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Biomedical subjects

T Barrett

Publications and source records attributed to T Barrett.

At least 163 records · Page 9Linked to original sources
PubMed1990

Characterisation of the European seal morbillivirus.

The ELISA test originally developed for the detection of serum antibodies to rinderpest virus has been shown to detect cross-reacting antibodies in sera of diseased common and grey seals. Analysis of sera collected from various seal populations is in progress to establish the correlation between different morbillivirus neutralisation tests, ELISA tests and the disease status of the animals. RNA purified from post-mortem tissues removed from diseased seals has been analysed by hybridisation with cloned cDNAs made to various genes of canine distemper, peste des petits ruminants, rinderpest and measles viruses. This study has confirmed the presence of RNA sequences characteristic of a morbillivirus, but shown that the virus is not identical with any known morbillivirus. Work is in progress to determine the nucleotide sequences of clones carrying inserts homologous to morbillivirus genes isolated from cDNA made on a template of infected seal tissue RNA.

Animals↗
PubMed1990

Effect of exercise level on ventilatory adaptation to respirator use.

The effect of exercise on the adaptation to an air-purifying respirator type load (dead space + inspiratory resistance) was studied in a group of 13 volunteers with a rapidly incremental exercise protocol. The difference between loaded and unloaded breathing at each exercise level was determined for each subject for a series of parameters describing the ventilatory work to overcome the respirator load pattern of breathing and metabolic work. Linear regression and t tests determined the average effect of the respirator load and the extent to which this effect was affected by the level of exercise. The inspiratory time and duty cycle were increased by the load, and exercise did not significantly affect the magnitude of this adaptation. High exercise did, however, increase the magnitude of the effect of the respiratory load on ventilatory work. These findings suggest that constraints to respiratory pattern adjustment, which may decrease respirator tolerance, occur at high exercise levels.

Adaptation, Physiological↗
PubMed1990

Detection of phocine distemper virus using the polymerase chain reaction.

During the fatal seal epizootics in the North and Baltic Seas in summer 1988 a virus was isolated which was shown to be the causal agent. It was subsequently classified as morbillivirus by neutralization assays, reaction with monoclonal antibodies and nucleic acid hybridization studies. The virus (tentatively called Phocine Distemper Virus, PDV) is difficult to grow in culture making rapid diagnosis difficult. We have used the Polymerase Chain Reaction (PCR) as an alternative and fast method to detect the presence of virus-specific nucleic acid and we describe here the amplification of cell culture derived PDV RNA in a "one-tube" reaction using heterologous (Rinderpest Virus cDNA derived) F gene primers. The resulting 370 bp DNA fragment was shown to be morbillivirus derived by Southern blot hybridization using cloned RPV F gene as probe.

Animals↗
PubMed1989

Immune response and protection of cattle and pigs generated by a vaccinia virus recombinant expressing the F protein of rinderpest virus.

The immune response of cattle and pigs to a vaccinia recombinant virus containing the fusion (F) protein gene of rinderpest virus was examined. Half the cattle and all the pigs gave humoral response to primary vaccination and all the cattle gave an anamnestic response to a second vaccination 28 days after the primary vaccination. All the cattle after a single or secondary vaccination were completely protected clinically after exposure to a lethal dose of the Saudi 1/81 strain of virus. Prior vaccination with another TK- vaccinia recombinant (VVCAT) suppressed, but did not abrogate, the immune response to the rinderpest F recombinant. The pigs gave a humoral immune response in the absence of any local reaction at the site of vaccination.

Animals↗
PubMed1989

Effects of respirator dead space, inspiratory resistance, and expiratory resistance ventilatory loads.

The effects of respiratorlike inspiratory resistance (IR), expiratory resistance (ER), and dead space (DS) were assessed in a group of 11 normal volunteers during moderate steady-state (SS) and rapidly incremented (RI) exercise. The physiologic effects of IR were predominant, increasing inspiratory time, duty cycle, and several measures of ventilatory work. Effects of DS appear related to increased minute ventilation and include increasing flow rates and duty cycle and requiring greater ventilatory work; during RI exercise, the DS effect became relatively smaller at higher exercise levels. ER compressed expiratory time. These results characterize the response to IR, ER, and DS loads and suggest that DS may be relatively less physiologically significant than IR.

Airway Resistance↗
PubMed1989

Immunization with a vaccinia recombinant expressing the F protein protects rabbits from challenge with a lethal dose of rinderpest virus.

A cDNA clone containing the complete coding sequence of the rinderpest fusion protein (F) gene was inserted into the thymidine kinase gene of vaccinia virus (WR strain) under the control of the 7.5K early/late vaccinia virus promoter. All forms of the F protein, i.e., the glycosylated F0 precursor, the unglycosylated F1 protein, and the glycosylated F2 protein, were detected in cells infected with the recombinant virus. Vaccination of rabbits with the recombinant virus induced antibodies which reacted in an ELISA system specific for rinderpest. The rabbit sera contained neutralizing antibodies against rinderpest virus and precipitated the F protein from lysates of rinderpest infected cells. Rabbits vaccinated with the recombinant rinderpest F gene vaccinia virus were protected from a lethal challenge with the lapinized Nakamura 3 strain of rinderpest virus. Variations in the severity of clinical symptoms correlated with the level of anti-F protein antibodies produced.

Animals↗
PubMed1989

Differentiation of rinderpest and peste des petits ruminants viruses using specific cDNA clones.

The morbilliviruses which infect ruminants, rinderpest (RPV) and peste des petits ruminants (PPRV), are difficult to distinguish serologically. They can be distinguished by differential neutralisation tests and by the migration of the major virus structural protein, the nucleocapsid protein, on polyacrylamide gels. Both these methods are time consuming and require the isolation of live virus for identification; they are not suitable for analysis of material directly from post-mortem specimens. We describe a rapid method for differential diagnosis of infections caused by RPV or PPRV, which uses specific cDNA probes, derived from the mRNAs for the nucleocapsid protein of each virus, which can be used to distinguish unequivocally the two virus types rapidly.

Animals↗
PubMed1989

Relationship of subjective tolerance of respirator loads to physiologic effects and psychophysical load sensitivity.

The degree to which subjective tolerance of respirator loads is related to physiologic effects and to psychophysical load sensitivity was investigated in this study. Fifty-two normal volunteers walked on a treadmill while breathing through a variety of respirator-type resistance and dead-space loads. Visual analog scales measuring perceived time limit of exercise and discomfort were both related to the ventilatory work imposed by the loads. Respiratory timing was related to discomfort but not to time limit. Psychophysical sensitivity to added resistive loads (LSS) was measured by the magnitude estimation method. Persons with higher objectively measured LSS had greater subjective intolerance induced by respirator use than persons of lower LSS. These findings suggest that subjective respirator tolerance is related to a person's psychophysical characteristics and to the actual physiologic effects. Furthermore, discomfort may be dissociated from actual exercise limitation.

Efficiency↗
PubMed1989

Sch 38519, a novel platelet aggregation inhibitor produced by a Thermomonospora sp. Taxonomy, fermentation, isolation, physico-chemical properties, structure and biological properties.

The complex containing a new platelet aggregation inhibitor, Sch 38519, was recovered from the fermentation filtrate of Thermomonospora sp. SCC 1793. A chemically defined medium was developed which favored the production of Sch 38519. The antibiotic was isolated from the fermentation filtrate by absorption on macroreticular resin and further purified by ion exchange chromatography and reverse phase HPLC. Sch 38519 is an isochromanequinone structurally related to medermycin, lactoquinomycin and granaticin. It inhibits thrombin-induced aggregation of human platelets with an IC50 of 68 micrograms/ml. Sch 38519 is also active against Gram-positive and Gram-negative bacteria.

Actinomycetales↗
PubMed1988

Determinants of pattern of breathing during respirator use.

The relationship between the pattern of breathing in response to respirator-type loads and an individual's psychophysiologic sensitivity to loads (load scaling sensitivity, LSS) was investigated in the study of 11 normal volunteers. LSS was measured by having the subjects numerically rate a series of resistors; Steven's Psychophysical Law was used to evaluate sensitivity as the slope relating log (sensation) to log (stimulus). Peak pressure and actual added resistance were the stimuli. Inspiratory time, peak pressure, duty cycle, and tidal volume were inversely related to independently measured LSS during exercise and with a respiratory-type dead space and inspiratory resistance load. Because the need for changes in respiratory timing is a major adaptation in respirator use, it suggests that workers who are very sensitive to loads may have limited ability to adapt to respirator use.

Adult↗
PubMed1988

Pneumovirus-like characteristics of the mRNA and proteins of turkey rhinotracheitis virus.

Electronmicroscopy has indicated that turkey rhinotracheitis virus (TRTV), the causative agent of an acute respiratory disease in turkeys, is a member of the Paramyxoviridae family. To determine if TRTV belongs to one of the three defined genera of this family (Paramyxovirus, Morbillivirus and Pneumovirus) we have analysed the RNA and proteins induced during replication of TRTV in Vero cells. Following replication in the presence of actinomycin D 10 polyadenylated RNA bands, ranging in Mr from 0.22 to 2.0 X 10(6), were detected in infected cells; some bands probably contained 2 or more RNA species. Viral proteins were studied after radiolabelling in the presence of [35S]methionine and [3H]glucosamine. Comparison of the polypeptides in mock-infected and infected cells, virions and nucleocapsids and after lentil-lectin chromatography and immunoprecipitation revealed seven virus-specific polypeptides (p), some of which were glycosylated (gp): gp82 (Mr 82K), gp68, gp53, gp15, p43, p40 and p35. These are considered to be analogous to the large glycopolypeptide (HN, H and G), fusion protein precursor F0, the F protein cleavage products F1 and F2, nucleocapsid (N), phosphorylated (P) and matrix (M) polypeptides, respectively, of the Paramyxoviridae. Two other polypeptides (Mr 200K and 22K) were also detected, as was a glycopolypeptide of Mr 97K, probably related to gp82. Tunicamycin inhibited glycosylation of gp53 and gp15 but gp82 was little affected, most glycans still being present on a glycopolypeptide of approximately 79K. This finding, indicating that gp82 has mostly O-linked glycans, considered with the mRNA profile and the molecular weight of the N protein shows that of the three genera in this family, TRTV most closely resembles the Pneumovirus genus.

Animals↗
PubMed1988

Subjective tolerance of respirator loads and its relationship to physiological effects.

Subjective and physiological responses to a variety of respiratory loads were measured in a group of 52 normal volunteers during steady, moderate treadmill exercise. Subjective response (SR) was determined with two visual analogue scales developed for this study: EXERT (perceived limitation of exercise duration) and DISC (perceived discomfort). There was a linear relationship between inspiratory resistance and SR. Expiratory and inspiratory resistance loading produced similar subjective effects. Dead space loading, however, produced very little subjective effect on either scale. The study suggests that subjective response can be measured quantitatively and should be considered in respirator design.

Adult↗
PubMed1988

Malassezia furfur: a cause of occlusion of percutaneous central venous catheters in infants in the intensive care nursery.

Growth of Malassezia furfur in the intravascular catheter used for administration of lipid emulsion resulted in occlusion of deep intravascular Silastic catheters in 12 infants in 2 intensive care nurseries. At the time of occlusion visible growth was noted in the clear catheter which was connected to the Silastic intravascular line. Five infants showed clinical signs suggestive of sepsis. The yield of M. furfur from blood cultures and catheter tips was low even when oil enrichment was used. The highest yield of M. furfur was found in the connecting catheter (11 of 11). The source from and the route by which M. furfur entered the catheter remain unclear. The potential portals of entry include the proximal and distal ends of the connecting catheter as well as the colonized skin of the infants and caretakers.

Catheterization, Central Venous↗
PubMed1987

The nucleotide sequence of the gene encoding the F protein of canine distemper virus: a comparison of the deduced amino acid sequence with other paramyxoviruses.

The nucleotide sequence of the gene encoding the fusion protein of canine distemper virus was determined from cDNA clones derived from virus genome RNA and poly(A)+ RNA extracted from infected cells. The mRNA encoding the F protein is about 2300 nucleotides in length including the 3' poly(A) tail. There is a large open reading frame from nucleotides 86 to 2071 which begins at the first AUG codon in the F mRNA. This reading frame encodes a protein of 662 amino acid residues with a calculated mol. wt. of 73001. The first major hydrophobic domain in the amino acid sequence of the deduced protein (residues 104 to 130) may represent all or part of a signal sequence for cleavage of the N terminal part of the F2 protein. There are four potential N glycosylation sites in the F protein located within the F2 part of the molecule or the putative signal sequence, and one in the F1 portion. A second hydrophobic region corresponds to the proteolytic cleavage site which generates the F2 and F1 subunits. This stretches from residue 225 to 262 and the N terminal part of the F1 protein shows sequence conservation with the other paramyxoviruses. A third major hydrophobic domain near the C terminus of the F protein probably represents the membrane anchor for the F protein (residues 602 to 630). The F1 proteins of six paramyxoviruses are compared and shown to have substantial conservation of those residues important in the maintenance of tertiary structure of this protein.

Amino Acid Sequence↗
PubMed1987

Comparison of proteins induced in cells infected with rinderpest and peste des petits ruminants viruses.

The two morbilliviruses rinderpest virus (RPV) and peste des petits ruminants virus (PPRV) are closely related and cause severe disease in large and small ruminants, respectively. They show distinct epidemiological patterns and are distinguishable by reciprocal cross-neutralization tests. We have analysed the proteins induced by these viruses in infected cells and have shown that they can be distinguishable by a very marked difference in the apparent mol. wt. of the nucleocapsid (N) protein. The N protein of PPRV is almost identical in mobility on polyacrylamide gels to the N proteins of measles virus and canine distemper virus (60K). Several strains of RPV and PPRV from widespread geographical locations were studied and found to show this difference in the N protein.

Antibodies, Monoclonal↗
PubMed1987

Qualitative and quantitative determination of enterobacterial common antigen (ECA) with monoclonal antibodies: expression of ECA by two Actinobacillus species.

The presence and quantity of the enterobacterial common antigen (ECA) in several species belonging to the family Enterobacteriaceae as well as to other gram-negative families were determined by a solid-phase enzyme-linked immunosorbent assay system and Western blotting by using mouse monoclonal antibodies specific for ECA. Except for Erwinia chrysanthemi, previously known to be an exception, all species known or presumed to belong to Enterobacteriaceae produced ECA (89 of 90 species). Most species not belonging to Enterobacteriaceae did not produce ECA (25 of 28 species), with one already known (Plesiomonas shigelloides) and two hitherto unknown (Actinobacillus equuli and Actinobacillus suis) exceptions. Interestingly, all strains of P. shigelloides produced ECA, regardless of the presence of the Shigella sonnei cross-reacting O antigen. Quantitation of the amount of ECA in members of the family Enterobacteriaceae revealed a remarkable heterogeneity among genera and species as well as within one species. We conclude that the rapid, sensitive, and reliable determination of ECA is a useful aid in taxonomic classification and may help to characterize the relatedness of the family Enterobacteriaceae to other families. However, a quantitative analysis of ECA appears to be without value for these purposes.

Actinobacillus↗
PubMed1987

The molecular biology of the morbillivirus (measles) group.

The morbilliviruses are a closely related group of important human and animal pathogens. The best known members of the group are measles virus in man and canine distemper virus in dogs. The group also includes two other serious animal diseases, rinderpest or cattle plague and peste des petits ruminants in sheep and goats. The latter viruses are of great economic importance in Africa, Asia and the Middle East. Persistence of these viruses in some form is a possible mechanism whereby life-long immunity is conferred on an infected individual. In addition to the severe, often fatal, acute disease these viruses can, in rare cases, lead to a fatal chronic disease of the CNS. Molecular biological studies will be described which are beginning to elucidate their evolutionary relationships and to provide a basis for understanding the role of individual virus genes in pathogenesis.

Animals↗