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Biomedical subjects

J A Allen

Publications and source records attributed to J A Allen.

At least 19 recordsLinked to original sources
PubMed2003

Incomplete sexual isolation in sympatry between subspecies of the butterfly Danaus chrysippus (L.) and the creation of a hybrid zone.

Subspecies chrysippus, dorippus and alcippus of the butterfly Danaus chrysippus differ at three biallelic colour gene loci. They have partially vicariant distributions, but their ranges overlap over a substantial part of central and East Africa, where hybridism is commonplace. We now report that the West African subspecies alcippus differs from other subspecies, not only in nuclear genotype but also in mitochondrial haplotype in both allopatry and sympatry. The maintenance of concordant nuclear and cytoplasmic genetic differences in sympatry, and in the face of hybridisation, is prima facie evidence for sexual isolation. Other evidence that suggests alcippus may be isolated from chrysippus and dorippus include differences in sex ratio (SR), heterozygote deficiency at one site and deduced differences in patterns of migration. We suggest that, within the hybrid zone, differential infection of subspecies by a male-killing Spiroplasma bacterium causes SR differences that restrict female choice, triggering rounds of heterotypic mating and consequent heterozygote excess that is largely confined to females. The absence of these phenomena from hybrid populations that test negative for Spiroplasma supports the hypothesis. The incomplete sexual isolation and partial vicariance of alcippus suggests that it is a nascent species.

Animals↗
PubMed2002

Use of questionnaire screening for vibration white finger in a high risk industrial population.

OBJECTIVES: To compare the results of questionnaire screening with those of objective testing in the identification of vibration white finger (VWF) in a high risk population. METHODS: Three groups of men (79 riveters, 52 healthy controls and 79 compensation claimants) were assessed for VWF by a detailed questionnaire covering occupational and general medical history and incorporating specific questions related to the presence or absence of relevant symptoms in their hands. Each then underwent provocative cold testing under controlled conditions using established protocols. The presence or absence of digital vasospasm following cooling was determined by finger systolic pressure measurements using laser Doppler flowmetry. The test protocols used have been evaluated in patients with a clear clinical diagnosis of non-occupational Raynaud's syndrome. RESULTS: 6.3% of the riveters and 83.5% of the claimants reported specific Raynaud's syndrome symptoms but 30.4% of the riveters and only 19% of the claimants tested positive for vasospasm after middle phalangeal cooling to 10 degrees C for 5 min. Using a more severe cooling protocol provoked vasospasm in 46.8% of the claimants. Lack of sensitivity or specificity of the objective testing could not explain the large discrepancies between the findings in the riveters and in the claimants. CONCLUSIONS: Questionnaire responses concerning VWF symptoms can be influenced by the context in which they are recorded. It is important to employ more objective methods in assessing all workers at risk of developing VWF.

Adult↗
PubMed2000

Digital vascular responses and serum endothelin-1 concentrations in primary and secondary Raynaud's phenomenon.

OBJECTIVE: To determine circulating endothelin-1 levels (ET-1) in patients with primary or secondary associated Raynaud's phenomenon (RP) under resting conditions and in response to cold provocation. METHODS: Patients were categorised as primary RP (18) or scleroderma associated RP (14). Finger blood flow was measured by venous occlusion plethysmography at finger temperatures of 32 degrees C and 24 degrees C. Vasospasm was detected as a finger systolic pressure of 0 mm Hg after standardised provocative cooling. Severity of vasospasm was assessed by the level of cooling required to provoke spasm. Plasma ET-1 levels were measured in antecubital blood withdrawn under baseline conditions (finger 32 degrees C) and at the point of vasospasm. Measurements were also made in 19 matched control subjects. RESULTS: Finger blood flow was lower in patients with RP than in controls, with no difference between the two RP groups. Vasospasm occurred in all patients with RP but not in any control subjects and a grading system of severity was established. Baseline plasma ET-1 levels were similar in patients with RP and controls. Increases in ET-1 levels at the point of vasospasm in patients or corresponding timepoint in controls were also similar. There was no significant difference between the ET-1 levels in the two RP subgroups when the fingers were warm or when vasospasm was present. CONCLUSIONS: These results do not support the hypothesis that ET-1 plays a part in the pathogenesis of RP. Objective testing is a useful adjunct to the clinical diagnosis of RP and allows assignment of a severity grade.

Adult↗
PubMed1999

Unemployment, depression, and health: a look at the African-American community.

OBJECTIVES: While the unemployment rate of African-American people is more than twice that of the white population, the research on the impact of unemployment on the health of this population is scarce. This study analysed the impact of unemployment on depression and well being among African-American people, and the factors associated with well being. METHODS: Logistic and multiple regression models were used to analyse panel data collected in the National Survey of Families and Households 1987-1992. African-American (1369) and white (6660) respondents were analysed separately. Outcome variables included an index of depression and self reported health status. MAIN FINDINGS: Differences between employment and unemployment groups were less significant for African-Americans than for the white population in predicting depression and well being. Health enhancing factors such as education and wealth were significantly associated with better health and lower depression indices among the white population but not consistently so among African-Americans. Satisfaction with personal relationships was the strongest predictor of well being for both groups. CONCLUSION: Research should focus on the special needs and circumstances of African-Americans, because protective factors may not have the same impact in different groups of the population.

Adolescent↗
PubMed1996

Hydrostatic pressure has different effects on the assembly of tubulin, actin, myosin II, vinculin, talin, vimentin, and cytokeratin in mammalian tissue cells.

Hydrostatic pressures in the range of hundreds of atmospheres are known to disrupt cytoskeletal organization in tissue culture cells, with profound changes in cell shape. The molecular mechanisms of these effects are poorly understood. To determine the effect of pressure on the cytoskeleton, and thus to provide better indicators of the molecular mechanisms, we used fluorescent antibody staining to compare the organizations of seven different cytoskeletal proteins in HeLa cells and rat osteosarcoma cells (ROS-17/2.8) subjected to different pressures up to 400 atm. Pressures of 300 atm or more caused cells of both lines to "round up" and to withdraw their lamellar extensions. However, this response varied within a population of cells, with some cells remaining spread at pressures that caused their neighbors to round up. The most resistant to rounding were those cells touching other cells, and the occasional giant cells. As expected, the rounded cells showed disruption of actin stress fibers and of vinculin and talin at focal contacts. The unrounded cells showed less disruption in the organization of these same proteins. Microtubules and myosin II filaments appeared resistant to 400 atm pressure in both cell types, whether rounded or unrounded. However, in HeLa cells, the intermediate filaments, vimentin and cytokeratin, depolymerized and formed small vesicles when pressures exceeded 200 atm, and this occurred in rounded as well as unrounded cells. In osteosarcoma cells, which do not have cytokeratin, vimentin did not depolymerize. We discuss different mechanisms that might explain these responses to pressure, including direct effects on the equilibria of protein polymerization and less direct effects on regulatory mechanisms, such as phosphorylation pathways, that control cytoskeletal organization. The later type of explanation seems more consistent with both the variability of response within cell populations and the difference in vimentin's response in one cell line compared with the other.

Actins↗
PubMed1996

Acute effects of vibration on peripheral blood flow in healthy subjects.

OBJECTIVES: The main objective was to study the acute vascular effects in the hands of normal healthy subjects of a complex vibration spectrum similar to that generated by many industrial hand held tools. The effects of repeated bouts of vibrations and alterations in the intensity of vibration were also studied. METHODS: Blood flow was measured by venous occlusion plethysmography with strain gauges. Vibration across a frequency range of 0.4 to > 4000 Hz was generated by a pneumatic chisel and applied to the right hand. Blood flow was measured in both middle fingers, both big toes, or both forearms before, during, and after a two minute period of vibration. Systolic pressure of a finger and heart rate were also measured. RESULTS: Vibration was associated with a significant bilateral reduction in finger and toe blood flow (P < 0.01 and P < 0.03) and a significant increase in heart rate (P < 0.05) but had no effect on forearm blood flow. The finger response was not abolished by repeated bouts of the vibration but was initially most notable during the first minute of vibration. Increasing the intensity of vibration delayed recovery. CONCLUSIONS: Hand vibration causes a generalised increase in sympathetic tone in the heart and extremities. This may be a factor in the development of vasospastic disease in habitual users of hand held industrial vibrating tools.

Adolescent↗
PubMed1994

Vascular responses in chain saw operators.

The intensive use of chain saws is associated with development of the hand-arm vibration syndrome (vibration white finger). Objective testing for cold induced vasospasm was carried out on the fingers of 12 chain saw operators and 12 matched control men from a similar working environment. Two of the chain saw operators tested positive for vasospasm in the laboratory and another three had an abnormal result. All of the control subjects tested negative. Measurements of finger blood flow at different temperatures and during vibration of the hand were similar in the chain saw operators and controls. Use of the chain saw did not cause significant alterations in the plasma concentrations of von Willebrand factor antigen in either the long or the short term.

Adult↗
PubMed1994

Peripheral autonomic impairment in patients newly diagnosed with type II diabetes.

OBJECTIVE: To measure both peripheral and central autonomic function in patients newly diagnosed with type II diabetes. RESEARCH DESIGN AND METHODS: Measurements were made on 49 diabetic patients (8 with long-standing diabetes and neuropathic complications, 41 with newly diagnosed type II diabetes) and on 49 healthy, age- and sex-matched, control subjects. Five of the 41 newly diagnosed type II diabetic patients had retinopathy, and 4 had clinical evidence of neuropathy. No patient or control subject had significant vascular disease. Cardiac autonomic function was investigated by using standard cardiovascular reflex tests. The digital vasoconstrictor responses to deep breathing and body cooling were measured using venous occlusion plethysmography. RESULTS: The vasoconstrictor responses to a deep breath and body cooling were significantly reduced (P < 0.001) in the fingers and toes of the neuropathic patients compared with their matched control subjects, as were the heart rate responses (P < 0.02). The vasoconstrictor responses were significantly reduced in the toes (P < 0.001) and fingers (P < 0.05, P < 0.01) of the newly diagnosed patients compared with the corresponding responses in the control subjects. There was no significant difference in the heart rate or blood pressure responses of these patients and control subjects during standard tests of cardiac autonomic function. CONCLUSIONS: Patients with type II diabetes may have impaired peripheral autonomic function at diagnosis.

Adult↗
PubMed1994

Genotoxicity testing of pidotimod in vitro and in vivo.

The mutagenic potential of pidotimod ((R)-3-[(S)-(5-oxo-2- pyrrolidinyl)carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) was assessed in a series of five assays designed to measure gene mutation, chromosomal damage and primary DNA damage. All tests were carried out in accordance with appropriate EEC and OECD Guidelines. No indications of mutagenic potential were observed in any of the assays.

Animals↗
PubMed1993

'Strawberry gums'--a case of Wegener's granulomatosis.

We report a case of Wegener's granulomatosis (WG), localised to the upper aerodigestive tract, which presented as an unusual form of hyperplastic gingivitis in a 36-year-old female. The clinical, serological and histopathological findings are described. The resemblance of the affected gums to over-ripe strawberries is emphasised, in order to draw attention to this characteristic oral manifestation of a rare and potentially life-threatening condition. The response to co-trimoxazole as sole therapy is noted.

Adult↗
PubMed1993

Early cystic/necrotic changes after hyperfractionated radiation therapy in children with brain stem gliomas. Data from the Childrens Cancer Group.

BACKGROUND: A higher total dose of radiation therapy administered in fractionated lower individual doses twice daily (hyperfractionated radiation therapy) has been reported to improve survival for children with brain stem gliomas. However, this higher dose of radiation therapy may cause more sequelae. METHOD: Eighty-eight children with brain stem gliomas were treated with 100 cGy twice daily to a total dose of 7200 cGy. Patients were carefully followed up for treatment-related clinical or radiographic worsening. RESULTS: Thirteen (15%) had intralesional cystic/necrotic changes within 8 weeks of completion of treatment. Children with these changes had a variable clinical course, including steady deterioration in one child; initial improvement, followed by progressive deterioration in three; and initial improvement, followed by deterioration, with subsequent improvement or prolonged stabilization of condition without additional antineoplastic treatment in nine. CONCLUSION: This latter "triphasic" course suggests that "early" worsening after hyperfractionated radiation therapy at 7200 cGy may be a sequelae of therapy, rather than a symptom of progressive tumor growth. This has substantial implications for patient care and evaluation of the efficacy of treatment.

Adult↗
PubMed1993

Autonomic reflexes in patients with cardioinhibitory carotid sinus syncope.

Autonomic reflexes were investigated in patients with the cardioinhibitory carotid sinus syndrome. Heart rate, blood pressure and forearm blood flow responses were recorded during prolonged head-up tilt, the Valsalva manoeuvre, lower body negative pressure and sequential respiratory cycles in ten patients and nine age-matched controls. The mean maximum R-R interval prolongation during carotid sinus massage was 4.4 s. Three patients had syncope during prolonged head-up tilt. Heart rate and blood pressure responses were similar for patients and controls who completed tilt. Responses to lower body negative pressure and Valsalva manoeuvre were similar for both groups. Respiratory sinus arrhythmia was significantly less marked in patients, 7 bpm (0 to 20 bpm) versus 15 bpm (6 to 35 bpm; p = 0.05). Therefore, neck massage and deep breathing produce abnormal cardiac vagal responses, whereas other reflexes, including response to lower body negative pressure and the Valsalva manoeuvre are within the normal range in cardioinhibitory carotid sinus syndrome.

Aged↗
PubMed1993

Strawberry gums: a clinicopathological manifestation diagnostic of Wegener's granulomatosis?

AIMS: To highlight an uncommon but characteristic gingival lesion associated with Wegener's granulomatosis, emphasising the presence of pseudoepitheliomatous hyperplasia, microabscesses, and multinucleate giant cells; and the paucity of the currently accepted histopathological criteria of Wegener's granulomatosis--namely necrosis, vasculitis, and granulomata. METHODS: The histopathological features of a gingival biopsy specimen from a case of Wegener's granulomatosis limited to the upper aerodigestive tract in a 36 year old woman were compared with those of 14 similar reported cases. RESULTS: Pseudoepitheliomatous hyperplasia, microabscesses, and multinucleate giant cells were recorded as present in almost all cases of gingival Wegener's granulomatosis. Necrosis, vasculitis, and granuloma formation were present in only a few cases. CONCLUSIONS: The combination of pseudoepitheliomatous hyperplasia, microabscesses, and multinucleate giant cells in a gingival biopsy specimen from erythematous, swollen gums, clinically resembling over-ripe strawberries, in a patient with a severe systemic upset, is so typical of Wegener's granulomatosis as to be virtually diagnostic. Recognition of this characteristic lesion may aid early diagnosis and treatment in cases where other diagnostic variables are absent.

Abscess↗
PubMed1993

An investigation into the acute vascular effects of riveting.

Measurements were made on 46 pairs of riveters and matched control subjects before and after a morning's work. Before starting work, the mean resting finger systolic pressure was 112 (SEM 3.3) mm Hg in the riveters, similar to 117 (1.7) in the control subjects. After cooling the middle phalanx to 10 degrees C for five minutes, 16 riveters but only one control subject exhibited digital vasospasm and these numbers were unaltered after a morning's work. A subgroup of riveters whose role was always to provide counter pressure to the rivet gun showed a higher incidence (45%) of cold induced vasospasm than did riveters who invariably held the gun (10%) or rotated between both roles (27%). Plasma levels of three markers of vascular activity, endothelin-1 (ET-1), von Willebrand factor antigen (vWFAg), and angiotensin converting enzyme (ACE), were measured in non-smoking riveters and control subjects. Before work, ET-1 concentrations were slightly lower (p < 0.05) in the riveters, but vWFAg concentration and ACE activity were similar in riveters and control subjects. Riveting for a morning did not alter ET-1 concentration or ACE activity but did induce a small increase (p < 0.05) in vWFAg concentration, which may indicate damage to the endothelium. This type of vascular assessment may be helpful in assessing vasospastic complications in workers exposed to vibration.

Adult↗
PubMed1993

Autonomic function in neuropathic diabetic patients with foot ulceration.

OBJECTIVE: The aim of this study was to compare peripheral autonomic function in neuropathic diabetic subjects with and without foot ulceration. RESEARCH DESIGN AND METHODS: Measurements were made on 57 diabetic subjects; 35 subjects had evidence of peripheral neuropathy, 14 of these had a history of foot ulceration, and 22 subjects had no evidence of peripheral neuropathy. No patient had peripheral vascular disease. Measurements were made of motor and sensory nerve conduction. Autonomic function was investigated by using standard cardiovascular reflex tests and by measuring blood flow variability in the foot. The vasoconstrictor responses to deep breathing and body cooling were measured by using venous occlusion plethysmography. RESULTS: Peripheral sympathetic function was significantly worse in the DU group. The vasoconstrictor response to deep breathing in the DU group was significantly smaller than the response in the DN group (15.3 +/- 2.7 vs. 38 +/- 4%, P < 0.001). The response to body cooling in the DU group was significantly smaller than the response in the DN group (6.2 +/- 3.1 vs. 20.8 +/- 3.5%, P < 0.01). Tests of cardiac autonomic function and measurements of motor and sensory nerve conduction were similar in both neuropathic groups. CONCLUSIONS: Peripheral autonomic neuropathy is associated with the development of foot ulceration in diabetic subjects.

Autonomic Nervous System↗
PubMed1993

Evaluation of the mutagenicity of a-dihydroergocryptine in vitro and in vivo.

The mutagenic potential of the ergot alkaloid a-dihydroergocryptine (a-DEC, CAS 14271-05-7) was assessed in a series of 5 assays designed to measure gene mutation, chromosomal damage and primary DNA damage. All tests were carried out in accordance with appropriate EEC and OECD Guidelines. No indications of mutagenic potential were observed in any of the assays.

Animals↗
PubMed1993

Demonstration of silicon in sites of connective-tissue disease in patients with silicone-gel breast implants.

BACKGROUND AND DESIGN: Silica, Silastic, and silicone (any organic compound in which silicon replaces carbon) have been associated with a number of connective-tissue diseases, most commonly systemic sclerosis (scleroderma). Silicone is known to leak from breast implants and spread to surrounding tissues, including lymph nodes, but silicone's role in the origin and pathogenesis of the inflammation and fibrosis related to such conditions remains controversial. Synovial tissue, alveolar macrophages, and skin, each from three different patients with silicone-gel implants, plus the breast implant capsules from each of the three patients, were examined by light microscopy, transmission electron microscopy, and electron probe microanalysis for the presence of silicon-containing material. RESULTS: Silicon was identified within the fibrous breast capsule of each case, associated with a chronic inflammatory cell infiltrate. Silicon was also identified within tissues involved by chronic inflammation and fibrosis, namely, synovium, skin, and alveolar macrophages, in association with clinical, serologic, and histologic evidence of connective tissue disease. All three patients improved after removal of the silicone-gel breast implants. CONCLUSIONS: The presence of silicon-containing material within sites of connective-tissue disease supports a role for silicon in the origin or pathogenesis of such conditions in patients with silicone-gel breast implants. All patients with connective-tissue disease should be questioned about exposure to various forms of silicon. In those patients with known exposure, tissue specimens should be examined carefully for silicon-containing material and, if found, the source should be removed.

Adult↗