Comparison of the effects of papain and vitamin A on cartilage. II. The effects on organ cultures of embryonic skeletal tissue

The histological effects of copper and zinc on chick embryo skeletal tissues in organ culture

1. The effects of copper and zinc on organ cultures of chick embryo cartilage and bone maintained in low-trace-metal, chemically defined media for up to 8 d were studied macro-scopically, histologically and histochemically. Length and wet-weight measurement of explants were assessed statistically.

2. No effects were found with Cu concentrations of 0·5–1·5μg/ml medium. Between concentrations of 5 and 40μg Cu/ml medium, lengths and wet-weights of cartilage cultures decreased significantly (P< 0·001) compared with controls. The decrease was directly proportional to increasing Cu concentration, and that of the length was greater with increasing period of culture (P< 0·001).

3. With 5–20μg Cu/ml medium cartilage and bone became yellow in colour, and chondrocytes were swollen, rounded and basophilic. They were detached from their lacunae and the quantity of matrix was reduced. Loss of alkaline phosphatase (EC3.1.3.1) activity and disappearance of glycogen accompanied the degeneration. Osteogenesis ceased, cells failed to divide and mature, lost their enzymes and died. Cu did not accumulate in the bone matrix.

4. The direct toxic effects of Cu for cartilage and bone may underlie some of the skeletal changes in hepatolenticular degeneration (Wilson’s disease).

5. As Zn concentrations were increased from 2·5 to 7·5μg/ml medium, lengths and wet-weights of cartilaginous cultures were significantly increased (P< 0·001). As Zn concentrations were further increased (from 10 to 40μg/ml medium), lengths and wet-weights were significantly decreased (P< 0·001).

6. Zn stimulated chondrocyte division and vacuolation of cytoplasm. With higher Zn concentrations toxic changes of granular basophilia, lacunar detachment and necrosis were seen. Differentiation and functioning of osteoblasts, osteoclasts and chondroclasts were stimulated by Zn.

7. Zn was found in bone matrix, osteoblasts, osteocytes and hypertrophied chondrocytes.

CHANGES IN CONNECTIVE TISSUE AND INTESTINE CAUSED BY VITAMIN A IN AMPHIBIA, AND THEIR ACCELERATION BY HYDROCORTISONE

In view of the theory that an excess of vitamin A causes release of cathepsins from intracellular lysosomes, hypervitaminosis A was induced orally in the larvae of Xenopus laevis. It was predicted that the tails of these amphibia would undergo resorption prior to metamorphosis, since the presence of abundant lysosomes, associated with measurable increases of catheptic activity, had previously been demonstrated in the resorbing tails of amphibia during metamorphosis. This prediction was confirmed; after 3 to 4 weeks of hypervitaminosis A, the tails of treated animals underwent partial resorption. Other transitory appendages, the rostral tentacles, collapsed after 2 weeks of treatment with an excess of vitamin A, an effect analogous to the collapse of rabbits' ears after intravenous papain. These effects were related to the loss of metachromatic extracellular material in these appendages. Excess of vitamin A caused kyphoscoliosis and prognathos in the larvae. The hypervitaminotic larvae always developed a mucinous diarrhea, which was associated with a remarkable overgrowth of metachromatic goblet cells of the intestine. The entire intestine of the treated animals was more advanced in development than that of control larvae at equivalent stages. All the effects of hypervitaminosis A were accelerated by the simultaneous administration of hydrocortisone. This was held to be due to liberation of vitamin A from hepatic stores by the steroid, and is in contrast to the retardation of hypervitaminosis A by hydrocortisone in vitro.

Comparison of the effects of papain n vitamin A on cartilage. I. The effects in rabbits

The administration of large amounts of vitamin A to rabbits has been shown to result in depletion of cartilage matrix. The normal basophilic, metachromatic, and Alcian blue staining properties of the matrix are lost, especially in articular and epiphyseal cartilage. The cartilage cells remain intact, but are reduced in size. These changes sometimes appeared as early as 48 hours after the initiation of daily injection of 1 million units of vitamin A, and were usually well established by 5 days. Some rabbits failed to show changes in cartilage, even after 5 daily injections. Increased amounts of material presumed to be chondroitin sulfate were present in the sera of vitamin A-treated rabbits, usually by 72 hours after the first injection. This was demonstrated by a turbidimetric procedure using hexamminecobaltic chloride. In rabbits given sulfur-35 (Na(2)S(35)O(4)) 5 days before the initiation of vitamin A treatment, it was shown that sulfur-35 was lost from articular and epiphyseal cartilage. This was associated with an increase in the non-dialyzable sulfur-35 in both serum and in the cobalt-precipitable material. These rabbits also excreted more sulfur-35 than rabbits not given vitamin A. There was a reduction in sulfur-35 activity in chondromucoprotein extracted from the ear cartilage of vitamin A-treated rabbits. The changes are interpreted as indicating that the administration of large amounts of vitamin A to rabbits results in removal of chondroitin sulfate from cartilage matrix. The administration of small amounts of crude papain causes histologic changes in cartilage that are remarkably similar to those seen in vitamin A-treated rabbits. The possibility is suggested that the changes in cartilage produced by administration of vitamin A to rabbits may be the result of activation of a proteolytic enzyme or enzymes, with properties similar to those of papain.

The effect of hydrocortisone on the response of fetal rat skin in culture to ultraviolet irradiation

1. The effect of hydrocortisone on the development of fetal rat skin in organ culture, and on its repair after exposure to a mixed beam from a mercury lamp, are described. 2. The addition of hydrocortisone (7.5 µg/ml) to the culture medium (HC medium) caused accelerated differentiation and keratinisation of the epidermis followed by atrophic changes as in vivo. 3. Explants were grown for 2 days in either normal or HC medium and then irradiated with light from an Hanovia lamp. 4. Irradiation of the control explants produced severe necrosis in both epidermis and dermis and much disorganisation of the dermal intercellular material; 2 days after exposure the s. corneum with adherent cellular debris had become either completely detached from the denuded dermis, or raised to form a fluid-filled blister. Epidermal regeneration had begun by the 4th day after irradiation and was usually complete by the 6th day. 5. Hydrocortisone modified the response to irradiation as follows: (1) reduced and retarded cellular breakdown, (2) prevented vesication, (3) preserved the organisation of the dermal intercellular material, (4) hastened epithelialisation, (5) accelerated the differentiation of the new epidermis. Effects (2), (3), and (4) were probably secondary to (1). 6. Experiments with various light filters showed that the effective wavelengths for producing lesions in the skin explants were those below 3000 A. 7. It is suggested that the beneficial effect of hydrocortisone on the repair of irradiated skin explants might be due, at least in part, to a reduced proteolytic activity in the damaged tissue through a stabilising action of the hormone on the lysosomes. 8. The relationship of these findings to clinical observations is discussed.

The influence of hydrocortisone on the action of excess vitamin A on limb bone rudiments in culture

The effect of hydrocortisone has been studied in organ cultures of the cartilaginous long bone rudiments from 7-day chick embryos and of the well ossified limb bones from late fetal mice. In the chick rudiments, which grow rapidly in culture, the growth rate was much reduced by hydrocortisone, less intercellular material was formed, and the hypertrophic cells of the shaft were much smaller than in the controls in normal medium. In the late fetal mouse bones, which grow very little in culture, hydrocortisone had no obvious effect on growth but arrested resorption of the cartilage. These effects resemble those described by others in the skeleton of animals treated with cortisone or hydrocortisone. The influence of hydrocortisone on the response of the chick and mouse explants to excess vitamin A was investigated. In the presence of excess vitamin A, cartilage (chick, mouse) and bone (mouse) rapidly disintegrated, but when hydrocortisone also was added to the medium, this dissolution of the intercellular material was much retarded, though not suppressed. The retardative action of hydrocortisone on the changes produced by excess vitamin A in skeletal tissue in culture, contrasts sharply with the strongly additive effect of the two agents on the skeleton in the intact animal (Selye, 1958). It is suggested that this discrepancy between the results obtained in vitro and in vivo is probably due to systemic factors that operate in the body but are eliminated in organ cultures.

THE EFFECT OF ANTISERUM, ALONE AND WITH HYDROCORTISONE, ON FOETAL MOUSE BONES IN CULTURE

1. The effects of normal rabbit serum and of rabbit antiserum to whole foetal mouse tissues, on the isolated limb bones of late foetal mice were studied in organ culture, and the influence of hydrocortisone on these effects was investigated. 2. Unheated normal serum caused slight loss of metachromatic material from the cartilage matrix, and some resorption of both cartilage and bone. 3. In unheated antiserum to foetal mouse tissues, the terminal cartilage was smaller and less metachromatic than in paired controls in normal serum, while osteoclasis was so intense that in many explants the bone had almost disappeared. The amount of necrosis varied with different batches of antiserum. 4. The changes produced by normal serum and antiserum could be largely prevented by heating the sera to 57 degrees C for 45 minutes. 5. The effects could also be inhibited by the addition of hydrocortisone to the unheated sera; as little as 0.1 microg hydrocortisone per ml of medium had a well marked protective action. 6. It is suggested that (a) unheated antiserum causes a release of lysosomal enzymes with consequent breakdown of intercellular material, (b) this release is due to an indirect action on the lysosome via an increased permeability of the cell membrane, (c) hydrocortisone does not affect the antigen-antibody reaction, but inhibits the autolytic changes that normally follow this reaction, possibly by stabilising both the lysosomal and cell membranes.

THE SUSCEPTIBILITY OF CHICK EMBRYO SKIN ORGAN CULTURES TO INFLUENZA VIRUS FOLLOWING EXCESS VITAMIN A

The conversion of chick embryonic epidermis to mucous epithelium by excess vitamin A in organ culture as reported by Fell and Mellanby (5) was shown to be accompanied by a corresponding change of susceptibility to influenza and vaccinia viruses. Untreated epidermis of 10- to 12-day chick embryos supported the growth of influenza (PR8) virus in organ cultures and a maximum infectivity (EID(50)) titer was reached 2 to 3 days after infection. At the same time) the epidermis showed squamous keratinization, beginning about the 4th day of cultivation. Addition of excess vitamin A (40 microg per ml) to the skin organ culture induced the following changes: (a) mucous metaplasia of the epidermis which was usually first evident after 4 to 5 days in the vitamin A medium, (b) increase in the daily and maximum yield of influenza virus, if the epidermis had been grown for 4 or more days in the vitamin A medium before infection took place, and (c) decrease in the production of vaccinia virus under similar conditions. The maximum yield of both viruses remained unchanged, however, if excess vitamin A was introduced to the organ culture at the time of virus inoculation. The magnitude of increase in the yield of influenza virus in this organ culture system was found to be proportionally related to the concentration of vitamin A added 4 or more days before inoculation of this virus. Increasing doses of vitamin A however, had no effect on the short-term growth of influenza virus in tissue cultures of chorio-allantoic membrane. Observation on the early period (2 to 12 hours) of influenza virus growth initiated in the 4-day organ cultures of chick embryonic skin showed no significant difference in virus production between the normal and the vitamin A medium groups. The change of virus specificity apparently is not due to the presence of excess vitamin A per se, but appears to be related to the change of differentiation produced in the organ culture system.

THE EFFECTS OF PAPAIN, VITAMIN A, AND CORTISONE ON CARTILAGE MATRIX IN VIVO

The extreme and, apparently, selective vulnerability of chondromucoprotein in cartilage matrix to the action of proteolytic enzymes in vivo provides a useful model for studying factors involved in the transport, inhibition, and activation of a protease, papain, in the blood and tissues. The lysis of cartilage matrix which occurs in hypervitaminosis A is the result of release, probably from chondrocytes, of cathepsins normally contained within lysosomes. Cortisone possesses two properties which are not only of importance for this experimental model but also may have more general bearing on the physiological functions of this hormone with respect to connective tissue. One property is to prevent the resynthesis or deposition of chondroitin sulfate in cartilage matrix, after depletion of the latter. The other, which may be relevant to the "anti-inflammatory" actions of cortisone, is to increase the stability of lysosomes and prevent release of the acid hydrolytic enzymes contained in these organelles.

A model for osteoarthritis of the temporomandibular joint

There is a need for a simple, reproducible animal model of advanced osteoarthritis of the temporomandibular joint (TMJ). In this study, gentle removal of the condylar articular layer in the sheep TMJ resulted in an eburnated condyle with peripheral osteophytes, thin or perforated discs, and temporal surface proliferation. This model can be used for both the study of osteoarthritis and the evaluation of therapeutic methods.

Radiobiologic response of CHO-KI cells treated with vitamin A

Treatment of CHO-KI cells with vitamin A altered their response to subsequent gamma irradiation. In general longterm preincubation with low doses of the vitamin caused a relative increase in the number of cells surviving a given radiation dose. The effect resulted in an increase in the D0 of the survival curve. Long or short term exposure to high concentrations of the vitamin caused a decrease in the number of surviving cells leading to a decrease in the extrapolation number of the survival curve. Recovery of cells from radiation damage, assessed using the split dose technique, was also impaired by vitamin A pretreatment. A mechanism involving repair of potentially lethal damage may explain the protective effect of vitamin A since this was highly dependent on the cell density of cultures at the time of irradiation. However, in view of the data showing that the vitamin A concentrations necessary to alter the radiation survival curve shoulder caused a significant release of sialic acid into the medium, a mechanism involving membrane stability may account for both the reduction in repair/recovery capacity of the treated cells and the radioprotective effect.

Advances in understanding cell interactions in tissue resorption. Relevance to the pathogenesis of periodontal diseases and a new hypothesis

Much of the connective tissue degradation that takes place in periodontal diseases is mediated by proteolytic enzymes. Previous studies have focused on the action of proteinases released by invading polymorphonuclear neutrophils and macrophages, and bacterial enzymes. In view of recent work establishing that resident connective tissue cells can be induced by cytokines to bring about the destruction of their own matrix, we propose a new hypothesis. In this we envisage that a critical step is the interaction of bacterial antigens with inflammatory cells, resulting in the production of a cytokine, interleukin-1. Our interpretation of in vitro evidence is that the loss of connective tissue attachment and bone matrix resorption in periodontal diseases is mediated by metalloproteinases such as collagenase and stromelysin released by cells of the periodontium. Such proteolytic destruction can be induced by interleukin-1, whose production may not be dependent on a specific microbial flora but may be triggered by a number of organisms. It is now clear that interleukin-1 has multiple actions on both immune and non-immune cells; these include the induction of lymphocyte differentiation and proliferation and the stimulation of bone and cartilage resorption, and prostaglandin and metalloproteinase synthesis by connective tissues. It seems likely that further knowledge about the production and function of this cytokine will have an increasing impact in many diseases that involve resorption, particularly since interleukin-1-like molecules can be produced by cell types other than monocytes/macrophages, including keratinocytes and fibroblasts.

Retinoic acid enhances the displacement of newly synthesized hyaluronate from cell layer to culture medium during early phases of chondrogenesis

Chondrogenic differentiation in mouse limb bud mesenchymal cells cultured at high density was suppressed by supplementation of the medium with retinoic acid (1 microgram/ml or 3.3 X 10(-6) M). Since in control medium overt chondrogenesis begins on day 3, retinoic acid was introduced on day 2 so that the relationship between initial biosynthetic changes and inhibition of chondrogenesis could be studied. During the first 24 h of exposure the treated cells remained viable but suffered 10% inhibition in growth and synthesized [3H]glucosamine-labeled glycosaminoglycan at a level 24% below untreated cells. The amount of labeled hyaluronic acid released into the culture medium by the treated cells was, however, 2-fold greater, on a per cell basis, than that in the untreated cultures. It is suggested that the displacement of hyaluronate may play a role in the disruption of mesenchymal cell differentiation and of limb morphogenesis as observed in other systems.

Cartilage growth inhibition and necrosis in vitro caused by prostaglandin A1

This paper details experiments using the Fell technique of organ culture of 8-day chick embryo femoral and tibial rudiments to test the effects of prostaglandin A1 (PGA1) on cartilage growth. Growth was studied during 8 days in vitro by measurement of rudiment length and wet and dry weight, and by histology. PGA1 inhibited explant growth in a dose-related manner. Linear growth was significantly decreased by 20 and 25 microgram/ml PGA1 at 2, 4, 6 and 8 days, and by 15 microgram/ml at 6 and 8 days. Linear growth was unaffected by 1 and 10 microgram/ml doses. Weight measurements were significantly reduced by 25 microgram/ml PGA1 (2, 4 and 8 days) and by 20 microgram/ml (8 days). Chondroblast degeneration was caused by doses of 15, 20 and 25 microgram/ml PGA1. Progressive degeneration was seen at the 25 microgram/ml concentration after 2 days in vitro. Cellular changes as early as 27 h in vitro were seen using electron microscopy. Tritiated thymidine autoradiography confirmed reduced chondroblast proliferation in the presence of PGA1 (25 microgram/ml). The mechanisms of prostaglandin-induced changes in embryonic cartilage remain uncertain. The possible role of intracellular cyclic nucleotides in the reaction is discussed.

The effects of prostaglandin A1 and prostaglandin B1 on the differentiation of cartilage in the chick embryo

In organ cultures of chick embryonic limb rudiments the mean length of explants treated with 25 microgram/ml prostaglandin B1 (PGB1) was significantly smaller than that of paired controls (P < 0.001) after 4, 6 and 8 days in vitro. The deceleration of linear growth was constant during 8 days in vitro. Growth inhibition was confirmed by a statistically significant decrease in explant dry weight after 8 days of culture. However, PGB1 caused no observable alteration in the histological structure of the explants. The possible role of PGB1 in the physiological control of cartilage growth is postulated. Explants similarly treated with prostaglandin A1 (PGA1) at concentrations of 15 microgram/ml for 8 days or 20 microgram/ml for 4 and 8 days exhibited "comma" and "inverted commas" phenomena, caused by the intermingling of chondroblasts from the epiphyseal and flattened-cell zones, which thus ceased to be distinct entities. Adenylate cyclase in the plasma membrane may be involved in this disturbance of cartilage differentiation.

Wound healing: a review. III. Nutritional factors affecting wound healing

Wound healing proceeds more efficiently and quickly in well-nourished individuals who are in good general health at the time that they have to undergo surgery. Per contra, individuals who are malnourished and chronically ill heal less well and are in general at greater risk of complications during and after surgery. For the latter, elective surgery may be deferred until nutritional improvement is attained, but for emergency or urgent operations, institution of measures promoting good nutrition has to be concurrent with necessitous surgery and continued postoperatively. In this paper, the importance to wound healing of proteins, carbohydrates, fats, vitamins, and trace elements and minerals is reviewed.

Effect of vitamin A and methylprednisolone on canine prostate in organ culture

Organ explants from the canine prostate with and without methylprednisolone pretreatment were cultivated for ten days in Trowell's T-8 medium or medium supplemented with testosterone and/or vitamin A. Upon termination of the experiments, explants were fixed and examined histologically. All glands from the most central section of each explant were graded according to epithelial type, and from these grades the proportion of acini with maintained columnar cells was calculated for each explant. Stromal cellular maintenance was also estimated. While a small proportion of explants from the vitamin-treated and methylprednisolone-pretreated groups showed epithelial maintenance, a combination of these treatments significantly increased such maintenance. Stromal maintenance was enhanced with methylprednisolone pretreatment but not by vitamin A. These results are in accord with the hypothesis that methylprednisolone acts to stabilize the lysosomal membrane, thus protecting tissue against the effects of ischemic shock. In protected explants vitamin A is able to maintain a columnar glandular epithelium. In a subsequent experiment a series of linoleic acid dosages was tested in the presence or absence of vitamin A. In neither case was this fatty acid of value in improving epithelial or stromal maintenance.

Virus-induced lysosomal enzyme dissolution of nasal turbinate cartilage

The mechanism of laryngotracheitis virus-induced dissolution of chick nasal turbinate cartilage was studied by lysosomal enzyme histochemistry. Five-day-old chicks were infected by intranasal instillation, and changes in lysosomal enzyme distribution were followed at daily intervals through the tissue regeneration stage, Day 28. In the mucosa the lysosomes were activated beginning on Day 1, and glycerol acid phosphatase and a diffuse form of beta-glucuronidase were released concomitant with tissue cell destruction. In the chondrocytes (where glycerol acid phosphatase was absent), beginning on Day 2, particulate (lysosomal) beta-glucuronidase decreased as diffuse beta-glucuronidase increased and extended out into the matrix. The cartilage lost its metachromatic staining properties and became soft and pliable. Regeneration of the mucosa started on Day 6 and gradual reappearance of metachromatic staining of the cartilage began on Day 8 with considerable recovery of original turbinate structure by Day 12. A lysosomal membrane labilizer, vitamin A, exacerbated the cartilage pathology, whereas a stabilizer, cortisone, retarded it.

Laryngotracheitis virus in chickens. A model for study of acute nonfatal desquamating rhinitis

Infectious laryngotracheitis can be produced in chickens as an experimental model of severe nonfatal rhinitis and sinusitis. Inoculated intranasally into unanesthetized baby chicks it remains limited to the nasal fossa, produces acute desquamation of all nasal epithelia, results in functional recovery of the respiratory epithelium, but leaves important residual abnormalities. From the earliest recognizable lesions through 4(1/2) months' convalescence, the principal changes are as follows: 1. Initial lesions, or small syncytia of intranuclear "inclusions", first identifiable in the mucociliated cells of the shallowest portion of the epithelium at about 21 hr postinoculum (the inner surface of the maxillary conchal scroll). 2. Acute sloughing, (about 3 to 7 days), marked by: (a) spread of lesions from cell to cell via multinucleated "giant cells" which progressively slough and desquamate respiratory, olfactory, and sinus epithelia, epithelial neural elements and blood vessels; (b) appearance of numbers of eosinophilic leukocytes along the basement membrane at the sites of lesions just previous to sloughing; intensive infiltration of the submucosa with small lymphocytes after sloughing begins; (c) histochemical change in the intracellular mucus of the cells which comprise the syncytia: this mucus stains with Alcian blue alone when stained with AB-PAS; and (d) all cartilages of the maxillary conchae become flaccid, and the cell nuclei and matrix lose both basophilic and Alcian blue staining properties, effects which recede by about the 8th day. 3. Repair (about 8 to 21 days), marked by rapid initial spread of a sheet of epithelial cells over the infiltrated subrmucosa, appearance of numbers of plasma cells circulating in the tissues, formation of encapsulated secondary nodules, and mucosal adhesions. 4. Convalescence (about 1 to 4(1/2) months when experiments terminated), marked by functional restoration of the mucociliary lining of the nasal fossa. However, at 4(1/2) months eight specimens all show complete metaplasia of the olfactory organ (end nerves, supporting cells, and glands of Bowman) to mucociliated epithelium, all show abnormal formation and alignment of mucous acini, and about 50% have severe persistent sinusitis.