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Biomedical subjects

M Krohn

Publications and source records attributed to M Krohn.

At least 19 recordsLinked to original sources
PubMed2004

Cross-talk of phosphoinositide- and cyclic nucleotide-dependent signaling pathways in differentiating avian nasal gland cells.

In many bird species, the nasal glands secrete excess salt ingested with drinking water or food. In ducks ( Anas platyrhynchos), osmotic stress results in adaptive cell proliferation and differentiation in the gland. Using 'naive' nasal gland cells isolated from animals that had never ingested excess salt or 'differentiated' cells from animals fed with a 1% NaCl solution for 48 h, we investigated the allocation of metabolic energy to salt excretory processes and to other cellular activities. Activation of muscarinic acetylcholine receptors (carbachol) or beta-adrenergic receptors (isoproterenol) in nasal gland cells resulted in a transient peak in metabolic rate followed by an elevated plateau level that was maintained throughout the activation period. Activation of cells using vasoactive intestinal peptide, however, had only marginal effects on metabolic rate. In differentiated cells, sequential stimulation with carbachol and isoproterenol resulted in additive changes in metabolic rate during the plateau phase. Naive cells, however, developed supra-additive plateau levels in metabolic rates indicating cross-talk of both signaling pathways. Using bumetanide, TEA or barium ions to block different components of the ion transport machinery necessary for salt secretion, the relative proportion of energy needed for processes related to ion transport or other cellular processes was determined. While differentiated cells in the activated state allocated virtually all metabolic energy to processes related to salt secretion, naive cells reserved a significant amount of energy for other processes, possibly sustaining cellular signaling and regulating biosynthetic mechanisms related to adaptive growth and differentiation.

Adaptation, Physiological↗
PubMed2000

The amniotic fluid index in normal twin pregnancies.

OBJECTIVE: We sought to investigate the amniotic fluid index for individual gestational sacs of twin pregnancies. STUDY DESIGN: Four hundred eighty-eight patients with normal diamniotic twins were examined between 14 and 40 weeks' gestation. The dividing membrane between twin fetuses was identified. An amniotic fluid index was then obtained for each gestational sac. RESULTS: The median amniotic fluid index in individual twin gestational sacs rises slowly from 14 to 16 weeks' gestation to 23 to 28 weeks' gestation and then gradually declines. The median amniotic fluid index values by gestational age for twin A and twin B are not statistically different. Although twin pregnancies have a slightly lower median amniotic fluid index value than singleton pregnancies, the difference is also not statistically significant. CONCLUSION: Individual amniotic fluid indices can be obtained in twin pregnancies, and the values are comparable with those of singleton gestations.

Amniotic Fluid↗
PubMed2000

Predicting cesarean delivery with decision tree models.

OBJECTIVE: The purpose of this study was to determine whether decision tree-based methods can be used to predict cesarean delivery. STUDY DESIGN: This was a historical cohort study of women delivered of live-born singleton neonates in 1995 through 1997 (22,157). The frequency of cesarean delivery was 17%; 78 variables were used for analysis. Decision tree rule-based methods and logistic regression models were each applied to the same 50% of the sample to develop the predictive training models and these models were tested on the remaining 50%. RESULTS: Decision tree receiver operating characteristic curve areas were as follows: nulliparous, 0.82; parous, 0.93. Logistic receiver operating characteristic curve areas were as follows: nulliparous, 0.86; parous, 0.93. Decision tree methods and logistic regression methods used similar predictive variables; however, logistic methods required more variables and yielded less intelligible models. Among the 6 decision tree building methods tested, the strict minimum message length criterion yielded decision trees that were small yet accurate. Risk factor variables were identified in 676 nulliparous cesarean deliveries (69%) and 419 parous cesarean deliveries (47.6%). CONCLUSION: Decision tree models can be used to predict cesarean delivery. Models built with strict minimum message length decision trees have the following attributes: Their performance is comparable to that of logistic regression; they are small enough to be intelligible to physicians; they reveal causal dependencies among variables not detected by logistic regression; they can handle missing values more easily than can logistic methods; they predict cesarean deliveries that lack a categorized risk factor variable.

Adolescent↗
PubMed1997

A specific domain in alpha-catenin mediates binding to beta-catenin or plakoglobin.

The E-cadherin-catenin adhesion complex has been the subject of many structural and functional studies because of its importance in development, normal tissue function and carcinogenesis. It is well established that the cytoplasmic domain of E-cadherin binds either beta-catenin or plakoglobin, which both can assemble alpha-catenin into the complex. Recently we have identified an alpha-catenin binding site in beta-catenin and plakoglobin and postulated, based on sequence analysis, that these protein-protein interactions are mediated by a hydrophobic interaction mechanism. Here we have now identified the reciprocal complementary binding site in alpha-catenin which mediates its interaction with beta-catenin and plakoglobin. Using in vitro association assays with C-terminal truncations of alpha-catenin expressed as recombinant fusion proteins, we found that the N-terminal 146 amino acids are required for this interaction. We then identified a peptide of 27 amino acids within this sequence (amino acid positions 117-143) which is necessary and sufficient to bind beta-catenin or plakoglobin. As shown by mutational analysis, hydrophobic amino acids within this binding site are important for the interaction. The results described here, together with our previous work, give strong support for the idea that these proteins associate by hydrophobic interactions of two alpha-helices.

Animals↗
PubMed1996

Transcriptional pausing of RNA polymerase in the presence of guanosine tetraphosphate depends on the promoter and gene sequence.

We have studied the response of the effector molecule guanosine 3',5'-bisdiphosphate (ppGpp) on RNA polymerase pausing during in vitro transcription elongation. Pausing was followed during single round extension of stalled ternary complexes excluding possible ppGpp effects on initiation. The ppGpp dependences of early pausing sites within different transcription systems controlled by promoters with known response to enhanced ppGpp levels in vivo were quantitatively characterized. Transcription of stable RNAs and mRNA genes were analyzed. In addition, the in vitro pausing behavior of two promoter variants directing the same sequence but differing in their in vivo ppGpp sensitivity were compared. In the presence of ppGpp we noted a slight general enhancement of specific pauses in all transcription systems. However, genes known to be under stringent or growth rate control in vivo revealed a notably stronger pausing enhancement. The sites of pausing are not changed by the presence of ppGpp but appear to be sequence-specific. The effect of ppGpp on the extent of pausing depends on the particular promoter and closely adjacent sequences that the RNA polymerase has passed during initiation. Pausing enhancement requires the presence of ppGpp during elongation but not during initiation. The results underline the importance of pausing for transcription regulation and offer a plausible explanation for inhibition of stable RNA expression under conditions of elevated concentrations of ppGpp.

Base Sequence↗
PubMed1996

Does an abortion increase the risk of intrapartum infection in the following pregnancy?

Spontaneous and induced abortions have been suggested to increase the risk of intrapartum infection in the following pregnancy. We conducted a case-control study using data from the Washington State Birth Registry for the years 1989-1991. The study population comprised women delivering a singleton livebirth. A case was defined by the presence of intrapartum fever (N = 2,550). Controls (1:3) were selected from the remaining births (N = 7,326). We calculated Mantel-Haenszel summary odds ratios by stratified analysis. We evaluated the validity of intrapartum fever recorded on the birth certificate using data from an ongoing case-control study on clinical amnionitis in Washington State. We found intrapartum fever to be highly specific (0.98) and moderately sensitive (0.57) for a diagnosis of clinical amnionitis. We saw no increased risk of intrapartum fever after a fetal loss or termination when using women with no prior pregnancy as the reference group. On the other hand, we found a threefold elevated risk for both induced and spontaneous abortion when using women with a prior livebirth as the reference group. Our findings indicate that an abortion in a woman's first pregnancy does not have the same protective effect of lowering the risk for intrapartum infection in the following pregnancy as does a livebirth.

Abortion, Induced↗
PubMed1992

[Subjective stress of adjuvant chemotherapy in breast cancer patients].

50 patients, suffering from carcinoma of the breast pT1-3 with concomitant metastatic affection of the lymph nodes with no evidence of distant metastases, and who received adjuvant chemotherapy (either CMF od AC/EC) were examined. Somatic and psychic interferences, the feeling of well-being and general condition, as well as a critical estimation of the clinical situation were assessed. Besides nausea and vomiting, and still prior to hair fall out, chemotherapy activated the memory of the carcinoma. 92% of the patients agreeing to chemotherapy described their decision as having been based exclusively on the medical information. Nevertheless, 30% feel insufficiently informed, so the fear of side effects, the waiting period prior to application, and the confrontation with the seriously ill, were described as a negative experience. An optimistic view with respect to improving the prognosis of the disease were correlated with chemotherapy: 74% would agree to a further chemotherapy. Psychic abnormalities, e.g. depressions, could not be shown following chemotherapy when compared to a reference population.

Adaptation, Psychological↗
PubMed1992

Effects of template topology on RNA polymerase pausing during in vitro transcription of the Escherichia coli rrnB leader region.

Transcription elongation catalysed by DNA-dependent RNA polymerase does not occur at a constant rate. Instead, during the transcription of many genes pausing occurs at defined template positions. Pausing is known to be influenced by the intracellular NTP concentration, the secondary structure of the growing transcript or by transcription factors like NusA. We have investigated the effects of the template topology of transcriptional pauses in the presence and absence on purified NusA protein. Taking advantage of a method for quantifying transcriptional pauses we have studied pausing behaviour during in vitro transcription of the early region of a plasmid-encoded ribosomal RNA operon. Plasmid templates with different superhelical densities (sigma between +0.0017 and -0.055) were employed in transcription elongation assays. If linearized or relaxed templates are used, some of the characteristic pauses can no longer be detected. For the stronger pauses we could demonstrate a direct correlation between pause strength and the negative superhelical densities of the templates used. This correlation is observed regardless of whether or not pauses are dependent upon NusA. Changes in the average transcription elongation rate, caused by variations in the NTP concentration or the temperature, do not appear to have a comparable effect on transcription pausing. The results are consistent with the assumption that the template topology has a regulatory function in transcription elongation of rRNA genes in Escherichia coli.

Bacterial Proteins↗
PubMed1989

[Secretory breast cancer. A special morphologic entity, especially in children and young females].

We are reporting a rare case of secretory breast cancer with axillary node involvement in a 16-year-old patient. Symptomatic systemic spread occured unusually early during adjuvant chemotherapy, suggesting primary resistance of the tumour to chemotherapy. We are unaware of any such case reports published world wide. Due to the small number of similar case reports in the literature, the natural history of this type of cancer remains uncertain, offering no development of firm treatment guidelines.

Adolescent↗
PubMed1988

A case-control study of chorioamnionic infection and histologic chorioamnionitis in prematurity.

To study the role of infection in prematurity, we studied the demographic and obstetrical characteristics, chorioamnionic cultures, and placental histologic features of women who delivered prematurely and compared these findings with those in women who delivered at term. Microorganisms were isolated from the area between the chorion and the amnion (chorioamnion) in 23 of 38 placentas (61 percent) from women with preterm labor who delivered before 37 weeks' gestation and in 12 (21 percent) of 56 placentas from women without preterm labor who delivered at term (odds ratio, 5.6; 95 percent confidence interval, 2.1 to 15.6). The most frequent isolates from the placentas of those whose infants were delivered prematurely were Ureaplasma urealyticum (47 percent) and Gardnerella vaginalis (26 percent). The recovery of any organism from the chorioamnion was strongly associated with histologic chorioamnionitis (odds ratio, 7.2; 95 percent confidence interval, 2.7 to 19.5) and with bacterial vaginosis (odds ratio, 3.2; 95 percent confidence interval, 1.1 to 6.6). When multiple logistic regression was used to control for demographic and obstetrical variables, premature delivery was still related to the recovery of organisms from the chorioamnion (odds ratio, 3.8; 95 percent confidence interval, 1.5 to 9.9) and with chorioamnionitis (odds ratio, 5.0; 95 percent confidence interval, 1.6 to 15.3). The proportion of placentas with evidence of infection was highest among those who delivered at the lowest gestational age. We conclude that infection of the chorioamnion is strongly related to histologic chorioamnionitis and may be a cause of premature birth.

Adult↗
PubMed1988

Development of wound infections among women undergoing cesarean section.

Sixty consecutive wound infections were studied among 1104 women undergoing cesarean section. Wound infections caused by cervical-vaginal flora were associated with prolonged labor, particularly with greater duration of fetal monitoring and number of vaginal examinations, and with organisms isolated from the endometrium at cesarean section. In contrast, women with wound infections caused by Staphylococcus aureus had neither prolonged labor nor S aureus isolated at cesarean section. The 25% of wound infections associated with S aureus represent potentially preventable conditions that presumably arise from exogenous sources.

Cesarean Section↗
PubMed1987

Long latency precedes overt seroconversion in sexually transmitted human-immunodeficiency-virus infection.

Signs of latent HIV infection were sought in stored serum samples collected before overt seroconversion, confirmed by enzyme-linked immunosorbent assay (ELISA), from 9 subjects with human-immunodeficiency-virus (HIV) infection, in serum from 25 seronegative sexual partners of HIV-seropositive men and from 23 other seronegative, homosexually active men. Free HIV antigen and/or low-titre antibodies to recombinant structural (core, env) or non-structural (3' orf, sor, tat) proteins were seen 6-14 months before seroconversion in all 9 subjects who seroconverted. Antibodies against core proteins detected by western blot were usually the first sign of latent HIV infection. 5 of the 25 ELISA-negative exposed partners have shown HIV antigenaemia and antibodies against core proteins for 16-34 months. By in-situ hybridisation, HIV-specific RNA was detected in peripheral-blood non-lymphoid mononuclear cells in some of the latently infected partners. All subjects with latent HIV infection had normal numbers of T4 lymphocytes but half of them lost their in-vitro proliferative T-cell response to a recall antigen (purified protein derivative of tuberculin). Early HIV infection, characterised by a low-level and restricted antibody response towards HIV core and regulatory proteins, seems mainly to affect antigen-presenting cells.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Correlates of placental abruption.

All cases (884) of placental abruption reported on Washington State birth or fetal death certificates in 1980 and 1981 were compared with 789 randomly selected births from the same time period. The incidence of reported cases of placental abruption was 6.5 per 1000 total births. The combined stillbirth and first month death rate of all abruption cases was 21%. Increased risks of placental abruption were associated with pre-eclampsia, diabetes, and unmarried status. Neither parity nor maternal age was associated with an increased risk. Infants born after abruption were significantly smaller-for-gestation than control infants, more likely to be male, and had malformations more frequently than control infants. Apgar scores of liveborn abruption infants were significantly lower than those of controls after adjustment for infant weight, gestational age, and sex.

Abruptio Placentae↗
PubMed1977

Tonography and projection perimetry. Relationship according to receiver operating characteristic curves.

Previous large scale tonographic studies revealed a significant overlap of coefficient of outflow (C) values for normal and glaucomatous eyes, but their differential diagnosis rested primarily on tangent screen visual field tests. To determine whether projection perimetry would make a difference in the correlation of outflow coefficients with glaucoma, 434 eyes from normal, ocular hypertensive (those without scotomas but with elevated intraocular pressure) and glaucomatous categories were evaluated. Results support the conclusions of earlier work concerning C value overlap and demonstrate the relatively better specificity of the initial intraocular pressure over one coefficient of outflow (Po/C) in distinguishing normal from glaucomatous eyes. It also shows that ocular hypertensives as a group are no different from glaucoma patients with regard to their aqueous outflow. Tonographic tests are, therefore, useful in identifying those eyes that need to be watched closely for the development of glaucomatous change.

Aqueous Humor↗
PubMedDate not supplied

[Statistical and dynamic analysis of crime in relation to primary dimensions in various countries].

The examination of the effects of social change on crime has experienced a revival of interest in the past decade. With the increasing availability of cross-national data such analyses are being done in a comparative perspective. The current effort is designed to examine the relationship between three variables which have been shown to be empirically and theoretically pertinent to the study of social change and crime indices. Specifically, the variables of population, gross national product per capita and political orientation are regressed on the homicide rates, property crime rates and total crime rates for a number of countries. This analysis is done statically for 1965 and dynamically, for the change in the variables from 1960 to 1965. The data for the independent variables were acquired from the World Handbook of Political and Social Indicators, Second Edition. The source of the dependent variables was the International Crime Statistics published by the International Criminal Police Organization (Interpol). The problems with such data are recongized and discussed. The results indicate that in the static analysis the three variables explain a substantial amount of the variance in property crime rates and total crime rates whereas they do not explain much of the variance in the homicide rate. Gross national product per capita contributes the most to the explained variance in all the analyses. A theoretical perspective combining the ideas incorporated in control theory and in environmental opportunity theory was employed to account for the results. The results of the dynamic analyses parallel those of the static analyses, with the exception of the equation employing the total crime rate at the dependent variable. The total variance explained in this equation was significantly lower than in the static analysis for the total crime rate. Durkheim's notions of the functions of crime and the expected stability in crime rates were offered as an explanation for this finding.

Africa↗