Biomedical subjects

B K Berkovitz

Publications and source records attributed to B K Berkovitz.

At least 19 recordsLinked to original sources

PubMed2001

The distribution of retinaldehyde dehydrogenase-2 in rat and human orodental tissues.

Retinoic acid is an important signalling molecule in embryological development and continues to be important in the adult animal because it modulates growth and differentiation in many epithelial tissues. The distribution of the enzyme retinaldehyde dehydrogenase-2 (RALDH 2), which is involved in the synthesis of retinoic acid, was studied using immunocytochemical techniques in: (1) the developing orodental region of rats aged between 15 days in utero and 6 months; and (2) in archival human autopsy material consisting of abdominal skin and mucosa from various regions of the mouth. In developing tooth germs, RALDH 2 was absent in the enamel organ and dental papilla, its presence only being noted at the periphery of the dental follicle adjacent to parts of the developing alveolar crypt. In adult teeth, the presence of RALDH 2 was limited to blood vessels in the periodontal ligament. In embryos, the connective tissue beneath the nasal epithelium and the meninges stained strongly positively for RALDH 2, as did the connective tissue beneath nasal epithelium in an adult rat. Both keratinized and non-keratinized human oral epithelia and abdominal skin stained positively for RALDH 2. Staining was present throughout the stratified epithelium, except in the keratinized layer and in the basal layer associated with the dorsal surface of the tongue. In addition, the adnexia as well as the ductal lining of mucous glands stained positively for RALDH 2.

Adult↗

PubMed2000

Collagen crimping in the intra-articular disc and articular surfaces of the human temporomandibular joint.

The presence of crimping within soft fibrous connective tissues has a considerable role in determining the biomechanical properties of the tissue. However, there is little or no information on crimping of collagen in the human temporomandibular joint. To remedy this situation, the presence and nature of any crimping was studied in sections of human temporomandibular joints from individuals varying in age from between 4.5-63 years, using polarized light microscopy and differential interference contrast microscopy. The presence of crimping was looked for in collagen within the intra-articular disc and the articular surfaces of the mandibular fossa and mandibular condyle. By polarized light, crimping was seen throughout all three tissues at all ages studied. Quantification from micrographs enlarged to x250 showed that the periodicity of the banding (representing half a complete crimp wave) had a mean varying between about 15-20 microm. Crimping was also directly visualized by differential interference contrast microscopy. The presence of such a fundamental feature needs to be considered when explaining the normal function of the temporomandibular joint.

Adolescent↗

PubMed2000

An immunohistological study of cytokeratin 20 in human and mammalian oral epithelium.

Cytokeratin (CK) 20 is a low molecular-weight intermediate filament reportedly expressed only by benign and malignant gastrointestinal epithelium, urothelium and Merkel cells. The main aims here were to map its expression in normal oral mucosa of humans and other mammals, and to determine whether it was expressed by abnormal human oral epithelium. Salivary and odontogenic epithelium were also analysed. An immunoperoxidase method was used on wax-embedded and cryostat sections. In addition, double-labelling experiments were undertaken to determine the association between CK 20 expression and that of CK 8/18 or S100 protein. Normal human oral mucosa from four sites, together with abdominal skin, was studied in autopsy samples from 32 individuals. CK 20-positive, basally situated, round or angular cells, consistent with Merkel cells, were recorded in 24/32 (75.0%) samples of mandibular gingiva, 25/32 (78.1%) samples of hard palate, 7/32 (21.9%) samples of buccal mucosa, 0/32 samples of lateral border of tongue, and 2/32 (6.3%) samples of abdominal skin. Double-labelling showed that all CK 20-positive Merkel cells also expressed CK 8/18 and S100. The only other cells to express CK 20 were human taste buds. There was no expression by dysplastic or invasive oral epithelium from biopsy samples. Colonic mucosa showed luminal-cell positivity in man, marmoset, ferret, rabbit and guinea-pig, but oral mucosa was universally negative in non-human species. It is concluded that in oral mucosa CK 20 is a specific marker of Merkel cells and taste buds, that Merkel cells are more frequently present in keratinized than non-keratinized oral mucosa, that CK 20-positive Merkel cells are also S100-positive, that there may be interspecies variations in CK 20 polypeptide composition and that, by contrast to urothelium, CK 20 has no value in the diagnosis of oral epithelial dysplasia.

Adult↗

PubMed2000

Age changes in the cells of the intra-articular disc of the temporomandibular joints of rats and marmosets.

Cells in the intra-articular disc of the temporomandibular joint were studied ultrastructurally at three different ages to investigate any age changes. Rats aged 2, 15.5 months, and 2.5 years, and marmosets aged 21 months, 7 years, and between 10.5 and 14 years were studied. In the first two age groups of the rat and the first of the marmoset, the cells were generally rounded and had moderate amounts of rough endoplasmic reticulum and other organelles associated with protein synthesis and secretion. Many cells had conspicuous amounts of microfilamentous material and cell membranes were closely applied to the collagen fibrils of the extracellular matrix. Occasionally, a narrow, irregular space containing microfilamentous material lay adjacent to the cell membrane. In the 2.5-year-old rats and the two older age groups of marmosets, cells with chondrocyte-like morphology were present. These cells were surrounded by a conspicuous pericellular matrix devoid of collagen fibrils and composed of microfilamentous material embedded in an amorphous ground substance. They resembled cells described in fibrocartilage from other sites, but differed from chondrocytes in hyaline cartilage by lacking a pericellular capsule. Thus, rats and marmosets both show cellular age changes in the intra-articular disc of the mandibular joint, which can be considered as changing from fibrous to fibrocartilaginous with age, a condition similar to that reported in humans.

Actin Cytoskeleton↗

PubMed2000

Crimping of collagen in the intra-articular disc of the temporomandibular joint: a comparative study.

Very occasional reference is made to the presence of collagen crimps in the fibre bundles of the intra-articular disc (IAD) of the temporomandibular joint (TMJ). As the crimp structure may confer important biomechanical properties on the IAD, the present study was undertaken to determine its distribution in a variety of mammals, including humans. IADs from the rat, rabbit, guinea pig, ferret, sheep, marmoset and human were either sectioned or examined as whole mount preparations with polarized light. Apart from the guinea pig, where fibre bundles in the central region of the disc showed considerable overlap and masking of the crimp structure, the anteroposterior aligned fibres in the central region of all remaining animals showed the conspicuous presence of crimps. The periodicity of the crimp distance varied between about 10 and 30 microm. There was variation of the crimp periodicity between animals and between regions of the same disc. The crimping was associated with undulations along the length of the collagen fibres visible at the light microscope level using routine staining. The possible significance of crimping in association with internal derangement is discussed.

Animals↗

PubMed1998

Caroline Crachami, the Sicilian dwarf (1815-1824): was she really nine years old at death?

Caroline Crachami (C.C.) considered to have had the Seckel syndrome was one of the most extreme cases of dwarfism ever recorded. Reputedly born in Sicily in 1815, she attracted much attention when exhibited in England before her death on 3 June 1824. Although she is said to have been 9 years old at death, published descriptions give her a dental age varying from 2 to 7 years. Examination of her skull in the Royal College of Surgeons of England demonstrated a more or less erupted complete deciduous dentition, with no erupted permanent teeth. Radiographs showed agenesis of several permanent teeth. It was concluded that the dental age of C.C. was 3 years (+/- 6 months). Perikymata were evident in the surface enamel encircling the crown of the partially exposed maxillary left first permanent molar. Their distribution and spacing were normal, with no evidence of developmental retardation. The distance between the periradicular bands in the root near the cement-enamel junction was also normal. We conclude that the dental age of C.C. was similar to her chronological age and that at death she was about 3 and not 9 years old. The reason that she was said to be nearly 9 when exhibited in England we believe was related to financial considerations, as people would be generally less impressed with a dwarf only 3 years old. The new age we give C.C. has implications on the diagnosis of her medical condition.

Age Determination by Skeleton↗

PubMed1998

Interspecies variations in oral epithelial cytokeratin expression.

The aim of this study was to determine the degree to which the epidermis and oral epithelium of species other than man express cytokeratin (CK) intermediate filaments, which are markers of epithelial differentiation. Fixed, wax-embedded samples of skin, buccal mucosa and gingiva from rhesus monkey, marmoset, cow, sheep, pig, ferret, hamster, axolotl and trout were tested for CK expression using a panel of antihuman CK antibodies and an immunoperoxidase procedure. Human skin and oral mucosa were also stained to act as positive control. The results showed that antihuman CK antibodies stained animal tissues, but the patterns of staining were not always identical to the established human CK profile. Of particular interest was the expression of CK18, typically only detected in 'simple' epithelium in man, in bovine, ferret and hamster stratified epithelium from different sites. However, there was evidence of variable anti-CK antibody cross-reactivity, both as a result of intrinsic variations in CK polypeptide structure and as artifacts of fixation. We conclude that some CK are conserved between species, but that biological variables, for example local functional requirements, and technical factors affect the results. These considerations need to be borne in mind in animal studies of epithelial differentiation employing CK immunohistochemistry. Biochemical characterisation is ultimately necessary to determine specific differences between human and animal CK.

Ambystoma↗

PubMed1997

The structure of bovine periodontal ligament with special reference to the epithelial cell rests.

The aim of this study was to determine the structure of the bovine periodontal ligament, with special reference to epithelial cell rests (ECR) and their cytokeratin content. Periodontal ligament was obtained from bovine molar teeth and studied at both the light microscopic and electron microscopic levels. Cytokeratin content was determined using immunohistochemistry against a number of cytokeratin antibodies and specificity tested against bovine and human oral mucosa. Collagen fibril diameters and the area of a fiber bundle occupied by collagen were determined using a digital planimeter with a digitizing tablet. The majority of periodontal fibroblasts possessed considerable quantities of roughened endoplasmic reticulum, indicating rapid synthesis and secretion of collagen, but no intracellular collagen profiles were present. Endothelial cells showed Weibel-Palade bodies. Collagen fibril diameters showed a unimodal distribution with a mean collagen fibril diameter of 55.3 nm. The mean percentage area of the extracellular matrix occupied by collagen was 42%. Structurally, ECR were unusual in exhibiting large numbers of microvilli and conspicuous amounts of cytokeratin filaments. Bovine ECR showed a positive reaction to the pancytokeratin MNF116 (which reacts with the cytokeratins 5, 6, 8, 17, and probably 19), to PCK-26 (which reacts with the type II cytokeratins 1, 5, 6, and 8) and to cytokeratin 13. There was no reaction for cytokeratins 1, 4, 10, 11 and 18. Structurally, bovine periodontal ligament showed features common to other species. However, ECR in terms of both structure and cytokeratin content showed features indicative of important species differences which may have relevance when considering the etiology of radicular cysts.

Actin Cytoskeleton↗

PubMed1995

The distribution of cellular retinoic acid-binding protein I (CRABPI) and cellular retinol-binding protein I (CRBPI) during molar tooth development and eruption in the rat.

The distribution of cellular retinoic acid-binding protein (CRABPI) and cellular retinol binding protein (CRBPI) was studied in a series of prenatal and early postnatal rats, covering the main stages of development and eruption of the molar teeth. CRABPI positive cells were found in the mesenchymal cells of the dental follicle from the cap stage and in the dental papilla from the early bell stage. In the dental papilla, CRABPI positive cells were situated adjacent to the enamel organ in the cervical loop region and in the subodontoblastic region. Newly formed odontoblasts were CRABPI positive for a short period of time. The enamel organ was CRBPI and CRABPI negative, except for the presence of CRABPI positive cells in the internal enamel epithelium over the tip of cusps and in parts of the stratum intermedium. During root formation, CRABPI positive cells were found in the developing periodontal ligament, in the dental papilla adjacent to the epithelial root sheath and in the subodontoblastic zone. During crown formation, CRBPI positive cells were mainly localized to the mesenchymal cells of the dental papilla during the cap stage of crown development. The periosteum of the developing mandible contained CRABPI positive cells while some osteoclasts appeared to show a weak but positive reaction to CRBPI. The findings were considered in terms of the possible significance of retinoid-binding proteins during tooth and bone development.

Aging↗

PubMed1993

The effect of rate of eruption on periodontal ligament glycosylaminoglycan content and enamel formation in the rat incisor.

The rate of eruption of rat mandibular incisors was either increased by cutting one tooth out of occlusion or eliminated by means of pinning. The effects of such changes in eruption rate on the sulphated glycosylaminoglycan content of the periodontal ligaments was analysed. The length of the enamel secretory zone and the composition of the developing enamel matrix protein was also compared. Sulphated glycosylaminoglycan content of the periodontal ligament increased fourfold (P < 0.001) during accelerated eruption but decreased to a corresponding extent (P < 0.001) in the absence of eruption, when compared with controls. The length of the enamel secretory zone was also significantly reduced in the immobilised teeth, although the protein content was similar compared with controls. The results demonstrate the differential response to varied eruption rates of the periodontal ligament and enamel, particularly in respect of the extracellular matrix. The data are consistent with the view that the ground substance of the periodontal ligament plays a role in the generation of the eruptive force.

Amelogenin↗

PubMed1993

The distribution of cellular retinoic acid-binding protein I during odontogenesis in the rat incisor.

Retinoids are important molecules in various aspects of embryological development. Here the distribution of cellular retinoic acid-binding protein I (CRABPI) was studied in the continuously growing incisor of adult rats using an affinity-purified rabbit polyclonal antibody. CRABPI was present throughout the presecretory and secretory ameloblast layer. The protein disappeared from that layer during its maturation phase. The adjacent dental mesenchyme of the developing pulp stained positively for CRABPI, especially in the layer immediately beneath the fully differentiated odontoblasts. Little CRABPI was present in the odontoblast layer itself. The distribution of CRABPI, both in the undifferentiated basal region of the incisor tooth and associated with the cells during hard-tissue formation, suggests a role for this molecule during differentiation and hard-tissue genesis.

Ameloblasts↗

PubMed1993

Ultrastructural quantification of collagen in the articular disc of the temporomandibular joint of the rabbit.

Collagen fibril diameters were quantified in two regions of the articular disc of this joint. One region was the thinner, translucent central part of the disc; the other was from the thicker, opaque peripheral part more anteriorly. Mean collagen fibril diameters in the thicker zone were small and had a unimodal distribution. In contrast, mean collagen fibril diameters in the thinner central region were larger and with a much wider range of values, as indicated by the larger standard deviations. It was concluded that regional variations exist in the collagen of the rabbit articular disc and may reflect the mechanical loads to which the disc is subjected.

Actin Cytoskeleton↗

PubMed1993

Ultrastructural quantification of collagen in human chordae tendineae.

OBJECTIVE: To determine collagen fibril diameter distributions in the chordae tendineae and to see whether there are any differences between right and left sides of the human heart. DESIGN: Collagen fibril diameters and the percentage volume occupied by collagen fibrils (as opposed to ground substance) were determined by means of a planimeter with a digitising tablet from electron micrographs printed at a magnification of 136; 000. MATERIAL: Human chordae tendineae were obtained at postmortem examination from seven subjects aged 50-75 years. MEASUREMENTS AND MAIN RESULTS: Histograms of collagen fibril diameter distributions showed a sharp, unimodal distribution. The mean collagen fibril diameters associated with the tricuspid and mitral valves were 41.1 nm and 40.5 nm respectively. The percentage volume occupied by collagen was about 39% for each valve. There were no significant differences for any of these values between the right and left sides of the heart. CONCLUSIONS: The greater pressures present on the left side of the heart are not reflected in any difference in collagen fibril diameters within the chordae tendineae compared with the right side.

Aged↗

PubMed1993

Cellular retinoic acid binding protein in the periodontal ligament.

As retinoic acid is an important signaling molecule during embryological development. Since periodontal tissues are thought to have fetal-like properties, the present study was to determine the presence and distribution of cellular retinoic acid-binding protein I(CRABPI) in the periodontal tissues of the rat. Following demineralization, wax sections of the molar teeth of four adult male rats were cut in a plane parallel to the molar tooth row. Five representative sections from each jaw were then processed and stained to reveal the presence of CRABP. This protein was identified by immunochemistry utilizing an affinity-purified rabbit polyclonal antibody. The IgG antibody was used at a dilution of 1 microgram ml-1 and immunoreactivity detected with a kit according to protocol. Immunoreactivity was detected with diaminobenzidine and sections counterstained with hematoxylin. Results showed that virtually all the cells of periodontal ligament, the vast majority representing fibroblasts, contained CRABP. Fibroblasts in the gingiva above the level of the alveolar crest also stained positively for CRABP. The periodontal tissues of all three molar teeth were similarly affected. Fibroblasts in other regions of the oral cavity, such as the dermis of the skin of the cheek or the lamina propria of the buccal mucosa or of the diastema region, exhibited little or no staining for CRABP. Because of its properties as a signaling molecule and its ability to interact with other regulatory molecules, retinoic acid and cellular retinoic acid-binding protein may play an important role in the biology of the periodontal tissues.

Animals↗

PubMed1992

Ultrastructural quantification of collagen fibrils in the central region of the articular disc of the temporomandibular joint of the cat and the guinea pig.

This quantitative ultrastructural analysis was made on articular discs from four guinea pigs and four cats. Mean diameters of collagen fibrils were small (approximately 45 nm) and showed unimodal distributions. These features are consistent for connective tissues subjected to compressional forces. The relatively high percentage volume of the extracellular matrix occupied by collagen in the articular disc of the guinea pig (approximately 60 per cent) and the presence of crimping is, however, more typical of a connective tissue subjected to tension. Two differences were discernible between the collagen in the articular discs of the guinea pig and cat. First, the percentage volume occupied by collagen for the guinea pig disc was significantly higher than for the cat. Second, the frequency distribution of collagen fibril diameters for the cat, although unimodal, was skewed. These differences possibly reflect the different types of movement at the temporomandibular joints in the two species.

Actin Cytoskeleton↗

PubMed1991

Ultrastructural quantification of collagen fibrils in chordae tendineae of the sheep and rabbit.

Collagen fibril diameters and the volume occupied by collagen were quantified at the ultrastructural level in the chordae tendineae of the rabbit and the sheep. Collagen fibril diameter distribution was unimodal and significant differences were found between values on the left and right sides, those on the left being greater than those on the right. The differences are discussed in terms of mechanical loading and compared with results obtained from other tendinous structures subjected to continuous loading.

Animals↗

PubMed1991

An assessment of the control of matrix turnover by a quantitative ultrastructural analysis of fibroblasts of the periodontal ligament in rats.

A quantitative structural analysis of the synthetic and degradative organelles of fibroblasts of rat incisor and molar periodontal ligaments was conducted. The results showed that in these tissues which are reported to have significantly different rates of turnover of their functional matrix collagen the rate of synthetic activity was the same. However, there were differences in the pattern of degradation with the molar ligament having between 5 and 6 times more phagocytosed collagen than the incisor. It is suggested that post-synthesis processing may control collagen turnover rather than modulation of rates of synthesis.

Animals↗

PubMed1991

A quantitative study of the ultrastructure of fibroblasts within the enamel-related connective tissue of the rat incisor.

A quantitative ultrastructural study was made of the fibroblasts of the enamel-related connective tissue and periodontal ligament of the rat incisor. The two populations of fibroblasts were very similar in morphology, the only difference found in the parameters measured being the increased number of microtubules in the enamel-related connective tissue. The data do not lend support to the idea that the fibroblasts of the periodontal ligament generate the eruptive force by their motility or contractility.

Actin Cytoskeleton↗