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Biomedical subjects

J Lawrence

Publications and source records attributed to J Lawrence.

At least 127 records · Page 7Linked to original sources
PubMed1993

NADH oxidase activity of rat liver plasma membrane activated by guanine nucleotides.

The activity of a hormone- and growth-factor-stimulated NADH oxidase of the rat liver plasma membrane responds to guanine nucleotides, but in a manner that differs from that of the classic trimeric and low-molecular-mass monomeric G-proteins. In the absence of added bivalent ions, both GTP and GDP as well as guanosine 5'-[gamma-thio]triphosphate (GTP[gamma-S]) but not guanosine 5'[beta-thio]diphosphate (GDP[beta-S]) stimulate the activity over the range 1 microM to 100 microM. Other di- and tri-nucleotides also stimulate, but only at concentrations of 100 microM or higher. Added bivalent ions are not required either for NADH oxidation or guanine nucleotide stimulation. Bivalent ions (Mg2+ > Mn2+ > or = Ca2+) alone stimulate only slightly at low concentrations and then inhibit at high concentrations. The inhibitions are augmented by GDP or GTP [gamma-S] but not by GTP. Although the activity is the same, or less, in the presence of 0.5 mM MgCl2, GTP at 1-100 nM and other nucleotides at 0.1 mM or 1 mM still stimulate in its presence. The NADH oxidase is activated by mastoparan but aluminum fluoride is weakly inhibitory. Cholera and pertussis toxins elicit only marginal responses. Both the Mg2+ and the GDP and GTP[gamma-S] inhibitions (but not the GTP stimulations) shift to higher concentrations when the membrane preparations are first solubilized with Triton X-100. The results suggest a role for guanine nucleotides in the regulation of plasma membrane NADH oxidase, but with properties that differ from those of either trimeric or the low-molecular-mass G proteins thus far described.

Animals↗
PubMed1993

Good laboratory practice and laboratory accreditation.

Principles of good laboratory practice (GLP) and laboratory accreditation programs, particularly as they pertain to the environmental sector, are reviewed. The multitude of programs is proving costly for many laboratories and there is mounting pressure to develop reciprocity agreements between programs and to consolidate nationally and internationally. Inclusion of GLP and laboratory accreditation requirements in government regulations is resulting in a significantly increased number of laboratories participating in these programs.

Accreditation↗
PubMed1993

Formative evaluation: implementation of primary nursing.

Staff nurses initiated the change from a total patient care to a primary nursing delivery system. The effects of the change were measured on the following: nurses' perceptions of their work environment; communication and collaboration with other health care professionals; parent satisfaction and quality of care provided, and direct and indirect nursing activities. The measurements were taken prior to, six months and twelve months post implementation. Action was taken based on the findings of this evaluation process which enabled the facilitation of the change process.

Attitude of Health Personnel↗
PubMed1993

Effects of ectoderm co-culture and conditioned medium on the limb mesoderm in vitro.

Undissociated mesoderm placed onto collagen gels forms three subpopulations of mesenchyme which differentiate along myogenic, chondrogenic and fibrogenic phenotypes. Co-culture with ectoderm appears to inhibit the formation of distinct cartilage elements and myotubes by interfering with the differentiation of chondrogenic and fibrogenic progenitors. Addition of CCM enriched in ES antigens enhances the effects of the ectoderm on chondrogenesis. Culture in the presence of CCM alone retards chondrogenesis and almost completely inhibits myogenesis. These results suggest that the primary effect of ectoderm or CCM in our culture system is on myogenic and chondrogenic differentiation, and ES antigens, if responsible for these effects, appear to have no role in pattern formation.

Animals↗
PubMed1993

The development of a tool to assess neonatal pain.

The objectives of this study were to (1) develop a behavioral assessment tool for the measurement of pain in the preterm and full-term neonate; (2) establish the construct and concurrent validity, interrater reliability, and internal consistency of the tool; and (3) examine the relationship between the pain scores and infant characteristics. Thirty-eight infants contributed to the 90 procedures videotaped for the study. The Neonatal Infant Pain Scale (NIPS) was used to score behavioral responses before, during, and after each intrusive procedure. The significant difference in NIPS scores over time indicates that the scale provides a measurement of intensity of infant responses to intrusive procedures. Concurrent validity was established by correlations, ranging from .53 to .84, between NIPS scores at each minute of observation and scores on the Visual Analogue Scale. Interrater reliability was high: Pearson correlations ranged from .92 to .97 across successive minutes of observation. The six component scores of the NIPS had high internal consistency: Cronbach's alphas were .95, .87, and .88 for before, during, and after the procedures, respectively. Although gestational age and five-minute Apgars were positively associated with NIPS scores over time, there was no association between these factors and responsiveness to pain, as measured by change in NIPS scores from before to during the procedure. Results are discussed in terms of the use of the NIPS in clinical trials and its clinical application in a neonatal intensive care unit.

Apgar Score↗
PubMed1992

The human XIST gene: analysis of a 17 kb inactive X-specific RNA that contains conserved repeats and is highly localized within the nucleus.

X chromosome inactivation in mammalian females results in the cis-limited transcriptional inactivity of most of the genes on one X chromosome. The XIST gene is unique among X-linked genes in being expressed exclusively from the inactive X chromosome. Human XIST cDNAs containing at least eight exons and totaling 17 kb have been isolated and sequenced within the region on the X chromosome known to contain the X inactivation center. The XIST gene includes several tandem repeats, the most 5' of which are evolutionarily conserved. The gene does not contain any significant conserved ORFs and thus does not appear to encode a protein, suggesting that XIST may function as a structural RNA within the nucleus. Consistent with this, fluorescence in situ hybridization experiments demonstrate localization of XIST RNA within the nucleus to a position indistinguishable from the X inactivation-associated Barr body.

Base Sequence↗
PubMed1992

Stimulation of NADH oxidase activity from rat liver plasma membranes by growth factors and hormones is decreased or absent with hepatoma plasma membranes.

Plasma membranes of rat liver isolated by aqueous two-phase partition exhibited basal levels of NADH oxidase activity that were increased approx. 2-fold by addition of hormones and growth factors to which liver cells were known to respond. In contrast, hepatoma plasma membranes demonstrated an intrinsically increased level of NADH oxidase, which was not stimulated further by addition of growth factors. The results suggest that the NADH oxidase of the hepatoma plasma membrane is no longer correctly coupled to hormone and growth-factor receptors. This biochemical defect may parallel the loss of growth control that is characteristic of neoplastic transformation in hepatocarcinogenesis and other transformation systems.

Animals↗
PubMed1992

NADH-activated cell-free transfer between Golgi apparatus and plasma membranes of rat liver.

This report concerns development of a cell-free system from rat liver to study transport of membrane constituents from the Golgi apparatus to the plasma membrane. Highly purified Golgi apparatus as donor and a mixture of sheets and vesicles as plasma membrane acceptor fractions were combined to analyze requirements for lipid and protein transport. In the reconstituted system, the Golgi apparatus donor was in suspension. To measure transfer, membrane constituents of the donor membranes were radiolabeled with [3H]acetate (lipids) or [3H]leucine (proteins). The plasma membrane vesicles were used as the acceptor and were unlabeled and immobilized on nitrocellulose for ease of recovery and analysis. The reconstituted cell-free transfer was dependent on temperature, but even at 37 degrees C, the amount of transfer did not increase with added ATP, was not specific for any particular membrane fraction or subfraction nor was it facilitated by cytosol. ATP was without effect both in the presence or absence of a cytosolic fraction capable of the support of cell-free transfer in other systems. In contrast to results with ATP, NADH added to the reconstituted system resulted in an increased amount of transfer. A further increase in transfer was obtained with NADH plus a mixture of ascorbate and dehydroascorbate to generate ascorbate free radical. The transfer of labeled membrane constituents from the Golgi apparatus to the plasma membrane supported by NADH plus ascorbate radical was stimulated by a cytosol fraction enriched in less than 10 kDa components. This was without effect in the absence of NADH/ascorbate radical or with ATP as the energy source. Specific transfer was inhibited by both N-ethylmaleimide and GTP gamma S. The findings point to the possibility of redox activities associated with the trans region of the Golgi apparatus as potentially involved in the transport of membrane vesicles from the Golgi apparatus to the cytoplasmic surface of the plasma membrane.

Animals↗
PubMed1992

GenBank.

The GenBank nucleotide sequence database now contains sequence data and associated annotation corresponding to 85,000,000 nucleotides in 67,000 entries from a total of 3,000 organisms. The input stream of data coming into the database is primarily as direct submissions from the scientific community on electronic media, with little or no data being keyboarded from the printed page by the databank staff. The data are maintained in a relational database management system and are made available in flatfile form through on-line access, and through various network and off-line computer-readable media. The data are also distributed in relational form through satellite copies at a number of institutions in the U.S. and elsewhere. In addition, GenBank provides the U.S. distribution center for the BIOSCI electronic bulletin board service.

Animals↗
PubMed1992

Acetabular micromotion as a measure of initial implant stability in primary hip arthroplasty. An in vitro comparison of different methods of initial acetabular component fixation.

Micromotion has been shown to affect bony ingrowth into cementless components. This study was designed both to quantitate initial micromotion at the prosthesis-periacetabular bony interface and to compare different methods of commonly employed acetabular component fixations, ie, a press-fit hemispherical titanium cup, a press-fit hemispherical titanium cup with one and two dome screws, a press-fit titanium hemispherical cup with three spikes, and a cemented chromium-cobalt cup. The press-fit component without screws demonstrated the greatest motion equaling 162 microns at the ilium, 97 microns at the publis, and 54 microns at the ischium. With one and two screws placed into the dome, the mean ileal displacement decreased by 28 microns (17%) and 36 microns (22%), respectively. Dome screw placement demonstrated a minimal effect at the pubis and ischium. Compared to the press-fit component without augmentation, the tri-spike motion was less at the pubis and ischium. The cemented prosthesis provided the least amount of motion in all three areas tested. This experiment demonstrates that the ilium provides the least amount of support to immediate acetabular fixation, while the pubis (anterior column) and ischium (posterior column) provide more stability. One dome screw does not affect the stability of a hemispherical prosthetic cup significantly. A two dome screw fixation provides an added method of support at the ilium, but fails to decrease motion at the pubis or ischium significantly. The tri-spike fixation does not restrict motion at the ilium to the extent as the dome screws, but its effect at the ischium and pubis is much more pronounced. The obvious difference between initial motion seen with cemented versus uncemented components may suggest that before surgery, patients may need a period of protected weight bearing until ingrowth has occurred.

Acetabulum↗
PubMed1992

Childhood through the eyes of child psychiatrists and paediatricians.

Attitudes to childhood in general and towards one's own childhood in particular are compared in a survey of 152 Australian and New Zealand child psychiatric and paediatric trainees. Results confirm the findings of Enzer et al that paediatricians view childhood more positively than do child psychiatrists. Although there is a significant difference between the two groups on measures of their perceptions of the parenting they received with child psychiatrists rating their own parents as less caring than do paediatricians, there is no relationship between attitudes to childhood and perceptions of the parenting they received. Implications of these findings are examined, both in terms of motivation for choosing one or other specialty and for the working relationship between the two professions.

Adult↗