Search PubMed⌕ Search

Biomedical subjects

B M Schneider

Publications and source records attributed to B M Schneider.

9 recordsLinked to original sources
PubMed1998

Chimeric chemoreceptors in Escherichia coli: signaling properties of Tar-Tap and Tap-Tar hybrids.

The Tap (taxis toward peptides) receptor and the periplasmic dipeptide-binding protein (DBP) of Escherichia coli together mediate chemotactic responses to dipeptides. Tap is a low-abundance receptor. It is present in 5- to 10-fold-fewer copies than high-abundance receptors like Tar and Tsr. Cells expressing Tap as the sole receptor, even from a multicopy plasmid at 5- to 10-fold-overexpressed levels, do not generate sufficient clockwise (CW) signal to tumble and thus swim exclusively smoothly (run). To study the signaling properties of Tap in detail, we constructed reciprocal hybrids between Tap and Tar fused in the linker region between the periplasmic and cytoplasmic domains. The Tapr hybrid senses dipeptides and is a good CW-signal generator, whereas the Tarp hybrid senses aspartate but is a poor CW-signal generator. Thus, the poor CW signaling of Tap is a property of its cytoplasmic domain. Eighteen residues at the carboxyl terminus of high-abundance receptors, including the NWETF sequence that binds the CheR methylesterase, are missing in Tap. The Tart protein, created by removing these 18 residues from Tar, has diminished CW-signaling ability. The Tapl protein, made by adding the last 18 residues of Tar to the carboxyl terminus of Tap, also does not support CW flagellar rotation. However, Tart and Tapl cross-react well with antibody directed against the conserved cytoplasmic region of Tsr, whereas Tap does not cross-react with this antibody. Tap does cross-react, however, with antibody directed against the low-abundance chemoreceptor Trg. The hybrid, truncated, and extended receptors exhibit various levels of methylation. However, Tar and Tapl, which contain a consensus CheR-binding motif (NWETF) at their carboxyl termini, exhibit the highest basal levels of methylation, as expected. We conclude that no simple correlation exists between the abundance of a receptor, its methylation level, and its CW-signaling ability.

Bacterial Proteins↗
PubMed1995

Distinct area distribution differences of micronuclei induced by clastogenic and aneuploidogenic chemicals in the bone marrow of the CD-1 mouse.

To distinguish between aneuploidogenic and clastogenic effects of test chemicals, area distributions of micronuclei (MN) in polychromatic erythrocytes (PE) from the mouse bone marrow were measured using an image analysis system. Triethylenemelamine (TEM), cytosine-beta-D-arabinofuranoside (ara-C), urethane (URT), cyclosphamide (CP), mitomycin C (MMC), colcemid (COL) and tubulazole C (TUB) were investigated for the induction of micronucleus area distributions. The area distribution of micronuclei of untreated mice was also determined. Reproducible small differences between the clastogens and the aneuploidogens were observed after measuring 1100-1200 micronuclei. A common feature of the distribution curves was a shoulder region in the same area range for all clastogens. The aneuploidogens COL and TUB showed a plateau (= wide peak) in this clastogenic shoulder region. For all clastogens, the integrated area of shoulder over a fitted function (shoulder strength) was evaluated. MMC and CP, thought to have some aneuploidogenic potential, showed an increased shoulder strength compared to TEM, ara-C and URT. The control area distribution had no similarities to the area distribution of either clastogens or aneuploidogens. In a further experiment, we attempted to correlate the size of micronuclei determined after treatment with the aneuploidogenic chemicals to the size of whole chromosomes. Micronuclei found by image analysis which bear chromosome-like structures (judged by light microscopy) were manually identified. This selection of micronuclei was area-distributed to determine the mean size of these micronuclei. None of the peaks and plateaus in the area distributions obtained with the aneuploidogenic chemicals could be attributed to the size of a chromosome.

Aneuploidy↗
PubMed1990

Influence of insecticide treatment on German cockroach (Dictyoptera: Blattellidae) movement and dispersal within apartments.

Two similar studies were done to investigate effects of insecticide treatments on German cockroach, Blattella germanica (L.), movement and dispersal within individual units in multifamily housing. In the first study, Whitmire PT-565 Pyrethrum Insect Fogger (pyrethrins), Diazinon 4E (diazinon), Protector (permethrin), and Baygon 1.5 (propoxur) did not induce any significant changes in cockroach distribution, and rates of movement within apartments decreased. In the second study, populations treated with sublethal doses of pyrethrins and resmethrin settled to their original distribution 24 h after treatment. Results from both studies indicate that thorough insecticide applications do not significantly affect German cockroach population dispersal or movement patterns within apartments.

Animals↗
PubMed1989

[Bone marrow micrometastases in colorectal cancers].

To date, the detection of individual micrometastases or disseminated tumor cells has not been possible with conventional diagnostic procedures. With the aid of new immunocytochemical investigation, however, histogenetically different cells can now be detected in the bone marrow. The monoclonal antibody, cytokeratin component 18, is most suitable for the detection of micrometastases from colorectal carcinoma. In 22 out of 82 patients with colorectal carcinoma, we were able to detect CK2-positive cells. The incidence of these "micrometastases" is represented as a function of primary tumor size, lymph node involvement, distant metastasis, and degree of malignancy of the tumor, age and sex of the patient, and tumor localization.

Adult↗
PubMed1980

Aplasia cutis congenita complicated by sagittal sinus hemorrhage.

An infant with aplasia cutis congenita complicated by sagittal sinus hemorrhage is described. In cases of large defects, plastic surgical repair has been recommended for prevention of hemorrhage and infection. The complication of sagittal sinus hemorrhage should be considered in patients with large midline scalp defects, especially when associated with absence of the underlying cranium.

Cranial Sinuses↗
PubMed1971

MLA exchange.

Explore the source record for details and available documents.

Libraries, Medical↗
PubMedDate not supplied

Comparison of single/multiple-dose protocols using triethylenemelamine and procarbazine hydrochloride for the mouse bone marrow micronucleus test.

Treatment of mice with a single dose of either 4.8 mg/kg of triethylenemelamine (TEM) or 348 mg/kg of procarbazine hydrochloride (PC) induced higher frequencies of micronucleated polychromatic erythrocytes (MPE) after 48 h than after 24 h. The same observation was made when animals were treated with 1.6 or 8 mg/kg of TEM or 116 or 580 mg/kg of PC for 2 consecutive days (double-dose protocol). Surprisingly, the third dose of either 1.6 or 8 mg/kg of TEM caused lower MPE frequencies at the 72-h than at the 48-h sampling time. The observation that lower MPE frequencies after 72 h were also accompanied by reduced bone marrow toxicity might have reflected a drug-related adaptive reaction of the animals, for example the induction of detoxifying enzymes. Mean MPE frequencies as well as bone marrow toxicity were also slightly decreased after the third dose of either 116 or 580 mg/kg of PC, but statistical analysis showed no differences between the 48-h and the 72-h sampling times as regards the MPE frequencies and bone marrow toxicity. In addition to the high mean MPE frequency observed after 2 doses of 116 mg/kg of PC at the 48-h sampling time, a late increase in micronucleus induction was also seen after triple dosing at the 96-h sampling time. The present experiments with TEM and PC showed similar sensitivity for the multiple-dose assays when compared with the single-dose micronucleus test. In the case of the triple-dose assay, bone marrow toxicity proved to be a critical factor for appropriate dose selection. The computerized image analysis system was a convenient and time-saving tool for the automatic scoring of large quantities of cells for micronuclei as well as for the evaluation of bone marrow depression from the entire cell population analyzed for micronuclei.

Animals↗