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Biomedical subjects

H Gross

Publications and source records attributed to H Gross.

At least 19 recordsLinked to original sources
PubMed2006

Significant changes in physical activity among pregnant women in the UK as assessed by accelerometry and self-reported activity.

OBJECTIVE: Research on the impact of maternal physical activity on pregnancy outcomes has often employed subjective measures of physical activity obtained by diary or questionnaire. This study investigates the feasibility of using accelerometry as an objective measure of physical activity of pregnant women compared with subjective data obtained via activity recall among pregnant women. DESIGN: Activity data were collected prospectively on 57 women at 12, 16, 25, 34 and 38 weeks of gestation. Total daily physical activity was assessed by ambulatory accelerometer and activity interview (self-report). Maternal personality variables (health value, extroversion) were assessed by established scales. SETTING: Leicestershire, UK. SUBJECTS: Pregnant women were recruited by voluntary participation via antenatal booking clinics. In all, 64 pregnant women with low-risk pregnancy were enrolled onto the study, of whom 57 completed the study. RESULTS: Mean 24 h physical activity levels (PAL) decreased significantly from second to third trimester as assessed by self-report interview (1.51-1.29 Metabolic Equivalent TEE-h/day, P<0.01) and accelerometry (200.05-147.42 counts/min, P<0.01). The correlation between the two measures declined as pregnancy progressed (r value ranging from 0.55 to 0.08). Compliance with the accelerometers declined from 90% at 12 weeks to 47% at 34 weeks (P<0.01). Compliance with the self-report interviews was 100%. Those who fully complied with the accelerometry demonstrated a significantly higher health value (P<0.05) and a significantly greater level of extroversion (P<0.05) than those who did not. CONCLUSIONS: Accelerometers and self-reported activity interviews both indicated a significant decline in PAL during pregnancy. Although subjects showed a willingness to use both methods, accelerometers resulted in variable compliance with 72 h monitoring. Both techniques may be limited by the need to measure low levels of physical activity during the third trimester. SPONSORSHIP: Cambridge Neurotechnology Ltd, UK, assisted with the provision of Actiwatch accelerometers.

Adult↗
PubMed2002

[Coronary interventions in old patients presenting with cardiogenic shock].

HISTORY AND CLINICAL FINDINGS: A 80-year-old unconscious woman was admitted to our hospital. She had suffered from angina pectoris and progressive dyspnea for three days. She had been in pulmonary edema 6 months ago. Clinical examination revealed low blood pressure of 90/60 mmHg, central cyanosis and signs of pulmonary congestion. INVESTIGATIONS: Laboratory findings comprised elevated creatinkinase, troponin and lactate dehydrogenase as well as reduced sodium. CLINICAL COURSE: After intubation and mechanical ventilation the patient underwent cardiac catheterization because of the cardiogenic shock. Coronary angiography revealed severe coronary artery disease with high grade stenoses of the right coronary artery and of the main stem of the left coronary artery. After initiating intraaortic balloon counterpulsation, transcatheter revascularization of the right and left coronary artery was performed, leading to an improvement of the systolic left ventricular function. But the patient finally died due to cardiac pump failure. CONCLUSION: Elderly patients presenting with cardiogenic shock and additional risk factors have the highest mortality. Thus the decision for cardiac catheterization and eventual intervention should be made on a case-by-case basis. Successful angioplasty may reduce mortality by approximately 20 %. Due to the usually severe comorbidity absolute mortality is nevertheless very high.

Aged↗
PubMed2001

Triplex forming oligonucleotide targeted to 3'UTR downregulates the expression of the bcl-2 proto-oncogene in HeLa cells.

The bcl-2 proto-oncogene is overexpressed in a variety of human cancers and plays an important role in programmed cell death. Recent reports implied that the 3'-untranslated region (3'UTR) functions effectively in the regulation of gene expression. Here, we attempt to assay the ability of triplex forming oligonucleotides (TFOs) to inhibit expression of a target gene in vivo and to examine the potential of the 3'UTR of the bcl-2 proto-oncogene in the regulation of bcl-2 gene expression. To do this, we have developed a novel cellular system that involves transfection of a Doxycyclin inducible expression plasmid containing the bcl-2 ORF and the 3'UTR together with a TFO targeted to the 3'UTR of the bcl-2 proto-oncogene. Phosphorothioate-modified TFO targeted to the 3'UTR of the bcl-2 gene significantly downregulated the expression of the bcl-2 gene in HeLa cells as demonstrated by western blotting. Our results indicate that blocking the functions of the 3'UTR using the TFO can downregulate the expression of the targeted gene, and suggest that triplex strategy is a promising approach for oligonucleotide-based gene therapy. In addition, triplex-based sequence targeting may provide a useful tool for studying the regulation of gene expression.

3' Untranslated Regions↗
PubMed2001

Correlation of topographic surface and volume data from three-dimensional electron microscopy.

Three-dimensional(3D) reconstructions from tilt series in an electron microscope show in general an anisotropic resolution due to an instrumentally limited tilt angle. As a consequence, the information in the z direction is blurred, thus making it difficult to detect the boundary of the reconstructed structures. In contrast, high-resolution topography data from microscopic surface techniques provide exactly complementary information. The combination of topographic surface and volume data leads to a better understanding of the 3D structure. The new correlation procedure presented determines both the height scaling of the topographic surface and the relative position of surface and volume data, thus allowing information to be combined. Experimental data for crystalline T4 bacteriophage polyheads were used to test the new method. Three-dimensional volume data were reconstructed from a negatively stained tilt series. Topographic data for both surfaces were obtained by surface relief reconstruction of electron micrographs of freeze-dried and unidirectionally metal-shadowed polyheads. The combined visualization of volume data with the scaled and aligned surface data shows that the correlation technique yields meaningful results. The reported correlation method may be applied to surface data obtained by any microscopic technique yielding topographic data.

Algorithms↗
PubMed2000

The aquaporin sidedness revisited.

Aquaporins are transmembrane water channel proteins, which play important functions in the osmoregulation and water balance of micro-organisms, plants, and animal tissues. All aquaporins studied to date are thought to be tetrameric assemblies of four subunits each containing its own aqueous pore. Moreover, the subunits contain an internal sequence repeat forming two obversely symmetric hemichannels predicted to resemble an hour-glass. This unique arrangement of two highly related protein domains oriented at 180 degrees to each other poses a significant challenge in the determination of sidedness. Aquaporin Z (AqpZ) from Escherichia coli was reconstituted into highly ordered two-dimensional crystals. They were freeze-dried and metal-shadowed to establish the relationship between surface structure and underlying protein density by electron microscopy. The shadowing of some surfaces was prevented by protruding aggregates. Thus, images collected from freeze-dried crystals that exhibited both metal-coated and uncoated regions allowed surface relief reconstructions and projection maps to be obtained from the same crystal. Cross-correlation peak searches along lattices crossing metal-coated and uncoated regions allowed an unambiguous alignment of the surface reliefs to the underlying density maps. AqpZ topographs previously determined by AFM could then be aligned with projection maps of AqpZ, and finally with human erythrocyte aquaporin-1 (AQP1). Thereby features of the AqpZ topography could be interpreted by direct comparison to the 6 A three-dimensional structure of AQP1. We conclude that the sidedness we originally proposed for aquaporin density maps was inverted.

Aquaporin 1↗
PubMed2000

Rotary and unidirectional metal shadowing of VAT: localization of the substrate-binding domain.

AAA-ATPases have important roles in manifold cellular processes. VAT (valosine-containing protein-like ATPase of Thermoplasma acidophilum), a hexameric archaeal member of this family, has the tripartite domain structure N-D1-D2 that is characteristic of many members of this family. N, the N-terminal domain of 20.5 kDa, has been implicated in substrate binding. We have applied rotary and unidirectional shadowing to VAT and an N-terminally deleted mutant, VAT(Delta N), in order to map the location of this domain. For the analysis of data derived from unidirectionally shadowed samples we used a new approach combining eigenvector analysis with surface relief reconstruction. Averages of rotary shadowed particles as well as relief reconstructions map the N-terminal domains to the periphery of the hexameric complex and reveal their bipartite structure. Thus, this method appears to be well suited to study the conformational changes that occur during the functional cycle of the protein.

Adenosine Triphosphatases↗
PubMed2000

Molecular events that contribute to lysyl oxidase enzyme activity and insoluble collagen accumulation in osteosarcoma cell clones.

Maximum collagen synthesis and maximum accumulation of insoluble collagen occur at different phenotypic stages in developing osteoblastic cell cultures. Insoluble collagen accumulation depends in part on the activity of extracellular enzymes including procollagen N-proteinases, procollagen C-proteinase (derived from the BMP1 gene), and lysyl oxidase. In addition to its action on procollagen, procollagen C-proteinase processes prolysyl oxidase to mature 32-kDa lysyl oxidase. The regulation of extracellular activities that control insoluble collagen accumulation has not been studied extensively. The present study compares molecular events that control production of a collagenous mineralized extracellular matrix in vitro among five different murine osteosarcoma cell clones derived from the same tumor, but which differ in their ability to produce an insoluble mineralized matrix. Levels of insoluble type I collagen, insoluble calcium, bone morphogenetic protein 1 (BMP-1), and lysyl oxidase expression, lysyl oxidase biosynthesis, lysyl oxidase activity, and prolysyl oxidase processing activity were determined. Results surprisingly indicate that lysyl oxidase activity is not related closely to lysyl oxidase messenger RNA (mRNA) levels among the different cell clones. However, it appears that BMP-1-dependent prolysyl oxidase processing could contribute to the observed lysyl oxidase activity. Highest collagen and BMP-1 mRNA levels, prolysyl oxidase processing activity, and lysyl oxidase activity occurred in a cell clone (K8) that showed the highest levels of insoluble collagen accumulation. Culture media from a cell clone (K37) that accumulates little insoluble collagen or calcium but expresses high levels of lysyl oxidase mRNA contained low molecular weight fragments of lysyl oxidase protein and showed low lysyl oxidase activity. By contrast the K14 cell line exhibits relatively high lysyl oxidase activity and collagen accumulation, but low levels of mature lysyl oxidase protein. Together, these studies indicate that catabolic as well as anabolic activities are important in regulating insoluble collagen accumulation in osteoblastic cells. In addition, results suggest that products of genes homologous to lysyl oxidase may contribute to observed lysyl oxidase activity.

Animals↗
PubMed1999

Crystallization of the human, mitochondrial voltage-dependent anion-selective channel in the presence of phospholipids.

Overexpressed human voltage-dependent anion-selective channel VDAC or porin from mitochondrial outer membranes has been purified to homogeneity. Electron microscopic analysis of VDAC in detergent solution revealed a uniform particle population consisting of porin monomers. After dialysis of detergent-solubilized porin in the presence of dimyristoylphosphatidylcholine at lipid-to-protein ratios between 0.2 and 0.5 (percentage by weight), mostly multilamellar crystals were obtained. Crystals adsorbed to carbon films flattened during negative staining and air-drying and exhibited different structural features due to differences in the vertical stacking of several crystalline layers, each consisting of one membrane bilayer. Adsorbed, frozen-hydrated multilamellar membrane crystals revealed uniform diffraction patterns with sharp diffraction spots extending to 8.2 A. The surface structure of VDAC was reconstructed from freeze-dried and unidirectionally metal-shadowed crystals. Major protein protrusions were observed from two VDAC monomers present in the unit cell. Differences in the surface structural features indicate alternate orientations of VDAC molecules with respect to the lipid bilayer, allowing the simultaneous imaging of both the cytosolic and intramitochondrial surfaces. Each VDAC molecule consists of a pore lumen with a diameter of 17-20 A surrounded by a protein rim of nonuniform height, suggesting an asymmetrical distribution of protein mass around the diffusion channels.

Amino Acid Sequence↗
PubMed1998

Purified lens major intrinsic protein (MIP) forms highly ordered tetragonal two-dimensional arrays by reconstitution.

Lens major intrinsic protein (MIP) is the founding member of the MIP family of membrane channel proteins. Its isolation from ovine lens fibre cell membranes and its two-dimensional crystallization are described. Membranes were solubilized with N-octyl-beta-D-glucoside and proteins fractionated by sucrose gradient centrifugation containing decyl-beta-D-maltoside. MIP was purified by cation exchange chromatography, and homogeneity was assessed by mass analysis in the scanning transmission electron microscope. Purified MIP reconstituted into a lipid bilayer at a low lipid-to-protein ratio formed highly ordered tetragonal two-dimensional crystals. The square unit cell had a side length of 6.4 nm, and exhibited in negative stain four stain-excluding elongated domains surrounding a central stain-filled depression. Projection maps of freeze-dried crystals exhibited a resolution of 9 A, and revealed a monomer structure of MIP consisting of distinct densities. Despite significant differences in the packing of tetramers in the crystals, the projection map of the MIP monomer was similar to that of aquaporin-1 (AQP1), the first member of the MIP family which had its structure resolved to 6 A. Our protocols for the purification and reconstitution of MIP establish the feasibility for future work to visualize structure elements which determine the diverse functional properties of the MIP family members.

Animals↗
PubMed1998

An atomic model of crystalline actin tubes: combining electron microscopy with X-ray crystallography.

The packing of the G-actin monomers within crystalline actin tubes was investigated at atomic detail. To achieve this, we have chosen an integrated structural approach which combines intermediate resolution electron microscopy based 3-D reconstruction and surface metal shadowing of crystalline actin tubes with atomic resolution X-ray data of the G-actin monomer. Distinct from the parallel, half-staggered packing of the actin subunits within F-actin filaments, the arrangement of actin monomers within the crystalline tubes involves antiparallel packing into dimers with p2 symmetry. Within the crystalline tubes, the actin monomers are oriented so that the filament axis runs parallel with the sheet plane and the intersubunit contacts in this direction are similar to those existing along the two long-pitch helical strands of the F-actin filament. The other intersubunit contacts within the crystalline tubes are not found in the actin filament. The ability of actin to form a variety of polymorphic oligomers is still not fully understood, and the functional implications of this variability have yet to be deciphered. Regularly packed actin assemblies such as sheets, tubes or ribbons may ultimately yield structural relationships to in vivo relevant actin oligomers such as, for example, the "lower dimer".

Actins↗
PubMed1998

Image reconstructions of microtubules decorated with monomeric and dimeric kinesins: comparison with x-ray structure and implications for motility.

We have decorated microtubules with monomeric and dimeric kinesin constructs, studied their structure by cryoelectron microscopy and three-dimensional image reconstruction, and compared the results with the x-ray crystal structure of monomeric and dimeric kinesin. A monomeric kinesin construct (rK354, containing only a short neck helix insufficient for coiled-coil formation) decorates microtubules with a stoichiometry of one kinesin head per tubulin subunit (alpha-beta-heterodimer). The orientation of the kinesin head (an anterograde motor) on the microtubule surface is similar to that of ncd (a retrograde motor). A longer kinesin construct (rK379) forms a dimer because of the longer neck helix forming a coiled-coil. Unexpectedly, this construct also decorates the microtubule with a stoichiometry of one head per tubulin subunit, and the orientation is similar to that of the monomeric construct. This means that the interaction with microtubules causes the two heads of a kinesin dimer to separate sufficiently so that they can bind to two different tubulin subunits. This result is in contrast to recent models and can be explained by assuming that the tubulin-kinesin interaction is antagonistic to the coiled-coil interaction within a kinesin dimer.

Animals↗
PubMed1998

Surface analysis of the photosystem I complex by electron and atomic force microscopy.

Two-dimensional (2D) crystals of the photosystem I (PSI) reaction center from Synechococcus sp. OD24 were analyzed by electron and atomic force microscopy. Surface relief reconstructions from electron micrographs of freeze-dried unidirectionally shadowed samples and topographs recorded with the atomic force microscope (AFM) provided a precise definition of the lumenal and stromal PSI surfaces. The lumenal surface was composed of four protrusions that surrounded an indentation. One of the protrusions, the PsaF subunit, was often missing. Removal of the extrinsic proteins with the AFM stylus exposed the stromal side of the PSI core, whose surface structure could then be imaged at a resolution better than 1.4 nm. This interfacial surface between core and extrinsic subunits, had a pseudo-2-fold symmetry and protrusions that correlated with the surface helices e and e' or were at the sites of putative alpha-helix-connecting loops estimated from the 4 A map of the complex. The molecular dissection achieved with the AFM, opens new possibilities to unveil the interfaces between subunits of supramolecular assemblies.

Amino Acid Sequence↗
PubMed1998

Identification, culture, and characterization of pancreatic stellate cells in rats and humans.

BACKGROUND & AIMS: Until now, the basic matrix-producing cell type responsible for pancreas fibrosis has not been identified. In this report, retinoid-containing pancreatic stellate cells (PSCs) in rat and human pancreas are described, and morphological and biochemical similarities to hepatic stellate cells are shown. METHODS: Electron and immunofluorescence microscopy (collagen types I and III, fibronectin, laminin, alpha-actin, and desmin) was performed using pancreatic tissue and cultured PSCs. Extracellular matrix synthesis was shown using quantitative immunoassay and Northern blot analysis. RESULTS: PSCs are located in interlobular areas and in interacinar regions. Early primary cultured PSCs contain retinol and fatty acid retinyl-esters. Addition of retinol to passaged cells resulted in retinol uptake and esterification. During primary culture, the cells changed from a quiescent fat-storing phenotype to a highly synthetic myofibroblast-like cell expressing iso-alpha-smooth muscle actin (>90%) and desmin (20%-40%) and showing strong positive staining with antibodies to collagen types I and III, fibronectin, and laminin. As determined on protein and messenger RNA level, serum growth factors stimulated the synthesis of collagen type I and fibronectin. CONCLUSIONS: The identification of PSCs, particularly in fibrotic areas, and the similarities of these cells to hepatic stellate cells suggest that PSCs participate in the development of pancreas fibrosis.

Animals↗