Search PubMed⌕ Search

Biomedical subjects

J D Davis

Publications and source records attributed to J D Davis.

At least 73 records · Page 4Linked to original sources

Analysis of the microstructure of the rhythmic tongue movements of rats ingesting maltose and sucrose solutions.

The interlick interval distribution of rats while ingesting maltose under real and sham feeding conditions and while ingesting seven concentrations of sucrose under real feeding conditions was analyzed. The analysis revealed that the licking behavior of rats is organized into bursts of licking at a high rate. These bursts occurred in clusters that were separated by brief (250-500 ms) interruptions. The clusters were separated by intervals that ranged from 500 ms to many hundreds of seconds. Sham feeding increased the length of the meal by increasing the number but not the size of the clusters. Increasing the concentration of sucrose increased monotonically the size of the clusters but varied the number of clusters as an inverted-V-shaped function. This analysis revealed the details of the central nervous system's control over ingestive behavior.

Animals↗

Role conflict and role ambiguity among respiratory care managers.

UNLABELLED: The health occupations and management literature does not specifically address role stress among technical directors of respiratory care departments. We undertook an analysis of role conflict, role ambiguity, and job satisfaction among technical directors of respiratory care departments in Texas. METHODS & MATERIALS: We distributed a questionnaire designed to measure role conflict and ambiguity and a questionnaire to elicit demographic and organization data to 283 technical directors in all Texas hospitals with more than 75 beds. Organization characteristics and demographic factors were studied as moderators. RESULTS: Analysis of the 199 responses received revealed that both role conflict (mean [SD] 3.86 [0.97] on 7.0 scale) and role ambiguity (2.64 [0.93] on 7.0 scale) scores were low compared to the neutral point of measure. Role overload, a component of role conflict, was found to be above the neutral point (4.64 [1.85]). One-way analysis of variance revealed no significant differences between the role conflict or the role ambiguity measures based on age, race, gender, number of employees supervised, size of institution, and position to which the respondent reported. Role conflict and role overload were each found to have significant negative correlations with job satisfaction (p less than 0.01). CONCLUSION: We are encouraged by the low role-conflict and ambiguity scores observed but concerned about the elevated role-overload scores. We believe that an in-depth study of role overload among respiratory care managers is warranted.

Adult↗

Similar effect of raclopride and reduced sucrose concentration on the microstructure of sucrose sham feeding.

Raclopride, a dopamine D2 antagonist, decreases the intake of sucrose solutions during sham feeding tests and of water during sham drinking tests in rats. To determine whether the reduced intake of sucrose by raclopride was due to a decrease in the positive reinforcing effect of sucrose or to an impairment in licking movements, we compared the rate, efficiency and pattern of licking after two procedures each of which decreased sucrose sham intake about 50%; these were (a) pretreatment with raclopride (ID50), and (b) dilution of the sucrose concentration sham fed from 10 to 5%. Microstructural analysis failed to reveal significant differences in the rate, efficiency (licks/ml) or patterns of licking between these two procedures. When raclopride inhibited the sham drinking of water, the rate and efficiency of licking were normal, but the patterns of licking were qualitatively different from those observed when raclopride inhibited the sham feeding of sucrose. We conclude that raclopride decreases intake of 10% sucrose during sham feeding and intake of water during sham drinking by decreasing the positive reinforcing potency of the orosensory effect(s) of the two liquids on licking rather than by decreasing the ability to lick. These results provide strong evidence that interaction of dopamine at D2 receptors is necessary for the normal sensory and/or hedonic processing of the orosensory stimuli produced by sucrose during sham feeding and by water during sham drinking.

Animals↗

Learning to sham feed: behavioral adjustments to loss of physiological postingestional stimuli.

The progressive increase in intake of a concentrated (0.8 M sucrose) solution seen when rats are first exposed to the sham-feeding procedure can be prevented by interspersing two real-feeding tests between each sham-feeding test. Under these conditions, sham intake is significantly larger than real intake but significantly smaller than intake on the fifth consecutive sham-feeding test. This result indicates that there is a learned negative-feedback signal based on the association of the taste and postingestive effects of 0.8 M sucrose which extinguishes under consecutive sham-feeding tests. Analysis of the rate of ingestion during the tests revealed that the conditioned negative-feedback signal operates during the first 6 min of a sham-feeding test that follows real-feeding tests. The effect of the absence of an unconditional negative-feedback signal appears from approximately 6 to approximately 20 min during a sham-feeding test.

Adaptation, Psychological↗

Analysis of lick rate measures the positive and negative feedback effects of carbohydrates on eating.

Previous work has shown that measuring the rate of ingestion of liquid diets, rather than simply volume, reveals important features of ingestive behavior which can help to explain why a particular volume of a liquid is ingested. This study is an extension of that work to a variety of different test solutions. In this study the rate of ingestion of saccharin, two different concentrations of glucose and sucrose and their mixtures with saccharin and seven different concentrations of maltose were measured. The rate functions were fit by the least-squares method to a linear function to determine the intercepts and slope constants. Analysis of how these two parameters changed with the concentration and composition of the test solutions confirms, using different test solutions, a previously reported conclusion that the initial rate of ingestion (the intercept) measures palatability and that the slope constant is a measure of the rate of development of a negative feedback satiety signal.

Animals↗

Development of a taxonomy of therapist difficulties: initial report.

While psychotherapists discuss amongst themselves and in supervision the struggles they experience face-to-face with their patients, empirical study of therapists' experience of psychotherapy has been scant and there has been little investigation of therapists' difficulties. We require tools for such investigation and in this initial report we describe the development of a taxonomy of situations that psychotherapists experience as difficult and indicate lines of research to which the taxonomy might be applied. We also suggest that our procedure might serve as a model of collective self-study for other groups of practitioner-researchers. Using accounts of our own difficulties as therapists, we constructed a consensual set of experimental categories that could be applied to describe them. These were designated as Therapist (T)-Incompetent, T-Damaging, T-Puzzled, T-Threatened, T-Out of Rapport, T's Personal Issues, Painful Reality/T's Ethical Dilemma (a combined category), T-Stuck, and T-Thwarted. We then employed a fresh set of 30 accounts, which were also drawn from our own experience but had not contributed to the development of the taxonomy, to study the taxonomy's reliability. Each of us rated the presence and predominance of the categories for each of the 30 accounts. Both presence and predominance of all nine categories in the taxonomy could be reliably identified, with about three raters required to ensure good reliability for all categories; alphas (for our group of seven raters) were in the range 0.88-0.95 for presence-absence and 0.83-0.94 for predominance. We conclude that the taxonomy is a serviceable tool for further investigation. We also show that we are discriminable from one another as therapists in terms of the kinds of difficulty we reported, differences amongst us conforming to what we know of one another's therapeutic practice. We note implications for the diagnostic use of the taxonomy in training and supervision.

Clinical Competence↗

Isolation and partial chemical analysis of firmly bound exopolysaccharide from adherent cells of a freshwater sediment bacterium.

Cells of a freshwater sediment bacterium produced firmly bound extracellular polymers in laboratory cultures which, at the ultrastructural level, resembled those produced by natural sediment bacterial populations. Production of the exopolymers during subculture was maintained by using as a source of inoculum the population of cells which adhered to each other and to the wall of the glass culture vessel. The exopolymers were selectively released from the cells by blending and centrifugation in the presence of EDTA. Evaluation of glucose-6-phosphate dehydrogenase activity and 2-keto-3-deoxyoctonate concentration indicated that only small amounts of intracellular and cell wall components were released from the cells during exopolymer removal. Chemical analysis of the isolated crude exopolymer material indicated that it contained protein, polysaccharide, and DNA. The treatment promoted the selective isolation of firmly bound polymers from the surface of adherent cells.

Bacteria↗

Determination of the gram-positive bacterial content of soils and sediments by analysis of teichoic acid components.

Many gram-positive bacteria form substituted polymers of glycerol and ribitol phosphate esters known as teichoic acids. Utilizing the relative specificity of cold concentrated hydrofluoric acid in the hydrolysis of polyphosphate esters it proved possible to quantitatively assay the teichoic acid-derived glycerol and ribitol from gram-positive bacteria added to various soils and sediments. The lipids are first removed from the soils or sediments with a one phase chloroform-methanol extraction and the lipid extracted residue is hydrolyzed with cold concentrated hydrofluoric acid. To achieve maximum recovery of the teichoic acid ribitol, a second acid hydrolysis of the aqueous extract is required. The glycerol and ribitol are then acetylated after neutralization and analyzed by capillary gas-liquid chromatography. This technique together with measures of the total phospholipid, the phospholipid fatty acid, the muramic acid and the hydroxy fatty acids of the lipopolysaccharide lipid A of the gram-negative bacteria makes it possible to describe the community structure environmental samples. The proportion of gram-positive bacteria measured as the teichoic acid glycerol and ribitol is higher in soils than in sediments and increases with depth in both.

Aluminum Silicates↗

Reduction of food intake and body weight by chronic intraventricular insulin infusion.

This study examined the effect of chronic infusions of insulin in one of three doses (5, 7.5 or 10 mU/day) into the third ventricle, on food and water intake and body weight in the rat. Solutions were infused via osmotic minipumps at a rate of 1 microliter/hour for seven days. The two highest doses of insulin produced a dose-related suppression of food intake and weight loss, which was greater than the effect produced by 5 mU/day or a control infusion of Ringers solution. The effect of 5 mU/day on food and water intake and body weight was similar to the effect of the control infusion. All groups treated with insulin decreased food intake during the day and night, although only differences in nighttime food intake were statistically significant. Ten mU/day also produced a significantly greater reduction in water intake than each of the other solutions. Weight loss in the animals infused with insulin could not be explained by a decrease in caloric intake alone. Food intake returned to normal in all groups by the end of a seven day post-infusion period, with recovery being slowest among the animals receiving the highest doses of insulin. All animals recovered body weight at approximately the same rate. These results provide further evidence for the view that brain insulin plays a role in the regulation of food intake and body weight.

Animals↗

Small effect of brown adipose tissue and major effect of photoperiod on body weight in hamsters (Mesocricetus auratus).

It has been suggested that brown adipose tissue plays a special role in the control of body weight. This hypothesis was investigated by measuring the body weight of female hamsters over a two month period following removal of interscapular brown adipose tissue. Two groups of animals were used, one maintained on a short day (10:14 light: dark ratio) and the other on a long day (16:8 light: dark ratio) photoperiod. Under both photoperiod conditions hamsters with interscapular brown adipose tissue removed gained somewhat more weight than their corresponding sham operated controls. Photoperiod, however, had a much larger effect on body weight. Hamsters maintained on short days increased their body weight by about 60 percent during the two months of the experiment whereas the hamsters maintained on long days increased their body weight by only about 17 percent. It was concluded that brown adipose tissue plays a small non special role in the control of body weight in the female hamster, but that the light-dark ratio is quantitatively much more important under these experimental conditions.

Adipose Tissue, Brown↗

Slaying the psychoanalytic dragon: an integrationist's commentary on Yates.

The basis for Yates' (1983) rejection of the case for 'reconciliation and integration' of behaviour therapy and psychodynamic psychotherapy is questioned. His arguments reflect a misunderstanding of the position he rejects and merely establish that those who adopt extreme viewpoints will find their positions irreconcilable. Doubt is cast on his apparent belief that a competition between models will ultimately yield a winner.

Behavior Therapy↗

Bioelectric properties and ion transport of excised rabbit trachea.

Bioelectric properties and 22Na+ and 36Cl- isotopic flows across rabbit trachea, an airway epithelium without submucosal glands, were measured in vitro. One hundred twenty-two excised tracheas exhibited a mean transepithelial electric potential difference (PD) of 12 mV (lumen negative), a conductance (G) of 8.5 mS X cm-2, and a short-circuit current (Isc) of 90 microA X cm-2. G remained stable for more than 3 h, but Isc and PD fell slowly (10%/h). G was inversely correlated with PD, but Isc and G were not correlated. Na+ was absorbed under both open-circuit (1.7 mueq. cm-2 X h-1) and short-circuit (2.2 mueq X cm-2 X h-1) conditions. Net Na+ transport accounted for 70% of Isc of the short-circuited trachea. Net Cl- flow in the absorptive direction approximated that of Na+ under open-circuit conditions (1.6 mueq X cm-2 X h-1). Under short-circuit conditions the small net flow of Cl- in the direction of secretion (0.4 mueq X cm-2 X h-1) was not significant. Both unidirectional Cl- fluxes were correlated with G; [14C]-mannitol permeability and Na+ flows were weakly or not correlated with G. We found no evidence of net HCO-3 or proton transport. Acetylcholine (10(-4) M), phenylephrine (10(-5) M), or isoproterenol (10(-5) M) induced no change in bioelectric properties or ion flows. We conclude that the rabbit trachea is primarily a Na+ absorbing epithelium. The absence of a correlation between mannitol permeability and G suggests that much of the Cl- conductance is transcellular. Whereas insensitivity of rabbit trachea to cholinergic and alpha-adrenergic agents is compatible with the absence of glands, the lack of response to beta-adrenergic agonists denotes a species difference (compared with canine trachea) in airway-surface epithelial cell function.

Acetazolamide↗

Glycerol reduces food intake in diabetic rats.

Streptozotocin diabetic rats received four daily subcutaneous injections of glycerol or a glycerol solution in place of water for a seven day period. Both night and total food intake in the subcutaneous glycerol group were significantly suppressed below untreated diabetic controls. The oral glycerol group showed a nonsignificant decrease in night foot intake and a significant reduction in day and total food intake. Consumption of additional fluid calories by the oral glycerol group contributed to the suppression of food intake in this group, but suppression in the subcutaneous group was unrelated to calculated calories obtained from glycerol. The oral glycerol group also consumed more of the glycerol solution than the other diabetic groups did of water. Results of this study support previous findings that subcutaneous and oral glycerol suppress food intake in normal rats although suppression with oral glycerol may have related to caloric intake, and suggest that low plasma concentrations of insulin do not interfere with the effects obtained with glycerol in normal animals.

Animals↗

Diabetes enhances the palatability of glycerol and glucose.

Male rats were provided with flavored solutions (0.3 M glucose, 0.3 M glycerol or 0.6 M glycerol) or water before and after the induction of diabetes by streptozotocin. Normal animals given 0.3 M glucose showed a significant increase in fluid intake but normal animals offered the glycerol solutions did not show an increase in intake compared to animals given water. After the onset of diabetes, exposure to the same flavored solutions resulted in significant increases in fluid intake by animals offered both the glycerol and glucose solutions. The animals offered glucose consumed significantly more than did the animals offered the glycerol solutions. The animals offered 0.6 M glycerol consumed significantly more than did the animals offered 0.3 M glycerol on 8 out of the 10 days of exposure. Therefore, while diabetes does not appear to modify the palatability of glucose it seems to produce an enhanced palatability for glycerol not seen in normal rats.

Animals↗

Sustained intracerebroventricular infusion of brain fuels reduces body weight and food intake in rats.

Long-term infusion of glucose, beta-hydroxybutyrate, and glycerol into the third ventricle of the rat brain caused a stabilization of body weight at a lower than normal level. Among the glucose- and glycerol-treated animals this weight loss was caused in part by temporary hypophagia. Among the animals treated with beta-hydroxybutyrate the weight loss was unaccompanied by a reduction in food intake. The results are consistent with the view that the systems controlling food intake and body weight are sensitive to the availability of brain fuels. They are not consistent however, with the view that these control systems monitor calories independently of their source.

3-Hydroxybutyric Acid↗