Search PubMed⌕ Search

Biomedical subjects

B Robertson

Publications and source records attributed to B Robertson.

At least 307 records · Page 17Linked to original sources
PubMed1985

A comparison between wheat germ agglutinin-and choleragenoid-horseradish peroxidase as anterogradely transported markers in central branches of primary sensory neurones in the rat with some observations in the cat.

Horseradish peroxidase conjugates of either the lectin wheat germ agglutinin or choleragenoid, the binding subunit of cholera toxin, were injected into the L5 spinal ganglion of adult rats. This enabled comparison of these two conjugates as anterograde tracers in the primary sensory system. After a postoperative survival of 4 h to 30 days, the rats were perfused and frozen sections from spinal and medullary regions receiving primary afferents were processed for horseradish peroxidase histochemistry with tetramethylbenzidine as the chromogen. Additional observations were made in two adult cats. Following injection of wheat germ agglutinin-horseradish peroxidase the labelling appeared mostly as small-sized granules. The concentration of labelled primary afferents in the grey matter of the spinal cord was greatest in the marginal zone and the substantia gelatinosa and less pronounced in the deep parts of the dorsal horn. Labelling was also found in a region lateral to the central canal and in the ventral horn. Following injection of choleragenoid-horseradish peroxidase the labelling appeared mainly as larger-sized granular profiles. The concentration of labelled primary afferents was greatest in the deep part of the dorsal horn and pronounced in a region lateral to the central canal and in the ventral horn. All these regions are known to receive large calibre fibres. The marginal zone and the substantia gelatinosa, known to receive fine calibre fibres, showed almost no labelling in the rat. In the cat, however, there was somewhat more labelling in the substantia gelatinosa. Labelling of neuronal cell bodies indicating transneuronal transport was seen after injection of wheat germ agglutinin-horseradish peroxidase. Transneuronal labelling did not seem to occur after injection of choleragenoid-horseradish peroxidase. The present findings show that wheat germ agglutinin-and choleragenoid-horseradish peroxidase give rise to markedly different labelling patterns. A possible explanation for the different labelling in the marginal zone and substantia gelatinosa could be that certain primary sensory neurones lack either receptors for choleragenoid on their neuronal plasma membrane or the ability to transport the choleragenoid-horseradish peroxidase complex.

Animals↗
PubMed1985

Prolongation of inhibitory postsynaptic currents by pentobarbitone, halothane and ketamine in CA1 pyramidal cells in rat hippocampus.

Spontaneous inhibitory postsynaptic currents (i.p.s.cs) were recorded in voltage-clamped CA1 neurones in rat hippocampal slices. The exponential decay of i.p.s.cs was prolonged by concentrations of sodium pentobarbitone as low as 50 microM. With concentrations up to 100 microM, there was no change in the amplitude or rise time of the currents but current amplitude was depressed at 200 microM. The prolongation of currents increased with drug concentration within the range tested (50 to 200 microM). Halothane, at concentrations from 1 to 5%, also increased the time constant of decay of i.p.s.cs. The effect increased with concentration and was fully reversible. Ketamine, at a concentration of 0.5 mM, increased the time constant of decay of i.p.s.cs by 50 to 80% and the effect was reversible. Ethanol (10-200 mM), nitrous oxide (75-80%), and caffeine (10 microM-5 mM) had no detectable effect on the i.p.s.cs. It is suggested that pentobarbitone, halothane and ketamine increase the time constant of decay of the i.p.s.cs by stabilizing the open state of channels activated by gamma-aminobutyric acid.

Animals↗
PubMed1985

Bronchiolar epithelial lesions in spontaneously breathing premature newborn rabbits.

Premature rabbit neonates were stimulated to breathe for time periods varying between 5 and 150 min. The distribution of bronchiolar epithelial lesions was determined morphometrically. Animals breathing for 5-10 min had no lesions. Focal necrosis and desquamation of bronchiolar epithelium were found in 36 of 46 animals breathing for 15-150 min. These lesions were similar to those previously observed in premature rabbit neonates after a few minutes of artificial ventilation.

Animals↗
PubMed1985

Surfactant treatment and ventilation by high frequency oscillation in premature newborn rabbits: effect on survival, lung aeration, and bronchiolar epithelial lesions.

Premature rabbit neonates delivered at gestational age 27 days were ventilated by high frequency oscillation for 60 min with 100% O2, using a frequency of 7-8 Hz, 50% inspiration time and mean airway pressures of 6-8 cm H2O. Twenty-five animals received bovine surfactant (2 ml/kg body weight; phospholipid concentration 85-100 mg/ml) in the tracheal cannula before onset of ventilation, and 22 littermates served as controls. In the surfactant-treated group, average tidal volume was about 10 times larger than in controls, yet only 15% of the estimated dead space. Judged from ECG recordings, the treated animals also had a much higher survival rate: 96 versus 5% (p less than 0.001). Morphometrically, mean alveolar volume density was increased in the surfactant-treated animals in comparison with controls: 0.65 +/- 0.08 versus 0.37 +/- 0.08 (means +/- SD; p less than 0.005). Bronchiolar epithelial lesions were found in all control animals and were severe in almost all cases. In the surfactant-treated group, epithelial lesions were absent in 12, mild in 11, and fairly prominent in two animals. We conclude that after treatment with surfactant, the premature newborn rabbit can be ventilated adequately with high frequency oscillation at comparatively low mean airway pressures and that surfactant replacement effectively reduces the development of epithelial lesions in conducting airways during high frequency oscillation.

Animals↗
PubMed1985

Partial ureteric obstruction in weanling rats. I. Long-term effects on the renal morphology.

Partial obstruction of one ureter was created in weanling rats (3 weeks old) and its effects were studied after 3, 6, and 9 weeks. Within 3 weeks, a considerable hydronephrosis had appeared, which did not progress with time. No effect on parenchymal weight was observed, either on the obstructed side or on the contralateral, intact one. Histological examination revealed a marked deformation of the papilla in about 25% of the hydronephrotic kidneys and evidence of chronic pyelonephritis in 40%. However, the inflammatory changes were restricted to the attenuated circumhilar 'edges' of the parenchyma, thus involving only a minor portion of the kidney. The body weight of the animals obstructed for 9 weeks was 12% lower than that of normal, sham-operated controls. In summary, the effect on the renal parenchyma of partial ureteric obstruction, created in the weanling period, was relatively discrete and less pronounced than when obstruction is performed in the neonatal period.

Animals↗
PubMed1985

Physiological activity of pulmonary surfactant with low protein content: effect of enrichment with synthetic phospholipids.

A natural surfactant with low protein content (1%) was prepared by a sequence of cold centrifugation, heating to 90 degrees C, sucrose-gradient centrifugation, and extraction with chloroform:methanol. Some of the material was enriched with dipalmitoylphosphatidylcholine (DPPC) and unsaturated phosphatidylglycerol (PG) to relative concentrations of 56% and 10%, respectively. The in vitro physical properties of these preparations were evaluated with pulsating bubble and Wilhelmy balance and their in vivo activity with experiments on artificially ventilated premature newborn rabbits, delivered on day 27 of gestation. The animals were kept in body plethysmographs at 37 degrees C and ventilated artificially with a standardized sequence of insufflation pressures: 25, 20, and 15 cm H2O. The lungs were fixed by vascular perfusion and the alveolar expansion evaluated morphometrically in histologic sections. Enrichment of surfactant with DPPC and PG resulted in lower minimal surface tension during surface compression but did not further improve lung compliance or the alveolar expansion pattern. Treatment with nonenriched surfactant at a phospholipid concentration of 100 mg/ml (individual dose = 200 mg/kg) caused a markedly increased lung compliance at all insufflation pressure levels (p vs. controls less than .01). Our data indicate that pulmonary surfactant remains physiologically active after removal of most of its protein components and that enrichment with DPPC and PG reduces the in vitro minimal surface tension without adding to the in vivo efficacy.

Animals↗
PubMed1984

The effect of temperature on the growth and decay times of miniature end-plate currents in the mouse diaphragm.

The temperature dependence of both the growth and the decay phases of miniature end-plate currents was investigated in the mouse diaphragm. The relationship between the log of the time constant of decay and reciprocal temperature was linear, that between the growth phase duration and temperature was not linear, the Q10 being higher over the low end of the temperature range. The possible reasons for the non-uniform Q10 of the growth time of the miniature end-plate current are discussed.

Animals↗
PubMed1984

Lung morphology and phospholipids after experimental inhalation of soluble cadmium, copper, and cobalt.

Rabbits were exposed to chlorides of cadmium, copper, or cobalt, for 4-6 weeks (5 days/week and 6 hr/day) at levels ranging from 0.4 to 0.6 mg metal/m3. After exposure to Cd2+ the lungs were enlarged and an interstitial infiltration of neutrophils and lymphocytes as well as intraalveolar accumulations of large, vacuolated macrophages were observed. Morphometrical measurement of volume density of type II cells showed a 2.5-fold increase due to enhancement of cell size as well as cell number. The phospholipid content of lung tissue, determined in the lower left lobe, increased by 40%, mainly due to elevated levels of disaturated phosphatidylcholines. The results indicate that Cd2+ induces a reaction pattern similar to that seen following exposure to Ni2+, in addition to which Cd2+ causes interstitial alveolitis. Exposure to Cu2+ and Co2+ only affected the type II cells. Exposure to Cu2+ resulted in a 1.5-fold increase in volume density, probably due to enhanced number of cells. Following exposure to Co2+ the type II cells formed nodules protruding into the alveolar lumen. However, no significant increase in volume density occurred. The possible association between this abnormal growth pattern and early tumor formation deserves further investigation.

Aerosols↗
PubMed1984

Inhibitory post-synaptic currents in rat hippocampal CA1 neurones.

Spontaneous synaptic currents were recorded in voltage-clamped CA1 neurones in rat hippocampal slices at room temperature (21-25 degrees C). The currents, which could be seen at the resting membrane potential only when cells were loaded with chloride ions, were blocked by bicuculline. It was concluded that they were inhibitory post-synaptic currents (i.p.s.c.s) generated by the opening of chloride-selective channels activated by gamma-aminobutyric acid (GABA). In twenty-nine cells, ten to forty-five i.p.s.c.s were recorded at a potential between -75 and -85 mV. In every cell, i.p.s.c.s varied widely in amplitude with an average coefficient of variation of 28.7%. The mean amplitude varied from 0.22 to 1.16 nA with an average of 0.52 nA. Reversed (outward) currents could be recorded from cells voltage clamped at positive potentials. Null potentials varied between -20 and +20 mV, the variability being attributed to differences in chloride loading. Most currents had a rapid growth phase with a mean growth time (20-80% of peak) of 1.1 ms followed by a slower decay phase. The decay phase was exponential with a single time constant. The average decay time constant (tau D) ranged from 8.3 to 16.2 ms with a mean value of 11.0 ms. The rate of decay of currents was affected by membrane potential. tau D decreased exponentially with hyperpolarization in the range from +40 to -120 mV with an average volt constant (H value) of 146 +/- 9.6 mV (mean +/- 1 S.E. of mean, n = 17). The mean value of tau D at 0 mV was 19 ms. In some cells, growth times also decreased with hyperpolarization. The decay of currents was faster at higher temperatures but remained exponential. At 32 degrees C, the average tau D at 0 mV was 8.3 ms (n = 5) giving a Q10 value of 3.3 for the decay time constant at 0 mV. The frequency and mean amplitude of i.p.s.c.s were reduced by tetrodotoxin (TTX) or cadmium, indicating that many of the currents were generated by action potentials in presynaptic terminals. The spontaneous 'miniatures' remaining had the same time course and voltage sensitivity as currents recorded in normal solutions. Pentobarbitone (50-100 microM) greatly prolonged the decay of i.p.s.c.s but had no discernible effect on their amplitude or growth phase.

Action Potentials↗
PubMed1984

Lung expansion in premature newborn rabbits treated with emulsified synthetic surfactant; principles for experimental evaluation of synthetic substitutes for pulmonary surfactant.

This paper presents a sequence of tests for experimental evaluation of potential substitutes for pulmonary surfactant. Differential thermal analysis and the pulsating bubble technique were applied to identify an emulsified mixture of synthetic lipids with properties similar to those of natural surfactant. Instilled into the airways of premature newborn rabbits, this emulsion improved pulmonary pressure-volume characteristics and enhanced lung-thorax compliance during artificial ventilation. However, the in vivo effect was inferior to that of natural surfactant, especially as the emulsion failed to prevent the development of bronchiolar epithelial lesions.

Animals↗
PubMed1984

Technetium pertechnetate scintigraphy to detect ectopic gastric mucosa in Meckel's diverticulum.

Tc-pertechnetate scintigraphy was performed in 81 infants and children, clinically suspected to have Meckel's diverticulum with ectopic gastric mucosa. The predominant symptom was rectal bleeding and anemia. Twenty-two patients underwent laparotomy and 12 had Meckel's diverticulum with ectopic gastric mucosa. In operated patients the sensitivity of scintigraphy in detecting ectopic gastric mucosa was 0.75, the specificity 1.0 and the diagnostic accuracy 0.86; the diagnostic accuracy was estimated to 0.96 for the whole material. Histologic examination of the diverticula showed a smaller area of the ectopic mucosa in cases with negative scintigraphic findings. In addition, prominent fibrosis seemed to be a more consistent finding in cases with negative as opposed to those with positive scintigraphic findings. Presence of anemia may provide a guideline as to whether or not scintigraphy is indicated.

Adolescent↗
PubMed1984

Improved lung-thorax compliance in the premature rabbit neonate after treatment with dibuturyladenosine-3':5'-cyclic monophosphate.

Premature rabbit neonates, delivered on day 28 of gestation, were treated with a single dose of dibuturyladenosine-3':5'-cyclic monophosphate (cyclic AMP), 300 mg/kg, immediately after delivery, saline-injected litter-mates serving as controls. All animals were kept in body plethysmographs and ventilated artificially with 100% oxygen for 1 h, with a maximal tidal volume of 10 ml/kg body weight. Lung-thorax compliance was significantly improved in animals treated with cyclic AMP, both 30 and 60 min after onset of ventilation (0.92 +/- 0.09 vs. 0.59 +/- 0.08 ml/cm H2O.kg and 0.96 +/- 0.09 vs. 0.53 +/- 0.08, p less than 0.005), but there was no improvement in alveolar air expansion, evaluated histologically. Phosphatidylglycerol was absent in alveolar wash from all control animals, but present in 3 of the 8 pooled samples from the animals treated with cyclic AMP; this difference was not statistically significant, however.

Animals↗
PubMed1984

Toxicology of nickel.

Rabbits were exposed to low levels of airborne metals for 1-8 months, 5 days/week, 6 hours/day. After exposure, lung tissue was examined by light and electron microscopy. Macrophages lavaged from the left lung were examined morphologically and functionally. Phospholipids were analysed in lung tissue or lavage fluid. Metallic nickel dust, 0.1-1 mg/m3, affected alveolar macrophages, alveolar epithelial type II cells and phospholipids. In the lung tissue, nodular accumulation of macrophages was seen, and the volume density of alveolar type II cells was elevated. The amount of phospholipids was markedly increased, mainly due to an increase in disaturated phosphatidylcholines. After 1 month of exposure the macrophages appeared active. After 3 months they appeared 'overfed' and inactive. Metallic iron, chromium and cobalt did not produce the same effects as nickel. Exposure to 0.2 mg/m3 soluble nickel as nickel chloride produced almost identical effects to those of metallic nickel, indicating that the effect of the metallic nickel particles was caused by nickel ions. Exposure to cadmium chloride produced nearly all the effects produced by nickel chloride. However, cadmium chloride increased the level of lysozyme in the macrophages whereas nickel chloride decreased it. Cadmium chloride also produced interstitial alveolitis and cytoplasmic blebs on the surface of the macrophages. Cobalt chloride affected the growth of the type II cells, which formed nodules, but did not seem to affect the production of surfactant material by those cells. Copper chloride produced no effect apart from a slight increase in volume density of the type II cells. Thus, of four divalent metal ions, three (Ni2+, Cd2+ and Co2+) in similar concentrations in the inhaled air produced clear but different pathological effects in the lungs.

Animals↗
PubMed1984

Surfactant replacement in neonatal and adult respiratory distress syndrome.

Animal experiments and clinical trials have shown that the neonatal respiratory distress syndrome (RDS) can be treated effectively by surfactant replacement via the airways. This treatment facilitates the resorption of fetal pulmonary fluid, promotes uniform air expansion of the lungs, enhances gas exchange, reduces the protein leak across the alveolar epithelium, and prevents the development of bronchiolar epithelial lesions during artificial ventilation. Data from recent animal experiments indicate that surfactant replacement prevents epithelial lung lesions also during high frequency ventilation. Surfactant replacement restores blood gases to normal in adult experimental animals with severe respiratory insufficiency induced by repeated lung lavage, suggesting that this type of treatment might be effective in clinical adult RDS.

Animals↗