Papers by German A B Mahecha
Pesquisa Veterinária Brasileira., 2009
The ultrasonography (US) is a complementary technique of choice for the diagnostic of hepatic dis... more The ultrasonography (US) is a complementary technique of choice for the diagnostic of hepatic diseases in many domestics' species. In sheep however there are few reports about ultrasonography in hepatic diseases and there is not precise definition about the anatomic standards of normal liver limits in ultrasonographic examination. In this study 58 Santa Inês sheep breed were used and divided in 3 groups: n1=8 males, n2=10 not pregnant females and n3=40 pregnant females. The animals were scanned from the 12º to 8º intercostal spaces (EI) to observe the localization of the vena cava caudal (VC), gallbladder (VB) and to measure the liver thickness above the VC and vena portae VP under the 11º and 10º EI. The liver was examined on satisfactory way from the 12º till the 8º EI. Both the VC and the VP where observed from the 12º to 9º EI, however the VC could not be observed in 11 animals, 10 of them were over 50 kg. Between the two female groups the VC and VP where observed most frequently from the 11º to 10º EI and in all males examined from the 12º to 10º EI. The location of the gallbladder varies between the 10º to the 8º EI, with bigger incidence between the 9º and the 8º EI in pregnant and no pregnant females groups and underneath the 9º EI on the male group. Comparatively, the ecogenicity of the liver parenchyma was more intense than kidney cortex. There was a significant correlation between liver's weight and hepatic thikness above the vena portae on the 11º and 10º EI on the pregnant females group. The US supplied to important information about the topography and echogenicity of the liver and showed to be a useful tool to esteem the liver's weight.
Rev Bras Cienc Morfol, Dec 1, 1994
Cells Tissues Organs, 1998
Morphometric, anatomical and histological examinations were made in 10 species of owls of the fam... more Morphometric, anatomical and histological examinations were made in 10 species of owls of the families Tytonidae and Strigidae and compared with the eyes of other species of nocturnal birds including common potoo (Nictibiidae) and three species of nightjars (Caprimulgidae) and two diurnal species: the roadside hawk (Accipitridae) and the domestic duck (Anatidae). In owls and the common potoo the nictitating membrane is situated on the dorsal edge of the eye. In these birds, the scleral ring bears an additional, previously undescribed bone of various forms and dimensions (1.4–6.8 mm of length and 0.8–3.3 mm of width), located on the trajectory of the tendon of the pyramidal muscle which is attached to the nictitating membrane. This bone has a groove that encloses the tendon of the pyramidal muscle, preventing it from separating from the sclera during contraction, as well as diverting the trajectory of the tendon to impede it from projecting itself over the cornea. In the ferruginous ...
Revista Brasileira de Ciência Veterinária, 2019
Brazilian Journal of Poultry Science, Mar 1, 2014
Epididymal lithiasis (EL) histopathology is described using light and electronic microscopy in ro... more Epididymal lithiasis (EL) histopathology is described using light and electronic microscopy in roosters (Gallus gallus domesticus) naturally affected by EL in Minas Gerais, Brazil. The histologic and morphological changes by EL in roosters was performed regarding cellular and subcellular details through light and electron microscopy. Efferent ductules epithelium lysosomal increase in size and numbers, membrane rupture, cellular vacuolation, ciliary loss, basal membrane degeneration, inflammatory reaction with mononuclear infiltrations, edema, epithelial and vascular endothelium losses were described. All industrial and freerange chickens showed EL in varying degrees in the efferent ductules (ED). However, ED altered areas did not correlate with the presence of luminal stones. Non-ciliated ED epithelium cells presented several atypically large lysosomes. Plicae loss and basal vacuoles were observed in the epithelium of dilated regions. Cellular cilia loss and apical cytoplasmic membrane rupture resulted in leakage of the cytoplasmic contents to the ED lumen, and ED epithelium desquamation occurred with or without lesion to the basal membrane. Basal membrane alterations were associated with profound sub-epithelial connective tissue damage. Aggregations of desquamated epithelium and spermatozoa were seen in the lumen of ED and compact aggregates were considered the basis for calculi formation. The widespread occurrence and high severity of EL lesions are indicative of the importance of EL as a cause of infertility in male chickens.
The Journal of Steroid Biochemistry and Molecular Biology, May 1, 2021
Low circulating levels of vitamin D are common at older ages and have been linked to an increased... more Low circulating levels of vitamin D are common at older ages and have been linked to an increased risk of prostate disease, including cancer. However, it has not yet been determined whether aging affects the ability of prostate cells to locally metabolize vitamin D into its active metabolite calcitriol and thus mediate the vitamin D signaling in autocrine and paracrine ways. By using a suitable rat model to interrogate spontaneous prostatic modifications over the course of aging, here we showed that both CYP27B1 and CYP24A1 enzymes, which are key players respectively involved with calcitriol synthesis and deactivation, were highly expressed in the prostate epithelium. Furthermore, as the animals aged, a drastic reduction of CYP27B1 levels was detected in total protein extracts and especially in epithelial areas of lesions, including tumors. On the other hand, CYP24A1 expression significantly increased with aging and remained elevated even in altered epithelia. Such intricate unbalance in regard to vitamin D metabolizing enzymes was strongly associated with reduced bioavailability of calcitriol in the senile prostate, which in addition to decreased expression of the vitamin D receptor, further limits the protective actions mediated by vitamin D signaling. This evidence was corroborated by the increased proliferative activity exactly at sites of lesions where the factors implicated with calcitriol synthesis and responsiveness had its expression inhibited. Taken together, our results emphasize a set of modifications over the course of aging with a high potential to hamper vitamin D signaling on the prostate. These findings highlight a crosstalk between vitamin D, aging, and prostate carcinogenesis, offering new potential targets in the prevention of malignancies and other aging-related disorders arising in the gland.
The Cerebellum, Oct 24, 2020
Thiamine deficiency is associated with cerebellar dysfunction; however, the consequences of thiam... more Thiamine deficiency is associated with cerebellar dysfunction; however, the consequences of thiamine deficiency on the electrophysiological properties of cerebellar Purkinje cells are poorly understood. Here, we evaluated these parameters in brain slices containing cerebellar vermis. Adult mice were maintained for 12-13 days on a thiamine-free diet coupled with daily injections of pyrithiamine, an inhibitor of thiamine phosphorylation. Morphological analysis revealed a 20% reduction in Purkinje cell and nuclear volume in thiamine-deficient animals compared to feeding-matched controls, with no reduction in cell count. Under whole-cell current clamp, thiamine-deficient Purkinje cells required significantly less current injection to fire an action potential. This reduction in rheobase was not due to a change in voltage threshold. Rather, thiamine-deficient neurons presented significantly higher input resistance specifically in the voltage range just below threshold, which increases their sensitivity to current at these critical membrane potentials. In addition, thiamine deficiency caused a significant decrease in the amplitude of the action potential afterhyperpolarization, broadened the action potential, and decreased the current threshold for depolarization block. When thiamine-deficient animals were allowed to recover for 1 week on a normal diet, rheobase, threshold, action potential halfwidth, and depolarization block threshold were no longer different from controls. We conclude that thiamine deficiency causes significant but reversible changes to the electrophysiology properties of Purkinje cells prior to pathological morphological alterations or cell loss. Thus, the data obtained in the present study indicate that increased excitability of Purkinje cells may represent a leading indicator of cerebellar dysfunction caused by lack of thiamine.
Life Sciences, Feb 1, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
The Prostate, Mar 5, 2018
Background: Protective roles have been proposed for vitamin D in prostate cancer, which has the a... more Background: Protective roles have been proposed for vitamin D in prostate cancer, which has the advanced age as the major risk factor. However, little is known about the expression of the vitamin D receptor (VDR) in the aging prostate and its association with the development of epithelial lesions that affect tissue homeostasis and may precede prostate tumors. Methods: VDR expression in the prostatic complex of young adults to senile Wistar rats, a natural model to study age-related prostatic disorders, was evaluated by immunohistochemical, Western blotting, and image-assisted analyzes. Results were correlated with the plasma levels of vitamin D and testosterone, the occurrence of punctual histopathological changes in the aging prostate, and the expression of retinoid X receptors (RXR). Results: VDR was widely distributed in the prostatic complex at all ages analyzed, with the highest immunoexpression found in basal epithelial cells. As the animals aged, VDR levels increased, except in punctual areas with intraepithelial proliferation, metaplasia, or proliferative inflammatory atrophy, which had reduced expression of this receptor concomitantly with increased cell proliferation. Interestingly, RXR expression in the aging prostate was similar to that found for its partner VDR, indicating that components of the VDR/RXR complex required for vitamin D signaling are affected in aging-related prostatic lesions. Moreover, plasma vitamin D levels declined at the same ages when prostatic alterations appeared. Although circulating levels of testosterone also decreased with aging, the changes observed in the components of the vitamin D system were not correlated with androgens. Conclusions: Our data indicate that the aging prostate suffers from an imbalance on the intricate mechanism of tissue regulation by the vitamin D responsive system. We argue that the status of VDR expression might be determinant for the development of histopathological alterations in the aging prostate, which include premalignant lesions.
European Journal of Pharmacology, 2021
The participation of the peripheral opioid and cannabinoid endogenous systems in modulating muscl... more The participation of the peripheral opioid and cannabinoid endogenous systems in modulating muscle pain and inflammation has not been fully explored. Thus, the aim of this study was to investigate the involvement of these endogenous systems during muscular-tissue hyperalgesia induced by inflammation. Hyperalgesia was induced by carrageenan injection into the tibialis anterior muscles of male Wistar rats. We padronized an available Randal-Sellito test adaptation to evaluate nociceptive behavior elicited by mechanical insult in muscles. Western blot analysis was performed to evaluate the expression levels of opioid and cannabinoid receptors in the dorsal root ganglia. The non-selective opioid peptide receptor antagonist (naloxone) and the selective mu opioid receptor MOP (clocinnamox) and kappa opioid receptor KOP (nor-binaltorphimine) antagonists were able to intensify carrageenan-induced muscular hyperalgesia. On the other hand, the selective delta opioid receptor (DOP) antagonist (naltrindole) did not present any effect on nociceptive behavior. Moreover, the selective inhibitor of aminopeptidases (Bestatin) provoked considerable dose-dependent analgesia when intramuscularly injected into the hyperalgesic muscle. The CB1 receptor antagonist (AM251), but not the CB2 receptor antagonist (AM630), intensified muscle hyperalgesia. All irreversible inhibitors of anandamide hydrolase (MAFP), the inhibitor for monoacylglycerol lipase (JZL184) and the anandamide reuptake inhibitor (VDM11) decreased carrageenan-induced hyperalgesia in muscular tissue. Lastly, MOP, KOP and CB1 expression levels in DRG were baseline even after muscular injection with carrageenan. The endogenous opioid and cannabinoid systems participate in peripheral muscle pain control through the activation of MOP, KOP and CB1 receptors.
South American Journal of Herpetology, 2021
Abstract. Cloacae and peritoneal canals of species of Testudines, Crocodylia, and Aves were analy... more Abstract. Cloacae and peritoneal canals of species of Testudines, Crocodylia, and Aves were analyzed with the purpose of identifying and describing their morphology and investigating their possible relationship with other cloacal structures. Studies were conducted from dissections and routine histological preparations. The cloaca is located in the pelvic cavity and differs between Testudines and Crocodylia. In the former, the cloaca is divided into three compartments—the coprodeum, urodeum, and proctodeum—without folds separating them. In contrast, in Crocodylia the coprodeum, urodeum, and proctodeum are separated by discrete folds, the coprourodeal and uroproctodeal folds. The visceral layer of the peritoneum forms the peritoneal canal and also differs in Testudines and Crocodylia. In the former, the cranial opening of the peritoneal canal is lateral to the urogenital sinus and the canal is caudally projected into the phallus, laterally followed by the ejaculatory groove until the caudal end of the organ. In Crocodylia, the cranial opening of the peritoneal canal is lateral to the coprodeum and the canal extends caudally until reaching a papilla in the body of the phallus, where it terminates. Histologically, the mesothelium of the peritoneal canal has a simple pavement appearance. In Testudines, regions with a simple cubic epithelium were found, indicating intense cell activity. The lamina propria is characterized by a thickening of the connective tissue, moderately dense with a variable thickness and with a layer of bundles of smooth muscle arranged in different directions. In Caiman yacare, bundles of striated skeletal muscles were found on the loose connective tissue that involves the peritoneal canal. The cloacal and peritoneal fluids have a strong protein similarity. The peritoneal canal reflects functional characteristics related to reproduction. No peritoneal canals were found in birds.
Andrology, 2020
Prostate cancer remains one of the most common cancers in men. Macrophages are thought to be impo... more Prostate cancer remains one of the most common cancers in men. Macrophages are thought to be important regulators in cancers, and their potential involvement in prostate cancer should not be overlooked. Therefore, the association between macrophages and the pre‐tumorous changes in prostate epithelium during aging deserves further investigation.
Journal of hepatology, Jan 29, 2018
Liver is the main hematopoietic site in embryos, becoming a crucial organ in both immunity and me... more Liver is the main hematopoietic site in embryos, becoming a crucial organ in both immunity and metabolism in adults. However, how the liver adapts both immune system and enzymatic profile to face challenges in the initial periods after birth is still elusive. We analyzed liver samples from mice on day 0 after birth up to adults. Human biopsies from newborns and adults were also examined. Liver immune cells were phenotyped using mass cytometry (CyTOF) and expression of several genes belonging to immune and metabolic pathways were measured. Mortality rate, bacteremia and hepatic bacterial retention after E. coli challenge were analyzed using intravital and in vitro approaches. In a set of experiments, mice were prematurely weaned and the impact on gene expression of metabolic pathways was evaluated. Human and mouse newborns have a sharp different hepatic cellular composition and arrangement compared to adults. We also found that myeloid cells and B cells primarily compose the neonatal...
Chemosphere, 2018
The widely used herbicide atrazine is a potent endocrine disruptor known to cause increased aroma... more The widely used herbicide atrazine is a potent endocrine disruptor known to cause increased aromatase expression and transient increase in testicular weight followed by remarkable testis atrophy. However, whether the effects of atrazine on the testes are primary or secondary to dysfunctions in other components of male reproductive tract remains unknown. Given the high sensitivity of the efferent ductules to estrogen imbalance and the similarity to alterations previously described for other disruptors of these ductules function, and the testicular alterations observed after atrazine exposure, we hypothesized that the efferent ductules could be a target for atrazine. Herein we characterized the efferent ductules and the ventral prostate of adult Wistar rats treated with 200 mg/kg/day of atrazine for 7, 15, and 40 days. Additionally, we evaluated if the effects of atrazine in these organs could be reduced after discontinuation of the treatment. Atrazine exposure resulted in mild effect...
Reproductive Toxicology, 2017
Atrazine is an endocrine disruptor affecting testicular steroidogenesis, and promoting testicular... more Atrazine is an endocrine disruptor affecting testicular steroidogenesis, and promoting testicular atrophy and 3β-HSD reduction. However, it remains unknown whether these effects are reversible or permanent. To address this issue was the aim of this study. Exposition of rats to 200mg/kg of atrazine resulted in transient increase in testicular weight, seminiferous tubules dilation and atrophy, and reduction in Leydig cell 3β-HSD. Testicular atrophy and 3β-HSD reduction were more pronounced after the recovery period of 75 days. There was increase in aromatase expression after long-term exposure but it returned to control level after recovery. Moreover, there was increase in ED1-/ED2 + , ED1 + /ED2 + and ED1 + /ED2-macrophages, in the recovery group. These macrophages were positive for 3β-HSD, thereby raising possibility of their involvement in steroidogenesis. These findings further emphasize the adverse effects of atrazine on male reproduction, highlighting that testicular damages may be irreversible even after a recovery period longer than the spermatogenic cycle.
The Prostate, 2017
Estrogens acting through the receptors ERα and ERβ participate in prostate normal growth and canc... more Estrogens acting through the receptors ERα and ERβ participate in prostate normal growth and cancer. ERβ is highly expressed in the prostate epithelium, playing pro-apoptotic, anti-proliferative, and pro-differentiation roles. Apoptosis is activated by the intrinsic pathway after castration and by the extrinsic pathway after ERβ agonist treatment. This differential activation of apoptotic pathways is important since a major problem in the treatment of prostate cancer is the recurrence of tumors after androgen withdrawal. However, a comprehensive study about the pattern of apoptosis in the aging prostate is lacking, a knowledge gap that we aimed to address herein. Cellular age-related proliferative and apoptotic profiles of prostate tissue obtained from aging Wistar rats were evaluated. Cell death (caspase-3, -8, -9, TNFα) was assessed by immunohistochemistry, immunofluorescence, and TUNEL. Cell proliferation (MCM7) and cell survival factors (ERK1/2, p-ERK1/2, p-Akt, and NF-κB) were ...
Journal of morphology, Oct 22, 2017
The tongue of anteaters (Xenarthra, Pilosa, Vermilingua) is a highly specialized for myrmecophagy... more The tongue of anteaters (Xenarthra, Pilosa, Vermilingua) is a highly specialized for myrmecophagy. Here, we describe the topography and histology of the tongue, and compare it to that of other xenarthrans and other myrmecophagous eutherian mammals. The tongue of Vermilingua is long and slender, with an apical protuberance, which differs between Myrmecophagidae and Cyclopes didactylus. In the former, the rostral region is conical, and in the latter, it is dorsoventrally compressed, as observed in sloths. The tongue of Vermilingua has filiform and circumvallate papillae on the surface; foliate and fungiform papillae are absent. The filiform papillae of Myrmecophaga tridactyla are simple all over the tongue, differing from Tamandua tetradactyla and Cyclopes didactylus, which present composed filiform papillae in the rostral and middle regions. Histologically, the tongue has a peculiar organization of muscular and neurovascular tissues, differing from the usual mammalian pattern. Howeve...
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Papers by German A B Mahecha