Showing papers on "Low protein published in 2001"

The maternal diet during pregnancy programs altered expression of the glucocorticoid receptor and type 2 11beta-hydroxysteroid dehydrogenase: potential molecular mechanisms underlying the programming of hypertension in utero.

Abstract: Potential mechanisms underlying prenatal programming of hypertension in adult life were investigated using a rat model in which maternal protein intake was restricted to 9% vs 18% casein (control) during pregnancy Maternal low protein (MLP) offspring exhibit glucocorticoid-dependent raised systolic blood pressure throughout life (20-30 mm Hg above the control) To determine the molecular mechanisms underlying the role of alterations in glucocorticoid hormone action in the prenatal programming of hypertension in MLP offspring, tissues were analyzed for expression of the glucocorticoid receptor (GR), mineralocorticoid receptor (MR), 11betaHSD1, 11betaHSD2, and corticosteroid-responsive Na/K-adenosine triphosphatase alpha1 and beta1 GR protein (95 kDa) and messenger RNA (mRNA) expression in kidney, liver, lung, and brain was more than 2-fold greater in MLP vs control offspring during fetal and neonatal life and was more than 3-fold higher during subsequent juvenile and adult life (P < 001) This was associated with increased levels of Na/K-adenosine triphosphatase alpha1- and beta1-subunit mRNA expression Levels of MR gene expression remained unchanged Exposure to the MLP diet also resulted in markedly reduced levels of 11betaHSD2 expression in the MLP placenta on days 14 and 20 of gestation (P < 0001), underpinning similar effects on 11betaHSD2 enzyme activity that we reported previously Levels were also markedly reduced in the kidney and adrenal of MLP offspring during fetal and postnatal life (P < 0001) This programmed decline in 11betaHSD2 probably contributes to marked increases in glucocorticoid hormone action in these tissues and potentiates both GR- and MR-mediated induction of raised blood pressure In contrast, levels of 11betaHSD1 mRNA expression in offspring central and peripheral tissues remained unchanged In conclusion, we have demonstrated that mild protein restriction during pregnancy programs tissue-specific increases in glucocorticoid hormone action that are mediated by persistently elevated expression of GR and decreased expression of 11betaHSD2 during adult life As glucocorticoids are potent regulators not only of fetal growth but also of blood pressure, our data suggest important potential molecular mechanisms contributing to the prenatal programming of hypertension by maternal undernutrition in the rat

Rapid Degradation of Auxin/Indoleacetic Acid Proteins Requires Conserved Amino Acids of Domain II and Is Proteasome Dependent

Abstract: Auxin rapidly induces auxin/indoleacetic acid (Aux/IAA) transcription. The proteins encoded are short-lived nucleus-localized transcriptional regulators that share four conserved domains. In a transient assay measuring protein accumulation, an Aux/IAA 13–amino acid domain II consensus sequence was sufficient to target firefly luciferase (LUC) for low protein accumulation equivalent to that observed previously for full-length PSIAA6. Single amino acid substitutions in these 13 amino acids, corresponding to known auxin response mutants, resulted in a sixfold to 20-fold increase in protein accumulation. Naturally occurring variant amino acids had no effect. Residues identified as essential by single alanine substitutions were not sufficient when all flanking amino acids were alanine, indicating the importance of flanking regions. Using direct protein degradation measurements in transgenic Arabidopsis seedlings, full-length IAA1, PSIAA6, and the N-terminal 73 PSIAA6 amino acids targeted LUC for rapid degradation with 8-min half-lives. The C-terminal 109 amino acids did not affect LUC half-life. Smaller regions containing domain II also targeted LUC for rapid degradation, but the rates were not equivalent to those of the full-length protein. A single domain II substitution in the context of full-length PSIAA6 increased half-life 30-fold. Proteasome inhibitors affected Aux/IAA::LUC fusion protein accumulation, demonstrating the involvement of the proteasome.

Diabetes in Old Male Offspring of Rat Dams Fed a Reduced Protein Diet

Abstract: Restricted fetal growth is associated with increased risk for the future development of Type 2 diabetes in humans. The study aim was to assess the glucose tolerance of old (seventeen months) male rats, which were growth restricted in early life due to maternal protein restriction during gestation and lactation. Rat mothers were fed diets containing either 20% or 8% protein and all offspring weaned onto a standard rat diet. In old-age fasting plasma glucose concentrations were significantly higher in the low protein offspring: 8.4 (1.3)mmol/l v. 5.3 (1.3)mmol/l (p = 0.005), Areas under the curves were increased by 67% for glucose (p = 0.01) and 81% for insulin (p = 0.01) in these rats in intravenous glucose tolerance tests, suggesting (a degree of) insulin resistance. These results show that early growth retardation due to maternal protein restriction leads to the development of diabetes in old male rat offspring. The diabetes is predominantly associated with insulin resistance.

Small Intestine Epithelial Barrier Function Is Compromised in Pigs with Low Feed Intake at Weaning

Abstract: Compromising alterations in gastrointestinal architecture are common during the weaning transition of pigs. The relation between villous atrophy and epithelial barrier function at weaning is not well understood. This study evaluated in vitro transepithelial transport by Ussing metabolic chambers, local alterations in T-cell subsets and villous architecture at low energy intake level and their relation with lactose/protein ratios in the diet. Pigs (n = 66, 26 d old) were sampled either at weaning (d 0), d 1, 2 or 4 postweaning. Piglets received one of three diets at a low energy intake level, which differed in lactose and protein ratio as follows: low lactose/high protein (LL/HP), control (C), or high lactose/low protein (HL/LP). Mean digestible energy intake was 648 kJ/pig on d 1, 1668 kJ/pig on d 2, 1995 kJ/pig on d 3 and 1990 kJ/pig on d 4 postweaning. The CD4(+)/CD8(+) T-lymphocytes ratio decreased after weaning (P < 0.05). Decreased paracellular transport (P < 0.01), greater villous height (P < 0.01), shallower crypts and lower villus/crypt ratios (P < 0.01) were observed on d 2 compared with d 0. Piglets consuming the HL/LP diet tended to have less paracellular transport (P < 0.10) and greater villous height (P < 0.10) compared with piglets fed the other diets. During the first 4 d postweaning, the effect of diet composition on mucosal integrity was not as important as the sequential effects of low energy intake at weaning. Stress and diminished enteral stimulation seem to compromise mucosal integrity as indicated by increased paracellular transport and altered T-cell subsets.

Energy utilization of low-protein diets in growing pigs.

Abstract: Three trials were conducted to measure the effects of reducing the dietary CP content on digestive and metabolic utilization of N and energy in growing pigs. Sixty barrows weighing about 65 kg were used. In Trial 1, four semisynthetic diets with CP content decreasing from 18.9 to 12.3% were formulated. In Trials 2 and 3, two diets with 17.4 and 13.9% CP were formulated using conventional ingredients. In the three trials, diets were supplemented with variable amounts of industrial AA in order to maintain a constant standardized digestible lysine/NE ratio (0.76 g/MJ) and ratios between essential AA relative to lysine of at least 60, 65, 20, 60, and 70% for methionine + cystine, threonine, tryptophan, isoleucine, and valine, respectively. In Trials 1 and 2, feed was given in four meals per day, whereas, in Trial 3, two feeding frequencies (two and seven meals per day) were compared. Five or six N and energy balance (indirect calorimetry) measurements were conducted for each treatment, and components of heat production were estimated. Results of Trial 3 showed no effect of meal frequency on either N or energy utilization. Reduction of dietary CP content had no effect on N retention or animal performance but markedly decreased N excretion (-40% in Trials 2 and 3, and -58% in Trial 1). In the three trials, the lower N excretion with low-CP diets was accompanied by a reduction in urinary energy loss equivalent to 3.5 kJ/g of decrease in protein intake. Data of the three trials indicated that heat production was lower when CP was reduced (-7 kJ/g decrease in protein intake). This lower heat production was attributed to a reduction of the thermic effect of feed, whereas heat production associated with physical activity and maintenance were not affected. Reduction of dietary CP was associated with higher energy gain, mainly as fat. But, this effect was no longer significant when data were adjusted for similar NE intakes. These results confirm the possibility of limiting N excretion, while maintaining a high level of performance, by reducing CP level in the feed with adequate AA supplementation. This study also confirms the superiority of the NE system (in comparison with DE or ME systems) for predicting performance and energy gain of pigs and controlling carcass adiposity, especially in situations of feeds with variable CP contents.

NMR structural and dynamic characterization of the acid-unfolded state of apomyoglobin provides insights into the early events in protein folding.

Abstract: Apomyoglobin forms a denatured state under low-salt conditions at pH 2.3. The conformational propensities and polypeptide backbone dynamics of this state have been characterized by NMR. Nearly complete backbone and some side chain resonance assignments have been obtained, using a triple-resonance assignment strategy tailored to low protein concentration (0.2 mM) and poor chemical shift dispersion. An estimate of the population and location of residual secondary structure has been made by examining deviations of (13)C(alpha), (13)CO, and (1)H(alpha) chemical shifts from random coil values, scalar (3)J(HN,H)(alpha) coupling constants and (1)H-(1)H NOEs. Chemical shifts constitute a highly reliable indicator of secondary structural preferences, provided the appropriate random coil chemical shift references are used, but in the case of acid-unfolded apomyoglobin, (3)J(HN,H)(alpha) coupling constants are poor diagnostics of secondary structure formation. Substantial populations of helical structure, in dynamic equilibrium with unfolded states, are formed in regions corresponding to the A and H helices of the folded protein. In addition, the deviation of the chemical shifts from random coil values indicates the presence of helical structure encompassing the D helix and extending into the first turn of the E helix. The polypeptide backbone dynamics of acid-unfolded apomyoglobin have been investigated using reduced spectral density function analysis of (15)N relaxation data. The spectral density J(omega(N)) is particularly sensitive to variations in backbone fluctuations on the picosecond to nanosecond time scale. The central region of the polypeptide spanning the C-terminal half of the E helix, the EF turn, and the F helix behaves as a free-flight random coil chain, but there is evidence from J(omega(N)) of restricted motions on the picosecond to nanosecond time scale in the A and H helix regions where there is a propensity to populate helical secondary structure in the acid-unfolded state. Backbone fluctuations are also restricted in parts of the B and G helices due to formation of local hydrophobic clusters. Regions of restricted backbone flexibility are generally associated with large buried surface area. A significant increase in J(0) is observed for the NH resonances of some residues located in the A and G helices of the folded protein and is associated with fluctuations on a microsecond to millisecond time scale that probably arise from transient contacts between these distant regions of the polypeptide chain. Our results indicate that the equilibrium unfolded state of apomyoglobin formed at pH 2.3 is an excellent model for the events that are expected to occur in the earliest stages of protein folding, providing insights into the regions of the polypeptide that spontaneously undergo local hydrophobic collapse and sample nativelike secondary structure.

Pharmacokinetics of Levetiracetam

Abstract: Major considerations in the acceptance and impact of new antiepileptic drugs include their pharmacokinetics and their potential for interaction with other drugs. The pharmacokinetics of levetiracetam, a newly approved add-on antiepileptic agent for partial-onset seizures in adults, has been evaluated in 27 phase I and II studies. Consistent findings in these studies include rapid and complete oral absorption, linear dose kinetics, a minimal degree of protein binding, and predominantly renal excretion. Because of the lack of hepatic metabolism and low protein binding, the risk of interaction with other drugs is considered low.

Quantitative Trait Loci Associated with Milling and Baking Quality in a Soft × Hard Wheat Cross

Abstract: Hybridization between soft and hard wheat creates new associations among loci. Advantages include an increase Interclass hybridization between soft and hard wheat (Triticum in genetic diversity, a potential increase in grain yield, aestivum L.) results in new genetic combinations of potential value. and transfer of pest resistance genes. Both May et al. We investigated whether interclass hybridization could improve enduse quality of both classes. Our objectives were to analyze quality (1989) and Carver (1996) indicated that recovery of soft traits in a population of recombinant inbred lines (RILs) derived from or hard wheat quality characteristics was possible in a cross between the good quality soft white wheat NY6432-18 (NY18), interclass single crosses if genetic variation for grain and good quality hard white wheat Clark’s Cream (CC), identify quality was maintained at a high level within the segrequantitative trait loci (QTLs) for those traits, and use linkage analysis gating population. A better understanding of the underto determine which parent was contributing favorable alleles at spe- lying genetic structure influencing wheat quality would cific QTLs for a given trait. The population was assessed for milling, hasten the development of unique wheats possessing protein and dough mixing, hydration, cookie and loaf traits. Traits value-added traits as well as wheats suited to convenwere measured in two to six environments grown over three seasons tional end-uses. Specifically, we wondered if interclass in Ithaca, NY. The molecular map for the population contains 370 hybridization could create new associations among loci molecular markers including restiction fragment length polymorthat would actually improve end-use quality of both phisms (RFLPs), microsatellites, and markers derived from known function genes in wheat. Linkage groups have been located to all the hard and soft wheat. wheat chromosomes except for 7D. Pinb derived from the puroindo- Wheat flour is classified for use in baking on the basis line b gene on chromosome 5DS was the major QTL for milling, of its texture (soft vs. hard) and chemical properties hydration, and cookie baking traits. The major QTL for mixograph (primarily protein). In the USA, the main use of hard peak time was at the Glu-Dy1 marker, derived from Glu-D1-2 gene wheat flour is for bread baking and the main use of on chromosome 1DL. The Glu-Ax1 and Glu-By1 markers were QTLs soft wheat flour is for cookie baking. Cookie flour is for mixograph peak height and tolerance, respectively. QTLs for flour characterized by low water absorption, fine particleprotein quantity were detected on chromosome 2B. With the excep- size, and low protein content as compared with bread tion of the hydration traits, multiple regression models included alleles flour milled from hard wheat (Hoseney, 1988). During from both parents. Interclass hybridization may be an underexploited the initial milling step, soft wheat endosperm fractures wheat breeding strategy for improvement of agronomic and quality through cell walls and hard wheat endosperm fractures traits in wheat. at the cell wall. As a consequence, soft wheat flour particles are finer than those in hard wheat flours. Sub

Activated protein C versus protein C in severe sepsis.

Abstract: Objective: To delineate critical differences between activated protein C (APC) and its precursor, protein C, with regard to plasma levels in health and in severe sepsis, and to discuss the implications of these differences as they relate to treatment strategies in patients with severe sepsis. Data Source/Study Selection: Published literature including s, manuscripts, and review articles reporting studies in both experimental animal models and humans that provide an understanding of the relationship and the critical differences between circulating levels of APC and protein C. Data Extraction and Synthesis: The protein C pathway represents one of the major regulatory systems of hemostasis, exhibiting antithrombotic, profibrinolytic and anti-inflammatory properties. This pathway also plays a critical role in the pathophysiology of severe sepsis. Central to this pathway is the vitamin K-dependent serine protease, APC, and its precursor, protein C. The conversion of protein C to APC is dependent on the complex of thrombin and thrombomodulin, an integral endothelial surface receptor. The conversion of protein C to APC is further augmented by another endothelial surface protein, the endothelial protein C receptor. There are limited published data on APC levels in health and disease, probably due to the complexity of the assay methodology for measuring APC and the absence of commercially available diagnostic kits. In animals and humans with normal functioning endothelium, circulating levels of APC (1-3 ng/mL) are positively correlated with protein C (4000-5000 ng/mL) concentration and the amount of thrombin generated. In patients with severe sepsis, there is a generalized endothelial dysfunction, contributing to multiple organ failure with increased morbidity and mortality. Persistently low protein C levels are related to poor prognosis. Key to understanding the treatment strategy with APC or protein C is knowledge of the functional status of the endothelium and, specifically, whether the microvasculature in patients with severe sepsis can support the conversion of protein C to APC. To date, only APC (drotrecogin alfa [activated]) has been shown to reduce mortality in severe sepsis in a large, phase 3, placebo-controlled, double-blind international trial. In contrast, no data, other than open-label case studies, are available for evaluation of the effects of protein C in the treatment of severe sepsis. Conclusion: The limited data available indicate that lower levels of protein C in sepsis occur in the absence of appreciable conversion to APC. These observations indicate that treatment with APC may be more efficacious than protein C in severe sepsis, where generalized endothelial dysfunction may impair conversion of protein C to APC. Additional research is required to confirm these observations.

Protein adsorption to oligo(ethylene glycol) self-assembled monolayers: Experiments with fibrinogen, heparinized plasma, and serum

Abstract: Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of fibrinogen, serum, and plasma were studied by ellipsometry on a series of well-defined oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH2)15-CONH-EGn, where n = 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of fibrinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of fibrinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Significantly less serum adsorbed to methoxy tri(EG) than t...

Protein Intake and Bone Growth

Abstract: Among osteotrophic nutrients, proteins play an important role in bone development, thereby influencing peak bone mass. Consequently, protein malnutrition during development can increase the risk of osteoporosis and of fragility fracture later in life. Both animal and human studies indicate that low protein intake can be detrimental for both the acquisition of bone mass during growth and its conservation during adulthood. Low protein intake impairs both the production and action of IGF-I (Insulin-like growth factor-I). IGF-I is an essential factor for bone longitudinal growth, as it stimulates proliferation and differentiation of chondrocytes in the epiphyseal plate, and also for bone formation. It can be considered as a key factor in the adjustments of calcium-phosphate metabolism required for normal skeletal development and bone mineralization during growth. In healthy children and adolescents, a positive association between the amount of ingested proteins and bone mass gain was observed in both sexes at the level of the lumbar spine, the proximal femur and the midfemoral shaft. This association appears to be particularly significant in prepubertal children. This suggests that, like for the bone response to either the intake of calcium or weight-bearing exercise, the skeleton would be particularly responsive to the protein intake during the years preceding the onset of pubertal maturation.

Decreasing of p27(Kip1)and cyclin E protein levels is associated with progression from superficial into invasive bladder cancer.

Abstract: The p27Kip1(p27) protein is a cyclin-dependent kinase inhibitor of the transition from G1 to S phase. It has been reported that decreased p27 protein level is a negative prognostic indicator in human tumours including bladder cancer. We studied the relationship between protein levels of p27, cyclin E and Ki-67 and clinicopathological features of 145 consecutive Japanese patients with transitional cell carcinoma of the bladder using immunohistochemical staining. Low protein levels of p27 were associated with low staining of cyclin E (P = 0.0302), high Ki-67 index (P = 0.0306), poorly differentiated grade (P = 0.0006), muscle invasion (P = 0.0019) and lymph node metastsis (P = 0.0002). Low staining of cyclin E and high Ki-67 index correlated with poorly differentiated grade, muscle invasion and lymph node metastsis. Cyclin E protein levels was inversely related with Ki-67 index (P = 0.0002). Kaplan–Meier plots of survival rate in patients with low versus high p27 staining showed that low protein levels of p27 were associated with a shortened disease-free and overall survival (P< 0.0001 and P< 0.0001, respectively). Similarly, low staining of cyclin E and high Ki-67 index correlated with a shortened disease-free and overall survival. On multivariate analysis using Cox proportional hazards model, low protein levels of p27 and high Ki-67 index were independent predictors of shortened disease-free (P< 0.0001, P = 0.0031, respectively), and low protein levels of p27, low staining of cyclin E and high Ki-67 index of overall survival (P = 0.0017, P = 0.0009, P = 0.0003, respectively). In superficial bladder tumours (Ta, T1; 86 patients), significant correlations were observed between low p27 staining and high Ki-67 index and early recurrence (P = 0.0048, P = 0.0178, respectively). Among the recurrenced superficial tumours (35 patients), the tumours which remained at a low stage showed high protein levels of p27 and cyclin E, and the tumours which progressed to invasive disease showed a gradual decrease in p27 and cyclin E protein levels over time. Our findings suggest that decreased protein levels of p27 and cyclin E play a role in the progression of bladder cancer and to evaluate these protein levels may be useful in management of the diseases. © 2001 Cancer Research Campaign http://www.bjcancer.com

Protein adsorption to oligo(ethylene glycol) self-assembled monolayers: Experiments with é brinogen, heparinized plasma, and serum

Abstract: Low protein adsorption is believed advantageous for blood-contacting materials and ethylene glycols (EG)-based polymeric compounds are often attached to surfaces for this purpose. In the present study, the adsorption of e brinogen, serum, and plasma were studied by ellipsometry on a series of well-dee ned oligo(EG) terminated alkane-thiols self-assembled on gold. The layers were prepared with compounds of the general structure HS-(CH 2)15-CONH-EGn, where n D 2, 4, and 6. Methoxy-terminated tri(EG) undecanethiol and hydroxyl-terminated hexadecanethiol self-assembled monolayers (SAMs) were used as references. The results clearly demonstrate that the adsorption depends on the experimental conditions with small amounts of e brinogen adsorbing from a single protein solution, but larger amounts of proteins from serum and plasma. The adsorption of e brinogen and blood plasma decreased with an increasing number of EG repeats and was temperature-dependent. Signie cantly less serum adsorbed to methoxy tri(EG) than to hexa(EG) and more proteins remained on the latter surface after incubation in a sodium dodecyl sulfate (SDS) solution, indicating a looser protein binding to the methoxy-terminated surface. All surfaces adsorbed complement factor 3(C3)from serum and plasma, although no surface- mediated complement activation was observed. The present study points to the importance of a careful choice of the protein model system before general statements regarding the protein repellant properties of potential surfaces can be made.

Protein Z in ischaemic stroke

Abstract: Many risk factors associated with ischaemic stroke are known, including high levels of fibrinogen or factor VII Protein Z is a vitamin K-dependent coagulation factor, which was found to promote the assembly of thrombin with phospholipid vesicles that might promote coagulation Indeed, a low protein Z level may be associated with a varying bleeding tendency Therefore, we hypothesized that high protein Z levels could induce a hypercoagulable state and performed a case-control study to investigate a potential association between high protein Z plasma levels and ischaemic stroke We measured protein Z in plasma samples from 157 patients with stroke of unknown aetiology and 192 control subjects All patients had survived an ischaemic stroke or transient ischaemic attack (TIA) for at least 2 months We found an increased relative risk of ischaemic stroke with increasing protein Z levels, with an odds ratio of 43 [95% confidence interval (CI): 17--11] for protein Z plasma levels > or = 160% Excluding patients with a history of venous thromboembolism from the analysis, the same result was obtained (odds ratio 42; 95% CI: 16--112) Using a logistic regression model, this association also remained significant (P = 004) after adjustment for established risk factors Our data indicated that a high plasma level of protein Z is an independent risk factor for ischaemic stroke

Cupressaceae pollinosis: identification, purification and cloning of relevant allergens.

Abstract: Allergy to Cupressaceae pollen is a worldwide pollinosis caused by several species. Pollen extracts prepared from allergenic species belonging to this family are characterised by low protein and high carbohydrate content. The allergenic components represented in the pollen extracts from different species of the Cupressaceae family show high levels of cross-reactivity when probed with human IgE from allergic subjects and share a number of common epitopes also identified by polyclonal rabbit antisera and monoclonal antibodies. A close relationship has also been described with the Taxodiaceae and Podocarpaceae families. Although both proteic and carbohydrate epitopes appear to be involved in IgE recognition and allergenic cross-reactivity, a large portion of the IgE reactivity of Cupressaceae-allergic patients seems to be associated with sugar moieties present on the relevant allergenic molecules. From this point of view, Cupressaceae/Taxodiaceae allergens constitute a particularly useful model to study IgE cross-reactivity, as they have been shown to display different levels of homology. Moreover, the availability of the purified allergens, together with their recombinant counterparts, may shed light on the actual role played by carbohydrate in allergic sensitisation, IgE recognition and allergenic cross-reactivity.

Development of new carboxylic acid-based MMP inhibitors derived from functionalized propargylglycines.

Abstract: A series of carboxylic acids were prepared from a propargylglycine scaffold and tested for efficacy as matrix metalloproteinase (MMP) inhibitors. Detailed SAR for the series is reported for four enzymes within the MMP family. The inhibitors were typically potent against collagenase-3 (MMP-13) and gelatinase A (MMP-2), while they spared collagenase-1 (MMP-1) and only moderately inhibited stromelysin (MMP-3). Compound 40 represents a typical inhibition profile of a compound with reasonable potency. Introduction of polar groups was required in order to generate inhibitors with acceptable water solubility, and this often resulted in a loss of potency as in compound 63. High serum protein binding proved to be a difficult hurdle with many compounds such as 48 showing >99% binding. Some compounds such as 64 displayed approximately 90% binding, but no reliable method was discovered for designing molecules with low protein binding. Finally, selected data regarding the pharmacokinetic behavior of these compounds is presented.

A Protein-Restricted Diet during Pregnancy Alters in Vitro Insulin Secretion from Islets of Fetal Wistar Rats

Abstract: Previous studies indicate that insulin secretion from the fetuses of dams fed a low protein (LP) diet is reduced in response to leucine or arginine. The aim of this study was to locate the defect in the insulin secretion pathway induced by a LP diet during gestation. The effects of various secretagogues acting at different levels of the insulin secretion cascade were investigated in vitro in fetal islets from dams fed either a normal or a LP diet during pregnancy. Insulin content, insulin secretion and the cAMP content were then measured. Although insulin content of LP islets did not differ from that of control islets, insulin secretion from LP fetal islets was reduced when challenged by amino acids or cAMP enhancers. This reduction did not appear to be related solely to an altered islet cAMP content. An impairment of insulin secretion remained after stimulation of fetal LP islets with either metabolic or nonmetabolic secretagogues. The insulin secretion by LP islets was restored to normal, however, with barium or cytochalasin-B. These findings demonstrate that an in utero isocaloric LP diet impairs insulin secretion of the fetus. This alteration is located at the exocytosis step in the insulin secretion cascade and not in the insulin pool of the beta cell.

Natural rubber latex-related occupational asthma: Association with interventions and glove changes over time*

Abstract: Background Exposure to natural rubber latex (NRL) has been recognized as a cause of occupational asthma (OA), especially among health care workers (HCWs) associated with use of gloves. Little or no population-based data are available which chart the changes over time in the number of cases of OA as this problem was increasingly recognized and then interventions instituted. Methods We obtained the numbers of allowed asthma claims with exposure to latex by year in the province of Ontario, Canada from the Ontario Workplace Safety and Insurance Board; details of the cases from the largest teaching hospital were reviewed. Interventions included: (1) in 1996, the Board recommended in its focus for accommodation of sensitized workers, the reduction of aerosols of latex proteins and that hospital facilities use powder-free, low-protein or nonlatex gloves; and (2) hospitals instituted latex policies and glove changes at various dates. For example, at the largest teaching hospital, interventions included education and voluntary medical surveillance in 1994; substitution of low protein, “powder-free” NRL gloves for non-sterile powdered gloves in 1995; and replacement of powdered sterile NRL gloves by lower protein, “powder-free” NRL gloves in 1997. Results Through 1999, there were 60 allowed claims for asthma in Ontario with exposure to latex; of these 49 (82%) were among HCWs. The number of claims among HCWs changed from 0 to 2 per year up to 1990; increased to 7 to 11 per year between 1991–1994; and declined to 3 per year in 1995–1996 and 1 to 2 per year in 1997–1999. Of the ten institutions having two or more OA latex claims, all claims occurred in 1996 or earlier at 8 (80%). At the largest hospital, there were five accepted claims with year of diagnosis in 1993 (1 case), 1994 (3 cases), and 1995 (1 case). Conclusions These findings suggest that, despite the effect of increasing recognition, the introduction of gloves with reduced powder and/or protein, as well as other interventions have been associated temporally with declines in the number of cases of latex OA. Am. J. Ind. Med. 40:347–353, 2001. © 2001 Wiley-Liss, Inc.

Effect of nitrogen source in high-concentrate, low-protein beef cattle diets on microbial fermentation studied in vivo and in vitro.

Abstract: In Exp. 1, four Holstein heifers (112 ± 5.5 kg BW) fitted with ruminal cannulas were used in a 4 x 4 Latin square to evaluate the effects of N source on ruminal fermentation and urinary excretion of purine derivatives. A 2 x 2 factorial arrangement of treatments was used; the factors were the type of protein source (soybean meal, SBM, vs a 50:50 mixture of fish meal and corn gluten meal, FMCGM) and the partial substitution of protein source by urea (with vs without). Heifers were allowed to consume concentrate and barley straw on an ad libitum basis. Barley straw:concentrate ratio (12:88) and average ruminal pH (6.25) were not affected (P > 0.05) by treatment. Ruminal NH 3 N concentration and urinary excretion of purine derivatives were not affected (P > 0.05) by supplemental N source. In situ CP degradability of supplemented SBM was very low (50%). In Exp. 2, eight dual-flow continuous-culture fermenters were used to study diet effects on microbial fermentation and nutrient flow, using forage:concentrate ratio, solid and liquid passage rates, and pH fluctuation to simulate in vivo conditions. The treatment containing SBM without urea reached the greatest total VFA concentration (P < 0.01), molar percentage of acetate (P < 0.05), and NH 3 N concentration (P < 0.05), followed by treatments with partial substitution of protein source by urea, and finally by the treatment containing FMCGM. True OM digestion tended to increase (P = 0.13) in treatments containing SBM. These results suggest that amino N from SBM and NH 3 N concentration stimulated nutrient digestion. Microbial protein synthesis was lowest in treatments with FMCGM and without urea, indicating that rapidly available N limited microbial growth. The low CP degradability of SBM observed may have contributed to the limitation in N supply for microbial growth. Efficiency of microbial protein synthesis increased in treatments containing urea (P < 0.05). Protein source affected total (P < 0.05) and essential AA (P < 0.10) flows, which were greater in treatments containing FMCGM. Partial replacement of protein supplements by urea did not affect total and essential AA flows. Because mean dietary protein contribution to total N effluent was 46%, the AA profile of supplemental protein sources had a great impact on total AA flow and its profile.

Nitrogen recycling through proctodeal trophallaxis in the Japanese damp-wood termite Hodotermopsis japonica (Isoptera, Termopsidae)

Abstract: Trophallaxis is one of a variety of nutritional tactics that enable termites to conserve and recycle nitrogenous compounds. In this study, we designed three experiments to reveal the function and importance of proctodeal trophallaxis in the Japanese damp-wood termite Hodotermopsis japonica. First, our observations showed that younger instars and soldiers tended to behave as recipients of proctodeal fluid, while older instars acted mainly as donors. Secondly, nitrogen-deficient groups of termite individuals were introduced to groups of nourished individuals; results indicate that the frequency of proctodeal trophallaxis was significantly higher than in control groups. Additionally, the nitrogen content in the proctodeal fluid of nitrogen-deficient individuals increased after trophallactic interactions with well-nourished individuals. Finally, we set up three groups reared with different concentrations of nitrogenous compounds (amino acids) in their diet, to investigate the correlation between the frequency of trophallactic behavior and the protein concentration of proctodeal fluid. As expected, proctodeal fluid of low protein content was frequently exchanged among individuals in nitrogen-poor conditions, while high-protein proctodeal fluid was transferred less frequently under nitrogen-rich conditions. These results suggest that termites have plasticity of trophallactic behavior in response to their nutritional conditions, and trophallaxis contributes to the nutritional homeostasis of colonies.

Temperature-induced denaturation and renaturation of triosephosphate isomerase from Saccharomyces cerevisiae: evidence of dimerization coupled to refolding of the thermally unfolded protein.

Abstract: The thermal denaturation of the dimeric enzyme triosephosphate isomerase (TIM) from Saccharomyces cereVisiae was studied by spectroscopic and calorimetric methods. At low protein concentration the structural transition proved to be reversible in thermal scannings conducted at a rate greater than 1.0 °C min -1 . Under these conditions, however, the denaturation-renaturation cycle exhibited marked hysteresis. The use of lower scanning rates lead to pronounced irreversibility. Kinetic studies indicated that denaturation of the enzyme likely consists of an initial first-order reaction that forms thermally unfolded (U) TIM, followed by irreversibility-inducing reactions which are probably linked to aggregation of the unfolded protein. As judged from CD measurements, U possesses residual secondary structure but lacks most of the tertiary interactions present in native TIM. Furthermore, the large increment in heat capacity upon denaturation suggests that extensive exposure of surface area occurs when U is formed. Above 63 °C, reactions leading to irreversibility were much slower than the unfolding process; as a result, U was sufficiently long-lived as to allow an investigation of its refolding kinetics. We found that U transforms into nativelike TIM through a second-order reaction in which association is coupled to the regain of secondary structure. The rate constants for unfolding and refolding of TIM displayed temperature dependences resembling those reported for monomeric proteins but with considerably larger activation enthalpies. Such large temperature dependences seem to be determinant for the occurrence of kinetically controlled transitions and thus constitute a simple explanation for the hysteresis observed in thermal scannings. Triosephosphate isomerase (TIM) 1 is a dimeric enzyme formed by identical subunits of approximately 26 kDa each. Within each monomer, the polypeptide chain adopts a folding