Biomedical subjects

J Briggs

Publications and source records attributed to J Briggs.

At least 19 recordsLinked to original sources

PubMed2006

Reporter gene recombination in juxtaglomerular granular and collecting duct cells by human renin promoter-Cre recombinase transgene.

To assess the feasibility of using the renin promoter for expressing Cre recombinase in juxtaglomerular (JG) cells only, we generated five independent transgenic mouse lines (designated hRen-Cre) expressing Cre recombinase under control of a 12.2-kb human renin promoter. In the kidneys of adult mice Cre mRNA (RT-PCR) was found in the renal cortex, with Cre protein (immunohistochemistry) being localized in afferent arterioles and to a lower degree in interlobular arteries. Cre mRNA levels were regulated in a renin-typical fashion by changes in oral salt intake, water restriction, or isoproterenol infusion, indicating the presence of key regulatory elements within 12.2 kb of the 5'-flanking region of the human renin gene. hRen-Cre mice were interbred with both the ROSA26-EGFP and ROSA26-lacZ reporter strains to assess renin promoter activity from Cre-mediated excision of a floxed stop cassette and subsequent enhanced green fluorescent protein (EGFP) and beta-galactosidase (beta-gal) detection. In adult mice, beta-gal staining and EGFP were observed in afferent arterioles and interlobular arteries, overlapping with Cre protein expression. In addition, intense beta-gal staining was found in cortical and medullary collecting ducts where Cre expression was minimal. In embryonic kidneys, beta-gal staining was detected in the developing collecting duct system beginning at embryonic day 12, showing substantial activity of the human renin promoter in the branching ureteric bud. Our data indicate that besides its well-known activity in JG cells and renal vessels the human renin promoter is transiently active in the collecting duct system during kidney development, complicating the use of this approach for JG cell-specific excision of floxed targets.

Animals↗

PubMed2005

Reduced autoregulatory effectiveness in adenosine 1 receptor-deficient mice.

Adjustments of renal vascular resistance in response to changes in blood pressure are mediated by an interplay between the myocyte-inherent myogenic and the kidney-specific tubuloglomerular feedback (TGF) mechanisms. Using mice with deletion of the A(1) adenosine receptor (A1AR) gene, we tested the prediction that the absence of TGF, previously established to result from A1AR deficiency, is associated with a reduction in the efficiency of autoregulation. In anesthetized wild-type (A1AR+/+) and A1AR-deficient mice (A1AR-/-), glomerular filtration rate (GFR) and renal blood flow (RBF) were determined before and after reducing renal perfusion pressure through a suprarenal aortic clamp. In response to a blood pressure reduction by 15.9 +/- 1.34 mmHg in A1AR-/- (n = 9) and by 14.2 +/- 0.9 mmHg in A1AR+/+ mice (n = 8; P = 0.31), GFR fell by 187.9 +/- 37 mul/min and by 72.3 +/- 10 mul/min in A1AR-/- and A1AR+/+ mice, respectively (P = 0.013). Similarly, with pressure reductions of 14.8 +/- 1.1 and 13.3 +/- 1.5 mmHg in A1AR-/- (n = 9) and wild-type mice (n = 8), respectively (P = 0.43), RBF fell by 0.17 +/- 0.02 ml/min in A1AR-/- mice and by only 0.08 +/- 0.02 ml/min in wild-type animals (P = 0.0039). Autoregulatory indexes for both GFR and RBF were significantly higher in A1AR-/- compared with A1AR+/+ mice, indicating reduced regulatory responsiveness in the knockout animals. We conclude that autoregulation of renal vascular resistance is less complete in A1AR-deficient mice, an effect that is presumably related to absence of TGF regulation in these animals.

Animals↗

PubMed2004

Plasma renin in mice with one or two renin genes.

AIM: In the present study we have investigated whether the presence of a second renin gene exerts an overriding influence on plasma renin such that mice with two renin genes have consistently higher renin levels than mice with only one renin gene. METHODS: Plasma renin was determined as the rate of angiotensin I generation using a radioimmunoassay (RIA) kit with (plasma renin concentration, PRC) or without (plasma renin activity, PRA) the addition of purified rat angiotensinogen as substrate. RESULTS: In male 129SvJ, DBA/2 and Swiss Webster mice, strains possessing both Ren-1 and Ren-2, PRC (ng Ang I mL(-1) h(-1)) averaged 178 +/- 36, 563 +/- 57 and 550 +/- 43 while PRA was 2.9 +/- 0.5, 3.6 +/- 0.8 and 7.8 +/- 1.2. In male C57BL/6, C3H and BALB/c mice that express only Ren-1, PRC averaged 426 +/- 133, 917 +/- 105 and 315 +/- 72, and PRA was 3.4 +/- 1.0, 6.9 +/- 1.7 and 4.5 +/- 1.2. In the two renin gene A1AR-/- mice compared with the one renin gene A1AR+/+, PRC averaged 538 +/- 321 and 415 +/- 159 while PRA averaged 3.2 +/- 1.1 and 4.4 +/- 1.4 ng Ang I mL(-1) h(-1). Aldosterone levels showed no significant differences between one renin (C57BL/6, C3H and BALB/c) and two renin (129SvJ, DBA/2 and Swiss Webster) gene mice. Furthermore, by quantitative real-time polymerase chain reaction (RT-PCR) we found no correlation between the number of renin genes and whole kidney renin mRNA levels from one and two renin gene mice. CONCLUSION: Our data show that baseline plasma renin is not systematically higher in mice with two renin genes than in one renin gene mice. Thus, the presence of a second renin gene does not seem to be a major determinant of differences in PRC between different mouse strains.

Aldosterone↗

PubMed2004

Compensation of proximal tubule malabsorption in AQP1-deficient mice without TGF-mediated reduction of GFR.

AIM: By crossing aquaporin 1 (AQP1)-/- and adenosine 1 receptor (A1AR)-/- mice, we generated an animal model that combines a proximal tubular absorption defect with absence of tubuloglomerular feedback (TGF) regulation of glomerular filtration rate (GFR). The aim of studies in these animals was to determine whether a TGF-induced reduction of GFR is a prerequisite for preventing potentially fatal fluid losses. METHODS AND RESULTS: In contrast to AQP1 deficient mice, AQP1/A1AR-/- mice were found to have a normal GFR. TGF responses were abolished in these animals, in contrast to AQP1-/- mice in which TGF responses of single nephron glomerular filtration rate (SNGFR) were left-shifted. Proximal tubule fluid absorption in AQP1/A1AR-/- mice was reduced to levels previously reported for AQP1-/- mice. However, SNGFR was significantly higher in AQP1/A1AR-/- than AQP1-/- mice (10.6 +/- 0.8 nL min(-1) vs. 5.9 +/- 0.7 nL min(-1)). As a consequence of the normal GFR and the reduced proximal reabsorption distal fluid delivery was markedly higher in the double knockout compared with normal or AQP1-/- mice (5.5 +/- 0.5 nL min(-1) vs. 2.35 +/- 0.3 nL min(-1) in AQP1-/-). Despite the approximate doubling of distal fluid and Cl delivery, AQP1/A1AR-/- mice have a normal salt excretion, normal arterial blood pressure, and only a small increase in plasma renin concentration. CONCLUSION: The ability to compensate for proximal tubule malabsorption without a TGF-induced reduction of GFR attests to a remarkable adaptability of distal tubule transport mechanisms.

Absorption↗

PubMed2003

Economic costs associated with inadequate drug prescribing: an exploratory study in Chiapas, Mexico.

An exploratory study assessing the economic consequences of inadequate prescribing by health-care providers was carried out in two cities of Chiapas State, South Mexico. Two research methods were used: (a) an exit survey with pharmacy users (1190 interviews) and (b) in-depth individual interviews with patients at hospital level (19 interviews). For comparative purposes, three tracer conditions were selected: acute respiratory infection (ARI), diarrhoeal disease (DD) and hypertension. The main findings were that doctors, drug vendors at pharmacies, traditional healers, users of health-care services themselves (through self-prescription) and other health staff are all sources of inadequate prescribing and impose a substantial economic burden of unnecessary cost on health-care users. In general, treatment costs were high compared with standard treatments, and prescriptions included a high proportion of non-essential drugs (50-64%). Additional costs to the standard treatment were particularly high when the prescription was by a medical doctor (US$ 3.57 per ARI prescription and US$ 8.37 for DD). Losses attributable to inadequate prescribing averaged US$ 47 per patient. The study concludes that training programmes on rational drug use aimed exclusively at medical doctors can only have a limited effect in reducing economic losses due to inadequate prescribing. Such efforts should be extended to other providers who are very active in prescribing drugs and providing health advice. The main challenge that the Mexican health system will be facing in the foreseeable future is not only to improve equity of access to essential drugs, but also to improve quality of drug advice and prescription and rational use of drugs by the population.

Adult↗

PubMed2002

Cyclooxygenase cloning in dogfish shark, Squalus acanthias, and its role in rectal gland Cl secretion.

The present studies were carried out with the aims to determine the cDNA sequence for cyclooxygenase (COX) in an elasmobranch species and to study its role in regulation of chloride secretion in the perfused shark rectal gland (SRG). With the use of long primers (43 bp) derived from regions of homology between zebrafish and rainbow trout COX-2 genes, a 600-bp product was amplified from SRG and was found to be almost equally homologous to mammalian COX-1 and COX-2 (65%). The full-length cDNA sequence was obtained by 5'-RACE and by analyzing an EST clone generated by the EST Project of the Mt. Desert Island Biological Laboratory Marine DNA Sequencing Center. The longest open reading frame encodes a 593-amino acid protein that has 68 and 64% homology to mammalian COX-1 and COX-2, respectively. The gene and its protein product is designated as shark COX (sCOX). The key residues in the active site (Try(385), His(388), and Ser(530)) are conserved between the shark and mammalian COX. sCOX contains Val(523) that has been shown to be a key residue determining the sensitivity to COX-2-specific inhibitors including NS-398. The mRNA of sCOX, detected by RT-PCR, was found in all tissues tested, including rectal gland, kidney, spleen, gill, liver, brain, and heart, but not in fin. In the perfused SRG, vasoactive intestinal peptide (VIP) at 5 nM induced rapid and marked Cl(-) secretion (basal: <250 microeq x h(-1) x g(-1); peak response: 3,108 +/- 479 microeq x h(-1) x g(-1)). In the presence of 50 microM NS-398, both the peak response (2,131 +/- 307 microeq x h(-1) x g(-1)) and the sustained response to VIP were significantly reduced. When NS-398 was removed, there was a prompt recovery of chloride secretion to control values. In conclusion, we have cloned the first COX in an elasmobranch species (sCOX) and shown that sCOX inhibition suppresses VIP-stimulated chloride secretion in the perfused SRG.

Amino Acid Sequence↗

PubMed2001

Mediation of tubuloglomerular feedback by adenosine: evidence from mice lacking adenosine 1 receptors.

Adenosine is a determinant of metabolic control of organ function increasing oxygen supply through the A2 class of adenosine receptors and reducing oxygen demand through A1 adenosine receptors (A1AR). In the kidney, activation of A1AR in afferent glomerular arterioles has been suggested to contribute to tubuloglomerular feedback (TGF), the vasoconstriction elicited by elevations in [NaCl] in the macula densa region of the nephron. To further elucidate the role of A1AR in TGF, we have generated mice in which the entire A1AR coding sequence was deleted by homologous recombination. Homozygous A1AR mutants that do not express A1AR mRNA transcripts and do not respond to A1AR agonists are viable and without gross anatomical abnormalities. Plasma and urinary electrolytes were not different between genotypes. Likewise, arterial blood pressure, heart rates, and glomerular filtration rates were indistinguishable between A1AR(+/+), A1AR(+/-), and A1AR(-/-) mice. TGF responses to an increase in loop of Henle flow rate from 0 to 30 nl/min, whether determined as change of stop flow pressure or early proximal flow rate, were completely abolished in A1AR(-/-) mice (stop flow pressure response, -6.8 +/- 0.55 mmHg and -0.4 +/- 0.2 in A1AR(+/+) and A1AR(-/-) mice; early proximal flow rate response, -3.4 +/- 0.4 nl/min and +0.02 +/- 0.3 nl/min in A1AR(+/+) and A1AR(-/-) mice). Absence of TGF responses in A1AR-deficient mice suggests that adenosine is a required constituent of the juxtaglomerular signaling pathway. A1AR null mutant mice are a promising tool to study the functional role of A1AR in different target tissues.

Adenosine↗

PubMed2001

Molecular characterization of a novel recombinant strain of human astrovirus associated with gastroenteritis in children.

We report a naturally occurring human astrovirus (HAstV) strain detected in two different geographic locations. We identified two isolates of this strain in a diarrhea outbreak at a child care center in Houston, Texas; and two isolates in diarrhea stool samples from two children in Mexico City. All four isolates were detected in stool samples by enzyme immunoassay (EIA). One of the Mexican isolates was typed by EIA and all four isolates were HAstV-5 by typing RT-PCR. The four isolates were >97% nucleotide-identical in two different genomic regions: ORF1a (246 nt), and the 3' end of the genome (471 nt). One isolate from each geographic location was further sequenced in the transition region from ORF1b to ORF2 (1255 nt) and this region of the two isolates showed > or = 99% nt identity. Phylogenetic analyses of sequences of eight HAstV antigenic types and the novel strain in the transition region demonstrated the new strain being closely related to HAstV-3 in ORF1b, but closest to HAstV-5 in ORF2. These results and high sequence identity among all HAstV antigenic types in the transition region and RNA structural predictions supported a potential recombination site at the ORF1b/ORF2 junction. This is the first evidence that recombination occurs among human astroviruses.

Animals↗

PubMed2001

The reliability of the SCAN test: results from a primary school population in the UK.

The SCAN test utilizes a pre-recorded tape, with carrier phrase and target words spoken by an American English speaker, to screen for central auditory processing disorders in children. The aim of the present study was to establish whether the normative data, derived from American school children, are applicable to a UK primary school population. The SCAN test was administered to 133 British primary school children with normal hearing, stratified into one-year age bands. Mean scores from the UK sample were found to be significantly lower than US mean scores for the most of the age bands. Analysis of word errors indicates accent and word familiarity effects. This evaluation of the SCAN indicates that the test is not directly applicable to British children as currently normalized. The present study provides interim norms for the American recording for age bands six to 11 years. It is recommended that the test material is recorded by a UK English speaker, with substitution of high error-rate target words, followed by normative data collection for the new test material.

Child↗

PubMed2001

Educational opportunities in palliative care: what do general practitioners want?

It is important to support general practitioners (GPs) in maintaining and developing their palliative care skills as most of the final year of a patient's life is spent at home under the care of the primary health care team. The training needs and uptake of GPs have been explored, but little is known about how GP educational preferences vary. The aim of this study was to explore the current educational preferences of GPs in different geographical locations as part of an evaluation of an educational intervention. The methods used included postal questionnaires sent to 1061 GPs. Results from 640 (60%) of GPs revealed that half (51%) wanted education in symptom control for non-cancer patients. More inner-city GPs wanted education in opiate prescribing (43%), controlling nausea and vomiting (45%), and using a syringe driver (38%) than their urban and rural colleagues (26%, 29% and 21%, respectively). Increased educational preference and increased difficulty in accessing information was associated with reduced confidence in symptom control. To maximize educational uptake it will be important for educational strategies to be developed and targeted according to variations in demand, and in particular to respond to the need for palliative care education in symptom control for patients suffering from advanced non-malignant disease.

Adult↗

PubMed2000

pi-stacking interactions in cis-Bisfullerene

Experimental, molecular modeling, and model compound studies suggest that favorable fullerene[60] pi-stacking interactions in the ground state and in syn-transition states account for the high cis stereoselectivities observed in the reactions between C(60) and 6, 13-disubstituted pentacenes.

Journal Article↗

PubMed2000

High resolution mapping of the binding site on human IgG1 for Fc gamma RI, Fc gamma RII, Fc gamma RIII, and FcRn and design of IgG1 variants with improved binding to the Fc gamma R.

Immunoglobulin G (IgG) Fc receptors play a critical role in linking IgG antibody-mediated immune responses with cellular effector functions. A high resolution map of the binding site on human IgG1 for human Fc gamma RI, Fc gamma RIIA, Fc gamma RIIB, Fc gamma RIIIA, and FcRn receptors has been determined. A common set of IgG1 residues is involved in binding to all Fc gamma R; Fc gamma RII and Fc gamma RIII also utilize residues outside this common set. In addition to residues which, when altered, abrogated binding to one or more of the receptors, several residues were found that improved binding only to specific receptors or simultaneously improved binding to one type of receptor and reduced binding to another type. Select IgG1 variants with improved binding to Fc gamma RIIIA exhibited up to 100% enhancement in antibody-dependent cell cytotoxicity using human effector cells; these variants included changes at residues not found at the binding interface in the IgG/Fc gamma RIIIA co-crystal structure (Sondermann, P., Huber, R., Oosthuizen, V., and Jacob, U. (2000) Nature 406, 267-273). These engineered antibodies may have important implications for improving antibody therapeutic efficacy.

Antibody-Dependent Cell Cytotoxicity↗

PubMed2000

Directed mutation of the basic domain of v-Jun alters DNA binding specificity and abolishes its oncogenic activity in chicken embryo fibroblasts.

Overexpression of v-Jun in chicken embryo fibroblasts (CEF) leads to oncogenic transformation phenotypically characterized by anchorage independent growth and release from contact inhibition (focus formation). The mechanisms involved in this oncogenic conversion however, are not yet clear. Because Jun is a transcription factor, it has been assumed that oncogenic transformation results directly from deregulated AP-1 target gene expression. However, a number of experimental observations in avian cell culture models fail to correlate oncogenesis with AP-1 activity suggesting that transformation induced by v-Jun may occur through an indirect mechanism. To test this possibility, we introduced point mutations into the basic DNA binding domain of v-Jun and created mutants that exhibit altered binding specificity. When expressed in CEF, these mutants fail to deregulate three known v-Jun target genes (JTAP-1, apolipoprotein A1, c-Jun) thus demonstrating in vivo specificity changes. Each of the binding specificity mutants was also tested for its ability to induce oncogenic transformation. Interestingly, expression of these mutants in CEF results in a phenotype indistinguishable from the vector control with respect to growth rate, focus formation and the ability to form colonies in soft agar. These results are consistent with a model requiring direct AP-1 target deregulation as a prerequisite of v-Jun induced cell transformation. With this in mind, we generated a series of additional mutants that retain the ability to bind AP-1 sequence elements, but vary in their oncogenic potential. We demonstrate the use of these mutants to screen v-Jun induced gene targets for a functional role in cell transformation.

Amino Acid Substitution↗

PubMed2000

The chicken c-Jun 5' untranslated region directs translation by internal initiation.

The 5' untranslated region (UTR) of the chicken c-jun message is exceptionally GC rich and has the potential to form a complex and extremely stable secondary structure. Because stable RNA secondary structures can serve as obstacles to scanning ribosomes, their presence suggests inefficient translation or initiation through alternate mechanisms. We have examined the role of the c-jun 5' UTR with respect to its ability to influence translation both in vitro and in vivo. We find, using rabbit reticulocyte lysates, that the presence of the c-jun 5' UTR severely inhibits translation of both homologous and heterologous genes in vitro. Furthermore, translational inhibition correlates with the degree of secondary structure exhibited by the 5' UTR. Thus, in the rabbit reticulocyte lysate system, the c-jun 5' UTR likely impedes ribosome scanning resulting in inefficient translation. In contrast to our results in vitro, the c-jun 5' UTR does not inhibit translation in a variety of different cell lines suggesting that it may direct an alternate mechanism of translational initiation in vivo. To distinguish among the alternate mechanisms, we generated a series of bicistronic expression plasmids. Our results demonstrate that the downstream cistron, in the bicistronic gene, is expressed to a much higher level when directly preceded by the c-jun 5' UTR. In addition, inhibition of ribosome scanning on the bicistronic message, through insertion of a synthetic stable hairpin, inhibits translation of the first cistron but does not inhibit translation of the cistron downstream of the c-jun 5' UTR. These results are consistent with a model by which the c-jun message is translated through cap independent internal initiation. Oncogene (2000) 19, 2836 - 2845

3T3 Cells↗

PubMed2000

Propionibacterium acnes as a cause of visually significant corneal ulcers.

PURPOSE: To report Propionibacterium acnes as a cause of vision-threatening infectious keratitis and to discuss culture isolation and antibiotic treatment. METHODS: Retrospective case series presentation collected from three academic medical centers. RESULTS: Six cases of P. acnes infectious keratitis are presented, all of which were associated with a compromised corneal barrier or environment. All cases were culture-positive on thioglycolate broth; none became positive before 7 days of growth. No other organisms were isolated from any culture, and the growth of P. acnes occurred in some cases despite negative gram stains. CONCLUSION: P. acnes can produce vision-debilitating keratitis when the cornea is compromised. Growth in culture should be monitored for at least 10 days to ensure isolation of this fastidious organism. P. acnes may respond to several different antibiotics that have gram-positive coverage, but it should be treated with vancomycin to enhance clearance of the organism.

Adult↗

PubMed2000

A managed behavioral health organization operated by an academic psychiatry department.

As a means of adapting to managed care, the psychiatry department at Wake Forest University developed a managed behavioral health organization (MBHO) to manage the care of enrollees in QualChoice, the health maintenance organization of the Wake Forest University Baptist Medical Center. Before the academic MBHO was created, care was managed by a for-profit MBHO. In this case study, financial and utilization data were obtained from both MBHOs and from QualChoice. The data confirm that the academic MBHO was able to offer competitive rates for its services. It also was able to increase enrollees' use of the medical center's own providers and facilities by making more referrals than were made by the for-profit MBHO. Developing a managed behavioral health organization can allow academic psychiatry departments, either individually or as consortia, to preserve the patient base they require for teaching, research, and financial stability.

Academic Medical Centers↗

PubMed2000

Using case vignettes to train clinicians and utilization reviewers to make level-of-care decisions.

Dr. Rosenquist and his colleagues describe how their academically based health maintenance organization joined in training for level-of-care decision making with the external managed behavioral health organization that was providing utilization review and case management decisions. The academic department later took over its own utilization review and in so doing internalized the utilization review function. This development, which is beginning to occur in several states, is an important solution to the "assault" that many providers of care have experienced as a result of the utilization review process. Having taken this step to deal with the realities of 21st-century health care, the authors then seize the opportunity to use their own data to improve decision making within the clinic. This process is how we get to best practices.

Behavior Therapy↗

PubMed2000

Providing palliative care in primary care: how satisfied are GPs and district nurses with current out-of-hours arrangements?

The complex needs of palliative care patients require an informed, expert, and swift response from out-of-hours general medical services, particularly if hospital admission is to be avoided. Few general practitioners (GPs) reported routinely handing over information on their palliative care patients, particularly to GP co-operatives. District nurses and inner-city GPs were least satisfied with aspects of out-of-hours care. Most responders wanted 24-hour availability of specialist palliative care. This indicates a need to develop and evaluate out-of-hours palliative care procedures and protocols, particularly for GP co-operatives, and to improve inter-agency collaboration.

Adult↗