Transtympanic facial nerve paralysis

In order to ascertain the immediate histopathological changes of rat brain following experimental surgical injury, fragments of left parietal cortex were obtained through craniotomy and fixed by immersion. Next, the animals were killed by perfusion with the same fixative used for the respective biopsy. Five groups of rats were tested, each for one different fixative. Dark neurons were by far the most prominent feature in surgically traumatized tissue, following both immersion and perfusion with all five fluids. They were morphologically identical at both sites, and fixatives with widely different chemical composition, e.g. Bouin's fluid and buffered glutaraldehyde, had no influence on their aspect. It is suggested that shrunken neurons are not to be interpreted systematically as artefacts, but also represent a form of short-latency cellular reaction to injury.     

In vitro study of the protective effect of trehalose and dextran during freezing of human red blood cells in liquid nitrogen

Our previous studies showed that neurons became argyrophilic following different kinds of brain injuries. In the present study we demonstrated that astrocytes could also become argyrophilic following compressive or concussive head injuries and following intraperitoneal administration of pentylenetetrazole or kainic acid. Furthermore the soma, nucleus and processes of these argyrophilic astrocytes were shown in other preparations to be hyper-basophilic with the light microscope, and hyper-electron dense and shrunken at the ultrastructural level. When the head injuries were inflicted either at the 15th min. of perfusion-fixation or at the 30th min. of transcardial perfusion with chilled physiological saline, several astrocytes also became argyrophilic, hyper-basophilic, shrunken and hyper-electron dense. These data indicate that (i) the intracellular pathological event in these astrocytes is similar to that of "dark" neurons or "dark" cells of non-neural tissues, (ii) the formation of "dark" astrocytes can be independent of the actual state of metabolism, and (iii) the "dark" morphological state of astrocytes might have a role in neuropathological processes.     

Transmucosal delivery of oxytocin to rabbits using a mucoadhesive buccal patch

Sections from the human somatosensory cortex were observed with a light microscope. The neurons were classified into light and dark ones. The light neurons were slightly stained with thionin, luxol fast blue MBS and azocarmine G (80% of all neurons). The dark neurons were more or less shrunken, and stained intensely with these dyes (20% of all neurons). Double staining with luxol fast blue MBS and azocarmine G was especially useful to demonstrate the dark neurons, since it clearly stained even their fine processes. Neither light nor dark neurons were reactive to nick end labeling for detection of DNA fragmentation. Triple staining with Golgi's silver nitrate (or Gallyas's ammoniacal silver carbonate), luxol fast blue MBS and azocarmine G show that the majority of the dark neurons were argyrophilic (argyrophilic dark neurons, 15% of all neurons), while some of them were not argyrophilic (non-argyrophilic dark neurons, 5% of all neurons). Triple staining also showed that the light neurons were only occasionally argyrophilic (argyrophilic light neurons, 5% of all neurons); usually, the light neurons were not argyrophilic (non-argyrophilic light neurons, 75% of all neurons). The results confirm that dark neurons usually represent certain populations of neurons in the human brain, and that they are basically identical to the argyrophilic neurons. The discussion suggests that the argyrophilic light and dark neurons are excited cells, the non-argyrophilic dark neurons are exhausted cells, and the non-argyrophilic light neurons are resting cells. Triple staining further demonstrated that some glial cells were darkened and stained with Golgi's silver nitrate or Gallyas's silver carbonate. Additional Golgi's silver block staining showed that the argyrophilic neurons stained by the conventional block staining method usually possessed a shrunken cell body, which was characteristic of the dark neurons.     

Mammalian parathyroids: morphological and functional implications

Fixation with aldehydes is achieved either by immersion or perfusion. The parenchyma of parathyroid glands fixed by immersion consists of dark cells containing a lot of membranes of these organelles which are concerned with hormone secretion, light cells which are poor in these organelles, intermediate forms between the two, and multinuclear syncytial cells. They have been attributed to represent different functional stages of secretory activity, the dark cell being in an active form, the light cell in a resting form. Studies of the parathyroids of mice, rats, rabbits, cats, dogs, pigs, cattle, sheep, goats, and horses employing various fixation protocols clearly demonstrate that light cell variants and multinuclear syncytial cells are formed during improper immersion fixation as a result of membrane disintegration. Parathyroids fixed by perfusion or by immersion in an appropriate fixation medium comprise only one cell type which correspond to the dark chief cell. Parathyroid cells are polar cells bearing some of the rough endoplasmic reticulum in the basal pole, the rest of it, the Golgi complex, and secretory granules in the apical pole. The secretory product is released by exocytosis at the apicolateral domain of the plasma membrane into the intercellular space. Secretory activity can be altered experimentally, leading to drastic changes in the amount of cell membrane related to hormone synthesis, intracellular transport, exocytic release, and secretion coupled membrane retrieval. The sensitive reaction of parathyroid cells to both the mode of fixation and to fixation media demands careful evaluation of the fixation protocol. This and the polarity of parathyroid cells have to be borne in mind for estimating secretory activity on the basis of morphological criteria.     

Influence of alkyl chain lengths in dialkylglycerophosphocholines towards phospholipase A2 inhibition in macrophages

Immunocytochemistry using antibodies against various molecular forms of the Ca++ and Zn(++)-binding S100 proteins predominantly labelled astrocytes. However, especially in the neocortex the staining pattern is variable. Methods of tissue preparation have been evaluated with the aim to preserve as much S100 immunoreactivity as possible. Optimal results were obtained after perfusion fixation with 4-5% aldehydes, 0.1 M sodium cacodylate, 0.1% CaCl2, pH 7.3. In such preparations, astrocytes were completely labelled including their lamellar compartments in large parts of the central nervous system. Ca(++)-withdrawal had adverse affects on S100 immunoreactivity. Cryostat sections treated with EDTA-containing solutions before fixation showed that Ca(++)-free S100 can apparently not be fixed to the tissue. Perfusion fixatives containing EDTA resulted in inhomogeneous loss of S100 staining, indicating a differential susceptibility of astrocytic subpopulations. A different type of reduction in S100 immunoreactivity occurred around large neocortical blood vessels. Perivascular defects in immunostaining occasionally appeared even after optimal fixation, but could be regularly provoked by mildly acidic fixation (pH 6.6) or prolonged barbiturate anaesthesia. These defects might be based on S100 release into the cerebrospinal fluid. Presumably under none of the conditions studied can the immunoreactivity of all S100-forms and -fractions be completely preserved in the tissue. However, recommendations are presented for optimizing tissue preparation, to the extent that premortal modifications affecting the stainability of astrocytes may be detected by S100 immunohistochemistry in fixed brain tissue.     

Fixation of canine tendons to metal

For the purpose of developing a method to attach tendons directly to the prosthesis, canine supraspinatus tendons were attached in vitro to a metallic surface, using 3 different fixation devices: a spiked polyacetal washer (Synthes), a spiked soft tissue fixation plate (Synthes), and a newly designed Enhanced Tendon Anchor (ETA), which straddled the tendon with interlocking spikes oriented at a 20-degree angle. 2 methods were used: 1) the tendon was fixed directly to the metallic surface, or 2) a bone block containing the tendon insertion was fixed to the metallic surface. The specimens were tested for initial fixation strength in tension to failure; intact bone-muscle-tendon-bone units were used as controls. Bone block fixations were stronger than direct tendon fixations when the spiked washer or the ETA was used; this was not true of the fixation plate. The ETA was stronger than the other techniques in ultimate strength in both direct tendon fixation and bone block fixation. The soft tissue fixation plate was found to be weaker than the other techniques in bone block fixation.     

Semen backflow after insemination and its effect on fertilisation results in sows

Formalin fixation, the chemical process in which formaldehyde binds to cells and tissues, is widely used to preserve human brain specimens from autolytic decomposition. Ultrastructure of cellular and mitochondrial membranes is markedly altered by vesiculation, but this does not interfere with diagnostic evaluation of neurohistology by light microscopy. Serious difficulties are encountered, however, when immunocytochemical staining is attempted. Antigens that are immunoreactive in unfixed frozen sections and protein extracts appear to be concealed or destroyed in formalin-fixed tissues. In dilute aqueous solution, formaldehyde is in equilibrium with methylene glycol and its polymeric hydrates, the balance by far in favor of methylene glyco. Carbonylic formaldehyde is a reactive electrophilic species well known for crosslinking functional groups in tissue proteins, nucleic acids, and polysaccharides. Some of its methylene crosslinks are readily hydrolyzed. Others are stable and irreversible. During immunostaining reactions, intra- and inter-molecular links between macromolecules limit antibody permeation of tissue sections, alter protein secondary structure, and reduce accessibility of antigenic determinants . Accordingly, immunoreactivity is diminished for many antigens. Tissues are rapidly penetrated by methylene glycol, but formaldehyde binding to cellular constituents is relatively slow, increasing progressively until equilibrium is reached. In addition, prolonged storage in formalin may result in acidification of human brain specimens. Low pH favors dissociation of methylene glycol into formaldehyde, further reducing both classical staining and antigen detectability. Various procedures have been devised to counter the antigen masking effects of formaldehyde. Examples include pretreatment of tissue sections with proteases, formic acid, or ultrasound. Recently, heating of mounted sections in ionic salt solution by microwave energy was found to restore many antigens. Theory and practice of microwave antigen retrieval are covered extensively in the handbook Microwave Cookbook for Microscopists. A concise overview of microwave methods in the neurosciences has been published, and clinical applications have been reviewed. In this context, it should be noted that fresh tissues may be stabilized for immunocytochemistry by reversible, non-chemical binding processes such as cryosectioning after microwave treatment and freeze-drying. Thus, it may be possible to enhance immunostaining for some antigens by microwave irradiation of unfixed as well as fixed specimens. Parameters to be optimized for microwave retrieval of specific antigens include temperature, irradiation time, tissue buffer composition, salt concentration, and pH. Temperature, irradiation time, and pH are key variables. With this in mind, an optimal method was developed for retrieval of a wide variety of antigens in human brain tissues. Typical microwave protocols employ elevated temperatures that may reach 100 degrees C, where denaturation causes irreversible uncoiling and disruption of protein secondary and tertiary structures. Under these conditions, stable covalent bonds securing methylene crosslinks between polypeptides remain intact, but more reactive links formed by Schiff bases may be hydrolyzed. Resultant conformational changes presumably expose buried loops of continuous amino acids and protruding regions, increasing accessibility of their epitopes. Protein denaturation seems to be a reasonable explanation for the effects of microwaves on antigen retrieval. This idea is supported by the observation that denaturing solutions such as 6 M urea increase immunoreactivity of some antigens. Still, the molecular basis of these effects remains unresolved, in part due to the complex chemistry of formaldehyde reactions with tissue constituents. Indeed, some methylene bridges between similar groups such as NH2 and NH may be hydrolyzed by washing fixed tissues in distilled wa     

Antiphospholipid antibody syndrome in a case with redo coronary artery bypass grafting under cardiopulmonary bypass

Until now 'c-series' polysialogangliosides were known to exist in human brain only during development and in some pathological conditions like Alzheimer's disease. Using thin-layer chromatography (TLC) and immunostaining with Q211 antibody (TLC-overlay technique) we have analysed 'c-series' gangliosides in four human cerebella (age 20, 47, 52 and 54 years). Four distinct ganglioside bands, most probably corresponding to GT1c, GQ1c, GP1c and GH1c were found to exist in the analysed brains, which is convincing demonstration of the existence of 'c-series' gangliosides in normal adult human brain. Immunohistochemical analysis was performed to locate polysialogangliosides in the analysed tissue. Q211 antibody was found to bind specifically to a single subpopulation of neurons in the molecular layer of adult cerebellum. According to their position and morphology these cells correspond to stellate neurons.     

Increased ipsilateral expression of Fos following lateral hypothalamic self-stimulation

Immunohistochemical labeling of Fos protein was used to visualize neurons activated by rewarding stimulation of the lateral hypothalamic level of the medial forebrain bundle (MFB). Following training and stabilization of performance, seven rats were allowed to self-stimulate for 1 h prior to anesthesia and perfusion. Brains were then processed for immunohistochemistry. Two control subjects were trained and tested in an identical manner except that the stimulator was disconnected during the final 1 h test. Among the structures showing a greater density of labeled neurons on the stimulated side of the brains of the experimental subjects were the septum, lateral preoptic area (LPO), medial preoptic area, bed nucleus of the stria terminalis, substantia innominata (SI), and the lateral hypothalamus (LH). Several of these structures, the LPO, SI, and LH, have been implicated in MFB self-stimulation by the results of psychophysical, electrophysiological, and lesion studies.     

The neurobiology of hepatic encephalopathy

We have developed a monoclonal antibody (9C5) for immunohistochemical localization of tartrate-resistant acid phosphatase (TRAcP). This antibody reacts with a denatured epitope of TRAcP and requires enhancement methods to promote antigenicity in paraffin-embedded tissues. We used this antibody to systematically examine proteolytic digestion and heat denaturation conditions for epitope enhancement in both paraffin sections and fixed smears. The goal was to increase the sensitivity of the immunohistochemical stain for TRAcP. Optimal conditions for proteolytic digestion were established. Denaturation in a conventional boiling water bath was compared to microwave irradiation in several commonly used solutions. Immunohistochemistry was compared directly to TRAcP cytochemistry in fixed smears from hairy cell leukemia specimens to gauge the level of sensitivity of our improved method. Attempts were made to "retrieve" the 9C5 epitope from overfixed tissues and aged smears. Maximal immunoreactivity of TRAcP was achieved by microwave irradiation in a citrate or Tris buffer of pH 6.0-8.0 without the need for a subsequent protease digestion step. With this method of epitope enhancement, immunohistochemistry with antibody 9C5 was as sensitive as direct cytochemical staining of TRAcP activity. However, once a tissue specimen had been overfixed or a smear stored for a year or more, the 9C5 epitope was no longer retrievable. The key element in epitope enhancement for 9C5 immunohistochemistry is heat denaturation of the target epitope. Immunohistochemistry of TRAcP in paraffin sections would be a great asset to the study of specialized forms of the monocyte/macrophage lineage and to the process of macrophage activation. It would also provide another means for more precise evaluation of residual disease in bone marrow of patients treated for hairy cell leukemia.     

Factors influencing dark nitrogen fixation in a blue-green alga

Nitrogen-fixing activity declines first rapidly and then more gradually when Anabaenopsis circularis is transferred from light into dark conditions. The rate and duration of dark acetylene reduction (nitrogen fixation) depend upon conditions prevailing during the preceding light period. Factors (such as light intensity, CO2 concentration, and supply of glucose), which in the light affect photosynthesis and the accumulation of reserve carbon, have a profound effect on dark nitrogen fixation. Glucose greatly promotes nitrogen fixation in the light and supports prolonged nitrogenase activity in the dark. The results suggest that heterotrophic nitrogen fixation by blue-green algae in the field may be important both under light and dark conditions.     

Effect of dynamic glutaraldehyde fixation on the viscoelastic properties of bovine pericardial tissue

We have previously proposed dynamic fixation as an alternative method to fix a porcine aortic heart valve xenograft with better tissue fixation and better preservation of its natural biomechanical properties. Bovine pericardium was fixed under dynamic conditions, low pressures (< 4 mmHg) and low vibration rate (1.2 Hz) in a 0.5% glutaraldehyde phosphate buffer (pH 7.4, 0.2 M). After fixation, tensile testing (i.e. relaxation and stress-strain curves) was performed at low and high extension rates (3 and 30 mm s(-1)) and tissue denaturation temperatures were determined by the hydrothermal isometric tension method. Conventional fresh and statically fixed pericardium were used as controls. In this instance, we found no significant biomechanical differences between the dynamically and statically fixed pericardial tissue (e.g. moduli and stress relaxation). However, differences in tissue extensibility were delineated, since the extensibility of the dynamically fixed tissue was closer to that of the fresh tissue compared to that of the statically fixed tissue. The final relaxation rate of the dynamically fixed tissue (-3.5 +/- 1.0% of stress remaining per log(second)) was similar to that of the statically fixed tissue (-3.2 +/- 0.60% log(s(-1))) and significantly lower than the fresh tissue(-9.5 +/- 1.2% log(s(-1))). The denaturation temperatures of the dynamically fixed pericardial tissue (mean +/- SD) (86.0 +/- 1.2 degrees C) and the statically fixed (85.2 +/- 1.6 degrees C) were similar but significantly higher than that of the untreated (fresh) valves (69.3 +/- 0.4 degrees C). The results suggest a similar degree of internal cross-linking for both statically and dynamically fixed pericardium. Although fundamental structural differences exist between both porcine and bovine xenograft tissue, how these differences contribute to biomechanical differences in the effects of dynamic versus static fixation remain to be explained.     

Neuronal protection by intraischemic brain perfusion: an electron microscopy study in the rat

Organ perfusion with bloodless solutions is an established clinical method for protecting the heart against ischemic damage. In our study, we evaluated the effects of intraischemic bloodless brain perfusion on postischemic ultrastructural neuronal changes in a model of severe incomplete forebrain ischemia produced by hemorrhagic hypotension combined with temporary carotid occlusion in the rat. Four groups of rats were compared. During an ischemic insult of 30 min, the brains of two groups were perfused via both external carotids with either a normosmolar normothermic magnesium-enriched perfusate (MgSO4, 30 mM; NaCl, 37 mM; mannitol, 180 mM; n = 10) or a normothermic normal saline solution (n = 9) at a rate of 6 ml/h. Two other groups (ischemia without perfusion, n = 8; no ischemia and no perfusion, n = 7) served as controls. After 30 min of ischemia, withdrawn blood for hemorrhagic hypotension was reinfused, the carotid arteries reopened, and the brains reperfused for 2 h. After perfusion-fixation, qualitative and quantitative evaluation of postischemic cell changes of hippocampal CA1 neurons was performed by electron microscopy. Brain perfusion with the magnesium-containing solution significantly protected neurons against ischemic cell changes and provided an ultrastructural pattern similar to that seen in the nonischemic control group. In contrast, brain perfusion with normal saline solution did not result in neuronal protection. We conclude that intraischemic intracarotid brain perfusion with magnesium-enriched perfusate protects hippocampal neurons significantly against ischemic cell changes in the early reperfusion period after transient severe forebrain ischemia.     

Microwave techniques for diagnostic laboratories

Microwaves (MWs) were first introduced as a method of fixation just over 20 years ago. In recent years their use has extended far beyond that of a safe, clean and rapid method of fixation of tissue blocks and large specimens, including brains. MWs accelerate the action of cross-linking fixatives and can greatly accelerate the various stages of tissue processing to produce a paraffin block in 30 min. An extensive range of ultrafast MW-stimulated special stains has been developed, and immunohistochemical procedures can be completed in 20 min by employing MWs. Cellular antigens are distinctly better preserved in tissues fixed by MWs than by conventional cross-linking fixatives. Also, the cytomorphology of cryostat sections irradiated in Wolman's solution is clearly improved. MWs can similarly be applied for fixation and staining of preparations for transmission and scanning electron microscopy, and they also greatly accelerate polymerisation of resins. In the current climate of cost containment, this wide range of applications makes the MW oven an invaluable addition to the diagnostic laboratory.     

A highly sensitive immunofluorescence procedure for analyzing the subcellular distribution of GABAA receptor subunits in the human brain

We designed a protocol to improve the immunohistochemical analysis of human brain structures, which overcomes the limited detection sensitivity, high background, and intense autofluorescence commonly associated with human tissue. This procedure was evaluated by using antibodies against major GABAA receptor subunits (alpha1, alpha2, alpha3, gamma2) in autopsy and surgical specimens. Tissue blocks were briefly fixed by immersion and pretreated with microwave irradiation in sodium citrate buffer. Immunoperoxidase staining revealed a marked enhancement of cell surface immunoreactivity and reduction of background in microwave-irradiated tissue, irrespective of its origin. For confocal laser scanning microscopy, immunofluorescence staining was optimized with the tyramide signal amplification (TSA) technique. This procedure not only dramatically increased the sensitivity for antigen detection but also totally suppressed autofluorescence, thus revealing the cellular and subcellular distribution of GABAA receptor subunits. A distinct neuron-specific expression pattern of the alpha-subunit variants was observed in cerebral cortex and hippocampal formation, along with widespread expression of the gamma2-subunit. Of particular interest was the prominent alpha2- and alpha3-subunit staining on the initial axon segment of pyramidal neurons. This protocol represents a major improvement for high-resolution studies of human brain tissue aimed at investigating morphological alterations underlying neurological diseases.     

Effects of saccades on the activity of neurons in the cat lateral geniculate nucleus

Effects of saccades on individual neurons in the cat lateral geniculate nucleus (LGN) were examined under two conditions: during spontaneous saccades in the dark and during stimulation by large, uniform flashes delivered at various times during and after rewarded saccades made to small visual targets. In the dark condition, a suppression of activity began 200-300 ms before saccade start, peaked approximately 100 ms before saccade start, and smoothly reversed to a facilitation of activity by saccade end. The facilitation peaked 70-130 ms after saccade end and decayed during the next several hundred milliseconds. The latency of the facilitation was related inversely to saccade velocity, reaching a minimum for saccades with peak velocity >70-80 degrees /s. Effects of saccades on visually evoked activity were remarkably similar: a facilitation began at saccade end and peaked 50-100 ms later. When matched for saccade velocity, the time courses and magnitudes of postsaccadic facilitation for activity in the dark and during visual stimulation were identical. The presaccadic suppression observed in the dark condition was similar for X and Y cells, whereas the postsaccadic facilitation was substantially stronger for X cells, both in the dark and for visually evoked responses. This saccade-related regulation of geniculate transmission appears to be independent of the conditions under which the saccade is evoked or the state of retinal input to the LGN. The change in activity from presaccadic suppression to postsaccadic facilitation amounted to an increase in gain of geniculate transmission of approximately 30%. This may promote rapid central registration of visual inputs by increasing the temporal contrast between activity evoked by an image near the end of a fixation and that evoked by the image immediately after a saccade.     

微波合成Mg2Si1-xSnx热电固溶体

为了解决传统方法制备Mg2Si1-xSnx(0≤x≤1.0)固溶体过程中带来Mg的氧化和挥发等问题,引进微波低温合成法制备Mg2Si1-xSnx热电固溶体,用XRD及SEM分析手段对合成的块体的物相和形貌进行表征,并研究Mg2Si1-xSnx化合物的热电特性和在微波场中的加热特性以及合成工艺对Mg2Sil xSnx压坯制备的影响。结果表明:Mg2Si1-xSnx压坯在微波场中的加热升温曲线与Mg2Si1-xSnx压坯密度相关,随压坯密度增大,升温速率降低;XRD分析表明在微波辐射下Mg2Si1-xSnx形成了良好的固溶体;在测试温度范围内,Mg2Si1-xSnx在500 K温度下最高的ZT值达到0.26。     

A histochemical examination of the staining of kainate-induced neuronal degeneration by anionic dyes

Anionic dyes, notably acid fuchsine, strongly stain the nuclei and cytoplasm of neurons severely damaged by injury or disease. We provide detailed instructions for staining nervous tissue with toluidine blue and acid fuchsine for optimal demonstration of injured neurons. Degeneration was induced in the hippocampus of the mouse by systemic administration of kainic acid, and the resulting acidophilia was investigated using paraffin sections of the Carnoy- or Bouin-fixed brains. The affected cells were bright red with the toluidine blue-acid fuchsine sequence. Their nuclei were stainable also with alkaline Biebrich scarlet and with the 1,2-naphthoquinone-4-sulfonic acid-Ba(OH)2 method; all staining was blocked by benzil but was relatively refractory to deamination by HNO2. These properties indicated an arginine-rich protein. The nuclei were strongly acidophilic in the presence of a high concentration of DNA (strong Feulgen reaction), and acidophilia could not be induced in normal neuronal nuclei by chemical extraction of nucleic acids. The cytoplasmic acidophilia of degenerating hippocampal neurons was due to a protein rich in lysine (extinguished by alkalinity, easily prevented by deamination, and unaffected by benzil). Stainable RNA was absent from the perikarya of the affected cells, but normal neuronal cytoplasm did not become acidophilic after extraction of nucleic acids. We suggest that kainate-induced cell death is preceded by increased production of basic proteins, which become concentrated in the nucleus and perikaryon. Groups of small, darkly staining neurons were seen in the cerebral cortex in control and kainate-treated mice. These shrunken cells were purple with the toluidine blue-acid fuchsine stain, and were attributed to local injury incurred during removal of the unfixed brain.     

Preliminary technique of laparoscopic extraperitoneal infrarenal paraaortic lymphadenectomy in the porcine model

The prevalence of Parkinson's disease (PD) is higher in whites than in nonwhites and it increases with advancing age. The pathological hallmarks of PD are loss of pigmented neurons in the substantia nigra pars compacta (SNpc) and presence of Lewy bodies. With increasing age, a similar loss of pigmented neurons in the SNpc has been reported. Hence, age and race possibly play a role in the pathogenesis of PD. The objectives of this study were to count the number of melanized neurons in the SNpc in normal human brains from India and study the change in neuronal count with advancing age and to compare the neuronal counts from this Indian population with counts reported in normal brains from the United Kingdom. Melanized neurons in the SNpc were counted in 84 normal human brains (age range, 5-84 years) in a single 7-microm section at the level of emergence of the oculomotor nerve. In the brains from India, there was no loss of melanized nigral neurons with advancing age. The absolute number of these melanized neurons was about 40% lower than the brains from UK. Despite a low number of melanized nigral neurons in the brains from India, individuals function normally and have dopamine levels comparable with their Western counterparts, suggesting that it is not the absolute number of melanized nigral neurons but the percent loss of nigral neurons that results in dopaminergic deficiency in PD. There is no significant loss of pigmented nigral neurons with age, suggesting that the loss seen in PD is exclusively due to the disease process itself. Indians have a lower prevalence of PD despite having a low count of melanized nigral neurons, suggesting that better protective mechanisms may be present in the Indians to prevent the loss of nigral neurons.     

Neuronal damage following transient cerebral ischemia and its restoration by neural transplant

The middle cerebral artery (mca) was intraluminally occluded for one hour prior to reperfusion in the rat. Neuronal damage as well as motor imbalance were assessed in both acute and chronic stages with or without neural transplant in the striatum. In acute stage, argyrophil III staining demonstrated "collapsed" dark neurons in the ipsilateral striatum, cortex, reticular thalamus, amygdala and sometimes in the hippocampus. They had shrunken somata and corkscrew-like dendrites. In accordance with the appearance of dark neurons, the immunoreactivity for calpain of endogenous inactive form decreased or disappeared in ischemic areas. In chronic stage, ischemic core area (striatum and cortex) got into porencephaly, and animals made rotations following methamphetamine injection. Neural transplant (fetal striatal cells) was made during 2 to 4 weeks after the ischemia. Once the transplant survived and grew in the striatum, the methamphetamine rotations were attenuated. Using mca ischemic model rats we report here pathophysiological processes that lead to neuronal damage and infarct. Neural transplants into these animals brought partial restoration in motor disturbance, offering a valuable information concerning therapeutic possibility.