Histogenesis of the Gubernaculum During Testis Descent in the Goat Fetus (Capra marghoz) / Histogénesis del Gubernaculum Durante el Descenso Testicular en el Feto de Cabra (Capra marghoz)

SUMMARY: Testicular descent is a complex process that only occurs in mammals. The role of the gubernaculum during testicular descent has been explained mainly by its capacity for dilatation and contraction. This study tried to investigate the changes in the structure of the fibers and cells of the gubernaculum in different age levels of testicular descent in goat fetuses. Embryo samples were collected and grouped in such a way that 60 male goat fetuses were obtained from 100 pregnant does (Capra marghoz). The samples were classified based on the average length (CRL) of the used embryos into 6 age groups. Tissues of the gubernaculum were stained using Masson's Trichrome method to observe collagen fibers under light microscopy. In the present study, growth and orientation of collagen fibers of gubernaculum were observed from the age of 51 days in a manner that the arrangement and order of fibroblasts and collagens to be associated with the onset of testicular migration order and collagen fibers until the end of the third month. Further, changes in the cell arrays and strings were observed after the age of 111 days in such a way that near the birth date, the gubernaculum converted into atrophy tissue. It can be said that from the beginning of the period of testicular descent until its completion, the tissue of the gubernaculum undergoes cellular changes, such as deformation and increase and secretion in connective fibers.

El descenso testicular es un proceso complejo que solo ocurre en los mamíferos. El papel del gubernaculum durante este proceso se ha explicado principalmente por su capacidad de dilatarse y contraerse. En este trabajo, se investigaron los cambios en la estructura de las fibras y células del gubernaculum en diferentes etapas del descenso testicular y edades en fetos de cabra. Se recolectaron muestras de embriones, agrupándose de manera que se obtuvieron 60 fetos de macho cabrío a partir de 100 hembras preñadas (Capra marghoz). Las muestras se clasificaron según la longitud media (CRL) de los embriones utilizados, dividiéndose en seis grupos de edad. Los tejidos del gubernaculum se tiñeron utilizando la técnica de Tricrómico de Masson para observar las fibras de colágeno bajo microscopía óptica. En el presente estudio, se observó el crecimiento y la orientación de las fibras colágenas del gubernaculum a partir de los 51 días de edad. La disposición y el orden de los fibroblastos y colágeno se asociaron con el inicio de la migración testicular, observándose las fibras colágenas hasta el final del tercer mes. Además, se detectaron cambios en las matrices y cadenas de células después de los 111 días de edad. Cerca de la fecha de nacimiento, el gubernaculum se convirtió en tejido atrofiado. En conclusión, desde el inicio hasta la finalización del período de descenso testicular, el tejido del gubernaculum sufre cambios celulares, como deformación y aumento de secreción en las fibras conectivas.

Biomechanics Characterization of Autonomic and Somatic Nerves by High Dynamic Closed-Loop MEMS force sensing.

The biomechanics of peripheral nerves are determined by the blood-nerve barrier (BNB), together with the epineural barrier, extracellular matrix, and axonal composition, which maintain structural and functional stability. These elements are often ignored in the fabrication of penetrating devices, and the implant process is traumatic due to the mechanical distress, compromising the function of neuroprosthesis for sensory-motor restoration in amputees. Miniaturization of penetrating interfaces offers the unique opportunity of decoding individual nerve fibers associated to specific functions, however, a main issue for their implant is the lack of high-precision standardization of insertion forces. Current automatized electromechanical force sensors are available; however, their sensitivity and range amplitude are limited (i.e. mN), and have been tested only in-vitro. We previously developed a high-precision bi-directional micro-electromechanical force sensor, with a closed-loop mechanism (MEMS-CLFS), that while measuring with high-precision (-211.7µN to 211.5µN with a resolution of 4.74nN), can be used in alive animal. Our technology has an on-chip electrothermal displacement sensor with a shuttle beam displacement amplification mechanism, for large range and high-frequency resolution (dynamic range of 92.9 dB), which eliminates the adverse effect of flexural nonlinearity measurements, observed with other systems, and reduces the mechanical impact on delicate biological tissue. In this work, we use the MEMS-CLFS for in-vivo bidirectional measurement of biomechanics in somatic and autonomic nerves. Furthermore we define the mechanical implications of irrigation and collagen VI in the BNB, which is different for both autonomic and somatic nerves (~ 8.5-8.6 fold density of collagen VI and vasculature CD31+ in the VN vs ScN). This study allowed us to create a mathematical approach to predict insertion forces. Our data highlights the necessity of nerve-customization forces to prevent injury when implanting interfaces, and describes a high precision MEMS technology and mathematical model for their measurements.

Rosette-scan video-rate atomic force microscopy: Trajectory patterning and control design.

We present an analysis and a systematic design methodology for a novel nonraster scan method based on a rosette pattern and demonstrate its application in video-rate atomic force microscopy. This pattern is traced when the lateral axes of a parallel kinematic scanner are commanded to follow a combination of two sinusoids with identical amplitudes and different frequencies. We design an internal-model-based controller to enhance the tracking performance of this pattern and implement the scheme on a microelectromechanical system scanner. The results reveal high-precision tracking of the rosette pattern in order to acquire time-lapsed atomic force microscope images at the rate of 10 frames/s.

Note: A silicon-on-insulator microelectromechanical systems probe scanner for on-chip atomic force microscopy.

A new microelectromechanical systems-based 2-degree-of-freedom (DoF) scanner with an integrated cantilever for on-chip atomic force microscopy (AFM) is presented. The silicon cantilever features a layer of piezoelectric material to facilitate its use for tapping mode AFM and enable simultaneous deflection sensing. Electrostatic actuators and electrothermal sensors are used to accurately position the cantilever within the x-y plane. Experimental testing shows that the cantilever is able to be scanned over a 10 µm × 10 µm window and that the cantilever achieves a peak-to-peak deflection greater than 400 nm when excited at its resonance frequency of approximately 62 kHz.

High-stroke silicon-on-insulator MEMS nanopositioner: control design for non-raster scan atomic force microscopy.

A 2-degree of freedom microelectromechanical systems nanopositioner designed for on-chip atomic force microscopy (AFM) is presented. The device is fabricated using a silicon-on-insulator-based process and is designed as a parallel kinematic mechanism. It contains a central scan table and two sets of electrostatic comb actuators along each orthogonal axis, which provides displacement ranges greater than ±10 µm. The first in-plane resonance modes are located at 1274 Hz and 1286 Hz for the X and Y axes, respectively. To measure lateral displacements of the stage, electrothermal position sensors are incorporated in the design. To facilitate high-speed scans, the highly resonant dynamics of the system are controlled using damping loops in conjunction with internal model controllers that enable accurate tracking of fast sinusoidal set-points. To cancel the effect of sensor drift on controlled displacements, washout controllers are used in the damping loops. The feedback controlled nanopositioner is successfully used to perform several AFM scans in contact mode via a Lissajous scan method with a large scan area of 20 µm × 20 µm. The maximum scan rate demonstrated is 1 kHz.

Experimental wound healing using microamperage electrical stimulation in rabbits.

We investigated the effects of microamperage electrical stimulation (MES) on the healing of skin incision in rabbits. Thirty male adult rabbits were randomly divided into sham-treated and experimental groups. Each group was divided into three subgroups, based on the duration of experiment (4, 7, and 15 days). A full-thickness incision was made on the skin of each rabbit. The experimental group received an MES of 200 microamperes current intensity for 2 h/day. Morphometrical and biomechanical evaluations were carried out. The mean number of fibroblasts at day 7 and the mean of tensile strength at day 15 were found to be significantly higher for the experimental group than for those in the sham-treated group (p < 0.01 and p < 0.05, respectively). Daily application of MES significantly accelerated the wound-healing process of full-thickness incision in the rabbits' skin.