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D W Morris

Publications and source records attributed to D W Morris.

48 records · Page 3Linked to original sources
PubMed1976

DNA of Myxococcus phage MX-1. Pyrimidine isostichs and the recognition of a minor pyrimidine.

DNA was isolated from bacteriophage MX-1 and was hydrolysed with acids. Hydrolysis with 90% formic acid produced several interconvertable fluorescent artefacts. These substances were produced in greater quantity following hydrolysis with H2SO4. In the course of the course of the study it was found that DNA extracted from phage by 4-aminosalicylate and phenol contained 4-aminosalicylate and breakdown products derived from 4-aminosalicylate following acid hydrolysis. Pyrimidine oligonucleotides released by formic acid-diphenylamine hydrolysis were fractionated by two-dimensional paper chromatography and by ion-exchange chromatography. In this way, the pyrimidine isostichs were obtained and further fractionated. The distribution and with isostich patterns from a variety of DNA sources. MX-1 DNA was found to contain an unusually high frequency of cytosine-rich isostichs 5 and 6 and very low occurrence of the sequence R-Y-R. Based on its absorption spectrum and the fact that it can be labelled in vivo with [14C] orotic acid, we suggest that H-base is a pyrimidine.

Aminosalicylic Acids↗
PubMed1976

DNA of Myxococcus bacteriophage MX-1: macromolecular properties and restriction fragments.

1. Bacteriophage MX-1 is a virulent DNA phage whose hosts include strains of Myxococcus xanthus, M. fulvus and M. virescens. DNA was extracted from purified phage preparations. The molecular weight of phage DNA was measured by sedimentation-velocity and by rate-zonal ultracentrifugation. The apparent molecular weight was found to vary for reasons discussed in the text. From rate-zonal ultracentrifugation, using calibrated sucrose gradients, the molecular weight was calculated to be 149 (+/-22) X 10(6) daltons. The base composition of the DNA was estimated by different methods and was found to be 50-52% (G + C). The DNA demonstrated an anomalous thermal denaturation profile in dilute buffer. Denatured DNA was fractionated by ion-exchange chromatography and by buoyant-density centrifugation. No significant strand separation was obained and it was concluded that overall base compositions of the two strands are very similar. 2. DNA from bacteriophage MX-1 was hydrolysed with restriction endonucleases R. EcoRI, R.EcoRII and R. HindIII. The restriction fragments were catelogued and their apparent molecular weights calculated from electrophoresis gels calibrated with fragments from the DNA of coliphage lambda. From the total fragments obtained with nuclease R.EcoRI, the minimum apparent molecular weight of MX-1 DNA was found to be 130 X 10(6) daltons.

Bacteriophages↗
PubMed1976

Restriction in Myxococcus virescens.

1. The plating efficiency of bacteriophage MX-1 on Myxococcus xanthus strains A and B and M. virescens V2 were compared. Comparison of strains V2 and A suggest that V2 is restrictive and A is not (restriction coefficient was approximately 8). A derivative of M. virescens V2 (strain V2-9) was obtained by repeated exposure of strain V2 to ultraviolet radiation. Strain V2-9 was also unrestrictive. Strain B is apparently unrestrictive too but analysis of phenotypic changes in phage derived from hosts V2, B and A suggested that some of the host-cell processes differ from orthodox restriction and modification. 2. Cell-free extracts from M. virescens V2 were fractionated by ion-exchange chromatography and two restriction endonucleases, R. MviV2I and R. MviV2II were identified. Nuclease I was found to hydrolyse coliphage lambdaDNA at apparently one site only and MX-1 DNA at approximatley 10 sites; nuclease II was found to hydrolyse MX-1 DNA at a very large number of sites and its restriction sequence was of comparable frequency with that of R. EcoRII. "Modified MX-1 DNA", obtained from phage whose last host was M. virescens V2 was hydrolysed by nuclease II but not by nuclease I. The significance of these findings for restriction in myxococci is discussed.

Bacteriophages↗
PubMed1976

Phage and defective phage of strains of Myxococcus.

1. Phage-like particles were found in the supernatants of cultures of strains of Myxococcus xanthus, M. virescens and M. fulvus. The largest number of such particles was associated with M. virescens V2. Most of the particles were similar in morphology to the virulent Myxococcus phage, MX-1. 2. Several new phages were isolated from soil and animal droppings. A new phage was isolated from cultures of M. virescens V2. All resembled phage MX-1 in morphology and were related to phage MX-1 serologically. One of these phage, om, was characterized by fractionation of its proteins by SDS-polyacrylamide gel electrophoresis and by analysis of restriction fragments of its DNA. The very close relatedness with MX-1 was confirmed by these techniques. Phage om, was found to exist in a state of pseudolysogeny with strains of M. virescens and M. fulvus. 3. Two types of bacteriocin-like activity were found associated with Myxococcus strains. In one case, the activity was extracted from chloroformkilled or from sonicated cells. In the second case it was associated with extracellular material. Strains of Salmonella and Cytophaga were found to be good indicators for this latter activity. These strains were found to be killed by phage MX-1. 4. The significance of these data for origin of the phages of myxococci are discussed and it is proposed that MX-1 and the newly isolated phages may be virulent mutants of a family of lysogenic phages.

Bacteriocins↗
PubMed1976

Reliability of chemical tests for fecal occult blood in hospitalized patients.

In 39 hospitalized patients with suspected gastrointestinal bleeding and given intravenous 51Cr-labeled red cells, reactions of three chemical spot tests for fecal occult blood were compared with the "true" blood loss as determined by stool radioassay. Guaiac reagent and orthotolidine (Hematest) tablets were extremely sensitive, but yielded false-positive reaction rates of 72% and 76%, respectively on the 240 stool specimens compared. A modified guaiac test (Hemoccult) exhibited a false positive rate of 12%. Of the 27 patients entering the study due to positive guaiac or Hematest screening tests, 17 (63%) were not bleeding. Hemoccult, approximately 1/4 as sensitive as guaiac and Hematest, could miss lesions with low rates of bleeding unless multiple stools were tested. While barium had no effect, iron therapy or laxatives tended to lower both false-positive and false-negative reactions for all reagents. A positive Hemoccult test usually indicated significant gastrointestinal bleeding and would appear to be the test of choice provided at least 3 stools are tested to minimize false-negative results.

Barium Sulfate↗
PubMed1976

The effect of oral and intravenous metoclopramide on human lower esophageal sphincter pressure.

Lower esophageal sphincter (LES) pressure was evaluated in response to oral or intravenous metoclopramide in normal subjects and in patients with symptomatic gastroesophageal reflux. Both the oral and intravenous administration of metoclopramide gave a dose-related increase in LES pressure. Complete dose-response curves to the oral compound showed greater absolute responsiveness in normals as compared to patients with LES incompetence. The generally accepted oral dose of 10.0 mg of metoclopramide gave a slight increase in LES pressure which was not consistent in all symptomatic patients. These studies suggest that higher doses of metoclopramide may be required for treating symptomatic gastroesophageal reflux secondary to LES incompetence.

Administration, Oral↗
PubMed1975

Prospective, randomized study of diagnosis and outcome in acute upper-gastrointestinal bleeding: endoscopy versus conventional radiography.

Sixty patients with mild to moderate upper-gastrointestinal bleeding were admitted to a prospective, controlled study of diagnosis and management, and were randomized to endoscopy or upper-gastrointestinal (UGI) barium series as the initial study. Definitive localization of the source of bleeding was made initially in 69% of the endoscopy group and 21% of the UGI group (P less than 0.0005). Of 54 patients undergoing both studies, endoscopy was definitive in 67% and UGI series in 22%. Thus, endoscopy also made more diagnoses when used as the second study (P less than .01). The use of endoscopy as the initial procedure led to significantly more rapid diagnosis than with UGI series. However, there were no significant differences between the two groups in clinical outcome. Endoscopy is the initial diagnostic procedure of choice in patients with mild to moderate upper-gastrointestinal bleeding because it enables detection of superficial bleeding lesions and has significantly increased the speed of diagnosis.

Acute Disease↗
PubMed1965

Role of aminoacyl-transfer ribonucleic acid in the regulation of ribonucleic acid synthesis in Escherichia coli.

Morris, D. W. (University of California, San Diego), and J. A. DeMoss. Role of aminoacyl-transfer ribonucleic acid in the regulation of ribonucleic acid synthesis in Escherichia coli. J. Bacteriol. 90:1624-1631. 1965.-A leucine auxotroph of Escherichia coli was examined for its rate of ribonucleic acid (RNA) synthesis and the level of charged leucine-, arginine-, and valine-specific transfer RNA (tRNA) during the exponential growth period and when growth was limited by leucine starvation. During the logarithmic growth period, the leucine-specific tRNA was 70% charged, arginine-specific tRNA was 30% charged, and the valine-specific tRNA was 80% charged. When leucine became limiting, RNA synthesis was inhibited and the levels of charged arginine- and valine-specific tRNA remained constant, whereas the level of charged leucine-specific tRNA dropped to 40%. Examination of the leucyl-tRNA during the leucine starvation period showed that this 40% level is maintained by protein turnover. Addition of chloramphenicol or puromycin to a leucine-starved culture derepressed RNA synthesis. In the presence of chloramphenicol, the leucine-specific tRNA was fully charged; however, in the presence of puromycin the amount of charged leucine-specific tRNA remained at the starved level. Therefore, during leucine starvation the level of uncharged leucine-specific tRNA is not invariably correlated with the rate of RNA synthesis. We propose that it is the availability of charged tRNA and not the amount of uncharged tRNA which is the important factor in the amino acid control of RNA synthesis.

Chloramphenicol↗
PubMedDate not supplied

Female hypoactive sexual disorder: case studies of physiologic androgen replacement.

Menopause, surgical or naturally occurring, with reduced or deficient ovarian functioning has a major impact on morbidity and mortality in mid- to late life. A growing body of literature notes the role of androgens in maintaining women's health and emotional well-being. The administration of physiologic levels of testosterone replacement therapy as an adjunct to estrogen replacement requires further investigation. The Sexual Energy Scale was used to measure the patient's subjective experience of vitality or sexual energy with androgen replacement therapy. Three cases of women who had undergone a total abdominal hysterectomy with bilateral oophorectomy with complaints consistent with female hypoactive sexual desire disorder and free testosterone levels of < 2.0 pg/ml are presented. Physiologic androgen replacement is helpful in increasing sexual desire for some women.

Adult↗