Increase of cdk5 is related to neurofibrillary pathology in progressive supranuclear palsy

BACKGROUND

Progressive supranuclear palsy (PSP) is characterized by a pure neurofibrillary tau pathology involving mainly basal ganglia and brainstem nuclei. In addition to a haplotype of the tau gene potentially favoring tau aggregation, lipoperoxidation has been shown to be associated with PSP tau pathology.

OBJECTIVE

To analyze cdk5/p35 complex, a kinase that regulates neurite outgrowth, as a potential cellular mechanism underlying tau phosphorylation in brain tissues from PSP and control cases and comparatively in cerebral cortex from subjects with AD.

METHODS

Cdk5/p35 protein levels and distribution were evaluated by immunoblotting and immunocytochemistry in brain regions from seven PSP, six AD, and seven control cases, with similar postmortem intervals.

RESULTS

Total cdk5 protein levels were significantly increased by more than threefold in PSP tissue and were augmented in PSP neurons, codistributed with tau immunoreactivity. P35, the regulatory subunit of cdk5, was degraded by postmortem proteolysis to the same extent in PSP, AD, and control tissues.

CONCLUSIONS

The proteolysis in vivo of p35, the regulatory subunit of the kinase, is not ascertainable because it is masked by its postmortem degradation. The study, however, indicates that in PSP, the alteration of cdk5 is different from that described in AD and suggests that the absence of amyloid beta protein deposition may account for the different pathways responsible for the same kinase activation.

Changes of retinal neurons and glial fibrillary acid protein immunoreactive astrocytes in spontaneously hypertensive rats

OBJECTIVE

The influence of arterial hypertension on retinal neurons and glial fibrillary acid protein (GFAP) immunoreactive astrocytes was investigated in spontaneously hypertensive rats (SHRs).

METHODS

The retinas of 4- and 6-month-old SHRs and age-matched Wistar-Kyoto rats (WKY) were investigated. A group of SHRs, treated from 4 to 6 months with the hypotensive drug hydralazine, was also examined. Microanatomical and immunohistochemical techniques associated with image analysis and the terminal deoxyribonucleotidyl transferase (TdT)-mediated biotin-16-dUTP nick-end labelling (TUNEL) technique for apoptosis or necrosis were used, as well as astrocyte molecular biology (Western blot) techniques.

RESULTS

In 4-month-old SHR and WKY rats, retinal morphology and the number of retinal neurons and of GFAP-immunoreactive astrocytes were similar, with the exception of the occurrence of 1% of TUNEL-positive ganglionic neurons in SHRs. In 6-month-old SHRs a decrease of retinal volume and of the number of ganglionic neurons and photoreceptors was observed, compared with age-matched normotensive WKY rats or younger SHR and WKY rats. Two per cent of ganglionic neurons and 5% of photoreceptors were also TUNEL positive. In 6-month-old SHRs, hypertrophic perivascular GFAP-immunoreactive astrocytes were found, whereas their number was unchanged compared to younger cohorts or WKY rats. An increased expression of GFAP was also noticeable in SHRs by Western blot analysis. Hypotensive treatment with hydralazine partly countered retinal changes occurring in SHRs.

CONCLUSIONS

The occurrence of neuronal and astroglial changes when a stable hypertension was developed, and their sensitivity to antihypertensive treatment, suggest that they may represent a hypertension-related phenomenon.

Androgen responsiveness and intrarenal localization of transcripts coding for the enzymes of polyamine metabolism in the mouse

Polyamines, spermidine (SPD), and spermine (SPM) are intracellular polycations required for cell growth and differentiation. Their biosynthetic precursor, the diamine putrescine (PUT), is produced by regulatory ornithine decarboxylase (ODC). Spermidine/spermine N1-acetyltransferase (SSAT) is the ODC counterpart in the degradation pathway which retroconverts SPM and SPD into PUT. Castration of male mice for 7 days resulted in a 40% decrease of the renal levels of both SSAT and ODC transcripts. Administration of 5-alpha-dihydrotestosterone (DHT) to castrated mice for the last 3 days before sacrifice caused the levels of ODC and SSAT mRNAs to increase by 250% and 180%, respectively. Thus activation of the retroconversion pathway of polyamine metabolism appears to contribute towards the increase in PUT production known to be caused by androgens in the mouse kidney. In situ hybridization histochemistry experiments showed that the SSAT transcript is expressed only by the epithelial cells of the straight and convoluted distal tubules of the nephron, while the expression of the ODC transcript is confined to the epithelium of the convoluted and straight portion of the proximal tubules. The separation of the biosynthetic from the degradation pathway along the nephron suggests that PUT is mostly produced in the distal tubule, where it may play a physiological role, independent of androgen action, in protecting tubular cells from the very low osmolarity to which they are exposed in this nephron segment.

Microanatomical changes of intracerebral arteries in spontaneously hypertensive rats: a model of cerebrovascular disease of the elderly

Changes occurring in intracerebral arteries of 24-week-old spontaneously hypertensive rats (SHR) compared with age-matched normotensive Wistar-Kyoto (WKY) rats were assessed using microanatomical techniques associated with image analysis. Morphometric parameters investigated included arterial diameter, lumen area, wall area, and wall-to-lumen ratio. Intracerebral arteries (lumen diameter>46 microm) and arterioles (lumen diameter 46-10 microm) of frontal cortex, striatum, and hippocampus were examined. In frontal cortex of SHR arterial wall hypertrophy and luminal narrowing were observed. In striatum, an increase of wall area not accompanied by luminal narrowing predominates resulting in arterial hypertrophy without vasoconstriction. In hippocampal arteries of SHR, luminal narrowing, without changes of wall area was found indicating the occurrence of remodeling. In brain areas investigated, hypertensive changes affected primarily arterioles. The demonstration of a sensitivity of intracerebral arteries to hypertension suggests that changes of these vessels may represent a cause of brain structural alterations occurring in hypertension. The specificity of alterations occurring in intracerebral arteries of brain areas investigated may account for the different localization of cerebral lesions in cerebrovascular disease. The possibility that microanatomical changes developed in intracerebral arteries of SHR may represent a model of cerebrovascular disease of the elderly is discussed.

Glial reaction to volkensin-induced selective degeneration of central neurons

Volkensin, a highly toxic protein retrogradely transported through axons, was used to target primary neuronal death in brainstem precerebellar relays after injection in the cerebellar cortex of rats. The reaction of astrocytes and microglia was studied with immunohistochemistry in the inferior olivary and pontine nuclei from 6 h to 14 days. Neurodegenerative features were evident since the first hours, especially in the pontine nuclei, and neuronal loss reached a plateau at 7 days in the inferior olive and at 10 days in the pons. Astrocytic activation, revealed by glial fibrillary acidic protein immunoreactivity, was concomitant with early signs of neuronal death and gradually increased. Microglia activation, revealed by OX-42 immunoreactivity, was evident at 2 days and became rapidly intense in precerebellar relays. At 1 week, marked ED-1 immunoreactivity also revealed phagocytic features of microglia, which persisted during the second week. In addition, major histocompatibility complex antigens (MHC) class I and II were induced in cells exhibiting microglial features. In the inferior olive, MHC I immunoreactivity was evident since 4 days and persisted at 14 days, whereas MHC II induction was intense at 7 days and subsided at 2 weeks. In the pontine nuclei high expression of both MHC antigens persisted instead at 14 days, probably reflecting the progression of neuronal death. Thus, targeted lethal injury of central neurons elicited prompt activation of both astrocytes and microglia; the marked microglia activation resulted in phagocytic features and immunophenotypic changes, with a temporal regulation that paralleled the evolution of neurodegenerative phenomena.

The hippocampus in spontaneously hypertensive rats: a quantitative microanatomical study

The influence of hypertension on the morphology of hippocampus was assessed in spontaneously hypertensive rats of two, four and six months and in age-matched normotensive Wistar-Kyoto rats. Values of systolic pressure were slightly increased in two-month-old spontaneously hypertensive rats in comparison with age-matched Wistar-Kyoto rats and augmented progressively with age in spontaneously hypertensive rats. No microanatomical changes were observed in the hippocampus of spontaneously hypertensive rats of two months in comparison with age-matched Wistar-Kyoto rats, whereas a decrease of white matter volume was observed in the CA(1) subfield and in the dentate gyrus of four-month-old spontaneously hypertensive rats. In the hippocampus of six-month-old spontaneously hypertensive rats a reduction of grey matter volume both in the CA(1) subfield and in the dentate gyrus, a loss of neurons affecting to a greater extent the CA(1) subfield and an increase of glial fibrillary acid protein-immunoreactive astrocytes was found. The occurrence of apoptosis and/or necrosis identified using the terminal deoxyribonucleotidyl transferase-mediated biotin-16-dUTP nick end labelling technique was also observed in the CA(1) subfield and to a lesser extent in the dentate gyrus. The only change noticeable in the CA(3) subfield of six-month-old spontaneously hypertensive rats was a slight increase in the number of glial fibrillary acid protein-immunoreactive astrocytes. These findings indicate the occurrence of neuronal loss and of astrocyte changes in the hippocampus of spontaneously hypertensive rats of six months, being the CA(1) subfield the area most affected. The relevance of these neurodegenerative changes in hypertension and the possible occurrence of apoptosis and/or necrosis as expression of hypertensive brain damage is discussed.

Occupancy by oral administration of nicardipine of L-type calcium channels in rat brain

The occupancy of L-type Ca2+ channels by treatment with an oral dose of the dihydropyridine-type Ca2+ antagonist nicardipine (sustained-release formulation) was evaluated in membrane preparations of rat frontal cortex and hippocampus using a radioligand binding assay technique, with [3H]-nicardipine as a ligand. Three hours after nicardipine administration, specific binding was decreased by about 15-20%, both in the frontal cortex and hippocampus. This indicates that oral nicardipine occupied approximately 15-20% of L-type Ca2+ channels. A progressive occupancy of Ca2+ channels was observed between six and 12 h after nicardipine administration. Twelve hours after drug administration, approximately 65-70% of Ca2+ channels were occupied. These findings indicate that oral treatment with 3 mg/kg of nicardipine (sustained-release formulation) occupies L-type Ca2+ channels in rat brain by more than 40% from the 6th to the 24th h after drug administration. This suggests that an oral dose of nicardipine (sustained-release formulation) in duces a significant occupancy of L-type Ca2+ channels in rat frontal cortex and hippocampus for about one day. The possible clinico-therapeutic relevance of this observation is discussed.

Oxidative stress induces increase in intracellular amyloid beta-protein production and selective activation of betaI and betaII PKCs in NT2 cells

Amyloid beta-protein (Abeta) aggregation produces an oxidative stress in neuronal cells that, in turn, may induce an amyloidogenic shift of neuronal metabolism. To investigate this hypothesis, we analyzed intra- and extracellular Abeta content in NT2 differentiated cells incubated with 4-hydroxy-2,3-nonenal (HNE), a major product of lipid peroxidation. In parallel, we evaluated protein kinase C (PKC) isoenzymes activity, a signaling system suspected to modulate amyloid precursor protein (APP) processing. Low HNE concentrations (0.1-1 microM) induced a 2-6 fold increase of intracellular Abeta production that was concomitant with selective activation of betaI and betaII PKC isoforms, without affecting either cell viability or APP full-length expression. Selective activation of the same PKC isoforms was observed following NT2 differentiation. Our findings suggest that PKC beta isoenzymes are part of cellular mechanisms that regulate production of the intracellular Abeta pool. Moreover, they indicate that lipid peroxidation fosters intracellular Abeta accumulation, creating a vicious neurodegenerative loop.

Neuronal loss up-regulates clusterin mRNA in living neurons and glial cells in the rat brain

The aim of this study was to examine the time course and cellular localization of clusterin mRNA after neurodegeneration. Selective neuronal death was achieved in the rat inferior olivary complex after volkensin injection in the contralateral cerebellar cortex. Quantitative analysis of the in situ hybridization signal demonstrated over-expression of clusterin mRNA in living neurons at 6 days and outside the neuronal cell bodies at 10 days post-injection. We conclude that, in our experimental model, clusterin over-expression occurs as an early and transient neuronal and as a delayed glial response to selective neuronal death, supporting the view that clusterin may be involved in cytoprotection and tissue remodeling.

Determination of xanthine oxidase in human serum by a competitive enzyme-linked immunosorbent assay (ELISA)

Xanthine oxidase was purified from human milk and used to immunise rabbits. A competitive immunoenzymatic assay with purified enzyme and rabbit antiserum was optimised to measure xanthine oxidase in human serum, the lowest detectable amount being 0.03 pmol of enzymatic protein. Thus, the test (i) is sensitive enough to determine xanthine oxidase in human serum, being more sensitive than the spectrophotometric method, (ii) it is more convenient for clinical laboratories than other sensitive tests and (iii) it has the advantage over the enzyme activity-based assays of also detecting inactive enzyme molecules. A competitive enzyme-linked immunosorbent assay (ELISA) was used to measure the serum xanthine oxidase level in healthy donors and in patients with liver diseases, and it was found that any concentration below 1 mg/L is in the normal range.

Changes in the activity of cdk2 and cdk5 accompany differentiation of rat primary oligodendrocytes

Oligodendrocytes, the myelinating cells of the central nervous system, are terminally differentiated cells that originate through asynchronous waves of proliferation and differentiation of precursors present at birth. Withdrawal from cell cycle and onset of differentiation are tightly linked and depend on an intrinsic program modulated by the action of growth factors. p27 plays a central and obligatory role in the initiation of oligodendrocyte differentiation and cessation of proliferation. In this paper, we have characterized the role of modulation of cdk2 and cdk5 kinase activity during the process of oligodendrocyte precursor differentiation. As rat primary oligodendrocytes differentiate in culture there is a fall in cdk2 activity and a rise in cdk5 activity as well as an increase in the cdk inhibitor, p27 protein. The decline in cdk2 activity is not accompanied by a drop in cdk2 protein level, suggesting that it results from inhibition of cdk2 activation rather than decreased protein expression. Taken together, these data suggest that oligodendrocytes may withdraw from the cell cycle at G1-S transition through inactivation of cdk2 activity, possibly initiated by increasing amount of p27, and that cdk5 may have a role until now unrecognized in the differentiation of oligodendrocytes.

Immunocytochemical discrimination between early and late S phase: a new approach to the study of gingival epithelium proliferation in rats

The renewal of the free gingival margin epithelium in rats was studied evaluating 5-bromodeoxyuridine (BrdU) incorporation in proliferating cells by means of an immunocytochemical method. We found a close correspondence between light and electron microscopy patterns of BrdU incorporation at a nuclear level. BrdU was localized in the inner interchromatin regions in cells starting DNA synthesis, while it was localized in the peripheral heterochromatin domains in cells terminating the S phase. This possibility of discriminating cells in early S phase from cells in late S is able to provide far more information as to the time at which a labeled cell starts proliferation than that obtainable with 3H-thymidine autoradiography. This, in turn, permits detection of cells that start proliferation in a wide period of time by means of a single BrdU administration. Rats treated at 7 a.m. demonstrated higher proliferation than rats treated at 7 p.m., supporting the existence of circadian variations in the epithelial renewal. Proliferative events take place by consecutive activation of at least three replication waves, producing clusters of labeled cells which could be observed in rats sacrificed at 10 a.m. In rats treated once with BrdU at 7 a.m., the clusters were localized in both the basal and suprabasal layer of the epithelium; in rats further injected with BrdU at the same time, the clusters increased in size, progressively extending throughout the epithelium. In this way, the renewal of the free gingival margin epithelium does not proceed randomly, but by consecutive activation of discrete units or clusters of basal cells, which then extend to the upper layers. This can be followed at a morphological level as a progression of labeled cells, which move from the basal layer to the epithelium surface in approximately 82-85 hours.

Vascular and neuronal hypertensive brain damage: protective effect of treatment with nicardipine

AIM

The brain is sensitive to hypertension, which causes a variety of vascular and neuronal cerebral changes. The present study was designed to assess the effect of long-term treatment with the Ca2+ channel blocker nicardipine on intracerebral (intraparenchymal) arteries in spontaneously hypertensive rats (SHR) by using microanatomical techniques associated with image analysis. The effects of hypertension and treatment with nicardipine on nerve cells and glial fibrillary acid protein (GFAP)-immunoreactive glial cells were also evaluated.

EFFECTS OF NICARDIPINE ON BLOOD PRESSURE

In SHR a significant increase in systolic blood pressure in comparison with age-matched normotensive Wistar-Kyoto (WKY) rats was noticeable. Treatment with nicardipine significantly reduced systolic pressure in the SHR. The media: lumen ratio and the thickness of the tunica media were increased in medium (diameter between 150 and 50 microns and small (diameter < 50 microns intracerebral arteries. This phenomenon was accompanied by luminal narrowing. Treatment with nicardipine significantly reduced the thickness of the tunica media, the media: lumen ratio and increased the luminal area, primarily at the level of small pial arteries and of intracerebral arteries.

EFFECTS OF NICARDIPINE IN THE BRAIN

In control SHR, the number of neurones in the frontal and occipital cortex was reduced in comparison with normotensive WKY rats. GFAP-immunoreactive astrocytes were increased in number (hyperplasia) and in size (hypertrophy), both in the frontal cortex and in the occipital cortex of control SHR. In the CA1, field of the hippocampus, the number of neurones and their size were decreased in SHR in comparison with normotensive WKY rats. Hyperplasia of GFAP-immunoreactive astrocytes of white matter and hypertrophy of those of grey matter was also noticeable. No important changes were found in other portions of the hippocampus. Treatment with nicardipine increased the number of neurones in the frontal cortex and in the occipital cortex of SHR and countered hyperplasia and hypertrophy of GFAP-immunoreactive astrocytes. Moreover, it increased the number of neurones in the CA1 field of the hippocampus and decreased the number and the size of astrocytes of the white matter and grey matter, respectively.

CONCLUSIONS

These findings show that treatment of SHR with nicardipine significantly reduced systolic blood pressure and induced moderate vasodilation of both extracerebral and intracerebral arteries regulating cerebrovascular resistance. The compound also countered some microanatomical changes occurring in the hypertensive brain. The frontal and occipital (visual) cortex and the CA1 field of the hippocampus were the cerebral areas more sensitive to treatment with nicardipine. This suggests that nicardipine induces moderate cerebrovascular dilation and exerts neuroprotective effects on SHR neurones. The possible relevance of the neuroprotective actions of nicardipine in the hypertensive brain deserves to be evaluated in future studies.

Different localization of spermidine/spermine N1-acetyltransferase and ornithine decarboxylase transcripts in the rat kidney

In situ hybridization histochemistry of transverse sections from male rat kidney showed that the mRNA of the regulatory enzyme of polyamine degradation, spermidine/spermine N1-acetyltransferase, has a spotty distribution in the cortex, is low and diffused in the outer stripe and high and diffused in the inner stripe of the outer medulla. At the cellular level, this mRNA is solely expressed by the epithelium of the distal straight and convoluted nephron tubules. Since biosynthetic ornithine decarboxylase mRNA is solely found in the proximal straight tubules, it is proposed that polyamine biosynthesis and degradation occur at separate sites along the nephron.

Suicide retrograde transport of volkensin in cerebellar afferents: direct evidence, neuronal lesions and comparison with ricin

Volkensin and ricin, either free or conjugated with colloidal gold, were injected into the cerebellar cortex of rats. The inferior olive and pontine nuclei were examined to verify the retrograde axonal transport of these two toxins, and the consequent neuronal damage. No evidence was obtained of a retrograde axonal transport of ricin in these pathways. Injection of gold-conjugated volkensin in the cerebellar cortex resulted in retrogradely labelled neurones in the inferior olive after 3 h, and in the pontine nuclei after 6 h. Degenerative changes were very severe in the retrogradely labelled neurones 48 h after the gold-conjugated volkensin injection. In the Nissl-stained material, neuronal degeneration started to be evident in the inferior olive 12 h, and in pontine nuclei 6 h, after volkensin injection. The neuronal degeneration in both the inferior olive and pons increased up to 4 days after the injection. These findings provide direct evidence of the retrograde axonal transport of volkensin in the central nervous system, and the time course of the consequent degenerative changes in the afferents to the cerebellar cortex.

Nicardipine and treatment of cerebrovascular diseases with particular reference to hypertension-related disorders

Nicardipine is a second generation dihydropyridine-type Ca2+ antagonist with high vascular selectivity and strong cerebral and coronary vasodilatory activity. The compound is used in the treatment of hypertension, primarily in the elderly. In this review the main evidence of the cerebrovascular activity of nicardipine in preclinical studies using in vitro and in vivo models is detailed. A particular physico-chemical property of nicardipine is the almost complete protonation in acid environment. This allows its accumulation in ischemic brain regions and makes it a candidate for the treatment of cerebrovascular disorders characterised by impaired brain perfusion. The main clinical data on the use of nicardipine in cerebral ischemia and related disorders, subarachnoid haemorrhage and stroke, are also reviewed. These studies included 5940 patients affected by chronic cerebrovascular insufficiency (cerebral ischemia, cerebral atherosclerosis mainly associated with hypertension, transient ischemic attacks, sequelae of cerebral infarction, thrombosis or embolia, hypertensive encephalopathy), 1540 patients affected by sequelae of subarachnoid haemorrhage and 206 patients affected by stroke. Both preclinical studies and clinical trials have shown that nicardipine is a safe Ca2+ antagonist with powerful cerebrovascular activity. This suggests its possible use in cerebrovascular disorders in which blockade of Ca2+ channels of the L-type and/or selective cerebral vasodilatation is desirable. Further studies are necessary to establish if modulation of neuronal Ca2+ channels of the L-type by nicardipine may have a neuroprotective effect independent by the cerebrovascular activity of the compound.

Molecular diagnosis of transthyretin Met30 mutation in an Italian family with familial amyloidotic polyneuropathy

We report the molecular analysis of the transthyretin gene in a large Italian pedigree with familial amyloidotic polyneuropathy and demonstrate the presence of a Met30 mutation. The usefulness of the genetic analysis in the identification of presymptomatic persons and the diagnosis of individuals with partial symptoms is discussed.

Increased levels of clusterin mRNA in the ventral prostate of the aging rat are associated to increases in cuboidal (atrophic) cell population and not to changes in apoptotic activity

In the ventral prostate of the intact rat, clusterin mRNA is expressed in a small population of cuboidal epithelial cells undergoing apoptosis, but not in the columnar cells comprising the vast majority of the glandular epithelium. Upon castration, clusterin mRNA expression and apoptotic activity are turned off in the cuboidal cells and turned on in the columnar ones. We show here that the progressive enhancements in the abundance of clusterin mRNA, occurring in the rat ventral prostate upon aging, are based on increases of the cuboidal cells at the expense of the columnar ones. DNA fragmentation, a typical sign of apoptosis, assayed both by agarose gel electrophoresis and in situ staining, was undetectable in 3-month-old rats but was evident among the cuboidal cells of 24-month-old animals and columnar cells of 1-day castrates. The DNA content of the ventral prostate did not change significatively between young and old rats, indicating that no increase in the rate of cell death occurs within the age interval examined. It is concluded that the enhancement in cuboidal cell population, the consequent augmented accumulation of clusterin mRNA, and the increased frequency of DNA fragmentation that we have detected in the aging rat ventral prostate are not directly related to the rate of apoptosis.

Gene relaxation and aging: changes in the abundance of rat ventral prostate SGP-2 (clusterin) and ornithine decarboxylase mRNAs

Sulfated glycoprotein 2 (SGP-2) mRNA progressively increased in the ventral prostate of the aging rat, reaching, at 24 months, 4-fold higher than at 3 months. Ornithine decarboxylase (ODC) mRNA peaked at 6 months (4-fold increase), and at 12 and 24 months was maintained at higher levels than at 3 months. ODC enzymatic activity was enhanced at 6 months to a much smaller extent than its own mRNA, the values at 12 and 24 months dropping to below those at 3 months. Putrescine (Put), spermidine (Spd) and spermine (Sp) concentrations also peaked at 6 months (100% increase for Put, 50% for Sp and Spd). At 24 months, Put and Spd were diminished, and Sp was unchanged with respect to the 3-month values. Under the same conditions, glyceraldehyde-3-phosphate dehydrogenase mRNA did not undergo significant alterations.

Immunological properties of ribosome-inactivating proteins and a saporin immunotoxin

Antibodies have been raised in rabbits against plant ribosome-inactivating proteins (RIPs) and used to demonstrate cross-reactivity between RIPs from plants belonging to the same family, but little or no cross-reactivity between RIPs from taxonomically unrelated plants. When an immunotoxin consisting of saporin conjugated to bovine IgG was injected into rabbits, the animals formed antibodies against both saporin and bovine IgG.

Muscarinic cholinergic receptors in the human right coronary artery: a receptor binding and autoradiographic study

We used a combination of radioreceptor binding and autoradiographic techniques to study the pharmacological characteristics and anatomical localization of [3H]-quinuclidinyl benzilate (QNB) binding sites in the human right coronary artery. The ligand was bound to sections of the human right coronary artery in a manner consistent with the labelling of muscarinic receptors. The addition of pirenzepine or of carbachol to the incubation medium to generate displacement curves was indicative of the presence of M1 and M2 receptors in the right coronary artery. Autoradiography showed the localization of M1 sites primarily in the medial layer of the right coronary artery. M2 sites were located primarily in the adventitia. No [3H]-QNB binding sites were observed in the endothelium. A possible role of muscarinic receptors in the pathogenesis of coronary vasospasm is discussed.

The characterization of an acidic calmodulin-binding protein in brain cytoskeleton and membrane fractions

One of the most abundant acidic proteins in rat brain has an Mr of 68,000 and a pI of 5.6 (68K 5.6 protein) when analysed by two-dimensional gel electrophoresis. The 68K 5.6 protein was found in large relative amounts in brain cytoskeleton preparations and in membrane and supernatant fractions. High-salt washing and proteolytic digestion did not remove this protein from the membrane elements. The 68K 5.6 protein was also found in the microtubule-associated protein fraction of purified microtubules and was present in large relative amounts in preparations of intermediate-filament proteins. The 68K 5.6 protein binds to calmodulin in the presence of Ca2+ ions, and we found it to be an abundant acidic calmodulin-binding protein in brain tissue.

In vitro studies of the biosynthesis of brain tubulin on membranes

Membrane elements in brain tissue contain relatively large amounts of alpha- and beta-tubulin (FIGURES 2 and 3). We have investigated the subcellular sites of tubulin biosynthesis in order to determine the origin of this membrane-associated tubulin. Free and membrane-bound polysomes from rat forebrain were separated by differential centrifugation, and the products of translation from these polysome populations were analyzed by 2DGE (FIGURES 4 and 6). Alpha- and beta-tubulin subunits were synthesized by the free polysome population (FIGURES 4 and 5A and B). The membrane-bound polysome fraction synthesized a protein with similar (but not identical) characteristics to alpha-tubulin (denoted as "MB" in FIGURE 6), including isoelectric point, molecular weight, peptide map, and copurification with microtubules after aggregation-disaggregation. Tubulin subunits synthesized in vitro by free polysomes could associate posttranslationally with a microsome fraction (FIGURE 7A). The association of the tubulin translation products with membranes was not disrupted by high salt; the associated tubulin, however, was susceptible to proteolytic digestion, with the exception of one of the beta-tubulin subunits (FIGURE 7B). There was an identical protease-resistant beta-tubulin subunit among the native proteins of the smooth microsome fractions. Our data is consistent with the conclusion that at least one beta subunit of membrane-associated tubulin is synthesized by free polysomes and becomes posttranslationally added to membrane structures. It is unlikely that a cotranslational mechanism is responsible, in which there is a signal-mediated insertion of a growing polypeptide chain to membrane. Our results, however, are consistent with a "membrane trigger" mechanism proposed by Wickner in which the membrane lipid bilayer triggers the folding of a polypeptide into a configuration that allows integral membrane insertion. The association of tubulin with membranes may also be secondary to the interaction of hydrophobic elements. The amino acid sequence of beta tubulin is known to contain several hydrophobic domains. Tubulin can be incorporated into phospholipid vesicles and various subcellular membrane elements. In our studies, in vitro synthesized tubulin from free polysome was found to be purified by hydrophobic affinity chromatography with ethane-sepharose (FIGURE 8). Thus, the hydrophobic characteristics of newly synthesized tubulin could be partially responsible for the posttranslational association of tubulin subunit with membranes. Native tubulin in a soluble fraction of CNS tissue was not purified by hydrophobic affinity chromatography.(ABSTRACT TRUNCATED AT 400 WORDS)

Cellular origin and biosynthesis of rat optic nerve proteins: a two-dimensional gel analysis

High resolution 2DGE (two-dimensional gel electrophoresis) was used to characterize neuronal and glial proteins of the rat optic nerve, to examine the phases of intraaxonal transport with which the neuronal proteins are associated, and to identify the ribosomal populations on which these proteins are synthesized. Neuronal proteins synthesized in the retinal ganglion cells were identified by injecting the eye with L-[35S]methionine, followed by 2DGE analysis of fast and slow axonally transported proteins in particulate and soluble fractions. Proteins synthesized by the glial cells were labeled by incubating isolated optic nerves in the presence of L-[35S]methionine and then analyzed by 2DGE. A number of differences were seen between filamentous proteins of neurons and glia. Most strikingly, proteins in the alpha- and beta-tubulin region of the 2D gels of glial proteins were distinctly different than was observed for axonal proteins. As expected, neurons but not glia expressed neurofilament proteins, which appeared among the slow axonally transported proteins in the particulate fraction; significant amounts of the glial filamentous protein, GFA, were also labeled under these conditions, which may have been due to transfer of amino acids from the axon to the glial compartment. The fast axonally transported proteins contained relatively large amounts of high-molecular-weight acidic proteins, two of which were shown to comigrate (on 2DGE) with proteins synthesized by rat CNS rough microsomes; this finding suggests that rough endoplasmic reticulum may be a major site of synthesis for fast transported proteins. In contrast, the free polysome population was shown to synthesize the principal components of slow axonal transport, including tubulin subunits, actin, and neurofilament proteins.

Characterization and biosynthesis of cyclic-AMP-binding proteins in the rat central nervous system

Cyclic-AMP-binding proteins in membrane and soluble fractions from rat forebrain were compared; membrane fractions included smooth and rough microsomes and a plasma membrane fraction enriched in synaptic membranes. Protein fractions were treated with 8-azido-[32P]cyclic AMP and ultraviolet irradiation to covalently tag cyclic-AMP-binding proteins. Labeled proteins were then analyzed by two-dimensional gel electrophoresis (2DGE) and fluorography. The soluble CNS proteins contained two major cyclic-AMP-binding species at 48K (48K 5.5 and 48K 5.45), differing slightly in their isoelectric points. Another protein was seen at 54K (54K 5.3) adjacent to the beta-tubulin subunits in the 2D electrophoretogram. The analysis of the smooth microsome and plasma membrane fractions differed from the soluble fraction in that there were two cyclic-AMP-binding proteins adjacent to the beta-tubulin region (54K 5.3 and 52K 5.3) differing slightly in apparent molecular weight. The membrane fractions also contained a cyclic-AMP-binding protein at 54K 5.8. The 52K 5.3 and 54K 5.8 species were unique to the membrane fractions. The rough microsomes did not contain detectable amounts of cyclic-AMP-binding proteins. Free polysomes were isolated from brain tissue, and translation products were analyzed by cyclic AMP affinity chromatography and immunopurification with antibodies to the brain specific type II regulatory subunit. The translation products that were found to bind cyclic AMP Sepharose are as follows: 48K 5.5, 48K 5.45, 52K 5.3, and 54K 5.8. These species comigrated with proteins that were photoaffinity-labeled in cytosol and membrane fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties and function of brain carbonic anhydrase

This chapter has described the characterization and biogenesis of soluble and membrane-bound CA in the central nervous system. The two forms of the enzyme appear to be quite similar in their molecular characteristics, however the data strongly indicate that they are synthesized on separate polysomal populations; the membrane-bound form resulting from synthesis on the RER. Our preliminary data suggest that the partitioning of mRNA for CA on the different polysomes results from the interaction of partial nascent chains with a specific receptor on the RER. We feel a function of membrane-associated synthesis is for the targeting of CA to sites in the cell where there are enzymes that can rapidly utilize the protons and bicarbonate produced by CA catalytic activity for ion exchange reactions. We have also presented arguments that CA may function as a bicarbonate source in the control of metabolism specifically in the acceleration of fatty acid synthesis in the oligodendrocyte.

Characterization and biosynthesis of soluble and membrane-bound carbonic anhydrase in brain

Carbonic anhydrase from both the cytoplasmic and membrane fractions of the forebrains of rats was characterized with respect to enzymatic activity, immunoreactivity, and in vitro biosynthesis. A procedure for the rapid purification of both membrane-bound and soluble brain carbonic anhydrase is presented that permits retention of full enzymatic activity. Both forms of the enzyme were found to show specific activities of approximately 5500 Units/mg protein when CO2 hydrating activity was determined. In addition, they exhibited similar esterase activity when assayed with p-nitrophenyl acetate. The membrane-bound form, although requiring detergent for extraction from membranes, was freely soluble in aqueous buffers after purification. The molecular weights of both soluble and membrane-bound carbonic anhydrase are 30,000 daltons, and mixing experiments failed to show any significant differences with respect to size. The two forms also exhibit isoelectric points of 7.2. However, the two proteins were found to differ in two respects. Complement fixation indicated that antibodies to soluble carbonic anhydrase had a higher affinity for the soluble form than for the membrane-bound form. The failure to observe any precursor-product relationship between these two proteins with pulse chase studies and the establishment that carbonic anhydrase-like proteins are synthesized on both free polysomes and the rough endoplasmic reticulum indicated that these proteins are synthesized by two separate mechanisms. In vitro synthesis on both free and bound polysomes was determined by two independent methods using different antibodies and different analytical procedures. The basis for these findings and their physiologic importance are discussed.

Studies on the cell-free biosynthesis of CNS membrane proteins

The biosynthesis of CNS membrane proteins was studied in cell-free systems containing membrane-bound polysomes (rough endoplasmic reticulum; RER) or free polysomes from rat forebrain. In previous studies of CNS membrane proteins using two-dimensional gel electrophoretic analysis, five proteins (mol. wt. -pI: 75K, 5.4, 68K 5.6, 61K 5.1, 58K 5.1, and 36K 5.6) were found in cell membrane fractions including preparations enriched in RER, smooth endoplasmic reticulum, and plasma membranes. One of these proteins, 68K 5.6, was also present in cytosol and comigrated with a microtubule-associated protein. In our present study, cell-free systems containing RER were found to synthesize the 75K, 5.4, 61K 5.1, and 58K 5.1 proteins. A protein, 34K 5.65, similar (but not identical) to the 36K 5.6 protein was also synthesized. After cell-free synthesis, 75K 5.4 and 58K 5.1 proteins could be purified by concanavalin A affinity chromatography. Of the five common membrane proteins previously identified, only 68K 5.6 protein was synthesized by the free polysome population. The free polysomes were also found to synthesize cyclic AMP binding proteins at 48K and 54K, known from previous studies to be present in both cytosol and plasma membrane fractions in mammalian brain tissue. In conclusion, RER synthesized proteins found exclusively in CNS membrane fractions, whereas free polysomes synthesized those proteins found in both soluble and membrane compartments.

Characterization of postmortem human brain proteins by two-dimensional gel electrophoresis

The proteins of membrane and cytosol fractions from frozen human postmortem brain were analyzed by two-dimensional gel electrophoresis (isoelectric range: 5.1-6.0) and both Coomassie-blue and ammoniacal silver staining. Cytosol preparations were analyzed from six different postmortem brains from patients with various neurologic diagnoses and immediate causes of death. Intervals between death and brain freezing (-70 degrees C) ranged from 2 to 20 h. The vast majority of proteins detected in these cytosol fractions had identical molecular weights and isoelectric points in each of six human brains examined. However, in some tissue samples tubulin was either quantitatively decreased or undetectable. The possibility that this partial or complete depletion of tubulin was related to postmortem interval and/or brain freezing was studied using rat forebrain tissue. Rat brain incubated at room temperature for up to 24 h did not reproduce the changes seen in the region of human cytosol tubulin. However, other changes seen in the two-dimensional electrophoretic pattern of rat cytosol proteins did relate to postmortem interval, brain freezing, or both. Rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum were prepared from three human brains, with highly reproducible two-dimensional patterns. Protein analysis of these membrane fractions revealed that human RER contained significant amounts of tubulin, in contrast to rat RER which contained no detectable tubulin. This discrepancy was elucidated by allowing rat brains to remain at room temperature for 24 h before freezing; gels of rat RER prepared from this tissue showed that tubulin subunits were present.

Studies on the biosynthesis of intermediate filament proteins in the rat CNS

The biosynthesis of brain intermediate filament proteins [neurofilament proteins and glial fibrillary acidic protein (GFA)] was studied with cell-free systems containing either rat spinal cord polysomes (free polysomes or rough microsomes) and rabbit reticulocyte factors or wheat germ homogenate containing spinal cord messenger RNA. The products of translation were isolated by immunoaffinity chromatography and then analyzed by two-dimensional gel electrophoresis (2DGE) followed by fluorography. The free polysome population was found to synthesize two neurofilament proteins (MW 145K, pI 5.4, and MW 70K, pI 5.3) and three isomers of GFA (alpha, beta, and gamma) that differ in isoelectric point. Wheat germ homogenate containing messenger RNA extracted from free cord polysomes synthesized two proteins that comigrated with neurofilament protein standards at 145K 5.4 and 70K 5.3; these proteins were partially purified by neurofilament affinity chromatography. The wheat germ system also synthesized the alpha, beta, and gamma isomers of GFA as characterized by immunoaffinity chromatographic purification and comigration with standards in 2DGE analysis. Our data are consistent with the conclusion that synthesis of neurofilament proteins requires multiple messenger RNAs. Also, synthesis of intermediate filament proteins occurs in the free polysome population; detectable amounts of these proteins were not synthesized by the rough microsomes.

Vimentin in the central nervous system. A study of the mesenchymal-type intermediate filament-protein in Wallerian degeneration and in postnatal rat development by two-dimensional gel electrophoresis

Intermediate filament proteins were identified by two-dimensional gel electrophoresis in urea extracts of rat optic nerves undergoing Wallerian degeneration and in cytoskeletal preparations of rat brain and spinal cord during postnatal development. The glial fibrillary acidic (GFA) protein and vimentin were the major optic nerve proteins following Wallerian degeneration. Vimentin was a major cytoskeletal component of newborn central nervous system (CNS) and then progressively decreased until it became barely identifiable in mature brain and spinal cord. The decrease of vimentin occurred concomitantly with an increase in GFA protein. A protein with the apparent molecular weight of 61,000 and isoelectric point of 5.6 was identified in both cytoskeletal preparations of brain and spinal cord, and in urea extracts of normal optic nerves. The protein disappeared together with the polypeptides forming the neurofilament triplet in degenerated optic nerves.

The characterization of tubulin in CNS membrane fractions

Rough endoplasmic reticulum (RER), smooth endoplasmic reticulum (SER), and a plasma membrane (PM) fraction enriched in synaptic membranes were isolated from rat forebrain. The proteins in these membrane fractions were analyzed by two-dimensional gel electrophoresis (2DGE) in the isoelectric range of 5.1 to 6.0 by a modification of the O'Farrell procedure. Proteins were detected by Coomassie Brilliant Blue staining of the electrophoretograms. The results of these analyses were compared with 2DGE analysis of cytosol proteins, with particular attention given to tubulin subunits and actin. The RER contained one major protein (53K 5.4) in the beta-tubulin region with a molecular weight of 53,000 and an isoelectric point of 5.4. The SER contained at least two major proteins in the alpha-tubulin region; one with a migration identical to 53K 5.4 and other proteins with slightly higher apparent molecular weights and more acidic isoelectric points (54K, 5.4 to 5.3), identical to cytoplasmic beta-tubulin. The PM fraction also contained multiple overlapping proteins (54K, 5.4 to 5.3) in the beta-tubulin area and a trace amount of the 53K 5.4 protein. The proteins in the beta-tubulin region were removed from the 2DGE electrophoretogram and digested by Staphylococcus aureus V8 protease, and the peptides separated on one-dimensional polyacrylamide gels. The peptide patterns of 53K 5.4 protein from RER and SER were almost identical and differed significantly from the cytoplasmic beta-tubulin pattern; however, the peptide maps of the PM and SER beta-tubulin region were identical to the cytoplasmic beta-tubulin. The 2DGE analysis of RER did not contain proteins in the region of cytoplasmic alpha-tubulin. SER and PM contained proteins in the alpha-tubulin region with a similar, but not identical, peptide analysis to cytoplasmic alpha-tubulin. Significant amounts of actin were detected in 2DGE analysis of SER and PM, and the peptide analysis of the actin was identical to the cytoplasmic actin analysis. The RER fraction contained only trace amounts of actin. The cytosol and all membrane fractions contained a protein (68K 5.6) found among microtubule-associated proteins, as judged by molecular weight and isoelectric point. Several proteins present in all membrane fractions (61K 5.1 and 58K 5.1) bound to concanavalin A agarose.

Variations in brain cortical polysome translation products among rats of the same strain

Studies were undertaken to determine whether there exist variations among the translation products of polysomes from different brains of animals of the same strain. Polysomes were prepared from individual rat cortices and translated in a reticulocyte protein-synthesizing system containing rabbit reticulocyte factors and L-[35S]methionine; he resulting radioactive proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis autoradiography. Comparison of the autoradiographs revealed that two acidic proteins, A and B, of apparent 54,000 M. W. occur as three phenotype: A only, B only, or A plus B. These proteins were not detectable by Coomassie brilliant blue staining of two-dimensional electrophoretograms of brain protein preparations. Messenger RNA was extracted from pooled cortices and translated in a wheat germ extract, and both A and B proteins were detected among the products of translation. Cyclic AMP affinity chromatography of the translation products of cortical polysomes showed that both A and B proteins bind to cyclic AMP. Our data are consistent with the conclusion that there are qualitative differences in the polysome translation products that bind to cyclic AMP among individual cortices of rats of the same strain.

The subunit composition of cerebellar tubulin: evidence for multiple beta tubulin messenger RNAs

Cytoplasmic proteins were isolated from adult rat forebrain and cerebellum and analyzed by two-dimensional gel electrophoresis under conditions which the major subunits of tubulin were separated. Forebrain cytoplasmic tubulin consisted of two groups of alpha subunits (alpha 1 and alpha 2) and a minimum of two beta subunits (beta 1 and beta 2). However, the rat cerebellar cytoplasmic proteins contained greatly decreased amounts of the beta 1 tubulin subunit relative to the analysis of forebrain proteins. Messenger RNA (mRNA) was purified from cerebellum and forebrain and translated in wheat germ homogenate. Analysis of the translation products of cerebellar mRNA indicated only a trace amount of the beta 1 subunit, whereas the expected amount of beta 1 was found among the translation products of forebrain mRNA. This data is consistent with the conclusion that the beta 1 and beta 2 subunits of tubulin are synthesized from different mRNAs. A decrease in beta 1 mRNA relative to other tubulin mRNAs may be one of the factors responsible for the low steady state amounts of beta 1 tubulin in the cerebellum.

In vitro synthesis of human brain proteins including tubulin and actin by purified postmortem polysomes

Polysomes were prepared from human brain tissue 2-6 h postmortem; the polysomes were active in a cell-free protein synthesis system containing rabbit reticulocyte factors. Protein synthesis was totally dependent upon added MgCl2, ATP, the reticulocyte factor fraction, and the human polysome fraction. Human brain proteins synthesized in the presence of L-[35S]methionine were analyzed by one- and two-dimensional polyacrylamide gel electrophoresis. Over 250 proteins were synthesized and they extended in size up to 250,000 d; many of the most abundant native human brain proteins were synthesized, including tubulin and actin. It was shown that human brain alpha and beta tubulin and actin isomers synthesized in vitro from human postmortem polysomes have the same apparent molecular weights and isoelectric points as the corresponding proteins synthesized by rat polysomes from fresh cortices. The corresponding tubulin and actin synthesized by human and rat brain polysomes also yield the same radioactive methionine-containing peptides after digestion with Staphylococcus aureus V8 protease. These analyses indicate that postmortem polysomes contain active messenger RNA which can direct the partial and/or complete synthesis of actin and tubulin subunits and other human brain proteins.

Tubulin synthesis in rat forebrain: studies with free and membrane-bound polysomes

Free and membrane-bound polysomes were prepared from rat forebrain and added to a cell-free system containing rabbit reticulocyte factors and L-[35S]methionine. The translation products were analyzed by two-dimensional gel electrophoresis followed by autoradiography. The free polysomes synthesized actin and at least four major tubulin subunits (alpha 1, alpha 2, beta 1, and beta 2) that are found in rat forebrain cytoplasm. The membrane-bound polysomes synthesized predominantly one protein (MB) in the tubulin region of the two-dimensional gel. MB has a molecular weight and isoelectric point similar to alpha-tubulin. Only trace amounts of alpha- and beta-tubulin and action were synthesized by the membrane-bound polysomes. MB co-purified with cytoplasmic tubulin after two cycles of aggregation and disaggregation. MB synthesized in vitro (from membrane-bound polysomes) and alpha- and beta-tubulin and actin subunits (synthesized from free polysomes) were digested with Staphylococcus aureus V8 protease, and the resulting peptides were separated by slab gel electrophoresis followed by autoradiography. The peptide pattern of MB was similar but not identical to the peptide patterns of alpha- and beta-tubulin; MB yielded peptides not found in tubulin. We conclude that membrane-bound polysomes from rat forebrain do not synthesize significant amounts of the predominant tubulin subunits synthesized by free polysomes. A major protein (MB) is synthesized by membrane-bound polysomes and is similar, but not identical, to alpha-tubulin synthesized by free polysomes on the basis of molecular weight, isoelectric point, and peptide analysis.

The preparation of biologically active messenger RNA from human postmortem brain tissue

Messenger RNA (mRNA) was extracted from human postmortem brain tissue by alkaline phenol extraction of polysomes followed by oligo (dT)-cellulose chromatography. The mRNA preparations stimulated protein synthesis in a cell-free system containing wheat germ homogenate. The products of protein synthesis were analyzed by one- and two-dimensional gel electrophoresis. These analyses indicated that numerous polypeptides, including tubulin subunits and actin isomers, were synthesized by the human mRNA. The molecular weight range of polypeptides synthesized by human mRNA fractions from two brain specimens were identical, and analysis by two-dimensional gel electrophoresis indicated qualitatively similar products. The yield of mRNA extracted per gram of human tissue was less than the yield obtained with rat forebrains from animals sacrificed immediately before brain removal and mRNA purification. A decrease in the amount of polysomes isolated from human tissue relative to rat brain tissue was a major factor contributing to the low yield. The molecular weight distribution of polypeptides synthesized by human and rat brain mRNA fractions in wheat germ homogenate was similar; thus, there was no indication for selective breakdown or inactivation of high molecular weight mRNA species in the human tissue. Our studies indicate that it is possible to utilize postmortem tissue for molecular biological investigations of human brain mRNA.

Characterization and comparison of neurofilament proteins from rat and mouse CNS

Rat and mouse CNS neurofilament proteins (NFPs) were characterized and compared, in terms of electrophoretic properties on polyacrylamide gels and by peptide mapping, with one another and with other co-purifying lower-molecular-weight CNS proteins, including alpha and beta tubulin. NFPs were partially purified by modification of the axon flotation procedure of Norton and co-workers and were demyelinated with Triton X-100. On one-dimensional SDS polyacrylamide gels the molecular weights of the triad of NFPs from both rat and mouse were approximately 200,000, 140,000, and 70,000. Prominent lower-molecular-weight proteins (63,000-16,000) as well as minor amounts of tubulin and actin were observed after gel electrophoresis. On two-dimensional gels (isoelectric focusing followed by SDS gel electrophoresis) each of the NFPs appeared to be composed of more than one component and the corresponding NFPs from rat and mouse had similar isoelectric points. Gel electrophoresis peptide mapping using Staphylococcus aureus V8 protease indicated the following: (1) the triad of NFPs of different sizes have different peptide maps; (2) alpha and beta tubulin have nonidentical digestion products, which are dissimilar to those of the NFPs; (3) other proteins that co-purify by the axon flotation procedure also have nonidentical peptide maps; and(4) the corresponding NFPs from rat and mouse have similar peptide maps. The co-purifying proteins examined in detail (63,000-49,000) do not appear to be derived by proteolytic cleavage of NFPs and may represent other cytoskeletal constituents.

Sununit structure of synaptosomal tubulin

The subunit structure of rat brain synaptosomal tubulin was examined by high resolution two-dimensional gel fractionation. Whole brain cytoplasmic tubulin consists of two groups of alpha subunits (alpha1 and alpha2), and a minimum of two beta subunits (beta1 and beta2). Both alpha subunits consist of a major relatively acidic form and minor relatively basic forms. In contrast, tubulin purified from synaptoplasm contains an additional subunit, alpha3, which has the same isoelectric point but slightly faster electrophoretic mobility than alpha1 and alpha2. All synaptosomal alpha subunits are the relatively acidic forms and the minor basic forms are absent. The synaptosomal beta subunits have electrophoretic properties similar to the corresponding cytoplasmic forms. The alpha3 synaptosomal tubulin subunit has affinity for colchicine, has a tryptic peptide map similar to whole brain cytoplasmic alpha tubulin, and can be purified by a standard tubulin purification method.

Effect of intraventricularly injected ricin on protein synthesis in rat brain

Ricin, a protein from the seeds of Ricinus communis which inhibits protein synthesis by eukaryotic ribosomes, is highly toxic when injected intraventricularly to rats, the LD50 being 0.241 micrograms/rat at 72 hr and 0.084 micrograms/rat at 7 days. Poisoned animals showed signs of central depression; they did not die before 20 hr of intoxication. Incorporation of amino acids in vivo into brain total protein and into brain ribosomes was impaired, as was protein synthesis in vitro by microsomes isolated from the brain of poisoned rats.

Nonsteroidal antiinflammatory agents. 2. Synthesis and biological activity of 2-chloroindolecarboxylic acids

The Vilsmeier and the Arndt-Eistert reactions have been employed for the synthesis of 1-phenyl-2-chloroindole-3-acetic acid (4). The antiinflammatory activity of 2-chloroindole-3-carboxylic acid (1), 1- methyl-2-chloroindole-3-carboxylic acid (2), 1-phenyl-2-chloroindole-3-carboxylic acid (3), and 4 was compared with the activity of indomethacin in the carrageenin rat edema. The best results are given by compounds 1 and 2 bearing H or CH3 at position 1 and COOH at position 3.

Effect of alpha-amanitin on brain RNA and protein synthesis and on retention of avoidance conditioning

The effect of a sublethal dose of alpha-amanitin given intraventricularly to rats on retention of passive and active avoidance conditioning has been studied, together with the effect on brain RNA and protein synthesis in vivo. The toxin brings about a significant impairment of retention of both passive and active conditioning in rats poisoned 6 hr or 24 before training. Brain RNA synthesis is decreased at 6 hr after poisoning, whilst protein synthesis decreases at a later stage (not before 12 hr after poisoning). Thus in rats poisoned with alpha-amanitin memory consolidation is impaired when RNA synthesis is decreased, and before protein synthesis is affected.

Recovery of amnestic effect of alpha-amanitin by post-training administration of d-amphetamine in the rat

alpha-Amanitin, an inhibitor of RNA polymerase II, given intraventricularly 6 or 24 h before training, impaired consolidation of both passive and active avoidance responses in rats. Administration of d-amphetamine sulfate (0.5 mg/kg intraperitoneally) immediately after training produced a clear-cut antiamnestic effect in alpha-amanitin-injected rats without modifying consolidation in control animals. Examination of several parameters of conditioning enabled the authors to rule out an impairment in locomotor performance of alpha-amanitin-treated rats both in training and in test sessions. The amnestic effect of alpha-amanitin and recovery by means of d-amphetamine were discussed in relation to RNA synthesis inhibition and a possible restoring effect of d-amphetamine upon alpha-amanitin-induced decrease of brain RNA content.

Studies on the proteins from the seeds of Croton tiglium and of Jatropha curcas. Toxic properties and inhibition of protein synthesis in vitro

1. Proteins extracted from the seeds of the Euphorbiaceae croton tiglium and Jatropha curcas were separated into three major peaks (I,II,and III) by Sephadex chromatography. 2. The crude protein from both seeds and peaks I and II from Croton and peak I from Jatropha were toxic to mice, to different extents. 3. The crude protein and peak I and peak II from both seeds, inhibited protein synthesis by a reticulocyte lysate; maximum inhibition was exerted by peak II from both seeds. None of these preparations affected protein synthesis in vitro by Ehrlich ascites cells.