Role of differentially expressed LBX1 in Adolescent Idiopathic Scoliosis (AIS) paraspinal muscle phenotypes and muscle-bone crosstalk through modulating myoblasts

AIS is three-dimensional spinal deformity with unclear etiopathogenesis. LBX1 is so far the only multi-centers validated AIS predisposing gene. The imbalance of posterior paraspinal muscles is an important factor in AIS etiopathogenesis. It is poorly understood how LBX1 contributes to the abnormal paraspinal muscles and onset/progression of AIS. We aimed to evaluate the expression of LBX1 in paraspinal muscles at the concave and convex side in AIS, and whether alternation of LBX1 expression could affect myoblastsactivities and potentially influence muscle-bone interaction via myokines expression. Paraspinal muscles from AIS and age- and curvature-matched congenital scoliosis (CS) patients were collected for fiber types analysis. Biopsies were also subjected to qPCR to validate expression of myogenic markers, selected myokines and LBX1. Human skeletal muscle myoblast (HSMM) was used for LBX1 loss-of-function study in vitro. Muscle fiber types analysis showed type I and type IIX/IIAX fibers proportion were significantly different between AIS concave and convex but not in two sides of CS. LBX1, myogenic markers and one myokine were significantly imbalanced in AIS but not in CS. Loss-of-function study showed knockdown of LBX1 could inhibit myogenic markers expression and myokines as well. This study provides new insight into the association between imbalanced paraspinal muscle and potential muscle-bone crosstalk in AIS patients and the biological function of predisposing gene LBX1. Further investigation with appropriate animal models is warranted to explore if asymmetric expression of LBX1 could result in distinct muscle phenotypes and bone qualities thus affect the progression of spine curvature in AIS.

Detection of Local Recurrence in Patients with Head and Neck Squamous Cell Carcinoma Using Voxel-Based Color Maps of Initial and Final Area under the Curve Values Derived from DCE-MRI

BACKGROUND AND PURPOSE

Early detection of local recurrence is important to increase the chance of cure because local recurrence is the main cause of treatment failure in head and neck squamous cell carcinoma. We evaluated the added value of voxel-based color maps of dynamic contrast-enhanced MR imaging compared with conventional MR imaging alone for detecting local recurrence of head and neck squamous cell carcinoma.

MATERIALS AND METHODS

We retrospectively enrolled 63 consecutive patients with head and neck squamous cell carcinoma after definitive treatment and posttreatment surveillance MR imaging studies that demonstrated focal enhancement at the primary site. Three independent readers assessed conventional MR imaging and a pair of color maps of initial and final 90-second time-signal intensity areas under the curve from dynamic contrast-enhanced MR imaging. The sensitivities, specificities, and accuracies of both conventional MR imaging alone and combined interpretation of conventional and dynamic contrast-enhanced MR imaging were assessed using the clinicopathologic diagnosis as the criterion standard. κ statistics were used to evaluate interreader agreement.

RESULTS

There were 28 patients with subsequently documented local recurrence and 35 with posttreatment change. Adding dynamic contrast-enhanced MR imaging to conventional MR imaging significantly increased the diagnostic accuracies for detecting local recurrence (48%-54% versus 87%-91%; P < .05), with excellent interreader agreement (κ = 0.8; 95% CI, 0.67-0.92 to κ = 0.81; 95% CI, 0.69-0.93). By all 3 readers, the specificities were also significantly improved by adding dynamic contrast-enhanced MR imaging to conventional MR imaging (22%-43% versus 87%-91%; P < .001) without sacrificing the sensitivities (68%-82% versus 86%-89%; P > .05).

CONCLUSIONS

Adding voxel-based color maps of initial and final 90-second time-signal intensity areas under the curve from dynamic contrast-enhanced MR imaging to conventional MR imaging increases the diagnostic accuracy to detect local recurrence in head and neck squamous cell carcinoma by improving the specificity without sacrificing the sensitivity.

Intratumoral Polymorphism of Peroxisome Proliferator-Activated Receptor Delta-87 T>C in Colorectal Cancer

Peroxisome proliferator activated receptor delta (PPARD) is a nuclear receptor transcription factor whose single nucleotide polymorphism (SNP), especially PPARD-87 T>C (rs2016520), may play an important role in expression regulation of PPARD. But its expression patterns as well as contribution in colorectal cancer (CRC) are still controversial. In this study, whether the intratumoral heterogeneity of polymorphism of PPARD-87 T>C (rs2016520) existed and its influence in CRC were investigated. Tumor masses from primary CRC patients were collected during the operation of tumorectomy, specimens at the different sites of the same tumor mass were sampled and stored individually. The SNP of PPARD-87 T>C was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and the expression of PPARD in vivo was observed by immunohistochemistry. The correlation of PPARD -87 T>C intratumoral polymorphism and the clinicopathological parameters of patients was analyzed statistically. Tumor samples were collected from 106 CRC patients (70 males and 36 females) with an average age of 61.04±13.67 years. A total number of 808 samples (7.60±1.60 per patient) were mainly harvested at peripheral superficial (n=376), central superficial (n=163), invasive front (n=112) and mesenteric cancer foci (n=42) of tumor tissues as well as cancerous adjacent mucosa (n=104). PCR-RFLP analysis showed that T/T (n=460, 56.9%) and T/C (n=334, 41.3%) were the main genotypes of -87 T>C among these samples. Furthermore, intratumoral genotype of -87 T>C was homogeneous in 90 patients and heterogeneous in other 16 patients. The intratumoral heterogeneity was related to patients' age (P=0.016), tumor location (P=0.011) and the grade of differentiation (P=0.022). For patients with intratumoral heterogeneity, immunochemistry showed the expressions of PPARD were not influenced by T/T or T/C genotypes. Intratumoral heterogeneity of PPARD-87 T>C wildly existed in CRC, and associated with patients' age, tumor location and differentiation. However, the immunochemistry assay revealed that there's no significant link between heterogeneity and expression of PPARD.

[Measurement of morphological parameters of internal acousticmeatus using thin-section CT]

Objective: This study aimed to measure the morphological parameters of the internal acoustic meatus(IAM) and its adjacent structures using temporal-bone thin-section CT(computed tomography). Methods: CT images were obtained from 50 Chinese adult patients (25 males and 25 females, 100 sides) which had no visible lesion in the petrous part of the temporal bone and inner ear, the morphological parameters of all inner ear parts were sectionally measured on the specified plane using SPSS 22.0 software for statistical analysis. Results: The integral morphological characteristics of the IAM were observed. These results revealed that anterior-posterior diameter of the internal acoustic poer(IAP)(CD) was (6.93±1.85)mm, the superior-inferior diameter of the IAP(EF) was (4.40±0.86)mm, the length of the IAM(AB) was (9.30±1.60)mm, the superior-inferior diameter of the IAM(the intersection of inner 1/3 section and middle 1/3 section) was (4.13±0.83)mm, the superior-inferior diameter of the IAM(the intersection of middle 1/3 section and outer 1/3 section) was (4.61±1.02)mm, the anterior-posterior diameter of the IAM(the intersection of inner 1/3 section and middle 1/3 section) was (6.62±1.92)mm, the anterior-posterior diameter of the IAM(the intersection of middle 1/3 section and outer 1/3 section) was (6.28±1.65)mm, the depth of transverse crest (superior wall) was (3.10±0.75)mm, the depth of transverse crest (interior wall)the was (1.46±0.59)mm, the distance from transverse crest vertex A to the superior wall of the IAM was (2.05±0.42)mm, the distance from transverse crest vertex A to the interior wall of the IAM was (2.93±0.41)mm, the thickness of the superior bone wall of the IAM (the intersection of inner 1/3 section and middle 1/3 section) was (4.45±1.34)mm, the thickness of the superior bone wall of the IAM (the intersection of middle 1/3 section and outer 1/3 section) was (4.32±1.12)mm, the thickness of the superior bone wall of the IAM (the intersection of outer 1/3 section and transverse crest vertex) was (4.37±1.28)mm, and the appearance ratio of the cells in the whole IAM superior wall was 32%.The whole IAM assumed the shape of short cylinder, inclining about 1 cm outward, with the upper-lower diameter and anterior-posterior diameter about 5 mm. Conclusion: It is necessary for carrying out preoperative the temporal-bone thin-section CT to obtain the morphological parameters of the IAM, determine its basic morphology, and provide references to avoid damaging the other important structures during IAM surgeries.

A novel binding of GTP stabilizes the structure and modulates the activities of human phosphoglucose isomerase/autocrine motility factor

Phosphoglucose isomerase (PGI) catalyzes the interconversion between glucose 6-phosphate and fructose 6-phosphate in the glycolysis pathway. In mammals, the enzyme is also identical to the extracellular proteins neuroleukin, tumor-secreted autocrine motility factor (AMF) and differentiation and maturation mediator for myeloid leukemia. Hereditary deficiency of the enzyme causes non-spherocytic hemolytic anemia in human. In the present study, a novel interaction between GTP and human PGI was corroborated by UV-induced crosslinking, affinity purification and kinetic study. GTP not only inhibits the isomerization activity but also compromises the AMF function of the enzyme. Kinetic studies, including the Yonetani-Theorell method, suggest that GTP is a competitive inhibitor with a K_i value of 63 μM and the GTP-binding site partially overlaps with the catalytic site. In addition, GTP stabilizes the structure of human PGI against heat- and detergent-induced denaturation. Molecular modelling and dynamic simulation suggest that GTP is bound in a syn-conformation with the γ-phosphate group located near the phosphate-binding loop and the ribose moiety positioned away from the active-site residues.

Chinese herbal medicine-induced anticholinergic poisoning in Hong Kong

OBJECTIVE

To study the epidemiology, causes, and clinical course of Chinese herbal medicine-induced anticholinergic poisoning in Hong Kong.

DESIGN

Case series.

SETTING

Hong Kong.

PATIENTS

All case histories of Chinese herbal medicine-induced anticholinergic poisoning (with laboratory confirmation) recorded by the Hong Kong Poison Information Centre over a 93-month period were accessed for analysis.

RESULTS

During the relevant period, 22 clusters of Chinese herbal medicine-induced anticholinergic poisoning involving 32 patients were retrieved. The commonest clinical features were mydriasis (n=32, 100%) and confusion (n=24, 75%). No gastro-intestinal decontamination was performed. None of these patients underwent intubation, defibrillation, cardioversion, pacing, fluid resuscitation, inotropic support or dialysis. Of the 32 patients, 17 (53%) were treated with physostigmine because of confusion, three of whom had previously received intravenous benzodiazepines. No patient could be effectively treated with benzodiazepines alone. There was no mortality, and all the patients were discharged within 3 days. None of them re-attended the emergency department within 1 week of discharge. The commonest cause was the substitution of flos campsis (Campsis grandiflora) by the flower of the Datura species (7 clusters [32%] in 10 patients).

CONCLUSION

Mydriasis and confusion were the commonest clinical features of Chinese herbal medicine-induced anticholinergic poisoning in Hong Kong. Physostigmine was frequently used in the treatment; benzodiazepines appeared ineffective. The commonest cause was the substitution of flos campsis (Campsis grandiflora) by the flower of the Datura species.

A huge malignant peripheral nerve sheath tumor with hepatic metastasis arising from retroperitoneal ganglioneuroma

Ganglioneuromas (GNs) are the rarest and most benign of the neuroblastic tumors. We experienced a case of huge retroperitoneal GN which differentiated into malignant peripheral nerve sheath tumors (MPNST) with hepatic metastasis. The tumor was located in the upper right quarter of the abdomen and pressed the right lobe of the liver, which was initially misdiagnosed as a liver carcinoma. The tumor shared blood supply with the right liver lob and had rich blood supplies from the abdominal aorta, renal artery and hepatic artery. It was also associated with skin pigment and recurrence shortly following resection. Our finding demonstrated that MPNST is a potent invasive malignant tumor and metastasis earlier with very poor prognosis.

P2-13-02: Parent of Origin of BRCA Mutation May Determine Age at Breast Cancer Diagnosis

Background: Genetic diseases may display parent-of-origin effects. In such cases, the risk depends on the specific parent or origin allele. Imprinting effect is evident in autosomal dominant hereditary paraganglioma leads to tumors only if inherited from paternal germline. Cancer penetrance in mutations carriers may be determined by the parent origin of BRCA mutation.

Methods: From 2007–2010 we analyzed 1889 consecutive (136 ovarian + 1753 breast) breast (BrCa) or ovarian cancer (OvCa) patients presenting for treatment at our outpatient facility. In 130 patients with BRCA 1 or 2 mutations the parent of origin for the mutation was known. Of the 130 patients 2 had both BRCA1 and BRCA2 mutated paternally inherited and were excluded from this analysis. Of the breast cancer patients: 28 patients had paternal and 29 had maternal BRCA1 mutations, 24 had paternal and 21 had maternal BRCA 2 mutations. Of the ovarian cancer patients 6 had paternal and 10 had maternal BRCA1 mutations, 7 had paternal and 3 had maternal BRCA2 mutations. In carriers of BRCA mutations the mean age at diagnosis for ovarian cancer was 51 (range 21–70) and for breast cancer was 43 (range 24–78).

Two-sample t-test was used to compare the mean age at diagnosis in patients with BRCA 1 or 2 mutations of paternal or maternal inheritance.

For breast cancer maternal allele versus paternal allele 2-sample t-test and p-value were compared for the age at first diagnosis. For breast cancer patients BRCA1 maternal inheritance (mean+SD yrs) 45.73+11.22 versus paternal inheritance 38.04+7.14 2-sample t-test p-value p&lt;0.0020. For breast cancer BRCA2 maternal inheritance (mean+SD yrs) 50.65+10.44 versus paternal inheritance 41.68+6.16, 2-sample t-test p-value p&lt;0.0008.

Results: Significantly younger age at breast cancer diagnosis was observed in paternal vs. maternal inheritance of BRCA1 mutation (38 vs 46, respectively, p&lt;0.0020) and BRCA2 mutation (42 vs 51 respectively, p&lt;0.0008). There was no significant difference between paternal and maternal age of ovarian cancer diagnosis of BRCA1 (p&lt;0.1415) or BRCA2 mutation (p&lt;0.3470).

Conclusion: The restrospective nature of the study may introduce ascertainment bias. However, the breast and ovarian cancers cases in BRCA1 & 2 carriers with maternal or paternal inheritance mirror the Mendelian autosomal dominant pattern in our unselected consecutive cohort of patients. Maternal and paternal inherited BRCA alleles may not be exchangeable. Women with paternally inherited mutations in BRCA gene mutations develop breast cancer at younger age compared with women who inherit the gene mutations from their mothers. In this small sample, clear differences at age of cancer diagnosis are apparent in paternal inheritance of BRCA gene mutation. If this observation duplicates in larger cohorts results will have important implications for recommendation of surgical risk reduction in BRCA mutation carriers.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-13-02.

Uranium toxicity and speciation during chronic exposure to the tropical freshwater fish, Mogurnda mogurnda

The effects of chronic uranium (U) exposure on larval Northern trout gudgeon, Mogurnda mogurnda, were assessed in two experiments using a newly-developed 28d survival and growth toxicity test. Significant effects were observed in both tests, but toxicity was markedly higher in Test 2 than Test 1. The LC50s for Tests 1 and 2 were 2090microgL(-1) and 1070microgL(-1), respectively. Larval growth IC10s for Tests 1 and 2 were 860microgL(-1) and 660microgL(-1) (dry weight), and 1160microgL(-1) and 850microgL(-1) (length), respectively. Uranium speciation modelling showed that a lower pH in Test 2 (mean of 6.0) compared to Test 1 (mean of 6.7) resulted in a greater proportion of free uranyl ion (UO(2)(2+)), the predominant bioavailable form of U. A higher dissolved organic carbon concentration (DOC) in Test 2 (4.2mgL(-1)) compared to Test 1 (2.1mgL(-1)) resulted in a higher proportion of U-DOC in Test 2, but this was insufficient to counter the effect of pH on the proportion of UO(2)(2+). The difference in U toxicity between the two tests could be explained by normalising for UO(2)(2+); the concentrations of UO(2)(2+) at the LC50s for Tests 1 and 2 were calculated to be 13.3 and 13.7microgL(-1), respectively. Finally, the results of this study, and comparisons with other studies suggest that U toxicity to M. mogurnda appears to be as much, if not more, a function of exposure water quality and feeding regime, as exposure duration.

Oral cimetidine prolongs clarithromycin absorption

The present study was conducted to identify any potential interaction between oral cimetidine and clarithromycin. Twelve healthy subjects were administered single doses of clarithromycin alone and with oral cimetidine dosed to steady state. Cimetidine prolonged the absorption of clarithromycin, as evidenced by decreased peak concentrations of both clarithromycin and 14-OH-clarithromycin (14OHC) in serum (46 and 43%, respectively), a delay in the formation of 14OHC (increase of 68%), and increases in both of their half-lives (75 and 82%, respectively), despite no changes in total oral clearance or area under the concentration-time curve for either compound. No mechanism for this interaction has been identified.

Effect of grapefruit juice on clarithromycin pharmacokinetics

To investigate whether grapefruit juice inhibits the metabolism of clarithromycin, 12 healthy subjects were given water or grapefruit juice before and after a clarithromycin dose of 500 mg in a randomized crossover study. Administration of grapefruit juice increased the time to peak concentration of both clarithromycin (82 +/- 35 versus 148 +/- 83 min; P = 0.02) and 14-hydroxyclarithromycin (84 +/- 38 min versus 173 +/- 85; P = 0.01) but did not affect other pharmacokinetic parameters.

Paradoxic excitation with diphenhydramine in an adult

Although paradoxic excitation may rarely occur in children and adults with conventional dosages of antihistamines, few case reports have appeared in the literature. We cared for a 46-year-old patient who became extremely agitated after receiving a dose of intravenous diphenhydramine.

Clinical and echocardiographic features of mitral valve prolapse patients in a local population

Mitral valve prolapse (MVP) is a commonly diagnosed condition with varied clinical presentations but local data is lacking. In our study, we reviewed 98 patients (54 males, 44 females) with echocardiographic mitral valve prolapse diagnosed between 1991 and 1993 to study the clinical profile and echocardiographic features of patients with this condition in our local population. The mean and median age at presentation/detection were 42 years and 38 years respectively. The majority of the patients were asymptomatic (59%); the rest presented with palpitations (21%), congestive heart failure (4%) and infective endocarditis (5%). On clinical examination, 64 patients had mitral regurgitation (13 patients had both mitral regurgitation murmur and a systolic click), while one or more systolic clicks were heard in another 32 patients. Six patients also had associated Marfan syndrome. 2D echo revealed isolated anterior and posterior leaflet involvement in 55 and 19 patients respectively. Another 24 patients had involvement of both leaflets. Mitral regurgitation was detected on colour Doppler study in 78 patients. Nine patients had associated tricuspid valve prolapse. Of the 98 patients, 8 patients developed flail mitral valve. Four were detected at presentation/diagnosis, while the other 4 were diagnosed incidentally on routine follow-up 2D echo. Of these 8 patients, one developed cardiac failure. The patients had been on follow-up for a mean period of 9 months. During this period, mitral regurgitation progressed in 3 patients resulting in valve surgery. Only 20 patients had arrhythmias detected on ambulatory ECG monitoring, most of them were frequent atrial and ventricular premature beats. No patient was found to have haemodynamically significant arrhythmia. In summary, most patients with MVP had anterior mitral valve leaflet prolapse and mitral regurgitation. Although most patients with MVP are asymptomatic or have minor symptoms, it is associated with significant morbidity.

Nuclear magnetic resonance spectroscopic analysis of homoallylic and bis homoallylic substituted methyl fatty ester derivatives

Using a combination of selective irradiation 1H nuclear magnetic resonance experiments and two-dimensional 1H-13C correlation spectroscopy spectral analysis of homoallylic and bis homoallylic substituted (azido, acetoxy, chloro and oxo) fatty ester derivatives, the carbon shifts of the ethylenic carbon atoms were determined. In the case of methyl 12-azido-9Z-octadecenoate (homoallylic), the carbon chemical shifts of the ethylenic C-9 and C-10 carbon nuclei are 133.092 and 124.596 ppm, respectively. In methyl 9-azido-12Z-octadecenoate (bis homoallylic), the carbon chemical shift of the ethylenic C-12 and C-13 carbon nuclei are 128.118 and 131.243 ppm, respectively.

Effects of xanthone glycoside on ephedrine-induced biting behavior and motor activity

1-Hydroxy-3,4,7,8-tetramethoxyxanthone, beta-sitosterol, uvaol-3-palmitate, and sweroside have been isolated from the fresh whole plant of Tripterospermum lanceolatum (Hayata) Haraex Satake (Gentianaceae). Our results on the pharmacological studies of xanthone glycoside and lanceoside suggested that they have a CNS depressant effect.

Effect of glucocorticoids on oncogene transformed NIH3T3 cells

We studied the differential response of oncogene transformed NIH3T3 cells to glucocorticoids. As demonstrated for transformed human fibroblasts, the morphology of neu-, ras-, src- and sis-transformed mouse fibroblasts became more normal after glucocorticoid treatment. This change was not due to inhibition of the expression of oncogene mRNA or protein. However, the abl-transformed NIH3T3 cells were resistant to glucocorticoid-induced morphology change. These results indicate that the glucocorticoid-induced morphology change is specific to certain oncogene-transformed NIH3T3 cells. Transformed human fibroblasts generally have reduced amounts of cell surface fibronectin. When treated with glucocorticoids, they incorporate higher levels of fibronectin in their extracellular matrix, which correlates with their change in morphology. However, we found that, except for abl-transformed cells, the fibronectin level of the other oncogene transformed mouse cells was similar to non-transformed cells. Moreover, treatment of the neu-, ras-, src- and sis-transformed cells with glucocorticoids resulted in a change in morphology but no increase in cell surface fibronectin. These studies demonstrate that the glucocorticoid-induced morphological change of oncogene-transformed NIH3T3 cells is not due to enhanced expression of fibronectin. Therefore, other mechanisms are responsible for this glucocorticoid-induced phenotypic change of oncogene-transformed cells.

Novel inhibitory actions on platelet thromboxane and inositolphosphate formation by xanthones and their glycosides

Xanthones and their glycosides were tested for their antiplatelet activities in washed rabbit platelets. Tripteroside acetate and norathyriol acetate were the most potent inhibitors. Tripteroside acetate inhibited platelet aggregation and ATP release induced by ADP, arachidonic acid, platelet-activating factor (PAF), collagen, ionophore A23187 and thrombin. The IC50 values of tripteroside acetate toward arachidonic acid- (100 microM) and collagen- (10 micrograms/ml) induced platelet aggregation were 10 and 30 micrograms/ml respectively. It inhibited thromboxane B2 formation of washed platelets caused by arachidonic acid, collagen, thrombin and ionophore A23187 and also that caused by the incubation of lysed platelet homogenate with arachidonic acid. Tripteroside acetate decreased the formation of inositolphosphate caused by thrombin, collagen and PAF, whereas it had no direct effect on fibrinogen-platelet interaction. It is concluded that xanthone derivatives inhibited platelet aggregation and release reaction by diminishing thromboxane formation and phosphoinositide breakdown.

Enzyme immunoassay using a novel recombinant polypeptide to detect human immunodeficiency virus env antibody

A unique antigen, CBre3, has been synthesized from a genetically engineered clone to detect human immunodeficiency virus (HIV) env antibodies with high sensitivity and specificity. The antigen contains sequences derived from both envelope proteins of HIV, i.e., gp120 and gp41, and was purified free of Escherichia coli proteins detectable by Coomassie stain or immunoblotting with E. coli antiserum. The purified recombinant polypeptides were used as antigen in an enzyme immunoassay (EIA) to screen serum samples from healthy and HIV-infected individuals. The same samples were also tested by radioimmunoprecipitation (RIP) for gp120 and gp160 HIV antibodies. All samples containing gp120 and gp160 antibodies by RIP had CBre3 EIA values greater than 0.35 (n, 122; range, 0.37 to 2.1+; median, 1.65). All RIP HIV antibody-negative samples had CBre3 EIA values less than 0.25 (n, 140; mean, 0.052; standard deviation, 0.045; range, 0.00 to 0.22). The endpoint titer of a standard positive control serum was 1:10,000 by RIP and by CBre3 EIA. The assay was 100% accurate in three proficiency panels. It easily detected six samples from individuals whose infections were confirmed by culture; these samples were reactive only with p24 by Western blot. The samples also were positive for gp120 and gp160 antibodies by RIP. These data suggest that the CBre3 EIA can detect env antibodies as sensitively and specifically as RIP and with more sensitivity than Western blot.

Two calmodulins in Naegleria flagellates: characterization, intracellular segregation, and programmed regulation of mRNA abundance during differentiation

Flagellates of Naegleria gruberi contain two calmodulins that differ in apparent molecular weight and intracellular location. Calmodulin-1, localized in flagella, has an apparent molecular weight of approximately 16,000, approximately the size of other protozoan calmodulins, whereas calmodulin-2, localized in cell bodies, is 15,300. Both proteins, purified, are calmodulins by several criteria, including Ca2+-dependent stimulation of calmodulin-dependent cyclic nucleotide phosphodiesterase and affinity for antibodies to vertebrate calmodulin. The finding of two calmodulins is unusual. Since the only known difference is apparent molecular weight, one calmodulin could be derived from the other, except that both calmodulins are synthesized in a wheat germ, cell-free system directed by RNA from differentiating Naegleria. Translatable mRNAs encoding calmodulins 1 and 2, not detected in amebas, appear and subsequently disappear concurrently during the 100-min differentiation of Naegleria from amebas to flagellates. Furthermore, these mRNAs increase and then decrease in abundance concurrently with those for flagellar tubulins, which suggests the possibility that the expression of the unrelated genes for calmodulin and tubulin may be under coordinate control during differentiation.

The status of tyrosyl residues in a Formosan cobra cardiotoxin

Spectrophotometric titration of Formosan cobra cardiotoxin showed that two of the three tyrosyl residues were titrated freely with a normal apparent pKa of 9.6 whereas the remaining one ionized at pH above 11.0. Nitration of cardiotoxin in Tris . HCl buffer with tetranitromethane resulted in the selective nitration of tyrosine 11 and tyrosine 22. It also revealed that tyrosine 51 was the abnormal one in the spectrophotometric titration. Complete nitration occurred in the presence of 6.0 M guanidine hydrochloride. Compared with the conformation of native cardiotoxin, the peptide conformation of the partially nitrated cardiotoxin did not change significantly but the conformation of the completely nitrated cardiotoxin changed remarkably. The biological activity of cardiotoxin was indeed affected by nitration, but the immunological activity was nearly intact even when all the tyrosine residues were nitrated.

Location of disulfide bridges in cardiotoxin from the venom of Formosan cobra (NAJA NAJA ATRA)

The location of the four disulfide bridges in cardiotoxin from the venom of the Formosan cobra, Naja naja atra, was determined by isolating cystine-containing peptides from the enzymic and partial acid hydrolyzates of the intact toxin. The results indicate that the disulfide bridges are formed by half cystine residues 3--21, 14--38, 42--53, and 54--59. The amino acid sequence at the position 48--49 was revised to -Leu-Val- instead of Val-Leu- as reported previously.