Neural correlates to seen gaze-direction and head orientation in the macaque monkey amygdala.

Human neuropsychological studies suggest that the amygdala is implicated in social cognition, in which cognition of seen gaze-direction, especially the direct gaze, is essential, and that the perception of gaze direction is modulated by the head orientation of the facial stimuli. However, neural correlates to these issues remain unknown. In the present study, neuronal activity was recorded from the macaque monkey amygdala during performance of a sequential delayed non-matching-to-sample task based on gaze direction. The facial stimuli consisted of two head orientations (frontal; straight to the monkey, profile; 30 degrees rightwards from the front) with different gaze directions (directed toward and averted to the left or right of the monkey). Of the 1091 neurons recorded, 61 responded to more than one facial stimulus. Of these face-responsive neurons, 44 displayed responses selective to the facial stimuli (face neurons). Most amygdalar face neurons discriminated both gaze direction and head orientation, and exhibited a significant interaction between the two types about information. Furthermore, factor analysis on the response magnitudes of the face neurons to the facial stimuli revealed that two factors derived from these facial stimuli were correlated with two head orientations. The overall responses of the face neurons to direct gazes in the profile and frontal faces were significantly larger than that to averted gazes. The results suggest that information of both gaze and head direction is integrated in the amygdala, and that the amygdala is implicated in detection of direct gaze.

Rat hippocampal theta rhythm during sensory mismatch.

It has been suggested that sensory mismatch induces motion sickness, but its neural mechanisms remain unclear. To investigate this issue, theta waves in the hippocampal formation (HF) were studied during sensory mismatch by backward translocation in awake rats. A monopolar electrode was implanted into the dentate gyrus in the HF, from which local field potentials were recorded. The rats were placed on a treadmill affixed to a motion stage translocated along a figure 8-shaped track. The rats were trained to run forward on the treadmill at the same speed as that of forward translocation of the motion stage (a forward condition) before the experimental (recording) sessions. In the experimental sessions, the rats were initially tested in the forward condition, and then tested in a backward (mismatch) condition, in which the motion stage was turned around by 180 degrees before translocation. That is, the rats were moved backward by translocation of the stage although the rats ran forward on the treadmill. The theta (6-9 Hz) power was significantly increased in the backward condition compared with the forward condition. However, the theta power gradually decreased by repeated testing in the backward condition. Furthermore, backward translocation of the stage without locomotion did not increase theta power. These results suggest that the HF might function as a comparator to detect sensory mismatch, and that alteration in HF theta activity might induce motion sickness.

Hippocampal place cell activity during chasing of a moving object associated with reward in rats.

Hippocampal place cells encode location of animals in the environment. However, it remains unknown whether the hippocampal place cells encode a continuously moving object in the environment. To investigate this topic, we analyzed the place cell activity of freely moving rats when a toy car was introduced into an arena. First, in a freely moving task without the car, the rats freely navigated inside the arena to earn an intracranial stimulation (ICS) reward for each 150 cm traveled. Second, they were divided into two groups and tested using two different tasks. In the car-dependent navigation (CDN) task, the car was placed inside the arena, and the rat received ICS if it chased and came within 20 cm of the car. In the car-independent navigation (CIN) task, the rat acquired ICS rewards if it traveled 150 cm regardless of its relation to the car. Place fields remapped more frequently in the CDN than the CIN tasks. In both the CDN and CIN tasks, the place cell activity inside the place fields displayed moderate tuning to the movement parameters of the rats and car, and the distance between the car and rats. However, tuning of the place cells to movement variables of the car was more selective in the CDN than the CIN tasks, while information regarding movement variables of the car represented by the place cell activity was larger in the CDN than the CIN task. These results indicated that place cell activity within the place fields represents not only an animal's own location but also the movement variables of another moving object if that object is associated with rewards. The present results provide new evidence that place cell activity conveys relevant information in a task even if this information is derived from other moving objects.

Conjunctive effects of reward and behavioral episodes on hippocampal place-differential neurons of rats on a mobile treadmill.

Previous studies reported context (or behavior)-dependent activities of hippocampal place cells, which are suggested to be the neural basis of episodic memory. However, it remains unclear what distinctive items these context-dependent activities encode. We investigated separately the effects of space, locomotion, and episodes with positive/negative reinforcements on activity of place-differential neurons in the hippocampal CA1 area. Rats were placed on a treadmill affixed to a motion stage translocated along a figure 8-shaped track. The track could be navigated by two different routes that shared a common central stem. The stage was paused at the start and end of the routes, where conditioned response tasks with different reinforcements were imposed. As the rats passed the common central stem, some neurons fired differently depending on the route. Comparison of hippocampal spatial firing patterns across different conditions with and without treadmill operation and/or the tasks indicated that these route-dependent spatial firing patterns were sensitive to locomotion, the tasks, and vestibular sensation or visual cues such as optic flow. The results suggest that external sensory inputs, path integration, and reinforcement context are all integrated in the hippocampus, which might provide the neural basis of episodic memory.

Unambiguous representation of overlapping serial events in the rat hippocampal formation.

The hippocampal formation is suggested to be crucial in unambiguous representation of overlapping temporal sequences in episodic memory. We hypothesized that, if this was true, the hippocampal formation neurons would differentially respond to the same elements even in different temporal sequences. The present study was designed to investigate hippocampal formation CA1 neuronal activity of rats during performance of a conditional delayed stimulus-response association task in which three stimuli were conditionally and serially presented with a delay. In the task, the pairs of the second and third stimuli were overlapped across the trials, but separated by the preceding first stimuli. Conditioned tones coming from one of three possible directions were followed, after a short delay, by one of three pairs of reinforcement series. The pairs consisted of air puff (aversive sensory stimuli) and tube protrusion (which allowed licking sucrose behavior) in the following combinations: air puff-tube protrusion, tube protrusion-tube protrusion and tube protrusion-air puff. The pairs were interposed by a 2 s delay. The three conditioned tone directions were associated with these three pairs in a one-to-one correspondence, and its association was conditional to three possible conditioned tone frequencies (300, 530, and 1,200 Hz). The responses of 107 neurons to the air puff and tube protrusion were analyzed by two-way ANOVA (task condition x reinforcement situation). Of 42 air puff-responsive and 64 tube protrusion-responsive neurons, 36 and 53 displayed significant main effects and/or significant interaction, respectively. Furthermore, neural responses during the delay periods were dependent on the task conditions. The results indicated that the majority of the hippocampal formation neurons showed task condition- and/or reinforcement situation-dependent responses, suggesting a crucial role of the hippocampal formation in representation of overlapping serial events in episodic memory.

Retionic acid and its receptors are required for expression of aryl hydrocarbon receptor mRNA and embryonic development of blood vessel and bone in the medaka fish, Oryzias latipes.

Retinoic acid (RA), the active derivative of vitamin A, is essential for normal embryonic development of vertebrates because both the lack and excess of RA result in developmental malformations. We previously reported that aryl hydrocarbon receptor (AHR) is also required for vascular and bone formation by regulating cytochrome P450 expression. However, little is known about the roles of retinoic acid receptors (RAR) and retinoid X receptors (RXR) in the embryonic development of blood vessels and molecular cross-talk between RAR/RXR and AHR. We report for the first time that RA and RAR/RXR are required for expression of AHR mRNA and the embryonic development of blood vessel and bone. The embryonic organogenesis of medaka fish was specifically inhibited by an inhibitor of RA synthesis (diethylaminobenzaldehyde), antagonists of RAR (Ro41-5253) and RXR (Ro71-4595), agonist (beta-naphthoflavone) and antagonist (alpha-naphthoflavone) of AHR, and excess RA. These reagents are useful for future studies to elucidate molecular mechanisms for vascular and bone formation in the medaka embryogenesis. Our results also show that medaka embryos may be useful for screening inhibitors of vascular formation for anti-cancer drugs.

Differential activation in the medial temporal lobe during a sound-sequence discrimination task across age in human subjects.

To elucidate the brain mechanisms to encode sequential events, event-related potentials (ERPs) were recorded during a sound-sequence discrimination task using young and middle-aged adult subjects. In the task, a series of six or 12 kinds of natural sounds were sequentially presented; 70-80% of the stimuli were presented in a fixed order (Non-target), but the remaining stimuli, in a random order (Target). The subjects were instructed to detect the Targets and press a button at the end of each Target. In a control task, the same sounds were randomly presented (Control), and they were instructed to press the button at the end of each sound. Behavioral results indicated that the young subjects learned the task faster than did the middle-aged subjects. Positive ERP waves were evoked by Targets and Non-targets in the parieto-occipital area around 300-700 ms after stimulus onset. The mean amplitudes during this period in the young subjects were larger in Target than Control conditions, and those in Target condition were larger in the young than middle-aged subjects. Furthermore, the mean amplitudes in the Target condition were significantly correlated with behavioral performance. Equivalent dipoles for the ERPs evoked by Targets were estimated in the medial temporal lobe including the hippocampal formation and parahippocampal gyrus. The results suggest that the ERPs around 300-700 ms latency are involved in sound-sequence information processing. Furthermore, decrease in amplitudes of this positivity in the middle-aged subjects suggests that age-related memory decline is associated with deficits in encoding and retrieval of unfamiliar sequence.

Estrogen inhibits development of yolk veins and causes blood clotting in transgenic medaka fish overexpressing estrogen receptor.

We established three transgenic medaka fish lines overexpressing the medaka estrogen receptor under the constitutive medaka beta-actin promoter. The transgenic embryos became hypersensitive to estrogens (17 beta-estradiol and 17alpha-ethinylestradiol), and failed to develop yolk veins while blood clots formed in the blood island within 3 days after exposure to the estrogens. The embryos developed normally if exposed to estrogen after an early neurula stage, suggesting that the sensitive stage is before neurulation. The developmental defects were recovered by incubation with an anti-estrogen, tamoxifen. These results indicate that activation of estrogen receptor caused the estrogen-induced developmental defects. Our results show that the transgenic embryos can be used to assay the blood clotting activity of estrogenic compounds in vivo.

[Hypoglycemic hemiplegia: a report of three cases].

Hemiplegia is a rare complication accompanied with hypoglycemia. We reported three cases of hypoglycemic hemiplegia (HH). Case 1: A 74-year-old female had medication for diabetes mellitus (DM). She had right hemiplegia and aphasia. Case 2: A 72-year-old male had DM, and was admitted to our hospital having loss of consciousness and right hemiplegia. Case 3: An 82-year-old female suffered from consciousness disturbance with tetraplegia, and had left hemiparesis later. She had no DM, but suffered from iatrogenic hypoglycemia. The brain CT of these three cases showed atrophy, and MRI demonstrated multiple infarction. The angiography of case 1 showed the stenosis of bilateral internal carotid artery and the origin of the left vertebral artery. The angiography of case 2 showed severe stenosis of the left internal carotid artery. The cases above had hypoglycemia at admission. The value of the case 1 was 48 mg/dl, case 2 was 35 mg/dl and case 3 was 38 mg/dl. But these symptoms of the three cases disappeared rapidly after glucose infusion. The literature regarding HH was reviewed, and the pathogenesis was discussed. We emphasize the importance of checking blood sugar levels for the emerging patients with hemiplegia, because it is difficult to discriminate by clinical history or neurological findings.

The embolization of ruptured aneurysms in acute stage with guglielmi detachable coils.

We have treated 43 ruptured aneurysms in 42 patients with Guglielmi Detachable Coils (GDC) in acute period. Thirty-one patients (74%) were independent on discharge. Among the patients of Hunt and Hess Grade I, II and III, 27 patients (84%) were independent. Acute rerupture occurred in two elderly patients with insufficient embolization and another patient experienced rerupture 45 days after the embolization. Symptomatic vasospasm was reported in 16% of patients and its permanent morbidity rate resulted in 3.1%. Although the long term results remain to be determined, embolization with GDC is a safe and promising treatment for acutely ruptured aneurysms.

[Clinical features of Japanese children infected with Cryptosporidium parvum during a massive outbreak caused by contaminated water supply].

A massive outbreak of cryptosporidiosis occurred at a local town of Saitama Prefecture, in 1996. During this outbreak, we investigated the clinical features of children seen at Saitama Medical School. Cryptosporidium parvum (C. parvum) was detected from 10 out of 28 (36%) children with diarrhea during June and August, 1996. The average ages of the children who were positive and negative for C. parvum were 6.5 and 5 year old, respectively. Among the children infected with C. parvum, colic pain was observed in 3 children and 4 children had vomiting. However, none of the children showed fever over 38.0 degrees C nor bloody stools. Family members of children infected with C. parvum also had diarrhea and/or vomiting (5/6). C. parvum was repeatedly detected from 2 out of 3 children. All infected children had an improvement of abdominal symptoms in 4 to 10 days. C. parvum should be included as a pathogen which causes enterocolitis in Japanese children.

Increased cerebral choline-compounds in Duchenne muscular dystrophy.

We investigated the hypothesis that cell membrane function is abnormal in brains of subjects with Duchenne muscular dystrophy (DMD) using proton-nuclear magnetic resonance (NMR) spectroscopy of human brain extracts. The total amount of choline-containing compounds was significantly higher (about three times) than in normal controls and patients with other myopathies, while N-acetyl-L-aspartic acid and creatine were within the normal range. These findings indicate that abnormal cell membrane function may be correlated with the abnormal dystrophin or lack of dystrophin in the brain of patients with DMD.

Neuronal maturation and N-acetyl-L-aspartic acid development in human fetal and child brains.

The developmental changes in N-acetyl-L-aspartic acid (NAA) were assessed in human fetal and child brains by means of high resolution proton magnetic resonance spectroscopy (MRS). NAA was detected in the cerebral cortex and white matter of fetuses of 16 weeks' gestation. NAA increased gradually from 24 weeks' gestation and remarkably from 40 weeks' gestation to 1 year of age. The developmental changes in tissue NAA in postnatal brains were found to be similar to those of NAA/Cr on clinical proton MRS. As the neuronal cell density in the cerebral cortex decreases with dendritic maturation, an increase in NAA with age may reflect the normal and abnormal development of axons, dendrites and synapses as well as neuronal soma.

Occurrence of high ratio of males after introduction of minocycline in a colony of Leptotrombidium fletcheri infected with Orientia tsutsugamushi.

In colonies of Leptotrombidium fletcheri mites infected with Orientia tsutsugamushi (Ot), the agent of scrub typhus, males rarely appear. In the present study, the development of a high ratio of males was observed after introduction of minocycline (MC). A high dose of MC was injected subcutaneously into a mouse, and by feeding unfed larvae from an infected mite colony on this mouse, the Ot in the mites were successfully killed. Of a total of 130 unfed larvae attached to the mouse, 29 developed into females; of these, 9 laid an average of 112.4 eggs/female. Unfed larvae in the succeeding generations were attached to untreated mice. All adults in the P and F1 generation were females, and males started to appear at the F2 generation. The ratio of males to females was 332:7, 108:13, 263:61 and 71:9 at the F2, F3, F4 and F5 generations, respectively. These data suggest that Ot in the ovary or gonad may suppress the development of males.

Seasonal development of Leptotrombidium akamushi (Acari: Trombiculidae) under field temperatures.

Engorged larvae of Leptotrombidium akamushi (Brumpt), a vector of scrub typhus, were reared in small plastic containers placed on the ground and fed fresh eggs of the collembolan Sinella curviseta Brook. Engorged larvae obtained in October developed into deutonymphs through protonymphs approximately 1 mo before winter and became dormant in the cold winter season (approximately 3 mo). Most deutonymphs developed into tritonymphs in April and adults in May. Females began laying eggs in mid-June and the numbers of unfed larvae showed a peak in August. The mites reared from July rapidly developed into adults by August, and laid eggs in September. Larvae were most abundant in October, and adults became dormant in the winter. The same adults laid eggs from early May to late June and, upon hatching, the larval population peaked in early July of the 2nd summer. Most larvae died before the 2nd winter. Eggs hatched approximately 3 wk after oviposition and longevity of unfed larvae was 2 mo. Because of this very short incubation period, L. akamushi larvae occur in the summer, whereas L. pallidum Nagayo, Miyagawa, Mitamura & Tamiya, and L. scutellare Nagayo, Miyagawa, Mitamura, Tamiya & Tenjin occur in the autumn, although 3 species lay eggs from May to August.

Nuclear magnetic resonance (NMR) analysis on the serum lipids of rabbits infected with Schistosoma japonicum: oxidative modifications of diene system in fatty chains.

Proton nuclear magnetic resonance (1H NMR) spectroscopy was used to characterize the oxidized products in the serum lipoprotein lipids (LPL) of rabbits infected with Schistosoma japonicum. The loss of bis-allylic and allylic methylenes proton peaks (2.7 and 2.0 p.p.m.) of unsaturated systems of the LPL and the appearance of the signals of the conjugated diene systems of hydroperoxide (5.43-6.45 p.p.m.) and epidioxide (2.45 p.p.m.) of the fatty chains of the serum demonstrated the lipids degradation associated with the Schistosoma infection.

Failed vertical transmission of Rickettsia tsutsugamushi (Rickettsiales: Rickettsiaceae) acquired from rickettsemic mice by Leptotrombidium pallidum (Acari: trombiculidae).

Larvae of Leptotrombidium pallidum (Nagayo, Miyagawa, Mitamura & Tamiya) from uninfected laboratory colonies were fed on mice infected with Rickettsia tsutsugamushi (Hayashi) Ogata. Infection of the chiggers with R. tsutsugamushi was determined by passage of chigger exudates into ddY mice. The passage method was modified so that an inoculum was considered to be positive when R. tsutsugamushi or anti-R. tsutsugamushi antibody, or both, were detected in mice up to the third blind passage. R. tsutsugamushi was detected in six of 18 larvae (33.3%) and in all developmental stages. In adults, five of 18 males and 10 of 46 females were infected with R. tsutsugamushi. In L. fuji (Kuwata, Berge & Philip), R. tsutsugamushi was not found in 57 engorged larvae fed on rickettsemic mice but was found in a very low percentage of deutonymphs and adults. Female L. pallidum from larvae fed on infected mice were paired individually, and F1 larvae were collected. Although eight females were found to be positive for R. tsutsugamushi, the rickettsia was not detected in 12 pools (249 larvae) of F1 larvae from these infected females. We concluded that uninfected mites became infected by feeding on rickettsemic mice at comparatively high rates depending on the species and transmitted this infection transstadially to succeeding life stages, but not vertically to larvae in the following F1 generation.

An ultrastructural study of vertical transmission of Rickettsia tsutsugamushi during oogenesis and spermatogenesis in Leptotrombidium pallidum.

Rickettsia tsutsugamushi in Leptotromibidium pallidum was observed by electron microscopy and rickettsiae were found in the various tissues and organs of both larvae and adults. Budding of rickettsiae, a manner of release from the host cells, was observed only in the rudiments of the reproductive organs in larvae. Oogonia and maturing oocytes in adult females and eggs after oviposition contained the microorganisms. In adult males, rickettsiae were also found in the spermatogonia, spermatocytes, and spermatids in the early stage of spermatogenesis, but were eliminated from these cells during maturation. Only the maturing spermatids, but not the eliminated rickettsiae, migrated to another rickettsia-free area of the testis, resulting in the separation of spermatids from rickettsiae and in the production of rickettsia-free spermatophores. Based on these observations, the mechanism of vertical transmission of the rickettsiae to the progeny occurs only in the female parents. Most rickettsiae in the somatic cells of larvae and adults were coccoid, but some rickettsiae in the ovary and the testis of adult mites showed bacillary forms and were enveloped by a membrane of unknown origin.

How antenatal ultrasound diagnosis of congenital malformations has contributed to fetal outcome: a 22-year review.

We herein reviewed 630 malformed fetuses delivered from 24 weeks of gestation onwards in our institute over the past 22 years. These fetuses were divided into 2 groups: 210 from 1970 to 1982 (group 1) and 420 from 1983 to 1991 (group 2). Twenty-two varieties of congenital malformations were diagnosed antenatally in group 1, whereas 55 additional malformations became diagnosable in group 2. Thirty-four varieties of congenital malformations still remained undiagnosed throughout the 22-year study period. Cases receiving 'fetal therapy' and 'close obstetric care' increased, with statistical significance, from 1.8 to 15.7%, and from 22.9 to 55.7% in groups 1 and 2, respectively. A significant increase was also noted in the survival rate from group 1 (63.3%: 105/166) to group 2 (75.5%: 259/343). This study has revealed that the steady advancement in antenatal diagnosis of congenital malformations, along with great efforts in terms of intensive care, has contributed to improved fetal outcome.