Biomedical subjects

D L Williams

Publications and source records attributed to D L Williams.

At least 109 records · Page 6Linked to original sources

PubMed1998

Lacrimal pseudotumour in a young bull terrier.

An inflammatory mass arising from the lower lacrimal canaliculus of unknown cause is reported in a dog. A 10-month-old Staffordshire bull terrier was presented with a history of epiphora and a red mass protruding from the left lower lacrimal punctum. The tissue was removed and histopathological examination of the lesion revealed a mass of highly vascularised granulation tissue with areas of epithelial ulceration and multiple stromal haemorrhages. Fibrosis and collagen deposition were evident as was a cellular infiltrate composed primarily of neutrophils and plasma cells. Regrowth necessitated further attempts at complete excision before a permanent cure was achieved.

Animals↗

PubMed1998

Contribution of rpoB mutations to development of rifamycin cross-resistance in Mycobacterium tuberculosis.

The contributions of 23 insertion, deletion, or missense mutations within an 81-bp fragment of rpoB, the gene encoding the beta-subunit of the DNA-dependent RNA polymerase of Mycobacterium tuberculosis, to the development of resistance to rifamycins (rifampin, rifabutin, rifapentine, and KRM-1648) in 29 rifampin-resistant clinical isolates were defined. Specific mutant rpoB alleles led to the development of cross-resistance to all rifamycins tested, while a subset of mutations were associated with resistance to rifampin and rifapentine but not to KRM-1648 or rifabutin. To further study the impact of specific rpoB mutant alleles on the development of rifamycin resistance, mutations were incorporated into the rpoB gene of M. tuberculosis H37Rv, contained on a mycobacterial shuttle plasmid, by in vitro mutagenesis. Recombinant M. tuberculosis clones containing plasmids with specific mutations in either codon 531 or 526 of rpoB exhibited high-level resistance to all rifamycins tested, whereas clones containing a plasmid with a mutation in codon 516 exhibited high-level resistance to rifampin and rifapentine but were susceptible to both rifabutin and KRM-1648. These results provided additional proof of the association of specific rpoB mutations with the development of rifamycin resistance and corroborate previous reports of the usefulness of rpoB genotyping for predicting rifamycin-resistant phenotypes.

Anti-Bacterial Agents↗

PubMed1998

Inducible expression of protein kinase Calpha suppresses steroidogenesis in Y-1 adrenocortical cells.

We have previously shown that protein kinase C (PKC) suppresses steroidogenesis in Y-1 adrenocortical cells. To ask directly if the PKCalpha isoform mediates this suppression, we have developed Y-1 cell lines in which PKCalpha is expressed from a tetracycline-regulated promoter. Induction of PKCalpha expression in these cell lines results in decreased P450 cholesterol side-chain cleavage enzyme (P450-SCC) activity as judged by the conversion of hydroxycholesterol to pregnenolone. Transcription of a P450-SCC promoter-luciferase construct is also reduced when PKCalpha expression is increased. However, expression of PKCalpha has no effect on 8-bromo-cAMP induction of steroidogenesis, indicating that these pathways function independently to regulate steroidogenesis. To determine the relationship between endogenous PKC activity and steroidogenesis, we examined 12 Y-1 subclones that were isolated by limited dilution cloning. In each of these subclones, steroid production correlates inversely with total PKC activity and with the expression of PKCalpha but not PKCepsilon or PKCzeta. These studies define for the first time the role of a specific PKC isoform (PKCalpha) in regulating steroidogenesis and P450-SCC activity in adrenocortical cells.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1998

Expression and microvillar localization of scavenger receptor, class B, type I (a high density lipoprotein receptor) in luteinized and hormone-desensitized rat ovarian models.

Steroidogenic cells in rats and mice obtain most of their cholesterol for steroid production and cholesteryl ester (CE) storage via the selective uptake pathway in which high density lipoprotein CE (HDL-CE) is taken into the cell without the uptake and degradation of the HDL particle. A number of recent studies show that the scavenger receptor, class B, type I (SR-BI) can mediate HDL-CE selective uptake in cultured cells and suggest that this receptor may be responsible for HDL-CE selective uptake in steroidogenic cells in vivo. In the current study we examine the relationship between SR-BI expression and HDL-CE selective uptake in the gonadotropin-primed, luteinized rat ovary and in the ovary that is desensitized by multiple gonadotropin treatments. Results from this study demonstrate a tight association between expression of SR-BI and measurements of HDL-CE selective uptake regardless of the steroidogenic state of the ovary. Thus, in the luteinized ovary (which is actively producing progestins), HDL-CE selective uptake is high, as is the expression of SR-BI. In the desensitized ovary (where CE content is reduced by 90% and progestin production is virtually absent), HDL-CE selective uptake and SR-BI are induced 2- to 3-fold compared with those in the luteinized ovary. These data argue that SR-BI can be regulated by the cholesterol status of the luteal cell independently of gonadotropic stimulation. Immunostaining at the light microscopic level showed strong expression of SR-BI specifically on the surface of luteal cells in the luteinized and desensitized ovary. Immunolocalization at the electron microscopic level showed that SR-BI was associated with microvilli and microvillar channels of the luteal cell surface. This result supports the hypothesis that microvilli and microvillar channels represent a cell surface compartment that is specialized for the selective uptake of lipoprotein cholesterol into steroidogenic cells.

Animals↗

PubMed1998

Adenovirus-mediated inducible nitric oxide synthase gene transfer inhibits hepatocyte apoptosis.

BACKGROUND: Apoptosis limits hepatocyte viability in bioartificial livers in vitro and may contribute to liver dysfunction in vivo. Nitric oxide (NO) inhibits hepatocyte apoptosis; however, methods to deliver NO in a sustained manner to hepatocytes are limited. Here, we tested the feasibility of inducible NO synthase (iNOS) gene transfer as an approach to deliver an intracellular source of NO to inhibit spontaneous and tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis in cultured hepatocytes. METHODS: An adenoviral vector carrying the human iNOS gene (AdiNOS) was used to overexpress iNOS in cultured rat hepatocytes. Spontaneous apoptosis was induced by prolonged culture (4 days), and stimulated apoptosis was induced by exposure to TNF-alpha + actinomycin D (TNF-alpha ActD). Nitrite (NO2-), cell viability, and cellular caspase-3-like protease activity were measured. RESULTS: AdiNOS gene transfer resulted in sustained NO production and protected hepatocytes from spontaneous and TNF-alpha + ActD-induced apoptosis. Apoptosis was associated with increases in caspase-3-like protease activity, which was suppressed by iNOS gene transfer in an NO-dependent manner. Dithiothreitol partially reversed the NO-induced suppression of caspase-3-like activity, which is consistent with S-nitrosylation of caspase-3. CONCLUSIONS: Adenovirus-mediated iNOS gene transfer effectively blocks spontaneous and TNF-alpha + ActD-induced cell killing in hepatocytes. iNOS gene transfer could be used to suppress apoptotic hepatocyte death in vitro and possibly in vivo.

Adenoviridae↗

PubMed1997

Scavenger receptor class B, type I (SR-BI) is the major route for the delivery of high density lipoprotein cholesterol to the steroidogenic pathway in cultured mouse adrenocortical cells.

The class B, type I scavenger receptor, SR-BI, binds high density lipoprotein (HDL) and mediates the selective uptake of HDL cholesteryl ester (CE) by cultured transfected cells. The high levels of SR-BI expression in steroidogenic cells in vivo and its regulation by tropic hormones provides support for the hypothesis that SR-BI is a physiologically relevant HDL receptor that supplies substrate cholesterol for steroid hormone synthesis. This hypothesis was tested by determining the ability of antibody directed against murine (m) SR-BI to inhibit the selective uptake of HDL CE in Y1-BS1 adrenocortical cells. Anti-mSR-BI IgG inhibited HDL CE-selective uptake by 70% and cell association of HDL particles by 50% in a dose-dependent manner. The secretion of [3H]steroids derived from HDL containing [3H]CE was inhibited by 78% by anti-mSR-BI IgG. These results establish mSR-BI as the major route for the selective uptake of HDL CE and the delivery of HDL cholesterol to the steroidogenic pathway in cultured mouse adrenal cells.

Adrenal Cortex↗

PubMed1997

Targeting nitric oxide (NO) delivery in vivo. Design of a liver-selective NO donor prodrug that blocks tumor necrosis factor-alpha-induced apoptosis and toxicity in the liver.

We have designed a drug that protects the liver from apoptotic cell death by organ-selective pharmacological generation of the bioregulatory agent, nitric oxide (NO). The discovery strategy involved three steps: identifying a diazeniumdiolate ion (R2N[N(O)NO]-, where R2N = pyrrolidinyl) that spontaneously decomposes to NO with a very short half-life (3 s) at physiological pH; converting this ion to a series of potential prodrug derivatives by covalent attachment of protecting groups that we postulated might be rapidly removed by enzymes prevalent in the liver; and screening the prodrug candidates in vitro and in vivo to select a lead and to confirm the desired activity. Of five cell types examined, only cultured hepatocytes metabolized O2-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO) to NO, triggering cyclic guanosine 3',5'-monophosphate (cGMP) synthesis and protecting the hepatocytes from apoptotic cell death induced by treatment with tumor necrosis factor-alpha (TNF alpha) plus actinomycin D. In vivo, V-PYRRO/NO increased liver cGMP levels while minimally affecting systemic hemodynamics, protecting rats dosed with TNF alpha plus galactosamine from apoptosis and hepatotoxicity. The results illustrate the potential utility of diazeniumdiolates for targeting NO delivery in vivo and suggest a possible therapeutic strategy for hepatic disorders such as fulminant liver failure.

Animals↗

PubMed1997

Nitrosating agents: is peroxynitrite a likely candidate?

The reagents capable of effecting electrophilic and free radical nitrosation are briefly reviewed, together with the appropriate mechanisms, and in the light of these findings the possibilities of peroxynitrite/peroxynitrous acid acting as a nitrosating species are considered. The conclusion is that it is not to be expected that conventional direct nitrosation would occur. However, the very low yields of some nitrosation products can be accounted for in terms of nitrosation via the nitrogen oxide decomposition products of peroxynitrite. Thus NO could react with a radical substrate, or be converted to N2O3 (a well-known nitrosating species), whereas NO2 if formed can nitrosate via N2O4. A short post-script is added reviewing the Cu+-mediated reaction of S-nitrosothiols, generating (at low [thiol]) nitric oxide.

Copper↗

PubMed1997

Evolving costs of long-term left ventricular assist device implantation.

BACKGROUND: To examine the long-term costs of implanting a left ventricular assist device, we reviewed the initial hospitalization and outpatient costs for 12 patients who received a vented electric left ventricular assist device, and projected the first-year costs. METHODS: We used the ratio-of-cost-to-charges method to measure hospital costs and payments for physician time. We examined time trends in the resource use of 50 pneumatic left ventricular assist device recipients, using actuarial techniques and regression modeling. RESULTS: The average actual cost of left ventricular assist device support is $221,313 over an average of 9.5 months. If there had been no Food and Drug Administration regulatory policy precluding hospital discharge before 30 days, this value would have been $201,148. Based on this latter figure, the average predicted first-year cost is $219,139. The length of the intensive care unit stay, one of the most costly components of care, decreased significantly over time. CONCLUSIONS: The high costs of left ventricular assist device implantation are similar to those reported for cardiac transplantation. Given their success in supporting survival, we anticipate that these devices will be similarly cost-effective. However, further research is imperative to determine the cost-effectiveness of these devices beyond the introductory phase, when costs, benefits, and Food and Drug Administration requirements have stabilized.

Actuarial Analysis↗

PubMed1997

Quality of life with an implanted left ventricular assist device.

BACKGROUND: With the increasing use of left ventricular assist devices (LVADs) for longer-term support of patients awaiting cardiac transplantation, we must now consider whether to use these devices as alternatives to medical therapy when biologic hearts are needed but not forthcoming. This expansion of use depends as much on quality of life as it does on survival. To draw an inference about long-term quality of life with implanted LVADs, we studied "bridged" patients at our institution. METHODS: We elicited, by standard gamble, the utilities (preferences) of bridged patients at three points in their care: before LVAD implantation, during LVAD support, and after cardiac transplantation. RESULTS: Utility was 0.548 (+/-0.276) before implantation, 0.809 (+/-0.136) during LVAD support, and 0.964 (+/-0.089) after transplantation. For patients interviewed during all three states of health, the utilities were significantly different (p = 0.0009 by analysis of variance). CONCLUSIONS: The quality of life with an LVAD was substantially better than with medical therapy, on par with renal transplantation (as established by others), and not as good as after cardiac transplantation. These results portend an acceptable quality of life for long-term use of LVADs for patients with end-stage heart failure and contribute to the growing body of evidence supporting a clinical trial to test this new use.

Female↗

PubMed1997

Studies of canine leucocyte antigens: a significant advance in canine immunology.

The Canine Leucocyte Antigen Workshop (CLAW) was set up to produce and circulate monoclonal antibodies directed against cell surface molecules defining specific leucocyte cell types in the dog. The antibodies produced by the workshop have been used in studies of the canine immune system. While many similarities between the dog and other animals have been demonstrated, workshop studies have identified some anomalies in this species: CD4 antigen for example is expressed not only on helper/inducer T-lymphocytes but also at high density on canine neutrophils. Workshop antibodies have been used to investigate lymphocyte populations in the normal dog and in a range of diseases from lymphocytic neoplasms through conditions with an immune-mediated component such as Leishmaniasis to potentially autoimmune disorders such as rheumatoid arthritis and chronic superficial keratitis.

Animals↗

PubMed1997

A comparative approach to topical cyclosporine therapy.

Topical cyclosporine has been used by veterinary ophthalmologists since 1989 for the treatment of ocular surface inflammatory disease and keratoconjunctivitis sicca (KCS). As well as ameliorating clinical signs of ocular surface lymphocyte-driven inflammation in the dog, cat and horse, topical cyclosporine significantly raises tear production in both normal and KCS-affected animals. A licensed ointment preparation of 0.2% cyclosporine, Optimmune (Schering-Plough), is now available for administration to dogs. In this paper we examine the mechanisms by which cyclosporine exerts both its immunomodulatory and its lacrimogenic actions. The pharmacokinetics of topical cyclosporine are examined to determine whether these effects are truly local or are influenced by generalised immunosuppression caused by systemic absorption of topically applied drug. The paper reviews the few side effects of cyclosporine preparations in the experience of veterinary ophthalmologists and the experimental evidence which appears to implicate the vehicle rather than the active agent cyclosporine as causing many of these effects. Given that topical cyclosporine has been so widely accepted as a valuable ophthalmic preparation in the veterinary world and licensed as such, it is surprising that human ophthalmologists have not employed the drug to the same extent for conditions from vernal keratoconjunctivitis to Sjögren's syndrome.

Administration, Topical↗

PubMed1997

PCR identification of Mycobacterium bovis BCG.

The attenuated bacillus Calmette-Guérin (BCG) vaccine strain is derived from a virulent strain of Mycobacterium bovis. BCG is difficult to differentiate from other strains of M. bovis and other members of the M. tuberculosis complex by conventional methods. Recently, a genomic region designated RD1 was found to be present in all virulent M. bovis and M. tuberculosis strains tested but deleted from all BCG strains tested. With this information, a multiplex PCR method was developed to detect the RD1 deletion. A large collection of BCG and other M. tuberculosis complex strains from diverse host and geographic origins was tested. RD1 was deleted in 23 of 23 BCG strains. RD1 was present in 129 of 129 other M. tuberculosis complex strains. This multiplex PCR method can be used as a tool for the rapid and specific identification of BCG.

Animals↗

PubMed1997

Renal protection by a dual ETA/ETB endothelin antagonist, L-754,142, after aortic cross-clamping in the dog.

Renal insufficiency is a significant complication that occurs after surgical procedures, requiring cross-clamping of the aorta. The mechanism for this renal dysfunction is currently not known, but studies suggest a potential role of endothelin in mediating the insufficiency. Accordingly, the role of endothelin was assessed using the nonpeptidyl, dual ETA/ETB endothelin antagonist L-754,142 in a model of renal insufficiency in the anesthetized dog induced by cross-clamping the suprarenal aorta for 60 min, followed by 2 h of reperfusion. In vehicle-treated animals (saline, n = 8) after 2 h of reperfusion, plasma [ET-1] increased 66% and renal blood flow (RBF) was reduced by 38% compared with baseline. This decline was associated with an 84% increase in renal vascular resistance and a 54% reduction in GFR (baseline, 46 +/- 5 ml/min; 21 +/- 3 ml/min at 2 h; P < 0.01) and sodium reabsorption (baseline, 6.7 +/- 0.7 microEq/min; 3.0 +/- 0.5 microEq/min at 2 h, P < 0.01). After baseline measurements, pretreatment with L-754,142 at 0.3 mg/kg bolus + 0.1 mg/kg per h continuous infusion (low dose; n = 8) or 3.0 mg/kg bolus + 1 mg/kg per h infusion (high dose; n = 8) initiated 45 min before aortic cross-clamp led to a dose-dependent normalization of RBF and renal vascular resistance within 2 h of cross-clamp removal. GFR was also improved and returned to within 75% of baseline (P < 0.01 versus vehicle) by 2 h of reperfusion with L-754,142 (baseline, 55 +/- 5 ml/min; 42 +/- 5 ml/min at 2 h with the high dose). The improvement of GFR with L-754,142 treatment was associated with a preservation of sodium reabsorption compared with vehicle-treated animals. This study supports a role of endothelin in the pathogenesis of renal insufficiency after aortic cross-clamping and demonstrates that pretreatment with the dual ETA/ETB endothelin antagonist L-754,142 preserves RBF and sodium reabsorption, leading to a significant improvement in GFR.

Acetamides↗

PubMed1997

Perfusion during coronary and mitral valve surgery utilizing minimally invasive Port-Access technology.

Minimally invasive surgery has been used in the treatment of some cardiovascular diseases. Port-Access surgery is a new minimally invasive technique that utilizes cardiopulmonary by-pass and a specialized catheter system that provides cardiopulmonary support and myocardial preservation. Extrathoracic cardiopulmonary support is established with femero-femoral bypass with kinetic assisted venous drainage. An endovascular catheter system allows for all the benefits of mechanical support as well as myocardial preservation. This catheter system includes an endoaortic balloon catheter which functions as an aortic cross clamp and antegrade cardioplegia delivery catheter, endopulmonary vent, and endocoronary sinus catheter used for administration of retrograde cardioplegia. An initial cohort of 20 patients was treated by the Port-Access surgical approach with cardiopulmonary bypass. Ten patients had coronary artery surgery and 10 patients had mitral valve surgery. The average bypass times were 94.4 min (coronary artery) and 152.8 min (mitral valve). The mean aortic occlusion times were 49.7 min (coronary artery) and 112.6 min (mitral valve). All patients were weaned from bypass. This initial patient series demonstrated that Port-Access surgery was feasible in selected patients.

Adult↗

PubMed1997

Effect of macrophage stimulation on collagen biosynthesis in the healing wound.

Immunomodulators that enhance macrophage function have been shown to be beneficial in a number of wound-healing models in humans and in experimental animals. The exact mechanism of this improved healing is unclear. To assess the role of collagen biosynthesis, the immunomodulator glucan phosphate was utilized in two murine models of wound healing, i.e., colon anastomosis and full-thickness skin incision. Tensile strength was evaluated using computer-assisted constant velocity tensiometry. Collagen biosynthesis was determined by assaying hydroxyproline content of wound hydrolysates by N-(9-fluorenyl)methoxycarbonyl/o-phthalaldehyde high-performance liquid chromatography. Experimental animals were treated with (1-3)-beta-D-glucan phosphate (250 mg/kg) intravenously 24 hours prior to colon anastomosis or skin incision. A second dose of glucan phosphate was given immediately postoperatively. Control animals received dextrose and water (5% w/v) intravenously. Tensile strength and hydroxyproline content were measured on postoperative Day 3. In the skin wound model, glucan phosphate treatment increased (P < 0.05) tensile strength by 42 per cent (342.5 +/- 12.2 vs 241.8 +/- 4.8 g), and hydroxyproline content was increased by 23.5 per cent (242.0 +/- 14.4 vs 196.8 +/- 10.5 pmol/microg; P < 0.05). In the glucan phosphate group, colon tensile strength was significantly (P < 0.05) increased by 34 per cent (34.2 +/- 2.3 g vs 45.8 +/- 2.1 g), and hydroxyproline content was increased by 7 per cent (47.45 +/- 3.31 vs 44.34 +/- 3.74 pmol/microg). These data indicate that macrophage modulation with glucan phosphate will increase tensile strength in experimental colon and skin wounds. In addition, we observed a positive correlation between glucan phosphate treatment, wound tensile strength, and collagen biosynthesis.

Adjuvants, Immunologic↗

PubMed1997

Role of polymerase chain reaction in the diagnosis of early leprosy.

For 39 patients suspected of early leprosy, skin biopsies of the lesions were done and bisected. One piece was used for histopathologic examination and the other for polymerase chain reaction (PCR) studies to detect Mycobacterium leprae. The diagnosis of early leprosy was made clinically in 14 patients and by histopathologic study in 26 patients. Acid-fast bacilli were seen in the histopathologic sections of only two patients, and M. leprae were detected using PCR techniques in 11 patients. In one patient the diagnosis of leprosy was made only because of the detection of M. leprae in the PCR study. Since even in endemic countries the profile of leprosy is changing, detection of leprosy lesions in their early stages has become increasingly important. Since the finding of M. leprae is crucial in the confirmatory diagnosis of early leprosy, it is suggested that PCR studies to detect M. leprae be done wherever possible in conjunction with histopathologic examination. It is also recommended that the feasibility and the cost-effectiveness of both of these methods to find M. leprae be evaluated.

Adolescent↗

PubMed1996

Regulation by adrenocorticotropic hormone of the in vivo expression of scavenger receptor class B type I (SR-BI), a high density lipoprotein receptor, in steroidogenic cells of the murine adrenal gland.

The class B, type I scavenger receptor, SR-BI, binds high density lipoprotein (HDL) and can mediate selective uptake of HDL cholesteryl esters by cultured cells. The high levels of expression of SR-BI in steroidogenic tissues and the importance of selective uptake from HDL as a source of cholesterol for steroidogenesis raised the possibility that SR-BI may participate in cholesterol delivery to steroidogenic tissues in vivo. We have used immunoblotting and immunohistochemical methods to show that SR-BI is specifically expressed in a distinctive pattern on the surfaces of steroid-producing cells in the murine adrenal gland's cortex and that its expression in vivo is induced by adrenocorticotropic hormone and suppressed by glucocorticoids. Thus, expression of SR-BI protein is coordinately regulated with adrenal steroidogenesis. These data provide strong support for the hypothesis that SR-BI is a physiologically relevant HDL receptor that provides substrate cholesterol for steroid hormone synthesis.

Adrenal Glands↗