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T Jansson

Publications and source records attributed to T Jansson.

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

Computer-assisted realignment of light micrograph images from consecutive section series of cat cerebral cortex.

Two computer- and image-analysis-based procedures for realignment of images of consecutive light micrographs of nerve tissue (cat motor cortex) have been developed. One procedure (CENT) was interactive, employing the subjective overall 'best fit' of two images to each other and the other (AUTOCENT) was based on an automatic comparison of two images (image thresholding and binary comparison). Images of light micrographs of several hundred consecutive sections were realigned using the interactive and the automatic methods. The interactive procedure was easy to use; realignment of an image took only a few minutes in the hands of an experienced operator and should be easy to implement on commercially available smaller computers like PCs and workstations, but the realignment was possibly disturbed by the operator's subjective expectancy of regular forms. The automatic procedure realigned 1-4 images per hour, might be implemented on smaller computers if the programming is made more efficient, was probably objective and restored the 'true position of images'.

Animals↗
PubMed1991

Genotoxicity testing of extracts of a Swedish moist oral snuff.

The present study was designed to investigate the potential genotoxicity of aqueous and methylene chloride extracts of Swedish moist oral snuff. The test systems were selected to provide optimal data for the prediction of carcinogenicity in rodents and included assays for the induction of mutation in bacteria, sister-chromatid exchanges (SCE) in human lymphocytes, of chromosome aberrations and gene mutations in V79 Chinese hamster cells and of micronuclei in mouse bone marrow cells. In addition, the methylene chloride extract was tested for the induction of sex-linked recessive lethal mutations in Drosophila melanogaster. The aqueous extract of 'Snus' induced SCE in human lymphocytes and chromosome aberrations in V79 cells, the latter effect being observed both with and without metabolic activation. No induction of point mutations was detected with the Ames test or in V79 cells and the micronucleus test in mice was negative. It was demonstrated that the induction of chromosome aberrations without metabolic activation may be due to a high salt concentration, indicating that the clastogenic agent(s) in this extract required metabolic activation. The methylene chloride extract showed genotoxicity in the Ames test, the SCE test and the chromosome aberration test, whereas no induction of gene mutations in V79 cells was observed. Once again, the results suggested that metabolism is required for genotoxicity. The methylene chloride extract did not cause induction of micronuclei in mice or of sex-linked recessive lethal mutations in Drosophila melanogaster. These combined data on genotoxicity were analyzed using various models for the prediction of carcinogenicity. In a sequential testing model, the probabilities that the aqueous and methylene chloride extracts of 'Snus' are carcinogenic due to a genotoxic mechanism were both predicted to be low. Using carcinogenicity prediction by battery selection (CPBS), the probabilities of the methylene chloride and aqueous extracts being correctly identified as non-carcinogens are 71 and 77%, respectively. Up to date, the CPBS approach has been validated primarily for individual compounds, so some caution should at present be exercised in interpreting the results using this method. Based on these results, the carcinogenic potential of Swedish 'Snus' should be considered to be low, a conclusion in agreement with the low incidence of oral cancer in Sweden compared to other countries.

Animals↗
PubMed1991

The microsphere technique in anaesthetized and awake pregnant guinea-pigs: reproducibility of repeated blood flow measurements.

Repeated microsphere injections are extensively employed for measurements of uteroplacental blood flows in experimental animals. However, this technique has not been systematically validated in pregnancy. In the present series of experiments the effects of three consecutive microsphere injections on central haemodynamics and regional blood flows were studied in 43 late pregnant guinea-pigs. In group A (n = 13) experiments were carried out in the awake chronically catheterized animal. In group B (n = 8) animals were studied under anaesthesia. In two additional anaesthetized groups reference withdrawal rate (C, n = 7) and the amount of injected spheres (D, n = 7) were increased 2-3 fold. Cardiac output, mean arterial blood pressure, heart rate as well as regional blood flows to placenta, ovaries, kidneys, heart, liver and carcass remained unaltered in all protocols. Myoendometrial blood flow increased in group A and C and a similar pattern could be demonstrated in group B and D but was not statistically significant. Adrenal blood flow was enhanced in groups A and C and brain blood flow increased in group C and D. The gastrointestinal tract especially the stomach was sensitive to repeated microsphere injections since blood flow reductions were apparent in all groups but were statistically significant only for groups A and D. In group E (n = 8), the three microsphere labels were injected simultaneously. The coefficients of variability for these blood flow measurements were in the range of 3.6-6.8% for different organs. It is concluded that repeated microsphere injection in an ideal method to measure placental blood flow. However, the technique may provide inaccurate results with respect to the myoendometrium and gastrointestinal tract.

Animals↗
PubMed1991

Cerebral function of the guinea pig neonate after chronic intrauterine exposure to khat (Catha edulis Forsk.).

Cerebral function in normoxia and its reactions to standard periods of hypoxia of increasing severity were studied in 30 newborn guinea pigs less than 3 days old. Intrauterine growth retardation was induced either by uterine artery ligation at midgestation or by feeding the female in late gestation with khat leaves, an amphetamine-like stimulant chewed by men and women in several countries in eastern Africa and Arabia. After spontaneous delivery, the neonates were anesthetized and ventilated. Cardiovascular, metabolic, and neurophysiologic (somatosensory evoked potentials) parameters were monitored. Under normoxia, the khat-exposed group showed prolonged latency of the primary response of the somatosensory evoked potentials and a reduced amount of secondary components. Under hypoxia, this group also has a greater reduction of amplitude of the somatosensory evoked potentials. It is concluded that khat exposure during fetal life has an impact on the cerebral function during the neonatal period (at least up to 3 days of age) which is not solely explained by the concomitantly produced growth retardation.

Animals↗
PubMed1991

ECG waveform, short term heart rate variability and plasma catecholamine concentrations in response to hypoxia in intrauterine growth retarded guinea-pig fetuses.

After unilateral uterine artery ligation in midpregnancy twelve guinea-pig does were anesthetized at 63 days of gestation. The ST waveform of the fetal electrocardiogram and the short term heart rate variability were studied during normoxia and in response to acute hypoxia in growth retarded fetuses (n = 12, mean +/- SEM, 58.5 +/- 3.9 g) and their normal sized littermates (n = 12, 94.3 +/- 3.5 g). Hypoxia was induced by letting the doe breathe a low-oxygen gas mixture. After 10 min of hypoxia fetal blood was sampled by decapitation and blood gases, acid-base status and catecholamine concentrations were analyzed. The does responded to decrease in inspired oxygen concentration with changes in oxygen tension (13.8 +/- 0.8 to 4.3 +/- 0.2 kPa) and oxygen saturation (99.9 +/- 0.1% to 70.5 +/- 1.8%). Fetal blood gases and plasma catecholamine concentrations did not differ between the groups. In the growth retarded group standard bicarbonate was significantly lower compared to controls. The T/QRS ratio (the quotient between T wave height and QRS peak to peak amplitude) was normal and similar in both groups prior to the hypoxic period. In response to hypoxia T/QRS ratio increased in the normal sized group and T/QRS was correlated to carbon dioxide tension, oxygen saturation, pH, lactate, standard bicarbonate concentration, standard base excess and plasma noradrenaline concentration, respectively. The growth retarded fetuses presented a completely different pattern where 7 out of 12 fetuses showed a biphasic ST waveform during hypoxia with depression and downward sloping of the ST segment and negative T wave.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of hypovolemia on blood flow, arterial [HCO3-], and HCO3- output in the rat duodenum.

The effects of bleeding-induced hypovolemia on duodenal blood flow (microsphere technique), arterial [HCO3-], and duodenal HCO3- secretion (in situ titration) were investigated in chloralose-anesthetized rats. A 10% decrease in blood volume reduced duodenal HCO3- secretion by 44%, duodenal blood flow by 31%, and arterial [HCO3-] by 11%. In a group with cervically cut vagal nerves, basal duodenal HCO3- secretion was greater than 50% lower compared with controls. Basal blood flow and arterial [HCO3-] were on similar levels as in nonvagotomized animals. Furthermore, bleeding failed to lower duodenal alkaline output in rats with cut vagal nerves, although blood flow and arterial [HCO3-] were reduced to a similar extent as in the vagally intact controls. In a yohimbine-treated group, a 10% bleeding reduced duodenal blood flow by 28% and arterial [HCO3-] by 7% without influencing duodenal HCO3- secretion. We suggest that the hypovolemia-induced inhibition of duodenal alkaline secretion is not caused by a decrease in blood and/or arterial [HCO3-]. Instead, other factors may be of importance, for example, neural effects on enteric secretomotor neurons or directly on the secreting epithelium.

Animals↗
PubMed1990

Placental transfer of glucose and amino acids in intrauterine growth retardation: studies with substrate analogs in the awake guinea pig.

After experimentally inducing growth retardation by unilateral uterine artery ligation in midpregnancy, placental blood flow (PBF) (microsphere technique) and placental transfer of 14C-aminoisobutyric acid (AIB) and 3H-methylglucose (MG) were studied at d 44, 50, or 63 of gestation in 19 chronically catheterized awake guinea pigs. At d 44, fetal wt (FW) and placental wt were reduced by 16 and 18%, respectively, in the ligated horn and FW/PBF was increased by 122%. Placental efficiency to transfer MG and AIB (fetal dpm/g placenta) was maintained in the ligated horn, feto-placental extraction (feto-placental dpm/PBF) was increased, and placental transfer of the substrate analogs (fetal dpm/g fetus) was unchanged. At d 50 and 63, placental wt and FW were reduced in proportion (approximately 40%) in the growth-retarded group and FW/PBF was increased by 80 and 51%, respectively. Placental transfer of AIB was reduced by 33% at d 50 and by 18% at d 63. In addition, placental efficiency to transfer AIB was reduced by 36% at d 50 and by 22% at d 63 in the growth-retarded group. Fetal uptake of MG per g fetus was slightly reduced (-6%) at d 50 of gestation, but unaffected at d 63. Extraction of MG from the maternal PBF was increased, whereas the wt-specific transfer capacity of the placenta was unaltered.(ABSTRACT TRUNCATED AT 250 WORDS)

3-O-Methylglucose↗
PubMed1990

Decreased responsiveness to noradrenaline, but not to diclofenac, of the growth-retarded guinea pig placental vasculature.

To examine vascular responsiveness of the growth-retarded placenta to noradrenaline and the cyclooxygenase inhibitor diclofenac, unilateral uterine artery ligation was carried out in 13 guinea pigs at 32 to 36 days gestation. Uteroplacental blood flows were measured with the microsphere technique at 49 to 52 days gestation in the chronically catheterized awake animal. During infusion of noradrenaline (1.5 nmol/min per kg) mean arterial blood pressure increased by 12% (P less than 0.001), placental blood flow in the normal-sized group decreased by 15% (P less than 0.01), while the growth-retarded placentas showed a different reactivity (P less than 0.001) in that an 8% increase in blood flow was observed. Diclofenac (1.5 mg/kg) caused small and statistically non-significant reductions in mean arterial blood pressure and blood flow to placentas of normal-sized and growth-retarded fetuses. It is concluded that the vessels supplying the growth-retarded placenta have a attenuated responsiveness to circulating noradrenaline and a delay in the pregnancy-induced sympathetic denervation is suggested as a mechanism. However, normal-sized and growth-retarded placentas did not differ in vascular response to inhibition of prostaglandin synthesis.

Animals↗
PubMed1990

ECG wave form, short term heart rate variability and plasma catecholamine concentrations in intrauterine growth-retarded guinea-pig fetuses.

Electrocardiogram waveform, short term heart rate variability and catecholamine concentrations were studied with maternally-induced anesthesia in eleven growth-retarded guinea-pig fetuses and their normal-sized littermates at 63 days of gestation. Intrauterine growth retardation was induced by unilateral uterine artery ligation performed between day 32 and 35. In the growth-retarded group fetal weight was reduced by 45%. Blood gases, acid-base status and oxygen content were similar in the two groups. The growth-retarded guinea-pig fetuses were hypoglycemic and demonstrated a rise in hemoglobin concentration. The T/QRS ratio (T wave amplitude/QRS amplitude) was similar in both groups. The short-term heart rate variability was significantly reduced in the growth-retarded group. Plasma catecholamine concentrations were increased in growth-retarded fetuses but differed only significantly for noradrenaline compared to controls. We suggest that similar T/QRS ratio in both groups of fetuses indicates that aerobic myocardial metabolism is maintained among growth-retarded fetuses. The mechanism behind the reduced variability is unclear.

Acid-Base Equilibrium↗
PubMed1988

Responsiveness to norepinephrine of the vessels supplying the placenta of growth-retarded fetuses.

The effects of intravenous norepinephrine infusions on uteroplacental blood flow were studied in seven awake, chronically catheterized guinea pigs at 63 to 64 days' gestation after unilateral uterine artery ligation at days 31 to 37. An initial subpressor dose of norepinephrine (1.54 +/- 0.18 nmol/kg.min) (+/- SEM) was given, followed by a pressor dose (4.57 +/- 0.59 nmol/kg.min) that caused a 14% increase in mean arterial blood pressure. Placental blood flow as measured by the microsphere technique decreased by 24% in 11 placentas with normal-sized fetuses during the subpressor dose and by 46% during the pressor dose. In 11 placentas with growth-retarded fetuses the two norepinephrine doses reduced blood flow by 19% and 43%, respectively. These results indicate that there is no difference in adrenergic responsiveness between the vessels supplying the placenta of a normal-sized fetus and the arteries of the placenta of a growth-retarded guinea pig. It is suggested that an increase in circulating maternal catecholamine levels would affect a growth-retarded fetus more severely than the normal-sized fetus because the growth-retarded fetus even during normal conditions exists at, or even beyond, the border of imminent asphyxia and hypoglycemia.

Animals↗
PubMed1988

In vitro studies of the biological effects of cigarette smoke condensate. III. Induction of SCE by some phenolic and related constituents derived from cigarette smoke. A study of structure-activity relationships.

Since our earlier studies of 23 individual weakly acidic constituents of cigarette smoke indicated that benzenes having vicinal oxygenation or a conjugated double bond induce sister-chromatid exchanges (SCE), we have now selected and examined a complementary set of 27 smoke constituents for their SCE-inducing properties. Of the 50 compounds tested in all, 23 were found to induce SCE, and these include all benzaldehydes but one and the majority of the compounds having a conjugated carbon-carbon double bond as well as several of the guaiacols. These groups of active compounds comprise important flavourants such as vanillin, ethylvanillin, isoeugenol and guaiacol. The structure-activity relationships encountered here may be useful in predicting the SCE-inducing activity of related compounds.

Benzaldehydes↗
PubMed1987

Effect of the khat alkaloid (+)norpseudoephedrine on uteroplacental blood flow in the guinea pig.

In order to investigate effects of khat chewing on uteroplacental blood flow (+)norpseudoephedrine (NPE) infusions were given to 11 anesthetized guinea pigs in late pregnancy (62-66 days) after unilateral uterine artery ligation at days 30-32. Regional blood flows were determined with radioactive microspheres. Mean arterial blood pressure increased with 25% and heart rate with 9% during NPE infusion. Myoendometrial blood flow was reduced by 31%. Placental vascular resistance (PVR) increased by 56% in the control horn (17 fetuses) and by 82% in the ligated horn (17 fetuses). This vasoconstriction was counteracted by the systemic vasopressor response since placental blood flow remained unchanged. When considering only the 13 growth-retarded fetuses, however, PVR increased by 98% and a 19% reduction of placental blood flow could be demonstrated. These results suggest that the placenta of the growth-retarded fetus may be more sensitive to adrenergic stimulation than the normal placenta. Furthermore, since one of the active constituents of khat, (+)norpseudoephedrine, causes vasoconstriction in the uteroplacental vascular bed it is possible that khat chewing could reduce placental blood flow and, as a consequence, impair fetal growth.

Animals↗
PubMed1986

Osseointegration in maxillofacial prosthetics. Part I: Intraoral applications.

Osseointegrated implants can provide anchorage and promote prosthesis stability in a variety of oral defect situations. The application of proven TIP fixture principles and techniques to these patients has allowed high level of function to be attained with great promise for longevity.

Dental Implantation, Endosseous↗
PubMed1986

In vitro studies of biological effects of cigarette smoke condensate. II. Induction of sister-chromatid exchanges in human lymphocytes by weakly acidic, semivolatile constituents.

Cigarette smoke condensate is known to enhance the frequency of sister-chromatid exchanges (SCE) in human lymphocytes in vitro and some of the activity has been found in the most volatile part of the particulate phase, the semivolatile fraction. In this study we have investigated the chemical composition and the SCE-inducing activity of the weakly acidic, semivolatile fraction of a cigarette smoke condensate. A number of individual weakly acidic compounds were also tested for their SCE-inducing effects. The weakly acidic fraction was separated by preparative gel chromatography into 11 subfractions (F1-F11). The chemical composition was determined by gas chromatography and gas chromatography-mass spectrometry. Measurements of the effects on SCE in human lymphocytes were used to evaluate the genotoxic effects. All fractions except F11 induced SCE in a dose-dependent way. The most active fraction was F4 which contained mainly alkyl-2-hydroxy-2-cyclopenten-1-ones. The individual compounds to be tested for induction of SCE were selected on the basis of their abundance in the weakly acidic subfractions and on the basis of their occurrence in the environment. Of 23 tested compounds, most of which were alkylphenols, 7 induced SCE, i.e., catechol, 2-(1-propenyl)phenol, cyclotene, maltol, isoeugenol, 2-methoxyphenol (guaiacol) and vanillin. Many of these are important flavor components that occur not only in tobacco and tobacco smoke but also in food, candies, beverages and perfumes.

Acids↗