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Biomedical subjects

R M Lang

Publications and source records attributed to R M Lang.

At least 145 records · Page 8Linked to original sources
PubMed1982

Pattern dystrophy of the retinal pigment epithelium.

The pattern dystrophies are a group of hereditary macular dystrophies characterized by lesions of the retinal pigment epithelium (RPE) arranged in various patterns of dots, lines, and branched figures. This report of two pedigrees expands the clinical spectrum. The onset is usually in the second and third decade, there is great variation in fundus appearance, vision may be severely affected, the EOG is not always abnormal, and the fundus lesions change with time. The lesions resemble those of Best's vitelliform degeneration and fundus flavimaculatus, and, possibly, also represent abnormal lipofuscin accumulation within degenerating retinal pigment epithelial cells.

Adolescent↗
PubMed1981

A new morphologic manifestation of Langerhans cells in guinea pig corneal transplants.

Langerhans cells are virtually never seen in the normal undisturbed corneal epithelium. They may be stimulated to migrate into the corneal epithelium by a variety of chemical and mechanical stimulation, including penetrating keratoplasty. We have found a previously undescribed morphologic manifestation of the Langerhans cell in guinea pig eyes undergoing corneal transplantation. These cells are found around the graft, and in high concentration around sutures. They may be a motile form of the typical Langerhans cell or a specialized form which captures or distributes antigen.

Animals↗
PubMed1981

Effects on the corneal endothelium of anterior chamber reconstituents instilled during intracapsular cataract extraction.

Intracapsular cataract extractions with a standardized technique were performed on a series of patients. The loss of corneal endothelial cells was found to vary predictably with the material instilled into the eye to reconstitute the anterior chamber. Reconstitution with Miochol was associated with minimal constant cell loss, while reconstitution with air resulted in greater cell loss in the early than in the late postoperative period. The additional instillation of phenylephrine enhanced the endothelial cell loss in both the early and late postoperative periods. In the ideal operation, attention should be paid not only to be amount of corneal manipulation but also to the material chosen to reconstitute the anterior chamber.

Acetylcholine↗
PubMed1981

Extraocular muscle recession with a suture loop in dogs.

Extraocular muscle recessions with loops of silk suture were performed in 10 dogs. When, after a 5-mm section of the medial rectus muscle was resected, suture loops 5 mm long were inserted near the functional equator (8 mm behind the muscle's original insertion) an effective pseudotendon was produced in 71% of the eyes. This procedure may be a useful addition to the surgical methods of correcting horizontal strabismus.

Animals↗
PubMed1980

Muscle recession with a suture loop in rabbits.

We recessed extraocular muscles in rabbits using loops of silk sutures. The effectiveness of the pseudotendons produced depended on their relation to the functional equator of the eye and on the length adherent to the sclera. Loops about 5 mm long inserted at or near the functional equator produced effective pseudotendons. If the loops were inserted in front of the functional equator they adhered to the sclera and the advantage of using them was negated.

Animals↗
PubMed1976

Nasopharyngeal cancer in Bermuda.

Six cases of nasopharyngeal carcinoma (NPC) were diagnosed in residents of Bermuda in the 7-year period 1966-1972. While epidemiologic study revealed no history of common environmental exposures, two of the six cases occurred in adult sibs from a family in which a third adult sib developed NPC in 1963. These three cases were from a large, possibly in-bred Portuguese family with origins in the Azores Islands. The remaining four cases were all in black children ages 10-15; two of these were first cousins. These observations suggest the possibility that genetic influence may contribute to the etiology of NPC.

Adolescent↗
PubMedDate not supplied

Improved quantification of left ventricular function by applying signal averaging to echocardiographic acoustic quantification.

The acoustic quantification technique for on-line detection of endocardial boundaries currently provides continuous left ventricular area or volume signals and beat-to-beat ejection fraction. However, the distortion of individual waveforms by noise results in a wide beat-to-beat variability in these parameters. We developed an automated algorithm for the evaluation of left ventricular function by averaging acoustic quantification signals. End-diastolic and end-systolic area, stroke area, and fractional area change are measured directly from the average waveform. Peak ejection and peak filling rates and time to peak filling rate are obtained from its time derivative. Area signals obtained from eight normal subjects were used to evaluate the performance of this algorithm. Parameters of left ventricular function obtained with the automated algorithm were highly consistent and in excellent agreement with those obtained by repeated manual operator-dependent selections. This algorithm provides a fast and easy method for noise reduction in acoustic quantification signals, which significantly improves the noninvasive assessment of left ventricular function.

Acoustics↗
PubMedDate not supplied

Doppler echocardiographic evaluation of severe rheumatic submitral valve stenosis.

The submitral apparatus may play a predominant role in rheumatic mitral stenosis and should be evaluated aggressively with Doppler echocardiography, especially in patients in whom percutaneous mitral balloon valvotomy is being considered. The following case presents a patient with rheumatic mitral valve stenosis in whom some noninvasive clues alerted us to the presence of predominant submitral stenosis.

Adult↗
PubMedDate not supplied

Double-chambered left ventricle: submitral accessory valvular tissue causing inlet and outlet obstruction.

We report a patient with a large submitral ridge of muscular and fibrous tissue that divides the left ventricle into two distinct chambers causing inlet and outlet obstruction. Doppler echocardiography revealed obstruction to both filling and ejection. Echocardiography demonstrated that the obstruction was in series with the mitral apparatus. Surgery was done with resection of much of this ring of tissue. Subsequent studies revealed morphologic and hemodynamic improvement.

Adult↗
PubMedDate not supplied

Pulsus paradoxus: a definition revisited.

Pulsus paradoxus is associated with many clinical conditions and is defined as a greater than 10 mm Hg end-inspiratory decrease in systolic blood pressure. Kussmaul's original definition of pulsus paradoxus is presented, along with an explanation of his choice of the term "pulsus paradoxus." A case of pulsus paradoxus is graphically described using simultaneous two-dimensional targeted M-mode, Doppler echocardiographic, and high-fidelity pressure recordings.

Blood Pressure↗
PubMedDate not supplied

Contrast echocardiographic quantification of regional myocardial perfusion: validation with an isolated rabbit heart model.

Quantification of regional myocardial tissue blood flow (RMBF) based on contrast echocardiography has yet to be achieved. This study validated our recently proposed algorithm for quantification of RMBF with colored microspheres. Experiments were carried out in an isolated rabbit heart preparation (n = 11). Aortic root injections of perfluoropropane-filled albumin microsphere solution (FS069) and colored microspheres were performed at five levels of coronary flow achieved by altering perfusion pressure. During each injection of contrast material, consecutive end-diastolic images of the heart and an extracardiac reference chamber were acquired with a 7.5 MHz transducer and digitized. Time-intensity curves from the reference chamber and myocardial regions of interest, corresponding to the anatomic segments used for colored microsphere analysis, were analyzed for RMBF. Blood flow was calculated as the intravascular volume fraction (ratio of areas under myocardial and reference curves) divided by mean transit time (deconvolution of impulse response) and compared with those obtained with colored microspheres. Injections of FS069 resulted in highly reproducible enhancement of myocardial contrast. Analysis of time-intensity curves provided consistent measurements of RMBF (r = 0.91), which correlated highly with microsphere data (r = 0.84). The use of this new algorithm allows accurate quantification of RMBF in the isolated heart model. Further validation of this approach in an animal model with peripheral intravenous injections of contrast material will allow noninvasive clinical measurements of RMBF.

Albumins↗
PubMedDate not supplied

Echocardiographic contrast agents and left ventricular contractility: evaluation using an isolated rabbit heart model.

The effects of Albunex (Molecular Biosystems, Inc., San Diego, Calif.) and a second generation contrast agent, FS069, on left ventricular (LV) contractility were evaluated using an isolated rabbit heart model under constant loading conditions and heart rate. Contrast injections (2 ml total volume) were performed in two separate protocols (N1 = 6, N2 = 6). In protocol 1, various doses of Albunex (0.1 to 2.0 ml in saline solution) were used, and paired control injections of a matched dose of 5% solution of human albumin in saline solution were administered. In protocol 2, LV contractility was assessed during injections of the following solutions: (1) 1:250 suspension of FS069 in saline solution, which caused optimal myocardial contrast enhancement; (2) a 1:25 suspension of FS069; (3) a 1:25 suspension of FS069 prefiltered using an 8 microns pore filter; and (4) 2 ml saline solution as a control. Instantaneous LV pressure was analyzed for variations in peak systolic pressure (peak P) and maximum pressure derivative (peak P'), both indices of LV contractility under conditions of fixed heart rate and chamber volume. Albumin alone caused a transient, dose-dependent depression of LV contractility, reflected by decreases in both peak P and peak P' values. These decreases presumably were caused by the decreasing availability of ionized calcium as a result of calcium binding. No further decrease in contractility was noted when Albunex microspheres were present in the solution. Saline injections caused a transient minor increase in LV contractility, reflected by increases of 4.5% +/- 1.1% and 10.6% +/- 3.8% in peak P and peak P' values, respectively. These levels returned to baseline levels within 2 minutes. A similar response was observed when a 1:250 suspension of FS069 was used. The 1:25 suspension of FS069 caused a bimodal response, with initial rises in peak P and peak P' levels (5.2% +/- 3.6% and 12.8% +/- 6.5%, respectively), followed by minor reductions in contractility (2.0% +/- 2.4% and 1.7% +/- 2.1%, respectively). The latter decrease in contractility caused by the 1:25 suspension of FS069 was eliminated by filtering. The isolated rabbit heart model is a highly sensitive tool that allows accurate and direct assessment of possible adverse effects of intravascular contrast agents on LV contractility. Using this model, we showed that neither Albunex microspheres nor FS069 microspheres impaired myocardial contractility.

Albumins↗
PubMedDate not supplied

Aortic elastic properties with transesophageal echocardiography with automated border detection: validation according to regional differences between proximal and distal descending thoracic aorta.

We have previously described the use of transesophageal echocardiography with automated border detection to quantify regional aortic elastic properties. The purpose of this study was to validate this technique further by measuring regional variations of aortic elastic properties and comparing them with previously published data acquired by invasive methods. In nine anesthetized, closed-chest dogs, aortic pressure and lumenal area (transesophageal echocardiography with automated border detection) signals were recorded simultaneously at two aortic sites: just distal to the branching site of the left subclavian artery (proximal) and at the level of the diaphragm (distal). Instantaneous wall thickness was estimated by combining M-mode measurement of aortic end-diastolic thickness with instantaneous lumenal area. Data were acquired over a wide range of loading conditions, generated by inferior vena caval balloon occlusion. Aortic compliance per unit length, midwall radius, midwall stress, and incremental elastic modulus were computed. Aortic midwall radius and incremental elastic modulus values for proximal and distal aortic sites were compared at a common level of midwall stress. Compliance per unit length was higher in the proximal compared with the distal descending thoracic aorta (0.013 +/- 0.003 versus 0.008 +/- 0.003 cm2/mm Hg; mean +/- SD; p = 0.0011). Midwall radius was larger at the proximal location (0.76 +/- 0.07 cm versus 0.64 +/- 0.07 cm; p = 0.0001), whereas incremental elastic modulus was greater distally (0.799 +/- 0.052 dynes x 10(6)/cm2 versus 0.912 +/- 0.130 dynes x 10(6)/cm2; p = 0.02). Lower compliance values at the distal site of the descending thoracic aorta resulted from greater wall stiffness and a smaller radius. Transesophageal echocardiography with automated border detection provides reliable measurements of instantaneous aortic areas necessary for quantifying regional elastic properties.

Animals↗
PubMedDate not supplied

An echocardiographic approach to the assessment of aortic stenosis.

An accurate echocardiographic assessment of aortic stenosis is critical for the cost-effective diagnosis and management of patients with the clinical suspicion of this diagnosis. Although the concepts involved in the echocardiographic determination of aortic pressure gradients and valve areas are relatively simple, acquisition of the data required to perform these calculations can at times be technically challenging. After reviewing the clinical signs and symptoms and the hemodynamics of aortic stenosis, this article reviews in detail the technical aspects involved in obtaining accurate gradients and valve areas emphasizing potential pitfalls.

Aortic Valve↗
PubMedDate not supplied

Evaluation of ventricular and arterial hemodynamics in anesthetized closed-chest mice.

Transgenic and knock-out mice with cardiovascular phenotypes have created the need for methods to measure murine arterial and ventricular mechanics. The aims of this study were (1) to develop a method for the assessment of wall stress (sigma es)-rate corrected velocity of fiber shortening (Vcfc) relation and (2) to assess the feasibility of quantifying global arterial function in normal mice. This method can thus serve as a reference for future studies in genetically altered mice by establishing normal values for comparison. Ten anesthetized closed-chest mice were studied with targeted M-mode echocardiography of the left ventricle recorded simultaneously with high-fidelity aortic pressures. Data were acquired at baseline and during infusions of methoxamine and isoproterenol. Tracings were digitized to obtain end-systolic wall stress (sigma es) and rate-corrected velocity of fiber shortening (Vcfc) relationships and plots of systolic meridional wall stress. Instantaneous aortic pressures and continuous wave aortic Doppler velocities were digitized to study arterial hemodynamics. The Vcfc-sigma es relationship was inverse and linear in all mice studied with a median value of r2 = 0.94. Isoproterenol resulted in an upward shift from the baseline contractility line obtained with methoxamine (mean shift = 2.0 +/- 0.3 circ/sec). Relative to baseline the integral of wall stress decreased with isoproterenol and increased with methoxamine. Methoxamine increased mean arterial pressure and total vascular resistance and decreased heart rate, cardiac output, and arterial compliance. Isoproterenol decreased total vascular resistance and increased cardiac output. Stress-shortening relationships, systolic wall stress, and evaluation of vascular function can be obtained in a closed-chest mouse model.

Adrenergic alpha-Agonists↗