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Biomedical subjects

L A Miller

Publications and source records attributed to L A Miller.

At least 73 records · Page 4Linked to original sources
PubMed1997

Nitric oxide and proteoglycan turnover in rabbit articular cartilage.

Articular chondrocytes are known to synthesize large amounts of nitric oxide in response to exposure to interleukin-1, but the role of this radical in proteoglycan turnover remains controversial. In this study, we used two different inhibitors of nitric oxide synthase, NG-methyl-L-arginine and thiocitrulline, to study the effects of nitric oxide on the synthesis and breakdown of proteoglycan in rabbit articular cartilage. Synthesis of nitric oxide by cartilage slices in response to treatment with interleukin-1 and a partially purified mixture of synovial cytokines known as chondrocyte-activating factors peaked during the first 2 days of culture and then fell to low levels, despite daily replenishment with fresh medium and cytokines to the cultures. The production of nitric oxide was completely inhibited by NG-methyl-L-arginine and thiocitrulline. Interleukin-1 and the chondrocyte-activating factors inhibited proteoglycan synthesis and accelerated proteoglycan breakdown in the slices of cartilage. Both nitric oxide synthase inhibitors substantially counteracted the suppression of proteoglycan synthesis but exacerbated proteoglycan catabolism occurring in response to interleukin-1 and the chondrocyte-activating factors. The accelerated catabolism was associated with increased levels of matrix metalloproteinases in the conditioned medium. This dual effect of nitric oxide complicates decision making with regard to the possible clinical applications of nitric oxide agonists or antagonists in diseases of cartilage.

Animals↗
PubMed1997

Comparative efficacy of two immunocontraceptive vaccines.

As part of our research program to develop immunocontraception as a wildlife management tool, we compared the physiological responses of wild Norway rats (Rattus norvegicus) to two immunocontraceptive vaccines; one involved mouse zona pellucida peptide (MZPP); the other involved gonadotropin releasing hormone (GnRH). Efficacy was monitored by immune, hormonal, and natality responses. Both vaccines were effective, but GnRH was much more effective (100% sterility of both sexes vs. 50% sterility of MZPP-treated females). Breeding success of control rats was 88% with litters of 5-9 pups; breeding success of MZPP rats was 50% with litters of 2-8; GnRH rats produced no young. In GnRH-treated male rats monitored for up to 17 months, testosterone was nondetectable and testes were atrophied to about 10% of their original volume for 10-13 months. There were no notable differences in mortality or body weights among groups, and, with the exception of testicular regression, there were no changes in general appearance. The GnRH vaccine is potentially a good rat reproductive control agent that may be effective over the normal lifespan of a rat under natural conditions in the wild.

Animals↗
PubMed1997

Propofol sedation during awake craniotomy for seizures: patient-controlled administration versus neurolept analgesia.

This prospective study evaluated the safety and efficacy of patient-controlled sedation (PCS) using propofol during awake seizure surgery performed under bupivacaine scalp blocks. Thirty-seven patients were randomized to receive either propofol PCS combined with a basal infusion of propofol (n = 20) or neurolept analgesia using an initial bolus dose of fentanyl and droperidol followed by a fentanyl infusion (n = 17). Both groups received supplemental fentanyl and dimenhydrinate for intraoperative pain and nausea, respectively. Comparisons were made between groups for sedation, memory, and cognitive function, patient satisfaction, and incidence of complications. Levels of intraoperative sedation and patient satisfaction were similar between groups. Memory and cognitive function were well preserved in both groups. The incidence of transient episodes of ventilatory rate depression (<8 bpm) was more frequent among the propofol patients (5 vs 0, P = 0.04), particularly after supplemental doses of opioid. Intraoperative seizures were more common among the neurolept patients (7 vs 0, P = 0.002). PCS using propofol represents an effective alternative to neurolept analgesia during awake seizure surgery performed in a monitored care environment.

Adjuvants, Anesthesia↗
PubMed1997

Interpretive criteria for testing susceptibility of staphylococci to mupirocin.

To determine appropriate mupirocin susceptibility testing interpretive criteria, 177 staphylococci were tested by agar dilution, disk diffusion, and E test. E test was found to be a reliable method for determining susceptibility of staphylococci to mupirocin. The agar dilution and disk diffusion results were plotted on a scattergram, and error rates were calculated. No errors were found with susceptibility breakpoints of > or = 4 microg/ml (MIC) and > or = 14 mm (zone diameter).

Anti-Bacterial Agents↗
PubMed1997

Analysis of a vertical compliance prosthetic foot.

Mechanical testing of the Re-Flex VSP Foot was conducted on the pylon alone and on the pylon and forefoot system. Values for spring and damping correspond well to values reported in the literature for spring and damping of physiological limbs. Pylon stiffness was 49.4 kN/m for a 600 N subject and 91.4 kN/m for an 800 N subject. The vertical stiffness of the pylon and forefoot together was 31.9 kN/m and 37.8 kN/m, respectively. Gait parameters of two persons with transtibial amputation who used vertically compliant feet for walking, jogging in place, and curb descent were investigated. Ground reaction forces, vertical trunk movement, event timing, and pylon compression were observed. The spring-loaded telescoping pylon was immobilized for half the trials. The trials were repeated the following week with the vertical compliance feature mobilized. Significant differences in vertical trunk motion and timing were found between the prosthetic limb and normal limb, as might be expected. Vertical compliance appeared to cause little change in gait parameters during normal walking. The largest differences appeared during the higher impact events such as fast walking and jogging in place.

Adult↗
PubMed1996

Inhibition of TGF-alpha gene expression by vitamin A in airway epithelium.

The autocrine/paracrine growth mechanism has been implicated in the regulation of bronchial epithelial cell proliferation. By inhibiting the expression of the transforming growth factor-alpha (TGF-alpha) gene product, vitamin A is able to suppress the proliferation of tracheobronchial epithelial cells in culture. Similar repressions in TGF-alpha mRNA levels by retinol were observed in airway explant cultures and in a cell line immortalized from normal human bronchial epithelial cells. Both the nuclear run-on transcriptional assay and the transfection study with the chimeric construct of the TGF-alpha promoter and chloramphenicol acetyltransferase reporter gene partly suggest a transcriptional downregulation mechanism of TGF-alpha gene expression by the retinol treatment; however, this inhibition at the transcriptional level cannot account for the total inhibition at the mRNA level. These results suggest that a downregulation of the expression of the TGF-alpha gene at the transcriptional and post-transcriptional levels by vitamin A may precede the essential event associated with the homeostasis of normal conducting airway epithelium.

Animals↗
PubMed1996

Sequential ultrastructural and biochemical changes induced by microcystin-LR in isolated perfused rat livers.

The cyanobacterial hepatotoxin, microcystin-LR (MCLR), is a potent protein phosphatase inhibitor that disrupts actin microfilament, cytokeratin intermediate filament, and microtubule networks in hepatocytes. To determine ultrastructural and biochemical changes that develop concurrently with microcystin-induced cytoskeletal disorganization, isolated rat livers were perfused with MCLR at 0.1 to 5.0 micrograms/ml for 5 to 40 min. Lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase changed over time, but trends for toxin-treated and control livers did not differ. The earliest toxin-induced ultrastructural changes, observed in livers perfused at 0.1 microgram/ml for 15-20 min or at 0.3 microgram/ml for 5-10 min, were loss of hepatocyte microvilli in the space of Disse, widening of sinusoidal fenestrae, disruption of sinusoidal endothelium, dilation of bile canaliculi with loss of microvilli, and widening of hepatocyte intercellular spaces. Lesions progressed with increasing toxin concentrations and exposure times. In livers perfused with MCLR at 0.5 microgram/ml for 10-20 min, hepatocytes had plasma membrane blebs and concentric whorls of rough endoplasmic reticulum, and there was marked disassociation of hepatocytes resulting in disrupted hepatic cords. At toxin concentrations of 2.0 or 5.0 micrograms/ml for 10-20 min, there was mild dilation of mitochondrial cristae, cytoplasmic vacuolization or invagination of plasma membranes, redistribution of organelles, and sometimes nuclear degenerative change. Some hepatocytes exhibited clusters of plasma membrane blebs radiating from round cytoplasmic structures, which may be composed primarily of condensed microfilaments.

Animals↗
PubMed1996

Effects of focal brain lesions on visual problem-solving.

In this study, the relative contributions of different brain regions to visual problem-solving were explored using a new test of divergent thinking. Seventy-three patients with focal brain lesions and 20 normal control subjects performed a set of matchstick problems, similar to those described by Guilford [15] as a measure of adaptive flexibility. For each problem, subjects were to demonstrate as many ways as possible of removing a particular number of sticks from a two-dimensional geometric design to achieve a specified resultant shape. Patients with left temporal-occipital, right temporal-occipital, or left frontal lesions displayed no significant difficulty. Evidence of general deficiencies in the ability to manipulate this visual material was seen in patients with parietal and/or central-area lesions (right worse than left). In contrast, patients with right frontal-lobe damage demonstrated a selective impairment in the ability to shift strategy. The results confirm the importance of the right suprasylvian region in the ability to process and act on visual information. They also provide evidence of the specific role played by the right frontal lobe, and particularly the ventral region, in permitting a flexible approach to visual problem-solving.

Adolescent↗
PubMed1996

Evaluation of 500 gram negative isolates to determine the number of major susceptibility interpretation discrepancies between the Vitek and MicroScan Walkaway for 9 antimicrobial agents.

Although the Vitek and MicroScan Walkaway are two of the most commonly used automated antimicrobial susceptibility test systems, few studies have been performed comparing discrepancies between these systems. In this study, 500 Gram negative clinical isolates were tested against ampicillin, ampicillin/sulbactam, ticarcillin, ticarcillin/clavulanate, imipenem, ciprofloxacin, norfloxacin, mezlocillin, and piperacillin to determine the number of major interpretation discrepancies between the two systems. The 500 isolates consisted of 100 isolates each of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis and Enterobacter species. Each isolate was tested simultaneously in both systems using the same standardized inoculum. Eighty-four major discrepancies occurred, of which 48 were reproducible. The reproducible discrepancy rate, for the 4,500 isolate/antimicrobic combinations tested, was 48 of 4500 (1.06%). The rate for individual antimicrobics varied from 17 of 500 (3.4%) for ampicillin to no discrepancies for ticarcillin or ciprofloxacin. Of the 48 reproducible discrepancies, 44 (92%) were Vitek resistant, MicroScan susceptible. Fifteen (31%) of the Vitek and 21 (44%) of the MicroScan results were confirmed by broth microdilution. Disk diffusion results were in agreement with 15 (31%) of the Vitek and 21 (44%) of the MicroScan results. Twelve (25%) of the broth microdilution and 12 (25%) of the disk diffusion results were intermediate. The broth microdilution and disk diffusion results for the 48 isolates with reproducible discrepancies were in agreement more often with MicroScan. However, there was less very major error comparing the Vitek results for these isolates to the broth microdilution and disk diffusion. Overall, the result of this evaluation indicate that the number of major interpretation discrepancies between the two systems is minimal for the isolate/antimicrobic combinations tested.

Ampicillin↗
PubMed1996

Care of the elective intracoronary stent patient.

Recently, the Palmaz-Schatz coronary stent was approved by the FDA as an alternative to coronary angioplasty in the treatment of de novo native coronary stenosis. Developed by Dr. Julio Palmaz and Dr. Richard Schatz, the Palmaz-Schatz intracoronary stent design was implanted in 1987 at Brooke Army Medical Center. During the past 7 years, The University of Texas Health Science Center-San Antonio (clinical sites include University Hospital, Brooke Army Medical Center, and Audie Murphy Veterans Administration Hospital) has used this intracoronary stent to treat more than 300 patients. Nursing care for this patient population is both distinct and challenging. Successful patient outcomes require a knowledgeable staff and a team approach. This article will emphasize the nursing care and patient education required both before and after the stent procedure, as well as considerations for long-term follow-up.

Aftercare↗
PubMed1996

Acquisition of services recommended by a multidisciplinary medical diagnostic team for children under three years of age evaluated for developmental delays.

After multidisciplinary medical diagnostic teams evaluate children with developmental delays, they recommend to parents that they seek specific services, but the team rarely knows which services are obtained. We sought to determine which services pursued by the parents were actually acquired and to determine if there were barriers to the acquisition of services. In a diagnostic clinic located in a teaching hospital in an urban setting, we evaluated 92 children less than 3 years of age mainly from an inner city population. At a family conference, the parents had indicated an interest in pursuing an average of 1.87 +/- 1.34 social services, 1.70 +/- 1.32 educational services, and 3.61 +/- 2.31 medical services recommended by the team. Four months after the family conference, the actual services obtained by families included 38.5% of the social services, 70.87% of the educational services, and 71.36% of the medical services. Significantly fewer social services were obtained than educational and medical services.

Chicago↗
PubMed1996

Stability of amoxicillin-clavulanate in BACTEC medium determined by high-performance liquid chromatography and bioassay.

The stabilities of amoxicillin (16 micrograms/ml) and clavulanate (8 micrograms/ml), alone and in combination in BACTEC medium (Middlebrook 7H12B medium), were determined by high-performance liquid chromatography (HPLC) and bioassay. By HPLC, the half-life of amoxicillin (trihydrate and sodium) in combination with clavulanate in nonradiolabelled 7H12B medium was 6.7 days, whereas the half-life of clavulanate in combination with amoxicillin was 2.0 days. By bioassay, the half-lives of amoxicillin trihydrate and clavulanate in radiolabelled 7H12B medium were comparable (7 and 2 days, respectively) to those determined by HPLC. When clavulanate was tested alone, the half-life was determined to be 1.88 days by HPLC and 1.87 days by bioassay. The relatively short half-life of clavulanate can be adjusted by a procedure of "topping up," or adding one-half the concentration of clavulanate every second day, in order to allow accurate amoxicillin-clavulanate MIC testing with the BACTEC mycobacterial susceptibility system.

Amoxicillin↗
PubMed1996

Prospective neuropsychological assessment of nondemented patients with biopsy proven senile plaques.

Senile plaques are characteristic of Alzheimer's disease but also occur as an age-related change in some neurologically normal individuals at autopsy. The significance of these "incidental" senile plaques, with regard to the development of dementia, is unknown and cannot be assessed by postmortem studies. Patients with biopsy proven senile plaques offer an important opportunity for prospective followup. We identified senile plaques in temporal lobectomy specimens, removed in the surgical treatment of intractable epilepsy, from 11 patients. Review of preoperative neuropsychological test results showed no suggestion of dementia in any of the patients with senile plaques and no significant difference compared with controls. Postoperative followup ranged from 2 to 7 years (mean, 3.7 yr). There was no evidence of generalized cognitive deterioration in any of the study patients. These findings indicate that an abundance of senile plaques may be present without associated dementia and without cognitive deterioration for at least several years.

Adult↗
PubMed1996

In vivo enzymatic removal of alpha 2-->6-linked sialic acid from the glomerular filtration barrier results in podocyte charge alteration and glomerular injury.

The epithelial polyanion (podocalyxin) on the foot processes (pedicels) of podocytes plays a pivotal role in maintaining slit pore integrity and excluding proteins from the glomerular filtrate. Chromatographically purified recombinant sialidase from Vibrio cholerae, a corresponding heat-inactivated enzyme, truncated enzyme (missing the last 17 amino acids from the carboxyl terminus), and the sialidase from Salmonella typhimurium strain LT2 were inoculated intraperitoneally into mice, and the resultant renal alterations were documented by a variety of functional, morphologic, and histochemical techniques. Proteinuria and renal failure developed in a dose-dependent manner after a single inoculation of sialidase from Vibrio cholerae, but not with the corresponding heat-inactivated enzyme, truncated enzyme, or the sialidase from Salmonella typhimurium strain LT2. Biotinylated lectins of known sialyl linkage specificity demonstrated that Vibrio cholerae sialidase primarily removed alpha 2-->6-linked sialic acids from the glomerulus. Furthermore, the use of a poly-L-lysine cationic gold ultrastructural probe confirmed a transient loss of charge from the endothelium and epithelium of the glomerular filtration barrier. Loss of the epithelial polyanion was accompanied by the effacement of pedicels and the apparent formation of tight junctions between adjacent podocytes. The anionic charge returned to endothelial and epithelial sites within 2 days of sialidase inoculation, but the foot process loss remained. This animal model, in addition to providing an opportunity to study basic mechanisms of renal physiology, seems to mimic minimal change disease in children, diabetic nephropathy, and the renal effects of some bacterial infections.

Albuminuria↗
PubMed1995

Comparison of partner notification at anonymous and confidential HIV test sites in Colorado.

We compared health department-initiated partner notification at a single anonymous human immunodeficiency virus (HIV) test site in Denver to 13 confidential HIV test sites throughout Colorado over an 18-month period. The average number of named, notified, and counseled in-state partners was from 30 to 50% greater among confidential site index cases than anonymous site index cases, and the seropositivity rate in newly tested partners of confidential site index cases was more than twice the rate in partners of anonymous test site index cases. When analyses were restricted to gay/bisexual male index cases, the results were the same as for the total group. We recommend that state and local health departments collect data to evaluate and improve the delivery of partner notification services.

AIDS Serodiagnosis↗
PubMed1995

Comparative pathology of microcystin-LR in cultured hepatocytes, fibroblasts, and renal epithelial cells.

The cyanobacterial toxin microcystin-LR (MCLR) is a potent inhibitor of protein phosphatases 1 and 2A, and is selectively toxic to the liver in vivo and to isolated hepatocytes in vitro. This selectivity is believed to be due to toxin uptake via bile acid carriers. We investigated at the light and ultrastructural levels the effects of high concentrations of MCLR and long incubation times to determine in vitro whether fibroblasts and kidney cells (non-target cells) respond in the same manner as do hepatocytes (target cells) at low concentrations and short incubation times. Cultured rat skin fibroblasts (ATCC 1213) and rat kidney epithelial cells (ATCC 1571) were incubated with with MCLR at 133 microM for 1-24 hr. Lesions in these cells were compared with those in cultured hepatocytes incubated MCLR at 13.3 microM from 1 to 32 min. Lesions in hepatocytes, kidney cells, and fibroblasts were noted at 4 min, 1 hr, and 8 hr, respectively, after initial exposure to MCLR. Lesions in all three cell types progressed and included plasma membrane blebbing, loss of cell-to-cell contact, clumping and rounding of cells, cytoplasmic vacuolization, and redistribution of cytoplasmic organelles. Loss of microvilli, whorling of rough endoplasmic reticulum, dense staining and dilated cristae in mitochondria, and pinching off of membrane blebs were noted only in hepatocytes. Nuclear changes typical of apoptosis were observed only in fibroblasts and kidney cells. Similarities in responses of different cell types to MCLR exposure probably reflect a common biochemical mechanism of action, i.e., inhibition of protein phosphatases 1 and 2A as described by others.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

A survey of beta-lactamase-producing Haemophilus influenzae. An evaluation of 5750 isolates.

Previous studies have reported that 15%-34% of Haemophilus influenzae produce beta-lactamase. A surveillance program was developed by SmithKline Beecham Clinical Laboratories to determine the current percentage of beta-lactamase-producing H. influenzae from five selected geographic locations in the United States. In 1993, results of 5750 isolates from specimens submitted to five reference clinical laboratories were evaluated. Data were collected from 29 states and the District of Columbia. The percentages of beta-lactamase-producing H. influenzae was 33% and ranged from 22%-40% for the individual states.

Adolescent↗