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J L Williams

Publications and source records attributed to J L Williams.

At least 109 records · Page 6Linked to original sources
PubMed1998

Inhibition of the interaction between tyrosine-based motifs and the medium chain subunit of the AP-2 adaptor complex by specific tyrphostins.

Several intracellular membrane trafficking events are mediated by tyrosine-containing motifs found within the cytosolic domains of certain integral membrane proteins. Many of these tyrosine motifs conform to the consensus YXXPhi (where Phi represents a bulky hydrophobic residue). This YXXPhi motif has been shown to interact with the medium chain subunits of adaptor complexes that generally link relevant integral membrane protein cytosolic domains to the clathrin coat involved in vesicle formation. The motif YXXPhi is also very similar to motifs that are targets for phosphorylation by tyrosine kinases. Tyrosine kinase inhibitors known as tyrphostins are structural analogues of tyrosine, and so it is possible that tyrphostins could also inhibit interactions between medium chains and YXXPhi motifs. TGN38 is a type I integral membrane protein containing a tyrosine motif, YQRL, within the cytosolic domain. We have previously shown that this motif interacts directly with the medium chain subunit of the plasma membrane localized AP-2 adaptor complex (mu2). We have investigated a range of tyrphostins and demonstrated a specific inhibition of the interaction between mu2 and the TGN38 cytosolic domain by tyrphostin A23 through in vitro analysis and the yeast two-hybrid system. These data raise the exciting possibility that different membrane traffic events could be inhibited by specific tyrphostins.

Adaptor Protein Complex 1↗
PubMed1998

Efficiency of cationic lipid-mediated transfection of polarized and differentiated airway epithelial cells in vitro and in vivo.

Systematic analysis of a large number of different cationic lipids has led to the identification of novel structures (GL-67) and formulations of cationic lipid:plasmid DNA (pDNA) complexes that facilitate high levels of gene expression in lungs of mice. However, despite significant improvement in gene transfer activity, we show here that the efficiency of GL-67-mediated gene transduction of intact airway epithelia is still relatively low. Administration of GL-67:pCF1-CFTR (encoding the cystic fibrosis transmembrane conductance regulator) complexes into the nasal epithelium of cystic fibrosis (CF) transgenic mice resulted only in marginal correction of the ion transport defects. Measurements of nasal potential differences (PD) showed no correction of the sodium (Na+) transport defect, and only partial restitution of the chloride (Cl-) transport defect was achieved in a small proportion of the animals after perfusion of the nasal epithelium with the complexes. Furthermore, in contrast to results obtained following instillation of GL-67:pDNA complexes into the lungs of mice, perfusion of GL-67:pDNA into the nasal epithelium resulted only in a moderate enhancement of gene transduction activity relative to that attained with naked pDNA alone. To determine the basis for this low efficiency of transfection, a series of studies was conducted to identify some of the barriers governing cationic lipid-mediated gene transfer to the airway epithelium. We show here that the transfection activity of GL-67 was affected by the polarization, differentiation, and proliferative state of the cells. Diminished transfection activity was observed with nonmitotic, highly polarized and differentiated airway epithelial cells. This observed reduction in gene expression with nonmitotic cells was determined to be due in part to inefficient nuclear translocation of the pDNA from the cytoplasm. Together these data indicate that much improvement in the ability of cationic lipids to transfect polarized and differentiated airway epithelial cells is a necessary prerequisite for effective cationic lipid-mediated gene therapy of airway diseases such as CF.

Animals↗
PubMed1998

Thrombopoietin requires additional megakaryocyte-active cytokines for optimal ex vivo expansion of megakaryocyte precursor cells.

Little is known concerning the interaction of thrombopoietin (TPO) with other megakaryocyte-active cytokines in directing the early events of megakaryocyte development. Culture of CD34(+) cells in interleukins (IL) -1, -6, -11, plus stem cell factor (SCF; S) results in a 10- to 12-fold expansion in total cell numbers, whereas total CD41(+) megakaryocytes are expanded approximately 120-fold over input levels. Addition of TPO to IL-1, -6, -11, S generates a biphasic proliferation of CD41(+) cells, accelerates their rate of production, and results in an ex vivo expansion of more than 200-fold. The addition of Flt-3 ligand (FL) increases CD41+ cell expansion to approximately 380-fold over input levels. In the absence of TPO, approximately 95% of the expanded cells show the phenotype of promegakaryoblasts; TPO and/or FL addition increases CD41 antigen density and ploidy in a subpopulation of promegakaryoblasts. A moderate (approximately sevenfold) expansion of megakaryocyte progenitor cells (colony-forming unit-megakaryocyte) occurs in the presence of IL-1, -6, -11, S, and the addition of TPO to this cocktail yields an approximately 17-fold expansion. We conclude that early proliferative events in megakaryocyte development in vitro are regulated by multiple cytokines, and that TPO markedly affects these early developmental steps. However, by itself, TPO is neither necessary nor sufficient to generate a full proliferative/maturational in vitro response within the megakaryocyte compartment. TPO clearly affects terminal differentiation and the development of (some) high-ploidy human megakaryocytes. However, its limited in vitro actions on human cell polyploidization suggest that additional megakaryocyte-active cytokines or other signals are essential for the maximal development of human megakaryocytes.

Adult↗
PubMed1998

Respiratory system compliance decreases after cardiopulmonary resuscitation and stomach inflation: impact of large and small tidal volumes on calculated peak airway pressure.

The purpose of the present study was to evaluate respiratory system compliance after cardiopulmonary resuscitation (CPR) and subsequent stomach inflation. Further, we calculated peak airway pressure according to the different tidal volume recommendations of the European Resuscitation Council (7.5 ml/kg) and the American Heart Association (15 ml/kg) for ventilation of an unintubated cardiac arrest victim. After 4 min of ventricular fibrillation, and 6 min of CPR, return of spontaneous circulation (ROSC) after defibrillation occurred in seven pigs. Respiratory system compliance was measured at prearrest, after ROSC, and after 2 and 4 l of stomach inflation in the postresuscitation phase; peak airway pressure was subsequently calculated. Before cardiac arrest the mean (+/- S.D.) respiratory system compliance was 30 +/- 3 ml/cm H2O, and decreased significantly (P < 0.05) after ROSC to 24 +/- 5 ml/cm H2O, and further declined significantly to 18 +/- 4 ml/cm H2O after 2 l, and to 13 +/- 3 ml/cm H2O after 4 l of stomach inflation. At prearrest, the mean +/- S.D. calculated peak airway pressure according to European versus American guidelines was 9 +/- 1 versus 18 +/- 3 cm H2O, after ROSC 12 +/- 2 versus 23 +/- 4 cm H2O, and 15 +/- 2 versus 30 +/- 5 cm H2O after 2 l, and 22 +/- 6 versus 44 +/- 12 cm H2O after 4 l of stomach inflation. In conclusion, respiratory system compliance decreased significantly after CPR and subsequent induction of stomach inflation in an animal model with a wide open airway. This may have a significant impact on peak airway pressure and distribution of gas during ventilation of an unintubated patient with cardiac arrest.

Airway Resistance↗
PubMed1998

Genetic variation within the Hereford breed of cattle.

Genetic differentiation among Hereford populations from Britain, Ireland, Sweden, Canada and New Zealand together with six other beef breeds was assessed using blood type polymorphisms. Changes in the genetic structure of the British Hereford population over time were also examined. Loci surveyed were seven red cell antigen systems (A, B, C, F, L, S, Z), and two serum protein loci (transferrin and albumin). Within group variation was measured by the average expected heterozygosity, and between group relationships by genetic distance. There was significant genetic differentiation among Hereford populations from different countries. Differences between Hereford groups, however, were not as large as differences between breeds. There were also significance differences among British herds. The proportion of Canadian genes in the British 'hybrid' population was estimated to have increased from 0.42 (+/- 0.34) in the 1970s to 0.98 (+/- 0.11) in the 1990s. Canadian Hereford groups were found to be less heterozygous than other groups, and replacement of the British population with Canadian animals may lead to loss of variation. Breeding strategies that preserve original native genes in British Hereford populations should be considered by commercial breeders, in order to prevent the long-term loss of genetic variation within the breed.

Alleles↗
PubMed1998

Genetic relationships among European cattle breeds.

Genetic relationships among 37 European cattle breeds were investigated using blood group and serum protein polymorphisms. The 18,859 animals included in the study represented a random sample from pedigree populations in the UK. Within-breed variation was estimated by average heterozygosity and number of alleles observed, and breed relationships were evaluated by genetic distance. Standard errors of the heterozygosity, number of alleles and genetic distance were obtained by bootstrapping. The significance of breed differences was tested using an exact test of differentiation. French, Italian and Channel Island breeds were found to have generally higher heterozygosities and a greater number of alleles than breeds from mainland Britain and North Europe. Genetic distances ranged between 0.011 (+/- 0.005) and 0.309 (+/- 0.071). Two major breed groups were identified; a group of French, Italian and Channel Island breeds together with the Simmental and Gelbvieh, and a second group consisting of the mainland British and North European breeds. The exact test of breed differentiation showed all breeds to be significantly different from one another (P < 0.0001). Overall relationships among breeds reflected their geographical origin and common ancestry rather than the agricultural use for which the breeds have been selected.

Alleles↗
PubMed1998

Bovine microsatellite loci are highly conserved in red deer (Cervus elaphus), sika deer (Cervus nippon) and Soay sheep (Ovis aries).

We tested 174 bovine microsatellite primer pairs for use in a primitive breed of sheep and two species of deer. Of 173 markers, 127 (73.4%) gave a product in Soay sheep (Ovis aries) of which 54 (42.5%) were polymorphic. One hundred and twenty-nine of 174 (74.1%) markers gave a product in red deer (Cervus elaphus) of which 72 (55.8%) were polymorphic. In sika deer (Cervus nippon) 126 of 171 (73.7%) microsatellite primers gave a product with 47 (37.3%) polymorphic. The proportion of bovine microsatellite loci conserved across artiodactyl species was significantly greater in this study than previously reported. Reasons for this high degree of microsatellite conservation are discussed. We suggest that a high resolution comparative map of the artiodactyls can be constructed using microsatellites.

Alleles↗
PubMed1998

Influence of tidal volume on the distribution of gas between the lungs and stomach in the nonintubated patient receiving positive-pressure ventilation.

OBJECTIVES: When ventilating a nonintubated patient in cardiac arrest, the European Resuscitation Council has recently recommended a decrease in the tidal volume from 0.8 to 1.2 L to 0.5 L, partly in an effort to decrease peak flow rate, and therefore, to minimize stomach inflation. The purpose of the present study was to examine the validity of the European Resuscitation Council's recommendation in terms of gas distribution between lungs and stomach in a bench model that simulates ventilation of a nonintubated patient with a self-inflatable bag representing tidal volumes of 0.5 and 0.75 L. DESIGN: A bench model of a patient with a nonintubated airway was used consisting of face mask, manikin head, training lung (lung compliance, 50 mL/cm H2O; airway resistance, 5 cm H2O/L/sec), adjustable lower esophageal sphincter pressure (LESP) and simulated stomach. SETTING: University hospital laboratory. SUBJECTS: Thirty healthcare professionals. INTERVENTIONS: Healthcare professionals performed 1-min bag-mask ventilation at each LESP level of 5, 10, and 15 cm H2O at a rate of 12 breaths/min, using an adult and pediatric self-inflating bag, respectively. Volunteers were blinded to the LESP, which was randomly varied. MEASUREMENTS AND MAIN RESULTS: Both types of self-inflating bags induced stomach inflation, with higher stomach and lower lung tidal volumes when the LESP was decreased. Lung tidal volume with the pediatric bag was significantly (p < .05) lower at all LESP levels when compared with the adult bag, and ranged between 240 mL at an LESP of 15 cm H2O and 120 mL at an LESP of 5 cm H2O. Stomach tidal volume with the adult bag ranged between 250 mL at an LESP of 15 cm H2O and increased to 550 mL at an LESP of 5 cm H2O. Stomach tidal volume with the pediatric bag was significantly lower (p < .05) at all LESP levels when compared with the adult bag and ranged between 70 mL at an LESP of 15 cm H2O and 300 mL at an LESP of 5 cm H2O. CONCLUSIONS: Our data support the recommendation of the European Resuscitation Council to decrease tidal volumes to 0.5 L when ventilating a cardiac arrest victim with an unprotected airway. A small tidal volume may be a better trade-off in the basic life support phase, as this may provide reasonable ventilation while avoiding massive stomach inflation.

Adult↗
PubMed1998

Total shoulder arthroplasty biomechanics: a study of the forces and strains at the glenoid component.

The objective of this study was to examine how changes in glenohumeral joint conformity and loading patterns affected the forces and strains developed at the glenoid. After removal of soft tissue (muscles, ligaments, and labrum), force-displacement data were collected for both natural and prosthetically reconstructed joints. Joints were shown to develop higher forces for a given translation as joint conformity increased. A rigid body model of joint contact forces was used to determined the so-called effective radial mismatch of each joint. For the purposes of this study, the effective radial mismatch is defined as the mismatch required for a rigid body joint to have the same force-displacement relationship as the joint in question. This parameter is an indication of the deformation at the articular surface. The effective radial mismatch dramatically increased with increasing medial loads, indicating that under physiological loads, the effective radial mismatch of a joint is much greater than its measured mismatch at no load. This increase in effective mismatch as medial loads were increased was found to be threefold greater in cartilaginous joints than in reconstructed joints. Rosette strain gages positioned at the midlevel of the glenoid keel in the reconstructed joints revealed that anterior/posterior component loading leads to fully reversible cyclic keel strains. The highest compressive strains occurred with the head centered in the glenoid, and were larger for nonconforming joints (epsilon = 0.23 percent). These strains became tensile just before rim loading and were greater for conforming joints (epsilon = 0.15 percent). Although recorded peak strains are below the yield point for polyethylene, the fully reversed cyclic loading of the component in this fashion may ultimately lead to component toggling and implant failure.

Aged↗
PubMed1998

Differential modulation of G1-S-phase cyclin-dependent kinase 2/cyclin complexes occurs during the acquisition of a polyploid DNA content.

Despite a growing understanding of the biochemical mechanisms controlling the cell cycle, information regarding the temporal ordering of S phase and M phase remains scarce. Polyploid cells represent a useful model for examining S- and M-phase control, because their cell cycle machinery must be modulated to retain high levels of DNA content (ploidy) within a single nucleus. To evaluate the mechanisms of S-phase control during the process of polyploidization, we investigated the modulations that occur in cyclin-dependent kinase (CDK) complexes during the induction of megakaryocyte differentiation in human erythroleukemia cells. We report that during polyploidization, megakaryocytic human erythroleukemia cells undergo a dramatic modulation in the subunit composition of G1-associated and S phase-associated CDK complexes and a marked increase in their specific activities. This, in turn, is facilitated by a differential loss of the p21 or p27 CDK-inhibitory protein/kinase-inhibitory proteins (CIP/KIP) bound to specific cyclin/CDK complexes. The data show that the loss of S- and M-phase control in polyploid cells occurs within the context of an up-regulated function in those CDK complexes associated with both G1-S-phase transit and S-phase progression. Additional studies regarding the regulation of these complex CDK interactions will be important to understand cell cycle control in such diverse processes as megakaryocyte differentiation or the types of genomic instability that occur in cancer cells.

CDC2-CDC28 Kinases↗
PubMed1997

Verification of the identity of bovine semen using DNA microsatellite markers.

Over the past 30 years cattle have been identified by blood typing, but recently the use of DNA markers has provided a more precise method of identifying individuals and verifying their parentage. This article describes the use of microsatellite-based DNA markers for confirming the identity of semen, as part of the evidence presented in a legal dispute. Two panels of markers and two methods for identifying allelic variation are compared; for both approaches the likelihood of finding two Charolais individuals with the same genotype was less than one in a million. Animals can therefore be identified conclusively from DNA samples, a technique which could be of use when their identity is in dispute.

Alleles↗
PubMed1997

Autoregulation of blood flow to choroid plexus of rabbits.

Blood flow to the choroid plexus (CP) of rabbits was measured before and during an increase in arterial pressure (AP). Blood flow returned to control levels in the CP of the lateral and fourth ventricles of the brain when AP was increased 63% by i.v. infusion of norepinephrine. However, when AP was increased 68% by occlusion of the descending thoracic aorta, blood flow to the CP of the fourth ventricle remained elevated, while blood flow to the CP of the lateral ventricles returned to the control level. Our findings suggest that blood flow to the CP of the lateral ventricles autoregulates during nonpharmacological or pharmacological increases in AP, while blood flow to CP of the fourth ventricle does not autoregulate during nonpharmacological increases in AP.

Animals↗
PubMed1997

A medium-density genetic linkage map of the bovine genome.

A cattle genetic linkage map was constructed which covers more than 95 percent of the bovine genome at medium density. Seven hundred and forty six DNA polymorphisms were genotyped in cattle families which comprise 347 individuals in full sibling pedigrees. Seven hundred and three of the loci are linked to at least one other locus. All linkage groups are assigned to chromosomes, and all are orientated with regards to the centromere. There is little overall difference in the lengths of the bull and cow linkage maps although there are individual differences between maps of chromosomes. One hundred and sixty polymorphisms are in or near genes, and the resultant genome-wide comparative analyses indicate that while there is greater conservation of synteny between cattle and humans compared with mice, the conservation of gene order between cattle and humans is much less than would be expected from the conservation of synteny. This map provides a basis for high-resolution mapping of the bovine genome with physical resources such as Yeast and Bacterial Artificial Chromosomes as well as providing the underpinning for the interpolation of information from the Human Genome Project.

Animals↗
PubMed1997

Cosmid-derived markers anchoring the bovine genetic map to the physical map.

The mapping strategy for the bovine genome described in this paper uses large insert clones as a tool for physical mapping and as a source of highly polymorphic microsatellites for genetic typing, and was one objective of the BovMap Project funded by the European Union (UE). Eight-three cosmid and phage clones were characterized and used to physically anchor the linkage groups defining all the bovine autosomes and the X Chromosome (Chr). By combining physical and genetic mapping, clones described in this paper have led to the identification of the linkage groups corresponding to Chr 9, 12, 16, and 25. In addition, anchored loci from this study were used to orient the linkage groups corresponding to Chr 3, 7, 8, 9, 13, 16, 18, 19, and 28 as identified in previously published maps. Comparison of the estimated size of the physical and linkage maps suggests that the genetic length of the bovine genome may be around 4000 cM.

Animals↗