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Biomedical subjects

T Jansson

Publications and source records attributed to T Jansson.

At least 91 records · Page 5Linked to original sources
PubMed1986

Placental blood flow and fetal weight following uterine artery ligation. Temporal aspects of intrauterine growth retardation in the guinea pig.

Placental blood flow (microsphere distribution), placental weight and fetal weight were examined at three stages of gestation following unilateral uterine artery ligation at days 30-32 in 23 guinea pigs. Placental blood flow and placental weight were reduced in the ligated horn at days 45, 55, and 65. The fetal weight was decreased at days 55 and 65. We suggest that ligation of the uterine artery reduces placental blood flow which, in turn, restricts placental growth without any significant effect on fetal weight before day 45. At this stage of gestation no correlation was found between fetal weight and placental blood flow. Later in gestation, however, fetal growth becomes limited by placental blood flow, and between days 45 and 55 ligation impedes the increase in blood flow, and consequently the fetal growth rate declines.

Animals↗
PubMed1986

Osseointegrated dental implants.

Endosseous implants of commercially pure titanium have been demonstrated to give success rates of more than 90 per cent over 10 years of follow-up. This high level of clinical function depends on an implant direct anchorage in bone without any interposed soft tissue layers and on a reaction-free soft tissue surrounding the abutments. Provided a correct protocol is followed, such osseointegrated dental implants may be looked upon as a routine procedure in the treatment of edentulousness.

Biocompatible Materials↗
PubMed1985

Relationship between myoelectric activity in masticatory muscles and bite force.

Myoelectric activity in the anterior and posterior temporalis and in the masseter muscle was assessed in five subjects biting unilaterally on a bite fork at 50, 100 and 200 N for 60 s. The bite fork was placed between the right first premolars and the first molars. The ipsilateral muscle activity was recorded first, and the contralateral side was evaluated 1 wk later. The relationship between exerted force and EMG-activity was expressed as ratios between EMG-activity and related bite force. EMG-activity increased with increasing force for all muscles tested. Linearity was found for the anterior temporal muscle, but not for the other muscles. Four of the subjects participated in an endurance test, exerting maximum bite force on the right side for as long as possible. The EMG activity of the right masseter muscle was closely related to bite force, in contrast to the other tested muscles. The activity of the left muscles increased at the end of the endurance test.

Adult↗
PubMed1984

Evaluation of the biological activity of cigarette-smoke condensate fractions using six in vitro short-term tests.

The biological activity of the volatile part of the particulate phase of cigarette-smoke condensate, the semivolatile fraction, has been examined, since the constituents of this material are accessible to selective filtration. Such a process offers a possibility to reduce the biological activity of total cigarette smoke without appreciably affecting the taste. Cigarette-smoke condensate, obtained from domestic American blend type cigarettes, was therefore separated into a nonvolatile and a semivolatile fraction, and the latter was fractionated by liquid-liquid extractions into four subfractions; acids, phenols, bases, and neutrals. The biological activity of these fractions was investigated using six in vitro short-term tests, of which two, the Ames test and the induction of sister chromatid exchanges, provided information on their genotoxicity, and the other four provided information on their cytotoxicity by measuring inhibition of cell growth, inhibition of oxidative metabolism, membrane damage, and ciliotoxicity. Sister chromatid exchanges were found to be induced by the total condensate, the nonvolatile and the semivolatile fractions, and the subfractions derived from the semivolatile fraction, except the bases. The Ames test showed the total condensate and the nonvolatile fraction to contain direct-acting base-pair mutagens as well as indirect-acting frameshift mutagens. While the semivolatile fraction was found nonmutagenic, two of its subfractions, acids and phenols, were shown to contain base-pair mutagens, which did not require metabolic activation. The total condensate and the nonvolatile and semivolatile fractions showed similar activity in the four cytotoxicity tests. Of the semivolatile subfractions, the acids and the phenols exhibited the highest activity and the bases the lowest; the toxicity observed for the neutrals varied with the test system used.

Animals↗
PubMed1982

Mutagenicity of some indoles and related compounds in the Ames test.

A series of indole derivatives and some analogues were tested for mutagenic activity using a histidine-requiring mutant of Salmonella typhimurium (TA 98). Quantitative tests were performed with and without addition of a liver fraction (S-9) from rats induced with Aroclor 1254. Three compounds, 2,3-dimethylindole, 2,3,5-trimethylindole and 2,3,6-trimethylindole, showed a mutagenic effect which was not increased on metabolic activation. The influence on the mutagenic activity of the number and positions of the substituents attached to the indole skeleton is discussed.

Animals↗
PubMedDate not supplied

Comparison between measurements of maternal placental blood flow with dynamic placental scintigraphy and radioactive microspheres.

Two methods for measurements of maternal placental blood flow were compared, dynamic placental scintigraphy using 113mIndium and the radioactive microsphere distribution technique which was the reference method. These methods were both used before and after the blood flow was altered by a noradrenaline infusion in pregnant monkeys (Macaca fascicularis). The change of the blood flow values obtained by the two methods were compared. A statistically significant correlation between the two methods was found (r = 0.90, p less than 0.01). It is concluded that dynamic placental scintigraphy can be used as a technique for clinical measurements of relative changes of the maternal placental blood flow.

Animals↗
PubMedDate not supplied

In vitro studies of biological effects of cigarette smoke condensate. I. Genotoxic and cytotoxic effects of neutral, semivolatile constituents.

Much of the biological activity of cigarette smoke resides in the neutral fraction of the particulate phase. Since the volatile constituents of this material, the semivolatiles, are accessible to selective filtration, some of the biological activity of cigarette smoke might be reduced. In view of this, the genotoxic and cytotoxic effects and the chemical composition of the semivolatile neutral material of a cigarette smoke condensate was investigated. Cigarette smoke condensate obtained from domestic American blend type cigarettes, was separated into a volatile, a nonvolatile and a semivolatile fraction. The semivolatile constituents were fractionated by liquid-liquid extraction into 4 subfractions: acids, phenols, bases and neutrals. The neutral material was separated further by silica gel chromatography into 7 subfractions of varying polarity. The major components of these were identified by gas chromatography-mass spectrometry. These fractions were studied using 4 in vitro short-term tests, of which 2, the Ames test and induction of sister-chromatid exchanges, provided information on their genotoxicity and the other 2 provided information on their cytotoxicity by measuring inhibition of cell growth and inhibition of oxidative metabolism. Sister-chromatid exchanges were induced by the neutral fraction and the 7 subfractions, the activities of which increased with increasing polarity. Neither the total neutral material, nor the subfractions showed any mutagenic activity in the Ames test. The cytotoxic effect of the fractions of medium polarity, was greater than that of the total neutral material, while the most and the least polar fractions were less toxic.

Adipose Tissue, Brown↗
PubMedDate not supplied

Effect of khat on maternal food intake, maternal weight gain and fetal growth in the late-pregnant guinea pig.

Khat chewing is a widespread male social habit in countries around the southern shore of the Red Sea and in eastern Africa and is also practiced by women, even during pregnancy and lactation. In order to study the potentially adverse effects of khat chewing during pregnancy, guinea pigs were fed 2.2 g/kg of khat leaves daily throughout the third trimester. Control animals were given aspen leaves. Maternal daily food intake was significantly reduced during the first 10 days of feeding and maternal weight gain was slightly lower in the khat group. Khat feeding of the mother significantly reduced the mean birth weight of the offspring by 7% without any effect on litter size or length of gestational period. Since low birth weight is a well-established risk factor for both perinatal and young infant death, khat chewing during pregnancy may be one of the factors contributing to infant mortality.

Animals↗
PubMedDate not supplied

Effect of khat on uteroplacental blood flow in awake, chronically catheterized, late-pregnant guinea pigs.

In order to investigate effects of khat chewing on uteroplacental blood flow, eight awake, chronically catheterized guinea pigs were fed 2.2 g khat leaves/kg in late pregnancy and regional blood flows were measured with the microsphere technique. Seven animals fed with aspen leaves in the same amounts served as controls. The mean concentration of (+)-norpseudoephedrine in urine 3 h after the end of the feeding was 4.6 micrograms/ml in the khat-fed group with no detectable amounts in the controls. Placental blood flow was reduced by 10% 75 min and by 24% 180 min after khat feeding. Since the khat dose used gave urinary concentrations of (+)-norpseudoephedrine of the same magnitude as those reported in khat chewing women, khat chewing in pregnancy may reduce placental blood flow and impair fetal growth.

Animals↗
PubMedDate not supplied

Computer-assisted 3D analysis of cell distributions in the normal and epileptic cerebral cortex: description of a methodology in progress.

This paper describes software routines that (a) visualizes a stack of several thousands of aligned sequential photographic two-dimensional (2D) images stored in an image processing system; (b) creates a data base containing information about objects identified sequentially from the 2D images; (c) transfers the data base to a graphical terminal; (d) reconstructs a three-dimensional (3D) object space; and (e) supports on-line interaction between the image processing system and the graphical terminal. As an application example, the cell content of a prism of motor cerebral cortex of the cat is reconstructed. Preliminary results from reconstructing human epileptic temporal cortex (cortical microdysgenesia) are also reported.

Adult↗
PubMedDate not supplied

3D reconstruction of biological objects from sequential image planes--applied on cerebral cortex from cat.

A prism of cat cerebral cortex was reconstructed with a method for three-dimensional (3D) representation of biological objects. A series of 918 semithin sections were digitized into an image analysis system. The images were aligned and analyzed, and a data base with the coordinates and a classification of the cells was created. The data base (i.e., the cortical prism) was visualized in a 3D graphic terminal, and parameters such as columnar and lamellar organization, clustering, and cell density were analyzed. A neuronal perikaryon and its neurites was reconstructed and shown together with the cortical prism.

Algorithms↗
PubMedDate not supplied

Fetal growth restriction: a workshop report.

Intrauterine growth restriction (IUGR) is associated with significantly increased perinatal morbidity and mortality as well as cardiovascular disease and glucose intolerance in adult life. A number of disorders from genetic to metabolic, vascular, coagulative, autoimmune, as well as infectious, can influence fetal growth by damaging the placenta, leading to IUGR as a result of many possible fetal, placental and maternal disorders. Strict definitions of IUGR and of its severity are needed in order to eventually distinguish among different phenotypes, such as gestational age at onset, degree of growth restriction and presence of hypoxia. This report explores and reviews some of the most recent developments in both clinical and basic research on intrauterine growth restriction, by seeking mechanisms that involve genetic factors, utero-placental nutrient availability and vascular growth factors. New exciting findings on the genomic imprinting defects potentially associated with IUGR, and the placental anomalies associated with the decreased nutrient transport are summarized. Moreover, recent data on angiogenic growth factors as well as new information arising from application of gene chip technologies are discussed.

Adult↗