Plasma monocyte chemoattractant protein-1 and pulmonary vascular resistance in chronic thromboembolic pulmonary hypertension

The pathogenesis of severe pulmonary hypertension seems to be related to inflammatory response in diseased sites. Monocyte chemoattractant protein-1 (MCP-1) has been reported to play a role in the development of congestive heart failure. In this immunological response, activation and migration of leukocytes including macrophages to the inflammatory region are important factors. We hypothesized that the severity of pulmonary hypertension may be related to MCP-1, which is thought to be upregulated by blood pressure or shear stress in pulmonary vasculature as well as by immunological and inflammatory reactions in chronic thromboembolic pulmonary hypertension (CTEPH). Circulating levels of MCP-1, interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha) were measured by sandwich ELISA in 14 patients with CTEPH. The plasma level of MCP-1 was significantly correlated with pulmonary vascular resistance. In IL-1beta and TNF-alpha, on the other hand, there was no correlation between cytokines and pulmonary hemodynamics. Pathological specimens obtained from the patients with CTEPH undergoing thromboendarterectomy demonstrated immunoreactivity of MCP-1 in endothelium, smooth muscle cells, and macrophages within neointima in the hypertensive large elastic pulmonary artery. We conclude that MCP-1 is upregulated in the remodeling of pulmonary arteries in close association with increased pulmonary vascular resistance in CTEPH.

Hippocampal synthesis of estrogens and androgens which are paracrine modulators of synaptic plasticity: synaptocrinology

Hippocampal pyramidal neurons and granule neurons of adult male rats are equipped with a complete machinery for the synthesis of pregnenolone, dehydroepiandrosterone, testosterone, dihydrotestosterone and 17beta-estradiol. Both estrogens and androgens are synthesized in male hippocampus. These brain steroids are synthesized by cytochrome P450s (P450scc, P45017alpha and P450arom), hydroxysteroid dehydrogenases and reductases from endogenous cholesterol. The expression levels of enzymes are as low as 1/300-1/1000 of those in endocrine organs. Synthesis is dependent on the acute Ca(2+) influx upon neuron-neuron communication via NMDA receptors. Estradiol is particularly important because estradiol rapidly modulates neuronal synaptic transmission such as long-term potentiation via synaptic estrogen receptors. Xenoestrogens may also act via estrogen-driven signaling pathways.

Evolutionary characteristics of influenza B virus since its first isolation in 1940: dynamic circulation of deletion and insertion mechanism

New antigenic variants of B/Yamagata/16/88-like lineage which appeared in the season of 1997 as a minor strain tended to predominate in the following season. Also, we could observe for the first time, three peaks of activity caused by H3N2 virus and two variants of B influenza virus. Antigenic and phylogenetic analyses revealed that B/Victoria/2/87-like variants appeared again in Japan in 1997 after a nine-year absence. Influenza B viruses evolved into three major lineages, including the earliest strain (I), B/Yamagata/16/88-like variants (II), which comprised of three sublineages (II-(i), II-(ii), II-(iii)), and B/Victoria/2/87-like variants (III). Evolution of influenza B virus hemagglutinin was apparently distinguishable from that of influenza A virus, showing a systematic mechanism of nucleotide deletion and insertion. This phenomenon was observed to be closely related to evolutionary pathways of I, II-(i), II-(ii), II-(iii) and III lineages. It was noteworthy to reveal that the nucleotide deletion and insertion mechanism of influenza B virus completed one cycle over a fifty-year period, and that a three nucleotide deletion was again observed in 1997 strains belonging to lineage II-(iii). It was evident that amino acid substitutions accompanying nucleotide insertions were highly conserved.

Low dose carvedilol inhibits progression of heart failure in rats with dilated cardiomyopathy

The cardioprotective properties of carvedilol (a vasodilating beta-adrenoceptor blocking agent) were studied in a rat model of dilated cardiomyopathy induced by autoimmune myocarditis. Twenty-eight days after immunization, surviving Lewis rats (32/43=74%) were divided into three groups to be given 2 mg kg(-1) day(-1) (Group-C2, n=10) or 20 mg kg(-1) day(-1) (Group-C20, n=10) of carvedilol, or vehicle (0.5% methylcellulose, Group-V, n=12). After oral administration for 2 months, body weight, heart weight (HW), heart rate (HR), rat alpha-atrial natriuretic peptide (r-ANP) in blood, central venous pressure (CVP), mean blood pressure (mean BP), peak left ventricular pressure (LVP), left ventricular end-diastolic pressure (LVEDP), +/-dP dt(-1) and area of myocardial fibrosis were measured. Values were compared with those for normal Lewis rats (Group-N, n=10). Two out of 12 (17%) rats in Group-V died from day 28 to day 42 after immunization. No rat died in Groups-C2, -C20 and -N. Although the CVP, mean BP, LVP and +/-dP dt(-1) did not differ among the three groups, the HW, HR and r-ANP in Group-C2 (1.14+/-0.03, 339+/-16 and 135+/-31) and Group-C20 (1.23+/-0.04, 305+/-8 and 156+/-24) were significantly lower than those in Group-V (1.36+/-0.04 g, 389+/-9 beats min(-1) and 375+/-31 pg ml(-1), respectively). The LVEDP in Group-C2 was significantly lower than that in Group-V (7.4+/-1.4 and 12.2+/-1.2 mmHg, respectively, P<0. 05). The area of myocardial fibrosis in Group-C2 was smaller than that in Group-V (12+/-1 and 31+/-2%, P<0.01). These results indicate that a low dose of carvedilol has beneficial effects on dilated cardiomyopathy.

Prediction of life expectancy in patients with primary pulmonary hypertension. A retrospective nationwide survey from 1980-1990

Primary pulmonary hypertension (PPH) is a progressive disease of unknown etiology usually followed by death within 5 years after diagnosis. Although heart-lung or lung transplantation is now offered to patients with advanced PPH, adequate criteria assessing an accurate prediction of life expectancy in PPH has been difficult to establish. The aims of this study were to identify the characteristic features associated with a poor prognosis in patients with PPH, and to attempt to establish an individual prognostic index that predicts with great accuracy survival or death of PPH after one year, thereby helping to define criteria for patient selection for transplantation. In 1991, a retrospective nation-wide survey on PPH was conducted in Japan, and the clinical and cardiorespiratory variables of 223 PPH cases (female; 144, male; 79) in the period from 1980-1990 were obtained. The mean pulmonary arterial pressure (PPA) was 57.5+/-17.2 mm Hg (mean+/-SD), and the overall median survival time was 32.5 months since the first diagnostic catheterization. The characteristic features of 61 patients who died within one year of catheterization (Nonsurvivors group) were compared to 141 patients who survived one year or more from the time of catheterization (Survivors group). Among several clinical and cardiorespiratory variables, heart rate, PPA, right atrial pressure (PRA), stroke volume index (SI), pulmonary vascular resistance, and partial pressure of carbon dioxide (PaCO2) were significantly different between the two groups. As the independent factors, PPA, PRA, SI, and PaCO2 were selected for the multiple logistic analysis. Using a 0.7 probability cut-point to separate Nonsurvivors from Survivors, 84.6% of Nonsurvivors and Survivors could be correctly predicted from this logistic regression equation. Predictive equations like the present preliminary one can be used in the future to better assess life expectancy in patients with PPH in whom transplantation will be considered.

The efficacy of pulmonary thromboendarterectomy on long-term gas exchange

It has not been delineated in detail how pulmonary thromboendarterectomy (PTE) affects gas exchange through long-term follow-up. In Japan, this surgery has been undertaken in a limited number of institutions, and the results of PTE have not been well publicized. A total of 25 patients were operated on during the period from 1985 to 1996 at our institution, and the overall mortality rate was 16%. Our criteria for PTE were based on the following: 1) thrombi surgically accessible as judged by angiographic study; 2) mean pulmonary arterial pressure > or = 30 mmHg. The efficacies of PTE were analysed on haemodynamics as well as gas exchange at one month postsurgery and during follow-up (6-24 months). Significant haemodynamic improvement was obtained as early as 1 month after surgery. Improvement of gas exchange lagged, but was then observed during follow-up, and the improvement level of pulmonary haemodynamics was sustained. The early postoperative restrictive impairment and ventilation-perfusion abnormality on lung perfusion scan resolved during the follow-up period. It was concluded that the early postoperative efficacy of pulmonary throm-boendarterectomy was mainly achieved due to the reduction of pulmonary hypertension, whereas improvement in gas exchange was obtained over the longer term.

Feasibility of combination chemotherapy with cisplatin and etoposide for haemodialysis patients with lung cancer

Cancer chemotherapy for haemodialysis patients has never been established. To elucidate the feasibility of cisplatin-based combination chemotherapy for haemodialysis patients with lung cancer, a dose escalation study was conducted. Five haemodialysis patients with lung cancer were treated with cisplatin and etoposide. A starting dose of 40 mg m(-2) of cisplatin on day 1 and 50 mg m(-2) of etoposide on days 1, 3 and 5 were administered as the first course for the first patient. Membrane haemodialysis was regularly performed three times a week and soon after the completion of therapy. By monitoring toxicity and pharmacokinetics data, the dose was escalated course by course and patient by patient. Dose escalation was completed for the first two patients resulting in full-dose chemotherapy consisting of 80 mg m(-2) of cisplatin on day 1 and 100 mg m(-2) of etoposide on days 1, 3 and 5. Multiple courses of the full-dose chemotherapy were administered to the other three patients. Toxicity was manageable and tolerable for all. Pharmacokinetics data were comparable to those from patients with normal renal function, except for potential long-lasting higher levels of free platinum in the renal insufficiency group. In conclusion, this standard-dose combination chemotherapy was feasible even for haemodialysis patients.

Myocardial CD36 expression and fatty acid accumulation in patients with type I and II CD36 deficiency

Long-chain fatty acids (LCFA) are one of the major cardiac energy substrates, so understanding LCFA metabolism may help in elucidating the mechanisms of various heart diseases. CD36 is a multifunctional membrane glycoprotein that acts not only as a receptor for thrombospondin, collagen and oxidized low density lipoprotein but also as a receptor for LCFA. We investigated the relationship between CD36 expression in myocardial capillary endothelial cells and myocardial LCFA uptake in patients with CD36 deficiency. We analyzed CD36 expression in blood cells from 250 patients with heart diseases by means of a flow cytometer. In 218 patients, myocardial LCFA scintigraphy was performed with 123I-beta-methyl-p-iodophenyl pentadecanoic acid (BMIPP). In 5 patients, myocardial capillary endothelial cells were examined immunohistochemically for CD36 expression. Eleven patients (4%) showed signs of type I CD36 deficiency (neither platelets nor monocytes expressed CD36). Twenty patients (8%) had type II CD36 deficiency (monocytes expressed CD36 but platelets did not). In all 11 patients with type I CD36 deficiency, no BMIPP accumulation was observed in the heart, but in 13 patients with type II CD36 deficiency, BMIPP accumulation in the heart was focally reduced, but there were no patients without BMIPP accumulation in the heart. Although the myocardial capillary endothelial cells from two CD36-positive patients expressed CD36, those from two patients with type I CD36 deficiency did not. In a patient with type II CD36 deficiency, some capillary endothelial cells displayed patchy CD36 expression. CD36 deficiency was documented in 31 (12%) patients with heart diseases. Because CD36 was not expressed in the myocardial capillary endothelial cells in patients with type I CD36 deficiency, type I CD36 deficiency is closely related to lack of myocardial LCFA accumulation and metabolism in the myocardium.

Association of clinical features with HLA in chronic pulmonary thromboembolism

The aetiology of chronic thromboembolic pulmonary hypertension (CTEPH) is largely unknown and may be heterogeneous, because there are several ethnic differences in the clinical characteristics of CTEPH. Female predominance and a higher ratio of chronic to acute pulmonary thromboembolism have been reported in Japan as compared with the USA. Because such ethnic differences may be controlled by genetic factors, the current study investigated HLA polymorphisms in Japanese patients with CTEPH. HLA typing by serological and/or DNA typing methods was performed (for HLA-A, B, DPB1, DRB1) in 80 patients and 678 controls, and the association of clinical characteristics with HLA alleles was studied. The frequencies of HLA-B*5201 (40 versus 24%) and DPB1*0202 (19 versus 6%) were significantly higher in the patients. HLA-B*5201 positive patients showed a significant female predominance. Total pulmonary vascular resistance and mixed venous oxygen tension were better in the HLA-B*5201 positive patients. In contrast, cardiac index and gas exchange parameters were worse in the HLA-DPB1*0202 positive patients. In the patients carrying HLA-B*5201 and/or -DPB1*0202, the frequency of deep vein thrombosis was significantly lower than the other patients. These observations suggested that both the susceptibility and clinical characteristics of chronic thromboembolic pulmonary hypertension were controlled in part by the HLA-B and -DPB1 loci.

Influenza vaccination levels and influenza-like illness in long-term-care facilities for elderly people in Niigata, Japan, during an influenza A (H3N2) epidemic

Surveys on influenza vaccination and illness in long-term-care facilities in Niigata Prefecture during an influenza A (H3N2) epidemic revealed that >20% of facilities had outbreaks and >10% of residents experienced influenza. Outbreaks and number of cases were significantly reduced by vaccination, which should be strongly recommended for institutionalized elderly people.

Comparison of gastroduodenal, renal and abdominal fat biopsies for diagnosing amyloidosis in rheumatoid arthritis

The aim of the study was to determine the frequency of amyloidosis detected by gastroduodenal biopsy in rheumatoid arthritis (RA) patients, and to investigate correlations between the results of gastroduodenal biopsy and abdominal fat and renal biopsies. A total of consecutive 1006 RA patients underwent gastroduodenal biopsy. The 71 patients who tested positive for gastrointestinal (GI) amyloidosis were asked to undergo renal and abdominal fat biopsies, and 21 did so. Renal biopsies were also performed on 12 patients with no amyloidosis but indicators of drug-induced renal damage, and abdominal fat biopsies were performed on 50 RA patients with no indication of amyloidosis. The prevalence of GI amyloidosis was 7.1%. Urinary abnormalities and GI symptoms were common in GI amyloidisis, and inflammatory markers were elevated. Sixty-one (86%) had either depressed creatinine clearance or urinary symptoms. Nineteen of the 21 patients (91%) with GI amyloidosis who underwent renal biopsies also had renal amyloid deposits. Eleven of the 21 (52%) had amyloidosis on abdominal fat biopsy. None of the 12 patients without GI amyloidosis had renal amyloidosis on renal biopsy, and none of the 50 patients without GI amyloidosis had amyloidosis on abdominal fat biopsy. Gastroduodenal biopsy reveals a high prevalence of amyloidosis in RA patients. Amyloidosis is often associated with signs of renal impairment. Results of GI biopsy are highly correlated with those of renal biopsy, but the results of fat biopsy are not. We recommend GI biopsy for RA patients for the screening of systemic amyloidosis.

Angiotensin II receptors in the rat urinary bladder smooth muscle: type 1 subtype receptors mediate contractile responses

Angiotensin II (Ang II) receptors in the rat urinary bladder smooth muscle were investigated by in vitro responses of smooth muscle strips to exogenous Ang II stimulation and in radioligand binding assays. Ang II (10(-10) M. to 10(-5) M.) caused a potent contractile response in a concentration-dependent manner. Using the recently developed nonpeptide subtype-selective antagonists, the Ang II-induced contractile response was further characterized. The Ang II-induced contractile response was inhibited weakly by the type 2 subtype (AT2)-selective antagonist PD123319 but was potently inhibited by the type 1 subtype (AT1)-selective antagonist DuP 753 with a pA2 value of 9.03, suggesting that the response is mediated predominantly by AT1 receptors. [125I]Ang II was used to specifically label a single class of binding sites with a dissociation constant of 0.31 nM. and a maximal binding capacity of 41.5 fmol./mg. of protein. DuP 753 could completely antagonize the binding of Ang II in a particulate fraction of rat bladder (Ki = 14 nM), whereas PD123319 did not have any effect in the concentration range of 10(-9) to 10(-5) M. The results suggest that AT1 receptors rather than AT2 receptors predominantly mediate Ang II-induced contraction in the rat urinary bladder.

Behaviour of bone marrow osteoblast-like cells on mineral trioxide aggregate: morphology and expression of type I collagen and bone-related protein mRNAs

AIM

To investigate the in vitro behaviour of rat bone marrow cells (RBM) on mineral trioxide aggregate (MTA) (ProRoot, MTA Root Canal Repair Material; Dentsply Tulsa, Tulsa, OK, USA) compared with intermediate restorative materials (IRM) (Dentsply Caulk, Milford, DE, USA).

METHODOLOGY

RBM were obtained from rat femur and were primary cultured and then subcultured. Cells were then seeded on three dishes of each material, and cultured for 3 days, after which they were evaluated morphologically using scanning (SEM) and transmission (TEM) electron microscopy. Furthermore, the calcium released from hydrated material, the cell proliferation ratio and alkaline phosphatase (ALP) activity were analysed, and the expression of type I collagen and bone-related protein mRNAs were evaluated. The data were averaged and analysed via one-way analysis of variance (anova) and were then compared by the Scheffe's test.

RESULTS

SEM showed that RBM attached to MTA and had a flattened appearance without nuclear protrusions and microspikes. TEM showed that the cells attached in the same manner as the control group, but gaps larger than 2 microm were frequently seen. The calcium released from hydrated MTA was about 130 ppm after 3 days of immersion in saline. The ALP activity was similar to the control group. Cell proliferation and expression of type I collagen mRNA was significantly lower, while the expression of osteopontin mRNA was significantly higher than the control group at the third day of culture. In IRM groups, a few rounded cells were observed on the material but no living cells were seen.

CONCLUSIONS

MTA is a material of low toxicity which does not inhibit cell growth, but does suppress the differentiation of osteoblast-like cells.

Medical decisions concerning the end of life: a discussion with Japanese physicians

OBJECTIVES

Life-sustaining treatment at the end of life gives rise to many ethical problems in Japan. Recent surveys of Japanese physicians suggested that they tend to treat terminally ill patients aggressively. We studied why Japanese physicians were reluctant to withhold or withdraw life-support from terminally ill patients and what affected their decisions.

DESIGN AND PARTICIPANTS

A qualitative study design was employed, using a focus group interview with seven physicians, to gain an in-depth understanding of attitudes and rationales in Japan regarding medical care at the end of life.

RESULTS

Analysis revealed that physicians and patients' family members usually make decisions about life-sustaining treatment, while the patients' wishes are unavailable or not taken into account. Both physicians and family members tend to consider withholding or withdrawing life-sustaining treatment as abandonment or even killing. The strongest reason to start cardiopulmonary resuscitation- and to continue it until patients' family members arrive-seems to be the family members' desire to be at the bedside at the time of death. All physicians participating in our study regarded advance directives that provide information as to patients' wishes about life-sustaining treatment desirable. All expressed concern, however, that it would be difficult to forego or discontinue life-support based on a patient's advance directive, particularly when the patient's family opposed the directive.

CONCLUSION

Our group interview suggested several possible barriers to death with dignity and the appropriate use of advance directives in Japan. Further qualitative and quantitative research in this regard is needed.

Ehlers-Danlos syndrome type IV with few extrathoracic findings: a newly recognized point mutation in the COL3A1 gene

Ehlers-Danlos syndrome type IV (EDS IV) is caused by mutation within the COL3AI gene, resulting in the disorder of type III procollagen. The diagnosis is confirmed by demonstrating the synthesis of abnormal type III procollagen molecules from cultured dermal fibroblasts or by identifying the mutation in the COL3A1 gene. The authors report a case of EDS IV caused by a novel point mutation in the COL3A1 gene in a 16-yr-old female. Recurrent haemoptysis and cavitary formation of the lung were evidence of pulmonary involvement. However, extrathoracic manifestations of EDS IV were mostly absent. To the best of the authors' knowledge, all previously reported Ehlers-Danlos syndrome IV patients with respiratory disease had the characteristic findings or histories of Ehlers-Danlos syndrome IV. In the present case, connective tissue friability was suspected due to tissue laceration observed in the biopsied lung specimen, and the diagnosis was made beginning from this pivotal finding.

Effect of electromyogram biofeedback on daytime clenching behavior in subjects with masticatory muscle pain

PURPOSE

Although daytime clenching is believed to be one of the oral parafunctions leading to dental problems, a treatment strategy has not yet been devised. Electromyogram (EMG) biofeedback training was performed to ascertain its effect on the regulation of daytime clenching behavior.

MATERIALS AND METHODS

Twenty subjects (mean age, 30.9±5.6 years) who had mild to moderate masticatory muscle pain with daytime clenching behavior were randomly divided into either a biofeedback group (BF) or control group (CO). Subjects were fitted with a hearing-aid-shaped EMG recording and biofeedback apparatus which was used to record EMG data under natural conditions from the temporal muscle, continuously for five hours on four consecutive days. EMG data on Days 1 and 4 were recorded without biofeedback as pre-test and post-test, respectively, and on Days 2 and 3, subjects in the BF group noticed their clenching behaviors via an alert sound from the EMG biofeedback apparatus. No alert sound was given for the CO group throughout the recording sessions.

RESULTS

There was no significant difference in the number of clenching events for five hours between the BF group (4.6±2.5) and CO group (4.6±0.9) on Day 1, however a significant decrease was found in the BF group between Day 1 (4.6±2.5) and Day 4 (2.4±1.7; P<0.05).

CONCLUSION

Daytime clenching was reduced in the short-term with the help of an EMG biofeedback system under natural circumstances. Further research is needed to confirm a long-lasting effect.

Advance directives and other medical decisions concerning the end of life in cancer patients in Japan

The purpose of our survey was to investigate the experience of physicians regarding advance directives and other medical decisions concerning the end of life. A postal questionnaire was sent to 500 Japanese physicians who were most involved in medical care of terminal patients. A total of 339 (68%) physicians responded. In dealing with terminal patients, approximately half gave priority to their patients' wishes for medical care, if known, regardless of the patient's competency. Of the respondents, 149 had been presented with advance directives by their patients and 35% followed all advance directives presented in their practice. Cardiopulmonary resuscitation (CPR) for arrested patients to enable their family to be at the bedside at the time of the death was common. More than 60% of the respondents thought that active euthanasia and assisted suicide were never ethically justified. Our study indicates that the wishes of patients are currently not always given top priority in medical decisions concerning the end of life.

Two new potent inhibitors of xanthine oxidase from leaves of Perilla frutescens Britton var. acuta Kudo

A known and a new caffeic ester (1 and 2), new inhibitors of xanthine oxidase (XO), were isolated from leaves of Perilla frutescens var. acuta and their structures have been established as (Z,E)-2-(3,4-dihydroxyphenyl)ethenyl ester (1) and (Z,E)-2-(3,5-dihydroxyphenyl)ethenyl ester (2) of 3-(3,4-dihydroxyphenyl)-2-propenoic acid, respectively, based on detailed spectral studies, including 2D COSY, long range COSY, difference NOE, etc. Both caffeic esters strongly inhibited XO in vitro and especially, the inhibition by 1 was as potent as that by allopurinol. The inhibition mode of 1 was also shown to be non-competitive.

Survey of Japanese physicians' attitudes towards the care of adult patients in persistent vegetative state

OBJECTIVES

Ethical issues have recently been raised regarding the appropriate care of patients in persistent vegetative state (PVS) in Japan. The purpose of our study is to study the attitudes and beliefs of Japanese physicians who have experience caring for patients in PVS.

DESIGN AND SETTING

A postal questionnaire was sent to all 317 representative members of the Japan Society of Apoplexy working at university hospitals or designated teaching hospitals by the Ministry of Health and Welfare. The questionnaire asked subjects what they would recommend for three hypothetical vignettes that varied with respect to a PVS patient's previous wishes and the wishes of the family.

RESULTS

The response rate was 65%. In the case of a PVS patient who had no previous expressed wishes and no family, 3% of the respondents would withdraw artificial nutrition and hydration (ANH) when the patient did not require any other life-sustaining treatments, 4% would discontinue ANH, and 30% would withhold antibiotics when the patient developed pneumonia. Significantly more respondents (17%) would withdraw ANH in the case of a PVS patient whose previous wishes and family agreed that all life support be discontinued. Most respondents thought that a patient's written advance directives would influence their decisions. Forty per cent of the respondents would want to have ANH stopped and 31% would not want antibiotics administered if they were in PVS.

CONCLUSIONS

Japanese physicians tend not to withdraw ANH from PVS patients. Patients' written advance directives, however, would affect their decisions.

Ca(2+)-dependent and -independent components of transmitter release at the frog neuromuscular junction

1. When a Ca2+ chelator, bis (O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), was loaded into the presynaptic nerve terminal of the frog neuromuscular junction (NMJ), facilitation, measured as an increase in endplate potential (EPP) amplitudes during a train of ten stimulations at 100 Hz, was greatly decreased within 20 min of BAPTA-AM (the acetoxymethyl ester of BAPTA) perfusion, and remained at a constant low level thereafter, suggesting that [Ca2+]i at the presynaptic nerve terminal was buffered by BAPTA. 2. Detailed examination of the two components of facilitation of EPP amplitude in the BAPTA-loaded NMJs showed that the fast component was lost almost completely, while the slow component was unaffected by loaded BAPTA. Augmentation and potentiation were also unaffected by BAPTA. 3. Under external Ca(2+)-free conditions (with 1 mM-EGTA), both augmentation and potentiation of miniature endplate potential (MEPP) frequency were clearly observed after tetanic stimulation in the normal NMJ, and were also unaffected by loaded BAPTA. 4. The above findings strongly support the residual Ca2+ hypothesis for the fast component of facilitation, and suggest that the three slower processes (the slow component of facilitation, augmentation and potentiation) occur independently of [Ca2+]i. This Ca2+ independence was supported by the fact that facilitation and potentiation have multiplicative effects on the amount of release. 5. The quantal content of the first EPP in the train remained unchanged throughout the time course of BAPTA loading for most NMJs. This suggests that [Ca2+]i immediately adjacent to Ca2+ channels at the active zone triggers transmitter release and is little affected by loaded BAPTA. 6. MEPP frequency was almost unchanged during BAPTA loading, suggesting that the basal [Ca2+]i remained unchanged close to the dissociation constant of BAPTA for Ca2+ (108 nM). 7. The slow component of facilitation had a multiplicative relationship with augmentation and potentiation, suggesting that the underlying mechanism for the slow component of facilitation differs from that for augmentation and potentiation.