The effects of glycol methacrylate as a dehydrating agent on the dimensional changes of liver tissue

The dimensional changes of liver sections during the course of processing with glycol methacrylate (GMA) or with ethanol are described. Tissue processing with ethanol served as a control. During prolonged processing steps (24 h each), linear shrinkage of tissue specimens dehydrated with GMA at room temperature was 13.2%. Subsequent infiltration with GMA resulted in trivial swelling, and polymerization in slight shrinkage (2.3%). In comparison, processing with cold GMA resulted in shrinkage during dehydration (about 10.8%), a slight swelling in pure GMA, followed by shrinkage during polymerization (2.2%). Short routine processing schedules resulted in similar shrinkage/swelling patterns, although precise values differed slightly. In all experiments, ethanolic dehydration resulted in smaller dimensional tissue changes than did GMA dehydration. The dimensional changes of tissue sections during stretching on water, mounting and drying compensated for the major part of the shrinkage manifested during processing.

Estrous cycle-dependent neural plasticity in the caudal brainstem in the female golden hamster: ultrastructural and immunocytochemical studies of axo-dendritic relationships and dynamic remodeling

During the short four-day estrous cycle of the female hamster various behavioral (lordosis, vocalization and aggression) and autonomic adaptations occur. Presumably, these changes are under ovarian control. Recently, we described a distinct estrogen receptor-alpha immunoreactive (ER-alpha-IR) cell group, now called nucleus para-retroambiguus (NPRA), in the caudal ventrolateral medulla (Gerrits et al., 2008). Neurons of this group project to the ipsilateral intermediolateral cell column in the thoracic and upper lumbar cord. Clearly, the NPRA is part of an estrogen-sensitive neuronal network and the same applies to the region containing the commissural part of the solitary tract nucleus (NTScom) and the A2 group, here called NTScom/A2. Estrogen is known to modulate neuronal ultrastructure in various brain areas and spinal cord, but not in the caudal brainstem. Because we assumed that the NPRA plays a role in estrous cycle related adaptations, we hypothesized the occurrence of plasticity in this nucleus. In the present study we examined morphological changes of axo-dendritic relationships in NPRA and NTScom/A2 in estrous, diestrous and ovariectomized (OVX) hamsters, using immuno-electron microscopy and the 1D5 anti-ER-alpha antibody. Ultrastructural analysis revealed that the ratio "axon terminals surface/dendrite surface" was significantly increased in both the NPRA and NTScom/A2 during the estrous phase compared to the OVX and diestrous conditions. Remodeling of axon terminals due to axonal sprouting into large terminal fields filled up with pleomorphic vesicles resulted in contacts with more dendrites, and was the main cause for the "axonal terminal-dendritic-ratio" shift.

IN CONCLUSION

Estrous cycle-induced axonal and dendritic plasticity is present in the NPRA, and in the NTScom/A2 group. Our findings support our hypothesis that estrogen-sensitive neuronal networks in the caudal brainstem display structural plasticity, probably to modulate steroid hormone dependent behaviors or autonomic adaptations.

The nucleus para-retroambiguus: a new group of estrogen receptive cells in the caudal ventrolateral medulla of the female golden hamster

Receptive female hamsters display very rigid lordotic postures. Estradiol facilitates this behavior via activation of estrogen receptors. In the hamster brainstem estrogen receptor-alpha-immunoreactive neurons (ER-alpha-IR) are present in various brainstem regions including nucleus retroambiguus (NRA) in the caudal ventrolateral medulla (CVLM) and nucleus of the solitary tract. ER-alpha-IR neurons in the CVLM project to the thoracic and upper lumbar cord. However, A1 neurons in this region do not project to the spinal cord, in contrast to overlapping C1 neurons. The question now arises: are ER-alpha-IR cells in the CVLM part of the A1/C1 group, or do they belong to the NRA or do they compose a separate cluster. A study in ovariectomized female hamsters using a combination of double immunostaining and retrograde tracing techniques and measurement of soma diameters was carried out. The results showed that A1/C1 neurons in the CVLM are almost never ER-alpha-positive; neurons inside or bordering the NRA can be divided in two different types: large multipolar and small; the large NRA-neurons, projecting caudally, are neither tyrosine hydroxylase- (TH) nor ER-alpha-IR; the small neurons, bordering the NRA and projecting caudally, are ER-alpha-IR but not TH-IR. From the available evidence and the present findings it can be concluded that the group of small ER-alpha-IR neurons in the CVLM has to be considered as a distinct entity, probably involved in the autonomic physiological changes concurring with successive phases of the estrous cycle. Because the location is closely related to the NRA itself the nucleus is called nucleus para-retroambiguus, abbreviated (NPRA).

Retroambiguus projections to the cutaneus trunci motoneurons may form a pathway in the central control of mating

Our laboratory has proposed that the nucleus retroambiguus (NRA) generates the specific motor performance displayed by female cats during mating and that it uses direct pathways to the motoneurons of the lower limb muscles involved in this activity. In the hamster a similar NRA-projection system could generate the typical female mating posture, which is characterized by lordosis of the back as well as elevation of the tail. The present study attempted to determine whether this elevation of the tail is also part of the NRA-mating control system. The basic assumption was that elevation of the tail is a function of the cutaneous trunci muscle (CTM), which was verified by bilateral tetanic stimulation of the lateral thoracic nerves innervating the CTM. It resulted in upward movement of the tail to a position similar to the tail-up position during the lordosis posture. Retrograde tracing results showed that CTM motoneurons are located in the ventral and ventrolateral part of the C(7)-C(8) ventral horn, those innervating the tail region ventrolateral to those innervating the axillary region. Anterograde tracing studies showed that NRA fibers terminate bilaterally in both parts of the CTM motoneuronal cell groups. Electron microscopical studies revealed that labeled NRA terminals make monosynaptic contacts with retrogradely labeled dendrites of CTM motoneurons. Almost all of these terminal profiles had asymmetric synapses and contained spherical vesicles, which suggests an excitatory function. The observation that 15% of the labeled NRA terminals make more than one synaptic contact with a retrogradely labeled CTM motoneuronal dendrite within the same section indicates how powerful the NRA-CTM projection is. The results indicate that during mating the NRA not only could generate the lordosis posture but also the elevation of the tail.

Estrogen receptor-alpha-immunoreactive neurons in the mesencephalon, pons and medulla oblongata of the female golden hamster

Recent studies have revealed brainstem-spinal pathways involved in the generation of receptive behavior in hamster and cat, and the enormous influence of estrogen on these pathways. The present study gives an overview of the location of estrogen receptor-alpha-immunoreactive neurons (ER-alpha-IR) in the brainstem of the female hamster. In the mesencephalon, ER-alpha-IR cells were found in the arcuate and peripeduncular nuclei as well as throughout the rostrocaudal extent of the periaqueductal gray (PAG), and the laterally adjoining tegmentum. In the caudal brainstem, groups of ER-alpha-IR cells were present in the ventrolateral parabrachial nucleus, the solitary nucleus, and in contrast to the cat, in the nucleus retroambiguus. No ER-alpha-IR cells were found in any other part of the brainstem. The functional implications of these findings are discussed.

[Characteristics of pedigree cat breeding in the Netherlands: breeds, population increase and litter size]

A survey of the Dutch Cat Fancy was carried out to determine reproductive, patterns of pedigree cats. The data of the present study were obtained by questioning the pedigree registers of the cat clubs participating in the foundation 'Overleg Platform van de Nederlandse Cat Fancy'. The Dutch Cat Fancy registers 34 different cat breeds. From 1992 up to 1996 a total of 25.985 litters were registered. Over this period the number of litters increased from 4989 to 5313. Litters from Longhair and Exotic Shorthair cats comprised the biggest group and accounted for 55% of the total number of litters. However, over this period, the number of Longhair and Exotic Shorthair litters decreased by 9%. Litters from British Shorthair, Birman, Maine Coon and Norwegian Forrest Cat increased in number as did litters from small breeds such as Ragdoll, Bengal and Sphynx. Litters from Abyssinian, Siamese, Oriental Shorthair cats remained relatively the same. The average litter size of the total cat population, based on pedigree certificates, was calculated at 3.3 kittens per litter. For different breeds litter size varied from 2.7 (Longhair and Exotic Shorthair) to 4.3 (Burmese and Maine Coon). Taking into account an average age of 14 years, the total Dutch pedigree cat population was estimated at 240,000 viz. about 10% of the total cat population.

Descending projections from the nucleus retroambiguus to the iliopsoas motoneuronal cell groups in the female golden hamster: possible role in reproductive behavior

In the cat, the nucleus retroambiguus (NRA) projects to expiratory motoneurons in the brainstem and spinal cord. Recently, it has been demonstrated that the NRA sends fibers to a specific set of motoneurons in the lumbosacral cord, which pathway is thought to play a crucial role in mating behavior. The question is whether such projections exist in the hamster, because the female of this species displays a very distinctive receptive behavior. In the hamster, lumbosacral cord injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) combined with hemisection 1 or 2 segments rostral to injection sites in three of the five cases demonstrated retrogradely labeled neurons in the NRA at levels 1.0-2.25 mm caudal to the obex, contralateral to the injection sites. Injections of WGA-HRP into the NRA and adjoining reticular formation revealed that NRA fibers crossed the midline in the caudal medulla and descended in the contralateral lateral and ventrolateral funiculi to terminate bilaterally, but mainly contralaterally, in the motoneuronal cell groups of the abdominal wall and iliopsoas muscles. NRA projections to levels caudal to lumbar segment 5 were virtually absent. Electron microscopic examination revealed that, of the 162 labeled NRA terminal profiles found in the ultrathin sections, 144 (89%) made monosynaptic contacts with retrogradely labeled dendrites of iliopsoas motoneurons. These NRA terminals formed asymmetrical synapses and contained spherical vesicles indicative of an excitatory function. The results indicate that, in the hamster, direct contralateral NRA projections exist to iliopsoas motoneurons. A concept is discussed in which this pathway plays a crucial role in mating behavior.

[Organization of the Dutch Cat Fancy]

The present study of the foundation 'Overleg Platform van de Nederlandse Cat Fancy' describes the organization and structure of the Dutch Cat Fancy, and is subdivided into three parts. The first part presents a survey of the number of cat clubs, date of their establishment, number of members, associated breed clubs and participation in the foundation 'Overleg Platform van de Nederlandse Cat Fancy'. The second part describes the basic organization of Dutch cat clubs, including their membership, cattery registration, breed registration, exhibitions and judges, cat magazines, health care and welfare, and breed clubs. The third part focuses attention on other organizational forms such as clubs for a particular breed, seen within the Dutch Cat Fancy.

The lumbar cord location of the motoneurons innervating psoas and iliacus muscles: a single and double labeling study in the female Syrian golden hamster

The spinal cord location of the motoneurons innervating the psoas and iliacus muscles was determined in the golden hamster. The results of single and double labeling studies, using the retrograde tracers horseradish peroxidase (HRP) and cholera toxin B-subunit (CTB), showed that both psoas and iliacus motoneurons were present ventrolaterally in the ventral horn in the caudal L1 to rostral L5 lumbar spinal segments with their motoneurons intermingled in one cell group. Further retrograde tracing studies demonstrated abdominal muscle motoneurons ventrolaterally in the ventral horn of the L1 and upper L2 segments. Double labeling experiments revealed that at these levels (caudal L1 and rostral L2), the abdominal muscle motoneurons were located dorsomedial to the psoas and iliacus motoneurons.

Motoneuronal location of the external urethral and anal sphincters: a single and double labeling study in the male and female golden hamster

The location of external urethral (EUS) and anal sphincter (EAS) motoneurons was investigated in the golden hamster using the retrograde tracers horseradish peroxidase and cholera toxin B-subunit. Single and double labeling studies revealed that the motoneurons of the EUS and EAS were present in the same nucleus (nucleus of Onuf) ventrolaterally in the ventral horn of the caudal first sacral segment and throughout the second sacral segment. Within Onuf's nucleus the EAS motoneurons were located dorsomedial to the EUS motoneurons, which were located at the border of the gray and white matter. This location is similar to that in cat, dog, monkey and man, but differs from that in rat, Mongolian gerbil and domestic pig.

Pontine and medullary projections to the nucleus retroambiguus: a wheat germ agglutinin-horseradish peroxidase and autoradiographic tracing study in the cat

The nucleus retroambiguus (NRA) in the caudal medulla oblongata plays a role in expiration, vocalization, vomiting, and possibly lordosis. The present study tried to determine which structures, in turn, control the NRA. One cell group is the periaqueductal gray (PAG), which is considered to be the final integrator of defensive and aggressive behaviors, micturition, vocalization, and lordosis. Structures rostral to the PAG seem to bypass the NRA. With respect to the existence of cell groups caudal to the PAG projecting to the NRA, the situation is less clear. Therefore, in five adult female cats, injections of wheat germ agglutinin-horseradish peroxidase were centered on the NRA, and the resulting retrogradely labeled neurons were plotted. In the areas containing retrogradely labeled cells, the anterograde autoradiographic tracer [3H]-leucine was injected in 66 cats. The combined results demonstrated that NRA afferents not only originate from the PAG but also from specific cell groups in the pontine and medullary lateral tegmental field, i.e., the ventrolateral parabrachial nucleus, the nucleus Kölliker-Fuse, the retrotrapezoid nucleus, and the ventrolateral part of the medulla caudal to the facial nucleus including the Bötzinger and pre-Bötzinger complex and the periambigual region. Afferents also originate from the solitary nucleus and two cell groups in the ventral part of the medullary medial tegmental field, one at the level of facial nucleus and one just rostral to the hypoglossal nucleus. It can be concluded that many respiratory-related cell groups have direct access to the NRA. The cell groups in the medial tegmental field, which have not yet been found to play an important role in respiration, might serve as relay for certain limbic system cell groups to reach the NRA in the context of specific emotional behavior.

The effect of gonadectomy on the clinical course of chronic experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an animal model for the human neurological disease multiple sclerosis (MS). Upon immunization with guinea pig spinal cord under a low dose of Cyclosporin A, male Lewis rats develop a severe chronic (relapsing) course of EAE (CR-EAE). By contrast, female Lewis rats develop a more mitigated course of EAE: only half of the female rats develop relapses. To further analyze factors determining this sexual dimorphism in the course of EAE, in the present study male and female Lewis rats were gonadectomized before induction of CR-EAE. Now both male and female rats all developed a severe chronic course of EAE, showing extensive pathological changes in the CNS. In the female sham-gonadectomy (control) group only one third of the rats developed relapses. These female rats only showed mild pathological changes in the CNS. In the male sham-gonadectomy (control) group all rats developed relapses of EAE and showed extensive pathological changes in the CNS. From these data we conclude that the presence of the ovaries (partially) protects female rats against relapses of EAE and CNS injury. Presence or absence of the testes apparently makes no difference on the course of EAE. We propose that sex hormones produced in the ovaries protect female rats against relapses of EAE and underlying CNS injury.

Glycol methacrylate embedding of alginate-polylysine microencapsulated pancreatic islets

A method for processing and embedding alginate-polylysine microencapsulated pancreatic tissue in glycol methacrylate resin (GMA) is described. Fixation in 4% phosphate buffered formaldehyde, processing in ascending concentrations of glycol methacrylate monomer and embedding in Technovit 7100 results in well preserved morphological details of hydrogels, hydrogel-cell interfaces, and encapsulated pancreatic tissue. Routine staining with Loeffler's methylene blue, hematoxylin and eosin, and Romanovsky-Giemsa gave excellent images of the GMA embedded alginate polylysine membrane and tissues allowing cells on the outside of the capsule to be analyzed effectively as part of the foreign body reaction against the capsule membrane.

Effects of storing initiated 2-hydroxyethyl methacrylate solutions for embedding tissues for light microscopy: some practical implications

The effects of storing 2-hydroxyethyl methacrylate (HEMA) solutions for embedding tissues for light microscopy were studied using three commercially available HEMA embedding kits: Technovit 7100, Technovit 8100, and JB-4. These HEMA solutions were examined at various times of storage over a period of one year using a panel of physicochemical techniques including gas chromatography, titration, viscosimetry, determination of the maximum polymerization temperature and the time required to reach the maximum temperature, and detection of degradation products of HEMA monomers by histochemical procedures. The quality of the resin blocks was examined by the observation of mini-folds in sections. Data obtained from these tests showed that the release of by-products as a result of the degradation of the HEMA monomer during storage of HEMA solutions does not occur. Development of cross-linking agents by transesterification of HEMA monomer was not detected either. Gradual decrease of the inhibitor concentration during storage proved to be the main cause of the reduction of shelf-life of HEMA solutions. Inconsistent tissue infiltration after storage may be due to decreased rates of tissue penetration as a result of HEMA chain lengthening. Guidelines for safe and economical handling of HEMA mixtures are given.

In vitro NMR micro imaging of the spinal cord of chronic relapsing EAE rats

Chronic relapsing experimental allergic encephalomyelitis (Cr-EAE) was induced in Lewis rats with an emulsion of guinea pig spinal cord tissue in complete Freund's adjuvant enriched with Mycobacterium tuberculosis H37 RA. The sensitized rats developed Cr-EAE showing two to three relapses during the first 40 days. In vitro transverse T2-weighted spin echo images of the spinal cord of Cr-EAE rats, sacrificed at the clinical height (hind leg paralysis and urinary incontinence) of the third bout and their controls, were compared with the corresponding histopathology. Lesions extended over the entire spinal cord, however, the larger lesions were predominantly present in the cervical and upper thoracic regions. In the white matter only areas of demyelination and large perivascular demyelination were discernable on the MR images. Size and shape of these lesions correlated well with the morphological characteristics revealed by histopathology. Plaques in the ventrolateral funiculus were generally located peripherally, while plaques in the dorsal funiculus were mainly present in the medial part. The NMR images, however, could not distinguish between demyelination, remyelination, inflammation, and oedema. Also lesions in the gray matter could not be distinguished with MR imaging techniques. However, if lesions were localized at the interface of the gray and white matter the boundary between the gray and white matter was less well defined.

A new subdivision of the rat midbrain periaqueductal gray based on its myeloarchitecture

A new subdivision of the periaqueductal gray (PAG) based on its myelin content is described. Using a methacrylate-resin embedding technique for high resolution light microscopy, a myeloarchitectonic map of the normal rat PAG was made. Six main columns were distinguished. Column I is the central thin subependymal layer, in which myelinated axons are virtually absent. This layer is surrounded by column II with many rostrocaudally oriented fibers. Lateral and dorsolateral to column II lies column III, which contains rostrocaudally as well as tangentially oriented fibers. Column III is divided into a ventral and a dorsal part by column IV. This column is located in the dorsolateral part of the PAG and contains very few, mostly tangentially oriented fibers. Column V is located ventrally and contains a mixture of rostrocaudally and tangentially oriented fibers. Column VI is only present in the most caudal part of the PAG and contains mainly tangential fibers.

Staining myelin and myelin-like degradation products in the spinal cords of chronic experimental allergic encephalomyelitis (Cr-EAE) rats using Sudan black B staining of glycol methacrylate-embedded material

A high-resolution light-microscopical (HRLM) technique is described to visualize myelin, and macrophages containing degradation products of myelin, in the spinal cords of chronic relapsing experimental allergic encephalomyelitis (Cr-EAE) rats. This HRLM technique was developed to optimalize the correlation between nuclear magnetic resonance (NMR) characteristics and histopathological images in this well-established animal model for multiple sclerosis (MS). Spinal cords were fixed by perfusion with a combination of cacodylate-buffered glutaraldehyde and formaldehyde, post-fixed in Dalton's fixative (containing osmium tetroxide), rinsed in water, processed in ethanol, acetone, and embedded in glycol methacrylate resin (Technovit 7100/HistoResin). Semi-thin sections were stained with Sudan Black B and counterstained with Cresyl Fast Violet, resulting in black staining of myelin and its degradation products, with blue/violet staining of demyelinated axons and other tissue elements. These dyes were selected with the aid of a numerical model of staining, which took both access and lipophilicity into account. The staining procedure is simple and highly reproducible. The resulting images are contrast rich, and combine excellent morphology with a high degree of lipid retention.

Staining sections of water-miscible resins. 2. Effects of staining-reagent lipophilicity on the staining of glycol-methacrylate-embedded tissues

Glycol methacrylate (GMA) sections of animal tissues were stained with a group of twenty-seven reagents of very varied chemical characteristics. The artefactual background staining of the resin was found to be dependent on the hydrophilic/lipophilic character of the staining reagent, as estimated from the logarithm of its octanol-water partition coefficient (log P). Intense background staining occurred with lipophilic stains, whose log P greater than 2. In keeping with this, use of GMA semi-permeable membranes for enzyme histochemistry failed to give staining when using a lipophilic substrate, probably because the substrate was trapped in the membrane. An analysis of other routine histochemical stains--in terms of the probable occurrence of high resin background staining and low tissue sensitivity--is made. A numerical guide is provided to help avoid artefacts resulting from hydrophobic and size effects. Note: small, hydrophilic reagents (log P less than 0; molecular weight less than 550 Da) are least likely to show either type of artefact. Conversely, reagents which are lipophilic, or/and of intermediate size (log P greater than 2; 550 less than ionic weight less than 1000 Da), give strong background staining.

Glycol methacrylate embedding in diagnostic pathology. A standardized method for processing and embedding human tissue biopsy specimens

A standardized "low-cost" processing and embedding procedure is described for the preparation of semithin glycol methacrylate (GMA) sections of human tissue biopsy specimens for use in routine diagnostic pathology. The method is highly reliable and reproducible and is based on many years of experience in fundamental GMA research. The procedure combines the application of new, less toxic, plasticizers and the preparation of high-quality GMA mixtures. Microwave irradiation was used to improve staining qualities and to reduce staining times. An improved reticulin staining procedure is presented as well.

Staining sections of water-miscible resins. 1. Effects of the molecular size of stain, and of resin cross-linking, on the staining of glycol methacrylate embedded tissues

Penetration of hydrophilic acid and basic dyes into sections cut from glycol methacrylate (GMA)-embedded tissues was studied; as were the effects on such staining of superficial coatings of thin layers of GMA. Dye size was a major factor in controlling penetration of resin and staining of tissues. 'Large' dyes (greater than 1000 Da) entered GMA very slowly, and only stained those tissue components poorly infiltrated by resin. 'Small' dyes (less than 550 Da) penetrated GMA readily, and stained tissue components whether or not they were resin-infiltrated. Dyes of intermediate size penetrated the resin, but the staining of resin-infiltrated tissue elements was slow. Background staining of resin also varied with dye size. Large dyes gave no staining of GMA. Small dyes did, but were readily removed by water washing. Dye of intermediate size penetrated resin slowly, and once inside were lost slowly. This gave background staining which required use of the plasticizing solvent ethanol for its removal. Increases in resin cross-linking also reduced staining rates. As a consequence, it is possible to predict the probable suitability, or otherwise, of various staining reagents proposed for use with GMA sections; and also the probable influences of histoprocessing on stain penetration. In particular it is suggested that penetration of colloidal metals and macromolecular reagents (e.g. labelled antibodies and lectins) will be limited to resin-free structures, and to the surface of resin sections. The use of superficial GMA coatings as convenient semipermeable membranes for enzyme histochemistry is also noted.

A numerical procedure for choosing effective, low toxicity plasticizers for glycol methacrylate embedding

A numerical method for selecting low toxicity plasticizers for glycol methacrylate (GMA) embedding mixtures is described. It involves use of various numerical parameters, namely; molecular weight, melting point, solubility parameter, and toxicity data. On the basis of these parameters, nine plasticizers were selected. Their effects on microtomy and tissue processing, and also their influence on tissue morphology and staining, were investigated. For tissue processed at low temperatures into GMA, using ethanol dehydration, the following compounds were as satisfactory as 2-butoxyethanol whilst being less toxic: 2-isopropoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, 2-(n-butoxyethoxy)ethanol. However for tissues processed using the plasticizer as dehydrating agent, the optimum plasticizers were 2-isopropoxyethanol, 2-(2-methoxyethoxy)ethanol and 2-(2-ethoxyethoxy)ethanol. It is possible to give a numerical specification of the preferred plasticizers, and for the first procedure this is: a solubility parameter in the range 21-26 J0.5 cm-1.5 or higher, a melting point well below 0 degree C, and a rat oral LD50 greater than 12.52 mmol kg-1. It was also possible to analyse the differential effects of the dehydrating agents on histochemical and enzyme histochemical staining on a numerical basis, using a structure-activity relations approach.

A modified mallory-cason staining procedure for large cryosections

The classic Mallory-Cason staining procedure has been modified for application to sections "on tape" obtained from large deep frozen tissue specimens. These 20 microns cryosections are collected on tape from a large heavy duty cryomicrotome. The stained sections provide anatomical details that are not revealed by other techniques. The merit of this procedure is found in the support of modern medical modalities, both for research and educational purposes.

Enzyme histochemical demonstration of alkaline phosphatase activity in plastic-embedded tissues using a Gomori-based cerium-DAB technique

We describe a new method for light microscopic demonstration of alkaline phosphatase (ALP) activity in plastic-embedded sections. Rat tissues were fixed in acetone (-20 degrees C), infiltrated in glycol methacrylate (GMA), and embedded at 0 degrees C. Sections were cut at 1 and 2 microns, dried at room temperature, and incubated in the conventional Gomori medium. Cerium chloride was used to convert calcium phosphate into cerium phosphate, which was subsequently converted into cerium perhydroxide. The slight yellow precipitate of cerium perhydroxide was amplified using 3,3'-diaminobenzidine tetrahydrochloride (DAB). For comparison, tissue sections were processed according to the calcium-cobalt method. The method described combines exact localization of ALP activity with optimal preservation of tissue morphology.

Use of tissue-free glycol methacrylate sections as semi-permeable membranes: a simple way to shorten incubation times and to improve localization in enzyme histochemistry

Placing 2-microns sections of tissue-free glycol methacrylate on top of tissue sections is a simple way of forming semipermeable membranes to enhance enzyme histochemical staining. For demonstrating alkaline phosphatase in glycol methacrylate-embedded kidney by a standard azo dye method, such membranes enabled incubation times to be reduced to 1-2 hr, with azo dye reaction product being more crisply localized as compared to sections stained without membranes. Such effects are possible because the membranes are highly permeable to small molecules (e.g., substrate and diazonium salt), slightly permeable to molecules of moderate size (e.g., the final reaction product), and impermeable to large molecules (e.g., alkaline phosphatase and other tissue biopolymers). The implications of these findings for enzyme histochemistry and for enzyme-labeled antibody staining are discussed.

Formaldehyde fixation and microwave irradiation

Formaldehyde is the most commonly used fixative in pathology laboratories. However, due to time pressures, this fixative is often not optimally exploited. The majority of biopsies are only partly fixed when histoprocessing is started, with adverse effects. This paper reports how formaldehyde fixation is improved, by using 1.5 min of microwave irradiation of tissue previously soaked for four hours in the fixation solution. It is argued that this beneficial effect of microwave irradiation can be attributed to the acceleration of the reaction of formaldehyde to the tissue. Formation of free formaldehyde, by the dehydration of methylene glycol present in the tissue when the irradiation starts, is also enhanced. Five different formaldehyde-containing fixatives were evaluated, using five different working protocols. Spleen was taken as a suitable tissue for these tests. The technique described leads to uniform microscopical results. It is a simple method and is suitable for use in routine laboratories.

Immunohistochemical antigen demonstration in plastic-embedded lymphoid tissue

We describe a method for post-embedding immunohistochemical demonstration of a wide range of antigens in glycol methacrylate-embedded tissue. Rat spleen and thymus tissues were fixed by immersion in fixatives containing different concentrations of paraformaldehyde, washed in sucrose phosphate buffer, dehydrated in acetone, infiltrated in a glycol methacrylate mixture in which the commonly used softener 2-butoxyethanol was replaced by butaandiol monoacrylate, and embedded. Trypsin was used to re-expose the masked antigenicity. Excellent results were obtained with a panel of monoclonal antibodies (MoAbs) directed against T-cells, B-cells, Ia-positive cells, macrophages, follicular dendritic cells, and leucocyte common antigen-bearing cells. The method described combines exact localization of antigens with optimal tissue morphology.

Microwave-stimulated staining of plastic embedded bone marrow sections with the Romanowsky-Giemsa stain: improved staining patterns

Staining plastic sections with the Romanowsky-Giemsa method is both time-consuming and difficult. This paper reports how the staining time can be reduced to 25 min using microwave irradiation of the staining solution. It is shown that staining results depend on the fixative used, staining temperature, dye concentration and pH of the staining solution as well as on several parameters of the microwave irradiation technique. The staining patterns are improved when compared with those obtained by conventional staining of plastic sections. The colors are more brilliant and greater contrasts are observed. Basophilia, polychromasia, and orthochromasia accompanying red cell maturation are more pronounced. For white cell maturation the initial appearance of specific granules (neutrophil, basophil, and eosinophil) is more evident. Thus, cell classification is easily accomplished using the described technique. It is suggested that microwave-stimulated staining be considered for routine use.

Glycol methacrylate embedding in histotechnology: the hematoxylin-eosin stain as a method for assessing the stability of glycol methacrylate sections

Glycol methacrylate (GMA) samples containing inhibitor in the range of 200-300 ppm were included in a standard embedding mixture. The pH of the GMA samples was measured as a 10% solution of the sample in distilled water. The acidity of GMA due to methacrylic acid causes background staining of sections after basic dyes. The concentration of GMA and the amount of impurities such as methacrylic acid (MA) and ethylene glycol dimethacrylate (EDMA) were measured by gas chromatography. Distinct variations in purity were found among five samples of GMA. Sections derived from GMA samples containing more than 2% EDMA showed few, if any, minifolds after staining with hematoxylin and eosin and were more stable in alcoholic and basic solutions; sections from purer GMA showed minifolds and were less stable. Addition of crosslinkers, EDMA or triethylene glycol dimethacrylate (TEDMA) prevented these artifacts. Crosslinkers clearly influence dimensional changes in sections. Addition of crosslinkers to GMA samples containing minimal amounts of MA improved the results. The possibility of obtaining a high quality GMA embedding medium is discussed.

Floating on a water bath and mounting glycol methacrylate and hydroxypropyl methacrylate sections influence final dimensions

This paper reports the dimensional changes occurring in the different steps of the histoprocessing of tissues for light microscopy. Two water-miscible methacrylates used for embedding, namely 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, were investigated. It was found that during stretching on the water bath and in the mounting step considerable size changes occur, which are of the same magnitude as during the dehydration step of histoprocessing. The final dimensions of the sections and of microscopic images are dependent on the response to surface tension at the water surface and mounting of the glycol and hydroxypropyl methacrylate sections, respectively. Between the two resins under study, significant differences in the size of the resin sections, with and without embedded liver tissue, were found. It is shown that the temperature at which the sections are mounted is of great importance. These observations indicate the importance of standardizing histotechniques if morphometry is to be applied.

The application of a microwave technique for the preparation of cell blocks from sputum

Microwaves stimulate diffusion in tissue and affect the proteins and membrane of the cell. These actions can be used to shorten the time required to fix and prepare cell blocks from sputum. The fixative containing ethyl alcohol and polyethylene glycol is particularly suitable for microwave enhanced fixation. Applying a commercially available domestic microwave oven, in which the temperature and power level can be set, cell blocks can be prepared from fresh sputum in 35 min. The microscopical results are of a superior quality because of the microwave-induced homogeneous distribution of the effects of the applied immersion fluids on the cells. The method is very successful for all specimens containing a large amount of mucous. Health hazards for laboratory personnel are nil in this cell blocking method; in contrast to when fresh sputum containing infectious agents is used for smear preparation.

The application of lipid-soluble stains in plastic-embedded sections

The present study was designed to develop a routine method for direct demonstration and precise localization of lipid substances in tissue sections. A panel of lipid-rich tissues was fixed in 4% buffered formaldehyde, infiltrated, and embedded in the water-soluble plastics Technovit 7100, EFL-67, and JB-4. The use of alcohol containing fluids was avoided. Staining with the lipid-soluble dyes Sudan Black B and Oil Red O revealed excellent preservation of tissue lipids in Technovit 7100 embedded sections when compared with cryostat sections of the same tissue specimens. Lipid preservation in EFL-67 and JB-4 embedded sections was inconsistent, even when infiltration and polymerization procedures were performed at 4 degrees C. Combination of lipid-soluble dyes with the periodic acid Schiff, Jones' methenamine silver, or Gomori' reticulin method allowed for an exact localization of lipids in high-quality Technovit 7100 embedded sections. The procedure herein is easily applicable in routine histopathology practice.

A new, less toxic polymerization system for the embedding of soft tissues in glycol methacrylate and subsequent preparing of serial sections

The paper describes a new polymerization system for embedding soft tissues in glycol methacrylate (GMA). The polymerization of GMA is initiated by means of a barbituric acid derivative in combination with chloride ions and dibenzoyl peroxide. The catalyst system contains no aromatic amines which constitutes a toxicological advantage over the commonly employed system of peroxide/aromatic amine. Clear blocks are obtained from which 1-2 micrometers sections are easy to cut. In combination with an appropriate softener, polyethylene glycol 400, serial sectioning may be practiced.

The effects of embedding in water-soluble plastics on the final dimensions of liver sections

This paper describes the morphometric changes liver samples undergo in the course of fixation, dehydration, infiltration and embedding in different mixtures of water-soluble plastics. The plastics used were: three different mixtures of glycolmethacrylate (GMA) and the commercially available material JB4. Buffered formaldehyde fixation did not produce significant morphometric changes in the liver specimens. Dehydration obviously affects the volume of the liver specimen (linear shrinkage about 9.3%). The dehydration is followed by an infiltration phase. During this phase a slight swelling (linear, 2-5%) occurs. The final polymerization of the plastic resulted in a further linear shrinkage of 1-2%. The influence of different technical factors on the stretching of sections of pure plastic and of plastic embedded liver appeared to be considerable. The difference in stretching between 2 and 3 micron sections has been studied. A significant influence of temperature upon section stretching was noted. Sections of all plastic mixtures stretched at a temperature of 293 K showed 3% more linear stretch than at a temperature of 333 K. Differences between the four plastic mixtures are discussed. Correction factors must be used in morphometrical and stereological investigations (see for review: Weibel, 1979). It was concluded that in the application of water-soluble plastics as embedding media it is essential to apply a standardized procedure, particularly in the cutting and stretching phase.

A new plastic for morphometric investigation of blood vessels, especially in large organs such as the human liver

In this paper a technique is described, using Araldite CY 223 and hardener HY 2967 as injection material, for preparing corrosion casts or histological sections. The plastic has a viscosity (at 39-40 degrees C) similar to that of blood, a gelling time of approximately 17 min (at 40 degrees C), and an exothermic transition energy of delta H = 80.28 +/- 3.20 cal/gm. The influence of the plastic on the tissue is discussed. The histological sectioning of fixed tissue containing Araldite-filled blood vessels after embedding in 2-hydroxyethyl-methacrylate (GMA) is described. When using GMA in a modification of the mixtures of Ruddell (1967) and Sims (1974), methylbenzoate is recommended as an intermedium in order to obtain a more uniform infiltration and reproducible section thickness. At the same time methylbenzoate is recommended as a storing fluid. Sections of 2-3 micrometers afford satisfying morphologic and morphometric results. This method allows various arterial wall dimensions to be measured easily, and provides a suitable means to compare histometric values with SEM data derived from corrosion casts.