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Biomedical subjects

T Gilbert

Publications and source records attributed to T Gilbert.

At least 37 records · Page 2Linked to original sources
PubMed1996

Early defect in branching morphogenesis of the ureteric bud in induced nephron deficit.

Development of the metanephric kidney during embryogenesis can be altered both in vivo and in vitro by exposure to gentamicin, which may lead to oligonephronia. To study the role of the ureteric bud in nephron deficit genesis, we used metanephros organ cultures exposed to gentamicin as a model of impaired nephrogenesis. Ultrastructural localization of the antibiotic showed that by eight hours it was already present within the epithelial cells of the ureteric bud and in its growing ends, and also trapped in the adjacent blastema. Using confocal microscopy and image analysis, we devised a quantitative approach to analyze the branching pattern of the ureteric bud, and showed that by 24 hours of culture, despite no change of explants growth, gentamicin had significantly decreased the number of branching points. This effect involved the early branching events and was limited to end buds that had no nephron anlagen nearby. Our findings indicate that impaired branching morphogenesis of the ureteric bud is the likely event of gentamicin-induced nephron deficit.

Animals↗
PubMed1995

Recognition of emotional distress in physically healthy primary care patients who perceive poor physical health.

This study examines the recognition and treatment of emotional distress in physically healthy primary care patients who perceive themselves to be in fair or poor physical health. Patients (N = 892) from three private primary care practices completed a mental health screening form prior to their medical visit which included an overall assessment of their physical health (1 = excellent, 2 = good, 3 = fair, 4 = poor). Following the visit, their physicians completed a questionnaire that included the same physical health assessment item. The study group, physically healthy patients who perceive poor physical health (HPPPH), included those patients who rated their physical health as 2 or 3 points more impaired than it was rated by their physician. HPPPH (N = 39) were significantly more likely than other patients (N = 853) to report a prior psychiatric hospitalization (p < 0.05), marital difficulties (p < 0.01), recent missed work due to a mental health problem (p < 0.001), and a range of anxiety, depressive, and psychosomatic symptoms. However, HPPPH were also significantly more likely than other patients to receive excellent emotional health ratings (p < 0.001) from their physicians and were less likely to receive mental health treatment (p < 0.05). Detection of emotional distress may be particularly difficult in physically healthy patients who have low physical health perceptions. Identification of pessimistic physical health perceptions may serve as an indicator for underlying emotional distress.

Adolescent↗
PubMed1995

Nursing: empowerment and the problem of power.

The concept of empowerment is one which is often invoked in discussions over the nature of nursing practice in a range of health and welfare services. A short excursion through the Cumulative Index to Nursing and Allied Health Literature reveals that over the last 10 years 378 papers are identified which list empowerment as one of the topics discussed. In 1993, the number is 55. These papers cover a diverse range of health related issues: health promotion and HIV; breast feeding; mental health; management and leadership; change, training and education; feminism and women's issues; sexual abuse and violence; advocacy and working with immigrants; professionalism; and nursing theory. However, few of these papers discuss the relationship between empowerment and the notion of power itself. This gives rise to particular problems for nursing practice, for without a clear conceptualization of what is meant by power it is difficult to convincingly argue that one form of practice is more or less empowering than another. Alternatively, this dilemma may be stated in the following question: how do we work to empower others when we have no clear notion of what power is? This paper demonstrates that the concept of power demands a very specific consideration. In order to illustrate this it briefly identifies problems within two models of power which are drawn upon in nursing. It also demonstrates the way in which the work of Michel Foucault can be drawn upon to inform nursing in the analysis of the relationship between power and health.

Humans↗
PubMed1995

Assessing health needs in people with severe learning disabilities: a qualitative approach.

The nursing assessment, and the contribution it makes to the identification of an individual's health needs, is often a complex and multidimensional process. This is always true when the individual concerned has a severe learning disability. The nurse should develop the assessment in partnership with individuals who may experience major communication difficulties, or have unappreciated levels of perceptual or cognitive dysfunction. They may also live with the ongoing possibility that their affective or behavioural responses may be misinterpreted as 'challenging behaviour'. This case study focuses upon one particular young man with a severe learning disability living in a community home. Drawing upon the principles of qualitative research methods, especially those of 'grounded theory', this study aims to demonstrate how these can be used to develop a uniquely person-centered assessment. A systematic process of observation, analysis and reflection produces a detailed picture of the individual and his or her particular health states. The strength of this approach is threefold. Firstly, the person is considered as an active participant and remains the central focus. Secondly, in contrast to many other forms of assessment, the person is viewed as dynamic with ever changing needs. Thirdly, the process of nursing judgement is made explicit and integrated into the assessment process.

Health Services Needs and Demand↗
PubMed1994

Cloning and analysis of the Saccharomyces cerevisiae MNN9 and MNN1 genes required for complex glycosylation of secreted proteins.

Proteins secreted by the yeast Saccharomyces cerevisiae are usually modified by the addition at asparagine-linked glycosylation sites of large heterogeneous mannan units that are highly immunogenic. Secreted proteins from mnn1 mnn9 mutant strains, in contrast, have homogeneous Man10GlcNAc2 oligosaccharides that lack the immunogenic alpha 1,3-mannose linkages. We have cloned and sequenced the MNN9 and MNN1 genes, both of which encode proteins with the characteristics of type II membrane proteins. Mnn9p is a membrane-associated protein with unknown function that is required for the addition of the long alpha 1,6-mannose backbone of the complex mannan, whereas Mnn1p is most likely the alpha 1,3-mannosyltransferase located in the Golgi apparatus.

Amino Acid Sequence↗
PubMed1994

Intrauterine growth retardation leads to a permanent nephron deficit in the rat.

Intrauterine growth retardation (IUGR) was induced in Sprague-Dawley rats by partial artery ligation of one uterine horn in the mother on day 17 of gestation or by feeding the mother a 5% protein diet from day 8 of gestation. The controls were pups of the contralateral uterine horn or pups born to mothers fed a normal (22%) protein diet. The number of nephrons present at birth and the final number of nephrons in 2-week-old rats were counted throughout the entire kidney. The number of nephrons present at birth and the final number of nephrons were significantly correlated with birth weight for growth-retarded rats of both groups and their corresponding controls (P < 0.02 for the poorest correlation). Clearance experiments and morphometric studies of 2-week-old rats born to mothers with uterine artery ligation indicated that, despite a large compensatory hypertrophy of the nephrons in those animals born with a nephron deficit of about 30%, the overall renal function was impaired. We conclude that IUGR is accompanied by a nephron deficit which may not be fully compensated for within the first weeks after birth.

Animals↗
PubMed1994

Mitochondrial biogenesis and development of respiratory chain enzymes in kidney cells: role of glucocorticoids.

We have previously shown that the activity of several mitochondrial oxidative enzymes increased greatly in the medullary thick ascending limb of Henle's loop (MTAL) of developing rat kidney between 16 days after birth and the adult stage. These changes were triggered by the postnatal rise in circulating glucocorticoids. To determine whether these increases are related to a mitochondrial biogenesis we have studied the changes in mitochondrial density of MTAL cells and mitochondrial DNA content in the inner stripe of the outer medulla during the postnatal period. The activities of respiratory chain (RC) complexes II and IV, located in the inner mitochondrial membrane (IMM), were also assayed, and developmental changes in the ultrastructure of the IMM were quantified. Quantitative electron-microscopic data showed a doubling in mitochondrial density from day 16 to the adult, accompanied by twofold increase in mitochondrial DNA, as determined by slot-blot experiments. The surface density of IMM increased by 77%, and there was a concomitant large rise in the activity of both RC enzymes. A possible role of glucocorticoids on the regulation of mitochondrial biogenesis was examined in similar experiments performed in adrenalectomized rat pups. The data demonstrated that glucocorticoids are essential for the rise in RC enzymes and the development of IMM but do not regulate postnatal changes in mitochondrial density and mitochondrial DNA content. Finally, ontogenic changes in oxidative capacities of MTAL cells could be a critical factor in the development of kidney urine concentrating mechanisms in weanling rats.

Adrenalectomy↗
PubMed1994

Defect of nephrogenesis induced by gentamicin in rat metanephric organ culture.

BACKGROUND: In the rat, in utero exposure to gentamicin during early renal differentiation leads to a permanent nephron deficit. The aim of the present study was to analyze, in vitro, the potential direct effect of gentamicin on early nephrogenesis. EXPERIMENTAL DESIGN: We used paired rat metanephric organ cultures from 14 (F14) or 15-day-old (F15) fetuses. We measured gentamicin accumulation into explanted metanephroi and then assessed in vitro growth in the absence or presence of the drug. Glomerular labeling and counting were performed on the whole explant to analyze the effect of antibiotics on early nephrogenesis. RESULTS: Growth of F14 metanephric explants in the presence of 50 micrograms of gentamicin/ml was significantly reduced from 4 days onwards as compared to controls, whereas F15 explants grown with gentamicin displayed a normal in vitro development. After 6 days of culture, F14 and F15 explants had the same accumulation of gentamicin (1 microgram/mg protein) but the gentamicin content was 4 times larger in F15 explants. At both ages, gentamicin-exposed metanephric explants exhibited a significant reduction in their number of nephrons. However, the effects of 50 micrograms of gentamicin/ml on nephrogenesis were significantly more drastic on F14 than F15 explants (35% versus 18%). When grown with 0.5 microgram of gentamicin/ml, F14 explants still exhibited a 16% defect in nephrogenesis as compared with controls, and about the same reduction was observed for cultures in the presence of 100 micrograms/ml of streptomycin and 100 IU/ml of penicillin. Incubation of F14 explants with streptomycin alone for 6 days had no effect on nephrogenesis. CONCLUSIONS: These results indicate that gentamicin induces a significant reduction in the number of nephrons in metanephric explants and that this effect is more important on less differentiated metanephroi. Metanephric organ culture combined with glomerular labeling represents a useful model to test the effect of various growth factors and other drugs on early nephrogenesis.

Animals↗
PubMed1993

Learning disability nursing: from normalization to materialism--towards a new paradigm.

For almost 2 decades the 'normalization principle' has provided the dominant paradigm for the planning and evaluation of nursing services to people with a learning disability within the United Kingdom. This has reflected the international influence of this philosophy in services to a wide range of disadvantaged and marginalized groups. However, this paper will argue that nurses working with this client group are facing a range of social and political changes which expose the weaknesses in this paradigm. This calls for a new approach to the way the relationship between practitioners and their clients is conceptualized. Here it is argued that a materialist paradigm provides a more realistic framework upon which to base future nursing practice.

Culture↗
PubMed1993

Isolation of glucagon antagonists by random molecular mutagenesis and screening.

Glucagon has an important role in the regulation of glucose homeostasis, and glucagon antagonists may be effective therapeutic agents in the control of diabetes mellitus. We were able to identify a number of analogs with antagonist activity by creating libraries of mutant glucagon coding sequences, expressing them in a yeast (Saccharomyces cerevisiae) secretion system, and screening for clones that produce analogs that inhibit the glucagon stimulation of rat hepatocyte membrane adenylate cyclase. These libraries were constructed by allowing random misincorporation during the synthesis of oligonucleotides that contained the complete coding sequence for mammalian glucagon or for an analog (desHis1-glucagon) that had partial antagonist activity. We developed and used a simplified screening assay to test culture broths from > 3500 individual transformant yeast clones for their ability to inhibit glucagon-dependent adenylate cyclase activity. Ultimately, > 20 different analogs with antagonist activity were identified by recovering and sequencing plasmid DNA from yeast strains that were positive in the screening assay. Interestingly, several analogs were identified repeatedly in independent yeast clones and certain amino acid substitutions occurred in more than one analog. This clustering of randomly isolated mutations clearly delineates the regions of the glucagon molecule that are important for designing improved glucagon antagonists. A subset of the antagonists identified in yeast broth were produced by peptide synthesis to confirm their activities as pure compounds.

Adenylyl Cyclases↗
PubMed1992

Cloning and expression of a cellular high density lipoprotein-binding protein that is up-regulated by cholesterol loading of cells.

Plasma membranes of cultured cells contain high affinity receptors for high density lipoprotein (HDL) that appear to mediate removal of excess intracellular cholesterol. Recent studies using ligand blot analysis have identified a 110-kDa membrane protein which has features predicted for an HDL receptor, in that it preferentially binds HDL apolipoproteins and undergoes up-regulation in response to cholesterol loading of cells. In this study, we isolated a cDNA clone from an expression library using an antibody raised against partially purified 110-kDa HDL-binding protein. This clone encodes a novel cell protein, designated HBP, comprised mostly of 14 imperfect tandem repeats of approximately 70 amino acids in length. Each repeat appears to contain two amphipathic helices. Expression of HBP in cultured cells was increased severalfold when cells were loaded with cholesterol, as evident by increases in both HBP mRNA and membrane-associated protein. Overexpression of HBP in mammalian cell transfectants was associated with higher HDL binding to isolated cell protein and with modest increases in HDL binding to the cell surface. Proteins identified by ligand blot analysis had lower apparent M(r) than the primary HBP gene product and varied in M(r) and in HDL binding activity between cell types, suggesting that HBP undergoes cell-specific processing. These results provide preliminary evidence that HBP is a component of a cellular pathway that facilitates removal of excess cholesterol from cells, perhaps through its interaction with HDL. However, the predicted structure of HBP does not conform to that of any known receptor, suggesting that it does not function as a classic plasma membrane receptor.

Amino Acid Sequence↗
PubMed1991

Microtubular organization and its involvement in the biogenetic pathways of plasma membrane proteins in Caco-2 intestinal epithelial cells.

We characterized the three-dimensional organization of microtubules in the human intestinal epithelial cell line Caco-2 by laser scanning confocal microscopy. Microtubules formed a dense network approximately 4-microns thick parallel to the cell surface in the apical pole and a loose network 1-micron thick in the basal pole. Between the apical and the basal bundles, microtubules run parallel to the major cell axis, concentrated in the vicinity of the lateral membrane. Colchicine treatment for 4 h depolymerized 99.4% of microtubular tubulin. Metabolic pulse chase, in combination with domain-selective biotinylation, immune and streptavidin precipitation was used to study the role of microtubules in the sorting and targeting of four apical and one basolateral markers. Apical proteins have been recently shown to use both direct and transcytotic (via the basolateral membrane) routes to the apical surface of Caco-2 cells. Colchicine treatment slowed down the transport to the cell surface of apical and basolateral proteins, but the effect on the apical proteins was much more drastic and affected both direct and indirect pathways. The final effect of microtubular disruption on the distribution of apical proteins depended on the degree of steady-state polarization of the individual markers in control cells. Aminopeptidase N (APN) and sucrase-isomaltase (SI), which normally reach a highly polarized distribution (110 and 75 times higher on the apical than on the basolateral side) were still relatively polarized (9 times) after colchicine treatment. The decrease in the polarity of APN and SI was mostly due to an increase in the residual basolateral expression (10% of control total surface expression) since 80% of the newly synthesized APN was still transported, although at a slower rate, to the apical surface in the absence of microtubules. Alkaline phosphatase and dipeptidylpeptidase IV, which normally reach only low levels of apical polarity (four times and six times after 20 h chase, nine times and eight times at steady state) did not polarize at all in the presence of colchicine due to slower delivery to the apical surface and increased residence time in the basolateral surface. Colchicine-treated cells displayed an ectopic localization of microvilli or other apical markers in the basolateral surface and large intracellular vacuoles. Polarized secretion into apical and basolateral media was also affected by microtubular disruption. Thus, an intact microtubular network facilitates apical protein transport to the cell surface of Caco-2 cells via direct and indirect routes; this role appears to be crucial for the final polarity of some apical plasma membrane proteins but only an enhancement factor for others.

Alkaline Phosphatase↗
PubMed1991

Long-term effects of mild oligonephronia induced in utero by gentamicin in the rat.

Renal clearance studies and morphologic observations were performed in rats aged 14, 21, and 28 d and 3, 6, 9, and 12 mo born with a 20% reduction in nephron number after administration of 75 mg/kg/d of gentamicin to their mothers during the second half of gestation. Gentamicin was still present in urine 3 mo after birth. Morphologic damage characteristic of gentamicin accumulation was observed in the kidney on d 14 and 21. Adequate compensatory adaptation to oligonephronia occurred for glomerular function within 14 d of birth, but tubular phosphate reabsorption was significantly low on d 21. On d 28, no evidence of histologic or functional damage to the kidney was observed. At 3 mo, mesangial lesions were observed in rats of the gentamicin group, whereas they were rarely present in 6-mo-old control rats. Furthermore, glomerular sclerotic lesions were already evident in about 5% of the juxtamedullary nephrons. The same percentage of injured nephrons was not observed before 12 mo in controls. Complementary morphologic data obtained in 24-mo-old rats showed that glomerulosclerosis involved 40% of the juxtamedullary nephron population at this age in animals of the gentamicin group versus 21% in controls. It is concluded that in the young rats born with oligonephronia of gentamicin-treated mothers neither the gentamicin remaining in the kidney cells nor the injuries it caused them prevented compensatory adaptation of the kidney to a reduced number of nephrons. However, although this oligonephronia was mild, it might have been sufficient to cause early development of glomerular sclerosis in the adults.

Abnormalities, Drug-Induced↗
PubMed1991

Induction of vacuolar apical compartments in the Caco-2 intestinal epithelial cell line.

Complete disruption of the microtubular network by colchicine or nocodazole in Caco-2 intestinal epithelial cells results in the appearance of basolateral microvilli and brush border-containing intracellular vacuoles (vacuolar apical compartment: VAC). These vacuoles are surrounded by a terminal web, express apical markers and exclude basolateral markers. The vacuoles do not originate from internalized apical or basolateral plasma membrane and their development is blocked by protein synthesis inhibitors, suggesting that they are newly synthesized. After removal of the microtubule inhibitors, VACs are usually degraded and/or released into the lateral intercellular space. Rarely was fusion with the apical membrane observed. These experiments support a role for microtubules in the biogenesis of the apical surface and indicate that, under some conditions, apical plasma membrane assembly may occur in the cytoplasm, as observed in some human pathological states.

Cell Line↗