[Evaluation of inhibitory effect of isoflurane on the hypoxic pulmonary vasoconstriction response in dogs]

The effect of isoflurane on hypoxic pulmonary vasoconstriction (HPV) was examined using the separately ventilated left lower lobe lung model in dogs. When the HPV was induced with anoxic gas ventilation of the left lower lobe, the magnitude of HPV inhibition by isoflurane of 2 MAC was predominant, as assessed by the index of pressure-flow curve which is a novel indicator of pulmonary vascular tone in the left lower lobe. However, isoflurane 2 MAC attenuated the HPV by only 16%, as assessed by indices of the changes in left lower lobe blood flow rate and PaO2. This weak HPV inhibition, as shown by the latter parameters, may result from the net effect of isoflurane-induced HPV inhibition and secondary HPV enhancement due to decreases in cardiac output and pulmonary arterial pressure by isoflurane. However, none of the parameters showed inhibition of HPV when the HPV was induced by collapse of the left lower lobe. This discrepancy in the results may be caused by a lack of isoflurane reaching the hypoxic lobe when the HPV is induced with atelectasis. These results show that potency of HPV inhibition with isoflurane depends on the method of induction or evaluation of HPV, and that inhibition of HPV response with isoflurane at clinical concentrations is negligible in an atelectasis-induced HPV, in which no isoflurane is directly reaching the hypoxic lobe.

Effect of progesterone pretreatment on cadmium toxicity in male Fischer (F344/NCr) and Wistar (WF/NCr) rats

A previous report indicated that progesterone pretreatment can markedly reduce cadmium (Cd) toxicity in male NAW mice. Therefore we examined the effects of progesterone pretreatment on Cd toxicity in male Fischer (F344) and Wistar (WF) rats. A single subcutaneous injection of 10 or 30 mumole (CdCl2)/kg proved nonlethal over 24 hr but caused the typical spectrum of testicular lesions in these rats. Moreover, when F344 rats were pretreated with progesterone (100 mg/kg, sc, at -48, -24, and 0 hr) and then given cadmium (20 mumole CdCl2/kg, 0 hr), this dose of cadmium proved very toxic, unexpectedly causing 53% mortality. Progesterone pretreatment had no effect on cadmium-induced lethality in WF rats or on testicular lesions in either strain. Significant elevations in serum lactate dehydrogenase (LDH) activity, indicative of hepatotoxicity, were also observed in progesterone-pretreated F344 rats given cadmium as compared to rats given Cd alone. Progesterone did not induce increases in hepatic or renal metallothionein (MT) and hepatic or testicular MT-I mRNA levels in F344 rats. In contrast, levels of the testicular cadmium-binding protein (TCBP) in progesterone-pretreated F344 rats were doubled. This increase in TCBP provided no protection against cadmium toxicity in the testes. These results indicate that, in contrast to previously reported data for mice, progesterone pretreatment increased the lethality of cadmium in male F344 rats and had no effect on cadmium-induced testicular toxicity in F344 and WF rats.

Niacin attenuates acute lung injury induced by lipopolysaccharide in the hamster

Lipopolysaccharide plays a major role in the development of lung injury induced by Gram-negative bacteria, but a protective agent to attenuate the LPS-induced lung injury has not been found. The aim of this study was to examine the effects of niacin on LPS-induced acute lung injury. We administered LPS (Escherichia coli) 0.01 mg.100 g-1 body weight, transtracheally into the lungs of hamsters. Niacin (250 or 500 mg.kg-1 body weight) was injected intraperitoneally 24 h before, and 1 h after the LPS administration. LPS treatment increased wet/dry lung weight, albumin content and neutrophil counts in bronchoalveolar lavage fluid. In hamsters treated with niacin, wet/dry lung weight, albumin content and intra-alveolar cell counts were normal. Nicotinamide adenine dinucleotide (NAD) was significantly decreased in lung tissue of hamsters treated with LPS alone, but was increased in hamsters treated with LPS and niacin. Histopathological examination revealed that niacin-treated LPS-administered hamsters had lungs with no or occasional inflammatory cell infiltration in alveolar spaces, in contrast to the lungs of LPS-treated hamsters, which were infiltrated with numerous inflammatory cells. We conclude that niacin attenuates LPS-induced acute lung injury, probably, in part, by preventing the depletion of NAD.

Bulky plasmacytoma of the bone with intracranial invasion

A 56-year-old man with left anterior chest pain showed two well-defined tumors in the left anterior chest wall and left parietal region. A large osteolytic lesion in the parietal bone and several punched-out lesions in the temporal bone were revealed by a skull X-ray examination. He showed monoclonal gammopathy (IgG, kappa type) and Bence Jones proteinuria, but no proliferation of plasma cells was observed in the bone marrow. The tissue specimens from both lesions consisted of abnormal plasma cells, indicating plasmacytoma. Although a bulky intracranial plasmacytoma was present, the patient did not exhibit intracranial hypertensive symptoms, or neurological abnormalities.

Niacin attenuates acute lung injury induced by lipopolysaccharide in the hamster

Lipopolysaccharide plays a major role in the development of lung injury induced by Gram-negative bacteria, but a protective agent to attenuate the LPS-induced lung injury has not been found. The aim of this study was to examine the effects of niacin on LPS-induced acute lung injury. We administered LPS (Escherichia coli) 0.01 mg.100 g-1 body weight, transtracheally into the lungs of hamsters. Niacin (250 or 500 mg.kg-1 body weight) was injected intraperitoneally 24 h before, and 1 h after the LPS administration. LPS treatment increased wet/dry lung weight, albumin content and neutrophil counts in bronchoalveolar lavage fluid. In hamsters treated with niacin, wet/dry lung weight, albumin content and intra-alveolar cell counts were normal. Nicotinamide adenine dinucleotide (NAD) was significantly decreased in lung tissue of hamsters treated with LPS alone, but was increased in hamsters treated with LPS and niacin. Histopathological examination revealed that niacin-treated LPS-administered hamsters had lungs with no or occasional inflammatory cell infiltration in alveolar spaces, in contrast to the lungs of LPS-treated hamsters, which were infiltrated with numerous inflammatory cells. We conclude that niacin attenuates LPS-induced acute lung injury, probably, in part, by preventing the depletion of NAD.

Evaluation of 3-[18F]fluoro-alpha-fluoromethyl-p-tyrosine as a tracer for striatal tyrosine hydroxylase activity

3-[18F]Fluoro-alpha-fluoromethyl-p-tyrosine (3-F-FMPT) was evaluated as a tracer for CNS tyrosine hydroxylase (TH) activity in rodents and in a rhesus monkey. Results of in vitro experiments using rat striatal homogenates showed that the introduction of fluorine into the 3-phenyl position did not significantly alter the ability of FMPT to act as a TH-activated L-aromatic amino acid decarboxylase (L-AAAD) inhibitor. These studies further showed that 3-F-FMPT-induced L-AAAD inhibition was dose-dependent. Furthermore, striatal homogenates prepared from rats pretreated with the potent TH inhibitor alpha-methyl-p-tyrosine was found to have diminished 3-F-FMPT-induced L-AAAD inhibition. However, despite these promising in vitro results, the biodistribution of this compound in mice showed low brain uptake and fast clearance through the kidneys. A PET study using a Rhesus monkey injected with 3-[18F]F-FMPT confirmed the results obtained in mice, i.e. negligible brain uptake but high localization in the bladder. We conclude that 3-[18F]F-FMPT would not be useful as a tracer for cerebral TH activity.

Investigation of type IIC von Willebrand disease

Type II von Willebrand disease (vWD) is characterized by qualitative abnormality of von Willebrand factor (vWF). It is characterized by the absence of the largest, or the largest and intermediate-size plasma vWF multimers. Type IIC vWD is a very rare variant subtype. We report the tenth case of type IIC vWD who is a 32-year-old Japanese with a history of lifelong mild bleeding problems. The multimeric analysis of vWF of the patient's plasma revealed that the multimers were composed of the increased smallest multimer and progressively decreased larger multimers, with each multimer replaced by a single band instead of a normal triplet structure. The family study highly suggested that the propositus is the first case of homozygote for type IIC vWD gene, although previous studies have suggested that type IIC vWD is due to double heterozygosity of two different mutant genes. The patient's von Willebrand factor antigen showed a slight response to 1-deamino-8-D-arginine vasopressin (DDAVP), whereas his ristocetin cofactor showed no response. The patient responded very well to an intermediate-purity factor VIII concentrate, and then underwent cholecystectomy without bleeding problems.

[Psoriasis exacerbated by alpha-interferon therapy in a case of chronic myelogenous leukemia]

A 49-year old male with chronic myelogenous leukemia (CML) and psoriasis was admitted for interferon treatment. He was given 6 MU of human lymphoblastoid interferon (HLBI), a natural alpha-interferon, daily for 1 month followed by 3 MU every other day for 1.5 months and twice a week for 1 month. Because HLBI administration showed no favorable effects on the hematological findings and because of the exacerbated psoriasis of the patient, it was discontinued. Subsequently his psoriasis improved to the initial findings observed at the admission. We reported a case of CML in which psoriasis was exacerbated during interferon therapy.

Minoxidil sulfation in the hair follicle

The in vivo model which may be the most accurate for the ability to predict hair growth in humans, and which was utilized in the preclinical development of minoxidil, is the adult stumptailed macaque. Previous reports have suggested that the enzyme activity which accounts for the activation of minoxidil, i.e., minoxidil sulfotransferase, is present in skin. We have demonstrated that scalp skin from the stumptailed macaque contains minoxidil sulfotransferase activity, and further with dissection of that scalp skin into epidermis, dermis and hair follicle, most of sulfotransferase activity was present in the follicle. Sulfotransferase activity in the hair follicle in freeze-dried scalp skin sections from 9 stumptailed macaques ranged from 47 to 84% of the total (mean 61 +/- 12%). Much less minoxidil sulfotransferase activity was measured in the epidermis (mean 18 +/- 11%, with a range of 2-37%) and the dermis (mean 21 +/- 8%, with a range of 4-35%) of these scalp sections. These results indicate that the scalp skin from the stumptailed macaque contains minoxidil sulfotransferase activity and this activity is largely localized in the hair follicle which may account for its ability to stimulate hair growth in this animal model.

Effect of L-ascorbic acid pretreatment on cadmium toxicity in the male Fischer (F344/NCr) rat

Some studies have indicated that cadmium-induced lethality and selective injurious effects to specific tissues, such as testes or liver, can be prevented by pretreatment with the antioxidant L-ascorbic acid (ascorbic acid). However, the basis of this tolerance is unclear. We examined the effects of ascorbic acid pretreatment on cadmium toxicity in male Fischer (F344/NCr) rats. Cadmium treatment alone (25 mumol CdCl2/kg, s.c.) proved lethal, causing a 93% mortality within 72 h, but in rats pretreated with ascorbic acid (2 g/kg, s.c. 24, 12 and 1 h) cadmium-induced lethality was nearly prevented. Hepatic lesions, including hepatocellular necrosis, induced by cadmium were at least partially ameliorated by ascorbic acid pretreatment. Ascorbic acid pretreatment had no effect on cadmium-induced testicular lesions nor on cadmium content in testes, liver, kidney and urine. Ascorbic acid alone modestly increased hepatic metallothionein (MT), but not renal MT and had no effect on induction of hepatic or renal MT by cadmium. In contrast to liver and kidney, testicular cadmium-binding protein (TCBP) in rats exposed to cadmium alone decreased markedly. Moreover, the level of TCBP decreased unexpectedly in ascorbic acid pretreated rats as compared with control. These results indicate that ascorbic acid pretreatment decreases the toxicity of cadmium in the rat without markedly modifying its toxicokinetics or markedly stimulating MT synthesis.

Effect of sevoflurane on hypoxic pulmonary vasoconstriction in the perfused rabbit lung

BACKGROUND

In vitro studies have shown that isoflurane, enflurane, and halothane inhibit the hypoxic pulmonary vasoconstriction (HPV) with essentially the same potency. The aim of this study is to compare the effects of sevoflurane and isoflurane on HPV in constant-flow perfused rabbit lungs.

METHODS

Constant-flow perfused lungs from Japanese white rabbits were tested. The lungs were divided into three groups: isoflurane alone (n = 6), sevoflurane alone (n = 6), and sevoflurane with ibuprofen pretreatment (n = 6). Baseline HPV responses were measured as the pulmonary arterial pressure increased after changing inspired oxygen concentration from 95% for 15 min to 3% (with 5% CO2) for 5 min without anesthetic administration. Next, three different concentrations of anesthetics were added to the inspired gas for 15 min in random order. The HPV response in the presence of anesthetic was expressed as a percentage of the pressor response in the absence of anesthetics, and dose-response relationships were calculated using the nonlinear least-squares method.

RESULTS

Isoflurane and sevoflurane both depressed the HPV response in a dose-related manner. The half-inhibition values (ED50) of HPV with isoflurane and sevoflurane were 0.85 +/- 0.22 MAC and 1.00 +/- 0.12 MAC (mean +/- SD), respectively, and were not statistically different. Ibuprofen pretreatment did not alter ED50 and slope of dose-response curve, although the absolute value of pressor response in the sevoflurane group with ibuprofen pretreatment was greater than that in the sevoflurane alone group at every concentration of sevoflurane.

CONCLUSIONS

Sevoflurane inhibits the HPV response in a dose-related manner, and its potency is similar to that of isoflurane in vitro. Cyclooxygenase products do not mediate the inhibition of HPV by sevoflurane.

Cell proliferation not associated with carcinogenesis in rodents and humans

Cell proliferation has often been found to be associated with carcinogenesis in rodents and humans at different stages of the multistage carcinogenesis process. The multistage process includes initiation, promotion, and progression phases. At each phase, increasing the normal level of cell turnover of target cells may enhance carcinogenesis. However, we present evidence that normal levels of cell turnover, or increasing the rate of cell turnover at these different stages, do not necessarily lead to enhanced carcinogenesis. In normal tissues, the length of the cell cycle depends on the age of the host and varies from tissue to tissue. Tissues with normal short cell cycles, such as intestine and bone marrow, do not show a high rate of spontaneous tumors in most species. Cells with higher turnover should be more susceptible to carcinogens at the initiation stage of carcinogenesis if cell proliferation per se causes cancer and if these cells or their progeny survive. Cancer in humans is more often associated with specific etiological factors rather than with the natural proliferative rate of specific tissues. For many tissues of humans and rodents, age-related diseases develop in a progressive, irreversible manner. Often, naturally occurring chronic degenerative and inflammatory changes in a tissue (e.g., kidney, liver, heart, reproductive tract) lead to chronic regeneration of the damaged tissue. Yet, cancer is rarely found in these tissues. In rodent carcinogenesis experiments, chronic toxic lesions, accompanied by increases in normal levels of cell turnover, have sometimes been observed in target organs of nongenotoxic carcinogens. More often, however, organ-specific nongenotoxic toxins are not carcinogens. These toxins include compounds toxic for the liver, kidney, and nasal cavity. In 19 inhalation bioassays conducted by the National Toxicology Program, 5/5 nasal carcinogens and 12/14 nasal noncarcinogens caused nasal lesions usually associated with chronic cell proliferation. Although cell proliferation may contribute to multistage carcinogenesis, cell proliferation is not necessarily a tumor promoter or cocarcinogen.

The age of biosenescence and the incidence of cerebral beta-amyloidosis in aged captive rhesus monkeys

Autopsy surveillance of 186 rhesus monkeys aged 20 to 36 years revealed that development of major geriatric diseases such as emphysema, coronary sclerosis, and cancer increased rapidly after the age of 25 years, and nearly 70% of the monkeys in each cohort group died by 30 years. According to our 12-year longitudinal survey, the age of biosenescence in captive rhesus monkeys begins around 25 years and the maximum longevity is 36 years. The incidence of cerebral beta-amyloidosis associated with plaque formation and cerebral angiopathy was observed in 51 brains of rhesus monkeys aged 25 to 36 years. Lesions were found in 31 of 51 aged brains (60%) and 6 monkeys over 34 years of age were all severely affected. Despite the size of the plaque, nearly all of them showed immunopositive beta-amyloid. Cerebral angiopathy coexisted in 10 of 31 plaque-positive brains. The basal prefrontal gyrus was the most common site and contained the highest density of plaques, followed by the amygdala region. The amyloid in the liver, spleen, adrenal and pancreatic islets in visceral amyloidosis showed no positivity to the beta-amyloid demonstrated in the brain. As in aged human brains, the incidence of age-dependent cerebral beta-amyloidosis in captive rhesus monkeys showed great individual variation.

[Successful chronic daily administration of oral etoposide for a case of adult T cell leukemia]

A 54-year-old woman with leucocytosis and skin lesion was hospitalized and diagnosed as chronic type adult T cell leukemia (ATL) in August 1989. Since her ATL cell count and LDH level increased after hospitalization, oral administration of etoposide was started at a dose of 100 mg/day for seven days. The oral administration of etoposide induced another chronic state of ATL. After 10 months without medication, she was readmitted because of an acute ATL crisis. After daily administration of etoposide at a dose of 50 mg/day, the white blood cell count and serum LDH level decreased to the normal range, and abnormal lymphocytes of peripheral blood disappeared. The low-dose daily administration of etoposide at a dose of 25 approximately 50 mg/day could be maintained over six months. No severe side effects except for alopecia and mild myelosuppression were noted during the treatment. Chronic daily administration of oral etoposide is one candidate for the treatment of ATL in an outpatient clinic.

Alterations in populations of GST-p-immunoreactive single hepatocytes and hepatocellular foci after a single injection of N-nitrosodiethylamine with or without phenobarbital promotion in male F344/NCr rats

The fate of placental glutathione S-transferase (GST-P)-immunoreactive hepatocytes, detectable in livers of rats soon after treatment with N-nitrosodiethylamine (DEN), was examined sequentially with or without phenobarbital (PB) promotion. Group 1 male F344/NCr rats were administered a single i.p. injection of 200 mg DEN per kg body weight at 5 weeks of age. Group 2 rats were given 500 ppm PB in the diet two weeks after the DEN treatment. Groups of six rats were sequentially sacrificed 16, 42, 70, 126 and 238 days after DEN injection. In DEN-treated rats, GST-P immunoreactive hepatocytes (single cells and multiple cell foci) were detectable 16 days after DEN, the total numbers decreasing by day 70 and thereafter rising again. In the early stages the proportion of single immunoreactive hepatocytes was prominent, but with time a gradual increase in small GST-P+ hepatocellular foci and larger foci became evident. Feeding of PB to rats for 16-238 days after a single DEN injection resulted in increases of both single cells and foci, especially foci composed of more than three hepatocytes. The growth response was increasingly pronounced with time. Adenomas or carcinomas were only observed at 126 or 238 days. Numbers of GST-P+ foci far exceeded the numbers of foci visible in hematoxylin-eosin (H & E) stained sections, and a few H & E foci were negative for GST-P. Many GST-P+ foci smaller than ten cells were composed of histologically normal hepatocytes. Almost all GST-P+ foci identifiable in H&E stained sections were larger than ten cells, consisted of clear cells (in both groups) or mixed (clear-eosinophilic) cells in PB-exposed rats, and appeared to be evenly distributed throughout the three zones of the liver. These results suggest that the promotive effect of PB is most evident as an increase in larger hepatocyte populations composed of more than three GST-P+ hepatocytes, rather than in increasing the populations of single GST-P immunoreactive cells. PB may cause clonal expansion of these single GST-P reactive hepatocytes. This study provides evidence for the hypothesis that some of the GST-P reactive hepatocytes are initiated cells.

Chemical agents and peptides affect hair growth

During the past decade we have examined both the therapeutic and the prophylactic effects of several agents on the macaque model of androgenetic alopecia. Minoxidil and diazoxide, potent hypotensive agents acting as peripheral vasodilators, are known to have a hypertrichotic side effect. Topical use of both agents induced significant hair regrowth in the bald scalps of macaques. The application of a steroid 5 alpha-reductase inhibitor (4MA) in non-bald preadolescent macaques has prevented baldness, whereas controls developed it during 2 years of treatment. The effects of hair growth were determined by 1) phototrichogram, 2) folliculogram (micro-morphometric analysis), and 3) the rate of DNA synthesis in the follicular cells. These effects were essentially a stimulation of the follicular cell proliferation, resulting in an enlargement of the anagen follicles from vellus to terminal type (therapy) or a maintenance of the prebald terminal follicles (prevention). A copper binding peptide (PC1031) had the effect of follicular enlargement on the back skin of fuzzy rats, covering the vellus follicles; the effect was similar to that of topical minoxidil. Analyzing the quantitative sequences of follicular size and cyclic phases, we speculate on the effect of agents on follicular growth. We also discuss the triggering mechanism of androgen in the follicular epithelial-mesenchymal (dermal papilla) interaction.

Immunohistochemistry and morphology of reactive lesions in lymph nodes and spleen from rats and mice

The use of immunohistochemistry with anatomical and systematized classifications of nonneoplastic lesions in hematopoietic pathology of lymph nodes and spleens from rats and mice is described. Polyclonal antisera and monoclonal antibodies to leukocyte and other antigens can be used with frozen or fixed tissue sections to identify changes in cell populations in these tissues in response to tissue injury and aging. A classification for reactive lesions of lymph nodes and spleen is proposed that can be utilized for computerized pathology and toxicology data systems. These classifications are based on a systematized anatomic distribution of the lesions with the aid of immunohistochemistry. The association of some lesions with early leukemia or lymphoma of rats and mice is also discussed.

The tonotopic representation in the auditory cortex of the guinea pig with optical recording

We examined spatio-temporal characteristics of the tonotopic representation in the auditory cortex of the anesthetized guinea pig with a multichannel optical method using voltage-sensitive dye. The response latencies increased, and the response field in the cortex became small when the stimulus intensity levels were decreased. Low frequencies were represented rostrally and high frequencies caudally. The two fields responding to different frequencies at higher intensity levels gradually overlapped as time after stimulus onset increased, though these response field did not overlap at the beginning of the response. These findings indicate that tonotopic representation varies dynamically with time after stimulus onset.

Pathogenesis of SIVmac251 after atraumatic inoculation of the rectal mucosa in rhesus monkeys

Intrarectal inoculation of rhesus monkeys with low doses of SIVmac led to a prolonged clinical and virological latency that was not observed for high intrarectal doses or for intravenous inoculation. Animals infected intrarectally with low virus doses remained negative for serum antibody responses to SIV for at least one year even though they readily transferred SIV to naive recipients via transfusion of whole blood.

Pathology of preneoplastic and neoplastic renal tubular lesions induced in F-344 rats by sodium barbital, a nongenotoxic renal carcinogen and nephrotoxin

Sodium barbital (NaBB), a long-duration sedative/hypnotic barbiturate, is a nongenotoxic nephrotoxin and induces chronic persistent increases in rates of cell proliferation in renal cortical tubules of male F-344/NCr rats. In 5 of our 2-stage carcinogenesis experiments with NaBB at doses of 500, 1,000, or 4,000 ppm for periods of up to 106 wk of age, renal tubular cell tumors were found in incidences of up to 25% in rats receiving only NaBB while fewer than 1% of controls had renal epithelial tumors. We reviewed renal tubular proliferative lesions found in these studies and classified the lesions based on morphology, histogenesis, and immunohistochemical findings. Renal dysplastic tubules (DTs; atypical hyperplasia), putative preneoplastic lesions rarely seen in controls, were found in the renal cortex of more than 50% of the NaBB-exposed rats. DTs were classified into grades 1-3, based on lesion size and growth patterns. All renal adenomas were usually of the basophilic phenotype, and 70% of basophilic adenomas displayed solid patterns, while tumors with papillary, cystic, or tubular patterns were seen less commonly. By serial or step sectioning of the DTs and tumors, evidence was found indicating that the high grades (grade 2 or 3) of DTs, some of which arose in the P1 or P2 segment of the proximal tubules, were sometimes connected to the adenomas. Vimentin expression was demonstrated immunohistochemically in NaBB-induced renal tubular adenomas but not in normal tubules. Tumors were usually not immunoreactive for glutathione S-transferase, placental form, but heterogeneous immunoreactivity was also seen in some tumors. Lysozyme was absent in preneoplastic and neoplastic lesions induced by NaBB, while some intact normal proximal convoluted tubules were immunoreactive. The common tumor phenotype induced by NaBB, the basophilic solid adenoma, was similar to the most common type of spontaneous renal tumor found in untreated aging F-344 rats. NaBB may promote naturally occurring renal preneoplastic or neoplastic tubular lesions of this unique phenotype, but it is also possible that it may induce these lesions de novo.

Effect of progesterone pretreatment on cadmium toxicity in the male Fischer (F344/NCr) rat

A previous report has indicated that progesterone pretreatment can markedly reduce cadmium toxicity in male NAW mice. Therefore we examined the effects of progesterone pretreatment on cadmium toxicity in male Fischer (F344/NCr) rats. A single sc injection of 20 mumol CdCl2/kg proved nonlethal over 24 hr but caused the typical spectrum of testicular lesions in these rats. However, when rats were pretreated with progesterone (100 mg/kg, sc, -48, -24, and 0 hr) and then given cadmium (20 mumol CdCl2/kg, 0 hr), this dose of cadmium proved very toxic, unexpectedly causing a 53% mortality. Progesterone pretreatment had no effect on cadmium-induced testicular lesions in surviving rats. Significant elevations in serum lactate dehydrogenase (LDH) activity, indicative of hepatotoxicity, were also observed in progesterone-pretreated rats given cadmium as compared to rats given cadmium alone. Progesterone pretreatment had no effect on the distribution of cadmium to liver, kidney, or testes. Progesterone pretreatment also had no effect on the cadmium-induced increases in hepatic or renal metallothionein (MT) or hepatic or testicular MT mRNA levels. In contrast, levels of the testicular cadmium-binding protein (TCBP) in progesterone-pretreated rats were doubled. These results indicate that, contrary to previously reported data for the mouse, progesterone pretreatment increased the lethality of cadmium in male Fischer (F344/NCr) rats and had no effect on cadmium-induced testicular toxicity. The mechanism by which progesterone enhanced cadmium toxicity, especially cadmium-induced hepatotoxicity, deserves further study.

Visualization of dopamine nerve terminals by positron tomography using [18F]fluoro-beta-fluoromethylene-m-tyrosine

[18F]-6-Fluoro-beta-fluoromethylene-m-tyrosine ([18F]FFMMT) was evaluated as a potential imaging agent for dopamine nerve terminals using positron emission tomography (PET). Biodistribution and time course of this tracer in mice after i.p. injection was consistent with the distribution of dopamine. PET imaging studies involving rhesus macaques showed specific uptake in the dopamine-rich caudate-putamen region. This specific localization was blocked by inhibiting the enzyme L-aromatic amino acid decarboxylase and the transport of the tracer into brain was shown to be stereospecific. These results show the promise of L-[18F]FFMMT as a PET tracer in monitoring degeneration of the CNS dopamine system.

Vimentin metaplasia in renal cortical tubules of preneoplastic, neoplastic, aging, and regenerative lesions of rats and humans

Vimentin expression was studied immunohistochemically in renal cortical tubules of untreated male rats of various ages, rats exposed to toxins (barbital sodium, folic acid) and carcinogens (streptozotocin, N-bis(2-hydroxypropyl)nitrosamine, barbital sodium, and in humans of various ages with or without renal epithelial tumors. Fetal, neonatal, and young adult rats did not express vimentin in renal cortical tubules. Regenerative renal tubular lesions from rats with aging nephropathy and from rats with toxic nephropathy both expressed vimentin. Mitogenic lesions induced by folic acid at 24 hours, however, were not immunoreactive for vimentin. Carcinogen-induced preneoplastic renal cortical tubular lesions in rats were most often focally immunoreactive whereas strong vimentin expression was found in almost all induced renal tumors. In kidneys of three children (younger than 2 years of age), vimentin was not found in renal cortical tubular cells except in rare individual cells in one case. Vimentin was abundant in basophilic regenerative tubules in kidneys of aged individuals, however. Most (7/10) human renal carcinomas and latent preneoplastic or neoplastic renal tubular lesions found incidentally at autopsy (2/4) showed vimentin expression. The authors suggest that the switching to vimentin expression in phenotypically normal renal cortical tubular cells in rats and humans, which do not usually express the intermediate filament protein vimentin, should be considered vimentin metaplasia. Vimentin expression is dissociated from increased cell proliferation in hyperplastic and neoplastic lesions, however. Instead the degree of dedifferentiation of the tubule cells and changes in phenotype were associated with vimentin expression.