Solid-Supported Oligonucleotide Systems for Special Biomedical Applications

Abstract

The use of composite beads consisting of a 6 μm polystyrene core with 30 nm surface-bound silica particles to routine automatic oligodeoxynucleotide (ODN) synthesis is described.     

Effects of partial bulbar section on inhibition of jaw-opening reflexes induced by central gray matter stimulation in the cat

The effects of severing the spinal trigeminal tract and its caudal nucleus on high-threshold jaw-opening reflex elicited by tooth pulp stimulation were investigated during experiments on cats under chloralose-Nembutal anesthesia. Low-threshold jaw-opening reflex produced by stimulating the A--infraorbital nerve at an intensity 2–3 thresholds in relation to the most excitable fibers on this nerve was also observed, as well as suppression of these reflexes induced by central gray matter stimulation. It was found that spinal trigeminal tract section produces a 8–52% increase in high-threshold reflex. The amplitude of low-threshold reflex either remained unchanged or showed a slight tendency to rise or fall. Brief stimulation of the central gray matter produced a 100% decrease in high-threshold reflex in intact animals compared with a 40–60% decrease after section of the trigeminal tract. Protracted stimulation of the central gray brought about an 80% decline in high-threshold reflex in intact animals as against 25–30% after section. The degree to which brief stimulation of the central gray produced depression of low-threshold stimulation remained unchanged by trigeminal tract section. Protracted stimulation of the central gray matter brought about a 25–50% reduction in low-threshold reflex in intact animals and a reduction of 75% in three animals and 15–20% in four animals. This implied that the caudal nucleus of the spinal trigeminal tract exerts a more substantial influence on the process of high- than low-threshold reflex inhibition when the central gray matter is stimulated.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 362–368, May–June, 1987.     

Effects of stimulating the superior colliculus on motoneurons of the neck muscle in the cat

Postsynaptic potentials produced by stimulating three sites of the midbrain superior colliculus were examined in motoneurons innervating the sternocleidomastoid, the trapezius, and the platysma cervical muscles in anesthetized cats. Stimulating the ipsilateral colliculus produced EPSP in the motoneurons as well as action potentials with a latency of 1.5–3.5 msec, averaging 2.6 ± 0.1 msec. Stimulation of the contralateral colliculus evoked EPSP with a latency of 1.5–3.2 msec and averaging 2.1 ± 0.1 msec together with IPSP with latency ranging from 2.6 to 5.0 msec. It is postulated that these postsynaptic responses are both monosynpatic and bisynaptic in nature. This type of synaptic action is assumed to be one of the mechanisms responsible for coordinated head movements produced by tectofugal impulses.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 2, pp. 197–202, March–April, 1986.     

Postsynaptic potentials of neck muscle motoneurons evoked by horizontal semicircular canal stimulation in cats

Postsynaptic potentials evoked by stimulation of ipsilateral and contralateral horizontal semicircular canals in motoneurons of muscles tilting and turning the head were investigated in acute experiments on cats anesthetized with chloralose and pentobarbital. Stimulation of the ipsilateral canal evoked EPSPs with latent periods varying from 1.8 to 10.0 msec in 25 of these motoneurons and IPSPs with latent periods varying from 1.9 to 3.9 msec in 10 of them. Calculation of the impulse conduction time from the ipsilateral semicircular canal through Deiters' nucleus to the cervical motoneurons indicates that EPSPs with latent periods of under 3.8 msec may be regarded as disynaptic, and those with latent periods of over 3.8 msec as polysynaptic. Stimulation of the contralateral canal evoked EPSPs with latent periods varying from 1.8 to 6.0 msec in 19 motoneurons and IPSPs with latent periods varying from 3.2 to 3.9 msec in two cells. The possible pathways of transmission of these influences and their functional role are discussed.     

Corticofugal influences on neurons of the main trigeminal sensory nucleus

The effects of stimulation of the ipsilateral sensomotor cortex were studied on 88 neurons in the region of the main trigeminal sensory nucleus of a cat. The cortex was stimulated via a coaxial electrode by single impulses. Stimulation of the cortex caused the appearance of EPSPs and action potentials in these neurons; a small number of these responses were monosynaptic. The polarity of the impulse applied to the cortex had a significant effect on the magnitude of the latent period of the response and the postsynaptic reaction, which is apparently caused by the stimulation of different types of cortex neurons. Apparently, corticofugal pulsation regulates the level of sensitivity of the trigeminal sensory neurons.A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 47–53, July–August, 1969.     

Inhibition of jaw opening reflexes by stimulation of the central gray matter and raphe nuclei in cats

The effect of stimulation of the mesencephalic central gray matter and raphe nuclei on jaw opening reflexes evoked by excitation of high-threshold (dental pulp) and low-threshold (A-alpha) fibers of the infraorbital nerve afferents was studied in cats anesthetized with chloralose and pentobarbital. The jaw opening reflex evoked by stimulation of the dental pulp was shown to be effectively suppressed by conditioning stimulation of the central gray matter and raphe nuclei. The reflex evoked by stimulation of low-threshold infraorbital nerve afferents also was depressed (but less deeply and for a shorter period than the reflex evoked by stimulation of the dental pulp) during stimulation of the raphe nuclei and caudal zone of the central gray matter, but was unchanged after stimulation of the points located in the rostral zone of the central gray matter. Application of single stimuli or bursts of five stimuli with a frequency of 100 Hz had no effect on the reflexes studied. Short-term stimulation with a burst of 10–20 stimuli with a following frequency of 200–400 Hz led to inhibition of the reflexes, which lasted 450–1000 msec. Long-term stimulation of the central gray matter and raphe nuclei for 30 sec with a frequency of 50 Hz caused inhibition of jaw opening reflexes evoked by stimulation of both high- and low-threshold afferents for 60 min. Impulses from the central gray matter and raphe nuclei thus have a mainly inhibitory action on the jaw opening reflex evoked by stimulation of high-threshold afferents, but they act less effectively on the reflex evoked by stimulation of low-thres-hold afferents. The duration of inhibition depends essentially on the parameters of stimulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 3, pp. 374–387, May–June, 1984.     

Monosynaptic excitation of motoneurons of the accessory nerve nucleus by reticulofugal impulses

Acute experiments on cats anesthetized with chloralose and pentobarbital showed that excitation of fast-conducting (130 m/sec) reticulospinal fibers, arising during stimulation of the ipsilateral medullary reticular gigantocellular nucleus evoked monosynaptic EPSPs in motoneurons of the accessory nerve nucleus. The EPSPs had latent periods of between 0.6 and 1.0 msec (mean 0.7 msec), they reached their maximal amplitude (4.0 mV) after 2.0–2.5 msec, and lasted about 10 msec. The EPSPs underwent only weak potentiation through the different types of stimulation of the gigantocellular nucleus and were not transformed into action potentials.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 62–66, January–February, 1980.     

EPSPs of masseter motoneurons evoked by stimulation of low-threshold infraorbital nerve afferents in cat

Stimulation of the infraorbital nerve at strengths 1.4–2.5 times higer than the threshold of excitation of A fibers in cats anesthetized with chloralose and pentobarbital evoked EPSPs with an amplitude up to 3.0 mV and a duration of 9–15 msec in 69% of masseter motoneurons after 1.5–3.0 msec. These EPSPs were complex and formed by summation of simpler short-latency and long-latency EPSPs. The short-latency EPSPs appeared in response to infraorbital nerve stimulation at 1.1–1.5 thresholds and had a slow rate of rise (2.5–4.5 msec, mean 3.7±0.4 msec), low amplitude (under 2.0 mV), and short duration (5–6 msec). Their latent period varied from 1.5 to 3.0 msec (mean 2.1±0.2 msec). The shortness of the latent period and its constancy during stimulation of the nerve at increasing strength, and also the character of development of facilitation and inhibition of the EPSP during high-frequency stimulation suggests that these EPSPs are monosynaptic. The slow rate of rise suggested that these EPSPs arise on distal dendrites of the motoneurons. Long-latency EPSPs appeared 7–9 msec after stimulation of the infraorbital nerve at 1.1–1.5 thresholds. Their amplitude reached 1.5–2.0 mV and their duration 7–9 msec. The long duration of the latent period combined with low ability to reproduce high-frequency stimulation (up to 30/sec) points to the polysynaptic origin of these EPSPs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 6, pp. 583–591, November–December, 1977.