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Biomedical subjects

K E Nelson

Publications and source records attributed to K E Nelson.

At least 37 records · Page 2Linked to original sources

Characteristics of injection drug using parents who retain their children.

While it is known that injection drug users (IDUs) often have their children removed or place them voluntarily, little is known about factors associated with whether IDU parents live with their children. We identified a community sample of 391 IDU parents with at least one child under age 14 (index IDU parents). For these IDU parents, 62% did not have any of their children under age 14 living with them. We assessed whether certain health factors, risk related behaviors, social indicators, and active drug use were related to whether children of IDUs were living with the index IDU parent. IDU parents who were living with their children were overwhelmingly more likely to be female, more likely to have health insurance, and engage in no-risk or low-risk drug practices, as compared to moderate/high-risk practices. Additionally, HIV negative and HIV positive asymptomatic parents were about three times more likely to be living with their children than HIV positive parents with clinical symptoms commonly seen among those suffering from HIV-related illnesses. HIV-related clinical symptoms, rather than HIV status per se, seem to be associated with retention of children.

Adolescent↗

Concentration by evaporation and the prebiotic synthesis of cytosine.

The efficient prebiotic synthesis of cytosine from urea and cyanoacetaldehyde (CA) has recently been claimed to be invalid on the basis of possible side reactions of the starting materials and the inapplicability of prebiotic syntheses using drying beach conditions. We therefore have investigated the synthesis of cytosine and uracil from urea and cyanoacetaldehyde at 100 degrees C under dry-down conditions, and in solution at 4 degrees C and -20 degrees C. We find that cytosine is produced from the low temperature experiments more efficiently than calculated from the Arrhenius extrapolation from higher temperatures, i.e., 60-120 degrees C. In addition, we find that CA dimer is as efficient as the monomer in cytosine synthesis. We also studied whether evaporating very dilute solutions of nonvolatile organic compounds will concentrate according to theory. Solutions as dilute as 10(-4) M concentrate from pure water approximately according to theory. Similar solutions in 0.5 M NaCl have less than theoretical concentrations due to absorption, but concentrations near dryness were very high.

Acetaldehyde↗

Neostigmine combined with bupivacaine, clonidine, and sufentanil for spinal labor analgesia.

UNLABELLED: We previously found that spinal clonidine prolongs labor analgesia when combined with spinal bupivacaine and sufentanil. We sought to determine whether the addition of spinal neostigmine to these drugs would further enhance labor analgesia. By use of a combined spinal/epidural technique, 36 patients were randomized to receive a hyperbaric spinal injection of bupivacaine 2.5 mg plus clonidine 50 microg and sufentanil 10 microg with or without neostigmine 10 microg. Pain, maternal hemodynamics, fetal heart rate, nausea, pruritus, sedation, motor block, sensory levels to pinprick, and maternal oxygen saturation were assessed at regularly specified intervals after spinal injection until additional analgesia was requested. The duration of spinal analgesia was similar between groups (215 +/- 60 min in the Control group versus 205 +/- 62 min in the Neostigmine group). Likewise, pain scores, the duration of labor, Apgar scores, and side effects were similar between groups except that patients administered neostigmine experienced significantly more nausea and vomiting (53% vs 7%, P = 0.01). We conclude that spinal neostigmine 10 microg produces severe nausea and does not potentiate the duration of spinal analgesia in laboring women from spinal bupivacaine, clonidine, and sufentanil. IMPLICATIONS: Spinal neostigmine 10 microg as an adjunct to spinal bupivacaine, clonidine, and sufentanil produces severe nausea and fails to potentiate analgesia in laboring women.

Adjuvants, Anesthesia↗

Interaction patterns between children and their teachers when using a specific multimedia and communication strategy: observations from children with autism and mixed intellectual disabilities.

This study reports on observed interaction patterns between 20 children with autism and mixed intellectual disabilities (mean chronological age = 11:4 years; language age = 4:7 years) and their nine teachers working with a specially developed multimedia program aiming to increase literacy skills. An increase in verbal expression was found over time for the total group. Children with autism also showed increased enjoyment and willingness to seek help from their teachers. Teachers for both diagnostic groups reduced their instructions on how to handle the computer during the program but the decrease was greater in the teachers for children with autism. When the total group of children was subdivided according to language age (high versus low), it appears that those with a low language age showed an increase in verbal expressiveness from start to end of training. Those with a high language age showed increased enjoyment. It is concluded that more detailed studies of the interaction patterns between teachers and children are needed, and these should be related to children's language level as well as to diagnostic group.

Adolescent↗

Comparative genomics of microbial drug efflux systems.

The complete genome sequences of 36 microorganisms have now been published and this wealth of genome data has enabled the development of comparative genomic and functional genomic approaches to investigate the biology of these organisms. Comparative genomic analyses of membrane transport systems have revealed that transporter substrate specificities correlate with an organism's lifestyle. The types and numbers of predicted drug efflux systems vary dramatically amongst sequenced organisms. Microarray and gene knockout studies to date have suggested that predicted drug efflux genes often appear to be a) non-essential and b) expressed at detectable levels under standard laboratory growth conditions.

Bacteria↗

Cranial rhythmic impulse related to the Traube-Hering-Mayer oscillation: comparing laser-Doppler flowmetry and palpation.

The primary respiratory mechanism (PRM) as manifested by the cranial rhythmic impulse (CRI), a fundamental concept to cranial osteopathy, and the Traube-Hering-Mayer (THM) oscillation bear a striking resemblance to one another. Because of this, the authors developed a protocol to simultaneously measure both phenomena. Statistical comparisons demonstrated that the CRI is palpably concomitant with the low-frequency fluctuations of the THM oscillation as measured with the Transonic Systems BLF 21 Perfusion Monitor laser-Doppler flowmeter. This opens new potential explanations for the basic theoretical concepts of the physiologic mechanism of the PRM/CRI and cranial therapy. Comparison of the PRM/CRI with current understanding of the physiology of the THM oscillation is therefore warranted. Additionally, the recognition that these phenomena can be simultaneously monitored and recorded creates a new opportunity for further research into what is distinctive about the science and practice of osteopathic medicine.

Blood Flow Velocity↗

Evidence of Trypanosoma cruzi infection (Chagas' disease) among patients undergoing cardiac surgery.

BACKGROUND: Trypanosoma cruzi, the agent of Chagas' heart disease, is transmitted by triatomine insects and by blood transfusion. The emigration of several million people from T cruzi-endemic countries to the United States has raised concerns regarding a possible increase in cases of Chagas' heart disease here, as well as an increased risk of transfusion-transmitted T cruzi. To investigate these 2 possible outcomes, we tested a repository of blood specimens from multiply transfused cardiac surgery patients for antibodies to T cruzi. METHODS AND RESULTS: Postoperative blood specimens from 11 430 cardiac surgery patients were tested by enzyme immunoassay, and if repeat-reactive, were confirmed by radioimmunoprecipitation. Six postoperative specimens (0.05%) were confirmed positive. Corresponding preoperative specimens, available for 4 of these patients, were also positive. The other 2 patients had undergone heart transplantations. Tissue samples from their excised hearts were tested for T cruzi by polymerase chain reaction and were positive. Despite the fact that several of these 6 patients had histories and clinical findings suggestive of Chagas' disease, none of them were diagnosed with or tested for it. Patient demographics showed that 5 of 6 positive patients were Hispanic, and overall, 2. 7% of Hispanic patients in the repository were positive. CONCLUSIONS: No evidence for transfusion-transmitted T cruzi was found. All 6 seropositive patients apparently were infected with T cruzi before surgery; however, a diagnosis of Chagas' disease was not known or even considered in any of these patients. Indeed, Chagas' disease may be an underdiagnosed cause of cardiac disease in the United States, particularly among patients born in countries in which T cruzi is endemic.

Animals↗

Correlates of enrollment in methadone maintenance treatment programs differ by HIV-serostatus.

OBJECTIVES: To identify correlates of enrollment in methadone maintenance treatment programs (MMTP) among a prospective cohort of injection drug users (IDUs) in Baltimore, Maryland. METHODS: A total of 1480 IDUs undergoing semi-annual HIV tests and interviews were studied between 1994 and 1998, during which time a needle exchange program was introduced. Longitudinal analysis using generalized estimating equations was used to identify correlates of MMTP participation over time. RESULTS: Although similar proportions of HIV-seropositive and -seronegative IDUs enrolled in MMTP during follow-up (26 versus 22%, respectively), correlates of enrollment differed by HIV-serostatus. Among HIV-seropositive participants, older age [adjusted odds ratio (AOR, 1.37)] was associated with enrollment in MMTP. Among HIV-seronegative IDUs, factors associated with not enrolling in MMTP were being African American (AOR, 0.22) and having been recently incarcerated (AOR, 0.62) or homeless (AOR, 0.72). In both groups, females were twice as likely to be enrolled in MMTP, and those with Medicaid were 1.5 times more likely to be enrolled. When behavioral factors were lagged one visit, needle exchange program attendance was positively associated with MMTP enrollment among HIV-negative IDUs (AOR, 2.10); however, this association diminished significantly over time as dedicated treatment slots for needle exchange program participants became saturated. CONCLUSIONS: These findings underscore the need to improve access to MMTP, especially to certain subgroups such as African-Americans, the homeless, incarcerated and uninsured. Our data suggest that health care providers and needle exchange programs can facilitate enrollment into MMTP provided that adequate treatment slots are consistently available to this particularly vulnerable population.

Adult↗

DNA sequence of both chromosomes of the cholera pathogen Vibrio cholerae.

Here we determine the complete genomic sequence of the gram negative, gamma-Proteobacterium Vibrio cholerae El Tor N16961 to be 4,033,460 base pairs (bp). The genome consists of two circular chromosomes of 2,961,146 bp and 1,072,314 bp that together encode 3,885 open reading frames. The vast majority of recognizable genes for essential cell functions (such as DNA replication, transcription, translation and cell-wall biosynthesis) and pathogenicity (for example, toxins, surface antigens and adhesins) are located on the large chromosome. In contrast, the small chromosome contains a larger fraction (59%) of hypothetical genes compared with the large chromosome (42%), and also contains many more genes that appear to have origins other than the gamma-Proteobacteria. The small chromosome also carries a gene capture system (the integron island) and host 'addiction' genes that are typically found on plasmids; thus, the small chromosome may have originally been a megaplasmid that was captured by an ancestral Vibrio species. The V. cholerae genomic sequence provides a starting point for understanding how a free-living, environmental organism emerged to become a significant human bacterial pathogen.

Base Sequence↗

The natural history of hepatitis C virus infection: host, viral, and environmental factors.

CONTEXT: Hepatitis C virus (HCV) infection may resolve (viral clearance), persist without complications, or cause end-stage liver disease (ESLD). The frequency and determinants of these outcomes are poorly understood. OBJECTIVE: To assess the incidence and determinants of viral clearance and ESLD among persons who acquired HCV infection from injection drug use. DESIGN AND SETTING: Community-based prospective cohort study with enrollment in 1988-1989 and a median follow-up of 8.8 years. SUBJECTS: A total of 1667 persons aged 17 years or older with a history of injection drug use and an HCV antibody-positive test result during follow-up. MAIN OUTCOME MEASURES: Viral clearance was assessed in a subset of 919 patients and defined as failure to detect HCV RNA in at least 2 consecutive samples collected 5 or more months apart. End-stage liver disease was assessed at semiannual visits and by review of medical records and death certificates and defined by the presence of ascites, esophageal varices, or hepatic encephalopathy, or when ESLD was stated as a cause of death. RESULTS: Viral clearance was observed in 90 persons who were compared with 722 with persistent viremia, while the viremia of 107 was not resolved. Viral clearance occurred more often in nonblacks (adjusted odds ratio [OR], 5.15; 95% confidence interval [CI], 2.60-10.17) and those not infected with human immunodeficiency virus (HIV) (adjusted OR, 2.19; 95% CI, 1.26-3.47). Forty cases of ESLD were observed throughout follow-up (incidence, 3.1 per 1000 person-years). In a multivariate model, risk of ESLD was higher for persons aged 38 years or older at enrollment (adjusted relative incidence, 3.67; 95% CI, 1.96-6.88) and who reported ingestion of more than 260 g of alcohol per week (adjusted relative incidence, 3.60; 95% CI, 1.73-7.52). Of 210 patients without ESLD randomly selected for biopsy, only 2 had cirrhosis. CONCLUSIONS: Our results indicate that although HCV infection can be self-limited or associated with ESLD, the majority of adults have persistent viremia without clinically demonstrable liver disease. Further research is needed to explain the less frequent clearance of HCV infection among black persons and to improve utilization of treatment for those infected in the context of injection drug use. JAMA. 2000;284:450-456

Adult↗

Peptide nucleic acids rather than RNA may have been the first genetic molecule.

Numerous problems exist with the current thinking of RNA as the first genetic material. No plausible prebiotic processes have yet been demonstrated to produce the nucleosides or nucleotides or for efficient two-way nonenzymatic replication. Peptide nucleic acid (PNA) is a promising precursor to RNA, consisting of N-(2-aminoethyl)glycine (AEG) and the adenine, uracil, guanine, and cytosine-N-acetic acids. However, PNA has not yet been demonstrated to be prebiotic. We show here that AEG is produced directly in electric discharge reactions from CH(4), N(2), NH(3), and H(2)O. Electric discharges also produce ethylenediamine, as do NH(4)CN polymerizations. AEG is produced from the robust Strecker synthesis with ethylenediamine. The NH(4)CN polymerization in the presence of glycine leads to the adenine and guanine-N(9)-acetic acids, and the cytosine and uracil-N(1)-acetic acids are produced in high yield from the reaction of cyanoacetaldehyde with hydantoic acid, rather than urea. Preliminary experiments suggest that AEG may polymerize rapidly at 100 degrees C to give the polypeptide backbone of PNA. The ease of synthesis of the components of PNA and possibility of polymerization of AEG reinforce the possibility that PNA may have been the first genetic material.

Biopolymers↗

Complete genome sequence of Neisseria meningitidis serogroup B strain MC58.

The 2,272,351-base pair genome of Neisseria meningitidis strain MC58 (serogroup B), a causative agent of meningitis and septicemia, contains 2158 predicted coding regions, 1158 (53.7%) of which were assigned a biological role. Three major islands of horizontal DNA transfer were identified; two of these contain genes encoding proteins involved in pathogenicity, and the third island contains coding sequences only for hypothetical proteins. Insights into the commensal and virulence behavior of N. meningitidis can be gleaned from the genome, in which sequences for structural proteins of the pilus are clustered and several coding regions unique to serogroup B capsular polysaccharide synthesis can be identified. Finally, N. meningitidis contains more genes that undergo phase variation than any pathogen studied to date, a mechanism that controls their expression and contributes to the evasion of the host immune system.

Antigenic Variation↗

Preventive intervention to reduce sexually transmitted infections: a field trial in the Royal Thai Army.

BACKGROUND: During 1991 through 1993, sexually transmitted infections among conscripts in the Royal Thai Army in the upper-northern provinces were common: human immunodeficiency virus (HIV) prevalence at induction was 12%, HIV incidence was 2.4% per year, and incidence of sexually transmitted diseases was 17% per year. We evaluated a behavioral intervention to reduce incident sexually transmitted infections among conscripts inducted into the Thai Army in 1993. METHODS: We developed a preventive intervention that addressed consistent condom use, reducing alcohol consumption and brothel patronage, and improving sexual negotiation and condom skills. Companies were assigned to 1 of 3 groups matched on military mission: 450 men were in the intervention group, 681 were in barracks at the same base but did not receive the intervention (diffusion group), and 414 were in distant camps (controls). Baseline HIV serological testing and behavioral interviews were conducted during basic training in 1993. The intervention was applied for 15 months, and men were followed up at 6-month intervals (with repeated HIV serological testing, sexually transmitted disease assessments, and behavioral interviews) through May 1995. RESULTS: Incident sexually transmitted diseases were 7 times less frequent among men assigned to the intervention than the combined controls (relative risk, 0.15; 95% confidence interval, 0.04-0.55), after adjusting for baseline risk factors (P<.005). There was no diffusion of the intervention to adjacent barracks. The intervention decreased incident HIV by 50% in the intervention group. CONCLUSION: Intensive interventions in structured institutions can successfully reduce risk in settings confronting expanding heterosexual HIV epidemics.

Adult↗

A novel lipothrixvirus, SIFV, of the extremely thermophilic crenarchaeon Sulfolobus.

We describe a novel lipothrixvirus, SIFV, of the crenarchaeotal archaeon Sulfolobus islandicus. SIFV (S. islandicus filamentous virus) has a linear virion with a linear double-stranded DNA genome. These two features coincide in several crenarchaeotal but not in any other viruses. The SIFV core is formed by a zipper-like array of DNA-associated protein subunits and is covered by a lipid envelope containing host lipids. We sequenced approximately 96% of the virus genome excepting the DNA termini, which were modified in an unusual, yet uncharacterized, manner. Both, the 5' and the 3' DNA termini were insensitive to enzymatic degradation and labelling. Two open reading frames (ORFs) of the SIFV genome are likely to encode helicases and resemble uncharacterized ORFs from other archaea in sequence. Three ORFs showed sequence similarity with each other and each contained a glycosyl transferase motif. Another ORF of the SIFV genome showed significant sequence similarity to the ORF a291 from the well characterized, spindle-shaped Sulfolobus virus SSV1. Due to its structure, SIFV is classified as a lipothrixvirus.

Amino Acid Sequence↗

Structural analysis of DNA sequence: evidence for lateral gene transfer in Thermotoga maritima.

The recently published complete DNA sequence of the bacterium Thermotoga maritima provides evidence, based on protein sequence conservation, for lateral gene transfer between Archaea and Bacteria. We introduce a new method of periodicity analysis of DNA sequences, based on structural parameters, which brings independent evidence for the lateral gene transfer in the genome of T.maritima. The structural analysis relates the Archaea-like DNA sequences to the genome of Pyrococcus horikoshii. Analysis of 24 complete genomic DNA sequences shows different periodicity patterns for organisms of different origin. The typical genomic periodicity for Bacteria is 11 bp whilst it is 10 bp for Archaea. Eukaryotes have more complex spectra but the dominant period in the yeast Saccharomyces cerevisiae is 10.2 bp. These periodicities are most likely reflective of differences in chromatin structure.

Chromatin↗