Biomedical subjects

J S Smith

Publications and source records attributed to J S Smith.

At least 19 recordsLinked to original sources

PubMed1996

Guanidine hydrochloride unfolding of peptide helices: separation of denaturant and salt effects.

To provide a model for understanding the unfolding of proteins by the chemical denaturant guanidine hydrochloride, we have measured helix unfolding for homologous series of peptides with the repeating sequence Ala-Glu-Ala-Ala-Lys-Ala and chain lengths from 7 to 50 residues. The free energy for helix unfolding varies as a function of guanidinium chloride (GdmCl) for all the peptides. The slope of the linear plot of the free energy of helix formation as a function of the molar concentration of GdmCl, termed the m-value, was found to be strongly dependent on the total ionic strength of the solution. A comparison of the m-value for urea denaturation of the same series of peptides [Scholtz, J. M., Barrick, D., York, E. J., Stewart, J. M., & Baldwin, R. L. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 185-189] reveals that, under many conditions, GdmCl is roughly twice as effective as a denaturant than urea on a molar basis, in agreement with many studies on proteins. However, when the ionic strength of aqueous GdmCl is controlled with additional NaCl, it is possible to separate the observed m-value for GdmCl solutions into two components: one that is identical to that found for urea and a second which depends only on the molar concentration of the chloride anion. Therefore, for these peptides, an equimolar mixture of urea and NaCl is nearly as effective as GdmCl in unfolding the helical conformation.

Amino Acid Sequence↗

PubMed1996

Biochemical and biophysical comparison of native and chemically synthesized phospholamban and a monomeric phospholamban analog.

Phospholamban (PLB) was rapidly isolated from canine cardiac sarcoplasmic reticulum using immunoaffinity chromatography and prepared by solid phase peptide synthesis. The two proteins are indistinguishable when analyzed by SDS-polyacrylamide gel electrophoresis and exhibit pentameric oligomeric states. They are similarly detected on Western blots, are phosphorylation substrates, have identical amino acid compositions that directly reflect their predicted values, yield the same internal amino acid sequences upon CNBr digestion, and have molecular mass values agreeing with the expected value (approximately 6123 Da). Native and synthetic PLB reduced the calcium sensitivity of Ca2+ATPase, which is reversed by anti-PLB antibody. A Cys-to-Ser PLB analog, where the cysteines (36, 41, and 46) were substituted by serines, is monomeric on SDS-polyacrylamide gel electrophoresis, can be phosphorylated, and is recognized by polyclonal antisera. PLB migrates with a sedimentation coefficient of 4.8 S in sedimentation velocity ultracentrifugation experiments, whereas Cys-to-Ser PLB does not sediment, consistent with a monomeric state. Circular dichroism spectral analysis of PLB indicates about 70% alpha-helical structure, whereas Cys-to-Ser PLB manifests only about 30%. Because the physiochemical properties of native and synthetic PLB appear identical, the more readily available synthetic protein should be suitable for more extensive structural studies.

Adenosine Triphosphatases↗

PubMed1996

Molecular cloning of prohormone convertase 1 from the atrial gland of Aplysia.

We have screened an Aplysia atrial gland cDNA library using a prohormone convertase (PC)1 probe prepared by polymerase chain reaction (PCR) and have isolated an Aplysia PC1-related full-length 3.6-kb cDNA clone. The cDNA sequence (3,565 bp) encoded a putative preproendoprotease (APC1) of 703 amino acid residues that showed considerable sequence identity with other eukaryotic PC1s, and indicated a high degree of sequence identity with an Aplysia nervous system PC sequence (aPC1B). Northern blot analysis of atrial gland RNA identified two APC1 transcripts of 3.9 kb and 5.0 kb. APC1 is a candidate PC that may play an important role in the processing of egg-laying hormone (ELH)-related precursors in atrial gland secretory cells and represents one of the first examples of PC1 expression in an exocrine tissue.

Animals↗

PubMed1996

Single-voxel proton brain spectroscopy exam (PROBE/SV) in patients with primary brain tumors.

OBJECTIVE: The Single-Voxel Proton Brain Exam (PROBE/SV) is an automated MR spectroscopic technique. The purpose of this study was to investigate the use of PROBE/SV as a diagnostic tool in patients with primary brain tumors and to compare our findings with the known information obtained from conventional nonautomated MR spectroscopic techniques. SUBJECTS AND METHODS: We used PROBE/SV to image 10 normal adults and 46 patients with primary brain tumors: 29 glioblastoma multiformes (GBMs), five anaplastic astrocytomas, and 12 low-grade astrocytomas. All studied were performed on a 1.5-T Signa unit. Average voxel sizes were 6-8 cm3. A corresponding point-resolved spectroscopy spectrum was obtained from normal-appearing brain parenchyma in each patient for comparison with the spectra from known areas of pathology. RESULTS: In patients with low-grade gliomas (grades 1 and 2), we observed decreased N-acetylaspartate (12 of 12) and slightly increased choline (11 of 12) when we compared these metabolites with those in the spectra of patients' normal brains. This comparison in patients with GBM yielded markedly decreased N-acetylaspartate (29 of 29) and prominently increased choline (27 of 29). In the short TE spectra, we frequently saw lipid signal in high-grade tumors, especially in GBMs (12 of 20). We identified lactate peaks in high-grade tumors (anaplastic astrocytoma and GBM, 29 of 34) and also in low-grade tumors (four of 12). The creatine signal in all gliomas was slightly less than that of healthy brain tissue. The lowest N-acetylaspartate, choline, and creatinine levels in conjunction with the highest lactate levels were usually found in necrotic portions of high-grade tumors. CONCLUSION: PROBE/SV is a simplified MR spectroscopy technique that reduces setup time and provides automatic on-line data processing and display. The voxel location can be selected to focus on the area of interest and to minimize voxel contamination from unwanted tissue. The results from our experimentation with PROBE/SV in patients with brain tumors generally concur with published reports of tumor spectra obtained by conventional MR spectroscopic techniques. The ease and accuracy of this new technique make it a useful clinical tool in differentiating human brain tumor grades.

Adolescent↗

PubMed1995

Rabies surveillance in the United States during 1994.

In 1994, 48 states, the District of Columbia, and Puerto Rico reported 8,224 cases of rabies in nonhuman animals and 6 cases in human beings to the Centers for Disease Control and Prevention. Nearly 93% (7,632 cases) were wild animals, whereas 7% (592 cases) were domestic species. The total number of reported cases decreased 13.4% from that of 1993 (9,498 cases), with most of the decline resulting from 19.2% fewer cases of rabies in raccoons. Two previously described epizootics of rabies involving the raccoon variant of the rabies virus have converged in North Carolina, and the resulting region is now continuous from Alabama and Florida in the South to Maine in the North. Epizootics of rabies in foxes in west central Texas and in dogs and coyotes in southern Texas continue to expand, with this state reporting 144 rabid foxes, 53 rabid dogs, and 77 of the 85 cases in coyotes during 1994. Maine and New Hampshire reported cases of rabies in foxes (6 and 9, respectively) for the first time in 10 years. Nationally, reported cases of rabies in dogs (153) increased by 17.7%, whereas cases in cattle (111) and cats (267) decreased by 14.6 and 8.3%, respectively. Cats continued to be the domestic animal most frequently reported rabid. Twenty-eight states and the District of Columbia reported decreases in rabies in animals in 1994, compared with 22 states, the District of Columbia, and Puerto Rico in 1993. Hawaii and Nebraska were the only states that did not report cases of rabies in 1994.

Adolescent↗

PubMed1995

Rabies and African wild dogs in Kenya.

Three packs of African wild dogs (Lycaon pictus) ranging to the north of the Masai Mara National Reserve in southwestern Kenya were monitored from 1988 to 1990. During a six week period (August 2-September 14, 1989), 21 of 23 members of one of these packs died. Histological examination of two brain samples revealed eosinophilic intracytoplasmic inclusions (Negri bodies), supporting a diagnosis of rabies viral encephalitis. An additional brain sample tested positive for rabies with a fluorescent antibody test. Nucleotide sequence of the rabies viral N and G genes from isolates of four African wild dogs (including an individual from Tanzania) indicated that infection was with a viral variant common among domestic dogs in Kenya and Tanzania. A hypothesis linking African wild dog rabies deaths to researcher handling is evaluated and considered implausible.

Animals↗

PubMed1995

Selection of specific phage-display antibodies using libraries derived from chicken immunoglobulin genes.

In chickens, single functional immunoglobulin variable and joining gene segments at each of the heavy and light chain loci undergo V(D)J rearrangement. Diversity is subsequently introduced by conversions templated by upstream pseudo V region genes in such a way that practically all V regions in mature B cells have identical ends. This greatly simplifies the representative amplification of V region genes. Furthermore, the entire naive repertoire of the adult chicken is produced in the bursa of Fabricius of the young bird. These special properties of the generation of immunoglobulin diversity in chickens have been exploited in the development of procedures to produce large libraries of diverse antibody combining sites derived from chicken Ig genes and expressed on filamentous bacteriophage. The utility of this library was assessed by selection of specifically binding phage using three solid phase-bound protein antigens, hen egg white lysozyme, bovine thyroglobulin and bovine serum albumin. The sequences of the V region genes thus isolated demonstrated that selection was specific and that the library contained useful diversity of binding sites. This library provides access to a repertoire whose diversity is based on a mechanism different from that underlying previously available libraries. The demonstrated feasibility of generating chicken phage antibodies may lead to the production of monoclonal reagents from immunised chickens, and the derivation of reagents for studying immunoglobulin mediated selection in avian B cell development.

Amino Acid Sequence↗

PubMed1995

Divalent cation modulation of the ribonuclease functions of human immunodeficiency virus reverse transcriptase.

The stimulatory effect of Mg2+ and Mn2+ on the ribonuclease H (RNase H) functions of HIV-1 reverse transcriptase (RT) has been evaluated using a model 90-nt RNA template/36-nt DNA primer. Wild type enzyme exhibits similar endonuclease and directional processing activities in response to both cations, while RNase H activity (hydrolysis of double-stranded RNA) is only evident in the presence of Mn2+. Enzyme altered at the p66 residue Glu478 (Glu478-->Gln478), which participates in metal ion binding, is completely inactive in Mg2+. However, Mn2+ restores specifically its endoribonuclease activity. In the presence of Mn2+, mutant RT also catalyzes specific removal of the tRNA replication primer, eliminating the possibility of contaminating Escherichia coli RNase H in our recombinant enzyme. However, the efficiency with which mutant RT catalyzes transfer of nascent DNA between RNA templates (an event mandating RNase H activity) is severely reduced. These findings raise the possibility that directional processing activity is required to accelerate transfer of nascent DNA between templates during retroviral replication.

Base Sequence↗

PubMed1995

Rabies virus glycoprotein gene contains a long 3' noncoding region which lacks pseudogene properties.

Analysis of a limited number of laboratory strains of rabies virus had demonstrated the presence of a genome region bounded by two transcription termination and polyadenylation-like (TTP) signals (approximately 400 to 450 nucleotides apart) which was located between the end of the glycoprotein (G) coding sequence and the beginning of the L polymerase coding sequence. Although this region had been suggested to represent a remnant or pseudogene (psi), no detailed analysis had been carried out to examine this possibility. Here we present the nucleotide sequence analysis of this genome region for several laboratory rabies virus strains and a large number of diverse rabies viruses detected directly in brain tissue of naturally infected animals. Only one distinct lineage of the laboratory strains and none of the wild-type rabies viruses contained the upstream TTP-like signal, indicating that only the downstream TTP motif is the authentic G mRNA transcription termination and polyadenylation and signal. Phylogenetic analysis of sequence differences provided no evidence of laboratory strains containing the two TTP-like signals being ancestral to any of the viruses possessing only the downstream TTP sequence motif. These data indicate that this region of the rabies virus genome encodes a G mRNA with a long 3' noncoding region with no evidence of a pseudogene.

Animals↗

PubMed1995

Unilateral injury of posterior parietal cortex and spatial learning in hooded rats.

The influences of bilateral or unilateral injuries within the posterior parietal cortex (PPC) upon spatial learning in a water maze were examined in three experiments. Place-learning and response-learning were investigated in a four-alley 'Greek-cross' shaped water maze with extra-maze visual cues available. No differences were detected on any of several measures sensitive to learning between the lesion groups on the place-learning task. Microanalysis of behavior within trials revealed that animals with either bilateral or right unilateral PPC injuries committed significantly more total errors, initial alley entrance ('reference memory') errors, and re-entry ('working memory') errors in the response-learning paradigm than did either the control or left PPC-injured rats. No differences were detected between the latter two groups on these measures. Unilateral lesions resulted in asymmetrical placing responses ipsilateral to the injury 10 days after surgery whereas bilateral injuries resulted in asymmetrical placing with mixed directionality. The acquisition of the response-learning problem in the absence of visual cues was studied on animals prepared with unilateral lesions and housed post-operatively either in isolation or in a 'complex environment.' In the absence of visual cues both right and left PPC-injured rats committed more errors than sham controls, and differential post-surgical housing did not attenuate these impairments. These same animals were trained on the landmark navigation task. Although no differences appeared between the lesion groups, a generalized but transient facilitation of learning was observed in animals housed in the 'complex' environment. Unilateral injuries placed in sham controls failed to disturb retention of the landmark navigation strategy. Because none of the PPC-injured animals were deficient in the landmark task, a result which is contrary to observations in other laboratories, the influence of post-surgical recovery interval upon acquisition of the landmark navigation strategy was explored. Animals were prepared with right PPC injuries and trained following either a 5 or 35 day recovery interval. Only those animals limited to the short recovery interval proved to have a spatial deficit in the landmark task. It is concluded that injuries in the PPC of either hemisphere disturb egocentric spatial functions. However, animals with left PPC injuries are able to compensate by using allocentric visual cues if they are available. It is due to the special role played by the right PPC in complex visuospatial functions that animals with this injury are unable to compensate.

Animals↗

PubMed1995

The comparison of injury severity instrument performance using likelihood ratio and ROC curve analyses.

BACKGROUND: The relative merits of injury severity instruments are often difficult to determine because the statistical techniques, study populations, and outcomes used in trauma research tend to obscure rather than elucidate differences in performance. OBJECTIVE: To describe the advantages of likelihood ratio and receiver operator characteristic (ROC) curve analyses and to demonstrate them using study populations and outcomes that facilitate instrument discrimination. MATERIALS AND METHODS: Previously published data on the performance of the "Injury Severity Score" and of four triage instruments in the prediction of mortality; paired comparison of two instruments in a previously unpublished trauma registry dataset; use of likelihood ratio and ROC analyses. MEASUREMENTS AND MAIN RESULTS: In a comparison of triage instruments this study clearly showed that CRAMS, PHI, and RTI, which contain nonphysiological information, have higher performance levels than the Revised Trauma Score (RTS), which is restricted to physiological information. Absolute performance gains of these instruments over the RTS ranged from 5.9% to 43.5%. This study also noted that the ISS performs equally well for blunt and penetrating trauma, and affirms concerns about the adequacy of its performance. CONCLUSIONS: Likelihood ratio and ROC curve analyses demonstrate differences in injury severity instrument performance that were obscured by less rigorous methods of comparison.

Humans↗

PubMed1995

Fast spin-echo, magnetic resonance imaging-measured hippocampal volume: correlation with neuronal density in anterior temporal lobectomy patients.

To assess the value of magnetic resonance imaging (MRI)-measured hippocampal volume in the detection of hippocampal sclerosis, we studied 28 patients undergoing anterior temporal lobectomy for medically intractable mesial temporal lobe epilepsy. Hippocampal volumetry and visual analysis of T2 signal change were performed using fast spin-echo T2-weighed MRI. Quantitative neuronal density measurements were performed in the resected hippocampal specimens. There was a significant correlation between MRI-measured absolute hippocampal volume (AHV) and neuronal density in CA1, CA2, and CA3 subfields (p < 0.0001, p < 0.01, and p < 0.05, respectively). Differential hippocampal volume (side-to-side volume difference) failed to detect bilateral atrophy in three patients, but the bilateral hippocampal atrophy was recognized by considering AHV in these patients. This study suggests that MRI-measured AHV can be of value in elevating patients with mesial temporal lobe epilepsy, especially when there is no side-to-side difference in hippocampal volumetry.

Adolescent↗

PubMed1995

Cross-protection of mice against a global spectrum of rabies virus variants.

Rabies, a continuing worldwide problem, kills tens of thousands of people and millions of animals each year. The problem is most severe in developing countries, where cell culture-derived vaccines are unaffordable and the available nervous tissue-derived vaccines are often of questionable immunogenicity and may produce neurological complications. To determine the feasibility of developing a vaccine with worldwide applicability, we investigated whether recombinant vaccinia viruses expressing either the glycoprotein (G), the nucleoprotein (N), or both the G and N (GN) of the challenge virus strain (CVS) of rabies virus would cross-protect mice against 17 rabies virus isolates representing the spectrum of rabies virus variants found worldwide. The results were compared with the commercially available human diploid cell vaccine (HDCV). Among mice injected with any of the 17 viruses, > or = 95% were protected by vaccination with recombinant viruses expressing G or GN, and > or = 85% of the mice were protected by the HDCV. The recombinant virus expressing N was less protective, protecting against only 11 of the 17 viruses. Antibody prepared against the G of the strains used in the vaccines neutralized all 17 viruses, and sera from mice infected with any one virus variant cross-neutralized all of the other viruses. Thus, no antigenic differences that would potentiate vaccine failures were identified. These studies suggest that a single rabies virus strain or its G would protect globally against wild-type rabies viruses.

Animals↗

PubMed1995

Animal rights activism and animal welfare concerns in the academic setting: levels of activism and the perceived importance of research with animals.

Past research suggests that public support for the use of animal models as means to improve the human condition is present but many individuals have expressed ambivalence. In the present study, various sectors of the academic community (students and faculty) as well as the general population, were surveyed to assess their positions on the need for, and value of animal research, the value of psychological research in which animals are employed, and the respondents' consummatory habits. The results suggested that more information needs to be provided about the role of animal experimentation, including a discussion of the benefits produced by using animals to answer psychological questions.

Adolescent↗

PubMed1995

Influence of the alpha 2 noradrenergic antagonist piperoxane on longevity in the Fischer-344 rat: a preliminary report.

Piperoxane is an alpha 2-noradrenergic antagonist with demonstrated excitatory effects on neurons in the locus coeruleus, causing a corresponding increase in norepinephrine in many forebrain areas. 16 male Fischer-344 rats approximately 16 months of age were injected with 3 mg/kg of piperoxane or .09% saline. The piperoxane-treated rats lived an average of 127.1 days longer than the saline-treated rats. The results are discussed in terms of the effects of strategies designed to enhance brain levels of catecholamine and their effect on the aging process. A discussion of further research is also presented.

Adrenergic alpha-Antagonists↗

PubMed1994

Rabies surveillance in the United States during 1993.

In 1993, 49 states, the District of Columbia, and Puerto Rico reported 9,495 cases of rabies in nonhuman animals and 3 cases in human beings to the Centers for Disease Control and Prevention. Greater than 93% (8,889 cases) were wild animals, whereas 6.4% (606 cases) were domestic species. The total number of reported cases increased 9.9% over that of 1992 (8,645 cases), with most of the increase resulting from continued spread of rabies in raccoons (37.1% increase in reported cases over 1992). The 2 epizootics of rabies in raccoons (Northeastern/mid-Atlantic and Southeastern regions) approach convergence in North Carolina (106 cases of rabies in 1993, compared with 49 in 1992). Maine, Rhode Island, and Vermont remained the only New England states without reported cases associated with the raccoon variant of the rabies virus. New York reported 2,747 cases of rabies, the largest number of cases ever reported during a single year by any state. Increases in reported cases of rabies in Texas and 8 other geographically dispersed states were attributed mainly to larger numbers of reported cases of rabies in bats. Texas reported 71 of the 74 cases in coyotes during 1993 (70 of 75 cases in 1992). Nationally, reported cases of rabies in dogs (130) and cattle (130) each decreased by 29% in 1993, whereas cats (291 cases in 1993, compared with 290 in 1992) continued to be the domestic animal most frequently reported rabid. Twenty-two states and Puerto Rico reported decreases in rabies in animals in 1993, compared with 20 states, the District of Columbia, and Puerto Rico in 1992. Hawaii was the only state that did not report a case of rabies in 1993.

Aged↗

PubMed1994

Genome-wide search for loss of heterozygosity in transgenic mouse tumors reveals candidate tumor suppressor genes on chromosomes 9 and 16.

A genome-wide scan for loss of heterozygosity (LOH) in tumors provides a powerful route to the identification of genes involved in tumorigenesis. This approach has not previously been applied to transgenic mice, despite the considerable advantages they afford for genetic dissection. Here, we report a genome-wide LOH analysis of insulinomas and carcinoid tumors in transgenic mice expressing the simian virus 40 large tumor oncogene. Although the overall genome-wide rate of LOH was quite low, chromosomes 9 and 16 showed high rates of allelic loss. About one-third of tumors showed partial LOH, allowing localization of the likely tumor suppressor genes to intervals of approximately 11 centimorgans. The locus on chromosome 9, named Loh-1, lies in a region with synteny conservation to human chromosomes 3q, 6q12, 15q24, and 3p21, while the locus on chromosome 16, named Loh-2, lies in a region corresponding to human chromosomes 3q and 22q. Of particular note is the synteny conservation with human 3p21, which shows frequent loss in human cancers. These regions do not encode two tumor suppressors, pRB and p53, known to interact with large tumor oncoprotein, suggesting the presence of new genes whose loss of function contributes to multistage tumorigenesis.

Alleles↗

PubMed1994

Epizootic canine rabies transmitted by coyotes in south Texas.

Prior to 1988, rabies was reported only sporadically in coyotes. However, in the final 4 months of 1988, Starr County, Tex, which is situated on the US-Mexico border, experienced an epizootic of canine rabies, consisting of 6 laboratory-confirmed cases of rabies in coyotes and of 2 cases in domestic dogs. The first 3 cases were detected in coyotes, and the first case in a domestic dog was observed 84 days after the index case. Adjacent Hidalgo County reported 9 cases of rabies in dogs during the same time that rabid dogs were being reported in Starr County. In 1989, the epizootic primarily involved dogs: 15 dogs in Starr County and 19 dogs in Hidalgo County. Five rabid coyotes were reported in Starr County in 1989, and 1 rabid coyote was reported from Hidalgo County. In 1990, rabies was reported in 3 coyotes and in 31 dogs in Starr County; cases were not detected in Hidalgo County. During 1991, the epizootic expanded approximately 160 km northward, resulting in laboratory-confirmed cases in 42 coyotes and 25 dogs in 10 counties. In 1992, Webb and Willacy Counties became involved; 70 rabid coyotes and 41 rabid dogs were reported in 1992 from the 12-county area. During the first 6 months of 1993, there were 31 rabid coyotes and 38 rabid dogs reported from the same 12 south Texas counties. In May 1993, a raccoon infected with the canine rabies ecotype was reported from Cameron County. Antigenic and genetic analysis revealed the virus ecotype affecting dogs and coyotes to be that associated with urban canine rabies along the US-Mexico border.

Animals↗