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Biomedical subjects

J B Morrison

Publications and source records attributed to J B Morrison.

At least 55 records · Page 3Linked to original sources
PubMed1982

N-Nitroso-N-methyldodecylamine and N-nitroso-N-methyltetradecylamine in household dishwashing liquids.

Eleven household dishwashing liquids and four household surface cleaners were analysed for N-nitroso-N-methyldodecylamine and N-nitroso-N-methyltetradecylamine by gas chromatography with detection using a Thermal Energy Analyzer. Both nitrosamines were found in three of the dishwashing detergents and one of the surface cleaners. [1-14C]-N-Nitroso-N-methyldodecylamine was used to determine recoveries, which were between 65 and 88%. Levels of N-nitroso-N-methyldodecylamine ranged from 112 to 661 ppb and those of N-nitroso-N-methyltetradecylamine from 46 to 151 ppb. A simple method was developed to screen the products for N,N-dimethyldodecylamine-N-oxide, a surfactant ingredient suspected of being the source of these nitrosamines. By application of this method it was established that all of the products formulated with this amine oxide contained these two nitrosamines, whereas in products that did not contain this ingredient, these nitrosamines were not detected.

Chromatography, Gas↗
PubMed1982

N-nitroso-N-methyldodecylamine and N-nitroso-N-methyltetradecylamine in hair-care products.

N-Nitroso-N-methyldodecylamine and N-nitroso-N-methyltetradecylamine, which cause urinary bladder tumours in experimental animals, were detected in several hair-care products formulated with N,N-dimethyldodecylamine oxide. Quantitative determinations were made using a gas-liquid chromatograph interfaced with a thermal energy analyser and using [1-14C]N-nitroso-N-methyldodecylamine as an internal standard. The presence of the two nitrosamines was confirmed by high-pressure liquid chromatography with a thermal energy analyser as detector, by photolysis of samples and by combined gas chromatography-mass spectometry. To test the reproducibility of the method, a single shampoo was selected for replicate analysis and was found to contain 90 +/- 8 ppb N-nitroso-N-methyldodecylamine and 37 +/- 11 ppb N-nitroso-N-methyltetradecylamine. Levels of N-nitroso-N-methyldodecylamine in other hair-care products ranged from 11 to 873 ppb and those of n-nitroso-N-methyltetradecylamine from 8 to 254 ppb.

Carcinogens↗
PubMed1982

Influence of respiratory heat transfer on thermogenesis and heat storage after cold immersion.

1. Ten male subjects were cooled on three occasions to a rectal temperature of 35 degrees C by immersion to the neck in water at 11.3 degrees C. The subjects were rewarmed for 60 min, once by metabolic heat production alone (shivering), once by inhalation rewarming with spontaneous breathing of saturated air at 47 degrees C (control) and once by inhalation rewarming with ventilation regulated at 40 litres/min by respiring a controlled fraction of CO2 (hyperventilation). 2. Metabolic heat production was substantially reduced by inhalation rewarming (P less than 0.05), from 913 kJ when shivering to 766 kJ (control) and 613 kJ when hyperventilating. The fall in metabolic heat production was greater than the corresponding respiratory heat gain, which increased from a loss of 41 kJ when shivering to gains of 85 kJ (control) and 169 kJ (hyperventilation). 3. As differences in mean skin temperatures were small (less than 1.0 degrees C), it is concluded that the lower metabolic heat production in response to increased respiratory heat input must result from more rapid central temperature gains. This conclusion is supported by the relative values of rectal and tympanic temperatures. It was calculated that the percentage of the total heat supply which was donated to the core increased from 13% during shivering to 16% for the control and 23% in hyperventilation. Results imply that respiratory heat input is more efficient than metabolic heat production in elevating central temperature.

Adult↗
PubMed1981

Effects of CO2 insensitivity and respiratory pattern on respiration in divers.

In a study of respiratory function under hyperbaric conditions one diver (TM) was found to have an extremely low ventilatory response to exercise with a postinspiratory pause typical of certain "carbon dioxide retaining divers." The respiratory function of diver TM is compared with that of four other divers having a normal ventilatory response. In exercise at 4 ATA hypoventilation and hypercapnia were potentiated to a greater extent in TM than in the other divers. Diver TM maintained a ventilation 25%-50% lower than that of the other divers and whereas their end-tidal Pco2 remained within reasonable limits (Pco2 less than or equal to 55 mmHg), that of TM rose to levels considered hazardous (Pco2 less than or equal to 76 mmHg). Results suggest that when a diver exhibits a postinspiratory pause in the breathing cycle, mixing of alveolar and dead space gas takes place. As a result, physiological dead space calculated according to the Bohr formula is unusually small. As alveolar Pco2 will rise during postinspiratory pause, mean arterial Pco2 may be lower than end-tidal Pco2. Such a respiratory pattern has a greater ventilatory efficiency than normal and may afford the diver some protection, albeit incomplete, from hypercapnia.

Atmospheric Pressure↗
PubMed1980

Accidental hypothermia: the effect of initial body temperatures and physique on the rate of rewarming.

After cooling in sea water, 14 subjects having varied core temperatures were rewarmed by inhalation of saturated air at 44 degrees C. Multiple linear regression analyses were computed for best possible subsets relating rectal and tympanic rewarming rates, phi i (i = R, T), to physiological and anthropometric measures. It was found that there was a good correlation between phi i and metabolic or ventilatory rates (0.61 less than r less than 0.74). Rewarming rates phi i could be more closely predicted by a combination of initial core temperatures and (height/weight)0.5 or by a combination of initial core temperatures and initial skin temperatures (0.75 less than r less than 0.88). The effectiveness of inhalation rewarming has been challenged and experimental studies appear contradictory. It is shown that the different inhalation rewarming rates measured are predictable and can be explained largely in physiological terms.

Adolescent↗
PubMed1979

Thermal increment provided by inhalation rewarming from hypothermia.

To quantify the core temperature gain derived from inhalation rewarming, 10 subjects were immersed in seawater (mean temperature 12 degrees C) until a 2 degree C drop in rectal temperature occurred, and were then rewarmed by breathing hot saturated air at 45 degrees C for 30 min. Each subject was rewarmed once breathing air and once rebreathing a controlled fraction of expired air adjusted to produce a hyperventilation of 50 l/min. After 30 min of rewarming mean rectal temperature had increased 0.39 degrees C in subjects breathing air compared with 0.77 degrees C in those hyperventilating (P less than 0.01). Corresponding gains in tympanic temperatures were 1.1 and 1.5 degrees C, respectively. Calculations indicate that the additional heat input with hyperventilation yielded a core (rectal) temperature gain of 5.1 X 10(-4) degrees C/l. It is concluded that each additional 10 l/min of ventilation of hot saturated air will increase the rate of core rewarming from hypothermia by approximately 0.3 degrees C/h.

Adult↗
PubMed1979

Breathing pattern and ventilatory response to carbon dioxide in divers.

The breathing pattern and ventilatory response to carbon dioxide of 10 experienced divers was compared with that of 10 nondivers of similar age and build. Breathing pattern was described by the equation VE = M (VT - K) and the response to carbon dioxide by VE = S(PCO2 - B). The divers exhibited a value form 27% lower than the nondivers; S was 33% lower. The difference was significant (P less than 0.05) in both cases. B was significantly higher (P less than 0.05) in the divers than nondivers. These differences are not attributable to age, build, or vital capacity. S was well correlated with M when all subjects were considered a single group. Within the diving group no correlation of S and M with diving experience was found.

Adaptation, Physiological↗
PubMed1978

Observations after loss of consciousness under water.

Two diving incidents were investigated in which 1) an experienced professional diver (A) lost consciousness during an air dive to 69 meters, and 2) an amateur sports diver (D) lost consciousness during a 40-meter air dive. In subsequent tests both divers' ventilatory responses to inspired carbon dioxide were found to be extremely low. Under simulated diving conditions, Divers A and D exhibited marked carbon dioxide retention during exercise at 30 meters (end-tidal PCO2 = 65 and 57 mmHg, respectively) and at 70 meters, Diver A stopped work in less than 3 min because of severe dizziness. Reduced sensitivity to carbon dioxide, perhaps caused by the interaction of hypercapnia and nitrogen narcosis, is thought to have been partly responsible for these incidents.

Carbon Dioxide↗
PubMed1976

Effects of increased O2-N2 pressure and breathing apparatus on respiratory function.

The ventilatory response of four subjects was measured at rest and various intensities of exercise. Experiments were conducted in a dry pressure chamber (1) at 1 ATA and 4 ATA with the subjects breathing from a low-resistance mouthpiece, and (2) at ATA with the subjects breathing from open-circuit breathing apparatus (Royal Naval Swimmers' Air Breathing Apparatus). At 4 ATA there was significant hypoventilation and hypercapnia, together with an increased tidal volume and lower respiratory frequency. The use of the breathing apparatus tended to amplify these changes in ventilatory response. In addition, the extent of hypercapnia at 4 ATA was related to the exercise intensity. When subjects breathed from a low-resistance mouthpiece, oxygen uptake was significantly greater at 4 ATA than at the surface for the same ergometric work load, but when they breathed from the breathing apparatus, the increase in oxygen uptake was not significant in comparison to surface values. At 4 ATA bradycardia was evident at all levels of exercise but was not affected significantly by the presence of the breathing apparatus.

Atmosphere Exposure Chambers↗
PubMed1975

Serum digitoxin concentrations in infants and children.

Serum digitoxin levels were measured in 18 infants (under two years) and in 23 children (aged 2-13 years) receiving maintenance therapy. Digitalization was carried out because of heart failure in 17 infants and 13 children and for control of dysrhythmia in one infant and 10 children. Mean maintenance dosage for infants was 0.0042 plus or minus 0.0008 (sd) mg/kg/day and for children was 0.0031 plus or minus 0.0012 mg/kg/day. The mean serum digitoxin level was not significantly different in infants (30 plus or minus 10 ng/ml, range 14-58) from that found for children (34 plus or minus 11 ng/ml, range 19-61). Both values were significantly different (P smaller than 0.001) from those determined in this laboratory for adults (mean 24 plus or minus 7 ng/ml, range 5-39). In four infants with electrocardiographic or other evidence of toxicity, the mean serum level was 71 plus or minus 2 ng/ml (range 68-72), and in four children with electrocardiographic or other evidence of toxicity, the mean serum level for digitoxin was 72 plus or minus 14 ng/ml (range 53-84). The data suggest that infants and children tolerate a higher serum digitoxin concentration without any evidence of toxicity and may require more digitoxin (mg/kg) for therapeutic effect than do adults. Serum digitoxin levels may serve as an important guide in determining the adequacy of digitalization and in the recognition and management of digitalis toxicity.

Adolescent↗