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Overall and differentiated ratings of perceived exertion at the respiratory compensation threshold: effects of gender and mode.

Research on gender differences in ratings of perceived exertion (RPE) has been equivocal with few studies comparing exercise modes and differentiated RPE. The current study examined gender differences in overall and differentiated RPE at the respiratory compensation threshold (RCT) during cycling and treadmill exercise. Each minute during a maximal treadmill and maximal cycling test, men (n=18) and women (n=16) estimated RPE corresponding to overall (RPE-O), legs (RPE-L), and breathing/chest (RPE-C) exertion. A 2 (gender) x 2 (mode) x 3 (RPE-O, RPE-L, RPE-C) repeated measures MANOVA revealed no significant mode x gender or RPE x gender interactions. The exercise mode x RPE interaction approached significance (P=0.055) when cycling [mean (SD) 14.8 (2.9)] and treadmill exercise [12.8 (2.9)] were compared. No main effects for gender [men: 13.7 (2.6), women: 13.4 (2.6)] were detected. Main effects for mode showed RPE to be significantly greater during cycling [14.4 (2.8)] versus treadmill exercise [12.7 (2.9)]. Main effects for differentiated RPE showed RPE-L [13.8 (2.6)] to be significantly greater than RPE-O [13.5 (2.6)] and RPE-C [13.3 (2.6)]. Results suggest that overall and differentiated RPE at the RCT are not significantly different between genders during cycling or treadmill exercise. While RPE-L was statistically greater than RPE-O and RPE-C, the magnitude of the differences makes this result of little practical significance. The marginal interaction suggests greater RPE-L values might be expected at the RCT during cycling versus treadmill exercise. However, results suggest that minimal RPE differences exist between men and women during cycling and treadmill exercise.

Adaptation, Physiological↗

Introduction of GDC embolization in the clinical practice as treatment synergical to surgery: impact on overall outcome of patients with subarachnoid hemorrhage.

The GDC endovascular approach represent an effective alternative to surgery for treatment of intracranial aneurysms. Anyway no data are available about the impact of endovascular embolization with GDC on overall outcome of patients with subarachnoid hemorrhage. We analyse retrospectively a series of 234 patients admitted for ruptured intracranial aneurysm. Results were then compared with results of three surgical series from the literature. The 95.7% of patients underwent aneurysm treatment; 56.4% of patients were classified as good recovery, 12.8% presented moderate disability, 10.3% were severely disabled, 3% were in persistent vegetative state and 17.5% were dead. Patients older than 60 years accounted for 37% of all cases and good outcome in this group accounted for 54.7%. Good results were obtained in 90.1%, 61.7% and 22.8% of patients with Hunt-Hess grade I-II, III and IV-V respectively. Finally good outcome was observed in 82.8% of patients with aneurysms of the posterior circulation. Introduction of GDC embolization in clinical practice contributed to the extension of indication for aneurysm treatment leading to a reduction of overall mortality. GDC utilisation does not affect the overall percentage of patients with good outcome reflecting an increase of severely disabled patients. Endovascular treatment seems an effective theraputic choice in selected grade I-II patients. Results in grade III patients suggest that surgery may be advantageous because of washing and decompression of the basal cisterns while results in grade IV and V patients are unsatisfactory. GDC embolization clearly improves the prognosis of patients with posterior circulation aneurysms and probably is an advantageous theraputic choice in elderly patients.

Adolescent↗

Association of genetic variation in tamoxifen-metabolizing enzymes with overall survival and recurrence of disease in breast cancer patients.

Tamoxifen has been a mainstay of adjuvant therapy for breast cancer for many years. We sought to determine if genetic variability in the tamoxifen metabolic pathway influenced overall survival in breast cancer patients treated with tamoxifen. We examined functional polymorphisms in CYP2D6, the P450 catalyzing the formation of active tamoxifen metabolites, and UGT2B15, a Phase II enzyme facilitating the elimination of active metabolite in a retrospective study of breast cancer patients. We also examined whether the combination of variant alleles in SULT1A1 and UGT2B15 had more of an impact on overall survival in tamoxifen-treated patients than when the genes were examined separately. We conducted a retrospective study using archived paraffin blocks for DNA extraction and data from pathology reports and hospital tumor registry data for information on clinical characteristics, treatment, and outcomes (162 patients receiving tamoxifen and 175 who did not). Genotypes for CYP2D6 and UGT2B15 were obtained and Cox proportional hazards modeling was performed. After adjusting for age, race, stage of disease at diagnosis, and hormone receptor status, we found no significant association between CYP2D6 genotype and overall survival in either group of breast cancer patients. Tamoxifen-treated patients with UGT2B15 high activity genotypes had increased risk of recurrence and poorer survival. When UGT2B15 and SULT1A1 'at-risk' alleles were combined, women with two variant alleles had significantly greater risk of recurrence and poorer survival than those with common alleles. These studies indicate that genetic variation in Phase II conjugating enzymes can influence the efficacy of tamoxifen therapy for breast cancer.

Antineoplastic Agents, Hormonal↗

Influence of angiotensin II receptors blocking on overall left ventricle's performance of patients with acute myocardial infarction of limited extent. Echocardiographic assessment.

INTRODUCTION: Recent studies documented the beneficial effect of angiotensin-receptor blockers (ARBs) on patients (pts) with acute myocardial infarction (AMI) combined with left ventricle (LV) systolic dysfunction. The present study intended to assess the impact of the ARB irbesartan, on the overall LV performance in pts with uncomplicated AMI of limited extent. METHODS: Forty consecutive pts with first inferior AMI (AMI-I) and preserved LV-systolic function were enrolled. They were allocated into two groups: (a) 20 pts received the conventional treatment of AMI-I and placebo (CT) and (b) 20 pts administered irbesartan additionally to the conventional treatment (IR). Twenty four healthy individuals of matching age and sex were recruited as control group (CG). Complete echocardiographic examination, Tei index of overall LV function and systolic blood pressure (SBP) were measured on the 8th post-infarct day. RESULTS: The Tei index of IR group (0.53+/-0.03) was significantly lower compared to that of CT group (0.78+/-0.05) (p<0.001) and was similar to that of CG (0.45+/-0.03)(p=NS). Irbesartan induced a considerable decrease in both isovolumic relaxation (115+/-7 ms vs 140+/-7 ms; p<0.01) and contraction time (52+/-2 ms vs 64+/-3 ms; p<0.01) and a significant increase in ejection time (279+/-6 ms vs 256+/-8 ms; p<0.05). SBP in pts of IR group was similar to that of CT group (112+/-3 mmHg vs 113+/-4 mmHg; p=NS). CONCLUSIONS: Therapy with Irbesartan improves overall LV function of pts with AMI-I. Irbesartan leads to acceleration of the LV relaxation, which possibly indirectly ameliorates LV systolic performance too. This beneficial influence is possible attributed to a direct tissue effect of the drug and not to its hemodynamic action.

Angiotensin II Type 1 Receptor Blockers↗

Health-related and overall quality of life of patients with chronic hip and knee complaints in general practice.

BACKGROUND: Information about quality of life of patients with chronic hip or knee complaints in general practice is scarce. This study describes the health-related and overall quality of life (HRQL) of these complaints. METHODS: Data were obtained from a cohort study in general practice. HRQL at three months follow-up was analysed. HRQL was measured as: symptoms, physical, psychological and social functioning, and general health perceptions, using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and the MOS 36-item short-form-health survey (SF-36). Overall quality of life was measured using a 5-point rating scale. RESULTS: The results show that patients with chronic hip or knee complaints have a substantial lower HRQL compared to patients who had recovered from baseline hip or knee complaints. The largest effect was found on symptoms and physical functioning: up to 2.9 standard deviations below patients who had recovered from baseline hip or knee complaints. Scores of patients with both chronic hip and knee complaints were significantly worse than scores of patients with only knee complaints on most subscales. CONCLUSION: In patients with chronic hip or knee complaints the worst scores were seen on scales that measure symptoms and physical functioning, but still a substantially lower score was obtained for overall quality of life. Quality of life was poorer for patients with both chronic hip and knee complaints compared to those with chronic hip or knee complaints only.

Chronic Disease↗

Osmotic myelinolysis following chronic hyponatremia corrected at an overall rate consistent with current recommendations.

Rapid correction of chronic hyponatremia (CH) may lead to the development of osmotic myelinolysis (OM), a condition with high mortality and high incidence of devastating neurological sequelae. Treatment guidelines suggest "safe" overall rates of correction of serum sodium concentration ([Na](s)) over the first 24 and 48 hours of treatment of CH. We report a patient with CH who developed fatal OM despite overall rates of correction of [Na](s) that were within the recommended rates. The potential risk factors for the development of OM in this patient included short (within a few hours) rises in [Na](s) exceeding 0.5 mmol/l per hour and the presence of severe protein malnutrition. We suggest that the rate of correction of [Na](s) in CH should be uniformly slow and that the overall rate of correction should be slower than the currently recommended rate in severely malnourished patients.

Aged↗

Reaction time, impulse speed, overall synaptic delay and number of synapses in tactile reaction neuronal circuits of normal subjects and thinner sniffers.

In control subjects, warned auditory reaction time (RT) for a given effector organ was less than the warned visual RT for the same organ. The RT of the circuits between eye or ear or sites of tactile stimulation (SOS) and the index fingers were significantly shorter than that between eye or ear or the same SOS and the right or left big toes. The greater the distance between the SOS and the brain the longer the RT of the response by a given effector organ. The overall signal speed (OASS) from the neck to the index finger was less than that from the neck to the big toe. The OASS from the neck to a given effector was less than that from the toe to the same effector. Sensory nerve impulse speed was slightly faster than motor nerve impulse speed. The overall synaptic delay and estimated number of synapses (ENOS) of simple tactile reaction neuronal circuits of normal subjects did not significantly vary with site of tactile stimulation or effector organ. The mean number of synapses of various tactile reaction neuronal circuits of normal subjects was estimated to be between 69 and 77, which is far greater than the number of synapses in the touch-tactile and motor pathways combined. The overall synaptic delay in the tactile reaction neuronal circuits between SOS and the left and right big toes were significantly lower in sniffers than in control subjects. This may be due to a decrease in either the average synaptic delay, the number of synapses, or both in the tactile reaction neuronal circuits between sites of stimulation and big toes (but not index fingers) in sniffers.

Adolescent↗

A comparison of the effects of d-amphetamine, cocaine, imipramine and pentobarbital on local and overall rates of responding maintained under a four-component multiple fixed-interval schedule.

Key pecking of pigeons was maintained under a four-component multiple fixed-interval schedule with values of 1-min, 3-min, 5-min and 10-min. Each schedule value was correlated with a different key color, each of which controlled distinctively different performances. This schedule generated a range of response rates both within and across the different interval components that permitted a direct comparison of drug effects on local and overall rates of responding. d-Amphetamine, cocaine, imipramine and pentobarbital all increased low local response rates at doses that did not affect or decreased higher rates within each fixed interval. Similar effects were obtained when different overall rates of responding were analyzed except that imipramine and pentobarbital also increased the highest overall rates occurring under the 1-min schedule.

Animals↗

Dose, fractionation and overall treatment time in radiation therapy--the effects on local control for cancer of the larynx.

The effect of total tumor dose, split course treatment and overall treatment time on local control was analysed in a retrospective series of 997 patients with carcinoma of the larynx, treated with megavoltage radiotherapy only. Primary tumors were classified by site (glottis and supraglottis) and T-stage. Continuous course (CC, n = 594) treatment was given primarily to small tumors. Split course radiation (SC, n = 403) was generally given to patients with larger field sizes. Total doses of irradiation ranged from 50 to 79 Gy, with a mean of 64 Gy in CC and 66 Gy in SC. Most of the treatments were given with fraction sizes between 2.0 and 2.1 Gy (91%). Overall treatment times ranged between 25 and 60 days in the CC group (mean, 45 days) and between 45 and 120 in the SC group (mean, 76 days). A local recurrence was observed in 256 patients. T-stage was the only tumor characteristic strongly related to local failure. Corrected for T-stage, no difference in local relapse rate was observed between glottic and supraglottic tumors, or between node-negative (n = 886) and node-positive patients (n = 111). After correction for T-stage the local failure rate of SC-treated tumors was 2.1 (95% confidence limits: 1.4-3.1) times higher than of CC-treated tumors. However, this effect could not be explained as an effect of the overall treatment time (OTT) itself, as no effect of OTT was found within the SC and the CC group, even though the variation in OTT's was considerable in the SC group. A higher tumor dose was associated with a lower local failure rate in the CC group (p = 0.005), but not in the SC group (p = 0.56).

Adolescent↗

Origins of radiotherapy and radiobiology: separation of the influence of dose per fraction and overall treatment time on normal tissue damage by Reisner and Miescher in the 1930s.

The effect of fractionation on the response of normal tissues to irradiation was already investigated in the 1930s. Reisner (Reisner, A. Hauterythem und Röntgenstrahlung. Erg. Med. Strahlenforsch, 6: 1-60, 1933) measured the time course of skin erythema on thighs of humans by applying different doses per fraction while keeping constant total dose and overall treatment time. The results showed that acute skin damage was reduced with small doses per fraction. Two years later Miescher (Miescher, G. Tierexperimentelle Untersuchungen über den Einfluss der Fraktionierung auf den Späteffekt. Acta Radiol, 16: 25-38, 1935) published his results on late radiation effects in rabbit skin. He also reported that the main influencing factor for tissue tolerance was dose per fraction. In addition, he found indications that there was no impact of overall treatment time on the development of late reactions. Strandqvist in his famous monograph on the time factor in treatment of skin cancer (Strandqvist, M. Studien über die kumulative Wirkung der Röntgenstrahlen bei Fraktionierung. Erfahrungen aus dem Radiumhemmet an 280 Haut -und Lippenkarzinomen. Acta Radiol. (Suppl.) 55: 1-300, 1944), however, postulated that total dose and overall treatment time were the main determinants of local control as well as of normal tissue damage, apparently omitting to consider the findings of Reisner and Miescher in his own analysis. It is our impression that mainly due to the large influence of Strandqvist's work on radiobiological thinking the early findings on the normal tissue sparing effect of small fraction size have been forgotten and had to be rediscovered about 40 years later.

Animals↗

Comparison of site-specific and overall tumor incidence analyses for 81 recent National Toxicology Program carcinogenicity studies.

Eighty-one recent carcinogenicity studies carried out by the National Toxicology Program (NTP) were evaluated to determine how the utilization of statistical analyses based on the proportion of animals with primary tumors (all sites) or the proportion of animals with malignant neoplasms (all sites) affected the interpretation of the data compared to analyses of site-specific effects. Utilizing site-specific analyses, the NTP concluded that 45 of the 81 studies (56%) showed carcinogenic responses, 7 (9%) produced equivocal effects, and 29 (36%) showed no evidence of carcinogenicity. An analysis of tumors at all sites often resulted in site-specific carcinogenic responses going undetected. Less than half of the 45 carcinogens identified as producing site-specific carcinogenic responses showed a significant increase in the incidence of primary tumors (22 chemicals) or malignant tumors (21 chemicals). Among the 29 chemicals interpreted as not carcinogenic based on site-specific effects, only two showed significant increases in overall tumor incidence. Two major problems are associated with an evaluation based on overall (all sites) tumor rates: The pooling of various tumor types reduces study sensitivity for detecting chemically related increases in site-specific tumor incidences, and the biological relevance of combining the incidences of tumors of varying morphologies and topographies is questionable. Most national and international guidelines for studying chemicals for carcinogenicity in rodents (or in humans) emphasize site-specific effects. Thus, despite purported advantages of analyses based on overall tumor rates (e.g., simplicity; reducing concerns regarding false positive results) primary emphasis should continue to be on site-specific analyses.

Animals↗

Economics of a dry-cow anthelmintic drenching programme for dairy cows in New Zealand. Part 1. Overall response in 47 herds.

Trials were conducted on 47 seasonal supply dairy farms (greater than 5500 cows) to assess the economics of a dry-cow anthelmintic drenching programme. The programme was administered during the autumn/winter of 1983 and consisted of two treatments, the first shortly after drying off (late April-early June) and the second shortly before calving (mid-July-late August). The effects of the programme on the body condition of cows over winter and their subsequent milk production and reproductive performance were assessed. Overall, the treatment did not result in a worthwhile improvement in cow condition over winter. However, there was a small, but significant overall increase in milk production (2.24 kg milkfat/cow/lactation = 51.5 l milk; P less than 0.01). Young cows (3 years old) did not respond significantly better than mature cows, but high quality cows (as assessed on the basis of the previous season's milk production) responded significantly better than those of poorer quality. The pre-calving condition of cows did not significantly influence the magnitude of their response. Calving data for the year following the trials indicated that conception rates and time of conception were unaffected by the drench programme. At prices prevailing at the time of the trials, the programme proved to be only marginally economic overall (approximately 1 kg milkfat/cow was required simply to cover the cost of the anthelmintic used). However, levels of response in the individual herds involved varied considerably.

Animals↗

Cell repopulation and overall treatment time.

Prolongation of the overall treatment time in radiotherapy, especially of squamous cell carcinomas of the head and neck, decreases the chances of cure. This is most likely because of the proliferation of surviving clonogenic tumor cells between dose fractions. Between the 3rd and 7th week of conventional radiotherapy of head and neck cancers, on average 0.5 to 0.7 Gy are lost per day by repopulation. As this represents an average value, repopulation may be even more efficient in subgroups of faster tumors. There is little information on repopulation rates during the first 2 weeks of radiotherapy. Prolongation of the overall treatment time in radiotherapy helps to avoid severe side effects from acutely responding tissues, especially oral mucosa. This sparing effect of increasing overall treatment time is mainly caused by the regeneration of mucosal stem cells and transit cells. This repopulation is slow in the first 2 weeks and accelerates dramatically thereafter. The nature of the trigger for acceleration is not known but seems to be related to a critical threshold of acute tissue hypoplasia and the development of the inflammatory reaction of the connective tissue. It is not known whether accelerated tumor repopulation is stimulated by the same or a similar mechanism as the normal epithelium. During accelerated repopulation the oral mucosa is able to compensate a considerably higher proportion of the daily dose fraction than the tumor. These factors have to be taken into account when treatment strategies are designed to cope with the problem of accelerated repopulation.

Cell Division↗

Retrospective analysis of 5037 patients with nasopharyngeal carcinoma treated during 1976-1985: overall survival and patterns of failure.

This is a retrospective analysis of 5037 patients with squamous cell carcinoma of the nasopharynx treated during the years 1976-1985. The stage distribution according to Ho's classification was 9% Stage I, 13% II, 50% III, 22% IV, and 6% Stage V. Only 4488 (89%) patients had a full course of megavoltage radiation therapy. The median equivalent dose to the nasopharyngeal region was 65 Gy and cervical region in node-positive patients 53 Gy. Seventy percent (906/1290) of the node-negative patients had no prophylactic neck irradiation. The overall actuarial 10-year survival rate was 43%, and the corresponding failure-free survival 34%. Altogether, 4157 (83%) patients achieved complete remission lasting more than 6 months, but 53% (2205/4157) of them relapsed after a median interval of 1.4 years. The 10-year actuarial local, regional, and distant failure-free rates were 61%, 64%, and 59%, respectively. Thirty-eight percent (338/891) of all patients with local recurrence achieved second local remission. The local complete remission rate with aggressive re-irradiation alone was 47% (333/706). But 37% (124/338) of the responders recurred the second time. The incidence of distant failure correlated significantly with both the N-stage and the T-stage, with the highest (57%) occurring in patients with N3 disease. The incidence of nodal relapse in node-negative patients was 11% (44/384) among those given prophylactic neck irradiation, but 40% (362/906) among those without. Therapeutic irradiation achieved a complete regional remission rate of 90% (306/339). However, despite successful salvage, these patients had a significantly higher distant failure rate than those without nodal relapse, even if they remained local-failure-free (21% vs 6%). Patients treated during 1981-1985 achieved significantly better treatment results than those treated during 1976-1980, especially in terms of the overall survival (57% vs 47% at 5-year), the overall failure-free survival (42% vs 35% at 5-year), and the local failure-free rate (70% vs 63% at 5-year). The possible contributing factors are discussed.

Adolescent↗

The decreased influence of overall treatment time on the response of human breast tumor xenografts following prolongation of the potential doubling time (Tpot).

PURPOSE: Repopulation during fractionated radiotherapy has been postulated to result in a significant loss in local control in rapidly proliferating tumors. Clinical data suggest that accelerated fractionation schedules can overcome the influence of repopulation by limiting the overall treatment time. Unfortunately, accelerated therapy frequently leads to increased acute reactions, which may become dose limiting. An alternative to accelerated fractionation would be to decrease the rate of repopulation during therapy. To test the potential efficacy of this alternative, we examined the effect of reducing tumor proliferation rate on the response of MCF-7 human breast carcinoma xenografts treated with a short vs. a long course of fractionated therapy. To reduce the proliferation rate, we deprived nude mice transplanted with MCF-7 xenografts of the growth-stimulating hormone estradiol (E2). We have previously reported that E2 deprivation increases the potential doubling time (Tpot) for MCF-7 xenografts from a mean of 2.6 days to 5.3 days (p < 0.001). METHODS AND MATERIALS: E2-stimulated and E2-deprived MCF-7 breast carcinoma xenografts were clamped hypoxically and irradiated with four fractions of 5 Gy each, using either a short (3-day) or long (9-day) treatment course. E2 stimulation was restored in all animals at the completion of irradiation. Radiation response was determined by regrowth time and regrowth delay of the irradiated tumors as compared to unirradiated controls. RESULTS: Prolongation of therapy in rapidly proliferating, E2-stimulated tumors (Tpot approximately 2.6 days) resulted in a significant decrease in regrowth time in two identical experiments. With results pooled for analysis, the regrowth times for the short and long treatments were 62 and 32 days, respectively (combined p < 0.001). The shorter regrowth times suggest that there was less overall tumor damage with the longer fractionated radiotherapy course. No significant difference in regrowth time was observed in the more slowly proliferating, E2-deprived tumors (Tpot approximately 5.3 days) treated with either the short or long regimen. Median regrowth times were 48 and 54.5 days for the short and long treatments, respectively (combined p = 0.14). Similar changes were observed in regrowth delay. CONCLUSIONS: Reduction in the rate of cell proliferation, induced by E2 deprivation in MCF-7 human breast xenografts during fractionated radiotherapy, resulted in a significantly decreased dependence on overall treatment time in comparison to the more rapidly proliferating E2-stimulated tumors. This model suggests that pharmacologically induced reduction in the rate of tumor cell proliferation during a course of fractionated radiotherapy may be a viable alternative to accelerated fractionation for the treatment of rapidly proliferating tumors.

Animals↗

Radiotherapy alone for carcinoma of the vagina: the importance of overall treatment time.

PURPOSE: Review treatment results, complications, and the importance of overall treatment time for carcinoma of the vagina treated with radiotherapy alone. METHODS AND MATERIALS: Between October 1964 and October 1990, 65 patients with histologically confirmed carcinoma of the vagina received definitive radiotherapy at the University of Florida. All patients had a minimum 2-year follow-up. Most patients were treated with a combination of external-beam radiotherapy and brachytherapy. The probability of pelvic control, cause-specific survival, and complications was calculated and multivariate analyses were performed. The log-rank test was used to determine significance levels between the curves. RESULTS: The 5-year cause-specific survival rates were, Stage 0 (six patients), 100%; Stage I (17 patients), 94%; Stage IIA (six patients), 80%; Stage IIB (ten patients), 39%; Stage III (twn patients), 79%; and Stage IVA (six patients), 62%. The pelvic control rates at 5 years were: Stage 0, 100%; Stage I, 87%; Stage IIA, 88%; Stage IIB, 68%; Stage III, 80%; and Stage IVA, 67%. The parameters of stage, patient age, total dose to primary site, and overall treatment time were evaluated in a multivariate analysis. The single most important predictor of pelvic control was overall treatment time. If the entire course of radiotherapy (external beam + implant) was completed within 9 weeks (63 days), the pelvic control rate was 97%. The pelvic control rate was only 54% if treatment time extended beyond 9 weeks (p = .0003). The rate of severe complications was 12%, and the incidence increased with increasing total primary dose. CONCLUSION: Radiotherapy alone can cure a significant proportion of patients with carcinoma of the vagina. Treatment should be completed without significant interruption, preferably within 9 weeks.

Brachytherapy↗

The continuing effectiveness of active management of first labor, despite a doubling in overall nulliparous cesarean delivery.

OBJECTIVE: The purpose of this study was to determine the continuing effectiveness of active management of labor, a protocol that involves early detection and correction of dystocia with oxytocin in spontaneous cephalic nulliparous labor, by analysis of the contribution of this cohort to a doubled overall nulliparous cesarean delivery rate. STUDY DESIGN: This was a retrospective analysis of annually collated institutional data on cesarean delivery and perinatal outcome. RESULTS: From 1989 to 2000, 81,855 women were delivered at the National Maternity Hospital, of whom 34,201 women (42%) were nulliparous; the annual proportion of nulliparous women in spontaneous labor decreased progressively from 83% to 60%; the overall nulliparous cesarean rate increased from 8.1% to 16.6%. Cesarean birth rate among nulliparous women in spontaneous labor, although showing a significant upward trend between 1989 and 2000 (2.4%-4.8%; P = .001), was stable, averaging 5% for the last 8 years (P = .705); the peripartum death rate in this group fell significantly (P = .024). Comparing results for 1989 with results for 2000, nulliparous women in spontaneous labor accounted for 14% of the overall increase in cesarean deliveries (dystocia, 5%), compared with 51% for nulliparous women with induced labor. The perinatal mortality rate in term infants was unchanged. CONCLUSION: Active management of spontaneous first labors remains an effective protocol for the promotion of vaginal delivery with low peripartum mortality rates; factors other than dystocia in spontaneous labor account for the progressive increase in the nulliparous cesarean delivery rate.

Cesarean Section↗

Influence of mass transfer resistance on overall nitrate removal rate in upflow sludge bed reactors.

A kinetic model with intrinsic reaction kinetics and a simplified model with apparent reaction kinetics for denitrification in upflow sludge bed (USB) reactors were proposed. USB-reactor performance data with and without sludge wasting were also obtained for model verification. An independent batch study showed that the apparent kinetic constants k' did not differ from the intrinsic k but the apparent Ks' was significantly larger than the intrinsic Ks suggesting that the intra-granule mass transfer resistance can be modeled by changes in Ks. Calculations of the overall effectiveness factor, Thiele modulus, and Biot number combined with parametric sensitivity analysis showed that the influence of internal mass transfer resistance on the overall nitrate removal rate in USB reactors is more significant than the external mass transfer resistance. The simulated residual nitrate concentrations using the simplified model were in good agreement with the experimental data; the simulated results using the simplified model were also close to those using the kinetic model. Accordingly, the simplified model adequately described the overall nitrate removal rate and can be used for process design.

Biodegradation, Environmental↗