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Biomedical subjects

R E Hayden

Publications and source records attributed to R E Hayden.

At least 55 records · Page 3Linked to original sources
PubMed1988

Improved survival of acute skin flaps with amino acids as free radical scavengers.

Oxygen-derived free radicals have been shown to be important mediators in ischemia-reperfusion injury to skin flaps. Agents that reduce the level of these free radicals have been used to improve flap survival in model systems. An in vitro study of the interactions between amino acids and hydroxyl radicals by electron spin resonance spectroscopy suggests an intrinsic radical scavenging activity of certain amino acids. The ability of these amino acids to improve acute axial-random skin flap survival was examined in a rat model. Cysteine, methionine, proline, hydroxyproline, histidine, and phenylalanine, given intravenously, significantly improved flap survival over saline controls; alanine gave an intermediate result, while aspartic acid showed no improvement. The in vitro data were generally a good predictor of free radical scavenging ability as manifested by improved flap survival in vivo. Biochemical mechanisms and clinical applications are described.

Amino Acids↗
PubMed1988

The effect of hydroxyl radical scavenging on acute axial-random skin flap survival.

Dimethyl thiourea (DMTU), a known hydroxyl radical scavenger, was tested for its ability to improve survival in acute island skin flaps. Rats receiving 500 mg/kg DMTU 1 hour after flap elevation showed a 23.5% improved survival over saline controls. The role of the hydroxyl radical in ischemia/reperfusion injury, and its proposed mechanism, is discussed.

Animals↗
PubMed1987

Neck evaluation with barium-enhanced radiographs and CT scans after supraglottic subtotal laryngectomy.

Supraglottic subtotal laryngectomy (SSL) is a radical, yet voice-conserving, surgical procedure commonly performed for carcinoma of the supraglottic larynx. The pharyngograms and computed tomographic (CT) scans of 35 patients obtained after SSL were evaluated retrospectively. These examinations reliably demonstrated the changes in anatomy caused by removal of the epiglottis, aryepiglottic folds, and false vocal cords. Fourteen patients had documented recurrence of cancer; five mucosal, nine extramucosal. Three of five macroscopic mucosal recurrences in the larynx/pharynx were detected on the barium pharyngograms; the two mucosal lesions not seen were in the base of the tongue and tonsillar fossa. CT enabled detection of five of five recurrences and was superior to pharyngography in demonstrating the soft-tissue extent of disease. CT findings mimicking recurrence were seen in two patients: one with diffuse histiocytic lymphoma; the second, with benign hyperkeratosis. Barium and CT examinations are useful adjuncts to the clinical examination in detecting recurrent squamous cell carcinoma in patients following SSL.

Adult↗
PubMed1987

The effect of glutathione and vitamins A, C, and E on acute skin flap survival.

Vitamins A, C, and E act as antioxidants and as free radical scavengers in biological systems. Glutathione is involved in several reactions in vitamin metabolism and also plays an important role in cell membrane protection against lipid peroxidation by free radicals. We sought to use these natural defense mechanisms against oxygen free radicals formed during reperfusion of ischemic skin flaps. An acute axial random skin flap model was utilized in the rat. Vitamins or glutathione were administered by oral gastric tube or intravenously in the perioperative period, and survival of the flap was measured at 1 week. Glutathione, beta-carotene, ascorbic acid and alpha-D-tocopherol showed mean flap survival of 84% to 89%, each of which was significantly improved over saline controls (67% p less than .0005). The mechanisms and biochemistry of these vitamins, and their interactions with other vitamins and with glutathione, are discussed, along with clinical implications of free radical scavenging and skin flap survival.

Animals↗
PubMed1986

Neck neoplasms: MR imaging. Part I. Initial evaluation.

Untreated neoplasms of the neck (tumors of the oropharynx, supraglottic area, carotid body, and thyroid, in addition to malignant lymphadenopathy) were evaluated in 23 patients with magnetic resonance (MR) imaging. The results were compared with computed tomographic (CT) scans in 20 patients. Contrast between tumor and fat was best on relatively T1-weighted images (500/30-35 [TR msec/TE msec]), whereas separation of tumor and muscle was best with relatively T2-weighted pulse sequences (1,500/90). Balanced images (1,500/30-35) provided best overall image quality and best demonstrated vascular anatomy. MR imaging was usually superior to CT in showing the relationship of tumor mass to muscle. MR imaging and contrast material-enhanced CT were equivalent in most patients in defining vascular anatomy, but MR imaging was superior when intravenous contrast material was not administered. However, CT was more helpful in showing bone and cartilage anatomy, and in some patients CT also was better in showing airway abnormalities. Despite these limitations, MR imaging is a promising imaging technique for studying neoplasms of the neck.

Adult↗
PubMed1986

Neck neoplasms: MR imaging. Part II. Posttreatment evaluation.

Thirty-three patients who had undergone prior surgery and/or radiation therapy for malignant neoplasms of the neck were studied with magnetic resonance (MR) imaging. Twenty-seven of these patients were also evaluated with computed tomography (CT). Ten patients were healthy posttreatment volunteers, and 23 had documented tumor recurrence. MR images better demonstrated normal muscular landmarks, especially in patients with obliterated fat planes. Areas of posttreatment fibrosis or scarring were low in signal intensity with all MR pulse sequences. However, in three patients, high signal intensity from postradiation edema of the supraglottic area mimicked neoplasm. In patients with recurrent tumor, MR imaging was superior to CT in defining the relationship of tumor and muscle and in demonstrating vascular anatomy when no intravenous contrast material was given during the CT examination. In two patients tumor and fibrosis were separated on MR images because of signal intensity differences. CT scans, however, showed adjacent bone and cartilage anatomy better. Our data indicate that an MR examination may be helpful in patients in whom CT is indeterminate either because of anatomical distortion or suboptimal demonstration of vascular anatomy.

Head and Neck Neoplasms↗
PubMed1984

The neck after total laryngectomy: CT study.

Computed tomographic scans in 23 patients who had undergone total laryngectomy were analyzed retrospectively to determine normal postoperative appearance and to evaluate the role of CT in assessing recurrent neoplasm. Nine patients without clinical evidence of recurrence illustrated the normal postoperative changes: a round or ovoid neopharynx connecting the base of the tongue with the cervical esophagus and intact fat planes surrounding the neopharynx, neurovascular bundles, and sternocleidomastoid muscles. In the 12 patients with recurrent neoplasm, the CT manifestations included masses involving the internal jugular lymph node chain (adjacent to the neopharynx, neurovascular bundles, or sternocleidomastoid muscles), tracheostomy site, or paratracheal region. Recurrence was mimicked on CT in two patients, one with an abscess and one with metastases from an adenocarcinoma of unknown primary site. In eight patients, a distended neopharyngeal lumen correlated with benign or malignant stricture. CT supplemented physical examination and indirect mirror examination, providing data regarding presence and extent of recurrent tumor and aiding in planning the mode and scope of therapy.

Aged↗
PubMed1984

An unusual case of airway obstruction.

An unusual case of airway obstruction is presented. A 56 year old woman was admitted with stridor. She gave a history of intermittent upper airway obstruction of four years' duration. Examination revealed gross hypertrophy of the lingual tonsils extending to involve the valleculae and the entire epiglottis. Histological examination confirmed the presence of normal lymphoid tissue. The patient underwent epiglottectomy and cryosurgery to the lingual tonsils with complete resolution of symptoms. A review of the literature is presented and the investigative and treatment modalities are discussed.

Airway Obstruction↗
PubMed1971

The distribution of cutaneous receptors in the rabbit's hind limb and differential electrical stimulation of their axons.

1. The receptive field properties and conduction velocities of single dorsal root axons, activated from the sural and cutaneous branches of the posterior tibial (medial plantar) nerves, were examined in anaesthetized rabbits.2. The sural nerve sample included all types of units previously recorded from the saphenous nerve (Brown & Iggo, 1967). In particular it was shown that electrical stimulation of the sural nerve at strengths up to 1.3T produced a volley of impulses in a pure population of slowly adapting units (Type I units).3. The medial plantar sample showed an absence of Type I slowly adapting units and Type T hair follicle units. Corresponding to this there were no touch corpuscles or tylotrich hairs in the skin of the hind foot and the fastest medial plantar axons conducted at 60-70 m/sec as opposed to 80-85 m/sec for the sural nerve. Stimulation of the medial plantar nerve at stimulus strengths close to threshold produced a volley of impulses in a nearly pure population of Type G hair follicle units.

Animals↗
PubMedDate not supplied

Real time multivariable laser Doppler analysis of arterial and venous compromise.

Laser Doppler perfusion monitoring was used to assess microcirculatory blood flow, volume, and velocity before and after total arterial or total venous occlusion in 18 buttock island flaps. Critical analysis of these three laser Doppler perfusion values was found to be useful in differentiating adequately perfused skin from inadequately perfused skin, as well as in distinguishing arterial from venous compromise. Multivariable laser Doppler analysis demonstrated that arterial occlusion produced a more rapid and greater percentage decrease in flow and volume values than did venous occlusion. Arterial occlusion produced an insignificant percentage change in velocity values, whereas venous occlusion produced a substantial percentage decrease in velocity values. The substantial intrasubject and intersubject variability in absolute laser Doppler perfusion values suggests that normalized or percentage change values are more revealing than absolute values, although they require the acquisition of reliable baseline data.

Animals↗
PubMedDate not supplied

Prevention of cutaneous phototoxicity in photodynamic therapy.

Photodynamic therapy using hematoporphyrin derivative (Hpd), or its semipurified form, dihematoporphyrin ether (DHE), in combination with light, has proven effective in the treatment of several types of neoplasms including squamous cell carcinoma. A major disadvantage of this therapy is the long-term retention of these drugs in skin, which may result in cutaneous phototoxicity for weeks after treatment. Singlet oxygen has been identified as the primary cytotoxic product in the reaction of Hpd and light in vitro. This study demonstrates the protective effect in vivo of the singlet oxygen scavengers 1,3 diphenylisobenzofuran and L-tryptophan on the skin of young rats exposed to light after receiving DHE.

Animals↗
PubMedDate not supplied

Verdins in photodynamic therapy of squamous cell carcinoma.

Photodynamic therapy (PDT) is a relatively new treatment modality employing photoactive drugs in combination with light to destroy malignant tissue. Porphyrins (ie, hematoporphyrin derivative and dihematoporphyrin ether) have been the most thoroughly investigated photoactive drugs. The primary limitation of the use of porphyrins in PDT is the shallow depth of effective tumor kill. Each photoactive drug is activated maximally by light of a particular wavelength, and longer wavelengths are able to penetrate tissue to a greater depth. Hematoporphyrin derivative and its semipurified form, dihematoporphyrin ether, are activated by light at 630 nm, which penetrates tissue to a maximum of 8 mm. The search for more effective photosensitizers is under way. Verdins, photoactive compounds in the class of chlorins, have recently been synthesized with activating wavelengths near 700 nm. This longer activation wavelength should theoretically allow a greater depth of tumor kill. Verdins have been shown to be effective photosensitizers in a urothelial carcinoma model in rats. In this study, we investigated the effectiveness of these compounds on squamous cell carcinoma in the hamster cheek pouch model.

Animals↗
PubMedDate not supplied

Free flap reconstruction of recalcitrant hypopharyngeal stricture.

A case report is presented of the use of a jejunal microvascular free flap for the reconstruction of a hypopharyngeal stricture caused by caustic ingestion. Although the airway was reestablished, there was aspiration and diplophonia. This case is discussed as an example of an effective treatment of a difficult problem, but one posing secondary problems arising from the use of jejunum.

Adolescent↗
PubMedDate not supplied

Recurrent respiratory papillomatosis: progression to invasion and malignancy.

Recurrent respiratory papillomatosis is the most common benign tumor of the larynx in children. The disease often runs a protracted course necessitating multiple endolaryngeal procedures. Rarely, these papillomata become invasive and/or undergo malignant degeneration. A case report of malignant degeneration and widespread invasion in long-standing laryngeal papillomatosis and a review of the relevant literature are presented.

Adult↗
PubMedDate not supplied

Cutaneous photoprotection using a hydroxyl radical scavenger in photodynamic therapy.

Photodynamic therapy (PDT) is emerging as an effective therapy for a variety of malignant diseases, including head and neck cancer. Prolonged cutaneous photosensitivity following therapy, however, remains the most significant side effect. The biochemical mechanism of this sensitivity, and indeed of the tumoricidal effect of PDT, is uncertain, but is believed to involve formation of singlet oxygen and possibly other oxygen-derived free radicals. This laboratory recently reported that a singlet oxygen scavenger, diphenylisobenzofuran (DPIBF), afforded cutaneous photoprotection to 67% of animals treated with PDT. Those results, the first from an in vivo study, supported the idea that singlet oxygen plays a significant role in PDT and its associated toxicity. They also, however, suggested that it is not the sole intermediate. The current study looks at the photoprotective effects of the hydroxyl radical scavenger dimethyl thiourea, alone and in conjunction with DPIBF. Our results strongly support a role for the hydroxyl radical in producing the cutaneous phototoxicity associated with PDT.

Animals↗