Search PubMed⌕ Search

Biomedical subjects

T A Jackson

Publications and source records attributed to T A Jackson.

At least 37 records · Page 2Linked to original sources
PubMed1993

Nonexponential protein relaxation: dynamics of conformational change in myoglobin.

The picosecond evolution of the tertiary conformation of myoglobin (Mb) after photodissociation of MbCO was investigated at room temperature by probing band III, a weak iron-porphyrin charge-transfer transition near 13,110 cm-1 (763 nm) that is sensitive to the out-of-plane displacement of the iron. Upon photolysis, the iron moves out of the plane of the porphyrin, causing a blue-shift of band III and a concomitant change in the protein conformation. The dynamics for this functionally important motion are highly nonexponential, in agreement with recent molecular dynamics simulations [Kuczera, K., Lambry, J.-C., Martin, J.-L. & Karplus, M. (1993) Proc. Natl. Acad. Sci. USA 90, 5805-5807]. The conformational change likely affects the height of the barrier to ligand rebinding and may explain nonexponential NO rebinding.

Circular Dichroism↗
PubMed1992

Antagonism of kainic acid lesions in the mouse hippocampus by U-54494A and U-50488H.

A morphometric study of kainic acid- (KA) induced lesions was designed for the study of the interaction of the diamines U-5449A and U-50488H with excitatory amino acids, and the dose-response relationship thereof. IC50S determined for binding at the kappa receptor and other opioid receptors demonstrated the lack of kappa activity of U-54494A, a structurally related analog of U-50488H. Both opiate kappa receptor related anticonvulsant diamines were tested for their ability to protect the mouse hippocampus from the cytopathological changes induced by KA in neurons and glia. The damage observed with i.c.v. KA in mouse was restricted to neurons of the CA3 pyramidal region and glia of the hippocampus. It involved massive cell loss and shrunken neurons with dark cytoplasm and nuclei. Groups treated with combinations of KA and U-54494A or U-50488H showed scarce damage, but patches of necrotic changes were still observed. Control animals treated with saline (i.c.v.) and U-54494A (s.c.) or U-50488H (s.c.) did not suffer any noticeable alterations of the polymorphic layers of the hippocampal formation. Image analysis of the CA3 area of the hippocampus was used to quantitate the vacuolization induced by KA lesions in the control and treated groups. By this method, both U-54494A and U-50488H were shown to protect this area in a dose-related fashion as evidenced by reduced vacuolization. The anticonvulsant properties of these compounds may result in the antagonism of the excitotoxic lesions. More specifically, the ability of these diamines to block depolarization-induced influxes of Ca++ may protect the CA3 cells from the cytotoxic effects of persistent depolarization.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1984

Experimental infection of fetal and newborn Suffolk sheep with scrapie virus.

Fetal (n = 21) and newborn (n = 7) Suffolk sheep were inoculated with scrapie virus isolated from other Suffolk sheep. Twenty fetuses, 76 to 109 days of gestational age, were inoculated IM in the neck through the uterine wall and were examined for virus 47 to 322 days later by mouse inoculation. Scrapie virus was not detected before 254 days of age; only traces of virus were detected in 3 of 7 lambs examined thereafter (2 at 254 days of age and 1 at 322 days of age). Virus was limited to the supra-pharyngeal, prescapular, and mesenteric lymph nodes. Seven lambs were inoculated into the palatine tonsils with scrapie virus as newborns (3 to 12 days old) and were examined for virus when they were 147 to 210 days old. Virus was not detected in the lymphoreticular tissues or terminal portion of ileum of any lamb. Failure to find scrapie virus in these lambs and in most lambs inoculated as fetuses might indicate few had became infected. However, if most lambs and fetuses had become infected, the long zero phase of the infection could have accounted for failure to find scrapie virus in many of them examined too soon after inoculation. The limited findings of this study indicate that efforts to demonstrate prenatal or neonatal transmission of scrapie by detecting virus are hampered by the slowness of its replication.

Animals↗
PubMed1981

Intrauterine transmission of ovine progressive pneumonia virus.

Ovine fetuses, newborn lambs, and ovine colostrum were examined for ovine progressive pneumonia virus. The lambs and colostrum were also examined for specific antibody. Virus was isolated from 1 fetus, from 2 newborn lambs, and from most samples of colostrum. The fetus was about 100 days old and was carried by a seronegative ewe in contact with seropositive sheep. Both newborn lambs were carried by seropositive ewes. One lamb was dead at birth; the other lamb was normal and had not nursed. Antibody specific for the virus was present in the colostrum of 12 of 14 seropositive ewes and in the serum of 8 of 11 lambs that had nursed seropositive ewes, but not in the serum of lambs that had not nursed.

Animals↗
PubMed1979

Lesions of ovine progressive pneumonia: interstitial pneumonitis and encephalitis.

Lesions in sheep with ovine progressive pneumonia are described. Lungs were mottled grayish-pink, firm, and large (two to three times normal weight). There was chronic diffuse interstitial pneumonitis characterized by extensive hyperplasia of lymphoid cells around airways and blood vessels and by accumulation of mononuclear cells in the interstitium. In some lungs, this reaction was accompanied by excessive fibrous tissue and smooth muscle and less frequently by hyperplastic epithelium of terminal bronchioles and alveoli. Secondary bronchopneumonia was common. Lymphocytic meningitis, choroiditis, and leukoencephalitis were seen in a few sheep. Meninges and choroid plexuses were infiltrated with lymphoid cells, and subependymal blood vessels were cuffed with lymphoid cells. Much subependymal white matter was demyelinated and had foci of necrosis and gliosis.

Animals↗
PubMed1978

Diagnostic features of ovine progressive pneumonia.

Ovine progressive pneumonia, a chronic, insidious disease of adult sheep, has a relentless course leading to dyspnea, emaciation, and death. Clinical observations and serologic tests are adequate for making a tentative diagnosis. The agar gel immunodiffusion test seems to be the best serologic procedure for indicating infection with the virus but cannot be used to predict morphologic changes or clinical disease, inasmuch as many clinically unaffected animals carry the virus. A definitive diagnosis is based on finding lesions and isolating virus. Affected lungs are large and heavy as a result of interstitial accumulation of lymphoid cells and fibromuscular tissue. Frequently, interstitial lesions are accompanied by bronchopneumonia from secondary bacterial infection. The causal virus can be isolated from infected lungs by cocultivation with primary ovine or bovine cells.

Animals↗
PubMed1977

Equine herpesvirus 1 infection of horses: studies on the experimentally induced neurologic disease.

Experimental infection with equine herpesvirus 1 (rhinopneumonitis) resulted in neurologic disease in 8 of 15 inoculated horses. Nonpregnant animals did not develop clinical disease, and microscopic examination of tissues revealed no changes. In all mares between 3 and 9 months of gestation, a neurologic syndrome appeared 6 to 8 days after inoculation. Mares inoculated when 10 months pregnant did not develop neurologic disorders, but several aborted. The histopathologic change common to both sequelae was vasculitis, involving smaller arteries and veins. Although blood vessel changes were detected in endometrium of all pregnant mares, vascular changes were present in the central nervous system only in mares having neurologic disease. Concomitant degeneration of nervous tissue occurred within the central nervous system and, in many sites, anatomic and temporal relationships of vasculitis and nervous tissue degeneration suggested a cause-effect relationship. This theory was strengthened by the lack of usual histopathologic indications of encephalomyelitis. In cerebrospinal fluid from affected mares, there was an increase in protein but not pleocytosis.

Abortion, Veterinary↗
PubMed1977

Immunodiffusion test for ovine progressive pneumonia.

An agar gel immunodiffusion test was developed to detect precipitating antibody against ovine progressive pneumonia (OPP) virus. The test was conducted in plastic petri dishes containing 6 ml of 1% purified agar in tris buffer and 8% sodium chloride. Wells for serum and antigen were 8 mm in diameter and were cut in a hexagonal pattern 3 cm from a central well. Tests were read at 24 and 48 hours. Soluble antigen for the test consisted of concentrated nutrient medium removed every 2 weeks from a cell culture persistently infected with isolate WLC 1 of OPP virus. Specificity of results was verified by testing serums from experimentally exposed sheep and appropriate controls. Two lines of precipitate formed with some serums from experimentally inoculated sheep. Serums taken soon after exposure of sheep to the virus and those taken 3 to 4 years after exposure frequently formed only 1 line of precipitate. Of 37 lambs inoculated with OPP virus, 25% of those tested were positive by postinoculation (PI) month 1, 79% of those tested were positive by PI month 3, and all of those tested were positive by PI month 6. The test appears adequate to detect exposure of sheep to OPP virus.

Animals↗
PubMed1977

Prevalence of ovine progressive pneumonia in a sampling of cull sheep from western and midwestern United States.

Ovine progressive pneumonia was found to be prevalent in many major sheep-producing areas in the United States. The incidence was determined in a sampling of cull sheep (5 to 10 years of age) at slaughter. Diagnostic criteria were based on finding viral-specific immunoglobulins, virus, or lesions. Each method indicated a high incidence in samplings from midwestern and northwestern states and a relatively low incidence in the sampling from southwestern states. Of those sheep examined, precipitating immuno-globulin to the causal virus was seen in 1.0% to 67.5%, virus was isolated from the lungs of 0% to 46.2%, and lymphoid hyperplasia was seen in the lungs of 0% to 38.5%. The most common lesions in the lungs (from which virus was isolated) were multiple lymphoid nodules and increased fibromuscular tissue.

Animals↗
PubMed1975

Virus-like particles in buffy coat cells of normal goats and goats infected with progressive pneumonia virus.

By electron microscopy, virus-like particles (VLP) were seen in neutrophils and lymphocytes from buffy coats prepared from 5 goats inoculated with progressive pneumonia virus (PPV) and 3 noninoculated goats. The VLP were 80 to 120 nm in diameter, limited by a unit membrane, and resembled PPV, visna virus, and other members of the oncornavirus family. Some VLP seemed to have electron-dense nucleoids and external spikes. In neutrophils, VLP were observed budding into vacuoles; rarely, intravacuolar clusters were seen. In lymphocytes, VLP were seen in vacuoles. Free VLP and budding of VLP from external cell surfaces were not seen. In vitro incubation of buffy coat cells with mitogens did not affect the frequency of VLP. Although the VLP are similar to PPV, the exact nature of the particles and their relationship to PPV is not clearly understood.

Animals↗