Abstract P6-08-01: Analysis of patient-reported outcomes following nipple-sparing mastectomy and implant reconstruction

Background: Nipple-sparing mastectomy (NSM) is gaining popularity among women undergoing prophylactic and therapeutic mastectomy. Using the BREAST-Q, a validated condition-specific patient-reported outcome instrument which measures postsurgical patient satisfaction and health-related quality of life (HR-QoL), we sought to determine whether satisfaction and HR-QoL differ between patients undergoing NSM and skin-sparing mastectomy (SSM) with immediate implant reconstruction.

Methods: From 2005 to 2012, a total of 572 patients underwent mastectomy; of these 261 patients (46%) had NSM. All mastectomy patients were mailed the BREAST-Q reconstruction questionnaire consisting of 3 scales (scored 0-100): Satisfaction with Breasts, Satisfaction with Outcome, and Psychosocial Well-Being. Excluded from this analysis were males, autologous tissue reconstruction, and conversion from NSM to SSM. Comparisons were made between NSM and SSM groups using univariable analysis and multivariable linear regression models (MVA).

Results: The BREAST-Q completion rate was 27% with a median time from surgery to survey of 36 months (range 4 to 86). Women undergoing NSM, compared to SSM, were younger (mean 46 v 50 years; p = 0.01), more likely to be married (80% v 52%; p = 0.001), have bilateral mastectomies (79% v 59%; p = 0.01), and had less time between surgery and BREAST-Q completion (median 25 v 49 months; p<0.001). 19 NSM patients (25%) and 7 SSM patients (13%) underwent prophylactic mastectomy (p = 0.07). There were no differences regarding tumor characteristics or treatment. Patients undergoing NSM, compared to SSM, had a higher unadjusted mean score for Satisfaction with Breasts (71 v 60; p<0.001), Satisfaction with Outcome (80 v 69; p = 0.003), and Psychosocial Well-Being (84 v 74; p = 0.006). On MVA analysis, NSM (compared to SSM) was associated with greater Satisfaction with Breasts (adjusted mean difference: +13, 95% Confidence Interval[CI]: 6-21, p = 0.001), Satisfaction with Outcome (adjusted mean difference: +17, 95% CI: 7-27, p = 0.001), and Psychosocial Well-Being (adjusted mean difference: +12, 95% CI: 3-22, p = 0.013), after controlling for age at mastectomy, marital status, laterality, cancer vs. non-cancer diagnosis, post-mastectomy radiation treatment, and time from mastectomy to BREAST-Q completion. Not being married (adjusted mean difference: +8, 95% CI: 2-15, p = 0.014) and having a bilateral mastectomy (adjusted mean difference: +8, 95% CI: 1-14, p = 0.029) were also significant predictors of increased Satisfaction with Breasts.

Conclusion: These findings suggest that, in the setting of implant reconstruction, NSM is associated with higher patient satisfaction with their breasts, overall outcome, and improved emotional/social well being.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-08-01.

Quality assurance review center: Role in multi-institutional breast cancer trials

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Background: Central review is an important trial management and validation tool. Multisite trials require data systems to accommodate diverse image acquisition and review. Breast cancer is challenging as its imaging objects are not always easily shared across departments. Quality Assurance Review Center (QARC) has a diverse portfolio of facile data acquisition and powerful informatics support that meets these needs. We report on the role of QARC in three of the current breast cancer trials from the American College of Surgeons Oncology Group.

Methods: QARC data management system includes secure network infrastructure and a validated relational operating database (MAX). QARC has data acquisition/imaging re-distribution expertise for real time response reviews, response measuring tools and corresponding data archive for secondary reviews. MAX includes query ability; records link to digital information. QARC underwent systematic information systems validation process for 21 CFR Part 11. DICOM/non-DICOM files are stored in the QARC PACS. On-site/remote reviewers use MAX to retrieve, view, annotate and save images. Data extracted is securely sent to partner statistical centers.

Results: In Z1031, a neoadjuvant endocrine therapy trial, all of the mammographic exams are archived at QARC. For Z1071, a sentinel lymph node trial, pre- and post-treatment ultrasound (US) images of 321 patients were remotely reviewed. For Z1072, the cryoablation US, pre and post-cryoablation MRI for 40 of 47 cases were remotely archived, retrieved and transferred to investigator workstation for post-processing and review. The other 7 patients did not have evaluable imaging studies. In all three trials, the costs of shipping hardcopies of exams and travel to QARC for central review functions were eliminated.

Conclusions: QARC data management systems provide diverse informatics supports for multi-institutional trials, ranging from archives of images, provide remote access and download of data, and central review. The vibrant informatics supports meet the growing needs of clinical trials. Future directions include radiation field review for breast cancer trials and the incorporation of pathology microarray analysis as DICOM objects.

Use of intraoperative breast cancer sentinel lymph node (SLN) assay to predict of ≥4 positive (+) lymph nodes (LN)

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Background: Predicting which patients will have ≥4 +LN and may need radiation therapy affects immediate breast reconstruction. We hypothesized that model s to predict the likelihood of ≥4+LN may be improved by incorporation of quantitative real time RT-PCR analysis of SLN. Methods: 728 patients were enrolled in 2 prospective studies of the GeneSearch BLN Assay (Veridex LLC) for SLN metastases. 205 (28.2%) were found to have +SLN by hematoxylin-eosin staining. Of these, 115 pts (15.8%) had tumors ≤5 cm in size with >4 total LN removed, forming the cohort of interest for this study. Quantitative cycle times (CT) for mammaglobin (MG) and CK19 were correlated with finding ≥4+LN on final pathology. Results: Median tumor size was 2.0 cm (range; 0.2–5.0 cm). Median number of SLN removed was 3 (range; 1–11). 18 patients (15.7%) had ≥4 +LN on final pathology. Median CT for MG was 29.1 (interquartile range (IQR): 24.7–39.0) in patients with <4 +LN vs. 21.4 (IQR: 18.5–26.8) in those with ≥4 +LN, p<0.001. Median CT for CK19 was 23.7 (IQR: 20.9–28.2) in patients with <4 +LN vs. 19.6 (IQR: 17.8–20.7) in those with ≥4 +LN, p<0.001. Tumor size ≥2cm, proportion of SLN+ >50%, MG CT <25.8 and CK19 <20.8 were correlated with ≥4 +LN on final pathology. On multivariate analysis, tumor size, MG CT and CK19 CT were significant (see table). A simplified CPR was created with 1 point given if tumor size was ≥2cm, 1 point if MG CT <25.8 and 2 points if CK19 CT<20.8. Of the 24 patients (20.9%) with 0 points, only 1 (4.2%) had ≥4 +LN; of the 12 patients (10.4%) with 3 points, 8 (66.7%) had ≥4 +LN on final pathology, p<0.001. Area under the receiver-operator curve was 86.2% (95% CI: 76.1%-96.2%). Conclusions: Intraoperative quantitative RT-PCR of SLN improves prediction of ≥4 +LN; further validation of this model will have clinical utility regarding the use of immediate, delayed, or delayed-immediate reconstruction approaches.

[Table: see text]

[Table: see text]

Breast cancer in patients with residual invasive carcinoma is more accurately staged with additive tumor size assessment

BACKGROUND

Accurate assessment of tumor size for patients with breast cancer undergoing re-excision following breast-conserving therapy is important for appropriate staging and adjuvant treatment. We investigated the accuracy of additive vs. nonadditive size assessment in determining final tumor stage.

METHODS

Patients with infiltrating carcinoma in the initial excision and in at least one additional re-excision (re-excision positive; n = 89) had tumor size assessed with additive and nonadditive techniques. This group was compared with patients undergoing re-excision but without identifiable residual carcinoma (re-excision negative; n = 105) regarding rates of lymph node (LN) metastasis.

RESULTS

The re-excision positive patients had a different median final tumor size depending on the size assessment technique used (nonadditive: 1.8 cm; additive: 3.0 cm; P <.0001). Both groups of patients had a median tumor size consistent with T1c staging in nonadditive size assessment. However, re-excision positive patients had a significantly higher incidence of LN metastasis (P <.05) than did re-excision negative patients. Both groups were then separated into T1 and T2 stages and the LN metastasis rates were assessed. Compared with nonadditive size assessment, additive size assessment distributed re-excision positive patients into T stages whereby the LN metastasis rates more closely approximated those of re-excision negative patients (T1, 3% vs. 6% difference; T2, 4% vs. 13% difference).

CONCLUSIONS

With regard to LN metastasis, staging for patients with residual invasive carcinoma in re-excision specimens is more accurate with additive tumor size assessment.

Hidden-Markov methods for the analysis of single-molecule actomyosin displacement data: the variance-Hidden-Markov method

In single-molecule experiments on the interaction between myosin and actin, mechanical events are embedded in Brownian noise. Methods of detecting events have progressed from simple manual detection of shifts in the position record to threshold-based selection of intermittent periods of reduction in noise. However, none of these methods provides a "best fit" to the data. We have developed a Hidden-Markov algorithm that assumes a simple kinetic model for the actin-myosin interaction and provides automatic, threshold-free, maximum-likelihood detection of events. The method is developed for the case of a weakly trapped actin-bead dumbbell interacting with a stationary myosin molecule (Finer, J. T., R. M. Simmons, and J. A. Spudich. 1994. Nature. 368:113-119). The algorithm operates on the variance of bead position signals in a running window, and is tested using Monte Carlo simulations to formulate ways of determining the optimum window width. The working stroke is derived and corrected for actin-bead link compliance. With experimental data, we find that modulation of myosin binding by the helical structure of the actin filament complicates the determination of the working stroke; however, under conditions that produce a Gaussian distribution of bound levels (cf. Molloy, J. E., J. E. Burns, J. Kendrick-Jones, R. T. Tregear, and D. C. S. White. 1995. Nature. 378:209-212), four experiments gave working strokes in the range 5.4-6.3 nm for rabbit skeletal muscle myosin S1.

Recurrence rates in patients with central or retroareolar breast cancers treated with mastectomy or lumpectomy

BACKGROUND

Although breast conservation with lumpectomy and radiation treatment has become a commonly used treatment for breast cancer, there are little data to support the use of lumpectomy for central and retroareolar breast cancers. In this study, we investigate the local and distant recurrence rates of patients with central or retroareolar breast cancers treated with lumpectomy compared with mastectomy.

METHODS

This study provides a retrospective analysis of 99 patients, from 1981 to 2000, with central or retroareolar breast cancers treated with mastectomy or lumpectomy to determine the frequency of local and distant recurrence. The mastectomy and lumpectomy patients were compared with respect to recurrence and other prognostic factors including: tumor location, tumor size, axillary nodal status, and final surgical margins.

RESULTS

The overall frequency of local recurrence was 5 of 99 (5.0%) in the entire group, 3 of 67 (4.5%) and 2 of 32 (6.3%) of patients who underwent mastectomy and lumpectomy, respectively (P >0.99). Overall, 3 patients experienced a distant recurrence as a first event, with 2 patients (3.0%) in the mastectomy group and 1 patient (3.1%) in the lumpectomy group (P >0.99). The type of surgical management was not statistically significant related to either local or distant disease recurrence, with median time to local recurrence of 3.0 years for the mastectomy patients and 5.0 years for lumpectomy patients. Of the patients with central tumors who underwent mastectomy 2 of 42 (4.8%) developed local recurrences compared with those who had a lumpectomy, 1 of 21 (4.8%). Similarly for retroareolar tumors, the local recurrence rate was 1 of 25 (4.0%) for patients undergoing mastectomy and 1 of 11 (9.1%) for those undergoing lumpectomy (P >0.99).

CONCLUSIONS

In this study there was no significant difference in local or distant failure rates of those patients with central or retroareolar tumors treated with mastectomy versus lumpectomy. We conclude lumpectomy to be a reasonable treatment option for selected patients with central or retroareolar breast cancers.

Methylene blue dye as an alternative to isosulfan blue dye for sentinel lymph node localization

Isosulfan blue dye has been used with increasing frequency in localizing sentinel lymph nodes in breast cancer patients. Few alternative types of dye have been investigated. In a prospective study of 30 patients, methylene blue dye was used instead of isosulfan blue dye to localize the sentinel lymph node. The methylene blue dye localization technique was successful in 90% of patients. These results are similar to those for isosulfan blue dye. This study describes methylene blue dye localization as a successful alternative to isosulfan dye in identifying the sentinel node in breast cancer patients. The methylene blue dye technique offers a substantial cost reduction.

Models of motor-assisted transport of intracellular particles

One-dimensional models are presented for the macroscopic intracellular transport of vesicles and organelles by molecular motors on a network of aligned intracellular filaments. A motor-coated vesicle or organelle is described as a diffusing particle binding intermittently to filaments, when it is transported at the motor velocity. Two models are treated in detail: 1) a unidirectional model, where only one kind of motor is operative and all filaments have the same polarity; and 2) a bidirectional model, in which filaments of both polarities exist (for example, a randomly polarized actin network for myosin motors) and/or particles have plus-end and minus-end motors operating on unipolar filaments (kinesin and dynein on microtubules). The unidirectional model provides net particle transport in the absence of a concentration gradient. A symmetric bidirectional model, with equal mixtures of filament polarities or plus-end and minus-end motors of the same characteristics, provides rapid transport down a concentration gradient and enhanced dispersion of particles from a point source by motor-assisted diffusion. Both models are studied in detail as a function of the diffusion constant and motor velocity of bound particles, and their rates of binding to and detachment from filaments. These models can form the basis of more realistic models for particle transport in axons, melanophores, and the dendritic arms of melanocytes, in which networks of actin filaments and microtubules coexist and motors for both types of filament are implicated.

Postgraduate training in breast surgery

Dramatic changes have taken place in the field of breast surgery within the past ten years. Much of the change in practice is due to the advent of less invasive surgical procedures and increased technology such as the evolution of sentinel node biopsies. Many surgeons choose to undergo additional postgraduate training to gain an increased proficiency in the diagnosis and surgical treatment of benign and malignant disorders of the breast.

Skin-sparing mastectomy with immediate breast reconstruction: a critical analysis of local recurrence

PURPOSE

The purpose of this study was to provide follow-up data regarding the incidence of local breast cancer recurrence in patients undergoing skin-sparing mastectomy versus conventional non-skin-sparing mastectomy methods.

PATIENTS AND METHODS

A retrospective follow-up study and analysis were performed of patients who underwent mastectomies for invasive breast cancer at The New York Presbyterian Hospital, Cornell University Medical College and Strang-Cornell Breast Center between 1990 and 1998.

RESULTS

A total of 198 patients were identified in this study, and the mean follow-up was 49 months. This group included 71 patients who underwent skin-sparing mastectomy and 127 who underwent non-skin-sparing mastectomy procedures. No statistical differences in local recurrence rates were demonstrated between patients treated with skin-sparing mastectomy and those who underwent non-skin-sparing mastectomy. Local recurrence was present in four of 71 (5.6%) patients undergoing skin-sparing mastectomy and in five of 127 (3.9%) of those undergoing non-skin-sparing mastectomy.

CONCLUSIONS

The use of skin-sparing mastectomy does not lead to an increase in local recurrence rates when compared with conventional non-sparing mastectomies and provides for improved aesthetic results after immediate reconstruction.

Predictive factors associated with axillary lymph node metastases in T1a and T1b breast carcinomas: analysis in more than 900 patients

BACKGROUND

Axillary lymph node metastasis (ALNM) represents the single most important prognostic indicator in patients diagnosed with breast cancer. The proportion of < or = 1-cm (T1a, T1b) invasive breast carcinomas is increasing. The incidence and predictive factors associated with ALNM in patients with < or = 1-cm tumors remains unclear and the role of axillary lymph node dissection in these patients has been questioned. The purpose of this study was to determine clinical and pathologic factors predictive of ALNM in patients with < or = 1-cm invasive breast carcinomas by univariate and multivariate analyses.

STUDY DESIGN

Review analysis from a prospective database identified patients with < or = 1-cm invasive breast cancers treated at our institution between 1990 and 1996. All patients underwent a resection of the primary tumor and axillary lymph node dissections. Routine patient and tumor characteristics evaluated included: age, race, tumor size, histologic grade, estrogen and progesterone receptor status, and lymphatic and vascular invasion. Univariate and multivariate analyses were performed. Adjusted odds ratios (OR) and 95% confidence intervals (CI) are presented.

RESULTS

A total of 919 patients were identified in this study with tumors < or = 1 cm. These included 199 patients (21.7%) with T1a tumors and 720 patients (78.3%) with T1b tumors. ALNM was detected in 165 patients with an overall incidence of 18.0%. Of the ALNM group, 32 patients (19.4%) had T1a tumors and 133 patients (80.6%) had T1b tumors. Four variables were found to be significant in univariate analysis. These included: increasing tumor size, poor histologic grade, presence of lymphatic or vascular invasion, and younger age of the patient. An increase in tumor size was associated with a significant risk of ALNM (OR = 2.66, 95% CI = 1.28 to 5.75; p = 0.01). Poor tumor grade and the presence of lymphatic or vascular invasion were also associated with an increased risk of ALNM (OR = 2.69, p = 0.003 and OR = 5.52, p = 0.0001, respectively). Patients with ALNM were more likely to have a tumor grade of 3 (25.0% ALNM versus 12.5% node-negative, p = 0.004) and lymphatic or vascular invasion (16.9% ALNM versus 3.5% node-negative, p < 0.0001). In multivariate analysis, an increased risk of ALNM was demonstrated with increasing tumor size (0.1-cm increments), poor histologic grade, and younger age.

CONCLUSIONS

This study investigated clinical and pathologic factors influencing ALNM in patients with T1a and T1b breast carcinomas. We have identified three factors by multivariate analysis as significant independent predictors of ALNM in this group of patients. These include increasing tumor size, poor histologic grade, and younger age. Given the significant amount of ALNM demonstrated in this study (overall 18%) and the inability to identify a subgroup of patients that had an acceptable low risk of ALNM, the complete omission of assessing the axilla for metastatic disease in patients with small breast cancers cannot be advocated. Our recommendation for patients diagnosed with T1a and T1b tumors is to have their axilla investigated for metastatic disease either by traditional axillary lymph node dissections or by intraoperative lymphatic mapping and sentinel lymph node biopsy techniques.

Local and distant recurrence rates in skin-sparing mastectomies compared with non-skin-sparing mastectomies

BACKGROUND

Skin-sparing mastectomies (SSMs) are being used more frequently to treat many cases of breast cancer. This type of surgery maximizes breast skin preservation and facilitates immediate reconstruction, resulting in a superior cosmetic appearance after mastectomy and a more satisfied patient. Although SSMs are becoming more common, there are few data regarding the local and distant recurrence rates.

METHODS

A total of 231 patients treated with mastectomies from 1990 to 1998 were studied, including 77 SSM and 154 non-skin-sparing (NSSM) mastectomy patients.

RESULTS

The local recurrence rates for SSM and NSSM were 3.90% (3 of 77 patients) and 3.25% (5 of 154 patients), respectively. The local recurrence-free survival at 5 years was 95.3% for SSM patients and 95.2% for NSSM patients (P = .28). The distant recurrence rates of SSM and NSSM were 3.9% (3 of 77 patients) and 3.9% (6 of 154 patients), respectively. The distant recurrence-free actuarial survival at 5 years was 90.2% for SSM patients and 92% for NSSM patients (P = .07).

CONCLUSIONS

Mastectomies using the skin-sparing technique do not appear to result in any increase in local or distant recurrence and improve aesthetic results of the immediate reconstruction.

The evaluation of high risk and pre-invasive breast lesions and the decision process for follow up and surgical intervention

Atypical epithelial hyperplasia, lobular carcinoma in situ (lobular neoplasia), radial scar, and ductal carcinoma in situ are considered high-risk lesions that predispose toward the future development of non-invasive or invasive breast cancer. Generally, those women with atypical epithelial hyperplasia, radial scar, or lobular carcinoma in situ can be managed conservatively by close surveillance. The minority of women may consider prophylactic mastectomy. Ductal carcinoma in situ can usually be managed by lumpectomy with or without radiation, with some patients requiring mastectomy due to extensive disease.

Characterization of neuropeptide Y-induced feeding in mice: do Y1-Y6 receptor subtypes mediate feeding?

The stimulation of food consumption after i.c.v. administration of various neuropeptide Y (NPY) receptor agonists was examined in CD-1 mice. These agonists, including endogenous peptides NPY, peptide YY (PYY), and pancreatic polypeptide, as well as several N-terminal truncated and synthetic peptides that are prototypic receptor agonists at Y1-Y6 NPY receptors ([Leu31Pro34]NPY, NPY2-36, NPY3-36, NPY13-36, PYY3-36, Pro34PYY, and D-Trp32NPY), showed varying abilities to elicit food consumption such that PYY > NPY2-36 = NPY = PYY3-36 > Pro34PYY > NPY3-36 >> [Leu31Pro34]NPY > NPY13-36 = D-Trp32NPY = pancreatic polypeptide. Published reports have suggested that NPY-induced feeding is mediated via the Y1 or the Y5 receptor subtypes. However, the relative ability of the various peptide analogs to elicit feeding differed from the relative ability of these peptides to bind to cloned Y1-Y6 receptors. The effects of prototypic Y1 receptor antagonists on NPY-induced feeding were also evaluated after i.c.v. administration. GR231118 (1229U91), a peptide Y1 antagonist, did not block NPY-induced feeding at the doses tested. BIBP3226, a nonpeptide Y1 receptor antagonist, as well as its opposite enantiomer, BIBP3435, which is inactive at Y1 receptors, blocked feeding elicited by NPY, [Leu31Pro34], or PYY at doses that did not cause overt behavioral dysfunction. The lack of effects with GR231118 and the nonstereoselective effects of BIBP3226 suggested that NPY-induced feeding in mice was not mediated via the Y1 receptor. Thus, by using currently available prototypic peptide NPY receptor agonists for Y1-Y6 receptors and peptide and nonpeptide Y1 receptor antagonists GR231118 and BIBP3226, the mediation of NPY-induced feeding cannot be unequivocally attributed to any one of the known NPY receptors. It is possible that NPY-induced feeding is mediated either by a combination of more than one NPY receptor subtype or by a unique NPY receptor subtype. Additional subtype-selective receptor antagonists, when available, will help to clarify this issue further.

Single-molecule biomechanics with optical methods

Single-molecule observation and manipulation have come of age. With the advent of optical tweezers and other methods for probing and imaging single molecules, investigators have circumvented the model-dependent extrapolation from ensemble assays that has been the hallmark of classical biochemistry and biophysics. In recent years, there have been important advances in the understanding of how motor proteins work. The range of these technologies has also started to expand into areas such as DNA transcription and protein folding. Here, recent experiments with rotary motors, linear motors, RNA polymerase, and titin are described.

Kainate GluR5 receptor subtype mediates the nociceptive response to formalin in the rat

In order to study the roles of the AMPA and kainate subtypes of non-NMDA glutamate receptors in the processing of persistent nociceptive information, compounds with varying activities at these receptors were examined for effects on the formalin-induced paw-licking behavior in rats. The selective AMPA antagonist, LY300164 and the mixed AMPA/kainate antagonist, NBQX, were compared for their effects on formalin-induced pain behavior. NBQX (3, 10, 20 mg/kg, i.p.), caused antinociception as well as ataxia whereas the selective AMPA antagonist, LY300164 (3,5,10 mg/kg, i.p.), did not cause antinociception at doses that did not produce ataxia. In view of the well documented distribution of kainate receptors on C fibres and of the kainate-preferring iGluR5 subtype on dorsal root ganglia (DRG), we tested a series of three decahydroisoquinolines with different profiles of activity between iGluR5 and AMPA receptors and all without activity on iGluR6, iGluR7 or KA2 subtypes. LY293558 (0.1, 1, 3, 5 mg/kg, i.p.), which had low micromolar affinity for both iGluR5 and 2 caused, like NBQX, both antinociceptive and ataxic effects. However, the selective iGluR5 antagonist LY382884 (5, 10, 30, 100 mg/kg, i.p.), exhibited antinociceptive actions without ataxia while the iGluR2 preferring antagonist LY302679 (5 mg/kg, i.p), caused ataxia but did not produce antinociceptive effects at that dose. These actions were stereoselective since the enantiomeric compounds, LY293559 and LY302680, were ineffective in these tests. The data strongly suggest an involvement of iGluR5 in the processing of nociceptive information.

ErbB-2 protein in sera and tumors of breast cancer patients

We compared levels of erbB-2 oncoprotein among three groups: Group I included 60 asymptomatic women; Group II had 51 women with benign breast biopsies; and Group III had 67 women with node-negative breast cancer. Serological levels of erbB-2 protein were measured in all participants; tumor levels were measured for Groups II and III. Forty-three percent of usable tumors (25/58), including three of seven lobular tumors, were erbB-2 positive. Tumor and blood oncoprotein levels were unrelated. Blood levels, however, were positively related to tumor volume, but only when the tumor had both a ductal carcinoma in situ (DCIS) component and an invasive component, suggesting a role for erbB-2 protein in progression of DCIS to invasive carcinoma. In Groups I and II serological levels of erbB-2 protein were directly related to age, and inversely related to having had a live birth. Therefore, a model that determined the threshold levels of serological erbB-2 positivity in Group III included age and nulliparity as independent variables. Only three of the 67 women (4.5%) in Group III were positive for serological erbB-2. In a multivariate model, with serological erbB-2 as the dependent variable, and in which the independent variables included Study Group, there was a statistical trend for younger women, in which Group III had the highest serological levels of erbB-2, followed by Group II, and then Group I. In women who were over the age of 50 years the trend was reversed; i.e., levels of erbB-2 tended to be lowest in Group III, followed by Group II, and finally Group I.

5HT1A receptor antagonists enhance the functional activity of fluoxetine in a mouse model of feeding

Fluoxetine has been reported to suppress food intake in animal models of feeding. Fluoxetine increases extracellular serotonin in the brain. 5HT1A autoreceptors regulate synaptic levels of serotonin. A combination of a 5HT1A receptor antagonist and fluoxetine has been previously reported to enhance extracellular levels of serotonin over what is obtained with fluoxetine alone. Thus, a combination of fluoxetine and a 5HT1A antagonist could enhance the ability of fluoxetine to suppress appetite. Fluoxetine was tested in a model of feeding, in which CD-1 mice were trained to drink sweetened condensed milk. Fluoxetine was found to attenuate milk drinking, in a dose-dependent manner, at doses greater than 10 mg/kg, i.p. A 10 mg/kg dose of fluoxetine, which was ineffective by itself, was then combined either with 5-hydroxytryptophan (5HTP), a serotonin precursor, or with S(-) pindolol, a 5HT1A/beta adrenergic receptor antagonist or with LY206130, a more selective 5HT1A receptor antagonist. These treatment paradigms resulted in significant attenuation of the consumption of sweetened condensed milk. Since fluoxetine has been shown to be useful in the treatment of eating disorders and to promote weight loss in obese humans, although at doses greater than those required for the treatment of depression, a combination of fluoxetine with a 5HT1A receptor antagonist could be of clinical utility in the treatment of eating disorders and obesity.

Elasticity and unfolding of single molecules of the giant muscle protein titin

The giant muscle protein titin, also called connectin, is responsible for the elasticity of relaxed striated muscle, as well as acting as the molecular scaffold for thick-filament formation. The titin molecule consists largely of tandem domains of the immunoglobulin and fibronectin-III types, together with specialized binding regions and a putative elastic region, the PEVK domain. We have done mechanical experiments on single molecules of titin to determine their visco-elastic properties, using an optical-tweezers technique. On a fast (0.1s) timescale titin is elastic and force-extension data can be fitted with standard random-coil polymer models, showing that there are two main sources of elasticity: one deriving from the entropy of straightening the molecule; the other consistent with extension of the polypeptide chain in the PEVK region. On a slower timescale and above a certain force threshold, the molecule displays stress-relaxation, which occurs in rapid steps of a few piconewtons, corresponding to yielding of internal structures by about 20 nm. This stress-relaxation probably derives from unfolding of immunoglobulin and fibronectin domains.

LY303870, a centrally active neurokinin-1 antagonist with a long duration of action

The selective neurokinin (NK)-1 antagonist LY303870 has high affinity and specificity for human and guinea pig brain NK-1 receptors labeled with 125I-substance P. It has approximately 15- to 30-fold lower affinity for rat and mouse brain NK-1 receptors, consistent with previously reported species differences in the affinities of nonpeptide antagonists for NK-1 receptors. In vivo, LY303870 blocked the characteristic, caudally directed, biting and scratching response elicited by intrathecal administration of the selective NK-1 agonist Ac-[Arg6,Sar9,Met(O2)11]substance P6-11 in conscious mice. The potentiation of the tail-flick response elicited by intrathecal administration of the NK-1 agonist [Sar9,Met(O2)11]substance P in rats was also selectively blocked by LY303870. When tested in a model of persistent nociceptive activation induced by tissue injury (the formalin test), LY303870 blocked licking behavior in the late phase of the formalin test, in a dose-dependent manner. After oral administration of 10 mg/kg, the blockade of the late-phase licking behavior was evident for at least 24 hr. Ex vivo binding studies in guinea pigs showed that orally administered LY303870 potently inhibited binding to central and peripheral NK-1 receptors labeled with 125I-substance P. This inhibition was long-lasting, consistent with other in vivo activities. LY306155, the opposite enantiomer of LY303870, was less active in all of the functional assays. In rodents, LY303870 did not exhibit any neurological, motor, cardiovascular, gastrointestinal or autonomic side effects at doses of < or = 50 mg/kg p.o. Thus, LY303870 is a potent, centrally active, NK-1 antagonist in vivo, with long-lasting oral activity.

Quantitative measurements of force and displacement using an optical trap

We combined a single-beam gradient optical trap with a high-resolution photodiode position detector to show that an optical trap can be used to make quantitative measurements of nanometer displacements and piconewton forces with millisecond resolution. When an external force is applied to a micron-sized bead held by an optical trap, the bead is displaced from the center of the trap by an amount proportional to the applied force. When the applied force is changed rapidly, the rise time of the displacement is on the millisecond time scale, and thus a trapped bead can be used as a force transducer. The performance can be enhanced by a feedback circuit so that the position of the trap moves by means of acousto-optic modulators to exert a force equal and opposite to the external force applied to the bead. In this case the position of the trap can be used to measure the applied force. We consider parameters of the trapped bead such as stiffness and response time as a function of bead diameter and laser beam power and compare the results with recent ray-optic calculations.

3-Aryl-1,2-diacetamidopropane derivatives as novel and potent NK-1 receptor antagonists

Early structure-activity studies on racemic tryptophan ester and amide NK-1 antagonists 5-7 led to the discovery that the potency of the series could be markedly increased by moving the carbonyl function in these molecules to an off-chain position as in the 3-aryl-1,2-diacetamidopropane 9. Further medicinal chemistry incorporating this change resulted in the discovery of a novel series of highly potent aryl amino acid derived NK-1 antagonists of the R stereoisomeric series (IC50's = 100 pM to > 5 microM). Compounds in this series were shown to be competitive antagonists using an in vitro NK-1 smooth muscle assay, and this data correlated well with observed human NK-1 binding affinities. Two of these agents, (R)-25 and (R)-32, blocked intrathecal NK-1 agonist-driven [Ac-[Arg6,Sar9,Met(O2)11]- substance P 6-11 (Ac-Sar9)] nociceptive behavior in mice. Both compounds potently blocked the neurogenic dural inflammation following trigeminal ganglion stimulation in the guinea pig after intravenous administration. Further, upon oral administration in this model, (R)-32 was observed to be very potent (ID50 = 91 ng/kg) and have a long duration of action (> 8 h at 1 micrograms/kg). Compound (R)-32, designated LY303870, is currently under clinical development as an NK-1 antagonist with a long duration of action.

Single myosin molecule mechanics: piconewton forces and nanometre steps

A new in vitro assay using a feedback enhanced laser trap system allows direct measurement of force and displacement that results from the interaction of a single myosin molecule with a single suspended actin filament. Discrete stepwise movements averaging 11 nm were seen under conditions of low load, and single force transients averaging 3-4 pN were measured under isometric conditions. The magnitudes of the single forces and displacements are consistent with predictions of the conventional swinging-crossbridge model of muscle contraction.

Salvage surgery for recurrence after breast conservation

Breast conservation surgery and radiation therapy are chosen with increasing frequency in breast cancer management. In addition to the risk of developing a contralateral malignancy, these women are at risk for local recurrence or a new primary lesion in the conserved breast. Most of these ipsilateral recurrences can be treated successfully with salvage mastectomy. The prognosis with salvage mastectomy depends on several factors, including the method of diagnosis of the recurrent tumor, the size of the recurrence, the extent of breast involvement at recurrence, the time interval from initial surgery to recurrence, the involvement of axillary nodes at the initial diagnosis and at the time of recurrence, and the histopathology of the recurrent tumor.

Force on single actin filaments in a motility assay measured with an optical trap

We have used an optical trap to measure or exert a force on single actin filaments via the attachment of polystyrene beads which were coated with NEM-modified HMM. In the simplest experiment, beads were attached to rhodamine phalloidin labelled actin filaments and observed to move on an HMM coated surface in the presence of ATP. Moving beads were steered into the vicinity of the trap using a PZT operated microscope stage. The minimum force needed to stop a moving bead was measured by lowering the trap strength until the bead resumed movement. By aligning the optical trap with the centre of a quadrant detector placed in an image plane of the microscope, it was possible to measure the force exerted on a filament by measuring the displacement of the bead position from the centre of the trap. In each of these experiments, the trap was calibrated by applying a Stokes force to a bead in free solution. The characteristics of the trap were studied, and the displacement of the bead from the centre of the trap was shown to be directly proportional to the applied force over a large part of the total range of the trap. The compliance of the trap could be substantially reduced by the use of feedback control to deflect the laser beam via an acousto-optic modulator. The advantages and limitations of this technique will be discussed.

Synthesis and pharmacological characterization of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines as dopamine receptor ligands

A series of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines have been prepared as ring-contracted analogues of the prototypical D1 dopamine receptor antagonist SCH23390 [(R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H- 3-benzazepine]. The affinity and selectivity of these isoquinolines for D1 receptors was determined by three biochemical endpoints in membrane homogenates prepared from rat corpus striatum: the potency to complete for [3H]SCH23390 binding sites; the potency to compete for [3H]spiperone (a D2 receptor ligand) binding sites; and effects on dopamine-stimulated adenylate cyclase. Competitive binding measurements at D1 sites showed SCH23390 to possess the highest affinity, followed by 1-phenyl greater than 1-benzyl greater than 4-phenyl for the isoquinolines. These results were highly correlated with the ability of the test compounds to antagonize dopamine-stimulated adenylate cyclase (r = 0.98). None of the compounds alone stimulated cAMP formation at concentrations of 10 nM to 100 microM. D2 competition binding showed the 1-benzyl derivative to possess the highest affinity, followed by 4-phenyl greater than SCH23390 greater than 1-phenyl. The tertiary 1-phenyl derivative was more potent than the secondary 1-phenyl analogue in all assays. Interestingly, resolution and single-crystal X-ray analysis of the tertiary N-methyl-1-phenyltetrahydroisoquinoline showed the most active enantiomer to possess the S absolute configuration, in contrast to the benzazepine (R)-SCH23390.

Binding of [3H]prazosin and [3H]p-aminoclonidine to alpha-adrenoceptors in rat spinal cord

alpha-Adrenoceptors in spinal cord appear to play a role in a number of physiologic processes including the control of blood pressure, pain and motor function. In order to evaluate more clearly these potential roles, the characteristics of binding of [3H]prazosin ([3H]PRZ) to spinal alpha 1 adrenoceptors and [3H]p-aminoclonidine ([3H]PAC) to spinal alpha 2 adrenoceptors were determined. Binding of each ligand to their respective adrenoceptors was saturable and Scatchard analysis revealed binding of each to a single class of adrenoceptors with characteristics of [3H]PRZ binding of Bmax = 78 fmol/mg protein and Kd = 0.75 nM and [3H]PAC binding Bmax = 70 fmol/mg protein and Kd = 1.39 nM. Whereas [3H]PRZ specific binding (Bmax) was unaltered by guanine nucleotides. [3H]PAC binding was increased with addition of 10 microM guanosine triphosphate (GTP) (P less than 0.05) and decreased with either 50 microM GTP or guanyl-5'-yl-imidodiphosphate [Gpp(NH)p] (P less than 0.01). Competition for specific [3H]PRZ and [3H]PAC binding by various alpha 1 and alpha 2 adrenoceptor agonists and antagonists of known pharmacologic activity revealed that [3H]PRZ defines alpha 1 adrenoceptors (Ki = 2.1 nM for prazosin vs 4300 nM for yohimbine) and [3H]PAC defines alpha 2 adrenoceptors (Ki = 1.06 nM for yohimbine vs 15480 nM for prazosin). Regional spinal cord studies demonstrated that dorsal spinal cord in the lumbar region contains the highest density of both [3H]PRZ (Bmax = 93 +/- 14 fmol/mg protein) and [3H]PAC (Bmax = 101 +/- 6 fmol/mg protein) binding. In contrast, lowest binding was evident in thoracic cord with equal levels in both dorsal and ventral regions (Bmax = 44-48 fmol/mg protein). The regional distribution of both alpha 1 and alpha 2 adrenoceptors in spinal cord compares to the localization previously classified functionally utilizing various pharmacological agonists and antagonists at norepinephrine receptors.

The stiffness of frog skinned muscle fibres at altered lateral filament spacing

When the surface membrane is removed from a frog muscle fibre the myofibrils swell, so that the spacing between the filaments increases by 10-30%. In this study, the stiffness of skinned fibres was measured when the lateral spacing of the filament lattice was reduced osmotically using polyvinyl pyrrolidone (PVP), a synthetic linear polymer. In the absence of PVP, the apparent stiffness of relaxed skinned fibres measured during ramp stretches was about 0.05-0.1 of the stiffness of intact fibres. The stiffness increased when the lattice spacing was decreased. The mechanical characteristics of resting stiffness in the presence of PVP (or bovine serum albumin) were similar to those of the short-range elastic component of resting intact fibres. However, when the spacing of skinned fibres was reduced osmotically to that of the intact lattice, the stiffness of skinned fibres was about 1.6 times higher. In the absence of PVP, Ca2+-activated skinned fibres were less stiff than are fully active intact fibres during isometric tetani. The skinned fibre force-extension relation was markedly curved. As the filament spacing was reduced, the stiffness of the Ca2+-activated skinned fibres increased, with little change in isometric tension, and the force-extension curve became more linear. Experiments at varied filament overlap and during feed-back control of sarcomere length, monitored by laser diffraction, showed that PVP increased the stiffness of the sarcomeres. The increase of active stiffness in the presence of PVP could be partially dissociated from the increase of resting stiffness by inclusion of Mg tripolyphosphate in the bathing solutions. It is concluded that the low stiffness and the non-linearity of the force-extension curve observed in fully activated skinned fibres are due primarily to the increase of filament separation that occurs when a fibre is skinned. The mechanism may be related to an increased angle between the subfragment-2 part of the cross-bridge and the backbone of the thick filament, perhaps leading to buckling of cross-bridges under compression.

Tension transients during the rise of tetanic tension in frog muscle fibres

Tension transients were recorded from fibres isolated from the tibialis anterior muscle of the frog during the rise of tetanic tension at 0.8-2.5 degrees C. The length of a central segment of the fibre was controlled by feed-back from a spot-follower device. Length steps complete within 0.2 ms were applied at one end of the fibre, and tension changes were recorded at the other end with a transducer having a natural frequency of 10.8 kHz. The tension transients measured during the rise of force showed the four phases characteristic of transients recorded during the plateau of a tetanus and during shortening. The extreme tension change reached during a length change was smaller for a given size of step during the rise of tension than at the plateau, but by less than in proportion to the developed force, suggesting that stiffness increases earlier than tension. Stiffness changes were further assessed by matching the tension records from one fibre with the responses of an analogue circuit (delay line) representing the mechanical properties of the fibre and force transducer. Stiffness derived from these comparisons varied in approximately the same proportion as stiffness assessed from the extreme tension change. During the rise of tension, there was a roughly constant lag of tension behind stiffness, ranging from 11 to 16 ms in different fibres. Steps applied during the latent period showed a lag of about 10 ms from the first increase of stiffness to the first appearance of tension. The partial recovery of tension immediately following the step, phase 2, was faster at the low tension levels early in the tetanus. The intermediate level, T2, to which tension recovers during phase 2 scaled in approximate proportion to the tension level immediately preceding the step. This result is unlike the relative decrease in T2 levels we have recently described for steps applied during steady shortening, and suggests that the increased stiffness-tension ratio seen during the rise of tetanic force is not due to shortening within the sarcomeres. The results can be explained if the attachment of cross-bridges in the rising phase takes place in two steps, the initial state of attachment resulting in the production of little or no tension. Several such schemes are considered.

Tension transients during steady shortening of frog muscle fibres

Single intact fibres from frog muscle at 0-1 degrees C were stimulated to produce isometric tetani at a sarcomere length of about 2.25 micron, using a spot-follower apparatus to control the length of the central part of a fibre. When the plateau of the tetanus was reached the fibre was forced to shorten by applying a step and ramp length change in an approximation to an isotonic release. When tension had reached a steady level, Ti, during shortening, tension transients were elicited by applying step changes of length, complete within 0.2 ms, ranging from a stretch of 1.5 nm per half-sarcomere to a release of 6 nm per half-sarcomere. The tension transients recorded during shortening were qualitatively similar to those previously recorded in isometric tetani. There were four phases: phase 1, the change of tension during the step; phase 2, a rapid partial recovery of tension; phase 3, a delay or reversal of recovery; phase 4, a slower recovery of tension to the level before the step was applied. Measurements were made of the extreme tension, T1, attained during a step, and the level, T2, to which tension recovers in phase 2. The excursion of tension, [T1-Ti], during a small step of given size, fell with increase of shortening velocity, reaching about 40% of the isometric value near the maximum velocity of shortening. T2 fell as shortening velocity was increased and the fraction of steady tension recovered, T2/Ti, also decreased, so that the proportion of tension recovery in phase 4 increased. All the recovery phases became progressively more rapid with increase of shortening velocity. The early tension response was matched with a delay-line simulator so as to estimate the value of the instantaneous stiffness. Stiffness during shortening was found to decrease approximately linearly with tension, reaching about 35% of the isometric value as tension approached zero. It was impossible to match the early tension response in a rapidly shortening fibre without assuming decreased stiffness. The decline of stiffness is interpreted as due largely to reduced number of attached cross-bridges, but quantitative estimates would be affected by possible filament compliance and non-linearity of cross-bridge stiffness. The decrease in T2 also suggests fewer cross-bridges are attached as shortening velocity increases, but uncertainties about the processes determining phase 2 during shortening do not permit a precise estimate of stiffness to be made.(ABSTRACT TRUNCATED AT 400 WORDS)

A mechanical study of regulation in the striated adductor muscle of the scallop

Chemically skinned fibre bundles were prepared from the striated adductor muscle of the sea scallop, Placopecten magellanicus. The relation between tension and calcium concentration was determined in activating solutions containing 5 mM-MgATP, ionic strength 0.2, pH 7.1 at 20 degrees C. The isometric tension rose from zero to its maximum value between pCa 6.0 and 5.2. The steepness of the relation cannot be accounted for in terms of the binding of calcium to the two known sites on myosin and suggests that there must be an additional, co-operative mechanism. The regulatory light chain content of the fibre bundles was determined by urea gel electrophoresis and was found to be approximately 2 light chains per myosin molecule. The regulatory light chains were removed completely by treatment with EDTA at 25-30 degrees C. Fibre bundles then showed a total loss of control over contraction; a high tension was generated whether or not calcium was present in the bathing solution. Complete removal of the regulatory light chains did not greatly affect the tension generated or the stiffness in the rigor state. Control of contraction could be restored completely by the addition of regulatory light chains from scallop muscle. Treatment with EDTA at 0-12 degrees C resulted in the removal of 0.76-2.0 regulatory light chains per myosin molecule. Fibre bundles for which removal was less than complete were partially sensitive to calcium, i.e. tension was higher in the presence of calcium than in its absence. The results indicate that the normal mechanism of tension generation in scallop muscle is mediated primarily through myosin and not thin filament control. This finding is consistent with previous studies of the ATPase activity of myofibrils from scallop muscle.

Control of sarcomere length in skinned muscle fibres of Rana temporaria during mechanical transients

A new technique is described for high-speed measurement of striation spacing of single skinned muscle fibres. A galvanometer mirror directs helium-neon laser light on to the muscle fibre at a variable angle. Light diffracted by the cross-striations is collected by a position-sensitive photodetector. The incident angle necessary to centre the diffracted light beam on to the photodetector is related to sarcomere length. The instrument was tested by comparison with measurements obtained with a compound microscope. Discrepancies of several nanometers per half sarcomere were observed between these two methods. When the incident angle of the laser beam was varied sinusoidally about its mean position the magnitude of the discrepancy was reduced. During steady passive shortening of the muscle fibres the output of the diffraction instrument often displayed pauses and brief periods of rapid shortening. These irregularities were eliminated by averaging the sarcomere length output over a range of illumination angles by oscillating the incident angle of the laser beam. The results suggest that at the spatial resolution of several nanometers per half sarcomere, volume diffraction effects can cause the apparent sarcomere length measured from the angle of coherent light diffraction to differ from the mean striation spacing. With incident-angle oscillation the time and spatial resolution of the equipment were satisfactory for the sarcomere length signal to be fed back to a length controller for a 'sarcomere length clamp'. In active contractions, stiffness was closely related to steady developed tension at sub-saturating calcium concentrations. Skinned fibres are less stiff than intact fibres at a given level of developed tension.

The dependence of force and shortening velocity on substrate concentration in skinned muscle fibres from Rana temporaria

The force-velocity relation was determined in fully activated skinned fibres from frog muscle at concentrations of the substrate, magnesium adenosine triphosphate (MgATP), ranging from 10 microM to 10 mM. The ionic strength of the solutions was 200 mM, temperature 0-5 degrees C, pH 7.1. The activation procedure of Moisescu (1976) was used to raise the calcium concentration rapidly in the interior of the fibres. A re-phosphorylating system (creatine kinase and creatine phosphate) was used to maintain the MgATP concentration in the fibres. Isotonic releases were performed using a fast servo-controlled motor and tension transducer. Releases to a pre-determined tension level relative to the isometric tension were made using a novel normalizing circuit. In some of the experiments changes of sarcomere length were recorded using the diffraction device described in the preceding paper (Goldman & Simmons, 1984). There was satisfactory agreement between velocities determined from the total length change and the sarcomere length change. The isometric tension showed a biphasic dependence on MgATP concentration. Tension increased with MgATP concentration from 1 microM to reach a peak at about 30-100 microM and decreased by about 20% from the value at the peak with further increase in the MgATP concentration to 5 mM (about the physiological concentration). At 5 mM-MgATP, the isometric tension was approximately the same as in intact fibres, if allowance is made for the increase in cross-sectional area that occurs when the surface membrane is removed. The maximum velocity of shortening, Vmax, was obtained by fitting the force-velocity relation using Hill's (1938) equation. Vmax showed a roughly hyperbolic dependence on MgATP concentration, with a Km of 0.47 mM. At 5 mM-MgATP, the value of Vmax was 2.16 muscle lengths per second, which is similar to that of intact fibres. a/P0, the parameter of Hill's (1938) equation that is related to the curvature of the force-velocity relation, showed a slight decrease with increasing MgATP concentration. Its value at 5 mM-MgATP of 0.16 is somewhat lower than found for intact fibres. The results are discussed in terms of a simple model based on the biochemical cycle of hydrolysis of ATP by actomyosin in solution. The decrease of tension from about 30 microM to higher concentrations of MgATP can be related to the dissociating effect of MgATP on actomyosin. The increase of isometric tension from 1 to 30 microM-MgATP is discussed in terms of two types of rigor attachment of cross-bridges which support different amounts of tension.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in the lateral filament spacing of skinned muscle fibres when cross-bridges attach

When a skinned fibre prepared from frog skeletal muscle goes from the relaxed to the rigor state at a sarcomere length of about 2.2 micron, the 1, 0 transverse spacing of the filament lattice, measured by X-ray diffraction, decreases by about 11%. In measurements at various sarcomere lengths, the decrease in the spacing was approximately proportional to the degree of overlap between the thick and thin filaments. This suggests that the shrinkage of the lattice is caused by a lateral force produced by cross-bridges. In order to estimate the magnitude of the lateral force, the decrease of spacing between relaxed and rigor states was compared with the shrinkage caused osmotically by adding a high molecular weight polymer, polyvinylpyrrolidone, to the bathing solution. The results indicate that the lateral force produced per unit length of thick filament in the overlap zone is of the same order of magnitude as the axially directed force produced during maximum isometric contraction (10(-10) to 10(-9) N/micron). Experiments in the presence of a high concentration of polyvinylpyrrolidone (100 g/l) show that when the lattice spacing is decreased osmotically beyond a certain value, the lateral force produced when the fibre goes into rigor changes its direction, causing the lattice to swell. This result can be explained by assuming that there is an optimum interfilament spacing at which the cross-bridges produce no lateral force. At other spacings, the lateral force tends to displace the filament lattice toward that optimum value.

Changes in the X-ray reflections from contracting muscle during rapid mechanical transients and their structural implications

During normal contractions of vertebrate striated muscle, it is believed that the cross-bridges which produce the sliding force undergo asynchronous cyclical changes in their structure. Thus, an X-ray diffraction diagram from a muscle under these conditions will give structural information averaged over the whole range of cross-bridge states. Such diagrams show characteristic and informative differences from those given by relaxed muscle, but can give little information about changes in the configuration of the cross-bridges at different stages of their working stroke. However, it is possible to effect a partial synchronization of these changes by applying very rapid changes in length, completed in less than one millisecond to an otherwise isometrically contracting muscle. If the amplitude of these length changes is comparable to the length of the cross-bridge stroke (say 100 A per half-sarcomere), then it should bring about a transient but significant redistribution of cross-bridge states, which would show up in the X-ray diagram. We have made use of synchrotron radiation as a high intensity X-ray source in order to record such patterns with the necessary time resolution (1 ms or less) and have found major changes in the intensity of the 143 A meridional reflection accompanying the rapid length changes of the muscle. These changes appear to arise from specific configurational changes in the cross-bridges during the working stroke. A model is suggested in which the 143 A meridional intensity in a contracting muscle arises mainly from attached cross-bridges and is generated by the part of the myosin head near the S1-S2 junction. During normal contraction, cross-bridges go through their structural cycle asynchronously with each other, since they start at different times, but if the S2 changes in length rather little, then the configurational changes in the myosin heads are synchronized with the actin filament movement in such a way that the S1-S2 junction remains relatively fixed in its axial position. In a quick release, it is suggested that bringing many S1 heads simultaneously to the end of their working strokes on actin disrupts the 143 A axial repeat of their distal ends near S2, and brings about the large decrease of the 143 A meridional reflection. This model therefore involves a large change in the position of part of the myosin head structure relative to actin during the working stroke of the cross-bridge.

Branched skeletal muscle fibers not associated with dysfunction

We report the occurrence of large clefts and branches in some amphibian vertebrate skeletal muscle fibers. Such fibers can be isolated intact from various skeletal muscles of fully mature animals and apparently are normal in other respects. Electron micrographs showed no signs of degeneration in most fibers. Electrical and mechanical studies revealed that all branches were excitable and able to contract. Branches evidently can arise in the absence of abnormal influences such as experimentally induced overload. The apparent cause may be either fusion or splitting of fibers.

The results of 100 operations for velopharyngeal incompetence--selected on the findings of endoscopic and radiological examination

Of one hundred patients with velopharyngeal incompetence subjected to a pharyngoplasty selected on the results of endoscopic and radiological examination 97% were cured of unacceptable nasal escape and 93% of unacceptable nasal resonance on the criteria described. It was considered that this provided a vindication of the system of treatment. Critical examination of the morbidity revealed an unacceptably high proportion of hyponasality. This appeared to be due to ignoring the criteria for selection for pharyngoplasty and opting for the more radical operation resulting in over-treatment in some cases. With the numbers available in the smaller treatment groups it was not possible to state that there was no significant difference in the results between the different pharyngoplasties in the groups for which they were selected. It is expected that there will be a larger proportion of patients receiving less radical treatment without detriment to the success rate, but with a lower morbidity. Assuming that it is accepted that as much accurate information as possible prior to operation is needed for the correct selection of operation, simultaneous endoscopic and radiological examination provide a time- and cost-efficient system the benefit of which becomes overwhelming for revision of the failed pharyngoplasty.

Millisecond time-resolved changes in x-ray reflections from contracting muscle during rapid mechanical transients, recorded using synchrotron radiation

Low-angle x-ray diffraction diagrams have been recorded from frog sartorius muscles by using synchrotron radiation as a high-intensity x-ray source. This has enabled changes in some of the principal reflections of interest to be followed with a time resolution of 1 ms, during small but very rapid length changes imposed on a contracting muscle. The 143-A meridional reflection, which is believed to arise from a repeating pattern of myosin cross-bridges along the length of the muscle, shows large changes in intensity in these circumstances. During both rapid releases and rapid stretches, by amounts that produce a translation of actin and myosin filaments past each other by about 100 A and that are completed in about a millisecond (i.e., before significant cross-bridge detachment would be expected), an almost synchronous decrease in 143-A intensity occurs, by 50% or more. This is followed, in the case of quick releases, by a rapid partial recovery of intensity lasting 5--6 ms (which may represent cross-bridge release and reattachment) and then by a more gradual return to the normal isometric value. Quick stretches show only the slower return of intensity. Immediately after the length change, the initial drop in 143-A intensity can be reversed if the release (or stretch) is reversed. These changes provide evidence of a more direct kind than has hitherto been available that the active sliding of actin filaments past myosin filaments during contraction is produced by longitudinal movement of attached cross-bridges.