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Biomedical subjects

R Haas

Publications and source records attributed to R Haas.

At least 343 records · Page 19Linked to original sources
PubMed1983

Improved preparation of lipoteichoic acids.

A procedure is described for measuring the extraction of lipoteichoic acids from gram-positive bacteria in absolute terms. Virtually complete extraction was achieved from various bacteria by hot phenol/water if the cells were disrupted. Extraction of whole and delipidated cells and of the membrane fraction gave considerably lower yields. Most of the nucleic acids co-extracted from disrupted cells was removed by treatment with nucleases. Nuclease-resistant nucleic acid, protein, polysaccharide, and teichoic acid were separated from lipoteichoic acid by anionexchange chromatography on DEAE-Sephacel or hydrophobic interaction chromatography on octyl-Sepharose. Purified preparations were essentially free of polymeric contaminants, retained their alanine ester substitution, and were in the sodium salt form. Hydrophobic interaction chromatography also made it possible to recognize contamination of lipoteichoic acid with its deacylated and lyso-form, and to discriminate molecular species containing two and three, or two and four acyl groups.

Acetylation↗
PubMed1983

Plasma hypercoagulability after termination of oral anticoagulants.

The effect of discontinuation of a long term oral anticoagulant therapy with phenprocoumon on blood clotting parameters has been evaluated in patients in a controlled prospective trial. After termination of phenprocoumon the prothrombin time normalized within 15 days and the thrombotest coagulation value within 57 days. Fibrinopeptide A (FPA) increased significantly during the observation period. FPA release in vitro also rose after discontinuation of anticoagulants. In control patients on a phenprocoumon maintenance therapy no alterations of the above mentioned parameters occurred within the same period. The data indicate that plasma hypercoagulability is found in many patients, orally anticoagulated because of myocardial infarction, when the anticoagulant therapy is discontinued.

4-Hydroxycoumarins↗
PubMed1983

Translation of satellite tobacco necrosis virus RNA modified by (not equal to)-r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene is inhibited in a wheat germ cell-free system.

It has been shown that (not equal to)-r-7-,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) modification of rabbit globin mRNA results in inhibition of translational initiation. In order to explore the possibility that modification of the 5' cap structure was responsible for this inhibition, the naturally non-capped mRNA from satellite tobacco necrosis virus (STNV) was reacted with BPDE and translated in a wheat germ cell-free system. The extent of modification was 1.3 and 2.9 BPDE residues/molecule. High performance liquid chromatography of the modified nucleosides from enzymatically hydrolyzed STNV RNA revealed that greater than 90% of the nucleoside adducts were substituted at the exocyclic amino group of guanosine. The translational ability of the lower and higher modified STNV, measured by incorporation of [14C]amino acids into acid-precipitable polypeptides is inhibited by 55% and 63%, respectively. Polyacrylamide gel electrophoretic analyses of the translation products indicate that predominantly full-length coat proteins are synthesized but with the carcinogen-modified STNV the amount is reduced. On the other hand, 80S initiation complex formation is not inhibited as measured by binding of the BPDE-modified STNV to ribosomes and followed by glycerol gradient centrifugation. Under these conditions, aurintricarboxylic acid completely inhibits 80S initiation complex formation in the presence of either modified or native STNV. These results suggest that inhibition of in vitro translation of BPDE-modified STNV, in contrast to that of globin mRNA, is not at the level of initiation complex formation but possibly by premature termination of growing polypeptides.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1983

Effects of octanoate on rat brain and liver mitochondria.

Octanoate increased state 3 and state 4 respiration in rat liver mitochondria. The respiratory control rates decreased because state 4 was disproportionately affected. The ADP:O ratio was not affected. Octanoate produced a fall in the protonmotive force (delta p) of 30 mV during state 3 and state 4. The mitochondrial inner membrane proton conductance (Cm,H+) increased twofold during state 4. Similar effects were observed in polarographic assays of brain mitochondria, but measurements of delta p and Cm,H+ were not possible. Octanoate produces loose coupling in isolated mitochondria. This effect may play a role in the pathogenesis of Reye's syndrome.

Adenosine Diphosphate↗
PubMed1982

Brain stem gliomas: an autopsy study of 25 cases.

The study analyzed the extent of tumor at autopsy in 25 patients with a brainstem glioma. Primary tumor in the pons comprised the majority of cases, followed by medulla and midbrain. Histologically, 48% of the tumors were glioblastoma multiforme. The tumor spread was found to be dependent on the site of origin and the grade. Pontine tumors involved the adjacent structures more extensively than the tumors of midbrain and medulla. Contiguous cephalad and caudad involvement was frequent with Grade III and Grade IV tumors. The extent of meningeal involvement was limited to those surrounding the main tumor mass. It is concluded that in the treatment of brainstem gliomas, irradiation through fields limited to the brainstem, adjoining temporal lobes, cerebellum, and proximal spinal cord would be adequate.

Adolescent↗
PubMed1982

Radiation therapy for subclinical carcinoma in cervical lymph nodes.

Radiotherapy alone was used to treat 187 patients with a head and neck cancer and clinically uninvolved lymph nodes. Delayed lymph node metastases developed in 35 (19%) patients, and concomitant tumor at the primary site was present in 90% of them. In two (1%) of the 187 patients, delayed metastases developed in the irradiated nodes with the primary tumor controlled; both of these patients received a radiation dose of less than 5,000 rad. Metastases in supraclavicular and posterior cervical regions occurred in 4% of the patients; and these sites were not included in the original radiation fields. The following conclusions were reached: (1) a radiation dose of 5,000 rad or more can eradicate 99% of the subclinical carcinomas in lymph nodes; (2) whole-neck irradiation is not indicated in patients with N0 stage tumor; and (3) surgical resection of primary tumors alone, without added neck dissection, may be adequate if postoperative radiation therapy is planned.

Carcinoma, Squamous Cell↗
PubMed1982

Properties and fate of plasma fibronectin bound to the tissue culture substratum.

Plasma fibronectin (pFn) is a serum protein which, when adsorbed to a glass or plastic substratum, mediates the adhesion of fibroblasts in culture. We have studied some of the details of its adsorption and subsequent fate. By using 125I-labeled pFn, we show that a substratum incubated with pFn adsorbs approximately 0.4 microgram/cm2 pFn (a monomolecular layer), and one incubated with medium containing serum adsorbs approximately 7 ng/cm2 pFn (a 12-fold enrichment relative to a random selection of the soluble proteins). SDS-polyacrylamide gel electrophoresis (SDS-PAGE) suggests the bound serum proteins (eluted with SDS) are primarily BSA and beta-globulins. The bound pFn adheres so tightly, though, that most resists elution, as assayed 1) with pFn radioiodinated before binding, 2) with pFn radioiodinated after binding, or 3) by the cell spreading activity of the bound pFn retained after SDS treatment. Under culture conditions, there is a continuous "turnover" of substratum-bound pFn: soluble pFn can bind to a serum-coated substratum, while bound pFn is gradually removed by incubation with serum proteins. The presence of fibroblasts increases the rate of this removal several-fold. By SDS-PAGE the material removed (as well as that eluted from the substratum with SDS after cell detachment) is intact pFn or large (possibly proteolytically generated) fragments. Thus, pFn binds preferentially to the tissue culture substratum, but can be removed subsequently by the combined action of cells and other serum proteins.

Adsorption↗
PubMed1982

Protonmotive force in muscle mitochondria.

The protonmotive force (delta p) of muscle mitochondria was measured by estimating the distribution of 14C-labeled TPMP (trimethylphenylphosphonium iodide) and 14C-labeled acetate across the inner membrane of muscle mitochondria. The matrix volume was simultaneously determined using 3H-labeled H2O and 3H-labeled mannitol and repeated drying to distinguish the label in these 2 compounds. Rapid separation of mitochondria from the incubation medium by centrifugation through silicone oil avoids the problems of potential anaerobic conditions associated with conventional centrifugation and large volumes of trapped media associated with filtration. The value for delta p (mean +/- SD) was 192+/- 26 mV in 30 determinations with rat muscle mitochondria during state 4. Measurement of oxygen consumption allowed calculation of membrane conductance (Cm,H+) which was 0.49 +/- 0.18 nmol of H+/min/mg protein/mV. The values for delta p and Cm,H+ are reported for a variety of experimental conditions and are consistent with Mitchell's chemiosmotic theory. Biopsy specimens obtained from human muscle gave state-4 delta p values of 197+/- 30 mV (n =5) and Cm,H+ values of 0.52 +/- 0.12 nmol of H+/min/mg/mV (n = 4). This delta p assay is the first described for coupled mammalian muscle mitochondria and will be useful in assessing membrane function.

Animals↗