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Biomedical subjects

M Brenner

Publications and source records attributed to M Brenner.

At least 19 recordsLinked to original sources
PubMed1992

Directed establishment of rat brain cell lines with the phenotypic characteristics of type 1 astrocytes.

Interest in obtaining cell lines for use in studies on the development and biochemistry of the central nervous system has motivated efforts to establish cells from primary brain cultures by the use of oncogene-transfer techniques. In previous reports, cell lines derived from astrocytes in this way have had immature or abnormal phenotypes. We have explored the possibility of specifically "targeting" expression of exogenous oncogenes to differentiated astrocytes by using the promoter of the gene encoding glial fibrillary acidic protein, which is expressed almost exclusively in such cells. We report here that cell lines displaying the phenotypic characteristics of type 1 astrocytes can be established reproducibly in this manner. Given the heterogeneity of primary cultures, the availability of clonal cell lines displaying characteristics of type 1 astrocytes should greatly facilitate our understanding of the biology of these cells.

Animals↗
PubMed1992

Use of cell-free retroviral vector preparations for transduction of cells from the marrow of chronic phase and blast crisis chronic myelogenous leukemia patients and from normal individuals.

Marrow cells were exposed to the LNL6 or G1N safety-modified variants of the N2 retrovirus, which contain the G418 bacterial resistance gene neo. The frequency of acquisition of the G418 resistance phenotype following exposure to LNL6 or G1N was compared among hematopoietic progenitor cells from the marrow of patients with chronic phase chronic myelogenous leukemia (CML), blast crisis CML, or from nonleukemic individuals. Under the conditions of our experiments, the myeloid committed progenitor cells from 3 of 6 nonleukemic individuals, 9 of 18 chronic-phase CML patients, and 2 of 4 blast crisis CML patients acquired resistance to at least 1 mg/ml G418 following incubation with cell-free supernatants from the PA317 LNL6 or PA317 G1N producer cell lines. Ten of the 32 colonies growing up in 0.8 mg/ml G418 from chronic-phase marrow exposed to LNL6 were shown to contain the neo gene by polymerase chain reaction (PCR) assay of DNA. These results were consistent with estimates of the transduction frequency based on acquisition of resistance to G418 as the number of colonies growing under G418 selection was always greater at 0.8 mg/ml G418 than at higher concentrations of G418 (1.0-1.4 mg/ml). The average transduction frequency at each G418 concentration (1.0, 1.2, and 1.4 mg/ml) in cells from blast crisis CML cells ranged from 2 to 14%, as measured by acquisition of G418 resistance. Chronic-phase CML showed slightly lower average frequencies of transduction (0.6-2.8% of the colonies are G418 resistant). The average transduction frequency of cells from nonleukemic marrow was as high as that seen from the marrow of chronic-phase CML individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1992

Is there energy conservation in amenorrheic compared with eumenorrheic distance runners?

The female distance runner is considered at high risk for secondary amenorrhea and reduced spinal bone mineral, and recent studies have suggested that these disturbances might be nutritionally or metabolically linked. The present study investigated 1) whether there is a physiological basis by which the amenorrheic runner might maintain weight at a lower than expected caloric intake, i.e., conservation of energy, and 2) the potential interactions of reduced energy intake, secondary amenorrhea, and reductions in bone density. Subjects included 13 elite female distance runners, 8 amenorrheic and 5 eumenorrheic, and 5 untrained female controls. Body composition by hydrostatic weighing, bone density and mineral content by dual-photon absorptiometry, and blood samples for hormonal analyses (once per week for 4 wk) were obtained, as were duplicate measures for resting metabolic rate, thermic effect of a meal, and the energy cost of specific (treadmill) and nonspecific (cycle ergometer) physical activity. Energy intake and energy expenditure were estimated by 3-day logs. Energy intakes did not differ (1,781, 1,690, and 1,763 kcal), nor did energy expenditures (2,480, 2,314, and 2,268 kcal), for the amenorrheic and eumenorrheic runner and control groups, respectively. The difference between reported energy intake and estimated energy expenditure of 500-700 kcal was likely due to underreporting or restricting intake, inasmuch as there was no evidence of energy conservation. A possible link was suggested between disordered eating, secondary amenorrhea, and bone mineral loss.

Adaptation, Physiological↗
PubMed1992

Pulmonary and oxygen transport effects of intravenously administered endotoxin in normal humans.

Little data are available describing the initial changes in pulmonary function and oxygen transport during human endotoxemia. We studied 26 normal humans after intravenously administered endotoxin (4 ng/kg). To evaluate alterations in gas exchange, hemodynamic monitoring was performed in nine subjects given endotoxin and six subjects given saline only. Compared with the control subjects, no changes in gas exchange occurred at 3 h, but after volume loading (mean, 2.2 L saline infused from 3 to 5 h) the PaO2 fell (86.1 +/- 2.3 mm Hg, p = 0.042), and the AaPO2 widened (18.5 +/- 1.7 mm Hg, p = 0.005). Oxygen consumption and delivery both increased significantly at 3 h (219 +/- 17 and 1,030 +/- 43 ml/min.min2) and 5 h (203 +/- 7 and 949 +/- 48 ml/min.min2) (p less than or equal to 0.035), whereas oxygen extraction fell at 3 h (p = 0.041). Seventeen subjects underwent bronchoalveolar lavage 14 +/- 4 days before and at 1.5 to 3 h (n = 8) or 5 h after (n = 9) the administration of endotoxin. No increase in the total number of cells or percent or absolute number of neutrophils was found at either time point. The rate of clearance of inhaled 99mTc-diethylenetriamine pentacetate aerosol, a measure of alveolar epithelial permeability, increased in subjects scanned before 3 h (n = 8; p less than 0.05), whereas no significant changes occurred in subjects scanned 5 h after endotoxin (n = 5) or in control subjects (n = 6). Early inflammatory responses after intravenous administration of endotoxin to normal humans results in alterations in gas exchange and lung permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Multiple interacting sites regulate astrocyte-specific transcription of the human gene for glial fibrillary acidic protein.

The gfa gene encodes glial fibrillary acidic protein, an intermediate filament protein found almost exclusively in astrocytes. Transient transfection studies with a chloramphenicol acetyltransferase reporter gene were used to identify regions of the gfa gene responsible for its expression. Three regions, A, B, and D, were found to be important. The D region is located near the basal promoter, while A and B are next to each other about 1500 bp further upstream. The regions contain several sequences homologous to binding sites of known transcription factors, and in addition, each contains an identical novel 10-bp motif. The A, B, and D regions act in a cell-specific manner; when joined to the SV 40 early promoter, they enhance transcription in the glial cell line U251, but not in the nonglial cell line HepG2. Consistent with this observation, the DNase I footprint produced in these regions by nuclear extract from U251 cells differs from that produced by an extract from HepG2 cells. The B region appears to be the most active of the three, as by itself it stimulates strong cell-specific transcription, whereas addition of the other two regions has little effect. When the B region is at its normal distance from the basal promoter, deletion of D severely reduces transcription, but when B is placed near the promoter, D is unimportant. This suggests that the D region may function primarily to promote interactions that bring B close to the promoter.

Astrocytes↗
PubMed1991

Thoracoscopic carbon dioxide laser treatment of bullous emphysema.

A new technique of thoracoscopic laser ablation of pulmonary bullae suitable for patients with multiple bullae and diffuse emphysema was developed and assessed in 22 patients. 20 of 22 patients survived. Pre-operative and postoperative functional evaluation is available for the 11 patients followed up for more than a month; at 1 to 3 months postoperatively there were increases in FVC (mean 2.0 litres pre-operatively to 2.7 litres postoperatively, p less than 0.001), in FEV1 (0.74 to 1.06 litres, p = 0.01), and in maximum exercise treadmill times (5.4 min to 8.0 min, p less than 0.01). Postoperative air leaks lasted a mean of 13 days and usually resolved spontaneously. Other complications were bleeding (1 patient) and unilateral acute lung injury (1 patient). These results suggest that selected patients with diffuse emphysema and pulmonary bullae may benefit from thoracoscopic carbon dioxide laser ablation.

Cysts↗
PubMed1991

Quantitation of ColE1-encoded replication elements.

Replication of the Escherichia coli plasmid ColE1 initiates from an RNA primer. This primer is formed by a ColE1 RNA II molecule that remains hybridized to its DNA template in the origin region after transcription. Continued hybridization is inhibited by prior binding to RNA II of another ColE1 transcript, RNA I; and this interaction is regulated by the plasmid-encoded Rom protein. To understand the quantitative aspects of regulation of ColE1 synthesis, we have measured the levels of RNA I, RNA II, and Rom protein in vivo, as well as the half-lives of the RNAs. The intracellular concentrations of RNA I, RNA II, and Rom protein were found to be about 1 microM, 7 nM, and 1 microM, respectively; and the RNAs had half-lives of about 2 min. A simple model derived from these results indicates that the plasmid copy number is little affected by the rate of RNA II synthesis but is strongly dependent on that of RNA I.

Bacterial Proteins↗
PubMed1991

Molecular analysis of retroviral transduction in chronic myelogenous leukemia.

We have developed a polymerase chain reaction (PCR) assay for detection of integrated retroviral transgenomes containing the neo G418 resistance gene in colonies (40 cells or more) grown in G418 selection after exposure to the neo-positive retrovirus LNL6. This assay also provides for simultaneous characterization of these colonies as belonging to a chronic myelogenous leukemic (bcr-abl positive) or nonleukemic population (bcr-abl negative). Using these techniques, we assessed transduction of the LNL6 retrovirus into the normal and leukemic cells of a blast-crisis chronic myelogenous leukemia (CML) patient. This work was designed to support the use of the LNL6 retroviral marker to help identify the origin of relapse after autologous marrow infusion. The data from these experiments show that the majority of CML blast crisis cells that, following exposure to the LNL6 virus, produce colonies under rigorous G418 selection are indeed transduced by the virus, as shown by the presence of the neo retroviral gene. Most of these colonies are also shown to be leukemic by PCR detection of the bcr-abl RNA. This demonstrates the feasibility of the study of CML marrow for retroviral marking. These procedures will be of use in establishing if relapse arises from leukemic blasts which contaminate purged autologous bone marrow infused following intensive therapy for leukemia.

Base Sequence↗
PubMed1991

Speech analysis as an index of alcohol intoxication--the Exxon Valdez accident.

As part of its investigation of the EXXON VALDEZ tankship accident and oil spill, the National Transportation Safety Board (NTSB) examined the master's speech for alcohol-related effects. Recorded speech samples were obtained from marine radio communications tapes. The samples were tested for four effects associated with alcohol consumption is available scientific literature: slowed speech, speech errors, misarticulation of difficult sounds ("slurring"), and audible changes in speech quality. It was found that speech immediately before and after the accident displayed large changes of the sort associated with alcohol consumption. These changes were not readily explained by fatigue, psychological stress, drug effects, or medical problems. Speech analysis appears to be a useful technique to provide secondary evidence of alcohol impairment.

Accidents, Occupational↗
PubMed1991

The metabolic consequences of low and moderate intensity exercise with or without feeding in lean and borderline obese males.

The purpose of this study was to investigate the role of exercise intensity on the post-exercise thermogenic effect (PETE), with or without feeding, in five lean (less than 15 percent body fat) and five borderline obese (between 20 and 25 percent body fat) individuals when the total caloric expenditure during exercise was equated to 720 kcal by adjusting exercise duration. Each subject participated in six testing sessions, including the measurement of resting metabolic rate (RMR), dietary induced thermogenesis (DIT) following a 720 kcal liquid meal, and four exercise trials including: (1) exercising on a treadmill at both 30 percent and 60 percent of VO2 max followed by a 720 kcal liquid meal (30F and 60F); and (2) exercising on a treadmill at both 30 percent and 60 percent of VO2 max followed by a non-caloric liquid meal substitute (water) matched by volume to the caloric liquid meal (30NF and 60NF). Indirect calorimetry was used to determine metabolic rate prior to each treatment (0-30 min RMR) and at 0-30, 50-60, 80-90, 110-120, 140-150, and 170-180 min following the feeding, exercise only, or exercise and feeding treatments. A significant difference in the post-exercise oxygen consumption was found between the two calorically equated exercise bouts (720 kcal) at 30 percent and 60 percent of each subject's VO2 max without feeding when all measurement periods following exercise were averaged together (60NF = 13.5 percent increase and 30NF = 5.5 percent). This difference was observed in both the lean and borderline obese subjects, with no significant difference between the two groups. In addition, when walking at either 30 percent or 60 percent of VO2 max preceded feeding, a significant attenuation in the rise of post-feeding RER values was observed in both groups with the higher exercise intensity showing the greatest RER attenuation when compared to the DIT trial. These results suggest that exercise intensity may play a significant role independent of the total energy expenditure in potentiating a person's post-exercise oxygen consumption rate and post-exercise substrate utilization for periods of up to 180 mins.

Adult↗
PubMed1990

A downstream initiation element required for efficient TATA box binding and in vitro function of TFIID.

The gfa gene encodes glial fibrillary acidic protein, an intermediate filament protein expressed in glial cells. In vitro transcription analysis has shown that the human gfa promoter contains two initiation elements that can independently specify the transcription startpoint. One of the elements is a TATA box 25 base pairs (bp) upstream from the transcription startpoint; the other is located between 10 and 50 bp downstream from the transcription initiation site. We have now shown by transfection that both elements are required for efficient transcription in cultured cells. A partially purified natural human TATA box-binding factor (TFIID) from HeLa cells gave footprints that extended from upstream of the TATA box through the downstream initiator. Deletion of the downstream initiator inhibited both TFIID binding to the TATA box and transcription in vitro. In contrast to natural human TFIID, clone human and yeast TFIIDs expressed in bacteria gave footprints covering only the TATA box region, although hypersensitive sites were observed in the downstream region. The cloned TFIIDs also showed less dependence than natural human TFIID on the downstream initiator for both TATA box binding and in vitro transcription. These results suggest that natural human TFIID contains an additional component(s) that contribute(s) to stable TFIID binding and effective transcription by interacting with the downstream initiator.

Base Sequence↗
PubMed1990

Characterization of human cDNA and genomic clones for glial fibrillary acidic protein.

Both a partial cDNA clone and a complete genomic clone have been isolated for human gfa, the gene encoding the major component of astrocyte intermediate filaments, glial fibrillary acidic protein (GFAP). The nucleotide sequence of the entire coding region and 102 bp of the 5' flanking DNA was determined. The mRNA start site was identified by primer extension and probe protection experiments, and a novel in vitro transcription and translation procedure was then used to establish that the first ATG in the mRNA initiates GFAP synthesis. The predicted amino-terminal sequence for human GFAP differs greatly from that previously deduced for mouse GFAP from its gene sequence, despite otherwise high homology. This discrepancy was resolved by determining that the published mouse genomic sequence has an incorrect additional base. The corrected sequence produces strong homology between human and mouse GFAP in their predicted amino acid sequences, and suggests that human and mouse GFAP initiate at homologous positions. The beginning sequence deduced here for both proteins is matched closely by that previously obtained for porcine GFAP by direct sequencing of its amino-terminal end. This supports the protein initiation sites proposed, and also indicates that GFAP is not processed at its amino-terminal end.

Base Sequence↗
PubMed1990

An RNA polymerase II promoter containing sequences upstream and downstream from the RNA startpoint that direct initiation of transcription from the same site.

The gfa gene encodes glial fibrillary acidic protein (GFAP), an intermediate-filament protein expressed primarily in glial cells. We have used in vitro transcription studies to show that the basal level of transcription of the human gene encoding GFAP is controlled by two distinct initiators--i.e., promoter elements that direct transcription from a specific start site. One initiator is located about 25 base pairs upstream from the transcription start site, contains a TATA box, and apparently acts together with a sequence found around the transcription start site. The other initiator is located between +11 and +50 bp downstream from the transcription start site. Most of this second region overlaps with the protein-encoding sequence, which starts at bp +17. The sensitivity of transcription to alpha-amanitin indicates that both initiators are used by RNA polymerase II.

Amino Acid Sequence↗
PubMed1990

Effects of clinical maneuvers on sonographically determined internal jugular vein size during venous cannulation.

We sought to define variations in internal jugular vein (IJV) anatomy and the effect of recommended cannulation maneuvers on a population of ICU patients. Maneuvers that decreased IJV lumen cross-sectional area were carotid artery palpation (1.48 to 0.82 cm2, p less than .05) and advancement of the needle (1.57 to 0.75 cm2, p less than .001). The head-down (modified Trendelenburg) position increased IJV lumen cross-sectional area (1.18 to 1.62 cm2, p less than .05). There was wide variability in IJV anatomic features, although most patients had patent veins.

Carotid Arteries↗
PubMed1990

The effects of heterologous platelet transfusion on pulmonary function during ARDS.

Pulmonary platelet sequestration has been implicated in the pathophysiology of ARDS. Since HPTs are frequently given therapeutically to patients with ARDS, a serious concern clinically has been the possibility that platelet transfusions might worsen pulmonary function in such patients. To prospectively evaluate this issue, we assessed the effects of HPT on two parameters of pulmonary function: (1) Qs/Qt; and (2) PVR. Measurements were made immediately before and at 1 hour and 4 hours after HPT in 16 patients during 18 separate episodes of ARDS and in 11 control patients. The ARDS had been present for at least 48 hours in all patients at the time of study. Prior to HPT, patients with ARDS had significantly worse pulmonary function compared to control subjects. Although a small number of patients with ARDS had large changes in PVR and Qs/Qt after HPT, no group showed significant changes in any pulmonary parameter following transfusion. Neither individual changes in the platelet count after HPT nor the duration of ARDS before HPT was associated with changes in pulmonary function after platelet administration. We concluded that therapeutically required HPT did not significantly worsen pulmonary function at up to four hours after transfusion in this group of patients with well-defined and fully evolved (greater than 48-hour duration) ARDS. The reason for this absence of effect was not known, but the pathogenesis of ARDS might only be susceptible to alteration during the early developmental stage.

Carbon Dioxide↗