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Biomedical subjects

D A Rubin

Publications and source records attributed to D A Rubin.

At least 55 records · Page 3Linked to original sources
PubMed1994

Myocardial ischemia after orthotopic liver transplantation.

A hypercoagulable state exists after orthotopic liver transplantation. This hematologic abnormality may predispose patients to coronary thrombosis and unstable angina. The incidence of postoperative myocardial ischemia in such patients is unknown. Suitable electrocardiograms and clinical events of consecutive patients undergoing orthotopic liver transplantation (n = 45) and major intraabdominal surgery (n = 28) during a 3-month period at a major university teaching hospital and transplant center were examined retrospectively. Clinical myocardial ischemia or ischemic electrocardiographic changes, or both, occurred in 6 transplant patients compared with no patient in the nontransplant or comparison group. In 4 of the 6 patients with dramatic electrocardiographic changes and ischemic events, coronary arteriography failed to demonstrate significant obstructive disease. It is concluded that severe myocardial ischemia may occur in patients after orthotopic liver transplantation in the absence of significant coronary disease. A hypercoagulable state may predispose to coronary thrombosis in this setting, providing insight (and a future model for study) into the development of unstable angina.

Abdomen↗
PubMed1994

Cloning of a growth hormone from a primitive bony fish and its phylogenetic relationships.

Growth hormone (GH), prolactin, and their relatives constitute a multigene family which is considered to have evolved from a common ancestor. The structural and functional domains of GH appear to be highly conserved among vertebrates. In order to investigate the phylogenetic relationships among GHs in the Actinopterygii and Sarcopterygii, we have cloned and sequenced GH from the pituitary of the primitive bony fish, Amia calva. Bony fishes (teleosts) and Amia (Halecomorphi) are purported sister-groups within the Neoptergii, hence studies on this perspective group of fish can provide insights into the evolution of GH. The deduced amino acid (aa) sequence from A. calva GH (amGH) cDNA revealed that the mature GH consists of 190 residues. Phylogenetic comparisons with GH aa sequences from blue shark, sturgeon, four teleosts (eel, carp, porgy, flounder), and two sarcopterygians (African lungfish and bullfrog) indicated, in the most parsimonious cladogram, that amGH clusters as the sister-group to the teleosts, that sturgeon is the sister-group to the Neopterygii, and that the African lungfish and bullfrog are in the same clade.

Amino Acid Sequence↗
PubMed1994

Increased plasma atrial natriuretic peptide levels after heart transplant: relation to ventricular expression and severity of rejection.

To determine whether elevated plasma atrial natriuretic peptide (ANP) levels observed after cardiac transplant are related to ventricular ANP expression and/or the severity of rejection, 59 ambulatory patients with cardiac transplant underwent hemodynamic evaluation, endomyocardial biopsy, and plasma ANP sampling. Forty-two of the 59 patients had right ventricular (RV) biopsy specimens immunohistochemically stained for the presence of ANP. Plasma ANP levels were elevated (p < 0.0001) in transplant patients (172 +/- 12 pg/ml) compared to normal subjects (36 +/- 4 pg/ml). Sixty-four percent of transplant patients showed stainable RV ANP on endomyocardial biopsy. There was no significant difference in plasma ANP levels between patients with or without RV ANP. The degree of RV staining did not correlate with plasma ANP levels, degree of rejection, mean atrial or systemic pressures, or specific immunosuppressive regimen. Plasma ANP levels were higher in patients with moderate or severe rejection (237 +/- 17 pg/ml) compared to patients with mild or no rejection (163 +/- 12 pg/ml; p 0.03), but there was significant overlap of values. These data suggest that ventricular ANP secretion may account for some of the increase in plasma ANP levels in cardiac transplant patients. However, increased plasma ANP levels in some transplant patients who have no RV ANP and the lack of correlation between the amount of stainable RV ANP and plasma ANP levels suggest that other mechanisms are also likely responsible for plasma ANP elevations in this setting.

Adult↗
PubMed1994

MR diagnosis of meniscal tears of the knee: value of fast spin-echo vs conventional spin-echo pulse sequences.

OBJECTIVE: Contrast can be similar on fast spin-echo and conventional spin-echo MR images, but data acquisition is faster with fast spin-echo sequences. This study was designed to evaluate the performance of fast spin-echo sequences in the detection of meniscal tears in the knee, with the established conventional spin-echo technique used as a reference standard. SUBJECTS AND METHODS: We imaged 66 consecutive patients (129 menisci) who were referred for MR examination with suspected meniscal tears. We used our routine two-dimensional, multisection, long repetition time/double-echo spin-echo sequence and one of two fast spin-echo sequences. The fast spin-echo parameters were chosen to minimize the loss of high-resolution detail while otherwise maintaining the sequence as close as possible to the spin-echo sequence. We then did a retrospective evaluation of the fast spin-echo images, using the spin-echo images as the gold standard. RESULTS: Fast spin-echo images showed only 30 (65%) of the 46 meniscal tears seen on the conventional spin-echo images. In addition, four of the 30 tears seen with both sequences were diagnosed with greater confidence on the conventional spin-echo images. In the cases in which both sequences allowed a diagnosis of definite meniscal tear, the abnormalities tended to be more conspicuous on the spin-echo images. CONCLUSION: Our results suggest that the fast spin-echo sequence should not be used for the diagnosis of meniscal tears.

Adult↗
PubMed1994

MR imaging of the musculoskeletal system: technical considerations for enhancing image quality and diagnostic yield.

MR imaging has revolutionized the diagnostic evaluation of musculoskeletal disorders, becoming the study of choice for many indications. Without the use of ionizing radiation, MR imaging can safely produce high-contrast, high-resolution cross-sectional images of the body in virtually any imaging plane. To maximize the diagnostic information of musculoskeletal MR studies, the radiologist must consistently produce the highest quality images possible, which in turn depends on a complex interaction among multiple technical factors. We present our perspectives on some of these factors, stressing the impact each has for specific indications. The material presented herein should be viewed as guidelines for improving image quality and diagnostic yield. However, individual systems and applications vary considerably, and the radiologist must "fine-tune" protocols to reflect the available resources, patient population, and preferences of the referring clinicians.

Adipose Tissue↗
PubMed1993

A subunit interaction site in human luteinizing hormone: identification by photoaffinity cross-linking.

The sites of noncovalent association between the alpha- (common) and beta- (hormone-specific) subunits in the glycoprotein hormones [LH, human CG (hCG), FSH, and TSH] remain to be completely defined. This information is essential to efforts to map the three-dimensional structure of the hormones and to help explain the stability of the hormone heterodimer in the circulation. Among numerous approaches that have been employed to identify these sites of subunit interaction, chemical or photoaffinity cross-linking has the advantage of identifying the complementary sites of contact on the respective subunits. We have used the stable photoaffinity ligand, L-benzoylphenylalanine (Bpa), to evaluate subunit interaction by the hLH beta sequence (1-15). A peptide from this region of hCG beta has been shown previously to inhibit subunit association. The 3H-labeled Bpa was incorporated into the peptide at position 8 (Trp) during solid-phase synthesis. After incubation with alpha under long-wavelength (366 nm) ultraviolet light, a Bpa- (1-15)-labeled-alpha-fraction was isolated. Control experiments showed the binding to be covalent and specific to (1-15). Two other Bpa-labeled beta-fragments, the receptor-binding loop (38-57) and the (30-43) peptide containing the highly conserved CAGY sequence, did not cross-link. The site of contact in alpha was localized by peptide mapping and sequence analysis to the N-terminal fragment (18-33), most likely at Met-29 or Gly-30. Both the alpha- and beta-sites are adjacent to or overlapping receptor-binding regions. Subunit contact sites and receptor-binding segments may thus be oriented in close proximity to provide a multicomponent receptor-binding domain imparting full activity to the native hormone.

Affinity Labels↗
PubMed1993

Aortic annular abscess complicating prosthetic valve endocarditis with group G streptococcus: detection during life with transesophageal echocardiography.

Infection with group G streptococcus is an unusual but virulent cause of endocarditis. Aortitis and abscess formation due to this organism have been described in one previous report, but only at necropsy. We present here a patient with group G streptococcal endocarditis and aortic annular abscess diagnosed during life by transesophageal echocardiography, leading to successful surgical intervention.

Abscess↗
PubMed1992

In vitro effects of homologous prolactins on testosterone production by testes of tilapia (Oreochromis mossambicus).

The tilapia, Oreochromis mossambicus, produces two prolactins designated tPRL177 and tPRL188 to indicate the number of amino acid residues in each. The direct in vitro actions of tPRL177 and tPRL188 on basal and ovine luteinizing hormone (LH)-induced testosterone production in minced testes of courting and noncourting (bachelor) tilapia were examined. Courting males were housed with females and were used as soon as they built a spawning pit; noncourting males were housed with other males and were used when they appeared female-like in coloration. The in vitro culture system consisted of two phases. In phase 1 (0-10 hr), testicular tissue was incubated without (control) or with the tPRLs--both alone and together and in doses ranging from 0.5 to 32 microM. In phase 2 (10-16 hr), the culture medium was replaced with medium containing 6.25 microM (0.25 micrograms/ml) ovine LH. Testosterone production during both phases was determined by radioimmunoassay of the medium. The tPRLs stimulated testosterone production during phase 1 in courting males (by 25%) but not in noncourting males. Exposure to either or both tPRLs in phase 1 enhanced the response of testicular tissue from courting males to ovine LH (by 10%) and inhibited the response of minced testes taken from noncourting males (by 12%). This is the first evidence to demonstrate direct gonadal activity of homologous PRL in a teleost.

Animals↗
PubMed1992

Reversible late potentials due to ischemia.

The role of ischemia in the development of reversible late potentials was assessed in 19 patients undergoing percutaneous transluminal coronary angioplasty. Signal-averaged electrocardiograms were performed before angioplasty, during ischemia caused by balloon inflation and after angioplasty. Five of 19 patients developed late potentials that reverted to normal after angioplasty. Age, sex, ejection fraction, left ventricular end diastolic pressure, vessels involved, and extent of myocardium in jeopardy did not predict the development of late potentials. Patients with a prior history of myocardial infarction were more likely to develop late potentials. Therefore, patients with prior myocardial infarction appear more likely to develop the substrate for reentrant ventricular tachycardia during periods of ischemia.

Angioplasty, Balloon, Coronary↗
PubMed1992

Prospective evaluation of heart block complicating early Lyme disease.

Lyme disease is a recognized cause of heart block/carditis. The incidence of heart block complicating early Lyme disease has not been prospectively evaluated. In this study, 61 patients with early Lyme disease documented by the rash of erythema migrans were prospectively evaluated for carditis. Fifty five of 61 patients had a repeat examination 3 to 4 weeks after initiation of antibiotic therapy. Only one of 61 patients (1.6%) presented with heart block, which resolved with antibiotics. None of the 54 patients without heart block on initial presentation had a change in any measured electrocardiographic parameter or progressed to heart block after antibiotics. Therefore, early Lyme disease appears to be infrequently complicated by heart block. Early administration of antibiotics may prevent the development of heart block/carditis.

Adult↗
PubMed1990

Interhemispheric fissure width in neonates on ECMO.

The neurosonograms of fifty-eight patients treated over a four-year period with ECMO support were retrospectively reviewed for analysis of changes in interhemispheric (IHF) width while on ECMO. To correlate these measurements with patterns of development of total body edema as reflected by chest wall thickening on portable chest radiographs, patients were divided into three categories based on the pattern and severity of body edema development. Patterns of IHF widening were compared between these categories, and to the pattern of development of chest wall edema within each category. Results indicate that IHF width tends to progressively increase during ECMO and that the pattern of IHF widening tends to parallel development of overall body edema. Additionally, IHF widening was found to resolve following termination of ECMO support, as demonstrated on follow-up cranial CT examinations. Our results suggest that IHF widening in infants on ECMO is an intracranial manifestation of the generalized edema accumulation that frequently occurs during ECMO.

Analysis of Variance↗