Evaluation of drug physical form during granulation, tabletting and storage

An active pharmaceutical ingredient (API) was found to dissociate from the highly crystalline hydrochloride form to the amorphous free base form, with consequent alterations to tablet properties. Here, a wet granulation manufacturing process has been investigated using in situ Fourier transform (FT)-Raman spectroscopic analyses of granules and tablets prepared with different granulating fluids and under different manufacturing conditions. Dosage form stability under a range of storage stresses was also investigated. Despite the spectral similarities between the two drug forms, low levels of API dissociation could be quantified in the tablets; the technique allowed discrimination of around 4% of the API content as the amorphous free base (i.e. less than 1% of the tablet compression weight). API dissociation was shown to be promoted by extended exposure to moisture. Aqueous granulating fluids and manufacturing delays between granulation and drying stages and storage of the tablets in open conditions at 40◦C/75% relative humidity (RH) led to dissociation. In contrast, non-aqueous granulating fluids, with no delay in processing and storage of the tablets in either sealed containers or at lower temperature/humidity prevented detectable dissociation. It is concluded that appropriate manufacturing process and storage conditions for the finished product involved minimising exposure to moisture of the API. Analysis of the drug using FT-Raman spectroscopy allowed rapid optimisation of the process whilst offering quantitative molecular information concerning the dissociation of the drug salt to the amorphous free base form.

Impact of biomass burning on aerosol properties over tropical wet evergreen forests of Arunachal Pradesh, India

Effects of solar wind magnetosphere coupling recorded at different geomagnetic latitudes: Separation of directly-driven and storage/release systems

The effect on geomagnetic activity of solar wind speed, compared with that of the strength of the interplanetary magnetic field, differs with geomagnetic latitude. In this study we construct a new index based on monthly standard deviations in the H-component of the geomagnetic field for all geomagnetic latitudes. We demonstrate that for this index the response at auroral regions correlates best with interplanetary coupling functions which include the solar wind speed while mid- and low-latitude regions respond to variations in the interplanetary magnetic field strength. These results are used to isolate the responsible geomagnetic current systems.

Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) wet season campaign

Ozone and its precursors were measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the monsoon season 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) campaign. One of the main features observed in the west African boundary layer is the increase of the ozone mixing ratios from 25 ppbv over the forested area (south of 12° N) up to 40 ppbv over the Sahelian area. We employ a two-dimensional (latitudinal versus vertical) meteorological model coupled with an O3-NOx-VOC chemistry scheme to simulate the distribution of trace gases over West Africa during the monsoon season and to analyse the processes involved in the establishment of such a gradient. Including an additional source of NO over the Sahelian region to account for NO emitted by soils we simulate a mean NOx concentration of 0.7 ppbv at 16° N versus 0.3 ppbv over the vegetated region further south in reasonable agreement with the observations. As a consequence, ozone is photochemically produced with a rate of 0.25 ppbv h−1 over the vegetated region whilst it reaches up to 0.75 ppbv h−1 at 16° N. We find that the modelled gradient is due to a combination of enhanced deposition to vegetation, which decreases the ozone levels by up to 11 pbbv, and the aforementioned enhanced photochemical production north of 12° N. The peroxy radicals required for this enhanced production in the north come from the oxidation of background CO and CH4 as well as from VOCs. Sensitivity studies reveal that both the background CH4 and partially oxidised VOCs, produced from the oxidation of isoprene emitted from the vegetation in the south, contribute around 5–6 ppbv to the ozone gradient. These results suggest that the northward transport of trace gases by the monsoon flux, especially during nighttime, can have a significant, though secondary, role in determining the ozone gradient in the boundary layer. Convection, anthropogenic emissions and NO produced from lightning do not contribute to the establishment of the discussed ozone gradient.

Microbial relatives of the seed storage proteins of higher plants: conservation of structure and diversification of function during evolution of the cupin superfamily.

This review summarizes the recent discovery of the cupin superfamily (from the Latin term "cupa," a small barrel) of functionally diverse proteins that initially were limited to several higher plant proteins such as seed storage proteins, germin (an oxalate oxidase), germin-like proteins, and auxin-binding protein. Knowledge of the three-dimensional structure of two vicilins, seed proteins with a characteristic beta-barrel core, led to the identification of a small number of conserved residues and thence to the discovery of several microbial proteins which share these key amino acids. In particular, there is a highly conserved pattern of two histidine-containing motifs with a varied intermotif spacing. This cupin signature is found as a central component of many microbial proteins including certain types of phosphomannose isomerase, polyketide synthase, epimerase, and dioxygenase. In addition, the signature has been identified within the N-terminal effector domain in a subgroup of bacterial AraC transcription factors. As well as these single-domain cupins, this survey has identified other classes of two-domain bicupins including bacterial gentisate 1, 2-dioxygenases and 1-hydroxy-2-naphthoate dioxygenases, fungal oxalate decarboxylases, and legume sucrose-binding proteins. Cupin evolution is discussed from the perspective of the structure-function relationships, using data from the genomes of several prokaryotes, especially Bacillus subtilis. Many of these functions involve aspects of sugar metabolism and cell wall synthesis and are concerned with responses to abiotic stress such as heat, desiccation, or starvation. Particular emphasis is also given to the oxalate-degrading enzymes from microbes, their biological significance, and their value in a range of medical and other applications.

Barley oxalate oxidase is a hexameric protein related to seed storage proteins: evidence from X-ray crystallography

The oxalate oxidase enzyme expressed in barley roots is a thermostable, protease-resistant enzyme that generates H2O2. It has great medical importance because of its use to assay plasma and urinary oxalate, and it has also been used to generate transgenic, pathogen-resistant crops. This protein has now been purified and three types of crystals grown. X-ray analysis shows that the symmetry present in these crystals is consistent with a hexameric arrangement of subunits, probably a trimer of dimers. This structure may be similar to that found in the related seed storage proteins.

Microbial relatives of seed storage proteins: conservation of motifs in a functionally diverse superfamily of enzymes

Plant storage proteins comprise a major part of the human diet. Sequence analysis has revealed that these proteins probably share a common ancestor with a fungal oxalate decarboxylase and/or related bacterial genes. Additionally, all these proteins share a central core sequence with several other functionally diverse enzymes and binding proteins, many of which are associated with synthesis of the extracellular matrix during sporulation/encystment. A possible prokaryotic relative of this sequence is a bacterial protein (SASP) known to bind to DNA and thereby protect spores from extreme environmental conditions. This ability to maintain cell viability during periods of dehydration in spores and seeds may relate to absolute conservation of residues involved in structure determination.

Formulation of a live bacterial vaccine for stable room temperature storage results in loss of acid, bile and bile salt resistance

Live bacterial vaccines have great promise both as vaccines against enteric pathogens and as heterologous antigen vectors against diverse diseases. Ideally, room temperature stable dry formulations of live bacterial vaccines will allow oral vaccination without cold-chain storage or injections. Attenuated Salmonella can cross the intestinal wall and deliver replicating antigen plus innate immune activation signals directly to the intestinal immune tissues, however the ingested bacteria must survive firstly gastric acid and secondly the antimicrobial defences of the small intestine. We found that the way in which cells are grown prior to formulation markedly affects sensitivity to acid and bile. Using a previously published stable storage formulation that maintained over 10% viability after 56 days storage at room temperature, we found dried samples of an attenuated S. typhimurium vaccine lost acid and bile resistance compared to the same bacteria taken from fresh culture. The stable formulation utilised osmotic preconditioning in defined medium plus elevated salt concentration to induce intracellular trehalose accumulation before drying. Dried bacteria grown in rich media without osmotic preconditioning showed more resistance to bile, but less stability during storage, suggesting a trade-off between bile resistance and stability. Further optimization is needed to produce the ultimate room-temperature stable oral live bacterial vaccine formulation.

Introducing improved cultivars: Understanding farmers' seed drying and storage practices in central Ghana

Improved upland rice cultivars introduced in Volta Region, Ghana, have been perceived to store poorly compared to farmers' traditional cultivars. A survey was conducted in 2003 in the Hohoc district of this region, where a participatory Varietal Selection programme had started in 1997, to gain insight into fanners' seed production and storage practices that are likely to affect seed quality in storage. Farmers rated keeping quality (p < 0.001), tolerance to storage pests (p < 0.001), seed quality (p < 0.001) and establishment of their local cultivars Kawomo, Viono and Wuwulili as much better than the improved cultivar IDSA 85. Initial seed moisture content ranged from 12.8 to 18% and germination from 0 to 82%. There was a significant relationship between seed moisture content and duration of drying prior to storage (p < 0.001) and storage method (p = 0.015). Germination loss in storage was rapid at high moisture content and slow at low moisture content. Between 60 and 80% of seeds germinated after six Months storage at 12.8% moisture content. The viability equation predicted accurately germination of farmer-saved seed stored under ambient temperature in Ghana. Except for the japonica rice cultivar WAB 126-18-HB, the traditional cultivars Kawomo, Viono and Wuwulili survived better in storage than improved cultivars. There is a need to improve seed quality of improved cultivars if farmers are to benefit from their higher yields and grain quality and to improve storage practices.

Priming and re-drying improve the survival of mature seeds of Digitalis purpurea during storage

Most priming studies have been conducted on commercial seed lots of unspecified uniformity and maturity, and subsequent seed longevity has been reported to both increase and decrease. Here a seed lot of Digitalis purpurea L. with relatively uniform maturity and known history was used to analyse the effects of priming on seed longevity in air-dry storage. Seeds collected close to natural dispersal and dried at 15 % relative humidity (RH), 15 degrees C, were placed into experimental storage (60 % RH, 45 degrees C) for 14 or 28 d, primed for 48 h at 0, -1, -2, -5, -10 or -15 MPa, re-equilibrated (47 % RH, 20 degrees C) and then returned to storage. Further seed samples were primed for 2 or 48 h at -1 MPa and either dried at 15 % RH, 15 degrees C or immediately re-equilibrated for experimental storage. Finally, some seeds were given up to three cycles of experimental storage and priming (48 h at -1 MPa). Priming at -1 MPa had a variable effect on subsequent survival during experimental storage. The shortest lived seeds in the control population showed slightly increased life spans; the longer lived seeds showed reduced life spans. In contrast, seeds first stored for 14 or 28 d before priming had substantially increased life spans. The increase tended to be greatest in the shortest lived fraction of the seed population. Both the period of rehydration and the subsequent drying conditions had significant effects on longevity. Interrupting air-dry storage with additional cycles of priming also increased longevity. The extent of prior deterioration and the post-priming desiccation environment affect the benefits of priming to the subsequent survival of mature seeds. Rehydration-dehydration treatments may have potential as an adjunct or alternative to the regeneration of seed accessions maintained in gene banks for plant biodiversity conservation or plant breeding.

Temperature sensitivity of the low-moisture-content limit to negative seed longevity-moisture content relationships in hermetic storage

Background and Aims The negative logarithmic relationship between orthodox seed longevity and moisture content in hermetic storage is subject to a low-moisture-content limit (m(c)), but is m(c) affected by temperature? Methods Red clover (Trifolium pratense) and alfalfa (Medicago sativa) seeds were stored hermetically at 12 moisture contents (2-15 %) and five temperatures (-20, 30, 40, 50 and 65 degrees C) for up to 14.5 years, and loss in viability was estimated. Key Results Viability did not change during 14.5 years hermetic storage at -20 degrees C with moisture contents from 2.2 to 14.9 % for red clover, or 2.0 to 12.0 % for alfalfa. Negative logarithmic relationships between longevity and moisture contents > m(c) were detected at 30-65 degrees C, with discontinuities at low moisture contents; m(c) varied between 4.0 and 5.4 % (red clover) or 4.2 and 5.5 % (alfalfa), depending upon storage temperature. Within the ranges investigated, a reduction in moisture content below m(c) at any one temperature had no effect on longevity. Estimates of m(c) were greater the cooler the temperature, the relationship (P < 0.01) being curvilinear. Above m(c), the estimates of C-H and C-Q (i.e. the temperature term of the seed viability equation) did not differ (P > 0.10) between species, whereas those of K-E and C-W did (P < 0.001). Conclusions The low-moisture-content limit to negative logarithmic relationships between seed longevity and moisture content in hermetic storage increased the cooler the storage temperature, by approx. 1.5 % over 35 degrees C (4.0-4.2 % at 65 degrees C to 5.4-5.5 % at 30-40 degrees C) in these species. Further reduction in moisture content was not damaging. The variation in m(c) implies greater sensitivity of longevity to temperature above, compared with below, m(c). This was confirmed (P < 0.005).