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Biomedical subjects

R Lohmann

Publications and source records attributed to R Lohmann.

At least 19 recordsLinked to original sources
PubMed2001

Atmospheric distribution of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs), and non-ortho biphenyls (PCBs) along a North-South Atlantic transect.

Air samples were taken on board the RRS Bransfield (typically for 24-72 h), during an Atlantic cruise from the U.K. to Antarctica in October-December 1998, to investigate the global scale distribution of PCDD/Fs and coplanar PCBs. Highest concentrations of Cl2-8DD/Fs all occurred between 25 and 52 degrees N; lowest concentrations were measured around approximately 60 degrees S and further south. Cl3DFs showed highest overall concentrations (up to 9800 fg/m3), followed by Cl2DFs (up to 5300 fg/m3) and OCDD (up to 1300 fg/m3). Lowest concentrations, measured in the remote Southern hemisphere, were generally 2 orders of magnitude lower than their highest concentrations over the North Atlantic. Concentrations of PCB-77 were higher in the northern hemisphere, while PCB-126 and PCB-169 exhibited highest concentrations around the equator. Evidence was obtained for substantial emissions of PCDD/Fs off west Africa and while in the port of Montevideo, Uruguay. Shifts in PCDD/F profile distribution were observed on increasing distance from source regions, such that those from the most remote locations were dominated by Cl3DF (approximately 40% of the total) and OCDD (approximately 20%). Gas-particle partition data was obtained for all samples. Cl4-6DD/Fs showed the widest range, varying between 10 and 90% of the total in the gas phase, depending on location/ temperature. The study gave limited evidence for the influence of OH-radical initiated depletion reactions of gaseous PCDD/Fs. The global atmospheric burden is estimated to be on the order of 350 kg sigmaCl4-8DD/Fs and approximately 3 kg sigmaTEQ.

Air Pollutants↗
PubMed2001

Further developments in the use of semipermeable membrane devices (SPMDs) as passive air samplers for persistent organic pollutants: field application in a spatial survey of PCDD/Fs and PAHs.

Semipermeable membrane devices (SPMDs) were deployed at 19 sites in northwest England to test their efficacy as passive atmospheric samplers for polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) and polycyclic aromatic hydrocarbons (PAHs). SPMDs were found to be efficient samplers for vapor phase species in the atmosphere, with good reproducibility between samplers. Species which are partially or completely particle associated under ambient U.K. conditions were also sampled by the SPMDs but with poorer reproducibility. It is suggested that SPMDs could be used to indicate "hotspots" of particulate associated species, however. Differences in absolute and relative concentrations of all PCDD/Fs and PAHs sequestered bythe SPMDs were observed between sites. High amounts were sequestered in SPMDs at sites where previous active monitoring has indicated relatively high atmospheric concentrations, confirming the potential of SPMDs as a tool for semiquantitative spatial monitoring of atmospheric species. SPMDs also respond to differences in the mixture of compounds present in the atmosphere, thereby aiding source apportionment studies.

Air Pollution↗
PubMed2001

The significance of PCBs in the atmosphere of the southern hemisphere.

Air monitoring stations were set up at 2 sites in the southern hemisphere--Moody Brook, Falkland Island (51 degrees 25' S, 57 degrees 56' W) and Halley, Research Station, Antarctica (75 degrees 35' S, 26 degrees 30' W). PCBs were monitored at the stations throughout 1999. Highest concentrations were observed when temperatures were greater. In general, concentrations were greater at Moody Brook than at Halley, although the difference in concentrations between sites was less for more chlorinated congeners. Air concentrations at both sites were compared with samples collected nearby over-water. Over water air concentrations were found to be greater than over land air concentrations. Concentrations were also compared with literature data for air concentrations at a remote site in the Canadian Arctic. Atmospheric concentrations of tri-chlorinated biphenyls were found to be approximately double those reported for Ellesmere Island in the Canadian Arctic, whilst concentrations in samples from Antarctica were very similar to those found in the high Arctic. Most other PCBs were a factor of 2-4 greater in the Canadian Arctic.

Air Movements↗
PubMed2000

Quadruple tacrolimus-based induction therapy including azathioprine and ALG does not significantly improve outcome after liver transplantation when compared with standard induction with tacrolimus and steroids: results of a prospective, randomized trial.

BACKGROUND: Tacrolimus in combination with prednisolone has been proven to be a safe and effective immunosuppressive induction therapy in solid organ transplantation. However, it remains unclear whether a tacrolimus-based quadruple induction regimen with azathioprine and an antilymphocytic preparation could further improve the results after orthotopic liver transplantation. Therefore, we designed a prospective, randomized study to compare the immunosuppressive efficacy of dual (tacrolimus and prednisolone) and quadruple (tacrolimus, azathioprine, ALG Merieux and prednisolone) induction after liver transplantation. METHODS: After randomization, 120 consecutive patients of primary liver transplants were divided into the dual group (n=59) and the quadruple group (n=61) and followed for a minimum of 3 years. RESULTS: Patient survival at 3 years was 88.2% in the dual versus 94.9% in the quadruple group. Overall 25 patients in each group (41 and 42%, respectively) developed acute rejection. There was no difference in the number and severity of rejections. In each group only four patients required OKT3-therapy, however, although three of four patients in the quadruple group responded to OKT3 and cleared rejection, none of the four patients in the dual group were treated successfully with OKT3 (P<0.02). Rejection in these patients resolved only after additional treatment with mycophenolate mofetil. Adverse events and infections were equally distributed in both groups. Asymptomatic Cytomegalovirus infections were more common in the quadruple group (P<0.02). As of today, only one patient developed posttransplant lymphoproliferative disease (dual group). CONCLUSIONS: The data from our single-center study indicate that both tacrolimus-based dual and quadruple immunosuppressive induction regimens yield similar safety and effectiveness after liver transplantation.

Adult↗
PubMed2000

Muscle-dependent and hormone-dependent differentiation of the vocal control premotor nucleus robustus archistriatalis and the motornucleus hypoglossus pars tracheosyringealis of the zebra finch.

Sex differences in the vertebrate brain (brain sex) are thought to develop owing to the tissue specific action of gonadal hormones similar to the development of secondary sex characteristics of the body. Small sex differences in body anatomy could, however, retrogradely control the sexual differentiation of the central nervous system. This possibility has so far been verified only for motorneuron pools, since the connectivity of sex-specific higher brain areas to the sexual dimorphic periphery is frequently not well known. Here, we tested whether somatic sex differences feed back on higher brain areas by bilateral denervation of the syringeal musculature of zebra finches before, during, and after onset of estrogen-sensitive sexual differentiation of forebrain vocal nuclei such as RA (nucleus robustus archistriatalis). In the zebra finch, the sound-producing musculature (the syrinx), the syrinx motornucleus hypoglossus pars tracheosyringealis (nXIIts), and the RA are much larger in males compared to females. Tract tracing studies revealed that the volume and neuron size distribution of the nXIIts was sexually dimorphic in intact but not in animals denervated as juveniles. In contrast, the volume of RA and size of RA neurons of denervated animals were highly sexually dimorphic. Furthermore, estrogen masculinized the RA of denervated females. Thus, sexual differentiation of the RA but not of the nXIIts appears independent of somatic sex differences. The syrinx muscles are, however, important for the soma size of those RA neurons that project to the nXIIts.

Animals↗
PubMed2000

Hepatic glutamine transporter activation in burn injury: role of amino acids and phosphatidylinositol-3-kinase.

Burn injury elicits a marked, sustained hypermetabolic state in patients characterized by accelerated hepatic amino acid metabolism and negative nitrogen balance. The transport of glutamine, a key substrate in gluconeogenesis and ureagenesis, was examined in hepatocytes isolated from the livers of rats after a 20% total burn surface area full-thickness scald injury. A latent and profound two- to threefold increase in glutamine transporter system N activity was first observed after 48 h in hepatocytes from injured rats compared with controls, persisted for 9 days, and waned toward control values after 18 days, corresponding with convalescence. Further studies showed that the profound increase was fully attributable to rapid posttranslational transporter activation by amino acid-induced cell swelling and that this form of regulation may be elicited in part by glucagon. The phosphatidylinositol-3-kinase (PI3K) inhibitors wortmannin and LY-294002 each significantly attenuated transporter stimulation by amino acids. The data suggest that PI3K-dependent system N activation by amino acids may play an important role in fueling accelerated hepatic nitrogen metabolism after burn injury.

Amino Acids↗
PubMed2000

An object-oriented approach for structuring the electronic medical record.

We implemented a framework for modelling the electronic medical record on top of an object-oriented model. Clinical patient data are structured in a uniform way through the use of a comprehensive data model. The meaning of the information elements is explicitly determined by a medical data dictionary. The data structures of both, medical record and data dictionary are implemented, using a semantically rich, object-oriented data model. We examined several possibilities for the graphical preparation of the inherently recursive data structures. Again, we use object-oriented frameworks for the implementation of flexible user interfaces to the electronic medical record with a consistent look-and-feel.

Data Collection↗
PubMed1999

Strain and substrain differences in context- and tone-dependent fear conditioning of inbred mice.

The performance of C57BL/6J (6J), C57BL/6N (6N), DBA/2J (2J) and DBA/2N (2N) mice in context- and tone-dependent fear conditioning was determined 24 h after fear conditioning to evaluate and compare different behavioral measures as indices of emotional learning. Freezing, the change in activity and the size of the explored area were evaluated as behavioral parameters indicating fear. Additionally, the heart rate (HR) increase elicited by tone presentation was evaluated as an autonomic indicator of fear. During the context-dependent memory test, freezing was high only in 6J and 6N mice, whereas a drop of activity and a reduced exploratory area was measured in all strains. During the tone-dependent memory test, high freezing, low activity, reduced exploratory area and a strong HR increase were demonstrated only in 6N and 6J mice, whereas behavioral and HR changes of 2J and 2N mice were always low. In extinction tests, context- and tone-dependent freezing of 6J mice decayed significantly faster than the freezing of 6N mice, whereas in both substrains the conditioned tachycardia to tone extinguished similarly in the home cage. The data demonstrate that monitoring of additional behavioral measures besides freezing and autonomic measures is necessary to interpret differences in associative learning performance of mouse strains that could be related to a differential expression of fear.

Acoustic Stimulation↗
PubMed1999

Extended resections for hilar cholangiocarcinoma.

OBJECTIVE: To evaluate different strategies for extended resections of hilar cholangiocarcinomas on radicality and survival. SUMMARY BACKGROUND DATA: Surgical resection of hilar cholangiocarcinoma is the only potentially curative treatment. Resection of central bile duct carcinomas, however, cannot always comply with the general principles of surgical oncology to achieve wide tumor-free margins with no-touch techniques. METHODS: From 1988 to 1998, 95 patients underwent resection of hilar cholangiocarcinoma. Eighty patients had hilar and hepatic resections and 15 had liver transplantation and partial pancreatoduodenectomy (LTPP; i.e., eradication of the entire biliary tract using a no-touch technique). RESULTS: The 60-day death rate was 8%. The overall 1- and 5-year survival rates were 67% and 22%, respectively. Five-year survival rates after R0, R1, and R2 resections were 37%, 9%, and 0%. In a multivariate analysis, surgical radicality was the strongest determinant of survival (p < 0.001). The rate of formally curative resection (R0 resection) was significantly lower in hilar resections (29%) than in liver resections (left hemihepatectomy 59%, right hemihepatectomy 55%, right trisegmentectomy 65%; p < 0.05). The highest rate of R0 resection was observed after LTPP (93%; p < 0.05). Right trisegmentectomies achieved the highest rate of 5-year survival after R0 resection (57%). In a multivariate analysis of patient survival after R0 resection, additional portal vein resection was the only significant factor. The 5-year survival rate after formally curative liver resection with portal vein resection was 65% versus 28% without. CONCLUSION: Extended resections, especially right trisegmentectomies and LTPP, resulted in the highest rate of R0 resection. Right trisegmentectomy together with portal vein resection best represents the principles of surgical oncology and may be regarded as the surgical procedure of choice. Immunosuppression limits the applicability of LTPP.

Aged↗
PubMed1999

Rat liver endothelial cell glutamine transporter and glutaminase expression contrast with parenchymal cells.

Despite the central role of the liver in glutamine homeostasis in health and disease, little is known about the mechanism by which this amino acid is transported into sinusoidal endothelial cells, the second most abundant hepatic cell type. To address this issue, the transport of L-glutamine was functionally characterized in hepatic endothelial cells isolated from male rats. On the basis of functional analyses, including kinetics, cation substitution, and amino acid inhibition, it was determined that a Na+-dependent carrier distinct from system N in parenchymal cells, with properties of system ASC or B0, mediated the majority of glutamine transport in hepatic endothelial cells. These results were supported by Northern blot analyses that showed expression of the ATB0 transporter gene in endothelial but not parenchymal cells. Concurrently, it was determined that, whereas both cell types express glutamine synthetase, hepatic endothelial cells express the kidney-type glutaminase isozyme in contrast to the liver-type isozyme in parenchymal cells. This represents the first report of ATB0 and kidney-type glutaminase isozyme expression in the liver, observations that have implications for roles of specific cell types in hepatic glutamine homeostasis in health and disease.

Amino Acid Transport Systems, Basic↗
PubMed1999

[Psychogenic impairment and current feelings in the elderly. Which options are offered by the biographical perspective?].

In the Eldermen study funded by the German Research Association (DFG), a consecutive sample of patients, aged > or = 60 (n = 120) and being treated for a variety of internal medical complaints in an acute geriatric hospital were examined with the help of comprehensive somatic diagnostics, standardised questionnaires, and a semi-structured biographical interview. The study investigates the relationship between burdensome and supportive biographical experiences and the extent of psychogenic impairment as well as aspects of feeling tone and self-concept in later life. For the degree of psychogenic impairment (Impairment Score. IS; Schepank 1995), subjectively experienced burdens and support were found to be more relevant than "objective" burdens. As expected, subjective burdens consistently experienced over several life phases, particularly in association with limited experienced support, were found to be associated with greater psychogenic impairment and a higher "case risk" in later life. However, the patients with the highest values for current life satisfaction as well as a more positive self-concept were not those patients who never experienced more burdens than support in their biographies, but rather those who experienced more burden than support in one life phase. The results are presented in relation to models of learning theory and object relation theory and discussed for their clinical relevance.

Aged↗
PubMed1999

Preemptive therapy in CMV-antigen positive patients after liver transplantation--a prospective trial.

OBJECTIVE: Preemptive therapy with intravenous ganciclovir and CMV-hyperimmunoglobulin in asymptomatic CMV pp65-antigen positive patients was compared with treatment of only symptomatic CMV-disease after liver transplantation in an open prospective study. PATIENTS AND METHODS: 48 out of 200 liver transplant recipients became positive during six weeks follow-up after transplantation. 17 out of these 48 patients who were already symptomatic at the time of positive antigen testing were successfully treated with ganciclovir and CMV-hyperimmunoglobulin. 31 asymptomatic antigen-positive patients were randomised to receive preemptive therapy or to receive therapy only at onset of clinical symptoms. RESULTS: Only two out of 15 patients in this latter group without preemptive therapy developed CMV-syndrome and were successfully treated with intravenous ganciclovir. 13 patients did not experience any clinical symptoms or disease and were therefore spared unneccessary toxicity and costs. The overall incidence of CMV-infection and -disease in the whole study population of 200 liver transplant recipients was 25% and 10%. As expected, CMV-negative patients who received an organ from a seropositive donor were at a higher risk of CMV-infection and -disease, but did not show more severe infections clinically. Patients with IL-2 receptor antibody induction therapy seemed to have a higher risk for CMV-infection and -disease.

Adult↗
PubMed1998

Dioxins and furans in air and deposition: a review of levels, behaviour and processes.

This paper is a comprehensive, critical review of the levels, behaviour and processes affecting polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) in air and deposition. Aspects of sampling, analysis and quality assurance/control are discussed initially, before a review of the PCDD/F concentrations in ambient air is presented. The general trend in sigma P4-8 CDD/F (and sigma TEQ) is: remote sites < 0.5 pg/m3 (sigma TEQ < 10 fg/m3); rural sites approximately 0.5-4 pg/m3 (sigma TEQ approximately 20-50 fg/m3); and urban/industrial sites approximately 10-100 pg/m3 (sigma TEQ approximately 100-400 fg/m3). The commonly held view that a consistent mixture of PCDD/Fs in air exists is evaluated and questioned. Issues of seasonality and short-term changes in air concentrations are also critically discussed, with respect to the possibility of seasonal emission sources to air and seasonally dependent loss processes. Data on the gas-particle partitioning of PCDD/Fs in air are reviewed; the limited database to date is believed to provide evidence for an exchangeable transfer of PCDD/Fs between these two phases. The potential importance of photolytic and radical reaction degradation processes and wet/dry deposition processes in modifying the mixture of PCDD/Fs in air is discussed. Some homologue/congener specific 'weathering' of the mixture of PCDD/Fs emitted to the atmosphere clearly occurs, but in general PCDD/Fs have 'long' atmospheric residence times, rendering them subject to long-range atmospheric transport. Data are reviewed which relate the mixture of PCDD/Fs in air to that in deposition; this leads to the conclusion that different homologue groups (which are partitioned differently between the gas and particulate phase) are transferred to the earth's surface with broadly similar efficiencies.

Air Pollutants↗