Biomedical subjects

D R Brown

Publications and source records attributed to D R Brown.

At least 235 records · Page 13Linked to original sources

PubMed1994

Formation of multiple complexes between actinomycin D and a DNA hairpin: structural characterization by multinuclear NMR.

The solution conformations of a DNA oligomer and its complexes with the anticancer drug actinomycin D (ActD) were characterized using homo- and heteronuclear NMR techniques. Previous high-resolution NMR investigations of ActD-DNA complexes employed symmetric double-stranded DNA oligomers, yielding two identical symmetry-related complexes. In order to understand the important effects that neighboring base pairs and/or unusual nucleic acid structures may have on ActD binding specificity and orientation, we chose to study the oligonucleotide d(TCGCGTTTTCGCGA), which adopts a hairpin structure in solution. NOE cross-peak intensities were used to generate distance constraints for molecular dynamics simulations and structure determinations of the free oligonucleotide and for both complexes. A total of 86 intermolecular NOEs were identified for each complex, 27 of which involve exchangeable protons. These intermolecular NOEs along with changes in the phosphorus chemical shifts were used to determine the drug binding site on the DNA. As expected, ActD intercalated exclusively at the single d(GC) step in the DNA hairpin. Interestingly, although the two complexes, which differ by the orientation with which the asymmetric drug chromophore intercalates the DNA, were not formed in equal concentrations, their conformations are very similar. The RMS difference of the DNA hairpin in the two complexes is only 1.10 A. The structures of the minor groove binding pentapeptide rings are not affected by any of the changes in the normal double-helical structure imposed by the hairpin loop. The total pairwise RMS difference over all atoms for the four peptides (two per complex) in the calculated structures is 0.72 A. Conversely, the structure of the hairpin loop is not appreciably changed upon binding--the RMS difference between the free DNA loop region and the loop region in the two complexes is 1.68 A and only 0.43 A between the two complexes. Our data also support a possible conformation of the d(T)4 loop that does not possess a thymine-thymine "wobble" base pair.

Amino Acid Sequence↗

PubMed1994

A multicenter review of the treatment of major truncal necrotizing infections with and without hyperbaric oxygen therapy.

To examine the effectiveness of hyperbaric oxygen (HBO) therapy in the treatment of major truncal necrotizing infections, a retrospective (1980 to 1992) analysis of the medical records of 30 patients treated with HBO therapy and 24 patients treated without HBO therapy was undertaken. The two groups were similar; however, there was a selection bias towards more frequent clostridial infections in a younger population in the HBO group. There was no difference in length of hospital stay, intensive care unit (ICU) stay, or duration of antibiotic therapy between groups. The mortality rates were 9/30 (30%) in the HBO group versus 10/24 (42%) (nonsignificant difference) in the non-HBO group. The total number of operations was greater in the HBO-treated group. This study failed to show that the use of HBO in the treatment of major truncal necrotizing infections statistically reduced mortality or the number of débridements. We believe, however, that the apparent selection bias and the trend towards increased survival in the HBO-treated group (12%) justifies the continued use of and research with HBO therapy.

Anti-Bacterial Agents↗

PubMed1994

Umbilical arterial catheter use: report of an audit conducted by the Study Group for Complications of Perinatal Care.

The Study Group for Complications of Perinatal Care through 13 of its participating neonatal intensive care units conducted an audit of umbilical artery catheter (UAC) use over 3 months. Of 1941 patient admissions, 582 (30%) had a UAC inserted and left in place for a mean of 4.9 days. The mean supplemental oxygen concentration (FIO2) at removal was 0.35 with over 55% of UACs remaining in place until FIO2 was less than 0.26. Institutional practices varied widely for positioning the catheter tip, use of heparin, and types of infusates, as did the frequency of adverse events that prompted removal of the UAC. Most institutions with multiple physicians found less consistency in practice patterns within their own units than presumed prior to the audit. Just two institutions preferred catheter placement in the abdominal aorta (low) with the others selecting a low site only after detecting a malposition below the initially sought thoracic level. All but one group routinely used heparin, although in varying concentrations and total doses. Patient weight and catheter duration were inversely correlated, with smaller patients having catheters left in place for significantly longer periods (P < 0.01). Similarly, smaller patients had a higher likelihood of catheter removal because of an adverse event; the adverse events were not necessarily related to longer duration. A significant relationship existed between positioning a catheter tip in the abdominal aorta and removal for adverse events (P < 0.05).

Catheterization, Peripheral↗

PubMed1994

Religious predictors of cigarette smoking: findings for African American women of childbearing age.

Data from a community-based survey of 252 African American women 18 to 44 years of age were used to examine the relation between cigarette smoking and two measures of religious involvement. Findings indicated that cigarette smoking among African American women of childbearing age is related to their denominational affiliation. Specifically, Pentecostal women had significantly lower odds of being a current smoker and higher odds of quitting smoking than did women who belonged to other religious denominations. No significant association was found, however, between smoking and the degree of religiosity. Older age and lower level of education predicted current smoking, whereas having few daily hassles was associated with quitting smoking.

Adolescent↗

PubMed1994

Detection of multiple human papillomavirus types in condylomata acuminata from immunosuppressed patients.

Using the hybrid capture method, condylomata acuminata from healthy patients (controls) and patients with altered cell-mediated immunity were analyzed for multiple human papillomavirus (HPV) DNA: 82.9% and 38.0% of lesions from 41 controls and 21 patients, respectively, were HPV DNA-positive only with probes for low-risk HPV types (P = .00035). Using probes for both low- and high-risk HPV types, 16.3% and 52.3% of lesions from 43 controls and 21 patients, respectively, were positive for both probes (P = .0038). Evidence of multiple HPV types was also found by Southern blot and in situ hybridization studies. The mean HPV copy number detected by either probe did not differ significantly among patient groups. Using sensitive techniques, such as hybrid capture, multiple HPV types, including those associated with genital malignancy, can be detected in condylomata acuminata. Serial biopsies demonstrate the dynamic nature of genital HPV infection and that changes in the predominant HPV types may be reflected in tissue pathology.

Biopsy↗

PubMed1994

Sympathetic nervous activity and arterial blood pressure control in conscious rat during rest and behavioral stress.

The object of this experiment is to analyze the neural control of arterial blood pressure (BP) during rest and a sudden behavioral stress. Sprague-Dawley rats were classically conditioned by following a 15-s tone (CS+) with a 0.5-s tail shock. Bipolar renal nerve electrodes and a caudal artery catheter were implanted. Two days later BP and sympathetic nervous activity (SNA) were recorded in the behaviorally trained animals. The CS+ evoked a large initial increase in BP (peak, 14 +/- 5 mmHg, mean +/- SD; n = 12) that lasted 3.9 +/- 0.8 s. An abrupt (latency = 0.16 +/- 0.03 s), short (duration = 0.58 +/- 0.12 s), and intense (4.09 +/- 1.02 times average control) burst in sympathetic activity preceded this first component (C1) of the BP conditional response. The size of C1 was related to the magnitude of the SNA burst. SNA then fell below control; this quiet period preceded a fall in BP after the C1 peak. Pressure rose again (C2; peak = 6 +/- 3 mmHg, average increase = 3 +/- 3 mmHg) for the remainder of the CS+. SNA increased to 1.24 +/- 0.14 of control during this second component of the BP conditional response. Ganglionic blockade eliminated the BP and SNA conditional response (n = 3). The C1 pressure increase appears to result from an "open-loop" process in which a brief barrage of nerve activity governs BP changes lasting several seconds. The quite period probably results from a negative feedback (i.e., baroreflex) relationship between SNA and BP.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed1994

Sympathetic activity and blood pressure are tightly coupled at 0.4 Hz in conscious rats.

Interactions of sympathetic nerve activity (SNA) with blood pressure (BP) and heart rate (HR) were assessed in conscious rats while they rested quietly in a cloth sock (n = 7), roamed freely in their home cage (n = 6), and then after anesthesia with pentobarbital (30 mg/kg; n = 7). The power and coherence spectra below 3 Hz were calculated from data collected for 9.56 min. In the conscious rat, SNA spectral power peaked at 0.4 Hz, whereas the majority of spectral power for both BP and HR occurred at frequencies lower than 0.4 Hz. However, there was an inconspicuous peak in the BP power spectra at 0.4 Hz that was not seen in the HR spectra. Coherence between SNA and BP peaked at a frequency of approximately 0.4 Hz, the same frequency at which the SNA spectral peaks occurred. In contrast, at frequencies below 0.4 Hz where maximum BP power occurred, the coherence was considerably lower. Anesthesia with pentobarbital lowered spectral power for BP, SNA, and HR but essentially did not change the coherence between SNA and BP. Interactions between respiration and each of the other variables were weak in the conscious rat. However, prominent respiratory interactions at approximately 1.2 Hz were evident after anesthesia. These data indicate a close coupling between SNA and BP at 0.4 Hz, raising the possibility that the BP spectral power at 0.4 Hz reliably reflects sympathetic activity.

Anesthesia, General↗

PubMed1994

Modulation of gap-junction channel gating at zebrafish retinal electrical synapses.

1. Transmission at electrical synapses is modulated by a variety of physiological signals, and this modulation is a potentially general mechanism for regulating signal integration in neural circuits and networks. In the outer plexiform layer of the retina, modulation of horizontal-cell electrical coupling by dopamine alters the extent of spatial integration in the horizontal-cell network. By analyzing the activity of individual gap-junction channels in low-conductance electrical synapses of zebrafish retinal horizontal cells, we have defined the properties of these synaptic ion channels and characterized the functional changes in them during modulation of horizontal-cell electrical synapses. 2. Zebrafish horizontal-cell gap-junction channels have a unitary conductance of 50-60 pS and exhibit open times of several tens of milliseconds. The kinetic process of channel closure is best described by the sum of two rate constants. 3. Dopamine, and its agonist, (+/-)-6,7-dihydroxy-2-amino-tetralin (ADTN), modulates electrical synaptic transmission between horizontal cells predominantly by affecting channel-gating kinetics. These agents reduced the open probability of gap-junction channels two- to threefold by reducing both the duration and frequency of channel openings. Both time constants for channel open duration were reduced, whereas the duration of shut periods was increased. Similar changes in open-time kinetics were observed in power spectra of higher conductance gap junctions. 4. These results provide a description of rapid electrical synaptic modulation at the single channel level. The description should be useful in understanding the mechanisms of plasticity at these synapses throughout the vertebrate central nervous system.

Animals↗

PubMed1994

Stability of visceral behavior in the awake rat during rest.

Brady and colleagues have championed the importance of careful delineation and control of a subject's behavioral state. In this paper we develop the concept of visceral behavior from a physiological perspective. Sprague-Dawley rats were instrumented to record arterial blood pressure, renal sympathetic nerve activity, and respiration. The rats were restrained in a conical cloth sock. Rats that were well adapted to the sock restraint showed a regular respiratory pattern and consistent pressure recordings; they rested quietly in the sock and moved only occasionally to adjust their position. Fourier analysis of blood pressure and nerve activity showed a concentration of power below 1 Hz. The coherence between the two signals was strong (0.83 +/- 0.03) at 0.42 Hz. Conversely, during their initial adjustment to the sock restraint, the rats tended to show large fluctuations in blood pressure associated with episodic apneic breathing; 1 animal displayed this pattern of visceral behavior throughout most of the experiment. Despite this instability in pressure, the rats' overt behavior was stable: They rested quietly in the sock with only occasional position shifts. Spectral analysis and coherence computations showed large shifts in the distribution of power and frequency range over which arterial pressure and sympathetic activity were tightly coupled. These data are consistent with the view that an animal's circulatory adjustments, as well as adjustments in other aspects of its physiological state, constitute an important aspect of behavior, and that this behavior can influence the interpretation of biobehavioral data.

Animals↗

PubMed1994

Religious involvement and health status among African-American males.

Previous studies document the importance of religious involvement in African-American communities. This study examines the extent to which religious involvement is associated with health status among African-American males. The data come from a community sample of 537 males residing in a major US urban area. Three indicators of religious involvement were used: denominational affiliation, frequency of church attendance, and overall religiosity. Measures of health status included a self-assessment of physical health, depressive symptoms, self-reported hypertension, cigarette smoking, and daily drinking of alcohol. The results show significant associations between selected indicators of religious involvement and measures of health status. Fewer depressive symptoms are associated with having a denominational affiliation, while no or low frequency of church attendance is associated with current smoking and daily drinking. Implications for health-related interventions with African-American males are discussed in light of these findings.

Adolescent↗

PubMed1994

Prevention of chemotherapy- or X-irradiation-induced monocytopenia by oral administration of lipophilic muramyl tripeptide.

Subsequent to systemic administration of doxorubicin or whole-body X-irradiation, C57BL/6 mice exhibit a depletion in lymphoid cells (macrophages) lasting 2-3 weeks and returning to normal by 4 weeks after either treatment. We evaluated the ability of repeated oral administration of the synthetic macrophage activator muramyl tripeptide phosphatidylethanolamine (MTP-PE), either in free form or encapsulated into multilamellar liposomes, to reverse or prevent the decline in macrophages after cytoreductive therapies. The number of both resident peritoneal macrophages and peritoneal exudate cells elicited by thioglycollate-induced inflammation increased after the oral administration of MTP-PE (three times a week) for at least 3 weeks. The depletion of macrophage number from the peritoneal cavity that occurred after two IV injections of doxorubicin or X-irradiation with 1.5 or 3.0 Gy was prevented by repeated oral feedings of MTP-PE. Moreover pretreatment of mice with oral MTP-PE prevented depletion of macrophages resulting from IV injections of doxorubicin. Modest protection was also noted for blood leukocytes in mice receiving oral MTP-PE following systemic DXR. Similar effects were achieved when MTP-PE was encapsulated into phospholipid liposomes: this formulation also allowed macrophages to be readily activated to the tumoricidal state. The oral administration of MTP-PE offers an additional strategy for protection of host defense cells during cytoablative therapies.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1994

Screening for lead poisoning in an urban pediatric clinic using samples obtained by fingerstick.

OBJECTIVE: To assess the false positive rate of blood lead (BPb) determinations on samples obtained by fingerstick from children screened in an urban clinic. METHOD: From a single fingerstick (N = 1573), blood was collected in a capillary tube for determining lead concentration (CPb) by graphite furnace and an additional sample was absorbed onto a filter paper for determining lead concentration (FPb) by atomic absorption spectrophotometry with Delves cup. Zinc protoporphyrin (ZPP) was measured immediately and a confirmatory venous lead (VPb) specimen was obtained at the same visit if the ZPP was > or = 35 micrograms/dL (0.6 mumol/L); children with either a CPb or FPb > or = 15 micrograms/dL (0.7 mumol/L) were later recalled for determining VPb. RESULTS: For the 172 children who had a VPb on the same day as the screening tests, the false positive rates (95% confidence intervals) at a lead threshold of 15 micrograms/dL (0.7 mumol/L) were: CPb, 13.5% (6.7-20.3); FPb, 19.1% (11.8-26.4). Analyses using all 679 screens with a paired venous specimen (mean delay between screen and venous testing = 30 days) yielded much higher false positive rates (CPb, 31.3%; FPb, 46.0%). CONCLUSIONS: Screening for lead poisoning is feasible within an urban pediatric clinic by direct measurement of lead concentration in blood samples obtained by fingerstick. The false positive rate that can be obtained is acceptable given the precision of measuring BPb concentration. Practitioners using a staged screening protocol may incorrectly attribute a higher false positive rate to the screening tests, when much of the error may be due to the temporal variability of BPb resulting from both biologic variability in BPb concentration and intermittent exposures.

Child↗

PubMed1994

Wild-type human p53 activates the human epidermal growth factor receptor promoter.

We show that wild-type human p53 transactivates the human epidermal growth factor receptor (EGFR) promoter in vivo in a dose-dependent manner, implicating p53 in promotion of cell proliferation. This activation is sensitive to the expression of cellular oncoprotein MDM2 and human papillomavirus type 18 (HPV-18) E6 protein. The p53 response element is localized within -15 and -569 of the promoter. The EGFR promoter does not have a TATA box, and has low activity in Saos-2 cells in the absence of p53. Results from our in vivo transient transfection assays suggest that p53-binding sites, without any other known promoter element, can act as bidirectional promoters in the presence of wild-type p53. Gel retardation analyses suggest that p53 may serve to nucleate TBP on a promoter. We propose that p53 successfully nucleates the transcription complex, possibly via direct interaction with TFIID, and activates the EGFR promoter.

Base Sequence↗

PubMed1993

Molecular cloning and structural analysis of canine gastric H+,K(+)-ATPase.

Gastric hydrogen-potassium ATPase (H+,K(+)-ATPase) is a heterodimeric protein which participates in the formation of hydrochloric acid. We cloned canine H+,K(+)-ATPase alpha and beta subunit cDNAs from canine gastric cDNA libraries and the alpha subunit gene from a canine genomic library. The alpha subunit gene is 13 kb in length and contains 21 introns ranging from 77 to 1,076 bp. Its 5'-flanking region contains putative regulatory motifs for transcription that are similar to those found in H+,K(+)-ATPase genes from other species. The open reading frames of alpha and beta subunit cDNAs are 3,500 and 870 bp in length and encode proteins of 1,034 and 290 amino acids, respectively. They are 80-90% homologous to corresponding cDNAs previously identified in porcine and rodent gastric tissues.

Amino Acid Sequence↗

PubMed1993

Developmental regulation of insulin-like growth factor binding protein-2 in chick embryo serum and vitreous humor.

The chick embryo is a useful vertebrate model for studying developmental embryogenesis. Insulin-like growth factor I (IGF-I), a potent mitogen, is thought to contribute to the general growth of the embryo as an endocrine factor, and as a paracrine factor to the development of the early embryo and of specific organs such as the eye. Recent data suggest that a family of at least six IGF binding proteins (IGFBPs) complex IGF-I and modulate its biological actions. In the present study, we examine the expression of IGFBPs in chicken serum and vitreous humor at different stages of embryonic development, and compare it with that of IGF-I. As determined by ligand blotting, the predominant IGFBP in chick serum and vitreous humor between embryonic days 4 and 22 (E4-E22) is a 30 kDa IGFBP. This IGFBP was specifically immunoprecipitated by a polyclonal antiserum raised against rat IGFBP-2, the predominant IGFBP in fetal human and rat serum. Although IGFBP-2 is present in both chick fluids at all times examined, serum IGFBP-2 increased progressively between E10-E22, whereas vitreous IGFBP-2 was highest during eye organogenesis (E4-E8). This suggests that vitreous IGFBP-2 is synthesized locally. Like serum IGFBP-2, levels of immunoreactive IGF-I in serum are higher in the second week of embryogenesis than the first. Despite this correlation, changes in IGFBP-2 do not appear to be regulated by IGF-I: (a) serum IGF-I decreases after day 15, whereas IGFBP-2 levels remain stable until hatching; (b) vitreous IGF-I, like serum IGF-I, is higher in the second week of embryogenesis, whereas vitreous IGFBP-2 is highest in the first week; (c) embryos cultured ex ovo express IGFBP-2 at E15-E19, although they lack the normal mid-embryogenesis surge in IGF-I. We conclude that vitreous IGFBP-2 is synthesized locally in the eye, and that the expression of IGFBP-2 in chick embryos is not directly regulated by IGF-I.

Animals↗

PubMed1993

The human gastrin/cholecystokinin type B receptor gene: alternative splice donor site in exon 4 generates two variant mRNAs.

Gastrin and its carboxyl-terminal homolog cholecystokinin (CCK) exert a variety of biological actions in the brain and gastrointestinal tract that are mediated in part through one or more G protein-coupled receptors which exhibit similar affinity for both peptides. Genomic clones encoding a human gastrin/CCKB receptor were isolated by screening a human EMBL phage library with a partial-length DNA fragment which was based on the nucleotide sequence of the canine gastrin receptor. The gene contained a 1356-bp open reading frame consisting of five exons interrupted by 4 introns and was assigned to human chromosome 11p15.4. A region of exon 4, which encodes a portion of the putative third intracellular loop, appears to be alternatively spliced to yield two different mRNAs, one containing (452 amino acids; long isoform) and the other lacking (447 amino acids; short isoform) the pentapeptide sequence Gly-Gly-Ala-Gly-Pro. The two receptor isoforms may contribute to functional differences in gastrin- and CCK-mediated signal transduction.

Alternative Splicing↗

PubMed1993

p53 and SV40 T antigen bind to the same region overlapping the conserved domain of the TATA-binding protein.

In this report we demonstrate that the cloned human TATA-binding protein (TBP) interacts with T antigen. TBP co-immunoprecipitates with T antigen when incubated with the T antigen-specific monoclonal antibody PAb419, and Protein-A agarose. Gel retention analysis with a radiolabeled TATA box-containing probe showed that the complex of TBP and T antigen can bind to the TATA box. Recently, p53 has also been shown to interact with TBP. Using TBP deletion mutants and co-immunoprecipitation experiments with p53 or T antigen, we show that both p53 and T antigen bind to the same region, amino acids 203-275, within the conserved C-terminal domain of TBP. Binding of p53 and T antigen to the same domain on TBP may lead to competition between the two proteins for transcriptional function.

Amino Acid Sequence↗

PubMed1993

Cycloheximide stabilizes insulin-like growth factor-binding protein-1 (IGFBP-1) mRNA and inhibits IGFBP-1 transcription in H4-II-E rat hepatoma cells.

The insulin-like growth factor-binding proteins (IGFBPs) are a family of six proteins that modulate the biological activity of IGF-I and IGF-II and determine their bioavailability to tissues. One of the IGFBPs, IGFBP-1, is distinctive in the dynamic response of its levels in human plasma to metabolic changes. Parallel changes occur in IGFBP-1 mRNA and IGFBP-1 transcription in rat liver. Using the well differentiated H4-II-E rat hepatoma cell line as a model system, we demonstrated previously that IGFBP-1 transcription is positively regulated by dexamethasone and negatively regulated by insulin. We now examine the effect of the protein synthesis inhibitor, cycloheximide, on the hormonal regulation of IGFBP-1 gene expression. Preincubation of H4-II-E cells with 10.7 microM cycloheximide for 1.5 h did not prevent the induction of IGFBP-1 mRNA and IGFBP-1 transcription (determined in nuclear run-on assays) by dexamethasone. By contrast, cycloheximide treatment abolished the decrease in IGFBP-1 mRNA induced by insulin. Insulin rapidly decreased IGFBP-1 transcription in the absence of cycloheximide (> 50% inhibition in 20 min) and caused a similar decrease in cells pretreated with cycloheximide. Cycloheximide alone also decreased IGFBP-1 transcription. Similar results were observed with a second protein synthesis inhibitor, anisomycin, which also prevented the insulin-induced decrease in IGFBP-1 mRNA without abolishing the insulin-induced inhibition of IGFBP-1 transcription. These results suggest that although insulin decreases IGFBP-1 gene transcription in the presence of protein synthesis inhibitors, IGFBP-1 mRNA levels are maintained because of stabilization of the mRNA. Stabilization was demonstrated directly in actinomycin D-treated cells, where the t1/2 of IGFBP-1 mRNA increased from approximately 2 to approximately 20 h in the presence of cycloheximide; insulin did not affect IGFBP-1 mRNA turnover. Thus, cycloheximide-sensitive labile proteins contribute to the maintenance of basal IGFBP-1 promoter activity and the rapid turnover of IGFBP-1 mRNA, which determine the dynamic regulation of IGFBP-1 gene expression.

Animals↗