Search PubMed⌕ Search

Biomedical subjects

David R Nelson

Publications and source records attributed to David R Nelson.

89 records · Page 5Linked to original sources
PubMed2003

Long-term interleukin 10 therapy in chronic hepatitis C patients has a proviral and anti-inflammatory effect.

An imbalance in Th1 and Th2 cytokine production is implicated in disease progression of HCV. Our aim was to determine the effect of IL-10 administration in patients with HCV-related liver disease. Thirty patients with advanced fibrosis who had failed antiviral therapy were enrolled in a 12-month treatment regimen with SQ IL-10 given daily or thrice weekly. Liver biopsies were performed before and after therapy. Serum and PBMC were collected for HCV RNA, ALT, and functional T-cell analysis. IL-10 led to significant improvement in serum ALT (mean ALT: day 0 = 142 +/- 17 vs. month 12 = 75 +/- 10; P <.05). Hepatic inflammation score decreased by at least 2 in 13 of 28 patients (mean decrease from 4.6 +/- 0.3 to 3.7 +/- 0.3, P <.05) and 11 of 28 showed a reduction in fibrosis score (mean change from 5.0 +/- 0.2 to 4.5 +/- 0.3, P <.05). Serum HCV RNA levels increased by 0.5 log during therapy (mean HCV RNA day 0: 12.3 +/- 3.0 Meq/mL; 12 months: 38 Meq/mL; P <.05) and returned to baseline at the end of follow-up (11.0 +/- 2.4 Meq/mL). Five patients developed viral loads of greater than 120 Meq/mL and two of these developed an acute flare in serum ALT. IL-10 caused a decrease in the number of HCV-specific CD4+ and CD8+ IFN-gamma secreting T cells and alterations in PBMC cytokine production towards a Th2 dominant profile. These changes parallel the improvement in ALT and rise in HCV RNA. In conclusion, long-term rIL-10 therapy appears to decrease disease activity, but also leads to increased HCV viral burden via alterations in immunologic viral surveillance.

Adult↗
PubMed2003

Lack of antiviral effect of a short course of mycophenolate mofetil in patients with chronic hepatitis C virus infection.

Mycophenolate mofetil (MMF) is an immunosuppressive agent that is widely used in the management of liver transplant recipients. MMF inhibits the inosine monophosphate dehydrogenase that has been shown to have in vitro antiviral properties against flaviviruses, suggesting the possibility that it might also inhibit the hepatitis C virus (HCV). The goal of this short-term dose escalation study was to assess the antiviral effects of MMF on HCV replication. Patients with chronic hepatitis C who had not undergone liver transplantation were randomized to 8 weeks of treatment with one of four mycophenolate dose regimens (1000 mg orally twice daily, 500 mg orally twice daily, 250 mg orally twice daily, or a matched oral placebo twice daily). All groups were double-blinded. Quantitative HCV RNA levels and serum alanine aminotransferase were assessed at baseline, at weeks 2, 4, and 8 of dosing, and at weeks 4 and 8 of follow-up. Thirty patients met inclusion criteria, enrolled, and were randomized. HCV RNA levels did not change significantly during treatment. Specifically, no subject became virus negative or had a one-log decrease in virus level. Serum aminotransferase level did not normalize in any subject. The most common side effects were headache, nausea, and diarrhea. Mycophenolate alone does not appear to have a significant antiviral or biochemical effect in patients with chronic hepatitis C.

Adult↗
PubMed2003

Expression of spoT in Borrelia burgdorferi during serum starvation.

Borrelia burgdorferi, the causative agent of Lyme disease, is transmitted by the tick Ixodes scapularis. A 2.9-kb fragment containing a putative spoT gene was isolated from B. burgdorferi genomic DNA by PCR amplification and cloned into a pBAD24 vector. The cloned gene complemented Escherichia coli mutant strain CF1693, which contains deletions of both the relA and spoT genes. The spoT gene in E. coli encodes a bifunctional enzyme capable of synthesizing and degrading (p)ppGpp, which mediates the stringent response during carbon source starvation. B. burgdorferi has been reported to have a stress response to serum starvation. Thin-layer chromatography was used to detect (p)ppGpp extracted from H(3)(32)PO(4)-labeled B. burgdorferi cells starved for serum in RPMI. B. burgdorferi spoT gene expression was characterized during fatty acid starvation. Northern analysis of spoT revealed detectable message at 2.5 min of starvation in RPMI. Expression of spoT during serum starvation increased approximately 6-fold during the 30 min that starvation conditions were maintained. Further, expression of spoT decreased when serum was added to serum-starved cells. Reverse transcriptase PCR (RT-PCR) was used to detect spoT mRNA from approximately 10(6) cells starved for serum in RPMI for 2.5 to 30 min or incubated in tick saliva for 15 min. Northern blot analysis suggests that spoT transcript was approximately 900 nucleotides in length. RT-PCR amplification of the transcript using several sets of primers confirmed this finding. Additionally, a truncated clone containing only the first 950 bp of the 2,001-bp spoT open reading frame was able to complement E. coli CF1693. The data suggest that B. burgdorferi exhibits a stringent response to serum starvation and during incubation in tick saliva.

Animals↗
PubMed2002

C-reactive protein, arterial endothelial activation, and development of transplant coronary artery disease: a prospective study.

BACKGROUND: Arterial endothelial expression and raised serum concentrations of the soluble form of intercellular adhesion molecule-1 (ICAM-1) are implicated in development of transplant coronary artery disease. We investigated whether C-reactive protein, known to stimulate ICAM-1, was associated with increased ICAM-1 concentration and subsequent development of coronary artery disease. METHODS: With sandwich ELISAs, we measured C-reactive protein and soluble ICAM-1 in serial serum samples obtained during the first 3 months after transplantation in 109 heart-transplant patients. Matching endomyocardial biopsy samples were screened immunohistochemically for arterial endothelial ICAM-1. Serial coronary angiograms were assessed for development, severity, and progression of coronary artery disease. FINDINGS: We showed a significant correlation (p=0.001) between raised concentrations of C-reactive protein and arterial endothelial ICAM-1 expression in endomyocardial biopsy samples. We also noted a significant relation between C-reactive protein and soluble ICAM-1 concentrations soon after transplantation (p=0.003). Early raised C-reactive protein concentrations were associated with development (p=0.004), increased severity (p=0.02), and enhanced rate of progression (p=0.01) of coronary artery disease, and with heightened frequency of ischaemic events (p=0.049) and graft failure (p=0.04). INTERPRETATION: C-reactive protein concentration can be used to identify heart-transplant patients at increased risk of coronary artery disease and graft failure. Treatments directed at reduction of C-reactive protein concentration could improve patients' outcome.

Biopsy↗
PubMed2002

Single molecule statistics and the polynucleotide unzipping transition.

We present an extensive theoretical investigation of the mechanical unzipping of double-stranded DNA under the influence of an applied force. In the limit of long polymers, there is a thermodynamic unzipping transition at a critical force value of order 10 pN, with different critical behavior for homopolymers and for random heteropolymers. We extend results on the disorder-averaged behavior of DNA's with random sequences [D. K. Lubensky and D. R. Nelson, Phys. Rev. Lett. 85, 1572 (2000)] to the more experimentally accessible problem of unzipping a single DNA molecule. As the applied force approaches the critical value, the double-stranded DNA unravels in a series of discrete, sequence-dependent steps that allow it to reach successively deeper energy minima. Plots of extension versus force thus take the striking form of a series of plateaus separated by sharp jumps. Similar qualitative features should reappear in micromanipulation experiments on proteins and on folded RNA molecules. Despite their unusual form, the extension versus force curves for single molecules still reveal remnants of the disorder-averaged critical behavior. Above the transition, the dynamics of the unzipping fork is related to that of a particle diffusing in a random force field; anomalous, disorder-dominated behavior is expected until the applied force exceeds the critical value for unzipping by roughly 5 pN.

Base Pairing↗
PubMed2002

Interleukin-10 inhibition of nitric oxide biosynthesis involves suppression of CAT-2 transcription.

Interleukin-10 (IL-10) has been shown to attenuate lipopolysaccharide (LPS) stimulation of inducible nitric oxide synthase (iNOS) in various cell types. Guanosine triphosphate cyclohydrolase I (GTPCH) and type-2 cationic amino acid transporter (CAT-2) are enzymes that regulate iNOS activity. We therefore sought to assess the effects of IL-10 on the expression of these regulatory enzymes in LPS-stimulated macrophages that are known to express iNOS. Five minutes after adding LPS to these macrophage cultures, various doses of recombinant human IL-10 were also added. The samples were harvested for analysis 18 h after exposure to both LPS and IL-10. In LPS-stimulated macrophages, IL-10 attenuated the upregulation of nitric oxide and iNOS protein but not iNOS mRNA. IL-10 also attenuated the LPS-induced upregulation of CAT-2 mRNA. However, IL-10 and LPS had no effect on GTPCH mRNA expression. We therefore conclude that IL-10 inhibits nitric oxide formation in LPS-stimulated macrophages partly by decreasing iNOS protein expression. Moreover, our data suggests that transcriptional control of CAT-2 plays a role in IL-10 mediated influences upon nitric oxide biosynthesis.

Animals↗
PubMed2002

Increased sperm nuclear DNA damage in normozoospermic infertile men: a prospective study.

OBJECTIVE: To evaluate levels of sperm nuclear DNA damage in infertile men with normal and abnormal standard semen parameters. DESIGN: Prospective study. SETTING: Male infertility clinic. PATIENT(S): Ninety-two men seeking infertility treatment and 16 fertile volunteers. INTERVENTION(S): Standard semen analysis was performed according to the World Health Organization guidelines. MAIN OUTCOME MEASURE(S): Sperm DNA damage was assessed by sperm chromatin structure assay and the results expressed as %DFI. RESULT(S): Of the 92 patients, 21 (23%) had normal standard sperm parameters (concentration, motility, and normal sperm forms), while 71 (77%) had an abnormality in one or more of these parameters. The %DFI [median (25th and 75th percentiles)] in infertile men with normal sperm parameters [23 (15, 32)] was significantly higher than fertile donors [15 (11, 20)] (P=.02), but not significantly different from infertile men with abnormal sperm parameters [28 (18, 41)] (P=.27). CONCLUSION(S): The results of this study indicate that a significant increase in SCSA-defined DNA damage can be found in sperm from infertile men with normal standard sperm parameters. Therefore, sperm DNA damage analysis may reveal a hidden abnormality of sperm DNA in infertile men classified as idiopathic based on apparently normal standard sperm parameters.

Cell Nucleus↗
PubMed2002

Effect of cigarette smoking on levels of seminal oxidative stress in infertile men: a prospective study.

OBJECTIVE: To investigate levels of seminal oxidative stress (OS) and sperm quality in a group of infertile men with a history of cigarette smoking. DESIGN: A prospective clinical study. SETTING: Male infertility clinic, Urological Institute, the Cleveland Clinic Foundation, Cleveland, Ohio. PATIENT(S): Infertile men who smoked cigarettes (n = 20), infertile men who were nonsmokers (n = 32), and healthy nonsmoking donors (n = 13). INTERVENTION(S): Genital examination, standard semen analysis, sperm DNA damage. MAIN OUTCOME MEASURE(S): Levels of seminal reactive oxygen species (ROS) and total antioxidant capacity (TAC) measured by a chemiluminescence assay and seminal OS assessed by calculating a ROS-TAC score. Sperm DNA damage was measured by sperm chromatin structure assay. RESULT(S): Smoking was associated with a 48% increase in seminal leukocyte concentrations (P<.0001), a 107% increase in ROS levels (P=.001), and a 10-point decrease in ROS-TAC scores (P=.003). Differences in standard sperm variables and DNA damage indices between the infertile smokers and infertile nonsmokers were not statistically significant. CONCLUSION(S): Infertile men who smoke cigarettes have higher levels of seminal OS than infertile nonsmokers. Given the potential adverse effects of seminal OS on fertility, physicians should advise infertile men who smoke cigarettes to quit.

Analysis of Variance↗
PubMed2002

Combination of interferon alfa-2b and ribavirin in liver transplant recipients with histological recurrent hepatitis C.

Recurrent hepatitis C virus (HCV) infection is an important cause of fibrosis and cirrhosis after liver transplantation (LT), with histological recurrence developing in at least 50% of patients within the first year. The aim of this study is to assess the safety and efficacy of interferon alfa-2b plus ribavirin in treating histological recurrent HCV after LT. Since 1998, patients with HCV with significant histological recurrence (fibrosis >/= 3 and/or histological activity index >/= 5) or progressive cholestatic disease after LT were treated with interferon alfa-2b (3 million units subcutaneously three times weekly) plus ribavirin (800 to 1,000 mg/d) for 12 months. Immunosuppression was tapered to cyclosporine/FK506 monotherapy. HCV RNA was assessed at entry, week 24, end of treatment, and 6 months after therapy. The primary end point was loss of HCV RNA 6 months after therapy, whereas the secondary end point was histological response. Fifty-four patients met criteria for treatment and have completed follow-up. Patients were mainly men (71% men; mean age, 51 +/- 5 years) with genotype 1 infection (88%) and high viral load (mean HCV RNA, 38 +/- 9 mEq/mL). Dose modification was required in 72% of patients because of cytopenia or side effects. Intent-to-treat analysis showed that serum HCV RNA was undetectable in 19 patients (35%) week 24, 21 patients (38%) week 48, and 16 patients (30%) at the 6-month follow-up. Paired liver biopsy results (before and within 6 months after treatment) were available for 35 patients. Patients who achieved viral eradication had no significant progression of fibrosis after 1 year of therapy. In summary, combination therapy is a reasonable antiviral option for recurrent HCV infection for established post-LT hepatitis and appears to prevent histological progression of disease if viral eradication is successful.

Adult↗
PubMed2002

Electronic analysis of intrinsic laryngeal muscles in canine sound production.

This study explores the relationship between voice production and intrinsic laryngeal muscle (ILM) activities as expressed by orderly recruitment of their specific motor units. In 5 dogs, both the recurrent laryngeal nerve (RLN) and the vagus nerve (cranial nerve X) were stimulated via tripolar electrodes with stimulating frequencies (Fs) of 10 to 60 Hz and 0 to 7 mA during application of symmetric 600 Hz, 7 to 0 mA blocking currents. The fundamental frequency (Fo) and the intensity (I) of sounds generated by tracheal insufflation of humidified air were recorded while electromyograms of the cricothyroideus (CT), thyroarytenoideus (TA), and posterior cricoarytenoideus (PCA) were obtained via surface electrodes. Contractions of the CT were concurrently induced by stimulating the superior laryngeal nerve (SLN). The recruitment rates were highly specific and were affected by which nerve was stimulated. For the RLN, PCA ramping was lowest for Fs of < or =50 Hz. For Fs of 10 to 30 Hz, the recruitment rate of the TA was significantly steeper than that for the other ILMs, and the CT had the highest rate for Fs of 40 to 50 Hz. Conversely, for the vagus nerve, PCA recruitment was highest for Fs of > or =30 Hz. The average Fo was significantly higher with the RLN than with the vagus nerve. When the TA recruited faster than the CT (ie, via the RLN, but not the vagus nerve), the Fo was higher. While only CT ramping was significantly related to changes in sound intensity, there was a trend toward a decrease when PCA ramping was higher than CT ramping, as occurred when only the vagus nerve was stimulated. Stimulation of the SLN always increased Fo and loudness. We conclude that changes in Fo occur mainly through RLN-mediated CT and TA contraction. Loudness is controlled by the CT. The PCA exerts reciprocal coupling on both functions via the vagus nerve, and they are boosted across the board by the SLN. These findings may allow artificial manipulation of voice.

Animals↗
PubMed2000

Serum-starvation-induced changes in protein synthesis and morphology of Borrelia burgdorferi.

It has been demonstrated previously that motile Borrelia burgdorferi cells transform into non-motile cyst-forms when incubated for several weeks in BSKII (a complex medium) lacking rabbit serum. B. burgdorferi cells cannot synthesize fatty acids de novo and serum is thought to provide a source of fatty acids and lipids. When B. burgdorferi cells were serum-starved in defined RPMI medium, -90% of the cells formed spherical cysts within 48 h. Cyst formation was inhibited by tetracycline. Cyst opening and recovery of vegetative cells was rapidly induced by the addition of either BSKII or rabbit serum. The percentage of viable cells recovered from cysts ranged from 2.9% to 52-5%. Viability was inversely proportional to cyst age. Protein synthesis by B. burgdorferi during serum starvation was examined by labelling cells with Tran35S-Label and analysing the labelled proteins by two-dimensional gel electrophoresis and fluorography. The synthesis of over 20 proteins was induced during serum starvation. Western blots of proteins from vegetative cells and cysts probed with sera from either B. burgdorferi-infected humans or monkeys revealed that several cyst proteins were antigenic. These data suggest that cells of B. burgdorferi, although possessing a small genome and extremely limited biosynthetic capabilities, rapidly respond to conditions of serum starvation by inducing changes in protein synthesis and cell morphology. This study may help explain how cells of B. burgdorferi can survive periods of nutrient deprivation in different hosts and host tissues.

Animals↗
PubMedDate not supplied

New semen quality scores developed by principal component analysis of semen characteristics.

The purpose of this study was to determine whether semen characteristics can be reduced to 2 semen quality (SQ) scores and whether these new scores can help the clinician in assessing the reproductive outcome. A cross-sectional sample of 250 patients seeking infertility treatment were analyzed for semen characteristics. In addition, 177 male-factor patients (prostatitis with infection, n = 40; varicocele, n = 77; varicocele with infections, n = 11; and vasectomy reversal, n = 43) were also assessed. Sperm motion kinetics were measured by computer-assisted semen analysis (CASA) (concentration, percent motility, curvilinear velocity [VCL], straight-line velocity [VSL], average path velocity [VAP], linearity [LIN], and amplitude of lateral head displacement [ALH]). Sperm morphology was assessed by both World Health Organization (WHO) guidelines and Tygerberg strict criteria. The principal component analysis model was used to construct an SQ score and a relative semen quality (RQ) score. A separate set of 25 normal donors was included as controls to determine normal ranges of the semen scores. Among the patient samples, SQ and RQ scores (median and 25% and 75% interquartile values) were 89.9, 25.1, and 130.4 and 106.1, 45.2, and 165.9, respectively. The SQ score for the varicocele and varicocele with infection groups was comparable (78.6 +/- 17.4 and 84.8 +/- 20.6) but significantly different from the control (100 +/- 10, P <.001 and.03). Vasectomy reversal patients had an SQ score of 78.2 plus or minus 16.8 that was significantly lower than controls (P <.001). The correlation among semen characteristics allows for the efficient combining of semen measures. The composite scores can summarize overall SQ and quantity. Both SQ and RQ scores provide meaningful information on the quality of semen specimens for the clinician.

Humans↗
PubMedDate not supplied

The use of novel semen quality scores to predict pregnancy in couples with male-factor infertility undergoing intrauterine insemination.

The purpose of this study was to determine whether 2 new semen quality (SQ) scores could predict pregnancy in patients undergoing intrauterine insemination (IUI) for male-factor infertility and whether an overall score could help in counseling these couples with assisted reproductive technique (ART) options. Ninety-three couples with male-factor infertility were examined for semen analysis. Samples were prepared by density gradient separation (47% and 90%), and IUI was performed. On the basis of the 2 semen scores (SQ and relative quality [RQ]), the IUI-semen pregnancy score (IUI-SPS) was calculated. Of the 192 IUI cycles, 14% (27 of 192) resulted in pregnancy. Both prewash SQ and RQ scores were significantly related to pregnancy (P =.02 and P <.001), as was the postwash RQ score (P <.001). Of the IUI cycles in which the postwash RQ score was greater than 125, 40% (13 of 32) resulted in pregnancy compared to 9% of cycles (14 of 160) in which the postwash SQ score was less than 125. The prewash IUI-SPS score was significantly related to IUI-induced pregnancy (P <.001). Both the pre- and postwash SQ and RQ scores can predict pregnancy in male infertility patients undergoing IUI. Patients with an IUI-SPS less than 150 may be advised to seek in vitro fertilization (IVF), whereas those with an IUI-SPS greater than 150 may be advised to seek IUI.

Female↗
PubMedDate not supplied

Development of an inexpensive artificial vagina for semen collection from rabbits.

The rabbit is well suited for infertility research because of the animal's size, relatively low cost, and accessibility of the genitalia. There are several studies reporting sperm count and motility in rabbits; however, no easily reproducible or inexpensive device for semen collection has been reported. Herein, we report the construction of an inexpensive, effective artificial vagina assembled from easily obtainable products that may be used to collect rabbit ejaculates. This device was used to perform 243 ejaculation trials on 17 rabbits. Eighty-six percent (209/243) of the trials resulted in rabbit mounts. Overall, 91% (191/209) of mounts resulted in successful semen collection. After 60 mounts, a 98% successful ejaculate collection rate was achieved. The cost of the reusable device is 2.64 US dollars, plus silicone condoms at 7.50 each US dollars. This practical artificial vagina for semen collection is an inexpensive and effective means of obtaining semen from rabbits for andrologic study.

Animals↗
PubMedDate not supplied

Effects of temperature on sperm motion characteristics and reactive oxygen species.

OBJECTIVE: To evaluate the effect of temperature on sperm motility, sperm motion characteristics, and production of reactive oxygen species (ROS) in semen. METHODS: We collected semen samples from 12 infertile patients and 12 healthy donors and divided each sample into four aliquots just after liquefaction. One aliquot was analyzed immediately after liquefaction and the remaining three were analyzed after one hour of incubation at 4 degrees C, 25 degrees C, and 37 degrees C. Sperm motility and motion characteristics were measured by computer-assisted sperm analysis (CASA). Levels of ROS were determined in washed sperm suspensions using a chemiluminescence assay and results were expressed as x10(6) counted photons per minute (cpm)/20 million sperm/mL. RESULTS: Motility, curvilinear velocity, straight-line velocity, average path velocity, and amplitude of lateral head displacement decreased significantly from baseline values in both the patients and donors after incubation at 4 degrees C. Percentage motility was highest and ROS levels were lowest in the samples that were incubated at 37 degrees C. CONCLUSION: Based on our results, we suggest that semen samples be stored at 37 degrees C after collection and during transportation and processing.

Adult↗