Biomedical subjects

M A Vogelbaum

Publications and source records attributed to M A Vogelbaum.

10 recordsLinked to original sources

PubMed2001

Successful treatment of vancomycin-resistant enterococcus meningitis with linezolid: case report and review of the literature.

OBJECTIVE: To describe the successful treatment of a case of vancomycin-resistant enterococcus meningitis with linezolid. DESIGN: Case report and review of the literature. PATIENTS: The patient is a 35-yr-old man who suffered a cerebellar hemorrhage after embolization of a cerebellar arteriovenous malformation. The patient underwent ventriculostomy drainage and craniectomy. The patient was on broad-spectrum antibiotics for pneumonia including vancomycin. The patient remained febrile and grew vancomycin-resistant Enterococcus faecium from the cerebrospinal fluid. INTERVENTIONS: The patient was treated with intravenous chloramphenicol without success. On postoperative day 16, the patient was begun on intravenous linezolid. MAIN RESULTS: The patient received 4 wks of intravenous linezolid with complete eradication of the meningitis. CONCLUSIONS: Intravenous linezolid appears to be a safe and effective therapy for vancomycin-resistant enterococcus meningitis.

Acetamides↗

PubMed1999

Overexpression of bax in human glioma cell lines.

OBJECT: Cells that lose their ability to undergo apoptosis may promote the development of neoplasms and result in resistance to clinical treatment with DNA-damaging modalities such as radio- and chemotherapy. Four established human glioma cell lines that are resistant to apoptosis were transfected with the proapoptotic gene bax and assessed for their sensitivity to a proapoptotic stimulus. METHODS: Two cell lines had a wild-type p53 genotype (U87 and D247MG) and two had mutant p53 genotypes (U138 and U373). Constitutive overexpression of murine bax was achieved in U138 and U373 only, which resulted in an increased sensitivity of these lines to the apoptosis-inducing effect of cytosine arabinoside (ara-C). Multiple attempts to produce constitutive overexpression of bax in U87 and D247MG cells resulted in spontaneous, near-complete cell loss. Vector-only control transfections were successful in all four cell lines. Inducible overexpression of bax was achieved in the U87 cells and elevated levels of BAX were observed as early as 6 hours after gene induction. This overexpression of BAX resulted in the spontaneous induction of apoptosis in these cells. CONCLUSIONS: Overexpression of BAX in four human glioma cell lines resulted in increased sensitivity to apoptosis. In the two lines that had a wild-type p53 genotype, overexpression of BAX produced spontaneous apoptosis. In contrast, the lines that had mutant, nonfunctional P53 did not undergo spontaneous apoptosis, but they were rendered more sensitive to the apoptosis-inducing effect of ara-C. Modulation of BAX expression may be a useful therapeutic modality for gliomas, regardless of p53 genotype.

Animals↗

PubMed1998

Developmental regulation of apoptosis in dorsal root ganglion neurons.

The survival of dorsal root ganglion (DRG) neurons, both in vivo and in vitro, is dependent on the availability of nerve growth factor (NGF) for a transient period early in development after which these neurons become independent of NGF for survival. The precise molecular mechanism by which developing DRG neurons gain independence from NGF has not been determined. We used an in vitro model of DRG neuronal development to test hypotheses that independence from NGF in mature DRG neurons could be caused by developmental regulation of either elements of the NGF withdrawal signal transduction pathway or of proteins important for activation of the apoptosis output pathway. Interruption of phosphotidylinositol-3 kinase activation, by treatment with the specific inhibitor LY294002, resulted in apoptosis in immature but not mature DRG neurons in a manner similar to that observed with NGF withdrawal. Further downstream along the signal transduction pathway, c-JUN phosphorylation occurred in both immature and mature DRG neurons after NGF withdrawal or treatment with LY294002, despite the fact that the older neurons did not undergo apoptosis. In contrast, the ratio of expression of the proapoptotic gene bax to antiapoptotic gene bcl-xL was many times higher in immature than mature neurons, both in vivo and in vitro. Taken together, these results strongly suggest that developmental regulation of NGF withdrawal-induced apoptosis in DRG occurs via control of the relative level of expression of members of the bcl-2 gene family.

Animals↗

PubMed1998

Management of uncomplicated skull fractures in children: is hospital admission necessary?

OBJECTIVE: This study was undertaken to determine the necessity for routine hospital admission of children with skull fractures, a normal neurological exam, a normal head CT, and no other injuries ('uncomplicated skull fracture'). METHODS: A prospective study of closed-head injuries in children was done over a 2-year period at St. Louis Children's Hospital. All patients with closed head injuries underwent skull radiographs and a head CT scan. From this cohort, children with uncomplicated skull fractures were identified and studied. For comparison, a retrospective analysis was also performed of the hospital admission records of children admitted over a 5-year period (1990-1994) with the diagnosis of epidural hematoma (EDH) to identify the typical time intervals between injury and documentation of the lesion in these cases. RESULTS: Forty-four patients with uncomplicated skull fractures were identified; all had been admitted for observation. Mean age was 1.8 years. Average time between injury and hospital admission was 6.35 h with half of this time being spent in the emergency room. Average LOS was 35 h, but 50% of patients were hospitalized less than 24 h. No patient in this study group suffered a complication related to their inury. Twenty-three patients with EDH had been admitted during the 5-year review period. Slightly more than one-half of patients had their EDH detected within 6 h of injury. The others were diagnosed more than 6 h after injury due to a delay in medical evaluation or a delay in obtaining a computed tomographic (CT) scan after an initial medical evaluation. CONCLUSIONS: Patients with uncomplicated skull fractures, in the absence of recurrent emesis and/or evidence of child abuse, can be considered for discharge home. The definition of an uncomplicated skull fracture requires that a head CT be performed on these patients.

Adolescent↗

PubMed1998

Transfection of C6 glioma cells with the bax gene and increased sensitivity to treatment with cytosine arabinoside.

OBJECT: Genes known to be involved in the regulation of apoptosis include members of the bcl-2 gene family, such as inhibitors of apoptosis (bcl-2 and bcl-xl) and promoters of apoptosis (bax). The authors investigated a potential approach for the treatment of malignant gliomas by using a gene transfection technique to manipulate the level of an intracellular protein involved in the control of apoptosis. METHODS: The authors transfected the murine bax gene, which had been cloned into a mammalian expression vector, into the C6 rat glioma cell line. Overexpression of the bax gene resulted in a decreased growth rate (average doubling time of 32.96 hours compared with 22.49 hours for untransfected C6, and 23.11 hours for clones transfected with pcDNA3 only), which may be caused, in part, by an increased rate of spontaneous apoptosis (0.77 +/- 0.15% compared with 0.42 +/- 0.08% for the vector-only transfected C6 cell line; p = 0.038, two-tailed Student's t-test). Treatment with 1 microM cytosine arabinoside (ara-C) resulted in significantly more cells undergoing apoptosis in the cell line overexpressing bax than in the vector-only control cell line (23.57 +/- 2.6% compared with 5.3 +/- 0.7% terminal deoxynucleotidyl transferase-mediated biotinylated-deoxyuridine triphosphate nick-end labeling technique-positive cells; p = 0.007). Furthermore, measurements of growth curves obtained immediately after treatment with 0.5 microM ara-C demonstrated a prolonged growth arrest of at least 6 days in the cell line overexpressing bax. CONCLUSIONS: These results can be used collectively to argue that overexpression of bax results in increased sensitivity of C6 cells to ara-C and that increasing bax expression may be a useful strategy, in general, for increasing the sensitivity of gliomas to antineoplastic treatments.

Animals↗

PubMed1997

Radiation-induced apoptosis in dorsal root ganglion neurons.

Ionizing radiation (IR) results in apoptosis in a number of actively proliferating or immature cell types. The effect of IR on rat dorsal root ganglion (DRG) neurons was examined in dissociated cell cultures. After exposure to IR, embryonic DRG neurons, established in cell culture for six days, underwent cell death in a manner that was dose-dependent, requiring a minimum of 8 to 16 Gy. Twenty-five per cent cell loss occurred in embryonic day 15 (E-15) neurons, grown in cell culture for 6 days ('immature'), and then treated with 24 Gy IR. In contrast, only 2% cell loss occurred in E-15 neurons maintained in culture for 21 days ('mature') and then treated with 24 Gy IR. Staining with a fluorescent DNA-binding dye demonstrated clumping of the nuclear chromatin typical of apoptosis. Initiation of the apoptosis occurred within 24 h after exposure to IR. Apoptosis was prevented by inhibition of protein synthesis with cycloheximide. Apoptosis induced by IR occurred more frequently in immature than in mature neurons. Immature DRG neurons have a lower concentration of intracellular calcium ([Ca2+]i) than mature neurons. Elevation of [Ca2+]i by exposure to a high extracellular potassium ion concentration (35 microM) depolarizes the cell membrane with a resultant influx of calcium ions. The activation of programmed cell death after nerve growth factor (NGF) withdrawal is inversely correlated with [Ca2+]i in immature DRG neurons. When treated with high extracellular potassium, these immature neurons were resistant to IR exposure in a manner similar to that observed in mature neurons. These data suggest that [Ca2+]i modulates the apoptotic response of neurons after exposure to IR in a similar manner to that proposed by the "Ca2+ setpoint hypothesis" for control of NGF withdrawal-induced apoptosis.

Animals↗

PubMed1993

Mutant circadian period as a marker of suprachiasmatic nucleus function.

Fetal suprachiasmatic nucleus (SCN) tissue transplanted into the third ventricle of hamsters bearing complete SCN lesions restores the circadian locomotor rhythm with a period that depends exclusively on the genetically determined period of the tissue donor. If the host is only partially lesioned and thus retains rhythmicity with its own genetically determined period, an implant from an animal of a different genotype can induce a second rhythm with a period determined by the donor genotype. Both rhythms can be present simultaneously in the record of such a "temporal chimera," interacting only superficially (i.e., not at the level of the pacemaker). Our data support the interpretation that under such circumstances the graft is able to capture part of the locomotor output of the circadian system, but does not make functional connections with the host SCN pacemaking system.

Animals↗

PubMed1992

Temporal chimeras produced by hypothalamic transplants.

The expression of locomotor activity by golden hamsters is temporally controlled by circadian oscillators contained within the suprachiasmatic nuclei. A genetic mutation has been found that alters the freerunning period of the locomotor activity rhythm from the wild-type value of approximately 24 to approximately 20 hr in homozygous mutants. It has been shown previously that a transplant of fetal hypothalamic tissue containing the suprachiasmatic nuclei to a host rendered arrhythmic by a complete lesion of the suprachiasmatic nuclei restores rhythmicity with the freerunning period that is normally expressed by the donor genotype. We made partial lesions of the suprachiasmatic nuclei of wild-type hosts, which did not completely abolish their circadian rhythmicity, and then placed hypothalamic implants from homozygous mutant fetal donors into the lesion site. The resulting complex patterns of locomotor activity contain rhythmic components with periods of both host and donor circadian oscillators, and suggest the presence of both stimulatory and inhibitory inputs from the circadian system to the centers controlling locomotor behavior.

Animals↗

PubMed1986

The influence of static stress on the corrosion behavior of 316L stainless steel in Ringer's solution.

The decrease in corrosion resistance of 316L stainless steel due to static stress was studied in vitro using a 37 degree C Ringer's solution electrolyte. Both potentiodynamic polarization and coulometric techniques were used. Cyclic anodic polarization tests with highly loaded fracture mechanics samples revealed a lowering of breakdown potential and disruption of passive films compared to unstressed controls. Measurements of the time-averaged current density due to a 100 mV anodic overpotential showed that a stress level causing plastic deformation increases the current density by more than an order of magnitude compared to samples stressed to the yield stress or nonloaded controls. The significance of these findings for surgical implant devices in service is discussed.

Alloys↗

PubMedDate not supplied

Factors determining the restoration of circadian behavior by hypothalamic transplants.

The expression of locomotor activity by golden hamsters is temporally controlled by circadian oscillators contained within the suprachiasmatic nucleus (SCN). A genetic mutation has been found that alters the freerunning period of the locomotor activity rhythm from the wild-type value of approximately 24 hours to approximately 20 hours in homozygous mutants. It has been shown previously that a transplant of fetal hypothalamic tissue containing the SCN to a host rendered arrhythmic by a complete lesion of the SCN restores rhythmicity with the freerunning period which is normally expressed by the donor genotype. To investigate the mechanisms by which the SCN controls the temporal organization of behavior, we made partial lesions to the SCN of hosts of one genotype, and then placed hypothalamic implants from fetal donors of a different genotype into the lesion site. By varying the size of the host's partial SCN lesion and the duration of time between lesioning and transplantation, we have attempted to alter the relative amount of host and donor control over the expression of locomotor activity. We found that the expression of donor rhythmicity requires the presence of a lesion to the host SCN, and that the incidence of donor expression increased as a function of host SCN lesion size. Neither the duration of time between lesioning and transplantation, nor the location of the transplant within the third ventricle had independent effects on the incidence of donor rhythm expression; however, there was a strong suggestion of an effect of their interaction.

Animals↗