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Biomedical subjects

B Jackson

Publications and source records attributed to B Jackson.

At least 55 records · Page 3Linked to original sources
PubMed1998

The role of ATP citrate-lyase in the metabolic regulation of plasma lipids. Hypolipidaemic effects of SB-204990, a lactone prodrug of the potent ATP citrate-lyase inhibitor SB-201076.

ATP citrate (pro-S)-lyase (EC 4.1.3.8), a cytosolic enzyme that generates acetyl-CoA for cholesterol and fatty acid synthesis de novo, is a potential target for hypolipidaemic intervention. Here we describe the biological effects of the inhibition of ATP citrate-lyase on lipid metabolism in Hep G2 cells, and plasma lipids in rats and dogs, by using SB-204990, the cell-penetrant gamma-lactone prodrug of the potent ATP citrate-lyase inhibitor SB-201076 (Ki=1 microM). Consistent with an important role of ATP citrate-lyase in the supply of acetyl-CoA units for lipid synthesis de novo, SB-204990 inhibited cholesterol synthesis and fatty acid synthesis in Hep G2 cells (dose-related inhibition of up to 91% and 82% respectively) and rats (76% and 39% respectively). SB-204990, when administered orally to rats, was absorbed into the systemic circulation; pharmacologically relevant concentrations of SB-201076 were recovered in the liver. When administered in the diet (0.05-0. 25%, w/w) for 1 week, SB-204990 caused a dose-related decrease in plasma cholesterol (by up to 46%) and triglyceride levels (by up to 80%) in rats. This hypolipidaemic effect could be explained, at least in part, by a decrease (up to 48%) in hepatic very-low-density lipoprotein (VLDL) production as measured by the accumulation of VLDL in plasma after injection of Triton WR-1339. SB-204990 (25 mg/kg per day) also decreased plasma cholesterol levels (by up to 23%) and triglyceride levels (by up to 38%) in the dog, preferentially decreasing low-density lipoprotein compared with high-density lipoprotein cholesterol levels. Overall these results are consistent with the concept that ATP citrate-lyase is an important enzyme in controlling substrate supply for lipid synthesis de novo and a potential enzyme target for hypolipidaemic intervention.

ATP Citrate (pro-S)-Lyase↗
PubMed1998

Phase I study of a human monoclonal antibody directed against the CD4-binding site of HIV type 1 glycoprotein 120.

A phase I dose escalation study was conducted with the human monoclonal anti-gp120 antibody F105, to evaluate the safety, pharmacokinetics, and functional activity of F105 in HIV-1-infected individuals. F105 is an IgG1(kappa) antibody reactive with a discontinuous epitope that overlaps the CD4-binding site of gp120. F105 neutralizes laboratory strains of HIV-1 and some primary isolates, and synergizes with other antibodies in neutralizing an expanded spectrum of isolates. Four patients each with CD4 counts between 200 and 500/mm3 received a single dose of F105 at 100 or 500 mg/m2, intravenously. Sustained levels of F105 were obtained in plasma, and there was no evidence of an immune response to F105 as determined by a double-antigen immunoassay. No patient experienced any toxicity. Infused antibody retained full functional activity as detected by the ability of sera to block the binding of labeled F105 to HIV-1-infected cells. Of note, all patients had preexisting antibody to the gp120 CD4-binding site. The ability to culture virus by quantitative microculture remained unchanged by this single dose of antibody. Thus, it can be concluded that F105 is safe and nontoxic as a single injection at the doses tested. Furthermore, the antibody retains full gp120-binding activity. In these patients, with preexisting CD4-binding site antibody, there is no evidence of anti-HIV-1 activity following a single antibody infusion.

Adult↗
PubMed1998

Prostate, breast and gynecological cancer markers RAK with homology to HIV-1.

Breast and gynecological cancer-associated antigens RAK p120, p42 and p25 exhibit molecular, immunological and genetic homology to HIV-1 proteins. Normal tissues, including the majority of tissues adjacent to cancer, do not express these unique cancer markers. Antigens RAK are now detected in 100% of prostate cancer and in the majority of prostate benign hyperplasia (BPH) cases. Polymerase chain reaction (PCR) with HIV-1 gp41-derived primers revealed prostate cancer-associated DNA fragments of similar size (140 bp) as in HIV-1 genome. Ninety-five percent of BPH samples obtained from prostate cancer patients tested PCR-positive. For comparison, only 61.9% of BPH samples obtained from cancer-free patients tested PCR-positive. The DNA fragments amplified in prostate cancer and in BPH showed more than 90% homology to the HIV-1 gene for gp41. The obtained results strongly suggest that a retrovirus related to HIV-1 may be associated with cancers of the reproductive system.

Antigens, Neoplasm↗
PubMed1998

Effect of dopamine on NaCl transport in the medullary thick ascending limb of the rat.

The aim of the present study was to determine whether dopamine affects NaCl reabsorption in the medullary thick ascending limb of the loop of Henle. Basolateral dopamine (10(-6) M) significantly inhibited Cl- reabsorption in the in vitro microperfused rat medullary thick ascending limb by 21 +/- 2% (P < 0.01). The response to 10(-6) M dopamine was completely blocked by pretreatment with the dopamine D1 receptor antagonist R(+)-SCH-23390 (5 x 10(-5) M), and was mimicked by the dopamine D1 receptor agonist A-77636 (10(-6) M; delta - 36 +/- 2%; P < 0.05). In contrast, basolateral administration of the dopamine D2 receptor agonist (+)-bromocriptine (10(-6) M) transiently increased Cl- reabsorption by 49 +/- 18% (P < 0.05). Neither the D1 nor the D2 agonist affected Cl- reabsorption when selectively administered to the luminal membrane. These data suggest that the predominant effect of dopamine on the medullary thick ascending limb of the rat is to inhibit the reabsorption of NaCl, a response which is mediated by dopamine D1 receptors.

Adamantane↗
PubMed1998

Changes in virologic markers as predictors of CD4 cell decline and progression of disease in human immunodeficiency virus type 1-infected adults treated with nucleosides. AIDS Clinical Trials Group Protocol 175 Team.

The associations of CD4 cell count, plasma human immunodeficiency virus (HIV) type 1 RNA, infectious HIV titer in peripheral blood mononuclear cells, immune complex-disrupted (ICD) p24 antigen, and MT-2 assays with measures of disease progression after drug treatment were assessed in a subset of patients enrolled in AIDS Clinical Trials Group Study 175. Baseline plasma RNA levels and changes in RNA values at weeks 8 or 56 were more important predictors of disease progression than were baseline or changes in CD4 cell counts. Each 10-fold lower HIV RNA concentration at baseline and each 10-fold decrease in HIV RNA between baseline and week 8 was associated with increases of 49-61 CD4 cells/mm3 at weeks 56 and 104. In multivariate analyses, neither baseline values nor changes in infectious HIV titer nor ICD p24 antigen concentrations were associated with long-term changes in CD4 cell count. Plasma HIV-1 RNA appears to be the best predictor of long-term CD4 cell count responses and disease progression.

Adult↗
PubMed1998

Human immunodeficiency virus type 1-like DNA sequences and immunoreactive viral particles with unique association with breast cancer.

RAK antigens p120, p42, and p25 exhibit molecular and immunological similarity to the proteins encoded by human immunodeficiency virus type 1 (HIV-1) and are expressed by 95% of breast and gynecological cancer cases in women and prostate cancer cases in men. The binding of an epitope-specific anti-HIV-1 gp120 monoclonal antibody (MAb) (amino acids 308 to 322) to cancer RAK antigens has been found to be inhibited by a peptide derived from variable loop V3 of HIV-1. Breast cancer DNAs of 40 patients were PCR amplified with HIV-1 gp41-derived primers, and all of the samples were found to be positive. The DNA fragments amplified in seven blindly selected breast cancer samples were sequenced. The breast cancer DNA sequences showed at least 90% homology to the HIV-1 gene for gp41. Antisense oligonucleotides complementary to the HIV-1-like sequences inhibited reverse transcriptase activity and inhibited the growth of breast cancer cells in vitro. Viral particles detected in breast cancer cell lines were strongly immunogold labeled with the anti-HIV-1 gp120 MAb. The results obtained strongly suggest that the long-postulated breast cancer virus may, in fact, be related to HIV-1.

Antibodies, Monoclonal↗
PubMed1998

Effects of neutral endopeptidase inhibition in the rat remnant kidney model.

The orally active neutral metalloendopeptidase (NEP) inhibitor SCH34826 was given by oral gavage in a dose of 90 mg/kg twice daily for 3 days to rats with subtotal nephrectomy (n = 7) and effects were compared to a placebo group receiving phosphate buffer (n = 5). Inhibition of neutral endopeptidase in the remnant kidney was measured by in vitro autoradiography using the specific radioligand [125I]-SCH 47896. Treatment with the NEP inhibitor SCH34826 caused a 60% reduction in the neutral endopeptidase radioligand-binding site density in the kidneys of the SCH34826-treated animals compared to the placebo group (81.6+/-3.7 versus 214.5+/-4.2 dpm/mm2, p<0.01). This was associated with a marked increase in urinary atrial natriuretic peptide (ANP) from 3,930+/-295 to 9,094+/-1,089 pg/24 h in the SCH34826-treated group (p<0.01). Concomitantly there was a transient increase in natriuresis in the SCH34826-treated group [baseline 2.03+/-0.55 to 3.77+/-0.58 mmol/24 h on treatment day 1 (p = 0.02) and 2.58+/-0.19 mmol/24 h on treatment day 3 (p = 0.09)] which was not observed in the placebo group. Urinary protein excretion, glomerular filtration rate (determined by 99mTc-DTPA clearance), systemic blood pressure, plasma ANP concentration and urinary cyclic GMP excretion were not changed by SCH34826 treatment. These results suggest that oral administration of the NEP inhibitor SCH34826 inhibits renal neutral endopeptidase, increases urinary ANP and modulates natriuresis without alteration of systemic blood pressure, plasma ANP and renin level, glomerular filtration or protein excretion.

Analysis of Variance↗
PubMed1997

Innervation of orbital and choroidal blood vessels by the pterygopalatine ganglion in pigeons.

Orbital and choroidal blood vessels in mammals are known to receive a parasympathetic innervation from the pterygopalatine ganglion, which appears to utilize vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) to increase choroidal blood flow. The present studies were undertaken to elucidate the anatomical and neurotransmitter organization of the pterygopalatine ganglion input to orbital and choroidal blood vessels in pigeons. Single- or double-label immunohistochemistry were employed on paraformaldehyde-fixed cryostat sections of the pigeon eye and surrounding orbital tissue to localize 1) VIP+ neurons and fibers; 2) choline acetyltransferase (CHAT)-containing cholinergic neurons and fibers; 3) axons containing the 3A10 neurofilament-associated antigen; and 4) neuronal NO synthase (nNOS)-containing neurons and fibers. NOS+ neurons and fibers were also identified by NADPH-diaphorase histochemistry in sections and whole-mount specimens. The pterygopalatine ganglion was found to consist of an interconnected series of three to four main microganglia of about 50-200 neurons each and numerous lesser microganglia. The major microganglia of the pterygopalatine network in pigeon lie along the superior aspect of the Harderian gland, with many additional fibers and microganglia of the network encircling the gland. Neurons of all microganglia were extremely rich in VIP, nNOS, and NADPH-diaphorase and moderate in CHAT. The majority of the pterygopalatine ganglion neurons were observed to co-contain VIP and nNOS. Axons labeled for VIP, nNOS, NADPH-diaphorase, or the 3A10 antigen could be traced from the pterygopalatine ganglion network to perivascular fiber plexi on orbital blood vessels. These orbital vessels, many of which enter the choroid posteriorly and nasally, appear to be a conduit by which pterygopalatine postganglionic fibers reach the choroid. The pterygopalatine postganglionic fibers were also seen to innervate the Harderian gland and contribute branches to the nearby ophthalmic nerve. Within the choroid, VIP+ fibers were widely scattered and sparse but were most abundant in nasal choroid. A few VIP+ and NADPH- diaphorase+ neurons were also observed in the choroid. These results suggest that pterygopalatine ganglion neurons of birds use VIP and NO to exert vasodilatory control over blood flow to and within the avian choroid.

Animals↗
PubMed1997

Effect of dexamethasone on voltage-gated Ca2+ channels and cytosolic Ca2+ in rat chromaffin cells.

The present study examined whether the synthetic glucocorticoid dexamethasone (DEX) can modulate voltage-gated Ca2+ channel (VGCC) activity, and as a consequence agonist-induced increases in cytosolic Ca2+, in cultured rat adrenal medullary chromaffin (RAMC) cells. Exposure to 1 microM DEX for 48 h significantly increased peak VGCC current (delta +140%). DEX treatment also significantly potentiated the increases in cytosolic Ca2+ in response to submaximal stimulatory concentrations of KCl (delta +64%) and nicotine (delta +32%). The Ca2+ channel agonist BAY K-8644 increased both VGCC current (delta +109%) and potentiated the KCl-stimulated increase in cytosolic Ca2+ (delta +35%) to a comparable extent to that seen with DEX. These data suggest that DEX treatment increases VGCC activity, and that this increased Ca2+ influx leads to potentiation of agonist-induced increases in cytosolic Ca2+ in RAMC cells.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1997

SR-12813 lowers plasma cholesterol in beagle dogs by decreasing cholesterol biosynthesis.

SR-12813 inhibits cholesterol biosynthesis in Hep G2 cells via an enhanced degradation of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. Here we also show that SR-12813 inhibits cholesterol biosynthesis in vivo. A sterol balance study was performed in normolipemic beagle dogs. The dogs were given SR-12813 orally at dosages of 10 and 25 mg/kg/day for a period of 9 days. After 7 days plasma cholesterol was decreased by 15% in the 10 mg/kg/day group and by 19% in the 25 mg/kg/day group. Using a dual isotope technique no effects on intestinal cholesterol absorption were observed. The sterol balance indicated that endogenous synthesis of cholesterol was reduced by 23% in the 10 mg/kg/day group and by 37% in the 25 mg/kg/day group. Plasma lathosterol-cholesterol levels in dogs treated with 25 mg/kg/day SR-12813 were reduced by 56%, confirming a reduction of the cholesterol biosynthesis. Treatment with SR-12813 or the HMG-CoA reductase inhibitor lovastatin resulted in a large decrease in low density lipoprotein (LDL) cholesterol. It is concluded that SR-12813 reduces cholesterol biosynthesis in the dog model which results in a decrease of bile acid excretion, cholesterol excretion and plasma cholesterol level. The in vivo profile of SR-12813 is very similar to that of direct HMG-CoA reductase inhibitors, although the mode of action of the compound is unique.

Administration, Oral↗
PubMed1997

Viral RNA in the resolution of human immunodeficiency virus type 1 diagnostic serology.

BACKGROUND: Assays for human immunodeficiency virus (HIV) antibody testing are characterized by very high levels of sensitivity and specificity. Nonetheless, serologic testing of HIV-infected individuals before they produce multispecific HIV antibodies will not detect and confirm those individuals as positive for HIV. This study was carried out to determine whether viral RNA in such specimens is detectable in a quantitative RNA polymerase chain reaction assay. STUDY DESIGN AND METHODS: Study specimens were identified through the United States military HIV testing program. Thirty-five individuals were studied whose HIV type 1 (HIV-1) infection status was serologically inconclusive at initial testing (i.e., reactive on enzyme immunoassay, nondiagnostic or nonreactive on Western blot), but who were documented to be infected (n = 15) or uninfected (n = 20) through the testing of subsequently collected (follow-up) sera. HIV-1 RNA was detected in sera by the use of a commercially available, quantitative, reverse transcriptase-polymerase chain reaction assay. RESULTS: Specimens from 15 individuals subsequently confirmed to be positive for HIV antibody were all positive for HIV-1 RNA. Specimens from 19 of 20 individuals subsequently confirmed to be negative for HIV antibody were negative for HIV-1 RNA. In the one HIV-1 RNA-positive serum from this group, the RNA copy number was low; specimen contamination during prior laboratory testing was suspected. CONCLUSION: Viral RNA was detected in specimens collected for serologic diagnosis of HIV infection in which no special precautions had been taken to preserve the nucleic acid. Such molecular methods potentially add a much needed tool to current HIV testing algorithms.

AIDS Serodiagnosis↗
PubMed1997

Cardiac hypertrophy in diabetic spontaneously hypertensive rats: role of angiotensin II?

1. In the present study the role of angiotensin II (AngII) in the development of cardiac hypertrophy in diabetes combined with hypertension was investigated. 2. Diabetes was induced in 8-week-old male spontaneously hypertensive rats (SHR) by intravenous injection of streptozotocin (45 mg/kg bodyweight). Diabetic SHR were treated with the angiotensin-converting enzyme (ACE) inhibitor ramipril at a dose of 0.4 mg/kg per day. 3. Twelve weeks following the onset of diabetes, hearts were arrested in diastole and were perfusion-fixed. The right ventricle and left ventricle plus septum were weighted and the volume of the ventricular walls was determined using the Cavalieri principle. 4. Induction of diabetes in SHR led to a significant reduction in bodyweight compared with non-diabetic control SHR and this was not affected by ramipril treatment. The development of hypertension was not as great in diabetic SHR compared with controls, such that at 12 weeks following the onset of diabetes systolic blood pressure (SBP) averaged 191 +/- 3 and 230 +/- 4 mmHg in diabetic SHR and controls, respectively. Ramipril treatment significantly lowered SBP in diabetic SHR. 5. The left ventricle plus septum volume:bodyweight ratio (LV vol:BW) was significantly higher in diabetic SHR compared with controls (3.83 +/- 0.19 and 3.26 +/- 0.16 mm3/g, respectively). Ramipril treatment did not affect growth of the left ventricle in diabetic SHR with the LV vol:BW ratio averaging 3.95 +/- 0.14 mm3/g. Similar trends on growth were observed in the right ventricle. 6. In conclusion, the development of cardiac hypertrophy in diabetic SHR appears to occur by mechanisms independent of AngII and the elevation of blood pressure.

Angiotensin II↗
PubMed1997

The Family Atherosclerosis Risk Intervention Study (FARIS): risk factor profiles of patients and their relatives following an acute cardiac event.

BACKGROUND: Relatives of patients with coronary heart disease have a heightened risk of cardiovascular disease. Attendance at a family-based screening clinic after an acute cardiac event could motivate patients and relatives to modify their lifestyles. AIMS: The Family Atherosclerosis Risk Intervention Study (FARIS) aimed to determine (i) whether a high proportion of patients and relatives would attend a special screening and prevention programme; (ii) whether the risk factor profiles of relatives would be worse than those in the general community; and (iii) whether ongoing management of patients and families together in a special clinic would improve risk factor profiles. METHODS: Consecutive patients, together with spouse, siblings and offspring, aged 18 to 69 years, were randomly allocated three months after an acute cardiac event to attend a special outpatient clinic, a screening and advice group, or a control group. Risk factor measures were total cholesterol, HDL cholesterol (HDLC), systolic blood pressure (SBP), body mass index (BMI) and smoking behaviour. This paper presents the risk factor profiles of all FARIS attenders and compares those of family members, age adjusted, with risk factors measured in a multicentre urban cross-sectional survey conducted in the same period. Differences between groups were compared using t-tests for numerical variables and ANOVA and chi-square for categorical variables. RESULTS: Six hundred and twenty-eight patients and 1723 family members were enrolled, representing 85.9% and 82.7% of eligible patients and relatives respectively. Risk factors were significantly worse amongst family members than among those in the population survey.

Adult↗