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S Byers

Publications and source records attributed to S Byers.

17 recordsLinked to original sources
PubMed1992

Fibroblast growth factor receptors contain a conserved HAV region common to cadherins and influenza strain A hemagglutinins: a role in protein-protein interactions?

The first extracellular domain of the cadherins has been shown to exhibit extensive sequence homology with the amino termini of the HA1 chains of influenza strain A hemagglutinins. These regions of homology are known to be functionally important in both the cadherins and the hemagglutinins. The homologous regions harbor the tripeptide HAV, which has been identified as being the cadherin cell adhesion recognition sequence. Here we report that members of the rapidly expanding family of fibroblast growth factor receptors also possess HAV-containing regions. These regions are homologous to the HAV-containing regions present within both the hemagglutinins and the cadherins and appear to be involved in regulating the function of the fibroblast growth factor receptors. We speculate that the HAV motif may represent an evolutionarily conserved amino acid sequence that will prove to be functionally important in a wide variety of proteins.

Amino Acid Sequence↗
PubMed1992

Immunolocation analysis of glycosaminoglycans in the human growth plate.

Monoclonal antibodies were used in this study to immunolocate glycosaminoglycans throughout the human growth plate. Chondroitin-4-sulfate, chondroitin-6-sulfate, and keratan sulfate were observed in the extracellular matrix of all zones of the growth plate and persisted into the cartilage trabeculae of newly formed metaphyseal bone. Also present in the extracellular matrix was an oversulfated chondroitin/dermatan sulfate glycosaminoglycan which appeared to be specific to the proliferative and hypertrophic zones of the growth plate. As with the other extracellular matrix molecules, this epitope persisted into the cartilage trabeculae of the metaphyseal bone. Zonal differences between the extracellular and pericellular or lacunae matrix were also observed. The hypertrophic chondrocytes appeared to synthesize chondroitin sulfate chains containing a non-reducing terminal 6-sulfated disaccharide, which were located in areas immediately adjacent to the cells. This epitope was not found to any significant extent in the other zones. The pericellular region around hypertrophic chondrocytes also contained a keratan sulfate epitope which was also observed in the resting zone but not in the proliferative zone. These cell-associated glycosaminoglycans were not found in the cartilage trabeculae of metaphyseal bone, indicating their removal as the terminal hypertrophic chondrocytes and their lacunae are removed by invading blood vessels. These changes in matrix glycosaminoglycan content, both in the different zones and within zones, indicate constant subtle alterations in chondrocyte metabolic products as they proceed through their life cycle of proliferation, maturation, and hypertrophy.

Aging↗
PubMed1992

Carbon monoxide exposure of subjects with documented cardiac arrhythmias.

The impact of low-level carbon monoxide exposure on ventricular arrhythmia frequency in patients with ischemic heart disease has not been thoroughly studied. The issue is of concern because of the potential proarrhythmic effect of carbon monoxide in patients with ischemic heart disease. We studied 30 subjects with well-documented coronary artery disease who had an average of at least 30 ventricular ectopic beats per hour over a 20-hour monitoring interval. By using appropriate inclusion and exclusion criteria, subjects were selected and enrolled in a randomized double-blind study to determine the effects of carbon monoxide exposure on ventricular arrhythmia frequency at rest, during exercise, and during ambulatory activities. The carbon monoxide exposure was designed to result in 3% or 5% carboxyhemoglobin levels, as measured by gas chromatography. The carbon monoxide exposure protocol produced target levels in 60 minutes, and the levels were maintained for an additional 90 minutes to provide adequate time to assess the impact of carbon monoxide on the frequency of ventricular ectopic beats. The data on total and repetitive ventricular arrhythmias were analyzed for seven specific time intervals: (1) two hours before carbon monoxide exposure; (2) during the two-hour carbon monoxide or air exposure; (3) during a two-hour rest period; (4) during an exercise period; (5) during an exercise recovery period; (6) six hours after carbon monoxide or air exposure; and (7) approximately 10 hours after exposure, or the remaining recording interval on the Holter monitor. There was no increase in ventricular arrhythmia frequency after carbon monoxide exposure, regardless of the level of carboxyhemoglobin or the type of activity. During steady-state conditions at rest, the number of ventricular ectopic beats per hour was 115 +/- 153 (SD) for room air exposure (0.7% carboxyhemoglobin), 121 +/- 171 for the lower carbon monoxide exposure (3.2% carboxyhemoglobin), and 94 +/- 129 for the higher carbon monoxide exposure (5.1% carboxyhemoglobin). The frequency of complex ventricular ectopy was not altered at the levels of carbon monoxide studied. Secondary analysis of the impact of carbon monoxide on ventricular ectopic beat frequency stratified by baseline ejection fraction, baseline ventricular ectopic beat frequency, and exercise-induced ST-segment changes did not indicate an effect of carbon monoxide on ventricular arrhythmias. In conclusion, low levels of carbon monoxide exposure resulting in blood levels of 3.2% and 5.1% carboxyhemoglobin, as measured by gas chromatography, do not have a proarrhythmic effect on patients with coronary artery disease and frequent ventricular ectopy.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1991

Development of Sertoli cell junctional specializations and the distribution of the tight-junction-associated protein ZO-1 in the mouse testis.

Basally located tight junctions between Sertoli cells in the postpubertal testis are the largest and most complex junctional complexes known. They form at puberty and are thought to be the major structural component of the "blood-testis" barrier. We have now examined the development of these structures in the immature mouse testis in conjunction with immunolocalization of the tight-junction-associated protein ZO-1 (zonula occludens 1). In testes from 5-day-old mice, tight junctional complexes are absent and ZO-1 is distributed generally over the apicolateral, but not basal, Sertoli cell membrane. As cytoskeletal and reticular elements characteristic of the mature junction are recruited to the developing junctions, between 7 and 14 days, ZO-1 becomes progressively restricted to tight junctional regions. Immunogold labeling of ZO-1 on Sertoli cell plasma membrane preparations revealed specific localization to the cytoplasmic surface of tight junctional regions. In the mature animal, ZO-1 is similarly associated with tight junctional complexes in the basal aspects of the epithelium. In addition, it is also localized to Sertoli cell ectoplasmic specializations adjacent to early elongating, but not late, spermatids just prior to sperm release. Although these structures are not tight junctions, they do have a similar cytoskeletal arrangement, suggesting that ZO-1 interacts with the submembrane cytoskeleton. These results show that, in the immature mouse testis, ZO-1 is present on the Sertoli cell plasma membrane in the absence of recognizable tight junctions. In the presence of tight junctions, however, ZO-1 is found only at the sites of junctional specializations associated with tight junctions and with elongating spermatids.

Animals↗
PubMed1991

Technical note: calculation of age at formation of radiopaque transverse lines.

A simple method for determining the age of an individual at the time of radiopaque transverse (Harris) line formation is presented. To use this method, only two measurements are required: total bone length and distance of line to nearest bone end; these are put into formulae that calculate the percent of total bone growth when the line appeared. The result of this calculation is compared with tables of percent bone growth per year (one to 16 years in females and one to 18 years in males) to arrive at estimations of age at line formation. Since these tables are presented for the femur, tibia, humerus, and radius, this technique can be used on any one of the major long bones exhibiting lines.

Age Determination by Skeleton↗
PubMed1990

Distribution of sodium-potassium ATPase in the rat testis and epididymis.

Sodium-potassium ATPase (Na+K(+)-ATPase) is a ubiquitous plasma membrane enzyme which uses the hydrolysis of ATP to regulate cellular Na+ and K+ levels and fluid volume. This ion pumping action is also thought to be involved in fluid movement across certain epithelia. There are several different genes for this enzyme, some of which are tissue specific. Using an antibody specific for the catalytic subunit of canine kidney Na+K(+)-ATPase, we have localized immunoreactivity in the seminiferous and epididymal epithelium of rats of various ages. There was no specific staining of 10-day-old rat testis. Faint staining was detected at 13 days and appeared to be associated with the borders of Sertoli cells. At 16 days prominent apical and lateral staining but no basal staining of Sertoli cell membranes was observed. This type of distribution continued until spermatids were present in the epithelium. In the adult rat testis, specific staining was detected in Sertoli cell crypts associated with elongating spermatids, and on the apical and lateral Sertoli cell membrane. In some instances immunoreactivity was concentrated at presumed sites of junctional specializations. In the excurrent ducts of immature and mature rats, Na+K(+)-ATPase staining was heavy in the efferent ducts and somewhat lighter in the epididymis. In all regions, the staining was basolateral although there were variations in intensity among the different parts of the epididymis. These results show 1) that rat testis and epididymal Na+K(+)-ATPase share some immunological determinants with the canine enzyme; 2) that the epididymal enzyme is located in the conventional basolateral position; and 3) that the distribution of Sertoli cell Na+K(+)-ATPase is probably apical and lateral rather than basal.

Aging↗
PubMed1990

Perioperative and long-term prognostic value of intravenous dipyridamole thallium scintigraphy in patients with peripheral vascular disease.

The prognostic value of long-term risk stratification of patients with peripheral vascular disease who undergo intravenous dipyridamole thallium scintigraphy has not been well studied. We screened 131 patients with peripheral vascular disease who underwent intravenous dipyridamole thallium testing to determine cardiac event rates over an average follow-up of 18 +/- 10 months. Of the 131 patients, 111 subsequently had peripheral vascular surgery. The patients with abnormal thallium scans after dipyridamole had a significantly higher risk of death or myocardial infarction, both in the perioperative phase (7% versus 0%; p less than 0.001) and at late follow-up (17% versus 6%; p less than 0.01). The risk of a cardiac event was two-fold greater when a reversible as compared to a fixed thallium defect was present. Multivariate analysis selected the number of thallium segments with perfusion defects, prior history of angina pectoris, and chest pain during dipyridamole testing as perioperative predictors of a cardiac event. A reversible thallium defect was the only predictor of death or nonfatal myocardial infarction during late follow-up. Thus intravenous dipyridamole thallium scintigraphy is a useful noninvasive test for risk stratification of patients before peripheral vascular surgery and provides prognostic information as to the risk of a cardiac event in the 2-year period after the test. A reversible thallium defect is associated with a significant increased risk and would indicate that coronary angiography should be considered and preoperative coronary revascularization.

Aged↗
PubMed1989

Prognostic value of intravenous dipyridamole thallium scintigraphy after an acute myocardial ischemic event.

Seventy-seven patients recovering from an acute coronary event were studied by intravenous dipyridamole thallium scintigraphy to evaluate the prognostic value and safety of the test in this patient subset. Forty-four patients (58%) had unstable angina and 33 (42%) had an acute myocardial infarction. One death occurred within 24 hours of testing. Sixty-eight patients were followed for an average of 12 months; 25, 31 and 23% had a fixed, reversible or combined thallium defect on their predischarge thallium scan. During follow-up, 10 patients died or had a nonfatal myocardial infarction; in each case, a reversible or combined myocardial thallium defect was present. Univariate analysis of 17 clinical, scintigraphic and angiographic variables showed that a reversible thallium defect and the angiographically determined extent of coronary artery disease were predictors of future cardiac events. The extent of coronary disease and global left ventricular ejection fraction were predictors of subsequent reinfarction or death. Logistic regression analyses revealed that a reversible thallium defect (p less than 0.001) and the extent of coronary disease (p less than 0.009) were the only significant predictors of a cardiac event. When death or reinfarction were the outcome variables, the extent of coronary disease (p less than 0.02) and left ventricular ejection fraction (p less than 0.06) were the only variables selected. Thus, intravenous dipyridamole thallium scintigraphy after an acute coronary ischemic syndrome is a useful and relatively safe noninvasive test to predict subsequent cardiac events.

Aged↗
PubMed1989

Determination of adult stature from metatarsal length.

The results of a study to determine the value of foot bones in reconstructing stature are presented. The data consist of length measurements taken on all ten metatarsals as well as on cadaver length from a sample of 130 adults of documented race, sex, stature, and, in most cases, age. Significant correlation coefficients (.58-.89) are shown between known stature and foot bone lengths. Simple and multiple regression equations computed from the length of each of these bones result in standard errors of estimated stature ranging from 40-76 mm. These errors are larger than those for stature calculated from complete long bones, but are approximately the same magnitude for stature calculated from metacarpals and fragmentary long bones. Given that metatarsals are more likely to be preserved unbroken than are long bones and given the ease with which they are accurately measured, the formulae presented here should prove useful in the study of historic and even prehistoric populations.

Adult↗
PubMed1989

Prognostic importance of silent myocardial ischemia detected by intravenous dipyridamole thallium myocardial imaging in asymptomatic patients with coronary artery disease.

One hundred seven asymptomatic patients who underwent intravenous dipyridamole thallium imaging were evaluated to determine prognostic indicators of subsequent cardiac events over an average follow-up period of 14 +/- 10 months. Univariate analysis of 18 clinical, scintigraphic and angiographic variables revealed that a reversible thallium defect, a combined fixed and reversible thallium defect, number of segmental thallium defects and extent of coronary artery disease were significant predictors of subsequent cardiac events. Of the 13 patients who died or had a nonfatal infarction, 12 had a reversible thallium defect. Stepwise logistic regression analysis selected a reversible thallium defect as the only significant predictor of cardiac events. When death or myocardial infarction was the outcome variable, a combined fixed and reversible thallium defect was the only predictor of outcome. In patients without previous myocardial infarction, the cardiac event rate was significantly greater in those with an abnormal versus normal thallium scan (55% versus 12%, p less than 0.001). Thus, intravenous dipyridamole thallium scintigraphy is a useful noninvasive test to risk stratify asymptomatic patients with coronary artery disease. A reversible thallium defect most likely indicates silent myocardial ischemia in a sizable fraction of patients in this clinical subset and is associated with an unfavorable prognosis.

Aged↗
PubMed1988

Safety and diagnostic accuracy of dipyridamole-thallium imaging in the elderly.

The noninvasive diagnosis of coronary artery disease in the elderly can occasionally be difficult. Intravenous dipyridamole-thallium imaging is a potentially useful diagnostic test to determine presence and severity of coronary disease; however, the safety of the procedure has not been determined in an older population. The side effect profile and frequency of severe ischemic responses after 0.56 mg/kg of intravenous dipyridamole were compared in 101 patients greater than or equal to 70 years old and 236 patients less than 70 years old. There were no side effects in 64% and 62% of patients greater than or equal to 70 and less than 70 years old, respectively (p = NS). Among the 337 patients tested, there were no complications of myocardial infarction or death. The most common cardiac side effect was chest pain, which occurred in 21 (21%) of the 101 patients aged greater than or equal to 70 years and in 64 (27%) of the 236 patients less than 70 years (p = NS). Aminophylline was required to reverse cardiac or noncardiac side effects in 15 (15%) and 36 (15%) of the patients greater than or equal to 70 and less than 70 years old, respectively (p = NS). A severe ischemic response occurred in 2% and 2.5% of patients greater than or equal to 70 and less than 70 years old, respectively (p = NS). The sensitivity of intravenous dipyridamole-thallium imaging for obstructive coronary artery disease was 86% (25 of 29) and 83% (68 of 82) in older and younger patients, respectively (p = NS); the specificity was 75% (6 of 8) and 70% (16 of 23), respectively (p = NS). Thus, intravenous dipyridamole-thallium imaging is a safe noninvasive method for assessment of older patients with obstructive coronary disease; its side effect profile and diagnostic accuracy are similar to those seen in younger patients. The technique is associated with severe ischemic responses in only a small minority of patients.

Adult↗
PubMed1988

Isolation and characterization of epididymal epithelial cell plasma membranes.

Sperm maturation and storage occur in a unique milieu created in large part by the epididymal epithelium. To learn more about the interaction of the epididymal epithelial cell with both luminal and systemic environments, we now report on the preparation and characterization of epididymal epithelial cell plasma membranes. A preparation enriched for epididymal epithelial cell plasma membranes was isolated from collagenase-digested epididymal tubule fragments by hand-Dounce homogenization, differential centrifugation, and sucrose gradient centrifugation. The final membrane fraction was enriched 11-fold for the plasma membrane marker 5'-nucleotidase; 2.6-fold for the lysosomal marker acid phosphatase, and 3-fold for the Golgi marker thiamine pyrophosphatase. No enrichment was observed for mitochondrial or endoplasmic reticulum enzyme markers. Specific and saturable transferrin-binding activity was also detected in the final preparation. Electron microscopy revealed the presence of vesicles and sheets of membranes as well as an occasional Golgi apparatus. The plasma membrane fraction was used to generate monoclonal antibodies. Of 102 wells exhibiting growth, 12 were positive by immunofluorescent staining of frozen sections. Ten of these recognized determinants in epithelial cells, and 2 stained peritubular smooth muscle cells. Most of the epithelial cell-specific antibodies stained brush border alone or in combination with the basolateral plasma membrane. Three antibodies stained the Golgi apparatus. Most antibodies were specific for particular epididymal regions, 3 also recognized determinants in the kidney, and 1 stained residual bodies in the testis.

Animals↗
PubMed1987

The effect of zwitterionic detergents on the extraction and functional properties of cartilage proteoglycans.

A range of structurally related zwitterionic detergents, Zwittergents 3-06, 3-08, 3-10, and 3-12, and a derivative of cholic acid (Chaps) were examined for their ability to enhance the extraction of newly synthesized, intracellular proteoglycans and for their effect on the functional properties of cartilage proteoglycan. Although none of the detergents could extract greater than 4% of the intracellular proteoglycans when used alone, Zwittergents 3-10, 3-12, and Chaps proved equally as effective when used in combination with 4 M guanidine HCl extracting greater than 90% of newly synthesized proteoglycans. Rate zonal centrifugation of aggregates containing either 3H-link protein or 3H-monomer, which had been incubated with 2% (w/v) detergent indicated that none of the test detergents caused a disassembly of intact aggregates. However, both Zwittergents 3-10 and 3-12 prevented the reaggregation of components dissociated with 4 M guanidine HCl. Similar to the finding with aggregate, none of the detergents caused a disassembly of monomer-link protein complexes prepared from purified 3H-link protein and proteoglycan monomer, while Zwittergents 3-10 and 3-12 prevented their assembly from free link protein and monomer. However, monomer-link protein complexes once formed were able to associate with hyaluronic acid to form link-stable ternary complexes in the presence of all detergents tested including Zwittergents 3-10 and 3-12.

Animals↗
PubMed1985

Carrageenin-induced arthritis. VI. Alterations in amino acid transport by articular cartilage in acute inflammatory arthritis.

The mechanism of transport of alanine and aminoisobutyric acid into chondrocytes in rabbit articular cartilage was shown to be mediated by transport systems similar to that described for other eukaryotic cells namely the A, ASC, and L systems. Three days after the initiation of an acute inflammatory arthritis by the intra-articular injection of carrageenin into one knee joint the rate of transport of both these amino acids was decreased. Although all three transport systems were depressed, it appeared that the A and ASC systems were partially susceptible to damage by the induced inflammation. The rate of amino acid transport by the affected cartilage had recovered by 28 days after carrageenin treatment. This depression in amino acid transport is discussed in relation to a decrease in general metabolic processes in chondrocytes as a consequence of inflammation.

Alanine↗
PubMed1977

Transoral resection of a condylar osteochondroma: report of case.

A rare case of osteochondroma (osteocartilaginous exostosis) of the mandibular condyle is described; this represents the seventh documented case in the English language literature. Treatment consisted of transoral surgical resection which maintained condylar integrity. No maxillomandibular fixation was placed and the patient's mandibular function was undisturbed. Postoperatively, mandibular deviation was minimal.

Aged↗