Changes in cochlear antioxidant enzyme activity after sound conditioning and noise exposure in the chinchilla.

Exposure to low level noise prior to a high level exposure reduces noise-induced hearing loss in mammals. This phenomenon is known as sound conditioning or 'toughening'. Reactive oxygen intermediates have been implicated in noise-induced cochlear damage. To evaluate if in situ antioxidant processes may play a role in the toughening phenomenon initiated by low level noise exposure we analyzed glutathione reductase, gamma-glutamyl cysteine synthetase, and catalase in stria vascularis and organ of Corti fractions from cochleae of chinchillas exposed to a sound conditioning paradigm. Chinchillas were either (A) kept in quiet cages (control), (B) exposed to conditioning noise of a 0.5 kHz octave band (90 dB for 6 h/day for 10 days), (C) exposed to high level noise (105 dB for 4 h) or (D) exposed to conditioning noise (B) followed by exposure to the higher level noise (C). Each of the noise exposure conditions (B, C, D) induced changes in the levels of these three antioxidant enzymes. The enzyme-specific activity data for the four subject groups support the following two hypotheses. (1) Changes in glutathione reductase, gamma-glutamyl cysteine synthetase, and catalase play a role in attenuating hearing loss associated with sound conditioning followed by high level noise. (2) Hair cells in the organ of Corti are protected from noise-induced damage by increasing stria vascularis levels of catalase, a hydrogen peroxide scavenging enzyme, and of enzymes involved in maintaining glutathione in the reduced state. The model formulated by these hypotheses suggests that agents that protect or augment the glutathione system in the cochlea may be protective against noise-induced hearing loss.

Autologous collagen dispersion (Autologen) as a dermal filler: clinical observations and histologic findings.

OBJECTIVE: To assess the histologic behavior and clinical efficacy of autologous collagen dispersion (Autologen) in augmenting human dermis. SUBJECTS: Adult patients of the Facial Plastic Surgery Clinic at The New York Eye and Ear Infirmary who were undergoing facial aesthetic surgery with skin excision. METHODS: Five patients were injected intradermally with Autologen in one postauricular area and bovine cross-linked collagen (Zyplast) on the contralateral side. Patients were examined clinically for signs of infection, skin necrosis, or implant rejection/allergy 2, 4, and 12 weeks postinjection. Impressions and photographs of all implant sites were taken at all follow-up visits. Biopsy specimens of each implant were taken 4 and 12 weeks after injection and examined histologically for signs of integration, rejection, and resorption. RESULTS: All implants were well tolerated. No identifiable differences were noted in the clinical persistence of Zyplast vs Autologen. Histologically, there was more variability in the degree of fibroblast infiltration of Autologen vs Zyplast deposits. CONCLUSIONS: Our trial suggests that autologous collagen dispersion may represent a viable alternative to bovine collagen. Clinical persistence and histologic behavior of Autologen appear to be at least as favorable as those of Zyplast, and Autologen obviates the need for allergy testing and eliminates the possibility of disease transmission. Arch Facial Plast Surg. 2000;2:48-52

Evaluation of acellular dermal graft in sheet (AlloDerm) and injectable (micronized AlloDerm) forms for soft tissue augmentation. Clinical observations and histological analysis.

OBJECTIVES: To evaluate the histological and clinical properties of (1) subdermally implanted acellular dermal graft (AlloDerm) sheets vs intradermal bovine collagen and (2) subdermally or intradermally injected micronized AlloDerm vs type I bovine collagen cross-linked with glutaraldehyde (Zyplast). PATIENTS: Twenty-five adult patients testing nonallergic to bovine collagen. METHODS: (1) Stacked disks of AlloDerm were implanted subdermally behind one ear, and bovine collagen was injected intradermally behind the other. The soft tissue augmentation caused by the implants was measured by digital photography at 1, 4, and 12 weeks, and biopsy specimens of each implant type were examined at 3 months after implantation. (2) Micronized AlloDerm was injected intradermally and subdermally in 2 different locations behind one ear, and bovine collagen was injected in the same manner behind the other. The soft tissue augmentation caused by the implants was measured by digital photography at the time of implantation and at 1 and 4 weeks after implantation. All implants were examined 1 month after implantation. RESULTS: All patients tolerated both implants well. (1) AlloDerm implants retained a higher percentage of the original implant volume than Zyplast at 1 and 3 months after implantation. Histologically, AlloDerm implants were extensively invaded by host fibroblasts without any foreign body reaction. (2) Intradermally injected micronized AlloDerm implants retained a higher percentage of the original implant volume at 1 month after implantation than intradermal Zyplast. Histologically, micronized AlloDerm implants were extensively invaded by host fibroblasts without any foreign body reaction. No significant differences were noted between subdermally injected micronized AlloDerm and Zyplast. CONCLUSIONS: The macroscopic and microscopic behavior of subdermally implanted AlloDerm sheets and subdermally and intradermally injected micronized AlloDerm was compared with intradermally injected Zyplast. AlloDerm sheet volume persisted to a significantly (P < .001) greater degree than bovine collagen during the first 3 months after placement. Clinically, intradermally injected micronized AlloDerm volume persisted to a significantly (P = .01, .04, and .01, respectively) greater degree than intradermal Zyplast or subdermal micronized AlloDerm or Zyplast. Histologically, micronized AlloDerm and AlloDerm are well tolerated at 1 and 3 months, respectively. Host tissue incorporation with fibroblast in-growth and collagen deposition is seen in both materials. AlloDerm and micronized AlloDerm hold promise for use in facial soft tissue augmentation.

Evaluation of acellular dermal graft (AlloDerm) sheet for soft tissue augmentation: a 1-year follow-up of clinical observations and histological findings.

OBJECTIVES: To evaluate and compare the long-term clinical persistence and histological appearance of subdermally implanted acellular dermal graft (AlloDerm) sheets and intradermal type I bovine collagen cross-linked with glutaraldehyde (Zyplast). PATIENTS: Ten adult patients (5 men and 5 women; average age, 46 years; age range, 37-59 years) not allergic to bovine collagen. METHODS: AlloDerm sheets were implanted surgically in a subdermal plane in one postauricular crease, and Zyplast was injected intradermally on the opposite side. AlloDerm and Zyplast implants were digitally photographed and their apparent volumes calculated at 1, 3, 6, 9, and 12 months after implantation. A specimen was removed at 3 and 12 months and examined histologically for collagen persistence, host tissue invasion, and inflammatory reaction. RESULTS: The apparent implant volume of the AlloDerm sheets decreased during the first 6 months and then stabilized over the next 6 months. By contrast, Zyplast was progressively absorbed, with complete loss of clinical effect by 6 months. Histological analysis of implanted AlloDerm sheets demonstrated progressive repopulation of the graft with minimal inflammation. CONCLUSIONS: AlloDerm sheets seem to provide stable soft tissue augmentation after an early period of resorption and are clearly superior to Zyplast injections for long-term, large-volume, soft tissue correction. Recommendations for clinical use include routine overcorrection, with subsequent augmentation delayed by at least 6 months.

[Evolution of pacing modes in patients with implanted pacemakers. Personal considerations on a case load of 171 patients]. / Evoluzione della modalità di stimolazione nei pazienti portatori di pace-maker. Considerazioni personali su una casistica di 171 casi.

In this study retrospectively analyse pacemaker-implantation activity carried out during the last 5 years at the Laboratory of Electrophysiology, affiliated with the Cattedra di Cardiologia of the University of Naples--II Ateneo. Evolution in pacing modes is considered with regard to the patient age, the underlying pathologies and the technical progress in the field. The study has been performed in our laboratory, which is fit up for electrophysiologic studies and implantation of either temporary or permanent pacemakers. Patients included in this study have been implanted in our laboratory either for urgency or for election. They have been retrospectively divided into two groups (age < 65 yrs, 129 patients, and age < 65 yrs, 42 patients); in addition the patients have been classified according to the pathology leading to the implantation: atrio-ventricular block (second degree or third degree), low frequency fibrillation, sick sinus syndrome and carotid sinus syndrome. 171 patients have been examined, of whom 129 > 65 yrs. and 42 < 65 yrs. As for the pacing indication, 54 were atrio-ventricular block (56.1%), 50 were sick sinus syndrome (31.6%), 20 low frequency fibrillation (11.7%), and 1 was carotid sinus syndrome (0.6%). The ratio between single- and dual-chamber pacemakers has been progressively changing: in 1987 we implanted 33 single-chamber and no dual-chamber pacemaker, compared to 7 single- and 23 dual-chamber pacemaker implanted in the last year. This trend is in good agreement with literature data.

Alloplastic implants for orbital wall reconstruction.

Nonabsorbable alloplastic implants for orbital wall reconstruction have been widely accepted by surgeons because of their ready availability, stability, and biocompatability. Many complications have arisen with this class of implants because the lack of host tissue integration allows for implant migration, implant extrusion, recurrent hemorrhage, and infection. Porous polyethylene implants provide a welcome alternative as they have the unique properly of supporting tissue ingrowth in vivo. Their semirigid structure provides structural stability when used around the orbit, and their malleability allows for easy contouring. This paper presents our surgical approach to reconstructing orbital defects with porous polyethylene implants, including orbital floor, and superior, medial, and lateral wall defects, and discusses the advantages/disadvantages of other nonabsorbable alloplasts.

Transconjunctival versus transcutaneous approach in upper and lower blepharoplasty.

In this article, we review the traditional transcutaneous upper lid blepharoplasty technique and contrast it to the newly described transconjunctival upper lid blepharoplasty technique that has limited indications. The technique and application of the skin-muscle flap transcutaneous lower lid blepharoplasty and the transconjunctival lower lid blepharoplasty are also discussed. We prefer the transconjunctival lower lid blepharoplasty as it circumvents the risk of lower eyelid retraction associated with the transcutaneous approach. We also discuss application of adjunctive procedures to the transconjunctival approach to enhance cosmetic results.

Nasal reconstruction using porous polyethylene implants.

Nasal reconstruction presents a significant challenge to the facial plastic surgeon. The dual goals of reconstruction are restoration of the desired aesthetic nasal contour and an improved nasal airway. Autologous cartilage and bone are considered optimal grafting material, but their supply is often limited and harvesting entails additional morbidity. Many synthetic materials have been introduced in nasal reconstruction, but high infection and extrusion rates limited their use. Porous high density polyethylene implants present an alternative to autologous material as they allow for fibrovascular ingrowth, leading to stability of the implant and decreased rates of infection. Herein we describe the use of porous high density polyethylene implants for reconstruction of the platyrrhine nose and in revision rhinoplasty. The use of preformed nasal-dorsal tip and alar batten implants are described, as well as the use of columellar strut and premaxillary plumper implants. We believe that porous high density polyethylene implants provide a safe, desirable alternative in functional and aesthetic nasal reconstruction.