Biomedical subjects

B J Masterson

Publications and source records attributed to B J Masterson.

At least 19 recordsLinked to original sources

PubMed1992

Presence of epidermal growth factor, platelet-derived growth factor, and their receptors in human myometrial tissue and smooth muscle cells: their action in smooth muscle cells in vitro.

Immunohistochemical observations indicate that human myometrial smooth muscle cells express epidermal growth factor (EGF) and platelet-derived growth factor (PDGF)-AB and contain EGF and PDGF-beta receptors with no variation in intensity with phases of the menstrual cycle. Furthermore, immunofluorescent microscopic studies revealed that primary myometrial smooth muscle cell cultures also express EGF, PDGF-AB, and contain EGF and PDGF-beta, but not alpha-receptor. Incubation of subconfluent smooth muscle cells in serum-free medium leads to quiescence within 48 h as demonstrated by 3H-thymidine incorporation and labeling index. Exposure of quiescent cells to 10% fetal bovine serum stimulates resumption of DNA synthesis and proliferation in a time-dependent manner with a doubling time of 41.6 h. EGF (1.5-50 ng/ml) and PDGF-AB (1-10 ng/ml) in a dose- and time-dependent manner significantly stimulated 3H-thymidine incorporation by quiescent myometrial smooth muscle cells (P less than 0.05). Combinations of EGF (15 ng/ml) and PDGF-AB (10 ng/ml) significantly increased 3H-thymidine incorporation induced by either growth factor alone (P less than 0.05). PDGF-BB at 10 ng/ml also stimulated 3H-thymidine incorporation and its effect was similar to that induced by PDGF-AB at the same concentration. 17 beta-Estradiol (E2) at 1 microM inhibited 3H-thymidine incorporation by the smooth muscle cells (P less than 0.05). E2 also reduced the stimulatory effect of EGF (15 ng/ml) and PDGF (3 ng/ml). Progesterone at 1 microM either alone or in combination with E2 did not have any effect on 3H-thymidine incorporation or alter the mitogenic action of EGF and PDGF. The effect of EGF and PDGF on cell growth and 3H-thymidine incorporation by myometrial smooth muscle cells was independent of phases of the menstrual cycle. In summary, the results of present studies indicate that human myometrial tissue and myometrial smooth muscle cells in primary culture locally produce EGF and PDGF-AB and contain EGF and PDGF-beta, but not alpha-receptors. Moreover, the myometrial smooth muscle cells in culture respond to the mitogenic action of EGF and PDGF.

Autoradiography↗

PubMed1992

Platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and EGF and PDGF beta-receptors in human endometrial tissue: localization and in vitro action.

Human endometrial tissue and primary stromal cell culture contain immunoreactive epidermal growth factor (EGF), platelet-derived growth factor (PDGF)-AB as well as EGF and PDGF-beta receptors. The immunostaining for EGF, EGF receptor, and PDGF beta-receptor were associated with endometrial luminal and glandular epithelial and stromal cells, whereas only the stromal cells contain immunoreactive PDGF-AB. The immunostaining intensity of EGF, EGF receptor, and PDGF-AB was similar in both phases of the menstrual cycle, whereas, PDGF-beta receptor immunostaining was highest in proliferative phase and considerably reduced, particularly in luminal and glandular epithelial cells in the secretory phase. In addition primary stromal cell cultures express EGF, PDGF-AB, and contain EGF and PDGF-beta receptors, and very low levels of PDGF-alpha receptor. 3H-Thymidine incorporation indicate that after 48 h of incubation in serum-free medium approximately 75-80% of stromal cells are quiescent. Incubation of quiescent stromal cells with 10% fetal bovine serum stimulate 3H-thymidine incorporation in a time-dependent manner reaching maximal after 30-48 h, with a doubling time of 38.2 h. EGF (1.5-15 ng/ml) stimulates 3H-thymidine incorporation by quiescent stromal cells (P less than 0.001). This effect was significantly reduced at concentrations above 15 ng/ml (P less than 0.005). PDGF-AB (3-10 ng/ml) and PDGF-BB (0.5-10 ng/ml) also stimulate 3H-thymidine incorporation in quiescent stromal cells compared to controls (P less than 0.005). The action of EGF (15 ng/ml) and PDGF-AB (10 ng/ml) was time dependent, reaching maximal after 36 and 48 h of incubation (P less than 0.002). Addition of PDGF-AB (10 ng/ml) to EGF (15 ng/ml) significantly enhanced the action of EGF or PDGF-AB used individually (P less than 0.001). 17 beta-estradiol or progesterone at 1 microM did not stimulate 3H-thymidine incorporation, although they were stimulatory in combination (P less than 0.001), they did not alter the action of EGF or PDGF when added in combination. These observations provide further evidence that human endometrial tissue contains specific immunoreactive EGF receptors. It also demonstrates the presence of immunoreactive EGF, PDGF-AB, and PDGF-beta receptors in endometrial tissue as well as stromal cells in primary culture. Both EGF and PDGF are mitogenic for endometrial stromal cells, suggesting an autocrine/paracrine role in modulation of endometrial cell growth and differentiation.

Cell Division↗

PubMed1991

Selection of incisions for gynecologic procedures.

Progress is being made in the employment of abdominal incisions. The use of mass closure has greatly decreased the incidence of disruption. The avoidance of subcutaneous sutures has likewise decreased the rate of wound infections, and modern aggressive management has lessened the time that patients must contend with incisional abscesses when they do occur. There will always be considerable discussion and debate on the choice of an abdominal incision. However, the primary consideration remains always to choose and construct a surgical incision large enough to operate through comfortably and effectively.

Abdomen↗

PubMed1990

Tissue reactivity and degradation patterns of absorbable vascular ligating clips implanted in peritoneum and rectus fascia.

Absorbable vascular ligating clips are finding increasing use in intraabdominal surgery. We report the results of a light and scanning electron microscope investigation of the tissue reactivity and clip degradation patterns of two such materials, Absolok (polydioxanone) and Lactomer (copolymer of glycolic and lactic acid), implanted in the fascia and peritoneum of rabbits for intervals of 2 to 70 days. Cellular response to the clips, defined as the number of inflammatory cells/10(4) microns 2, was maximum at day 4 postimplantation, then gradually declined as the duration of implantation increased. This pattern, seen with both types of clips, was similar to that seen with polydioxanone (PDS) suture, but significantly greater than that associated with polypropylene (Prolene) suture. Although cellular response to the clips was greater in peritoneum than in fascia, especially on two occasions associated with adhesion formation, this was not statistically significant. Based on our morphological observations, the signs of clip degradation which were indicated by the appearance of surface crazing and cracks occurred earlier in peritoneum than in fascia.

Abdomen↗

PubMed1990

Stress relaxation of organic suture materials.

Sutures fabricated from synthetic polymeric materials exhibit the phenomenon of stress relaxation, that is, when held under tension at a fixed elongation, there is a gradual realignment of the microstructure to accommodate the developed tensile stress. This property has been characterized for three modern suture materials, polypropylene, polydioxanone and poly(glycolic acid). All three materials exhibited stress relaxation but to different degrees, with polypropylene exhibiting the greatest stress relaxation (to approximately 40% of the initial load). The initial rate of stress relaxation increased with the rate of loading but the residual stress level was found to be independent of elongation rate except at extremely low rates of loading.

Biocompatible Materials↗

PubMed1990

In vivo and in vitro degradation of monofilament absorbable sutures, PDS and Maxon.

Two new absorbable monofilament suture materials polydioxanone and Maxon are being employed increasingly in abdominal surgery because of increased strength retention and decreased tissue reactivity compared with previously available materials. As part of our investigation of the behaviour of suture materials, 3-0 sutures of polydioxanone and Maxon were enclosed in nylon pouches, a technique developed for in vivo experiments to prevent cellular interaction with implanted devices. The pouched sutures were gas sterilized, then implanted in either the extrafascial space or peritoneal cavity for periods of 1-5 wk. Sterilized sutures were also incubated in Ringer's lactate at 37 degrees C. Tensile strength of the exposed sutures was measured. For a given suture material and duration of incubation, there was no significant difference in tensile strength degradation among the three test environments. Although the strength of unexposed Maxon is greater than that of polydioxanone, the residual strength of Maxon decreases more rapidly in use, so that, after 2 wk, the strength of polydioxanone is greater. Scanning electron microscope examination of the suture surfaces reveals that polydioxanone develops surface crazing with time, whereas the surface morphology of Maxon remains relatively unaltered.

Animals↗

PubMed1990

Chromic gut pelviscopic loop ligature. Effect of the number of pulls on the tensile strength.

The failure load of a pelviscopic loop ligature (PLL) was determined after tightening the slip knot with one, two or three pulls. The PLL showed a significant decrease in strength when tightened with three or more pulls. In each group some PLLs failed from slippage rather than from fracture of the suture material at the base of the knot. Slippage occurred more frequently with each additional pull. The findings indicate that the surgeon should apply only one pull on the device for the most secure knot. In addition, there was no strength difference between the suture material itself and the junction of the suture and its plastic tail grip. The plastic tail grip of the PLL will not release the tail end of the suture material before either the suture material or the slip knot fails.

Catgut↗

PubMed1989

Hemostasis in blood vessels after ligation.

The length of time required to achieve hemostasis after ligation of blood vessels with a diameter of 1.0 to 3.5 mm was studied. Canine limb vessels were ligated with stainless steel clips. These were removed at 48, 60, 72, 84, or 96 hours after ligation, and the degree of hemostasis was evaluated by observing the effect of varying amounts of trauma applied to the vessels. The vessels were first observed for 1 minute. In the second phase the vessels were stroked for 15 seconds and then observed for 1 minute. In the second phase the vessels were stroked for 15 seconds and then observed for any bleeding. An additional 15 seconds of stroking followed by observation completed the evaluation. All blood vessels achieved hemostasis after 96 hours of secure ligation despite the trauma. All ligating devices must provide secure ligation to achieve hemostasis for at least 96 hours. The presence of disease processes or medications interfering with clotting would necessitate a longer period of secure ligation to achieve hemostasis.

Animals↗

PubMed1988

A comparative scanning electron microscopic study on degradation of absorbable ligating clips in vivo and in vitro.

Using scanning electron microscopy, the degradation characteristics of two absorbable ligating clips, Absolok (polydioxanone) and Lactomer (poly-L-lactide-co-30%-glycolide) have been studied under in vivo and in vitro conditions. The rate of Absolok clip degradation was significantly greater than that of Lactomer clip degradation both in vitro and in vivo. The rate of degradation of Lactomer clips significantly increased and they showed a greater change in proportion of breakdown in vivo than in vitro compared to Absolok clips. The Absolok clip breakdown began with the formation of surface undulations which later developed into fissures. The undulations appeared on the clip surface as early as 7 days and by 2 weeks developed into fissures. The initial appearance of the fissures was at the edge of the clips particularly at the mating surface. The thickness of layers forming the fissures gradually decreased and by 15 weeks the layers appeared as very thin sheets of materials. The high energy areas (locking and molding points) were more resistant to breakdown and the remains of the clips were still present 25 weeks after initiation of the experiments. The Lactomer clips showed very little sign of degradation in vitro even after 10 weeks of incubation. However, in the in vivo experiments undulations formed on the clip surface as early as 2 weeks postimplantation. These clips also showed fissures similar to those observed on Absolok clips.

Animals↗

PubMed1988

Locking mechanism strength of absorbable ligating devices.

The locking mechanism strengths of the absorbable Absolok and Lactomer ligating clips and the absorbable Lactomer staple have been determined following implantation in an animal model. Three sizes of each type of clip and the single size of staple were enclosed in open mesh nylon pouches and implanted subcutaneously in rabbits for periods of 4, 7, 14, 21, and 28 days before tensile testing of the lock mechanisms. No change in the lock mechanism strength was detected for the Absolok clips before 21 days. The Lactomer clips and staples, however, showed significant decrease in lock mechanism strength within 7 days of implantation, this loss increasing with longer implantation times. A proportion of all the devices were found to have dissolved to an extent that precluded testing at 21 and 28 days. The findings indicate that the lock mechanisms of absorbable ligating clips differ significantly in their short-term (30 days) durability.

Animals↗

PubMed1988

Tensile characteristics of PTFE sutures.

The tensile strength load to failure and knotting characteristics of the six gauges of a new PTFE suture have been studied. In its unstressed state, the suture comprises 50% by volume of air but this diminishes upon stretching so that its diameter appears to be very large and the tensile strength low. The low surface-surface friction necessitates fairly complex knotting regimens (3 = 1 = 3 = 2 or 3 = 1 = 3 = 3) to ensure stable knot configurations, i.e. failure of the loop before knot failure. However, the relatively simple 2 = 1 = 1 = 1 configuration was found to have an adequate tensile strength.

Microscopy, Electron, Scanning↗

PubMed1988

Tensile properties of suture materials.

The tensile properties of three new sutures, two non-absorbable and one absorbable material, have been evaluated and compared with those of polypropylene and nylon sutures. It was found that the five materials differed significantly in their tensile strengths and elastic/plastic deformation characteristics but displayed comparable elongations at failure. All sutures showed a decrease in failure load and elongation at failure when knotted. Most materials showed an increased tensile strength and decreased elongation at failure for smaller suture gauges, and this behaviour is thought to be related to their internal molecular organization.

Biocompatible Materials↗

PubMed1988

Characterization of surgical needles.

The acuity (sharpness) of surgical needle points was assessed by measuring the force required for repeat needle penetrations through a medium-gauge latex sheet glued to a perforated Plexiglas frame. The data on the variation in the applied force with repeat penetrations showed that needles obeyed the general relation: P = A + B.n; where P is the applied penetration force in grams, n is the number of penetrations and A and B are constants. Constant A characterized the needle-point acuity and B the maintenance of acuity. This relationship indicated both needle acuity and acuity maintenance with repeated passes through a reproducible target material. Determining the microhardness of needles provided data on their strength which helped to account for differences in the acuity of apparently similar needles. The tensile strength of the union between suture and needle was determined to evaluate the security of suture attachment.

Latex↗

PubMed1988

Oral contraceptive agents: current status.

Oral contraceptives are the most widely prescribed and ingested drug in human history. The difficulty in establishing their clear-cut side effects is compounded by the rarity of these side effects and their occurrence with multiple other factors and cofactors that may be etiologically more important. For the prudent surgeon, suffice it to say that should operation require bedrest postoperatively, oral contraceptives should be stopped at least 2 weeks preoperatively and barrier methods begun. Barrier methods should also be used when drugs that interfere with oral contraceptives are prescribed. Oral contraceptives and anticoagulants should not be given together because of the chemical changes in the blood caused by the steroid content of the contraceptive. As surgeons, we must remember the contraindications noted herein and become familiar with the current literature as new developments unfold in the dynamic field of conception control.

Contraceptives, Oral↗

PubMed1988

Skin preparation.

Preoperative skin preparation, whether it is the patient's or the surgeon's, should be a brief event. Successful wound healing is determined more by what is done in the wound than what is done on the wound. More than $1 billion annually is wasted on prolonged skin preparation that is not useful to the patient.

Disinfection↗

PubMed1988

Effects of bacterial infection on absorbable vascular ligating clips.

Electron microscopic observations of two implanted absorbable clips, Absolok and Lactomer, infected with Escherichia coli and Streptococcus faecalis, were carried out. An overgrowth of bacteria was observed over the entire surface of the clips. The mating surfaces of the Lactomer clips and the locking mechanisms of both types of clip were more heavily infected--that is, provided better support for bacterial growth--than other areas of the clips in the initial postimplantation period. However, with longer periods (up to seven days), the initial bacterial deposits developed into a thick, plaquelike layer. This layer appeared to restrict access to the surfaces such that the infected clips degraded at a much slower rate than did the noninfected clips, particularly Lactomer clips, on which little morphologic change was detectable seven days after implantation.

Animals↗

PubMed1988

Tissue reactions to absorbable ligating clips.

Scanning electron microscopy was used in a comparative ultrastructural study of biodegradable ligating clips, the Absolok (polydioxanone) and the Lactomer (copolymer of glycolic and lactic acids), implanted subcutaneously in rabbits. The inflammatory response and tissue reactions to the implanted clips and their effects on clip breakdown were studied. By the first week after implantation, numerous inflammatory cells adhered to the clip surfaces, with occasional fibroblasts present. By two weeks after implantation there was a reduction in the number of inflammatory cells, but the number of fibroblasts gradually increased, resulting in encapsulation of the clips. The thickness of the fibrous tissue capsule, formed by a variety of collagen fibers, gradually increased 5-25 weeks after implantation. Residues from the Lactomer clips were still present within the encapsulating tissue at 25 weeks. In contrast, clips enclosed in nylon pouches were totally degraded, and no residues were detectable at 25 weeks. Tissue reactions similar to those observed for nonpouched implanted clips were seen over the entire external surface of the pouches.

Animals↗

PubMed1987

The use of nylon pouches to prevent cellular attachment to implanted materials.

A nylon pouch system has been developed to permit the in vivo exposure of implantable materials to tissue fluids without complications arising from cellular attachment or from the bacterial attack. SEM observations have indicated that the pouches were effective in reducing the ingress of bacteria as well as reducing, and in some cases eliminating, cell infiltration through their mesh structure. Over a 7 d implantation period, the exterior surfaces of the nylon pouches were heavily infested with microorganisms but there was minimal growth of bacteria within the pouches. Non-infected pouches that were implanted for up to 25 wk showed heavy deposits of cellular matter on the external surfaces of the pouches and minimal deposits within the pouches.

Absorption↗