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T Hammond

Publications and source records attributed to T Hammond.

18 recordsLinked to original sources
PubMed2006

Prevalence of equine herpesvirus type 2 (EHV-2) DNA in ocular swabs and its cell tropism in equine conjunctiva.

Equine herpes virus 2 (EHV-2), a gamma(2)-herpesvirus, is common in horses of all ages. Its role as a primary pathogen is unclear but there is an association between EHV-2, respiratory disease and keratoconjunctivitis. The purpose of this study was to gain more information on the prevalence of EHV-2 DNA in conjunctival swabs from horses with and without ocular disease and to define the anatomical site and cell type harbouring viral genome or antigen. By polymerase chain reaction (PCR) 22 out of 77 (28.6%) ocular swabs of clinically healthy and only 4 out of 48 (8.3%) samples from diseased horses were positive. To define the main virus reservoir ocular tissue from 13 randomly selected horses without pathological evidence of ocular disease were analysed by nested PCR. In two horses optic nerve, lacrimal gland and conjunctiva, in further two cases lacrimal gland and conjunctiva and in four horses the conjunctiva only were EHV-2 PCR positive. For specifying the target cell we focused on conjunctivae and selected 3 out of 15 clinically healthy slaughterhouse horses positive for EHV-2 by PCR. In situ hybridisation on sections of these paraffin embedded conjunctivae localized viral genome in histiocyte-like cells of the submucosa. Immunohistochemical staining with an EHV-2 or S100 specific polyclonal antiserum demonstrated that Langerhans cells were co-localized in the same region of the sample section where virus positive cells were detected. Furthermore, we concluded that detection of viral antigen revealed a productive virus infection.

Animals↗
PubMed2001

Bone marrow micronucleus assay in Brown-Norway rats exposed to diphenyl-methane-4,4'-diisocyanate.

Four groups of young adult male Brown-Norway rats (strain: BN/RijHsd) were either exposed whole-body (WB) to filtered air (negative control) or to respirable aerosols of monomeric diphenylmethane-4,4'-diisocyanate (MDI) at actual breathing zone concentrations of 9.2 +/- 1.5 and 118 +/- 8.6 mg/m3. One additional group was exposed to 11,0 +/- 14.4 mg/m3 MDI using a nose-only (NO) mode. Exposure was 1 h/day, one exposure per week on 3 consecutive weeks. MDI aerosols were generated using either a condensation (WB) or a dispersion-condensation (NO) principle with resultant MMADs of 2.4-3.1 microm and 1.2 microm (GSD approximately l.5), respectively. Humidity ranged from approximately 40% (WB) to approximately 5% (NO). Positive controls received cyclophosphamide and colcemid. Micronuclei in polychromatic erythrocytes (MN-PCE) were counted in bone marrow smears prepared after the final exposure on post-exposure days 1, 2 and 7 and stained with acridine orange or Wright-Giemsa. Both the WB-exposure regimen and the 7-day sampling time point were based upon a previous study in which a significant increase in MN-PCE was reported to occur. Rats exposed to 118 (WB) and 110 mg/m3 MDI (NO) exhibited signs of respiratory distress, including hypothermia, and increased lung weights when compared to WB-exposed rats. The intensity of changes appeared to be slightly more pronounced in NO-exposed rats. At no time point did this study provide any evidence of an MDI-induced effect on the frequency of MN-PCE. No differences in outcome existed following staining with acridine orange or Wright-Giemsa. There was an absence of any effect on the frequency of mast cells and their frequency was low enough not to interfere with the outcome of study. Positive control groups exhibited significant increases in MN-PCE. In summary, monomeric MDI aerosol did not induce cytogenetic damage in Brown-Norway rats when investigated according to current testing guidelines.

Aerosols↗
PubMed2001

Three-dimensional tissue assemblies: novel models for the study of Salmonella enterica serovar Typhimurium pathogenesis.

The lack of readily available experimental systems has limited knowledge pertaining to the development of Salmonella-induced gastroenteritis and diarrheal disease in humans. We used a novel low-shear stress cell culture system developed at the National Aeronautics and Space Administration in conjunction with cultivation of three-dimensional (3-D) aggregates of human intestinal tissue to study the infectivity of Salmonella enterica serovar Typhimurium for human intestinal epithelium. Immunohistochemical characterization and microscopic analysis of 3-D aggregates of the human intestinal epithelial cell line Int-407 revealed that the 3-D cells more accurately modeled human in vivo differentiated tissues than did conventional monolayer cultures of the same cells. Results from infectivity studies showed that Salmonella established infection of the 3-D cells in a much different manner than that observed for monolayers. Following the same time course of infection with Salmonella, 3-D Int-407 cells displayed minimal loss of structural integrity compared to that of Int-407 monolayers. Furthermore, Salmonella exhibited significantly lower abilities to adhere to, invade, and induce apoptosis of 3-D Int-407 cells than it did for infected Int-407 monolayers. Analysis of cytokine expression profiles of 3-D Int-407 cells and monolayers following infection with Salmonella revealed significant differences in expression of interleukin 1alpha (IL-1alpha), IL-1beta, IL-6, IL-1Ra, and tumor necrosis factor alpha mRNAs between the two cultures. In addition, uninfected 3-D Int-407 cells constitutively expressed higher levels of transforming growth factor beta1 mRNA and prostaglandin E2 than did uninfected Int-407 monolayers. By more accurately modeling many aspects of human in vivo tissues, the 3-D intestinal cell model generated in this study offers a novel approach for studying microbial infectivity from the perspective of the host-pathogen interaction.

Apoptosis↗
PubMed1999

ANIT-induced disruption of biliary function in rat hepatocyte couplets.

alpha-Naphthylisothiocyanate (ANIT) induces intrahepatic cholestasis in rats, involving damage to biliary epithelial cells; our study aims to investigate whether disruption of biliary function in hepatocytes can contribute to early stages of ANIT-induced intrahepatic cholestasis. Isolated rat hepatocyte couplets were used to investigate biliary function in vitro by canalicular vacuolar accumulation (cVA) of a fluorescent bile acid analogue, cholyl-lysyl-fluorescein (CLF), within the canalicular vacuole between the two cells. After a 2-h exposure to ANIT, there was a concentration-dependent inhibition of cVA (cVA-IC50; 25 microM), but no cytotoxicity (LDH leakage or [ATP] decline) within this ANIT concentration range. There was no loss of cellular [GSH] at low ANIT concentrations, but, at 50 microM ANIT, a small but significant loss of [GSH] had occurred. Diethylmaleate (DEM) partially depleted cellular [GSH], but addition of 10 microM ANIT had no further effect on GSH depletion. Reduction in cVA was seen in DEM-treated cells; addition of ANIT to these cells reduced cVA further, but the magnitude of this further reduction was no greater than that caused by ANIT alone, indicating that glutathione depletion does not enhance the effect of ANIT. F-actin distribution (by phalloidin-FITC staining) showed an increased frequency of morphological change in the canalicular vacuoles but only a small, non-significant (0.05 < p < 0.1) increase in proportion of the F-actin in the region of the pericanalicular web. The results are in accord with a disruption of hepatocyte canalicular secretion within two h in vitro, at low, non-cytotoxic concentrations of ANIT, and the possible involvement of a thiocabamoyl-GSH conjugate of ANIT (GS-ANIT) in this effect.

1-Naphthylisothiocyanate↗
PubMed1998

Inhibition of nuclear factor-kappaB-mediated adhesion molecule expression in human endothelial cells.

The transcriptional regulatory protein nuclear factor-kappaB (NF-kappaB) participates in the control of gene expression of many modulators of the inflammatory and immune responses, including the adhesion molecules E-selectin and intercellular adhesion molecule-1 (ICAM-1). NF-kappaB is found in the cytoplasm complexed with its inhibitory protein IkappaB. On activation, IkappaB is phosphorylated and degraded, thereby freeing NF-kappaB for translocation to the nucleus. We have generated populations of endothelial cells expressing wild-type and a proteolysis-resistant mutation of IkappaB that is lacking the 36 N-terminal amino acids (IkappaBdeltaN) in order to examine the effects of expression of the mutated IkappaB on tumor necrosis factor-alpha (TNF-alpha)-induced E-selectin and ICAM-1 expression. Wild-type and IkappaBdeltaN were introduced into primary endothelial cells using retrovirus infection followed by selection with G418. The IkappaBdeltaN protein remained at untreated control levels in endothelial cells treated with TNF-alpha and also remained complexed with the NF-kappaB family member p65. Furthermore, TNF-alpha-induced NF-kappaB DNA binding activity was inhibited in the population of endothelial cells expressing IkappaBdeltaN. That population of cells was also refractory to upregulation of E-selectin and ICAM-1 after treatment with TNF-alpha. The use of a truncated IkappaBalpha protein to prevent NF-kappaB-mediated gene expression provides a novel and specific approach for investigating the role of NF-kappaB in processes associated with adhesion molecule expression during inflammation.

Cell Adhesion Molecules↗
PubMed1998

Alveolar macrophage apoptosis and TNF-alpha, but not p53, expression correlate with murine response to bleomycin.

Apoptosis is considered to be a protective mechanism that limits lung injury. However, apoptosis might contribute to the inflammatory burden present in the injured lung. The exposure of mice to bleomycin (BLM) is a well-established model for the study of lung injury. BLM exposure induces DNA damage and enhances tumor necrosis factor (TNF)-alpha expression in the lung. To evaluate the importance of alveolar macrophage (AM) apoptosis in the pathogenesis of lung injury, we exposed BLM-sensitive (C57BL/6) and BLM-resistant (BALB/c) mice to BLM (120 mg/kg) and studied the induction of apoptosis [by light-microscopy changes (2, 8, 12, 24, 48, and 72 h) and annexin V uptake by flow cytometry (24 h)], the secretion of TNF-alpha (measured by ELISA), and the expression of p53 (by immunoblotting) in AM retrieved from these mice. BLM, but not vehicle, induced apoptosis in AM from both murine strains. The numbers of apoptotic AM were significantly greater (P < 0.001) in C57BL/6 mice (52.9%) compared with BALB/c mice (40.8%) as demonstrated by annexin V uptake. BLM induction of apoptosis in AM was preceded by an increased secretion of TNF-alpha in C57BL/6 but not in BALB/c mice. Furthermore, double TNF-alpha receptor-deficient mice, developed on a C57BL/6 background, demonstrated significantly (P < 0.001) lower numbers of apoptotic AM compared with C57BL/6 and BALB/c mice. BLM also enhanced p53 expression in AM from both murine strains. However, p53-deficient mice developed BLM-induced lung injury, exhibited similar lung cell proliferation (measured as proliferating cell nuclear antigen immunostaining), and accumulated similar amounts of lung hydroxyproline (65 +/- 6.9 microgram/lung) as did C57BL/6 (62 +/- 6.5 microgram/lung) mice. Therefore, AM apoptosis is occurring during BLM-induced lung injury in a manner that correlates with murine strain sensitivity to BLM. Furthermore, TNF-alpha secretion rather than p53 expression contributes to the difference in murine strain response to BLM.tumor necrosis factor; strain susceptibility

Animals↗
PubMed1996

Cloning of an aquaporin homologue present in water channel containing endosomes of toad urinary bladder.

Regulation of total body water balance in amphibians by antidiuretic hormone (ADH) contributed to their successful colonization of terrestrial habitats approximately 200-300 million years ago. In the mammalian kidney, ADH modulates epithelial cell apical membrane water permeability (Pf) by fusion and retrieval of cytoplasmic vesicles containing water channel proteins called aquaporins (AQPs). To determine the role of AQPs in ADH-elicited Pf in amphibians, we have identified and characterized a unique AQP from Bufo marinus called AQP toad bladder (AQP-TB). AQP-TB possesses many structural features common to other AQPs, AQP-TB is expressed abundantly in ADH-responsive tissues, including toad urinary bladder and skin as well as lung, skeletal muscle, kidney, and brain. In a manner identical to that reported for the mammalian ADH-elicited water channel AQP2, AQP-TB expression is increased significantly by intervals of dehydration or chronic ADH stimulation. However, expression of AQP-TB protein in Xenopus laevis oocytes does not significantly increase oocyte Pf. The lack of expression of functional AQP-TB water channels in oocytes may result from intracellular sequestration of AQP-TB due to the presence of a YXRF sequence motif present in its carboxyterminal domain.

Amino Acid Sequence↗
PubMed1996

Immunocytochemical study of proteoglycans in vocal folds.

We evaluated the proteoglycan composition of normal vocal folds using immunocytochemical techniques. Frozen sections of 14 normal cadaveric vocal folds were obtained within 12 hours of death and sectioned immediately. Vocal fold sections were stained with antibodies against keratan sulfate, chondroitin sulfate, heparan sulfate proteoglycan (HSPG), decorin, and hyaluronate receptor. We found that the lamina propria has diffuse staining of fibrillar components with keratan sulfate and decorin. Intense staining was observed in the vocal ligament area with keratan sulfate. The HSPG was localized to be basement membrane zone. Chondroitin sulfate, HSPG, and hyaluronate receptor were detected in the cytoplasm of interstitial cells with immunocytochemical characteristics of macrophages. The keratan sulfate distribution suggests that fibromodulin may be significant in normal vocal folds. Production of HSPG and probably versican occurs in macrophages and fibroblasts in the lamina propria.

Chondroitin Sulfate Proteoglycans↗
PubMed1994

Experimental basis for separation of membrane vesicles by preparative free-flow electrophoresis.

In practice it has been possible to separate membrane particles of different origins but of similar chemical composition by preparative free-flow electrophoresis. Examples include the vacuolar (tonoplast) and plasma membranes of plants and membranes derived from the cis and trans regions of the rat liver Golgi apparatus. Yet, when analyzed for intrinsic molecules that might contribute to significant differences in surface charge, the separated membranes were surprisingly similar. As more information was generated, it became apparent that the membranes with greatest electrophoretic mobility (i.e. lysosomes, rightside-out tonoplast vesicles and membranes from the trans region of the Golgi apparatus), where those membranes with an inherent ability to acidify their interiors. By so doing, the vesicles generate a membrane potential, negative outside, which might serve as a basis for enhanced electrophoretic mobility. To test the hypothesis, tonoplast membranes were incubated with ATP to drive proton import or with monensin to dissipate the ATP-supported proton gradient. With ATP, mobility was enhanced. Also, when ATP-treated vesicles were analyzed in the presence of monensin, the ATP effect on mobility was reversed. Similarly with Golgi apparatus, mobility of the most electrophoretically mobile portions of the separation was enhanced by ATP and the ATP effect was reversed with monensin. A trans origin of the vesicles was verified by assay of the trans Golgi apparatus marker, thiamine pyrophosphatase. Finally, incubation with ATP (and reversal by monensin) was employed as an aid to the free-flow electrophoretic separation of kidney endosomes from complex mixtures. These lysosomal derivatives also are capable of acidification of their interiors in an ATP-dependent process and of generating, at the same time, a negative (outside) membrane potential. The findings provide both an experimental basis to enhance membrane separations by preparative free-flow electrophoresis and, at the same time, a theoretical basis to help explain why certain membranes of very similar overall chemical composition may be separated by electrophoretic methods.

Adenosine Triphosphatases↗
PubMed1992

Fabrication of an obstructive sleep apnea prosthesis.

Obstructive sleep apnea, a sleep disorder, is becoming more prevalent and requires prompt and effective treatment by the dental and medical specialties. Conservative treatment modalities (ie, intraoral devices that prevent or minimize airway obstruction by the tongue) are recommended for treating mild to moderate forms of OSA. This article describes a simplified technique for fabricating an intraoral OSA prosthesis.

Humans↗
PubMed1992

Functional and structural characterization of endosomes from toad bladder epithelial cells.

Previous functional studies of toad bladder endosomes have been complicated by the presence of multiple endosome subpopulations each possessing different permeability characteristics. To identify and characterize both water channel-containing vesicles (WCV) and other endosome subpopulations, we combined flow cytometry, electron microscopy, stop-flow fluorometry, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Flow cytometry of endosomes identified distinct populations of fluorescein-labeled endosomes in bladders after removal of antidiuretic hormone (ADH) stimulation (ADH withdrawal). Centrifugation separated the larger fluorescein-labeled vesicles, sedimenting at lower speed (intermediate pellet, IP), from the smaller fluorescein-labeled vesicles, sedimenting at high speed (high-speed pellet, HSP). Permeability and structural studies of these subpopulations revealed the following. 1) IP endosomes labeled 10 min after ADH withdrawal (ADH IP) represented a highly purified population of WCV with high water permeability (Pf) that exhibited a low-activation energy and sensitivity to organic mercurials. 2) IP endosomes from unstimulated bladders did not contain functional water channels. 3) HSP from either ADH withdrawal or unstimulated bladders exhibited low Pf and acidified after addition of extravesicular ATP; moreover, protein compositions of purified HSP were distinct from those of purified IP. These results suggest that HSPs represent constitutive and not ADH-sensitive endosomes. 4) High permeability to protons (PH+) was seen in ADH IP endosomes but not the other fractions, providing strong evidence that the ADH water channel conducts protons. 5) Multivesicular bodies (MVB) exhibited low Pf and PH+, indicating that they do not possess functional water channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The effect of exercise on bone mass of osteoporotic patients on fluoride treatment.

The study was conducted in order to determine the effect of exercise on osteoporotic patients with a mean age of 65 years. The majority of these patients had been on sodium fluoride for at least 2 years. Thirty-eight patients were assigned to either the hospital or home group. Nineteen were in the former group, which performed the 1 hour exercise twice weekly in the Hospital. The patients in the latter group were taught the exercises and were expected to continue them at home. The exercise protocol consisted of muscle-strengthening and aerobic activities. Bone mineral mass was determined by neutron activation analysis, which measured total calcium in the trunk and pelvis. It is expressed as a calcium bone index (CaBI), with a normal range of 0.75 to 1.2. The level of physical performance was determined by calculating the maximum oxygen uptake, VO2max, attained by a graded exercise test on the treadmill. Calcium bone index and VO2max were obtained before and after the 12.5 month study. Prior to the study, the hospital and home groups had low calcium bone index values (0.68 and 0.66 respectively). Both groups showed a significant increase in calcium bone index (p less than 0.001 for the hospital group, p less than 0.01 for the home group) after the study. When compared to the home group the hospital group was found to have a significantly higher post-study calcium bone index value (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Nuchal cords and neonatal outcome.

To assess the significance of nuchal cords, 110 affected woman-infant pairs at term gestation were compared with 110 control pairs. Newborns with a nuchal cord had an increased prevalence of umbilical artery acidemia (22 of 110 versus 13 of 110; P less than .05) and more variable fetal heart rate (FHR) decelerations in the first stage of labor (mild = 41 versus 20; P less than .0001; moderate-severe = 21 versus 5; P less than .0001) and the second stage of labor (moderate-severe = 46 versus 21; P less than .0001). In newborns with a nuchal cord, the umbilical artery acidemia was usually mixed (68%) or respiratory (23%) in origin, and pure metabolic acidemia was infrequent (9%). We conclude that nuchal cords are associated with an increased prevalence of variable FHR decelerations in the first and second stages of labor and with an increased incidence of umbilical artery acidemia.

Acidosis, Respiratory↗