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Biomedical subjects

R Lyon

Publications and source records attributed to R Lyon.

At least 19 recordsLinked to original sources
PubMed2006

Changes of three-dimensional back contour following posterior fusion for idiopathic scoliosis.

Twenty-nine patients received both pre and post operative Quantec evaluation (Raster stereophotograph) and spinal radiography. Mean age at surgery was 13.9 years and mean age at follow-up was 15.9 year old. Patients have been followed at least 6 months post-surgically, ranging from 6 months to 5 years. The study found that except for an improvement of Cobb angles (from 49.64 degrees to 24.81 degrees in the thoracic; from 56.08 degrees to 20.08 degrees in the thoracolumbar), corrections of rib hump (from 16.88 to 11.40 vs. normal range 0 to 10.) and truncal asymmetry (from 36.97 to 21.92 vs. normal range 5 to 20) are critical factors in successful spinal surgery.

Adolescent↗
PubMed2002

Apoptosis in lymph node granulomas from white-tailed deer (Odocoileus virginianus) experimentally infected with Mycobacterium bovis.

Apoptosis is a morphologically and biochemically distinct mechanism of cell death seen in many physiological conditions as well as in various infectious diseases. To examine apoptosis in tuberculous white-tailed deer, 32 deer were each given an intra-tonsillar injection of 300 colony-forming units of Mycobacterium bovis. Medial retropharyngeal lymph nodes were collected at 15, 28, 42, 56, 89, 180, 262 and 328 days after inoculation. Microscopical sections of lymph nodes were labelled for apoptotic cells by the terminal deoxynucleotidyl transferase nick end labelling (TUNEL) method. TUNEL, and other morphological changes within developing granulomas, were analysed and quantified by computerized image analysis. TUNEL within granulomas was greatest 28 days after inoculation and had declined to negligible levels by 328 days. Granuloma enlargement was due primarily to an increase in size of the caseo-necrotic core of the granuloma and not to increased inflammatory cellular infiltrate. These findings suggested that cell death within M. bovis -induced granulomas in white-tailed deer was due mainly to mechanisms other than apoptosis.

Animals↗
PubMed2000

Three-dimensional rotations of the thoracic spine after distraction with and without rib resection: a kinematic evaluation of the apical vertebra in rabbits with induced scoliosis.

An experimental model of induced scoliosis in New Zealand rabbits was studied to evaluate the effects of rib resection on the apical vertebra during distraction for scoliosis surgery. After concave distraction, three-dimensional rotations of the apical vertebra were measured using a motion analysis system, which included three cameras and six reflective markers. Distraction with rib resection on the convexity produced minimal rotations in the coronal plane (0.77 degrees), sagittal plane (0.96 degrees), and transverse plane (0.61 degrees) compared with no rib resection. The distraction maneuver with rib resection has no significant effect on derotation of the apical vertebra in the coronal and transverse plane, but slightly greater forward rotation was apparent in the sagittal plane (p < 0.05). Resection of three convex ribs directly corrects the rib prominence and does not seem to improve derotation.

Animals↗
PubMed2000

Slimgraft: a percutaneous endovascular graft system.

PURPOSE: To describe an in vitro feasibility trial of a new percutaneous endograft delivery technique. METHODS AND RESULTS: A water flow model of 9-mm (inner diameter) transparent plastic tubing was used to test the feasibility of sequentially delivering the components of an endograft through a 7-F sheath for assembly in situ. The tubular endovascular graft was fabricated from a 10-mm x 68-mm Wallstent and 50-microm-thick Dacron graft. The graft material was formed into a tube, attached with a suture to a guidewire, and delivered into the plastic tubing. The Wallstent was then delivered through the tubular graft and deployed, affixing the graft to the plastic tube wall. In 4 trials, only 1 attempt was not successful. CONCLUSIONS: These concepts and techniques may have implications in the development of percutaneously deliverable endovascular grafts.

Blood Vessel Prosthesis↗
PubMed1998

The short-term economic implications of prosthetic selection in hemiarthroplasty of the hip.

This retrospective study assessed the economic impact of prosthetic selection in the treatment of displaced intracapsular fractures. The records of 28 patients were divided into two groups: 16 patients who received an Austin-Moore, nonmodular device and 12 patients (6 men and 6 women; mean age, 77 years) who received a modular, bipolar device. The bipolar group had significantly greater mean operative times, total charges for the device, and total charges for supplies. Surgeons treating hip fractures should consider implant cost, functional outcome, and patient demands when selecting a prosthesis for hemiarthroplasty care.

Aged↗
PubMed1996

Surgical management of brachioaxillary-subclavian vein occlusion.

OBJECTIVE: The possibility of using RING PTFE graft as venous bypass to preserve arteriovenous graft function and reduce upper extremity swelling. METHODS: Twenty-two patients with stenosis/occlusion of the brachial-axillary-subclavian vein segment in haemodialysis patients (n = 19) and patients with penetration injury (n = 3) who were not candidates for balloon angioplasty were treated with ring PTFE venous bypass in renal patients and jugular to axillary vein transposition for trauma patients and followed for 10-87 months (mean 31) using venography, Doppler analysis and Duplex scanning. RESULTS: There was no death or neurologic deficit resulting from the venous bypass. Resolution of swelling occurred in 8-48 h. 19/22 (86%) of the bypasses and 3/3 transpositions remained patent after a mean follow-up of 31 months (10-87) months. The attrition was due to AV graft occlusion (n = 2) and infection requiring graft removal (n = 1). CONCLUSIONS: Ring PTFE graft is an acceptable venous bypass for brachial-axillary-subclavian stenosis/occlusion to reduce arm swelling and preserve the function of AV grafts in patients with lesions not amendable with balloon angioplasty or thrombolytic therapy. Jugular-axillary transposition is inappropriate for renal patients.

Adult↗
PubMed1996

Changing patterns of infections in patients with AIDS: a study of 279 autopsies of prison inmates and nonincarcerated patients at a university hospital in eastern Texas, 1984-1993.

Reports on autopsies of 279 persons infected with human immunodeficiency virus (HIV) were reviewed retrospectively to determine changes in survival rates and infections and to identify differences between prison inmates and nonincarcerated patients. The 78 cases from 1984 through 1988 were compared with 201 from 1989 through 1993, on the basis of use of antiretroviral therapy and (after 1988) prophylaxis against Pneumocystis carinii pneumonia (PCP). Risk factors for HIV infection were homosexuality/bisexuality (30%), injection drug use (IDU; 22%), transfusion (5%), heterosexual contact (4%), and combinations of the above or unknown factors (38%); 95% of patients were males and 41% were state prison inmates in Texas. IDU was more common and homosexuality/ bisexuality was less common among inmates than among nonincarcerated patients. Mean survival time was 12 months in the first period studied and 23 months in the later period (P < .05). Cytomegalovirus infection was the most common type in both periods. The number of cases of PCP declined and the number of cases of bacterial infections increased significantly in the later period. Tuberculosis was significantly more common in inmates than in nonincarcerated patients. Tuberculosis and disseminated histoplasmosis (noted at autopsy) and deaths due to disseminated Mycobacterium avium complex and histoplasmosis were significantly more common among injection drug users than among homosexuals/bisexuals. Invasive candidiasis was more common in homosexuals/ bisexuals and in those who survived > 3 years. Antiretroviral therapy, prophylaxis for PCP, and risk factors for HIV infection appear to influence the mortality rate and prevalence of certain infections found at autopsy.

AIDS-Related Opportunistic Infections↗
PubMed1995

Comparison of the BacT/Alert and Isolator blood culture systems for recovery of fungi.

The recovery of fungi by the BacT/Alert (Organon Teknika Corporation, Durham, NC) and Isolator (Wampole Laboratories, Cranbury, NJ) blood culture systems was compared by retrospective review of 2,174 matched cultures from 715 patients collected from April 1, 1993 to February 28, 1994. One hundred five isolates were recovered from 44 patients by one or both culture systems. All patients were fungemic with one organism. In all cases of fungemia, collection times for both culture systems were within 6 hours of each other. Of 22 isolates of Candida spp, the Isolator recovered all 22 isolates whereas the BacT/Alert recovered 15 (68.2%) (P < .05). The Isolator detected more isolates of Cryptococcus neoformans (10 of 11) than did the BacT/Alert (7 of 11). All 64 isolates of Histoplasma capsulatum (P < .0001) and 6 isolates of Malassezia furfur (P < .05) were recovered by the Isolator system only. For 20 isolates recovered by both systems for which time to recovery could be determined, the mean time to detection of growth was 2.9 days (range 0-9 days) for the Isolator and 2.1 days (range 0-5 days) for the BacT/Alert. In conclusion, the Isolator blood culture system is superior to BacT/Alert for the detection of fungemia, including fungemias caused by Candida spp, H capsulatum, and M furfur.

Blood↗
PubMed1994

Administration of an anti-IgE antibody inhibits CD23 expression and IgE production in vivo.

High IgE responder BDF1 mice were immunized intraperitoneally (i.p.) with dinitrophenol4 (DNP4)-ovalbumin (OVA) in alum concomitant with intravenous (i.v.) administration of an anti-IgE monoclonal antibody (mAb). IgE levels were undetectable in mice treated with the anti-IgE antibody, whereas mice treated with isotype-matched irrelevant mAb had IgE levels comparable to that of untreated, immunized mice. Subsequent antigen challenges with DNP4-OVA, either at weekly or monthly intervals, failed to evoke an IgE response for greater than 2 months in mice treated with anti-IgE during the primary sensitization, even though the terminal half-life of the anti-IgE antibody was 7 days. This inhibition was specific for DNP4-OVA since the DNP4-OVA-suppressed mice were able to respond to keyhole limpet haemocyanin (KLH). To investigate the effects of antibody treatment at the cellular level, passive transfer experiments were performed. The primary DNP-specific IgE response of adoptive transfer recipient mice was the same whether the donor cells were from mice treated with IgG or anti-IgE. Transfer of enriched T- or B-cell populations indicated that T-cell help was not compromised by administration of the anti-IgE mAb. However, splenocytes from the anti-IgE-treated mice failed to synthesize IgE in vitro, and flow cytometric analysis of B cells from anti-IgE-treated mice showed a dose-dependent decrease in CD23+ cells following antibody treatment, which correlated with decreased serum IgE levels. Taken together, the results of these studies suggest that anti-IgE treatment suppresses IgE responses via effects on B cells rather than T cells, possibly through effects on CD23-dependent pathways.

Animals↗
PubMed1993

Nutrition interventions for intensive therapy in the Diabetes Control and Complications Trial. The DCCT Research Group.

As part of an intensive treatment regimen that had as its goal achieving and maintaining blood glucose levels in the normal range in individuals with insulin-dependent diabetes mellitus, dietitians in the Diabetes Control and Complications Trial implemented varying nutrition intervention strategies to counsel patients to attain normoglycemia. Dietary management encompassed recommendations on altering insulin dosages for varying food intake. Nutrition intervention was tailored to best meet a participant's life-style, motivation, ability to grasp information, diet history, and specific intensive insulin therapy. Dietitians were integral participants in the team management of individuals in the intensive treatment group. Selected nutrition interventions--Healthy Food Choices, exchange systems, carbohydrate counting, and total available glucose--and behavior management approaches were coupled with intensive insulin therapy. Case presentations illustrate each nutrition intervention in the attainment of normoglycemia.

Adult↗
PubMed1993

Pharmacokinetic profile of recombinant human (rh) inhibin A and activin A in the immature rat. I. Serum profile of rh-inhibin A and rh-activin A in the immature female rat.

The serum pharmacokinetics of recombinant human inhibin A (rh-inhibin A) and rh-activin A were examined in immature female Sprague Dawley-derived rats after iv and sc injection of the drugs. After iv administration of rh-inhibin A (120 micrograms/kg), the serum concentrations were described by a biexponential equation. The weight-normalized clearance was 21.3 ml/min.kg, and the initial (t1/2 alpha) and terminal (t1/2 beta) half-lives were 2.9 min and 37.9 min, respectively. Subcutaneous administration of 120 micrograms/kg rh-inhibin A resulted in a peak serum concentration of 10.6 ng/ml at 30.8 min after injection. Approximately 24% of the sc administered material was absorbed. Serum concentrations of rh-activin A also declined biexponentially after iv injection of the drug (120 micrograms/kg). The clearance of rh-activin A was 5.1 ml/min.kg, the t1/2 alpha was 6.1 min, and the t1/2 beta was 46.3 min. The peak serum concentration of rh-activin A (104.7 ng/ml) was achieved 24.7 min after sc delivery of the drug. The bioavailability of the sc dose was 38%. Iodinated rh-inhibin A and rh-activin A were used to examine the serum forms and metabolites of the drugs. [125I]rh-inhibin A and [125I]rh-activin A associated with two serum-binding proteins. Within 2 min of iv injection, the labeled hormones bound follistatin and alpha-2-macroglobulin. Even though rh-inhibin A and rh-activin A are structurally similar and appear to bind to the same serum proteins, their disposition in the immature rat differ.

Activins↗
PubMed1993

Pharmacokinetic profile of recombinant human (rh) inhibin A and activin A in the immature rat. II. Tissue distribution of [125I]rh-inhibin A and [125I]rh-activin A in immature female and male rats.

The tissue distribution of recombinant human inhibin A (rh-inhibin A) and rh-activin A was determined in immature female Sprague Dawley-derived rats after iv administration of radiolabeled proteins. [125I]rh-Inhibin A and [125I]rh-activin A diverge in their distribution to tissues of the immature female rat as examined histologically (whole body autoradiography and thin section analysis) and by computing the percent dose and tissue to blood ratios for individual tissues. [125I]rh-inhibin A accumulated in the spleen, adrenal, bone marrow, and ovary after iv injection. Iodinated rh-inhibin A was also found in the anterior and posterior pituitary. [125I]rh-activin A was found in the ovary and pituitary after iv injection. Little specific binding was found in the spleen or adrenal. The bone marrow accumulated some [125I]rh-activin A which was competed by rh-activin A. The primary route of excretion for radioactivity was the kidney, with the label appearing in the bladder by 10 min after iv injection. Not only do rh-inhibin A and rh-activin A have different pharmacokinetics, but fewer tissues accumulate radioactive rh-activin A than rh-inhibin A.

Activins↗
PubMed1993

Intensive conventional insulin therapy for type II diabetes. Metabolic effects during a 6-mo outpatient trial.

OBJECTIVE: To determine whether tight glycemic control can be obtained using intensive conventional split-dose insulin therapy in the outpatient management of type II diabetes without development of unacceptable side effects. RESEARCH DESIGN AND METHODS: Fourteen type II diabetic subjects were treated with an intensive program of conventional insulin (subcutaneous NPH and regular insulin before breakfast and supper) for 6 mo. Insulin dose adjustments were based on an algorithm built on frequent CPG measurements (4-6 times/day). Patients were monitored biweekly as outpatients and admitted 1 day/mo for metabolic evaluation. RESULTS: Glycemic control was achieved by 1 mo (mean plasma glucose fell from 17.5 +/- 0.9 to 7.7 +/- 0.7 mM, P < 0.001) and remained in this range thereafter. Hypoglycemic events at 1 mo were infrequent (mean +/- SE events per patient per month: 4.1 +/- 0.3) and mild in nature, and progressively decreased to 1.3 +/- 0.5 events/mo by 6 mo. After treatment, basal HGO fell 44% from 628 +/- 44 to 350 +/- 17 mumol.m-2.min-1 (P < 0.001), and maximal rates of glucose disposal measured by hyperinsulinemic euglycemic clamp (1800 pmol.m-2.min-1) improved from 1418 +2- 156 to 1657 +/- 128 mumol.m-2.min-1 (P < 0.05). The total dose of exogenous insulin required was 86 +/- 13 U at 1 mo and 100 +/- 24 U at 6 mo. During treatment, mean serum insulin levels increased from 308 +/- 80 to 510 +/- 102 pM (P < 0.05), while body weight increased from 93.5 +/- 5.8 to 102.2 +/- 6.8 kg (P < 0.001). Both pre- and posttreatment glucose disposal rates correlated with the total exogenous insulin dose required to achieve glycemic control (r = -0.75 and -0.78, both P < 0.005). Weight gain was inversely related to the pretreatment glucose disposal rate (r = -0.53, P < 0.05) and directly correlated with both mean day-long serum insulin level (r = 0.67, P < 0.01) and total exogenous insulin dose (r = 0.62, P < 0.02). CONCLUSIONS: Intensive CIT, when combined with CBG measurements, can be used to rapidly improve glycemic control in type II diabetes without development of unacceptable hypoglycemia. This degree of metabolic improvement, however, requires large doses of exogenous insulin to overcome peripheral insulin resistance and results in greater hyperinsulinemia with progressive weight gain.

Algorithms↗
PubMed1989

The pharmacokinetics and pharmacodynamics of a human relaxin in the mouse pubic symphysis bioassay.

The effects of dose, route, regimen, and the presence or absence of a repository vehicle [benzopurpurine (BPP)] were determined for a human relaxin (hRlx) in the mouse pubic symphysis bioassay. Administration of 88 micrograms/kg hRlx sc in 1% BPP resulted in delayed, prolonged absorption. Although peak hRlx concentrations were lower, serum concentrations remained elevated longer in the presence of BPP compared to a single sc administration of hRlx in saline at the same dose. The bioavailabilities with and without BPP were similar (109 and 96%, respectively). While the pharmacodynamic effect (i.e. lengthening of the pubic ligament in estrogen-primed mice) was approximately maximum at 88 micrograms/kg hRlx sc with BPP, single sc administration of hRlx without BPP up to 264 micrograms/kg had no effect on pubic ligament length. In the absence of the BPP vehicle, manipulation of the regimen (e.g. multiple sc doses) showed that emulation of the serum concentration-time profile observed for hRlx in the presence of BPP resulted in similar pharmacodynamic effects. It appears that BPP delays the absorption of hRlx after sc administration, resulting in prolonged, elevated hRlx serum concentrations. hRlx has been shown to be effective in this model without BPP if it is administered by a multidose sc schedule. As has been observed with other protein therapeutics, the dosage regimen employed for hRlx delivery appears to be an important determinant of the expression of its pharmacodynamic effects.

Animals↗
PubMed1986

Rapid induction of forestomach tumors in partially hepatectomized Wistar rats given butylated hydroxyanisole.

Rats subjected to two-thirds partial hepatectomy (PH) and given the antioxidant butylated hydroxyanisole (BHA) at a dietary concentration of 2% for 3 months developed forestomach lesions. Histologically, these lesions were classified as hyperplasia, dysplasia of the basal cell, papillomas, and carcinomas in situ. In intact rats forestomach carcinomas were seen by other investigators after feeding 2% BHA for 15-20 months. Histochemical studies of tumors revealed a marked increase in the phenotypic expression of the oncofetal enzyme, gamma-glutamyl transpeptidase (GGT) in the tumors of treated rats.

Animals↗
PubMed1985

An inexpensive device for freeze drying and plastic embedding tissues at low temperatures.

The preparation of biological tissues for electron microscopy by rapid freezing retains the original localization of ions and molecules. A reproducible freezing regime was established by quenching tissues in liquid propane according to the method of Elder et al. (1981). Tissue was thereafter freeze dried in a custom built freeze drying device with a liquid nitrogen cooled stage to prevent ice recrystallization during drying. The device was also designed to allow the vacuum embedding of tissue in low temperature resin such as Lowicryl and polymerization in situ. This paper describes the design of the device and an example of its use in the freeze drying of cartilage. The results show that minimal ice damage occurs to the chondrocytes and that intracellular organelles are clearly visible. The regime described may prove a useful and pragmatic alternative to cutting tissue in the frozen state. Translocation of elements is unlikely except perhaps in the case of very labile elements such as Na and K, but this remains to be fully elucidated.

Animals↗