Search PubMed⌕ Search

Biomedical subjects

R Keller

Publications and source records attributed to R Keller.

At least 289 records · Page 16Linked to original sources
PubMed1984

Antibody-free target cells stimulate chemiluminescence in polymorphonuclear leukocytes: an artifact due to mycoplasma contamination.

The generation of toxic oxygen species represents a significant mechanism in the killing of microorganisms and antibody-coated cells by phagocytic cells. We have investigated the possibility that antibody-free target cells stimulate reactive oxygen generation in polymorphonuclear leukocytes (PMNL) using the measurement of luminol-dependent chemiluminescence (CL). It was found that the induction of CL consistently correlated with a mycoplasma contamination of the target cells. Free mycoplasma organisms of two species found frequently as contaminants in cell culture also stimulated CL. Upon artificial infection with mycoplasma, cultured cells acquired the capacity to evoke CL generation in PMNL. Our experiments strongly suggest that the induction of reactive oxygen generation by antibody-free target cells is an artifact due to mycoplasma contamination of the target cell cultures.

Animals↗
PubMed1984

Natural cytotoxicity in lymphatic metastasis. I. In vitro studies using the rat tumor BSp73 and its variants.

Serial transplantation of primary BSp73 ascites cells to a subcutaneous (SC) site gave rise to the appearance of two solid variants differing in their capacity to metastasize via the lymphatics. Tissue cultures derived from variant AS (nonmetastasizing) showed epithelioid morphology, while cultures derived from variant ASML (metastatic) showed spherical morphology. Upon cloning, both variants proved to be operationally homogeneous. Susceptibility of cultured BSp73 cells to NK and macrophage-mediated cytotoxicity was closely correlated to morphology, inasmuch as epithelioid cells were susceptible, while spherical cells were resistant, to lysis. With stimulated effector cells a general increase in cytotoxicity was observed, but epithelioid cells still showed a higher susceptibility level. Resistance of ASML-type cells to natural cytotoxicity was not due to the lack of recognition structures or to a general increase in the mechanical stability of spherical cells. This was concluded from cold target inhibition and from hypotonic shock treatment experiments, respectively.

Animals↗
PubMed1984

The hyperglycemic neuropeptide of the terrestrial isopod, Porcellio dilatatus. I. Isolation and characterization.

From isolated sinus glands of Porcellio dilatatus, a hyperglycemic neuropeptide (CHH) was purified by means of a single, two-step purification procedure which consisted of gel chromatography on Sephadex G-50, followed by high-performance liquid chromatography. The 5800- to 6100-Da peptide contains 50-52 amino acids residues. The amino acid composition is (Pro, Ile)1; His1-2; (Thr, Ser, Gly, Met, Tyr)2; (Val, Phe, Lys)3; (Ala, 1/2Cys, Leu, Arg)4; Glx5; Asx7; Trp, n.d. The amino acid composition differs from that of two decapod CHHs analyzed thus far. The N-terminus is blocked. The neuropeptide exhibits little or no interspecific hyperglycemic effect in the brachyuran, Uca pugilator, and its cross-reactivity and potency in the RIA for Carcinus-CHH is very low.

Amino Acids↗
PubMed1984

The hyperglycemic neuropeptide of the terrestrial isopod, Porcellio dilatatus. II. Immunocytochemical demonstration in neurosecretory structures of the nervous system.

By use of an rabbit antiserum raised against the crustacean hyperglycemic hormone (CHH) of the shore crab, Carcinus maenas, CHH-producing perikarya were detected in the brain of the isopod, Porcellio dilatatus, by the double-antibody immunofluorescence technique. The course of the secretory axons to the neurohemal organ, the sinus gland, could be traced. The sinus gland also exhibited strong fluorescence. The reaction was very specific, no other structures gave appreciable immunofluorescence. There are two CHH cells in each hemisphere of the brain, located in the medio-rostral part of the protocerebrum. This area appears to correspond to the medulla terminalis of decapods. The cells are aldehyde fuchsin-positive and have been previously described as beta 1 cells. The immunofluorescence could be inhibited by preabsorption of the antiserum with pure Carcinus-CHH.

Animals↗
PubMed1984

Accuracy of single- and two-feed test weighing in assessing 24 h breast milk production.

The breast milk intake at a single feed (one-feed method) or the mean intake at two feeds (two-feed method) multiplied by the number of feeds per day was compared with the results of test weighing at every feed during a 24 h period. Six subjects were followed longitudinally from days 1-9 and 21-56 postpartum and the data analyzed by linear regression. There was a reasonable relationship between the mean values for milk intake obtained from the one- and two-feed methods and the 24 h test weights between days 3 and 9 of lactation. However, there was no relationship in full lactation (days 21-56). During both time periods, individual values for the one- and two-feed methods were associated with a large unsystematic error. The one- and two-feed methods may be useful only in situations where mean milk intake for a large population is desired and 24 h test weighing is not possible.

Adult↗
PubMed1984

Cathepsin B-like proteinase as a marker for metastatic tumor cell variants.

Serial transplantation of a spontaneous BDX rat tumor, classified as an anaplastic sarcoma, gives rise to two variants; a rapidly growing nonmetastatic line (AS) and a slowly growing, invasive, and highly metastatic variant (ASML). The availability of two cell lines of the same origin but with markedly differing metastatic potential offers an ideal model for the identification of the cellular properties involved in invasive and/or metastatic behavior. The present work focuses on the pattern of various proteinases in the two tumor cell variants. The findings disclosed one major consistent difference which relates to a cathepsin B-like cysteine proteinase. The metastatic ASML variant manifests exceedingly high intracellular cathepsin B-like activity; in the nonmetastatic AS variant, the activity of this proteinase is significantly lower. Other proteinases, in particular elastase-like, chymotrypsin-like, collagenase-like enzymes and plasminogen activator, showed low, essentially comparable activity patterns. Thus, cathepsin B-like proteinase is a marker enzyme of the metastatic ASML tumor cell variant.

Animals↗
PubMed1984

Oxygen affinity of erythrocytes and pulmonary gas exchange in patients on continuous ambulatory peritoneal dialysis.

In 11 patients on continuous ambulatory peritoneal dialysis 2,3-diphosphoglycerate, oxygen (O2) affinity of red cells (P50), blood gases, ventilation, and O2 consumption were studied. Contrary to patients on maintenance hemodialysis, 2,3-diphosphoglycerate and P50 were normal in patients on continuous ambulatory peritoneal dialysis; they were correlated with each other. Arterial O2 pressure was normal; under the conditions of dialysis with 35 mmol lactate per liter dialysis fluid a slight metabolic acidosis persisted; it was combined with a moderate respiratory alkalosis. Position had no influence upon pulmonary gas exchange with the exception of the alveolo-arterial gradient which was elevated when the abdominal cavity was filled with dialysis fluid and the patients assumed the supine position. Ventilation was in the normal range, whereas O2 consumption was low, possibly due to a reduction in muscle mass in some of the patients. It is concluded that pulmonary gas exchange and erythrocyte O2 transport were normal and that O2 requirements tended to be low in this group of patients on continuous ambulatory peritoneal dialysis.

2,3-Diphosphoglycerate↗
PubMed1984

Single step purification of locust adipokinetic hormones I and II by reversed-phase high-performance liquid chromatography, and amino-acid composition of the hormone II.

Locust adipokinetic hormones I (AKH I) and II (AKH II) are separated by reversed-phase high-performance liquid chromatography using a mu-Bondapak phenyl column with a trifluoroacetic acid/acetonitrile gradient. The eluant was monitored at 210 nm and the hyperlipaemic activity was detected using a bioassay. The amino-acid composition of AKH II was determined after acid hydrolysis with HCl or methane-sulfonic acid. It contained the following amino-acid residues in almost equimolar amounts: Asp, Ser, Glu, Gly, Ala, Leu, Phe and Trp.

Amino Acids↗
PubMed1984

Isolation and amino-acid composition of the adipokinetic hormone of Manduca sexta.

An adipokinetic hormone was purified from corpora cardiaca of au adult Manduca sexta (tobacco hornworm)by reversed-phased high performance liquid chromatography. The following amino-acid composition was determined: 2 Thr, 2 Ser, Glx, Gly, Leu, Phe, Trp. The adipokinetic activity was tested in adult Manduca. In a bioassay in which activation of fat body glycogen phosphorylase was measured in ligated larvae, the hormone elicited a maximal response at the same concentration as it did in the bioassay for hyperlipaemic activity.

Amino Acids↗
PubMed1984

Induction of chemiluminescence during interaction of tumoricidal effector cell populations and tumor cells is dependent on the presence of mycoplasma.

A variety of host cells, such as activated macrophages, natural killer (NK) cells, and polymorphonuclear leukocytes (PMNL), are cytotoxic for an array of non-antibody-coated tumor cells. Because such effector cells appear to use oxygen-dependent mechanisms to effect tumor cell destruction in certain systems, the possibility of an involvement of toxic oxygen species has been considered. To investigate whether interaction of effector cells with neoplastic cells induces the generation of reactive oxygen species, resting and activated rat macrophages and rat spleen cells (as a source of NK activity) were exposed to viable tumor cells of varied origin, and chemiluminescence was monitored. This sensitive indicator of reactive oxygen generation was stimulated only when tumor cells or culture supernatants were contaminated with mycoplasma. Mycoplasma-free tumor cells and culture supernatants were in no case able to trigger chemiluminescence in any of these effector cell populations. On the other hand, tumor targets were equally susceptible to killing by effector cells irrespective of whether mycoplasma were present. The data suggest that generation of chemiluminescence during interaction of natural cytotoxic cells and neoplastic cells is an artifact and that reactive oxygen species do not function as an effector mechanism in antibody-independent natural killing effected by activated macrophages and NK cells.

Animals↗
PubMed1983

Surgical treatment of tracheal dyskinesia.

The syndrome of tracheal dyskinesia characterized by weakening of the posterior membranous wall is a rather uncommon obstructive airway disease of still unknown etiology. The diagnosis is mainly based upon a typical history, extensive and differentiated lung function tests, and bronchoscopic examinations. Only the primary forms with predominating tracheal obstruction should be treated by surgery using a connective tissue graft to stabilize the collapsing trachea. If attention is paid to the preoperative criteria, a favorable outcome of the surgical treatment can be expected with long-term relief of symptoms and marked improvement of overall pulmonary function.

Bronchoscopy↗
PubMed1983

Biosynthesis of proteokeratan sulfate in the bovine cornea. 2) Isolation of subcellular membrane fragments from bovine cornea cells with keratan sulfate synthesizing activity.

Cornea cells were isolated from bovine corneae after collagenase treatment. Subcellular fragments were fractionated by density gradient centrifugation. The density gradient run was monitored by determination of the marker enzyme activities for mitochondria, plasma membranes, lysosomes and endoplasmatic reticulum, of the enzyme activities involved in keratan sulfate synthesis and of the protein content. The fractions were further investigated by electron microscopy. Two membrane fractions with keratan sulfate-synthesizing activity (UDP-N-acetylglucosamine:keratan-N-acetylglucosaminyl-transferase, UDPgalactose:keratan galactosyltransferase and keratan sulfotransferase) were detected: a heavy fraction separated from the other organells investigated and a light fraction exhibiting the same density as plasma membranes. The activities of the three enzymes were found in the same density gradient fractions with a similar distribution pattern between the fractions, which suggests a joint localization of these 3 enzymes at the same intracellular sites.

Animals↗
PubMed1983

Elicitation of macroscopic metastases via surgery: various forms of surgical intervention differ in their induction of metastatic outgrowth.

Surgical removal of a primary tumor implant established in a hind limb frequently gives rise to the emergence of macroscopic lymph node metastases. The present work, utilizing various kinds of surgical intervention, sets out to assess the extent to which surgery itself and/or the associated trauma were responsible for the enhancement of secondary tumor growth. The findings show that a hind limb control amputation did not affect the frequency, size or location of metastases. In contrast, comparable amputation of the tumor-bearing limb resulted in a marked increase in the incidence of macroscopic metastases. These and other findings make it likely that the more frequent and enhanced outgrowth of metastases occurring upon removal of the primary tumor implant is not the result of the operative procedure as such. Additional findings, showing that in animals bearing primary tumor implants on the limb, partial hepatectomy resulted in an enhanced outgrowth of macroscopic metastases developing in diverse locations, are more difficult to interpret. Possibly the often enhanced growth of the primary tumor implant may well favor the spread and the establishment of neoplastic cells at secondary sites; alternatively, putative growth-promoting agents, released by the regenerating liver, may stimulate primary and secondary tumor growth. The present findings diminish the likelihood that nonspecific operative stress is a major contributory factor in the enhancement of metastatic tumor growth following certain types of surgical intervention; they indicate, however, that in certain special situations of the host, such as after hepatectomy, both primary and secondary tumor growth may be enhanced.

Animals↗