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Biomedical subjects

A L Weber

Publications and source records attributed to A L Weber.

At least 19 recordsLinked to original sources
PubMed1992

Imaging of the salivary glands.

Salivary gland diseases are very common disorders and require radiologic evaluation. Several radiologic methods are used for assessment of these diseases. Conventional films of the parotid and submandibular glands demonstrate opaque stones in the duct system, whereas sialography depicts nonopaque stones, provides additional information on the position of the stones, and differentiates it from other calcific densities near the duct system, as well as providing information concerning ectasia of the ducts. CT has been used for evaluating mass lesions and extraglandular inflammatory disease, including abscesses. CT also depicts stones that may not be visible on conventional films. MR imaging has become an important modality in the diagnosis and definition of benign and malignant tumors and cysts and it will probably replace CT as the primary imaging modality for the assessment of these lesions. Gadolinium may be used in the examination, especially if a malignant tumor is suspected (because of irregularity and intraglandular extension).

AIDS-Related Complex↗
PubMed1991

Focal amyloidosis of the head and neck: evaluation with CT and MR imaging.

Localized amyloidosis of the head and neck was found retrospectively in the nasopharynx (n = 3) and orbit (n = 1) of four female patients (mean age, 32 years), three of whom had a prior history of antigenic stimulation. In all patients, computed tomography revealed a slightly high absorption and a relatively homogeneous, partially calcified mass. In the one patient who underwent magnetic resonance (MR) imaging, a distinctive loss of signal intensity was seen on the long repetition time/echo time sequence. This enhanced T2 relaxation may be due to (a) static or slowly fluctuating internal magnetic fields arising from adjacent amyloid protons held in relatively fixed positions within the beta-pleated sheet, resulting in quick phase dispersion; (b) chemical exchange and spin-spin interaction with adjacent water protons; and (c) diffusion through differences in diamagnetic susceptibility. This unusual appearance at MR imaging may improve the ability of radiologists to distinguish focal amyloidosis from many other diseases that affect the head and neck.

Adult↗
PubMed1990

Energy-rich glyceric acid oxygen esters: implications for the origin of glycolysis.

The apparent Gibbs free energy change of hydrolysis (delta G degrees', pH 7) of the 2- and 3-O-glyceroyl esters of 2- and 3-O-L-glyceroyl-L-glyceric acid methyl ester were measured at 25 degrees C. The 2- and 3-glyceroyl esters were found to be 'energy-rich' with delta G degrees' values of -9.1 kcal mol-1 and -7.8 kcal mol, respectively. This result indicates that the analogous 2- and 3-glyceroyl esters of polyglyceric acid are also 'energy-rich' and, therefore, could have acted as an energy source for primitive phosphoanhydride synthesis.

Energy Metabolism↗
PubMed1979

Delay of constant light-induced persistent vaginal estrus by 24-hour time cues in rats.

The normal ovarian cycle of female rats is typically replaced by persistent estrus when these animals are housed under constant light. Evidence presented here shows that the maintenance of periodicity in the environment can at least delay (if not prevent) the photic induction of persistent vaginal estrus. Female rats in constant light were exposed to vaginal smearing at random times or at the same time every day. In another experiment, female rats were exposed to either constant bright light, constant dim light, or a 24-hour photic cycle of bright and dim light. The onset of persistent vaginal estrus was delayed in rats exposed to 24-hour time cues even though the light intensities were the same as or greater than those for the aperiodic control groups. The results suggest that the absence of 24-hour time cues in constant light contributes to the induction of persistent estrus.

Animals↗
PubMed1979

The formation of dipeptides from amino acids and the 2'(3')-glycyl ester of an adenylate.

The yields of dipeptide obtained from the reaction of 0.2M 2'(3')-O-(glycyl)-adenosine-5'-(O-methylphosphate) and 0.2M amino acid at pH 8.2 ranged from 0.1% to 35.5% for a group of 15 amino acids. The yields of glyser (35.3%), gly-cys (11.8%) and gly-thr (5.4%) were considerably greater than dipeptide yields obtained from any of the other 12 amino acids (less than or equal to 1.7%). Aminolysis of 0.05M 2'(3')-O-(glycyl)-adenosine-5-'-(O-methylphosphate) by 0.4M serine ethyl ester yielded 53% glycylserine diketopiperazine, via N-(glycyl)-serine ethyl ester as a transient intermediate. The prebiotic significance of these reactions is discussed.

Adenosine Monophosphate↗
PubMed1979

The formation of peptides from glycine thioesters.

The condensation products obtained from 0.01M S-glycyl-N-acetyl-cysteamine at different pH's were investigated. The highest yields of diketopiperazine (approx. 50%) were observed in phosphate buffers between pH 7.5 and 8.5. The highest yields of diglycine (46%), triglycine (10%) and tetraglycine (2%) were observed in carbonate buffers at pH 9.5. At pH 8.0, over 90% of the glycyl residues of 0.15M S-glycyl-N-acetylcysteamine were incorporated into condensation products, mainly DKP (60--70%). The yields of products from the condensation of S-glycyl-ethanethiol under similar conditions closely resembled those obtained with S-glycyl-N-acetylcysteamine.

Esters↗
PubMed1979

Evaluation of mucoceles of the paranasal sinuses with computed tomography.

Eighteen patients with mucoceles of the paranasal sinuses were studied by plain radiography, pluridirectional tomography, and computed tomography (CT). Sixteen of the lesions had a homogeneous appearance on CT but demonstrated variable absorption characteristics, with acutely infected mucoceles showing rim enhancement. Plain radiography and pluridirectional tomography were usually sufficient for making a diagnosis and defining the extent of the lesion, but CT more accurately demonstrated orbital and intracranial extension. Both transverse and coronal CT are essential for adequate evaluation.

Adolescent↗
PubMed1978

The formation of peptides from the 2'(3')-glycyl ester of a nucleotide.

We have synthesized 2'(3')-O-(glycyl)-adenosine-5'-(O-methylphosphate), an analogue of the 3'-terminus of aminoacylated tRNA. A 0.4M solution of this compound maintained at pH 8.2, yields 5.5% of diglycine and 11.5% of diketopiperazine, in addition to the hydrolysis products glycine and adenosine-5'-(O-methylphosphate). Under the same conditions, glycine ethyl ester reacts much more slowly, but ultimately gives similar yields of diglycine and diketopiperazine. The aminolysis of 2'(3')-O-(glycyl)-adenosine-5'-(O-methylphosphate) by free glycine is relatively inefficient, but serine reacts 20 times more rapidly and yields up to 50% of N-glycylserine. The prebiotic significance of these reactions is discussed.

Adenosine Monophosphate↗
PubMed1978

Genetic code correlations: amino acids and their anticodon nucleotides.

The data here show direct correlations between both the hydrophobicity and the hydrophilicity of the homocodonic amino acids and their anticodon nucleotides. While the differences between properties of uracil and cytosine derivatives are small, further data show that uracil has an affinity for charged species. Although these data suggest that molecular relationships between amino acids and anticodons were responsible for the origin of the code, it is not clear what the mechanism of the origin might have been.

Amino Acids↗
PubMed1978

Amino acid activation with adenosine 5'-phosphorimidazolide.

Amino acids are activated by reaction with adenosine 5'-phosphorimidazolide in aqueous imidazole buffers. If adenosine 5'-(O-methylphosphate), an analogue of the 3'-terminus of t-RNA is present, 2'(3')-O-aminoacyladenosine 5'-(O-methylphosphate) is formed. Fifteen percent of this compound accumulated at pH 5.8, but less was formed at higher pHs. The highest efficiency of utilization if ImpA attained in our experiments was about 24%. Analogous reactions occured with several other amino acids, including a number that have functional side-chains.

Adenosine Monophosphate↗
PubMed1978

Computed tomography of the paranasal sinuses and face: part I. Normal anatomy.

With the ability to image both bone and soft tissue structures, computed tomography (CT) is capable of visualizing many normal anatomical structures of the paranasal sinuses and face not seen with other radiological techniques. The superficial and deep fat planes, all of the muscles of mastication, and many of the facial muscles are readily identified. The extraocular muscles, optic nerves, and globes are clearly seen. The purpose of this report is to review the normal anatomy of the paranasal sinuses and face imaged by CT in both the transverse and coronal planes.

Face↗
PubMed1978

Computed tomography of the paranasal sinuses and face: part II. Pathological anatomy.

Computed tomography (CT) has added an important new dimension to the radiological evaluation of diseases of the paranasal sinuses and face. Using transverse and coronal scans, accurate assessment of the character and extent of mass lesions in this region can be achieved. Erosion of thin bony lamine and involvement of soft tissue structures of the face can be seen. Most important, CT is capable of precisely defining the extension of lesions into the pterygopalatine fossa, orbit, and cranial cavity, information that is essential for therapeutic planning.

Adult↗