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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 109 records · Page 6Linked to original sources
PubMed2000

Self-organized patterning of an insulator-on-metal system by surface faceting and selective growth: NaCl/Cu(211)

We report experimental results on an insulator-on-metal system which is inherently unstable against lateral pattern formation on the nanometer scale. NaCl deposition on Cu(211) at substrate temperatures >300 K leads to faceting into (311) and (111) facets and selective NaCl growth on (311) facets only, thereby creating alternating stripes of bare Cu and NaCl-covered areas. The mesoscopic restructuring process is brought about by (1) the tendency to form (100)-terminated NaCl layers, (2) epitaxial matching between NaCl(100) and Cu(311), and (3) sufficient mobility of the Cu substrate surface.

Journal Article↗
PubMed2000

[Trabeculotomy in congenital glaucoma: comparison to goniotomy].

PURPOSE: To compare the efficacy of trabeculotomy (TO) and that of goniotomy (GO) as a primary surgical procedure in congenital glaucoma. PATIENTS AND METHODS: We retrospectively analyzed 39 eyes of 22 children with congenital glaucoma who underwent TO with or without a small trabeculectomy. The results were compared to data on 34 eyes of 21 children who underwent GO for congenital glaucoma. RESULTS: The mean preoperative intraocular pressure (IOP) was 28.2 +/- 6.7 mmHg in TO eyes and 31.0 +/- 7.9 mmHg in GO eyes. Mean IOP at the end of follow-up was 17.7 +/- 6.0 mmHg in TO eyes and 18.9 +/- 9.1 mmHg in GO eyes. In 31 of 39 TO eyes (79.5%) and in 26 of 34 (76.5%) GO eyes the IOP was 21 mmHg or lower at the end of follow-up. Combining the criteria of an IOP greater than 21 and an IOP drop of at least 20%, the success rate was 71.8% (28/39) in TO eyes and 70.6% (24/34) in GO eyes. CONCLUSION: In this study the value of TO in controlling IOP was comparable to that of GO.

Child↗
PubMed2000

Trabeculotomy in congenital glaucoma.

BACKGROUND: Congenital glaucoma is a potentially blinding disease that requires surgical therapy. This paper describes the outcome of trabeculotomy in primary congenital glaucoma. METHODS: Thirty-nine eyes of 22 children with congenital glaucoma who underwent trabeculotomy with or without a simultaneous trabeculectomy between 1992 and 1997 were retrospectively analyzed. RESULTS: Mean follow-up was 24.7+/-17.9 months. A mean of 1.3 operations per eye were performed. The mean IOP at the end of follow-up (n=39) was 17.7+/-6.0 mmHg; in 8 eyes (20.5%) the IOP was >21 mmHg, in 31 eyes (79.5%) it was < or =21 mmHg. The mean difference between pretreatment IOP and IOP at the end of follow-up (n=39) was -10.5+/-9.4 mmHg (-37.2%). Success rates were calculated: IOP was < or =21 mmHg in 36/39 eyes (92.3%) after 1/2 year of follow-up, in 25/27 eyes (92.6%) after 1 year, in 15/18 eyes (83.3%) after 2 years, in 8/12 (66.7%) eyes after 3 years, in 4/8 eyes (50%) after 4 years and in 4/4 (100%) eyes after 5 years of follow-up. Complications included hypotony (three eyes), subchoroidal bleeding (one eye ), detachment of Descemet's membrane (one eye) and macular pucker (one eye in which later mitomycin C was used). Visual acuity (VA) was tested with various methods in 35 eyes. VA was within the normal nomogram range in 12 eyes and below the normal range in 23 eyes at the end of follow-up. Axial length measurements showed normalization according to the age nomogram in 22 of 35 eyes. CONCLUSION: This study shows that trabeculotomy is an effective surgical procedure in congenital glaucoma with satisfactory success rates up to 5 years of follow-up.

Child↗
PubMed2000

Functional reconstitution of ICln in lipid bilayers.

Reconstitution of purified ICln in lipid bilayer leads to functional ion channels showing varying rectification. The reconstituted single channels have a conductance of approximately equal to 3 pS and their open probability is sensitive to nucleoside analogues. Mutation of a putative nucleotide binding site identified at the predicted extracellular mouth of the ICln channel protein leads to the reduction of the nucleoside-analogue sensitivity. Reconstituted ICln channels can be permeated both by cations and anions. The relative permeability of cations over anions depends on the presence of calcium. In the presence of calcium reconstituted ICln channels are more permeable to bromide than chloride, and more permeable to potassium than sodium. Similarly in NIH3T3 fibroblasts, the relative permeability of cations over anions of swelling-dependent chloride channels depends on extracellular calcium. Site-directed mutagenesis revealed the calcium-binding site responsible for the shift of the selectivity from cations towards anions of reconstituted ICln channels. Additional indirect structural information has been obtained by mutating a histidine in the predicted pore region of ICln. This histidine seems to have access to the ion-conducting tunnel of the pore. Our experiments show that ICln can act as an ionic channel, which does not exclude additional functions of the protein in regulatory mechanisms of the cell. Since knocking down the ICln protein in fibroblasts and epithelial cells leads to an impaired regulatory volume decrease (RVD) after cytoplasmic swelling and reconstituted ICln channels show several biophysical features of ion channels activated after swelling, ICln is a molecular candidate for these channels.

3T3 Cells↗
PubMed2000

The femoral hernia: an ideal approach for the transabdominal preperitoneal technique (TAPP).

BACKGROUND: We designed a study to determine the rate of intra- and postoperative complications as well as the rate of recurrences in elective operated femoral hernias treated via the laparoscopic technique. METHODS: Between 1993 and 1998, we performed 1,097 operations in our department using the laparoscopic transabdominal preperitoneal (TAPP) technique. Femoral hernias amounted to only 4.6% (51 cases) of these patients. The male/female ratio was 1:2. The data concerning the operations and pre- and postoperative treatment were recorded prospectively. The patients were followed up at 2 weeks and 1 year after the operation. RESULTS: We encountered one intraoperative bladder lesion, one subcutaneous port site infection, two postoperative hematomas that required reoperation, and two nerve irritation syndromes, which disappeared spontaneously after 6 months. Two patients developed an ileus; one required laparoscopic reintervention, and the other was treated with conventional open reoperation and intestinal resection. There were no recurrences. CONCLUSIONS: The application of the laparoscopic approach to the treatment of femoral hernias using the TAPP technique in nonemergency situations is highly effective. To date, we have seen no recurrences. Although the rate of major complications is low, current surgical techniques need to be perfected to avoid the type of complication recognized in this study.

Adult↗
PubMed2000

The cutaneous nerves encountered during laparoscopic repair of inguinal hernia: new anatomical findings for the surgeon.

BACKGROUND: With an incidence rate of 2%, injury to the nerves of the lumbar plexus is the most common complication of laparoscopic hernioplasty, particularly when the transabdominal preperitoneal (TAPP) technique is used. METHODS: The course of the genitofemoral nerve, lateral femoral cutaneous nerve, and ilioinguinal nerve within the operation site was investigated in 53 adult dissecting-room bodies. Their relationship to the deep inguinal ring, iliopubic tract, and anterior superior iliac spine was also examined. RESULTS: Both the femoral and genital branches of the genitofemoral nerve may penetrate the abdominal wall lateral to the deep ring and cranial to the iliopubic tract. The lateral femoral cutaneous nerve and the ilioinguinal nerve may run immediately lateral to the anterior superior iliac spine. CONCLUSION: Contrary to the previously accepted opinion, dissection and the placement of staples either cranial to the iliopubic tract or lateral to the anterior superior iliac spine can result in injury to the nerves.

Adult↗
PubMed2000

Laparoscopic repair of traumatic diaphragmatic hernias.

BACKGROUND: Traumatic diaphragmatic hernias are serious complications of blunt abdominal or thoracic trauma. In the early posttraumatic period, they are often missed, and they may be followed by a variety of subacute or chronic symptoms due to pulmonary or intestinal obstruction. METHODS: We present three cases of traumatic diaphragmatic hernias. Two of them were successfully treated by laparoscopy and direct suturing during the early posttraumatic period; the other was treated 10 years after the trauma. RESULTS: We found that laparoscopy is a safe, successful, and gentle procedure not only for diagnosis but for treatment as well. The postoperative course was uneventful in all cases. All patients remained asymptomatic during long-term follow-up (42-60 months). These results are promising. We expect the same good long-term results after laparoscopic repair as after open conventional surgery. CONCLUSION: We recommend that surgeons with sufficient experience in laparoscopy use a minimally invasive approach to treat chronic as well as acute traumatic diaphragmatic hernias in hemodynamically stable patients.

Abdominal Injuries↗
PubMed2000

Glycoprotein C of bovine herpesvirus 5 (BHV-5) confers a distinct heparin-binding phenotype to BHV-1.

Bovine herpesvirus type 1 (BHV-1) causes respiratory and genital diseases in cattle, whereas the closely related BHV-5 can induce severe meningoencephalitis in calves. To characterize BHV-5 glycoprotein C (gC5) within the backbone of BHV-1, three consecutive recombinant viruses were constructed: A deletion mutant (rBHV-1delta gC blue) with gC replaced by the lacZ gene, an exchange mutant (rBHV-1gC5) with the lacZ of BHV-1delta gC blue exchanged by gC5, and a rescue mutant (rescue BHV-1) from rBHV-1gC5 with an additional XbaI site in gC1. The recombinant and wildtype viruses were characterized on MDBK cells. Although no significant differences were observed in growth behaviour and entry kinetics, rBHV-1gC5 showed a distinct phenotype in a heparin blocking assay. The gC5 was able to transfer the heparin binding phenotype of BHV-5 to BHV-1. This indicates that gC1 and gC5 differ in their receptor binding qualities, which might modulate the ability of the viruses to spread within the central nervous system.

Alphaherpesvirinae↗
PubMed2000

Composition and immunofluorescence studies of biliary "sludge" in patients with cholesterol or mixed gallstones.

BACKGROUND/AIMS: Gallbladder bile from patients with cholesterol or mixed gallstones frequently contains biliary "sludge", a suspension of cholesterol monohydrate crystals and pigment granules embedded in mucin and proteins. The composition of biliary "sludge" and the preferential localization of mucin and proteins could be an indicator for its potential role in gallstone formation. METHODS: Ultracentrifugation (100000 g/l h) was used to precipitate "sludge" from bile, and the concentration difference of its main components between native bile and ultracentrifuged bile samples was calculated. After purification of the sediment, immunolocalization was performed for the detection of mucin, IgA, albumin, aminopeptidase, and anionic polypeptide fraction using polyclonal and monoclonal antibodies. RESULTS: The amount of sludge in gallbladder bile was 4.26 mg/ml-0.78 (mean+/-SEM) in patients with cholesterol and 2.51 mg/ml+/-0.39 in patients with mixed stones and cholesterol was the main component (48.9+/-4.6% and 44.4+/-7.1%). The sediment appeared as a mixture of vesicular aggregates and pigment particles which were linked by a gel matrix of mucin containing cholesterol crystals. While anionic polypeptide fraction and aminopeptidase were associated to pigments, IgA was uniformly spread in the crystalline parts of "core-like" structures, and albumin, when it was present, appeared as randomly located small spots. CONCLUSIONS: Our study demonstrates that the cholesterol content and the distribution pattern of mucin and different proteins is similar in the sediments of biliary "sludge" to that previously shown in cholesterol and mixed gallstones. This suggests that biliary "sludge" represents an early stage of gallstone formation in these patients.

Apoproteins↗
PubMed2000

[Venous thromboembolism and cancer].

INTRODUCTION: Thromboembolic venous disease, which includes both peripheral venous thrombosis and pulmonary embolism, is a frequent disorder in patients with cancer. Although thromboembolic manifestations may precede the diagnosis of cancer, the value of extensive clinical search for potential underlying cancer when faced with venous thromboembolic manifestations has not been demonstrated. CURRENT KNOWLEDGE AND KEY POINTS: Clinical and biological studies have demonstrated that acquired abnormalities in blood hemostasis, especially procoagulant factors, account for the onset of thromboembolic manifestations in patients with cancer. Classical anticoagulant therapy is associated with low efficacy and tolerance in patience with cancer who are at high risk for hemorrhagic complications and recurrence of thromboembolic disease. FUTURE PROSPECTS AND PROJECTS: Recent data suggest the value of anticoagulant therapy using either low molecular weight heparin or warfarin at low doses (INR < 2) according to the specific surgical or medical context.

Anticoagulants↗
PubMed2000

Effect of cement type on retention of a tapered post with a self-cutting double thread.

OBJECTIVES: The aim of this in vitro study was to examine the effect of varying the cement type on the retention of a prefabricated tapered titanium post with a self-cutting double thread (Perma-tex activ). METHODS: A total of 130 suitable roots from extracted human permanent teeth were selected. Post holes were prepared using the instruments supplied with the post system. One-hundred-twenty posts (medium size) were luted with one of four luting agents: a zinc-phosphate cement (Harvard), a glass-ionomer cement (Ketac Cem), a compomer luting agent (Dyract Cem), and a new capsulated composite luting system (Compolute). The cement groups were subdivided into three treatment groups with 10 posts each: group 1 (4-week water storage at 37 degrees C), group 2 (4-week water storage at 37 degrees C, 4000 cycles 5-55 degrees C), group 3 (4-week water storage at 37 degrees C, 4000 cycles 5-55 degrees C, 3 x 4 min mechanical stress: 40N vibrations). Another 10 posts inserted without cement and stored like group 1 served as a control. Retention was measured on a universal testing machine (Zwick Z050/TH3A) with a crosshead speed of 0.1cm/min. Data were analyzed using ANOVA with a Bonferroni or Tamhane adjustment for multiple comparisons (significance level alpha=0.05). RESULTS: In group 1, Dyract Cem was significantly more retentive than the other three cements and the control group (no cement). In group 2, Compolute demonstrated significantly higher retention than Harvard and Ketac Cem. In group 3, Compolute, Dyract Cem, and Ketac Cem obtained higher retentive values than Harvard without differing from one another. Within the cement groups, thermocycling (group 2) caused a significant decrease in retention compared to group 1 only for Dyract Cem. All cements except Compolute were different from group 1 after a combination of thermocycling and mechanical stress (group 3). CONCLUSIONS: The retention of the tapered post with a self-cutting double thread was significantly influenced by the cement type used.

Analysis of Variance↗
PubMed2000

Effects of testosterone administration on selective aspects of object-location memory in healthy young women.

Previous work has indicated that object-location memory is sensitive to sex differences as well as variations in the menstrual cycle. The goal of the present study was to further examine the hormonal basis of human spatial memory by assessing the effects of a single dose of exogenous testosterone in healthy young women on three recall conditions: positional reconstruction; object-to-position-assignment; and the combined condition in which subjects both have to reconstruct the precise locations and to link the different objects to the correct places. In the latter condition, delayed recall (3 min delay) improved with testosterone. Although the effects were only small and need further substantiation, they support the idea that testosterone may have an activational effect on selective aspects of cognitive functioning.

Adolescent↗
PubMed2000

Effects of phospholipase A2, free fatty acids and 2-lysolecithin on the crystallization of cholesterol in gallbladder bile.

BACKGROUND: Phospholipase A2 (PLA2) and its enzymatic products free fatty acids (FFAs) and 2-lysolecithin are physiological constituents of bile. Their role in the crystallization of cholesterol in gallbladder bile of patients with cholesterol gallstones is still controversial. DESIGN: To clarify this issue we evaluated the activity of PLA2 and the concentration and pattern of FFAs in the gallbladder bile of cholesterol stone patients. We furthermore added PLA2, FFAs and 2-lysolecithin to isotropic gallbladder bile, determined the crystal observation time (COT) and counted the cholesterol crystals in a crystal growth assay for up to 21 days. RESULTS: A PLA2 activity of 1.8 +/- 1.2 U L(-1) and total FFA concentrations of 1.32 +/- 0.71 mmol L(-1) were determined. After incubation of bile for 24 h at 37 degrees C total FFAs increased to 2.72 +/- 1.29 mmol L(-1) (P<0.005). Biliary saturated and unsaturated FFAs were found in equal proportions before and after incubation, pointing to an additional presence of lipases other than PLA2. A COTof 1 day was observed in all gallbladder biles and increased to 1.7 +/- 0.5 days after addition of 5 U L(-1) of PLA2 (P<0.01). An even higher COT of 2.5 +/- 0.8 days was seen after addition of 5 mmol L(-1) of a 'biliary' mixture of FFAs (P<0.005) but the COT remained unchanged after addition of 5 mmol L(-1) of 2-lysolecithin. However, in the crystal growth assay in gallbladder bile addition of 5 U L(-1) of PLA2, of 5 mmol L(-1) of 'biliary' FFAs and of 5 mmol L(-1) of 2-lysolecithin decreased significantly the number of cholesterol crystals formed during follow-up. CONCLUSION: An elevated activity of PLA2 in gallbladder bile may counteract the formation of cholesterol crystals through increased formation of FFAs and 2-lysolecithin. However, regarding the comparatively low activity of PLA2 in gallbladder bile PLA2 seems to be of only minor pathophysiological importance in the formation of cholesterol gallstones.

Adult↗
PubMed2000

Complications of emergency tracheal intubation in severely head-injured children.

A high incidence of unsuccessful attempts and complications has been reported when emergency tracheal intubation (ETI) is performed outside the hospital in severely injured children. The aim of this prospective series was to analyse the incidence and related risk factors of complications of emergency tracheal intubation. The time to complete successful ETI and occurrence of incidents, e.g. cough reflex, hypoxia or spasm were related to the experience of the physician performing intubation and the use of drugs to facilitate ETI. The incidence of hypoxia, hypercarbia, postintubation complications such as extubation stridor and long-term sequelae were noted. Of the 188 children, 78% were successfully intubated at the site of the accident, 10% upon arrival at a local hospital from where they were secondarily transferred and 12% upon admission to our trauma centre. The most severely injured children were intubated in the field in 98% of cases without failure, nor life-threatening complications related to ETI. The experience of the operator influenced the number of attempts and the time to complete successful intubation. Immediate incidents were noted in 25% of children, e.g. cough in 18%. The regimen of drugs, but not level of consciousness, influenced the incidence of immediate incidents; without drugs, more than 67% experienced incidents. Early tracheal intubation and controlled ventilation resulted in adequate ventilation upon arrival (mean PaO2 of 35.8+/-24 kPa, mean PaCO2 of 4.35+/-1 kPa). Long-term complications, including transient stridor upon extubation in 33% of the cases, and laryngeal granuloma or tracheal stenosis, were comparable to those in other series. ETI in shocked patients and pulmonary infection in hospital, but not the technique of ETI, increased the risks of long-term complications. Emergency tracheal intubation can be performed safely in the field, and results in adequate ventilation during transportation of severely injured children, provided that it can be performed by trained physicians using adequate drugs to facilitate intubation.

Child↗
PubMed2000

Neural network analysis of oxygenation signals in infants during sleep.

The use of artificial neural networks (ANNs) to interpret sleep monitoring signals is described. Recordings from ten infants with apparent life threatening episodes were assigned into training feedforward R-PROP networks. In order to separate good signal from artefact, 60 second time frames of SaO2 and TcPO2 signals were processed and the mean and standard deviation values were used as inputs to the networks. Intra-human errors were minimized using this method whilst inter-human errors remained significant. To decrease the latter, the number of hidden units was increased to eight. Sensitivity figures of the SaO2 network were 0.93 and 0.9 for the training and test sets respectively whilst the specificity figures were 0.7 and 0.65 respectively. For the TcPO2 signals the above figures were 0.92, 0.85, 0.77 and 0.61 respectively.

Apnea↗
PubMed2000

Production of bovine herpesvirus type 1-seronegative latent carriers by administration of a live-attenuated vaccine in passively immunized calves.

The consequences of the vaccination of neonatal calves with the widely used live-attenuated temperature-sensitive (ts) bovine herpesvirus type 1 (BHV-1) were investigated. The ts strain established acute and latent infections in all vaccinated calves either with or without passive immunity. Four of seven calves vaccinated under passive immunity became clearly BHV-1 seronegative by different serological tests, as did uninfected control calves after the disappearance of maternal antibodies, and they remained so for long periods. A cell-mediated immune response was detected by a BHV-1 gamma interferon assay, but this test failed to detect the seronegative latent carriers (SNLCs). While they are not detected, SNLCs represent a threat for BHV-1-free herds or countries. This study demonstrates that SNLCs can be easily obtained by inoculation with a live-attenuated BHV-1 under passive immunity and that latent carrier animals without any antibody do exist. Consequently, this situation could represent a good model to experimentally produce SNLCs.

Animals↗
PubMed2000

Effects of bovine herpesvirus type 1 infection in calves with maternal antibodies on immune response and virus latency.

The presence of maternally derived antibodies can interfere with the development of an active antibody response to antigen. Infection of seven passively immunized young calves with a virulent strain of bovine herpesvirus type 1 (BHV-1) was performed to determine whether they could become seronegative after the disappearance of maternal antibodies while latently infected with BHV-1. Four uninfected calves were controls. All calves were monitored serologically for 13 to 18 months. In addition, the development of a cell-mediated immune response was assessed by an in vitro antigen-specific gamma interferon (IFN-gamma) production assay. All calves had positive IFN-gamma responses as early as 7 days until at least 10 weeks after infection. However, no antibody rise was observed after infection in the three calves with the highest titers of maternal antibodies. One of the three became seronegative by virus neutralization test at 7 months of age like the control animals. This calf presented negative IFN-gamma results at the same time and was classified seronegative by enzyme-linked immunosorbent assay at around 10 months of age. This calf was latently infected, as proven by virus reexcretion after dexamethasone treatment at the end of the experiment. In conclusion, this study demonstrated that BHV-1-seronegative latent carriers can be obtained experimentally. In addition, the IFN-gamma assay was able to discriminate calves possessing only passively acquired antibodies from those latently infected by BHV-1, but it could not detect seronegative latent carriers. The failure to easily detect such animals presents an epidemiological threat for the control of BHV-1 infection.

Aging↗