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Biomedical subjects

M Schmidt

Publications and source records attributed to M Schmidt.

At least 433 records · Page 24Linked to original sources
PubMed1997

Graafian follicles are cooler than neighbouring ovarian tissues and deep rectal temperatures.

In order to establish appropriate culture temperatures for in-vitro maturation of pig ovarian oocytes, large Graafian follicles (7-10 mm diameter) were sensed by infra-red technology during the latter part of a spontaneous oestrous cycle. Temperatures were measured under systemic anaesthesia almost instantaneously upon revealing the ovaries at mid-ventral laparotomy. Temperature differentials were observed within all 16 ovaries sensed in 14 animals. Ovaries were always cooler than deep rectal temperatures (mean rectal temperature was 38.0 +/- 0.4 degrees C; range 37.5-38.6 degrees C) and mature follicles always cooler than ovarian stroma (35.6 +/- 0.3 degrees C versus 37.3 +/- 0.2 degrees C respectively; P < 0.01). Such follicles were frequently 1.5-1.8 degrees C cooler than the adjacent stroma, the mean being 1.7 +/- 0.4 degrees C. Small Graafian follicles (< 5-6 mm diameter) and recent ovulations did not show this differential. The control experiment of excising an ovary, deep freezing it in liquid nitrogen, and then restoring it to the body cavity before further sensing indicated that intra-ovarian temperature gradients depended on the activity of living tissues and/or a functional blood supply. Furthermore, calculation of anticipated rates of cooling for exposed Graafian follicles strongly suggested that artefacts could not have been solely responsible for the observed temperatures. Endothermic reactions within mature follicles were thus brought into focus. It is concluded that follicular temperatures may influence the meiotic progression and cytoplasmic maturation of oocytes and act to regulate enzymatic activity in the biosynthetic pathways for steroid and/or peptide hormones.

Animals↗
PubMed1997

Effect of Lys175 mutation on structure function properties of Propionibacterium shermanii superoxide dismutase.

The role of electrostatic factors in the enzyme-substrate encounter process of manganese and iron containing superoxide dismutases has been studied in the enzyme from Propionibacterium shermanii by chemical neutralization of lysine residues and site-directed mutagenesis of the highly conserved residue Lys175. Lysine residues have been neutralized by carbamoylation and Lys175 has been selectively replaced by isoleucine and arginine. Catalytic measurements show a dramatic decrease of the activity in the chemically modified enzyme. Electrostatic potential calculations evidence in the modified enzyme a large contraction of the positive potential areas which surround the active sites in the native enzyme, indicating that electrostatic factors are critical in the enzyme-substrate encounter process of Mn- and Fe-superoxide dismutases. The activity drastically decreases also in Lys175-->Ile but not in the Lys175-->Arg mutant. Brownian dynamics simulations indicate that the decrease of activity in the Lys175-->Ile mutant cannot be due only to a decrease of the enzyme-substrate association rate, suggesting that Lys175 plays a relevant role also in the structural stabilization of the active site.

Binding Sites↗
PubMed1997

Biogenesis of eukaryotic 20S proteasomes: the complex maturation pathway of a complex enzyme.

Eukaryotic 20S proteasomes harbor a remarkably complex architecture and unique proteolytic properties. Its catalytic mechanism places this enzyme in a new kind of protease family. The recently solved crystal structure of the yeast 20S complex, along with elucidation of the maturation pathway of human proteasomes, has allowed insight into structure/function relationships. Although not all of the unusual enzymatic properties such as broad substrate specificity, predominant generation of peptides with a specific size, or susceptibility to activating complexes can be explained in detail, knowledge of the structure provides important hints for an explanation of underlying mechanisms. Except for ribosome biogenesis, the complexity of eukaryotic proteasome maturation is without precedence. It is a slow process that involves a series of precisely ordered events. Proteasome structure formation is characterized by an initial cooperative formation of an alpha ring matrix, providing docking sites for a defined subset of beta subunits. Subsequent structural rearrangement allows the residual subunits to bind, followed by dimerization of two half-proteasomes. The prosequences of beta subunits exert specific functions during this process and are removed by cis- and trans-autocatalysis, most likely in the completely assembled proteasome cylinder.

Animals↗
PubMed1997

Mouse model to study the replication of primate foamy viruses.

A mouse model was developed to study the virus-host interaction of molecularly cloned human foamy virus (HFV) in vivo. The infectious process was analysed in two mouse strains, CBA/Ca and C57BL/6J, over a period of 24 weeks by PCR on DNAs from various animal tissues; virus serology was examined by immunoblotting. The infection persisted in both mouse strains and did not induce clinical symptoms. Upon infection of adult CBA/Ca mice HFV became detectable by PCR in an increasing number of organs over time. In contrast, in C57BL/6J mice, after an initial phase of dissemination, viral DNA sequences were found only in a few organs. Interestingly, the different course of infection was accompanied by differences in the antiviral immune response. In particular, C57BL/6J mice were high responders with respect to antibodies to the viral Bet protein, while CBA/Ca mice were low responders.

Animals↗
PubMed1997

Pain threshold for low energy intracardiac cardioversion of atrial fibrillation with low or no sedation.

UNLABELLED: Recent studies have shown that internal cardioversion of atrial fibrillation is safe and effective. In this randomized prospective study, we have tried to evaluate the influence of different waveforms on the perception of pain during internal cardioversion in patients with chronic atrial fibrillation. METHODS: Internal cardioversion was performed with minimal or no sedation in 31 consecutive patients. R wave triggered, biphasic shocks of 6 ms/6 ms or 3 ms/3 ms duration (randomly selected) and approximately 65% tilt were used starting with a 50-V test shock. The shock intensity was increased in 40-V steps up to a maximum voltage of 520 V Shocks were applied via two custom-made catheters (Elecath, Rahway, NJ). In 16 patients (3 females, age 61 +/- 11 years, left atrium diameter 58 +/- 5 mm, duration of atrial fibrillation 4 +/- 4 months), 6/6 waveforms were used, and in 15 patients (1 female, age 62 +/- 5 years, left atrium diameter 59 +/- 4 mm, duration of atrial fibrillation 5 +/- 2 months), 3/3 waveforms were used. After cardioversion, each patient was asked to quantify their pain on a scale from 0-10 (0 = no pain, 10 = intolerable). Fourteen of the 15 patients in the 3/3 ms and 15 of the 16 patients in the 6/6 ms group were successfully cardioverted. Patients from the 6/6 waveform group were cardioverted with a lower mean voltage of 254/92 versus 355/127 V (P < 0.02), at lower pain score 1.8 +/- 1.3 versus 4.2 +/- 2.2 (P < 0.05) with equivalent energy (6.8 +/- 2.8 versus 6.2 +/- 1.5 J, n.s.) and required lower doses of midazolam of 2.2 +/- 1.9 versus 4.0 +/- 1.8 mg IV (P < 0.02). The waveform used in internal cardioversion seems to have a major impact on the patients' perception of pain. These results imply that energy determines the success of a shock, but voltage determines the pain perceived by the patient. The use of waveforms that deliver greater energy at lower peak voltages offers the possibility of internal cardioversion with less sedation and greater patient tolerance.

Atrial Fibrillation↗
PubMed1997

Intravascular MR imaging of atherosclerotic plaque: ex vivo analysis of human femoral arteries with histologic correlation.

PURPOSE: To assess the potential role of intravascular magnetic resonance (MR) imaging with receiver coils mounted to an inflatable balloon in characterizing atherosclerotic plaque. MATERIALS AND METHODS: Twelve human harvested segmental femoral arteries with atherosclerotic changes were studied with a 5-F imaging balloon catheter equipped with a single-loop wire receiver coil. Imaging was performed with an open-configuration 0.5-T (n = 6) or a 1.5-T (n = 6) MR system, with T1- and T2-weighted sequences. Histologic analysis was the reference standard, and MR images were analyzed with regard to vessel wall thickness, plaque area, and components. RESULTS: Images acquired at 1.5 T were characterized by better in-plane resolution (117 x 104 microm). Resolution at 0.5 T (234 x 178 microm) was sufficient to discriminate the wall layers. On T2-weighted images, adventitia, media, and thickened intima could be discriminated. T1-weighted images did not permit differentiation between wall layers. There was good correlation between MR and histologic measurements of wall thickness (r = .97) and plaque area (r = .98). Plaque characterization was possible on T2-weighted images. Calcified plaque was identified as areas of low signal intensity (134 +/- 98) and could be differentiated from fibrous structures containing collagen (1,968 +/- 680) or fatty components (762 +/- 394). CONCLUSION: Intravascular MR imaging on the basis of the balloon catheter design enables differentiation of wall layers and plaque components.

Aged↗
PubMed1997

High levels of Gs alpha in platelets of euthymic patients with bipolar affective disorder.

OBJECTIVE: Previous investigations have suggested the involvement of signal-transducing guanine-nucleotide-binding proteins (G proteins) both in the mechanism of action of lithium and in the pathophysiology of bipolar affective disorder. To determine whether such G protein abnormalities are a trait phenomenon, the authors investigated the levels of G protein alpha subunits in platelets and lymphocytes of euthymic patients with bipolar affective disorder. METHOD: Selective antibodies were used to quantitate levels of G protein alpha subunits regulating adenylylcyclase activity (Gs alpha-both 45- and 52-kDa forms- and Gil-2 alpha) and those regulating phosphoinositide turnover (Gq/11 alpha) in both platelets and lymphocytes of 44 euthymic patients with bipolar affective disorder and 27 matched comparison subjects. RESULTS: Levels of both Gs alpha 45 and Gs alpha 52 were higher in the platelets of the euthymic bipolar patients (both bipolar I and bipolar II) than in those of the comparison subjects. CONCLUSIONS: These findings are consistent with previous reports of high Gs alpha levels in bipolar affective disorder and, furthermore, suggest that such levels may be a trait abnormality for this condition.

Adult↗
PubMed1997

Genetic engineering of baker's and wine yeasts using formaldehyde hyperresistance-mediating plasmids.

Yeast multi-copy vectors carrying the formaldehyde-resistance marker gene SFA have proved to be a valuable tool for research on industrially used strains of Saccharomyces cerevisiae. The genetics of these strains is often poorly understood, and for various reasons it is not possible to simply subject these strains to protocols of genetic engineering that have been established for laboratory strains of S. cerevisiae. We tested our vectors and protocols using 10 randomly picked baker's and wine yeasts all of which could be transformed by a simple protocol with vectors conferring hyperresistance to formaldehyde. The application of formaldehyde as a selecting agent also offers the advantage of its biodegradation to CO2 during fermentation, i.e., the selecting agent will be consumed and therefore its removal during down-stream processing is not necessary. Thus, this vector provides an expression system which is simple to apply and inexpensive to use.

Drug Resistance, Microbial↗
PubMed1997

Allergenic crossreactivity between Lepidoglyphus destructor and Blomia tropicalis.

BACKGROUND: In general, the non-pyroglyphid mites Lepidoglyphus destructor and Blomia tropicalis show a different geographical distribution. Allergic sensitization to both species have been demonstrated in several investigations. However, whether this reflects cross-reactivity or dual sensitization is so far not known. OBJECTIVE: The aim of the study was to investigate the allergenicity and allergenic crossreactivity of L. destructor and B. tropicalis using sera from Sweden and Brazil. METHODS: Allergens in extracts of L. destructor and B. tropicalis were identified with SDS-PAGE and immunoblotting and the crossreactivity was studied by an immunoblot inhibition method. In addition to mite extracts, a recombinant major allergen of L. destructor, Lep d 2, was used. RESULTS: The extract prepared from L. destructor contained 21 IgE-binding components when using the Swedish or the Brazilian sera. A 15 kDa allergen was recognized by 85% of the Swedish sera and 78% of the Brazilian. The B. tropicalis extract exposed 23 IgE-binding components when the Brazilian sera were used and 19 when the Swedish sera were used. A total of 83% of the Brazilian sera and 80% of the Swedish sera identified a 14.5 kDa allergen. The IgE response of the Swedish serum pool to 10 B. tropicalis allergens was inhibited by L. destructor extract. Likewise, the response of the Brazilian serum pool to four different L. destructor allergens was inhibited by B. tropicalis extract. The recombinant Lep d 2 allergen inhibited 33% of the IgE binding of the Swedish serum pool to the 14.5 kDa allergen in the B. tropicalis extract. CONCLUSION: Crossreactivity with several proteins from L. destructor and B. tropicalis was demonstrated. The results suggest that a B. tropicalis 14.5 kDa allergen is antigenically crossreactive with recombinant L. destructor allergen Lep d 2.

Allergens↗
PubMed1997

[Pleurodesis in malignant pleural effusion: bleomycin vs. mitoxantrone].

In a controlled clinical trial we investigated 102 patients with malignant pleural effusion due to breast cancer, lung cancer, ovarian cancer and other tumors to compare the therapeutic effect and adverse events of pleurodesis with bleomycin (BMC) or mitoxantrone (MIT) via chest tube. Finally 96 patients had been treated according to the protocol. Age, gender, Broca index, performance score or distribution of primary tumors were not statistically different between the BMC (n = 49) or MIT group (n = 47). We found no differences between intention-to-treat and according-to-protocol groups as well. 30 days after BMC pleurodesis we found remissions of the effusion in 91% of patients (complete remission [CR] 51%, partial remission [PR] 40%), after 90 days in 83% (40% CR, 43% PR). 30 days after MIT instillation we found remission in 73% of patients (35% CR, 38% PR), after 90 days in 61% (29% CR, 32% PR) (30 and 90 days: p < 0.05). Adverse events were not different between BMC and MIT group. BMC is a safe and effective sclerosing agent for pleurodesis via chest tube.

Aged↗
PubMed1997

The HSM sentence test as a tool for evaluating the speech understanding in noise of cochlear implant users.

The German HSM Sentence Test, available on compact disc (CD), consists of 30 lists of 20 everyday sentences. It was developed in the desire to have a sufficient number of test sentences for the repeated evaluation of speech understanding of CI users. A noise with speech-shaped spectrum on the CD allows the evaluation of speech understanding in noise. With the HSM Sentence Test we evaluated the speech understanding of participants of the Combi-40 European Multicentric Study. Results are shown for sentences presented without noise and with signal-to-noise ratios of 15, 10, 5 and 0 dB.

Adult↗
PubMed1997

Long-term stability of fitting parameters with the COMBI 40.

Having experience with the COMBI 40 for over two years, it is now possible to look at the development of patient fittings over a longer period of time. In this study we look at patient fitting data (thresholds, dynamic ranges, etc.) at two days, one month, three months, six months and twelve months post first fitting. Subjects are CI-users participating in the COMBI 40 European Multicentric Study. Long-term fitting parameters show a favourable development. Stable fitting parameters and the safety features implemented in the COMBI 40 serve as a basis for a reliable long-term speech understanding.

Auditory Threshold↗
PubMed1997

[Complications after 106 laparoscopic hysterectomies].

At our hospital in Hamburg 106 patients underwent laparoscopic hysterectomies. 92 patients had no complications, but 6 had major and 10 minor ones. As major complications occurred: one vesico-vaginal fistula, one uretero-vaginal fistula, one ureter injury, one lesion of the small intestine and two bladder injuries. As minor complications could be found: six urinary tract infections, one anemia (Hb 7,1 g/dl) and one febrile morbidity. The overall complication rate is 13.2%.

Adult↗