Recognition memory in alzheimer''s disease

Recognition memory for several types of stimulus material was examined in patients clinically diagnosed as having early Alzheimer's disease and in normal elderly controls. Although performance deficits were demonstrated for verbal and abstract stimuli (geometric shapes and histology slides), memory for faces was relatively intact in the patient group. Patients made more false positive responses than controls, but this could not be accounted for by a general disinhibition of responding. It is suggested that a contextual processing deficit may explain the pattern of false positive responding and this is discussed in relation to previous findings of drug studies in Alzheimer's disease.     

Attentional networks in normal aging and Alzheimer's disease

By combining a flanker task and a cuing task into a single paradigm, the authors assessed the effects of orienting and alerting on conflict resolution and explored how normal aging and Alzheimer's disease (AD) modulate these attentional functions. Orienting failed to enhance conflict resolution; alerting was most beneficial for trials without conflict, as if acting on response criterion rather than on information processing. Alerting cues were most effective in the older groups--healthy aging and AD. Conflict resolution was impaired only in AD. Orienting remained unchanged across groups. These findings provide evidence of different life span developmental and clinical trajectories for each attentional network.     

Qualitative and quantitative glial changes in the hippocampus of aged rats

Ultrastructure of the glial cells in the CA 1 hippocampal field and some quantitative parameters characterizing the astrocytes in stratum lacunosum-moleculare (str. L-M) of the CA 1 hippocampal field of young-mature (3-month old) and aged (24-month old) rats were examined. The qualitative observations showed structural changes in astrocytes, oligodendrocytes and microglial cells in all layers of the CA1 hippocampal field in aged rats. The quantitative analysis demonstrated a considerable increase in total and individual volume fractions of astrocyte processes, in number of astrocyte profiles per square area of neuropil and in percentage area of neuropil occupied by astrocyte process profiles. These changes as well as the increased number of astrocyte nuclei suggest the appearance of hypertrophy and hyperplasie of astrocytes in str. L-M of the CA 1 hippocampal field of rats in aging.     

Morphological changes in nerve cells during normal aging

During normal aging, widespread loss of nerve cells does not occur. Neuronal loss is limited to restricted regions of the nervous system and is slight (probably no more than 10%). The commonest age-related structural changes undergone by nerve cells are as follows: dendrites decrease in number and length and many dendritic spines are lost; axons decrease in number and their myelin sheaths may become less compact and undergo segmental demyelination followed by remyelination; and significant loss of synapses occurs. These changes probably make a significant contribution to the behavioral impairment and cognitive decline that often accompany normal aging.     

Immunoglobulins, cognitive status and duration of illness in alzheimer''s disease

Immunologic changes have been reported in the dementing illnesses of mid and late life. The results of two studies of drug-free males meeting research diagnostic criteria for primary neuronal degeneration of the Alzheimer's type suggest that serum IgG levels decrease with the progression of dementia. Serum IgG levels were inversely correlated with duration of illness and the levels of psychiatric symptomatology. Performance on the mini-mental status examination was positively associated with serum IgG concentrations.     

The molecular genetic approach to familial alzheimer''s disease

There is indeed a strong case to be made for locating the genetic defect underlying at least some proportion of AD cases. A strategy involving linkage analysis with DNA markers has already been implemented and has good prospects for success. The ultimate identification of a linked marker could, however, be hastened by the identification, documentation, sampling and banking, of additional large kindreds in which AD appears to inherit as an autosomal dominant defect.     

Qualitative and quantitative changes in beta-1,4-glucosidase accompanying growth of Aspergillus nidulans

A comparative study of the wild type A. nidulans and a mutant strain aco-T69 (lacking conidia and cleistothecia) revealed the better production of beta-1,4-glucosidase in the former. The relative distribution of the enzyme levels in various morphological structures viz. somatic hyphae, spores and cleistothecia also showed a variation. Highest specific activity was found in the cleistothecial extracts. The electrophoretic analysis of the wild type strain demonstrated the presence of three isoenzymes of beta-1,4-glucosidase i.e. beta-GLU I, beta-GLU II and beta-GLU III, the number of which varies from one to three during the growth of the organism. The parallel study of the mutant strain showed complete absence of beta-GLU II. All three forms were present in the somatic hyphae and cleistothecial extracts while spore extracts depicted the absence of beta-GLU III in the wild type.     

Comments on review by coleman and flood ‘neuron numbers and dendritic extent in normal aging and alzheimer''s disease.’ density measures: Parameters to avoid

Alterations in cell numbers in human brain structures of more than a factor or two may be missed when only cell density is measured.     

Specificity of inhibitory deficits in normal aging and Alzheimer's disease

Deficits of suppression abilities are frequently observed in normal aging and Alzheimer's disease. However, few studies have explored these deficits in the two populations simultaneously using a large battery of tasks. The aim of the present study was to explore if the pattern of performance presented by elderly subjects and AD patients is in agreement with theoretical frameworks [Wilson, S.P., Harnishfeger, K.K., 1998. The development of efficient inhibition: Evidence from directed forgetting tasks. Dev. Rev. 18, 86-123; see also Nigg J.T., 2000. On inhibition/disinhibition in developmental psychopathology: views from cognitive and personality psychology and a working inhibition taxonomy. Psychol. Bull. 126, 220-246], distinguishing between the concepts of inhibition (a voluntary suppression of irrelevant information) and interference (an automatic suppression process occurring prior to conscious awareness). The results obtained demonstrated that (1) there is an alteration of the inhibitory process in normal elderly subjects; (2) inhibitory and interference resolution processes are quantitately less efficient in AD, since these patients present a correct performance only for information which leaves weak traces in memory.     

Memory changes with normal aging: Behavioral and electrophysiological measures

We examined performance in young and elderly on an implicit (lexical decision) and an explicit (recognition) memory test. The difference in lexical decision times between old and new words was equivalent in the two groups, although the elderly were slower. In both groups, recognition accuracy (lower in the elderly) was higher following semantic than nonsemantic encoding, whereas lexical decision times were unaffected. Divergent brain potentials for old and new words during lexical decisions constituted a repetition effect, which reflected greater positivity (200–800 ms) for old words, particularly over the left hemisphere; this effect was smaller and later in the elderly. An electrophysiological marker of enhanced recollection for words from the semantic encoding task took the form of a left-sided positivity (500–800 ms). The effect was smaller in the elderly than the young, providing an additional index of their impaired recognition processes.     

Neuron numbers and dendritic extent in normal aging and Alzheimer''s disease

Evidence is reviewed regarding neuron numbers and dendritic extent in normal aging in rodent, monkey and human brain and in Alzheimer's disease (AD) in man. Neuron loss and change in dendritic extent appear to be regionally specific but not identical in rodents and primates. In AD there is excess neuron loss and dendritic regression in some but not all brain regions. Overlap between AD and control groups, however, is known to occur. Methods to assess dynamic morphology of the living brain may be superior to analysis of static, post-mortem brain structure in explaining functional deficits in AD and normal aging.     

Qualitative and quantitative changes in the brain phospholipid spectrum of rats with metrazol seizures

Kh. Abovyan Armenian Pedagogic Institute. Institute of Experimental Biology, Academy of Sciences of the Armenian SSR, Erevan. (Presented by Academician of the Academy of Medical Sciences of the USSR A. N. Klimov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 1, pp. 7–9, January, 1991.     

Arteries and veins of the normal dog lung: Qualitative and quantitative structural differences

As a necessary preliminary step to the study of pulmonary hypertension and edema, the structure of the pulmonary vasculature of seven normal dogs was examined in detail to distinguish arteries and veins. For light microscopy and morphometry, the left lung was injected from the arterial and venous sides with pigmented gelatin masses of different colors. The right lung was fixed for electron microscopy. The percentage of medial muscle thickness of arteries was greater (P < 0.05) than that of veins, for vessels over 200 μm diameter. Smooth muscle cells extended more peripherally into arteries (including in vessels less than 50 μm) than into veins. The larger arteries were elastic or transitional in type, whereas larger veins were muscular. The arteries branched with the airways. Fifty percent of arteries under 50 μm and more than 50% of veins under 200 μm were surrounded by alveoli. Muscular arteries had a thick media between distinct internal and external elastic laminae, whereas veins had no internal lamina but had a thin media separated from a thick adventitia by an external elastic lamina. By electron microscopy, the muscular arteries had tightly packed smooth muscle cells with few myoendothelial junctions; the venous smooth muscle cells were arranged loosely, and more numerous myoendothelial junctions were seen. No definite differences were noted between nonmuscular arteries and veins. The functional implications of these morphological findings (differential reactions to pharmacological agents, distensibility of pulmonary arteries and veins, and responses of small vessels to alveolar pressure) are discussed.     

Processing of semantic relations in normal aging and Alzheimer's disease.

The decline in semantic memory observed in Alzheimer's disease is presumed to result from progressive loss of the attributes underlying category representation. Here, we explored the possibility that semantic deterioration would affect attributes differently, depending on the type of semantic relationship connecting the subject and the object of the attribution. We compared the performance of 50 patients with probable Alzheimer's disease (APs) to that of 30 elderly controls in two semantic tasks: a verbal sentence verification task and a visual test of analogical relations, both including several types of semantic relations. On the sentence verification task, the performance of APs was comparable to that of elderly controls when statements were true, but deteriorated significantly when statements were false. This result was interpreted as a failure of controlled processes to successfully search semantic space when statements were incongruent or false. In addition, all participants found some semantic relations more difficult to process than others, with relative difficulty being consistent across tasks. Taxonomic semantic relations were the most difficult, while part/whole relations were the easiest, but also the ones to deteriorate most rapidly. In contrast, functional attributes were comparatively preserved as the disease progressed. These results emphasize the role of attention and semantic context in jointly determining access to relevant attributes and categories. Furthermore, they suggest that semantic memory impairments in Alzheimer's are affected by the type of processing and semantic relationship required by the task.     

Phonoangiography: Qualitative and quantitative

Bruit analysis (phonoangiography) has been performed for many years as a method of characterizing arterial disease. Time displays of arterial bruits, particularly at the carotid bifurcation, have been used in an attempt to quantitate arterial narrowing. Despite the generalization that longer bruits and bruits which look and sound higher in frequency are often associated with severe disease, prospective studies have shown no useful predictive value for qualitative phonoangiography. In marked contrast, spectral bruit analysis or quantitative phonoangiography has been quite accurate in predicting the location and extent of carotid stenosis, and in distinguishing intrinsic from transmitted bruits. With this method, the peak systolic portion of the bruit is subjected to fast Fourier transform analysis. The peak frequency, beyond which amplitude drops as frequency increases further, is directly related to the residual lumen diameter of the stenotic common or internal carotid artery. Several blinded trials of this method have given results accurate to within 1 mm of angiographic values in 83–93% of cases studied. When used in conjunction with duplex doppler ultrasound scanning, 95% accuracy in diagnosis of patients with and without bruits may be achieved. This completely noninvasive method deserves more widespread use and may also be applicable to other cardiovascular sounds.     

Apoptotic-like changes in Lewy-body-associated disorders and normal aging in substantia nigral neurons.

In Parkinson's disease and other Lewy-body-associated disorders, the substantia nigra pars compacta undergoes degeneration, but the mechanism of cell death has not been previously described. The substantia nigra of normal and Alzheimer's disease cases were compared with substantia nigra from patients with Lewy-body-associated disorders (Parkinson's disease, concomitant Alzheimer's/Parkinson's disease, and diffuse Lewy body disease) using in situ end labeling to detect fragmented DNA. In situ end-labeled neurons demonstrated changes resembling apoptosis: nuclear condensation, chromatin fragmentation, and formation of apoptotic-like bodies. Ultrastructural analysis confirmed nuclear condensation and formation of apoptotic-like bodies. Apoptotic-like changes were seen in the substantia nigra of both normal and diseased cases; concomitant Alzheimer's/Parkinson's disease and diffuse Lewy body disease cases had significantly higher amounts of apoptotic-like changes than normal controls or Alzheimer patients. The finding of neuronal death by apoptosis may have relevance for the development of new treatment strategies for Parkinson's disease and related disorders.