Plant biology. Pollen tube guidance--right on target.
Explore the source record for details and available documents.
Adhesiveness↗
Biomedical subjects
A Y Cheung
Publications and source records attributed to A Y Cheung.
Hydroxyproline-rich glycoproteins in plant reproductive tissues: structure, functions and regulation.
The plant reproductive process of pollination involves a series of interactions between the male gametophyte (the pollen grain or pollen tube) and extracellular matrix (ECM) molecules secreted by different cell types along the pollen tube growth pathway in the female organ, the pistil. These interactions are believed to signal and regulate the pollen tube growth process to effect successful delivery of the sperm cells to the ovules where fertilization takes place. Hydroxyproline-rich glycoproteins secreted by plant cells are believed to play a broad range of functions, ranging from providing structural integrity to mediating cell-cell interactions and communication. The pistil and pollen tube ECM is enriched in these highly glycosylated proteins. Our discussions here will focus on a number of these proteins for which most information has been available, from Nicotiana tabacum, its self-incompatible relative N. alata, and Zea mays. In addition, the regulation of the synthesis and glyco-modification of one of these proteins, TTS (transmitting tissue-specific) protein from N. tabacum will be discussed in the light of how differential glycosylation may be used to regulate molecular interactions within the ECM.
Extracellular Matrix↗
Polarized cell growth in higher plants.
Pollen tubes and root hairs are highly elongated, cylindrically shaped cells whose polarized growth permits them to explore the environment for the benefit of the entire plant. Root hairs create an enormous surface area for the uptake of water and nutrients, whereas pollen tubes deliver the sperm cells to the ovule for fertilization. These cells grow exclusively at the apex and at prodigious rates (in excess of 200 nm/s for pollen tubes). Underlying this rapid growth are polarized ion gradients and fluxes, turnover of cytoskeletal elements (actin microfilaments), and exocytosis and endocytosis of membrane vesicles. Intracellular gradients of calcium and protons are spatially localized at the growing apex; inward fluxes of these ions are apically directed. These gradients and fluxes oscillate with the same frequency as the oscillations in growth rate but not with the same phase. Actin microfilaments, which together with myosin generate reverse fountain streaming, undergo rapid turnover in the apical domain, possibly being regulated by key actin-binding proteins, e.g., profilin, villin, and ADF/cofilin, in concert with the ion gradients. Exocytosis of vesicles at the apex, also dependent on the ion gradients, provides precursor material for the continuously expanding cell wall of the growing cell. Elucidation of the interactions and of the dynamics of these different components is providing unique insight into the mechanisms of polarized growth.
Actin Cytoskeleton↗
The effect of vertebral rotation of the lumbar spine on dual energy X-ray absorptiometry measurements: observational study.
OBJECTIVE: To estimate how axial rotation of lumbar vertebrae quantitatively affects bone mineral density, as measured by dual energy X-ray absorptiometry in the anteroposterior plane. DESIGN: Observational study. SETTING: University teaching hospital, Hong Kong. PATIENTS: Cadaver lumbar vertebrae (L2 to L4) were removed from four adults. MAIN OUTCOME MEASURES: Using dual energy X-ray absorptiometry, the bone mineral content, bone area, and bone mineral density were measured in the neutral position and with vertebral axial rotation in increments of 7.5 degrees, up to a maximum of 45 degrees. RESULTS: Correlation analysis showed a significant positive correlation between the degree of rotation and measured bone area, a significant negative correlation between degree of rotation and bone mineral density measurements, but no significant correlation between degree of rotation and measured bone mineral content. The measured bone area increased approximately 24% and the bone mineral density decreased approximately 19% when the vertebrae were rotated by 45 degrees. CONCLUSIONS: These results suggest that for patients with rotational deformity of the spine, such as scoliosis, measurements of lumbar spine bone mineral content by dual energy X-ray absorptiometry is not affected, while bone mineral density measurements are not reliable.
Absorptiometry, Photon↗
A pollen tube growth-promoting arabinogalactan protein from nicotiana alata is similar to the tobacco TTS protein.
Upon germination on the stigma, pollen tubes elongate in the stylar transmitting tract, aided by female factors, with speed and directionality not mimicked in in vitro pollen tube growth cultures. We have shown that a stylar transmitting tissue arabinogalactan protein (AGP) from Nicotiana tabacum (tobacco), TTS protein, stimulates pollen tube growth in vivo and in vitro and attracts pollen tubes grown in a semi-in vivo culture system. It has been reported that the self-incompatible Nicotiana alata produced a stylar glycoprotein, GaRSGP, which had a backbone polypeptide that shared 97% identity with those of TTS proteins but some of its properties were different from those described for TTS proteins. We report here the characterization of a family of stylar transmitting tissue glycoproteins from N. alata that is virtually identical to tobacco TTS proteins and which we refer to as NaTTS proteins. Like their tobacco counterparts, NaTTS proteins are recognized by the traditional AGP-diagnostic reagent beta-glucosyl Yariv reagent, and they are also recognized by JIM13, a monoclonal antibody against AGP. NaTTS proteins also stimulate pollen tube elongation in vitro and attract pollen tubes in a semi-in vivo pollen tube culture system. Biochemical and immunological characterization of NaTTS proteins revealed that they have extraordinary variability in the extent of sugar modifications of their polypeptide backbones. The extent of sugar modifications on NaTTS proteins significantly affects their biochemical properties, influences how they interact with the transmitting tissue extracellular matrix, and affects their solubility from this matrix. Our results suggest that the strategy used to purify GaRSGP only recovered a less glycosylated, more tightly extracellular matrix-bound sub-population of the entire spectrum of N. alata TTS proteins.
Electrophoresis, Gel, Two-Dimensional↗
Metastatic adenocarcinoma of the uterine cervix to the thyroid gland.
Clinically diagnosed metastasis to the thyroid gland is rare. The authors present the first reported case of metastasis to the thyroid gland from a primary adenocarcinoma of the uterine cervix.
Adenocarcinoma↗
Outcomes and prognostic factors of Chinese children with acute lymphoblastic leukemia in Hong Kong: preliminary results.
BACKGROUND: The Chinese population is the biggest ethnic group in the world. However, there are few reports on the treatment outcome of childhood acute lymphoblastic leukaemia (ALL) among the Chinese population. PROCEDURE: Sixty-five children with ALL were treated with a modified protocol of the Medical Research Council United Kingdom Acute Lymphoblastic Leukaemia protocol X(MRC UKALL X) at the Prince of Wales Hospital, Hong Kong. Most patients were ethnic Chinese. They were divided into groups A and B, depending on whether their presenting leucocyte count being was less or greater than 50 x 10(9)/l, respectively. Group A patients of received induction, early intensification (week 5), cranial irradiation, and maintenance for 3 years. Group B patients received an additional late intensification (week 20). RESULTS: The median follow-up duration was 6.8 years(range: 3.4-10.1 years). The event-free and overall survival rates of all patients at 7 years were 66% (confidence interval [CI] 53-76) and 75% (CI 63-84), respectively. The event-free survival rates of groups A and B at 7 years were 67% (CI 52-79) and 60% (CI 32-80), respectively (P= 0.39). The overall survival rates of groups A and B at 7 years were 80% (CI 66-89) and 60% (CI 32-80), respectively (P = 0.07). With this treatment protocol, the factors which adversely affected the outcome were age (<2 years and >10 years) and T-cell subtype. Sex, white blood count at diagnosis, and FAB subtypes were not statistically significant prognostic factors. CONCLUSIONS: The treatment outcomes were comparable with those reported from the MRC UKALL X trials.
Adolescent↗
Two-hour post-glucose loading plasma glucose is the main determinant for the progression from impaired glucose tolerance to diabetes in Hong Kong Chinese.
Explore the source record for details and available documents.
Blood Glucose↗
Hydroxyurea-induced fever in cervical carcinoma: case report and review of the literature.
This is a case presentation of a rarely seen hydroxyurea-induced fever in a patient with cervical adenocarcinoma receiving oral hydroxyurea given concurrently with external beam radiotherapy to the pelvis. In the fourth week of treatment, the patient developed recurrent febrile episodes, with no obvious etiology. Eventually, hydroxyurea was discontinued with no further recurrence of fever. A review of the medical literature on fever induced by hydroxyurea suggests a mechanism of delayed hypersensitivity. Since hydroxyurea is an often-used chemotherapeutic drug for various malignancies, clinical oncologists need to be aware of this unusual side effect. The diagnosis is by clinical exclusion and by the recurrent pattern of fever on rechallenge of the drug.
Adenocarcinoma↗
Evaluation of modern pathologic nomenclature, tumor imaging and treatment of pituitary adenomas in a recent surgical series.
This study reviews retrospectively 49 patients with pituitary adenomas, using a modern, immunohistochemically and ultrastructurally-based nomenclature. It also compares tumor imaging by CT and MRI scans, and analyzes the results of recent neurosurgical and radiotherapeutic treatments. Based on the findings of the study, several recommendations on clinical management of pituitary macroadenoma are made.
Adenoma↗
Determinants of axial and peripheral bone mass in Chinese adolescents.
OBJECTIVE: To determine the relation of puberty, physical activity, physical fitness, and calcium intake with bone mineral content (BMC) of the distal radius, and on bone mineral density (BMD) of the L2 to L4 vertebrae in a group of healthy Chinese adolescents. DESIGN: Cross sectional survey. SUBJECTS: A group of 179 healthy Chinese adolescents (92 boys and 87 girls) aged 12 to 13 years enrolled in the first year of the Tii Junior High School in Shatin, Hong Kong. Ninety four of the pupils enrolled were in the physical education major class (PE), and the other 85 were in the art major class (ARTS). MAIN OUTCOME MEASURES: Correlation of BMC of the distal radius and BMD of the L2 to L4 vertebrae with level of physical activity, physical fitness (isometric and isokinetic), muscle strength of the upper and lower limb, and calcium intake. RESULTS: BMC of the distal radius and BMD of the L2 to L4 vertebrae were significantly positively correlated. Univariate and regression analysis showed that age, pubertal staging, physical fitness, and muscle strength were significantly associated with bone mass in a positive way. Calcium intake and type of sport practised did not exert a significant influence on BMC of the distal radius and BMD of the L2 to L4 vertebrae in boys. The results for the BMD of the L2 to L4 vertebrae were similar in girls and boys; however, in girls, the BMC of the distal radius had a negative correlation with calcium intake. Physical fitness was a significant positive predictor of BMD of the L2 to L4 vertebrae. CONCLUSIONS: Among Chinese adolescents bone mass was positively influenced by certain measures of physical fitness as well as by age, weight, and pubertal stage.
Adolescent↗
Secular trend in the sexual maturation of southern Chinese girls.
In 1993, a cross-sectional study of sexual maturation of normal Chinese schoolgirls was performed in Hong Kong. The aim of the study was to obtain an up-to-date reference for normal pubertal development in Chinese girls. Breast development was assessed in 3749 girls aged 7-19 y, and pubic hair rating was assessed in 3745 girls. Menstrual status was recorded in 6467 girls over 6 y of age. The median age of onset of puberty as indicated by breast stage II or above was 9.78 (95% CI 9.70-9.85) y. The median age of onset of pubic hair development was 11.64 (95% CI 11.56-11.72) y. The median age of menarche was 12.38 (95% CI 11.98-12.78) years. Percentile values for the age at which each puberty staging appeared were constructed and incorporated into the height-for-age charts. When comparison is made with similar studies done in 1962 and 1979, a significant downward secular trend in sexual maturation is observed (p < 0.01). Except for breast development the downward secular trend in sexual maturation appears to be diminishing and may be coming to a halt in the Chinese girls in Hong Kong. Their median ages of sexual maturation are now among one of the earliest medians recorded in the world population studied.
Adolescent↗
Locally advanced head and neck cancer: combined chemotherapy and radical radiation therapy for organ and function preservation (interim report).
PURPOSE: This phase II study was performed to assess the feasibility of organ preservation after combined chemotherapy and radical radiation therapy in patients with resectable, locally advanced head and neck cancer. MATERIALS AND METHODS: Twenty-four patients had surgically resectable stage III (n = 9) and stage IV (n = 15) squamous cell carcinoma of the head and neck. Initially, they received two to three courses of neoadjuvant chemotherapy (5-fluorouracil and cisplatin). Patients in whom response was seen were then treated definitively with two courses of cisplatin chemotherapy administered concomitantly with radical radiation therapy. Patients in whom no response was seen underwent salvage surgery or other standard therapy. RESULTS: The response rate after induction chemotherapy was 84% (including 42% complete remission). Complete remission after concomitant chemotherapy and radical radiation therapy was 83%. After a median follow-up of 18 months (maximum, 3.5 years), 18 patients (75%) remained recurrence free. Grade 3 or 4 treatment-related toxicity was experienced, but there was no treatment-related mortality. CONCLUSION: Combined chemotherapy and radical radiation therapy used in this study resulted in organ and function preservation in the majority of patients with resectable stage III and IV head and neck cancer.
Adult↗
Tuberculoma of the liver presenting as a hyperechoic mass on ultrasound.
An unusual case of hepatic macronodular tuberculoma is presented. As demonstrated by CT, the tuberculoma replaced the entire lateral segment of the left lobe of liver and resembled an infiltrative tumour. On ultrasound, the tuberculoma presented as a hyperechoic lesion, in contrast to a round hypoechoic mass which is usually seen in this condition. Hepatic macronodular tuberculomas are not uncommonly misdiagnosed as primary or secondary liver tumours by imaging studies, and the definite diagnosis is usually established by liver biopsy. The prognosis of hepatic macronodular tuberculoma is usually very good with effective treatment.
Adult↗
Predictors of relapse in elderly diabetic patients admitted with sulphonylurea-induced severe hypoglycaemic attacks.
Explore the source record for details and available documents.
Aged↗
Organ-specific and Agamous-regulated expression and glycosylation of a pollen tube growth-promoting protein.
Transmitting tissue-specific (TTS) protein is a pollen tube growth-promoting and attracting glycoprotein located in the stylar transmitting tissue extracellular matrix of the pistil of tobacco. The TTS protein backbones have a deduced molecular mass of about 28 kDa, whereas the glycosylated stylar TTS proteins have apparent molecular masses ranging between 50 and 100 kDa. TTS mRNAs and proteins are ectopically produced in transgenic tobacco plants that express either a cauliflower mosaic virus (CaMV) 35S promoter-TTS2 transgene or a CaMV 35S-promoter-NAG1 (NAG1 = Nicotiana tabacum Agamous gene) transgene. However, the patterns of TTS mRNA and protein accumulation and the quality of the TTS proteins produced are different in these two types of transgenic plants. In 35S-TTS transgenic plants, TTS mRNAs and proteins accumulate constitutively in vegetative and floral tissues. However, the ectopically expressed TTS proteins in these transgenic plants accumulate as underglycosylated protein species with apparent molecular masses between 30 and 50 kDa. This indicates that the capacity to produce highly glycosylated TTS proteins is restricted to the stylar transmitting tissue. In 35S-NAG transgenic plants, NAG1 mRNAs accumulate constitutively in vegetative and floral tissues, and TTS mRNAs are induced in the sepals of these plants. Moreover, highly glycosylated TTS proteins in the 50- to 100-kDa molecular mass range accumulate in the sepals of these transgenic, 35S-NAG plants. These results show that the tobacco NAGI gene, together with other yet unidentified regulatory factors, control the expression of TTS genes and the cellular capacity to glycosylate TTS proteins, which are normally expressed very late in the pistil developmental pathway and function in the final stage of floral development. The sepals in the transgenic 35S-NAG plants also support efficient pollen germination and tube growth, similar to what normally occurs in the pistil, and this ability correlates with the accumulation of the highest levels of the 50- to 100-kDa glycosylated TTS proteins.
Caulimovirus↗
Prevalence and prognostic significance of tumor-associated tissue eosinophilia in nasopharyngeal carcinoma.
BACKGROUND: Tumor-associated tissue eosinophilia (TATE) has been associated with an improved prognosis in a variety of neoplasms. METHODS: Diagnostic biopsy specimens from 96 patients with nasopharyngeal carcinoma (NPC) were reviewed for the presence of TATE by an observer blinded to the patients' clinical histories. Comparisons between patients with and without TATE with respect to the probabilities of local recurrence, distant metastasis, and survival were performed using the log rank test on Kaplan-Meier product-limit estimates and the Cox proportional hazards model. RESULTS: The prevalence of TATE in these patients was 32%, and was not significantly associated with local recurrence, distant metastasis, or survival. CONCLUSIONS: These results are discordant with those of studies in other tumor models, although comparison is hampered by varying definitions of TATE. The differing results may be due to variations in the degree of activation of the eosinophils present in TATE in different tumors.
Carcinoma↗
Pollination induces mRNA poly(A) tail-shortening and cell deterioration in flower transmitting tissue.
Pollination induces many physiological responses in the flower, including deterioration and death in specific pistil cell types. It is shown here that within the style of tobacco, pollination-induced cell deterioration was restricted to the transmitting tissue while the surrounding cortical tissue was not affected. It was distinct from general senescence since exogenously applying the senescence-inducing hormone ethylene, or its precursor aminocyclopropane-1-carboxylic acid (ACC), to the flower or the pistil induced overall deterioration in the entire flower. Furthermore, both pollen tube growth and ethylene action were needed for the entire spectrum of cellular changes associated with this pollination-induced transmitting tissue deterioration process. It is also shown that pollination-induced mRNA poly(A) tail-shortening for at least three major classes of transmitting tissue-specific mRNAs. As is commonly observed for poly(A) tail-shortened mRNAs, the levels of two of these three mRNA classes decline after pollination. On the other hand, the third class of mRNAs, transmitting tissue-specific (TTS) mRNAs, was maintained at a very high level subsequent to pollination, even after substantial poly(A)-tail shortening. TTS mRNAs encode a pollen tube growth-promoting and -attracting protein needed for optimal in vivo pollen tube growth. The specific preservation of TTS mRNAs in the deteriorating transmitting tissue cells suggests that these cells can distinguish molecules needed in the pollinated styles from those that are dispensable, and protect them from degradation. It is suggested that the pollination-induced mRNA poly(A) tail-shortening and cell death are programmed processes suited to the post-pollination transmitting tissue environment. Results showing that ACC is a candidate signal molecule for the pollination-induced mRNA-shortening which is accentuated by ethylene and mediated via a protein phosphorylation-dependent signal transduction pathway are also presented.
Amino Acids↗