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Biomedical subjects

C Seymour

Publications and source records attributed to C Seymour.

49 records · Page 3Linked to original sources
PubMed1981

Studies on selection of LaCrosse virus variants by natural vertebrate hosts and vector mosquitoes.

The effect of passage in natural hosts on LaCrosse virus plaque size, mouse neurovirulence, and plaquing efficiency was studied. Seven field strains, as previously unpassaged naturally infected Aedes triseriatus suspensions, were inoculated into chipmunks Tamias striatus and thence into colonized Ae. triseriatus. The prototype strain, with seven prior laboratory passages, was also passed through the same natural host species. The field strains changed in neurovirulence and plaque size at various passage levels, but with no consistent pattern. The prototype strain was relatively unvarying in plaque size, but changed moderately in neurovirulence. For all eight strains, chipmunk passage reduced plaquing efficiency beyond the nonspecific inhibition normally found in chipmunk blood. We conclude that natural hosts may select variants in unpredictable patterns from highly variable unpassaged field strains, but that prior laboratory passage reduced the prototype strain to a relatively homogeneous population resistant to change in at least one aspect.

Aedes↗
PubMed1978

Venezuelan encephalitis virus infection in neotropical bats. I. Natural infection in a Guatemalan enzootic focus.

A serological survey of 939 Neotropical bats of 22 species from an enzootic focus of Venezuelan encephalitis (VE) virus on the Pacific lowlands of Guatemala during 1971--1975 revealed VE virus specific antibodies in seven species, three belonging to the genus Artibeus. VE virus was isolated from the blood of one Uroderma bilobatum. Antibody frequency was considerably lower in bats than in terrestrial mammals, and tended to vary within any given species from locality to locality and from year to year. At the village of La Avellana where VE virus was most active, antibody rates in the two best-sampled Artibeus species were 0.14 in 1971, 0.11 in 1972, 0.03 in 1973, and 0.11 in 1975. The positive rate of 0.10 over all years at La Avellana for the genus Artibeus suggests that these and possibly other bats regularly are infected by VE virus, and may possibly serve as alternate hosts to maintain virus circulation if most terrestrial animals become immune.

Animals↗
PubMed1978

Venezuelan encephalitis virus infection in neotropical bats. II. Experimental infections.

Eighty-nine Neotropical bats of five species were inoculated subcutaneously with epizootic or enzootic strains of Venezuelan encephalitis (VE) virus. Viremia was detected in 92.5% of all bats, but no illness attributable to virus infection was observed. Detectable viremias averaged slightly over 4 days in Artibeus jamaicensis and A. lituratus, and 2.8 days in Phyllostomus discolor, and maximal viremia titers in these three species averaged 6.9, 6.6, and 4.6 log10 SMicLD50 per ml of blood, respectively. In general Artibeus developed and maintained detectable levels of both hemagglutination-inhibition (HI) and neutralizing antibody for as long as tested (up to 506 days), although HI antibody to enzootic VE virus strains disappeared in some A. lituratus. The detectable antibody response of P. discolor was slower and of lower magnitude and shorter duration than that of Artibeus, although individual P. discolor which had lost detectable HI and N antibody resisted challenge. Vertical passage of antibody was observed in three A. lituratus offspring. Artibeus jamaicensis were found to be only slightly less susceptible to VE virus infection than a U.S. subspecies of the cotton rat (Sigmodon hispidus). No virus was recovered by mouse inoculation of organ pools of bats killed as early as 2 days and as late as 299 days after the last day of detectable viremia.

Animals↗
PubMed1978

Venezuelan encephalitis virus infection in neotropical bats. III. Experimental studies on virus excretion and non-arthropod transmission.

A total of 80 Neotropical bats of five species was inoculated with one of four strains of Venezuelan encephalitis (VE) virus. Virus was detected in the oropharynges of 56% of bats, and most regularly in Artibeus jamaicensis (75%). Titers of virus in oropharyngeal secretions were occasionally very high (8.5 log10 SMicLD50/ml in one A. jamaicensis). Only 2 of 123 urine samples from 50 bats and 2 of 86 fecal samples from 46 bats yielded VE virus. No contact or aerosol virus transmission from bat to bat was detected. VE virus passed transplacentally from two infected mothers to their fetuses, which were aborted. Virus did not pass from one infected mother to her nursing young.

Animals↗
PubMed1976

Ecologic studies of Venezuelan encephalitis virus and isolations of Nepuyo and Patois viruses during 1968-1973 at a marsh habitat near the epicenter of the 1969 outbreak in Guatemala.

Ecologic studies of Venezuelan encephalitis (VE) virus at a marsh habitat near the epicenter of the 1969 outbreak in Guatemala revealed that the virus was enzootic there. VE virus was isolated yearly during 1968-1973 from sentinel hamsters exposed during the rainy seasons and from mosquitoes collected during July and August 1970. Hamsters yielded 41 strains of VE virus and virus was detected within 2 km of the edge of the marsh, in its interior, and at its western extreme 18 km from the central study site at La Avellana. One strain of virus came from a hamster that died in the dry season of January 1970. Culex mosquitoes yielded 20 strains of VE virus and Mansonia and Aedes one each. Culex (Melanoconion) and Aedes taeniorhynchus were most prevalent near the marsh. Hemagglutination-inhitibion (HI) and neutralization antibody tests of sera showed that wild terrestrial mammals (opossums and rodents), humans, and dogs, but not wild birds, were frequently infected. Seven of 16 susceptible residents of villages at the edge of the marsh developed antibodies without symptoms during an 18-month period between September 1971 and February 1973. Only 1 of 5 sentinel rabbits, and none of 30 sentinel chickens developed VE HI antibody during August-September 1971, a period when virus activity was readily detected by the use of sentinel hamsters. Five strains of group C arbovirus (one identified as Nepuyo) were recovered from sentinel hamsters during 1968 to 1970, and one strain of Nepuyo virus was isolated from the blood of a person with a febrile illness during 1972. Two strains of Patois group arboviruses were isolated from Culex mosquitoes during 1970.

Adolescent↗
PubMed1975

Relative contributions of history-taking, physical examination, and laboratory investigation to diagnosis and management of medical outpatients.

To evaluate the relative importance of the medical history, the physical examination, and laboratory investigations in the diagnosis and management of medical outpatients some physicians recorded their diagnosis and a prediction of the method of managementafter reading the patient's referral letter, again after taking the history, and againafter performing the physical examination. These diagnoses and predictions were compared with the diagnosis and method of management which had been adopted two months after the patient's initial attendance. A diagnosis that agreed with the one finally accepted was made after reading the referral letter and taking the history in 66 out of 80 new patients; the physical examination was useful in only seven patients, and the laboratory investigations in a further seven. In only one of six patients in whom the physician was unable to make any diagnosis after taking the history and examining the patient did laboratory investigations lead to a positive diagnosis.

Clinical Laboratory Techniques↗
PubMed1971

Pharmacological emptying of the stomach with metoclopramide.

This paper evaluates the use of metoclopramide (Maxolon) in emptying human stomach contents into the duodenum and beyond. A method of quantitative assessment of content by barium swallow radiography is used in the study, and the method is recommended as a diagnostic manoeuvre in patients presenting for emergency surgery in whom the stomach content is in doubt. Oral metoclopramide was found effective in emptying stomachs challenged by water load, and the intravenous route has been found effective in emptying semisolid contents in emergency clinical situations. A radiographic scan of the resting stomach was made on patients waiting for routine surgery who had received a variety of common premedication; it was shown that significant residues occur.We believe that metoclopramide deserves further investigation in order to exploit its potential in reducing the hazard of regurgitation and vomiting in patients requiring emergency anaesthesia and surgery.

Adolescent↗
PubMedDate not supplied

Changes in protein expression during melanoma differentiation determined by computer analysis of 2-D gels.

Cytodifferentiation in many melanocytic cells is regulated through the adenylate cyclase-cAMP pathway. To analyse the molecular changes associated with this process we have compared the proteins produced by two closely related cell lines which, though derived from a single cell line, respond very differently to modulation of this signalling pathway. The human melanoma cell line DX3 shows little change in in vitro characteristics following treatment with cAMP elevating agents; in contrast the more malignant DX3 LT5.1 variant, derived from the DX3 parental line, shows pronounced dendrification, decreased proliferation and a reduction in metastatic capacity after similar treatment. The two cell lines were treated with phosphodiesterase inhibitors for 5 days and then processed for two-dimensional gel characterization using an immobilized pH gradient for the IEF dimension. Proteins were detected by silver staining the gels and protein intensities were digitized using a laser densitometer. Two-dimensional gel patterns were edited, matched and a melanoma protein database of 637 spots constructed using PDQUEST software on an Orion 1/05 computer. Eleven proteins were lost and four new proteins were detected in both cell lines following treatment. Twenty-two proteins were present in DX3 LT5.1 after treatment but not in untreated lines or treated DX3. These differentially expressed proteins may be associated with the observed changes in differentiation patterns and metastasis. Our results illustrate the resolving power of this technique and suggest potential applications to the study of cellular differentiation.

Animals↗
PubMedDate not supplied

The Dynamic Stabilizing Innersole System (DSIS): the management of hyperpronation in children.

In a study of 50 children, the Dynamic Stabilizing Innersole System (DSIS) was found to decrease the mean resting calcaneal stance position (RCSP) by an average of 6 degrees. A comparison between the neutral calcaneal stance position and the RCSP with the DSIS showed no statistically significant difference between the means for the right or left foot, indicating that the DSIS is capable of returning severe flat foot deformities to their neutral calcaneal stance position. The RCSP with and without the DSIS differed significantly, indicating that the DSIS provides a considerable and statistically significant amount of correction in the RCSP in our study population. Furthermore, the results of linear regression showed that the DSIS appears to be sensitive to the severity of the deformity, preventing overcorrection of less severe flatfoot deformities and providing a long awaited alternative to traditional pediatric corrective flatfoot devices.

Adolescent↗
PubMedDate not supplied

Genomic instability, bystander effects and radiation risks: implications for development of protection strategies for man and the environment.

The last few years has seen what people are now referring to as a "shifting Paradigm" in our way of thinking about radiation effects on biological systems. The concept of the central role of DNA damage due to double strand breaks induced by a radiation "hit" has been itself hit by many studies showing persistent effects in the distant progeny of radiation exposed cells. This phenomenon is known as radiation induced genomic instability. More recently evidence has been accumulating that not even the parent cell need be exposed to radiation (the bystander effect). The new paradigm suggests that cellular stress responses or damage signalling through a range of signal transduction pathways are involved and that cell-cell contact or secretion of damage signalling molecules can induce responses in undamaged and unirradiated cells. Are these new effects relevant to risk assessment, or does it matter HOW radiation affects cells if we have good epidemiological evidence of which to base our risk estimates? The aim of this paper is to introduce the new concepts and to consider reasons why they might alter our methods of risk estimation. The paper also considers the impact of the new concepts on environmental protection and discusses the need for research in the field of comparative radiobiology if we are to develop policies which can adequately protect biodiversity.

Animals↗
PubMedDate not supplied

Relevance of radiation-induced bystander effects for environmental risk assessment.

A novel mechanism involving a medium borne signalling factor has been identified following irradiation of populations of cells to doses ranging from 5 mGy-5 Gy gamma-rays or to as little as 1 alpha particle traversal in a culture containing hundreds of cells. The factor can be released into culture medium and can induce responses in unexposed cultures. It has been called a "radiation-induced bystander factor". The effect is obviously relevant to risk assessment as it happens at very low doses. It could also offer new avenues for development of drugs aimed not at cell destruction but at restoring the tissues own control and coordination of response following DNA damage. The effect is clearly induced by radiation and probably by other substances. While these effects are now accepted to happen both in vitro and in vivo, their relevance and function is unknown. The investigation and modelling of the mechanism and the variation in level and type of effect in relation to genetic background and clinical history are key questions which need to be addressed in the field. The key driving hypothesis of the work being done by our laboratory is that radiation-induced bystander effects (RIBE) reflect emergent control in complex tissues and communicating cell systems, which can be harnessed for therapeutic gain.

Bystander Effect↗
PubMedDate not supplied

Children with parents in prison: child welfare policy, program, and practice issues.

As the rate at which adults are being incarcerated in the United States escalates, child welfare professionals are encountering growing numbers of children who have parents in prison. Current estimates indicate that as many as 1.5 million children have an incarcerated parent; many thousands of others have experienced the incarceration of a parent at some point in their lives. These vulnerable children face unique difficulties, and their growing numbers and special needs demand attention. Challenges facing the child welfare system as it attempts to work with this population are explored.

Adult↗