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Biomedical subjects

R Lehner

Publications and source records attributed to R Lehner.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cloning and expression of a cDNA encoding a hepatic microsomal lipase that mobilizes stored triacylglycerol.

A microsomal triacylglycerol hydrolase (TGH) was recently purified from porcine liver [Lehner and Verger (1997) Biochemistry 36, 1861-1868]. To gain further insight into the function of TGH, we have cloned a cDNA encoding TGH from a rat liver cDNA library and generated McArdle RH7777 rat hepatoma cell lines that stably express the rat TGH. The putative protein derived from the cDNA sequence contains a cleavable signal sequence and a catalytic site serine residue present within a pentapeptide motif (GXSXG) that is conserved in all known lipases. TGH-transfected cells showed a 2-fold increase, compared with control cells, in the rate of depletion of prelabelled triacylglycerol stores. Thus, TGH is capable of hydrolysis of stored triacylglycerol. In contrast, the rate of turnover of labelled phosphatidylcholine was similar in both the vector- and TGH-transfected cells. Studies in TGH-transfected cells demonstrated that utilization of intracellular triacylglycerol pools for secretion was approx. 30% higher than in vector-transfected cells. Whereas phosphatidylcholine secretion was essentially the same in control and TGH-transfected cells, TGH-transfected cells also secreted an approx. 25% greater mass of triacylglycerol into the medium and had increased levels of apolipoprotein B100 in the very-low-density lipoprotein density range compared with control cells. The results suggest that the microsomal TGH actively participates in the mobilization of cytoplasmic triacylglycerol stores, some of which can be used for lipoprotein assembly.

Animals↗
PubMed1999

Subcellullar localization, developmental expression and characterization of a liver triacylglycerol hydrolase.

The mechanism and enzymic activities responsible for the lipolysis of stored cytosolic triacylglycerol in liver and its re-esterification remain obscure. A candidate enzyme for lipolysis, a microsomal triacylglycerol hydrolase (TGH), was recently purified to homogeneity from pig liver and its kinetic properties were determined [Lehner and Verger (1997) Biochemistry 36, 1861-1868]. We have characterized the enzyme with regard to its species distribution, subcellular localization, developmental expression and reaction with lipase inhibitors. The hydrolase co-sediments with endoplasmic reticulum elements and is associated with isolated liver fat droplets. Immunocytochemical studies localize TGH exclusively to liver cells surrounding capillaries. Both TGH mRNA and protein are expressed in rats during weaning. The enzyme covalently binds tetrahydrolipstatin, an inhibitor of lipases and of triacylglycerol hydrolysis. The enzyme is absent from liver-derived cell lines (HepG2 and McArdle RH7777) known to be impaired in very-low-density lipoprotein (VLDL) assembly and secretion. The localization and developmental expression of TGH are consistent with a proposed role in triacylglycerol hydrolysis and with the proposal that some of the resynthesized triacylglycerol is utilized for VLDL secretion.

Animals↗
PubMed1999

Contraceptive knowledge and behavior of conventionalists, careerists, idealists, bouncers, desperadoes, and outsiders.

The aim of the survey was to determine the contraceptive behavior and knowledge on contraceptive methods of adolescents. We defined six clusters according to personality, leisure activities, and sociodemographic characteristics: conventionalists, careerists, idealists, bouncers, desperadoes, and outsiders. 1010 Austrian adolescents aged 14-24 years participated in the survey. 96%-100% indicated that they were familiar with the condom and the contraceptive pill. The two most popular contraceptive methods cited were the condom (39%) and OC (34%). Whereas 40% of conventionalists reported that OC were their preferred method of contraception, 53% of idealists indicated that they preferred the condom. 66% of the desperadoes indicated that they considered the pill expensive. 85% of conventionalists and careerists believe that OC offer the best protection against pregnancy. Clusters with higher self-esteem and those with a higher educational level were more likely to believe that this method is unreliable. The results obtained indicate that outsiders, desperatoes, and bouncers show deficits in sex education; only careerists and idealists appeared to be better informed. Research on adolescent contraceptive behavior should drop the traditional stratifying criteria and appreciate the diversity of adolescent populations in order to be better able to classify adolescents according to their contraceptive attitudes.

Adolescent↗
PubMed1998

Unsuspected primary tubal carcinoma during operative laparoscopy.

OBJECTIVE: To evaluate the possible risk of dealing with an unsuspected primary carcinoma of the fallopian tube during laparoscopic surgery. METHODS: We performed a countrywide survey in Austria concerning laparoscopic procedures in cases of primary carcinoma of the tube. The questionnaire consisted of questions regarding the pre-, intra-, and postoperative management. RESULTS: Of 18,435 laparoscopies in cases of an adnexal mass, 5 cases were reported, when laparoscopy was performed on an unsuspected carcinoma of the tube. Therefore, the risk of detecting this malignancy during laparoscopy after preoperative evaluation is 1 in 3687 cases (0.028%). CONCLUSION: The risk of encountering an unsuspected primary carcinoma of the fallopian tube during laparoscopy in Austria is an extremely rare situation. In case of a malignancy, a staging or debulking laparotomy should be performed immediately or as soon as possible.

Aged↗
PubMed1998

[Cold deformation elements for attaching an implantable hearing aid transducer to ear ossicles or perilymph].

Development and short-term implantation results of the Tübingen implantable hearing aid (TI = Tübingen implant) have been presented. The TI is designed for patients with sensorineural hearing loss due to a malfunction of the cochlear amplifier. This can be identified by the presence of positive recruitment and the absence of TEOAE (transitory evoked otoacoustic emissions). The Tübingen implant functions in two ways: it allows electronic amplification of the auditory signal and electromechanical signal transduction into a micromechanical vibratory stimulus. There are two paths by which vibratory stimulus reaches the cochlea: (1) directly through a perforation in the stapes foot plate into the perilymph or (2) via the ossicular chain. Made of pure titanium, the casing of the helium-tight welded transducer includes the piezoelectric actuator. An implantable manipulator device is designed for transducer positioning and anchoring in the mastoid cavity. Usually, the transducer probe tip is directly coupled to the body of the incus. This functions without a special coupling device by utilization of an Erbium-YAG laser. Special anatomical situations or the loss of incus and/or stapes suprastructure, however, requires coupling of the vibratory signal to other points of the ossicular chain or to the perilymph. A major problem, however, was an intraoperative, irreversible link between the titanium probe tip and coupling elements. To overcome this problem, the coupling elements were made of gold. A crimp technique was developed, allowing the surgeon to induce cold deformation of the gold. The cold deformation technique (crimp) results in an irreversible coupling between the titanium probe tip and the golden coupling element.

Cochlear Implantation↗
PubMed1998

[Value of Schüller conventional roentgen diagnosis and computerized tomography of the temporal bone in preoperative diagnosis of the Tübingen implantable cochlear amplifier].

Recently, the transducer and microphone of a cochlea amplifier implant (CAI) for the treatment of sensorineural cochlear hearing loss have been developed further for implantation into the mastoid cavity. At present, the University of Tuebingen implantable cochlea amplifier consists of an implantable microphone and an implantable piezoelectric transducer. It has been implanted into the first patients. Successful future application of this new implant depends on the suitable fit of the CAI within a patient's mastoid cavity. Using conventional X-ray and CT scans, we analyzed 50 cadaver specimens of the temporal bone before total mastoidectomy. After total mastoidectomy, the volume of the mastoid cavity was measured using CT scans and water volume determination. Finally, the CAI was implanted into those temporal bones that were large enough to house it. Our results demonstrate that the degree of pneumatization in the conventional Schüller X-ray is already a good parameter for preoperative evaluation.

Cochlear Implantation↗
PubMed1998

[An osseointegrated micromanipulator as anchor for implantable hearing aid transducers. 1: Fitting to the surgical anatomy of the temporal bone and surgical technical properties].

The first electronic implantable hearing aids for patients with hearing loss are coupled to the ossicular chain or perilymph during implantation and are now available. Our new Tübingen implant designed for sensorineural hearing loss (SNHL) is the combination of an implantable microphone and piezotransducer. To avoid hearing losses during implantation, the Tübingen piezotransducer will be (1) fixed to the mastoid cavity and (2) positioned to one of the ossicular target points. This can be done with a micromanipulator which will be implanted together with transducer and microphone in the mastoid cavity. The manipulator weights 0.7 g. With four degrees of freedom, it allows highly secure and safe positioning of the transducer's probe tip to the ossicular chain under close to stereotactic conditions. The main advantages of the present micromanipulator are (1) easy handling during surgery, (2) the transducer's precise positioning to the ossicular target point with sufficient degrees of freedom, and (3) the transducer's stable fixation in the mastoid cavity in the final position. Following integrated safety as the leading principle, ossicular or inner ear injuries caused, e.g., by the patient's head movement or unintentional manual contact by the surgeon, are minimized. The micromanipulator is, as it were, the surgeon's vibration-free "artificial hand". The manipulator's development and its optimization to the mastoid cavity by test implantation in 50 human temporal bones are shown in detail. While coupling the transducer to the body of the incus, transducer, microphone, and micromanipulator can be implanted into 76% of all mastoid cavities without protrusion. In the case of transducers coupling to the long process of the incus, the protrusion-free implantation rate of the above-mentioned three implant modules is 78%.

Bone Plates↗
PubMed1998

[A micromanipulator for intraoperative vibratory hearing assessment with an implantable hearing aid transducer].

First concepts of implantable hearing aids to be coupled to the ossicular chain are available for patients with combined or sensorineural hearing loss (SNHL). To ensure that hearing can be improved intraoperative coupling of a test transducer to the ossicular chain is mandatory for allowing surgical anatomy to be checked and vibratory hearing tests to be performed. To achieve this, the test transducer has to be held and positioned securely in situ for some minutes, avoiding risks for middle or inner ear structures. This is not possible using conventional surgical instruments. Thus, a micromanipulator to hold the test transducer during intraoperative hearing tests was developed. This surgical device allows the surgeon safe, risk-free, and controlled coupling of the test transducer to the ossicular chain with one axial and three rotational degrees of freedom. With the aid of a conventional ear retractor (2x2 prongs), the manipulator is fixed at the patient's ear. In conjunction with a piezoelectric test transducer, the manipulator was used in nine patients during local anesthesia. The test transducer is part of an electronic hearing implant (Tübingen implant) specifically designed for SNHL that may be coupled to a middle ear ossicle or the perilymph of the cochlea. The micromanipulator was easy to handle. It allowed accurate positioning of the test transducer in the ear and the desired coupling of the transducer's probe tip to the ossicular chain during auditory tests. According to the principles of integrated safety, the intraoperative risk of ossicular or inner ear injuries caused, for instance, by the patient's head movement is minimized. The design of the manipulator system is universal, also allowing its use for other electronic hearing implants or minimal invasive surgery after minor modifications.

Ear Ossicles↗
PubMed1998

Successful treatment of a heterotopic pregnancy by sonographically guided instillation of hyperosmolar glucose.

OBJECTIVE: To describe a new conservative approach in the treatment of heterotopic pregnancy. DESIGN: Case report. SETTING: A university hospital and an outpatient IVF center. INTERVENTION(S): Transvaginal ultrasonography-guided puncture of the ectopic gestational sac and instillation of hyperosmolar glucose. RESULT(S): The ectopic pregnancy resolved without further intervention. The intrauterine pregnancy resulted in a full-term live birth. CONCLUSION(S): Transvaginal injection of hyperosmolar glucose may be an effective conservative treatment for unruptured ectopic pregnancies in cases of heterotopic pregnancy.

Adult↗
PubMed1998

Influence of delayed staging laparotomy after laparoscopic removal of ovarian masses later found malignant.

OBJECTIVE: To determine whether delayed laparotomy after attempted laparoscopic excision of an ovarian mass later found to be malignant has an impact on the stage of disease. METHODS: A questionnaire regarding laparoscopic management of ovarian masses later found to be malignant was mailed to all gynecologic departments in Austria. Of the 70 cases reported, laparotomy was performed after laparoscopy in 48 cases. In 24 of these cases, laparotomy was performed within 17 days of laparoscopy, whereas 24 cases involved a delay of more than 17 days. Twenty-two patients in whom laparotomy was performed immediately after laparoscopy were used as controls. RESULTS: In patients with borderline tumors who underwent laparotomy more than 17 days after laparoscopy, the odds ratio (OR) for International Federation of Gynecology and Obstetrics (FIGO) stage IIB-IV disease was 5.3 (95% confidence interval [CI] 0.40, infinity), compared with patients undergoing immediate laparotomy (multivariate analysis). Patients with invasive ovarian cancer who underwent laparotomy more than 17 days after laparoscopy had an OR of 9.2 (CI 0.92, 481) for stage IIB-IV disease compared with patients undergoing immediate laparotomy (multivariate analysis). In patients with borderline tumors, multivariate analysis showed that the timing of laparotomy is an independent prognostic factor for the stage of disease. In invasive ovarian cancer, none of the factors evaluated by multivariate analysis was found to be an independent prognostic factor for the distribution of disease stage. A delay between laparoscopy and laparotomy may affect adversely the distribution of disease stage. CONCLUSION: The timing of subsequent laparotomy was found to be a factor predictive of the distribution of disease stage.

Adolescent↗
PubMed1998

Improved laparoscopic operating techniques using a digital enhancement video system.

We conducted a prospective, randomized trial in a piglet model to assess the advantages of a digital enhancement video system during difficult endoscopic procedures. Laparoscopic pelvic lymphadenectomy was performed with either conventional two-dimensional or digitally enhanced videoendoscopy. With equal amounts of extirpated lymph nodes, the operations performed with digitally enhanced videoendoscopy were significantly shorter (left lymphadenectomy p = 0.0001, right lymphadenectomy p = 0.001), had less blood loss and fewer false movements, and were associated with no complications, compared with those performed with a two-dimensional videosystem. Thus the accuracy of difficult laparoscopic techniques can be improved by three-dimensional visual perception.

Animals↗
PubMed1998

Lectin histochemistry of fallopian tube epithelial cells. Relation to ovum transport and ovum pickup.

OBJECTIVE: Data on histochemical and biochemical characteristics of the human oviduct are scarce. The exact mechanisms of ovum transport and pickup are not fully understood. STUDY DESIGN: Human fallopian tubes were obtained and prepared for histochemistry. We analyzed the distribution of negatively charged groups on the oviduct epithelium and cumulus cells and examined the distribution of glycoconjugates by means of lectin histochemistry. We tested the possible influence of poly-L-lysine and considered ABO blood group expression since these characteristics are determined by specific terminal sugar residues. RESULTS: A negatively charged glycocalyx exists on tubal epithelial cells and cumulus cells. Adherence by affinities similar to sugar-lectin binding forces could be disproven in case of commonly used lectins. Poly-L-lysine inhibited the cationic binding reaction but did not influence lectin binding. The blood group A glycoprotein presents terminal D-N-acetyl-galactosamine residues, which are demonstrated by HPA lectin binding. CONCLUSION: Our study indicates that it is unlikely that electrostatic interactions play a major role in ovum transport or pickup. Since poly-L-lysine has been described as inhibiting ovum transport, sugar-lectin binding affinities seem not to operate in ovum transport or pickup.

ABO Blood-Group System↗
PubMed1997

Purification and characterization of a porcine liver microsomal triacylglycerol hydrolase.

We have purified an enzyme from porcine liver microsomes which catalyzes hydrolysis of triacylglycerols. The enzyme was solubilized from the membranes by the zwitterionic detergent 3-[(3- cholamidopropyl)dimethylammonio]-l-propansulfonate (CHAPS) and was purified to apparent homogeneity by sequential chromatography on Q-Sepharose, hydroxyapatite, Affi-Gel heparin, and Mono-Q. The purified hydrolase migrated in SDS-polyacrylamide gel electrophoresis (PAGE) as a single polypeptide band of an apparent molecular mass of 60 kDa. The enzyme hydrolyzed long-, medium-, and short-chain triacylglycerols, as well as a chromogenic lipase substrate, 1,2-O-dilauryl-rac-glycero-3-glutaric acid resorufin ester. The highest specific activity was obtained with tributyroylglycerol (240 mumol.min-1.mg-1). The reaction rate was maximal at pH 8.5. Sulfhydryl-directed reagents, such as N-ethylmaleimide (NEM), 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), and dodecyldithio-5-(2-nitrobenzoic acid) (C12-TNB) had no effect on the hydrolase activity; however, the enzyme was sensitive to HgCl2. Serine reagents, such as diethyl-p-nitrophenyl phosphate (E600) and diisopropyl fluorophosphate (DFP), used in 100-fold molar excess completely inhibited the activity, suggesting that it is a serine esterase. These results suggest that the enzyme may participate in the intracellular neutral lipid metabolism since the enzyme is located in the endoplasmic reticulum, an organelle where de novo triacylglycerol synthesis and assembly of lipoproteins take place.

Amino Acid Sequence↗
PubMed1997

[New methods of type II tympanoplasty in erosion of the long incus process].

Reliable methods of reconstruction of the ossicular chain in the situation of an isolated errosion of the long process of the incus using a tympanoplasty type II have not been available until recently. Instead, the tympanoplasty type III has been generally performed with the interposition of an autologous incus. In this presentation, we are describing two methods for reconstruction of the ossicular chain between the in-situ residing incus and the stapes on the other side so that the direct connection eventually will result in a tympanoplasty type II. In the first case, we used ionomeric cement in a way that features two characteristics: the direct connection between the stapes and the long process of the incus could be achieved as well as an articulation that was created on the head of the stapes. Hence, a too stiff connection between the head of the stapes and the long process of the incus could be avoided. In addition, a new method for precise microapplication of cooled bone cement (IONOCAP LV) with a syringe will be presented. In the second method titanium-gold-angle prostheses have been crimped to the long process of the incus and positioned onto the head of the stapes in the way of an articulation. So far, comparison of the audiological results of those two methods of a tympanoplasty type II reveal in average better results than postoperative conductive hearing thresholds of the conventional tympanoplasty type III. If the achieved results can be reproduced on a larger number of patients, the expected audiological results are likely to resemble those of stapes surgery.

Auditory Threshold↗
PubMed1997

In vitro cytokine and prostaglandin production by amnion cells in the presence of bacteria.

OBJECTIVE: Our goal was to evaluate the effect of group B streptococci on cytokine and prostaglandin production by amnion cells in vitro. STUDY DESIGN: Amnion cells from placentas obtained immediately after primary cesarean section were incubated for 48 hours with heat-inactivated group B streptococci at increasing concentrations. Samples for quantification of interleukin-1 beta, interleukin-6, interleukin-8, tumor necrosis factor-alpha, and prostaglandin E2 were collected at 6, 12, 24, and 48 hours. RESULTS: Basal cytokine production was not demonstrable for any of the cytokines investigated. Incubation of amnion cells with bacterial antigen led to a significant increase in interleukin-6 and interleukin-8 production, whereas secretion of interleukin-1 beta and tumor necrosis factor-alpha was not enhanced. In contrast to cytokines, basal prostaglandin E2 production was measurable but failed to increase after addition of antigen. CONCLUSION: Amnion cells can be stimulated to secrete interleukin-6 and interleukin-8 in response to streptococcal antigen. However, this rise in cytokines does not induce an increase in prostaglandin E2. This may be explained by the lack of interleukin-1 and tumor necrosis factor-alpha production, two cytokines that have been shown to activate prostaglandin E2 secretion by amnion cells.

Amnion↗