Role of protein kinase C subtypes alpha and delta in the regulation of bradykinin-stimulated phosphoinositide breakdown in astrocytes

Cultured astrocytes express bradykinin (BK) receptors coupled to phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis. Short term (10- or 90-min) treatment of cells with 1 microM 12-O-tetradecanoylphorbol-13-acetate (TPA) decreased BK-induced PI breakdown, but this inhibitory action was lost after 3-hr TPA treatment. Extended (6- or 24-hr) pretreatment resulted in marked potentiation of the BK response. Western blot analysis using protein kinase C (PKC) isozyme-specific antibodies indicated that astrocytes express PKC-alpha, PKC-delta, and PKC-zeta. With TPA treatment of the cells for various times (10 min, 90 min, 3 hr, 6 hr, or 24 hr), translocation of PKC-alpha and PKC-delta from the cytosol to the membrane was seen after 10- or 90-min treatment and restoration to basal levels in the membrane fraction was seen after 3-hr treatment. However, partial or complete down-regulation of PKC-alpha and PKC-delta was seen after 6- or 24-hr treatment, respectively. No translocation or down-regulation of PKC-zeta was seen after either short term or long term TPA treatment. The inactive phorbol ester alpha-TPA had no effect on BK-induced PI hydrolysis or on the translocation or down-regulation of PKC-alpha and PKC-delta. These results suggest that, in unstimulated astrocytes, both PKC-alpha and PKC-delta, but not PKC-zeta, may exert tonic inhibition of BK-mediated PI turnover. After 10- or 90-min TPA treatment, AIF4(-)--but not Ca2+ ionophore-induced PI hydrolysis was inhibited, whereas [3H]BK binding was unaffected, indicating that the site of action of PKC-alpha and PKC-delta in the BK receptor/G protein/PLC pathway is after the receptor and before PLC, i.e., the G protein. After down-regulation of PKC-alpha and -delta, increases in both AIF4(-)-induced inositol phosphate formation and [3H]BK binding contributed to marked potentiation of BK-induced PI responses. Scatchard plot analysis showed an increase in both the maximal number of binding sites and the binding affinity. Both the up-regulation of [3H]BK binding and the subsequent BK-induced PI turnover were blocked by 0.5 microM cycloheximide, a protein synthesis inhibitor. The increase in AIF4(-)-induced PI hydrolysis after 24-hr TPA treatment was also inhibited by cycloheximide, indicating that new synthesis of BK receptors and G proteins was required after down-regulation of PKC-alpha and PKC-delta.(ABSTRACT TRUNCATED AT 400 WORDS)

Glomus tumors of the upper extremity: experience with twelve cases

BACKGROUND

The glomus tumor is an uncommon tumor of the hand, which presents with much pain. It is a benign neoplasm composed of a glomus body, which is located in the dermis. Glomus tumors present a classic clinical picture of pain, sensitivity to cold and local tenderness over the lesion.

METHODS

Twelve patients underwent surgical removal for glomus tumors of the upper extremity from 1983 to 1992. There were three males and nine females; their average age was 37 years (25 to 60 years). The clinical manifestations were pain and local tenderness in 12 patients, and cold intolerance in 6 patients.

RESULTS

There was a difference in gender in the anatomical site of the tumor. In three male patients, only one tumor was found in the digit. In female patients, all nine tumors were located in the digits. The average tumor size was 0.6 cm in diameter. After follow-up of 4.5 years (average), no recurrence, no residual pain or cold intolerance was noted.

CONCLUSIONS

The treatment of glomus tumor consisted of local excision or curettage, with or without reconstruction of the nail bed. Recurrence is not a problem after complete removal of the tumor tissue. Permanent nail deformity is still a problem. Efforts to prevent this sequelae are worth trying.

The study of pollen and Der p mite-specific IgE antibodies in children with allergic rhinitis

The role of pollens and house dust mites in perennial chronic rhinitis has been investigated for the Taipei area. Fifty-four serum specimens were collected from children with chronic rhinitis. EIA kits (Phadezyme RAST) were used to detect specific IgE antibody of nine allergens, including house dust mite (Der p) and eight common pollens. The children were divided into allergic (AR) and nonallergic (NAR) groups, based on the results of skin tests, inhalant allergen-specific IgE screen (Phadiatop), physical examination, past history and family history. The results showed: (1) 41 (76%) patients were defined as allergic rhinitis; (2) Der p specific IgE was detected in 41 (100%) AR patients and 7 (54%) NAR patients (P < 0.005), a strong positive reaction (> 2+) in 83% AR and none NAR patients (P < 0.005); (3) one, or more than one, pollen-specific IgE were found in 13 (32%) AR and 4 (31%) NAR patients. No strong positive reaction was detected in either group.

THE CONCLUSION

(1) three-fourths of the children with chronic rhinitis are allergic by nature; (2) house dust mite is the major allergen of allergic rhinitis; (3) in the Taipei area, pollen does not play an important role for children with allergic rhinitis.

Effects of Ganoderma lucidum and krestin on cellular immunocompetence in gamma-ray-irradiated mice

The effects of Ganoderma lucidum (Gl) and Krestin (PSK) extracts on cellular immunocompetence, leukocyte counts and differential count in gamma-irradiated mice were investigated in this study. ICR strain male mice were used and randomly divided into five groups. Group A is normal control. Group B, the experimental control, was treated with Gl. Group C, the radiation treatment control, was treated with whole body exposure to 4 Gy gamma-irradiation (RT). Group D was treated with RT and Gl. Group E was treated with RT and PSK. The dosage of Gl was 400 mg/day/kg body weight and PSK was 500 mg/day/kg body weight. After irradiation, six mice from each group were sacrificed on day 7 and the other six on day 28. Cellular immunocompetence was measured by means of 3H-thymidine incorporation with splenic cells stimulated through mitogens such as PHA, Con A and LPS. The results revealed that relative splenic weight in Groups D and E were higher than group C on day 28 after gamma-irradiation, Group D was the highest in all the experimental groups. Leukocyte counts were decreased significantly in Groups D and E on day 7, the former was a little higher than the latter. Gl administration showed an increase in the leukocyte count in Group D on day 28. The blastogenic response of splenocytes to PHA and Con A in groups D and E were higher than in Group C on days 7 and 28. We suggested that Gl and PSK were effective in enhancing the recovery of cellular immunocompetence from gamma-ray irradiation.

Effects of Ganoderma lucidum and krestin on subset T-cell in spleen of gamma-irradiated mice

Effects of Ganoderma lucidum (Gl) and Krestin (PSK) extracts on spleen, thymus and splenocytes in gamma-irradiated mice were investigated in this study. ICR strain male mice were divided into five groups. Group A was the normal control. Group B, the experimental control, was treated with Gl. Group C, the radiation treatment control, was treated with whole body exposure to 4 Gy gamma-irradiation (RT). Group D was treated with RT and Gl. Group E was treated with RT and PSK. The dosage of Gl was 400 mg/day/kg body weight and PSK was 500 mg/day/kg body weight. Our results indicated that the relative thymus weight in groups D and E were higher than group C on day 28 after gamma-irradiation. Group D was the highest in all the experimental groups. CD4 and CD8 splenocytes in group D were higher than group C on days 7 and 28. Gl was better than PSK in repairing the damage of subset T-cells in the spleen of gamma-irradiated mice.

The role of C-reactive protein and erythrocyte sedimentation rate in the diagnosis of infected hydronephrosis and pyonephrosis

Serum C-reactive protein levels and erythrocyte sedimentation rates were prospectively evaluated in 38 patients with dilated pyelocaliceal systems in an attempt to distinguish simple hydronephrosis from infected hydronephrosis and pyonephrosis. The clinical presentations of infected hydronephrosis and pyonephrosis were extremely variable, ranging from no constitutional complaints to urosepsis. Renal sonography detected only 6 of 16 patients with pyonephrosis (specificity 96%, sensitivity 38%, accuracy 72.5%). Using a cutoff value of 3.0 mg./dl. for C-reactive protein and 100 mm. per hour for erythrocyte sedimentation rate, the diagnostic accuracy of detecting infected hydronephrosis and pyonephrosis increased to 97%, with a specificity of 89% and sensitivity of 100%. Based on our experience, we believe that the serum C-reactive protein and erythrocyte sedimentation rate levels can be used as screening tests to distinguish pyonephrosis and infected hydronephrosis from simple, uncomplicated hydronephrosis.

Percutaneous nephroscopy in the diagnosis of renal pelvic filling defect: a report of two cases

The major differential diagnosis of a radiolucent filling defect within the renal pelvis is among tumor, blood clot and radiolucent stone. In some cases, it is difficult to distinguish tumor from other benign lesions by imaging study. Two patients with renal pelvic filling defect were diagnosed by percutaneous nephroscopy, using the 27 Fr. rigid nephroscope (Olympus, Tokyo, Japan). Both patients got conclusive diagnosis by percutaneous nephroscopy; the morbidity was extremely minimal. The diagnostic percutaneous nephroscopy was a safe and effective procedure with minimal morbidity. For those patients without a conclusive diagnosis in noninvasive procedures, the percutaneous nephroscopy could be an alternative for flexible ureteroscopy, especially for the extremely tortuous ureters.

Comparison of radiotherapy and surgical results of early stage glottic cancer: a retrospective analysis

From March 1977 to October 1989, 85 patients with early stage glottic cancer were treated with either radiotherapy or surgery at Chang Gung Memorial Hospital (CGMH). Patients were excluded from the analysis of local control if they died or remained disease-free with a follow-up period of less than two years. Of the 26 patients treated with definitive radiotherapy, initial control of the primary lesions was achieved in 100% of stage T1s, 76% of T1, and 57% of T2 patients. Surgical salvage of radiation failure was achieved in 83% of the patients, giving the ultimate local control of 100% for T1s, 94% for T1, 86% for T2 patients. Of the 44 patients treated with definitive surgery, initial control of the primary lesions was achieved in 100% for T1s, 95% for T1, and 78% for T2 patients. Salvage of the surgical failure was 50%, giving the ultimate control in this group of 100% for T1s, 95% for T1, 83% for T2. There was no difference in either initial or ultimate control of T1 and T2 lesions between patients treated with primary radiotherapy and primary surgery. Voice preservation rates were 73% and 34% in the radiotherapy and surgery group, respectively. When divided into two groups according to the times they were being treated, we found that surgery preserved a comparable number of larynges as radiotherapy did after 1988 (60% vs 77%, p = 0.33). It is concluded that radiotherapy and surgery could achieve the same good local control results and long-term survival and comparable functional results of early stage glottic cancer, if conservative surgery is carefully selected for each patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Experience using extracorporeal shock-wave lithotripsy to treat urinary calculi in problem kidneys

Seventeen patients with urolithiasis in problem kidneys which comprised horseshoe kidneys, medullary sponge kidneys (MSKs), polycystic kidneys and duplex kidneys presented to our hospital and were evaluated for treatment with extracorporeal shock-wave lithotripsy (ESWL). A total of 21 renal units were treated with ESWL. Auxiliary procedures included preoperative retrograde ureteral catheterization (1 horseshoe kidney) placement of a retrograde double-J catheter stent (1 MSK), percutaneous nephrolithotomy (PCNL; 2 MSKs) and postoperative PCNL (1 MSK). The outcome showed that 5 renal units (23.8%) were stone free, 15 renal units (71.4%) had a decreased stone load with residual stone and improved symptoms, and 1 renal unit (4.8%) had residual stone with persistent symptoms. We conclude that ESWL can be used as a primary management tool for calculi in problem kidneys.

[Improving the curative effect of chemotherapy on gynecological malignant tumor by catheterization of internal iliac artery]

Seventeen cases of gynecological malignant tumor received 27 infusion chemotherapy by selective catheterization via internal iliac artery. Among them, 14 cases (82.4%) were cancer of advanced stage. All of the cases were followed up. 77.8% of cases showed short-term good response. The intermittent mean duration without tumor growth was 12.5 months. The determination of platinum confirmed that the vascular embolism chemotherapy of tumor is one of the best approaches for pelvic tumors.

Study on the concentrations of cerebrospinal fluid immunoglobulin G and albumin in children

Concentrations of immunoglobulin G (IgG) and albumin in cerebrospinal fluid (CSF) and serum were measured in 118 "normal" Chinese children from birth to 15 years old to obtain the reference values for the evaluation of the blood-brain barrier (BBB) function. The values of the CSF/serum IgG ratio, CSF/serum albumin ratio and IgG index (IgG ratio/albumin ratio) were then calculated for each subject. A relation was found between the content of IgG in CSF and serum depending on age. The gradual decrease of CSF IgG and IgG ratio during the first 6 months indicated a postnatal impediment of the diffusion of IgG from the blood to the CSF. In the meanwhile the CSF/serum albumin ratio continued to drop until the age of one year. The slower slope of the decrement of the latter ratio further demonstrated the differential permeability of the BBB in favor of the shift of small molecular protein. The change of the protein permeability within the first year of life shows a characteristic of the maturational process of the BBB. Nevertheless, IgG index has no age-dependent variation throughout the childhood period. It remains constant in the absence of inflammation within the central nervous system.

Congenital bronchoesophageal fistula in the adult: a case report

The case of a 50-year-old woman with congenital bronchoesophageal fistula is presented. The patient had symptoms of hemoptysis provoked by ingestion of liquids for 2 years. A barium swallow examination showed a bronchoesophageal fistula communicating between the middle third of the esophagus and right intermediate bronchus. An orifice of the fistula at the esophagus was revealed by esophagoscopy. The clinical and operative features and diagnosis of congenital origin are discussed.

Diagnostic value of cerebrospinal fluid immunoglobulin G (IgG) in pediatric neurological diseases

A total of 71 cerebrospinal fluid (CSF) specimens with paired serum samples from 16 controls and 55 patients with various neurologic diseases ranging in age from 1 to 15 years old were studied using a rate nephelometer to measure their immunoglobulin G (IgG) and albumin levels in both their CSF and serum. The patients included 15 cases of encephalitis, 6 cases of purulent meningitis, 20 cases of aseptic meningitis, 2 cases of multiple sclerosis and 12 cases of other noninflammatory neurologic diseases. The values of the CSF IgG quotient, IgG index, and de novo central nervous system (CNS) IgG synthesis were then calculated for each subject. In the control group, the mean values were as follows: CSF IgG, 1.45 mg/dl; IgG quotient, 6.2%; IgG index, 0.55; and de novo IgG synthesis, -1.17 mg/day. Those with CNS inflammatory diseases had significantly higher CSF IgG levels and IgG quotients compared with controls (p less than 0.05). The IgG index was selectively elevated in cases of encephalitis (p less than 0.005). The values for de novo IgG synthesis showed significant increase in all types of CNS inflammatory diseases except for the group with aseptic meningitis. In the noninflammatory diseases, none of the CSF parameters revealed any significant differences from those of the control group. Six cases (40%) of encephalitis showed normal CSF protein value, but an abnormal IgG component, IgG index and de novo IgG synthesis. Quantitation of IgG and other derivatives in CSF gives a sensitive supplementary reference for the detection of CNS infection.

Stress fracture of the diaphysis of the ulna

Stress fracture of the diaphysis of the ulna is rare and only 6 cases were found in a literature review. We present a further case occurring in a weightlifter.

Cell-cell contacts mediated by E-cadherin (uvomorulin) restrict invasive behavior of L-cells

L-cells were cotransfected with plasmids coding for mouse E-cadherin (uvomorulin) and the neophosphotransferase gene, and stable transfectants expressing E-cadherin at the cell surface were selected and cloned. Control transfection was done with the neophosphotransferase gene alone. The invasive migration of transfected and untransfected L-cells into three-dimensional collagen gels was then analyzed. L-cells not expressing E-cadherin migrated efficiently into the gels, whereas invasion of the E-cadherin-expressing L-cells was restricted in a cell density dependent manner. At sparse density, when the cells exhibited little cell-cell contacts, no difference was observed between the level of invasion of the cadherin-expressing cells and the control cells. However, with increasing cell density, decreasing amounts of the cadherin-expressing cells but increasing amounts of the control cells migrated into the gels. At confluent density hardly any cadherin-expressing cells were able to migrate into the gels. The inhibition of the invasion of the cadherin-expressing cells could be reverted if confluent cells were cultured in the presence of monoclonal antibodies against E-cadherin. Since the expression of E-cadherin did not influence the invasive mobility of single cells, these results indicate that E-cadherin-mediated cell-cell contacts inhibited invasive cellular migration. Time-lapse videoscopy and studies of cell migration from a monolayer into a cell-free area demonstrated that the restricted invasion could be explained by contact inhibition of cell movement of the cadherin-expressing cells.

[Scavenging of probimane on semiquinone free radical formation by doxorubicin in rat heart]

Probimane, dl-bis (4-morpholin-methyl 3,5-dioxopipweazin-1-yl) propane first synthesized in China, is a dioxopiperazin compound with antineoplastic, antimetastatic and radiopotentiating activities. In order to evaluate the mechanisms of cardiotoxicity protective action of probimane, the free radical induced by doxorubicin were analysed by electron spin resonance (ESR) techniques. Our studies showed that doxorubicin stimulated the formation of semiquinone free radicals in the rat heart homogenate and heart cell mitochondria systems, and probimane inhibited the free radical formation in both systems, with the dose-dependent and time-dependent responses. The inhibitory rates of doxorubicin free radical formation in rat heart homogenate system by probimane 0.6 mmol.L-1 at time of 3, 5, 10, 15, 30, 45 and 60 min were 44.6%, 43.0%, 51.5%, 74.3%, 68.1%, 56.1% and 39.9% respectively. The inhibitory rates of semiquinone free radical formation in mitochondria system by probimane at the concentration of 0.02, 0.06, 0.6, 1.2 and 2.4 mmol.L-1 were 17.07%, 29.87%, 63.95%, 64.62% and 83.64%, respectively. Probimane had no effect on NADH2, but inhibited NADH dehydrogenase activity at higher concentration.

Factors influencing radiation exposure during the extracorporeal shock wave lithotripsy

A prospective evaluation of 89 consecutive sessions of extracorporeal shock wave lithotripsy (ESWL) was undertaken to try and find the best way of minimising the amount of exposure to radiation. Forty-two patients were randomly allocated to undergo ESWL treatment by experienced surgeons (group A), and 47 to undergo the treatment by inexperienced surgeons (group B). The mean calculated entrance radiation exposure was 3.01 rads (group A: 2.64 (0.97) rads, range 1.00-4.48, group B: 3.38 (0.86) rads, range 1.11-5.75). Among factors that influenced radiation exposure, the tissue: air ratio should be borne in mind and the level of skill in controlling movement of gantry was the most important in reducing the exposure to radiation.

Retroperitoneal abscesses

Abscesses developing within the retroperitoneal spaces are complicated serious surgical infections marked by an insidious, occult process lead to considerable mortality and morbidity. In a retrospective review of 39 retroperitoneal abscesses in our hospital. Attention is directed to clinical presentation, diagnosis and treatment. On average, 19.2 days was required to establish the diagnosis and overall mortality is 7.7%. Two patients suffered from complications of discharged sinus and recurrent abscess respectively. Computed tomography (CT) is thought to be the best diagnostic modality of retroperitoneal abscesses. Only 2 patients (5.3%) shows bilateral lesions. Detailed anatomic reviews detailing the pathogenesis of bilateral retroperitoneal abscess are also discussed.

Pulmonary infarction presenting as aseptic cavitation

A case of pulmonary infarction presenting as aseptic cavitation was reported. Basically, the patient suffered from rheumatic heart disease, mitral stenosis and insufficiency, and atrial fibrillation with predominant right heart enlargement. Hemoptysis, chest pain and dyspnea were present. Chest film simulated a thin wall lung abscess. The clinical picture suggested aseptic cavitation, which was confirmed by 99mTc-MAA lung scan.

Massive pulmonary hemorrhage in polyarteritis nodosa (PN); report of a case

We report a case of massive pulmonary hemorrhage which emerged in the course of polyarteritis nodosa (PN). Pulmonary hemorrhage was the major manifestation which determined the mortality of this patient, though severe renal failure concurrently developed. The diagnosis of PN should be considered in all cases of pulmonary hemorrhage coexisting with renal failure. As pulmonary hemorrhage can be life-threatening, early diagnosis is essential for the prompt start of adequate therapy.

Polycystic kidney of autosomal dominant inheritance, polycystic liver and congenital hepatic fibrosis in a single kindred

A family with clear evidence of concomitant congenital hepatic fibrosis, polycystic liver and adult-type polycystic kidney is reported. The autosomal dominant inheritance of polycystic kidney in association with either liver cyst or hepatic fibrosis in this family suggests that various combinations of hepatic and renal fibrocystic lesions are possible to occur. Additionally, in the proband a very rare association of congenital hepatic fibrosis and cerebral aneurysm was present.

Complete atrioventricular block, retrograde atrial activation and intra-atrial block

A case of complete atrioventricular block, retrograde atrial activation, and intra-atrial block was reported. Inhomogeneous inhibition of the atrioventricular junction and the so-called summation of impulses may both act together to make retrograde conduction possible when third-degree atrioventricular block was present. In lead 2, P waves were dome-shaped, and in lead V1, P waves were biphasic; narrow and peaked P waves intermittently appeared, denoting third-degree intra-atrial block. The peaked P waves signified that the right atrium was activated while the left atrium was not depolarized.

Atrial tachycardia, 2:1 alternate Wenckebach periodicity, and atrial standstill

A case of atrial tachycardia, 2:1 alternate Wenckebach periodicity and atrial standstill is reported in an 80-year-old woman who complained of exertional dyspnea and occasional syncope for two years. Two blocked P' waves appeared after each Wenckebach period suggesting type B alternating Wenckebach phenomenon (Mobitz type II 2:1 A-V block distal, and Wenckebach conduction proximal).

Computed tomography of a meniscal cyst

A meniscal cyst of the knee is a rare lesion, and a palpable large meniscal cyst is even more rare. This article suggests that CT scan demonstrates clear location, size, contents, and connection of the cyst with meniscus and peripheral tissue. By a combination of arthrography and CT scan, detection of the cysts in zone 3 (parameniscal area) is possible with ample demonstration of whether the cyst is associated with a meniscal tear. This provides a guideline in determining the treatment of the lesion.

1,25-Dihydroxyvitamin D3-mediated inhibition of human B cell differentiation

We have examined the mechanisms of 1,25-dihydroxyvitamin D3 (D3)-mediated inhibition of human B cell differentiation to immunoglobulin (Ig) secreting cells. B lymphocytes were purified from human tonsils and peripheral blood mononuclear cells. Mononuclear cells were separated into adherent cells and nonadherent cells. Cells were stimulated with Staphylococcus aureus Cowen I (SAC) or pokeweed mitogen (PWM) for 7 days and immunoglobulin production was measured by ELISA assay, 1,25-dihydroxyvitamin D3 was added at different times during cultures. 1,25-Dihydroxyvitamin D3, in a dose-dependent manner, inhibited both SAC and PWM-induced Ig production by mononuclear cells. The maximum inhibition was observed when 1,25-dihydroxyvitamin D3 was added at the beginning of culture, but inhibition could still be observed when 1,25-dihydroxyvitamin D3 was added on day 4 of cultures. The inhibitory effect of 1,25-dihydroxyvitamin D3 on Ig production was significantly greater on mononuclear cells than on nonadherent cells. Addition of in vitro purified IL-1 to nonadherent cells enhanced 1,25-dihydroxyvitamin D3-induced inhibition of Ig production. 1,25-Dihydroxyvitamin D3 also inhibited the expression of IL-2 receptors on B cells activated with SAC. 1,25-dihydroxyvitamin D3 did not inhibit Ig production by SAC preactivated B cell blasts in response to T cell supernatants. These data suggest that vitamin D3 inhibits Ig production by inhibiting IL-2 receptor expression on B cells and via its effect on adherent macrophages. Vitamin D3 does not influence the effect of differentiation factors on activated B cells that have already expressed growth/differentiation factor receptors.

Application of a new spatial signal averaging device for the beat-to-beat detection of cardiac late potentials

A new high resolution digital signal averaging device was developed to record precordial late potentials. The subjects examined included 8 normals (including medical patients with normal cardiovascular status), and 21 patients with coronary artery disease (CAD) and myocarditis of probable viral origin. Late potentials were evident in 11 cases (CAD 8 cases and myocarditis in 3 cases). In 10 patients, multiple ventricular premature beats and in 3 others, attacks of ventricular tachycardia had been present. Sudden cardiac death occurred later in one patient. It was concluded that late potentials as recorded by this simple new device are predictive of ventricular arrhythmias--sometimes life threatening. As no triggering is necessary, both conventional and beat-to-beat signal averaging can be carried out and the presence of various arrhythmias is negligible.

The kinetics of dissolution of tooth enamel--a constant composition study

The kinetics of dissolution of powdered bovine enamel and of human enamel, both untreated and extracted with either hypochlorite or chloroform, has been studied using a constant solution composition technique in undersaturated solutions of calcium phosphate (total molar calcium concentration, TCa = 0.3 to 13.1 X 10(-3) mol L-1, total molar phosphate, Tp = 0.18 to 7.9 X 10(-3) mol L-1) at an ionic strength of 0.15 mol L-1, and pH = 4.5. The kinetic equations describing the dissolution reactions suggest a surface dislocation mechanism, and the presence of fluoride ion markedly retarded the reaction. For human enamel, a fluoride level of only 0.5 ppm reduced the rate of dissolution ten-fold. In contrast, the dissolution of hydroxyapatite, HAP, is best interpreted in terms of a polynucleation process.

Clinical significance of bifid T waves

An attempt was made to analyze bifid T waves which appeared in different clinical conditions. Bifid T waves occurred in 16% of 600 normal children, 92% of 37 cases of childhood ventricular septal defect (VSD), 6 of 10 cases of tetralogy of Fallot (children) and 33% of 193 patients with cerebrovascular accidents (including 3 children). Sixteen cases of bifid T waves which appeared after amiodarone treatment were also analyzed. It was thought that in normal children, bifid T waves might be due to right ventricular preponderance. In VSD, the bifid T waves assumed a peculiar "dome and dart" appearance. In cerebrovascular accidents, autonomic imbalance might be at fault. In cases of treatment with adriamycin, myocardial toxicity is the most probable cause. The conclusion was made that bifid T waves can appear in different clinical settings, which must be considered individually.