Chronic hypoxia causes opposite effects on glucose transporter 1 mRNA in mature versus immature rat brain

We have shown previously that chronic hypoxia can regulate the expression of membrane proteins. Since there are virtually no glucose stores in the brain and glucose transport can be rate-limiting during stress, the role of glucose transporters becomes crucial for cell survival under stress. In the present study, we asked whether mRNA levels for glucose transporter 1 (GT1), which is expressed in a variety of cells in the brain, especially in the microvessels for glucose transport from blood vessels to brain, change in response to chronic hypoxia. Because major developmental changes occur in the rat CNS in-utero and in the first few weeks postnatally, we studied brain GT1 mRNA using Northern blot analysis at different ages after exposure of fetuses (from embryonic day 10 to birth), developing rats (from birth to 30 day old) or adult rats (from 90 to 120 day old) to hypoxia (Fractional inspired O2 9%). Our data show that (i) GT1 mRNA level was much lower in the newborn than in the adult and increased with age; (ii) chronic hypoxia caused a decrease of approximately 65% in GT1 mRNA in adult brain but induced an increase in fetal (more than 50%) and developing (approximately 80%) rats and (iii) the response of housekeeping gene (glyceraldehyde 3-phosphate dehydrogenase) was not similar to that of GT1, suggesting that the changes of GT1 mRNA are specific to glucose transporter.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of neutrophil influx in glomerulonephritis in the rat with anti-macrophage inflammatory protein-2 (MIP-2) antibody

The role of the chemokine, macrophage inflammatory protein-2 (MIP-2), during anti-glomerular basement membrane (GBM) antibody (Ab) glomerulonephritis (GN) was studied. Rat MIP-2 cDNA had been cloned previously. Recombinant rat MIP-2 (rMIP-2) from Escherichia coli exhibited neutrophil chemotactic activity and produced neutrophil influx when injected into the rat bladder wall. By using a riboprobe derived from the cDNA and an anti-rMIP-2 polyclonal Ab, MIP-2 was found to be induced in glomeruli with anti-GBM Ab GN as mRNA by 30 min and protein by 4 h, with both disappearing by 24 h. The expression of MIP-2 correlated with glomerular neutrophil influx. A single dose of the anti-MIP-2 Ab 30 min before anti-GBM Ab was effective in reducing neutrophil influx (40% at 4 h, P < 0.01) and periodic acid-Schiff deposits containing fibrin (54% at 24 h, P < 0.01). The anti-rMIP-2 Ab had no effect on anti-GBM Ab binding (paired-label isotope study). Functional improvement in the glomerular damage was evidenced by a reduction of abnormal proteinuria (P < 0.05). These results suggest that MIP-2 is a major neutrophil chemoattractant contributing to influx of neutrophils in Ab-induced glomerular inflammation in the rat.

Polyclonal antibodies against human melanocortin MC1 receptor: preliminary immunohistochemical localisation of melanocortin MC1 receptor to malignant melanoma cells

Peptides of 11 and 15 residue lengths were synthesised according to the sequence of the N-terminal region of the human MC1 melanocyte stimulating hormone receptor. The peptides were conjugated to thyroglobulin and used for preparation of antisera in the rabbit. Each of the conjugates raised antisera which showed high titre and specificity for its respective peptide antigen when evaluated in an ELISA test. Both types of antisera immunostained MC1 receptor expressing COS-7 cells. By contrast, the sera did not stain control COS-7 cells not expressing the MC1 receptor. Moreover, preimmune sera or antiserum preadsorbed with its respective peptide did not stain the MC1 receptor expressing cells. The antisera were used to immunostain sections of normal human skin, as well as samples of cutaneous malignant melanoma tumours obtained from a patient. The cells of the melanoma tumours were very strongly immunostained with the MC1 receptor antisera. By contrast, melanocytes which were present in the normal skin could not be visualised with our antisera.

[A comparative study on the effect of absorbable components of several drugs on the growth and population doublings of rat diploid fibroblast]

Embryonic skin fibroblast of Sprague-Dawley rats cultivated in vitro was used in this experiment. The cultural medium was added with absorbable components of several drugs. The result reveals that Yan Shou recipe, vitamin E and Huan Jing Jian have conspicuous promotive effect on the growth of diploid fibroblast and also help to increase population doublings. The experiment suggests that all these drugs possess anti-aging effect on the skin diploid fibroblast of rats.

The CYP2D6B mutant allele is overrepresented in the Lewy body variant of Alzheimer's disease

Approximately one-fourth of neuropathologically confirmed cases of Alzheimer's disease (AD) also have brainstem and neocortical Lewy bodies, constituting a Lewy body variant of AD. Because Lewy bodies are a pathologic hallmark of Parkinson's disease (PD), this subpopulation of AD subjects may have the same risk factors as PD subjects. Analyses of the cytochrome P450 CYP2D6-debrisoquine 4-hydroxylase mutant B allele, a susceptibility gene for PD, revealed a higher representation of this allele in the Lewy body variant of AD than in pure AD or non-AD without Lewy bodies.

Apolipoprotein-E epsilon-4 is associated with increased neurofibrillary pathology in the Lewy body variant of Alzheimer's disease

Brains from demented patients with both Alzheimer's disease (AD) pathology and brainstem and neocortical Lewy bodies have fewer neurofibrillary tangles than pure AD, but share with AD an increased apolipoprotein-E epsilon-4 (APOE4) allelic frequency. We applied the Braak and Braak AD neuropathology staging protocol, based on entorhinal and neocortical neurofibrillary pathology, to 40 such Lewy body variants of AD (LBV) and 97 cases of pure AD and compared the results in APOE4 positive and APOE4 negative subgroups. APOE4 was associated with more severe neurofibrillary pathology in LBV but not in pure AD, where a ceiling effect appears to be operative.

Pericardiocentesis and drainage by a silicon rubber line without echocardiographic guidance. Experience in 55 consecutive patients

Pericardiocentesis and drainage with a silicon rubber line were performed safely in 55 patients via the subxiphoid (80 times) or apical (1 time) approach at the bedside without echocardiographic guidance. The subxiphoid approach, which is close to the posterior of the sternum or the costal cartilage with a small acute-angle (15-30 degrees) to the parietal pericardium in front of the right ventricle, can avoid injuring the heart, liver and lungs. A line with sideholes near the distal end, which provides convenient drainage and has better histocompatibility, can be kept in place for a long period of time (1-82 days). It was also convenient to inject air, drugs or fluid through the line. There were no procedure-related serious complications or deaths. Emergency drainage with the Seldinger technique, especially for small to moderate effusions, is safe and simple.

The apolipoprotein E allele epsilon 4 is overrepresented in patients with the Lewy body variant of Alzheimer's disease

We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap.

New restriction endonuclease CviRI cleaves DNA at TG/CA sequences

A new type II restriction endonuclease, CviRI, was isolated from virus XZ-6E infected chlorella cells. CviRI is the first restriction endonuclease to recognize the sequence 5'-TGCA-3' and cleaves DNA between the G and C residues to produce blunt-end termini. Methylation of the adenine or cytosine in 5'-TGCA-3' sequences prevents CviRI cleavage. Due to its sequence specificity, CviRI may be especially useful for detecting mutant alleles of many heritable human genetic diseases.

Viewing method for improving underwater visibility by reduction of backscatter

For improved underwater visibility a method that uses a special intervallic series of light pulses and two acts of emitting and receiving is performed by two specially designed optical shutters and by control signals that are synchronously delayed. Calculations show that the apparent contrast of the target can be improved, and thus the distance over which it is visible can be increased. This method has several advantages that can make it practical for actual use, and its feasibility is demonstrated in experiments.

The difference in EEG theta waves between concentrative and non-concentrative qigong states--a power spectrum and topographic mapping study

The differences in EEG theta waves between concentrative and non-concentrative Qigong states were studied by means of power spectrum analysis and EEG mapping. The adult subjects included 20 practitioners of concentrative Qigong, 30 practitioners of non-concentrative Qigong and 23 control subjects. The results showed frontal mid-line theta rhythm was related to concentrative Qigong state. As the theta rhythm has been suggested to be one of the normal EEG patterns occurring in mental concentration, it is concluded that the theta rhythm is an indicator of mental concentration during Qigong state. This finding clarifies the implication of the theta rhythms appearing in Qigong and other meditation.

The relationship between genetic and physical distances in the cloned a1-sh2 interval of the Zea mays L. genome

A 470-kb segment from the long arm of chromosome 3 of Zea mays (inbred LH82), encompassing the a1-sh2 interval, was cloned as a yeast artificial chromosome. Comparison of the sizes of the restriction fragments generated from the cloned DNA fragment and from the DNA isolated from the maize inbred line LH82 established the colinearity of the a1-sh2 interval in these DNAs. By utilizing a chromosome fragmentation technique, a yeast artificial chromosome encompassing the a1-sh2 interval was separately fragmented at the a1 and sh2 loci. Comparison of the sizes of these fragmentation products established the physical distance between the a1 and sh2 loci to be 140 kb. Furthermore, these fragmentation experiments established the physical orientation of the a1 and sh2 genes relative to the maize centromere. The molecular cloning of the contiguous region between the a1 and sh2 loci made it possible to define the relationship between physical and genetic distances over a relatively large segment of the maize genome. In this interval, the relationship between physical and genetic distances is 1560 kb/centimorgan, which compares with 1460 kb/centimorgan for the entire maize genome, and 217 kb/centimorgan for a 1-kb segment within the a1 locus. Therefore, these findings are consistent with the hypothesis that genes per se are preferred sites for meiotic recombination rather than the hypothesis that genes reside in large recombinationally active segments of the genome.

Dissociation of depolarization-activated and swelling-activated Cl- channels

In many cells, patch excision and depolarization induce outwardly rectifying Cl- channels (ORDIC channels) whose function and normal mode of regulation are unknown. One possible function is the mediation of swelling-activated Cl- conductance, because in many cells rectifying Cl- currents are activated by cell swelling. However, swelling-activated Cl- channels in some epithelia have larger conductances than ORDIC channels and inactivate more rapidly, although both have similar anion selectivity and are blocked by stilbenes. Thus it has not been possible to determine whether the two types of channel current arise from distinct proteins or alternate states of a single protein. We studied 14 cell lines and found 2 lines, C127 mouse mammary epithelial cells and IEC-6 rat intestinal crypt cells, with very low levels of ORDIC channels. However, despite the near absence of ORDIC channels in these rodent cells, a large swelling-activated Cl-conductance was demonstrated by whole cell, efflux, and single-channel methods. Thus it is likely that ORDIC and swelling-activated channel currents arise from different channel proteins.

Postnatal development of voltage-sensitive Na+ channels in rat brain

Previous studies have shown that mammalian neuronal excitability increases with age, and this excitability may be related to development of Na+ channels. In addition, evidence suggests that Na+ channels are involved in the neuronal response to O2 deprivation. Because of this, we wished to examine the pharmacologic properties and neuroanatomical distribution of the Na+ channels in newborn brain and as a function of age. In this study, we used ligand-binding techniques and autoradiography with 3H-saxitoxin (STX) to investigate Na(+)-channel distribution in brains of rats at postnatal days 0, 3, 10, 21, 35, and 120. We found that (1) in each area examined, the Scatchard plots for STX binding were linear in both immature and mature brains in a ligand concentration range of 0.4-64 nM; the slopes, however, were different between areas or ages, with Kd values ranging between 1 and 5 nM; (2) STX-binding density was more than tenfold lower in the rostral brain and cerebellum at birth than in the adult and increased with age; (3) binding density in the newborn brainstem was higher than in other areas such as the cortex and cerebellum, which is opposite to the distribution in the adult; and (d) the brainstem had a different developing pattern with an early-peak density level (P10-21) and a lower adult level.(ABSTRACT TRUNCATED AT 250 WORDS)

Myenteric ganglia from the adult guinea-pig small-intestine in tissue-culture

Myenteric ganglia dissociated from the small intestine of adult guinea-pigs survived in long-term culture (1-2 months) and progressed to structural organization resembling the myenteric plexus in situ. Developmental changes were similar to cultures derived from neonatal intestine. After one week, the neurons gathered into clusters on a glial cell carpet. Processes from the neurons branched and ramified over the glial substrate. As the cultures matured, the processes joined into tracts and the neurons and glia formed compact aggregates reminiscent of ganglia interconnected by fibre bundles. Injection of dye revealed characteristic Dogiel I and II neuronal morphology. Electrical recording identified electrical and synaptic behaviour comparable to intact myenteric plexus, longitudinal muscle preparations, except slow synaptic excitation was absent. Pharmacological responses to forskolin and 5-hydroxytryptamine were essentially the same as in freshly dissected preparations. Lucifer yellow injected into single glial cells spread to a broad population indicative of the dye coupling found among glia in the myenteric plexus in situ. The results suggest that adult myenteric ganglia in culture are a useful model for investigation of aspects of enteric neurobiology including: (a) formation of connections in microcircuits; (b) cellular neurophysiology of enteric neurons; (c) neuropharmacology; and (4) cell biology of neuronal-glial interactions in the myenteric plexus.

Products of the TAL2 oncogene in leukemic T cells: bHLH phosphoproteins with DNA-binding activity

The TAL2 gene is activated as a result of the (7;9) (q34;q32) translocation, a chromosome defect found in the malignant cells of some patients with T-cell acute lymphoblastic leukemia (T-ALL). TAL2 potentially encodes a basic helix-loop-helix motif that is highly related to those specified by TAL1 and LYL1, distinct genes that have also been implicated in T-ALL. In this report we show that leukemic cells bearing the (7;9) (q34;q32) translocation express a TAL2 gene product of 108 amino acids. In leukemic cells this product exists in both a phosphorylated (pp13TAL2) and an unphosphorylated (p12TAL2) form. Serine residue 100 is the major site of TAL2 phosphorylation in vivo, and it serves as an effective in vitro substrate for mitogen-activated protein (MAP) kinases such as ERK1. TAL2 polypeptides interact in vivo with the E2A gene products (E47 and E12) to form bHLH heterodimers that bind DNA in a sequence-specific manner. The TAL2 polypeptides do not bind DNA by themselves, however, suggesting that their functional properties may be contingent upon association with other bHLH proteins. Taken together, the properties of TAL2 evaluated here broadly resemble those described previously for TAL1, and therefore support the idea that both proteins promote T-ALL by a common mechanism.

Interleukin-1 alpha stimulates KC synthesis in rat mesangial cells: glucocorticoids inhibit KC induction by IL-1

To assess the possible role of the production of chemokines by intrinsic glomerular cells in the generation of inflammation in glomerulonephritis, the chemokine, KC, was cloned from a rat macrophage cDNA library. Transfection of rat KC into COS-7 cells resulted in increased neutrophil chemotactic activity. The KC cDNA was expressed as a fusion protein in Escherichia coli for generation of an antibody. By using a riboprobe derived from the cDNA and the antibody, interleukin-1 (IL-1) was found to induce the expression of KC in rat mesangial cells. The induction of KC by IL-1 could be inhibited by dexamethasone (DEX). The protein synthesis inhibitor cycloheximide reversed the DEX-mediated inhibition, which suggested that new protein synthesis was necessary for the inhibitory effect. A nuclear runoff analysis indicated that DEX inhibited the transcription of KC induced by IL-1. The stability of KC mRNA was not decreased in the presence of DEX. Furthermore, immunoblots showed that DEX also inhibited KC expression at the level of translation. Together the inhibition of transcription and translation of the KC gene by DEX contribute to decreased KC expression in mesangial cells. The finding that mesangial cells express KC in response to proinflammatory cytokines, such as IL-1, points to a central role for the mesangial cell as a chemotactic source in glomerular inflammation.

Extracellular matrix accumulation in immune-mediated tubulointerstitial injury

The accumulation of excessive extracellular matrix (ECM) following tubular injury likely represents an imbalance between ECM production and degradation. We assessed the temporal relationship between the accumulation of ECM, cell adhesion molecules, matrix degrading proteinases, and their inhibitors in a rat model of anti-tubular basement membrane (TBM) antibody-associated tubulointerstitial nephritis (TIN) by the RNase protection assay and immunohistochemistry. There was an increase in the steady state expression of fibronectin (FN) and alpha 2(IV) collagen mRNAs beginning on day 7 with the onset of neutrophil infiltration. An increase in alpha 1(III) collagen and alpha 1-integrin did not occur until days 9 and 10, respectively, at which time mononuclear leukocytes were the predominant infiltrating cell. Increased levels of FN, alpha 1(III), alpha 2(IV) and alpha 1-integrin mRNAs occurred through day 14. By immunohistochemistry, increased accumulation of collagen IV, heparan sulfate proteoglycan, and laminin were detected along the thicken TBM; collagens I and III were immunolocalized within the tubulo-interstitium, while FN was present in both the TBM and interstitium in rats with TIN on day 14. The increase in matrix accumulation was associated with little or no increase in proteinases. u-PA transcripts fell beginning on day 8, with recovery to control values by day 12. Transin mRNA was found at low levels only on days 8 and 9, and the protein could not be detected by Western blotting. In contrast, these changes were associated with an increase in proteinase inhibitors, so that TIMP and PAI-1 mRNAs increased beginning on day 7 and persisted through day 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of K+ channels in neuropeptide Y-induced vasoconstriction in rabbit cerebral basilar artery

The role of K+ channels in the direct vasoconstrictive response induced by neuropeptide Y was investigated in isolated basilar arteries of rabbits and in vivo in rats. K+ channel openers, either BRL38227 or diazoxide, caused dose-dependent and complete relaxation of isolated arteries precontracted by neuropeptide Y. Exposure to both BRL38227 and diazoxide shifted the concentration-response curves for neuropeptide Y to the right without changing the maximal response. However, BRL38227 antagonized the angiotensin II-induced vasoconstriction noncompetitively. In vivo, the pressor responses produced by neuropeptide Y were significantly inhibited by pretreatment with BRL38227 in anesthetized rats. These results show that K+ channel openers antagonize neuropeptide Y-induced vasoconstriction in a competitive manner and suggest that blockade of K+ channels contributes, at least in part, to the direct vasoconstrictive effect of neuropeptide Y.

Diffusion and relaxation mapping of cartilage-bone plugs and excised disks using microscopic magnetic resonance imaging

Spatially resolved maps of proton self-diffusion coefficients (D) and relaxation times (T1 and T2) were obtained on cartilage-bone plug samples and on excised disks of canine cartilage at a transverse resolution of 30 microns, using microscopic magnetic resonance imaging (micro-MRI). Results are compared for excised disks of cartilage and intact cartilage-bone plugs. Correlations between the absolute water concentration, the self-diffusion coefficient and the T1 relaxation are reported. The diffusion coefficient is not a linear function of water concentration. The thickness of the disks is 600 microns, compared with the ca. 900 microns observed for the cartilage-bone plugs, presumably due to the absence of the interfacial or tidemark layer of interdigitated cartilage and bone in the former samples. Our results suggest that excised disks of cartilage are excellent models for the articular surface and the first 500 or so microns of tissue. The molecular parameters of spin-spin and spin-lattice relaxation times, as well as the water self-diffusion coefficient, are virtually identical in the two types of samples. However, the cartilage-bone plugs have the additional feature of permitting the study of the tidemark region, a region that likely plays a major role in the transmission of mechanical force.

Functional properties of rat and human neocortical voltage-sensitive sodium currents

1. The functional properties of sodium currents in acutely dissociated adult human, neonatal rat [postnatal day (P) 3 and P10], and mature rat (P21-23) neocortical pyramidal neurons were studied using whole-cell patch-clamp techniques. 2. The voltage dependence of activation and steady-state inactivation of neonatal rat sodium currents was shifted in the positive direction when compared with mature rat sodium currents. In contrast, no difference was detected between the voltage dependence of activation and steady-state inactivation of mature rat and adult human sodium currents. 3. The fast inactivation of rat (neonatal and mature) and human neocortical sodium currents were best fit with three components; a fast decay component, a slow decay component, and a persistent component. The magnitude of the persistent current in neocortical neurons averaged 1-3% of the peak current. Inactivation was faster for sodium currents in neonatal rat neocortical neurons than in mature neurons. No difference was detected in the kinetics of inactivation between mature rat and adult human sodium currents. 4. Saxitoxin (STX) inhibited neuronal sodium currents at nanomolar concentrations in neonatal and mature rat and adult human neocortical neurons. STX-insensitive channels were not detected. 5. STX affinity was also assayed using 3H-STX. A single high-affinity binding site was found in neonatal rat, mature rat, and adult human neocortical tissue. A developmental increase in STX binding site density in the rat neocortex was tightly correlated with the increase in the sodium current density (normalized to cell capacitance). Human neocortical tissue and mature rat neocortical tissue did not differ in STX binding site density or sodium current density. 6. From these electrophysiological and autoradiographic studies we conclude that 1) the increase in the normalized sodium current density and STX binding density with age postnatally reflects an increase in binding sites of sodium channels functionally expressed on neuronal membranes, 2) the functional differences in channel behavior with maturation can explain the higher threshold for excitation in neonatal neocortical neurons and the increase in accommodation or adaptation in firing in the mature neuron, and 3) mature rat neocortical neurons represent a valid model for the study of adult human pyramidal neocortical neurons in terms of Na+ channel expression and function.

Voltage-sensitive Na+ channels increase in number in newborn rat brain after in utero hypoxia

The effect of chronic in utero hypoxia on voltage-sensitive Na+ channels in newborn rat brain was investigated by means of ligand binding and autoradiography with [3H]saxitoxin (STX, Na+ channel ligand). We found that: (a) binding properties were different between hypoxic and control brains with alinear Scatchard plots in hypoxic brain versus linear ones in the control; (b) STX binding density increased greatly in response to hypoxic stimulation; and (c) the hypoxia-induced increase in STX binding was heterogeneous in various brain areas. We conclude that chronic hypoxia in utero alters the expression of Na+ channels and induces an up-regulation of Na+ channel density as a function of brain area. This is the first report of this phenomenon and we believe that the increased Na+ channels may play an important role in the etiology of neurological disorders such as epilepsy.

Alternative splicing of the NC1 domain of the human alpha 3(IV) collagen gene. Differential expression of mRNA transcripts that predict three protein variants with distinct carboxyl regions

Three clones of NC1 of alpha 3(IV) collagen, named Q1, L5, and V, were isolated from human kidney; these predict three variant alpha 3(IV) NC1 domains of 232-, 60-, and 199-amino acid residues, respectively, with unique COOH-termini. The human collagen IV gene (COL4A3) was isolated and characterized, and it was shown that the cDNA variants arose from alternative splicing by deletion of exon 4 in L5 and deletion of exon 2 in V. The mRNA transcripts were differentially expressed in fetal and adult human kidney with Q1 the major species. Exon 4-L5 lacked 183 residues from the carboxyl terminus with a frameshift producing a unique 11-amino acid terminal peptide. In exon 2-V a frameshift resulted in a unique V carboxyl terminus of 53 novel peptides with a new glycosylation site. The size of recombinant proteins indicated the frameshifts and new stop codons were as predicted. The multiple forms of the alpha 3(IV) NC1 region may contribute to autoimmune glomerular disease and hereditary nephritis, in which this portion of the collagen IV molecule is thought to play an important role.

Stimulation of formation of cAMP by 5-hydroxytryptamine in myenteric ganglia isolated from guinea pig small intestine

Effects of 5-hydroxytryptamine (5-HT) and related agonists and antagonists on formation of cAMP were determined for enzymatically dissociated ganglia from the myenteric plexus of the guinea-pig small intestine. Formation of cAMP was stimulated by 5-HT in both dose- and time- dependent manners. The stimulatory action of 5-HT was suppressed by the 5-HT1P antagonist, renzapride, but not by the 5-HT3 antagonist, tropisetron (formerly ICS 205-930). Neither renzapride nor cisapride increased the levels of cAMP. Levels of cAMP were suppressed by concentrations of tropisetron greater than 1.0 microM. Levels of cAMP were unaffected by the 5-HT3 agonist, 2-methyl-5-hydroxytryptamine. A putative 5-HT4 receptor agonist, 5-methoxytryptamine, stimulated formation of cAMP, but to a lesser extent than 5-HT. We conclude that 5-HT acts to stimulate adenylate cyclase and the formation of cAMP in myenteric ganglia. The 5-HT1P receptor is the most likely subtype involved in 5-HT action on cAMP formation.

Molecular cloning of cDNA encoding an unrecognized component of amyloid in Alzheimer disease

A neuropathological hallmark of Alzheimer disease (AD) is a widespread amyloid deposition. We analyzed the entire amino acid sequences in an amyloid preparation and found, in addition to the major beta/A4-protein (A beta) fragment, two unknown peptides. We raised antibodies against synthetic peptides using subsequences of these peptides. These antibodies immunostained amyloid in neuritic and diffuse plaques as well as vascular amyloid. Electron microscopic analysis demonstrated that the immunostaining was localized on amyloid fibrils. We have isolated an apparently full-length cDNA encoding a 140-amino-acid protein within which two previously unreported amyloid sequences are encoded in tandem in the most hydrophobic domain. We tentatively named this 35-amino acid peptide NAC (non-A beta component of AD amyloid) and its precursor NACP. NAC is the second component, after A beta, identified chemically in the purified AD amyloid preparation. Secondary structure predictions indicate that the NAC peptide sequence has a strong tendency to form beta-structures consistent with its association with amyloid. NACP is detected as a M(r) 19,000 protein in the cytosolic fraction of brain homogenates and comigrates on immunoblots with NACP synthesized in Escherichia coli from NACP cDNA. NACP mRNA is expressed principally in brain but is also expressed in low concentrations in all tissues examined except in liver, suggesting its ubiquitous and brain-specific functions. The availability of the cDNA encoding full-length NACP should help to elucidate the mechanisms of amyloidosis in AD.

Cloning two isoforms of rat cyclooxygenase: differential regulation of their expression

Two isoforms of cyclooxygenase (COX) have been identified in eukaryotic cells: COX-1 encoded by a 2.8-kb mRNA, and a mitogen-inducible COX-2 encoded by a 4-kb mRNA. We have cloned the COX-1 and COX-2 cDNAs from the cDNA library constructed from lipopolysaccharide (LPS)-stimulated rat peritoneal macrophages. The deduced amino acid sequence showed that COX-1 contained 602 amino acids, whereas COX-2 contained 604 amino acids. There is 95% conservation of the nucleotide sequence in the open reading frame of COX-1 between the rat and the mouse, while the homology of the 3' untranslated region is 68% except for a 150 bp segment adjacent to the stop codon which is nonhomologous with the mouse. Transfection of both COX cDNAs into Cos-7 cells resulted in increased COX activity. In rat vascular smooth muscle cells, interleukin-1 beta selectively increased the expression of COX-2, but not that of COX-1, as assessed by enzyme activity, immunoprecipitation of COX proteins, and mRNA analysis. Only the brain among tissues tested exhibits basal expression of COX-2 as the major form of the enzyme. However, COX-2 mRNA was expressed in vivo in the lung and kidney, but not in the heart, after systemic administration of LPS, suggesting that COX-2 but not COX-1 plays a major role in producing COX-derived products of arachidonic acid during endotoxic shock. Thus, the two COX isoforms were differentially expressed, and COX-2 was selectively induced in response to inflammatory stimuli in rats.

Sulfonylurea receptor expression in rat brain: effect of chronic hypoxia during development

Sulfonylurea receptors are believed to be related to ATP-sensitive potassium channels and play a key role during hypoxia/ischemia in the CNS. Our previous work has shown that these receptors in rat brainstem neurons are more important in the adult rat than in the newborn during hypoxia. In the present study, we studied the time course of postnatal development of sulfonylurea receptors in detail and the effect of chronic hypoxia on receptor density in newborn pups and adult rats exposed to hypoxia either as fetuses or as 90-d-old rats using receptor binding and autoradiography. Our current results show that sulfonylurea receptor density 1) was very low at birth and developed fast within the first 2 postnatal wk and then gradually reached adult levels and 2) continued to increase in the cortex and cerebellum but decreased in the brainstem with little or no change in other areas after postnatal wk 5. Chronic hypoxia 1) decreased body weight, brain size, and brain protein concentration and 2) increased sulfonylurea receptor density in utero but had much less of an effect in the adult. From these data, we conclude that sulfonylurea receptors develop mostly in the first 2 wk postnatally and chronic hypoxia increases sulfonylurea receptor expression in utero in spite of the fact that overall protein decreases.

Adenine DNA methyltransferase M.CviRI expression accelerates apoptosis in baculovirus-infected insect cells

The adenine DNA methyltransferase M.CviRI (TGCmA) gene from chlorella virus XZ-6E was cloned into the Autographa californica nuclear polyhedrosis virus (AcMNPV) genome and expressed in Spodoptera frugiperda insect cells under the control of two tandemly arranged viral promoters, the early ETL promoter and the late polyhedrin promoter. M.CviRI activity was first detected at 10 hr p.i and reached a maximum at 48 hr p.i. Viral DNA synthesized in insect cells infected with M.CviRI expressing virus (AcMTRI) was methylated at all TGCA sites. Unexpectedly, AcMTRI-infected cells lysed 48 hr earlier than wild-type AcMNPV-infected cells. Moreover, cellular DNA, but not viral DNA, from AcMTRI-infected cells was degraded to fragment sizes characteristic of apoptosis. These results suggest that M.CviRI methylation influences the onset of viral cytopathic effects and induces an apoptosis-like response.

Cloning a novel form of rat PDGF A-chain with a unique 5'-UT: regulation during development and in glomerulonephritis

An unique form of rat platelet-derived growth factor A-chain (PDGF A-chain), with a novel 5' UT region, was cloned from a rat macrophage cDNA library and expressed. In the 5' UT, the homology of the 79 bp sequence adjacent to the ATG codon between rat and human was 92%; however, the homology of the remainder in the 5' UT was less than 30%. RNase mapping indicated this form was differentially expressed during development and immune glomerular injury, and that it probably arose from alternative splicing. We propose that the variant mRNAs reflect different levels of the control of PDGF A-chain expression.

Functional expression of rat alpha 2B-adrenoceptor in Escherichia coli

Rat alpha 2B-adrenoceptor was expressed in Escherichia coli using 'ATG vector' containing cDNA encoding the 'non-glycosylated rat alpha 2-adrenoceptor' (RNG alpha 2). The highest receptor binding activity (using the alpha 2-adrenoceptor ligand [3H]MK 912) was found when transfected bacteria cultures were grown at 30 degrees C for about 4 h after induction with isopropyl beta-D-thiogalactopyranoside (IPTG). Saturation experiments showed that the radioligand bound to a single saturable site with a Kd of 1.42 +/- 0.09 nM and capacity of 281 +/- 6 fmol/mg protein. Binding constants of 14 compounds for the rat alpha 2B-adrenoceptor expressed in E. coli were determined and compared to the values previously obtained for the rat alpha 2B-adrenoceptor when expressed in COS cells as well as for native neonatal rat lung alpha 2B-adrenoceptors. The results indicate that when the rat alpha 2B-adrenoceptor is expressed in E. coli it retains identical ligand binding properties to those found when the receptor is present in the eukaryotic system. Expressing alpha 2B-adrenoceptors in E. coli would, therefore, seem to constitute a valid alternative in, e.g., drug screening and structure analysis of the alpha 2B-adrenoceptors.

LPS-induced MCP-1, IL-1 beta, and TNF-alpha mRNA expression in isolated erythrocyte-perfused rat kidney

The capacity of the lipopolysaccharide (LPS)-stimulated isolated erythrocyte-perfused rat kidney (IEPK) to produce monocyte chemoattractant protein-1 (MCP-1), interleukin-1 beta (IL-1 beta), and tumor necrosis factor-alpha (TNF-alpha) mRNA was investigated. The IEPK was chosen to exclude the influence of circulating neutrophils and monocytes that can produce both these mediators when exposed to LPS. The control minimal LPS group (LPS < 10 pg/ml) showed a small increase in mRNA expression for MCP-1, IL-1 beta, and TNF-alpha in the cortex and medulla after 80 min of perfusion when compared with the unperfused left kidney in which no IL-1 beta or TNF-alpha mRNA and only minimal amounts of MCP-1 mRNA were detected. LPS stimulation (1 microgram/ml for 40 or 80 min) increased MCP-1, IL-1 beta, and TNF-alpha mRNA expression, which was found predominately in peritubular capillary endothelial cells by in situ hybridization. The changes were not due to a marked perturbation of LPS on renal hemodynamics. The renal vascular resistance (RVR) remained constant (40 min LPS exposure) or increased only slightly during the last 5-10 min (80 min LPS exposure) compared with a progressive increase in RVR of the minimal LPS group. The hemodynamic effects of LPS on the IEPK appear to counteract the gradual increase in RVR seen in the minimal LPS group.

Neuroanatomical distribution and binding properties of saxitoxin sites in the rat and turtle CNS

Since saxitoxin (STX) binds to voltage-sensitive sodium channels and blocks their function, it has been widely used in the study of these channels. There is, however, limited information on STX binding properties and the neuroanatomical distribution of the Na+ channel as a function of brain region in the rat and in lower vertebrates such as the turtle. In the present study, we used a broad range of 3H-STX concentration (up to 64 nM) to examine saturation profiles and density distribution in both adult rat and turtle brains. We found that (1) STX sites do not vary greatly in affinity (most Kds = 2 to 5 nM) in various regions of the adult rat brain; (2) STX binding distribution was very heterogeneous in the rat with much higher density in the cortex, hippocampus, amygdala, and cerebellum than in the brainstem and spinal cord; (3) STX sites are mostly localized in layers made mostly of neurons with low density in white matter; and (4) turtle brain STX sites had similar binding properties, but its brain had much fewer STX sites than the rat, especially in the cerebellum and rostral areas such as the cortex. We conclude that (a) adult brain sodium channels have similar STX binding affinity in spite of the existence of multiple sodium channel subtypes; (b) the brainstem is very different from rostral brain areas in channel density; and (c) the turtle brain has a much lower sodium channel density than the rat brain.

Genomic structure, chromosomal location, and evolution of the mouse Hox 8 gene

We isolated genomic clones containing the mouse Hox 8 gene, a member of the msh gene family. We show that Hox 8 comprises two exons of approximately 600 and 691 bp separated by a 3.5-kb intron, and that it cosegregates with previously mapped markers in the distal region of mouse chromosome 13. In midgestation embryos, the Hox 8 gene produces transcripts of 1.4 and 2.2 kb. Both transcripts are present in facial tissues of the newborn mouse, though the ratio of the 2.2-kb transcript to the 1.4-kb transcript is reduced relative to the ratio observed for midgestation embryos. An alignment of the homeobox sequences of previously characterized members of the msh family revealed three subclasses: Hox 7-like genes, Hox 8-like genes, and msh-like genes. Both the Hox 7-like genes and Hox 8-like genes are present throughout the vertebrates. Representatives of the third subclass, the msh-like genes, are found in a protostome (Drosophila) and a deuterostome (Ciona) and are thus likely to be phylogenetically widespread. To investigate the distribution of Hox 8-like genes outside the chordates, we used the polymerase chain reaction and degenerate Hox 8 primers to screen genomic DNA of the purple sea urchin (Strongylocentrotus purpuratus, Phylum Echinodermata). We isolated a gene with greater sequence similarity to mouse Hox 8 than to members of the Hox 7 or msh subfamilies, demonstrating that the Hox 8 subfamily has been in existence at least since the echinoderms diverged from the lineage that gave rise to the chordates.(ABSTRACT TRUNCATED AT 250 WORDS)

GABA transporter mRNA: in vitro expression and quantitation in neonatal rat and postmortem human brain

A previously isolated rat cDNA clone encoding the membrane transporter for the neurotransmitter gamma-aminobutyric acid was expressed in transfected COS cells. The resultant transporter protein was characterized kinetically and pharmacologically. The apparent Kt (6.1 microM) and the pharmacological profile of a neuronal-type transporter observed in these mammalian cells were consistent with previous data obtained in Xenopus laevis oocytes. Post-natal levels of gamma-aminobutyric acid transporter mRNA in rat cerebellum, cerebral cortex and striatum (as measured by nuclease protection assay) transiently exceeded levels present in the adult brain. Human gamma-aminobutyric acid transporter mRNA also was measured by nuclease protection assay using as probe a human transporter cDNA homolog obtained by polymerase chain reaction. These studies suggest that quantitation of rat and human gamma-aminobutyric acid transporter mRNAs may provide a useful index of transporter gene expression.

Evidence for the existence of two forms of alpha 2A-adrenoceptors in the rat

The alpha 2A-adrenoceptors in rat spleen, kidney, spinal cord and cerebral cortex were studied using [3H]-RX821002 radioligand binding. In the spleen, spinal cord and cerebral cortex, the ligand bound to saturable sites with a Kd of about 1 nmol/l and capacities of 134, 240 and 290 fmol/mg protein, respectively. Computer modelling competition curves for 39 drugs, including those for alpha 2A-, alpha 2B- or alpha 2C-adrenoceptor selective drugs, indicated that the sites labelled by [3H]-RX821002 in the spleen consisted of a single population of alpha 2A-adrenoceptors. However, the competition curves for guanoxabenz were definitely biphasic and resolved into two site fits, indicating that guanoxabenz was binding to both high affinity (Kd = 35 nmol/l) and low affinity (Kd = 8900 nmol/l) alpha 2A-adrenoceptor sites in the proportions 57% and 43%, respectively. The KdS for a number of alpha 2-adrenoceptor subtype selective drugs, measured in competition with [3H]-RX821002 in cerebral cortex and spinal cord, were highly correlated with those obtained in the spleen indicating their alpha 2A-adrenoceptor nature. However, by contrast to the results with the spleen, the guanoxabenz competition curves for the spinal cord and cerebral cortex were monophasic and resolved only into one site fits, the Kd of guanoxabenz being about 4000 nmol/l for both tissues. Drug KdS for kidney alpha 2A-adrenoceptors were also determined using [3H]-RX821002. For nearly all drugs tested, the KdS were highly correlated with those found for the alpha 2A-adrenoceptors in the other rat tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Further evidence for the existence of two forms of alpha 2B-adrenoceptors in rat

Analysis of saturation isotherms of the novel alpha 2-adrenoceptor antagonist radioligand [3H]-MK 912 revealed that the ligand labelled a homogenous population of alpha 2B-adrenoceptors in the neonatal rat lung with a Kd of 0.77 nM and a Bmax of 231 fmol/mg protein. In rat kidney, combined saturation and competition experiments, using [3H]-MK 912 and the alpha 2A-adrenoceptor selective drug guanfacine, revealed that approximately 81% of the sites labelled by [3H]-MK 912 were alpha 2B-adrenoceptors and approximately 19% alpha 2A-adrenoceptors; the Kds of [3H]-MK 912 being 1.1 and 2.0 nM and the Bmax 134 and 33 fmol/mg protein, respectively. The kidney alpha 2B-adrenoceptors were studied separately by using approximately 1.5 nM [3H]-MK 912 in the presence of 0.32 microM guanfacine, the latter which blocked ligand binding to alpha 2A-adrenoceptors completely. Analysis of drug competition curves obtained during these conditions revealed that 18 out of 20 different agonists and antagonists yielded steep and uniphasic competition curves which modelled best into one site fits. However, both guanoxabenz and LT 11 appeared to inhibit [3H]-MK 912 binding at two sites; the Kds of guanoxabenz differing approximately 120-fold and that of LT 11 differing approximately 35-fold for the two sites. Moreover, the addition of mutual fixed concentrations of either 20 microM guanoxabenz or 20 microM LT 11 completely prevented the binding of the other compound to its high affinity site, indicating that both compounds labelled the same site with the high affinity. The analysis indicated that 29% of the sites were of high and 71% of low affinity. However, in the neonatal rat lung guanoxabenz and LT 11 (as well as 15 other compounds) yielded competition curves which modelled only into one site fits. The Kds obtained in the lung correlated well with the Kds obtained in the kidney for alpha 2B-adrenoceptors; for guanoxabenz and LT 11 the values from the lung were close to those determined in the kidney for the low affinity site for guanoxabenz and LT 11. Moreover, when the rat RNG alpha 2B-adrenoceptor was expressed in COS-7 cells and its binding properties tested using [3H]-MK 912 binding, guanoxabenz, LT 11 as well as a number of other drugs inhibited the ligand binding at a single alpha 2-adrenoceptor site; the drug Kds being practically the same as those found for the neonatal rat lung. It is suggested that rat alpha 2B-adrenoceptors may exist in two forms: alpha 2B1 and alpha 2B2.(ABSTRACT TRUNCATED AT 400 WORDS)

CFTR channels in immortalized human airway cells

The cystic fibrosis (CF) gene codes for CF transmembrane regulator (CFTR), a small-conductance linear Cl- channel, but numerous studies have identified a larger conductance, rectifying Cl- channel as the adenosine 3',5'-cyclic monophosphate (cAMP)-regulated channel that is defective in airway cells. We examined Cl- conductance in a bronchial epithelial cell line that expresses CFTR, 16HBE14o-, (CFTR+) and in an airway cell line that does not, 9HTEo-/S, (CFTR-). Ionomycin or hypotonic Ringer increased iodide efflux from both cell lines; however, forskolin increased iodide efflux or whole cell Cl- currents only in CFTR+ cells. Forskolin-stimulated whole cell currents were linear, voltage independent, and blocked by iodide. Cell-attached and outside-out patches from confluent CFTR+ but not CFTR- cells revealed 6-pS channels having linear current-voltage relations, permselectivity Cl > I (partial block by external iodide), and little or no inhibition by 5-nitro-2-(3-phenylpropylamino)-benzoate. The number of active channels per patch increased from 0.6 to 3.0 after forskolin. Channels closed after excision with tau = 4 s, but activity could be prolonged with ATP or protein kinase A plus ATP. Channels were modeled with one open and four closed states and show apparent cooperativity in gating. Rectifying Cl- channels previously implicated in CF were not seen in cell-attached recordings from either cell line but were abundant in excised patches from both cell lines. Thus CFTR channels are the pathway for cAMP-mediated Cl- conductance in these human airway cells, Ca2+ and swelling-induced channels do not require CFTR, and CFTR-cells display a CF phenotype.

[3H]-MK 912 binding delineates two alpha 2-adrenoceptor subtypes in rat CNS one of which is identical with the cloned pA2d alpha 2-adrenoceptor

1. Simultaneous computer modelling of control and guanfacine-masked [3H]-MK 912 saturation curves as well as guanfacine competition curves revealed that the drugs bound to two alpha 2-adrenoceptor subtypes in the rat cerebral cortex with very different selectivities. These alpha 2-adrenoceptor subtypes were designated alpha 2A and alpha 2C. The Kd value of [3H]-MK 912 for the alpha 2A-subtype was 1.77 nM and for the alpha 2C-subtype 0.075 nM; the receptor sites showing capacities 296 and 33 fmol mg-1 protein, respectively. The Kds of guanfacine were 19.9 and 344 nM, respectively. 2. Binding constants of 26 compounds for the two rat cerebral cortex alpha 2-adrenoceptor subtypes were determined by simultaneous computer modelling of control and guanfacine-masked drug competition curves as well as plain guanfacine competition curves using [3H]-MK912 as labelled ligand (i.e. a '3-curve assay'). Of the tested drugs WB4101, corynanthine, rauwolscine, yohimbine, ARC 239 and prazosin were found to be clearly alpha 2C-selective with selectivities ranging from 16 to 30 fold whereas guanfacine, oxymetazoline, BRL 44408 and BRL 41992 were found to be alpha 2A-selective with selectivities ranging from 9 to 22 fold. 3. The Kds of compounds obtained for the cerebral cortex alpha 2C-adrenoceptors showed an almost 1:1 correlation with the corresponding Kds for alpha 2-adrenoceptors expressed by the pA2d-gene (the rat 'alpha 2-C4' adrenoceptor) in CHO-cells. The cerebral cortex alpha 2A-adrenoceptors did not correlate well with the pA2d alpha 2-adrenoceptor Kds. 4. In the rat spinal cord [3H]-MK 912 bound to alpha 2A- and alpha 2C-adrenoceptor sites with similar affinities as in the cerebral cortex and with densities 172 and 7.4 fmol mg-1 protein, respectively. Drug affinities for some compounds showing major selectivity for alpha 2A- and alpha 2C-adrenoceptors were fully compatible with the notion that the spinal cord sites were alpha 2A- and alpha 2C-adrenoceptors.

Dopamine transporter mRNA content in human substantia nigra decreases precipitously with age

The dopamine transporter is the primary means of inactivating synaptic dopamine as well as a major site of action for psychostimulants (such as cocaine and amphetamine) and for neurotoxins that induce parkinsonism. In the present study, a human dopamine transporter partial cDNA clone obtained by polymerase chain reaction exhibited 87% and 89% identity at the nucleic acid and amino acid levels, respectively, with transmembrane domains 3-5 of the rat homolog. This clone was used to quantitate human dopamine transporter mRNA by nuclease protection assay. The postmortem content of dopamine transporter mRNA in the substantia nigrae of 18- to 57-yr-old subjects was relatively constant, while in subjects greater than 57 yr old, a precipitous (greater than 95%) decline in substantia nigra dopamine transporter mRNA was evident. In contrast, tyrosine hydroxylase mRNA in the same samples declined in a linear manner with increasing age. In situ hybridization experiments confirmed the profound loss of dopamine transporter gene expression in melanin-positive (presumptive dopamine) nigral neurons. These data may begin to shed light on compensatory changes occurring in human dopamine neurons during normal aging.

Quantitation of rat dopamine transporter mRNA: effects of cocaine treatment and withdrawal

Dopamine transporter mRNA levels in the rat substantia nigra were quantified using a sensitive nuclease protection assay with a highly homologous human dopamine transporter cDNA clone. The same probe was also used to visualize dopamine transporter mRNA in the substantia nigra by in situ hybridization. Repeated cocaine administration (15 mg/kg, twice a day for 6.5 days) resulted in a greater than 40% decrease in nigral dopamine transporter mRNA levels. In contrast, dopamine transporter mRNA levels were unchanged after either acute treatment (4 h before death) or repeated cocaine treatment followed by a 72-h withdrawal period. Thus, blockade of the dopamine transporter by repeated cocaine administration may result in the down-regulation of dopamine transporter gene expression in dopamine neurons.

Ontogeny and distribution of GABAA receptors in rat brainstem and rostral brain regions

Previous studies from our laboratory and others have shown that there are major age-related differences in brainstem neuronal function. Since GABAA receptors are major targets for GABA-mediated inhibitory modulation and play a key role in regulating cardiorespiratory function, especially during O2 deprivation, we examined differences in GABAA receptor density and distribution during postnatal development. Using quantitative receptor autoradiography, the present study was performed to examine the postnatal expression of GABAA receptors in the rat brainstem and rostral brain areas at five ages, i.e. postnatal day 1 (P1), P5, P10, P21 and P120. Ten-micrometer brain sections at different brain levels were labelled with [3H]muscimol in Tris-citrate buffer. We found that (i) GABAA receptors appeared very early in almost all the brainstem as well as rostral areas; (ii) at P1, the brainstem had a higher GABAA receptor binding density than rostral areas and its density peaked at P5 or P10; and (iii) receptor densities of the cerebellum and rostral brain areas such as cortex, thalamus and dentate gyrus increased with age, especially between P10 and P21, but most other subcortical areas like caudate-putamen and hippocampal CA1 area did not increase remarkably after birth. We conclude that: (i) GABAA receptors exist in most brain areas at birth; (ii) there are several patterns of postnatal development of GABAA receptors in the CNS with dramatic differences between the brainstem and cortex; (iii) brainstem functions rely more on GABAA receptors in early postnatal life than at more mature stages. We speculate that GABAA receptors develop earlier in phylogenetically older structures (such as brainstem) than in newer brain regions (such as cortex).