Search PubMed⌕ Search

Biomedical subjects

C Nelson

Publications and source records attributed to C Nelson.

At least 55 records · Page 3Linked to original sources
PubMed1998

The value of orbital echography in orbital practice.

Twenty-three consecutive patients with orbital masses who were referred to a major medical center and later had biopsies underwent ophthalmic echographic evaluation. The efficacy of orbital echography was compared with both the clinical evaluation and other orbital imaging methods (computed tomography and magnetic resonance imaging). Echography was successful in all patients (100%) in detecting the orbital mass. The diagnosis was accurate in 18 of 22 patients (82%) echographically, 12 of 14 patients (86%) clinically, and 11 of 13 patients (85%) radiologically when a short differential was attempted. If all the patients examined were considered, echographic evaluation arrived at an accurate diagnosis in 18 of 23 patients (78%), clinical impression was accurate in 12 of 23 patients (52%), and radiologic evaluation was accurate in 11 of 20 patients (55%). In three patients, echography was the only imaging method used. The role of ophthalmic echography in the diagnosis of orbital masses is discussed.

Adult↗
PubMed1998

A population-based survey of Haemophilus influenzae type b nasopharyngeal carriage prevalence in Lombok Island, Indonesia.

BACKGROUND: The Haemophilus influenzae type b (Hib) nasopharyngeal carriage prevalence and invasive disease incidence rates are unknown in Indonesia; consequently Hib vaccine is not included in the routine vaccine schedule. METHODS: To determine carriage prevalence we conducted a population-based, island-wide prospective study of a systematic sample of 484 children 0 to 2 years of age in Lombok, Indonesia. We conducted a risk factor questionnaire and determined serotypes and antibiotic sensitivity patterns. RESULTS: We identified 155 H. influenzae isolates, of which 22 were type b and 12 were encapsulated but not type b. The age- and population-weighted Hib carriage prevalence, adjusted for the sampling design, was 4.6% (95% confidence interval, 3.7 to 5.5%). Children younger than 6 months of age had a carriage prevalence less than one-half that of older children, and carriage varied within the four administrative regions of the island; otherwise no risk factors for Hib carriage were identified. All Hib specimens were sensitive to ampicillin and 20 (91%) were sensitive to chloramphenicol. CONCLUSIONS: The Hib carriage prevalence in Lombok is similar to that found in developed countries before vaccine introduction. This suggests that further studies should proceed to determine whether Lombok has invasive disease rates as high as those that justified vaccine introduction in developed countries.

Carrier State↗
PubMed1998

Haploinsufficiency of MSX1: a mechanism for selective tooth agenesis.

Previously, we found that the cause of autosomal dominant selective tooth agenesis in one family is a missense mutation resulting in an arginine-to-proline substitution in the homeodomain of MSX1. To determine whether the tooth agenesis phenotype may result from haploinsufficiency or a dominant-negative mechanism, we have performed biochemical and functional analyses of the mutant protein Msx1(R31P). We show that Msx1(R31P) has perturbed structure and reduced thermostability compared with wild-type Msx1. As a consequence, the biochemical activities of Msx1(R31P) are severely impaired, since it exhibits little or no ability to interact with DNA or other protein factors or to function in transcriptional repression. We also show that Msx1(R31P) is inactive in vivo, since it does not display the activities of wild-type Msx1 in assays of ectopic expression in the limb. Furthermore, Msx1(R31P) does not antagonize the activity of wild-type Msx1 in any of these assays. Because Msx1(R31P) appears to be inactive and does not affect the action of wild-type Msx1, we propose that the phenotype of affected individuals with selective tooth agenesis is due to haploinsufficiency.

Amino Acid Substitution↗
PubMed1998

A prefilled injection device for outreach tetanus immunization by Bolivian traditional birth attendants.

This study evaluated the performance, acceptability, and appropriateness of a new, single-use, prefilled injection device called UniJect for an outreach immunization application. Between April and June 1995, UniJect devices were used by 36 traditional birth attendants to administer tetanus toxoid injections to 2,240 pregnant women during routine, antenatal home visits in the Northern, Ichilos, and Warnes Districts of Santa Cruz, Bolivia. Because tetanus toxoid is relatively heat stable, the traditional birth attendants were able to keep the tetanus toxoid-filled UniJect devices in their homes for up to one month without refrigeration. The devices were stored, transported, and disposed of in an outreach carrier designed to reduce the risks of improper handling and disposal. Data were collected from injection recipients, traditional birth attendants, and supervisors via observation, questionnaires, and post-study interviews. The performance of the UniJect device and its acceptability among all groups was very high. The traditional birth attendants used UniJect properly and safely; there were no reports or observations of device misuse, reuse, or needle-stick. Advantages cited included the fact that the device required no assembly, offered assured sterility, and reduced vaccine wastage sometimes associated with multi-dose vials. The ability to store and transport the vaccine-filled devices without ice also greatly simplified logistics.

Bolivia↗
PubMed1998

National Ambulatory Medical Care Survey: 1993 summary.

OBJECTIVE: This report describes ambulatory care visits made to private office-based settings in the United States during 1993. Ambulatory medical care services are described in terms of physician, patient, and visit characteristics. METHODS: The data presented in this report are from the 1993 National Ambulatory Medical Care Survey (NAMCS). This survey is part of the ambulatory care component of the National Health Care Survey (NHCS), which measures health care utilization across a variety of providers. The NAMCS is a national probability sample survey of visits to office-based physicians in the United States. Sample data were weighted to produce annual estimates. RESULTS: During 1993, an estimated 717.2 million visits were made to physician offices in the United States, resulting in an average of 2.8 visits per person per year. This rate did not differ significantly from the overall visit rate of 3.0 in 1992. Females made 60 percent of the visits. White persons had a significantly higher rate of visits to physicians than black persons (3.0 visits per person per year and 1.8 visits per person per year, respectively). Over one-quarter (27.6 percent) of the visits were to general and family physicians. About 84 million, or 12 percent, of the visits were injury related. The annual rate of injury-related office visits was 33.0 visits per 100 persons. Essential hypertension was the most common diagnosis made by physicians in 1993 as it has been since the survey began in 1973. Two-thirds of the visits resulted in another scheduled appointment and the mean duration was 18 minutes.

Adolescent↗
PubMed1997

A cysteine-rich domain defined by a novel exon in a slo variant in rat adrenal chromaffin cells and PC12 cells.

cDNA libraries from rat chromaffin cells and PC12 cells were screened for homologs to the mouse mSlo gene that encodes a large conductance, calcium (Ca2+)- and voltage-activated potassium channel (BK channel). One Slo variant contained sequence encoding a cysteine-rich, 59-amino acid insert for a previously described site of alternative splicing. This insert is reminiscent of zinc-finger domains. The exon was found in RNA from pancreas, anterior pituitary, cerebellum, and hippocampus. Expression in Xenopus oocytes of a Slo construct containing this exon conferred a -30 to -20 mV shift of the conductance-voltage curve. A previously uncharacterized alternative splice junction near the C-terminal end of Slo was also identified. In contrast to BK channels in rat chromaffin cells, none of the Slo variants exhibited inactivation when expressed in Xenopus oocytes. PCR screening of chromaffin cell RNA failed to reveal a homolog of an accessory beta subunit known to influence Slo channel function. Furthermore, a beta-subunit-dependent Slo channel activator, dehydrosoyasaponin I, was without effect on chromaffin cell BK current. The results argue that an accessory subunit may not be a required component of the native chromaffin cell BK channel.

Adrenal Medulla↗
PubMed1997

Exercise training by individuals with predialysis renal failure: cardiorespiratory endurance, hypertension, and renal function.

The purpose of this study was to determine the effects of 4 months of exercise training (ET) on cardiorespiratory function and endurance, blood pressure, muscle strength, hematology, blood lipids, and renal function in individuals with chronic renal failure (CRF) who were not yet on dialysis. Sixteen subjects were recruited to volunteer for participation in this study, but only eight completed all study phases. Subjects were first evaluated before and after a 2-month baseline (BL1 and BL2), after 4 months of ET, and again after 2 months of detraining (DT). ET did not change hematology, blood lipids, or echocardiographic measurements of left ventricular function and mass. Resting systolic and diastolic blood pressures decreased significantly from BL after the ET (146 +/- 15.7/87 +/- 9 mm Hg to 124 +/- 17.5/78 +/- 9.5 mm Hg; P < 0.02), and then increased significantly after DT (139 +/- 14.7 mm Hg and 87 +/- 9.9 mm Hg; P < 0.01). Peak oxygen consumption (pVO2) changed significantly during the study (1.3 +/- 0.3 L/min, 1.5 +/- 0.3 L/min, and 1.4 +/- 0.3 L/min for BL2, ET, and DT, respectively; P < 0.02), as did the VO2 at the ventilatory threshold (0.65 +/- 0.18 L/min, 0.92 +/- 0.19 L/min, and 0.68 +/- 0.23 L/min for BL2, ET, and DT, respectively; P < 0.01). Knee flexion peak torque increased after ET (43.4 +/- 25.6 Nm to 51.0 +/- 30.5 Nm; P < 0.02). GFR, as measured by creatinine clearance, continued to deteriorate during the course of the study (25.3 +/- 12.0 mL/min, 21.8 +/- 13.2 mL/min, and 21.8 +/- 13.2 mL/min for BL2, ET, and DT, respectively; P < 0.001). Individuals with predialysis CRF who undergo ET improve in functional aerobic capacity, muscular strength, and blood pressure.

Adult↗
PubMed1997

In vivo dopamine metabolism is altered in iron-deficient anemic rats.

Previous studies of dopamine metabolism in iron-deficient rats demonstrated an elevation in extraneuronal levels of dopamine and a depression in the number of dopamine D2 receptors; however, the importance of anemia per se and the reversibility of these observations are not completely resolved. The purpose of this study was to determine if in vivo reuptake of caudate dopamine is altered by iron deficiency anemia, if it is reversible with iron therapy, and if anemia per se produced the same effects on dopamine metabolism. Male Sprague-Dawley rats (21-d old) were fed an iron-deficient diet (4 mg Fe/kg diet) and then iron repleted (5 mg iron dextran), or were fed an iron adequate diet (35 mg Fe/kg diet) and then given phenylhydrazine to induce hemolytic anemia. In vivo microdialysis was performed in steady-state conditions both before and after iron or no therapy and was followed by an intraperitoneal injection of a dopamine reuptake blocker (cocaine-HCl 30 mg/kg). Thirty percent higher extracellular dopamine levels in the caudate-putamen were observed in iron-deficient rats compared with control rats, but no differences were observed in tissue levels. Hemolytic anemic and iron-repleted rats had normal extracellular dopamine levels. The response to dopamine reuptake blockade was significantly attenuated in iron-deficient rats compared with control, iron-repleted, or hemolytic anemic rats. These experiments provide evidence that iron deficiency blunts the dopamine reuptake mechanism, that this is a reversible process in postweaning rats, and that anemia per se does not cause the increased extracellular dopamine levels.

Anemia, Hemolytic↗
PubMed1997

Cloning and characterization of a human leptin receptor using a biologically active leptin immunoadhesin.

Leptin, the product of the ob gene, is a hormone secreted by fat cells which is primarily involved in the regulation of body weight. We have generated a leptin immunoadhesin (leptin-IgG) which was more potent than leptin alone at reducing body weight and food intake when injected into ob/ob mice. This molecule was used to identify high affinity binding sites on human embryonic 293 kidney cells and subsequently to isolate a cDNA encoding the leptin receptor from this cell line by expression cloning. This receptor corresponds to the short form of the recently isolated leptin receptor. Analysis of the expression pattern of the two forms of receptor by Northern blot, in situ hybridization and quantitative PCR showed that the receptor is expressed in most tissues but that the long form is prevalent in the hypothalamus.

Animals↗
PubMed1997

Assessment of health risks due to hazardous air pollutant emissions from electric utilities.

Hazardous air pollutant (HAP) emissions from electric utilities were evaluated. Cancer risks, as well as noncancer effects, due to inhalation exposure were assessed for 67 HAPs. Also, cancer risks due to multipathway exposure to radionuclide emissions were assessed. In addition, an assessment of the fate of mercury (Hg) through various environmental media was included. Results suggest arsenic, chromium, and nickel are the HAPs that present the highest cancer risk due to inhalation exposure. For noncancer effects due to inhalation exposure, hydrogen chloride appears to present the greatest potential concern. The risks due to multipathway exposure to radionuclides are estimated to be of similar magnitude to the risks posed by inhalation of arsenic and nickel. Mercury is of potential concern for multipathway exposures because it persists in the environmental and bioaccumulates in the aquatic food web. The study suggests there is a plausible link between Hg emissions from utilities and the Hg found in soil, water, and freshwater fish.

Air Pollutants↗
PubMed1996

Function of the conserved Pit-1 gene distal enhancer in progenitor and differentiated pituitary cells.

Pit-1 is a homeodomain transcription factor that is required for the function and survival of the hormone-secreting somatotrope, lactotrope and thyrotrope cells of the anterior pituitary gland. Within the upstream region of the mouse Pit-1 gene at around -10 kb, a complex transcriptional enhancer confers autoregulation and response to hormones and morphogens upon the gene. We demonstrate that this enhancer is conserved in both sequence and function and that related sequences are present in other rodents. Enhancer sequences from mouse, rat and hamster Pit-1 genes activated transcription from Pit-1 promoter reporter genes in a pituitary progenitor cell line, in somatolactotrope cells and conferred pituitary cell-specific activation on heterologous promoters. Elements allowing regulation by vitamin D3, pituitary-specific factors and Pit-1-dependent response to retinoic acid are well conserved. Studies comparing distal enhancer activity with that of a second proposed enhancer sequence at -3 to -5 kb in the rat Pit-1 gene revealed that the distal enhancer has markedly higher activity than the -3 to -5 kb region in both progenitor and differentiated pituitary cell lines. The functional conservation of the distal enhancer element suggests that it is crucial to the maintenance and cell-specific regulation of the Pit-1 gene.

Animals↗
PubMed1996

Glycerophosphorylethanolamine (GPEA) identified as an hepatocyte growth stimulator in liver extracts.

Extracts from weanling pig liver were found to act synergistically with growth factors such as hepatocyte growth factor and transforming growth factor-alpha to stimulate hepatocyte growth in serum-free cultures. In the absence of added growth factors, the extracts had no activity. The compound responsible for this activity was isolated by passing heat-treated liver extract through anion-exchange and heparin columns followed by gel filtration at neutral and low pH, reversed-phase HPLC, and a final gel filtration column at low pH. The activity was followed throughout the purification by its ability to increase substantially the incorporation of [3H]thymidine into primary rat hepatocytes cultured serum-free in the presence of hepatocyte growth factor. The active compound was identified by NMR and mass spectrometry as glycerophosphorylethanolamine (GPEA), a breakdown product of the phospholipid phosphatidylethanolamine. The ethanolamine portion of the molecule was critical for the observed activity, whereas the glycerol phosphate portion was not necessary. In the absence of added growth factors, neither GPEA nor ethanolamine had any stimulatory effect on the cells. These results demonstrate that hepatocytes grown in culture, and especially those grown in serum-free media, require a supplement of ethanolamine and/or GPEA. In the absence of these compounds, their response to growth stimuli is greatly reduced.

Animals↗
PubMed1996

Decreased food intake does not completely account for adiposity reduction after ob protein infusion.

The effects of recombinantly produced ob protein were compared to those of food restriction in normal lean and genetically obese mice. Ob protein infusion into ob/ob mice resulted in large decreases in body and fat-depot weight and food intake that persisted throughout the study. Smaller decreases in body and fat-depot weights were observed in vehicle-treated ob/ob mice that were fed the same amount of food as that consumed by ob protein-treated ob/ob mice (pair feeding). In lean mice, ob protein infusion significantly decreased body and fat-depot weights, while decreasing food intake to a much lesser extent than in ob/ob mice. Pair feeding of lean vehicle-treated mice to the intake of ob protein-treated mice did not reduce body fat-depot weights. The potent weight-, adipose-, and appetite-reducing effects exerted by the ob protein in ob protein-deficient mice (ob/ob) confirm hypotheses generated from early parabiotic studies that suggested the existence of a circulating satiety factor of adipose origin. Pair-feeding studies provide compelling evidence that the ob protein exerts adipose-reducing effects in excess of those induced by reductions in food intake.

Adipose Tissue↗
PubMed1996

Direct cultivation of the causative agent of human granulocytic ehrlichiosis.

BACKGROUND: Human granulocytic ehrlichiosis is a potentially fatal tick-borne infection that has recently been described. This acute febrile illness is characterized by myalgias, headache, thrombocytopenia, and elevated serum aminotransferase levels. The disease is difficult to diagnose because the symptoms are non-specific, intraleukocytic inclusions (morulae) may not be seen, and the serologic results are often initially negative. Little is known about the causative agent because it has never been cultivated. METHODS: We studied three patients with symptoms and laboratory findings suggestive of human granulocytic ehrlichiosis, including unexplained fever after probable exposure to ticks, granulocytopenia, and thrombocytopenia. Peripheral blood was examined for ehrlichia microscopically and with use of the polymerase chain reaction (PCR). Blood was inoculated into cultures of HL60 cells (a line of human promyelocytic leukemia cells), and the cultures were monitored for infection by Giemsa staining and PCR. RESULTS: Blood from the three patients, only one of whom had inclusions suggestive of ehrlichia in neutrophils, was positive for human granulocytic ehrlichiosis on PCR. Blood from all three patients was inoculated into HL60 cell cultures and caused infection, with intracellular organisms visualized as early as 5 days after inoculation and cell lysis occurring within 12 to 14 days. The identity of the cultured organisms was confirmed by immunofluorescence microscopy, PCR analysis, and DNA sequencing. DNA from the infected cells was sequenced in regions of the 16S ribosomal gene reported to differ between the agent of human granulocytic ehrlichiosis and closely related species, including Ehrlichia equi and E. phagocytophila which cause infection in animals. The sequences from all three human isolates were identical and differed from the strain of E. equi studied in having guanine rather than adenine at nucleotide 84. CONCLUSIONS: We describe the cultivation of the agent of human granulocytic ehrlichiosis in cell culture. The ability to isolate this organism should lead to a better understanding of the biology, treatment, and epidemiology of this emerging infection.

Agranulocytosis↗
PubMed1996

A new method for the correction of gamma camera nonuniformity due to spatial distortion.

A methodology for correcting scintillation camera nonuniformity resulting from spatial linearity distortion is described. The method simultaneously corrects for both variations in count density and distortions in spatial linearity without altering the intrinsic sensitivity or resolution of the imaging system. This approach to linearity correction requires only a single flood image from which the spatial shift vectors are derived. The algorithm has been implemented on a PC-based, EISA bus microcomputer, and reduces the measurement of integral uniformity for 201Tl from 25% to 5%. Combined with regional correction for photopeak pulse-heights shifts (i.e. energy correction), the algorithm represents a novel technique for implementing uniformity correction completely within software.

Algorithms↗
PubMed1996

Identification of T-cell determinants in natural immune responses to the Plasmodium falciparum apical membrane antigen (AMA-1) in an adult population exposed to malaria.

AMA-1 of Plasmodium falciparum is a promising candidate antigen in malaria vaccine development. In this study, we have mapped the immunodominant T-cell determinants in this antigen by using synthetic peptides. From the amphipathic scores, 17 putative T-cell determinants were identified. Nine of the 17 peptides complementary to the putative T-cell determinants induced proliferation of peripheral blood mononuclear cells (PBMC) from Kenyan residents who had lifelong exposure to malaria; none of these peptides induced proliferation of PBMC from donors who were not previously exposed to malaria. This indicates that AMA-1 peptides were stimulating T cells that were previously primed by prior exposure to P. falciparum. Many positive responders showed reactivity to more than one peptide, and some of the potent proliferative T epitopes were found to be localized in the highly conserved regions of AMA-1, suggesting that it may be possible to induce T-cell memory that can recognize different variant forms of the parasite. This information on the natural immune responses against the AMA-1 vaccine antigen in clinically immune adults will be helpful in the development of an AMA-1 antigen-based malaria vaccine and may also guide testing of AMA-1-based vaccine formulations.

Adult↗