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K Sandberg

Publications and source records attributed to K Sandberg.

At least 73 records · Page 4Linked to original sources
PubMed1992

Intercellular communication between follicular angiotensin receptors and Xenopus laevis oocytes: medication by an inositol 1,4,5-trisphosphate-dependent mechanism.

In Xenopus laevis oocytes, activation of angiotensin II (AII) receptors on the surrounding follicular cells sends a signal through gap junctions to elevate cytoplasmic calcium concentration ([Ca2+]i) within the oocyte. The two major candidates for signal transfer through gap junctions into the oocyte during AII receptor stimulation are Ins(1,4,5)P3 and Ca2+. In [3H]inositol-injected follicular oocytes, AII stimulated two- to fourfold increases in phosphoinositide hydrolysis and production of inositol phosphates. Injection of the glycosaminoglycan, heparin, which selectively blocks Ins(1,4,5)P3 receptors, prevented both AII-stimulated and Ins(1,4,5)P3-induced Ca2+ mobilization in Xenopus follicular oocytes but did not affect mobilization of Ca2+ by ionomycin or GTP. These results indicate that the AII-regulated process of gap junction communication between follicular cells and the oocyte operates through an Ins(1,4,5)P3-dependent mechanism rather than through transfer of Ca2+ into the ooplasm and subsequent Ca(2+)-induced Ca2+ release.

Angiotensin II↗
PubMed1992

Cloning of highly polymorphic microsatellites in the horse.

We have isolated equine microsatellites by screening a genomic library with (TG)n and (TC)n probes. TG microsatellites were found to be more abundant than TC repeats, with an estimated frequency of one per 100,000bp. Sequence analysis of eight TG-positive clones revealed varying structures of the repeat regions; perfect stretches of TG repeats, imperfect stretches of TG repeats and compound regions of TG and TC repeats. Five loci were analysed by PCR and showed extensive polymorphism; three to seven alleles and heterozygosities of 0.40-0.76 were observed when screening 20-30 unrelated individuals. The high degree of polymorphism, their abundance and the possibility of automating the typing procedure make these loci ideal for standardized paternity testing in the horse. Furthermore, we demonstrate that single hairs can be used as starting material for the PCR analysis.

Animals↗
PubMed1992

Interferon-alpha but not -beta genes require de novo protein synthesis for efficient expression in human monocytes.

Monocytes produce interferon-alpha (IFN)-alpha) and -beta when human peripheral blood mononuclear cells (PBMCs) are stimulated in vitro by Sendai virus (SV). We found that about 70% of the IFN-producing cells (IPCs) expressed both IFN-alpha and -beta mRNA; the rest expressed only IFN-beta mRNA. In the presence of the protein synthesis inhibitor cycloheximide (CHX), the frequency of IFN-alpha mRNA-containing cells, measured after 6h, was decreased by 85-90%. Results of nuclear run-on transcription assays showed that CHX inhibited IFN-alpha gene expression. The frequency of IFN-beta mRNA-containing cells was not reduced by CHX. Actually, a threefold increase was observed at the lower CHX concentrations. Studies on the kinetics of IFN-alpha/beta mRNA induction showed that CHX accelerated the appearance of IFN-beta mRNA-containing cells, increased IFN-beta mRNA levels, and delayed the normally occurring post-inductional decrease of IFN-beta mRNA. Unexpectedly, an initially normal or even accelerated IFN-alpha mRNA response was seen in the presence of CHX during the first 3-4 h after SV stimulation. This occurred in a small proportion of the potential IPCs. However, CHX prevented the subsequent marked increase of IFN-alpha mRNA levels. Preincubation of PBMCs for 6 h in conditioned medium (CM) containing IFN and other cytokines prevented the CHX-mediated inhibition of IFN-alpha mRNA. Without preincubation this was not seen. The preincubation in CM caused an accelerated appearance of IFN-alpha mRNA, resembling that of IFN-beta mRNA. The results suggest that IFN-alpha and -beta genes are differentially regulated in the same monocytes, the former requiring de novo synthesis of intracellular protein(s) for efficient expression.

Blotting, Northern↗
PubMed1992

DNA fingerprinting in horses using a simple (TG)n probe and its application to population comparisons.

A synthetic polynucleotide (TG)n was hybridized to equine DNA digested with HinfI and hypervariable hybridization patterns were obtained. Mendelian inheritance of these DNA fingerprinting patterns was confirmed by pedigree analysis. Estimates of the probabilities of identical band patterns in unrelated individuals of different breeds (Swedish Trotters, North Swedish Trotters, Thoroughbreds and Arabians) were in the range 1 x 10(-4) - 7 x 10(-6). The variability derived with the (TG)n probe in horses was higher than what we obtained with several other commonly used probes for DNA fingerprinting. Individuals within breeds tended to be more similar to each other with regard to DNA fingerprint pattern than to individuals of other breeds. Moreover, a parsimony analysis made on the basis of the hybridization patterns gave clustering of individuals within breeds. The possibility of using hypervariable probes for the identification of breed-specific characters is discussed.

Animals↗
PubMed1991

Phorbol ester-mediated inhibition of IFN-alpha/beta gene transcription in blood mononuclear leukocytes.

The phorbol ester PMA efficiently inhibits the in vitro IFN-alpha and -beta responses in human blood monocytes induced by Sendai virus and in natural IFN-producing cells induced by glutaraldehyde-fixed herpes simplex virus-infected human amnion (WISH) cells. This PMA-mediated inhibition of IFN-alpha/beta secretion is correlated with considerably reduced levels of IFN-alpha/beta mRNA, as determined by Northern blot analysis. Nuclear run-on assays further show that, at least in monocytes, PMA inhibits transcription of the IFN-alpha and -beta genes. The synthetic diacylglycerol 1-oleoyl-2-acetylglycerol has the same effects as PMA, and the protein kinase inhibitor staurosporine prevents the PMA-mediated inhibition of IFN-alpha/beta expression. These results suggest a role for protein kinase C in the inhibition of IFN-alpha/beta responses. The PMA does not inhibit the accumulation of IFN-beta mRNA in monocytes stimulated by Sendai virus in the presence of cycloheximide, indicating that the inhibitory action of the phorbol ester requires de novo protein synthesis.

Alkaloids↗
PubMed1991

Amphibian myocardial angiotensin II receptors are distinct from mammalian AT1 and AT2 receptor subtypes.

High-affinity receptors for angiotensin II were identified on Xenopus laevis cardiac membranes and characterized by binding-inhibition studies with peptide and non-peptide AII antagonists. Scatchard analysis of the binding data identified a high-affinity site with Kd1 = 1.6 nM and Bmax1 = 3.7 pmol/mg protein and a low-affinity site with Kd2 = 22 nM and Bmax 2 = 9.5 pmol/mg protein. Treatment with dithiothreitol reduced the number of binding sites by greater than 70%. The rank order of potency for ALL analogs was (agent, IC50) [Sar1,Ile8]AII, 0.91 nM greater than AII, 2.0 nM greater than AI, 5.3 nM greater than [Sar1, Ala8]AII, 19 nM much greater than CGP42112A, 1.2 microM much much greater than DuP 753 approximately PD-123177, greater than 100 microM. The relative potencies of these compounds differ markedly from their activities on the two known mammalian AII receptor subtypes, AT1 and AT2. These results indicate that amphibian AII receptors are pharmacologically distinct from both the AT1 and AT2 receptors characterized in mammalian tissues.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1991

Flow cytometric analysis of natural interferon-alpha producing cells.

Herpes simplex virus-infected cells induce high interferon-alpha (IFN-alpha) production in infrequent cells among peripheral blood mononuclear cells (PBMC), designated natural IFN-alpha producing (NIP) cells. The properties of such NIP cells were compared with defined populations of leucocytes by means of flow cytometric analysis and sorting. The NIP cells are characterized as a discrete population of cells with high forward and low to intermediate orthogonal light scattering, similar to that of early progenitors of myeloid and lymphoid cells. However, they appear to lack the stem cell-associated molecule CD34. Furthermore, NIP cells cannot be localized to the myeloid line of cell differentiation, because they do not express the CD33, CD13, CD11b, CD15 or CD14 antigens. Neither do they express CD10 and CD19 antigens which are present in all stages of B-cell differentiation plasma cells excepted, nor CD7 antigens expressed on early T cells. In combination with previous results, our data support the view that the NIP cell is a unique and distinct cell type in peripheral blood, possibly with a physiological role in the defence against certain viral infections.

Antigens, CD↗
PubMed1991

Surfactant improves gas mixing and alveolar ventilation in preterm lambs.

Prophylactic treatment with ovine surfactant was evaluated in preterm lambs at risk for development of hyaline membrane disease. Eight mechanically ventilated newborn lambs were treated before delivery and 10 served as controls (gestational age 129-131 d). Lung mechanics, functional residual capacity, alveolar ventilation, efficiency of ventilation, and distribution of ventilation were tested using pressure, flow, and nitrogen elimination (nitrogen washout during 100% oxygen breathing) measurements in the endotracheal tube. The surfactant-treated animals showed significantly improved gas mixing efficiency in the lung with improved alveolar ventilation. Single exponential washout pattern dominated in both groups. Adequate functional residual capacity was established earlier after birth in the treated lambs than in the control animals. Lung mechanics in the treated group showed significant improvement in dynamic lung compliance. Surfactant treatment also improved gas exchange and reduced respirator pressure requirement. We speculate that the main functional effect of surfactant treatment in preterm lambs at risk to develop hyaline membrane disease is to maintain the patency of the peripheral airways in the lung, which improves diffusive gas mixing, alveolar ventilation, and gas exchange. The techniques used in this study should also be useful to evaluate lung function in preterm human infants after specific adaptation of the equipment size.

Age Factors↗
PubMed1991

Lung volume, gas mixing, and mechanics of breathing in mechanically ventilated very low birth weight infants with idiopathic respiratory distress syndrome.

We assessed pulmonary function in 14 mechanically ventilated newborn very low birth weight infants with idiopathic respiratory distress syndrome by means of a face-out, volume displacement body plethysmograph and nitrogen washout analyses. Specially designed computer programs were used for calculations of lung volumes, ventilation, gas mixing efficiency, and mechanical parameters. In addition to very low compliance and moderately elevated resistance of the respiratory system, there were considerably impaired gas mixing efficiency and low functional residual capacity (FRC). No correlations between positive end-expiratory pressure and mean airway pressure versus compliance, resistance, or FRC could be found. Neither could correlations be found between FRC and compliance or FRC and the calculated right to left shunt.

Female↗
PubMed1991

A plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants.

We have developed and tested a plethysmographic method for assessment of lung function in mechanically ventilated very low birth weight infants during intensive care. Information about the mechanics of the respiratory system is obtained from the respiratory flow as measured by volume displacement plethysmography and from airway pressure measured in the artificial airway. Data on lung volumes, ventilation, and distribution of ventilation is obtained simultaneously by combining the respiratory flow measurements with nitrogen concentration analyses of the respiratory gas. No significant differences were found when the estimations of mechanical parameters and FRC were compared with reference methods and when determinations of the same parameters were repeated in the same subjects. The plethysmograph was shown to be safe and convenient to use, even in studies lasting several hours.

Evaluation Studies as Topic↗
PubMed1991

Novel angiotensin II antagonists distinguish amphibian from mammalian angiotensin II receptors expressed in Xenopus laevis oocytes.

Angiotensin II (AII) stimulates rapid increases in cytosolic Ca2+ concentrations in Xenopus laevis oocytes after binding to specific receptors located in the surrounding follicular cells. In follicular oocytes, the peptide AII receptor antagonists saralasin (IC50 = 25 nM) and CGP 42112A (IC50 = 400 nM) were orders of magnitude more potent than the non-peptide antagonists DuP 753 and PD-123177 (IC50 greater than 10 microM) as inhibitors of AII-induced Ca2+ mobilization. The relative potencies of the AII antagonists at the Xenopus AII receptor were completely different from their activities at the two known mammalian AII receptor subtypes. These results indicate that the ligand-binding domain of the amphibian AII receptor has a unique conformation that distinguishes with high specificity between peptide and non-peptide AII antagonists. The amphibian AII receptor is pharmacologically distinct from the AT1 receptor subtype, which mediates phosphoinositide hydrolysis and Ca2+ mobilization in mammalian adrenal cells.

Aequorin↗
PubMed1990

A distinct population of nonphagocytic and low level CD4+ null lymphocytes produce IFN-alpha after stimulation by herpes simplex virus-infected cells.

Human PBMC were stimulated for 6 h in vitro by HSV or Sendai virus (SV) and analyzed by flow cytometry. IFN-alpha producing cells (IPC) were identified through their content of IFN-alpha mRNA by in situ hybridization using a 35S-labeled IFN-alpha 2 cRNA probe. The IPC induced by HSV-infected WISH cells lacked capacity to adhere to and phagocytose latex particles. The induction of IFN-alpha by free infectious SV occurring in monocytes was abolished by phagocytosis of latex particles present in the cultures during the induction period. Such latex particles actually enhanced the IFN-alpha response induced by glutaraldehyde-fixed HSV- or SV-infected WISH cells or by free intact HSV. The HSV-induced IPC did not express the CD14 Ag expressed on monocytes. Cell sorting was performed on HSV-induced PBMC labeled with phycoerythrin-conjugated anti-CD3 and FITC-conjugated anti-CD4 mAb. A small population consisting of 1.4% of all PBMC, which was CD3- but expressed low but significant levels of CD4, contained the majority of the IPC with a 50-fold increase of their frequency. This cell population had a forward- and right-angle light scatter different from typical monocytes/macrophages. The results therefore further delineate IPC among PBMC into monocytes, being stimulated by viruses such as SV. Another distinct population of infrequent but highly efficient IPC, tentatively designated natural IFN-alpha producing cells, is activated by stimuli such as HSV.

Antibodies, Monoclonal↗
PubMed1990

Angiotensin II-induced calcium mobilization in oocytes by signal transfer through gap junctions.

Angiotensin II (AII) stimulates rapid increases in the concentration of cytosolic calcium in follicular oocytes from Xenopus laevis. This calcium response was not present in denuded oocytes, indicating that it is mediated by AII receptors on the adherent follicular cells. The endogenous AII receptors differed in their binding properties from mammalian AII receptors expressed on the oocyte surface after injection of rat adrenal messenger RNA. Also, the calcium responses to activation of the amphibian AII receptor, but not the expressed mammalian AII receptor, were blocked reversibly by octanol and intracellular acidification, treatments that inhibit cell coupling through gap junctions. In addition, AII increased the rate of progesterone-induced maturation. Thus, an AII-induced calcium-mobilizing signal is transferred from follicle cells to the oocyte through gap junctions and may play a physiological role in oocyte maturation.

Aequorin↗
PubMed1989

Metabolism of inositol pentakisphosphate to inositol hexakisphosphate in Xenopus laevis oocytes.

The formation and metabolism of inositol pentakis-and hexakisphosphates (InsP5 and InsP6) were investigated in Xenopus laevis oocytes. After [3H]inositol injection, [3H]InsP5 and subsequently [3H]Insp6 increased progressively over 72 h. In intact oocytes, [3H]InsP5 was progressively converted to [3H]InsP6 from 6 to 72 h of incubation and was not metabolized to lower inositol phosphates. In contrast, [3H]InsP6 remained unmetabolized for up to 72 h. These data are consistent with the kinetics of the increases in [3H]InsP5 and [3H]InsP6 in [3H]inositol-labeled oocytes. The highly phosphorylated inositols showed significant changes during oogenesis and maturation. In oocytes incubated for 48 h after [3H]inositol injection, the radioactive incorporation into polyphosphoinositols increased progressively from stage 3 to stage 6, with 5- and 6-fold rises (cpm/mg protein) for [3H]InsP5 and [3H]InsP6, respectively. These developmental changes were associated with 5-fold increases in [3H]inositol tetrakisphosphate between stages 3 and 6 of oogenesis. Induction of oocyte maturation by progesterone (1 microM) during the last 12 of a 36-h incubation with [3H]inositol doubled the levels of [3H]InsP6 relative to [3H]InsP5, suggesting that the activity of inositol pentakisphosphate kinase increases during maturation. These results provide direct evidence for metabolic conversion of InsP5 to InsP6 in animal cells and show that the higher inositol polyphosphates, unlike the lower phosphoinositols, are extraordinarily stable. These species increase markedly during ovum development and may play a regulatory role in oogenesis and maturation.

Animals↗
PubMed1989

Studies on the intoxication pathway of tetanus toxin in the rat pheochromocytoma (PC12) cell line. Binding, internalization, and inhibition of acetylcholine release.

Tetanus toxin was found to be a potent inhibitor of neurosecretion in the rat pheochromocytoma cell line PC12, a system in which biochemical and functional studies could be performed in parallel. Incubation of the cells with 10 nM tetanus toxin (3 h) led to an inhibition of acetylcholine release by 75-80% when evoked by 200 microM veratridine, 1 mM carbachol, or 2 mM Ba2+. The main characteristics of the inhibition process are: 1) the toxin is very potent, with threshold doses of 10 pM; 2) the action of toxin is blocked at low temperature (0 degrees C) and by antitoxin; 3) the effects are dose- and time-dependent; 4) a concentration-dependent lag phase precedes the onset of the inhibitory effects. Thus the PC12 cultures are a valid system for studies on the underlying molecular process in tetanus action. This system was exploited by the use of long term incubation studies to examine the processes responsible for the lag phase. When cells were incubated with 0.1 nM 125I-tetanus toxin, cell-associated toxin reached a plateau of 16 fmol of toxin/mg of protein, yet the toxic effects did not appear until 12 h. Further, PC12 cells were found to rapidly internalize tetanus toxin, with a half-life of 1-2 min, once it was bound to the surface of the cells. Thus, the lag phase results from steps that occur in the intracellular compartment after internalization. An important discovery was that the differentiation state of the PC12 cells was a critical factor in determining sensitivity to tetanus toxin. Cells that were cultured with nerve growth factor for 8-12 days were very sensitive to toxin. In contrast, acetylcholine release from nondifferentiated, autodifferentiated, or dexamethasone-treated cultures was insensitive to tetanus toxin. Since differential expression of high affinity tetanus toxin receptors cannot explain these results, it is concluded that PC12 cells are capable of expressing different forms of excitation-secretion coupling mechanisms. Tetanus toxin should prove a valuable probe to further distinguish these processes.

Acetylcholine↗
PubMed1989

Induction of mRNA for HLA-DR beta in human keratinocytes cocultured with interferon-gamma.

Explanted human keratinocytes exposed in vitro to recombinant interferon-gamma (IFN-gamma) were investigated for the appearance of mRNA for HLA-DR. Using in situ hybridization with a (35S)UTP-labelled HLA-DR beta cRNA probe, mRNA-positive cells were detected already within 6 h with maximal numbers of positive cells as well as the amount of mRNA per cell after 48 h. The corresponding protein HLA-DR, as analysed by immunoperoxidase staining, was detected on 20%-40% of the cells after 24 h and on almost all cells within 48 h. The expression of HLA-DQ and -DP antigens were always exceeded by that of HLA-DR. Whereas an increase in the concentration of IFN-gamma above 50 U/ml did not affect the maximal level of HLA-DR reactive cells, there was a fourfold increase in the frequency of cells reactive with HLA-DQ and a twofold increase for HLA-DP when the IFN-gamma concentration was raised from 50 to 500 U/ml. When IFN-gamma was withdrawn from the cultures, HLA-DR mRNA and protein synthesis ceased--indicating the continuous need for IFN-gamma to maintain the HLA-DR synthesis in keratinocytes.

DNA↗
PubMed1989

Genetic polymorphism of horse serum protein 3 (SP3).

Two-dimensional agarose gel (pH 8.6)-horizontal polyacrylamide gel (pH 9.0) electrophoresis of horse serum samples, followed by general protein staining, revealed genetic polymorphism of an unidentified protein tentatively designated serum protein 3 (SP3). The SP3 fractions appeared distinctly when a 14% concentration of acrylamide was used in the separation gels. The 2-D mobilities of SP3 fractions were quite similar to that of albumin. Family data were consistent with the hypothesis that the observed SP3 phenotypes were controlled by four co-dominant, autosomal alleles (D, F, I, S). Evidence was provided that the F allele can be further divided into two alleles (F1 and F2); the mobilities of F1 and F2 variants were very similar. Each of the SP3 alleles gave rise to one fraction and each of the heterozygous types showed two fractions. More than 600 horses representing five different breeds (Swedish Trotter, North-Swedish Trotter, Thoroughbred, Arab and Polish Tarpan) were typed for SP3, and allele frequency estimates were calculated. SP3 was highly polymorphic in all breeds studied.

Animals↗