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C Stephens

Publications and source records attributed to C Stephens.

At least 19 recordsLinked to original sources
PubMed2025

Chromosome scale genomes of two invasive Adelges species enable virtual screening for selective adelgicides.

Two invasive hemipteran adelgids are associated with widespread damage to several North American conifer species. Adelges tsugae, hemlock woolly adelgid, was introduced from Japan and reproduces parthenogenetically in North America, where it has rapidly decimated Tsuga canadensis and Tsuga caroliniana (the eastern and Carolina hemlocks, respectively). Adelges abietis, eastern spruce gall adelgid, introduced from Europe, forms distinctive pineapple-shaped galls on several native spruce species. While not considered a major forest pest, it weakens trees and increases susceptibility to additional stressors. Broad-spectrum insecticides that are often used to control adelgid populations can have off-target impacts on beneficial insects. Whole genome sequencing was performed on both species to aid in development of targeted solutions that may minimize ecological impact. Adelges abietis was sequenced using Illumina Linked-Read technology from 30 pooled individuals, with Hi-C scaffolding performed using data from a single individual collected from the same host plant. Adelges tsugae used Oxford Nanopore long-read sequencing from pooled nymphs. The assembled A. tsugae and A. abietis genomes, pooled from several parthenogenetic females, are 220.75 Mbp and 253.16 Mbp, respectively. Each consists of eight autosomal chromosomes, as well as two sex chromosomes (X1/X2), supporting the XX-XO sex determination system. The genomes are over 96% complete based on BUSCO assessment. Genome annotation identified 11,424 and 12,060 protein-coding genes in A. tsugae and A. abietis, respectively. Comparative analysis of proteins across 29 hemipteran species and 14 arthropod outgroups identified 31,666 putative gene families. Gene family evolution analysis with CAFE revealed lineage-specific expansions in immune-related aminopeptidases (ERAP1) and juvenile hormone binding proteins (JHBP), contractions in juvenile hormone acid methyltransferases (JHAMT), and conservation of nicotinic acetylcholine receptors (nAChR). These genes were explored as candidate families towards a long-term objective of developing adelgid-selective insecticides. Structural comparisons of proteins across seven focal species (Adelges tsugae, Adelges abietis, Adelges cooleyi, Rhopalosiphum maidis, Apis mellifera, Danaus plexippus, and Drosophila melanogaster) revealed high conservation of nAChR and ERAP1, while JHAMT exhibited species-specific structural divergence. The potential of JHAMT as a lineage-specific target for pest control was explored through virtual drug and pesticide screening.

adelgids↗
PubMed1992

Policy directions in urban health in developing countries--the slum improvement approach.

The urban development, or housing, sector has a longer experience of addressing the problems of the urban poor in developing countries than the health sector. In recent years the policy of 'slum improvement', which involves both sectors, has attracted the support of international donors. This article documents the development of the slum improvement approach and addresses key issues of the approach which have implications for health planning: covering the poorest dwellers; relocation; land tenure; gentrification; debt burdens and the impact on women. Questions about the approach which still need answering are defined and a summary of the constraints in slum improvement and potential solutions is presented.

Developing Countries↗
PubMed1991

Fibronectin and VLA-4 in haematopoietic stem cell-microenvironment interactions.

The self-renewal and differentiation of haematopoietic stem cells occurs in vivo and in vitro in direct contact with cells making up the haematopoietic microenvironment. In this study we used adhesive ligands and blocking antibodies to identify stromal cell-derived extracellular matrix proteins involved in promoting attachment of murine haematopoietic stem cells. Here we report that day-12 colony-forming-unit spleen (CFU-S12)5 cells and reconstituting haematopoietic stem cells attach to the C-terminal, heparin-binding fragment of fibronectin by recognizing the CS-1 peptide of the alternatively spliced non-type III connecting segment (IIICS) of human plasma fibronectin. Furthermore, CFU-S12 stem cells express the alpha 4 subunit of the VLA-4 integrin receptor, which is known to be a receptor for the CS-1 sequence, and monoclonal antibodies against the integrin alpha 4 subunit of VLA-4 block adhesion of CFU-S12 stem cells to plates coated with the C-terminal fibronectin fragment. Finally, polyclonal antibodies against the integrin beta 1 subunit of VLA-4 inhibit the formation of CFU-S12-derived spleen colonies and medullary haematopoiesis in vivo following intravenous infusion of antibody-treated bone marrow cells.

Animals↗
PubMed1991

Subacute cutaneous lupus erythematosus--the annular variant. A histological and ultrastructural study of five cases.

Subacute cutaneous lupus erythematosus is an uncommon, non-scarring variant of lupus erythematosus which has received scant attention in the pathology literature. Its recognition as a distinct entity is important, as, although mild systemic features may be associated, there is characteristically a relative absence of life-threatening renal or central nervous systemic involvement. Subacute cutaneous lupus erythematosus may be clinically sub-divided into the more common annular and the rarer papulosquamous (psoriasiform) variants. A clinicopathological study of five cases of the annular variant is presented with a review of the literature. We highlight the histological and ultrastructural appearances. Discriminatory features from the other variants of lupus erythematosus and additional conditions with which it may be confused, including lichen planus and acute graft-versus-host disease, are discussed.

Adult↗
PubMed1991

Is rheumatoid arthritis in Indians associated with HLA antigens sharing a DR beta 1 epitope?

HLA class II antigens were identified in a group of 44 patients with rheumatoid arthritis (RA) originating largely from the north or northeast of the Indian subcontinent and resident now in east London. Compared with 67 locally typed east London Asian controls, the prevalence of three HLA-DR antigens was raised in the patients: DR1 18.2% v 6.0% chi 2 = 3.99, DR4 20.5% v 11.9% chi 2 = 1.48, and DRw10 27.3% v 8.9% chi 2 = 6.56. These differences were also found when the patients with RA were compared with a larger control group of 110 northern Indians: DR1 18.2% v 7.2% chi 2 = 4.02, DR4 20.5% v 7.2% chi 2 = 5.56, and DRw10 27.3% v 8.1% chi 2 = 9.7. Twenty five (57%) of the patients expressed at least one of these antigens. All patients were also characterised for HLA-Dw types by mixed lymphocyte culture typing. The prevalence of the HLA-DR4 associated Dw types in the patients was: Dw4 2.3%, Dw10 0%, Dw14 11.4%, and Dw15 6.8%. The DR beta 1 chains of DR1 and DRw10 together with the Dw types of DR4 other than Dw10 share amino acid residues in a region of the third hypervariable region considered to be critical in antigen presentation. It is concluded that RA in Indians is associated with these HLA antigens, and data from this study support the hypothesis of a cross reactive epitope common to HLA specificities associated with RA.

Arthritis, Rheumatoid↗
PubMed1991

Newly synthesized glycoconjugates from two cell lines derived from rat osteogenic sarcoma: effects of Matrigenin activity from bone.

An activity isolated from bovine bone was previously shown to stimulate proteoglycan synthesis by several connective tissue cell lines from normal tissues (Matrigenin activity). The effect of this activity on glycoconjugate synthesis by two osteoblastic cell lines, ROS 17/2 and UMR-106, derived from rat osteogenic sarcoma, was examined after labelling of the cells with [3H]glucosamine and [35S]sulfate. The glycoconjugates from the cell layers and the media were separated by DEAE-Sephacel chromatography and the anionic glycoconjugates of the media were further analyzed by chromatography on Sepharose CL-2B and enzymatic digestion of the papain-released glycosaminoglycans. The ROS 17/2 cells secreted at least two distinct species of proteoglycan (one heparan sulfate rich and the other chondroitin sulfate rich), whereas the UMR-106 secreted primarily an anionic glycoprotein. The addition of Matrigenin activity to the ROS 17/2 cells resulted in stimulation of incorporation of radioactivity into the proteoglycan and hyaluronic acid, but in UMR-106 cultures it resulted in decreased incorporation into the anionic glycoprotein. The decrease in incorporation into the anionic glycoprotein from the medium was shown, by alkaline beta-elimination, to have occurred mainly in the oligosaccharide fraction, relative to control cultures.

Animals↗
PubMed1991

Teaching problem handling in general practice: a computer assisted learning software package for medical students.

A computer assisted learning software package for medical students, EnMesh, designed to increase understanding of the problem-handling skills needed in general practice has been developed at the University of Liverpool. Users access the system anonymously and respond in sequence to problems in the form of clinical vignettes. Responses to each problem, in the form of up to six two-line text statements, are generated by the user with a simple word processing facility. Users compare their responses with those of established general practitioners, searching for similar or matching ideas. After completing not less than four problems users are provided with feedback on their performance in relation to the physical, psychological and social dimensions of the problems. The frequency with which the system is being used and the results of self scoring are monitored by a parallel teacher programme. The programmes are designed to run on a wide range of microcomputers. EnMesh was designed to provide an informal learning resource within an established clinical course. The challenge of valid problems, the option to respond anonymously, self scoring and feedback on performance are features designed to attract student participation in computer assisted learning. Although in EnMesh the expert data is categorized in three dimensions, in designing such software the number of categories is limited solely by the range of responses which feedback is required to reflect.

Computer-Assisted Instruction↗
PubMed1991

Urbanization and health in developing countries.

In developing countries the level of urbanization is expected to increase to 39.5% by the end of this century and to 56.9% by 2025. The number of people living in slums and shanty towns represent about one-third of the people living in cities in developing countries. This article focuses upon these poor urban populations and comments upon their lifestyle and their exposure to hazardous environmental conditions which are associated with particular patterns of morbidity and mortality. The concept of marginality has been used to describe the lifestyle of the urban poor in developing countries. This concept is critically examined and it is argued that any concept of the urban poor in developing countries being socially, economically or politically marginal is a myth. However, it can certainly be claimed that in health terms the urban poor are marginal as demonstrated by some of the studies reviewed in this article. Most studies of the health of the urban poor in developing countries concentrate on the environmental conditions in which they live. The environmental conditions of the urban poor are one of the main hazards of the lifestyle of poor urban residents. However, other aspects of their way of life, or lifestyle, have implications for their health. Issues such as smoking, diet, alcohol and drug abuse, and exposure to occupational hazards, have received much less attention in the literature and there is an urgent need for more research in these areas.

Developing Countries↗
PubMed1991

Complement activation during prolonged extracorporeal membrane oxygenation.

Short-term cardiopulmonary bypass activates the complement system, possibly resulting in pulmonary dysfunction from granulocyte aggregation and pulmonary endothelial damage. These effects may be inhibited by steroids. Prolonged extracorporeal membrane oxygenation (ECMO) is used for newborn respiratory failure, but the effects of ECMO on complement activation are unknown. Twenty-one newborn infants with respiratory failure treated with ECMO were randomly assigned to group I (control, no steroids) or group II (30 mg/kg intravenous methylprednisolone before ECMO). Depletion assays of C3 and C5 were performed in each group at intervals before and during ECMO (declining values indicate complement activation). The groups were compared for complement levels, survival, time on ECMO and on the ventilator, and total hospitalization time. Steroids significantly shortened the time on ECMO and time on the ventilator after ECMO but did not affect survival or total hospitalization time. Steroids also enhanced activation of C3 and C5. Complement activation occurs during ECMO. Steroid administration paradoxically causes earlier complement activation but shortens ECMO and ventilator times. Complement activation during ECMO is of questionable significance. The benefits of steroids during ECMO may be mediated through other mechanisms.

Birth Weight↗
PubMed1990

Prognostic determinants in extracorporeal membrane oxygenation for respiratory failure in newborns.

Extracorporeal membrane oxygenation (ECMO) is becoming an accepted therapeutic modality for newborn respiratory failure, but there is little information available regarding the prognostic determinants with this technique. One hundred thirty-five newborns treated with ECMO over a 4-year period were critically analyzed with regard to the influence that birth weight, gestational age, age at initiation of ECMO, best blood gases before ECMO, number of hours on ECMO, renal failure, intracerebral hemorrhage, and long-distance air transport had on survival. Infants with meconium aspiration and those undergoing long-distance transfer showed significant differences in blood gases before ECMO, with survivors having more normal pH and carbon dioxide tension values. Intracerebral hemorrhage and renal failure that developed during ECMO were grave prognostic signs, with few survivors in either group. These data show that ability to ventilate patients before ECMO, giving normal carbon dioxide tension and pH values, is an important prognostic sign in infants with meconium aspiration and undergoing long-distance transfer for ECMO, whereas renal failure and intracerebral hemorrhage are usually lethal complications of ECMO. Each center performing ECMO should continually reevaluate this invasive technique and its results and complications.

Acute Kidney Injury↗
PubMed1990

Holograms as substitutes for orthodontic study casts: a pilot clinical trial.

A pilot study of holograms as substitutes for study casts during routine clinical treatment was carried out by four clinicians on 56 patients over a 6-month period. Three of the clinicians found holograms to be as informative as study casts and equally or more convenient, but one clinician considered holograms to be inferior to study casts in both these respects. In addition, replicate quantification of malocclusions by means of the Summers index showed very similar rates of random error for holograms and for study casts and no significant systematic error between the scores obtained. Currently available holograms merit further investigation as alternatives to study casts. Refinement to further improve the convenience, informativeness, and economy of the holograms is also being undertaken.

Holography↗
PubMed1989

A critical analysis of extracorporeal membrane oxygenation for congenital diaphragmatic hernia.

Despite advances made in the care of infants with congenital diaphragmatic hernia (CDH), survival remains poor. New therapy, such as extracorporeal membrane oxygenation (ECMO), is controversial but may improve survival. Thirty-two newborns with CDH were treated. Thirteen infants were treated with jugular vein-carotid artery ECMO after CDH repair elsewhere; six (46%) survived. Three of the remaining 19 were moribund shortly after birth and first received ECMO, then underwent repair; two (67%) survived. The other 16 underwent CDH repair; 8 of 9 (89%) recovered with conventional therapy, and 4 of 7 (57%) survived when ECMO was used after conventional therapy failed. Overall survival was 63%. Parameters with which physicians may attempt to predict survival or the need for ECMO after repair--such as A-aDO2, ventilatory index versus PCO2, presence of a "honeymoon period" (PaO2 greater than 100 mm Hg after repair), or oxygenation index--were unreliable. ECMO can improve survival in infants with CDH, probably through reversal of pulmonary hypertension. Presently available methods of predicting survival after CDH repair with or without ECMO are not accurate, and thus no infant should be excluded from repair or ECMO support.

Extracorporeal Membrane Oxygenation↗
PubMed1987

Differential splicing yields novel adenovirus 5 E1A mRNAs that encode 30 kd and 35 kd proteins.

In addition to the protein products of the adenovirus E1A 13S and 12S mRNAs, monoclonal antibodies specific for the E1A proteins immunoprecipitate polypeptides with relative mol. wt of 30,000 (30 kd) and 35,000 (35 kd) from extracts of infected cells. The 30 kd and 35 kd proteins are encoded by novel mRNAs referred to as the 10S and 11S mRNAs, respectively. These two mRNAs arise from differential splicing of the E1A precursor RNA. For the 10S mRNA, the precursor is spliced twice, once removing the region between nucleotides 637 and 854 and once between 974 and 1229. The splice between nucleotides 974 and 1229 is identical to the one used for the processing of the 12S mRNA. Synthesis of the 11S mRNA also utilizes two splicing events. One of these is identical to the 637/854 splice of the 10S mRNA, and the other removes the region between nucleotides 1112 and 1229, a splice junction also found in the 13S mRNA. All four mRNAs used the same reading frame and, therefore, code for related proteins. The products of the 10S and 11S mRNAs are identical to the products of the 12S and 13S mRNAs, respectively, except for an internal stretch of 27 amino acids removed by the 637/854 splice. Within this segment is a group of amino acid residues that is highly conserved between different adenovirus serotypes. Mutant adenoviruses in which the wild-type E1A sequences have been replaced with cDNA copies of the 10S or 11S mRNAs are defective for growth on HeLa cells suggesting that this region is important for viral growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenovirus Early Proteins↗
PubMed1987

Comparison of the stimulation of glycosaminoglycan synthesis in cultures of mononuclear cells from blood and of fibroblastic cells.

A small molecular weight factor, derived from bovine bone ('matrigenin'), stimulated glycosaminoglycan and proteoglycan synthesis of cultured human fibroblastic cells but not of mononuclear cells from human blood. However, proteoglycan synthesis and secretion by the mononuclear cells was stimulated by the addition of concanavalin A. The proteoglycan from the concanavalin-A-stimulated mononuclear cells was of smaller molecular weight than the proteoglycan from the 'matrigenin'-stimulated fibroblastic cells. The major increase in proteoglycan synthesis and secretion occurred much later during the culture period for concanavalin-A-stimulated mononuclear cells than for 'matrigenin'-stimulated fibroblastic cells.

Cells, Cultured↗
PubMed1987

Electrophoresis of glycosaminoglycans isolated from normal human plasma. Direct evidence for the presence of a heparin-like molecule.

It has frequently been suggested that there may normally be small quantities of heparin in human blood, but amounts so small that their direct demonstration is not possible by available methods [1-4]. In this communication, we provide direct electrophoretic visualization that heparin or a closely related substance, is present in normal human plasma. After isolating glycosaminoglycans (GAGs) from 2-3 mls of plasma, a modification of the discontinuous high voltage electrophoretic method developed by Cappelletti et al. was used to successfully separate and identify the GAGs present in six normal adults (4 men and 2 women). In each case, in addition to chondroitin-4-SO4, chondroitin-6-SO4, and heparan-SO4, we were able to show the presence of a band which corresponds to that of heparin.

Electrophoresis, Cellulose Acetate↗