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Biomedical subjects

J Owen

Publications and source records attributed to J Owen.

At least 127 records · Page 7Linked to original sources
PubMed1994

Cerebellar modulation of ventilatory response to progressive hypercapnia.

The cerebellar contribution to the ventilatory response to progressive hypercapnia was examined in 18 anesthetized tracheotomized spontaneously breathing cats. The absolute values for minute ventilation (VE), tidal volume (VT), respiratory frequency (f), inspiratory duty cycle (TI/TT), and mean inspiratory flow (VT/TI) were measured. Progressive hypercapnia [35-65 Torr end-tidal PCO2 (PETCO2)] was induced using the rebreathing method. The respiratory variables at each level of PETCO2 and the slopes of ventilatory (VT and f) responses to hypercapnia were compared across the intact, decerebellate, and decerebellate-vagotomized preparations. In 12 cats, decerebellation preceded vagotomy, and in 6 cats the order of the surgical procedures was reversed. The results show that, compared with intact control, decerebellation had little effect on respiratory variables when PETCO2 was 30-35 Torr. However, during a hypercapneic challenge (40-65 Torr PETCO2), VE and the slope of the VE response were significantly reduced. Bilateral vagotomy increased VT and decreased f but failed to alter the ventilatory response in the PETCO2 range of 35-55 Torr. However, combination of decerebellation and vagotomy, regardless of the surgical order, severely blunted VE (35-65 Torr PETCO2) and the slopes of VE, VT and f responses. When decerebellation followed vagotomy, significant decreases in VT (absolute values and slopes) were noted with little further alteration in f response. We conclude that the cerebellum and its interaction with the vagus nerves play a facilitatory or disinhibitory role in the ventilatory responses to hypercapnia.

Animals↗
PubMed1994

Fibrinogen New Britain: characterization of an A alpha Arg 16-->His variant human fibrinogen.

Routine laboratory screening identified an abnormal fibrinogen in an asymptomatic patient from New Britain, Connecticut. This paper reports the characterization of the abnormal fibrinogen. Clinical clotting studies showed marked prolongation of both the thrombin and Reptilase times. A discrepancy was noted between the fibrinogen concentration as determined by a rate-dependent clotting assay (0.73 milligrams) vs immunological determination (2.27 milligrams). Polymerase chain reaction (PCR) based DNA sequencing was used to identify the underlying molecular defect. Fibrinogen New Britain was found to have a point mutation in exon 2 of the A alpha chain. This mutation results in the amino acid substitution Arg-->His at position 16 of the A alpha chain, the site of thrombin cleavage. The substitution results in delayed polymerization of fibrin clot due to impaired release of fibrinopeptide A by thrombin. Studies of fibrin fibre dimensions and structure showed New Britain fibrin fibres to have a larger mean diameter and an increased mass/length ratio when compared with normal fibrin fibres formed under the same conditions.

Amino Acid Sequence↗
PubMed1993

The effect of low-dose aspirin on fetal urine output and amniotic fluid volume.

OBJECTIVE: Patients given prostaglandin synthetase inhibitors in doses sufficient to inhibit labor are at risk for developing oligohydramnios (possibly related to a reduction in fetal urine output). We sought to ascertain whether the fetuses of women who received 60 mg of aspirin daily had a lower urine output than those whose mothers were given a placebo. STUDY DESIGN: Nulliparous women with singleton gestations in a double-blind preeclampsia prevention trial were randomly selected at 24 weeks' gestation to receive either 60 mg of aspirin daily or a placebo. Urine output was assessed in 59 fetuses (aspirin 32, placebo 27) by serial ultrasonographic measurement of their bladder volume (volume = 4/3 pi r3). Biochemical evidence of aspirin compliance was defined as an 80% reduction in maternal serum thromboxane B2 levels when comparing values obtained at randomization with those at 34 to 36 weeks' gestation. RESULTS: Visual assessment of amniotic fluid volume was similar in both groups. Four-quadrant amniotic fluid indexes also were similar (13.5 cm in aspirin group vs 12.2 cm in placebo group, p = 0.15). Mean fetal urine outputs were similar in the aspirin (57.7 ml/hr) and placebo (55.1 ml/hr) groups (p = 0.71). Moreover, the 23 women with a fourfold thromboxane B2 reduction had a higher mean fetal urine output (63.5 vs 51.8 ml/hr, p = 0.08) than did the remaining 35 patients. This study has a 96% chance (1-beta) of detecting a 50% (30 ml) reduction in fetal urine output. CONCLUSIONS: Daily maternal ingestion of 60 mg of aspirin did not decrease fetal urine output or amniotic fluid volume.

Adult↗
PubMed1993

The effect of low-dose aspirin on umbilical artery Doppler measurements.

OBJECTIVE: Our purpose was to determine if the maternal administration of low-dose (60 mg) aspirin from 24 weeks' gestation until delivery is associated with significant changes in longitudinal umbilical artery Doppler index values. STUDY DESIGN: Healthy, young nulliparous women with singleton gestations who were enrolled in a double-blind trial of low-dose aspirin for preeclampsia prevention underwent prerandomization and monthly postrandomization continuous-wave umbilical artery Doppler evaluations. The systolic-to-diastolic ratio and the resistance index were determined at each examination. Compliance with the medical regimen was assessed by pill counts and measurement of maternal serum thromboxane B2 levels. RESULTS: The prerandomization Doppler index values were similar between the two randomization groups in the 538 (aspirin 266, placebo 272) patients studied. We found no significant differences with univariate comparisons and multiple linear regression modeling in the postrandomization Doppler index values (p = 0.21 to 0.96). No differences were found when patients were assessed by randomization assignment group (intent to treat) or by biochemical evidence for compliance and absence of crossover with maternal serum thromboxane B2 levels. CONCLUSION: The use of low-dose aspirin from 24 weeks' gestation until delivery does not significantly affect umbilical artery Doppler index values.

Aspirin↗
PubMed1993

Randomized trial of prophylactic antibiotic therapy after preterm amnion rupture.

OBJECTIVE: Our purpose was to determine whether maternal administration of prophylactic ampicillin or erythromycin after preterm amnion rupture is associated with maternal or neonatal benefits. STUDY DESIGN: Women with singleton pregnancies between 24 and 33 weeks 6 days of gestation were eligible if they had no immediate indication for delivery. After giving informed consent, patients were randomized either to receive ampicillin (erythromycin if penicillin allergic) until delivery or to enter a control group. Women whose cervical cultures were positive for either group B streptococci or Neisseria gonorrhoeae received treatment. Tocolytics and corticosteroids were not used. RESULTS: From January 1990 to February 1992 117 patients (antibiotics 59, control 58) were recruited and analyzed. Prophylactic antibiotics were associated with a longer latent phase (mean 12 vs 7.0 days, p = 0.004) and fewer maternal infectious complications (29% vs 60%, p = 0.001). A higher incidence of neonatal necrotizing enterocolitis was observed in the treatment group (14% vs 3.5%, p = 0.05). Other neonatal complications, including death, were lower in the treatment group, but none attained statistical significance (p = 0.09 to 0.33). CONCLUSION: The use of prophylactic antibiotics in selected patients after preterm amnion rupture appears to have a demonstrable maternal benefit. Large, multicenter trials may demonstrate a significant neonatal benefit or confirm any adverse outcomes.

Adult↗
PubMed1993

Management of patients taking anticoagulants and platelet inhibitors prior to dermatologic surgery.

BACKGROUND: The use of anticoagulants and platelet inhibitors can increase the risk of intraoperative and postoperative hemorrhagic complications in cutaneous surgery. Currently there are no general guidelines and no consensus among dermatologic surgeons on how to manage patients taking these medicines. OBJECTIVE: To address many of the issues involved in the management of these patients. CONCLUSION: General recommendations are made for managing patients taking anticoagulants and platelet inhibitors prior to dermatologic surgery.

Anticoagulants↗
PubMed1993

Platelet activation and fibrinopeptide formation in pulmonary hypertension.

Intravascular thrombosis is postulated to cause or to contribute to the development of uncharacterized ("primary") pulmonary hypertension (PPH). To assess whether there is ongoing platelet-fibrin thrombosis in patients with PPH, we measured specific markers of platelet activation: platelet factor 4 (PF4) and beta-thromboglobulin (BTG); of fibrin formation: fibrinopeptide A (FPA); and of fibrin dissolution: fibrinopeptide BB1-42 (FPBB1-42) in peripheral venous blood from 10 patients with PPH (group 2). Results were compared with those of normal volunteers (group 1, n = 9) and with results from patients with pulmonary hypertension secondary to congenital heart disease (group 3, n = 7). Both groups 2 and 3 exhibited severe pulmonary hypertension (mean pulmonary arterial pressure = 62 +/- 20 mm Hg and 70 +/- 13 mm Hg, respectively). Mean level of PF4, BTG, FPA, and FPBB1-42 in patients with pulmonary hypertension, either primary or secondary to congenital heart disease, did not differ from levels in normal subjects. Within group 2, levels of platelet proteins and fibrinopeptides did not differ between patients who were classified clinically as having plexogenic arteriopathy vs thromboembolic disease. These observations suggest that a sustained state of abnormal platelet activation and fibrin formation or dissolution is not present in patients with established pulmonary hypertension.

Adult↗
PubMed1992

Melatonin suppression in human subjects by bright and dim light in antarctica: time and season-dependent effects.

Full-spectrum light, of sufficiently high intensity, will suppress the secretion of melatonin at night in humans. Individual sensitivity to such suppression is variable, and the factors determining such sensitivity are largely unknown. By analogy with animal work previous short or long-term exposure to different light intensities may be an important determinant. We exploited the Antarctic environment to investigate these possibilities. Groups of healthy men, living on the British Antarctic Survey Base at Halley (75 degrees South) were exposed to dim (range 290-310 lux) and bright (range 2100-2300 lux) light either from 01.00-02.00 h or 05.00-0.600 h, both in winter and in summer. Plasma melatonin concentrations were determined by radioimmunoassay in serial blood samples taken before, during and after light treatment, and in control (darkness) conditions. Light suppression of melatonin was more effective in the latter part of the night in winter and this was particularly well-differentiated for dim light.

Adult↗
PubMed1992

Top down, bottom up.

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Diagnosis-Related Groups↗
PubMed1992

Seminoma of the testis: long-term beneficial and deleterious results of radiation.

PURPOSE: The followup of 387 patients in a USA national survey of seminoma treated with radiation in 1973 and 1974 has been extended beyond 15 years to assess the long-term benefits and problems resulting from treatment. RESULTS: Survival at 15 years is 83% for Stage I, 68% for Stage II; freedom from recurrence at 15 years is 93% for Stage I, 96% for Stage II; NED survival at 15 years is 80% for Stage I, 68% for Stage II; cause specific freedom from cancer death is 98% for Stage I and 97% for Stage II at 15 years. Second malignancy rates were 8% at 15 years, and observed in 14 patients versus 4.2 expected (p < .001). Deaths due to these second cancers were also increased with seven observed versus two expected (p < .01). Non-cancer intercurrent disease death occurred in 23 patients versus 7.5 expected (p < .01). The most frequent cause was cardiac death which appeared in 10 patients versus 4.4 expected (p < .05) and 8 of the 10 patients received mediastinal radiation. Two additional patients died of pulmonary fibrosis after mediastinal radiation. Mediastinal radiation correlated with all intercurrent disease and cardio-pulmonary deaths (p < .05), but not with second malignancies. With the exception of one, all patients experiencing cardiac death after mediastinal irradiation were 40 years or older at the time of treatment, with a range of 32-58 years and a mean interval to death of 9.8 years. CONCLUSIONS: Recommendations for the future management of seminoma include: reducing the irradiated volume in the treatment of Stage I patients, completely eliminating mediastinal radiation in the treatment of patients with Stage IIA seminoma and treating patients with Stage IIB seminoma with chemotherapy. Radiation dose should not exceed 30 Gy for Stage I or 35 Gy for Stage IIA.

Adolescent↗
PubMed1992

Transverse uterine incision closure: one versus two layers.

OBJECTIVE: Closure of a low transverse cesarean incision with one layer of suture results in less operating time, better hemostasis, and less infectious morbidity than a two-layer closure. STUDY DESIGN: At our institution 906 women were randomized to closure of a low transverse cesarean incision with either one continuous layer of a locking No. 1 chromic suture and a CTX needle (n = 457) or two continuous layers of No. 1 chromic suture with the first layer locked (n = 449). The Student t test, chi 2 test of proportion, and Wilcoxon rank sum test were used to compare groups of patients. RESULTS: A one-layer closure required less operative time, 43.8 versus 47.5 minutes (p = 0.0003). Fewer additional uterine hemostatic sutures were required in 369 women in whom either the one- (n = 179) or the two-layer (n = 190) closure did not achieve hemostasis (p = 0.046). Endometritis was similar in both groups, 83 (22%) in the one-layer group versus 65 (18%) in the two-layer group (p = 0.17). In no outcome assessment was the two-layer closure superior to the one-layer closure. CONCLUSION: We recommend a one-layer closure when its use is anatomically feasible.

Adult↗
PubMed1992

Midtrimester pregnancy termination: a randomized trial of prostaglandin E2 versus concentrated oxytocin.

OBJECTIVES: The purpose of this study was to determine whether a concentrated oxytocin infusion can reliably effect uterine evacuation in the midtrimester and whether such an infusion is associated with fewer side effects than prostaglandin E2 vaginal suppositories. STUDY DESIGN: Patients received either prostaglandin E2 (n = 42) or oxytocin (n = 45) for indicated midtrimester abortions in a prospective, randomized trial. Treatment consisted of either prostaglandin E2 vaginal suppositories (one every 4 hours) or infusions of an escalating concentration of oxytocin (one every 4 hours). Unless delivery had occurred or was imminent after 24 hours, the agent was considered to have failed, and patients were crossed to the alternative method. RESULTS: Delivery indications were similar between the two groups. There were 6 (14%) first-agent failures with prostaglandin E2 and 9 (20%) with oxytocin (p = 0.48). Considering the failures and subsequent crossovers, 103 patient trial regimens were completed. Fever, nausea, vomiting, and diarrhea were more frequent with prostaglandin E2 (p < 0.005). CONCLUSIONS: Concentrated oxytocin is a satisfactory alternative to prostaglandin E2 for midtrimester abortion.

Abortifacient Agents↗
PubMed1992

Anesthesia for selective dorsal rhizotomy in children.

Anesthetic records for the first 71 children who underwent selective dorsal rhizotomy (SDR) at our hospital were reviewed. Anesthesia during SDR must preserve muscle contraction in response to direct electrical stimulation of the dorsal nerve rootlets. In our experience, halothane, isoflurane, and narcotics do not interfere with electrophysiologic monitoring, even though relatively large doses are required during SDR. Propofol proved to be unacceptable as an anesthetic because of severe muscle spasms during electrical stimulation of the nerve rootlets. The body temperature rises predictably during the stimulation phase of SDR and active warming measures should be avoided.

Journal Article↗
PubMed1992

Lithium treatment: a comparison of once- and twice-daily dosing.

The effects of once- and twice-daily dosing with lithium carbonate were compared in a non-blind, cross-over study on 20 consecutive patients with mood disorders. Mental status, side effects and target organ function were examined after a minimum of a 1-month treatment with each regimen. Eighteen patients completed the study and 2 withdrew because of side effects. There were no significant differences between the 2 groups on the Hamilton Rating Scale for Depression, the Bech-Rafaelsen Mania Scale, the UKU Side Effects Scale or in serum lithium, electrocardiogram and urine volumes. Most blood tests showed no significant difference between the 2 treatment schedules except for white blood cells, ionized calcium and phosphate concentration. The once-daily regimen was associated with a higher white cell count, increased serum phosphate and elevated serum ionized calcium. We conclude that patients are able to tolerate once-daily dosing with lithium carbonate as well as twice-daily dosing.

Adolescent↗