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Biomedical subjects

E D Miller

Publications and source records attributed to E D Miller.

At least 19 recordsLinked to original sources
PubMed2001

Separation of human immunodeficiency virus type 1 replication from nef-mediated pathogenesis in the human thymus.

Human immunodeficiency virus type 1 (HIV-1) is frequently attenuated after long-term culture in vitro. The attenuation process probably involves mutations of functions required for replication and pathogenicity in vivo. Analysis of attenuated HIV-1 for replication and pathogenicity in vivo will help to define these functions. In this study, we examined the pathogenicity of an attenuated HIV-1 isolate in a laboratory worker accidentally exposed to a laboratory-adapted HIV-1 isolate. Using heterochimeric SCID-hu Thy/Liv mice as an in vivo model, we previously defined HIV-1 env determinants (HXB/LW) that reverted to replicate in vivo (L. Su, H. Kaneshima, M. L. Bonyhadi, R. Lee, J. Auten, A. Wolf, B. Du, L. Rabin, B. H. Hahn, E. Terwilliger, and J. M. McCune, Virology 227:46-52, 1997). Here we further demonstrate that HIV-1 replication in vivo can be separated from its pathogenic activity, in that the HXB/LW virus replicated to high levels in SCID-hu Thy/Liv mice, with no significant thymocyte depletion. Restoration of the nef gene in the recombinant HXB/LW genome restored its pathogenic activity, with no significant effect on HIV-1 replication in the thymus. Our results suggest that in vitro-attenuated HIV-1 lacks determinants for pathogenicity as well as for replication in vivo. Our data indicate that (i) the replication defect can be recovered in vivo by mutations in the env gene, without an associated pathogenic phenotype, and (ii) nef can function in the HXB/LW clone as a pathogenic factor that does not enhance HIV-1 replication in the thymus. Furthermore, the HXB/LW virus may be used to study mechanisms of HIV-1 nef-mediated pathogenesis in vivo.

Animals↗
PubMed2000

Developmental changes in the neurotransmitter regulation of correlated spontaneous retinal activity.

Synchronized spontaneous rhythmic activity is a feature common to many parts of the developing nervous system. In the early visual system, before vision, developing circuits in the retina generate synchronized patterns of bursting activity that contain information useful for patterning connections between retinal ganglion cells and their central targets. However, how developing retinal circuits generate and regulate these spontaneous activity patterns is still incompletely understood. Here we show that in developing retinal circuits, the nature of excitatory neurotransmission driving correlated bursting activity in ganglion cells is not fixed but undergoes a developmental shift from cholinergic to glutamatergic transmission. In addition, we show that this shift occurs as presynaptic glutamatergic bipolar cells form functional connections onto the ganglion cells, implicating the role of bipolar cells in providing endogenous drive to bursting activity later in development. This transition coincides with the period when subsets of ganglion cells (On and Off cells) develop distinct activity patterns that are thought to underlie the refinement of their connectivity with their central targets. Here, our results suggest that the differences in activity patterns of On and Off ganglion cells may be conferred by differential synaptic drive from On and Off bipolar cells, respectively. Taken together, our results suggest that the regulation of patterned spontaneous activity by neurotransmitters undergoes systematic change as new cellular elements are added to developing circuits and also that these new elements can help specify distinct activity patterns appropriate for shaping connectivity patterns at later ages.

2-Amino-5-phosphonovalerate↗
PubMed2000

Improved outcomes of veterans' compensation and pension examinations using nurse practitioners.

A historic change to improve outcomes of a long-standing problem in completing veterans' compensation and pension examinations has resulted in increased access to care, higher client satisfaction, and increased system efficiencies. This article describes the change from medical care as the exclusive responsibility of physicians to an innovative use of nurse practitioners in a system that exists in a highly structured, centrally coordinated patient care practice.

Adult↗
PubMed1999

Restoration of a stem-loop structure required for potato virus X RNA accumulation indicates selection for a mismatch and a GNRA tetraloop.

The 5' region of potato virus X (PVX) RNA contains a stem-loop structure, stem-loop 1 (SL1), that is required for efficient plus-strand RNA accumulation. To determine how changes to individual elements in SL1 are accommodated by the virus, we inoculated PVX transcripts containing modifications in the terminal tetraloop (TL), stem C (SC), and stem D (SD) regions onto Nicotiana benthamiana plants and analyzed progeny RNAs over a series of passages. Several progeny RNAs isolated from plants inoculated with the TL mutants containing changes to the first nucleotide of the GAAA motif or deletion of the entire TL sequence were found to contain multiple A insertions within the terminal loop region. The wild-type TL motif, GAAA, was recovered for all TL mutants by the second passage, suggesting that the sequence and potential structure of this element are crucial for PVX infection. Revertant RNAs isolated from plants inoculated with mutants in SD and the central region of SC indicated that increased stem length is tolerated. Restoration of SD length to the 4 bp typical of the wild-type PVX RNA was accompanied by A insertion into loop C. Mutants with a conversion of the C55-C78 mismatch to a G-C pair, relocation of this mismatch within the central region of SC, or deletion of C55-C78 were unable to infect protoplasts and plants. In contrast, the mutant with a conversion of the C55-C78 mismatch to an A-C mismatch, which exhibited low levels of PVX plus-strand RNA in protoplasts, was able to infect plants and quickly reverted to the wild-type C-C mismatch. These data indicate that important sequence and secondary structural elements within SL1 are required for efficient viral infection and that multiple A insertions within the TL and loop C regions, potentially by polymerase stuttering, accompany restoration of SL1 structure.

Adenosine↗
PubMed1998

Stem-loop structure in the 5' region of potato virus X genome required for plus-strand RNA accumulation.

Computer-generated thermodynamic predictions and solution structure probing indicated two stem-loop structures, stem-loop 1 (SL1; nt 32-106) and stem-loop 2 (SL2; nt 143-183), within the 5' 230 nt of potato virus X (PVX) RNA. Because the existence of SL1 was further supported by covariation analysis of several PVX strains, the functional significance of this structure was investigated by site-directed mutational analysis in a tobacco protoplast system. In general, mutations that reduced genomic plus-strand RNA accumulation similarly affected coat protein accumulation, indicating that subgenomic plus-strand RNA was also affected. In contrast, minus-strand RNA levels remained relatively unchanged. Mutational analysis of the stem C (SC) region of SL1 indicated that pairing was more important than sequence, which was consistent with the covariation analysis. Alterations that increased length and stability of either SC or stem D (SD) were deleterious to plus-strand RNA accumulation. The formation of internal loop C between SC and SD, as well as specific nucleotides within this loop, were also required. Several modifications were made to the terminal GAAA tetraloop, a motif known for enhanced RNA stability. Both GANA and GAAG motifs resulted in wild-type levels of RNA accumulation. However, a UUCG tetraloop was detrimental, indicating that the sequence of this element was important beyond just providing stabilization of the structure. These data indicate that multiple features of SL1 are critical for accumulation of PVX plus-strand RNA.

Base Sequence↗
PubMed1998

History of coat protein-mediated protection.

A decade of research has proven that plants can be genetically engineered to resist virus infection through expression of viral CP genes, as well as other viral genes and sequences. Additional opportunities for development of resistant plants will require research focused on mechanisms of protection, improvements in expression vector design, and transformation of new crop species. As each of these technologies is utilized singly or in combination to generate resistant crop varieties, the full impact of such engineered resistance will be realized.

Capsid Proteins↗
PubMed1997

Exposure workups.

Exposure workups are an important responsibility for infection control personnel. A well-designed plan for investigating exposures, which includes appropriate algorithms, will enable infection control personnel to evaluate exposures rapidly and consistently so that nosocomial transmission is minimized. Infection control personnel should use their own data to develop policies and procedures that suit the needs of their facility. After they have implemented the plan, infection control personnel should continue to collect data on exposures so they can continuously improve their performance.

Algorithms↗
PubMed1993

Esmolol hydrochloride, sodium nitroprusside, and isoflurane differ in their ability to alter peripheral sympathetic responses.

To demonstrate that esmolol, sodium nitroprusside, and isoflurane differ in their abilities to alter adrenal medullary blood flow and other peripheral sympathetic responses to hypotension, 16 mongrel dogs anesthetized with pentobarbital were allocated randomly to one of four test groups and given two hypotensive stimuli, separated by 1 h, to a mean arterial blood pressure of 60 mm Hg for 10 min. The first stimulus, induced by blood loss into a pressurized bottle system, constituted the control for each animal. The second hypotensive stimulus was created by either repeat blood loss (Group 1), esmolol infusion (Group 2), sodium nitroprusside infusion (Group 3), or isoflurane administration (Group 4). Before and 10 min into hypotension, the variables of abdominal organ blood flow, adrenal medullary blood flow, arterial norepinephrine and epinephrine concentrations were measured. In the control animals (Group 1), comparable decreases in abdominal organ blood flow and similar increases in adrenal medullary blood flow, norepinephrine, and epinephrine were elicited by the first and second hypotensive stimulus. Esmolol-induced hypotension (Group 2) abolished the increase in adrenal medullary blood flow and attenuated the increase in epinephrine by 65% (P < 0.03). The decrease in abdominal organ blood flow and the increase in norepinephrine were similar to that observed during baseline hemorrhagic hypotension. In contrast, sodium nitroprusside-induced hypotension (Group 3) abolished abdominal organ vasoconstriction whereas the increases in adrenal medullary blood flow, norepinephrine, and epinephrine were comparable to baseline hemorrhagic hypotension. In fact, abdominal organ blood flow increased 2.5-fold (P < 0.001) during hypotension with SNP. Isoflurane 2%, 1.54 minimum alveolar anesthesia concentration (Group 4), abolished the increases in adrenal medullary blood flow, norepinephrine, and epinephrine observed during baseline hemorrhagic hypotension and attenuated the decrease in abdominal organ blood flow by 70% (P < 0.001). These data demonstrate that esmolol, sodium nitroprusside, and isoflurane differ radically in their ability to alter or blunt peripheral sympathetic responses to hypotension, and suggest that isoflurane is the drug most effective in blunting multiple responses of the peripheral sympathetic system.

Adrenergic beta-Antagonists↗
PubMed1993

Isoflurane-induced splanchnic sympathectomy.

To ascertain whether isoflurane produces a peripheral splanchnic sympathectomy as compared to fentanyl or pentobarbital anesthesia, 12 mongrel dogs (30-45 kg) were allocated randomly to one of three anesthetic test groups, tracheally intubated, surgically prepared, and subjected to unilateral electrical stimulation of the greater splanchnic nerve. Anesthetically, Group 1 animals (n = 4) received pentobarbital, Group 2 animals (n = 4) were administered fentanyl, and Group 3 animals (n = 4) received isoflurane. Stimulation continued for 90 min. Each second of stimulation consisted of 20 stimuli of 0.5 minimum alveolar anesthetic concentration duration and 5 V intensity, delivered during a 0.2-s interval, followed by an 0.8-s pause. To assess splanchnic sympathetic responses, mean arterial blood pressure, heart rate, pulmonary artery diastolic, cardiac output, adrenal blood flow, adrenal and arterial norepinephrine (N) and epinephrine (E) were obtained before and at 5, 10, 15, 30, 45, 60, and 90 min during stimulation. In Group 1 animals (pentobarbital), electrical stimulation elicited marked increases in mean arterial blood pressure, pulmonary artery diastolic, and cardiac output (P < 0.001). Examination of the adrenal effluent, which was exteriorized from the animal during the protocol, revealed that adrenal blood flow, adrenal vein N and E concentrations dramatically increased (P < 0.0001). Arterial N and E concentrations remained unchanged. Results of Group 2 animals (fentanyl) were similar to those of Group 1; mean arterial blood pressure, pulmonary artery diastolic, and cardiac output increased (P < 0.005). Adrenal blood flow, adrenal vein N and E increased dramatically (P < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Pregnancy alters the hemodynamic responses to cocaine in the rat.

To test our hypotheses that the hemodynamic response to cocaine may be altered during pregnancy, cocaine (0.33 mg/kg/min) was infused intravenously to chronically catheterized pregnant and nonpregnant female rats. Cardiac output and regional blood flow were measured, and cocaine concentrations in plasma and tissues, as well as plasma cholinesterase activity were determined. Results were compared between pregnant and nonpregnant groups. Cocaine produced a significant decrease in heart rate, accompanied by a fall in cardiac output, and decreased cerebral, myocardial, and placental blood flow in pregnant rats. The plasma cocaine concentration in pregnant animals was lower than that of nonpregnant ones, but tissue concentrations were similar in both groups. These results indicate that pregnancy enhances cardiovascular responses to subtoxic doses of cocaine. There was little placental transfer of cocaine with a fetal to maternal plasma concentration ratio of 0.28.

Animals↗
PubMed1991

Subarachnoid blockade alters homeostasis by modifying compensatory splanchnic responses to hemorrhagic hypotension.

To demonstrate that sympathetic responses transmitted by the splanchnic nerve help maintain intravascular stability, 12 mongrel dogs (35-45 kg each), anesthetized with pentobarbital, were given two separate but identical hypotensive stimuli (mean arterial blood pressure of 60 mm Hg for 15 min) by the withdrawal of appropriate amounts of blood. The first stimulus was performed in the absence of drug or surgical manipulation. The second stimulus was performed after animals were subjected to no intervention (n = 4), bilateral splanchnic nerve section (n = 4), or spinal anesthesia (n = 4). Before and 10 min after the onset of hypotension, arterial epinephrine concentration and adrenal medullary and abdominal organ blood flow were measured. In the group without intervention, the second hypotensive stimulus (like the first) elicited 3-fold increases in adrenal medullary blood flow, 40-fold increases in arterial epinephrine concentration, and a 61% reduction in abdominal organ blood flow (P greater than 0.002). The volume of blood withdrawn to produce hypotension was similar (approximately 21 ml.kg-1). Bilateral splanchnic nerve section attenuated the adrenal medullary blood flow, arterial epinephrine concentration, and abdominal organ blood flow responses to hypotension by 86, 64, and 66%, respectively (P less than 0.008), and the blood volume withdrawn was reduced by 42% (P less than 0.02). Spinal anesthesia eliminated the adrenal medullary blood flow response to hypotension, attenuated the arterial epinephrine concentration and abdominal organ blood flow responses by 78 and 57%, respectively (P less than 0.01), and decreased the blood volume extracted by 55% (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Medulla↗
PubMed1989

Hemodynamic effects of dobutamine in patients following mitral valve replacement.

Mitral valve replacement is frequently complicated by a low cardiac output syndrome and elevated pulmonary arterial pressures. In the present study, we used dobutamine to increase cardiac index and measured the pulmonary hemodynamic effects in 10 patients with increased pulmonary vascular tone following mitral valve replacement. Using increasing doses of dobutamine up to 10 micrograms.kg-1.min-1, we observed a statistically significant increase in mean cardiac index (from 2.39 +/- .14 liters.min-1.m-2 to 3.52 +/- .33, P less than 0.01) and mean heart rate (from 71.6 +/- 5.2 beats.min-1 to 84.3 +/- 8.1, P less than 0.01). This was associated with stable mean systemic arterial pressures and mean pulmonary arterial pressures. Both mean systemic and pulmonary vascular resistances decreased significantly (from 1210 +/- 99 dynes.sec.cm-5 to 809 +/- 90 [P less than 0.01], and from 195.9 +/- 30.6 dynes.sec.cm-5 to 129.4 +/- 41.2 [P less than 0.01] respectively) with dobutamine. Intrapulmonary shunt flow increased significantly in the five patients studied. Though increases in heart rate and pulmonary shunt flow may limit it use, dobutamine increases cardiac output and decreases pulmonary vascular resistance in patients with increased pulmonary arterial pressure following mitral valve replacement.

Adult↗