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J M Vaughan

Publications and source records attributed to J M Vaughan.

11 recordsLinked to original sources
PubMed1992

Isolation and characterization of hypothalamic growth-hormone releasing factor from common carp, Cyprinus carpio.

A growth hormone-releasing factor (GRF)-like peptide was isolated from the hypothalamus of common carp, Cyprinus carpio, by acid extraction, gel filtration chromatography, immunoaffinity chromatography using antiserum directed against rat GRF, and multiple steps of HPLC using octadecyl columns. Based on Edman degradation and peptide mapping, this teleost GRF was established to be a 45-residue peptide with the following primary structure: His-Ala-Asp-Gly-Met-Phe-Asn-Lys-Ala-Tyr-Arg-Lys-Ala-Leu-Gly-Gln-Leu-Ser- Ala-Arg - Lys-Tyr-Leu-His-Thr-Leu-Met-Ala-Lys-Arg-Val-Gly-Gly-Gly-Ser-Met-Ile-Glu- Asp-Asp-Asn-Glu-Pro-Leu-Ser. Carp GRF is closely related structurally to peptides of the glucagon-secretin superfamily, and more particularly to mammalian vasoactive intestinal peptide (VIP) precursors and the N-terminal portion of mammalian GRFs. A synthetic replicate of this peptide is highly potent [50% effective dose (ED50) approximately 0.08 nM] in stimulating GH release from cultured goldfish pituitary glands and in elevating serum GH levels 30 min after injection (0.1 micrograms/g) in goldfish.

Amino Acid Sequence↗
PubMed1989

Observation of Brillouin scattering from single muscle fibres.

The propagation of sound waves along relaxed single fibres of glycerinated rabbit psoas muscle has been observed using Brillouin scattering at frequencies up to 1.6 GHz. Two types of waves were observed: one with a velocity of 1508 +/- 7 m s-1, which is attributed to sound waves in intra-cellular saline, the other with a velocity of 912 +/- 25 m s-1, which is attributed to waves propagating along the protein filaments within individual sarcomeres. The latter sound velocity is much higher than that which has been reported by Stienen and Blangé (1985) for 50 microseconds tension transients, and the difference is attributed to the much higher stiffness of the protein filaments compared to the cross-bridges which determine the low-frequency elasticity of muscle fibres.

Acoustics↗
PubMed1989

Characterization of melanin-concentrating hormone from rat hypothalamus.

A melanin-concentrating hormone (MCH)-like peptide was isolated from rat hypothalamus by acid extraction, gel filtration chromatography, immunoaffinity chromatography using antiserum directed against salmon MCH, and two steps of HPLC using octadecyl columns. Several zones of immunoreactivity were isolated, and Edman degradation in a gas phase sequencer indicated that the amino acid sequence of all zones was identical. Rat hypothalamic MCH is a nonadecapeptide which differs from salmon MCH by an N-terminal extension of two amino acids and four additional substitutions. Rat MCH has the following primary structure: Asp-Phe-Asp-Met-Leu-Arg-Cys-Met-Leu-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Gln- Val.

Amino Acid Sequence↗
PubMed1984

Extrahypothalamic growth-hormone-releasing factor (GRF) secretion is a rare cause of acromegaly: plasma GRF levels in 177 acromegalic patients.

To assess the frequency with which acromegaly is caused by ectopic secretion of GRF, we collected plasma samples from 177 unselected acromegalic patients. The samples together with those of three acromegalic patients with previously diagnosed tumors secreting GRF and of normal subjects were assayed in 3 independent GRF RIAs. Plasma immunoreactive GRF (IR-GRF) levels in normal subjects were either undetectable or detectable at levels up to 62.5 pg/ml. In none of the 177 specimens from acromegalic patients were IR-GRF values detectable in all assays, and in the most sensitive assay, the levels were similar to those in normal subjects, with the highest level measuring 82 pg/ml. In contrast, plasma IR-GRF found in the 3 patients with tumors that secreted GRF ranged from 2.0-24.4 ng/ml. These data suggest that extrahypothalamic GRF secretion is a rare cause of acromegaly. However, it is important that this rare cause of acromegaly be diagnosed before the patient has unnecessary surgery and/or irradiation directed at the pituitary. We recommend that plasma IR-GRF be measured in each new acromegalic patient.

Acromegaly↗
PubMed1983

Assessment of late patency of profundaplasty by arteriography.

We have reviewed 34 cases of profundaplasty to determine patency rates in arteriographic rather than clinical terms. These patients had required subsequent arteriography for a variety of reasons not always related to their original operation. Clinical improvement following profundaplasty could be due to maturation of the collateral circulation rather than to prolonged patency of the reconstructed segment, but in this series all the profundaplasties were patent except where the external iliac and common femoral arteries supplying the profundaplasty had themselves occluded. These patients with profundaplasty failure showed an adverse pattern of proximal disease. The state of the distal vascular bed did not appear to influence the patency rate of the profundaplasties significantly, although this may affect the outcome for the limb itself.

Adult↗
PubMed1982

Versatile stem cells in bone marrow.

The question of whether there is a single pluripotent haemopoietic stem cell or a variety of stem cells each with a capacity for self-replication is still unresolved. Evidence from radiation-chimaeras and from patients with marrow grafts indicates that haemopoietic stem cells are not a homogeneous population. It is suggested that in marrow there is a variety of stem cells, some controlled by recognised factors and others by as yet unknown factors. It is postulated that some of these cells are pluripotent, whereas others are differentiated for a single line, so both polyphyleticists and monophyleticists may have been partly right.

Animals↗
PubMed1982

The measurement and interpretation of Brillouin scattering in the lens of the eye.

Brillouin scattering from hypersonic waves in the eye lenses of many animals has been observed with a multipass Fabry Perot interferometer. The measured values of speed and attenuation range widely among the different species and in different parts of any one lens. These variations correlate broadly with the observed stiffness and the densities that have been measured with a graded column. From the spectroscopic and density measurements high-frequency elastic moduli may be derived. The results are also evaluated at a macromolecular level in terms of scattering of hypersonic waves from spherical entities composed of the crystallins and their aggregates. Reasonable agreement is obtained for the hypersonic speed for lower protein concentration; the hypersonic attenuation and variation with scattering vector are consistent with the presence of large aggregates (of order 100 nm radius) in certain of the materials.

Animals↗
PubMed1980

Brillouin scattering, density and elastic properties of the lens and cornea of the eye.

Brillouin spectra of biological systems may ultimately be related to their intrinsic molecular properties. In some instances the optical properties may be associated with the elastic ones and ultimately with the force constants of the molecules involved. In the present work we have used a triple-pass Fabry-Perot interferometer to measure Brillouin light scattering spectra for refractive tissues of the eye, including cornea, capsule and lens. Combined with corresponding measurements of density, estimates of the real and imaginary parts M' and M'' of the longitudinal bulk modulus have been made for the first time. Measurements have extended over four classes of vertebrate: Mammalia, Aves, Pisces and Amphibia; only small differences have been found between the various samples of cornea, whereas marked differences occur between the different lenses. Hence this account concentrates largely on the latter. The implications of this work lie not so much at the ophthalmological level as at the macromolecular and offer, in conjunction with other scattering techniques, opportunities for probing the lens and its proteins topographically as a function of growth.

Acoustic Stimulation↗