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Biomedical subjects

S Anderson

Publications and source records attributed to S Anderson.

At least 235 records · Page 13Linked to original sources
PubMed1997

Role of angiotensin II in diabetic nephropathy.

Classically, the renin-angiotensin system (RAS) in diabetes was thought to be suppressed, and relatively unimportant in the regulation of hemodynamics and the development of complications. However, recent developments have caused reconsideration of this notion. Studies of pharmacological interruption of the RAS with angiotensin converting enzyme (ACE) inhibition have implicated this hormonal system in the progression of diabetic nephropathy, both experimentally and clinically. Preliminary evidence also suggests a beneficial effect of angiotensin II (ANG II) receptor antagonists. The relative roles of the systemic versus intrarenal RAS in the pathogenesis of diabetic nephropathy have recently been evaluated. Although plasma renin level is generally low, it is not yet clear whether RAS component processing is normal in diabetes; there may be subtle changes in ANG II metabolism that sustain relatively higher plasma ANG II levels. Furthermore, the intrarenal RAS may not be suppressed. Renal renin levels tend to be disproportionately elevated, as compared with plasma renin values. Renal ANG II levels are normal, and renal mRNAs for RAS components have been variable. In general, lack of RAS suppression (despite plasma volume and increased exchangeable sodium) may indicate inappropriate activity of the RAS in diabetes. RAS-mediated injury may occur via stimulation of a number of sclerosing mediators, and there is evidence that hyperglycemia acts synergistically with ANG II to promote cellular injury. Finally, various RAS candidate genes for development of diabetic nephropathy have been examined and, although controversy remains, ACE gene polymorphisms may be involved. Together, these recent investigations lend further support to the notion that the RAS plays an important role in diabetic nephropathy, and are beginning to shed light on the mechanisms of progressive renal injury.

Angiotensin II↗
PubMed1997

Type XII collagen contributes to diversities in human corneal and limbal extracellular matrices.

PURPOSE: To characterize diversities in the extracelhtlar matrices (ECMs) of the corneal and the surrounding limbal epithelium and stroma. METHODS: Immunohistochemical analyses were employed for screening monoclonal antibodies (mAbs) developed against ECM components of the human corneal epithelial basement membrane (BM) zone. In the current study, mAb BM8 was used as the monospecific probe to characterize its antigen (AgBM8) immunochemically, and to immunoselect a complementary DNA (cDNA) clone encoding AgBM8. Direct biochemical and cDNA sequence analyses were performed for the further characterization of AgBM8. An indirect colloidal gold-conjugated antibody technique was employed for immunoelectron microscopic analysis to study the distribution of AgBM8 in the corneal ECMs. RESULTS: The protein AgBM8, isolated from rabbit corneal stromal and epithelial tissues, was identified as the long-splice variant form of type XII collagen based on its size (approximately 340 kDa disulfide-linked subunits), the presence of collagenous domain(s) and a noncollagenous domain of approximately 300 kDa in its subunit structure, and its internal amino acid sequences. The identity of AgBM8 was further confirmed from the amino acid sequence (517 amino acids) deduced from the sequence of a cDNA immunoselected with mAb BM8. Immunofluorescence analyses indicated that the long form of type XII collagen is present in the ECMs of corneal stroma and in the sclera, as well as in the corneal epithelial BM zone but is absent in the limbal and conjunctival epithelial BM zones. It was not detectable in the subepithelial loose connective tissues in the limbus and in the bulbar conjunctiva. Immunoelectron microscopic analyses indicated that the long variant form of type XII collagen is present in corneal epithelial BM, Bowman's membrane, and the interfibrillar matrix of the corneal stroma. In the stroma, colloidal gold was distributed along the collagen fibrils with a periodicity of 150 to 200 nm. CONCLUSIONS: The long variant form of human type XII collagen, a member of the fibril-associated collagens with interrupted triple helices, referred to as FACITs, contributes to the differences in the BM zones of the cornea and limbus. Although many of the dense connective tissues in adult animals contain the short variant form of type XII collagen, human corneal stroma, the BM zone, and the sclera contain the long variant form as the predominant form of type XII collagen. In the corneal stroma, type XII collagen may be organized along the collagen fibrils in a uniform head-to-tail pattern.

Aged↗
PubMed1997

Role of local and systemic angiotensin in diabetic renal disease.

Classically, the renin-angiotensin system (RAS) in diabetes was thought to be suppressed, and relatively unimportant in the regulation of hemodynamics and the development of complications. However, studies of pharmacologic interruption of the RAS with angiotensin converting enzyme (ACE) inhibition have implicated the RAS in the progression of diabetic nephropathy. Preliminary evidence also suggests a beneficial effect of angiotensin II receptor antagonists. The relative roles of the systemic versus intrarenal RAS in this process are under active investigation. Though plasma renin is generally low, there may be subtle changes in angiotensin (Ang) II metabolism that sustain relatively higher plasma Ang II levels. Furthermore, the intrarenal RAS may not be suppressed. Renal renin levels tend to be disproportionately elevated, as compared to plasma values. Renal Ang II levels are normal, and renal mRNAs for RAS components have been variable. In general, lack of intrarenal RAS suppression (despite plasma volume and increased exchangeable sodium) may indicate inappropriate activity of the local tissue RAS, and act as a proximate cause of the systemic RAS suppression. Ang II-mediated injury may occur via stimulation of sclerosing mediators, and there is evidence that hyperglycemia acts synergistically with Ang II to promote cellular injury. Together, these recent investigations lend further support to the notion that the RAS plays an important role in diabetic nephropathy, and are helping to shed light on the mechanisms of progressive renal injury.

Angiotensin II↗
PubMed1996

A severe and consistent deficit in marrow and circulating primitive hematopoietic cells (long-term culture-initiating cells) in acquired aplastic anemia.

We examined the stem cell compartment of patients with acquired aplastic anemia (AA) using the long-term culture-initiating cell assay (LTC-IC), in parallel with measurements of CD34+ cells and mature hematopoietic progenitors. Secondary colonies from cells surviving 5 weeks of long-term bone marrow culture (LTBMC) were determined for the peripheral blood (PB) of 68 AA patients and 13 normal controls and for BM of 49 AA patients and 14 controls; because of low cell numbers, formal limiting dilution analysis could only be performed in 10 patients. The relationship of cell input in LTBMC and the output of secondary colonies was linear, allowing quantification of LTC-IC number from bulk cultures. Secondary colony formation was markedly abnormal in severe AA. In contrast to 7.8 colony-forming cells (CFC)/10(5) mononuclear cells in normal BM and 0.14 CFC/10(5) normal PB mononuclear cells, patients with severe disease showed 0.024 CFC/10(5) in BM and 0.0068 CFC/10(5) in PB. Under limiting dilution conditions, patients' cells also showed markedly lower colony-forming ability. In contrast to 4.3 +/- 1 colonies/normal LTC-IC, we obtained only 1.27 +/- 0.09 and 2.0 +/- 0.35 colonies from BM of acute and recovered cases, respectively. These values were used to extrapolate LTC-IC numbers from secondary colony formation in suspension cultures. In PB, calculated LTC-IC were decreased 7.4-fold in new and relapsed severe AA and 2.8-fold in recovered AA. In BM, LTC-IC were decreased 10-fold in new and relapsed AA and sixfold in recovered cases. Compared with measurements obtained on presentation, LTC-IC were lower in post-treatment samples from patients who had failed to recover after intensive immunosuppression and relatively higher in cases at relapse. In recovered patients, LTC-IC number increased but remained below the normal range in 20 of 25. In patients studied serially for 3 to 12 months after treatment, LTC-IC numbers remained stable but low. LTC-IC number correlated with concurrently determined CD34+ cell number and primary hematopoietic colony formation. These results indicate that stem cell numbers, as quantitated by the LTC-IC assay, are markedly diminished in number in all severe AA. Additionally, the function of the stem cell or the stem cell compartment in AA is also abnormal, as inferred from the low clonogenic potential in secondary colony assays. Early hematologic improvement in some patients occurs without increasing numbers of LTC-IC, and a minority of recovered cases show apparent repopulation of the LTC-IC compartment years after treatment.

Anemia, Aplastic↗
PubMed1996

Alanine point-mutations in the reactive region of bovine pancreatic trypsin inhibitor: effects on the kinetics and thermodynamics of binding to beta-trypsin and alpha-chymotrypsin.

In an effort to relate structural, kinetic, and thermodynamic features in a model macromolecular recognition process, the amino acid residues in the reactive surface of bovine pancreatic trypsin inhibitor (BPTI) and surrounding residues were substituted individually by alanine, and the effects of the point-mutations on the kinetics and thermodynamics of inhibition by BPTI toward trypsin and chymotrypsin were investigated. Fifteen alanine mutants were produced. The majority of the BPTI mutants exhibited a binding affinity similar to that of the wild-type protein. The exceptions were the primary specificity site (PI) mutant and those mutants that seem to have nonlocal perturbations of structure, as revealed by circular dichroism and thermostability measurements. The mutation at the P1 site caused a reduction in the binding free energy of 10 and 1.8 kcal mol-1 for trypsin and chymotrypsin, respectively. The losses in binding affinity were determined almost exclusively by an increase in the dissociation rate constant. However, the rate of association of the P1 mutant, Lys-15-Ala, with trypsin was also drastically reduced (> 200-fold). Calorimetric measurements of the heats of binding for the association of chymotrypsin with the wild-type inhibitor and its alanine mutants allowed determination of the relative contributions of the changes in enthalpy and entropy to the free energy of binding. Compensatory changes in the two parameters were observed in several cases, which were attributed to desolvation effects at the binding interface.

Alanine↗
PubMed1996

Mutation of the Emx-1 homeobox gene disrupts the corpus callosum.

Expression of the Emx-1 homeobox gene is largely restricted to the developing and mature cerebral cortex. To study its function, two lines of mice were generated using gene targeting methods that have a deletion that includes the N-terminal coding region of Emx-1. Mice homozygous for the deletion were viable and fertile and exhibited no obvious behavioral defects. However, 100% of homozygous mice lack most or all of their corpus callosum, the principle fiber tract that connects the left and right cerebral hemispheres. Heterozygotes show partial penetrance for the corpus callosum abnormality. The histology and various molecular properties of the cerebral cortex appear normal in the mutant mice.

Agenesis of Corpus Callosum↗
PubMed1996

Novel transcribed sequences represented in the complex genomic region 5q13.

YACs from the complex repetitive human genomic region 5q13, spanning the spinal muscular atrophy (SMA) locus, have been searched for transcribed sequences using the method of End Ligation Coincident Sequence Cloning. Six transcripts (PT1-6) have been identified, three of which (PT4, PT5 and PT6) are novel. Five of these elements hybridise to multiple loci in 5q13, but PT5 is single copy and maps very close to markers that show linkage disequilibrium with SMA.

Base Sequence↗
PubMed1996

Induction of Th1 cell-mediated protective immunity to Schistosoma mansoni by co-administration of larval antigens and IL-12 as an adjuvant.

In this study, rIL-12, which is a powerful inducer of Th1 lymphocyte development, was administered to mice as an adjuvant in conjunction with a soluble lung-stage Ag preparation (SLAP) derived from lung-stage larvae of Schistosoma mansoni to potentiate Th1-mediated immune responses and induce resistance to reinfection. Immunization of mice with one or two doses of SLAP + IL-12 elicited a dominant population of Ag-specific Th1 lymphocytes in the draining lymph nodes, as judged by the secretion of abundant IFN-gamma but undetectable levels of IL-4, upon antigenic restimulation in vitro. In contrast, SLAP alone induced a mixed population of Th1 and Th2 cells with secretion of IFN-gamma, IL-4, and IL-10. The development of a biased Th1 cell population in mice immunized with SLAP + IL-12 was reflected in enhanced levels of Ag-specific IgG2a but decreased levels of IgG1 and total IgE serum Abs. Ablation of NK1.1+ cells before the administration of a single dose of SLAP + IL-12 reduced Th cell proliferation and almost completely inhibited secretion of IFN-gamma by in vitro-cultured lymph node cells. This indicates that NK cells stimulated by IL-12 shortly after vaccination are critical to the subsequent development of Ag-specific Th1 cells. Finally, it is demonstrated that the delivery of two doses of SLAP + IL-12 to mice is sufficient to elicit moderate but highly significant levels of protective immunity against challenge infection.

Adjuvants, Immunologic↗
PubMed1996

High-level production of uniformly ¹⁵N- and ¹³C-enriched fusion proteins in Escherichia coli.

An approach to produce 13C- and 15N-enriched proteins is described. The concept is based on intracellular production of the recombinant proteins in Escherichia coli as fusions to an IgG-binding domain, Z, derived from staphylococcal protein A. The production method provides yields of 40-200 mg/l of isotope-enriched fusion proteins in defined minimal media. In addition, the Z fusion partner facilitates the first purification step by IgG affinity chromatography. The production system is applied to isotope enrichment of human insulin-like growth factor II (IGF-II), bovine pancreatic trypsin inhibitor (BPTI), and Z itself. High levels of protein production are achieved in shaker flasks using totally defined minimal medium supplemented with 13C(6)-glucose and (15NH4)2SO4 as the only carbon and nitrogen sources. Growth conditions were optimized to obtain high protein production levels and high levels of isotope incorporation, while minimizing 13C(6)-glucose usage. Incorporation levels of 13C and/or 15N isotopes in purifies IGF-II, BPTI, and Z were confirmed using mass spectrometry and NMR spectroscopy. More than 99% of total isotope enrichment was obtained using a defined isotope-enriched minimal medium. The optimized systems provide reliable, high-level production of isotope-enriched fusion proteins. They can be used to produce 20-40 mg/l of properly folded Z and BPTI proteins. The production system of recombinant BPTI is state-of-the-art and provides the highest known yield of native refolded BPTI.

Animals↗
PubMed1996

Ro 15-4513 alteration of pentobarbital dependence.

This study investigated the ability of the benzodiazepine inverse agonist, Ro 15-4513, to alter the expression of physical dependence on pentobarbital. Male Sprague-Dawley rats were made physically dependent on pentobarbital by continuous. IP, infusion of escalating doses of pentobarbital for 12 days. In Experiment 1, pentobarbital dependent rats received either vehicle or Ro 15-4513, in doses of 5, 10, or 15 mg/kg, IP, periodically during the pentobarbital abstinence period. As expected, Ro 15-4513 produced a significant, dose-dependent, exacerbation of withdrawal signs in the pentobarbital dependent rats. In Experiment 2, either vehicle or Ro 15-4513, at a dose of 15 mg/ kg, was administered, IP, once daily during the 12 days of continuous pentobarbital infusion. During the subsequent pentobarbital abstinence period it was noted that the withdrawal signs were significantly reduced in the rats receiving the daily administration of Ro 15-4513. It is hypothesized that the benzodiazepine inverse agonist, Ro 15-4513, may inhibit the development of physical dependence on pentobarbital through an opposing action on the GABA-A receptor.

Animals↗
PubMed1996

Stem cell mobilization in normal donors for allogeneic transplantation: analysis of safety and factors affecting efficacy.

The use of peripheral blood stem cells instead of bone marrow as the source of haemopoietic cells for allogeneic transplantation is being increasingly explored. We have analysed data from 17 normal donors who underwent stem cell mobilization for allogeneic transplantation with an identical protocol using G-CSF at a dose of 10 micrograms/kg/d, with the first leukapheresis (LP) on the day following the fourth dose of G-CSF. Both G-CSF administration and leukapheresis were well tolerated. Donors under-went a median of two leukaphereses (range one to three) and a median of 6.80 x 10(6) CD34+ cells/kg recipient weight (range 2.4-15.6 x 10(6)) were collected. The median number of CD34+ cells per kg donor weight was 6.05 x 10(6), when corrected for a 12 litre leukapheresis, this gave a median total of 3.89 x 10(6) CD34+ cells/kg donor weight. When analysed with respect to factors which might influence the efficacy of mobilization, male donors were associated with a superior yield. The median number of CD34+ cells/kg/LP harvested was 4.96 x 10(6) in males and 2.79 x 10(6) in females (P < 0.05). The results suggested that, given a recipient of 75 kg, in a male donor a single 12 litre leukapheresis should yield sufficient CD34+ cells (4 x 10(6)/ kg), whereas a female donor would be likely to need two leukaphereses. Age was not found to affect donor yield. In summary, these data confirm that leukapheresis is a safe procedure in normal donors and suggest that males may be more efficient mobilizers of stem cells than females.

Adult↗