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Biomedical subjects

N Lee

Publications and source records attributed to N Lee.

At least 325 records · Page 18Linked to original sources
PubMed1974

Direction of transcription of the regulatory gene araC in Escherichia coli B-r.

The protein product of the regulatory gene araC can be synthesized in a cell-free, protein-synthesizing system programmed with a lambdaparaC(+)B DNA template. Hybrid, renatured phage DNA molecules prepared with DNA from phages lambdaparaC(+)B and lambdaparaC3B (araC3 is a nonsense mutation) were used to program the cell-free synthesis of the araC protein. The findings observed lead to the conclusion that the codogenic strand of the araC gene is on the light strand of the phage DNA. The araB gene is on the heavy strand, as determined by DNA.RNA hybridization. Thus, with regard to the standard E. coli map, araC is transcribed in a clockwise direction, whereas transcription of the araBAD operon has a counterclockwise orientation. The technique described should allow one to determine the direction of transcription of any gene that can be incorporated into the genome of a specialized transducing phage.

Arabinose↗
PubMed1974

Metabolism of D-arabinose by Escherichia coli B-r.

The pathway for d-arabinose metabolism in Escherichia coli B/r has been determined. Evidence is presented to support the following metabolic scheme: d-arabinose d-ribulose right harpoon-up d-ribulose-5-phosphate d-xylulose-5-phosphate.

Aldehyde-Lyases↗
PubMed1965

Positive control of enzyme synthesis by gene C in the L-arabinose system.

Englesberg, Ellis (University of Pittsburgh, Pittsburgh, Pa.), Joseph Irr, Joseph Power, and Nancy Lee. Positive control of enzyme synthesis by gene C in the l-arabinose system. J. Bacteriol 90:946-957. 1965.-The l-arabinose gene complex consists of genes D, A, B, and C, linked in that order between the markers thr and leu, and an unlinked gene E. Genes D, A, B, and E are the structural genes for three inducible enzymes and permease, respectively. Gene C, with two mutant alleles, C(-) and C(c), is the regulatory gene exhibiting positive and negative control. C(-) mutants are deficient and C(c) mutants are constitutive for all three enzymes and permease. Complementation analysis, employing sexual merozygotes (A(-)C(+) x A(+)C(-)), with six different C(-) mutants, demonstrates that C(-) is recessive to C(+) (positive control). A total of 61 C(c) mutants, isolated as clones resistant to d-fucose inhibition, are linked to the leu ara region of the chromosome, and the 22 C(c) mutants that were analyzed in detail mapped within the C gene among the C(-) mutant sites. C(c) mutants produce various but coordinate levels of the two enzymes measured, and permease. Complementation analysis (A(-)C(c) x A(+)C(-), A(-)C(c) x A(+)C(+)) shows that C(c) is dominant to C(-) (positive control) and recessive to C(+) (negative control). Deletion mutants that extend into the C gene are l-arabinose permease-negative, thus supporting the positive regulatory role of the C gene. The name "activator gene" is proposed for genes of the C type to accentuate their positive role in gene expression. A working model consistent with these results is presented.

Arabinose↗
PubMedDate not supplied

Clinical decision-making and mammography referral.

BACKGROUND: Physician characteristics, practice/structural factors, and patient characteristics have all been found to influence mammography referral. The relationship of a patient's advanced age and comorbidity to the physician's decision has not received much attention. METHODS: Community-based, primary care physicians (n = 132) in two medium-sized U.S. cities completed questionnaires. RESULTS: Physicians report that they refer nearly all (89%) of the women ages 50-64 in their practice, slightly fewer of those 65-74 (83%), but many fewer (57%) of those 80 and over. Foreign medical graduates and physicians who are not board certified reported lower referral rates, and those who were residency trained reported substantially lower rates for the oldest patient group. Common reasons for not referring included assuming a gynecologist or another physician will make the referral, patient cost, comorbidity, and type of encounter, i.e., whether the patient is being seen for an acute condition. However, the lowest rate of referral was associated with believing that the patient was too old to benefit from early detection. CONCLUSIONS: Results are discussed in terms of the debate about whether guidelines should be based on patient age or functional status and the need to openly discuss and evaluate the decision rules being used.

Adult↗
PubMedDate not supplied

Patterns of internal echoes in lymph nodes in the diagnosis of lung cancer metastasis.

In 1989-90, all 37 lung cancer patients scheduled for surgery underwent transesophageal endoscopic ultrasonography (EUS) for pre-operative detection of hilar and mediastinal lymph node metastases. An electronic ultrasonic fiberscope with a linear array (EPB-503-FS, Machida-Toshiba) was used. Of 380 nodes surgically removed and that could have been detected by EUS, the detection rates for histologically metastatic and non-metastatic nodes were 65% (33 of 51) and 44% (144 of 329), respectively (p less than 0.01). Metastatic nodes were detected readily in every lymph node site, especially subaortic and subcarinal. Non-metastatic nodes were detected at low rates, especially in the superior mediastinum, paratracheal, and tracheobronchial locations. For greater long or short axes of the detected nodes, or for rounder nodes, the metastasis rate was higher. Detected nodes were classified into six types by their internal echo patterns; three were rarely metastatic (called "negative") and the other three were often metastatic (called "positive"). Of the "negative" nodes histologically proved to be metastatic, metastasis was often diffuse. The "positive" nodes found to be metastatic tended to have one of two patterns of internal echoes when invasion was diffuse and a third pattern when it was localized. In an examination of the diagnostic usefulness of EUS, we made more correct diagnoses from the internal echo pattern than by reference to either the long or short axis alone. The short axes, node shape, and internal echoes were examined by Hayashi's second method of quantification. The sensitivity, specificity, and accuracy of the diagnoses were 85%, 84%, and 84%, respectively, superior to those by computed tomography done of the same patients.

Adenocarcinoma↗
PubMedDate not supplied

MR imaging of orbital mass lesions with contrast agent: a preliminary report.

To investigate the advantage and limit of contrast enhancement in the examination of orbital mass lesions, precontrast T1- and T2-weighted, and postcontrast T1-weighted spin-echo images were retrospectively compared by two experienced observers. Using contrast material, intraocular tumors were well detected and characterized, and several orbital tumors were characterized as to whether cystic or necrotic and intracranial involvement was better evaluated. On the other hand, tumor-fat interface lost conspicuity when tumors showed enhancement. We conclude that gadopentetate-dimeglumine-administered T1-weighted images were helpful in detecting, differentiating and characterizing tumors of the orbit. However, the loss of contrast with fatty tissue is a disadvantage to be considered.

Contrast Media↗
PubMedDate not supplied

Peripheral findings in MR using surface coil.

Incidental peripheral lesions found during neuroradiological MR examinations with surface coils are reviewed. These include intracranial metastases during orbital examinations, cerebellar and thyroid lesions during cervical spine examinations, and dissecting and saccular abdominal aneurysms, as well as renal and intrapelvic abnormalities during lumbar spine examinations. Because of the reduced field-of-view and rapid signal drop-off in deeper portions of the body when examinations are performed with surface coils, peripheral and deep regions also need careful attention during routine evaluation.

Aged↗
PubMedDate not supplied

Design and SAR study of a novel class of nucleotide analogues as potent anti-HCMV agents.

We have developed a novel class of 2-phosphonate 1,3-dioxolane nucleotide analogues, from which the guanine derivative displayed weak anti-HCMV activity. Further SAR studies led to the identification of both cis and trans guanine derivatives of tetrahydrofuran analogues as potent anti-HCMV agents, both in vitro and in vivo, compared to ganciclovir and HPMPC.

Animals↗
PubMedDate not supplied

Comparison of transdermal and oral estrogen-progestin replacement therapy: effects on cardiovascular risk factors.

OBJECTIVE: To determine the effects of oral and transdermal hormone replacement therapy on lipid profile and hemostatic factors in postmenopausal women. DESIGN: Twenty subjects were treated with oral E2 valerate (2 mg) combined with cyproterone acetate (1 mg) (group I) and 21 with transdermal E2 (1.5 mg) plus oral medroxyprogesterone acetate (5 mg) (group II). The effects on lipid profile and hemostatic parameters were evaluated at baseline and after 3, 6, and 12 months of treatment. RESULTS: Group I showed a stronger increase of high-density lipoprotein (HDL) cholesterol levels (2-8%) and stronger reduction of atherogenic indices (total cholesterol/HDL cholesterol and low-density lipoprotein/HDL cholesterol) than group II. Group II showed a more pronounced reduction of triglyceride (21-31%) and factor VII (6-10%) levels than group I. Both groups showed reduced concentrations of total cholesterol, low-density lipoprotein cholesterol, tissue plasminogen activator, plasminogen activator inhibitor-1, antithrombin III, and protein S, whereas protein C was increased after 12 months of treatment. CONCLUSIONS: The cardioprotective effects of hormone replacement therapy are demonstrated by favorable effects on lipid profile and fibrinolytic activity. Oral hormone replacement therapy showed a more prominent effect on lipoprotein metabolism than did transdermal administration, but transdermal medication had a stronger effect on triglyceride and coagulation factors. However, it needs to be considered that there is an increased risk of venous thrombotic events in the first year of treatment.

Administration, Cutaneous↗