Malignant tumors of the paranasal sinuses are often found to be greatly advanced by the time a clinical or radiologic diagnosis is established. Therefore, the overall cure rate is low, even when surgery and radiation therapy are combined. The clinical manifestations and pathologic findings are analyzed in 200 cases to illustrate the wide spectrum of these tumors as to their type, specific location, and the extent to which they can spread within the sinuses and to adjacent anatomic areas. The various radiologic modalities, including conventional x-ray films, angiography, and conventional and computed tomography are presented. Their relative merit in the diagnosis and staging of these tumors is evaluated.

Adenocarcinoma↗

PubMedDate not supplied

A model for the coevolution of the genetic code and the process of protein synthesis: Review and assessment.

The contemporary genetic code and the process of protein biosynthesis most assuredly evolved from a simpler code and process. We believe that there was obligatory coevolution of the two and that the earlier code and process must have involved a more direct linkage between the amino acids and the information macromolecule. We propose that an early form of translating existed in which amino acids were attached directly to the 'messenger' RNA along the backbone as 2'OH aminoacyl esters. These esters then condensed with each other on the RNA backbone yielding a peptide covalently attached to the RNA, without the use of tRNA's and ribosomes. THis presentation is concerned with experimental data which indicate that such a simple translation system is possible and must have involved the following steps: (1) formation of the aminoacyl adenylate anhydride, (2) transfer of the amino acid from the adenylate to immidazole, (3) transfer of the amino acid from imidazole to 2'OH groups along the backbone of RNAs, (4) condensation of the amino acids to yield peptides. Steps (1)-(3) have been confirmed in chemical systems. Our preliminary evidence indicates step (4) is also possible. The aminoacylation of polyribonucleotides and the subsequent formation of peptides is a dynamic and experimentally accessible system for studying genetic coding specfities and our present studies are now concentrated on step (4), looking for such specifities.

Acylation↗

PubMedDate not supplied

Carotid artery hemorrhage resulting from temporal bone fracture.

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Adult↗

PubMedDate not supplied

The sugar model: catalysis by amines and amino acid products.

Ammonia and amines (including amino acids) were shown to catalyze the formation of sugars from formaldehyde and glycolaldehyde, and the subsequent conversion of sugars to carbonylcontaining products under the conditions studied (pH 5.5 and 50 degrees C). Sterically unhindered primary amines were better catalysts than ammonia, secondary amines, and sterically hindered primary amines (i.e. alpha-aminoisobutyric acid). Reactions catalyzed by primary amines initially consumed formaldehyde and glycolaldehyde about 15-20 times faster than an uncatalyzed control reaction. The amine-catalyzed reactions yielded aldotriose (glyceraldehyde), ketotriose (dihydroxyacetone), aldotetroses (erythrose and threose), ketotetrose (erythrulose), pyruvaldehyde, acetaldehyde, glyoxal, pyruvate, glyoxylate, and several unindentified carbonyl products. The concentrations of the carbonyl products, except pyruvate and ketotetrose, initially increased and then declined during the reaction, indicating their ultimate conversion to other products (like larger sugars or pyruvate). The uncatalyzed control reaction yielded no pyruvate or glyoxylate, and only trace amounts of pyruvaldehyde, acetaldehyde and glyoxal. In the presence of 15 mM catalytic primary amine, such as alanine, the rates of triose and pyruvaldehyde of synthesis were about 15-times and 1200-times faster, respectively, than the uncatalyzed reaction. Since previous studies established that alanine is synthesized from glycolaldehyde and formaldehyde via pyruvaldehyde as its direct precursor, the demonstration that the alanine catalyzes the conversion of glycolaldehyde and formaldehyde to pyruvaldehyde indicates that this synthetic pathway is capable of autocatalysis. The relevance of this synthetic process, named the Sugar Model, to the origin of life is discussed.

Acetaldehyde↗

PubMedDate not supplied

Metastatic renal cell carcinoma manifesting as a nasal mass: CT findings.

The clinical and radiological findings in a 71-year-old woman with a metastatic renal cell carcinoma to the right nasal cavity are presented. The kidney tumor manifested clinically as epistaxis. Computed tomography revealed an expansile lesion in the right nasal cavity with extension to the right antrum, right ethmoid sinus, and left nasal cavity. There was no lytic bone destruction, but there was displacement of bone caused by the expansile tumor mass.

Aged↗

PubMedDate not supplied

MR imaging of a lymphangioma involving the masseter muscle.

Lymphangiomas and cystic hygromas are tumors of lymphatic origin that are relatively common in the head and neck area. However, based on our literature review of this subject, the masseter muscle has never been implicated as a primary tumor site. It is our purpose to report such a case and to emphasize the value of magnetic resonance imaging for diagnosing a mass located in the masseteric region.

Adult↗

PubMedDate not supplied

X-ray of the month.

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Abscess↗

PubMedDate not supplied

X-ray of the month. Lymphoepithelioma of the nasopharynx.

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Adolescent↗