[Correction of spectral interferences in inductively coupled plasma atomic emission spectrometry with a modified chemometric method based on matrix projection]

A modified chemometric method based on matrix projection was developed to correct the spectral interferences in inductively coupled plasma atomic emission spectrometry (ICP-AES). The accuracy of the correction was significantly improved by reevaluating the residuals. The excellent analytical results for some rare earth elements proved the method fairly feasible.

Financial strain, received support, anticipated support, and depressive symptoms in the People's Republic of China

The purpose of this study is to examine the interface between financial strain, informal received economic support, informal anticipated financial support, and psychological distress in later life. Data provided by a large probability sample of older adults in the People's Republic of China reveal that the relationship between financial difficulty and psychological distress is stronger for older adults who receive more economic assistance. However, the results involving anticipated support are in the opposite direction. More specifically, the association between financial problems and psychological distress is lower for older adults who believe that others stand ready to help in the future should the need arise. A detailed theoretical rationale is developed to explain these results.

Norplant consensus statement and background review

This review has highlighted the attributes of a very important new method of contraception. The signatories to this document agree that, with the provision of appropriate information and instruction for the user, Norplant is a good contraceptive choice to be made available worldwide in family planning programs that have the resources for appropriate training and counseling. The signatories to this document are acting in their own personal capacity and not as representatives of any particular organization.

[Three-dimensional cardiac simulation model of finite element--theoretical basis of cardiac simulation of 3D model]

Cardiac simulation model is a frontier topic in the theoretical field of cardiac simulation. In this paper, dissipating energy model is presented to solve element equation and hence to reveal the rule of activities of heart.

[Purification and application of viral capsid antigen of Epstein-Barr virus]

The viral capsid antigen of Epstein-Barr virus was purified from sf9 cells infected with recombinant Baculoviruses and the purified protein was used to establish ELISA and immuno-strip method for detection of VCA/IgG and VCA/IgA antibodies in human sera. A sensitive, specific and cost-effective method has been developed for serological mass survey.

[Study on atomic emission spectrum and spectral interferences of rare earth elements with a high resolution inductively coupled plasma atomic emission spectrometer.--II. Spectral intererences of Samarium matrix]

The rare earth elements play a very important role in today's manufacture and life. For their complex spectra it is difficult to determine the trace elements in rare earth element matrix. This work investigated the spectral interferences of samarium matrix on other rare earth elements with a high resolution inductively coupled plasma atomic emission spectrometer. A lots of spectrum information and spectral interferences were obtained, which are quite useful in the selection of analytical lines that free of spectral interferences and the elimination of the concomitant's interferences.

[Chemical constitutents of Podocarpus imbricatus BI. (II)]

From Podocarpus imbricatus five compounds were isolated and identified as 2"-O-rhamnosylvitexin (I), hinokiflavone (II), ecdysterone (III), beta-sitosteryl heptadecoate (IV) and daucosterol(V) on the basis of spectral studies (UV, IR, 1HNMR, 13CNMR, MS) and chemical reactions. I, II, III, IV are obtained from this plant for the first time, and IV is obtained as beta-sitosteryl odd number carboxylic ester for the first time.

Safety, efficacy, and acceptability of medical abortion in China, Cuba, and India: a comparative trial of mifepristone-misoprostol versus surgical abortion

OBJECTIVE

We investigated safety, efficacy, and acceptability of an oral regimen of medical abortion compared with surgical abortion in three developing countries.

STUDY DESIGN

Women (n = 1373) with amenorrhea < or = 56 days chose either surgical abortion (as provided routinely) or 600 mg of mifepristone followed after 48 hours by 400 micrograms of misoprostol. This is the appropriate design for studying safety, efficacy, and acceptability among women selecting medical abortion over available surgical services.

RESULTS

The medical regimen had more side effects, particularly bleeding, than did surgical abortion but very few serious side effects. Failure rates for medical abortion, although low, exceeded those for surgical abortion: 8.6% versus 0.4% (China), 16.0% versus 4.0% (Cuba), and 5.2% versus 0% (India). Nearly half of failures among medical clients were not true drug failures, however, but surgical interventions not medically necessary (acceptability failures or misdiagnoses). Women were satisfied with either method, but more preferred medical abortion.

CONCLUSION

Medical abortion can be safe, efficacious, and acceptable in developing countries.

Effect of a mechanical vs a pharmacologic increase in aortic pressure on coronary blood flow and thrombolysis induced by IV administration of a thrombolytic agent

This study was designed to compare the effect of a mechanical vs a pharmacologic increase in BP on coronary artery blood flow and thrombolysis induced by IV administration of recombinant tissue plasminogen activator. We employed a canine model of coronary thrombosis induced by injection of radioactive blood clot in the left anterior descending coronary artery. Subsequently, all dogs underwent phlebotomy to decrease systolic BP to 75 mm Hg and this decreased coronary blood flow by 50%. BP was increased to 130 mm Hg by norepinephrine (NE) infusion or by inflation of a Fogarty catheter placed in the descending aorta. Interventions with NE or with a Fogarty balloon catheter increased coronary artery blood flow to similar values and rates of coronary thrombolysis were similar. However, cardiac output was significantly higher with NE. These results indicate coronary clot lysis is dependent on perfusion pressure and coronary blood flow, not cardiac output.

[Determination of loganin in the fruit of Cornus officinalis Sieb. et Zucc]

A high performance liquid chromatographic method has been developed for the determination of loganin in the fruit of Cornus of ficinalis. The method is rapid, accurate and sensitive.

Old-age support system and policy reform in China

"With the on-going economic transition from the central planned system to a market-oriented system, the population aging process in China is also accelerating, and the support system for the elderly becomes an important issue demanding attention. With data from Chinese national statistics and a regional probability sampling survey in Wuhan Area, two supporting systems for the aged in China are examined in this paper. After a briefing of the population aging process in China, a detailed discussion of the two supporting systems, i.e. the formal and the informal support systems for the aged, including arrangement, operation and funding mechanisms of the systems, is made in terms of policy reform. Then follows an international comparison to highlight features and problems of the Chinese systems. Finally, solutions are proposed for the restructuring of China's pension systems."

Induction of antitumor immunity and treatment of preestablished tumor by interleukin-6-gene-transfected melanoma cells combined with low-dose interleukin-2

Transfer of cytokine genes into tumor cells has proven a valuable approach for cancer treatment. In order to generate a more effective cancer vaccine, we transfected the human interleukin-6 (IL-6) gene into B16 melanoma cells. A B16 cell clone secreting the highest level of IL-6 was obtained by G418-resistant selection, limiting dilution and IL-6 assay. The IL-6-gene-transfected tumor cells exhibited in vitro growth inhibition, reduced tumorigenicity and decreased metastatic competence. After immunization with the inactivated IL-6-gene-transfected vaccine, the murine cytotoxic T lymphocyte activity, natural killer activity and lymphokine-activated killer activity increased markedly. After treatment with the vaccine, the tumor-bearing mice showed significant growth inhibition of subcutaneous tumor, reduction in pulmonary metastases and extension of survival time. The above therapeutic effect was better when low-dose IL-2 was administered simultaneously, although this dosage of IL-2 had no in vivo antitumor effect. These data demonstrated that IL-6-gene-transfected cancer vaccine has a potent antitumor effect via efficient induction of antitumor immunity, and a better therapeutic effect could be achieved when the vaccine is combined with low-dose IL-2 as adjuvant.

Flows of social support and health status among older persons in China

As a consequence of the political, social, and economic developments in contemporary China, there have been considerable changes in the patterns of flows of social support between Chinese older people and their significant others. There is evidence that Chinese elders are now under strong pressure to provide more social support, instrumental support in particular, to their children and other relatives while they receive less. Such a change in the direction of flows of social support has been reported to worsen the elders' health. This paper describes the general pattern of social support both to and from the Chinese elders, using data of a probability sample survey conducted in Wuhan, China in 1991. The association between social support, both receiving and providing, and old-age health status is also analysed within a multivariate framework. The results of two probit models suggest that emotional support received plays a crucial role in affecting an elder's health status, while instrumental support received does not have explicit impacts. In addition, there is no empirical evidence that increased instrumental support from elders has worsened their health status as reported.

Sex, marital status, and psychological distress in later life: a comparative analysis

Some investigators maintain that while married men experience less distress than married women, the opposite may be true for those who are not married. In this instance, women are thought to report fewer symptoms of distress than men. The purpose of this study is to examine the relationships among gender, marital status, psychological distress and alcohol use in five culturally-diverse groups of older adults: U.S. whites, U.S. blacks, Japanese, Taiwanese and elderly people in the People's Republic of China. We find little evidence of the pattern described above. Instead, the data suggest that being single is equally detrimental for older men and women regardless of the cultural setting.

Effectiveness of Norplant implants through seven years: a large-scale study in China

The effectiveness of Norplant implants over a seven year period of continuous use was studied in a multicenter trial. Pregnancy rates were 0.4 per 100 in both year six and year seven. More than 3,600 women completed 6 years and more than 2,400 women completed 7 years. Pregnancy rates increased with weight (p < .05) and decreased with age, but in years 6 and 7 combined, the pregnancy rate neither reached nor exceeded 1 per 100 woman years in any 5 year age group or in any 10 kg weight group.

Intravenous administration of recombinant tissue plasminogen activator. Optimizing the rate of coronary thrombolysis

Although many studies have confirmed the efficacy of thrombolytic therapy in treatment of acute myocardial infarction, few studies have been designed to determine which dose regimen optimizes the rate of coronary thrombolysis. This study was designed to compare the efficacy of coronary thrombolysis obtained with intravenous administration of three dose regimens of recombinant tissue plasminogen activator (rtPA). The same total dose was administered as a bolus, over 30 min, or over 90 min. A canine model was employed. Coronary thrombosis was induced by injection of radioactive blood clot through a catheter placed in the left anterior descending coronary artery. Subsequently, 18 dogs were randomized into 3 groups of 6 dogs each. In group 1 dogs, 0.5 mg/kg of rtPA was administered intravenously as a bolus; in the group 2 dogs, rtPA was administered intravenously over 30 min (rtPA30); in the group 3 dogs, the drug was administered over 90 min (rtPA90). Coronary thrombolysis was assessed with a gamma camera. While at 100 min, the extent of clot lysis was similar between groups, 15 and 30 min after the start of rtPA administration, coronary thrombolysis was significantly less in the rtPA90 group. These results indicate that for a given total dose of rtPA, the rate of intravenous administration may significantly affect the rate of coronary thrombolysis.

[Study on the optimums for Pseudomonas maltophilia HCG receptor expression]

According to the design of orthogonal experiment, the optimums for expression of Pseudomonas maltophilia with HCG receptor were studied by radioassay. The results showed that the optimums influencing the specific binding percentage of Pseudomonas maltophilia were the cultures of No. 3 solid medium added with 0.5% galactose and incubated at a temperature of 37 C for 72 hours. Under these conditions, the binding percentage of Pseudomonas maltophilia to HCG was higher than those under other conditions.

An increase in low aortic pressure increases coronary artery flow and coronary thrombolysis induced by intravenous administration of recombinant tissue plasminogen activator

PURPOSE

Our study investigated the effects of an increase in aortic pressure, induced by norepinephrine (NE) administration on coronary artery flow in a clotted artery, and rate of coronary thrombolysis induced by intravenous (i.v.) administration of recombinant tissue plasminogen activator (rtPA).

METHODS

A canine model of coronary thrombosis, induced by intracoronary injection of radioactive autologous blood clots, was used to test the hypothesis that an increase in aortic blood pressure will increase coronary artery flow and the rate of clot lysis induced by i.v. administration of rtPA.

RESULTS

After clot injection, 11 dogs were phlebotomized to decrease systolic aortic pressure to 75 mm Hg. Subsequently, .25 mg/kg of rtPA was administered intravenously over two 15-minute intervals, one during hypotension, and the other after NE infusion had increased systolic blood pressure to 130 mm Hg. In six dogs the hypotensive condition was studied first, and in five dogs the NE-induced normotensive condition was studied first. In all dogs, coronary artery flow and the rate of clot lysis were significantly increased in the normotensive condition.

CONCLUSIONS

These results indicate that an increase in a low coronary artery perfusion pressure may enhance coronary artery flow and the rate of thrombolysis.

[Chemical compositions of Podocarpus imbricatus]

Twelve components were isolated from Podocar pus imbricatus, of which ten were identified as imbricatafiavone A (1), imbricataflavone B (2), robustaflavone (3), robustaflavone-7"-methyl ether (4), podocarpusflavone A (5), sandaracopimaric acid (6), beta-sitosterol (7), p-hydroxybenzoic acid (8), n-C34H69OH (9) and 10-nonacosanone (10). 4, 5, 8, 9 and 10 are obtained from the species for the first time.

Effects of progressive vascular occlusion on slope and intercept of the pulmonary artery pressure-flow relationship

Pulmonary hemodynamics may be described by mean pulmonary arterial pressure (PAP)-cardiac output (CO) plots. The slope of the PAP-CO relationship may define the incremental resistance (IR), and the extrapolated pressure intercept (P(I)), the effective outflow pressure. The authors investigated the effects of progressive pulmonary vascular occlusion on the IR and P(I) of the PAP-CO plot. Nine experimental and nine time control dogs were studied. In the former group, PAP-CO plots were obtained in three conditions: (1) Baseline, (2) following occlusion of the right pulmonary artery, and (3) following occlusion of the right pulmonary artery and blood flow to the left upper lobe. Following progressive occlusion, there was a corresponding increase in the IR of the PAP-CO plot, from 1.95 to 3.62 to 5.16 mmHg.1-1.min (all P < 0.05). In contrast to the increase in IR, P(I) remained constant. Over the same interval, there were no changes in IR or P(I) in the time control group. These findings indicate that changes in the slope of the PAP-CO plot correspond to changes in the number of parallel vascular units.

Effect of rate of administration of recombinant tissue plasminogen activator on efficacy of coronary thrombolysis

The authors employed a canine model of coronary thrombosis, induced by injection of radioactive blood clot, via a catheter placed in the left anterior descending (LAD) coronary artery, to compare effects of different rates of administration of recombinant tissue plasminogen activator (rtPA) on efficacy of coronary thrombolysis. In one group of dogs 0.75 mg/kg of rtPA was administered via the catheter placed in the LAD coronary artery over fifteen minutes. In a second group of dogs the same dose of rtPA was administered over forty-five minutes. Compared with the group in which the drug was administered over forty-five minutes, by thirty and forty-five minutes after onset of treatment, the extent of coronary thrombolysis was significantly greater (P < 0.05) in the group who received the drug over fifteen minutes. These results demonstrate that the rate of intracoronary administration of rtPA may significantly affect thrombolytic efficacy.

A five-year evaluation of NORPLANT II implants in China

A five-year study of NORPLANT II rod implants was undertaken in four large cities and metropolitan areas in eastern China. Designed to test the safety, efficacy and acceptability of these implants, the study involved 1,208 women and was conducted concurrently with a similar study of NORPLANT capsule implants. At the end of five years, the gross pregnancy rate was 0.65 per 100, and the continuation rate was 65.3 per 100. Both these values were similar to and not statistically different from the rates of the capsule implant users. In 4,828 woman-years of use, there were few severe adverse events reported. Users and providers found the method to be an acceptable long-term contraceptive method of great reliability.

Intraaortic balloon counterpulsation enhances coronary thrombolysis induced by intravenous administration of a thrombolytic agent

OBJECTIVES

This study was designed to test the hypothesis that in the presence of moderate hypotension, intraaortic balloon counterpulsation would enhance coronary thrombolysis induced by intravenous administration of recombinant tissue-type plasminogen activator (rt-PA).

BACKGROUND

Although many studies have confirmed the efficacy of thrombolytic therapy in acute myocardial infarction, few have systematically investigated the effects of alterations in aortic pressure on coronary thrombolysis, and none have previously investigated the effects of intraaortic balloon counterpulsation on thrombolysis.

METHODS

The effects of intraaortic balloon counterpulsation on aortic pressure, coronary blood flow and coronary thrombolysis were studied in a canine model. Coronary thrombosis was induced in eight dogs by injection of radioactive blood clot through a catheter placed in the left anterior descending coronary artery. Subsequently, dogs underwent phlebotomy to decrease systolic aortic pressure to approximately 90 mm Hg. After phlebotomy, during a 15-min interval of intravenous administration of rt-PA, coronary thrombolysis and coronary flow were determined during and in the absence of counterpulsation.

RESULTS

Intraaortic balloon counterpulsation significantly increased aortic diastolic pressure. Corresponding to the increase in pressure, intraaortic balloon counterpulsation significantly increased the rate of rt-PA-induced coronary thrombolysis. Although not statistically significant, peak diastolic coronary flow tended to increase with counterpulsation.

CONCLUSIONS

These results indicate that in the presence of moderate systemic hypotension, intraaortic balloon counterpulsation enhances the rate of rt-PA-induced coronary thrombolysis.

p53 gene mutations in Chinese human testicular seminoma

Genomic deoxyribonucleic acid from 17 primary human testicular seminomas was screened for the presence of mutations in exons 5 to 8 of gene p53, using the single strand conformation polymorphism assay, followed by direct deoxyribonucleic acid sequencing. The p53 mutations in 1 allele leading to an amino acid change but a normal (wild-type) sequence in the remaining allele were identified in 4 of 17 seminomas (23.5%). Sites of mutations were in exon 5 (codon 141), exon 7 (codon 238, codon 258) and exon 8 (codon 270). The present study suggested that mutation of the p53 gene is involved in the development of human testicular seminoma as in the case of several other types of human cancers.

Mesonephric contribution to testis differentiation in the fetal mouse

Testes from 11.5-day-old mouse embryos, with and without attached mesonephroi, were cultured for 7 days. Isolated testes failed to develop well-differentiated testis cords: however, when cultured attached to a mesonephros from either a male or a female donor embryo, testes developed cords that were normal in appearance. Testes cultured next to a mesonephric region but separated from it by a permeable filter, did not develop normal cords, nor did testes grafted to fragments of embryonic limb or heart. When testes were grafted to mesonephric regions from mice carrying a transgenic marker, the marker was found in some of the peritubular myoid cells and other interstitial cells of the testis, but not in the Sertoli cells or the germ cells. We conclude that after 11.5 days post coitum, cells can migrate from the mesonephric region into the differentiating testis and can contribute to the interstitial cell population, and that this contribution is necessary for the establishment of normal cord structure. The germ cells in all cultured testes, whether or not differentiated cords were present, were T1 prospermatogonia: no meiotic germ cells were seen.

Digital subtraction angiography in the diagnosis of congenital heart diseases: analysis of 60 cases

Ninety-one IVDSA and/or IADSA examinations with 192 injections were performed in 60 patients with congenital heart disease (CHD), including 31 anatomic anomalies. Axial projection was used in 23 patients. Analysis of the results of this series showed that accurate diagnosis by DSA confirmed by cardiac surgery together with definite diagnosis by DSA were obtained in 54 cases (90%). Two cases of nondiagnosis by DSA resulted from a suboptimal DSA method; four cases of partially accurate or mistaken diagnosis determined by cardiac surgery occurred because the axial view was not used and/or the anomalies were too small to be visualized by DSA. To increase the diagnostic accuracy of DSA in CHD, an optimal method of DSA must be selected according to the position of the anomaly and the hemodynamic data, and the axial view should be used to visualize the anomaly clearly in complex cases. In addition, DSA may fail to define a mild anomaly because of its lower spatial resolution.

Marked systemic hypotension depresses coronary thrombolysis induced by intracoronary administration of recombinant tissue-type plasminogen activator

OBJECTIVES

This study was designed to test the hypothesis that the level of aortic blood pressure affects the rate and extent of coronary thrombolysis induced by intracoronary administration of recombinant tissue-type plasminogen activator (rt-PA).

BACKGROUND

Although many studies have confirmed the efficacy of thrombolytic therapy in the treatment of acute myocardial infarction, the effects of altered blood pressure on coronary thrombolysis have not been studied. Because the aortic pressure represents the coronary artery inflow pressure, first principles predict that changes in blood pressure will affect the delivery of the thrombolytic agent and thus affect thrombolysis.

METHODS

The effects of large changes in blood pressure on coronary thrombolysis were studied in a canine model. Coronary thrombosis was induced by injection of radioactive blood clot through a catheter placed in the left anterior descending coronary artery. Subsequently, 24 dogs were classified into three groups of 8 dogs each: Group 1 dogs underwent phlebotomy to adjust systolic blood pressure to 130 mm Hg; Group 2 dogs underwent phlebotomy to decrease systolic blood pressure to 75 mm Hg. Dogs in Group 3 also underwent phlebotomy to achieve a systolic blood pressure of 75 mm Hg and then received norepinephrine to increase this pressure to 130 mm Hg. After adjustment in blood pressure, all dogs received an infusion of rt-PA (0.25 mg/kg body weight) over 30 min through the left anterior descending artery catheter. In a fourth group of six dogs, the effect of altered blood pressure on the rate of coronary thrombolysis was assessed.

RESULTS

In dogs in Groups 1 and 3, the rate and extent of coronary thrombolysis were significantly increased compared with values in Group 2. In each of the six Group 4 dogs the rate of coronary thrombolysis increased when norepinephrine increased systolic blood pressure from 75 to 130 mm Hg.

CONCLUSIONS

These results indicate that a moderate increase in coronary inflow pressure increases the rate and extent of coronary thrombolysis compared with values during marked systemic hypotension.

Social support among the aged in Wuhan, China

"This study provides information on supportive social relations in a sample of 2,762 elderly people in Wuhan, China. The elderly concerned were found to be actively engaged in exchanges of social support with their families and kin. They not only receive assistance but also provide a substantial amount of help to others. These supportive ties were highly positive and satisfactory to the great majority of the respondents. Only moderate correlations were found among various dimensions of social support. These results underscore the multi-dimensional nature of social support and suggest that caution needs to be exercised in extrapolating interpersonal exchanges from social embeddedness."

Pulmonary vascular pressure-flow characteristics. Effects of dopamine before and after pulmonary embolism

We compared the general hemodynamic effects of dopamine and dobutamine in dogs with acute pulmonary hypertension complicated by a decrease in cardiac output (CO). The pulmonary hypertension was induced by injection of autologous blood clot. Emboli markedly increased mean pulmonary artery pressure (Ppa) and decreased CO (both p < 0.001). Both dopamine and dobutamine increased CO 50% (p < 0.05) and decreased pulmonary vascular resistance (PVR) (p < 0.05), calculated as (PAP - left ventricular end diastolic pressure)/CO. Mean PVR (mm Hg/L/min) decreased from 16.1 to 12.4 with dopamine and from 16. to 11.9 with dobutamine, both p < 0.05. Ventricular filling pressures were not affected. In another 12 dogs we investigated the effects of both drugs on pulmonary pressure-flow (P-Q) characteristics. P-Q characteristics were determined in dogs with normal Ppa values and in those with embolic pulmonary hypertension. The slope of the P-Q relationship defines the incremental vascular resistance and the extrapolated pressure intercept, the effective vascular outflow pressure. All P-Q relationships were described well by a linear equation. Despite significant systemic effects in both groups and despite a decrease in PVR with both drugs in embolized dogs, neither drug significantly affected pulmonary P-Q characteristics. The discrepancy between PVR and incremental resistance is explained by an incorrect assumption in PVR that the left ventricular filling pressure is the effective vascular outflow pressure. We conclude that both before and after the induction of pulmonary hypertension, both dopamine and dobutamine improve CO without affecting pulmonary vascular tone.

Coronary thrombolysis. Comparative effects of intracoronary administration of recombinant tissue plasminogen activator and urokinase

We employed a canine model of coronary thrombosis, induced by injection of radioactive blood clot, via a catheter placed in the left anterior descending coronary artery, to compare effects of intracoronary administration of recombinant tissue plasminogen activator (rtPA) and urokinase (UK) on rate and extent of coronary thrombolysis. Two doses of UK, 15,000 U/kg (UK15) and 30,000 U/kg (UK30) and two doses of rtPA, 0.25 mg/kg (rtPA.25) and 0.75 mg/kg (rtPA.75) were given. Drugs were infused over 45 min. Compared with the other regimens, rate and extent of coronary thrombolysis were significantly increased with rtPA.75. Also, despite a much higher dose of UK, coronary thrombolysis was similar with UK30 and rtPA.25. Compared with UK15, rate and extent of coronary thrombolysis were increased with rtPA.25. These results indicate that intracoronary administration of rtPA is superior to intracoronary UK in inducing thrombolysis.

Effect of low-molecular-weight heparin on recombinant tissue plasminogen activator-induced thrombolysis in canine pulmonary embolism

We employed a canine model of pulmonary embolism induced by radioactive blood clots to determine if low-molecular-weight heparin augments recombinant tissue plasminogen activator (rtPA)-induced thrombolysis. Following embolization, dogs were randomized: group 1 dogs received heparin; group 2 dogs received low-molecular-weight heparin; group 3 dogs received 1.5 mg/kg of rtPA over 45 minutes; group 4 dogs received rtPA 3 mg/kg over 45 minutes; and group 5 dogs received 1.5 mg/kg of rtPA plus low-molecular-weight heparin. Over three hours, little thrombolysis occurred in groups 1 and 2. In contrast, significant thrombolysis occurred in groups 3 to 5, 46 percent, 49 percent, and 46 percent, respectively (all p less than 0.01 compared with groups 1 and 2). We conclude that there is an upper limit to the dose-thrombolytic rate relationship with rtPA, and that low-molecular-weight heparin does not augment rtPA-induced thrombolysis.

Digital angiographic impulse response analysis of regional myocardial perfusion. Estimation of coronary flow, flow reserve, and distribution volume by compartmental transit time measurement in a canine model

A system impulse response function that describes the kinetics of radiographic contrast material transit through the coronary circulation was calculated from 175 selective digital angiograms of normal and stenotic arteries in 10 dogs during rest and hyperemia. The goal of the study was to determine if the flow and distribution volume characteristics of the epicardial coronary arteries and the myocardial microcirculation could be stimulated by specific mathematical compartments of a lagged normal density model impulse response function in which the flow/distribution volume ratio is the inverse of the mean transit time. The arterial compartment mean transit time correlated with flow (r = 0.75); however, the correlation was significantly improved in individual dogs (r = 0.83 +/- 0.13; p less than 0.005) and was highly dependent on the length of the conduit vessel. The microcirculation compartment mean transit time was distributed as two populations with respect to flow. There was a linear correlation during hyperemia (r = 0.87) and a nonlinear relation during rest, which was characteristic of an autoregulating system. Resting values of microcirculation compartment mean transit time correlated with coronary flow reserve (r = 0.84) and differed significantly between vessels that were normal and those with subcritical stenosis, critical stenosis, or total occlusion (p less than 0.01 for all comparisons). The estimated microcirculation compartment distribution volume increased from a minimum of 4.0 +/- 1.5 ml/100 g myocardium in normal vessels with resting flow to 11.2 +/- 3.5 ml/100 g during hyperemia. These data suggest that the model compartments functionally describe the physiological behavior of their anatomic analogues and permit the quantification of microcirculatory autoregulation from a single measurement at rest without provoking hyperemia.