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P A Parsons

Publications and source records attributed to P A Parsons.

At least 19 recordsLinked to original sources
PubMed1992

Fluctuating asymmetry: a biological monitor of environmental and genomic stress.

Increased fluctuating asymmetry (FA) of morphological traits occurs under environmental and genomic stress. Such conditions will therefore lead to a reduction in developmental homeostasis. Based upon temperature extreme experiments, relatively severe stress is needed to increase FA under field conditions. Increasing asymmetry tends, therefore, to occur in stressed marginal habitats. Genetic perturbations implying genomic stress include certain specific genes, directional selection, inbreeding, and chromosome balance alterations. It is for these reasons that transgenic organisms may show increased FA. As there is evidence that the effects of genomic and environmental stress are cumulative, organisms in a state of genomic stress may provide sensitive biological monitors of environmental stress.

Animals↗
PubMed1991

Monoclonal immunofluorescence compared with silver stain for investigating Pneumocystis carinii pneumonia.

Two hundred and eighty two specimens from 220 patients positive for HIV with respiratory tract symptoms, or febrile illness, or both, were examined for the presence of Pneumocystis carinii. Specimens were either induced sputum samples or bronchoalveolar lavage fluids. To establish the optimal method for laboratory diagnosis a comparison was made of detection of the organism by use of monoclonal antibody and immunofluorescence with conventional silver staining methods. Three commercially available reagents for immunofluorescence were also compared. Immunofluorescence was significantly more sensitive than the silver stain and the best results for immunofluorescence were obtained using. Northumbria Biologicals Ltd reagents.

Bronchoalveolar Lavage Fluid↗
PubMed1990

Radiation hormesis: an evolutionary expectation and the evidence.

Fundamental to evolutionary biology is the tendency for organisms to become progressively adapted to those environments to which they are most frequently exposed. Since background radiation is a universal component of our environment, radiation hormesis is an evolutionary expectation. Whole-of-life experiments and more numerous (and evolutionarily more artificial) shorter duration and higher dose-rate experiments are consistent with this expectation. Additional research is needed especially at the molecular level to search for underlying mechanisms, and implications for radiation protection guidelines need to be analyzed.

Adaptation, Physiological↗
PubMed1990

Fluctuating asymmetry: an epigenetic measure of stress.

(1) Fluctuating asymmetry (FA) is a useful trait for monitoring stress in the laboratory and in natural environments. (2) Both genomic and environmental changes can increase FA which represents a deterioration in developmental homeostasis apparent in adult morphology. Genetic perturbations include intense directional selection and certain specific genes. Environmental perturbations include temperature extremes in particular, protein deprivation, audiogenic stress, and exposure to pollutants. (3) There is a negative association between FA and heterozygosity in a range of taxa especially fish, a result consistent with FA being a measure of fitness. (4) Scattered reports on non-experimental populations are consistent with experiments under controlled laboratory conditions. FA tends to increase as habitats become ecologically marginal; this includes exposure to environmental toxicants. (5) In our own species, FA of an increasing range of traits has been related to both environmental and genomic stress. (6) Domestication increases FA of the strength of homologous long bones of vertebrate species due to a relaxation of natural selection. (7) FA levels are paralleled by the incidence of skeletal abnormalities in stressful environments. (8) Increased FA is a reflection of poorer developmental homeostasis at the molecular, chromosomal and epigenetic levels.

Animals↗
PubMed1989

Selection for increased desiccation resistance in Drosophila melanogaster: additive genetic control and correlated responses for other stresses.

Previously we found that Drosophila melanogaster lines selected for increased desiccation resistance have lowered metabolic rate and behavioral activity levels, and show correlated responses for resistance to starvation and a toxic ethanol level. These results were consistent with a prediction that increased resistance to many environmental stresses may be genetically correlated because of a reduction in metabolic energy expenditure. Here we present experiments on the genetic basis of the selection response and extend the study of correlated responses to other stresses. The response to selection was not sex-specific and involved X-linked and autosomal genes acting additively. Activity differences contributed little to differences in desiccation resistance between selected and control lines. Selected lines had lower metabolic rates than controls in darkness when activity was inhibited. Adults from selected lines showed increased resistance to a heat shock, 60Co-gamma-radiation, and acute ethanol and acetic acid stress. The desiccation, ethanol and starvation resistance of isofemale lines set up from the F2s of a cross between one of the selected and one of the control lines were correlated. Selected and control lines did not differ in ether-extractable lipid content or in resistance to acetone, ether or a cold shock.

Acetates↗
PubMed1989

Oesophageal symptoms, their causes, treatment, and prognosis in patients with the acquired immunodeficiency syndrome.

In a prospective study of 154 AIDS patients, 48 (31%) complained of pain on swallowing both liquids and solids and 32 (21%) of these also had dysphagia. While candidiasis was the most common cause of symptoms (26 patients), discrete ulceration of the oesophagus occurred in 12 instances in 10 patients (four cytomegalovirus, four herpes simplex virus, three aphthous ulcer, one peptic ulcer). One patient had a diffuse oesophagitis caused by Mycobacterium avium intracellulare. No cause was found for the oesophageal symptoms in four patients. Kaposi's sarcoma (KS) was found in seven patients associated with other pathology in four. All 26 patients with oesophageal candidiasis only, also had oral involvement. All the patients with herpes simplex virus (four) and aphthous ulcers (three) had obvious perioral involvement. Three of the four patients with cytomegalovirus ulceration had evidence of disease elsewhere (colon or retina). All patients with Kaposi's sarcoma lesions had skin and buccal cavity involvement. The cause of oesophageal disease was usually obvious at endoscopy. The appearance of candidiasis was typical and the various ulcerating lesions also had different macroscopic configurations. Cytomegalovirus infection produced deep linear ulcers in the distal oesophagus, herpes simplex oesophagitis is similar in appearance to the typical perioral lesions of fluid filled vesicles. Diagnostic radiology was not helpful in most patients. In nine of 17 patients with candidiasis, the barium swallow examination performed within 24 hours of presentation was normal. In only three of seven patients with oesophageal ulceration (three cytomegalovirus, two herpes simplex virus, one aphthous, one peptic) was there evidence of an abnormality. Treatment produces symptomatic relief. All patients with candidiasis responded to ketoconazole, the four with herpes simplex virus to acyclovir and one of three with aphthous ulceration had a dramatic response to thalidomide. The three patients with cytomegalovirus infection who were treated with foscarnet had a prolonged remission of symptoms. The overall prognosis of patients with oesophageal symptoms is poor, with an average survival time from a definitive diagnosis of five months (range one to 13).

Acquired Immunodeficiency Syndrome↗
PubMed1979

Changes in the main submandibular salivary duct of rabbits resulting from ductal ligation.

Normal submandibular ducts from rabbits have been examined by mucosubstance histochemistry, transmission and scanning electron microscopy. The results were compared with the appearances of ducts removed 4...6 weeks after ligation. The normal ducts were composed mainly of columnar "light" cells and basal cells but, in addition, some "dark" cells and scattered goblet containing sulphated mucins were always present. The luminal surface of the ductal cells possessed numerous microvilli protruding into the lumen, and a rim of negatively charged mucin was present on this surface of these cells. After ligation the ducts became greatly distended by their fluid contents which remained under pressure until the duct was incised. The epithelial cells were flattened and appeared to contain less cytoplasm per cell; "light" cells, basal cells and "dark" cells were still recognisable. Goblet cells were much more plentiful than in the control ducts and often protruded into the lumen despite the increased intraluminal pressure. The development of a number of ciliated cells had also occurred and they were often situated close to goblet cells. Lymphatic vessels were more prominent around the ligated ducts. Luminal microvilli were less numerous than in the control ducts but the rim of negatively charged mucin on the luminal surface of ductal cells was more conspicuous. Mixed inflammatory cells were present within the lumina of ligated ducts especially in those parts adjacent to the ductal cells. No inflammatory cell has been observed passing through the wall of a main duct and the possibility exists that these cells had entered lumina within the gland and migrated from there to the main duct. The above findings may serve to help our understanding or physiological events in the ducts.

Animals↗
PubMed1978

Habitat selection and evolutionary strategies in Drosophila: an invited address.

There is an association among resource utilization divergence, habitat selection, and taxonomic divergence in the genus Drosophila. Given permissive conditions of temperature, humidity, and light intensity, an enormous vairety of resources is used in a diversity of habitats. These resources are considered in the cosmopolitan and endemic Australian fauna, providing evidence for habitat selection in the laboratory and field. Lek behavior in picture-winged species of subgenus Hirtodrosophila, a case of parallel evolution with lek behavior in subgenus Drosophila in Hawaii, is discussed in detail. Other examples of habitat selection discussed concern behavioral reactions of larvae to alcohol and other metabolites and the avoidance by adults of extreme physical environments. Evolutionary strategies involved in habitat selection are considered at various taxonomic levels in Drosophila. These considerations show that it is essential to relate results from laboratory studies to natural environments in order to explore the genetics of habitat selection.

Animals↗
PubMed1977

Adrenergic influences on the permeability of rabbit submandibular salivary glands to blood-borne horseradish peroxidase.

Horseradish peroxidase (HRP) administered close-arterially, has been found to enter rabbit submandibular saliva elicited by parasympathetic nerve stimulation. Adrenalin, superimposed on parasympathetic nerve stimulation, increased the passage of HRP into the saliva. Use of alpha- and beta-adrenoceptor agonists, either separately or together, and use of alpha- or beta-adrenoceptor antagonists together with adrenalin indicate that both alpha- and beta-receptor stimulation is necessary for this increase in glandular permeability to occur. Histochemical assessment showed that HRP had permeated the interstitial spaces of the gland and entered the spaces between adjacent parenchymal cells. However, in unstimulated glands it had only reached the lumina of striated ducts, but after adrenalin administration, peroxidase was also observed within acinar lumina. This work indicates that the predominant pathway taken by the HRP was via intercellular spaces and it is suggested that the permeability between junctional complexes of parenchymal cells is capable of being modified in vivo.

Animals↗