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Biomedical subjects

R Christiansen

Publications and source records attributed to R Christiansen.

13 recordsLinked to original sources
PubMed1988

The field integrated dose modification (FIDM): three typical clinical applications of a new irradiation technique.

In addition to an earlier developed "compensator integrated modification technique", a method is derived which uses as basic principle the "field integrated dose modification" (FIDM) without need for computer tomographic data. The method enables the radiotherapist to introduce one or more volumes within which doses can be delivered which are different from the one in the main irradiation volume. The steps of practical preparation and clinical application are described in detail. The radiobiological aspects of FIDM, especially those in case of acceleration and hyperfractionation, are elucidated by discussing three typical examples.

Humans↗
PubMed1987

[Field-integrated dose modification. 1: Clinical significance of the procedure].

A method is derived from a previously published compensator-integrated modification proceeding which maintains the principle of a field-integrated dose modification without needing CT input data. Three typical clinical examples are presented in order to describe this considerably simplified technique thus suited for everyday practice. The authors discuss the interesting radiobiological aspects involved.

Abdominal Neoplasms↗
PubMed1986

Teaching skills in medical information retrieval to medical students.

Most students are admitted to medical school with little or no prior training in medical information retrieval. Despite the increasing dependence of physicians on new information tools, such as computer data bases and on-line literature searching, few medical schools have included more than token emphasis on information retrieval skills in their curricula. Reports on information skills courses have revealed that the courses often encounter serious obstacles, including poor student acceptance. The authors here describe a project that attempts to overcome the principal obstacles and to provide an efficient and effective method of teaching information retrieval skills to second-year medical students. The method includes a pretest that contains case scenarios, a diagnosis of individual students' deficiencies in information skills, a self-paced individual learning module, and a posttest. Evaluation of the program showed that the students had deficiencies in information retrieval skills and that the students who used the self-instruction module had significantly higher scores on the posttest than the students who did not.

Illinois↗
PubMed1978

Focal sclerosing glomerulopathy with adverse effects during pregnancy.

Exacerbation of focal sclerosing glomerulopathy (FSGN) during pregnancy was noted in the three patients. All had antecedent asymptomatic proteinuria. Toxemia developed in two of the women during pregnancy and progressed rapidly to renal failure. Severe nephrotic syndrome developed in one patient with pregnancy and remitted after delivery. These cases suggest a deleterious effect of pregnancy on the course of FSGN and indicate the necessity for doing renal biopsy in women of childbearing age with asymptomatic fixed proteinuria or nephrotic syndrome so that those patients with FSGN can be properly counseled about future pregnancies.

Adult↗
PubMed1976

The glycerophosphateacyltransferases and their function in the metabolism of fatty acids.

1. From different studies on the cellular localization, postional specificity, and regulatory properties of acyl-CoA: glycerophosphate acyltransferase (EC 2,3,1.15) AND ACYL-CoA: 1-ACYLGLYCEROPHOSPHATE ACYLTRANSFERASE (EC 2,3,1....) the following conclusions can be drawn: The glycerophosphate acyltransferase is localized in the endoplasmatic reticulum (microsomes) and in the outer membrane of the mitochondria of the animal cell. Its reaction product is 1-acylglycerophosphate (1-lysophosphatidic acid). The mitochondrial enzyme shows a high preference for saturated fatty acids while the microsomal enzyme is less specific (alternatively the microsomes contain more than one glycerophsophate acyltransferase). 2. The 1-acylglycerphosphate acyltransferase is localized in the endoplasmatic reticulum (microsomes) in the animal cell. Possibly a minor fraction of this enzyme is localized to the outer membrane of the mitochondria. This enzyme shows a strong preference for unsaturated fatty acids. 3. Both the microsomal and the mitochondrial dihydroxyacetonephosphate acyltransferase show similar fatty acid specificity as the corresponding glycerophosphate acyltransferases. It cannot be excluded that dihydroxy-acetonephosphate and glycerophosphate are acylated by the same enzymes. 4. The activity of the glycerophosphate acyltransferase(s) in the liver decreases in fasting or fat feeding and increases upon feeding of carbohydrate. The activity of carnitine palmityltransferase varies exacty opposit. These enzymes do not show dietary variations in heart and adipose tissue. 5. Under the otherwise identical conditions the rate of carnitine acylation in isolated mitochondria decreases more than the rate of glycerophosphate acylation when the concentration of palmityl-CoA is reduced. 6. In isolated liver cells (which has lost most of their carnitine) addition of carnitine increases the rate of fatty acid oxidation and decreases the rate of triglyceride formation. 7. Glycerol and fructose lower the rate of fatty acid oxidation, probably by lowering the levels of acyl-CoA and acyl-carnitine in the cells. 8. It is concluded that the relative activities of glycerophosphate acyltranse and carnitine palmityltransferase probably influence the fate of fatty acids in the cell.

Acyltransferases↗
PubMed1976

The role of acyltransferases in fatty acid utilization.

Glycerophosphate and carnitine as competing acyl acceptors and the oxidation of different long chain acylcarnitines in isolated mitochondria have been investigated. In the presence of low concentrations of palmitate, glycerophosphate is the preferred acyl acceptor in isolated liver mitochondria, indicating that the glycerophosphate acyltransferase has a lower Michaelis constant (Km) for palmityl-CoA than has the carnitine palmityltransferase. Liver mitochondria from starved rats make more palmitylcarnitine and less palmitylglycerophosphate than do mitochondria from starved/refed rats. In heart mitochondria glycerophosphate has less effect on palmitylcarnitine formation because of glycerophosphate acyltransferase activity is lower and the carnitine palmityltransferase activity is higher in liver mitochondria. Carnitine esters of C22 fatty acids, especially erucic acid (22:1omega9,cis) are more slowly oxidized compared to palmitylcarnitine in heart than in liver mitochondria. They also inhibit palmitylcarnitine oxidation. The inhibition is relatively stronger in heart than in liver mitochondria. These observations are discussed in relation to organ differences in the utilization of fatty acids.

Acylation↗