Mourning the professionalization of midwifery.
Explore the source record for details and available documents.
Attitude of Health Personnel↗
Biomedical subjects
L Wilson
Publications and source records attributed to L Wilson.
The insulin-like growth factor binding protein superfamily: new perspectives.
The insulin-like growth factor (IGF) binding proteins (IGFBPs) were initially identified as carrier proteins for IGF-I and IGF-II in a variety of biologic fluids. Their presumed function was to protect IGF peptides from degradation and clearance, increase the half-life of the IGFs, and deliver them to appropriate tissue receptors. The concept of IGFBPs as simple carrier proteins has been complicated, however, by a number of observations: 1) the six IGFBPs vary in their tissue expression and their regulation by other hormones and growth factors; 2) the IGFBPs are subjected to proteolytic degradation, thereby altering their affinities for the IGFs; 3) IGFBP-3 and IGFBP-5, in addition to binding IGFs, also can associate with an acid-labile subunit, thereby increasing further the half-life of the IGFs; 4) in addition to modifying the access of IGF peptides to IGF and insulin receptors, several of the IGFBPs may be capable of increasing IGF action; 5) some of the IGFBPs may be capable of IGF-independent regulation of cell growth; 6) some of the IGFBPs are associated with cell membranes or possibly with membrane receptors; and 7) some of the IGFBPs have nuclear recognition sites and may be found within the nucleus. Additionally, a number of cDNAs identified recently have been found to encode proteins that bind IGFs, but with substantially lower affinities than is the case with IGFBPs. The N-terminal regions of the predicted proteins are structurally homologous to the classic IGFBPs, with conservation of the cysteine-rich region. These observations suggest that these low-affinity binders are members of an IGFBP superfamily, capable of regulating cell growth by both IGF-dependent and IGF-independent mechanisms.insulin-like growth factor, insulin-like growth factor binding proteins.
Humans↗
A note to fathers: it's you she wants.
Explore the source record for details and available documents.
Delivery, Obstetric↗
Detection of GTP and Pi in wild-type and mutated yeast microtubules: implications for the role of the GTP/GDP-Pi cap in microtubule dynamics.
Microtubule dynamics are believed to be controlled by a stabilizing cap of tubulin dimers at microtubule ends that contain either GTP or GDP and Pi in the exchangeable nucleotide site (E-site) of the beta-subunit. However, it has been difficult to obtain convincing evidence to support this hypothesis because the quantity of GTP and Pi in the E-site of assembled brain tubulin (the tubulin used in most studies thus far) is extremely low. In this study, we have measured the amount of GTP and Pi in the E-site of wild-type and mutated yeast assembled tubulins. In contrast to brain microtubules, 6% of the tubulin in a wild-type yeast microtubule contains a combination of E-site GTP and Pi. This result indicates that GTP hydrolysis and Pi release are not coupled to dimer addition to the end of the microtubule and supports the hypothesis that microtubules contain a cap of tubulin dimers with GTP or Pi in their E-sites. In addition, we have measured the E-site content of GTP and Pi in microtubules assembled from two yeast tubulins that had been mutated at residues T107 and T143 in beta-tubulin, sites thought to interact with the nucleotide bound in the E-site. Previous studies have shown that microtubules containing these mutated tubulins have modified dynamic behavior in vitro. The results from these experiments indicate that the GTP or GDP-Pi cap model does not adequately explain yeast microtubule dynamic behavior.
Animals↗
Antiproliferative mechanism of action of cryptophycin-52: kinetic stabilization of microtubule dynamics by high-affinity binding to microtubule ends.
Cryptophycin-52 (LY355703) is a new synthetic member of the cryptophycin family of antimitotic antitumor agents that is currently undergoing clinical evaluation. At high concentrations (>/=10 times the IC50), cryptophycin-52 blocked HeLa cell proliferation at mitosis by depolymerizing spindle microtubules and disrupting chromosome organization. However, low concentrations of cryptophycin-52 inhibited cell proliferation at mitosis (IC50 = 11 pM) without significantly altering spindle microtubule mass or organization. Cryptophycin-52 appears to be the most potent suppressor of microtubule dynamics found thus far. It suppressed the dynamic instability behavior of individual microtubules in vitro (IC50 = 20 nM), reducing the rate and extent of shortening and growing without significantly reducing polymer mass or mean microtubule length. Using [3H]cryptophycin-52, we found that the compound bound to microtubule ends in vitro with high affinity (Kd, 47 nM, maximum of approximately 19.5 cryptophycin-52 molecules per microtubule). By analyzing the effects of cryptophycin-52 on dynamics in relation to its binding to microtubules, we determined that approximately 5-6 molecules of cryptophycin-52 bound to a microtubule were sufficient to decrease dynamicity by 50%. Cryptophycin-52 became concentrated in cells 730-fold, and the resulting intracellular cryptophycin-52 concentration was similar to that required to stabilize microtubule dynamics in vitro. The data suggest that cryptophycin-52 potently perturbs kinetic events at microtubule ends that are required for microtubule function during mitosis and that it acts by forming a reversible cryptophycin-52-tubulin stabilizing cap at microtubule ends.
Antineoplastic Agents↗
Separation of tubulin subunits under nondenaturing conditions.
The dissociation and separation of the tubulin alpha- and beta-subunits have been achieved by binding alpha-subunits to an immunoadsorbent gel and selectively inducing release of free beta-subunits. The immunoadsorbent gel was prepared by coupling the monoclonal antibody YL1/2 to Sepharose 4B which specifically recognizes the C-terminal end of tyrosinated alpha-subunits. Extensive tubulin subunit dissociation and separation occurred in Tris buffer at neutral pH but was greatly enhanced at basic pHs (8. 0-8.5). The binding of colchicine to heterodimeric tubulin resulted in a marked protection against dissociation. The dissociation of tubulin subunits was accompanied by loss of colchicine binding capacity, and ability to polymerize into microtubules. As shown by circular dichroism, loss of functional properties was not due to extensive denaturation of tubulin, as tubulin retained most of its secondary structure. Neither of the separated alpha- or beta-subunits was able to bind colchicine, but functional tubulin that was able to bind colchicine could be reconstituted from the dissociated subunits by changing the buffer to a neutral mixture of Tris and Pipes. The yield of reconstitution, as estimated from kinetic measurements of colchicine binding capacity, amounted to about 25%. Such a yield can probably be improved with minor changes in experimental conditions. The quantitative dissociation of tubulin into separated "native" alpha- and beta-subunits should provide a powerful tool for further studies on the properties of the individual tubulin subunits and the structure-function relationships of the tubulins.
Animals↗
4-Chloro-o-phenylenediamine: a 26-week oral (in feed) mutagenicity study in Big Blue mice.
4-Chloro-o-phenylenediamine (4-C-o-PDA) is a liver carcinogen in mice and was found to be weakly mutagenic in the liver of female Big Blue mice after short term treatment. In the present study the test compound was given subchronically in the diet for 26 weeks at doses of 0, 5000 and 10,000 ppm. The corresponding average test substance intake was 2166 mg kg-1 day-1 (males: 1794 mg kg-1 day-1; females: 2539 mg kg-1 day-1) and 4610 mg kg-1 day-1 (males: 3926 mg kg-1 day-1; females 5925 mg kg-1 day-1) at the low and high dose, respectively. After sacrifice, tissues were flash frozen in liquid nitrogen. The lacI mutant frequency in the liver was determined from three male and three female mice per dose group. The genomically integrated transgene was recovered by packaging into lambda phage using Transpack packaging extract (Stratagene, La Jolla, USA) followed by infection of Escherichia coli strain SCS-8. Blue mutant plaques were scored against a background of clear non-mutant plaques. Food consumption decreased initially at 10,000 ppm, while no treatment related effect on food intake was observed at 5000 ppm. Body weight gain was found to be decreased in all treated animals. Absolute and relative liver weight increased in a dose-related manner, but only the latter effect was statistically significant. A clear dose dependent increase in lacI mutant frequencies was observed in the liver of both sexes. The following mutant frequencies (x10(-5)) were observed: 2.73+/-1.01 (males, untreated), 7.24+/-1.50 (females, untreated), 18.91+/-5.30 (5000 ppm, males), 24.91+/-7.58 (5000 ppm, females), 20.47+/-6.68 (10,000 ppm, males) and 36.17+/-14.98 (10,000 ppm, females). It is therefore concluded that 4-C-o-PDA is a strong mutagen in the liver of mice treated subchronically for 26 weeks.
Animal Feed↗
Low potency of taxol at microtubule minus ends: implications for its antimitotic and therapeutic mechanism.
In many cells, low concentrations of Taxol potently block mitosis at the transition from metaphase to anaphase, with no change in microtubule polymer mass and no microtubule bundling. Mitotic block ultimately results in apoptotic cell death and appears to be the most potent antitumor mechanism of Taxol (M. A. Jordan et al., Cancer Res. 56: 816-825, 1996). Mitotic inhibition results, at least in part, from stabilization of growing and shortening dynamics, specifically at the plus ends of microtubules, by the binding of very few Taxol molecules to the microtubule surface (M. A. Jordan et al., Proc. Natl. Acad. Sci. USA, 90: 9552-9556, 1993; W. B. Derry et al., Biochemistry, 34: 2203-2211, 1995). A number of actions of Taxol on mitotic spindle function may be due to its effects on microtubule dynamics at the minus ends of microtubules, effects that previously have not been described. Here, we determined the effects of Taxol on minus ends of purified microtubules at steady state. In contrast to the strong stabilizing effects on plus ends, substoichiometric ratios of Taxol bound to tubulin in microtubules did not affect growing, shortening, or dynamicity at minus ends. Thus, in blocked mitotic cells, Taxol can potently suppress dynamics at plus ends of spindle microtubules, whereas its impotence at minus ends permits continued microtubule depolymerization at the spindle poles. Differential effects of Taxol at opposite microtubule ends may explain Taxol's actions on spindle structure and function and its unique potent antitumor action.
Animals↗
Assembly and colchicine binding characteristics of tubulin with maximally tyrosinated and detyrosinated alpha-tubulins.
The posttranslational removal and readdition of tyrosine at the C-terminus of alpha-tubulin is associated with generation of microtubule populations that differ in intracellular distributions, turnover rates, and sensitivities to microtubule-depolymerization agents. Here, we compared the in vitro assembly and colchicine binding characteristics of tubulin dimer preparations composed of alpha-tubulin that had been maximally tyrosinated (approximately 40% tyrosinated) by tubulin-tyrosine ligase and maximally detyrosinated (100% detyrosinated) by carboxypeptidase A. Maximally tyrosinated and detyrosinated tubulins had similar critical concentrations for polymerization and similar association constants for colchicine binding. Microtubules polymerized from the two tubulins also had similar steady-state mean lengths and length distributions. The growing and shortening dynamics (dynamic instability parameters) of individual microtubules made from maximally tyrosinated or detyrosinated alpha-tubulin as determined by video-enhanced dark-field microscopy were similar, but subtle differences in the growing and shortening rates were found. On balance, however, the dynamicity and thus the overall kinetic stability of the two microtubule populations were indistinguishable. The results support the idea that detyrosination of alpha-tubulin does not by itself generate stable microtubules.
Animals↗
Development of an immunoassay specific for the PSA-ACT complex without the problem of high background.
We have developed an assay specific for the PSA-ACT (PSA-alpha 1-antichymotrypsin) complex that effectively diminishes the problem of high assay background commonly reported by other investigators. The assay follows a two-site ELISA format. Polyclonal anti-PSA antibodies were coated on the microplate to capture the PSA complex from the serum, whereas the biotinylated anti-ACT polyclonal antibodies and HRP-conjugated streptavidin were used for detection. The high background ordinarily associated with this assay was greatly reduced when milk casein was added in addition to albumin for blocking and when the Super Block was also included in the diluents for sample dilution and dilution of enzyme conjugated detecting antibodies. The assay has a sensitivity of 0.05 ng/mL. The within-run precision ranges from 4.2-7.2% and the between-run precision falls between 5.8-8.5%. Cross reactions with ACT and free PSA (fPSA) are 0.0001% and 0.02%, respectively. The highest concentration of PSA-ACT complex in the maternal sera was < 0.4 ng/mL by this assay, much less than reported in the literature. Using this improved assay, the sum of fPSA and PSA-ACT concentrations were less than that of their corresponding total PSA (tPSA) most of the time. We believe that this improved assay should be used to replace the current tPSA assay for screening, monitoring, and managing patients with prostate cancer.
Enzyme-Linked Immunosorbent Assay↗
Microtubule treadmilling: what goes around comes around.
"I'll see it when I believe it" Daniel Mazia Microtubules are centrally involved in many essential cell functions, including mitosis, vesicle motility, and the control of morphogenesis. Further, they appear to be involved in the control of cell cycle progression. To carry out these tasks properly, microtubules assume a protean array of different stability states and degrees of organization and they respond rapidly to requirements of the cell by modification of their organization and stability. In the typical fibroblast cell in culture, microtubules rapidly exchange their subunits with tubulin in the cytoplasmic pool, and control of this rapid turnover appears to be essential to their intrinsic capacity to perform such tasks as the separation of chromosomes in mitosis. Microtubules are not simple equilibrium polymers, but rather, they are capable of unusual nonequilibrium dynamic behaviors. One such behavior, termed treadmilling, involving the intrinsic flow of subunits from one polymer end to the other, is created by differences in the critical subunit concentrations at the opposite microtubule ends. Treadmilling was considered by many to be an in vitro dynamic behavior that did not play an important role in microtubule function in cells. However, recent evidence has established that treadmilling is a major in vivo mechanism underlying the dynamics of microtubule arrays.
Animals↗
Extracoelomic fluid osmometry and electrolyte composition during early gestation in the baboon.
OBJECTIVE: Access to extracoelomic fluid offers the opportunity to assess and potentially treat genetic disorders early in pregnancy. We have been using the pregnant baboon as a model to develop techniques and evaluate the feasibility of sampling extracoelomic fluid. The aim of this study was to determine the osmolality, oncotic pressures, and electrolyte composition of the baboon's extracoelomic fluid between days 39 and 41 of gestation and to compare them with those of maternal blood. STUDY DESIGN: The optimal time to perform the coelocentesis procedure was determined in 14 timed pregnant baboons. Six coelocenteses were then performed in aseptic conditions, under continuous transvaginal ultrasonographic guidance and avoiding the amniotic or yolk sacs. Between 3 and 5 mL extracoelomic fluid was aspirated from each baboon with a 10-mL syringe. Only 1 attempt at sampling was performed for each of the 6 animals. Pregnancies were tracked by transabdominal ultrasonographic evaluations on postprocedure day 3 and then weekly until day 140 of pregnancy. Oncotic pressures and biochemical measurements were determined with 1 mL extracoelomic fluid and 1 mL heparinized maternal venous blood. RESULTS: Data analysis suggests that maternal blood and extracoelomic fluid have similar osmolalities and concentrations of electrolytes but different colloid osmotic pressures (P <.001). CONCLUSION: This nonhuman primate model can be used to gain some insight into the physiologic changes in the composition of the extracoelomic fluid and to evaluate the safety of the coelocentesis procedure. The data suggest that the chorion laeve behaves as a semipermeable membrane at 40 days' gestation.
Animals↗
Use of drugs to study role of microtubule assembly dynamics in living cells.
Explore the source record for details and available documents.
Alkaloids↗
Microtubules and actin filaments: dynamic targets for cancer chemotherapy.
Microtubules and actin filaments play important roles in mitosis, cell signaling, and motility. Thus these cytoskeletal filaments are the targets of a growing number of anti-cancer drugs. In this review we summarize the current understanding of the mechanisms of these drugs in relation to microtubule and actin filament polymerization and dynamics. In addition, we outline how, by targeting microtubules, drugs inhibit cell proliferation by blocking mitosis at the mitotic checkpoint and inducing apoptosis. The beta-tubulin isotype specificities of new anticancer drugs and the antitumor potential of agents that act on the actin cytoskeleton are also discussed.
Actin Cytoskeleton↗
Morphine inhibits nocturnal oxytocin secretion and uterine contractions in the pregnant baboon.
Morphine is a potent inhibitor of nocturnal uterine contractions (UCs) in the pregnant baboon, and these contractions are known to be induced by oxytocin (OT). The purpose of this study was to determine the mode of action of morphine in inhibiting nocturnal UCs by examining the effect of morphine on OT secretion, OT clearance, and uterine responsiveness to OT. A tethered pregnant baboon model during the last third of gestation was used for these experiments. In study 1, the effects of morphine or control saline on OT release and on spontaneous nocturnal UCs were examined. Study 2 determined the effects of morphine or control saline on the pharmacokinetics of OT after a bolus injection of OT. To exclude/include direct opiate effects on UCs, study 3 examined the responsiveness of the uterus to exogenous OT after morphine or control saline administration. Plasma OT levels were analyzed by RIA after extraction. UCs were assessed by frequency, amplitude, duration, and area under the curve. During nocturnal UCs, morphine, but not saline, administration resulted in the precipitous suppression of integrated OT levels (p < 0.05) to 42% of pretreatment values at 0-15 min postinjection and 17% at 30-45 min. Simultaneously, UCs were significantly suppressed (p < 0.05) by 75% at the 30- to 45-min interval. By 1 h, 5 of 7 animals showed no UCs. In study 2, morphine consistently increased the metabolic clearance rate (MCR) of OT in all trials (p < 0.05), although the magnitude of this effect was small (median 9%). Finally, study 3 demonstrated that myometrial responsiveness to the challenge of exogenous OT was not depressed by opiate administration (p > 0.05). To summarize, the decrease in nocturnal UCs after morphine is primarily due to an inhibition of OT release, and perhaps, but to a much lesser extent, an increase in OT MCR. There was no evidence of a direct tocolytic effect of morphine on the uterus. In conclusion, opioids such as morphine are potent inhibitors of nocturnal UCs and act by suppressing OT release in the pregnant baboon.
Animals↗
Spontaneous onset of back pain.
OBJECTIVES: To assess the frequency with which patients attribute low back pain to spontaneous onset. DESIGN: A consecutive sample of two distinct groups of patients seeking treatment for back pain: those without need to identify cause (study group, n = 4,689) and those required to report a specific event to qualify for benefits paid for by a third party (compensated group, n = 6,687). SETTING: Active exercise-based back pain rehabilitation clinics. SUMMARY OF BACKGROUND DATA: Research on the natural history of back pain has revealed frequent reports of spontaneous recovery, usually within 8-12 weeks after onset. There is little comparable literature pertaining to the report of spontaneous onset. METHODS: Data were collected for two groups of consecutive patients who attended for initial assessments of their back pain at 16 Canadian Back Institute locations, between May 1, 1994 and February 28, 1995. Patient responses were collected using a standardized, professionally administered questionnaire. RESULTS: In the group without need to identify cause, 66.7% of patients could not identify an event producing their symptoms. For those required to report a specific event, only 9.8% of patients failed to attribute cause. Multivariate logistic regression revealed that the required-to-report group was approximately 15 times more likely to report an event (odds ratio = 14.95; 95% confidence interval = 13.44, 16.65) than the study group; those pursuing litigation were more than 2.5 times more likely to report a causative event (odds ratio = 2.68; 95% confidence interval = 2.09, 3.49). CONCLUSIONS: Back pain occurred spontaneously in approximately 67% of patients seeking treatment in the study group. The authors consider spontaneous onset to be part of the natural history of back pain for this group.
Adult↗
The phosphorylcholine epitope undergoes phase variation on a 43-kilodalton protein in Pseudomonas aeruginosa and on pili of Neisseria meningitidis and Neisseria gonorrhoeae.
Phosphorylcholine (ChoP) is a component of the teichoic acids of Streptococcus pneumoniae and has been recently identified on the lipopolysaccharide of Haemophilus influenzae, also a major pathogen of the human respiratory tract. Other gram-negative pathogens that frequently infect the human respiratory tract were surveyed for the presence of the ChoP epitope as indicated by binding to monoclonal antibodies (MAbs) recognizing this structure. The ChoP epitope was found on a 43-kDa protein on all clinical isolates of Pseudomonas aeruginosa examined and on several class I and II pili of Neisseria meningitidis. The specificity of the anti-ChoP MAb was demonstrated by the inhibition of binding in the presence of ChoP but not structural analogs. As in the case of H. influenzae, the expression of this epitope was phase variable on these species. In P. aeruginosa, this epitope was expressed at detectable levels only at lower growth temperatures. Expression of the ChoP epitope on piliated neisseriae displayed phase variation, both linked to pilus expression and independently of fully piliated bacteria.
Antigenic Variation↗
A low pH-inducible, PhoPQ-dependent acid tolerance response protects Salmonella typhimurium against inorganic acid stress.
The acid tolerance response enables Salmonella typhimurium to survive exposures to potentially lethal acidic environments. The acid stress imposed in a typical assay for acid tolerance (log-phase cells in minimal glucose medium) was shown to comprise both inorganic (i.e., low pH) and organic acid components. A gene previously determined to affect acid tolerance, atbR, was identified as pgi, the gene encoding phosphoglucoisomerase. Mutations in pgi were shown to increase acid tolerance by preventing the synthesis of organic acids. Protocols designed to separate the stresses of inorganic from organic acids revealed that the regulators sigma38 (RpoS), Fur, and Ada have major effects on tolerance to organic acid stress but only minor effects on inorganic acid stress. In contrast, the two-component regulatory system PhoP (identified as acid shock protein ASP29) and PhoQ proved to be important for tolerance to inorganic [corrected] acid stress but had little effect against organic acid stress. PhoP mutants also failed to induce four ASPs, confirming a role for this regulator in acid tolerance. Acid shock induction of PhoP appears to occur at the transcriptional level and requires the PhoPQ system. Furthermore, induction by acid occurs even in the presence of high concentrations of magnesium, the ion known to be sensed by PhoQ. These results suggest that PhoQ can sense both Mg2+ and pH. Since phoP mutants are avirulent, the low pH activation of this system has important implications concerning the pathogenesis of S. typhimurium. The involvement of four regulators, two of which are implicated in virulence, underscores the complexity of the acid tolerance stress response and further suggests that features of acid tolerance and virulence are interwoven.
Acids, Noncarboxylic↗