Biomedical subjects

N Murakami

Publications and source records attributed to N Murakami.

At least 469 records · Page 26Linked to original sources

PubMed1988

Endogenous peroxidase activity in primary culture of human thyroid cells. Localization and measurement.

Intracellular localization of and an assay method for endogenous peroxidase (PO) activity were studied using primary culture of thyroid cells obtained from patients with hyperthyroidism. PO activity was visualized by cytochemical reaction and was located mainly in perinuclear cisternae and rough endoplasmic reticulum. With increased culture time, the number of cells showing positive PO activity and amount of the enzyme reaction product in individual cells showed a parallel decrease. For measurement of PO activity, cultured thyroid cells were frozen and thawed and then incubated with citric acid buffer solution containing o-phenylenediamine (opd) and hydrogen peroxide. After incubation, the optical density (OD) of the solution colorized by endogenous peroxidase was measured at 405 nm using a microplate reader. About 1 X 10(4) cells were sufficient for assay of PO activity. Using the above method to assay PO activity and sandwich enzyme immunoassay for thyroglobulin (TG), chronological changes in the PO activity and TG concentration in the culture medium were examined. Although the cells showed no decrease in number, PO activity and TG concentration decreased chronologically. When the ratio of PO activity to TG concentration was calculated, in 3 cases the ratio was almost constant, and in the remaining two, it decreased chronologically. The present biochemical method thus seems useful for determining peroxidase activity of cultured thyroid en masse.

Cells, Cultured↗

PubMed1988

Ventromedial hypothalamus is highly sensitive to prostaglandin E2 for producing fever in rabbits.

1. The febrile responses induced by intraventricular or intrapreoptic (bilateral) injections of prostaglandin E2 (PGE2) were investigated in the same group of rabbits. Both injections produced dose-dependent fever over a range of 100-2000 ng. However the magnitude of febrile responses induced by ventricular injections was significantly greater than those by intrapreoptic injections. This indicates that there exist regions more sensitive to PGE2 than the preoptic region for producing fever. 2. To explore the regions sensitive to PGE2, the effects of microinjection (1 microliter) of PGE2 (50 and 100 ng) on the rectal temperature were extensively examined in the forty regions of the brain stem. The results showed that the preoptic and anterior hypothalamic region, and the ventromedial hypothalamic region are highly sensitive to PGE2 for producing fever. 3. The febrile responses to PGE2 (50-1000 ng) microinjected into the preoptic region were compared with those induced by injection in the ventromedial hypothalamic region. Fever induced by injection in the ventromedial hypothalamic region was significantly greater than that by injection into the preoptic region. 4. Fever induced by PGE2 injected into the ventromedial hypothalamic region was due to increased heat production in the cold environment (10 degrees C), while in 24 degrees C environment heat losses were reduced without significant changes in heat production. 5. The present results show that the ventromedial hypothalamic region is the most sensitive region to PGE2 for producing fever.

Animals↗

PubMed1988

Multiple control of fever production in the central nervous system of rabbits.

1. The effects of microinjection of prostaglandin D2, E2 and F2 alpha and of endogenous pyrogen on the rectal temperature of rabbits were extensively examined in sixty-eight brain regions and in the third cerebral ventricle. 2. Intracerebroventricular injection of both prostaglandins E2 and F2 alpha produced dose-dependent fever over a range of 100-1000 ng. The selective brain regions, the nucleus broca ventralis, preoptic area, anterior hypothalamus and the ventromedial hypothalamus, responded to microinjections of a small dose (less than 200 ng) of prostaglandins E2 and F2 alpha by producing fever. Furthermore, the lateral hypothalamus, ventral thalamus, substantia nigra and the trigeminal nucleus were also sensitive to high concentrations of prostaglandins E2 and F2 alpha, fever being produced. It is likely that prostaglandin D2 is not involved in fever induction. 3. The ventricular injection of endogenous pyrogen also produced fever. However, brain regions sensitive to microinjection of endogenous pyrogen were exclusively localized to regions near the organum vasculosum laminae terminalis (OVLT), such as the nucleus broca ventralis and the preoptic area. In contrast to the monophasic fever induced by prostaglandins E2 and F2 alpha, about 30 min after ventricular or cerebral injection of endogenous pyrogen the rectal temperature gradually started to rise and the fever was prolonged over 4 h. 4. We investigated the effect of an inhibitor of prostaglandin synthesis, sodium salicylate, on biphasic fever induced by intravenous injection of bacterial endotoxin. The microinjections of sodium salicylate into the bilateral regions near the OVLT suppressed the second peak but had no effect on the first peak. 5. The present study clarifies that there exist two separate mechanisms of induction of biphasic fever. Correlating with the first peak of biphasic fever, prostaglandins synthesized outside the blood-brain barrier act on multiple sites in the central nervous system to induce fever. Correlating with the second peak, endogenous pyrogen acts on regions near the OVLT to synthesize and release pyrogenic prostaglandins.

Animals↗

PubMed1988

Is the central arachidonic acid cascade system involved in the development of acute-phase response in rabbits?

1. In the present study, endogenous pyrogen (EP), prostaglandin E2 or arachidonic acid was injected into the cerebral ventricle to investigate whether central arachidonic acid metabolites are involved in the development of the acute-phase response. The central effects of a cyclo-oxygenase inhibitor, indomethacin, and of a lipoxygenase inhibitor, nordihydroguairetic acid (NDGA), on the acute-phase response induced by an intracerebroventricular injection of EP were also examined. 2. The ventricular injection of EP decreased the plasma concentrations of iron and zinc, while increasing those of copper and fibrinogen and the circulating leucocyte count. However, ventricular injection of prostaglandin E2 affected neither of them, indicating that prostaglandin E2 does not contribute to the acute-phase response production by itself. 3. Both the ventricular injections of indomethacin and NDGA had no effect on the changes in the plasma concentrations of iron, copper and fibrinogen which were induced by ventricular injection of EP. In addition, when arachidonic acid was administered into the cerebral ventricle, the changes in the plasma levels of iron, copper and fibrinogen were not induced. 4. In contrast, EP-induced hypozincaemia was observed upon pre-treatment with NDGA, but not upon pre-treatment with indomethacin. However, plasma zinc increased after the ventricular injection of arachidonic acid. Ventricular injection of EP alone and of EP with NDGA increased the number of circulating leucocytes 8 and 24 h after the ventricular injection, while ventricular injections of arachidonic acid, and of EP with administration of indomethacin induced leucocytosis 8 h after injections. 5. These results suggest that arachidonic acid metabolites do not participate in the genesis of the acute-phase response.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute-Phase Reaction↗

PubMed1988

Changes in hypothalamic temperature modulate the neuronal response of the ventral thalamus to skin warming in rats.

1. The influence of hypothalamic temperature on the activity of warm-excited neurones, which responded to skin warming with an increased firing rate, in the ventro-basal (VB) complex of the thalamus of rats was examined electrophysiologically. 2. The warm-excited neurones were classified into three types: hypothalamus-cold neurones in which the firing rate increased with hypothalamic cooling, hypothalamus-warm neurones in which the firing rate increased with hypothalamic warming and hypothalamus-insensitive neurones in which the firing rate was not affected by hypothalamic temperature. The majority of hypothalamus-cold and hypothalamus-warm neurones increased their firing rate at hypothalamic temperature below and above 38 degrees C, respectively. 3. The threshold temperature at which hypothalamus-warm neurones responded to skin warming was lowered by hypothalamic warming. However, hypothalamus-cold neurones responded to lower skin temperatures during hypothalamic cooling. 4. These results show that the neuronal activity of the VB complex in the thalamus, responding to skin warming, is affected by hypothalamic temperature. Thus thermal information from the peripheral thermoreceptors is modulated by hypothalamic temperature at the level of the relay nuclei of the thalamus.

Action Potentials↗

PubMed1988

Effect of prostaglandin E2 on thermoresponsive neurones in the preoptic and ventromedial hypothalamic regions of rats.

1. We investigated the effect of microinjection of prostaglandin E2 (PGE2) into the preoptic (POA) or the ventromedial hypothalamic (VMH) region on rectal temperature in rats. Fever was induced by microinjection of PGE2 into the POA or the VMH regions. The febrile responses induced by PGE2 injected into the VMH region were significantly greater than those induced by injection into the POA region. 2. The effect of temperature on neuronal activity in the POA and the VMH regions was investigated by using slice preparations from rats. It was revealed that there exist many thermoresponsive neurones in the VMH region as well as in the POA region, and that the proportion of thermoresponsive neurones out of the total neurones examined in the VMH region was almost identical to that in the POA region. In addition, the warm-responsive neurones in the VMH region exhibited larger thermal coefficients than those in the POA region. 3. When PGE2 was applied in a recording chamber where the tissue slice was perfused, most of the neurones in the VMH region which responded to PGE2 showed a decrease in their firing rate, while those in the POA region showed an increase in their firing rate, regardless of their thermoresponsiveness. In the POA region, PGE2 began to affect the activities of the warm-responsive neurones in the range of 5 x 10(-7) to 7 x 10(-6) M, whereas maximum responses were obtained between the concentrations of 5 x 10(-6) and 5 x 10(-5) M. In the VMH region, PGE2 began to change the activities of the warm-responsive neurones in the range of 5 x 10(-8) to 5 x 10(-7) M, and the maximum effect of PGE2 on the VMH warm-responsive neurones occurred between the concentrations of 8 x 10(-7) and 4 x 10(-5) M. 4. The present results show that neurones exhibit different responsiveness to PGE2 and different sensitivity to PGE2 between the POA and the VMH regions. Nevertheless, microinjection of PGE2 into either the POA or the VMH region produces fever. Therefore, it is suggested that fever is produced by complex neuronal networks in the central nervous system.

Action Potentials↗

PubMed1988

Pattern differences in experimental fevers induced by endotoxin, endogenous pyrogen, and prostaglandins.

To distinguish pattern differences in experimentally induced fevers, we investigated febrile responses induced by intravenous (IV), intracerebroventricular (ICV), and intra-preoptic/anterior hypothalamic (POA) administration of bacterial endotoxin (lipopolysaccharide, LPS), endogenous pyrogen (EP), human recombinant interleukin-1 alpha (IL-1), and prostaglandins E2 and F2 alpha (PGE2 and PGF2 alpha). Intravenous LPS, EP, or IL-1 in high concentrations caused biphasic fever. In low concentrations, they induced only the first phase of fever. Latency to onset and time to first peak of fever induced by IV injection of LPS or EP were almost the same as those after ICV or POA injection of PGE2. Fever induced by ICV or POA administration of LPS, EP, IL-1, or PGF2 alpha had a long latency to onset and a prolonged time course. There were significant differences among the latencies to fever onset exhibited by groups that received ICV or POA injections of LPS, EP, or PGF2 alpha and by groups given IV injections of LPS or EP and ICV or POA injections of PGE2. Present observations indicate different patterns of fever produced by several kinds of pyrogens when given by various routes. These results permit us to consider the possibility that there are several mediators or multiprocesses underlying the pathogenesis of fever.

Animals↗

PubMed1988