Central retinal vein occlusion: report of two familial cases

The authors report a 46-year-old father and 17-year-old son who each presented with unilateral central retinal vein occlusion (CRVO) and bilateral abnormalities of retinal vascular perfusion. The son presented with a nonperfused CRVO in the left eye, developed traction-rhegmatogenous retinal detachment treated with vitreous surgery, and developed prolonged arteriovenous filling in the retina of the fellow eye. The father presented with progressive CRVO in the right eye, developed choroido-vitreal neovascularization following laser treatment to create a chorioretinal anastomosis, underwent vitrectomy for retinal detachment and vitreous hemorrhage in that eye, and developed prolonged arm-eye and retinal arteriovenous circulation times in the fellow eye. An extensive evaluation (including hematological studies and imaging of the major vessels of the neck) failed to reveal a predisposing cause in either patient although echocardiography disclosed a mitral valve thrombus in the father. After institution of coumadin therapy, the circulatory parameters in the fellow eye of each patient improved.

Central retinal vein occlusion: review of management

Central retinal vein occlusion is usually a disease of the elderly and is often associated with systemic vascular disease, e.g., hypertension, diabetes mellitus, arteriosclerotic vascular disease. Younger patients, especially those less than 45 years of age, with retinal vein occlusion should be evaluated carefully for the possibility of an underlying thrombotic tendency. The authors describe the ocular manifestations, pathogenesis, associated conditions, patient evaluation, and treatment of patients with central retinal vein occlusion.

Relative osteopenia after treatment for acute lymphoblastic leukemia

Osteoporosis in adult life is associated with a significant morbidity and may be predisposed to by osteopenia and failure to reach peak bone mass in childhood. Children treated for acute lymphoblastic leukemia (ALL) may be at risk of osteopenia as a result of previous therapy or as a consequence of the disease process itself. Dual energy x-ray absorptiometry measurements of bone mineral content (BMC) for the whole body and at the lumbar spine and hip were taken in 35 (14 male) long-term survivors of ALL and compared with results in 20 (10 male) survivors of other malignancies and 31 (17 male) healthy sibling controls. The measured BMC was expressed as a percentage of a predicted value derived from the control group and based on the variables that had influence upon it. BMC (%) was reduced at the spine in the ALL group compared with controls [92.4 (8.0)% versus 100.4 (9.7)%, respectively; p < 0.005] and at the hip compared with both other malignancies and controls [89.0 (11.5)% versus 96.1 (11.7)% and 100.4 (9.2)%, respectively; p < 0.0005]. Increasing length of time off therapy was associated with a significant increase in %BMC at both the spine and the hip. For the spine, this association was significantly different between the ALL group and other malignancies, suggesting that any gain in %BMC after therapy was slower in children treated for ALL. Both exercise capacity and levels of physical activity were correlated with %BMC at the hip (r = 0.44, p < 0.001 and r = 0.29, p < 0.01, respectively). Previous exposure to methotrexate, ifosfamide, and bleomycin was associated with a reduction in %BMC at the spine. Exposure to 6-mercaptopurine and cisplatin was associated with a reduction at the hip. In conclusion, children treated for ALL are osteopenic. The mechanism is probably multifactorial but is partially related to previous chemotherapy, limited exercise capacity, and relative physical inactivity.

Strength and its relationship to changes in fat-free mass, total body potassium, total body water and IGF-1 in adults with growth hormone deficiency: effect of treatment with growth hormone

The present investigation examined changes in strength in growth hormone deficient (GHD) adults following treatment with recombinant human growth hormone (rhGH), and assessed their relationship to changes in fat-free mass (FFM), total body potassium (TBK), total body water (TBW), the concentration of TBK and TBW per kg FFM, and insulin like growth factor-1 (IGF-1). The investigation was double-blind and placebo-controlled for a period of 6 months; this was followed by a period of open treatment for a further 6 months. Patients were assigned randomly to experimental (E) and control (C) groups. In the first 6 months group E received rhGH and group C placebo; in the second 6 months both groups received rhGH. Serial data were analysed for 23 males (11 group E, 12 group C) and 20 females (10 group E, 10 group C). Body composition was assessed by dual energy X-ray absorptiometry, TBK and TBW. Muscle strength was recorded for arm flexion, leg extension and hand grip. Significant increases in FFM occurred in the first 6 months in group E (2.3 kg males, 1.4 kg females) and in the second 6 months in group C (2.4 kg males, 1.4 kg females). There was a modest increase in absolute strength with time, although only three increments were significant (knee extension in group E males and arm flexion in groups E and C females), all of which occurred during the 6-12 month period. Allometric scaling did not improve the identification of significant increments of strength. The mean concentrations of TBK (males 57.0-58.6, females 51.4-53.9 mmol) and TBW (males 0.65-0.69, females 0.65-0.68 l) per kg FFM, were significantly smaller at all stages of the trial than the reference values, suggesting that treatment had not fully normalized these variables. Likewise, the relationship between most of the increments of regional and total strength, and the corresponding increments of FFM, were generally poor and not significant. It was concluded that the reduced concentrations of TBK and TBW per kg FFM, which may be the effect of an inappropriate dose regime or mode of delivery, may, in part, contribute to the anomaly between increases in strength and FFM.

Composition and functional analysis of the Saccharomyces cerevisiae trehalose synthase complex

In the yeast Saccharomyces cerevisiae, trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP), which convert glucose 6-phosphate plus UDP-glucose to trehalose, are part of the trehalose synthase complex. In addition to the TPS1 (previously also called GGS1, CIF1, BYP1, FDP1, GLC6, and TSS1) and TPS2 (also described as HOG2 and PFK3) gene products, this complex also contains a regulatory subunit encoded by TSL1. We have constructed a set of isogenic strains carrying all possible combinations of deletions of these three genes and of TPS3, a homologue of TSL1 identified by systematic sequencing. Deletion of TPS1 totally abolished TPS activity and measurable trehalose, whereas deletion of any of the other genes in most cases reduced both. Similarly, deletion of TPS2 completely abolished TPP activity, and deletion of any of the other genes resulted in a reduction of this activity. Therefore, it appears that all subunits are required for optimal enzymatic activity. Since we observed measurable trehalose in strains lacking all but the TPS1 gene, some phosphatase activity in addition to Tps2 can hydrolyze trehalose 6-phosphate. Deletion of TPS3, in particular in a tsl1Delta background, reduced both TPS and TPP activities and trehalose content. Deletion of TPS2, TSL1, or TPS3 and, in particular, of TSL1 plus TPS3 destabilized the trehalose synthase complex. We conclude that Tps3 is a fourth subunit of the complex with functions partially redundant to those of Tsl1. Among the four genes studied, TPS1 is necessary and sufficient for growth on glucose and fructose. Even when overproduced, none of the other subunits could take over this function of Tps1 despite the homology shared by all four proteins. A portion of Tps1 appears to occur in a form not bound by the complex. Whereas TPS activity in the complex is inhibited by Pi, Pi stimulates the monomeric form of Tps1. We discuss the possible role of differentially regulated Tps1 in a complex-bound or monomeric form in light of the requirement of Tps1 for trehalose production and for growth on glucose and fructose.

Introducing antisense oligodeoxynucleotides into Paramecium via electroporation

A method utilizing electroporation to deliver antisense oligodeoxynucleotides into Paramecium tetraurelia has been developed. For these studies antisense oligonucleotides directed to different regions of the calmodulin mRNA were used. It was found that a pulse delivered at 150-250 V (375-625 V/cm field strength) for 3.9-4.2 ms using a 275 microF capacitor with resistance set at 13 Ohms was sufficient to achieve measurable incorporation of fluorescently-labeled oligodeoxynucleotides in up to 95% of the cells treated. Optimal parameters included using oligodeoxynucleotides of at least 12 bases in length with a 3' blocking group at a dose of around 10 microM. In addition, multiple oligodeoxynucleotides directed to the same target mRNA resulted in at least a 10-fold reduction in the dose of oligodeoxynucleotide required to achieve the desired effects. Taken together, these results indicate that the use of antisense oligodeoxynucleotides can be an easy and useful method for linking genes to specific functions in Paramecium tetraurelia. Finally, this report discusses how different 3' blocking groups and the use of combinations of oligodeoxynucleotides directed to different regions of the same target mRNA can help address concerns about specificity.

On PMWs and two-stroke engines

On Saturday, August 24, 1996, a 40-year-old man from Edmonton was riding a personal motorized watercraft (PMW, a Seadoo or Jet Ski type of machine) on Shuswap Lake, in south-central British Columbia. He was approximately 200 m offshore. The man motioned to his sister, who was riding another PMW, to follow him across the lake. She did so, but as the turned her head to check for other boat traffic, her brother suddenly slowed down and her machine rode right up on his back, crushing him against his handlebars. His sister, a nurse, held her brother's head above water until help arrived but, 48 minutes after the moment of impact, he was pronounced dead at the Shuswap Lake General Hospital. He had suffered a ruptured aorta.

Daily energy expenditure and physical activity in survivors of childhood malignancy

Changes in body composition, in particular the onset of obesity, may result from reductions in total daily energy expenditure (TDEE) as a consequence of relative physical inactivity. Children previously treated for acute lymphoblastic leukemia (ALL) become obese, yet the mechanism remains undefined. TDEE and physical activity levels [PAL = TDEE/basal metabolic rate (BMR)] were measured in 34 long-term survivors of ALL and compared with results from 21 survivors of other malignancies and 32 healthy sibling control subjects using the flex-heart rate technique. Body composition was measured by dual energy x-ray absorptiometry. The median TDEE was reduced in the ALL group (150 kJ x kg d(-1)) compared with other malignancies and controls (207 and 185 kJ x kg d(-1), respectively, p < 0.01). This reduction was accounted for mainly by a relative decrease in the PAL of the ALL group (1.24) compared with both other malignancies and controls (1.58 and 1.47, respectively, p < 0.01). TDEE and PAL were correlated with percentage body fat (r = -0.39, p < 0.001 and r = -0.24, p < 0.05, respectively). Obesity in survivors of ALL may, in part, be explained by a reduction in TDEE as a consequence of reduced PAL. The cause of such reduction is uncertain.

Changes in glutamate receptor subunit composition in hippocampus and cortex in patients with refractory epilepsy

An assessment of glutamate receptor subunit profiles was made in hippocampus and temporal lobe cortex of patients with refractory epilepsy. Molecular biological analyses using reverse transcription reaction (RT) followed by polymerase chain reaction (PCR) revealed changes in the distribution profile of the transcripts of AMPA/KA glutamate receptor subunits in hippocampal and cortical tissue from patients with refractory epilepsy when compared to similar tissue from six human and four non-human primate samples with no history of seizures or seizure medication. A severe mean decrease (38% of control) in mRNA for the GluR1 subunit was found in 400 mm cross-sections of hippocampus from patients with epilepsy. Less severe but significant reductions in that GluR1 subunit expression (54% of control) were exhibited in samples of excised temporal pole cortex from the same subjects. Message for the GluR4 subunit was also significantly decreased in hippocampus (68% of control), but in contrast to GluR1, GluR4 mRNA level was not decreased in temporal cortex. Levels of GluR2 mRNA were not significantly changed in epileptic hippocampal and cortical tissue relative to control samples. Protein levels of the GluR1 and GluR4 subunits quantified by Western blot analysis were also reduced in hippocampal and cortical tissue from epilepsy patients. Two other kainate subunit transcripts, GluR6 and KA1 also showed significant changes compared to non-epileptic tissue (136% and 71% of control, respectively). Results are discussed in terms of possible mechanisms by which protracted seizures could produce selective loss of certain AMPA/KA subunits.

Physiological and morphological effects of genetic alterations leading to a reduced synthesis of UDP-glucose in Saccharomyces cerevisiae

Yeast cells lacking UDP-Glc pyrophosphorylase (UGPase) encoded by UGPI are not viable. Two strategies were developed to drastically reduce the intracellular concentration of UDP-Glc in order to study the consequences of this metabolic engineering on physiology and morphology. Firstly, UGP1 was placed under the strongly regulatable THI4 promoter. This resulted in a 95% reduction of UGPase activity in the presence of thiamine. The phenotypic effects of this reduction were slightly stronger than those of glucose on the GALI0/CYC1-UGP1 gene fusion [Daran et al. (1995) Eur. J. Biochem. 230, 520-530]. A further reduction of flux towards UDP-Glc was achieved by deletion of the two phosphoglucomutase genes in the ugp1 conditional strain. The growth of this new mutant strain was hardly affected, while it was extremely sensitive to cell wall interfering drugs. Surprisingly, UDP-Glc levels were reduced only by 5-fold, causing a proportional decrease in both glycogen and beta-glucans. Taken altogether, these results indicate that a few percent of enzymatic activities leading to the formation of UDP-Glc appears sufficient to provide the UDP-Glc demands required for cell viability, and that the loss of function of UGP1 is lethal mainly because of the inability of yeast cells to properly form the cell wall.

Crystal Engineering Using Trisphenols. Three-Dimensional Hydrogen-Bonding Networks in 1,1,1-Tris(4-hydroxyphenyl)ethane, its Hydrated Adduct with 1,4-Diazabicyclo[2.2.2]octane (1/1/1) and its Adduct with Piperazine (4/3)

In 1,1,1-tris(4-hydroxyphenyl)ethane, C20H18O3 (1), monoclinic la, a = 7.9781 (10), b = 18.558 (3), c = 11.1995 (13) Å, \beta–101.668 (9)°, with Z = 4, each of the hydroxyl groups acts as both a donor and an acceptor of hydrogen bonds of the type O—H...O. The molecules are thus connected into square nets, graph set R^4_4(38), pairs of which are then interwoven; the nets are themselves interconnected by further hydrogen bonds to give a continuous three-dimensional network. In 1,1,1-tris(4-hydroxyphenyl)ethane-l,4-diazabicyclo[2.2.2]octane–water (1/1/1), C20H18O3.C6H12N2.H2O (2), triclinic P\overline 1, a = 10.421 (2), b = 10.734 (2), c = 10.9756 (13) Å, \alpha = 76.645 (12), \beta 74.513 (11), \gamma = 89.305 (13)°, with Z = 2, the water molecules are linked to the trisphenol and the diamine units by O—H...O and O—H...N hydrogen bonds, respectively, to form a linear aggregate. These aggregates are linked into chains by the formation of O—H...N hydrogen bonds between the trisphenol and the neighbouring diamine; however, alongside hydrogen-bond formation between the trisphenol and the diamine, there is also partial transfer of a proton, so that the intra-chain links between trisphenol and diamine units are in fact a mixture of O—H...N and N—H...O hydrogen bonds. These chains in the [101] direction are cross-linked by further O—H...O hydrogen bonds, involving only trisphenol O atoms, which form chains in both the [010] and [001] directions, thus generating a continuous three-dimensional network. Adduct (3), 1,1,1-tris(4-hydroxyphenyl)ethane–piperazine (4/3), (C20H18O3)4.(C4H10N2)3, triclinic P\overline 1, a = 12.5049 (11), b = 12.7046 (10), c = 14.6226 (9) Å, \alpha = 113.738 (6), \beta = 100.839 (6), \gamma = 102.438 (7)°, with Z = 1, has two independent trisphenol molecules in general positions and three independent piperazine molecules lying about centres of inversion. The five independent components of the asymmetric unit are linked together by means of three O—H...N and one O—H...O hydrogen bonds to form an open aggregate containing no hydrogen-bonded rings. These aggregates are connected into three sets of interlinked chains in the [010], [001] and [\overline 110] directions: the [010] and [\overline 110] chains employ only O—H...O hydrogen bonds, while the [001] chains employ both O—H...N and N—H...O hydrogen bonds. Additionally, the inversion symmetry at each piperazine unit gives rise to further interlinks.

Relationship between cardiopulmonary response to exercise and adiposity in survivors of childhood malignancy

Many long term sequelae result from previous treatment for malignancy in childhood. However, little information exists on cardiopulmonary response and energy expenditure during exercise and their possible associations with excess body fat. Measurements of body composition and exercise capacity both at low intensity and maximal aerobic capacity were made on 56 long term survivors of childhood malignancy (35 survivors of acute lymphoblastic leukaemia (ALL) and 21 survivors of other malignancies) and 32 siblings acting as controls. Female survivors of ALL had significantly greater mean (SD) body fat than survivors of other malignancies and siblings (32.5 (6.4)% v 24.3 (4.4)% and 26.3 (8.5)% respectively, p < 0.005). Energy expenditure at low intensity exercise was reduced in survivors of ALL, and negatively correlated with body fat after controlling for weight (partial r range -0.21 to -0.47, p < 0.05). Stroke volume, measured indirectly, was reduced and heart rate raised in ALL survivors at sub-maximal exercise levels. Peak oxygen consumption was significantly reduced in girls and boys treated for ALL compared with siblings (30.5 v 41.3 ml/kg/min for girls, p < 0.05 and 39.9 v 47.6 ml/kg/min for boys, p < 0.05 respectively). Reduced exercise capacity may account in part for the excess adiposity observed in long term survivors of ALL.

Body habitus and coronary heart disease in men. A review with reference to methods of body habitus assessment

Table 1 is a synopsis of the major findings from an extensive literature on the association between human body habitus and coronary heart disease. Whilst some studies have used quite sophisticated laboratory procedures to quantify body fat most have relied upon anthropometric measurements to determine some component of body habitus. Of these, body weight and height are the simplest measurements and are, therefore, well-suited to large-scale prospective studies. Height and weight are highly reproducible measurements, although in the short term, weight can have considerable physiological variation associated with gastric emptying and state of hydration. Less reliable measurements than height and weight are skinfolds and body circumferences, both of which have been used extensively in cross-sectional and prospective analyses. For skinfolds, both the inter and intra-observer variability is affected by the measurement technique, location of the skinfold site, the skinfold caliper used and skinfold compressibility. As measurement error has been shown to be a function of skinfold thickness, accurate and repeatable skinfold measurements are particularly difficult to make in the obese. In these subjects, it is not always possible to locate a specific anatomical bony landmark or to pull a parallel skinfold away from the underlying tissue. Furthermore, in the extremely obese it is sometimes possible for a skinfold to be thicker than the jaws of the currently available commercial calipers. Alternately, body circumferences are obtainable in all subjects and have greater reproducibility than skinfolds. They are, therefore, the preferred method in obese subjects. However, there is considerable work to be done to establish their association with body fatness. The evidence examined in this review suggests that body weight is a poor predictor of coronary heart disease. Some studies have reported no difference in the body weight of coronary heart disease patients compared to subjects free of the disease, others found the body weight of subjects with coronary heart disease to be slightly greater, and one found the body weight of cardiac patients to be less than controls. Height, however, is associated with coronary heart disease in prospective studies with long-term and shorter-term follow-up periods and case-control designs. Fetal, infant and childhood under-nutrition may link shorter adult height and susceptibility to cardiovascular disease. Many researchers have studied the relationship between overweight and coronary heart disease by using a surrogate measurement of body fatness such as relative weight or a weight-for-height index. In general, results produced by these studies suggest weight-for-height indices, particularly the often used body mass index, are not strong predictors of coronary heart disease. Indeed case-control designs have consistently failed to show a relationship between body mass index and coronary heart disease. Inconsistent results from prospective studies, however, are difficult to interpret. To further confuse the situation, the body mass index has been examined in relation to different coronary heart disease end-points and adjusted for different confounding variables. Explaining the inconsistent results on the basis of length of follow-up is also not straightforward. When follow-up periods exceed 20 years, and sample size is small, however, this closer association has not been found, even with a long follow-up period. Whilst some studies have found no association after 15, 13 and 12 years others have reported a relationship after 8.5, 10, 12, 10 and 7 years. The 22 year follow-up evidence from the Framingham Study shows the strongest 'independent' association between body mass index and coronary heart disease. (ABSTRACT TRUNCATED)

Teaching and assessing clinical skills using virtual reality

The need to improve the teaching and assessing of students' procedural skills has been well 0 encounters, often with little or no supervision. Assessment of these skills has depended on rudimentary physical models, or standardized patients. The limitations of these methods also are well known. A new technology known as "Virtual Reality" has tremendous potential to assist medical educators in teaching and assessing clinical skills of students, residents and physicians in practice. Virtual Reality consists of a computer-generated three-dimensional simulation in which the user both views and manipulates the contents of the environment. Various degrees of immersion may be experienced that may include elements such as vision, touch or sound. It can provide an environment that so closely represents an actual clinical situation that skills learned will transfer to patients. Many variations in anatomy or other complications can be presented, and trainees can practice hundreds of times until their skills are perfected. This paper describes current activities in this area in the Dalhousie Faculty of Medicine and elsewhere. Various forms of Virtual Reality are described and their application to particular clinical areas are described.