Cremasteric reflex test as an objective indicator of spinal anaesthesia

Fabrication of Fine Electrodes on the Tip of Hypodermic Needle Using Photoresist Spray Coating and Flexible Photomask for Biomedical Applications

We have introduced a fabrication method for electrical impedance spectroscopy (EIS)-on-a-needle (EoN: EIS-on-a-needle) to locate target tissues in the body by measuring and analyzing differences in the electrical impedance between dissimilar biotissues. This paper describes the fabrication method of fine interdigitated electrodes (IDEs) at the tip of a hypodermic needle using a photoresist spray coating and flexible film photomask in the photolithography process. A polyethylene terephthalate (PET) heat shrink tube (HST) with a wall thickness of 25 µm is employed as the insulation and passivation layer. The PET HST shows a higher mechanical durability compared with poly(p-xylylene) polymers, which have been widely used as a dielectric coating material. Furthermore, the HST shows good chemical resistance to most acids and bases, which is advantageous for limiting chemical damage to the EoN. The use of the EoN is especially preferred for the characterization of chemicals/biomaterials or fabrication using acidic/basic chemicals. The fabricated gap and width of the IDEs are as small as 20 µm, and the overall width and length of the IDEs are 400 µm and 860 µm, respectively. The fabrication margin from the tip (distance between the tip of hypodermic needle and starting point of the IDEs) of the hypodermic needle is as small as 680 µm, which indicates that unnecessarily excessive invasion into biotissues can be avoided during the electrical impedance measurement. The EoN has a high potential for clinical use, such as for thyroid biopsies and anesthesia drug delivery in a spinal space. Further, even in surgery that involves the partial resection of tumors, the EoN can be employed to preserve as much normal tissue as possible by detecting the surgical margin (normal tissue that is removed with the surgical excision of a tumor) between the normal and lesion tissues.

On the Origin of Descended Scrotal Testicles: The Activation Hypothesis

Male gonads contained in an unprotected skin sack located outside the body cavity are a peculiar mammalian anomaly. We advance the hypothesis that descended scrotal testicles in humans and many other mammals evolved to provide a situation specific means of activating sperm. As a result of consistent temperature differences between the male and female reproductive tracts (i.e., scrotal temperatures are typically maintained at 2-3°C below body temperature), we propose that the rise to body temperature that accompanies insemination into the vagina serves as one of several triggers for the activation of sperm. We explore some of the features of mammalian reproduction and behavior that are consistent with this hypothesis, make some testable predictions, and examine the psychological and behavioral adaptations that have evolved to protect otherwise vulnerable scrotal testicles from damage.