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A Löffler

Publications and source records attributed to A Löffler.

At least 19 recordsLinked to original sources
PubMed2006

Coherent photonic coupling of semiconductor quantum dots.

We report a new type of coupling between quantum dot excitons mediated by the strong single-photon field in a high-finesse micropillar cavity. Coherent exciton coupling is observed for two dots with energy differences of the order of the exciton-photon coupling. The coherent coupling mode is characterized by an anticrossing with a particularly large line splitting of 250 microeV. Because of the different dispersion relations with temperature, the simultaneous photonic coupling of quantum dot excitons can be easily distinguished from cases of sequential strong coupling of two quantum dots.

Journal Article↗
PubMed2004

Strong coupling in a single quantum dot-semiconductor microcavity system.

Cavity quantum electrodynamics, a central research field in optics and solid-state physics, addresses properties of atom-like emitters in cavities and can be divided into a weak and a strong coupling regime. For weak coupling, the spontaneous emission can be enhanced or reduced compared with its vacuum level by tuning discrete cavity modes in and out of resonance with the emitter. However, the most striking change of emission properties occurs when the conditions for strong coupling are fulfilled. In this case there is a change from the usual irreversible spontaneous emission to a reversible exchange of energy between the emitter and the cavity mode. This coherent coupling may provide a basis for future applications in quantum information processing or schemes for coherent control. Until now, strong coupling of individual two-level systems has been observed only for atoms in large cavities. Here we report the observation of strong coupling of a single two-level solid-state system with a photon, as realized by a single quantum dot in a semiconductor microcavity. The strong coupling is manifest in photoluminescence data that display anti-crossings between the quantum dot exciton and cavity-mode dispersion relations, characterized by a vacuum Rabi splitting of about 140 microeV.

Journal Article↗
PubMed2003

Efficient elimination of chronic lymphocytic leukaemia B cells by autologous T cells with a bispecific anti-CD19/anti-CD3 single-chain antibody construct.

Recently, we have shown that a novel recombinant bispecific single-chain antibody construct (bscCD19 x CD3), induces highly efficacious lymphoma-directed cytotoxicity mediated by unstimulated peripheral T lymphocytes. Functional analysis of bscCD19 x CD3 has so far been exclusively performed with human B lymphoma cell lines and T cells from healthy donors. Here we analysed the properties of bscCD19 x CD3 using primary B cells and autologous T cells from healthy volunteers or patients with B-cell chronic lymphocytic leukaemia (B-CLL). We show that bscCD19 x CD3 induces T-cell-mediated depletion of nonmalignant B cells in all four cases and depletion of primary lymphoma cells in 22 out of 25 cases. This effect could be observed at low effector-to-target (E:T) ratios and in the majority of cases without additional activation of autologous T cells by IL-2. Even in samples derived from patients heavily pretreated with different chemotherapy regimens, strong cytotoxic effects of bscCD19 x CD3 could be observed. The addition of bscCD19 x CD3 to patients' cells resulted in an upregulation of activation-specific cell surface antigens on autologous T cells and elevated levels of CD95 on lymphoma B cells. Although anti-CD95 antibody CH-11 failed to induce apoptosis in lymphoma cells, we provide evidence that B-CLL cell depletion by bscCD3 x CD3 is mediated at least in part by apoptosis via the caspase pathway.

Aged↗
PubMed2001

Efficiency of root torquing auxiliaries.

In an experimental typodont study simulating the third stage of Tip-Edge treatment, the effect of five torquing auxiliaries on upper four incisors was assessed using the method of laser reflection. The auxiliaries analysed were: (1) Two-Spurs 0.016", (2) Four-Spurs 0.016", (3) Reciprocal Lateral Torque 0.016", (4) Torque Bar 0.022x0.018", 20 degrees, and (5) Torque Bar 0.022x0.018, 30 degrees. When comparing the wires, the efficiency (amount and speed of root tipping) varied considerably: (1) The Two-Spurs wire was the most efficient auxiliary of the five tested and showed good torque effect on the central incisors. (2) The Four-Spurs wire acting on all four incisors was less efficient than the Two-Spurs wire. (3) The Reciprocal Lateral Torque wire exhibited good palatal root torque on the central incisors and labial root torque on the lateral incisors. (4) The Torque Bars (20 degrees and 30 degrees ) were the least efficient wires of the auxiliaries tested and showed only small torque effects on the central and lateral incisor teeth. In clinical work using the Tip-Edge technique, the Two-Spurs torquing auxiliary should be the wire of choice for an efficient palatal root torque of the upper central incisors.

Journal Article↗
PubMed2000

A recombinant bispecific single-chain antibody, CD19 x CD3, induces rapid and high lymphoma-directed cytotoxicity by unstimulated T lymphocytes.

Although bispecific antibodies directed against malignant lymphoma have been shown to be effective in vitro and in vivo, extended clinical trials so far have been hampered by the fact that conventional approaches to produce these antibodies suffer from low yields, ill-defined byproducts, or laborious purification procedures. To overcome this problem, we have generated a small, recombinant, lymphoma-directed, bispecific single-chain (bsc) antibody according to a novel technique recently described. The antibody consists of 2 different single-chain Fv fragments joined by a glycine-serine linker. One specificity is directed against the CD3 antigen of human T cells, and the other antigen-binding site engages the pan-B-cell marker CD19, uniformly expressed on the vast majority of B-cell malignancies. The construct was expressed in Chinese hamster ovary cells and purified by its C-terminal histioline tag. Specific binding to CD19 and CD3 was demonstrated by fluorescence-activated cell sorter analysis. By redirecting unstimulated primary human T cells derived from the peripheral blood against CD19-positive lymphoma cells, the bscCD19 x CD3 antibody showed significant cytotoxic activity at very low concentrations of 10 to 100 pg/mL and at effector to target cell ratios as low as 2:1. Moreover, strong lymphoma-directed cytotoxicity at low antibody concentrations was rapidly induced during 4 hours even in experiments without any T-cell prestimulation. Thus, this particular antibody proves to be much more efficacious than the bispecific antibodies described until now. Therefore, the described bscCD19 x CD3 molecule should be a suitable candidate to prove the therapeutic benefit of bispecific antibodies in the treatment of non-Hodgkin lymphoma. (Blood. 2000;95:2098-2103)

Antibodies, Bispecific↗
PubMed1998

The effect of tissue expansion on the expression of collagen type I and type III mRNA in distinct areas of skin in the dog as an animal model.

To evaluate the transcriptional response of skin to tissue expansion in the dog, the expression of procollagen alpha 1(I) mRNA and procollagen alpha 1(III) mRNA were analyzed by in situ hybridization. This expression was evaluated in distinct skin areas (subepidermal zone, dermis, capsular zone) after 4-85 days of expansion. Within the first 4 days of expansion expression of procollagen alpha 1(I) and alpha 1(III) mRNA was not affected in the subepidermal and dermal zone. Only a slightly elevated level of type III procollagen mRNA was demonstrated in tissue surrounding the implanted silicone expander. After 7 days of expansion an enhanced level of procollagen alpha 1(III) mRNA was observed in the dermis and capsular zone. A slightly enhanced type I collagen mRNA level occurred in all zones of the dermis that was even stronger in the capsular zone after 9 days of expansion. Concurrently, the number of transcriptionally active cells was significantly higher. Return to the basal level of procollagen alpha 1(I) mRNA was attained after 40 days. At this time a significant expression of procollagenase mRNA was observed. Procollagen III mRNA expression reached its basal level on day 85.

Animals↗
PubMed1997

C-Mannosylation of human RNase 2 is an intracellular process performed by a variety of cultured cells.

C2-alpha-Mannosyltryptophan was discovered in RNase 2 from human urine, representing a novel way of attaching carbohydrate to a protein. Here, we have addressed two questions related to the biosynthesis of this modification: (i) is C-mannosylation part of the normal intracellular biosynthetic route, and (ii) how general is it, i.e. which organisms perform this kind of glycosylation? To answer the first question, RNase 2, which is identical to the eosinophil-derived neurotoxin, was isolated from intracellular stores of cultured human HL-60 cells. The enzyme was C-mannosylated at Trp-7, showing that the modification occurs intracellularly, before secretion of the protein. The second question was investigated by immunological and chemical analysis of RNase 2 purified from the supernatant of transiently transformed cells from different organisms. This revealed that C-mannosylation occurs in cells from man, green monkey, pig, mouse, and hamster. The observation that pig kidney cells contain the machinery for C-mannosylation of Trp-7 of human RNase 2 but that the homologous RNase from porcine kidney is not a substrate, since it does not contain a tryptophan at position 7, strongly suggests that C-mannosylated proteins other than RNase 2 exist. Recombinant RNase 2 isolated from insect cells, plant protoplasts, and Escherichia coli was not C-mannosylated. These results not only form the basis for further studies on the biochemical aspects of C-mannosylation but also have implications for the choice of cells for production of recombinant glycoproteins.

Animals↗
PubMed1997

[Spontaneous retroperitoneal hematoma in adrenal metastasis].

HISTORY AND CLINICAL FINDINGS: A 58-year-old man was hospitalized because of acute dull upper abdominal pain, radiating into the right flank and lower abdomen. The past history was unremarkable expect for thyroidectomy, performed 30 years previously for thyroid carcinoma. There was painful resistance on palpation of the right upper abdomen. The patient had not recently sustained any trauma. BIOCHEMICAL AND IMAGING INVESTIGATIONS: Erythrocyte sedimentation rate was increased to 38 mm/h, haemoglobin concentration was 11.7 g/dl but fell to 9.9 g/dl within the first 24 hours. Ultrasound and computed tomography (CT) revealed a large retroperitoneal mass (5 x 6.5 x 15 cm), its density of 64 Hounsfield units most strongly suggesting an haematoma. CT also showed enlargement of the right adrenal. Chest radiography demonstrated a space-occupying lesion in the right upper lobe. DIAGNOSIS, TREATMENT AND COURSE: As a retroperitoneal haematoma of uncertain aetiology was suspected, a laparotomy was performed. The haematoma was evacuated and the adrenal, showing tumours changes, was excised. Histologically it was a mucocellular metastasis. The chest radiograph suggested carcinoma of the lung as the primary. The illness took a rapidly fatal course. Autopsy confirmed a poorly differentiated adenocarcinoma of the lung. CONCLUSION: Trauma or anticoagulation should be considered first in the differential diagnosis of retroperitoneal haematoma of uncertain aetiology. However, adrenal metastasis should be thought of as a rare possibility.

Adenocarcinoma↗
PubMed1997

The base specificities of tomato ribonuclease (RNase LE) and its Asp44 mutant enzyme expressed from yeast cells.

RNase LE from cultured tomato cells is a member of the RNase T2 family. It is, however, distinguishable from RNase Rh from Rhizopus niveus, a typical RNase of the RNase T2 family, by its CD spectrum in the 200-250 nm region. In order to reinvestigate the base specificity of RNase LE and to study the role of Asn44 in RNase LE, which is considered to correspond to the base recognition site Asp51 of RNase Rh, RNase LE, and its Asp mutant at the 44th position were expressed from yeast cells with the same expression system as RNase Rh [K. Ohgi, et al., J. Biochem., 109, 776-785 (1991)]. RNase LE with four extra amino acid residues at the 2nd amino acid residue of mature RNase LE and its Asp44 mutant were secreted from yeast cells to give a yield of 10 mg/liter and 0.5 mg/liter culture broth, respectively. The expressed RNase LE (RNase RNAP LE) had the same characteristics as native RNase LE in the CD spectrum and specific activity. This is the first example of the expression of plant RNase from microbes and in sufficient amount to perform further enzymological research. The base specificity of RNase LE was guanylic acid preferential and that of N44D was changed to a more adenylic acid preference as compared to that of RNase LE. These experiments showed that Asn44 of RNase LE is crucial for base recognition as the case of Asp51 in RNASE Rh, and also suggested that the base recognition mechanism of RNase LE is very similar to that of RNase Rh.

Amino Acid Sequence↗
PubMed1996

Spectroscopic and protein chemical analyses demonstrate the presence of C-mannosylated tryptophan in intact human RNase 2 and its isoforms.

Recently, the C-mannosylation of a specific tryptophan residue in RNase 2 from human urine has been reported [Hofsteenge, J., et al. (1994) Biochemistry 33, 13524-13530; de Beer, T., et al. (1995) Biochemistry 34, 11785-11789]. In those studies, identification of this unusual modification was accomplished by mass spectrometric and NMR spectroscopic analysis of peptide fragments. The evidence for the occurrence of C2-alpha-mannosyltryptophan [(C2-Man-)Trp] in the intact protein relied exclusively on the detection of the same phenylthiohydantoin derivatives during Edman degradation. In this paper, we have (1) excluded the possibility that (C2-Man-)Trp arose artificially under the acidic conditions previously employed for protein and peptide isolation and analysis, by maintaining the pH > 5 throughout these procedures, (2) demonstrated the occurrence of (C2-Man-)Trp in the intact protein, by NMR spectroscopy, (3) showed that (C2-Man-)Trp is not unique for RNase 2 from urine but that it is also present in the enzyme isolated from erythrocytes, and (4) found also that high-molecular mass isoforms of urinary RNase 2 are C-mannosylated. These observations firmly establish C-mannosylation as a novel way of post-translationally attaching carbohydrate to protein, in addition to the well-known N- and O-glycosylations. Furthermore, the NMR data, in combination with molecular dynamics calculations, indicate that in the native protein the mannopyranosyl residue is in a different conformation than in the glycopeptide or denatured protein, due to protein-carbohydrate interactions.

Amino Acid Sequence↗
PubMed1996

[Osteosynthesis in the mid-face and forehead area].

BACKGROUND: In the beginning of the development of facial osteosynthetic techniques only relatively thick plates were available. Since then various mini- and micro-plating systems were developed for the midfacial and forehead regions. As so many different systems with different sizes are available, it is important to know which systems are appropriate for which indications. Therefore, the aim of this study was to add knowledge to some aspects of the differential indications of different systems for the middle and upper facial regions. METHODS AND PATIENTS: 1. The pull-out forces of seven different mini- and microscrews were measured. 2. The thicknesses of the facial bone were measured at 11 different points in 10 skulls. 3. The clinical experiences of midfacial and upper facial osteosynthesis in 45 patients were summarised. RESULTS: The pull-out forces increase with increasing bone- and screw-thickness and also substantially depend on the design of the screws. Although the bone thicknesses in the mid and upper facial region vary considerably, all investigated regions are suitable for osteosynthesis. In none of our patients any complication occurred that was related to the osteosynthesis. CONCLUSIONS: Microsystems with screw diameters of 0.8 mm (Howmedica) are suited for fractures of the nasoethmoidal complex. Providing the same thickness as the microplates the Panfixsystem (Howmedica) offers a better holding strength especially when using the 1.3 mm screws, and is easier to handle. For stabilising fractures of the zygoma, which might dislocate postoperatively due to the pulling force of the masseteric muscle, we still feel that the miniplating technique with compression is the method of choice.

Adult↗
PubMed1995

The hexopyranosyl residue that is C-glycosidically linked to the side chain of tryptophan-7 in human RNase Us is alpha-mannopyranose.

Recently, the novel C-glycosidic linkage of a hexopyranosyl residue to the indole ring of tryptophan residue 7 of human RNase U(s) was reported [Hofsteenge, J., Müller, D. R., de Beer, T., Löffler A., Richter, W. J., & Vliegenthart, J. F. G. (1994) Biochemistry 33, 13524-13530]. Identification of this monosaccharide is a prerequisite for studies of its biosynthesis and its biological relevance. Using vicinal proton-proton coupling constants and rotating-frame nuclear Overhauser enhancements, ewe demonstrate that the C-linked substituent is alpha-mannopyranose. Furthermore, the nuclear magnetic resonance (NMR) data indicate that the mannopyranose moiety in a glycopeptide derived from RNase U(s) adopts several conformations on the NMR time scale.

Amino Acid Sequence↗
PubMed1995

cDNA structure and regulatory properties of a family of starvation-induced ribonucleases from tomato.

In previous work we have determined the primary structure of two of the five ribonucleases which are induced by phosphate starvation in cultured tomato cells. Here, we present the isolation and characterization of the cDNAs for the extracellular ribonuclease LE and the intracellular, but extravacuolar ribonuclease LX. Structural analysis of these cDNAs together with partial protein-sequencing of vacuolar ribonucleases LV1, LV2 and LV3 revealed a family of very similar ribonucleases. From these data we assume identify between ribonucleases LE and LV3 for which the targeting mechanism has to be shown. Furthermore, RNase LV1 and RNase LV2 might be posttranslational processing products of RNase LX which travel to the vacuoles after splitting off the putative ER retention signal present at RNase LX. Additionally, we show by northern blot analysis that phosphate starvation in plant cells leads to an increase in the steady-state level of this type of enzymes revealing close similarities of the plant response to a limited supply of inorganic phosphate with the PHO regulation in bacteria and fungi.

Amino Acid Sequence↗
PubMed1995

[Clip migration in the common bile duct and consecutive calculus formation after laparoscopic cholecystectomy].

In 1991 a 64-year old woman underwent laparoscopic cholecystectomy for symptomatic gallstones. The follow-up was uneventful. Two years later a painless obstructive jaundice appeared. Endoscopic retrograde cholangio-pancreatography revealed a freely floating surgical clip within the common bile duct. It was a FILSHIE-Clip, commonly used to ligate the cystic duct. The endoscopic extraction of the foreign body was unsuccessful because the clip slipped into a small intrahepatic bile duct. Smaller gallstones that had probably crystallized around the clip could be extracted. Finally the clip itself disappeared spontaneously after endoscopic sphincterotomy through the papilla. It is discussed why movement of a surgical clip into the common bile duct appears after laparoscopic cholecystectomy.

Cholecystectomy, Laparoscopic↗