Dynamics of childhood obesity in Hong Kong throughout the COVID-19 pandemic before and after the school closures: a 3-year longitudinal study

OBJECTIVE

This study is to evaluate if there is any difference in the balance between incidence of and remission from overweight/obesity in Hong Kong school-age children before and during the COVID-19 pandemic over three years.

METHODS

This is a retrospective longitudinal study that involved children aged 6-16 years from a database of the School Physical Fitness Award Scheme.

RESULTS

2765 students were longitudinally followed up for two years. The prevalence of childhood overweight/obesity was increased between the 2019 and 2021 academic years (P < 0.001). During the COVID-19 pandemic, the rate of obesity remission significantly reduced by 7.9 % (P = 0.003), at a background of a plateau of obesity among children and adolescents.

CONCLUSIONS

Our study provides evidence on the impact of school closure and home confinement as a standard infection control measure for the prevention of COVID-19, which are likely to break the balance between incidence of and remission from childhood obesity.

Case report: Xanthogranulomatous pyelonephritis masquerading as cystic renal cell carcinoma

Background: Xanthogranulomatous pyelonephritis (XGP) is a rare chronic bacterial inflammation of the renal parenchyma and is often a diagnostic dilemma.Case Presentation: We present a challenging case of a patient with XGP. Initially thought to have had renal cell cancer she was treated accordingly with a partial nephrectomy. However, on the final pathology, she was found to have XGP and required further antibiotic therapy and referral to the infectious disease service.Discussion: Management of XGP and diagnostic pitfalls are discussed.Conclusion: XGP is a diagnostic and therapeutic dilemma. Partial Nephrectomy may be appropriate in management of XGP in select cases.

Caeco-peritoneal band as a potential cause of right iliac fossa pain in children

BACKGROUND

A caeco-peritoneal band (CPB) has been observed during diagnostic laparoscopy for chronic right iliac fossa (RIF) pain. This has a veil-like configuration and arises along a broad base from the caecum and ascending colon and attaches to the anterior abdominal wall.

METHODS

Retrospective analysis of a prospectively collected database of 31 patients, aged 11-16, who underwent diagnostic laparoscopy for ongoing RIF pain over a 10-year period was analysed for intra-operative presence of the CPB. The patients' symptoms, past medical history, diagnostic workup, surgical findings and outcome were evaluated.

RESULTS

CPB was identified in five patients. All presented with chronic RIF pain and had inconclusive preoperative investigations. Two patients underwent previous surgery. In all cases, the CPB was the sole abnormal finding on diagnostic laparoscopy. Symptoms resolved following division of the CPB with no recurrence of pain at a mean follow-up of 575 days.

CONCLUSIONS

CPB is a potential cause of chronic RIF pain in patients with unremarkable examination findings and negative serological and radiological investigations. Laparoscopic identification and division of the CPB has produced symptom resolution in this cohort of patients.

'Intergenic' blr gene in Escherichia coli encodes a 41-residue membrane protein affecting intrinsic susceptibility to certain inhibitors of peptidoglycan synthesis

In the annotation of genomic sequences, small open reading frames (ORFs) are often neglected, particularly if they have no homology to other ORFs or proteins. A mini-TnphoA insertion in a 602 bp 'intergenic' region of the Escherichia coli chromosome at genomic nucleotide 1702674 gave rise to a membrane-bound PhoA fusion protein and a two- to fourfold increase in the intrinsic susceptibility to a wide spectrum of beta-lactam antibiotics without affecting beta-lactamase activity or susceptibility to tetracycline, chloramphenicol, gentamicin or quinolones. Susceptibility was also increased to cycloserine and bacitracin, but not to fosfomycin or valinomycin; these drugs, like beta-lactams, inhibit peptidoglycan synthesis, although by different mechanisms. A clone bearing only 358 bp of this 'blr' region restored resistance to the parental level. Two amber mutations in the clone prevented such restoration and were counteracted by an amber suppressor, proving that the active species is a protein. The Blr protein has 41 amino acids, with a single predicted transmembrane helix, but no clear homology to any other protein. A transcriptional start exists 39 bp upstream from the translational start. The membrane location of Blr suggests that it may be part of an efflux pump or involved in murein metabolism. The results indicate that genes for other very small functional proteins may lie within 'intergenic' regions.

Catastrophic hemorrhage on sternal reentry: still a dreaded complication?

BACKGROUND

To define the incidence of catastrophic hemorrhage (CH) during reoperations, the experience of the University of New Mexico was reviewed and compared with the practice of surgeons contacted by questionnaire.

METHODS

At the University of New Mexico, 610 reoperations were reviewed and 210 deemed high risk because of multiple reoperation, aneurysm, patent grafts, chamber's enlargement, conduit or previous mediastinitis. In the questionnaire, we asked about reentry technique, occurrence and outcome of CH, and precautions for high-risk patients.

RESULTS

At the University of New Mexico there were 4 CH with 1 death, and in the questionnaire there were 2,046 CH with 392 deaths. Our rate per surgeon was lower than that of the questionnaire. Rate of CH according to the saw was 2.09 for reciprocating, 2.0 for sagittal, and 1.74 for stryker in the questionnaire. Our rate was lower (0.65) with a micro sagittal saw. High-risk category predicted CH during sternotomy (p = 0.01) but only conduit (p = 0.005) was significant by univariate analysis.

CONCLUSIONS

The risk of CH could be as high as 1%. The sagittal micro oscillating saw is the safest reported to date. Presence of a conduit increases the risk by 2.5 fold.

Doppler ultrasound accurately screens patients with appendicitis

Ultrasound (US) has been reported as a useful aid to increase the sensitivity and specificity of the diagnosis of appendicitis. To determine the accuracy of US, we performed a prospective study of patients evaluated in the emergency department for acute appendicitis. US results of 125 consecutive patients over an 11-month period were correlated with operative and pathologic findings and clinical follow-up. The appendix was visualized as a noncompressible structure in 19 patients, and 18 had appendicitis (95%). Ten of the 12 patients with abnormal Doppler activity in the appendix had appendicitis (83%). Conversely, the appendix could not be visualized in 102 patients, and 100 did not have appendicitis (98%). One hundred five of the 113 patients (93%) with absent abnormal Doppler activity did not have appendicitis. Ninety-four of the 125 patients had neither visualization of the appendix nor abnormal activity, and 2 had appendicitis. The sensitivity of US for appendicitis was 90 per cent, and the specificity was 94 per cent. Visualization of the noncompressible appendix or abnormal Doppler activity strongly suggests appendicitis. More importantly, the absence of both of these ultrasonographic findings defines a patient subset that may be safely discharged from the emergency department without admission.

Pulsed-field gel electrophoretic migration of DNA broken by X irradiation during DNA synthesis: experimental results compared with Monte Carlo calculations

Synchronous CHO cells were X-irradiated in G1 or mid-S phase with 30-750 Gy, and then the size distribution of DNA molecules resulting from DNA double-strand breaks (DSBs) was studied by pulsed-field gel electrophoresis (PFGE). Cells irradiated in S phase also were pulse-labeled with [3H]dThd for 15 min to compare the migration patterns of replicating DNA with those of DNA mass, measured by imaging with a CCD camera. When cells were irradiated immediately after pulse labeling, a large amount of the 3H-labeled replicating DNA was trapped in the plug, i.e. > 90% for doses < 100 Gy. As the dose increased, the percentage trapped decreased, i.e. to approximately 50% for 750 Gy. The same results were observed for DNA mass when cells were irradiated in S phase, except that much less of the DNA was trapped, i.e. approximately 60% for 70-100 Gy, which produced approximately 2-Mbp molecules, compared to approximately 10% for 750 Gy, which produced approximately 0.3-Mbp molecules. These results and the migration patterns of DNA released into the lane indicated that large molecules are trapped more readily than small molecules because they contain more replicating regions (bands with bubbles) of DNA than small molecules. Our interpretation is that as the dose increases, a greater fraction of the breaks occur between the replicating bands, thus releasing linear molecules that are not replicating. The relatively small amount of 3H-labeled replicating DNA that is released from the PFGE plug migrates aberrantly, with a small amount migrating like linear G1-phase molecules and a large amount, depending on dose, migrating much more slowly than the DNA mass from cells irradiated in G1 or S phase. To explain these results, a Monte Carlo computer program was written to introduce DSBs randomly into DNA that is configured according to a model of DNA replication that is developed in a related study (Dewey and Albright, Radiat. Res. 148, 421-434, 1997). In relating the experimental observations to the results of the Monte Carlo calculations, we assumed that (a) molecules containing replication bubbles with and without forks are trapped in the PFGE plug, (b) linear molecules and molecules with replication forks only that are < or = 8 Mbp are released into the lane, and (c) molecules having replication forks migrate more slowly than linear molecules.

Enhancement of extracellular production of a Cellulomonas fimi exoglucanase in Escherichia coli by the reduction of promoter strength

The enzymatic approach to the treatment of cellulosic wastes depends on the availability of cost-effective means for the production of cellulases. We have engineered an excretion construct, tacIQpar8cex, to investigate the extracellular production of a Cellulomonas fimi exoglucanase (Exg) in Escherichia coli. The overall yield of Exg expressed by the culture of JM101 (tacIQpar8cex) was 2-11 times higher than that obtained using other systems. Over 20% of the activity was detected in the medium. When the culture was induced with IPTG, the overall production of Exg dropped dramatically. The lower yield was found to be caused by both rapid cell death and plasmid curing. A derivative of tacIQpar8cex containing the weaker lacUV5 promoter, designated lacUV5par8cex, was constructed to enhance excretion of Exg from strain JM101. Even with IPTG induction, the JM101 (lacUV5par8cex) culture was found to show a high level of cell viability and plasmid stability as well as the ability to provide efficient expression and excretion of Exg. Upon IPTG induction for 12 h, the activity and specific activity of the excreted Exg obtained from the lacUV5par8cex construct were 143 U ml-1 and 793 U mg-1 protein, respectively, which are 2-5 times higher than that detected from the tacIQpar8cex construct and from the best construct expressing the same gene reported previously.

Microbial evaluation: 139 implants removed from symptomatic patients

Possible adverse effects of microbial organisms have been implicated in symptomatic silicone implant patients. In the literature, numerous authors have investigated the possible role of infection with respect to implant problems. To date, various bacterial species have been reported, including Staphylococcus aureus, Staphylococcus epidermidis, peptostreptococci, and Clostridium perfringens. Infections in polyurethane-coated prostheses also have been shown to prolong morbidity. Antibiotic use has been relatively empirical in this regard. The purpose of this study was, first, to determine the frequency, type, and clinical relevance of microbial colonization on implant surfaces removed from symptomatic patients and, second, to determine possible effects of microbial colonization on implant integrity (gel bleed, rupture). A total of 139 implants from 72 symptomatic patients were entered into the prospective clinical study between February of 1993 and July of 1994 at the UCLA Medical Center. The implant shell types included smooth (79 percent), polyurethane (8 percent), textured (7 percent), and smooth and Dacron (6 percent). The implant locations were subglandular (71 percent), submuscular (28 percent), and subcutaneous (1 percent). Of the 139 implants removed, 69 percent were intact and 31 percent were ruptured. Forty-seven percent of 139 implants were culture-positive. Propionibacterium acnes was isolated most frequently (57.5 percent), followed by Staphylococcus epidermidis (41 percent), and then Escherichia coli (1.5 percent). No fungal infections were identified. Culture positivity was not significantly associated with systemic symptoms. Sixty-seven percent of the positive culture implants were intact; 33 percent were ruptured. The frequency (47 percent) and types (P. acnes and S. epidermidis) of microbial colonization are determined in symptomatic silicone implant patients.

Aortoesophageal fistula after repair of descending aortic dissection

The development of aortoesophageal fistula after aortic repair is rare. We describe a patient who presented with hematemesis 4 months after emergent repair of a descending thoracic aortic dissection using a prosthetic graft. Diagnosis was supported by computed tomographic, angiographic, and endoscopic findings. Resection of the involved graft was performed through a left thoracotomy after placement of an ascending aorta-to-abdominal aorta conduit through an anterior approach. The patient died of uncontrollable bleeding a few hours after the procedure. Surgical intervention offers the potential for cure in this otherwise uniformly fatal condition. But like medical therapy, operative management has thus far been associated with 100% mortality.

The effect of the length of a malarial epitope on its antigenicity and immunogenicity in an epitope presentation system using the Pseudomonas aeruginosa outer membrane protein OprF as the carrier

This study showed that the antigenicity of a malarial epitope increased with the length of the epitope when inserted at positions aa26 (amino acid position 26) and aa196, but not at aa213, of the Pseudomonas aeruginosa major outer membrane protein OprF (326 amino acids). Immunization studies showed that a 19-aa epitope was significantly more immunogenic than a 7-aa epitope when inserted at aa26 of OprF, while neither an 11- nor a 19-aa epitope fused to the C-terminus of glutathione S-transferase was immunogenic.

Isolated microspore culture of Chinese flowering cabbage (Brassica campestris ssp. parachinensis)

Microspores of several genotypes of Brassica campestris ssp. parachinensis have been cultured in vitro and induced to undergo embryogenesis and plant formation. Conditions favourable for embryogenesis in this species include a bud size of 2-2.9 mm, NLN-13 culture medium (Nitsch and Nitsch 1967; Lichter 1981, 1982; Swanson 1990), and an induction through exposure to 32°C for a period of 48 h. Longer periods of an elevated temperature for induction of embryogenesis resulted in embryo abortion at early developmental stages. With the protocol developed here, microspores of 60-80% of donor plants could be induced to produce embryos, although embryo yields were low, i.e. 2-5 embryos per 10 buds. Some genotypes responded to culture conditions with high numbers of embryo formation (100-150 embryos per 10 buds) but most of these subsequently failed to mature. The pattern of cell division and morphological changes of the microspores in culture were studied using various microscopic techniques.

Multiple polyposis and adenocarcinoma arising in Barrett's esophagus

Adenomatous polyps of the esophagus are rare in comparison with those of the lower gastrointestinal tract. Like adenomatous colon polyps, they have been associated with malignancy. We describe a case of early adenocarcinoma and multiple polyposis of the esophagus arising in a Barrett's epithelium, treated with surgical resection.

Is follow-up of lung cancer patients after resection medically indicated and cost-effective?

BACKGROUND

There are no guidelines for the appropriate follow-up of patients after pulmonary resection for lung cancer.

METHODS

Three-hundred fifty-eight consecutive patients who had undergone complete resections of non-small cell lung cancer between 1987 and 1991 were evaluated for tumor recurrence and development of second primary tumors. Recurrences were categorized by site (local or distant), mode of presentation (symptomatic or asymptomatic), treatment given (curative intent or palliative), and duration of overall survival.

RESULTS

Recurrences developed in 135 patients (local only, 32; local and distant, 13; and distant only, 90). Of these, 102 were symptomatic and 33 were asymptomatic (most diagnosed by screening chest roentgenogram). Forty patients received treatment with curative intent (operation or radiation therapy > 50 Gy) and 95 were treated palliatively. The median survival duration from time of recurrence was 8.0 months for symptomatic patients and 16.6 months for asymptomatic patients (p = 0.008). Multivariate analysis shows that disease-free interval (greater than 12 months or less than or equal to 12 months) was the most important variable in predicting survival after recurrence and that mode of presentation, site of recurrence, initial stage, and histologic type did not significantly affect survival. New primary tumors developed in 35 patients.

CONCLUSIONS

Although detection of asymptomatic recurrences gives a lead time bias of 8 to 10 months, mode of treatment and overall survival duration are not greatly affected by this earlier detection. Disease-free interval appears to be the most important determinant of survival. Screening for asymptomatic recurrences in patients who have had lung cancer is unlikely to be cost-effective. Frequent follow-up and extensive radiologic evaluation of patients after operation for lung cancer are probably unnecessary.

Clinical significance of intracapsular fluid in patients' breast implants

Clinical reports on the incidence and clinical significance of intracapsular fluid are lacking in the literature. It remains unknown whether the presence of intracapsular fluid has any relation to implant infection or colonization. The purpose of this study was to determine the frequency and type of intracapsular fluid, specifically, whether intracapsular fluid causes implant infection, implant rupture, or bacterial colonization. A total of 139 implants from 72 symptomatic patients were entered into the prospective clinical study. Our study demonstrated the presence of intracapsular fluid in 21 of 139 (15%) implants. Positive microbial cultures were identified in 39% of the implants in the positive intracapsular fluid group, compared to 43% in the negative fluid group. There was no statistically significant difference between these groups. Also, no adverse clinical relationship was demonstrated between local symptoms and presence of intracapsular fluid. There was, however, a positive trend toward the presence of fluid when implant shell types were nonsmooth (polyurethane and textured silicone implants). Further studies are indicated to elucidate the fluid production mechanism and possible secretory activity of prosthetic capsules interfacing the textured breast implant surface.

Clinical experience with a microvascular anastomotic device in head and neck reconstruction

BACKGROUND

Despite numerous refinements in microsurgical technique and instrumentation, the microvascular anastomosis remains one of the most technically sensitive aspects of free-tissue transfer reconstructions.

MATERIALS AND METHODS

Concurrent with the development of microsurgical techniques, various anastomotic coupling systems have been introduced in an effort to facilitate the performance and reliability of microvascular anastomoses. The microvascular anastomotic coupling device (MACD) studied here is a high-density, polyethylene ring-stainless steel pin system that has been found to be highly effective in laboratory animal studies. Despite its availability for human clinical use over the last 5 years, reported clinical series remain rare. Our clinical experience with this MACD in 29 head and neck free-tissue transfers is reported herein.

RESULTS

Thirty-five of 37 (95%) attempted anastomoses were completed with 100% flap survival with a variety of donor flaps, recipient vessels, and clinical contexts. Two anastomoses were converted to conventional suture technique intraoperatively, and one late postoperative venous thrombosis occurred after fistulization and vessel exposure.

CONCLUSIONS

We conclude that the MACD studied here is best suited for the end-to-end anastomosis of soft, pliable, minimally discrepant vessels. Previous radiation therapy does not appear to be a contraindication to its use. Interpositional vein grafts may also be well suited to anastomosis with the device. When carefully and selectively employed by experienced microvascular surgeons, this MACD can be a safe, fast, and reliable adjunct in head and neck free-tissue transfer reconstructions, greatly facilitating the efficiency and ease of application of these techniques.

Osteogenesis imperfecta and cardiovascular diseases

Aortic and mitral valvular insufficiency in patients with osteogenesis imperfecta result from an underlying defect in connective tissue formation. The surgical cases reported in the literature have included mechanical and bioprosthetic valve replacement as well as attempts at repair and reconstruction. Despite complications related to bleeding and tissue friability, acceptable results have been obtained. In this report, we describe aortic regurgitation secondary to osteogenesis imperfecta treated with homograft replacement. The unique cardiovascular complications of osteogenesis imperfecta and the available therapeutic options are discussed in light of the literature review.

Esophago-airway fistula in AIDS

Fistula formation between the esophagus and airway in acquired immunodeficiency syndrome is extremely unusual. We report 2 cases, the first in a patient who did not undergo definitive surgical management and died shortly after diagnosis. The second patient was managed successfully for 5 months by insertion of a Celestin endoesophageal prosthesis. This procedure can be performed with low morbidity and mortality, and may become the treatment of choice for this complex problem.

Analysis by pulsed-field gel electrophoresis of DNA double-strand breaks induced by heat and/or X-irradiation in bulk and replicating DNA of CHO cells

For a given amount of cell killing, heat alone (10-80 min, 45.5 degrees C) induced very few double-strand breaks (dsbs) compared with X-rays. Furthermore, 10 min at 45.5 degrees C immediately prior to X-rays caused only a 1.3-fold increase in the slope of the X-ray-induced dsb dose-response curve, i.e. 0.67 +/- 0.006 (95% confidence) dsbs/100Mbp/Gy for heated cells compared with 0.53 +/- 0.005 for unheated control cells. However, this same heat treatment caused > 5-fold inhibition in the rate of repair of dsbs induced by 60-Gy X-rays, with the degree of inhibition being much less in thermotolerant (TT) cells than in non-tolerant (NT) cells. This reduced inhibition of repair in TT cells correlated with the more rapid removal of excess nuclear protein from nuclei isolated from TT cells than from NT cells. These results plus a TT ratio of 2-3 for both heat-induced radiosensitization and heat-inhibition of repairing dsbs are consistent with the hypothesis that heat radiosensitization results primarily from heat aggregation of nuclear protein interfering with access of repair enzymes to DNA dsbs. The selective heat-radiosensitization of S-phase cells, however, may result from an increase in radiation-induced dsbs in or near replicating regions. For example, a preferential increase in dsbs in replicating DNA compared with bulk DNA was found following either hyperthermia alone (10-30 min, 45.5 degrees C) or a combined treatment (10 min, 45.5 degrees C before 60 Gy). A 30-min treatment at 45.5 degrees C induced dsbs equivalent to approximately 10 Gy in replicating DNA compared with 3-5 Gy in bulk DNA. When cells were heated immediately before irradiation, the increase in dsbs induced in the replicating DNA by 60 Gy was equivalent to 200 Gy. We hypothesize that the observed 2-fold increase in single-stranded regions in replicating DNA after heat resulted in radiation selectively inducing dsbs at or near the replication fork where the heat-induced increase in single-stranded DNA should occur. Thus, this preferential increase in dsbs in the replicating DNA by heat alone and especially when heat was combined with radiation may explain at least in part, the high sensitivity of S-phase cells to heat killing and heat radiosensitization.

Pseudomonas aeruginosa outer membrane protein OprF as an expression vector for foreign epitopes: the effects of positioning and length on the antigenicity of the epitope

OprF, the major outer membrane (OM) protein of Pseudomonas aeruginosa, has been proposed to be comprised of a series of beta-strands separated by periplasmic or surface-exposed loop regions. In this study, a simple malarial epitope was used to demonstrate that OprF can be used as an expression vector to present foreign peptide sequences, namely, the 4-amino-acid (aa) repeating epitope (Asn-Ala-Asn-Pro = NANP) of the circumsporozoite protein of the human malarial parasite Plasmodium falciparum. Eight permissive sites, that allowed the expression and surface exposure of the malarial epitope, were identified throughout OprF. Using a monoclonal antibody (mAb) specific for the malarial epitope, we investigated the effects of positioning and length of the epitope on its antigenicity in the OprF expression vector system. It was demonstrated that the malarial epitope inserted at aa26 was significantly more reactive with the epitope-specific mAb (i.e., more antigenic) when assayed in the context of whole cells whereas those at aa213 and aa290 were more antigenic when assayed in the OM. The malarial epitope inserted at aa188 and aa196 was moderately antigenic, while this epitope inserted at aa215 and aa310 showed low antigenicity with the same mAb in both whole cell and OM assays. For two insertion sites, aa26 and aa213, we demonstrated that the insertion of multiple copies of the epitope enhanced reactivity with the malarial epitope-specific mAb. These data are discussed with respect to the local OprF sequences into which the epitope was inserted.

Air embolus complicating transthoracic percutaneous needle biopsy

Transthoracic percutaneous needle biopsy has become popular for evaluation of pulmonary nodules. However, it is a procedure with morbidity and mortality that is not negligible. In this article, we report massive air embolus complicating needle biopsy in a patient with amyloidosis. A negative biopsy does not exclude malignancy, and if surgical excision will be performed regardless of the result, preoperative assessment using this technique may not be necessary.

Hyperthermia can reduce cytotoxicity from etoposide without a corresponding reduction in the number of topoisomerase II-DNA cleavable complexes

The chemotherapeutic drug etoposide (VP-16) causes the equilibrium reaction between noncleavable and cleavable topoisomerase II-DNA complexes to shift in favor of the cleavabel complex [H. Zang, P. D'Arpa, and L.F. Liu, Cancer Cells (Cold Spring Harbor), 2:23-27, 1990]. Pulsed-field gel electrophoresis was used to study induction and removal of cleavable complexes in cells heated before, during, or after VP-16 treatment. Pulsed-field gel electrophoresis results were evaluated both as the fraction of activity (DNA) released from the plug and as the number of double-strand breaks (DSBs) calculated from molecular weight distributions; both end points led to the same conclusions. When cells were heated at 42 degrees C during treatment with VP-16 (12 micrograms/ml up to 60 min), a slight decrease in cleavable complexes (from 30 to 20 DSBs/100 megabase pairs) was detected immediately after treatment when compared with cells treated with the drug at 37 degree C. Furthermore, heating at 42 degrees C caused a slight decrease in drug cytotoxicity as measured by less than a 2-fold increase in clonogenic survival. When cells were heated for 10 min at 45.5 degrees C prior to or after treatment with the drug, there was a reduction (approximately 50%) immediately after treatment in the number of DSBs/100 megabase pairs compared with unheated cells. The rate of removal of cleavable complexes was decreased slightly by heat. After 120 min at 37 degrees C, the number of DSB/100 megabase pairs decreased to approximately 6 for both unheated cells and those heated prior to drug treatment and to approximately 8 for cells heated after drug treatment. In agreement with a low effect of heat on the number of cleavable complexes after drug treatment, there was no significant effect of this heating protocol on drug cytotoxicity. However, heating at 45.5 degrees C prior to drug treatment at 37 degrees C protected cells from drug cytotoxicity (e.g., increased survival after 12 micrograms/ml for 60 min by approximately 100-fold) despite the similarity in the induction and rate of removal of cleavable complexes when compared with nonheated cells. Thus, when cells are heated prior to administration of VP-16, drug cytotoxicity does not correlate with the number of cleavable complexes measured either immediately after treatment or 180 min later when approximately 75% of the initial number have been removed. Finally, since hyperthermia can actually decrease drug cytotoxicity, the use of hyperthermia as an adjuvant to chemotherapy involving topoisomerase II poisons, such as VP-16, should be approached with caution.