A feasibility study on quantitating myocardial perfusion with Albunex, an ultrasonic contrast agent.

Quantitating regional myocardial perfusion has been the much sought-after but still elusive goal of many intensive investigations over the years. Videodensitometry of the variation of myocardial echogenicity in two-dimensional (2-D) echocardiograms as a function of time in conjunction with the injection of a bolus of an ultrasound contrast agent has been used clinically as a tool for a direct assessment of regional myocardial perfusion, despite that the precise relationship between tissue echogenicity observed on an image and the echoes detected by the ultrasonic probe is unknown. A study was undertaken to determine whether ultrasonic backscatter calculated from unprocessed radio frequency (RF) echoes returned from myocardium could be used to quantitate regional myocardium perfusion. A real-time ultrasonic scanner has been modified and interfaced to a microcomputer to acquire RF data at a rate up to 10 frames per second. Preliminary experimental data were obtained from four open-chest dogs following intracoronary injection of a bolus of Albunex and two dogs following intravenous injection with this modified scanner. On one hand, these results indicate that the integrated backscatter measured from the region of myocardium perfused by the coronary artery where Albunex is injected and selected for monitoring initially increases, reaches a peak, and then decreases as the contrast agent is washed out and that the magnitude of the peak is approximately linearly proportional to the volume concentration of Albunex microspheres injected, clearly demonstrating the feasibility of this approach for quantitating region myocardial perfusion. On the other hand, intravenous injections did not result in any appreciable change in myocardial backscatter in the left ventricle although a response could be observed in the left ventricular blood pool.

Impact of HIV infection on mortality and accuracy of AIDS reporting on death certificates.

To assess the impact of HIV infection on mortality and the accuracy of AIDS reporting on death certificates, we analyzed data from 6704 homosexual and bisexual men in the San Francisco City Clinic cohort. Identification of AIDS cases and deaths in the cohort was determined through multiple sources, including the national AIDS surveillance registry and the National Death Index. Through 1990, 1518 deaths had been reported in the cohort and 1292 death certificates obtained. Of the 1292 death certificates, 1162 were for known AIDS cases, but 9% of the AIDS cases did not have HIV infection or AIDS noted on the death certificate. Only 0.7% of the decedents had AIDS listed as a cause of death and had not been reported to AIDS surveillance. AIDS and HIV infection was the leading cause of death in the cohort, with the highest proportionate mortality ratio (85%) and standardized mortality ratio (153 in 1987), and the largest number of years of potential life lost (32,008 years). The devastating impact of HIV infection on mortality is increasing and will require continued efforts to prevent and treat HIV infection.

Course of HIV-I infection in a cohort of homosexual and bisexual men: an 11 year follow up study.

OBJECTIVE--To characterise the natural history of sexually transmitted HIV-I infection in homosexual and bisexual men. DESIGN--Cohort study. SETTING--San Francisco municipal sexually transmitted disease clinic. PATIENTS--Cohort included 6705 homosexual and bisexual men originally recruited from 1978 to 1980 for studies of sexually transmitted hepatitis B. This analysis is of 489 cohort members who were either HIV-I seropositive on entry into the cohort (n = 312) or seroconverted during the study period and had less than or equal to 24 months between the dates of their last seronegative and first seropositive specimens (n = 177). A subset of 442 of these men was examined in 1988 or 1989 or had been reported to have developed AIDS. MAIN OUTCOME MEASURES--Development of clinical signs and symptoms of HIV-I infection, including AIDS, AIDS related complex, asymptomatic generalised lymphadenopathy, and no signs or symptoms of infection. MEASUREMENTS AND MAIN RESULTS--Of the 422 men examined in 1988 or 1989 or reported as having AIDS, 341 had been infected from 1977 to 1980; 49% (167) of these men had died of AIDS, 10% (34) were alive with AIDS, 19% (65) had AIDS related complex, 3% (10) had asymptomatic generalised lymphadenopathy, and 19% (34) had no clinical signs or symptoms of HIV-I infection. Cumulative risk of AIDS by duration of HIV-I infection was analysed for all 489 men by the Kaplan-Meier method. Of these 489 men, 226 (46%) had been diagnosed as having AIDS. We estimated that 13% of cohort members will have developed AIDS within five years of seroconversion, 51% within 10 years, and 54% within 11.1 years. CONCLUSION--Our analysis confirming the importance of duration of infection to clinical state and the high risk of AIDS after infection underscores the importance of continuing efforts both to prevent transmission of HIV-I and to develop further treatments to slow or stall the progression of HIV-I infection to AIDS.

Kaposi's sarcoma in a cohort of homosexual and bisexual men. Epidemiology and analysis for cofactors.

Acquired immunodeficiency syndrome (AIDS) surveillance data for both the United States and San Francisco indicate that Kaposi's sarcoma is more common in homosexual and bisexual men with AIDS than in other adults with AIDS, and that the proportion of newly diagnosed AIDS cases presenting with Kaposi's sarcoma has been significantly declining over time. The changing epidemiology of Kaposi's sarcoma was analyzed in a well-characterized cohort of homosexual and bisexual men; laboratory and interview data from a sample of these men were evaluated for determinants of and cofactors associated with Kaposi's sarcoma. Among 1,341 men with AIDS, the proportion presenting with Kaposi's sarcoma declined from 79% in 1981 to 25% in 1989. Compared with other men with AIDS, men with Kaposi's sarcoma had a shorter interval from human immunodeficiency virus (HIV) seroconversion to AIDS diagnosis (median, 77 vs. 86 months). Men with and without Kaposi's sarcoma did not significantly differ with respect to number of sexual partners, history of certain sexually transmitted or enteric diseases, use of certain recreational drugs (including nitrite inhalants), or participation in certain specific sexual practices. The decline in Kaposi's sarcoma may at least partly be due to a shorter latency period from infection to disease. Although cofactors for the development of Kaposi's sarcoma may exist, many previously hypothesized agents were not supported by this analysis.

Impact of AIDS on mortality in San Francisco, 1979-1986.

We used death certificate data for San Francisco residents from 1979 to 1986 to calculate the number of deaths and years of potential life lost before age 65 (YPLL) for leading causes of death. Acquired immune deficiency syndrome (AIDS)-related deaths were defined as including cytomegalovirus infection (ICD-9 078.5); cryptococcal infection (ICD-9 117.5); Pneumocystis carinii pneumonia (ICD-9 136.3); other malignant neoplasms of the skin, site unspecified (ICD-9 173.9); deficiency of cell-mediated immunity (ICD-9 279.1); and unspecified immunity deficiency (ICD-9 279.3). These deaths increased from 5 (0.1% of all deaths) in 1979 to 534 (6.6%) in 1986. Of the 1,225 deaths caused by AIDS-related diseases during this period, 1,032 (84%) occurred in men aged 20-49 years. AIDS-related deaths increased between 1979 and 1986 from 0 to 44 (25% of all deaths), 0 to 257 (44%), and 0 to 150 (35%) in men aged 20-29 years, 30-39 years, and 40-49 years, respectively. In 1986, AIDS-related diseases were the third leading cause of deaths and the leading cause of YPLL among male San Francisco residents.

Relationship between AIDS latency period and AIDS survival time in homosexual and bisexual men.

We identified 277 homosexual and bisexual men diagnosed with acquired immune deficiency syndrome (AIDS) whose estimated human immunodeficiency virus (HIV) seroconversion dates, ranging from 1977-85, could be well approximated. These men were from a cohort of 6,705 homosexual and bisexual men originally recruited for studies of sexually transmitted hepatitis B in San Francisco in 1978-80. We compared the time from HIV seroconversion to the initial disease diagnostic of AIDS (AIDS latency period) with the time from first AIDS diagnosis to death (AIDS survival time) and found no significant overall correlation between latency period and survival time. Both Kaplan-Meier and Cox proportional hazard stepwise analyses found the initial AIDS diagnosis to be significantly associated with latency period, with individuals first diagnosed with Kaposi's sarcoma (KS) having a shorter latency but longer survival than those first diagnosed with Pneumocystis carinii pneumonia (PCP) or other AIDS diagnoses. Individuals with KS tended to be diagnosed earlier in the epidemic compared to those with PCP and other non-KS diagnoses. The AIDS survival time was significantly associated with the initial AIDS diagnosis but not with the estimated year of seroconversion, the year of first AIDS diagnosis, age at seroconversion, or racial/ethnic group. The information presented here on the relationship between the AIDS latency period and survival times suggests a model for the pathogenesis of HIV infection in which there is continual deterioration of the immune system. The wider use of antiviral and prophylactic therapies both preceding and following a diagnosis of AIDS may change this model as both latency and survival times are improved.

The epidemiology of AIDS in Asian and Pacific Islander populations in San Francisco.

To evaluate the epidemiology of HIV infection in Asian and Pacific Islander populations in San Francisco, we compared cases of AIDS reported in Asians and Pacific Islanders with those reported in other racial and ethnic groups. The incidence of AIDS in Asians and Pacific Islanders was significantly lower than in Whites, Blacks, Latinos and American Indians and Alaska natives. AIDS cases among Asians and Pacific Islanders have increased 177% since 1985 compared with 54% in other racial and ethnic groups, with the greatest increase in homosexual and bisexual men and transfusion recipients. Among Asian and Pacific Islander ethnic groups, the incidence of AIDS was 168 cases per 100,000 in Polynesians, 141 per 100,000 in Japanese, 92 per 100,000 in 100 Filipinos, 72 per 100,000 in southeast Asians, and 21 per 100,000 in Chinese. We conclude that AIDS cases are disproportionately increasing in Asians and Pacific Islanders in San Francisco.

PIP: In Asia and in people of Asian and Pacific Islander ancestry in the United States, AIDS is a rare disease. San Francisco, with the highest incidence of AIDS in the United States, also has the highest percentage (21%) of Asians and Pacific Islanders. To understand the potential for AIDS in this select population, trends over time and the demographics of reported AIDS cases among the select population in San Francisco were analyzed. Records were reviewed of AIDS cases reported to the San Francisco Department of Health, which had a substantiated 98% report rate. As of March 31,1988, 83 (1.8%) of the 4689 cases and 42 (1.5%) of the 2831 deaths reported were among the select population. The incidence of AIDS among the select population (58.5/100,000) was significantly lower than among whites (1108.8/100,000), blacks (368.9/100,000), and latinos (421.0/100,000). Among the select population, however, AIDS increased more rapidly since 1985 than among the whites, blacks, or latinos. Of the 83 cases reported, 69 were homosexual or bisexual men without intravenous drug use, 3 homosexual or bisexual men with histories of intravenous drug use, 6 were transfusion recipients, 3 were heterosexual intravenous drug users, 1 was a heterosexual contact of a person at risk for AIDS, and 1 was a hemophiliac. Comparison of transmission categories of the select population with those of the other racial and ethnic groups showed a significantly greater (P 0.001) number of transfusion recipients and a significantly lower (P 0.02) number of homosexual and bisexual intravenous drug users. The greatest increase in cases among the select population was in homosexual and bisexual men without histories of intravenous drug use, which was greater than the increase among nonAsian or Pacific Islander homosexual and bisexual men (P 0.10). These findings support the theory that HIV entered the select population communities later than it did nonAsian or Pacific Islander communities.

Determination of parameters effecting proton relaxation of hepatic and gallbladder biles in dogs.

The parameters which are important in causing changes in the T1 and T2 proton magnetic relaxation times of dogs bile were investigated. Three factors were found to be important in causing relaxation in bile: (i) total bile salt concentration; (ii) total protein concentration, and (iii) viscosity. The T1 and T2 values of hepatic and gallbladder biles were found to be independent of specific gravity, osmolarity and electrolyte concentrations. In vitro experiments were conducted with taurocholic acid, bovine serum albumin and porcine stomach mucin to examine the effects of intermolecular interactions on proton relaxation. Relative to each of the molecules alone, various combinations of the bile salt and proteins exhibit relaxation rates of 20 to 60% below theoretically expected values. This influence of in vitro molecular interactions on T1 and T2 is also likely to occur in hepatic and gallbladder biles in vivo. Thus, the effects of complex intermolecular interactions associated with the gallbladder microenvironment complicate but likely will not preclude direct assessment of physiologic data with magnetic resonance imaging.

Biodistribution of GdCl3 and Gd-DTPA and their influence on proton magnetic relaxation in rat tissues.

The biodistribution and relative molar effectiveness of the ionic (GdCl3) and chelated (Gd-DTPA) forms of gadolinium (Gd) to enhance proton relaxation rates in rat kidney, liver and spleen were evaluated. Rats were given intravenous injections of either GdCl3 (100 mumol/kg) or Gd-DTPA (178 mumol/kg). Gd-DTPA was primarily contained in the vascular compartment and was quickly accumulated in the kidney after injection with a relaxivity of 4.3 sec-1 (mumol/g kidney)-1. It was eliminated quickly from the body with only 2% of the injected dose remaining after 120 min. After GdCl3 injection, Gd was found primarily in liver and spleen. It accumulated continuously reaching 72% of the injected does in these two tissues after 120 min. Despite this continuous increase in tissue Gd concentration, the relaxation rates showed saturation in liver and spleen. The results suggest that after GdCl3 was injected it distributed either in a protein bound form that was effective at causing relaxation or in a colloid form that was not effective. The biodistribution of GdCl3 was such that it was determined by the phagocytic action of the recticuloendothelial system on a colloid. The biodistribution and tissue relaxivity of Gd-DTPA suggest it will be a useful vascular MRI contrast agent. However, the usefulness of GdCl3 as an MRI contrast agent is limited not only by its acute toxicity but also by its saturable effect on tissue relaxation rates. Consequently, GdCl3 has only a modest influence on tissue relaxivity.

Influence of paramagnetic ions and pH on proton NMR relaxation of biologic fluids.

The extent to which various concentrations of the paramagnetic metal ions [gadolinium (III), manganese (II), chromium (III), iron (III), nickel (II), copper (II), and cobalt (II)] affect proton magnetic relaxation times of distilled water, 4% human serum albumin (HSA), and dog plasma was studied in vitro. The pH of water and HSA varied from 4 to 8. Nuclear magnetic resonance relaxation parameters, T1 and T2, were measured at 10.7 MHz using inversion recovery and spin-echo radiofrequency sequences, respectively. The presence of Mn(II), Gd(III) and Cr(III) in water significantly reduced T1, while Fe(III), Ni(II), Cu(II) and Co(II) had only a minimal effect. In 4% HSA and dog plasma Mn(II) and Cu(II) had the greatest effect on T1. At neutral pH, Gd(III) and Cr(III) had little effect on T1, while Mn(II) induced a large shortening of T1. All of the metal ions changed T2 less than T1. These differences in proton relaxation enhancement caused by the various ions in the three solutions studied are due to variations in the effective magnetic moment, the degree of binding of the ions to protein, and the chemical form of the ion associated with changes in pH. Thus, it is impossible to predict the effect of metal ions on proton relaxation in vivo based solely on in vitro studies, because of the complexity of various biologic fluids in vivo.

Influence of Mn(II) on NMR relaxation times of biological fluids.

The extent that various concentrations of the paramagnetic metal ion manganese [Mn(II)] affect nuclear magnetic resonance (NMR) relaxation times was studied in vitro. Serial dilutions of Mn(II) were prepared in distilled water, 4% human serum albumin, dog plasma, dog gallbladder bile, and dog hepatic bile. T1 and T2 of each were measured at 10.7 M Hz using magnetization recovery and spin-echo radiofrequency sequences, respectively. The results show that relaxation rates (1/T1 and 1/T2) increase in a linear manner with increasing concentration of Mn(II) in all of the solutions tested. Mn(II) dissolved in dog gallbladder and hepatic bile, dog plasma, and 4% human serum albumin reduced relaxation times to a greater extent than Mn(II) in water. T1 times were reduced to a greater extent than T2 values. Thus, in T1 weighted magnetic resonance images, the NMR signal used to produce images would be more sensitive to the presence of Mn(II) in these biological fluids than in water. Furthermore, the magnitude of this in vivo effect of Mn(II) on NMR relaxation parameters depends not only on the concentration of this paramagnetic ion, but also on the constituents comprising the biological fluids (intra- and extracellular water, bile, plasma) and the nature of the chemical molecular interactions between these constituents and Mn(II).

Biliary excretion of infused conjugated sulfobromophthalein in sheep heterozygote for the transport defect present in mutant Corriedale sheep.

Biliary excretion of dye was measured in 2 clinically normal and 2 heterozygote Corriedale sheep (the mutant Corriedale is characterized by depressed biliary transport of conjugated sulfobromophthalein (SBP) compounds) during infusion of the preformed glutathione conjugate of SBP. Maximal rates of excretion of conjugated SBP compounds in bile were comparable in heterozygote Corriedale and clinically normal sheep. These 2 heterozygote sheep do not express the biliary transport defect observed in mutant Corriedale sheep during SBP-glutathione infusion.

Uptake of iopanoic acid and its glucuronide conjugate by rat hepatocytes in primary culture.

Uptake of iopanoic acid (IOP) and iopanoate glucuronide (IOP-G) was studied in 3-day primary cultures of rat hepatocytes isolated by the collagenase perfusion method. 125I activity of cells after incubation with 125I-IOP (10-100 microM) and 125I-IOP-G (10-100 microM) was used as a measure of uptake. At each concentration, uptake was linear for the first 45 sec. In the absence of albumin, the initial uptake velocity was directly proportional to the concentration or IOP or IOP-G and was nonsaturable up to 100 microM. The calculated uptake rate constants for IOP and for IOP-G were 0.059 and 0.048 nmole/(mg protein X min X microM), respectively. IOP uptake was not inhibited by sodium taurocholate nor by the contrast agents iodipamide, ipodate, and iopronic acid. The data indicate that the enhancement of IOP excretion by bile salts noted in vivo does not occur at the uptake step and that the hepatic uptake of both IOP and IOP-G in the absence of albumin is limited by diffusion.

Uptake of iopanoic acid by isolated rat hepatocytes in primary culture.

Uptake of iopanoic acid (IOP) was studied in 3-day primary cultures of rat hepatocytes isolated by the collagenase perfusion method. 125I activity of cells after incubation with 125I-IOP (1.0-100 microM) was used as a measure of uptake. At each IOP concentration uptake was linear for the first 45 s. The initial uptake velocity was directly proportional to IOP concentration and was nonsaturable up to 100 microM. The calculated uptake rate constant was 0.67 nmol . mg prot-1 . min-1 . microM-1. Uptake was only slightly reduced when the incubation was performed at 4 degrees C and was independent of sodium concentration. Albumin in the medium reduced IOP uptake. Uptake, however, was always greater than that predicted from the unbound IOP concentration alone. The data indicate that the hepatocyte uptake of IOP occurs by both a passive process and a saturable process. The saturable uptake component depends on an albumin-IOP-hepatocyte interaction. The influence of albumin on uptake occurs possibly by an undefined specific cell surface phenomenon of albumin that promotes uptake of IOP or by enhancement of the diffusibility of IOP across the unstirred layer.