Development of New CD38 Targeted Peptides for Cancer Imaging

PURPOSE

Multiple myeloma (MM) affects over 35,000 patients each year in the US. There remains a need for versatile Positron Emission Tomography (PET) tracers for the detection, accurate staging, and monitoring of treatment response of MM that have optimal specificity and translational attributes. CD38 is uniformly overexpressed in MM and thus represents an ideal target to develop CD38-targeted small molecule PET radiopharmaceuticals to address these challenges.

PROCEDURES

Using phage display peptide libraries and pioneering algorithms, we identified novel CD38 specific peptides. Imaging bioconjugates were synthesized using solid phase peptide chemistry, and systematically analyzed in vitro and in vivo in relevant MM systems.

RESULTS

The CD38-targeted bioconjugates were radiolabeled with copper-64 (64Cu) with100% radiochemical purity and an average specific activity of 3.3 - 6.6 MBq/nmol. The analog NODAGA-PEG4-SL022-GGS (SL022: Thr-His-Tyr-Pro-Ile-Val-Ile) had a Kd of 7.55 ± 0.291 nM and was chosen as the lead candidate. 64Cu-NODAGA-PEG4-SL022-GGS demonstrated high binding affinity to CD38 expressing human myeloma MM.1S-CBR-GFP-WT cells, which was blocked by the non-radiolabeled version of the peptide analog and anti-CD38 clinical antibodies, daratumumab and isatuximab, by 58%, 73%, and 78%, respectively. The CD38 positive MM.1S-CBR-GFP-WT cells had > 68% enhanced cellular binding when compared to MM.1S-CBR-GFP-KO cells devoid of CD38. Furthermore, our new CD38-targeted radiopharmaceutical allowed visualization of tumors located in marrow rich bones, remaining there for up to 4 h. Clearance from non-target organs occurred within 60 min. Quantitative PET data from a murine disseminated tumor model showed significantly higher accumulation in the bones of tumor-bearing animals compared to tumor-naïve animals (SUVmax 2.06 ± 0.4 versus 1.24 ± 0.4, P = 0.02). Independently, tumor uptake of the target compound was significantly higher (P = 0.003) compared to the scrambled peptide, 64Cu-NODAGA-PEG4-SL041-GGS (SL041: Thr-Tyr-His-Ile-Pro-Ile-Val). The subcutaneous MM model demonstrated significantly higher accumulation in tumors compared to muscle at 1 and 4 h after tracer administration (SUVmax 0.8 ± 0.2 and 0.14 ± 0.04, P = 0.04 at 1 h; SUVmax 0.89 ± 0.01 and 0.09 ± 0.01, P = 0.0002 at 4 h).

CONCLUSIONS

The novel CD38-targeted, radiolabeled bioconjugates were specific and allowed visualization of MM, providing a starting point for the clinical translation of such tracers for the detection of MM.

Mixed IgG Fc immune complexes exhibit blended binding profiles and refine FcR affinity estimates

Immunoglobulin G (IgG) antibodies coordinate immune effector responses by interacting with effector cells via fragment crystallizable γ (Fcγ) receptors. The IgG Fc domain directs effector responses through subclass and glycosylation variation. Although each Fc variant has been extensively characterized in isolation, during immune responses, IgG is almost always produced in Fc mixtures. How this influences effector responses has not been examined. Here, we measure Fcγ receptor binding to mixed Fc immune complexes. Binding of these mixtures falls along a continuum between pure cases and quantitatively matches a mechanistic model, except for several low-affinity interactions mostly involving IgG2. We find that the binding model provides refined estimates of their affinities. Finally, we demonstrate that the model predicts effector cell-elicited platelet depletion in humanized mice. Contrary to previous views, IgG2 exhibits appreciable binding through avidity, though it is insufficient to induce effector responses. Overall, this work demonstrates a quantitative framework for modeling mixed IgG Fc-effector cell regulation.

Mixed IgG Fc immune complexes exhibit blended binding profiles and refine FcR affinity estimates

Immunoglobulin (Ig)G antibodies coordinate immune effector responses by selectively binding to target antigens and then interacting with various effector cells via the Fcγ receptors. The Fc domain of IgG can promote or inhibit distinct effector responses across several different immune cell types through variation based on subclass and Fc domain glycosylation. Extensive characterization of these interactions has revealed how the inclusion of certain Fc subclasses or glycans results in distinct immune responses. During an immune response, however, IgG is produced with mixtures of Fc domain properties, so antigen-IgG immune complexes are likely to almost always be comprised of a combination of Fc forms. Whether and how this mixed composition influences immune effector responses has not been examined. Here, we measured Fcγ receptor binding to immune complexes of mixed Fc domain composition. We found that the binding properties of the mixed-composition immune complexes fell along a continuum between those of the corresponding pure cases. Binding quantitatively matched a mechanistic binding model, except for several low-affinity interactions mostly involving IgG2. We found that the affinities of these interactions are different than previously reported, and that the binding model could be used to provide refined estimates of these affinities. Finally, we demonstrated that the binding model can predict effector-cell elicited platelet depletion in humanized mice, with the model inferring the relevant effector cell populations. Contrary to the previous view in which IgG2 poorly engages with effector populations, we observe appreciable binding through avidity, but insufficient amounts to observe immune effector responses. Overall, this work demonstrates a quantitative framework for reasoning about effector response regulation arising from IgG of mixed Fc composition.

Summary points

The binding behavior of mixed Fc immune complexes is a blend of the binding properties for each constituent IgG species.An equilibrium, multivalent binding model can be generalized to incorporate immune complexes of mixed Fc composition.Particularly for low-affinity IgG-Fcγ receptor interactions, immune complexes provide better estimates of affinities.The FcγR binding model predicts effector-elicited cell clearance in humanized mice.

Comparative Study of Thyroxine Assays Employing Kit Radio-Ligand Reagents

A comparative study of some ‘kit’ radiometric procedures for the determination of thyroxine in serum is reported. Four manufacturers' competitive-binding reagents and methods—three incorporating prior extraction and one employing column elution—are examined. Considerable discrepancies exist between the manufacturers' ‘standards’ which, in the main, account for the differences in results obtained by the different methods. Other deficiencies include susceptibility to metal ion interference, variation (up to 8%) in thyroxine extraction and non-specific, i.e. ‘mimic T-4’, measurement.

Radio-ligand reagent ‘kits’ need to be critically assessed before being used routinely. Separation of hypo-and hyperthyroid from euthyroid patients is achieved as well with some competitive protein-binding T-4 methods as with serum PBI.

Accuracy and Standardisation of Serum Thyroxine Assays

Serum thyroxine was assayed concurrently by at least two of three different radio-displacement analysis kits—‘Tetralute’ (Ames), ‘Tetrasorb’ (Abbott) and ‘Thyopac-4’ (Radiochemical Centre). Repeated and careful cross checking by each of the methods was carried out on the ‘standard’ sera supplied with the kits and on other commercially available control sera. Differences of −3 to + 32% in apparent T-4 concentration were found. An unacceptable variability in T-4 content amongst batches of the same control sera was also evident which can be explained only by a lack of constancy in the commercial serum T-4 ‘standards’.

The molar extinction coefficients, water and tri-iodothyronine contents of commercial ‘pure’ thyroxine preparations indicate purities of 89–99 %. An examination of published ‘euthyroid’ ranges and those found by the ‘kit’ radiometric methods suggests that many normal serum T-4 values are based on the use of an impure primary or doubtful secondary standard. A primary standardisation of the assay with thyroxine of known purity and of known concentration, as determined from its molar extinction at 324 nm is advocated. Using this procedure, the normal euthyroid range for serum T-4 is 55–148 nmol T4/1 (2.8–7.5 μg T-4I/100 ml) or close to it—in agreement with the earlier findings of Howarth and Maclagan (1969) and Ekins et al. (1969).

During the period studied, ‘Tetralute’ produced the most accurate results.

The role of partnership dynamics in determining the acceptability of condoms and microbicides

Microbicides are a class of substances under development that could reduce the sexual transmission of HIV and other sexually transmitted diseases when applied locally to genital mucosal surfaces. Microbicide acceptability research has largely focused on product characteristics, rather than processes of negotiation within relationships about use. Gender relations, decision-making power and communication within sexual relationships are recognised as important determinants of condom and contraceptive use, and are likely to determine microbicide use also. As part of social science research linked to the Microbicides Development Programme (MDP) we combine relationship-based theories with anthropological work conducted with women and men using a placebo gel. We explore communication and decision-making in gel and condom use, including constructions of risk and trust. During the MDP301 Phase III pilot study, in-depth interviews were conducted at sites in South Africa, Tanzania, Uganda and Zambia. Following four weeks of placebo gel use, women and their partners were asked about gel use and acceptability, partner involvement, sexual practices and condom use. Data from 45 couples at five sites were analysed using a grounded theory approach in NVivo. Participation in the study did not require women to inform their partners, yet our data shows women seeking permission from their partners, negotiating disclosure, exchanging information and persuading or motivating for gel use. Although gel was supposedly 'woman-controlled', men exercised considerable influence in determining whether and how it was used. Despite this, negotiations around use were largely successful, since the gel increased sexual pleasure and provided opportunities for intimate communication and the building of trust. Decisions about condom and microbicide use are made in a dyadic context and involve a complex negotiation of risk and trust. Whilst preferences relating to product characteristics are largely individual, use itself is dependent on partnership dynamics and the broader social context in which sexual risk management occurs.

An exploration of the meanings and experiences of cancer of Chinese people living and working in London

This paper investigates the meanings and experiences of cancer of Chinese people living and working in London, in order to help the future development of culturally sensitive cancer information for Chinese people in the United Kingdom. A focus group interview method was used. Five focus groups (n = 35) were conducted in 2003 in London; these included Chinese health professionals, asylum seekers, immigrants with unknown status, Chinese young adults and Chinese elders. We found that the participants' understanding of cancer reflected Chinese cultural beliefs about health and illness. There are some misunderstandings and lack of knowledge and information about cancer treatments, but they understand cancer to be life threatening. There is also a great reluctance to talk about cancer. The participants suggested that as well as receiving appropriate and early treatment, by either biomedicine or traditional Chinese medicine, or preferably, a combination of the two, an individual's chances of surviving cancer could be enhanced by being provided with spiritual guidance and by being in a happy, positive mood. There is a need to improve knowledge about cancer in the Chinese community through the provision of culturally appropriate and accessible information on a variety of topics, including healthy lifestyles, cancer prevention and treatments, and by encouraging openness about cancer issues.

Cancer and communication: similarities and differences of men with cancer from six different ethnic groups

This paper reports the communication aspects of a pilot study, which explored the cancer meanings and experiences of six men with cancer and their significant others from different ethnic groups. A case study design was applied using the principles of phenomenology. In-depth semi-structured individual interviews were conducted in participants' own homes, in London, UK. This paper will only deal with the communication aspects of the findings. Ten themes emerged from the comparative analysis of the study's data, with communication as a cross-cutting theme. Further analysis of this theme revealed similarities and differences of the participants' experiences of communicating with health professionals; families or friends; and God/Allah. In addition, similarities and differences in communicating meanings of cancer in different cultures were revealed. The findings revealed similarities in the way that men from these six cultures communicate with health professionals and their families following a diagnosis of cancer, and differences in how they communicated with God/Allah, which depended on their religious beliefs and practices.

Ethiopian refugees in the UK: migration, adaptation and settlement experiences and their relevance to health

OBJECTIVE

The study explores Ethiopian refugees' and asylum seekers' experiences of migration, adaptation and settlement in the UK and their health beliefs and practices.

DESIGN

Data was collected using semi-structured depth interviews and a semi-structured questionnaire. The sample consisted of 106 Ethiopians resident in the UK.

RESULTS

The majority of the participants fled Ethiopia due to political reasons. Whilst 65% of them had lived in the UK for over five years only 7% had full refugee status. Many of the participants faced difficulties with the immigration system, housing and social services and felt socially isolated. Many also had problems with gaining employment or employment appropriate to their qualifications, and 29% were unemployed. The majority of the participants believe that happiness is a prerequisite to healthiness and also an indication of healthiness. On the other hand the majority believed that sickness is caused by disease and mental illness is caused by both supernatural and psychosocial causes. Most of the participants sought the help of their GP in the first instance of illness although some had experienced difficulties accessing health services due to language problems and poor understanding of the primary healthcare system. The participants also believed that the stress of adaptation and settlement affected their mental health and led to depression.

CONCLUSION

Migration, adaptation and settlement experiences impact on the health of refugees and are dependent on a number of barriers and enablers, both at a personal and societal level. These should be taken into account in the provision of health and social care services, in particular services should be provided in a culturally competent manner.

Cancer and men from minority ethnic groups: an exploration of the literature

The authors reviewed literature which has been published in the last 20 years. Cancer is the second leading cause of death in developed countries and is expected to become a significant cause of death in developing countries. Whilst there are a large number of studies on cancer and men, there is a paucity of data on men from minority ethnic groups. In the USA, African Americans are more likely to develop cancer than any other ethnic group. Although cancer rates amongst minority ethnic groups in the UK are thought to be low, 11% of Indian and African men and 19% of Caribbean men died from cancer during 1979-1983. There is also further evidence in the USA that African American, Filipinos and Native Americans have the lowest cancer survival rates. Service utilization, especially tertiary care, is also thought to be low amongst minority ethnic groups from the USA and the UK. Reasons for these variations include artefactual, cultural, materialist and social selectivist explanations as well as the effects of migration, racism and genetic disposition. This area is under-researched, in particular cultural beliefs about cancer. Further research into this area should apply culturally competent methods to ensure valid data to inform cancer policy, education and practice.

The revised Beliefs About Voices Questionnaire (BAVQ-R)

BACKGROUND

We present a revised Beliefs About Voices Questionnaire (BAVQ-R), a self-report measure of patients' beliefs, emotions and behaviour about auditory hallucinations.

AIMS

To improve measurement of omnipotence, a pivotal concept in understanding auditory hallucinations, and elucidate links between beliefs about voices, anxiety and depression.

METHODS

Seventy-one participants with chronic auditory hallucinations completed the BAVQ-R, and 58 also completed the Hospital Anxiety and Depression Scale.

RESULTS

The mean Cronbach's alpha for the five sub-scales was 0.86 (range 0.74-0.88). The study supports hypotheses about links between beliefs, emotions and behaviour, and presents original data on how these relate to the new omnipotence sub-scale. Original data are also presented on connections with anxiety and depression.

CONCLUSIONS

The BAVQ-R is more reliable and sensitive to individual differences than the original version, and reliably measures omnipotence.

Nursing students' early exposure to clinical practice: an innovation in curriculum development

This paper describes a pilot study addressing issues surrounding the balance and status given to both theory and practice in the foundation part of a pre-registration programme. Contemporary thinking seems to suggest that there is a need to reverse recent trends which have placed an emphasis on theory. To facilitate this a framework for clinical learning was adapted to guide students' early exposure to clinical practice. The focus was to develop the students' observational and reflective skills whilst also providing the students with a frame of reference within which they could explore their theoretical studies. The information and experiences gained as a result of this study have led to the integration of an Orientation Framework to support students' early clinical experiences in a pre-registration programme.

Benefits of nurse teachers returning to clinical practice

This article outlines an action research study developed to facilitate nurse teachers returning to clinical practice. The article explores how the teachers established partnerships with clinicians through which they were able to share the experience of returning to an area of nursing that they had previously only visited. It discusses four categories: expectations of self and others; entering someone else's world; more awareness of student needs; and teaching theory and practising nursing. These categories emerged following the analysis of journals, focus group interviews and individual interviews and led to a number of recommendations concerning the implications for other teachers wishing to return to clinical practice.

Interpreting the equatorial diffraction pattern of collagenous tissues in the light of molecular motion

The equatorial diffraction pattern associated with collagenous tissues, particularly type I collagen, is diffuse and clearly unlike that from crystals. Hukins and Woodhead-Galloway proposed a statistical model that they termed a "liquid crystal" for collagen fibers in tendons. Fratzl et al. applied this model to both unmineralized and mineralized turkey leg tendon, a model that ignores the organization imposed by the well-known cross-linking. The justification for adopting this model is that the curve fits the data. It is shown that the data can be equally well matched by fitting a least-squares curve consisting of a second-order polynomial plus a Gaussian. The peak of the Gaussian is taken as the equatorial spacing of the collagen. A physical explanation for this model is given, as is a reason for the changes in the spacing with changes in water content of the tissue. The diffusion is attributed to thermally driven agitation of the molecules, in accordance with the Debye-Waller theory including the Gaussian distribution. The remainder of the diffusion is attributed to other scattering sources like the mineral crystallites.

Improving transfusion practices in a busy teaching hospital

A retrospective audit of blood transfusions was carried out in Cardiff Royal Infirmary (CRI) to investigate how efficiently blood was requested and used by the various clinical directorates. Excessive crossmatch/transfusion (C/T) ratios were found for a number of operations. In an attempt to improve practices, a pilot study was carried out between the Department of Haematology and the largest single requesting group, the Orthopaedic Directorate. As a result of a preliminary retrospective audit, crossmatch guidelines were revised, with more reliance on the group and antibody screen (G & S) for low-risk operations. A subsequent prospective audit showed major reductions in crossmatch requests and a general decrease in C/T ratios to very efficient levels without any patient morbidity. Blood was freed for urgent use elsewhere, and significant cost improvements resulted. This study, using the orthopaedic surgery department as a model, shows the value of inter-departmental audit and supports the experience of other centres using similar methods to make considerable savings in the amount of blood crossmatched unnecessarily.

Effect of sodium chloride solutions on mineralized and unmineralized turkey leg tendon

Previous studies showed that the equatorial diffraction spacing of the collagen molecules in mineralized tissues decreases when the tissue is dried and that the spacing in totally dried tissue is about the same (1.1 nm) whether mineralized or not. Here we report that spacing decreases were observed in both mineralized and unmineralized turkey leg tendon after soaking in various sodium chloride solutions up to 4.0 M concentration. The effect was seen by X-ray diffraction as well as by neutron diffraction. No effect was seen in turkey leg tendon soaked in 3.0 M ethylene glycol solution. The spacing in unmineralized tissue decreased from 1.459 +/- 0.011 nm in 0.15 M saline to 1.403 +/- 0.025 nm in 1.5 M saline, a change of 0.056 +/- 0.03 nm or 3.84%. In mineralized turkey leg tendon the corresponding spacings were 1.387 +/- 0.012 and 1.321 +/- 0.019 nm, a change of 0.046 +/- 0.02 nm or 3.4%. No significant dimensional change was noted in the thickness even though the equatorial diffraction spacing decreased by 3.4%. Electron microscopy showed the collagen fibrils within the mineralized turkey leg tendon to be surrounded by highly mineralized material. Presumably the composition of the extrafibrillar material is different from the intrafibrillar and therefore the extrafibrillar material is a different kind of composite. If it is assumed that the extrafibrillar material does not change dimensions significantly, then the collagen molecules in the fibrils can be mobile within the dimensionally stable cage-like structure.

Immune response to murine cell lines of glial origin transplanted into the central nervous system of adult mice

Temperature-sensitive simian virus 40 (SV40) T antigen-transformed central nervous system (CNS)-derived murine cell lines were used to analyse the host response to transplantation in the mouse adult brain. The cell lines were shown to be susceptible to immune recognition in vitro by cytotoxic effector cells indicating that tissue-specific privilege was not in operation. Histological examination at time points post-implantation showed characteristic responses similar to those seen during graft rejection. Astrocytosis and up-regulation of major histocompatibility complex (MHC) class I and MHC class II activation of resident microglia and recruitment of macrophages were observed in both allogeneic and syngeneic hosts 10 days post-implantation suggesting a trauma-induced response. However, the response in allogeneic hosts was more widespread and evident when the syngeneic responses had returned to normal levels. Evidence of T-cell infiltration was also more pronounced in the allogeneic hosts. Despite quite extensive host reactions to these cellular grafts at early time-points the implants appeared to survive in the host CNS long after the responses had abated and could be detected at the maximum time-point studied of 40 days.

X-ray diffraction analysis of tendon collagen at ambient and cryogenic temperatures: role of hydration

Equatorial (d) and meridional (D) spacings of native rat tail tendon (RTT) and unmineralized native turkey leg tendon (UTLT) were measured at ambient and liquid-nitrogen temperatures, using X-ray diffraction. Cooling of air-dried RTT or UTLT caused little change in d, which was approximately equal (1.1 nm) in the two tissues before and after cooling. For fully hydrated RTT or UTLT, cooling caused the familiar broad equatorial diffraction pattern to increase in sharpness to more resemble the pattern seen in dehydrated tissue. The d-spacings of hydrated RTT and UTLT fell by 0.12 nm (8.5%) and 0.19 nm (13%), respectively to values seen (at ambient temperature) when the tissue water content is the maximum possible in the absence of unbound water (0.5 g water/g dry collagen). These results can be explained by the movement of water within the fibril. In tissue with a water content of greater than 0.5 g/g dry collagen the spacings reflecting the lateral packing of the axially-linked tropocollagen molecules comprising a collagen fibril are determined partly by the unbound component of intermolecular hydration. As the bulk water between the fibrils freezes, this mobile component remains initially unfrozen as the tissue is cooled below zero degree C. It diffuses from the intermolecular spaces into the interfibrillar spaces where it also rapidly freezes. This allows the d-spacing to decrease to the value appropriate for the presence of bound intermolecular water only. The mechanism is likely to be an energetically favourable relaxation of the lateral positions of the tropocollagen molecules from a quasi-hexagonal arrangement to hard-disk liquid-like packing. The results and methods of this study may be applicable in the elaboration of more complex collagenous systems.

Visualization of crystal-matrix structure. In situ demineralization of mineralized turkey leg tendon and bone

A technique to correlate the ultrastructural distribution of mineral with its organic material in identical sections of mineralized turkey leg tendon (MTLT) and human bone was developed. Osmium or ethanol fixed tissues were processed for transmission electron microscopy (TEM). The mineralized tissues were photographed at high, intermediate, and low magnifications, making note of section features such as fibril geometry, colloidal gold distribution, or section artifacts for subsequent specimen realignment after demineralization. The specimen holder was removed from the microscope, the tissue section demineralized in situ with a drop of 1 N HCl, then stained with 2% aqueous vanadyl sulfate. The specimen holder was reinserted into the microscope, realigned with the aid of the section features previously noted, and rephotographed at identical magnification used for the mineralized sections. A one to one correspondence was apparent between the mineral and its demineralized crystal "ghost" in both MTLT and bone. The fine structural periodic banding seen in unmineralized collagen was not observed in areas that were fully mineralized before demineralization, indicating that the axial arrangement of the collagen molecules is altered significantly during mineralization. Regions that had contained extrafibrillar crystallites stained more intensely than the intrafibrillar regions, indicating that the noncollagenous material surrounded the collagen fibrils. The methodology described here may have utility in determining the spatial distribution of the noncollagenous proteins in bone.

Some acoustical properties of the otic bones of a fin whale

The otic bones in this report are the tympanic bulla, the periotic, and the three ossicles (malleus, incus, and stapes) of an adult fin whale (Balaenoptera physalus). The purpose was to determine if the periotic was denser than the other otic bones. It was found in one male adult fin whale that the density of all the otic bones is approximately the same, 2.50 kg/m3 with a maximum of 2.58. The lowest density was observed in the stapes (2.36). The sonic velocity seems to vary as the density but there also seems to be a structural effect. The maximum sonic velocity was 4.89 km/s in the malleus. The specific acoustic impedance was as high as 12.5 megarayles in the periotic. These values compare with those for human femur of 1.95 for the density, 3.73 for the sonic velocity, and 7.33 for the specific acoustic impedance. The ossicles weigh as much as 200 times as much as human ossicles. The density of whale ossicles are about ten percent greater than human ossicles. The mechanical natural frequency of the whale ossicles must be very low. The approximate uniformity of the properties of this whale's otic bones may be characteristic of the middle ear. The density of the otic bones of land mammals is less than for whales. The density of the horse petrosal (2.29 g/cc) is essentially the same as the density of adult human ossicles (2.23-2.27 g/cc). The high density of the otic bones for all mammals suggests it may be related to hearing acuity perhaps by increasing the specific acoustic impedance, which increases the acoustic contrast with the other body tissues.

Efficacy of ivermectin against benzimidazole-resistantNematodirus spathigerin sheep

Eighteen helminth-free lambs were randomly allocated to six groups of three. Each lamb was dosed with 3300 infective larvae pooled from two isolates of Nematodirus spathiger known to be benzimidazole resistant. One lamb from each group was treated with oral ivermectin, one with oral oxfendazole and one left untreated 21 days after infection. All lambs were humanely killed 14 days later and small intestine worm counts performed. No Nematodirus were found in the ivermectin-treated lambs. Nematodirus numbers were reduced by 13% in oxfendazole-treated lambs relative to the control lambs.

Comparison of dosage-dependent effects of beta-aminopropionitrile, sodium fluoride, and hydrocortisone on selected physical properties of cortical bone

BAPN, sodium fluoride, and hydrocortisone are reported to induce altered mineralization states. Three separate sets of experiments, one set for each agent, were performed using male New Zealand white rabbits. In each experiment the rabbits were segregated into groups, each fed a specified weight-determined dose for 13 weeks and then sacrificed. Compact bone from the left femur and tibia were tested for density, composition, sonic velocity, longitudinal elastic modulus, equatorial diffraction spacing of mineralized collagen, diaphyseal cross-sectional area, and relative load stress. beta-Aminopropionitrile (BAPN) induced monotonic degradation of all properties at all dose levels, corresponding to the decreasing density with dosage level. The elastic moduli show a decrease; the equatorial diffraction spacing of the collagen increases. The cross-sectioned diaphysis resembled woven bone. The variability in properties increased with dosage. The total cross-sectional area for a given weight increased, implying that the decreased elastic properties were compensated for by a larger area to support the weight. There was a slight increase in average density and other properties for fluoride-treated rabbits, peaking at 20 mg/kg BW/day. For higher dosages the properties are degraded and the values were much lower at high fluoride dosages than for BAPN. There was no peak for the equatorial diffraction spacing, which increased with dosage. It is inferred that the fluorosed apatite is denser than normal apatitic mineral and therefore has a smaller specific volume. A greater weight fraction of fluorosed mineral has a smaller volume fraction than the equivalent normal apatitic mineral. The bone sections look more normal, except for the porosis. The total cross-sectional area decreases when the bone density increases and then increases as the density falls, again implying that the area required to support body weight depends on the magnitude of the elastic moduli. There was a small change in some of the properties of the bones of the hydrocortisone-treated rabbits, but the effects on others were undetectable within the uncertainty of the procedures. There was no change in the cross-sectional areas of the diaphyses.

The loci of mineral in turkey leg tendon as seen by atomic force microscope and electron microscopy

Transmission electron micrographs of fully mineralized turkey leg tendon in cross-section show the ultrastructure to be more complex than has been previously described. The mineral is divided into two regions. Needlelike-appearing crystallites fill the extrafibrillar volume whereas only platelike crystallites are found within the fibrils. When the specimen is tilted through a large angle, some of the needlelike-appearing crystallites are replaced by platelets, suggesting that the needlelike crystallites are platelets viewed on edge. If so, these platelets have their broad face roughly parallel to the fibril surface and thereby the fibril axis, where the intrafibrillar platelets are steeply inclined to the fibril axis. The projection of the intrafibrillar platelets is perpendicular to the fibril axis. The extrafibrillar volume is at least 60% of the total, the fibrils occupying 40%. More of the mineral appears to be extrafibrillar than within the fibrils. Micrographs of the mineralized tendon in thickness show both needlelike-appearing and platelet crystallites. Stereoscopic views show that the needlelike-appearing crystallites do not have a preferred orientation. From the two-dimensional Fourier transform of a selected area of the cross-sectional image, the platelike crystallites have an average dimension of 58 nm. The needlelike-appearing crystallites have an average thickness of 7 nm. The maximum length is at least 90 nm. Atomic force microscopy (AFM) of unstained, unmineralized turkey leg tendon shows collagen fibrils very much like shadow replicas of collagen in electron micrographs. AFM images of the mineralized tendon show only an occasional fibril. Mineral crystallites are not visible. Because the collagen is within the fibrils, the extrafibrillar mineral must be embedded in noncollagenous organic matter. When the tissue is demineralized, the collagen fibrils are exposed. The structure as revealed by the two modalities is a composite material in which each component is itself a composite. Determination of the properties of the mineralized tendon from the properties of its elements is more difficult than considering the tendon to be just mineral-filled collagen.

Measuring the microelastic properties of biological material

We have used the atomic force microscope (AFM) to measure the local rigidity modulus at points on the surface of a section of hydrated cow tibia. These data are obtained either from contrast changes that occur as the contact force is altered, or from force versus distance curves obtained at fixed points. These two methods yield the same values for rigidity modulus (at a given point). At low resolution, the elastic morphology and topography mirror the features seen in optical and electron micrographs. At high resolution we see dramatic variations in elastic properties across distances as small as 50 nm.

X-ray diffraction by collagen in the fully mineralized cortical bone of cow tibia

X-ray diffraction patterns were recorded from fully mineralized and demineralized sections of the cortical bone from cow tibia. The results were used to obtain a measure, d, of the mean side-to-side spacing (equatorial diffraction spacing) of the molecules in the type I collagen fibrils of bone. Mineralized bone yielded a d value of 1.23 nm; for the demineralized tissue this value increased to 1.52 nm. Thus it appears that mineralization of bone compacts its collagen molecules within the fibrils.

Effect of fluoride dosage on bone density, sonic velocity, and longitudinal modulus of rabbit femurs

Relationships between the fluoride dosage administered to weanling New Zealand white male rabbits and some mechanical properties of the compact bone were investigated for a wide range of dosages. The measured quantities were density, longitudinal sonic velocity in the radial direction, and fluoride ion concentration in compact bone. The longitudinal elastic modulus was estimated from the product of the density and the square of the sonic velocity. The relative static load stress was estimated from the ratio of the final body weight to the cross-sectional area of the femur. These measurements and derived quantities provide quantitative measures of bone quality. A slight peak (2% greater than reference) was determined for the density and a slightly larger peak (5% above reference) for the longitudinal sonic velocity at a dosage of approximately 20 mg/kg/day. The longitudinal elastic modulus exhibited a substantial peak, 14% greater than reference. The relative static load stress showed a very slight peak as a function of dosage and also as a function of fluoride concentration in the bone. When plotted against the elastic modulus, a nonlinear monotonic increase was observed with modulus, showing that the cross-sectional area of the bone is responsive to the stiffness of the tissue. Stiffer tissue produces a smaller cross section, whereas a more compliant tissue requires a marked increase in the area.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of some properties of mineralized turkey leg tendon

Several macroscopic physical properties of mineralized turkey leg tendon were measured including wet density, composition, volume fractions of the major components, sonic velocity in three axes, longitudinal modulus and dimensional changes on drying. Where possible the properties were related to density. Typically the wet density of unmineralized tissue is 1.09 g/cc, where for fully mineralized tissue it is 1.6 g/cc (compared with 2.06 to 2.10 g/cc for compact cow bone). Longitudinal sonic velocity axially is 3.22 km/sec, 2.57 km/sec transversely and 2.21 km/sec in thickness. The axial longitudinal modulus is 16.7 GPa compared to the axial Young's modulus of 8.53 GPa. MTLT shrinks 0.5% axially, 4.75% transversely and 4.15% in thickness. The anisotropy is equally exhibited in its microscopic structure when observed optically. Least squares second order curves were fitted to the water, mineral and organic component experimental values. Apparently the water in MTLT is replaced by mineral, unlike the process in bone where there is less organic matter as the mineral content increases and the water fraction changes much less. The generalized packing model for collagen was used to relate the data to the ultrastructure. The distribution of the major components between the intrafibrillar and extrafibrillar volumes as a function of the density was calculated. The results show the intrafibrillar volume fraction increases with density, the water content of the intrafibrillar volume remains almost constant, but the water fraction of the extrafibrillar volume decreases from 51 to 8% of the water in the tissue. It is concluded that the mineralization process in MTLT differs from that in bone.

The design of a stress-management programme for nursing personnel

This study identifies the stressors and coping strategies of nursing staff (students, trained staff and those who had left the profession before qualification) in a variety of ward specialisms. The research instruments included an open-ended interview concerning pre-nursing experience, perceived stressors and satisfactions, and ways of coping, and psychometric tests of self-esteem, assertion, ways of coping and personality. The five most frequently cited stressors were understaffing, conflict with nurses, dealing with death and dying, overwork and conflict with doctors. Experience of stressors was related to role and seniority of respondents, with different aspects of the same stressor differentially affecting nurses at different levels of experience. Coping strategies also depended on experience. Trained staff showed more use of problem-focused ways of coping, whilst students and leavers relied more on emotion-focused strategies to deal with stressful situations. These differences were related to personality characteristics of respondents and to self-esteem as well as to situational characteristics of the stressful episode. Social support was important in times of work-related stress, with students in particular making good use of peer group support. Respondents were generally lacking in assertiveness and high in anxiety. Although self-esteem was generally high, leavers scored markedly less than other subject groups in the areas of personal and social self-esteem. Leavers had little prior knowledge or experience of nursing before entering training and knew few nurses or doctors: consequently, nursing failed to meet their expectations. Stress was identified as the major cause of attrition and the sources of stress are identified. This study informed a major programme of stress-management training for student nurses which began in 1988 at the North Wales School of Nursing and which is currently under evaluation. It includes relaxation therapy, assertiveness training, and on-going group discussions which foster peer-group support and which explore the stressors and coping strategies relevant to different stages of training and ward specialisms.

BAPN dose dependence of mature crosslinking in bone matrix collagen of rabbit compact bone: corresponding variation of sonic velocity and equatorial diffraction spacing

Crosslinking density in demineralized bone matrix collagen was found to depend on the beta-aminopropionitrile (BAPN) dose level for compact bone from rabbit femurs. The dependence was demonstrated for the hydroxypyridinium (HP) concentration, a mature crosslink. A more consistent dependence on BAPN dosage was observed for the fraction of the demineralized bone matrix insoluble in 0.5 M acetic acid (AIF) corresponding to the remaining crosslinked collagen. The average HP concentration in 21 week old controls was 0.24 moles HP/mole collagen which decreased to 0.13 +/- 0.04 for the same age rabbits dosed with 1 gm BAPN/kg/day for 13 wks. The comparable mean AIF values were 0.91 for controls and 0.75 for maximum dose level. Most of the effect of BAPN on crosslinking was observed at the lower dosages below 0.2 g/kg/day. On the other hand, overt osteolathyritic symptoms are seen only for BAPN dosages greater than 0.2 g/kg/day. The mean sonic plesio-velocity was previously found to decrease from 3.4 to 3.03 km/sec as the BAPN dosage was increased. A similar close relationship was discovered for the equatorial diffraction spacing in fully mineralized bone which increased from 1.235 for normal rabbit bone to 1.28 nm for maximum dose. Most of the effect on these physical properties is exhibited at the highest BAPN dosage after much of the decrease in mature crosslinking density has been observed and when the further decrease in mature crosslinking density proceeds very slowly with increased drug dosage. These observations suggest that osteolathyrism does not become manifest until practically all mature crosslinking that can be affected has been inhibited. The mineralization process apparently can be maintained in the newly laid collagen even in the presence of severe osteolathyritic conditions. Intermolecular crosslinking in bone collagen appears to play an important role in the development of bone properties whether by direct or indirect processes. Much of the effects on bone properties occur at the higher BAPN dosages where overt osteolathyrism is observed and where there seem to be only small changes in crosslinking density.

Studies of compact hard tissues and collagen by means of Brillouin light scattering

A measure of the elastic properties of tissue can be found from the propagation of sound in the tissue. Longitudinal sonic velocities were measured for mineralized turkey leg tendon (density 1.50 g/cc), deer antler (1.77 g/cc) and cow tibia (2.05 g/cc) in the 10 GHz frequency regime by means of Brillouin light scattering using a nine pass Fabry-Perot interferometer. Wet, air dried, mineralized and demineralized specimens were tested. Sonic velocity in each tissue increased with mineral content and decreased when the tissue was wet. All wet values are higher than for wet rat tail tendon collagen, axially and radially, but with considerably less anisotropy. The results are interpreted to indicate that bone matrix collagen is more highly crosslinked than tail tendon collagen. The loss of anisotropy is taken to correspond to a much higher crosslinking density between adjacent collagen molecules in mineralized tissue compared to rat tail tendon. The axial sonic velocity of dried rat tail tendon is almost that for low density dried mineralized tissue and greater than the radial sonic velocity of these tissues, but the radial sonic velocity for dried rat tail tendon is much lower, again corresponding to less crosslinking in this tissue. Longitudinal modulus, K, is defined as the tissue density times the square of the velocity. The compliance, 1/K, was found to be a linear function of density for each of the four conditions. It suggests that a Reuss formalism describes the elastic properties. Since the difference between the compliance for wet and dry tissue is also a linear function of density, the effect of water on the compliance is additive. The axial sonic velocity for cow bone is essentially constant over a frequency range spanning 10 orders. Presumably the axial sonic velocity is controlled by the continuity of the collagen fibers lying along the bone axis. The radial velocity decreases by 30% over this frequency range, probably due to the many levels of structure observed in long bone like osteons, Haversian canals and blood vessels, as well as internal surfaces like cement lines and between lamellae. The sonic anisotropy of hard tissues decreases considerably with increasing frequency. While rat tail tendon collagen is very anisotropic both sonically and optically, hard tissues whether wet, dry, mineralized or demineralized show much less anisotropy. The optical index of refraction, both axially and radially, was found by Brillouin scattering for the air dried demineralized tissues. A close match was found between optical and sonic anisotropy for all the demineralized tissues.

The locus of mineral crystallites in bone

The organic content of mineralized tissues has been found to decrease with increasing tissue density, from about 60% of the mineral weight in light bone like deer antler to 1 to 2% in hyperdense bone like porpoise petrosal. The ratio of the weight of mineral that can fill the collagen hole zones to the total mineral content can be no greater than 20% for deer antler and decreases to less than 5% for hyperdense bone. Moreover, the dimensions of hydroxyapatite crystallites have been determined by various investigators to be larger than the intermolecular spacing of collagen molecules. Such crystallites can only be fitted within the collagen fibril if collagen molecules are packed differently from the accepted models. Electron micrographs of fish dentin, at a very early stage of mineralization, show the needle-like crystallites lying in dense strips between collagen fibrils and practically no crystallites within the fibrils. A similar pattern of dense strips of crystallites between fibrils can be identified in examples from more advanced stages of mineralization, taken from fish dentin, cat dentin and cow tibia, even though some of the needle-like crystallites are superimposed on the fibril banded pattern. In every instance there are regions of the fibrils where there are no visible needle-like crystallites. Examination of the work of others shows a similar distribution of the mineral component, except that none exactly resemble the micrograph of the earliest stage of fish dentin provided in this report. The collagen banding is observed to be in spatial phase over many fibrils. The needle-like crystallites may be observed to be bunched in phase with the collagen banding and with the same spatial periodicity. The bunching is most obvious in the least densely mineralized specimens. This observation can account for the x-ray and neutron diffraction patterns which shown the axial period of the mineral to be like that of the collagen axial macroperiod and to be in phase with the hole zones of collagen fibrils. These prior studies were interpreted to show that the crystallites must be within the hole zones. Our images are interpreted to show that most of the mineral is outside of the collagen fibrils in the extrafibrillar volume. The interpretation is in agreement with neutron diffraction studies of various mineralized tissues as well as with earlier diffraction studies of mineralized turkey leg tendon and with the calculations of the amount of mineral that can be contained within the collagen of mineralized tissue.

Vapor pressure isotherms, composition and density of hyperdense bones of horse, whale and porpoise

Water adsorption studies of three types of hyperdense bone show vapor pressure isotherms and enthalpy to be different from that for pure apatitic mineral. The mineral content of these bones varied from 80 to 98%, much greater than for the better known cortical bone. The high mineral content of all these bones and the variation of mineral content from one type of bone to the next make it possible to evaluate the contribution of the mineral component in bone to water adsorption. Both water content and the fractional shrinkage when dried decrease with increasing mineral content of the bone and increase with the organic component. The total water content of hyperdense bone is much less than the maximum water adsorbed by the equivalent pure mineral powder or by anorganic bone. It was concluded that: (1) Very little water appears to be adsorbed by the mineral in hyperdense bone; (2) It is likely that the mineral crystallites are coated with noncollagenous organic matter; (3) Water is taken up by organic matter both intra- and extrafibrillar; and (4) the enthalpy associated with the adsorption of water by HAP is higher than for hyperdense bone at all corresponding vapor pressures.

Considerations regarding the structure of the mammalian mineralized osteoid from viewpoint of the generalized packing model

The relative magnitudes of mineral, organic and water contents of dense mammalian bone are calculated by a new theory based on recent findings: (1) The neutron diffraction studies of mineralized tissues with different densities demonstrated an inverse relationship between wet density and the equatorial diffraction spacing of the collagen. (2) The neutron studies showed there was very little mineral within the collagen fibrils. (3) A generalized packing model for collagen has been advanced to show how the equatorial spacing can be varied depending on tissue type, water content, and mineral content. (4) The water content of collagen fibrils when calculated from the generalized packing model matches the experimentally determined values for rat tail tendon fibers, bone matrix, and fully mineralized bone. A computational model was developed based on the generalized packing model. It provides a unifying approach to explain many features of mineralized fibrous collagenous tissues. The results are presented as estimates of the mineralized collagen fibril density, the volume fraction of collagen in bone, the density of the extrafibrillar space, the fraction of the e.f. space occupied by mineral and the ratio of mineral within collagen to total mineral content, each expressed as a function of wet bone density. A useful data base, available from previous studies, related mineral, organic and water weight fractions to wet bone density, for a density range from 1.7 g/cc for deer antler to 2.7 g/cc for porpoise petrosal. A second order polynomial was found for each weight fraction component, with bone density as the input variable, with a standard deviation less than 2% of total bone weight. This permits the bone properties to be related to a single variable, the wet bone density. It is seen that compacting the collagen fibrils as well as reducing the organic component weight fraction are two important factors determining the structure of the mineralized osteoid. It was concluded that voids and pore spaces may occupy at least 5% of the bone volume.

An unusual intracellular infection in ducks

An infection causing mortality was encountered on seven occasions in Muscovy (Cairina moschata) and domestic ducks (Anas platyrhynchos domestica). In all cases the principal lesion was a severe pneumonitis associated with the presence of numerous organisms in the cytoplasm of the blood capillary endothelial cells. Cultural examination for bacterial and fungal agents consistently failed to yield significant isolates. In tissue sections the organisms were poorly stained by haematoxylin and eosin but were strongly positive to the periodic acid-Schiff and periodic acid-silver methenamine methods. Electron microscopy showed round (0.5 microm to 1.0 microm diameter) or oval (1 microm x 1.7 microm) forms possessing a complex cell wall, cytoplasmic lamellar bodies and an apparently membrane-bound nuclear structure. On the available evidence, the identity of the organism and its classification as either a prokaryote or eukaryote were not resolved.

Equatorial diffraction spacing as a function of water content in fully mineralized cow bone determined by neutron diffraction

Variation of the equatorial diffraction spacing of soft type I collagen tissues with water content using X-rays has been known for many years. Recently, a generalized model for collagen molecule packing within fibrils was deduced from this information for different collagenous tissues. It is now known that the eq. diff. sp. of mineralized tissues can be less than for soft tissues and is inversely dependent on the wet density. A determination of the eq. dif. sp. dependence on water content using neutron diffraction of fully mineralized cow bone was undertaken for comparison. Specimens with various partial water content between 0 and 100% were tested. Data show collagen molecules pack more closely together as water content decreases, just as for soft tissues.

Major histocompatibility complex restriction fragment length polymorphisms define three diabetogenic haplotypes in BB and BBN rats

Class I and II major histocompatibility complex (MHC) probes can be used to subdivide diabetes-prone BB rats and their BBN control strain, coderived from the same outbred colony by selection against diabetes. Class II probes (A-alpha in particular) distinguish four restriction fragment length polymorphisms (RFLP), termed 1a, 1b, 2a, and 2b, in the BBN population, only one of which (2a) is found in BB rats. The degree of class II RFLP in the population studied is RT1.B-alpha greater than or equal to RT1.B-beta greater than RT1.D-alpha greater than or equal to RT1.D-beta, suggesting that intra-class II region dynamics may be different in rats compared with mice. A class I probe (S16) absolutely distinguished BB from BBN rats, since all BB rats exhibit an RFLP pattern termed 2a0, while 2a BBN rats can be subdivided into 2a1 and 2a2 forms. Serologic evaluation has shown that 2a0, 2a1, and 2a2 rats express RT1.AuBu, 1a rats express RT1.AaDa, and 1b rats express neither RT1a nor RT1u at the loci tested. A breeding study was carried out to determine the diabetogenicity of the MHC-defined RFLP's. As expected, the BB-derived 2a0 is diabetogenic. The BBN-derived 2a1 and 2a2 RFLPs are also diabetogenic, while 1a and 1b rats do not carry MHC-linked diabetogenic genes. The MHC-linked diabetes gene acts in a functionally recessive manner, since there is a 10-fold higher incidence in homozygotes than in heterozygotes. Analysis of the RFLP patterns leads us to hypothesize that the 2a1 RFLP results from a crossover between 1a and 2a0 MHCs and that the diabetogenic MHC-linked gene is on the class II side of Qa and T1. The availability of three diabetogenic MHC haplotypes should help localize the MHC-linked diabetogenic gene of rats.