Thermogenesis and the effect of injected catecholamines on the oxygen consumption of cafeteria-fed rats.

1. The oxygen consumption (VO2) of unrestrained rats given a 'cafeteria' (high energy, high fat) or control diet was studied. The resting values of VO2 were the same in each dietary group, whether maintained at 26 degrees C or 6 degrees C. This negative finding suggests that cafeteria feeding is not an important cause of diet-induced thermogenesis (DIT). 2. The response of each group of rats to injected noradrenaline or dopamine was also studied. Each catecholamine could increase VO2 values but the response was much less in cold-adapted rats measured at 6 degrees C. In all experimental circumstances the dopamine response exceeded that of noradrenaline. There was no evidence that the cafeteria diet consistently increased the response to either catecholamine. 3. These results suggest that DIT cannot be equated with non-shivering thermogenesis (NST). Furthermore, it is suggested that dopamine would be a better agent for measuring the oxygen equivalent of NST, since it would stimulate the dopamine receptors as well as the alpha- and beta-adrenoreceptors of brown fat.

The value of cat ownership to elderly women living alone.

A survey of elderly women was carried out to discover their attitudes towards pet cats. The women were living in publicly-owned pensioner housing in two New Zealand cities. In one city cats were allowed in the pensioners' housing and in the other city they were not. Attitudes towards cats were more positive in the city where cats were allowed, and more positive if pensioners owned a cat, or wished to own one. As positive attitudes towards cats outweighed negative ones, the City Authority which had prohibited cats reversed its policy. There was conflicting evidence about the role of cats in reducing feelings of loneliness. It appears that "loneliness" signifies the loss of many aspects of social interaction and that pets may substitute for only some of these interactions.

Diet-induced thermogenesis in cafeteria-fed rats: a myth?

Oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory quotient were measured in rats given a high-fat cafeteria diet of the type that is said to promote diet-induced thermogenesis. No significant difference in the measurements as compared with controls was found at room temperature, at 5 degrees C, or in animals exposed to cold for several weeks. The result was the same whether open- or closed-circuit methods were used. The stimulatory effect of norepinephrine on the VO2 was identical in each dietary group. These results cast doubt on the alleged identity of diet-induced and nonshivering thermogenesis and may reflect the change in body composition of the animals rather than a primary response to dietary variation.

The effect of theophylline on regional cerebral blood flow responses to hypoxia in newborn piglets.

Theophylline attenuates cerebral hypoxic hyperemia in several adult models and this is thought to be due to receptor-mediated antagonism of adenosine, a proposed mediator of hypoxic hyperemia. This attenuation of hypoxic hyperemia reduces cerebral oxygen delivery and may thus jeopardize cerebral oxidative metabolism. With these considerations in mind, and because theophylline is widely used in neonatal medicine, the present study was designed to investigate the effect of theophylline on regional cerebral blood flow, cerebral oxygen delivery, and cerebral metabolic rate for oxygen during normoxia and hypoxia in the newborn piglet model. In 16 newborn piglets, regional cerebral blood flow (microspheres) increased 250-350% during hypoxia (PaO2 20-30 torr), while cerebral oxygen delivery and cerebral metabolic rate for oxygen were maintained at normoxic levels. Eight of these piglets were then given 10 mg/kg theophylline ethylenediamine intravenously and studies during normoxia and hypoxia were repeated; the remaining eight piglets served as time controls. Regional cerebral blood flow, cerebral oxygen delivery, and cerebral metabolic rate for oxygen during normoxia and hypoxia were not influenced by theophylline, despite plasma theophylline levels of 55-65 mumol/liter, and cerebrospinal fluid theophylline levels of 30-40 mumol/liter. These negative results are reassuring with respect to hypoxic cerebral blood flow control in theophylline-medicated infants. However, they do not support a role for adenosine as a mediator of cerebral hypoxic hyperemia in this model.

The action of dopamine upon glycerol and fatty acid release by rat brown adipose tissue.

Dopamine was shown to be effective in releasing glycerol and nonesterified fatty acid from brown fat adipocytes. The response was inhibited by dopamine-antagonists, and by a beta-blocker. This is further evidence that dopamine may be important in the release of energy from brown fat in newborn and cold-adapted animals.

Effects of neutrophil migration inhibitory factors on neonatal neutrophils.

Neonatal neutrophil migration was inhibited by preincubation with a lymphokine/monokine-rich medium conditioned by phytohemagglutinin-stimulated mononuclear leucocytes. Medium conditioned by unstimulated mononuclear cells or nonconditioned medium had no effect on neonatal neutrophil migration. Similar results were obtained with adult neutrophils. Migration distances in the presence and absence of a chemotactic gradient were much lower for neutrophils from neonates than adults when comparing treatments with the corresponding medium, i.e. medium conditioned by phytohemagglutinin-stimulated mononuclear leucocytes, medium conditioned by unstimulated mononuclear leucocytes, or medium unconditioned by mononuclear leucocytes (p less than 0.01). Although locomotion of both neonatal and adult neutrophils was inhibited by treatment, the percent inhibition of random migration was slightly but significantly less for neonates than adults (p less than 0.05). These results demonstrate that neutrophils from neonates are modulated by mononuclear leucocyte-derived mediators.

Immersible probe for continual monitoring of the population density of microorganisms grown in liquid media.

A common technique of measuring population density of microorganisms grown in liquid media is to withdraw a sample of the suspension and measure its apparent optical density with a spectrophotometer. The device we describe is capable of continually and automatically monitoring the population density of microorganisms grown in suspension.

An enzyme-linked immunosorbent assay for the quantitation of human IgG subclasses using monoclonal antibodies.

An enzyme-linked immunosorbent assay was established for the quantitation of human IgG1, IgG2, IgG3 and IgG4 using IgG subclass-specific monoclonal antibodies. The method could detect 1-10 ng/ml of the Ig subclasses. The technique is suitable for measuring IgG subclass concentration in sera of healthy adults and in supernatants from human lymphocytes cultured in the presence of pokeweed mitogen.

IgG subclass deficiency in children with IgA deficiency presenting with recurrent or severe respiratory infections.

A group of 22 children presenting with recurrent or severe respiratory tract infections who had low IgA levels (more than 2 SD below the mean for age) were examined for IgG subclass deficiency. Patients were screened for possible defects in neutrophil chemotaxis, bactericidal, fungicidal, and quantitative iodination activity, as well as for complement function. The majority of the patients showed IgG subclass levels below the mean for age. Nine of the children showed definite IgG subclass deficiency and at least two showed definite deficiency of more than one IgG subclass. The predominant subclass deficiency was found to be IgG1. While nine children showed IgG4 levels below the level detectable by the technique used, it is not possible to assess whether these patients are deficient in this isotype since some healthy subjects also give values below the level of detection. Most of the patients who had very low (1-6 mg/dl) or undetectable (less than 1 mg/dl) levels of serum IgA did not show IgG subclass deficiencies, while IgG subclass deficiencies were common among those with borderline low IgA levels (slightly more than 2 SD below the mean for age). Nine children showed total IgG levels close to 2 SD below mean for age, and at least six of these showed IgG subclass deficiency. The result suggests that patients with recurrent and/or severe respiratory infections who have borderline IgA and IgG levels may have IgG subclass deficiencies and if they do could benefit from immunoglobulin therapy.

Inhibition of the respiratory burst of human neutrophils by the polyamine oxidase-polyamine system.

The addition of the polyamines, spermine and spermidine, to human neutrophils caused a depression of the hexose-monophosphate (HMP) shunt activity of neutrophils stimulated with latex particles but not of unstimulated cells. The effect was dependent on the presence of bovine serum and was not observed when normal human serum was substituted for bovine serum. The polyamine oxidase (PAO) in bovine serum was probably responsible for generating the activity since normal human serum lacks PAO. A role for PAO was further supported by the finding that partially purified bovine PAO in the presence of polyamines similarly mediated inhibition of HMP shunt activity in stimulated neutrophils. Catalase failed to prevent the inhibitory effects of the PAO-polyamine system suggesting that H2O2 is not the responsible product. In addition, our results show that human pregnancy serum known to contain PAO activity in the presence of polyamines mediated a similar inhibition of the respiratory burst.

Indomethacin therapy of patent ductus in preterm infants controlled by plasma levels.

Indomethacin was given by suppository to 18 neonates for the treatment of patent ductus arteriosus. The plasma levels of the drug were measured by high pressure liquid chromatography. Permanent closure of the ductus was achieved in 12 of 21 treatments and took up to 48 h. Successful treatment was strongly associated with a plasma indomethacin level greater than 0.5 micrograms/ml in the 8 h after a dose. Decreased urinary output was more likely at the same level, but was also found with substantially lower figures. It is suggested that indomethacin therapy for patent ductus should be rationalized by measurement of the plasma level.

Diurnal variation in oxygen consumption of laboratory rats.

Oxygen consumption (VO2) was measured in Porton albino rats using a closed circuit apparatus. The groups studied were controls, cold-adapted animals, and those which had accumulated brown adipose tissue as a result of a cafeteria diet with a high energy content. It was possible to show in each group studied a difference in VO2 according to the time of day at which it was measured. This was consistent within each group studied. The diurnal variation shown (higher in the morning than in the afternoon) is characteristic of nocturnal animals. Measurement of VO2 then must be made within the same time-period or integrated over 24 h. Spurious correlations may otherwise occur.

Urinary catecholamine levels in the newborn infant.

The urinary concentrations of dopamine, noradrenaline and adrenaline were measured by a radioenzymatic method in 212 full-term and premature newborns. The ranges, means and standard deviations from birth to 4 days + are presented. The excretion of dopamine was ten times that of noradrenaline or adrenaline. The absolute concentrations of each catecholamine were reduced as birth weight decreased. The values were increased in babies with fetal distress. Any changes found in hypoglycaemic or jaundiced infants were attributable to prematurity. Very high levels were found in a few infants given tolazoline. We speculate that the role of dopamine production and excretion in the newborn has been underestimated. Dopamine may have an important role to play in the homeostatic mechanisms of the newborn.

The problem of mucus plugging in children with asthma.

The problem of mucus plugging of the lung was evaluated in 73 asthmatic children who had suffered a total of 187 episodes. The condition presented in young children, mostly with severe asthma, without any specific precipitating factor other than a severe attack of wheezing. Multiple lobe involvement was common, and the right lung was most often affected. Bronchoscopy was unnecessary but chest physiotherapy was found to be useful in the treatment of this complication of asthma.

The action of dopamine upon brown adipose tissue.

We increased the mass of interscapular brown adipose tissue in rats by dietary manipulation ("cafeteria" feeding), cold exposure, or by both. The animals were then used to determine the temperature response of the interscapular brown adipose tissue to dopamine or norepinephrine. These results, and the increase in blood glycerol values, were very similar for either catecholamine. These findings suggest that dopamine may have a role in releasing energy from brown adipose tissue similar to that of norepinephrine in the newborn infant.

A system to measure the forces and moments at the knee and hip during level walking.

The forces and moments in the sagittal plane at the knee and hip were calculated using gait data collected during level walking. Accelerations were measured by accelerometers attached to the legs, and the force reactions at the foot were measured by a force plate. The recorded accelerations and the foot forces were used to determine the joint reactions through a Newtonian formulation modeling the leg as articulated, rigid links. Twelve normal subjects were included in this study along with nine lower limb amputees. Obvious differences were observed when comparing amputee data to normal data both at the knee and hip. Gait data obtained by this system can be readily used to form criteria for objective gait analysis and improved prosthesis design.

Geometrical constraints on the rotational function of the femoral adductors in man.

Various authors have ascribed differing roles to the adductor muscles of the thigh in producing rotation of the femur. In the present study, measurements have been made on the changes in distance between origin and insertion of the adductor muscles which occur with rotation of the femur. Increases in distance indicate the muscle cannot produce a particular movement, while a decrease in length supports an argument that the muscle has a particular function. Measurements were made for positions of flexion-extension and adduction-abduction as well as anatomical rest. The adductor magnus was found to decrease in length during internal rotation while the adductor longus decreased in length during external rotation in most of the positions studied.