Regeneration electrode units: implants for recording from single peripheral nerve fibers in freely moving animals

Implantable electrode assemblies that become penetrated by regenerating axons were used to record signals from single sensory and motor nerve fibers associated with leg movement in unrestrained amphibians (Xenopus laevis). Such neuroimplants may provide a means for establishing the roles of various muscle afferents and efferents in posture and locomotion, and have potential clinical applications.     

Effects of ketamine on electroencephalographic and autonomic arousal and segmental reflex responses in the cat

Objective To provide evidence concerning doses of ketamine that affect electroencephalographic (EEG) and autonomic signs of arousal during nociceptive stimulation. Study design Prospective psychophysical test in people. Single injection or progressively increasing infusions of ketamine in cats. Animals and people Seven people (20–60 years old) and three cats (3–5 kg) for EEG recording and six cats for EMG recordings. Methods In order to define innocuous and nociceptive stimulus intensities which could be applied to cats to evaluate arousal, psychophysical evaluations of sensations elicited by compression of the skin overlying phalangeal bones of the hand were obtained from human subjects. Then, following administration of ketamine, recordings of EEG frequency and of autonomic responses (heart rate, respiratory rate and arterial blood pressure) were obtained before and during stimulation of the tails of cats at pressures identified by human observers as either innocuous or nociceptive. Observations of withdrawal reflexes of the hindlimbs following interdigital skin stimulation were interposed between recording periods. In separate sessions, stretch reflex activity was assessed during awake and anesthetic conditions by recording electromyographic activity from soleus muscles and resistive force to dorsiflexion of the tibiotarsal joint. Results There were no changes in either total EEG (0.5–30.0 Hz), low‐frequency (0.6–7.5 Hz) or high‐frequency (7.5–30.0 Hz) power produced by nociceptive stimulation for a period of 18–24 minutes following an intramuscular bolus dose of ketamine (33.0 mg kg^?1), although withdrawal reflexes were present. Thereafter, nociceptive stimulation produced EEG arousal responses in the low‐frequency and total power range and increased systolic blood pressure and respiration rate. In tests after intravenous infusion of ketamine (10.0–22.2 mg kg^?1 hour^?1), total and low‐frequency EEG power and autonomic responses to nociceptive stimulation were eliminated. Organized motor responses were never elicited during IV infusion, but withdrawal reflexes were observed at each dosage. Also, stretch reflexes were shown by quantitative analysis to be retained at all doses of ketamine infusion. Conclusions and clinical relevance These results show that testing of withdrawal reflexes does not reveal the adequacy of ketamine anesthesia. Segmental stretch and withdrawal reflexes are preserved and can be investigated during infusion of ketamine at doses that eliminate arousal from brief periods of nociceptive stimulation.     

Effects of mycorrhizal Bermuda grass on low-range soil matric suction

Journal of Soils and Sediments - Soil matric suction, or negative water potential, contributes to soil physical stability (e.g., slope). Plants retain soil matric suction as they take up and...     

Characteristics and Aquaculture Information Needs of Crayfish Farmers in Akwa-Ibom State,Nigeria

This study investigated the characteristics and aquaculture information needs of crayfish farmers in Akwa-Ibom State of Nigeria. Ninety crayfish farmers formed the sample for the study. Percentage, mean score, and multiple regression were used in data analysis. The findings show that the respondents had no extension contact and no access to crayfish and agriculture-related information. Information on adaptation to the effects of climate change on aquatic animals, especially crayfish, was needed by these farmers. Primary occupation, monthly income from crayfish enterprise, household size, and number of extension contacts were determinants of output on crayfish. The restriction of fishing activities on traditional festival days was a challenge, while the use of modern boats and durable nets were strategies for improving harvesting of crayfish.     

A climatological basis for conserving groundwater and reducing overflow in aquaculture ponds in the Southeast United States

Drop-fill water management schemes for aquacultural ponds reduce both groundwater use and effluent release. A drop-fill scheme assumes that pond water level will be allowed to decrease to the “drop” depth before makeup water is used to return it to the “fill” depth, which is typically some fraction (e.g., 1/2) of the drop depth. This paper compares predicted performance of drop-fill schemes at five sites in the Southeast U.S. (Thompsons, TX, Stuttgart, AR, Stoneville, MS, Clemson, SC, and Fairhope, AL). The locations were chosen to assess the effect of the east–west precipitation gradient and the south–north change from maritime to continental characteristics on the drop-fill approach in this region.

Performance of the drop-fill schemes was based on calculated daily water balances for ponds using 40-year (1961–2000) precipitation (P) and evaporation (E) records at the sites. Pond evaporation is assumed to be 0.8 × pan evaporation. Since performance differences based on regional P minus E (P−E) records was the subject of this work, ponds were assumed identical in other respects (i.e., all ponds were assumed to be levee-type and to have zero infiltration).

Simulated drop-fill schemes tested included (in cm): 0/0, 5/2.5, 10/5, 15/7.5, 20/10, 25/12.5, 30/15, 45/22.5, 60/30, 90/45, and 120/60. Each scheme was simulated using daily time steps for 40 years at each site. Results suggested that rigorous adherence to even a modest drop-fill scheme results in substantial reductions in both groundwater use and effluent release. It also appears that P−E conditions at all sites allow implementation of more aggressive drop-fill schemes in properly designed ponds that will require no supplemental groundwater for most years. This was also true with respect to effluent release at three of five sites. At two sites, precipitation was sufficiently large that zero effluent years were either not predicted (Fairhope) or relatively uncommon (Clemson) for any drop-fill scheme.