Antioxidant activity of thiosulfinates derived from garlic.

Garlic extract significantly inhibited the oxidation of methyl linoleate in homogeneous acetonitrile solution, whereas the antioxidant effect of allicin-free garlic extract, prepared by removing allicin by prepared by removing allicin by preparative HPLC, was much lower than that of the garlic extract. These results suggest that the antioxidant properties are mostly attributed to the presence of allicin in the garlic extract. Allicin a major component of the thiosulfinates in garlic extract, was found to be effective for inhibiting methyl linoleate oxidation, but its efficiency was less than that of alpha-tocopherol. Next, the reactivity of allicin toward the peroxyl radical, which is a chain-propagating species, was investigated by direct ESR detection. The addition allicin to 2,2'-azobis(2,4-dimethylvaleronitrile)-peroxyl radical solution caused the signal intensity of the peroxyl radical to dose-dependently decrease, indicating that allicin is capable of scavenging the the peroxyl radical and acting as an antioxidant. Finally, we studied the structure-anioxidant activity relationship for thiosulfinates and suggested that the combination of the allyl group (-CH2CH=CH2) and the -S(O)S- group is necessary for the antioxidant action of thiosulfinates in the garlic extract. In addition, one of the two possible combinations, -S(O)S-CH2CH=CH2, was found to make a much larger contribution to the antioxidant activity of the thiosulfinates than the other, CH2=CH-CH2-S(O)S-.

Tissue accumulation of cadmium following oral administration to metallothionein-null mice.

To verify the roles of intestinal metallothionein (MT) as a barrier against ingested cadmium (Cd) and as a transporter of mucosal Cd to the kidneys, the distribution of orally administered Cd was compared between normal and MT-I and -II knock-out (MT-null) mice. Following single administration of a low dose of Cd (0.1 mg/kg), hepatic Cd levels and the sum of total Cd in the liver and kidney (K + L) were significantly less in the controls than in MT-null mice. The ratio of Cd in the kidney to the liver (K/L) was significantly lower in the MT-null mice. On the other hand, at a high Cd dose (2.0 mg/kg), K + L and K/L were not significantly different between the two groups. However, following oral pretreatment with zinc (Zn) to the high dose control mice, K + L significantly decreased and K/L significantly increased. No such effects of Zn pretreatment were observed in MT-null mice. Similar differences in K + L and K/L were also observed between the control and MT-null mice groups following the Zn pretreatment. Repeated administration of Cd for 4 weeks resulted in significantly larger K/L distribution in control mice over null mice. These results suggest that MT in the intestinal mucosa functions both as a protective barrier against Cd absorption and as an extracellular transporter of Cd to the kidney.

Central control of sexual behavior.

Neuronal activity changes in the medial preoptic area (MPOA) of the male monkey were related to the commencement of sexual behavior, penile erection and the refractory period following ejaculation. Similarly, changes in the female MPOA were related to the commencement of sexual behavior and presentation. Increased neuronal activity in the dorsomedial hypothalamic nucleus (DMH) in the male monkey and in the ventromedial hypothalamic nucleus (VMH) in the female monkey was synchronized to each mating act. Stimulation study and neuronal activity recordings in the MPOA, DMH and VMH suggest involvement of MPOA neurons in sexual arousal, and of male DMH and female VMH neurons in the copulatory act. Stimulation experiment on the various parts in the hypothalamus of the female monkey also supports the conclusion.

Proceptive presenting elicited by electrical stimulation of the female monkey hypothalamus.

Proceptive presenting by female macaque monkeys was evoked by electrical stimulation of the ventromedial hypothalamic nucleus and the medial preoptic area, under conditions of partial restraint while sitting in a primate chair. This behavior could be elicited only when a male monkey was in close proximity and not when he was removed or was replaced with a female monkey or the human experimenter. This seems to be the first report on the effects of electrical brain stimulation on proceptivity in the female monkey.

Responsiveness of monkey preoptic thermosensitive neurons to non-thermal emotional stimuli.

Responsiveness of 143 preoptic neurons to changes in hypothalamic temperature and to non-thermal emotional stimuli were investigated while rewarding (foods) and aversive objects (hypertonic saline, a toy snake, an air puffer) were given. About 71% of thermosensitive neurons and 32% of thermally insensitive neurons changed the activity when emotional stimuli were shown to and/or tasted by the monkey. Such responses were modulated by satiety/hunger state and were dependent on the degree of perturbation of emotional state. About half of the neurons tested responded when the monkey opened the mouth and protruded the tongue or moved fingers in trying to obtain foods with strong motivation, but did not when the animal made such movements less readily or reluctantly with the progress of satiation. This response was most frequently found among warm-units. The results raise a possibility that preoptic thermosensitive neurons, besides their postulated thermoregulatory functions, might be involved in the response of coordination with thermal and non-thermal emotional behaviors controlled in the hypothalamus.