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Anatomical and physiological relationships between central serotonin and vasopressin

Wed, 01 Jan 1992 00:00:00 GMT

Title: Anatomical and physiological relationships between central serotonin and vasopressin Authors: Faull, Christina M. Abstract: The role of serotonin (51M in the physiological regulation of AVP secretion is controversial. Neuroanatomical studies, largely in rats but also in human brains, have suggested that 5HT may have a direct modulatory effect on magnocellular vasopressin (AVP) secretion. Pharmacological and neurophysiological studies in animals have provided further evidence to support this and suggest that increase in 5HT neurotransmission leads to a rise in plasma AVP and that 5HT may be important in osmoregulated AVP secretion Studies investigating the importance of 511T as a modulator of AVP release in humans have not be undertaken. Indirect evidence of a putative role derives from the occurrence of hyponatraemia, and possible inappropriate AVP secretion,associated with the clinical use of drugs, particularly antidepressants, which have effects on 5HT neurotransmission. In addition there has been some suggestion that AVP secretion may be abnormal in depression where there is a putative abnormality of the 5HT nervous system. This research has approached the study of anatomical and physiological relationships between 5HT and AVP in 3 ways. Firstly through studies in normal man, secondly by studies in depressed patients, as a putative disease model of 5HT neurotransmission, and thirdly to more extensively explore the effect of pharmacological manipulation of 5HT neurotransmission using an animal model of osmoregulation. Studies in man found no evidence that 7 days treatment with a 5HT reuptake inhibitor (Fluoxetine) had a significant effect on osmoregulated AVP secretion. Studies in elderly depressed patients showed that there was an apparent deficiency of osmoregulated AVP secretion with normal ageing but found no evidence that either moderate depressive il lness, or treatment of the depression with Fluoxetine, had significant effect on water balance. Studies in the rat model of osmoregulation showed that acute 5HT reuptake inhibition stimulated basal AVP secretion and increased the osmotic sensitivity of AVP secretion but had no effect on the osmotic threshold of secretion. Chronic treatment (21 days) with the reuptake inhibitor had no significant effect on basal AVP secretion or on the osmotic threshold but significantly decreased the osmotic sensitivity of AVP secretion. Studies with the 5HT2/5HTIc antagonist, Ritanserin, and the 5HT2 agonist, DOI, suggested that this modulatory effect was not mediated through these receptor subtypes. Autoradiographic studies identified a low density of 5HT2 and 5HTIa receptors in the vicinity of the magnocellular neurons of the rat hypothalamus. The results suggested that 5HT modulates AVP secretion indirectly, possibly by inhibition of inhibitory afferent stimuli. This is of little physiological consequencien the normal rat and probably in healthy man where there is rapid accommodation and autoregulation. In situations where there is a dysfunction of the normal adaptive mechanisms such as in depression,the role of 5HT may be more important and occasionally may lead to severe hyponatraemia. Description: PhD Thesis

Factors limiting the abundance abd distribution of hirola (Beatragus hunteri) in Kenya

Tue, 01 Jan 2002 00:00:00 GMT

Title: Factors limiting the abundance abd distribution of hirola (Beatragus hunteri) in Kenya Authors: Andanje, Samuel A. Abstract: This study investigates the factors limiting the abundance and distribution of hirola, or Hunter's antelope, (Beatragus hunteri), in Kenya's Tsavo East National Park (ex-situ population) and Garissa (in-situ popUlation). The hirola is widely recognized as the most severely threatened monotypic species of antelope in sub-Saharan Africa. Data were collected between 1996 and 2000 on the ex-situ population, with occasional comparative sampling of the in-situ population. The study was carried out almost entirely in the field. Hirola were located by ground searching, by radio tracking and occasionally using aircraft; animals were observed from a landrover. In Tsavo NP the population was found to be static (71.1±9.3 in 844 km2 range), while the Garissa population was declining with about 672 animals remaining in a 5,171 km2 range. Calving in Tsavo took place between August and March, with the peak occurring in late October and early November. About 69.8% of calves died or disappeared within the first 6 months of life and about 18.0% survived to the age of 2 years. Mortality in Tsavo was predominantly associated with predation, while in Garissa, mortality was associated with disease and poaching. Hirola occurred in 8 distinct family groups in Tsavo, each with an adult male and a number of females and their offspring; temporary separations involving the adult male, or females with young, were also recorded. Remarkably, offspring left their natal groups at about 6-15 months of age and spent a period isolated or with other young animals; females eventually rejoined a family group or joined a lone male to form a new group. Young males generally formed bachelor groups and eventually separated as adults to become solitary. Hirola were most active in the early morning hours and late evening when it was cool; hot times of the day were spent resting in the shade of trees and bushes. Densities of other ungulate species within the hirola range varied seasonally, being more abundant in the wet season. Controlling for the relative abundance of other herbivore species, hirola in Tsavo were found to associate predominantly with Grant's gazelle (Ga~ella granfii), while in Garissa they associated mainly with topi (Damaliscus korrigwn). The presence of fewer associates and fewer alternative prey in the dry season appears to have increased the risk of predation to hirola, perhaps due to reduced detection and dilution effects. Home ranges occurred on generally elevated areas associated with red soils (in Tsavo) or sandy soils (in Garissa), and scattered seasonal waterholes. Vegetation in these areas was composed of tall, fairly open bushes interspersed with short green grass patches, that offered preferred food, shade and cover. In Tsavo, hirola fed on a total of 56 plant species (grasses, 74.9%; forbs, 24.2; and sedges, 0.9%) while in Garissa, 27 plant species were eaten (grasses 85.2% and forbs 14.8%). Hirola selected short green grasses and forbs, eating an entire plant (leaf, stem and inflorescence) at a mean bite height of 7.4±3.93SD cm. The nutrient content of the preferred plant species were measured on a seasonal basis. The Garissa population has declined as a result of range reduction, caused by human encroachment. In addition, it has been further affected by poaching and spread of diseases from cattle. The factors limiting the Tsavo population were investigated by multivariate analysis of the relationship between the main candidate factors (estimates of predation pressure, food abundance, shade tree densities, competitors, etc) and variation in the size, reproduction and mortality rates across the hirola family groups studied. The main limiting factors in the Tsavo population appeared to be predation pressure and the amount of specific microhabitats available for shade, cover against predators, and food. Finally, I discuss how these results may shape the development of conservation management strategies for hirola in the future. Recommendations include the restoration of protected areas in Garissa and the establishment of further ex-situ populations, preferably in predator free environments, to allow a rapid increase in numbers and to spread the risk of species extinction. Description: PhD Thesis

An epidemiological study of malajustment in childhood

Fri, 01 Jan 1960 00:00:00 GMT

Title: An epidemiological study of malajustment in childhood Authors: Brandon, Sydney Abstract: The object of this thesis is to present an epidemiological study of maladjustment in children drawn from a sample population. The work has been carried out as part of a more extensive longitudinal study of morbidity in childhood which has come to be known as the Newcastle Thousand Families Survey. Before describing the work upon which this thesis is based I would like to desoibe briefly the historical development of the present concepts of maladjustment and the approach to its study and treatment. In order to appreciate the background of the present work it will also be necessary to give some account of the City of Newcastle, from which the sample was drawn, and of the development of the Thousand Families Survey. Description: MD Thesis

The nature of guilt-proneness among young Saudi Arabian males and its relationship to illicit drug use and criminal offending

Mon, 01 Jan 1996 00:00:00 GMT

Title: The nature of guilt-proneness among young Saudi Arabian males and its relationship to illicit drug use and criminal offending Authors: Ben-Hussain, Abdulaziz Mohammed Abstract: While a number of Western personality and clinical psychologists have explored the adaptive functions of guilt-proneness in relation to a wide variety of behavioural patterns, the investigation of guilt-proneness in the Arabian-Islamic culture remains a neglected field Perhaps one reason for the absence of research dealing with guilt-proneness and its therapeutic application in the Arab world, and in the Saudi culture in particular, is the lack of an empirically-based measure of guilt-proneness. In this study, a new psychometric instrument, the Guilt-Proneness Scale (GPS), has been developed and used to investigate the role of guilt-proneness in inhibiting involvement in deviant behaviour with particular reference to juvenile illicit drug use and offending behaviour in Saudi Arabia. Exploratory factor analysis of the GPS (based on 214 Ss) has revealed three aspects of guilt-proneness phenomenon among Saudi subjects: (1) religious-related guilt (RG), (2) social-related guilt (SOG), and (3) self-oriented guilt (SG). The GPS total and these three subscales have demonstrated satisfactory levels of reliability in terms of both test-retest and internal consistency criteria. A confirmatory factor analysis examination using Structural Equation Modelling techniques (SEM), has confirmed this three-factor model for guilt-proneness. SEM was performed on the data of three subject groups: the first was 206 Ss., the second was 227 Ss., and the third (a combined group) was 433 Ss. Regarding the scale validation, the attempts to establish evidence of the criterion-related, construct, and disciminant validity of the GPS measure of guilt-proneness have been largely successful. The GPS has been utilised in investigating the role of guilt-proneness in inhibiting involvement in illicit drug taking and criminal behaviour of Saudi male juveniles. A study was conducted comparing individual differences in guilt-proneness between voluntarily admitted illicit drug patients (N = 64), convicted illicit drug users (N = 58), non-drug-abusing offenders (N = 71), and normal controls (N = 68). Based on a discussion of current theoretical and empirical approaches dealing with the relationship of guilt-proneness to involvement in illicit drug use and crime, a number of hypotheses were formed. It was hypothesised that: (H1) Normal subjects should manifest greater amount of religious-related guilt than would the voluntary drug abusers, convicted drug abusers, or offenders. (H2) Voluntarily admitted drug abusers should score higher on the three guilt-proneness subscales than would either the convicted drug abusers or the offender group. (H3) Guilt-proneness as measured by the GPS scales should be associated negatively with level of psychopathy. (H4) There should be significant differences in mean guilt-proneness scores among groups varying in their drug preference. (H5) Guilt-proneness in the offender group should be associated negatively with the number of convictions. (H6) The offenders who had committed violent crimes should display significantly lower level of guilt-proneness than those who had been involved in non-violent crimes. In addition to the these hypotheses, the interaction between guilt and selected variables was also examined. The analyses yielded promising results with regard to the measurement of individual differences in guilt predisposition between the groups tested. Both the convicted drug abusers and the non-drug-abusing offenders were marked by low susceptibility to experiencing guilt. Unlike the convicted drug abusers and the non-drug-abusing offenders, the voluntarily admitted drug abusing patients tended to maintain a healthy level of susceptibility to experiencing guilt which is postulated to be significantly influential in their decision to seek treatment. The normal controls manifested the highest religious-related guilt (RG) scale. The findings also revealed that the voluntarily admitted drug patients were distinguished from both the convicted drug takers and the non-drug-abusing offenders. However, no significant differences were found between the convicted drug takers or the offenders. An examination of the relationship of guilt-proneness to psychopathy indicated a significant negative correlation. This pattern of correlation, revealed for the first time for subjects of an Arabian culture, seems in line with most research exploring the relationship of guilt-proneness to psychopathy in Western juveniles. With regard to the examination of the individual difference in guilt-proneness between heroin users, alcohol users, and multi-drug users, it was found that all the three guilt-proneness scales differentiated significantly (p =<0.005) between the three groups of illicit drug taking. In addition, an examination of the relationship between level of guilt-proneness and experience with illicit drug use indicated that those newly involved in taking illicit drugs manifested significantly higher RG, SOG, and SG than the long-term users (p =<0.01). The results of the present study also showed that the RG, SOG, and SG scales differentiated significantly between the recidivists and first time offenders, and between offenders who had committed violent offences and those who had committed non-violent offences. Consistency of the effect of guilt-proneness in inhibiting involvement in deviant behaviour relating to the use of illicit drugs and commission of crimes, has been examined in a 33-month follow-up study. The follow-up study demonstrates that the re-admitted illicit drug patients had significantly lower GPS scores (p =<0.001) than those showing recovery from illicit drug dependence. The results derived by the follow-up also reveal an interesting relationship between relapse (readmission) and having low scores on the three GPS subscales. With regard to the offender group, the results demonstrated a significant correlation (p =<0.01) between the GPS scores of the Recidivists, taken at the time of the first and second testing with a 33 month interval. Hence evidence of the predictability of guilt-proneness as measured by the GPS scales, appears to be very promising. In general, the results of the comparison study as well as the follow-up study provide support for the positive role of guilt-proneness in inhibiting involvement in illicit drug taking and offending behaviour in the Saudi juveniles. In addition, these findings have demonstrated the effectiveness of the GPS as a measure of guilt and in predicting the occurrence of a particular class of behaviour. The final part of the present research was aimed at providing extended individual-case examples of use of the GPS. I have employed a personal construct theory approach through the use of the Repertory Grid technique. Individual GPS profiles, as well as Rep Grid data, were obtained for five in-patient illicit drug abusers and one incarcerated offender. Based on the use of cluster analysis, construct intercorrelation, and principal components analyses, the results of individual grids of each of the six cases were analysed. These demonstrated a pronounced and statistically significant agreement between GPS profiles and Rep Grid indicators of the individual's level of willingness to giving up the use of illicit drugs or involvement in crimes (p =<0.05). These findings demonstrate further the value of guilt-proneness in predicting the individual's response to rehabilitation. They clearly extend support for the GPS as a powerful and useful diagnostic tool. Its use in conjunction with the repertory grid technique with both drug abusers and criminal offenders seems very promising and encourages further research. Description: PhD Thesis