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A Huber

Publications and source records attributed to A Huber.

At least 127 records · Page 7Linked to original sources
PubMed1996

The transient receptor potential protein (Trp), a putative store-operated Ca2+ channel essential for phosphoinositide-mediated photoreception, forms a signaling complex with NorpA, InaC and InaD.

The transient receptor potential protein (Trp) is a putative capacitative Ca2+ entry channel present in fly photoreceptors, which use the inositol 1,4,5-trisphosphate (InsP3) signaling pathway for phototransduction. By immunoprecipitation studies, we find that Trp is associated into a multiprotein complex with the norpA-encoded phospholipase C, an eye-specific protein kinase C (InaC) and with the InaD protein (InaD). InaD is a putative substrate of InaC and contains two PDZ repeats, putative protein-protein interaction domains. These proteins are present in the photoreceptor membrane at about equimolar ratios. The Trp homolog analyzed here is isolated together with NorpA, InaC and InaD from blowfly (Calliphora) photoreceptors. Compared to Drosophila Trp, the Calliphora Trp homolog displays 77% amino acid identity. The highest sequence conservation is found in the region that contains the putative transmembrane domains S1-S6 (91% amino acid identity). As investigated by immunogold labeling with specific antibodies directed against Trp and InaD, the Trp signaling complex is located in the microvillar membranes of the photoreceptor cells. The spatial distribution of the signaling complex argues against a direct conformational coupling of Trp to an InsP3 receptor supposed to be present in the membrane of internal photoreceptor Ca2+ stores. It is suggested that the organization of signal transducing proteins into a multiprotein complex provides the structural basis for an efficient and fast activation and regulation of Ca2+ entry through the Trp channel.

Amino Acid Sequence↗
PubMed1996

Phosphorylation of the InaD gene product, a photoreceptor membrane protein required for recovery of visual excitation.

In an approach directed to isolate and characterize key proteins of the transduction cascade in photoreceptors using the phosphoinositide signaling pathway, we have isolated the Calliphora homolog of the Drosophila InaD gene product, which in Drosophila InaD mutants causes slow deactivation of the light response. By screening a retinal cDNA library with antibodies directed against photoreceptor membrane proteins, we have isolated a cDNA coding for an amino acid sequence of 665 residues (Mr = 73,349). The sequence displays 65.3% identity (77.3% similarity) with the Drosophila InaD gene product. Probing Western blots with monospecific antibodies directed against peptides comprising amino acids 272-542 (anti-InaD-(272-542)) or amino acids 643-655 (anti-InaD-(643-655)) of the InaD gene product revealed that the Calliphora InaD protein is specifically associated with the signal-transducing rhabdomeral photoreceptor membrane from which it can be extracted by high salt buffer containing 1.5 M NaCl. As five out of eight consensus sequences for protein kinase C phosphorylation reside within stretches of 10-16 amino acids that are identical in the Drosophila and Calliphora InaD protein, the InaD gene product is likely to be a target of protein kinase C. Phosphorylation studies with isolated rhabdomeral photoreceptor membranes followed by InaD immunoprecipitation revealed that the InaD protein is a phosphoprotein. In vitro phosphorylation is, at least to some extent, Ca 2+ dependent and activated by phorbol 12-myristate 13-acetate. The inaC-encoded eye-specific form of a protein kinase C (eye-PKC) is co-precipitated by antibodies specific for the InaD protein from detergent extracts of rhabdomeral photoreceptor membranes, suggesting that the InaD protein and eye-PKC are interacting in these membranes. Co-precipitating with the InaD protein and eye-PKC are two other key components of the transduction pathway, namely the trp protein, which is proposed to form a Ca2+ channel, and the norpA-encoded phospholipase C, the primary target enzyme of the transduction pathway. It is proposed that the rise of the intracellular Ca2+ concentration upon visual excitation initiates the phosphorylation of the InaD protein by eye-PKC and thereby modulates its function in the control of the light response.

Amino Acid Sequence↗
PubMed1996

The TRH-like peptides in rabbit testis are different from the TRH-like peptide in the prostate.

Human seminal fluid contains a number of tripeptide amides with similar structures to thyrotropin releasing hormone (TRH), two of which have been identified as pGlu-Glu-Pro amide and pGlu-Phe-Pro amide. To determine whether these peptides originate in the same tissues and have the same molecular origin, TRH-immunoreactive peptides were extracted from the prostate and testis of the rabbit, purified by ion exchange chromatography and HPLC, and identified by co-chromatography with 3H-labelled marker peptides. In addition, trypsin digestion was used to release TRH-like tripeptides from N-extended forms of these peptides. The sole TRH-like peptide in the prostate was shown to be pGlu-Glu-Pro amide; it was not accompanied by a detectable amount of pGlu-Phe-Pro amide. The prostate also appeared to contain a very small amount of N-extended forms of these peptides. In contrast to the prostate, the testis contained high concentrations of N-extended forms of pGlu-Phe-Pro amide but essentially no tripeptide. The testis also contained N-extended forms of two other neutral TRH-like peptides which were less hydrophobic than pGlu-Phe-Pro amide. Neither the prostate nor the testis contained a significant amount of TRH. The results show that in the rabbit the TRH-like peptides pGlu-Glu-Pro amide and pGlu-Phe-Pro amide occur in different tissues and appear to be formed from different precursors.

Amino Acid Sequence↗
PubMed1996

Isolation of genes encoding photoreceptor-specific proteins by immunoscreening with antibodies directed against purified blowfly rhabdoms.

The proteins which perform and regulate key steps in phototransduction are assumed to be localized in the rhabdomeric membrane of invertebrate photoreceptor cells. We have employed antibodies raised against rhabdoms purified from blowfly eyes in order to isolate copy deoxyribonucleic acid (cDNA) clones encoding proteins that are required in the phototransduction machinery. By immunoscreening a Calliphora retinal cDNA library, we obtained clones of genes coding for five different proteins. As revealed by partial cDNA sequence analysis, three of these genes represent the Calliphora homologs of Drosophila trp, inaC and InaD, while the other two displayed no homology to known genes. Northern blot analysis confirmed that trp, inaC and InaD transcripts were present in RNA isolated from the retina, but not in RNA isolated from brain or thorax. Specific antibodies directed against trp, inaC and InaD protein were raised using recombinantly expressed proteins or synthetic peptides. Western blot analyses revealed that trp, inaC and InaD protein are specifically associated with the rhabdomeral photoreceptor membrane. Extraction of membranes with buffers of different ionic strengths suggested that the trp gene product is an integral membrane protein, whilst the inaC and InaD gene products are peripherally bound membrane proteins. This demonstrates that the immunoscreening approach used here can be successfully applied to isolate genes that code for either integral or peripheral photoreceptor membrane proteins.

Amino Acid Sequence↗
PubMed1996

Vertical Duane's retraction syndrome.

PURPOSE: We report three patients with a rare variant of Duane's retraction syndrome. METHODS: Eye movements were recorded by electro-oculography. One patient underwent electro-myography. RESULTS: All patients showed V-incommitance and twitch abduction on vertical saccades. Electromyography showed lateral rectus muscle firing activity during upgaze and downgaze. CONCLUSION: Our patients showed synergistic innervation between the lateral rectus muscle and ipsilateral vertical acting muscles documented by electromyography.

Adolescent↗
PubMed1996

Regulation of VIP release from rat enteric nerve terminals: evidence for a stimulatory effect of NO.

The basal release of vasoactive intestinal polypeptide (VIP) from freshly prepared enriched synaptosomes was 159.1 +/- 17.3 fmol/mg protein (100%), which constituted 2.5% of the total VIP content. Basal VIP release was reduced by 65% by removal of external Ca2+. Release of VIP was stimulated by depolarization with KCl (65 mM, 143%) and in the presence of veratridine (10(-6) M, 184%), monensin (10(-5) M, 131%), and the Ca2+ ionophore A-23187 (10(-6) M, 160%). Stimulation of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent mechanisms using isoproterenol (10(-6)-10(-4) M) and forskolin (10(-6) and 10(-5) M) had no stimulatory influence on VIP release. In contrast, sodium nitroprusside (10(-4) M, 198%), the nitric oxide (NO) donor 3-(morpholino)sydnonimine (10(-4) M, 155%), and the guanosine 3',5'-cyclic monophosphate (cGMP) analogue 8-bromo cGMP (10(-4) M, 196%) caused a significant release of VIP. L-Arginine (10(-3) M, 246%) also caused a significant increase of VIP release that was antagonized by the NO synthase inhibitor N omega-nitro-L-arginine methyl ester (5 x 10(-4) M, 131%), which had no effect when given alone. The results demonstrate that VIP can be released from enriched synaptosomes by Ca(2+)-dependent mechanisms by NO agonists or NO-dependent mechanisms. It is speculated that this VIP release is induced by a presynaptic stimulatory mechanism of NO and this effect could enhance or contribute to the action of NO.

Animals↗
PubMed1996

[Tumor of the gastrointestinal autonomic nervous system (GAN-tumor or plexus sarcoma)].

GAN-tumors or plexosarcomas, first described by Herrera et al. in 1984, are uncommon neurogenic stromal spindle cell tumors of the intestinal tract mainly located in the stomach and the small intestine. The distinctive immunohistochemical pattern is the positive staining for vimentin and neuron-specific-enolase. Ultrastructural features are neuron-like cells with interdigitating cytoplasmic processes, dense-core neurosecretory granules, the lack of basement membranes and the presence of interstitial skeinoid fibers. Pain, chronic and acute bleeding are the most frequent but not specific symptoms and the diagnostic delay is reflected by a large average diameter of these tumors. For even smaller tumors and those with a low mitotic rate may metastasize, GAN-tumors must be considered malignant and need a radical surgical resection.

Aged↗
PubMed1996

[Vision disorders in retrochiasmatic lesions of the visual pathways].

Anatomic elements of the retrochiasmatic pathway. Synopsis of homonymous pathway. Synopsis of homonymous hemianopia: unilateral forms [quadrant, total], bilateral forms [tunnel field, cerebral blindness], homonymous scotomas, horizontal hemianopsias, checkerboard hemianopsias, sparing of temporal crescent. Additional disorders: hemi-neglect, color agnosia, hemi-achromatopsia, alexia, abnormal optokinetic nystagmus, cog-wheel pursuit movement, hemianopic pupillary defect, statokinetic dissociation [Riddoch phenomenon], hallucinations, illusions, visual agnosia, prosopagnosia.

Aged↗
PubMed1996

[True aneurysm of the femoral profunda artery].

Aneurysms of arteriosclerotic origin in the profunda femoris artery are rare. Twenty-nine cases were reported in the world literature. In addition two own cases are presented. This total of 31 patients with 34 true aneurysms of the profunda femoris artery is analyzed. The risk of complications such as rupture, thrombosis and embolization amounts to above 50% and seems to be higher than in popliteal or femoral aneurysms. Acute dilatation and rupture occurred in 34.5%. Nearly half of the patients suffered from one or more additional arterial aneurysms. This number emphasizes the need of a complete angiological investigation in patients with aneurysms of the profunda femoris artery. The treatment of choice consists of aneurysm resection and reconstruction by an autologous vein bypass. In selected cases with patent superficial femoral artery, a simple resection may be sufficient.

Aged↗
PubMed1995

[Sigmoid volvulus--clinical, radiological and therapeutic aspects of rare disease].

Volvulus of the sigmoid colon is a common cause of colonic obstruction in many parts of the world, mainly in developing countries and in Scandinavia, but is rare in the Western Hemisphere, where it occurs in elderly patients who often have serious coexisting diseases, especially cardiovascular and neuropsychiatric disorders. Although many patients present with the typical triad of abdominal pain, distension and constipation, the disease is correctly diagnosed only in about 62%. Diagnostic delay is due in part to the relative rarity of the illness, in part to the variety of the clinical and radiologic presentation, and it might contribute to the high mortality. Treatment consists in endoscopic decompression, whenever there are no compromised intestines, followed by an elective, sigmoid resection in otherwise healthy patients, because the risk of recurrence is high after nonoperative decompression alone. Hartmann's procedure is the safest procedure in patients with ischemic necrosis of the sigmoid colon. The site of primary resection and anastomosis with viable bowel remains controversial. Knowledge of sigmoid volvulus is of general interest with respect to the growing number of elderly patients, especially those residing in nursing homes and psychiatric institutions.

Aged↗
PubMed1995

Macular sparing as a perimetric artifact.

PURPOSE: We studied the hypothesis that the typical macular sparing of a few degrees was based on an unstable fixation coupled with a nystagmiform searching movement in the direction of the seeing hemiretina. METHODS: By means of microperimetry with a scanning laser ophthalmoscope, we recently tested the visual fields of 15 hemianoptic patients, through direct visual control of the retina. The tests provided us with accurate information about all fixation shifts that occurred. RESULTS: Twelve patients showed macular sparing of 1 to 5 degrees both in the Goldmann visual field and in the scanning laser ophthalmoscope field. Their fixation shifted regularly 1 to 10 degrees toward the seeing hemiretina one to two times per second, then returned rapidly to the foveola. Conversely, three patients showed greater macular sparing, and they all had particular characteristics--extensive fixation shifts, dual fixation, and limited quadrantanopsia. CONCLUSIONS: We believe that macular sparing could be interpreted as a perimetric (not an anatomic) artifact, provided that the results of these tests on 15 patients are confirmed by further similar studies.

Adolescent↗
PubMed1995

Purification and characterization of the Bacillus subtilis levanase produced in Escherichia coli.

The enzyme levanase encoded by the sacC gene from Bacillus subtilis was overexpressed in Escherichia coli with the strong, inducible tac promoter. The enzyme was purified from crude E. coli cell lysates by salting out with ammonium sulfate and chromatography on DEAE-Sepharose CL-6B, S-Sepharose, and MonoQ-Sepharose. The purified protein had an apparent molecular mass of 75,000 Da in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which is in agreement with that expected from the nucleotide sequence. Levanase was active on levan, inulin, and sucrose with Km values of 1.2 microM, 6.8 mM, and 65 mM, respectively. The pH optimum of the enzyme acting on inulin was 5.5, and the temperature optimum was 55 degrees C. Levanase was rapidly inactivated at 60 degrees C, but activity could be retained for longer times by adding fructose or glycerol. The enzyme activity was completely inactivated by Ag+ and Hg2+ ions, indicating that a sulfhydryl group is involved. A ratio of sucrase to inulinase activity of 1.2 was found for the purified enzyme with substrate concentrations of 50 mg/ml. The mechanism of enzyme action was investigated. No liberation of fructo-oligomers from inulin and levan could be observed by thin-layer chromatography and size exclusion chromatography-low-angle laser light scattering-interferometric differential refractive index techniques. This indicates that levanase is an exoenzyme acting by the single-chain mode.

Bacillus subtilis↗