Investigating Substituent Interactions with Cationic Catalysts

Rates of isothiourea catalyzed silylation and acylation reactions were measured for substrates with various electronic substituents at the aryl group. Through these measurements, the intermolecular interactions between cationic catalyst intermediates and different aryl groups were explored. These studies were performed to understand how changes in the catalyst structure affected electrostatic intermolecular interactions. Three different catalysts (N-methylimidazole and two isothioureas) were employed that varied in their ability to delocalize their cationic nature. The results show that more delocalization on the catalyst reduces the sensitivity to the electronics on the aryl group. Surprisingly, the isothiourea with a fused benzene ring provided additional points of interaction with groups that contained lone-pairs, significantly affecting the overall rate. This work helps explore the interactions that dominate in these types of catalytic systems, to aid in future organocatalysis development. Density functional theory (DFT) studies further confirmed isothiourea/aryl ring interaction with the alcohol substrate in the acylation process, which confirmed these hypotheses. Electron rich or lone-pair bearing functional groups stabilize the cationic catalyst core, thereby stabilizing the transition states and accelerating the reaction. It was also discovered that in one case, the formation of a stable substrate dimer was responsible for its lower reactivity.

[Comparative analysis on prevalence of tobacco and e-cigarettes uses in junior middle school students in Shanghai, 2013 and 2019]

Objective: To examine the prevalence and trend of tobacco and e-cigarettes uses and identify the influencing factors for smoking behavior in junior middle school students in Shanghai, and provide data support and scientific basis for the development of tobacco control intervention strategy in adolescents. Methods: Multi-stage stratified random sampling method was used to select junior middle school students in 8 districts and 10 districts in Shanghai in 2013 and in 2019 respectively. Information about tobacco and e-cigarettes uses in the students were collected by using self-administrated questionnaire. The prevalence of tobacco and e-cigarettes uses were calculated, the difference between two years was compared with χ² test. The influencing factors were identified by multivariate logistic regression analysis. Results: In 2019, the current smoking rate was 0.6% in junior middle school students in Shanghai, and the smoking attempt rate was 2.9%, both were lower than the levels in 2013 (0.7% and 6.9%). The current use rate of e-cigarettes was 0.6% in 2019,with no significant change compared with 2013 (0.6%). The proportion of the students who had heard of e-cigarettes in 2019 (78.4%) was higher than that in 2013 (47.2%). In 2019, the second-hand smoke (SHS) exposure rate at home, in both indoor and outdoor public places and on public transportations was 72.5%, which was slightly lower than the level in 2013 (73.0%), the differences were all significant (P<0.05). In 2019, the students seeing close friend smoking (OR=27.381, 95%CI: 12.037-62.287), seeing someone smoking in school (OR=2.477, 95%CI: 1.155-5.312), believing that SHS may not be harmful (OR=8.471, 95%CI: 1.464-49.005) had higher possibility of smoking. Being aged ≥15 years (compared with being aged ≤12 years, OR=8.688, 95%CI: 1.922-39.266), exposure to SHS in outdoor public place (OR=8.608, 95%CI: 1.048-70.692), close friend smoking (OR=8.115, 95%CI: 1.754-37.545) were positively associated with e-cigarettes use, and believing that smoking results in uncomfortable social contact [compared with believing that smoking results in comfortable social contact (OR=0.105,95%CI: 0.018-0.615)] were negatively associated with e-cigarettes use, the difference was significant (P<0.05). Conclusion: The prevalence of tobacco and e-cigarette uses in junior middle school students in Shanghai remained at a low level in recent years. The SHS exposure rate in junior middle school students is high. Smoking behavior of junior middle school students is closely related to personal attitude and awareness of tobacco, exposure to SHS, peer smoking and the situation of tobacco control in schools. Prevention and intervention should be carried out from multi-dimensions to effectively protect teenagers from tobacco hazards.

Sodium dodecyl sulfate modulates the structure and rheological properties of Pluronic F108-poly(acrylic acid) coacervates)

Micelles formed within coacervate phases can impart functional properties, but it is unclear if this micellization provides mechanical reinforcement of the coacervate whereby the micelles act as high functionality crosslinkers. Here, we examine how sodium dodecyl sulfate (SDS) influences the structure and properties of Pluronic F108-polyacrylic acid (PAA) coacervates as SDS is known to decrease the aggregation number of Pluronic micelles. Increasing the SDS concentration leads to larger water content in the coacervate and an increase in the relative concentration of PAA to the other solids. Rheological characterization with small angle oscillatory shear (SAOS) demonstrates that these coacervates are viscoelastic liquids with the moduli decreasing with the addition of the SDS. The loss factor (tan δ) initially increases linearly with the addition of SDS, but a step function increase in the loss factor occurs near the reported CMC of SDS. However, this change in rheological properties does not appear to be correlated with any large scale structural differences in the coacervate as determined by small angle X-ray scattering (SAXS) with no signature of Pluronic micelles in the coacervate when SDS concentration is >4 mM during formation of the coacervate, which is less than that observed (6 mM SDS) in initial Pluronic F108 solution despite the higher polymer concentration in the coacervate. These results suggest that the mechanical properties of polyelectrolyte-non-ionic surfactant coacervates are driven by the efficicacy of binding between the complexing species driving the coacervate, which can be disrupted by competitive binding of the SDS to the Pluronic.

Mechanistic investigations of alcohol silylation with isothiourea catalysts

The mechanism of the asymmetric silylation of alcohols with isothiourea catalysts was studied by employing reaction progress kinetic analysis. These reactions were developed by the Wiskur group, and use triphenyl silyl chloride and chiral isothiourea catalysts to silylate the alcohols. While the order of most reaction components was as expected (catalyst, amine base, alcohol), the silyl chloride was determined to be a higher order. This suggested a multistep mechanism between the catalyst and silyl chloride, with the second equivalent of silyl chloride assisting in the formation of the reactive intermediate leading to the rate-determining step. Through the addition of additives and investigating changes in the silyl chloride, an understanding of the catalyst equilibrium emerged for this reaction and provided pathways for further reaction development.

Urinary biomarkers of early renal injury in antiretroviral-naïve HIV-positive persons in Shanghai, China: comparison with the general population

Objectives

People living with HIV (PLWH) have a high risk of kidney injury. Measurement of serum creatinine, along with proteinuria, is not sensitive to detect early kidney injury. Here, we investigated novel urinary biomarkers of early renal injury in PLWH.

Methods

We performed a cross‐sectional study of 166 antiretroviral‐naïve PLWH and 99 HIV‐negative persons who all had an estimated glomerular filtration rate > 90 mL/min/1.73 m². We compared the levels of seven urinary biomarkers between the two groups using the propensity score matching (PSM) approach and explored the risk factors associated with elevated urinary biomarkers in PLWH.

Results

Eighty‐three pairs were successfully matched based on PSM. Compared with the HIV‐negative group, the HIV‐positive group had higher ratios of N‐acetyl‐β‐D‐glucosaminidase (NAG) to urine creatinine (UCr), alpha1‐microglobulin (α1‐M) to UCr, kidney injury marker‐1 (KIM‐1) to UCr, neutrophil gelatinase‐associated lipocalin to UCr, and epidermal growth factor to UCr, whereas the Tamm–Horsfall protein to UCr ratio and the abnormal albumin to UCr ratio were not significantly different. Positive correlations were observed between HIV RNA level and NAG: UCr (r_s = 0.32; P < 0.001) and α1‐M:UCr (r_s = 0.24; P = 0.002) ratios, and negative correlations were observed between CD4 cell count and NAG:UCr (r_s = –0.34; P < 0.001), KIM‐1:UCr (r_s = –0.16; P = 0.042) and α1‐M:UCr (r_s = –0.36; P < 0.001) ratios. In multivariate linear regression analyses, older age, lower total cholesterol and higher HIV RNA were independently associated with higher NAG:UCr; older age, lower total cholesterol and lower CD4 cell count were independently associated with higher α1‐M:UCr.

Conclusions

In comparioson with HIV‐negative participants, PLWH were more likely to have tubular injury. Early antiretroviral treatment might mitigate the development of kidney injury.

A transcription factor network responsive to high CO2/hypoxia is involved in deastringency in persimmon fruit

Plant responses to anaerobic environments are regulated by ethylene-response factors (ERFs) in both vegetative and productive organs, but the roles of other transcription factors (TFs) in hypoxia responses are poorly understood. In this study, eight TFs (DkbHLH1, DkMYB9/10/11, DkRH2-1, DkGT3-1, DkAN1-1, DkHSF1) were shown to be strongly up-regulated by an artificial high-CO2 atmosphere (1% O2 and 95% CO2). Dual-luciferase assays indicated that some TFs were activators of previously characterized DkERFs, including DkMYB10 for the DkERF9 promoter, DkERF18/19 and DkMYB6 for the DkERF19 promoter, and DkERF21/22 for the DkERF10 promoter. Yeast one-hybrid and cis-element mutagenesis confirmed these physical interactions with one exception. The potential roles of these TFs in persimmon fruit deastringency were analysed by investigating their transient over-expression (TOX) in persimmon fruit discs, which indicated that DkMYB6TOX, DkMYB10TOX, DkERF18TOX, and DkERF19TOX were all effective in causing insolubilization of tannins, concomitantly with the up-regulation of the corresponding genes. These results indicated that multiple TFs of different classes are responsive to high-CO2/hypoxia in fruit tissues, and that a TF-TF regulatory cascade is involved in the hypoxia responses involving the Group VII DkERF10, and DkERFs and DkMYBs.

[Treatment of patients with different degree of acute respiratory distress syndrome caused by inhalation of white smoke]

Objective: To summarize the treatment experience of patients with different degree of acute respiratory distress syndrome (ARDS) caused by inhalation of white smoke from burning smoke bomb. Methods: A batch of 13 patients with different degree of ARDS caused by inhalation of white smoke from burning smoke bomb, including 2 patients complicated by pulmonary fibrosis at the late stage, were admitted to our unit in February 2016. Patients were divided into mild (9 cases), moderate (2 cases), and serious (2 cases) degree according to the ARDS Berlin diagnostic criteria. Patients with mild and moderate ARDS were conventionally treated with glucocorticoid. Patients with severe ARDS were sequentially treated with glucocorticoid and pirfenidone, and ventilator-assisted breathing, etc. were applied. The vital signs, arterial oxygenation index, changes of lung imaging, pulmonary ventilation function, general condition, and the other important organs/systems function were timely monitored according to the condition of patients. The above indexes were also monitored during the follow-up time of 10-15 months post injury. Data were processed with SPSS 18.0 statistical software. Results: (1) The symptoms of respiratory system of patients with mild and moderate ARDS almost disappeared after 3 days' treatment. Their arterial oxygenation index was decreased from post injury day 1 to 4, which almost recovered on post injury day 7 and completely recovered one month post injury. The symptoms of respiratory system of patients with severe ARDS almost disappeared at tranquillization condition 1-3 month (s) post injury. Their arterial oxygenation index was decreased from post injury day 3 to 21, which gradually recovered 1-3 month (s) post injury and was normal 15 months post injury. (2) Within 24 hours post injury, there was no obvious abnormality or only a little texture enlargement of lung in image of chest CT or X-rays of patients with mild and moderate ARDS. One patient with moderate ARDS had diffuse patchy and ground-glass like increased density shadow (pulmonary exudation for short) at post injury hour 96. Chest iconography of all patients with mild and moderate ARDS showed no abnormalities 10 months post injury. Both lungs of each of the two patients with severe ARDS showed obvious pulmonary exudation at post injury hours 45 and 75, respectively. One patient with severe ARDS showed no abnormality in chest image 10 months post injury, but there was still a small mesh-like increased density shadow in double lobes with slight adhesion of pleura in the other patient with severe ARDS 15 months post injury. (3) All patients showed severe restrictive hypoventilation when admitted to hospital. Pulmonary ventilation function of patients with mild and moderate ARDS recovered to normal one month post injury, and they could do exercises like running, etc. Pulmonary ventilation function of one patient with severe ARDS recovered to normal 6 months post injury, and the patient could do exercises like running, etc. The other patient with severe ARDS showed mild restrictive hypoventilation 15 months post injury and could do exercises like rapid walking, etc. (4) The condition of all mild and one moderate ARDS patients was better on post injury day 3, and they were transferred to the local hospital for subsequent treatment and left hospital on post injury day 21. One patient with moderate ARDS healed and left hospital on post injury day 29. Patients with severe ARDS healed and left hospital on post injury day 81. During the follow-up time of 10-15 months post injury, the other important organs/systems of all patients showed no abnormality, and there was no adverse reaction of glucocorticoid like osteoporosis, femoral head necrosis, or metabolic disorder. Two patients with severe ARDS did not have any adverse reaction of pirfenidone like liver function damage, photosensitivity, anorexia, or lethargy. Conclusions: Early enough and uninterrupted application of glucocorticoid can significantly reduce the ARDS of patients caused by inhalation of white smoke from burning smoke bomb. Sequential application of glucocorticoid and pirfenidone can effectively treat pulmonary fibrosis at the late stage.

Outbreak of Occupational Brucellosis at a Pharmaceutical Factory in Southeast China

Brucellosis is an occupational disease affecting workers in butcher shops, the milking and dairy product industry, causing more than 500 000 new cases around the world. As a national statutory B infectious disease in China, morbidity of brucellosis is rapidly increasing in recent years. We report an occupational outbreak of brucellosis infection in a pharmaceutical factory. Exposure was a result of manual operation in the process line, close contact with sheep placentas, insufficient disinfection and repeated using of protective suits and infected by aerosol dissemination. Improved preventive methods, appropriate public health measures and spread of health education would be helpful to prevent the occupational outbreak of brucellosis in future.

Involvement of DkTGA1 Transcription Factor in Anaerobic Response Leading to Persimmon Fruit Postharvest De-Astringency

Persimmon fruit are unique in accumulating proanthocyanidins (tannins) during development, which cause astringency in mature fruit. In ‘Mopanshi’ persimmon, astringency can be removed by treatment with 95% CO₂, which increases the concentrations of ethanol and acetaldehyde by glycolysis, and precipitates the soluble tannin. A TGA transcription factor, DkTGA1, belonging to the bZIP super family, was isolated from an RNA-seq database and real-time quantitative PCR indicated that DkTGA1 was up-regulated by CO₂ treatment, in concert with the removal of astringency from persimmon fruit. Dual-luciferase assay revealed that DkTGA1 had a small (less than 2-fold), but significant effect on the promoters of de-astringency-related genes DkADH1, DkPDC2 and DkPDC3, which encode enzymes catalyzing formation of acetaldehyde and ethanol. A combination of DkTGA1 and a second transcription factor, DkERF9, shown previously to be related to de-astringency, showed additive effects on the activation of the DkPDC2 promoter. Yeast one-hybrid assay showed that DkERF9, but not DkTGA1, could bind to the DkPDC2 promoter. Thus, although DkTGA1 expression is positively associated with persimmon fruit de-astringency, trans-activation analyses with DkPDC2 indicates it is likely to act by binding indirectly DkPDC2 promoter, might with helps of DkERF9.

A pediatric case of severe fever with thrombocytopenia syndrome in Zhejiang Province, China

This report describes a pediatric case of severe fever with thrombocytopenia syndrome (SFTS), which is an emerging disease that is caused by a novel bunyavirus. Interestingly, the previously reported SFTS cases typically involved elderly patients, while our case involved a 5-year-old child from Zhejiang Province, China. In this report, we describe our investigation of the clinical and epidemiological characteristics of this case, to improve our understanding of this emerging disease. Our principle finding was that the present case's clinical symptoms were milder than those that have been reported in adult cases of SFTS. Therefore, we recommend more careful screening of pediatric patients who present with mild symptoms that are consistent with SFTS.

[Patient-controlled analgesia with lornoxicam in patients undergoing gynecological surgery]

OBJECTIVE

To assess the analgesic effect and side effects of PCA with lornoxicam compared with morphine and tramadol.

METHODS

89 patients, scheduled for elective hysterectomy or hysteromyomectomy, were randomly divided into Group L, Group M and Group T. Three drugs administered i.v. via a patient-controlled analgesia for up to 24 h postoperatively.

RESULTS

Efficacy was assessed by comparing total pain relief (TOTPAR) and sum of pain intensity difference (SPID) over 24 h. Statistically significant equivalence of lornoxicam, morphine and tramadol was shown by TOTPAR values 15.2 +/- 3.9, 16.4 +/- 3.5 and 15.9 +/- 4.4, by SPID values 10.3 +/- 3.1, 9.0 +/- 2.0 and 9.2 +/- 4.7, respectively (P > 0.05). Lornoxicam caused fewer adverse events than morphine and tramadol (10.0%, 26.7% and 17.2% of patients, respectively).

CONCLUSION

The study suggests that lornoxicam provides an alternative to morphine or tramadaol for the treatment of postoperative pain.

[Isolation and cytological identification of a desynaptic variant in rice]

A sterile variant was found from the population of a japonica rice variety Lunhui 422. Cytological investigation was conducted in meiosis. It is showed that the sterility was caused by desynapsis. As there were 8.69 bivalents in average occurred to be desynaptic, moreover, the most number of the desynaptic bivalents reached 12 at post diakinsis. It can be considered that the desynaptic variation is a complete desynapsis found in rice so far.

p53 inactivating mutations in chinese breast carcinomas

While previous reports on breast cancers indicate that Caucasian women have a low frequency of p53 mutations, higher frequencies of mutations are reported in some Japanese populations. There are few reports regarding p53 mutations in Chinese breast carcinomas. Using a previously established sensitive p53 yeast functional assay, we screened 23 Chinese breast carcinomas for mutations. The p53 was mutated in 5/23 (21.7%) specimens. Two of these mutations were detected in exon 5 and one was detected in each of exons 6, 7 and 8. All of these mutations have previously been shown to be mutated in Caucasian and Japanese breast cancers, but two have not previously been observed in Chinese breast cancers and one has also not been observed in Japanese.

Growth enhancement in transgenic Atlantic salmon by the use of an "all fish" chimeric growth hormone gene construct

We have developed an "all fish" growth hormone (GH) chimeric gene construct by using an antifreeze protein gene (AFP) promoter from ocean pout linked to a chinook salmon GH cDNA clone. After microinjection into fertilized, nonactivated Atlantic salmon eggs via the micropyle, transgenic Atlantic salmon were generated. The presence of the transgene was detected by polymerase chain reaction (PCR) using specific oligonucleotide primers. A number of these transgenic fish showed dramatic increases in their growth rate. At one year old, the average increase of the transgenic fish was 2 to 6 fold and the largest transgenic fish was 13 times that of the average non-transgenic control.

The tcl-3 proto-oncogene altered by chromosomal translocation in T-cell leukemia codes for a homeobox protein

The t(10;14)(q24;q11) chromosomal translocation found in malignant cells of 5-10% of patients with T-cell acute lymphoblastic leukemia (T-ALL) involves the T-cell receptor delta chain gene on chromosome 14 and a breakpoint cluster region on chromosome 10. The candidate proto-oncogene tcl-3, thought to be involved in the pathogenesis of t(10;14) T-ALL, was cloned and found to be elevated in expression in leukemic cells harboring the t(10;14) translocation. Sequence analysis revealed that tcl-3 is a new homeobox-containing gene. Comparison of the tcl-3 cDNA and its 5' genomic sequences with DNA sequences from the t(10;14) translocation breakpoints showed that this gene is structurally altered in four patients with t(10;14)(q24;q11) T-ALL. These findings suggest that homeobox-containing genes that normally act as transcription factors may contribute to T-cell leukemogenesis when abnormally expressed.

Structure and expression of the polyubiquitin gene in sea urchin embryos

A cloned Lytechinus pictus cDNA has been identified, which includes seven direct repeats of a 228 bp sequence encoding ubiquitin and about 450 bp of 3' noncoding sequence. The deduced amino acid sequence is identical to that of ubiquitins of other animals (though repeats 3 and 5 each have single amino acid substitutions at different positions). Southern blot analysis revealed that the sea urchin genome contains a single copy of the polyubiquitin gene, and the number of 228 bp repeat units appears to vary from seven to ten among different alleles; no other ubiquitin coding sequences were detected. The size distribution of polyubiquitin mRNA is polymorphic among different individuals, probably corresponding to the differences in copy number of the repetitive coding sequence. The abundance of cytoplasmic polyubiquitin RNA is constant throughout embryogenesis and is similar in ectoderm, endoderm, and mesoderm cells. The constant prevalence of polyubiquitin mRNA apparently results from a balance between ontogenetic changes in its rate of synthesis and its stability in the presence of actinomycin D. Accumulation of polyubiquitin RNA was not heat shock-inducible during embryogenesis.

Multiple levels of regulation of tubulin gene expression during sea urchin embryogenesis

The expression of the tubulin genes during embryogenesis of the sea urchin Lytechinus pictus has been analyzed. Single strand tracer excess titrations of alpha- and beta-tubulin mRNA and RNA gel blot hybridizations indicate that tubulin mRNA remains at a constant 1.3 X 10(5) transcripts per embryo during cleavage stages, increases during ciliogenesis shortly before hatching (12 hr PF), declines until midgastrula (30-35 hr PF), and then gradually increases 3-fold to about 6 X 10(5) per pluteus larva (72 hr PF). Tubulin synthesis changes in concert with its mRNA, except that during cleavage the relative rate of tubulin synthesis increases without a corresponding increase in tubulin mRNA abundance. The relative rates of tubulin gene transcription were assayed by a run-on assay in isolated nuclei. The synthesis of alpha- or beta-tubulin RNA results in little supplementation of maternal tubulin RNA during cleavage stages, but the rate increases at least 18-fold during ciliogenesis and then gradually decreases thereafter. The accumulation of tubulin mRNA after gastrulation can be accounted for by an ontogenetic increase in tubulin RNA stability, assayed by actinomycin D chase and RNA gel blot hybridization. The rates of synthesis, stabilities, and abundances of alpha- and beta-tubulin mRNAs were similar, suggesting coordinate regulation. These observations indicate the importance of translational regulation during cleavage, transcriptional regulation during ciliogenesis, and regulation of mRNA stability by the level of unpolymerized tubulin during later development.

Stabilization of tubulin mRNA by inhibition of protein synthesis in sea urchin embryos

An increased level of unpolymerized tubulin caused by depolymerization of microtubules in sea urchin larvae resulted in a rapid loss of tubulin mRNA, which was prevented by nearly complete inhibition of protein synthesis. Results of an RNA run-on assay indicated that inhibition of protein synthesis does not alter tubulin gene transcription. Analysis of the decay of tubulin mRNA in embryos in which RNA synthesis was inhibited by actinomycin D indicated that inhibition of protein synthesis prevents the destabilization of tubulin mRNA. The effect was similar whether mRNA was maintained on polysomes in the presence of emetine or anisomycin or displaced from the polysomes in the presence of puromycin or pactamycin; thus, the stabilization of tubulin mRNA is not dependent on the state of the polysomes after inhibition of protein synthesis. Even after tubulin mRNA declined to a low level after depolymerization of microtubules, it could be rescued by treatment of embryos with inhibitors of protein synthesis. Tubulin mRNA could be induced to accumulate prematurely in gastrulae but not in plutei if protein synthesis was inhibited, an observation that is indicative of the importance of the autogenous regulation of tubulin mRNA stability during embryogenesis. Possible explanations for the role of protein synthesis in the control of mRNA stability are discussed.

Autogenous regulation of tubulin synthesis via RNA stability during sea urchin embryogenesis

When pluteus embryos of Lytechinus pictus were treated with colcemid, the incorporation of [35S]methionine into tubulin declined by 5- to 15-fold within 4 h. This was mostly accounted for by a rapid decline in the concentration of alpha- and beta-tubulin mRNA in the cytoplasm. Treatment with other microtubule depolymerizing agents (colchicine, nocodazole, low concentrations of vinblastine) had similar effects. Treatment of embryos with the microtubule-stabilizing agent, taxol, or high concentrations of vinblastine resulted in increased synthesis of tubulin. The concentration of tubulin mRNA increases during development and becomes increasingly sensitive to colcemid and decreasingly sensitive to taxol. The transcriptional activity of tubulin genes, estimated by an RNA run-on assay in isolated nuclei, was not altered after colcemid treatment. On the other hand, the rate of decay of tubulin mRNA in prism embryos treated with actinomycin D was increased several fold by colcemid treatment, while taxol treatment led to an increased half-life of tubulin mRNA. These observations suggest that tubulin synthesis is autogenously regulated at the level of mRNA stability by the level of unpolymerized tubulin. The increasing polymerization of microtubules and declining level of unpolymerized tubulin during embryogenesis would result in a stabilization of tubulin mRNA accounting for the increasing concentration of tubulin mRNA and rate of tubulin synthesis, as well as the increasing sensitivity of tubulin synthesis to microtubule-depolymerizing agents. Evidence is also presented for a rapid influence of the level of unpolymerized tubulin on the efficiency of translation of tubulin mRNA.

Microtubule formation from maternal tubulins during sea urchin embryogenesis: measurement of soluble and insoluble tubulin pools

The mass of tubulin protein in developing embryos of the sea urchin Lytechinus pictus was measured using a radiodilution immunoassay based on densitometric analysis of immunoprecipitated tubulins resolved electrophoretically. The tubulins constitute an average of 360 +/- 35 pg per egg, or 0.66% of the total protein, and there is no significant change in their concentration during embryogenesis. The masses of soluble and polymerized tubulin were measured for extracts prepared under conditions that stabilize microtubules. In eggs, a maximum of 14% of the tubulin is insoluble, and this increases throughout embryogenesis to 67% at pluteus stage (72 hr). The concentration of tubulin in eggs is at least 500 micrograms/ml, well above the critical concentration for tubulin assembly in vitro, yet microtubules have not been observed in eggs. The mass of newly synthesized tubulin, estimated from the mass of tubulin mRNA per embryo, accounts for a small fraction of the total tubulin by the end of gastrulation but for over half of the tubulin by the 72-hr pluteus stage. These observations are consistent with a model in which the declining level of unpolymerized tubulin controls the stability of tubulin mRNa, providing an autogenous regulation of the ontogenetic pattern of tubulin synthesis during sea urchin embryogenesis (Gong and Brandhorst, Development 102: 31-43).

Stimulation of tubulin gene transcription by deciliation of sea urchin embryos

Deciliation by hypertonic shock of embryos of the sea urchin Lytechinus pictus resulted in an increase in synthesis of alpha- and beta-tubulins, the consequence of an increased concentration of RNA encoding the tubulins. RNA run-on assays in isolated nuclei indicated that this response is due to a transient increase in the rate of synthesis of tubulin RNA beginning within 5 min of deciliation. This enhancement of tubulin gene transcription also occurred in deciliated embryos treated with the microtubule-depolymerizing agent colcemid; thus the reaction to deciliation is not a response to a reduction in concentration of unpolymerized tubulin utilized for ciliogenesis. In deciliated embryos treated with colcemid, the elevated level of tubulin RNA declined rapidly, due to its destabilization by the elevated concentration of unpolymerized tubulin. The increased transcription of tubulin genes is a response to the loss of cilia, not to the hypertonic shock, and occurs even when cilium regeneration is prevented. Inhibition of protein synthesis with puromycin or emetine did not prevent the transcriptional enhancement but stabilized tubulin mRNA, resulting in increased accumulation of tubulin mRNA after deciliation.

Calmodulin gene expression during sea urchin development: persistence of a prevalent maternal protein

Calmodulin gene expression during embryogenesis of the sea urchin Strongylocentrotus purpuratus was investigated. Several identical bacteriophages containing a cDNA insert encoding sea urchin calmodulin (CM-1) were identified by screening a lambda gt10 library of S. purpuratus gastrula-stage cDNAs with a chicken calmodulin cDNA sequence. A 1.2-kb cDNA fragment from CM-1 was subcloned into pUC-8 to give plasmid pCAL-8. pCAL-8 contains a single open reading frame encoding 79 amino acids, a termination codon, and 0.9 kb of 3'-untranslated message. This sea urchin amino acid sequence shows 95% homology to amino acid residues 69-148 of the predicted sequence of chicken calmodulin. Northern analysis showed that pCAL-8 hybridizes to a single size (3.2 kb) of mRNA in both embryonic and adult somatic tissues. Genome blots suggested that there is a single calmodulin gene in the S. purpuratus genome. We used pCAL-8 to study calmodulin mRNA accumulation in S. purpuratus embryos. Calmodulin mRNA is present in the unfertilized egg at the level of a typical rare-class mRNA (1000-2000 transcripts) and accumulates approximately 100-fold to levels representing about 1/10th of 1% of the total mRNA in pluteus-stage cells. Synthesis of calmodulin, identified by two-dimensional gel electrophoresis, shows a similar developmental pattern. However, in spite of the very active synthesis of calmodulin during embryogenesis, most of the calmodulin in the pluteus is apparently provided for by an enormous store of calmodulin in the egg, corresponding to about 2% of the mass of total protein.