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C Lau

Publications and source records attributed to C Lau.

At least 55 records · Page 3Linked to original sources
PubMed2000

First results of the Canadian and European Single lead DDD Studies. A report of two multicenter studies on Vena Cava Atrial Stimulation (VECATS).

The first results of a new, single lead DDD pacing system consisting of two bipolar combinations of floating atrial ring electrodes, with the proximal ring at the vena cava superior junction, and which can be used separately for atrial sensing and pacing (VECATS) are reported. Uncomplicated implantation of the pacing system was performed in 78 patients with VDD indications. Pacing and sensing parameters were measured at implantation, before discharge (days 1-3), at 1 and 3 months in various positions and during activity. Atrial pacing threshold (AT) and diaphragmatic stimulation threshold (DT) were 3.3 +/- 1.1 V and 7.2 +/- 2.2 at implant, and 4.3 +/- 0.5 and 7.9 +/- 1.1 V at 3 months, respectively, in the European group. In the Canadian group AT increased and DT decreased during follow-up, leaving a safety margin of 1 V. Reliable intraoperative atrial pacing was possible in 93% of patients. Failures were caused by no capture (3%) or AT > DT (4%). At 3 months, 54% of the atria were consistently paced. Atrial pacing failures were due to no atrial capture (8%), and AT > DT (38%). We conclude that atrial pacing was safe and initially possible in the majority of patients with the VECATS pacing system, though diaphragmatic stimulation became more prevalent over time, due to an increase in AT threshold and a decrease in DT.

Aged↗
PubMed1999

Identification of a large region of secondary structure in the 3'-untranslated region of chicken elastin mRNA with implications for the regulation of mRNA stability.

Synthesis of aortic elastin peaks in the perinatal period and then is strongly down-regulated with postnatal vascular development. Our laboratory has previously shown that changes in elastin mRNA stability contribute to this developmental decrease in elastin production. Here we identify a large region of stable secondary structure in the 3'-untranslated region (3'-UTR) of chicken elastin mRNA. Reverse transcriptase polymerase chain reaction or polymerase chain reaction amplification of the 3'-UTR consistently resulted in products with an approximately 328-bp deletion from the central region of the 3'-UTR, suggesting the presence of secondary structure. The presence of this structure was confirmed by probing the 3'-UTR with RNases with selectivity for single- or double-stranded RNA. Gel migration shift assays using cytosolic extracts from 2-day old chicken aorta demonstrate specific binding of a cytosolic protein to riboprobes containing the 3'-UTR of elastin but not to riboprobes either corresponding to other areas of the message or containing the 3'-UTR but lacking the region of secondary structure. Binding of cytosolic protein was particularly prominent in aortic extracts from 2-day old chickens, a time when elastin message is stable, as compared with 8- and 15-week old chickens, when the elastin message is relatively unstable, suggesting that this region of secondary structure may play a role in developmental regulation of stability of elastin mRNA.

Animals↗
PubMed1999

Serum theorem

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Journal Article↗
PubMed1999

Feeding strategies for premature infants: randomized trial of gastrointestinal priming and tube-feeding method.

BACKGROUND: Data on enteral feeding management of premature infants are limited and often not the subject of randomized clinical trials. Several small studies suggest benefits from the early initiation of feeding, but do not assess the combined effects of time of initiation of feeding, tube-feeding method, and type of milk used. Either singly or in combination, these treatments may affect growth, bone mineralization, biochemical measures of nutritional status, and feeding tolerance, and, ultimately, the duration of hospitalization. METHODS: A total of 171 premature infants, stratified by gestational age (26 to 30 weeks) and diet (human milk or preterm formula) were assigned randomly among four treatment combinations in a balanced two-way design comparing the presence or absence of gastrointestinal (GI) priming for 10 days and continuous infusion versus intermittent bolus tube-feeding. RESULTS: The major outcome, time required for infants to attain full oral feeding, was similar among treatments. GI priming was not associated with any measured adverse effect and was associated with better calcium and phosphorus retention, higher serum calcium and alkaline phosphatase activity, and shorter intestinal transit times. The bolus tube-feeding method was associated with significantly less feeding intolerance and greater rate of weight gain than the continuous method. In addition, the greater the quantity of human milk fed, the lower the morbidity. CONCLUSIONS: Early GI priming with human milk, using the bolus tube-feeding method, may provide the best advantage for the premature infant.

Body Weight↗
PubMed1999

Feeding strategies for premature infants: beneficial outcomes of feeding fortified human milk versus preterm formula.

BACKGROUND: In a large-scale study of feeding strategies in premature infants (early vs later initiation of enteral feeding, continuous vs bolus tube-feeding, and human milk vs formula), the feeding of human milk had more effect on the outcomes measured than any other strategy studied. Therefore, this report describes the growth, nutritional status, feeding tolerance, and health of participating premature infants who were fed fortified human milk (FHM) in comparison with those who were fed exclusively preterm formula (PF). METHODS: Premature infants were assigned randomly in a balanced two-way design to early (gastrointestinal priming for 10 days) versus late initiation of feeding (total parenteral nutrition only) and continuous infusion versus intermittent bolus tube-feeding groups. The type of milk was determined by parental choice and infants to receive their mother's milk were randomized separately from those to receive formula. The duration of the study spanned the entire hospitalization of the infant. To evaluate human milk versus formula feeding, we compared outcomes of infants fed >50 mL. kg-1. day-1 of any human milk (averaged throughout the hospitalization) with those of infants fed exclusively PF. Growth, feeding tolerance, and health status were measured daily. Serum indices of nutritional status were measured serially, and 72-hour nutrient balance studies were conducted at 6 and 9 weeks postnatally. RESULTS: A total of 108 infants were fed either >50 mL. kg-1. day-1 human milk (FHM, n = 62) or exclusively PF (n = 46). Gestational age (28 +/- 1 weeks each), birth weight (1.07 +/- 0.17 vs 1.04 +/- 0.19 kg), birth length and head circumference, and distribution among feeding strategies were similar between groups. Infants fed FHM were discharged earlier (73 +/- 19 vs 88 +/- 47 days) despite significantly slower rates of weight gain (22 +/- 7 vs 26 +/- 6 g. kg-1. day-1), length increment (0.8 +/- 0.3 vs 1.0 +/- 0.3 cm. week-1), and increment in the sum of five skinfold measurements (0.86 +/- 0.40 vs 1.23 +/- 0.42 mm. week-1) than infants fed PF. The incidence of necrotizing enterocolitis and late-onset sepsis was less in the FHM group. Overall, there were no differences in any measure of feeding tolerance between groups. Milk intakes of infants fed FHM were significantly greater than those fed PF (180 +/- 13 vs 157 +/- 10 mL. kg-1. day-1). The intakes of nitrogen and copper were higher and magnesium and zinc were lower in group FHM versus PF. Fat and energy absorption were lower and phosphorus, zinc, and copper absorption were higher in group FHM versus PF. The postnatal retention (balance) surpassed the intrauterine accretion rate of nitrogen, phosphorus, magnesium, zinc, and copper in the FHM group, and of nitrogen, magnesium, and copper in the PF group. CONCLUSIONS: Although the study does not allow a comparison of FHM with unfortified human milk, the data suggest that the unique properties of human milk promote an improved host defense and gastrointestinal function compared with the feeding of formula. The benefits of improved health (less sepsis and necrotizing enterocolitis) associated with the feeding of FHM outweighed the slower rate of growth observed, suggesting that the feeding of FHM should be promoted actively in premature infants.

Animals↗
PubMed1999

The use of human milk and breastfeeding in premature infants.

Human milk is beneficial in the management of premature infants. The beneficial effects generally relate to improvements in host defenses, digestion, and absorption of nutrients, gastrointestinal function, neurodevelopment, and maternal psychological well-being. The use of fortified human milk generally provides the premature infant adequate growth, nutrient retention, and biochemical indices of nutritional status when fed at approximately 180 mL/kg/day compared with unfortified human milk. Human milk can only support the needs of the premature infant if adequate milk volumes are produced. Intensive efforts at lactation support are desirable. Therefore, neonatal centers should encourage the feeding of fortified human milk for premature infants along with skin-to-skin contact as a reasonable method to enhance milk production and promote success with early breastfeeding, while potentially facilitating the development of an enteromammary response.

Breast Feeding↗
PubMed1999

Perforated appendicitis is not a contraindication to laparoscopy.

Recent studies have reported an increased risk of intra-abdominal abscess formation following laparoscopic operation for perforated appendicitis. We undertook this study to compare laparoscopic versus open appendectomy in the treatment of perforated appendicitis. Records of all patients undergoing an appendectomy between January 1994 and June 1997 were reviewed, classifying appendicitis as acute, gangrenous, or perforated based on the intraoperative findings. Operative procedures were categorized as open, laparoscopic converted to open, or laparoscopic. The study group included 690 patients; four hundred fourteen (60%) were acute, 77 (11%) were gangrenous, and 199 (29%) were perforated. Although mean length of stay was shorter for all patients undergoing laparoscopic appendectomy, patients with perforated appendicitis had similar length of stay between treatment groups. Mean operative time for open appendectomy was significantly shorter than for converted or laparoscopic appendectomy regardless of diagnosis (P<0.01). Ten patients (1.4%) developed an intra-abdominal abscess: six after open appendectomy (1.7%), one after converted appendectomy (3.7%), and three after laparoscopic appendectomy (1%). There was no significant difference in rate of abscess formation in patients with perforated appendicitis undergoing open, converted, or laparoscopic appendectomy. We conclude that laparoscopic appendectomy for perforated appendicitis is not associated with an increased rate of intra-abdominal abscess formation.

Adolescent↗
PubMed1998

Sample preparation and high-performance liquid chromatographic analysis of deoxyribonucleoside triphosphates in individual rat embryos.

A rapid, robust, and sensitive method has been developed to measure concentrations of deoxyribonucleoside triphosphates in individual, day 14 rat embryos by modifying and optimizing existing methods for cellular extracts. Significant changes include: (i) oxidative degradation of ribonucleoside triphosphates using methylamine at lower pH (decreased from 6.5 to 4.0) to improve poor HPLC peak shape of early eluting nucleotides; (ii) glass fiber disc solid-phase extraction of the reaction mixture, which dramatically reduces impurities that interfere with nucleotide measurement, eliminates the necessity of column regeneration, and allows mobile phase recycling; and (iii) lower ionic strength (reduced from 0.4 to 0.26 or 0.12 M ammonium phosphate) and higher pH (increased from 3.25 to 5.55 or 6.98, respectively) mobile phase, conditions which are less destructive to the column's bonded phase and silica support, thereby contributing to longer column life. Enhancements include: (i) filtration of the sample prior to HPLC injection and addition of an in-line filter, guard column, and saturating precolumn of silica in the mobile phase flow, which aids substantially in extending column life and improves chromatographic stability, and (ii) inclusion of an internal standard to correct for mechanical losses. Limits of determination at a signal to noise ratio of 6:1 range from 5.5 to 12 pmol on-column or 0.41 to 0.87 pmol/mg of embryonic tissue depending on the specific nucleotide. Recoveries are quantitative for all nucleotides, and interassay variabilities are between 5 and 7% when quantified by peak height. The method has also been applied successfully to analysis of murine erythroleukemic cell cultures and this, when coupled with the embryo results, suggests its general utility.

Animals↗
PubMed1998

Quality ratings of a hospital foodservice department by inpatients and postdischarge patients.

OBJECTIVES: To examine quality of food and nutrition services using the ratings of inpatients and patients who had been discharged (postdischarge patients). DESIGN: Questionnaires were used to collect perceptions of inpatients and postdischarge patients on the quality of food and nutrition services. A 5-point scale allowed subjects to rate quality from very poor to very good. SUBJECTS: Questionnaires were completed by 252 inpatients and 437 postdischarge patients of a midwestern teaching hospital. STATISTICAL ANALYSIS: Analysis of variance was used to assess differences in quality ratings on the basis of demographic variables. Stepwise regression was used to determine variables that best predicted overall satisfaction. Paired t tests were conducted to compare matched inpatient and postdischarge ratings. RESULTS: Ratings of food and nutrition services indicated that patients were satisfied; few differences were found in ratings on the basis of patient demographics. Food quality was the best predictor of overall satisfaction for both inpatients and postdischarge patients. As patient expectations were increasingly met or exceeded, patient ratings of quality increased. The majority of patients in the matched sample gave the same ratings on the inpatient and postdischarge questionnaires. APPLICATIONS: Foodservice managers who desire to improve patient satisfaction should focus attention on meeting or exceeding patient expectations for food quality.

Adult↗
PubMed1998

Early feeding, feeding tolerance, and lactase activity in preterm infants.

OBJECTIVE: We sought to ascertain whether the timing of feeding initiation affected the development of intestinal lactase activity and whether there are clinical ramifications of lower lactase activity. STUDY DESIGN: Preterm infants (26 to 30 weeks' gestation; n = 135) were randomly assigned to begin enteral feedings at either 4 (early group) or 15 days of age (standard group). At 10, 28, and 50 days of age lactase activity was determined by measuring the urinary ratio of lactulose/lactose after the 2 sugars were administered. RESULTS: Lactase activity increased significantly over time. Infants in the early group had greater lactase activity at 10 days of age (by 100%) and 28 days of age (by 60%) than the standard group. At 10 days of age lactase activity was greater in milk- versus formula-fed infants. The time required to achieve full enteral feedings, the number of abnormal abdominal x-ray examinations, and the total number of abdominal x-ray examinations were inversely related to lactase activity. CONCLUSIONS: Early feeding increases intestinal lactase activity in preterm infants. Lactase activity is a marker of intestinal maturity and may influence clinical outcomes. Whether the effects of milk on lactase activity were due to the greater concentration of lactose in human milk compared with that in formula must be determined.

Age Factors↗
PubMed1998

The development of sinoatrial dysfunction in pacemaker patients with isolated atrioventricular block.

The purpose of this paper is the assessment of sinus node competence over time in patients with isolated atrioventricular block (AV block). Patients implanted with AV synchronous pacemakers for isolated AV block between December 1993 and June 1995 were prospectively evaluated at predischarge, 6 weeks, and subsequent 6 months follow-up with respect to atrial rate monitors/24-hour Holter and modified exercise test. Patients unable to maintain AV synchronous pacing or complete a modified exercise test were excluded. Sinus node competency is interpreted as: (1) absence of atrial brady- or tachyarrhythmia, (2) ability to achieve a minimum heart rate of 100 beats/min with modified exercise test or during daily activities. There were 58 patients (22 women), mean age 71.0 +/- 13.8 with an average follow-up of 30.4 months (11-40). Three patients did not complete a modified exercise test, 4 patients were lost to follow-up, and 2 patients were unable to maintain AV synchronous pacing. Of the remaining 49 patients, 3 developed chronic or paroxysmal atrial fibrillation. No patient developed significant bradyarrhythmias. All patients achieved a heart rate of > or = 100 beats/min modified exercise test. In our group of patients with isolated AV block within a moderate follow-up period, development of sinoatrial dysfunction was rare (6%). A longer follow-up is required to delineate the natural history of sinoatrial dysfunction in patients with isolated AV block.

Aged↗
PubMed1998

When pacemakers fail: an analysis of clinical presentation and risk in 120 patients with failed devices.

Although pacemaker recalls are common, the optimal mechanism for risk assessment and triage of patients at risk for sudden loss of device system function is unknown. A retrospective chart review of 120 patients with factory proven failed devices was performed. Logistic regression analysis was used to determine clinical correlates of emergency room versus outpatient clinic presentation at time of device failure. Twenty-two patients (18%) presented to emergency and 98 (82%) to clinic. Sixty-three devices had no device output at the time of presentation. Multivariate logistic regression analysis revealed that antiarrhythmic drug use (odds ratio: 7.4, 95% CI: 2.0-28.0), atrioventricular nodal disease as an indication for pacing (odds ratio: 2.8, 95% CI: 1.2-3.0), and female gender (odds ratio: 2.2, 95% CI: 1.0-4.5) were the only significant correlates of emergency room presentations. Pacemaker dependency (escape heart rate < 40 beats/min) did not correlate with location of presentation even though no device output at the time of presentation was associated with emergency room presentation (odds ratio: 2.5, 95% CI: 1.1-5.8). Neither the presence of structural heart disease nor symptoms at the time of device implantation (syncope or presyncope) were correlated with location of presentation upon unexpected device failure. Although there were no deaths in the 120 failed devices studied, there were 26 deaths in the total group of 227 patients with recalled devices that could not be studied. Antiarrhythmic drug use, electrocardiographic pacing indication, and female gender may be more sensitive predictors of emergency room presentation and significant symptoms in the event of unanticipated pacemaker failure. The inability of any retrospective analysis to accurately assess mortality in the setting of pacemaker system failure underscores the need for prospective databases in recall situations.

Age Factors↗
PubMed1998

Early feeding, antenatal glucocorticoids, and human milk decrease intestinal permeability in preterm infants.

To determine the effects of age, feeding regimen, and antenatal glucocorticoids on intestinal permeability, preterm infants (n = 132) were stratified by gestational age and by diet (mothers' own milk versus preterm formula), and assigned randomly to one of four feeding regimens: early-continuous, early-bolus, standard-continuous, and standard-bolus. At 10, 28, and 50 d of age permeability was determined by measuring the ratio of lactulose/ mannitol in the urine after the two sugars were administered enterally for 30 h. The mean (+/-SE) birth weight and gestational age of the infants were 1044 +/- 13 g and 27 +/- 0.1 wk, respectively. Permeability changed as a function of age (p = 0.003). Early feeding was associated with a reduction in permeability at 10 d of age (p = 0.01). Antenatal steroid administration was associated with decreased permeability at 28 d of age (p = 0.017). The feeding of human milk (versus formula) was associated with decreased permeability at 28 d of age (p = 0.02). Continuous versus bolus feeding did not affect permeability.

Aging↗
PubMed1997

Nucleoside-mediated mitigation of 5-fluorouracil-induced toxicity in synchronized murine erythroleukemic cells.

5-Fluorouracil (5-FU) is a chemotherapeutic agent known to retard embryonic growth and induce cleft palate and limb deformities. The predominant mechanism underlying its toxic action is thought to be inhibition of thymidylate synthetase (TS), and hence thymidine triphosphate (dTTP) synthesis, resulting in alteration of the balance of deoxynucleotide (dNTP) pools and disruption of DNA synthesis. Indeed, previously we demonstrated retarded cell-cycle progression concurrent with a 60% decrease in TS activity in rat whole embryos following maternal exposure to 40 mg/kg 5-FU on Gestational Day 14 and in the murine erythroleukemic cell (MELC) suspension culture following exposure to 5-25 microM 5-FU for 2 hr. In the study described herein, we used high-performance liquid chromatography (HPLC) to demonstrate in both of these model systems that 5-FU exposure results in similar patterns of dNTP perturbations: a prolonged decrease in dTTP and dGTP levels and an increase in dCTP and dATP. In addition, we used centrifugal elutriation to synchronize MELC in the phases of the cell cycle (G0/G1 and early S) most sensitive to 5-FU to investigate the ability of nucleoside supplementation to mitigate 5-FU-induced toxicity. Our data indicate that following a 2-hr exposure to 5-25 microM 5-FU, supplementation with 1-10 microM thymidine (TdR) for 24 hr partially reverses 5-FU-induced toxicity as evidenced by increased cellular proliferation and cell-cycle progression and amelioration of 5-FU-induced perturbations of protein synthesis and cellular membrane permeability compared to unsupplemented 5-FU-exposed cells. However, TdR concentrations >/=100 microM inhibited growth or were cytotoxic. In comparison, supplementation with 10 microM-10 mM of deoxycytidine (CdR) was not toxic, but effected a dose-dependent recovery from 5-FU-induced toxicity. At 1-100 microM, neither deoxyadenosine nor deoxyguanosine supplementation reduced 5-FU-induced toxicity; at higher concentrations, both purine nucleotides inhibited cell growth. Although these results support the hypothesis that 5-FU disrupts the MELC cell cycle by depleting dTTP (a perturbation that is reversible by TdR supplementation), they also indicate that CdR supplementation offers an additional recovery pathway.

Animals↗
PubMed1997

Oral feeding in low birth weight infants.

To gain a better understanding of the development of sucking behavior in low birth weight infants, the aims of this study were as follows: (1) to assess these infants' oral feeding performance when milk delivery was unrestricted, as routinely administered in nurseries, versus restricted when milk flow occurred only when the infant was sucking; (2) to determine whether the term sucking pattern of suction/ expression was necessary for feeding success; and (3) to identify clinical indicators of successful oral feeding. Infants (26 to 29 weeks of gestation) were evaluated at their first oral feeding and on achieving independent oral feeding. Bottle nipples were adapted to monitor suction and expression. To assess performance during a feeding, proficiency (percent volume transferred during the first 5 minutes of a feeding/total volume ordered), efficiency (volume transferred per unit time), and overall transfer (percent volume transferred) were calculated. Restricted milk flow enhanced all three parameters. Successful oral feeding did not require the term sucking pattern. Infants who demonstrated both a proficiency > or = 30% and efficiency > or = 1.5 ml/min at their first oral feeding were successful with that feeding and attained independent oral feeding at a significantly earlier postmenstrual age than their counterparts with lower proficiency, efficiency, or both. Thus a restricted milk flow facilitates oral feeding in infants younger than 30 weeks of gestation, the term sucking pattern is not necessary for successful oral feeding, and proficiency and efficiency together may be used as reliable indicators of early attainment of independent oral feeding in low birth weight infants.

Bottle Feeding↗
PubMed1997

Is this the natural history of the retention wire? A case report.

We report on a 71-year-old man who had a dual chamber pacemaker implanted in 1991. A Class IV fracture of the Telectronics Accufix 330-801 atrial lead was observed on a chest X ray in December 1993. Serial chest X ray and fluoroscopy documented stable position of the migrated fractured J wire. The patient remained asymptomatic and a decision for conservative monitoring was made. A subsequent finding of a right atrial mass on echocardiography and evidence of pulmonary embolism on lung scan prompted a change of strategy. The patient underwent atriotomy, and a right atrial thrombus was discovered associated with the fractured J retention wire, both of which were extracted uneventfully. This case is illustrative that despite apparent stability of a Class IV fracture, it may result in endothelial injury with a thrombogenic nidus and resultant complications.

Aged↗
PubMed1996

Gene transfer into fetal rat intestine.

To assess the fetal intestine as a site for gene therapy, we have explored a xenograft model in which fetal rat intestine is grafted subcutaneously into nu/nu mice. Prior to grafting, the tissue was exposed to a replication-deficient retroviral vector bearing the neo gene. Transduction efficiency was assessed by quantitative polymerase chain reaction (PCR) of neo in DNA recovered from the grafts. Three methods of infection were employed: (i) simple flushing of the fetal intestine with the vector; (ii) incubation with the vector for 2 hr; and (iii) a combination of both. The first method gave the highest transduction efficiencies in terms of both the proportion of samples that were neo-positive and the number of neo-positive cells per sample. Using this approach, the time course of persistence of neo-positive cells was analyzed by collecting grafts at 1 versus 3 weeks post-infection. The results showed approximately five-fold more positive cells at the earlier time point than at the later, suggesting loss of transduced cells due to cell turnover. Nevertheless, the persistence of a portion of the positive cells for at least 3 weeks is encouraging for future studies with fetal intestine.

Animals↗