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Biomedical subjects

M Hamburger

Publications and source records attributed to M Hamburger.

At least 19 recordsLinked to original sources
PubMed1999

Pressurized liquid extraction of medicinal plants.

The suitability of pressurized liquid extraction (PLE) in medicinal plant analysis was investigated. PLE extracts from a selection of representative herbs were compared with extracts obtained according to Pharmacopoeia monographs with respect to yield of relevant plant constituents, extraction time and solvent consumption. In all cases a significant economy in time and solvents was realized, while extraction yields of the analytes were equivalent or higher.

Carbohydrate Sequence↗
PubMed1998

Repetition priming and experimental context effects.

The repetition priming effect has been taken as evidence that lexical entries are automatically activated in memory. However, contextual cues in an experiment may influence repetition priming, suggesting that this priming may not be the result of automatic processes. Five experiments used a primed shadowing task to explore the role of phonological context on repetition priming. In the first four experiments, high- and low-expectancy conditions were tested. Between experiments, the degree of phonological relatedness (high or low phonological similarity), percentage of related trials that were repetition trials (ID ratio), and modality of stimulus presentation (auditory or visual) were manipulated. Results indicate that repetition priming in auditory word recognition is eliminated by a low ID ratio. The fact that an external variable such as the ID ratio influences repetition priming suggests that repetition priming may be the product of processes extraneous to the automatic activation of lexical entries.

Automatism↗
PubMed1994

Antifungal tests in phytochemical investigations: comparison of bioautographic methods using phytopathogenic and human pathogenic fungi.

The detection limits in two bioautographic assays have been determined for a series of antifungal compounds, including clinically used antimycotics, fungicidal agrochemicals, and various classes of secondary plant metabolites. Target organisms were the filamentous fungus Cladosporium cucumerinum and the yeast Candida albicans. For clinical agents and agrochemicals, the detection limits in the two assays reflected to a certain extent their known spectrum of activity. Most of the plant-derived compounds tested showed a positive response in both assays, but with detection limits varying by a factor up to tenfold. For screening purposes, it is thus advisable to use both tests, as some activities would otherwise go undetected. The MIC values of these substances were determined in order to verify a possible correlation with the detection limit in the bioautographic assays.

Antifungal Agents↗
PubMed1994

Toxic inhibition of smooth muscle contractility by plant-derived sesquiterpenes caused by their chemically reactive alpha-methylenebutyrolactone functions.

1. Previous studies have shown that extracts of feverfew (Tanacetum parthenium) and parthenolide, a sesquiterpene alpha-methylenebutyrolactone obtained from it, inhibit smooth muscle contractility in a time-dependent, non-specific and irreversible manner. 2. The hypothesis that this toxic effect is due specifically to the presence in the sesquiterpene lactone of the potentially reactive alpha-methylene function was tested on rabbit isolated aortic ring preparations. This was done (a) by comparing the effects of two plant-derived sesquiterpene lactones purified from yellow star thistle (Centaurea solstitialis): cynaropicrin (an alpha-methylenebutyrolactone) and solstitialin 13-acetate (lacking the alpha-methylene function), and (b) by chemically inactivating the alpha-methylene functions in cynaropicrin and parthenolide by reaction with cysteine. 3. The results show that the characteristic smooth muscle inhibitory profile is demonstrated by the two alpha-methylenebutyrolactones (parthenolide and cynaropicrin), but not by the compound lacking this functional group (solstitialin 13-acetate), or by those previously active compounds in which it has been inactivated with cysteine. 4. Thus the alpha-methylene function is critical for this aspect of the toxic pharmacological profile of the sesquiterpene butyrolactones, which are natural products widely distributed in the Compositae family of flowering plants.

Animals↗
PubMed1993

Search for chlorinated sesquiterpene lactones in the neurotoxic thistle Centaurea solstitialis by liquid chromatography-mass spectrometry, and model studies on their possible artifactual formation.

An HPLC method has been developed for the analysis of sesquiterpene lactones of the neurotoxic plant Centaurea solstitialis (Asteraceae). The presence of sesquiterpene lactone chlorohydrins in extracts was investigated by means of liquid chromatography-thermospray mass spectrometry. In contrast to earlier reports of a series of mono- and dichlorohydrins from this plant, traces only of two monochlorohydrins could be detected in lipophilic extracts. Model studies carried out with extracts and with the genuine sesquiterpene diepoxide repin and its epimer subluteolide showed that (i) monochlorohydrins can be formed in CHCl3 under usual laboratory conditions; (ii) the epoxide moiety at C-4 of the sesquiterpenes is extremely labile, reacting immediately and quantitatively with traces of HCl to the corresponding monohydrins; (iii) epoxide ring opening at the acyl side chain occurs only at higher HCl concentrations. Confirmation of the peak identity was obtained by the isotope ratio of chlorinated compounds and comparison with authentic samples. The structures of the mono- and dichlorohydrins were established by NMR spectroscopy.

Chlorine↗
PubMed1993

Sinapic acid esters from Polygala virgata.

Three sinapoyl glycosides have been isolated from the roots of Polygala virgata. The structures were established on the basis of UV, mass 1H and 13C NMR spectral data, including homonuclear and heteronuclear 2D shift correlation and selective INEPT experiments. alpha-D-(3-O-Sinapoyl)fructofuranosyl-alpha-D-(3-O-acetyl-6-O-s inapoyl)glucopyranoside and beta-D-(3,O-sinapoyl)fructofuranosyl-alpha-D-(4-O-acetyl-6-O-si napoyl)glucopyranoside are new natural products, whereas beta-D-(3-O-sinapoyl)fructofuranosyl-alpha-D-(6-O-sinapoyl) glucopyranoside has already been reported from other plants.

Carbohydrate Sequence↗
PubMed1992

A comparison of two computer-administered versions of the NIMH Diagnostic Interview Schedule.

This study compared three versions of the NIMH Diagnostic Interview Schedule (DIS): "traditional" interviewer-administered DIS; computer-administered DIS (subject interacting alone with computer); computer-prompted DIS (interviewer using computer program as a guide). Kappas for 20 diagnoses ranged from .15 to .94, and averages for the three method pairs ranged from .57 to .64, which are comparable to other DIS reliability studies. Agreement between pairs of methods were comparable. Subjects' attitudes toward the computer interview were positive. While they felt they could better describe their feelings and ideas to a human, they found the computer contact less embarrassing. Overall, subjects had no preference for one method over another. Measures of social desirability and deviant response biases were correlated with diagnostic results. Reading ability did not affect subject's ability to respond to the DIS, although subjects with lower reading levels preferred the computer interview more.

Adult↗
PubMed1992

Toxic effects of solstitialin A 13-acetate and cynaropicrin from Centaurea solstitialis L. (Asteraceae) in cell cultures of foetal rat brain.

Extracts of the aerial parts of the yellow star thistle (Centaurea solstitialis L.) were prepared using petroleum ether, chloroform and methanol and toxicity assessed in primary cell cultures of striatum, frontal cortex and mesencephalon, containing the substantia nigra or raphe nucleus from the brain of the foetal rat. Chloroform extracts significantly reduced the percentage of live cells whereas the petroleum ether extract was inactive. The ability of the methanol extract to reduce the percentage of live cells could not be distinguished from the effects of the vehicle controls for methanol. Subsequently, the plant material was extracted with dichloromethane and 10 fractions were obtained by column chromatography. Fractions 5, 6, 7 and 8 caused concentration-dependent cell death in the culture of substantia nigra, the other fractions were not toxic at the concentrations used. In further studies, solstitialin A was isolated from fraction 9, solstitialin A 13-acetate from fraction 6 and solstitialin A-3 acetate and cynaropicrin from fraction 7. Solstitialin A 13-acetate and cynaropicrin were toxic to cultures of substantia nigra cells. It is concluded that, of the compounds identified, solstitialin A 13-acetate and cynaropicrin have toxic potential in cell cultures, containing cells from the substantia nigra of the rat, the specificity of action to cells of the substantia nigra remains to be shown, and that a toxic action in the midbrain may contribute to the nigro-pallidal encephalomalacia, caused by the ingestion of the yellow star thistle by horses.

Animals↗
PubMed1992

Prelexical facilitation and lexical interference in auditory word recognition.

Phonological priming effects were examined in an auditory single-word shadowing task. In 6 experiments, target items were preceded by auditorily or visually presented, phonologically similar, word or nonword primes. Results revealed facilitation in response time when a target was preceded by a word or nonword prime having the same initial phoneme when the prime was auditorily presented but not when it was visually presented. Second, modality-independent interference was observed when the phonological overlap between the prime and target increased from 1 to 3 phonemes for word primes but not for nonword primes. Taken together, these studies suggest that phonological information facilitates word recognition as a result of excitation at a prelexical level and increases response time as a result of competition at a lexical level. These processes are best characterized by connectionist models of word recognition.

Adult↗
PubMed1991

Minimal toxicity during protein A immunoadsorption treatment of malignant disease: an outpatient therapy.

Extracorporeal removal or modulation of circulating immune complexes (CIC) from plasma of animals and humans with malignant disease may be associated with induction of immune-mediated anti-tumor responses. Immunoadsorption columns containing heat-killed and formalin-fixed Staphylococcus aureus or staphylococcal protein A have been used for this purpose but treatments have often been associated with cardiopulmonary toxicity. Recently, an immunoadsorption device containing highly purified protein A covalently attached to a silica matrix (PROSORBA column) was used to treat 142 patients with refractory malignancies and 22 of 104 patients evaluated for anti-tumor response had objectively measurable reduction in tumor burden. In contrast to earlier experience with other devices, the procedures used in this trial were well tolerated and could be performed on an outpatient basis. The most common side effects observed among 1,306 treatments were chills (28% of treatments), low grade fever (28%), and musculoskeletal pain (16%). Side effects were mild to moderate and required no treatment or only symptomatic treatment. Treatment schedules were interrupted due to side effects for only six patients and there were no treatment-related deaths. Of 64 patients available for long-term follow-up evaluation (mean of 11 months), none exhibited evidence of long-term treatment-related side effects. None of the patient deaths in that period were associated with short or long-term treatment-related side effects. Protein A-silica (PROSORBA columns) can be used safely for development of further experimental treatments of malignant disease.

Adolescent↗
PubMed1991

Flavonol glycosides from Monnina sylvatica.

A new kaempferol triglycoside and three known kaempferol glycosides, among them two apiosides, have been isolated from the aerial parts of Monnina sylvatica. The structures were established on the basis of acid and enzymatic hydrolysis and spectral data (UV, 1H and 13CNMR, NOE difference measurements, D/CI and FAB-MS) of the isolates and of some derivatives. The triglycoside kaempferol 3-O-beta-D-glucosyl-(1----2)-O-[alpha-L-rhamnosyl(1----6)]-beta-D- galactoside is a new natural product. The configuration of the apiosyl moiety in kaempferol 3-O-beta-D-apiosyl(1----2)-beta-D-galactoside and kaempferol 3-O-beta-D-apiosyl(1----2)-O-[alpha-L-rhamnosyl(1----6)]- beta-D-galactoside was established through NOE difference measurements on the peracetate.

Carbohydrate Sequence↗
PubMed1989

Analytical aspects of drugs of natural origin.

The current importance of drugs of natural origin and their different phytotherapeutical preparations are mentioned. Analytical aspects related to vegetable drugs and their extracts are discussed. An overview is given on procedures used for the isolation of reference compounds, sample preparation for high-performance liquid chromatographic analysis, identification of vegetable drugs and detection of adulterants. The different approaches currently employed for the standardization of extracts are presented. The various aspects are discussed with the aid of illustrative examples.

Chromatography, High Pressure Liquid↗
PubMed1971

Light and scanning-beam electron microscopy of wall-defective Staphylococcus aureus induced by lysostaphin.

The serial morphological changes of Staphylococcus aureus after exposure to lysostaphin (one unit per ml) in hypertonic culture medium containing 5% NaCl were studied over an 8-hr period at 37 C. S. aureus stained gram-negative almost instantaneously upon contact with lysostaphin. Many cells were lysed, but wall-defective staphylococci with corrugated surface were detected as early as 5 min by use of scanning-beam electron microscopy. Wall-defective staphylococci enlarged progressively with increasing periods of incubation. The absorbance of the lysostaphin-treated culture decreased significantly by 2 min, remained stationary for 2 hr, and then progressively increased. The number of vegetative colony-forming units decreased progressively with increasing periods of incubation, whereas the number of L-colony-forming units remained the same.

Absorption↗