Biomedical subjects

V A Diwadkar

Publications and source records attributed to V A Diwadkar.

6 recordsLinked to original sources

PubMed2002

Abnormalities of the corpus callosum in first episode, treatment naive schizophrenia.

BACKGROUND: Structural alterations in the association cortices as well as in the corpus callosum (CC) have been described in schizophrenia, and have been considered to reflect developmental abnormalities. Areas of primary and association cortices have been topographically mapped in the CC. OBJECTIVE: To investigate whether, in schizophrenia, there are alterations in CC subdivisions that connect association, but not primary, cortices, and also to see if the normative, developmentally mediated increase in CC size with age is absent in this disorder. METHODS: The midsagittal magnetic resonance imaging scans of 31 first episode, neuroleptic naive, schizophrenic patients, 12 non-schizophrenic, psychotic patients, and 31 healthy controls were compared. The total area of CC as well as that of anterior, middle and posterior genu, body, isthmus, and anterior, middle, and posterior splenii were measured. RESULTS: Patients with schizophrenia as a group had a smaller CC, anterior genu, anterior body, isthmus, and anterior splenium than normal controls. Furthermore, the age related increase in CC size seen in normal subjects was absent in the patients. CONCLUSIONS: The observed reductions in size in selected regions of CC suggest a reduction in axonal connections between the heteromodal association cortices, which typically involve small diameter fibres. Furthermore, the absence of an age related increase in CC size in patients with schizophrenia suggests a neurodevelopmental abnormality that may extend into adolescence and early adulthood.

Adult↗

PubMed2000

Collaborative activity between parietal and dorso-lateral prefrontal cortex in dynamic spatial working memory revealed by fMRI.

Functional MRI was used to determine how the constituents of the cortical network subserving dynamic spatial working memory respond to two types of increases in task complexity. Participants mentally maintained the most recent location of either one or three objects as the three objects moved discretely in either a two- or three-dimensional array. Cortical activation in the dorsolateral prefrontal (DLPFC) and the parietal cortex increased as a function of the number of object locations to be maintained and the dimensionality of the display. An analysis of the response characteristics of the individual voxels showed that a large proportion were activated only when both the variables imposed the higher level of demand. A smaller proportion were activated specifically in response to increases in task demand associated with each of the independent variables. A second experiment revealed the same effect of dimensionality in the parietal cortex when the movement of objects was signaled auditorily rather than visually, indicating that the additional representational demands induced by 3-D space are independent of input modality. The comodulation of activation in the prefrontal and parietal areas by the amount of computational demand suggests that the collaboration between areas is a basic feature underlying much of the functionality of spatial working memory.

Acoustic Stimulation↗

PubMed1999

Postprandial low-density lipoproteins in type 2 diabetes are oxidized more extensively than fasting diabetes and control samples.

This study examined the kinetics of low-density lipoprotein (LDL) oxidation in the fasting and postprandial states of diabetic and control subjects to determine if LDL oxidation may contribute to accelerated atherosclerosis in diabetes. We compared in vitro oxidation of LDL from 12 control and 13 Type 2 diabetic subjects in the fasting and postprandial states. The extent of oxidation was assessed by length of lag phase, formation of conjugated dienes (CD), lipid peroxides, thiobarbituric acid reactive substances (TBARS), and percentage reduction in free amine groups. Diabetic subjects were significantly older and heavier. Comparisons between control and diabetic subjects in the postprandial state showed that the lag phase was significantly shorter in diabetic subjects than controls (P = 0.005), TBARS were significantly higher (P = 0.006), and levels of CD were higher at 60, 65, and 70 min (P < 0.01). In the fasting state, however, these comparisons were not significant. In diabetic subjects, postprandial samples had a significantly shorter lag phase (P = 0.003), higher TBARS (P = 0.006), and higher levels of CD at 60, 65 (P < 0.001), and 70 min (P = 0.0013) compared to fasting samples. Elevated levels of serum triglycerides in diabetic subjects were negatively correlated to lag phase, in fasting (P = 0.06) and postprandial states (P = 0.002). We conclude that accelerated oxidation of LDL seen in postprandial states in diabetes may be a critical contributor to cardiovascular risks. Elevated levels of serum triglycerides may contribute to the rapid oxidation of LDL seen in diabetic subjects.

Adult↗

PubMed1999

Antioxidant supplementation effects on low-density lipoprotein oxidation for individuals with type 2 diabetes mellitus.

OBJECTIVE: This study compared susceptibility to oxidation of low-density lipoproteins (LDL) of non-diabetic and diabetic (Type 2) men and examined the response of diabetic men to antioxidant supplementation (alpha-tocopherol, beta-carotene and ascorbate). RESEARCH DESIGN AND METHODS: Twenty adult non-diabetic and 20 diabetic men were recruited. Oxidation of LDL was assessed by four different assay systems, and the extent of oxidation was assessed by four different measurements. Diabetic men received eight weeks of placebo ("baseline"), twelve weeks of antioxidant supplements ("treated") and eight weeks of placebo ("post-treatment"). Supplements provided 24 mg of beta-carotene, 1000 mg of ascorbate and 800 IU of alpha-tocopherol daily. RESULTS: With Cu oxidation at 37 degrees C, thiobarbituric reactive substances (TBARS) formation was significantly higher (p=0.032) and loss of free amine groups was significantly greater (p=0.013) in the LDL from diabetic subjects than controls. Antioxidant supplementation of diabetic subjects significantly decreased all parameters of LDL oxidation with Cu at 30 degrees C and 37 degrees C. At 30 degrees C the lag phase increased from 55 to 129 minutes (p<0.0001); conjugated diene formation decreased from 1.23 to 0.62 OD units (p<0.0001); TBARS formation decreased from 78 to 33 nmoles MDA/mg LDL protein (p<0.0001); and free amine loss decreased from 41 to 12% (p<0.0001). With Cu oxidation at 37 degrees C, similar changes occurred. CONCLUSIONS: These studies indicate that the LDL from diabetic subjects are more susceptible to oxidation than LDL from non-diabetic subjects. Supplementation of diabetic subjects with antioxidant vitamins significantly decreases susceptibility of LDL to oxidation by Cu. These studies are consistent with epidemiological and intervention studies suggesting that antioxidant vitamin use significantly decreases risk for coronary heart disease.

Adult↗

PubMed1998

Selective effects of different antioxidants on oxidation of lipoproteins from rats.

Lipoprotein oxidation may contribute to development of atherosclerosis, and supplementation with antioxidants may reduce risk for atherosclerotic events. Genistein, a major isoflavone from soy protein, and catechins from green tea have important antioxidant properties. This study compared the effects of various diets containing antioxidant-rich foods or supplements on serum lipids and lipoprotein oxidation of male Sprague-Dawley rats. The control diet used was devoid of vitamin E. Test diets included these ingredients: green tea powder, 20 g/kg; beta-carotene, 250 mg/kg; a low isoflavone soy protein isolate; a genistein-rich soy protein isolate; and vitamin E, 4000 mg/kg. Ten-week-old rats were acclimatized for 1 week on a special custom diet without vitamin E. Following randomization and allocation to different diet groups, rats were fed the test diets for 3 weeks. Blood was drawn by cardiac puncture, and the plasma was separated by centrifugation. The VLDL-LDL fraction was isolated by ultracentrifugation. Oxidation kinetics of the VLDL-LDL fraction were determined by measuring the lag phase and formation of conjugated dienes, lipid peroxides, and TBARS. The vitamin E diet (P < 0.001) and high-genistein diet profoundly decreased all parameters of lipoprotein oxidation. The following alterations were noted with the high-genistein diet compared to the control diet: the lag phase was 49% longer (P=0.002); conjugated diene formation was decreased by 28% (P=0.01); lipid peroxide formation was decreased 31% (P=0.0059); and TBARS production was 35% lower (P=0.019). The low-isoflavone diet increased the lag phase by 43% (P=0.0019) but did not significantly alter other measures of oxidation. Green tea increased only the lag phase by 33% (P=0.012) compared to the control diet. Beta-Carotene had no significant effect on the oxidation of lipoproteins. The effect of genistein-rich soy protein isolates on lipoprotein oxidation in vitro suggests that either soy isoflavones or other antioxidants derived from soy protein, like vitamin E, may be transported in these lipoproteins. The minimal effects of the isoflavone-poor soy protein isolate suggests that either the small amount of isoflavones present have a potent effect or other components of soy protein are exerting these effects. Further studies are required to examine these results.

Administration, Oral↗

PubMed1997

Symmetry and asymmetry of human spatial memory.

Six experiments investigated the limiting conditions on and the causes of asymmetries in estimates of euclidean distance. Participants estimated distances between locations on recently learned maps or between buildings on their college campus. Estimates between landmarks and neighboring nonlandmarks were often asymmetric, but estimates between other pairs of locations were typically symmetric. These and other results were inconsistent with the predictions of models that attribute asymmetries to stimulus or to retrieval bias. A contextual scaling model of asymmetry is proposed. According to this model, asymmetries in proximity judgments are caused by general principles of human memory and judgment: (a) Stimuli differ in the contexts they establish in working memory and (b) magnitude estimates are scaled by the context in which they are made.

Attention↗