Effects of dopamine superfusion on the activity of rabbit carotid chemoreceptors in vitro.

The effect of different concentrations (0.001, 0.01, 0.1 and 1 mM) of dopamine on chemo-afferent activity was studied in the rabbit carotid body superfused in vitro. Excitation was the sole effect observed: it was always present for dopamine tests at 0.1 and 1 mM but was found in only 4 out of 9 tests at 0.01 mM and in 1 out of 5 tests at 0.001 mM. By comparison with a natural stimulus like hypoxia, dopamine excitation was delayed and had a much slower time course. Dopamine antagonists, (+)-butaclamol and haloperidol did not affect the responses to dopamine and to hypoxia. The results were not significantly altered when CO2 was added to the superfusing medium. It is concluded that dopamine is not a likely excitatory transmitter for chemoreception in the rabbit carotid body.

In vitro recording of chemoreceptor activity in catecholamine-depleted rabbit carotid bodies.

Carotid bodies, together with Hering's nerves, were excised from anesthetized rabbits 24, 48 or 72 h after single reserpine injections (5 mg kg-1, i.v. or i.p.) and were superfused in vitro. Some carotid bodies were processed for formaldehyde-induced fluorescence microscopy to assess catecholamine depletion. Twenty-four hours after reserpine treatment, most of the type I cell islets had lost their fluorescence and the number of spontaneously active chemoafferent units was dramatically reduced. Forty-eight hours after reserpine injection, both the fluorescence of type I cells had partially recovered and the number of chemoreceptor units was almost normal. A significant reduction of both the normoxic and hypoxic frequencies of discharge was demonstrated in carotid bodies examined 24 or 48 h after reserpine pretreatment. Superfusions with dopamine (1, 10, 100 microM) transiently restored the response to hypoxia. It is proposed that catecholamines contained in type I cells play a prominent role in the genesis of chemoafferent activity and in the chemoreceptor response to hypoxia.

Loss of chemoreceptive properties of the rabbit carotid body after destruction of the glomus cells.

Glomus cells of the rabbit carotid body were destroyed by local freezing. Electrophysiological recording of baroreceptor afferent activities showed that carotid sinus nerve regeneration was completed after 3 months. Nevertheless, ventilatory reaction as well as chemoreceptor afferent activity were no longer observed in response to the usual stimuli of arterial chemoreceptors (O2 test, NaCN). Results support the view that glomus cells are necessary for chemoreception and question the specificity of their afferent innervation.

Role of the carotid body cells: long-term consequences of their cryodestruction.

Rabbit carotid bodies were frozen in situ to destroy type I cells. After a one-year period of recovery allowing the sensory nerve fibres to regenerate, the animals were reexamined. Results showed that type I cells were not all destroyed in many instances but also that the presence of ventilatory reactions to chemoreceptor stimuli was always related to the presence of type I cells.

Changes in monoamine content of the rabbit carotid body following prolonged electrical stimulation of the carotid sinus nerve.

In the anaesthetized, paralysed and artificially ventilated rabbit the carotid sinus nerve (CSN) has been stimulated electrically for 6 h. At the end of the stimulation period, the carotid body (CB) has been removed, frozen and processed for measurement of the monoamines (MA) and of their catabolites with high-pressure liquid chromatography and electrochemical detection (HPLC-ECD). Results show a significant increase of dopamine (DA) and adrenaline (A) content and of all the metabolites. Besides an important augmentation of DA metabolism suggests that CSN efferent activity exerts some regulation on the MA content and turnover of the CB.

Effects of ion-containing liposomes upon the chemoafferent activity of the rabbit carotid body superfused in vitro.

The effects of calcium concentration changes in carotid body cells on the chemoreceptor discharges were studied in vitro on carotid bodies removed from anaesthetized rabbits. Addition of calcium-containing liposomes to the superfusing medium increased the chemoreceptors' discharges. This effect was abolished by hyperoxia or when EGTA-containing liposomes were simultaneously added with the calcium-containing liposomes. A histological control with ferritin-enriched liposomes showed that the liposome content was transferred into the cellular elements of the preparation except the nerve endings. Results suggest a relationship between calcium concentration changes in carotid body cells and chemoafferent activity.

Comparison of the monoamine and catabolite content in the cat and rabbit carotid bodies.

The monoamine and catabolite contents of a large number of rabbit (n = 95) and cat (n = 32) carotid bodies (CBs) have been measured by high performance liquid chromatography with electrochemical detection (HPLC-ED). The dopamine (DA) content as well as that of its precursors tyrosine (TYR), dihydroxyphenylalanine (DOPA) and catabolites dihydroxyphenylacetic acid (DOPAC), homovanilic acid (HVA) were approximately equal in both species. The noradrenaline (NA) content was 10 times larger in the cat than in the rabbit CBs. Twenty-nine out of the 32 cat CBs contained more NA than DA while the reverse was true in 92 out of 95 rabbit CBs. In 11 cats the right CB was sympathectomized and its DA and NA contents were compared to those of intact contralateral organs.

Personal constructs and homosexual stress.

This study introduced and elaborated a personal construct theory approach to the assessment of the potential for homosexual threat (homosexual stress). The measure, modified from personal construct research on death threat, was tested with 20 male and 20 female undergraduates. Those individuals who were more stressed by homosexuality were those with more negative attitudes toward homosexuality. Further, those individuals with the most negative attitudes toward homosexuals were those who saw homosexuality as invalidating more important constructs. Males who reviewed homosexuality as more stressful tended to construe homosexuality as a more personally meaningful issue; females showed the opposite tendency. The homosexual stress measure was independent of authoritarianism and was no highly related to religious fundamentalism. It is hoped that this new measure will give researchers a method of assessing the potential for homosexual threat that is both more direct and less obvious than existing face-valid questionnaires.

Dopamine metabolism in the rabbit carotid body in vitro: effect of hypoxia and hypercapnia.

Dopamine (DA) and noradrenaline (NA) were measured in the rabbit carotid body (CB) in vitro bv HPLC-ED under the following experimental conditions: 1h superfusion in normoxic, hypoxic (10% O2 in N2) or hypercapnic (8% CO2, 20% O2, 72% N2) medium, 5h superfusion in normoxia or hypoxia. The contents of DA and NA were decreased by hypoxia and hypercapnia after 1 h and 5h indicating a possible DA and NA secretion. Under the same experimental conditions synthesis of DA and NA and catabolism of DA were studied with enzymatic inhibition of tyrosine hydroxylase and monoamine oxidase (MAO) respectively. In hypoxia (1 h and 5h) the rate constant of DA synthesis was the same as in normoxia; however NA synthesis was decreased after 1 h hypoxia. On the contrary, hypercapnia, appeared to be a very effective stimulus of DA and NA synthesis.

Literalism, perspectivism, chaotic fragmentalism and psychotherapy techniques.

Literalism and chaotic fragmentalism have been advanced as two concepts to explain psychopathology while perspectivism has been used to explain psychological health (Landfield, 1980 a). It is hypothesized that, to the extent that they are therapeutic, all therapies move clients toward perspectivism and away from literalism and chaotic fragmentalism. Eight major schools of psychotherapy are discussed in terms of the principles of technique which enable them to change literalism and chaotic fragmentalism. The advantages of a unifying theory permitting diversity of techniques are discussed in relation to the ability of the clinician to be flexible yet not confused. Further, the unifying concepts of literalism, perspectivism, and chaotic fragmentalism are used to understand systematically the strengths and weaknesses of many therapeutic techniques. Finally, the implications of the differences in therapeutic techniques for changing different types of literalisms are discussed.

Psychopathology and the differentiation of values, emotions and behaviours: a repertory grid study.

Disturbed and non-disturbed subjects were compared on a Repertory Grid measure of the differentiation of values, emotions and behaviours. The disturbed subjects tended to show either excessively tightened or excessively loosened relationships between values, feelings and behaviours. Tight relationships denoted a close correspondence between a subject's assessment of these three items; loose relationships denoted a poor correspondence. Non-disturbed subjects showed more moderate relationships. Among the disturbed patients, loosened relationships were found in schizophrenics rather than neurotics or personality disorders and tightened relationships in neurotics and personality disorders rather than schizophrenics.

An investigation into variables affecting self-change on personal constructs.

This study investigated the relationship between the anticipation of change, construct meaningfulness, construct differentiation, and the amount of change occurring on personal constructs over a six-week period. The anticipation of change was defined as the degree of change the subject expected to occur over the six-week time period. The anticipation of change was positively related to the amount of change that occurred in the construing of the self. Construct meaningfulness was defined as the importance of the construct for understanding the self. There was a negative relationship between construct meaningfulness and the amount of change that occurred over the six-week interval. Construct differentiation was defined in terms of the relationship between constructs. A less differentiated construct has relationships with many other constructs; a more differentiated construct is more independent of other constructs. Although self-change was more likely to occur on more differentiated constructs, this relationship decreased to near zero when the effects of anticipating change and construct meaningfulness were controlled. In summary, self-change is most likely to occur on constructs on which the person sees change as likely, which are less important to the person, and are more independent of other constructs.

Mechanoreceptors sensitive to flow at the gastroduodenal junction of the cat.

Vagal afferent activity was recorded from the cervical vagus simultaneously with intraluminal pressure and flow rate at the proximal duodenum, in cats anesthetized with pentobarbital sodium. Thirty-seven mechanoreceptors that adapted slowly to maintained pressure changes were found to be sensitive to the flow of saline through the pylorus. The passage of liquid was associated with an increase of pressure equal to one-tenth of that necessary to trigger a response of the receptors during the distension of a small balloon. The frequency of discharge was increased by the passage of liquid for positive back pressures < or = 1.5 kPa but not when back pressure was negative. The relationship between the discharge of the receptor and the flow rate was complex and showed an hysteresis. We conclude that there exist slowly adapting mechanoreceptors sensitive to distension of the duodenum that can also sense the passage of liquid.

Localization of stretch and deflation receptors in the airways of the rabbit.

The localization of pulmonary stretch and deflation receptors was studied in anaesthetized, paralysed and artificially ventilated rabbits by recording the afferent activity in the vagus nerve while moving a double lumen balloon catheter along the tracheo-bronchial tree. The distributions of the two types of receptors were found to be parallel, with a proportion of 4 stretch receptors for 1 deflation receptor. A statistical analysis of the experimental results demonstrated that the distribution between stretch and deflation receptors was unbiased by the sampling procedure. However, in the localization of the stretch receptors along the tracheobronchial tree, there was a sampling bias, which constitutes a limit to the quantification of the results.

Chemoreceptor response to hypoxia and hypercapnia in catecholamine depleted rabbit and cat carotid bodies in vitro.

The response of single chemoafferent fibres to hypoxic and hypercapnic stimulation was studied in vitro under different experimental conditions: 1. control, 2. 24 h after reserpinization (5 mg/kg iv) and 3. 18 h after iv injection of alpha-methyl-p-tyrosine (100 mg/kg in the rabbit, and 1. control and 2. 24 h after reserpinization (5 mg/kg ip) in the cat. The spontaneous activity was decreased by monoamine depletion. The amplitude of the response to hypoxia and to hypercapnia was decreased by reserpinization in the rabbit and in the cat, the change being less marked in the latter species. Similarly, treatment with alpha-methyl-p-tyrosine decreased the ability of chemoreceptors to respond to hypoxia and hypercapnia and, in a few instances, these receptors could only be excited by superfusion of nitrogen-equilibrated medium. These results emphasize to possible role of monoamine, and particularly dopamine, in modifying the sensitivity of arterial chemoreceptors to their natural stimuli.

Organization scores of self and other on the repertory grid.

Traditional repertory grid studies of construct system organization have assumed that measures of organization derived from the construing of others are equivalent to measures derived from the construing of self. They also have assumed that constructs generated around the construing of others can be used to construe the self. Finally, they have assumed that the self is a unitary concept that does not vary across contexts. This study provides some empirical data on these assumptions by comparing the construction of self and others on repertory grids. Only moderate correlations between the organization of self and others were found on grid measures of construct independence and construct integration. Higher relationships were found on measures of construct system meaningfulness and the constructed use of categories. The implications of these data for repertory grid research are discussed.

Ultrastructural features of the carotid body after in vitro experiments: correlation with physiological results.

We have studied the ultrastructure and physiological properties of the rabbit carotid body superfused in vitro. After 3 h superfusion, the ultrastructural features of the carotid body cells, nerve fibres and nerve endings are similar to those observed after in vivo perfusion with fixative. After 5 h superfusion, the fluorescence of type I cells and sympathetic post-ganglionic nerve fibres appears normal, as demonstrated by the Falck method. After 6 h superfusion, some type I cells are characterized by a highly vacuolated cytoplasm whereas most of the nerve fibres and nerve endings still show a normal ultrastructure. Damaged cells are not more abundant in the centre of the organ than in the surface layer. Recordings from chemoafferent units demonstrate the possibility of superfusing the carotid body with an air-equilibrated medium without any noticeable excitation. Large and reproducible responses to hyperoxic and hypoxic superfusions are recorded. It is concluded that the in vitro superfused rabbit carotid body is a reliable and useful preparation for studying the mechanism of chemoreceptor excitation.

Monoamines and their catabolites in the rabbit carotid body. Effects of reserpine, sympathectomy and carotid sinus nerve section.

Monoamines and their metabolites have been measured by high performance liquid chromatography with electrochemical detection, in control rabbit carotid bodies and under several experimental conditions: 1) at different times (3 h, 6 h, 24 h, 48 h) after intravenous injection of reserpine (5 mg/kg); 2) 14 days after sympathectomy; 3) 14 days after section of the carotid sinus nerve. The results were analyzed with probability plotting methods. Dopamine was the most important monoamine in the carotid body (CB) and its variations were very large. It was almost entirely depleted by reserpinization without simultaneous increase in 3,4-dihydroxyphenylacetic acid. Sympathectomy increased dopamine content but did not change noradrenaline content. However data analysis suggested that noradrenaline might be compartmented in two pools: one with a large variance, located in the type I cells was increased after sympathectomy, the other, more constant, located in the sympathetic nerve endings was entirely depleted after sympathectomy. Section of the carotid sinus nerve increased dopamine and noradrenaline and quadrupled the serotonin content of the CB. It is proposed that carotid sinus and sympathetic innervations regulate the monoamine metabolism of the CB.