PubMed Health⌕ Search

Biomedical subjects

R Heckmann

Publications and source records attributed to R Heckmann.

At least 19 recordsLinked to original sources
PubMed2003

Diglucosyl-glycerolipids from the marine sponge-associated Bacillus pumilus strain AAS3: their production, enzymatic modification and properties.

The marine strain Bacillus pumilus strain AAS3, isolated from the Mediterranean sponge Acanthella acuta, produced a diglucosyl-glycerolipid, 1,2-O-diacyl-3-[beta-glucopyranosyl-(1-6)-beta-glucopyranosyl)]glycerol, with 14-methylhexadecanoic acid and 12-methyltetradecanoic acid as the main fatty acid moieties (GGL11). On a 30 l scale, using artificial seawater supplemented with glucose (20 g/l), yeast extract (10 g/l), and suitable nitrogen/phosphate sources, growth-associated glycoglycerolipid production reached its maximum yield of 90 mg/l after 11 h. Lipase-catalyzed modification of the native substance led to the deacylated parent compound (GG11), which could be reacylated using the same enzyme system to afford a new dipentenoyl-diglucosylglycerol (GGL12) as the major product upon addition of 4-pentenoic acid to the medium. GGL11 decreased the surface tension of water from 72 mN/m to 29 mN/m and the interfacial tension of the water/ n-hexadecane system from 44 to 5 mN/m. Anti-tumor-promoting studies on this class of diglucosyl glycerol products showed that the carbohydrate/glycerol backbone (GG11) has a more potent inhibitory activity than the acylated compounds. The diglucosyl-glycerol GG11 strongly inhibited growth of the tumor cell lines HM02 and Hep G2 (50% inhibition at approximately 1 microg/ml), while the glycerolipids GGL11 and GGL12 were less active or had no effect.

Animals↗
PubMed1998

Production and structure elucidation of di- and oligosaccharide lipids (biosurfactants) from Tsukamurella sp. nov.

The bacterium Tsukamurella sp. nov., isolated from soil, was found to produce novel glycolipids when grown on sunflower oil as the sole carbon source. The glycolipids were isolated by chromatography on silica columns and their structures elucidated using a combination of multidimensional NMR and MS techniques. The three main components are 2,3-di-O-acyl-alpha-D-glucopyranosyl-(1-1)-alpha-D-glucopyranose, 2,3-di-O-acyl-beta-D-glucopyranosyl-(1-2)-4,6-di-O-acyl-alpha-D- glucopyranosyl-(1-1)-alpha-D-glucopyranose and 2,3-di-O-acyl-beta-D-glucopyranosyl-(1-2)-beta-D-galactopyranosyl- (1-6)-4,6-di-O-acyl-alpha-D-glucopyranosyl-(1-1)-alpha-D- glucopyranosyl which are linked to fatty acids varying in chain length from C4 to C18. The glycolipids are mainly extracellular but are also found attached to the cell walls. During the cultivation the composition of the glycolipids changed from disaccharide- to tri- and tetrasaccharide lipids. The glycolipids show good surface-active behaviour and have antimicrobial properties.

Actinomycetales↗
PubMed1993

Reproducibility of urethral pressure profiles in clinically normal sexually intact female dogs by use of microtransducer catheters.

Urethral pressures profiles (UPP) obtained by use of microtransducer catheters were determined in 8 anestrous sexually intact female Beagles during general anesthesia. A UPP study consisted of 3 consecutive recordings, and 4 UPP studies were repeated at an interval of 5 days in each dog. Maximal urethral pressure (cm of H2O), bladder pressure (cm of H2O), and anatomic urethral length (cm) were recorded. Maximal urethral closure pressure (cm of H2O) was calculated. Mean +/- SD (for all measurements) maximal urethral closure pressure was 12.8 +/- 5.6 cm of H2O (range, 2.4 to 25.2 cm of H2O). Maximal urethral closure pressure was significantly (P < 0.05) decreased during the first recording period (11.4 +/- 5.8 cm of H2O), compared with the second (13.0 +/- 5.2 cm of H2O) or third (14.1 +/- 5.7 cm of H2O) recording periods within a UPP study (3 consecutive recordings). Mean maximal difference in urethral closure pressure during a single UPP study was 4.8 +/- 2.4 cm of H2O. Significant difference in maximal urethral closure pressure was not observed between studies. Mean (for all measurements) anatomic urethral length was 6.2 +/- 0.9 cm (4.1 to 7.8 cm). Anatomic urethral length was significantly (P < 0.05) less during the first recording period (6.1 +/- 0.9 cm), compared with values for the second and third periods (6.3 +/- 0.9 cm, 6.4 +/- 0.9 cm respectively). Anatomic urethral length for time 3 was significantly (P < 0.05) less than the value for time 1 (5.8 +/- 0.7 cm vs 6.6 +/- 0.8 cm).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Instrumentation for simultaneous recording of compound muscle action potentials and related force in the dog.

An examination apparatus for the study of both compound muscle action potentials and related isometric force of the target muscle after supramaximum electrical stimulation of the respective nerve is described. Force transducers were used to record forces from the forelimb paws and the jaws of the dog. The unit is suitable for the clinical examination of neuromuscular transmission disturbances and for testing the effect of relaxant agents.

Action Potentials↗
PubMed1992

Neuromuscular transmission studies in the healthy dog: EMG and muscle force measurement after repetitive nerve stimulation.

In 10 healthy anaesthetized female dogs the ulnar and the mandibular nerve were stimulated supramaximally by repetitive electric impulses according to a fixed programme. To evaluate the neuromuscular transmission system the course of the evoked compound muscle action potential and the near-isometric force of forelimb and masticatory muscles were studied respectively. The presented results are comparable to values obtained from small hand muscles of conscious, healthy human subjects. The simultaneous measurement of both the electrical and the force response may improve the diagnostic accuracy of the examination in presumed neuromuscular transmission failure in the dog, as it does in humans.

Action Potentials↗
PubMed1992

[Spinal muscular atrophy in Braunvieh calves].

Clinical, neurophysiological and histopathological findings of sixteen cases of spinal muscular atrophy in calves are described. The first clinical signs usually were noticed at 2-6 weeks of age. The animals showed weakness in the hindquarters, trembling and ultimate recumbency. There was a marked muscular atrophy in all four extremities. In addition, secondary bronchopneumonia was evident in 11 cases. Histopathological lesions consisted of degenerative changes in the neurons of the ventral horns and the axons of the spinal cord as well as degeneration of nerve axons in the extremities. Neurophysiological measurements revealed spontaneous activity in the muscles of the limbs. The conditions is autosomal recessive. So far 11 bulls have been identified and excluded from breeding.

Animals↗
PubMed1989

Significance of shape and size of the stimulating coil in magnetic stimulation of the human motor cortex.

Three different stimulating coil designs were evaluated for magnetic motor cortex stimulation by comparing threshold stimulus intensities at different sites over the scalp for exciting upper and lower limb muscles. Little difference was found between stimulation characteristics of two circular coils of different size, the smaller coil delivering slightly more focal stimuli. A twin coil composed of two single circular coils in series arranged side-by-side, produced significantly more powerful and more focal stimuli. It proved to be superior for exciting the leg muscles, in that less output energy was needed. For all coils, the orientation of the inducing current over the presumed motor area was the most critical stimulation parameter, and a sagittal current in anterior direction or coronal towards the stimulated hemisphere was optimal for the upper limb or lower limb muscles, respectively.

Adult↗
PubMed1989

[Transcranial magnetic stimulation of the motor cortex and percutaneous magnetic stimulation of the peripheral nervous structures in the dog].

The motor cortex was transcranially and peripheral nervous structures (motor roots, plexus, peripheral nerves) were percutaneously stimulated by magnetic pulses in awake dogs and in dogs awaking from general anesthesia. The compound muscle action potentials were recorded by surface or needle electrodes. The central motor conduction time as an information about central motor tracts was obtained by subtracting the peripheral latency from the corticomuscular latency. The peripheral latency was assessed by high voltage electrical and magnetic stimulation of motor roots and by the F-wave technique. The motor conduction velocity of the tibial nerve was measured by percutaneous magnetic and by electrical stimulation and the resulting values were compared.

Action Potentials↗
PubMed1982

Differentiation of spontaneous activity from normal and denervated skeletal muscle.

The discrimination of fibrillation potentials and endplate potentials based on the conventional EMG methods is difficult if there is only discrete denervation. The reliability of discrimination can be highly improved if the frequency behaviour of the potentials is taken into account. The average proportional consecutive interval difference is the best discrimination variable with 90% correct findings per analysed potential sequence. When three analyses per muscle are made, the accuracy increases to 97.2%. The second best variable is the mean consecutive difference followed by interval bandwidth, standard deviation of interval, minimum interval and finally maximum interval. The mean duration of intervals does not allow of any differentiation. The frequency analysis can be restricted to spontaneous activity sequences of ten seconds. It is immaterial which part of a prolonged sequence is analysed for ten seconds. The conventional evaluation of registered spontaneous activity either alone or with observation at the monitor under simultaneous acoustic control is inferior to the frequency analysis. The results do not allow a statement of the probability of wrong diagnosis in clinical routine work.

Action Potentials↗
PubMed1979

The effect of halothane on the action of alcuronium in the dog.

The effect of halothane on the action of alcuronium on neuromuscular transmission was studied in the intact dog. Electrical and mechanical evoked responses from stimulation of the ulnar nerve were recorded. The administration of 0.5% halothane prolonged the duration of action of alcuronium by about 50%.

Alcuronium↗