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Biomedical subjects

T W Scott

Publications and source records attributed to T W Scott.

At least 91 records · Page 5Linked to original sources
PubMed1988

A rapid dot immunoassay for the detection of serum antibodies to eastern equine encephalomyelitis and St. Louis encephalitis viruses in sentinel chickens.

A dot enzyme-linked immunosorbent assay utilizing a novel membrane, polyvinylidene difluoride, is described. This assay was developed for the rapid detection of serum antibodies to eastern equine encephalomyelitis virus and St. Louis encephalitis virus in sentinel chickens. Antigens were spot-filtered through the membrane. Membranes were dipped into small vials of sera. Antigen-antibody complexes were detected with enzyme-conjugated antiglobulin which, when exposed to substrate, produced a colored insoluble product. The antibody detection protocol was completed within 50 min and was compared with a standard plate enzyme immunoassay. Chickens were experimentally infected with eastern equine encephalomyelitis and St. Louis encephalitis and bled on a daily basis. The dot immunoassay correctly identified 99% (123/124) of the eastern equine encephalomyelitis virus and 100% (67/67) of the St. Louis encephalitis virus antisera. Sera from sentinel chicken flocks in Maryland were also assayed. These data indicate that the dot immunoassay should be considered as an alternative to current assays for the screening of sera for antibodies to virus antigens. This assay could easily be performed in the field and allows for the screening of antibodies to several different viruses in one test.

Alphavirus↗
PubMed1988

Detection of eastern equine encephalomyelitis virus antigen in equine brain tissue by enzyme-linked immunosorbent assay.

Sensitivity and specificity of an antigen-capture ELISA vs virus isolation in cell culture were evaluated for the detection of eastern equine encephalomyelitis (EEE) virus in the brain tissue of naturally infected equids. Brain specimens from 16 equids with neurologic disease were examined by ELISA and by inoculation onto baby hamster kidney cell cultures. Of 10 brain samples from which virus was isolated in the cell culture bioassay, all were correctly identified as containing EEE virus antigen by ELISA. None of the remaining 6 specimens, without detectable infectious EEE virus, contained detectable antigen. Sensitivity and specificity of the ELISA were 100% with no false-positive or false-negative results. The antigen-capture ELISA was a rapid, sensitive, specific, and simple alternative to a traditional bioassay for the detection of EEE virus.

Alphavirus↗
PubMed1987

A prospective field evaluation of an enzyme immunoassay: detection of eastern equine encephalomyelitis virus antigen in pools of Culiseta melanura.

A prospective field study was conducted to determine the sensitivity and specificity of an enzyme immunoassay (EIA) compared to virus isolation in cell culture for the detection of eastern equine encephalomyelitis (EEE) virus in naturally infected mosquitoes. A total of 10,811 adult female Culiseta melanura were collected in light traps during 1985 from four locations in Maryland. Eastern equine encephalomyelitis virus was isolated from 5 of 495 mosquito pools in African green monkey kidney and baby hamster kidney cell cultures. All five virus-infected pools were detected by the EIA, and all 490 uninfected pools were correctly scored as not containing virus. The EIA did not produce false positive or false negative results. Results support the assertion of previous researchers that the antigen detection EIA is a rapid, sensitive, specific, and simple alternative to traditional bioassays for the detection of EEE virus in mosquitoes.

Alphavirus↗
PubMed1986

Detection of eastern equine encephalomyelitis viral antigen in avian blood by enzyme immunoassay: a laboratory study.

An enzyme immunoassay (EIA) was evaluated for its efficacy at detecting eastern equine encephalomyelitis (EEE) virus in avian blood and brain specimens. Preliminary analysis of blood from experimentally infected house sparrows and naturally infected whooping cranes showed that EEE antigen could be detected with the EIA. Polyclonal mouse antibodies were selected for antigen capture, and rabbit antibodies were selected for antigen detection. Overnight antigen incubation increased sensitivity. The lower limit of EEE antigen detection was 10(3.5) TCID50/ml for a stock of virus. Sensitivity was 10% (2/20) for antigen detection in the blood of chicks inoculated with EEE virus less than 24 hr earlier. At 24 and 48 hr after infection, sensitivity was 100% (10/10). Sensitivity and specificity of antigen detection were excellent (100% for both) in house sparrows experimentally inoculated with EEE, Highlands J (HJ), western equine encephalomyelitis (WEE), or St. Louis encephalitis (SLE) virus and bled at 24 hr intervals. Cross-reactivity was observed, however, with high concentrations (10(5.5) TCID50/ml) of HJ virus. EEE antigen was detected in avian blood by the EIA after infectious virus had declined to undetectable levels. The EIA is a useful alternative to virus isolation in cell culture for diagnosis or detection of EEE virus infections in birds. The test has the advantages of being simple, rapid, and capable of detecting antigen in the absence of infectious virus.

Alphavirus↗
PubMed1985

Localized control of ligand binding in hemoglobin: effect of tertiary structure on picosecond geminate recombination.

The picosecond geminate rebinding of molecular oxygen was monitored in a variety of different human, reptilian, and fish hemoglobins. The fast (100 to 200 picoseconds) component of the rebinding is highly sensitive to protein structure. Both proximal and distal perturbations of the heme affect this rebinding process. The rebinding yield for the fast process correlates with the frequency of the stretching motion of the iron-proximal histidine mode (VFe-His) observed in the transient Raman spectra of photodissociated ligated hemoglobins. The high-affinity R-state species exhibit the highest values for VFe-His and the highest yields for fast rebinding, whereas low affinity R-state species and T-state species exhibit lower values of VFe-His and correspondingly reduced yields for this geminate process. These findings link protein control of ligand binding with events at the heme.

Animals↗
PubMed1984

The distribution and development of eastern equine encephalitis virus in its enzootic mosquito vector, Culiseta melanura.

The timing and sequence of eastern equine encephalitis (EEE) virus replication was studied in the organs from a colony strain of orally infected Culiseta melanura. Three methods of virus assay were used: fluorescent antibody (FA) staining of dissected organs; virus titration in cell culture of whole mosquitoes, dissected organs, hemolymph, and egg rafts; and transmission electron microscopy (TEM) of infected hindguts. EEE virus replicated rapidly in Cs. melanura, first in the posterior midgut, after which it disseminated into the hemocoel where hemolymph transported virus to other organs causing a systemic infection that eventually involved all organs examined, except ovarioles. No initial decrease in virus titer of whole mosquitoes or dissected organs was observed when mosquitoes were collected at daily intervals. Muscle tissue contained the greatest amount of specific fluorescence and the largest aggregates of virus that were visible by TEM. Dissemination of virus occurred rapidly, in some mosquitoes after less than or equal to 17 hours of extrinsic incubation (EI). All infected mosquitoes had disseminated infections after 3 days of EI. Maximum amounts of virus were obtained from whole mosquitoes on the 7th day of EI. FA staining of hindguts was determined to be a rapid and reliable method for detection of EEE virus dissemination and replication in Cs. melanura.

Alphavirus↗
PubMed1984

Rapid infection of salivary glands in Culiseta melanura with eastern equine encephalitis virus: an electron microscopic study.

Transmission electron microscopy was used to determine if eastern equine encephalitis (EEE) virus infects and replicates in the salivary glands of Culiseta melanura after 3 days of extrinsic incubation (EI). The Cs. melanura studied were from a colony strain, were orally infected, and had EI periods of 55-69 hours. Both naked nucleocapsids and enveloped virions were present in aggregates, suggestive of viral replication, within salivary gland acinar cells. Nucleocapsids were present in the cytoplasm below the plasma membrane that lined apical cavities. Enveloped virions occurred in the salivary matrix within apical cavities. Some nucleocapsids appeared to be budding through the plasma membrane around apical cavities and maturing into infectious virions. These results suggest that Cs. melanura is capable of biological transmission of EEE virus after less than or equal to 3 days of EI.

Alphavirus↗
PubMed1984

A field study on the effects of Fort Morgan virus, an arbovirus transmitted by swallow bugs, on the reproductive success of cliff swallows and symbiotic house sparrows in Morgan County, Colorado, 1976.

We studied the transmission of Fort Morgan (FM) virus within colonies of nesting Cliff Swallows and House Sparrows under three bridges in Morgan County, Colorado during 1976. Nests were examined, and blood or brain specimens were collected from nestlings once or twice a week. Flying birds and small mammals were also studied. We analyzed nesting activity, virus isolations from nestlings of both species, fledging success, multiple infections within a brood of nestlings, infection frequency by age of nestlings, nestling mortality, and infection frequencies by avian species and bridge site. Fort Morgan virus was isolated from 7% (80/1, 156) of the blood and brain samples collected from nestlings. The duration of viremia for nestling House Sparrows was at least 3-4 days based on virus isolation from sequential blood samples. Viremia of nestling Cliff Swallows and House Sparrows did not reduce fledging success, nor were young nestling sparrows viremic more frequently than older nestling sparrows. Nest destruction (by falling down) was a more important cause of nestling mortality than FM virus infection. All age groups of nestling sparrows were viremic at equal rates, but younger nestlings (less than or equal to 7 days old) were more likely than older nestlings (greater than 7 days old) to develop an encephalitic infection. Among nestling House Sparrows, FM virus infections were clustered in time and space. Nestling House Sparrows with FM virus-infected nest-mates were infected more often than conspecifics whose nest-mates were not infected. We concluded that nestling Cliff Swallows and symbiotic House Sparrows that reside in swallow nesting colonies are the principal vertebrate hosts for the maintenance and amplification of FM virus.

Animals↗
PubMed1983

The iron-proximal histidine linkage and protein control of oxygen binding in hemoglobin. A transient Raman study.

Time-resolved Raman studies have shown that communication between the heme oxygen binding sites and the surrounding globin occurs through the iron-proximal histidine linkage. By comparing the frequency of the Fe-His stretching mode in equilibrium deoxy- and photoinduced transient deoxyhemoglobins, we have found that ligand binding induces protein structural changes that strengthen the Fe-His linkage. The extent of this increase is observed to depend upon the quaternary state. This dependence is reflected in the restricted set of values observed in transient and equilibrium studies for the frequency of the Fe-His stretching mode in both R and T state deoxyhemoglobins. For T state hemoglobins the frequency increases from 215 cm-1 to approximately 222 cm-1 in going from the stable to the nanosecond transient deoxy species. The corresponding change for R state human hemoglobins is from approximately 222 cm-1 to approximately 230 cm-1. Studies on transients derived from Fe-Co hybrid hemoglobins reveal no subunit heterogeneity associated with the R state transient (230 cm-1) at high pH. We also observe that perturbations of the protein known to destabilize the structure of ligand-bound R state hemoglobins are associated with a decrease in the frequency of the iron-proximal histidine stretching mode in the corresponding transient species. Such effects can originate from changes in either quaternary state or solution conditions as well as species-specific variations in protein structure. These results indicate that modulation of the Fe-His linkage could be a general mechanism for regulating ligand binding properties in hemoglobin. A direct connection between ligand binding and the Fe-His bond is suggested from our finding that the structural parameter(s) regulating the barrier height for germinate recombination is likely to be the same as the one(s) modulating the frequency of the Fe-His stretching mode in the transient deoxy species. Based on the recent conclusion that the variation in the tilt of histidine with respect to the heme plane is primarily responsible for the spectrum of frequencies observed for the Fe-His stretching mode we have examined a model in which protein regulation of binding occurs via a protein-induced change in the histidine tilt.

Hemoglobins↗
PubMed1983

Experimental infections of birds with Turlock virus.

Two experiments were conducted with five gallinaceous and one passerine bird species to determine their responses to Turlock (TUR) virus inoculations. Inoculation of TUR strain 847-32 into bobwhites, chukars, ring-necked pheasants, chickens, and Japanese quail did not product detectable viremias. The first four species, however, did respond with neutralizing antibody. Inoculation of chickens with strain 69V-1095 resulted in a viremia which lasted 5 days and had a peak mean titer of 2.0 log 10 PFU per 0.2 ml of blood on the third day after infection. The observation that viremic birds exhibited no noticeable virus-associated morbidity or mortality suggested that TUR virus does not have a detrimental effect on free-ranging populations of the avian hosts studied during this investigation.

Animals↗
PubMed1980

Effect of feeding protected lipids on fatty acid synthesis in ovine tissues.

The effects of including protected lipid supplements in the sheep diet have been studied by measuring the incorporation of [1-14C]acetate into tissue fatty acids in vivo and in vitro. Supplementing the diet with protected lipid significantly (P > 0.05) depressed lipogenesis in adipose tissue both in vovo and in vitro. However, when protected lipids of different fatty acid composition were given to lambs, the protected safflower oil supplement containing high levels of linoleic acid was the only treatment to cause a significant (P > 0.05) depression in fatty acid synthesis in adipose tissue, the major site of lipogenesis in the sheep. Larger adipose cells in the lipid-supplemented sheep indicate that these sheep were fatter than those receiving the basal diet. Therefore, supplemented wethers deposited more fat than sheep receiving the basal diet and this fat was derived from the supplement rather than from de novo synthesis.

Acetates↗
PubMed1978

Effect of feeding protected cholesterol on ruminant milk fat secretion.

Feeding 1-2 g/day of cholesterol protected against ruminal hydrogenation caused a 20-30% drop in the secretion of milk fat by goats and cows. The effect was observed with goats fed conventional rations or with goats and cows fed rations supplemented with protected lipids, but was not observed with cows fed conventional rations, or when unprotected cholesterol and protected beta-sitosterol was fed to these animals. The results suggest that this depression in milk fat is due to a decreased uptake of plasma triacylglycerol fatty acids by the mammary gland, induced by dietary cholesterol.

Animals↗
PubMed1978

Ruminal hydrogenation of cholesterol.

Cholesterol was hydrogenated by anaerobic incubation with sheep rumen fluid for periods up to 20 hr. The principal product of cholesterol hydrogenation was identified as coprostanol. Cholesterol could be protected against in vitro ruminal hydrogenation by encapsulation in a matrix of formaldehyde-treated casein. Formaldehyde-treated casein-cholesterol preparations were also shown to be protected against hydrogenation in vivo and, when supplements containing 1 g per day of protected or unprotected cholesterol were fed to sheep over a period of 8-9 weeks, there were marked differences in the plasma cholesterol response. The plasma cholesterol of the sheep fed protected cholesterol increased by at least 60%. The plasma cholesterol of the sheep fed unprotected cholesterol also tended to increase during the first 5 weeks of supplementation but thereafter declined to almost control levels at 8 weeks.

Animals↗
PubMed1978

The effect of dietary fat supplements on cholesterol metabolism in ruminants.

The serum cholesterol on ruminant animals rises when supplemental fat is fed in a form that ensures the absorption of long-chain fatty acids. The effects of these fat supplements on cholesterol metabolism have been studied in sheep and goats. The proximal part of the small intestine was the major site of sterol synthesis in sheep. Supplementing the diet with fat significantly enhanced sterolgenesis in the small intestine both in vivo and in vitro, whereas in vitro sterolgenesis appeared to be suppressed in the liver. Increased intestinal sterolgenesis was seen with several varieties of fat, but was greatest when palm oil was fed. The reciprocal findings in the intestine and liver may reflect the increased requirement for cholesterol for the transport of triglyceride in chylomicrons and the secondary inhibiting effect of this cholesterol on sterol synthesis in the liver. Dietary fat supplementation did not alter the excretion of neutral steroids in the feces of goats but did not cause a marked reduction in the excretion of acidic steroids which may have been due to the decreased formation of sterols in the liver. In two lactating goats in which an injection of [14C] cholesterol was followed by daily intraruminal administration of labeled cholesterol, fat supplementation lowered the specific radioactivity of cholesterol in alimentary particles and in milk, being consistent with an increase in intestinally synthesized cholesterol. The hypercholesterolemia that develops in fat-fed ruminants appears to be primarily due to an increased intestinal biosynthesis of cholesterol but may also be partly due to a decreased fecal excretion of bile acids.

Acetates↗