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Biomedical subjects

M Malkin

Publications and source records attributed to M Malkin.

15 recordsLinked to original sources
PubMed1995

The relationship between the technical accuracy of stereotactic interstitial implantation for high grade gliomas and the pattern of tumor recurrence.

PURPOSE: To correlate the pattern of failure and subsequent survival with the technical accuracy of stereotactic brain tumor implantation. METHODS AND MATERIALS: The patterns of failure of 47 consecutive patients with primary or recurrent gliomas after stereotactic implantation delivering 60 Gy via removable high activity 125I sources were reviewed. When the tumor was covered at all levels by the chosen isodose distribution, the implant was considered to be "ideal." If the coverage was not complete, a numerical description of the volume of tumor outside the isodose was assigned. Criteria for "adequate" and "inadequate" implants were defined. Standard radiographic criteria, with pathologic confirmation in 26 cases, were used to categorize the patterns of failure into the following components: central, peripheral, distant (within the brain parenchyma), leptomeningeal, and spinal. A peripheral failure was scored as being in the "direction of error" when the prescribed isodose did not cover the tumor volume and the subsequent tumor progression was in this region. Survival was calculated from the date of implantation. RESULTS: Of 47 cases examined, 72% had an element of central and/or peripheral failure and 23% had a component of distant or meningeal failure. Among the patients with "adequate" or "inadequate" ("nonideal") implants who had a component of peripheral failure, only 19% were in the "direction of error." All patients with technically "inadequate" implants progressed in both the central and peripheral region. Among the groups who had "ideal," "adequate," and "inadequate" implants; 37%, 70%, and 75%, respectively, underwent reoperation [p = not significant (NS)]. Patients who underwent reoperation had a longer median survival than those who did not; 521 days vs. 298 days, respectively (p = 0.035). For patients with "nonideal" implants, a median survival of 470 days was found for patients undergoing reoperation vs. 184 days for those who did not (p = 0.016). CONCLUSIONS: (a) Patients with "inadequate" implants failed in both the central and peripheral region in all cases. This pattern, while less common in those with "ideal" or "adequate" implants, occurred in the majority of cases. (b) The technical excellence of the implant had no impact on survival. (c) Patients with "nonideal" implants were more likely to have reoperation than those with "ideal" implants, and this intervention was associated with a significant survival advantage.

Adult↗
PubMed1988

MR of cranial and spinal meningeal carcinomatosis: comparison with CT and myelography.

Thirty-nine patients with histologically proved primary neoplasms, focal neurologic deficits, and positive CSF cytology were evaluated by enhanced cranial CT and MR, or complete myelography and MR of the spine. Intracranial abnormalities were noted on CT in 56% of cases and included abnormal enhancement of subarachnoid space and ventricular walls, ventricular dilatation, obliteration of cortical sulci, and enhancing nodules within the subarachnoid cisterns and lumen of the lateral ventricles. Although the degree of ventricular enlargement and intraventricular tumor deposits were equally well seen on CT and MR, involvement of ventricular walls, tentorium, subarachnoid cisterns, or subarachnoid space interpreted as abnormal enhancement on CT was not readily appreciated on routine T1- and T2-weighted spin-echo sequences. Forty-four percent of CT and 65% of MR studies were interpreted as normal. There was high correlation of myelographic findings with clinical diagnosis, and no false-negative myelograms. Nodular filling defects within the subarachnoid space, thickening and crowding of roots of the cauda equina, irregularity of individual roots, and scalloping of the subarachnoid membranes were demonstrated. MR was rather insensitive in detecting these changes, revealing a definite abnormality of the subarachnoid space in 27% of patients with positive myelograms. False-negative interpretation of MR of the spine was made in 44% of cases.

Brain Neoplasms↗
PubMed1979

Fracture of the anterior nasal spine.

Fracture of the anterior nasal spine is so rare that clinicians do not specifically look for it if other fractures of the middle third of the face have been ruled out. However, as suggested by this case, the possibility of fracture of the nasal spine should not be overlooked.

Adolescent↗
PubMed1969

Fusidic acid: inhibition of factor T2 in reticulocyte protein synthesis.

The steroid antibiotic fusidic acid inhibits reticulocyte protein synthesis. This inhibition appears to be due to interference with the activity of the T(2) supernatant fraction, and strengthens the proposition that T(2) is functionally analogous to the G-factor of bacterial protein synthesis, which is also specifically inhibited by this antibiotic.

Adenosine Triphosphate↗
PubMed1969

A stimulation by cyclic 3',5'-adenosine monophosphate of amino acid activation and polymerization in reticulocyte hemolysates.

With reticulocyte supernatant, cyclic 3',5'-adenosine monophosphate at concentrations of 10(-3) to 10(-2)M causes stimulation of aminoacyl-tRNA synthetases for some, e.g., valine and leucine, but not all, amino acids; it is highest at nonsaturating concentrations of ATP. Similar concentrations of cyclic 3',5'-adenosine monophosphate are found to stimulate phenylalanine polymerization from phenylalanyl transfer ribonucleic acid on polyuridylic acid-charged reticulocyte ribosomes. The degree of stimulation is highest at low GTP concentrations. It is abolished by addition of phosphoenolpyruvate + pyruvate kinase, which stimulate similarly or more effectively at low GTP levels. Under the conditions of these experiments, cyclic 3',5'-adenosine monophosphate did not appreciably inhibit GTP hydrolysis.

Adenine Nucleotides↗