Study on network pharmacology of Ginkgo biloba extract against ischaemic stroke mechanism and establishment of UPLC-MS/MS methods for simultaneous determination of 19 main active components

INTRODUCTION

Ginkgo biloba extract (GBE) is an effective substance from traditional Chinese medicine (TCM) G. biloba for treating ischaemic stroke (IS). However, its active ingredients and mechanism of action remain unclear.

OBJECTIVES

This study aimed to reveal the potential active component group and possible anti-IS mechanism of GBE.

MATERIALS AND METHODS

The network pharmacology method was used to reveal the possible anti-IS mechanism of these active ingredients in GBE. An ultra-high-performance liquid chromatography triple quadrupole electrospray tandem mass spectrometry (UPLC-MS/MS) method was established for the simultaneous detection of the active ingredients of GBE.

RESULTS

The active components of GBE anti-IS were screened by literature integration. Network pharmacology results showed that the anti-IS effect of GBE is achieved through key active components such as protocatechuic acid, bilobalide, ginkgolide A, and so on. Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the possible anti-IS mechanism of GBE is regulating the PI3K-Akt signalling pathway and other signal pathways closely related to inflammatory response and apoptosis regulation combined with AKT1, MAPK, TNF, ALB, CASP3, and other protein targets. Nineteen main constituents in seven batches of GBE were successfully analysed using the established UPLC-MS/MS method, and the results showed that the content of protocatechuic acid, gallic acid, ginkgolide A, and so forth was relatively high, which was consistent with network pharmacology results, indicating that these ingredients may be the key active anti-IS ingredients of GBE.

CONCLUSION

This study revealed the key active components and the anti-IS mechanism of GBE. It also provided a simple and sensitive method for the quality control of related preparations.

[Analysis of 18 cases of malignant rhabdoid tumor in children]

Objective: To investigate the clinical characteristics, treatment and prognosis of malignant rhabdoid tumor (MRT) in children. Methods: Clinical data total of 18 children with MRT treated in the Department of Hematology and Oncology, Children's Hospital, the First Affiliated Hospital of Zhengzhou University between June 2015 to June 2021 were analyzed retrospectively. The patients were grouped according to age, gender, tumor type, clinical stage and other factors.Progression free survival (PFS) and overall survival (OS) were calculated by Kaplan-Meier method, survival differences among different groups were compared by Log-rank test, and prognostic factors were analyzed by Cox regression model. Results: Among the 18 patients, there were 5 males and 13 females. The age of disease onset was 30.5 (12.0, 75.0) months, the tumor diameter was (80±29) mm, and no integrase interactor 1 (INI-1) expression was detected by immunohistochemistry. There were 7 cases of malignant rhabdoid tumor of the kidney (MRTK), 6 cases of atypical teratoid rhabdoid tumor (ATRT) and 5 cases of extrarenal extracranial rhabdoid tumor (EERT). At the time of early diagnosis, 12 patients were clinically stage Ⅲ-Ⅳ, 11 patients had local or distant metastasis, and 4 patients had metastasis during treatment. Surgical excision is the preferred treatment. There were 3 cases with preoperative puncture biopsy, 13 cases with complete resection, 4 cases with partial resection, and 1 case without operation. Thirteen patients were treated with the domestic conventional chemotherapy regimen for Wilms' tumor, medulloblastoma and rhabdomyosarcoma, and 5 patients were treated with the international conventional chemotherapy regimen. Nine patients received radiotherapy, including 1 case of MRTK, 4 cases of ATRT and 4 cases of EERT. By the end of follow-up in January 2022, 7 patients survived and 11 patients died. The 3-year PFS and OS rates were (8±8) % and (14±12) %. Log-rank test showed that the 5-year OS of EERT group was higher than ATRT and MRTK groups (χ²=16.31, P<0.001), the tumor diameter <80 mm group was higher than that of the ≥80 mm group (χ²=4.49, P=0.034), and the radiotherapy group was higher than no radiotherapy group (χ²=3.97, P=0.046). The differences were statistically significant. There was no significant difference in the influence of tumor type, age, tumor diameter, radiotherapy and chemotherapy on OS by Cox regression model (all P>0.05). Log-rank test showed that the 3-year PFS of EERT group was higher than ATRT and MRTK groups (χ²=11.14, P=0.004),>3 years group was higher than ≤3 years group (χ²=10.10, P=0.001), the differences were statistically significant. Tumor type, clinical stage, tumor diameter, age, tumor rupture and radiotherapy were included in the Cox regression model, and the results showed that clinical stage (HR=0.49, 95%CI 0.26-0.94, P=0.031), tumor diameter (HR=8.67, 95%CI 1.84-40.89, P=0.006), age (HR=0.01, 95%CI 0.00-0.15, P=0.001) had statistical significance on PFS. Conclusions: MRT is one of the most aggressive and fatal cancers in early childhood and infancy. There is no standard treatment and the prognosis is extremely poor. Clinical stage, tumor size and age are risk factors for disease progression.

Genetic Structure Analysis of Y Chromosome STR and SNP in Population of Changshu

Abstract

Objective To provide a theoretical basis for building a Y chromosome database in specific regions by analyzing the pedigree specific core haplogroup and region specific genetic structure in Changshu. Methods One thousand seven hundred and two samples from unrelated Han male individuals in Changshu were collected. Then 27 Y-STR were genotyped through YfilerTM Plus PCR Amplification Kit, Y-SNP haplogroup of each sample was speculated using Y-Predictor software and some samples were verified by amplification refractory mutation system-polymerase chain reaction （ARMS-PCR）. Results A total of 1 556 haplotypes were found on the 27 Y-STR genetic markers of the 1 702 samples. The haplotype diversity （HD） value was 0.999 827. DYS385 （0.933） had the highest gene diversity （GD） value while DYS438 （0.409） had the lowest. By the Y-Predictor software, all samples were confirmed to be from 162 sub-haplogroups of C, D, N, O, Q and R. Samples were randomly selected to verify the prediction results by the software and the prediction accuracy of Y-Predictor software was as high as 95.74%. Conclusion This study found that 27 Y-STR genetic markers have relatively high polymorphisms in the Changshu population, and have good forensic individual identification and paternity testing ability.

Molecular Determinants Elucidate the Selectivity in Abscisic Acid Receptor and HAB1 Protein Interactions

The abscisic acid (ABA), as a pivotal plant hormone, plays a key role in controlling the life cycle and adapting to the environmental stresses. The receptors of ABA are the Pyrabactin resistance/Pyrabactin resistance-like/regulatory component of ABA receptors (PYR/PYL/RCAR, PYLs for simplicity), which regulate the protein phosphatase 2Cs (PP2Cs) in the signal pathway. As an important ABA-mimicking ligand, Pyrabactin shows the activation function to parts of members of PYLs, such as PYR1 and PYL1. Due to the antagonism of Pyrabactin to PYL2, it was used as a probe to discover a part of ABA receptors. Since then, many researchers have been trying to find out the determinants of the selective regulation of PYLs and PP2Cs interaction. However, the roles of residues on the selective regulation of PYR1/PYL2 and PP2Cs interaction induced by Pyrabactin are still ambiguous. This research investigated the selective activation mechanism of Pyrabactin through the sequence alignment, molecular docking, molecular dynamics simulation, and binding free energy calculation. Furthermore, the electrostatic and hydrophobic interaction differences induced by Pyrabactin and agonists were compared. The results indicate that Leu137/Val114, Ser85/Ser89, and Gly86/Gly90 from the pocket and gate of PYR1/PYL2 are the vital residues for the selective activation of Pyrabactin. Meanwhile, the electrostatic interaction between PP2Cs and PYLs complexed with agonists was improved. This mechanism provides strong support for the design of selective agonists and antagonists.

[Screening results and influencing factors of upper gastrointestinal carcinoma and precancerous lesions in Feicheng City]

Objective: To clarify the situation of the detection of upper gastrointestinal cancer and precancerous lesions in the Feicheng city and discuss the possible influencing factors. Methods: A cluster sampling method was used to determine the participants. A unified questionnaire was used to investigate the basic information including history of alcohol intake, smoking and chinese tea, as well as other eating habits, medical history of digestive tract and cancer. Endoscopy was used to to screen the patients with upper gastrointestinal cancer and precancerous lesions. Influential factors were explored by non-conditional logistic regression model. Results: 911 of 7 291participants were positive, and the total detection rate was 12.49%. The total positive detection rate of male and female was 17.94% and 8.71%, respectively (P<0.001). Multivariate logistic regression analysis showed that the sex (OR=0.527, 95%CI: 0.440-0.631), age (OR=2.037, 95%CI: 1.849-2.245), smoking (OR=1.240, 95%CI: 1.014-1.516) and alcohol consumption (OR=1.232, 95%CI: 1.012-1.500) , meat and protein intake (OR=0.794, 95%CI: 0.638-0.987) and drink tea (OR=1.233, 95%CI: 1.056-1.440) may be influencing factors of the total detection rate of upper gastrointestinal cancer and precancerosis. Conclusions: In Feicheng city, intake of meat and protein is the protective factor of the upper gastrointestinal cancer and precancerous lesions. Men, aged, smoking, drinking and tea will increase the risk of upper gastrointestinal cancer and precancerous lesions.

Computational Discovery of Potent and Bioselective Protoporphyrinogen IX Oxidase Inhibitor via Fragment Deconstruction Analysis

Tuning the binding selectivity through appropriate ways is a primary goal in the design and optimization of a lead toward agrochemical discovery. However, how to achieve rational design of selectivity is still a big challenge. Herein, we developed a novel computational fragment generation and coupling (CFGC) strategy that led to a series of highly potent and bioselective inhibitors targeting protoporphyrinogen IX oxidase. This enzyme plays a vital role in heme and chlorophyll biosynthesis, which has been proven to be associated with many drugs and agrochemicals. However, existing agrochemicals are nonbioselective, resulting in a great threat to nontargeted organisms. To the best of our knowledge, this is the first bioselective inhibitor targeting the tetrapyrrole biosynthesis pathway. In addition, the candidate showed excellent in vivo bioactivity and much better safety toward humans.

Human umbilical cord mesenchymal stem cells improve the reserve function of perimenopausal ovary via a paracrine mechanism

Background

Human umbilical cord mesenchymal stem cells (hUCMSCs) are a type of pluripotent stem cell which are isolated from the umbilical cord of newborns. hUCMSCs have great therapeutic potential. We designed this experimental study in order to investigate whether the transplantation of hUCMSCs can improve the ovarian reserve function of perimenopausal rats and delay ovarian senescence.

Method

We selected naturally aging rats confirmed by vaginal smears as models of perimenopausal rats, divided into the control group and the treatment group, and selected young fertile female rats as normal controls. hUCMSCs were transplanted into rats of the treatment group through tail veins. Enzyme-linked immunosorbent assay (ELISA) detected serum levels of sex hormones, H&E staining showed ovarian tissue structure and allowed follicle counting, immunohistochemistry and western blot analysis revealed ovarian expression of hepatocyte growth factor (HGF), vascular endothelial cell growth factor (VEGF), and insulin-like growth factor-1 (IGF-1), polymerase chain reaction (PCR) and western blot analysis revealed hUCMSCs expression of HGF, VEGF, and IGF-1.

Results

At time points of 14, 21, and 28 days after hUCMSCs transplantation, estradiol (E₂) and anti-Müllerian hormone (AMH) increased while follicle-stimulating hormone (FSH) decreased; ovarian structure improved and follicle number increased; ovarian expression of HGF, VEGF, and IGF-1 protein elevated significantly. Meanwhile, PCR and western blot analysis indicated hUCMSCs have the capacity of secreting HGF, VEGF, and IGF-1 cytokines.

Conclusions

Our results suggest that hUCMSCs can promote ovarian expression of HGF, VEGF, and IGF-1 through secreting those cytokines, resulting in improving ovarian reserve function and withstanding ovarian senescence.

[Drug resistance and influencing factors in adult AIDS patients receiving antiretroviral treatment in Dehong, Yunnan province]

OBJECTIVE

To investigate the incidence of drug resistance in adult AIDS patients receiving antiretroviral treatment(ART)and influencing factors in Dehong prefecture, Yunnan province during 2012-2014.

METHODS

For this cohort study, all the AIDS patients aged over 15 and receiving ART in Dehong were screened for HIV drug resistance in 2012, and 3 715 patients who had received ART for more than 6 months were enrolled for 12 months and 24 months follow up.

RESULTS

Among the 3 715 patients, 56.6% were males, 72.6% were aged 26-45 years and 76.0% were married. The main treatment regimen was nevirapine(NVP)+ lamivudine(3TC)+ zidovudine(AZT)(38.2%). A total of 3 556 patients(95.7%)received at least one viral load testing during the two years follow-up, among them 253(7.1%)patients had VL≥1 000 copies/ml, in which 211(83.4%)received drug resistance related gene mutation testing, the results indicated that the drug resistance developed in 52 and 39 patients in 2013 and 2014(1.43 per 100 person years and 0.88 per 100 person years)respectively. The overall HIV drug incidence was 1.13 per 100 person years. Multivariate regression analysis indicated that age ≤25 years, to be infected through drug use, treatment regimen as D4T+ 3TC +NVP and baseline CD4(+) T cells ≤200 cells/μl were the risk factor of HIV drug resistance. Eleven HIV gene subtypes were detected in the 82 patients with newly developed drug resistance, CRF_BC was predominant(31.7%), followed by CRF01_AE(22.0%)and C(19.5%). Ten patients were infected with mixed subtypes of CRF_BC/B', CRF_BC/CRF_01B and CRF_BC/C. Most of the 82 patients were resistant to NRTIs and NNRTIs, the main mutation loci were M184V and K103N.

CONCLUSIONS

The incidence of drug resistance in adult AIDS patients receiving ART was relatively low in Dehong. However, it is necessary to conduct the health education in young people and drug users to improve the treatment compliance and strengthen the surveillance for HIV drug resistance.

Shape of glucose curve can be used as a predictor for screening prediabetes in obese children

AIM

We attempted to classify obese children with glucose abnormalities into different categories based on the plasma glucose (PG) at 0, 60, 120 and 180 min and extract the metabolic information from the shape of the PG curve.

METHODS

We recruited 1205 obese children and 325 nonobese children. Their body weight, blood pressure, waist and hip circumferences were measured. An oral glucose tolerance test (OGTT) was carried out, and glucose, insulin and glucagon levels were tested.

RESULTS

There were six forms of abnormal glucose tolerance (AGT) curves in obese children in addition to normal glucose tolerance (NGT). 58.3% of obese children had AGT. BMI, waist circumference, waist-to-hip ratio and systolic blood pressure of each obese group were much higher than in nonobese children (p < 0.05). HOMA-IR increased significantly in obese children with high fasting PG and obese children with high fasting and 3-h PG (p < 0.05), and HOMA-β cell increased significantly in obese children with high 1- and 2-h but low 3-h PG (p < 0.05).

CONCLUSION

Abnormal glucose tolerance was highly prevalent when concerning with glucose values at 60 and 180 min. The shape of PG which contains a net of metabolic information can be a predictor for screening prediabetes.

[Effect of early high fat diet on pancreatic β cellularity and insulin sensibility in young rats]

OBJECTIVE

To study the effects of early high fat diet on sugar metaboliam, insulin sensibility and pancreatic β cellularity in young rats.

METHODS

Sixty male weaned young rats were randomly fed with high fat diet (high fat group) and normal diet (control group). The body weight, viscus fattiness and fasting plasma glucose (FPG) were measured after 3, 6 and 9 weeks. Serum insulin level was measured with radioimmunoassay. The ultrastructure of pancreas was observed under an electricmicroscope.

RESULTS

The high fat group had significantly higher body weight and visceral fat weight than the control group after 3 weeks. There were no significant differences in the FPG level between the two groups at all time points. The levels of fasting insulin and HOMAIR in the high fat group were significantly higher than those in the control group after 3, 6 and 9 weeks (P<0.01). Dilation of rough endoplasmic reticulum and mild swelling of mitochondria of islet β-cells were observed in the high fat group after 6 weeks.

CONCLUSIONS

Early high fat diet may induce a reduction in insulin sensitivity and produce insulin resistance in young rats. Endoplasmic reticulum expansion in β-cells may be an early sign of β-cell damage due to obesity.

[Dynamic expression of matrix metalloproteinases 2 and 8 in rat cervix]

OBJECTIVE

To elucidate the relationship between collagen degradation and cervical ripening by detecting dynamic expressions of matrix metalloproteinases 2 (MMP-2) and 8 (MMP-8) in rat cervix.

METHOD

SPF rats were divided into 5 groups (n=6), namely non-pregnancy estrus interval group, gestational days 10, 16, and 19 groups, and immediately postpartum group. The wet weight of the cervix was measured and HE staining was used to display the general structure of the cervix. VG staining was applied to visualize the collagen fibers and muscular fibers. Immunohistochemistry was performed to observe the expressions of MMP-2 and MMP-8 in the cervix.

RESULTS

HE staining showed that the rat uterine cervix consisted mainly of fibroblasts and fibrous connective tissues. A small quantity of neutrophils could be seen in the cervix stroma of the rats immediately after immediately parturition, but not at the other time points. The wet weight of the antepartum cervix had increased, and a more obvious increase was seen in the wet weight of the cervix immediately after parturition. The collagen fibers of the cervix consisted of collagen fibers and smooth muscle fibers, and their proportions showed no significant variation at the time points around the parturition. Immediately after parturition, the collagen fibers and muscular fibers in the cervix became loosened as compared with that before parturition. MMP-2 expression was found in the cervical stroma but not in the squamous epithelium in nonpregnancy, term pregnancy, and immediately after parturition; the smooth muscle cells, vascular wall, and stromal fibroblasts showed positive expression of MMP-2. Enhanced intensity of MMP-2 staining was seen in term pregnancy and postpartum group in comparison with that in the other groups. MMP-8 expression was observed in the cervix of rats immediately after parturition, with scattered neutrophils positive for MMP-8 spotted in the stroma of the ripened cervix. MMP-8 expression was not detected in the other groups.

CONCLUSION

Ripened cervical fibrous tissue becomes loose and broken, and cervical ripening is accompanied by infiltration of neutrophils from exogenous vessels. These changes are particularly evident after parturition. MMP-2 and MMP-8 cooperate to degrade the cervical fibers, leading to cervical softening and expansion.

Modification of granular activated carbon using low molecular weight polymer for enhanced removal of Cu(2+) from aqueous solution

Palm shell activated carbon was modified via surface impregnation with polyethyleneimine (PEI) to enhance removal of Cu(2+) from aqueous solution in this study. The effect of PEI modification on batch adsorption of Cu(2+) as well as the equilibrium behavior of adsorption of metal ions on activated carbon were investigated. PEI modification clearly increased the Cu(2+) adsorption capacities by 68% and 75.86% for initial solution pH of 3 and 5 respectively. The adsorption data of Cu(2+) on both virgin and PEI-modified AC for both initial solution pH of 3 and 5 fitted the Langmuir and Redlich-Peterson isotherms considerably better than the Freundlich isotherm.

High-density lipoprotein as a potential carrier for delivery of a lipophilic antitumoral drug into hepatoma cells

AIM: To investigate the possibility of recombinant high-density lipoprotein (rHDL) being a carrier for delivering antitumoral drug to hepatoma cells.

METHODS: Recombinant complex of HDL and aclacinomycin (rHDL-ACM) was prepared by cosonication of apoproteins from HDL (Apo HDL) and ACM as well as phosphatidylcholine. Characteristics of the rHDL-ACM were elucidated by electrophoretic mobility, including the size of particles, morphology and entrapment efficiency. Binding activity of rHDL-ACM to human hepatoma cells was determined by competition assay in the presence of excess native HDL. The cytotoxicity of rHDL-ACM was assessed by MTT method.

RESULTS: The density range of rHDL-ACM was 1.063-1.210 g/mL, and the same as that of native HDL. The purity of all rHDL-ACM preparations was more than 92%. Encapsulated efficiencies of rHDL-ACM were more than 90%. rHDL-ACM particles were typical sphere model of lipoproteins and heterogeneous in particle size. The average diameter was 31.26±5.62 nm by measure of 110 rHDL-ACM particles in the range of diameter of lipoproteins. rHDL-ACM could bind on SMMC-7721 cells, and such binding could be competed against in the presence of excess native HDL. rHDL-ACM had same binding capacity as native HDL. The cellular uptake of rHDL-ACM by SMMC-7721 hepatoma cells was significantly higher than that of free ACM at the concentration range of 0.5-10 µg/mL (P<0.01). Cytotoxicity of rHDL-ACM to SMMC-7721 cells was significantly higher than that of free ACM at concentration range of less than 5 µg/mL (P<0.01) and IC50 of rHDL-ACM was lower than IC50 of free ACM (1.68 nmol/L vs 3 nmol/L). Compared to L02 hepatocytes, a normal liver cell line, the cellular uptake of rHDL-ACM by SMMC-7721 cells was significantly higher (P<0.01) and in a dose-dependent manner at the concentration range of 0.5-10 μg/mL. Cytotoxicity of the rHDL-ACM to SMMC-7721 cells was significantly higher than that to L02 cells at concentration range of 1-7.5 μg/mL (P<0.01). IC50 for SMMC-7721 cells (1.68 nmol/L) was lower than that for L02 cells (5.68 nmol/L), showing a preferential cytotoxicity of rHDL-ACM for SMMC-7721 cells.

CONCLUSION: rHDL-ACM complex keeps the basic physical and biological binding properties of native HDL and shows a preferential cytotoxicity for SMMC-7721 hepatoma to normal L02 hepatocytes. HDL is a potential carrier for delivering lipophilic antitumoral drug to hepatoma cells.

[Bt gene flow of transgeic cotton]

This study was carried out to determine the gene flow of transgenic cotton under Chinese ecological environment. Transgenic cotton GK-12 containing the marker gene NPTII and Bt gene was planted in the 6 x 6 m2 plot, non-transgenic cotton CCRC 12 and Xinmian 13 were planted respectively around them. At varying distances from transgenic cotton, seeds produced by the non-transgenic cotton were collected and screened for marker gene and Bt gene using kanamycine sulphate and Dot-ELISA method. PCR technique was also used in some seeds to screen Bt gene. The result indicated that gene flow was found to be high at 0-6 m, and to decrease with distances; however gene flow occurred up to distance of 36 m from the transgenic cotton plot. Bt gene flow at 3-6 m increased with increasing the diversity of transgenic cotton in the plot, but gene flow increased little at long distance. The gene flow between species was lower than between cultivars at 0-6 m, and occurred at the distance of 72 m from transgenic plot. 72 m buffer zones would serve to limit gene flow of transgenic cotton from small-scale field test. The possibility of escapes of engineered gene to wild relatives of cotton species was also discussed.

Guinea pig cytomegalovirus immediate-early transcription

Guinea pig cytomegalovirus (GPCMV) immediate-early (IE) gene expression was analyzed. GPCMV IE RNA was defined as RNA obtained from GPCMV-infected guinea pig cells treated with cycloheximide for 1 h before infection and for 4 h postinfection. Mapping studies showed that GPCMV IE genes are located at several distinct sites on the GPCMV genome. A total of 17 GPCMV IE transcripts were identified, and 9 IE transcripts coded for by three specific regions of the genome (regions I, II, and III) were characterized in detail. A series of recombinant DNA clones were generated to identify the nine IE transcripts. Three of the IE transcripts from region I and three from region III were transcribed in the same direction from overlapping sequences. The 2.0-kilobase (kb) transcript encoded by the EcoRI E DNA fragment (region II) was the most abundant IE GPCMV transcript. The cloned GPCMV DNA subfragment that was used to identify the region II EcoRI E 2.0-kb transcript did not hybridize to GPCMV early or late RNA, indicating that this transcript is expressed only under IE conditions. Expression of RNAs from the IE genes was also measured during a natural GPCMV infection in the absence of cycloheximide. During the natural infection, the transcripts previously identified under IE cycloheximide block conditions were expressed, and the region II EcoRI E 2.0-kb transcript was the most abundant transcript at 1 h postinfection. In addition, a rise and fall in RNA levels was observed during the natural infection, demonstrating the transient nature of expression of these transcripts. We conclude that GPCMV IE gene expression is complex, involving a reasonably large number of genes, and demonstrates some similarities with IE transcription by other CMVs.

An analysis of the metabolism and cell wall composition of Candida albicans during germ-tube formation

The uptake of nutrients (glucose, glutamine, and N-acetylglucosamine), the intracellular concentrations of metabolites (glucose-6-phosphate, cyclic AMP, amino acids, trehalose, and glycogen) and cell wall composition were studied in Candida albicans. These analyses were carried out with exponential-phase, stationary-phase, and starved yeast cells, and during germ-tube formation. Germ tubes formed during a 3-h incubation of starved yeast cells (0.8 X 10(8) cells/mL) at 37 degrees C during which time the nutrients glucose plus glutamine or N-acetylglucosamine (2.5 mM of each) were completely utilized. Control incubations with these nutrients at 28 degrees C did not form germ tubes. Uptake of N-acetylglucosamine and glutamine was inhibited by cycloheximide which suggests that de novo protein synthesis was required for the induction of these uptake systems. The glucose-6-phosphate content varied from 0.4 nmol/mg dry weight for starved cells to 2-3 nmol/mg dry weight for growing yeast cells and germ tube forming cells. Trehalose content varied from 85 nmol/mg dry weight (growing yeast cells and germ tube forming cells) to 165 nmol/mg weight (stationary-phase cells). The glycogen content decreased during germ-tube formation (from 800 to 600 nmol glucose equivalent/mg dry weight) but increased (to 1000 nmol glucose equivalent/mg dry weight) in the control incubation of yeast cells. Cyclic AMP remained constant throughout germ-tube formation at 4-6 pmol/mg dry weight. The total amino acid pool was similar in exponential, starved, and germ tube forming cells but there were changes in the amounts of individual amino acids. The overall cell wall composition of yeast cells and germ tube forming cells were similar: lipid (2%, w/w); protein (3-6%), and carbohydrate (77-85%). The total carbohydrates were accounted for as the following fractions: alkali-soluble glucan (3-8%), mannan (20-23%), acid-soluble glucan (24-27%), and acid-insoluble glucan (18-26%). The relative amounts of the alkali-soluble and insoluble glucan changed during starvation of yeast cells, reinitiation of yeast-phase growth, and germ-tube formation. Analysis of the insoluble glucan fraction from cells labelled with [14C]glucose during germ-tube formation showed that the chitin content of the cell wall increased from 0.6% to 2.7% (w/w).

Germ tube induction in Candida albicans

A reproducible and simple system for the production of germ tubes from yeast cells of Candida albicans using glucose and glutamine as substrates has been described. During germ tube formation there was a doubling of the dry weight but the number of cells remained constant. Although the DNA content did not change for the first 4 h of germ tube formation, the RNA content more than doubled. The DNA and RNA content of C. albicans blastospores are 4.5 x 10(-15) g per cell and 48 x 10(-15) g per cell respectively. Nystatin, phenethyl alcohol, 2,4-dinitrophenol, azaserine, salicylhydroxamic acid, and 5-fluorocytosine were all effective inhibitors of germ tube formation. Cysteine, potassium cyanide, and polyoxin D did not prevent germination. The incorporation of both uracil and leucine occurred rapidly during germ tube formation. The inhibitors of RNA synthesis, actinomycin D. cordycepin, and daunomycin prevented germination and inhibited uracil incorporation. The translational inhibitors, trichodermin, aurin tricarboxylic acid, puromycin, and cyloheximide were effective in inhibiting both germ tube formation and leucine incorporation.