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Biomedical subjects

S A Petersen

Publications and source records attributed to S A Petersen.

At least 19 recordsLinked to original sources
PubMed1996

Higher rectal temperatures in co-sleeping infants.

The effect on deep body temperature of infants co-sleeping (with either or both parents) is investigated in this case control study. Overnight continuous recordings of rectal temperature were made from 34 babies co-sleeping with one or both parents throughout the night and 34 infants matched for age, feeding regimen, parental smoking, thermal environment, sleeping position, and sex who slept alone. The co-sleeping infants had significantly higher rectal temperatures from two hours after bedtime, when the initial fall in sleeping body temperature was complete. The mean rectal temperature of co-sleeping infants between two and eight hours was 0.1 degree C higher than that of infants sleeping alone (p < 0.04). Given the very small variance in rectal temperature this probably reflects a considerable physiological difference between the two groups.

Analysis of Variance↗
PubMed1995

Prone sleeping infants have a reduced ability to lose heat.

The heat loss coefficients of a group of infants have been calculated and compared to see if there is a difference in the ability to lose heat between prone and non-prone sleeping infants. For a group of 43 infants aged 4-29 weeks, a simple mathematical model of exponential cooling in a body has been fitted to the fall in rectal temperature which occurs in infants at bedtime. One of the parameters yielded by the fitting process is the coefficient of thermal heat loss. After validation against the estimated heat loss from supine sleeping infants, the heat loss coefficient was compared at different sleep positions and gender. The mean heat loss coefficient, measured from the non-prone sleeping infants (0.269 W/degrees C, S.D. 0.197) agreed well with the value calculated for supine sleepers with the same tog levels (0.4 W/degrees C). Prone sleeping infants were found to have a considerably smaller heat loss coefficient which was approximately 60% of the value for non-prone sleeping infants (P = 0.000097). Female infants were found to have a heat loss coefficient that was approximately 70% of that of male infants but this gender difference was only significant (P = 0.025) for non-prone sleeping infants. These results suggest that infants sleeping in the prone position may be unable to lose heat as rapidly as those infants sleeping non-prone.

Body Temperature Regulation↗
PubMed1995

Lower body temperature in sleeping supine infants.

Night time rectal temperature recordings were made from 103 infants sleeping in their own home in different sleeping positions. In most cases sleeping position was verified by video monitoring throughout the night. In the period before an adult-like night time body temperature pattern appeared there was no significant effect of sleeping position upon night time body temperature, in line with previous reports. Once an adult-like night time temperature pattern appeared, infants sleeping supine reached significantly lower rectal temperatures than those sleeping prone or lateral. Babies sleeping supine moved significantly more during the night and were more likely to uncover their hands and arms. These findings suggest that supine sleepers are in a different physiological condition from those sleeping prone or lateral, which may be associated with their lower vulnerability to sudden unexpected infant death.

Body Temperature↗
PubMed1995

Urinary excretion of cortisol after immunisation.

Urinary cortisol excretion and rectal temperature were measured in 66 infants before and after immunisation against diphtheria, tetanus, pertussis, and Haemophilus influenzae type b. Immunisation produced a significant increase of rectal temperature the next night at all ages. Infants without an adult-like night time body temperature pattern had a significant increase in urinary cortisol excretion night and morning after immunisation. Once an adult-like night time body temperature pattern developed immunisation no longer significantly raised urinary cortisol output.

Age Factors↗
PubMed1995

Factors affecting rectal temperature in infancy.

The recordings of 1197 overnight rectal temperatures from infants of up to 24 weeks of age have been analysed with respect to 12 variables, including a number of risk factors for sudden infant death syndrome. Multivariable regression was used to identify if parental smoking, bottle feeding, sleeping position, and birth weight affect the overnight rectal temperature of infants. The rectal temperature, averaged over the period from three to five hours after the infants were put to bed, correlated well (R = 0.36) with the collected variables. An increase in the infant's age, birth weight, and the supine sleeping position all decreased the night time rectal temperatures. However, an increase in the night time room temperature, weight, and the combination of bottle feeding and parental smoking produced an increase in rectal temperature. The individual effects of bottle feeding and parental smoking were not significant. The results show that some of the major risk factors have the effect of raising the rectal temperature of sleeping infants.

Birth Weight↗
PubMed1994

Interactions between infant care practices and physiological development in Asian infants.

Asian infants are less likely to suffer cot death despite apparently higher prevalence of some risk factors. This paper compares the development of night time body temperature patterns in a small sample of Asian babies with the pattern already established for white infants, where babies who develop an adult-like night time temperature pattern later than usual share characteristics with victims of SIDS. The Asian infants had similar body temperature patterns to whites, but tended to develop the adult-like pattern later, not earlier as might have been expected. More Asian infants than white in our sample slept in the parental bed, and, before the adult-like body temperature patterns appeared, co-sleeping infants had higher body temperatures than those in their own cots. Asian infants slept in significantly warmer rooms than whites, but under similar amounts of bedding. These studies do not therefore reveal any physiological difference between Asians and whites which might account for low vulnerability to cot death, indeed, if anything the reverse.

Adult↗
PubMed1994

The coracoacromial arch: MR evaluation and correlation with rotator cuff pathology.

The relative prevalence of various acromial shapes, appearance of the coracoacromial ligament and enthesophytes along the inferior aspect of the acromioclavicular joint in patients with and without rotator cuff tears were evaluated. Of 76 patients with clinical instability and impingement, 31 had a normal rotator cuff and 45 demonstrated a partial or full tear of the supraspinatus tendon at surgery. Results were compared with those from magnetic resonance (MR) scans of 57 asymptomatic volunteers. Of the 45 patients with a supraspinatus tear, 38% (17) had a flat acromial undersurface (type I), 40% (18) had a concave acromial undersurface (type II), 18% (8) had an anteriorly hooked acromion (type III), and 4% (2) had an inferiorly convex acromion (type IV). Among the 31 patients with a normal rotator cuff at surgery and the 57 asymptomatic volunteers, the respective prevalences of the type I acromion were 39% (12) and 44% (25), of type II 48% (15) and 35% (20), type III 3% (1) and 12% (7), and type IV 10% (3) and 9% (5). Shoulders with surgically proven rotator cuff tears showed a tendential association with a type III acromion (8/45) and statistically significant associations with a thickened coracoacromial ligament (17/45) and acromioclavicular enthesophytes (18/45). For the association between inferiorly directed acromioclavicular joint enthesophytes and rotator cuff tears, age appears to be a confounding factor. The type IV acromion, newly classified by this study, does not have a recognizable association with rotator cuff tears.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromioclavicular Joint↗
PubMed1994

Body temperature changes before minor illness in infants.

This study aimed to examine the overnight temperature pattern of babies during the prodromal phase of minor illnesses. The overnight rectal temperature pattern of 123 babies was recorded weekly from about 6 to at least 16 weeks old, while parents maintained detailed records of signs of illness. By analysis of patterns of signs and visits to the general practitioner, 86 periods of minor illness were identified, mostly upper respiratory tract infections, though it was not usually possible to identify the infection by conventional virology. Data were analysed separately for babies who had developed an adult-like night time temperature pattern and those who had not. In both groups, obvious signs of illness were preceded by a disturbance of night time temperature pattern. Temperature was significantly raised over control weeks, though few babies were clinically febrile. The greatest temperature disturbances were seen in the three days before illness, though some disturbances were seen up to seven days before. A similar disturbance of temperature was seen the night after diphtheria, pertussis, and tetanus immunisation, and individual responses to natural infection and immunisation were well correlated, suggesting that the temperature change is more a function of the host response than the infecting agent.

Body Temperature↗
PubMed1994

Unicompartmental knee arthroplasty. Sequential radiographic and scintigraphic imaging with an average five-year follow-up.

Clinical, radiographic, and scintigraphic results of 33 consecutive unicompartmental knee arthroplasties were reviewed after a mean follow-up period of 68 months (range, 24 to 112 months). Clinical grades employing criteria established by the Hospital for Special Surgery showed 74% good to excellent and 11% fair to poor results. Four knees (15%) required revision to a total knee arthroplasty after an average postoperative interval of 7.4 years. Within the subset of surviving medial compartment arthroplasties (23 knees), superior clinical results were associated with a central or slightly medialized mechanical axis (p < 0.05). Periprosthetic radiolucency showed no correlation with clinical scores or failures resulting in revision surgery. There was no radiographic evidence of progressive arthrosis within the unreplaced compartments. Comparative analysis of preoperative and annual postoperative technetium bone scans showed no temporally related changes indicative of impending prosthetic failure or disease progression within the unoperated compartments. The surgically treated compartments maintained uniformly intense femorotibial activity, whereas the unoperated compartments, including the patellofemoral joint, remained scintigraphically quiescent. Disease progression in unreplaced compartments is unusual after contemporary unicompartmental knee arthroplasty. Most failures and poor results arise from mechanical inadequacies amendable to surgical technique and/or future design considerations.

Aged↗
PubMed1992

ATP overflow from the mouse isolated vas deferens.

1. A modified form of the highly specific luciferin-luciferase assay was used to measure the overflow of adenosine 5'-triphosphate (ATP) from the field-stimulated mouse vas deferens in vitro. Precise timing of the stimulation, superfusate collection and assay minimized ATP degradation before assay, offering the opportunity for quantitative studies. 2. Stimulation with between 50 and 200 supramaximal pulses at 5 Hz increased ATP overflow by between 7 and 28 times over basal. 3. ATP overflow increased steadily with increasing numbers of stimuli from 50 to 200 pulses. Increasing the frequency of stimulation initially had no effect, but above 10 Hz there was increased overflow, suggesting an interaction between facilitated release and the rate of degradation by extracellular ATPases. 4. Contractions of the vas induced by exogenous (-)-phenylephrine produced only a small increase in ATP overflow, suggesting that the stimulation induced increase in ATP overflow is mostly pre-junctional in origin, though tetrodotoxin eliminated stimulation-induced overflow only in a proportion of preparations.

Adenosine Triphosphate↗
PubMed1992

Factors affecting the development of night time temperature rhythms.

The rectal temperature of 26 infants between 6 and 16 weeks old was monitored continuously for one night each week. Rectal temperature always decreased with sleep but the minimum temperature attained changed with age. Some time between 8 and 16 weeks old the minimum sleeping rectal temperature decreased abruptly from around 36.8 degrees C to around 36.4 degrees C. This change was complete within one week and did not normally revert unless the infant became ill. Some infants changed as early as 8 weeks old, others not until 16 weeks. Breast fed infants changed significantly earlier than bottle fed infants. Girls changed significantly earlier than boys. First born infants changed significantly earlier than second or subsequent infants. Early changes were significantly more likely to be sleeping lateral or supine, and to have older mothers. They tended to come from more affluent families. There was no association between the time of change and the thermal environment in which the infant slept or the number of episodes of minor illness in the early weeks of life.

Aging↗
PubMed1992

MR imaging of the shoulder: appearance of the supraspinatus tendon in asymptomatic volunteers.

MR imaging has been shown to be accurate in the diagnosis of rotator cuff disruption and tear. Uncertainty remains about the significance of increased signal intensity in the critical zone of the supraspinatus tendon without visible disruption of tendon fibers and about the significance of other secondary findings commonly encountered with rotator cuff abnormalities, such as musculotendinous retraction or obliteration and fluid in the subacromial space. We evaluated proton density-weighted and T2-weighted coronal images (obtained on a 1.5-T superconductive MR imager) of 55 shoulders in 32 asymptomatic volunteers for signal intensity in the supraspinatus tendon, location of the musculotendinous junction, fluid in the subacromial-subdeltoid space, and appearance of the fat plane. In 89% of shoulders, the supraspinatus tendon showed focal, linear, or diffuse increased signal intensity with or without loss of the low-signal-intensity tendon margin on proton density-weighted images. None of these findings were confirmed on T2-weighted images. The musculotendinous junction was always located within an area 15 degrees medial to 30 degrees lateral to the highest point (12 o'clock) on the humeral head convexity. A peribursal fat plane was poorly defined or absent in 49%, and fluid in the subacromial-subdeltoid space was found in 20%. Increased signal intensity in the supraspinatus tendon on proton density-weighted images without a corresponding increase on T2-weighted images, the presence of small amounts of fluid in the subacromial space, and the lack of preservation of the subdeltoid fat plane are common findings in asymptomatic shoulders and by themselves are poor predictors of rotator cuff disease.

Adult↗
PubMed1991

MRI in the evaluation of patients with suspected instability of the shoulder joint including a comparison with CT-arthrography.

Thirty-two patients with clinical suspicion of shoulder instability were the subject of this assessment of MRI (1.5 T G. E. Signa) and its comparison with CT-arthrography (GE8800 and GE9800) of the shoulder. Twenty-seven patients had a final diagnosis established by arthroscopy and five by arthrotomy. The imaging examinations were interpreted independently by three radiologists blinded against history, surgical diagnosis and results of the compared test. The statistical analysis included ROC-curves, sensitivity, specificity and accuracy as well as predictive values. The significance of the comparative results was assessed by the McNemar Sign test. MRI showed significantly better diagnostic results in the evaluation of labral structures (sensitivity 85%, specificity 90%, accuracy 88%) and humeral head impression fractures (75, 82, 78 %). None of the tests were of sufficient diagnostic value to identify capsular abnormalities. CT and MRI results regarding the biceps tendon and loose bodies were similar, however, statistically not significant. MRI proved to be of high diagnostic value in the assessment of the unstable shoulder and compared favorably with CT-A.

Adolescent↗
PubMed1991

Effects of suramin on the concentration--response relationship of alpha, beta-methylene ATP on the mouse vas deferens.

1. The effect of suramin on the concentration-effect curve for the contractile response of the isolated mouse vas deferens to alpha, beta-methylene ATP (alpha, beta-meATP) was investigated. 2. The concentration-response curve to alpha, beta-meATP had a consistent discontinuity at about 3 x 10(-6) M, giving it a biphasic appearance. 3. Suramin in a dose-dependent, reversible manner both shifted the curve to the right and at the same time elevated the maximum response. 4. The P2y inhibitor Reactive Blue 2, on the other hand, both shifted the curve to the left and elevated the maximum response. 5. These results show that alpha, beta-meATP in this preparation is an agonist both at excitatory, presumably P2y receptors and inhibitory P2y receptors, and that suramin antagonizes both effects.

Adenosine Triphosphate↗
PubMed1991

Development of night time temperature rhythms over the first six months of life.

Continuous recordings of night time rectal temperature were made at regular intervals over the first six months of life in 49 babies. In the first two weeks of life rectal temperature changed little overnight, but by 6 weeks of age rectal temperature at bedtime was significantly higher than later in the night. By around 12 weeks of age sleeping deep body temperature fell below 36.5 degrees C, and by 16 weeks of age all babies exhibited a consistent rhythm of rectal temperature. This fell by about 0.8 degrees C within two hours of bedtime, and then remained low until an hour or two before waking. As babies got older the mean interval between bedtime and first disturbance of parents got longer. Sleeping rectal temperature fell below 36.5 degrees C at about the time babies slept for seven hours. From 6 weeks of age, as individual baby's rectal temperatures fell more with sleep, sleep got longer.

Body Temperature↗