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Biomedical subjects

P Voss

Publications and source records attributed to P Voss.

At least 19 recordsLinked to original sources
PubMed2006

The nuclear proteasome and the degradation of oxidatively damaged proteins.

The accumulation of oxidized proteins is known to be linked to some severe neurodegenerative diseases like Alzheimer's, Parkinson's and Huntington's disease. Furthermore, the aging process is also accompanied by an ongoing aggregation of misfolded and damaged proteins. Therefore, mammalian cells have developed potent degradation systems, which selectively degrade damaged and misfolded proteins. The proteasomal system is largely responsible for the removal of oxidatively damaged proteins form the cellular environment. Not only cytosolic proteins are prone to oxidative stress, also nuclear proteins are readily oxidized. The nuclear proteasomal system is responsible for the degradation of these proteins. This review is focused on the specific degradation of oxidized nuclear proteins, the role of the proteasome in this process and the regulation of the nuclear proteasomal system under oxidative conditions.

Animals↗
PubMed1995

Delayed matching-to-sample performance: Effects of relative reinforcer frequency and of signaled versus unsignaled reinforcer magnitudes.

Six pigeons were trained on a delayed red-green matching-to-sample task that arranged four delays within sessions. Matching responses intermittently produced either 1.5-s access to food or 4.5-s access to food, and nonmatching responses produced either 1.5-s or 4.5-s blackout. Two phases were conducted: a signaled phase in which the reinforcer magnitudes (small and large) were signaled by houselights (positioned either on the left or right of the chamber), and an unsignaled phase in which there was no correlation between reinforcer magnitude and houselight position. In both phases, the relative frequency with which red and green matching responses produced food was varied across five values. Both matching accuracy and the sensitivity of performance to the distribution of reinforcers for matching responses decreased with increasing delays in both phases. In addition, accuracy and reinforcer sensitivity were significantly lower on signaled small-reinforcer trials compared with accuracy and sensitivity values on signaled large-reinforcer trials and on both types of unsignaled trials. These results are discussed in the context of research on both nonhuman animal and human memory.

Journal Article↗
PubMed1994

[Noninvasive serum test for prenatal detection of Down syndrome, other chromosome abnormalities and open neural tube defects--a prospective study].

Between September 1st 1990 and Juli 31st 1993, 5071 pregnant women were screened prospectively by the "triple-test", including maternal serum alpha-fetoprotein, human chorionic gonadotropin and unconjugated oestriol in order to detect chromosomal anomalies and open neural tube defects. The serum samples were collected in collaboration with the obstetricians of the region of West-Mecklenburg and North-West-Brandenburg. Laboratory testing using radioimmunoassays was performed between weeks 15 and 20 of gestation, all serum specimens being investigated in only one institution. The original alpha-software from Wald et al. was the basis for calculating the statistical risk for Down's syndrome. Pregnant women with a high risk for Down's syndrome (cutoff > or = 1:250) were taken care of in a special outpatient clinic including procedures like amniocentesis and fetal blood sampling. Amongst 5071 pregnant women, 21 fetal anomalies were seen. Five cases of Down's syndrome, three of trisomy 18, one trisomy 13, two cases of triploidy and four cases of open neural tube defects, one 46 xy/45 x mosaic karyotype and one case of gastroschisis could be diagnosed correctly. One case of trisomy 21, one case of trisomy 18 and two open neural tube defects showed false negative results. Using the cutoff of 1:250 for prenatal detection of Down's syndrome and performing ultrasound routinely to determine gestational age, the sensitivity of the "triple-test" was 83.33% having a specificity of 92.68%. The predictive value of a positive test for prenatal diagnosis of Down's syndrome was 1.33%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Leaving patches: Effects of travel requirements.

Five pigeons were trained in an analogue foraging procedure in which, by completing a travel requirement, they entered a "patch" in which a reinforcer might be available after an unpredictable time. They also had the opportunity, by emitting a defined response, to exit the patch and travel to another patch. Prey availability in a patch was not signaled. Data were collected on the length of time that subjects stayed in patches before exiting (residence times) as a function of various travel requirements: travel for a fixed time in blackout, fixed-interval schedule traveling, fixed-time traveling with an added response required to terminate traveling, and fixed-ratio traveling. For each of these conditions, the required amount of travel (time or responses) was varied over a wide range. As previously reported, residence times increased with increases in fixed-time traveling, as they did with increasing fixed-interval or fixed-ratio traveling. There was no evidence that adding response or work requirements systematically affected residence time except via increased travel time, although 3 of the 5 birds stayed longer in a patch under higher fixed-ratio values. A "threshold-maximization" model described the data well with a single parameter that was consistent across subjects, procedures, and experiments.

Journal Article↗
PubMed1993

Stimulus control and response bias in an analogue prey-detection procedure.

The present study compared the performance of 6 pigeons trained to detect luminance differences in two different signal-detection procedures. Exposed to a three-key array, the pigeons were trained to peck the left key when the brighter of two light intensities had been presented on the center key and to peck the right key when the dimmer of two light intensities had been presented on the center key. Procedure A was a standard signal-detection procedure in which left/bright and right/dim responses produced food reinforcement and left/dim and right/bright responses produced periods of timeout. Procedure B was designed to simulate some of the contingencies operating in a prey-detection situation. Left-key responses produced reinforcement following the brighter center-key stimulus and a period of timeout following the dimmer center-key stimulus. Right-key responses always produced a short period of timeout irrespective of the stimulus. Within each procedure, the duration of timeout arranged for false alarms (left/dim responses) was varied between 3 s and 120 s. Measures of accuracy and response bias were compared between the two procedures. The timeout manipulation produced systematic, but relatively small, changes in these measures when right/dim responses (i.e., correct rejections) produced reinforcement (Procedure A). Arranging timeout for right/dim responses in Procedure B produced greater variability in accuracy and response bias than did arranging reinforcement, but this variability was not related to timeout duration. Overall, discrimination accuracy was considerably higher when right/dim responses produced timeout than when they resulted in reinforcement, and accuracy was accompanied by a large bias toward the response associated with reinforcement. These results are consistent with a recently proposed model of signal detection.

Journal Article↗
PubMed1989

[Reference values for progesterone, beta-HCG, estriol and human placental lactogen in the 10th-16th weeks of pregnancy].

Progesterone, beta-hCG, estriol and hPL in sera from 745 pregnant women have been measured in weeks 10 to 16 of pregnancy. The determined reference intervalls included the 10th and 90th percentile. All confidence intervalls have been calculated for a probability level of 10 per cent. The following levels were determined during the concerning weeks of pregnancy: progesterone 32-165 nmol/l, beta-hCG 31.5-260 micrograms/l, estriol 0.04-4.94 nmol l, and hPL 0.03-2.65 mg/l. The levels of progesterone are increasing weakly with the rising weeks of pregnancy, but the levels of beta-hCG are going down continuously. The levels estriol and hPL are showing a marked growth.

Chorionic Gonadotropin↗
PubMed1989

[Detection of carcinoembryonic antigen (CEA) in cervico-vaginal irrigation fluids].

CEA estimations are effected in serum samples and in cervico vaginal fluids (n = 144) of patients with cervical condylomas, cytological undecided and cytological positive findings and in follow up performed histology. 21 healthy women were used as a control group. For taking cervico-vaginal fluids 5 ml isotonic NaCl solution were instilled in the fornix vaginae. After that 5 ml of the solution mixed with cervico vaginal fluids were aspirated. A polyclonal anti-CEA-antiserum was applied to radioimmunoassay. Remarkable high concentrations were found in cervico vaginal fluids compared with serum values. (Table: see text). In cases of cervical condylomas and cervical intraepithelial neoplasia significant increased CEA levels were determined in fluids compared with the control group. These results must be seen in consideration that the local CEA concentrations are scattered over a brand range. Regarding to CEA serum concentrations only slight increased values were found in cases of CIN I/II. (table; see text) Therefore CEA-serum estimations are not a diagnostic tool in CIN. The normal range of 10 micrograms/l was exceeded in only one sample of CIN II.

Adenocarcinoma↗
PubMed1989

[CEA studies in endometrial cancer].

In the years 1983 to 1986 concentrations of CEA in serum samples of 63 female patients with endometrial cancer have been estimated with help of a radioimmunoassay. In all histopathological stages 25 per cent elevated CEA-concentrations could be found pretherapeutically. It is given the semilogarithmic representation of the CEA-values of the individual basic lines in the posttherapeutical follow up. Main field for estimations of CEA-concentrations in serum is only the performance of a posttherapeutical monitoring of the operated and irradiated endometrial cancer.

Adenocarcinoma↗
PubMed1989

[Determining binding proteins of progesterones in patients with breast diseases].

We estimated serum levels of progesterone and the most important binding proteins in follicular and luteal phase at women without breast disease with biphasic or anovulatory cycle and female patients with benign or malignant breast diseases. There was an increase of the median value of acidic alpha-1-glycoprotein in the luteal phase at female patients with premenopausal breast cancer. The importance of serum levels of the bioavailable sexual steroids for the recognition of women with breast diseases is discussed.

Biological Availability↗
PubMed1988

[CEA determination in aspired fluid of cystic ovarian tumors and ovarian cysts and in ascites and serum samples of patients with ovarian tumors].

Carcinoembryonic antigen (CEA) was assayed by radioimmunoassay in serum of 47 patients with cystic ovarian tumors, in 51 cases of cyst fluids of ovarian tumors and ovarian cysts, and in 16 cases of peritoneal effusions (ascites). In order to differentiate between cystic tumors and retentional cysts there was found, in consideration of a changed prevalence (0.65), a sensitivity of 55% and a specificity of 94%. The predictive value in regard to a positive assay result was 94% and in regard to a negative one was 53%. Elevated CEA-levels in ovarian tumor cyst fluids are mainly diagnostic for mucinous ovarian tumors. In regard to elevated CEA-levels in cyst fluids of ovarian tumors it is claimed the laparotomy and histological investigation.

Ascitic Fluid↗
PubMed1988

[Protein studies in cystic and peritoneal fluids of ovarian tumors with special reference to CEA].

The levels of total protein, Ig, AFP, beta-HCG, CEA, SC, SP1 and alpha 2-PAG were measured in cystic and peritoneal effusions obtained from 70 females with benign and malignant ovarian tumors. This study was carried out to test out parameters those are useful for tumor monitoring of ovarian cancer. Our results indicate that determining CEA in peritoneal effusions could be one of useful methods in tumor monitoring of mucinous cystadenocarcinomas in cases of known histology and praetherapeutic estimated CEA levels in cystic or peritoneal effusions. Our results demonstrate that CEA-levels greater than 100 micrograms/l are mostly found in mucinous cystadenocarcinomas and in mucinous cystadenomas, too. High cystic CEA levels support the histology aiming for demonstration of mucinous component.

Adolescent↗