87 research outputs found
Multi-step optimization strategy for fuel-optimal orbital transfer of low-thrust spacecraft
No full textAn effective method for the design of fuel-optimal transfers in two- and three-body dynamics is presented. The optimal control problem is formulated using calculus of variation and primer vector theory. This leads to a multi-point boundary value problem (MPBVP), characterized by complex inner constraints and a discontinuous thrust profile. The first issue is addressed by embedding the MPBVP in a parametric optimization problem, thus allowing a simplification of the set of transversality constraints. The second problem is solved by representing the discontinuous control function by a smooth function depending on a continuation parameter. The resulting trajectory optimization method can deal with different intermediate conditions, and no a priori knowledge of the control structure is required. Test cases in both the two- and three-body dynamics show the capability of the method in solving complex trajectory design problem
Spermatocyte chromosomes in some species of the family Aplysiidae (Gastropoda, Opisthobranchia).
No full textMorphological organization and variability of the reproductive apparatus in gobies.
No full text"Among all vertebrates, gobies are second in diversity only to the teleost family Cyprinidae. The Gobiidae consists of more than 200 genera and nearly 2,000 species and make up the largest family of marine fishes. Gobies account for as much as 50% of the energy flow in coral reef communities. Their small size, ability to adapt to numerous ecological niches and to be bred in aquaria has led to numerous studies both in the field and laboratory. Gobies are found from above the high tide line to depths of over 1,100 m. Some species are found only within caves, others deep inside sponges, and some others climb waterfalls to return to their native streams. They vary reproductively from gonochoric to hermaphrodite, monogamy to polygyny and promiscuity, some have short life spans and reproduce only once while others have longer life spans reproducing one or more times per year. The Biology of Gobies written by over 30 experts from 15 countries summarizes what is known about the systematics, ecology, zoogeography, and general biology of the Gobiiformes. This foundation will provide the basic information necessary for future studies"--Provided by publisher
A Retrospective Study of Those Histopathologic Parameters Predictive of Invasion of the Lymphatic System by Canine Mammary Carcinomas
No full textThe aim of the present study was to determine which histopathologic parameters of primary canine mammary carcinomas (CMCs) could predict metastatic spread via the lymphatic system. A modification of the World Health Organization classification was applied to 245 CMCs. In addition to tumor subtype, neoplastic infiltration of the surrounding mammary stroma, vasculogenic mimicry, and micropapillary pattern were evaluated, and 2 histologic grading systems were used for each sample. A statistical analysis was undertaken to determine the relationship between these histopathologic parameters and the detection of lymphatic vessels invasion (LVI) and regional lymph node metastases (RLM). To compare the predictive value for lymphatic spread of the 2 histologic grading systems, the Akaike information criterion was measured. The classification into tumor subtypes was significant (P < .01) in predicting the risk of LVI and RLM. Peripheral infiltration, vasculogenic mimicry, and micropapillary pattern were found in 170 of 245 (69.4%), 32 of 245 (13.1%), and 54 of 245 (22.0%) CMCs. The presence of peripheral infiltration was significantly associated (P < .001) with both LVI and RLM, and a similar relation (P < .05) was found for the micropapillary pattern. Vasculogenic mimicry was not predictive of invasion of the lymphatic system. Both histologic grading systems were significant predictors (P < .001) of the risk of LVI and RLM. The grading system that included a more rigorous evaluation of the neoplastic mitotic activity had the lower Akaike information criterion values, thus indicating a better predictive ability. The study confirms the significant prognostic role for the modified World Health Organization classification of CMCs and the prognostic value of additional histopathologic parameters
Oestrogen and progesterone receptor expression in subtypes of canine mammary tumours in intact and ovariectomised dogs.
No full textThe objective of this study was to investigate as a potential prognostic indicator the relationship between histological subtype of canine mammary tumours (CMTs) and oestrogen-α (ORα) and progesterone (PR) receptor expression. Using immunohistochemistry, receptor expression in neoplastic epithelial cells was assessed in 12 different subtypes in 113 CMTs (34 benign, 79 malignant) and 101 surrounding normal tissues. Sixty-eight and 45 CMTs were from intact and ovariectomised bitches, respectively. Histological subtype strongly influenced ORα/PR expression: simple and complex adenomas as well as simple tubular carcinomas exhibited the greatest expression, whereas immunohistochemical labelling for these receptors was weakest in carcinoma and malignant myoepitheliomas, as well as in solid/anaplastic carcinomas and comedocarcinomas. Receptor expression was generally higher in benign relative to malignant neoplasms, and in the latter it was significantly lower in ovariectomised vs. intact bitches. Lymphatic invasion, mitotic index, nodule diameter, and tumour grade were significantly associated with ORα/PR expression. Although not found to be an independent prognostic indicator, tumours from dogs with <10% cells with ORα/PR expression had a poorer prognosis. Lymphatic invasion, the state of the margins of excision, and mitotic index were found to be independent prognostic indicators. Overall, the results suggest that differences in histological subtype and whether or not a bitch has been ovariectomised should be considered when evaluating the significance of ORα and PR expression in CMTs
CLASSIFICATION AND GRADING OF CANINE MAMMARY TUMORS.
No full textMammary neoplasms are the most common neoplasm in female dogs. Two histologic classification systems for canine mammary tumors and dysplasias have been published: the first in 1974 and a modification in 1999. This article provides a brief overview of the two histologic classification systems. Since the publication of the second system, several new histologic subtypes of canine mammary neoplasms have been described. These have been incorporated into the proposed new classification system. This article also compares the grading systems for canine mammary carcinomas and their use for prognosis, along with the histologic classification
TUMORE MAMMARIO CANINO: ESPRESSIONE DEI RECETTORI DI ESTROGENO E PROGESTERONE IN DIVERSI SOTTOTIPI TUMORALI.
No full textI recettori estrogenici e progestinici (ER, PR) rivestono un importante ruolo prognostico nel tumore al seno. A fini prognostico-terapeutici e comparativi, diversi studi hanno valutato l’espressione di tali recettori nel tumore mammario canino (TMC), che è risultato prevalentemente di tipo ormone-dipendente. Il valore prognostico di ER e PR nel TMC è tuttavia ancora oggetto di controversie. Sebbene si riscontri una significativa variazione di espressione tra tessuto mammario sano e neoplastico, e tra tumore mammario benigno e maligno, mancano informazioni dettagliate relative all’espressione nei diversi sottotipi tumorali. Nel presente studio si è indagata mediante metodica immunoistochimica l’espressione di ER e PR in 12 tipi istologici di tumore mammario canino, di cui alcuni di recente classificazione (Goldschimdt et al., 2011), e nel tessuto sano circostante. Sono stati analizzati un totale di 113 campioni di TMC (34 benigni e 79 maligni) e 101 di tessuto sano, appartenenti a 68 femmine intere e 45 femmine non intere. Si è valutato inoltre l’effetto dell’ovariectomia e di diverse caratteristiche istopatologiche sull’espressione recettoriale e il loro valore prognostico. Il tipo istologico è risultato influenzare in modo altamente significativo l’espressione recettoriale di ER e PR sia in termini di percentuale di positività cellulare sia di intensità di segnale. In particolare: l’adenoma semplice, l’adenoma complesso, e il carcinoma tubulare semplice hanno mostrato i valori più elevati, mentre il carcinoma solido, il carcinoma anaplastico e il carcinoma comedonico, i valori più bassi. ER e PR non sono risultati tuttavia di valore prognostico. I risultati del presente studio suggeriscono l’importanza di tenere in considerazione la differenza di espressione recettoriale esistente tra le diverse classi istologiche, che potrebbe influenzare significativamente i risultati relativi ai livelli di espressione
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