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Biomedical subjects

S Petersen

Publications and source records attributed to S Petersen.

At least 127 records · Page 7Linked to original sources
PubMed1990

Normal fetal growth evaluated by longitudinal ultrasound examinations.

Fetal weight estimation was evaluated using the equations of Warsof, Shepard and Hadlock in 192 patients, less than 3 days before delivery. Warsof's and Hadlock's equations resulted in significantly better weight estimates compared to Shepard's equation. No systematic error was found below 2500 g by use of Warsof's equation, whereas Shepard's and Hadlocks's equations resulted in significant over-estimation in the low weight group. In a study of 5 fetuses, of 27-38 weeks gestational age, the intra-observer variation was calculated to 4.6%, whereas the coefficient of variation among observer means was 2.9%. The mixed intra- and inter-observer coefficient of variation was 6.5%. Thirty-five low-risk, uncomplicated pregnancies with reliable last menstrual dates were investigated longitudinally with ultrasound measurements of fetal weight. Population growth curves of fetal weight, fetal femur length, abdominal circumference and biparietal diameter were constructed by weighted polynomial regression. After 27 weeks of gestational age the weight growth curve showed only insignificant non-linearity. Compared to a Danish growth curve based on birth weights, significant higher mean weight was found, especially before 31 weeks of gestational age. The 10th and 90th percentiles for the individual percentage deviation change was +/- 4.4% per 28 days.

Body Weight↗
PubMed1990

Visual evoked potentials in term light-for-gestational-age infants and infants of diabetic mothers.

The latency and amplitude of the first negative peak of visual evoked potentials (VEP) were evaluated in 52 term infants, investigated within 48 h after birth. Sixteen were light-for-gestational-age (LGA), 16 were appropriate-for-gestational-age (AGA) and 20 were infants of diabetic mothers (IDM). The VEP latency was shorter in LGA infants compared to AGA infants, and it was closely related to the birth weight deviation. The VEP latency was inversely related to gestational age and positively related to head circumference. When corrected for gestational age and head circumference, the VEP latency was not significantly different between the subgroups, nor related to the birth weight deviation, ponderal index or skinfold thickness. Thus, it could be argued that the high conduction velocity in LGA infants is due to stress maturation or alternatively due to the smaller head circumference. The VEP amplitude was higher in LGA infants when compared with AGA infants, and inversely related to the birth weight deviation. No differences were found in VEP latency or VEP amplitude between IDM and AGA infants.

Birth Weight↗
PubMed1990

Nitrofurantoin versus trimethoprim prophylaxis in recurrent urinary tract infection in children. A randomized, double-blind study.

The efficiency of nitrofurantoin and trimethoprim prophylaxis in preventing recurrent urinary tract infections (UTI) was compared by means of actuarial percentage recurrence-free curves in a randomized, double blind study in 130 children (126 girls, 4 boys) aged 1 to 14 years (mean 7.5). The children received the antibiotics for 6 months. Nitrofurantoin proved to be the most efficient prophylactic drug in patients with abnormal urography and/or reflux (n = 60) as evaluated by actuarial percentage recurrence-free analysis (p = 0.0025). However, no differences was found in patients without urinary tract abnormalities. Nitrofurantoin prophylaxis altered neither the pattern of resistance nor the bacteriological constellation, while patients receiving trimethoprim prophylaxis had 76% trimethoprim resistant bacteria during prophylaxis, compared with 8% before (p less than 0.0001) and 17% after (p less than 0.0001) prophylaxis. The percentage of recurrences due to E. coli (70-80%) was unaffected by trimethoprim prophylaxis, but the proportion due to trimethoprim resistant E. coli was significantly higher during prophylaxis (65%) than before (6%, p less than 0.0001) and after (11%, p less than 0.001). The percentage of Staphylococcus epidermidis UTI was significantly higher during trimethoprim prophylaxis (27%) than before (2%, p less than 0.0003). Following prophylaxis there was no difference in the actuarial percentage recurrence-free curves of the two regimens. Side effects occurred more frequently in the nitrofurantoin group (37%) than in the trimethoprim group (21%) (p = 0.05). The majority of side effects in the nitrofurantoin group derived from gastrointestinal symptoms. In conclusion, nitrofurantoin is recommended as the first choice prophylactic treatment of children with recurrent UTI and urinary tract abnormalities.

Adolescent↗
PubMed1990

Influence of concentric resistance training on concentric and eccentric strength.

This study investigated the effects of isokinetic concentric training on isokinetic concentric and eccentric torque outputs. Sixteen female subjects (mean age in years +/- SE = 21 +/- 1) were randomly assigned to either a training or a control group. Concentric and eccentric torques of the right knee extensors were assessed at 1.05rad.s-1 using a KinCom isokinetic dynamometer system. Each test consisted of a set of four maximal concentric and four maximal eccentric contractions of the knee extensors. The peak and average torques for each contraction were calculated using the computer software supplied by the KinCom manufacturer. On a separate day, after abstaining from heavy exercise for at least 12 hours, a single cross-sectional image of the thigh at midfemur was obtained using computer tomography (CT) scanning. From this image, cross-sectional area of the quadriceps femoris group was calculated using the computer software associated with the General Electric 9800 CT Scanning System. Training group subjects trained three days weekly for six weeks on a Cybex II+ isokinetic dynamometer, completing five sets of ten maximal effort knee extensions at an angular velocity of 1.05rad.s-1. Each set of exercise was separated by two minutes of self-selected recovery. Torque outputs were monitored daily to ensure that adequate recovery was provided between sets of exercise, and to document changes in strength as the program progressed. Significant (p less than .01) increases in peak and average concentric torque (11% and 12%, respectively), peak and average eccentric torque (18% and 21%, respectively), and muscle cross-sectional area (3.2%) were observed for training group subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Limited responsiveness of LHRH neurons to norepinephrine may account for failure of locus coeruleus or medullary A1 electrical stimulation to increase plasma LH in estrogen-treated ovariectomized rats.

We recently reported that electrical stimulation (ES) of the locus coeruleus (LC) or the medullary A1 noradrenergic cell groups markedly increased LH secretion. However, these amplifying effects occurred only in rats in which preliminary electrochemical stimulation (ECS) of the medial preoptic nucleus (MPN) was performed. In contrast, ES of either LC or A1 alone did not alter basal LH secretion. Possible explanations for this dichotomy in LH response include: (1) LHRH neurons in unanesthetized, estrogen-treated ovariectomized (OVX) rats are relatively unresponsive to NE, (2) the chloral hydrate anesthesia used in our brain stimulation studies elevates the threshold of excitability of LHRH neurons to norepinephrine (NE) and/or pituitary responsiveness to LHRH, (3) preliminary MPN-ECS reduces thresholds of responsiveness of LHRH neurons to NE, and (4) the LHRH secreted after MPN-ECS sensitizes the pituitary gland to the subsequent small amounts of LHRH released following LC- or A1-stimulation. To provide answers to these questions, 3 experiments were performed in estrogen-treated OVX rats into which had been inserted the third ventricle and jugular cannulae. In the first study, the effects of artificial cerebrospinal fluid (ACSF) or ACSF + NE (5, 20, or 45 micrograms) on plasma LH concentrations in unanesthetized, unrestrained rats were examined. The intracerebroventricular (ICV) infusion of 5 micrograms of NE increased plasma LH by 61.3% above basal levels within 10 min whereas 20 or 45 micrograms NE elevated LH values 166.9 and 182.8%, respectively. The next study examined the effects of anesthetic drugs on LH response produced by ICV infusions of 45 micrograms of NE. Regardless of whether rats were anesthetized with ether, chloral hydrate, urethane, Saffan (alphaxolone + alphadolone) or ketamine + acepromazine, peak LH responses to ICV NE were not significantly different from unanesthetized controls. In a second study we observed that ICV NE (45 micrograms) markedly amplified and prolonged the release of LH after MPN-ECS. Moreover, the peak LH responses in these animals were approximately 10 x greater than those obtained in rats which received ICV NE but not MPN-ECS. The third series of studies demonstrated that pituitary responsiveness to LHRH was not an important factor in dictating the LH response obtained after NE ICV infusions. These data suggest that LHRH neurons in estrogen-primed OVX rats are not particularly responsive to NE and that following MPN-ECS, LHRH neuronal responsiveness to this catecholamine markedly increases.

Animals↗
PubMed1989

Total body bone mineral in light-for-gestational-age infants and appropriate-for-gestational-age infants.

Dual-photon-absorptiometry using 153Gd in a whole body scanner was used to measure total body bone mineral in 51 newborn infants. In preterm light-for-gestational-age infants total body bone mineral was 12.6 g v.s. 25.6 g in preterm appropriate-for-gestational-age infants (p less than 0.05). In term light-for-gestational-age infants total body bone mineral was 41.4 g v. 84.2 g in term appropriate-for-gestational-age infants (p less than 0.001). The correlations between gestational age and total body bone mineral was best described by exponential regression lines.

Bone and Bones↗
PubMed1989

Fetal abdominal circumference rather than fetal femur length/abdominal circumference ratio predicts fetal malnutrition in high risk pregnancies.

The aim of this study was to compare the ability of abdominal circumference (AC) and fetal femur length/abdominal circumference ratio (FFL/AC) measured by ultrasound within a period of 2 weeks before birth to predict low birth weight percentile and neonatal signs related to fetal malnutrition. From longitudinal ultrasound measurements in 35 normal pregnancies reference data of AC and FFL was obtained. FFL/AC ratio was constant from 21 weeks until term (mean 20.9, SD 1.2) (figure 1). In 350 risk pregnancies AC standard deviation score (AC-SDS) correlated far better than FFL/AC ratio with the deviation of birth weight from normal (figure 3). Furthermore AC-SDS correlated better with ponderal index (PI) and skinfold thickness (ST) than did FFL/AC ratio. Using cut-off levels on AC-SDS and FFL/AC ratio, which selected about 30% of the population, the sensitivity of AC-SDS in predicting the infant being LGA was 81.8% versus 42.9% using FFL/AC ratio (table II). The prediction of the infant being SGA was not improved when the change in AC-SDS or FFL/AC over the last 6-8 weeks of pregnancy was considered. We conclude that AC-SDS correlates well with birth weight deviation and predicts the infant being SGA with a precision equal to the best results reported in the literature, and that FFL/AC ratio is unreliable even when GA is not known because of a high false positive rate.

Abdomen↗
PubMed1988

Lean body mass in small for gestational age and appropriate for gestational age infants.

Dual photon absorptiometry using 153Gd in a whole-body scanner was used to measure lean body mass (LBM) in 51 newborn infants. LBM% decreased exponentially with increasing gestational age in both small for gestational age (SGA) and appropriate for gestational age (AGA) infants. In preterm SGA and AGA infants LBM was 104% and 103%, respectively, indicating that no fat was detectable. In term SGA infants LBM was 98%, which corresponded to 48 gm fat on average, and in term AGA infants LBM was 87%, which corresponded to 452 gm fat on average. The LBM%, ponderal index, and skinfold thickness were significantly different between AGA and SGA infants. Infants with clinical signs of intrauterine wastage had significantly higher LBM% than did infants without signs of weight loss. Our results on LBM% by dual photon absorptiometry agree with earlier dissection data; the clinically applicable methods of (1) height combined with weight (i.e., ponderal index), (2) skinfold thickness, and (3) scoring by clinical observations are useful for the estimation of lack of fat as an indicator of intrauterine growth retardation.

Adipose Tissue↗
PubMed1988

Pattern of platelet-associated immunoglobulin (classes and IgG subclasses) in childhood immune thrombocytopenic purpura.

Platelet-associated Ig classes and IgG subclasses were studied by a semiquantitative platelet ELISA test in 17 children with immune thrombocytopenic purpura (ITP). An elevation of PAIg was found in 94% of the children. In nearly all cases increased amounts of PAIgG of subclass G1 was seen, and in half of the cases increased amounts of PAIgM were also seen. No statistical difference in the composition of PAIg classes and PAIgG subclasses in acute and in chronic ITP was found. However, a correlation of increased amount of PAIgG3 and very low platelet count (20 x 10(9)/l) was observed.

Autoantibodies↗
PubMed1986

Alloimmune neonatal thrombocytopenia and hydrocephalus. Platelet antigen Zwa, ABO-antigens and HLA-antigens in mothers to infants with hydrocephalus.

In 27 mothers to infants with hydrocephalus determinations of platelet antigen Zwa, HLA-typing and ABO-typing were performed in order to evaluate whether undiagnosed alloimmune neonatal thrombocytopenia (AINT) could be an aetiological factor in hydrocephalus. All mothers were Zwa-positive, and the frequency of HLA-antigens and ABO-antigens was as in the normal population. Though sporadic cases of hydrocephalus following AINT are reported, this is not a common cause of intracranial haemorrhage and hydrocephalus.

ABO Blood-Group System↗
PubMed1985

Reversible abnormalities of myocardial relaxation in hypothyroidism.

Fifteen selected hypothyroid patients without symptoms or signs of cardiovascular disease and an equal number of matched control subjects underwent simultaneous recording of electrocardiogram and phono-, apex-, and echocardiography to assess dynamic systolic and diastolic left ventricular function. Both the systolic preejection period and the isovolumic relaxation period were significantly increased in the hypothyroid group. However, whereas the rate of myocardial contraction, assessed from the echocardiograph of the left ventricular posterior wall, was identical in patients and control subjects, the diastolic thinning rate of the muscle was markedly slowed in the hypothyroid individuals. The abnormalities demonstrated were in the main completely reversed after 3 months of T4 therapy. These results demonstrate a relatively selective and readily reversible disturbance of the rate of myocardial relaxation in hypothyroidism, suggesting an intrinsic abnormality of cardiac muscle. This allows an intriguing parallel to be drawn with the delayed relaxation phase of voluntary muscle contraction, long recognized as a direct measure of tissue thyroid function in hypothyroidism. The abnormality of diastolic function we have described is of similar character to that found in patients with other cardiomyopathies and which has been shown to be a major cause of disturbance of global cardiac action.

Adult↗
PubMed1984

Effect of tubocurarine on static and dynamic muscle contractions in man.

The effect of a bolus injection of tubocurarine (0.1 mg X kg-1 i.v.) was followed in six young subjects by registration of static, and slow (30 degrees X s-1) and fast (150 degrees X s-1) dynamic (isokinetic) maximal voluntary leg extensions. Mechanograms from both unblocked and curarized muscle contractions showed a "notch" after about 440 ms separating two relative maxima. The mechanograms were divided by an arbitrary straight line connecting the starting point of the contraction curve and the notch. The line separated an area (Nm X s) above and to the left (alpha-component) from an area below and to the right (beta-component) of the line. Tubocurarine affected the beta-component selectively until about 70% reduced in the static contractions. With further curarization the alpha-component was also reduced in size. The alpha-component was equally affected during the three types of contractions, while the faster the contraction the more the beta-component was reduced. The results suggest that static as well as dynamic human muscle contractions can be divided into two parts with a different sensitivity for tubocurarine, one of which seems to have a sensitivity which depends on the contraction velocity.

Adult↗
PubMed1984

Fatigue of voluntary contractions in normal and myasthenic human subjects.

The effect of fatigue developed during 96 repeated rapid maximal voluntary finger muscle contractions (MVC), 12 contractions per minute, was followed in 4 control subjects and 4 myasthenic patients. The tension-time integral (T-TI) was determined during either the first 1 or 1.25 s of each contraction. Fatigue decreased the T-TI by 21% in the control subjects and by 65% in the patients. While ordinary MVC showed a slow rate of rise of tension and gradually increasing electromyographic activity, rapid MVC from both groups showed a steep rate of rise of tension, a 'notch' after about 0.3-0.4 s separating two relative maxima and a larger electromyographic activity during the first half second of the contraction. The mechanograms from rapid MVC were divided by an arbitrary straight line connecting the starting pint of the contraction curve and the notch. The line separated an area (N X s) above and to the left (alpha-component) from an area below and to the right (beta-component of the line. Fatigue affected the beta-component selectively in both control subjects and myasthenic patients. Only when the beta-component was reduced by more than 80%, was a reduction of the alpha-component also seen. At any time during a sustained contraction, the patients could briefly increase their instantaneous strength, but for only about one half second. The results suggest that human muscle contractions can be divided into two parts with a different sensitivity to fatigue in both control subjects and myasthenic patients.

Adolescent↗