Development and validation of a physical model to investigate the biomechanics of infant head impact

Head injury in childhood is the single most common cause of death or permanent disability from injury. However, despite its frequency and significance, there is little understanding of the response of a child's head to injurious loading. This is a significant limitation when making early diagnoses, informing clinical and/or forensic management or injury prevention strategies. With respect to impact vulnerability, current understanding is predominantly based on a few post-mortem-human-surrogate (PMHS) experiments. Researchers, out of experimental necessity, typically derive acceleration data, currently an established measure for head impact vulnerability, by calculation. Impact force is divided by the head mass, to produce a "global approximation", a single-generalised head response acceleration value. A need exists for a new experimental methodology, which can provide specific regional or localised response data. A surrogate infant head, was created from high resolution computer tomography scans with properties closely matched to tissue response data and validated against PMHS head impact acceleration data. The skull was 3D-printed from co-polymer materials. The brain, represented as a lumped mass, comprised of an injected gelatin/water mix. High-Speed Digital-Image-Correlation optically measured linear and angular velocities and accelerations, strains and strain rates. The "global approximation" was challenged by comparison with regional and local acceleration data. During impacts, perpendicular (at 90°) to a surface, regional and local accelerations were up to three times greater than the concomitant "global" accelerations. Differential acceleration patterns were very sensitive to impact location. Suture and fontanelle regions demonstrated ten times more strain (103%/s) than bone, resulting in skull deformations similar in magnitude to those observed during child birth, but at much higher rates. Surprisingly, perpendicular impacts produced significantly greater rotational velocities and accelerations, which are closer to current published injury thresholds than expected, seemingly as a result of deformational changes to the complex skull geometry. The methodology has proven a significant new step in characterising and understanding infant head injury mechanics.

Vein grafts to augment flexor tendon repairs: a biomechanical study on strength and gap resistance

The ultimate tensile repair strength and gap formation of the pig extensor tendons repaired with a standard 4-strand Savage with epitendinous suture repair, was compared with a new technique of adding a vein sleeve. Force and displacement data were recorded, and video images during linear cyclic loading up to failure. At 35 N, video-graphic observation detected significantly smaller gap lengths in the standard and vein repair specimens compared with standard repair specimens (p = 0.047). The incidence of 3 mm gaps between the repaired tendon ends in the standard repair group was 20 %, but no 3 mm gaps were seen in the standard and vein specimens. The addition of a vein sleeve increased the ultimate tensile strength of the standard repair from 50.4 N (4.5) to 55.4 N (4.5); this was statistically significant (p = 0.03). This study demonstrated that the addition of a vein graft prevented gap formation and increased ultimate tensile strength of tendon repair.

Medical engineering at Cardiff University. Part 2: Postgraduate programmes of study

The Medical Engineering team within the School of Engineering, Cardiff University, delivers two postgraduate programmes of study. Established over 10 years ago, the part-time MSc programmes in Orthopaedic Engineering and Clinical Engineering offer the opportunity of further study while remaining within full-time employment. Both programmes deliver 120 taught credits over two academic years via a series of residential weekends, with successful completion enabling the student to undertake and then defend a 60-credit research dissertation. Fulfilling a specific role on the career pathway for both student cohorts, the strength of each programme is indicated by the consistent number of applicants.

Medical engineering at Cardiff University. Part 1: Undergraduate programmes of study

Cardiff University has offered a medical engineering undergraduate programme since 2001 and hence delivers one of the longest-running and most established medical engineering programmes within the UK. It currently offers BEng (Hons) and MEng (Hons) programmes that are both accredited by the Institution of Mechanical Engineers and include the option to undertake a year in industrial employment. The admissions policy ensures that the intake consists of a diverse range of students and is typically very successful in attracting female students. The programmes consist of six key academic threads which ensure that the content is both relevant and continuous, with all threads tailored to provide a patient-focused learning environment. Students initially learn core and fundamental principles in years 1 and 2, supported by a range of laboratories and practical experimentation. The latter years then encourage the students to corroborate and apply this knowledge, including involvement in a range of project-based learning exercises. The programme is delivered by a core of experienced academic medical engineers, with support from other engineering colleagues, as well as colleagues from the School of Biosciences, the School of Medicine, and the National Health Service. Thus, the programme delivers a wide range of modules which guarantee that graduating students have a thorough understanding of all possible career options. These two factors are significant in making it possible for students to follow their chosen career path upon graduation.

Lubrication regime of the contact between fat and bone in bovine tissue

Fat pads are masses of encapsulated adipose tissue located throughout the human body. Whilst a number of studies describe these soft tissues anatomically little is known about their biomechanics, and surgeons may excise them arthroscopically if they hinder visual inspection of the joint or bursa. By measuring the coefficient of friction between, and performing Sommerfeld analysis of, the surfaces approximating the in vivo conjuncture, this contact has been shown to have a coefficient of friction of the order of 0.01. The system appears to be lubricated hydrodynamically, thus possibly promoting low levels of wear. It is suggested that one of the functions of fat pads associated with subtendinous bursae and synovial joints is to generate a hydrodynamic lubricating layer between the opposing surfaces.

The functional anatomy of Kager's fat pad in relation to retrocalcaneal problems and other hindfoot disorders

Kager's fat pad is a mass of adipose tissue occupying Kager's triangle. By means of a combined magnetic resonance imaging, ultrasound, gross anatomical and histological study, we show that it has three regions that are closely related to the sides of the triangle. Thus, it has parts related to the Achilles and flexor hallucis longus (FHL) tendons and a wedge of fat adjacent to the calcaneus. The calcaneal wedge moves into the bursa during plantarflexion, as a consequence of both an upward displacement of the calcaneus relative to the wedge and a downward displacement of the wedge relative to the calcaneus. During dorsiflexion, the bursal wedge is retracted. The movements are promoted by the tapering shape of the bursal wedge and by its deep synovial infolds. Fibrous connections linking the fat to the Achilles tendon anchor and stabilize it proximally and thus contribute to the motility of its tip. We conclude that the three regions of Kager's fat pad have specialized functions: an FHL part which contributes to moving the bursal wedge during plantarflexion, an Achilles part which protects blood vessels entering this tendon, and a bursal wedge which we suggest minimizes pressure changes in the bursa. All three regions contribute to reducing the risk of tendon kinking and each may be implicated in heel pain syndromes.

Review of the vascularisation of the human Achilles tendon

A region of avascularity mid-way along the length of the Achilles tendon has long been associated with rupture. Whilst it is agreed that this region is the location most common to rupture, the exact vascular distribution appears unclear. Regions of avascularity identified within the tendon have included the origin and insertion, as well as the midsection. This review aims to analyse critically and summarise all previous studies of the vascularisation of the healthy human Achilles tendon, in order to determine the most likely region of avascularity and, thereby establish whether a relationship exists between vascularisation and rupture. Whilst no definitive conclusion was reached, it was concluded that the vascularisation does affect the tensile strength and so rupture vulnerability of the healthy Achilles tendon, although it is unlikely to be either the sole, or most significant, contributor. Other factors, such as thinning and twisting of the tendon at the midsection are mechanical influences that will increase the incidence of rupture by increasing the concentration of stress.

A conical piezoelectric transducer with integral sensor as a self-calibrating acoustic emission energy source

The experimental results of a conical piezoelectric transducer with integral backing sensor as a self-calibrating simulated acoustic emission (SAE) energy source are presented. It has been shown that there is a negative linear relationship between the energy of SAE signal detected by the backing sensor and the relative strength (signal energy) of SAE source in the structure detected by a reference sensor under different transducer-to-structure coupling efficiencies, with AC drives of the same wave packet, frequency and peak amplitude to excite the conical transducer as a SAE source at all the investigated frequencies over the frequency range of interest in AE measurements (nominally from 50 kHz to around 1 MHz). This should enable the relative strength of the SAE source in a structure to be determined using the SAE measurement from the backing sensor for the selected electrical inputs to the conical transducer, and hence to remove the concerns about inconsistent transducer-to-structure coupling affecting the relative strength of the SAE source for calibration.

Corticotropin releasing factor (CRF) agonists with reduced amide bonds and Ser7 substitutions

Strategies to generate competitive antagonists of bioactive peptides include several possible structural modifications such as the introduction of D-residues and of reduced amide bonds, the substitution of amino acid side chains, dimerization of fragments, and deletion of part of the sequence, among others. Whereas we have identified the two most likely residues responsible for receptor activation in corticotropin releasing factor (CRF) (Ser7 and Leu8)1 and generated potent antagonists by deleting residues 1-8,2,3 the question remained as to whether we could generate CRF antagonists with enhanced affinity after reduction of amide bonds at the N-terminus of CRF or through subtle alteration of those residues' side chains. Reduced amide bond replacements (psi[CH2NH]) between residues 6-9 in oCRF(5-41) (11, 12, 15) analogues consistently yielded potencies of <1% that of oCRF. Except for the 10psi11 and 12psi13 analogues 19 and 20, reduced amide bond replacements were generally well-tolerated in the longer hCRF(4-41) analogues, with the 7psi8-, 8psi9-, and 9psi10-modified peptides (13, 14, 18) yielding potencies that were 2-4 times that of hCRF. Although somewhat promising as agonists, they were, however, 3-7 times less potent than the parent [D-Pro4Nle21,38]-hCRF(4-41) (2). Since O-alkylation of Tyr3 in vasopressin yields an antagonist, and since Ser7 is one of the eight fully conserved residues in the CRF family (inclusive of sauvagine, urocortins, and urotensins) and likely to be critical for receptor binding, we synthesized cyclo(30-33)[Ser(OMe)7,D-Phe12,Nle21,Glu30,Lys33 ,Nle38]Ac-hCRF(7-41) (22), which was found to exhibit full efficacy and 40% of the potency of cyclo(30-33)[D-Phe12,Nle21,Glu30,Lys33, Nle38]Ac-hCRF(7-41) (5). Other substitutions at position 7 included aminoglycine (23, 24) and alkylated and/or acylated [alpha or alpha'-methyl (25-28), alpha'-formyl (29, 30), alpha'-formyl, alpha'-methyl (31), alpha'-acetyl (32), alpha'-acetyl, alpha'-methyl (33)], D- or L-aminoglycines. All analogues were active although less potent than the parent compound 2, and all elicited maximal ACTH response as compared to hCRF. The most potent analogue in this series (33) had the bulkiest side chain, Agl(Me, Ac), and was 60% and 80% as potent as the Ser7 analogue 5 and the Ala7 analogue 6, respectively. In conclusion, we found that neither reduction of the individual amide linkages between residues 6-11 and 12-13 nor introduction of a carbamide moiety in lieu of the side chain of Ser7 led to CRF antagonists.

Gonadotropin-releasing hormone antagonists with N omega-triazolylornithine, -lysine, or -p-aminophenylalanine residues at positions 5 and 6

In order to be used as fertility regulators in humans, gonadotropin releasing hormone (GnRH) antagonists must be extremely potent and long acting and exhibit negligible side effects such as stimulating histamine release. To this aim, we have recently synthesized a series of analogues with the standard Ac-DNal1-DCpa2-DPal3 substitutions, where the N omega-amino function of ornithine, lysine, or p-aminophenylalanine (Aph) was converted to the aminotriazolyl (atz) derivatives at positions 5 and 6 with further modifications at positions 7 and 10. The analogues were tested for their ability to bind to pituitary cell membranes, to release histamine in a mast cell assay, to inhibit luteinizing hormone (LH) secretion by castrated male rats or cultured pituitary cells, and to interfere with the ovulation in intact female rats. While the subcutaneous (sc) injection of 50 micrograms of Azaline A (7, [Ac-DNal1,DCpa2,DPal3,Lys5(atz),DLys6++ +(atz),ILys8,DAla10]GnRH) dissolved in 0.2 mL of an aqueous media significantly inhibited LH release in the castrated male rat for 24 h, the same dose of Azaline B (11), [Ac-DNal1,DCpa2,DPal3,Aph5(atz),DAph6++ +(atz),ILys8,DAla10]GnRH, inhibited LH release for 72 h. A similar long duration of action was observed for Antide ([Ac-DNal1,DCpa2,DPal3,Lys5(Nic),DLys6(Nic ),ILys8,DAla10]GnRH) but not for Nal-Glu ([Ac-DNal1,DCpa2,DPal3,Arg5,4-(pmethoxybenzoy l)-D-2-Abu6,DAla10]GnRH). In the same paradigm, a 5-fold dilution of the peptide (50 micrograms in 1 mL) and the use of three injection sites rather than one resulted in significantly shorter duration of action for most of the peptides tested. This suggested that long duration of action might be the result of slow release from the injection site(s). In order to investigate this possibility, Nal-Glu and Azaline B were injected intravenously (i.v.) at three doses (10, 50, 250 micrograms) to castrated male rats. At all doses, both peptides significantly lowered LH levels for 8 h. By 24 h, Nal-Glu (250 micrograms) and Azaline B (50 and 250 micrograms) still measurably inhibited LH secretion. Finally, only Azaline B (250 micrograms) was still active at 48 h. These findings demonstrate that subtle structural modifications will yield peptides with different half-lives after iv administration. These findings led us to investigate the effects of other structural modifications on duration of action. We observed that systematic substitutions at positions 7 (NMeLeu) and 10 (Pro9-NHEt, and Gly-NH2) were found to be deleterious. Of interest was the observation that only the DAla10-NH2 substitution led to long duration of action and enzymatic stability under the conditions tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Novel gonadotropin-releasing hormone antagonists: peptides incorporating modified N omega-cyanoguanidino moieties

In order to minimize the deleterious effects of histamine release resulting from the administration to rats and humans of some potent gonadotropin-releasing hormone (GnRH) antagonists, various arginine residues were replaced with the less basic N omega-cyano-N omega-alkyl- or -arylhomoarginine, -arginine, or -p-aminophenylalanine and N omega-triazolyllysine, -ornithine or -p-aminophenylalanine residues in active analogues. These novel analogues were synthesized on a solid-phase support via a two-step modification of the N omega-NH2 of lysine, ornithine, or p-aminophenylalanine residues in otherwise protected resin bound peptides. Most analogues were tested in the rat antiovulatory assay (AOA) and three in vitro assays; a pituitary cell culture assay, a binding assay to pituitary cell membranes, and a histamine release assay. Introduction of the cyanoguanidino and N omega-triazolyl moieties into GnRH analogues yielded several water-soluble antagonists which showed a desirable therapeutic ratio (low histamine release activity to high in vivo potency). Among them, "Azaline" (10, [Ac-DNal1,DCpa2,DPal3,Lys5(atz), DLys6(atz),ILys8,DAla10]GnRH), inhibited ovulation in the rat by 90% at 2 micrograms/rat with an ED50 in the in vitro histamine release assay comparable to that of GnRH itself.

Gonadotropin releasing hormone antagonists: novel structures incorporating N omega-cyano modified guanidine moieties

A series of GnRH antagonists with substitutions at positions 1, 2, 3, 5 and 6 that included the recently reported homoArg-N omega-cyano-N omega'-alkyl- or Lysine-N epsilon-5'-(3-amino-1H-1,2,4-triazole) [Lys(atz)] amino acid derivatives was synthesized, characterized and tested for antiovulatory and anaphylactoid activities and binding affinity. Overall, these analogs were found to be considerably more soluble at neutral pH than their homologs Nal-Glu or Antide. The decapeptides with these substitutions in positions 5 and/or 6 retained high in vivo potency while those with similar substitutions at positions 1, 2 and 3 were significantly less potent than Nal-Glu or Antide. Of the 16 new analogs reported here, Azaline (Ac-DNal1, DCpa2, DPal3, Lys5(atz),DLys6(atz), ILys8,DA1a10]-GnRH) showed the most promising physico-chemical and biological properties [Lys(atz) = N epsilon-5'-(3-amino-1H-1,2,4-triazole) lysine]. Azaline is readily soluble in dilute buffers at pH 7.0, completely inhibits ovulation at 2.0 to 3.0 micrograms per rat, is equipotent to GnRH in releasing histamine in the rat and has a weaker anaphylactoid response in the rat than other analogs such as Nal-Glu or even Antide.

Objective demonstration of cervical softening with a prostaglandin F2 alpha gel during first trimester abortion

In a prospective study the cervix softening and dilating effects of intracervically applied prostaglandin F2 alpha gel were investigated in 100 patients during induced abortion in the 7-12th week of pregnancy. A specially designed tonometer was used to measure the resistance of the cervical canal before as well as 6-8 h, 4 days and 5-6 weeks after gel application. The cervix of 99 patients proved to be freely passable without use of undue force for at least Hegar 8 after treatment. Measurements in 96 patients 5-6 weeks after the operation showed good general agreement with those values obtained before gel application. No spontaneous or operation-induced lesions of the cervix occurred. Intracervical prostaglandin gel application proved itself to be a safe, practicable and gentle method for avoiding dilation-induced complications during first trimester abortions.

Three cases of choriocarcinoma (author's transl)

Report on three cases of choriocarcinoma which showed interesting features. In the first case a living male infant was delivered two years following chemotherapy for choriocarcinoma and the infant showed no chromosomal abnormalities. In the second case a choriocarcinoma developed three years following a post-partum tubal ligation and the localized tumor was successfully treated by hysterectomy without chemotherapy. In the third case the uterine tumour was refractory to chemotherapy with Actinomycin D and methotrexate and required a hysterectomy. The value of HCG and HPL titres in the differential diagnosis and the value of the microscopic results of the currettings are discussed. The possibility of chromosomal damage to infants born following chemotherapy of the mother is mentioned.