Search

The link between initiation of torpor and reduction of blood glucose concentrations is investigated in Siberian hamsters. Results showed that changes in blood glucose concentrations may be a consequence rather than a cause of the torpid state and leads to the question whether induction of torpor by 2-deoxy-D-glucose is due to its general glucoprivic actions. Analysis indicates that the critical signal for torpor onset may be one of several adipocyte feedback mechanisms.

Monoterpenes are nonnutritive dietary components found in the essential oils of citrus fruits and other plants. A number of these dietary monoterpenes have antitumor activity. For example, d-limonene, which comprises >90% of orange peel oil, has chemopreventive activity against rodent mammary, skin, liver, lung and forestomach cancers. Similarly, other dietary monoterpenes have chemopreventive activity against rat mammary, lung and forestomach cancers when fed during the initiation phase. In addition, perillyl alcohol has promotion phase chemopreventive activity against rat liver cancer, and geraniol has in vivo antitumor activity against murine leukemia cells. Perillyl alcohol and d-limonene also have chemotherapeutic activity against rodent mammary and pancreatic tumors. As a result, their cancer chemotherapeutic activities are under evaluation in Phase I clinical trials. Several mechanisms of action may account for the antitumor activities of monoterpenes. The blocking chemopreventive effects of limonene and other monoterpenes during the initiation phase of mammary carcinogenesis are likely due to the induction of Phase II carcinogen-metabolizing enzymes, resulting in carcinogen detoxification. The post-initiation phase, tumor suppressive chemopreventive activity of monoterpenes may be due to the induction of apoptosis and/or to inhibition of the post-translational isoprenylation of cell growth-regulating proteins. Chemotherapy of chemically induced mammary tumors with monoterpenes results in tumor redifferentiation concomitant with increased expression of the mannose-6-phosphate/insulin-like growth factor II receptor and transforming growth factor [Beta]1. Thus, monoterpenes would appear to act through multiple mechanisms in the chemoprevention and chemotherapy of cancer. KEY WORDS: * chemoprevention * rats * hamsters * chemotherapy * isoprenoid

The food intake, plasma glucose levels and estrous cyclicity of Syrian hamsters were analyzed after the administration of 2,5-anhydro-D-mannitol (2,5-AM). The fructose analog triggered food intake in Syrian hamsters due to the depletion of intracellular adenosine 3',5'-triphosphate. High doses of 2,5-AM also induced anestrus in Syrian hamsters without changing food intake or body weight. Furthermore, 2,5-AM-induced changes in peripheral glucose and fatty acid oxidation were not necessary or sufficient for the metabolic control of metabolism.

The effects of long day length (DL) exposure on the photoperiodic responses of hamsters to short DL were analyzed under simulated natural photoperiods (SNP). Hamsters exposed to short long DL did not undergo gonadal repression and weight loss during exposure to short DL. Long DL also lengthened the period of the evening oscillator and increased the coupling between E and M oscillators. Furthermore, adult photononresponsiveness does not increase in adult hamsters maintained in short DLs.

The feeding behavior of Siberian hamsters were analyzed after undergoing partial surgical lipectomy (LIPX) to determine the relationship between food hoarding and body fat. Siberian hamsters subjected to LIPX increased food hoarding without affecting body fat. On the other hand, Siberian hamsters subjected to bilateral lesions of the paraventricular nucleus of the hypothalamus exhibited elevated body fat. The effects of partial surgical LIPX indicated the inverse relationship between body fat and level of food hoarding in brain-intact hamsters.

The effects of aging on the inhibitory activity of the serotonin (5-HT) agonist, 8-OH-DPAT, on photic phase resetting of circadian rhythm were analyzed in juvenile and senescent hamsters. Pretreatment of young and old hamsters with the serotonin agonists indicated the presence of age-related deficits in the responsiveness of the rodent circadian system to the phase-resetting effects if 8-OH-DPAT. Altered serotonergic modulation of photic phase resetting during senescence was mediated by changes in the structure of several loci in the circadian system.

The role of neurogenic plasma exudation in mediating upper plasma airway injury mucosa was analyzed in hamsters during exposure to grain sorghum dust (GDE). Intravital analysis of hamster oral mucosa after exposure to an aqueous extract of GDE indicated the presence of specific neurogenic plasma exudation which led to oral muscosa inflammation. However, GDE-induced elevations in macromolar efflux in hamster cheek pouch was attenuated by neurokinin 1 receptor antagonist.

The effects of fasting on the metabolic regulation of reproduction were analyzed in Syrian hamsters to determine the role of vagally transmitted signals and methyl palmoxitrate (MP) treatment on the estrous cycle. The effects of metabolic challenge on the estrous cycle of Syrian hamsters were not affected by vagally transmitted signals. Furthermore, administration of MP induced the anestrus phase in Syrian hamsters.

The role of metabolic fuel availability in the modulation of ovulatory cycles was analyzed in the four-day estrous cycle of Syrian hamsters. Administration of 2-deoxy-D-glucose (2-DG) in sham-operated and ovariectomized Syrian hamsters initiated the estrous cycle and stimulated the neurons in the caudal brain stem. Furthermore, central glucoprivation is sufficient in initiating the estrous cycle of Syrian hamsters.

The effects of interleukin-1beta (IL-1beta) on bradykinin-induced responses of the oral mucosa were analyzed in adult, male golden Syrian hamsters after the administration of recombinant human IL1-beta. Bradykinin-induced macromolecular efflux in golden Syrian hamsters was increased by suffusions of recombinant human IL-1beta. However, the effects of recombinant human IL-1beta were inhibited by recombinant human IL-1beta and bradykinin B2-receptor antagonist.

The effects of food deprivation on the food hoarding behavior and food intake of female Siberian hamsters were analyzed during lactation and pregnancy. Analysis of feeding behavior in female Siberian hamsters based on a simulated burrow systems indicated the role of 32-hours of fasting in increasing the frequency of food hoarding during pregnancy. The pregnant and lactating Siberian hamsters also exhibited increased food intake due to the energy requirements of pregnancy and lactation.

Lipectomized adult male Siberian hamsters were analyzed after initial exposure to short winter-like days (SD) and long summer-like days (LD) to determine the effects of lipectomy on body fat gain. SD-housed recrudescing Siberian hamsters under food restriction exhibited reduced adipocyte density. The levels of retroperitoneal and inguinal white adipose tissue (WAT) was also increased by epedidymal WAT lipectomy of the paraventricular nucleus of the hypothalamus in food restricted hamsters.

The dorsal skinfold microcirculation of conscious hamsters was analyzed to determine the ability of Hemolink in restoring normal blood macro- and capillary circulation. Normal arterial pressure, systemic blood gas and metabolic parameters were restored by hypovolemic shed blood replacement with autologous whole blood and Hemolink. However, hemodynamic, respiratory and metabolic instability were not restored by resuscitation with Dextran and Ringer lactate.

The mechanisms of liver mitochondria proton leakage were analyzed in liver tissues isolated from mice, hamsters and rats. Liver mitochondria proton leak per milligram of protein was dependent on total body mass while maximal electron transport chain activity did not correlate with body mass in mice, hamsters and rats. Furthermore, changes in body mass also alters the surface area and phospholipid fatty acid composition of the mitochondrial membrane.

The effects of pineal melatonin (Mel) on juvenile reproductive responses were analyzed in juvenile hamsters after receiving Mel infusions of two durations. The gonadal growth of long-duration-gestated hamsters was inhibited during the 18th and 25th day after the administration of Mel infusions for three days. However, the gonadal growth of long-duration hamsters was not altered on the 18th day after receiving Mel infusions but gonadal growth was attenuated on the 25th and 32nd day.

Changes in the body temperature rhythms of 3-12-month old Siberian hamsters was analyzed after exposure to a 16-hour light/day (LD) cycle for 2-4 months. Thirteen of the 22 Siberian hamsters were unable to reentrain to a 5-hour phase delay of the LD cycle after phase shift and exhibited unstable entrainment intervals. Furthermore, the body temperature and locomotory activity rhythms of the hamsters was altered for several days after the phase shift with eight hamsters exhibiting arrythmia.