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Biomedical subjects

K McEntee

Publications and source records attributed to K McEntee.

At least 109 records · Page 6Linked to original sources
PubMed1979

ATP-dependent renaturation of DNA catalyzed by the recA protein of Escherichia coli.

The product of the recA gene of Escherichia coli has been purified to near-homogeneity by a simple three-step procedure. Incubation of the recA protein with complementary single strands of DNA, Mg2+, and ATP results in the rapid formation of large DNA aggregates containing many branched structures. As judged by resistance to S1 nuclease and by electron microscopy, these aggregates contain both duplex and single-stranded regions. The renaturation and aggregation of DNA catalyzed by the recA protein is coupled to the hydrolysis of ATP. The recA protein purified from a cold-sensitive recA mutant does not catalyze DNA renaturation or aggregation at 28 degrees C, but does so at 37 degrees C, a finding which correlates with the recombination defect observed in vivo and indicates that this activity is an intrinsic function of the recA protein. These results suggest that the recA protein plays a specific role in strand transfer during recombination and possibly in postreplication repair of damaged DNA.

Adenosine Triphosphate↗
PubMed1979

Initiation of general recombination catalyzed in vitro by the recA protein of Escherichia coli.

Homogeneous recA protein catalyzes the hybridization of single-stranded DNA to homologous regions in duplex DNA. The products are D-loops, which are formed with equal efficiency in linear and supercoiled molecules. This assimilation reaction can be separated into two partial reactions. In the first, recA protein binds to duplex DNA and produces a reA protein-DNA complex. The binding shows a sigmoidal dependence on recA protein concentration, requires ATP, GTP or the gamma-thio analog of ATP, and Mg2+, but does not require hydrolysis of the nucleoside triphosphate. In the second reaction, single-stranded regions of the recA protein-ATP-duplex DNA intermediate hybridize with free complementary single strands to produce D-loop structures. This reaction is coupled to ATP hydrolysis and is analogous to the renaturation of single-stranded DNA catalyzed by the recA protein [Weinstrock, G.M., McEntee, K. & Lehman, I.R. (1979) Proc. Natl. Acad. Sci. USA 76, 126-130]. Hydrolysis of ATP appears to be required in these reactions for dissociation of recA protein from the DNA.

Adenosine Triphosphate↗
PubMed1978

Lambda transducing phages for the nalA gene of Escherichia coli and conditional lethal nalA mutations.

Defective lambda transducing phages for the nalA region of the Escherichia coli chromosome were isolated from a lysogen in which lambda is inserted in the nearby glpT gene. The three classes of transducing phages designated lambdanrdA, lambdaubiG, and lambdadnalA contained bacterial DNA extending from glpT through nrdA, ubiG, and nalA, respectively. The bacterial genes are in the left arm of the lambda chromosome. Of the eleven polypeptides coded by lambdadnalA that were resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate only one was not also specified by lambdadubiG. This 105,000 dalton polypeptide is the nalA gene product. The electorphoretic mobility and isoelectric point of this protein were unaffected by a nalA mutation (nalA48) that confers nalidixic acid resistance. Temperature-sensitive and amber mutations in the nalA gene were isolated using a lambdadnalA48 lysogen which is heterodiploid for nalA. The conditional lethality of these mutations proves that nalA is an essential locus.

Bacterial Proteins↗
PubMed1978

Pathological evaluation of paratuberculosis in naturally infected cattle.

Thirty-two of 51 cattle infected with Mycobacterium paratuberculosis had chronic enteritis, chronic lymphangitis or mesenteric lymphadenopathy, or all three, at slaughter. Granulomatous inflammatory lesions were mild to advanced and predominantly involved the distal small intestine. Rectal involvement was seen only in five cattle. Fourteen had microgranulomas in the liver. There were three cytological forms of macrophages: histiocytic, polygonal and epithelioid. The latter two types had engulfed moderate numbers of acid-fast bacilli. The histiocytic macrophages usually were packed with acid-fast bacilli. Except in the liver and occasionally its nodes, remote lesions of paratuberculosis were not found in other organs. One animal had endocardial and aortic calcifications. Most cattle with signs of diarrhea had globule leukocytes in or around myenteric ganglion cells. The thymus of 3- to 8-year-old cattle with clinical signs frequently had mild to advanced involution. The thymus of similarly aged infected animals without clinical signs, and of paratuberculosis-negative animals, had not involuted.

Animals↗
PubMed1978

Ductuli efferentes in the epididymis of boar, goat, ram, bull, and stallion.

Dutculi efferentes were studied by microdissection and histologic methods in 2 boar, 6 goat, 5 ram, 25 bull, and 19 stallion epididymides. On the basis of the present findings and the data of others and relating them to the total number of specimens examined in each species, an estimate (narrow range) was made of the minimal-maximal numbers of efferent ductules as follows: dog 13 to 15; cat 14 to 17; boar 14 to 16; goat 18 to 19; ram 17 to 20; bull 13 to 16; and stallion 14 to 17. The histologic appearance of the efferent ductules of the bull, including measurements of their diameter, lumen, and epithelium, was briefly described. Attention was focused on the presence of blind-ending ductules, because it was thought that they might be a factor in the cause of spermiostasis. Blind-ending ductules were found in 1 of 2 porcine, 1 of 6 caprine, 2 of 5 ovine, 8 of 25 bovine, and 13 of 19 equine ductules per affected male were 4 in the boar, 1 in the goat, 2 to 3 in the ram, 1 to 5 in the bull, and 1 to 14 in the stallion. From our work, it appears that in the bull and stallion at least, blind-ending ductules were present in sufficient numbers to be considered a factor in spermiostasis and the infertility resulting from it.

Animals↗
PubMed1977

Protein X is the product of the recA gene of Escherichia coli.

The inducible protein X of Escherichia coli has been compared to the recA+ protein made by specialized recA transducing phages. The molecular weights and isoelectric points of these proteins are identical. Two mutations located in the recA gene that alter the electrophoretic mobility or the isoelectric point of protein X have been studied. A recA12 mutant strain, deficient in homologous recombination and repair, produces a smaller-than-normal protein X. A transducing phage carrying the recA12 allele directs the synthesis of a smaller recA protein after infection of irradiated cells. A transducing phage carrying the recA region of a tif-1 mutant strain codes for a recA protein with an isoelectric point more basic than that of the lambdaprecA+ product. The protein X of a tif-1 mutant strain shows an identical shift in its isoelectric properties. Examination of several tsl- recA- strains indicates that protein X can be induced in several missense recA mutants but is not detected in tsl- strains carrying amber or deletion mutations of the recA gene. These results demonstrate that protein X is the product of the recA gene and that the tif-1 mutation alters the properties of the recA protein. A model is suggested for autoregulation of the recA protein in the induction of functions expressed in response to DNA damage (SOS functions).

Bacterial Proteins↗
PubMed1977

Genetic analysis of the Escherichia coli K-12 srl region.

Specialized transducing lambda derivatives, deletion mapping, and Plkc transductional crosses have been used to analyze the genetic organization and regulation of the srl genes. Transducing phages obtained from a secondary site lambda insertion in srlA are of two types: lambdapsrlC1 and lambdaprecA are substituted in the b2 region of the lambda chromosome (galtype) and carry the srlC gene but not srlD; lambdapsrlD is substituted in the early region of the phage deoxyribonucleic acid (biotype) and carries the srlD gene but not srlC. The lambdapsrlC1 phage, which lysogenizes at attlambda, complements srlC mutants in trans, indicating that this gene codes for a diffusable positive regulatory element. The srl genes have been ordered relative to the cysC, recA, and alaS genes by two- and three-factor P1kc crosses. The order, cysC...srlD-srlA-srlC-recA-alaS, has been obtained. The srlA and srlD genes comprise an operon with srlD operator distal. From the secondary site lysogen, it has been possible to obtain deletion mutants of this region that are sensitive to ultraviolet light and are recombination deficient. Genetic evidence suggests that these deletions extend from srl into the recA gene.

Chromosome Mapping↗
PubMed1976

Male pseudohermaphroditism, cryptorchism, and Sertoli cell neoplasia in three miniature Schnauzers.

A syndrome of male pseudohermaphroditism, cryptorchidism, and testicular neoplasia was diagnosed in 3 Miniature Schnauzers. The dogs had clinical signs of hyperestrogenism and were either unilateral or bilateral cryptorchids. At surgery, it was discovered that the dogs were male pseudohermaphrodites, having intra-abdominal testes containing Sertoli cell tumors and uteri that had undergone endometrial cystic hyperplasia.

Animals↗
PubMed1976

Identification and radiochemical purification of the recA protein of Escherichia coli K-12.

The product of the recA gene of E. coli has been identified by labeling proteins synthesized in UV-treated cells after infection with specialized transducing phages carrying the recA gene. Following infection of UV-treated cells by lambda precA, which carries the recA+ gene, a major protein with a molecular weight of 43,000 is detected on polyacrylamide gels containing sodium dodecyl sulfate. This protein is also made after infection of suppressing hosts by lambda precA99, which carries an amber recA- mutation, but is not synthesized after infection of nonsuppressing hosts by this transducing phage. A spontaneous recatrevertant of lambda preca99 induces synthesis of this protein after infection of a nonsuppressing host. The product of the recA gene is a soluble protein found in a complex with a molecular weight of approximately 150,000 after mild detergent lysis of cells.

Bacterial Proteins↗
PubMed1976

Tumours of the ovary.

Ovarian tumours are common in animals, the majority occurring in bitches and cows. The two most important germ cell tumours were dysgerminoma and teratoma; these morphologically resemble their counterparts in women, with the exception that teratomas in animals tend less to malignancy. The granulosa cell tumour is the most frequent sex cord-stromal tumour in all six species and it may contain luteinized areas or show differentiation towards a Sertoli cell pattern. The canine papillary adenoma and papillary adenocarcinoma, which are as common as granulosa tumours, have several features in common with their counterparts in women: they are of similar histological appearance, are frequently bilateral, and the adenocarcinomas have a great propensity for peritoneal implantation metastasis. Ovarian cysts are frequent in the bitch, sow, and cow and may originate from five different anatomical structures in the ovary.

Animals↗
PubMed1976

Tumours of the female genital tract.

Tumours of the female tubular genital tract are comparatively rare, with the exception of leiomyomas in cows and bitches, uterine carcinomas and vaginal fibropapillomas in cows, and transmissible venereal tumours in bitches. Uterine adenocarcinomas of cows are highly scirrhous, often causing minimal gross lesions that remain undetected until metastatic lesions in pelvic nodes and lungs are found. Cats and bitches also develop uterine carcinomas, but less frequently than cows; when present, they are predominantly discrete masses of well differentiated, non-sclerosing adenocarcinoma. Fibropapillomas are caused by the virus of verrucca vulgaris and can be transmitted to the penis of the bull. Adenomyosis is not uncommon in the cat, cow, and bitch. There is a marked difference in the frequency with which cervical carcinomas occur in man compared with other mammals; in the latter we could find no instance of an unequivocal primary cervical carcinoma. There are a few reports describing invasive carcinomas involving the cervix, but invasion from either a uterine or a vaginal carcinoma could not be ruled out.

Animals↗
PubMed1976

Tumours of the prostate and penis.

Tumours of the male genital tract, excluding the testes, are relatively rare in the six major domestic animals. The most important tumours are prostate carcinoma and transmissible venereal tumour of the penis in dogs, fibropapilloma of the penis in bulls, squamous papilloma and squamous cell carcinoma in horses, and squamous papilloma in pigs. Four histological types of canine prostate carcinoma exist: alveolar papillary, acinar, organoid, and poorly differentiated. The biological behaviour of prostate carcinomas is similar to that in man, with frequent metastasis to the regional pelvic nodes, bones, and lungs. There appears to be no relationship between the common diffuse glandular hyperplasia and carcinoma in the prostate of dogs. A unique lesion of dogs is squamous metaplasia of the prostate related to estrogen-producing Sertoli cell tumours of the testis. Three different transmissible tumours of the penis occur in domestic animals. The canine venereal tumours can be transmitted only by intact tumour cells during licking and coital contact, whereas bovine fibropapillomas and porcine squamous papillomas can be transmitted by cell-free material. In cattle, the fibropapillomas are caused by the same virus that produces cutaneous papillomatosis. All three tumours are benign and usually regress spontaneously.

Animals↗
PubMed1975

Pathogenetic studies of infection of the bovine fetus with bovine viral diarrhea virus. II. Ocular lesions.

Twenty-three susceptible pregnant heifers were inoculated with bovine viral diarrhea virus at 150 +/- 1 days of gestation. Seven additional heifers were inoculated between 65 and 115 days of gestation. Acute ocular lesions were seen in fetuses taken 17-21 days after inoculation of the dams at 150 days. By the fourth week, the acute lesions were beginning to resolve, and in newborn animals focal to total retinal atrophy was seen. The acute lesions were characterized by a mild to moderate retinitis that resulted in various degrees of destruction of the different layers, mononuclear cuffing of inner retinal vessels, proliferation of pigment epithelium, and choroiditis. Residually there was an absence of cellular elements in the atrophied areas of the retina, frequently a loss of layering and various numbers of pigment-containing cells. Moderately severe acute inflammation was seen in the retina of the fetus taken at 22 days after inoculation of its dam at 95 days. Ocular lesions did not occur in the other fetuses taken from heifers inoculated at earlier stages of gestation.

Animals↗
PubMed1975

Cestrum diurnum poisoning in Florida cattle.

Cestrum diurnum poisoning was described in a Florida bull. Clinical signs included chronic wasting and progressive lameness. Plasma calcium was elevated for long periods of time but decreased toward low normal values. There was pronounced C-cell hyperplasia. Osteopetrosis was very severe and reflected retarded osteocytic osteolysis and chondrolysis. Further negative effects on the osteocytes eventually lead to osteonecrosis. Soft tissue calcinosis involved tendons and ligaments, major arteries and veins but kidneys and lungs were spared. Whereas the osteopetrosis could be explained by hypercalcitoninism, the osteonecrosis was believed to result from direct action by the Cestrum diurnum factor, previously shown to have an action similar to that of 1,25-dihydroxy-cholecalciferol, which is the biologically active metabolite of vitamin D3.

Adrenal Glands↗