Distribution and quantification of human immunodeficiency virus type 1, strain JC499, proviral DNA in tissues from an infected chimpanzee.

Data are accumulating to show that the natural history of human immunodeficiency virus type 1 (HIV-1) in chimpanzees closely reproduces that in humans and is influenced by biologic properties of the infecting HIV-1 strain. To determine the distribution and relative amounts of HIV-1, proviral DNA in multiple tissues from a chimpanzee euthanized because of an abdominal tumor and kidney failure was quantified by nested PCR limiting-dilution assays. At death, 21 months after infection with HIV-1(JC499), this animal had a CD4(+) T-cell count of 268 and 1.7 x 10(5) copies of virion RNA/ml of plasma. The highest proviral burdens were in peripheral lymph nodes and blood, followed by lung, colon, and spleen; values ranged from 130 to 3350 proviral copies/microg DNA (equivalent to DNA in 150,000 cells). The lowest levels of virus were in the spinal cord, brain, and cecum (0.3 to 2.5 copies/microg DNA), with all other tissues harboring intermediate levels (6.8 to 114 copies/microg DNA). Viral burdens in all tissues were comparable to or greater than those reported for HIV-1-infected humans in all stages of disease. Immunohistochemistry for HIV-1 p24 Gag antigen revealed (i) trapping of HIV-1 on follicular dendritic cells in lymph node germinal centers and (ii) virus in the brain, where it was localized primarily to capillary endothelial cells in the cerebral cortex. Analysis of the genetic diversity of the Env V3 loop in tissues indicated that there was no apparent compartmentalization of HIV-1 variants. Of interest, in 83 of 94 (88.3%) clones sequenced, the unique GYGR motif at the tip of the V3 loop of HIV-1(JC499) had reverted to the more common GPGR. The results support the conclusion that HIV-1 has the potential to maintain high viral burdens in chimpanzees and to disseminate to most organs, including the central nervous system. The use of the chimpanzee model with HIV-1(JC499) (or related strains) in vaccine efficacy studies should prove valuable, especially when assessing protection against disease. Furthermore, comparison of both replicative properties of HIV-1(JC499) with SIVcpz strains and immune responses of chimpanzees infected with these viruses might provide new information about HIV pathogenesis.

Transgenic mice with a mutated collagen promoter display normal response during bleomycin-induced fibrosis and possess neurological abnormalities.

We have previously identified a potential TGF-beta activation element (TAE) in the rat collagen alpha1(I) promoter at -1624 upstream of the transcriptional start site [Ritzenthaler et al., 1991, 1993]. To determine the importance of the TAE in vivo, we produced transgenic mice carrying 3.6 kb of the rat collagen alpha1(I) promoter linked to the reporter gene chloramphenicol acetyl transferase with and without site-directed mutations that eliminate DNA-protein binding at the TAE site. Tissue-specific expression of the reporter gene in transgenic mice with the mutated collagen promoter was similar to that of transgenic mice with the normal promoter in two genetic backgrounds as judged by in situ hybridization, reporter assays, and immunochemistry. Endotracheal instillation of bleomycin induces lung fibrosis, mediated in part by TGF-beta. Earlier studies indicated that expression of wild-type collagen-reporter gene was upregulated in transgenic mice lungs in response to endotracheal instillation of bleomycin. A similar level of reporter gene upregulation was observed in transgenic mice carrying the mutation in the TAE. Two lines of transgenic mice carrying the mutated promoter construct displayed unexpected neurological abnormalities. In the FVB genetic background, there was a higher than normal incidence of mortality, spontaneous seizures, and an inability to nurture offspring. Histological evidence demonstrated clear abnormalities, including disorderly arrangement of neurons in the hippocampus and significant laminar cortical necrosis in the cerebrum in animals after seizures. In the C57Bl/6 background, there was a high incidence of severe communicating hydrocephalus, early runting, and increased mortality similar to that in transgenic animals with astroglial overexpression of TGF-beta. These animals provide an interesting model system to investigate molecular mechanisms responsible for seizures and hydrocephalus.

Elevated vascular cell adhesion molecule-1 in AIDS encephalitis induced by simian immunodeficiency virus.

AIDS encephalitis is a common sequela to HIV-1 infection in humans and simian immunodeficiency virus (SIVmac) infection in macaques. Although lentiviral-infected macrophages comprise parenchymal inflammatory infiltrates in affected brain tissue, the mechanisms responsible for leukocyte trafficking to the central nervous system in AIDS are unknown. In this study, we investigated the expression of various endothelial-derived leukocyte adhesion proteins in SIVmac-induced AIDS encephalitis. Encephalitic brains from SIVmac-infected macaques, but not uninflamed brains from other SIVmac-infected animals, were found to express abundant vascular cell adhesion molecule-1 (VCAM-1) protein on the majority of arteriolar, venular, and capillary endothelial cells. Soluble VCAM-1 concentrations in cerebrospinal fluid (CSF) from encephalitic animals were increased approximately 20-fold above those from animals without AIDS encephalitis. Expression of other endothelial-related adhesion molecules, including E-selectin, P-selectin, and intercellular adhesion molecule-1 (ICAM-1), was not uniformly associated with AIDS encephalitis. Thus, the presence of VCAM-1 in both brain and CSF was uniformly associated with SIVmac-induced disease of the central nervous system, and this expression may, at least in part, influence monocyte and lymphocyte recruitment to the central nervous system during the development of AIDS encephalitis. Moreover, measurement of soluble VCAM-1 in CSF may assist in the clinical assessment of animals or people with AIDS.

Effects of carotenoid administration on bladder cancer prevention.

Bladder cancer was induced in male B6D2F1 strain mice by the administration of N-butyl-N-(4-hydroxybutyl)nitrosamine. Mice supplemented with beta-carotene for 5 weeks before receiving the carcinogen and maintained on beta-carotene for an additional 26 weeks developed significantly fewer tumors than did unsupplemented mice. Mice receiving canthaxanthin for the same time period showed no protection against the development of bladder cancer.

Distribution of [14C]canthaxanthin and [14C]lycopene in rats and monkeys.

The absorption and distribution of [14C]-canthaxanthin and [14C]lycopene were studied in rats and in rhesus monkeys following the oral administration of [14C]canthaxanthin or [14C]lycopene in olive oil supplemented with 1 mg alpha-tocopherol/mL. For canthaxanthin and lycopene, peak accumulation of radioactivity in plasma occurred between 4 and 8 h in rats and between 8 and 48 h in monkeys. In rats, the liver contained the largest amount of both kinds of radioactive pigments. In monkeys, with the exception of one stomach sample, liver was also the major depot organ for both canthaxanthin and lycopene. The other organs tested accumulated various amounts of pigment. No labeled metabolic products of either canthaxanthin or lycopene were found.

Effect of chewing rawhide and cereal biscuit on removal of dental calculus in dogs.

The effect of chewing rawhide and cereal biscuit on removal of dental calculus was studied in 67 dogs. Two methods were used to measure supragingival calculus and calculus removal as a function of time and acceptability. Trial 1 used a quantitative method based on actual measurement of the area of calculus on a tooth, and trial 2 used a quantitative method based on an arbitrary grading system to establish a supragingival calculus index. Analysis was performed, using 2-factor (trial 1) and a 3-factor (trial 2) analysis of variance. Results indicated that dogs removed calculus from their teeth by chewing rawhide; some teeth were cleaned better than others. The optimal amount or frequency of rawhide treatment was not necessarily determined. It was determined that regular consumption of up to 3 rawhide strips/d for 3 weeks was safe. Processed biscuits were sometimes effective in removing calculus from dog's teeth; however, biscuits were not as effective as the rawhide in removing supragingival calculus.

The metabolism of [14C]beta-carotene and the presence of other carotenoids in rats and monkeys.

The metabolism of beta-carotene has been studied in both rats and Rhesus monkeys, following the oral administration of [14C]beta-carotene in olive oil supplemented with 1 mg/mL alpha-tocopherol. In the rats, peak serum accumulation of [14C]retinol occurred 4 h after a single oral dose, but we were not able to detect [14C]beta-carotene in rat sera at any time up to 72 h after dosing. Small amounts of [14C]beta-carotene were found in the livers, although 88-94% of the recovered radioactivity was localized in the retinol fraction after saponification. Although radioactivity was also found in fractions other than beta-carotene and retinol, the amounts were too small to allow characterization. In the monkeys, peak accumulation of [14C]retinol in serum occurred between 8 and 24 h after supplementation. Some [14C]beta-carotene was also present. Most of the absorbed radioactivity was stored in the liver as [14C]retinol, although 2-8% was present as [14C]beta-carotene. Other organs also contained [14C]beta-carotene, confirming the ability of the monkey to absorb intact beta-carotene. In addition, monkey livers and other organs were found to contain lutein, zeaxanthin, alpha-cryptoxanthin, beta-cryptoxanthin and beta-carotene, presumably arising from dietary sources.

Regulation of calciotropic hormones in vivo in the New Zealand white rabbit.

Serum levels of ionized calcium, 25-hydroxyvitamin D (25OHD), and 1,25-dihydroxyvitamin D[1,25-(OH)2D], intact immunoreactive PTH and calcitonin were measured in the laboratory rabbit to evaluate the role of these calciotropic hormones in calcium homeostasis in this species. We confirm the finding of previous researchers that the resting serum ionized and total calcium concentrations are elevated in rabbits compared to those in other species (ionized calcium, 1.70 +/- 0.13 mmol/liter; total calcium, 3.23 +/- 0.25 mmol/liter). The serum calcium concentrations in animals maintained on a breeding farm or in the laboratory did not differ significantly despite nearly 3-fold higher levels of vitamin D in the feed at the farm, which were associated with 3- to 4-fold higher concentrations of 25OHD and 1,25-(OH)2D. Baseline intact PTH levels for the farm and laboratory populations also did not differ significantly and averaged 69.4 +/- 43.6 human pgeq/ml (laboratory animals, 52.1 +/- 28.4; breeding farm animals, 86.0 +/- 49.5 human pgeq/ml). Infusions of calcium gluconate or EDTA for 15 min into anesthetized animals in the laboratory induced dramatic reciprocal changes in the measured circulating levels of PTH. Calcium gluconate infusions (190-300 nmol/g BW) produced 50-85% increases in serum ionized calcium, which were accompanied by 74-91% decreases in PTH levels (from 68.8 +/- 29.2 at time zero to 10.1 +/- 3.1 human pgeq/ml at 15 min) as well as 7-fold increases in calcitonin levels. EDTA infusions (14-120 nmol/g BW) reduced serum ionized calcium by 9-49%, while PTH levels increased by 68-560% (from 61.4 +/- 32.3 at time zero to a maximum of 138 +/- 48.6 human pgeq/ml at 3 min). During the EDTA infusion, the PTH response was variable after 3 min despite further decreases in ionized Ca2+, indicating either exhaustion of PTH reserves or regulation of the secretory response by some parameter other than ionized calcium concentration per se. Thus, the rabbit appears to defend its serum ionized calcium concentration against hypo- and hypercalcemia by rapid changes in PTH secretion and calcitonin. Unlike other mammalian species, however, the changes in PTH occur at relatively high levels of calcium, suggesting that the parathyroid gland of the rabbit is reset to respond to changes in ionized Ca2+ within the physiological range in that species. The relative insensitivity of the rabbit parathyroid to extracellular calcium is analogous to that observed in primary hyperparathyroidism and may be a useful model to study the control of normal and abnormal PTH secretion.

Pregnancy toxemia (eclampsia) in Syrian golden hamsters.

Late-term pregnant Syrian golden hamsters (Mesocricetus auratus) died within 24 hours of arrival in our facility. Disseminated thrombi were found in many organs, particularly in the kidneys, liver, intestines, and placenta. Pathogenic bacteria were not identified in bacterial cultures of the liver.