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Biomedical subjects

J N Davidson

Publications and source records attributed to J N Davidson.

At least 55 records · Page 3Linked to original sources
PubMed1982

Isolation of a human repetitive sequence and its application to regional chromosome mapping.

Recombinant lambda phage Charon 4A with repetitive human DNA inserts have been constructed by using cellular DNA from a human-Chinese hamster ovary cell hybrid retaining the complete hamster genome and a single human chromosome 12. One recombinant phage, 12-11, contains several repetitive sequences, each with a different repetition pattern in the human genome. A 2.2-kilobase (kb) EcoRI fragment of this phage was subcloned in pBR325. This sequence has fewer than 5,000 copies in the human genome and does not cross-hybridize with Chinese hamster DNA. When the labeled 2.2-kb probe was hybridized to human chromosome 12 DNA digested with EcoRI, there was an intense band at the 2.2-kb position and a series of other discrete bands. The band pattern at positions other than 2.2 kb appears to be distinct for each human chromosome. The 2.2-kb fragment is composed of at least three subregions. The ends of the fragment are repeated more frequently in the genome than is the middle portion. Hybridization of chromosome 12 DNA with probes made to these subregions yielded simpler band patterns. By using a series of cell hybrids containing various deletions of human chromosome 12, five sequences related to the 2.2-kb fragment have been assigned regionally to a specific portion of the short arm of chromosome 12. These results demonstrate that certain repetitive sequences in the human genome can be used as genetic markers and may permit detailed regional mapping of human chromosomes.

Animals↗
PubMed1982

Isolation and chromosomal localization of unique DNA sequences from a human genomic library.

Recombinant bacteriophage lambda from a human genomic library were screened to indentify human DNA inserts having only unique sequences. Unique human inserts were found in about 1% of the phage screened. One recombinant phage, P3-2, was studied in detail. It contains a human insert of 14.7 kilobases with four internal EcoRI cleavage sites. A restriction map was constructed for EcoRI and BamHI sites. Hybridization of the 32P-labeled P3-2 probe to a Southern blot of EcoRI-digested total human DNA yielded distinct bands at positions corresponding to the human insert fragments contained in P3-2. By using a series of human-Chinese hamster somatic cell hybrids containing unique combinations of human chromosomes, the human DNA segment in phage P3-2 was assigned to human chromosome 22 by blot hybridization and synteny analysis. In addition, another human DNA segment, 11.4 kilobases, in phage P3-10 was assigned to human chromosome 10 by similar procedures. With this approach, more unique DNA sequences can be isolated, assigned to specific human chromosomes, and used as genetic markers for gene mapping and linkage, polymorphism, and other genetic studies in the human genome.

Animals↗
PubMed1982

Studies on the composition and antibacterial activity of uterine fluid from mares.

Forty uterine fluid samples were obtained during oestrus and dioestrus of successive cycles from 4 mares classified as resistant to bacterial infection of the uterus. The flushings were assayed for peroxidase activity and ability to influence phagocytosis by polymorphonuclear neutrophils. Uterine fluid volumes and protein concentrations and serum oestrogen values were similar during oestrus and dioestrus. Serum progesterone concentrations were depressed during oestrus. Equine neutrophils adherent to glass slides were exposed to a genital strain of Streptococcus zooepidemicus suspended in saline. Neutrophil phagocytosis was significantly higher when cells were incubated with oestrous uterine fluid than with dioestrous fluid. The addition of 5% serum to the incubation medium increased the rates of in-vitro phagocytosis, but these did not differ between oestrus and dioestrus. Rates of phagocytosis with and without serum were not correlated with serum oestrogens or progesterone, or with protein content of uterine fluid. Peroxidase activity of uterine fluid in the absence of infection was negligible throughout the oestrous cycle. There were no significant correlations between peroxidase levels and serum oestrogens or progesterone, but the correlation between peroxidase and protein concentration of uterine fluid was significant (r = 0 X 87). Bacterial or fungal infections led to increased protein content of uterine fluid, and usually marked increases in peroxidase, both probably derived from the visibly obvious populations of leucocytes.

Animals↗
PubMed1981

Relationship between serum immunoglobulin values and incidence of respiratory disease in calves.

Severe respiratory disease, with high morbidity and high mortality, occurred in 2 groups of bull calves (14 to 64 days old) raised in th same facility. Necropsy findings included lesions of acute or chronic bronchopneumonia. Serum immunoglobulin G (IgG) values were determined for all calves at 3 to 6 days of age. Calves that died of respiratory disease had an average IgG value of 1,267 mg/100 ml, whereas calves that lived had an average IgG value of 2,698 mg/100 ml. Calves with low serum IgG values had higher morbidity, had to be treated earlier in life, and had to be treated more frequently per day, when compared with calves that had high serum IgG values.

Animals↗
PubMed1981

Organization of a multifunctional protein in pyrimidine biosynthesis. Analyses of active, tryptic fragments.

The multifunctional protein which catalyzes the first three steps of pyrimidine biosynthesis in hamster cells can be cleaved by trypsin into enzymatically active fragments. When the fragments are separated by nondenaturing polyacrylamide gel electrophoresis, three major polypeptide bands appear. Carbamyl phosphate synthetase (EC 2.7.2.9), aspartate transcarbamylase (EC 2.1.3.2), and dihydroorotase (EC 3.5.2.3) activities are associated with 129,000-, 660,000-, and 94,000-dalton bands, respectively. Further analysis of these fragments by denaturing polyacrylamide gel electrophoresis has shown that the aspartate transcarbamylase band seen on the nondenaturing gel is actually a large aggregate of 39,000-dalton fragments and the dihydroorotase band is a dimer of 44,000-dalton fragments. The data reported here indicate that (i) this multifunctional protein is composed of three enzymatically independent domains, (ii) the sum of the molecular weights of these three domains (129,000 + 39,000 + 44,000 = 212,000) is similar to that of the undigested monomer (220,000 daltons), and (iii) a site important to the formation of the native multimeric protein is probably near the aspartate transcarbamylase domain.

Amidohydrolases↗
PubMed1981

Two-dimensional electrophoresis of human-CHO cell hybrids containing human chromosome 11.

Two-dimensional electrophoresis-electrofocusing with polyacrylamide gels is described in which the pattern of peptide spots obtained from hybrid cells of CHO containing the single human chromosome 11 are compared with those from the hybrid which has undergone reversion so as to lose this chromosome. At least eight distinct spots unique to the cell containing chromosome 11 have been located on the electrophoretogram. Experiments are described demonstrating applicability of the method to hybrids containing specific deletion mutants of chromosome 11, an approach which makes possible regional mapping of the loci responsible for specific peptides. The methodology appears applicable to study of gene expression under the influence of hormones and other agents and to the comparison of normal and disease situations.

Animals↗
PubMed1980

Leptospirosis in lambs.

Two major episodes of acute hemolytic disease in lambs were associated with high mortality. Clinical signs were severe depression, dyspnea, and tachycardia. Gross postmortem findings included hemoglobinuria and icterus. Histologic examination revealed tubular necrosis and periacinar hepatocellular necrosis. Leptospira interrogans serotype pomona was proposed as the causative agent because high serum antibody titers for this bacterium were found in lambs and ewes in the affected flocks.

Animals↗
PubMed1980

Microscopic examination of stools from nonhuman primates as a way of predicting the presence of Shigella.

Microscopic examination of stool samples from captive nonhuman primates with diarrhea for the presence or absence of leukocytes or erythrocytes or both as a means of predicting the presence of Shigella spp. was performed. Analysis of the data multivariately by means of a log linear model did not show a three-way association between diarrhea, Shigella, and the presence or absence of cells.

Animals↗
PubMed1980

Conception rates of Holstein bulls for artificial insemination on a California dairy.

Data of milk production and reproduction were collected from a 2,500-cow dairy in California for measuring conception rates of bulls for artificial insemination. The bulls were placed into groups of low, medium, or high conception rates. Mean conception rates were 38.2%, 55.7%, and 66.1%, range 34% to 70%. To predict the conception-rate group of a bull required 30 services. There were no differences in average number of lactations and days to first service of the cows bred to the three groups of bulls. Cows bred to the bulls with high conception rate produced 667 kg more milk than cows bred to bulls with low conception rate. Cows bred to the low bulls were bred, on the average, in mid-July, whereas cows bred to the other two groups were bred in June and May. The cost to this dairy for using low conception rate bulls was $21,000.

Animals↗
PubMed1980

An outbreak of haemophilus parahaemolyticus pneumonia in growing pigs.

An outbreak of pneumonia characterized by peracute death, low morbidity and a high case fatality rate is reported from a New York hog farm. The disease was confined to pigs in the weight range of 27-45 kg Sulfathiazole administered orally in the drinking water helped reduce losses.

Animals↗
PubMed1979

Biochemical genetic analysis of pyrimidine biosynthesis in mammalian cells: III. Association of carbamyl phosphate synthetase, aspartate transcarbamylase, and dihydroorotase in mutants of cultured Chinese hamster cells.

Carbamyl phosphate synthetase (EC 2.7.2.9), aspartate transcarbamylase (EC 2.1.3.2), and dihydroorotase (EC 3.5.2.3), the first three enzymes in de novo pyrimidine synthesis in Chinese hamster ovary cell strain Kl (CHO-Kl), cose diment through a glycerol gradient. When an extract from Urd- A, a pyrimidine-requiring auxotroph reduced in all three activities, is run on a glycerol gradient, the enzyme activities appear in two peaks higher in the gradient, a peak of aspartate transcarbamylase separated from a peak of carbamyl phosphate synthetase and dihydroorotase. Revertants of Urd- A have increased activity of all three enzymes and give glycerol gradient patterns similar to either CHO-Kl or Urd- A. The gradient pattern for Urd- A and some of its revertants can be mimicked by treating the CHO-Kl cell extract with trypsin. Hybrids made between a CHO-Kl purine-requiring auxotroph (Ade- C) and a Urd- A revertant gave a glycerol gradient pattern which is a composite of the CHO-Kl and revertant patterns. A model is presented for the structure of this multifunctional protein.

Amidohydrolases↗
PubMed1979

Alteration in structure of multifunctional protein from Chinese hamster ovary cells defective in pyrimidine biosynthesis.

A combined genetic, biochemical, and immunological approach has clarified structural relationships involving the first three enzymes of de novo pyrimidine biosynthesis. A procedure involving antibody and protein A-Sepharose was used to isolate the enzymes carbamoyl-phosphate synthase [ATP:carbamate phosphotransferase (dephosphorylating, amido-transferring), EC 2.7.2.9], aspartate transcarbamoyltransferase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2), and dihydro-orotase (L-5,6-dihydroorotate amidohydrolase, EC 3.5.2.3) from Chinese hamster ovary cell CHO-K1, the uridine-requiring auxotroph Urd(-)A, and selected Urd(-)A revertants. The enzymes of Urd(-)A and the Urd(-)A revertants were significantly altered in activity, native structure, and molecular weight from those of CHO-K1. The results presented permit the conclusion that (i) these three enzymes reside in a single multifunctional 220,000-dalton polypeptide; (ii) the aspartate transcarbamoyltransferase activity is located on a portion ( approximately 20,000 daltons) at one end of the polypeptide; (iii) this portion may also be required for monomers to aggregate into the multimeric from present in mammalian cells; (iv) the mutations in Urd(-)A and the Urd(-)A revertants lie in the structural gene for this multifunctional protein; and (v) increased sensitivity to proteases could account for the alterations in the structure of these enzymes in the mutants.

Amidohydrolases↗
PubMed1978

Erythromycin resistance and the chloroplast ribosome in Chlamydomonas reinhardi.

Five classes of erythromycin-resistant mutants of Chlamydomonas reinhardi have been identified. Each class corresponds to a different genetic locus, three nuclear and two chloroplast. The three nuclear loci appear to be unlinked, while Conde et al. (1975) have shown that the two chloroplast loci are linked, but not allelic. Mutants in each class have a unique pattern of cross-resistance in vivo to other antibiotics (lincomycin, carbomycin, and cleocin) that affect chloroplast protein synthesis. The chloroplast ribosomes from each class have a distinctive erythromycin-binding reaction in vitro.--Haploid and diploid strains containing combinations of different genes affecting the chloroplast ribosome were constructed to probe ribosome structure. New phenotypes were obtained by such combinations, demonstrating interactions between the gene products of a number of loci specifying ribosome components.

Chlamydomonas↗
PubMed1976

Bacterial competition as a means of preventing neonatal diarrhea in pigs.

Baby pigs orally inoculated with a porcine strain of enterotoxigenic Escherichia coli (K88+,Ent+) showed signs of depression, severe diarrhea, and, in some instances, death. Few, if any, signs of illness occurred if baby pigs were first inoculated with a K88 possessing non-enterotoxin-producing strain of E. coli.

Animals↗
PubMed1975

Use of the K88 antigen for in vivo bacterial competition with porcine strains of enteropathogenic Escherichia coli.

Infant mice were used to measure the amount of fluid accumulation (enterosorption) in the intestinal tract after oral inoculation of a porcine strain of enteropathogenic Escherichia coli (K88-+, Ent-+). Significant reduction in the amount of fluid found in the intestinal tract was observed if the mice were first inoculated with a K88-possessing, non-enterotoxigenic strain of E. coli. The protection provided is thought to be due to specific competition for attachment sites on cells of the small intestine.

Agglutination Tests↗