Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Formates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources
PubMed1996

Evaluation of nitric oxide formation from nitrates in pig coronary arteries.

To clarify the hypothesis that organic nitrates are converted to nitric oxide (NO) via nitrite ion (NO2-) by glutathione S-transferase, the metabolic conversion of four nitrates was examined in pig coronary arteries and compared with that in rat liver. Nitrates caused the relaxation of the artery muscles with the order of nitroglycerin > isosorbide dinitrate > nicorandil > or = nipradilol, whereas the order of NO formation in the arteries was nitroglycerin > isosorbide dinitrate > nipradilol > nicorandil. The same order of NO formation from the nitrates was also observed in liver cytosol. Nicorandil may cause more relaxation than nipradilol by both NO releasing and other (unknown) actions. Although the order of the potency in NO2- formation from the nitrates in liver cytosol was the same as that seen in NO formation, NO2- was not detected in pig coronary arteries. Thus NO2- formation from the nitrates correlated with NO formation in liver cytosol but not in pig arteries. When nonenzymatic and enzymatic NO formations from nitroglycerin were examined in the arteries, the enzymatic NO formation, which was not inhibited by glutathione S-transferase inhibitors, was 13% of the total NO. These results indicate that in pig coronary arteries, nitrates release NO mostly through a nonenzymatic manner, although there is a slight amount of enzymatically produced NO, and glutathione S-transferase may not contribute to the enzymatic NO formation.

Animals↗
PubMed2003

A synthetic peptide fragment of human MEPE stimulates new bone formation in vitro and in vivo.

UNLABELLED: Matrix extracellular phosphoglycoprotein (MEPE) was proposed as a candidate for the phosphaturic hormone phosphatonin. We found that a synthetic peptide fragment of MEPE containing the RGD and SGDG sequence stimulated new bone formation in vitro and in vivo. INTRODUCTION: Matrix extracellular phosphoglycoprotein (MEPE) was recently identified as a candidate for the phosphaturic hormone phosphatonin, which has been implicated in disturbed phosphate metabolism, rickets, and osteomalacia associated with X-linked hypophosphatemic rickets (XLH) and oncogenic hypophosphatemic osteomalacia (OHO). MEPE expression was predominantly found in osteoblasts, and mice deficient in a homolog of MEPE showed increased bone density, suggesting that MEPE produced in osteoblasts negatively regulates bone formation. In this study, we examined the effects of a synthetic 23mer peptide fragment of MEPE (AC-100, region 242-264) containing the RGD (integrin-binding) and SGDG (glycosaminoglycan-attachment) motif on bone formation in vitro and in vivo. MATERIALS AND METHODS: The osteogenic activity of AC-100 was examined in organ cultures of neonatal mouse calvariae and in vivo by injecting AC-100 onto the calvariae of mice. RESULTS: Histomorphometric examination showed that AC-100 stimulated new bone formation with increased numbers of osteoblasts in neonatal mouse calvariae in organ culture. In contrast, synthetic MEPE fragment peptides without either the RGD or SGDG motif failed to increase new bone formation. Repeated daily subcutaneous injections of AC-100 onto the calvariae in mice increased bone thickness and stimulated new bone formation as determined by the calcein double-labeling technique. However, peptides in which the RGD or SGDG sequence was scrambled did not stimulate new bone formation in vivo. AC-100 increased cell proliferation and alkaline phosphatase activity and activated focal adhesion kinase (FAK) and extracellular signal-regulated protein kinase (ERK) in human primary osteoblasts. CONCLUSION: Our results show that a synthetic peptide corresponding with the sequence of human MEPE fragment stimulates new bone formation with increased number of osteoblasts. The results also suggest that the RGD and SGDG motifs are critical to the osteogenic activity of AC-100, presumably through activating integrin signaling pathways in osteoblasts. The anabolic effects of AC-100 may be beneficial for bone diseases associated with decreased bone formation.

Amino Acid Motifs↗
PubMed2005

Differential effect of BMP4 on NIH/3T3 and C2C12 cells: implications for endochondral bone formation.

UNLABELLED: After intramuscular implantation, BMP4-expressing NIH/3T3 fibroblasts and BMP4-expressing C2C12 myoblasts can promote ectopic cartilage and bone formation. Fibroblasts tend to undergo chondrogenesis, whereas myoblasts primarily undergo osteogenesis. These results suggest that endochondral bone formation may involve different cell types, a finding that could have major implications for the tissue engineering of bone and cartilage. INTRODUCTION: The delivery of BMP4 through cell-based gene therapy can trigger ectopic endochondral bone formation in skeletal muscle. We hypothesized that, when stimulated with or transduced to express BMP4, different types of cells residing within skeletal muscle might participate in different stages of endochondral bone formation. MATERIALS AND METHODS: We compared the responses of a fibroblast cell line (NIH/3T3), a myoblast cell line (C2C12), primary fibroblasts, and primary myoblasts to BMP4 stimulation in vitro. We then transduced the four cell populations to express BMP4 and compared their ability to promote ectopic endochondral bone formation in skeletal muscle. RESULTS: Under the influence of BMP4 in vitro and in vivo, NIH/3T3 cells differentiated toward both chondrogenic and osteogenic lineages, whereas most C2C12 cells underwent primarily osteogenic differentiation. NIH/3T3 cells genetically modified to express BMP4 induced delayed but more robust cartilage formation than did genetically modified C2C12 cells, which promoted rapid ossification. These differences in terms of the timing and amount of cartilage and bone formation persisted even after we introduced a retrovirus encoding dominant negative Runx2 (DNRunx2) into the C2C12 cells, which interferes with the function of Runx2. Superior osteogenic potential was also displayed by the primary myoblasts in vitro and in vivo compared with the primary fibroblasts. The different proliferation abilities and differentiation potentials exhibited by these cells when influenced by BMP4 may at least partially explain the differing roles that BMP4-expressing myogenic cells and BMP4-expressing fibroblastic cells play in endochondral bone formation. CONCLUSIONS: Our findings suggest that the process of endochondral bone formation in skeletal muscle after delivery of BMP4 involves different cell types, including fibroblastic cells, which are more involved in the chondrogenic phases, and myoblastic cells, which are primarily involved in osteogenesis. These findings could have important implications for the development of tissue engineering applications focused on bone and cartilage repair.

Alkaline Phosphatase↗
PubMed2005

Sympathetic nervous system does not mediate the load-induced cortical new bone formation.

UNLABELLED: The contribution of the SNS to bone's response to mechanical loading is unclear. Using a noninvasive model of axial loading of the murine tibia, we found that sciatic neurectomy enhances load-induced new cortical bone formation and that pharmacological blockade of the SNS does not affect such responses, indicating that the SNS does not mediate the osteogenic effects of loading in cortical bone. INTRODUCTION: There is increasing evidence that the sympathetic nervous system (SNS) contributes to the regulation of bone mass and may influence remodeling by modulating bones' response to mechanical load-bearing. The aim of this study was to examine the effect of sciatic neurectomy (SN) on the changes in cortical bone formation induced in response to mechanical loading and to investigate whether the SNS is directly involved in such load-induced responses. MATERIALS AND METHODS: Accordingly, load-induced responses were compared in tibias of growing and adult control C57Bl/J6 mice and in mice submitted to unilateral SN; noninvasive axial loading that induced 2,000 microstrain on the tibia lateral midshaft cortex was applied cyclically, 5 or 100 days after surgery, for 7 minutes, 3 days/week for 2 weeks, and mice received calcein on the third and last days of loading. Tibias were processed for histomorphometry, and transverse confocal images from diaphyseal sites were analyzed to quantify new cortical bone formation. Chemical SNS inactivation was achieved by prolonged daily treatment with guanethidine sulfate (GS) or by the introduction of propranolol in drinking water. RESULTS: Our results show that new cortical bone formation is enhanced by loading in all tibial sites examined and that load-induced periosteal and endosteal new bone formation was greater in the SN groups compared with sham-operated controls. This SN-related enhancement in load-induced cortical bone formation in tibias was more pronounced 100 days after neurectomy than after 5 days, suggesting that longer periods of immobilization promote a greater sensitivity to loading. In contrast, the increases in new bone formation induced in response to mechanical loading were similar in mice treated with either GS or propranolol compared with controls, indicating that inactivation of the SNS has no effect on load-induced cortical new bone formation. CONCLUSIONS: This study shows that SN, or the absence of loading function it entails, enhances loading-related new cortical bone formation in the tibia independently of the SNS.

Animals↗
PubMed1997

Quantification of biochemical markers of bone turnover by kinetic measures of bone formation and resorption in young healthy females.

The quantification of biochemical markers of bone formation and resorption with kinetic measures of bone turnover is an essential step in their validation. Some biochemical markers have been validated by quantification against formation and resorption rates measured by calcium kinetics in adults with bone disease. However, none has been validated in healthy individuals who are undergoing skeletal growth and bone consolidation. Therefore, we have measured biochemical markers of bone formation (serum osteocalcin [OC], bone-specific alkaline phosphatase [BAP], and total alkaline phosphatase [ALP]) and resorption (serum tartrate resistant acid phosphatase [TRAP], urinary cross-linked N teleopeptides of type I collagen/creatinine [NTx/Cr], and hydroxyproline/creatinine [OHP/Cr]) in healthy females aged 11-32 years (n = 31) after an overnight fast to determine their relationship with bone formation (Vo+) and bone resorption (Vo-) as measured by calcium kinetics and balance. All biochemical markers were highly intercorrelated (r > 0.6, p < 0.001) as were Vo+ and Vo- (r = 0.91, p < 0.001). Highly significant correlations were present between bone formation measured by calcium kinetics (Vo+) and serum levels of bone biochemical markers (OC, r = 0.82, p = 0.001; ALP, r = 0.92, p = 0.001; and BAP, r = 0.90, p = 0.001) and between bone resorption measured by calcium kinetics (Vo-) and fasting serum levels and urine creatinine ratios of biochemical markers (TRAP, r = 0.77, p < 0.001; OHP/Cr, r = 0.79, p < 0.001; and NTx/Cr, r = 0.70, p < 0.001). Thus, biochemical markers of bone formation and resorption can be used to predict calcium kinetic rates during skeletal growth and the early years of formation of peak bone mass, ages at which strategies to build peak bone mass are important. Biochemical markers of formation and resorption are equally useful in predicting either the bone formation rate or the resorption rate.

Acid Phosphatase↗
PubMed1998

Estrogen via the estrogen receptor blocks cAMP-mediated parathyroid hormone (PTH)-stimulated osteoclast formation.

Several lines of evidence indicate that estrogen inhibits parathyroid hormone (PTH)-induced bone resorption in vivo and in vitro. However, its precise mechanism remains unknown. The present study was performed to investigate whether osteoclast precursor cells possess the receptors for PTH/PTH-related protein (PTHrP) and/or estrogen and to clarify the mechanism by which estrogen affects PTH-induced osteoclast-like cell (Ocl) formation. The polymerase chain reaction (PCR) product corresponding in size to the mouse PTH/PTHrP receptor cDNA was detected in mouse hemopoietic blast cells supported by granulocyte-macrophage colony-stimulating factor (GM-CSF) as well as in osteoblastic MC3T3-E1 cells. The nucleotide sequence of the PTH/PTHrP receptor PCR product of hemopoietic blast cells was found to be 95.4% identical to that of PTH/PTHrP receptor cDNA of rat osteoblastic ROS cells. The PCR product corresponding in size to the mouse estrogen receptor cDNA was detected in mouse hemopoietic blast cells supported by GM-CSF as well as in MC3T3-E1 cells. The nucleotide sequence of the estrogen receptor PCR product of hemopoietic blast cells was completely identical to that of mouse estrogen receptor cDNA. 17Beta-estradiol (17beta-E2) but not 17alpha-E2 dose dependently antagonized Ocl formation stimulated by human (h) PTH(1-34) at a minimal effective concentration of 10(-10) M in the hemopoietic blast cell culture. 17Beta-E2 also significantly inhibited Ocl formation stimulated by 10(-8) M hPTHrP(1-34), while it did not affect 1,25-dihydroxyvitamin D3-induced Ocl formation. However, 10(-8) M 17beta-E2 significantly inhibited Ocl formation stimulated by dibutyryladenosine cAMP (10(-4) M) and Sp-cAMPS (10(-4) M), an activator of cAMP-dependent protein kinase (PKA) as well as forskolin (10(-5) M). In contrast, 17beta-E2 did not affect Ocl formation by either phorbol myristate acetate (10(-7) M), an activator of protein kinase C (PKC), or A23187 (10(-7) M), a calcium ionophore. The pretreatment with 17beta-E2 significantly inhibited Ocl formation induced by the combined treatment with PTH and PKC inhibitors (H7 or staurosporine), while it did not affect Ocl formation stimulated by the combined treatment with PTH and Rp-cAMPS, a PKA inhibitor. The present data indicate that estrogen inhibits PTH-stimulated Ocl formation by directly acting on hemopoietic blast cells, possibly through blocking a PKA pathway but not a calcium/PKC pathway.

Animals↗
PubMed1998

Chinese hamster ovary cells expressing alpha4beta1 integrin stimulate osteoclast formation in vitro.

It is reported that Chinese hamster ovary cells transfected with human alpha4 cDNA (alpha4CHOs) and expressing functional alpha4beta1 integrin developed bone metasasis in nude mice. To clarify the role of alpha4beta1 integrin in bone metastasis, in terms of tumor-mediated bone destruction, we examined whether alpha4CHOs stimulate osteoclast formation in cocultures with mouse bone marrow cells. The number of osteoclast-like cells identified as tartrate-resistant acid phosphatase positive multinucleated cells (TRAP(+) MNCs) formed from bone marrow cells increased with the increasing number of alpha4CHOs cocultured. The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and prostaglandin E2 (PGE2) on TRAP(+) MNC formation were enhanced in cocultures with alpha4CHOs. TRAP(+) MNCs induced by alpha4CHOs possessed calcitonin receptors and resorbed calcified tissues. In cocultures, alpha4CHOs and bone marrow stromal cells were in contact with each other and bone marrow stromal cells expressed vascular cell adhesion molecule-1 (VCAM-1), which is one of the ligands for alpha4beta1 integrin. TRAP(+) MNC formation was not stimulated in cocultures where direct contact between alpha4CHOs and bone marrow cells was inhibited by membrane filters. Alpha4CHOs do not support TRAP(+) MNC formation in cocultures with spleen cells but do support TRAP(+) mononuclear cell and MNC formation from spleen cells in the presence of osteoblastic cells. Cultured media from alpha4CHOs, bone marrow cells, and cocultures of alpha4CHOs and bone marrow cells did not stimulate TRAP(+) MNC formation or enhance the effects of 1,25(OH)2D3 and PGE2 in bone marrow cultures. The concentrations of PGE2 and interleukin-6 (IL-6) in cultured media were not different between the cultures of bone marrow cells and the cocultures of bone marrow cells and alpha4CHOs. Anti-human alpha4 and anti-mouse VCAM-1 antibodies inhibited TRAP(+) MNC formation induced by alpha4CHOs. These results indicate that alpha4CHOs stimulated TRAP(+) MNC formation through direct cell-to-cell interaction between alpha4beta1 and VCAM-1. It is suggested that in addition to various soluble factors regulating osteoclast formation, cell-to-cell interaction between tumor cells and bone marrow cells is important for inducing osteoclasts at the site of bone metastasis and leading to bone destruction.

Acid Phosphatase↗
PubMed2003

Shock wave application enhances pertussis toxin protein-sensitive bone formation of segmental femoral defect in rats.

UNLABELLED: Extracorporeal shock waves (ESWs) elicit a dose-dependent effect on the healing of segmental femoral defects in rats. After ESW treatment, the segmental defect underwent progressive mesenchymal aggregation, endochondral ossification, and hard callus formation. Along with the intensive bone formation, there was a persistent increase in TGF-beta1 and BMP-2 expression. Pretreatment with pertussis toxin reduced ESW-promoted callus formation and gap healing, which presumably suggests that Gi proteins mediate osteogenic signaling. INTRODUCTION: Extracorporeal shock waves (ESWs) have previously been used to promote bone repair. In our previous report, we found that ESWs promoted osteogenic differentiation of mesenchymal cells through membrane perturbation and activation of Ras protein. In this report, we show that ESWs elicit a dose-dependent effect on the healing of segmental defects and that Gi proteins play an important role in mediating ESW stimulation. MATERIALS AND METHODS: Rats with segmental femoral defects were subjected to ESW treatment at different energy flux densities (EFD) and impulses. Bone mass (mineral density and calcium content), osteogenic activities (bone alkaline phosphatase activity and osteocalcin content), and immunohistochemistry were assessed. RESULTS: An optimal ESW energy (500 impulses at 0.16 mJ/mm2 EFD) stimulated complete bone healing without complications. ESW-augmented healing was characterized by significant increases (p < 0.01) in callus size, bone mineral density, and bone tissue formation. With exposure to ESW, alkaline phosphatase activity and osteocalcin production in calluses were found to be significantly enhanced (p < 0.05). After ESW treatment, the histological changes we noted included progressive mesenchymal aggregation, endochondral ossification, and hard callus formation. Intensive bone formation was associated with a persistent increase in transforming growth factor-beta 1 (TGF-beta1) and bone morphogenetic protein-2 (BMP-2) expression, suggesting both growth factors were active in ESW-promoted bone formation. We also found that pertussis toxin, an inhibitor of membrane-bound Gi proteins, significantly reduced (p < 0.01) ESW promotion of callus formation and fracture healing. CONCLUSION: ESW treatments enhanced bone formation and the healing of segmental femoral defects in rats. It also seems likely that TGF-beta1 and BMP-2 are important osteogenic factors for ESW promotion of fracture healing, presumably through Gi protein-mediated osteogenic signaling.

Absorptiometry, Photon↗
PubMed2006

[Effect of beta-TCP containing the bone-growth promoting compound, TAK-778, on the vertex bone of rat--change of volmetric bone formation corresponding to the containing volume of TAK-778].

PURPOSE: This study was conducted to histomorphologically determine the quantity of bone formation induced by TAK-778, a 3-benzothiepin derivative, (Takeda Pharmaceutical Co.Ltd.), in various amounts, using b-tricalcium phosphate granules (beta-TCP; OLYMPUS Corp.) as a carrier for the osteogenetic agent. METHODS: Ten-week-old female SD rats were used. An incision was made over the parietal region of the head. The cranial periosteum was ablated and a titanium tube was fixed with an adhesive resin cement to the central part of the head, through which a mixture of TAK-778 and beta-TCP was implanted under various conditions. Tissue specimens were prepared at 4, 8, and 16 weeks after the implantation for histomorphological examination, and the proportion of new bone formation was compared at fixed time points using the NIH imaging software. The amount of new bone formation was examined every week after the implantation of TAK-778 at various doses, and the mean values were compared using Fisher's PSLD test (P< 0.05). RESULTS: The histomorphological observations revealed new bone formation in all the groups, irrespective of the amount and the duration of implantation of TAK-778. A comparative study revealed that the amount of new bone formation was the largest at 16 weeks following the implantation of a mixture of beta-TCP and 100 mg of TAK-778. CONCLUSIONS: 1. The present study confirmed the acceleration of new bone formation soon after TAK-778 implantation. 2. The results suggested that the action of TAK-778 could be maintained over time if the agent was used in combination with beta-TCP. 3. The time-course of bone formation differed depending on the proportion of TAK-778 and beta-TCP in the mixture used. 4. TAK-778 at the dose of 10 mg or 50 mg was more effective than that at the dose of 100 mg for the early formation of new bone. These results indicate that TAK-778 accelerates the formation of new bone and that beta-TCP is a useful carrier for TAK-778.

Animals↗
PubMed2002

Physiologic subperiosteal new bone formation: prevalence, distribution, and thickness in neonates and infants.

OBJECTIVE: The objective of our study was to determine the prevalence, distribution, and thickness of physiologic subperiosteal new bone formation in neonates and infants. MATERIALS AND METHODS: High-detail postmortem skeletal radiologic surveys of 101 neonates and infants who had died from sudden infant death syndrome were reviewed. The average age at the time of death was 2.6 months (range, 2 weeks-8 months 2 weeks). The location, distribution, and thickness of subperiosteal new bone formation of the long bones were noted and measured with an ocular magnification system. RESULTS: subperiosteal new bone formation was identified in 35 infants (35%), all of whom were between 1 and 4 months of age. The prevalence of subperiosteal new bone formation involving one or more bones was 37% for ages 1-2 months, 55% for ages 2-3 months, and 35% for ages 3-4 months. subperiosteal new bone formation involved the tibia in 29 infants (bilateral involvement in 19) and the femurs in 14 infants (bilateral involvement in 11). The humerus was a site of subperiosteal new bone formation in 12 infants; the ulna, in seven infants; and the radius, in two infants. The thickness of the subperiosteal new bone formation was never more than 1.8 mm, and the average thickness for the various long bones ranged from 0.7 to 0.9 mm. CONCLUSION: Our results suggest that subperiosteal new bone formation is a common finding in infants 1-4 months of age. It is potentially an abnormal finding in neonates (CI = 0.0, 0.007) and in infants older than 4 months of age (CI = 0.0, 0.003). A thickness of 2 mm or more in subperiosteal new bone formation is likely to be abnormal and should prompt further diagnostic evaluation.

Femur↗
PubMedDate not supplied

Reduction of adhesion formation by intraperitoneal administration of anti-inflammatory peptide 2.

Adhesion formation is a major source of postoperative morbidity and mortality. Therefore, the reduction of postoperative adhesion formation would be of clinical benefit. Various modalities have been shown to reduce adhesion formation, including fibrinolytic enzymes, nonsteroidal anti-inflammatory drugs, and barriers that reduce the apposition of sites of potential adhesion formation. This study examined the ability of a phospholipase A2 inhibitor, anti-inflammatory peptide 2 (antinflammin), to reduce the formation of intraperitoneal adhesions in two rabbit models of adhesion formation. In the sidewall model, antinflammin was administered via Alzet miniosmotic pump for the entire postoperative interval, and there was a dose-dependent reduction in the area of the sidewall injury that was involved in adhesions to the cecum and the bowel. In the double uterine horn model, antinflammin was administered via Alzet miniosmotic pump to the area of injury for either 1, 2, 3, or 7 days. Administration of antinflammin for as little as 24 h after surgery significantly reduced the extent of adhesion formation. Administration of the peptide for longer periods of time did not further increase the reduction in adhesion formation. These studies clearly demonstrate that postoperative administration of antinflammin to the site of injury reduced the formation of postoperative adhesions in two animal models.

Animals↗
PubMed1976

The significance of varying SRBC/lymphocyte ratio in T cell rosette formation.

The incubation ratio of sheep red blood cells (SRBC) to lymphocytes is a critical factor in rosette formation, whereas the length of time SRBC and lymphocytes are incubated together does not significantly affect the percentage of lymphocytes forming rosettes. The graph obtained by plotting percentage of rosette formation against the ratio of SRBC to lymphocytes is similar to that resulting from the formation of bimolecular complexes. If rosette formation is analogous to formation of bimolecular complexes, maximal rosette formation occurs when the system is saturated, i.e., with excess SRBC, and is a measure of the total capacity of a lymphocyte population to form rosettes. In addition, the percentage of rosette formation observed at a limiting SRBC/lymphocyte ratio gives an indication of the avidity of the lymphocytes for SRBC. This interpretation may provide an explanation for the difference between the "active" and "total" rosettes. When the log of the SRBC/lymphocyte ratio is plotted against percentage of rosette formation, a straight line is obtained, suggesting that within a given normal lymphocyte sample, T cell subsets with different avidities are not detected by rosette formation at different SRBC/lymphocyte ratios.

Blood Cell Count↗
PubMed2001

Identification of the human cytochromes p450 responsible for in vitro formation of R- and S-norfluoxetine.

The formation of R- and S-norfluoxetine was analyzed in vitro in human liver microsomes. Low apparent K(m) values for R-norfluoxetine formation of < or =8 microM and S-norfluoxetine of <0.2 microM were determined. R-Norfluoxetine formation rates in a characterized microsomal bank correlated with the catalytic activities for cytochrome P450 (CYP) 2D6, CYP2C9, and CYP2C8. Expressed CYP2C9, CYP2C19, and CYP2D6 formed R-norfluoxetine following incubation with 1 microM R-fluoxetine and exhibited apparent K(m) values of 9.7, 8.5, and 1.8 microM, respectively. Multivariate correlation analysis identified CYP2C9 and CYP2D6 as significant regressors with R-norfluoxetine formation. Antibodies to the CYP2C subfamily and CYP2D6 each exhibited moderate inhibition of R-norfluoxetine formation. Therefore, CYP2D6 and CYP2C9 contribute to this biotransformation. At pharmacological concentrations of S-fluoxetine, S-norfluoxetine formation rates in the bank of microsomes were found to correlate only with CYP2D6 catalytic activity and only expressed CYP2D6 was found to be capable of forming S-norfluoxetine. Thus, it would appear that both CYP2D6 and CYP2C9 contribute to the formation of R-norfluoxetine, whereas only CYP2D6 is responsible for the conversion to S-norfluoxetine. Since the enantiomers of fluoxetine and norfluoxetine are inhibitors of CYP2D6, upon chronic dosing, the CYP2D6-mediated metabolism of the fluoxetine enantiomers would likely be inhibited, resulting in R-norfluoxetine formation being mediated by CYP2C9 and S-norfluoxetine formation being mediated by multiple high K(m) enzymes.

Antibodies, Monoclonal↗
PubMed2003

Stereoselectivity in trans-tramadol metabolism and trans-O-demethyltramadol formation in rat liver microsomes.

AIM: To study the stereoselectivity in trans-tramadol [(+/-)-trans-T] metabolism and trans-O-demethyltramadol (M1) formation. METHODS: (+)-, (-)-, Or (+/-)-trans-T was separately incubated with rat liver microsomes in vitro. The concentrations of (+/-)-trans-T and M1 enantiomers were determined by high performance capillary electrophoresis (HPCE). RESULTS: When each enantiomer of (+/-)-trans-T was incubated with rat liver microsomes, the metabolic rate of (+)-trans-T was lower than that of (-)-trans-T. The kinetics of (+)-, (-)-M1 formation was found to fit the single-enzyme Michaelis-Menten model. The Vmax and CLint of (+)-M1 formation were lower than those of (-)-M1 formation. When (+/-)-trans-T was used as the substrate, the metabolic rates of (+)-, (-)-trans-T, and the formation rates of (+)-M1, (-)-M1 decreased to different extents. Dextromethorphan (Dex), propafenone (Pro), and fluoxetine (Flu) could inhibit both the metabolism of (+/-)-trans-T enantiomers and the formation of M1 enantiomers. Pro and Flu were shown to enhance the stereoselectivity in both (+/-)-trans-T metabolism and M1 formation, and Dex could only enhance that in M1 formation. CONCLUSION: (+/-)-Trans-T metabolism and M1 formation were stereoselective, (-)-trans-T being preferentially metabolized and (-)-M1 being preferentially formed. There was interaction in metabolism between (+/-)-trans-T enantiomers. Dex, Pro, and Flu had different effects on the stereoselectivity.

Analgesics, Opioid↗
PubMed1992

Extracellular matrix stimulation of guinea pig megakaryocyte proplatelet formation in vitro is mediated through the vitronectin receptor.

We have used an in vitro culture system to study the role of extracellular matrix (ECM) in the fragmentation of guinea pig bone marrow megakaryocytes (MK) and the formation of proplatelet fragments from these cells. Proplatelet formation is stimulated by culturing the cells on a hydrated type I collagen gel in the presence of serum. MK express integrin proteins alpha 5, alpha 6, beta 1, and the alpha v beta 3 complex as demonstrated by immunofluorescence. A monoclonal antibody, LM 609, to the alpha v beta 3 vitronectin receptor blocked proplatelet formation, whereas the monoclonal antibodies to the beta 1, alpha 5, and alpha 6 integrin proteins did not inhibit proplatelet formation. The tetrapeptide Arg-Gly-Asp-Ser (RGDS) inhibits proplatelet formation; however, there was no inhibition by the fibronectin receptor-specific peptide GRGDdSP. The fibrinogen gamma chain peptide HHLGGAKQAGDV, which binds to the platelet membrane glycoprotein complex IIb-IIIa but not to the vitronectin receptor (VnR), did not inhibit proplatelet formation, nor did two different laminin peptides. In the absence of serum, 5.7% of MK spontaneously formed processes or fragmented. The addition of 50 micrograms/ml of vitronectin to serum-free cultures increased proplatelet formation to 21.5% of the MK, equal to cultures with 10% serum. Stimulation of proplatelet formation by vitronectin in serum-free cultures was inhibited by LM 609. Antibody staining with anti-bovine vitronectin antibody showed that MK contain intracellular vitronectin. These data show that guinea pig MK express alpha 5, alpha 6, beta 1, and alpha v beta 3 integrins. However, only the MK vitronectin receptor and its interaction with vitronectin plays an essential role in proplatelet formation in vitro.

Amino Acid Sequence↗
PubMed2004

Alfacalcidol prevents age-related bone loss and causes an atypical pattern of bone formation in aged male rats.

The current study was designed to investigate the skeletal effects of alfacalcidol in aged rats. Eighteen-month-old male rats were treated with 0, 0.1, or 0.2 microg/kg/d of alfacalcidol by daily oral gavage, 5 days/week for 12 weeks. At the beginning of the treatments, one group of rats was euthanized to serve as a baseline control. At the end of the study, the second lumbar vertebrae and the right tibial diaphysess were processed for bone histomorphometric analysis. The fourth lumbar vertebrae were subjected to strength testing. The control group of rats at 21 months of age had decreased serum testosterone levels and decreased cancellous bone mass associated with increased bone turnover on the trabecular surface. The older rats had increased bone turnover on the endocortical surface and decreased bone formation on the periosteal surface compared with the 18-month group. In contrast, alfacalcidol treatment increased cancellous and cortical bone mass in aged male rats. Trabecular bone resorption was decreased whereas bone formation was maintained or increased in the rats treated with alfacalcidol. In addition, endocortical bone formation was decreased whereas periosteal bone formation was increased in the rats treated with alfacalcidol compared with vehicle-treated rats. Marrow trabecular bone area was increased by alfacalcidol treatment in tibial diaphyses. Furthermore, bone strength of the lumbar vertebral body was increased after alfacalcidol treatment. An atypical pattern of bone formation on endosteal bone surfaces was seen in the rats treated with alfacalcidol. The atypical bone formation is characterized by small, focal packets of newly formed bone on trabecular and endocortical bone surfaces. This gave the appearance of the formation of "bone buds" emanating from trabecular surfaces. These bony outgrowths were mineralized and demonstrated significant fluorochrome label indicating recent mineralization. Also, lamellae of the bony buds did not run parallel to those of the trabecular plate to which they are attached. Arrest lines presented in most of the "bone buds". In summary, alfacalcidol treatment increased cancellous and cortical bone mass and improved bone strength, resulting in the prevention of age-related bone loss in aged male rats. An atypical pattern of bone formation observed in this study may be a result of minimodeling based bone formation stimulated by alfacalcidol treatment.

Aging↗
PubMed2005

Electronically signed documents in health care--analysis and assessment of data formats and transformation.

OBJECTIVES: Our objectives were to analyze and assess data formats for their suitability for conclusive and secure long-term archiving and to develop a concept for legally secure transformation of electronically signed documents that are not available in data formats appropriate for long-term archiving. METHODS: On the basis of literature review and Internet searches we developed general evaluation criteria to assess data formats with regard to their suitability for conclusive and secure long-term archiving. The assessment of data formats refers to format specifications and available literature. For the analyses of the transformation of signed documents we analyzed legal requirements on the basis of laws and ordinances as well as technical requirements by means of literature reviews, Internet searches and technical specifications. RESULTS: The following evaluation criteria are suited for this kind of assessment of data formats: transparency and standardization, stability, presentation and security. According to our assessment the following data formats are most suitable for conclusive and secure long-term archiving: PDF for formatted and unstructured text documents, XML for markup languages, TIFF for images in general, DICOM for medical images and S/MIME for the storage of e-mail. To transform electronically signed documents we propose an elementary procedure and universal basic model in form of an XML schema definition that includes the necessary legal and technical information. CONCLUSIONS: If electronic documents are to replace paper-based documents in patient records, they have to conform to the criteria for secure long-term archiving. The analyzed data formats are to be extended by mechanisms to guarantee the long-term security of electronic signatures. To transform large quantities of documents in a legally secure way, our basic model has to be extended for automated procedures.

Archives↗
PubMed1990

Vasopressin-induced polyphosphoinositide and phosphatidylcholine degradation in fibroblasts. Temporal relationship for formation of phospholipase C and phospholipase D hydrolysis products.

Cultured fibroblasts (REF52 cells) were employed to investigate phospholipid degradation in response to vasopressin (VP) treatment. There have been few studies in fibroblasts which characterize the pattern and relationship of phosphatidylinositol 4,5-bisphosphate (PIP2) and non-phosphoinositide hydrolysis elicited by VP. Here we demonstrate that VP-induced PIP2 hydrolysis is closely accompanied by phosphatidylcholine (PC) degradation by phospholipase D. Cells prelabeled with [3H]arachidonic acid showed rapid formation and diminution of [3H]diacylglycerol (DG) (5-15s) when treated with VP; this was accompanied by a reduction in polyphosphoinositide radioactivity. Radiolabeled inositol trisphosphate was generated with a similar time frame. In cells prelabeled with [3H]myristic acid, which is predominantly incorporated into cellular PC, VP elicited the generation of [3H]myristoyl phosphatidate (PA) as early as 15 s, in the absence of an increase in labeled DG. In the presence of ethanol the pattern of [3H]myristoyl phosphatidylethanol (PEt) formation coincided with [3H]myristoyl-PA formation in the absence of ethanol. PEt was similarly formed, in response to VP treatment, in cells prelabeled with 1-O-[3H]hexadecyl-2-lyso-sn-glycero-3-phosphocholine. The formation of PC-derived [3H]myristoyl-DG was characterized by a lag period of approximately 1 min, after which DG increased steadily over a 10-min period. Biphasic formation of DG was observed in cells prelabeled with [3H]arachidonic acid, and the formation of [3H]PA occurred in an uninterrupted fashion. Two protein kinase C agonists, phorbol diester and dioctanoylglycerol, elicited the formation of [3H]myristoyl-PEt. The inclusion of staurosporine, a protein kinase C inhibitor, blocked VP-induced [3H]myristoyl-PEt formation by 88%. These data demonstrate that VP elicits the coordinated hydrolysis of PIP2 by phospholipase C and PC hydrolysis by phospholipase D. This event results in the prolonged generation of PA and biphasic formation of DG. From the time courses shown, we hypothesize that the early generation of PA, heretofore ascribed to products of the polyphosphoinositide cycle, are in part derived from PC by phospholipase D.

Animals↗