Biomedical subjects

K Sandberg

Publications and source records attributed to K Sandberg.

At least 19 recordsLinked to original sources

PubMed1998

Transgenic expression of IFN-alpha in the central nervous system of mice protects against lethal neurotropic viral infection but induces inflammation and neurodegeneration.

Type I IFNs, which include IFN-alpha, appear to have complex and broad-ranging actions in the central nervous system (CNS) that may result in protection or injury. To better understand these issues, we generated transgenic mice that produce IFN-alpha1 chronically from astrocytes. These glial fibrillary acidic protein-IFN-alpha transgenic mice developed a progressive inflammatory encephalopathy, with marked calcium mineralization, meninoencephalitis, gliosis, and neurodegeneration. Many features of this murine encephalopathy resembled those found in certain human encephalopathies of unknown etiology; these diseases, exemplified by Aicardi-Goutières syndrome and some viral encephalopathies, show increased intrathecal production of IFN-alpha. Our data suggest that IFN-alpha overproduction may be the primary factor initiating these human diseases. Following intracerebral infection with lymphocytic choriomeningitis virus, glial fibrillary acidic protein-IFN-alpha mice had significantly increased survival rates associated with markedly reduced virus titers and immune pathology in the brain but normal peripheral CTL responses. Therefore, the production of IFN-alpha in the CNS can be a two-edged sword that on the one hand confers protection against a lethal viral infection but on the other causes significant injury to the brain. These transgenic mice provide a novel animal model in which to further evaluate the mechanisms that underlie the diverse actions of type I IFNs in the intact CNS.

Animals↗

PubMed1998

A novel molecular determinant for cAMP-dependent regulation of the frog heart Na+-Ca2+ exchanger.

Na+-Ca2+ exchanger is one of the major sarcolemmal Ca2+ transporters of cardiac myocytes. In frog ventricular myocytes the exchanger is regulated by isoproterenol via a beta-adrenoreceptor/adenylate-cyclase/cAMPdependent signaling pathway providing a molecular mechanism for the relaxant effect of the hormone. Here, we report on the presence of a novel exon of 27-base pair insertion, which generates a nucleotide binding motif (P-loop) in the frog cardiac Na+-Ca2+ exchanger. To examine the functional role of this motif, we constructed a full-length frog heart Na+-Ca2+ exchanger cDNA (fNCX1a) containing this exon. The functional expression of fNCX1a in oocytes showed characteristic voltage dependence, divalent (Ni2+, Cd2+) inhibition, and sensitivity to cAMP in a manner similar to that of native exchanger in frog myocytes. In oocytes expressing the dog heart NCX1 or the frog mutant (DeltafNCX1a) lacking the 9-amino acid exon, cAMP failed to regulate Na+-dependent Ca2+ uptake. We suggest that this motif is responsible for the observed cAMP-dependent functional differences between the frog and the mammalian hearts.

Adenylyl Cyclases↗

PubMed1998

Regulation of cytosolic proteins binding cis elements in the 5' leader sequence of the angiotensin AT1 receptor mRNA.

RNA binding proteins (BPs) have been identified which bind within a -271 to -174 nt domain in the 5' leader sequence (5'LS) of the rat type 1 angiotensin (AT1) receptor mRNA and which encompass RNA cis elements upstream of -239. A 100 kDa RNA-protein complex is observed by UV-crosslinking in several tissues including brain, lung, and spleen. 5'LS RNA transcripts of the 1a and 1b AT receptor subtypes are strong competitors of 5'LS-protein complex formation. In contrast, antisense 5'LS AT1a transcripts, plasmid transcripts, poly U and poly A RNAs, or 5'LS AT1a cDNA are poor competitors. Deoxycorticosterone acetate (DOCA) decreased 5'LS-BP activities in the forebrain and hypothalamus under conditions known to significantly increase AT1 receptor expression. DOCA had no effect on 5'LS-BP activities in the pituitary which correlates with its lack of effect on pituitary AT1 receptor expression. These results indicate that DOCA differentially regulates 5'LS-BP activities in a tissue-specific manner and suggest that physiologically mediated changes in AT1 receptor expression are mediated by alterations in 5'LS-BP activities, which represents a previously unrecognized level of regulation for the renin angiotensin system.

Animals↗

PubMed1998

Shared determinants of receptor binding for subtype selective, and dual endothelin-angiotensin antagonists on the AT1 angiotensin II receptor.

Site-directed interspecies amino acid exchange was used to compare the binding determinants of a novel dual endothelial-angiotensin receptor ligand, L-746,072, with type-1 angiotensin receptor (AT1) selective antagonists on AT receptors expressed in COS cells. These studies suggest that residues on AT receptors which are non-conserved between amphibian and mammalian species play a greater role in subtype selective ligand recognition than for dual receptor ligands. These data also support the hypothesis that a common non-peptide binding site exists within transmembrane domains on peptidergic receptors.

Amino Acid Sequence↗

PubMed1998

Moment analysis of multibreath nitrogen washout in healthy preterm infants.

Moment analysis (MA) of multibreath nitrogen washout (MBNW) has not previously been applied to newborn infants. The aim of the present study was to adapt this method to healthy preterm infants using an improved technique suitable for small infants, and to determine reference values of MA. Twenty healthy preterm infants with a mean birth weight (+/-SD) of 1,666+/-402 g and a mean gestational age of 31.3+/-2.1 weeks were studied during their first 7-28 days of life. Computerized bedside equipment with very low dead space was constructed. The limits of normal variability were determined from results of duplicate studies. Outcome variables included functional residual capacity (FRC), the first-to-zeroth moment ratio (M1/M0), the second-to-zeroth moment ratio (M2/M0), and the lung clearance index (LCI). The starting point for MA had considerable impact on the results. Mean M1/M0 and M2/M0 were 2.18+/-0.18 and 8.71+/-1.24, respectively. No significant relation between moment ratios and weight, gender or age was found. Intrasubject coefficients of variation (CV) for M1/M0 (7.9+/-5.9%) and for M2/M0 (12.1+/-9.1%) and intersubject CV for M1/M0 (8%) and M2/M0 (14%) were similar to those reported in children and adults. Mean lung clearance index was 10.8+/-1.4 and intra- and intersubject CVs were 11.3+/-8.9% and 13%, respectively. Mean functional residual capacity (FRC) was 22.5+/-2.1 ml/kg. Mean intra- and intersubject CVs for FRC were 8.3% and 9%, respectively. We conclude that the MBNW test can be performed by a simple bedside method and that MA appears to be a suitable method for measuring gas mixing in preterm infants.

Breath Tests↗

PubMed1998

A primary male autosomal linkage map of the horse genome.

A primary male autosomal linkage map of the domestic horse (Equus caballus) has been developed by segregation analysis of 140 genetic markers within eight half-sib families. The family material comprised four Standardbred trotters and four Icelandic horses, with a total of 263 offspring. The marker set included 121 microsatellite markers, eight protein polymorphisms, five RFLPs, three blood group polymorphisms, two PCR-RFLPs, and one single strand conformation polymorphism (SSCP). One hundred markers were arranged into 25 linkage groups, 22 of which could be assigned physically to 18 different chromosomes (ECA1, ECA2, ECA3, ECA4, ECA5, ECA6, ECA7, ECA9, ECA10, ECA11, ECA13, ECA15, ECA16, ECA18, ECA19, ECA21, ECA22, and ECA30). The average distance between linked markers was 12.6 cM and the longest linkage group measured 103 cM. The total map distance contained within linkage groups was 679 cM. If the distances covered outside the ends of linkage groups and by unlinked markers were included, it was estimated that the marker set covered at least 1500 cM, that is, at least 50% of the genome. A comparison of the relationship between genetic and physical distances in anchored linkage groups gave ratios of 0.5-0.8 cM per Mb of DNA. This would suggest that the total male recombinational distance in the horse is 2000 cM; this value is lower than that suggested by chiasma counts. The present map should provide an important framework for future genome mapping in the horse.

Animals↗

PubMed1998

Impaired gas mixing and low lung volume in preterm infants with mild chronic lung disease.

The aim of this study was to assess the possible role of gas mixing inefficiency in spontaneously breathing infants with mild chronic lung disease (CLD) of prematurity in relation to changes in other functional parameters. A simple bedside technique for recording and analysis of multiple breath nitrogen washout curves was applied together with occlusion mechanics. Fifteen preterm infants with mild or moderately severe CLD were studied at a mean postconceptional age of 35 wk, together with 15 healthy preterm infants at the same maturity. All infants breathed spontaneously, and the test was performed by a continuous bypass flow system, connected to a face mask, a pneumotachograph, and a nitrogen meter. The results showed impaired gas mixing with moment ratios above the 95th percentile of the normal group in 11/15 infants with CLD. Functional residual capacity (FRC) was low in 13/15 infants, but specific compliance and resistance of the respiratory system did not differ between the groups. As FRC and moment ratios were not correlated, it is suggested that they may reflect different aspects of the pathophysiology in CLD. It is concluded that low FRC and disturbed gas mixing are characteristic disturbances in CLD at different degrees of severity. The multiple breath nitrogen washout test, followed by moment analysis of end-tidal nitrogen concentrations, is a simple and sensitive method for detection of these disturbances and for monitoring purposes.

Breath Tests↗

PubMed1998

Assessing substance abuse problems in deaf and hard of hearing individuals.

Professionals who provide services to deaf and hard of hearing individuals may encounter situations related to abuse of alcohol and other drugs. Getting access to an agency that can provide an appropriate chemical dependency assessment for a deaf or hard of hearing person is difficult because there are no formalized assessment tools normed or specifically designed to use with such individuals. Additionally, most assessors are unfamiliar with how to work with deaf and hard of hearing people, less likely to be fluent in American Sign Language, and unaware of appropriate treatment options. The present article provides an overview of chemical dependency, assessment issues, and considerations unique to the deaf and hard of hearing population. A chemical dependency assessment tool developed by the Minnesota Chemical Dependency Program for Deaf and Hard of Hearing Individuals is described, as well as a case study that illustrates application of the assessment process.

Adult↗

PubMed1998

Balanced affinity AT1/AT2 receptor nonpeptide binding site determinants on the AT1 angiotensin receptor.

Angiotensin II (Ang II), a potent modulator of cardiovascular homeostasis, mediates its effects through two Ang II receptor subtypes (AT1 and AT2) which share less than 30% amino acid homology and can be differentiated by specific nonpeptide ligands. We investigated the structural determinants of ligand binding to the AT1 receptor for L-163,017 which belongs to a newly developed class of nonpeptides that have equivalent affinities for AT1 and AT2 receptors. Nonpeptide binding affinities were determined in radioreceptor binding assays in membranes from COS cells transfected with wild-type and mutant receptor cDNAs. The amphibian AT receptor variant, xCM46, recognized L-163,017 with an affinity (IC50=8±2 nM) that was only 1.5-fold lower than for the rat AT1 receptor (IC50=5±1 nM) which is in striking contrast to the poor affinity of the amphibian xATa wild-type receptor (IC50 >50 µM). Analysis of single point rAT1 receptor mutants in which individual mammalian residues were replaced by the corresponding frog amino acids revealed significant overlap but also distinct differences in ligand binding interactions between dual receptor and subtype selective non-peptides. These data suggest that AT1-selective and dual receptor nonpeptides share overlapping but distinct binding pockets on the AT1 receptor. These findings may lead to improved therapeutics for the treatment of cardiovascular diseases involving both AT receptor subtypes.

Journal Article↗

PubMed1997

Genetical and physical assignments of equine microsatellites--first integration of anchored markers in horse genome mapping.

Twenty equine microsatellites were isolated from a genomic phage library, and their genetical and physical localization was sought by linkage mapping and fluorescent in situ hybridization (FISH). Nineteen of the markers were found to be polymorphic with, in most cases, heterozygosities exceeding 50%. The markers were mapped in a Swedish reference family for gene mapping, comprising eight half-sib families from Standardbred and Icelandic horse sires. Segregation was analyzed against a set of 35 other markers typed in the pedigree. Thirteen of the microsatellites showed linkage to at least one other marker, with a total of 21 markers being involved in these linkages. In parallel, 18 of the microsatellites could be assigned to their chromosomal region by FISH. These assignments involved eight equine autosomes: ECA1, 2, 4, 6, 9, 10, 15, and 16. The genetical and physical mappings revealed by this study represent a significant extension of the current knowledge of the equine genome map.

Alleles↗

PubMed1997

Production of interferon-alpha/beta by murine dendritic cell lines stimulated by virus and bacteria.

The interferon-alpha and -beta (IFN-alpha/beta) producing ability of the two murine dendritic cell (DC) lines D2SC/1 and FSDC was studied. The D2SC/1 cells produced IFN-alpha and -beta when stimulated by herpes simplex virus (HSV), Sendai virus (SV) or by the bacteria Escherichia coli or Staphylococcus aureus Cowan I. Precultivating (priming) D2SC/1 cells with recombinant IFN-beta or a combination of IFN-beta and granulocyte-macrophage colony-stimulating factor increased production of IFN-alpha/beta induced by HSV or the bacteria, but not by SV. Also, the kinetics of IFN-alpha/beta responses were different for SV compared to HSV and the bacteria, suggesting different induction mechanisms. The FSDC cells differed from the D2SC/1 cells mainly in that predominantly IFN-beta was produced, that little or no IFN-alpha/beta production was induced by the bacteria, and that the IFN-alpha/beta responses were most efficiently primed by IFN-gamma. Priming the DC lines with tumour necrosis factor-alpha, interleukin-10 (IL-10) or IL-4 did not affect the IFN-alpha/beta response induced by HSV. The results show that the two DC lines provide a convenient tool to study the induction and control of the IFN-alpha/beta response, as well as the immunoregulatory role of IFN-alpha/beta produced by DC.

Animals↗

PubMed1996

Identification of nonconserved amino acids in the AT1 receptor which comprise a general binding site for biphenylimidazole antagonists.

Mutational analysis based on pharmacological differences between mammalian and amphibian angiotensin II receptors (AT receptors) previously led to construction of a mutant receptor that gained > 25000-fold affinity for the biphenylimidazole, Losartan. This variant frog receptor also bound with high affinity other nonpeptides in the biphenylimidazole chemical class according to the following rank order of potency (expressed in Fmut values=mutant IC50/rAT1b IC50): Losartan, 0.91; L-162,389, 1.0; L-163,491, 1.9; L-158,809, 3.5; L-163,017, 3.9; SC-51,316, 3.9. In contrast, the imidazoleacrylic acids, SKF-108,566 (Fmut= 160) and SB-203,220 (Fmut = 170), bound with markedly less affinity. Thus, nonconserved residues determining the molecular requirements for biphenylimidazole recognition are conserved in general, but are not identical to nonconserved residues necessary for high affinity binding of imidazoleacrylic acids.

Amino Acid Sequence↗

PubMed1996

Ontogeny of angiotensin II receptors.

Aside from the well known role of angiotensin II (Ang II) in blood pressure regulation and fluid homeostasis, accumulating evidence suggests that the octapeptide hormone also plays a role in growth and development. There are two major classes of Ang II receptors (AT1 and AT2) which mediate Ang II action. Both classes are members of the large superfamily of seven transmembrane domain spanning receptors. Fetal tissue express high levels of AT receptors. Throughout fetal and postpartum life, the AT1 and AT2 tissue distribution changes dramatically. The evolution of each receptor type is distinct and varies according to the organ. Thus, the different patterns of temporal expression of each receptor class could be related to various roles that Ang II may play during development.

Age Factors↗

PubMed1996

A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses.

The melanocyte-stimulating hormone receptor gene (MC1R) is the major candidate gene for the chestnut coat color in horses since it is assumed to be controlled by an allele at the extension locus. MC1R sequences were PCR amplified from chestnut (e/e) and non-chestnut (E/-) horses. A single-strand conformation polymorphism was found that showed a complete association to the chestnut coat color among 144 horses representing 12 breeds. Sequence analysis revealed a single missense mutation (83Ser-->Phe) in the MC1R allele associated with the chestnut color. The substitution occurs in the second transmembrane region, which apparently plays a key role in the molecule since substitutions associated with coat color variants in mice and cattle as well as red hair and fair skin in humans are found in this part of the molecule. We propose that the now reported mutation is likely to be the causative mutation for the chestnut coat color. The polymorphism can be detected with a simple PCR-RFLP test, since the mutation creates a TaqI restriction site in the chestnut allele.

Alleles↗

PubMed1996

The interferon-alpha/beta responses of mice to herpes simplex virus studied at the blood and tissue level in vitro and in vivo.

Murine mononuclear leucocytes from bone marrow, spleen, lymph node and blood stimulated in vitro by UV-irradiated herpes simplex type I virus (HSV) produced about equal proportions of IFN-alpha and -beta determined by immunoassay. Thymocytes produced only IFN-alpha. The frequency of IFN-alpha/beta mRNA containing cells detected by in situ hybridization was highest with bone marrow (15 per 10(4) cells), followed by spleen (4/10(4)), lymph node (2/10(4)), blood (1/10(4)) and thymus (0.2/10(4)). Such IFN-alpha/beta producing cells (IPCs) were heavily labelled in autoradiographs, each producing about 0.4 U of IFN. After one intravenous injection of UV-irradiated HSV in mice, high levels of IFN-alpha and -beta were present in blood at 3-9h and little or none at 24h or later. Frequent cells strongly positive for IFN-alpha mRNA at in situ hybridization and for IFN-alpha/beta at immunohistochemical staining were found almost exclusively in the marginal zones of spleens. Occasional IPCs were detected in lymph nodes but not in bone marrow, liver and kidneys. The marginal zone IPCs may be the major source of IFN in blood, and high splenic levels of IFN-alpha/beta should have efficient antiviral and immunoregulatory functions.

Animals↗

PubMed1996

Herpes simplex virus induces appearance of interferon-alpha/beta-producing cells and partially interferon-alpha/beta-dependent accumulation of leukocytes in murine regional lymph nodes.

As in vivo experimental system involving the local induction of interferon-alpha/beta (IFN-alpha/beta) responses was established in mice by injecting s.c. ultraviolet (UV)-inactivated herpes simplex virus (HSV) in the right ears, the left ears receiving phosphate-buffered saline (PBS) as a control. Circulating IFN-alpha/beta was present in blood as early as 6 h postinjection, and little or none was found 24 h postinjection. Identification of IFN-alpha/beta-producing cells, carried out by immunohistochemistry and in situ hybridization, demonstrated that the IFN response occurred mainly in the lymph node draining the HSV-injected ear and not in the contralateral lymph node. Occasionally, IFN-alpha/beta-producing cells were found in the spleen and in the skin. The injected HSV caused an inflammatory reaction in the skin and an almost threefold enlargement of the draining lymph node within 6 h. The latter was characterized by a general accumulation of all major lymphocyte subsets and a striking infiltration of neutrophils. Injection s.c. of neutralizing anti-IFN-alpha/beta antibodies before HSV injection reduced the increase in size of the draining lymph node by approximately 50% at 6 h, and no significant effects were seen at 24 h. The localization of cells producing IFN-alpha/beta in the lymph node and the capacity of such IFN-alpha/beta to at least partially mediate an early accumulation of cells suggest that the local IFN-alpha/beta response may have an important role in the initiation of early antiviral immune responses.

Animals↗

PubMed1996

Interaction of biphenylimidazole and imidazoleacrylic acid nonpeptide antagonists with valine 108 in TM III of the AT1 angiotensin receptor.

Interspecies amino acid exchange, based on pharmacological differences between mammalian AT1 and amphibian xAT angiotensin II receptors, previously demonstrated that Val108 in transmembrane III (ValIII:08) is a critical structural requirement for binding the biphenylimidazole, losartan. Here, we investigated a series of biphenylimidazole and imidazoleacrylic acid nonpeptides to determine the general role of Val108 in nonpeptide recognition. Substitution of Val108 in the rAT1b receptor with Ile, the corresponding residue in xATa, significantly reduced ligand affinities from both nonpeptide classes (Fmut values (mutant IC50/rAT1bIC50): losartan > L-162,389 > L-16,313 > L-162,017 = L-163,491 > SB-203,220 > SK&F-108,566). While distinct molecular requirements exist for biphenylimidazole and imidazoleacrylic acid binding, these results suggest that Val108 is a common structural determinant of nonpeptide recognition on the AT1 receptor.

Angiotensin I↗

PubMed1996

Properties of AT1a and AT1b angiotensin receptors expressed in adrenocortical Y-1 cells.

Adrenocortical Y-1 cells were stably transfected with the AT1a and AT1b subtypes of the rat angiotensin (ANG)IIAT1 receptor cDNA to study the pharmacological and functional properties of the two receptors. Selected clones of transfected cells expressing the AT1a or AT1b receptor subtypes bound the native ligand ANG II and the peptide antagonist [Sar1,Ile8]ANG II with similar affinities, but they differed in their relative affinities for the nonpeptide antagonist losartan (half-maximal inhibitory concentration 9.7 and 4.7 nM), ANG III (126 and 33 nM), and the peptide antagonist [Sar1,Gly8]ANG II (6.2 and 1.2 nM). Photoaffinity labeling of the expressed receptors revealed a single component of 65 kDa for both receptor subtypes, suggesting that both receptors were glycosylated in a similar manner. The sensitivity of 125I-ANG II binding to AT1a and AT1b receptors to guanine nucleotides was unaffected by pertussis toxin treatment. ANG II stimulated the formation of inositol phosphates and increased the level of cytoplasmic Ca2+ in both At1a- and AT1b-transfected Y-1 cells. However, ANG II had little effect on forskolin-induced adenosine 3',5'-cyclic monophosphate accumulation, causing only minor inhibition in AT1a-transfected cells and slight enhancement in AT1b-transfected cells. These data indicate that AT1a and AT1b receptors show small but significant differences in their binding pharmacology and, upon activation, are coupled through Gq/G11 to the phosphoinositide-Ca2+ signaling pathway. However, neither AT1a nor AT1b receptors exhibit coupling to Gi and inhibition of adenylate cyclase when expressed in murine adrenal tumor cells.

Adenylate Cyclase Toxin↗