Electrical Current Levels Research Articles

Transdermal Delivery of Human Insulin to Albino Rabbits Using Electrical Current

The transdermal route of administration for medication has many potential advantages over other routes of administration. However, the stratum corneum is an effective barrier to the absorption of most chemicals from the external environment into the body. To evaluate techniques for alteration of transdermal permeability, the authors studied the effect of low levels of electrical current on transport of a protein across the stratum corneum. Transcutaneous insulin absorption was used as an indicator of altered permeability. Twenty-six albino rabbits had acute diabetes mellitus induced by the intravenous administration of 125 mg/kg of alloxan. The animals then received either cutaneous patches containing insulin and an electrical current of 0.4 mA (active) or patches containing an equal amount of insulin but without electrical current (passive). At 10 and 12 hours after the placement of the patches, animals with active patches had significant elevations in serum insulin levels (p less than .05) and reduction in blood glucose levels (p less than .01). No changes were seen in controls. Animals with active patches also had significant differences from control animals in mean insulin response and peak insulin response (p less than .05). No cutaneous toxicity was observed in any of the animals. The authors conclude that low levels of electrical current can induce changes in stratum corneum permeability that are sufficient to produce the transdermal absorption of physiologic doses of a protein such as human insulin.

Acoustic parameters measured by a formant-estimating speech processor for a multiple-channel cochlear implant.

In order to assess the limitations imposed on a cochlear implant system by a wearable speech processor, the parameters extracted from a set of 11 vowels and 24 consonants were examined. An estimate of the fundamental frequency EF 0 was derived from the zero crossings of the low-pass filtered envelope of the waveform. Estimates of the first and second formant frequencies EF 1 and EF 2 were derived from the zero crossings of the waveform, which was filtered in the ranges 300-1000 and 800-4000 Hz. Estimates of the formant amplitudes EA 1 and EA 2 were derived by peak detectors operating on the outputs of the same filters. For vowels, these parameters corresponded well to the first and second formants and gave sufficient information to identify each vowel. For consonants, the relative levels and onset times of EA 1 and EA 2 and the EF 0 values gave cues to voicing. The variation in time of EA 1, EA 2, EF 1, and EF 2 gave cues to the manner of articulation. Cues to the place of articulation were given by EF 1 and EF 2. When pink noise was added, the parameters were gradually degraded as the signal-to-noise ratio decreased. Consonants were affected more than vowels, and EF 2 was affected more than EF 1. Results for three good patients using a speech processor that coded EF 0 as an electric pulse rate, EF 1 and EF 2 as electrode positions, and EA 1 and EA 2 as electric current levels confirmed that the parameters were useful for recognition of vowels and consonants. Average scores were 76% for recognition of 11 vowels and 71% for 12 consonants in the hearing-alone condition. The error rates were 4% for voicing, 12% for manner, and 25% for place.

Pseudo-Boolean Logic Circuits

A new class of switch-level logic circuits intended for modeling digital MOS VLSI circuits is presented. These circuits, which are called pseudo-Boolean, are composed of a single (voltage) source, connectors, switches, attenuators, and wells. The latter two devices are digital versions of resistors and capacitors, respectively, and may assume an arbitrary but finite number of different sizes. Signals are bidirectional, and are assigned a finite set of values of the form (v, s) where v corresponds to voltage level and s corresponds to electrical current or charge level (logical strength). It is shown that these signal values and the associated logical operations form a generalization of Boolean algebra called pseudo-Boolean or Heyting algebra. The analysis of pseudo- Boolean circuits using discrete counterparts of Kirchoff's current law and the superposition principle is discussed, as well as the application of pseudo-Boolean techniques to digital simulation.

Restoration of Upper Extremity Function

Functional neuromuscular stimulation has been shown to be a viable means of Providing controlled movements in paralyzed limbs. Low levels of electrical current are effective in eliciting impulses in nerves, which then propagate to and result in a contraction of the muscle. The FNS technique encompasses many aspects of the physical and biological sciences. When properly performed, electrical stimulation can be applied effectively for extended periods of time with no significant detrimental effects to the tissue. The muscle contractions that result can be graded in strength and will fatigue minimally with time. Several clinical applications of FNS to paralyzed patients have been investigated. The technique has demonstrated its viability in applications to both the upper and the lower limbs in patients sustaining a variety of neurological diseases, including stroke, cerebral palsy, and spinal cord injury. This technique promises to be an important adjunct to clinical care in the future.

Stimulation-produced analgesia: Evidence for somatotopic organization in the midbrain

The somatotopic organization of structures in the midbrain which mediate stimulation-produced analgesia (SPA) was studied by stimulating a series of neural loci using a movable electrode. The strength and distribution of analgesia at 7 fields on the body surface, as measured by the application of noxious pinch, was clearly related to the dorsoventral stimulation locus. SPA at dorsal sites was distributed at the ears and, to a lesser extent, at the forepaws. At progressively more ventral loci, maximal analgesia appeared successively at the forepaws, hindpaws and tail. This organization was organization was maintained throughout the rostrocaudal extent of the midbrain. However, rostral stimulation sites tended to produce analgesia in smaller, more discrete fields than those produced by caudal stimulation sites. Further studies showed that the relationship between SPA and stimulation site is influenced by the electrical stimulation current level. Each site had an optimum current level, so that current intensities higher or lower than the optimum produced decreased analgesia. These results reveal a possible neural mechanism for somatotopic organization in hyperstimulation analgesia in which an intense somatic input at a body site produces analgesia in the same or adjacent segments.

Signal detection theory pain measures: Empirical validation studies and adaptation-level effects

Proponents of the use of signal detection theory (SDT) in the assessment of pain modulation have generally looked for changes in d′ to indicate a reduction of sensory function, and a change in criterion to indicate a modification of the subject's response bias or attitudinal predisposition. In the first experiment, both assumptions failed to receive empirical verification. Discrimination d′ was equivalent before and after two strong levels of electrical current were reduced. The criterion parameter appeared to shift in a more conservative direction after the stimulus diminution. These results are used to question the validity of both detection and discrimination indices in the measurement of pain. An alternative means for describing the experimental results revealed a striking adaptation-level effect with implications for the assessment of both experimentally induced and endogenous pain. The outcome of a second experiment reinforced the adaptation-level theory interpretation of the results and provided additional evidence concerning the difficulties in evaluating SDT parameters in studies of potential analgesics.

The effects of minute direct electrical currents on cultured chick embryo trigeminal ganglia

The effects of low levels of electric current were determined on organ cultures of 6- to 19-day-old chick embryo trigeminal ganglia. Current levels ranged from 0.00115 to 11.5 nA/mm2; the time of electrical treatment varied from 2 h to 96 h. Low levels of electricity were found to have at least three major effects on this system of mixed cellular types: (1) Outgrowth of nerve fibers from the explant was enriched. This resulted in a greater number of fibers which were longer and more highly branched than those in control cultures. (2) Survival of neurons within the original explanted ganglion was enchanced by treatment with electricity. The presence of healthy neurons was found in 93.1% of the treated cultures and in 53.5% of untreated cultures. (3) Neurons, fibers and non-neural cells were stimulated to grow in the direction of the cathode. The rate of cathodal migration was calculated to be 0.1 mm/h (2.4 mm/day) in an explant from 12-day-old embryo. No differences were observed between surviving treated and control cultures in histochemical tests for acetycholinesterase. A similarity between the action of low levels of electrical current and nerve growth factor (NGF) is suggested.

Potentiation of animal “hypnosis” with low levels of electric current

Hypnotic trance durations of rabbits were prolonged by whole head stimulation with low levels of electric current (0·2 mA.). Effective frequencies were 4, 8, and 100 cycles/second. Localized stimulation with still lower current levels (30 μA.) was also effective in prolonging hypnosis duration when the anteroventral thalamus and the pontine reticular formation were stimulated. Caudate stimulation enhanced trance duration at the 90 per cent. level of confidence. Stimulation of two other brain areas, the amygdala and the hippocampus, was not generally effective in potentiating hypnosis. The relevance of this research is discussed with respect to previous reports of electrosleep studies.