PubMed Health⌕ Search

Biomedical subjects

S M Hughes

Publications and source records attributed to S M Hughes.

17 recordsLinked to original sources
PubMed1992

Muscle fiber pattern is independent of cell lineage in postnatal rodent development.

Muscle fibers specialized for fast or slow contraction are arrayed in characteristic patterns within developing limbs. Clones of myoblasts analyzed in vitro express fast and slow myosin isoforms typical of the muscle from which they derive. As a result, it has been suggested that distinct myoblast lineages generate and maintain muscle fiber pattern. We tested this hypothesis in vivo by using a retrovirus to label myoblasts genetically so that the fate of individual clones could be monitored. Both myoblast clones labeled in muscle in situ and clones labeled in tissue culture and then injected into various muscles contribute progeny to all fiber types encountered. Thus, extrinsic signals override the intrinsic commitment of myoblast nuclei to particular programs of gene expression. We conclude that in postnatal development, pattern is not dictated by myoblast lineage.

Animals↗
PubMed1992

Clinical and endocrinological changes in women following ovulation induction using buserelin acetate/human menopausal gonadotrophin augmented with biosynthetic human growth hormone.

Biosynthetic human growth hormone added to an ovarian stimulation regime of human menopausal gonadotrophin (HMG) for IVF treatment improves the response of women who were previously resistant. This study investigated the efficacy of growth hormone (GH)/buserelin/HMG treatment in women with a previous normal response to buserelin/HMG stimulation. Ten patients (28-36 years, mean 32.5 years) were treated with GH (6 IU/day) plus buserelin/HMG. A control group of 10 women (28-37 years mean 31.0 years) received buserelin/HMG alone. All were given buserelin 500 micrograms and 2 ampoules (150 IU) HMG daily once pituitary suppression had been confirmed. There was no improvement in the GH group as assessed by follicular growth rate or number, oocyte number per woman and pregnancy rate. There was no effect of GH upon the serum oestradiol level and the follicular fluid levels of oestradiol, GH and inhibin. Serum IGF-1 increased significantly during GH administration, returning to pre-treatment levels 2 days after the last dose of GH. Follicular IGF-1 was much higher in the GH-treated group than the controls. Significant correlations were found in the GH-treated group between follicular fluid GH and follicular fluid oestradiol concentrations and between follicular GH and follicular size. Follicular IGF-1 was correlated with the serum IGF-1 concentration on day 8 of the GH/HMG treatment. In conclusion GH/buserelin/HMG treatment in women with a previous normal response to buserelin/HMG stimulation increased their serum and follicular IGF-1 concentrations. However, it does not improve the clinical ovarian response or the follicular secretion of oestradiol or inhibin.

Adult↗
PubMed1991

MAP1B is encoded as a polyprotein that is processed to form a complex N-terminal microtubule-binding domain.

Microtubule-associated protein 1B (MAP1B), an abundant developmentally regulated neuronal protein, is a stoichiometric complex of a heavy chain and two light chains (light chain 1 and light chain 3). We find that light chain 1 is encoded within the 3' end of a previously reported MAP1B heavy chain cDNA. Amino acid sequencing, epitope mapping, Northern blotting, and Southern blotting indicate that the light chain and heavy chain are encoded by the same mRNA within the same open reading frame. In addition, amino acid sequencing of a 120 kd microtubule-binding and light chain-binding fragment of the heavy chain reveals that light chain 1 binds near the heavy chain N-terminus. Together these data indicate that the heavy chain and light chain 1 are produced by proteolytic processing of a MAP1B polyprotein and form a complex microtubule-binding domain.

Amino Acid Sequence↗
PubMed1991

Modulation of MHC class II antigen expression in human myoblasts after treatment with IFN-gamma.

Some investigators have proposed myoblast transfer as a potential therapy for the treatment of Duchenne muscular dystrophy. Little is known about the immunobiology of myoblast transplantation. Transplantation rejection is mediated to a large extent by CD8+ T cells, which recognize alloantigens encoded by class I HLA genes, and by CD4+ T cells, which recognize alloantigens encoded by class II HLA genes. Gamma interferon (IFN-gamma) is a potent inducer of HLA class II molecules as well as beta 2-microglobulin, which is co-expressed with HLA class I. IFN-gamma may be a critical cytokine involved in graft rejection. We purified human myoblasts by flow cytometry and incubated them in vitro for varying time periods with recombinant human IFN-gamma. The inducibility of HLA-DR and -DP molecules raises a note of caution concerning possible rejection phenomenon which might occur following myoblast transplantation.

Cells, Cultured↗
PubMed1990

Migration of myoblasts across basal lamina during skeletal muscle development.

Basal lamina is a sheet of extracellular matrix that separates cells into topologically distinct groups during morphogenesis and is thought to form a barrier to cell migration. We have examined whether, during normal muscle development, myoblasts--mononucleate muscle precursor cells--can cross the basal lamina that surrounds each multinucleate muscle fibre. We marked myoblasts in vivo by injecting replication-defective retroviral vectors encoding LacZ into muscle tissue and analysed the fate of their progeny by the expression of beta-galactosidase. A dual labelling method with broad application to retroviral lineage-marking studies was developed to ensure that most clusters of labelled cells were clones derived from a single precursor cell. Most of the myoblasts that were infected at a late stage of rat hindlimb development, when each fibre with its satellite myoblasts is individually encased in a basal lamina sheath, gave rise to clones that contributed to several labelled fibres. Our results show that myoblasts from healthy fibres migrate across basal lamina during normal development and could contribute to the repair of fibres damaged by injury or disease.

Animals↗
PubMed1988

Ciliary neurotrophic factor induces type-2 astrocyte differentiation in culture.

We have been studying a population of bipotential glial progenitor cells in the perinatal rat optic nerve and brain in an attempt to understand how cells choose between alternative fates in the developing mammalian central nervous system (CNS). This cell population gives rise initially to oligodendrocytes and then to type-2 astrocytes, both of which apparently collaborate in sheathing axons in the CNS. In vitro studies suggest that oligodendrocyte differentiation is the constitutive pathway of development for the oligodendrocyte-type-2-astrocyte (O-2A) progenitor cell, whereas type-2 astrocyte differentiation depends on a specific inducing protein. This protein is present in the developing optic nerve when type-2 astrocytes are differentiating and can induce O-2A progenitor cells in vitro to express glial fibrillary acidic protein (GFAP), a marker of astrocyte differentiation. Here we show that the type-2-astrocyte-inducing protein is similar or identical to ciliary neutrotrophic factor (CNTF), which promotes the survival of some types of peripheral neurons in vitro, including ciliary ganglion neurons. This suggests that CNTF, in addition to its effect on neurons, may be responsible for triggering type-2 astrocyte differentiation in the developing CNS.

Animals↗
PubMed1988

Type-2 astrocyte development in rat brain cultures is initiated by a CNTF-like protein produced by type-1 astrocytes.

O-2A progenitor cells are bipotential glial precursors that give rise to both oligodendrocytes and type-2 astrocytes on a precise schedule in the rat CNS. Studies in culture suggest that oligodendrocyte differentiation occurs constitutively, while type-2 astrocyte differentiation requires an exogenous inducer such as fetal calf serum. Here we describe a rat brain cell culture system in which type-2 astrocytes develop on schedule in the absence of exogenous inducers. Coincident with type-2-astrocyte development, the cultures produce an approximately 20 kd type-2-astrocyte-inducing factor(s). Purified cultures of type-1 astrocytes can produce a similar factor(s). Under conditions where they produce type-2-astrocyte-inducing factor(s), both brain and type-1 astrocyte cultures produce a factor(s) with ciliary neurotrophic (CNTF)-like activity. Purified CNTF, like the inducers from brain and type-1 astrocyte cultures, prematurely induces type-2 astrocyte differentiation in brain cultures. These findings suggest that type-2 astrocyte development is initiated by a CNTF-like protein produced by type-1 astrocytes.

Aging↗
PubMed1987

Sequelae of orbital fractures.

Many injuries and complications of orbital fractures are instantaneous and unpreventable, some develop over time, and some are a result of surgery. Most complications can either be managed or prevented and are anticipated based on the fracture location and size. A thorough search for probable complications is mandatory, especially ocular injuries and intracranial complications. Most patients are carefully followed for 7-14 days, and the significant residual sequelae are managed. Some complications, however, require urgent care.

Eye Diseases↗
PubMed1987

An inducer protein may control the timing of fate switching in a bipotential glial progenitor cell in rat optic nerve.

In rat optic nerve, oligodendrocytes and type-2 astrocytes develop from a common (O-2A) progenitor cell. The first oligodendrocytes differentiate at birth, while the first type-2 astrocytes differentiate in the second postnatal week. We previously showed that the timing of oligodendrocyte differentiation depends on an intrinsic clock in the O-2A progenitor cell. Here we provide evidence that the timing of type-2 astrocyte differentiation, by contrast, may depend on an inducing protein that appears late in the developing nerve. We show that extracts of 3- to 4-week-old, but not 1-week-old, rat optic nerve contain a protein (apparent Mr approximately 25,000) that induces O-2A progenitor cells in culture to express glial fibrillary acidic protein (GFAP), an astrocyte-specific marker in the rat central nervous system.

Age Factors↗
PubMed1985

Lacrimal surgery in children.

Of 142 children who underwent major lacrimal surgery (160 dacryocystorhinostomies, one congenital fistula excision, one dacryocystectomy, and one canaliculostomy), 49 had congenital nasolacrimal duct obstruction (34%). Lacrimal obstruction was also associated with canaliculitis, punctal agenesis, trauma, congenital fistula, dacryocystitis, craniofacial defects, and functional eyelid abnormalities. Although the timing and technique of the surgery varied according to the abnormalities, an overall functional success rate of 90% (144 of 160 procedures) was achieved.

Adolescent↗
PubMed1979

Growth of the skull in the mutant dwarf mouse.

By following the development of individual mice from birth to 200 days of age, it was found that the skull of the homozygous mutant (dwdw) was 5% shorter than that of the normal phenotype at birth and some 30% shorter at 200 days of age. During post-natal growth of the skull, the cranium was least altered but the facial skeleton was greatly affected. The differences seen in different parts of the skull are attributed to the peak growth velocities of the various parts occurring at different times.

Animals↗