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N Gill

Publications and source records attributed to N Gill.

29 records · Page 2Linked to original sources
PubMed1998

Effect of tenotomy on extensor digitorum longus muscle in Sprague Dawley rats.

The effect of tenotomy on Extensor Digitorum Longus (EDL) muscle, brought about by removal of anterior tibialis muscle was studied in the rat. Hypertrophy as well as hyperplasia of the muscle fibres were observed following tenotomy of intact muscle. The transplanted muscle regenerated after tenotomy in the form of a flat strap. The weight, length, breadth and total muscle area of intact muscle increased but decreased in transplanted muscle following tenotomy. The number of muscle fibres/microscopic field increased during the entire experiment in intact muscle after tenotomy, while in transplant the number of fibres first decreased and then increased. The diameter of intact and transplanted muscle increased after tenotomy. The number and diameter of nuclei was normalized at the end of experiment in both groups. The DNA and RNA content was increased in intact muscle after tenotomy. In transplant DNA and RNA content first increased but than decreased. The protein content was increased in intact muscle at the end of the experiment but decreased in transplant after tenotomy.

Animals↗
PubMed1997

Neural circuit mediating tentacle withdrawal in Helix aspersa, with specific reference to the competence of the motor neuron C3.

The tentacle withdrawal reflex in the terrestrial snail Helix aspersa involves bending and retraction of the tentacles. When elicited by mechanical stimulation of the tentacle, the reflex is mediated by the conjoint action of the central and peripheral nervous systems. The neural circuit underlying the stimulus-response pathways was studied in vitro using a combination of morphological and physiological techniques. Sensory input caused by stimulation of the nose (situated at the superior tentacle's tip) first passes into the tentacle ganglion. Motor fibers are likely excited in the tentacle ganglion to form a peripheral stimulus-response pathway. While still in the tentacle ganglion, the excitation caused by a brief stimulus is transformed into a prolonged neuronal discharge. This modified signal travels, via the olfactory nerve, to the cerebral ganglion where it excites the giant motor neuron C3 along with numerous smaller motor neurons. Afferent input to C3 also arrives from several other sources. The afferent convergence is followed by a marked divergence of C3's output. C3 innervates the muscles mediating both tentacle retraction and tentacle bending through multiple cerebral nerves. Thus C3's pattern of effector innervation allows this single cell to elicit and coordinate both components of the tentacle withdrawal reflex. Lesion experiments indicate that C3 is responsible for 85% of the central contribution to tentacle retraction, though C3 is actually sufficient to mediate maximal muscle contraction as evidenced by intracellular stimulation. In addition to C3, three groups of putative central motor neurons were identified through nerve backfills and nerve recordings. The additional motor neurons mediating tentacle retraction are important for maximizing the rate of muscle contraction, whereas those mediating tentacle bending are likely more important for nondefensive behaviors. These neurons are arranged in parallel with C3, but unlike C3, each of these neurons innervates only a single effector or portion thereof. Given C3's direct innervation of multiple effectors and its sufficiency to evoke strong responses in those effectors, we conclude that C3 is paramount in eliciting and coordinating tentacle withdrawal.

Animals↗
PubMed1995

Potent 2'-amino-2'-deoxypyrimidine RNA inhibitors of basic fibroblast growth factor.

Screening of random oligonucleotide libraries with SELEX [systematic evolution of ligands by exponential enrichment; Tuerk, C., & Gold, L. (1990) Science 249, 505-510] has emerged as a powerful method for identifying high-affinity nucleic acid ligands for a wide range of molecular targets. Nuclease sensitivity of unmodified RNA and DNA, however, imposes considerable restrictions on their use as therapeutics or diagnostics. Modified RNA in which pyrimidine 2'-hydroxy groups have been substituted with 2'-amino groups (2'-aminopyrimidine RNA) is known to be substantially more resistant to serum nucleases. We report here on the use of SELEX to identify high-affinity 2'-aminopyrimidine RNA ligands to a potent angiogenic factor, basic fibroblast growth factor (bFGF). High-affinity ligands with the same consensus primary structure have been isolated from two independent libraries of approximately 6 x 10(14) molecules containing 30 or 50 randomized positions. Compared to unmodified RNA with the same sequence, 2'-aminopyrimidine ligands are at least 1000-fold more stable in 90% human serum. The sequence information required for high-affinity binding to bFGF is contained within 24-26 nucleotides. The minimal ligand m21A (5'-GGUGUGUGGAAGACAGCGGGUGGUUC-3'; G = guanosine, A = adenosine, C = 2'-amino-2'-deoxycytidine, U = 2'-amino-2'-deoxyuridine, and C = 2'-amino-2'-deoxycytidine or deoxycytidine) binds to bFGF with an apparent dissociation constant (Kd) of 3.5 +/- 0.3) x 10(-10) M at 37 degrees C in phosphate-buffered saline (pH 7.4). Disassociation of m21A from bFGF is adequately described with a first-order rate constant of (1.96 +/- 0.08) x 10(-3) s-1 (t1/2 = 5.9 min). The calculated value for the association rate constant (kon = k(off)/Kd) was 5.6 x 10(6) M-1 s-1. Highly specific binding of m21A to bFGF was observed: binding to denatured bFGF, five proteins from the FGF family (acidic FGF, FGF-4, FGF-5, FGF-6, and FGF-7), and four other heparin binding proteins is substantially weaker under the same conditions with KdbFGF/Kdprotein values ranging from (4.1 +/- 1.4) x 10(-2) to > 10(-6). Heparin but not chondroitin sulfate competed for binding of m21A to bFGF. In cell culture, m21A inhibited [125I]bFGF binding to both low-affinity sites (ED50 approximately 1 nM) and high-affinity sites (ED50 approximately 3 nM) on CHO cells expressing transfected FGF receptor-1.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Is risk of Kaposi's sarcoma in AIDS patients in Britain increased if sexual partners came from United States or Africa?

OBJECTIVE: To determine whether the risk of Kaposi's sarcoma in patients with AIDS is increased by sexual contact with groups from abroad with a high incidence of Kaposi's sarcoma. DESIGN: Analysis of risk of Kaposi's sarcoma in patients with AIDS, according to country of origin of their sexual partners. SETTING: United Kingdom. PATIENTS: 2830 patients with AIDS reported to the Communicable Disease Surveillance Centre and the Communicable Disease (Scotland) Unit up to March 1990, of whom 566 had Kaposi's sarcoma. MAIN OUTCOME MEASURES: Percentage of patients with AIDS who had Kaposi's sarcoma. RESULTS: 537 of 2291 homosexual or bisexual men (23%) with AIDS had Kaposi's sarcoma; 10% (14/135) of the men and women who acquired HIV by heterosexual contact had Kaposi's sarcoma. None of the 316 subjects who acquired HIV through non-sexual routes had Kaposi's sarcoma. Kaposi's sarcoma was more common among homosexual men whose likely source of infection included the United States (171/551, 31%) or Africa (9/34, 26%) than among those infected in the United Kingdom (119/625, 19%) (p less than 0.05). CONCLUSION: The data suggest that Kaposi's sarcoma is caused by a sexually transmissible agent which was introduced into the British homosexual population mainly from the United States [corrected].

Acquired Immunodeficiency Syndrome↗