PubMed Health⌕ Search

Biomedical subjects

S Mohan

Publications and source records attributed to S Mohan.

At least 55 records · Page 3Linked to original sources
PubMed2001

Localization of the IGF binding domain and evaluation of the role of cysteine residues in IGF binding in IGF binding protein-4.

Our previous findings suggest that binding of IGF binding protein-4 (IGFBP-4) to IGFs is essential for the inhibitory effect of IGFBP-4 on the activity of IGFs, both in vitro and in vivo. Therefore, understanding the structural determinants of IGF binding in IGFBP-4 is important to the general understanding of the biology of the IGF system. This study sought to further localize the IGF binding domain and to evaluate the role of Cys residues in IGF binding. Our data revealed that full-length IGFBP-4 peptides lacking the residues Leu(72)-Ser(91) or Leu(72)-His(74) or Gly(75)-Ser(91) failed to bind to IGF-I or IGF-II, whereas deletion of the residue Leu(72) or residues Met(80)-Ser(91) led to a 2- to 3-fold reduction in IGF-I and IGF-II binding activity. The IGF-I and IGF-II binding activities were dramatically reduced by the single mutation, Cys9/Arg (>25-fold), and to a lesser degree, by the single mutation, Cys12/Arg (the first N-terminal Cys residue was designated Cys1). The mutation Cys17/Ser or Cys18/Tyr or Cys20/Ser each resulted in a similar but moderate ( approximately 5-fold) reduction in IGF-II binding activity. The IGF-I binding activity was also dramatically reduced by the mutation Cys18/Tyr, and to a lesser extent, by the mutation Cys17/Ser or Cys20/Ser. These data suggest: 1) the IGF-I and IGF-II binding domain in IGFBP-4 involves a hydrophobic motif (Leu(72)-Met(80)) located in the distal part of the conserved N-terminal region, and 2) the N-terminal Cys residues (Cys9 and Cys12) are more critical than the C-terminal Cys residues (Cys17 and Cys20) in affecting the IGF-I and IGF-II binding. Based on these data, we speculate that the structural determinants of IGF-I and IGF-II binding in IGFBP-4 are very similar, if not identical.

Binding Sites↗
PubMed2001

Estrogen receptor specificity in the regulation of the skeleton in female mice.

There are two known estrogen receptors, estrogen receptor-alpha (ER alpha) and estrogen receptor-beta (ER beta), which may mediate the actions of estrogen. The aim of the present study was to compare fat content, skeletal growth and adult bone metabolism in female mice lacking ER alpha (ERKO), ER beta (BERKO) or both ERs (DERKO). We demonstrate that endogenous estrogens decrease the fat content in female mice via ER alpha and not ER beta. Interestingly, the longitudinal bone growth was decreased in ERKO, increased in BERKO, but was intermediate in DERKO females, demonstrating that ER alpha and ER beta exert opposing effects in the regulation of longitudinal bone growth. The effects on longitudinal bone growth were correlated with similar effects on serum levels of IGF-I. A complex regulation of the trabecular bone mineral density (BMD), probably caused by a disturbed feedback regulation of estrogen and testosterone, was observed in female ER-inactivated mice. Nevertheless, a partial functional redundancy for ER alpha and ER beta in the maintenance of the trabecular BMD was observed in the female mice at 60 days of age. Thus, ER alpha and ER beta may have separate effects (regulation of fat), opposing effects (longitudinal bone growth) or partial redundant effects (trabecular BMD at 60 days of age), depending on which parameter is studied.

Absorptiometry, Photon↗
PubMed2000

Differential protein profile in the ear-punched tissue of regeneration and non-regeneration strains of mice: a novel approach to explore the candidate genes for soft-tissue regeneration.

Wound repair/regeneration is a genetically controlled, complex process. In order to identify candidate genes regulating fast wound repair/regeneration in soft-tissue, the temporal protein profile of the soft-tissue healing process was analyzed in the ear-punched tissue of regeneration strain MRL/MpJ-Fas(lpr) (MRL) mice and non-regeneration strain C57BL/6J(B6) mice using surface-enhanced laser desorption and ionization (SELDI) ProteinChip technology. Five candidate proteins were identified in which responses of MRL to the ear punch were 2-4-fold different compared to that of B6. Their corresponding genes were predicted using an antigen-antibody assay validated mass-based approach. Most of the predicted genes are known to play a role or are likely to play a role in the wound repair/regeneration. Of the five candidate proteins, the amount of the 23560 Da protein in the ear-punched tissue was significantly correlated with the rate of ear healing in six representative strains of mice, making it a good candidate for fast wound repair/regeneration. We speculate that the increased concentration of the 23560 Da protein in the wound tissue could stimulate the expression of various growth-promoting proteins and consequently speed up the wound repair/regeneration processes. Here, we have shown that examination of protein expression profile using SELDI technology, coupled with database search, is an alternative approach to search for candidate genes for wound repair/regeneration. This novel approach can be implemented in a variety of biological applications.

Animals↗
PubMed2000

Concentrations of insulin-like growth factor (IGF)-I, -II, and IGF binding protein-4, and -5 in human bone cell conditioned medium do not change with age.

We examined the effects of age on the secretion of insulin-like growth factor (IGF)-I, -II, and IGF binding protein-4, and -5 in long-term bone cell cultures from 71 female donors, aged 28-79 years. Our results suggest that under basal conditions, the intrinsic capacity of human bone cells to produce these IGF components is largely preserved with age.

Adult↗
PubMed2000

Evidence that the interaction between insulin-like growth factor (IGF)-II and IGF binding protein (IGFBP)-4 is essential for the action of the IGF-II-dependent IGFBP-4 protease.

A variety of human cell types, including human osteoblasts (hOBs), produce an IGFBP-4 protease, which cleaves IGFBP-4 in the presence of IGF-II. Recently, the pregnancy-associated plasma protein (PAPP)-A has been determined to be the IGF-II-dependent IGFBP-4 protease produced by human fibroblasts. This study sought to define the mechanism by which IGF-II enhances IGFBP-4 proteolysis. Addition of PAPP-A antibody blocked the IGFBP-4 proteolytic activity in hOB conditioned medium (CM), suggesting that PAPP-A is the major IGFBP-4 protease in hOB CM. Pre-incubation of IGFBP-4 with IGF-II, followed by removal of unbound IGF-II, led to IGFBP-4 proteolysis without further requirement of the presence of IGF-II in the reaction. In contrast, prior incubation of the partially purified IGFBP-4 protease from either hOB CM or human pregnancy serum with IGF-II did not lead to IGFBP-4 proteolysis unless IGF-II was re-added to the assays. To further confirm that the interaction between IGF-II and IGFBP-4 is required for IGFBP-4 protease activity, we prepared IGFBP-4 mutants, which contained the intact cleavage site (Met135-Lys136) but lacked the IGF binding activity, by deleting the residues Leu72-His74 in the IGF binding domain or Cys183-Glu237 that contained an IGF binding enhancing motif. The IGFBP-4 protease was unable to cleave these IGFBP-4 mutants, regardless of whether or not IGF-II was present in the assay. Conversely, an IGFBP-4 mutant with His74 replaced by an Ala, which exhibited normal IGF binding activity, was effectively cleaved in the presence of IGF-II. Taken together, these findings provided strong evidence that the interaction between IGF-II and IGFBP-4, rather than the direct interaction between IGF-II and IGFBP-4 protease, is required for optimal IGFBP-4 proteolysis.

Antibodies↗
PubMed2000

Estrogen receptor specificity in the regulation of skeletal growth and maturation in male mice.

Androgens may regulate the male skeleton directly through a stimulation of androgen receptors or indirectly through aromatization of androgens into estrogen and, thereafter, through stimulation of estrogen receptors (ERs). The relative importance of ER subtypes in the regulation of the male skeleton was studied in ERalpha-knockout (ERKO), ERbeta-knockout (BERKO), and double ERalpha/beta-knockout (DERKO) mice. ERKO and DERKO, but not BERKO, demonstrated decreased longitudinal as well as radial skeletal growth associated with decreased serum levels of insulin-like growth factor I. Therefore, ERalpha, but not ERbeta, mediates important effects of estrogen in the skeleton of male mice during growth and maturation.

Animals↗
PubMed2000

Disproportional skeletal growth and markedly decreased bone mineral content in growth hormone receptor -/- mice.

Growth hormone (GH) is important for skeletal growth as well as for a normal bone metabolism in adults. The skeletal growth and adult bone metabolism was studied in mice with an inactivated growth hormone receptor (GHR) gene. The lengths of femur, tibia, and crown-rump were, as expected, decreased in GHR-/- mice. Unexpectedly, GHR-/- mice displayed disproportional skeletal growth reflected by decreased femur/crown-rump and femur/tibia ratios. GHR-/- mice demonstrated decreased width of the growth plates in the long bones and disturbed ossification of the proximal tibial epiphysis. Furthermore, the area bone mineral density (BMD) as well as the bone mineral content (BMC)/body weight were markedly decreased in GHR-/- mice. The decrease in BMC in GHR-/- mice was not due to decreased trabecular volumetric BMD but to a decreased cross-sectional cortical bone area In conclusion, GHR-/- mice demonstrate disproportional skeletal growth and markedly decreased bone mineral content.

Animals↗
PubMed2000

Body proportions in Fanconi anemia heterozygotes.

To study the anthropometric ratios in parents (heterozygotes) of children with Fanconi anemia. The study was carried out in the Department of Hematology, Institute of Child Health & Hospital for Children, Chennai. Parents of children with Fanconi anemia were the subjects of the study. Applying standard instruments and methods, various body measurements were recorded. 31 fathers and 37 mothers were included in the study. A hundred male and female controls of the same ethnic group were also studied for the same parameters. The ratios were calculated and statistically analyzed. It was observed that fathers (male heterozygotes) had shorter forearms, the ratio of upper arm: forearm was significantly increased compared to male controls. In mothers (female heterozygotes) the inter-pupillary distance was increased, the ratio of head circumference to inter-pupillary distance was decreased compared to female controls.

Anthropometry↗
PubMed2000

Development and application of a synthetic peptide-based osteocalcin assay for the measurement of bone formation in mouse serum.

The mouse is frequently used as an animal model to study skeletal mechanisms relevant to humans. Biochemical markers of bone formation and resorption provide one of the key parameters for assessing skeletal metabolism. One biochemical marker that has proven to be useful in the studies of mouse skeletal metabolism is osteocalcin. Assay for osteocalcin is available in the mouse. The present study describes development of an osteocalcin radioimmunoassay (RIA) using a synthetic peptide. Intact osteocalcin purified from mouse bone extracts shows parallel displacement with synthetic peptide. Sensitivity of the RIA was 19 ng/ml. The average (n = 9) intra- and interassay coefficient of variation for two controls was less than 10%; the averaged recoveries were 106%. The osteocalcin concentration measured by peptide RIA shows a high correlation (r = 0.88, n = 117, P < 0.0001) with an intact osteocalcin assay. In addition, when the intact assay and peptide assays were applied to evaluate skeletal perturbation, similar results were obtained. Accordingly, osteocalcin levels measured by both intact and peptide-based RIA in 8-week C57BL/6J (n = 8) mice treated with PTH 1-34 were twofold higher compared with the vehicle-treated control group. Further studies of the application of the peptide-based RIA for osteocalcin revealed that osteocalcin levels in 4-week postovariectomized (OVX) C57BL/6N mice (n = 10) were 80% higher than the sham-operated (n = 10) mice receiving vehicle. OVX mice receiving weekly injections of estradiol (400 microg/kg body weight) were 38% lower compared with the OVX group treated with vehicle. In conclusion, the peptide-based RIA has analytical and a discriminative power similar to that of the intact osteocalcin assay but has the advantage that the resources for this assay are much easier to accrue.

Animals↗
PubMed2000

Calcitonin increases the concentration of insulin-like growth factors in serum-free cultures of human osteoblast-line cells.

The current studies were intended to determine whether the anabolic effects of calcitonin (CT) on human osteoblast-line cells were (1) unique to osteosarcoma cells or also evident in osteoblast-line cells derived from normal human bone; and/or (2) associated with effects on several insulin-like growth factor (IGF) system components. Preliminary studies identified several osteoblastic cell lines, derived from normal human bone, which showed calcitonindependent increases in cell proliferation, alkaline phosphatase activity, and/or (45)Ca uptake (P < 0.05-P < 0.001). Two of these cell lines-(human vertebrae) HBV-155 and HBV-163-were included with the human osteosarcoma cell line, SaOS-2, in most of our subsequent studies of calcitonin effects on selected IGF system components: IGF-II, IGF-I, and IGF binding proteins -3, -4, and -5. The results of those studies revealed that a 48 hour exposure to salmon CT caused a dose-dependent (0.03-3 mU/ml) increase in the net extracellular level of IGF-II (r = 0.96, P < 0.01) in serum-free cultures of SaOS-2 cells, with a maximal 60% increase at the highest tested dose (P < 0.02). Similar effects were seen with HBV-163 cells (r = 0.90, P < 0.01) and HBV-155 cells (r = 0.55, P < 0.02). The effect of calcitonin on the extracellular level of IGF-II was biphasic with respect to time: it decreased at 6 hours (P < 0.005 and P < 0.001, for SaOS-2 cells and HBV-163 cells, respectively) and increased at 24 hours (P < 0.02 and P < 0.05). These calcitonin-dependent increases in the extracellular level of IGF-II were associated with parallel increases in IGF-I (P < 0.005 for SaOS-2 cells and P < 0.03 for HBV-163 cells), but calcitonin did not affect the extracellular level of transforming growth factor (TGF)-beta. The calcitonin-dependent changes in IGF-II were not associated with changes in the extracellular levels of IGF binding proteins -3, -4, or -5. Finally, our studies showed that two other members of the CT superfamily-CT gene-related peptide and amylin-did not mimic the effect of CT to increase the extracellular level of IGF-II. Together, these data demonstrate that human osteoblast-line cells derived from normal human bone can respond to CT, and that those responses can include CT dose- and time-dependent increases in the extracellular levels of IGF-I and IGF-II.</hea

Alkaline Phosphatase↗
PubMed2000

Development and application of a serum C-telopeptide and osteocalcin assay to measure bone turnover in an ovariectomized rat model.

Biochemical markers applicable to the ovariectomized rat model can provide important tools for studying the bone remodeling process in this animal model of postmenopausal osteoporosis. We describe the development and application of two biochemical markers, a C-telopeptide (of type-I collagen) enzyme-linked immunosorbent assay (ELISA) for measuring bone resorption and an osteocalcin radioimmunoassay (RIA) for measuring bone formation in rat serum. The C-telopeptide ELISA is based on an affinity purified polyclonal antibody generated against human sequence DFSFLPQPPQEKAHDGGR. The antibody epitope involves amino acid sequence, which is similar in rat and human carboxyl terminal peptide of type-I (alpha 1) collagen. Sensitivity of the ELISA was 0.3 ng/ml. The averaged intra- and interassay variation was CV <7%. Averaged dilution and spiked recoveries were 91% and 105%, respectively. The second marker developed is a synthetic peptide-based osteocalcin RIA, which does not require isolation and purification of intact osteocalcin from rat bone. Osteocalcin antiserum used in the RIA was generated in rabbits against a synthetic peptide comprising amino acids 33-49 of the rat osteocalcin sequence. The sensitivity of the RIA was 0.15 ng/ml of peptide. The averaged intra (n = 10) and interassay variations for two controls were CV <9% and 12%, respectively. The averaged dilution and spiked recoveries were 99.6%. In vivo validation of the C-telopeptide ELISA and osteocalcin RIA was performed in an ovariectomized (OVX) rat model. In 12-week-old OVX Sprague Dawley rats, the C-telopeptide and osteocalcin concentrations were approximately 65% and 40%, respectively, higher than the sham group. Estradiol repletion significantly lowered the C-telopeptide and osteocalcin concentration to the levels of the sham group. In addition, changes in serum C-telopeptide concentration correlated negatively with trabecular BMD measured by pQCT (r = -0.51, P < 0.001). In conclusion, the C-telopeptide ELISA and osteocalcin RIA exhibited required sensitivity, accuracy, and adequate discriminatory power to be used for measuring bone resorption and bone formation in the ovariectomized rat model.

Amino Acid Sequence↗
PubMed2000

Serum insulin-like growth factor binding protein (IGFBP)-4 and IGFBP-5 in children with chronic renal failure: relationship to growth and glomerular filtration rate. The European Study Group for Nutritional Treatment of Chronic Renal Failure in Childhood. German Study Group for Growth Hormone Treatment in Chronic Renal Failure.

Growth retardation in children with chronic renal failure (CRF) is partly due to an inhibition of insulin-like growth factor (IGF) activity by an excess of high-affinity IGF-binding proteins (IGFBPs). The aim of this study was to analyze the serum levels and forms of IGFBP-4 and IGFBP-5 in CRF patients using specific, recently developed radioimmunoassays (RIAs) and immunoblot analysis. We examined 89 children [age 11.5 (2.8-19.0) years] with CRF [glomerular filtration rate 26.6 (7.0-67.4) ml/min per 1.73 m2], nine of them with end-stage renal disease undergoing peritoneal dialysis. Serum-immunoreactive IGFBP-4 levels were fourfold increased in CRF (prepubertal 1080+/-268 ng/ml; pubertal 989+/-299 ng/ml) compared to healthy prepubertal controls (265+/-73 ng/ml). In contrast, serum IGFBP-5 levels were not significantly increased neither in prepubertal (361+/-120 ng/ml vs 282+/-75 ng/ml in controls) nor pubertal CRF children (478+/-165 ng/ml vs 491+/-80 ng/ml in controls). Immunoblot analysis showed the presence of intact as well as fragmented IGFBP-4 and IGFBP-5. Serum IGFBP-4, but not IGFBP-5, levels were inversely correlated with GFR (r=-0.39, P<0.001). In prepubertal children, IGFBP-4 levels were inversely correlated with standardized height (r=-0.40; P<0.005). In contrast, IGFBP-5 levels were positively correlated both with standardized height (r=0.32, P<0.02) and baseline height velocity (r=0.45, P<0.005). A 3-month therapy with rhGH stimulated serum IGFBP-5 levels by 43% (P<0.01); there was no consistent effect on IGFBP-4 levels. There was a positive correlation between IGFBP-4 and IGFBP-2 (r=0.46, P<0.001); IGFBP-5 was positively correlated with IGF-I (r=0.59, P<0.001), IGF-II(r=0.42, P<0.001)and IGFBP-3 (r=0.47, P<0.001) and inversely correlated with IGFBP-1 (r=-0.41, P<0.001). In summary, serum IGFBP-4 is fourfold elevated in children with CRF in relation to the degree of renal dysfunction and contributes to the marked increase in IGF-binding capacity in CRF serum. The inverse correlation of serum IGFBP-4 with standardized height is consistent with its role as another inhibitor of the biological action of the IGFs on growth plate cartilage. In contrast, serum IGFBP-5 is not elevated in CRF serum and circulates mainly as proteolysed fragments. The positive correlation of serum IGFBP-5 with growth and its increase during GH therapy indicate that IGFBP-5 is a stimulatory IGFBP in patients with CRF, either by enhancing IGF activity through better presentation of TGF to its receptor or by an IGF-independent effect through activation of a specific, recently described putative IGFBP-5-receptor.

Adolescent↗
PubMed2000

Comparison of bone formation responses to parathyroid hormone(1-34), (1-31), and (2-34) in mice.

In this study we used a mouse model system to compare the in vivo effects of parathyroid hormone(1-34) [PTH(1-34)] with that of PTH(1-31) or PTH(2-34) analogs. Daily subcutaneous administration of PTH(1-34) for 15 days caused a dose-dependent increase in the serum osteocalcin level and bone extract alkaline phosphatase activity, markers of bone formation. PTH(2-34) was much less potent, whereas PTH(1-31) was equipotent in stimulating bone formation parameters in mice. PTH(1-34) caused significant increases in serum calcium (after 4 h) and tartrate-resistant acid phosphatase activity in bone extract (after 4 h), whereas PTH(2-34) and PTH(1-31) were less potent. Because PTH(1-31) caused a smaller increase in bone resorption parameters compared to PTH(1-34), despite similar effects on bone formation parameters, we evaluated the long-term anabolic effects of PTH(1-31) and PTH(1-34) in mice. Weekly evaluations of serum osteocalcin levels demonstrated that daily injections of PTH(1-34) and PTH(1-31) at 80 microg/kg body weight increased serum osteocalcin levels within 1 week of the start of treatment, which were maintained during the entire 22 week treatment. Assessment of bone density at the end of the treatment period with peripheral quantitated computed tomography (pQCT) revealed that PTH(1-34) caused a significantly greater increase in femoral bone density compared to PTH(1-31) at the middiaphysis (18% vs. 9% over vehicle control; p < 0.001). Both PTH(1-34) and PTH(1-31) increased periosteal circumference compared to vehicle (p < 0.01) without a significant difference between the two treatments. In contrast, PTH(1-34) caused a significantly greater reduction in endosteal circumference than PTH(1-31) (p < 0.001). Both analogs significantly increased maximum load and area of moment of inertia over the vehicle group. In conclusion, our findings suggest that PTH(1-34) and PTH(1-31) may exhibit different anabolic effects at the periosteum vs. endosteum in the long bones of mice.

Animals↗
PubMed2000

Development and evaluation of C-telopeptide enzyme-linked immunoassay for measurement of bone resorption in mouse serum.

The mouse is increasingly being used as an animal model for the study of skeletal phenotypes in humans, mainly because of the ease of genetic manipulation. Biochemical markers of bone metabolism provide a valuable parameter for the assessment of skeletal metabolism. In the mouse model, assays for bone formation have been available for a long time; however, little is known about bone resorption markers. The present study describes the development of a serum C-telopeptide enzyme-linked immunoassay (ELISA), which measures degradation products of type I collagen that are generated by osteoclastic bone resorption. The C-telopeptide ELISA uses affinity-purified antibodies generated against human sequence DFSFLPQPPQEKAHDGGR. The epitope involves an amino acid sequence, which is identical in the mouse and human C-terminal peptide of type I collagen (alpha1 chain). Sensitivity of the ELISA used was <0.1 ng/mL. The average intra- (n = 10) and interassay (n = 8) coefficient of variation for two controls was <12%. The average dilution and spike recovery rates were 98% and 97%, respectively. Application of the ELISA to measure C-telopeptide in 3-4-week postovariectomized (ovx) C57BL/6J (B6) mice (n = 9 or 10) showed a 45% higher C-telopeptide concentration than the sham-operated mice. Treatment of ovx mice with estradiol (400 microg/kg body weight) or alendronate (1.0 mg/kg body weight) resulted in a 20%-50% decrease in C-telopeptide levels compared to the vehicle-treated ovx group. In addition, B6 mice fed a calcium-deficient diet (0.01% calcium) showed a 50% higher C-telopeptide concentration compared to the B6 mice receiving a normal diet (0.6% calcium). In conclusion, the C-telopeptide ELISA exhibited acceptable analytical performance and sufficient discriminatory power to show expected directional changes in the rate of bone resorption following ovariectomy, ovx plus estradiol or alendronate treatment, and administration of a calcium-deficient diet. Therefore, the ELISA developed in this study could be used for measuring bone resorption in the mouse model.

Alendronate↗
PubMed2000

Identification of transcription activators that regulate gonococcal adaptation from aerobic to anaerobic or oxygen-limited growth.

Analysis of the Neisseria gonorrhoeae DNA sequence database revealed the presence of two genes, one encoding a protein predicted to be 37. 5% identical (50% similar) in amino acid sequence to the Escherichia coli FNR protein and the other encoding a protein 41% and 42% identical (54 and 51% sequence similarity) to the E. coli NarL and NarP proteins respectively. Both genes have been cloned into E. coli and insertionally inactivated in vitro. The mutated genes have been transformed into gonococci and recombined into the chromosome. The fnr mutation totally abolished and the narP mutation severely diminished the ability of gonococci to: (i) grow anaerobically; (ii) adapt to oxygen-limited growth; (iii) initiate transcription from the aniA promoter (which directs the expression of a copper-containing nitrite reductase, AniA, in response to the presence of nitrite); and (iv) reduce nitrite during growth in oxygen-limited media. The product of nitrite reduction was identified to be nitrous oxide. Immediately upstream of the narL/narP gene is an open reading frame that, if translated, would encode a homologue of the E. coli nitrate- and nitrite-sensing proteins NarX and NarQ. As transcription from the aniA promoter was not activated during oxygen-limited growth in the presence of nitrate, the gonococcal two-component regulatory system is designated NarQ-NarP rather than NarX-NarL. As far as we are aware, this is the first well-documented example of a two-component regulatory system working in partnership with a transcription activator in pathogenic neisseria. A 45 kDa c-type cytochrome that was synthesized during oxygen-limited, but not during oxygen sufficient, growth was identified as a homologue of cytochrome c peroxidases (CCP) of other bacteria. The gene for this cytochrome, designated ccp, was located, and its regulatory region was cloned into the promoter probe vector pLES94. Transcription from the ccp promoter was repressed during aerobic growth and induced during oxygen-limited growth and was totally FNR dependent, suggesting that the gonococcal FNR protein is a transcription activator of at least two genes. However, unlike AniA, synthesis of the CCP homologue was insensitive to the presence of nitrite during oxygen-limited growth.

Adaptation, Physiological↗
PubMed2000

Insulin-like growth factor system components in hyperparathyroidism and renal osteodystrophy.

BACKGROUND: The insulin-like growth factor (IGF) system plays a key role in regulation of bone formation. In patients with renal osteodystrophy, an elevation of some IGF binding proteins (IGFBPs) has been described, but there is no study measuring serum levels of both IGF-I and IGF-II as well as IGFBP-1 to -6 in different forms of renal osteodystrophy and hyperparathyroidism. METHODS: In a cross-sectional study, we investigated 319 patients with mild (N = 29), moderate (N = 48), preuremic (N = 37), and end-stage renal failure (ESRF; N = 205). The ESRF group was treated by hemodialysis (HD; N = 148), peritoneal dialysis (PD; N = 27), or renal transplantation (RTX; N = 30). As controls without renal failure, we recruited age-matched healthy subjects (N = 87) and patients with primary hyperparathyroidism (pHPT; N = 25). Serum levels of total and free IGF-I, IGF-II, IGFBP-1 to -6, and biochemical bone markers including intact parathyroid hormone (PTH), bone alkaline phosphatase (B-ALP), and osteocalcin (OSC) were measured by specific immunometric assays. IGF system components and bone markers were correlated with clinical and bone histologic findings. Mean values +/- SEM are given. RESULTS: With declining renal function a significant increase was measured for IGFBP-1 (range 7- to 14-fold), IGFBP-2 (3- to 8-fold), IGFBP-3 (1.5- to 3-fold), IGFBP-4 (3- to 19-fold), and IGFBP-6 (8- to 25-fold), whereas IGFBP-5 levels tended to decrease (1.3- to 1. 6-fold). In contrast, serum levels of IGF-I, free IGF-I, and IGF-II remained constant in most patients. Compared with renal failure patients, pHPT patients showed a similar decline in IGFBP-5 levels and less elevated levels of IGFBP-1 (3.5-fold), IGFBP-2 (2-fold), IGFBP-3 (1.2-fold), and IGFBP-6 (4-fold) but no elevation of IGFBP-4 levels. In all subjects, free and total IGF-I levels showed significant negative correlations with IGFBP-1, IGFBP-2, and IGFBP-4 (that is, inhibitory IGF system components) and significant positive correlations with IGFBP-3 and IGFBP-5 (that is, stimulatory IGF system components). A positive correlation was observed between IGF-II and IGFBP-6. ESRF patients with mixed uremic bone disease and histologic evidence for osteopenia revealed significantly (P < 0.05) higher levels of IGFBP-2 and IGFBP-4 but lower IGFBP-5 levels. Histologic parameters of bone formation showed significant positive correlations with serum levels of IGF-I, IGF-II, and IGFBP-5. In contrast, IGFBP-2 and IGFBP-4 correlated positively with indices of bone loss. Moreover, dialysis patients with low bone turnover (N = 24) showed significantly (P < 0.05) lower levels of IGFBP-5, PTH, B-ALP, and OSC than patients with high bone turnover. CONCLUSION: Patients with primary and secondary hyperparathyroidism showed lower levels of the putative stimulatory IGFBP-5 but higher levels of IGFBP-1, -2, -3, and -6, whereas total IGF-I and IGF-II levels were not or only moderately increased. The marked increase in serum levels of IGFBP-4 appeared to be characteristic for chronic renal failure. IGFBP-5 correlated with biochemical markers and histologic indices of bone formation in renal osteodystrophy patients and was not influenced by renal function. Therefore, IGFBP-5 may gain significance as a serological marker for osteopenia and low bone turnover in long-term dialysis patients.

Adult↗
PubMed2000

Diabetic retinopathy is associated with decreased serum levels of free IGF-I and changes of IGF-binding proteins.

In patients with diabetic retinopathy, elevated serum levels of total circulating insulin-like growth factor-I (IGF-I) have been implicated as an important mediator of the disease. There is no study, however, measuring free IGF-I levels in patients with diabetic retinopathy which mediate the biological effects of IGF-I and are modulated by a complex system of six specific IGF binding proteins (IGFBPs) and several IGFBP proteases.

Aged↗