Search PubMed⌕ Search

Biomedical subjects

Mark A Carlson

Publications and source records attributed to Mark A Carlson.

16 recordsLinked to original sources
PubMed2006

Technical note: assay of cell quantity in the fibroblast-populated collagen matrix with a tetrazolium reagent.

Determination of cell quantity in three-dimensional culture systems, such as the fibroblast-populated collagen matrix, can be difficult secondary to the abundance of extracellular collagen. The WST-1 assay, which can quantitate cellular processes in monolayer culture, was tested as a measure of relative cell quantity in a three dimensional culture system, the fibroblast-populated collagen matrix. The assay had acceptable accuracy and precision, and was not affected by the extracellular matrix. It was concluded that the assay was a reasonable alternative to other measures of cell quantity in the fibroblast-populated collagen matrix.

Cell Count↗
PubMed2005

Modeling dermal granulation tissue with the linear fibroblast-populated collagen matrix: a comparison with the round matrix model.

BACKGROUND: Wound contraction typically is not symmetrical; for example, a square-shaped wound will not yield a square scar. Interestingly, the round fibroblast-populated collagen matrix has been used as a model of wound contraction, even though contraction in this model is mostly symmetrical. OBJECTIVE: We wanted to compare the round versus linear fibroblast-populated collagen matrix to see which would be a better model of dermal granulation tissue. METHODS: Gross and microscopic morphology, contraction kinetics, cytoskeletal architecture, and apoptotic and proliferative indices were compared between the round versus the linear fibroblast-populated collagen matrix. A rat excisional wound model was used as an in vivo standard of healing. RESULTS: The rate of contraction was similar between the two models, although the mode of contraction was grossly asymmetric in the linear while remaining symmetric in the round model. Cellular survival and proliferation were both dependent on matrix attachment in both models; this was analogous to the attachment-dependence of granulation tissue. In the attached (restrained) condition, the level of cellular organization was higher in the linear than in the round matrix; the tissue architecture of the linear matrix, moreover, mimicked that of the excisional wound model. CONCLUSION: The round versus linear fibroblast-populated collagen matrix displayed a similar proliferative and survival response to matrix attachment. The latter model, however, demonstrated tissue organization with attachment and asymmetrical contraction after detachment analogous to that of the in vivo wound model. The linear fibroblast-populated collagen matrix appears to be the better model of dermal granulation tissue.

Apoptosis↗
PubMed2004

Minimally invasive surgery for achalasia: a 10-year experience.

Minimally invasive esophagomyotomy for achalasia has become the preferred surgical treatment; the employment of a concomitant fundoplication with the myotomy is controversial. Here we report a retrospective analysis of 53 patients with achalasia treated with laparoscopic Heller myotomy; fundoplication was used in all patients except one, and 48 of the fundoplications were complete (floppy Nissen). There were no deaths or reoperations, and minor complications occurred in three patients. Good-to-excellent long-term results were obtained in 92% of the subjects (median follow-up 3 years). Two cases (4%) of persistent postoperative dysphagia were documented, one of which was treated with dilatation. Postoperative reflux occurred in five patients, four of whom did not receive a complete fundoplication; these patients were well controlled with medical therapy. We suggest that esophageal achalasia may be successfully treated with laparoscopic Heller myotomy and floppy Nissen fundoplication with an acceptable rate of postoperative dysphagia.

Adult↗
PubMed2004

Effect of body mass index on nonalcoholic fatty liver disease in patients undergoing minimally invasive bariatric surgery.

The risk factors for nonalcoholic fatty liver disease in patients undergoing bariatric surgery are under study. We wanted to determine the correlation between nonalcoholic fatty liver disease and patient factors such as obesity and liver function tests. A retrospective analysis was performed on 177 nonalcoholic morbidly obese patients who underwent laparoscopic Roux-en-Y gastric bypass with liver biopsy, to identify risk factors for nonalcoholic fatty liver disease. The histologic grade of liver disease was compared with preoperative body mass index, age, and liver function tests. Simple steatosis and steatohepatitis were present in 90% and 42% of patients, respectively. Elevated transaminase levels were an independent risk for liver disease. Body mass index and liver disease were not correlated with univariate analysis. Regression analysis performed on age, body mass index, and liver disease demonstrated that the risk for liver disease increased with body mass index in the younger (<35 years old) age group and decreased with body mass index in the older (>45 years old) age group. There was a high incidence of steatosis and steatohepatitis in these nonalcoholic bariatric patients, and elevated transaminase level was indicative of disease. Body mass index was a positive risk factor for liver disease in younger patients but a negative risk factor in the older patients.

Adult↗
PubMed2004

Modulation of FAK, Akt, and p53 by stress release of the fibroblast-populated collagen matrix.

BACKGROUND: Fibroblast survival in a three-dimensional collagen matrix is dependent in part upon the rigid anchorage of the matrix to tissue culture plastic. We hypothesized that focal adhesion kinase (FAK) and protein kinase B (Akt) would be activated and that the p53 level would be low in the rigidly anchored (attached) collagen matrix; loss of anchorage (detachment) was hypothesized to have the opposite effects. MATERIALS AND METHODS: Human foreskin fibroblasts were cultured in attached bovine collagen matrices for 48 h before detachment as free-floating matrices. At various time points postrelease, matrix lysates were blotted for the proteins of interest, and the terminal deoxynucleotidyltransferase-mediated dUTP nick-end label assay was performed on both whole matrices and cytospin preparations. Irradiated monolayer fibroblasts were used as positive controls for the amount of p53 protein. RESULTS: Terminal deoxynucleotidyltransferase-mediated dUTP nick-end label positivity in attached versus detached matrices (at 24 h post detachment) was 0.7 +/- 03 versus 5.3 +/- 1.7% (P < 0.05, unpaired t test). FAK and Akt were phosphorylated (activated) in the attached matrix; there was a near complete of loss of both activated forms within 4 h of matrix detachment. Irradiated monolayer fibroblasts had increased levels of p53, mdm2, and p21. In contrast, the p53, mdm2, and p21 levels were just at the level of detection in the attached matrix, but were induced 5- to 10-fold within 2-4 h after matrix detachment. CONCLUSIONS: FAK and Akt are activated in the attached fibroblast-populated collagen matrix whereas the p53 level is relatively low; matrix detachment downregulates FAK and Akt activity and induces p53. The state of mechanical anchorage of the collagen matrix regulates the survival of embedded fibroblasts through a mechanism which may involve FAK.

Adhesiveness↗
PubMed2004

Wound splinting modulates granulation tissue proliferation.

Attachment of the extracellular matrix to a substratum is important for fibroblast survival and proliferation in three-dimensional in vitro culture systems. We hypothesized that wound matrix attachment in a wound splinting model would modulate wound cell proliferation in vivo. Male rats were excisionally wounded on the dorsum, and a splint was sutured to the wound edge. In one experiment (N = 12), 6 rats were desplinted on day 5, and then all were sacrificed 24 h later, 6 h after 5-bromo-2'-deoxyuridine (BrdU) injection. In the second experiment (N = 18), 6 rats each were desplinted, desplinted with wound edge release, or not disturbed, followed by BrdU injection and sacrifice 24 h later. BrdU-labeled nuclei were quantified on frozen sections of granulation tissue, cut at three different levels. In the first experiment, the percentage of BrdU-positive nuclei per high power field (hpf) in the splinted vs. desplinted animals was 6.15 +/- 2.45 (S.D.) vs. 3.03 +/- 1.58%* p<0.001, ANOVA. In the second experiment, the number of BrdU-positive per hpf was 33.1 +/- 17.4 vs. 14.5 +/- 17.1 vs. 10.2 +/- 9.1* (splinted vs. desplinted vs. desplinted/released); *p<0.001 [analysis of variance (ANOVA)]. Removal of the wound splint decreased the rate of BrdU-labeled cells in the granulation tissue by approximately 50%; complete disruption of wound matrix attachment may have decreased this rate even further. Wound cell proliferation is modulated by lateral attachment of the wound matrix.

Analysis of Variance↗
PubMed2004

Laparoscopic transgastric esophageal mucosal resection for high-grade dysplasia.

BACKGROUND: High-grade dysplasia of the esophageal mucosa has been shown to be a precursor to adenocarcinoma. In addition to esophagectomy, multiple ablative endoscopic techniques have evolved for the management of this condition. As a surgical alternative to esophagectomy, we describe for the first time a new option in the treatment of high-grade dysplasia. MATERIALS AND METHODS: Two patients with a history of gastroesophageal reflux disease (GERD) underwent upper gastrointestinal endoscopy which demonstrated high-grade dysplasia of the distal esophagus. The first patient had a short segment (0.5-1.0 cm), and the second patient had a longer (2 cm) segment of dysplasia. The patient is placed in the modified lithotomy position. Five trocars are placed as if to perform a fundoplication. A complete circumferential mobilization of the esophagus is performed. The short gastric vessels are divided with the harmonic scalpel, to free up the fundus of the stomach. An anterior horizontal gastrotomy is performed three to four centimeters below the gastroesophageal junction. A solution of epinephrine and normal saline (1:100,000) is injected into the mucosa at the Z-line and, utilizing specially designed hook electrocautery, the mucosa is incised circumferentially around a lighted bougie. Using blunt dissection the mucosa is undermined, elevated, and excised in four quadrants. Three centimeters of the distal esophageal mucosa are resected. The gastrotomy is then closed using a linear stapler, and a 360 degrees fundoplication is performed around a 50 Fr bougie. RESULTS: High-grade dysplasia was identified in the specimens from both patients; however, neither patient was found to have carcinoma in situ or invasive esophageal cancer. Our first patient has been followed for twenty months, the second for ten months. Both patients underwent routine upper gastrointestinal endoscopy for surveillance of the healing process. At eight months, the mucosa of the first patient showed complete regeneration of squamous epithelium. Our most recent patient appears to be progressing without complications and has also demonstrated normal squamous epithelium at ten months postoperatively, without changes of Barrett's epithelium. CONCLUSION: The technique of laparoscopic transgastric esophageal mucosal resection is feasible and may be proven to be an alternative to esophagectomy for the management of high-grade dysplasia.

Adult↗
PubMed2003

Wound splinting regulates granulation tissue survival.

PURPOSE: Fibroblast survival within an in vitro collagen matrix is dependent on matrix anchorage to a rigid substratum. The purpose of this study was to determine whether granulation tissue survival in vivo also is dependent on matrix anchorage. We hypothesized that splinting an excisional wound (i.e., anchoring the wound edges) would promote granulation tissue survival and that desplinting a splinted wound would produce granulation tissue apoptosis. METHODS: Eighteen Wistar rats (3 months, 350 g) underwent excisional wounding (2 x 2 cm, dorsal skin) with immediate wound splinting (a metal template affixed with sutures) on day 0. On day 6, rats (n = 6 per group) underwent splint removal (desplinted), splint removal with circumferential incision of the wound edge (desplint/release), or no intervention (splinted); sacrifice of all animals was on day 7. Frozen sections of granulation tissue were stained with TUNEL or H and E; data were analyzed with ANOVA and the unpaired t test. RESULTS: The cross-sectional and surface area of the desplinted and desplint/release granulation tissue both decreased compared to the splinted granulation tissue (*P < 0.05). The nuclear density of the desplint/release granulation tissue was 25% less compared to the splinted granulation tissue (*P < 0.05). The desplinted and desplint/release apoptotic rates were twice and >10x greater than the splinted apoptotic rate, respectively (*P < 0.05). CONCLUSIONS: The rate of cell death in a splinted wound (an in vivo equivalent of an anchored FPCM) is minimal to nil, which is consistent with our hypothesis. Desplinting and releasing the wound edge of a previously splinted wound (the in vivo equivalent of a detached FPCM) results in granulation tissue regression and a large increase in apoptosis. Desplinting a wound alone results in changes somewhat intermediate to the splinted and desplint/release conditions. Loss of wound anchorage acutely promotes granulation tissue apoptosis.

Animals↗
PubMed2003

Selective use of esophageal manometry and 24-Hour pH monitoring before laparoscopic fundoplication.

BACKGROUND: Preoperative esophageal manometry and 24-hour pH monitoring commonly are used in preoperative evaluation of patients undergoing fundoplication. Here we review our experience with the selective preoperative workup of patients undergoing fundoplication to treat gastroesophageal reflux disease. STUDY DESIGN: A series of 628 consecutive antireflux procedures was reviewed. History and physical examination, upper endoscopy, and upper gastrointestinal videofluoroscopy were obtained preoperatively on all patients; the first 30 patients also underwent esophageal manometry and pH monitoring (routine evaluation group). Thereafter, pH monitoring only was performed for atypical reflux symptoms, and manometry only was performed for a history of dysphagia, odynophagia, or for abnormal motility on videofluoroscopy (selective evaluation group). All patients underwent a laparoscopic floppy Nissen fundoplication, and then endoscopy and fluoroscopy at 3 months and 12 months postoperatively. RESULTS: Eighty-five of the patients in the selective evaluation group (14%) required manometry, and 88 (15%) underwent pH monitoring. Eighteen of the 115 patients who underwent manometry (16%) had evidence of dysmotility. None of these 18 patients had increased dysphagia postoperatively; 8 of 18 reported improvement with swallowing. Five patients in the selective group (0.8%) had persistent postoperative dysphagia caused by technical error (four patients) or with no identifiable cause (one patient). The estimated charge or collection reduction with use of the selective evaluation was 1,253,100 US dollars or 395,000 US dollars, respectively. CONCLUSIONS: Selective use of manometry and pH monitoring was cost effective and safe in this series. Although esophageal manometry and 24-hour pH monitoring might be necessary with abnormal findings on videofluoroscopy or atypical symptoms, in our experience, their routine use is not essential in preoperative evaluation of patients undergoing fundoplication for gastroesophageal reflux disease.

Adolescent↗
PubMed2002

A prospective, randomized trial of laparoscopic polytetrafluoroethylene (PTFE) patch repair vs simple cruroplasty for large hiatal hernia.

HYPOTHESIS: Large hiatal hernias are prone to disruption, resulting in reherniation, when repaired with simple cruroplasty. The use of mesh may decrease the rate of reherniation in the laparoscopic repair of large hiatal hernias. DESIGN: Prospective, randomized controlled trial. SETTING: University-affiliated private hospital. PATIENTS: Seventy-two individuals undergoing laparoscopic Nissen fundoplication with a hernia defect greater or equal to 8 cm in diameter. INTERVENTION: Nissen fundoplication with posterior cruroplasty (n = 36) vs Nissen fundoplication with posterior cruroplasty and onlay of polytetrafluoroethylene (PTFE) mesh (n = 36). MAIN OUTCOME MEASURES: Recurrences, complications, hospital stay, operative time, and cost. RESULTS: Patients in both groups had similar hospital stays, but the PTFE group had a longer operative time. The cost of the repair was $960 +/- $70 more in the group with the prosthesis. Complications were minor and similar in both groups. There were 8 hernia recurrences (22%) in the primary repair group and none in the PTFE group (P<.006). CONCLUSION: The use of prosthetic reinforcement of cruroplasty in large hiatal hernias may prevent hernia recurrences.

Adult↗
PubMed2002

Granulation tissue regression induced by musculocutaneous advancement flap coverage.

BACKGROUND: Clinical experience suggests that granulation tissue may be inhibited by coverage with a musculocutaneous flap. We hypothesized that coverage of an open wound with a musculocutaneous flap would result in regression and apoptosis of the wound's granulation tissue. METHODS: In the first experiment, 32 rats underwent excisional wounding; 16 underwent musculocutaneous flap coverage of their granulation tissue on postwounding day 8, and then 16 rats (8 controls + 8 flaps) were killed on both postwounding days 10 and 12 (2 and 4 days after the flap procedure, respectively). In the second experiment, 18 rats were wounded, and on postwounding day 5 the rats underwent flap coverage (n = 6), wound edge release/mobilization (the first step of the flap procedure) without flap coverage (n = 6), or dressing change only (n = 6); all rats were killed on postwounding day 6 (24 hours after the secondary intervention). Apoptosis was quantified with the terminal deoxynucleotidyl transferase-mediated nick-end labeling assay. RESULTS: Placement of a musculocutaneous flap over an 8-day-old excisional wound in the first experiment increased the apoptotic rate in the granulation tissue from 0% to 1% (controls) to 5% to 10% at both 2 and 4 days after flap coverage (P <.05). Cell population density decreased 50% in the flap-covered granulation tissue compared with the controls (P <.05). In the second experiment, circumferential release of the granulation tissue resulted in an equivalent increase in granulation tissue apoptosis over controls compared to that induced by the full flap procedure. CONCLUSIONS: Coverage of established granulation tissue with a musculocutaneous flap resulted in histologic regression of the wound's granulation tissue after 2 to 4 days of flap coverage and induced at least a 5-fold increase in the apoptotic rate of the granulation tissue. Releasing the wound edge increased granulation tissue apoptosis to a level equivalent to that produced by the musculocutaneous flap procedure, suggesting that alteration of the wound's mechanical environment is responsible for the acute induction of apoptosis in this model.

Animals↗
PubMedDate not supplied

The fibroblast-populated collagen matrix as a model of wound healing: a review of the evidence.

The fibroblast-populated collagen matrix (FPCM) has been utilized as an in vitro model of wound healing for more than 2 decades. It offers a reasonable approximation of the healing wound during the phases of established granulation tissue and early scar. The gross and microscopic morphology of the FPCM and the healing wound are similar at analogous phases. The processes of proliferation, survival/apoptosis, protein synthesis, and contraction act in similar directions in these two models, and the response to exogenous agents also is consistent between them. If its limitations are respected, then the FPCM can be used as a model of the healing wound.

Animals↗
PubMedDate not supplied

Wound matrix attachment regulates actin content and organization in cells of the granulation tissue.

Actin cytoskeletal polymerization is associated with a pro-proliferative, pro-survival state. We hypothesized that the actin polymerization of wound cells is increased in the presence of wound matrix attachment and is decreased after disruption of this attachment. Musculocutaneous flap and wound splinting models were used to investigate the effect of wound matrix attachment on the actin cytoskeleton. Disruption of wound matrix attachment was accomplished by incision of the wound matrix/dermis interface (wound matrix release) and/or desplinting. Polymerized actin was assayed with phalloidin labeling of wound specimens 24 hours after disruption of attachment and a method to quantify the content and organization of polymerized actin in granulation tissue was used. Disruption of wound matrix attachment decreased the content of polymerized actin, the actin staining intensity, and the actin fiber organization in the granulation tissue of both the flap and splint models. Disruption of wound matrix attachment decreased actin polymerization and fiber organization in the granulation tissue. Our data support the concept that the state of wound matrix attachment regulates the actin cytoskeleton of wound cells.

Actins↗
PubMedDate not supplied

Robotically assisted endoscopic ovarian transposition.

BACKGROUND: Ovarian transposition is the anatomical relocation of the ovaries from the pelvis to the abdomen. Transposition is beneficial in women who are to undergo pelvic radiation, because it allows maintenance of ovarian function and preservation of assisted reproductive capacity. METHODS: The da Vinci surgical system (Intuitive Surgical, Mountainview, CA, USA) was used to perform an endoscopic ovarian transposition. The ovaries were mobilized on their respective infundibulopelvic ligaments and sutured to the ipsilateral pericolic gutters. RESULTS: A series, of laboratory sessions using the da Vinci system was completed at our institution's training facility. Surgical experience included cadaveric pelvic dissection and abdominopelvic procedures on anesthetized porcine models. Additional didactic and laboratory training, including a certification examination, was obtained from Intuitive Surgical, Inc. The first clinical case of robotically assisted endoscopic ovarian transposition was performed. CONCLUSIONS: Robotically assisted endoscopy was successfully used for ovarian transposition.

Adult↗
PubMedDate not supplied

Postoperative gastrointestinal complaints after laparoscopic Nissen fundoplication.

OBJECTIVES: Approximately 80% of patients complain of various symptoms immediately after laparoscopic Nissen fundoplication. These symptoms typically are treated medically without an extensive evaluation to identify the cause. We reviewed our experience of laparoscopic Nissen fundoplication to determine the course of postoperative symptomatology in our patient population, and present a rational approach to this problem. METHODS: Over a 10-year period, 628 patients underwent primary laparoscopic Nissen fundoplication for gastroesophageal reflux disease; patients were evaluated with a standard set of questions for postoperative gastrointestinal complaints. Three- and 6-month follow-up data were compared by using the chi square test. RESULTS: One-year follow-up data were available for 615 patients (98%). All of these patients had symptoms during the first 3 postoperative months. Early satiety (88%), bloating/flatulence (64%), and dysphagia (34%) were the most common; however, 94% of patients had resolution of their symptoms by the 1-year follow-up visit, and most had resolved after 3 months. Patients with persistent reflux or dysphagia after 3 months typically had an anatomic failure of the operation. CONCLUSIONS: Most patients who have undergone laparoscopic Nissen fundoplication for gastroesophageal reflux disease will have gastrointestinal complaints during the initial 3 postoperative months. Nearly all of these patients will have resolved their symptomatology after 3 months. Those with persistent symptoms after 3 months warrant evaluation for operative failure.

Follow-Up Studies↗