peptides. PS1 is homologous to sel-12, a C. elegans protein that facilitates signaling mediated by the Notch/lin-12 family of receptors. Wild-type human PS1 complements an egg-laying defect in C. elegans lacking sel-12, while FAD-linked PS1 variants exhibit reduced rescue activity. These data suggested that mutant PS1 may cause disease as a result of reduction in PS1 function. To test the function of FAD-linked PS1 in mammals, we examined the ability of the A246E PS1 variant to complement the embryonic lethality and axial skeletal defects in mice lacking PS1. Finally, to examine the influence of reduced PS1 levels on Abeta production, we quantified Abeta1-42/43 peptide levels in PS1 heterozygous null mice (PS1[+/-] mice). We now report that both human wild-type and A246E PS1 efficiently rescue the phenotypes observed in PS1(-/-) embryos, findings consistent with the view that FAD-linked PS1 mutants retain sufficient normal function during mammalian embryonic development. Moreover, the levels of Abeta1-42/43 and Abeta1-40 peptides between PS1(+/-) and control mice are indistinguishable. Collectively, these data lead us to conclude that mutant PS1 causes AD not by loss of normal PS1 function but by influencing amyloid precursor protein (APP) processing in a manner that elevates Abeta1-42/43 production.

Proton nuclear magnetic resonance studies on brain edema

The water in normal and edematous brain tissues of rats was studied by the pulse nuclear magnetic resonance (NMR) technique, measuring the longitudinal relaxation time (T1) and the transverse relaxation time (T2). In the normal brain, T1 and T2 were single components, both shorter than in pure water. Prolongation and separation of T2 into two components, one fast and one slow, were the characteristic findings in brain edema induced by both cold injury and triethyl tin (TET), although some differences between the two types of edema existed in the content of the lesion and in the degree of changes in T1 and T2 values. Quantitative analysis of T1 and T2 values in their time course relating to water content demonstrated that prolongation of T1 referred to the volume of increased water in tissues examined, and that two phases of T2 reflected the distribution and the content of the edema fluid. From the analysis of the slow component of T2 versus water content during edema formation, it was demonstrated that the increase in edema fluid was steady, and its content was constant during formation of TET-induced edema. On the contrary, during the formation of cold-injury edema, water-rich edema fluid increased during the initial few hours, and protein-rich edema fluid increased thereafter. It was concluded that proton NMR relaxation time measurements may provide new understanding in the field of brain edema research.

Nationwide epidemiological survey of chronic pancreatitis in Japan

The aim of this study was to estimate the number of patients treated for chronic pancreatitis in 1994 in Japan and to explore the clinico-epidemiological features of chronic pancreatitis. Two surveys were conducted. Stratified random sampling was used to select departments in which patients with chronic pancreatitis were treated, and two different questionnaires were administered to obtain relevant information. From the first survey, the total number of patients treated for chronic pancreatitis in Japan in the year 1994 was estimated as 32,000 (95% confidence interval, 25,000-39,000). Clinico-epidemiological features, based on the 2,523 patients reported from the second survey, were subsequently clarified. The sex ratio (male/female) of the patients was 3.5. Alcoholic pancreatitis was the most common type in males (68.5%), and idiopathic pancreatitis in females (69.6%). Compared with the findings in the last survey in 1985, the proportion of patients with alcoholic pancreatitis has decreased slightly, from 58.7% to 55.5%, while that of idiopathic chronic pancreatitis has increased in both males and females. Patients diagnosed by advanced techniques such as computed tomography (CT) and endoscopic retrograde cholangiopancreatography (ERCP) accounted for 68.1% of the total. The number of patients with chronic pancreatitis treated in 1994 in Japan, was estimated as 32,000, with an overall prevalence rate of 45.4 per 100,000 population in males and 12.4 per 100,000 population in females.

Temporal and sequential changes of glial cells and cytokine expression during neuronal degeneration after transient global ischemia in rats

Background

How glial cells and cytokines are associated with the progression of delayed neuronal death induced by transient global ischemia is still unclear. To further clarify this point, we studied morphological changes in glial cells (microglial cells and astrocytes), and cytokine protein levels, during the progression of neuronal cell loss in CA1 (Cornu Ammonis 1) of the hippocampus after transient global ischemia.

Methods

Morphological changes in glial cells were studied immuno-histochemically. Nine cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, GM-CSF, IFN-γ and TNF-α) were simultaneously measured by a multiplexed bead-based immunoassay from 6 h to day21 after transient four vessel occlusion (4VO) in rats.

Results

During the process of neuronal loss, we observed four distinct phases: (1) lag phase day0-2 (no NeuN+ cell loss observed), (2) exponential phase day2-7 (NeuN+ cells reduced in number exponentially), (3) deceleration phase day7-14 (reduction rate of NeuN+ cells became low), (4) stationary phase day14 onward (NeuN+ cell loss progressed no longer). In the lag phase, activated glial cells were observed in the entire hippocampus but later were gradually restricted to CA1. Cytokine protein levels in the lag and exponential phases were lower than in the deceleration and stationary phases. IL-1α, IL-1β, IL-4, IL-6 and IFN-γ in 4VO were significantly higher in all four phases than in sham. Compared with sham level, GM-CSF was significantly high in the deceleration phase. TNF-α was significantly high in both the deceleration and stationary phases.

Conclusion

Ischemic stress in 4VO activated glial cells in areas beyond CA1 in the lag phase. Pyramidal neurons were injured in CA1 from the end of the lag phase and then neuronal cells reduced in CA1 in the exponential phase. After neuronal death began, the influence of dead cells on glial cells and cytokine expression gradually became stronger than the influence by ischemic stress. Therefore, from the deceleration phase, changes in glial cells and cytokine production were likely caused by dead cells. Cytokine interaction in the microenvironment may determine the functions of IL-1α, IL-1β, IL-4, IL-6 and IFN-γ in all four phases. The function of GM-CSF and TNF-α in the deceleration phase may be neurotrophic.

Fluid secretion in interlobular ducts isolated from guinea-pig pancreas

1. Pancreatic HCO3- and fluid secretion were studied by monitoring luminal pH (pHL) and luminal volume simultaneously in interlobular duct segments isolated from guinea-pig pancreas. The secretory rate and HCO3- flux were estimated from fluorescence images obtained following microinjection of BCECF-dextran (70 kDa, 20 microM) into the duct lumen. 2. Ducts filled initially with a Cl--rich solution swelled steadily (2.0 nl min-1 mm-2) when HCO3-/CO2 was introduced, and the luminal pH increased to 8.08. When Cl- was replaced by glucuronate, spontaneous fluid secretion was reduced by 75 %, and pHL did not rise above 7.3. 3. Cl--dependent spontaneous secretion was largely blocked by luminal H2DIDS (500 microM). We conclude that, in unstimulated ducts, HCO3- transport across the luminal membrane is probably mediated by Cl--HCO3- exchange. 4. Secretin (10 nM) and forskolin (1 microM) both stimulated HCO3- and fluid secretion. The final value of pHL (8.4) and the increase in secretory rate (1.5 nl min-1 mm-2) after secretin stimulation were unaffected by substitution of Cl-. 5. The Cl--independent component of secretin-evoked secretion was not affected by luminal H2DIDS. This suggests that a Cl--independent mechanism provides the main pathway for luminal HCO3- transport in secretin-stimulated ducts. 6. Ducts filled initially with a HCO3--rich fluid (125 mM HCO3-, 23 mM Cl-) secreted a Cl--rich fluid while unstimulated. This became HCO3--rich when secretin was applied. 7. Addition of H2DIDS and MIA (10 microM) to the bath reduced the secretory rate by 56 and 18 %, respectively. Applied together they completely blocked fluid secretion. We conclude that basolateral HCO3- transport is mediated mainly by Na+-HCO3- cotransport rather than by Na+-H+ exchange.

Solution structure of pituitary adenylate cyclase activating polypeptide by nuclear magnetic resonance spectroscopy

The solution structures of the recently discovered neuropeptides PACAP38 and PACAP27 have been investigated in aqueous solution containing varying amounts of trifluoroethanol (TFE) by circular dichroism (CD) spectroscopy and a combination of 2D 1H nuclear magnetic resonance (NMR) spectroscopy, distance geometry, and refined molecular dynamics and energy minimization calculations. In aqueous solution both peptides show only small transitory amounts of stable structure while in 50% TFE they adopt ordered structures. Qualitative NOE data and the use of the chemical shift index of the alpha-protons identified the positions of alpha-helical regions. A set of low-energy conformations compatible with the quantitative NOE data were obtained for both and each set were subjected to RMS analysis to determine the positions of the secondary structure elements. PACAP38 has an initial disordered N-terminal domain of eight amino acids, followed by an alpha-helical structure stretching from Ser-9 to Val-26, which contains a discontinuity between Lys-20 and Lys-21, and in the C-terminal region there is a short alpha-helix between Gly-28 and Arg-34. The structure of PACAP27 mirrors remarkably closely that of PACAP38 and shows no fraying of the C-terminal helix. The physiological significance of the three structural domains (1-8, 9-26, and 27-38) of PACAP38 is shown by a comprehensive review of recent in vitro and in vivo investigations of PACAP analogues. The correspondence of the global structural features of PACAP with other members of this family of peptides (namely, secretin, glucagon, GHRF1-29 and VIP) is demonstrated by inspection of the chemical shift indices of the alpha-protons.

Hemorrhagic and nonhemorrhagic stroke: diagnosis with diffusion-weighted and T2-weighted echo-planar MR imaging

PURPOSE

To determine if diffusion- and T2-weighted echo-planar magnetic resonance (MR) imaging can be used to detect acute hemorrhagic stroke and to differentiate hemorrhagic from nonhemorrhagic stroke.

MATERIALS AND METHODS

A total of 118 examinations (diffusion- and T2-weighted MR imaging) in 19 patients with 27 nonhemorrhagic strokes and in six patients with seven hemorrhagic strokes were performed. The ratios of apparent diffusion coefficient and of signal intensity on T2-weighted MR images in lesions to those in contralateral control areas were calculated.

RESULTS

Decreased ADC was shown in lesions of acute (0-3 days) hemorrhagic stroke, as well as in lesions of acute nonhemorrhagic stroke. Hypointense areas were seen on T2-weighted MR images in patients with acute hemorrhagic stroke, in contrast to normal to increased signal intensity in those with acute nonhemorrhagic stroke. Apparent diffusion coefficient tended to remain decreased in hemorrhagic stroke lesions even 100 days after onset, in contrast to the increased coefficient in nonhemorrhagic stroke lesions at the late chronic stage (31 days or older).

CONCLUSION

Diffusion- and T2-weighted echo-planar MR imaging can be used to detect and distinguish between acute hemorrhagic and nonhemorrhagic stroke.

Clinical comparison of Alzheimer's disease in pedigrees with the codon 717 Val-->Ile mutation in the amyloid precursor protein gene

Alzheimer's disease (AD) is the most common cause of dementia (32). Although the majority of cases of AD are sporadic, the most consistent risk factor detected in several epidemiological studies has been a positive family history of the disease (14,21). In addition, many large pedigrees have been described in which AD appears to be inherited as an autosomal dominant disorder. In one such pedigree (F23) a point mutation within the beta-amyloid precursor protein (APP) gene at codon 717 was identified and hypothesized to be pathogenic (10). The mutation results in a valine to isoleucine change in APP (APP717 Val-->Ile). Subsequent screening has revealed four other pedigrees, detailed in this study, in which this mutation co-segregates with AD (13,26,37). In addition, one other pedigree (Tor3) with this mutation has been described (15) and detailed clinical, neuropsychological, and neuropathological data are reported. Tor3 is discussed below in comparison to the findings in the families in this study. The five families we report with the mutation were identified in Britain (1 family), the United States (1 family), and Japan (3 families). The mutation has not been reported in the general population of any of these countries (3,13,26,33). On this basis alone it seems this mutation is pathogenic. Other APP codon 717 mutations have been identified which co-segregate with the disease (4,25). Also, a double mutation in APP at codons 670/671 has been shown to cosegregate with the disease in two large Swedish pedigrees (22). In all cases, there is complete co-segregation of the APP mutation with early onset AD, providing overwhelming statistical evidence that these mutations are pathogenic. We present the clinical features and limited neuropathology of AD in these families with the APP 717 Val-->Ile mutation.

Luminal ATP stimulates fluid and HCO3- secretion in guinea-pig pancreatic duct

1. The location of purinoceptors in the pancreatic duct and their role in regulating ductal secretion have been investigated by applying ATP and UTP to basolateral and luminal surfaces of pancreatic ducts isolated from the guinea-pig pancreas. 2. Changes in intracellular Ca2+ concentration were measured by microfluorometry in microperfused interlobular duct segments. Fluid and HCO3- secretion were estimated by monitoring luminal pH and luminal volume in sealed duct segments microinjected with BCECF-dextran. 3. Both ATP and UTP (1 microM) caused biphasic increases in intracellular Ca2+ concentration in pancreatic duct cells when applied to either the basolateral or luminal membrane. 4. Luminal application of both ATP and UTP evoked fluid and HCO3- secretion. The maximum response to 1 microM ATP or UTP was about 75 % of that evoked by secretin. By contrast, basolateral application of ATP or UTP inhibited spontaneous secretion by 52 % and 73 %, respectively, and secretin-evoked secretion by 41 % and 38 %, respectively. 5. The data suggest that luminal nucleotides may act in an autocrine or paracrine fashion to enhance ductal secretion while basolateral nucleotides, perhaps released from nerve terminals, may have an inhibitory effect. The fact that both apical and basolateral purinoceptors elevate intracellular Ca2+, but that they have opposite effects on secretion, suggests that additional signalling pathways are involved.

In vivo measurement of energy metabolism and the concomitant monitoring of electroencephalogram in experimental cerebral ischemia

The energy metabolites in rat brain in vivo were measured by using topical magnetic resonance (TMR) during the whole course of ischemia, in combination with the concomitant monitoring of electroencephalogram (EEG). Immediate loss of high energy phosphorus compounds, phosphocreatine (PCr) and ATP, resulted in the flattening of EEG after the induction of ischemia. PCr and ATP returned to almost normal level 30 min after recirculation of the ischemic brain, but EEG showed no recovery and the abnormality lasted for 12 h. The measurement of in vivo 31P-NMR is essential for the decision of the convalescence of cellular function in the brain.

Radial-sequence magnetic resonance imaging in evaluation of acetabular labrum

We investigated the usefulness of a radial-sequence magnetic resonance imaging (MRI) technique in the visualization of the acetabular labrum, which surrounds the acetabulum. In 22 hip joints of 12 volunteers, T2-weighted images were obtained on 24 radial planes of the acetabular rim, set at 15 degrees -intervals, using the small tip angle gradient echo method. We examined 7 planes in the weight-bearing portion. The acetabular labrum in the weight-bearing portion was depicted in good contrast to the surrounding tissues. The shape of the labrum differed among individuals and also in the anterior and posterior portions of the labrum. The signal intensity of the labrum was low or partially moderate. There was a high signal intensity band on the base of the acetabular labrum in several portions, which should be carefully interpreted to avoid confusion with abnormality. We concluded that radial-sequence MRI could be a useful technique for evaluation of the condition of the acetabular labrum in the weight-bearing portion.

Linear and conformation-dependent antigenic sites on the nucleoprotein of rabies virus

A set of 29 monoclonal antibodies (MAbs) specific for the rabies virus nucleoprotein (N protein) was prepared and used to analyze the topography of antigenic sites. At least four partially overlapping antigenic sites were delineated on the N protein of rabies virus by competitive binding assays. Indirect immunofluorescent antibody tests using MAbs with a series of rabies and rabies-related viruses showed that epitopes shared by various fixed and street strains of rabies virus were mainly localized at antigenic sites II and III, while epitopes representing the genus-specific antigen of Lyssavirus were widely presented at sites I, III and IV. All but one of seven MAbs specific for antigenic sites I, IV and bridge site (I and II) reacted with the antigen that had been denatured by sodium dodecyl sulfate or 2-mercaptoethanol, as well as with the denatured N protein in Western blotting assays. However, none of the MAbs against antigenic sites II and III reacted with the denatured antigen. These data indicate that antigenic sites I and IV, and sites II and III on the N protein of rabies virus are composed of linear and conformation-dependent epitopes, respectively.

In vivo studies of energy metabolism in experimental cerebral ischemia using topical magnetic resonance. Changes in 31P-nuclear magnetic resonance spectra compared with electroencephalograms and regional cerebral blood flow

The energy state of the brain during and after transient cerebral ischemia was examined in rats by in vivo measurement of 31P-nuclear magnetic resonance (NMR) spectra using a topical magnetic resonance spectrometer. EEGs and regional CBF (rCBF) were monitored on the same ischemic models. Immediately after the induction of ischemia, the height of the ATP and phosphocreatine peaks in the spectrum began to decrease with a concurrent increase of the inorganic phosphate (Pi) peak. The calculated pH from the chemical shift of Pi decreased during ischemia. The EEG pattern became flat immediately after ischemic induction. The rCBF decreased below the sensitivity level of the measuring instrument. With 30-min ischemia, the 31P-NMR spectrum returned to a normal pattern rapidly after recirculation. However, recovery of the EEG was delayed. The rCBF after recirculation showed postischemic hyperemia followed by hypoperfusion. In cases of 120-min ischemia, none of the spectra showed recovery. Thus, we could investigate the dynamic process of pathophysiological changes occurring in the ischemic brain in vivo.

Membrane potential and bicarbonate secretion in isolated interlobular ducts from guinea-pig pancreas

The interlobular duct cells of the guinea-pig pancreas secrete HCO(3)(-) across their luminal membrane into a HCO(3)(-)-rich (125 mM) luminal fluid against a sixfold concentration gradient. Since HCO(3)(-) transport cannot be achieved by luminal Cl-/HCO(3)(-) exchange under these conditions, we have investigated the possibility that it is mediated by an anion conductance. To determine whether the electrochemical potential gradient across the luminal membrane would favor HCO(3)(-) efflux, we have measured the intracellular potential (V(m)) in microperfused, interlobular duct segments under various physiological conditions. When the lumen was perfused with a 124 mM Cl- -25 mM HCO(3)(-) solution, a condition similar to the basal state, the resting potential was approximately -60 mV. Stimulation with dbcAMP or secretin caused a transient hyperpolarization (approximately 5 mV) due to activation of electrogenic Na+-HCO(3)(-) cotransport at the basolateral membrane. This was followed by depolarization to a steady-state value of approximately -50 mV as a result of anion efflux across the luminal membrane. Raising the luminal HCO(3)(-) concentration to 125 mM caused a hyperpolarization (approximately 10 mV) in both stimulated and unstimulated ducts. These results can be explained by a model in which the depolarizing effect of Cl- efflux across the luminal membrane is minimized by the depletion of intracellular Cl- and offset by the hyperpolarizing effects of Na+-HCO(3)(-) cotransport at the basolateral membrane. The net effect is a luminally directed electrochemical potential gradient for HCO(3)(-) that is sustained during maximal stimulation. Our calculations indicate that the electrodiffusive efflux of HCO(3)(-) to the lumen via CFTR, driven by this gradient, would be sufficient to fully account for the observed secretory flux of HCO(3)(-).

Significance of proton relaxation time measurement in brain edema, cerebral infarction and brain tumors

We examined the proton relaxation times in vitro in various neurological diseases using experimental and clinical materials, and consequently obtained significant results for making a fundamental analysis of magnetic resonance imaging (MRI) as followings. 1) In the brain edema and cerebral infarction, T1 prolonged and T2 separated into two components, one fast and one slow. Prolongation of T1 referred to the volume of increased water in tissue. The slow component of T2 reflects both the volume and the content of increased edema fluid in tissue. 2) In the edematous brain tissue with the damaged Blood-Brain-Barrier (BBB), the slow component of T2 became shorter after the injection of Mn-EDTA. Paramagnetic ion could be used as an indicator to demonstrate the destruction of BBB in the brain. 3) After the i.v. injection of glycerol, the slow component of T2 became shorter in the edematous brain with the concomitant decrease of water content. The effects of therapeutic drug could be evaluated by the measurement of proton relaxation times. 4) Almost all tumor tissue showed a longer T1 and T2 values than the normal rat brain, and many of them showed two components in T2. It was difficult to determine the histology of tumor tissue by the relaxation time alone because of an overlap of T1 and T2 values occurred among various types of brain tumors. 5) In vivo T1 values of various brain tumor were calculated from the data of MRIs by zero-crossing method, and they were compared with the in vitro T1 values which were measured immediately after the surgical operation. Though the absolute value did not coincide with each other due to differences in magnetic field strength, the tendency of the changes was the same among all kinds of tumors. It is concluded that the fundamental analysis of proton relaxation times is essentially important not only for the study of pathophysiology in many diseases but also for the interpretation of clinical MRI.

CO2 permeability and bicarbonate transport in microperfused interlobular ducts isolated from guinea-pig pancreas

Permeabilities of the luminal and basolateral membranes of pancreatic duct cells to CO2 and HCO3- were examined in interlobular duct segments isolated from guinea-pig pancreas. Intracellular pH (pHi) was measured by microfluorometry in unstimulated, microperfused ducts loaded with the pH-sensitive fluoroprobe 2'7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). When HCO3-/CO2 was admitted to the bath, pHi decreased transiently as a result of CO2 diffusion and then increased to a higher value as a result of HCO3- uptake across the basolateral membrane by Na+-HCO3- cotransport. When HCO3-/CO2 was admitted to the lumen, pHi again decreased but no subsequent increase was observed, indicating that the luminal membrane was permeable to CO2 but did not allow HCO3- entry to the cells from the lumen. Only when the luminal HCO3- concentration was raised above 125 mM was HCO3- entry detected. The same was true of duct cells stimulated with forskolin. Recovery of pHi from an acid load, induced by exposure to an NH4+ pulse, was dependent on basolateral but not luminal Na+ and could be blocked by basolateral application of methylisobutylamiloride and H2DIDS. This indicates that the Na+-H+ exchangers and Na+-HCO3- cotransporters are located exclusively at the basolateral membrane. In the presence of HCO3-/CO2, substitution of basolateral Cl- with glucuronate caused larger increases in pHi than substitution of luminal Cl-. This suggests that the anion exchanger activity in the basolateral membrane is greater than that in the luminal membrane. We conclude that the luminal and basolateral membranes are both freely permeable to CO2, but while the basolateral membrane has both uptake and efflux pathways for HCO3-, the luminal membrane presents a significant barrier to the re-entry of secreted HCO3-, largely through the inhibition of the luminal anion exchanger by high luminal HCO3- concentrations.

Pulsatile compression of the rostral ventrolateral medulla in hypertension

The rostral ventrolateral medulla (RVLM) has been known to be a major regulating center of sympathetic and cardiovascular activities. An association between essential hypertension and neurovascular compression of the RVLM has been reported in clinical observations, including magnetic resonance imaging (MRI) studies. To reconfirm this relationship, we performed MRI using a high-resolution 512 x 512 matrix in patients with essential and secondary hypertension and in normotensive subjects. The duration of hypertension and the degree of organ damage by hypertension were not significantly different between the two hypertension groups. Neurovascular compression of the RVLM was observed in 74% of the essential hypertension group, and the incidence of compression was significantly higher than in the secondary hypertension group (11%) or in the normotensive group (13%) (P < .01). These results from the clinical studies suggest that neurovascular compression of the RVLM is, at least in part, causally related to essential hypertension. Although blood pressure elevation by pulsatile compression of the RVLM in an experimental baboon model has already been reported, its underlying mechanism is not well known. Accordingly, we performed experiments to investigate whether pulsatile compression of the RVLM would increase arterial pressure and to elucidate the mechanism of the pressor response in rats. Sympathetic nerve activity, arterial pressure, heart rate, and plasma levels of epinephrine and norepinephrine were increased by pulsatile compression of the RVLM. The pressor response was abolished by intravenous treatment with hexamethonium or RVLM injection of kainic acid. In summary, the results from the MRI studies suggest that neurovascular compression of the RVLM is, at least in part, causally related to essential hypertension. This was supported by the results from experimental studies using rats indicating that pulsatile compression of the RVLM increases arterial pressure by enhancing sympathetic outflow.