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Biomedical subjects

J W Lewis

Publications and source records attributed to J W Lewis.

At least 163 records · Page 9Linked to original sources
PubMed1991

Transthoracic and transesophageal echocardiography in the diagnosis and surgical management of right atrial myxoma.

An asymptomatic patient was discovered to have a large right atrial myxoma by transthoracic echocardiography. Preoperative considerations included the possibility of satellite lesions, left atrial origin, and a question of tricuspid valve involvement. Subsequent operative transesophageal echocardiography demonstrated single-stalk attachment in the right atrial septal wall and no satellite lesions. Doppler and color flow examination immediately following tumor removal aided in the decision not to perform tricuspid annuloplasty as there was no significant tricuspid regurgitation. The combined use of transthoracic and transesophageal echocardiography with Doppler and color flow imaging aids in the preoperative and intraoperative diagnosis and surgical management of right atrial tumors.

Echocardiography↗
PubMed1991

The epidemiology of Taenia pisiformis infections in domestic dogs in Cairo.

The epidemiology of Taenia pisiformis infections in domestic dogs in Cairo, Egypt. Over 5000 street dogs humanely killed in a culling programme organized by the Egyptian Ministry of the Interior in the winter of 1986 and the spring of 1987 have been utilized to examine the final host epidemiology of the cestode Taenia pisiformis in Cairo. In the winter months the prevalence of infection was 63.4% and the mean intensity 2.82 per dog: by the spring of 1987 these values had risen to 70.8% and 3.78 respectively. These parasite burdens probably represent the highest infection levels with T. pisiformis yet described from urban dog populations anywhere in the world. The dispersion of T. pisiformis within the street dog population was assessed and found to be significantly aggregated and well described by a negative binomial model of overdispersion (variance/mean ratio: 5.16, coefficient k = 0.795). A separate analysis was carried out of infection in each of 18 circumscribed regional areas of Cairo which revealed considerable area-to-area differences with mean intensities varying between 1.62 and 6.54 and prevalences between 43.3% and 91.2%. The size structure of the winter and spring worm samples were very similar with about 45% of worms less than 35 cm in length, about 35% between 35 and 59 cm, about 20% between 60 and 100 cm and less than 5% greater than 100 cm in length. The epidemiological factors which lead to high T. pisiformis infection levels in Cairo dogs have been considered and the consumption of discarded rabbit offal containing Cysticercus pisiformis by street dogs is regarded as a crucial mode of transmission.

Animals↗
PubMed1991

Spectrophotometric quantitation of rhodopsin in the human retina.

The rhodopsin content of the human retina was determined spectrophotometrically. Retinas were removed completely by using an in vitro technique based on a simulation of retinal detachment. This method provides a total recovery of rod outer segments which contain the rhodopsin visual pigment or its apoprotein, opsin. Using this improved dissection method followed by a crude preparation of the retina, an opsin-rhodopsin content of 6.20 +/- 0.64 nmol/retina (n = 9) was found. This is larger than values previously reported. Regeneration with a threefold excess of 11-cis-retinal improved the recovery of rhodopsin dramatically because the corneas of these human donor eyes were removed for corneal transplant surgery under relatively bright light that bleaches the retina nearly completely. The amount of rhodopsin that can be isolated will be sufficient for studies on early events in visual transduction using laser photolysis.

Adult↗
PubMed1990

Nanosecond photolysis of rhodopsin: evidence for a new, blue-shifted intermediate.

Early photolysis intermediates of native bovine rhodopsin (RHO) are investigated by nanosecond laser photolysis near physiological temperature. Absorption difference spectra are collected after excitation with 477-, 532-, and 560-nm laser pulses of various energies and with 477-nm laser excitation at 5, 12, 17, 21, and 32 degrees C. The data are analyzed by using singular-value decomposition (SVD) and a global exponential fitting routine. Two rate constants associated with distinct spectral changes are observed during the time normally associated with the decay of bathorhodopsin to lumirhodopsin. Various models consistent with this observation are considered. A sequential model in which there is a reversible step between a bathorhodopsin intermediate and a new intermediate (BSI), which is blue-shifted relative to lumirhodopsin, is shown to best fit the data. The temperature dependence of the observed and calculated rate constants leads to linear Arrhenius plots. Extrapolation of the temperature dependence suggests that BSI should not be observable after rhodopsin photolysis at temperatures below -100 degrees C. The results are discussed with regard to the artificial visual pigments cis-5,6-dihydroisorhodopsin and 13-demethylrhodopsin. It is proposed that the rate of the BATHO to BSI transition is limited by the relaxation of the strained all-trans-retinal chromophore within a tight protein environment. The transition to LUMI involves chromophore relaxation concurrent with protein relaxation. While the first process is strongly affected by changes in the chromophore, the second transition seems to be determined more by protein relaxation.

Chemical Phenomena↗
PubMed1990

Early photolysis intermediates of the artificial visual pigment 13-demethylrhodopsin.

Nanosecond time-resolved absorption measurements are reported for the room temperature photolysis of a modified rhodopsin pigment, 13-demethylrhodopsin, which contains the chromophore 13-demethylretinal. The measurements are consistent with the formation of an equilibrium between a BA-THO-13-demethylrhodopsin species and a blue-shifted species (relative to the parent pigment), BSI-13-demethylrhodopsin. The results are compared to those acquired after photolysis of native bovine rhodopsin [Hug, S. J., Lewis, J. W., Einterz, C. M., Thorgeirsson, T. E., & Kliger, D. S. (1990) Biochemistry (preceding paper in this issue)] and to results obtained after photolysis of several modified isorhodopsin pigments in which the BSI species was first observed. It is concluded that in all of the pigments the results are consistent with the formation of an equilibrium between BATHO and BSI, which subsequently decays on a nanosecond time scale at room temperature to a lumirhodopsin intermediate.

Chemical Phenomena↗
PubMed1990

Premenstrual syndrome as a criminal defense.

Premenstrual syndrome may be effective as an affirmative defense to a criminal charge if the defendant can show that (i) she was suffering from premenstrual syndrome at the time the crime was committed; and (ii) because of her condition, either that the criminal act was an involuntary act or that at the time of the criminal act she did not possess the mental state required by law for the commission of a crime. Premenstrual syndrome has been successfully pleaded as a criminal defense in Great Britain but has not been tested in American criminal courts. It may now be possible, however, because of the increase of behavioral, psychological, and physiological studies precisely characterizing premenstrual syndrome and elucidating the necessary criteria for its accurate diagnosis, for the appropriate defendant to assert this defense in an American court. This paper discusses (i) the use of recent scientific data to demonstrate the existence of premenstrual syndrome; (ii) the use of standardized psychological tests or physiological assays to demonstrate that the defendant suffers from premenstrual syndrome; and, (iii) the legal choices to be made and evidentiary hurdles that must be overcome in presenting a premenstrual syndrome defense.

Crime↗
PubMed1990

Role of brachytherapy in the management of pulmonary and mediastinal malignancies.

Brachytherapy, the permanent or temporary implantation of radioactive sources, has been performed in limited numbers of patients with lung cancer over the last 50 years. Because of renewed interest in this modality, we reviewed our experience with 103 patients treated over a 7-year period. The mean age of this group was 55.5 years (range, 1 to 84 years). Primary lung cancer accounted for 82 patients (79.6%); metastatic lesions to the lung, 13 (12.6%); and mediastinal malignancies, 8 (7.8%). Indications for brachytherapy included mediastinal and chest wall invasion in 42 patients (40.8%), unresectable tumors and mediastinal adenopathy in 30 (29.1%), medical contraindications to extensive pulmonary resection in 20 (19.4%), and irradiation of excised lymph node beds in 11 (10.7%). Seeds labeled with radioactive iodine 125 alone were used in 65 patients (63.1%), afterloading catheters containing iridium 192 sources in 25 (24.3%), and both in 13 (12.6%). There were no operative deaths. With a mean follow-up of 18.6 months, the mean and median survivals for the entire group were 17.3 and 14.0 months, respectively. The 1-year, 2-year, and 3-year survivals for the entire group were 67.9%, 38.7%, and 27.8%, respectively. In summary, brachytherapy offers a useful surgical approach in patients in whom unresectable pulmonary or mediastinal malignancies are found at the time of thoracotomy or in patients previously treated with other modalities for whom limited therapeutic alternatives exist.

Adolescent↗
PubMed1990

Carcinoid tumors of the thymus.

Carcinoid tumors arising in the thymus are rare. Since Rosai and Higa in 1972 distinguished these neoplasms from thymomas, fewer than 100 cases have been reported in the world literature. In a 38-year review (1950 to 1988) of surgically treated thymic tumors at Henry Ford Hospital, only 7 cases of thymic carcinoids were identified. These 6 men and 1 woman ranged in age from 27 to 70 years (mean, 48 years) at diagnosis. Follow-up was available in all patients with the longest survival being 12 years in 2 patients, and the shortest, 1 year, in 1. Recurrences and/or metastases developed in 4 of 7 patients between 1 and 9 years after initial resection. Recurrences were treated by reexcision in addition to radiation treatment and chemotherapy in 3 patients and reexcision with radiation treatment alone in 1 patient. A review of the literature along with our experience suggests that thymic carcinoids have a biological behavior distinct from thymoma in terms of cell origin, associated syndromes, neoplastic behavior, and prognosis. An aggressive surgical approach with complete initial excision of the tumor and of subsequent recurrences, along with radiation and probably chemotherapy, is the best available treatment today.

Adult↗
PubMed1990

Can computed tomography of the chest stage lung cancer? Yes and no.

To determine the accuracy of computed tomography (CT) of the chest in the staging of lung cancer, we studied 418 patients with primary pulmonary carcinoma between 1979 and 1986. Each had a preoperative scan performed before detailed operative staging. Each CT scan was analyzed for components of the current TNM staging system. Computed tomography sensitivity and specificity for mediastinal lymph node metastasis were 84.4% and 84.1%, with corresponding positive and negative predictive accuracies of 68.7% and 92.9%, respectively. When TNM stages were derived from CT scans, only 190 of 418 (45.4%) completely agreed with operative staging. An additional 53 of 418 (12.7%) predicted the correct stage, although components of the TNM system were incorrect. In 94 of 418 scans (22.5%) CT overestimated the stage, whereas in 81 (19.4%) CT downgraded the stage. Computed tomography suggested metastatic lesions in liver, lung, adrenal gland, bone, or abdominal lymph nodes in 40 of 373 scans (10.7%); only five of 40 (12.5%) had documented metastasis. In summary, CT of the chest cannot accurately stage primary lung carcinoma according to the TNM classification. Because the negative predictive accuracy for mediastinal lymph node metastasis remains high (92.9%), invasive staging can be deferred for definitive thoracotomy when no lymphadenopathy is evident on CT. The high negative predictive accuracy for scans of the chest and upper abdomen makes CT a useful tool for exclusion of metastatic disease.

Adenocarcinoma↗
PubMed1990

Silastic prosthesis plombage for right postpneumonectomy syndrome.

In rare instances, right pneumonectomy can produce progressive exertional dyspnea and reduce ventilatory reserve because of extreme mediastinal shift (right postpneumonectomy syndrome). The diagnosis can be made by bronchoscopy and computed tomography. We report a case of a 43-year-old patient in whom plombage with two Silastic breast implants produced mediastinal derotation and symptomatic relief of this syndrome.

Adenocarcinoma↗
PubMed1989

The porcine bioprosthetic heart valve: experience at 15 years.

The porcine bioprosthetic valve has been in use at Henry Ford Hospital since 1971. In this review, 980 patients with 1,081 porcine bioprosthetic valves were examined from 1 month to 16.4 years after implantation with a 99% complete follow-up. Patient survival was 59% +/- 2.2% (+/- standard error of the mean) at 10 years and 38% +/- 4.0% at 15 years. Factors associated with decreased survival after hospital discharge were age greater than 35 years and New York Heart Association functional class IV. Freedom from thromboembolism was 92% +/- 1.2% at 10 years and 89% +/- 3.2% at 15 years. Freedom from endocarditis was 93% +/- 1.2% at 10 years and 92% +/- 1.3% at 15 years. Freedom from structural valve degeneration for all valves was 71% +/- 2.6% at 10 years and 31% +/- 5.6% at 15 years. Factors associated with increased risk of structural valve degeneration were age younger than 35 years, female sex, and preoperative cardiac index greater than 2 L/min/m2. Among a total of 172 patients undergoing removal of a degenerated valve, mortality was 12.5%, and significant risk factors for death at reoperation were emergency operation and functional class IV. Experience with the porcine bioprosthetic valve after 15 years suggests that its use be confined to older patients or patients with a contraindication of anticoagulation.

Adolescent↗
PubMed1989

Transition dipole orientations in the early photolysis intermediates of rhodopsin.

The linear dichroism spectrum of rhodopsin in sonicated bovine disk membranes was measured 30, 60, 170, and 600 ns after room temperature photolysis with a linearly polarized, 7-ns laser pulse (lambda = 355 or 477 nm). A global exponential fitting procedure based on singular value decomposition was used to fit the linear dichroism data to two exponential processes which differed spectrally from one another and whose lifetimes were 42 +/- 7 ns and 225 +/- 40 ns. These results are interpreted in terms of a sequential model where bathorhodopsin (BATHO, lambda max = 543 nm) decays toward equilibrium with a blue shifted intermediate (BSI, lambda max = 478 nm). BSI then decays to lumirhodopsin (LUMI, lambda max = 492 nm). It has been suggested that two bathorhodopsins decay in parallel to their products. However, a Monte Carlo simulation of partial photolysis of solid-state visual pigment samples shows that one mechanism which creates populations of BATHO having different photolysis rates at 77 K may not be responsible for the two decay rates reported here at room temperature. The angle between the cis band and 498-nm band transition dipoles of rhodopsin is determined to be 38 degrees. The angles between both these transition dipoles and those of the long-wave-length bands of BATHO, BSI, and LUMI are also determined. It is shown that when BATHO is formed its transition dipole moves away from the original cis band transition dipole direction. The transition dipole then moves roughly twice as much towards the original cis band direction when BSI appears. Production of LUMI is associated with return of the transition dipole almost to the original orientation relative to the cis band, but with some displacement normal to the plane which contains the previous motions. The correlation between the lambda max of an intermediate and its transition dipole direction is discussed.

Animals↗
PubMed1989

Photolysis intermediates of the artificial visual pigment cis-5,6-dihydro-isorhodopsin.

The photolysis intermediates of an artificial bovine rhodopsin pigment, cis-5,6-dihydro-isorhodopsin (cis-5,6,-diH-ISORHO, lambda max 461 nm), which contains a cis-5,6-dihydro-9-cis-retinal chromophore, are investigated by room temperature, nanosecond laser photolysis, and low temperature irradiation studies. The observations are discussed both in terms of low temperature experiments of Yoshizawa and co-workers on trans-5,6-diH-ISORHO (Yoshizawa, T., Y. Shichida, and S. Matuoka. 1984. Vision Res. 24: 1455-1463), and in relation to the photolysis intermediates of native bovine rhodopsin (RHO). It is suggested that in 5,6-diH-ISORHO, a primary bathorhodopsin intermediate analogous to the bathorhodopsin intermediate (BATHO) of the native pigment, rapidly converts to a blue-shifted intermediate (BSI, lambda max 430 nm) which is not observed after photolysis of native rhodopsin. The analogs from lumirhodopsin (LUMI) to meta-II rhodopsin (META-II) are generated subsequent to BSI, similar to their generation from BATHO in the native pigment. It is proposed that the retinal chromophore in the bathorhodopsin stage of 5,6-diH-ISORHO is relieved of strain induced by the primary cis to trans isomerization by undergoing a geometrical rearrangement of the retinal. Such a rearrangement, which leads to BSI, would not take place so rapidly in the native pigment due to ring-protein interactions. In the native pigment, the strain in BATHO would be relieved only on a longer time scale, via a process with a rate determined by protein relaxation.

Isomerism↗
PubMed1989

Color Doppler features of left ventricular pseudoaneurysm.

A patient had left ventricular pseudoaneurysm after mitral valve replacement surgery. The diagnosis was made by color flow Doppler demonstration of systolic flow between the left ventricular chamber and an echo-free space posterior to the heart which was initially interpreted as localized pleural effusion. Color Doppler features of this entity have not been previously described. Color flow cardiac Doppler enhances echocardiographic and pulsed Doppler diagnosis of left ventricular pseudoaneurysms.

Adult↗
PubMed1988

A three-part system for refining intraocular lens power calculations.

A three-part system that determines the correct power for an intraocular lens (IOL) to achieve a desired postoperative refraction is presented. The three components are (1) data screening criteria to identify improbable axial length and keratometry measurements, (2) a new IOL calculation formula that exceeds the current accuracy of other formulas for short, medium, and long eyes, and (3) a personalized "surgeon factor" that adjusts for any consistent bias in the surgeon's results, from any source, based on a reverse solution of the new formula; the reverse solution uses the postoperative stabilized refraction, the dioptric power of the implanted IOL, and the preoperative corneal and axial length measurements to calculate the personalized surgeon factor. The improved accuracy of the new formula was proven by performing IOL power calculations on 2,000 eyes from 12 surgeons and comparing the results to seven other currently used formulas.

Evaluation Studies as Topic↗
PubMed1988

Communication between physicians and physical therapists.

The purposes of this study were 1) to identify therapists' and physicians' attitudes and opinions about the physician-physical therapist communication dyad, 2) to identify potential areas for improvement in this communication process, and 3) to provide physical therapists and physical therapy students with basic guidelines for optimal communications. Ten physical therapists and 8 physicians participated in individual interviews that were taped and subsequently transcribed. The transcriptions were compiled and analyzed by an interpersonal communication expert (B.W.B.) for trends and themes. Findings of the study include 1) physical therapists want increased accessibility to and communication with physicians and 2) physicians want brief communication with clear objective data provided by the therapists. Basic guidelines developed for physical therapy students as a result of this study include 1) identify physicians with whom you can communicate most easily, 2) learn your physicians' schedules, 3) organize beforehand so that communication is clear and concise, 4) be polite but self-assured, 5) ask your supervisor or other staff therapists for advice, and 6) use the telephone discriminately. This study emphasizes that communication with physicians must be approached on an individual basis. Each physician differs in personality, philosophy of patient care, and expectations of physical therapy. Therapists should take the initiative in developing good rapport and maintaining a viable relationship with physicians.

Attitude of Health Personnel↗