Search PubMed⌕ Search

Biomedical subjects

D J Waters

Publications and source records attributed to D J Waters.

At least 37 records · Page 2Linked to original sources
PubMed1998

Ca2+-permeable non-NMDA glutamate receptors in rat magnocellular basal forebrain neurones.

1. Ionotropic glutamate receptor-mediated responses were recorded from rat magnocellular basal forebrain neurones under voltage clamp from a somatically located patch-clamp pipette. Currents were recorded from both acutely dissociated neurones and neurones maintained in culture for up to 6 weeks. 2. Non-NMDA and NMDA receptor-mediated events could be distinguished pharmacologically using the selective agonists (S)-alpha-amino-3-hydroxy-5-methyl-isoxazolepropionic acid (AMPA), kainate and N-methyl-D-aspartate (NMDA), and antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D(-)-2-amino-5-phosphonopentanoic acid (AP5). 3. Responses to rapid application of AMPA displayed pronounced and rapid desensitization. Responses to kainate showed no desensitization. Steady-state EC50 values for AMPA and kainate were 2.7 +/- 0.4 microM (n = 5) and 138 +/- 25 microM (n = 10), respectively. Cyclothiazide markedly increased current amplitude of responses to both agonists, whereas concanavalin A had no clear effect on either response. The selective AMPA receptor antagonist GYKI 53655 inhibited responses to kainate with an IC50 of 1.2 +/- 0.08 microM (n = 5) at -70 mV. These data strongly suggest that AMPA receptors are the predominant non-NMDA receptors expressed by basal forebrain neurones. 4. At -70 mV, approximately 6 % of control current amplitude remained, at a maximally effective concentration of GYKI 53655. This residual response displayed desensitization, was insensitive to cyclothiazide and was potentiated by concanavalin A, suggesting that it was mediated by a kainate receptor. 5. Current-voltage relationships for non-NMDA receptor-mediated currents were obtained from both nucleated patches pulled from neurones in culture and from acutely dissociated neurones. With 30 microM spermine in the recording pipette, currents frequently displayed double-rectification characteristic of non-NMDA receptors with high Ca2+ permeabilities. Ca2+ permeability, relative to Na+ and Cs+, was investigated using constant field theory. The measured Ca2+ to Na+ permeability coefficient ratio was 0.26-3.6; median, 1.27 (n = 15). 6. Current flow through non-NMDA receptors was inhibited by Ca2+, Cd2+ and Co2+ ions. At a holding potential of -70 mV, a maximally effective concentration of Cd2+ (> 30 mM) reduced current amplitude by approximately 90 %, with an IC50 of 44 microM. In six out of seven cells tested, block by Cd2+ was voltage sensitive. 7. Ca2+ permeability of many of the non-NMDA receptors expressed by magnocellular basal forebrain neurones may underlie the unusual sensitivity of cholinergic basal forebrain neurones to non-NMDA receptor-mediated excitotoxicity.

Animals↗
PubMed1998

Indium-111-DTPA-folate as a potential folate-receptor-targeted radiopharmaceutical.

UNLABELLED: Indium-111-labeled diethylenetriamine pentaacetic acid (DTPA)-folate was evaluated as a radiopharmaceutical for targeting tumor-associated folate receptors. METHODS: Athymic mice were subcutaneously inoculated with approximately 1.8 x 10(6) folate receptor-positive KB (human nasopharyngeal carcinoma) cells, yielding 0.2- to 0.6-g tumors in 15 days, at which time (111)In-DTPA-folate, (111)In-DTPA or (111)In-citrate was administered by intravenous injection. RESULTS: The (111)In-DTPA-folate conjugate afforded marked tumor-specific (111)In deposition in vivo using this mouse model. The involvement of the folate receptor in mediating tumor uptake of (111)In-DTPA-folate was demonstrated by the blocking of tumor uptake by coadministration of free folic acid (intravenous). The (111)In-DTPA-folate also shows folate receptor-mediated uptake and retention in the kidneys, presumably reflecting radiotracer binding to folate receptors of the proximal tubules. In control experiments, the (111)In-citrate radiopharmaceutical precursor was also shown to afford significant tumor uptake of (111)In, but with much poorer tumor-to-background tissue contrast than that obtained with (111)In-DTPA-folate. Unconjugated (111)In-DTPA showed no tumor affinity. CONCLUSION: Indium-111-DTPA-folate appears suitable as a radiopharmaceutical for targeting tumor-associated folate receptors.

Animals↗
PubMed1997

Wild-type and mutant HIV type 1 nucleocapsid proteins increase the proportion of long cDNA transcripts by viral reverse transcriptase.

HIV-1 nucleocapsid, p7, contains two retroviral zinc fingers, which are both necessary for efficient packaging of genomic RNA and infectivity. The nucleocapsid protein is bound tightly to genomic RNA in the mature virion. In this study, the effect of p7 on polymerization of nascent cDNA by viral reverse transcriptase (RT) was examined. An 874-base RNA of HIV-1 was synthesized and used as a template in RT assays with varying concentrations of intact p7, mutants of p7 that have transposed or repeated zinc fingers, and several different peptides that represent various structural regions of p7. Results indicate that at greater than or equal to 50% saturation of p7-binding sites, with p7, there is up to a 90% reduction in total cDNA synthesis, as measured by nucleotide incorporation. However, the cDNA products that are made are almost exclusively full length. Three zinc finger mutants exhibited effects similar to those of wild-type p7. N-terminal and C-terminal halves of p7 inhibited total nucleotide incorporation, but also inhibited synthesis of long cDNA products by RT. In the absence of p7 an array of short transcripts (< 200 bases) was produced by RT. These studies show that full-length p7 is necessary to increase the proportion of long cDNA transcripts produced by RT. The relative position of the two zinc fingers is not critical for this effect.

Amino Acid Sequence↗
PubMed1997

Prostatic intraepithelial neoplasia in dogs with spontaneous prostate cancer.

Prostatic intraepithelial neoplasia (PIN) is the most likely precursor of human prostate cancer. The prevalence and immunophenotype of PIN in dogs with spontaneous prostate cancer has not been previously described. To investigate the association between PIN and prostate cancer, we evaluated the prostates of dogs with spontaneous prostate carcinoma. The prevalence of PIN was determined in formalin-fixed prostates from 29 dogs with spontaneous prostate cancer. Using immunoperoxidase techniques, we compared basal cell layer integrity (high molecular weight keratin 34 beta-E12), proliferative index (MIB-1), and microvessel density (Factor VIII-related antigen) in 14 prostates which contained benign epithelium, PIN, and carcinoma. PIN was present in 19 of 29 (66%) prostates from dogs with spontaneous prostate cancer. The basal cell layer was intact in benign epithelium, disrupted in 72% of acini with PIN, and absent in carcinoma. The mean proliferative index was 17%, 25%, and 40% for benign epithelium, PIN, and carcinoma, respectively, and these differences were significant. The mean microvessel density in foci of PIN and carcinoma (32 and 39 vessels per mm2, respectively) was greater than in benign epithelium (23 vessels per mm2). High-grade PIN is common in the prostates of dogs with spontaneous carcinoma. The basal cell layer is partially disrupted in PIN, whereas it is absent in prostate cancer. The proliferative index and microvessel density of PIN are intermediate between benign epithelium and cancer. These results are similar to those reported for human PIN and prostate cancer, and indicate that PIN is part of a morphologic continuum in the progression of prostate cancer. To our knowledge, this is the first description of high-grade PIN spontaneously occurring in animals. The canine prostate may serve as a useful model for examining factors that modulate PIN and prostate cancer progression.

Animals↗
PubMed1997

Detection of pulmonary metastases with pathological correlation: effect of breathing on the accuracy of spiral CT.

BACKGROUND: CT of the chest for suspected pulmonary metastases in adults is generally performed using a breath-hold technique. The results may not be applicable to young children in whom breath-holding may be impossible. OBJECTIVE: Determine the effect of breathing on the accuracy of pulmonary metastasis detection by spiral CT (SCT). MATERIALS AND METHODS: Prior to euthanasia four anesthetized dogs with metastatic osteosarcoma underwent SCT with a collimation of 5 mm and a pitch of 2, during both induced breath-hold and normal quiet breathing. Images were reconstructed as contiguous 5-mm slices. Macroscopically evident metastases were noted at postmortem. Hard-copy SCT images were reviewed by ten radiologists, each of whom circled all suspected metastases. SCT images were compared with postmortem results to determine true and false positives. RESULTS: The pathologist identified 132 macroscopically evident pulmonary metastases. For metastasis detection, there was no significant difference between breath-hold SCT and breathing SCT. CONCLUSION: In our animal model, SCT can be performed during normal resting breathing without significant loss of accuracy in the detection of pulmonary metastases.

Animals↗
PubMed1997

Naturally occurring cancer in pet dogs: important models for developing improved cancer therapy for humans.

It has been said that "dog is man's best friend'. Comparative oncologists are demonstrating that pet dogs could hold the keys for advances in cancer treatment in people. Specific types of cancer that arise spontaneously in pet dogs could serve as important models of human cancer, having much greater similarity to their counterparts in humans than many currently used experimentally induced tumor models. In vivo models that are relevant to human cancer are greatly needed, particularly for evaluating new strategies for cancer therapy, such as augmentation of the immune system or blockade of the metastatic cascade. In addition, pet dogs could also be used to identify environmental carcinogens by acting as sentinels of cancer induced by these toxins.

Animals↗
PubMed1997

Comparative longevity of pet dogs and humans: implications for gerontology research.

The effect of breed and body weight on longevity in the pet dog was analyzed, and a method was developed to standardize the chronological age of dogs in terms of physiological time, using human year equivalents. Mortality data from 23,535 pet dogs were obtained from a computerized data base of North American veterinary teaching hospitals, and the median age at death was determined for pure and mixed breed dogs of different body weight. Body size in the dog was inversely related to longevity. Within each body weight category, the median age at death was lower for pure breed dogs compared with mixed breed dogs. The difference between the standardized physiological ages of mixed breed dogs of the same chronological age in the smallest and largest body weight categories varied from 8 to > 15 years, and between large and small pure breed dogs, the disparity was even greater. Laboratory research to explore the biological basis for these breed and body weight specific differences in life span among dogs may provide additional clues to genetic factors influencing senescence.

Aging↗
PubMed1997

Prostatic intraepithelial neoplasia occurs spontaneously in the canine prostate.

PURPOSE: Prostatic intraepithelial neoplasia (PIN) is the most likely precursor of human prostate cancer. Although the dog is the only non-human species in which spontaneous prostate cancer occurs frequently, the prevalence of PIN in the canine prostate is unknown. A naturally occurring animal model of PIN has not been described. MATERIALS AND METHODS: To determine if high grade PIN occurs spontaneously in the canine prostate, we evaluated totally embedded prostates from 35 outbred dogs that had no clinical evidence of prostatic disease. Prostates from three groups of dogs were analyzed: (1) 11 sexually intact dogs 7-17 years old (elderly sexually intact); (2) 13 sexually intact dogs 1-4 years old (young sexually intact); and (3) 11 dogs 7-17 years old that had been castrated (elderly castrated). The prevalence of PIN was determined by systematic evaluation of hematoxylin/eosin and high molecular weight keratin 34 beta-E12 stained tissue sections from formalin-fixed, paraffin embedded prostates that had been serially sectioned at 4 mm intervals. RESULTS: Canine high grade PIN showed cytologic features identical to the human counterpart, including cell crowding, loss of polarity, and nuclear and nucleolar enlargement. Foci of high grade PIN were present in the prostates of 6 of 11 (55%) elderly, sexually intact dogs but only 1 of 13 (8%) dogs less than 4 years old. Foci of high grade PIN were detected in 1 of 11 (9%) elderly castrated dogs. In elderly, sexually intact dogs with PIN, foci of high grade PIN were present in 13 of 83 (16%) tissue sections evaluated; one of these dogs had focal adenocarcinoma in addition to PIN. CONCLUSIONS: These results indicate that high grade PIN is frequently present in the prostate of elderly, sexually intact dogs. The prevalence of canine PIN, like human PIN, is apparently influenced by age and testicular androgens. The canine prostate may serve as a useful model to determine the factors that regulate the apparent progression from benign epithelium to PIN and invasive carcinoma.

Age Factors↗
PubMed1996

Transmission of human T cell leukemia virus type I to sheep: antibody profile and detection of viral DNA sequences.

Lambs were inoculated intraperitoneally with either 1.8 x 10(7) live peripheral blood cells from an HTLV-I-infected person (five lambs) or with 8 x 10(7) live cells from the HTLV-I-producing cell lines MT-2 (four lambs) or C10 MJ (five lambs). Four control lambs were inoculated with minimal essential medium supplemented with fetal calf serum. The animals were monitored during a period of 24 months. Beginning at 5 to 12 months after inoculation, four of the five lambs inoculated with the fresh HTLV-I-infected peripheral blood cells began to develop detectable levels of antibodies to a recombinant HTLV-I gp21env antigen, as determined by an enzyme-linked immunoassay (ELISA). The anti-gp21 antibodies persisted for the remaining observation period. These antibodies were not detected in the sera from the other sheep. Absorption and blocking experiments demonstrated the specificity of the gp21 reactivity. This reactivity was also confirmed by Western blot (WB). With the exception of the serum of an MT-2-inoculated sheep that formed a weak band with p19 by WB, none of the sera of the four gp21-positive sheep or of the other experimental sheep reacted with other structural or regulatory HTLV-I proteins, as determined by ELISA, WB, and radioimmunoassay. PCR analyses demonstrated the presence of the HTLV-I provirus in peripheral blood leukocytes of the four sheep showing antibodies to gp21env. The remaining sheep were negative. PCR analyses failed to detect BLV sequences in any of the experimental sheep. None of the sheep showed clinical abnormalities during the observation period. The potential value of the sheep model for studying atypical virus-host interactions in infected people is discussed.

Animals↗
PubMed1996

Tumor-selective radiopharmaceutical targeting via receptor-mediated endocytosis of gallium-67-deferoxamine-folate.

UNLABELLED: The receptor-mediated endocytosis uptake pathway for the vitamin folate was investigated as a target for tumor-selective radiopharmaceutical delivery. The molecular target for this delivery mechanism is a membrane-associated folate binding protein (FBP) that is overexpressed by a variety of malignant cell lines. METHODS: The ability of a 67Ga-labeled deferoxamine-folate conjugate (67Ga-DF-folate) to target tumor cells in vivo was examined using an athymic mouse tumor model. Subcutaneous inoculation of approximately 4 X 10(6) folate-receptor-positive KB (human nasopharyngeal carcinoma) cells into athymic mice yielded approximately 0.20 g tumors in 15 days, at which time either 67Ga-DF-folate, 67Ga-deferoxamine (67Ga-DF) or 67Ga-citrate was administered by intravenous injection. RESULTS: The 67Ga-DF-folate conjugate showed marked tumor-specific deposition in vivo, with 1.0 +/- 0.3% of the injected dose (%ID) in tumor at 4 hr postinjection (equating to 5.2 +/- 1.5 %ID/g tumor; n = 3 mice). Corresponding tumor-to-background ratios at 4 hr postinjection were: tumor/blood = 409 +/- 195; tumor/muscle = 124 +/- 47; tumor/liver = 11 +/- 3; and tumor/kidney = 2.6+/-0.9. Tumor uptake of 67Ga-DF-folate conjugate was effectively blocked by co-injection of 2.4+/-1.0 mg free folate. In control experiments, 67Ga-citrate exhibited tumor uptake of 2.2 +/- 0.4% of the injected dose (10.9 +/- 0.2 %ID/g tumor), but very poor target-to-background contrast (tumor/blood = 0.84 +/- 0.19; tumor/muscle = 5.4 +/- 0.7; tumor/liver = 2.3 +/- 0.2; and tumor/kidney = 2.4 +/- 0.3). Unconjugated 67Ga-deferoxamine showed no tumor affinity. CONCLUSION: Receptor-mediated endocytosis of radiolabeled folate-conjugates may offer a suitable mechanism for selectively delivering radiopharmaceuticals to tumors for diagnostic imaging and/or radiation therapy.

Animals↗
PubMed1995

Spontaneous metastasis of PC-3 cells in athymic mice after implantation in orthotopic or ectopic microenvironments.

The ability of subcutaneous, prostatic, and nonprostatic intraabdominal organ microenvironments to influence local tumor growth and metastasis of PC-3 human prostate carcinoma cells in athymic mice was determined. Tumorigenesis and metastasis of PC-3 were evaluated 60 days after subcutaneous and intraprostatic (orthotopic) implantation of 5 x 10(5) PC-3 cells in 6-week-old, male athymic mice. Intraprostatic implantation of PC-3 cells resulted in paraaortic lymph node metastases in 10 of 10 (100%) mice with prostatic tumors, whereas metastases were present in only 2 of 9 (22%) mice after subcutaneous implantation. Next, we determined whether the urinary bladder (nonprostatic, urogenital microenvironment) or stomach (nonurogenital, intraabdominal microenvironment) would facilitate the metastasis of PC-3 cells in athymic mice. Tumorigenesis and metastasis were 100% after subserosal implantation of PC-3 cells within the wall of the urinary bladder (n = 6 mice). Subserosal implantation of PC-3 cells into the stomach wall (n = 7 mice) also resulted in tumor formation and metastasis to regional lymph nodes in 100% of mice. In all experiments, regional lymph nodes were the most frequent site of metastasis, regardless of implantation site. We conclude that tumor microenvironment factors responsible for the metastasis of PC-3 cells in athymic mice may not be organ-specific, since nonprostatic visceral microenvironments are sufficient for predictable metastasis. Use of these models may further our understanding of how tumor microenvironment modulates expression of the metastatic phenotype by human prostate carcinoma cells.

Animals↗
PubMed1994

Portable cardiopulmonary bypass: resuscitation from prolonged ice-water submersion and asystole.

Accidental hypothermia associated with near-drowning and cardiac arrest has a high mortality, especially in the adult. We report the resuscitation of a 31-year-old man who suffered extended ice-water submersion, severe hypothermia (23 degrees C), and prolonged (> or = 78 minutes) cardiac asystole. A modified portable cardiopulmonary bypass system and femoral-femoral cannulation in the Emergency Department permitted the rapid institution of core rewarming, oxygenation, and controlled reperfusion, with a successful outcome. Rapid initiation of cardiopulmonary bypass outside the operating room can be an initial treatment option in this unique clinical situation.

Adult↗
PubMed1994

HTLV-I infection associated with disease in aboriginal Indians from British Columbia: a serological and PCR analysis.

BACKGROUND: Recent epidemiology studies have demonstrated the presence of HTLV-I and its close relative, HTLV-II in several aboriginal populations in North, Central and South America but not in Canadian Indian populations. HTLV-II appears to be more prevalent than HTLV-I in aboriginal populations of the Americas. Recently several clinical cases of HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) and a case of adult T-cell leukemia (ATL) have been identified in British Columbian Indians. This data suggests that a new endemic area of HTLV-I infection may be present within British Columbian Indian population. However, it has recently been shown that HTLV-II may also be associated with a neurological disease similar to HAM/TSP. OBJECTIVES: The purpose of the work reported here was to demonstrate whether HTLV-I, HTLV-II or both were responsible for the diseases seen in the British Columbian Indians. STUDY DESIGN: In this study serological and gene amplification techniques were used to determine whether HTLV-I or HTLV-II was present in four families and three unrelated individuals all from different bands of aboriginal Native Indians in British Columbia. In each family, one member had an HTLV-associated disease, three cases of HAM/TSP and one case of ATL. Of the three individual aboriginal natives unrelated to the four families, two had HAM/TSP while the third was asymptomatic for HTLV-associated diseases. RESULTS: This study demonstrated the presence of HTLV-I in the aboriginal Indians with disease and in some of their family members. HTLV-II was not detected in any of the British Columbian Indians tested in this study. CONCLUSIONS: These British Columbian Indians represent the first Canadian aboriginal Indians with HTLV-I infection and associated diseases. Furthermore, the British Columbian Indian population may represent a previously unrecognized endemic population of HTLV-I infection.

Journal Article↗
PubMed1994

Endemic transmission of HTLV type II among Kayapo Indians of Brazil.

Serological studies on 926 blood samples from 703 Brazilian Kayapo (Cayapo) Indians showed, by conventional definition of HTLV seropositivity, a 28% prevalence of human T lymphotropic virus (HTLV) infection, the highest yet reported. Immunoblot (WB) and SYNTH-EIA patterns indicate that the predominant infecting agent is type II. Of children under 15 years old, 12% were positive, and of persons over 60, more than 60%. Perinatal and heterosexual modes of transmission offer an adequate explanation of this incidence. Infection in infancy may include infection via breast milk from women other than the mother. Evidence of new infection in adults is apparent at an earlier age in women than in men. This pattern of antibody prevalence was not determined by cohort effects, as demonstrated by tests of serial specimens. Enzyme immunosorbent assay (EIA) absorbencies were not stable in the paired specimens: five serum pairs reverted and mean absorbencies declined over some age ranges. Many specimens with relatively high, but less than positive, EIA results were positive by immunoblot (WB). This suggests that the standard EIA end point does not identify all infected persons. If the WB alone indicates positivity, 47% of the whole population, and more than 80% of the older age groups, are infected with HTLV-II.

Adolescent↗
PubMed1993

Saphenous vein preparation for coronary artery bypass grafting using a cardioplegia delivery set.

Many techniques of saphenous vein preparation for coronary artery bypass grafting and their relation to endothelial preservation and graft patency have been published. We describe a method for final preparation of saphenous vein segments that uses the patient's undiluted heparinized blood infused at physiologic arterial pressure with a standard cardioplegia delivery apparatus. This method provides excellent demonstration of vein caliber and allows for quick identification and control of any previously undetected side branches or leaks. No additional equipment or instruments are required, and preparation can be performed before or after the institution of cardiopulmonary bypass.

Coronary Artery Bypass↗