Immunocytochemistry and laser capture microdissection for real-time quantitative PCR identify hindbrain neurons activated by interaction between leptin and cholecystokinin.

Current evidence suggests that leptin reduces food intake in part by enhancing the hindbrain neuronal response to meal-related gastrointestinal signals, including cholecystokinin (CCK), but the phenotypes of the relevant cells are not known. To identify neurons that participate in this interaction in the rat nucleus of the solitary tract (NTS), we induced c-Fos gene expression in NTS neurons with leptin and CCK. We focused on NTS catecholamine neurons because these cells have been implicated in the feeding response to CCK. Hindbrain sections from rats that received CCK with or without leptin pretreatment were immunostained for c-Fos and tyrosine hydroxylase (TH) by a double immunofluorescence procedure. Leptin pretreatment increased the number of NTS cells expressing c-Fos-like immunoreactivity (cFLI) 3-fold relative to CCK alone, but the number of TH-positive cells with cFLI was increased 6-fold. Next, cells detected by immunofluorescence for TH were collected by laser capture microdissection and pooled for real-time quantitative PCR of c-Fos mRNA. Here, neither le0ptin nor CCK alone affected the relative amount of mRNA in the TH cell-enriched samples, but leptin plus CCK substantially increased c-Fos mRNA content. These histochemical findings identify hindbrain catecholamine cells as potential mediators of the interaction between leptin and CCK.     

GERMINATION ECOLOGY OF SEDUM PULCHELLUM MICHX. (CRASSULACEAE)

Factors controlling the timing of seed germination were investigated in the small succulent winter annual Sedum pulchellum Michx. (Crassulaceae) in its natural habitat on unshaded limestone outcrops in northcentral Kentucky. At maturity in early July the dormant seeds are not dispersed but are retained in the fruits on the standing dead plants until September and October. Many, but not all, of the seeds afterripen in the fruits during summer, and at the time of dispersal some of them are dormant and some are nondormant. Germination and annual population establishment occur in September and October from seed reserves that have been in the soil for one or more years and from seeds produced in the current year. Germination of nondormant seeds may be prevented in autumn by lack of the appropriate combination of environmental factors including light, temperature and soil moisture in the seed's microsite. The effect of low winter temperatures on ungerminated seeds in the population is to induce nondormant seeds into secondary dormancy and to prevent afterripening of dormant seeds. Thus, in spring all the seeds in the population's seed reserve are dormant. During spring and summer some of these seeds afterripen, and they germinate in autumn when, and if, germination requirements are fulfilled.     

Multidrug chemotherapy of tuberculosis in rhesus monkeys

Occurrence of tuberculosis caused by Mycobacterium bovis in a colony of rhesus monkeys allowed evaluation of a modern multidrug therapeutic regimen. Fifteen tuberculin positive rhesus monkeys with disseminated tuberculosis were evaluated for extent of disease by radiographic techniques, physical examination and laparotomy prior to treatment. Monkeys were divided into treatment groups of 3, 6 and 12 months duration and were treated once daily with isoniazid, rifampin and ethambutol. All animals survived their treatment course, had marked clinical improvement and rapid resolution of radiographically demonstrable lesions. Lesion regression evaluated by necropsy and histopathology correlated positively with length of treatment interval. Mycobacterium bovis was not isolated from any animal following treatment. Multidrug chemotherapy of tuberculosis was considered successful and practical in rhesus monkeys at the 12 month treatment interval. Chemotherapy may provide a reasonable alternative to destruction of valuable animals infected with tuberculosis.     

Modifiers of mercaptopyruvate sulfurtransferase catalyzed conversion of cyanide to thiocyanate in vitro

The enzyme mercaptopyruvate sulfurtransferase appears to play an important role in the in vivo detoxification of cyanide. It does so by transferring sulfur to cyanide to produce thiocyanate, which is less toxic and may be excreted through the kidney. Several compounds were tested for their ability to affect the rate of enzyme catalyzed thiocyanate formation in vitro. The studies were carried out using both a partially purified bovine kidney extract and a highly purified enzyme preparation. Hypotaurine and methanesulfinic acid doubled sulfurtransferase activity in the partially purified extract at 30 mM, but inhibited the purified enzyme to 57% (hypotaurine) and 27% (methanesulfinic acid) of control activity at the same concentration. Pyruvate, phenylpyruvate, oxobutyrate, and oxoglutarate each inhibited the extract and purified forms of mercaptopyruvate sulfurtransferase. Phenylpyruvate was the most effective inhibitor, reducing activity to 0.2% of control values in the extract, and 11% of control values for purified MPST when added to the reaction at 30 mM. Other compounds tested (see Table 1) had a negligible effect on sulfurtransferase activity. A heat stable cofactor was found in boiled kidney extract which stimulated sulfurtransferase activity in the extract but inhibited sulfurtransferase activity in the purified enzyme, as was observed for hypotaurine and methanesulfinate. The boiled extract had no thiocyanate forming activity of its own. The cofactor operated in synergy with methanesulfinate, but independently of hypotaurine.     

Serial pathogenesis study of SIV brain infection

A serial study of early SIV brain infection revealed initial involvement of leptomeninges, followed by perivascular infection of brain parenchyma. Severity of SIV encephalitis correlated with severity of systemic disease rather than with length of infection. Diffuse white matter disease was not observed, and there was little evidence of SIV infection of brain endothelial cells. SIV infection of leptomeninges is separate from infection of the brain, which appears to be due to transvascular spread of infected monocytes/macrophages.     

Standardization of tritium-sensitive film for quantitative autoradiography

A method for the calibration of plastic tritium standards for use with LKB Ultrofilm is described and validated. This method uses 12-microns cryostat slices of frozen liver which have been labeled with [3H]-formaldehyde and extracted with chloroform-methanol to remove lipids. Quantitative autoradiographic measurement of 3H radioactivity in the liver slices was underestimated by 35% when lipids were not extracted. Plastic sections impregnated with tritium were calibrated in terms of lipid-extracted, tissue-equivalent radioactivity content. Calibrated standard curves for these plastic standards were closely fit (p = 0.99) by second order polynomial equations for exposures of 1, 4, 7, 13, 28, and 104 days. The equations are generally useful for any plastic tritium standards.     

Correlates of SIV encephalitis in rhesus monkeys.

Necropsy records from 204 SIV-infected rhesus monkeys that had been inoculated with various strains of SIV and had died of SIV-related disease were reviewed. The relationship of SIV encephalitis with other parameters was evaluated. Encephalitis was associated with the presence of syncytial cells in other tissues, with persistent or early recurrent antigenemia, with a selective decrease in CD4+CD29+ blood lymphocytes, and with a shortened time of survival. Monkeys whose lymphocytes produced high levels of virus in culture also had a higher incidence of encephalitis. SIV was more frequently isolated from the brains of animals with encephalitis. No other clear associations were detected.