Biomedical subjects

B J Rodgers

Publications and source records attributed to B J Rodgers.

11 recordsLinked to original sources

PubMed2001

Z-plasty: a concise review.

One of the most commonly used techniques in facial plastic surgery is the Z-plasty. Main reasons to perform these transposition flaps are to lengthen a pre-existing scar, to camouflage a scar, or to realign a scar. The classic 60 degrees Z-plasty allows a 75% increase in scar length and is the cornerstone against which all variations are compared. Understanding the classic Z-plasty permits the surgeon to expand his or her repertoire to include the numerous variations thereof. The double-opposing Z-plasty, unequal triangle Z-plasty, four-flap Z-plasty, compound Z-plasty, and planimetric Z-plasty are the most frequent variants of the basic Z-plasty. Each are presented with illustrations and clinical indications.

Cicatrix↗

PubMed2001

W-plasty and geometric broken line closure.

The decision to revise a scar should be based on risk versus benefit. Scars over 2 cm in length or scars greater than 2 mm in width can usually be improved with scar revision. Although many techniques exist, scar irregularization has been used for scar camouflage for many years. Two techniques commonly employed for scar irregularization are W-plasty and geometric broken line closure. W-plasty provides a regularly irregular scar, and geometric broken line closure provides an irregularly irregular scar. Each method can offer excellent results when performed correctly and in the appropriate situations. The advantages, disadvantages, and design of each method are discussed.

Cicatrix↗

PubMed2000

Histological study of injected autologous fascia in the paralyzed canine vocal fold.

OBJECTIVE: Several methods have been used for the treatment of the unilateral paralyzed vocal fold. Teflon injections have been used extensively but not without complications. The ideal substance for injection is yet to be determined. Injected autologous fascia has been reported as a means of achieving glottic closure. In review of the literature, there are no long-term results described using autologous fascia in this way. The purpose of this study was to examine the histological changes of the larynx after injection of autologous fascia into a paralyzed vocal fold. STUDY DESIGN: A prospective study with the contralateral side of the larynx used as the control. METHODS: Six adult dogs underwent severing of one of their recurrent laryngeal nerves. After the vocal folds were confirmed to be paralyzed by direct laryngoscopy, fascia lata that was harvested from the animal was minced and injected into the paralyzed vocal fold. The dogs were then killed at intervals ranging from 3 to 12 months and their larynges reviewed histologically. RESULTS: The larynges revealed muscle atrophy of the vocal fold, which is consistent with denervation, but there was no evidence of persistent fascia. In addition, there was no evidence of reaction to the injected fascia. Special stains for collagen were also performed which showed no significant change from the non-injected vocal fold. CONCLUSION: From this model, it is concluded that injected autologous minced fascia is not a good short- or long-term substance for vocal fold augmentation. Further study is warranted to confirm this observation.

Animals↗

PubMed1993

The effects of age and low-intensity endurance exercise on the contractile properties of single skinned fast- and slow-twitch skeletal muscle fibres.

Aged (25 month old) rats were subjected to a low-intensity exercise programme, consisting of 10-weeks endurance swimming. At the conclusion of training (at the age of 27 months), fresh single skinned muscle fibres were prepared from the extensor digitorum longus (EDL) and soleus (SOL) muscles of the hindlimb and activated in Ca(2+)- and Sr(2+)- buffered solutions to measure selected isometric contractile characteristics. The major fibre population of the SOL from trained aged animals demonstrated a higher threshold [Ca2+] and [Sr2+] for contraction and a reduced sensitivity to Sr2+. Few changes in contractile characteristics were observed in the EDL muscle fibres from exercised rats, except for fibre type specific changes in the steepness of the force-pCa and force-pSr relationship. The effect of ageing on the contractile characteristics of skinned muscle fibres was also investigated by comparing the data obtained from aged sedentary rats with that from adult (6-9 month old) sedentary rats. Ageing was shown not to have affected the single fibre contractile properties of the SOL, but did affect one of the two fibre populations of the EDL. This was illustrated by the higher sensitivity to Ca2+ in the aged muscle fibres with a concomitant decrease in the cooperative interactions within the thin filament during tension activation.

Aging↗

PubMed1991

Expression of the chicken homeobox-containing gene GHox-8 during embryonic chick limb development.

Homeobox-containing genes are thought to be involved in the regulation of pattern formation and specification of positional information during vertebrate limb development. Because of its accessibility to microsurgical manipulation, the developing chick limb bud provides a powerful system for investigating the role of homeobox-containing genes in patterning events. We report the isolation from a chick limb bud cDNA library of a chicken homeobox-containing cDNA, which on the basis of its nucleotide and deduced amino acid sequences has been identified as the chicken cognate of mouse Hox-8. The gene encoding this chicken (Gallus) homeobox-containing cDNA has been designated GHox-8, and is a member of a family of vertebrate homeobox-containing genes that are highly similar in sequence to the Drosophila msh gene. GHox-8 encodes an mRNA transcript of about 3 kb that is expressed at several early stages of chick limb development. In situ and dot-blot hybridization analyses have revealed that GHox-8 is expressed in limb bud mesoderm in a temporal and spatial fashion consistent with its involvement in specifying anterior positional identity. At early stages (stages 20-21) of chick limb development when positional values along the anterior-posterior (A-P) axis are being specified, GHox-8 is expressed in high amounts in the anterior mesoderm of the wing bud. Little expression of the gene is detectable in the middle region of the wing bud mesoderm or in the posterior mesoderm that contains the zone of polarizing activity, which is thought to be the source of a diffusible morphogen, possibly retinoic acid, that specifies the A-P positional values of the skeletal elements of the limb according to its local concentration. Similarly, at later stages of development (stages 23-25), high expression of GHox-8 is localized to the proximal anterior periphery of the wing bud, with no detectable expression in the proximal dorsal and ventral (myogenic) regions, or in the chondrogenic central core. In the proximal posterior periphery of the wing bud at these later stages of development, expression of GHox-8 is limited to a small region in the mid-proximal periphery corresponding to the posterior necrotic zone in which programmed cell death is occurring. The possible involvement of GHox-8 in programmed cell death during limb development is also suggested by the fact that it is expressed in the necrotic interdigital mesenchyme in 6-7 day (stage 31-32) wing buds.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1989

Promotion of embryonic chick limb cartilage differentiation by transforming growth factor-beta.

This study represents a first step in investigating the possible involvement of transforming growth factor-beta (TGF-beta) in the regulation of embryonic chick limb cartilage differentiation. TGF-beta 1 and 2 (1-10 ng/ml) elicit a striking increase in the accumulation of Alcian blue, pH 1-positive cartilage matrix, and a corresponding twofold to threefold increase in the accumulation of 35S-sulfate- or 3H-glucosamine-labeled sulfated glycosaminoglycans (GAG) by high density micromass cultures prepared from the cells of whole stage 23/24 limb buds or the homogeneous population of chondrogenic precursor cells comprising the distal subridge mesenchyme of stage 25 wing buds. Moreover, TGF-beta causes a striking (threefold to sixfold) increase in the steady-state cytoplasmic levels of mRNAs for cartilage-characteristic type II collagen and the core protein of cartilage-specific proteoglycan. Only a brief (2 hr) exposure to TGF-beta at the initiation of culture is sufficient to stimulate chondrogenesis, indicating that the growth factor is acting at an early step in the process. Furthermore, TGF-beta promotes the formation of cartilage matrix and cartilage-specific gene expression in low density subconfluent spot cultures of limb mesenchymal cells, which are situations in which little, or no chondrogenic differentiation normally occurs. These results provide strong incentive for considering and further investigating the role of TGF-beta in the control of limb cartilage differentiation.

Animals↗

PubMed1989

Stimulation of limb cartilage differentiation by cyclic AMP is dependent on cell density.

Cyclic AMP (cAMP) has been implicated in the regulation of limb cartilage differentiation. This study represents an attempt to clarify potential mechanisms by which cAMP might regulate chondrogenesis. We have found that the ability of cAMP to stimulate limb cartilage differentiation in vitro is dependent on cell density. Dibutyryl cAMP (dbcAMP) elicits a striking increase in the accumulation of Alcian blue, pH 1.0-positive cartilage matrix, and a corresponding three- to fourfold increase in the accumulation of 35S-labeled glycosaminoglycans (GAG) by limb mesenchymal cells cultured in low serum medium at densities greater than confluence (i.e. micromass cultures established with 1-2 x 10(5) cells in 10 microliters of medium). Moreover, dbcAMP causes a striking (two- to fourfold) increase in the steady-state cytoplasmic levels of mRNAs for cartilage-characteristic type II collagen and the core protein of cartilage-specific sulfated proteoglycan in these high density, supraconfluent cultures. In contrast, cAMP does not promote the chondrogenesis of limb mesenchymal cells cultured at subconfluent densities (i.e. cultures initiated with 2.5-5 x 10(4) cells in 10 microliters of medium). In these low density cultures, dbcAMP does not promote the formation of cartilage matrix, sulfated GAG accumulation or the accumulation of cartilage-specific mRNAs. These observations suggest that cAMP may exert its regulatory effect in part by facilitating cell-cell communication during the critical condensation phase of chondrogenesis.

Animals↗

PubMed1988

In situ hybridization analysis of the expression of the type II collagen gene in the developing chicken limb bud.

In situ hybridization with [32P]- or [35S]-labeled double-stranded DNA or single-stranded RNA probes was used to investigate the temporal and spatial distribution of cartilage-characteristic type II collagen mRNA during embryonic chick limb development and cartilage differentiation in vivo. When the type II collagen probes were hybridized to sections through embryonic limb buds at the earliest stages of their development (stages 18-25), an accumulation of silver grains representing type II collagen mRNA first became detectable in the proximal central core of the limb coincident with the prechondrogenic condensation of mesenchymal cells that characterizes the onset of cartilage differentiation. At later stages of development (stage 32; 7 days) intense hybridization signals with the type II collagen probes were localized over the well differentiated cartilage rudiments, whereas few or no silver grains above background were observed over the non-chondrogenic tissues. In contrast, sections hybridized with a probe complementary to mRNA for the alpha 1 chain of type I collagen exhibited an intense hybridization signal over the perichondrium and little or no signal over the cartilage primordia. At all stages of development examined, [32P]-labeled double-stranded DNA probes or single-stranded RNA probes labeled with either [32P] or [35S] provided adequate hybridization signals. Several experimental protocols were employed to control for the potential cross-hybridization and non-specific hybridization of the type II collagen probes. These included the utilization of labeled noncomplementary "sense-strand" type II collagen RNA as a control probe for nonspecific background, and prehybridization with a large excess of appropriate unlabeled RNA to block sequences in heterologous collagen RNAs that might cross-hybridize to the specific labeled probe.

Animals↗

PubMed1987

Separation of the myogenic and chondrogenic progenitor cells of undifferentiated limb mesenchyme.

Undifferentiated limb bud mesenchyme consists of at least two separate, possibly predetermined, populations of progenitor cells, one derived from somitic mesoderm that gives rise exclusively to skeletal muscle and one derived from somatopleural mesoderm that gives rise to the cartilage and connective tissue of the limb. In the present study, we demonstrate that the inherent migratory capacity of myogenic precursor cells can be used to physically separate the myogenic and chondrogenic progenitor cells of the undifferentiated limb mesenchyme at the earliest stages of limb development. When the undifferentiated mesenchyme of stage 18/19 chick embryo wing buds or from the distal subridge region of stage 22 wing buds is placed intact upon the surface of fibronectin (FN)-coated petri dishes, a large population of cells emigrates out of the explants onto the FN substrates and differentiates into an extensive interlacing network of bipolar spindle-shaped myoblasts and multinucleated myotubes that stain with monoclonal antibody against muscle-specific fast myosin light chain. In contrast, the cells of the explants that remain in place and do not migrate away undergo extensive cartilage differentiation. Significantly, there is no emigration of myogenic cells out of explants of stage 25 distal subridge mesenchyme, which lacks myogenic progenitor cells. Myogenic precursor cells stream out of mesenchyme explants in one or occasionally two discrete locations, suggesting they are spatially segregated in discrete regions of tissue at the time of its explantation. There are subtle overall differences in the morphologies of the myogenic cells that form in stage 18/19 and stage 22 distal subridge mesenchyme explants. Finally, groups of nonmyogenic nonfibroblastic cells which are fusiform-shaped and oriented in distinct parallel arrays characteristically are found along the periphery of stage 18/19 wing mesenchyme explants. Our observations provide support for the concept that undifferentiated limb mesenchyme consists of independent subpopulations of committed precursor cells and provides a system for studying the early determinative and regulatory events involved in myogenesis or chondrogenesis.

Animals↗

PubMed1986

Cartilage proteoglycan core protein gene expression during limb cartilage differentiation.

Changes in the steady-state cytoplasmic levels of mRNA for the core protein of the major sulfated proteoglycan of cartilage were examined during the course of limb chondrogenesis in vitro using cloned cDNA probes. Cytoplasmic core protein mRNA begins to accumulate at the onset of overt chondrogenesis in micromass culture coincident with the crucial condensation phase of the process, in which prechondrogenic mesenchymal cells become closely juxtaposed prior to depositing a cartilage matrix. The initiation of core protein mRNA accumulation coincides with a dramatic increase in the accumulation of mRNA for type II collagen, the other major constituent of hyaline cartilage matrix. Following condensation, there is a concomitant progressive increase in cytoplasmic core protein and type II collagen mRNA accumulation which parallels the progressive accumulation of cartilage matrix by the cells. The relative rate of accumulation of cytoplasmic type II collagen mRNA is greater than twice that of core protein mRNA during chondrogenesis in micromass culture. Cyclic AMP, an agent implicated in the regulation of chondrogenesis elicits a concomitant two- to fourfold increase in both cartilage core protein and type II collagen mRNA levels by limb mesenchymal cells. Core protein gene expression is more sensitive to cAMP than type II collagen gene expression. These results suggest that the cartilage proteoglycan core protein and type II collagen genes are coordinately regulated during the course of limb cartilage differentiation, although there are quantitative differences in the extent of expression of the two genes.

Age Factors↗

PubMed1983

Fluctuations in DNA synthesis by mammary tissue from the pregnant hamster, rat and three strains of mice.

1. DNA synthesis was determined at midnight and noon in mammary tissue from 13-day pregnant mice (C3H, C57B110 and BALB/c) and 14-day pregnant golden hamsters and Sprague-Dawley rats. 2. Mammary tissue from the hamster and the three mouse strains had elevated DNA synthesis at midnight compared with noon. 3. In contrast, DNA synthesis in mammary tissue from the rat was not different at these two time periods.

Animals↗