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Biomedical subjects

D Linke

Publications and source records attributed to D Linke.

At least 19 recordsLinked to original sources
PubMed2000

In vitro reconstitution and biophysical characterization of OEP16, an outer envelope pore protein of pea chloroplasts.

More than 30% of all proteins in the living cell are membrane proteins; most of them occur in the native membranes only in very low amounts, which hinders their functional and structural investigation. Here we describe the in vitro reconstitution of overexpressed Outer Envelope Protein 16 (OEP16) from pea chloroplasts, a cation-selective channel, which has been purified from E. coli inclusion bodies. Reconstitution in detergent micelles was monitored by CD and fluorescence spectroscopy. Electron microscopy showed a homogeneous size distribution of the reconstituted protein, and differential scanning calorimetry gave an estimate of the enthalpy of protein folding. First protein crystals were obtained that have to be further refined for X-ray structural analysis. The described methods of membrane protein reconstitution and biophysical analysis might prove helpful in the study of other membrane proteins.

Calorimetry, Differential Scanning↗
PubMed2000

Mapping the distribution of 3-hydroxylipins in the Mucorales using immunofluorescence microscopy.

The distribution of endogenous 3-hydroxylipins (3-OH oxylipins) in representatives of the Mucorales was mapped using immunofluorescence microscopy. Strains of each of the following genera were examined: Absidia, Actinomucor, Cunninghamella, Mortierella (subgenus Micromucor), Mortierella (subgenus Mortierella), Mucor and Rhizomucor. Immunofluorescence microscopy was carried out using an antibody that was raised against 3R-hydroxy-5Z,8Z, 11 Z, 14Z-eicosatetraenoic acid (3R-HETE), which cross-reacts with other 3-OH oxylipins. Subsequently, the occurrence and distribution of the antibody on the various reproductive stages of each fungus was noted. In Absidia, Actinomucor, Mortierella (subgenus Micromucor), Mucor and Rhizomucor, 3-OH oxylipins were found to be associated with the columellae and/or wall of the sporangium. In the representative of Cunninghamella, the 3-OH oxylipins were associated with the single-spored sporangiola. No 3-OH oxylipins were detected in the strains representing Mortierella (subgenus Mortierella).

Fatty Acids↗
PubMed1998

Biological dynamics and distribution of 3-hydroxy fatty acids in the yeast Dipodascopsis uninucleata as investigated by immunofluorescence microscopy. Evidence for a putative regulatory role in the sexual reproductive cycle.

Dipodascopsis uninucleata has been recently shown to produce 3-hydroxy polyenoic fatty acids from several exogenous polyenoic fatty acids. In order to examine whether endogenous 3-hydroxy fatty acids (3-OH-FA) may be implicated in the developmental biology of this yeast, we mapped by immunofluorescence microscopy their occurrence in fixed cells with or without cell walls using an antibody raised against 3R-hydroxy-5Z,8Z,11Z,14Z-eicosatetraenoic acid (3R-HETE), the biotransformation product from arachidonic acid (AA). This antibody turned out to cross-react with other 3-OH-FA. 3-OH-FA were detected in situ in gametangia, asci, as well as between released ascospores, and proved to be associated with the sexual reproductive stage of the life cycle of the yeast. Acetylsalicylic acid (1 mM), which is known to suppress the formation of 3-OH-FA from exogenous polyenoic fatty acids, inhibited the occurrence of immunoreactive material as well as the sexual phase of the life cycle suggesting a prominent regulatory role of 3-OH-FA for the latter.

Animals↗
PubMed1998

Phosphate availability affects the thylakoid lipid composition and the expression of SQD1, a gene required for sulfolipid biosynthesis in Arabidopsis thaliana.

Photosynthetic membranes of higher plants contain specific nonphosphorous lipids like the sulfolipid sulfoquinovosyl diacylglycerol in addition to the ubiquitous phospholipid phosphatidylglycerol. In bacteria, an environmental factor that drastically affects thylakoid lipid composition appears to be the availability of phosphate. Accordingly, we discovered an increase in the relative amount of sulfolipid and a concomitant decrease in phosphatidylglycerol in Arabidopsis thaliana grown on medium with reduced amounts of phosphate, as well as in the pho1 mutant of A. thaliana deficient in phosphate transport. To investigate the molecular basis of the observed change in lipid composition, we isolated a cDNA of A. thaliana, designated SQD1, that encodes a protein involved in sulfolipid biosynthesis as suggested by three lines of evidence. First, the cDNA shows high sequence similarity to bacterial sqdB genes known to be essential for sulfolipid biosynthesis; second, the SQD1 gene product is imported into chloroplasts where sulfolipid biosynthesis takes place; and third, transgenic plants expressing SQD1 in antisense orientation show a reduction in sulfolipid content. In the pho1 mutant as well as in wild-type plants grown under reduced phosphate availability, increased amounts of SQD1 mRNA and SQD1 protein are detected, suggesting that the increase in sulfolipid content under phosphate limitation is the result of an increased expression of at least one gene required for sulfolipid biosynthesis in A. thaliana. It is suggested that a certain amount of anionic thylakoid lipid is maintained by substituting sulfolipid for phosphatidylglycerol under reduced phosphate availability.

Amino Acid Sequence↗
PubMed1993

[The intracarotid amobarbital test. Neuroradiologic and neuropsychologic aspects].

In presurgical evaluation of epilepsy, unilateral cerebral inactivation by means of intracarotid injection of amobarbital is used for the determination of cerebral dominance for language and memory functions. This intracarotid amobarbital test (IAT) is intended to yield prognoses concerning postsurgical neuropsychological and neurological deficits. In the present review, neuroradiological and neuropsychological aspects of the procedure are discussed. Each IAT is preceded by a cerebral angiography to exclude or detect vascular anomalies that might be relevant to the interpretation of neuropsychological test data. The main methodological problems of the IAT are interference of various cognitive deficits and monitoring of the course of amobarbital action. Alternative procedures of determination of hemispheric asymmetries--positron emission tomography, electrical stimulation mapping, and noninvasive methods like tachistoscopy--mainly yield data complementary to the results of the IAT and hence are not taken as substitutes of that technique.

Amobarbital↗
PubMed1993

[The selective amobarbital test in epileptology].

Epileptic foci in the frontal or parieto-occipital cortex often cause epileptiform EEG changes in both hemispheres. Therefore, delineation of the primary epileptogenic area, which is necessary for epilepsy surgery, is not possible by electrophysiological methods. A temporary inactivation of the epileptogenic area by a selective injection of the short-acting barbiturate amobarbital (selective amobarbital test, SAT) can prove the relation between generalized EEG changes and a circumscribed epileptogenic area. The SAT may also be used for evaluation of the risk for additional functional deficits after epilepsy surgery in certain brain areas. During temporary inactivation of the brain area to be resected, the function of the motor system, speech and memory can be tested.

Amobarbital↗
PubMed1987

Technetium-99m HM-PAO brain SPECT in epileptic patients before and during unilateral hemispheric anesthesia (Wada test): report of three cases.

The lipophilic brain SPECT agent [99mTc]hexamethyl propylene amine oxime (HM-PAO) was used in three cases before and during unilateral anesthesia of one hemisphere for lateralization of speech dominance (Wada test). This procedure led to a decrease of regional cerebral blood flow (rCBF) in each of the hemispheres to 55 and 90%, respectively. Diminution of rCBF was significantly more pronounced in the dominant hemisphere. A second phenomenon observed during the Wada test was crossed cerebellar diaschisis. These findings support the assumption that HM-PAO allows monitoring of brain perfusion, as rapid changes of rCBF due to decreased neuronal activity cause respective alterations of cerebral and cerebellar uptake of this new brain agent.

Adolescent↗
PubMed1978

Blink reflex in facial-hypoglossal anastomosis.

The blink reflex was investigated in two patients after a facial-hypoglossal anastomosis had been performed. In each case the first component of the blink reflex could be demonstrated with normal latency on the operated side after ipsilateral supraorbital stimulation. These findings give further evidence that the first component of the blink reflex is not monosynaptic in nature. The second component of the blink reflex was distinctly retarded in the first case and was not seen at all in the second case. The second component of the blink reflex is influenced strongly by alteration of the intrabulbar and efferent part of the reflex circuits; it shows some correlation with voluntary motor activity.

Aged↗
PubMed1977

Neurophysiological experiments on intention tremor (author's transl).

During a postural innervation, cerebellar intention tremor can be produced by applying direct stimulus to the muscle. The stimulus is followed by a silent period of 160 to 200 ms, which exceeds the normal variation. Simultaneously, a massive rebound in the antagonistic muscle is evoked due to the tension reflex in the agonistic muscle. Passive shortening or stretching of the voluntarily activated muscle has no effect: there is no silent period in the shortened muscle, no rebound in the stretched muscle, and, consequently, little or no oscillation follows. The spindle apparatus seems irrelevant to the development of intention tremor. The feedback mechanism of the Golgi-inhibition systems is discussed. These findings cannot be explained by assuming a central pacemaker.

Cerebellum↗
PubMed1977

The use of hyperbaric oxygenation in the treatment of spinal cord lesions.

In 13 patients with compressive spinal cord lesions we performed a trial of treatment with hyperbaric oxygen (HO). This therapy was postoperatively administered when neurological deficit persisted. In order to assess the effect of each individual HO session (given daily at an inspiratory oxygen pressure (PO2) of 1.5 atmospheres absolute for 40 min) as well as of the entire HO therapy (consisting of 10-15 single sessions in each case) neurological and electromyographical follow-up examinations were regularly performed. In 6 of the 13 patients we found a marked improvement, particularly in motor functions. The other patients only showed little change in neurological status. Arterial and cerebrospinal fluid (CSF) PO2 were concurrently measured in 8 patients during HO sessions. The values of both showed a considerable increase. The rise in CSF PO2 may be regarded as indicative for an improved oxygenation of the spinal cord tissue during HO treatment. On the basis of these findings we may assume that repetitive HO treatment can be helpful in the management of compressive spinal cord lesions.

Adolescent↗