Effect of starting material particle size on its agglomeration behavior in high shear wet granulation

The effect of anhydrous lactose particle size distribution on its performance in the wet granulation process was evaluated. Three grades of anhydrous lactose were used in the study: “as is” manufacturer grade and 2 particle size fractions obtained by screening of the 60M lactose. Particle growth behavior of the 3 lactose grades was evaluated in a high shear mixer. Compactibility and porosity of the resulting granules were also evaluated. A uniaxial compression test on moist agglomerates of the 3 lactose grades was performed in an attempt to explain the mechanism of particle size effect observed in the high shear mixer. Particle growth of anhydrous lactose in the high shear mixer was inversely related to the particle size of the starting material. In addition, granulation manufactured using the grade with the smallest particle size was more porous and demonstrated enhanced compactibility compared with the other grades. Compacts with similar porosity and low liquid saturation demonstrated brittle behavior and their breakage strength was inversely related to lactose particle size in the uniaxial compression test, suggesting that material with smaller particle size may exhibit more pronounced nucleation behavior during wet granulation. On the other hand, compacts prepared at higher liquid saturation and similar compression force exhibited more plastic behavior and showed lower yield stress for the grade with smallest particle size. The lower yield stress of compacts prepared with this grade may indicate a higher coalescence tendency for its granules during wet granulation.     

Assembly of EcoKI DNA methyltransferase requires the C-terminal region of the HsdM modification subunit

The methyltransferase component of type I DNA restriction and modification systems comprises three subunits, one DNA sequence specificity subunit and two DNA modification subunits. Limited proteolysis of the EcoKI methyltransferase shows that a 55-kDa N-terminal fragment of the 59-kDa modification subunit is resistant to degradation. We have purified this fragment and determined by mass spectrometry that proteolysis removes 43 or 44 amino acids from the C-terminus. The fragment fails to interact with the other subunits even though it still possesses secondary and tertiary structure and the ability to bind the S-adenosylmethionine cofactor. We conclude that the C-terminal region of the modification subunit of EcoKI is essential for the assembly of the EcoKI methyltransferase.     

Renal dopamine receptors and hypertension

Dopamine has been recognized as an important modulator of central as well as peripheral physiologic functions in both humans and animals. Dopamine receptors have been identified in a number of organs and tissues, which include several regions within the central nervous system, sympathetic ganglia and postganglionic nerve terminals, various vascular beds, the heart, the gastrointestinal tract, and the kidney. The peripheral dopamine receptors influence cardiovascular and renal function by decreasing afterload and vascular resistance and promoting sodium excretion. Within the kidney, dopamine receptors are present along the nephron, with highest density on proximal tubule epithelial cells. It has been reported that there is a defective dopamine receptor, especially D(1) receptor function, in the proximal tubule of various animal models of hypertension as well as in humans with essential hypertension. Recent reports have revealed the site of and the molecular mechanisms responsible for the defect in D(1) receptors in hypertension. Moreover, recent studies have also demonstrated that the disruption of various dopamine receptor subtypes and their function produces hypertension in rodents. In this review, we present evidence that dopamine and dopamine receptors play an important role in regulating renal sodium excretion and that defective renal dopamine production and/or dopamine receptor function may contribute to the development of various forms of hypertension.     

Chloramine-T in radiolabeling techniques. III. Radioiodination of biomolecules containing thioether groups

A previously reported method for iodination of the tyrosine moiety of oxidation-sensitive biomolecules was found to cause unacceptable damage to biomolecules containing thiols and thioether groups. This was due to the oxidation of the sulfur-containing residues by molecular iodine (I(2)). To selectively iodinate the tyrosine moiety with minimum oxidation to the sulfur functionality, studies of the kinetics of the reactions between I-(3) and various amino acids and small peptides at various pH values in phosphate buffer were undertaken. Within the pH range studied (5.5-8.2), the results showed that the iodination reaction is strongly catalyzed by hydroxide ions, whereas the oxidation of the sulfur group was insensitive to pH. The results also showed that both reactions are strongly catalyzed by HPO-(4) ion. In a complex molecule, such as methionine-enkephalin, oxidation of the methionine residue (undesirable reaction) proceeds in parallel with iodination of the tyrosine residue (desirable reaction). If such a molecule was iodinated in 0.01 M phosphate buffer at pH values above 7.5, the iodination reaction would proceed much more rapidly than the oxidation reaction, resulting in a high yield of iodinated substrate with little oxidative damage.     

High affinity binding between lipoprotein lipase and lipoproteins involves multiple ionic and hydrophobic interactions, does not require enzyme activity, and is modulated by glycosaminoglycans

Lipoprotein lipase (LPL) physically associates with lipoproteins and hydrolyzes triglycerides. To characterize the binding of LPL to lipoproteins, we studied the binding of low density lipoproteins (LDL), apolipoprotein (apo) B17, and various apoB-FLAG (DYKDDDDK octapeptide) chimeras to purified LPL. LDL bound to LPL with high affinity (K(d) values of 10(-12) m) similar to that observed for the binding of LDL to its receptors and 1D1, a monoclonal antibody to LDL, and was greater than its affinity for microsomal triglyceride transfer protein. LDL-LPL binding was sensitive to both salt and detergents, indicating the involvement of both hydrophobic and hydrophilic interactions. In contrast, the N-terminal 17% of apoB interacted with LPL mainly via ionic interactions. Binding of various apoB fusion peptides suggested that LPL bound to apoB at multiple sites within apoB17. Tetrahydrolipstatin, a potent enzyme activity inhibitor, had no effect on apoB-LPL binding, indicating that the enzyme activity was not required for apoB binding. LDL-LPL binding was inhibited by monoclonal antibodies that recognize amino acids 380-410 in the C-terminal region of LPL, a region also shown to interact with heparin and LDL receptor-related protein. The LDL-LPL binding was also inhibited by glycosaminoglycans (GAGs); heparin inhibited the interactions by approximately 50% and removal of trace amounts of heparin from LPL preparations increased LDL binding. Thus, we conclude that the high affinity binding between LPL and lipoproteins involves multiple ionic and hydrophobic interactions, does not require enzyme activity and is modulated by GAGs. It is proposed that LPL contains a surface exposed positively charged amino acid cluster that may be important for various physiological interactions of LPL with different biologically important molecules. Moreover, we postulate that by binding to this cluster, GAGs modulate the association between LDL and LPL and the in vivo metabolism of LPL.     

Sociodemographic correlates of consanguineous marriage in the Muslim population of India

Using data derived from the 1992-1993 National Family Health Survey, the sociodemographic characteristics of consanguineous marriage were determined in the Muslim population of India. In this nationally representative sample of 8436 women, consanguineous marriages accounted for 22.0% of the total. No differences between the consanguineous and non-consanguineous groups were observed in terms of mean age at marriage or mean age at cohabitation. The study confirmed the negative association between consanguineous marriage and maternal education but also indicated that women in consanguineous unions were more likely to be employed, albeit mainly in agricultural work on behalf of the family. Consanguineous couples more frequently lived in smaller towns and in an extended family environment. Somewhat conflicting results were obtained with indicators of socioeconomic status, but the overall picture suggested that consanguineous households had greater access to consumer goods because of their larger number of co-resident persons.     

Shade and microbes enhance drought stress tolerance in plants by inducing phytohormones at molecular levels: a review

荫蔽和微生物可在分子水平上调控植物激素以增强植物的耐旱性 植物在其生命周期内会受到一系列不利环境的影响。其中,干旱胁迫是限制农业生产力的重要因素之一。为了在逆境的环境中得以生存,植物进化出了识别环境胁迫严重性的机制。植物可通过多种方式调节激素活性,以减轻干旱带来的不良影响。受荫蔽和微生物调控,植株的抗旱性提高,产量损失减少。脱落酸、生长素和乙烯等植物激素,可调控多种代谢途径,在荫蔽和微生物介导的植株抗旱性增强过程中起着重要作用。如我们的调控模型所示,CLAVATA3/EMBRYOSURROUNDING REGION-RELATED 25多肽因其可影响ABA合成而在此过程中具有重要作用。