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Biomedical subjects

K Weber

Publications and source records attributed to K Weber.

At least 325 records · Page 18Linked to original sources
PubMed1990

Detyrosination of alpha tubulin does not stabilize microtubules in vivo.

The relationship between alpha tubulin detyrosination and microtubule (MT) stability was examined directly in cultured fibroblasts by experimentally converting the predominantly tyrosinated MT array to a detyrosinated (Glu) array and then assaying MT stability. MTs in mouse Swiss 3T3 cells displayed an increase in Glu immunostaining fluorescence approximately 1 h after microinjecting antibodies to the tyrosinating enzyme, tubulin tyrosine ligase. Detyrosination progressed to virtual completion after 12 h and persisted for 30-35 h before tyrosinated subunits within MTs were again detected. The stability of these experimentally detyrosinated MTs was tested by first injecting either biotinylated or Xrhodamine-labeled tubulin and then measuring bulk turnover by hapten-mediated immunocytochemistry or fluorescence recovery after photobleaching, respectively. By both methods, turnover was found to be similarly rapid, possessing a half time of approximately 3 min. As a final test of MT stability, the level of acetylated tubulin staining in antibody-injected cells was compared with that observed in adjacent, uninjected cells and also with the staining observed in cells whose MTs had been stabilized with taxol. Although intense Glu staining was observed in both injected and taxol-treated cells, increased acetylated tubulin staining was observed only in the taxol-stabilized MTs, indicating that the MTs were not stabilized by detyrosination. Together, these results demonstrated clearly that detyrosination does not directly confer stability on MTs. Therefore, the stable MTs observed in these and other cell lines must have arisen by another mechanism, and may have become posttranslationally modified after their stabilization.

Alkaloids↗
PubMed1990

A myofibrillar protein of insect muscle related to vertebrate titin connects Z band and A band: purification and molecular characterization of invertebrate mini-titin.

We show that myofibrils of insect flight and leg muscle contain a doublet of polypeptides with apparent molecular weights of 700K (K = 10(3) Mr) (Hmp I) and 600K (Hmp II), respectively. In Locusta migratoria high ionic strength extraction solubilizes only Hmp II, which is readily purified in native form. It probably reflects a proteolytic derivative of the non-extractable Hmp I. On the basis of its viscosity radius and sedimentation coefficient, Hmp II has a molecular weight of 600K and seems to consist of a single polypeptide chain. The highly asymmetric structure of the molecule is confirmed by rotary shadowing. The flexible rods have a uniform diameter of 3-4 nm and an average length of 260 nm. Polyclonal antibodies show cross-reactivity between Hmp II and its putative precursor Hmp I. We discuss the similarities and differences between the larger titin I/titin II of vertebrate sarcomeric muscle and the smaller Hmp I/Hmp II of invertebrate muscle and conclude that the latter may reflect a mini-titin. In line with the smaller length, immunoelectron microscopy locates the insect mini-titin to the I band and a very short portion of the A band only, while vertebrate titin is known to connect the Z band to the M band. Mini-titin has also been purified from several other insects including Drosophila. Immunofluorescence microscopy on frozen sections shows that mini-titin is present in the sarcomeric muscles of various species from different invertebrate phyla. These include Annelida, Nematomorpha, Plathelmintha, Nemertea and Nematoda like Ascaris lumbricoides and Caenorhabditis elegans. This wide-spread occurrence of invertebrate mini-titin is confirmed by immunoblotting experiments.

Animals↗
PubMed1990

Cells of the cellular immune and hemopoietic system of the mouse lack lamins A/C: distinction versus other somatic cells.

Almost all somatic cells in adult murine tissues express all three nuclear lamins (A, B, C). Here we demonstrate that cells of the hemopoietic system of the adult mouse are an exception in that they express only lamin B. Thus T and B lymphocytes as well as granulocytes and monocytic cells directly isolated from spleen, thymus, blood or bone marrow do not express lamin A/C but only lamin B. In agreement with this observation the murine hemopoietic cell lines EL4, BW5147, HK22, 70Z/3, SP2/0 and PAI express only lamin B. In immunoblotting experiments used to confirm the immunofluorescence data no lamin A/C expression was detected. However, we noticed that murine lamin B occurs in two isoforms, which can be distinguished immunologically. These results reinforce the idea that a functional nuclear lamina can be formed from lamin B alone. They also pose the question of whether cells lacking lamin A/C are more plastic in their developmental programs than those that express all three lamins.

Animals↗
PubMed1990

Tailless keratins assemble into regular intermediate filaments in vitro.

To study the influence of the non alpha-helical tail domain of keratins in filament formation, we prepared a truncated keratin 8 mutant, K8/tailless. Using site-directed in vitro mutagenesis we introduced a stop codon in the position coding for amino acid number 417 of the K8/wild-type sequence, thereby deleting 86 amino acids of the non alpha-helical tail domain but leaving the consensus sequence at the end of the rod domain intact. Expression of the truncated keratin 8 in Escherichia coli allowed us to purify the protein by a two-step procedure. The filament-forming capacity of the truncated K8 with wild-type K18 and K19 was analyzed using in vitro reconstitution. The in vitro assembly studies with K8/tailless and K18 wild-type indicate that the C-terminal tail domain of a type II keratin, including the homologous subdomain H2, is not required for filament formation. Moreover, reconstitution experiments with K8/tailless and K19, a naturally occurring tailless keratin I, show that the tail domains of type I as well as type II keratins are not an essential requirement for in vitro filament formation. Our results suggest that in vitro filament elongation does not depend on interactions between head and tail domains, although the tail domain might have a role in stabilization of intermediate filaments arising from certain keratin pairs.

Amino Acid Sequence↗
PubMed1990

On the nature of serological tissue polypeptide antigen (TPA); monoclonal keratin 8, 18, and 19 antibodies react differently with TPA prepared from human cultured carcinoma cells and TPA in human serum.

A panel of monoclonal antibodies which recognize the rod domains of human keratin 8, 18, or 19 was tested for its capacity to replace TPA antiserum as anchoring antibody in a two-site TPA immuno-radiometric assay kit. All six antibodies could anchor a TPA preparation, with varying efficiencies, when iodinated TPA antiserum monitored antigen binding. Conversely, the soluble keratin 8, 18, and 19 rod complex could efficiently replace the TPA preparation as antigen when TPA antiserum anchored and detected antigen binding. Moreover, in immunoblots the TPA antiserum recognized the rod domains of human keratins 8, 18, and 19. In contrast to the general reaction of the keratin antibodies with a TPA preparation, the reactions with TPA in human serum were antibody and sample dependent. A keratin 19- and a keratin 8-specific antibody anchored TPA in all sera consistently and efficiently, while the other 4 antibodies anchored serological TPA inefficiently. TPA in human serum was found in immunoblots to be somewhat more heterogeneous in size than the standard TPA preparation. The data presented here indicate that TPA in patients' sera is a degradation product of keratins 8, 18, and 19. The significance of these findings is discussed.

Antibodies, Monoclonal↗
PubMed1990

Vimentin expression appears to be associated with poor prognosis in node-negative ductal NOS breast carcinomas.

Vimentin expression in tumors from 83 node-negative and 112 node-positive patients with infiltrative ductal not otherwise specified (NOS) breast carcinomas has been compared with 5-year survival. For node-negative, but not for node-positive patients, there was a significant inverse relation between vimentin expression and survival. Five-year survival of node-negative patients with vimentin-positive tumors was significantly worse compared with vimentin-negative tumors (P less than 0.0001). In the node-negative group, only 36% of patients with vimentin-positive tumors but 82% of patients with vimentin-negative tumors survived 5 years. Tumors of all eight node-negative patients with ductal NOS cancer who died in the first 27 months expressed vimentin. Multivariate analysis of the node-negative group showed a strong correlation of vimentin expression and overall survival, but weak and not significant correlation between histologic grade or size and overall survival at 5 years. Thus vimentin expression seems to be a strong indicator of poor prognosis in node-negative ductal NOS breast carcinomas.

Biopsy↗
PubMed1990

[Gastroscopy before cholecystectomy].

In a prospective study the routine endoscopy of the upper gastrointestinal tract was carried out in 100 patients before they underwent elective cholecystectomy for gallstones. In 31/100 patients we detected abnormalities which changed the plan of therapy. In 18/100 patients the cholecystectomy was performed 4 to 8 weeks later, after additional medical treatment. 7 patients were discharged from the cholecystectomy. The preoperative endoscopy of the upper gastrointestinal tract should be used in patients undergoing cholecystectomy to exclude other gastrointestinal disorders.

Cholecystectomy↗
PubMed1990

Vimentin is preferentially expressed in human breast carcinomas with low estrogen receptor and high Ki-67 growth fraction.

Vimentin expression, growth fractions (GF), and estrogen receptor (ER) levels were determined for 90 untreated primary breast carcinomas. Coexpression of keratin and vimentin was found in approximately 20% of the tumors regardless of menopausal status. Vimentin was expressed preferentially in tumor cells of high-grade ductal breast carcinomas (15 of 28 histologic grade 3 vs. 0 of 40 grades 1 and 2). Vimentin expression was found preferentially in tumors with high GF (greater than 15% Ki-67 positive by immunoperoxidase staining) and low ER levels (less than 60 fmols/mg protein by a monoclonal enzyme immunoassay). Sixty-eight percent of tumors in this group were vimentin positive and 88% of all vimentin-positive tumors fell into this category. More than 50% of the tumor cells coexpressed vimentin and keratin. Thus, vimentin expression may be helpful in identifying a substantial subset of ER-independent breast carcinomas with poor prognostic indicators.

Antigens, Surface↗
PubMed1990

Vimentin is preferentially expressed in high-grade ductal and medullary, but not in lobular breast carcinomas.

Two hundred sixty-two invasive breast carcinomas dating from 1979 to 1984 were tested for vimentin and keratin on formaldehyde-fixed paraffin-embedded sections. None of 26 lobular carcinomas expressed vimentin. Vimentin expression in 10% or more of tumor cells was found in 78% of medullary (14 of 18), in 16% of ductal not otherwise specified (NOS) (35 of 214), and in two of four mucinous carcinomas. A further seven tumors showed vimentin expression in less than 1% to 10% of the cells. Vimentin was expressed in tumor cells of 30% (28 of 93) of grade III invasive ductal NOS carcinomas versus 7% (7 of 105) of grade II and 0% of grade I carcinomas (0 of 10). Vimentin was found to be preferentially expressed in tumors growing in broad, often anastomosing bands or sheets with extensive necrosis, scanty supportive stroma, high nuclear grade, and numerous mitoses. The authors conclude that vimentin is not detected in lobular carcinomas, but is preferentially expressed in medullary and in high-grade ductal NOS breast carcinomas.

Biomarkers↗
PubMed1990

[Value and importance of treatment with OTC in selected patients with marginal periodontitis].

Over a period of 14 days we have treated 27 after special criterious selected patients with 250 mg OTC three times/day. We compared these results with those of 25 patients--of a placebo-group. The analysis included clinical and microbiological parameters. It could be pointed out, that the OTC-therapy results in a significant improvement of the examined parameters stile 6 months after starting with the therapy.

Adolescent↗
PubMed1989

Effects of cilazapril on hypertension, sleep, and apnea.

Epidemiologic studies revealed that up to 10 percent of middle-aged men show more than 10 cessations of breathing of more than 10 seconds' duration. In these patients, increased morbidity and mortality rates have been proved. More than 50 percent of apnea patients exhibit arterial hypertension, and up to 50 percent of hypertensive patients experience sleep apnea. Patients with sleep apnea and essential hypertension need special attention paid to their antihypertensive therapy because the following side effects of drugs have to be avoided: increases of cardiac insufficiency, hyperviscosity of the blood, intensification of the hypersomnia by central sedation, intensification of a pre-existing tendency towards arrhythmias, and deprivation of deep and rapid eye movement sleep. In this study, the effects of angiotensin-converting enzyme inhibitors in patients with sleep apnea and hypertension are examined. An interim evaluation of six patients (aged 50 to 57) yielded the following results: Average Broca index, 124; average blood pressure before therapy, 159/102 mm Hg; average blood pressure after therapy, 132/78; a decrease of the apnea and hypopnea index from x = 31 (range, 12 to 77) to x = 20 (range, two to 54). Therapy did not influence sleep structure: before therapy, an average of 19 percent of sleep episodes were of the rapid eye movement type (range, 11 to 32 percent); after therapy, 23 percent were of this type on average (range, 21 to 25 percent). A final evaluation will be carried out after the second study phase for 12 patients who have been treated in a double-blind scheme with metropolol versus cilazapril.

Adult↗
PubMed1989

Maturation of nuclear lamin A involves a specific carboxy-terminal trimming, which removes the polyisoprenylation site from the precursor; implications for the structure of the nuclear lamina.

Lamin A, a nuclear lamina protein of differentiated cells, is synthesized as a precursor of the mature molecule. Protein sequencing of the carboxy-terminal 14 kDa fragment shows a lack of the last 18 residues predicted by cDNA sequencing. The carboxy-terminal proteolytic maturation explains previous biochemical results including the loss of the polyisoprenylation site now located to the CXXM motif at the end of the chain. This view and earlier results on lamin B predict multiple post-translational modifications shared by lamins A and B. While retained by lamin B, which is present in all cells, they are lost by maturation from lamin A, which probably acts only as an additional lamina constituent in differentiated cells.

Amino Acid Sequence↗
PubMed1989

[A transdermal intermittent-release nitroglycerin system. Hemodynamic studies after acute and subchronic use].

The efficacy of a transdermal intermittent-release nitroglycerin system was investigated in a randomized double-blind trial on 24 patients (18 males and six females; median age 57.5 years [range 41-68]) with angiographically proven and haemodynamically significant coronary heart disease. Twelve patients had one plaster, containing 10 mg nitroglycerin, daily for eight days, the other twelve also had one plaster, but without drug, daily for eight days. Resting and exercise haemodynamics were measured on the first day, immediately before and two hours after application of the plaster, on the eighth day 24 hours after the last but one plaster application, and two hours after the last plaster. The mean pulmonary artery pressure, two hours after first plaster application, had dropped at rest from 18.6 to 13.3 mm Hg (29%; P less than 0.001) and after exercise from 43.9 to 34 mm Hg (23%; P less than 0.001). After eight days, 24 hours after application of the penultimate plaster, there was no significant haemodynamic change. Renewed plaster application, however, caused significant haemodynamic changes similar to those on the first day of the study. It is concluded from these findings that this intermittent-release system can achieve long-term results without development of tolerance.

Administration, Cutaneous↗
PubMed1989

Phosphorylation in vitro of vimentin by protein kinases A and C is restricted to the head domain. Identification of the phosphoserine sites and their influence on filament formation.

The in vitro phosphorylation of vimentin, the intermediate filament protein of mesenchymal cells, by kinases A and C is serine-specific and involves only the N-terminal head domain. In oligomeric protofilament units each kinase recognizes five sites, which have been identified by sequence analysis. Kinase C introduces 1.5 mol phosphate/mol vimentin, while kinase A treatment results in 4 mol phosphate/mol. Kinase-A-treated oligomers do not polymerize in standard assays whereas kinase C treatment has no inhibitory effect. Filaments exposed to kinase A remain stable and incorporate only 1.7 mol phosphate/mol vimentin. These phosphates are essentially restricted to two of the five kinase A sites found in protofilament units. Thus the head domain, previously related to in vitro assembly competence and filament stability, changes in accessibility between the oligomeric and polymeric state. We discuss the possibility that in vivo phosphorylation of vimentin filaments by kinase A may not necessarily be accompanied by an extensive depolymerization. It could instead involve a dynamic change of the filament surfaces, which could alter the interaction of the filaments with other cellular structures.

Adenosine Triphosphate↗
PubMed1989

Diagnosis of major tumor categories in fine-needle aspirates is more accurate when light microscopy is combined with intermediate filament typing. A study of 403 cases.

Intermediate filament (IF) typing of tumor cells with monoclonal antibodies was applied to 403 fine-needle aspirates. In 271 cases specific cytologic diagnosis of tumor type was apparent from clinical data and light microscopic study alone. Intermediate filament typing confirmed the tumor type in 262 cases and changed an erroneous cytologic diagnosis of major tumor type in nine cases. In a second group of 132 difficult cases, where the tumor type could not be revealed with certainty, IF typing confirmed the cytologic suggestion of tumor type in 50 cases, changed it in nine cases, and helped resolve ambiguities in cytologic diagnosis in 59 cases. It did not help in 14 cases. Thus IF typing adds independent objective differentiation specific information to descriptive tumor typing currently used in aspiration cytologic study. When combined with the morphologic analysis of tumor cells and clinical information it can refine the cytologic diagnosis of major tumor types and prevent error.

Adolescent↗
PubMed1989

Cytoplasmic intermediate filament proteins of invertebrates are closer to nuclear lamins than are vertebrate intermediate filament proteins; sequence characterization of two muscle proteins of a nematode.

The giant body muscle cells of the nematode Ascaris lumbricoides show a complex three dimensional array of intermediate filaments (IFs). They contain two proteins, A (71 kd) and B (63 kd), which we now show are able to form homopolymeric filaments in vitro. The complete amino acid sequence of B and 80% of A have been determined. A and B are two homologous proteins with a 55% sequence identity over the rod and tail domains. Sequence comparisons with the only other invertebrate IF protein currently known (Helix pomatia) and with vertebrate IF proteins show that along the coiled-coil rod domain, sequence principles rather than actual sequences are conserved in evolution. Noticeable exceptions are the consensus sequences at the ends of the rod, which probably play a direct role in IF assembly. Like the Helix IF protein the nematode proteins have six extra heptads in the coil 1b segment. These are characteristic of nuclear lamins from vertebrates and invertebrates and are not found in vertebrate IF proteins. Unexpectedly the enhanced homology between lamins and invertebrate IF proteins continues in the tail domains, which in vertebrate IF proteins totally diverge. The sequence alignment necessitates the introduction of a 15 residue deletion in the tail domain of all three invertebrate IF proteins. Its location coincides with the position of the karyophilic signal sequence, which dictates nuclear entry of the lamins. The results provide the first molecular support for the speculation that nuclear lamins and cytoplasmic IF proteins arose in eukaryotic evolution from a common lamin-like predecessor.

Amino Acid Sequence↗