Condition monitoring of rotary blood pumps

Long-term, trouble-free operation of ventricular assist devices (VADs) is critical to the patient. A catastrophic failure of the VAD could cost the patient's life, thus defeating the purpose of the device. The targeted 90% 5 year reliability also implies that the average device life would exceed the 5 year limit. Time based explantation of the device after the fifth year will replace many devices with significant additional life, subject the patient to unnecessary surgical risk, and increase costs. To preclude the need for time based replacements and prevent catastrophic failures, a condition monitor is proposed in this article for early detection of faults in VADs. To develop this monitor, the effectiveness of various sensing and monitoring methods for determining the VAD condition is investigated. A Hemadyne pump was instrumented with a set of eight sensors, and a series of experiments were performed to record and analyze signals from the normal and abnormal pumps with five different faults. Statistical, spectral, envelope, and ensemble averaging analyses were performed to characterize changes in sensor signals due to faults. Experimental results indicate that statistical and frequency information from the acceleration and dynamic pressure signals can clearly detect and identify various VAD faults.

The expression of voltage-dependent calcium channel beta subunits in human cerebellum

The beta subunits of voltage-dependent calcium channels, exert marked regulatory effects on the biophysical and pharmacological properties of this diverse group of ion channels. However, little is known about the comparative neuronal expression of the four classes of beta genes in the CNS. In the current investigation we have closely mapped the distribution of beta1, beta2, beta3 and beta4 subunits in the human cerebellum by both in situ messenger RNA hybridization and protein immunohistochemistry. To our knowledge, these studies represent the first experiments in any species in which the detailed localization of each beta protein has been comparatively mapped in a neuroanatomically-based investigation. The data indicate that all four classes of beta subunits are found in the cerebellum and suggest that in certain neuronal populations they may each be expressed within the same cell. Novel immunohistochemical results further exemplify that the beta voltage-dependent calcium channel subunits are regionally distributed in a highly specific manner and studies of Purkinje cells indicate that this may occur at the subcellular level. Preliminary indication of the subunit composition of certain native voltage-dependent calcium channels is suggested by the observation that the distribution of the beta3 subunit in the cerebellar cortex is identical to that of alpha(1E). Our cumulative data are consistent with the emerging view that different native alpha1/beta subunit associations occur in the CNS.

Differential localization of voltage-dependent calcium channel alpha1 subunits at the human and rat neuromuscular junction

Neurotransmitter release is regulated by voltage-dependent calcium channels (VDCCs) at synapses throughout the nervous system. At the neuromuscular junction (NMJ) electrophysiological and pharmacological studies have identified a major role for P- and/or Q-type VDCCs in controlling acetylcholine release from the nerve terminal. Additional studies have suggested that N-type channels may be involved in neuromuscular transmission. VDCCs consist of pore-forming alpha1 and regulatory beta subunits. In this report, using fluorescence immunocytochemistry, we provide evidence that immunoreactivity to alpha1A, alpha1B, and alpha1E subunits is present at both rat and human adult NMJs. Using control and denervated rat preparations, we have been able to establish that the subunit thought to correspond to P/Q-type channels, alpha1A, is localized presynaptically in discrete puncta that may represent motor nerve terminals. We also demonstrate for the first time that alpha1A and alpha1B (which corresponds to N-type channels) may be localized in axon-associated Schwann cells and, further, that the alpha1B subunit may be present in perisynaptic Schwann cells. In addition, the alpha1E subunit (which may correspond to R/T-type channels) seems to be localized postsynaptically in the muscle fiber membrane and concentrated at the NMJ. The possibility that all three VDCCs at the NMJ are potential targets for circulating autoantibodies in amyotrophic lateral sclerosis is discussed.

Immunohistochemical and in situ mRNA hybridisation techniques to determine the distribution of ion channels in human brain: a study of neuronal voltage-dependent calcium channels

The molecular, structural and functional characterisation of ion channels in the CNS forms an area of intense investigation in current brain research. For strategic and logistical reasons, rodents have historically been the species of choice for these studies. The examination of human CNS tissues generally presents the investigator with specific challenges that are often less problematic in animal studies, e.g. post-mortem delay/agonal status, and thus both the experimental design and techniques must be manipulated accordingly. Since much pharmaceutical interest is currently focused on neuronal ion channels, the examination of their expression in human brain material is of particular importance. We describe here the details of methods that we have developed and used successfully in the study of the expression of voltage-dependent calcium channels (VDCCs) in human CNS tissues. Presynaptic neuronal VDCCs control neurotransmitter release and are important new drug targets. They are composed of three subunits, alpha 1, beta and alpha 2/delta and multiple gene classes of each protein have been identified. Little is known, however, about the distribution of neuronal VDCCs in the human central nervous system, although initial studies have been performed in rat and rabbit.

Preparation and purification of antibodies specific to human neuronal voltage-dependent calcium channel subunits

Neuronal voltage-dependent calcium channels (VDCCs) each comprising of alpha 1, alpha 2 delta, and beta subunits, are one mechanism by which excitable cells regulate the flux of calcium ions across the cell membrane following depolarisation Studies have shown the expression of several alpha 1 and beta subtypes within neuronal tissue. The comparative distribution of these in normal human brain is largely unknown. The aim of this work is to prepare antibodies directed specifically to selected subunits of human neuronal VDCCs for use in biochemical and mapping studies of calcium channel subtypes in the brain. Previous studies have defined DNA sequences specific for each subunit Comparison of these sequences allows the selection of unique amino acid sequences for use as immunogens which are prepared as glutathione-S-transferase (GST) fusion proteins in E. coli. Polyclonal antibodies raised against these fusion proteins are purified by Protein A chromatography, followed by immunoaffinity chromatography and extensive adsorptions using the appropriate fusion protein-GST Sepharose 4B columns. The resultant antibodies are analysed for specificity against the fusion proteins by ELISA, and by immunofluorescence and Western immunoblot analysis of recombinant HEK293 cells stably transfected with cDNAs encoding alpha 1, alpha 2 delta and beta subunits.

The effect of delta-gluconolactone, an oxidised analogue of glucose, on the nonenzymatic glycation of human and rat haemoglobin

Nonenzymatic glycation of proteins and oxidative stress are considered independent factors important in the development of the complications of diabetes but may be interrelated by the process of autoxidative glycation. This pathway involves monosaccharide autoxidation to a reactive ketoaldehyde analogue and subsequent reaction with protein to form a ketoimine adduct. This study demonstrates that delta-gluconolactone (delta-GL), an oxidised analogue of glucose, is a potent glycating agent in vitro of haemoglobin present in blood samples from insulin-dependent diabetic and non-diabetic human subjects and from spontaneously diabetic, insulin-dependent BB/Edinburgh (BB/E) rats. The percentage glycated haemoglobin after incubation (37 degrees C, 5 h) with delta-GL (25 mmol/l) was significantly (P < 0.002) higher than that observed using an equimolar concentration of glucose. Intravenous administration of delta-GL (1 g/kg) to non-diabetic BB/E rats also significantly increased glycation of haemoglobin (6.0 +/- 0.1% vs 4.9 +/- 0.1%, P < 0.01) whereas intravenous injection of an identical dose of glucose had no significant effect (5.1 +/- 0.1% vs 5.0 +/- 0.2%). These results support the hypothesis that nonenzymatic glycation of proteins involves attachment by both native and oxidised monosaccharides. Further investigation of the interactions between diabetes-associated increases in oxidative stress and glycation on the development and progression of the vascular complications of diabetes is necessary.

Prevalence and associations of epiretinal membranes. The Blue Mountains Eye Study, Australia

PURPOSE

The purpose of the study is to determine the prevalence and associations of epiretinal membranes in a defined older Australian population and to assess their influence on visual acuity.

METHODS

Three thousand six hundred fifty-four persons 49 years of age or older, representing 88% of permanent residents from an area west of Sydney, underwent a detailed eye examination, including stereo retinal photography. Epiretinal membranes were diagnosed clinically and from photographic grading.

RESULTS

Signs of epiretinal membranes were found in 243 participants (7%; 95% confidence interval [CI], 6.1, 7.6), bilateral in 31%. The prevalence was 1.9% in persons younger than 60 years of age, 7.2% in persons 60 to 69 years of age, 11.6% in persons 70 to 79 years of age, and 9.3% in persons 80 years of age and older, with slightly higher rates in women. Two stages were identified: an early form without retinal folds, termed "cellophane macular reflex" present in 4.8%, and a later stage with retinal folds, termed "preretinal macular fibrosis" (PMF), found in 2.2% of the population. Preretinal macular fibrosis, but not cellophane macular reflex, had a small, significant effect on visual acuity. Preretinal macular fibrosis was significantly associated with diabetes, after age-gender adjustment, in subjects without signs of diabetic retinopathy (odds ratio, 3.2; 95% CI, 1.4, 7.2). Preretinal macular fibrosis also was associated with increased fasting plasma glucose (odds ratio, 1.2; 95% CI, 1.1, 1.3). Epiretinal membranes were found in 16.8% of persons who had undergone cataract surgery in one or both eyes (including PMF in 3.7%), in 16.1% of retinal vein occlusion cases (PMF in 12.5%), both significantly higher rates than in subjects without these conditions (P < 0.0001), and in 11% of persons with diabetic retinopathy (PMF in 3.6%), not significantly higher (P = 0.17).

CONCLUSIONS

This study has documented the frequency and mild effect on vision of epiretinal membranes in an older population. Diabetes was associated significantly with idiopathic cases, whereas well-known associations with past cataract surgery and retinal disease were confirmed.

Cytotoxic T-cell clone against rectal carcinoma induced by stimulation of a patient's peripheral blood mononuclear cells with autologous cultured tumor cells

In an effort to establish cytolytic T lymphocytes (CTLs) against colorectal carcinoma (CRC) by stimulating patients' lymphocytes with autologous tumor cells, we used peripheral blood mononuclear cells (PBMC) from a patient with minimal residual rectal carcinoma following removal of the primary lesion and involved regional lymph nodes as a source to generate CTLs in culture. A CTL line and clone were established from the patient's PBMC following stimulation of PBMC with autologous, cultured tumor cells and interleukin-2. The CTL line and the clone consisted predominantly of CD4+ lymphocytes. The CTL clone expressed two T-cell receptor variable alpha chains (V alpha11 and V alpha22) and one beta chain (Vbeta14). The cytokine secretion pattern of the CTL line was of the Th1-type. Both the CTL line and the clone lysed the autologous rectal carcinoma cells, but not the allogeneic, partially human lymphocyte antigen (HLA)-matched or nonmatched CRC cells, autologous Epstein-Barr virus-transformed B cells, K562 (natural killer target) cells or Daudi (lymphokine-activated killer target) cells. Lysis of autologous tumor cells most likely was HLA class I-restricted. Our unique success in generating CTLs against this tumor type may rest in the inclusion of a patient with minimal residual, rather than advanced, disease.

Gender, oestrogen, hormone replacement and age-related macular degeneration: results from the Blue Mountains Eye Study

PURPOSE

To determine whether females have a higher age-specific age-related maculopathy prevalence than males; whether there is an increased risk of age-related macular degeneration (AMD) with early menopause; and whether there is a decreased risk of AMD with use of hormone replacement therapy (HRT).

METHODS

Pooled data from three study populations that have used similar AMD diagnostic criteria were used to answer the first hypothesis: the Beaver Dam Eye Study (BDES), the Rotterdam study of the elderly, and the Blue Mountains Eye Study (BMES). The BMES population was used to answer the second and third hypotheses. This population included residents aged 49 or older with 2072 women participating, of whom 1899 postmenopausal women answered questions about menopause, menarche and HRT. AMD was diagnosed from graded retinal photographs using modified international criteria.

RESULTS

The overall pooled odds ratio (OR) for association between sex and AMD revealed a significant increase in AMD prevalence among females compared with males, adjusting for 10-year age categories, OR = 1.15 (1.10-1.21), with no significant heterogeneity between studies. A significant decrease in the odds of early AMD with increasing years from menarche to menopause was observed.

CONCLUSIONS

The results suggest that females may have a higher risk of AMD. The significant decrease in early AMD with increasing years from menarche to menopause supports the concept that a shorter duration of oestrogen production may increase risk of AMD.

Relationship between cup-disc ratio and optic disc diameter: the Blue Mountains Eye Study

PURPOSE

To determine the effects of optic disc size on vertical cup-disc ratio in subjects free of glaucoma and other optic nerve disease.

METHODS

Data were collected from 3654 people, 49 years of age of older, living in the Blue Mountains, west of Sydney (NSW, Australia). Examinations performed included subjective refraction and Zeiss colour stereo optic disc photographs. Eye and camera magnification effects were corrected.

RESULTS

Mean vertical disc diameter was 1.51 mm (95% confidence interval (CI) 1.504-1.516 mm) and the mean vertical cup-disc ratio was 0.43 (95% CI 0.425-0.435). Both parameters were distributed unimodally. The cup-disc ratio was strongly associated with disc diameter. Controlling for other variables, cup-disc ratio increased 0.270 (95% CI 0.250-0.290) per mm increase in disc diameter.

CONCLUSIONS

Vertical optic disc diameter and cup-disc ratio are distributed near normally in older Australians. Optic discs with larger vertical diameters have considerably greater vertical cup-disc ratios.

The diagnostic and treatment approach to two common conditions by the physician members of a community health maintenance organization

We retrospectively collected data from one community managed care organization on all ambulatory care patients initially diagnosed with pneumonia or acute bronchitis from October, 1, 1992, to March 31, 1993, and from November 1, 1993, to January 31, 1994. We considered treatment to be successful when patients did not return for any related service within 15 days of initial diagnosis. We identified 2,490 episodes of illness, 85.7% which were acute bronchitis and 14.3% which were pneumonia. Overwhelmingly, physicians approached these conditions empirically (no diagnostic test); just 8.6% of patients had a diagnostic test during the 15-day episode of illness. Two-hundred twenty-nine of the episodes (9.2%) were apparently related to initial diagnoses, as they occurred during the 15-day period. More branded prescriptions (vs. generic) were dispensed during these related episodes. One patient was hospitalized and 19 patients used the emergency room either for first or subsequent visits. Empiric treatment is associated with effective diagnosis and therapy in ambulatory care patients with acute bronchitis and pneumonia. It remains unclear, however, if this strategy is the most cost-effective or if it leads to the most effective utilization of services.

Functional effects of polymorphisms of house dust mite allergens

BACKGROUND

Sequence polymorphisms have been found in cDNA clones of commercial house dust mites. Here we report on the polymorphisms of Der p 1 found in environmental mites and the effect of the polymorphisms on T cell proliferation.

METHODS

Sequences were obtained from DNA amplified from single mites by PCR. Synthetic peptides were used to stimulate peripheral blood cells.

RESULTS

The polymorphism was limited to a few residues, but regional differences were detected in mites in Wagga. T cells were specific for the polymorphisms, so that in 16 of 17 responses, stimulation was achieved with one form of the peptide. This included peptides with Ala and Val at position 124 in the immunodominant 110-133 region. Peptide 45-63 also stimulated frequently, but only with Tyr at position 50 and not His, a residue only found in commercial mites.

CONCLUSIONS

Polymorphisms of Der p 1 are found in the environment and have a profound effect on polyclonal T cell stimulation to frequently recognised epitopes.

The development of Ca2+ channel responses and their coupling to exocytosis in cultured cerebellar granule cells

Using single-cell imaging, we investigated developmental changes in the modulation of KCl-evoked Ca2+ entry by various voltage-dependent Ca2+ channels and the coupling of these channels to exocytosis in cultured cerebellar granule neurons. A component of the KCl-evoked Ca2+ elevation sensitive to nifedipine and localized at cell somata, decreases with culture age. A component blocked by 200 nM omega-Agatoxin-IVA increases with age and whilst localized primarily at the cell somata, also becomes evident at the neurites. The change in activity between nifedipine-sensitive Ca2+ channels and omega-Agatoxin-IVA-sensitive Ca2+ channels occurs at 13 days in vitro at cell somata. A component of Ca2+ entry insensitive to nifedipine and 200 nM omega-Agatoxin-IVA is localized primarily at the neurites and is apparent at all ages. Single-cell imaging of exocytosis using FM1-43 destaining indicates that the residual, but not the nifedipine- or omega-Agatoxin-IVA-sensitive components of Ca2+ entry, modulates exocytosis. However cells cultured for 20-26 days develop a component of Ca2+ entry at the neurites which is sensitive to 200 nM omega-Agatoxin-IVA and omega-Conotoxin-MVIIC and which partially controls release. Immunolocalization studies reveal that binding sites for omega-Conotoxin-GVIA are present throughout development, even though this toxin does not inhibit KCl-evoked [Ca2+]c elevations or exocytosis. 300 nM omega-Agatoxin-IVA labels both somata and, at later developmental stages, neurites, consistent with the functional studies.

Open-angle glaucoma and diabetes: the Blue Mountains eye study, Australia

PURPOSE

The authors explore the relationship between diabetes and open-angle glaucoma in a defined older Australian population.

METHODS

Three thousand six hundred fifty-four people 49 to 96 years of age, living west of Sydney, underwent a detailed eye examination. This included automated perimetry, stereo optic disc photographs, and applanation tonometry; in addition, fasting plasma glucose levels were ascertained. Glaucoma was diagnosed if matching visual field and optic disc cupping were present, without reference to intraocular pressure (IOP) level. Ocular hypertension (OH) was diagnosed if IOP in either eye was > or = 22 mm and glaucomatous disc and visual field changes were absent.

RESULTS

Glaucoma prevalence was increased in people with diabetes, diagnosed from history or elevated fasting plasma glucose level (5.5%), compared with those without diabetes (2.8%; age-gender adjusted odds ratio [OR] 2.12, 95% confidence intervals [CI] 1.18-3.79). Ocular hypertension was also more common in people with diabetes (6.7%), compared with those without diabetes (3.5%; OR 1.86, CI 1.09-3.20). Diabetes was present in 13.0% of people with glaucoma, compared with 6.9% of those without glaucoma. This increase was highest for previously diagnosed glaucoma cases (16.7%; OR 2.82, CI 1.35-5.87). However, in 67% of such cases, glaucoma was diagnosed before the diabetes. For those not receiving glaucoma treatment, IOP was consistently slightly higher in people with diabetes, with the age-gender adjusted mean IOP 0.6 mm higher.

CONCLUSIONS

The significant and consistent association between diabetes and glaucoma found in our study, which appeared independent of the effect of diabetes on IOP, suggests that there is a real association between these two diseases.

Selection bias from sampling frames: telephone directory and electoral roll compared with door-to-door population census: results from the Blue Mountains Eye Study

Many Australian public health research studies use the telephone directory or the electoral roll as a sampling frame from which to draw study subjects. The sociodemographic, disease-state and risk-factor characteristics of subjects who could be recruited using only the telephone directory or only the electoral roll sampling frames were compared with the characteristics of subjects who would have been missed using only these sampling frames, respectively. In the first phase of the Blue Mountains Eye Study we interviewed and examined 2557 people aged 49 and over living in a defined postcode area, recruited from a door-to-door census. This represented a participation rate of 80.9 per cent and a response rate of 87.9 per cent. The telephone directory was searched for each subject's telephone number and the electoral roll was searched for each subject. Subject characteristics for those who were present in each of these sampling frames were compared with the characteristics of those subjects not included in the sampling frames. The telephone directory listed 2102 (82.2 per cent) of the subjects, and 115 (4.5 per cent) had no telephone connected. The electoral roll contained 2156 (84.3 per cent) of the subjects, and 141 subjects (5.5 per cent) could not be found in either the electoral roll or the telephone directory. Younger subjects, subjects who did not own their own homes and subjects born outside of Australia were significantly less likely to be included in either of these sampling frames. The telephone directory was also more likely to exclude subjects with higher occupational prestige, while the electoral roll was more likely to exclude unmarried persons and males. Researchers using the telephone directory and electoral roll to select subjects for study should be aware of the potential selection bias these sampling frames incur and need to take care when generalising their findings to the wider community.

Identification of pore-forming subunit of P-type calcium channels: an antisense study on rat cerebellar Purkinje cells in culture

Treatment of cerebellar neurones in culture with an antisense oligonucleotide (ODN) against alpha1A, reduced the whole-cell P-type calcium channel current relative to mismatch ODN treated controls (p < 0.001). Therefore, AgaIVA (50 nM) reduced whole-cell calcium current in mismatch and antisense treated cells by 70 +/- 4 and 19 +/- 3%, respectively.

Comparison of retention and release periods for implant overdenture attachments

The aim of this study was to compare the retention and release periods of the Nobel Biocare bar and clip (NBC), Nobel Biocare ball (NB), Zest anchor (ZA), Zest magnet (ZM), and Sterngold ERA (SE) attachments on an implant-retained overdenture model. The attachments were tested using two permanently placed Brånemark implants on a test model that was attached to an Instron machine (cross-head speed 50.8 mm/minute). Each attachment had one part embedded in a denture-like housing, and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in two directions simulating function: vertical and oblique. Eight tests were done in two directions with three samples of each attachment. The dislodging forces generated measurements of the peak load, break load, and displacement at peak load and break load. Release periods were calculated using displacements between the peak load and break load and the cross-head speed. Results showed the NBC to be significantly most retentive for the break load when subjected to vertical and oblique forces with mean values and standard deviations of 2104.5 +/- 506.7 g and 1958.1 +/- 165.4 g, respectively. Next most retentive was the SE, followed by the ZA and NB. The ZM was significantly least retentive (127.8 +/- 7.0 g and 143.5 +/- 19.7 g). For the release period, results showed the NBC to have significantly the fastest release period for vertical and oblique forces (1.86 x 10(-3) and 7.35 x 10(-4) minutes). The ZM significantly had the slowest release period for those forces (3.02 x 10(-2) and 2.35 x 10(-2) minutes). The data suggested that the NBC could be selected when a higher degree of retention and fast release period are desired. The next most retentive was the SE; ZM was the least retentive and had the slowest release period.