The cortical ancestry of oligodendrocytes: common principles and novel features.

Studies on the development of cortical oligodendrocytes indicate that although general principles that apply to other parts of the CNS are applicable, there are important differences that appear to be critical to the analysis of this lineage in the cortex. Herein, we review previous studies demonstrating that oligodendrocyte-type-2 astrocyte progenitor cells (or oligodendrocyte precursor cells; aka O-2A/OPCs) of the developing postnatal cortex exhibit a striking cell-intrinsic bias towards undergoing prolonged self-renewal in the relative absence of oligodendrocyte generation [Power et al., Dev Biol 2002;245:362-375]. This phenotype is quite distinct from that observed in comparable cells isolated from the optic tract. This predilection for self-renewal is associated with a lessened response to inducers of oligodendrocyte generation and of possible mechanistic importance in regards to these other properties. We also review studies on stem/progenitor cells isolated from the embryonic cortex that are able to generate oligodendrocytes. As for the studies on O-2A/OPCs, important differences also distinguish these early cells from those studied in other CNS regions in their response to signaling molecules and expression of the Dlx family of transcriptional regulators [He et al., J Neurosci 2001;21:8854-8862; Yung et al., Proc Natl Acad Sci USA 2002;99:16273-16278]. We also present new data on clonal analysis of A2B5+ precursor cells isolated from the E13.5 cortex, demonstrating that this tissue appears to contain a cell similar in properties to the tripotential glial-restricted precursor cell that has been isolated from embryonic spinal cord [Rao et al., Proc Natl Acad Sci USA 1998;95:3996-4001]. Moreover, the A2B5+ precursor cells isolated from embryonic cortex are much more heterogeneous than is seen in the spinal cord at this age, even to the point of including an A2B5/PSA-NCAM double-positive cell that can generate neurons.

Screening for cognitive impairment and dementia in the elderly.

OBJECTIVE: To review the evidence available to support or refute the recommendation to screen for cognitive impairment (cognitive deficits which do not affect daily function) and dementia in primary care. DATA SOURCES: Medline search using terms listed at the end of this article; consultation with experts in the field; review of other published recommendations. STUDY SELECTION: There were no articles which described a randomized controlled trial of screening versus no screening. Studies were therefore chosen which aided in the definition; natural history; interventions and outcomes including possible negative effects. DATA SYNTHESIS: No systematic synthesis was performed. Background papers were circulated to a panel of experts prior to the Canadian Consensus Conference on Dementia and conclusions endorsed by consensus. CONCLUSIONS: 1. There is insufficient evidence to recommend for or against screening for cognitive impairment or dementia. (C); 2. Memory complaints should be evaluated and the individual followed to assess progression. (B); 3. When caregivers or informants describe cognitive decline in an individual, these observations should be taken very seriously; cognitive assessment and careful follow-up are indicated. (A) (See Appendix).

Bedside percutaneous tracheostomy with bronchoscopic guidance in critically ill patients.

BACKGROUND: Bedside percutaneous dilational tracheostomy, a relatively new method of tracheal cannulation, provides safe and ready access to the trachea to relieve airway obstruction and tracheopulmonary secretions. The dilational technique has undergone various modifications during the past decade. Complications of this procedure are primarily related to the lack of direct visualization during tracheostomy tube placement and to poor patient selection. OBJECTIVE: To report the utility of percutaneous dilational tracheostomy with bronchoscopic guidance in 162 critically ill patients. MAIN OUTCOME MEASURES: Mortality rates and complications associated with this technique. RESULTS: Twenty-five patients (15.4%) died while hospitalized. No deaths were related to tracheostomy. There were four (2.5%) major complications: one pneumothorax and three posterior tracheal tears, which healed spontaneously. There were five (3.1%) minor complications: one posterior mucosal disruption, one minor bleeding episode, and three minor episodes of cellulitis. One hundred thirty-seven patients (84.6%) were discharged. Twenty-nine patients (21.2%) were available for follow-up and were experiencing no significant problems or complications following the procedure. Compared with standard open tracheostomy, charges were reduced by $1628.20 per patient ($263,768.40 total savings). CONCLUSIONS: Bedside percutaneous tracheostomy with bronchoscopic guidance is safe and cost-effective. Complications compare favorably with that of open tracheostomy. Major complications should be avoided with continuous bronchoscopic observation during the procedure.

Central serous chorioretinopathy in women.

BACKGROUND: Central serous chorioretinopathy is a disorder that typically affects young and middle-aged men. Although extensive information is available pertaining to the clinical features of central serous chorioretinopathy in men, little is known about this condition in women. MATERIALS AND METHODS: The authors reviewed the medical records and photographic files of women who received a diagnosis of central serous chorioretinopathy. The women were divided into three groups for data analysis: idiopathic, exogenous corticosteroid use, and pregnancy. RESULTS: Fifty-one women with active central serous chorioretinopathy were evaluated. These findings in women with idiopathic serous chorioretinopathy were similar to those described in men, with the exception that women tend to be older at the time of onset. Central serous chorioretinopathy in women taking exogenous corticosteroids more likely was characterized by bilateral involvement and subretinal fibrin. Central serous chorioretinopathy in pregnant women typically developed in the third trimester and resolved spontaneously within 1-2 months after delivery. CONCLUSION: Idiopathic central serous chorioretinopathy is similar in women and men, with the exception that women tend to be more older at the time of onset. The finding of exogenous corticosteroid use in a significant number of women in our study provides further support that cortisol may play a role in the development of central serous chorioretinopathy. The mechanism by which cortisol influences the development of central serous chorioretinopathy is unclear.

Branch retinal arterial occlusions in multifocal retinitis with optic nerve edema.

OBJECTIVE: To determine the natural history and visual prognosis of patients with branch retinal arterial occlusions secondary to multifocal retinitis. METHODS: Cases were reviewed for seven patients who exhibited multifocal retinitis and branch retinal arterial occlusion. The average age of the patients was 27 years (age range, 14 to 19 years). RESULTS: Six patients had systemic illnesses associated with their ocular findings. Four patients were scratched by a cat or exposed to a cat with fleas within 1 month of symptoms. Three of these patients were tested and had positive cat-scratch disease titers. At presentation, five patients complained of a scotoma, and two noted blurred vision. On examination, visual acuity was 20/25 or better in all but one eye. Five patients had vitritis, which was bilateral in three. Four patients exhibited optic nerve edema, which was bilateral in two. White intraretinal infiltrates were present in all patients, and were bilateral in five. The six patients who were examined within 1 week of symptoms had a white retinal infiltrate at the site of vascular occlusion. The retinal findings resolved in 2 to 6 weeks and did not recur. The final visual acuity was 20/20 OU in all patients. CONCLUSIONS: Branch retinal arterial occlusions represent a complication of multifocal retinitis and idiopathic optic nerve edema. The arterial occlusions are probably caused by a focus of retinitis. This self-limited disorder has an excellent visual prognosis and may be related to cat-scratch disease.

Variable intron content of the NADH dehydrogenase subunit 4 gene of plant mitochondria.

The gene nad4, encoding subunit four of the mitochondrial NADH dehydrogenase complex I, has been isolated and characterized from turnip, Brassica campestris. The 8 kb turnip nad4 gene contains four exons, which potentially encode a NAD4 polypeptide of 495 amino acids, and three large group II introns. Northern analysis identifies an abundant 2 kb transcript that most likely serves as the nad4 mRNA, while several larger transcripts (putative splicing intermediates) are also detected. Analysis of the nad4 locus in three distantly related dicotyledons indicates that introns 2 and 3 are optional. Mung bean has the same nad4 organization as turnip, whereas spinach nad4 contains introns 1 and 3, and lettuce nad4 has intron 1 only. We infer that all three group II introns were present in the nad4 gene of an angiosperm common ancestor and have persisted in certain lineages for over 200 million years, with two of the introns having been lost in other lineages.

An Approach to Assessing Dementia: Investigations suitable for use in the family physician's office.

Early tell-tale signs of dementia may not be manifest or recognized as significant by the patient or the physician. Often a spouse, relative, or someone close to the patient recognizes changes over time. While it might be argued that little is lost if the cause is irreversible, a small but significant number of cases have reversible causes and suffering can be alleviated. The recommendations of the Canadian Consensus Conference on the Assessment of Dementia take into account the family physician's perspective. This article looks at applications in the office setting.

Abnormal scleral collagen in nanophthalmos. An ultrastructural study.

Ten patients with bilateral nanophthalmos underwent sclerectomies for uveal effusion. Ultrastructural examination of the sclera revealed abnormal collagen in seven patients. Four showed dramatic fraying of the collagen fibrils into fine filaments 2 to 3 nm in diameter. In three of these cases and three other cases without fraying, there were foci of 10- to 35-nm small collagen fibrils, some appearing to arise by splitting of otherwise normal collagen fibrils. In areas of fraying, elastic fibers were absent. All patients had a wider range of collagen diameters than did control subjects. The youngest patient with fraying also had Hallermann-Streiff syndrome. In three patients, no collagen abnormality was found. The clinical feature correlating best with the presence of abnormal collagen was an extremely small eye, since the three patients without collagen abnormality had the largest eyes (range of anteroposterior diameters, 19.2 to 20.3 mm). Nanophthalmos appears to result from several distinct defects.

Effects of training in cardiopulmonary resuscitation on competence and patient outcome.

Between 1981 and 1985 we carried out a study in two medium-sized nonteaching community hospitals to determine the rate of deterioration of knowledge and skills in cardiopulmonary resuscitation (CPR) among physicians and nurses, the accuracy of their perceptions of their knowledge and skills, the effects of practice on retention and the effect of CPR training on mortality. The participants' knowledge and skills were measured before training and immediately after, 6 months after and 12 months after training. Information on all attempts at CPR involving hospital staff was collected from medical records and from interviews with the participants. A total of 31 physicians and 54 nurses were followed during the study. Six months after training there was no difference in CPR knowledge or skills between the physicians and the nurses. In both groups CPR skills had deteriorated to near pretraining levels. By 6 months the physicians' knowledge had deteriorated to a level not significantly different from that before training. The nurses maintained a significant improvement in knowledge test scores at 12 months over those before training (p = 0.037). The physicians had an accurate perception of their knowledge but not their skills 6 months and 12 months after training, whereas the nurses did not accurately perceive either their knowledge or their skills after training. Experience with CPR did not contribute to post-training knowledge or skills in either group. There was no evidence that death rates were lower when basic life support (BLS) was begun by trained staff than when it was begun by untrained staff. The probability of survival was greater when BLS was begun within 4 minutes of arrest than when it was begun after 4 minutes, regardless of whether advanced cardiac life support was begun within 10 minutes.

Punctate outer retinal toxoplasmosis.

Classic ocular toxoplasmosis initially involves inner retinal layers and is associated with marked vitreous reaction. We encountered three cases of punctate outer retinal toxoplasmosis, a subset of ocular toxoplasmosis that is characterized by multifocal gray-white lesions at the level of deep retina and retinal pigment epithelium and that is associated with little or no overlying vitreous reaction. Acute lesions may resolve to form fine granular white dots. Recognition of this uncommon presentation of toxoplasmosis is important, since there is some evidence that treatment of toxoplasmosis may be effective.

Toxemia of pregnancy pigment epitheliopathy masquerading as a heredomacular dystrophy.

Patients with toxemia of pregnancy may develop permanent alterations of the pigment epithelium that if first discovered in later life may be mistaken for a heredomacular dystrophy, a diffuse tapetoretinal dystrophy or other diseases. These nonprogressive changes are caused by multifocal areas of fibrous platelet occlusion of the choriocapillaris that usually occur just prior to or following delivery and is usually associated with a transient period of exudative retinal detachment. The pattern of pigment epithelial derangement is often sufficiently characteristic to suggest the correct diagnosis.

Filing reprints: can office staff help?

Filing systems for reprints must be tailored to the individual's practice profile, to maximize usefulness as a resource for clinical problem solving. However, the clerical time involved often reduces the physician's ability to maintain such a filing system. The authors tested two hypotheses that using the International Classification of Health Problems in Primary Care (ICHPPC) nurses or receptionists could code, cross reference and file reprints after the physician has selected the articles. Contents pages of five primary care journals were given to two academic family physicians, two practicing physicians, a research assistant and two receptionists, one of whom had used ICHPPC to record patient encounters. All coders except the second receptionist, who was unfamiliar with ICHPPC, reached good agreement in coding. Filing reprints may therefore be done by trained staff for groups of physicians.

Multifocal choroiditis and panuveitis. A syndrome that mimics ocular histoplasmosis.

A review of 28 cases of multifocal choroiditis with vitreous inflammatory cells demonstrates that these patients have chorioretinal scars similar to those in the presumed ocular histoplasmosis syndrome (POHS), but they have a low incidence of positive histoplasmin skin test reactions and calcified granulomata on chest x-ray films. Anterior chamber inflammation is a frequent finding. The epidemiologic background of these patients is different from those with POHS. The subjects in this study were also different from patients with birdshot or vitiliginous choroiditis and acute posterior multifocal placoid pigment epitheliopathy. However, unilateral cases are difficult to distinguish from cases of diffuse unilateral subacute neuroretinitis. While it is possible that a subretinal nematode may have caused some of the unilateral cases in this review, multiple causative agents are likely, including an unidentified agent that causes cross reactions to histoplasmin skin tests.