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Biomedical subjects

D E Johnson

Publications and source records attributed to D E Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1997

Implications of fine-needle aspiration in patients with resectable pancreatic cancer.

A 9-year experience with fine-needle aspiration (FNA) in patients with resectable pancreatic adenocarcinoma was reviewed to determine whether this procedure is associated with positive peritoneal cytology, peritoneal recurrences, or decreased survival in patients who had pancreatic resection with curative intent. Forty-one patients underwent pancreatic resection for primary pancreatic adenocarcinoma from July 1987 to February 1996. Nine patients had open biopsies prior to definitive resection and were excluded from this study. Of the remaining 32 patients, 21 (66%) had preoperative computed tomography-guided or fluoroscopically guided FNA biopsy of the pancreas for diagnosis. FNA confirmed the diagnosis of adenocarcinoma in 17 of 21 patients (80%). Fifteen of 21 FNA biopsies were performed in patients who went on to receive neoadjuvant chemoradiation. Twenty-eight of 32 patients (87%) had peritoneal washings at the time of laparotomy. Five patients had suspicious or positive washings (18%), and 23 patients had negative washings (82%). Three of 18 patients (16.7%) who had both FNA and peritoneal washings and 2 of 10 patients (20%) who had no FNA but had peritoneal washings had positive or suspicious peritoneal cytology. Eight of 32 patients ultimately failed in the peritoneum. Six of 21 patients (28%) who had prior FNA and 2 of 11 (18%) who had no prior FNA failed in the peritoneum. Although the number of patients is small, none of these differences proved to be statistically significant. No difference in median survival was observed between the FNA and no FNA groups. We conclude that FNA is a safe and useful tool to confirm the diagnosis of pancreatic cancer when patients are to be treated with neoadjuvant chemoradiation.

Adenocarcinoma↗
PubMed1996

Visual laser ablation of the canine prostate with a diffusing fiber and an 805-nanometer diode laser.

BACKGROUND AND OBJECTIVE: Although the popularity of visual laser ablation of the prostate (VLAP) as a treatment for symptomatic, benign prostatic hyperplasia (BPH) is increasing, the perceived advantages of VLAP over conventional transurethral electroresection of the prostate (TURP) is being debated because optimal technique and dosimetry for surgical lasers are still being refined. At this time, the 1.06 neodymium:yttrium-aluminum-garnet (Nd:YAG) laser and a laterally deflecting delivery system is the hardware combination most widely used for VLAP. STUDY DESIGN/MATERIALS AND METHODS: Reported here is a study of an alternate system, a 805-nm diode laser (Diomed 25 Diomedics, The Woodlands, TX) with a cylindrically diffusing fiber (Surgimedics Inc., The Woodlands, TX). Eight mongrel dogs were prostatectomized by transurethral irradiation of the prostate with 15,000 J of diode laser energy delivered via a fiber that diffuses the energy in a 1.5-cm-long cylindrical pattern. The dogs were sacrificed and prostates harvested at 3 hours and 1,4,7,14,21,35, and 49 days after the procedure, fixed with 10% buffered formalin, and examined histologically. RESULTS/CONCLUSIONS: It was found that this laser/fiber combination created volumes of tissue coagulation similar to those encountered in our previous work with the Nd:YAG laser in combination with both laterally deflecting and diffuser fibers, while offering the distinct advantages of simplified technique, lower cost hardware, and fewer postoperative complications in the dog model.

Animals↗
PubMed1996

Isolation of nitric oxide synthase in the rat uterus.

Nitric oxide synthase (NOS) was isolated from the uterus of adult female rats by diethylaminoethyl (DEAE) column and further purified by 2',5'-ADP agarose. The chromatographic properties revealed two isoenzymes, NOS1 and NOS2. The molecular weights of both isoenzymes was approximately 155 Kd by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS PAGE) which was similar to NOS1 and NOS2 from rat brain. The enzymes required nicotinamide adenine dinucleotide phosphate (NADPH), Ca+2 and calmodulin as cofactors. However, in the absence of calmodulin and/or calcium NOS1 was reduced by approximately 96%, while NOS2 was reduced by approximately 70%. This maximal enzyme activity was similar for brain. These results demonstrate that two isoforms of NOS are present in the rat uterus.

Animals↗
PubMed1996

Correlates of protective immunity against HIV-1 infection in immunized chimpanzees.

Several experimental vaccination strategies have been developed to prevent primary infection with human immunodeficiency virus (HIV), and as immunotherapeutics for infected individuals. Many of the putative vaccines have been tested in chimpanzees (p. troglodytes) to determine their safety, efficacy, and to delineate immune correlates of protection. To date, approximately 25 candidate vaccines representing active or passive strategies have been evaluated in chimpanzees, and efficacy has been based on protection against primary infection following intravenous or mucosal challenge with cell-free or cell-associated virus. Active immunization has been attempted with whole inactivated virus, envelope depleted viral preparation, vaccinia vector expressing gp 160 in combination with other viral gene products, and subunit vaccines containing recombinant gp 120 derived from different isolates. Polyclonal and monoclonal antibodies with neutralizing activity have been utilized for pre- and post-exposure passive immunization to block primary infection with HIV.

AIDS Vaccines↗
PubMed1996

Metabolic rate, organ mass, and mitochondrial proton leak variations in lean and obese rats.

The purpose of this study was to determine if differences in metabolic rate between lean and obese strains of rats were associated with differences in proton leak across the inner mitochondrial membrane. Metabolic rates were determined for each of five obese Zucker, Sprague-Dawley, and Fisher 344 rats and three lean Zucker rats by 24-hour indirect respiration calorimetry measurements. Feed intakes were different (P < 0.05) among all strains, with the obese Zucker rats having the greatest intakes. Adjusted to a common dietary intake, the obese Zucker rats had at least 21% lower heat productions than the lean strains of rats. Following the calorimetry measurements, the rats were sacrificed, internal organs were removed and weighed and mitochondria were isolated from the liver. Internal organs composed a larger proportion of lean body mass in obese compared to lean rats. Respiration rates and membrane potentials of the mitochondria were then determined. Proton leak kinetics were visualized by plotting proton leak (calculated from respiration rate) against membrane potential. The lean rats had a 2-3-fold higher proton leak rate than the obese Zucker rats at the same membrane potential. A low mitochondrial proton leak rate may explain part of the abnormal heat productions and bioenergetic efficiencies in the obese Zucker rat.

Animals↗
PubMed1996

Glass wool column filtration versus mini-Percoll gradient for processing poor quality semen samples.

OBJECTIVE: To compare the quality and number of spermatozoa recovered from laboratory-induced severe oligozoospermic specimens processed by mini-Percoll gradient and glass wool column filtration. DESIGN: Both sperm-processing procedures were compared in similar sperm samples adjusted to contain equal low numbers of motile spermatozoa using either dilution (oligozoospermia) or with the addition of killed sperm (oligoasthenozoospermia). The spermatozoa processed by both procedures samples were evaluated for motility, response to hypo-osmotic swelling test, and the hemizona assay. PATIENTS: Five healthy fertile sperm donors. SETTING: Private Andrology Laboratory and University Hospital. MAIN OUTCOME MEASURE: Sperm motility, hypo-osmotic swelling test, and hemizona assay results determined the efficacy of the sperm-processing procedures. RESULTS: The concentration of sperm recovered after both procedures was not affected by either preparation or processing methods. Glass wool-processed sperm had higher motility in oligoasthenozoospermic samples, bound tightly to hemizonae in higher mean numbers, and demonstrated a higher percentage of membrane-intact spermatozoa in oligozoospermic samples. CONCLUSION: Laboratory-prepared oligozoospermic samples subjected to glass wool filtration yielded more functionally intact spermatozoa than mini-Percoll gradient processing.

Cell Separation↗
PubMed1996

Effect of head orientation on posterior anterior cephalometric landmark identification.

This study examined the effect of head rotation about the vertical and transverse axes on posterior anterior cephalometric landmarks. Radiographs were taken on 25 skulls, first in a normal position, then in four positions each rotated 5 degrees from normal. The identification errors of 52 bilateral and midline landmarks were determined in the horizontal and vertical dimensions. The landmark identification errors for each of the five orientations were compared and those landmarks affected by 5 degrees rotation were identified. Landmarks with significantly larger identification error in a rotated position were: nasal cavity, mandible/occiput, foramen rotundum and orbitale. Best fit vertical and horizontal reference lines were determined, and the effect of head rotation on the choice of best fit reference lines was assessed. Rotation about the transverse axis did not affect the relationship of landmarks to the best vertical or horizontal lines. Rotation about the vertical axis did not affect the relationship of landmarks to the best horizontal line but did affect their relationship to the best vertical line.

Adult↗
PubMed1996

Association of oviduct-specific glycoproteins with human and baboon (Papio anubis) ovarian oocytes and enhancement of human sperm binding to human hemizonae following in vitro incubation.

The objectives of this study were 1) to determine whether or not human and baboon oviduct-specific glycoproteins (human OGP, baboon OGP) would associate with ovarian oocytes during in vitro incubation in a manner similar to that detected in vivo for oviductal oocytes and 2) to determine whether the association of OGP with ovarian oocytes influenced sperm binding. In vitro association of OGP with ovarian oocytes was assessed by indirect immunofluorescence assay using a polyclonal antibody prepared against human or baboon OGP. Human and baboon ovarian oocytes incubated in culture media containing OGP showed association of OGP with the zona pellucida (ZP) as detected by bright fluorescence. A similar pattern of fluorescence was observed in baboon oviductal oocytes (positive control). No fluorescence of the ZP was detected from ovarian oocytes incubated with culture medium alone. The pattern of fluorescence for ovarian oocytes incubated with OGP and serum albumin, the major oviductal fluid protein, was similar to that for oocytes incubated with OGP alone. A modified hemizona assay was used to assess whether association of human OGP with human ovarian oocytes influenced sperm binding. The number of sperm bound to hemizonae in the presence of human OGP was significantly greater (p < 0.01) than the number bound to hemizonae in the control culture medium. Addition of antibodies specific for human OGP to the incubation medium 1 h prior to addition of gametes blocked the enhancement of sperm binding seen in the presence of human OGP alone. Finally, human hemizona assays conducted in the presence of baboon OGP resulted in a significant decrease (p < 0.05) in the number of sperm bound per zona compared with that in culture medium alone despite high homology between human and baboon OGP. These results 1) suggest that human OGP associates with ovulated oocytes in vivo; 2) support the hypothesis that association of OGP with the ZP may play a role in fertilization, possibly through enhancing the binding of sperm to the ZP within the oviduct; and 3) suggest that a homologous system (i.e., gametes and oviductal glycoprotein from the same species) is necessary for study of the function of oviductal glycoproteins.

Animals↗
PubMed1996

Phenylacetic acid halides inhibit estrogen receptor (ER)-positive MCF-7 cells, but not ER-negative human breast cancer cells or normal breast epithelial cells.

Phenylacetic acid (PA) derivatives and conjugates have been reported to have antiproliferative and antitumor properties against various types of cancers. Based on these findings, recent in vitro experiments were devised to examine the antiproliferative properties of a series of para substituted (Br, Cl, F, H, NO2 and OCH3) PAs. The in vitro screening protocal involved the plating of MCF-7 cells in a 96-well plate assay. After 1 day, the cells were exposed to the PA derivatives for 2 days (log phase of MCF-7 growth curve). Cells growth was determined by the Alamar blue dye reagent. The optical density data was analyzed and IC50 concentration values determined. The results showed that PA halide derivatives caused a significant decrease in proliferation of the MCF-7 cells. The order of antiproliferative activity was BR > Cl > or = F, with IC50 values (nM) of 10 +/- 0.005, 100 +/- 0.02 and 100 +/- 0.04, respectively. The OCH3, H and NO2 compounds showed no significant antiproliferative activity. PA halide derivatives may have similar actions as tamoxifen because they show specificity for estrogen receptor-positive cells.

Antimetabolites, Antineoplastic↗
PubMed1996

Altered binding of the Cry1Ac toxin to larval membranes but not to the toxin-binding protein in Plodia interpunctella selected for resistance to different Bacillus thuringiensis isolates.

Immunoblotting and cytochemical procedures were used to determine whether toxin binding was altered in strains of the Indianmeal moth, Plodia interpunctella, selected for resistance to various strains of Bacillus thuringiensis. Each of these B. thuringiensis subspecies produces a mixture of protoxins, primarily Cry1 types, and the greatest insect resistance is to the Cry1A protoxins. In several cases, however, there was also resistance to toxins not present in the B. thuringiensis strains used for selection. The Cry1Ab and Cry1Ac toxins bound equally well over a range of toxin concentrations and times of incubation to a single protein of ca. 80-kDa in immunoblots of larval membrane extracts from all of the colonies. This binding protein is essential for toxicity since a mutant Cry1Ac toxin known to be defective in binding and thus less toxic bound poorly to the 80-kDa protein. This binding protein differed in size from the major aminopeptidase N antigens implicated in toxin binding in other insects. Binding of fluorescently labeled Cry1Ac or Cry1Ab toxin to larval sections was found at the tips of the brush border membrane prepared from the susceptible but not from any of the resistant P. interpunctella. Accessibility of a major Cry1A-binding protein appears to be altered in resistant larvae and could account for their broad resistance to several B. thuringiensis toxins.

Animals↗
PubMed1996

Construction of a flagellum-negative mutant of Proteus mirabilis: effect on internalization by human renal epithelial cells and virulence in a mouse model of ascending urinary tract infection.

To examine the role of flagella in pathogenesis of urinary tract infection caused by Proteus mirabilis, we constructed a nonmotile, nonswarming flagellum mutant of strain WPM111 (an hpmA hemolysin mutant of strain BA6163, chosen because of its lack of in vitro cytotoxicity in renal epithelial cell internalization studies). A nonpolar mutation was introduced into the flaD gene, which encodes the flagellar cap protein. This mutation does not affect the synthesis of flagellin but rather prevents the assembly of an intact flagellar filament. In in vitro assays, the genetically characterized nonmotile mutant was found to be internalized by cultured human renal proximal tubular epithelial cells in numbers less than 1% of those of the flagellated parent strain. Internalization of the nonmotile mutant was increased significantly (14- to 21-fold) by centrifugation onto the monolayer. To assess virulence in vivo, CBA mice were challenged transurethrally with 10(7) CFU of P. mirabilis BA6163 (wild type) (n = 16), WPM111 (hpmA mutant) (n = 46), or BB2401 (hmpA flaD mutant) (n = 46). Differences in quantitative cultures between the parent strain and the hemolysin-negative mutant were not significant. However, the hpmA flaD mutant was recovered in numbers approximately 100-fold lower than those of the hmpA mutant or the wild-type parent strain and thus was clearly attenuated. We conclude that while hemolysin does not significantly influence virulence, flagella contribute significantly to the ability of P. mirabilis to colonize the urinary tract and cause acute pyelonephritis in an experimental model of ascending urinary tract infection.

Animals↗
PubMed1996

In vivo and in situ measurements of forage protein degradation in beef cattle.

In vivo and in situ protein degradation measurements were compared using alfalfa (2.62% N) and prairie hay (.88% N) fed to six cannulated cows in a two-period crossover experiment. Additionally, two in situ procedures were evaluated: in P1 samples were ruminally incubated in cows fed the same forage as incubated; in P2 samples were incubated in the rumens of two steers fed a "standard" brome hay (1.38% N). Duplicate bags were incubated for 0, 2, 6, 10, 16, 24, 48, and 72 h. Protein degradability was estimated using residual N from all incubation times fit to a nonlinear, least squares model (full time-series), from the 16-h incubation alone (single-point) and from a combination of the 0-h and 16-h values (double-point). Protein degradability estimates from in vivo, in situ P1, in situ P2, single-point P1 and P2, and double-point P1 and P2 were 83.4 +/- 4.3, 91.5 +/- .6, 87.2 +/- .6, 94.0 +/- .2, 92.4 +/- .8, 90.4 +/- .4, and 88.3 +/- .5, respectively, for alfalfa, and 55.5 +/- 3.5, 58.3 +/- 1.3, 57.2 +/- .4, 50.0 +/- 1.7, 52.0 +/- 2.2, 55.5 +/- 2.1, and 60.0 +/- 2.3, respectively, for prairie hay. Although relatively large differences in rates of degradation and sizes of protein fractions were measured between P1 and P2, differences between procedures for protein degradability estimates were small relative to errors of in vivo measurement. Furthermore, differences in protein degradation using single-point values as compared with full time-series analysis were overcome with the double-point approach.

Animal Feed↗