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Biomedical subjects

H Kalimo

Publications and source records attributed to H Kalimo.

At least 217 records · Page 12Linked to original sources
PubMed1976

The role of the blood-brain barrier in perfusion fixation of the brain for electron microscopy.

Regions of the brain vascularized by capillaries of the blood-brain barrier (BBB) type require a different fixative from regions which have capillaries of the endocrine type. Fixative with isotonic buffer gives excellent ultrastructural preservation in the BBB regions, but cause severe shrinkage of cells in the endocrine regions. This is evidently due to the difference in the permeability of the capillary walls to solutes in the fixative. In the BBB regions in less permeable capillaries do not allow outflow of osmotically active particles to a harmful extent, whereas in the endocrine regions osomotic imbalances are created between the intra- and extracellular compartments. The diffusion rate of the fixative and the final volume of the fixed brain depend on the balance between the intravascular and intersitial hydrostatic and oncotic pressures across the capillary wall during the perfusion fixation, as those pressures regulate the amount of perfusate that will enter the parenchyma. Generally, as high a perfusion pressure as possible is recommended to obtain effective wash-out of blood and rapid diffusion of fixative into the tissue. Addition of macromolecules (2% PVP, mol. wt. 40,000) into the fixative slightly improved the ultrastructural preservation in the BBB regions of the central nervous system.

Animals↗
PubMed1976

Human adenohypophysis in Nelson syndrome. Ultrastructural and clinical study.

The manifestations that comprise the disease known as Nelson syndrome are pituitary hyperplasia and cutaneous hyperpigmentation, which sometimes follow bilateral adrenalectomy, in patients with hypercortisolism. We present a comprehensive endocrinologic, structural study of a patient in whom the evidence obtained supports the hypotheses that: (a) the primary disorder in this form of hypercortisolism is probably hypothalamic; (b) the hyperplasia of the adenohypophysis, following adrenalectomy, is closely associated with lowered plasma cortisol levels; and (c) the cillular hyperplasia in the adenohypophysis involves primarily the corticotroph, a cell believed to be associated with the secretion of adrenocorticotrophic hormone and melanocyte-stimulating hormone.

17-Ketosteroids↗
PubMed1975

Ultrastructural studies on the hypothalamic neurosecretory neurons of the rat. III. Paraventricular and supraoptic neurons during lactation and dehydration.

The ultrastructural features of paraventricular (PVN) and supraoptic (SON) neurons and of their axons were studied in lactating and dehydrated rats. Under both conditions of stimulation, the PVN and SON neurons and their axons enlarge. The protein synthesizing apparatus of the neurons becomes activated, but the number of neurosecretory granules (NSG) is decreased. No differences are seen between the PVN and SON neurons during lactation or dehydration. The similarity and simultaneity of the response of the PVN and SON neurons to these two different stimuli is discussed in the light of the theory of nuclear and neuronal specialization for the production of only one hormone. After prolonged lactation of over 2 1/2 weeks' duration, neurons with extreme vacuolation of the rough endoplasmic reticulum (RER) appear in the PVN and SON; the vacuolated neurons appear earlier and predominantly in the PVN involving a maximum of 10-15% of all PVN neurons. Vacuolated neurons were never seen in either nucleus during dehydration of up to 6 days' duration. The vacuolation is suggested to represent an exhaustion phenomenon due to an intense, long-lasting stimulus for oxytocin synthesis. The predominant location of the vacuolated neurons in the PVN supports the theory that oxytocin is produced predominantly in the PVN. The decrease in the number of NSGs during these states of enhanced hormone secretion is considered to corroborate the proposed existence of an extragranular fast axoplasmic transport mechanism in PVN and SON neurons. The possible existence of a reuptake mechanism into NSGs, similar to that in the vesicles of monoaminergic nerve endings is discussed.

Animals↗
PubMed1974

Influence of glutaraldehyde and-or osmium tetroxide on cell volume, ion content, mechanical stability, and membrane permeability of Ehrlich ascites tumor cells.

Effects of fixation with glutaraldehyde (GA), glutaraldehyde-osmium tetroxide (GA-OsO(4)), and osmium tetroxide (OsO(4)) on ion and ATP content, cell volume, vital dye staining, and stability to mechanical and thermal stress were studied in Ehrlich ascites tumor cells (EATC). Among variables investigated were fixation time, fixative concentration, temperature, osmolality of the fixative agent and buffer, total osmolality of the fixative solution, osmolality of the postfixation buffer, and time of postfixation treatment in buffer (Sutherland, R. M., et al. 1967. J. Cell Physiol.69:185.). Rapid loss of potassium, exchangeable magnesium, and ATP, and increase of vital dye uptake and electrical conductivity occurred with all fixatives studied. These changes were virtually immediate with GA-OsO(4) or OsO(4) but slower with GA (in the latter case they were dependent on fixative temperature and concentration) (Foot, N. C. 1950. In McClung's Handbook of Microscopical Technique. 3rd edition. 564.). Total fixative osmolality had a marked effect on cell volume with OsO(4) but little or no effect with GA or GA-OsO(4). Osmolality of the buffer had a marked effect on cell volume with OsO(4), whereas with GA or GA-OsO(4) it was only significant at very hypotonic buffer osmolalities. Concentration of GA had no effect on cell volume. Osmolality of the postfixation buffer had little effect on cell volume, and duration of fixation or postfixation treatment had no effect with all fixatives. Freezing and thawing or centrifugal stress (up to 100,000 g) had little or no effect on cell volume after all fixatives studied. Mechanical stress obtained by sonication showed that OsO(4) alone produced poor stabilization and that GA fixation alone produced the greatest stabilization. The results indicate that rapid membrane permeability changes of EATC follow fixative action. The results are consistent with known greater stabilizing effects of GA on model protein systems since cells were also rendered relatively stable to osmotic stress during fixation, an effect not noted with OsO(4). After fixation with GA and/or OsO(4) cells were stable to osmotic, thermal, or mechanical stress; this is inconsistent with several earlier reports that GA-fixed cells retain their osmotic properties.

Adenosine Triphosphate↗
PubMedDate not supplied

Microanalysis of perineural calcification in diabetic nephropathy.

Three different microanalytical methods were used to identify calcium deposits in the sciatic nerve perineurium of a 33-year-old woman who died after developing nephropathy, retinopathy, and neuropathy as complications of diabetes. Scanning electron microscopic x-ray microanalysis (SEM-XMA) enabled localization of calcium and phosphorus elements to the perineurium in whole nerve cross sections. With SEM-XMA and scanning-transmission electron microscopic x-ray microanalysis (STEM-XMA) of the minute crystallites in the perineurium, the approximate relative amounts of calcium and phosphorus in the deposits were found to correspond to those in calcium hydroxyapatite. Finally, the crystallites were specifically identified by selected area electron diffraction, and were found to be composed mainly of calcium hydroxyapatite.

Adult↗
PubMedDate not supplied

The early ultrastructural alterations in the rabbit cerebral and cerebellar cortex after compression ischaemia.

The ultrastructural alterations in the rabbit cerebral and cerebellar cortex resulting from 30 minutes complete, permanent cerebral ischaemia were studied. The ischaemia was induced by raising the intracranial pressure (ICP) above the systolic arterial pressure (compression ischaemia). Immediately after releasing the ICP the brain was fixed by intravascular glutaraldehyde perfusion. Samples from the cerebral and cerebellar cortex were processed for electron microscopy. The ultrastructural changes were relatively minor; there was a generalised, slight intracellular oedema, most prominent in the subpial area; the nuclear chromatin was clumped, the endoplasmic reticulum and cisternae of the golgi apparatus became somewhat dilated, the inner matrix of the slightly swollen mitochondria showed increased electron lucency, and microtubules and ribosomes began to loose their compact structure. These changes, unaccompanied by any extensive volumetric change of any cellular compartment, agree well with the recently presented hypothesis of two different types of anoxic-ischaemic nerve cell injury. This cellular reaction to complete, permanent compression ischaemia represents the type of injury that is seen resulting from ischaemic insults during which no flow of fluid irrigates the ischaemically injured cells.

Animals↗
PubMedDate not supplied

Significance of fluid flow for morphology of acute hypoxic-ischaemic brain cell injury.

It has been suggested that the presence or absence of hypoxic fluid flow during ischaemia determines the structural character of the ischaemic nerve cell injury. It is hypothesised that if a flow of fluid irrigates the injured neurons, there will be major shifts of ions and water, with consequent volumetric changes in the tissue and the 'dark' type of neuronal injury will result; otherwise, the structural changes are less striking and are designated as the 'pale' type. To test this hypothesis, rats were subjected to a global cerebral insult by filling the vasculature with a plasma substitute, which was either left stagnant or was flowing, and was either oxygenated (hypoxic flow) or nitrogenated (anoxic flow). Light and electron microscopy of the brain following 10 to 60 min of hypoxic or anoxic ischaemia disclosed that, under all three circumstances, the predominant nerve cell injury was of the pale type. The results indicate that some additional factors present in whole blood (but not in the plasma substitute) are needed during or after the insult to induce in quantity the dark type of ischaemic nerve cell injury.

Acute Disease↗
PubMedDate not supplied

Acetylcholinesterase activity and its fast axonal transport in rabbit sciatic nerves during the recovery phase of experimental allergic neuritis.

Acetylcholinesterase (AChE) activity and its fast axonal transport were studied in rabbit sciatic nerves with a double ligature system during the recovery phase of experimental allergic neuritis (EAN), 6-9 days after the maximal symptoms, in order to obtain biochemical evidence of possible axonal damage in this primary demyelinating disease. The stationary AChE activity was significantly decreased, but the amount of the fast transported enzyme activity remained at the level of the controls. The velocity of the orthograde transport of AChE was slowed by about 15%, but this decrease was not statistically significant. Our results lend further support for the suggested neuronal damage in EAN, which can provide an explanation to the finding that the clinical symptoms in demyelinating diseases of the peripheral nervous system do not always correlate with the state of myelin.

Acetylcholinesterase↗
PubMedDate not supplied

Structural changes in the rat brain after carotid infusions of hyperosmolar solutions: a light microscopic and immunohistochemical study.

A solution of mannitol or urea was infused into the carotid artery of rats to open the blood-brain barrier (BBB) and to find out if such a procedure results in brain injury. Paraformaldehyde-fixed, paraffin-embedded material was available to determine the localization and extent of albumin extravasation by immunochemistry. Other light microscopic and immunocytochemical techniques were applied on consecutive sections to find out if structural damage had occurred. The cerebral cortex, the hippocampus and the basal ganglia of the infused brain hemisphere contained within regions of albumin extravasation scattered, collapsed, acidophilic neurons. In addition, there were multifocal lesions with marked sponginess of the neuropil which contained numerous shrunken, acidophilic neurons and a perifocal astrocytic gliosis. A moderate macrophage infiltration was present in rats with 72 h survival. In conclusion, infusion of hypertonic mannitol or urea into the carotid artery of the rat may result in structural brain damage within regions showing BBB injury. The presence of acidophilic neurons and the macrophage response indicate that some of the brain changes are irreversible.

Albumins↗
PubMedDate not supplied

Parenchymal changes related to plasma protein extravasation in experimental seizures.

To determine whether the transient opening of the blood-brain barrier (BBB) during epileptic seizures may lead to permanent neuronal changes, seizures of a few minutes' duration were induced by intravenous (i.v.) administration of 0.3 mg/kg bicuculline to conscious rats with indwelling catheters for blood pressure (BP) and blood gas monitoring. The rats were killed 5 min to 7 days later, and the distribution of endogenous plasma albumin, fibrinogen, and fibronectin in the brain was studied by immunohistochemistry. Parallel sections were scrutinized for evidence of light-microscopic structural changes in the tissue. Extensive multifocal extravasation of plasma proteins throughout the brain and brainstem was observed. The original clearly focal distribution became more diffuse with prolongation of the recovery time. In addition, the intensity of the immunoreactivity decreased, most likely due to drainage into the cerebrospinal fluid (CSF) in the ventricles and the subarachnoidal space of the extravasated proteins, but some antialbumin-positive material was still visible after 7 days. In areas with extravasation, many nerve cells, especially cerebellar Purkinje cells, became strongly positive for albumin. In some of these areas, neurons appeared to be irreversibly injured. Thus, considerable amounts of plasma proteins are extravasated even during short epileptic seizures, and albumin appear to remain in the tissue for a long time, especially in Purkinje cells. The Purkinje cell loss in chronic epilepsy may be caused partly by cumulative bouts of plasma extravasations.

Animals↗