In vitro evaluation of the dehydration characteristics of silicone hydrogel and conventional hydrogel contact lens materials

PURPOSE

This study investigated the in vitro dehydration performance of silicone hydrogel and conventional hydrogel contact lens materials.

METHODS

In vitro dehydration was assessed using a gravimetric method. The mass loss over time of Focus Night&Day, PureVision, Optima, Acuvue and Proclear Compatibles was measured as the ambient temperature increased from room temperature to 34 degrees C under varying airflow and humidity conditions.

RESULTS

Dehydration data demonstrated a typical ogival form. The results were best fitted with a double exponential, non-linear regression model, which accounted for at least 99% of the variance. Regardless of material, increased airflow had a greater impact on dehydration rate than increased humidity (P<0.05). Relative dehydration amounts were strongly correlated with initial water content (r(2)=0.92), with higher water content materials dehydrating to a greater extent.

CONCLUSIONS

In vitro dehydration studies of conventional and novel silicone-containing hydrogel materials indicated that evaporation rates from materials are predominantly water content related, with only subtle differences between materials of similar water contents being seen. Environmental conditions have a significant impact on in vitro dehydration, with increased airflow having a greater impact than reduced humidity on increasing dehydration rates. In vitro dehydration is closely related to bulk water diffusion rates and, as a result of their low water content, silicone-containing hydrogel materials exhibit low levels of dehydration compared with high water content hydrogel contact lens materials. Further, in vivo studies are necessary to see if the in vitro dehydration behaviour of silicone hydrogel materials is predictive of in-eye performance.

A rapid screen of the severity of mild traumatic brain injury

This study investigated the sensitivity of information processing, recall and orientation tasks to the presence of mild Traumatic Brain Injury (mTBI). Fifty-six (40 male, 16 female) mTBI patients and 85 (57 male and 28 female) controls with orthopaedic injuries were tested within 24 hr of injury in the Department of Emergency Medicine. mTBI patients answered fewer orientation questions and recalled fewer words in delayed recall than orthopaedic patients. mTBI patients judged fewer sentences in 2 min than orthopaedic controls, and female mTBI patients judged fewer sentences than male mTBI patients. Male mTBI patients correctly recalled fewer words during immediate memory and learning than female mTBI patients and orthopaedic controls. Those mTBI patients with a history of previous head injuries did not perform more poorly than those mTBI patients without previous head injuries. These results indicate that tests of speed of information processing, word learning and orientation questions are sensitive to the acute effects of mTBI.

Patient satisfaction with store-and-forward teledermatology

We assessed patient satisfaction with a nurse-led store-and-forward teledermatology service in Manchester. A teledermatology nurse obtained the patient's history, took digital photographs of the patient's skin lesion and then sent the information to a hospital dermatologist, who responded with management advice the following week. Of 141 patients who attended their teledermatology appointment, 123 (50 male, 73 female) completed the study questionnaire (87%). The average age of respondents was 42 years (SD 17, range 18-90 years). Ninety-three per cent reported that they were happy with the teleconsultation while 86% reported that it was more convenient than going to the outpatient clinic. Forty per cent agreed that they would feel more comfortable seeing the dermatologist in person while only 58% were comfortable with not speaking to the dermatologist about their skin condition. The absence of interaction with the dermatologist and the delay in receiving management advice may have contributed to the somewhat low satisfaction rates.

Patient satisfaction with store-and-forward teledermatology

We assessed patient satisfaction with a nurse-led store-and-forward teledermatology service in Manchester. A teledermatology nurse obtained the patient's history, took digital photographs of the patient's skin lesion and then sent the information to a hospital dermatologist, who responded with management advice the following week. Of 141 patients who attended their teledermatology appointment, 123 (50 male, 73 female) completed the study questionnaire (87%). The average age of respondents was 42 years (SD 17, range 18-90 years). Ninety-three per cent reported that they were happy with the teleconsultation while 86% reported that it was more convenient than going to the outpatient clinic. Forty per cent agreed that they would feel more comfortable seeing the dermatologist in person while only 58% were comfortable with not speaking to the dermatologist about their skin condition. The absence of interaction with the dermatologist and the delay in receiving management advice may have contributed to the somewhat low satisfaction rates.

Domains of consultation research in primary care

The consultation is increasingly viewed as a crucial aspect of general practice medicine, but a variety of methods of conceptualising, describing and modifying its structure and content have been described. This article describes the historical background to the current interest in the consultation, and describes four qualitatively distinct approaches (or 'domains') to understanding the consultation: the psychodynamic; clinical-observational; social-psychological; and sociological. Four key dimensions along which the domains can be differentiated are described. These concern whether the critique of medical practice inherent in the domain is internal or external to the discipline of general practice; whether the focus of the domain is on the consultation participants' identities or activities; whether the key research methodology is quantitative or qualitative in character; and the degree to which the objective of research within the domain is to describe current practice or prescribe ways of conducting the consultation. Methods of encouraging work across domains are discussed.

Knowing patients and knowledge about patients: evidence of modes of reasoning in the consultation?

BACKGROUND

The idea that the patient is in some way known to the doctor is an important one in general practice. The thrust towards patient-centred medicine, the promotion of open and negotiative consultation skills and the development of a biopsychosocial model of primary care medicine all rely on the patient providing a history composed of more than a list of facts.

OBJECTIVE

Our aim was to explore the nature and importance of doctors' knowledge about patients.

METHODS

Fifteen GPs audio-recorded 25-30 consultations with consecutive consenting patients. They scored each consultation according to how satisfying they found it. Semi-structured interviews based on a selection of consultations were conducted to draw out the doctor's views on the factors that were important to their satisfaction. The interviews were transcribed verbatim. Qualitative analysis was inductive and iterative.

RESULTS

Within doctors' narratives, we found accounts of two ways of 'knowing' the patient. The first was a deductive mode of reasoning derived from facts about the patient. The facts that were known were specific to the context of the general practice consultation and led to biomedical and biographical knowledge. The second was an inductive mode of reasoning derived from a contextual interpretation of the facts about the patient which resulted in knowledge of their behaviour and cognitions. Both modes of reasoning gave the doctor knowledge of the patient and permitted action by the doctor in the consultation but led to different interpretations of the patient and different experiences of the consultation.

CONCLUSION

'Knowing the patient' is important to the way GPs attribute meaning to their work. Doctors were more likely to identify as 'known' those patients with whom they adopted an inductive mode of reasoning. In addition, their experience of the consultation was more likely to be positive.

Wisdom and aging: irrational preferences in college students but not older adults

A decision-maker is "irregular" if she would choose B from [A, B, C] but not from [A, B] (for example, preferring vanilla ice cream in a choice between vanilla and chocolate, but chocolate in a choice among vanilla, chocolate and strawberry). Similarly to previous studies we observed irregular choices by college students faced with hypothetical discount cards for supermarkets. However, older adults showed no such tendency. The same pattern was observed in three separate studies. We interpret the results in terms of a choice strategy by older adults that protects them from excessive spending.

A promising genetic approach to the treatment of beta-thalassemia

The stable introduction of a functional gene into autologous stem cells is a potentially powerful approach to treat a number of inherited or acquired diseases. One challenge facing this approach is to express adequate levels of the therapeutic transgene in a regulated and sustained fashion, eventually restricting expression to a single lineage developing from the transduced stem cells. Until now, low-level expression, position effects, and transcriptional silencing have hampered the effectiveness of retroviral-mediated gene transfer. In an effort to overcome these obstacles, we have systematically investigated vectors encoding the human beta-globin gene linked to selected combinations of proximal and distal genetic regulatory elements. Our results demonstrate that with thoughtful vector design one can successfully express long-term, therapeutic levels of virally encoded human beta-globin in the erythroid progeny of hematopoietic stem cells.

When protocols fail: technical evaluation, biomedical knowledge, and the social production of 'facts' about a telemedicine clinic

Telecommunications systems seem to offer health care providers, professionals and patients a plethora of opportunities to respond to social and geographical inequalities in health care provision, and a new field of health care endeavor has emerged--'telemedicine'. This paper presents results from a three year ethnographic study of the development and implementation of telemedicine systems in a British region. We explore how attempts to put into service one 'telemedicine' system failed to get beyond the draft of a written protocol. Our analysis focuses on the contests between clinicians, technical experts and external evaluators over what kinds of knowledge and practice count in developing a protocol and evaluating a clinical intervention. We show how the introduction and implementation of 'hard' technologies (systems hardware) can be undermined in practice by 'soft' technologies (the practices through which evaluative knowledge is produced).

Resisting and promoting new technologies in clinical practice: the case of telepsychiatry

New telecommunications technologies promise to profoundly change the spatial and temporal relationship between health professional and patient. This paper reports results from an ethnographic study of the introduction of a videophone or 'telemedicine' system intended to facilitate faster and more convenient referral of patients with anxiety and depression in primary care, to a community mental health team. We explore the reasons for contest over the telemedicine system in practice, contrasting professionals' critique of the technology in play with a more fundamental problem: the extent to which the telecommunications system threatened deeply embedded professional constructs about the nature and practice of therapeutic relationships.

Cell-type-specific regulation of the two foamy virus promoters

The foamy virus (FV) genome contains two promoters, the canonical long terminal repeat (LTR) promoter, containing three consensus AP-1 binding sites, and an internal promoter (IP) within the env gene. We investigated the regulation of the two promoters in lytic and persistent infections and found that in the presence of a constitutive source of the viral transactivator protein Tas, transactivation of the LTR promoter and that of the IP differ. In lytic infections, both the LTR promoter and the IP are efficiently transactivated by Tas, while in persistent infections, the IP is efficiently transactivated by Tas, but the LTR promoter is not. Analysis of proteins expressed from the LTR promoter and the IP during infection indicated that IP transcription is more robust than that of the LTR promoter in persistently infected cells, while the opposite is true for lytically infected cells. Coculture experiments also showed that LTR promoter transcription is greatest in cells which support lytic replication. Replacement of much of the LTR promoter with the IP leads to increased viral replication in persistent but not lytic infections. We also found that the induction of persistently infected cells with phorbol 12-myristate 13-acetate (PMA) greatly enhanced viral replication and transcription from the SFVcpz(hu) (new name for human FV) LTR promoter. However, mutation of three consensus AP-1 binding sites in the FV LTR promoter did not affect viral replication in lytically or persistently infected cells, nor did the same mutations affect LTR promoter transactivation by Tas in PMA-treated cells. Our data indicate that differential regulation of transcription is important in the outcome of FV infection but is unlikely to depend on AP-1.

Brain angiotensin and body fluid homeostasis

Angiotensinogen, the precursor molecule of the peptides angiotensin I, II, and III, is synthesized in the brain and the liver. Evidence is reviewed that angiotensin II, and possibly angiotensin III, that are generated within the brain act within neural circuits of the central nervous system to regulate body fluid balance. Immunohistochemical studies in the rat brain have provided evidence of angiotensin-containing neurons, especially in the hypothalamic paraventricular nucleus, subfornical organ, periventricular region, and nucleus of the solitary tract, as well as in extensive angiotensin-containing fiber pathways. Angiotensin immunoreactivity is observed by electron microscope in synaptic vesicles in several brain regions, the most prominent of these being the central nucleus of the amygdala. Neurons in many parts of the brain (lamina terminalis, paraventricular and parabrachial nuclei, ventrolateral medulla, and nucleus of the solitary tract) known to be involved in the regulation of body fluid homeostasis exhibit angiotensin receptors of the AT(1) subtype. Pharmacological studies in several species show that intracerebroventricular administration of AT(1) receptor antagonist drugs inhibit homeostatic responses to the central administration of hypertonic saline, intravenous infusion of the hormone relaxin, or thermal dehydration. Responses affected by centrally administered AT(1) antagonists are water drinking, vasopressin secretion, natriuresis, increased arterial pressure, reduced renal renin release, salt hunger, and thermoregulatory adjustments. We conclude that angiotensinergic neural pathways in the brain probably have an important homeostatic function, especially in regard to osmoregulation and thermoregulation, and the maintenance of arterial pressure.

Talocalcaneal luxation with plantar displacement of the head of the talus in a dog and a cat

A dog and a cat suffered talocalcaneal luxation with plantar displacement of the head of the talus. Each case was associated with luxation of the talocentral joint and subluxation of the calcaneoquartal joint. The collateral ligaments were not significantly disrupted and this made it technically difficult to reduce the luxations. However, after open reduction, the luxations were inherently stable and a positional screw provided long-term stability. Both animals returned to their previous level of activity with no detectable signs of lameness.

The prevalence of dementia in a statewide sample of new nursing home admissions aged 65 and older: diagnosis by expert panel. Epidemiology of Dementia in Nursing Homes Research Group

This study estimated the prevalence of dementia in 2,285 new admissions age 65+ to a statewide sample of 59 nursing homes in Maryland, 1992-1995. Dementia was ascertained according to DSM-III-R criteria by an expert panel of geriatric psychiatrists, neurologists, and a geriatrician using detailed information collected by trained lay evaluators from residents, family, staff, and medical records. Admissions to Maryland nursing homes are similar to admissions to nursing homes elsewhere in the United States. The prevalence of dementia was 48.2% (CI: 43.6-52.8) with an upper bound estimated at 54.5% (CI: 49.9-59.1). Prevalence is highest in facilities with <50 beds versus 200+ beds (65.5% vs 39.6%) and those in urban versus rural areas (50.0% vs 39.1%). Those who are non-White, married, and with fewer years of education are more likely to be demented. Prevalence is highest among those with 4+ physical impairments versus 0-1 (60.3% vs 27.7%) and lowest in those with 4+ comorbidities versus 0-1 (44.8% vs 52.0%). There was considerable overlap in the comorbid status of demented and nondemented admissions, and both groups contained members with only a few functional limitations. Results suggest that the level of medical supervision provided in nursing homes may not be required for some residents with dementia.

Mass cultured human fibroblasts overexpressing hTERT encounter a growth crisis following an extended period of proliferation

During the process of immortalization, at least two mortality checkpoints, M1 and M2, must be bypassed. Cells that have bypassed M1 (senescence) have an extended life span, but are not necessarily immortal. Recent studies have shown that ectopic expression of the catalytic subunit of telomerase (hTERT) enables normal human cells to bypass senescence (M1) and oncogene transformed cells to avert crisis (M2) and become immortal. However, it is unclear whether hTERT expression is sufficient for normal human fibroblasts to overcome both M1 and M2 and become immortal. We have investigated the role of telomerase in immortalization by maintaining mass cultures of hTERT-transduced primary human fetal lung fibroblasts (MRC-5 cells) for very long periods of time (more than 2 years). In the present studies, up to 70% of MRC-5 cells were transduced with retroviral vectors that express hTERT. hTERT-transduced cells exhibited high levels of telomerase activity, elongation of telomeres, and proliferation beyond senescence. However, after proliferating for more than 36 population doublings (PDLs) beyond senescence, the overall growth rate of hTERT-expressing cells declined. During theses periods of reduced growth, hTERT-transduced MRC-5 cells exhibited features typical of cells in crisis, including an increased rate of cell death and polyploidy. In some instances, very late passage cells acquired a senescence-like phenotype characterized by arrest in the G1 phase of the cell cycle and greatly reduced DNA synthesis. At the onset of crisis, hTERT-transduced cells expressed high levels of telomerase and had very long telomeres, ranging up to 30 kb. Not all cells succumbed to crisis and, consequently, some cultures have proliferated beyond 240 PDLs, while another culture appears to be permanently arrested at 160 PDLs. Late passage MRC-5 cells, including postcrisis cells, displayed no signs of malignant transformation. Our results are consistent with the model in which telomerase and telomere elongation greatly extends cellular life span without inducing malignant changes. However, these investigations also indicate that hTERT-expressing cells may undergo crisis following an extended life span and that immortality is not the universal outcome of hTERT expression in normal diploid fibroblasts.

Phospholipid monolayer of plant lipid bodies attacked by phospholipase A2 shows 80 nm holes analyzed by atomic force microscopy

In plant storage tissue, lipid bodies are composed of triacylglycerides and surrounded by a phospholipid monolayer which is stabilized by oleosins. At the onset of lipid body mobilization, cells express phospholipase A2, which partially degrades the monolayer and thus provides access for the subsequently acting triacylglyceride degrading enzymes. Analyzing the lipid body surface by atomic force microscopy we show that, at the stage of maximal phospholipase A2 expression, the monolayer contains holes of approximately 80 nm in width and 2.45 +/- 0.46 nm in depth. Non-contact mode imaging was performed with a lateral resolution of approximately 10 nm and a vertical resolution of less than 0.1 nm. The depth of the holes corresponds to the width of the monolayer, while the width of the channels is sufficiently large to provide access to 100 kDa enzymes, such as lipoxygenase and lipases.

Therapeutic haemoglobin synthesis in beta-thalassaemic mice expressing lentivirus-encoded human beta-globin

The stable introduction of a functional beta-globin gene in haematopoietic stem cells could be a powerful approach to treat beta-thalassaemia and sickle-cell disease. Genetic approaches aiming to increase normal beta-globin expression in the progeny of autologous haematopoietic stem cells might circumvent the limitations and risks of allogeneic cell transplants. However, low-level expression, position effects and transcriptional silencing hampered the effectiveness of viral transduction of the human beta-globin gene when it was linked to minimal regulatory sequences. Here we show that the use of recombinant lentiviruses enables efficient transfer and faithful integration of the human beta-globin gene together with large segments of its locus control region. In long-term recipients of unselected transduced bone marrow cells, tetramers of two murine alpha-globin and two human betaA-globin molecules account for up to 13% of total haemoglobin in mature red cells of normal mice. In beta-thalassaemic heterozygous mice higher percentages are obtained (17% to 24%), which are sufficient to ameliorate anaemia and red cell morphology. Such levels should be of therapeutic benefit in patients with severe defects in haemoglobin production.

Patients' perceptions of a telemedicine specialty clinic

We studied patients' perceptions of telemedicine (interactive video) as a means of delivering specialist oncology/haematology care. Semistructured telephone interviews were performed with 22 patients attending a tele-oncology/haematology clinic in Kansas. Interviews were audio-taped and thematic content analysis of the transcripts was done. The response rate was 96%. All participants expressed satisfaction with their tele-consultations. For 50% of respondents, satisfaction with the tele-oncology/haematology clinic was qualified by two factors: participants also saw the specialist in person on occasions and the clinic was perceived as providing mainly a 'monitoring' function. In addition, 9 of the 22 patients expressed concern about the role of the nurse as a proxy for the doctor in performing certain parts of the physical examination. Overall, participants valued improved access to specialist services but had clear views as to the limitations of such a service. As the use of telecommunications technology grows, patient perspectives merit greater attention.

Telepsychiatry evaluation in the north-west of England: preliminary results of a qualitative study

A telepsychiatry referral service for patients suffering from anxiety and depression was evaluated from a user perspective. Low-cost video-phones linked a psychiatrist to two general practices in the north-west of England. Quantitative data were collected using a semistructured interview schedule. Twenty-two patients and 13 doctors were interviewed after a video-link consultation. Some users were very positive about the service and recognized its potential benefits, while others were more ambivalent. Patients saw the service as a means of obtaining additional 'expert' advice. General practitioners felt that the service might adversely affect the doctor-patient relationship in psychiatry. Both patients and clinicians recognized that the video-link modified normal interaction. Users need to adapt to this form of communication. An induction session is recommended for both patients and clinicians.

A review of telemedicine cost-effectiveness studies

As interest in telemedicine grows, many of its proponents and vendors increasingly suggest that it is now time to move to full-scale implementation of telemedicine services in a variety of contexts throughout the world, and question the need for further evidence of its utility and cost-effectiveness. We have reviewed the published literature relating to cost-effectiveness studies in telemedicine and have identified some important weaknesses. Ten recommendations regarding the design of economic evaluations of telemedicine are suggested.

Cystic lesions of the pineal region--MRI and pathology

Pineal lesions are rare. Tumours in this location comprise 0.4-1% of intracranial tumours. They grow mainly as solid-mass lesions, and cystic tumours are not common. On MRI, a cystic configuration is associated usually with non-neoplastic pineal lesions rather than with a tumour, but analysis does not allow cystic pineal tumours to be distinguished from glial cysts with certainty. We compared neuroradiological and pathological data from 13 cystic pineal lesions, analysing preoperative MRI. Formalin-fixed, paraffin-embedded surgical specimens were stained routinely and immunocytochemically, using the streptavidin-biotin-complex method. Histology revealed six pineocytomas, four glial cysts, an arachnoid cyst, a low-grade astrocytoma and a teratoma. Signal characteristics of pineocytomas were similar in many respects to those of glial pineal cysts. Histomorphological analysis allowed unambiguous discrimination between pineocytomas and glial pineal cysts.

The cHS4 insulator increases the probability of retroviral expression at random chromosomal integration sites

Retroviruses are highly susceptible to transcriptional silencing and position effects imparted by chromosomal sequences at their integration site. These phenomena hamper the use of recombinant retroviruses as stable gene delivery vectors. As insulators are able to block promoter-enhancer interactions and reduce position effects in some transgenic animals, we examined the effect of an insulator on the expression and structure of randomly integrated recombinant retroviruses. We used the cHS4 element, an insulator from the chicken beta-like globin gene cluster, which has been shown to reduce position effects in transgenic Drosophila. A large panel of mouse erythroleukemia cells that bear a single copy of integrated recombinant retroviruses was generated without using drug selection. We show that the cHS4 increases the probability that integrated proviruses will express and dramatically decreases the level of de novo methylation of the 5' long terminal repeat. These findings support a primary role of methylation in the silencing of retroviruses and suggest that cHS4 could be useful in gene therapy applications to overcome silencing of retroviral vectors.