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Biomedical subjects

L Mao

Publications and source records attributed to L Mao.

At least 145 records · Page 8Linked to original sources
PubMed1994

Inhibition of glutamate uptake in the rostral ventrolateral medulla enhances baroreflex-mediated bradycardia in conscious rats.

The current investigation tested the hypothesis that inhibition of L-glutamate uptake in the rostral ventrolateral medulla (RVL) enhances the baroreceptor-mediated heart rate responses. In conscious freely moving rats, unilateral microinjection of the L-glutamate uptake blocker p-chloromercuriphenylsalfonic acid (PCMS, 0.1 nmol) elicited a 45% increase in the baroreflex-mediated bradycardic response tested by i.v. phenylephrine (-2.0 +/- 0.1 vs -2.9 +/- 0.2 beats/min/mmHg). In the same rats, evidence for the ability of PCMS to inhibit L-glutamate uptake at the site of its microinjection in the RVL was obtained. PCMS microinjected into the RVL did not influence basal blood pressure and heart rate. However, the cardiovascular responses elicited by L-glutamate (5 nmol) microinjected into the RVL were significantly enhanced by PCMS pretreatment. The pressor and bradycardic responses to L-glutamate increased 53% (from 28.3 +/- 2.4 to 43.4 +/- 4.7 mmHg) and 68% (from -59.6 +/- 13.1 to -100.0 +/- 7.2 beats/min), respectively after PCMS. An equal volume of ACSF microinjected into the RVL had no effect on BRS (-2.1 +/- 0.2 vs -1.9 +/- 0.1 beats/min/mmHg), nor on the pressor (29.9 +/- 7.4 vs 30.6 +/- 4.4 mmHg) and bradycardic (-50.3 +/- 12.0 vs -43.3 +/- 12.0 beats/min) responses elicited by L-glutamate. These findings suggest that: (i) glutamatergic pathways in the RVL serve a facilitatory role in processing the baroreceptor information, and (ii) L-glutamate uptake mechanisms exert a restraining influence on BRS and the cardiovascular effect of L-glutamate.

4-Chloromercuribenzenesulfonate↗
PubMed1994

Detection of oncogene mutations in sputum precedes diagnosis of lung cancer.

The Johns Hopkins Lung Project developed an archive of sputum specimens during a randomized trial of lung cancer screening (1974-1982). We identified 15 patients from that trial who later developed adenocarcinoma of the lung. The primary lung carcinomas from 10 of these 15 patients contained either a ras or a p53 gene mutation. Using a polymerase chain reaction-based assay, stored sputum samples obtained prior to clinical diagnosis were examined for the presence of these same oncogene mutations. In 8 of 10 patients, the identical mutation identified in the primary tumor was also detected in at least one sputum sample. The earliest detection of a clonal population of cancer cells in sputum was in a sample obtained more than 1 year prior to clinical diagnosis. These results provide the basis of a novel approach for detection of lung cancer based on the evolving molecular genetics of this disease.

Aged↗
PubMed1994

p53 gene mutations as markers of tumor spread in synchronous oral cancers.

OBJECTIVE: To demonstrate how genetic mutations may be used as specific markers for the study and management of head and neck squamous cell carcinomas. DESIGN: Mutations in the p53 gene were identified by DNA sequencing in synchronous primary head and neck squamous cell carcinomas from one patient. The polymerase chain reaction and mutant-specific oligomer probes were used to detect rare tumor cells in surgical margins, lymph nodes, and swabs of the oral cavity. PATIENTS: Selected from a consecutive series of individuals with head and neck squamous cell carcinomas at a tertiary referral center. RESULTS: Two synchronous primary invasive cancers displayed different missense mutations in the p53 gene. The mutated sequence from one primary tumor was detected in metastases from both sides of the neck. Infiltrating cells from this biologically aggressive tumor were also detected by a polymerase chain reaction-based assay in a histologically normal surgical margin, accurately predicting tumor recurrence. CONCLUSIONS: p53 gene mutations were useful as molecular markers to distinguish between tumors in this case. The potential utility of detection of tumor cells in surgical margins and saliva by molecular techniques merits further investigation.

Biomarkers, Tumor↗
PubMed1994

Gene mutations in saliva as molecular markers for head and neck squamous cell carcinomas.

BACKGROUND: Cancer is caused by the accumulation of mutations that activate proto-oncogenes and inactivate tumor suppressor genes. The result is a clonal expansion of genetically identical daughter cells that eventually become clinical malignancies. The specific mutations acquired by the progenitor cell are like a fingerprint carried by each cell of the tumor. These mutations can serve as very specific markers for the presence of tumor cells in a background of normal cells. METHODS: Mutations in the p53 gene recovered from head and neck squamous cell carcinomas were sequenced, and these altered DNA sequences were used retrospectively as tumor-specific genetic markers for cancer cells in the patient's saliva. Cloned p53 sequences amplified by the polymerase chain reaction from DNA extracted from banked preoperative saliva specimens were screened for the presence of tumor-specific mutations using radiolabeled oligonucleotide probes. RESULTS: We identified tumor-specific mutations in preoperative saliva samples of 5 of the 7 patients evaluated (71%). CONCLUSIONS: These results suggest a potential for clinical applications of this novel approach to cancer detection using gene mutations as molecular markers for carcinomas.

Biomarkers, Tumor↗
PubMed1994

In vivo assessment of left ventricular remodelling after myocardial infarction by digital video contrast angiography in the rat.

OBJECTIVE: The aim was to develop a digital video contrast angiographic method for assessing global left ventricular function and volume in vivo in the rat and then to apply it to a study of ventricular remodelling after coronary occlusion, with and without reperfusion. METHODS: Digital contrast angiography was performed on 29 rats, including the following groups: sham operated (n = 11), non-transmural myocardial infarction produced by reperfusion (n = 8), and transmural infarction produced by permanent occlusion (n = 10). Under anaesthesia three weeks later, biplane fluoroscopic images were acquired following venous contrast injection. Levophase images were digitised, and left ventricular end diastolic and end systolic volumes and ejection fractions were obtained using an area-length method. Left ventricular ejection fraction data also were calculated by videodensitometry from video density curves. RESULTS: Compared to the sham operated group, the reperfused group showed a significant decrease in left ventricular ejection fraction, at 53(SD 7) v 70(5)% (p < 0.01), and an increase in end diastolic volume. The permanent occlusion group showed a further decrease in the ejection fraction [40(8)%] and a further significant increase in end diastolic volume compared to the reperfused group (p < 0.01). Left ventricular ejection fraction correlated inversely with percent infarct size (r = 0.882) and showed a positive correlation with the spared epicardial area (r = 0.721). Most haemodynamic variables, including maximum left ventricular dP/dt, failed to discriminate between the groups. The methods showed reasonable accuracy when tested in vitro using contrast filled balloons. In vivo, the left ventricular ejection fraction calculated by densitometry showed adequate interobserver variability (2 SD +/- 8.5 percentage points), but the area-length method showed somewhat more scatter. CONCLUSIONS: Digital video contrast angiography is a feasible method for the assessing global left ventricular function in the rat and should be useful in other small animal models. Significant differences in left ventricular volumes and ejection fractions were detected between reperfused and permanent occlusion groups, whereas haemodynamic variables showed non-significant trends. Reperfusion after 45 min of occlusion caused sparing of the epicardium, prevented unfavourable remodelling, and improved the ejection fraction compared to permanent occlusion.

Angiography, Digital Subtraction↗
PubMed1994

ANG II receptor blockade prevents ventricular hypertrophy and ANF gene expression with pressure overload in mice.

There is increasing evidence that the renin-angiotensin system may play a important role in cardiac hypertrophy. To assess the role of angiotensin II in the induction of cardiac hypertrophy, three groups of adult mice were subjected to left ventricular pressure overload by transverse aortic constriction (TAC). For the next 7 days the groups received either the specific angiotensin II subtype 1 receptor (AT1) antagonist (losartan, 1.05 g/l; n = 17), an angiotensin enzyme inhibitor (captopril, 2 g/l; n = 17), or no treatment (n = 22) administered in the drinking water and compared with three similarly treated sham-operated groups (n = 7 each). TAC resulted in a significant increase in heart weight-to-body weight ratio (0.634 +/- 0.087 vs. 0.525 +/- 0.039, g/g x 100, P < 0.05), which was prevented by losartan (0.506 +/- 0.069, g/g x 100, P < 0.0001) despite similar hemodynamic load (proximal systolic pressure 146 +/- 31 vs. 136 +/- 32 mmHg, untreated vs. losartan, P = NS). Proximal systolic pressure was positively correlated with the development of ventricular hypertrophy. In the presence of AT1-receptor blockade, the increase in heart weight-to-body weight ratio at any given systolic pressure was significantly attenuated compared with untreated TAC mice. The increase in heart weight-to-body weight ratio was also significantly attenuated by captopril compared with untreated banded controls (0.542 +/- 0.091, g/g x 100, P = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin Receptor Antagonists↗
PubMed1994

Influence of needle gauge in Mantoux skin testing.

STUDY OBJECTIVE: To determine the influence of needle gauge in Mantoux skin testing for tuberculosis. DESIGN: Randomized selection of either a 27- or 30-gauge needle for Mantoux skin test placement; observer-blinded. SETTING: Annual hospital employee screening. PARTICIPANTS: Six hundred twenty-five employees working in clinical and laboratory research environments. RESULTS: Blinded observers found that the use of 27-gauge needles caused increased bleeding and bruising compared with 30-gauge needles (p < or = 0.007 for each). However, the 27-gauge needle produced larger blebs and less leakage of tuberculin solution (p < or = 0.0003). CONCLUSION: Smaller gauge needles could potentially cause false-negative screening results because of decreased antigen delivery. Use of needle gauges smaller than 27 gauge should be avoided until their reliability is validated.

Evaluation Studies as Topic↗
PubMed1993

Effect of caval-portal shunt on ovarian tissue in rats: I. Histological observation.

Forty-three female Sprague Dawley rats were divided into five groups, with groups 1-4 subjected to end-to-side caval-portal shunt (CPS). In addition to CPS, group 1 (n = 13), group 2 (n = 10), and group 3 (n = 7) rats had undergone removal of the right ovary and one-half of the left ovary, the left ovary, and one-half of the left ovary, respectively. Group 4 (n = 6) rats were not subjected to ovariectomy. Group 5 (n = 7) animals were not subjected to CPS but underwent left ovarian hemiresection. The ovarian volume of the hemiresected ovaries increased to 393.00 +/- 4.83 mm3 and 126.00 +/- 44.3 mm3 from 18.40 +/- 0.54 mm3 and 18.40 +/- 0.59 mm in groups 1 and 3, respectively, at the end of three postoperative months. The nonresected ovaries enlarged to 339.98 +/- 5.09 mm3 and 226.3 +/- 46.2 mm3 from 36.79 +/- 1.09 mm3 in groups 2 and 3, respectively. When no ovaries were resected, the CPS animals in group 4 showed an increment of ovarian volume of 1.75-2.2 times as much as the preoperative ones. In the animals that had undergone simple hemiovariectomy (group 5), the contralateral ovaries showed a significant increase in volume (40.2 +/- 8.3 mm3 to 243.1 +/- 114.8 mm3) at 3 months. The hemiresected ovarian volume increased from 27.1 +/- 5.5 mm3 to 44.1 +/- 11.8 mm3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Molecular study on null allolic RFLPs among rice varieties].

Null allele is an allele that produces no functional products. In RFLP analysis, null allele means that one probe can hybridize to plant DNA from one variety readily, but very faintly to DNA from another variety or even has no hybridization signal under experimental stringency and this may be an indication of deletion, insertion or major sequence rearrangement(s) in the corresponding regions. We report here about null alleles of RFLP among 52 rice varieties uncovered with rice random genomic probe RG684. The results show that this kind of null allele is most likely to occur in typical japonica varieties distributed geographically in Northeast China and Japan, and this tendency is consistent with the hypothesis that rice evolved with a trend of from wild type-->Indica-->Japonica. Sequence analysis indicates that the sequence of RG684 has no encoding function. Therefore, changes in this region may not influence the survival of the plant. Comparison of the sequence of RG684 and gypsy transposon bx34e long terminal repeats (LTR) of D. melanogater shows homology of 78.4% of 37 base pair and this leads to the consideration that the occurrence of null alleles in rice is related to transposition or transposition-like events.

Alleles↗
PubMed1992

Clinical and experimental studies on tong yu ling in the treatment of diabetic hyperlipemia.

72 diabetes mellitus patients (70 cases non-insulin-dependent) were treated routinely with D860. After one month, cases with persisting hyperglycemia and hyperlipemia were randomly divided into Group A to be treated with D860 plus Tong Yu Ling (TYL), and Group B to continue treatment with D860 alone, while Group C, comprising cases with persisting hyperlipemia only, were treated with TYL alone. Therapeutic results showed that of the total 50 cases of Group A and C, 26 were markedly improved, 14 improved, and 10 cases ineffective. The antihyperlipemic effect was pronounced in Group A, where the blood cholesterol, beta-lipoprotein and triglyceride showed remarkable decline, less pronounced in Group C, and insignificant in Group B. Experiments in rat models of non-insulin-dependent diabetes demonstrated that TYL was markedly effective in treating hyperlipemia.

Adult↗
PubMed1991

Dietary vitamin and mineral concentrations of two juvenile female giant pandas (Ailuropoda melanoleuca).

During a 7 mo exhibit loan, diets of two juvenile female giant pandas (Ailuropoda melanoleuca) were monitored. Mineral [calcium (Ca), copper (Cu), phosphorus (P), potassium (K), zinc (Zn)] and vitamin (beta-carotene and total tocopherol) concentrations in the diet were quantified as well as in a serum sample obtained from one of these animals. Diets consumed by the pandas contained (dry matter basis): 0.82% Ca, 0.62% P, 1.05% K, 14.3 mg/kg Cu, 31.8 mg/kg Zn, 12.2 mg/kg beta-carotene, and 12 mg/kg total tocopherol. Serum values for these vitamins and minerals were within reported normal limits for the spectacled bear (Tremarctos ornatus). This diet appeared to provide adequate nutrition for maintenance and growth.

Animal Feed↗
PubMed1990

Analgesic electrical stimulation of the hypothalamic arcuate nucleus: tolerance and its cross-tolerance to 2 Hz or 100 Hz electroacupuncture.

Focal electrical stimulation of the arcuate nucleus of the hypothalamus (ARH) for 5 min (1 session) produced a marked elevation of tail flick latency (TFL) to noxious heat in the pentobarbital-anesthetized rat. Repeated stimulation for a total of 11 sessions at 30 min intervals resulted in a gradual decline in the hypoalgesic action, and this tolerance may last for 7 days. Tolerance to the ARH analgesic stimulation reduced the analgesia produced by low (2 Hz) but not high (100 Hz) frequency electroacupuncture (EA); and tolerance to low frequency EA analgesia attenuated the ARH stimulation-produced analgesia without affecting high frequency EA analgesia. Alternatively, rats tolerant to high-frequency EA analgesia were still sensitive to either the ARH or low-frequency EA stimulation. These results suggest that the ARH stimulation and low-frequency EA administration produced analgesia via a common neural mechanism, supporting our hypothesis put forward previously that the ARH plays an important role in mediating low- but not high-frequency EA analgesia.

Acupuncture Therapy↗
PubMed1990

The arcuate nucleus of hypothalamus mediates low but not high frequency electroacupuncture analgesia in rats.

Electrolytic, kainic acid or sham lesions were made in the arcuate nucleus of the hypothalamus (ARH) in female Wistar rats to investigate the putative role of the ARH in the organization of low (2 Hz) or high (100 Hz) frequency electroacupuncture (EA) analgesia. Both electrolytic and chemical lesions lead to an almost total suppression of the low frequency EA analgesia as measured 4 and 6 days following the surgical intervention, leaving high frequency EA analgesia unaffected. In sham-operated animals, the antinociceptive effect induced by low or high frequency EA was essentially intact. These data indicate that neurones of the ARH most likely play an important role in mediating low, but not high frequency EA analgesia.

Analgesia↗
PubMed1988

Free transplantation of venous network pattern skin flap.

We report a patient treated by transplantation of a venous network pattern skin flap containing two superficial cutaneous veins. Through one of the veins, arterial blood passed into the capillaries, restoring circulation and ensuring survival of the flap.

Adult↗