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R G Mills

Publications and source records attributed to R G Mills.

51 records · Page 3Linked to original sources
PubMed1984

Cellular ions in intact and denervated muscles of the rat.

Tissue composition, membrane potentials and cellular activity of potassium, sodium and chloride have been measured in innervated and denervated rat skeletal muscles incubated in vitro. After denervation for 3 days, tissue water, sodium and chloride were increased but cellular potassium content and measured activity were little affected, despite a decrease of 16 mV in resting membrane potential which would have necessitated a decrease in cellular potassium activity of almost 50% were potassium distributed at electrochemical equilibrium. These findings, therefore, preclude a decreased electrochemical potential gradient for potassium as the cause of the membrane depolarization characteristic of denervated muscle fibers. Analysis of the data excludes an important contribution of rheogenic sodium transport to the resting potential of innervated muscles. These results strongly support the hypothesis that the decreased membrane potential in denervated fibers reflects a relative increase in the membrane permeability to sodium.

Animals↗
PubMed1983

Localization and characteristics of responses in cat medial preoptic region to stimulation of fornix.

Field potentials and units were recorded within the boundaries of the cat medial preoptic area (MPO) following stimulation of the fornix. The position of the recording electrode was marked by pressure injection of alcian blue dye. Stimulation of the medial and lateral aspects of the ipsilateral fornix produced a field consisting of four negative waves and a positive wave. The first and second negative waves had a short latency and duration and appeared to be produced by fornix axons in the MPO. The third negative wave had a longer duration and appeared to be generated by the monosynaptic activation of units in the MPO. The fourth negative wave had a long latency and very long duration and appeared to be generated by polysynaptic activation of neurons in the MPO. The positive wave was associated with inhibition of MPO neurons as a result of fornix excitation of inhibitory interneurons. Responses from nerve fibers in the MPO had latencies corresponding to peaks of the first and second peaks of the evoked potential. Monosynaptically evoked responses to ipsilateral fornix stimulation were recorded all over the dorsal two-thirds of the MPO. Units driven from the medial fornix lay in the periventricular nucleus. Units driven from the lateral fornix lay in the medial preoptic nucleus. Units driven from both medial and lateral fornix lay between units driven by the medial fornix medially and the lateral fornix laterally. Units driven polysynaptically from the ipsilateral fornix lay in the medial preoptic nucleus. About one-quarter of such units were also excited by stimulation of the contralateral fornix. Spontaneously discharging units were recorded all over the MPO. The geometric mean frequency was 2.1 +/- 1.7-2.8 Hz; n = 35. Fornix stimulation inhibited spontaneous units in the medial preoptic nucleus for 50-200 ms. Usually inhibition was evoked by lateral fornix stimulation or by medial or lateral fornix stimulation. Spontaneously discharging units in the periventricular nuclei were not inhibited by fornix stimulation. The position of fornix-excited units suggests they might be temperature sensitive and in female animals, play a role in controlling ovulation.

Animals↗
PubMed1979

A slow-release technique for inducing prolonged paralysis by tetrodotoxin.

A technique is described for the slow-release of tetrodotoxin in peripheral nerves using a constriction capillary. The capillary, which was implanted under the epineurium of the sciatic nerve, released tetrodotoxin from a 25 micrometer pore. Nerve block was complete after approximately 20 min and lasted 6--9 days. Replacement of the capillary enabled paralysis of the rat hindlimb to be maintained for periods of 21 days and longer. Studies with radioactively labelled compounds demonstrated that the efflux rate from the capillary was dependent on the size of the pore and the relative molecular mass of the compound.

Animals↗
PubMed1979

Responses in the diagonal band of Broca evoked by stimulation of the fornix in the cat.

1. Field potentials were recorded within the boundaries of the septal component of the diagonal band of Broca following stimulation of the fornix. The position of the recording electrode was marked by pressure injection of Alcian blue dye. 2. Stimulation of the medial aspect of the ipsilateral fornix produced a simple field caudally consisting of a short duration, short latency negative wave (N1) and a later small prolonged positive wave (P1). It is suggested that N1 is due to antidromic activation of the cells and P1 to their recurrent inhibition. 3. In the rostral part of the septal component of the diagonal band of Broca the field pattern was more complex, containing, in addition to N1 and P1, further negative waves, N2 and N3. N2 was compounded of antidromically and synaptically evoked components and N3 was associated with monosynaptic excitation of the cells. 4. Stimulation of the lateral margin of the fornix was shown to excite antidromically and synaptically the same cells as were excited by stimulation of the medial aspect of the fornix. 5. Stimulation of the medial and lateral aspects of contralateral fornix generated positive waves of similar character to P1. 6. Intracarotid injection of hyperosmotic saline solution caused behavioural signs of arousal and inhibition of spontaneous discharge in a third of the units tested. Spontaneously discharging units (mean frequency +/- S.E. of mean, 13.4 +/- 1.8, n = 55) were inhibited by stimulation of the medial and lateral ipsilateral and contralateral fornix. It is suggested that inhibitory interneurones receive contra- and ipsilateral input. Units with these characteristics were found. 7. The septal component of the diagonal band of Broca was compared with other septal nuclei and found to resemble them in its rostral portion in that it has a reciprocal relationship with ventral and dorsal hippocampus. The caudal portion is unique in the cells project to dorsal and ventral hippocampus but there is no reciprocal projection.

Animals↗
PubMed1979

The trophic influence of tetrodotoxin-inactive nerves on normal and reinnervated rat skeletal muscles.

1. Nerve impulses in the rat sciatic nerve were blocked for long periods by tetrodotoxin (TTX) released from capillary implants. The TTX capillaries did not block axonal transport, nor did they cause any sign of nerve degeneration. 2. A comparison of the effects of TTX paralysis and denervation was made on both extensor digitorium longus (e.d.l.) and soleus muscles over 21 days, a time when the products of nerve degeneration were unlikely to contribute to the changes associated with denervation. The resting membrane potential of TTX-paralysed muscles was significantly different (P less than 0.005) from that of the denervated muscles at all periods and at 21 days the decrease that can be attributed to inactivity was 61% (e.d.l.) and 49% (soleus) of that which follows denervation. This disparity was even more pronounced for the ACh receptor density where the increase in receptors due to inactivity was only 34% (e.d.l.) and 21% (soleus) of that due to denervation. 3. A similar comparison was made on muscles which had been reinnervated by TTX-inactive nerves. These muscles were found to have a significantly higher resting membrane potential and lower ACh receptor density than the denervated muscles (P less than 0.05). 4. The experiments on reinnervated muscles preclude the possibility that nerve degeneration products are solely responsible for the difference between the TTX-paralysed and denervated muscles and suggest that the difference can be attributed to the trophic influence of the nerve. 5. An observed increase in the m.e.p.p. frequency of the TTX-paralysed muscles indicated that nerve action potentials play a role in regulating the spontaneous release from nerve terminals.

Acetylcholine↗
PubMed1976

Sarcoidosis of the upper respiratory tract and its relation to lupus pernio.

The authors present a personally studied series of 32 patients with sarcoidosis affecting the upper respiratory tract and nose. Twenty-five of these patients had lupus pernio (LP), which in 8 instances was accompanied by sarcoidosis of the upper respiratory tract (SURT). The 7 other patients had SURT (mucosal disease) without LP. There was a female to male ratio of 7:1. SURT presented mainly in the third decade, whereas LP presented mainly in the fourth and fifth. Despite this, SURT was as much a chronic manifestation of sarcoidosis as LP. Five of 11 patients (45%) presenting with SURT progressed to LP within 2 yr. Overall 26 patients (81%) had intrathoracic sarcoidosis, 19 patients (59%) had skin lesions other than LP, 10 patients (31%) had bone sarcoidosis, 7 patients (22%) had ocular lesions, and 6 patients (19%) had peripheral lymphadenopathy. The Kveim-Siltzbach skin-test was positive in 12 of 12 patients with SURT, making it a useful aid in the differential diagnosis of sarcoid granulomas in the nose. Two patients had nasal perforations, both of which followed a submucous resection.

Adolescent↗
PubMed1976

Sarcoidosis of the upper respiratory tract and its association with lupus pernio.

In a series of 34 patients with sarcoidosis affecting the upper respiratory tract and nose, 26 had lupus pernio (LP) and 17 had sarcoidosis of the upper respiratory tract (SURT). In nine patients these features coexisted. A patient presenting with SURT carried a 50% risk of developing LP although one feature could be present without the other. Both were disorders of women of the child-bearing years of life. SURT, like LP, was an indicator of chronic fibrotic sarcoidosis, developing insidiously and progressing indolently over the years. It was complicated by ulceration, septal perforation, and LP. Three patients had nasal septal perforations, in two instances following submucous resection. This operation is contraindicated in patients with active sarcoidosis, particularly when granulomas are found on nasal biopsy. The Kveim-Siltzbach skin test was positive in all patients with SURT, making it invaluable in the differential diagnosis of granuloma of the nasal cavity.

Adolescent↗