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Biomedical subjects

L Gray

Publications and source records attributed to L Gray.

At least 145 records · Page 8Linked to original sources
PubMed1988

Clinical characteristics and outcomes in a cohort of patients who were assessed as in need of nursing-home care.

A cohort of 116 applicants who were assessed by the Bundoora Extended Care Assessment Team during the first six months of 1985 as requiring nursing-home care was followed-up in an attempt to detect the clinical characteristics that were associated with a delay in placement. The demographic and clinical features of this cohort are described. By the end of the follow-up period, 89 applicants had been admitted to nursing homes. The mean time from assessment to placement for this group was 97.1 days. A significant delay in placement was associated with an age of less than 80 years, an inability to speak English, the presence of an indwelling urinary catheter, and the need for assistance with feeding. We concluded that some clinical characteristics had an effect on the time to placement among the nursing-home applicants who were assessed in the catchment area of our team.

Activities of Daily Living↗
PubMed1988

Antigenic variation among group A streptococcal M proteins. Nucleotide sequence of the serotype 5 M protein gene and its relationship with genes encoding types 6 and 24 M proteins.

The 1479-base pair (bp) nucleotide sequence of the serotype 5 M protein gene (smp5) from Streptococcus pyogenes contains three distinct types of tandemly repeated sequences, designated A, B, and C. Repeat A (21 bp x 6, in the 5'-half of smp5), shares no homology with the types 6 or 24 M protein genes (Hollingshead, S. K., Fischetti, V. A., and Scott, J. R. (1986) J. Biol. Chem. 261, 1677-1686; Mouw, A. R., Beachey, E. H., and Burdett, V. (1988) J. Bacteriol., in press). Repeat B (75 bp x 3.6, in the center of smp5) is also present in the M6, but not in the M24 gene. Repeat C (105 bp x 2.7, just distal to the B repeats) shares homology with repeats in both the M6 and M24 genes. All three genes share extensive homology in their 3'-halves and in 5' sequences encoding the N-terminal signal peptides, but between these two regions there are highly variable sequences that are responsible for antigenic diversity. These relationships suggest that both intergenic and intragenic recombination has occurred during the evolution of distinct M protein serotypes. All three M proteins contain conserved hydrophobic and proline-rich sequences at their C-terminal ends, suggestive of a membrane anchor and a peptidoglycan spanning region.

Amino Acid Sequence↗
PubMed1988

The hemolysin of Escherichia coli.

Many strains of E. coli elaborate a hemolysin which is responsible for the zone of beta-hemolysis surrounding bacterial colonies on blood agar. The significance of this cytolysin as a determinant of bacterial pathogenicity has been established in animal models with the use of genetically engineered, isogenic bacterial strains. An analogous role in human infections has been inferred from the high association of hemolysin production with disease. Studies at a molecular genetical level have defined 4 genes that are required for the synthesis, post-translational modification and secretion of the hemolysin. The structural gene hlyA encodes for a 107-110,000 polypeptide, which must be modified in an unknown manner to its active form by the product of the neighboring hlyC gene. Genes hlyB and hlyD encode for proteins that export the molecule to the extracellular medium. The signal for secretion is contained in the C-terminal portion of the toxin molecule. The secreted hemolysin attacks plasma membranes of target mammalian cells by inserting as a monomer into the bilayer and generating hydrophilic transmembrane pores of approximately 2 nm effective diameter. The pores display a marked selectivity for cations over anions and pore-opening is dependent on the presence of a correct transmembrane potential. Binding to a membrane target does not require the presence of a specific receptor, and pores may be generated in planar lipid membranes consisting solely of phosphatidylcholine. Pore formation in nucleated cells can trigger secondary reactions such as stimulation of arachidonate metabolism with release of lipid mediators, probably initiated by passive influx of extracellular Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Use of short stay beds by nursing home applicants waiting for placement.

Implementation of the recent decision of the Commonwealth Department of Community Services and Health to set a uniform target ratio of 40 extensive care Nursing Home beds per 1000 persons aged 70 and over will result in substantial decreases in the availability of Nursing Home places in many Australian regions. The catchment area of the Bundoora Extended Care Assessment Team currently has a Nursing Home bed to population ratio which is very close to this target. It may serve as a model for the conditions likely to prevail when this target ratio is achieved in other Australian regions. Data from a cohort of 320 Nursing Home applicants from this catchment area assessed by the team suggests that at this level of Nursing Home bed provision, use of short stay institutional beds by applicants awaiting placement is substantial. Figures are provided which permit the estimation of short stay institutional bed use expected from regional populations where the level of nursing home bed provision is close to the CDCSH target.

Appointments and Schedules↗
PubMed1987

Multidimensional perceptual development: consistency of responses to frequency and intensity in young chickens.

The development of consistent responses to multidimensional acoustic stimuli was investigated in newborn chickens. Young chicks suppress their ongoing peeps when they hear a change in an acoustic stimulus, and the amount of that suppression is related to the amount of change. Durations of suppression can thus be interpreted as perceived differences between pairs of stimuli. The suppressions elicited by all possible transitions between pairs of 5 acoustic stimuli that differed in frequency, intensity, and repetition rate were measured at 2 ages. These data were analyzed with a multidimensional scaling program. Interpretable structure is evident in the results from 4-day-old chicks to a subset of the stimuli that vary in frequency and intensity. Newborn chicks, in contrast, showed inconsistent responses. Neither age group responded with interpretable structure to stimuli that differed in 3 dimensions. Thus, consistent responses to 2-dimensional acoustic stimuli emerge over the first few postnatal days. Perceptual dimensions become associated with the physical dimensions of frequency and intensity as animals mature.

Acoustic Stimulation↗
PubMed1987

Release of a chimeric protein into the medium from Escherichia coli using the C-terminal secretion signal of haemolysin.

Recently, we have identified a novel topogenic sequence at the C terminus of Escherichia coli haemolysin (HlyA) which is essential for its efficient secretion into the medium. This discovery has introduced the possibility of using this secretion system for the release of chimeric proteins from E. coli directly into the medium. We have now successfully fused this C-terminal signal to a hybrid protein containing a few residues of beta-galactosidase and the majority of the E. coli outer membrane porin OmpF lacking its own N-terminal signal sequence. We find that this chimeric protein is specifically translocated across the inner and outer membranes and is released into the medium. In addition, we have further localized the HlyA secretion signal to the final 113 amino acids of the C terminus. In fact, a specific secretion signal appears to reside at least in part within the last 27 amino acids of HlyA.

Amino Acid Sequence↗
PubMed1987

Dosimetry studies on prototype 241Am sources for brachytherapy.

Sealed sources of 241Am emit primarily 60 keV photons which, because of multiple Compton scattering, produce dose distributions in water that are comparable to those from 226Ra or 137Cs. However, americium gamma rays can be shielded by thin layers of high atomic number materials since the half value layer thickness is only 1/8th of a mm of lead for americium gamma rays as compared to a value of 12 mm for 226Ra gamma rays. This may allow effective in vivo shielding of critical organs, for example; the bladder can be partially shielded by hypaque solution, and the rectum and sigmoid colon by barium sulfate. In addition, the exposure to medical personnel involved in intracavitary application and patient care may be reduced substantially by the use of relatively thin lead aprons and light weight, portable shields. To investigate the feasibility of 241Am sources for intracavitary irradiation, dosimetry studies on prototype 241Am sources have been performed and a computer model for the determination of dose distributions around encapsulated cylindrical sources of 241Am has been developed and tested. Results of dosimetry measurements using ionization chambers, lithium fluoride thermoluminescent dosimeters, a scanning scintillation probe, and film dosimetry, confirm theoretical predictions that these sources can deliver dose rates adequate for intracavitary irradiation. Further dosimetry measurements in simulated clinical situations using lead foils and test tubes filled with hypaque or barium sulfate, confirm the predicted effectiveness of in vivo shielding which can be readily achieved with 241Am sources.

Americium↗
PubMed1987

Signal detection analyses of delays in neonates' vocalizations.

Signal detection analyses were applied to momentary delays in the regular peeping of newborn chicks that occur in response to acoustic stimuli. Pulsing 1000-Hz tones at various intensities were repeatedly presented to chicks at 0 and 4 days posthatch. Durations of delays on both stimulus and control (mock) trials were collected in histograms. These histograms were then used to draw receiver operating characteristics (ROC curves) given variable definitions of what constitutes a "yes" response. Areas under these ROC curves were used to evaluate various ways of measuring the delay, as well as the effects of habituation, intensity, and age. Time to the second poststimulus peep was identified as a sensitive indicator of responsiveness. Habituation decreased responsiveness by about 5% per trial over the first three trials. Each dB of intensity increased responsiveness by about 1%. Maturation increased responsiveness by about 21 dB over 4 days. These ROC curves show that momentary delays in the vocalizations of newborn chickens are appropriate measures of auditory signal detection. Similar analyses could be useful in other psychophysical studies that depend on the changing rate of repetitive responses.

Acoustic Stimulation↗
PubMed1987

The impact of federally funded CMHCs on local mental health service systems. Community Mental Health Centers.

To measure how much federally funded community mental health centers increased the quantity and range of mental health services, 63 catchment areas in which CMHCs began to receive federal funding in 1974-75 were matched individually with catchment areas that never received federal CMHC funding. The two groups of catchment areas were compared to determine average increases from 1973 to 1980 in amounts of services, mental health staff, expenditures, and accessibility and availability of services. Results showed that establishment of local CMHCs had a clear impact on the quantity and the availability and accessibility of services in the catchment area. The effect sizes resulting merely from the passage of time and from CMHC funding were compared.

Catchment Area, Health↗
PubMed1987

Microsphere determination of cochlear blood flow in chickens.

Chickens were injected with 9-micron-diameter radioactive microspheres. Cochleas were removed through the external auditory meatus, and the positions of all embedded microspheres were drawn under camera-lucida. Constant measurements of arterial pressures and postinjection blood-gas determinations confirmed that injections were made into normal circulatory systems. The averaged estimate of cochlear blood flow in chickens is 0.75 microliter/min. Variability in these data from chickens is similar to that reported from mammals. A potentially important but puzzling observation is an inverse relationship between blood flow to the cochlea and to the brain. The ease of cochlear extraction makes chickens ideal models for study of cochlear blood flow.

Animals↗
PubMed1987

Perspectives on nursing home placement--towards an analytical model.

A simplified account of some of the factors affecting placement of elderly disabled applicants into nursing homes is presented. The placement process is described as the task of matching applicants from a waiting list to beds as these become available. Some recent data from one Victorian region is presented to illustrate the discussion. Although the number of waiting applicants at any one time (queue length) is only one measure of the overall situation, it is a convenient one to discuss. Factors affecting the length of the queue include the admission rate which is in turn related to the average length of stay. The potential for assessment-based admission controls to decrease the queue length by decreasing the number of long stay admissions is briefly discussed. Mechanisms for making the whole process more smooth and effective from the perspective of both the applicant and nursing home administration are reviewed.

Aged↗
PubMed1986

The C-terminal, 23 kDa peptide of E. coli haemolysin 2001 contains all the information necessary for its secretion by the haemolysin (Hly) export machinery.

In this paper we show the construction of a plasmid pLG609 which carries the 3'-end of the haemolysin structural gene, hlyA under tac promoter control. Expression of pLG609 in an E. coli strain carrying the haemolysin export genes hlyB and hlyD led to the efficient secretion of the C-terminal, 23 kDa peptide of haemolysin. The discovery of a C-terminal topogenic sequence, which appears to be all that is required for secretion of the whole toxin, is so far quite unique in protein export.

Biological Transport↗
PubMed1986

The carboxy-terminal region of haemolysin 2001 is required for secretion of the toxin from Escherichia coli.

As a first step in the detailed analysis of the mechanism of secretion of haemolysin, we sought to identify sequences or domains within haemolysin A (HlyA) that are essential for its secretion. For this purpose we examined the properties of a deletion and Tn5 insertions into the region of the HlyA gene encoding the C-terminal part of the protein, since both of these are relatively simple to generate. We showed that removal of 27 amino acids from the C-terminus of HlyA is sufficient to inhibit secretion drastically, although the residual polypeptide is still haemolytically active. Cellular fractionation studies showed that haemolytic activity does not accumulate in large amounts within the periplasmic space during normal secretion. More significantly, activity does not appear to accumulate within this compartment when the export functions hlyB and hlyD are removed. These results are consistent with a mechanism in which interaction of the C-terminus of HlyA with the secretion machinery, located in the inner membrane, is followed by direct transfer of haemolysin to the medium.

Amino Acid Sequence↗