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Biomedical subjects

M Wong

Publications and source records attributed to M Wong.

At least 289 records · Page 16Linked to original sources
PubMed1987

Echocardiographic observations of calcium in operatively excised stenotic aortic valves.

Qualitative and quantitative 2-dimensional (2-D) echocardiographic methods were developed to define the anatomic and physiologic significance of valvular calcium in aortic stenosis (AS). Qualitative methods assigned etiologic diagnoses by matching patterns of calcium with anatomic criteria. Quantitative techniques measured echodensities from superimposed short-axis views of calcium. Fifty-five pathologic specimens procured from surgery were photographed and radiographed. Etiologic diagnoses were assigned from gross examination and radiodensities were planimetered. Echocardiographic and anatomic diagnoses were compared. Sensitivities for diagnosing the most common etiologies, congenitally bicuspid and degenerative, were 58% and 100% and specificities were 100% and 76%. Calcium tended to be heaviest in congenitally diseased valves and lightest in those with degenerative disease (p less than 0.2) and showed propensity for the right cusp in all etiologies except for those with degenerative disease. Correlation of echodensities to radiodensities was 0.82. The relation of calcific echodensities to orifice area was curvilinear; beyond a level of calcium, further deposits did not reduce the orifice more. A systematic echocardiographic examination of calcium in stenotic aortic valves can give a correct etiologic diagnosis in most patients and identify the severely narrowed orifice.

Adult↗
PubMed1987

Morphogenesis of the truncus arteriosus of the chick embryo heart: movements of autoradiographic tattoos during septation.

In order to trace tissue movements during septation of the embryonic truncus arteriosus into aortic and pulmonary cardiac outlets, the cephalic margin of the developing tubular heart of chick embryos was tattooed at Hamilton-Hamburger Stages 20-22 using diffusion micropipettes filled with 0.5% agarose and radioactive macromolecular precursors (tritiated thymidine, uridine, and leucine). Following further incubation for 2, 48, or 96 hours, the locations of such tattoos were determined by autoradiography of sectioned tissue and computer reconstruction of the developing outflow tract. Two hours after tattooing, radiolabeled cells were clustered at the right distal margin of the myocardial tube, as intended. Two days later, during septation of the outflow tract into the two arterial streams, label was concentrated along the posterior margin of the myocardium, between the developing aortic and pulmonary valve anlagen to the embryo's right and left, respectively. Four days following tattooing, as truncal septation neared completion, remaining label was found primarily to the left of the aortic valve ring posterior to the pulmonary outlet. The movements of thymidine tattoos during septation were demonstrated in a series of 31 embryos, 14 fixed at 2 hours, 12 at 2 days, and 5 at 4 days following tattooing; similar results were seen in uridine and leucine labeled hearts. The motion of such tattoos in the developing chick heart suggests that the left side of the definitive semilunar valve ring derives from the right distal margin of the primitive tubular heart and that normal morphogenesis of the great arterial streams involves both retraction and rotation of the embryonic truncus arteriosus.

Animals↗
PubMed1987

The 5'-proximal region of the wheat Cab-1 gene contains a 268-bp enhancer-like sequence for phytochrome response.

We have previously reported that the expression of the wheat Cab-1 gene is subject to phytochrome regulation and a 1.8-kb 5' upstream sequence of this gene is sufficient for the regulated expression. To delineate sequences for the phytochrome response we analyzed a series of 5' deletion mutants as well as chimeric gene constructs comprising different sequences of the Cab-1 upstream region in transgenic tobacco seedlings. We found that a deletion mutant containing a 357-bp 5' upstream sequence still exhibits maximal levels of phytochrome-regulated expression. A 268-bp enhancer-like element, located between -89 and -357, is responsible for the phytochrome response of the Cab-1 gene; sequences upstream from -357 to -843 and downstream from -124 to +1100 are probably not involved. Finally, we show that the Cab-1 mRNA stability is not regulated by phytochrome.

Base Sequence↗
PubMed1987

Orthostatic hypotension due to hypertrophic cardiomyopathy and autonomic failure.

A case of orthostatic hypotension due to the combination of hypertrophic obstructive cardiomyopathy and autonomic failure is described. The interacting pathophysiologic features of the two disorders and response to therapy are discussed. The value of dynamic cardiac auscultation and Doppler echocardiography in patients with postural blood pressure changes is demonstrated.

Aged↗
PubMed1987

The relative biological effectiveness of 670 MeV/A neon as a function of depth in water for a tissue model.

Linear energy transfer (LET infinity) spectra of identified charge fragments and primaries, produced by nuclear interactions of 670 MeV/A neon in water, were measured along the unmodulated Bragg curve of the neon beam. The relative biological effectiveness (RBE) values for spermatogonial cell killing, as reported on the basis of weight loss assay of mouse testes irradiated with beams of approximately constant single LET infinity, were summed over the particle LET infinity spectra to obtain an effective RBE for each charged-particle species, as a function of water absorber thickness. The resultant values of effective RBE were combined to obtain an effective RBE for the mixed radiation field. The RBE calculated in this way was compared with experimental RBEs obtained for spermatogonial cell killing in the mixed radiation field produced by neon ions traversing a thick water absorber. Discrepancies of 10-40% were observed between the calculated RBE and the RBE measured in the mixed radiation field. Part of this discrepancy can be attributed to undetected low-Z fragments, whose contribution is not included in the calculation, leading to an overestimated value for the calculated RBE. On the other hand, calculated values 10% greater than the measured RBE are explained as track structure effects due to the higher radial ionization density near neon tracks relative to the ionization density near the silicon tracks used to fit the RBE vs LET infinity data.

Animals↗
PubMed1986

Recovery of hormonal regulation in protein kinase defective adrenal cells through DNA-mediated gene transfer.

A cAMP-resistant mutant (Kin-8) isolated from Y1 mouse adrenocortical tumor cells harbors a specific lesion in the regulatory subunit of the type 1 cAMP-dependent protein kinase. This mutant also is resistant to the effects of corticotropin and cAMP on steroidogenesis, growth and morphology, suggesting an obligatory role for the protein kinase in regulation of adrenocortical functions. In this study, the cAMP-resistant phenotype of the Kin-8 mutant was reverted by transformation with DNA from cAMP-responsive Y1 cells, and the biochemical basis of the transformation was explored. Initially, Y1 mouse adrenocortical tumor cells were evaluated for their competence as recipients in DNA-mediated transformation experiments, by measuring their ability to incorporate and express a bacterial gene (neo) encoding resistance to neomycin. Y1 cells were transfected with the plasmid pSV2-neo (an SV40-neo hybrid vector designed for expression in animal cells) and screened for resistance to the neomycin analog, G418. Neomycin-resistant transformants were recovered from Y1 cells at a frequency of approximately one per 10(3) cells per 10 micrograms of DNA, and had specific neo sequences integrated into their high molecular weight (mw) DNA. The Y1 mutant, Kin-8, then was transformed with pSV2-neo DNA plus high mw DNA prepared from cAMP-responsive Y1 cells. Cells competent for transformation were recovered by selective growth in the neomycin analog G418, and these transformants were screened for recovery of morphological responses to cAMP. Several colonies capable of rounding up in the presence of cAMP were recovered after transformation with DNA from Y1 cells. These transformants also recovered the ability to round up in the presence of corticotropin, and were able to respond to both corticotropin and cAMP with increased steroidogenesis. Transformants generated from either Y1 or Kin-8 cells were unstable. Y1 cells lost resistance to neomycin when grown in the absence of G418 at a frequency of 4% per generation. Similarly, Kin-8 transformants lost their sensitivity to cAMP in subsequent culture passages. In some of the cAMP-responsive transformants, cAMP-dependent protein kinase activity was recovered and approached the activity seen in cAMP-responsive Y1 cells. The recovery of a normal protein kinase by transformation appeared to have been sufficient to reverse the cAMP-resistant phenotype of Kin-8 cells. In other cAMP-responsive transformants, protein kinase activity was not appreciably affected by cAMP.(ABSTRACT TRUNCATED AT 400 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

Coping with dental treatment: the potential impact of situational demands.

Coping strategies and anxiety responding of dental patients were studied in order to test the generalizability of previous findings based on volunteer blood donors. State and trait coping measures were administered once, and a process coping scale was administered at three points throughout treatment. Self-report, behavioral observation, and psychophysiological measures of anxiety were sampled for the same periods as process coping. Findings included the replication of a negative relationship between avoidant coping and patient anxiety ratings. Fluctuations in coping were evident across periods, and impact of situational demands and constraints was introduced as an explanation for these variations. A method for direct assessment of coping consistency was introduced. On the basis of the replicable associations with anxiety measures, the ability to detect changes in coping within a situation, and the ability to provide direct evidence of coping consistency, the use of process methodology for coping assessment is encouraged.

Adaptation, Psychological↗
PubMed1986

Simplified echocardiographic measurement of the mitral anulus.

Postmortem, clinical, and experimental observations suggest an approximate elliptical shape for the mitral valve anulus, limiting the accuracy of single-diameter measurements in estimating annular area and circumference. A detailed method has been reported which uses six apical echocardiographic views at 30-degree rotational intervals to measure the mitral anulus, providing results comparable with pathologic and experimental reports. Annular data from nine normal subjects and 18 patients with dilated cardiomyopathy were analyzed to test a simplified measurement procedure. Assuming an elliptical shape, mitral annular area (MAA) and mitral annular circumference (MAC) were calculated by means of major (usually corresponding to the four-chamber view) and minor diameters from two orthogonal apical planes. Assuming a circular shape, MAA and MAC were also estimated by means of single annular diameters obtained from both an apical four-chamber and a parasternal long-axis view. Systolic and diastolic points were analyzed together, providing an n = 54 in the linear regressions. The two-plane results in MAA and MAC were nearly identical to those from the six-plane method, with very close correlation (r = 0.982 to 0.990). The single-plane results systematically overestimated MAA and MAC, with less correlation (apical, r = 0.943 to 0.963; parasternal, r = 0.852). Thus, while single-diameter measurements may correlate with global changes in annular size, the two-plane method represents a simplified but accurate method for estimating MAA and MAC in humans.

Echocardiography↗
PubMed1986

The roles of cAMP and cAMP-dependent protein kinase in the regulation of adrenocortical functions: analysis using DNA-mediated gene transfer.

DNA-mediated gene transfer was used to evaluate the cause and effect relationship between mutations in cAMP-dependent protein kinase activity and cellular resistance of adrenocortical tumor cells to ACTH and cAMP. Protein kinase defective, Kin 8 adrenocortical tumor cells were transformed with genomic DNA from an ACTH- and cAMP-responsive adrenocortical cell line and screened for the recovery of morphological responses to the cAMP analog 8-bromo-cAMP (8BrcAMP). 8BrcAMP-responsive transformants were recovered with a frequency of approximately 0.5 per 10(3) transformation-competent cells. These transformants recovered the ability to round up in the presence of ACTH and were able to respond to both ACTH and 8BrcAMP with increased steroidogenesis. They also recovered cAMP-dependent protein kinase activity. The transformants, however, were unstable and concomitantly lost cAMP-dependent protein kinase activity and steroidogenic and morphological responses to ACTH and 8BrcAMP. These observations suggest that a single gene, probably the gene encoding the regulatory subunit of cAMP-dependent protein kinase, is responsible for the resistance of the Kin 8 mutant to ACTH and cAMP.

Adrenal Cortex Neoplasms↗
PubMed1986

Direct, neuronal action of atrial natriuretic factor in the rat brain.

The present investigation assessed the ability of atrial natriuretic factor (ANF) to affect hypothalamic neuronal excitability. Single neurons in the rostral septal-preoptic area of the female rat brain were recorded extracellularly and tested for responsiveness to iontophoretically applied and/or pressure-ejected ANF. Neurons responsive to ANF were detected in the lateral septal nucleus, the lateral paraolfactory area, the bed nucleus of the anterior commissure, and the medial preoptic area. The majority of neurons influenced by ANF (16 out of 18) exhibited a decrease in spontaneous firing rate during application of the peptide. In some cases, the inhibitory response outlasted the period of ANF application. When both iontophoretic and pressure ejection techniques were used to apply ANF to an individual neuron, the responses were similar. The results indicate that ANF is capable of modulating the membrane excitability of rat forebrain neurons and suggest that the peptide acts as a neuromodulator/neurotransmitter within the central nervous system.

Action Potentials↗
PubMed1986

Molecular analysis of 21-hydroxylase gene expression in mouse adrenal cells.

Two homologs of the gene encoding the adrenocortical 21-hydroxylase (21-OHase) are located within the S region of the mouse major histocompatibility complex. Only one of these homologs, however, encoded the full-length sequence of 21-OHase, directed the synthesis of 21-OHase RNA in the mouse adrenal gland, and was capable of restoring 21-OHase activity when transfected into 21-OHase-deficient Y1 adrenocortical tumor cells. Y1 cells transfected with the 21-OHase gene, when stimulated with ACTH, increased the number of 21-OHase transcripts up to 10-fold. The 21-OHase gene was not expressed when transfected into mouse fibroblast L cells, and was poorly expressed and poorly regulated by ACTH when transfected into a Y1 mutant harboring a defective cAMP-dependent protein kinase. Marked decreases in expression of the 21-OHase gene were noted when DNA constructs that contained fewer than 230 base pairs in the 5' flanking region of the gene were transfected into Y1 cells. These results indicate that the 21-OHase gene encodes information required for the tissue-specific expression and hormonal regulation of 21-OHase. The cAMP-dependent protein kinase is important for both aspects of gene expression. At most, 230 base pairs of 5' non-coding information are required for efficient expression of the 21-OHase gene in Y1 cells.

Adrenal Cortex↗
PubMed1986

Doppler ultrasound examination of prosthetic function and ventricular blood flow after mitral valve replacement.

Two-dimensional color Doppler echocardiography enables delineation of the spatial and temporal distribution of blood flow in the heart. In this study, the method was applied for investigation of flow dynamics in multiple planes in the region of prosthetic mitral valves for comparison with that of native mitral valves. In 15 healthy subjects there was normal flow toward the transducer, coded in red, in the left ventricle along the posterolateral wall (left ventricular inflow region) and blue-coded flow away from the transducer in the left ventricular outflow region during diastole. In 40 patients with St. Jude mitral valve prosthesis and 17 with bioprosthesis the flow pattern in the left ventricle was reversed. Mitral inflow was directed against the interventricular septum, accordingly, into the left ventricular outflow region while the outflow pattern was displaced posterolaterally into the left ventricular inflow region during diastole. The angle between the aortic valve ring and the mitral annulus was significantly smaller than in the healthy subjects. The angle between the central axis of the mitral prosthesis and the mitral inflow, which was 0 degrees in healthy subjects, was increased by the medial deviation in particular, in those with mechanical St. Jude prostheses. The maximal transprosthetic velocity, measured in 70 patients, and the maximal pressure gradient calculated according to the Bernoulli equation was substantially greater than the values in healthy subjects. In contrast to findings associated with normally-functioning prostheses, in four patients with prosthetic malfunction there was a diastolic peak velocity of more than 2 m/s as well as marked turbulence in the inflow region.

Bioprosthesis↗
PubMed1985

In vitro study of the pressure-velocity relation across stenotic orifices.

In a hand-driven, pulsatile in vitro model, the pressure-velocity relation across stenotic orifices was studied from simultaneous measurements recorded over a wide range of pressure and across different-sized orifices, individually and paired. Velocity spectra were recorded with continuous-wave Doppler ultrasound. In a rigid, noncompliant system, integrated instantaneous maximal velocities precisely register simultaneous integrated pressure gradients without measureable phase shift. Across stenotic orifices of 5 to 10 mm in diameter, the pressure-velocity relation is independent of orifice size for pressures extending from -30 to +240 mm Hg. The relation is quadratic and crosses 0. In this model, application of the simplified Bernoulli equation transforms the relation from curvilinear to linear with a bias toward the derived-pressure axis. In the presence of 2 different-sized orifices, the pressure-velocity relation remains constant, with a given pressure producing 2 identical velocities.

Animals↗
PubMed1985

Reproducibility of stand-alone continuous-wave Doppler recordings of aortic flow velocity across bioprosthetic valves.

Continuous-wave Doppler spectra of aortic flow velocity were recorded in duplicate in 20 consecutive patients with aortic porcine valves by 1 technician and 3 occasions: initially and 1 week and 1 month later. The highest maximal aortic velocity recorded from at least 2 transducer locations was taken from 5 consecutive beats that did not vary. The 120 tracings were coded and read by 1 observer. In blinded fashion, 20 records were read twice and 26 were read by 2 interpreters. Variability was calculated from the square root of pooled variances and expressed in meters per second and also related to the mean velocity and expressed as percent coefficient of variation for the following categories: interpretive [intraobserver +/- 0.019 (0.8%), interobserver +/- 0.071 (2.7%)], technical [duplication +/- 0.048 (1.9%)], temporal/biologic [+/- 0.125 (5.0%)]. Doppler measurements of aortic velocity can achieve excellent reproducibility by maintaining constant technique. With a methodologic variability of +/- 2%, the variability associated with the passage of time was significantly different at +/- 5% and was a result of fluctuations in the physiology of a few subjects. Thus, the technique can distinguish small method errors from minor drifts of the biology and, by implication, detect the onset of bioprosthetic degeneration.

Aged↗
PubMed1985

Insulin binding by normal and neoplastic colon tissue.

Insulin receptors in human colon tumours, normal colon tissue and mesenteric fat removed at surgery have been identified by measuring the binding of labelled insulin to cell membrane preparations. Insulin binding sites were readily detected in all tissues, with mean +/- SD binding site concentrations of 43 +/- 41, 44 +/- 39, and 44 +/- 35fmol/mg membrane protein, and dissociation constants of 0.73 +/- 0.61, 0.66 +/- 0.41, and 0.78 +/- 0.58nM for microsomal plasma membrane preparations of tumour (n = 23) respectively. The specificity of binding of labelled insulin was similar in tumour and normal colon samples. Binding in normal colon preparations was highest in the epithelium (84fmol/mg membrane protein) and lower in lamina propria (19fmol/mg), submucosa (25fmol/mg) and muscle wall (13fmol/mg). Degradation of labelled insulin was similar in tumour and normal colon preparations. Mean receptor levels were not significantly different between microsomal membrane preparations and plasma membranes partially purified on discontinuous sucrose gradients, quantitated against either unit membrane protein or unit 5'-nucleotidase specific activity. There was a significant negative correlation between insulin levels, but no significant relationship was seen between serum insulin and receptor levels in either colon tumour or tissue preparations from full-thickness normal colon wall. An inverse correlation between serum insulin and receptor levels was, however, apparent in preparations of colonic musosa. These data indicate that although insulin receptors in colon tumours share the same biochemical characteristics as those present in the normal colon, receptors in tumour tissue are less sensitive to down-regulation by ambient insulin than receptors in mesenteric fat cells and normal colonic mucosa.

Adipose Tissue↗