Biomedical subjects

Lifang Zhang

Publications and source records attributed to Lifang Zhang.

15 recordsLinked to original sources

PubMed2025

Decoding nitrogen uptake efficiency in maize and sorghum: insights from comparative gene regulatory networks.

Nitrogen (N) is an essential macronutrient for plant growth and yield, yet optimizing nitrogen use efficiency remains a challenge in agriculture. To better understand the regulatory basis of plant responses to N availability, we constructed a maize-specific nitrogen uptake efficiency gene regulatory network (mNUEGRN) comprising 1625 protein-DNA interactions (PDI) between 70 promoters and 301 transcription factors using enhanced yeast one-hybrid assays. We also projected a sorghum NUE GRN (spNUEGRN) based on maize orthologs and analyzed N-responsive subnetworks in both species using transcriptome profiling under N stress of early deprivation and recovery. Cross-species comparison with an existing Arabidopsis GRN revealed about 18% conserved interaction, corresponding to 11% of the mNUEGRN, particularly within the nitrate assimilation pathways. Notably, bZIP18 and bZIP30 emerged as central regulators in mNUEGRN, forming highly connected feed-forward loops (FFLs). From our time series data, we identified 19 236 and 23 864 differentially expressed genes in maize and sorghum, respectively. Gini correlation analysis uncovered 764 and 638 FFLs in mNUEGRN and spNUEGRN, respectively, of which 22 FFLs in maize and 35 in sorghum were identified in both leaf and root for each species. These FFLs may represent candidate regulatory motifs that contribute to modulating transcriptional responses under fluctuating N conditions, but their potential roles require further investigation. Together, our findings reveal evolutionarily conserved and species-specific regulatory strategies that mediate early N responsiveness, offering a foundation for engineering crops with improved NUE.

Sorghum↗

PubMed2006

Functional reorganization and recovery after constraint-induced movement therapy in subacute stroke: case reports.

Preliminary assessments of the feasibility, safety, and effects on neuronal reorganization measured with transcranial magnetic stimulation (TMS) from Constraint-Induced Movement Therapy (CIMT) of the upper extremity were made in eight cases of subacute stroke. Within fourteen days of their stroke, patients were randomly assigned to two weeks of CIMT or traditional therapy. Baseline motor performance and cortical/subcortical representation for movement with TMS were assessed before treatment. Post-treatment assessments were made at the end of treatment and at three months after the stroke. The TMS mapping showed a larger motor representation in the lesioned hemisphere of the CIMT patients as compared to the controls at the three-month follow-up assessment. The enlarged motor representation in the lesioned hemisphere for hand movement correlated with improved motor function of the affected hand, suggesting a link between movement representation size as measured with TMS and functionality. These results suggest that TMS can be safely and effectively used to assess brain function in subacute stroke and further suggest that CIMT may enhance cortical/subcortical motor reorganization and accelerate motor recovery when started within the first two weeks after stroke.

Aged↗

PubMed2006

[Synthesis and characterizations of poly (ethylene glycol)-block-poly (glutamate)].

Amine-terminated poly (ethylene glycol) (PEG) was prepared by two steps. Firstly, potassium naphthalene was added to a solution of methoxypolyethylene glycol 5,000 in benzene until the solution maintains green in half of an hour, then excess tosylchloride was introduced; secondly, the conversion of the tosylate into an amine was carried out by Gabriel synthesis. The block copolymer poly (ethylene glycol)-co-poly (gamma-benzyl L-glutamate ) could be obtained by ring-opening polymerization of gamma-benzyl-L-glutamate N-carboxy anhydride with amine-terminated PEG as macroinitiator. And the benzyl group could be removed by sodium hydroxide. The product structure was characterized by IR, 1HNMR, GPC. The cisplatin-loaded micelle was observed by transmission electron microscope (TEM). And the block copolymer is expected to be useful as functional materials including carrier systems in drug controlled delivery applications.

Drug Carriers↗

PubMed2005

HPRT gene alterations in umbilical cord blood T-lymphocytes in newborns of mothers exposed to tobacco smoke during pregnancy.

Prenatal exposure to tobacco smoke has been associated with an increased risk of pediatric malignancies, yet the transplacental induction of genetic alterations by tobacco smoke carcinogens and their implication to childhood diseases remain poorly understood. We characterized mutations in the HPRT gene in umbilical cord blood T-lymphocytes of self-reported 103 never-smoking mothers and 104 smoking mothers (54 mothers smoked throughout and 50 mothers quit smoking during pregnancy). The results showed the illegitimate V(D)J recombinase-mediated deletion of HPRT exons 2-3 was the most prominent alteration occurring in 48.2% (26/54) of mutants from neonates of the smoking mothers who smoked during pregnancy, compared with 28.0% (14/50) from those of smoking mothers who quit smoking during pregnancy (p=0.035, Fisher's exact test), 34.9% (36/103) from never-smoking mothers (p=0.08), or 32.7% (50/153) of those of neonates born from the latter two groups of mothers combined (p=0.043). There was no significant difference in the frequency of this deletion between neonates of the never-smoking mothers and the smoking mothers who quit smoking during pregnancy (34.9% versus 28.0%, respectively, p=0.39). The results show an increase in illegitimate V(D)J recombinase-mediated deletion of HPRT exons 2-3 in cord blood T-lymphocytes of newborns of mothers who smoked during pregnancy, compared with the group of mothers who did not smoke during pregnancy, implying an increase in illegitimate V(D)J recombinase-mediated alteration, a genetic recombination event associated with childhood malignancies, may be induced in utero during pregnancy by maternal exposure to tobacco smoke-derived genotoxicants.

Base Sequence↗

PubMed2005

Human papillomavirus infection and P53 codon 72 genotypes in a Hispanic population at high-risk for cervical cancer.

Cervical cancer mortality is high in Texas, especially among Hispanic women living in south Texas and adjacent Mexico. Though human papillomavirus (HPV) infection has a causal role in the development of cervical cancer, there are no published data on the prevalence of HPV genotypes in this underscreened region. We studied 398 Hispanic women on both sides of the border along the lower Rio Grande River to determine the prevalence of HPV genotypes and risk factors for cervical cancer. Using a nested PCR system HPV was detected in 62% of cervical specimens, including all the known high-risk HPV genotypes, with HPV16 and HPV18 the most frequent (30.6% and 23.0%, respectively). Multiple infections were common (29.4% of the infected specimens), and where this occurred we were more likely to find high-risk HPV genotypes. We examined host p53 codon 72 genotype frequencies and found that patients with cervical abnormalities and women with HPV16 and HPV18 infections had a lower genotype frequency of the homozygous (AA) previously reported to be associated with cervical cancer, than uninfected women with no abnormalities. In this US/Mexico border population high rates of potentially oncogenic HPV viruses and multiple infections are consistent with observed elevated cervical cancer rates. These data are further evidence that in this underserved population HPV infections are associated with high rates of malignancy, but that host p53 genotypic variations are unlikely to be primary factors in oncogenesis.

Adolescent↗

PubMed2004

Nested PCR with the PGMY09/11 and GP5(+)/6(+) primer sets improves detection of HPV DNA in cervical samples.

Based on epidemiological and research evidence, HPV has a causal role in cervical carcinogenesis. Several HPV detection methods exist to date; the most commonly used method for detection of genital HPVs consists of nested PCR using the MY09/11 and GP5(+)/6(+) primer sets (MY/GP(+)). Recently, the PGMY09/11 primer set, a modified version of the MY09/11 primer set, was introduced for single PCR and was found to detect a wider range of HPV types. The next logical step was taken and the efficacy of nested PCR using the PGMY09/11 and GP5(+)/6(+) primer sets (PGMY/GP(+)) to detect HPV in cervical samples was evaluated. In this comparative study, nested PCR using the novel PGMY/GP(+) primer set combination was found to be more type sensitive than the nested PCR with the MY/GP(+) primer sets, detecting a wider range of HPV types, low copy HPVs, and better characterizing samples infected with multiple strains of HPV. Standardization and use of the PGMY/GP(+) PCR system could aid physicians in providing more efficient HPV screening and better treatment for patients.

Cervix Uteri↗

PubMed2004

Verbal selective learning after traumatic brain injury in children.

Selective learning (SL), the ability to select items to learn from among other items, engages cognitive control, which is purportedly mediated by the frontal cortex and its circuitry. Using incentive-based auditory word recall and expository discourse tasks, we studied the efficiency of SL in children ages 6 to 16 years who had sustained severe traumatic brain injury (TBI) at least 1 year earlier. We hypothesized that SL would be compromised by severe TBI. Results indicated that children with severe TBI performed significantly worse than age-matched typically developing children on word- and discourse-level measures of SL efficiency with no significant group differences in number of items recalled from auditory word lists or declarative facts. We conclude that severe TBI disrupts incentive-based cognitive control processes, possibly due to involvement of frontal neural networks.

Acoustic Stimulation↗

PubMed2004

Psychosocial outcome of TBI in children with unilateral frontal lesions.

To evaluate effects of unilateral frontal lesions on psychosocial and global outcome of traumatic brain injury (TBI) in children, Study 1 compared matched groups of 22 school aged children who had sustained TBI either with or without unilateral frontal lesions. Study 2 evaluated effects of unilateral extrafrontal lesions in 18 TBI patients as compared with 18 nonlesional TBI patients. Communication, Daily Living, and Socialization domains and the Maladaptive Behavior Scale of the Vineland Adaptive Behavior Scales (VABS) were used to assess psychosocial outcome, and the Glasgow Outcome Scale (GOS) measured global outcome. All patients underwent magnetic resonance imaging at least 3 months post injury. Children with frontal lesions had worse scores on the Daily Living and Socialization domains and a higher frequency of maladaptive behavior than those without frontal lesions, but there was no difference in cognitive function. Disability was twice as common in the frontal lesion group relative to children without frontal lesions. Volume of frontal lesion was related to the Socialization domain. Side of lesion had no effect, nor did presence of an extrafrontal lesion (Study 2). Unilateral frontal lesions adversely affect late psychosocial outcome of TBI in children.

Activities of Daily Living↗

PubMed2004

Changes in working memory after traumatic brain injury in children.

The impact of traumatic brain injury (TBI) on working memory (WM) was studied in 144 children (79 with mild, 23 with moderate, and 42 with severe injuries) who underwent magnetic resonance imaging (MRI) at 3 months and were tested at baseline and at 3, 6, 12, and 24 months postinjury. An n-back WM task for letter identity was administered with memory load ranging from 1- to 3-back and a 0-back condition. A TBI Severity x Quadratic Tune interaction showed that net percentage correct (correct detections of targets minus false alarms) was significantly lower in severe than in mild TBI groups. The Left Frontal Lesions x Age interaction approached significance. Mechanisms mediating late decline in WM and the effects of left frontal lesions are discussed.

Adolescent↗

PubMed2004

Selective impairment of inhibition after TBI in children.

Inhibition was studied in 12 children who had had sustained as severe traumatic brain injury (TBI) at least 1 year earlier and in 15 control children. On the flanker task, which involved pressing a button corresponding to the direction of an arrow, the TBI group performed less accurately than controls under interference (flankers were incongruent with arrow) and go-no-go (adjacent stimulus signaled child to withhold response) conditions, but not neutral or facilitation (flankers were congruent) conditions. Response latency was related to age and task condition, but not group. Severe TBI in children may disrupt development of distributed networks mediating inhibition.

Adolescent↗

PubMed2004

Discourse macrolevel processing after severe pediatric traumatic brain injury.

The purpose of this study was to determine if discourse macrolevel processing abilities differed between children with severe traumatic brain injury (TBI) at least 2 years postinjury and typically developing children. Twenty-three children had sustained a severe TBI either before the age of 8 (n = 10) or after the age of 8 (n = 13). The remaining 32 children composed a control group of typically developing peers. The groups' summaries and interpretive lesson statements were analyzed according to reduction and transformation of narrative text information. Compared to the control group, the TBI group condensed the original text information to a similar extent. However, the TBI group produced significantly less transformed information during their summaries, especially those children who sustained early injuries. The TBI and control groups did not significantly differ in their production of interpretive lesson statements. In terms of related skills, discourse macrolevel summarization ability was significantly related to problem solving but not to lexical or sentence level language skills or memory. Children who sustain a severe TBI early in childhood are at an increased risk for persisting deficits in higher level discourse abilities, results that have implications for academic success and therapeutic practices.

Adolescent↗

PubMed2004

Components of executive function in typically developing and head-injured children.

To identify the key components of executive functions (EFs) in children following traumatic brain injury (TBI), data from a series of EF tests administered to 286 pediatric TBI patients at least 3 years postinjury were subjected to an exploratory factor analysis. A 5-factor model included discourse, EFs (e.g., problem solving, planning), processing speed (e.g., coding), declarative memory, and motor speed. Confirmatory factor analysis based on data obtained from 265 pediatric TBI patients at 3 months postinjury disclosed that the 5-factor model provided a good fit to the data. A second exploratory analysis of the 3-month postinjury data disclosed a 4-factor model in which processing speed and motor speed measures loaded on a common factor. Severity of TBI and age at test had significant effects on all factors in both the 5- and 4-factor models. Adaptive functioning, as measured by the Vineland Adaptive Behavioral Scale-Revised, was moderately related to factor scores at 3 years or longer postinjury, but weakly related to factor scores obtained at 3 months postinjury. The factor scores could be used in clinical trials to facilitate data reduction and appear to have validity as indicators of TBI outcome.

Activities of Daily Living↗

PubMed2004

Childhood head injury and metacognitive processes in language and memory.

We studied the metacognitive functioning of children with severe and mild traumatic brain injury (TBI) and typically developing children. To test metacognition for memory, children were tested on a modified Judgment of Learning task. We found that children with severe TBI were impaired in their ability to predict recall of specific items prior to study-recall trials, but were unimpaired in predicting recall on a delayed test when the judgment was made after study-recall trials. Metacognitive knowledge impairment for memorial abilities was also demonstrated in children with severe TBI by poor estimation of memory span and exaggerated overconfidence in performance. To test metacognition within the language domain, we gave children a sentence anomaly detection and repair task in which spoken sentences were monitored for semantic anomalies. Children with severe TBI were impaired on the detection of semantic anomalies, especially under conditions of high memory load. However, metalinguistic knowledge in the form of adequate repairs of anomalous sentences, was preserved. Results are discussed in terms of effects of age at test and injury severity.

Adolescent↗

PubMed2002

Working memory after traumatic brain injury in children.

To investigate the effects of traumatic brain injury on working memory in children, we administered semantic (letter identity) and phonological (letter rhyme) N-back tasks to children who were on average 5 years post-mild (n = 54) or -severe (n = 26) traumatic brain injury and 44 typically developing children who were comparable in age. The correct detection of targets and false alarms were measured for each task. Memory load (which varied from 0 to 3 letters back) and age significantly affected the detection of targets and false alarms in both tasks. The severity of traumatic brain injury affected the correct detection of letters on the identity task and false alarms on the rhyme task. Traumatic brain injury severity also interacted with memory load in its effect on false alarms on the rhyme task. Traumatic brain injury results in impaired working memory and diminished inhibition in children. The N-back working memory task is feasible for administration to brain-injured children and potentially could be useful for studying brain activation associated with working memory and effects of drug therapy in this group of patients.

Adolescent↗

PubMed2002

Selective learning in children after traumatic brain injury: a preliminary study.

Selective learning (SL) is the ability to select items to learn from among other items. It requires the use of the executive processes of metacognitive control and working memory, which are considered to be mediated by the frontal cortex and its circuitry. We studied the efficiency with which verbal items of greater value are selectively learned from among items varying in value in 14 children ages 8-15 years who had sustained severe traumatic brain injury (TBI) and in 39 typically developing age-matched children. We hypothesized that children with TBI would be disproportionately compromised in selective learning efficiency in contrast to memory span when compared to normally developing children. The results supported our hypothesis, as children with TBI performed significantly worse than controls on a measure of selective learning efficiency, but the two groups performed similarly on a measure of word recall within the same task. Furthermore, the effect of TBI on performance was demonstrated to take place at the time of encoding, rather than at retrieval.

Adolescent↗