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Biomedical subjects

U Barth

Publications and source records attributed to U Barth.

7 recordsLinked to original sources
PubMed2001

Determination of exchangeable protons in natural organic matter using a home-made hydrogen/carbon analyser.

A home made hydrogen/carbon analyser was used to determine the portion of exchangeable protons in aquatic humic substances. For this purpose, equal sample amounts were dissolved in H2O and D2O, respectively, dried and combusted in a stream of oxygen. The amount of water resulting from combustion was measured by an infrared detector which recorded the OH bending vibration of H2O. The bands stemming from HOD or D2O were not registered by the detection unit. Thus, combustion of organic samples containing exchangeable protons dissolved in D2O resulted in a significantly smaller signal compared to the signal observed for the same sample dissolved in H2O. The relative intensity loss of the H2O signal observed after combustion was used to derive the portion of exchangeable protons in a standard reference material, a humic substance isolated by the International Humic Substances Society (Suwannee River fulvic acid). According to this method about 20% of the sample protons could be identified as exchangeable protons. With regard to titration data the portion of protons bound to non acidic hydroxy functions could be estimated. The validity of this procedure was proved by combustion experiments using commercially available deuterated substances as well as organic model compounds dissolved in D2O and H2O, respectively.

Journal Article↗
PubMed2000

Abnormal pulmonary artery pressure response in asymptomatic carriers of primary pulmonary hypertension gene.

BACKGROUND: Familial primary pulmonary hypertension (PPH) is an autosomal-dominant inherited disease with incomplete penetrance and poor prognosis. This study was performed to examine whether asymptomatic carriers of a mutated PPH gene can be identified at an early stage by their pulmonary artery systolic pressure (PASP) response to exercise. METHODS AND RESULTS: Stress Doppler echocardiography during supine bicycle exercise and genetic linkage analysis were performed on 52 members of 2 families with PPH. In 4 PPH patients, the mean PASP was increased at rest (73+/-16 mm Hg). Fourteen additional family members with normal PASP at rest revealed an abnormal PASP response to exercise (from 23+/-4 to 56+/-11 mm Hg) without secondary cause (abnormal response [AR] group). Twenty-seven other members (NR group) revealed a normal PASP response (maximal pressure <40 mm Hg) to exercise (from 24+/-4 to 37+/-3 mm Hg, P<0. 0001). All 14 AR but only 2 NR members shared the risk haplotype with the PPH patients. The molecular genetic analysis supported linkage to chromosome 2q31-32 with a logarithm of the odds score of 4.4 when the 4 patients and the 14 AR members were classified as affected. CONCLUSIONS: We conclude that the pathological rise of PASP in asymptomatic family members is linked to chromosome 2q31-32 and is probably an early sign of PPH. Therefore, stress Doppler echocardiography may be a useful tool to identify persons at risk for PPH even before pulmonary artery pressures at rest are elevated.

Adolescent↗
PubMed2000

Effect of irrigating solution and irrigation temperature on the cornea and pupil during phacoemulsification.

PURPOSE: To evaluate the effect of irrigation solution and temperature on pupil diameter, corneal endothelium, and corneal pachymetry during and after phacoemulsification. SETTING: Klinik Dardenne, Bonn, Germany. METHODS: Eighty patients who had cataract surgery by phacoemulsification were assigned to 1 of 4 cross-classified groups and had intraoperative irrigation with room-temperature or refrigerated fortified balanced salt solution (BSS Plus) or modified Ringer's solution. Pupil diameters were recorded at different stages during the surgery. Epithelial cell counts and pachymetry were determined before and 1 day after surgery. RESULTS: The solution temperature did not affect any parameter. The type of solution did not influence endothelial cell loss; however, the solution had a significant effect on corneal pachymetry 1 day postoperatively. The corneas irrigated with BSS Plus were less swollen than the corneas irrigated with Ringer's solution. By day 14, corneal thickness was equal among all groups. CONCLUSION: Long-term results were equally favorable in all 4 groups. However BSS Plus induced less short-term corneal swelling than Ringer's solution. From these findings, it appears that BSS Plus may decrease corneal risk in cases with compromised corneas or prolonged surgery.

Adult↗
PubMed1994

[The necessity for alternative methods of hygienic testing of air technical designs for operating rooms].

The performance assessment of technical systems for the supply of clean air is fraught with problems which are caused by the present assessment procedures and norms. Until now the distribution of germs in a clean room has been considered as stationary and has been tested as though it was independent of the measuring time. Accordingly the quality of clean air rooms has to date been determined by measurements of particle or germ concentrations (Federal Standard 209; European Standard 209-WG-1; VDI 2083/1). By contrast different methods demonstrate that the contaminations introduced into a clean air room as particles or as particle-bound bacteria are eliminated according to an exponential function in a time-dependent manner. Therefore the measurements of single concentrations without the consideration of the time-dependence of concentration changes must needs lead to extremely faulty results. Furthermore the influence of disturbing factors (test persons, properties of different air supply ceilings, measuring instruments). As a consequence of the poor reliability and lacking validity of presently valid assessment methods, there is a discrepancy between the seemingly high performance of the clean air supply systems under laboratory conditions (DIN 4799) on the one hand, and the frequently unsatisfactory functioning of the same systems under practical conditions. This discrepancy has caused a significant loss of confidence towards the whole clean air technique, especially among the users. Therefore critical test and evaluation methods should be immediately set up for comprehensive testing of technical clean air systems, methods which include the time-dependence of particle or germ elimination as well as test-dependent disturbing factors.

Air Microbiology↗
PubMed1979

Do schizophrenics use linguistic rules in speech recall?

Varying degrees of organization of verbal material were presented to determine their use in sentence reproduction by acute and chronic schizophrenic subjects, a psychiatric (alcoholic) control group, and a healthy control group. The material consisted of six-word sentences presented over earphones, with background noise of differing intensity. The main result was that schizophrenics use verbal organization as effectively as healthy and psychiatric controls when reproducing the sentences. The noise distraction influenced performance of all groups similarly. Results suggest that performance of schizophrenics is facilitated by structured material (semantic and syntactic organization). The results do not suggest that either the linguistic repertoire or the application of linguistic rules is specifically affected in schizophrenia. The flatter performance slope of schizophrenics with increasing contexual constraints, found by some researchers, is explained by the unspecific effect of task difficulty.

Acute Disease↗