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Biomedical subjects

B Larsson

Publications and source records attributed to B Larsson.

At least 379 records · Page 21Linked to original sources
PubMed1981

The possible risks of a copper and an inert intrauterine device situated in the abdominal cavity: an experimental study in pigs and dogs.

The possible injurious effects of abdominal intrauterine devices (IUDs), including Cu-IUDs, inert IUDs, and "closed' IUDs, were evaluated in an experimental study. Pigs and dogs were used as they have, respectively, a propensity to form adhesions and a pronounced tendency to develop serious peritonitis. The reactions expected in humans might be intermediate to those found in these two kinds of experimental animals. The results of this study indicate that an inert or copper-bearing IUD usually remains in its initial position in the abdominal cavity, encapsulated by adhesions. The risk of strangulation of the intestine by a "closed' IUD seems minimal.

Animals↗
PubMed1981

Concentrations of copper in human secretions and weight of the copper wire during the 4 to 7 years after insertion of a Cu-IUD (intrauterine device).

The useful life span of the two most commonly used copper intrauterine devices (Cu-IUDs) (Gravigard and Cu-T) was investigated in a long-term study up to 90 months after insertion. Minor differences between the two types of devices were found that, however, probably do not contribute to a diverging contraceptive efficacy with time. To be able to ensure maximal contraceptive effect, the authors suggest on the basis of the present data that the time of use not exceed 5 to 6 years.

Adolescent↗
PubMed1981

Incorporation of thiouracil and some related compounds into growing melanin.

Several drugs, mainly polycyclic amines, are accumulated in melanin-containing tissues. They are bound to preformed melanin (both in vivo and in vitro). Thiouracil is accumulated into melanin according to another principle: It is incorporated as a false precursor during melanin formation. It is thus taken up only in growing melanin, e.g. in the eye of pigmented mouse foetuses or in melanomas. The acceptance of a foreign substance during the formation of a foetal tissue seems theoretically important. We are also interested in the practical viewpoint of using false melanin precursors as selective melanoma seekers. Some related substances are therefore compared with respect to incorporation into growing melanin. The thiouracil uptake in the ocular melanin of a 5 day old mouse was 276 times higher than that of a 3 month old mouse based on weight units of melanin. Thiourea is incorporated in growing melanin as well but also binds slightly to preformed melanin. Uracil and fluorouracil showed no specific uptake into growing melanin. It thus seems as if the sulfur is essential for the incorporation into the melanin polymer. 35S-thiouracil and 2-thio(2-14C)urcal showed the same high uptake, indicating that at least part of the uracil moiety is incorporated together with the sulfur. There seems to be a relation between the property to be incorporated into melanin and the tyrostatic activity. Both in the formation of melanin and thyroid hormones, tyrosine is the physiological precursor and both reactions are catalyzed by oxidizing enzymes. Properly labelled thiouracil derivatives seem to be promising melanoma seekers for diagnostic and radiotherapeutic purposes.

Animals↗
PubMed1981

WHO collaborative breast feeding study. II. Levels of lead and cadmium in Swedish human milk, 1978-1979.

Individual samples of human milk collected in Uppsala at 3 months post partum (18 samples) and 6 months post partum (23 samples) from 21-35-year-old healthy mothers were analysed for lead and cadmium by flameless atomic absorption spectrometry. The median lead content in the 41 samples was 2 microgram/kg fresh weight (range 0.5-9.0 microgram/kg), and the median cadmium level was 0.1 microgram/kg. There were no appreciable differences between the 3-month and 6-month samples as regards lead or cadmium levels. The calculated median weekly intakes of lead and cadmium by the 3-month-old infants (who received nothing else except breast milk) were approx. 2 microgram and 0.1 microgram/kg body-weight, respectively. There is no reason to believe that these low intakes of lead and cadmium constitute any risk to the health of the child. The intake of these metals by the breast-fed infant is likely to be the same as or somewhat lower than that of infants fed human milk substitutes and certainly less than that of children fed cereal-based infant foods.

Adult↗
PubMed1981

Binding of 14C-spermidine to melanin in vivo and in vitro.

It has been shown that melanin has the properties of a polyanion and may in vivo and in vitro bind inorganic cations and drugs which are positively charged at physiological pH by a cation-exchange mechanism. In the present study, we explored if the organic aliphatic polycation spermidine would bind to melanin in vivo after administration of 14C-spermidine to pigmented mice and in vitro at incubation with pigment from beef-eyes. The results showed a high labelling of the pigmented tissues in the mice after the administration of 14C-spermidine. At long survival intervals, the radioactivity in the melanin was higher than in any other tissue. A strong melanin affinity of 14C-spermidine was found in vitro. An analysis of the binding by the method of Scatchard showed that the data could be best fitted by the assumption of two classes of binding sites. The in vivo bound material could be displaced by in vitro incubation in solutions containing inorganic cation-chloride salts or HCl and HCl was also very effective in inhibiting the melanin-binding of 14C-spermidine in vitro. The results indicate that an electrostatic interaction between spermidine and melanin will occur both in vivo and in vitro.

Animals↗
PubMed1981

Radiation effects on cultured human lymphoid cells. Analysis using the growth extrapolation method.

The cloning efficiency of human normal and malignant lymphoid cells is usually low. Radiation effects in vitro on such cells can therefore not be analysed with conventional cloning. However, this problem can be circumscribed by using the growth extrapolation method. A panel of human leukemia-lymphoma cell-lines representing Epstein-Barr virus carrying lymphoblastoid cells of presumed nonneoplastic derivation and neoplastic T- and B-lymphocytes was used to test the efficiency of this method. The sensitivity to radiation could be determined for all these cell types. The growth extrapolation method gave generally the same result as conventional cloning demonstrated by comparison with one exceptional cell-line with capacity for cloning in agar. The sensitivity varied largely between the different cell types. A common feature was that none of the cell lines had a good capacity to accumulate sublethal radiation injury.

Cell Division↗
PubMed1980

Prostaglandins and thromboxanes in amniotic fluid during rivanol-induced abortion and labour.

Abortion or delivery were induced by extra-amniotic instillation of Rivanol during the second trimester in twelve patients and during the third trimester in two patients with fetal death and one patient with fetal acrania. Serial sampling of amniotic fluid was performed through a transabdominal catheter and the levels of free arachidonic acid (AA), prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TXB2) were determined. The levels of AA, PGF2 alpha, PGE2, 6-keto-PGF1 alpha and TXB2 in amniotic fluid increased significantly during induction with the exception of AA in fetal death which was high and remained constant during induction. Furthermore, PGF2 alpha, 6-keto-PGF1 alpha and TXB2 were all significantly correlated to AA. These observations suggested that free AA is released during Rivanol-induction of abortion and labour giving an increased synthesis of PGF2 alpha, PGE2 prostacyclin and thromboxane A2 in the fetal membranes and the decidua but not in the fetus. This increase might be relevant for the initiation and progress of abortion and labour in these patients.

Abortion, Induced↗
PubMed1980

Vincristine reduces damage of the blood-brain barrier induced by high intravascular pressure.

A reversible opening of the structural blood-brain barrier (BBB) was accomplished in rats by rapidly increasing the hydrostatic pressure either through forced intracarotid infusion of autologous blood or i.v. administration of angiotensin, whose effect was exaggerated by previous injection of the vasodilator, papaverine. The extent of barrier damage was evaluated in terms of the extravasation of Evans blue-albumin complex or the brain uptake of circulating [14C]inulin. Pretreatment of the animals with the antimitotic agent, vincristine, significantly reduced the barrier damage. This is interpreted as an effect of vincristine on intracellular microtubule systems, which may be involved in the vesicular transport across the endothelial cells of brain microvessels.

Angiotensin II↗
PubMed1980

Survival of irradiated glia and glioma cells studied with a new cloning technique.

A method allowing cloning of monolayer cultured cells with a low plating efficiency was developed. Cells were grown in several small palladium squares to obtain a high cell density. These squares were surrounded by non-adhesive agarose to prevent large distance migration and thereby mixing of the clones. By using easily-cloned hamster cells for comparison it was found that the survival curves were similar to the curves obtained with conventional cloning. The new method was used to compare the radiosensitivity of cultured human glia and glioma cells which both have a low plating efficiency (less than 5 per cent) when seeded sparsely. The survival curves for the glioma cells had high Do-values (1.5--2.5 Gy) and large shoulders (extrapolation numbers around 5) indicating that they were rather resistant and had a high capacity for accumulation of sublethal damage. The survival curves for glia cells had lower Do-values (1.3--1.5 Gy) and no shoulders at all, indicating that they were more sensitive than the glioma cells.

Animals↗
PubMed1980

Inhibition of hepatic chylomicron remnant uptake in the cholestatic rat.

[3H]retinal- or [3h]cholesterol- and [14C]fatty acid-labeled chylomicrons and chylomicron remnants were injected intravenously into normal rats and rats subjected to partial or total obstruction of the bile duct 8 or 48 h earlier. The clearance from plasma of the [3H]retinyl and the [3H]cholesteryl esters in 30-120 min was markedly decreased in rats with total obstruction, and the uptake of 3H by the liver was significantly less than in control rats. The elimination of the [14C]triacylglycerol of the native chyle lipoprotein was not significantly affected, and the delayed plasma clearance was seen also when the [3H]lipid ester radioactivity was injected as chylomicron remnants prepared in vitro. If only one of the two main bile duct branches was ligated, the uptake of radioactivity did not differ markedly in the obstructed and unobstructed part of the liver and only small effects on the plasma disappearance were seen. The defective clearance of the chylomicron remnants was thus not related to the obstructed bile flow per se but rather to the consequences of the total obstruction, such as the high plasma bile acid level or the accumulation of abnormal lipoproteins in plasma.

Animals↗