Proteasome pathway operates for the degradation of ornithine decarboxylase in intact cells

Ornithine decarboxylase (ODC) is degraded in an ATP-dependent manner in vitro by the 26 S proteasome in the presence of antizyme, an ODC destabilizing protein induced by polyamines. In the present study we examined whether the proteasome catalyses ODC degradation in living mammalian cells. Lactacystin, the most selective proteasome inhibitor, strongly inhibited the degradation of ODC that had been induced in hepatoma tissue-culture (HTC) cells by refeeding with fresh medium. Furthermore the inhibitor inhibited the rapid degradation of ODC that had been induced by hypotonic shock. Interestingly, hypertonic shock was found to increase the proportion of OD present as a complex with antizyme (the ratio of ODC-antizyme complex to total ODC). Cycloheximide, which partly inhibited rapid ODC degradation caused by hypertonic shock, also part inhibited the increase in the ratio of ODC-antizyme complex total ODC. These results suggest that a common ODC degradation pathway, namely the antizyme-dependent and 26 proteasome-catalysed ODC degradation pathway, is also operating in intact cells for osmoregulated ODC degradation.

Newly identified pair of proteasomal subunits regulated reciprocally by interferon gamma

Interferon (IFN) gamma induces replacements of the proteasomal subunits X and Y by LMP7 and LMP2, respectively, resulting in an alteration of the proteolytic specificity. We found a third pair of proteasome subunits expressed reciprocally in response to IFN-gamma. Molecular cloning of a cDNA encoding one subunit designated as Z, downregulated by IFN-gamma, showed that it is a novel proteasomal subunit with high homology to MECL1, which is markedly induced by IFN-gamma. Thus, IFN-gamma induces subunit replacements of not only X and Y by LMP7 and LMP2, respectively, but also of Z by MECL1, producing proteasomes responsible for immunological processing of endogenous antigens. When processed from their precursors, three pairs of the 10 homologous, but distinct, beta-type subunits of eukaryotic proteasomes, that is, X/LMP7, Y/LMP2, and Z/MECL1, have an NH2-terminal threonine residue, assumed to be part of a catalytic center. These findings suggest that the altered molecular organization of the proteasome induced by IFN-gamma may be responsible for acquisition of its functional change.

[-Clinical features of 10 cases of tuberculous meningitis--with special reference to patient's delay and doctor's delay]

We retrospectively evaluated the clinical findings of 10 cases of tuberculous meningitis who had been admitted to our department from 1987 to 1994. Four patients were male and six were female. All of them were Japanese, and their age ranged from 17 to 74 years old. Regarding the patient's delay, nine patients visited a doctor in 1 to 20 days after the onset of headache, and one patient visited a doctor in 14 days after the onset of general malaise. It is suggested that the patient's delay could not be longer than 3 weeks because of progressively worsening symptoms of tuberculous meningitis such as severe headache and fever. The time interval between the first contact of the patient to a doctor and the commencement of antituberculous therapy (doctor's delay), ranged from 14 to 66 days. When the diagnosis of meningitis was obtained based on the findings of the cerebrospinal fluid (CSF), focal neurological signs including psychological symptoms, cranial nerve palsies and seizure were noted besides meningeal signs or the disturbance of consciousness in 4 patients. The CSF revealed an increase in cell counts with mononuclear cell dominance in 9 patients, but the findings typical for tuberculous meningitis such as increase in total protein content and a decrease in glucose concentration were obtained in only 5 patients. Mycobacterium tuberculosis had not been detected in all cases when the antituberculous chemotherapy was started. Later, it was found to be positive in the CSF sample from only three patients by culture or polymerase chain reaction (PCR) method. When the antituberculous therapy was completed, meningitis was cured without remaining any symptom or sign in all patients. All patients had no active pulmonary tuberculosis when the meningitis was diagnosed, and only one of them had sequels of lung tuberculosis. Four patients had the past history of tuberculosis, and 1 had the familial history of pulmonary tuberculosis. At the first contact to a doctor, seven patients were diagnosed as having common cold or headache related with fever because of the lack of typical signs of meningitis. Similarly three other patients were initially diagnosed as having meningitis due to viral infection or unknown etiology. In summary, it was difficult to obtain the solid diagnosis of tuberculous meningitis at the initial stage of this disease, since the symptoms and signs at its onset often similar to those of common cold or non-specific headache. Therefore, when we see the patients with subacute onset of headache and fever followed by the meningeal signs, tuberculous meningitis should always be included in the list of diseases requiring differential diagnosis. In addition, when tuberculous meningitis is suspected, the antituberculous therapy should be started without any delay.

Protein and gene structures of 20S and 26S proteasomes

The two types of proteasomes with apparent sedimentation coefficients of 20S and 26S consist of a number of heterogeneous polypeptides and are unusually large protein complexes of approximately 750 kDa and 2000 kDa, respectively. The 26S proteasome is a cylindrical caterpillar-shaped complex with a symmetrical assembly of a four-layered central 20S proteasome and two terminal 22S regulators each with a V-like structure. The central core and the terminal structures are formed by multiple polypeptides with molecular masses of 21-31 kDa and 28-112 kDa, respectively. We have been studying their detailed structures by protein-chemical and molecular biological techniques. In this review, we summarize the structural features of eukaryotic 20S and 26S proteasomes. We also discuss the possible function(s) of the terminal multi-protein regulator complex based on current information.

Calcitonin gene-related peptide (CGRP) and the regulation of cerebral parenchymal vessels

The role of calcitonin gene-related peptide (CGRP) in the cerebral microcirculation was examined in fourteen anesthetized cats. The local cerebral blood volume (CBV) and blood flow (CBF) in the temporoparietal cortex were measured by our photoelectric method. CBV represents the cumulative dimensions of the parenchymal vascular network. Intracarotid injection of 0.1, 1, and 10 micrograms/kg CGRP8-37, a CGRP antagonist, had no significant effects on CBV and mean arterial blood pressure (MABP). Intracarotid injection of 0.1 and 1 microgram/kg CGRP, but not 0.01 microgram/kg CGRP, increased CBV in a dose-dependent manner (P < 0.05). CBV was initially reduced following 1 microgram/kg CGRP injection, possibly reflecting the marked fall in MABP (P < 0.01) with this dose. Following injection of 0.1 and 1 microgram/kg CGRP, CBF was also increased by +7.3 +/- 7.7 (+10.7%) and +13.1 +/- 4.8 ml/100 g brain/min (+20.4%, P < 0.05) at 15 min. The CBV increase elicited by 1 micrograms/kg CGRP was inhibited (P < 0.05) by preinjection of 10 micrograms/kg CGRP8-37. It is concluded that CGRP has no significant role in the maintenance of resting tone of intracerebral microvessels. However, circulating CGRP dilates the small parenchymal vessels through a specific CGRP receptor, and thereby is involved in the evolution of pathologic conditions.

Pentoxifylline ameliorates postischemic delayed hypoperfusion of the cerebral cortex following cardiac arrest in cats

Two major events occurring in the cerebral hemodynamics after successful resuscitation from cardiac arrest are reactive hyperemia and postischemic hypoperfusion. We examined the effect of pentoxifylline on the feline cerebral hemodynamics following cardiac arrest. Fifteen cats were anesthetized and artificially ventilated. Using our photoelectric method, the local cerebral blood volume (CBV), mean transit time of blood (MTT), and cerebral blood flow (CBF) in the parietotemporal region were measured. Thoracotomy was performed, and cardiac arrest (ventricular fibrillation) was induced by direct application of a 2-V DC countershock. The heart was resuscitated with a DC countershock at 30 sec after cardiac arrest. In 9 cats, pentoxifylline (25 mg/kg) was infused into the femoral vein at 5 min before cardiac arrest (PTX group). The other 6 cats served as controls (control group). In both groups, the CBV, CBF and mean arterial blood pressure (MABP) overshot the control levels just after resuscitation, whereas the MTT was decreased. In the control group, postischemic hypoperfusion was detected at 30-180 min after resuscitation from cardiac arrest (CBF (ml/100 g/min): 51 +/- 4 (control), 38 +/- 4 (30 min, p < 0.05), and 23 +/- 3 (180 min, p < 0.05)). However, the postischemic hypoperfusion was not observed in the PTX group. Pentoxifylline ameliorated postischemic delayed hypoperfusion in the cerebral cortex after a short period of cardiac arrest. Pentoxifylline may be useful in the emergency situations following cardiac arrest.

Nin1p, a regulatory subunit of the 26S proteasome, is necessary for activation of Cdc28p kinase of Saccharomyces cerevisiae

The nin1-1 mutant of Saccharomyces cerevisiae cannot perform the G1/S and G2/M transitions at restrictive temperatures. At such temperatures, nin1-1 strains fail to activate histone H1 kinase after release from alpha factor-imposed G1 block and after release from hydroxyurea-imposed S block. The nin1-1 mutation shows synthetic lethality with certain cdc28 mutant alleles such as cdc28-IN. Two lines of evidence indicate that Nin1p is a component of the 26S proteasome complex: (i) Nin1p, as well as the known component of the 26S proteasome, shifted to the 26S proteasome peak in the glycerol density gradient after preincubation of crude extract with ATP-Mg2+, and (ii) nin1-1 cells accumulated polyubiquitinated proteins under restrictive conditions. These results suggest that activation of Cdc28p kinase requires proteolysis. We have cloned a human cDNA encoding a regulatory subunit of the 26S proteasome, p31, which was found to be a homolog of Nin1p.

[A case of spontaneous arteriovenous fistula presenting as the partial oculomotor nerve palsy]

We report a case of partial oculomotor nerve palsy due to spontaneous arteriovenous fistula. A 62-year-old man noticed double vision on downward gaze and periorbital pain. Clinical examination revealed inability to move the left eye downwards and to the right, and also anisocoria. No conjunctival injection or proptosis was noted. Findings of computed tomographic scan, magnetic resonance imaging and magnetic resonance angiography of the orbits, cavernous sinus region and brainstem were all normal. Carotid angiography demonstrated arteriovenous fistula via the left ophthalmic artery, the dural branch of the left external carotid artery, and the dural branch of the right internal carotid artery. Partial oculomotor palsy in this case indicated that the left inferior branch of the oculomotor nerve was affected. Inferior branch palsy of the oculomotor nerve in spontaneous arteriovenous fistula has not been described in the literature, while it is reported in cases of trauma, tumor, or aneurysm of the cavernous sinus.

Non-amoeboid locomotion of cultured microglia obtained from newborn rat brain

The movements of cultured microglia obtained from newborn rat brain were examined by video enhanced-differential interference contrast (VEC-DIC) microscopy. Active microglia measured 9.03 +/- 1.06 microns in diameter (mean +/- SD, n = 33; range, 7.03-10.36 microns). The microglia appeared to become smaller with spread of lamellipodia. The short axis of actively moving microglia measured 7.03 +/- 0.49 microns (n = 7). The lamellipodia were thin, transparent and developed rapidly around the cell body (maximal speed of extension, 4 or 5 microns/s). When shear stress from the medium was applied to the surface of cultured cells, the microglia swam with flat lamellipodia serving as sails in the stream. Spontaneous non-amoeboid movements of microglia were observed: they pivoted, circled and marched in various directions using their lamellipodia. The angular speed of rotation was maximally 3 degrees/s. In 5 marching cells, the average speed (distance/s) was calculated at 1.01 +/- 0.54 microns/s (ca. 60 microns/min or 3.6 microns/h).

Primary structures of two homologous subunits of PA28, a gamma-interferon-inducible protein activator of the 20S proteasome

The primary structures of two proteins that comprise PA28, an activator of the 20S proteasome, have been determined by cDNA cloning and sequencing. These protein subunits, termed PA28 alpha and PA28 beta, are about 50% identical to one another and are highly conserved between rat and human. PA28 alpha and PA28 beta are homologous to a previously described protein, Ki antigen, whose function is unknown. PA28 alpha, but neither PA28 beta nor Ki antigen, contains a 'KEKE motif', which has been postulated to promote the binding of proteins having this structural feature. PA28 alpha and PA28 beta were coordinately regulated by gamma-interferon, which greatly induced mRNA levels of both proteins in cultured cells. The mRNA level of the Ki antigen also increased in response to gamma-interferon treatment, but the magnitude of the increase was less than that for the PA28s, and the effect was transient. These results demonstrate the existence of a new protein family, at least two of whose members are involved in proteasome activation. They also provide the basis for future structure/function studies of PA28 subunits and the determination of their relative physiological roles in the regulation of proteasome activity.

Ordered structure of the crystallized bovine 20S proteasome

Eukaryotic proteasomes are multicatalytic proteinase complexes with a molecular weight of 750 kDa, containing, respectively, two copies of a hetero-heptamer of alpha-type subunits and one of beta-type subunits, (alpha 1-7 beta 1-7)2. Proteasome was purified from bovine liver and crystallized into a hexagonal system with cell dimensions of a = b = 121.83(2) A, c = 930.68(6) A. A cylindrical particle size of 122 A diameter and 155 A height was determined from the molecular packing in a unit cell. The crystal gave diffraction spots up to at least 4.4 A resolution, which was the minimum spacing of the camera used. The overall temperature factor of the enzyme was estimated to be in the range of 36.2 to 25.8 A2. These results imply that the enzyme complex has a unique ordered structure comprising multisubunits with two types of hetero-heptamer. This ordered structure may facilitate highly organized cooperation of individual functions of subunits within the enzyme complex.

Effects of ventricular arrhythmia on the cerebral microcirculation in cats

To test the widely believed but poorly proved hypothesis that the cerebral symptoms observed during ventricular arrhythmia are caused by a reduced cerebral blood supply, we examined the effects of single and multiple ectopic ventricular beats (or ventricular tachycardia of short duration) on the cerebral microcirculation. Six anesthetized cats were used. Ectopic ventricular systoles of various sequences were produced by electrically stimulating the ventricle through a bipolar needle-type electrode for 1 to 50 times at a rate of 300/min. The local cerebral blood volume (CBV) and blood flow (CBFLD) in the cortex were measured continuously employing the photoelectric and laser Doppler methods. CBV reflects the cumulative dimensions of the cerebrocortical microvessels. Ectopic ventricular contractions, as confirmed by electrocardiograms, always reduced the CBV and arterial blood pressure in a total of 104 attempts. The CBV reductions ranged from 0.20 +/- 0.03 vol% for a single ectopic beat to approximately 0.6-0.8 vol% for runs of 8 or more beats. The CBFLD reductions measured with the laser Doppler flowmeter were 10-35%. The reductions in CBV and CBFLD during the ventricular arrhythmia could be attributed to the abrupt and marked reductions in arterial blood pressure. Runs of ectopic ventricular beats have significant effects on the cerebral microcirculation, whether clinically apparent or not.

Activated leukocytes, endothelial cells, and effects of pentoxifylline: observations by VEC-DIC microscopy

Using video-enhanced contrast (VEC)-differential interference contrast (DIC) microscopy, ultrastructural observations were made of the activation of polymorphonuclear leukocytes (PMNLs), the interaction between activated PMNLs and endothelial cells (ECs), and the effects of pentoxifylline (PTX). The ECs were obtained from a commercial source as human umbilical cord vein endothelial cells (HUVECs) or were obtained from pig or rat brains. They were cultured on a coverglass with DMEM for about 1 week. The human PMNLs were obtained from the authors' venous blood. The control appearance of the PMNLs resembled an elastic ball covered with fine villi. The PMNL was activated spontaneously and became flattened on the glass surface within 10 min in the observation chamber. The activation of the PMNLs was estimated arbitrarily from the polymorphous changes in cell shape, agitation of the intracellular granules, and apparent increase in adhesiveness. Preadministered PTX prevented such PMNL activation, and the PMNLs remained round for more than 15 min. PMNL activation was accelerated by chemoattractants (PAF, fMLP, and PMA). In one case, a PMNL that had been activated by PMA tended to recover its round shape with PTX, but finally ended by swelling and bursting. When PMNLs were introduced into the EC-containing chamber, they became entrapped by the ECs and activated, with degranulation followed by release of a smoke-like material. After about 3 h, the EC with an attached PMNL shrank and fell into a state of coagulation necrosis. When PTX was introduced at the time of adhesion of the flattened PMNL, the PMNL appeared to be deactivated, becoming smaller and assuming its previous round shape, and detached from the EC. PTX prevented the spontaneous activation of PMNLs, and of deactivated PMNLs even after their adherence to the endothelium.

Role of nitric oxide in regulation of cerebral microvascular tone and autoregulation of cerebral blood flow in cats

The role of nitric oxide in the regulation of cerebrocortical microvascular tone and autoregulation of cerebral blood flow (CBF) was examined in 24 anesthetized cats. The local cerebral blood volume (CBV), mean transit time of blood (MTT), and CBF in the cortex were measured by our photoelectric method. CBV represents the cumulative dimensions of the cerebral microvessels. Intravenous injection of 0.35-0.7 mg/kg/min NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthesis, significantly increased mean arterial blood pressure (MABP; 8.4-14.1%, P < 0.01), decreased CBV (15.2-28.7%, P < 0.01), and decreased CBF (20.0-29.8%, P < 0.01) in a dose-related manner. The changes in MABP, CBV, and CBF elicited by L-NMMA were inhibited (P < 0.05) by simultaneous infusion of 35 mg/kg/min L-arginine. Autoregulation of CBF was examined during controlled hypotension of -30 to -40 mmHg (artificial bleeding) and recovery of blood pressure (reinfusion of blood). Although CBF remained constant with blood pressure changes in the control state (delta CBF/delta MABP of 0.037 +/- 0.155 with hypotension), CBF became dependent on blood pressure changes (delta CBF/delta MABP of 0.478 +/- 0.135, P < 0.05) during infusion of 0.35 mg/kg/min L-NMMA. It is concluded that nitric oxide participates in both the regulation of basal tone of cerebral microvessels and the autoregulation of CBF.

Purification and characterization of the 26 S proteasome from spinach leaves

The 26 S proteasome complex catalyzing ATP-dependent breakdown of ubiquitin-ligated proteins was purified from spinach leaves to near homogeneity by chromatography on DEAE-cellulose, gel filtration on Biogel A-1.5, and glycerol density gradient centrifugation. The purified enzyme was shown to degrade multi-ubiquitinated, but not unmodified, lysozymes in an ATP-dependent fashion coupled with ATPase activity supplying energy for proteolysis and isopeptidase activity to generate free ubiquitin. By nondenaturing electrophoresis, the purified enzyme was separated into two distinct forms of the 26 S complex, named 26 S alpha and 26 S beta proteasomes, with different electrophoretic mobilities. The 26 S proteasome was found to consist of multiple polypeptides with molecular masses of 23-35 and 39-115 kDa, which were thought to be those of a 20 S proteasome with multicatalytic proteinase activity and an associated regulatory part with ATPase and deubiquitinating activities, respectively. The subunit multiplicity of the spinach 26 S proteasome closely resembled that of rat liver with minor differences in certain components. No sulfhydryl bond was involved in the assembly of this multicomponent polypeptide complex. Electron microscopy showed that the 26 S proteasome complex had a "caterpillar"-like shape, consisting of four central protein layers, assumed to be the 20 S proteasome, with asymmetric V-shaped layers at each end. These structural and functional characteristics of the spinach 26 S proteasome showed marked similarity to those of the mammalian 26 S proteasomes reported recently, suggesting that the 26 S proteasome is widely distributed in eukaryotic cells and is of general importance for catalyzing the soluble energy- and ubiquitin-dependent proteolytic pathway.

Cerebral vasodilatory effect of high-dose, intravascular endothelin-1: inhibition by NG-monomethyl-L-arginine

The effects of intracarotid administration of endothelin-1 on the cerebral microvessels were examined in anesthetized cats. The local cerebral blood volume in the cortex, which reflects the cumulative dimensions of the cerebral microvessels, was measured by our photoelectric method. A low dose of endothelin-1 (0.1 nmol) elicited mild but significant declines in cerebral blood volume. Following a high dose of endothelin-1 (3 nmol), the cerebral blood volume was initially reduced, probably due to the marked fall in arterial blood pressure, but was subsequently increased significantly. The increase in cerebral blood volume was not secondary to the rise in blood pressure, since it was unaffected by inhibition of the blood pressure changes with BQ-123 (1 mg/kg), an endothelin antagonist. However, the cerebral blood volume increase was prevented by continuous administration of NG-monomethyl-L-arginine (0.35 mg/kg per min), an inhibitor of nitric oxide synthesis, plus BQ-123. BQ-123 itself had no significant effects on cerebral blood volume or blood pressure. We conclude that while a low dose of intravascular endothelin-1 steadily constricts the cerebral microvessels, a high dose dilates the cerebral microvessels through the induction of nitric oxide synthesis, probably in the endothelium.

Midpontine tegmentum infarction with "one-and-a-half syndrome" demonstrated by magnetic resonance imaging

Magnetic resonance imaging (MRI) revealed a small midpontine tegmentum infarction in a patient with Fisher's one-and-a-half syndrome. The lesion was extremely restricted to the unilateral paramedian area of the midpontine tegmentum involving both the paramedian pontine reticular formation and medial longitudinal fasciculus. The typical form of this syndrome, that is, a combination of lateral gaze palsy and unilateral internuclear ophthalmoplegia, can be caused by a midpontine lesion.

Dilatation of cerebral microvessels mediated by endothelin ETB receptor and nitric oxide in cats

The functional role of the endothelin (ET)B receptor in the cerebral microvessels was examined in seven anesthetized cats. The effects of intracarotidly injected IRL1620, a selective ETB receptor agonist, on the cerebral blood volume (CBV) in the cortex were examined by a photoelectric method. CBV reflects the cumulative dimensions of the cerebral microvessels. High doses of IRL1620 (0.1-1 nmol/kg) elicited a transient fall in CBV, followed by a marked and dose-related increase of CBV (P < 0.01). The CBV increase was significantly inhibited (P < 0.01) by simultaneous administration of 0.35 mg/kg/min NG-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthesis. The marked, but transient, depressor effect of IRL1620 was also attenuated (P < 0.01) by L-NMMA. The ETB receptor subtype and production of nitric oxide, probably in the endothelium, mediate the vasodilatory action of ET in the cerebral microvessels.

[Creutzfeldt-Jakob disease with a point mutation at codon 232 of prion protein--a case report]

We report a 50-year-old female with sporadic Creutzfeldt-Jakob disease who revealed a point mutation at codon 232 of prion protein (Met to Arg). The initial symptom was visual disturbance. The patient then developed progressive dementia, cerebellar ataxia and myoclous. About eight months after the onset, the patient went into the state of akinetic mutism. The electroencephalogram showed periodic synchronous discharges. From the prion protein's DNA sequencing of the patient's family members, the 84-year-old father without any neurological symptoms was also detected to have a point mutation at codon 232. These findings which, have not been reported before, are interesting when considering the relation between the pathogenesis of Creutzfeldt-Jakob disease and mutations of prion protein gene.

Interferon-gamma induces different subunit organizations and functional diversity of proteasomes

To obtain information on the role of proteasomes in the immune system, we examined the effect of a major immunomodulatory cytokine, gamma interferon (IFN-gamma), on the expressions, structures, and functions of proteasomes. IFN-gamma greatly increased the levels of the mRNAs encoding LMP2 and LMP7, putative immuno-proteasome subunits encoded by genes within the class II MHC region, and these two subunits synthesized were assembled completely into the proteasomal multi-subunit complex in various types of human cells. The subunit organization of proteasome changed in response to IFN-gamma stimulation, due to assembly of newly synthesized subunits through up- and down-expressions of at least 6 proteasome genes including LMP2/LMP7 without change in the structure of pre-existing proteasomes. Interestingly, IFN-gamma dramatically stimulated the trypsin-like and chymotrypsin-like activities of the multifunctional proteasome and depressed the peptidylglutamyl-peptide-hydrolyzing activity, without affecting the activity for ATP-, ubiquitin-dependent proteolysis. These results indicate that IFN-gamma modifies not only the structural organization of the proteasome, but also its functions. Based on these findings, we discuss the role in the antigen processing/presentation pathway of proteasomes with functional diversity acquired through alteration of their subunit assembly in response to IFN-gamma stimulation.

Constriction/dilatation of the cerebral microvessels by intravascular endothelin-1 in cats

The effects of intracarotidly injected endothelin (ET)-1 (0.01-3 nmol) on the local cerebral blood volume (CBV) in the parietotemporal cortex were examined by the photoelectric method in 17 anesthetized cats. CBV reflects the cumulative dimensions of the cerebral microvessels. Low doses of ET-1 (0.01 and 0.1 nmol) elicited mild but significant reductions in CBV without changes in the systemic arterial blood pressure (SABP). High doses of ET-1 (3 nmol) initially induced marked declines of CBV, which were attributable to the significant falls in SABP. CBV subsequently exhibited significant increases. The CBV increases were not secondary to the accompanying elevations of SABP, since they were unaffected by inhibition of the SABP changes after preinjection of BQ-123 (1 mg/kg), an ET antagonist specific to the ETA receptors. The CBV increases, however, were prevented by continuous administration of NG-mono-methyl-L-arginine (0.35 mg/kg/min), an inhibitor of nitric oxide synthesis, plus BQ-123. We conclude that while low doses of intravascular ET-1 constrict the cerebral microvessels, high doses of ET-1 dilate the cerebral microvessels through the induction of nitric oxide probably in the cerebrovascular endothelium.

Effects of sumatriptan on the cerebral intraparenchymal microcirculation in the cat

1. Sumatriptan, a 5-hydroxytryptamine (5-HT)1-like receptor agonist, is effective against the headache of migraine. The effects of sumatriptan injected via the carotid artery on the cerebral microcirculation were studied in 10 anaesthetized cats. 2. The local cerebral blood volume (CBV), mean transit time of blood (MTT) and cerebral blood flow (CBF) in the parieto-temporal cortex were measured by a photoelectric method. CBV represents the cumulative dimensions of the cerebral microvessels. 3. Sumatriptan at 5 and 50 micrograms kg-1 had no significant effects on the CBV, MTT, CBF, and mean arterial blood pressure (MABP); 500 micrograms kg-1 of sumatriptan reduced the CBV, prolonged the MTT, and decreased the CBF (approximately -20%) without affecting the MABP. Sumatriptan, 5 mg kg-1, elicited transient reductions in CBV and CBF, which were attributable to the rapid and marked falls of MABP seen with this dose. 4. Thus, while a high dose of sumatriptan (500 micrograms kg-1) exhibits direct vasoconstrictor actions on the cerebral vessels, low doses of sumatriptan, within the therapeutic range, elicit no vasoconstriction. The data do not support a vasoconstrictor action of sumatriptan playing a primary role in reversing the headache of migraine.

Molecular characterization of the "26S" proteasome complex from rat liver

The molecular properties of an ATP/ubiquitin-dependent "26S" proteasome complex purified from rat liver were examined by physicochemical, biochemical, and morphological analyses. On ultracentrifugation, the proteasome complex sedimented as almost a single component with a sedimentation coefficient of 30.3S. Dynamic light-scattering measurements indicated that it has a diffusion coefficient of 1.38 x 10(-7) cm2/sec and a Stokes radius of 15.5 nm. From these two coefficients, the protein complex was estimated to have the high molecular weight of 2.02 x 10(6). Static light-scattering analysis indicated a molecular weight of 1.91 x 10(6) and a radius of gyration of 16.8 nm. The proteasome complex was found to be composed of multiple subunits of the 20S proteasome with molecular weights of 2.1-3.1 x 10(4) and 15-20 protein species with molecular weights of 3.5-11.0 x 10(4), which were directly associated with the 20S proteasome. The electron micrographic finding that the 26S proteasome complex had a caterpillar shape, direct electronmicroscopic observations on the subunit arrangement of the 20S proteasome, and classification of the subunits of the latter into two groups with respect to sequence homology suggested that the 26S complex is a symmetrical assembly of two domains, each containing a large terminal subset and half the central 20S subset of components. For clarification of the molecular structure of the 26S proteasome complex in solution, its physicochemical parameters were calculated theoretically using a model based on this caterpillar-shaped complex. The values obtained for the Stokes radius and radius of gyration of 12.2 and 14.9 nm were consistent with the experimental values. These results provide evidence that the 26S proteasome complex is a cylindrical caterpillar-like structure of "30S" in solution, consisting of a 20S proteasome component with proteolytic function and multiple other components, which possibly have regulatory roles.

Ticlopidine improves the enhanced erythrocyte aggregability in patients with cerebral infarction

BACKGROUND AND PURPOSE

We examined the effect of ticlopidine hydrochloride on the enhanced erythrocyte aggregability in 14 patients with cerebral infarction during the chronic phase (over 1 month after onset).

SUMMARY OF REPORT

Ticlopidine (100 mg BID) was administered for 8 weeks. We measured the rate of erythrocyte aggregation (aggregability), using the whole-blood erythrocyte aggregometer that we developed, before and at 4 and 8 weeks after the initiation of ticlopidine administration. Concomitant measurements were made of such blood factors as the hematocrit, albumin-globulin ratio, and fibrinogen concentration. The erythrocyte aggregation rates before and at 4 and 8 weeks after were 0.147 +/- 0.017/s, 0.138 +/- 0.019/s, and 0.133 +/- 0.017/s, respectively. The erythrocyte aggregation rates at 4 and 8 weeks were significantly lower (P < .05 by Bonferroni's modified t test) than those before ticlopidine administration. At 4 and 8 weeks after the initiation of ticlopidine treatment, the hematocrit value and concentration of fibrinogen were also significantly (P < .05) reduced.

CONCLUSIONS

Our results suggest that ticlopidine can improve the enhanced erythrocyte aggregability in patients with cerebral infarction during the chronic phase.

Purification and characterization of the 26S proteasome complex catalyzing ATP-dependent breakdown of ubiquitin-ligated proteins from rat liver

An ATP/ubiquitin-dependent proteasome complex with an apparent sedimentation coefficient of 26S was purified from rat liver to near homogeneity by an improved method based on procedures reported previously. Two electrophoretically distinct forms of the 26S complex, named 26S alpha and 26S beta, with very similar subunit compositions were found not only in purified preparations but also in crude extracts, indicating that the 26S proteasome is present as two isoforms. The 26S proteasome was shown to degrade multi-ubiquitinated, but not unmodified, lysozymes in an ATP-dependent fashion, to have ATPase activity supplying energy for proteolysis, and to contain isopeptidase activity to generate free ubiquitin Mg2+/ATP-dependently. The 26S proteasome also catalyzed the ATP-independent hydrolyses of three types of fluorogenic peptides with basic, neutral, and acidic amino acids at their cleavage sites, respectively. These peptides are also good substrates for the 20S proteasome, but their degradation by the free 20S proteasome and by its assembled form in the 26S complex differ markedly, suggesting a functional difference between the two forms of proteasomes. Electrophoretic and immunochemical analyses showed that the large 26S complex was composed grossly of two different structures: a core 20S proteasome with multicatalytic proteinase functions and an associated part possibly with a regulatory role. These two structures both consisted of multiple polypeptides with molecular masses of 21-31 and 35-110 kDa, respectively. The subunit multiplicity of the rat 26S proteasome closely resembled that of the human counterpart, showing only minor species-specific differences in certain components. The assembly of this multi-component complex was found not to involve a sulfhydryl bond. Electrophoretic peptide mapping with lysyl-endopeptidase indicated the non-identity of the multiple subunits of the 26S proteasome. From these structural and functional characteristics, the 26S proteasome, which is widely distributed in mammals, is suggested to be a new type of multi-molecular complex catalyzing the soluble energy- and ubiquitin-dependent proteolytic pathway.

Molecular structure of 20S and 26S proteasomes

Eukaryotic proteasomes are unusually large protein complexes with characteristic sets of subunits and have been classified into two isoforms with apparent sedimentation coefficients of 20S and 26S, respectively. The 20S proteasome (previously named the multicatalytic proteinase complex) is a cylindrical particle with a molecular weight (MW) of approximately 750 kD. It is a dimeric assembly of two symmetrical discs, each consisting of 7 alpha-type subunits and 7 beta-type subunits, having the molecular organization alpha n[1-7)beta n[1-7)beta n[1-7)alpha n[1-7), where 'n' indicates the number of heterogeneous 7 subunits with MWs of 21-32 kD. The alpha-type and beta-type subunits constitute a unique multi-gene family encoding previously unidentified, but homologous, polypeptides that have been conserved during evolution. Interestingly, some beta-type subunits with catalytic functions appear to be replaced by very homologous, but distinct, gene products that might be generated by gene duplication in response to extracellular signals, such as gamma-interferon, suggesting that the 20S proteasome exists in cells as a heterogeneous population with functional diversity. The 26S proteasome is a eukaryotic ATP-dependent protease, selectively degrading various cellular proteins with specific degradation signals such as a multi-ubiquitin chain. It is a cylindrical caterpillar-shaped complex with a MW of about 2,000 kD. The 26S proteasome is a symmetrical assembly of a central 20S proteasome and a large terminal polypeptide complex with an apparent sedimentation coefficient of 22S. The terminal 22S subset consists of multiple components with MWs of 30-110 kD, which possibly have regulatory functions, and contains multiple ATPases, a de-ubiquitinating enzyme and the recognition molecule(s) for the target proteins. Thus the 26S proteasome is a multi-molecular assembly, consisting of the 20S proteasome and the 22S regulatory subunit complex.

Transient cerebral vasodilatory effect of neuropeptide Y mediated by nitric oxide

The effects of intracarotidly injected neuropeptide Y (NPY; 0.1 micrograms/kg) on the local cerebral blood volume (CBV) and blood flow (CBF) in the parieto-temporal cortex were examined by the photoelectric method in 17 anesthetized cats. CBV reflects the cumulative crosssectional area of the cerebral microvascular beds. NPY immediately caused transient but significant increases in CBV and CBF, which lasted for less than 5 min. Thereafter, CBV returned to and remained at the control level, although CBF was decreased by 30-40% for 60 min during the monitoring period. The CBV increases after NPY were prevented by a 15-min preinjection of 0.35 mg/kg/min of NG-monomethyl-L-arginine (L-NMMA), which is a competitive blocker of nitric oxide synthesis. The CBV increases after NPY reappeared following a 15-min administration of 0.25 mg/kg/min of L-arginine, which is a precursor of nitric oxide. We conclude that NPY administered in vivo exerts a previously unreported effect of transient vasodilatation on the cerebral microvessels. This action appears to be mediated by nitric oxide, which is a major candidate as an endothelium-derived relaxing factor (EDRF).

Cerebral microcirculatory changes during and following transient ventricular tachycardia in cats

Although reduced cerebral perfusion is believed to be the cause of syncope due to cardiac arrhythmias, investigations on the cerebral microcirculation during cardiac arrhythmias have been rare. We therefore studied the effects of transient ventricular tachycardia on the local cerebral blood volume and blood flow. Experimental ventricular tachycardia was induced in cats by electrically stimulating the ventricle of the heart at a rate of 300/min for 1 min. Using our photoelectric method, the local cerebral blood volume, mean transit time of blood, and cerebral blood flow in the parieto-temporal region were measured during and for 3 h after ventricular tachycardia. Transient ventricular tachycardia of as short as 1 min caused cerebral ischemia with a blood flow reduction of approximately 30%. This was considered to be due to reduced blood pressure plus transient autonomic dysfunction, or dysautoregulation, during the ventricular tachycardia. Mild and transient reactive hyperemia occurred immediately after termination of the dysrhythmia, but continuous reductions of cerebral blood flow were observed thereafter for 3 h. This delayed hypoperfusion is attributable to either vasoconstriction of the large resistance vessels or changes in the hemorheological properties of the blood caused by cerebral ischemia. Ventricular tachycardia of the type reported has significant and long-lasting effects on the cerebral microcirculation.

Demonstration that a human 26S proteolytic complex consists of a proteasome and multiple associated protein components and hydrolyzes ATP and ubiquitin-ligated proteins by closely linked mechanisms

It is known that two types of high-molecular-mass protease complexes are present in the cytosol of mammalian cells; a 20S latent multicatalytic proteinase named the proteasome, and a large proteolytic complex with an apparent sedimentation coefficient of 26S that catalyzes ATP-dependent breakdown of proteins conjugated with ubiquitin. In this work, we first demonstrated that a low concentration of SDS was required for activation of the latent proteasome, whereas the 26S complex degraded substrates for proteasomes in the absence of SDS. Moreover, the 26S complex was greatly stabilized in the presence of 2 mM ATP and 20% glycerol. Based on these characteristics, we next devised a novel procedure for purification of the 26S proteolytic complexes from human kidney. In this procedure, the proteolytic complexes were precipitated from cytoplasmic extracts by ultracentrifugation for 5 h at 105000 x g, and the large 26S complexes were clearly separated from the 20S proteasomes by molecular-sieve chromatography on a Biogel A-1.5 m column. The 26S enzyme was then purified to apparent homogeneity by successive chromatographies on hydroxyapatite and Q Sepharose, then by glycerol density-gradient centrifugation. Electrophoretic and immunochemical analyses showed that the purified human 26S complex consisted of multiple subunits of proteasomes with molecular masses of 21-31 kDa and 13-15 protein components ranging in molecular mass over 35-110 kDa, which were directly associated with the proteasome. The purified 26S proteolytic complex degraded 125I-labeled lysozyme-ubiquitin conjugates in an ATP-dependent manner. The 26S enzyme also showed high ATPase activity, which was copurified with the complex. Vanadate and hemin strongly inhibited not only ATP cleavage, but also ATP-dependent breakdown of ubiquitinligated proteins, suggesting that the 26S complex hydrolyzes ATP and ubiquitinated proteins by closely linked mechanisms. These findings indicate that the 26S complex consists of a proteasome with proteolytic function and multiple other components including an ATPase that regulates energy-dependent, ubiquitin-mediated protein degradation.

Animal species differences in erythrocyte aggregability

Species differences in erythrocyte aggregability were investigated employing our whole blood erythrocyte aggregometer. Blood was sampled from seven species, including humans and anesthetized (30 mg/kg pentobarbital) animals. The erythrocyte aggregation rates were the following (in s-1): cats, 0.213 +/- 0.027 (means +/- SD); dogs, 0.164 +/- 0.027; men, 0.112 +/- 0.025; rats, 0.111 +/- 0.005; domestic rabbits, 0.049 +/- 0.021; and mongolian gerbils, 0.034 +/- 0.015. Domestic fowls did not exhibit erythrocyte aggregograms like those seen in the other species. Statistical analysis revealed significant differences among the erythrocyte aggregation rates of the different species (multiple-comparisons with an overall significance level of 0.05) except between men and rats and between rabbits and gerbils. No single factor which is known to accelerate the erythrocyte aggregation rate (hematocrit, fibrinogen, etc.) was correlated with the erythrocyte aggregation rate except the globulin concentration in the blood. The failure to detect erythrocyte aggregation in domestic fowls was probably attributable to their erythrocyte shape. These results suggest that each species has its own proper tendency for erythrocyte aggregation. This factor must be taken into consideration when the blood circulation is discussed among different animal species.

Monoclonal antibody against platelet thrombospondin decreases erythrocyte aggregation rate

The effect of thrombospondin, a major glycoprotein in the platelet alpha-granule, on the erythrocyte aggregation rate was investigated. Venous blood was sampled from 8 healthy male volunteers and anticogulated with 1.1 mg/ml EDTA(K2). The erythrocyte aggregation rate of each blood sample was measured with a whole-blood erythrocyte aggregometer before and after incubation with murine monoclonal antibody against human platelet thrombospondin. After 15 min incubation, the erythrocyte aggregation rate exhibited a significant decrease to 0.055 +/- 0.022/s, representing 71.9 +/- 8.7% of the control value (0.075 +/- 0.028/s) (p less than 0.0005). The results obtained suggest that thrombospondin may participate in the control of erythrocyte aggregability in the circulating blood.

Improved method for preparation of ubiquitin-ligated lysozyme as substrate of ATP-dependent proteolysis

A simple method was developed for preparation of proteins conjugated with ubiquitin. Heat-denatured 125I-labeled lysozyme was highly ubiquitinated by incubation at pH 9.0 with a ubiquitin-protein ligase system consisting of E1, E2 and E3 that had been partially purified from rabbit reticulocytes by affinity chromatography with ubiquitin as a ligand. The resulting conjugates were separated from free lysozyme and other proteins by successive chromatographies on anion and cation ion-exchange resins. The ubiquitinated 125I-lysozymes recovered in the fraction not adsorbed to either resin served as an efficient substrate for ATP-dependent proteolysis in a reticulocyte lysate or with a purified 26 S protease complex. By the present method, 125I-lysozyme-Ub conjugates can be prepared in 3 h with a high yield of 15-20%.

[Myelofibrosis with marked subcapsular bleeding of the spleen--a case report]

A 22-year old male was admitted to Ashikaga Red Cross Hospital because of the progressing abdominal distension in May 1988. The physical examinations disclosed marked hepato-splenomegaly, lymphadenopathy and cachexic state. In the laboratory examinations, anemia, leukocytosis with left shift of nuclei and severe inflammatory reactions were found. Bone marrow aspirations were dry taps, and the biopsy showed myelofibrotic changes. Abdominal computed tomography and ultrasonography revealed a marked hepatomegaly and a giant splenomegaly with subcapsular hematoma. Philadelphia chromosome was negative and neutrophilic alkaline phosphatase score was slightly high. A little amount of peritoneal effusions was obtained and yielded S. aureus. A diagnosis of myelofibrosis with subcapsular hematoma due to spontaneous rupture of spleen and peritonitis of unknown cause was made. Operative indication was considered, but his family did not agree with it. Then conservative therapies for general conditions, those are, administrations of antibiotics and diuretics, and blood transfusions were taken. On the enlarged spleen, total irradiation was done. After the therapies, his spleen got smaller and hematoma was going to be absorbed. A rare case of myelofibrosis with splenic hematoma is reported and the conservative therapies were effective to this case.

The mechanical filtration coefficient (Lp) of the cell membrane of cultured glioma cells (C6)

The mechanical filtration coefficient (Lp) of the membrane of cultured glioma cells was determined from the rate of swelling of the cells. The swelling was induced by exposing the cells to distilled water. Assuming that cells swell in a symmetrical manner, Lp was 2.2 x 10(-8) cm/s.mmHg, or 1.7 x 10(-4) microns/s.cmH2O when calculated from changes of the cell diameter.

[Relapse of acute monocytic leukemia present with skin and tracheal involvement]

A 34 year-old female was admitted because of anemia and leukopenia. Her bone marrow contained abundant blastic cells, which were histochemically positive for peroxidase and alpha-naphthyl butyrate esterase, but negative for ASD chloroacetate esterase. She was diagnosed as acute monocytic leukemia (FAB, M5a). Complete remission was achieved after the administration of BHAC, daunorubicin, 6MP and prednisolone, and she was discharged after consolidation therapies. But shortly later, she noticed hoarseness and erythematous nodules on her breast and abdomen. Though the examinations of peripheral blood and bone marrow did not show any abnormality, hoarseness rapidly worsened and she complained of dyspnea. X-ray and CT scan demonstrated narrowing of the trachea under the cricoid cartilage, and trans-tracheal biopsy revealed leukemic involvement. In addition, erythematous skin lesion showed the infiltration of leukemic cells by biopsy. Although radiation and chemotherapy was initiated, she died of pneumonia. We tried to discuss the laryngo-tracheal and skin involvement of acute monocytic leukemia as early symptoms of relapse.

B-cell lymphoma associated with eosinophilia

A case of non-Hodgkin's lymphoma associated with eosinophilia is reported. The lymphoma was of the diffuse, large-cell type and was of B-cell origin. The number of eosinophils decreased with combination chemotherapy, along with a reduction in the size of the lymph nodes. Eosinophilia reappeared with the regrowth of lymphoma. The relationship between B-cell lymphoma and eosinophilia is discussed.

Enhanced erythrocyte aggregability in occlusive cerebrovascular disease

We measured the rate of erythrocyte aggregation using our whole-blood aggregometer in 80 patients with occlusive cerebrovascular disease during the acute and chronic phases. We compared the data with values for 38 age-matched healthy controls. Mean +/- SD erythrocyte aggregability of the patients during both the acute phase (0.145 +/- 0.21/sec, n = 35) and the chronic phase (0.139 +/- 0.21/sec, n = 45) was higher than that in the controls (0.123 +/- 0.21/sec, n = 38; p less than 0.01). Erythrocyte aggregability was positively correlated with the plasma concentration of globulin and fibrinogen and inversely correlated with the albumin:globulin ratio. However, these correlations did not necessarily exclude the possibility that some unknown substance(s) released from ischemic tissue might enhance erythrocyte aggregability.