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Biomedical subjects

P Johnson

Publications and source records attributed to P Johnson.

At least 487 records · Page 27Linked to original sources
PubMed1983

Increased 5-HT2 receptor number in brain as a probable explanation for the enhanced 5-hydroxytryptamine-mediated behaviour following repeated electroconvulsive shock administration to rats.

Following electroconvulsive shock (ECS) administration daily for 10 days there was an increase (35%) in 5-hydroxytryptamine2 (5-HT2) receptor number in rat frontal cortex 24 h after the last ECS, compared with handled controls. A similar increase was seen after intermittent ECS administration (5 ECS over 10 days) given during halothane anaesthesia, compared with halothane-treated controls. The dissociation constant was also increased at this time. A single ECS had no effect. Treatment of rats with pentylenetetrazol, p-chlorophenylalanine or alpha-methyl p-tyrosine during the intermittent ECS administration abolished the increase in 5-HT2 receptor binding. Since enhanced 5-HT-mediated behavioural responses are seen after repeated ECS but not when the ECS is given with the drug treatments outlined above, it is suggested that ECS-induced enhancement of 5-HT-mediated behaviour results from an increase in 5-HT2 receptor number.

Animals↗
PubMed1983

Upper airway dynamics during breathing and during apnoea in fetal lambs.

We have done experiments to determine the site(s) of resistance to the outward flow of lung fluid during apnoea and the inward flow of fluid during breathing in fetal lambs. Pressures were measured at various sites in the upper airway of ten chronically instrumented fetal lambs. Three fetuses were tracheostomized, two fetuses had nasopharyngeal tubes, one fetus had a tube through the body of its larynx only and four fetuses were studied with their upper airway intact. During apnoea, oropharyngeal pressure as well as tracheal pressure was greater than amniotic pressure. Tracheostomy or insertion of a nasopharyngeal tube (that extended from the amniotic cavity to the oropharynx) eliminated the standing pressure gradient between trachea and amniotic cavity. During normal breathing, negative phasic changes in oropharyngeal pressure occurred only when there was substantial posterior cricoarytenoid activity. Tracheostomy substantially attenuated phasic changes in tracheal pressure during breathing. From these data we conclude that the larynx provides a substantial resistance to the movement of fluid towards the lungs during normal breathing despite the presence of laryngeal abductor activity but does not offer a resistance to the secretion of lung fluid. The small positive tracheal pressure during apnoea most likely results from the secretion of lung fluid into a closed pharyngeal and buccal cavity or against a high nasal and oral resistance.

Airway Resistance↗
PubMed1983

Effect of tracheostomy on lung development in fetal lambs.

The effects of fetal tracheostomy on lung development in lambs have been investigated. Seven ewes, all with twin fetuses, were given a general anesthetic. One fetus in each set of twins was tracheostomized and the other fetus was sham operated (117-122 days gestation). The fetuses were delivered by cesarean section between 137 and 140 days gestation. Fetal tracheostomy decreased lung weight and volume, altered DNA concentration and the structural development of the acinus, and decreased lung distensibility. However, tissue and airway saturated phosphatidylcholine and lung stability during deflation were not significantly affected by fetal tracheostomy. It seems that tracheostomy in fetal lambs alters lung growth but does not affect the formation or release of surfactant. These data support the hypothesis that lung volume is actively maintained and lung growth promoted by the secretion of lung fluid against the resistance of the upper airway in fetal lambs.

Animals↗
PubMed1983

Relative fatty acid composition of serum lecithin in the normal puerperium.

21 women who had been followed regularly during their normal pregnancies were examined in the puerperium. The relative fatty acid composition of serum lecithin was analyzed by means of gas-liquid chromatography. Palmitic acid decreased and stearic acid increased, which indicates a shift to more pathway II-synthesized lecithin in the puerperal period. Linoleic acid increased and the longer polyunsaturated fatty acids decreased. These changes were slow as compared to the changes in the saturated fatty acids. No correlations were found between the saturated fatty acids and linoleic acid dominating the polyunsaturated fatty acids. The results indicate different incorporational ways into the lecithin molecule of these fatty acid groups. It is suggested that the deacylation-reacylation cycle is responsible for the high content of longer polyunsaturated fatty acids still 1 week after delivery. 6 weeks after delivery normal values were recorded. Breast-feeding did not seem to influence the fatty acid pattern of serum lecithin.

Adult↗
PubMed1983

Standards.

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Health Facilities↗
PubMed1983

Phase characteristics of breathing movements in healthy newborns.

In the neonatal period, respiratory distortion of the chest wall in active sleep has been reported to reduce the thoracic gas volume. In order to investigate whether the distortion influences the tidal volume, a thorough quantification of the phase differences between the movements of the chest wall and the abdominal wall and the relation of the phase differences to the ventilation was performed on fifteen newborn infants sleeping in prone position. The changes in the circumference of the chest and abdomen were measured with mercury-in-silastic strain gauges; nasal air flow was monitored with a pneumotachograph. During quiet sleep, the movements of the chest wall and the abdominal wall were congruent and regular, and the tidal volume was not dependent on the observed phase differences between them. In active sleep, the breathing movements were incongruent, the tidal volume was negatively correlated with the phase shift between the movements of the chest wall and the abdominal wall, and the mean inspiratory flow was increased. Ventilation (ml/min) did not differ between the sleep states. This study thus suggests that, in healthy newborns in active sleep, the chest wall distortion leads to a reduction of the tidal volume, but ventilation is upheld by compensatory mechanisms, i.e. increased breathing rate and increased amplitude of movements of the diaphragm.

Abdominal Muscles↗
PubMed1983

Isolated congenital enterokinase deficiency. Recent findings and review of the literature.

We report a 13-mo-old patient with isolated congenital enterokinase deficiency and review the clinical features, diagnostic approach, and management of all 8 reported patients. Our patient presented with failure to thrive, diarrhea, and hypoproteinemia since birth. A normal sweat chloride with small intestinal histology, and nondetectable trypsin activity in the duodenal fluid should alert the physician to the possibility of isolated enterokinase deficiency. All reported patients, including our own, responded favorably to pancreatic enzyme replacement. In vitro studies of the small intestinal mucosal biopsy specimen suggest that enterokinase deficiency at least in part is due to altered enzymes with low enterokinase activity.

Diarrhea, Infantile↗
PubMed1983

Serum protein changes in grass sickness.

Polyacrylamide gel electrophoresis was used to compare serum taken from ponies before and during clinical illness confirmed as grass sickness. A consistent rise in the level of haptoglobin was seen in serum from animals which had shown symptoms for more than two days. Serum albumin was also shown to have altered mobility at the onset of clinical disease. Estimation of the haemoglobin-binding capacity confirmed the haptoglobin increase. This haptoglobin has been purified and some of its properties determined. In contrast to the situation in acute inflammatory conditions no other acute-phase proteins increased to a significant extent in grass sickness. It is concluded that the neurotoxin known to be present in sera of animals experiencing acute grass sickness cannot itself be detected by polyacrylamide gel electrophoresis but may be bound to serum albumin.

Animals↗
PubMed1982

Birth asphyxia.

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Acidosis, Respiratory↗
PubMed1982

Fluorescent triplet probes for measuring the rotational diffusion of membrane proteins.

We have previously described a method for measuring the rotational diffusion of membrane proteins by using fluorescent triplet probes [Johnson & Garland (1981) FEBS Lett. 135, 252-256]. We now describe the criteria by which the suitability of such probes may be judged. In general, the greatest sensitivity is achievable with probes where the ratio of the quantum yields for prompt fluorescene (phi f) and triplet formation (phi t) are high, as with Rhodamine (phi f/phi t congruent to 10(3)). However, considerations of heat generation at the sample membrane, of time resolution of fast rotations and of irreversible bleaching of the fluorescent probe also apply. The immediate environment of a probe molecule at a membrane protein must also be important in determining the performance of a given probe. Nevertheless, we describe guidelines for evaluating the likely usefulness of fluorescent triplet probes in measurements of membrane protein rotation.

Diffusion↗
PubMed1982

Sweat gland tumors of the head and neck.

Surgeons performing soft-tissue surgery in the head and neck area occasionally will encounter other varieties of neoplasms, such as skin-appendage tumors, in addition to basal cell carcinoma and squamous cell carcinoma. Sweat gland tumors are the most common variety of the skin-appendage tumors and the most easily confused with basal cell carcinoma and squamous cell carcinoma. We report this case to illustrate this fact. The classification of sweat gland tumors and their suggested management are reviewed.

Adenoma, Sweat Gland↗
PubMed1982

Effects on labeling index as a predictor of response to chemotherapy in the 13762 adenocarcinoma.

A series of 24 experiments was carried out, in which treatment effect was determined in vivo on rats bearing measurable implants of 13762 adenocarcinoma treated with a variety of chemotherapeutic agents, alone or in combination. In 11 experiments, a reduction in mean tumor area was observed after treatment (response), while 13 showed no such effect (no response). For each experiment, cells from tumor-bearing animals were placed in suspension culture (10 experiments) or in two-layer soft-agar culture (14 experiments) after 24 h of exposure to drug-containing plasma or control plasma. Cells were harvested from cultures at 24-h intervals thereafter for determination of the thymidine labeling index in treated versus control populations. The sum of labeling indices in control plasma divided by that in treated plasma was determined to combine the available data over time (overall ratio). Critical values for this ratio were defined, which demonstrated significant depression of the labeling index. Significant labeling index depression occurred in nine of 11 experiments where response in vivo occurred, and in one of 13 in which no response was seen (P = 0.0004 by Fisher's exact test). When experiments carried out in soft agar culture or in suspension culture were examined separately, the association of labeling index depression in vitro and response in vivo remained statistically significant. In this model system, labeling index depression by drug-containing plasma is highly predictive of response to therapy.

Adenocarcinoma↗