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Biomedical subjects

J Nilsson

Publications and source records attributed to J Nilsson.

At least 271 records · Page 15Linked to original sources
PubMed1989

XbaI restriction fragment length polymorphism of apolipoprotein B in Swedish myocardial infarction patients.

Apolipoprotein B (apoB) is a major importance to the metabolism of lipoproteins, and there is also evidence which suggests that apoB plays a central role in atherogenesis. In order to study whether there is a link between one of the mutations of the apoB gene and premature coronary heart disease, the frequency of the XbaI RFLP for the apoB gene was analysed in 52 male myocardial infarction patients. These were compared with a control group matched for age and sex (n = 52), and a random population sample of middle-aged men (n = 106). Two alleles were identified by the presence (X2) or the absence (X1) of an XbaI cleavage site. A somewhat higher frequency of the X2 allele was seen among the patients, however there was no significant difference between patients and controls regarding the genotypes or allele frequencies. This observation does not confirm one earlier report where a higher frequency of the X1 allele was seen in myocardial infarction patients. Differences between the studied populations or epidemiological designs of the studies might explain the diverging results. Further studies are evidently needed to fully resolve the relation between the XbaI RFLP and risk of atherosclerotic disease or lipoprotein metabolism.

Adult↗
PubMed1989

Ground reaction forces at different speeds of human walking and running.

In this study the variation in ground reaction force parameters was investigated with respect to adaptations to speed and mode of progression, and to type of foot-strike. Twelve healthy male subjects were studied during walking (1.0-3.0 m s-1) and running (1.5-6.0 m s-1). The subjects were selected with respect to foot-strike pattern during running. Six subjects were classified as rearfoot strikers and six as forefoot strikers. Constant speeds were accomplished by pacer lights beside an indoor straightway and controlled by means of a photo-electronic device. The vertical, anteroposterior and mediolateral force components were recorded with a force platform. Computer software was used to calculate durations, amplitudes and impulses of the reaction forces. The amplitudes were normalized with respect to body weight (b.w.). Increased speed was accompanied by shorter force periods and larger peak forces. The peak amplitude of the vertical reaction force in walking and running increased with speed from approximately 1.0 to 1.5 b.w. and 2.0 to 2.9 b.w. respectively. The anteroposterior peak force and mediolateral peak-to-peak force increased about 2 times with speed in walking and about 2-4 times in running (the absolute values were on average about 10 times smaller than the vertical). The transition from walking to running resulted in a shorter support phase duration and a change in the shape of the vertical reaction force curve. The vertical peak force increased whereas the vertical impulse and the anteroposterior impulses and peak forces decreased. In running the vertical force showed an impact peak at touch-down among the rearfoot strikers but generally not among the forefoot strikers. The first mediolateral force peak was laterally directed (as in walking) for the rearfoot strikers but medially for the forefoot strikers. Thus, there is a change with speed in the complex interaction between vertical and horizontal forces needed for propulsion and equilibrium during human locomotion. The differences present between walking and running are consequences of fundamental differences in motor strategies between the two major forms of human progression.

Adaptation, Physiological↗
PubMed1989

Turnover of sulphur compounds in the endolymphatic sac: an autoradiographic study in the Mongolian gerbil.

Complex macromolecules are suggested to play an important role for the function of the endolymphatic sac (ES). As proposed in previous experimental studies, proteoglycans are supposed to be present in the ES. As they are composed of a proteic core linked to chains of glycosaminoglycans, chemical identification of the glycosaminoglycans is of particular importance, bearing in mind that all but hyaluronic acid contain sulphur. In order to follow the short-term turnover of sulphur in the ES, an autoradiographic study has been carried out in the Mongolian gerbil using 35S as tracer. Radioactive labelling of the gerbilline ES was controlled 15, 20, 30 and 60 min after intraperitoneal injection. While the first signs of the presence of radioactive sulphur were noticed after 20 min in the blood vessels and in the basal aspect of the ES epithelium, after 60 min it was possible to observe the presence of the tracer both within the epithelial cell layer as well as in the lumen of the ES. These findings are consistent with the presence of a fast turnover of sulphur molecules in the gerbilline ES.

Animals↗
PubMed1989

Reciprocal inhibition in patients with hand cramps.

We studied inhibition of median nerve H-reflex produced by radial nerve stimulation in both arms of 14 patients with hand cramps and 15 normal volunteers. Median nerve stimulation was delivered 1 and 0.5 msec before and 0, 0.5, 1, 2, 10, 20, 30, 50, 75, 100, 200, 500, and 1,000 msec after radial nerve stimulation. Recordings were from surface electrodes positioned over flexor carpi radialis. We identified three periods of attenuation of median nerve H-reflex amplitude in the control group. When radial nerve conditioning stimuli were delivered simultaneously, 10 and 75 msec before median nerve test stimuli, H-reflex amplitude diminished to 47%, 61%, and 69%. In the patient group we also found three periods of attenuation at the same delays, but the amount of attenuation was significantly less than in controls. Dividing the patients into two groups, dystonic hand cramp and simple hand cramp, both showed less inhibition than the control group, but the abnormality was greater in the dystonic cramp group. This test is the first to demonstrate physiologic disturbance in patients with hand cramps.

Adult↗
PubMed1988

Coupling between inositol phosphate formation and DNA synthesis in smooth muscle cells stimulated with neurokinin A.

The two mammalian neuropeptides substance P (SP) and neurokinin A (NKA) have been demonstrated to stimulate DNA synthesis in connective tissue cells, suggesting that peripheral neurons may play a role in development and tissue regeneration. In this study we have tried to identify intracellular messengers required for SP- and NKA-induced DNA synthesis. SP and NKA, as well as platelet-derived growth factor (PDGF) stimulated formation of inositol phosphates in smooth muscle cells (SMC), whereas no effect on inositol phosphates formation occurred in response to nonmitogenic neuropeptides. Pretreatment of the cells with pertussis toxin markedly decreased DNA synthesis induced by NKA. This toxin inhibits formation of inositol phosphates by acting on a regulatory G-protein. Calcium and calmodulin antagonists also inhibited NKA-induced DNA synthesis. These results imply that the mitogenic signal(s) produced by activated neuropeptide receptors involves formation of inositol phosphate and activation of a calcium/calmodulin dependent process. We further report that other neuropeptides occurring in peripheral neurons, i.e., vasoactive intestinal polypeptide, calcitonin gene-related peptide, neuropeptide Y, somatostatin, or cholecystokinin, are without growth-stimulatory effect on cultured SMC.

Animals↗
PubMed1988

Stimulus artifact compensation using biphasic stimulation.

The feasibility of using biphasic stimulation as a method of reducing stimulus artifact was explored in several different circumstances. Sensory and muscle evoked potentials were compared using monophasic and biphasic constant-current stimuli. The monophasic stimulus was a negative rectangular pulse with a duration of 0.1-0.2 msec. The biphasic stimulus was a negative rectangular pulse of 0.1-0.2 msec duration followed, after a variable delay, by a positive rectangular pulse of the same duration and variable amplitude. When the conducting distances were long, stimulus artifact did not disturb either monophasically or biphasically evoked potentials. When the conducting distances were short, stimulus artifact occurred with monophasic stimulation but could be diminished readily using biphasic stimulation. The method can be accomplished easily using standard instruments with dual stimulators.

Electric Stimulation↗
PubMed1988

Growth-inhibitory properties of vasoactive intestinal polypeptide.

It has recently been demonstrated that several neuropeptides can affect cell growth. The mammalian tachykinins substance P and neurokinin A, which are present in peripheral sensory neurons, stimulate growth of cultured connective tissue cells. Substance P-like immunoreactivity has been demonstrated in neuroblastoma cell lines. Neuroblastoma cells also produce other neuropeptides, among them vasoactive intestinal polypeptide (VIP). We report here that VIP is a potent inhibitor of serum-induced DNA synthesis in cultured smooth muscle cells (SMC), whereas no growth-inhibition was seen in SMC exposed to neurokinin A, calcitonin-gene related peptide, neuropeptide Y, somatostatin, or cholecystokinin. The growth-inhibitory effect of VIP was closely related to its ability to induce formation of cyclic AMP. Our results raise the possibility that peptides released by neurons, endocrine cells, as well as by transformed cells, may not only function as mitogens but also as inhibitory modulators of cell growth.

Animals↗
PubMed1988

Diagnosis of deep vein thrombosis with a new radionuclide method--99Tcm-albumin test.

The diagnostic efficiency of 99Tcm-albumin test (AT), a new radionuclide method, was evaluated in 90 consecutive patients with suspected deep vein thrombosis (DVT) admitted to the medical emergency ward. Phlebography was used as reference method. The sensitivity of the AT test was 92% and the specificity was 61%. As the method is objective, rapid and convenient for the patients, it can be recommended as an initial examination method to be followed by phlebography, in cases with a positive test result. Criteria with high specificity, 98%, have also been defined but these criteria should be further investigated.

Adult↗
PubMed1988

Lumbar back muscle activity during locomotion: effects of voluntary modifications of normal trunk movements.

The mechanisms of adaptation of the trunk to changed mechanical conditions were studied during locomotion in man. The myoelectrical (EMG) activity in lumbar back muscles and the movements of the trunk were recorded in nine healthy subjects during walking and running on a motor-driven treadmill. Two different types of voluntary modifications of the movement pattern were used: (1) The trunk was kept in an extreme forward or backward tilted position. In both these situations the basic EMG pattern with two periods of activity per stride cycle was maintained during walking, whereas a major shift relative to the stride cycle (25% of the stride cycle duration) occurred in running with the trunk tilted backwards. The synchrony of the back muscle activation at both sides increased when locomotion was performed with the trunk tilted forwards. The relative duration of the EMG bursts was similar to normal locomotion and corresponded to 15-26% of the stride cycle duration in walking and 23-37% in running. (2) In the other type of modification the subjects were instructed to exaggerate the angular trunk movements either in the sagittal or in the frontal plane. The basic EMG pattern and phase relationships remained in most cases unchanged. One exception was running with exaggerated lateral movements, in which only one period of back muscle activity per stride cycle was observed. The relative duration of the bursts was longer in trials with exaggerated trunk movements as compared to normal locomotion. In walking and running with the trunk tilted forwards or backwards the lumbar back muscles were not always involved as prime movers of the trunk. This was in contrast to the more dynamic situations, in which the back muscle activity appeared to be directly involved in braking and reversing the exaggerated trunk movements.

Adaptation, Physiological↗
PubMed1987

Perception of similarity and laterality effects in tactile shape recognition.

Similarity judgements were made about pairs of shapes explored haptically with the hands moving in the same (congruent), or opposite direction. Scanning shapes using an opposite manual direction was slower and less accurate. These results enabled stimulus selection for a further experiment that examined laterality effects in the haptic modality. Pairs of shapes were explored and the presence/absence of a target shape indicated using a pedal switch. Males showed a right hand disadvantage, whereas females were equally accurate at recognising target shapes with either hand, and were equivalent to males' left hand recognition accuracy. Direction of hand movements (congruent vs opposite) and target type also interacted with sex. These interactions and the 1-2 sec longer decision time by females suggest sex differences in the use of cognitive strategies rather than in hemispheric specialization of function.

Adult↗
PubMed1987

Adaptability in frequency and amplitude of leg movements during human locomotion at different speeds.

In this study of human locomotion we investigate to what extent the normal frequency and amplitude of leg movements can be modified voluntarily at different constant velocities, and how these modifications are accomplished in terms of changes in duration and length of the support and swing phases of the stride cycle. Eight healthy male subjects performed walking and running on a motor-driven treadmill at speeds ranging from 1.0 to 3.0 m s-1 (walking) and 1.5 to 8.0 m s-1 (running), respectively. At each speed the subjects walked and ran with: normal stride frequency; the highest possible stride frequency, and the lowest possible stride frequency. Time for foot contact was measured with a special pressure transducer system under the sole of each shoe. At all speeds of walking and running it was possible to either increase or decrease the frequency of leg movements; that is, to decrease or increase stride cycle duration. The range of variation decreased with increasing speed. The mean overall stride frequency range was 0.41 (low frequency walk 1.0 m s-1)-3.57 Hz (high-frequency run 1.5 m s-1). Stride length ranged 0.40 (high frequency walk 1.0 m s-1)-5.00 m (low frequency run 6.0 m s-1). At normal frequency the overall ranges of stride frequency and length were 0.83-1.95 Hz and 1.16-4.10 m, respectively. The stride frequency increased with speed in low frequency walking and running (as in normal frequency) and decreased in high frequency, despite the effort to maintain extreme frequencies. Only in high frequency walking could the stride frequency be kept approximately constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1986

DNA synthesis induced by the neuropeptide substance K correlates to the level of myc-gene transcripts.

Neuropeptides have recently been implicated in regulation of normal and neoplastic cell growth. Substance K is a neurotransmittor candidate that has been identified as a mitogen for smooth muscle cells and fibroblasts. However, the ability to respond to stimulation with substance K declines rapidly in cells serum-starved for more than 24 h and in parallel with a decrease in the intracellular level of myc-gene transcripts. Contrarily, myc-transformed cells, that inspite of a decrease demonstrated a high level of myc mRNA after 48 h in serum-free medium, maintained their ability to initiate DNA synthesis when stimulated with substance K. The results suggest that the intracellular signal of substance K-induced DNA synthesis interacts with the myc protein.

Animals↗
PubMed1986

Return to normal of 99mTc-plasmin test after deep venous thrombosis and its relationship to vessel wall fibrinolysis.

Fourteen patients with deep venous thrombosis (DVT) and a positive 99mTc-plasmin test were followed up to determine how soon a negative test was obtained. Localization and extension of the thrombi were determined by phlebography. Plasminogen activator activity in vein walls and local fibrinolytic activity after venous occlusion were measured in order to find out what the prerequisites for impaired thrombolysis are. The time required to obtain a negative 99mTc-plasmin test showed considerable variation, ranging from less than 1 week to more than 6 months. The 99mTc-plasmin test had returned to normal in 64% of the patients after 6 months. No relationship was found between vessel wall fibrinolysis and time to normalization. Instead, we found an association between the time to normalization of the 99mTc-plasmin test and the size of the thrombus, according to phlebography, as well as between the time to normalization of the 99mTc-plasmin test and the extension of leg points with a positive 99mTc-plasmin test at admission. The finding of abnormal 99mTc-plasmin test results more than 6 months after acute DVT is of practical importance and warrants caution when evaluating patients with symptoms and signs suggestive of acute recurrent DVT.

Adult↗
PubMed1986

Increased platelet-derived mitogenic activity in plasma of young patients with coronary atherosclerosis.

The early state of atherosclerosis is characterized by a nodular proliferation of smooth muscle cells in the arterial intima. It has been suggested that this proliferation is initiated by platelet-derived growth factor (PDGF) released from aggregating platelets in connection with endothelial injury. In the present study platelet reactivity and mitogenic activity of plasma and serum were compared in young male survivors of myocardial infarction with angiographically demonstrable coronary atherosclerosis and in healthy subjects of similar age. Young post-infarction patients with coronary atherosclerosis had lower ED50 values of ADP-induced platelet aggregation. Furthermore plasma and serum from the patients contained increased amounts of mitogenic activity. Experiments using antibodies against platelet-derived growth factor indicated that the increase in mitogenic activity represented elevated concentrations of free PDGF growth factor in plasma. The results raise the possibility of a connection between increased levels of free PDGF and the proliferative reaction that characterizes early lesion progression.

Adenosine Diphosphate↗