The Role of Central Neck Lymph Node Dissection in the Management of Papillary Thyroid Cancer

Papillary thyroid cancer (PTC) is the most common thyroid malignancy, and cervical nodal metastases are frequent at presentation. The most common site for nodal metastases from PTC is the central compartment of the ipsilateral neck in the paratracheal and pretracheal regions. The decision to resect these lymph nodes at the time of thyroidectomy often depends on if nodes with suspected malignancy can be identified preoperatively. If nodal spread to the central neck nodes is known, then the consensus is to remove all nodes in this area. However, there remains significant controversy regarding the utility of removing central neck lymph nodes for prophylactic reasons. Herein, we review the potential utility of central neck lymph node dissection as well as the risks of performing this procedure. As well, we review the potential of molecular testing to stratify patients who would most benefit from this procedure. We advocate a selective approach in which patients undergo clinical neck examination coupled with ultrasound to detect any concerning lymph nodes that warrant additional evaluation with either fine needle aspiration or excisional biopsy in the operating room. In lieu of clinical lymphadenopathy, we suggest the use of patient and disease characteristics as identified by multiple groups, such as the American Thyroid Association and European Society of Endocrine Surgeons, which include extremes of ages, large primary tumor size, and male gender, when deciding to perform central neck lymph node dissection. Patients should be educated on the potential long-terms risks versus the lack of known long-term benefits.

A Review of Apparatus for Investigating the Mechanical Properties of Soft Animal Tissue in Vitro

This paper contains a review of the systems developed for testing skeletal muscle in vitro and it demonstrates how many of the design features and performance figures obtained are similar even though a range of engineering techniques have been used. The main topic considered is the uniaxial testing of skeletal muscle but it is also shown, by example, that similar ideas have been incorporated into machines for the uniaxial and multi-axial testing of other soft tissues.

NK Cell-Mediated Antitumor Effects of a Folate-Conjugated Immunoglobulin Are Enhanced by Cytokines

Optimally effective antitumor therapies would not only activate immune effector cells but also engage them at the tumor. Folate conjugated to immunoglobulin (F-IgG) could direct innate immune cells with Fc receptors to folate receptor-expressing cancer cells. F-IgG bound to human KB and HeLa cells, as well as murine L1210JF, a folate receptor (FR)-overexpressing cancer cell line, as determined by flow cytometry. Recognition of F-IgG by natural killer (NK) cell Fc receptors led to phosphorylation of the ERK transcription factor and increased NK cell expression of CD69. Lysis of KB tumor cells by NK cells increased by about 5-fold after treatment with F-IgG, an effect synergistically enhanced by treatment with IL2, IL12, IL15, or IL21 (P< 0.001). F-IgG also enhanced the lysis of chronic lymphocytic leukemia cells by autologous NK cells. NK cells significantly increased production of IFNγ, MIP-1α, and RANTES in response to F-IgG-coated KB target cells in the presence of the NK cell-activating cytokine IL12, and these coculture supernatants induced significant T-cell chemotaxis (P< 0.001). F-IgG-coated targets also stimulated FcR-mediated monocyte effector functions. Studies in a murine leukemia model confirmed the intratumoral localization and antitumor activity of F-IgG, as well as enhancement of its effects by IL12 (P =0.05). The antitumor effect of this combination was dependent on NK cells and led to decreased tumor cell proliferation in vivo Thus, F-IgG can induce an immune response against FR-positive tumor cells that is mediated by NK cells and can be augmented by cytokine therapy.

Cytopathologic evaluation of the in situ margin in patients undergoing hepatectomy

BACKGROUND

Margin status is a predictor of outcome for patients with liver malignancies, although what constitutes a negative margin is controversial. Traditionally, the completeness of resection is estimated by surgical histopathology of the resected specimen margin, despite the in situ margin being potentially more important. The true margin is often altered by parenchymal transection techniques. The authors propose that cytologic assessment of the in situ margin is more specific for determining the true margin.

METHODS

A total of 84 patients with primary or metastatic liver tumors who were undergoing surgical resection were enrolled in this prospective Institutional Review Board-approved study. Specimen and in situ (patient) margins were assessed using a "scrape preparation" cytologic technique and compared with traditional surgical histopathology. Patients were followed for assessment of local disease recurrence.

RESULTS

Follow-up data were complete for 64 patients for a median of 37 months (range, 12 months-56 months). Twenty patients were excluded because of perioperative death (6 patients; 7%) or a follow-up of < 12 months. Seven patients (12.2%) had positive histopathologic specimen margins, but only 1 was found to be positive by cytology (1.8%). No in situ cytologically positive margins were identified along the cut edge of the liver remnant. The rate of intra- or extrahepatic recurrences was 56.7%, whereas the local recurrence rate was 1.8%. One patient with local recurrence demonstrated simultaneous intra- and extrahepatic disease recurrences and had negative margins by all methods of evaluation.

CONCLUSIONS

To the authors' knowledge, the current study is the first to demonstrate that in situ margins can be assessed using cytopathology. This method is quick and can be universally applied. Given the difficulty of accurately assessing margins after hepatectomy, cytopathologic evaluation may be more reflective of the true margin. Cancer (Cancer Cytopathol) 2012. © 2012 American Cancer Society.

Prognostic factors and staging for soft tissue sarcomas: an update

Soft tissue sarcoma (STS) staging is a constantly evolving process. Grading is still of utmost importance and has been adapted into a three-tier system. The STS most difficult to categorize are those with uncertain malignant potential, such as solitary fibrous tumors, gastrointestinal stromal tumors, and glomus tumors, some of which have developed completely separate staging systems and may not even be considered sarcomas. Beyond the current TNM staging system, a multitude of prognostic factors for STS will continue to be discovered and ultimately incorporated into future revisions of the staging system.

Repeat hepatectomy for metastatic colorectal cancer is safe but marginally effective

BACKGROUND

Although hepatectomy for metastatic colorectal cancer (mCRC) offers prolonged survival in up to 40% of people, recurrence rates are high, approaching 70%. Many patients experience recurrent disease in the liver after initial hepatectomy. We examined our experience with repeat hepatectomy for mCRC.

METHODS

After Institutional Review Board approval, we reviewed the records of all patients at a single institution who underwent hepatectomy for mCRC. Repeat hepatectomy was defined as partial liver resection any time after the initial hepatectomy for recurrent mCRC. We estimated time to recurrence and survival by using the Kaplan-Meier method and compared outcomes between groups by using the log-rank test.

RESULTS

From 1998 to 2008, 405 patients underwent hepatectomy for mCRC, and 215 (53%) experienced disease recurrence at a median of 13 months. Of 150 patients with liver-only or liver-predominant recurrence, 52 (35%) underwent repeat hepatectomy. The median time to recurrence after repeat hepatectomy was 10 months, and median overall survival was 19 months. There was one (1.9%) perioperative death, and there were 14 (27%) major complications. The median overall survival in the repeat hepatectomy group from the time of recurrence after initial hepatectomy was 22 months, compared with 15 months in the 98 patients with liver recurrence who were not selected for repeat hepatectomy (P=0.02).

CONCLUSIONS

Repeat hepatectomy for mCRC is feasible in highly selected patients, with acceptable perioperative morbidity and mortality. Although repeat hepatectomy should be considered, recurrence rates are high. Although the initial hepatectomy for mCRC is potentially curative, recurrence of metastatic disease in the liver is unlikely to be cured.

Use of a nanoporous biodegradable miniature device to regulate cytokine release for cancer treatment

The clinical management of locally recurrent or unresectable malignant melanoma continues to pose a significant challenge. These lesions are typically painful and currently available treatments, such as repeated intratumoral injections of interferon-alpha (IFN-α), are costly and inconvenient. Nanotechnology offers promise as a novel means of drug delivery. A capsule-like nanoporous miniature device (NMD) based on a biodegradable polymer, poly(polycaprolactone) (PCL) was developed for controlling the local delivery of immunological agents to the tumor microenvironment. The device consists of a nanoporous release gate, a fabricated drug reservoir loaded with IFN-α and a protective layer. To improve the biocompatibility of the device, a hydrophilic poly(ethylene glycol) monoacrylate was applied to the outside wall of the device via covalent bonding techniques. Microscopic visualization of the nanoporous gate from in vitro experiments exhibited good pore stability over a two-month period. In vitro experiments demonstrated a constant release rate of IFN-α from the NMD and showed that the release rate could be regulated by the gate area. The released IFN-α was biologically functional. Cytokine-containing supernatants from release experiments phosphorylated signal transducer and activator of transcription (STAT1) in peripheral blood mononuclear cells. Subcutaneous implantation of the NMDs was well tolerated and associated with an anti-tumor effect in a human xenograft model of melanoma. There was no evidence of a significant inflammatory response to the NMD or encapsulation of the NMD by fibrosis. These experiments show that the NMD can be fabricated and employed in vivo as a versatile drug delivery platform.

Abstract 2686: Anti-tumor effects of a folate-immunoglobulin conjugate are enhanced by cytokine treatment in vitro and in vivo

Folate conjugation is a means of selectively targeting therapeutics to folate receptor (FR)-expressing cancer cells. A novel folate-bound immunoglobulin (F-IgG) was tested for its ability to target natural killer (NK) cells to folate-receptor expressing cancer cells in the presence or absence of NK-activating cytokines.

FR expression by the KB and HeLa cell lines was confirmed by immunoblot analysis (IB) and flow cytometry. Binding of F-IgG to NK cell Fc receptors led to increased phosphorylation of the epidermal growth factor related kinase (ERK) as measured by IB. Lysis of FR+ KB tumor cells by NK cells was increased 8-fold following treatment with F-IgG as compared to C-IgG (p&lt;0.0001 across E:T ratios from 6.25:1 to 50:1). NK cell lysis of F-IgG- coated KB target cells was significantly enhanced following treatment of NK cells with IL-2, IL-12, IL-15 and IL-21 (all at 10ng/mL). NK cell production of IFN-γ, RANTES and MIP-1α was significantly enhanced by IL-12 in response to F-IgG-coated KB target cells as compared to control-treated cells (p&lt;0.005; IFN-γ-2100 vs. 1000pg/mL, RANTES-800 vs. 150pg/mL, MIP-1α 1800 vs. 500pg/mL, respectively). Studies using the L1210JF murine leukemia model confirmed the anti-tumor activity of F-IgG and the ability of NK-activating cytokines to significantly enhance its effects. NK cell depletion in tumor-bearing mice demonstrated that the anti-tumor effects of IL-12 and F-IgG are dependent on NK cells.

These studies indicate that F-IgG induces an immune response by NK cells against FR-positive cancer cell lines and that cytokine treatment has a synergistic effect on this response both in vitro and in vivo. Thus F-IgG has a potential to be used as a therapeutic antibody for the treatment of FR-positive cancers in combination with immune modulatory cytokines.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2686. doi:10.1158/1538-7445.AM2011-2686

IL-12 enhances the antitumor actions of trastuzumab via NK cell IFN-γ production

The antitumor effects of therapeutic mAbs may depend on immune effector cells that express FcRs for IgG. IL-12 is a cytokine that stimulates IFN-γ production from NK cells and T cells. We hypothesized that coadministration of IL-12 with a murine anti-HER2/neu mAb (4D5) would enhance the FcR-dependent immune mechanisms that contribute to its antitumor activity. Thrice-weekly therapy with IL-12 (1 μg) and 4D5 (1 mg/kg) significantly suppressed the growth of a murine colon adenocarcinoma that was engineered to express human HER2 (CT-26(HER2/neu)) in BALB/c mice compared with the result of therapy with IL-12, 4D5, or PBS alone. Combination therapy was associated with increased circulating levels of IFN-γ, monokine induced by IFN-γ, and RANTES. Experiments with IFN-γ-deficient mice demonstrated that this cytokine was necessary for the observed antitumor effects of therapy with IL-12 plus 4D5. Immune cell depletion experiments showed that NK cells (but not CD4(+) or CD8(+) T cells) mediated the antitumor effects of this treatment combination. Therapy of HER2/neu-positive tumors with trastuzumab plus IL-12 induced tumor necrosis but did not affect tumor proliferation, apoptosis, vascularity, or lymphocyte infiltration. In vitro experiments with CT-26(HER2/neu) tumor cells revealed that IFN-γ induced an intracellular signal but did not inhibit cellular proliferation or induce apoptosis. Taken together, these data suggest that tumor regression in response to trastuzumab plus IL-12 is mediated through NK cell IFN-γ production and provide a rationale for the coadministration of NK cell-activating cytokines with therapeutic mAbs.

Clinical factors predictive of malignant and premalignant cystic neoplasms of the pancreas: a single institution experience

BACKGROUND

As cystic neoplasms of the pancreas are discovered with advanced imaging techniques, pancreatic surgeons often struggle with identifying who is at risk of having or developing pancreatic cancer. We sought to review our experience with the surgical management of cystic neoplasms of the pancreas to determine pre-operative clinical indicators of malignancy or premalignant (i.e. mucinous) lesions.

METHODS

Between 1996 and 2007, 114 consecutive patients with cystic neoplasms of the pancreas underwent a pancreatectomy. Invasive adenocarcinoma was identified in 35 whereas 79 had benign lesions. Mucinous lesions were considered premalignant and consisted of 29 intraductal papillary mucinous neoplasms (IPMN) and 17 mucinous cystic neoplasms (MCN). The remaining 33 benign lesions were serous microcystic adenomas. Descriptive statistics were calculated and multivariate logistic regression was performed. Receiver-operating characteristic (ROC) curves were constructed for continuous variables and the area under the curves compared. Likelihood ratios were calculated from the combinations of predictors.

RESULTS

Patients with pancreatic cancer arising from a cystic neoplasm were older than those with benign cysts. Mucinous lesions with or without associated cancer were more likely to be symptomatic and present with elevated serum carbohydrate antigen (CA)19-9 levels. Cancers more commonly presented in the head of the pancreas and were associated with longer hospitalizations after resection. Using multivariate logistic regression, size and elevated CA19-9 were predictors of malignancy whereas male gender and size were predictors of mucinous lesions with or without malignancy. Size, however, was not an accurate test to determine premalignant or malignant lesions using area under the ROC curve analysis whereas CA19-9 performed the best regardless of gender or lesion location.

CONCLUSIONS

Based upon our single institution experience with resection of cystic neoplasms of the pancreas, we advocate an aggressive surgical approach to any patient with a cystic neoplasm of the pancreas and associated elevated CA19-9.

VEGF secretion is inhibited by interferon-alpha in several melanoma cell lines

Interferon-alpha (IFN-alpha) is employed in the treatment of malignant melanoma; however, it mediates regression of disease in only 10-15% of patients. Currently, its mechanism of action is uncharacterized. Low-dose IFN-alpha exerts anti-angiogenic effects when used in the treatment of life-threatening hemangiomas of infancy, suggesting anti-angiogenesis as a mechanism of action. IFN-alpha may exert its anti-tumor effect in the setting of advanced malignancy by inhibiting the secretion of vascular endothelial growth factor (VEGF), a pro-angiogenic substance. We hypothesized that IFN-alpha would decrease the release of VEGF by melanoma tumors. We studied the effect of IFN-alpha on VEGF production in nine human melanoma cell lines. We also examined VEGF levels in 49 patients with advanced malignancies who received low-dose IFN-alpha and interleukin-12 (IL-12) on an NCI-sponsored phase I trial. Human melanoma cell lines produced varying amounts of VEGF in vitro (60-1500 pg/mL at 48 h). Certain melanoma cell lines such as 18105 MEL secreted low levels of VEGF (152 pg/mL) after 48 h of culture, whereas other lines secreted very high levels (FO-1 3,802 pg/mL). Treatment of melanoma cells with IFN-alpha (2000 U/mL) decreased VEGF secretion by 40-60% in VEGF-high cell lines; however, this effect was not demonstrated in VEGF-low cell lines. In cancer patients, pretreatment VEGF plasma levels varied from 471 to 4200 pg/mL. A decrease in VEGF plasma levels after treatment directly correlated with the number of treatment cycles administered (Pearson correlation, p = 0.04). In summary, IFN-alpha inhibits VEGF secretion by melanoma cell lines in vitro and may have similar actions in malignancies that respond to IFN-alpha treatment.

Cryopreservation and plant regeneration from somatic embryos of Pinus patula

 Embryogenic tissue of Pinus patula Scheide et Deppe was cryopreserved for 8 weeks using sorbitol and dimethylsulfoxide (DMSO) as cryoprotectants. Results indicate that 0.3 M sorbitol and 5% DMSO had the best cryoprotecting effect. The recovered tissue initially underwent a lag phase but then continued to proliferate normally on MSG3 maintenance medium. Recovered tissue was placed onto MSG5 maturation medium, and embryos were isolated and germinated. Plantlet regeneration from the recovered tissue was achieved.

Vibration analysis in the detection of total hip prosthetic loosening

This present paper reports on experiments which seek to obtain evidence of the usefulness of vibration in the diagnosis of implant loosening by utilizing extra information by considering the amplitude response at all frequencies (within a certain range) as well as spectral analysis of particular waveforms. This frequency response is essentially a study of the manner in which the amplitude of vibration of a system varies as the frequency of an input force of fixed amplitude is varied. The experimental technique involved the application of a sinusoidal force to the distal end of a femur containing an implanted prosthesis and collecting the output signal using an accelerometer placed at the proximal end. The output signal was stored on a computer with a digital signal processing board and subsequently analysed using the two signal processing techniques mentioned above. Data were collected when the implanted prosthesis was secure, and at various stages of loosening. Analysis of these data shows that prosthetic instability can be detected using both modalities of vibration analysis.

The design of an optical fiber pressure transducer for use in the upper airways

The development of an optical fiber transducer for use in biomedical applications has been presented. The design was targeted for use in the upper airways of patients with sleep disorders stemming from partial or total occlusion of the airway. The transducer's preliminary specification was suited for that of upper airway manometry: a resolution of 10 Pa over the range +/- 5 kPa, a single transducer being less than 0.94 mm in diameter. Amplitude modulated optical fiber sensors are susceptible to loss due to bending of the fiber core and cladding. The design of the transducer uses a series of three optical fibers, one emitting and two receiving, the combination of the two receiving optical fibers is used to reduce effects of light loss: a bend radius of 50 mm is typical for the insertion into the naso-pharynx. The transducer transduction element is a silicone gel coated with reflective titanium dioxide, the meniscus deforms under pressure and modulates the intensity of light reflected back into the receiving optical fibers. The main disadvantage of optical fiber pressure transducers is their susceptibility to temperature drift. Temperature in the airway rarely changes more than 17 degrees C. The frequency of breathing and the high thermal mass of the catheter means that temperature drift in this application is not significant, and will cause an insignificant error of 12 Pa. The transducer is inexpensive to produce, and may be deemed disposable: approximately $20 in material costs (using current manufacturing techniques this can be halved). The system has the added advantage of being electrically, magnetically, and chemically passive. The potential for miniaturization is limited only by the mechanical strength of the optical fibers as mechanical problems associated with fragile elastic membranes do not apply.

Loosening of total hip arthroplasty. Diagnosis by vibration analysis

The early diagnosis of aseptic loosening of a total hip replacement by plain radiography, scintigraphy and arthrography has been shown to be unreliable. It has been suggested that it may be possible to distinguish between a secure and a loose prosthesis using a vibration technique. We have assessed the use of this technique in vitro using models of early and late loosening. Late loosening with an unstable prosthesis can be reliably detected by vibration analysis, but this method was shown to have a very poor diagnostic sensitivity in early loosening when there is no obvious prosthetic instability.

Loosening of total hip arthroplasty. Diagnosis by vibration analysis

The early diagnosis of aseptic loosening of a total hip replacement by plain radiography, scintigraphy and arthrography has been shown to be unreliable. It has been suggested that it may be possible to distinguish between a secure and a loose prosthesis using a vibration technique. We have assessed the use of this technique in vitro using models of early and late loosening. Late loosening with an unstable prosthesis can be reliably detected by vibration analysis, but this method was shown to have a very poor diagnostic sensitivity in early loosening when there is no obvious prosthetic instability.

New signal processing techniques for the decomposition of EMG signals

This paper relates to the use of knowledge-based signal processing techniques in the decomposition of EMG signals. The aim of the research is to automatically decompose EMG signals recorded at force levels up to 20 per cent maximum voluntary contraction (MVC) into their constituent motor unit action potentials (MUAPS), and to display the MUAP shapes and firing times for the clinician. This requires the classification of nonoverlapping MUAPs and superimposed waveforms formed from overlapping MUAPs in the signal. Nonoverlapping MUAPs are classified using a statistical pattern-recognition method. The decomposition of superimposed waveforms uses a combination of procedural and knowledge-based methods. The decomposition method was tested on real and simulated EMG data recorded at force levels up to 20 per cent MVC. The different EMG signals contained up to six motor units (MUs). The new decomposition program classifies the total number of MUAP firings in an EMG signal with an accuracy always greater than 95 per cent. The decomposition program takes about 15s to classify all nonoverlapping MUAPs in EMG signal of length 1.0s and, on average, an extra 9s to classify each superimposed waveform.

Selective noninvasive electrode to study myoelectric signals

The paper describes the design and construction of a selective surface electrode for use in a clinical environment. The main criterion of the design was to enable the recognition of individual motor unit action potential trains (MUAPTs) at moderate force levels. The main features of the electrode are, first, a small concentric bipolar arrangement to avoid electrode/muscle fibre alignment problems and to allow measurements within a small, well defined probed volume; secondly, the non-requirement for conducting paste or gel; and thirdly, the casing acting as an earth plate. All of these simplify its use. The results of tests undertaken with the electrode showed that it was able to pick up individual MUAPTs at up to 20 per cent of maximum voluntary contraction from the first dorsal interosseous muscle. Tests were carried out on the small hand muscles to further demonstrate the usefulness of the electrode. A computer program was written to calculate the shift in frequency of the power spectrum of the recorded myoelectric signal with muscle fatigue and hence indirectly to demonstrate the ability of the electrode to detect the reduction in muscle fibre conduction velocity.

Hydraulic input impedance measurements in physical models of the arterial wall

A white noise method was used to measure the hydraulic input impedance and transmission characteristics in physical models of an arterial system made of single, unbranched latex tubes. The experimentally obtained impedance curves show a rise in modulus and a positive phase at high frequencies in the absence of wave reflections. Using the impedance moduli in the presence of wave reflections, wave velocity and attenuation were calculated. The influence of wall nonlinearity on hydraulic impedance was also examined. It is concluded that, in the model used neither wave reflections nor wall nonlinearity can account for the deviations of the experimental impedance curves from the theoretically predicted ones. Impedance moduli in the presence of reflections may be used to study transmission characteristics (wave velocity and attenuation) of the model.

Frequency response of the arterial wall

The high frequency response of human common iliac arterial segments in vitro was investigated. It was found that at those high frequencies the response resembles that of a second order underdamped system. However, to stimulate the arterial response throughout the frequency range, a higher order model is required. A fifth order system appears to describe the observed behaviour in a satisfactory way between 0.02 and 200 Hz.

Circumferential and longitudinal viscoelasticity of human iliac arterial segments in vitro

A random noise technique was used to measure the circumferential and longitudinal dynamic elasticity of human common iliac arteries in vitro. For circumferential measurements the frequency ranged from 0.016 to 20 Hz; the phase lag of diameter behind pressure was found to be almost constant (about 5 degrees) and the Young's modulus of elasticity to increase rapidly at first and then more gradually beyond 1-2 Hz. Somewhat similar results were obtained for longitudinal elasticity. Arterial segments were found to be anisotropic when kept at in vivo length and under normal distending pressure.

Arterial system configuration and wave reflection

On the assumption that the arterial segments between branching points are cylindrical, the relationship between total arterial cross-sectional area and the distance from the heart for the entire length of the arterial system is derived. Based on this relationship, a model of the whole arterial system is proposed; it is composed of three tubes of common origin and of unequal lengths and cross-sectional areas. This model may be useful for simulation purposes, with particular reference to pulse wave reflections.

Physical modelling of the arterial wall. Part 2: Simulation of the non-linear elasticity of the arterial wall

In part 1 it was established that the elasticity of tubes made from natural rubber is, at low pressures, close to that of the arterial wall; in this part a method is described for reinforcing the walls of rubber tubes so that they may be used for simulating arterial elasticity at higher pressures. The technique is versatile in that, within reasonable limits, wall non-linearity can be modified; tubes with non-linear wall elasticity were produced and tested. A modification of the method enabled us to produce geometrically non-uniform rubber tubes which may be useful in the construction of physical models of the arterial system.

Physical modelling of the arterial wall. Part 1: Testing of tubes of various materials

Tubes of various elastic materials were tested using a purpose-built apparatus to select those most appropriate for physical simulation of the arterial wall. The influences of temperature and longitudinal stress were measured in selected tubes. It was found that the static elasticity of latex tubes is close to that of the arterial wall for intraluminal pressures corresponding to the lower range of intra-arterial pressures.

Photoelectric transducer for measuring the length and diameter of elastic vessels

This photoelectric transducer was developed to measure diameter and length variations in arterial segments in vitro and in elastic tubes. Its construction is simple, its nonlinearity small and its sensitivity adequate. The cut-off frequency is 300 Hz and its small phase lag changes linearly with frequency.

A low-cost colorimeter

A need for a colorimeter with low capital and maintenance costs has been suggested for countries with foreign exchange problems and no local medical instrumentation industry. This paper puts forward a design for such a device based on a domestic light-bulb, photographic filters and photovoltaic cells. The principle of the design is the use of a balancing technique involving twin light paths for test solution and reference solution and an electronic bridge circuit. It is shown that proper selection of the components will allow the cost objectives to be met and also provide acceptable linearity, precision, accuracy and repeatability.

A first-degree course in electronics, with medical instrumentation as a background topic

A course is described in which undergraduate students of electronics can study aspects of medical instrumentation throughout a three-year period. This course includes as much electornics as a normal B.Sc programme in Electronics but contains a background theme of medical engineering and bioengineering amounting to 20% of the total work load. The course is compared with two similar courses in Britain and also with courses abroad. Some consideration is given to the educational content of this course as well as to employment opportunities and social trends.

Natural selection and birthweight

Mean birthweight, even before induced births became commonplace, is slightly lower than the birthweight at which perinatal mortality is lowest. This finding, once hard to explain by natural selection, is shown to be exactly in line with predictions from natural selection theory.