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Biomedical subjects

J Smith

Publications and source records attributed to J Smith.

At least 595 records · Page 33Linked to original sources
PubMed1995

In vivo and in vitro pressor effects of erythropoietin in rats.

Hypertension (HTN) is a common complication of recombinant erythropoietin (EPO) therapy, but the mechanism of the EPO-associated HTN is uncertain. In the present study we examined the effects of EPO and the vehicle alone on rat caudal artery contractile response and basal and thrombin-stimulated platelet cytosolic Ca2+ concentration ([Ca2+]i) in vitro and on blood pressure (BP) and heart rate in vivo. At high concentrations (200 U/ml) EPO caused a small but consistent contraction in the caudal artery rings (P < 0.01) without affecting the response to either angiotensin II (ANG II) or the alpha 1-agonist methoxamine. Incubation with EPO significantly increased basal platelet [Ca2+]i (P < 0.01) and augmented the thrombin-induced rise of [Ca2+]i in Ca(2+)-free medium (P < 0.05). Long-term EPO administration led to a significant elevation of BP within 2 wk regardless of whether the hematocrit was allowed to rise or was kept constant by dietary iron deficiency. In contrast, single intravenous administration of high-dose EPO (400 and 5,000 U/kg), estimated to yield plasma concentrations comparable with those employed in vitro, failed to either alter BP or modify the BP response to ANG II during a 60-min observation period. This was associated with a significant rise in plasma guanosine 3',5'-cyclic monophosphate but no discernible change in plasma atrial natriuretic peptide, suggesting enhanced nitric oxide (NO) release. Thus, at high concentrations, EPO appears to possess a fast-acting pressor effect in vitro but not in vivo. The observed discrepancy may be due to enhanced NO release with EPO administration in vivo. However, HTN does occur with repeated EPO administration in a time-dependent and hematocrit-independent manner. This suggest that expression of the hypertensive effect of EPO in vivo involves a gradual conditioning process.

Animals↗
PubMed1995

Activity of costal and crural diaphragm during progressive hypoxia or hypercapnia.

Because costal and crural diaphragm segments have different functional characteristics, ventilatory stimulation with hypoxia or hypercapnia may elicit differential segmental function. We report measurements of diaphragm segmental length, shortening, and electromyogram (EMG) activity from 11 canines that were chronically implanted with sonomicrometry transducers and EMG electrodes and then studied a mean of 18 days postimplantation while awake and breathing spontaneously during CO2 rebreathing and progressive isocapnic hypoxia. Ventilatory responses to hypercapnia and progressive hypoxia were moderate at 1.13 +/- 0.31 (SD) 1. min-1. mm-1 arterial Pco2 and -0.98 +/- 0.51 l. min-1.%arterial O2 saturation-1. When tidal values for breathing pattern and segmental function were compared at matching tidal volumes that correspond to mean CO2 of 49.4 arterial Pco2 and 77% arterial O2 saturation, there was no significant difference in resting length, tidal shortening, or tidal EMG of costal or crural segments. Intrabreath profiles of flow, shortening, and EMG activity at matched tidal volumes showed that 1) inspiratory flow during hypoxia was significantly greater during early inspiration, 2) crural EMG activity preceded costal EMG activity in early inspiration during both hypercapnia and hypoxia, 3) both segments showed increased postinspiratory inspiratory activity with stimulated ventilation, and 4) postinspiratory shortening and EMG were greatest for the crural segment during hypoxia. These results suggest that costal and crural diaphragm segments exhibit differential function during chemical stimulation, especially during postinspiration.

Algorithms↗
PubMed1995

Maximum and medium security: the interface.

This paper examines transfer delays for patients moving between medium and maximum security hospitals. Delays appear to be getting shorter and Special Hospitals in particular respond very quickly to requests for admission. Recommendations are made for further improvements in transfer procedures. The authors argue that with closer working relationships between clinicians in Special Hospitals and Regional Secure Units, and the new proactive approach to transfers, the system will become increasingly flexible and responsive. Consequent improvements in the quality of care in Special Hospitals are anticipated, making the arguments for closing them, in turn, less convincing.

Adult↗
PubMed1995

Balance deficits accompanying renal disease are related to diabetic status.

Balance deficits were examined in a sample of kidney-transplant candidates (60 men, 30 women) using an ordinal scale. Normal performance was defined as unilateral standing for more than 20 sec. Only 52% of the subjects balanced normally. A significant relationship between balance performance and diabetic status was found. Diabetic patients were more likely to show impaired balance. This finding is consistent with prior reports of gait and strength deficits among kidney-transplant candidates.

Adult↗
PubMed1995

Update on women's footwear.

Shoes have been implicated as being responsible for the majority of foot deformities and problems that physicians encounter in women. In our original study of 356 women, the majority of women studied wore shoes that were too small for their feet, had foot pain and deformity, and had increased in shoe size since the age of 20. The women without foot pain or deformities also wore shoes that were smaller than their feet but to a lesser degree. In the present study, data on 255 of the original 356 women are evaluated. Tracings were made of the standing foot and the shoe. Measurements were made of forefoot and the heel width. An index of forefoot width to heel width was developed. The indices do not vary much among women. Based on linear measurements, as forefoot width increases, so does heel width. As foot length increases, forefoot width increases to a greater extent than heel width.

Adult↗
PubMed1995

Presurgical localization of functional cortex using magnetic source imaging.

The boundaries of somatosensory cortex were localized noninvasively by means of a large-array biomagnetometer in six patients with mass lesions in or near eloquent cortex. The results were used by neurosurgeons and neurologists in preoperative planning and for reference in the operating room. The magnetic source imaging (MSI) localizations from somatosensory evoked potentials were used to predict the pattern of phase reversals measurable intraoperatively on the cortical surface, providing a quantitative comparison between the two measures. The magnetic localizations were found to be predictive in all six cases, with the two sets of localizations falling within an 8-mm distance on average. Somatosensory localizations using MSI offer accuracy in localizing somatosensory cortex stereotactically and in depicting its relationship to lesions. Such data are valuable preoperatively in assessing the risks associated with a proposed surgical procedure and for optimizing subsequent minimum-risk surgical strategy.

Adult↗
PubMed1995

Phantom limb pain and chemotherapy in pediatric amputees.

OBJECTIVE: To determine the frequency of phantom limb pain in pediatric patients with cancer-related amputations and the relationship between phantom limb pain and chemotherapy (CHRx). DESIGN: We retrospectively reviewed the medical records of all pediatric patients who underwent major limb amputations between 5 and 17 years of age during the period from Oct. 1, 1983, to Oct. 1, 1993, and were treated at the Mayo Clinic. MATERIAL AND METHODS: One investigator reviewed 293 medical records and selected cases on the basis of specific inclusion and exclusion criteria. The study group consisted of 75 patients (67 with cancer-related and 8 with trauma-associated amputations). All reports of phantom limb pain and its temporal relationship to administration of CHRx were recorded. Data were analyzed by use of descriptive statistics. RESULTS: Phantom limb pain was reported in 48% of patients with cancer-related amputations in comparison with 12% of patients with trauma-associated amputations. Among patients with cancer, phantom limb pain was experienced by 74% who were exposed to CHRx before or at the time of amputation, 44% who received CHRx after amputation, and 12% who never received CHRx. Patients with trauma-related amputations and those who did not receive CHRx reported phantom limb pain at similar intervals after amputation (a mean of 6 days). In comparison, 76% of patients with cancer and a history of exposure to CHRx reported phantom limb pain within 72 hours after amputation. Three of four patients who first received CHRx after amputation reported phantom limb pain on the day CHRx was begun (a mean of 12.3 days after amputation). CONCLUSION: Our observations suggest that (1) phantom limb pain occurs more often in pediatric amputees with cancer than in those with trauma and (2) the hypothesis that CHRx may be a risk factor in the development of phantom limb pain in pediatric amputees should be investigated further.

Adolescent↗
PubMed1995

Characterization of clone 13, a naturally attenuated avirulent isolate of Rift Valley fever virus, which is altered in the small segment.

The 74HB59 strain of Rift Valley fever (RVF) virus, isolated from a human case in the Central African Republic, was shown to be composed of a heterogeneous population of viruses when plaque-purified clones were analyzed for their reactivity with monoclonal antibodies (MAbs) directed against the nucleocapsid (N) protein or the nonstructural (NSs) protein. One of these clones, C13, was of particular interest in that it proved to be avirulent in mice and hamsters, and highly immunogenic. Although C13 showed normal reactivity with a large panel of MAbs directed at the glycoproteins, it failed to react with specific MAbs or polyclonal antibodies directed at the NSs protein and with a specific MAb recognizing the N protein of the Egyptian strains. Consequently, the small RNA segment, which encodes the N and NSs proteins in an ambisense strategy, was sequenced and compared with the existing sequence of the attenuated MP-12 RVF virus strain. We found that the NSs gene contained, in addition to two conservative coding changes, a large internal deletion of 549 nucleotides that removes 69% of the open reading frame but conserves in-frame the N and C termini of the predicted translation product. In addition, the sequence revealed that the N protein of C13 contained a single amino acid change. Clone C13 replicated normally in certain cell types in vitro and in Culex pipiens mosquitoes after intrathoracic inoculation, but established abortive infections in MRC-5 human fibroblasts.

Animals↗
PubMed1995

Programmed cell death in dystrophic (mdx) muscle is inhibited by IGF-II.

The pathology of Duchenne Muscular Dystrophy (DMD) is characterised by unstable muscle fibres and by increased cell turnover due to the absence of functional dystrophin protein. We have used skeletal muscle, primary muscle stem cell cultures (Smith and Schofield, 1994; Smith et al., paper submitted) and clonal cell lines of the mouse DMD model (mdx) and its congenic control (C57BI) to demonstrate that programmed cell death (PCD) and apoptotic morphology is increased in dystrophic (mdx) muscle and in cultured muscle cells. We also show that the peptide growth factor (IGF-II), which is thought to play a role in mammalian myogenesis, reduces PCD in mammalian skeletal muscle myoblasts both in vivo and in vitro. This is the first time that apoptosis or PCD have been demonstrated in normal mammalian skeletal muscle. We discuss the potential of this system in determining the role of PCD in mammalian myogenesis and skeletal muscle maturation, its significance in dystrophic muscle, and suggest a novel therapeutic route whereby the pathology of DMD may be alleviated using the survival properties of IGF-II.

Journal Article↗
PubMed1995

Portal pyelophlebitis identified by CT scan in a patient with ischemic bowel.

A 65-year-old male was found to have hepatic portal venous gas (HPVG) by computed tomogram secondary to ischemic bowel. Despite aggressive surgical and antibiotic treatment, the patient died within 12 hours. Portal pyelophlebitis, when identified by air in the portal venous system, is a grave indicator of ischemic bowel with a very high mortality rate, except in patients with inflammatory bowel disease.

Aged↗
PubMed1995

Retinopathy of prematurity in a south Australian neonatal intensive care unit.

PURPOSE: To establish the incidence and severity of retinopathy of prematurity (ROP) in an Australian population of premature infants, and define risk factors for this population. METHODS: A survey of neonates born weighing less than 1501 g and/or with gestational age below 33 weeks, was undertaken at a neonatal intensive care unit in South Australia. RESULTS: ROP was diagnosed in 16.0% of the 94 neonates who were screened until retinal vascularisation was complete. Threshold disease occurred in 4.2%. Logistic regression identified three significant risk factors for the development of ROP: days of mechanical ventilation, multiple birth and female sex. CONCLUSIONS: The incidence of ROP was relatively low when compared with figures recently published for two large populations studied in the United States and England. This difference was due to a lower incidence of mild forms of the disease. Days of mechanical ventilation, multiple birth and female sex were independently predictive of the occurrence of ROP. As small numbers of infants with ROP are managed at individual Australian centres each year, a national ROP register is recommended to facilitate the study of the disease in this country.

Female↗