Search PubMed⌕ Search

Biomedical subjects

W Fischer

Publications and source records attributed to W Fischer.

At least 397 records · Page 22Linked to original sources
PubMed1978

[Frequency domain analysis of the dynamic properties of the encoder in the slowly adapting crayfish stretch receptor neuron].

The transfer properties of the slowly adapting stretch receptor neuron can be suitably described in the frequency domain. The measurements are carried out by means of sinusoidally varying intracellular currents. The frequency response at low stimulation frequencies has been calculated from responses to current steps. At very low input frequencies the amplitude-frequency characteristic in the Bode diagram is nearly parallel to the abscissa. With increasing stimulation frequency the gain becomes larger and has a maximum at 1--3 Hz (stimulation frequency/carrier frequency (f/fo approximately 0.2). The amplitude-frequency characteristic decreases then, at first slowly then more rapidly, and reaches in the range of carrier frequency (f/fo approximately 1) small values. The phase-frequency characteristic shows at low input frequencies a small positive magnitude of 8--10(0). With higher stimulation frequencies the phase angle decreases and reaches negative values. In the range of carrier frequency the phase shift runs to -180 degrees. The present findings demonstrate also that the transfer function of the encoder depends on the carrier frequency of the receptor neuron. Larger carrier frequencies cause a decrease of the gain but the peak remains. This maximum shifts with increasing fo in direction to higher stimulation frequencies. The elimination of the encoder adaptation by means of a suitable model results in the frequency response of the real encoder. The above statements hold for higher stimulation frequencies too, but the typical differential behaviour at low frequencies disappears.

Animals↗
PubMed1978

[Na-K ionic pump and spike adaptation in the slowly and rapidly adapting stretch receptor neuron of the crayfish Orconectes limosus (RAF.)].

A very important cause of the spike adaptation in the slowly adapting stretch receptor neuron (SN1) is the Na-K ionic pump. An increasing inhibition of the ionic pump, produced by gradual reduction of the external K+-concentration or application of rising doses of ouabain, is correlated with an adequate diminution of frequency decay. But even high concentrations of ouabain (10(-3) -- 5 . 10(-3) M) can not completely abolish the spike adaptation. Immediately after the onset of a current step the impulse frequency still declines. In agreement with these findings the gain in the Bode diagram shows a maximum further on. The spike adaptation in the rapidly adapting neuron (SN2) can only in a smaller part be attributed to the action of the ionic pump. Application of ouabain causes in the SN2, contrary to SN1, only a low depolarization of the membrane potential. The decay of impulse frequency is considerably diminished but a long lasting nearly stationary discharge like in the SN1 can never be observed.

Animals↗
PubMed1977

The polar lipids of group B Streptococci. I. Glucosylated diphosphatidylglycerol, a novel glycopholipid.

1. From group B Streptococci a novel glycophospholipid was isolated, which contained D-glucose, glycerol, acyl groups and phosphorus in a molar ratio of approx. 1:3:4:2. It was established to be 2'-O-alpha-D-glucopyranosyl-, 1',3'-bis-(1,2-diacyl-sn-glycero-3-phospho)-glycerol. 2. The structure of the deacylated core was accomplished by analyses of the breakdown products obtained on (i) strong alkaline hydrolysis, (ii) Smith-degradation, and (iii) periodate oxidation with subsequent hydrazinolysis. The four acyl groups were located by sequential degradation of the native lipid with phospholipase A2 and 98% acetic acid. 2. In group B Streptococci approximately 25% of diphosphatidylglycerol occurs in the form of its glucosylated derivative which accounts for 18% of the lipid phosphorus. The glucosylated phosphatidylglycerol analogue could not be detected. A phosphoglucolipid, however, was present, which was tentatively identified as glycerophosphodiglucosyldiacylglycerol.

Carbohydrates↗
PubMed1977

The polar lipids of group B Streptococci. II. Composition and positional distribution of fatty acids.

1. The polar lipids from group B Streptococci have been isolated. Unless overlapping fractions are worked up on each step molecular species can be lost resulting in a fatty acid composition different from the original one. 2. The lipids were shown to be 1(3),2-diacyl-3(1)-O-alpha-D-glucopyranosyl-sn-glycerol, 1(3),2-diacyl-3(1)-O-[alpha--D-glucopyranosyl-(1,2)-O-alpha-D-glucopyranosyl]-sn-glycerol, 1,2-diacyl-sn-glycero-3-phospho-1'-sn-glycerol, lysylphosphatidylglycerol and 1'-3'-bis(1,2-diacyl-sn-glycero-3-phospho-glycerol. The sterochemical configuration of the phospholipids was achieved by combinations of chemical degradations. 3. The fatty acid composition of group B Streptococci lipids is qualitatively the same as in other Streptococci, but differs by a high content of stearic acid and by a low degree of unsaturation and cyclopropanization. 4. The forementioned polar lipids as well as the glucosyldiphsphatidylglycerol,, which is also found in this organism, showed a very similar composition and the same non-radom positional distribution of fatty acids. Apart from short chain fatty acids the positioning differentiates between saturated and unsaturated fatty acids: short chain and unsaturated fatty acids are accumulated at Position 2, saturated acids are preferentially linked to Position 1. 5. The uniform fatty acid make-up in all polar lipids favours the hypothesis that their diacylglycerol portions are derived from a common phosphatidic acid precursor with negligible postsynthetic rearrangements of the constituent fatty acids.

Chromatography, Thin Layer↗
PubMed1977

[Experiences with bladder-uterus fistulae].

The present summary reports 5 cases of vesicocervical fistula, 9 cases of vesicocervico-vaginal fistula and 1 of vesicocervicocorporeal fistula seen over the last 20 years. When compared with the period between 1941 and 1955 the number of such fistula cases has increased fourfold. All thses fistulas, with just one exception, arose as a consequence of obstetric treatment. Conservative therapie was successful only in one case while all the other fistulas had to been operated upon. The preferred operating technique was that of vaginal metroplasty (Wolkowitsch-Küstner's technique). Hysterectomy or stump exstirpation with cystorraphy were performed in 4 cases. The combined vesicocervico-corporeal fistula required a vaginoabdominal treatment. 14 patients were brought to recovery. Increases in the number of vesicouterine fistulas as observed over recent years are considered to be related to a more concentrated therapy and to a higher frequency of cesarean sections. The vaginal route is all the more justified for fistula operations the nearer the fistula is located to the vagina. Operations of that kind require adequate skill in urinary bladder-ureteral- and uterosurgery.

Abortion, Spontaneous↗
PubMed1977

[Enzyme patterns in connective tissue proliferations (author's transl)].

In a series of benign or semimalignant connective tissue proliferations (4 desmoids, 1 recurrence of a dermatofibrosarcoma protuberans, 4 fibromas, 1 neurofibroma, 3 keloids, 3 Dupuytren's contractures) and a normal fascia for comparison the pattern of 18 enzymes from different metabolic pathways was investigated. It should be clarified whether alterations of the enzyme pattern wouldoccur, asthey are found in malignant tumours. The activity of most of the enzymes investigated increased about twofold in the latter of two extirpations (16 months interval) of a recurring desmoid. In the recurrence of a dermatofibrosarcoma protuberans and in a recurrance of a fibroma a remarkably high activity of glucose-6-phosphate dehydrogenase and pyruvate kinase was found. High activities of these enzymes are known to be characteristic of experimental tumours of animals and human malignant neoplasms. Therefore it is assumed that these differences from the normal patternof enzyme activity are related to recidivity and may be regarded as first signs of a deviation from benignity. Based on these results further studies haveto be done with the aim to find a biochemical tool for, evaluation and prognosis of the course of these diseases.

Dupuytren Contracture↗
PubMed1977

[Therapy of bilateral lesions of the ureter during or after surgery for gynecologic carcinoma].

Special conditions for plastic surgery on the upper urinary tract in cases of gynaecological radical hysterectomy are discussed in conjunction with one case of bilateral ureteral injury inflicted during the operation and one case of postoperative bilateral ureterovaginal fistulas. Today, Boari grafting is preferred rather than direct implantation. Oblique submucous canalisation (antireflux effect) in unnecessary in most cases. Two-stage operations would provide a better protection of the bladder than one-stage restorative treatment. In emergency cases unilateral nephrostomy or ureterostomy in situ may be considered as interim solution. Transperitoneal access is necessary only in cases of injury during operation or when a one-stage plastic operation has to be carried out. For subsequent reconstructive operations performed in two stages we would prefer the extraperitoneal approach.

Female↗
PubMed1976

The stereochemical configuration of lysobisphosphatidic acid from rat liver, rabbit lung and pig lung.

Lysobisphosphatidic acid known also as bis(monoacyl-glycerol)phosphate, was isolated from liver of rats treated with Triton WR1339, and from rabbit and pig lung. Alkaline hydrolysates of all these samples of lysobisphosphatidic acid were essentially similar and contained phosphorus, total glycerol, free glycerol, total glycerophosphates, beta-glycerophosphate, total alpha-glycerophosphates, sn-glycero-1-phosphate and sn-glycero-3-phosphate in a molar ratio of 1.0 : 2.0 : 1.0 : 1.0 :0.6 : 0.4 : 0.38 : 0.04. This proves that the backbone of the principal lysobisphosphatidic acid from all three sources has the structure of 1-sn-glycerophospho-1-sn-glycerol.

Animals↗