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Biomedical subjects

H Gross

Publications and source records attributed to H Gross.

At least 19 recordsLinked to original sources
PubMed1992

Thermography.

Explore the source record for details and available documents.

Electromyography↗
PubMed1992

Scanning tunneling microscopy of biological macromolecular structures coated with a conducting film.

We have studied the capability of scanning tunneling microscopy (STM) to reveal the three-dimensional structure of biological macromolecular structures that have been rendered conductive by metal-coating. The sample preparation used has been derived from a well established method in transmission electron microscopy (TEM). It includes adsorption, freezing and dehydration by vacuum-sublimation, followed by metal-shadowing of the specimen. As an alternative to adsorption and coating, fluid biomaterials can be replaced by conductive freeze-fracture replica. We give an introduction into the sample preparation of metal-coated specimens and discuss how each step can affect the structural preservation and thereby the quality of the data. Some aspects of the data acquisition and the quantitative evaluation of STM data are shown. Possible contributions of STM in the biological macromolecular research are pointed out.

Animals↗
PubMed1991

Crystallization of mitochondrial creatine kinase. Growing of large protein crystals and electron microscopic investigation of microcrystals consisting of octamers.

Mitochondrial creatine kinase isolated from chicken cardiac muscle was crystallized by vapor diffusion techniques. Depending on the growth conditions, fine needles and platelets as well as large single crystals appeared after a few days. Large crystals were shown to diffract to at least 3.2 A resolution (Schnyder, T., Winkler, H., Gross, H., Sargent, D., Eppenberger, H. M., and Wallimann, T. (1990) Biophys J. 57, 420 and thus are suited for a detailed X-ray analysis in the future. The relatively high density of single crystals measured by a linear organic solvent density gradient indicates a tight packing of mitochondrial creatine kinase molecules within the crystals. Microcrystals, however, were subjected to electron optical examination either after prefixation with glutaraldehyde followed by conventional negative staining or by freeze-fracturing crystals in mother liquor and heavy metal replication with platinum/carbon. In both cases the crystals exhibited a square lattice with parameters of a = b = 139 A and a = b = 132 A in negatively stained and replicated crystals, respectively. No other lattice parameters were found, suggesting that these microcrystals represent a quasi-cubic three-dimensional lattice, which is in accordance with the finding that the building blocks of the crystals are the cube-like octamers described (Schnyder, T., Engel, A., Lustig, A., and Wallimann, T. (1988) J. Biol. Chem. 263, 16954-16962). Digital image processing applied to electron micrographs of crystals clearly revealed the arrangement of mitochondrial creatine kinase octamers in the crystal lattice as well as the subdivision of the octamer into its subdomains at a resolution of 23 A.

Animals↗
PubMed1991

Circular harmonic averaging of rotary-shadowed and negatively stained creatine kinase macromolecules.

The structure of mitochondrial creatine kinase is investigated by high-resolution shadowing at very low temperature and conventional negative staining. The electron microscopic images are analyzed with circular harmonic averaging, a method suited for the processing of single molecules. The rotational alignment and averaging is performed with the circular harmonic components, which allows data compression and several steps of noise reduction to be carried out within the averaging procedure. In addition, the symmetry can be deduced. For the mitochondrial creatine kinase, a fourfold symmetry is found that is compatible with the biochemical and biophysical characterization of the molecule.

Creatine Kinase↗
PubMed1991

Structure of the mitochondrial creatine kinase octamer: high-resolution shadowing and image averaging of single molecules and formation of linear filaments under specific staining conditions.

The combination of high-resolution tantalum/tungsten (Ta/W) shadowing at very low specimen temperature (-250 degrees C) under ultrahigh vacuum (less than 2 x 10(-9) mbar) with circular harmonic image averaging revealed details on the surface structure of mitochondrial creatine kinase (Mi-CK) molecules with a resolution less than 2.5 nm. Mi-CK octamers exhibit a cross-like surface depression dividing the square shaped projection of 10 x 10 nm into four equally sized subdomains, which correspond to the four dimers forming the octameric Mi-CK molecule. By a combination of positive staining (with uranyl acetate) and heavy metal shadowing, internal structures as well as the surface relief of Mi-CK were visualized at the same time at high resolution. Computational image analysis revealed only a single projection class of molecules, but the ability of Mi-CK to form linear filaments, as well as geometrical considerations concerning the formation of octamers by four equal, asymmetric dimers, suggest the existence of at least two distinct faces on the molecule. By image processing of Mi-CK filaments a side view of the octamer differing from the top-bottom projections of single molecules became evident showing a funnel-like access each form the top and bottom of the octamer connected by a central channel. The general structure of the Mi-CK octamer described here is relevant to the localization of the molecule at the inner-outer mitochondrial contact sites and to the function of Mi-CK as an "energy channeling" molecule.

Animals↗
PubMed1991

Platinum/iridium/carbon: a high-resolution shadowing material for TEM, STM and SEM of biological macromolecular structures.

Thin Pt/Ir/C coating films (1.5 nm) show a fine granularity and provide a high structural resolution in the transmission electron microscope (TEM) when applied to freeze-dried biological macromolecules. They keep their structure when exposed to atmospheric conditions, without the need of an additional stabilizing carbon layer, in contrast to conventional high-resolution shadowing materials such as Ta/W and Pt/C. However, the correct ratio of the components has turned out to be crucial. When evaporating Pt/Ir/C from the source electrode in an electron-beam-heated evaporator, the ratio of the three elements changes progressively, and, consequently, the properties of such films depend strongly on the mass that has been pre-evaporated. In this paper we present a quantitative analysis of the composition of Pt/Ir/C films by wavelength-dispersive X-ray analysis (WDX) undertaken in association with TEM experiments. We applied Pt/Ir/C shadowing to two regular biological test specimens, the phage T4 type III polyhead and the HPI-layer of Deinococcus radiodurans. It turns out that Pt/Ir/C films containing at least 25% C are three-dimensionally stable on the freeze-dried macromolecular samples. By the dramatically improved resolution power of the latest scanning electron microscopes (SEM) and the invention of the scanning tunnelling microscope (STM), two new surface-sensitive tools for the investigation of biological macromolecular structures became available. The Pt/Ir/C coating has proved to be well suited for STM and SEM imaging of freeze-dried biological structures because of its good electrical conductivity and its direct three-dimensional stability. We compare STM, SEM and TEM images of freeze-dried and Pt/Ir/C-coated polyheads.

Carbon↗
PubMed1989

Scanning tunneling microscopy of uncoated recA-DNA complexes.

Uncoated recA-DNA complexes were imaged with the scanning tunneling microscope (STM). The images, which reveal the right-handed helical structure of the complexes with subunits clearly resolved, are comparable in quality to STM images of metal-coated specimens. Possible conduction mechanisms that allow STM imaging of biological macromolecules are discussed.

Acetates↗
PubMed1989

Utilization and outcome in the medical patient referred to surgery.

The objective of this study was to test the hypothesis that hospitalized patients referred to a general surgical service from a medical service for a surgical procedure would have higher hospital costs and longer lengths of stay per diagnosis-related group (DRG) than patients admitted directly to the general surgical service. Hospital costs by DRG, exclusive of physician's fees, were analyzed for all adult general surgical admissions treated at our hospital from January 1, 1985 to March 31, 1986 (3,028 patients) to yield a population of patients in those DRGs with patients referred to general surgery from medicine (1,495 patients). Patients within each DRG were then disaggregated by either direct admission to general surgery (1,412 patients) or referral to the general surgical service from the medical service (83 patients). Mean cost per patient was 146.5 percent higher for referral patients than for direct admission patients, as was the total length of stay. Mortality was higher for referral patients than for direct admission patients. Factors analyzed which contributed to this greater resource utilization and higher mortality were (1) a greater severity of illness, (2) higher diagnostic costs, and (3) delays in diagnosis or treatment. The DRG payment for referral patients also produced a substantial deficit for the hospital, whereas direct admission patients produced a profit of +1,105,596. This data suggests that direct admission to the surgical service of patients likely to need surgery might lower their hospital costs and improve the quality of their care.

Diagnosis-Related Groups↗
PubMed1989

Socioeconomic concerns in vascular surgery: a survey of the role of age, resource consumption, and outcome in treatment cost.

Surgical hospital payment issues and socioeconomic concerns are likely to attract more attention in the future, especially regarding access and the quality of surgical care. We analyzed all peripheral vascular surgical admissions (n = 1240) by age treated at the Long Island Jewish Medical Center from 1985 to 1987. Hospital cost and length of stay per patient increased with age, as did losses under diagnostic related group (DRG) prospective hospital payment. Hospital cost by hospital service showed considerable variation by age category; outliers, mortality, and the number of diagnoses and procedures generally rose with age. Use of hospital resources, such as emergency or surgical intensive care unit admission, or the need for blood or plasma products was high in general for patients undergoing peripheral vascular surgery. This study demonstrates a number of findings regarding the socioeconomic factors for hospitalized patients undergoing peripheral vascular surgery. Surgical health policy analysis of this specialty vis-a-vis current changes proposed to the federal medicare DRG system in the U.S. Congress and Health Care Financing Administration suggests a relatively greater impact on the specialty of peripheral vascular surgery demonstrated in this study by the use of higher resources of the same.

Adolescent↗
PubMed1989

[Difficult intubation and anesthesia in Pfaundler-Hurler disease].

Because of increasing dyspnea, adenoidectomy and tonsillectomy were indicated in a 6-year-old girl with Pfaundler-Hurler disease. The main symptoms were cardiac insufficiency and chronic bronchitis. Because of the large skull with hypoplastic cervical spine, anomalies of facial bones, larynx and jawbone normal intubation was impossible. We therefore performed intubation during spontaneous breathing under inhalation anesthesia and topical anesthesia of the larynx. After exploratory laryngoscopy a preformed Woodbridge tube was inserted into the trachea blind and by ear during of inspiration. The patient's cardiac insufficiency and chronic bronchitis made a balanced anesthesia with reduced dosage of rapifen and halothane necessary. In spite of the poor general prognosis, after the operation a considerable relief of the patient's suffering was noted, because she was able to breathe freely.

Adjuvants, Anesthesia↗
PubMed1988

Scanning tunneling microscopy of recA-DNA complexes coated with a conducting film.

A link between scanning tunneling microscopy (STM) and conventional transmission electron microscopy has been established for biological material by applying STM on freeze-dried recA-DNA complexes coated with a conducting film. The topography of the complexes observed by means of STM revealed a right-handed single helix composed of about six recA monomers per helical turn.

DNA↗
PubMed1988

Diagnosis related groups and the transfer of general surgical patients between hospitals.

This study tested the hypothesis that financial risk would be generated by surgical patients transferred to our hospital from other acute care hospitals under diagnosis related group (DRG) reimbursement. Hospital costs by DRG (exclusive of physician fees) were analyzed for all adult general surgical patients transferred to our medical center from another acute care hospital between Jan 1, 1985, and Dec 31, 1986. Transferred patients (n = 97) had significantly higher resource utilization (ie, hospital costs) than nontransferred patients (n = 2976) within the same surgical DRGs as follows: total mean cost per patient, $17,348 vs $9,460; mean length of stay 21.4 days vs 10.9 days; mean laboratory cost per patient, $1849 vs $975; and mean radiologic cost per patient, $794 vs $397. Transferred patients generated a yearly deficit of $238,717 ($4922 loss per patient) for the hospital, whereas other patients within the same DRGs generated a profit of $727,632 ($489 profit per patient). These data support the hypothesis that DRG reimbursement will provide a financial disincentive for teaching hospitals to accept surgical transfer patients from other acute care hospitals, thus potentially decreasing the access of care for the complexly ill surgical patient.

Academic Medical Centers↗