Biomedical subjects
Publications and source records attributed to K B Andersen.
A case of asymptomatic benign mediastinal teratoma is presented. The necessity for definite diagnosis of mediastinal tumours is stressed together with the need for conferences involving several specialties.
We have studied the mechanism for mobilization of retinol from stellate cells. Our data show that perisinusoidal stellate cells isolated from liver contained retinol-binding protein (RBP) mRNA. By Western blot analysis we found that cultivated liver stellate cells secreted RBP into the medium. Cultivated stellate cells loaded in vitro with [3H]retinyl ester mobilized radioactive retinol as a complex with RBP. Furthermore, exogenous RBP added to the medium of cultured stellate cells increased the secretion of retinol to the medium. These data suggest that liver stellate cells in vivo mobilize retinol directly to the blood and that a transfer to parenchymal cells for secretion as holo-RBP is not required. The direct mobilization of retinol from liver stellate cells as retinol-RBP to blood is indirectly supported by the demonstration of RBP mRNA production and RBP secretion by lung stellate cells. The data suggest that the same mechanism for retinol mobilization may exist in hepatic and extrahepatic stellate cells. This is, vitamin A-storing stellate cells in liver, lungs, and probably also in other organs may synthesize their own RBP (or alternatively use exogenous RBP) and mobilize holo-RBP directly to the blood.
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The effect of proteases on retrovirus-induced cell fusion was studied. Both 'fusion from within' (fusion between infected and uninfected cells) and 'fusion from without' (fusion of uninfected cells by virus addition) was enhanced after treatment with proteases. An enhancement of up to 10-fold, giving 30% fusion of the cells, was observed. Protease treatment of infected cells or of virus particles enhanced fusion, indicating that cleavage of the virus surface proteins is important for cell fusion. Cell fusion is believed to reflect the virus-cell membrane fusion which occurs during the entry of enveloped viruses into cells. It is therefore possible that proteolytic cleavage of virus surface components during entry is involved in virus infection.
The surface protein gp70 of an ecotropic murine retrovirus was followed during entry of [3H]glucosamine-labelled virions into SC-1 mouse fibroblasts. Upon entry, gp70 was cleaved into fragments with molecular weights 35K, 30K and 17K. The 35K and 17K fragments were also observed after trypsin or thermolysin cleavage of the virion, indicating that certain locations on the gp70 molecule are easily accessible from the outside of the virion. The conformation of gp70 on the membrane was shown to have a major effect on the cleavage. This protein is known to be important for early interactions with the cell (binding and membrane fusion). The results indicate that gp70 cleavage may be important for membrane fusion.
The changes of concentrations of prostaglandins (PG) are cyclic in the uterine tissues and related to steroid ovarian hormones. The role in normal menstruation is presumably related to a local haemodynamic effect. PGF2 alpha vasoconstricts the endometrial vessels during menstruation and contracts the smooth muscle of the myometrium. PGE2 vasodilates the vessels of the endometrium, and PGI2 relaxes smooth muscle, vasodilates the vessels of the myometrium and inhibits thrombocyte aggregation. The pathological conditions dysmenorrhea and menorrhagia relates to symptoms which seem to be exaggerations of normal activities, probably due to increased PG levels. Prostaglandin synthesis inhibitors (PGSI) in women have not been able to prevent ovulation, but animal experiments have shown that the bursting of the follicle demands prostaglandins. In vitro experiments with human tissue have shown that PG is necessary for the occurrence of dissociation of connective tissue around the apex. Luteolysis is due to PG in several species, but it has not been possible to find this direct effect of PG upon luteolysis in women. However, there are indications that the PG functions as a mediator for or is mediated by catecholamines and/or oxytocin.
A main factor which might cause cardiac arrhythmias and arterial hypotension during thoracic operations is surgical manipulation around the pericardium and the lung hilus. Halothane and enflurane were compared as to the occurrence of arrhythmias and hypotension caused by standardized surgical stimulation. Twenty-eight patients scheduled for thoracotomy were studied. The patients were selected in randomized order, and the anaesthetic agent in use was unknown to the surgeon. ECG, intra-arterial blood pressure and central venous pressure were recorded continuously. Six patients in the halothane group (n = 14) and nine patients in the enflurane group (n = 14) developed premature atrial contractions and nodal rhythm, while nine patients in the halothane group and five in the enflurane group developed a fall in systolic blood pressure of more than 20 mmHg (2.7 kPa). No statistically significant difference in the occurrence of cardiac arrhythmias and hypotension was found between the two anaesthetic groups.
The kinetics of the viral surface protein gp70 and the viral core proteins p30 and p15C were followed during retrovirus entry into mouse fibroblasts. All three proteins were internalized, but whereas essentially all the gp70 was degraded, approximately one-third of the core proteins remained stable in the cells. These diverging routes of the different proteins are in agreement with the proposed route, that retrovirus enters the cells by endocytosis followed by a membrane fusion between the virus membrane and the vesicle membrane.
We have studied the entry of murine retrovirus into mouse fibroblasts by following the fate of both radioactively (protein) labeled virus particles and infectious virus particles. Physical and infectious particles bound to the cell surface with a half time of 1.5-2 hr. Both types of particles were internalized with a half time of approximately 3 hr as measured by the resistance to externally added proteases. The binding proceeded both at 37 and 0 degrees, whereas the internalization was blocked at 0 degrees. The internalized physical particles followed two routes: they either were degraded or remained stable in the cell. Degradation was blocked by lysosomotropic bases and is therefore believed to occur in the lysosomes. Infection could also be inhibited by lysosomotropic bases when present in the first hours after the internalization, indicating that the infectious route also is leading through the lysosomes or another acidic compartment of the cell.
The protease inhibitor leupeptin was shown to inhibit retrovirus infection in mouse fibroblasts at a step shortly after internalization of the virus particles. The inhibited step most likely was the passage of virus particles through the lysosomes or other acid vesicles. Leupeptin was also shown to inhibit degradation of virus particles in the lysosomes. The results are discussed with respect to the involvement of proteases in the infectious route.
Protein-protein interaction of Moloney murine leukaemia virus was studied by an assay where one protein preparation was coupled covalently to Sepharose, and binding of radiolabelled proteins to the protein-Sepharose was examined. It was found that the virus proteins gp70, p30, p15E and p15 in solution could associate weakly to disrupted virus particles and to p30. However, when the disrupted virus particles and p30 were coupled to Sepharose in the presence of Triton X-100, stronger binding of the four proteins was observed. Only low or no binding of p12 and p10 was observed to these protein-Sepharoses. The results are discussed with respect to the assembly and structure of the virus particle.
Batch cultures of Escherichia coli were grown in minimal media supplemented with various carbon sources which supported growth at specific growth rates from 0.2 to 1.3/h. The respiration rates of the cultures were measured continuously. With few exceptions, the specific rate of oxygen consumption was about 20 mmol of O2/h per g (dry weight), suggesting that the respiratory capacity was limited at this value. The adenosine triphosphate (ATP) required for the production of cell material from the different carbon sources was calculated on the basis of known ATP requirements in the biochemical pathways and routes of macromolecular synthesis. The calculated ATP requirements, together with the measured growth rates and growth yields on the different carbon sources, were used to calculate the rate of ATP synthesis by oxidative phosphorylation. This rate was closely related to the respiration rate. We suggest that aerobic growth of E. coli in batch cultures is limited by the rate of respiration and the concomitant rate of ATP generation through oxidative phosphorylation.
A methionyl-tRNA-Met-f deacylase was found in ribosomal salt wash from cultured human cells of the HeLa line. This enzyme was purified by the use of DEAE-cellulose, ammonium sulfate precipitation, gel filtration and isoelectric focusing, and appears to be a protein with a native molecular weight of 80,000, which consists of two 40,000-Mr subunits. The mechanism of the Met-tRNA-Met-f deacylase is shown to involve end-product inhibition by the deacylated form of Met-tRNA-Met-f. The methionyl-tRNA-Met-f deacylase is rather specific for Met-tRNA-Met-f as opposed to Met-tRNA-Met-m, has a KCl optimum of 85 mM, is inhibited by MgCl2 and is inhibited by GTP and NAD+ at physiological concentration. 40-S and 60-S subunits inhibit the enzyme, possibly by binding to it. The stability of translational initiation complexes, containing methionyl-tRNA-Met-f, was investigated in the presence of the enzyme. Purified ternary complex was slowly broken down by the enzyme, while the 40-S-subunit . Met-tRNA-Met-f complex was stable in the presence of enzyme. The 80-S complex formed with A-U-G trinucleotide as the message molecule was broken down, whereas the 80-S complex formed with globin mRNA was stable in the presence of the enzyme. The physiological role of this enzyme is unclear, but it might act to regulate initiation by deacylating Met-tRNA-Met-f.
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Methods for measurements of catabolic reduction charge (defined as NADH/(NADH+NAD+)) and anabolic reduction charge (defined as NADPH/(NADPH + NADP+)) are described using [14C]nicotinamide labeling of Escherichia coli cultures. Together with these parameters the adenylate energy charge (ATP + 1/2ADP)/(ATP + ADP + AMP) was measured using labeling with [2-3H]adenine. These three charges were found under different exponential growth conditions to have values independent of the growth conditions: catabolic reduction charge, 0.05; anabolic reduction charge, 0.45; and adenylate energy charge, 0.9. The charges were examined during interruption of growth primarily affecting catabolism, respiration, or anabolism, leading to changes of the charges. The changes of charges are evaluated as a possible regulation of the metabolic rates utilizing or producing the nucleotides by their respective charges.
A vacuum-tight cell for infrared spectroscopic investigations of extremely corrosive melts, e.g., molten fluorides, has been constructed and tested up to 750 degrees C. The cell has a gold-lined sample chamber and a diamond window transparent for the infrared light. It can be furnished with a gold piston that enables the recording of short-path-length FTIR spectra of liquid samples. Solutions of Nb(V) in LiF-NaF-KF eutectic (FLINAK) with and without oxide additions have been investigated by FTIR and Raman spectroscopy. The presence of NbF7(2-), NbOF5(2-), and NbO2F4(3-) complexes was established in the molten state at 600 degrees C. After solidification NbF7(2-) was still the only Nb(V) all-fluoro complex present. Three oxofluoro complexes, NbOF6(3-), NbOF5(2-), and NbO2F4(3-), have been identified in the solid state. Typical frequency regions for the different complexes are established. Finally, it was shown that K2NbF7 can be used as an indicator to determine the oxide content of the sample melts.