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Biomedical subjects

M A Goldstein

Publications and source records attributed to M A Goldstein.

At least 19 recordsLinked to original sources
PubMed1992

Primary sequence analysis of Clostridium cellulovorans cellulose binding protein A.

The cbpA gene for the Clostridium cellulovorans cellulose binding protein (CbpA), which is part of the multisubunit cellulase complex, has been cloned and sequenced. When cbpA was expressed in Escherichia coli, proteins capable of binding to crystalline cellulose and of interacting with anti-CbpA were observed. The cbpA gene consists of 5544 base pairs and encodes a protein containing 1848 amino acids with a molecular mass of 189,036 Da. The open reading frame is preceded by a Gram-positive-type ribosome binding site. A signal peptide sequence of 28 amino acids is present at its N terminus. The encoded protein is highly hydrophobic with extremely high levels of threonine and valine residues. There are two types of putative cellulose binding domains of approximately 100 amino acids that are slightly hydrophilic and eight conserved, highly hydrophobic beta-sheet regions of approximately 140 amino acids. These latter hydrophobic regions may be the CbpA domains that interact with the different enzymatic subunits of the cellulase complex.

Amino Acid Sequence↗
PubMed1992

Cardiac morphology after conditions of microgravity during COSMOS 2044.

Light- and electron-microscopic studies were performed on cardiac muscle from rats flown on COS-MOS 2044 and from four control groups. Average cross-sectional area of myofibers was measured by video analysis of the light-microscopic images of papillary and ventricular muscle samples from all animals. This cross-sectional area was significantly decreased in flight rats (P = 0.03) compared with synchronous controls. Additional findings at the electron-microscopic level consistent with this atrophy were obtained by stereological analysis and optical diffraction analysis of papillary muscle samples. Slightly higher mitochondrial volume density values and mitochondria-to-myofibril ratios as well as normal A-band spacings (d1,0) and Z-band spacings of myofibrils were observed in the tail-suspension and flight groups. General morphological features similar to those in ventricular samples from the previous COSMOS 1887 flight were observed.

Animals↗
PubMed1991

Similar features in Z bands of both skeletal and cardiac muscle revealed by image enhancement.

We have shown previously that the small square (ss) and basket weave (bw) states of the Z band lattice in cardiac and skeletal muscle are related to the contractile state of the muscle. We have used two-dimensional image processing techniques on digitized electron micrographs to enhance the structural features of each projected lattice form in cardiac and skeletal muscle. Four different processing techniques were employed to assess the effect of enhancement artifacts on the resulting Z band images. We observed only slight differences between enhanced images of a particular Z band form produced by the four different techniques. Every enhanced image showed an approximate four-fold symmetry independent of muscle type or Z band lattice form. Each enhanced image showed four cross-connecting Z-filaments which appeared to connect each axial filament to the four nearest axial filaments. In bw images from both cardiac and skeletal muscle, axial filaments had a greater apparent diameter and a greater interaxial filament spacing than in the ss images. In both muscle types, the cross-connecting Z-filaments appeared to overlap half-way between axial filaments in the ss images while the bw images showed no such overlap. These structural features are consistent with a dynamic Z band lattice that participates in muscle contraction.

Algorithms↗
PubMed1991

Role of the Z band in the mechanical properties of the heart.

In striated muscle the mechanism of contraction involves the cooperative movement of contractile and elastic components. This review emphasizes a structural approach that describes the cellular and extracellular components with known anatomical, biochemical, and physical properties that make them candidates for these contractile and elastic components. Classical models of contractile and elastic elements and their underlying assumptions are presented. Mechanical properties of cardiac and skeletal muscle are compared and contrasted and then related to ultrastructure. Information from these approaches leads to the conclusion that the Z band is essential for muscle contraction. Our review of Z band structure shows the Z band at the interface where extracellular components meet the cell surface. The Z band is also the interface from cell surface to myofibril, from extra-myofibrillar to myofibril, and finally from sarcomere to sarcomere. Our studies of Z band in defined physiologic states show that this lattice is an integral part of the contractile elements and can function as an elastic component. The Z band is a complex dynamic lattice uniquely suited to play several roles in muscle contraction.

Animals↗
PubMed1991

Hydrogen peroxide pretreatment of perfused canine vessels induces ICAM-1 and CD18-dependent neutrophil adherence.

BACKGROUND: Cytotoxic products of neutrophils (polymorphonuclear leukocytes, PMNs) contribute to ischemia-reperfusion injury of several tissues. Hydrogen peroxide (H2O2), one of the cytotoxic products of PMNs, also promotes the adherence of PMNs to cultured vascular endothelial cells in vitro. The present study was undertaken to determine if H2O2 also augmented adhesion of PMNs to intact vessels perfused ex vivo and to determine if H2O2-induced PMN adherence to intact canine carotid arteries and external jugular veins or to cultured canine venous endothelium is mediated by specific adherence ligands on the neutrophil and/or the endothelium. METHODS AND RESULTS: Vessels were perfused for 20 minutes with oxygenated Krebs-Henseleit bicarbonate buffer with and without H2O2, washed with buffer alone, and then exposed to 111In-labeled isolated PMNs (10(7) cells/vessel) under static conditions for up to 20 minutes before being washed again. Residual radioactivity retained by the washed vessel was counted as an index of PMN retention. The adherence of unlabeled PMNs to cultured endothelial cells was determined by a visual assay method after pretreatment of the endothelium with H2O2 for brief periods followed by washing. Perfusion of vessels with H2O2 produced a transient, concentration-dependent increase in PMN adhesion to both canine carotid arteries and external jugular veins that was two to four times that of control values at 1 mmol/l and declined at higher H2O2 concentrations. Peak retention of PMNs by canine carotid arteries occurred 10 minutes after exposure to 1 mmol/l H2O2 and then rapidly declined to control values; this effect was replicated by a second 20-minute exposure of canine carotid arteries to 1 mmol/l H2O2 60 minutes after the first exposure. Scanning and transmission electron microscopy revealed not only adherence of PMNs to but migration through the vascular endothelium of the carotid artery after H2O2 perfusion. The endothelium was intact in H2O2-treated arteries not exposed to PMNs. H2O2-induced PMN retention was completely inhibited by addition of catalase or the hydroxyl radical scavenger dimethylthiourea to the perfusate by incubation of the PMN with a monoclonal antibody (Mab) against CD18 (R15.7) or by perfusion of the H2O2-treated vessel with CL18/6, a Mab against canine ICAM-1 (intercellular adhesion molecule-1). Similar effects of Mabs on PMN adhesion to H2O2-pretreated cultured endothelium were noted. The retention of PMNs by vessels mechanically denuded of endothelial cells was markedly increased. H2O2 pretreatment of these vessels did not further augment PMN adherence, and no inhibitory effect of R15.7 was noted. Incubation of carotid arteries and PMNs with a specific platelet-activating factor antagonist, WEB2086, completely inhibited the H2O2-induced increased PMN retention by these vessels. CONCLUSIONS: These results indicate that H2O2 in the absence of evidence for permanent endothelial cell injury, can induce a transient, reversible, platelet-activating factor-dependent adherence of PMNs to vessels by mechanisms that depend on an intact endothelium and involve CD18 on the PMN and ICAM-1 on the endothelium.

Animals↗
PubMed1990

Efficacy of transtelephonic electrocardiographic monitoring in pediatric patients.

The results of transtelephonic electrocardiography for transient symptomatic event recording in 61 consecutive pediatric patients (aged 4 months to 21 years) were reviewed. In 13 (21%) of 61 patients, previous arrhythmia diagnoses had been made by electrophysiologic study; monitoring was utilized to evaluate symptoms before or after pharmacological/surgical therapy. Transtelephonic electrocardiography was used to study undocumented symptomatic events consistent with an arrhythmia in the remaining 48 (79%) of 61 patients. Adequate transmissions during symptoms were obtained in 36 (59%) of 61 patients. Goals of monitoring were achieved in all 13 patients with previous diagnoses. Of the 25 of 48 patients without prior diagnoses who provided transmissions during symptoms, 15 had sinus rhythm, while 10 manifested an arrhythmia. Abnormal transmissions were most common in patients with palpitations and never evident in patients with symptoms of chest pain.

Adolescent↗
PubMed1990

Two structural states of the vertebrate Z band.

Ultrastructural analysis of the vertebrate Z band suggests that two reversible states of a single intricate lattice are essential for the contractile process. The two structural states of the Z band lattice (ss and bw) have been described in cross section in skeletal and cardiac muscle in different physiological states. The lattice responds to active tension but resists passive deformation. Changes in Z band form and dimension are correlated with cross-bridge binding. Two-dimensional image processing techniques show enhanced structural features that vary with the observed changes in lattice dimension. All projected images from all lattices show an approximate four-fold symmetry. Each image reveals differences in the appearance of axial filaments which enter from opposite sides of the Z band and cross-connecting filaments of similar curvature which appear to connect each axial filament to four nearest axial filaments. In the ss images, the apparent diameter of cross-cut axial filaments and the Z band interaxial filament spacing are smaller than in bw images. Cross-connecting filaments appear to overlap in the region half-way between axial filaments in ss images. We conclude that the Z band is an essential and dynamic part of the sarcomere, uniquely suited to transmit tension while maintaining dimensions appropriate for cross-bridge interaction.

Animals↗
PubMed1989

Two structural states of Z-bands in cardiac muscle.

We have compared the form and dimensions of the Z-band lattice in rat papillary muscle fixed at rest with and without ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) using electron microscopy and optical diffraction. In unstimulated muscle, the Z-band lattice form called basket weave predominated, and the Z-spacing (defined as the repeat distance of a tetragonal array of cross-cut thin filaments from the same sarcomere) was 23.93 +/- 0.37 nm. Muscles exposed to EGTA exhibited the small square-lattice form, and the Z-spacing was 20.50 +/- 0.19 nm. The Z-spacings in the two lattice forms were similar in cardiac and skeletal muscles such that the decrease in Z-spacing in the transition from basket weave to small square in this study was similar to the increase in Z-spacing previously demonstrated in skeletal muscle in the transition from small square to basket weave. The Z-lattice form and dimensions in unstimulated cardiac muscle resembled those in tetanized skeletal muscle. These findings are consistent with the higher resting tension in cardiac muscle and suggest that Ca2+ may be important for the maintenance of the expanded Z-lattice form.

Actin Cytoskeleton↗
PubMed1985

Cytochemical studies of a glycogen-sarcoplasmic reticulum complex.

Enzymatically active cardiac sarcoplasmic reticulum (SR) fractions contain glycogen. Previous biochemical and morphological studies indicate that the glycogen particles are membrane associated. In the present study, further evidence for membrane-associated glycogen particles in these cardiac SR fractions is presented: (1) morphological parameters, (2) enzymatic digestion by glucoamylase and alpha-amylase and (3) cytochemical staining by two different methods. Dense granules comparable in size (20-30 nm diameter), electron density and substructure to glycogen particles observed in intact cardiac muscle and in glycogen preparations isolated from skeletal muscle were seen. Most of these glycogen particles were removed by amylase digestion except for glycogen particles closely adhering to vesicle membranes. Two different cytochemical techniques (bismuth subnitrate and silver proteinate) revealed a positive reaction product over the glycogen particles. These findings provide further support for the biochemical finding of a structured enzyme complex involving the SR, glycogenolytic enzymes and glycogen.

Animals↗
PubMed1979

Microtubules in mammalian heart muscle.

Sections of adult mammalian cardiac muscles fixed at room temperature reveal numerous microtubules (24--28 nm in diameter) both near the nucleus and in the extra-myofibrillar space. Microtubules encircle the nucleus, are associated with the myofibrils in a helical arrangement, and form a network that runs transversely at the level of the I band and axially between the myofibrils. Microtubules are more numerous in muscle cells than previously recognized and may perform more than cytoskeletal function.

Animals↗
PubMed1979

The Z lattice in canine cardiac muscle.

Filtered images of mammalian cardiac Z bands were reconstructed from optical diffraction patterns from electron micrographs. Reconstructed images from longitudinal sections show connecting filaments at each 38-nm axial repeat in an array consistent with cross-sectional data. Some reconstructed images from cross sections indicate two distinctly different optical diffraction patterns, one for each of two lattice forms (basket weave and small square). Other images are more complex and exhibit composite diffraction patterns. Thus, the two lattice forms co-exist, interconvert, or represent two different aspects of the same details within the lattice. Two three-dimensional models of the Z lattice are presented. Both include the following features: a double array of axial filaments spaced at 24 nm, successive layers of tetragonally arrayed connecting filaments, projected fourfold symmetry in cross section, and layers of connecting filaments spaced at intervals of 38 nm along the myofibril axis. Projected views of the models are compared to electron micrographs and optically reconstructed images of the Z lattice in successively thicker cross sections. The entire Z band is rarely a uniform lattice regardless of plane of section or section thickness. Optical reconstructions strongly suggest two types of variation in the lattice substructure: (a) in the arrangement of connecting filaments, and (b) in the arrangement of units added side-to-side to make larger myofilament bundles and/or end-to-end to make wider Z bands. We conclude that the regular arrangement of axial and connecting filaments generates a dynamic Z lattice.

Animals↗
PubMed1978

Snake-to-human transmission of Aeromonas (Pl) shigelloides resulting in gastroenteritis.

A healthy young man developed acute gastroenteritis after handling an infected bao constrictor. The animal died after contracting "mouth-rot disease", a progressive ulcerative stomatitis of snakes charactistically caused a Aeromonas species. Stool cultures from the patient yielded a heavy growth of Aeromonas (Plesiomonas) shigelloides but no other enteric pathogens. Treatment wit sulfamethoxazole-trimethoprim resulted in rapid relief of clinical symptoms. Aeromonas species are not considered part of the normal human fecal flora and gastroenteritis due to this organism is rare. Furthermore, this case appears to represent a new zoonosis: human Aeromonas (Plasiomonas) gastroenteritis derived from contact with an infected animal host.

Acute Disease↗
PubMed1977

Alterations in cell free brain protein synthesis following ethanol withdrawal in physically dependent rats.

The effects of ethanol withdrawal were determined on cell free brain protein synthesis in physically dependent rats. Following the development of physical dependence, ethanol abstinence for 24 h resulted in decreased protein synthesis in cerebral tissue. The observed inhibition of [14C]leucine incorporation into protein was found to be reversible after 7 days of ethanol withdrawal. Although the ribosomes from control, ethanol-treated and ethanol-withdrawn animals were highly responsive to polyuridylic acid stimulation, the ribosomes from the control group consistently exhibited higher activity. The determination of protein content of the ribosomal fraction showed a significant increase following ethanol administration and was further enhanced by ethanol abstinence. The results suggest that ethanol-induced changes at the ribosomal level may result in defective association of mRNA causing depression of brain protein synthesis.

Alcoholism↗