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Biomedical subjects

R A Klein

Publications and source records attributed to R A Klein.

At least 91 records · Page 5Linked to original sources
PubMed1972

A new bacterial sphingophospholipid containing 3-aminopropane-1,2-diol.

1. A new sphingophospholipid has been isolated from the bacterial fraction of sheep rumen contents. 2. This new lipid has been characterized as a ceramide phosphate moiety esterified to 3-aminopropane-1,2-diol through the primary alcohol group. 3. Mass spectrometry has shown the intact lipid to contain a vicinal hydroxyl amino grouping, and oxidation with periodate converts it quantitatively into a new phospholipid which is probably ceramide phosphorylglycolaldehyde. 4. The sphingophospholipid contains a mixture of saturated long-chain bases mainly with branched-chain alkyl groups, which are typical of a microbial origin. 5. A Gram-negative bacterium isolated from rumen contents contains about 30% of the new lipid in its phospholipids when grown in pure culture.

1-Propanol↗
PubMed1972

Mass spectrometry of the phosphatidyl amino alcohols: detection of molecular species and use of low voltage spectra and metastable scanning in the elucidation of structure.

The basic fragmentation mechanisms occurring in the mass spectra of the phosphatidylcholines have been described previously, and evidence was adduced to show that many of the more abundant ions are related by electron impact-induced processes. A molecular ion was demonstrated for dioleoyl glycerylphosphorylcholine by accurate mass measurement and by metastable scanning. In the present paper, results are reported which further extend the previous work by including a more detailed investigation of "nonapparent" fragment ions for a series of phosphatidylcholines with different acyl side chains and also for a series of phosphatidyl amino alcohols of fixed acyl composition. The results demonstrate the effect of the choline quaternary nitrogen on the stability of the molecular ion, and estimates for the appropriate rate constants are given. Nitrogen-containing fragments have been demonstrated by recording spectra at low electron voltages. The work has also been extended to include natural phosphatidylcholine preparations of mixed acyl composition, and the possibility of detecting particular molecular species has been established. Quantitative estimates may be made using suitable synthetic phosphatidylcholines, and results are presented to show the variation of the molar correction factor with acyl chain length.

Brain Chemistry↗
PubMed1971

Mass spectrometry of the phosphatidylcholines: fragmentation processes for dioleoyl and stearoyl-oleoyl glycerylphosphorylcholine.

Mass spectra for the various phosphatidylcholines, together with accurate mass measurements on the more abundant fragment ions, have been described in a previous paper (Ref. 5). No detailed fragmentation sequence was proposed on the evidence available. In the case of dioleoyl glycerylphosphorylcholine, some question arose as to whether certain ions were produced by electron impact or by pyrolysis. In this paper, results are reported which enable a more detailed fragmentation sequence to be proposed. By observing metastable transitions in the first field free region of a double-focusing mass spectrometer, it can be shown that the major ions in the spectrum are produced by electron impact processes, and not by pyrolysis; moreover, many of these ions are directly related to one another by metastable processes. In particular, it has been demonstrated that the ions at m/e 603 for dioleoyl glycerylphosphorylcholine and at m/e 604 for stearoyl-oleoyl glycerylphosphorylcholine are derived from the appropriate molecular ions by an electron impact-induced process. From measurements of the metastable ion intensities, as well as from the appearance potentials and ionization efficiency curves, conclusions may be drawn about many of the fragmentation mechanisms, allowing a distinction to be made between rearrangement and cleavage reactions.

Chemical Phenomena↗
PubMed1971

Mass spectrometry of the phosphatidylcholines: dipalmitoyl, dioleoyl, and stearoyl-oleoyl glycerylphosphorylcholines.

Mass spectra of the diacyl glycerylphosphorylcholines have been obtained using a direct insertion probe, with a source temperature of 250 degrees C at an ionizing potential of 70 ev. Fragmentation patterns are described for dipalmitoyl, dioleoyl, and 1-stearoyl-2-oleoyl glycerylphosphorylcholines. Significant differences are observed in the fragmentation patterns, and the fragment ions have been identified by high resolution mass measurements. Ions associated with the hydrocarbon chains, glycerol esters, and phosphorylcholine have been identified, and the presence of metastable transitions have been used as confirmatory evidence for some of the steps involved in the fragmentation sequence. A molecular ion was tentatively identified in the case of dioleoyl glycerylphosphorylcholine. The mass spectrum of 1-stearoyl-2-oleoyl glycerylphosphorylcholine shows an important rearrangement ion at m/e 604 and some evidence for the differential cleavage, or stability, of the stearoyl- and oleoyl-containing fragments. Strong similarities exist between the observed spectra for the diacyl glycerylphosphorylcholines and those for the corresponding glycerides.

Chemical Phenomena↗
PubMedDate not supplied

Treatment of coccidioidal meningitis with fluconazole.

Fluconazole was administered at doses of 50-400 mg/d to 18 patients (15 men, three women) with coccidioidal meningitis. After a mean duration of treatment of 9.8 months, 10 (67%) of 15 assessable patients had responded, one (7%) of 15 had partially responded, and four (27%) of 15 had not responded to therapy. Five (63%) of eight assessable patients receiving fluconazole as sole therapy responded or partially responded. Two patients discontinued fluconazole after initially responding to therapy, and both experienced relapse. The toxicity of fluconazole remains minimal at doses to 400 mg/d. The penetration of fluconazole into cerebrospinal fluid is substantial at all doses studied. Thus fluconazole continues to show promise even as sole therapy against coccidioidal meningitis. Not all patients respond, however, and relapse may be a problem with the currently studied doses and durations of therapy.

Adolescent↗