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Biomedical subjects

C Wilhelm

Publications and source records attributed to C Wilhelm.

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

Algae displaying the diadinoxanthin cycle also possess the violaxanthin cycle.

According to general agreement, all photosynthetic organisms using xanthophyll cycling for photoprotection contain either the violaxanthin (Vx) cycle or the diadinoxanthin (Ddx) cycle instead. Here, we report the temporal accumulation of substantial amounts of pigments of the Vx cycle under prolonged high-light stress in several microalgae thought to possess only the Ddx cycle. In the diatom Phaeodactylum tricornutum, used as a model organism, these pigments also participate in xanthophyll cycling, and their accumulation depends on de novo synthesis of carotenoids and on deepoxidase activity. Furthermore, our data strongly suggest a biosynthetic sequence from Vx via Ddx to fucoxanthin in P. tricornutum. This gives experimental support to the long-stated hypothesis that Vx is a common precursor of all carotenoids with an allenic or acetylenic group, including the main light-harvesting carotenoids in most chlorophyll a/c-containing algae. Thus, another important function for xanthophyll cycling may be to optimize the biosynthesis of light-harvesting xanthophylls under fluctuating light conditions.

Carotenoids↗
PubMed1999

Spectroscopic and molecular characterization of a long wavelength absorbing antenna of Ostreobium sp.

One of the strains of the marine green alga Ostreobium sp. possesses an exceptionally large number of long wavelength absorbing chlorophylls (P. Haldall, Biol. Bull. 134, 1968, 411-424) as evident from a distinct shoulder in the absorption spectrum at around 710 nm while in the other strain this shoulder is absent. Therefore, Ostreobium offers a unique possibility to explore the origin of these red-shifted chlorophylls, because strains with and without these spectral forms can be compared. Here, we characterize these red forms spectroscopically by absorption, fluorescence and CD spectroscopy. In the CD spectra at least three spectroscopic red forms are identified which lead to an unusual room temperature fluorescence spectrum that peaks at 715 nm. The gel electrophoretic pattern from thylakoids of Ostreobium sp. shows an intense band at 22 kDa which correlates with the presence or absence of long wavelength absorbing pigments. By protein sequencing of the N-terminus of the 22-kDa polypeptide and sequence alignments, this was identified as an Lhca1-type light-harvesting complex. The abundance of this polypeptide - and a possibly co-migrating one - in Ostreobium sp. indicates an antenna size of approximately 340 chlorophyll molecules (Chl a and Chl b) per PS IIalpha reaction center, which is significantly larger than in higher plants ( approximately 240). The red forms are more abundant in the interior of the thalli where a 'shade-light' light field is expected than in the white-light exposed surface. This demonstrates that algae exist which may be able to up-regulate the synthesis of large amounts of LHCI and associated red forms under appropriate illumination conditions.

Amino Acid Sequence↗
PubMed1999

Fatal rupture of a sacrococcygeal teratoma during delivery.

We report the case of premature infant born at 32 weeks' gestation with a sacrococcygeal teratoma diagnosed in utero. During delivery by cesarean section, profound bleeding due to rupture of the teratoma occurred. Despite volume expansion with saline, albumin, and whole blood, a satisfactory peripheral perfusion of the infant was only briefly achieved. Surgical intervention to stop the bleeding was unsuccessful. Resuscitation of the infant was discontinued after 55 minutes. The relevant literature is discussed, and suggestions for the management of infants with sacrococcygeal teratomas are made.

Cesarean Section↗
PubMed1998

Fetal cerebral AV-malformation and cardiomegaly, diagnostic and therapeutic problems.

Intracerebral aneurysms are rare. However they are potentially life-threatening. Today by means of ultrasound investigations these malformations can occasionally be identified prenatally. In these cases questions of intrauterine therapy, mode and time of delivery and postnatal treatment have to be discussed with the parents. We describe two cases with prenatal diagnosis of intracerebral arteriovenous malformations, diagnostic workup, therapeutic options and fetal outcome.

Adult↗
PubMed1997

Fatal sepsis caused by Corynebacterium amycolatum in a premature infant.

Corynebacterium amycolatum has not been reported as a cause of human infections up to now, but usually the bacterium is misidentified in clinical specimens as Corynebacterium xerosis. We report the first case of neonatal sepsis due to Corynebacterium amycolatum with a fatal outcome in a premature infant.

Corynebacterium↗
PubMed1997

Intrauterine insemination for treatment of male infertility.

Intrauterine inseminations (IUI) have been performed since the beginning of this century for treatment of infertility. Despite its widespread use the clinical value of this technique remains unclear. Today, indications for IUI include male factor, cervical factor, immunological and unexplained infertility and infertility due to ejaculatory disorders. IUI is superior to intravaginal (IVI) or intracervical insemination (ICI). Before insemination, semen has to be processed using one of the established sperm preparation techniques. Different techniques seem to be equally effective in preparing a highly concentrated sperm fraction with progressively motile, morphologically normal sperm. Ovarian stimulation further improves pregnancy rates achieved by insemination. Human menopausal gonadotropin (HMG) stimulation seems to be superior to clomiphene citrate stimulation. Among other factors, timing and number of inseminations are crucial when influencing the outcome of IUI treatment.

Female↗
PubMed1996

Tamm-Horsfall protein as a marker of tubular maturation.

Tamm-Horsfall protein (THP), a glycoprotein with a molecular weight of 95 kilodaltons, is produced and secreted in the ascending loop of Henle. To evaluate the measurement of THP in the assessment of fetal renal development and function, we stained fetal kidney sections for THP and measured THP concentrations in 129 amniotic fluid samples from healthy pregnancies, together with other parameters such as transferrin, albumin, alpha 1- and beta 2-microglobulin. After the 16th week of gestation THP could be detected immunohistochemically in the distal tubular cells, but was not consistently detected by sandwich enzyme immunoassay until after the 20th week of gestation (detection limit 50 ng/ml). Between the 15th and 19th week of gestation THP was only detected occasionally, but after the 20th week of gestation the concentration increased significantly reaching levels of 0.4-4 mg/l at term. The THP concentration was lower in samples taken directly before birth than in the corresponding first urine after birth, indicating that THP is produced from the fetal kidney only and does not pass the placental barrier. This pattern was different from other proteins studied. Transferrin and albumin were significantly lower in the first urine voided, microglobulins remained unchanged, and the creatinine concentration increased. This indicates that maternal to fetal exchange or transport is likely for most of the other proteins. Measurement of THP concentrations, in addition to other proteins in the amniotic fluid, can improve fetal renal assessment, but because the range of THP concentrations is wide accurate predictions are still not possible.

Alpha-Globulins↗
PubMed1995

[Thrombomodulin is a marker of microvascular, but not for macrovascular endothelial cell damage].

UNLABELLED: Plasma levels of thrombomodulin are increased in diseases associated with microangiopathia. The target of this study was to examine whether plasma thrombomodulin is also influenced by macroangiopathia. There was no variation of plasma thrombomodulin in a sample of 183 diabetic patients with or without peripheral arterio-occlusive disease of the lower limbs. In a second sample of 33 patients with peripheral arteriosclerosis of the lower limbs, without any indication of diabetes, plasma levels of thrombomodulin were not significantly increased compared to a control group. Since thrombomodulin is also found in thrombocytes, we analysed whether plasma thrombomodulin levels were influenced by platelet activation. Neither platelet activation after hyperthermal limb perfusion not the PGE1-treatment showed any effect on plasma thrombomodulin level. CONCLUSION: Thrombomodulin is a marker for microvascular but not for macrovascular endothelial cell damage.

Adult↗
PubMed1995

FDDI information management system for centralizing interactive, computerized multimedia clinical experiences in pediatric rheumatology/Immunology.

This paper describes the design, authoring, and development of interactive, computerized, multimedia clinical simulations in pediatric rheumatology/immunology and related musculoskeletal diseases, the development and implementation of a high speed information management system for their centralized storage and distribution, and analytical methods for evaluating the total system's educational impact on medical students and pediatric residents. An FDDI fiber optic network with client/server/host architecture is the core. The server houses digitized audio, still-image video clips and text files. A host station houses the DB2/2 database containing case-associated labels and information. Cases can be accessed from any workstation via a customized interface in AVA/2 written specifically for this application. OS/2 Presentation Manager controls, written in C, are incorporated into the interface. This interface allows SQL searches and retrievals of cases and case materials. In addition to providing user-directed clinical experiences, this centralized information management system provides designated faculty with the ability to add audio notes and visual pointers to image files. Users may browse through case materials, mark selected ones and download them for utilization in lectures or for editing and converting into 35mm slides.

Allergy and Immunology↗
PubMed1994

Therapeutic strategies in cervical pregnancy.

Cervical pregnancy is a rare condition associated with a high maternal morbidity rate. Standard recommendations for the management of this ectopic pregnancy are not available. This paper presents a case report and reviews the respective literature. In many cases hysterectomy was the ultimate solution. In order to avoid hysterectomy chemotherapy using methotrexate has been suggested. Local injections of prostaglandins or vasopressin have also been proposed. Based on data collected from the literature and our own experience it is concluded that the management of cervical pregnancy requires individualized therapeutic strategies to minimize the rate of hysterectomies.

Adult↗
PubMed1994

Transvaginal sonography of myometrial invasion depth in endometrial cancer.

The myometrial invasion depth of endometrial cancer is an important prognostic factor. The preoperative assessment is decisive for the appropriate surgical treatment. In 96 patients with endometrial cancer, the myometrial invasion depth (greater than 50% or less than 50%) was measured preoperatively using transvaginal sonography (TVS). The sonographic results were compared to the histopathological findings. A sensitivity of 93% was obtained for invasion depths greater than 50%. The predictive value of an invasion depth less than 50% was 93% as well. In 16% of the cases the invasion depth was overestimated while, in only 3% it was underestimated. The diagnostic accuracy was 81%. Forty-five patients were examined preceding a diagnostic dilatation and curettage and fifty-one were examined following a diagnostic dilatation and curettage. The diagnostic accuracy in both groups was equivalent. Using transvaginal sonography, the spread of cancer to the cervix was observed in five of the seven cases in which it was postoperatively confirmed. TVS is a valuable, non-invasive diagnostic method for patients with endometrial cancer. When the TVS data are combined with results from other preoperative tests, the prognostic information obtained provides a useful basis in choosing the appropriate therapy.

Aged↗
PubMed1994

[Selectivity of glomerular proteinuria and liver function in gestosis].

Proteinuria in preeclamptic women was qualitatively differentiated and in cases of pure glomerular proteinuria three groups according to the low-, medium- or high selectivity of glomerular proteinuria were formed. In these patients the incidence of liver dysfunction and severe proteinuria together with an increase in mean arterial blood pressure was investigated. The aim of this study was to find out if there is any connection between glomerular proteinuria of different selectivity and disturbed liver function. In patients with EPH-gestosis a pure glomerular proteinuria in SDS-PAA-disc electrophoresis of the urine was found. Together with the increase in glomerular selectivity an increase in quantitative urinary protein loss was found. In patients with high selective glomerular proteinuria the extent of proteinuria was about three times higher than in patients with low selectivity. In all patients a moderate elevation of the liver enzymes was found. In all patients disturbed liver function returned to normal within a few days after delivery. We conclude from these data that glomerular functional lesions pregnancy in patients with preexisting glomerulopathies or pregnancy induced renal dysfunction are accompanied in a high rate by moderate disorders of liver function.

Alanine Transaminase↗
PubMed1993

Why do thylakoid membranes from higher plants form grana stacks?

Chloroplasts contain a system of membrane sacs, the thylakoids, some of which are stacked to form grana (singular, granum), whereas others float freely in the stroma. It is on the thylakoid membranes that the electron carriers necessary for photosynthesis reside. There has been continuous speculation and discussion about the function of the grana ever since Menke postulated their lamellar nature in 1939. On the basis of new insights into the biophysics of the two photosystems and the molecular organization of thylakoid membranes of algae that exhibit a different lateral heterogeneity from that of higher plants, we propose that the membrane stacking found in the chloroplasts of higher plants and green algae is just one way in which Nature implements a general principle, namely that of physically separating a slow (PS II) and a fast (PS I) photosystem.

Chlorophyta↗
PubMed1993

Kinetics of pore size during irreversible electrical breakdown of lipid bilayer membranes.

The kinetics of pore formation followed by mechanical rupture of lipid bilayer membranes were investigated in detail by using the charge-pulse method. Membranes of various compositions were charged to a sufficiently high voltage to induce mechanical breakdown. The subsequent decrease of membrane voltage was used to calculate the conductance. During mechanical breakdown, which was probably caused by the widening of one single pore, the membrane conductance was a linear and not exponential function of time after the initial starting process. In a large number of experiments using various lipids and electrolytes, the characteristic opening process of the pore turned out to be independent of the actual membrane potential and electrolyte concentration. Our theoretical analysis of the pore formation suggested that the voltage-induced irreversible breakdown is due to a decrease in edge energy when the pore had formed. After initiation of the pore, the electrical contribution to surface tension is negligible. The time course of the increase of pore size shows that our model of the irreversible breakdown is in good agreement with mechanical properties of membranes reported elsewhere.

Biophysical Phenomena↗