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Biomedical subjects

P Abraham

Publications and source records attributed to P Abraham.

At least 91 records · Page 5Linked to original sources
PubMed1999

Spectrogram analysis of arterial Doppler signals for off-line automated hits detection.

Recently, a time processing of arterial Doppler signals was proposed to detect automatically high-intensity transient signals (HITS). This technique provided satisfactory detection results, but was not always constantly accurate, particularly with high-resistance blood velocity profiles. A time-frequency processing, based on the spectrogram, is presented to detect the presence of emboli in the arterial Doppler signals. The method uses the narrow-band hypothesis and extracts the detection criterion from the time-frequency representation (TFR). A first database of 560 peripheral arterial Doppler HITS was created to study microemboli and to define the normal limits to be used in our method. A threshold was experimentally defined using this database, and then applied to 38 recordings from 12 patients. Using another database, 6 human expert Doppler users reported 140, 176, 155, 161, 161 and 146 HITS, corresponding to a total of 197 different observed HITS. When an event was detected by at least 6, 5, 4, 3, 2 and 1 of the observers, sensitivity of the automatic detection was 93.9, 91.7, 89.6, 88.7, 84.7 and 73.1%, respectively. The sensitivity of our automatic detection is, thus, highly associated with the number of observers in agreement. A preliminary experiment has been performed to test the method in the case of long recording duration. In 15 patients, 6 h 24 min of recordings have been analyzed. The proposed automated processing provided an overall sensibility of 91.5%. The present work shows that this detection scheme preserves good sensibility and improves the positive predictive value compared with the time-processing recently proposed.

Arteries↗
PubMed1999

Does venous microemboli detection add to the interpretation of D-dimer values following orthopedic surgery?

The identification of risk factors for deep venous thrombosis (DVT) following orthopedic surgery remains unclear. We have investigated the relationship between plasma levels of D-dimer (DD), the presence or absence of microemboli 1 day after surgery, and the occurrence of DVT 7 days after total hip or knee replacement. The prevalence of DVT was 25 (13.3%) among 188 patients and was lower in 112 patients with DD < 2808 ng mL(-1) than in the 56 patients with higher DD levels: respectively, 8.0% vs. 21.4% (p < 0.05). D-dimer is not suitable for individual estimation of DVT risk. Microemboli were found in 112 (60%) of 186 subjects. The presence/absence or the frequency of the microemboli showed no relationship with the occurrence of DVT. Last, when evaluating the risk of DVT in orthopedic surgery, microemboli detection does not add to the interpretation of DD concentration.

Aged↗
PubMed1999

Improved sensitivity of reverse transcriptase polymerase chain reaction for hepatitis C virus using random hexamer primers.

The use of specific primers and random primers for the detection of hepatitis C virus RNA by reverse transcriptase-polymerase chain reaction was compared. The cDNA obtained from using both methods was amplified by the same protocol. Of the 30 plasma specimens tested, 6 (20%) were hepatitis C virus RNA-positive using specific primers and 19 (63%) were positive using random primers, demonstrating that the use of random hexamer-primed reverse transcriptase-polymerase chain reaction significantly improves the sensitivity (p < 0.01).

DNA Primers↗
PubMed1999

Comparison of two different methodologies for the detection of hepatitis B virus DNA in plasma.

In this study, two different methodologies were compared for the detection of hepatitis B virus (HBV) DNA in the plasma of 28 patients and 36 controls. Method 1 was a nested polymerase chain reaction (PCR) followed by product detection in an ethidium bromide stained gel, whereas method II was a commercial single step PCR with digoxigenin labeled product captured by a probe and then detected in a digoxigenin-antidigoxigenin enzyme-linked immunosorbent assay (DIG ELISA). The results indicate that both methods are comparable showing a concordance of 98.4%, there was no statistically significant difference in the detection rates. We feel that any one of these assays may be suitable in a clinical laboratory setting, though the commercial assay may offer some advantages to laboratories without sufficient skilled staff in trouble-shooting PCR related problems.

DNA, Viral↗
PubMed1999

Estimation of intraoperative aortocoronary bypass saphenous vein graft circumference from its preoperative compliance.

The aim of this study was to determine if the intraoperative circumference of aortocoronary saphenous vein bypass grafts could be predicted from preoperative measurement with B-mode ultrasound sonography in 50 patients. The circumference of the saphenous vein was measured during stepwise increments of a thigh congestive cuff from 0 to 60 mmHg. The circumference of the corresponding segment of the coronary bypass vein graft was measured intraoperatively with callipers. The intraoperative circumference was higher (11.8+/-2.3 mm) than the preoperative circumference (10.2+/-2.4 mm, P=0.006) matched to its corresponding intraoperative mean arterial pressure (57+/-15 mmHg). The prediction of the intraoperative circumference by estimation from the preoperative pressure-circumference relationship fitted by a linear model (r = 0.412, P = 0.004) did not improve on the preoperative circumference matched by arterial pressure alone (r = 0.429, P = 0.003). The intraoperative circumference of the graft vein exceeded its preoperative circumference by 12%. Prediction of the intraoperative graft vein circumference is underestimated by a linear model of its preoperative compliance.

Aged↗
PubMed1999

Transcutaneous carbon dioxide threshold during exercise.

BACKGROUND: To study the possible use of transcutaneous carbon dioxide pressure measurements to estimate ventilatory threshold during exercise. METHODS EXPERIMENTAL DESIGN: comparative study. SETTINGS: Institutional practice, ambulatory care. Patients and measures: seventy-nine subjects. INTERVENTION: incremental exercise tests with simultaneous recordings of breath by breath gas exchange and transcutaneous carbon dioxide pressure. MEASURES: Six reviewers determined the ventilatory threshold using both the graphs for the carbon dioxide excretion to oxygen consumption relationship: V slope technique (VTa), and the ventilatory equivalent for oxygen uptake changes over time: (VTb), the respiratory compensation point (RCP) on ventilatory equivalent for carbon dioxide, and the transcutaneous threshold (Ttc) on the transcutaneous carbon dioxide pressure changes over time respectively. RESULTS: A Ttc could be defined by all observers in 85% of the subjects. Correlation between Ttc and VT expressed as oxygen consumption absolute values ranged from 0.971 to 0.975 on the mean values of six observers. Using the Bland-Altmann approach, differences (mean +/- SD) were 13 +/- 215, -40 +/- 204, 231 +/- 221 ml.min-1 between Ttc and VTa, RCP respectively. A difference of 38 +/- 173 ml.min-1 was found between VTa and VTb. This suggests that Ttc shows little difference with VT but not with RCP. CONCLUSIONS: We suggest that a carbon dioxide transcutaneous threshold can be found close to the ventilatory threshold. Potential clinical use of transcutaneous device are vast.

Adolescent↗
PubMed1999

[Essential thrombocythemia and cerebral ischemic accident: discussion of two cases].

Not only the total number of platelets but their normal or abnormal function are essential points to be analyzed in case of stroke associated with thrombocytemia. When possible the treatment of arterial episodes in thrombocytemia should not be surgical. Anti-platelet agents and the rigorous control of the different risk factors are warranted to limit the activation of abnormal platelets on early endothelial lesions and thereby limit the risk of recurrent accidents. We report two typical cases illustrating these different points.

Adult↗
PubMed1999

Profile of extrahepatic portal venous obstruction in Mumbai.

AIM OF THE STUDY: To study the clinical profile of extrahepatic portal venous obstruction (EHPVO) in a tertiary referral centre in Mumbai. METHODOLOGY: Retrospective analysis of records of 113 patients with EHPVO, treated between January 1984 and May 1996. RESULTS: Thirty eight of 54 (70.4%) patients in whom information was available were delivered at home. Eleven of the 50 (22%) had umbilical sepsis after birth. Median disease duration was 5 years (range 4 months-31 years), with age at initial presentation 13 (range 0.5-45) years; 24 (20%) patients presented after age 20 years. Eleven presenting initially with splenomegaly bled after 3 (1-14) years. Number of bleeding episodes per patient was 2.5 (1-12). 13 of 44 (29.6%) patients bled (first bleed or recurrence) after age 20 years. Twenty five (22.3%) had ascites at some time, 17/102 (16.7%) had hypersplenism, and hypoalbuminaemia was present in 20/103 (19.2%). Endoscopic sclerotherapy obliterated varices in 47/52 (90.4%) in 10.5 (3-40) sessions over 7 (1-100) months. Twenty three patients underwent surgery: devascularisation in 20 (with splenectomy in seven), distal lieno-renal shunt in two, and meso-caval shunt in one patient. Follow-up was available in 68 (60.2%) patients. Rebleeding after sclerotherapy occurred in 27/64 (42.2%), with median one (1-5) per patient; recurrence of varices was noted in 15/35 (42.9%) patients over 12 (3-39) months. Varices were present in 12 patients 163 (33-305) months after surgery. CONCLUSIONS: Home delivery and umbilical sepsis may be risk factors in the development of EHPVO. A significant number of patients present or continue to bleed from varices after age 20. Variceal sclerotherapy is effective for eradication of oesophageal varices.

Adolescent↗
PubMed1999

Decreased activity of hepatic alkaline protease in rats with carbon tetrachloride-induced liver cirrhosis.

To investigate the cause of accumulation of oxidised proteins in the livers of rats with carbon tetrachloride (CCl4) induced liver cirrhosis, the activity of alkaline protease (a high molecular weight, multisubunit cysteine proteinase) was determined in the cirrhotic livers. A significant decrease (P < 0.05) in the activity of hepatic alkaline protease was observed in the cirrhotic rats. Decreased activity of alkaline protease in the liver of cirrhotic rats may contribute to the accumulation of the oxidised proteins in the liver.

Animals↗
PubMed1998

Synthesis and transporter binding properties of (R)-2 beta, 3 beta- and (R)-2 alpha, 3 alpha-diaryltropanes.

(R)-2-Aryl-2-tropinone (9) was synthesized from (R)-2-carbomethoxy-3-tropinone (5) and was used as the key intermediate for the synthesis of (R)-2 beta, 3 beta- and (R)-2 alpha, 3 alpha-diaryltropanes. Inhibition of radioligand binding studies at the dopamine, serotonin, and norepinephrine transporters showed that the (R)-3 beta-(4-methylphenyl)-2 beta-phenyltropane (3b, RTI-422) possessed an IC50 value of 1.96 nM at the dopamine transporter and was highly selective for this transporter relative to the serotonin and norepinephrine transporters.

Carrier Proteins↗
PubMed1998

Non-nociceptive capsaicin-sensitive nerve terminal stimulation allows for an original vasodilatory reflex in the human skin.

A significant increase of cutaneous laser Doppler flowmetry was found before blood flow decreases with increasing pressure during a 5 mmHg min-1 increase of pressure strain on the finger. Pre-treatment with a local anaesthetic or chronically applied capsaicin, resulted in the disappearance of the vasodilatory response. These results suggest an original vasodilatory axon reflex response to non-noxious pressure strain which is initiated by capsaicin-sensitive nerve terminals in the human skin.

Capsaicin↗
PubMed1998

Synthesis and ligand binding of tropane ring analogues of paroxetine.

(3S,4R)-4-(4-Fluorophenyl)-3-[[3,4-(methylenedioxy)phenoxy]methyl] piperidine [(3S,9R)-3, paroxetine] is a selective serotonin reuptake inhibitor (SSRI) used as an antidepressant in humans. In previous studies, we reported that certain (1R)-3 beta-(substituted phenyl)nortropane-2 beta-carboxylic acid methyl esters (2a) exhibited high affinity and reasonable selectivity for the serotonin transporter (5-HTT). The major structural differences between 2a and (3S,4R)-3 are that 2a possesses a different absolute stereochemistry and has an ethylene bridge not present in 3. In addition, 2a possesses a carbomethoxy substituent adjacent to the aryl ring, whereas (3S,4R)-3 contains a [3,4-(methylenedioxy)phenoxy]methyl group. In this study, we present the synthesis and biological evaluations of six of the possible eight isomers of 3-(4-fluorophenyl)-2-[[3,4-(methylenedioxy)phenoxy]methyl]nortropane+ ++ (4). The data for inhibition of [3H]paroxetine binding show that (1R)-2 beta, 3 alpha-4c, which has the same stereochemistry as paroxetine, has the highest affinity at the 5-HTT. Strikingly, the most potent compounds for inhibition of [3H]WIN-35,428 binding were not the (1R)-2 beta, 3 beta-isomers but rather (1R)-2 beta, 3 alpha-4c and (1S)-2 beta, 3 alpha-4f. Conformational analyses show that these isomers exist in a flattened boat conformation with pseudoequatorial substituents. Thus, the binding data show that this conformation is recognized by the DAT-associated binding site and also suggest that this conformation of paroxetine is recognized by the 5-HTT-associated binding site.

Binding, Competitive↗
PubMed1998

Cutaneous vasodilation induced by local warming, sodium nitroprusside, and bretylium iontophoresis on the hand.

Local warming alone induces a cutaneous vasodilation considered as maximal. The argument that local warming generates a maximum flow is being tested by vasodilation with alternate approaches to see if a greater vasodilation is possible: blockade of the release of transmitters from the adrenergic nerve endings with bretylium tosylate or direct pharmacological action on vascular smooth muscle using sodium nitroprusside. Nine healthy subjects participated in two experiments in which SkBF was measured simultaneously by laser Doppler flowmetry on the dorsal aspects of both hands. In the first protocol the vasodilator effects of 20 min of local warming at 44 degreesC were measured on one hand and the effects of iontophoresis of sodium nitroprusside on the other. The second protocol was like the first except that iontophoresis of bretylium tosylate instead of sodium nitroprusside was performed. Local warming induced an increase of SkBF from 17.6 +/- 4.4 to 140.2 +/- 33.2 AU (P < 0.01) while it rose from 16.7 +/- 4.0 to 114.7 +/- 11.0 AU (P < 0.001) during sodium nitroprusside iontophoresis. During the second protocol local warming induced an increase of SkBF from 14.9 +/- 2.1 to 117.7 +/- 25.4 AU (P < 0.01) while it rose from 19.6 +/- 2.6 to 120.5 +/- 11.3 AU (P < 0.001) during bretylium iontophoresis. However, in both experiments, the increase of SkBF attained during iontophoresis did not differ significantly from the increase achieved by local warming. We conclude that the effects of iontophoresis of sodium nitroprusside or of bretylium produce a cutaneous vasodilation as high as a local warming on the dorsal aspect of the hand.

Adult↗
PubMed1998

The narrow band hypothesis: an interesting approach for high-intensity transient signals (HITS) detection.

We propose a new approach to detect microemboli automatically using the narrow band hypothesis. An initial database of 560 peripheral arterial Doppler high-intensity transient signals (HITS) was created to study microemboli and to define the normal limits to be used in our method. When a HITS occurs, our approach consists of modelling the Doppler signal using amplitude and frequency wave modulation. A threshold was defined experimentally using this database and then applied to 38 recordings from 12 patients. Using another database, six expert Doppler users reported 140, 176, 155, 161, 161 and 146 HITS, corresponding to a total of 197 different observed HITS. When an event was detected by 6, 5, 4, 3, 2 and 1 of the observers, the sensitivity of the automatic detection was 94.8%, 75.9%, 55.6%, 42.9%, 30% and 0%, respectively. The sensitivity of our automatic detection thus is highly associated with the likelihood (defined as the ratio of observers in agreement to the total number of observers) of an event: r = 0.99 for p < 0.0001. Although future research would result in improvement of the specificity, the narrow band hypothesis appears to be a promising technique for the detection of HITS.

Blood Flow Velocity↗
PubMed1998

Calf vein compliance increases following bed rest after aortocoronary bypass surgery.

Early post-operative ambulation (< 3 days) is expected to decrease the risk of venous thrombosis, whereas late ambulation (> 7 days) increases the risk of orthostatic hypotension. The effect of post-operative bed rest on calf vein compliance was studied before (D - 1) and 7 days (D + 7) after aortocoronary bypass surgery in 50 patients (41 men and nine women, 65 +/- SD 10 years). Calf vein compliance was measured by strain gauge plethysmography and stepwise increases in thigh congestive pressure from 20 to 60 mmHg. Calf compliance [median (25 percentile-75 percentile)] increased significantly by 48% from D - 1 to D + 7 [0.044 (0.039-0.051) vs. 0.065 (0.048-0.083) ml (100 ml mmHg)-1, P < 0.001]. This increase was reflected as increased calf volume for the 50 mmHg [D-1 2.10 (1.75-2.65) vs. D + 7 2.60 (1.70-3.00) ml 100 ml-1, P < 0.01] and 60 mmHg [D - 1 2.50 (2.10-2.95) vs. D + 7 3.20 (2.30-4.00) ml 100 ml-1, P < 0.001] occlusion pressure levels. The associated pathologies (diabetes and arterial hypertension) and NYHA grades had no significant influence on the increase in compliance. Among the vasoactive therapeutic regimens, calcium channel blockers contributed significantly to the increased calf compliance, but only on D-1. The increase in venous compliance following aortocoronary bypass surgery is multifactorial but should be considered for prophylactic management of these patients.

Aged↗