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Biomedical subjects

G Sandberg

Publications and source records attributed to G Sandberg.

At least 91 records · Page 5Linked to original sources
PubMed1985

Studies on thymocyte subpopulations in guinea pigs. VI. Differentiation of precursor cells in vivo and in vitro.

The relation between six subpopulations of guinea pig thymocytes, separated on the basis of PNA binding and buoyant density, was studied. Incubation in vitro of either unseparated thymocytes or isolated large, low density cells, caused a shift towards smaller cells with high buoyant density. In order to determine whether these changes reflect a normal differentiation we pulsed labelled thymocytes with 3H-Thymidine and traced the labelling in the separate subpopulations after different intervals by autoradiography. Both in vivo and in vitro, the thymidine was initially incorporated mainly into PNA+ cells (85% of all labelled cells), particularly into PNA+ low-density cells (called PNA+Ia), which constitute 14% of all thymus cells (1). Correlation with autoradiographic sections of the thymus indicated that these cells were mainly located in the subcapsular and juxtamedullary cortex. At 24 h after labelling in vivo, more than 95% of the labelled cells were smaller, high density cells, both PNA+ and PNA-. At this time, labelled cells were present throughout the thymus with no preferential localization. Labelling and incubation in vitro were accompanied by similar changes after a 24-h time period when cells were cultured in the presence of serum. We conclude that the labelled PNA+Ia cells represent precursor cells, located in the subcapsular and juxtamedullary parts of the cortex. Within 24 h these cells differentiate into high density cells, some of which are PNA-. The corresponding results obtained in vitro indicate that these differentiation steps may also occur in the absence of a thymic microenvironment, and the study of histological sections indicate that these steps were not associated with any major relocalization within the thymus.

Animals↗
PubMed1985

Metabolic response of simultaneous versus sequential intravenous administration of amino acids and energy substrates to rats.

Three groups of rats were maintained on total intravenous nutrition for ten days. Group SA and SB were infused sequentially (2 X 12 h periods per day), SA received amino acids (AA) during the night and carbohydrates (CHO) + FAT during the day. The SB group received nutrients in the opposite order. A control group received a mixed solution simultaneously for 24 h/day. The sequentially fed groups showed a lower weight gain (2.4 +/- 0.4, 2.6 +/- 0.2 vs 4.9 +/- 0.3 g/day), nitrogen balance (95 +/- 7, 95 +/- 6 vs 139 +/- 7 mg/day) and nitrogen utilization (69 +/- 3, 67 +/- 3 vs 87 +/- 3%) compared with the control group. Administration of energy substrate in the SA and SB was a stronger denominator for O2 consumption and changes in RQ than the periods of physical activity. Control animals did not show any diurnal variations in O2 and RQ. Glucose, FFA and insulin were higher with CHO + FAT administration compared to AA infusion or simultaneous AA/CHO/FAT administration. In conclusion, the results suggest that simultaneous administration of a mixture of AA/CHO/FAT is preferable for whole body nitrogen economy during TPN.

Amino Acids↗
PubMed1985

Identification and Quantification of Indole-3-methanol in Etiolated Seedlings of Scots Pine (Pinus sylvestris L.).

Combined gas chromatography-mass spectrometry has been used to identify indole-3-methanol in a purified buffer extract from etiolated seedlings of Pinus sylvestris L. Quantitative estimates obtained by high performance liquid chromatography with fluorescence detection, corrected for losses occurring during purification, indicated that etiolated seedlings of P. sylvestris contained 19.7 +/- 1.4 nanograms (+/- standard deviation) indole-3-methanol per gram fresh weight. The stability of indole-3-methanol at different pH levels was investigated. The rate of conversion, to a less polar unidentified substance, was enhanced with increasing acidity.

Journal Article↗
PubMed1985

The adenosine receptor activity of EMD 28422, a purine derivative with reported actions on benzodiazepine receptors.

The effects of a novel purine derivative, N6-[2-(4-chlorophenyl)-bicyclo-2.2.2.octyl-(3)]-adenosine (EMD 28422), that has been found to influence central benzodiazepine receptors, has been compared to those of other adenosine analogues such as L-phenylisopropyladenosine (L-PIA), cyclohexyladenosine (CHA) and adenosine-5'-N-ethyl-carboxamide (NECA). EMD 28422 was about 30 times less potent than CHA and 4 times less potent than NECA in displacing bound [3H]-L-PIA from specific binding sites in the rat brain, presumably reflecting adenosine A1-receptors. A similar relative potency was found using depression of field e.p.s.p. in the hippocampal slice in vitro. In isolated fat cells EMD 28422 was antilipolytic, but some 1000 times less potent than L-PIA. In rat isolated hippocampal slices, which have adenosine A2-receptors, EMD 28422 was more than 300 times less potent than NECA and in guinea-pig thymocytes, which similarly have A2-receptors, EMD 28422 was about 60 times less potent. The results are compatible with the opinion that EMD 28422 is a rather weak agonist at adenosine receptors, with limited selectivity for A1- or A2-receptors. The compound is highly lipophilic, which plays a role in determining its potency in a given biological system. The results are discussed in relation to reported adenosine modulation of benzodiazepine receptors.

Adenosine↗
PubMed1985

A simple method for electronic counting of rosette forming human blood lymphocytes.

We investigated the possibility of using a standard electronic laboratory cell counter, of a type which permits manual settings of discriminator and sensitivity levels, for the quantitation of E rosette forming human blood lymphocytes. The electronic counting was performed on rosette specimens prepared from 10 healthy donors, nine lymphoma patients and eight patients with chronic lymphocytic leukaemia (CLL) of B cell type. The simple procedure which was earlier developed for the electronic counting of thymocyte rosettes in guinea-pigs was used and now supplemented with a method for rapid, graphical determination of rosette frequency. The low level of E rosettes in CLL patients was easily distinguished from the higher level seen in the other groups and there was a good agreement between electronic and visual determinations. In samples with a high rosette frequency, the cell counter initially gave 10-30% lower values than when recorded visually. This discrepancy was corrected, however, by a minor adjustment of discriminator level and the introduction of a correction procedure for the presence of double rosettes. We conclude that the electronic counter can well be used for the counting of human rosette forming blood lymphocytes and, due to a high precision and large capacity, this approach would prove to be useful when screening of a large number of samples is required.

Electronics↗
PubMed1984

Studies on thymocyte subpopulations in guinea pigs. IV. A subpopulation sensitive to a natural, cold reactive cytotoxic factor in autologous serum.

Guinea pig serum was shown to be cytotoxic against a subpopulation of autologous thymocytes. The sensitive cells belonged to the population of small, high-density cells, constituting the majority of cortical thymocytes. In this respect, the activity resembled that of some heterologous sera tested (rat, rabbit) and allogeneic serum. The same population was also particularly reactive in rapid early (RE) migration [Sandberg, 1981] induced by rat serum. Human serum differed from other tested sera both as regards cytotoxicity and RE migration. The cytotoxic effect of autologous serum was demonstrated at 4 degrees C, whereas it was absent at 37 degrees C. The latter is in contrast to the cold reactive thymocytotoxic autoantibodies previously described in some mouse strains, and it is also in contrast to thymocytotoxic factors in heterologous serum. In all tested sera, the activity was completely inhibited by incubation at 56 degrees C for 30 min. The results may be relevant for the understanding of normal cell death in the thymus, and are discussed in relation to lymphocytotoxic autoantibodies in various disease states in man and animals.

Animals↗
PubMed1984

Studies on thymocyte subpopulations in guinea pigs. V. Rosette formation as a tool to separate thymocyte growth factor responsive and mitogen reactive cells.

78% of guinea pig thymocytes formed rosettes after 1 h incubation with rabbit erythrocytes. They were separated from nonrosetting cells by layering over a Percoll solution and centrifugation. The nonrosetting cells (RE-) contained a large proportion of spontaneously DNA synthesizing cells as well as cells able to cooperate in a proliferative response to the mitogenic lectins concanavalin A and phytohemagglutinin. In contrast, cells which responded to a thymocyte growth factor were rosette forming (RE+). Proliferating thymus cells were earlier shown to reside in a low density population called Ia. Here we show that, whereas both RE+ and RE- cells of population Ia contain proliferating cells, only the RE+ respond to the growth factor. Thus, the formation of 'early' rosettes can form the basis for enrichment of thymocyte growth factor responsive cells and the simultaneous separation of these from mitogen reactive cells.

Animals↗
PubMed1983

Regulation of thymocyte proliferation by endogenous adenosine and adenosine deaminase.

Spontaneous proliferation of thymocytes after 20-25 h of culture was significantly increased by the presence of adenosine deaminase (ADA) or theophylline. The effect of ADA was counteracted by the ADA inhibitor EHNA. When given alone, EHNA inhibited proliferation. This effect was not blocked by inhibition of adenosine uptake with dipyridamol. These results suggest that proliferation in culture is regulated by a balance between endogenous adenosine and ADA, controlling the influence of adenosine on the intracellular cyclic AMP level via an adenosine receptor on the surface of thymocytes. According to the hypothesis, ADA would stimulate proliferation by decreasing extracellular adenosine levels and theophylline by blocking adenosine receptors on thymocytes. EHNA would inhibit proliferation by increasing extracellular adenosine levels. In accordance with this interpretation, the adenosine analogue phenylisopropyl adenosine (PIA) inhibited proliferation and the effect could be inhibited by theophylline. The postulated effect of endogenous adenosine could not be mimicked by a single administration of exogenous adenosine. Whereas most doses of adenosine were without effect, a high dose of adenosine (0.1 mM) in combination with EHNA unexpectedly stimulated proliferation. Since the effect was blocked by dipyridamol, an intracellular site of action for adenosine is suggested in this case.

Adenine↗
PubMed1983

Inhibition by xanthine derivatives of adenosine receptor-stimulated cyclic adenosine 3',5'-monophosphate accumulation in rat and guinea-pig thymocytes.

The effect of stable adenosine analogues, including adenosine 5'-N-ethylcarboxamide (NECA) and N6-L-phenylisopropyl-adenosine (L-PIA), were studied on cyclic adenosine 3', 5'-monophosphate (cyclic AMP) accumulation in rat and guinea-pig thymocytes. NECA was approximately 10 times more potent than L-PIA, in thymocytes from both species. D-PIA was more potent in guinea-pig than in rat thymocytes. The effect of a number of adenosine analogues followed the order: NECA greater than 2-chloro-adenosine greater than L-PIA greater than N6-cyclohexyl-adenosine (CHA), an order of potency characteristic for adenosine receptors of the A2-subtype. Thymocytes may be used as a model system to study the pharmacology of such receptors. Several xanthines were studied as antagonists of the NECA (1 microM)-induced cyclic AMP accumulation. The order of potency was: 1,3-diethyl-8-phenylxanthine greater than 8-phenyl-theophylline greater than IBMX = 8-p-sulphophenyltheophylline = verrophylline greater than theophylline greater than caffeine greater than enprofylline greater than theobromine greater than pentoxiphylline. The pA2 value for 8-phenyltheophylline was 0.35 microM, and the antagonism was shown to be competitive. The order of potency of the xanthine is virtually identical to that found earlier in several other systems in which the receptors are of the A1-subtype. None of the xanthine derivatives tested thus seem to discriminate between A1 and A2-receptor-mediated adenosine actions.

Adenosine↗
PubMed1983

Leukocytes from patients allergic to chromium and nickel examined by the sealed capillary migration technique.

Leukocytes from patients allergic to chromium and nickel were studied by a sealed capillary migration test. The migration indices were determined at 2, 5 and 24 h. The chromium-allergic group could be differentiated from the control group at all investigated times, and especially at 2 and 5 h, by using a potassium dichromate concentration of 1.7 x 10(-5) M in the capillaries. The migration indices in the nickel-allergic group could not be used for discrimination from the controls. The highest chromate (1.1 x 10(-4) M) and nickel sulfate (3.8 x 10(-4) M0 concentrations inhibited the migration of leukocytes from both patients and controls, indicating toxic effects.

Cell Migration Inhibition↗
PubMed1983

Studies on thymocyte subpopulations in guinea pigs. 2. Three subpopulations differing in rosette-forming ability, as detected by both visual and electronic counting of rosettes.

Rosette-forming cells were counted in three thymocyte subpopulations separated by density gradient centrifugation with Percoll. A method for the electronic counting of rosettes is described which resulted in excellent agreement with results of visual counting. By both methods, significant differences in the rosette-forming ability of the studied subpopulations were detected. Thus, in population Ia, earlier shown to consist of large cells of low density and with high spontaneous proliferative activity, the rosette frequency was 54% as compared with 70% in the whole thymus population and 83% in population II, known to consist of small, immunologically incompetent cells. The third population studied (Ib), consisting of intermediate density cells, had 74% rosette-forming cells.

Animals↗
PubMed1983

Studies on thymocyte subpopulations in guinea pigs. III. Physical and functional characterization of six subpopulations separated by density gradient centrifugation and PNA binding.

Thymocytes were separated according to increasing buoyant density into the three subpopulations Ia (25% of recovered cells), Ib (20%) and II (55%), and according to binding to peanut agglutinin (PNA)into PNA+ (65%) and PNA- cells (35%). The frequency of PNA+ was 56% in Ia, 60% in Ib and 66% in population II. Electronic cell volume determinations disclosed mean volumes of 160 fl for Ia, 130 fl for Ib and 100 fl for population II. PNA+ and PNA- cells were very similar as regards cell volume. Thus, PNA+ and PNA- cells are remarkably uniformly distributed among cell categories of different density and cell volume. The rapidly cycling thymocytes, regarded as the most immature cells in the thymus, and the target cells for a thymocyte growth factor both belonged to the PNA+ cells of population Ia. The mitogen-responsive thymocytes also belonged to population Ia, but were PNA-. The largest subpopulation of thymocytes, apparently corresponding to the small, non-cycling cortical cells, were recovered as PNA+ cells of population II.

Animals↗
PubMed1982

Studies on thymocyte subpopulations in guinea pigs. Differences in cell volume and proliferative ability in vitro of two populations separated by density gradient centrifugation with Percoll.

Thymus cells from guinea pigs were separated according to buoyant density by centrifugation with PVP-coated colloidal silica particles (Percoll). By creating an S-shaped density gradient, two populations (referred to as peak-I and peak-II cells) were obtained which differed in size as well as ability to spontaneous proliferation in vitro. Peak I contained low density cells of large size and was highly enriched with DNA-synthesizing cells. These continued to proliferate in culture for at least 30 h as demonstrated by mitotic studies in the intervals 0-10 and 20-30 h. In order to grow in vitro, however, the cycling cells of peak I depended on the medium (RPMI 1640) being supplemented with L-alanine. The high density cells of peak II constituted 70% of the thymocytes and had a small and uniform volume. This population was depleted of proliferating cells. The simple and rapid separation of these two major populations is considered a useful first step for the further characterization of thymocyte subpopulations. We suggest that peak I primarily includes proliferating precursor cells from the cortex as well as mature, immunocompetent cells. Peak II consists largely of small cortical cells.

Animals↗
PubMed1981

RE migration: an in vitro phenomenon of certain lymphoid cells induced by heterologous serum.

RE (rapid, early) migration designates the greatly increased migration of guinea pig thymus cells in glass capillaries upon addition of a high concentration of normal human serum. Such migration exceeded random locomotion sevenfold and was terminated within 60 min. Serum activity was abolished by treatment at 56 degrees C for 30 min and was inhibited by addition of homologous serum. Neither spleen nor lymph node cells were induced to migrate in this manner by serum. The presence of inhibitory cells in these organs, and their presence in variable but lower amounts also in the thymus, is suggested. Normal human serum was highly cytotoxic for thymus cells and somewhat less toxic for lymph node cells. However, the results indicate the RE migration is either independent of the cytotoxic effect of heterologous serum or else requires that a very high percentage of the cells are killed. The killing of thymocytes by several other means did not induce RE migration. In addition to demonstrating and quantitating this thymocyte-reactive factor in various sera, RE migration may be used for characterization of subpopulations of lymphocytes.

Animals↗
PubMed1981

Regulation of thymocyte proliferation: effects of L-alanine, adenosine and cyclic AMP in vitro.

Thymocyte proliferation in culture was studied by measuring the mitotic activity at hourly intervals during two periods, 0-13 and 18-30 h after the start of incubation. In particular, we investigated the effect of increased levels of cyclic AMP which are generated during preparation of the cells due to influence of endogeneously released adenosine. This cycle AMP surge, which could be blocked by combined treatment with adenosine deaminase and theophylline, caused a transient inhibition of proliferation at a stage 4 h prior to mitosis, suggesting a cyclic AMP-sensitive step in that part of the cell cycle. The temporary rise of cyclic AMP did not trigger any resting cells to proliferate. Addition of adenosine deaminase plus theophylline stimulated mitotic activity in the 18-30 h interval, possibly by blocking the influence of continuously released adenosine. The growth of thymocytes was partly synchronous, which was independent of the early cyclic AMP peak. About half of the cycling cell population was shown to be critically alanine dependent. L-alanine deprivation inhibited these cells at a stage in the cell preparation, release of prostaglandins and changes in cell viability could not explain the synchronous growth. The selective elimination of late S- and G2-phase cells during preparation of thymocytes is offered as a possible explanation instead.

Adenosine↗
PubMed1981

Growth and nitrogen utilization in rats on continuous and intermittent parenteral nutrition with and without fat (Intralipid 20%).

A rat model relevant to paediatric praxis was designed in order to evaluate possible differences between total parenteral nutrition (TPN) with fat (Intralipid 20%), and isocaloric TPN without fat and also to compare continuous TPN (24 hours/day) versus intermittent TPN (12 hours/day). TPN with fat resulted in better growth and nitrogen utilization. Continuous TPN with fat resulted in statistically significant better nitrogen utilization. The results suggest that TPN in paediatric praxis should be continuous and include fat.

Animals↗
PubMed1980

Serum factors modulating in vitro migration of thymus lymphocytes.

Migration of guinea pig thymocytes in sealed glass capillaries was measured in 3 intervals during 24 h of incubation. Two factors present in guinea pig sera which stimulated migration were partly characterized. One factor, with a molecular weight between 10,000 and 100,000 (as judged by ultrafiltration), stimulated migration during the first 2 h of incubation but not later. Only about one third of the sera had this activity. The other factor, which was present in most sera, had a molecular weight exceeding 100,000 and stimulated migration only at later times. Both factors were heat stable and resisted freezing and thawing as well as lyophilization, but were inactivated by storage of sera. Normal human sera stimulated migration from 2 h after start of incubation but, in contrast to guinea pig sera, had a slightly inhibitory effect during the first 2 h. Thymectomy had no effect on guinea pig or human sera as regards ability to modulate migration. Patients with defects in cell mediated immunity did not exhibit any specific alterations in serum activity. However, active disease as well as operations performed on guinea pigs reduced the late stimulatory activity. Additional experiments indicated that migration of thymus cells in glass capillaries depends partly on factors other than cell motility.

Animals↗