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Biomedical subjects

R A Preston

Publications and source records attributed to R A Preston.

At least 19 recordsLinked to original sources
PubMed2005

The vertical profile of winds on Titan.

One of Titan's most intriguing attributes is its copious but featureless atmosphere. The Voyager 1 fly-by and occultation in 1980 provided the first radial survey of Titan's atmospheric pressure and temperature and evidence for the presence of strong zonal winds. It was realized that the motion of an atmospheric probe could be used to study the winds, which led to the inclusion of the Doppler Wind Experiment on the Huygens probe. Here we report a high resolution vertical profile of Titan's winds, with an estimated accuracy of better than 1 m s(-1). The zonal winds were prograde during most of the atmospheric descent, providing in situ confirmation of superrotation on Titan. A layer with surprisingly slow wind, where the velocity decreased to near zero, was detected at altitudes between 60 and 100 km. Generally weak winds (approximately 1 m s(-1)) were seen in the lowest 5 km of descent.

Journal Article↗
PubMed2005

Mapping of an autosomal dominant gene for Dupuytren's contracture to chromosome 16q in a Swedish family.

Mapping of an autosomal dominant gene for Dupuytren's contracture to chromosome 16q in a Swedish family.Dupuytren's contracture (DC) (OMIM 126900) is the most common connective tissue disease of mankind and has both heritable and sporadic forms. The inherited form is most frequently observed among the xanthochroi peoples of Northern Europe where its most common manifestations are thickening of the palmar fascia and contracture of the fingers. We ascertained a five-generation Swedish family in which DC is inherited in an autosomal dominant manner with high, but incomplete, penetrance by the end of the fifth decade. Blood was collected from all affected and informative unaffected family members for the performance of a genome-wide scan at a resolution of approximately 8 cM for all autosomes. Linkage was established to a single 6 cM region between markers D16S419 and D16S3032 on chromosome 16. A maximal two-point logarithm of odds (LOD) score of 3.18 was achieved at microsatellite marker D16S415 with four other markers in the region producing LODs of >1.5.

Chromosome Mapping↗
PubMed2001

Century of Jackson-Weiss syndrome: further definition of clinical and radiographic findings in "lost" descendants of the original kindred.

Jackson-Weiss syndrome (JWS) is a condition consisting of craniosynostosis characterized by premature fusion of the cranial sutures and/or characteristic radiographic anomalies of the feet. The condition is inherited as an autosomal dominant trait with high penetrance and variable expressivity. Six different mutations in the fibroblast growth factor receptor 2 have been identified in patients with the clinical diagnosis of JWS. Jabs et al. [1994: Nat Genet 8:275-279] identified an Ala344Gly substitution in two branches of the family in which the clinical syndrome was originally described. This is the only publication to document this mutation in a family with the clinical diagnosis of JWS. In this study, we have identified a previously unrecognized branch of the original family with individuals that meet the clinical criteria for the diagnosis of JWS. We demonstrate that a mutation that produces the Ala344Gly substitution is present in affected members. This family illustrates the widely variable expression of the mutation, including a novel phenotype in the proband with a leg-length discrepancy and unilateral absence of the fifth digital ray in her right foot. We identify the clinical and detailed radiographic features of each affected individual and offer considerations when making the diagnosis of JWS.

Acrocephalosyndactylia↗
PubMed2001

Pharmacokinetics of pantoprazole in patients with moderate and severe hepatic dysfunction.

BACKGROUND: Patients with impaired hepatic function usually require gastric acid-suppressant therapy but are at increased risk for drug interactions and may require dosage adjustments. The proton pump inhibitor pantoprazole is rapidly absorbed and eliminated, primarily by cytochrome P450 (CYP) 2C19 isozymes. OBJECTIVE: This study sought to determine whether dosage adjustment of pantoprazole is required in patients with moderate or severe hepatic impairment by comparing the pharmacokinetic profile of pantoprazole in such patients with that in healthy slow metabolizers of pantoprazole, in whom no dosage adjustment is required. METHODS: Patients with moderate (Child-Pugh class B) and severe (Child-Pugh class C) hepatic impairment received oral pantoprazole 40 mg once daily on days 1 through 4 and then on alternate days (days 6 and 8). Serial blood samples were collected on days 4 and 8 for analyses of plasma pantoprazole concentrations. Pharmacokinetic data were compared between the 2 groups with hepatic impairment and against historical data from 17 healthy subjects who were genetically slow CYP2C19 metabolizers of pantoprazole. RESULTS: Twenty-two patients participated in the study, 13 in the Child-Pugh class B group and 9 in the Child-Pugh class C group. No clinically significant differences in pantoprazole pharmacokinetics were noted between the patients with hepatic impairment and the healthy slow metabolizers of pantoprazole on days 4 and 8. Pantoprazole was well tolerated. Four Child-Pugh class B patients and 3 Child-Pugh class C patients reported > or = 1 adverse event. Adverse events were generally mild or moderate, and were similar to those reported in healthy subjects. Two patients discontinued the study because of severe events related to their underlying disease. CONCLUSIONS: The pharmacokinetics and tolerability of pantoprazole were similar in patients with moderate hepatic impairment, patients with severe hepatic impairment, and healthy slow metabolizers of pantoprazole, in whom no dosage adjustment is required. Thus, no dosage adjustment of pantoprazole is required in patients with hepatic impairment, regardless of its severity. However, caution should be exercised when giving pantoprazole to patients with severe hepatic impairment.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2001

Inhibition of apoptosis: a potential mechanism for syndromic craniosynostosis.

The biologic pathogenesis of syndromic craniosynostosis remains unknown. The purpose of this investigation was to determine whether specific biologic differences exist between normal calvarial osteoblasts and osteoblasts derived from patients with syndromic craniosynostosis. This study (1) examined the apoptotic rate and cell cycle of osteoblasts derived from patients with syndromic craniosynostosis, and (2) investigated for the presence of soluble factors released from syndrome-derived osteoblasts. Osteoblast cell lines were established from calvarial specimens of patients with clinically diagnosed syndromic synostosis and from normal controls. A co-culture technique was used to investigate for the presence of elaborated soluble factors. Apoptotic rate and cell cycle analyses were performed by using flow cytometry after staining with annexin V-fluorescein isothiocyanate and propidiumiodide, respectively. The apoptotic rate was significantly reduced in syndrome-derived osteoblasts as compared with control osteoblasts. Control osteoblasts co-cultured with syndromic osteoblasts demonstrated a dramatic reduction in their apoptotic rate as compared with those co-cultured with control osteoblasts. These results indicate that osteoblasts derived from patients with syndromic craniosynostosis display a lower apoptotic rate, a normal DNA synthetic rate, and the capability to reduce the apoptotic rate in normal calvarial osteoblasts through the elaboration of soluble factors.

Apoptosis↗
PubMed2001

Comparative pharmacokinetics and pharmacodynamics of amlodipine in hypertensive patients with and without type II diabetes mellitus.

Recent clinical trials aimed at attenuating complications in diabetes mellitus have generated interest in the impact of drug formulation and altered pharmacokinetics and pharmacodynamics in diabetes. Specifically, it has been proposed that the diabetic state may alter the pharmacokinetics of several cardiovascular drugs, including some calcium antagonists. The present study investigates the effects of diabetes mellitus on the pharmacokinetics and pharmacodynamics of amlodipine in hypertensive subjects with and without diabetes mellitus to determine whether the diabetic state alters these parameters. This trial consisted of a 2-week placebo washout phase, a 2-week titration phase, and a 2-week maintenance phase. Study patients included 18 hypertensive patients with type II diabetes mellitus and 10 nondiabetic hypertensive patients. Blood samples were collected after administration of amlodipine and AUC, Cmax, and tmax were determined. The acute 24-hour pharmacodynamic response to amlodipine was assessed by blood pressure and telemetric heart rate measurements. There were no significant differences for either amlodipine 5 or 10 mg in AUC (p = 0.40 for 5 mg; p = 0.59 for 10 mg), Cmax (p = 0.41 for 5 mg; p = 0.45 for 10 mg), and tmax (p = 0.79 for 5 mg; p = 0.67 for 10 mg) between diabetic and nondiabetic hypertensive subjects. Similarly, the 24-hour pharmacodynamic effects of amlodipine on systolic blood pressure, diastolic blood pressure, and heart rate did not differ between diabetic and nondiabetic subjects as assessed by repeated-measures analysis of variance. Because of the theoretical basis for anticipating that diabetes mellitus may provoke important pharmacokinetic and pharmacodynamic alterations, our study provides an important database in clearly demonstrating that the diabetic milieu did not alter the pharmacokinetics or pharmacodynamics of amlodipine.

Adult↗
PubMed2000

Mapping of a gene for severe pediatric gastroesophageal reflux to chromosome 13q14.

CONTEXT: Gastroesophageal reflux (GER) has not previously been widely regarded as a hereditary disease. A few reports have suggested, however, that a genetic component may contribute to the incidence of GER, especially in its severe or chronic forms. OBJECTIVE: To identify a genetic locus that cosegregates with a severe pediatric GER phenotype in families with multiple affected members. DESIGN: A genome-wide scan of families affected by severe pediatric GER using polymorphic microsatellite markers spaced at an average of 8 centimorgans (cM), followed by haplotyping and by pairwise and multipoint linkage analyses. SETTING: General US community, with research performed in a university tertiary care hospital. SUBJECTS: Affected and unaffected family members from 5 families having multiple individuals affected by severe pediatric GER, identified through a patient support group. MAIN OUTCOME MEASURES: Determination of inheritance patterns and linkage of a genetic locus with the severe pediatric GER phenotype by logarithm-of-odds (lod) score analysis, considering a lod score of 3 or greater as evidence of linkage. RESULTS: In these families, severe pediatric GER followed an autosomal dominant hereditary pattern with high penetrance. A gene for severe pediatric GER was mapped to a 13-cM region on chromosome 13q between microsatellite markers D13S171 and D13S263. A maximum multifamily 2-point lod score of 5.58 and a maximum multifamily multipoint lod score of 7.15 were obtained for marker D13S1253 at map position 35 cM when presumptively affected persons were modeled as unknown (a maximum multipoint score of 4.88 was obtained when presumptively affected persons were modeled as unaffected). CONCLUSION: These data suggest that a gene for severe pediatric GER maps to chromosome 13q14. JAMA. 2000;284:325-334

Child↗
PubMed2000

Placebo-associated blood pressure response and adverse effects in the treatment of hypertension: observations from a Department of Veterans Affairs Cooperative Study.

BACKGROUND: The use of placebo in clinical trials has been vigorously debated. Placebo control may be useful in disease states, such as stage 1 and stage 2 hypertension as defined by the Sixth Report of the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure (JNC VI), in which response rates for placebo are high or close to response rates for effective therapies, or when established interventions have significant adverse effects. OBJECTIVE: To compare rates for the control of blood pressure and adverse effects of placebo vs active treatment in patients with stage 1 and stage 2 hypertension. METHODS: This study is a randomized controlled trial evaluating the blood pressure response and adverse effects of placebo vs 6 active treatments administered in 15 Veterans Affairs hypertension centers. The 1292 subjects of the Veterans Affairs Cooperative Study receiving single-drug therapy for hypertension were randomly allocated to receive treatment with 1 of 6 active drugs (n= 1105) or placebo (n=187). Treatment success was defined as maintaining a diastolic blood pressure of less than 95 mm Hg for at least 1 year. We compared treatment success rates for the control of blood pressure and adverse effects of placebo vs active treatment. Using the Kaplan-Meier method, we also compared rates of discontinuation from placebo vs active drug treatment over time as a result of adverse drug effects and blood pressure exceeding safety limits. RESULTS: At the end of the titration phase, 58 patients who were treated with placebo (31%) achieved a goal diastolic blood pressure lower than 90 mm Hg and 57 (30%) achieved success at 1 year. Older white patients who received placebo had a success rate of 38% vs 23% to 27% for the other age-race subgroups. The rates of discontinuation as a result of adverse drug effects were 13% for patients receiving placebo vs 12% for patients receiving active treatment (P=.40). The rates of discontinuation for blood pressure being too high were 14% for patients receiving placebo vs 7% for patients receiving active treatment (P=.01). CONCLUSIONS: Placebo control provides an important benchmark for both efficacy and adverse effects. It continues to have an appropriate place in certain therapeutic trials, particularly those involving the treatment of stage 1 and stage 2 hypertension.

Adult↗
PubMed2000

Refined localization of a gene for pediatric gastroesophageal reflux makes HTR2A an unlikely candidate gene.

Our objective in this study was to determine whether mutations in the gene for the 5-hydroxytryptamine receptor 2A (HTR2A) cause the autosomal dominant form of severe pediatric gastroesophageal reflux (GER), which we had previously mapped to a 21-cM region at chromosome 13q14. Direct sequencing of the HTR2A gene was carried out on DNA from affected and unaffected members of families with severe pediatric GER displaying genetic linkage to the HTR2A locus. In addition, we performed high-resolution linkage mapping within the GER gene region using additional polymorphic markers closely linked to HTR2A. Several previously reported polymorphisms in the HTR2A gene were identified in three families affected with GER. In addition, we identified a novel polymorphism at nucleotide -1273 in the HTR2A promoter. No mutant allele cosegregated exclusively with the GER phenotype in any family. Linkage analysis using additional polymorphic markers narrowed the region of the GER gene to a 9 cM interval between markers D13S263 and CAGR1, formally excluding HTR2A as a candidate gene. In conclusion, sequence analysis of HTR2A and linkage analysis argue against mutations in HTR2A being a cause of severe pediatric GER.

Child↗
PubMed2000

University of Miami Division of Clinical Pharmacology Therapeutic Rounds: the water-intolerant patient and perioperative hyponatremia.

Perioperative hyponatremia has been recognized as a serious in-hospital complication for many years. Because the kidney responds to changes in extracellular fluid tonicity by adjusting water excretion, a defect in any of several key elements of water excretion can lead to water retention and hyponatremia. Most cases of hyponatremia are caused by impaired renal water excretion in the presence of continued water intake. For the kidney to excrete excess free water and thereby protect the extracellular fluid against hyponatremia, there must be an adequate glomerular filtration rate (GFR), adequate delivery of glomerular filtrate to the diluting segments of the distal nephron, intact tubular diluting mechanisms, and appropriate inhibition of antidiuretic hormone (ADH) synthesis and release. Virtually all of the clinical disorders producing hyponatremia are based on abnormalities of these few mechanisms of water regulation. Finding the reason for impaired renal water excretion is the key to diagnosing the cause of hyponatremia. Impaired renal water excretion may be caused by impaired GFR (renal failure), impaired water delivery to the diluting segments of the distal nephron because of increased proximal reabsorption (decreased extracellular fluid volume and edematous states), impaired renal diluting mechanism (thiazide diuretics), the syndrome of inappropriate ADH (SIADH) due to a variety of causes including the perioperative state, and hypothyroidism or adrenal insufficiency. Any of the states that impair water excretion can produce hyponatremia in a patient with an initially normal serum sodium concentration if sufficient free water is supplied. Therefore, a patient who has one of the conditions listed above, including the perioperative state, may be considered "water intolerant" even if the serum sodium is normal. Such a patient is at risk for developing severe hyponatremia if given hypotonic IV fluids or a large oral water load. An understanding of the basic mechanisms leading to impaired water excretion and "water intolerance" is therefore an important key to avoiding perioperative hyponatremia.

Female↗
PubMed1999

Renoprotective effects of antihypertensive drugs.

Regardless of the specific antihypertensive agent used, the most important aspect of the management of the patient with coexistent hypertension and renal disease is adequate control of the blood pressure. The current JNC VI recommendation is for a reduction to a target blood pressure of 130/85 mm Hg, or to a lower value of 125/75 in patients with greater than 1 g proteinuria per day. Impaired renal sodium excretion leading to extracellular fluid volume (ECFV) expansion is the most clinically important mechanism leading to renal parenchymal hypertension. Sodium restriction and loop diuretics constitute the cornerstone of effective antihypertensive therapy. Control of blood pressure in patients with chronic renal disease may be difficult without measures that address ECFV. JNC VI recommends the use of angiotensin converting enzyme (ACE) inhibitors in patients with hypertension and chronic renal disease to control hypertension and to slow progressive renal failure. ACE inhibitors have been found by clinical trials to be useful agents in the settings of established insulin-dependent diabetes mellitus (IDDM) nephropathy, non-insulin-dependent diabetes mellitus (NIDDM) nephropathy, IDDM patients with normal blood pressures and microalbuminuria, NIDDM patients with microalbuminuria and normal renal function, and a variety of nondiabetic renal diseases, especially in the setting of significant proteinuria. Calcium antagonists are effective for treating hypertensive patients with chronic renal impairment but have not been studied as intensively as ACE inhibitors with regard to their ability to slow the progression of renal insufficiency independently of their blood-pressure-lowering effects. The initial results for calcium antagonists and for combination calcium antagonist-ACE inhibitor therapy have been promising. The angiotensin II antagonists have theoretical advantages for use in renal impairment, and seem to have similar renal hemodynamic and antiproteinuric effects to ACE inhibitors, but further clinical study is needed.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Clinical presentation and management of patients with uncontrolled, severe hypertension: results from a public teaching hospital.

CONTEXT: There is relatively little data available on the management of patients with severe, uncomplicated hypertension and severe hypertension with stable hypertensive complications. OBJECTIVE: To determine the incidence, clinical features, acute management, and clinical course of severe, uncomplicated hypertension and severe hypertension with stable hypertensive complications presenting for emergency department care in a large public teaching hospital. DESIGN: Chart survey of consecutive emergency department visits. PATIENTS: Ninety-one of 2898 consecutive visits to a public teaching hospital emergency department were specifically for severe, uncomplicated hypertension. RESULTS: Of 2898 consecutive medical emergency department visits, there were 142 (4.9%) patient visits specifically for systolic blood pressure (SBP) > or =220 mm Hg or diastolic blood pressure (DBP) > or =120 mm Hg. Ninety-one of the 142 patient visits were for severe hypertension in the absence of acute target organ impact or neuroretinopathy. Eighty-nine patients received acute drug therapy. Twenty-nine patients received two drugs, and 15 received three drugs. Sixty-eight patients (75%) received clonidine, and 15 (16.5%) received short-acting nifedipine despite widely published concerns about the safety of this practice. We found a wide variability of blood pressure response to treatment. The average decline in SBP was 50+/-31 mm Hg and the average decline of DBP was 34+/-20 mm Hg over 4.2+/-2.9 h. Forty-two patients (46%) had the SBP reduced to less than 160 mm Hg, and 46 patients (50%) the DBP to less than 100 mm Hg. Long-term management and follow-up were suboptimal. Of 74 patients discharged from the emergency room, 22 patients (30%) returned because of uncontrolled hypertension within an average of 33+/-28 days, 10 patients with hypertensive complications. CONCLUSIONS: Severe hypertension continues to present an important and common problem. Physicians appear to place a strong emphasis on acute lowering of the blood pressure to near-normal levels. Patients are frequently lost to follow-up and have a very high rate of recurrent emergency department visits and hypertensive complications. This study points to a need for detailed, specific practice guidelines and comprehensive disease management protocols for severe, uncomplicated hypertension.

Acute Disease↗
PubMed1999

University of Miami division of clinical pharmacology therapeutic rounds: issues in prescribing for geriatric patients and emerging practice guidelines.

The geriatric population accounts for over 12% of the United States population and consumes over 25% of all prescription medications. Polypharmacy and patient noncompliance are often encountered in caring for these patients. These issues along with a variety of age-related physiologic changes and the presence of multiple medical illnesses place the elderly at an increased risk for adverse drug reactions. Especially worrisome is the use of long-acting benzodiazepines and anticholinergic medications in this population. The problem of adverse drug reactions is a common clinical problem that is of great public concern as the number of older persons in the United States continues to grow. In response, a variety of proactive measures have been developed. These measures include the development of consensus criteria for inappropriate medications, federal government regulation, expansion of the role of clinical pharmacists, and computer-assisted prescribing protocols.

Aged↗
PubMed1999

Inappropriate medication prescribing in homebound older adults.

OBJECTIVES: Little is known about the prescribing of medications in the growing population of homebound older adults. We report on the prevalence and pattern of inappropriate medications in a nursing home-eligible, homebound population. DESIGN: A cross-sectional design. SETTING: A managed care plan for individuals meeting nursing home eligibility. PARTICIPANTS: 2193 homebound people older than age 60. MEASUREMENTS: We reviewed the pharmacy profiles of all older homebound enrollees. We identified the average number of medications per patient and the most commonly prescribed classes of drugs. The medication profiles were also analyzed in the context of the 26 drugs/groups listed as inappropriate by the explicit criteria of Beers [Arch Intern Med 1997; 157:1531-1536]. RESULTS: A total of 2193 people aged 60 to 106 (mean 82.8 +/- 8.8) were taking an average of 5.3 +/- 2.9 drugs (range 0-22). Cardiac drugs and benzodiazepines were the medications most commonly prescribed. We found 1152 of the total 11,689 prescriptions (9.9%) to be inappropriate. Eight hundred seventy-one (39.7%) of these 2193 residents had at least one inappropriate prescription, and 230 (10.4%) had two or more. Of particular concern were 285 people prescribed excessive doses of temazepam and zoldipem, 211 people taking first-generation antihistamines, 115 taking doxepin or amitriptyline, 106 taking an ergoloid, 98 taking dipyridamole, and 85 prescribed a long-acting benzodiazepine. CONCLUSIONS: Our study revealed a high prevalence of psychotropic medications and inappropriate drug use among older homebound residents, a group that is at the highest risk for adverse drug reactions. Because this group is not subject to oversight by regulatory agencies, further interventional studies and provider education will be important.

Aged↗
PubMed1998

Age-race subgroup compared with renin profile as predictors of blood pressure response to antihypertensive therapy. Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents.

CONTEXT: Renin profiling and age-race subgroup may help select single-drug therapy for stage 1 and stage 2 hypertension. OBJECTIVE: To compare the plasma renin profiling and age-race subgroup methods as predictors of response to single-drug therapy in men with stage 1 and 2 hypertension as defined by the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure. DESIGN: The Veterans Affairs Cooperative Study on Single-Drug Therapy of Hypertension, a randomized controlled trial. SETTING: Fifteen Veterans Affairs hypertension centers. PATIENTS: A total of 1105 ambulatory men with entry diastolic blood pressure (DBP) of 95 to 109 mm Hg, of whom 1031 had valid plasma and urine samples for renin profiling. INTERVENTIONS: Randomization to 1 of 6 antihypertensive drugs: hydrochlorothiazide, atenolol, captopril, clonidine, diltiazem (sustained release), or prazosin. MAIN OUTCOME MEASURE: Treatment response as assessed by percentage achieving goal DBP (<90 mm Hg) in response to a single drug that corresponded to patients' renin profile vs a single drug that corresponded to patients' age-race subgroup. RESULTS: Clonidine and diltiazem had consistent response rates regardless of renin profile (76%, 67%, and 80% for low, medium, and high renin, respectively, for clonidine and 83%, 82%, and 83%, respectively, for diltiazem for patients with baseline DBP of 95-99 mm Hg). Hydrochlorothiazide and prazosin were best in low- and medium-renin profiles; captopril was best in medium- and high-renin profiles (low-, medium-, and high-renin response rates were 82%, 78%, and 14%, respectively, for hydrochlorothiazide; 88%, 67%, and 40%, respectively, for prazosin; and 51%, 83%, and 100%, respectively, for captopril for patients with baseline DBP of 95-99 mm Hg). Response rates for patients with baseline DBP of 95 to 99 mm Hg by age-race subgroup ranged from 70% for clonidine to 90% for prazosin for younger black men, from 50% for captopril to 97% for diltiazem for older black men, from 70% for hydrochlorothiazide to 92% for atenolol for younger white men, and from 84% for hydrochlorothiazide to 95% for diltiazem for older white men. Patients with a correct treatment for their renin profile but incorrect for age-race subgroup had a response rate of 58.7%; patients with an incorrect treatment for their renin profile but correct for age-race subgroup had a response rate of 63.1% (P = .30). After controlling for DBP and interactions with treatment group, age-race subgroup (P<.001) significantly predicted response to single-drug therapy, whereas renin profile was of borderline significance (P= .05). CONCLUSIONS: In these men with stage 1 and stage 2 hypertension, therapeutic responses were consistent with baseline renin profile, but age-race subgroup was a better predictor of response.

Adult↗
PubMed1998

Overview and initial results of the very long baseline interferometry space observatory programme

High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli-arc-second-scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.

Journal Article↗