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J R Baker

Publications and source records attributed to J R Baker.

At least 307 records · Page 17Linked to original sources
PubMed1980

Isotope decay range distribution curves for use in the analysis of electron microscope autoradiographs.

Analysis of autoradiographs at the electron microscope level requires special procedures, since the size of the radioactive structures visualized are comparable to the range of the radioactive decay particles emitted. Quantitative analysis in these circumstances requires that the sizes, shapes, and juxtaposition of the various structures be taken into account in relation to the range distribution of silver grains, produced by the decays, from a point source for the particular isotope and autoradiographic conditions employed. We present the distribution of silver grains about a point source for the four electron capture isotopes 51Cr, 55Fe, 111In, and 125I. Thin radioactive line sources were constructed and the distribution of autoradiographic grains measured. The grain distributions are discussed in relation to the number of particles per disintegration and their energy and range. A simple calculation enables these line source distributions to be converted into point source distributions, which can then be used for whichever method of quantitative analysis is considered appropriate for a particular problem. An outline is given of some of the more important aspects of various methods of analysis.

Autoradiography↗
PubMed1980

The effects of glutaraldehyde and formaldehyde fixation on the retention and subcellular location of [3H]5-hydroxytryptamine in rabbit platelets: a study using liquid scintillation counting and E.M. autoradiography.

The retention and loss of [3H]5-hydroxytryptamine (5-HT) from rabbit platelets during fixation was studied using liquid scintillation counting and quantitative electron-microscopic autoradiography. The results were at variance with previously reported data on human platelets. Following treatment of the platelets with either 2.0% formaldehyde or 2.5% glutaraldehyde for 2 min or 1 h it was found that a significantly increased proportion of the radioactivity was lost from treated as compared with untreated platelets. Using a method of analysis which accounts for cross-scatter of decay particles between cell compartments, electron-microscopic autoradiography revealed that 50% of the radioactivity following incubation of platelets with [3H]5-HT was associated with dense bodies and 30% in the cytoplasm when fixation was in formaldehyde or glutaraldehyde. The only major difference in the labelling pattern was that whereas glutaraldehyde appeared to retain no activity in the surface connected system the latter contained 12% of total retained activity following fixation with formaldehyde.

Aldehydes↗
PubMed1979

Radioimmunoassay of the link proteins associated with bovine nasal cartilage proteoglycan.

Link proteins from bovine nasal cartilage have been purified by preparative polyacrylamide gel electrophoresis in sodium dodecyl sulfate (Baker, J.R., and Caterson, B. (1979) J. Biol. Chem. 254, 2387-2393) and used to raise antisera in rabbits. A sensitive radioimmunoassay procedure utilizing binding of 125I-labeled antigen . antibody complexes to Protein A of Staphylococcus aureus has served to demonstrate the specificity of the antisera for the link proteins. The lack of reactivity with proteoglycan fractions indicates that link proteins and proteoglycan do not share antigenic determinants. This result is in accord with published cyanogen bromide peptide cleavage data (Baker, J.R., and Caterson B. (1977) Biochem. Biophys. Res. Commun. 77, 1-10) which showed proteoglycan and link protein to be structurally dissimilar. The radioimmunoassay procedure has been used to quantitate small amounts of link protein which remain associated with proteoglycan after purification by equilibrium density gradient centrifugation in 4 M guanidine HCl and by gel chromatography in sodium dodecyl sulfate.

Animals↗
PubMed1979

Four cases of chondrodystrophy in fallow deer.

The gross and microscopic pathology in four cases of chondrodystrophy in a herd of captive fallow deer is described. The gross pathology was similar in all cases with shortening of all the bones, especially of the limbs, but at the microscopic level two distinct types of abnormality were present in the epiphyseal plates. In one type there was failure of proliferation of chondrocytes and in the other proliferation and vascularisation were irregular.

Animals↗
PubMed1979

The isolation and characterization of the link proteins from proteoglycan aggregates of bovine nasal cartilage.

A preparation containing the link proteins may be obtained from bovine nasal cartilage by extraction with 4 M guanidine hydrochloride and by equilibrium density gradient centrifugations of the extract as commonly employed in the isolation of proteoglycan monomers. In the present paper, protein-rich proteoglycans have been removed from such a preparation to give purified link proteins by chromatography on Sepharose CL-6B in 1% sodium dodecyl sulfate. The individual link proteins, which in order of increasing electrophoretic mobility are termed link proteins 1, 2, and 3, have been separated and isolated in a subsequent preparative gel electrophoresis step. The link proteins present in largest amount, link proteins 1 and 2, have essentially the same amino acid compositions, and following partial digestion with the V8 protease from Staphylococcus aureus and analytical electrophoresis in sodium dodecyl sulfate, their peptide patterns closely resemble each other. Therefore,it is probable that link proteins 1 and 2 are structurally similar. Link protein 1 contains more carbohydrate than link protein 2 (9.5% and 3.0%, respectively) and it is suggested that the major difference between them is in carbohydrate content.

Amino Acids↗
PubMed1979

Neoplasms in rats and mice fed butylurea and sodium nitrite separately and in combination.

In projected 485-day studies, Fischer 344 rats and C57BL/6 mice were fed 0.58% butylurea and 0.50% sodium nitrite mixed in the diet separately or in combination. The number and type of neoplasms were not significantly increased in either species receiving butylurea or sodium nitrite only. Feeding the two chemicals simultaneously induced neoplasms of the lung, Zymbal's gland, forestomach, intestine and hemopoietic tissues in rats, and malignant lymphomas in mice. The increased incidence of neoplasms in rats and mice fed butylurea and sodium nitrite in combination may result from in vivo formation of the carcinogen, N-butyl-N-nitrosourea.

Animals↗
PubMed1978

Equine sarcoids.

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Animals↗
PubMed1978

The isolation of "link proteins" from bovine nasal cartilage.

Methods of isolating the water insoluble 'link proteins' from preparations of bovine nasal cartilage proteoglycan aggregates have been investigated. Upon chromatography on Sepharose 4B in 0.1% sodium dodecyl sulfate, the 'link proteins' are found in a discrete, included peak, whereas the bulk of the proteoglycan emerges at the void volume. Some low molecular weight proteoglycan is associated with the 'link proteins'. An alternative procedure, i.e. chromatography on DEAE-cellulose in sodium dodecyl sulfate, has also been examined. In 0.1% sodium dodecyl sulfate, proteoglycan monomer is not absorbed by the column, whereas 'link proteins' are. Subsequently, the 'link proteins' with a minor fraction of the proteoglycan are eluted with 1.0% sodium dodecyl sulfate. Both procedures serve to separate the 'link proteins' from the bulk of proteoglycan present in an aggregate preparation, but additional steps are necessary to achieve homogeneity. Thus a 'link protein' preparation, fractionated from proteoglycan aggregate by equilibrium density gradient centrifugation under dissociative conditions, can be finally purified by chromatography on DEAE-cellulose in sodium dodecyl sulfate.

Amino Acids↗
PubMed1978

Trypanosoma (Schizotrypanum) dionisii: effect of various agents on attachment and entry to macrophages in vitro and on morphogenesis.

The attachment and entry of Trypanosoma dionisii to mouse peritoneal macrophages in vitro were studied. Both occurred to a similar extent whether parasites were alive or heat-killed, and whether macrophages were obtained from normal or immunized mice. Attachment occurred equally at 4 and 37 degrees C, but entry only occurred at the higher temperature. Neither was affected by pretreatment of parasites with active or inactivated complement. Entry, but not attachment, was inhibited by cytochalasin B; both were inhibited by trypsin. Immune mouse plasma (if inactivated) stimulated attachment but not entry (within 24 h). It also stimulated intracellular replication of T. dionisii by multiple fission and subsequent differentiation (probably within macrophages) to small extracellular trypomastigotes. No extracellular parasite and only scanty intracellular forms survived 120 h in cultures containing non-inactivated immune mouse plasma. It was concluded that attachment (in the absence of antibody) occurred to non-specific receptors in the macrophage membrane and was followed by phagocytosis of the parasites rather than their active penetration of the cell.

Animals↗
PubMed1978

Trypanosoma (Schizotrypanum) dionisii: influence of mouse peritoneal macrophages and calf sera on extracellular growth in vitro at 37 degrees C.

Macrophages and certain batches of sera were essential for extracellular multiplication of Trypanosoma dionisii in vitro in medium 199 with 20% (v/v) calf serum at 37 degrees C. In mixtures of 'good' and 'bad' batches of sera, multiplication increased as the proportion of the former was increased. Mixtures of 'bad' and 'intermediate' sera permitted virtually no growth. Phagocytosis of parasites by macrophages was unaffected by different batches of sera, though reduced in medium 199 alone. Replacement of supernatant medium by medium containing 'bad' serum reduced the macrophage infection rate no more than did transfer to medium containing 'good' serum. Daily addition of medium conditioned by prior contact with macrophages in vitro to cultures of trypanosomes without macrophages resulted in growth at least as good as that in the presence of macrophages. Extracellular replication in medium 199 at 37 degrees C apparently required at least two factors: 'M factor' provided by macrophages, but not required at 28 degrees C; and 'S+ factor' present in some batches of calf serum, essential also at 28 degrees C but not required by intracellular parasites. Some sera appeared to contain an inhibitory 'S- factor'.

Animals↗
PubMed1978

Entry of Trypanosoma (Schizotrypanum) dionisii to macrophages in vitro and its subsequent fate therein.

Observations by phase contrast, fluorescence and electron microscopy showed that epimastigotes of Trypanosoma (Schizotrypanum) dionisii (grown in vitro) were phagocytosed posterior end first by mouse peritoneal macrophages in vitro. Many were subsequently digested as a result of phagosome-lysosome fusion but others survived by apparently inhibiting this fusion and/or escaping from the phagosome into the host cell's cytoplasm. These survivors replicated as amastigotes. Long trypomastigotes, separated from populations grown in vitro by passage down a column of glass beads (with or without prior exposure to guinea-pig serum), were phagocytosed by either pole and all were subsequently digested.

Animals↗