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Biomedical subjects

R Lehmann

Publications and source records attributed to R Lehmann.

At least 163 records · Page 9Linked to original sources
PubMed1996

[Pregnancy in hyperprolactinemic patients].

In a retrospective study we analysed the outcome of 27 pregnancies in 17 hyperprolactinaemic patients. Cranial CT or MRI scans showed a microadenoma in 9, a macroadenoma in 7 and no change in 1 case. In 5 patients macroadenomas were surgically removed but a residual hyperprolactinaemia remained. In 2 patients with selectively removed microadenomas through the transsphenoidal route only in one case normal prolactin levels could be achieved. This patient became two times pregnant. In 24 patients pregnancy was induced by dopaminergic treatment whereas another patient with microadenoma became spontaneously pregnant after surgery and treatment with bromocriptine. The treatment was discontinued as soon as the pregnancy was recognised. 19 pregnancies were finished by spontaneous delivery and 3 by Caesarean section. Termination of pregnancy was artificially induced in 3 patients. One miscarriage was observed. Another patient was suffering from an extrauterine pregnancy. During pregnancy prolactin levels increased in comparison to basal levels. After delivery and lactation the same prolactin level was found compared to basal levels in patients with microprolactinomas. In patients suffering from macroadenomas prolactin levels decreased in comparison to basal levels. CT of MRI scan evaluations performed after delivery revealed a clinical not relevant increase as well as a decrease of tumor size in 2 cases, respectively. During pregnancy there was no complication due to tumor found in treated patients for hyperprolactinaemia. Only about one half of mothers were able to perform regular breast feeding.

Adult↗
PubMed1995

Capillary electrophoresis, a rapid and sensitive method for routine analysis of apolipoprotein A-I in clinical samples.

A method for the determination of apolipoprotein A-I, the major protein compartment of HDL, in human serum is described. Rapid and easy serum sample preparation, well separated Apo A-I peaks in the human serum electropherogram and good linearity of the peak area vs. concentration plot, covering the range of the clinically relevant Apo A-I serum contents, suggest the introduction of this method routinely in clinical laboratories.

Apolipoprotein A-I↗
PubMed1995

[Diabetic nephropathy: significance of microalbuminuria and proteinuria in Type I and Type II diabetes mellitus].

Diabetic nephropathy is a progressive renal disease and represents a serious late complication of diabetes. There are familial clustering and huge ethnic differences in the occurrence of diabetic nephropathy, which point to a genetic predisposition. Diabetic nephropathy is defined by persistent albuminuria (albumin excretion rate [AER] > 300 mg/day), declining glomerular filtration rate and rising blood pressure. Several years of incipient nephropathy, characterized by worsening microalbuminuria (AER 30 to 300 mg/day or 20 to 200 micrograms/min), which is Albustix-negative and detectable by special assays only, are followed by established nephropathy. The natural history of nephropathy differs between insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetes mellitus. In IDDM, nephropathy develops in 30 to 40% of cases. The incidence peaks after 15 to 16 years of diabetes. In NIDDM, estimates of prevalence range from 15 to 20%, and nephropathy often supervenes after a shorter known duration of diabetes than in IDDM. GFR is often increased above normal (hyperfiltration) from the onset of IDDM due to increased renal blood flow, glomerular capillary hypertension and increased filtration surface. The glomeruli are hypertrophied and the kidneys enlarged. In both IDDM and NIDDM, GFR begins to decline irreversibly, when AER has risen to 100 to 300 mg/day at an average rate of 10 ml/min. per year. This is due to progressive reduction of the filtration surface area through mesangial expansion. Serum creatinine levels begin to rise when GFR falls below 50 ml/min, and then end-stage renal failure follows after an average of five years.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1995

Capillary electrophoresis of human serum proteins and apolipoproteins.

Capillary electrophoresis (CE) analysis of human serum proteins and apolipoproteins is described and compared with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and cellulose acetate membrane electrophoresis. Under optimized CE conditions apolipoproteins I could be determined directly in the serum and quantitated with a linear correlation between peak area and concentration up to a concentration of 100 mg/dL.

Apolipoprotein A-I↗
PubMed1995

Dual-energy X-ray absorptiometry at the lumbar spine in German men and women: a cross-sectional study.

A cross-sectional, population-based study of 238 randomly selected females and 224 males with German ethnic background (aged 20-80 years) was carried out to establish lumbar spine bone mineral density (BMD) values, using dual X-ray absorptiometry (DXA), for a German population. Comparison was made to the reference range provided by the manufacturer of the DXA equipment. No sex difference in peak spine BMD was found in our study (1.091 +/- 0.114 g/cm2 for males versus 1.070 +/- 0.113 g/cm2 for females, n.s.). Different patterns of bone loss could be detected in both sexes. In premenopausal women there was no significant correlation between age and BMD (y = 1.044 + 0.00047x, r = 0.03, P = 0.73) whereas reduction of female BMD at the spine was demonstrated in postmenopausal women (y = 1.189-0.0041x, r = -0.28, P = 0.01), underscoring the important role of the menopause for later manifestation of spinal osteoporosis in women. In contrast, in males we found no significant change of BMD with aging (y = 1.071-0.0007x, r = -0.08, P = 0.25). Employing commonly used exclusion criteria, BMD values of the study subjects were found mostly within the normal range of BMD. The major finding of our study was good concordance between female data of our study population and the reference data provided by the manufacturer. Clinically significant discrepancies between our data and the Hologic reference range for males could be detected. Our data on males (30-39 years of age) were up to 7% lower than those provided by the manufacturer, probably due to differences in sampling procedures.

Absorptiometry, Photon↗
PubMed1995

Loss of abdominal fat and improvement of the cardiovascular risk profile by regular moderate exercise training in patients with NIDDM.

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with an increased cardiovascular risk. Glycaemic control alone is often insufficient to control diabetic dyslipidaemia and other cardiovascular risk factors associated with NIDDM. The present trial was designed to evaluate the effects of physical activity as an adjunct to standard diabetes therapy on the lipid profile, blood pressure, glycaemic control, weight and body fat. Sixteen well-controlled (HbA1c 7.5%) patients with NIDDM participated in a regular aerobic exercise training programme at 50-70% maximal effort over 3 months. Thirteen age- and sex-matched patients with NIDDM served as a control group. The 3-month intervention with an increase in physical activity from 92 (mean +/- SD) +/- 79 to 246 +/- 112 min per week (p < 0.001) by means of a structured activity programme resulted in significant improvement of plasma lipids with a 20% decrease in triglycerides (p < 0.05), unchanged total cholesterol and increases in high-density lipoprotein and high-density lipoprotein-3 subfraction of 23% (p < 0.001) and 26% (p < 0.001), respectively. Systolic and diastolic blood pressure decreased significantly from 138 +/- 16 to 130 +/- 17 mm Hg (p < 0.05) and 88 +/- 10 to 80 +/- 10 mmHg (p < 0.001), respectively. Resting heart rate decreased from 81 +/- 13 to 74 +/- 14 beats per minute (p < 0.001), waist-hip circumference ratio decreased from 0.96 +/- 0.11 to 0.92 +/- 0.10 (p < 0.001) and body fat decreased from 35.3 +/- 7.2 to 33.0 +/- 8.0% (p < 0.001). These effects occurred independently of changes in body weight and glycaemic control, which did not change during the study. This study shows that improvement in physical fitness by introducing regular physical exercise as part of the treatment programme in patients with NIDDM results in a significant amelioration of their cardiovascular risk profile.

Abdomen↗
PubMed1995

Clinical comparison of Provisc and Healon in cataract surgery.

This prospective, randomized, multicenter clinical trial compared the safety and efficacy of the Provisc and Healon viscoelastics. Sixty-one eyes of 61 patients had an extracapsular cataract extraction with implantation of a posterior chamber intraocular lens with the aid of Provisc (n = 32) or Healon (n = 29). Mean changes in preoperative versus postoperative corneal thickness and intraocular pressure and the incidence and magnitude of postoperative corneal edema and iritis were not significantly different between the two groups. Observed complications were considered consequences of the surgery and unrelated to viscoelastic use. No adverse medical events occurred. These results indicate Provisc and Healon are clinically equivalent in terms of safety and efficacy when used as surgical aids.

Cataract Extraction↗
PubMed1995

Transcallosal removal of lesions affecting the third ventricle: an anatomic and clinical study.

A series of 54 patients with lesions affecting the third ventricle with a wide range of pathology were operated on by the transcallosal approach. Hydrocephalus was present in 68.5% of all patients, and preoperative shunting was performed in 73.0% of them. Before the partial callosotomy, 16 patients were studied by the use of a cognitive, affective, and behavioral battery, which was repeated 10 and 100 days after the operation. No physiological consequences were ever observed after the partial commissurotomy. The postoperative callosal defect was verified by magnetic resonance imaging. Furthermore, 40 formalin-fixed brains were sectioned to study the variations of the anterior cerebral arteries. On the other hand, magnetic resonance imaging measurements of the corpus callosum in 40 normal subjects were performed to establish a classification system for the corpus callosal area. The results showed a wide variability of the cross-sectional area of the corpus callosum. The differences in the thickness of the truncus were responsible for this variability; the length of the corpus callosum was uniform. This may suggest that subjects with a large corpus callosum may have more interhemispheric connections with higher specialization of each hemisphere and that a smaller number of callosal connections may correlate with more ipsilateral pathways and more independent hemispheres. The results and the clinical as well as anatomical material indicate that the anterior transcallosal route is a safe and feasible alternative in the management of a wide spectrum of pathological lesions within the third ventricle and deserves preference over the transcortical technique.

Adult↗
PubMed1995

nanos is an evolutionarily conserved organizer of anterior-posterior polarity.

In Drosophila melanogaster, nanos functions as a localized determinant of posterior pattern. Nanos RNA is localized to the posterior pole of the maturing egg cell and encodes a protein that emanates from this localized source. Nanos acts as a translational repressor and thereby establishes a gradient of the morphogen Hunchback. Here we show that the mechanism by which nanos acts in Drosophila is a common developmental strategy in Dipteran insects. We used cytoplasmic transplantation assays to demonstrate that nanos activity is found in posterior poleplasm of five diverse Dipteran species. Genes homologous to nanos were identified from Drosophila virilis, the housefly Musca domestica, and the midge Chironomus samoensis. These genes encode RNAs that are each localized, like nanos, to the embryonic posterior pole. Most importantly, we demonstrate that these homologues can functionally substitute for nanos in D. melanogaster. These results suggest that nanos acts in a similar pathway for axis determination in other insects. Comparison of the Nanos sequences reveals only 19% overall protein sequence similarity; high conservation of a novel zinc finger near the carboxy terminus of the protein defines a region critical for nanos gene function.

Amino Acid Sequence↗
PubMed1995

Localization of oskar RNA regulates oskar translation and requires Oskar protein.

The site of oskar RNA and protein localization within the oocyte determines where in the embryo primordial germ cells form and where the abdomen develops. Initiation of oskar RNA localization requires the activity of several genes. We show that ovaries mutant for any of these genes lack Oskar protein. Using various transgenic constructs we have determined that sequences required for oskar RNA localization and translational repression map to the oskar 3'UTR, while sequences involved in the correct temporal activation of translation reside outside the oskar 3'UTR. Upon localization of oskar RNA and protein at the posterior pole, Oskar protein is required to maintain localization of oskar RNA throughout oogenesis. Stable anchoring of a transgenic reporter RNA at the posterior pole is disrupted by oskar nonsense mutations. We propose that initially localization of oskar RNA permits translation into Oskar protein and that subsequently Oskar protein regulates its own RNA localization through a positive feedback mechanism.

Animals↗
PubMed1995

Magnetic resonance imaging of a glioblastoma of the optic chiasm. Case report.

Malignant optic glioma causing blindness was difficult to diagnose prior to the introduction of computerized tomography (CT) and magnetic resonance (MR) imaging, because earlier neuroradiological procedures often gave negative results and the clinical symptoms for this entity are not specific. In such cases only a craniotomy or postmortem examination revealed the tumor. The authors found no precise description in the literature of a malignant optic glioma diagnosed with modern imaging methods. They present a patient in whom biopsy results confirmed the CT and MR findings of glioblastoma multiforme of the optic chiasm.

Aged↗
PubMed1995

Multicenter German reference data base for peripheral quantitative computer tomography.

The wide spread use of bone densitometers in Germany and other European countries has required the establishment of a validated reference population data base. A semianthropomorphic forearm cross-calibration phantom (EFP), developed during a concerted research action of the European Union's programme in Biomedical Engineering (COMAC-BME), was used to cross-calibrate the peripheral quantitative computer tomography (pQCT) devices at four German centers participating in the multicenter study. In total, 723 women and 208 men were included in the normal data base. No significant regional differences were found between the data of the different centers. In addition to the manufacturers calibration standard, proper calibration of the pQCT devices could be monitored during collection of the normal female and male data base. As a merit of the COMAC-BME study the measurements obtained with all pQCT devices thus ensured an uniform reference data base for distal radius measurements in Germany.

Adult↗
PubMed1994

[Assessment of hypoglycemia].

Hypoglycemia is characterized by a set of symptoms, but is not a diagnosis in itself. Initial attention should focus on documentation of the condition by typical symptoms (low blood sugar and disappearance of symptoms after glucose ingestion) before further testing is considered. To evaluate acute hypoglycemia, it is important to make an initial classification into one of three categories based on history: medication- or toxin-induced, fasting (not specifically associated with meals and usually occurring over 4 hours from the last meal) or postprandial hypoglycemia. A pathophysiologic approach to well-documented hypoglycemia leads to a straightforward strategy and to a diagnosis in most cases. True fasting hypoglycemia is almost invariably associated with a significant pathology, whereas postprandial hypoglycemia is not. An observed fast over 48-72 hours is diagnostic in nearly 100%. The diagnosis rests on several simultaneous features: hypoglycemia < 2.2 mmol/l, neuroglycopenic symptoms, and inappropriately elevated plasma insulin (> 30-40 pmol/l) and C-peptide levels (> 200 pmol/l) to document endogenous insulin release. Once the diagnosis of hyperinsulinism has been established, localization of the causative insulinoma (solitary adenomas in 80-90%) has traditionally been by means of the surgeon's fingers at laparotomy. In expert hands most tumors can be accurately located and removed. Although virtually every imaging technique has been advocated for preoperative localization of insulinomas, none has proved sufficiently reliable and surgical exploration is necessary even in the presence of a negative preoperative localization. Most patients who seek evaluation of reactive hypoglycemia describe a postprandial syndrome, which occurs with some regularity 2-4 hours after meals.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis, Differential↗
PubMed1994

Translational regulation of nanos by RNA localization.

Localization of the maternally synthesized nanos (nos) RNA to the posterior pole of the Drosophila embryo provides the source for a posterior-to-anterior gradient of Nos protein. Correct spatial regulation of nos activity is essential for normal pattern formation. High local concentrations of Nos protein in the posterior of the embryo are necessary to inhibit translation of the transcription factor Hunchback in this region, and thus permit expression of genes required for abdomen formation (see ref. 5 for review). By contrast, misexpression of Nos protein at the anterior of the embryo prevents translation of the anterior morphogen Bicoid, suppressing head and thorax development. Posterior localization of nos RNA is mediated by sequences within the nos 3' untranslated region (3'UTR) and requires the function of eight genes of the 'posterior group'. Although the unlocalized nos RNA is stable in embryos from females mutant for any of the posterior group genes, these embryos appear to lack nos activity because they develop the abdominal defects characteristic of embryos produced by nos mutant females. We report here that unlocalized nos RNA is translationally repressed. Translational repression is mediated by the nos 3'UTR and can be alleviated either by replacement of the 3'UTR with heterologous 3'UTR sequences or by posterior localization. Thus, RNA localization provides a novel mechanism for translational regulation.

Animals↗
PubMed1994

Germ plasm formation and germ cell determination in Drosophila.

In organisms as diverse as frogs, worms and flies germline precursor cells are set aside from the somatic cells early in development. It has been proposed that specific molecules, referred to as germ cell determinants, are deposited in the egg and direct the germ cell fate, but the molecular nature and function of these determinants is not fully understood. Genetic and molecular analysis in Drosophila melanogaster indicates that germ cell determination involves not only the synthesis of specific germ cell factors but also the proper localization and assembly of a morphologically distinct germ plasm. A pathway for germ plasm assembly has been established in which the oskar gene has a central role. The amount of oskar product in the embryo controls the number of germ cells formed and mislocalization of oskar RNA and protein in the egg cell leads to the formation of ectopic germ cells in the embryo. In addition to its role in anchoring germ cell-specific signals, the germ plasm also serves as the source of abdomen-specific signal. Such a colocalization of morphogenetic signals involved in germ cell formation and in the specification of the body axis is not unique to Drosophila but is also found in Caenorhabditis elegans and Xenopus.

Animals↗