Atomic motion in enzymatic reaction coordinates.

Atomic excursions of reactants in enzymatic catalytic sites can be estimated from high-resolution crystal structures of enzyme complexes with substrates, transition state analog inhibitors and products. Transition state structures, defined from kinetic isotope effect studies, are compared to crystallographic structures to validate the properties of the transition state analog. Atomic excursions in enzymatic catalytic sites can differ from those in solution and define the role of the enzymatic catalyst in directing atomic motion.

Adjuvant chemotherapy for high-risk squamous-cell carcinoma of the head and neck.

A prospective clinical trial was developed to evaluate efficacy, toxicity, and patient compliance to adjuvant chemotherapy following surgery and postoperative radiation therapy in patients with squamous-cell carcinoma of the head and neck with extracapsular spread of tumor in cervical metastases. Following postoperative radiation therapy, 18 courses of methotrexate (MTX) and 5-fluorouracil (5-FU) were administered over 6 months. Fifty patients were registered. A total of 771 doses were administered. Dose reduction was required 72 times. Therapy was stopped in one patient (2%) because of toxicity. Three patients (6%) refused to complete the adjuvant therapy. Adjusted 2-year no evidence of disease (NED) survival is 66%. This study demonstrates that patients with advanced squamous-cell carcinoma of the head and neck can undertake an aggressive program of adjuvant MTX/5-FU with acceptable compliance and toxicities. Preliminary data generated in this nonrandomized study support the call for a prospective randomized multiinstitutional trial of this program.

Transition state variation in enzymatic reactions.

Experimental analysis of enzymatic transition states by kinetic isotope effect methods has established geometric variation in related transition state structures. Differences are apparent in development of the reaction coordinate, in solvolytic transition states relative to those in enzymatic catalytic sites, in the stereochemistry of related substrates at the transition state, and in reactions catalyzed by related enzymes.

Enzymatic N-riboside scission in RNA and RNA precursors.

N-ribohydrolases and transferases act on nucleosides, nucleotides and oligonucleotides to effect base removal. Advances in mechanistic and structural analysis have established that enzymes of N-riboside scission act by combinations of leaving-group and ribosyl activation. Alternative O-riboside substrates have been developed for mechanistic diagnosis. Transition-state structures have been determined, and powerful inhibitors have been designed from structural and transition-state information.

Immucillin-H binding to purine nucleoside phosphorylase reduces dynamic solvent exchange.

The rate and extent of hydrogen/deuterium (H/D) exchange into purine nucleoside phosphorylase (PNP) was monitored by electrospray ionization mass spectrometry (ESI-MS) to probe protein conformational and dynamic changes induced by a substrate analogue, products, and a transition state analogue. The genetic deficiency of PNP in humans is associated with severe T-cell immunodeficiency, while B-cell immunity remains functional. Inhibitors of PNP have been proposed for treatment of T-cell leukemia, to suppress the graft-vs.-host response, or to counter type IV autoimmune diseases without destroying humoral immunity. Calf spleen PNP is a homotrimer of polypeptide chains with 284 amino residues, molecular weight 31,541. Immucillin-H inhibits PNP with a Kd of 23 pM when only one of the three catalytic sites is occupied. Deuterium exchange occurs at 167 slow-exchange sites in 2 h when no catalytic site ligands are present. The substrate analogue and product prevented H/D exchange at 10 of the sites. Immucillin-H protected 32 protons from exchange at full saturation. When one of the three subunits of the homotrimer is filled with immucillin-H, and 27 protons are protected from exchange in all three subunits. Deuterium incorporation in peptides from residues 132-152 decreased in all complexes of PNP. The rate and/or extent of deuterium incorporation in peptides from residues 29-49, 50-70, 81-98, and 112-124 decreased only in the complex with the transition state analogue. The peptide-specific H/D exchange demonstrates that (1) the enzyme is most compact in the complex with immucillin-H, and (2) filling a single catalytic site of the trimer reduces H/D exchange in the same peptides in adjacent subunits. The peptides most highly influenced by the inhibitor surround the catalytic site, providing evidence for reduced protein dynamic motion caused by the transition state analogue.

Cisplatin--5-fluorouracil chemotherapy for advanced inoperable squamous carcinoma of the head and neck.

Patients with locally advanced, inoperable squamous cell carcinoma of the head and neck were offered three courses of cisplatin and 96-h 5-fluorouracil (5-FU) infusion. Subsequent therapy included surgery when feasible, irradiation therapy, and a maintenance program of methotrexate (MTX)-5-FU. Thirty-three patients were evaluated prospectively. Seven patients underwent a single course of chemotherapy. Five patients underwent two courses of chemotherapy. Twenty-one patients underwent three courses of adjuvant chemotherapy. The overall response rate was 48% (16 of 33). Fifteen of 21 patients (76%) receiving three courses of chemotherapy evidenced a response; this included three complete responses (CRs) (9%). No responses were seen in patients receiving only one or two courses of chemotherapy. Among responding patients, the initial favorable response to chemotherapy was apparent after the first course of chemotherapy. Patients who failed to demonstrate any response after two courses of chemotherapy did not respond after a third course. A significant group of patients fail to respond and should be offered participation in other investigational protocols as they become available.

A hypothesis to explain the substrate reactivity of ribosomal and stem-loop RNA with ricin A-chain.

A hypothesis is proposed which explains the low catalytic efficiency of ricin A-chain on artifical stem-loop RNA substrates, relative to the high catalytic efficiency found on intact mammalian ribosomes. The enzymatic binding energy required to reach the transition state is greater than that to stabilize the stem structure of stem-loop RNA molecules. When artifical stem-loop complexes bind, the base-pairing of the stem is lost rapidly relative to catalysis. Loss of secondary structure causes movement of the susceptible adenine to a catalytically unfavorable geometry and most of the enzyme-substrate complexes dissociate without catalysis. The protein architecture of intact ribosomes, when bound to ricin A-chain, is proposed to stabilize the stem-loop structure to maintain adenine 4324 in a configuration external to the RNA phosphodiester backbone. The slow catalysis observed with small stem-loop structures is a consequence of the relative probabilities for stem-melting induced by the enzyme and for reaching the transition state. Catalysis with a ten-base stem-loop RNA shows product formation at a rate of up to 0.02 hr-1, but fails to achieve a full catalytic turnover with long incubations. The substoichiometry of product formation with small stem-loops is proposed to be a consequence of the competing rates of catalysis and enzyme denaturation under in vitro assay conditions. Rates for these processes are estimated from the kinetic parameters for ricin A-chain hydrolysis of ribosomes and stem-loop structures.

Chordoma and chondrosarcoma of the cranial base: an 8-year experience.

Between 1980 and 1988, 8 patients with chordomas and 9 with low-grade chondrosarcomas involving the cranial base were treated. All the patients were investigated preoperatively and postoperatively with computed tomographic or magnetic resonance imaging scans, according to a standard protocol. The tumors and the involved bony structures were surgically removed in one or more operations using different operative approaches. Ten patients underwent postoperative radiation therapy, either at our institution or prior to their referral to us. Total removal was defined as the absence of identifiable tumor on magnetic resonance imaging or computed tomographic obtained 3 months postoperatively, and was accomplished in 9 patients. The ability to achieve total removal was greatly increased in patients with tumors that had not previously been operated on. We believe that these tumors must be treated by aggressive surgical resection when initially diagnosed, and this can be accomplished with low morbidity. The follow-up period in our patients was too short to allow us to determine whether such total removals can result in a cure or in long-term control of these formidable tumors.

Operative exposure and management of the petrous and upper cervical internal carotid artery.

The exposure and operative management of the petrous and upper cervical internal carotid artery (ICA) in 29 patients is detailed. Twenty-seven of these patients had extensive cranial base neoplasms (benign or malignant), 1 had an inflammatory cholesteatoma, and 1 had an aneurysm of the upper cervical ICA immediately proximal to the carotid canal. Preoperative studies useful in the evaluation of these patients included computed tomography, magnetic resonance imaging, cerebral and cervical angiography, and a balloon occlusion test of the ICA with evaluation of neurological status and of cerebral blood flow. The exposure of the upper cervical and petrous ICA was useful to obtain proximal control of the cavernous ICA, aided in the operative approach to extensive petroclival, intracavernous, and parapharyngeal neoplasms, and enabled the total resection of 23 of 27 such tumors. A subtemporal and preauricular infratemporal fossa approach was most commonly used for the exposure of the artery. Intraoperative arterial management consisted of exposure and decompression only, dissection from encasing neoplasm, resection of the invaded arterial segment and vein graft reconstruction, or intentional arterial occlusion. Vascular complications included 1 stroke due to delayed arterial occlusion, 1 stroke and death due to infection spreading from the nasopharynx with bilateral ICA rupture, and 1 pseudoaneurysm formation secondary to wound infection necessitating postoperative balloon occlusion of the ICA. Nonvascular complications included facial nerve paralysis in 10 patients (usually temporary), glossopharyngeal and vagal paralysis in 13 patients requiring Teflon injection of the vocal cord in 9, temporary difficulties with mastication in 9 patients, and wound infection in 3. The surgical exposure and management of the upper cervical and petrous ICA may permit a total operative resection of extensive cranial base neoplasms and is also an alternative for the management of vascular lesions involving these segments of the artery. With malignant neoplasms extending from the nasopharynx, postoperative infection remains a problem and may best be resolved by the use of a vascularized rectus abdominis muscle flap to reconstruct defects of the nasopharynx. Bilateral ICA encasement by neoplasms is also a major problem to be solved. The value of such an aggressive approach to the management of malignant neoplasms remains to be proven.

Subtemporal-preauricular infratemporal fossa approach to large lateral and posterior cranial base neoplasms.

A subtemporal-preauricular infratemporal fossa approach to remove 22 large neoplasms involving the lateral and posterior cranial base is detailed. The areas from which a neoplasm could be removed by this approach included the sphenoid and clival bone; the medial half of the petrous temporal bone; the infratemporal fossa; the nasopharynx; the retro- and parapharyngeal area; the ethmoid, sphenoid, and maxillary sinuses; and the intradural clivus-foramen magnum area. The pathology of the neoplasms included benign tumors such as meningioma, malignant cartilaginous neoplasms such as chordoma, and other malignant lesions such as nasopharyngeal carcinoma. This approach offers many advantages over other anterior and lateral approaches to the lateral and posterior cranial base: these include minimal brain retraction; direct access to the ipsilateral petrous and upper cervical internal carotid artery; reconstruction of extensive cranial base defects, often with the use of a vascularized rectus abdominus flap; preservation of the hearing conduction mechanism when it is not involved by tumor; and the maintenance of excellent facial nerve function postoperatively. The use of an anterior extradural approach (transethmoidal) and of an intradural approach (frontotemporal or retromastoid), either concurrently or separately, is necessary in some patients to effect total tumor removal. The most serious complication in this series was the death of a patient due to postoperative infection and bilateral carotid artery rupture, which may have been avoided by the use of a rectus abdominis muscle flap for reconstruction. Among the 21 surviving patients, 18 had a good outcome, two had a fair outcome, and one with preexisting neurological deficits had a poor outcome. One of the surviving patients with a chordoma died of pulmonary metastases 1 year later, without evidence of local recurrence. The length of postoperative follow-up evaluation in these patients is insufficient to make any judgment about the effectiveness of this surgical approach in achieving a cure or long-term control of the tumors described.

Cervical lymph node metastasis after local excision of early squamous cell carcinoma of the oral cavity.

A total of 54 patients with stage I and stage II squamous cell carcinoma of the oral cavity were reviewed as to treatment modality, adequacy of treatment, and site of failure. Surgery was employed as the sole initial treatment modality in 52 patients. Forty-three underwent primary tumor excision alone and 9 underwent elective neck dissection at the time of primary tumor excision. The patients who underwent elective neck dissection at the time of excision of the primary tumor had a 3 year survival rate of 88 percent, in comparison to a survival rate of 77 percent in those patients whose initial therapy was directed solely at the primary tumor. A low incidence of local recurrence (2 percent) and a high incidence of neck recurrence (42 percent) were documented in those patients treated by primary tumor excision alone. Patients who underwent salvage neck dissection for recurrent neck node metastases had a 3 year survival rate of 56 percent. This study has documented a high incidence of cervical node recurrence in patients with T1 and T2 squamous cell carcinomas of the oral cavity treated by primary tumor excision alone and a poor survival rate after salvage therapy. A small group of patients who underwent elective neck dissection had a demonstrably high survival rate. These observations lend support to the call for elective neck dissection in patients with stage I and II oral cavity carcinoma but are not conclusive. Therapeutic decisions regarding elective treatment of the neck will continue to be made according to the best judgment and prejudices of the individual surgeon until a prospective, randomized multi-institutional study addressing this specific issue is undertaken.

Microsurgery for macrodefects: microvascular free-tissue transfer for massive defects of the head and neck.

Despite defect location and the fear of creating complex massive defects, coverage of large areas of soft tissue loss, with or without exposed calvaria, dura, and brain, can be reconstructed reliably with microvascular free tissue transfer. This technique permits separation of the oronasopharynyx from the intracranial contents, coverage of dural grafts, restoration of composite tissue loss, and achievement of superior aesthetic results in a single stage. When choosing vascular anastomotic sites, free-flap transfer permits a greater latitude in flap orientation, tailoring, and inset than is possible when using fixed pedicled rotation flaps. When confronted with a deeply invasive or gigantic malignancy, a multidisciplinary team approach is optimal. The risk associated with sophisticated ablative and reconstructive operative procedures is justified when dealing with potentially curable lesions. The success of these extensive procedures is related not only to the functional result and the aesthetic appearance, but most importantly to the resultant quality of life they allow.

Inflammatory and neoplastic masses of the nose and paranasal sinus in children.

This study categorizes the diseases of 376 children with inflammatory or neoplastic masses of the nose and paranasal sinuses treated at the University of Pittsburgh or reviewed at the Armed Forces Institute of Pathology. The presenting symptoms and signs of these masses, patient evaluations, and the outcome of management are reviewed. A plan for therapy of the various masses presenting in this area is suggested based on the outcome of this study.

Physician and patient-induced diseases in otolaryngology office practice.

"Theragenic" diseases produce common ENT complaints. They are frequently and predictably induced by self or physician treatment. Fifteen percent of first office visits in various practice situations stem from therapeutically-induced disease. Self treatment by cotton tip applicator ear cleaning, nasal decongestants, mouth washes, and lozenges produce symptoms which mimic other etiologies. Prescription medications produce diseases with ENT symptoms which are based on pharmacologic toxicity, multiple drug therapy, drug intolerance, and occasional idiopathic hypersensitivity. The treatment of these diseases is simple and effective once their etiology is discovered.

Sinus complications of frontal craniotomy.

Frontal sinusitis, or inflamatory complications of sinusitis, may occur as a consequence of frontal craniotomy when the sinus has been entered during the craniotomy. This may happen particularly during surgery to treat an aneurysm or to excise a tumor in the sellar area. These complications may also occur if the sinus is entered during routine craniotomy when the sinus is high or asymmetrical, or during reduction of frontal bone fractures. This presentation describes the etiology of such inflammatory complications and describes the approach to treatment of such complications, as well as outlining their prevention.

Nasal polyps in children.

The inflammatory nasal polyp is the most common benign or malignant nasal mass seen in children. Nasal polyps in the pediatric population appear to occur as inflammatory responses to bacterial infections. In 33% of the patients with polyps whom we studied, antral choanal polyps were noted, and in 20% of the patients the polyps were unilateral but not antral choanal. In 18% of the patients the polyps were bilateral and in an additional 29% they occurred bilaterally in association with cystic fibrosis. History of an allergy is infrequently associated with nasal polyps; allergies are potentially major contributing factors to nasal polyps only in patients without cystic fibrosis whose nasal polyps are bilateral. Patients with antral choanal polyps are most successfully managed by simultaneous Caldwell-Luc antrostomy and polypectomy. Sixty percent of patients with nasal polyps and cystic fibrosis are adequately managed with a single intranasal polypectomy. Simultaneous sinus surgery and polypectomy should be considered for all patients with recurrent polyps and for all patients with clinical or radiographic evidence of significant sinusitis. Complications, including epistaxis and intranasal synechia, occurred in 3% of the 170 surgical procedures performed.

Management of nasopharyngeal salivary gland malignancy.

OBJECTIVE: The objective of this study was to evaluate the oncological outcome and complication rate following surgical treatment of nasopharyngeal salivary gland malignancy. STUDY DESIGN: Retrospective case review at tertiary care skull base center. METHODS: Pertinent medical records were reviewed from 23 patients presenting with minor salivary gland malignancy. Clinical presentation, prior treatment, histological type and grade, clinical stage, details of surgical treatment, and postoperative adjuvant radiation therapy were studied. Survival and recurrence data were analyzed using the Kaplan-Meier and Cox proportional hazards methods. RESULTS: Histological types included 11 adenoid cystic carcinomas, 8 mucoepidermoid carcinomas, and 4 cases of adenocarcinoma not otherwise specified. All patients underwent primary surgical resection, and the lateral infratemporal middle fossa approach was used in 20 patients. Prior radiation therapy had been administered in 6 patients who presented for treatment of recurrent disease, and the remaining 17 patients underwent planned postoperative radiation therapy. Elective neck dissection was undertaken in 15 patients, and occult neck disease was present in 47%. Disease specific survival was 67% at 5 years and 48% at 10 years. High-grade tumors had a significantly poorer outcome (P =.035) with a relative risk of 4.6 compared with low-grade disease. Local control was seen to be 77% at 5 years. CONCLUSIONS: Planned combined surgery and radiation therapy achieves survival outcomes and recurrence rates in nasopharyngeal salivary gland malignancy comparable to results reported using the same treatment for minor salivary gland tumors cancer originating elsewhere in the head and neck. Because of the high rate of occult neck metastases, we recommend elective neck dissection as part of the surgical treatment with this disease entity. The lateral infratemporal middle fossa approach provides safe and adequate access to resect the vast majority of these tumors with acceptable complication rates. A reliable form of vascularized reconstruction is necessary to prevent serious postoperative complications, and we currently prefer the gastro-omental free flap.

Radiation-associated disease: disease incidence and cost effectiveness of follow-up.

The organization, costs and outcome of a metropolitan area-wide recall campaign for patients irradiated for benign disease is documented. The campaing resulted in an increase in the number of thyroid malignancies discovered in both the irradiated and the nonirradiated population. The organization of the campaign cost $100,000. An estimated excess of 100 thyroid carcinomas were found in the 17 months following the campaign compared to the 17 months prior to the campaign in the Pittsburgh Standard Metropolitan Statistical Area. Of 150 patients who were radium exposed as infants and remained in the Pittsburgh area, 60% knew of their exposure only by direct hospital contact and were not reached by media public education. Seven of those 150 patients had thyroid carcinoma on 35 year follow-up, and 30% had some benign or malignant tumor.

Gelfoam paste injection for vocal cord paralysis: temporary rehabilitation of glottic incompetence.

Vocal cord paralysis frequently results in open glottic incompetence with aspiration, an ineffective cough, and poor voice production. Glottic competence can be restored temporarily be injecting the true vocal cord with Gelfoam paste. This clinical use of Gelfoam for temporary rehabilitation is indicated in : 1) situations in which paralysis may be temporary, 2) patients for whom an open operative procedure must be delayed, and 3) circumstances in which it is desirable to determine the effect of vocal cord injection prior to placement of nonabsorbable material. The injection of Gelfoam paste results in minimal tissue reaction. Absorption is gradual over a period of six to ten weeks, allowing time for some glottic compensation. The injection may be repeated without adverse effects until the paralysis resolves or intervention of a permanent nature is indicated.

Surgical management of early epidermoid carcinoma of the anterior floor of the mouth.

Therapy for early carcinoma of the floor of the mouth is difficult because of the tendency for local invasion of muscle and extension onto the mandible and alveolus. Nearly 100% local control of disease without mandibular complication has been possible with a wide local three-dimensional resection including marginal mandibulectomy with split thickness skin grafting. The operative technique and special considerations including management of the mandible, submandibular ducts, and airway are detailed. Lymph node metastases habe been uncommon. The primary disease and pathology are correlated with regional metastasis, and based on this a treatment plan is recommended.