Types Of Degenerative Changes Research Articles

Morphological and functional characteristics of arpa (receptor potential absent) visual mutant of the blowfly (Calliphora erythrocephala)

1. We have discovered a previously unreported visual mutant of the blowfly,Calliphora erythrocephala. It shows a reduced or absent visual performance, e.g., in escape and optomotor behavior. The effects of this mutation on the ultrastructure were studied by electron microscopy (Figs. 3–8) and on electrophysiological function, by intracellular recordings (Figs. 1 and 2). 2. The genetic basis of this spontaneous mutation was studied by test crosses of mutant and wild-type flies. The defect appears to be in an autosomal recessive gene (Table 1). 3. Of the mutant stock studied soon after eclosion (n = 18) 35% shows optomotor reactions, whereas only 6% studied in later life (n = 240) shows any optomotor behavior. 4. The absence of the receptor potentials in photoreceptor cells is not directly associated with structural disorders in the early life of these mutant flies, but several types of degenerative changes are manifested in the retinular cells later on. The optomotorically blind specimens have normal (about −60 mV) resting membrane voltages but no detectable receptor cell voltage response to light, indicating a block in phototransduction. The spectral and polarization sensitivities of optomotor-positive flies are normal (Fig. 2). 5. At the beginning of degeneration the number of lysosomes in the receptor cells is increased compared with normal flies, but their number as well as that of other components of the cell interior decrease later on. During the progression of the degeneration, the rhabdomeres shrink while the mitochondria swell and disintegrate (Figs. 6–8). 6. The blocking of phototransduction is proposed to lead to disturbance of the turnover of the rhabdomeres and finally to degeneration of the receptor cells.

Changes of CSF neuropeptides after environmental stimulation in dementia

Reduced dendritic branching has been reported in animals reared in a poor environment.This has been found during brain development and in adults as well. The same type of degenerative changes has also been observed in dementia of Alzheimer type in man. These findings raise the possibility that a poor environment, in addition to biological factors, may contribute to morphological and biochemical changes in the central nervous system of demented patients. To test the hypothesis whether environmental stimulation can influence biochemical alterations in dementia, cerebrospinal fluid (CSF) concentrations of cholecystokinin (CCK), corticotropin releasing factor (CRF) and somatostatin were analysed before and after two months' of environmental stimulation in two groups of demented patients with senile onset. The experimental group of demented patients (n=11) participated in a program with intensified intellectual, emotional and environmental stimulation during a two month period. A control group of demented pati...

Free fatty acids in the subretinal fluid.

Free fatty acids (FFA) were determined in 50 samples of subretinal fluid (SRF) by the colorimetric method of Duncombe. The level of blood serum FFA was determined simultaneously. FFA in the SRF ranged between 0.01 and 1.0 mumol/ml in normal distribution with the maximum at low concentrations. No correlation was found between the level of FFA in the SRF and in the blood serum. Analysis of the correlation between the concentration of FFA in SRF and the clinical picture of retinal detachment show a relationship between the level in SRF and the age of the patients, the etiological factors and the type of degenerative changes of the retina.

The distribution of melanin in the developing optic cup and stalk and its relation to cellular degeneration

The early distribution of melanin in the developing optic cup and stalk and its relationship to cellular degeneration have been studied during intrauterine development in hamsters, mice, ferrets, and humans. The extensive degenerative changes that occur in the region of the optic fissure do not involve any pigment-bearing cells. Melanin is not formed at the site of the fissure until after the processes of fusion and the associated degenerative changes are complete. In contrast to this, there is a small region near the junction of the cup and stalk where melanin is particularly related to degenerative changes. Melanosomes form dense clumps associated with basophilic, apparently degenerate areas of cytoplasm, and these melanosome complexes themselves undergo further degenerative changes. The two types of degenerative changes, pigmented and unpigmented, are limited to the same two regions of the developing eye in all four species. However, the pigment degeneration is more extensive in ferrets and humans than in mice and hamsters. These observations raise the possibility that the lysis of melanosomes plays a significant but undefined local role in ocular development.

Ultrastructural features of the isolated suprasylvian gyrus in the cat.

AbstractAn ultrastructural study has been made of the suprasylvian gyrus of the cat after its complete surgical isolation. In acute experiments (36 to 48 hours after isolation) the distribution and type of degenerative changes in axons and axon terminals belonging to extra‐gyral fibers have been studied. The number of dark degenerating boutons nerver reaches 15% of the synaptic population. Such boutons are scattered throughout all cortical layers, but they are more numerous in the superficial than in the deeper layers. The majority of the dark degenerating boutons establish synaptic contact on dendritic spines, less frequently they synapse on dendritic shafts, and only rarely on neuronal perikarya. In some instances the degeneratin presynaptic boutons and their postsynaptic spines seem to follow a simultaneous degenerative process, as they are apparently entrapped in the same astrocytic cytoplasm. Nevertheless, free postsynaptic spines, bearing normal‐looking postsynaptic densities are occasionally observed in the neuropil of the acutely isolated cortex, as well as in subacute (13 days after isolation) and chronic (30 to 46 days after isolation) animals.In the chronically isolated gyrus, except for the intense, diffuse gliosis, the presence of numerous dark, degenerating, small myelinated fibers and the persistence of some degenerating boutons, the nervous parenchyma seems, from a qualitative assessment, to have a normal appearance.A quantitative coparison of the various kinds of synapses in the unoperated suprasylvian gyrus and in the chronically isolated gyrus, has been carried out, since this is the only way to study the final result of deafferentation on the synaptic arrangement in the isolated cortex. The number of axon terminals is decreased by 20 to 30% in the chronic preparation. This diminution of synapses is more marked in the superficial than in the deeper layers: thus, the index of synapses in superficial layers is one synapse/10/μm2 in control animals, and decreases to one synapse/17/μm2 in chronic animals. However, in the deeper layers it is one synapse/13/μm2 in control animals and only decreases to one synapse/16/μm2 in chronic animals. The large majority of the lost boutons formerly synapsed on dendritic spines.In addition to the loss of synapses and to the intense gliosis, other morphological alterations were observed: reduction in the size of all cortical neuronal perikarya, modification of some vascular beds with dilatation of the Virchow's spaces, and spread of the basal membranes for long distances from the capillaries.A number of pathological features are encountered in the chronically isolated suprasylvian gyrus: (1) loss of afferent fibers, (2) loss of dendritic spines, (3) neuronal atrophy, (4) intense marginal and interstitial gliosis, and (5) alterations of some perivascular spaces; the last feature may give a morphological explanation for the particular electrophysiology observed in this type of cortex; since it may give rise to alterations in the permeability of the vascular barrier, resulting in chemical modifications of the interstitial milieu which may be the cause of the altered neuronal activity.

Studies on the exoerythrocytic stages of Plasmodium gallinaceum during the “transitional phase”

Studies made during the transitional stage infection of P. gallinaceum in chicks (i.e., the period of transition from tissue parasitism to parasitemia) have yielded the following results: 1. 1. The relative frequency of exoerythrocytic stages expressed as number of parasites per square millimeter of section is fairly consistent for the two birds examined except for the kidney and spleen. The brain ranked low in relation to kidney, lung, heart, and liver as the organ of localization. 2. 2. At the time when the preponderance of parasites in the fixed tissue consisted of large schizonts and segmenters the preponderance of eryth-rocytic parasites consisted of young trophozoites. The larger schizonts and segmenters were fairly equally distributed among the different organs whereas in one of the birds 32% of the exoerythrocytic stages of the lung were small trophozoites. It would appear that not only were large numbers of exoerythrocytic merozoites changing to erythrocytic stages but that relatively few of them were continuing as exoerythrocytic stages. 3. 3. Degenerative changes in the exoerythrocytic stages, possibly due to the development of antibodies by the host, were seen as early as 53 hours after the first observed parasitemia. The type of degenerative change in the parasite was similar to that observed previously as the result of the action of natural immunity and of antimalarial drugs. 4. 4. So-called macromerozoites and micromerozoites were found to be only the extremes in size of a population of merozoites with normal variation in size. Thus, no dimorphism exists in the schizonts of this species. 5. 5. It is believed that, although no dimorphism of the schizonts exists, the average size of the merozoite decreases during the transitions from a condition in which the host cells are predominantly of the lymphoid-macrophage system to the condition in which they are predominantly endothelial in type, and then to the stage where the erythrocytes are the cells which are predominantly inhabited. 6. 6. The prevalent view that the smaller merozoites are destined to produce erythrocytic stages while the larger merozoites are destined to continue the exoerythrocytic cycle has not been adequately proved.