Mechanical and pathologic consequences of induced concentric anular tears in an ovine model

STUDY DESIGN

Relations between induced concentric tears in the sheep disc and the mechanics of the intervertebral joint and vertebral body bone were analyzed.

OBJECTIVE

To examine the effect of concentric disc tears on the mechanics of the spine.

SUMMARY OF BACKGROUND DATA

Degeneration of the intervertebral disc results in changes to the mechanics and morphology of the spine, but the effect of concentric disc tears is unknown.

METHODS

In this study, 48 merino wethers were subjected to surgery, and discs were randomly selected for either a needlestick injury or induction of a concentric tear in the anterior and left anterolateral anulus. Sheep were randomly assigned to groups for killing at 0, 1, 3, 6, 12, and 18 months. From each sheep, two spine segments were mechanically tested: one with a needlestick injury and one with a concentric tear. Macroscopic disc morphology was assessed by three axial slices of the disc. Sagittal bone slices were taken from cranial and caudal vertebral bodies for histologic analysis.

RESULTS

Induced concentric tears decrease the stiffness of intact spine segments in left bending and the disc alone in flexion. In all other mechanical tests, the needlestick injury had the same effect as the induced concentric tear. In the isolated disc, the disc stiffness at 6 months was increased for right bending, as compared with the response at 1 month. This was associated with increased anterior lamellar thickening and increased vertebral body bone volume fraction.

CONCLUSIONS

Concentric tears and needlestick injury in the anterior anulus lead to mechanical changes in the disc and both anular lamellar thickness and vertebral body bone volume fraction. A needlestick injury through the anulus parallel to the lamellae produces progressive damage.

Treatment of unstable distal radial fractures by intrafocal, intramedullary K-wires

Displaced distal radial fractures with extensive dorsal comminution and plastic cancellous deformation are unstable and frequently cause treatment problems since there is no single, reliable method of treatment, notably in osteoporotic bone. We present a method of holding unstable distal radial fractures with blunt ended K-wires via intrafocal and intramedullary insertion, so modifying the Kapandji technique. Wires were placed dorsally, radially and when necessary from the volar direction depending on fracture configuration. Over a 7-year period (1992-1999) we treated 102 patients with unstable distal radial fractures in this way. Of these, 80 were followed up for 6-42 weeks according to clinical need and scored radiologically and functionally using modified Lidstrom scoring system. Results showed that 92 and 95% of these patients achieved good or excellent results in these scoring systems, respectively. We present this as a useful and reliable method of treating these common fractures, particularly in osteoporotic bone.

Activation of Akt (protein kinase B) in mammary epithelium provides a critical cell survival signal required for tumor progression

Activation of Akt by the phosphatidylinositol 3'-OH kinase (PI3K) results in the inhibition of proapoptotic signals and the promotion of survival signals (L. P. Kane et al., Curr. Biol. 9:601-604, 1999; G. J. Kops et al., Nature 398:630-634, 1999). Evidence supporting the importance of the PI3K/Akt signaling pathway in tumorigenesis stems from experiments with transgenic mice bearing polyomavirus middle T antigen under the control of the mouse mammary tumor virus long terminal repeat promoter. Mammary epithelium-specific expression of polyomavirus middle T antigen results in the rapid development of multifocal metastatic mammary tumors, whereas transgenic mice expressing a mutant middle T antigen decoupled from the phosphatidylinositol 3'-OH kinase (MTY315/322F) develop extensive mammary gland hyperplasias that are highly apoptotic. To directly assess the role of Akt in mammary epithelial development and tumorigenesis, we generated transgenic mice expressing constitutively active Akt (HAPKB308D473D or Akt-DD). Although expression of Akt-DD interferes with normal mammary gland involution, tumors were not observed in these strains. However, coexpression of Akt-DD with MTY315/322F resulted in a dramatic acceleration of mammary tumorigenesis correlated with reduced apoptotic cell death. Furthermore, coexpression of Akt-DD with MTY315/322F resulted in phosphorylation of the FKHR forkhead transcription factor and translational upregulation of cyclin D1 levels. Importantly, we did not observe an associated restoration of wild-type metastasis levels in the bitransgenic strain. Taken together these observations indicate that activation of Akt can contribute to tumor progression by providing an important cell survival signal but does not promote metastatic progression.

Galactorrhoea and hyperprolactinaemia associated with protease-inhibitors

We describe four patients with galactorrhoea as an isolated endocrine abnormality after use of protease inhibitors (PIs) as part of both highly active antiretroviral therapy (HAART) and postexposure prophylaxis (PEP). This reaction may be a direct effect of PIs or may be indirectly mediated by the effect of PIs on the cytochrome P450 system, thus potentiating the dopamine antagonist effects of other drugs.

Comparison of health promotion and deterrent prompts in increasing use of stairs over escalators

This study compared the effectiveness of two point-of-decision prompts within the same environmental setting. The effects of a health promotion sign were compared with activity change resulting from a deterrent sign. Individuals were observed using the upward stairs or upward escalator at a midwest regional air port during a 5-week period in which intervention signs were compared with no sign conditions on activity choice. During Weeks 1, 3, and 5 behaviors were assessed without any prompts. During Week 2, a health promotion sign was posted at the behavioral choice point which read "Keep your heart healthy, use the stairs." During Week 4, a deterrent sign which read "Please limit escalator use to staff and those unable to use the stairs" was posted at the same behavioral choice point. Younger (<40) women (14.8%) and men (10.8%) used the stairs more frequently, followed by older women (9.3%) and older men (6.9%). A hierarchical log linear analysis showed that stair use increased during both interventions, which was significantly moderated by age. Point-of-decision prompts appear to be effective environmental interventions for promoting increases in physical activity.

An audit of subcutaneous syringe drivers in a non-specialist hospital

The use of syringe drivers as a method of drug delivery to control symptoms in palliative care is a common and accepted practice, but one which has evolved rather than been subject to close multiprofessional scrutiny and guideline formation. There is evidence that adverse incidents may arise as a result of syringe driver use (Medical Devices Agency (MDA), 1998), for example, errors in drug calculations, drug stability, equipment failure (including disconnection) and the wrong rate of infusion. Inadequate user training, poor servicing of equipment and inadequate documentation and record keeping are all thought to be contributing factors (MDA, 1998). In the hospital where this audit was carried out, syringe drivers are used to administer drugs to patients with cancer during the palliative phase of illness. The purpose of this clinical audit was to establish the standard of current practice in wards where syringe drivers were being used. A retrospective study of 13 cases of syringe driver use is presented. The results highlight many areas of unregulated practice with regard to setting up, monitoring and maintenance of syringe drivers. The choice of drugs and doses prescribed, evaluation of treatment responses and review of treatment regimens were also areas of concern. Guidelines for the use of syringe drivers in non-specialist hospitals are put forward.

Severe cardiotoxicity during 5-fluorouracil chemotherapy: a case and literature report

The chemotherapeutic agent 5-fluorouracil (5-FU) is a widely accepted part of many cancer treatment protocols. Its cardiotoxic potential is known, but considered uncommon and usually not life threatening, although some cases of severe cardiotoxicity related to 5-FU have been reported. The pathogenesis of cardiotoxicity caused by 5-FU is not clear. We report a case of sudden onset of severe cardiac failure, without ischemic symptoms or signs, during 5-FU treatment with serious consequences, in a previously healthy 23-year-old patient with squamous cell carcinoma of the tongue. Endomyocardial biopsy showed proliferation of the sarcoplasmic reticulum with marked vacuolization, similar to that found with doxorubicin cardiotoxicity. Because 5-FU cardiotoxicity is unpredictable and can have potentially fatal consequences, it requires, in our opinion, further clarification. With this well-documented case, including an endomyocardial biopsy, we hope to encourage additional efforts to investigate the pathophysiologic mechanisms of 5-FU cardiotoxicity.

Transforming growth factor beta (TGF-beta) and obliterative bronchiolitis following pulmonary transplantation

BACKGROUND

Obliterative bronchiolitis (OB) characterised by small-airway fibrosis is a major cause of morbidity and mortality after lung transplantation. TGF-beta has been implicated in the pathogenesis of fibrosis.

METHODS

We immunohistochemically examined 380 transbronchial biopsies (from 91 pulmonary transplants) using TGF-beta polyclonal antibodies. OB and interstitial fibrosis were diagnosed and graded in all biopsies. Other potential histologic and clinical risk factors for OB were analysed.

RESULTS

Procedures were heart and lung (n = 32), bilateral sequential lung (n = 18), and single lung transplantation (n = 41). The incidence of OB in this group was 28.5%. In all patients with OB, TGF-beta was immunolocalized in the airways and lung parenchyma. TGF-beta expression was greater in OB patients (median score 8, range 5-12) in comparison to patients without OB (median score 4, range 1-13), p < .0001. Positive TGF-beta staining preceded the histologic confirmation of OB by 6 to 18 months. The development of OB was associated with two HLA mismatches at the A locus (p = .02); recurrent acute rejection episodes (p < .0005); lymphocytic bronchiolitis (p = .0001); and tissue eosinophilia, regardless of the rejection grade (p < .0001).

CONCLUSIONS

Increased expression of TGF-beta is a risk factor for the development of OB. Other risk factors are recurrent acute rejection, lymphocytic bronchiolitis, tissue eosinophilia, and two mismatches at the HLA-A locus. This suggests that the pathogenesis of progressive small airway fibrosis characteristic of OB may be inflammatory damage, followed by an aberrant repair process due to excessive TGF-beta production following allograft injury. Hence, modulation of TGF-beta levels or function by antagonists may represent an important approach to control OB.

Autosomal dominant hereditary spastic paraparesis with cognitive loss linked to chromosome 2p

A family initially considered to have 'pure' autosomal dominant hereditary spastic paraparesis (HSP), was found on neuropsychological testing to have evidence of late onset cognitive impairment. This family showed genetic linkage to the SPG4 locus on chromosome 2p previously reported for pure HSP. Of 56 living members, 44 were examined, 30 of whom were > 30 years of age and 12 members were found to be affected with HSP including four asymptomatic cases. One other family member (III-5), aged 62 years, died prior to this study of a 4-year dementing illness. Neuropsychological assessment of 11 affected members and 11 matched, unaffected, family controls showed no significant differences between the two groups. However, the neuropsychological test profile in four of 11 affected members tested (mean age 47.2 years) and one of 11 family controls (mean age 41.5 years) showed global cognitive impairment. The pattern of cognitive dysfunction was the same for all five family members identified and was similar to that found in subcortical dementia. The presence of cognitive impairment appeared to be related to age and not the severity of the paraplegia. Both the severity of the paraplegia and the age of onset (21-60 years) varied considerably in this family.

Letters

A NEW CLASSIFICATION OF LEG ULCERS CYTOCOMPATIBILITY OF HYDROCOLLOID DRESSINGS CORRECTION.

Tumor angiogenesis and p53 mutations: prognosis in head and neck cancer

OBJECTIVES

To assess how p53 gene mutations and microvessel density (MVD) may be used as prognostic markers for the study and management of head and neck squamous cell carcinomas and to investigate putative associations between p53 gene mutations and MVD and the relationship of these factors to tumor response to radiotherapy and/or chemotherapy at 6 weeks.

PATIENTS AND DESIGN

Thirty-nine patients with squamous cell carcinoma of the head and neck, stages I to IV, who were examined at Rush-Presbyterian-St Luke's Medical Center, Chicago, Ill, and its affiliated hospitals between 1993 and 1995 were monitored. Mutations in the p53 gene were identified by microdissection of tumor cells on frozen sections, followed by single-strand conformation polymorphism analysis of the products of polymerase chain reaction amplification of exons 5 to 9. The microvessels were immunostained with monoclonal antibodies to factor VIII and/or CD31. Microvessel counts were done by 2 investigators blinded to each other's counts and to the p53 gene status. Intratumoral or peritumoral microvascular "hot spots" were assessed and counts were done with an ocular grid in 3 x 200 fields of hot spots by each investigator. The mean of the highest values was considered. Statistical analysis was done with the Wilcoxon rank sum test, the log-rank test, and proportional hazard models.

RESULTS

Of the 39 patients, 13 had mutations in exons 5 to 9. Mutations in the p53 gene were associated with unfavorable overall (P=.003) and disease-free (P=.02) survival. A strong inverse relationship was seen between MVD and p53 mutations (P=.01). No statistically significant relationship was seen between mean MVD and overall and disease-free survival. The response to therapy differed significantly (P=.03) by p53 mutations, whereas there was no statistical significance with MVD counts.

CONCLUSION

In this study a strong inverse relationship was seen between MVD and p53 mutations. p53 Mutations in exons 5 through 9 were associated with unfavorable survival, whereas MVD showed no association with survival.

Mutation of p53 in squamous cell cancer of the head and neck: relationship to tumor cell proliferation

Rapid proliferation of squamous cell carcinomas of the head and neck (SCCHN) during therapy may contribute to treatment failure. We have investigated the presence of p53 abnormalities in patients with SCCHN as a correlate of proliferation rate and other pathologic and clinical variables. p53 Mutation, as determined by polymerase chain reaction and single-strand conformation polymorphism analysis of microdissected frozen sections of tumor biopsies, was significantly associated with a high labeling index, as determined by in vivo infusion of IUdR and BrdU (P = 0.017). p53 Protein expression was detected by immunohistochemistry with two different antibodies, followed by quantitative image analysis. Many cases exhibited strong p53 protein expression in the absence of mutations within the conserved region of the gene, and expression was not related to proliferation. The presence of p53 mutations was related to tumor differentiation in this group of patients.

Cyclin D1 expression in squamous cell carcinomas of the head and neck and in oral mucosa in relation to proliferation and apoptosis

Deregulation of expression of the cell cycle regulator cyclin D1 (cD1) may be responsible for rapid proliferation of squamous cell carcinoma of the head and neck (SCCHN). We have studied the expression of cD1 in 46 SCCHNs using immunohistochemistry. Before biopsy, the patients received an in vivo infusion of iododeoxyuridine (IdUrd) for cell proliferation assessment. Additionally, the level of apoptosis was estimated using in situ end labeling (ISEL). Among 33 tumors, the proportion of cD1(+) cells varied from 0.5 to 51.3% (19.9 +/- 2.2%). Thirteen tumors did not express cD1. The fraction of S-phase (IdUrd-positive) cells was 26.3 +/- 1.8% in cD1(+) versus 20.0 +/- 2.4% in cD1(-) tumors (P = 0.06). The percentages of cD1(+) cells and of S-phase cells were not correlated (P = 0.37). Apoptosis was detected by ISEL in 15 of 33 tumors studied. ISEL-positive tumors contained a significantly higher proportion of cD1(+) cells (14.9 +/- 2.6%) than cD1(-) ones (7.9 +/- 2.8%; P = 0.03). There was a positive correlation between the percentage of cD1(+) cells and the degree of ISEL (r = 0.54; P < 0.001). In noninvolved oral mucosa, cD1(+) cells were located primarily in the suprabasal layers (29.3 +/- 3.8% versus 1.2 +/- 0. 2% in the basal layer). Only 23 of 44 mucosal specimens contained cD1(+) cells. All cD1(-) samples were proliferatively active and contained IdUrd-labeled cells. The percentage of cD1(+) cells in the oral epithelium from nontumor controls (uvula samples) was significantly higher than in the SCCHN group in both basal (2.4 +/- 0.4%; P = 0.008) and suprabasal (42.7 +/- 3.3%; P = 0.005) layers. Additionally, whereas in uvuli, cD1(+) cells were distributed evenly along the epithelial lining, in SCCHN samples the regions showing cD1 expression alternated with areas in which cD1 expression was undetectable. These data indicate that cD1 expression in SCCHN varies among tumors and is not correlated with cell proliferation. In noninvolved oral mucosa, cD1 expression differs from that in truly normal epithelium obtained from nontumor patients. A correlation between cD1 expression and the extent of ISEL positivity suggests a possible involvement of cD1 expression in the apoptotic pathways.

Proliferation of epithelia of noninvolved mucosa in patients with head and neck cancer

BACKGROUND

Morphologically noninvolved mucosa in patients with head and neck cancer is altered by carcinogens. These alterations may include chromosome alterations, gene mutations, and other molecular abnormalities which may explain very high incidence of second tumors in this group of patients. The purpose of this study was to investigate the in vivo proliferative characteristics in epithelial tissues adjacent to the tumor in a series of patients with head and neck cancer.

METHODS

Twenty-one patients with head and neck tumors received IV infusions of iododeoxyuridine (IdUrd) and/or bromodeoxyuridine (BrdUrd). Surgical specimens containing normal-appearing epithelium adjacent to the tumor were selected and stained with the respective monoclonal antibody. The percentage of S-phase cells (labeling index, LI) was counted in the basal and suprabasal layers of the epithelium.

RESULTS

In 27 samples of oral epithelium obtained from 14 previously untreated patients, labeled (S-phase) cells were predominantly located in suprabasal layers with LI 31.6 +/- 3.1% (range 13.5-73.2%). In contrast, the LI of the basal layer was very low: 1.6 +/- 0.2% (range 0.5%-8.8%). There was no statistically significant difference between normal appearing and dysplastic samples (p > 0.05). In 10 samples obtained from 7 patients whose biopsies were studied 2 days to 2 month after concomitant radiation and chemotherapy, the LI of the oral mucosa basal layer was significantly higher (21.0 +/- 4.1%, range 6.3-39.2%). The LI of the suprabasal layer in treated patients was 14.3 +/- 2.4% (range 5.9-31.1%). The LI of nasal pseudostratified epithelium (4 samples) was 11.2%. The average LI of "basal" cells was 8.3% (range 5.9-11.9%) and that of "suprabasal" cells was 13.8% range (3.2-29.5%). The basal layer of the skin (5 samples) contained 9.3% labeled cells (range 3.3-16.3%); the LI of suprabasal layers of skin was 21.3% (range 7.8-33.2%).

CONCLUSION

Both the frequency and the spatial distribution of S-phase cells are disordered in noninvolved epithelia in patients with head and neck tumors. These observations suggest that disordered proliferation may be an early consequence of field cancerization, a consequence that occurs prior to appearance of morphologically apparent hyperplasia or dysplasia.

Neuropsychological assessment in multiple sclerosis: methodological issues and concerns

A brief overview of research findings in five key areas pertaining to the study of neuropsychological aspects of multiple sclerosis is presented. The areas covered are: (1) general and specific cognitive deficits (2) prevalence of these deficits (3) attempts to correlate these deficits with clinicopathological features (4) attempts to investigate the relationship between deficits and abnormalities detected on magnetic resonance scanning and (5) longitudinal studies of cognitive deficits and MS. Based on this review, methodological issues that continue to hinder comparison between research reports, and across research centres, are outlined. Problem areas identified are (1) patient selection (2) selection of control subjects (3) lack of consensus regarding test selection (4) problems with statistical procedures (5) the relationship between depression and cognition (6) problems with measuring disability and MR abnormalities and (7) lack of longitudinal data.

Continued malignant cell proliferation in head and neck tumors during cytotoxic therapy

The effect of cytotoxic therapy on the proliferation of squamous cell carcinoma of the head and neck in vivo in patients was evaluated before and 15-35 days after the start of therapy. To accomplish this, iododeoxyuridine was administered at t = 0, and bromodeoxyuridine was administered 15-35 days later during treatment with a tumor biopsy obtained for study immediately after each pyrimidine infusion. Monoclonal antibodies specific for the halogenated pyrimidines were used to identify cells that were in the S-phase at the time of the infusions. Eleven patients were studied prior to treatment. Of those, the intratreatment biopsy of eight patients contained tumor tissue. In the other three patients, tumor tissue was not present in the second biopsy. Continued precursor incorporation into DNA-synthesizing cells during treatment was detected in six of eight tumor specimens. In two tumor specimens, an increase in the percentage of S-phase cells was noted, in two specimens tumor cells synthesizing DNA were not detected, and in four specimens the percentage of S-phase tumor cells was lower than that in the pretherapy specimen. Patients in whom there were no S-phase cells detected during treatment or in whom no tumor was detected in the second biopsy had a favorable treatment outcome in comparison to those patients in whom continued tumor proliferation during treatment was detected. The number of cells in S-phase prior to the initiation of treatment was not predictive of whether or not proliferation would continue during cytotoxic therapy. Evidence for reentry of kinetically quiescent cells into the cycle during treatment was noted. Additionally, cytotoxic therapy altered the proliferation pattern of normal-appearing mucosa as well. The results of this study demonstrate that tumor cell proliferation does continue in some squamous cell carcinoma of the head and neck during intensive cytotoxic therapy.

Clavicular nonunion. 31/32 healed after plate fixation and bone grafting

We report the long-term results in 32 patients with established nonunion of the clavicle; 15 treated with AO Dynamic Compression Plate and autologous cancellous bone graft and 17 treated with an AO reconstruction plate and autologous cancellous bone graft. The patients were followed up for a mean of 8 (4-21) years from injury and 7 (4-12) from non-union operation, both by clinical review and radiographs. 31/32 nonunions united successfully. One fracture which initially failed to unite was replated and subsequently united. 6 compression plates and 7 reconstruction plates were removed for discomfort or cosmesis. None broke. Both plates give equally good results, but we feel that the reconstruction plate is easier to contour to the complex form of the clavicle.

Assessment of apoptosis in relation to proliferation and mutational status of p53 gene in head and neck cancers

The present studies were undertaken to determine the incidence of apoptosis in plastic embedded head and neck (HN) tumor biopsies (n=31) using in situ end labeling (ISEL) of fragmented DNA. The extent of spontaneous apoptosis in untreated tumors was correlated with histological grade, percent S-phase cells (Labeling Index, LI) and with the mutational status of p53 gene in these tumors. Additionally, the in vivo effects of chemo- and/or radiotherapy on apoptosis were evaluated in seven patients. In the majority of tumors studied (25/31) spontaneous apoptosis was virtually undetectable or was very low (1-15% positively labeled cells). Only 6 tumors showed intermediate to high apoptosis (>15% positively labeled cells). High apoptosis was more frequent in poorly differentiated tumors (similar to 50%), as compared to well and moderately differentiated tumors. The median LI for 31 tumors studied was 20.2%. The mean LI for moderately differentiated tumors (23.7+/-1.7%) was significantly higher than that in well differentiated (15.1+/-2.1%, p=0.005) and was comparable in poorly differentiated tumors (24.5%). Cytotoxic therapy significantly increased the degree of apoptosis in 5/7 specimens studied (p=0.03). Double labeling of 5 of these tumors before and after the therapy, combining ISEL with detection of IUdR/BrdU, showed compartmentalized apoptosis and proliferation with virtually no double labeled cells in any specimen. Interestingly, tumors with a mutated p53 gene (n=6) showed intermediate to high degree of pretherapy, baseline apoptosis in contrast to low or undetectable levels of apoptosis in tumors bearing wild-type p53 (n=13, p=0.034). It appears that low levels of apoptosis and high proliferation may be characteristic of HN tumors. The spontaneous apoptosis in HN tumors seems unrelated to mutations in the p53 gene. Moreover, our data also show that despite overall increase in apoptosis induced by cytotoxic therapy, some proliferating tumor cells escaped the effects of therapy, which may contribute to the tumor relapse.

The Functional Limitations Profile may be a valid, reliable and sensitive measure of disability in multiple sclerosis

This pilot study was designed to evaluate the usefulness of the Functional Limitations Profile (FLP), a validated interval measure of self-report of disability, in studies of multiple sclerosis (MS). It is compared with the standard measure of disability in MS, the Kurtzke Expanded Disability Status Scale (EDSS), and the Illness Severity Score (ISS), which is an interval score derived from the EDSS. Inherent problems of all measures are discussed. On two occasions separated by 6 months, 50 MS patients were assessed prospectively by a neurologist and a psychologist, using the above measures. Validity was reflected in correlation and in agreement between measures. The FLP Physical dimension correlated significantly with the EDSS for both visits (at visit 1: r = 0.77; at visit 2: r = 0.77). Agreement between the interval measures, FLP and ISS, was satisfactory (mean difference +0.18, SD 6.8). The reliability of FLP was assessed by comparing FLP Physical dimension scores in the 30 patients who had not changed clinically between visits (EDSS change < 1.0, ISS change < 3.8). For this unchanged group the mean difference was +0.56 (SD 6.2); the 95% confidence interval (CI) was -2.87 to +1.75. For sensitivity of the FLP the 20 MS patients who had clinically changed between visits were assessed (EDSS =/> 1.0, ISS =/> 3.8). For this changed group the mean difference was -8.0 (SD 9.21); 95% CI was -12.3 to -3.69. The FLP Physical dimension in this pilot study seems to be a valid, reliable and sensitive measure of MS disability. If confirmed by larger studies it would be useful in prospective clinical studies of treatments for MS.

In vivo labelling with halogenated pyrimidines of squamous cell carcinomas and adjacent non-involved mucosa of head and neck region

The frequency and distribution of labelled cells were studied immunohistochemically in 37 squamous cell carcinomas (SCC) of head and neck after in vivo infusion of IdUrd and BrdUrd. Tumours were classified according to their labelling patterns. Low and moderate grade SCC consisted of tumour islands separated by interstitial tissue. In some tumours labelled cells only appeared near the basal layer while in others proliferative cells were evenly distributed within the neoplastic island. In anaplastic carcinomas labelled cells were distributed either randomly or around blood vessels (cord structures). While the basal layer in adjacent normal epithelium contained very few labelled cells (LI = 1.6 +/- 0.2%), the LI of basal cells in tumour islands were much higher than the average LI of the tumour (47.2 +/- 2.8% and 23.8 +/- 1.6%, respectively). In patients who had received cytotoxic therapy up to two months before the biopsy, the LI in the basal layer of normal epithelium was 19.0 +/- 3.5%. In sequential biopsies obtained 1-2 weeks after the infusion of IdUrd and BrdUrd some labelled tumour cells were found in necrotic foci and in pearl structures. Additionally, in six tumours, we found areas of cells labelled with IdUrd alone, even though the IdUrd infusion had been followed by a BrdUrd infusion 1 h later. This is in agreement with the phenomenon of intermittent tumour blood flow described earlier in experimental tumours.