Benign symmetrical lipomatosis

Benign symmetrical lipomatosis is an unusual disorder of fat metabolism that results in a characteristic accumulation of adipose tissue around the head and neck. Surgical extirpation is the only known effective therapy. Physical examination does not provide a comprehensive delineation of tumor extent. We present the first reported use of CT scanning to investigate the anatomic limits of BSL and to plan the operative approach.     

Enantioselective metabolism and cytotoxicity of R-ifosfamide and S-ifosfamide by tumor cell-expressed cytochromes P450.

The anticancer prodrug ifosfamide (IFA) contains a chiral phosphorous atom and is administered in the clinic as a racemic mixture of R-IFA and S-IFA. Hepatic cytochrome P450 (P450) enzymes exhibit enantioselective preferences in the metabolism of R-IFA and S-IFA; however, the impact of this selectivity on P450-dependent anticancer activity is not known. Presently, the metabolism and cytotoxicity of R-IFA and S-IFA were determined in 9L gliosarcoma and Chinese hamster ovary tumor cells expressing an IFA-activating P450 enzyme and by in vitro steady-state kinetic analysis using cDNA-expressed P450 enzymes. Tumor cells expressing P450 enzyme CYP3A4 were the most sensitive to R-IFA cytotoxicity, whereas tumor cells expressing CYP2B1 or CYP2B6 were most sensitive to cyclophosphamide (CPA), an isomer of IFA. Correspondingly, CYP3A4-expressing cells and cDNA-expressed CYP3A4 metabolized R-IFA to yield the active, 4-hydroxylated metabolite at a 2- to 3-fold higher rate than they metabolized S-IFA or CPA. CYP2B cells and cDNA-expressed CYP2B enzymes metabolized CPA almost exclusively by 4-hydroxylation, whereas R-IFA and S-IFA were substantially converted to inactive, N-dechloroethylated metabolites. Further investigation revealed that CYP3A1, a rat enzyme, exhibited superior kinetic properties compared with the human enzyme CYP3A4, with R-IFA and S-IFA both metabolized with high catalytic efficiency by 4-hydroxylation and with a K(m) value of 200 microM, approximately 5-fold lower than CYP3A4. Based on these kinetic parameters and metabolic profiles, R-IFA is expected to exert greater anticancer activity than S-IFA or CPA against tumors that express CYP3A enzymes, whereas tumors expressing CYP2B enzymes may be more sensitive to CPA treatment.     

Regional flow during experimental hemorrhage and crystalloid resuscitation: persistence of low flow to the splanchnic organs.

BACKGROUND AND METHODS. Rapid changes in cardiac output (CO) and organ perfusion occur with hemorrhagic shock and fluid resuscitation. To assess regional alterations of flow, 40 Sprague-Dawley male rats were subjected to hemorrhagic shock and crystalloid resuscitation under halothane anesthesia. Polyethylene microspheres were injected before and after hemorrhage and after resuscitation. At sacrifice, brain, lungs, heart, liver, intestine, spleen and kidneys were harvested, weighed and radioactivity counted. Changes in mean arterial pressure, oxygen consumption, organ flow and CO were also measured. RESULTS: Cardiac output decreased during hemorrhage (P less than 0.01), it increased with resuscitation but did not return to baseline even with infusion of fluid volumes of three times the blood loss. Flow decreased during hemorrhage in all organs, but the difference was not statistically significant in the liver (P greater than 0.05), since a larger percentage of CO was maintained as hepatic perfusion. During resuscitation, flow to brain and kidneys increased over the percentage values expected by increased CO (P less than 0.01), but flow to the liver did not increase significantly. Flow to small bowel remained depressed (P less than 0.005). CONCLUSIONS: Following hemorrhage there is hypoperfusion of all splanchnic organs; however, flow to the liver decreases least. Crystalloid resuscitation in our model failed to return CO to baseline. Blood supply to intestine remained depressed in disproportion to CO both after hemorrhage and resuscitation and hepatic blood flow remained decreased after resuscitation.     

Diagnosis of traumatic cardiac contusion

Cardiac contusion following blunt chest trauma remains a diagnostic problem because of a lack of sensitive diagnostic tests. This study evaluated thallous chloride Tl 201 single-photon-emission computed tomography in a series of 48 patients following blunt chest trauma. Of the 48 patients, 23 had normal scans. None of these patients proved to have serious arrhythmias during three days of continuous monitoring. Of 25 patients with abnormal or ambiguous studies, five (20%) developed serious arrhythmias requiring therapy. Single-photon-emission computed tomography scanning thus was sensitive in indicating that group of patients at risk of serious arrhythmias, and may therefore prove to be a useful screening test to determine the need for hospitalization and arrhythmia monitoring following blunt chest trauma.     

Metabolism of methotrexate and gamma-tert-butyl methotrexate by human leukemic cells in culture and by hepatic aldehyde oxidase in vitro

The cellular uptake and metabolism of methotrexate (MTX) and gamma-tert-butyl methotrexate (TBM) were compared in CEM human leukemic lymphoblasts and a highly MTX-resistant subline (CEM/MTX) in which MTX uptake is defective. The CEM/MTX cells were found previously to be as sensitive as the parent line to TBM. While MTX was polyglutamylated extensively in the CEM cells, giving abundant levels of non-effluxing conjugates, polyglutamylation in CEM/MTX cells was reduced severely, even after exposure to a high MTX concentration (100 microM) in the medium. This treatment provided free intracellular MTX in greater than 100-fold excess over the dihydrofolate reductase level. In contrast to MTX, the ester TBM was unmetabolized in either cell line. Uptake levels after incubation of CEM and CEM/MTX cells with 2 microM TBM for 24 hr were 17 and 15 pmol/mg protein respectively. Thus, TBM accumulated equally in both cells and was well retained despite the lack of polyglutamylation. These results, together with the previously observed affinity of the drug for dihydrofolate reductase, provide a plausible rationale for the comparable sensitivity of CEM and CEM/MTX cells to TBM. Experiments were also performed to determine the susceptibility of TBM to metabolic detoxification by hepatic aldehyde oxidase. Km values were 8-fold lower for TBM than for MTX in assays using an enzyme preparation from rabbit liver, and Vmax values were 8-fold higher. Neither MTX nor TBM was oxidized to its 7-hydroxy derivative in intact CEM or CEM/MTX cells. Because TBM is capable of overcoming at least one of the modalities of MTX resistance, defective polyglutamylation, and may be more efficiently detoxified than MTX by the action of hepatic aldehyde oxidase, it has the potential to be a useful agent for the treatment of MTX-resistant tumors.     

Two types of Na(+)-currents in cultured rat optic nerve astrocytes: changes with time in culture and with age of culture derivation.

Na+ channel expression was studied in cultures of rat optic nerve astrocytes using whole-cell voltage-clamp recordings. Astrocytes from postnatal day 7 rat optic nerve (RON) expressed two distinct types of Na+ currents, which had significantly different h infinity curves. Stellate, GFAP+/A2B5+ astrocytes showed currents with h infinity curve midpoints close to -65 mV, similar to Na+ currents in most neurons. In contrast, flat fibroblast-like GFAP+/A2B5- astrocytes showed Na+ currents with h infinity midpoints around -85 mV, almost 20 mV more hyperpolarized than in neurons or A2B5+ astrocytes. Interestingly, Na+ current expression was maintained in A2B5+ astrocytes but began to decrease in A2B5- astrocytes after 6 days in vitro (DIV) and fell to or below the level of detection (i.e., 1 pA/pF) at 12 DIV. Astrocytes cultured from neonatal rats (P0) are almost exclusively GFAP+/A2B5-. These cells did not display measurable Na+ currents when studied at 2 DIV; however, Na+ current was observed after 5 DIV in A2B5- astrocytes from these neonatal (P0) cultures. These findings were substantiated by immunocytochemical experiments using 7493, an antibody raised against purified rat brain Na+ channels; in P0-derived astrocyte cultures 7493 antibody staining was initially lacking (up to 3 DIV), but it was prominent in cultures after 5 DIV, suggesting that Na+ current expression in RON astrocytes occurs postnatally.     

Type II sodium channels in spinal cord astrocytes in situ: Immunocytochemical observations

The expression of sodium channel α-subunit isoforms in astrocytes in adult rat spinal cord and optic nerve was examined utilizing immunocytochemical methods with antibodies generated against conserved and subtype-specific sequences of the sodium channel. In adult rat spinal cord, astrocytes within the dorsal and ventral funiculi were immunolabelled with antibody SP20, which recognizes a conserved sequence within sodium channel types I, II, and III. In addition, astrocytes within these spinal cord white matter tracts were immunostained with antibody SP11-II, which recognizes sodium channel type II. Antibodies SP11-I and SP32-III, which are directed against subtype-specific sequences in sodium channel types I and III, respectively, did not label astrocytes in the dorsal and ventral funiculi of the spinal cord. In optic nerves, astrocytes were immunostained with antibody SP20. However, no detectable labelling of cells within the optic nerve was observed with antibodies SP11-I, SP11-II, and SP32-III. These observations demonstrate that sodium channel II is expressed by astrocytes in spinal cord white matter. Moreover, these data suggest that regional factors regulate the level of sodium channel isoform expression in astrocytes.