Dopamine-induced protection of striatal neurons against kainate receptor-mediated glutamate cytotoxicity in vitro

The effects of dopamine on glutamate-induced cytotoxicity were examined using the primary cultures of rat striatal neurons. Cell viability was significantly reduced by exposure of cultures to glutamate or kainate for 24 h. In contrast, similar application of N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) did not induce cytotoxicity. Kainate-induced cytotoxicity was significantly inhibited by kynurenate but not by MK-801. Dopamine at concentrations of 1-100 microM dose-dependently reduced kainate-induced cytotoxicity. Forskolin also significantly reduced kainate cytotoxicity. The neuroprotective effect of dopamine was antagonized by SCH 23390, a D1 receptor antagonist, but not by domperidone, a D2 receptor antagonist. Moreover, kainate-induced cytotoxicity was prevented by SKF 38393, a D1 receptor agonist, or forskolin but not by quinpirole, a D2 receptor agonist. The patch clamp study revealed that the same striatal neurons responded to both kainate and NMDA. During voltage clamp recording, neither kainate-induced currents nor NMDA-induced currents were affected by dopamine. Moreover, dopamine did not affect glutamate- or kainate-induced Ca2+ influx measured with fura-2. These findings indicate that dopamine prevents kainate receptor-mediated cytotoxicity without affecting the kainate receptor activities and intracellular Ca2+ movement. Dopamine-induced neuroprotection may be mediated by an increased intracellular cAMP formed following activation of D1 receptors.

Inhibitory effects of 7-OH-DPAT, dopamine D3-receptor agonist, on nucleus accumbens neurons

Effects of 7-hydroxy-2-(N,N-di-n-propylamino)tetralin (7-OH-DPAT), a dopamine D3-receptor agonist, on neuronal activities of the nucleus accumbens (Acc) were examined in chloral hydrate-anesthetized rats. Spikes elicited by stimulation of the parafascicular nucleus were dose-dependently inhibited by microiontophoretic application of dopamine and 7-OH-DPAT. Glutamate-induced firing was also inhibited by these drugs. These findings suggest that D3 receptors are also involved in the postsynaptic inhibition of Acc neuron by dopamine.

[Early detection of breast cancer by mass screening using mammography]

A mass screening trial for breast cancer using mammography was carried out in Tokushima Prefecture, either itinerant screening in the communities or center screening at the workplace. Craniocaudal and lateral oblique imagings of the breast using two-view film mammography were performed at the first stage of screening. In addition, physical examination of the breast was also performed on subjects independently. A total of 8 cases with breast cancer were found in these trials by mammography alone, and no cases with breast cancer were detected by physical examination. The detection rates were 0.19% in itinerant screening, and 0.92% in center screening, respectively. This was much higher than the level (0.10%) obtained by mass screening using physical examination alone in Japan. Moreover, in elderly patients (age over 50 years), the detection rates were higher (0.54%, 1.21%). The number of clinical stage for cases with breast cancer detected by these screening were 5 cases in TIS and 3 in stage I. Thus, all cases were patients with early-stage breast cancer. From these results, mass screening using mammography should be mandatory for elderly women (over 50 years) with asymptomatic breasts.

p53 alteration correlates with negative ER, negative PgR, and high histologic grade in breast cancer

Seventy tumors of invasive ductal carcinoma of the breast were examined for p53 alteration by the RT-PCR-SSCP method. Sixty-five samples (92.9%) were investigated in the regions of codons 101-200 and 201-300. In total, 16 samples (24.6%) showed p53 gene alteration. We found that p53 gene alteration showed a correlation with (1) a negative ER status, (2) a negative PgR status, and (3) a high histologic grade (especially numerous mitotic figures) of the tumor. However, we found no correlation between p53 gene alteration and the lymph node status or clinical stage. Thus, p53 gene alteration in breast cancer may occur in highly malignant breast cancer other than advanced clinical stage cancer or node-positive cancer.

5-HT1A receptor-mediated inhibition of lateral vestibular nucleus neurons projecting to the abducens nucleus

Electrophysiological studies were performed using cats anesthetized with alpha-chloralose, to elucidate the 5-hydroxytryptamine (5-HT) receptor subtypes involved in the 5-HT-induced inhibition of the lateral vestibular nucleus (LVN) neurons projecting to or through the abducens nucleus. The effects of 5-HT receptor subtype agonists and antagonist were examined in polysynaptic neurons activated by stimulation of the ipsilateral abducens nucleus (IAN) antidromically, since these neurons are sensitive to 5-HT as shown in our previous study. Iontophoretic application of 5-HT and 8-hydroxy-2-(di-n-propylamino)tetrain (8-OH-DPAT), a selective 5-HT1A agonist, inhibited orthodromic spikes elicited by vestibular nerve stimulation in the majority of polysynaptic neurons activated by stimulation of ipsilateral IAN antidromically. There was a good correlation between the effects of 5-HT and 8-OH-DPAT. Iontophoretically applied 5-HT and 8-OH-DPAT also inhibited glutamate-induced firing in these neurons. Simultaneous application of 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine (NAN-190), a 5-HT1A agonist/antagonist, significantly antagonized the 8-OH-DPAT-induced inhibition of glutamate-induced firing, although NAN-190 alone also caused weak suppression of glutamate-induced firing. Microiontophoretically applied 1-(3-chlorophenyl)piperazine (mCPP), a 5-HT1B agonist inhibited the orthodromic spike elicited by vestibular nerve stimulation and glutamate-induced firing in only a small number of the LVN neurons. 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), a 5-HT2 agonist, rarely affected these neurons. We postulate that postsynaptically located 5-HT1A receptors are mainly involved in the 5-HT-induced inhibition of polysynaptic neurons projecting in the region of the IAN.

LTP of mossy fiber-stimulated potentials in CA3 during learning in rats

The study was done to determine whether long-term potentiation (LTP) of the potentials occurs at mossy fiber (MF)-CA3 synapses with the advance of learning in unrestrained and unanesthetized rats. The rats were divided into two groups, the test and control groups. The test group was given daily learning tasks in the radial arm maze, whereas the control group was similarly handled without learning tasks. Complete acquisition of learning was observed in the test group on day 5, and the learning was maintained over 3 days. Under freely moving conditions, a significant increase in population spikes (PS) elicited by MF stimulation with the progress in learning was observed in the test group, and the PS potentiation remained stable after day 4. Furthermore, on day 7, when MF stimulation-induced PS in the test group were compared with that in the control group in pentobarbital-anesthetized rats, the responses were comparatively higher in the former. As the training-induced PS potentiation in CA3 occurred with the advance of learning, these findings suggest that LTP in CA3 induced by learning may be related to memory storage.

Inhibition by topiramate of seizures in spontaneously epileptic rats and DBA/2 mice

The effects of topiramate, a novel antiepileptic drug, on tonic and absence-like seizures in spontaneously epileptic rats (SER; zi/zi, tm/tm) and on sound-induced seizures in DBA/2 mice were investigated. Topiramate (20 and 40 mg/kg i.p.) inhibited both tonic and absence-like seizures in a dose-dependent manner, whereas phenytoin (20 mg/kg i.p.) and zonisamide (40 mg/kg i.p.) inhibited only the tonic seizures. The inhibitory effects of topiramate on absence-like seizures were antagonized by pretreatment with haloperidol (0.5 mg/kg i.p.), but those on the tonic seizures remained unaffected. Topiramate inhibited sound-induced seizures in DBA/2 mice (ED50 = 8.6 mg/kg p.o.). These findings suggest that topiramate may be effective for treatment of both convulsive and absence seizures of human epilepsy. The inhibitory effect of topiramate on absence-like seizures in SER may be mediated through the central dopaminergic system.

Protective action of dopamine against glutamate neurotoxicity in the retina

PURPOSE

The electrophysiologic study using patch-clamp techniques demonstrated that NMDA-induced currents had properties similar to those recorded in the brain.

METHODS

Primary cultures obtained from the fetal rat retina (gestation days 16 to 19) were used for the experiment. Immunocytochemical and electrophysiologic studies were done to identify the cultured cells. The neurotoxic effects of glutamate or N-methyl-D-aspartate (NMDA) on the retinal cultures were quantitatively assessed using the trypan blue exclusion method.

RESULTS

The immunocytochemical study revealed that the major component of the rat retinal cultures was neurons including amacrine cells. The electrophysiologic study using patch-clamp techniques demonstrated that exposure to NMDA-induced currents with properties characteristic of those recorded in the brain. Brief exposure of these neurons to glutamate or NMDA induced delayed cell death. Glutamate neurotoxicity was prevented by the application of dopamine and forskolin. The protective action of dopamine was antagonized by a D1 receptor antagonist (SCH 23390) but not by D2 receptor antagonists (domperidone and sulpiride). A D1 receptor agonist (SKF 38393) protected glutamate-induced neurotoxicity in a concentration-dependent manner, whereas a D2 receptor agonist (quinpirole) did not affect it.

CONCLUSIONS

These findings demonstrate that dopamine protects retinal neuronal cells against NMDA receptor-mediated glutamate neurotoxicity via D1 receptors.

Excitation by talipexole, a dopamine D2 agonist, of caudate nucleus neurons activated by nigral stimulation

An electrophysiological study using cats anesthetized with alpha-chloralose was performed to elucidate whether or not talipexole (B-HT 920 CL2: 6-allyl-2-amino -5, 6, 7, 8-tetrahydro-4H-thiazolo [4, 5 -d] -azepine-dihydrochroride), a dopamine D2 agonist, acts on postsynaptic dopamine receptors in the caudate nucleus (CN) neurons receiving excitatory input from the pars compacta of substantia nigra (SN). Extracellular neuron activities were recorded in the CN using a glass-insulated silver wire microelectrode attached along a seven-barreled micropipette, each of which was filled with talipexole, quinpirole (dopamine D2 agonist), domperidone (dopamine D2 antagonist), glutamate and 2M NaCl. These drugs were microiontophoretically applied to the immediate vicinity of the target neuron. In the same neurons in which the spikes elicited by the SN stimulation were blocked by microiontophoretically applied domperidone, microiontophoretic application of talipexole and quinpirole induced a dose-dependent increase in spontaneous firing. This increase in firing by talipexole and quinpirole was blocked during simultaneous application of domperidone, although glutamate-induced firing remained unaffected by domperidone. In the CN neurons, in which the SN stimulation-induced spikes were not blocked by domperidone, spontaneous firing was not affected by talipexole or quinpirole. These findings suggest that talipexole activates CN neurons receiving a dopaminergic input from SN via D2 receptors, as does quinpirole.

Tumor progression accompanied by increase in proliferation rate in breast cancer: a preliminary report

Forty consecutive cases with invasive ductal carcinoma of the breast (samples of both the primary invasive area and the involved node were available for 19 cases, multiple sections of breast tissue including both the primary invasive area and forefront intraductal cancerous area were available for 15 cases; and multiple sections of breast cancerous tissue and the involved node were available for six cases) were examined by immunohistochemical analysis for evaluation of their proliferation rate. In this study, we selected the PCNA index as a marker of the proliferation rate of the tumor cells. We demonstrated that the PCNA index of the primary invasive area was significantly higher than that of the forefront intraductal area (P = 0.0017), and the PCNA index of the involved nodes was significantly higher than that of the primary invasive area (P = 0.0004). These preliminary findings suggest that the progression from the tumor cells of the intraductal cancerous area to the metastatic tumor cells must be accompanied by two phases of increase in the proliferation rate.

Release of sympathetic neurotransmitter evoked by electrical stimulation is increased in the chronically decentralized artery

The present study was performed to confirm our previous proposal that the increase in neurotransmitter release is responsible for the supersensitivity of chronically decentralized artery to transmural nerve stimulation (TNS) in the rabbit. The ear artery was decentralized unilaterally by removing the preganglionic fiber proximal to the superior cervical ganglion (SCG), and the ear arteries and SCG were dissected 8 weeks after the operation. The increase in the tritium overflow induced by TNS from the chronically decentralized artery, which had been incubated with 3H-noradrenaline (NA) for 1 hr, was markedly increased at lower frequencies (0.1 and 0.2 Hz) than that from the control artery, whereas there was no difference at higher frequencies (> 0.5 Hz). No difference was observed in the neuronal uptake of 3H-NA during incubation for 1 hr between the control and decentralized arteries. There was also no change in the contents of catecholamines in both the artery and SCG after chronic decentralization, when assayed by a radioenzymatic procedure. In conclusion, the results obtained indicate that the supersensitivity to TNS after chronic decentralization is not due to the deranged catecholamine uptake and storage mechanisms in adrenergic nerve terminals and augmented transmitter biosynthesis, but due to the increased release of transmitter in response to low frequencies of TNS.

Enhancement of D2 receptor agonist-induced inhibition by D1 receptor agonist in the ventral tegmental area

1. A microiontophoretic study was performed on chloral hydrate-anaesthetized rats to examine the role of D1 receptors in the ventral tegmental area (VTA) neurones, which are inhibited by autoreceptor and D2 receptor agonists. 2. Inhibition by microiontophoretic application of quinpirole (a D2 agonist) of antidromic spikes elicited by stimulation of the nucleus accumbens in dopaminergic neurones of the VTA, was significantly enhanced by simultaneous application of SKF 38393 (D1 agonist), although SKF 38393 alone had little effect on the neurones. 3. In addition, quinpirole-induced inhibition was antagonized by iontophoretic application of domperidone (D2 antagonist), but was not affected by SCH 23390 (D1 antagonist). 4. Furthermore, SKF 38393-induced enhancement of inhibition by quinpirole was antagonized by simultaneous application of SCH 23390. 5. These results suggest that activation of D1 receptors located on the VTA dopaminergic neurones or on non-dopaminergic nerve terminals is not essential for inducing inhibition of the dopaminergic neurones, but enhances D2 receptor-mediated inhibition directly or indirectly via inhibitory neurones.

Frequency of spontaneous p53 mutations (CpG site) in breast cancer in Japan

Sixty-five tumors of invasive ductal carcinoma of the breast were examined for p53 alteration by the reverse transcription-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) method and sequencing analysis. In total, 16 samples (24.6%) showed p53 gene alteration. Sixteen of these alterations were evaluated by sequencing analysis, and 15 showed missense point mutations while one showed a 9-base pair deletion. In the 15 point mutations, G:C to A:T transitions constituted the majority (53%), and five tumors (33%) had a transition at the CpG site, which are mutational patterns not commonly found in breast tumors from Europe and America. On the other hand, there were no G:C to T:A transversions in our cases, which were frequently observed transversions in Europe and America. These p53 mutation patterns in breast cancer in Japan are not similar to those in Europe and America reported by Hollstein et al. and Coles et al.. These findings suggest that there are some differences between mechanisms of breast cancer in Japan and in Europe and America.

A mechanism underlying dopamine D1 and D2 receptor-mediated inhibition of dopaminergic neurones in the ventral tegmental area in vitro

1. An intracellular recording study was performed to elucidate the mechanism underlying D1 and D2 receptor-mediated inhibition of neuronal activities of dopaminergic neurones in the ventral tegmental area (VTA) using slice preparations of the rat brain. 2. VTA neurones were classified into type I and type II neurones according to the shape of the action potential, which correspond to dopaminergic and non-dopaminergic neurones, respectively. 3. Addition of dopamine (10 microM) and quinpirole (1-100 microM) to the bath hyperpolarized the membrane of the type I neurones concomitantly with an increase in membrane conductance and an inhibition of action potentials which occurred spontaneously and were elicited by depolarizing pulses applied to the cell. However, quinpirole (10 microM) had no effect on the threshold for action potentials induced by a depolarizing pulse. 4. These quinpirole (10 microM)-induced effects were antagonized by simultaneous application of domperidone (5 microM), a D2 receptor antagonist. 5. The amplitude of quinpirole (10 microM)-induced hyperpolarization was decreased by increasing the potassium concentration in the perfusing fluid or simultaneous application of tetraethylammonium (10 microM). 6. SKF 38393 (10 or 100 microM), a D1 receptor agonist, had no effect on the resting membrane potential or action potential firing induced by a depolarizing pulse applied to the cell. However, when SKF 38393 (10 microM) was applied simultaneously with quinpirole (10 microM), the threshold for action potential generation was elevated by 5-6 mV, although there was no enhancement of hyperpolarization induced by quinpirole. 7. The elevation of the threshold for action potentials induced by SKF 38393 in the presence of quinpirole was antagonized by simultaneous application of SCH 23390 (5 microM), a D1 receptor antagonist.8. Dopamine (10 microM), quinpirole (10 or 100 microM) and SKF 38393 (10 or 100 microM) had no effect on the resting membrane potential or spontaneously occurring action potentials in type II neurones.9. These findings suggest that activation of dopamine D2 receptors of dopaminergic neurones in the VTA increases potassium conductance, thereby hyperpolarizing the membrane and eventually inhibiting neuronal activities. They also suggest that simultaneous activation of both D1 and D2 receptors enhances the D2 receptor-mediated inhibitory effects by elevation of the threshold for action potential generation.

Relatively immediate relaxant effects of cholera toxin on isolated rabbit blood vessels

A study was made on the relatively immediate relaxant effect of cholera toxin (CTX) on the isolated ear artery, thoracic aorta and saphenous vein of the rabbit. Both preparations of CTX, containing sodium azide (NaN3) and azide-free, showed no effect on the non-precontracted artery, but CTX containing NaN3 relaxed the moderately precontracted blood vessels with methoxamine promptly, i.e., with a time course of min order. However, the immediate relaxation produced by CTX containing NaN3 was attributed mainly to NaN3. Azide-free CTX, on the other hand, at 1-10 micrograms/ml gradually produced concentration-dependent relaxation of the precontracted vessels. The relaxant effects of CTX on the vessels were slow and long-lasting, i.e., with a time course of 10 min order. The relaxation induced by CTX was not influenced by the removal of endothelium nor by pretreatment with 10 microM indomethacin, 3 microM atropine or 3 microM propranolol. Activation of protein kinase C by a phorbol ester inhibited the relaxant effect of CTX. These results indicate that CTX relaxes the blood vessels by directly acting on the smooth muscles, without mediation by known endogenous relaxing factor, such as endothelium-derived relaxing factor (EDRF = NO) or prostaglandin I2 (prostacyclin) and by muscarinic receptor or beta-adrenoceptor.

The coexistence of lobular carcinoma in a fibroadenoma with a malignant phyllodes tumor in the opposite breast: report of a case

It is very unusual for a carcinoma of the breast to coexist with a phyllodes tumor, or for a carcinoma to arise within a fibroadenoma. We present herein an extremely rare case of lobular carcinoma in situ arising in a fibroadenoma, associated with a malignant phyllodes tumor in the opposite breast. A 49-year-old woman was admitted to our hospital with a large mass in the right breast and a small mass in the left breast. Microscopic examination of biopsy materials revealed a malignant phyllodes tumor in the right breast and a fibroadenoma in the left breast, for which a right standard radical mastectomy and left lumpectomy were performed. Microscopic findings of the material excised from the left breast showed the presence of multiple lobular carcinoma in situ within the tumor mass of the fibroadenoma. However, histological examination did not detect any metastasis to the bilateral axillary lymph nodes. To our knowledge this is the only such case ever to be reported in Japan.

Ifenprodil prevents glutamate cytotoxicity via polyamine modulatory sites of N-methyl-D-aspartate receptors in cultured cortical neurons

Neuroprotective effects of ifenprodil, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, against glutamate cytotoxicity were examined in cultured rat cortical neurons. The viability of the cultures was markedly reduced by a 10-min exposure to glutamate followed by incubation with glutamate-free medium for 60 min. Ifenprodil and its derivative SL 82.0715 dose-dependently prevented cell death induced by glutamate. The NMDA antagonists MK-801 and 3-[(+/-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid also prevented glutamate cytotoxicity with a potency similar to that of ifenprodil. Ifenprodil as well as MK-801 prevented NMDA-induced cytotoxicity, but did not affect kainate-induced cytotoxicity. Glutamate cytotoxicity was inhibited by removing extracellular Ca++ during and immediately after glutamate exposure. Ifenprodil and MK-801 reduced NMDA-induced Ca++ influx measured with rhod-2. Either spermidine, a polyamine modulatory site agonist, or glycine, a strychnine-insensitive glycine site agonist, potentiated NMDA- and glutamate-induced cytotoxicity. The protective effects of ifenprodil against NMDA- and glutamate-induced cytotoxicity were significantly reduced by spermidine, but not by glycine. These findings indicate that ifenprodil protects cortical neurons against glutamate cytotoxicity by selective antagonism of the polyamine modulatory site of the NMDA receptor complex.

Decreased dopamine and increased norepinephrine levels in the spontaneously epileptic rat, a double mutant rat

Dopamine (DA) and norepinephrine (NE) brain levels and turnover rate were examined in the spontaneously epileptic rat (SER: zi/zi, tm/tm), a double mutant rat obtained by mating tremor heterozygotes (tm/+) with zitter homozygotes associated with epileptic seizures composed of spontaneously occurring tonic convulsion and absence-like seizure. DA and NE levels were also determined in age-matched male zitter, tremor and Kyo: Wistar rats. DA levels in caudate nucleus were significantly lower in adult age (10-12 weeks) SER, which showed epileptic seizures, and zitter rats than in adult Kyo: Wistar and tremor rats. DA levels in other areas such as thalamus-hypothalamus, midbrain, and pons medulla were not different among SER, zitter, tremor, and Kyo: Wistar rats at age 10-12 weeks. Except in cerebral cortex and hippocampus, there were no differences in brain DA levels between young seizure-free SER (age 5 weeks) and young Kyo: Wistar rats. Furthermore, the turnover rate of DA was significantly lower in caudate nucleus of adult SER than of Kyo: Wistar rat, whereas in pons-medulla there was no difference between the two strains. In contrast, NE levels in the thalamus-hypothalamus, midbrain, cerebellum and pons-medulla were higher in SER and zitter rats at age 10-12 weeks than in age-matched tremor and Kyo: Wistar rats. Higher NE levels were also observed in midbrain, cerebellum, and pons-medulla of young SER as compared with young Kyo: Wistar rats. Turnover rates of NE were significantly lower in pons-medulla and cerebellum of the adult SER than in those of Kyo: Wistar rat.(ABSTRACT TRUNCATED AT 250 WORDS)

The dopamine D1 receptor agonist SKF 38393 suppresses detrusor hyperreflexia in the monkey with parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

A pharmacological study using monkeys, in which parkinsonism was induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), was undertaken to elucidate the mechanism underlying urinary bladder dysfunctions in Parkinson's disease. Under ketamine anesthesia, cystometrograms showed that, in MPTP-treated monkeys, a contraction of the urinary bladder was induced with smaller bladder volume than that in normal monkeys. In MPTP-treated monkeys, subcutaneously injected SKF 38393, a dopamine D1 receptor agonist, significantly increased the bladder volume and pressure thresholds for inducing the micturition reflex without affecting those in normal monkeys. In contrast, subcutaneous injections of quinpirole, a dopamine D2 receptor agonist, and apomorphine, a dopamine D1 and D2 receptor agonist, slightly, but significantly reduced the volume threshold of the bladder for the micturition reflex in both normal and MPTP-treated groups. These results indicate that, in parkinsonism, the degeneration of dopaminergic neurons in the substantia nigra leads to the detrusor hyperreflexia, probably due to a failure of activation of dopamine D1 receptors.

Blockade of retinal NMDA receptors by sodium nitroprusside is probably due to nitric oxide formation

Effects of a nitric oxide (NO)-producing agent, sodium nitroprusside, on N-methyl-D-aspartate (NMDA) receptor activation in the cultured retinal neurons of rats were examined. NMDA in a Mg(2+)-free medium evoked inward currents at the resting membrane potential. Inward currents were also evoked by kainate. Sodium nitroprusside markedly reduced the NMDA-induced currents without affecting those induced by kainate. These results suggest the possible existence of a negative feed back system of NO which serves to regulate the activation of NMDA receptors in retinal neurons.

Juvenile gigantomastia: report of a case

Juvenile gigantomastia in a 12-year-old girl was treated by a bilateral reduction mammoplasty with free transplantation of the areolae and nipples and the removal of 3,980 g of breast tissue. Regrowth of the residual breast tissue has been suppressed by the administration of tamoxifen, an antiestrogen drug, since the surgery. This case was positive for estrogen receptors (ER) by the dextran-coated charcoal method, while tissue staining for ER and estradiol resulted in a darker staining of the epithelial contents, especially of fibroadenoma-like nodules, using an immunocytochemical assay. It is thus suggested that the etiology of this disease might be related to a local hypersensitivity to estrogen.

The quality of mass screening for breast cancer by physical examination

Mass screening for breast cancer using physical examination alone has been carried out since 1983 in Zentsuji, Kagawa Prefecture, Japan. Over a 7-year period, breast cancer was detected in 11 of a total 8,271 examinees, the detection rate being high at 0.13%. The detected cases included a few early-staged breast cancers, suggesting that mass screenings are of slight efficacy. Seven cases of interval cancer were found by breast self-examination after the mass screenings, supporting the value of breast self-examination. A relatively large number of interval breast cancers was detected in 1985 and 1986, when the rates of required further examination remained under 1%. The sensitivity and specificity of this screening were 61.1% and 94.5%, respectively, indicating a low sensitivity. These results suggest that the qualitative diagnoses made from the first screening by physical examination alone were often revealed to be false negatives. Therefore, the existing diagnosis should be employed in the first screenings. It is recommended that mammography be introduced to detect breast tumors which are nonpalpable or undetectable by physical examination alone.

Effects of protein kinase C on the muscarinic excitation of rat adrenal chromaffin cells

The role of protein kinase C (PKC) in the muscarinic excitation of chromaffin cells freshly isolated from rat adrenal medullae was examined by the patch-clamp recording method. Acetylcholine and McN-A-343, a M1-receptor agonist, depolarized the cell and induced action potentials. Phorbol 12,13-dibutyrate (PDBu), an activator of PKC, increased acetylcholine-induced firing concomitant with a persistent depolarization. Under voltage-clamp recording, both McN-A-343 and PDBu decreased the cesium-sensitive K+ current, which was induced by shifting the membrane potential between -140 mV and -40 mV. These results suggested that the stimulation of muscarinic M1-receptors by cholinergic drugs activated phospholipase C to degrade phosphoinositide, consequently producing diacylglycerol, and diacylglycerol activates PKC to induce excitation of adrenal chromaffin cells.

Abnormal excitability of hippocampal CA3 pyramidal neurons of spontaneously epileptic rats (SER), a double mutant

The spontaneously epileptic rat (SER:zi/zi, tm/tm), a double mutant, shows both tonic convulsions and absence-like seizures characterized by low-voltage fast waves and by 5-7 Hz spike and wave-like complexes in the cerebral cortical and hippocampal EEG, respectively. Characteristics of hippocampal CA3 pyramidal neurons were examined to determine whether these neurons are abnormally excitable. When a single stimulus was given to the mossy fiber, there was repetitive firing and a depolarization shift in neurons of mature SER (over 12 weeks old), in which epileptic seizures had fully developed. However, in young SER (7-8 weeks old) and littermates (zi/zi, tm/+), which did not show any seizures, only a single spike was elicited with each single stimulation of the mossy fiber. Intracellular recording showed that the resting membrane potential was not significantly different among young and mature SER and littermates, but a long-lasting (100-200 ms) depolarizing shift accompanied by repetitive firing was observed following a single stimulation of the mossy fiber in half of the CA3 neurons of mature SER. Furthermore, the input impedance of the CA3 neurons in mature SER was lower than that in young SER and in littermates. These results indicate that SER hippocampal CA3 neurons become abnormally excitable in conjunction with the development of epileptic seizures.