Incorporation and release of vancomycin from poly(D,L-lactide-co-glycolide) microspheres.

Spherical monolithic microspheres, with a honeycomb-like internal architecture, composed of PLCG 50:50 and PLCG 75:25 and containing a range of vancomycin loadings, have been fabricated using a W/O emulsification with solvent evaporation technique. Microspheres were generated in high yield (80 wgt%) and vancomycin incorporation, confirmed using the displacement of DSC thermograms, had no significant effect on microsphere size distribution (5-50 microns). The vancomycin encapsulation efficiency was high (> 64%) and release profiles were characterized by a substantial initial burst release and a subsequent low-level sustained release extending up to 30 days depending upon the fabrication polymer, % vancomycin loading and incubation medium used. In both Hank's buffer and newborn calf serum the mean total cumulative release of vancomycin from microspheres increased significantly with theoretical percentage loading.

Vancomycin release from blended polyester microspheres.

O/W emulsification with solvent evaporation was used to fabricate spherical (5-100 microm) vancomycin loaded microspheres, either smooth surfaced with macroporous interior (PLCG 50:50), smooth surfaced and monolithic (PEAD), smooth surfaced (50% PEAD/50% PLCG 50:50), or with a slightly rugose and possibly microporous surface (75% P[HB-HV]/25% PLCG 50:50). Blending PLCG 50:50 with either PEAD or P(HB-HV) marginally increased microsphere diameter, and vancomycin incorporation resulted in the deposition and embedding of vancomycin particles at the microsphere surface. The mean vancomycin encapsulation efficiencies for PLCG 50:50, PEAD, and 50% PEAD/50% PLCG 50:50 were high (>64%) but values for 75% P(HB-HV)/25% PLCG 50:50 were lower and not significantly influenced by the extent of vancomycin loading. Vancomycin release profiles were characterized by an initial burst release followed by a low level sustained release extending up to 20 days. The extent of both release phases depended on the composition of the fabrication polymer and the incubation medium used. The initial burst release of vancomycin was greatest from 75% P(HB-HV)/25% PLCG 50:50 microspheres. However, the mean total cumulative release of vancmycin from PLCG 50:50, PEAD, and 50% PEAD/50% PLCG 50:50 microspheres was significantly greater and detectable over a longer period of time in newborn calf serum than in Hank's buffer. Irrespective of the incubation medium used, blending PEAD with PLCG 50:50 only marginally increased the mean cumulative release of vancomycin from microspheres.

Photosynthetic characteristics of Flindersia brayleyana and Castanospermum australe from tropical lowland and upland sites.

Photosynthetic responses to temperature, light and carbon dioxide partial pressure were studied in two-year-old Flindersia brayleyana F. Muell. and Castanospermum australe Cunn. & C. Fraser ex Hook. growing on coastal lowland and upland rainforest sites in tropical Queensland, Australia. Climatic conditions ranged from moist and cool (17-19 degrees C) to dry and warm (22-24 degrees C). The optimum temperature for photosynthesis was 23.7-25.6 degrees C for C. australe and 21.2-24.6 degrees C for F. brayleyana. Mean maximum rate of electron transport for each species did not differ between sites but was higher (60-62 &mgr;mol m(-2) s(-1)) in F. brayleyana than in C. australe (42-44 &mgr;mol m(-2) s(-1)). Ribulose-bisphosphate carboxylation rate did not differ significantly between sites or species. Maximum rates of photosynthesis at 1000 &mgr;Pa Pa(-1) CO(2) did not differ significantly between sites for each species, but did differ significantly between species. At 350 &mgr;Pa Pa(-1) CO(2), photosynthetic light use efficiencies of F. brayleyana and C. australe were 0.05 and 0.015, respectively, at the upland site, and the corresponding values at the lowland site were 0.025 and 0.05. In C. australe, these differences were reflected in significantly greater maximum rates of photosynthesis at 350 &mgr;Pa Pa(-1) CO(2) at the lowland site than at the upland site (5.2 versus 3.3 &mgr;mol m(-2) s(-1)).

Detection of intravaginal spermatozoa after natural mating in the bitch.

Mismating is one of the most frequently presented reproductive problems presented to veterinarians. Confirming whether or not a mismating has occurred is necessary to determine if therapy will be instituted. Detection of spermatozoa in the vagina is irrefutable evidence of copulation; however, absence of sperm in a vaginal cytology cannot rule out coitus. In order to improve detection of spermatozoa post-coitus, a prospective study was initiated utilizing natural breedings of purebred beagles.

Comparison of the effects of PGF(2)alpha and bromocryptine in pregnant beagle bitches.

Termination of pregnancy (abortion) was successful in four of four bitches that received PGF(2)alpha (125 mug/kg bid s.c.) and in two or four bitches that received bromocryptine (62.5 mug/kg bid po) for up to 6 d beginning 43 to 45 d post ovulation. Four sham-treated controls whelped normally at term. The incidence of side effects, primarily emesis and loose stools, was similar for both experimental groups. Bitches that failed to abort following treatment with bromocryptine whelped normally at term.

Equine artificial insemination.

Artificial insemination is an effective technique for improving utilization of the stallion while maintaining normal conception rates in the mare. However, procedures for collection, evaluation, and insemination of semen must be followed carefully to achieve good results. Techniques for preservation of equine semen in the liquid or frozen state could potentially allow for more widespread use of genetically superior stallions. Further acceptance of artificial insemination and the use of cooled or frozen transported semen by breed registries is needed before this will occur. More work is needed to perfect methods of semen preservation, even though semen from some stallions can be cooled or frozen quite successfully at the present time.

Photosynthesis in an Australian rainforest tree, Argyrodendron peralatum, during the rapid development and relief of water deficits in the dry season.

Rates of apparent photosynthesis were measured in situ at five positions between the upper crown and a lower branch of a 34 m tall Argyrodendron peralatum (F.M. Bailey) H.L. Edlin ex I.H. Boas tree, and on an understorey sapling of the same species growing in a northern Australian rainforest. At the end of the dry season, rapid reductions in photosynthetic rates occurred in the upper crown within three days after a rain event, but changes in the lower crown and the sapling were less marked. Complete recovery of photosynthesis followed a second rain event. At high photon flux densities, stomatal conductance to water vapour decreased in a curvilinear fashion as the vapour pressure difference between leaf and air increased. Apparent photosynthesis was linearly related to stomatal conductance on the first clear day after each rain event, but there was no relationship between these parameters at the end of a brief natural drying cycle. Under conditions of adequate water supply, stomatal conductances of both upper crown and understorey leaves increased linearly with increasing photon flux density up to about 300 µmol m-2 s-1. During water deficits, stomatal conductances in leaves from the understorey increased much more rapidly at very low photon flux densities than did conductances in leaves from the upper canopy.