Bonner sphere measurements of 241Am-B and 241Am-F neutron energy spectra unfolded using high-resolution a priori data

High-resolution neutron energy spectra, covering the entire energy range of interest, for two standard radionuclide neutron sources ((241)Am-B and (241)Am-F) have been derived from Bonner sphere measurements by using high-resolution a priori data in the unfolding process. In each case, two a priori spectra were used, one from a two-stage calculation and also one from a combination of the calculated spectrum with a high-resolution measured spectrum. The unfolded spectra are compared with those published elsewhere and show significant differences from the ISO- and IAEA-recommended spectra for (241)Am-B and (241)Am-F, respectively. Values for the fluence-average energy and fluence-to-dose-equivalent conversion coefficients are presented for the new spectra, and the implications of the new spectra for the emission rates of the sources when measured by the manganese bath technique are also determined.

Bioprospecting keratinous materials

The concept of bioprospecting for bioactive peptides from keratin-containing materials such as wool, hair, skin and feathers presents an exciting opportunity for discovery of novel functional food ingredients and nutraceuticals, while value-adding to cheap and plentiful natural sources. The published literature reports multiple examples of proline-rich peptides with productive bio-activity in models of human disease including tumour formation, hypertension control and Alzheimer’s disease. Bioactive peptides have been identified from food and other protein sources however the bioactivity of keratin-related proteins and peptides is largely unknown. Considering the high representation of proline-rich peptides among proven bioactive peptides, the proline-rich character of keratinous proteins supports current research. A selection of mammalian (cow epidermis, sheep wool) and avian (chicken feather) keratinous materials were subjected to enzymatic hydrolysis using established processing methods. A bio-assay of determining inhibition of early stage amyloid aggregation involved using a model fibril-forming protein – reduced and carboxymethylated bovine K-casein (RCMk-CN) and quantitation of fibril development with the amyloid-specific fluorophore, Thioflavin T (ThT). The assay was fully validated for analytical repeatability and used together with appropriate positive controls. Peptide library products derived from chicken feather (n=9), sheep wool (n=9) and bovine epidermis (n=9) were screened in the fibril inhibition assay based on K-casein. 3 of 27 products exhibited interesting levels of bio-activity with regard to fibril inhibition. HPLC profiles provide an indication of the complexity of the assemblage of peptides in the three active products. We conclude the bioprospecting research using keratinous materials shows promise for discovery of useful bioactive peptides.

Location of Keratin-associated Proteins in Developing Fiber Cuticle Cells using Immunoelectron Microscopy

AIMS

To investigate the location of keratin-associated proteins (KAPs) in developing hair fiber cuticle cells using transmission electron microscopy with immunogold techniques and specific antibodies. Other studies were aimed at detecting the presence of cornified envelope proteins including involucrin and loricrin. MATEIALS AND METHODS: Polyclonal antibodies were produced in rabbits against peptides from KAPS 5.1, KAPS 10.1 ultra high-sulfur proteins.

RESULTS

The KAP proteins were found to form part of the developing exocuticle and a- layer. Cornified envelope proteins (involucrin and loricrin) were absent consistent with recent findings.

CONCLUSIONS

The results have been discussed in terms of a revised model for fiber cuticle surface barriers including their role in fiber cuticle surface function.

Recent developments in radionuclide neutron source emission rate measurements at the National Physical Laboratory

This paper outlines the key features of the new manganese bath facility of the National Physical Laboratory and describes the measurements performed to characterise and validate the facility. Other developments have focused on the use of MCNP to calculate the fraction of neutrons captured by nuclei other than manganese and the fraction escaping from the bath. This has highlighted the large difference in the oxygen(n,alpha) capture fraction when different cross-section evaluations are applied. This can change the value obtained for the neutron emission rate of a source by up to 0.8%.

Characterization and utilization of a Bonner sphere set based on gold activation foils

Bonner sphere (BS) sets which use activation foils as the central thermal neutron sensor have advantages over active BS systems in certain environments, for example, pulsed fields, or fields with high photon components. In such environments, they may be the only type of neutron spectrometer which can be used. This paper describes work, using both measurements and calculations, to validate the response functions for a BS set based on gold activation foils. As an illustration of the use of such a system, a measurement is described of the contaminant neutron spectrum in the treatment room of a 21 MV hospital linear accelerator providing photon beams for radiotherapy.

The content of 250Cf and 248Cm in 252Cf neutron sources and the effect on the neutron emission rate

One of the most common radionuclide neutron sources used for the calibration of detectors is (252)Cf. However, these sources also contain (250)Cf, which is present in the material from which the sources are made, and (248)Cm, which is formed as the daughter of (252)Cf via alpha-decay. Both decay by spontaneous fission with longer half-lives than (252)Cf. Consequently, as the source becomes older, the emission rate does not follow the decay curve of (252)Cf. Fits have been made to emission rate measurements of (252)Cf sources at NPL spanning over 30 y to deduce their (250)Cf and (248)Cm content. The emission rate of a source can be significantly underestimated if the presence of (250)Cf and (248)Cm is not taken into account, and this has been investigated for a typical (252)Cf source. The importance of this problem to other calibration laboratories and users of (252)Cf sources is emphasised.

Modelling of neutron survey instrument performance and experimental validation of those calculated response data

Three moderator-type neutron survey instruments have been modelled for energy and angle dependence of the response, in greater detail than before. These response data have been verified by comparison with published experimental measurements and measurements made specifically for this project. Influences on the instrument response have also been investigated. These have included its mode-of-use and perturbations caused by variations in the instrument manufacture. The implications of these new response data have been assessed by an extensive programme of folding the responses with workplace energy distributions.

Angle dependence of response characteristics of neutron survey instruments

Neutron area survey instruments are designed to have an approximately isotropic response. In practice, the response cannot be perfectly isotropic for instruments that do not have spherical symmetry, and for all instruments it is modified by the inclusion of batteries, electronics, handles, etc. This affects the ability of the survey instrument to measure accurately an isotropic dose equivalent quantity. Measurements of the angle dependence of response for four of the most commonly used designs of survey instrument (Harwell 0949, Mark 7 NRM, NM2 and Studsvik 2202D) have been performed in a low-scatter room using radionuclide and monoenergetic neutron sources. The Monte Carlo code MCNP has been used to model the responses and to investigate their sensitivity to the polyethylene density, counting gas pressure and other manufacturing tolerances. Preliminary modelling results are presented here.

Practical implications of neutron survey instrument performance

Improvements have been made to the Monte Carlo modelling used to calculate the response of the neutron survey instruments most commonly used in the UK, for neutron energies up to 20 MeV. The improved modelling of the devices includes the electronics and battery pack, allowing better calculations of both the energy and angle dependence of response. These data are used to calculate the response of the instruments in rotationally and fully isotropic, as well as unidirectional fields. Experimental measurements with radionuclide sources and monoenergetic neutron fields have been, and continue to be made, to test the calculated response characteristics. The enhancements to the calculations have involved simulation of the sensitivity of the response to variations in instrument manufacture, and will include the influence of the user and floor during measurements. The practical implications of the energy and angle dependence of response, variations in manufacture, and the influence of the user are assessed by folding the response characteristics with workplace energy and direction distributions.

A novel protocol to identify mutations in patients with wiskott-Aldrich syndrome

Mutations of WASP (Wiskott-Aldrich syndrome protein) underlie the severe immunodeficiency/platelet disorder Wiskott-Aldrich syndrome (WAS) and its milder variant X-linked thrombocytopenia (XLT). The affected gene, a 12-exon structure on the X-chromosome, is expressed exclusively in blood cells. The encoded product WASP is a 502-amino-acid scaffolding protein that functions in stimulus-induced nucleation of actin filaments to form dynamic cell surface projections. To date, more than 150 mutations have been identified in 300 WAS/XLT kindred worldwide, generally through methodologies that include sophisticated exon screening steps such as single-strand conformation analysis. We report here a simpler protocol, which was designed for use in clinical settings to identify the mutations of newly diagnosed patients. The approach relies on directly sequencing amplified exons according to a staggered schedule based on statistical evaluation of previous cases. In a 2 1/2-year trial, samples from 28 consecutive patients were analyzed; these included 3 "blindly labeled" previously studied cases. The mutations that were identified include a broad spectrum (8 missense, 3 nonsense, 5 splice site mutations, 11 small insertion/deletions, 1 large deletion) and were broadly distributed (in 10 of the 12 exons). All mutations were verified and no discrepancies were encountered. Per patient, a mean of six DNA sequencing reactions and 6-7 h of staff effort sufficed for mutation identification and verification, indicating that the protocol is cost-effective. This cumulative experience demonstrates the suitability, reliability, and versatility of the new protocol.

Effect of the proteasome inhibitor ALLnL on cisplatin sensitivity in human ovarian tumor cells

Small molecules suppressing proteasome function inhibit the post-translational ubiquitination of selected proteins. Ubiquitin H2A is an example of an abundant chromatin-associated protein that is known to be ubiquitinated, which is important for several proteins involved in the repair of DNA damage. We therefore studied the effect of the proteasome inhibitor, N-acetyl leucyl-leucyl norlucinal (ALLnL), on cisplatin sensitivity in three human ovarian tumor cell lines. The proteasome inhibitor ALLnL was administered for 4 h before cells were subsequently exposed to cisplatin for 1 h. Our results showed that ALLnL, at its respective IC20 concentration, increased cellular sensitivity to cisplatin in an additive manner in human ovarian cancer A2780, A2780/CP70, and OVCAR3 cells. We also demonstrated that ALLnL caused a 50% increase in total cellular accumulation of cisplatin, and reduced the rate of cisplatin efflux by about 50%. In addition, DNA damage levels were increased after ALLnL treatment. By contrast, DNA repair was inhibited 2 to 3-fold in ALLnL-pretreated cells, as compared to the controls. Furthermore, our study showed that ALLnL deubiquitinated nucleosomal histone H2A in these cells in a concentration-dependent fashion, as assessed by Western blot analysis. These data suggest that sublethal levels of exposure to agents that inhibit proteasome function may alter the subcellular pharmacology of platinum in human ovarian carcinoma cells.

The role of 18-methyleicosanoic acid in the structure and formation of mammalian hair fibres

Although branched chain fatty acids perform many functions in biological systems, the importance of the anteiso 18 methyleicosanoic acid (MEA) has only recently been recognized. In this first review on MEA its role and distribution is explored. MEA has been found in minor amounts in the fatty acid components of a wide range of biological materials, but the current interest results from it being the major covalently bound fatty acid in mammalian hair fibres, a finding which is unusual because protein-bound fatty acids are typically straight-chain, even-numbered acids (C14-C18). MEA is released by surface restricted reagents indicating that it is located exclusively in or on the surface of the cuticle cells, a conclusion that has been verified by analysis of isolated cuticle cells, X-ray photoelectron spectroscopy (XPS) and secondary-ion mass spectroscopy (SIMS) studies support these results in that they show the surface of the cuticle to be predominantly hydrocarbon. When either neutral hydroxylamine or acidic chlorine solutions are applied to hair and wool fibres fatty acids are liberated, indicating the presence of thioester bonds. Calculations, based on fatty acid and amino acid analysis, indicate that approximately one residue in 10 of the cuticular membrane protein is a fatty acid thioester of cysteine. Removal of this covalently linked fatty acid renders the fibre hydrophilic, thus offering a chemical explanation for many technological and cosmetic treatments of mammalian fibres. Examination of the fibre surface and that of isolated cuticle cells by transmission electron microscopy (TEM) confirms the presence of a thin non-staining continuous layer surrounding the cuticle cells. Alkaline treatments which remove the bound fatty acids were found to disrupt this layer. TEM examination of developing hair fibres has indicated that the fatty acid layer on the upper surface and scale edges of the cuticle cell differs from that of the underside of the cell. Similar structural studies of hair from patients with maple syrup urine disease (MSUD) support the findings that thioester-bound MEA is limited to the upper surface of fibre cuticle cells. The current model proposed for the boundary layer consists of crosslinked protein with surface thioester-linked fatty acids, forming a continuous hydrophobic layer on the upper surface and scale edges of the cells.

Intermediate filament structure: hard alpha-keratin

Structurally there are four classes of intermediate filaments (IF) with distinct but closely related axial organisations. One of these, hard alpha-keratin IF, has been studied to clarify several apparently exceptional features which include the number of molecules in the IF cross-section and the mode by which the axial organisation of its constituent molecules is stabilised. Using the dark-field mode of the STEM at the Brookhaven National Laboratory (USA) mass measurements were obtained from unstained IF isolated from hair keratin. The data thus obtained show that the number of chains in cross-section is about 30 (+/-3: standard deviation) and is very similar to the numbers determined in previous STEM experiments for the dominant filament type in other classes of IF (about 32). Furthermore, re-analysis of the low-angle equatorial X-ray diffraction pattern reveals, in contrast to earlier work, solutions that are compatible with the number of chains in cross-section indicated by the STEM data. The absence of the head-to-tail overlap between parallel molecules characteristic of most of IF may be compensated in hard alpha-keratin by a network of intermolecular disulfide bonds. It is concluded that native IF of hard alpha-keratin and desmin/vimentin--and probably many other kinds of IF as well--contain about 32 chains in cross-section, and that the axial structures of these various kinds of IF differ in small but significant ways, while generally observing the same basic modes of aggregation.

Hair keratinization in health and disease

The cells of the epidermis and its derivative, the hair follicle, undergo processes of terminal differentiation that involves the synthesis and assembly of classes of protein and enzymes to form the stratum corneum of the epidermis, and the hair fiber and its cuticle. Using genetic linkage and DNA sequencing methods, we now know that mutations in several genes encoding epidermal keratins or a transglutaminase enzyme cause ichthyosis-related diseases. Similar methods have now suggested that mutations in hair keratin genes underlie some cases of monilethrix, and a deficiency in a cuticle lipid metabolizing enzyme causes maple syrup urine disease. It is to be expected that further application of these methods will elucidate the molecular bases of other genetic hair diseases.

Investigation of structural proteins in human hair defects using anagen follicles

An alternative to using hair specimens for the study of inherited hair shaft defects has been to explore protein compositions in the context of hair formation. Hair follicles were obtained from patients with a hair disorder and the presumptive hair shaft (PHS) separated by microdissection for protein solubilization and electrophoretic experiments aimed at providing a new basis to help explain the mechanism of hair shaft defects. Two-dimensional electrophoresis (fluorographs) of labelled extracts was used to examine the major hair structural proteins and other polypeptide(s) found associated with PHS extracts in normal and aberrant specimens. Changes in either the intermediate filaments (IFs) or matrix polypeptides were not normally found in defective PHS specimens. The polypeptides showing greatest variation were associated with a PHS-specific component which was recently found in normal specimens. The variation in this polypeptide was manifested as multiple spots of different molecular weights. An investigation of the role of PHS-associated polypeptides as a likely part of the hair cross-linking mechanisms, involved examination of a PHS extract from a Menkes' patient. The observations suggest that formation of hair fibre shaft defects may be related to the status of PHS-associated polypeptides which could in turn be influenced by the presence of copper in the hair follicle.

Locations of synthesis of hair structural proteins in human anagen follicles

Live tissue containing cells of the presumptive hair shaft (PHS), was obtained by microdissection of human anagen hair follicles. Whole PHS, as well as PHS further dissected into three levels of hair development, were subsequently used in protein solubilization procedures. Single- and two-dimensional polyacrylamide gel electrophoresis (PAGE) of radiolabelled extracts, with fluorography, enabled comparison of hair and PHS keratin proteins. Fluorographs demonstrated the major classes of protein comprising the intermediate filaments (IF) and matrix of hair keratins. In addition, extracts from various levels of PHS tissue have provided direct evidence for the locations of synthesis of these protein moieties. Thus, IF and matrix proteins are synthesized sequentially in PHS. A previously unobserved polypeptide component, not present in hair extracts, has been identified and found to vary in relative proportions when compared with the major IF and matrix protein classes as PHS cells differentiate to form hair. In the absence of reliable methods for extraction of human hair, PHS provides an alternative source of material, despite the extra burden of follicle collection and specimen preparation. The procedures described provide a new basis for studying human hair defects and are potentially useful for comparing human hair proteins in a variety of situations.

Hairs from patients with maple syrup urine disease show a structural defect in the fiber cuticle

Models for the surface of cuticle cells in hair fibers consist of a monolayer of fatty acids covalently bound to the underlying protein membrane by thioester linkages. The most prominent of these fatty acids is 18-methyleicosanoic acid (C21a), the synthesis of which requires the oxidative decarboxylation of isoleucine. Maple syrup urine disease (MSUD) is caused by an inherited deficiency in the enzyme branched chain 2-oxo acid dehydrogenase, which leads to the accumulation of branched chain alpha-keto-acids derived from the amino acids, leucine, isoleucine, and valine. Transmission electron microscopy studies of developing hair fibers show a structural defect in the fiber shaft in hair from patients with MSUD. This defect is confined to the cuticle of the fiber, where the cuticle membrane directly apposes the intercellular material. Thus, the defect indicates that C21a is located exclusively on the upper surface of fiber cuticle cells. Lipid analysis of MSUD hairs has demonstrated significant changes in the relative abundance of the covalently bound fatty acids and an almost complete absence of C21a, whereas there was little difference in the amino acid composition compared with normal hair. These results provide further evidence for the existence of the surface lipid monolayer and its crucial role in cellular adhesion.

Formation of surface membranes in developing mammalian hair fibres

Mammalian hair fibres result from complex mechanisms involving synthesis, assembly and stabilisation of keratin proteins in the follicle. The developing hair shaft consists of outer cuticle cells surrounding cortical and medullary (optional) cell types. Presumptive fibre cuticle (FC) is contained by the inner root sheath (IRS) consisting of IRS cuticle, Huxley and Henle cells which are in turn enclosed in an outer root sheath (ORS) of epidermal-like cells. In the current structural studies we have used energy filtered transmission electron microscopy (Zeiss 902A) on Merino sheep skin biopsies to examine the fine sequence of morphological changes involved in forming the fibre surface membrane and the associated underlying structural bands comprising the a-layer and exocuticle. Prior to the development of the exocuticle, FC cells demonstrate a typical plasma-membrane apposed to IRS cuticle plasma-membranes separated by an intercellular space. The formation of exocuticular lamellae is followed by degradation of the residual FC surface membrane and the appearance of intercellular laminae demonstrating a stained central band. As maturation continues cleavage between IRS cuticle and FC occurs along this central band liberating hair into the pilary canal. The mature surface consists of keratinized cells containing a well developed exocuticle and a-layer coated with paired lamina (presumably two lipid containing bilayers) of material approximately 10-12 nm thick derived from the intercellular laminae. The current observations show FC surface formation is similar to processes occurring in epidermal stratum corneum and that the cuticle surface membrane of mammalian fibres is not derived from a modified plasma-membrane as previously documented.

Are hypertension or cardiac embolism likely causes of lacunar infarction?

We tested the hypothesis that hypertension is more common and cardiac embolism less common in patients with lacunar infarction than in patients with other types of cerebral infarction. We studied risk factor profiles in a series of 102 consecutive patients with a lacunar infarct and 202 consecutive patients with a carotid artery-distribution infarct involving the cortex registered in the Oxfordshire Community Stroke Project, a community-based study of first-ever stroke. The two groups did not differ in the prevalence of prestroke hypertension (defined in a number of ways) or in the prevalence of markers of sustained hypertension. The presence of atrial fibrillation and a history of myocardial infarction, particularly during the 6 weeks before the stroke, were significantly more common in the group with carotid-distribution infarcts involving the cortex. There was no significant difference in the prevalence of other accepted risk factors for ischemic stroke, including previous transient ischemic attack, cervical bruit, diabetes mellitus, peripheral vascular disease, or cigarette smoking. Our results suggest that hypertension is no more important in the development of lacunar infarction than it is in the development of other types of ischemic stroke that are presumed to be due to atherosclerotic thromboembolism in a major cerebral artery. Our data support the autopsy evidence that cardioembolic occlusion is an unusual cause of lacunar infarction.

Predisposing factors for cerebral infarction: the Oxfordshire community stroke project

The frequency of known causative factors of cerebral infarction was studied in 244 cases of first ever stroke due to cerebral infarction proved by computed tomography or at necropsy who were registered in the first two years of a prospective community based study. Risk factors for cerebral infarction were present in 196 (80%) cases; hypertension in 126 (52%); ischaemic heart disease in 92 (38%); peripheral vascular disease in 60 (25%); a cardiac lesion that was a major potential source of embolism to the brain in 50 (20%); transient ischaemic attacks in 35 (14%); cervical arterial bruit in 33 (14%); and diabetes mellitus in 24 (10%). Thirty one patients (13%) were in atrial fibrillation. Of the 48 patients who were free of risk factors or a major potential cardiac source of embolism at the time of the stroke, 18 were found to have hypertension after the stroke and 10 to have non-atheromatous non-embolic conditions (migrainous cerebral infarction (three), arteritis (two), inflammatory bowel disease (one), arterial trauma (one), autoimmune disease (one), carcinoma of the thyroid (one), and major operation (one). In 20 patients no causative factors could be identified. In this unselected series of patients with first ever stroke due to cerebral infarction most of the strokes were presumed to be due to either atheromatous arterial disease or embolism from the heart, and only 4% (95% confidence interval 2 to 7%) were probably due to non-atheromatous non-embolic causes. This has implications for research into strokes and allocation of public health expenditure.

Cooperative study on the value of long term anticoagulation in patients with stroke and non-rheumatic atrial fibrillation

The benefits of long term anticoagulant treatment of patients with non-rheumatic atrial fibrillation and cerebral infarction were studied by comparing two series of patients with stroke from centres with different policies on anticoagulant treatment. The long term prognosis of 50 patients from the Oxfordshire community stroke project, who did not receive anticoagulants, was compared with that of 70 similar patients from Maastricht, who were treated with anticoagulants. After a mean follow up of 27 months there was no significant difference in either the rate of survival or the rate of recurrent stroke between the two groups. These data suggest that any benefit of anticoagulation is modest. A large randomised trial is planned to establish whether long term anticoagulant treatment is of value and, if so, to what extent.

Studies of developing human hair shaft cells in vitro

Methods for studying aspects of hair formation in vitro have been devised on the basis of isolating developing hair shaft cells. These cells were obtained using a sterile microdissection technique. Plucked anagen follicles were dissected free of surrounding tissues (inner and outer root sheaths), and presumptive hair shaft cells (including germinal epithelia) were cultured directly on mammalian fibroblasts or in media preconditioned by fibroblasts. Specimens were cultured either as dispersions or in whole tissue pieces. Trypsinized whole tissue specimens in culture were sometimes observed to form increased bulk, while dispersed cells appeared to elongate and form larger colonies. In sections of these colonies examined by transmission electron microscopy, intracellular hard keratin intermediate filaments (IFs) together with IF-matrix hard keratin complexes were observed. Radiolabelled cysteine [35S] was added to cultures (3-20 days), showing a continuing but reduced synthesis of hard keratin IF proteins (low-sulfur) over the period of study. Matrix protein (high-sulfur) production was drastically reduced after 3 days. Monoclonal antibodies directed against hair keratin IF components were used in Western transfers and immunofluorescent studies to help assess the specificity of proteins synthesized in culture. Our observations indicate that, with some refinement, the presently described methods enable preparation of hair shaft precursor cells suitable for observing certain hair-forming processes in vitro.

Stroke and migraine in the Oxfordshire Community Stroke Project

A total of 323 cases of first-ever stroke were registered in the first 2 years of the Oxfordshire Community Stroke Project. Of these patients, 244 (76%) had a stroke due to cerebral infarction. There was a past history of migraine headaches in 56 (17%) of the 323 cases of stroke and in 44 (18%) of the 244 cases of cerebral infarction. A past history of migraine headaches was no commoner in patients with stroke due to cerebral infarction than in those with stroke due to intracranial haemorrhage. One hundred and seventy-three (71%) patients with cerebral infarction had at least one risk factor for ischaemic stroke; the frequency of such risk factors was similar in patients with and without a history of migraine. In 7 (3%) of the 244 patients the cerebral infarction was presumed to be "migrainous"; however, only 3 of these 7 (1.2% of the 24) were free of risk factors for ischaemic stroke. If all 7 cases were considered migrainous, the incidence rate of first migrainous cerebral infarction was 3.36 per 100,000 per year (95% confidence limits 0.87-5.86). If only the 3 patients who were free of risk factors were included, the incidence was 1.44 per 100,000 per year (95% confidence limits 0-3.07).

Isolation of intermediate filament assemblies from human hair follicles

We used developing human hair follicle cells for the isolation of hard alpha-keratin structural components. Intracellular dispersions examined by electron microscopy contained both individual alpha-keratin filaments and the tactoid-like filament assemblies observed in situ organized along subfibrillar arms of macrofibrils. The assemblies of average width 47 nm were composed of closely packed alpha-keratin filaments and originated from the initial filament arrays observed in sections of developing mammalian hair follicles. We have distinguished two types of assemblies: the para-like or hexagonally packed and the ortho-like spiral or whorl type. Axial banding extended across the width of filament assemblies, which suggested that hard alpha-keratin filaments pack in lateral register and form a lattice that contains interfilamentous bridges. We observed axial banding patterns with periods ranging from 20 to 22 nm, consistent with the 22-nm periodic structure deduced from x-ray diffraction studies and present in models proposed for hard alpha-keratin and other intermediate filaments. Preliminary biochemical studies of filaments and filament assemblies indicate that they consist of the closely related group of proteins (low-sulfur proteins) ubiquitous among extracts of hard mammalian keratins. Isolated hard alpha-keratin filament assemblies provide a new and valuable structural entity for investigating the assembly mechanisms involved in the formation of the filament-matrix framework found in hard mammalian keratin appendages.

Studies on microfibrils from alpha-keratin

alpha-Keratin microfibrils have been isolated from the presumptive cortex of developing mammalian hair follicles and purified by a centrifugation procedure. They have been obtained on a scale sufficient to enable their physical and chemical nature to be studied directly. The amino acid and protein compositions of the microfibril preparation closely resemble those of the low-sulphur protein fraction extracted from the fully keratinized fibre. High resolution electron microscopy of isolated microfibrils has indicated that they possess structural features in line with those observed in sectioned material.

Hypertension: medical and nursing implications

Hypertension is a major public health problem affecting 20 to 30 million people in the United States, many of whom are undetected, untreated, or inadequately treated. Because hypertension often is asymptomatic for decades, it must be systematically sought out in apparently well persons if the condition is to be treated in its earliest stages and complications prevented. With the recent advent of effective antihypertensive medications treatment is available, once the patient has been diagnosed. Physicians and nurses have a major responsibility to direct the patient into treatment and to assure the effectiveness of his follow-up care. Noncompliance is a direct challenge to everyone seeing the patient. The patient must be motivated to accept and continue therapy through education and, most important, by the establishment of a good interpersonal relationship with the nurse and/or the physician.

The isolation and characterization of alpha-keratin microfibrils

A method of isolating alpha-keratin microfibrils which avoids the degradation previously associated with the use of chemical, physical or enzymic procedures has been developed. Electron microscope studies of the isolation procedure establish that the microfibrils originate from the presumptive cortical cells. A purification procedure, monitored by electron microscopy, has enabled microfibrils to be isolated on a scale sufficient for chemical characterization. The amino acid composition of the microfibrils is very similar to that of low-sulphur protein fractions extracted from a range of hard mammalian keratins and thus provides direct experimental evidence for the assumption that the low-sulphur proteins comprise the microfibril in alpha-keratin.