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Biomedical subjects

B E Hoffman

Publications and source records attributed to B E Hoffman.

13 recordsLinked to original sources
PubMed2002

Pharmacological antagonism of lethal effects induced by O-isobutyl S-[2-(diethylamino)ethyl]methylphosphonothioate.

O-Isobutyl S-[2-(diethylamino)ethyl]methylphosphonothioate (VR) is a structural isomer of a more widely known chemical warfare agent O-ethyl S-[2(diisopropylamino)ethyl]methylphosphonothioate (VX). VR has the potential of being used as military threat/sabotage/terrorist agent. The development of a sound medical countermeasure will undoubtedly enhance not only our medical readiness and ability in VR casualty management, but also our defense posture against the deployment of VR in both combat and politically volatile environments. Acute exposure to a lethal dose of VR has been shown to cause cholinergic hyperfunction, incapacitation, seizures, convulsions, cardiorespiratory depression and death. In this study, pharmacological antagonism of VR-induced cardiorespiratory failure and lethality was investigated in guinea pigs chronically instrumented for concurrent recordings of electrocorticogram, diaphragmatic EMG, Lead II ECG, heart rate and neck skeletal muscle EMG. Thirty (30) min prior to intoxication with a 2 x LD50 dose of VR (22.6 micrograms/kg, s.c.), animals were pretreated with pyridostigmine (0.026 mg/kg, i.m.). Immediately after VR intoxication, animals were given pralidoxime chloride (2-PAM; 25 mg/kg, i.m.) and atropine sulfate (2, 8 or 16 mg/kg, i.m.). In animals that displayed seizures and convulsions, diazepam (5 mg/kg, i.m.) was administered 10 min following the onset of epileptiform activities. Responses to pretreatment/therapy modality were evaluated at 24 h post-VR. All animals survived the 2 x LD50 VR challenge. With the exception of an increased heart rate in response to atropine, the myocardial and diaphragmatic (respiratory) activity profiles appeared normal throughout the course of intoxication and recovery. Animals receiving 2 mg/kg atropine all developed fasciculations, seizures, signs of excessive mucoid/salivary secretion, and needed diazepam adjunct therapy. One-half (50%) of the animals receiving 8 mg/kg atropine developed seizure activities and were given diazepam, whereas the other half only showed a brief period of increase in CNS excitability. No fasciculations, seizures or convulsions were noted in animals receiving 16 mg/kg atropine. In summary, although lethality can be prevented with the pretreatment/therapy modality containing 2 mg/kg atropine and diazepam adjunct, a complete CNS and cardiorespiratory recovery from 2 x LD50 of VR requires a minimum of 8 mg/kg atropine.

Animals↗
PubMed2001

Presence of oligoclonal T cells in cerebrospinal fluid of a child with multiphasic disseminated encephalomyelitis following hepatitis A virus infection.

We have investigated the clonality of beta-chain T-cell receptor (TCR) transcripts from the cerebrospinal fluid (CSF) and peripheral blood from a 7-year old child who developed a multiphasic disseminated encephalomyelitis following an infection with hepatitis A virus. We amplified beta-chain TCR transcripts by nonpalindromic adaptor (NPA)-PCR-Vbeta-specific PCR. TCR transcripts from only five Vbeta families (Vbeta13, Vbeta3, Vbeta17, Vbeta8, and Vbeta20) were detected in CSF. The amplified products were combined, cloned, and sequenced. Sequence analysis revealed in the CSF substantial proportions of identical beta-chain of TCR transcripts, demonstrating oligoclonal populations of T cells. Seventeen of 35 (48%) transcripts were 100% identical, demonstrating a major Vbeta13.3 Dbeta2.1 Jbeta1.3 clonal expansion. Six of 35 (17%) transcripts were also 100% identical, revealing a second Vbeta13 clonal expansion (Vbeta13.1 Dbeta2.1 Jbeta1.2). Clonal expansions were also found within the Vbeta3 family (transcript Vbeta3.1 Dbeta2.1 Jbeta1.5 accounted for 5 of 35 transcripts [14%]) and within the Vbeta20 family (transcript Vbeta20.1 Dbeta1.1 Jbeta2.4 accounted for 3 of 35 transcripts [8%]). These results demonstrate the presence of T-cell oligoclonal expansions in the CSF of this patient following infection with hepatitis A virus. Analysis of the CDR3 motifs revealed that two of the clonally expanded T-cell clones exhibited substantial homology to myelin basic protein-reactive T-cell clones. In contrast, all Vbeta TCR families were expressed in peripheral blood lymphocytes. Oligoclonal expansions of T cells were not detected in the peripheral blood of this patient. It remains to be determined whether these clonally expanded T cells are specific for hepatitis A viral antigen(s) or host central nervous system antigen(s) and whether molecular mimicry between hepatitis A viral protein and a host protein is responsible for demyelinating disease in this patient.

Amino Acid Sequence↗
PubMed2000

Pre-mRNA splicing by the essential Drosophila protein B52: tissue and target specificity.

B52, an essential SR protein of Drosophila melanogaster, stimulates pre-mRNA splicing in splicing-deficient mammalian S100 extracts. Surprisingly, mutant larvae depleted of B52 were found to be capable of splicing at least several pre-mRNAs tested (H. Z. Ring and J. T. Lis, Mol. Cell. Biol. 14:7499-7506, 1994). In a homologous in vitro system, we demonstrated that B52 complements a Drosophila S100 extract to allow splicing of a Drosophila fushi tarazu (ftz) mini-pre-mRNA. Moreover, Kc cell nuclear extracts that were immunodepleted of B52 lost their ability to splice this ftz pre-mRNA. In contrast, splicing of this same ftz pre-mRNA occurred in whole larvae homozygous for the B52 deletion. Other SR protein family members isolated from these larvae could substitute for B52 splicing activity in vitro. We also observed that SR proteins are expressed variably in different larval tissues. B52 is the predominant SR protein in specific tissues, including the brain. Tissues in which B52 is normally the major SR protein, such as larval brain tissue, failed to produce ftz mRNA in the B52 deletion line. These observations support a model in which the lethality of the B52 deletion strain is a consequence of splicing defects in tissues in which B52 is normally the major SR protein.

Animals↗
PubMed1999

RNA aptamers as effective protein antagonists in a multicellular organism.

RNA aptamers selected against proteins can be used to modulate specific protein function. Expression of such reagents in cells and whole organisms could provide a means of dissecting and controlling molecular mechanisms in vivo. We demonstrate that Drosophila B52 protein can be specifically inhibited in vitro and in vivo by a multivalent RNA aptamer. This inhibitory aptamer RNA binds B52 avidly and inhibits B52-stimulated pre-mRNA splicing. It can be expressed in cultured cells and whole animals in a stable form that accumulates up to 10% of total mRNA. It binds B52 in vivo and suppresses all phenotypes caused by B52 overexpression. The strategies presented here should prove general in design and expression of functional and therapeutic RNAs.

Animals↗
PubMed1999

Poly(ADP-ribose) polymerase activation mediates 1-methyl-4-phenyl-1, 2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin that causes parkinsonism in humans and nonhuman animals, and its use has led to greater understanding of the pathogenesis of Parkinson's disease. However, its molecular targets have not been defined. We show that mice lacking the gene for poly(ADP-ribose) polymerase (PARP), which catalyzes the attachment of ADP ribose units from NAD to nuclear proteins after DNA damage, are dramatically spared from MPTP neurotoxicity. MPTP potently activates PARP exclusively in vulnerable dopamine containing neurons of the substantia nigra. MPTP elicits a novel pattern of poly(ADP-ribosyl)ation of nuclear proteins that completely depends on neuronally derived nitric oxide. Thus, NO, DNA damage, and PARP activation play a critical role in MPTP-induced parkinsonism and suggest that inhibitors of PARP may have protective benefit in the treatment of Parkinson's disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1997

Differential susceptibility to neurotoxicity mediated by neurotrophins and neuronal nitric oxide synthase.

NMDA neurotoxicity, which is mediated, in part, by formation of nitric oxide (NO) via activation of neuronal NO synthase (nNOS), is modulated by neurotrophins. nNOS expression in rat and mouse primary neuronal cultures grown on a glial feeder layer is significantly less than that of neurons grown on a polyornithine (Poly-O) matrix. Neurotrophins markedly increase the number of nNOS neurons, nNOS protein, and NOS catalytic activity and enhance NMDA neurotoxicity via NO-dependent mechanisms when neurons are grown on glial feeder layers. In contrast, when rat or mouse primary cortical neurons are grown on a Poly-O matrix, neurotrophins have no influence on nNOS neuronal number or NOS catalytic activity and reduce NMDA neurotoxicity. Primary neuronal cultures from mice lacking nNOS grown on a glial feeder layer fail to respond to neurotrophin-mediated enhancement of neurotoxicity. Together, these results indicate that nNOS expression and NMDA NO-mediated neurotoxicity are dependent, in part, on the culture paradigm, and neurotrophins regulate the susceptibility to NMDA neurotoxicity via modulation of nNOS. Furthermore, these results support the idea that NMDA neurotoxicity in culture is critically dependent on the developmental state of the neurons being assessed and suggest that, when cortical neurons are cultured on a glial feeder layer, they do not reach nearly as mature a phenotype as when grown on a Poly-O matrix.

Animals↗
PubMed1997

A specific RNA hairpin loop structure binds the RNA recognition motifs of the Drosophila SR protein B52.

B52, also known as SRp55, is a member of the Drosophila melanogaster SR protein family, a group of nuclear proteins that are both essential splicing factors and specific splicing regulators. Like most SR proteins, B52 contains two RNA recognition motifs in the N terminus and a C-terminal domain rich in serine-arginine dipeptide repeats. Since B52 is an essential protein and is expected to play a role in splicing a subset of Drosophila pre-mRNAs, its function is likely to be mediated by specific interactions with RNA. To investigate the RNA-binding specificity of B52, we isolated B52-binding RNAs by selection and amplification from a pool of random RNA sequences by using full-length B52 protein as the target. These RNAs contained a conserved consensus motif that constitutes the core of a secondary structural element predicted by energy minimization. Deletion and substitution mutations defined the B52-binding site on these RNAs as a hairpin loop structure covering about 20 nucleotides, which was confirmed by structure-specific enzymatic probing. Finally, we demonstrated that both RNA recognition motifs of B52 are required for RNA binding, while the RS domain is not involved in this interaction.

Animals↗
PubMed1992

U1 snRNP targets an essential splicing factor, U2AF65, to the 3' splice site by a network of interactions spanning the exon.

A description of cellular factors that govern alternative splicing of pre-mRNA is largely incomplete. In the case of the rat preprotachykinin gene, splicing of the alternative exon E4 occurs by a poorly understood mechanism in which exon selection is under the positive control of U1 snRNP. Because the binding of U1 snRNP to the 5' splice site of E4 is coincident with the selection of the 3' splice site of E4, this mechanism would appear to involve interactions that bridge across the exon. In this work, a UV cross-linking strategy was used to identify possible RNA-protein interactions involved in the proposed exon-bridging model. Of particular interest is a prominent 61-kD protein, p61, that binds to the 3' splice site of E4 in a manner that is clearly facilitated by a downstream 5' splice site and U1 snRNP particles. The identity of p61 is the essential splicing factor U2AF65, on the basis of copurification and selective binding to polypyrimidine tracts. These results indicate a model in which exon selection is positively regulated by the communication of U1 snRNP and U2AF65. That is, a natural deficiency in binding U2AF65 to the 3' splice site that leads to exon skipping might be overcome by a mechanism in which U1 snRNP facilitates the binding of U2AF65 through a network of template-directed and exon-bridging interactions.

Base Sequence↗
PubMed1991

Relationship between the piriform aperture and interalar nasal widths in adult males.

The piriform aperture of 182 skulls of black and white males in the United States was measured and compared with soft tissue readings taken previously. Statistical analysis indicated that nose width prediction formulas currently utilized in facial reconstruction required modification. Two revised formulas are proposed to improve accuracy of reconstructions: an addition prediction formula for ease of use and a multiplication prediction formula for more precise results on those skulls outside of the mean range.

Analysis of Variance↗
PubMedDate not supplied

Cardiorespiratory effects of O-isobutyl S-[2-(diethylamino)-ethyl] methylphosphonothioate -- a structural isomer of VX.

O-Isobutyl S-[2-(diethylamino)ethyl]methylphosphonothioate (VR) is a structural isomer of a more well-known chemical warefare agent, O-ethyl S-[2(diisopropylamino)ethyl]methylphosphonothioate (code designation VX). In this study, cardiorespiratory and central nervous system (CNS) effects of VR (2LD50 or 22.6 microg kg(-1); s.c.) were evaluated in urethane-anesthetized (Group 1) and unanesthetized (Group 2) guinea pigs instrumented for concurrent recordings of electrocorticogram (ECoG) and a variety of cardiorespiratory activities. The first sign of intoxication was a state of progressive bradycardia, vascular hypotension and arrhythmia (Group 1, approximately 13 min post-VR; Group 2, approximately 6 min post-VR). Bradypnea, excessive salivation and compensatory changes in blood pressure typically did not emerge until 3-5 min prior to apnea (Group 1, approximately 28 min post-VR; Group 2, approximately 15 min post-VR). An idioventricular rhythm, which signalled a failing myocardium, appeared at the same time or shortly after the development of a bradypneic profile. Another notable toxicity component of VR, based on arterial pH, pO2/pCO2 and bicarbonate (HCO3-) level data, was a state of combined hypercapnia, acidemia and hypoxemia during the development of bradypnea. Taken together, findings from this study indicated that changes in medullary respiratory unit activity and ECoG data displayed little, if any, notable signs of CNS perturbation prior to the terminal stage (approximately 1 min prior to respiratory failure). Thus, in addition to displaying a greater sensitivity to perturbation by VR, the peripheral cardiorespiratory system components also appeared to play a more important role in precipitating a progressively dysfunctional cardiorespiratory status that ultimately led to collapse of central respiratory mechanisms and death.

Acidosis↗