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Biomedical subjects

W Sander

Publications and source records attributed to W Sander.

At least 19 recordsLinked to original sources
PubMed2001

Reaction of 4-oxo-2,3,5,6-tetrafluorocyclohexa-2,5-dienylidene with acetylene: a carbene to carbene reaction.

The EPR spectrum of triplet 4-oxo-2,3,5,6-tetrafluorocyclohexa-2,5-dienylidene 1 was recorded in solid argon at 15 K. Carbene 1 reacts with acetylene under the conditions of matrix isolation yielding triplet vinylmethylene 4, which was characterized by its IR, UV-vis, and EPR spectrum. Carbene 4 is photolabile and is converted to spiro compound 5 on irradiation with lambda > 515 nm. The reaction of triplet carbene 1 with acetylene to produce triplet carbene 4 is predicted to be exothermic by 55 kcal mol(-1) at the B3LYP/6-31G(d,p) level of theory. The cis isomer is calculated to be only 0.4 kcal mol(-1) less stable than trans-4 at this level of theory. According to our calculations, singlet carbene S-4 is not a minimum on the C(8)F(4)H(2)O potential energy surface; however, at the T-4 geometry, the lowest lying singlet state is predicted to be 20.7 kcal mol(-1) higher in energy. The subsequent photochemical cyclization of T-4 yielding spiro compound 5 is exothermic by 10.3 kcal mol(-1) relative to T-4 and by 31.1 kcal mol(-1) relative to S-4. 4-Ethinyl-2,3,5,6-tetrafluorocyclohexa-2,5-dienone 9, the C-H insertion product of 1 and acetylene, was not observed experimentally, although it is favored energetically by 4.3 kcal mol(-1) over 5.

Journal Article↗
PubMed2001

Matrix isolation and spectroscopic characterization of perfluorinated ortho- and meta-benzyne.

The matrix isolation and spectroscopic characterization of two C6F4 isomers, the perfluorinated o-benzyne 4 and the m-benzyne 5, is reported. UV photolysis of tetrafluorophthalic anhydride 6 in solid argon at 10 K results in the formation of CO, CO2, and 1,2-didehydro-3,4,5,6-tetrafluorobenzene (4) in a clean reaction. On subsequent 350 nm irradiation 4 is carbonylated to give the cyclopropenone 7. 1,3-Didehydro-2,4,5,6-tetrafluorobenzene (5) was synthesized by UV irradiation of 1,3-diiodo-2,4,5,6-tetrafluorobenzene (8) via 2,3,4,6-tetrafluoro-5-iodophenylradical 9. Photolysis of 8 in solid neon at 3 K produces good yields of both radical 9 and benzyne 5, while in argon at 10 K no reaction is observed. Thus, the photochemistry in neon at extremely low temperature markedly differs from the photochemistry in argon. The formation of 5 from 8 via 9 is reversible, and annealing the neon matrix at 8 K leads back to the starting material 8. The benzynes 4 and 5 and the radical 9 were characterized by comparison of their matrix IR spectra with density functional theory (DFT) calculations.

Journal Article↗
PubMed2001

Dimesitylketone O-oxide: spectroscopic characterization, conformation, and reaction modes: OH formation and OH capture.

Dimesitylketone O-oxide 1b was synthesized by photolysis of dimesityldiazomethane dissolved in an oxygen saturated CCl3F solution at 140 K. Conformation and geometry of 1b were determined by comparing measured NMR chemical shifts with the corresponding chemical shifts calculated at the DFT-IGLO level of theory where it had to be considered that the molecule exists in two enantiomeric forms. Measured and calculated 1H chemical shifts agree within 0.1 ppm while the calculated 13C shift of the COO carbon (210.6 ppm) differs by only 0.4 ppm from the measured shift of 211.0 ppm. The two mesityl rings are perpendicular to each other and enclose angles of 40 and 57 degrees with the COO plane. The preferred rearrangement process of 1b is an H migration from one of the ortho-methyl groups to the terminal O atom of the COO unit. The calculated activation enthalpy of this process is 12.7 kcal/mol (B3LYP/cc-pVTZ). In contrast, the activation enthalpy for isomerization to dioxirane is 5 kcal/mol higher. In CCl3F, the activation barrier for the thermal decay was determined to be 13.8 +/- 0.2 kcal/mol and in acetonitrile 13.1 +/- 0.4 kcal/mol. H migration initiates cleavage of the OO bond and the production of an OH and a benzyl radical. Recombination of the latter in the solvent cage leads to the formation of 2-methylhydroxy-pentamethylbenzophenone, while escape of the OH radical from the solvent cage yields a ketone. These results confirm the possibility of OH production from carbonyl oxides in the solution phase.

Journal Article↗
PubMed2000

4-Oxo-2,3,5,6-tetrafluorocyclohexa-2,5-dienylidene--a highly electrophilic triplet carbene.

The 4-oxocyclohexa-2,5-dienylidenes are an interesting class of highly electrophilic carbenes. We investigated the reactivity of the 2,3,5,6-tetrafluorinated and -tetrachlorinated derivatives 1b and 1c with small molecules under conditions of matrix isolation. The reactions with molecular oxygen and with carbon monoxide produce the expected carbonyl O-oxides and ketenes, respectively. As a result of the extreme electrophilicity of 1b and c both carbenes insert with no or very small activation barriers into H2 or the CH bonds of hydrocarbons. Obviously, spin restrictions for these formally spin-forbidden reactions do not result in substantial thermal activation barriers.

Journal Article↗
PubMed2000

Dimerization of formic acid--an example of a "noncovalent" reaction mechanism

The pulse deposition technique allows selectively the isolation of monomeric or dimeric formic acid in argon matrices at 7 K. Warming of matrices containing the monomer M from 7 K to 40 K results in the decrease of M and formation of a dimer B. This dimer is also labile, and further warming finally produces a second dimer A. By comparison with density functional theory (DFT) calculations and gas phase IR spectra taken from the literature, the latter dimer A was identified as the C2h-symmetrical cyclic dimer. The unstable dimer B was identified as the acyclic Cs-symmetrical dimer. An activation energy of 2.3 kcal mol(-1) was calculated for the B --> A rearrangement at the B3LYP/ 6-311 ++ G(d,p) level of theory, which is in qualitative agreement with the experimental finding of a slow thermal reaction under the conditions of matrix isolation.

Journal Article↗
PubMed2000

[The diagnostic problems in magnetic resonance tomography of the bone marrow in patients with malignomas under G-CSF therapy].

AIM: To study the effect of G-CSF therapy directly by MRI and 1H MRS in the lumbar and femoral bone marrow and differentiate between malignant bone marrow infiltration (MBMI) and reconversion of red marrow. METHODS: Thirteen patients could be examined twice, before and during G-CSF medication and another six only during treatment. T1 weighted spin-echo and opposed-phase gradient-echo images as well as the spectroscopic data (T2 values, water content) were analysed. RESULTS: After G-CSF a pathologic bone marrow signal intensity was seen in 8/13 (lumbar) and 11/13 (femoral) patients respectively. The majority of the signal alterations were diffuse (6 and 8), the minority focal (2 and 3). If a patient was successfully stimulated, a significant increase in water content occurred (21% lumbar, 34% femoral). T2 values did not change significantly, nor did they correlate with the stimulation success. CONCLUSIONS: MR tomography and -spectroscopy are suitable to detect lumbar and femoral bone marrow stimulation by G-CSF quantitatively and qualitatively. The changes may simulate MBMI. The adequate judgement of G-CSF treated bone marrow without pretherapeutic images is not possible.

Adult↗
PubMed1997

Protocol for intervention and treatment of alcohol withdrawal.

The incidence of alcohol dependence/abuse in patients of a general health care facility is 35-50%. The diagnosis and treatment of patients experiencing or at risk of alcohol withdrawal is problematic. The admitting diagnosis is usually another medical condition, illness or injury. Signs and symptoms of alcohol withdrawal is complicated by pre-existing conditions. In an attempt to improve the quality of care, decrease the length of stay of these patients, and decrease demands on nursing staff, a protocol for intervention and treatment of alcohol withdrawal was developed on the orthopedic ward of Royal University Hospital. The protocol enables each nurse to assess. Intervene and initiate the proper referrals. The recognized tool of assessment used to identify at risk patients is the CAGE questionnaire. The Clinical Institute WithDrawal Assessment for Alcohol scale is used to determine when it is appropriate to use Benzodiazepines. General nursing considerations are addressed through a pre-printed care plan. Nurses refer to social work, Alcoholics Anonymous and make use of available resource material. The protocol enables nurses to provide safe and effective care with few associated costs. Except for mass immunization, there is no other single intervention in health care that has the same far reaching consequences (Sullivan, 1995).

Aged↗
PubMed1993

Catholicism and marriage in the United States.

This study examines the effects of a Catholic background on age at first marriage, the odds of never marrying, and the odds of ever divorcing. Estimates using Catholic upbringing are compared with estimates using Catholic at the time of the survey. A case is made that if the latter measure of Catholicism is used, serious selection bias problems occur in some cases because this measure excludes defectors and includes converts. Further, it is shown that a Catholic upbringing generally has no effect on men's age at first marriage and has a positive effect on the age when women marry. It is also shown that older Baptist men are substantially more likely than Catholic men to experience a divorce. Older Catholic women are somewhat less likely to experience a divorce than non-Baptist Protestant women. There is no Catholic effect on the odds that younger men and women will divorce.

Adult↗
PubMed1992

Unobserved variables and marital status: the schooling connection.

"This study focuses on the effect of schooling on marital status. A Hausman-type test shows that schooling cannot be legitimately treated as an exogenous determinant of marriage and divorce. It is shown that if schooling is treated as an exogenous variable, the negative effect of schooling on the odds of marriage is underestimated. Further, the results indicate that schooling has a significant negative effect on divorce if it is treated as an exogenous variable; the coefficient for schooling is positive if it is treated as an endogenous variable." The data, which concern the United States, are from the General Social Survey and cover the period 1986-1990.

Americas↗
PubMed1990

[Contribution to the mechanism of the "factor VIII bypassing activity" (FEIBA)-reaction].

The principle of the FEIBactivity hadn't been defined in a sufficient manner up to now. Probably the factor VII or factor VIIa are playing a key role. According to own experiments the factor VII activity increases considerably in activated prothrombincomplex concentrates together with the quotient factor VIIa/VII. Factor VII should be administered in his activated form for bypassing. Fractions with limitation of the activation process to factor VII are of a low thrombogenicity. Among activated coagulation factors factor VIIa persists longest in the circulation and a bypass efficacy can be provoked only by this.

Blood Coagulation↗
PubMed1990

[Activated prothrombin complex preparations for the treatment of anticoagulant hemophilia. Preparation--method of operation--supply possibility].

The mechanism of the bypass activity of prothrombin complex preparatives for treatment of haemophiliacs with circulating anticoagulants remains unclear up to now. The following parameters had been tested with preparatives produced in a different manner (absorption by DEAE-Sephadex A 50, Molselekt A 50, tricalcium phosphate or aluminium hydroxide): Coagulation factors II, VII, IX, X and XII, activated factors VIIa and Xa as well as the FEIB activity. The bypass activity is strongly correlated to the factor VIIa content of the preparatives, however. These results agree with the statements by HEDNER and KISIEL, which had used a factor VII a concentrate for treatment of haemophilia complicated by circulating anticoagulants with success. According to farther investigations factor VII is correlated with the lipid content of the starting plasma. This knowledge is important for optimizing the production procedure of prothrombin complex preparatives with bypassing activity.

Absorption↗
PubMed1985

[Steroid hormone receptors in normal, dystrophic, dysplastic and carcinomatous vulva tissues].

We employed the agar gel electrophoresis method to determine in 63 samples of vulva tissue the cytoplasmatic receptors for oestradiol, dihydrotestosterone and dexamethasone. Tissues with a binding capacity of more than 5 femtomol/mg (fmol = 10(-15) mol) cell proteins were considered receptor positive. The study comprised 17 normal tissues of the vulva, 13 vulva biopsies at the end of the pregnancy period, 7 dystrophically changed tissues, 11 premalignant changes of the vulva and 15 squamous cell carcinomas. In normal as well as in benign or malignantly changed vulva, specific receptors were found for all the four steroids (ER, PR, DHTR, DExaR). Receptors were most frequent in normal vulva tissue (ER = 94%, PR = 54%, DHTR = 38%, DexaR = 83%) with binding-capacities of 8-650 fmol/mg cell proteins. ER levels were higher during the postmenopausal period than during the premenopausal period. In dystrophia the receptor pattern was almost the same as in healthy tissue. Biopsies conducted at the end of the pregnancy period showed in all cases despite the high endogenous oestrogen levels positive ER values up to 875 fmol/mg cell proteins, whereas PR and DTHR were present in only 20% or 25% with low binding capacities. Loss of receptors, particularly of PR, was seen in premalignant changes (dysplasia of vulva, carcinoma in situ) and in case of squamous cell carcinomas. On comparing the receptor distribution of clinically changed vulva tissue with healthy tissue we found only differences by degree but no fundamental differences in principle.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1983

[Changes in thrombocyte counts in blood donors].

The behaviour of thrombocytes during blood donation of 400 ml is investigated in the present paper. In general, a short-term increase of thrombocyte numbers to double the amount on an average could be observed in all blood donors. In 19 donors of a total of 39 the increase occurred after collecting 100 ml.

Adolescent↗