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Biomedical subjects

B Nielsen

Publications and source records attributed to B Nielsen.

At least 235 records · Page 13Linked to original sources
PubMed1988

Natural cooling of the brain during outdoor bicycling?

Tympanic membrane temperature (Ttymp) and deep esophageal temperature (Tes) were measured in 8 subjects during normal outdoor bicycling. Metabolic rate (VO2) was determined by the Douglas bag method. Heart rate was sampled continuously. Skin surface temperatures were measured at the forehead, chest and shoulder, and core temperatures in the deep esophagus and at the tympanic membrane using a radio telemetry system. For each outdoor experiment an indoor experiment in a climatic chamber, adjusted to the same air temperature but in still air, was performed. The subjects exercised at the same VO2 as in the outdoor trial on a stationary bicycle ergometer. Measurements were taken with the same equipment as in the outdoor experiments. O2-consumption (l.min-1) and heart rates (beats.min-1) were similar during outdoor and indoor bicycling, averaging 2.38 +/- 0.018 (SE) and 2.26 +/- 0.07, 141 +/- 7 and 147 +/- 8, respectively. During steady state Tes was the same during outdoor and indoor bicycling (37.95 degrees C), while Ttymp was significantly lower during outdoor bicycling. delta (Tes-Ttymp) was 1.25 degrees C during outdoor and 0.5 degrees C during indoor exercise. It is concluded that, if tympanic temperature is lowered by counter-current cooling of its arterial supply, then cooling of the brain may also take place in humans during physical activity under normal outdoor conditions with convective air movements. But the magnitude of a possible brain cooling cannot be deduced from the fall in tympanic temperature.

Adult↗
PubMed1988

Heat balance during exercise in the sun.

10 male subjects, dressed only in white shorts, exercised for 120 min at 92 W on a bicycle ergometer suspended in a balance. For the first 60 min they were exposed to the sun, from 60.-90. min they were shaded, and from 90.-120. min again exposed to the sun. In 10 experiments they faced the sun, in 10 others their backs were exposed. The values (in W) in the heat balance equation M - W +/- C +/- R +/- E +/- L +/- S = 0 were measured by partitional calorimetry: M metabolic rate, W external work rate, C convective heat loss, R short and long wave radiation exchange, E evaporative sweat loss, L pulmonary evaporative loss, and S rate of heat storage. Means of the measured values (W) are shown below. R in the heat balance equation equals the radiative short wave (Rgs) and long wave (Rgl) heat gains minus the radiative long wave heat loss (Rll). (table; see text) The direct gain from solar radiation is approximately 100 W. In the shade period the reduction in radiant heat gain is compensated for by the decreased evaporation of sweat.

Adolescent↗
PubMed1988

Mixed lymphocyte reactions (MLR) in rainbow trout (Salmo gairdneri) sibling.

Suitable conditions for 2 way MLR were determined in random combinations of commercially cultured trout and were then applied to full siblings in two families reared for experimental purposes. The primary aim of the investigation was to determine whether the immunogenetic predictions from mammalian and avian experiments would apply, i.e. (i) that all full sibs, short of rare intra-MHC recombinants, can be assigned to a maximum of four different MHC genotypes, and (ii) that individuals of the same genotype are mutually histocompatible as tested in MLR. If both predictions apply, five or more siblings tested in all pairwise combinations should invariably display compatible pairs, so that a maximum of four groups of mutually incompatible individuals should emerge. The findings did not fit this model, and two alternative immunogenetic models are discussed.

Animals↗
PubMed1988

Localization of replication origins in pea chloroplast DNA.

The locations of the two replication origins in pea chloroplast DNA (ctDNA) have been mapped by electron microscopic analysis of restriction digests of supercoiled ctDNA cross-linked with trioxalen. Both origins of replication, identified as displacement loops (D-loops), were present in the 44-kilobase-pair (kbp) SalI A fragment. The first D-loop was located at 9.0 kbp from the closest SalI restriction site. The average size of this D-loop was about 0.7 kbp. The second D-loop started 14.2 kbp in from the same restriction site and ended at about 15.5 kbp, giving it a size of about 1.3 kbp. The orientation of these two D-loops on the restriction map of pea ctDNA was determined by analyzing SmaI, PstI, and SalI-SmaI restriction digests of pea ctDNA. One D-loop has been mapped in the spacer region between the 16S and 23S rRNA genes. The second D-loop was located downstream of the 23S rRNA gene. Denaturation mapping of recombinants pCP 12-7 and pCB 1-12, which contain both D-loops, confirmed the location of the D-loops in the restriction map of pea ctDNA. Denaturation-mapping studies also showed that the two D-loops had different base compositions; the one closest to a SalI restriction site denatured readily compared with the other D-loop. The recombinants pCP 12-7 and pCB 1-12 were found to be highly active in DNA synthesis when used as templates in a partially purified replication system from pea chloroplasts. Analysis of in vitro-synthesized DNA with either of these recombinants showed that full-length template DNA was synthesized. Recombinants from other regions of the pea chloroplast genome showed no significant DNA synthesis activity in vitro.

Chloroplasts↗
PubMed1988

Muscle blood flow is not reduced in humans during moderate exercise and heat stress.

The effect of heat stress on circulation in an exercising leg was determined using one-legged knee extension and two-legged bicycle exercise, both seated and upright. Subjects exercised for three successive 25-min periods wearing a water-perfused suit: control [CT, mean skin temperature (Tsk) = 35 degrees C], hot (H, Tsk = 38 degrees C), and cold (C, Tsk = 31 degrees C). During the heating period, esophageal temperature increased to a maximum of 37.91, 39.35, and 39.05 degrees C in the three types of exercise, respectively. There were no significant changes in pulmonary O2 uptake (VO2) throughout the entire exercise period with either one or two legs. Leg blood flow (LBF), measured in the femoral vein of one leg by thermodilution, remained unchanged between CT, H, and C periods. Venous plasma lactate concentration gradually declined over time, and no trend for an increased lactate release during the heating period was found. Similarly, femoral arteriovenous O2 difference and leg VO2 remained unchanged between the three exercise periods. Although cardiac output (acetylene rebreathing) was not significantly higher during H, there was a tendency for an increase of 1 and 2 l/min in one- and two-legged exercise, respectively, which could account for part of the increase in total skin blood flow during heating (gauged by changes in forearm blood flow). Because LBF was not reduced during exercise and heat stress in these experiments, the additional increase in skin blood flow must have been met by redistribution of blood away from vascular beds other than active skeletal muscle.

Adult↗
PubMed1988

Children admitted for observation for suspected meningitis. Problems in diagnosis in general practice.

Infectious diseases in children are common in general practice. It is crucial not to overlook a case of purulent meningitis, and the aim of the present study was to evaluate and suggest ways of improving the diagnostic ability of the general practitioners in this respect. During a seven-year period 157 children under the age of 16 years, out of a population of 10,500 children, were referred from general practice to a district hospital for observation with symptoms and signs that suggested a possible diagnosis of meningitis. Seventy-eight underwent lumbar puncture, but only 14 of them received a final diagnosis of purulent meningitis. During the same period three other children proved to be cases of purulent meningitis, though they had been referred with other diagnosis. Twenty children had aseptic meningitis or encephalitis. The clinical findings in the groups of children with and without purulent meningitis were very similar, but an impaired level of consciousness and presence of petechiae were commoner in the former. Children with purulent meningitis had a significantly shorter duration of symptoms than children without meningitis. The present study could not suggest any ways of improving the referral procedures.

Child↗
PubMed1988

Antikeratin antibodies in routine diagnostic pathology. A comparison of 10 different commercial antikeratins.

Ten commercially available antikeratin antisera were tested immunohistochemically on fresh frozen and formalin-fixed paraffin-embedded tissue. Eight of the antisera were in addition tested on protein-immunoblottings. For six of the antisera a good correspondence was found between our immunoblots and data given by the manufacturers. Two monoclonal antisera did not react with keratin proteins. On immunohistochemical testing two of the antibodies showed qualitatively identical staining on both frozen and paraffin sections without background staining. Three of the antibodies reacted weakly or not at all on paraffin sections but gave acceptable staining on frozen sections. Three of the antibodies showed acceptable staining on paraffin sections, but background staining on frozen sections and one antibody gave the reverse staining pattern. For one of the antibodies it was impossible to obtain an acceptable staining due to high non-specific binding of the secondary antibody. None of the antikeratins were true panepithelial tumour markers as all of them failed to detect keratin in at least one of the epithelial tumours. However, a combination of two or three antikeratins (Hybritech AE1 + AE3, Becton Dickinson No 7650, DAKO A622) covered most or all epithelial tumours examined. It is concluded that commercially available antisera show great variability with respect to quality and reactivity indicating that the majority need further purification, characterization and testing on tissues before they are introduced on the commercial market.

Antibodies↗
PubMed1988

Keratin patterns in prostatic hyperplasia and adenocarcinoma.

Keratin patterns in benign prostatic hyperplasia and prostatic adenocarcinoma were evaluated using frozen and formalin-fixed tissue. Five different commercially available antibodies were used. In frozen tissue basal cells of benign acinic and ductal structures stained with PKE, and to a lesser degree with MCA 144, CAM 5.2 and RCK 102. Luminal cells stained with MCA 144, CAM 5.2, RCK 102 and to a lesser degree with PKE. In formalin-fixed tissue basal cells stained exclusively with Z622, predominantly with PKE and RCK 102, and to lesser degree with MCA 144 and CAM 5.2. Luminal cells stained with MCA 144 and CAM 5.2 and to some degree with PKE and RCK 102, while Z622 stained luminal cells of ductal epithelium weakly, but acinic cells not at all. Luminal phenotype dominated in prostatic adenocarcinomas which were stained with MCA 144 and CAM 5.2 irrespective of differentiation, and independently of whether frozen or formalin-fixed tissue was used. However, the different keratin phenotype of benign and malignant prostatic epithelium depends to some degree on the immunohistochemical procedures used. In diagnostic pathology Z622 may be able to separate intraluminal neoplastic lesions from invasive carcinoma, a problem particularly seen when cribriform growth pattern is found.

Adenocarcinoma↗