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Biomedical subjects

G Sandberg

Publications and source records attributed to G Sandberg.

At least 73 records · Page 4Linked to original sources
PubMed1989

Studies on thymocyte subpopulations in guinea pigs. X. Rosette-forming ability of thymocyte subpopulations before and after incubation in vitro.

Thymocytes spontaneously proliferating in vitro were labelled with 3H-thymidine, and the distribution of label among rosette-forming cells (RFC+) and nonrosetting cells (RFC-), as well as in populations differing in buoyant density, was measured by liquid scintillation counting and autoradiography before and after incubation for 24 h. Initially most labelled cells (88%) belonged to the low-density (1a) subpopulation, the majority being RFC+. After incubation for 24 h, low-density nonrosetting thymocytes (1a, RFC-) contained the highest amount of label. A decreased rosette formation occurred not only in labelled cells but also in the population as a whole, and in separately incubated high-density cells. The decreased rosette formation was mainly caused by a change in rosette-forming ability of viable high-density cells, however in part also by decreased viability. A shift from low to high density occurred among labelled cells during incubation and was shown to occur in both RFC+ and RFC-. The decreased rosette formation of labelled cells during in vitro culture contrasts with the increase earlier observed in vivo and may therefore represent affinity alterations or a down-regulation of the rosette receptor in vitro. We conclude that the observed changes in density, but not in rosette-forming ability, may reflect normal differentiation.

Animals↗
PubMed1988

Analysis of Indole-3-Acetic Acid and Related Indoles in Culture Medium from Azospirillum lipoferum and Azospirillum brasilense.

Analysis of neutral and acidic ethyl acetate extracts from culture medium of Azospirillum brasilense 703Ebc by high-performance liquid chromatography (HPLC) and combined gas chromatography-mass spectrometry demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol, indole-3-methanol, and indole-3-lactic acid. IAA in media of 20 strains of A. brasilense and Azospirillum lipoferum was analyzed quantitatively by both the colorimetric Salkowski assay and HPLC-based isotopic dilution procedures. There was little correlation between the estimates obtained with the two procedures. For instance, the Salkowski assay suggested that the culture medium from A. brasilense 703Ebc contained 26.1 mug of IAA ml, whereas HPLC revealed the presence of only 0.5 mug of IAA ml. Equivalent estimates with A. brasilense 204Ed were 10.5 and 0.01 mug of IAA ml, respectively. The data demonstrate that the Salkowski assay is not a reliable method for measuring the IAA content of Azospirillum culture medium and that estimates in excess of 10 mug of IAA ml should be viewed with particular caution. Metabolism of [2'-C]IAA by A. brasilense 703Ebc yielded radiolabeled indole-3-methanol, whereas roots of maize (Zea mays L.) seedlings gave rise to [C]oxindole-3-acetic acid and an array of polar metabolites. Metabolism of [2'-C]IAA by maize roots inoculated with A. brasilense 703Ebc produced a metabolic profile characteristic of maize rather than Azospirillum species.

Journal Article↗
PubMed1988

On the nature of natural thymocytotoxic antibodies. A screening in neonatal, young, adult and pathological human sera.

The thymocytotoxic activity of human sera against guinea pig cells was earlier shown to be mediated by IgM and a heat-labile serum factor, presumably complement. It is not known if such natural cytotoxic activity represents background activity of preexisting clones of immunoglobulin-producing cells, cross-reacting antibodies appearing after immunization, physiological immune regulatory molecules, or components of an immune network. We have therefore examined the presence of thymocytotoxic IgM molecules in normal adult and neonatal sera and in a number of diseases which affect the lymphoid and immune system. The thymocytotoxic effect of serum was measured in different dilutions, both directly and after heat inactivation of the sera and supplementation with a standard amount of IgM-depleted serum, which is inactive in itself but provides a fixed amount of the heat-labile cofactor. The cytotoxic IgM was present in various amounts in all sera tested, although in neonates very small amounts were found. No specific aberration in toxic activity was seen in rheumatoid arthritis or a number of hematological diseases. In general, the cytotoxic activity correlated well with the total amount of IgM. However, in cases of chronic lymphocytic leukemia, idiopathic thrombocytopenic purpura and immunocytoma aberrant cytotoxic activities were found, but to ascertain a connection between these diseases and the factor would require a more extensive follow-up study. The results indicate that the naturally occurring thymocytotoxic IgM is widespread and may reflect a clone of B cells which is activated by an endogenous stimulus, or by some ubiquitous exogenous immunogen.

Adolescent↗
PubMed1988

Demonstration of C3d and the terminal complement complex on thymic large granular lymphocytes and common thymocytes after incubation with naturally thymocytotoxic serum.

Guinea pig thymocytes were incubated in vitro with normal human or rabbit serum, which resulted in lysis of a major part of the cells, or with autologous serum causing lysis of a fraction (30%) of the cells. By using antibodies against human C3d and a neoepitope on the terminal complement complex (TCC), activation of both the initial and terminal part of the complement cascade was demonstrated on the surface of thymocytes incubated in the presence of serum. With human serum both types of antigen were detected. With rabbit serum only TCC was detected since immunoglobulins were bound to thymocytes and prevented specific demonstration of C3d by the antirabbit secondary antibody. With autologous serum only C3d was demonstrated, due to lack of cross-reactivity of the monoclonal anti-TCC antibody with guinea pig. Heat-inactivated sera or human serum devoid of IgM neither caused lysis nor resulted in complement activation. Addition of heat-inactivated serum restored the complement activating ability of IgM-depleted serum, indicating that heat stabile IgM is an obligate but sufficient requirement for complement activation in this system. The TCC epitope was also identified on a considerable number of granulated cells, on the basis of morphology classified as large granular lymphocytes.

Animals↗
PubMed1988

Studies on thymocyte subpopulations in guinea pigs. VIII. Characterization of a thymocyte population resistant to the cytotoxic effect of normal rabbit serum.

Guinea pig thymocytes were incubated with normal rabbit serum, which resulted in the death of a great majority of the cells. The remaining rabbit serum-resistant cells, representing less than 10% of the thymocytes, contained euchromatic DNA and were of intermediate size and low density. Functional tests indicated that they were enriched in immunologically mature cells, which responded to the mitogenic lectins phytohemagglutinin and concanavalin A, and were depleted of immature, spontaneously proliferating cells and in cells responding to the thymocyte growth peptide. The described procedure for enrichment of immunologically mature thymus cells in guinea pigs may become useful since glucocorticoid treatment, used in mice for enrichment of mature thymocytes, cannot be used for this purpose in guinea pigs.

Animals↗
PubMed1988

Thymocytotoxic antibodies in synovial fluid.

Synovial fluid (SF), obtained from patients with juvenile rheumatoid arthritis (JRA), osteochondritis, traumatic synovitis and septic arthritis were tested for the presence of thymocytotoxic activity. Such activity, directed against guinea pig thymocytes, was earlier demonstrated in human serum and shown to be mediated by IgM antibodies and a heat labile factor, most likely complement. The cytotoxic activity was demonstrated in all SFs tested, and was abolished by either one of the following procedures: depletion of IgM by use of anti-IgM-antibody coated protein A-Sepharose, or heating to 56 degrees C for 30 min. Activity was regained when samples inactivated by these two procedures were recombined. The cytotoxic SFs produced similar distortion of cell volume distribution of the target thymocytes as previously has been shown with human serum. The findings indicate that the two cytotoxic activities are identical. In most cases the IgM levels and the cytotoxic activity were lower in SF than in normal serum. Although the material does not permit correlation of cytotoxic activity with specific joint conditions, a high SF cytotoxicity was noted in two out of four patients with JRA. The demonstration of IgM-associated thymocytotoxic activity is of interest both in connection with earlier observations of various specific antibodies in SF and in connection with speculations regarding local immune regulatory activity in the joint.

Arthritis, Rheumatoid↗
PubMed1987

Indole 3-acetic acid concentration in the leading shoot and living stem bark of Scots pine: seasonal variation and effects of pruning.

Seasonal changes in the concentration of indole-3-acetic acid (IAA) in the leading shoot and in the live tissue external to the xylem (living bark) of 2-3 m tall Scots pine (Pinus sylvestris L.) trees were observed over a period of three years. Both the leading shoot and the living bark showed a consistent pattern of seasonal variation in IAA content, with maxima of about 150 and 350 ng g(-1) (fresh weight), respectively. The IAA concentration in both tissues increased in late June at the time of shoot growth termination, decreased from late August, and by October reached a low value, which was maintained throughout the winter. Excision of current year shoots on the upper branches decreased the annual stem diameter increment without affecting the concentration of IAA in the living bark. However, excising the leading shoot, or girdling the mainstem beneath the leading shoot, caused a substantial reduction in the IAA content of the living stem bark.

Journal Article↗
PubMed1987

Dynamics of indole-3-acetic acid during germination of Picea abies seeds.

High performance liquid chromatography and combined gas chromatography-mass spectrometry were used to identify indole-3-acetic acid (IAA) and indole-3-ethanol as endogenous constituents of germinating Norway spruce (Picea abies (L.) Karst.) seeds. Indole-3-methanol was tentatively identified by multiple ion monitoring. The free IAA content of the seeds rose from about 20 ng g(-1) to about 60 ng g(-1) (dry weight) during the first five days of germination and thereafter declined to around 20 ng g(-1). Indole-3-acetic acid released by alkaline hydrolysis, which was initially present at about 110 ng g(-1), decreased to 5-10 ng g(-1) during the first week of germination. The IAA content of seed lots differing in germination behavior was investigated. The findings are discussed in relation to the metabolism of IAA in conifer seeds.

Journal Article↗
PubMed1987

Effect of growth factors on the proliferation of thymocytes in different functional and anatomical compartments.

The intrathymic location of cells responding to the thymocyte growth peptide (TGP) was investigated in guinea pigs. Thymus cells were labelled by topical application of a fluorescein isothiocyanate solution and the percentage of fluorescent cells analyzed by flow cytometry. Large cells forming rosettes with rabbit erythrocytes, known to respond to TGP, had a lower percentage of fluorescent cells than non-rosetting cells which do not respond to TGP. If the TGP-responding cells are anatomically segregated in the guinea pig thymus, this might indicate that they are preferentially located in the deep, juxtamedullary part of the cortex, where one major proliferating compartment is situated.

Animals↗
PubMed1987

Purification, identification and elimination of a natural human serum antibody with cytotoxic effect on guinea pig thymocytes.

Normal human sera contain one or several factors cytotoxic for normal guinea pig thymocytes, and when serum is precipitated with ammonium sulphate (60% saturated) and the precipitate dissolved and dialyzed, the activity is preserved. Gel chromatography with Sephadex G-150 and Sepharose CL-6B indicated a molecular weight of approximately 900,000 daltons. The active fractions contained a high amount of IgM according to single radial immunodiffusion and two-dimensional gel electrophoresis. Quantitation of the IgM band in one-dimensional gel electrophoresis preparations by gel scanning indicated that IgM accounted for 65% of the eluted proteins in active fractions. Purified human IgM from myeloma patients eluted as the active factor during gel chromatography. Elimination of IgM from serum by affinity chromatography eliminated the cytotoxic activity. The serum could also be inactivated by heating. The mixing of IgM-depleted serum with either polyclonal IgM or heat-inactivated serum restored the activity. Thus, the cytotoxic activity is due to IgM antibodies plus a heat-labile component (presumably complement). The presence of the cytotoxic activity in autologous (guinea pig) serum was recently demonstrated. The possible functional role of these antibodies in the elimination process of a large number of cortical thymocytes is suggested.

Animals↗
PubMed1987

Studies on a serum factor which blocks the effect of human natural thymocytotoxic antibodies.

Normal human serum contains an IgM associated cytotoxic activity acting on guinea pig thymocytes. The inhibition of this cytotoxic effect by normal guinea pig serum was investigated. The blocking effect could be detected within 1 min and seemed to act by interfering with the cytotoxic factor in solution, since preincubation of human serum with autologous guinea pig serum potentiated the blocking effect, whereas no irreversible blocking effect was obtained by pre-incubation of target cells with the blocking factor. The inhibitory factor was not absorbed by incubation with thymocytes. The blocking effect was heat stabile (56 degrees C, 30 min) and detectable at both 4 degrees C and 37 degrees C. The clear effect on the cytotoxic effect of heterologous serum at 4 degrees C was in contrast to the much lower effect on the cytotoxicity of autologous serum at this temperature.

Animals↗
PubMed1987

Dyspareunia: an integrated approach to assessment and diagnosis.

Dyspareunia, or painful intercourse, is frequently referred to as the most common female sexual dysfunction. It can occur singly or be manifested in combination with other psychosexual disorders. Diagnosis of dyspareunia is appropriate in cases in which the experience of pain is persistent and severe. There has been little agreement concerning the origin of dyspareunia. Organic conditions and psychological variables have alternately been presented as major factors in causality. There is a presumed high incidence of physical disease associated with dyspareunia when compared with other female sexual dysfunctions. In the majority of cases, however, organic factors are thought to be rare in contrast with sexual issues and interpersonal or intrapsychic difficulties as a cause of continuing problems. The finding of an organic basis for dyspareunia does not rule out emotional or psychogenic causes. Thorough and extensive gynecologic and psychological evaluation is essential in cases of dyspareunia. The etiology of dyspareunia should be viewed on a continuum from primarily physical to primarily psychological with many women falling in the middle area.

Dyspareunia↗
PubMed1986

Cytotoxic effect of heterologous and autologous serum factor on guinea pig thymocytes assayed by electronic cell volume distribution analysis.

The cytotoxic effect of serum on guinea pig thymocytes was studied by dye exclusion and by analysis of cell volume distribution curves obtained by means of a computer-assisted electronic cell volume distribution analyzer. Guinea pig, rabbit and human sera were shown to be cytotoxic for guinea pig thymocytes (incubation for 1 h at 37 degrees C or overnight at 4 degrees C). A similar, but less potent, activity was found in autologous guinea pig serum (4 degrees C). The activity was dialysable and lyophilizable but was destroyed by heating at 56 degrees C for 30 min. It was recovered after ammonium sulphate precipitation followed by dialysis. The effect of this dialysate was dose-dependent. A tentative definition of viable and dead cells was made on the basis of 'electronic' cell volume. The following results indicate that by this definition electronic cell volume distribution allowed detection of the cytotoxic serum factor: (1) sera and dialysates produced marked distortion of cell volume distribution curves, not seen in controls treated with heat-inactivated preparations; (2) the dose-response relationship was similar when dye exclusion and cell volume distribution was used as assay: (3) both methods detected similar differences in sensitivity of different thymocyte subpopulations to serum; (4) the electronic method could be used on separate thymocyte subpopulations although they differed in cell volume. This rapid, objective and reproducible method for studying the cytotoxic effect of sera may be useful during attempts to purify and identify the active factor(s).

Animals↗
PubMed1986

Kinetic study of Kurloff cells in guinea pig thymus.

One single injection of estradiol to male guinea pigs resulted in the appearance of Kurloff cells in the thymus and spleen in a maximal number after 2-3 weeks. In both organs, Kurloff cells of three categories were observed with different size and number of the inclusion(s). In the thymus, cells with small and medium-sized inclusions were present almost exclusively among low-density thymocytes. Cells with one large inclusion were initially present among low-density cells, but with time an increasing proportion were found among high-density thymocytes. This indicates that the different categories of Kurloff cells represent maturational stages and follow the normal differentiation step of thymocytes from low to high density. According to electronic cell volume distribution analysis, estradiol treatment was associated with a shift in cell volume towards larger cells, and this shift was correlated in time with the appearance of Kurloff cells with large inclusions. In thymus sections there was evidence for a massive and selective migration of Kurloff cells via interlobular lymph vessels. No difference in localization of Kurloff cells was noted at various times after estradiol treatment. Attempts to induce Kurloff cell formation from bone marrow, spleen or thymus cells during 2 weeks in vitro were unsuccessful, also when culturing the cells in serum from estradiol-treated animals. This negative result, the long lag phase of estradiol-induced Kurloff cell formation in vivo, and the reported lack of estradiol receptor in Kurloff cells indicate that the Kurloff cell induction by estradiol may be indirect.

Animals↗
PubMed1986

Mitogenic responses of splenic B and T lymphocytes in neonatally capsaicin-treated mice.

The proliferative response of spleen cells from neonatally capsaicin-treated mice to 5 mitogens (LPS, PWM, dextran sulfate, ConA and PHA) were tested. Both B- and T-lymphocyte responses were essentially unaffected by the capsaicin treatment, which is known to destroy certain small-sized neuropeptide containing primary sensory neurons. However, the capsaicin-treated mice displayed a shift in the dose response to PHA so that the maximal response was obtained with a lower dose of the mitogen. The results exclude major effects of the affected sensory neurons on the development or expression of immune competence, but point to a possible modulatory effect on some step in the response to PHA.

Animals↗
PubMed1985

Studies on thymocyte subpopulations in guinea pigs. VII. Characterization of cell populations responsive to guinea pig interleukin 1 and interleukin 2.

The properties of thymocytes responding by proliferation to a mitogenic lectin (PHA), interleukin 1 (IL 1), or interleukin 2 (IL 2) were studied and compared to the properties of cells known to respond to a separate thymocyte growth factor (TGP), which has so far only been studied in guinea pigs. Thymocytes from guinea pigs were separated into subpopulations by density gradient centrifugation with Percoll and by rosette formation with rabbit erythrocytes. PHA-responsive cells were recovered exclusively in a non-rosetting, low-density population designated Ia, RFC-, constituting approximately 4 per cent of all thymocytes. Thus, according to the prevailing view of lymphocyte mitogenesis, IL 1-producing, IL 2-producing as well as IL 2-responding cells are all present in this population. The mitogen-responsive cells could be further stimulated by addition of IL 1 or IL 2, indicating that the magnitude of the mitogenic response was regulated by the production of these factors and was not restricted by the number of IL 2-responding cells. IL 1, to some extent, also enhanced the mitogen response in a non-rosetting, intermediate density population designated Ib, RFC-. None of the factors could affect the lack of mitogen responsiveness in the high-density population II, constituting approximately 85% of the total population and probably including most small cortical thymocytes. We conclude that IL 2-responding thymocytes are present above all in the quantitatively small population Ia, RFC- (shown to contain also the mature, mitogen-responding cells) and to a smaller extent in Ib, RFC- (where a deficit in IL 1-producing cells may explain the poor mitogen responsiveness), but not in the major, high-density population II. From our data, it is also evident that the mitogen, IL 1- and IL 2-reactive cells can be separated from a population of intensely proliferating thymic precursor cells which are stimulated to grow by TGP. Therefore, the growth of these immature cells does not seem to be regulated by IL 1 or IL 2 in the guinea pig.

Animals↗