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Biomedical subjects

P Connolly

Publications and source records attributed to P Connolly.

At least 55 records · Page 3Linked to original sources
PubMed1991

Wood duck hatch date: relationship to pairing chronology, plasma luteinizing hormone, and steroid hormones during autumn and winter.

We examined variation in courtship activity and hormone levels of male and female wood ducks (Aix sponsa) in relation to hatch date. Young wood ducks were assigned in groups of 8 (4 males and 4 females) to 4 experimental pens; 2 pens contained early-hatched ducks (3-12 April) and 2 pens contained late-hatched ducks (7-16 June). Courtship behaviors occurred less frequently in October and November than in December and January-February for both early- and late-hatched groups. Early-hatched wood ducks participated in courtship more frequently and formed pair bonds sooner than late-hatched individuals. Testosterone (T) and androstenedione (AD) levels of males did not differ between treatment groups; however, average levels of luteinizing hormone (LH) were greater for early-hatched males. Differences in LH occurred in 2 of 12 samples (6 October and 3 November); otherwise, LH did not vary by treatment. Levels of T and LH in males varied temporally, but there was no significant temporal variation in AE levels. Temporal variation in hormone levels was similar for early- and late-hatched males. Estradiol (E), progesterone (P), and LH levels of females did not differ between treatment groups. There was temporal variation in levels of E and LH, but not of P; this variation was similar for early- and late-hatched females. These data indicate that behavioral differences occurring temporally and between early- and late-hatched wood ducks were not related to corresponding differences in hormone levels.

Animals↗
PubMed1991

Cell guidance by ultrafine topography in vitro.

Laser holography and microelectronic fabrication techniques have been employed to make grating surfaces in fused quartz with ultrafine period (260 nm) in an attempt to mimic the topography of aligned fibrillar extracellular matrix (ECM), which, in the past, has been shown to affect the behaviour of cells in vitro and in vivo. The alignment of BHK cells, MDCK cells and chick embryo cerebral neurones on 260 nm period grating surfaces (130 nm grooves separated by 130 nm) of various depths (100, 210 and 400 nm) was examined. While all gratings aligned BHK cell populations, the degree of alignment was dependent on depth. The response of single MDCK cells to the grating patterns was both to align precisely to the direction of the gratings, and to elongate; only their elongation was depth-dependent. MDCK cells that were part of epithelial cell islands, and the outgrowth of neurites from chick embryo neurones, were mainly unaffected by the grating surfaces. It is clear that topography on this scale can control cell behaviour, but guidance of this type is strongly dependent on cell type and cell-cell interactions.

Animals↗
PubMed1990

Effect of polymyxin B nonapeptide and polymyxin B sulphate on trichothecene mycotoxin sensitivity of yeasts using a conductimetric instrument.

The addition of polymyxin B sulphate (PBS), or an inactive by-product, polymyxin B nonapeptide (PBN) to a yeast bioassay system, increased its sensitivity to various toxic agents. The nil effect level (NEL) of T-2 toxin was reduced from 0.1 to 0.01 microgram/ml for Kluyveromyces fragilis GK 1005 in the presence of these agents when using a Malthus AT 192 conductimetric instrument. Other synergistic agents (DMSO, ethanol, cetyl trimethyl ammonium bromide and Triton X-100) gave poor results in the conductimetric system. PBN also increased sensitivity of K. fragilis GK 1005 towards cycloheximide in the Malthus system, and PBS reduced the NEL of T-2 toxin for K. fragilis GK 1005 in a disc diffusion assay from 0.2 to 0.04 microgram per disc. No yeasts were found sensitive to the trichothecene deoxynivalenol (DON) even at a DON concentration of 10 micrograms/ml, except in the presence of PBN and PBS. The minimal inhibitory concentration (mic) of DON in the presence of PBS was 2 micrograms/ml for K. fragilis GK 1005.

Anti-Infective Agents, Local↗
PubMed1990

An extracellular microelectrode array for monitoring electrogenic cells in culture.

This paper describes a planar array of microelectrodes developed for monitoring the electrical activity of cells in culture. The device allows the incorporation of surface topographical features in an insulating layer above the electrodes. Semiconductor technology is employed for the fabrication of the gold electrodes and for the deposition and patterning of an insulating layer of silicon nitride. The electrodes have been tested using a cardiac cell culture of chick embryo myocytes, and the physical beating of the cultured cells correlated with the simultaneous extracellular voltage measurements obtained. It was found that extracellular stimulation of the cells was possible via the same electrodes used for recording.

Action Potentials↗
PubMed1990

Topographical control of cell behaviour: II. Multiple grooved substrata.

Electronics miniaturization techniques have been used to fabricate substrata to study contact guidance of cells. Topographical guidance of three cell types (BHK, MDCK and chick embryo cerebral neurones) was examined on grooved substrata of varying dimensions (4-24 microns repeat, 0.2-1.9 microns depth). Alignment to within 10 degrees of groove direction was used as our criterion for guidance. It was found that repeat spacing had a small effect (alignment is inversely proportional to spacing) but that groove depth proved to be much more important in determining cell alignment, which increased with depth. Measurements of cell alignment and examination by scanning electron microscopy showed that BHK cells and MDCK cells interacted differently with grooved substrata, and also that the response of MDCK cells depended on whether or not the cells were isolated or part of an epithelial cell island. Guidance by a multiple topographical cue is greater than could be predicted from cells' reactions to a single cue (Clark et al. Development 99: 439-448, 1987). Substratum topography is considered to be an important cue in many developmental processes. Cellular properties such as cytoskeletal organisation, cell adhesion and the interaction with other cells are discussed as being factors determining a cells susceptibility to topography.

Animals↗
PubMed1988

A medium for the detection of yeasts using a conductimetric method.

A new medium is described for the detection of yeasts using a Malthus microbial growth analyser which measures conductivity. This medium is superior to previous media devised for use in the Malthus, and allows the detection of a wide range of yeasts including those important in food spoilage. The new medium was inferior to existing media used to detect yeasts in the Bactometer 32 instrument which measures impedance.

Colony Count, Microbial↗
PubMed1987

Intraocular pressure during cardiopulmonary bypass.

Intraocular pressure was measured in 24 patients undergoing elective cardiopulmonary bypass surgery. There was a rapid rise when the bypass circulation began, and this was maintained for about 30 minutes. A simultaneous drop in arterial perfusion pressure and packed cell volume occurred. We suggest that marked haemodilution is responsible for this effect, through increased ocular blood flow and low colloidal osmotic pressure. The possible aetiological significance in relation to ischaemic optic neuropathy complicating cardiopulmonary bypass is discussed.

Adult↗
PubMed1987

Topographical control of cell behaviour. I. Simple step cues.

The photolithographic techniques of the microelectronics industry have allowed us to fabricate patterned plastic substrata to investigate contact guidance of animal tissue cells. The reactions of cells to single steps on a substratum were examined using time-lapse videorecording and scanning electron microscopy. BHK cells and chick embryonic neural cell processes exhibited gradual inhibition of crossing steps with a concomitant increase in alignment at steps dependent on increasing step height. Comparison of these cells' reactions, with those of chick heart fibroblasts and rabbit neutrophils, at a 5 micron step revealed that the influence of topography is also dependent on cell type, the neutrophils being relatively unaffected. The presence of an adhesive difference at a series of steps altered BHK cells' reactions such that the frequency of crossing was dependent on the direction of approach to a step. Although our data are consistent with Dunn & Heath's proposal (1976) that the inflexibility of the cytoskeleton of a moving cell's protrusion is the cellular property determining such reactions to topography, we have found that, on encountering a topographical feature, the response of a cell may be predictable on a probabilistic basis, i.e. the topographical feature reduces the probability of a cell making a successful protrusion and contact in a given direction, that even the largest features tested did not act as absolute barriers to cell locomotion since a small proportion of a population of cells were able to overcome them, and that other guidance cues could significantly alter a cell's response. Even in situations where it is not the primary cue in directing cell locomotion, topographical control may be an important factor during morphogenesis since it must, at the very least, influence the efficiency of other cues.

Animals↗
PubMed1987

Novel methods for the guidance and monitoring of single cells and simple networks in culture.

The effects of the topography, adhesiveness and chemistry of surfaces in modulating the behaviour of cells in vivo and in vitro have been extensively researched. However, few natural systems are simple enough to allow straightforward conclusions to be drawn, as many different cues are likely to be present at one time. Microelectronic fabrication, normally employed in making integrated circuits, can produce substrates patterned on scales highly relevant to studies of cell behaviour. In this paper, we describe progress in fabricating simple artificial substrata both at the micrometre and sub-micrometre scales. The former can be considered as models for contact guidance along other cells or axonal processes: the latter, models for guidance along aligned collagen matrices. We have systematically studied the reactions of different cell types to simple cues (steps and grooves). Additionally, it may be possible to produce fine-resolution patterns with differential adhesiveness, or with other cell-specific surface-chemical properties, such as the differential deposition of proteins, e.g. cell adhesion molecules. We also describe early results in using topographic and other cues to guide cells onto patterned metal electrodes, forming simple electrically active networks of controlled design, from which long-term recordings can conveniently be made.

Animals↗
PubMed1984

Analyzing program cause as well as effect: a methods for program analysis.

Measuring the impact of therapeutic recreation services appears to be a major concern in the field. While effects and outcomes are of primary importance in determining service delivery impact, of equal importance is the documentation and evaluation of the intervention program presumed to cause the effect. Very little attention has been directed toward methods of analyzing intervention programs prior to attempting research studies which search for cause and effect relationships. Additionally, within research studies which purport to measure service delivery impact and effect, very little information tends to be given on the nature and structure of the intervention program that supposedly led to such effects. Thus, the Program Plan Description Form is presented as a method of program analysis to aid in the applied research process of analyzing the impact of therapeutic recreation service delivery programs.

Outcome and Process Assessment, Health Care↗
PubMed1982

GLC determination of phenacemide in tablets.

A GLC procedure was developed for phenacemide and was shown to be less time consuming than the official assay without sacrificing accuracy. The procedure involves extraction from powdered tablets and addition of pentylenetetrazol as the internal standard. The amount of phenacemide is determined by comparison of the ratio of the area under the curves to that of a standard.

Benzeneacetamides↗
PubMed1982

The influence of the replacement of dietary sucrose by maltose on the formation and biochemistry of human dental plaque.

Samples of 2-day plaque were collected before and during two 25-day diet periods from 24 subjects taking part in a double-blind cross-over study involving sucrose- and maltose-rich diets. The mean change in plaque pH measured after exposure to the respective sugar during the 3rd week of both diet periods was similar. The dry weight of plaque did not vary significantly as either diet progressed but the lowest mean value obtained was in the 4th week of the maltose diet. The extracellular polysaccharide content of plaque was lower in the maltose group than in the sucrose group (p = 0.052). Plaque-invertase activity was not affected significantly by the diets but maltase activity was significantly higher in the 2nd and 4th weeks of the maltose diet (p = 0.039; p = 0.012). The results suggest that the polysaccharide matrix of plaque formed in the presence of maltose as opposed to sucrose is different, which could be explained by the known effect of maltose in vitro on plaque glucosyl transferases.

Adult↗
PubMed1981

Altered transcriptional termination in a rifampicin-resistant mutant of Escherichia coli which inhibits the growth of bacteriophage T7.

A spontaneous rifampicin-resistant mutant of E. coli K12, RpoB26, which inhibits the growth of bacteriophage T7 has been isolated. The mutation is an RNA polymerase mutation; it also restores the wild-type effect of polar mutations in a rho-deficient strain, probably by restoring transcriptional termination. The efficiency of plating (e.o.p.) of wild-type T7, and of some early region deletion and point mutants of T7 tested, is reduced on RpoB26 by a factor of 10(-4). However, some deletion mutants are inhibited more severely (up to 10(-7) on RpoB26. We argue that these differences may reflect variations in the frequency of transcriptional termination before gene 1, an essential gene which codes for the T7 RNA polymerase (Summers and Siegel 1970; Chamberlin et al. 1970). We also present data which suggest that the product of a late T7 gene plays a role, by some interaction with the product of gene 1, in the inhibition of T7 in RpoB26. We suggest that different levels of expression of gene 1 may lead to different degrees of inhibition of T7 strains in RpoB26.

DNA-Directed RNA Polymerases↗