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Biomedical subjects

L Nelson

Publications and source records attributed to L Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1999

Liposomal prostaglandin E1 (TLC C-53) in acute respiratory distress syndrome: a controlled, randomized, double-blind, multicenter clinical trial. TLC C-53 ARDS Study Group.

OBJECTIVE: To evaluate the safety and efficacy of an intravenous liposomal dispersion of prostaglandin E1 as TLC C-53 in the treatment of patients with acute respiratory distress syndrome (ARDS). DESIGN: Randomized, prospective, multicenter, double-blind, placebo-controlled, phase III clinical trial. SETTING: Forty-seven community and university-affiliated hospitals in the United States. PATIENTS: A total of 350 patients with ARDS were enrolled in this clinical trial. INTERVENTION: Patients were prospectively randomized in a 1:1 ratio to receive either liposomal prostaglandin E1 or placebo. The study drug was infused intravenously for 60 mins every 6 hrs for 7 days starting with a dosage of 0.15 microg/kg/hr. The dose was increased every 12 hrs until the maximal dose (3.6 microg/kg/hr) was attained or intolerance to further increases developed. Patients received standard aggressive medical/surgical care during the infusion period. OUTCOME MEASURES: The primary outcome measure was the time it took to wean the patient from the ventilator. Secondary end points included time to improvement of the PaO2/FIO2 ratio (defined as first PaO2/FIO2 > 300 mm Hg), day 28 mortality, ventilator dependence at day 8, changes in PaO2/FIO2, incidence of and time to development/resolution of organ failure other than ARDS. RESULTS: A total of 348 patients could be evaluated for efficacy. The distribution of variables at baseline describing gender, lung injury scores, Acute Physiology and Chronic Health Evaluation II scores, PaO2/FIO2, pulmonary compliance, and time from onset of ARDS or from institution of mechanical ventilation to the first dose of study drug was similar among patients in the liposomal prostaglandin E1 (n = 177) and the placebo (n = 171) treatment arms. There was no significant difference in the number of days to the discontinuation of ventilation in the liposomal prostaglandin E1 group compared with the placebo group (median number of days to off mechanical ventilation, 16.9 in patients receiving liposomal prostaglandin E1 and 19.6 in those administered placebo; p = .94). Similarly, mortality at day 28 was not significantly different in the two groups (day 28 mortality, 57 of 176 (32%) in the liposomal prostaglandin E1 group and 50 of 170 (29%) in patients receiving placebo; p = .55). In contrast, treatment with liposomal prostaglandin E1 was associated with a significantly shorter time to reach a PaO2/FIO2 ratio of >300 mm Hg (median number of days to reaching a PaO2/FIO2 ratio >300 mm Hg: 9.8 days in the liposomal prostaglandin E1 group and 13.7 days in patients receiving the placebo; p = .02). Among the subgroups examined, time to off mechanical ventilation was significantly reduced in patients who received at least 85% of a full dose (i.e., > 45.9 microg/kg) of liposomal prostaglandin E1 (median number of days to discontinuation of ventilation, 10.3 in the liposomal prostaglandin E1 group and 16.3 days in patients receiving placebo; p = .05). The overall incidence of serious adverse events was not significantly different in the liposomal prostaglandin E1 (40%) or placebo-treated (37%) groups. Drug-related adverse events of all kinds were reported in 69% of the patients receiving liposomal prostaglandin E1 compared with 33% of the placebo group, with hypotension and hypoxia (occurring in 52% and 24% of the liposomal prostaglandin E1-treated patients, respectively, and 17% and 5% of the placebo-treated patients, respectively) being noted most frequently. CONCLUSIONS: In the intent-to-treat population of patients with ARDS, treatment with liposomal prostaglandin E1 accelerated improvement in indexes of oxygenation but did not decrease the duration of mechanical ventilation and did not improve day 28 survival.

Adult↗
PubMed1999

The effect of biphasic defibrillation on the immediate pacing threshold of a dedicated bipolar, steroid-eluting lead.

It is apparent that pacing threshold increases following an ICD shock, although the degree of change observed is dependent on the method used to assess pacing and the lead design used. We previously demonstrated a rise in postshock pacing threshold using a lead with integrated bipolar pacing in which the distal shocking coil also serves as the pacing anode. In this study, we sought to investigate whether the postshock pacing threshold increased significantly in an endocardial, steroid-eluting lead with dedicated bipolar pacing electrodes. Twenty patients (16 men, 4 women; median age 73, ejection fraction [EF] 0.17-0.58) were studied during pectoral ICD implantation (Medtronic active can model 7221Cx or 7223Cx with model 6932-65 lead). The diastolic pulse width pacing threshold at 1 or 2 V was determined. Pacing rate was set > or = 100/min at twice diastolic threshold output to assess pacing immediately following the first DFT test shock. For subsequent shocks, the output was adjusted to establish postshock thresholds as 1, 2, 3, or 4 times the diastolic threshold. The postshock threshold was defined as the output yielding 100% capture > or = 2.5 seconds following a shock. In 8 of 20 patients (ratio 0.40 +/- 0.11), a rise in the post-shock threshold was shown by failure of consistent capture when pacing at 2 times diastolic threshold > or = 2.5 seconds after a DFT test shock. Two of these patients failed at 3 times threshold, but none failed at 4 x threshold. Five of 12 patients with successful capture of 2 times threshold failed to capture at threshold. The postshock threshold increased by a mean factor of 2.83 +/- 0.83 in the group of patients with a threshold rise. Following ICD shock in an active can, steroid-eluting lead system with dedicated bipolar pacing, the post-shock threshold increases significantly. Our studies suggest a need for postshock pacing to be set at least 4 x threshold regardless of the lead design.

Adult↗
PubMed1998

Ingested interferon alpha suppresses type I diabetes in non-obese diabetic mice.

Type I diabetes mellitus is a chronic disorder that results from autoimmune destruction of the insulin-producing pancreatic beta cell. The non-obese diabetic mouse is a model of the human autoimmune disease Type I diabetes [1-3]. We have previously shown that ingested type 1 interferon inhibits chronic relapsing experimental autoimmune encephalomyelitis and the adoptive transfer of experimental autoimmune encephalomyelites by T cells, and decreases both antigen-specific and mitogen-induced pro-inflammatory cytokine secretion in this disorder. We therefore tried to determine whether ingested murine interferon alpha inhibits insulinitis and suppresses Type I diabetes mellitus in non-obese diabetic mice. Murine interferon alpha, given daily, decreased islet inflammation and suppressed diabetes. It increased the concanavalin A and ionomycin plus myristic acid palmitic ester-induced production of interleukin 4 and 10 and interferon gamma-secretion in spleen cells from treated mice. Adoptive transfer of unstimulated splenocytes secreting interleukin 4 and interleukin 10 from fed interferon alpha donors suppressed spontaneous diabetes mellitus in recipients. The protective effect of adoptively transferred unstimulated splenocytes shows the presence of ingested interferon alpha-activated regulatory splenic cell populations that may work via increased interleukin 4 or interleukin 10 production. Ingested interferon alpha administered during vulnerable periods in at-risk populations may potentially provide a continuous, convenient, non-toxic and effective treatment for Type I diabetes.

Adoptive Transfer↗
PubMed1998

Myotonic dystrophy is a significant cause of idiopathic polyhydramnios.

OBJECTIVE: Myotonic dystrophy, the most common form of muscular dystrophy seen in pregnant women, may be a significant cause of middle trimester polyhydramnios. Our purpose was to determine the prevalence of myotonic dystrophy in women with idiopathic polyhydramnios and to characterize the ultrasonographic findings associated with cases. STUDY DESIGN: We examined the cases of 67 patients who were delivered of infants at the University of Utah between 1992 and 1996 with a diagnosis of idiopathic polyhydramnios (amniotic fluid index >25). Women with diabetes mellitus, hydrops, or fetal anomalies known to cause polyhydramnios were excluded from the study. Amniotic fluid samples or cord blood samples were obtained from 41 patients, and polymerase chain reaction amplification and Southern blot analysis were performed to detect the presence of the myotonic dystrophy mutation. Ultrasonographic findings, prenatal course, and neonatal outcomes were reviewed in all cases. RESULTS: Four of the 41 patients tested had the myotonic dystrophy mutation, yielding a prevalence in our population of 9.7%. Three of the 4 patients reported a family history of myotonic dystrophy. Ultrasonographic findings associated with a positive result included abnormal posturing of extremities (3/4) and unilateral clubbed foot (3/4). No other structural or growth abnormalities were seen. Two of the patients were delivered before term, 1 at 26 weeks and 1 at 32 weeks. Three of the 4 infants were severely affected, necessitating admission to the intensive care unit, and 1 died on day 11 after birth. One infant, whose myotonic dystrophy mutation consisted of between 800 and 900 triplet repeats, did not require admission to the intensive care unit. CONCLUSION: Myotonic dystrophy may be seen as idiopathic polyhydramnios and should be considered as part of the differential diagnosis in these cases. Women with a familial history of myotonic dystrophy or ultrasonographic evidence of hypotonia, including positional abnormalities of the extremities, should be offered deoxyribonucleic acid testing for the myotonic dystrophy mutation.

Congenital Abnormalities↗
PubMed1998

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Community Health Services↗
PubMed1998

Factor V Leiden is not common in patients diagnosed with primary pulmonary hypertension.

Substantial evidence suggests that thrombosis contributes to the pathogenesis of primary pulmonary hypertension (PPH). An abnormal factor V (factor V Leiden) may contribute to thrombosis in the pulmonary microcirculation of PPH patients. A point mutation in which adenine is substituted for guanine at nucleotide 1691 (1691A) alters factor V so that it resists cleavage by activated protein C. Heterozygosity for the 1691A mutation is more common (2-8%) in Caucasian Europeans and Americans than in Africans (1%) and Asians (<1%). The aim of the study was to examine the prevalence of the mutation that codes for factor V Leiden in individuals with PPH. We identified 42 Caucasians diagnosed with PPH. We extracted deoxyribonucleic acid (DNA) from whole blood and assayed DNA samples for the point mutation (1691 A) that codes for factor V Leiden. One out of 42 (2.4%; 95% confidence interval=0.1-12.6) Caucasians diagnosed with PPH was heterozygous for the normal 1691G and mutant 1691A allele. All 10 individuals with familial PPH were homozygous for the normal 1691G allele. The prevalence of heterozygosity for the 1691A allele and the normal 1691G allele does not differ from that observed in reference (control) populations. The low prevalence of the 1691A mutation among individuals diagnosed with primary pulmonary hypertension provides evidence that factor V Leiden does not contribute to the pathogenesis of the disease in most patients.

Adult↗
PubMed1998

Analysis of prenatal and gestational care given to women with epilepsy.

OBJECTIVE: To assess past care practices of neurologists and obstetricians to identify areas in which practice patterns differ from currently accepted optimal care. METHODS: Retrospective chart review of 155 women identified as having a diagnosis of epilepsy (or seizure disorder) who had been pregnant any time between January 1988 and December 1995 and were admitted to Stanford University Hospital for delivery. A total of 161 pregnancies (132 women) were selected for study. RESULTS: An obstetrician was seen at some point during the pregnancy in 99% of the pregnancies, whereas a neurologist was seen at least once in only 64% of the pregnancies. In the 3 months before conception, an obstetrician was seen in 5% of the pregnancies and a neurologist was seen in 15%. Seventy-five percent of the patients taking antiepileptic medication and 65% of the untreated patients had documentation of folate supplementation at any time during pregnancy. Vitamin K supplementation in the final month of pregnancy was documented for only 41% of those receiving antiepileptic drugs. In over one-third of the pregnancies the mother did not have a maternal serum alpha-fetoprotein measure documented and a similar percentage did not receive genetic counseling. Monitoring of the maternal serum concentration of the non-protein-bound fraction of the prescribed antiepileptic drugs was not documented. CONCLUSIONS: We identified specific omissions of appropriate vitamin supplementation, genetic counseling, and drug level monitoring. Educational efforts should be targeted to improve the management of pregnancy in women with epilepsy.

Abortion, Induced↗
PubMed1998

The spread of state any willing provider laws.

OBJECTIVE: To describe the growth of any willing provider (AWP) and freedom of choice (FOC) laws applicable to managed care firms and to explore empirically the determinants of their enactment. STUDY SETTING: A 1996 compendium of state laws and state-level data from the 1991-1994 period. STUDY DESIGN: Pooled cross-section time-series logistic regression of the decision to enact various types of AWP and FOC laws. Analysis uses a public choice framework to examine enactment. Key variables include proxy measures of proponent and opponent strength and the political environment. PRINCIPAL FINDINGS: The model works well for laws affecting hospitals, but performs poorly for physician and pharmacy laws. More providers are associated with the enactment of AWP and FOC laws. More large employers are associated with a reduced likelihood of enactment of some forms of the laws but not others. Conservative states are more likely to enact laws limiting selective contracting with hospitals and physicians. States with greater interparty competition are also more likely to adopt some types of legislation. CONCLUSIONS: The empirical results generally are consistent with the view that AWP and FOC laws are often enacted as a defensive strategy on the part of providers, but additional research is needed to provide a more definitive assessment of the determinants of these laws. Suggestions for future research are provided.

Decision Support Techniques↗
PubMed1997

Angiotensinogen T235 expression is elevated in decidual spiral arteries.

Preeclampsia is associated with a common molecular variant of angiotensinogen (Met235Thr). This variant is in tight linkage disequilibrium with a mutation in the angiotensinogen promoter, G(-6)A, which leads to elevated expression in vitro. Since angiotensin II levels could play a role in atherotic changes of the uterine spiral arteries associated with preeclampsia, we investigated angiotensinogen expression in the first trimester uterus. We localized angiotensinogen transcription in uterine decidua using in situ reverse transcription PCR. We then compared decidual T235 expression levels to M235 levels in heterozygous women using an allele-specific ligation assay and a single nucleotide primer extension assay. In human decidua, angiotensinogen is expressed only in spiral artery smooth muscle cells. Heterozygous women have significantly elevated expression of the T235 allele compared to the M235 allele (P < 0.0001). These observations suggest that elevated expression of the T235 allele in decidual spiral arteries may cause first trimester atherotic changes leading to preeclampsia.

Alleles↗
PubMed1997

Leukodystrophy in patients with ovarian dysgenesis.

We describe clinical, biochemical, pathological, and spectroscopic findings in 4 women, aged 15 to 29 years, from three unrelated families who had a unique combination of a central nervous system white matter disease and primary ovarian failure. All had normal initial development but 3 had borderline low IQ and academic difficulties in primary school. Puberty did not develop in 2 patients and was arrested in a third patient. The fourth patient had premature ovarian failure at the age of 13 years. Head magnetic resonance imaging showed diffuse white matter disease, with frontal cortical atrophy in the most clinically advanced patient. All patients had normal karyotype and normal findings on extensive evaluations for known leukodystrophies, for other metabolic diseases, and for causes of ovarian failure. Proton magnetic resonance spectroscopic imaging showed reduction of choline-containing compounds in the affected white matter in all patients and reduction of N-acetylaspartate in the unaffected frontal white matter of 2 patients. All patients had evidence of primary gonadal insufficiency with a normal hypothalamic-hypophyseal axis. Pathological analysis showed streak ovaries in 1 patient and signs of hypomyelination, and gliosis on brain biopsy in another patient. In conclusion, we present a novel group of patients who have in common leukodystrophy, primary ovarian dysfunction, and magnetic resonance spectroscopic abnormalities.

Adolescent↗
PubMed1997

Hypothalamic-pituitary-adrenal activation by the bacterial superantigen staphylococcal enterotoxin B: role of macrophages and T cells.

Staphylococcal enterotoxin B (SEB) is a bacterial superantigen which stimulates T cells bearing the V beta 8 motif on the T-cell receptor. This stimulation is MHC class II dependent, and in vivo results in a rapid and pronounced T-cell cytokine response. Based on previous evidence that SEB stimulates corticosterone production in BALB/c mice, which possess a high percentage of V beta 8+ T cells, we explored the effects of SEB on the hypothalamic-pituitary-adrenal (HPA) axis and identified the peripheral immunologic cellular requirements for these effects. Administration of SEB stimulates corticosterone in a dose-dependent manner, with peak production of corticosterone occurring by 2 h after intraperitoneal challenge with 50 micrograms SEB. Challenge with staphylococcal enterotoxin A, which activates V beta 3+ and V beta 11+ T cells (deleted during ontogenesis in BALB/c mice), did not increase ACTH or corticosterone production. Furthermore, SEB challenge increased plasma ACTH, which accounted for the increased plasma corticosterone, and increased the expression of c-fos in the PVN region of the hypothalamus. In vivo elimination of macrophages did not prevent the corticosterone response to SEB, suggesting that pituitary-adrenal activation does not require macrophages. However, when mice were pretreated with the T-cell immunosuppressant cyclosporin A, the significantly increased ACTH and corticosterone production in response to SEB was dramatically attenuated. These results demonstrate that bacterial superantigens can stimulate the HPA axis, and that functional T cells may play an obligatory role in this effect.

Adrenal Glands↗
PubMed1997

Different excitation-contraction coupling mechanisms exist in squid, cuttlefish and octopod mantle muscle

Excitation-contraction (EC) coupling was studied in central zone mantle muscle fibres of a squid (Alloteuthis subulata), a cuttlefish (Sepia officinalis) and an octopod (Eledone cirrhosa). Thin slices of muscle were used for twitch experiments and enzymatic isolation of single fibres for whole-cell patch-clamp studies. The current required for a supramaximal twitch response during direct stimulation of muscle slices was lower for squid than for cuttlefish. In squid, but not in cuttlefish, the current-response relationship was independent of slice thickness (range 0.1-0.5 mm). Twitches of squid and cuttlefish slices were reversibly abolished by removal of extracellular Ca2+. In squid, but not in cuttlefish, the current-response relationship was Na+-dependent, and in the absence of Na+ higher current strengths were required to generate a supramaximal response. In whole-cell voltage-clamp experiments on isolated muscle fibres from squid, cuttlefish and Eledone cirrhosa, a sustained inward current was recorded upon depolarisation. This current was blocked by 5 mmol l-1 Co2+ and suppressed by 10 micromol l-1 nifedipine. In squid, an additional inward fast-activating transient current was seen which was blocked by 2 micromol l-1 tetrodotoxin and depolarised holding potentials. The fast current represents a voltage-activated Na+ channel, and the slow currents represent L-type Ca2+ channels. We conclude that squid possess a specialised rapid EC coupling mechanism in central zone fibres that is absent in cuttlefish and Eledone cirrhosa.

Journal Article↗