Biomedical subjects

M Dyson

Publications and source records attributed to M Dyson.

At least 37 records · Page 2Linked to original sources

PubMed1997

Regulation of follistatin production by rat granulosa cells in vitro.

The aims of this study were to apply enzyme-linked immunosorbent assays (ELISA) for human follistatins (FS) to measure total immunoreactive (ir-) rat FS and free rat FS, and investigate the regulation of production of total ir-FS and free FS by rat granulosa cells (GC) in vitro. Production of ir-inhibin was monitored as an index of GC function. The ELISAs for total ir-FS, based on an immunoradiometric assay developed recently for human FS, and free FS, based on capture of FS by a monoclonal antibody and detection by activin A binding, had sensitivities of 0.4 and 0.8 ng recombinant human (rh-) FS 288/ml, respectively, and did not cross-react with inhibin A, rLH, or FSH. rh-Activin did not cross react in the total ir-FS ELISA, but interfered with the measurement of free FS. Dilutions of GC-conditioned medium were parallel to the standard curve of rh-FS 288 for each assay. The values obtained in the free FS assay were 10- to 20-fold higher than those in the total ir-FS ELISA, suggesting that rat FS may be recognized by the antibodies differently than the human standard. Both total ir-FS and free FS production by undifferentiated GC from diethylstilbestrol (DES)-treated, immature rats increased with cell number and time in culture and were stimulated dose dependently by FSH, rh-activin A (except free FS, which was not measured because of interference), forskolin, and phorbol 12-myristrate. The effects of FSH and activin on FS production by undifferentiated GC were additive. There were significant effects of degree of differentiation of GC on basal FS production and responsiveness to FSH, LH, and rh-activin A. Both total ir-FS and free basal FS production increased up to 4-fold with the degree of differentiation of GC, produced by treating rats in vivo with DES (undifferentiated), DES plus FSH (partially differentiated), or DES plus FSH plus hCG (fully differentiated). The addition of FSH in vitro increased FS production by undifferentiated and partially differentiated GC, but not by fully differentiated GC. The only detectable effect of LH on FS production was on partially differentiated GC. Activin A stimulated total ir-FS production by undifferentiated and partially differentiated GC, but inhibited total ir-FS production by fully differentiated GC. Ir-inhibin production in these experiments was similar to that of FS with the following exceptions; phorbol 12-myristrate inhibited ir-inhibin production by undifferentiated GC, basal ir-inhibin decreased in fully differentiated GC, FSH stimulated ir-inhibin only in undifferentiated GC, and rh-activin A stimulated ir-inhibin at all stages. It is concluded that 1) FS protein production by cultured undifferentiated rat GC is up-regulated by FSH and activin, possibly via both protein kinase A and C pathways; 2) increasing GC differentiation is associated with a significant increase in basal FS production by rat GC and a change in the hormonal regulation of FS production; and 3) FS and ir-inhibin production by cultured rat GC can be differentially regulated. The results are consistent with the hypothesis that activin tone decreases within follicles as they develop due to increased production of the activin-binding protein FS.

Activins↗

PubMed1996

Differential responses of post-natal rat ovarian cells to FSH and activin.

A role for activin in the acquisition of gonadotropin responsiveness by the post-natal rat ovary was investigated. The inhibin/activin subunits in terms of protein and mRNA, were localised in granulosa cells of the rat ovary at days 4, 8 and 12 after birth. A characteristic pattern of responses to FSH for inhibin and progesterone (P) production was established using a dispersed ovarian cell bioassay. P production by day 4, 8 and 12 cultures was stimulated by FSH, but only when iso-butyl-methyl-xanthine (MIX) was present. In contrast, a basal level of inhibin production was measured in day 4 cultures which was not responsive to FSH or MIX. In day 8 and 12 cultures, inhibin production was FSH-responsive, but only in the absence of MIX. The addition of activin to cultures of day 4, 8 and 12 ovarian cells induced FSH-responsive P production and stimulated both basal and FSH-stimulated inhibin production. These studies indicate a differential response of neonatal ovarian cells to FSH in terms of P and inhibin production. Activin may play a role in facilitating the effects of FSH on signal transduction pathways leading to inhibin and steroid production and therefore be part of the mechanism which determines responsiveness of granulosa cells to FSH.

Activins↗

PubMed1996

Effect of laser pulse repetition rate and pulse duration on mast cell number and degranulation.

BACKGROUND AND OBJECTIVE: Mast cell activation by low-level laser therapy (LLLT), leading to degranulation and the release of mediators, may be one of the mechanisms by which LLLT can accelerate tissue repair in mammals. The objective of this work, part of an investigation to determine the optimum parameters for increasing mast cell number and degranulation in injured skin, was to determine the effect of different pulsing frequencies of LLLT. STUDY DESIGN/MATERIALS AND METHODS: Partial-thickness wounds in anaesthetized adult male Wistar rats were irradiated immediately after injury with monochromatic coherent light (wavelength 820 nm) pulsed at either 2.5, 20, 292, or 20,000 Hz at an average power density of 800 mW/cm2 for 27 seconds; the energy density was 21.6 J/cm2. The effects on mast cell number and degranulation were assessed 2 hours post-treatment by counting the numbers of intact and degranulated mast cells in Carnoy-fixed, toluidine blue-stained, sections of irradiated and sham-irradiated wounds. RESULTS: The total number of mast cells was increased significantly (P < 0.05) by all the frequencies when compared to the sham-irradiated group, but there was no significant difference between frequencies (P > 0.05). However, although the number of degranulated mast cells was higher in all laser-treated wounds, in comparison with the sham-irradiated group, only the 20 Hz (pulse duration 45 ms) and 292 Hz (pulse duration 3 ms) frequencies were significantly effective (P < 0.05). CONCLUSION: Increase in mast cell number is not pulsing frequency dependent, whereas degranulation is.

Animals↗

PubMed1996

Oestradiol and immunoreactive inhibin-like secretory patterns following controlled ovarian hyperstimulation with urinary (Metrodin) or recombinant follicle stimulating hormone (Puregon).

Inhibin (and its alpha-subunit) may be of particular value as a marker for follicular development in in-vitro fertilization (IVF) in comparison with the classic follicle stimulating hormone (FSH)-dependent marker oestradiol in patients following pituitary desensitization and treatment with recombinant FSH (rFSH). This preparation lacks luteinizing hormone (LH), which is essential for thecal cell androgen secretion and thus oestradiol production. Our study has assessed oestradiol and immunoreactive inhibin-like secretion following ovarian stimulation with rFSH or a purified urinary FSH preparation (Metrodin) (uFSH). A randomized, assessor-blind study was initiated using patients receiving a single treatment cycle of IVF (using fresh embryos) following pituitary desensitization with intranasal buserelin (500 microg daily) and the i.m. injection of either rFSH (n = 38) or uFSH (n = 17). Ovarian ultrasound examinations were performed and bloods (10 ml) collected prior to FSH treatment and every 1-2 days until ovulation induction with human chorionic gonadotrophin. LH and FSH concentrations were measured by an immunoradiometric assay, and inhibin-like immunoreactivity by a radioimmunoassay and an enzyme-linked immunosorbent assay, both with alpha-subunit specificity. Oestradiol concentration was measured with a coated tube radioimmunoassay. Following desensitization, basal LH, FSH and oestradiol concentrations were measured, as was that of immunoreactive inhibin. Following treatment with either rFSH or uFSH, LH concentrations remained low while FSH concentrations rose to a plateau of 5.6-6.7 IU/l in both groups. In contrast, the concentration of oestradiol was higher (P < 0.05) with rFSH than with uFSH in the last four days of treatment, a pattern that was repeated for inhibin-like immunoreactivity. The change in oestradiol and inhibin concentrations during treatment was approximately 2-fold higher with rFSH. The total number of follicles obtained with rFSH was similar to that with uFSH. However, the number of follicles with a diameter of >/= 15 mm was higher the rFSH group, and there was a concomitant increase in the number of oocytes recovered. Oestradiol concentration and inhibin-like immunoreactivity (determined by either method) were associated with total follicle number and number of follicles >/= 15 mm in diameter, as well as with each other (P < 0.001). When ovarian hormone output was normalized per follicle produced, oestradiol output was higher for rFSH than for uFSH P = 0.04). Inhibin output was clearly higher using rFSH than uFSH. There were seven pregnancies (one miscarriage) with rFSH and two with uFSH. Despite similar concentrations od FSH in patients, rFSH (Puregon) appears to be more potent in vitro in terms of follicular number, ovarian hormone secretion (both concentration and output/follicle) and oocyte recovery. In both groups, LH concentrations of approximately 1.3 IU/l were sufficient to support oestradiol secretion similar to that normally found in IVF programmes using human menopausal gonadotrophin preparations containing large amounts of LH. Despite known problems of specificity with the assays od inhibin, its measurement was of similar value to oestradiol as a marker of follicular development.

Adult↗

PubMed1996

The ontogeny of adhesion molecules expressed on the vascular endothelium of the developing human skin.

One of the important functions of adhesion molecules is to regulate the trafficking of lymphocytes and other leucocytes between the different organs and tissues of the body. These molecules are expressed on both the endothelial cells and the leucocytes, enabling them to adhere to one another and ultimately lead to extravasation of the leucocytes from the circulation into the surrounding tissue. P and E-selectin promote 'rolling' of leucocytes along the blood vessel walls, whereas ICAM-1 and VCAM-1 mediate subsequent firm adhesion, thus committing the leucocytes to extravasation. We have investigated the expression of the above endothelial adhesion molecules in relation to the developing dermal vasculature of fetal skin using histology and immunocytochemistry. This study showed that already at 11 wk of gestation some dermal vessels expressed P-selectin and ICAM-1. However, by 18 wk these molecules were identified on a significant number of vessels, including small capillaries supplying the forming dermal pegs. In contrast, E-selectin and VCAM-1 molecules were rarely seen in all specimens examined. Our results show that even at 11 wk of gestation, the fetal skin has a mechanism in place for circulating leucocytes to extravasate and provide primitive immunosurveillance. Furthermore, the similarities between the distribution of P-selectin and ICAM-1 in the 18 wk fetal skin and in the normal adult skin were striking. These findings may shed light on our understanding of how the fetus detects and reacts to infections and may, in the future, lead to advances in the management of some intrauterine infections.

Adult↗

PubMed1994

Use of splenic ultrasound: a new wave for immune thrombocytopenic purpura.

AIMS: To examine whether a therapeutic dose of ultrasound waves, when directed through the thoracic wall to the spleen, would significantly affect the platelet count in patients with stable immune thrombocytopenic purpura (ITP). METHODS: Continuous ultrasound at 1 W/cm2 spatial average-time average (SATA) intensity for up to one minute/5 cm2 treatment field was well tolerated in 13 patients with ITP and one with non-Hodgkin's lymphoma. Five healthy controls were also similarly treated. Peak platelet increments occurred four to eight hours after ultrasound treatment in the ITP group (n = 16 treatments). RESULTS: The mean peak platelet increment was 6.25 x 10(9)/l with a 5% confidence interval of the mean (95% CI) of 3.32 to 8.93 x 10(9)/l (p = 0.0004). The mean peak platelet increment of normal controls was 6.6 (n = 5; 95% CI = -2.3 to 15.5; p = 0.21) and for sham treated patients it was 0.66 (n = 11; 95% CI = -1.5 to 2.8; p = 0.60). There was a significant inverse correlation between patient age in the ITP group and peak platelet increment (r = -0.60; p = 0.015). CONCLUSIONS: Splenic ultrasound is a novel approach to the treatment of ITP, and may find a place in its diagnosis or management.

Adult↗

PubMed1993

The effects of follistatin, activin and inhibin on steroidogenesis by bovine thecal cells.

The paracrine actions of bovine follistatin (FS), human recombinant activin A and bovine inhibin on progesterone (P), androstenedione (A4) and inhibin production, were investigated using LH-stimulated immature bovine thecal cells. The presence of FS (3-100 ng/ml) alone caused a dose-dependent stimulation of P production by thecal cells induced by bovine LH (10 ng/ml). The stimulatory effect of FS on P production at 10 or 30 ng/ml was reversed to control levels with the addition of activin (10 or 30 ng/ml). Treatment with FS did not significantly effect on A4 production. Activin alone had no consistent effect on A4 production (measured using two different antibodies), but had a dose-dependent inhibitory effect on P production. Treatments of cells with inhibin had no significant effect on the LH-induced production of either P or A4. Testosterone production in FS; activin- or inhibin-treated cells was not different from controls. Northern analysis showed that inhibin beta subunit was not detected in thecal mRNA, whereas there were very faint bands of inhibin alpha subunit and FS which were attributed to contamination of granulosa cells (GC). We conclude that FS in vitro has a stimulatory effect on P production by bovine thecal cells, and that activin has the ability to reverse the stimulatory effect of P production. Unlike the rat and human thecal cells, activin and inhibin had no significant effect on LH-induced androgen synthesis by bovine thecal cells. We propose that FS secreted by the GC acts as a paracrine modulator upon thecal cells to directly stimulate the production of P independently of activin.(ABSTRACT TRUNCATED AT 250 WORDS)

Activins↗

PubMed1993

Histochemical heterogeneity of mast cells in rat dermis.

The dermal mast cells of Wistar rats were studied following fixation in either 10% phosphate buffered formalin or Carnoy's solution and staining with either toluidine blue or alcian blue:safranin O. Granules of mast cells appeared heterogeneous following fixation with formalin and staining with alcian blue:safranin O, but not when stained with toluidine blue. The number of mast cells observed in skin fixed in Carnoy's solution was greater than the number observed in equivalent samples of skin fixed in formalin (p < 0.01) when both samples were stained with toluidine blue. In formalin fixed skin stained with alcian blue:safranin O, there were three populations of mast cells designated as "blue," "red" or "mixed." "Blue" mast cells, containing only alcian blue stained granules, "red" mast cells, containing only safranin O stained granules, and "mixed" mast cells, containing both alcian blue and safranin O stained granules accounted for 77.6 +/- 3.0, 6.6 +/- 2.5 and 15.8 +/- 2.5% of the total mast cell population, respectively. In skin specimens fixed in Carnoy's solution and stained with alcian blue:safranin O the mast cells contained only blue granules (alcian blue positive). The number of mast cells observed in Carnoy's fixed skin sections was less than the number seen in formalin fixed skin sections when both were stained with alcian blue/safranin O. This indicates that there is a group of mast cells which do not stain with safranin O after fixation with Carnoy's solution.

Animals↗

PubMed1993

Responses of dermal mast cells to injury.

The effect on dermal mast cell numbers and degranulation of making a partial thickness skin wound on the right flank of Wistar rats was studied immediately after operation and 0.5, 1, 2, 4, 8, 16, 24 and 72 h postoperatively. An equivalent area of intact dermis on the left flank was used as a control. In the injured dermis the mean number of detectable mast cells in the experimental group immediately after making the partial thickness wound was not significantly different from the control side (P > 0.25) but it later decreased, reaching its lowest value after 2 h and increasing from 16 h to 72 h postoperatively when the final assessment was made. The possibility that the reduction in mast cell number per unit area might be an artefact resulting from increased tissue volume due to oedema was investigated and disproved. The total number of dermal mast cells in equivalent areas of the intact left flank remained unchanged throughout this period. The percentage of degranulating mast cells started rising 0.5 h postoperatively, increased gradually to reach its highest value after 2 h, remained high up to 8 h postoperatively and then decreased to reach its lowest value after 72 h. The percentage of degranulating mast cells of the intact dermis of the left flank did not alter during this period. The lack of a significant change in the control groups shows either the absence of any systemic effect or that the technique used was not sensitive enough to detect it.

Animals↗

PubMed1992

The direct effect of light therapy on endothelial cell proliferation in vitro.

During repair, new blood vessels are formed by the process of angiogenesis. The prerequisite to blood vessel formation is the proliferation of endothelial cells. The purpose of this study was to find out if light therapy is capable of affecting endothelial cell proliferation in vitro. The direct effect of light at wavelengths of either 660 or 820 nm was studied on primary cultures of bovine aortic endothelial cells using varying energy densities, of either 1, 2, 4, or 8 J/cm2. The proliferation of the endothelial cells was assessed over a period of five days after a single irradiation.

Animals↗

PubMed1992

Comparison of the effects of moist and dry conditions on the process of angiogenesis during dermal repair.

The effect of moist and dry conditions on the process of angiogenesis during dermal repair was investigated. The moist conditions were achieved by covering excised wounds on porcine flank skin with the adhesive polyurethane dressing Opsite and dry conditions were achieved by exposure to air through dry gauze dressings. Angiogenesis was assessed during the period from 3 to 60 d after injury. Quantitative studies, using computerized image analysis, were carried out on microfocal x-ray images of skin sections whose blood system had been perfused in vivo with a radio-opaque medium. The analytical technique yielded information with regard to vessel number per wound and also the area occupied by blood vessels per unit wound area. Three regions were assessed in each wound bed: upper zone, just below the surface of the wound; the lower zone, just above the base of the wound bed; and the middle zone, midway between the other two zones. The results showed that the wounds maintained in a moist environment revascularized at a greater rate than those maintained in a dry environment. This was apparent in all of the zones of the wound bed examined. The development of new vessels occurred in a more orderly manner in the moist wounds. There was an early increase in vessel number rising to a peak around days 3-5, then a gradual decrease in number starting around day 7. In contrast, in the dry wounds the development of blood vessels was less rapid. Peak vessel number in the upper zone was significantly less than that achieved in the moist wounds, and was not reached until 7 d after injury. The decrease in vessel number from the peak was less rapid in the dry wounds, suggesting that there was a delayed entry into the remodeling phase in comparison with the moist wounds. The results also showed that the total percentage area of the wound bed occupied by blood vessels was greater in the moist wounds than the dry wounds from 3 d after injury until day 7. This level of vascularization was maintained beyond 7 d after injury even when the vessel number in the moist wounds was significantly less than in the dry wounds, suggesting that the vessels in the moist wounds were larger and, presumably, more mature. In general, moist wounds showed a more rapid decline towards uninjured skin levels of vascularization than dry wounds.

Animals↗

PubMed1991

'Laser success'.

Explore the source record for details and available documents.

Humans↗

PubMed1991

Comparison of the effects of semi-occlusive polyurethane dressings and hydrocolloid dressings on dermal repair: 1. Cellular changes.

The effects on dermal repair of two wound dressings, one the semi-occlusive polyurethane sheet Opsite, the other the hydrocolloid Granuflex, were compared in full-thickness excised lesions on porcine skin during the period from 5 d to 6 months after injury. Quantitative studies were made of changes in the populations of polymorphonuclear leucocytes, macrophages, fibroblasts, and endothelial cells. The progress of repair in the wounds covered with the semi-occlusive dressing showed a decrease in the number of inflammatory cells (polymorphonuclear leukocytes and macrophages) from 5 to 60 d, whereas the number of proliferative phase cells (fibroblasts and endothelial cells) increased from 5 to 7 d. The total cellularity per unit area showed an increase between 5 and 7 d, that is, during the proliferative phase of repair, and then progressively decreased as the proliferative phase was succeeded by the remodeling phase. In contrast, the repair process in the hydrocolloid-dressed wounds was more complex. The number of inflammatory cells remained relatively high throughout and there were consistently fewer endothelial cells present throughout. Fibroblast number showed an initial fall from 5 to 14 d but then started to increase in number from 21 to 60 d. This chronic inflammatory reaction appeared to be in response to particulate matter that had been incorporated into the wound bed and hypodermis, and was still apparent 6 months after injury, when hydrocolloid particles were detectable microscopically in the hypodermis.

Animals↗

PubMed1990

Comparison of the effect of multi-wavelength light produced by a cluster of semiconductor diodes and of each individual diode on mast cell number and degranulation in intact and injured skin.

Intact skin and partial thickness wounds in adult male Wistar rats were irradiated by pulsed, monochromatic light of different spectral wavelength peaks simultaneously and the effects on mast cell number and degranulation were assessed. The light was produced by a Biotherapy 3ML (Omega Universal Technologies) device utilizing a 21 semiconductor diode cluster probe emitting 6 different wavelengths in the red and near infrared part of the spectrum simultaneously, only one of the wavelengths (820 nm) being coherent. The duration of treatment was 4 minutes. The average power density, distributed over the surface area of the probe (19.62 cm2) was 45 mW/cm2. The average energy density at the wound site was 10.8 J/cm2. The effect of each of the wavelengths incorporated in the cluster probe was then examined separately. The average power density for each single probe was 120 mW/cm2, except for the 820 nm diode which was 400 mW/cm2. The average energy density was maintained at 10.8 J/cm2 as with the cluster probe. After 2 hours the rats were killed and the skin was removed, processed for light microscopy, and stained with toluidine blue to identify the mast cells. The numbers of the intact and degranulated mast cells were counted in 100 high power fields (i.e., over a total area of 20 mm2) in each irradiated specimen and compared to the sham-irradiated and untreated groups. To avoid bias, the slides examined were coded and evaluated blind. In intact skin, the cluster probe irradiation was followed by a statistically significant increase in the total number of mast cells compared to the sham-irradiated group, but the percentage of the degranulated mast cells was not affected. In the partial thickness wound, the cluster probe irradiation was also followed by a statistically significant increase in the total number of mast cells compared to the sham-irradiated group; however, there was, in addition, a significant increase in the percentage of degranulated mast cells. Concerning the single probes, only the 660, 820, 940, and 950 nm wavelength emitters produced statistically significant increases in both mast cell number and degranulation in partial thickness wounds. However, when intact skin was irradiated with probes emitting these wavelengths, although the total number of mast cells was increased significantly, there was no change in degranulation compared with the sham-irradiated group. The effects observed were less than those of the cluster probe. No significant differences were found between the 870 and 880 nm wavelength-irradiated, sham-irradiated, and untreated groups in either intact or injured skin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Effect of therapeutic ultrasound on the healing of full-thickness excised skin lesions.

The effect of therapeutic ultrasound on the healing of the dermis of full-thickness excised lesions made in the flank skin of adult rats was assessed quantitatively by means of differential cell counts made in sections of the wound bed five and seven days after injury. Wounds were either sham-treated (control group) or exposed to pulsed ultrasound (2 ms on, 8 ms off) at an intensity of 0.1 W cm-2 SATA (frequency either 0.75 MHz or 3.0 MHz). By five days after injury, ultrasound-treated wounds contained more extensive granulation tissue, fewer polymorphonuclear leucocytes (polymorphs) and macrophages, and more fibroblasts (aligned in a manner conducive to efficient wound contraction) than the sham-irradiated controls. By seven days after injury there was no significant difference in cellularity between the controls and the ultrasonically-irradiated wounds. The results obtained suggest that ultrasound therapy can be useful in accelerating the inflammatory and early proliferative stages of repair.

Animals↗

PubMed1990

The effect of therapeutic ultrasound on angiogenesis.

The effect of therapeutic ultrasound on the formation of new blood vessels in full-thickness excised lesions in the flank skin of adult rats was assessed quantitatively using microfocal x-ray techniques. Wounds were either sham-treated (control group) or exposed to ultrasound for 5 min daily at an intensity of 0.1 W/cm2 SATA (frequency either 0.75 MHz or 3.0 MHz). By 5 days after injury there were more blood vessels in equivalent regions of the granulation tissue of the ultrasound-treated wounds than in the control wounds. This suggested that the ultrasound-treated wounds were at a more advanced stage in the repair process. By 7 days after injury there was no significant difference in blood vessel number between the three groups.

Animals↗

PubMed1990

Macrophage responsiveness to therapeutic ultrasound.

Macrophages are a source of many important growth factors which can act as wound mediators during tissue repair. The aim of this work was to find out if levels of ultrasound which accelerate repair could stimulate the release of fibroblast mitogenic factors from an established macrophage-like cell line (U937). The U937 cells were exposed in vitro to continuous ultrasound at a space average, temporal average intensity of 0.5 W/cm2 at either 0.75 MHz or 3.0 MHz, for 5 min. The macrophage-conditioned medium was removed either 30 min or 12 h after exposure, and placed on 3T3 fibroblast cultures. Fibroblast proliferation (defined here as increase in cell number) was assessed over a 5-day period. The results showed that 0.75 MHz ultrasound appeared to be effective in liberating preformed fibroblast affecting substances from the U937 cells, possibly by producing permeability changes, whereas 3.0 MHz ultrasound appeared to stimulate the cell's ability to synthesize and secrete fibroblast mitogenic factors.

Animals↗

PubMed1989

Macrophage responsiveness to light therapy.

Macrophages are a source of many important mediators of wound repair. It was the purpose of this study to see if light could stimulate the release of these mediators. In this study an established macrophage-like cell line (U-937) was used. The cells were exposed in culture to the following wavelengths of light: 660 nm, 820 nm, 870 nm, and 880 nm. The 820-nm source was coherent and polarised, and the others were non-coherent. Twelve hours after exposure the macrophage supernatant was removed and placed on 3T3 fibroblast cultures. Fibroblast proliferation was assessed over a 5-day period. The results showed that 660-nm, 820-nm, and 870-nm wavelengths encouraged the macrophages to release factors that stimulated fibroblast proliferation above the control levels, whereas the 880-nm wavelength either inhibited the release of these factors or encouraged the release of some inhibitory factors of fibroblast proliferation. These results suggest that light at certain wavelengths may be a useful therapeutic agent by providing a means of either stimulating or inhibiting fibroblast proliferation where necessary. At certain wavelengths coherence is not essential.

Animals↗