Huntington's disease gene: regional and cellular expression in brain of normal and affected individuals

Huntington's disease (HD) is an autosomal dominant disorder characterized by involuntary movements, dementia, and progressive, global, but regionally accentuated, brain atrophy. The disease affects the striatum most severely. An expansion of a trinucleotide repeat on chromosome 4p16.3 within the coding region of a gene termed IT15 has been identified as the mutation causing HD. The normal function of IT15 and the mechanisms by which the presence of the mutation causes HD are unknown. Although IT15 expression has been detected in the brain, as well as in other organ tissues, by Northern blot and in situ hybridization, it is not known whether a preferential regional or cellular expression of IT15 exists within the central nervous system of normal, affected, and presymptomatic individuals. Using quantitative in situ hybridization methods, we examined extensively the regional and cellular expression of IT15. In controls, IT15 expression was observed in all brain regions examined with the highest levels seen in cerebellum, hippocampus, cerebral cortex, substantia nigra pars compacta, and pontine nuclei. Expression in the striatum was intermediate and expression in the globus pallidus was low. IT15 was expressed predominantly in neurons; a low but significant level of expression was seen in glial cells. Analysis of grain counts per square micrometer in neurons showed that the regional differences in the level of mRNA expression were related to density and size of neurons in a given region and not primarily to differences in levels of mRNA expression in individual cells after correction for cell size. Neurons susceptible to degeneration in HD did not selectively express high levels of IT15 mRNA. In HD brains (grades 2-4), the distribution and levels of IT15 mRNA were comparable with controls in all areas except in neostriatum where the intensity of labeling was significantly reduced. Presymptomatic HD brains had a striatal expression similar to controls and surviving striatal neurons in more advanced HD had an expression of IT15 within normal limits. It is apparent from these results that the presence of expanded trinucleotide repeats in HD does not result in the absence of IT15 mRNA expression or in altered patterns or levels of expression. The lack of correlation between the levels of IT15 mRNA expression and susceptibility to degeneration in HD strongly suggests that the mutant gene acts in concert with other factors to cause the distinctive pattern of neurodegeneration in HD.

The population association of glucokinase gene with type 2 (noninsulin-dependent) diabetes mellitus in Chinese

The association of gluckinase (GCK) gene with type 2 (non-insulin-dependent) diabetes mellitus was investigated in 168 Chinese subjects (85 unrelated type 2 diabetics and 83 non-diabetic controls). The microsatellite polymorphism marker, GCK-5', was amplified with polymerase chain reaction. Four alleles were observed in Chinese population with length varying from 137bp to 143bp and the most common one being the 139bp allele 3. In comparison with non-diabetics, allele 4 was significantly increased in type 2 diabetes (10% versus 38, respectively; X2 = 6.773, P = 0.009); genotype 44 and 4X (X denotes any allele other than allele 4) were significantly increased in type 2 diabetes (16% versus 6% respectively; X2 = 6.439, P = 0.011). The frequency difference was also shown in overweight/obese subgroup comparison (X2 = 7.718, P = 0.021), but not in lean/normal-weight subgroup comparison. No differences of age of onset and frequency of positive family history were observed between type 2 diabetic patients with genotype 44 or 4X and those with XX. The risk for type 2 diabetes in Chinese with genotype 44 or 4X was about 3.5 times higher than in Chinese with genotype XX. Therefore, GCK gene was associated with Chinese type 2 diabetes.

Trichokonin VI, a new Ca2+ channel agonist in bullfrog cardiac myocytes

The effects of trichokonin VI (= gliodeliquescin A), a peptaibol isolated from the culture broth of Trichoderma koningii Oudemans, on L-type Ca2+ channel currents in single bullfrog atrial cells were investigated. Our results showed that trichokonin VI is a new potent agonist of L-type Ca2+ channels in cardiac membranes.

Oligonucleotides with novel, cationic backbone substituents: aminoethylphosphonates

Oligonucleotide (2-aminoethyl)phosphonates in which the backbone consisted of isomerically pure, alternating (2-aminoethyl)-phosphonate and phosphodiester linkages have been prepared and characterized. One of these single isomer oligonucleotides (Rp) formed a more stable duplex with DNA or RNA than its corresponding natural counterpart. Hybrid stability was more pH-dependent, but less salt-dependent than a natural duplex. The specificity of hybridization was examined by hybridization of an oligonucleotide containing one (2-aminoethyl)phosphonate to oligonucleotides possessing mismatches in the region opposite to the aminoethyl group. In contrast to oligonucleotides containing (aminomethyl)-phosphonate linkages, oligonucleotide (2-aminoethyl)phosphonates were completely stable to hydrolysis in aqueous solution. These oligonucleotides were resistant to nuclease activity but did not induce RNase H mediated cleavage of a complementary RNA strand. Incubation in a serum-containing medium resulted in minimal degradation over 24 hours. Studies of cell uptake by flow cytometry and confocal microscopy demonstrated temperature dependent uptake and intracellular localization. (2-Aminoethyl)phosphonates represent a novel approach to the introduction of positive charges into the backbone of oligonucleotides.

[Study on soluble proteins in human fetal lens]

Soluble proteins from corter of human fetal clear lenses were separated by column chromatography with Sepharyl S-300 (superfine) and determined by disc-PAGE and SDS-PAGE. The results documented from 18W, 21W (2 cases) and 24W fetal lenses suggested that a negative correlation tended to be presented between the age of fetus and fraction of alpha, beta 1 crystallins (r = -0.9542; r = -0.9674) and a positive correlation between the age of fetus and fraction of beta 2, gamma crystallins (r = 0.9666; r = 0.9970). There was no change in the alpha, beta 1, beta 2 crystallins on disc-PAGE. Among the fetuses of different ages, the blurred band of gamma crystallin seen in 18W and 21W fetal lenses was thickened in the 24W fetal lens. The SDS-PAGE showed that there was no significant difference among the polypeptides in each of alpha, beta 1, beta 2, gamma crystallins in the studied fetal lenses of different age groups. It is presumed that the normal lens is proportionally composed of four fractions of crystallin. This is hypothetically contributed to the maintenance of normal structure of the lens, why the proper proportion of four fractions of crystallins is depended either on proteins synthesis or on protein molecular assembly is not yet clear.

Refined 1.8 A resolution crystal structure of the porcine epsilon-trypsin

Porcine epsilon-trypsin is a three-chain inactivated trypsin from the limited autolysis of porcine beta-trypsin. It is cleaved at positions Lys60-Ser61 and Lys145-Ser146. The crystal structure has been determined by using the molecular replacement method, and refined at 1.8 A resolution. The R-value of final model is 0.184. Comparison with the electron density map of porcine beta-trypsin (PTRY) in complex (BBIT), and with that of native bovine beta-trypsin (HTNA), revealed no obvious changes except at the autolysis positions, and no changes at the active center were observed. The autolysis at positions Lys60-Ser61 and Lys145-Ser146 does not affect the conformation of His-57 in the active center and therefore cannot explain for a loss in porcine epsilon-trypsin activity.

IT15 gene expression in fetal human brain

To examine the expression of the gene which causes Huntington's disease (HD), IT15, during development, in situ hybridization of radiolabeled riboprobes was performed in human fetal (gestational ages 20-23 weeks) and adult brain. Optical densities of autoradiographs were determined in various brain regions and compared to cell density in those regions. IT15 expression was found in all regions of the fetal and adult brain, and there was a high degree of correlation of autoradiographic signal with cell number in all regions but germinal matrix in fetal brain and white matter in adult brain. These two regions are notable for their significant proportion of glial cells, and suggest that IT15 expression is predominantly neuronal. There was no preponderance of IT15 expression in striatal compartments in fetal brain as demonstrated by acetylcholinesterase activity, nor was there differential expression of IT15 in brain regions known to be particularly affected in HD. IT15 gene expression is present by 20 weeks gestation in human brain, and at that stage of development exhibits a pattern of distribution which is similar to adult brain. If a developmentally-regulated role for IT15 exists in the pathogenesis of HD, it must occur prior to 20 weeks gestation.

Synthesis and Properties of a Cuprate Superconductor Containing Double Mercury-Oxygen Layers

A cuprate superconductor containing double mercury layers was synthesized with a high-pressure, high-temperature technique. The compound, with chemical formula Hg(2)Ba(2)-Y1-xCaxCu(2)O(8-delta), contains a double HgO layer with structure similar to that of rock salt. The prototype compound Hg(2)Ba(2)YCu(2)O(8-delta) is an insulator. Superconductivity is induced in the system by partially replacing yttrium with calcium.

Studies on an artificial trypsin inhibitor peptide derived from the mung bean trypsin inhibitor: chemical synthesis, refolding, and crystallographic analysis of its complex with trypsin

The active fragment with Lys at the reactive site of mung bean trypsin inhibitor (MBILF) is composed of two peptide chains, A1 of 26 residues and A2 of 9 residues linked via two disulfide bonds. In the present study, a peptide of 22 residue comprising the sequence of chain A1 from position 3 to 24 was synthesized by the solid-phase method. This synthetic peptide with six Cys residues contains a reactive site at position Lys11I-Ser12I (I denotes an inhibitor residue). Air oxidation and HPLC purification resulted in two antitrypsin active components, SPC1 and SPC2. Neither SPC1 nor SPC2 can stoichiometrically inhibit trypsin. The Ki values of SPC1 and SPC2 are 1.2 x 10(-7) and 4.0 x 10(-8) M, respectively. The complexes of SPC1 and SPC2 with bovine beta-trypsin (BTRY) were crystallized by ammonium sulphate precipitation at pH 6.4 and 6.0, respectively. The two crystals have the same crystal form with space group P2(1)2(1)2(1) and cell dimension of a = 63.2(2) A, b = 63.5(6) A, and c = 69.8(4) A. The crystal structure of one complex, SPC1-BTRY, was determined and refined at 2.2 A resolution to a final R-value of 19.2%. From the resulting electron density map, 9 residues of SPC1, from position 9I to 17I, were identified clearly and three-dimension atomic model of the 9-residue reactive loop formed by a disulfide bridge, Cys9I-Cys17I, was built. No electron density corresponding to the other 13 residues was observed in the present map.(ABSTRACT TRUNCATED AT 250 WORDS)

Retrotrapezoid nucleus muscarinic receptor subtypes localized by autoradiography

Microinjection of muscarinic receptor subtype antagonists into the region of the cat retrotrapezoid nucleus (RTN) decreases blood pressure (greatest efficacy; M2 subtype) and both baseline phrenic activity and CO2 sensitivity (greatest efficacy; M3/M1 subtype). Here we examine, in cat medullary sections at the level of the RTN, the effects of the same antagonists on binding of the high affinity muscarinic agonist quinuclidinyl benzilate (QNB). 3H-QNB binding was saturated and highly specific at 1 nM concentration and stable over 30 to 120 min (Kd, 0.49 nM; Bmax, 136 fm/mg protein). Studied biochemically, we found IC50 values for whole sections of 4.9 x 10(-6) M (M1 antagonist pirenzepine); 1.0 x 10(-6) M (M2 antagonist AFDX); and 0.64 x 10(-7) M (M3 antagonist DAMP; P < 0.03 vs PZ). Densitometric analysis of whole medullary cross section autoradiograms resulted in similar IC50 values as in the biochemical approach. Specific analysis of the RTN region demonstrated the presence of 3H-QNB binding and similar competition by the antagonists. Average IC50 values determined by densitometry were 14 x 10(-6) M (pirenzepine); 1.3 x 10(-6) M (AFDX; P < 0.01 vs PZ); and 0.53 x 10(-7) M (DAMP; P < 0.01 vs PZ). All three subtypes of muscarinic receptors identifiable via pharmacological antagonists appear to be present in the RTN region but we could not distinguish a subtype-specific pattern of receptor distribution.

Association of peroxisome proliferator-activated receptor and Hsp72

In an effort to understand the relationship between a 72-kDa heat shock protein (Hsp72) and peroxisome proliferator-activated receptors (PPARs), we have characterized their interaction using clofibric acid-Sepharose chromatography and co-immunoprecipitation with antisera raised against either rat PPAR (rPPAR) or Hsp72. First, we observed that both rPPAR and Hsp72 elute in a clofibrate-dependent manner from the clofibric acid-Sepharose matrix. Second, we found that immunoprecipitation of either protein from solution resulted in the precipitation of the other. This result was obtained from rat liver cytosol, from Spodoptera frugiperda (Sf9) insect cells expressing rPPAR, and from reticulocyte lysate rPPAR expression systems. These results suggest that Hsp72 and rPPAR form a complex in vivo and that Hsp72 may play a role in the folding, subcellular localization, and/or signaling pathway of PPARs.

Infectious transcripts from PCR-amplified broad bean mottle bromovirus cDNA clones and variable nature of leader regions in RNA 3 segment

The genome of broad bean mottle bromovirus (BBMV) contains three positive-sense ssRNA segments, each capped with m7GpppA. Full-length transcribable cDNA clones for four strains of BBMV were constructed by employing reverse transcriptase-PCR (RT-PCR) and a high fidelity Vent DNA polymerase. The transcribed BBMV RNAs contained a 5' non-viral G residue and, although delayed, produced symptoms similar to those observed in plants infected with authentic virion RNAs. The transcripts replicated inefficiently in protoplasts. In contrast, transcript-derived progeny BBMV RNAs had the repaired termini, were as infectious as the authentic BBMV RNAs and replicated to high levels in protoplasts. In vitro translation of synthetic RNAs confirmed the previously proposed gene expression strategy for BBMV. Sequencing of virion RNAs from the Bawden strain revealed two forms of BBMV RNA3 components, the longer form containing 21 5' extra nucleotides derived by the duplication of two short 5' leader regions. The relative concentration of the two RNA 3 forms was found to be host-dependent, with the longer form prevailing in broad bean and Nictiana clevelandii infections and the shorter form in bean infections.

(Aminomethyl)phosphonate derivatives of oligonucleotides

Oligothymidylate (aminomethyl)phosphonates have been prepared, and their enzymatic and physicochemical properties have been studied. The individual isomers of the protected dimers have been separated, characterized, and incorporated into oligonucleotides in which the backbone consists of alternating (aminomethyl)phosphonate and phosphodiester linkages. One of these net neutral, single isomer oligonucleotides forms a duplex with its complementary sequence which is more stable than the corresponding natural counterpart, whereas the other isomer is considerably less stable. Specificity of hybridization is maintained, as determined by the reduction in melting temperature observed upon the introduction of mismatches into the complementary strand of the duplex. The (aminomethyl)-phosphonate linkage is stable toward enzymatic degradation but can be hydrolyzed in aqueous solution at elevated temperature.

Cloning of a new member of the peroxisome proliferator-activated receptor gene family from mouse liver

Peroxisome proliferators are postulated to elicit predictable pleiotropic responses in the liver by activating a peroxisome proliferator-activated receptor (PPAR). PPARs from mouse liver (mPPAR), rat liver (rPPAR), and Xenopus liver (xPPAR gamma) have been cloned recently. We now report the cloning of a new member from mouse liver which we designate mPPAR gamma. mPPAR gamma cDNA contained an open reading frame encoding a 475-amino acid protein exhibiting 75% amino acid similarity to xPPAR gamma, while it showed only 55% identity with mPPAR. The ligand-binding and DNA-binding domains are best conserved between mPPAR gamma, mPPAR, and xPPAR gamma. Like rPPAR, mPPAR gamma is able to impart peroxisome proliferator responsiveness to the promoter of peroxisomal bifunctional gene, which encodes the second enzyme of the peroxisomal fatty acid beta-oxidation system. Northern blot analysis revealed high expression of mPPAR gamma gene in mouse liver, kidney, and heart and low expression in the lung, testis, brain, skeletal muscle, and spleen. In mice treated with ciprofibrate, a peroxisome proliferator, a 2-fold increase in mPPAR gamma mRNA was observed in the liver and kidney. The presence of two PPARs in the mouse liver suggests the possibility of multiple signaling pathways for the peroxisome proliferator-induced pleiotropic responses.

[The 43KD polypeptide in the proteins of human lens]

The total proteins, water--soluble proteins and the urea--soluble proteins of the lens from fetal, adult and senile cataract were determined by SDS--PAGE. It was found that there was a 43KD polypeptide in the capsular--epithelium of all lens stated above. The band on SDS-PAGE corresponding to 43KD polypeptide was wide in the water--soluble proteins of the cortex and nucleus of the lenses obtained from over 14-year-old individuals. It became blurred in the urea--soluble proteins of cortex and nucleus of lens with aging, whereas it became almost disappeared in the senile cataract lens.

Rat mesangial cell hypertrophy in response to transforming growth factor-beta 1

Central features of progressive glomerular sclerosis are initial glomerular hypertrophy and subsequent accumulation of extracellular matrix proteins. Since TGF-beta 1 may play a key role in this glomerular response to injury, the present study sought to explore further TGF-beta 1 actions and regulated expression of its receptor in rat mesangial cells. The rat TGF-beta type II receptor (TGF-beta RII) homolog was cloned by screening a rat kidney cDNA library with a human TGF-beta RII cDNA probe, and sequenced. Expression of this receptor subtype in rat mesangial cells was then demonstrated by RNase protection assay, and by Northern blot analysis of poly (A)+ RNA, TGF-beta RII expression was down-regulated in cells treated with exogenous TGF-beta 1. Affinity cross linking studies demonstrated presence of this receptor on cell surface. Rat mesangial cells also expressed TGF-beta 1 and autoinduction by TGF-beta 1 was observed in the same cells, suggesting that this polypeptide may act in an autocrine fashion on mesangial cells, and that it may stimulate a positive autoamplification loop. TGF-beta 1 inhibited mesangial cell proliferation and stimulated significant overall protein and collagen production. Furthermore, mesangial cell size increased in response to chronic TGF-beta 1 treatment. These findings demonstrate that rat mesangial cells express key components of the TGF-beta system and raise the intriguing possibility that in the glomerular mesangium, TGF-beta 1 may not only induce extracellular matrix synthesis, but may also participate in the process of glomerular hypertrophy in response to injury.

Metabolism of carcinogenic nitrosamines in the rat and human esophagus and induction of esophageal adenocarcinoma in rats

The mechanism is discussed by which certain nitrosamines induce esophageal papillomas and squamous cancer in rats, and some evidence is presented for the view that nitrosamines also induce the same cancer in humans, especially in China and South Africa. Studies on the metabolism of nitrosamines by cytochrome P450 isozymes in rat and human esophagus, including the activation reactions of formaldehyde and pentaldehyde formation from methyl-n-amylnitrosamine (MNAN), are reviewed. These reactions are catalyzed by microsomes from the rat and human esophagus, probably because these microsomes contain specific cytochrome P450 isozymes. Evidence is reviewed for the occurrence of nitrosamines related to MNAN in fungus-infected corn. The incidence of esophageal adenocarcinoma is rising in Western countries. The precursor lesion, Barrett's esophagus, is associated with colon cancer, suggesting a role for bile salts in the induction of the esophageal tumor. Studies are described in which rats were subjected to esophago-duodenostomy (joining the duodenum to the esophagus) and then treated with nitrosamines that normally induce esophageal squamous cancer. Adenocarcinomas of the lower esophagus were induced as well as Barrett's esophagus (under one set of conditions). Feeding a high-fat diet with this system increased the incidence of esophageal adenocarcinoma. This tumor was not induced when the operation was changed to esophago-gastroplasty (widening the lower esophageal sphincter). These results support a role of reflux of duodenal contents (including bile and pancreatic juice) rather than of gastric contents in the etiology of human esophageal adenocarcinoma.

Single strand conformation polymorphism analysis of androgen receptor gene mutations in patients with androgen insensitivity syndromes: application for diagnosis, genetic counseling, and therapy

Recent studies indicate that mutations in the androgen receptor gene are associated with androgen insensitivity syndromes, a heterogeneous group of related disorders involving defective sexual differentiation in karyotypic males. In this report, we address the possibility of rapid mutational analysis of the androgen receptor gene for initial diagnosis, genetic counseling, and molecular subclassification of affected patients and their families. DNA from peripheral blood leukocytes of six patients from five families with various degrees of androgen insensitivity was studied. Exons 2 to 8 of the androgen receptor gene were analyzed using a combination of single strand conformation polymorphism analysis and direct DNA sequencing. Female family members were also studied to identify heterozygote carriers. Point mutations in the AR gene were identified in all six patients, and all mutations caused amino acid substitutions. One patient with incomplete androgen insensitivity was a mosaic for the mutation. Four of the five mothers, as well as a young sister of one patient, were carriers of the mutation present in the affected child. Our data show that new mutations may occur in the androgen receptor gene leading to sporadic androgen insensitivity syndrome. Molecular genetic characterization of the variant allele can serve as a primary tool for diagnosis and subsequent therapy, and can provide a basis for distinguishing heterozygous carriers in familial androgen resistance. The identification of carriers is of substantial clinical importance for genetic counseling.

Characterization of defective interfering RNA components that increase symptom severity of broad bean mottle virus infections

Several strains of the broad bean mottle virus (BBMV), an icosahedral tripartite plant RNA virus, which show distinct reactions on certain plant hosts have been described (K. M. Makkouk et al., Neth. J. Plant Pathol. 94, 195-212, 1988). Here we report defective interfering (DI) RNAs encapsidated in two BBMV strains from Morocco and Tunisia. While not effective in some plants, these DI RNAs exacerbated the severity of symptoms in others. The most dramatic, lethal effect of DI RNAs has been found on pea (Pisum sativum, cv. Rondo) seedlings. Sequence analysis has revealed that the DI RNAs were derived by single in-frame central deletions of 448 to 537 nt in the corresponding genomic RNA2 components. A comparison of the intensities of full-length RNA2 bands from DI molecule-containing and DI molecule-deficient virion RNA preparations revealed that the DI RNAs decreased the level of RNA2 components in total RNA preparations. The differences between corresponding virion RNAs were much smaller. This suggests an interference with RNA replication. In vitro assays and an analysis of the polyribosomal RNA fractions confirmed the translational activity of DI RNAs. This paper reports the first description of natural DI RNAs in tripartite isometric plant RNA viruses.

Hydroxylation and dealkylation of methyl-n-butylnitrosamine and role of certain cytochrome P-450 isozymes in these reactions

We studied the metabolism of methyl-n-butyl-nitrosamine (MBN), a carcinogen for the rat esophagus and liver. The 2-, 3- and 4-hydroxy derivatives were identified as new metabolites of MBN. In studies on tissue slices freshly removed from MRC-Wistar rats, MBN metabolism resembled that of the previously studied methyl-amylnitrosamine in the esophagus catalyzed 2- and 3- hydroxylation; liver, omega-1 hydroxylation; and lung, omega-hydroxylation of both nitrosamines. Liver microsomes from Sprague-Dawley rats catalyzed 2-, 3- and 4-hydroxylation of MBN, as well as the previously studied activating reactions of demethylation and debutylation. Phenobarbital induced all five reactions of MBN bh rat liver microsomes, especially debutylation; 3-methylhol-anthrene induced 3-hydroxylation and debutylation and isoniazid induced demethylation and debutylation. Monoclonal antibodies that inhibit specific cytochrome P-450 isozymes were used to identify the isozymes involved in each reaction. Antibody 4-7-1 appeared more specific than the previously used antibody 2-66-3 for inhibiting P-450 2B1 and/or 2B2. For the metabolism of both MBN and methylamylnitrosamine by rat liver microsomes, the antibody results indicated that P-450 2C11 mainly catalyzed demethylation and omega-1 hydroxylation, P-450 1A1 or 1A2 catalyzed 3-hydroxylation and debutylation or depentylation, P-450 2E1 produced demethylation and P-450 2B1 or 2B2 produced omega-1 hydroxylation, demethylation and debutylation or depentylation.

Inhibition by phenylethyl and phenylhexyl isothiocyanate of metabolism of and DNA methylation by N-nitrosomethylamylamine in rats

We investigated the effect of 2-phenylethyl and 6-phenylhexyl isothiocyanate (PEITC and PHITC) on the metabolism of the rat esophageal carcinogen, N-nitrosomethylamylamine (NMAA). PEITC was administered orally to MRC-Wistar rats as single doses of 0.1 or 1.0 mmol/kg, or by other regimens. When esophagi and liver slices from the treated rats were incubated with 23 microM NMAA, the formation of 2- to 5-hydroxy-NMAA was inhibited by 45-90% for esophagus and by 14-19% for liver slices. In contrast, when esophagi and liver slices from untreated MRC-Wistar rats were incubated in vitro with NMAA and 10 microM PEITC, the PEITC inhibited hydroxy-NMAA formation similarly (by 79-89%) in the two tissues. Also, PEITC inhibited the formation from NMAA of the hydroxy-NMAAs, formaldehyde and pentaldehyde by esophageal and liver microsomes to similar extents. In studies on DNA methylation by NMAA, 7- and O6-methylguanine (O6-MeG) were determined by HPLC with fluorimetric detection. Guanine methylation in esophageal and liver DNA was generally close to linear for doses of 5-50 mg NMAA/kg. With 50 mg NMAA/kg, guanine methylation in esophageal and liver DNA peaked after 5 h, and 8-11% of the peak O6-MeG persisted after 72 h. A single dose of 0.1 or 1.0 mmol PEITC/kg reduced the O6-MeG levels by 44-51% in the esophagus but by only 7-22% in the liver. Administration of the PEITC homolog, PHITC, inhibited NMAA metabolism by liver slices from the treated rats and the methylation of guanine in liver DNA, but had little effect in the esophagus, i.e. PHITC tended to have the opposite tissue specificity to PEITC. The finding that administration of PEITC specifically inhibited NMAA metabolism in the rat esophagus supports the view that PEITC may be a useful chemopreventive agent against esophageal carcinogenesis in humans.

Cerebellar control of expiratory activities of medullary neurons and spinal nerves

Expiratory-related activities of spinal nerves are augmented after stimulation of the infracerebellar nucleus of the cerebellum. These stimulations alter neither inspiratory spinal neural activities nor inspiratory and expiratory laryngeal neural activities. It was hypothesized that efferents from the infracerebellar nucleus impinge on spinal motoneurons by a pathway that bypasses the medulla. In decerebrate, paralyzed, and vagotomized cats, phrenic and expiratory triangularis sterni activities and activities of medullary respiratory neurons were recorded. During infracerebellar stimulation, activities increased for expiratory bulbospinal neurons and neurons with tonic discharge patterns. After unilateral ablation of the infracerebellar nucleus by kainic acid, triangularis sterni discharge was eliminated and activities of expiratory bulbospinal neurons continued at reduced frequencies. Stimulations of the anterior interposed nucleus caused both inspiratory and expiratory activities to increase, whereas no systematic changes followed stimulations of the vermis. Results establish that at least a portion of the changes in expiratory activities of spinal motoneurons after perturbations of the infracerebellar nucleus occurs secondarily to changes in activities of medullary neurons. The possibility of separate cerebellar projections to medullary and spinal neurons is discussed.

Conversion of lytic to persistent alphavirus infection by the bcl-2 cellular oncogene

Little is known about virus-host cell interactions that regulate the lytic potential of viruses during productive replication. Sindbis virus (SV), a single-stranded positive-sense RNA virus in the alphavirus genus (family Togaviridae), results in lytic infection in most vertebrate cell lines, but persistent productive infection in post-mitotic neurons. The cellular oncogene bcl-2, which encodes an inner mitochondrial membrane protein of M(r) 26,000 (ref. 2), blocks programmed cell death (apoptosis) in neurons. We therefore investigated whether SV infection induces programmed cell death in non-neuronal cells, and if so, whether virus-induced programmed cell death can be blocked by transfection with bcl-2. We demonstrate that SV infection of baby hamster kidney (BHK-2), mouse neuroblastoma (N18), and rat prostatic adenocarcinoma (AT-3) cells results in programmed cell death, whereas SV infection of bcl-2-transfected AT-3 cells results in long-term persistent productive infection. Thus cellular bcl-2 oncogene expression plays a role in the establishment of persistent viral infection by blocking virus-induced programmed cell death.

Refined 1.6 A resolution crystal structure of the complex formed between porcine beta-trypsin and MCTI-A, a trypsin inhibitor of the squash family. Detailed comparison with bovine beta-trypsin and its complex

The crystal structure of the complex formed by porcine beta-trypsin with the MCTI-A inhibitor (Momordica charantia, Linn. Cucurbitaceae) has been determined at 1.6 A resolution using the molecular replacement method. The sequence of MCTI-A was determined by recognizing the electron density, and shows that MCTI-A is a member of the squash family of trypsin inhibitors. We report the first high-resolution structure of porcine beta-trypsin. Detailed comparisons have been made on the overall structure, solvent structure and active-site geometries between this complex and bovine beta-trypsin and its complexes. On the basis of our results, we discuss the interaction patterns between inhibitor and trypsin. Unlike other complex structures formed by bovine trypsin with inhibitors, no out-of-plane distortion around the inhibitor's scissible peptide was observed. The role of the trypsin catalytic triad is also discussed on the basis of this structure.

Extracellular matrix-stimulated phospholipase activation is mediated by beta 1-integrin

beta 1-Integrins are major mediators of interactions between cells and extracellular matrix (ECM). Adhesion of rat glomerular epithelial cells (GEC) to collagen stimulated phospholipase C. As a result, 1,2-diacylglycerol (DAG) was increased, and inositol phospholipids were decreased in collagen-adherent cells, as compared with GEC adherent to plastic substrata. Adhesion to collagen also stimulated production of free arachidonic acid (the precursor for eicosanoids) due to metabolism of DAG through the DAG lipase pathway and due to phospholipase A2-induced hydrolysis of phospholipids. Phospholipase A2 appeared to be stimulated as a result of protein kinase C (PKC) activation, probably secondary to increased DAG. The collagen-induced increases in DAG and free arachidonic acid, as well as the decrease in inositol phospholipids, were partially inhibited by lowering extracellular Ca2+ concentration to 200 nM or less and by anti-beta 1-integrin antibody Fab. In contrast, anti-beta 1-integrin immunoglobulin G (IgG) enhanced collagen-mediated increases in DAG and arachidonic acid. Proliferation of GEC adherent to collagen was reduced in the presence of anti-beta 1-integrin IgG. The antiproliferative effect of anti-beta 1-IgG appeared to be mediated through PKC, since it was absent in PKC-depleted GEC. Immunoprecipitation with integrin subunit-specific antibodies demonstrated alpha 2 beta 1- and alpha 3 beta 1-integrins in GEC. Thus, in GEC, ECM induces activation of phospholipases C and A2, which is mediated, at least in part, by beta 1-integrins. Products of integrin-mediated phospholipase activation may modulate GEC proliferation.

Immunohistochemical localization of the D1 dopamine receptor in rat brain reveals its axonal transport, pre- and postsynaptic localization, and prevalence in the basal ganglia, limbic system, and thalamic reticular nucleus

D1 dopamine receptor localization was examined by immunohistochemistry using a polyclonal anti-peptide antibody which (i) immunoprecipitated a protein fragment encoded by a D1 receptor cDNA and (ii) on Western blots of solubilized striatal and hippocampal membranes recognized two proteins of approximately 50 kDa and 75 kDa, corresponding to reported sizes of D1 receptor proteins. Immunoreactivity overlapped with dopamine-containing pathways, patterns of D1 receptor binding, and mRNA expression. Staining was concentrated in prefrontal, cingulate, parietal, piriform, entorhinal, and hippocampal cortical areas and subcortically in the basal ganglia, amygdala, septal area, substantia inominata, thalamus, hypothalamus, and neurohypophysis. Prominent labeling was seen in the thalamic reticular nucleus, a region known to integrate ascending basal forebrain inputs with thalamocortical and corticothalamic pathways and in fiber bundles interconnecting limbic areas. In striatal neuropil, staining appeared in spines (heads and necks), at postsynaptic sites in dendrites, and in axon terminals; in the pars reticulata of the substantia nigra, labeling was prevalent in myelinated and unmyelinated axons and dendrites. These data provide direct evidence for the regional and subcellular distribution of D1 receptor protein in the brain and for its pre- and postsynaptic localization in the basal ganglia. The prominent immunoreactivity seen in the limbic system and thalamic reticular nucleus supports an important role for this receptor subtype in mediating integrative processes involved with learning, memory, and cognition.

Adhesion of rat glomerular epithelial cells to extracellular matrices: role of beta 1 integrins

Glomerular epithelial cells (GEC) maintain glomerular permselectivity and are a target of immunological glomerular injury, which may lead to proliferation or detachment from extracellular matrix (ECM). We studied adhesion mechanisms in rat GEC in culture, focusing on adhesion molecules of the beta 1 integrin family. At early time points (1 hr after plating of cells into culture wells that had been pre-incubated with purified ECM proteins), adhesion of GEC to collagen I, collagen IV, laminin, and fibronectin was inhibited with anti-beta 1 integrin antibody. The peptide RGDS inhibited adhesion to fibronectin and laminin. Immunoprecipitation studies demonstrated the presence of alpha 2, alpha 3, and beta 1 integrins; the alpha 1, alpha 4, alpha 5, alpha 6, alpha v, and beta 3 subunits were undetectable. Adhesion to all ECM proteins was dependent on divalent cations, but the effects of individual cations varied among substrata. In rat GEC, alpha 2 beta 1 and/or alpha 3 beta 1 integrins appear to mediate adhesion to collagen I, collagen IV, and laminin. The alpha 3 beta 1 integrin is also the likely receptor for fibronectin, interacting through an RGD binding site. Furthermore, single integrins or combinations of integrins appear to have distinct ligand-binding functions that are differentially regulated by divalent cations. Characterization of GEC adhesion molecules may facilitate the understanding of mechanisms of glomerular development, and cell detachment or proliferation in immune glomerular injury.

Metabolism of N-nitrosomethyl-n-amylamine by microsomes from human and rat esophagus

Asymmetric dialkylnitrosamines induce esophageal cancer in rats and hence might be involved in the etiology of this cancer in humans. As a test of this hypothesis, we examined whether nitrosamines can be activated by segments of human esophagus and by microsomes of human and rat esophagus and liver. Specimens of 8 human esophagi were removed less than 6 h after death, and segments were incubated for 6 h with 23 and 300 microM N-nitrosomethyl-n-amylamine (NMAA). Hydroxy-NMAA yields were determined by gas chromatography-thermal energy analysis and were insignificant except for those of 5-hydroxy-NMAA, which were low. Microsomes were prepared from 4 batches of human esophagi and samples with 0.6 mg protein were incubated for 20 min with NMAA and cytochrome P-450 cofactors. We determined hydroxy-NMAAs as before and aldehydes by high-performance liquid chromatography of their 2,4-dinitrophenylhydrazones. Incubation of these microsomes with 12 mM NMAA yielded mean values of 0.64 nmol formaldehyde ("demethylation"), 0.21 nmol pentaldehyde ("depentylation"), and 0.56 nmol total hydroxy-NMAAs/min/mg protein. Metabolite yields under various conditions were determined, including a demonstration that carbon monoxide inhibited 81% of NMAA demethylation, indicating that cytochrome P-450 enzymes were involved. We also examined N-nitrosodimethylamine (NDMA) demethylation by the same microsomes. Rat esophageal microsomes dealkylated NMAA and NDMA similarly to human esophageal microsomes, but with 2-6 times and twice the activity, respectively. Human and rat esophageal microsomes demethylated 6 mM NMAA 18-20 times as rapidly as they demethylated 5 mM NDMA, in contrast to liver microsomes of these species, which demethylated 6 mM NMAA only 0.9-1.4 times as rapidly as they demethylated 5 mM NDMA. However, liver microsomes of both species were more active than esophageal microsomes for NMAA depentylation. The occurrence of NMAA demethylation and (to a lesser extent) depentylation with both human and rat esophageal microsomes is important because these are the activating reactions, and suggests that both human and rat esophagus contain P-450 isozymes that specifically dealkylate asymmetric dialkylnitrosamines.

Construction of an Rb gene expression plasmid

We obtained an 844 bp Bg1II fragment from an Rb cDNA clone and inserted it into the expression vector pWR-13 to construct an Rb gene expression plasmid. When the Rb Bg1II fragment was fused in-frame into pWR-13, it was operated by a Lac Z promoter and produced a fusion protein which consisted of expressed Rb protein and a small peptide from Lac Z. The recombinants were transformed into E. coli with the CaCl2 method, screened by in situ hybridization, and restriction mapped. Total cellular protein of transformed clones was analyzed by SDS-PAGE and Commassie blue staining. The sense clones showed a unique band at 28,000. On Western blot, this band specifically reacted with 125I-labelled antibody against synthetic Rb peptide. This protein comprised more than 5% of total bacterial protein.

Introduction of a foreign gene (Escherichia coli lacZ) into rat neostriatal neurons using herpes simplex virus mutants: a light and electron microscopic study

Introducing genes into adult neurons in vivo may be a useful experimental tool for studying and modifying neuronal function. In this study two herpes simplex virus type 1 (HSV-1) mutants were used to examine the capability of different types of neostriatal neurons to express a foreign gene introduced through viral infection. In these HSV-1 mutants (7134 and RH105) the Escherichia coli gene, lacZ, under the control of viral promoters active during the early phase of infection, was substituted for viral genes (ICPO and TK, respectively) needed for efficient replication in the nervous system. Adult male rats received unilateral injections of HSV-1 mutant 7134 or RH105 into the neostriatum. Animals survived for 1 to 70 days with no apparent adverse physiological or behavioral effects. At the injection site, both mutant viruses produced focal tissue necrosis and reactive gliosis. Histochemical detection of the lacZ gene product, beta-galactosidase (beta Gal), revealed extensive labeling of neurons with mutant 7134 and relatively limited neuronal labeling with the mutant RH105. Mutant 7134, which is capable of some replication in cells, conferred beta Gal expression in cells over an area that was twofold greater than the necrotic area. In contrast, mutant RH105, which cannot replicate in cells, produced a zone of beta Gal-labeled cells only two-thirds the area of the necrotic core. Both medium- and large-sized neostriatal neurons were positive for beta Gal, and a higher proportion of large cells were labeled as compared to other neuronal populations in the normal striatum. A few glial cells were also beta Gal-positive. Retrograde transport of virus to the substantia nigra pars compacta and to the cortex was minimal and occurred only with mutant 7134. No evidence was seen for anterograde transport. Immunohistochemical localization of beta Gal at the ultrastructural level after inoculation with mutant 7134 revealed that both types of medium-sized neurons (spiny and aspiny types), as well as large neurons, were infected 3 days following inoculation. Immunoreactive neurons ranged from severely pathologic to remarkably healthy. Some of the axon terminals that contacted beta Gal-immunoreactive dendrites and spines were degenerated. These results demonstrate that in the adult rat replication-deficient HSV-1 vectors injected intrastriatally can be used to express a foreign gene in at least three types of neostriatal neurons, while maintaining the long-term survival and general health of the injected animals. The neurotoxicity induced by HSV-1 mutants may still be considerable, however, and ways of minimizing neuropathological effects need to be addressed.

Amino acid sequencing of a trypsin inhibitor by refined 1.6 A X-ray crystal structure of its complex with porcine beta-trypsin

The stoichiometric complex formed between porcine beta-trypsin and the Momordica charantia, Linn. Cucurbitaceae trypsin inhibitor-A (MCTI-A) was crystallized and its X-ray crystal structure determined using molecular replacement method. The primary sequence and topology of the inhibitor was determined by recognizing the electron density and refined to a final R value of 0.167 (7.0-1.6 A) with RMS deviation of bond lengths from standard values 0.012 A. The sequence was compared with those obtained by other groups and was found to be similar to the squash proteinase inhibitor. Its spatial structure and the conformation of its primary binding segment from Cys-3I (P3) to Glu-7I (P3') which contains the reactive scissile bond Arg-5I C-Ile-6I N were also very similar with other squash family proteinase inhibitors.

Methodologic study of direct preparation for chromosome analysis of human solid brain tumors

Human malignant glioma grown in athymic nude mice (NHG-1) and three freshly resected human solid gliomas were used in the study of factors influencing the direct preparation (DP) for chromosome analysis of human solid tumors. The results showed that: 1) the length of time after the blood supply was obstructed was a major factor in reducing the success rate of DP, i.e., a 2-hour delay resulted in a significantly lowered metaphase number and after 4 hours almost no metaphases could be seen; 2) preserving tumor cells at 4 degrees C may prolong the time limit to about 4 hours; 3) culture medium (RPMI 1640 and Eagle MEM) and bovine calf serum concentration (0%, 10%, 20%, and 30%) did not influence the success rate significantly; 4) colchicine concentration (0.025 micrograms/mL, 0.05 micrograms/mL, 0.1 micrograms/mL) and time of treatment (30 min, 90 min, or 180 min) mainly affected the quality of chromosomes observed but had little effect on the quantity of metaphases that might be obtained. Based on these results, we had a success rate of more than 80% in 72 xenografts and 22 human brain tumors.

Neurobiotin, a useful neuroanatomical tracer for in vivo anterograde, retrograde and transneuronal tract-tracing and for in vitro labeling of neurons

The biotin derivative, N-(2-aminoethyl) biotinamide hydrochloride, or Neurobiotin, has been shown recently to be a useful marker for intracellular and anterograde tracing. The properties of Neurobiotin as a tracer were further examined in this study by making pressure injections into different regions of the cerebral cortex or the rostral neostriatum of rats or by incubating striatal cells in culture with the tracer. Results showed extensive anterograde transport of Neurobiotin in cortical axons and terminals within the neostriatum 2-70 h after single or multiple cortical injections of the tracer. Similarly, profuse axonal projections to the medial portion of the globus pallidus were seen after an injection of Neurobiotin into the rostral neostriatum. Transneuronal labeling of medium-size neostriatal neurons was observed following injections of Neurobiotin into the prefrontal cortex. At the ultrastructural level, anterogradely labeled cortical axon terminals and transneuronally labeled neurons were readily identified in the caudate-putamen by the presence of both fine particulate and large punctate reaction products. Retrograde fillings of neurons resembling a Golgi-impregnation were seen in the ventral posterior complex of the thalamus after injections in the sensorimotor cortex. Neurons in the medial globus pallidus were also retrogradely labeled following tracer injections in the rostral caudate-putamen. Finally, Neurobiotin was readily and selectively taken up by striatal neurons in culture, where it extensively labeled somata and neurites. These results show that Neurobiotin is a versatile new tracer, which can be potentially useful for the study of neuronal organization in vivo and in vitro.