Biomedical subjects

S Tong

Publications and source records attributed to S Tong.

At least 91 records · Page 5Linked to original sources

PubMed1998

Aspartate improves recovery of the recently infarcted rat heart after cardioplegic arrest.

BACKGROUND: We have previously shown that aspartate improves the tolerance of normal hearts to cardioplegia. The aim of this study was to investigate whether aspartate is also beneficial in the recently infarcted heart. METHODS: Myocardial infarction was produced in rats by left coronary artery ligation. Twenty hours later their hearts were perfused on an isolated working rat heart apparatus and underwent cardioplegic arrest for 30 min at 37 degrees C with or without 20 mM aspartate in the cardioplegic solution (n = 11 per group). Functional recovery and myocardial high energy phosphate levels were measured at the end of arrest and after 30 min of reperfusion. RESULTS: There was no difference in pre-arrest pump function between the untreated and aspartate-treated groups. However, after reperfusion the aspartate group generated more power (3.4 +/- 0.2 mJ/s per g) than the untreated group (2.5 +/- 0.3 mJ/s per g; P < 0.05) such that the percentage recovery of pre-arrest power in the aspartate group (67.7 +/- 3.5%) was greater than in the untreated group (53.6 +/- 4.9%; P < 0.05). The aspartate group also showed increases in aortic flow and myocardial oxygen consumption compared to the untreated group (P < 0.05). There were no between-group differences in high energy phosphate levels at the end of arrest or after reperfusion. CONCLUSION: Aspartate improves functional recovery of the recently infarcted heart during cardioplegic arrest, and therefore has potential as a useful adjunct to myocardial protection in patients with recent myocardial infarction undergoing cardiac surgery.

Animals↗

PubMed1998

Lead exposure and cognitive development: persistence and a dynamic pattern.

OBJECTIVES: Although enormous effort has been focused over the past two decades on examining the potential adverse effects of exposure to environmental lead on human health, there has been a debate over the persistence and dynamic pattern of these effects. METHODOLOGY: Articles relevant to this issue which were published between January 1982 and December 1996 were retrieved from Medline and adjunct searching methods (i.e. hand searching of key journals, review of the bibliographies of reports known to be relevant, consulting with experts, and use of Science Citation Index). RESULTS: Currently available epidemiological evidence suggests that 'low' level exposure to lead in early childhood is likely to cause a moderate but real and detectable effect on cognitive development, and this effect appears to persist into later childhood. The findings from four long-term prospective studies seem to support the constant decrement model which assumes that cognitive deficits resulting from early lead exposure persist over an extended period of time even when exposure decreases. CONCLUSION: From a public health perspective, it is highly desirable and prudent to reduce the dispersive uses of lead. Since lead is ubiquitous and persistent in the environment and may have a subtle and persistent effect on cognitive development, how to set the environmental standards for lead exposure is an important scientific issue still open for debate.

Child↗

PubMed1998

Dizygotic twinning as a measure of human fertility.

There is widespread concern about a possible decline in human fertility in recent decades. The spontaneous dizygotic twinning rate provides a way of measuring a combination of male plus female fertility as it reflects the frequency of double ovulation, the probability of fertilization, and the survival of the zygote. There was a decline in dizygotic twinning rates in developed countries which began around 1960 and continued until the late 1970s. The exact cause of the fall remains unknown. We suggest that it could have been due to a depression in the twin ovulation rate in women who stopped taking the oral contraceptive pill. The rise in the dizygotic twinning rates which occurred from the 1980s onwards in developed countries is almost certainly due to increasing use of ovulation-inducing agents, but this rise may have masked a continuing decline in dizygotic twinning. Monozygotic twinning rates have remained remarkably constant or increased only very slightly in recent decades. This makes it possible to use the dizygotic:monozygotic twinning ratio to monitor dizygotic twinning in populations where true incidence rates cannot be calculated, e.g. in hospitals where there may be selective referral of twins.

Adolescent↗

PubMed1998

Three-dimensional ophthalmic contact B-scan ultrasonography of the posterior segment.

PURPOSE: A system to produce three-dimensional computer reconstructions of ophthalmic contact B-scan ultrasound was developed and investigated. METHODS: Investigators used ocular phantoms to measure the accuracy and reproducibility of linear, area, and volume measurements. RESULTS: In vitro calibration tests of linear and area measurements demonstrate accurate and reproducible findings throughout the imaged space. Phantom volume tests also show reasonable accuracy and reproducibility. CONCLUSIONS: Three-dimensional ultrasonography is effective in measuring length, area, and volume in an experimental model. The in vitro accuracy and reproducibility of measurements warrants further investigation into the clinical utility of this method in posterior segment tumors and other posterior segment pathology.

Equipment Design↗

PubMed1998

Prevalence of human melioidosis on Hainan Island in China.

Eight human cases of melioidosis were diagnosed at Hainan People's Hospital over a period of one year. Four of the cases were of septicemia form, while the rest were of chronic form with abscesses in different organs. All the isolates were intrinsically resistant to cefazolin, cefuroxime, and gentamicin, while being rather sensitive to ampicillin/sulbactam, ticarcillin/clavulanic acid, and imipenem. A serological survey of exotoxin antibodies at different farms showed that Xinglong was a farm seriously devastated by Burkholderia pseudomallei, while the mountainous farm of Licai had the lowest prevalence (P< 0.01). From the results of serological survey and melioidosis case distribution, it could be clearly seen that melioidosis predominantly exists in coastal plain regions around this island, where the altitude above sea-level is below 100 m, the annual rainfall is up to 2,300 mm and a rather warm climate in coldest months of December and January.

Adult↗

PubMed1998

Does breastfeeding at six months predict cognitive development?

There is controversy over whether the method of feeding in infancy affects intellectual development. We investigated the relationship between breastfeeding status at 6 months of age and long-term cognitive development in a cohort of 375 children born in Port Pirie, South Australia, between 1979 and 1982. Cognitive assessments were conducted at ages 2, 4, 7 and 11 to 13 years. After adjustment for sociodemographic, environmental and biomedical factors, a small, statistically non-significant, beneficial effect of breastfeeding on cognitive functioning was observed. Compared with the bottle-fed children, the breast-fed children had a 3.4 (95% CI -0.1 to 6.9), 1.3 (-2.3 to 4.9), 1.2 (-2.0 to 4.4) and 0.8 (-1.9 to 3.5) point advantage on the Bayley Mental Developmental Index at age 2 years, the McCarthy General Cognitive Index at age 4 years and the Wechsler Full-Scale IQ at ages 7 and 11 to 13 years, respectively. Our data suggest that any beneficial effect of breastfeeding on cognitive development is quite small in magnitude.

Analysis of Variance↗

PubMed1998

[Thermostable alkaline phosphatase from Thermus sp. FD3041: cloning of the gene and expression in Escherichia coli].

A genomic library of Thermus sp. FD3041 which produces thermostable alkaline phosphatase (FD-TAP) was constructed with the vector pUC118 and the host E. coli TG1. 3-10kb inserted fragments of foreign DNA were identified in 90 percent of the 12,000 clones thus obtained. Five positive clones were detected after screening the plated library by the method of colony coloration for TAP in situ. Preliminary analysis of the enzyme expressed from one recombinant plasmid pTAP362 showed that the properties of the recombinant enzyme, such as the thermal stability and optimal temperature of reaction, were identical to those of the native enzyme. The gene of FD-TAP was located on the 2.0kb BamHI-HindIII fragment of the pTAP362, determined by its physical map and the change of enzyme activity in different partially deleted plasmids. Results of thermostability experiment in PCR thermal cycle showed that the FD-TAP would be suitable for labelling of primers and detection of PCR amplified products.

Alkaline Phosphatase↗

PubMed1998

[Study on the determination of trace metals in complex matrices by chelation ion chromatography].

In this paper, a new method for determination of trace metal ions in complex matrices by chelation ion chromatography has been developed. In accordance to different analysis purpose, different interference should be selectively eliminated. On the chelating resins, all anions, alkali and alkaline earth metals could be eluted by ammonium acetate eluent (pH 5.5), tervalent cations could be eluted by pyrophosphoric acid/ammonium acetate eluent (pH 5.5). On sulfonated cation exchanger, heavy metals, transition metals, iron and aluminum could be eluted by hydrochloric acid/ethanol and oxalic acid/nitric acid eluents. Then, the concentrated lanthanides and transition metals (Pb, Cu, Cd, Ni, Zn and Co) were separated on bifunctional ion-exchange ion-exchange column by a proper concentration gradient of eluents, coupled with post-column spectrophotometric detection. Test samples could be injected directly into the column for analysis after the sample digestion. The detection limits of the method (signal-to-noise = 3:1) were at or below microgram/L level. The method has been systematically applied in rock, alloy, soil, plant and animal samples.

Chelating Agents↗

PubMed1997

Preliminary evidence for the evolution in complexity of heart rate dynamics during autonomic maturation in neonatal swine.

Previous studies suggest that the autonomic nervous system plays an important role in the generation of complex heart rate dynamics. Therefore, we hypothesized that the complexity (irregularity) of cardiac interbeat intervals would evolve with the maturation of autonomic innervation to the heart. Twelve healthy newborn piglets were implanted with ECG transmitters and studied at one or more different ages up to 33 days of age, the period during which pigs develop functional sympathetic innervation of the heart from the stellate ganglia. Three animals underwent right stellate ganglionectomy, two a left stellate ganglionectomy, two a right cardiac vagotomy and five a sham procedure. The statistic, approximate entropy (ApEn), was used to quantify the regularity of interbeat interval fluctuations. Sham-operated animals showed an increase in the standard deviation (SD) and irregularity (ApEn) of cardiac interval fluctuations with increasing age. Right stellate ganglionectomized piglets had lower interbeat interval ApEn values, but similar SD's by 26-27 days of age compared to sham-operated animals. Left stellate ganglionectomy, which affects cardiac inotropy rather than chronotropy, had no effect on cardiac interval irregularity, while vagotomy had an indeterminant effect. The increasing irregularity of interbeat interval dynamics during autonomic maturation and the apparent attenuation of heartbeat irregularity when right stellate ganglion innervation is interrupted, provides empirical support for the notion that complex heartbeat dynamics in the mature animal are the result of a network of autonomic neural pathways that enables an organism to adapt to stress.

Aging↗

PubMed1997

Gene identification and DNA sequence analysis in the GC-poor 20 megabase region of human chromosome 21.

In contrast to the distal half of the long arm of chromosome 21, the proximal half of approximately 20 megabases of DNA, including 21q11-21 bands, is low in GC content, CpG islands, and identified genes. Despite intensive searches, very few genes and cDNAs have been found in this region. Since the 21q11-21 region is associated with certain Down syndrome pathologies like mental retardation, the identification of relevant genes in this region is important. We used a different approach by constructing microdissection libraries specifically for this region and isolating unique sequence microclones for detailed molecular analysis. We found that this region is enriched with middle and low-copy repetitive sequences, and is also heavily methylated. By sequencing and homology analysis, we identified a significant number of genes/cDNAs, most of which appear to belong to gene families. In addition, we used unique sequence microclones in direct screening of cDNA libraries and isolated 12 cDNAs for this region. Thus, although the 21q11-21 region is gene poor, it is not completely devoid of genes/cDNAs. The presence of high proportions of middle and low-copy repetitive sequences in this region may have evolutionary significance in the genome organization and function of this region. Since 21q11-21 is heavily methylated, the expression of genes in this region may be regulated by a delicate balance of methylation and demethylation, and the presence of an additional copy of chromosome 21 may seriously disturb this balance and cause specific Down syndrome anomalies including mental retardation.

Chromosomes, Human, Pair 21↗

PubMed1997

Effects of cardiac autonomic imbalance on postnatal changes in the electrocardiographic Q-T interval in conscious swine.

The effects of partial autonomic denervation of the heart rate and Q--T interval were examined during maturation in swine. Four groups of newborns were prepared: right stellate ganglionectomy (RSG), left stellate ganglionectomy (LSG), right cardiac vagotomy (RCV) and sham-operated. Swine were studied postsurgically for eight weeks. Unexpected deaths of unknown cause occurred in five of the 20 denervated swine but in none of the 10 sham-operated controls. Prolongation of the Q--T interval was greatest in RSG animals and least in RCV as compared to controls. The results indicate that we have successfully developed an animal model of a long Q--T syndrome in swine.

Animals↗

PubMed1997

Use of dizygotic to monozygotic twinning ratio as a measure of fertility.

BACKGROUND: Monozygotic (Mz, identical) twinning occurs at a rate of around three per 1000 maternities in all populations, whereas dizygotic (Dz, fraternal) twinning is highly heritable, and varies with age and race. The Dz/Mz twinning ratio reflects the frequency of twin ovulations, and can provide a useful measure of human fertility. METHODS: 1625 pairs of twins of known sex were born in Isan Yuk Obstetric Hospital in Hong Kong during the period 1960-95. The yearly Dz/Mz ratio was calculated, and trends were analysed by chi 2 test with the Bonferroni correction. Ages of mothers of all opposite-sexed twins were recorded and trends analysed by ANOVA and linear regression. FINDINGS: The Dz/Mz ratio declined significantly from 1.12 in 1960 to 0.05 in 1978 (p < 0.001), and then rose significantly to an average of 0.86 in 1994-95 (p < 0.003). There was a significant declining trend in age of mothers of opposite-sexed twins from 1960 to 1978 (p < 0.001), but there were no significant changes in maternal age after 1978 (p = 0.38). INTERPRETATION: If we are correct in assuming that the frequency of Mz twinning remained constant during the study period, the declining Dz/Mz ratio from 1960 to 1978, which also occurred in many developed countries, could reflect some adverse environmental effect on human fertility. The increasing proportion of Dz twins in the past two decades is probably due to increasing use of ovulation-inducing drugs such as clomiphene citrate, which could mask a serious and continuing decline in human fertility. It is therefore important to continue to monitor the Dz/Mz ratio in the future in this and other subpopulations, after exclusion of any women who have taken drugs that stimulate fertility.

Adult↗

PubMed1997

Characterization of a novel transporter family that includes multiple Escherichia coli gluconate transporters and their homologues.

The nucleotide sequences of seven Escherichia coli genes that encode members of the gluconate permease (GntP) family have recently become available. These genes include gntP, gntU, gntW, ORf449, dsdX, and ORFo454. The deduced amino acid sequences of all seven E. coli genes are homologous to the gntP gene products from Bacillus subtilis and B. licheniformis as well as two additional gene products from Haemophilus influenzae. These 11 proteins are not demonstrably homologous to members of the major facilitator superfamily or other recognized permease families. Four of the E. coli gluconate transporter genes have been cloned and shown to encode gluconate transporters with apparent affinities ranging from 6 to 212 microM. These studies serve to characterize a novel family of bacterial permeases.

Bacillus↗

PubMed1997

Assignment of three human markers in chromosome 21q11 to mouse chromosome 16.

Three unique sequence microclones from human chromosome region 21q11 were assigned to mouse chromosome 16 using a mouse/Chinese hamster cell hybrid 96Az2 containing a single mouse chromosome 16. This comparative mapping provides further homology between human chromosome 21 and mouse chromosome 16 to include the very proximal portion of the long arm of human chromosome 21. Since this part of human chromosome 21 is associated with mental retardation in Down syndrome individuals, its homologous mouse region should also be included in the construction of mouse models for studying Down syndrome phenotypes including mental retardation.

Animals↗

PubMed1997

Molecular genetic characterization of the Escherichia coli gntT gene of GntI, the main system for gluconate metabolism.

The Escherichia coli gntT gene was subcloned from the Kohara library, and its expression was characterized. The cloned gntT gene genetically complemented mutant E. coli strains with defects in gluconate transport and directed the formation of a high-affinity gluconate transporter with a measured apparent Km of 6 microM for gluconate. Primer extension analysis indicated two transcriptional start sites for gntT, which are separated by 66 bp and which give rise to what appears on a Northern blot to be a single, gluconate-inducible, 1.42-kb gntT transcript. Thus, it was concluded that gntT is monocistronic and is regulated by two promoters. Both of the promoters have - 10 and -35 sequence elements typical of sigma70 promoters and catabolite gene activator protein binding sites in appropriate locations to exert glucose catabolite repression. In addition, two putative gnt operator sites were identified in the gntT regulatory region. A search revealed the presence of nearly identical palindromic sequences in the regulatory regions of all known gluconate-inducible genes, and these seven putative gnt operators were used to derive a consensus gnt operator sequence. A gntT::lacZ operon fusion was constructed and used to examine gntT expression. The results indicated that gntT is maximally induced by 500 microM gluconate, modestly induced by very low levels of gluconate (4 microM), and partially catabolite repressed by glucose. The results also showed a pronounced peak of gntT expression very early in the logarithmic phase, a pattern of expression similar to that of the Fis protein. Thus, it is concluded that GntT is important for growth on low concentrations of gluconate, for entry into the logarithmic phase, and for cometabolism of gluconate and glucose.

Bacterial Proteins↗

PubMed1997

Age-related effects of cardiac sympathetic denervation on the responses to cardiopulmonary receptor stimulation in piglets.

The effects of right stellate ganglionectomy (RSG) and bilateral stellate ganglionectomy (BSG) on cardiovascular responses to phenyl biguanide (PBG, 80 micrograms/kg) were studied in 1- and 8-wk-old piglets. Animals were anesthetized with Saffan, paralyzed, thoractomized, and ventilated with 100% O2. Recordings of the ECG (lead II) and aortic pressure (AoP) were used to compute the maximum R-R interval, heart rate (HR), and mean AoP, and to determine the occurrence of atrioventricular conduction block (AVB). Right atrial injections of PBG in 1-wk-old piglets elicited AVB as well as decreases in AoP and HR in all animals; this response pattern was not altered by either RSG or BSG. The PBG response of neurally intact 8-wk-old animals was comprised of a decrease of HR without change in AoP; AVB occurred in three of six animals. After RSG or BSG, AoP decreased along with decreased HR, and now AVB occurred in all animals; changes of AoP and maximum R-R interval were greater after BSG than after RSG. These results suggest that the stellate ganglia exert a neuroprotective influence on cardiovascular function, requiring some degree of maturation for expression. Our findings support the hypothesis that an imbalance of cardiac autonomic innervation favoring parasympathetic activity may produce immature responses to cardiopulmonary afferent stimulation in older maturing animals.

Aging↗

PubMed1997

[CT for diagnosis of parathyroid adenoma].

We analyzed Ct findings of 10 cases with parathyroid adenoma which had been verified by surgery and pathologic section. The correct localization of 9 adenomas was made by CT preoperatively. The method of CT scanning of parathyroid adenoma were elucidated. The results showed that most adenomas were located in the groove between trachea and esophagus. The contour of tumors was oval, the edge was smooth and regular. Enhancement CT images were helpful for differentiating the tumor from blood vessel. It is indicated that CT scanning is a good method for localizing the parathyroid adenoma.

Adenoma↗

PubMed1997

[Dynamic changes in cytokines in wound exudates from superficial II degree burns in rats].

We take rats as models to study the dynamic changes in cytokines in wound exudate at different time phases post-burn. 120 SD rats were divided into two groups: group 1 with subcutanous implantation of sponges only (S), and group 2 rats were inflicted 10% superficial II degrees burns of their total body surface immediatly after the implantation (Sb). The activities of IL-1, IL-6 and TNF alpha in wound exudates within sponges were measured at 6 h, 1 d, 3 d, 7 d, 10 d and 14 d after the injuries. The changes in activity of these cytokines in both groups showed somewhat the same type of fluctuations, i.e., temporarly ebb and flow in the early phases, and 72 hs later showing a steady increase. The activity of IL-6 reached the peak level in 6 hs while IL-1 and TNF alpha in 24 hs. Probably the early peak levels were produced by local cells responding to the injuries. At each peak level, there was an apparent difference between group S and group Sb (p < 0.01). In the early phases, the levels were S > Sb, and later, the reverse. In group S there was a positive correlation between IL-1 and IL-6, whereas in Sb only 6 h's exudate showed a weak positive correlation. We think the cause of the early differences was: 1. less number of cytokine secreting cells in Sb due to severer injury to local tissues, and 2. increased capillary permeability releasing cytokines from local tissues to the surroundings. The late differences suggest that repair was more complicated and time-consuming in Sb.

Animals↗