Return to fertility after extended chemical castration with a GnRH antagonist

BACKGROUND: Antagonistic analogues of GnRH for the treatment of prostate cancer may be used clinically in persons for whom return to fertility after such treatment is important or desirable. The purpose of this study was, therefore, to evaluate the effects of a long term treatment with orntide, a GnRH antagonist, on testosterone levels and fertility in male rats. METHODS: Two groups of male rats received either 120-day orntide microspheres (8.8 mg orntide/kg/120 days) or vehicle alone (control group). Serum orntide and testosterone levels in both groups were monitored at certain intervals for 9 months from the initiation of treatment. After recovery of normal serum testosterone levels in the treated animals, each rat was housed with two proven breeder, but drug-naive, females. RESULTS: All mates of treated rats achieved pregnancy as rapidly as the mates of control rats although two of the control rats did not sire a litter with either female and one sired only one litter. The mean size of the litters of treated (12.3 offspring per litter) and control (10.6 offspring per litter) were similar. All offspring were grossly normal morphologically and behaviorally during the time to weaning. CONCLUSIONS: These results suggest that lack of fertility due to testosterone suppression is reversible after cessation of treatment with this GnRH antagonist

Assessment of fertility in male rats after extended chemical castration with a GnRH antagonist

The purpose of this study was to assess whether male rats whose testosterone levels were suppressed to castration levels (<0.5 ng/mL) for a 1-year period by the sustained delivery of orntide acetate, a GnRH antagonist, would return to fertility (ie, produce offspring) after serum testosterone returned to control levels. Male rats comprising a treatment group (orntide microspheres, dose=27 mg/kg/y), a vehicle control group, and a control group of proven male breeders were used. For the treatment and vehicle control groups, serum orntide and testosterone levels were monitored at periodic intervals for 14 months from the initiation of treatment. After serum testosterone levels returned to vehicle control levels and orntide serum levels were no longer discernible for the treated group, each of the animals was housed with 2 drug-naive, female, proven breeders. All the breeder females produced offspring with the exception of 1 female housed with a male rat from the treatment group and the 2 females housed with a single male rat from the vehicle control group. The mean size and weight of the litters from each group were not statistically different. Further, fertility of the offspring from each group was assessed. The male and female offspring studied were all shown to be fertile. The results suggest that lack of fertility due to testosterone suppression in male rats is reversible after cessation of treatment with the GnRH analog, orntide

Return to fertility after extended chemical castration with a GnRH antagonist

Abstract Background Antagonistic analogues of GnRH for the treatment of prostate cancer may be used clinically in persons for whom return to fertility after such treatment is important or desirable. The purpose of this study was, therefore, to evaluate the effects of a long term treatment with orntide, a GnRH antagonist, on testosterone levels and fertility in male rats. Methods Two groups of male rats received either 120-day orntide microspheres (8.8 mg orntide/kg/120 days) or vehicle alone (control group). Serum orntide and testosterone levels in both groups were monitored at certain intervals for 9 months from the initiation of treatment. After recovery of normal serum testosterone levels in the treated animals, each rat was housed with two proven breeder, but drug-naive, females. Results All mates of treated rats achieved pregnancy as rapidly as the mates of control rats although two of the control rats did not sire a litter with either female and one sired only one litter. The mean size of the litters of treated (12.3 offspring per litter) and control (10.6 offspring per litter) were similar. All offspring were grossly normal morphologically and behaviorally during the time to weaning. Conclusions These results suggest that lack of fertility due to testosterone suppression is reversible after cessation of treatment with this GnRH antagonist.</p

In vivo release kinetics of octreotide acetate from experimental polymeric microsphere formulations using oil/water and oil/oil processes

The purpose of the present study was to characterize the in vivo release kinetics of octreotide acetate from microsphere formulations designed to minimize peptide acylation and improve drug stability. Microspheres were prepared by a conventional oil/wate (o/w) method or an experimental oil/oil (o/o) dispersion technique. The dosage forms were administered subcutaneously to a rat animal model, and serum samples were analyzed by radioimmunoassay over a 2-month period. An averaged kinetic profile from each treatment group, as a result, was treated with fractional differential equations. The results indicated that poly(l-lactide) microspheres prepared by the o/o dispersion technique provided lower area under the curve (AUC) values during the initial diffusion-controlled release phase, 7.79 ng×d/mL, versus 75.8 ng/sxd/mL for the o/w batch. During the subsequent erosion-controlled release phase, on the other hand, the o/o technique yielded higher AUC values, 123 ng×d/mL, versus 42.2 ng×d/mL for the o/w batch. The differences observed between the 2 techniques were attributed to the site of drug incorporation during the manufacturing process, given that microspheres contain both porous hydrophilic channels and dense hydrophobic matrix regions. An o/o dispersion technique was therefore expected to produce microspheres with lower incorporation in the aqueous channels, which are responsible for diffusion-mediated drug release

Eficiência dos dialelos circulantes na escolha de genitores Efficiency of circulant diallels in parental choice

O objetivo foi avaliar, por simulação de dados, a eficiência de dialelos circulantes em relação aos completos, nas estimativas de capacidade geral de combinação (CGC) e capacidade específica de combinação (CEC). Foram simuladas 50 linhagens com 100 genes com distribuição independente, efeitos iguais, sem epistasia. Consideraram-se herdabilidades de 10%, 20%, 50% e 75%, em modelos com interação alélica aditiva e dominância completa. Utilizaram-se também dados de experimentos disponíveis na literatura, ambos comparados por meio de: correlação entre estimativas de CGC e CEC, e proporções de estimativas nos circulantes que ocorreram nos intervalos de confiança dos completos. Os resultados permitiram concluir que os dialelos circulantes são tão eficientes quanto os completos, tanto na classificação dos pais quanto à CGC e à CEC, como na magnitude desses parâmetros, e que o número de cruzamentos (s) afeta as estimativas de CGC e de CEC, embora com um valor pequeno de s seja possível obter boa concordância com as estimativas obtidas nos dialelos completos; com baixa herdabilidade, é vantajoso aumentar o número de cruzamentos de cada pai, embora com a metade do número de pais envolvidos já se consiga alta eficiência dos dialelos circulantes.<br>This paper aimed to evaluate the efficiency of circulant diallel in relation to the complete ones, with data simulation based on estimates of general combining ability (GCA) and specific combining ability (SCA). Fifty lines with 100 independent genes of same effects and without epistasy were simulated. Heritabilities of 10%, 20%, 50% and 75% were considered, in models with addictive and complete dominant allelic interaction. Real data experiments presented in literature were used. They were compared by means of correlation between estimates of GCA and SCA, and also by means of proportions of estimates in the circulant that occurred in the confidence intervals of the complete ones. It was concluded that the efficiency is the same in both diallels, considering the parents classification in relation to GCA and SCA, and the magnitude of those parameters; that the number of crossings (s) affects the estimates of GCA and SCA, although with a small value of s it is possible to obtain good agreement with the estimates of the complete diallel; and, that with low heritability it is advantageous to increase the number of each parent crossings, although with the half of the number of parents involved, high efficiency of the circulant diallels is reached

Identification of chemically modified peptide from poly(D,L-lactide-co-glycolide) microspheres under in vitro release conditions

The purpose of this research was to study the chemical reactivity of a somatostatin analogue octreotide acetate, formulated in microspheres with polymers of varying molecular weight and co-monomer ratio under in vitro testing conditions. Poly(D,L-lactide-co-glycolide) (PLGA) and poly(D,L-lactide) (PLA) microspheres were prepared by a solvent extraction/evaporation method. The microspheres were characterized for drug load, impurity content, and particle size. Further, the microspheres were subjected to in vitro release testing in acetate buffer (pH 4.0) and phosphate buffered saline (PBS) (pH 7.2). In acetate buffer, 3 microsphere batches composed of low molecular weight PLGA 50∶50, PLGA 85∶15, and PLA polymers (≤10 kDa) showed 100% release with minimal impurity formation (<10%). The high molecular weight PLGA 50∶50 microspheres (28 kDa) displayed only 70% cumulative release in acetate buffer with significant impurity formation (∼24%). In PBS (pH 7.4), on the other hand, only 50% release was observed with the same low molecular weight batches (PLGA 50∶50, PLGA 85∶15, and PLA) with higher percentages of hydrophobic impurity formation (ie, 40%, 26%, and 10%, respectively). In addition, in PBS, the high molecular weight PLGA 50∶50 microspheres showed only 20% drug release with ∼60% mean impurity content. The chemically modified peptide impurities inside microspheres were structurally confirmed through Fourier transform-mass spectrometry (FT-MS) and liquid chromatography/mass spectrometry (LC-MS/MS) analyses after extraction procedures. The adduct compounds were identified as covalently modified conjugates of octreotide with lactic and glycolic acid monomers within polymeric microspheres. The data suggest that due to steric hindrance factors, polymers with greater lactide content were less amenable to the formation of adduct impurities compared with PLGA 50∶50 copolymers

Preparation and stability of poly(ethylene glycol) (PEG)ylated octreotide for application to microsphere delivery

The purpose of this study was to prepare poly(ethylene glycol) (PEG)ylated octreotide and investigate the stability against acylation by polyester polymers such as poly(lactic acid) and poly(lactic-co-glycolic acid). Octreotide was modified by reaction with monomethoxy PEG-propionaldehyde (molecular weight 5,000) in the presence of sodium cyanoborohydride. The mono-PEGylated fraction was isolated by reverse-phase high-performance liquid chromatography (HPLC) and characterized by matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Circular dichroism demonstrated no significant secondary structural differences between mono-PEGylated octreotide (mono-PEG-octreotide) and intact octreotide. As a test system for the stability study against acylation reaction, lactic acid (LA) solutions with various concentrations and pH values were prepared with water dilution and subsequent accelerated equilibration at 90°C for 24 hours. Native octreotide was found to be acylated in all the diluted LA solutions with different concentrations (42.5%, 21.3%, and 8.5%, wt/wt) and pH values (2.25, 1.47, and 1.85, respectively). The remaining amounts of intact octreotide continuously decreased to 50% through 30 days of incubation at 37°C. MALDI-TOF MS identified the octreotide to be acylated by LA units. However, acylation reaction of mono-PEG-octreotide in LA solutions was negligible, and the remaining amounts of intact one through 30 days of incubation in LA solutions were also comparable to the initial concentration. These data suggest that mono-PEG-octreotide may prevent the acylation reaction in degrading PLA microspheres and possibly serve as a new source for somatostatin microsphere formulation

Projeto Interdisciplinar do Pantanal - Fase Umida (IPE-1)

A field campaign was carried out in the South Mato Grosso Pantanal, as part of a broad experimental program to study the characteristics of the weather and the climate of the central region of Brazil. The aim of this experiment is to investigate the structure of the surface boundary layer above the Pantanal, during the flood season, in a site representative of the region (19°33'48" S; 57°00'53"W), located about 1.5 km from the Pantanal Studies Base of the Federal University of Mato Grosso do Sul (UFMS), in Passo do Lontra, MS.Pages: