Community-based participatory research to guide adoption of culturally responsive trauma-informed HIV care throughout Nashville, Tennessee

Background

Psychological trauma is a highly prevalent driver of poor health among people with HIV (PWH) in the Southern United States (U.S.). Trauma-informed care (TIC) has potential to advance national Ending the HIV Epidemic (EHE) goals, but formative research is needed to tailor TIC implementation to complex and interdependent HIV networks. Methods: We applied a community-based participatory research (CBPR) approach to iteratively engage personnel from high volume HIV care institutions in Nashville, Tennessee. Current practices and potential implementation determinants were identified through participatory process mapping (PM) and key informant interviews. The Consolidated Framework for Implementation Research (CFIR) was applied to deductively code interview data. Personnel attending a dissemination summit developed a network-wide implementation plan.

Results

Data were collected with personnel from five institutions (e.g., community-based organizations, primary care clinics, public health department), for PM (n=48), interviews (n=35), and the summit (n=17). Results suggest there are limited trauma screenings, assessments, and services across the network. Relevant Characteristics of Individuals included a trauma-sensitive workforce committed to continuous learning and TIC adoption. Relevant Inner Setting Factors were networks and communications, with strong tension for change, high compatibility with TIC, and need for advancing cultural responsiveness. Relevant Outer Setting Factors included patient needs and resources and cosmopolitanism, with need for better leveraged mental health services. Relevant Process domains were champions and leadership, with need to diversify championship among leaders. Relevant Intervention Characteristics included relative advantage and complexity, with need for personnel wellness initiatives and increased engagement with the community as service designers. Four recommendations included development of shared communication systems, personnel wellness campaigns, routine evaluations to inform practices, and culturally responsive care initiatives.

Conclusion

Modifiable TIC determinants were identified, and a community-created implementation plan was developed to guide adoption. Future research will focus on city-wide implementation and strengthening pre-implementation research in other settings.

Improved White Matter Cerebrovascular Reactivity after Revascularization in Patients with Steno-Occlusive Disease

BACKGROUND AND PURPOSE

One feature that patients with steno-occlusive cerebrovascular disease have in common is the presence of white matter (WM) lesions on MRI. The purpose of this study was to evaluate the effect of direct surgical revascularization on impaired WM cerebrovascular reactivity in patients with steno-occlusive disease.

MATERIALS AND METHODS

We recruited 35 patients with steno-occlusive disease, Moyamoya disease (n = 24), Moyamoya syndrome (n = 3), atherosclerosis (n = 6), vasculitis (n = 1), and idiopathic stenosis (n = 1), who underwent unilateral brain revascularization using a direct superficial temporal artery-to-MCA bypass (19 women; mean age, 45.8 ± 16.5 years). WM cerebrovascular reactivity was measured preoperatively and postoperatively using blood oxygen level-dependent (BOLD) MR imaging during iso-oxic hypercapnic changes in end-tidal carbon dioxide and was expressed as %Δ BOLD MR signal intensity per millimeter end-tidal partial pressure of CO₂.

RESULTS

WM cerebrovascular reactivity significantly improved after direct unilateral superficial temporal artery-to-middle cerebral artery (STA-MCA) bypass in the revascularized hemisphere in the MCA territory (mean ± SD, -0.0005 ± 0.053 to 0.053 ± 0.046 %BOLD/mm Hg; P < .0001) and in the anterior cerebral artery territory (mean, 0.0015 ± 0.059 to 0.021 ± 0.052 %BOLD/mm Hg; P = .005). There was no difference in WM cerebrovascular reactivity in the ipsilateral posterior cerebral artery territory nor in the vascular territories of the nonrevascularized hemisphere (P < .05).

CONCLUSIONS

Cerebral revascularization surgery is an effective treatment for reversing preoperative cerebrovascular reactivity deficits in WM. In addition, direct-STA-MCA bypass may prevent recurrence of preoperative symptoms.

Clinically Feasible Microstructural MRI to Quantify Cervical Spinal Cord Tissue Injury Using DTI, MT, and T2*-Weighted Imaging: Assessment of Normative Data and Reliability

BACKGROUND AND PURPOSE

DTI, magnetization transfer, T2*-weighted imaging, and cross-sectional area can quantify aspects of spinal cord microstructure. However, clinical adoption remains elusive due to complex acquisitions, cumbersome analysis, limited reliability, and wide ranges of normal values. We propose a simple multiparametric protocol with automated analysis and report normative data, analysis of confounding variables, and reliability.

MATERIALS AND METHODS

Forty healthy subjects underwent T2WI, DTI, magnetization transfer, and T2*WI at 3T in <35 minutes using standard hardware and pulse sequences. Cross-sectional area, fractional anisotropy, magnetization transfer ratio, and T2*WI WM/GM signal intensity ratio were calculated. Relationships between MR imaging metrics and age, sex, height, weight, cervical cord length, and rostrocaudal level were analyzed. Test-retest coefficient of variation measured reliability in 24 DTI, 17 magnetization transfer, and 16 T2*WI datasets. DTI with and without cardiac triggering was compared in 10 subjects.

RESULTS

T2*WI WM/GM showed lower intersubject coefficient of variation (3.5%) compared with magnetization transfer ratio (5.8%), fractional anisotropy (6.0%), and cross-sectional area (12.2%). Linear correction of cross-sectional area with cervical cord length, fractional anisotropy with age, and magnetization transfer ratio with age and height led to decreased coefficients of variation (4.8%, 5.4%, and 10.2%, respectively). Acceptable reliability was achieved for all metrics/levels (test-retest coefficient of variation < 5%), with T2*WI WM/GM comparing favorably with fractional anisotropy and magnetization transfer ratio. DTI with and without cardiac triggering showed no significant differences for fractional anisotropy and test-retest coefficient of variation.

CONCLUSIONS

Reliable multiparametric assessment of spinal cord microstructure is possible by using clinically suitable methods. These results establish normalization procedures and pave the way for clinical studies, with the potential for improving diagnostics, objectively monitoring disease progression, and predicting outcomes in spinal pathologies.

A Novel MRI Biomarker of Spinal Cord White Matter Injury: T2*-Weighted White Matter to Gray Matter Signal Intensity Ratio

BACKGROUND AND PURPOSE

T2*-weighted imaging provides sharp contrast between spinal cord GM and WM, allowing their segmentation and cross-sectional area measurement. Injured WM demonstrates T2*WI hyperintensity but requires normalization for quantitative use. We introduce T2*WI WM/GM signal-intensity ratio and compare it against cross-sectional area, the DTI metric fractional anisotropy, and magnetization transfer ratio in degenerative cervical myelopathy.

MATERIALS AND METHODS

Fifty-eight patients with degenerative cervical myelopathy and 40 healthy subjects underwent 3T MR imaging, covering C1-C7. Metrics were automatically extracted at maximally compressed and uncompressed rostral/caudal levels. Normalized metrics were compared with t tests, area under the curve, and logistic regression. Relationships with clinical measures were analyzed by using Pearson correlation and multiple linear regression.

RESULTS

The maximally compressed level cross-sectional area demonstrated superior differences (P = 1 × 10^-13), diagnostic accuracy (area under the curve = 0.890), and univariate correlation with the modified Japanese Orthopedic Association score (0.66). T2*WI WM/GM showed strong differences (rostral: P = 8 × 10^-7; maximally compressed level: P = 1 × 10^-11; caudal: P = 1 × 10^-4), correlations (modified Japanese Orthopedic Association score; rostral: -0.52; maximally compressed level: -0.59; caudal: -0.36), and diagnostic accuracy (rostral: 0.775; maximally compressed level: 0.860; caudal: 0.721), outperforming fractional anisotropy and magnetization transfer ratio in most comparisons and cross-sectional area at rostral/caudal levels. Rostral T2*WI WM/GM showed the strongest correlations with focal motor (-0.45) and sensory (-0.49) deficits and was the strongest independent predictor of the modified Japanese Orthopedic Association score (P = .01) and diagnosis (P = .02) in multivariate models (R² = 0.59, P = 8 × 10^-13; area under the curve = 0.954, respectively).

CONCLUSIONS

T2*WI WM/GM shows promise as a novel biomarker of WM injury. It detects damage in compressed and uncompressed regions and contributes substantially to multivariate models for diagnosis and correlation with impairment. Our multiparametric approach overcomes limitations of individual measures, having the potential to improve diagnostics, monitor progression, and predict outcomes.

Abstract P4-01-05: Improving the quality of mammographic positioning

Purpose:

Optimal breast positioning is a key component to high quality screening mammograms to allow the radiologist to make the best interpretation for the patient and referring physician. In addition, the success of newer imaging techniques also depends on breast positioning. The American College of Radiology (ACR) sets the standard of what images should include by outlining 13 criteria of breast positioning. An initial audit of over 100 mammograms at our institution in 2013 found that only a mean of 33% were achieving the ACR criteria. The goal of our project was to increase the percentage of screening mammograms achieving ACR criteria to 90% by June 2015.

Methods:

Our breast imaging center partnered with a quality improvement (QI) team driving a radiology department-wide program on quality improvement. Team members identified 5 key causes that barred achieving the ACR criteria: disagreement on what meets criteria, not having a standard work for acquiring and reading mammograms, lack of communication between the technologist and radiologist, not having a measurement system to track performance, and lack of coaching on technologist techniques for acquiring images. Developments to address these causes included: teaching modules on what meets ACR criteria, standard work for radiologists to recall mammograms that did not meet ACR criteria, system for the technologist to document why criteria were missed, auditing system to track performance, and feedback sessions between technologists and radiologists. Over 1,700 mammograms were audited from the time period of July 2014 to March 2015.

Results:

By October 2014, the percentage of mammograms achieving all 13 of the ACR criteria was 71%, with 4 criteria that prevented reaching the 90% goal. By March 2015, 10 of the 13 ACR criteria were being sustainably met by the target goal of 90% of mammograms, better in all criteria compared to our 2013 data, and better in all but one criterion compared to published 1993 data. Table 1 demonstrates that we have been able to sustain a composite percentage of 12 of the 13 ACR criteria greater than 90% for the last 2 consecutive months.

Table 1 shows the composite percentage of mammograms achieving 12 of the 13 ACR criteria over time.2013 Baseline8/20149/201410/201411/20141/20152/20153/201564%67%77%82%83%81%95%96%The excluded, most difficult criterion (visualization of the opposite breast cleavage) has been achieved at 32% per 1993 published data; we currently achieve it at 40%. 12/2014 audits were not performed due to holidays and changes in staffing.

Conclusion:

Few institutions have published positioning data, with the most recent QI publication on breast positioning dating to 1993. We have conducted a structured process to improve quality of mammographic positioning, including revision of processes that led to poor positioning outcomes and creation of an environment to sustain our improved outcomes. Three ACR criteria continue to be problematic in reaching the 90% goal, with future investigation into whether it is actually feasible to achieve the most difficult criterion at our goal of 90%. Future work also includes assessing how the recent hire of a mammography coach to spread best practices and real-time feedback is able to further improve results and maintain the infrastructure of ongoing QI.

Citation Format: Chen CA, Strain A, Mickelsen JL, Larson DA, Jesinger RA, Botelho D, Fromholz S, Obi CN, Crawley A, Lipson JA, Ikeda DM, Cooper C, Pal S. Improving the quality of mammographic positioning. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-01-05.

Frontotemporal correlates of impulsivity and machine learning in retired professional athletes with a history of multiple concussions

The frontotemporal cortical network is associated with behaviours such as impulsivity and aggression. The health of the uncinate fasciculus (UF) that connects the orbitofrontal cortex (OFC) with the anterior temporal lobe (ATL) may be a crucial determinant of behavioural regulation. Behavioural changes can emerge after repeated concussion and thus we used MRI to examine the UF and connected gray matter as it relates to impulsivity and aggression in retired professional football players who had sustained multiple concussions. Behaviourally, athletes had faster reaction times and an increased error rate on a go/no-go task, and increased aggression and mania compared to controls. MRI revealed that the athletes had (1) cortical thinning of the ATL, (2) negative correlations of OFC thickness with aggression and task errors, indicative of impulsivity, (3) negative correlations of UF axial diffusivity with error rates and aggression, and (4) elevated resting-state functional connectivity between the ATL and OFC. Using machine learning, we found that UF diffusion imaging differentiates athletes from healthy controls with significant classifiers based on UF mean and radial diffusivity showing 79–84 % sensitivity and specificity, and 0.8 areas under the ROC curves. The spatial pattern of classifier weights revealed hot spots at the orbitofrontal and temporal ends of the UF. These data implicate the UF system in the pathological outcomes of repeated concussion as they relate to impulsive behaviour. Furthermore, a support vector machine has potential utility in the general assessment and diagnosis of brain abnormalities following concussion.

Clinical features of patients with blepharospasm: a report of 240 patients

BACKGROUND AND PURPOSE

To characterize patients with benign essential blepharospasm (BEB) by diagnosis, environmental risk factors, and family history.

METHODS

Two hundred and forty patients with BEB were evaluated through a clinical examination and questionnaire. The questionnaire reviewed personal medical history, demographic factors, risk factors for the development of blepharospasm and family history of dystonia and other neurological conditions.

RESULTS

Benign essential blepharospasm was more commonly found in women (2.8:1) and 93% of the patients were Caucasian. Fifty percent had pure BEB, 31% had BEB/Meige's syndrome, and 4% had BEB and eyelid opening apraxia (+/- Meige's syndrome). A minority of patients reported preceding photophobia (25%) or other eye conditions (22%). The majority were non-smokers, had no exposure to anti-emetic or antipsychotic agents, had a normal birth history, and had no history of head trauma. Seventy-two percent did report a stressful event immediately prior to the development of symptoms. Treatments reported included botulinum toxin (BoNT), oral medications, surgical procedures, and acupuncture. Thirty-two percent of patients reported a family history of focal dystonia, and BEB was the most commonly reported.

CONCLUSION

This study confirms previous reports of usual age, sex, caffeine and tobacco use, and family history in patients with blepharospasm. New findings include a report on occupation, lower reports of preceding eye conditions and photophobia, and higher reported stressful events. Further, this study shows a change in treatment with an increase in BoNT use and decrease in surgical procedures.

Quantification of cerebrovascular reactivity by blood oxygen level-dependent MR imaging and correlation with conventional angiography in patients with Moyamoya disease

BACKGROUND AND PURPOSE

BOLD MR imaging combined with a technique for precision control of end-tidal pCO(2) was used to produce quantitative maps of CVR in patients with Moyamoya disease. The technique was validated against measures of disease severity by using conventional angiography; it then was used to study the relationship between CVR, vascular steal, and disease severity.

MATERIALS AND METHODS

A retrospective analysis comparing conventional angiography with BOLD MR imaging was performed on 11 patients with Moyamoya disease. Iso-oxic cycling of end-tidal pCO(2) between 2 target values was performed during BOLD MR imaging. CVR was calculated as the BOLD signal difference per Delta pCO(2). CVR was correlated with the presence of Moyamoya or pial collaterals and the degree of Moyamoya disease as graded by using a modified Suzuki score.

RESULTS

A good correlation between mean CVR and Suzuki score was found for the MCA and ACA territories (Pearson correlation coefficient, -0.7560 and -0.6140, respectively; P < .0001). A similar correlation was found between mean CVR and the presence of pial and Moyamoya collateral vessels for combined MCA and ACA territories (Pearson correlation coefficient, -0.7466; P < .0001). On a voxel-for-voxel basis, there was a greater extent of steal within vascular territories with increasing disease severity (higher modified Suzuki score). Mean CVR was found to scale nonlinearly with the extent of vascular steal.

CONCLUSIONS

Quantitative measures of CVR show direct correlation with impaired vascular supply as measured by the modified Suzuki score and enable direct investigation of the physiology of autoregulatory reserve, including steal phenomenon, within a given vascular territory.

Improving spatial signal homogeneity in MR 2D chemical shift imaging using outer volume saturation bands

Many endeavors of improving chemical shift imaging (CSI) techniques have been made during last two decades. Good examples of two-dimensional CSI and three-dimensional CSI can be found in the literature. However, clinical CSI using available sequences is still not satisfactory. The purpose of this study was to assess the effect of outer volume saturation bands on signal homogeneity in MR 2D chemical shift imaging. The 2D CSI scans were acquired using a point resolved spectroscopy (PRESS) CSI sequence on a phantom filled with brain metabolites. A single PRESS volume of interest was prescribed graphically. The acquisition matrix was 18x18 phase encodings over a 24-cm FOV. Identical acquisitions were obtained with and without outer-volume saturation bands. After initial acquisition was obtained, four more acquisitions were repeated for both studies with and without saturation bands. Identical five groups of voxels were compared for both studies. Standard deviations of metabolite ratios were calculated in each group for both studies. Spectra obtained without outer-volume saturation bands showed signal to noise gradient with higher concentration of signal within voxels at the center of the volume of interest. Outer volume saturation bands reduced this gradient. In general, standard deviations of metabolite ratios with saturation bands were smaller than those without saturation bands. Improved spatial homogeneity of spectra in voxels of CSI with saturation bands was obtained. Outer-volume saturation bands improve spatial signal homogeneity of chemical shift imaging.

Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism

The Antikythera Mechanism is a unique Greek geared device, constructed around the end of the second century bc. It is known that it calculated and displayed celestial information, particularly cycles such as the phases of the moon and a luni-solar calendar. Calendars were important to ancient societies for timing agricultural activity and fixing religious festivals. Eclipses and planetary motions were often interpreted as omens, while the calm regularity of the astronomical cycles must have been philosophically attractive in an uncertain and violent world. Named after its place of discovery in 1901 in a Roman shipwreck, the Antikythera Mechanism is technically more complex than any known device for at least a millennium afterwards. Its specific functions have remained controversial because its gears and the inscriptions upon its faces are only fragmentary. Here we report surface imaging and high-resolution X-ray tomography of the surviving fragments, enabling us to reconstruct the gear function and double the number of deciphered inscriptions. The mechanism predicted lunar and solar eclipses on the basis of Babylonian arithmetic-progression cycles. The inscriptions support suggestions of mechanical display of planetary positions, now lost. In the second century bc, Hipparchos developed a theory to explain the irregularities of the Moon's motion across the sky caused by its elliptic orbit. We find a mechanical realization of this theory in the gearing of the mechanism, revealing an unexpected degree of technical sophistication for the period.

Cognitive impairment associated with chemotherapy for breast cancer: An exploratory case-control study

8501

Background: There is evidence that some women suffer cognitive impairment after adjuvant chemotherapy (CT) for breast cancer and it may be sustained. We report a case-control study to explore underlying mechanisms with blood tests and functional imaging. Methods: Women diagnosed with breast cancer within 5 years were recruited to 3 groups of 20. Cases (group A) had received CT and self-reported cognitive dysfunction on a prototype FACT-COG questionnaire. There were 2 groups of controls: group B had received CT but did not report cognitive problems; group C had breast cancer but did not receive CT. Comprehensive tests of cognitive function (2.5 hr) were performed. Blood tests evaluated sex hormones, coagulation factors, 10 cytokines, and apolipoprotein genotype. Functional MRI (fMRI) scans were performed while subjects performed a mental task. Results: Currently, 60 women have completed FACT-COG, 39 have undergone neuropsychological assessment and 31 have completed fMRI; testing and analysis will be complete by May 2006. Median time from diagnosis was 2 years. There was increased self-report of cognitive impairment in CT vs non-CT patients (p<0.0001). Formal cognitive testing disclosed more impairment in group C (no CT) as compared to groups A and B: 29% vs 0% by classical tests (p=0.046), and 61% vs 47% and 25% (p=0.38) by computerized testing. This may be due to slight imbalance of demographic factors. Decreased activation in fMRI was seen in frontal areas and right parahippocampus of women who self-reported greater cognitive impairment (p<0.0005), while separate frontal areas show increased activity in women with greater objective cognitive impairment (p<0.0005). Patients who received CT reported more fatigue than non-CT patients (p=0.027). There was an association between fatigue and self-reported cognitive impairment (p=0.004) and anxiety and depression (General Health Questionnaire) (p=0.009), but not with objective cognitive testing. As yet there is no significant correlation between symptoms and cytokine levels. Conclusions: Self-reported cognitive impairment is associated with prior chemotherapy and changes in fMRI but not with formal cognitive testing. The larger sample size is required to confirm these changes and explore possible mechanisms.

No significant financial relationships to disclose.

Perfusion-weighted MR imaging studies in brain hypervascular diseases: comparison of arterial input function extractions for perfusion measurement

BACKGROUND AND PURPOSE

Brain hypervascular diseases are complex and induce hemodynamic disturbances on brain parenchyma, which are difficult to accurately evaluate by using perfusion-weighted (PWI) MR imaging. Our purpose was to test and to assess the best AIF estimation method among 4 patients with brain hypervascular disease and healthy volunteers.

METHODS

Thirty-three patients and 10 healthy volunteers underwent brain perfusion studies by using a 1.5T MR imaging scanner with gadolinium-chelate bolus injection. PWI was performed with the indicator dilution method. AIF estimation methods were performed with local, regional, regional scaled, and global estimated arterial input function (AIF), and PWI measurements (cerebral blood volume [CBV] and cerebral blood flow [CBF]) were performed with regions of interest drawn on the thalami and centrum semiovale in all subjects, remote from the brain hypervascular disease nidus. Abnormal PWI results were assessed by using Z Score, and evaluation of the best AIF estimation method was performed by using a no gold standard evaluation method.

RESULTS

From 88% to 97% of patients had overall abnormal perfusion areas of hypo- (decreased CBV and CBF) and/or hyperperfusion (increased CBV and CBF) and/or venous congestion (increased CBV, normal or decreased CBF), depending on the AIF estimation method used for PWI computations. No gold standard evaluation of the 4 AIF estimates found the regional and the regional scaled methods to be the most accurate.

CONCLUSION

Brain hypervascular disease induces remote brain perfusion abnormalities that can be better detected by using PWI with regional or regional scaled AIF estimation methods.

Comparing language lateralization determined by dichotic listening and fMRI activation in frontal and temporal lobes in children with epilepsy

We investigated the relationship between ear advantage scores on the Fused Dichotic Words Test (FDWT), and laterality of activation in fMRI using a verb generation paradigm in fourteen children with epilepsy. The magnitude of the laterality index (LI), based on spatial extent and magnitude of activation in classical language areas (BA 44/45, 21/22, 39) differed significantly for patients classified with unilateral left, compared to bilateral, language representation based on FDWT scores. Concordance with fMRI was higher for those classified with unilateral left, than bilateral language representation on the FDWT. Of note, asymmetry in temporal lobe, rather than frontal lobe, activation was more strongly related to the LI from the dichotic listening test. This study shows that the FDWT can provide a quick and valid estimate of lateralization in pre-surgical candidates, which can be readily adopted for other clinical or research purposes when an estimate of language dominance is desired.

Donepezil for dementia in Parkinson's disease: a randomised, double blind, placebo controlled, crossover study

OBJECTIVE

To study the safety and efficacy of a cholinesterase inhibitor, donepezil hydrochloride, for the treatment of dementia in Parkinson's disease (PD).

METHODS

This was a randomised double blind, placebo controlled, crossover study in 22 subjects with PD and dementia. Participants were randomised to receive either donepezil followed by identical placebo, or placebo followed by donepezil. Donepezil was administered at 5-10 mg/day. Treatment periods were 10 weeks with a washout period of 6 weeks between the two periods. The primary outcome measure was the Alzheimer's Disease Assessment Scale Cognitive Subscale (ADAScog).

RESULTS

Donepezil was well tolerated and most adverse events were mild. There was no worsening of PD symptoms as measured by the total or motor sections of the Unified Parkinson's Disease Rating Scale.There was a 1.9 point trend toward better scores on the ADAScog on treatment compared with placebo that was not statistically significant. The secondary cognitive measures showed a statistically significant 2 point benefit on the Mini Mental Status Examination and no change on the Mattis Dementia Rating Scale (MDRS). The Clinical Global Impression of Change (CGI) showed a significant 0.37 point improvement on donepezil. No improvement was observed on the MDRS or the Brief Psychiatric Rating Scale. Carryover between treatment periods was observed but was not statistically significant.

CONCLUSIONS

Donepezil was well tolerated and did not worsen PD. There may be a modest benefit on aspects of cognitive function. The possible clinical benefit measured by CGI was reflected in only one of the cognitive scales used in this study.

Porcine Ig isotypes: function and molecular characteristics

In pigs, protection against the toxigenic extra-cellular bacterium Actinobacillus pleuropneumoniae was correlated with an increased IgG(1):IgG(2) ratio of haemolytic toxin-specific antibodies. In all species so far studied, IgG isotype expression is controlled by Type 1 (IFN-gamma, IL-12) and Type 2 (IL-4, IL-10) cytokines which dictate immune response polarization to cell-mediated (CMI) or antibody-mediated immunity (AMI), respectively. Thus, immunoglobulin (Ig) isotypes reflect Type 1 or Type 2 immune responses. Immunoglobulin isotype production by porcine B-cells cultured in the presence of recombinant porcine (rp) cytokines varies by individual, however pigs tend to generate a high IgG(1):IgG(2) ratio in response to rp IL-10 and the inverse in response to rp IFN-gamma or rp IL-12. Differential Ig isotype production should favor an isotype with a functional advantage to control the inciting infection and disease. However, functions of porcine Ig isotypes have not been described. To compare function of porcine IgM, IgG(1) and IgG(2) of defined specificity for hen eggwhite lysozyme (HEWL), Ig isotypes were affinity purified from serum by HEWL specificity and by isotype-specific mouse monoclonal antibodies. Their ability to activate complement (C') and to opsonize was tested in vitro. Porcine IgG(2) had greater guinea pig C' activating ability than did IgG(1). Neither isotype opsonized HEWL-conjugated sheep erythrocytes in vitro. Amino acid sequence analysis of IgG isotypes revealed that all subclasses have putative C' binding sites but that IgG(2a), IgG(2b) and IgG(4) were more flexible in the middle hinge region than IgG(1) and IgG(3) and would likely activate C' more efficiently. Thus, porcine IgG isotypes associated with resistance and susceptibility to disease also differ in their actual and predicted biological functions.

Control of immunoglobulin isotype production by porcine B-cells cultured with cytokines

Cytokines regulate immunoglobulin (Ig) isotype production following the Th1/Th2 paradigm, derived from studies of inbred mice. In pigs, it is not known which, if any, Ig isotypes may reflect a Th1/Th2 response. To evaluate this, purified porcine CD21(+) B-cells were co-cultured with Staphylococcus aureus Cowan strain 1 or Escherichia coli lipopolysaccharide as B-cell mitogens together with recombinant human IL-2, and recombinant porcine (rp) interferon (IFN)-gamma, IL-12 or IL-10. While the mitogens increased B-cell proliferation, cytokines had no additional effect. A quantitative competitive enzyme-immuno assay was used to measure concentrations of porcine IgM, IgG(1) and IgG(2) in B-cell culture supernatants. In vitro, porcine B-cells produced IgG(2), 106 +/- 17.3 microg/ml; IgG(1) 107 +/- 38.3 microg/ml and IgM 25.6 +/- 8.45 microg/ml. In some individuals, Th1 cytokines such as rpIFN-gamma and IL-12, enhanced IgG(2) in the face of low concentrations of IgG(1). Furthermore, individual responses, in some cases, tended to be diametrically opposed, reminiscent of previously documented categorical immune responses in pigs such that some individuals produced high concentrations of IgG(1) in response to the various doses of rp cytokines, while others produced lower concentrations. Pigs may generate a high IgG(1):IgG(2) ratio in response to rpIL-10, and possibly to other Th2-associated cytokines. However, B-cell response to rp cytokines in vitro exhibits marked variation by pig, a feature that is likely a function of highly variable individual genotypes and their interaction with complex environments.

MRI mapping of cerebrovascular reactivity using square wave changes in end-tidal PCO2

Cerebrovascular reactivity can be quantified by correlating blood oxygen level dependent (BOLD) signal intensity with changes in end-tidal partial pressure of carbon dioxide (PCO2). Four 3-min cycles of high and low PCO2 were induced in three subjects, each cycle containing a steady PCO2 level lasting at least 60 sec. The BOLD signal closely followed the end-tidal PCO2. The mean MRI signal intensity difference between high and low PCO2 (i.e., cerebrovascular reactivity) was 4.0 +/- 3.4% for gray matter and 0.0 +/- 2.0% for white matter. This is the first demonstration of the application of a controlled reproducible physiologic stimulus, i.e., alternating steady state levels of PCO2, to the quantification of cerebrovascular reactivity.

Cortical activation during human volitional swallowing: an event-related fMRI study

Functional magnetic resonance imaging (fMRI) provides a safe, noninvasive method for studying task-related cortical neuronal activity. Because the cerebral cortex is strongly implicated in the control of human swallowing, we sought to identify its functional neuroanatomy using fMRI. In 10 healthy volunteers, a swallow event-related paradigm was performed by injecting 5 ml water bolus into the oral cavity every 30 s. Whole brain functional magnetic susceptibility -weighted spiral imaging data were simultaneously acquired over 600 s on a 1.5-T magnetic resonance scanner, utilizing the blood oxygenation level-dependent technique, and correlation maps were generated using both >99% percentile rank and spatial extent thresholding. We observed areas of increased signal change consistently in caudal sensorimotor cortex, anterior insula, premotor cortex, frontal operculum, anterior cingulate and prefrontal cortex, anterolateral and posterior parietal cortex, and precuneus and superiomedial temporal cortex. Less consistent activations were also seen in posterior cingulate cortex and putamen and caudate nuclei. Activations were bilateral, but almost every region, particularly the premotor, insular, and frontal opercular cortices, displayed lateralization to one or the other hemisphere. Swallow-related cortical activity is multidimensional, recruiting brain areas implicated in processing motor, sensory, and attention/affective aspects of the task.

Evaluation of gross and fine motor functions in children with hemidecortication: predictors of outcomes and timing of surgery

The purpose of this study is three-fold: First, to determine the levels of gross and fine motor functions in children before and after hemidecortication, using standardized measurement tools; second, to investigate if predictors of these outcomes can be characterized; and third, to explore if both clinical measures and functional magnetic resonance imaging (MRI) potentially can identify optimal timing of surgery. The Gross Motor Function Measure and the Quality of Upper Extremity Skills Test are shown to be comprehensive, standardized outcome measures of movement performance in affected children. Age at surgery and interval between age at seizure onset and age at surgery could be the most reliable predictors of clinical outcomes. Functional MRI studies are valuable in exploring the potential of the cortical reorganization that sustains residual sensorimotor function. The combination of clinical measures with functional MRI is a promising method of inquiry into developmental and plasticity processes.

Evaluation of fibroblast-mediated gene therapy in a feline model of mucopolysaccharidosis type VI

Fibroblast-mediated ex vivo gene therapy was evaluated in the N-acetylgalactosamine 4-sulfatase (4S) deficient mucopolysaccharidosis type VI (MPS VI) cat. Skin biopsies were obtained at birth from severely affected MPS VI kittens and used to initiate fibroblast outgrowths for retroviral transduction with the 4S cDNA. 4S gene expression in transduced cells was under the transcriptional control of the MoMLV long terminal repeat promoter or the cytomegalovirus (CMV) immediate-early promoter. Characterisation of gene-transduced fibroblasts demonstrated the cells to be over-expressing 4S activity. Twenty-four to forty million autologous, gene-corrected fibroblasts were implanted under the renal capsule of three MPS VI kittens at 8-16 weeks of age. Transient, low levels of 4S activity were detected in peripheral blood leukocytes shortly after implantation but were not detectable within 3-8 weeks' post-implantation. Long-term biochemical and clinical evaluation of these cats demonstrated identical disease progression to that previously described in untreated, clinically severe MPS VI cats.

Expression of Drosophila trithorax-group homologues in chick embryos

Mll, Brg1 and Brm are vertebrate homologues of Drosophila trithorax group (trxG) genes. We isolated chicken Mll cDNA clones, and examined patterns of Mll, Brg1 and Brm expression in chick embryos. All three genes were expressed from embryonic stage 2 onwards. Mll transcripts were just detectable in all tissues by in situ hybridization, with highest level in dorsal neural tube and notochord. Brg1 transcripts were readily detectable in all tissues, with highest levels in dorsal neural tube, dorsal trunk epithelium and limb bud epithelium and mesenchyme. Brm transcripts were more restricted, being found in dermomyotome, notochord, dorsal limb bud epithelium, eye and the roof and floor plates of the neural tube.

Mild feline mucopolysaccharidosis type VI. Identification of an N-acetylgalactosamine-4-sulfatase mutation causing instability and increased specific activity

The missense mutation, L476P, in the N-acetylgalactosamine 4-sulfatase (4S) gene, has previously been shown to be associated with a severe feline mucopolysaccharidosis type VI (MPS VI) phenotype. The present study describes a second mutation, D520N, in the same MPS VI cat colony, which is inherited independently of L476P and is associated with a clinically mild MPS VI phenotype in D520N/L476P compound heterozygous cats. Biochemical and clinical assessment of L476P homozygous, D520N/L476P compound heterozygous, and D520N homozygous cats demonstrated that the entire range of clinical phenotypes, from severe MPS VI, to mild MPS VI, to normal are clustered within a narrow range of residual 4S activity from 0. 5% to 4.6% of normal levels. When overexpressed in CHO-KI cells, the secreted form of D520N 4S was inactivated in neutral pH conditions. In addition, intracellular D520N 4S protein was rapidly degraded and corresponded to 37%, 14.5%, and 0.67% of normal 4S protein levels in the microsomal, endosomal, and lysosomal compartments, respectively. However, the specific activity of lysosomal D520N 4S was elevated 22. 5-fold when compared with wild-type 4S. These results suggest that the D520N mutation causes a rapid degradation of 4S protein. The effect of this is partially ameliorated as a result of a significant elevation in the specific activity of mutant D520N 4S reaching the lysosomal compartment.

Functional MRI of lateral occipitotemporal cortex during pursuit and motion perception

We performed functional imaging with a conventional 1.5-T magnetic resonance scanner in 9 normal subjects. We used a gradient-echo technique to examine changes in signal between periods when subjects viewed a stationary black-and-white grating, a moving grating, and when they followed a moving spot. We located image pixels with significant differences between the viewing conditions. In 7 subjects, these occurred in the lateral occipitotemporal cortex, a region previously identified as a putative human homologue of the motion-sensitive middle temporal area (MT, or V5) of monkeys. Signal intensity was greater during pursuit of the moving dot than during viewing of the moving grating with the eyes still, despite the fact that the moving grating generated more retinal image motion. In contrast, signal intensity in striate cortex was least during pursuit of the moving dot. These findings suggest that the lateral occipitotemporal cortex has extraretinal signals during pursuit. Such signals may include attentional input, corollary eye movement information, or even a pursuit command. Extraretinal signals suggest that the lateral occipitotemporal cortex may contain a human homologue not only of MT but also of other components of the monkey V5 complex, such as the medial superior temporal area.

Tissue and cellular patterning of the musculature in chick wings

Development of the musculature involves generation of a precise number of individual muscles arranged in appropriate locations, each with the correct cellular patterning. To find out the rules that govern muscle number and arrangement, the forearm musculature of chick wing buds was analysed following grafts of the polarizing region or application of retinoic acid. Muscle patterns appear symmetrical with ‘posterior’ muscles now forming in the anterior part of the wing. When the number of muscles that develop is reduced, pattern symmetry is maintained, with loss of anterior muscles in the mid-line, especially dorsally. Strict anteroposterior ordering of muscles in duplicated patterns does not always occur. The number of muscles that develops bears some relationship to the number of forearm elements. Each muscle has a characteristic pattern of fast and slow fibres. In duplicated wings, each pair of symmetrically arranged muscles has the same fibre type pattern. Not only are proportions of fast and slow fibres similar, but local variations in fibre type arrangement within the muscle are also reproduced. This suggests that the cellular pattern within the new ‘posterior’ muscles at the anterior of the limb has been re-specified. In manipulated limb buds, which will develop a duplicated muscle pattern, there are no detectable changes in distribution and number of potentially myogenic cells, and fibre type patterning within early muscle masses also appears normal. In contrast, the splitting process that divides up muscle masses is altered. The appropriate fibre type arrangement only emerges after splitting is complete. This suggests that tissue patterning and cellular patterning occur at different times during muscle development.

Expression of the connexin43 gap junctional protein in tissues at the tip of the chick limb bud is related to the epithelial-mesenchymal interactions that mediate morphogenesis

The pattern of connexin43 expression in developing chick limb buds was examined using a site-specific polyclonal antibody and confocal microscopy. Connexin43 is expressed at stages of limb development when epithelial-mesenchymal interactions are occurring that mediate morphogenesis. Extensive labeling was observed in the apical ectodermal ridge and labeling was also found in underlying mesenchyme cells at the tip of the bud. In mouse limb buds, the same gap junction protein is expressed only in the apical ridge. Manipulations of developing chick wing buds show that mesenchymal expression of connexin43 appears to be controlled by the apical ectodermal ridge. When the apical ridge is surgically removed and limb truncations result, mesenchymal labeling is markedly reduced and conversely the grafting of an additional ridge induces connexin43 expression between underlying mesenchymal cells which do not normally show expression at this stage of development. In addition, a treatment with retinoic acid that flattens the apical ridge and inhibits bud outgrowth reduces expression in both mesenchymal and epithelial tissues. The abolition of connexin43 expression in mesenchymal and epithelial domains when bud outgrowth is halted suggests that synthesis of this gap junction protein is related to the epithelial-mesenchymal interactions that mediate morphogenesis of the bud.

Quantitative evaluation of several partial Fourier reconstruction algorithms used in MRI

Partial Fourier reconstruction algorithms exploit the redundancy in magnetic resonance data sets so that half of the data is calculated during image reconstruction rather than acquired. The conjugate synthesis, Margosian, homodyne detection, Cuppen and POCS algorithms are evaluated using spatial frequency domain analysis to show their characteristics and where limitations may occur. The phase correction used in partial Fourier reconstruction is equivalent to a convolution in the frequency domain and the importance of accurately implementing this convolution is demonstrated. New reconstruction approaches, based on passing the partial data through a phase correcting, finite impulse response (FIR), digital filter are suggested. These FIR and MoFIR algorithms have a speed near that of the Margosian and homodyne detection reconstructions, but with a lower error; close to that of the Cuppen/POCS iterative approaches. Quantitative analysis of the partial Fourier algorithms, tested with three phase estimation techniques, are provided by comparing artificial and clinical data reconstructed using full and partial Fourier techniques.

Hox-4 gene expression in mouse/chicken heterospecific grafts of signalling regions to limb buds reveals similarities in patterning mechanisms

The products of Hox-4 genes appear to encode position in developing vertebrate limbs. In chick embryos, a number of different signalling regions when grafted to wing buds lead to duplicated digit patterns. We grafted tissue from the equivalent regions in mouse embryos to chick wing buds and assayed expression of Hox-4 genes in both the mouse cells in the grafts and in the chick cells in the responding limb bud using species specific probes. Tissue from the mouse limb polarizing region and anterior primitive streak respecify anterior chick limb bud cells to give posterior structures and lead to activation of all the genes in the complex. Mouse neural tube and genital tubercle grafts, which give much less extensive changes in pattern, do not activate 5′-located Hox-4 genes. Analysis of expression of Hox-4 genes in mouse cells in the grafted signalling regions reveals no relationship between expression of these genes and strength of their signalling activity. Endogenous signals in the chick limb bud activate Hox-4 genes in grafts of mouse anterior limb cells when placed posteriorly and in grafts of mouse anterior primitive streak tissue. The activation of the same gene network by different signalling regions points to a similarity in patterning mechanisms along the axes of the vertebrate body.

Position-dependent expression of two related homeobox genes in developing vertebrate limbs

Many genes that control pattern formation in insects contain a conserved homeobox region which encodes a domain involved in DNA binding. One approach to understanding pattern formation in vertebrates is to examine the role of homeobox-containing genes in the developing limb. Two such genes, Hox-7.1 and Hox-8.1, are expressed in distal mesoderm, but not in the proximal core, of mouse forelimb (refs 3, 4, and D.R.D., manuscript in preparation). The proximodistal cartilage pattern in the chick wing is progressively determined in the distal mesoderm, which is maintained as a 'progress zone' by the overlying apical ectodermal ridge. Indeed, proximal cells are reprogrammed to form distal structures when placed in the progress zone and we therefore expect that genes involved in controlling limb pattern should be activated in such grafts. We tested this requirement for Hox-7.1 and Hox-8.1 in mouse limb mesoderm placed in chick wing buds. Our results reported here indicate that both genes are rapidly activated by a signal from the apical ectoderm. These properties, taken with the DNA-binding properties of the homeodomain, strongly suggest that Hox-7.1 and Hox-8.1 have fundamental roles in limb-pattern formation.

The behaviour of cells from the distal tips of quail wing buds when grafted back into chick wings after micromass culture

In high density culture, cells from distal tips of developing limb buds differentiate into a continuous cartilage sheet, rich in type II collagen. When grafted back into limb buds, cells cultured for a short time differentiate into cartilage and a wide range of other connective tissues, whereas cells taken from older cultures give rise only to cartilage and perichondrium. Grafts placed distally give rise to more cell types than grafts placed proximally. The results strongly suggest that chondrogenesis in culture is the result of removing the signals that pattern differentiation within the limb bud.

Retinoic acid application to chick wing buds leads to a dose-dependent reorganization of the apical ectodermal ridge that is mediated by the mesenchyme

Local application of retinoic acid to wing buds of chick embryos leads to dose- and position-dependent changes in the pattern of cellular differentiation. Early effects of retinoid treatment on the apical ectodermal ridge coordinate pattern changes and morphogenesis. The length of the apical ridge increases when additional digits will form but decreases when digits are lost. These changes in length can be understood in terms of a threshold response to the local retinoid concentration that results in either disappearance or maintenance of the ridge (Lee & Tickle, J. Embryol. exp. Morph. 90, 139–169 (1985)). Here, we have analysed the mechanisms involved in ridge disappearance by locally applying retinoic acid to the apex of stage 20 chick wing buds. With this treatment regime, low doses give duplicated digit patterns and higher doses truncations. The height of the apical ridge is progressively reduced with increasing doses of retinoid and the time course of ridge flattening indicates that the height of the ridge is correlated with bud outgrowth. With high doses of retinoic acid, the typical ridge, a pseudostratified epithelium in which the columnar cells are tightly packed, disappears and the epithelium at the tip of the bud consists of loosely packed cuboidal cells. Shortly after treatment, there is a decrease in the number of gap junctions between ridge cells. This early change in cell contacts suggests that gap junctions may be involved in maintaining epithelial morphology. When treated epithelium is recombined with untreated mesenchyme, an apical ridge is reestablished and distal structures can be generated. In contrast, when treated mesenchyme is recombined with the epithelium from normal buds, only proximal structures are formed. Therefore, retinoids can lead to a reorganization of the apical ectodermal ridge which is mediated and maintained by the mesenchyme.

Analysis of upper beak defects in chicken embryos following with retinoic acid

Implanting inert carriers soaked in retinoic acid into the anterior margin of the developing limb of chicken embryos leads to orofacial malformations as well as affecting pattern formation in the limb. Using anion-exchange beads as carriers, and soaking solutions of 1–10 mg/ml retinoic acid, almost 100% of the embryos have malformations of the face. The effects on the treated limbs range from symmetrical patterns of duplicated digits (maximum number of digits being four) to truncations in which no digits were formed at all.

Typically, in the malformed faces the upper beak is completely absent, no nostrils are present and the front of the face forms a scalloped rim of tissue above the mouth. By reference to normal beak development, the seven bulges of tissue that make up the rim can be identified as derivatives of the masses of tissue that normally would fuse to form the upper beak. The roof of the mouth consists of three bulges of tissue flanked by widely separated palatal shelves. The defect can thus be classified as severe bilateral clefting of the primary palate.

By examining the morphology of the faces of treated embryos, the origin of the defect can be traced to failure of the frontonasal mass to enlarge. Thus, the oronasal fissures are very wide and fusion across them to form the primary palate cannot occur.

The way in which retinoic acid brings about the defect is discussed in relation to possible mechanisms involved in the production of cleft palate. The parallel is noted between the associated effects of retinoic acid on beak and limb morphogenesis and the chick mutation cpp, that also affects both face and limbs.

Analysis of upper beak defects in chicken embryos following with retinoic acid

Implanting inert carriers soaked in retinoic acid into the anterior margin of the developing limb of chicken embryos leads to orofacial malformations as well as affecting pattern formation in the limb. Using anion-exchange beads as carriers, and soaking solutions of 1-10 mg/ml retinoic acid, almost 100% of the embryos have malformations of the face. The effects on the treated limbs range from symmetrical patterns of duplicated digits (maximum number of digits being four) to truncations in which no digits were formed at all. Typically, in the malformed faces the upper beak is completely absent, no nostrils are present and the front of the face forms a scalloped rim of tissue above the mouth. By reference to normal beak development, the seven bulges of tissue that make up the rim can be identified as derivatives of the masses of tissue that normally would fuse to form the upper beak. The roof of the mouth consists of three bulges of tissue flanked by widely separated palatal shelves. The defect can thus be classified as severe bilateral clefting of the primary palate. By examining the morphology of the faces of treated embryos, the origin of the defect can be traced to failure of the frontonasal mass to enlarge. Thus, the oronasal fissures are very wide and fusion across them to form the primary palate cannot occur. The way in which retinoic acid brings about the defect is discussed in relation to possible mechanisms involved in the production of cleft palate. The parallel is noted between the associated effects of retinoic acid on beak and limb morphogenesis and the chick mutation cpp, that also affects both face and limbs.

Infiltration and survival: the behaviour of normal, invasive cells implanted to the developing chick wing

The invasiveness of mouse lymphocytes and thymocytes, rabbit peritoneal neutrophil granulocytes (PMNs), mouse peritoneal macrophages (both activated and non-activated) and pig endothelial cells was assayed by implanting these cells to the chick wing bud. Cells of each type moved into the wing mesenchyme, although activated macrophages invaded poorly. PMNs were the most invasive cells and had moved well into the limb after only a few hours. PMNs, lymphocytes and thymocytes were ingested by wing mesenchyme cells. Endothelial cells, however, ingested chick blood cells. The implanted cells showed differences in ability to survive in the limb: PMNs disappeared rapidly, lymphocytes and thymocytes sometimes persisted for 24 h, while grafts of macrophages and endothelial cells were present at 24 h. Mechanisms which might be involved in the invasiveness of these cells, and also in their different abilities to survive in the chick wing, are discussed with particular reference to the production of plasminogen activator.

Survival of cells implanted in the embryonic chick limb bud: a difference between normal and malignant rat brain cells

Cells from normal rat brain tissue did not survive and few cells could be found 1 d after grafting. In contrast, cells from a glioma and a carcinogen-treated rat brain survived well and many mitoses were observed. These malignant cells also invaded the limb. The behaviour of normal and malignant cells was followed at shorter times after grafting and some invasion by the normal cells was detected. The first signs of degeneration of normal cells were apparent around 7 h after grafting, and after this the grafts progressively deteriorated. These results support the ideal that the ability of cells to survive and grow in embryonic tissues is a characteristic of malignant cells. The findings are discussed in relation to mechanisms of tumour formation.

Mechanisms of invasiveness of epithelial tumours: ultrastructure of the interactions of carcinoma cells with embryonic mesenchyme and epithelium

Three different kinds of carcinoma cell, human breast tumours, mouse lung tumour and rat bladder tumours have been implanted into the developing chick wing to assay their invasive behaviour. We found that the majority of the carcinoma cells did not invade the mesenchyme but were positioned in the ectoderm. We examined the ultrasturcture of the interaction of the carcinoma cells with both the ectoderm and the mesenchyme to see if there are any differences. We found no specialized adhesive junctions between carcinoma cells and mesenchyme cells. In contrast, the carcinoma cells seem to be adhesive to the ectoderm cells; desmosomes between the two have been found and also frequent parallel alignment of membranes over long distances. This difference between the interaction of the carcinoma cells with the mesenchyme and the ectoderm may explain why the carcinoma cells can penetrate into the ectoderm but rarely do so into the mesenchyme. The carcinoma cells formed a smooth border with the mesenchyme even in the absence of a basal lamina. These results are discussed in relation to the mechanisms of invasion of epithelial tumours in vivo. In particular, the relative importance of the basal lamina, and cell adhesion within the tumour, in limiting invasiveness are assessed.

Cell movement and the mechanism of invasiveness: a survey of the behaviour of some normal and malignant cells implanted into the developing chick wing bud

A survey of the behaviour of a variety of normal and malignant tumours and cells has been carried out to gain insights into the mechanisms of tumour invasiveness. The tumours and cells were implanted into the developing chick wing bud, which is a loose mesenchyme bounded by ectoderm. The distribution of the grafted cells was examined histologically after one or two days. The special feature of this assay is that the behaviour of cells is tested in a 3-dimensional tissue. Cells from 3 different carcinomas, mouse lung tumour, rat bladder tumour and human breast tumour did not invade the mesenchyme, whereas trophoblast, sarcoma 180, cultured hamster fibroblasts (BHK, PyBHK, Nil 8, HSV Nil 8) and neuroblastoma cells did. Cells from embryonic pigmented retina and heart ventricle were non-invasive. These results suggest that cell movement may not be a common feature of all invasive tumours. The cells that did move into the mesenchyme appeared to do so by various mechanisms. Lack of contact inhibition of movement, although probably involved in the invasiveness of sarcoma 180 cells, does not appear to be necessary for invasion: cells that have been shown to exhibit contact inhibition of movement (BHK and PyBHK) also invade. Both normal and transformed cells (BHK and PyBHK; Nil 8 and HSV Nil 8) moved into the mesenchyme. Other invading cells, such as trophoblast, neuroblastoma and to a small extent, HSV Nil 8 cells, destroy the adjacent host tissue and this may be important in the invasiveness of these cells. The patterns of invasion and interactions with the host tissue were varied. Trophoblast and the fibroblasts were often elongated along the basement membrane at the ectoderm/mesenchyme border and also closely apposed to the endothelial linings of blood vessels. Sarcoma 180 and neuroblastoma cells clustered around nerves. The embryonic tissues and neuroblastoma cells were often associated with blood vessels. These results are discussed in relation to tumour invasion. A striking finding was that the carcinoma cells were frequently found positioned within the wing ectoderm on the basement membrane. This affinity of carcinoma cells for the epithelium rather than the mesenchyme leads to a reappraisal of the mechanisms involved in the invasiveness of carcinomas.

A quantitative study of blastemal growth and bone regression during limb regeneration in Triturus cristatus

Soft X-ray photographs show both the outlines of the soft parts of the regenerating limb and the bones. This enables one to make quantitative studies on bone regression and the growth of the regenerate, since good reference points are available. Bone regression of about 0.5 mm was observed to occur within about 20 days following amputation. Growth curves of regenerates cut at different levels confirm Spallanzani's old observation that the total time for regeneration is fairly constant for different levels of amputation – regenerates from proximal levels regenerate faster. However, the intrinsic growth rate curves are remarkably similar for different levels of amputation; the difference in final length arises because the short period of high intrinsic growth rate continues for slightly longer in regenerates from proximal levels.

In terms of the progress zone theory of limb development, three phases of regeneration are recognized: the formation of the blastema and progress zone; the laying down of the skeletal rudiments by the rapidly proliferating progress zone; and the subsequent slower growth of the rudiments. A quantitative model is put forward and it is shown that it can provide a good description of the observed growth curves. An important assumption is that the various skeletal rudiments are the same size when they leave the progress zone and the final differences in size reflect differences in the final growth phase. The progress zone model provides new quantitative insights into the relationship between the growth of the limb as a whole and the behaviour of individual cells.