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R M Wallace

Publications and source records attributed to R M Wallace.

12 recordsLinked to original sources
PubMed2005

Adsorption kinetics of p-nitrobenzenethiol self-assembled monolayers on a gold surface.

The adsorption kinetics of octadecanethiol (ODT) and p-nitrobenzenethiol (NBT) from ethanol solutions has been studied by means of contact angle, optical ellipsometry, angle-resolved X-ray photoelectron spectroscopy (ARXPS), and grazing angle attenuated total reflection Fourier transform infrared (FTIR) measurements. ODT data were used as a reference for the kinetics studies of film growth. The growth of self-assembled monolayers from dilute solutions follows Langmuir isotherm adsorption kinetics. A saturated film is formed within 5 h after immersion in solutions of concentrations ranging from 0.0005 to 0.01 mM. The density of the monolayer depends on the concentration of the solution.

Journal Article↗
PubMed1995

Secretory proteins compete for production in the mammary gland of transgenic mice.

To explore the possibility that genes might compete for expression, we have studied transgenic mice producing high levels of the sheep milk protein, beta-lactoglobulin (BLG), in the mammary gland. Mice carrying one or more transgene loci expressed BLG in milk at levels ranging from 7 to 33 mg/ml. The effects of BLG synthesis on the levels of endogenous milk gene expression were examined. No significant increase in total milk protein concentration was recorded even in mice expressing the largest amounts of BLG. Measurement of individual milk proteins showed that transgene protein was manufactured at the expense of host protein synthesized in the gland. Whey acidic protein production was more suppressed than casein production. Suppression of endogenous proteins was matched by a reduction in the corresponding steady-state mRNA levels; in double-transgenic mice, which expressed the largest amounts of BLG, beta-casein and whey acidic protein mRNA populations were reduced to 75 and 56% of control levels respectively. We demonstrate that an exogenous gene competes effectively for expression with endogenous genes. Possible mechanisms of competition are discussed.

Animals↗
PubMed1995

Restricted tissue-specific but correct developmental expression mediated by a short human alpha 1AT promoter fragment in transgenic mice.

The tissue-specific and developmental pattern of expression controlled by the proximal promoter (position-348 to +15) derived from the human alpha-1-antitrypsin (h alpha 1AT) gene was studied in transgenic mice. The short promoter segment was linked to the chloramphenicol acetyltransferase (CAT) reporter gene. The transgene showed highly specific expression in the liver and the correct developmental pattern of regulation. Interestingly, this short promoter targets expression to the liver with a greater specificity than that reported for larger alpha 1AT promoter fragments.

Animals↗
PubMed1995

Tissue-specific, temporally regulated expression mediated by the proximal ovine beta-lactoglobulin promoter in transgenic mice.

The ovine beta-lactoglobulin gene is expressed abundantly in the mammary gland. This study determines whether the ovine beta-lactoglobulin promoter is sufficient for targeting tissue-specific expression in transgenic mice. To address this, the expression profile of an ovine beta-lactoglobulin promoter driven bacterial chloramphenicol acetyltransferase reporter construct was analysed. Comparison of the expression frequency of this hybrid transgene to that of a genomic beta-lactoglobulin transgene indicates that additional sequences, downstream of the promoter, are required for position-independent expression in transgenic mice. Nevertheless, the hybrid transgene was expressed specifically in the mammary gland. Furthermore, the hybrid transgene was expressed in the appropriate temporal pattern during pregnancy and lactation. Thus, the proximal promoter of the ovine beta-lactoglobulin gene contains sufficient sequence information to target expression to the mammary. This construct constitutes the basis for a compact mammary expression vector.

Animals↗
PubMed1993

Characterization of the ovine LH beta-subunit gene: the promoter directs gonadotrope-specific expression in transgenic mice.

The alpha- and beta-subunits of the gonadotropin hormones are expressed in the gonadotrope cells of the anterior pituitary. There are no adequate in vitro systems for the analysis of beta-subunit gene expression. In this study, therefore, transgenic mice have been used to investigate the regulation of expression of the ovine luteinizing hormone beta-gene (oLH beta) in vivo. oLH beta was isolated, characterized, and 1.9 kb of the promoter fused to the bacterial reporter chloramphenicol acetyl-transferase (CAT). Three lines of transgenic mice were generated. CAT enzyme was detected in the pituitary of two lines, whereas the third line did not express. Measurement of endogenous luteinizing hormone and follicle stimulating hormone levels in both expressing lines revealed small differences when compared to controls, but these did not affect the fertility of the animals. Immunostaining of the anterior pituitary revealed that the oLH beta CAT transgene was expressed specifically in gonadotrope cells.

Amino Acid Sequence↗
PubMed1989

Fetal habituation to repeated sound stimulation.

Habituation is the progressive decrement of response with repeated stimulation. Neonatologists use this phenomenon to assess newborns for various pathological conditions of the CNS. The present study examined the time required for habituation of the startle response in 103 fetuses at various gestational ages (32 to 40 weeks). The external stimulus was produced by a door buzzer (80 to 90 db). Habituation time decreased as gestational age increased. About 85% of the fetuses showed habituation after less than 20 stimuli, and about 95% after less than 30 stimuli. In all cases habituation time never exceeded 50 stimuli.

Acoustic Stimulation↗
PubMed1983

Temperature dependence of the binding of [3H]mepyramine and related compounds to the histamine H1 receptor.

The extent of the promethazine-sensitive binding of [3H]mepyramine to a washed fraction from guinea pig cerebellum was little altered between 4 degrees and 30 degrees. The dissociation of [3H]mepyramine from the H1 receptor was markedly temperature-sensitive. An Arrhenius plot of the variation of the dissociation rate constant, k-1, with temperature was linear over the range 37 degrees -15 degrees (E alpha = 160 kJ mole-1). The association rate constant, k1, was also temperature-dependent, and an Arrhenius plot approximated well to a straight line between 30 degrees and 15 degrees (E alpha = 112 kJ mole-1). The linear relationship may hold down to 4 degrees. A consequence of the slow dissociation at 4 degrees is that the IC50 for mepyramine inhibition of promethazine-sensitive [3H]mepyramine binding at 4 degrees is independent of the concentration of [3H]mepyramine if the cerebellar homogenate is first incubated with the nonradioactive antagonist before addition of the 3H-ligand. Promethazine binding showed a temperature dependence similar to that of mepyramine, and for both antagonists and for chlorpromazine the affinity constant was not greatly increased (equal to or less than a factor of 2) at 4 degrees compared with 30 degrees. Tripelennamine showed a more rapid dissociation at 4 degrees than the other antagonists. Mequitazine dissociated slowly at 4 degrees, but the affinity constant was lower at 4 degrees than at 30 degrees.

Aminopyridines↗
PubMedDate not supplied

Metastatic breast carcinoma in cerebrospinal fluid. A cytomorphometric study.

A study was undertaken to quantitate the cellular characteristics of metastatic breast carcinoma in cerebrospinal fluid (CSF). Millipore filters of CSF from 15 patients with metastatic breast carcinoma were reviewed; 50 cells per case were evaluated when available. All cells in all cases shed singly or in loose clusters; tight balls or morulae were absent. All cells had regular, round-to-oval nuclei with finely granular chromatin. The majority of cells in all cases had single or multiple round nucleoli, granular cytoplasm with distinct borders and a mean nuclear-cytoplasmic ratio of close to 0.70. Cellular background, number of tumor cells per case, number and placement of nuclei and nuclear and cytoplasmic diameter varied both within and among the cases. There was significant variation in nuclear and cytoplasmic diameters both within and among the cases of infiltrating ductal carcinoma. Thus, the uniform appearance of the cells was due to consistent cytologic features, not to similarity in cell size. The cytologic profile of metastatic breast carcinoma is sufficiently characteristic to distinguish this tumor from other benign and malignant lesions that shed in the CSF.

Adult↗