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Biomedical subjects

J L Davis

Publications and source records attributed to J L Davis.

At least 145 records · Page 8Linked to original sources
PubMed1987

Visna virus exhibits a complex transcriptional pattern: one aspect of gene expression shared with the acquired immunodeficiency syndrome retrovirus.

A complex pattern of gene expression was found for visna virus in a highly permissive cell culture system in vitro. In addition to the genomic RNA (9.4 kilobases [kb]), five other mRNAs were detected. The three large RNA transcripts (5.0 kb and a doublet at 4.3 kb) arise by a single splicing event joining 5' sequences to sequences located at positions 3' to the pol gene. The two smallest transcripts (1.8 and 1.5 kb) are at least doubly spliced mRNAs which contain sequences derived from the 5' end of the genome, the region between the pol and env genes, and 3' terminal sequences. In addition to this complex pattern of transcription, the mRNAs appear to be regulated temporally. The 1.5-kb mRNA appears 6 h later than the other transcripts. The significance of this complex pattern of gene expression in the unique aspects of the lentivirus life cycle and pathogenesis is considered.

Endonucleases↗
PubMed1987

46,XX male. A case report.

The 46,XX male is rare, with an incidence of 1 in over 9,000 newborn males. The diagnosis is most often made in the postpubertal period. A case of a 46,XX male was diagnosed in the neonatal period and further confirmed by the results obtained from amniocentesis performed earlier, in the second trimester.

Adult↗
PubMed1987

Atypical squamous cells in Papanicolaou smears.

Between 1980 and 1984, 406 patients were referred to Tripler Army Medical Center's cervical clinic for the evaluation of atypical squamous cells in a Papanicolaou smear. Their evaluation included repeating the smear, colposcopy in all cases, colposcopically directed biopsies, and/or endocervical curettage in 70%. The results of the repeat Papanicolaou smear in 400 patients were 274 (68.5%) negative, 77 (19%) atypical squamous cells, 40 (10%) cervical intraepithelial neoplasia (CIN) 1, seven (2%) CIN 2, and two (0.5%) CIN 3. No invasive cancer was detected. Dysplasia was documented histopathologically in 18.7%, but a repeat smear was reported as negative in 10.9% of patients with biopsy-proven dysplasia. A Papanicolaou smear report of atypical squamous cells should not be considered normal, and further evaluation of the patient is required. If colposcopy is impractical, serial follow-up smears are recommended.

Biopsy↗
PubMed1986

QRS voltage measurements in autopsied men free of cardiopulmonary disease: a basis for evaluating total QRS voltage as an index of left ventricular hypertrophy.

Use of total 12-lead QRS electrocardiographic voltage as a criterion for left ventricular (LV) hypertrophy has been of recent interest. Although upper and lower limits of QRS voltage for individual electrocardiographic leads have been reported in clinically healthy men and women, the upper limit of total 12-lead QRS voltage has not been established in adults free of cardiopulmonary disease by clinical and necropsy criteria. Therefore, the total QRS voltage from all 12 electrocardiographic leads was determined in 30 autopsied men known to be free of cardiopulmonary disease by clinical assessment and by a special cardiac examination using postmortem coronary angiography and chamber partition determination of LV weight. Gross heart weight, LV weight and total QRS voltage are reported. Comparisons were made between disease-free patients and previously reported patients with aortic valve stenosis, aortic regurgitation and cardiac amyloidosis with respect to total QRS voltage and gross heart weight. Total QRS voltage and gross heart weight were significantly greater in patients with severe aortic stenosis (mean 245 mm) and severe aortic regurgitation (mean 274 mm) than in our patients (mean 127 mm). Total QRS voltage was significantly less, whereas gross heart weight was significantly greater in patients with cardiac amyloidosis (mean 101 mm) than in our normal subjects (mean 127 mm). These data provide a basis for evaluating the total 12-lead QRS voltage as a criterion for LV hypertrophy.

Adult↗
PubMed1986

Effects of reperfusion on myocardial wall thickness, oxidative phosphorylation, and Ca2+ metabolism following total and partial myocardial ischemia.

Coronary artery reperfusion following acute myocardial ischemia may salvage ischemic jeopardized cells. We studied the effects of early brief reperfusion on totally ischemic and on partially ischemic myocardium of open-chest pigs. In 10 animals, coronary flow was reduced to 0% for 30 minutes and was followed by 10 minutes reperfusion (group A). In another 10 animals, coronary flow was reduced to 25% of the baseline value for 30 minutes followed by 10 minutes of reperfusion (group B). In another eight animals coronary flow was reduced to 25% of the baseline value for 60 minutes and followed by 10 minutes of reperfusion (group C). Results showed that a brief 10-minute period of reperfusion of ischemic myocardium after total occlusion caused abnormal diastolic wall thickening with only partial return of systolic wall thickening. However, reperfusion of ischemic myocardium after partial occlusion, whether 30 or 60 minutes, caused little diastolic wall thickening and a partial return of systolic thickening. A marked elevation of myocardial Ca2+, a decrease in mitochondrial adenosine triphosphate (ATP) production and cellular ATP concentration, and a reduction in the rate of Ca2+ uptake by sarcoplasmic reticulum vesicles occurred in the totally ischemic myocardium but not in the partially ischemic myocardium. These results demonstrate that reperfusion of ischemic myocardium after 1 hour of coronary flow reduction to 25% of baseline is less damaging than reperfusion after a 30-minute total coronary occlusion, and suggest that preexisting states affecting coronary flow need to be evaluated in assessing the outcome of reperfusion.

Animals↗
PubMed1985

Retinal pigment epithelial cells release an inhibitor of neovascularization.

Human retinal pigment epithelial cells in culture were found to release a substance (or substances) that causes the regression of new blood vessels on the chick embryonic yolk sac and inhibits proliferation of fetal bovine aortic endothelial cells in vitro. Neither astrocytes nor fibroblasts, under identical test conditions, released detectable inhibitors of neovascularization or endothelial cell growth. Subconfluent and superconfluent cultures of human retinal pigment epithelial cells released higher levels of inhibitor than confluent cultures.

Angiogenesis Inhibitors↗
PubMed1985

High proline levels in the brains of mice as related to specific learning deficits.

Hyperprolinemic PRO/Re mice have been studied as potential models for hyperprolinemia in man. In addition to high proline levels, some heretofore unreported amino acid abnormalities in the brains of PRO/Re mice are described. The T-maze and shuttlebox learning abilities of PRO/Re mice were compared with those of CD-1 mice having normal proline levels. PRO/Re mice had a significant deficit for T-maze learning, but a significantly greater aptitude for shuttlebox learning when compared to CD-1 mice. By studying the F3 progency of the PRO/Re X CD-1 cross, these strain-specific differences in learning ability for different tasks were shown to be unrelated to the differences in brain proline levels. F3 mice could be subdivided into two distinct groups: those with high proline (HP+) and low proline (HP-) titers. Other amino acids in brain tissues were essentially identical in both groups. A comparison of learning abilities of these HP+ mice with their HP- littermates showed no meaningful differences. However, the slightly slower rate at which HP+ mice acquired shuttlebox learning was sufficiently consistent over the 8 day training period so that it became significant. These results do not support the hypothesis that high levels of proline in brain tissues and blood are necessarily accompanied by impaired learning and memory, but are in agreement with those studies of hyperprolinemia in man that suggest no consistent learning deficits in hyperprolinemic subjects. The results seem to validate the suitability of the PRO/Re mouse as a model for hyperprolinemia in man. The data suggest also that the altered amino acid pattern in brains of PRO/Re mice has multiple etiologies.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1985

Granulocytic sarcoma of the orbit. A clinicopathologic study.

A 9-year-old Latin American girl developed proptosis of the left eye associated with pain in the left ear of one month's duration. Ophthalmoscopic examination of the left eye disclosed retinal striae with venous tortuosity and papilledema. CT scan of the orbit showed a nonenhancing, irregular intraconal mass. CT scan of the brain demonstrated an enhancing left temporoparietal mass. Craniotomy revealed a 7 cm, extra-axial mass that was attached to the dura mater. Histologic examination, including a positive Leder stain, established the diagnosis of granulocytic sarcoma. At that time, the results of the laboratory studies, including complete cell blood count, were normal. Periodic clinical and hematologic evaluation was recommended. Twenty-five days after craniotomy, examination of the peripheral blood disclosed 56% myeloblasts and the bone marrow contained 30% blast cells. The problem in histologic differential diagnosis and a review of the literature is discussed.

Child↗
PubMed1985

Angiographic occurrence and clinical correlates of intraluminal coronary artery thrombus: role of unstable angina.

The importance of intraluminal coronary artery thrombus in acute myocardial infarction is now recognized. Coronary thrombi, however, may be important in ischemic syndromes other than infarction. The coronary angiograms of 268 consecutive patients undergoing diagnostic angiography were prospectively examined for intracoronary thrombus and form the basis of this study. Of these patients, 29 (11%) (25 men and 4 women) met the criteria for coronary artery thrombus. Of the 29 patients with thrombus, 24 (83%) had unstable angina before angiography. The five remaining patients with thrombus had had a transmural myocardial infarction 3 to 18 months before cardiac catheterization. In 21 patients, the thrombus was distal to a significant stenosis; in 8 it was proximal to or at the site of a significant stenosis. Coronary artery thrombus was identified in 24 (35%) of 67 patients with unstable angina compared with only 5 (2.5%) of 201 patients with stable angina (p less than 0.0001).

Angina Pectoris↗
PubMed1985

Use of computer memory chips as the basis for a digital albedo neutron dosimeter.

We have measured the sensitivity of commercially available dynamic random access memories (D-RAMs) to alpha particles. Using a beam of 14-meV neutrons and a 6LiF crystal as a converter we have measured sensitivities to neutron radiation as high as 9.25 memory errors per millirem. We estimate that an optimized converter would produce even higher sensitivities as an albedo dosimeter in realistic radiation fields. Such a device would have a number of operational advantages.

Alpha Particles↗
PubMed1985

Diaphanography in the diagnosis of breast cancer.

In diaphanography, a light source is applied to the breast to visualize lesions through a television camera sensitive to infrared light. Diaphanography and mammography were performed on 1,476 patients in a screening population. Twenty-six cancers in 24 patients were confirmed by biopsy; detection rates were 96% for mammography, 58% for diaphanography, and 62% for physical examination. Mammography was significantly more sensitive than either diaphanography or physical examination (p less than 0.005). Mammography detected 10 cancers that were missed at physical examination, whereas diaphanography detected five such lesions. It is concluded that diaphanography does not satisfy the criteria of a screening procedure, but because the examination is completely innocuous, it may serve as an adjunct to physical examination. In addition, the authors developed a breast model for diaphanography that appears to correlate with the human breast and demonstrates some of the physics and limitations of diaphanography.

Biopsy↗
PubMed1985

The effect of citrate and polyamines on human benign prostate in organ culture.

A technique for short-term cultivation of slices of human benign prostate tissue in an organ culture environment is described. Minimum essential medium utilized was supplemented with 10 percent fetal bovine serum and 25 mg/mL of citrate, spermine, and spermidine. Spermine in the presence of testosterone in the culture medium induced morphological changes, enhancing the morphology of the tissue. The epithelium was well preserved morphologically. Citrate or spermidine together with testosterone does not enhance any morphological change. After seven days of culture, necrosis was developed. The spent culture medium showed a pattern of prostatic acid phosphatase production. When treated with spermine, the maximum level was reached at four days, after which it decreased. With spermidine or citrate, the maximum level is reached at two days of culture. Tissue β-glucuronidase activity was enhanced by either spermidine, spermine, or citrate together with testosterone. The biochemical studies suggested that explants of human benign prostate can be well maintained in organ culture for a few days.

Citrates↗
PubMed1985

T cell chronic lymphocytic leukemia with lymphocytes of unusual immunologic phenotype and function.

This report discusses a case of T cell chronic lymphocytic leukemia (T-CLL) in an elderly white man whose lymphocytes expressed a post-thymic phenotype except for the coexpression of T4 and T8 on 80% to 95% of the cells. Because of the uncommon phenotype, in vitro functional assays were performed that showed decreased mitogenic responses but normal helper activity for B cell immunoglobulin secretion and normal suppressor activity of lectin-induced mitogenesis. Morphologic evaluation by both light and electron microscopy and cytochemical staining were consistent with the "knobby" type T-CLL. Adenosine deaminase and terminal deoxynucleotidyl transferase (TdT) levels were low, but the acetylcholinesterase level was normal, which is consistent with the peripheral T cell phenotype. The patient underwent splenectomy, and the spleen cells showed very low levels of T3 and T4 by immunoperoxidase and undetectable levels by immunofluorescence. The morphology of the splenic infiltrate was not significantly different from that in the initial bone marrow. Human T cell leukemia virus (HTLV) antigen and antibody tests were negative. The cells in this leukemia apparently are derived from a transitional stage of maturation between the cortical and medullary thymocyte. A small subset of lymphocytes of identical phenotype to this leukemia has been identified in normal individuals.

Antigens, Surface↗
PubMed1984

Water coordination by heme iron in metmyoglobin.

Using electron spin echo envelope spectroscopy, we have proven that the water close to heme in metmyoglobin is bound to the iron. For protein samples exchanged against D2O, we show that the electron nuclear coupling for 2H is 0.8 MHz. This coupling is considerably smaller in methemoglobin, pointing out a fundamental difference in bonding to water.

Animals↗
PubMed1984

The accessibility of type I Cu(II) centers in laccase, azurin, and stellacyanin to exchangeable hydrogen and ambient water.

The characteristic deuterium modulation pattern was observed in the electron spin-echo envelopes for laccase, decupro laccase (from which Type 2 copper had been removed), stellacyanin, and azurin that had been exchanged against D2O. From the decay rate of the modulation pattern and from a quantitative analysis of the modulation depth, we conclude that the Cu(II) sites in these proteins are directly accessible to solvent. Similar results were obtained for laccase and decupro laccase.

Azurin↗