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Biomedical subjects

J Hirsh

Publications and source records attributed to J Hirsh.

At least 181 records · Page 10Linked to original sources
PubMed1994

Uninephrectomy aggravates tubulointerstitial injury in rats with adriamycin nephrosis.

The effects of uninephrectomy on the function and structure of the remnant kidney were assessed in rats with Adriamycin-induced nephrosis, 12 weeks after the injection of Adriamycin. The kidney volume of Adriamycin-treated uninephrectomized rats (NX-AD) was 2.3 times that of sham-operated, Adriamycin-treated animals (SH-AD; p < 0.001). The marked renal enlargement in NX-AD animals was due to the development of large tubular cysts. Following uninephrectomy, the fractional volume of tubular lumen almost doubled (NX-AD, 0.33 +/- 0.02; SH-AD, 0.17 +/- 0.02; p < 0.001) and the absolute volume of tubular lumen increased more than fourfold (NX-AD, 0.51 +/- 0.08 ml; SH-AD, 0.12 +/- 0.02 ml; p < 0.001). The frequency of tubular lumen with a large cross-sectional area (> or = 40,000 microns 2) was 5.8 +/- 1.1% in NX-AD and 0.7 +/- 0.2% in SH-AD groups (p < 0.001). The fractional volume of interstitial fibrosis in NX-AD animals was larger than in SH-AD (0.09 +/- 0.02 versus 0.04 +/- 0.01%, p < 0.05). As opposed to the worsening of tubulointerstitial disease, single-kidney glomerular filtration rate, fractional protein clearance, glomerular volume and the extent of glomerular sclerosis did not differ significantly in NX-AD as compared to SH-AD groups. This study shows that uninephrectomy in rats with Adriamycin nephrosis worsens interstitial nephrosis and aggravates the formation of tubular cysts, leading to a macrocystic kidney disease. These changes are not associated with an increase in glomerular sclerosis.

Animals↗
PubMed1994

Effects on thrombin generation of single injections of Hirulog in patients with calf vein thrombosis.

STUDY OBJECTIVE: To determine whether single injections of Hirulog, a direct thrombin inhibitor, can inhibit thrombin generation in patients with calf vein thrombosis and, if so, if the inhibition is sustained. DESIGN: Phase II open label cohort study. SETTING: Tertiary-care referral centres, university affiliated hospitals. PATIENTS: 10 patients with venographically-demonstrated calf vein thrombosis. INTERVENTION: Patients received a single injection of Hirulog, either 1.0 mg/kg subcutaneously or 0.6 mg/kg as a 15 min intravenous infusion. Prothrombin fragment (F1++2) levels, as an index of thrombin generation, were measured before as well as 6 h post- and 24 h post-Hirulog administration. Patients were followed with non-invasive tests to detect thrombus extension into the proximal veins. RESULTS: There was a significant reduction in the levels of F1+2 with both regimens, 6 h after Hirulog. The F1+2 levels 24 h post-Hirulog showed a significant increase relative to the 6 h post-Hirulog results. One patient developed thrombus extension into the popliteal vein and was treated with conventional anticoagulants. CONCLUSION: The single injections of Hirulog used in the study produced incomplete and temporary suppression of F1+2. Complete and permanent inhibition of thrombin generation with Hirulog in patients with calf vein thrombosis may require higher doses, multiple subcutaneous injections and/or prolonged intravenous infusion.

Aged↗
PubMed1994

Effects of erythropoietin on glucose tolerance in hemodialysis patients.

Erythropoietin (EPO) therapy is widely used to correct the anemia of end-stage renal disease. It has been reported that this treatment affects various hormonal systems. The aim of the present study was to evaluate the effects of EPO therapy on glucose tolerance. Anemia was corrected with EPO in 10 patients on chronic hemodialysis therapy. Oral glucose tolerance tests (OGTT) were performed before and after correction of anemia. The following measurements were made: the areas under the glucose curves (AUCglue), the areas over basal glucose values (OABVglue), the areas under the insulin curves (AUCins) and the areas over basal insulin values (AOBVins). Hemoglobin concentration increased from 70 +/- 1.4 milligrams to 111 +/- 1 milligram. Fasting plasma glucose, insulin and glucagon levels were were not affected by correction of the anemia. Following administration of EPO, AOBVglue increased by 19%, from 2101 +/- 243 to 2508 +/- 230 mmol.min/l (p < 0.02), while AOBVins remained unchanged. AUCins and AUCglue remained unchanged. These data show that correction of anemia with EPO in hemodialyzed patients causes an increase in the glycemic response to an oral glucose load while not affecting the insulin response.

Anemia↗
PubMed1994

Factors influencing the reported sensitivity and specificity of impedance plethysmography for proximal deep vein thrombosis.

A number of recent studies have found a considerably lower sensitivity of the IPG for proximal DVT than originally reported. We reviewed the literature to try and identify reasons for the between study differences in sensitivity and specificity of the IPG for proximal DVT. A number of biases were identified which may have inflated the sensitivity reported by some earlier studies including: repeated IPG testing prior to venography; inclusion of data from patients used to derive the IPG discriminant line in the final calculation of sensitivity; and inclusion of patients with a known abnormal IPG in the study population. In addition, there is emerging evidence that, at least in some centers, the sensitivity of the IPG may have decreased due to a shift in the spectrum of proximal DVTs to smaller clots. Furthermore, rates of conversion during serial follow-up are considerably higher for IPG than for venous ultrasound, suggesting that IPG conversion is often due to extension of small missed proximal DVTs rather than just extension of calf vein clots. As the smaller proximal DVTs which IPG is prone to miss are likely to be clinically less important than more extensive clots, it is unclear whether the recently reported drop in sensitivity of the IPG places patients at increased risk. IPG users need to be aware of its limitations, and we recommend that additional testing is performed in patients with a high clinical suspicion of DVT who have a normal IPG, as the negative predictive value of IPG may be unacceptable in these circumstances.

Humans↗
PubMed1994

In vitro effect of hirudin on recalcification time.

Hirudin, in its recombinant form (r-hirudin), is emerging as an ideal anticoagulant. As with any anticoagulant, the true anticoagulant property of hirudin should be contingent not on clinical criteria nor on anticoagulant levels, but on a functional assay that monitors changes in the rate at which blood clots. The purpose of this study was to determine the recalcification time (RT) of whole blood and of plasma on incubation with hirudin in vitro. Citrated human venous blood (n = 6) and plasma (n = 9) were incubated at 37 degrees C with either saline or 0.2 U/mL final concentration hirudin. The RT was measured instrumentally after neutralization of the citrate with CaCl2. Compared with saline, mean RT +/- SD values (minutes) with hirudin in blood increased from 6.9 +/- 0.8 to 7.6 +/- 0.6 minutes (P = .04) and in plasma from 9.0 +/- 1.4 to 11.2 +/- 1.4 (P = .001). We conclude that hirudin increases the RT values in both blood and plasma. The increased RT value in plasma is greater compared with that in blood. Whether this method can be used to titrate the dosage of hirudin warrants in vivo assessment.

Blood Coagulation Tests↗
PubMed1994

Multicentric evaluation of a new PT reagent based on recombinant human tissue factor and synthetic phospholipids.

A new PT reagent based on recombinant human tissue factor and synthetic phospholipids (phosphatidyl choline and phosphatidyl serine) with defined fatty acid side chains was calibrated against BCT/253 and CRM 149R. A small but consistent bias in the International Sensitivity Index (ISI) value was obtained using either the human or rabbit brain reference material. ISI values were around 1.0 or slightly lower depending on the respective instrument. Mixing studies with factor deficient plasmas showed a high factor sensitivity especially for factor VII as compared to commercial rabbit brain or human placenta thromboplastin. In an international field trial the reagent was tested using fully or semi automated Electra coagulometers in 4 different laboratories. Results with normal samples were in excellent agreement among the different laboratories. Mean values were 10.9, 10.9, 11.0, 11.2 s with a range of 9.5 to 12.5 s. Results of males and females were not different. In patients with liver disease very similar PT activities were found as compared to sensitive rabbit brain or human placental thromboplastins. In normals and patients with oral anticoagulation INR values correlated very well against BCT (r = 0.98, regression line y = -0.07 + 0.9 x). The distribution of samples was linear over the whole range. In the comparison against sensitive rabbit brain thromboplastin or human placental thromboplastin similar correlations were found. In a few cases higher INR values were observed for the recombinant reagent especially in patients with intensive treatment. Factor assays in those patients showed at least the strong reduction of one vitamin K-dependent coagulation factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Ex-vivo and in-vitro evidence that low molecular weight heparins exhibit less binding to plasma proteins than unfractionated heparin.

We have compared the non-specific binding of unfractionated heparin (UFH) with that of low molecular weight heparin (LMWH) to plasma proteins both ex-vivo and in-vitro. Non-specific binding to plasma proteins was assessed by comparing the heparin levels measured as anti-factor Xa activity before and after the addition of low affinity heparin, which is essentially devoid of anti-factor Xa activity, in order to displace heparin bound to plasma proteins. For the ex-vivo studies, we compared the recovery of UFH and a LMWH (ardeparin) from the plasma of patients participating in a randomized trial of post-operative venous thrombosis prophylaxis. For the in-vitro studies, we compared the recovery of UFH and 4 different LMWHs when added to the plasma from healthy volunteers and from patients with suspected venous thromboembolic disease. The results indicate that the recovery of LMWH is much less affected by nonspecific binding to plasma proteins both ex-vivo and in-vitro. In addition, there are differences between the LMWHs with respect to their plasma protein-binding.

Blood Proteins↗
PubMed1994

A new visible light DNA fluorochrome for confocal microscopy.

We have developed a new DNA-specific fluorochrome that is excited by visible light. This chemically uncharacterized fluorochrome readily penetrates tissue in whole mounts, gives a strong signal, is inexpensive to make and very easy to use. This preparation has several advantages over existing DNA fluorochromes in confocal laser microscopy applications. Many DNA fluorochromes are excitable by ultraviolet light. These have limited utility in confocal microscopy, where commonly used lasers produce only visible wavelengths of light. Other DNA fluorochromes are available that are excitable by visible light, but some have difficulty penetrating all cell types, while others have high background or fade quickly. This new fluorochrome overcomes these problems and has an emission spectra that makes it compatible with either rhodamine or Texas Red labeled reagents for double-label experiments. The ability to label all nuclei in a tissue and make three-dimensional reconstructions by confocal microscopy is extremely useful in examining cellular distributions within specific tissues.

Animals↗
PubMed1994

Effect of enalapril on the microvascular albumin leakage in patients with diabetic microangiopathy and normal or mildly elevated blood pressure.

The transcapillary escape rate of albumin (TERalb) is often elevated in patients with diabetic microangiopathy. The objective of this study was to examine the effect of enalapril on the TERalb of diabetic patients with albuminuria and normal or mildly elevated blood pressure. Seventeen diabetic patients with diabetic retinopathy, albuminuria, a diastolic blood pressure below 100 mmHg and increased TERalb participated in the study. Blood pressure and TERalb were measured before and after 14 days of therapy with enalapril, 20 mg daily for 14 days. Systolic and diastolic blood pressure fell from 168 +/- 6 to 155 +/- 6 (p < 0.001) and from 87 +/- 2 to 81 +/- 2 mmHg (p < 0.005) respectively. Mean arterial pressure declined from 114 +/- 3 to 105 +/- 3 mmHg (p < 0.0001). The elevated TERalb decreased from 9.5 +/- 0.5 to 7.2 +/- 0.5%/hr (p < 0.005). In the hypertensive subset, systolic, diastolic and mean arterial pressure decreased significantly by 15, 7 and 10 mmHg (p < 0.005, p < 0.005 and p < 0.005 respectively); TERalb decreased from 9.5 +/- 0.6 to 7.3 +/- 0.6 (p < 0.03). In the normotensive subset, arterial pressure remained unchanged and TERalb decreased from 9.0 +/- 0.8 to 6.8 +/- 1.0%/hr (p < 0.03). Plasma fructosamine decreased from 373 +/- 23 to 347 +/- 20 (p < 0.05) in the hypertensive group and remained unchanged in the normotensive patients. No correlation could be demonstrated between variation in TERalb and changes in blood pressure. In conclusion, enalapril decreases microvascular albumin leakage in patients with diabetic microangiopathy and normal or mildly elevated blood pressure.

Blood Pressure↗
PubMed1994

Low molecular weight heparin: a critical analysis of clinical trials.

LMWHs are an important new class of antithrombotic agents. They differ from UFH in having relatively more anti-Xa activity, greater bioavailability at low doses, longer half-life, and more predictable anticoagulant response when administered in fixed doses. These properties allow LMWHs to be administered QD or at most BID and without laboratory monitoring. The incidence of heparin-induced thrombocytopenia also appears to be lower with an LMWH than with heparin. Given their favorable pharmacological profile, it was of interest to critically appraise clinical trials of thromboprophylaxis and treatment with these new agents. In orthopedic trials, it was noted that LMWH provided safe and effective thromboprophylaxis for patients undergoing major orthopedic surgery of the lower limb. In those having hip arthroplasty, LMWH was as effective as low-intensity warfarin therapy, but its use was associated with more wound hematomas. In those having total knee arthroplasty, LMWH was more effective than warfarin and did not increase bleeding. However, the prevalence of DVTs complicating this procedure as well as acute hip fracture remains unacceptably high, and additional studies of LMWH in combination with other prophylactic methods, such as external pneumatic compression, are needed. Only one adequately designed trial found less bleeding resulted from LMWH prophylaxis administered at an equivalent antithrombotic dose to UFH. In general medical patients, LMWH appeared to be as effective as UFH and had the advantages of less frequent injections and fewer injection site hematomas. In general surgical patients, there was a lower risk of thromboembolism but a trend toward an increase in bleeding events. Subjects with strokes and spinal cord injuries benefited from fewer thrombotic events, and the latter had fewer bleeding complications. Other potential indications for LMWH, such as cardiopulmonary bypass, hemodialysis, and preservation of graft patency, are presently under study. Perhaps the most impressive benefits of LMWH will be realized when it is used for the treatment of venous thromboembolism. The meta-analysis presented in this review showed a trend toward greater efficacy with LMWH and fewer major bleeding events in comparison with adjusted-dose intravenous UFH. Also, during the months following the thrombotic event, there was significantly less mortality in patients receiving LMWH. A further advantage was the subcutaneous route of administration and lack of requirement for laboratory monitoring. Additional treatment trials are presently in progress and may establish LMWH as the treatment of choice for patients with thromboembolic disorders.

Animals↗
PubMed1993

Distribution of thrombosis in patients with symptomatic deep vein thrombosis. Implications for simplifying the diagnostic process with compression ultrasound.

BACKGROUND: Two different diagnostic strategies are used to perform compression (real-time) ultrasound for the diagnosis of clinically suspected deep-vein thrombosis. One is to examine the entire proximal venous system from common femoral to distal popliteal vein; the other is a limited examination of only the common femoral and the entire popliteal vein. The latter strategy, which is less time-consuming and requires less expensive equipment, is based on a strong impression from prospective studies using limited compression ultrasound that proximal vein thrombi always involve the common femoral or popliteal vein. This impression, which is supported by the demonstrated safety at long-term follow-up of not treating patients whose limited compression ultrasound is normal at presentation and then repeated within the next week, has not been tested in a formal study. Therefore, we reviewed a large series of venograms performed in consecutive patients with clinically suspected venous thrombosis to determine the distribution of venous thrombosis in symptomatic patients. METHODS: Venograms were performed using 150 mL of radiographic contrast material. Before the study, a panel of experts agreed on the standardized criteria for the assessment of venograms. Venograms were adjudicated blindly for the presence of deep vein thrombosis and to determine the distribution of proximal vein thrombosis and isolated calf-vein thrombosis, the size of proximal thrombi, and whether they were occlusive or nonocclusive. Subsequently, the duration of symptoms was related to the venographic findings. RESULTS: Five hundred sixty-two venograms from consecutive patients with a first episode of clinically suspected deep vein thrombosis were adjudicated. Of these, 20 (3.6%) were inadequate for interpretation. In the remaining 542, venous thrombosis was demonstrated in 189 instances (prevalence, 35%; 95% confidence interval, 31% to 39%) and were located in the proximal veins in 166 (88%; 95% confidence interval, 82% to 92%) venograms. Isolated calf-vein thrombosis was present in the remaining 23 (12%; 95% confidence interval, 8% to 18%) venograms. Proximal with concurrent calf thrombosis was detected in 164 (99%) of the 166 patients. Proximal thrombi involved only the popliteal vein in 16 (10%); the popliteal and superficial femoral veins in 70 (42%); and the popliteal, superficial, and common femoral vein in eight (5%); whereas thrombi involving the entire proximal deep venous system were detected in 58 (35%) venograms. Isolated thrombosis of the superficial femoral, common femoral, and iliac vein was not observed. Proximal venous thrombi were occlusive in 146 (88%) patients. No relation between the duration of symptoms and the extent or the occlusiveness of venous thrombi could be demonstrated. CONCLUSIONS: Most symptomatic patients have extensive occlusive proximal vein thrombosis at the time of presentation. Thrombi isolated to the superficial femoral or iliac vein were not observed in this large sample of consecutive patients. Our data support the use of the relatively simple, inexpensive, and rapid compression ultrasound method that limits the examination of the proximal veins to the common femoral and popliteal veins.

Analysis of Variance↗
PubMed1993

Efficacy and cost of low-molecular-weight heparin compared with standard heparin for the prevention of deep vein thrombosis after total hip arthroplasty.

PURPOSE: To compare the efficacy, safety, and cost-effectiveness of low-molecular-weight heparin with standard heparin for the prevention of deep vein thrombosis after total hip arthroplasty. DATA IDENTIFICATION: Studies were identified by MEDLINE search and review of bibliographies of retrieved articles. Hospital resources used in treating deep vein thrombosis and bleeding complications after total hip arthroplasty were estimated using retrospectively collected data from 447 patients who participated in a recently completed randomized controlled deep vein thrombosis prophylaxis trial at our center. STUDY SELECTION: Randomized controlled trials directly comparing a low-molecular-weight heparin preparation with standard heparin for the prevention of deep vein thrombosis after total hip arthroplasty were potentially eligible for the meta-analysis. DATA EXTRACTION: Data from eligible studies were extracted independently by two of the authors. Multiple regression analysis of data from the patient cohort was used to estimate the effect of deep vein thrombosis and bleeding on length of hospital stay. A hypothetical North American price for low-molecular-weight heparin was determined based on the ratio between low-molecular-weight heparin and standard heparin in France. Costs were based on weighted per-diem hospital expenditures and physician fees for procedures and reported in 1992 U.S. dollars. RESULTS OF DATA SYNTHESIS: Meta-analysis of six eligible trials determined that low-molecular-weight heparin was significantly more effective than standard heparin at preventing deep vein thrombosis after total hip arthroplasty (common odds ratio, 0.72; 95% CI, 0.53 to 0.95). However, this benefit was restricted to the prevention of proximal deep vein thrombosis (common odds ratio, 0.40; CI, 0.28 to 0.59). No significant differences were found in the rates of distal deep vein thrombosis or total, major, or minor bleeding between the two groups. Based on a 2.6 to 1 price ratio between low-molecular-weight heparin and standard heparin, use of low-molecular-weight heparin would save the health care system about $50,000 per 1000 patients treated. Sensitivity analysis shows that if the low-molecular-weight heparin/standard heparin price ratio exceeds 3.7 (the threshold value lies between 0.8 and 5.5 based on the extremes of the 95% CI of the common odds ratios for deep vein thrombosis and bleeding complications), use of low-molecular-weight heparin is more expensive. At a price ratio of 10, it would cost more than $250,000 to treat 1000 patients with low-molecular-weight heparin compared with standard heparin or about $5000 for each additional deep vein thrombosis prevented with low-molecular-weight heparin. CONCLUSIONS: Low-molecular-weight heparin is more effective and is at least as safe as standard heparin for the prevention of deep vein thrombosis after total hip arthroplasty. Based on the current French price ratio of low-molecular-weight heparin to standard heparin, the use of low-molecular-weight heparin in North America would result in overall savings in cost; however, the relative cost-effectiveness is critically dependent on the price ratio between the two drugs. Further research is needed to compare the cost-effectiveness of low-molecular-weight heparin with other prophylactic regimens and postoperative deep vein thrombosis management strategies.

Cost-Benefit Analysis↗
PubMed1993

Comparison of the non-specific binding of unfractionated heparin and low molecular weight heparin (Enoxaparin) to plasma proteins.

The non-specific binding of anticoagulantly-active heparin to plasma proteins may influence its anticoagulant effect. We used low affinity heparin (LAH) essentially devoid of anti-factor Xa activity to investigate the extent and possible mechanism of this non-specific binding. The addition of excess LAH to platelet-poor plasma containing a fixed amount of unfractionated heparin doubled the anti-factor Xa activity presumably because it displaces anticoagulantly-active heparin from plasma proteins. Although dextran sulfates of varying molecular weights also increased the anti-factor Xa activity, less sulfated heparin-like polysaccharides had no effect. These findings suggest that the ability to displace active heparin from plasma protein binding sites is related to charge and may be independent of molecular size. In contrast to its effect in plasma containing unfractionated heparin, there was little augmentation in anti-factor Xa activity when LAH was added to plasma containing low molecular weight heparin (LMWH), indicating that LMWH binds less to plasma proteins than unfractionated heparin. This concept is supported by studies comparing the anticoagulant activity of unfractionated heparin and LMWH in plasma with that in buffer containing antithrombin III. The anti-factor Xa activity of unfractionated heparin was 2-fold less in plasma than in the purified system. In contrast, LMWH had identical anti-factor Xa activity in both plasma and buffer, respectively. These findings may be clinically relevant because the recovered anti-factor Xa activity of unfractionated heparin was 33% lower in plasma from patients with suspected venous thrombosis than in plasma from healthy volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III↗
PubMed1993

The additive effect of low molecular weight heparins on thrombin inhibition by dermatan sulfate.

The aim of this study was to investigate the mechanism by which the anticoagulant activity of dermatan sulfate (DS) is increased by low molecular weight heparin (LMWH). In platelet poor plasma, LMWH enhances the effect of DS on thrombin (IIa) inhibition as determined by thrombin clotting times and with a chromogenic substrate assay. Analysis of the results of the chromogenic assays using either the algebraic fractional or the graphic isobole method suggests that LMWH has an additive effect on the anti-IIa activity of DS. This additive effect was lost when the experiments were repeated in plasma immunodepleted of antithrombin III (ATIII), indicating that the anti-IIa activity of LMWH is ATIII-dependent. To further explore the mechanism of the interaction between LMWH and DS, 125I-labeled IIa was added to plasma in the presence or absence of DS and/or LMWH and the formation of IIa-inhibitor complexes was assessed using SDS-PAGE followed by autoradiography. DS addition selectively increases the formation of heparin cofactor II (HCII)-IIa complexes, whereas LMWH enhances ATIII-IIa complex generation. Compared to plasma containing DS alone, the formation of ATIII-IIa complexes also is increased when the combination of DS and LMWH is added. These findings suggest that the additive effect of LMWH on the anti-IIa activity of DS reflects their different modes of IIa inhibition; DS potentiates IIa inhibition by HCII, while LMWH catalyses ATIII-dependent IIa inactivation. The potential clinical significance of these findings requires further investigation.

Amino Acid Sequence↗