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Biomedical subjects

C L Stewart

Publications and source records attributed to C L Stewart.

85 records · Page 5Linked to original sources
PubMed1985

Transitional nephrology.

During growth from fetal life to early childhood, renal function and parameters used to assess renal function undergo developmental changes. This article provides a brief review of these maturational changes and how they affect the evaluation and management of young patients with diseases affecting the genitourinary system. Included is a discussion of renal blood flow, glomerular filtration, sodium and water balance, clinical assessment of renal function, and age-related effects of nephrotoxins.

Adult↗
PubMed1983

The effects of sodium nitroprusside on the hemodynamics of burn shock: results of an experimental sheep model.

A low cardiac output state is observed following major thermal injury in both experimental and clinical settings. The major determinants of cardiac output are preload, afterload, and the contractile state of the myocardium. The effects of afterload reduction in acute thermal injury are the focus of this experiment. Pure-bred young nonpregnant ewes of the Suffolk strain were utilized to determine the effect of afterload reduction on the cardiac index in experimental burn shock. Four groups of animals were studied; Group 1: unburned control (n = 5); Group 2: unburned-treated with sodium nitroprusside (n = 5); Group 3: 40% burned (n = 9); and Group 4: 40% burned-treated with sodium nitroprusside (n = 9). Pulmonary arterial, intravenous, and bladder catheters were placed in all animals. Following anesthesia with or without a burn, the animals were monitored for 24 hours. Measured and calculated parameters included cardiac index, pulmonary arterial and arterial pressures, pulmonary and systemic vascular resistance indices, shunt, arterial and mixed venous blood gases and pH, and hematocrit. When burned animals with and without nitroprusside were compared, significantly higher cardiac indices, expressed as per cent of baseline, were noted for the sodium nitroprusside-treated group at 8 and 12 hours postburn. The burned-treated animals' cardiac index was not significantly different from control animals' at 8 hours postburn. However, the burned-untreated animals had significantly depressed cardiac indices until 18 hours postburn.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Osteoarthritis of the TMJ in teenaged females: report of cases.

From the cases reported by Ogus and those presented here, it appears degenerative joint disease of the TMJ in young individuals is not a rare finding. The incidence of DJD of the temporomandibular joint has been reported to be 8% to 16%. In a review of 346 patients who were referred for jaw disorders, 23 patients were 19 years old or younger. Six patients (or 26%) had a diagnosis of osteoarthritis of the TMJ confirmed with charts, reviewed retrospectively, were considered as suggestive of degenerative joint disease. It has been reported that the symptoms of DJD continue for one to three years. The majority of patients have acute symptoms that usually last about nine months but gradually subside after nine months. It is important to rule out degenerative disease of the TMJ before beginning radical or irreversible dental procedures. Conservative management of these patients includes analgesics, antiarthritic drugs, muscle relaxants, antiinflammatory agents, the construction of hard or soft bite splints, exercise, warm moist heat applications, minor equilibration if indicated, and physical therapy. Injections of steroids into the joint are not recommended and anti-arthritic drugs should be used with caution because the safe usage of some of these drugs has not been demonstrated in children. Patients who still experience pain after one to three years, or patients who are refractory to conservative therapy, may be candidates for surgical treatment. Age should not be a deterrent to surgery or other treatment modality for treatment of severe degenerative joint disease that does not respond to conservative treatment and is intolerable to the patient.

Adolescent↗
PubMed1983

Experimental fixation of femoral osteotomies by cerclage with nylon straps.

Following the successful experience of Partridge in the fixation of human femoral fractures by nylon-strap cerclage, this research in 23 mature dogs was performed to compare nylon-strap with wire-loop cerclage for healing periods of up to 12 weeks. Supplemented by intramedullary fixation with Steinmann pins, long oblique femoral osteotomies were fixed in one femur of each dog by nylon straps and in the other femur by wire loops, at separate operations. The nylon straps were all secured at the same tension by a special "gun." The wire loops were all secured at the same tension by the Rhinelander tightener-twister. Half of the nylon straps had "bumps" along the inner surface, which were added by Partridge in an effort to circumvent the microvascular disturbance reported with Parham bands. On examination by microangiography and correlated histology, all of the osteotomies, regardless of the type of fixation, showed good progress toward osseous union. After fixation by wire cerclage no loss of position or disturbance of blood supply was noted. After fixation by nylon straps slight (clinically insignificant) longitudinal displacement, attributed to slight lengthening of the straps, with consequent loosening was noted in all cases. This loosening was considered advantageous because it appeared to be responsible for the unexpected lack of impairment of the vascularization of the underlying cortical bone by any of the straps. The bumps on the undersurface of some of the straps were, thus, of no vascular advantage, and their presence made accurate fixation of the ostectomy fragments more difficult on the small bones. These studies support the value of fixation by plain nylon straps and show their advantage over straps with bumps for fixation of long oblique single osteotomies of bones the size of the canine femur.

Animals↗
PubMed1982

De novo methylation and expression of retroviral genomes during mouse embryogenesis.

Retrovirus genomes introduced into mouse zygotes by microinjection of cloned DNA, or into morula stage pre-implantation mouse embryos by infection with Moloney murine leukaemia virus (M-MuLV), became de novo methylated and were blocked in expression. No restriction of virus expression and no de novo methylation were observed when post-implantation mouse embryos were infected with virus. Efficient de novo methylation activity may be an important characteristic of gene regulation in early mouse embryos.

Animals↗
PubMed1982

De novo methylation, expression, and infectivity of retroviral genomes introduced into embryonal carcinoma cells.

We have investigated the block to expression of Moloney murine leukemia virus in murine embryonal carcinoma (EC) cells. Infected EC cells were found to contain up to 100 integrated proviral genomes. However, expression of virus as measured by XC plaque and virus-specific RNA synthesis did not occur at significant levels, in contrast to productively infected differentiated cells. Analysis of the DNA in the infected EC cells revealed that the proviral genomes were highly methylated, as shown by their resistance to cleavage by Sma I. Integrated proviral genomes in infected differentiated cells were readily cut by Sma I and thus were not methylated at these sites. Transfection of DNA from infected EC cells to cells permissive for virus expression failed to induce virus expression. The proviral genomes, however, were potentially infectious because they induced XC plaques when the recipient cells for transfection were treated with 5-azacytidine. This drug is believed to interfere with DNA methylation. We conclude that expression of proviral genomes introduced into EC cells is suppressed and that this inactivation can be correlated with the de novo methylation of the viral DNA. De novo methylation activity thus may be a characteristic of early embryonic cells.

Animals↗
PubMed1982

Growth of tissue into a porous, low modulus coating on intramedullary nails: an experimental study.

The ingrowth of tissue into a coating of inert, highly porous, low-modulus composite of polytetrafluorethylene polymer and pyrolytic graphite on four-fluted intramedullary nails was used for stabilization of middiaphyseal femoral osteotomies and examined by microangiography. The observations were correlated with information obtained by histologic, microradiographic and tetracycline fluorescence technology. There was rapid healing of the osteotomy. The coating was invaded throughout by blood vessels and fibrous tissue. Invasion by bone was negligible. The composite thus appeared to retain its initial flexibility when implanted into the femoral intramedullary cavity. The force to distract both coated and uncoated nails was measured on intact femora. The unit retention strength increased to an average of 6.3 kg/cm2 up to 24 weeks, which is consistent with reported values. The composite would thus appear to have potential use as a coating for endoprostheses to produce enduring physiologic fixation.

Animals↗
PubMed1982

Formation of viable chimaeras by aggregation between teratocarcinomas and preimplantation mouse embryos.

The formation of viable teratocarcinoma-adult chimaeras, by aggregation rather than by microinjection, is described. Aggregation chimaeras were produced using two pluripotential EC cell lines, PSA-1/NG-2 and PSA-4/TG12. The frequency and distribution of chimaerism were assessed, for the EC cells, in conceptuses recovered from in utero and in adults. In utero 37% of the morphologically normal conceptuses formed from PSA-1/NG-2 aggregations and 73% of the morphologically normal conceptuses produced from PSA-4/TG12 aggregations were found to be chimaeric. However, the frequency of chimaeric adults formed from both cell lines was lower. The reason for the discrepancy appeared to be that in the chimaeric conceptuses, the predominant tissues colonized by the EC cells were the extraembryonic membranes.

Animals↗
PubMed1979

Experimental reaming of the proximal femur and acrylic cement implantation: vascular and histologic effects.

The technique of microangiography and correlated histology was used, in experiments on the proximal femora of mature mongrel dogs, to study the effects of simple medullary reaming and of reaming followed by insertion of acrylic cement. The hip joints were not disturbed. A segment of Steinmann pin, representing the stem of a hip prosthesis, was inserted into the cement as it was polymerizing. The most significant results, after reaming alone, were devascularization and apparent necrosis of large areas of the cortex of the subtrochanteric femoral diaphysis. Full recovery was observed in 6 months. However, when acrylic cement was introduced following the reaming, extensive necrosis of the inner layers of the diaphyseal cortex was still present after a year, when the observations were terminated. The presence of necrosis of bone was judged by the lack of visible osteocytes in the lacunae. After the devascularization caused by filling the diaphyseal medulla with acrylic cement, the apparently necrotic cortex was revitalized without osteoclasia. That is in contrast to the results in another study in which osteoclasia and osteoneogenesis were required to restore cortex with empty cell lacunae. This raises the question of dormant osteonecrosis in contrast to total osteonecrosis. These studies show, in thin histologic preparations, acrylic bone cement in situ in the tissues. A fibrous membrane was found at the cement-bone interface in most areas. It was thicker in the diaphysis than in the metaphysis. The physiologic effects of acrylic cement implantation are considered to be likely factors in the loosening which is observed clinically when the femoral components of hip prostheses are under protracted stress.

Acrylic Resins↗
PubMedDate not supplied

Correlations between plasminogen activator inhibitor-1 and peritoneal transport in pediatric CCPD patients.

OBJECTIVE: Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of plasminogen activators and has been shown to be involved in the accumulation of extracellular matrix (ECM) in various tissues. Since peritoneal ECM is a resistance site for peritoneal transport, the production and release of PAI-1 in the peritoneum may affect the peritoneal transport of water and small solutes. DESIGN: The linear correlations between the dialysate PAI-1 levels and the variables of peritoneal transport during peritoneal equilibration tests (PET) were examined. SETTING: A tertiary university hospital. PATIENTS: Six stable pediatric patients (age 10.8 +/- 4 years) undergoing continuous cycler-assisted peritoneal dialysis were included. INTERVENTIONS: None. RESULTS: All data are mean +/- SD. There was a positive correlation between the infused volume and the net ultrafiltration (UF, 198 +/- 127 mL, r = 0.82, p < 0.05). The dialysate PAI-1 levels increased during the dwell time (2.44 +/- 2.23 ng/mL or 2.46 +/- 1.72 micrograms at 4 hours vs 0.04 +/- 0.1 ng/mL or 0.04 +/- 0.09 micrograms at 0 hour, p < 0.05). The saturation indices (dialysate/plasma ratio) of PAI-1 and albumin at 4 hours were 1.05 +/- 1.21 and 0.028 +/- 0.004, respectively. The changes from 0 hour dwell to 4 hour dwell in the dialysate PAI-1 concentration (PAI4-0, 2.4 +/- 2.2 ng/mL) or amount corrected to body surface area (APAI4-0/BSA, 2.61 +/- 2.11 micrograms/m2) negatively correlated with UF or UF/body surface area and positively correlated with the number of episodes of peritonitis. There was no correlation between PAI4-0,APAI4-0/BSA, or plasma PAI-1 concentration and the mass transfer coefficient and clearance of either urea or creatinine. CONCLUSIONS: The elevated PAI-1 level during the PET was likely from the local production and release of PAI-1. It had an inverse relationship with the amount of ultrafiltration. Repeated inflammation of the peritoneum was associated with an increased production and release of PAI-1 into the peritoneum.

Adolescent↗