Cognitive impairment in late-onset depression. Limited to a decrement in information processing resources?

BACKGROUND: While cognitive dysfunction in late-onset depression (LOD) is common, the nature and determinants of this impairment are heterogeneous. It has been suggested that neuropsychological decrements in LOD patients might result from a deficit in processing resources. In order to address this issue, we analyzed processing resources in LOD to see if their decrease explains higher-level cognition (episodic memory and naming capacity) deficits. METHODS: Measures of processing speed, working memory, inhibition, episodic memory and naming capacity were administered to 14 LOD inpatients and 14 controls. RESULTS: The LOD patients performed significantly worse than the controls in all domains except for inhibition. Hierarchical regression analyses showed that naming capacity impairment was totally mediated by processing speed and working memory, whereas episodic memory dysfunction was only partially mediated by working memory. CONCLUSION: The reduction in certain processing resources (working memory, processing speed) in late-onset depressed patients appears to mediate impairments in episodic memory and naming capacity. However, episodic memory impairment cannot only be explained by processing resource decrement in LOD patients, suggesting that a primary episodic memory dysfunction is present in this condition.

Early changes in insulin secretion and action induced by high-fat diet are related to a decreased sympathetic tone.

To evaluate the relationship between the development of obesity, nervous system activity, and insulin secretion and action, we tested the effect of a 2-mo high-fat diet in rats (HF rats) on glucose tolerance, glucose-induced insulin secretion (GIIS), and glucose turnover rate compared with chow-fed rats (C rats). Moreover, we measured pancreatic and hepatic norepinephrine (NE) turnover, as assessment of sympathetic tone, and performed hypothalamic microdialysis to quantify extracellular NE turnover. Baseline plasma triglyceride, free fatty acid, insulin, and glucose concentrations were similar in both groups. After 2 days of diet, GIIS was elevated more in HF than in C rats, whereas plasma glucose time course was similar. There was a significant increase in basal pancreatic NE level of HF rats, and a twofold decrease in the fractional turnover constant was observed, indicating a change in sympathetic tone. In ventromedian hypothalamus of HF rats, the decrease in NE extracellular concentration after a glucose challenge was lower compared with C rats, suggesting changes in overall activity. After 7 days, insulin hypersecretion persisted, and glucose intolerance appeared. Later (2 mo), there was no longer insulin hypersecretion, whereas glucose intolerance worsened. At all times, HF rats also displayed hepatic insulin resistance. On day 2 of HF diet, GIIS returned to normal after treatment with oxymetazoline, an alpha(2A)-adrenoreceptor agonist, thus suggesting the involvement of a low sympathetic tone in insulin hypersecretion in response to glucose in HF rats. In conclusion, the HF diet rapidly results in an increased GIIS, at least in part related to a decreased sympathetic tone, which can be the first step of a cascade of events leading to impaired glucose homeostasis.

Inducing emotion by unilateral contraction of hand muscles.

Following 4 unilateral contractions of hand muscles, subjects told stories about pictures from the T.A.T. A propositional analysis of the stories showed that the emotional tone of stories told following left hand contractions were more negative than those told after right hand contractions. These results are comparable to those reported following unilateral facial contractions and are consistent with the arousal of the emotional properties of the hemisphere contralateral to the contractions. When the stories were compared to ones told in a control, no contraction condition, it was found that the differences between the left and right contractions were attributable to the effects of either one or the other depending on the control condition responses to the pictures. The results therefore provide evidence for both left and right hemisphere involvement in emotion.

Unilateral contraction of facial muscles do effect emotions: a "failed replication's" failure to perform a replication.

Kop, Merckelbach and Muris (1991) reported a failure to replicate Schiff and Lamon's (1989) finding that unilateral muscle contractions induce emotions and influence cognitions in a manner which reflect those emotions. However, the procedures they used were different from the original experiment in substantive ways. These differences are described and it is explained how they account for the failure to replicate. This discussion helps illustrate the nature of the phenomenon which has been shown to be both robust and clinically relevant.

Examination of Raynaud's phenomenon in traumatic vasospastic disorders.

Certain types of occupation-related vibrations can cause traumatic vasospastic disorders. Findings from clinical examination are often normal at the office consultation. Measurements of finger blood flow using plethysmography while the local ambient temperature is changed can give important information about the severity of traumatic vasospastic disorder and the concomitant disability. This technique can also be used for follow-up of the finger blood flow after withdrawal from vibrations.

Immunohistochemical and biochemical characterization of antisera raised to human tumor nucleoli.

Antinucleolar antisera were raised in rabbits, goats and sheep to nucleoli isolated from three human tumor cell lines. The antisera were shown to cross-react by immunofluorescence with human tumor cell lines originating from different organs and with frozen sections from a wide variety of human malignant and non-malignant tissues. Tumor versus normal tissue discrimination by several antisera was significantly improved by treatment of frozen tissues with a buffered glutaraldehyde/Triton X-100 solution prior to immunofluorescent staining. The molecular specificity of these antisera was determined by immunostaining electrotransfer nitrocellulose strips following SDS-PAGE of nucleolar preparations and nuclear extracts. Although different immunostaining patterns were obtained for individual antinucleolar antisera, nucleolar proteins of molecular weight 120, 100, 94, 68, 54, 38, 33, and 32 kDa were the most often recognized by antisera raised in the three different species. G187 antiserum strongly reacted with 100, 94, and 38 kDa proteins from freshly obtained leukemic specimens. The Immunoreactivity of the 100, 94, and 38 kDa proteins was unaffected by glutaraldehyde/Triton X-100 treatment when immunostained with antisera that demonstrated the greatest tumor specificity on sections treated with glutaraldehyde/Triton X-100. These three nucleolar proteins may be more highly associated with nucleoli of malignant cells than with nucleoli of normal cells.

Inducing emotion by unilateral contraction of facial muscles: a new look at hemispheric specialization and the experience of emotion.

Subjects who maintained voluntary contractions of the left facial muscles experienced sadness. Right facial contractions resulted in a more positive but difficult to characterize experience. These contractions had similar effects on the affective tone of stories told about an ambiguous picture. These findings indicate that emotions can be aroused by unilateral muscle contractions without intervening cognitions. They provide a new methodology for studying the roles of the cerebral hemispheres in emotional experience. Finally, they support the conclusion that the right hemisphere is involved with negative emotional experiences and indicate that the left hemisphere is involved with experiences that are more positive but not readily characterized.

3-Hydroxyproline content of normal urine.

Values for total 3-hydroxyproline and 4-hydroxyproline were obtained from 24-h urine specimens of 18 healthy human subjects of both sexes, whose ages ranged from the first to the sixth decade in age. Urinary 3-hydroxyproline levels, not earlier described to our knowledge, were determined by an isotope-dilution method requiring considerable purification and utilizing the amino acid analyzer for final measurement. 3-Hydroxyproline averaged 3% of the corresponding 4-hydroxyproline in individual urine samples. Like 4-hydroxyproline, 3-hydroxyproline excretion is increased in the second decade, and there is generally good correlation between the two values in individual urines. A hydroxyprolinemic subject excreting greatly elevated 4-hydroxyproline levels did not excrete excessive 3-hydroxyproline, consistent with independent catabolic pathways for the two compounds. 3-Hydroxyproline appears to be selectively excreted relative to 4-hydroxyproline when compared with the probable total body content of each amino acid. Possible explanations are: a more rapid turnover of basement membrane collagen than interstitial collagen or, alternatively, relatively greater resistance to the proteolytic cleavage of peptides containing 3-hydroxyproline.

Prolyl hydroxylase of earthworms. Substrate specificity of an enzyme from the subcuticular epithelium.

A relatively crude enzyme preparation derived from the subcuticular epithelium of earthworms catalyzed the formation of 4-hydroxyproline from prolyl residues in unhydroxylated natural collagens and in several synthetic collagen-like polypeptides. The specificity of hydroxylation differed from that of all vertebrate polyl hydroxylases in that (Gly-Pro-Ala)n was a much better substrate than (Gly-Ala-Pro)n. In contrast, however, only the so-called Y position proline (Gly-X-Y) was hydroxylated in Gly-Pro-Pro sequences derived either from natural collagen or from synthetic polypeptides; specificity of hydroxylation for the latter sequence is identical with that of the vertebrate enzymes. Little or no formation of 3-hydroxyproline could be demonstrated in preparations of the enzyme active as a 4-hydroxylase. In contrast with an earlier report from another laboratory, using a crude extract of earthworm body wall, we were unable to demonstrate either significant 3-hydroxyproline formation or efficient 4-hydroxylation of X position prolyl residues in synthetic polypeptides with the internal sequence Gly-Pro-Pro.

Sequence position of 3-hydroxyproline in basement membrane collagen. Isolation of glycyl-3-hydroxyprolyl-4-hydroxyproline from swine kidney.

The position of 3-hydroxyproline was investigated in the triplet sequences of peptides released by collagenase digestion of a collagen preparation from kidney cortex. Composition of the collagen preparation indicated that it was largely or wholly of basement membrane origin. 3-Hydroxyproline was detected in only one sequence, the tripeptide, glycyl-3-hydroxyprolyl-4-hydroxyproline, which accounted for a major fraction of the total 3-hydroxyproline obtained in the peptides released by collagenase. Preliminary data, based on sequencing the peptide mixture released by collagenase treatment, suggested that, in contrast, 4-hydroxyproline occurs predominantly if not exclusively in the Y position of Gly-X-Y triplet sequences in the collagen preparation studied.