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Biomedical subjects

M Spira

Publications and source records attributed to M Spira.

At least 19 recordsLinked to original sources
PubMed2001

Higgs radiation off top quarks at the Tevatron and the LHC.

Higgs bosons can be searched for in the channels pp macro/pp-->tt macro H + X at the Fermilab Tevatron and the Cern Large Hadron Collider (LHC). We have calculated the QCD corrections to these processes in the standard model at next-to-leading order. The higher-order corrections reduce the renormalization and factorization scale dependence considerably and stabilize the theoretical predictions for the cross sections. At the central scale mu = (2m(t)+M(H))/2 the properly defined K factors are slightly below unity for the Tevatron (K approximately 0.8) and slightly above unity for the LHC (K approximately 1.2).

Journal Article↗
PubMed2000

Increased free fat-graft survival with the long-term, local delivery of insulin, insulin-like growth factor-I, and basic fibroblast growth factor by PLGA/PEG microspheres.

The present investigation evaluates the effects of long-term, local delivery of insulin, insulin-like growth factor-1 (IGF-1), and basic fibroblast growth factor (bFGF) on fat-graft survival using a poly (lactic-co-glycolic-acid)-polyethylene glycol (PLGA/PEG) microsphere delivery system. Twelve-micrometer PLGA/PEG microspheres incorporated separately with insulin, IGF-1, and bFGF were manufactured using a double-emulsion solvent-extraction technique. Inguinal fat from Sprague Dawley rats was harvested, diced, washed, and mixed with (1) insulin microspheres, (2) insulin-like growth factor-1 microspheres, (3) basic fibroblast growth factor microspheres, (4) a combination of the insulin and IGF-1 microspheres, and (5) a combination of insulin, IGF-1, and bFGF microspheres. The treated fat grafts were implanted autologously into subdermal pockets in six animals for each group. Animals receiving untreated fat grafts and fat grafts treated with blank microspheres constituted two external control groups (six animals per external control group). At 12 weeks, all fat-graft groups were compared on the basis of weight maintenance and a histomorphometric analysis of adipocyte area percentage, indices of volume retention and cell composition, respectively. Weight maintenance was defined as the final graft weight as a percent of the implanted graft weight. All growth factor treatments significantly increased fat-graft weight maintenance objectively, and volume maintenance grossly, in comparison with the untreated and blank microsphere-treated controls. Treatment with insulin and IGF-1, alone or in combination, was found to increase the adipocyte area percentage in comparison with fat grafts treated with bFGF alone or in combination with other growth factors. In conclusion, the findings of this study indicate that long-term, local delivery of growth factors with PLGA/PEG microspheres has the potential to increase fat-graft survival rates. Further, the type of growth factor delivered may influence the cellular/stromal composition of the grafted tissue.

Adipose Tissue↗
PubMed2000

De novo adipose tissue generation through long-term, local delivery of insulin and insulin-like growth factor-1 by PLGA/PEG microspheres in an in vivo rat model: a novel concept and capability.

This study was undertaken to characterize the duration of long-term growth factor delivery by poly(lactic-co-glycolic-acid)-polyethylene glycol (PLGA/PEG) microspheres and to evaluate the potential of long-term delivery of insulin and insulin-like growth factor-1 (IGF-1) for the de novo generation of adipose tissue in vivo. PLGA/PEG microspheres containing insulin and IGF-1, separately, were produced by a double-emulsion solvent-extraction technique. In the first phase of the experiment, the in vitro release kinetics of the microspheres were evaluated for the optical density and polyacrylamide gel electrophoresis of solutions incubated with insulin-containing microspheres for four different periods of time (n = 1). The finding of increased concentrations of soluble insulin with increased incubation time confirmed continual protein release. In the second stage of the experiment, 16 rats were divided equally into four study groups (insulin, IGF-1, insulin + IGF-1, and blank microspheres) (n = 4). Insulin and IGF-1 containing microspheres were administered directly to the deep muscular fascia of the rat abdominal wall to evaluate the potential for de novo adipose tissue generation via adipogenic differentiation from native nonadipocyte cell pools in vivo. Animals treated with blank microspheres served as an external control group. At the 4-week harvest period, multiple ectopic islands of adipose tissue were observed on the abdominal wall of the animals treated with insulin, IGF-1, and insulin + IGF-1 microspheres. Such islands were not seen in the blank microsphere group. Hematoxylin and eosin-stained sections of the growth factor groups demonstrated mature adipocytes interspersed with fibrous tissue superficial to the abdominal wall musculature and continuous with the fascia. Oil-Red-O stained sections demonstrated that these cells contained lipid. Computer-aided image analysis of histologic sections confirmed that there were statistically significant increases in the amount of "ectopic" adipose neotissue developed on the abdominal wall of animals treated with growth factor microspheres. In conclusion, this study confirms the long-term release of proteins from PLGA/PEG microspheres up to 4 weeks and demonstrates the potential of long-term local insulin and IGF-1 to induce adipogenic differentiation to mature lipid-containing adipocytes from nonadipocyte cell pools in vivo at 4 weeks.

Abdominal Muscles↗
PubMed2000

Augmentation of adipofascial flaps using the long-term local delivery of insulin and insulin-like growth factor-1.

The adipofascial flaps currently described in the literature frequently lack the volume requirements for reconstructive goals. In this study, the authors examined the use of long-term local delivery of insulin and insulin-like growth factor-1 (IGF-1) using polylactic-coglycolic acid/polyethylene glycol (PLGA/PEG) microspheres to augment inguinal adipofascial flaps based on the inferior epigastric vessels in the rat. Two flap models, the island flap and the limited dissection flap, were used to demonstrate simultaneous treatment and pretreatment modalities, respectively. Experimental groups received 12.5 mg of insulin microspheres (carrying 1 IU of insulin) plus 12.5 mg of IGF-1 microspheres (carrying 2.5 microg of IGF-1). A group undergoing the operation only (no treatment with microspheres) and a group treated with blank microspheres (no growth factor) served as external controls for the surgical procedure and the drug delivery device, respectively. In all groups (n = 5 animals in each), the contralateral flap served as an internal control. Upon harvest on postoperative day 28, the insulin and IGF-1-treated flaps in both models weighed statistically more than the internal control flaps and the two external control flaps. Likewise, on gross inspection, the adipogenic growth factor-treated flaps had greater volumes than the internal control flap groups and both of the external control flap groups (operation only and blank microspheres). Other intergroup comparisons suggested the absence of a systemic insulin and IGF-1 effect on adiposity. A histomorphometric analysis suggested (1) that insulin and IGF-1 treatment does not alter flap cell composition and (2) that flap augmentation is secondary to the stimulation of cell proliferation and adipocytic differentiation rather than the hypertrophy of mature adipocytes. Further evidence in favor of cell proliferation and differentiation was the discovery of nonanatomic, ectopic fat islands on the pedicle sheath of the treated flaps and the lack of variation in cell size distribution among groups. The authors concluded that the long-term local delivery of insulin and IGF-1 with PLGA/PEG microspheres is an effective method of adipofascial flap augmentation; this method increases the number of mature adipocytes rather than increasing the size of preexisting cells.

Adipose Tissue↗
PubMed1999

Otoplasty: what I do now--a 30-year perspective.

The author presents his otoplasty technique, a variation on Mustardé's original procedure, which he has used for more than 30 years in more than 200 otoplasties. Timing, indications, and photographic documentation are discussed, and the operative procedure, including the preoperative work-up and anesthesia, is described in step-by-step detail. Postoperative care and early and late complications, from infection to the dissatisfied patient, are discussed extensively.

Ear, External↗
PubMed1998

Algorithms for the treatment of cleft lip and palate.

Developing standardized outcomes and algorithms of treatment is a constantly evolving task. This article examines four variables in this process: cleft type, operative technique, surgical experience, and timing. Input from international cleft lip and palate programs regarding techniques and treatment modalities provide a dynamic tool for assessment and the development of guidelines in the treatment of the cleft lip and palate patient.

Adolescent↗
PubMed1997

A comparative study of gut suture, human amnion collagen, bovine skin collagen and Vicryl suture implants in rats.

This study compares the persistence and histological characteristics of gut suture with those of human amnion collagen, bovine collagen, and Vicryl suture implants in rats. Gut suture and human amnion collagen more resembled living tissue than did bovine collagen and were characterized by their cellularity and the presence of numerous capillaries. The Vicryl suture implants were quickly absorbed. Picrosirius polarization revealed the synthesis of host collagen by rat fibroblasts which immigrated into the gut suture and human amnion collagen implants. The authors suggest the potential of gut suture as a soft tissue substitute to improve linear skin contour deficits.

Absorbable Implants↗
PubMed1997

Augmentation of random-flap survival by implantation of vascularized fascia allografts and temporary immunosuppression: implications for flap fabrication.

The purpose of this study was to explore the possible use of an allogeneic vascular source for flap fabrication. Epigastric fascia with its superficial epigastric vessel pedicle was harvested from the donor rat and microsurgically revascularized in the recipient rat across a major histocompatibility barrier. ACI rats (Rtl-a) served as donors, and Lewis rats (Rtl-1) served as recipients. The recipient rat was immunosuppressed with a daily dose of 2 mg/kg cyclosporin A plus 5 mg/kg prednisone for 4 weeks. Three experiments were performed for skin, muscle, and bone studies. In experiment 1 (20 Lewis rats), placement of the allotransplanted fascia underneath the epigastric skin significantly improved the survival of a random epigastric skin flap raised 3 weeks later (7.35 +/- 0.65 cm2 versus 6.09 +/- 0.90 cm2, p < 0.05). Immunosuppression was discontinued 10 days after flap elevation with no observable additional skin necrosis. In experiment 2 (13 Lewis rats) and experiment 3 (14 Lewis rats), segments of isogeneic muscle and bone were grafted successfully on the allotransplanted fascia, respectively. The survival of these grafts was confirmed by metabolic bone activity, bone labeling, microangiography, and histologic studies and further confirmed 2 weeks after cessation of immunosuppression. An allotransplanted fascia as a vascular source proved in this model its capability to improve the survival of a random skin flap and to accept a free bone or muscle graft with temporary immunosuppression. These findings hold promise for possible use of an allogeneic vascular source in flap fabrication.

Animals↗
PubMed1996

The French-line abdominoplasty.

This study presents 50 consecutive cases of abdominoplasty utilizing the authors' French-line method. This technique incorporates the basic principles of more traditional abdominoplasty procedures with significant modifications that allow for more aggressive plication of the fascia for accentuation of the waistline and relatively short oblique lateral incisions that are easily concealed within the French-cut one-piece bathing suit or reasonably modest bikini. The technique lends itself to adjunctive intra-abdominal procedures such as cholecystectomy or hysterectomy and is a safe method of abdominal reconstruction following transverse rectus abdominis musculocutaneous flap breast reconstruction. Complications are no more frequent than with "traditional" techniques. The only absolute contraindication is the presence of chronic obstructive pulmonary disease; relative contraindications are the same as for other abdominoplasty procedures.

Abdomen↗
PubMed1995

Electrophysiological characterization of a novel conotoxin that blocks molluscan sodium channels.

A novel peptide toxin, PnIVB, isolated from the venom of Conus pennaceus blocks voltage-gated sodium current in Aplysia neurons. Complete blockade is obtained at a PnIVB concentration of 80 +/- 2.2 nM and 50% blockade at 16 +/- 0.86 nM. The potency of PnIVB in blocking Aplysia sodium current is four orders of magnitude larger than that of tetrodotoxin. The toxin has no paralytic activity when injected into fish. The rapid blockade of sodium current by PnIVB is not associated with a change in the activation or inactivation kinetics of the current, or with the reversal potential. Sodium current blockade is reversible after a 30 min wash with 50 times the bath volume. The novel conotoxin PnIVB can be used as a powerful tool for mollusc neurobiological research and as a molecular probe to explore the structure-function relations of voltage-gated sodium channel subtypes.

Action Potentials↗
PubMed1995

Primary soft-tissue nocardiosis.

A 20-year-old Latin American man presented with a 4 1/2-year history of a left infrapatellar mass with multiple draining sinuses. Multiple courses of oral antibiotics before referral were unsuccessful in eradicating the mass. Microscopic examination of material obtained by punch, core needle, and incisional biopsies demonstrated nonspecific acute and chronic inflammation. Surgical resection demonstrated an inflammatory mass with multiple abscess cavities. Intraoperative cultures grew Nocardia asteroides. The infection was successfully treated with a prolonged course of a trimethoprim-sulfamethoxazole.

Adult↗
PubMed1995

Prefabricated flaps: experimental and clinical review.

Prefabricated flaps are a useful tool for the reconstructive surgeon and present a number of advantages: 1. Specific preferred tissue composites, regardless of their native vascular origin, can be transferred as free or pedicled flaps. 2. Larger flaps of specialized tissue may be transferred safely. 3. Donor-site morbidity is reduced. 4. The functional outcome for the patients may be more satisfactory. The various methods of flap prefabrication include vascular induction through stage transfer; pretransfer delay, expansion, and grafting; the use of alloplastic materials; and tissue bioengineering. We have reviewed both the experimental and clinical research on flap prefabrication, describing the theory, technique, and advantages of each method.

Animals↗